By S. Trompok. Great Lakes Maritime Academy.
Our smell receptors are obviously able to detect a difference between the two optical isomers prinivil 2.5mg mastercard. However the collagen triple helix in connective tissue is always a left handed helix purchase cheapest prinivil. You can check whether any helix has a right or left handed turn by using these definitions - try it yourself on spiral staircases buy prinivil australia, corkscrews, fusilli pasta and even knitting yarn. The shoots of some plants such as honeysuckle twist to the right (clockwise) whereas the shoots of others such as bindweed twist to the left (anticlockwise). The doomed marriage of these two plants was the subject of the classic song "Misalliance" by Flanders and Swann. In fact the Latin name of the ubiquitous climbing plant Common Ivy is Hedera helix, which itself means twisting. The soft curly tendrils of clinging plants such as grape vines and beans however, can have their helices reversed when the tendril touches a support. This so-called "tendril perversion" fascinated Charles Darwin and he wrote about it at length in his book "The Movements and Habits of Climbing Plants". When the tendril starts to curl and tighten up, since neither the stem nor the support can rotate, the total twist in the tendril cannot change. Therefore, as the tendril curls on itself, the coils of the spiral are reversed at some point and the two opposite spirals are separated by a small straight segment. This phenomenon can be likened in the modern sense to a coiled telephone cable, which is first completed extended, untwisted and then slowly released. There are many examples of handedness in synthetic molecules as well all right handed- try looking on the labels of toiletries, household chemicals and medicines when you go shopping. Left-handed (or negatively-refracting) materials turn out to transform space for electromagnetic fields and their vacuum fluctuations [2,10]. Philbin, Quantum levitation by left-handed metamaterials, New Journal of Physics 9, 254 (2007). Philbin, Quantum optics of spatial transformation media, Journal of Optics A (in press). Full, Evidence for van der Waals adhesion in gecko setae, Proceedings of the National Academy of Sciences 99, 12252 (2002). Boersma, A maritime analogy of the Casimir effect, American Journal of Physics 64, 539 (1996). Casimir, On the attraction between two perfectly conducting plates, Proceedings of the Royal Netherlands Academy of Arts and Sciences, B51, 793 (1948). Capasso, Quantum Mechanical Actuation of Microelectromechanical Systems by the Casimir Force, Science 291, 1941 (2001). Philbin, General relativity in electrical engineering, New Journal of Physics 8, 247 (2006). Pendry, Negative Refraction Makes a Perfect Lens, Physical Review Letters 85, 3966 (2000). Roukes, Quantum physics: Casimir force changes sign, Nature 419, 119 References 1. Researches on the molecular asymmetry of natural organic products, English translation of French original, published by Alembic Club Reprints (Vol. On the rotation of plane of polarisation of electric waves by a twisted structure, Proc. The Cure For All Cancers Including Over 100 Case Histories of Persons Cured Plus two revolutionary electronic circuits, one to diagnose and monitor progress, the other to zap parasites and bacteria! The cause is a certain parasite, for which I have found evidence in every can- cer case regardless of the type of cancer. So lung cancer is not caused by smoking, colon cancer is not caused by a low- roughage diet, breast cancer is not caused by a fatty diet, retinal blastoma is not caused by a rare gene, and pancreatic cancer is not caused by alcohol consumption. The dis- covery of the cause and cure of all cancers has stood the test of time and here it is! You may not have time to read this entire book first if you have cancer and are scheduled for surgery, chemotherapy or radiation treatment. You may wish to skip the first pages which describe how a parasite and a solvent cause cancer to develop. Go directly to the instructions on eliminating the parasite with herbs (Cancer Curing Recipe, page 19) or with electricity (Zapping Parasites, page 30). It does not matter how far progressed the cancer is— you can still stop it immediately. After you have stopped the cancer, you can turn your atten- tion to getting well (Part 2). Read the case histories to see how easy it is to stop even terminal cancers (Part 3). But if you do not wish to make your doctor angry, you could follow her or his wishes, too. Be careful not to lose any vital anatomical parts in surgery, though, because you may need them later when you are healthy! They have no way of knowing about the true cause and cure of cancer since it has not been published for them. I chose to publish it for you first so that it would come to your attention faster. The opinions expressed herein are based on my scientific research and on specific case studies involving my clients. Be advised that every person is unique and may respond differently to the treatments described in this book. Again, remember that we are all different and any new treatment should be applied in a cautious, common sense fashion. The treatments outlined herein are not intended to be a re- placement or substitute for other forms of conventional medical treatment. I have indicated throughout this book the existence of pol- lutants in food and other products. Complete instructions for building and using this device are contained in this book. The Syncrometer is more accurate and versatile than the best existing testing methods. However at this point it only yields positive or negative results, it does not quantify. The chance of a false positive or a false negative is about 5%, which can be lessened by test repetition. It is in the public interest to know when a single bottle of a single product tests positive to a serious pollutant. If one does, the safest course is to avoid all bottles of that product entirely, which is what I repeatedly advise. These recommendations should be interpreted as an intent to warn and protect the pub- lic, not to provide a statistically significant analysis. It is my fervent hope that manufacturers use the new electronic tech- niques in this book to make purer products than they ever have before.
