By J. Xardas. Gardner-Webb University. 2019.
Bottom: “Boot” shaped heart and decreased pulmonary vascular markings in a cyanotic patient with tetralogy of Fallot cheap 100mg sildigra otc. This group of congenital lesions can be divided by physiological principles into those that induce a volume load on the heart (most commonly due to a left-to-right shunt but also due to atrioventricular valve regurgitation or to abnormalities of the myocardium itself-the cardiomyopathies) and those that induce a pressure load on the heart (subvalvar purchase sildigra 120 mg with amex, valvar or great vessel stenoses) generic 100 mg sildigra with amex. The chest X-ray is a useful tool for differentiating between these two major categories, since heart size and pulmonary vascular markings will usually both be increased in the left-to-right shunt lesions. Classification of acyanotic congenital heart defects based on physiologic perturbation. The common pathophysiologic denominator in this group of lesions is a communication between the left and right sides of the circulation and the shunting of fully oxygenated blood back into the lungs. Although pulmonary Fetal Circulation & Congenital Heart Disease - Daniel Bernstein, M. As pulmonary resistance drops over the first month of life, the left-to-right shunt increases, and so does the intensity of the murmur and the symptoms. The increased volume of blood in the lungs is quantitated by pediatric cardiologists as the pulmonary to systemic blood flow ratio or Qp:Qs. This increase in pulmonary blood flow decreases pulmonary compliance and increases the work of breathing. Fluid leaks into the interstitium or alveoli causing pulmonary edema and the common symptoms: tachypnea, chest retractions, nasal flaring, poor feeding and wheezing (Table 1). In order to maintain a left ventricular output which is now several times normal (although most of this output is ineffective, since it returns to the lungs) heart rate and stroke volume must increase, mediated by an increase in sympathetic stimulation. The increased work of breathing and the increase in circulating catecholamines lead to an elevation in total body oxygen requirements, taxing the oxygen delivery capability of the circulation. Thus, the common symptoms of tachycardia, sweating, irritability and failure to thrive. The combination of left-to-right shunt and valve regurgitation increases the volume load on the heart and usually leads to earlier presentation and more severe symptomatology. As opposed to the left-to-right shunts, the cardiomyopathies (see below) cause heart failure directly due to diminished cardiac muscle function, leading to increased atrial and ventricular filling pressures, and to pulmonary edema secondary to increased capillary pressure. The common pathophysiologic denominator of these lesions is that, unless the stenosis is severe, cardiac output is maintained, thus, in children, symptoms of heart failure are often not present. This compensation is accomplished by a marked increase in cardiac wall thickness (hypertrophy). If the ductus arteriosus is still open, the oxygen saturation may be Fetal Circulation & Congenital Heart Disease - Daniel Bernstein, M. Coarctation of the aorta may present solely with a systolic murmur and with diminished pulses in the lower compared with the upper extremities. Thus, it is important to always palpate both the femoral and either the brachial or radial pulses simultaneously during a routine screening examination of any infant or child. A coarctation may be localized to the area of the descending aorta immediately opposite the ductus arteriosus (juxtaductal coarctation). In these patients, in the first few days or weeks of life the ductus arteriosus may remain partially patent and will serve as a conduit for blood flow to partially bypass the obstruction at the level of the coarctation. In more severe forms, coarctation involves hypoplasia of the transverse aortic arch, in which case it presents with a more significant obstruction to blood flow and usually causes heart failure and signs of poor perfusion in the neonatal period. This group of congenital heart lesions can be divided by physiological principles into those associated with decreased pulmonary blood flow (e. The chest X-ray is again an important primary initial diagnostic tool for differentiating between these two major categories. There are two basic pathophysiologic elements which underlie all of these lesions: First, is an obstruction to pulmonary blood flow at some level (tricuspid valve, sub- pulmonary muscle bundles, pulmonary valve, main or branch pulmonary arteries). It is important to remember that even with severe pulmonic stenosis, systemic desaturation will not occur unless there is right-to-left shunting at some level. Classification of cyanotic congenital heart lesions based on physiologic perturbation. In these lesions, the degree of clinical cyanosis will depend on the degree of obstruction to pulmonary blood flow. If the obstruction is mild, cyanosis may not be present at rest, but only with stress (these hypercyanotic episodes are known as "Tet spells"). If the obstruction is severe, pulmonary flow may be totally dependent on the patency of the ductus arteriosus. These infants present with profound cyanosis in the newborn period and require pharmacologic manipulation (prostaglandin E1) to maintain ductal patency until surgical intervention. Unlike the previous group of lesions, pulmonary blood flow is more than adequate in this group, yet because of the defect only a small portion of this oxygenated blood can enter the systemic circulation. Deoxygenated blood from the body returns to the right side of the heart and is pumped directly back to the body again. Oxygenated blood from the lungs returns to the left side of the heart and is pumped back into the lungs. If not for the persistence of fetal pathways such as the foramen ovale and ductus arteriosus, this lesion would not be compatible with life. These pathways allow for some degree of both left-to-right and right-to-left mixing of oxygenated and deoxygenated blood until surgical intervention can occur. Cardiac lesions resulting in a single or common ventricle are known as total mixing lesions. This is because deoxygenated systemic venous blood and oxygenated pulmonary venous blood usually mix totally in the heart resulting in equal oxygen saturations in the pulmonary artery and aorta. Unless pulmonary stenosis is present, pulmonary blood flow will be torrential and these infants usually present with both mild cyanosis and heart failure. If pulmonary stenosis is present, then pulmonary blood flow will be limited, and these infants usually present with more profound cyanosis without heart failure. Truncus arteriosus also results in total mixing of systemic and pulmonary venous blood, however in patients with truncus, mixing occurs at the great vessel level. However, even in many other subspecialties, you may likely be responsible for playing some role in the care of a child with congenital heart disease or an adult who has had repair of congenital heart disease during childhood. There are now, for the first time in history, more adults with congenital heart disease alive in the U. Whichever subspecialty you choose, it will be necessary to know some of the more common congenital heart diseases and how their cardiopulmonary systems respond to various perturbations, such as fluid shifts, anesthesia and infection, to name a few.
They were first identified in the late 1970s cheap sildigra 25mg mastercard,during studies of noradrenaline release from axon terminals of sympathetic post-ganglionic fibres in rat atria trusted 120mg sildigra. In recent years purchase 50mg sildigra with visa,a number of more potent and systemically active antagonists have been developed. A similar action on presynaptic Ca2 channels was presumed to underlie the block of neurotransmitter release by baclofen. This has now been demonstrated by recording Ca2 currents from presynaptic terminals directly (Takahashi,Kajikawa and Tsujimoto 1998). In several neuronal types baclofen was also shown to cause a postsynaptic hyperpolarisation due to the opening of K channels (E is more negative than V ). Each protein has a predicted structure consisting of a large N-terminal and seven transmembrane domains,similar to metabotropic glutamate receptors. However,the affinity of agonists was much lower than seen with native receptors and not all expected coupling to effector systems could be demonstrated (possibly because of inappropriate or inefficient linkage to G-proteins). The receptors can form as homomeric assemblies of r subunits but native receptors may be heteromeric assemblies of r subunits (e. Activation of these presynaptic receptors inhibits glutamate release from the bipolar cells. All three r subunits have been identified in brain,but their precise location and the functional significance of this expression is unclear. It is involved in many metabolic pathways,is an essential component of proteins,and is found throughout the brain. A neurotransmitter role for glycine was first identified in the spinal cord,where it was found to be differentially distributed between dorsal and ventral regions and shown to cause hyperpolarisation of motoneurons (Werman et al. Glycine-mediated neurotransmission plays a key role in spinal cord reflexes, mediating reciprocal and recurrent inhibition of motoneurons by Renshaw cells,and is important in motor control and sensory pathways. Glycine receptors are also found in higher brain centres including the hippocampus,cortex and cerebellum. The L-serine derived from glycine may be further