In the case of benzoic acids generic prinivil 2.5 mg on-line, direct conjugation is not possible buy cheap prinivil 2.5mg line, but in one resonance hybrid buy prinivil canada, as shown in figure 1. The electron-donating phenolic hydroxyl group, on the other hand, desta- bilizes the carboxylate anion by charge repulsion, making the substituted acid weaker. The pKa of a drug is important to its pharmacological activity since it influences both the absorption and the passage of the drug through cell membranes. In some cases, only the ionic form of a drug is active under biological conditions. Drug transport during the pharmacokinetic phase represents a compromise between the increased solubility of the ionized form of a drug and the increased ability of the non- ionized form to penetrate the lipid bilayer of cell membranes. A drug must cross many lipid barriers as it travels to the receptor that is its site of action. Ionic drugs are also more hydrated; they may therefore be “bulkier” than nonionic drugs. As a rule of thumb, drugs pass through membranes in an undissociated form, but act as ions (if ionization is a possibility). A pKa in the range of 6–8 would therefore seem to be most advantageous, because the nonionized species that passes through lipid membranes has a good probability of becoming ionized and active within this pKa range. This consid- eration does not relate to compounds that are actively transported through such membranes. A high degree of ionization can prevent drugs from being absorbed from the gastroin- testinal tract and thus decrease their systemic toxicity. This is an advantage in the case of externally applied disinfectants or antibacterial sulfanilamides, which are meant to remain in the intestinal tract to fight infection. Also, some antibacterial aminoacridine derivatives are active only when fully ionized. Ionization can also play a role in the electrostatic interaction between ionic drugs and the ionized protein side chains of drug receptors. Therefore, when conducting experiments on drug–receptor binding, it is advis- able to regulate protein dissociation by using a buffer. The degree of ionization of any compound can be easily calculated from the Henderson–Hasselbach equation: % ionized = 100/(1 + antilog [pH − pKa]) (1. The latter method provides very accurate electron-density maps, but only of molecules in the solid state; it cannot be used to pro- vide maps of the nonequilibrium conformers of a molecule in a physiological solution. To provide easily obtained yet rigorous assessments of electron distribution properties, quantum mechanics calculations are now employed (see section 1. Molecular quantum mechanics calculations provide several methods for calculating the orbital energies of atoms, combining the individual atomic orbitals into molecular orbitals, and deriving from the latter the probability of finding an electron at any atom in the molecule— which is tantamount to determining the electron density at any atom. There are several methods for doing this, with varying degrees of sophistication, accuracy, and reliability. These calculations permit quantification of the charge density on any atom in a drug molecule. Such atomic electron density values may be used when correlating molecu- lar structure with biological activity during the drug molecular optimization process. In addition to providing values for charge densities on individual atoms, quantum mechanics calculations may also be used to determine the energies of delocalized orbitals; such energy values may also be used when correlating molecular structure with pharmacologic activity. They are expressed in β units (a quantum-chemical energy parameter whose value varies from 150 to 300 U/mol). In addition to providing insights concerning correlation of molecular structure with pharmacologic bioactivity, quantum mechanics calculations of electron distribution may also be employed to understand the molecular basis of drug toxicity. For instance, overall p-electron density of polycyclic hydrocarbons has traditionally been assumed to correlate with the carcinogenicity of these compounds. According to this hypothesis, defined reac- tive regions on the molecule undergo metabolism to form reactive intermediates such as epoxides, which react with cell constituents such as the basic nitrogen atoms in nucleic acids. Although this model has been widely cited in the literature, it is appropriate to warn the reader that, however attractive, it is seriously questioned. However, p-electron density is very important in the chemical reactivity of aromatic rings. The synthetic preparation of new molecules is challenging, time consuming, and expensive. Theoretical chemistry, combined with modern compu- tational methods, offers a powerful solution to this prediction dilemma. The docking of a drug with its receptor site is a precise interaction between two mole- cules. The success of this interaction is dependent upon the geometry, conformation and electronic properties of the two molecules. Designing drugs requires techniques for deter- mining and predicting the geometry, conformation, and electronic properties of both small molecules (i. Molecular modeling is the evaluation of molecular properties and structures using computational chemistry and molecular graphics to provide three-dimensional visu- alization and representation of molecules. Quantum pharmacology is the application of the