metabolised,or released from glial cells to be taken up into neurons,forming a cycle analogous to the glutamine±glutamate cycle shown in Fig. Glycine can also be formed by the action of aminotransferases (such as alanine- glyoxylate transaminase or glycine transaminase),in which the amino group from a donor amino acid is transferred onto glyoxlate,producing glycine and a keto acid. This will be determined by the expression of the respective biosynthetic enzymes and plasma membrane transporters. The extent and significance of such co-release is unclear,but its effects will obviously depend on the types of pre- and postsynaptic receptors present at the synapse. Picrotoxin is also an effective glycine antagonist and in recombinant systems is selective for homomeric receptors Palacin et al. Glycine receptors were originally isolated from spinal cord membranes on the basis of strychnine binding,and found to be composed of two membrane-spanning polypeptides (termed a and b) and an associated cytoplasmic protein (gephyrin). To date,four a subunit genes (a1±4) and a single b subunit gene have been identified,with several additional variants of the a1 and a2 isoforms produced by alternative splicing (reviewed by Kuhse,Betz and Kirsch 1995; Rajendra,Lynch and Schofield 1997). In 3 recombinant expression systems the a subunits give rise to functional homomeric receptors or co-assemble to form heteromeric receptors. Native receptors in the adult spinal cord contain 3 a1and2b subunits whereas neonatal receptors are homomeric receptors formed from a2 subunits. In the brainstem,glycine receptors have also been shown to be present on presynaptic terminals,where they induce a small depolarisation that activates Ca2 channels and increases neurotransmitter release (Turecek and Trussell 2001). However,native and recombinant glycine receptors are positively modulated by a wide range of general anaesthetics,including diethyl ether,halothane,isoflurane,chloral hydrate,brometone and trichloroethylene. Subtypes of g-aminobutyric acidA receptors: classification on the basis of subunit structure and receptor function. Crestani,F,Low,K,Keist,R,Mandelli,M,Mohler,H and Rudolph U (2001) Molecular targets for the myorelaxant action of diazepam. Jonas,P,Bischofberger,J and Sandkuhler,J (1998) Corelease of two fast neurotransmitters at a central synapse. Kuhse,J,Betz,H and Kirsch,J (1995) The inhibitory glycine receptor: architecture,synaptic localization and molecular pathology of a postsynaptic ion-channel complex. Verleysdonk,S,Martin,H,Willker,W,Leibfritz,D and Hamprecht,B (1999) Rapid uptake and degradation of glycine by astroglial cells in culture: synthesis and release of serine and lactate. However, when peptides are being considered as transmitters, views tend to be more diverse. The definition of a peptide is a chain of amino acids which does not exceed 30 amino acids in length, the arbitrary cut-off before the molecule becomes a protein, which is too bulky to be stored, released and interact with a receptor molecule. Nevertheless, it is clear that signalling molecules can have roles in many places in the body so there is no reason why a transmitter substance can act as a hormone via the vasculature on a distant site as well as at closer range when released from a nerve terminal to act on an adjacent neuron. The increasing number of synthetic agonists and antagonists for the peptide receptors means that function can now be probed and novel therapeutic targets are achieved. It cannot be ignored that the therapeutic effects of morphine and its antagonist naloxone arise from an ability to act on a receptor that is there for the functional effects of endogenous opioid peptide systems. The study of the production of the propeptides have revealed a series of principles in that:. Some propeptides lead to the production of different, in terms of receptor affinities, peptides (substance P and neurokinin A act on neurokinin 1 and 2 receptors, respectively). Some propeptides produce multiple copies of similar peptides (met-enkephalin and leu-enkephalin act on the same delta opioid receptor). The whole process of production of a peptide is sluggish simply because the size of the precursor is so great. Once produced the precursor is packaged into vesicles and then transported down the axon to the terminal. Axonal transport is generally a slow process in that mm±cm/day is rarely exceeded. Thus in a long axon the arrival of the peptide at the release site at the terminal will not be quick. While the precursor is being transported it is processed further by peptidases within the vesicles that cleave the larger parent molecule into smaller fragments. It is easy to speculate that in an active neuron with a rapid firing pattern, the continued release of a peptide may eventually lead to depletion of the peptide occurring.