methods of modern computational chemistry to understanding drug action at the molecular and atomic level of structural refinement. A review of drug design papers in the Journal of Medicinal Chemistry and of pharmaceutically relevant papers in the Journal of the American Chemical Society, covering the year 2000, reveals that 43% of these papers included computational chemistry techniques in their design and analyses of drug molecule action. Clearly the dawn of the 21st century has emphasized the exponentially growing importance of molecular modeling and quantum pharmacology in drug design. Accordingly, a basic understanding of medicinal chemistry in the modern era requires an appreciation of the fundamentals of quantum mechanics, molecular mechanics, and the other techniques of computational chemistry as applied to drug design. The medicinal chemist who uses com- mercially available computer programs to design drugs should not treat them as merely “black boxes,” and should have some insight into their conceptual basis. This is best achieved by using a “mechanics” method that permits the geometry of a molecule to be expressed as a function of energy. By minimizing this energy function, one can ascertain the optimal geometry of the molecule. Quantum mechanics and molecular mechanics are the dominant “mechanics” methods in quantum pharmacology (see figure 1. Once the wavefunction is known for a particular system, then any physical property may in principle be determined for that system. However, ψ is just a normal mathematical function; it has no special mathematical properties. If the system being studied is a simple hydrogen atom with a single electron outside of a positively charged nucleus, the Schrödinger equation may be solved exactly. The wavefunctions which satisfy the Schrödinger equation for this simple hydrogen atom are called orbitals; a hydrogenic atomic orbital is therefore the three-dimensional mathe- matical function from which one may calculate the energy and other properties of a single electron. For single atoms that contain multiple electrons (polyelectronic mono-atomic systems), the wavefunction for the atom (ψ) is a product of one-electron wavefunctions (χi), one for each electron. Drug molecules may have their properties ascertained by either experimental or theoretical methods. Although experimental meth- ods, especially X-ray crystallography, are the “gold standard” methods, calculational approaches tend to be faster and do provide high quality information. Nonempirical techniques, such as ab initio quantum mechanics calculations, provide accurate geometries and electron distribution properties for drug molecules. In quantum pharmacology, the goal is to determine the wavefunction Ψ for the drug molecule so that the energy and properties of the drug may be calculated.
Evaluation for cosmeceutical effect must account for the following speciﬁc and distinct needs prinivil 10mg low cost. The customer’s perspective is more related to the individual’s perceptions of their skin appearance than to a meticulously quantitated numerical assessment of its condition prinivil 2.5 mg generic. These perceptions are more global than speciﬁc cheap prinivil 10mg with visa, and mandate an evaluation that is weighted toward overall appearance but adequately accounts for speciﬁc concerns of dryness, texture, wrinkling, skin color, and pigmentary unevenness. Cosmetic or therapeutic effects produced by the product are important to the consumer, but so are physical aspects of the product itself. A product that is not cosmetically elegant or that is drying or irritating to the skin will be less acceptable to the consumer in spite of alleged pharmaceutical properties. These aspects and physical attributes of cosmetics can be well quantitated by both con- sumer panel testing of the product as well as by speciﬁc instrumentation. Table 1 The Cosmeceutical Perspective Subject’s self-perceptions Customer cosmetic expectations Product physical attributes Regulatory aspects Marketing claims Degree of pharmacological activity 16 Cunningham Cosmeceutical properties of a therapeutic intervention are central to the discussion and may require both well-conducted studies of consumer satisfaction as well as adequate documentation and substantiation of cosmetic or therapeutic claims (e. Pharmaceutical testing of pharmacological effect is, by deﬁnition, the most stringent, requiring not only adequate trial design and execution but substantially more documentation of statistically signiﬁcant changes that are also clinically and consumer relevant. This is the area where proper application of biometrics to photoaging is most helpful and important (3). They note that their skin is rough, dry, wrinkled, and that their face and hands, in particular, have numbers of variously colored ﬂat spots. Tanning no longer produces an even darkening of the skin and, especially on the legs, numerous white spots have appeared. Occasionally they are aware of a less resil- ient quality of their skin, which in some areas tends to sag and not bounce back when it is stretched. Raised unsightly growths of cosmetic or medical concern to the patient may have appeared. Clinical Presentations Photoaging is most frequently progressive, yet modiﬁed by both environmental exposure and genetics (Table 3). The clinical presentation of photodamage is there- fore highly polymorphic but with many characteristic signs and