A variable that is associated with both the problem and the possible cause of a problem is a potental confounding variable order sildigra 50mg otc. The confounding variable may either strengthen or weaken the apparent relatonship between an outcome and a possible cause safe 120 mg sildigra. Therefore buy 25mg sildigra amex, in order to give a true picture of cause and efect, the confounding variables must be considered, either at planning stage of or during data analysis. Example: In a survey to investgate whether there is a relatonship between mothers who are cigarete smokers and weight of their newborn, the dependent variable is the newborn’s weight, the independent variable is the mother’s smoking habit. Two aspects need to be considered: defne the variables and state the scale of measurement. It should be objectve, observable and is sufciently clear and explicit to avoid ambiguity. The selecton for a scale is determined by the variable itself and the methods available for measuring it. A type of data in which the variables are divided into a number of named categories. Example: • Level of knowledge: poor, average, good; • Opinion of individual: fully agree, agree, disagree, and totally disagree. A type of variable in which there is an unlimited number of equally spaced categories; thus a contnuum of values is possible. Patent has Dengue fever confrmed by serology yes/No/Not available dengue fever (IgM positve or four-fold rise in Igg ttre) or virology. Social class Head of household’s main occupaton Detailed occupaton, as stated by respondent in answer classifed into social to a queston in a structured class I - V questonnaire. Haemoglobin Haemoglobin concentraton in g/dl capillary blood, measured by haemoglobinometer. We may not get results that refect the true picture if we use the wrong samplingWe may not get results that refect the true picture if we use the wrong sampling size and method. The frst step in sampling is to clearly defne the study populaton and its characteristcs. The study populaton should be the group with the problem or those potentally afected (at risk). These criteria are based on such factors as age, geographical locaton, disease severity or stage, previous treatment, presence of other medical conditons, etc. Include important demographic characteristcs, the inclusion/exclusion criteria and any other factors defning them. Identfy the control populaton from a group with similar characterictcs but without the disease/conditon being studied. The key factors determining the sample size are: a) the proporton/mean of the main variable of interest (outcome variable). Researchers should not be distressed with sample size calculaton but should get help. Ofen, you would need to increase the calculated size by 10-20% to ensure the minimum sample size is stll achieved afer drop-outs, non-response, missing records, etc. When you have limited resources, you may need to lower the power of the study to accept a smaller sample size. The sample is either selected by random procedure (probability sampling) or conveniently (non-probability sampling). If your objectves require you to make inferences (apply the results to the study populaton), you must select a random sample. If your objectves need: a) a simple, fast answer, or b) you do not have a list of your study populaton (sampling frame), then select a convenient sample. Learning points:Learning points: •• A representatve sample should possess all the important characteristcs of theA representatve sample should possess all the important characteristcs of the populaton from which it is drawn. These criteria are based on such factors as age, geographical locaton, disease severity or stage, previous treatment, presence of other medical conditons, etc. It is important that these criteria be clearly defned in an objectve manner, so that everyone involved in the study are consistent in selectng the sample. If it is important that the sample includes representatve sub-groups of individuals (for example, urban and rural residents; or age groups), then the sampling frame must be divided into sub-groups, or strata, for these characteristcs. Random or systematc samples of a pre-determined size will then have to be obtained from each stratum. Stratfed sampling is only possible when it is known what proporton of the study populaton belongs to each stratum. The investgator interviews as many people in each category as he can fnd untl he has flled his “quota”. This method is only useful when it is felt that a convenience sample would not provide the desired balance of elements in the populaton. However, in quanttatve research it is very important to do sample size calculatons before embarking on a study, because it may not be worthwhile to do a study at all if the feasible sample size is much less than the desirable sample size. Thus, the maximum sample size is determined by the availability of resources: tme, manpower, transport, and equipment. Sample size calculatons take into account the power of the study to “prove” fndings (ofen set at least 80-90%) and the signifcance level (ofen set at least 0. Sofware is available for sample size calculaton, provided certain simple parameters about the populaton to be studies are known. In selectng the sample it is important to determine the inclusion and exclusion criteria of subjects. Subjects may be excluded because they are biased, have pre- determined conditons that afect the current study, etc. The inclusion and exclusion criteria help the researcher determine the scope of the sample. So that we can collect informaton about our subject of study (people, objects,So that we can collect informaton about our subject of study (people, objects, phenomena) in a systematc way. If you follow the steps above, you should be able to identfy the appropriate technique. Learning points:Learning points: In any study, a variety of data collecton techniques can be used for one study. If possible, use or modify a pre-existng questonnaire (ask for permission to use and remember to acknowledge the source in your write-up).