symptoms (4). Table 2 Photoaging Signs and Symptoms Overall appearance older than chronological age Wrinkles, ﬁne and coarse Diverse pigmentary alterations Rough texture Dryness Sallow complexion Various neoplasms, benign and malignant Photoaging 17 Table 3 Functional Abnormalities of Photoaging Uneven tanning Skin easily distends Slow return to normal contour Thinned skin easily traumatized Sensory decrease Decrease in immune competence The most casual observation of the face or neck of an individual with photo- damaged skin, even by the untrained observer, consciously and subconsciously gives an overall impression of a person older than their chronological age. Visu- ally, wrinkles both ﬁne and coarse are frequently the hallmark of sun-damaged skin in many individuals, although genetic differences may, in some, favor pig- mentary alterations or thinning of the skin as the most prominent presenting sign. An overall sallow, or yellowish hue, is common and presumably due to the complex interplay of light absorption and reﬂection in photodamaged skin that is characterized by uneven thickness of the stratum corneum and abnormalities of melanization. Additionally, circulatory alterations of endogenous origin or as a consequence of photodamage produce variable contributions of heme pigment to overall skin color. Discrete alterations consistent with actinic lentigos, especially promi- nent on the face and hands, may alternate with mottled hyperpigmentation con- sisting of patchy and alternating lighter and darker macules due to diffuse abnor- malities of melanogenesis and melanosome distribution in keratinocytes. Diffuse pigmentary change may also present as melasma on the face due to either epider- mal melanin abnormalities or dermal macrophages containing melanin or heme pigment. Hypomelanotic macules are vitiligenous and are frequently observed most prominently on the lower extremities. Dryness and surface roughness, best perceived by tactile rather than visual means, are among the most common complaints related to aged and photoaged skin, but are not speciﬁc for either. Scaling due to dryness or perturbation in epidermal turnover is also common, but not speciﬁc to photodamage. Benign seborrheic keratoses are mostly cosmetic growths that appear in sun- exposed body areas. Grossly observed thinning and histological stratum corneum irregularity, epidermal thinning, and abnormal collagen and elastin result in skin that is easily traumatized with abrasions, cuts, and tears. Blood vessels can be easily seen through the skin and, because of epidermal thinning and decreased dermal integrity, the skin bruises and bleeds more easily than normal. Sensory decrease, not usually clinically obvious, has been partially docu- mented in increasing age, though not speciﬁcally in photoaging. Utilizing skin compliance and a two-point discrimination testing on the pad of the index ﬁnger, increasing age was correlated with decreased tactile sensitivity and said to be likely related to change in the nervous system (tactile discrimination), rather than change in skin itself (skin compliance) (5). An actual increase in intraepidermal nerve ﬁbers, correlated with severity of photodamage, was observed in a recent study of the ultrastructure of photodamaged skin and was theorized to be indica- tive of a neural involvement in the pathophysiology and/or repair of photodam- aged skin (6). This complicated interaction continues to be an extremely important area of research (7). Since the products will be applied at least to the face, and probably to other areas of the body, it must be cosmetically acceptable and preferably reﬁned or elegant. Exceptions are those individuals who will use a greasy oint- ment or malodored product thinking it must be therapeutic if it has those undesir- able characteristics. Product qualities and potential acceptance can be tested more rigorously by using a panel of trained individuals who note the various properties of the Photoaging 19 Table 4 Product Testing Product attributes by dermatosensory panel Claim substantiation Instrumentation Pharmaceutical testing formulation (Table 4). Even untrained individuals may be able to distinguish overall acceptability but use of trained panelists allows much greater reﬁnement of the overall and individual aspects of the product. Commercial testing is avail- able (entitled the DermatoSensory Proﬁle), which describes and grades or com- pares products for their characteristics of appearance and feel on the skin. Testing includes evaluation of the rate of absorption of the product into the skin, including spreadability and stickiness, immediate afterfeel, including shininess, greasy or oily feeling, drag (the sensation of resistance to motion over the skin), and residue (the sensation or perception of something remaining on the skin). Perception of residue after set periods of time such as 5, 15, and 30 min is called delayed afterfeel. Various descriptions of the product itself, aside from its characteristics on the skin such as color, odor, thickness, substantivity, consistency, grittiness, or smoothness can also be described. Many of these product characteristics are important in consumer acceptance of the cosmeceutical as well as in their percep- tion of beneﬁt. Cosmeceutical Testing No matter if cosmetic or pharmaceutical endpoints are sought, adequate trial de- sign is critical for accurate, precise, consistent, reproducible, and valid observa- tions in photoaging. The optimum trial for pharmaceutical, and to some extent cosmeceutical, purposes is double-blind, placebo (vehicle)-controlled, multicen- ter, and frequently, for the chronic process of photoaging, of at least several months’ duration. Cosmetic testing may be of much shorter duration in fewer subjects but should optimally follow the same basic logic. Study of the parameter that is most important to the product is essen- tial; a facial moisturizer designed for older females living in the north should not be artiﬁcially tested in male and female college students in the south. Overall severity rating for study entry and follow-up of global appearance has been accomplished with a photographically derived rating scale, with 0 20 Cunningham Figure 1 none, 1 to 3 mild, 4 to 6 moderate, and 7 to 9 severe photodamage (8). These evaluations may be performed by the investigator, by the subject, or by third persons comparing photographs of before and after in a randomized and blinded manner. This and similar rating scales may also be applied at baseline and follow-up to speciﬁc parameters such as wrinkles, surface roughness, mottled pigmentation, overall color, skin dryness, and texture. A 100-mm visual analogue scale has been successfully utilized to rate the overall appearance of the skin and speciﬁc parameters of ﬁne wrinkles, discrete pigmentation, shallowness, and texture. A clinical panel evaluation technique has been described that potentially allows precise, consistent, and completely unbiased evaluations of clinical state (9). Very high-quality photographic slides are obtained, prepared in matched ca- rousels, and placed on two random-access projectors in a rear-screen projection booth. Side-by-side comparison of each patient’s time-randomized baseline and end-of-treatment photographic slides by trained, but uninvolved, evaluators is thus accomplished in a completely blinded and randomized manner. Both global response and speciﬁc parameters of overall appearance, ﬁne wrinkles, and dis- crete pigmentation can be judged and graded on a 13-point balanced categorical Figure 2 Photoaging 21 scale with zero representing no difference between the two photographs.
Some hormones purchase 10mg prinivil, such as cortisol generic prinivil 5 mg amex, may spike too high and pull other hormones offline order prinivil us. Women younger than thirty may not yet feel affected by the aging process, but perhaps they want to get pregnant or avoid the diagnosis of breast cancer their mom just received. Those in their thirties may feel increasingly tense and overwhelmed, in need of better strategies on how to relax. They may want to prevent the high blood pressure, prediabetes, and accelerated aging that come with chronically high stress levels. Women in their forties and fifties may want to regain some of the buoyancy of their youth. Perhaps they want to wake up feeling restored again, without the brain fog from disrupted sleep. Women in their sixties, seventies, and eighties may want to optimize their cognitive and executive functioning—to improve their thinking, memory, and competitive edge. I don’t want women to suffer; I don’t want them to be underserved by their doctors, miseducated by the media, tired, frazzled, and ashamed. I’m not a magician who can turn back the hands of time and make you twenty- five again, nor do I believe that’s best for you. What I can do is return something you’ve lost: the properly proportioned hormonal organization that provides clarity, confidence, and longevity. The human body has an innate ability to repair and self-regulate, but that ability often gets bulldozed by the enduring stressors, distractions, and interruptions of modern life. Once you rediscover your body’s ability to shift toward balance, informed by the new science of integrative women’s health and aided by The Gottfried Protocol, you’ll find that it’s easier to move toward balance than to stay imbalanced. Attend to your hormones today, and the process will serve your mood, weight, energy, sex drive, sleep, and resilience for decades to come. I designed several questionnaires, which I use in my practice, to identify the most common hormonal problems that can occur during premenopause, perimenopause, and menopause. Then I’ll guide you toward the chapters that can best help you in your quest for hormonal balance. It’s the basis of a nourishing meal (like those we’re often too busy to prepare or enjoy). It’s a soul-infused pie chart, where all the pieces complement one another and feed our spirit. We know that balance can help us run the gauntlet of working, child rearing, grocery shopping, caregiving, errand running, and juggling our other interests while keeping our health and sanity intact. Balance enables us to take on those tasks in a less harried, frantic, and fragile way. It might be instead that your hormones are off, and that’s what’s making you feel off balance. When your hormones are disordered, you can feel lethargic, irritable, weepy, grumpy, unappreciated, anxious, depressed. The biological processes of our bodies, whether they’re functioning ideally or are disordered, affect our mood, psyche, and the way we live. Stress is the top reason behind most visits to the doctor, and it contributes to all the big causes of death, including heart disease, diabetes, stroke, and cancer. If any one of them is left out, we might not find the root cause of