A decoction is used in teaspoon and tablespoonful doses in various Ellingwood’s American Materia Medica buy sildigra 50mg free shipping, Therapeutics and Pharmacognosy - Page 323 aches and pains cheap sildigra 100 mg on line. Old rheumatics use poultices made from a strong decoction with cloths wrung out and bound tightly over the swollen joints generic sildigra 100mg without a prescription. It is as yet difficult to explain the fact that in some cases this agent is prompt, efficient and highly satisfactory, while in others the same preparation is inactive. This fact has created a wide difference of opinion between observers as to its usefulness. Specific Symptomatology—Wakefulness, disturbed sleep from mental worry, and exhaustion from cerebral fulness and from excitement, especially with feebleness. It is not usually efficient if the wakefulness is caused by pain, nor when the patient is in full strength. Nervous excitement, and irritation with muscular twitchings— evidences of approaching convulsions in childhood—with marked cerebral fulness are indications, and it is given at any time preceding or during convulsive paroxysms if it can be swallowed. The writer has given it at the onset of the spasm when the approaching symptoms were unmistakable, and has had the satisfaction of seeing all the symptoms disappear so promptly, that confidence has become established. It has controlled severe spasms while the irritating causes yet remained, and after all antispasmodics except anesthesia have been ineffectual. It can be relied upon to hold the spasms in check while the causes are being removed, and reduces their force and character. In epilepsy it lessens the number of the paroxysms, but to ward off the paroxysms the attack must be anticipated by a full dose of the remedy. Passiflora has hypnotic properties which differ from other agents of this class in that the sleep produced is normal in all its characteristics. The patient goes to sleep naturally, can be awakened as usual at any time, to fall into a quiet, natural slumber. He awakens at the usual time rested and refreshed, with no disturbance of the cerebral functions, no languor, dulness or other disagreeable sensations. Ellingwood’s American Materia Medica, Therapeutics and Pharmacognosy - Page 324 Dr. If given in doses sufficiently large, it may be relied upon to assist in the relaxation of the tonic spasm of meningitis, and local tetanic spasm. It may be given as an antidote to the spasms of strychnine poisoning, but it must be given in doses of from one-fourth to one-half ounce and frequently repeated. As an anti-spasmodic in cases where there is engorgement of the nerve centers, it is applicable. It has relieved tonic, and clonic spasms, and the spasms of sthenic as well as asthenic conditions. It may be given in conjunction with cimicifuga, gelsemium and pulsatilla, and if there be pain, due to menstrual or other disorders, it may be combined with cannabis indica, or Jamaica dogwood, in appropriate and properly regulated doses. One patient who had been on a spree for days suffering from persistent hiccough, took a teaspoonful of the tincture every hour. This gave him freedom from the hiccough and in a short time a quiet, natural, continued sleep, waking in the morning in nearly a normal condition. Freeman gives a combination of passiflora four drams, hyoscyamus one-half dram, cannabis indica one-half dram in a four ounce mixture, and to patients addicted to drug habits, who cannot sleep, he gives from one to two teaspoonfuls of this at early bedtime, repeated if necessary. One of the attending physicians in the tuberculosis wards of Cook County Hospital told this author that passiflora was his reliance in the sleeplessness of tuberculosis, especially controlling the cough. He would add two drams of passiflora to three ounces of water, and give a dram every half hour, the latter part of the day or early evening and during the night, and very seldom failed to secure satisfactory results. It has been used in erysipelas both externally and internally, and in acute Ellingwood’s American Materia Medica, Therapeutics and Pharmacognosy - Page 325 inflammatory skin disorders with nervous elements and nervous complications. Physiological Action—In its influence it is a tonic and mild nerve stimulant and sedative. Gaurelle, who first called attention to it, mentioned it as a most useful tonic in protracted convalescence. He had great confidence in it in persistent diarrheas, especially those of phthisis. Therapy-The fluid extract of this agent, given in doses of from ten to thirty minims, has been used specifically in the treatment of headaches, other than those due to actual disease of the stomach, as from catarrh or ulceration or cancer. In many forms of headache, and especially the form due to functional gastric derangement, known as “sick headache” it is certainly a serviceable agent. Specific Symptomatology—It is suggested in cases of chronic disease of the fauces, larynx, or pharynx, where the mucous membranes are relaxed and of purple color, irritable, sore and dry. Five drops of specific penthorum every two hours with a gargle of capsicum, quite strong, used three times Ellingwood’s American Materia Medica, Therapeutics and Pharmacognosy - Page 326 daily, will quickly relieve the troublesome condition. Therapy—It influences the functional activity of the stomach through the direct action on the glandular structure of the mucous membranes. It will impart tone to the stomach and increase the appetite and power of the digestion. It regulates the function also of the entire intestinal tract in a mild, but sometimes very desirable manner. The remedy has been employed in the treatment of cholera infantum, where a mild tonic astringent was needed, and in many forms of diarrhea. It has been lauded in the treatment of intestinal dyspepsia, and other forms of atonic indigestion, especially where nervous exhaustion is present. Scudder remarked that mucous membranes in any locality, which had suffered from acute inflammation, were markedly susceptible to the action of this remedy in its direct restorative influence. It will remove irritation, restore the functional activities of the glands, and conduce to the return of the normal condition. He gave it also for chronic catarrh, pharyngitis, bronchitis, vaginitis and other catarrhal disorders. The fluid extract of penthorum may be given in doses of from one-fourth to one dram, every three hours. Additional specific symptoms, are catarrhal inflammation, with profuse secretion, catarrhal gastritis, colitis, or iliocolitis, with mucous discharges and a spongy condition of the gums. Through a mild but persistent tonic influence, it is soothing to the nervous system of debilitated patient and of the aged.