the hormone imbalance. My questions have been adjusted over the years through my own study and experience with the women in my medical practice, and integrated with a hefty dose of evidence. I encourage my patients to see the path toward hormone balance as an epic journey—a womanly version of an odyssey. That’s what these questionnaires are: the journey-starting, readiness- testing task for balance- seeking sheroes. Quest(ionnaires) for Hormonal Balance The following questionnaires, similar to the ones I administer in my practice, are designed to identify correctly the undiagnosed hormone problems you may face. I use the results to find the sweet spot between mainstream medicine’s tendency to underdiagnose without the tendency to overdiagnose that I sometimes observe in alternative medicine. Read carefully through the list of symptoms, put a checkmark next to any you experience, and add up the checks within each grouping. Just like a Venn diagram of overlapping circles, you may have symptoms that fit into more than one part (such as infertility and mood issues). In other words, some of your answers may be repeated— but usually one or two areas will stand out as your key hormonal challenges. They are usually noncancerous and develop from friction, such as around bra straps. Interpreting the Questionnaires Said yes to three or more questions in one category? I created this test to distill the latest medical research into an actionable plan for you to get back into hormonal balance. Each questionnaire is designed to mirror what you’re thinking, feeling, and experiencing, regardless of your age. Thousands of women in my medical practice have found these questionnaires helpful in identifying the next steps to correcting their hormones. If you have more than three checks in one grouping of symptoms (for instance, Part A and Part C), move to the suggested chapter(s) after reading the following information. If you have more than five symptoms in one grouping and your symptoms are worsening or you feel moderately distressed (or worse) about it, you may need to work with your local and trusted doctor in order to tailor the treatment for you. Please understand that the questionnaires are signposts, helpful hints, designed as tools to clarify how you can most efficiently balance your hormones. The questionnaires are just the beginning of The Hormone Cure process, and by no means an end point. You’ll also find the latest version on my website (go to http://thehormonecurebook. Part A: High Cortisol This is by far the most common hormone imbalance affecting modern women. Fewer than three or unsure: I recommend asking your physician to test your blood (serum) cortisol level in the morning, before nine. You can also test yourself at home with salivary cortisol levels at four points throughout the day, in a method called the diurnal cortisol panel. Often, diurnal cortisol levels are more helpful because you can monitor your cortisol over the course of a day, rather than basing your findings on a single data point of a blood test. For more information: Read “Part A: The Nitty-Gritty on High Cortisol” in chapter 4 (page 75). Part B: Low Cortisol Remember, you can have both high and low cortisol— even on the same day, within a twenty-four-hour period.
We have: 2 variance of true values = σT 2 variance of measurement error discount prinivil 2.5 mg with mastercard, method A = σA 2 variance of measurement error cheap prinivil uk, method B = σB In the simplest model errors have expectation zero and are independent of one another and of the true value discount prinivil line, so that 2 2 variance of method A = σA + σT 2 2 variance of method B = σB + σT 2 covariance = σT (see appendix) Hence the expected value of the sample correlation coefficient r is 2 σ T ρ = 2 2 2 2 (σ A + σT )(σ B + σT ) 2 2 2 2 2 Clearly ρ is less than one, and it depends only on the relative sizes of σT , σA and σB. If σA and σB 2 are not small compared to σT , the correlation will be small no matter how good the agreement between the two methods. In the extreme case, when we have several pairs of measurements on the same individual, 2 σT = 0 (assuming that there are no temporal changes), and so ρ = 0 no matter how close the agreement is. They concluded that the two methods did not agree because low correlations were found when the range of cardiac output was small, even though other studies covering a wide range of cardiac output had shown high correlations. In fact the result of their analysis may be 308 explained on the statistical grounds discussed above, the expected value of the correlation coefficient being zero. Their conclusion that the methods did not agree was thus wrong - their approach tells us nothing about dye-dilution and impedance cardiography. As already noted, another implication of the expected value of r is that the observed correlation will increase if the between subject variability increases. Diastolic blood pressure varies less between individuals than does systolic pressure, so that we would expect to observe a worse correlation for diastolic pressures when methods are compared in this way. It is not an indication that the methods agree less well for diastolic than for systolic measurements. This table provides another illustration of the effect on the correlation coefficient of variation between individuals. Correlation coefficients between methods of measurement of blood pressure for systolic and diastolic pressures Systolic pressure Diastolic pressure sA sB r sA sB r Laughlin et al. A further point of interest is that even what appears (visually) to be fairly poor agreement can produce fairly high values of the correlation coefficient. They concluded that because the correlation was high and significantly different from zero, agreement was good. However, from their data a baby with a gestational age of 35 weeks by the Robinson method could have been anything between 34 and 39. For two methods which purport to measure the same thing the agreement between them is not close, because what may be a high correlation in other contexts is not high when comparing things that should be highly related anyway. It is unlikely that we would consider totally unrelated quantities as candidates for a method comparison study. The correlation coefficient is not a measure of agreement; it is a measure of association. At the extreme, when measurement error is very small and correlations correspondingly high, it becomes difficult to interpret differences. It is difficult to imagine another context in which it were thought possible to improve materially on a correlation of 0. Regression Linear regression is another misused technique in method comparison studies. This is equivalent to testing the correlation coefficient against zero, and the above remarks apply. These authors gave not only correlation coefficients but the regression line of one method, Teichholz, on the other, angiography. They noted that the slope of the regression line differed significantly from the line of identity. Their implied argument was that if the methods were equivalent the slope of the regression line would be 1. However, this ignores the fact that both dependent and independent variables are measured with error. In our previous notation the expected slope is 2 2 2 β = σT /(σA + σT ) and is therefore less than l. How much less than 1 depends on the amount of measurement error of the method chosen as independent. Similarly, the expected value of the intercept will be greater than zero (by an amount that is the product of the mean of the true values and the bias in the slope) so that the conclusion of Ross et al. We do not reject regression totally as a suitable method of analysis, and will discuss it further below. Asking the right question None of the previously discussed approaches tells us whether the methods can be considered equivalent. We think that this is because the authors have not thought about what question they are trying to answer. The questions to be asked in method comparison studies fall into two categories: (a) Properties of each method: How repeatable are the measurements? This may include both errors due to repeatability and errors due to patient/method interactions. Under properties of each method we could also include questions about variability between observers, between times, between places, between position of subject, etc. Most studies standardize these, but do not consider their effects, although when they are considered, confusion may result. Altman’s (1979) criticism of the design of the study by Serfontein and Jaroszewicz (1978) provoked the response that: “For the actual study it was felt that the fact assessments were made by two different observers (one doing only the Robinson technique and the other only the Dubowitz method) would result in greater objectivity” (Serfontein and Jaroszewicz, 1979). What we need is a design and analysis which provide estimates of both error and bias. We feel that a relatively simple pragmatic approach is preferable to more complex analyses, especially when the results must be explained to non-statisticians. It is difficult to produce a method that will be appropriate for all circumstances. What follows is a brief description of the basic strategy that we favour; clearly the various possible complexities which could arise might require a modified approach, involving additional or even alternative analyses. Properties of each method: repeatability The assessment of repeatability is an important aspect of studying alternative methods of measurement. Replicated measurements are, of course, essential for an assessment of repeatability, but to judge from the medical literature the collection of replicated data is rare. Repeatability is assessed for each measurement method separately from replicated measurements on a sample of subjects. We obtain a measure of repeatability from the within- subject standard deviation of the replicates. The British Standards Institution (1979) define a coefficient of repeatability as “the value below which the difference between two single test results... Provided that the differences can be assumed to follow a Normal distribution this coefficient is 2. For the purposes of the present analysis the standard deviation alone can be used as the measure of repeatability. It is important to ensure that the within-subject repeatability is not associated with the size of the measurements, in which case the results of subsequent analyses might be misleading. The best way to look for an association between these two quantities is to plot the standard deviation against the mean. If there are two replicates x1 and x2 then this reduces to a plot of | x1 – x2| against (x1 + x2)/2. From this plot it is easy to see if there is any tendency for the amount of variation to change with the magnitude of the measurements.
This acetylcholinesterase inhibitor is desulfurized selectively to the toxic malaoxon buy prinivil 10mg on line, but only by insect and not mammalian enzymes purchase 2.5mg prinivil visa. Higher organisms rapidly detoxify malathion by hydrolyzing one of its ester groups to the inactive acid effective 5 mg prinivil, a process not readily available to insects. This makes the compound doubly toxic to insects since they cannot eliminate the active metabolite. Novel polymers have permitted the development of membranes with controlled diffusion rates. The great advantage of this is that the constant release rate of 65 µg/day means that much less drug is released than with the use of oral contraceptive tablets. The transdermal delivery of scopolamine as an antiemetic for motion sickness represents another successful application of microporous membrane technology. Here the drug is applied in a plastic strip similar to a “Band-Aid,” usually behind the ear. Low-density lipoproteins and liposomes (drug-filled lipid–cholesterol vesicles measuring a fraction of a micrometer) are also being used to protect drugs from enzymatic destruction during transport in the bloodstream. Osmotic minipumps — cylinders measuring about 25 × 5 mm — are widely used to deliver constant amounts of drug solutions to experimental animals. The osmotic compartment swells in contact with tissue fluid and squeezes the drug reservoir, displacing the drug solution in a continuous flow. The rate of delivery is specified by the size of the opening in the container and the swelling rate of the osmotic “syringe. Although these interesting developments in bioengineering are not, strictly speaking, in the realm of drug design or even medicinal chemistry, they can nevertheless contribute substantially to the success of drug therapy. A useful drug is a drug molecule that is not only safe and efficacious, but also one that can pass government regulations, pass through multiple levels of human clinical trials, be economically produced in large quantities, be successfully marketed, and can ultimately help people with disease. Perhaps the greatest hurdle along the pathway of a molecule becoming a useful drug is the need to sequentially pass clinical trials. However, before a drug can be evaluated in human clinical trials, it must first successfully negotiate preclinical test- ing. This frequently involves five or six types of test, and is completed in non-human animals: 1. Acute toxicity — acute dose that is lethal in 50% of animals; usually two species, usually two routes of administration 2. Subacute toxicity — physiology, histology, autopsy studies; two species, sometimes with dosings over a 6 month time period 3. Mutagenic potential — effects on genetic stability of bacteria (Ames test) of mammalian cells in culture 5. Carcinogenic potential — required if drug is to be administered for prolonged periods of time 6. Reproductive performance effects — effects on animal progeny, production of birth defects Once a molecule successfully passes the preclinical testing, it is ready for human clin- ical trials. Phase 1 — the effects of the drug as a function of dose are measured in a small number (25–45) of healthy volunteers who do not have the disease under study; safety is primarily evaluated. Phase 2 — the drug is studied in a small number of people (20–150) who have the disease under study; both safety and efficacy are evaluated. The timeline for drug discovery and development is long, adding to the high cost of drug development. Phase 4 — once the drug has been approved for market, vigilant post-marketing sur- veillance is done to ascertain the possible appearance of previously undetected tox- icities or problems. During the drug development phases, toxicity is one of the most important hurdles to the success of a drug molecule. Toxicity can affect the person who is taking the medication (causing skin rashes, liver problems, bone marrow failure, etc. Toxicity problems have resulted in many drugs being withdrawn from the market, as shown in table 3. Successful completion of the four phases of human clinical trials enables a drug to be widely distributed for the treatment of human disease. However, a simple reality of drug discovery is that drugs are developed by industry. The lead compound may have been identified in an academic university-based laboratory, but the clinical trials are invariably completed by the industrial sector. Because of this, drug molecules tend to be developed only if they have a good prospect for being profitable. In order to be profitable, a drug molecule should be patented so that the vendor can enjoy exclusive rights to its marketing. Many drugs that are successful in the pharmacodynamic phase ultimately fail to become useful drugs. This pie-chart presents the reasons for failure at this stage of the development process. X-ray crystallography of drug molecule–macromolecule interactions as an aid to drug design. Toronto: Jones and Bartlett, (excel- lent description of syntheses of diazepam, ibuprofen, sertraline). Comparative study of lipophilicity versus topological molecular descriptors in biological correlations. Novel approaches to the design of safer drugs: soft drugs and site–specific delivery systems. Use of artificial intelligence in structure–activity relationships of anticonvulsant drugs. Quantitative structure–activity relationship methods: perspectives on drug discovery and toxicology. Sustained brain-specific delivery of estradiol causes long-term suppression of luteinizing hormone secretion. Structural, chemical topological, electrotopological and electronic structure hypotheses. The relation between the chemical structure of flavonoids and their estrogen-like activities. Quantitative structure–activity relationship study of histone deacetylase inhibitors. Building Blocks for the Framework Structure: C-C, C=C, C≡C, and C-H Bond Formation C-C Bond Formation 1. Oxymercuration–demercuration (Markovnikov regiochemistry) -C≡N Functional Group 52. Not all molecules are drugs, but certain properties enable a molecule to be a drug-like molecule and poten- tially a drug. Analogously, not all macromolecules are receptors, but certain properties enable a macromolecule to be a druggable target. With these two basic facts in place, it is then necessary to understand how to design drug-like molecules that can specifically interact with drug targets.
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