Sebum from the cow also contains triesters that contain 1 120 mg sildigra free shipping,2-diols with an α-hydroxyacid esteriﬁed to one of the hydroxyls and a normal fatty acid ester-linked to the other (36) purchase 120mg sildigra free shipping. The lactones constitute from about 50 to 70% of the total sebum mass and are formed by cyclization of 30- through 36-carbon ω-hydroxyacids sildigra 120mg otc. In general, the degree of unsaturation and methyl branching of the giant ring lactones from the different species of the equidae are in accord with the taxo- nomic relationships among these species (38). Equus caballus, the domestic horse, produces lactones that predominantly contain one double bond and a methyl branch on the penultimate carbon. The lactones of the donkey, Equus asinus, are made from 30-, 32-, and 34-carbon straight-chained ω-hydroxyacids. The lactones of the mule, Equus caballus/Equus asinus, are monounsaturated and 50% of the chains have the methyl branch while the other 50% are straight (38). First, it is a water repellent on the fur, which is clearly advantageous for aquatic mammals and for mammals living in moist environments. Second, 7-dehydrocholesterol secreted from the sebaceous glands onto the skin surface is photochemically converted to previta- min D, which is then converted to vitamin D in a temperature-dependent, nonen- 52 Wertz and Michniak zymatic reaction (39). When the animal licks its fur during grooming, the vitamin D is recovered by means of a salivary vitamin D binding protein (40). In humans, a function for sebum is less well established, and it is possible that sebum produc- tion is a functionless vestige of our ancestors. One clue in this regard comes from the species known to produce squalene as a component of their sebum. In addition to human sebum, squalene is found in the sebum of the otter, beaver, kinkajou, and mole, Scalopus aquaticus (41,42). The otter and beaver are aquatic; the kink- ajoo lives in the canopies of tropical rain forests; and Scalopus aquaticus lives in moist–wet soil. Could it be that our ancestors spent a great deal of their time in water along coasts or rivers and beneﬁted from the waterprooﬁng afforded by a coating of squalene? Sebum no doubt contributes a degree of lubrication to the skin surface, and it has sometimes been suggested that dry skin results from insufﬁcient sebum production. First, as has been pointed out, prepubertal children produce almost no sebum but most do not suffer dry skin or other skin problems (43). Second, in one study in which the sebum secretion rate was measured and subjects were surveyed about the condition of their skin, no correlation could be found between the occurrence of xerosis and sebum production (44). Sebum deﬁnitely does not contribute to the permeability barrier function of the skin. In fact, if human sebum is applied to neonatal rodent skin, barrier function is decreased (45). One possible function of sebum is a contribution to the antimicrobial de- fense of the skin. It has long been known that fatty acids produced by sebaceous triglyceride hydrolysis have antibacterial properties (46), and it has more recently been demonstrated that sebaceous lipids can interfere with the adherence of yeast to the stratum corneum (47). In addition to a decline in function of the immune system, the decline in sebum secretion with age could contribute to the increased incidence of bacterial and fungal infections of the skin in the elderly (48). The fact that prepubertal children do not have a high incidence of skin infections may be attributed to their healthy immune systems. So sebum is clearly not essential for the avoidance of skin infections, but it may be helpful in this regard in some individuals. In one study comparing age- and gender- matched subjects with moderate, mild, or no acne, the subjects with moderate acne had the highest sebum secretion rates, while those with mild acne had sebum secretion rates intermediate between those measured for subjects without acne Sebum 53 and those with moderate acne (49). The average sebum secretion rate for all subjects with acne was three times that for the subjects without acne, and in no case did a subject with acne have a sebum secretion rate that was not greater than the sebum secretion rate of the matched control. The initiating event is the formation of a keratinous plug, or comedo, that blocks the pore of the follicle. The follicular epithelium becomes thin, and an inﬂammatory response is induced as bacterial products diffuse into the surrounding tissue. It has been suggested that the development of acne may result from essen- tial fatty acid deﬁciency localized to the follicular epithelium (50). In experimen- tal systemic essential fatty acid deﬁciency, the skin becomes scaly and more permeable (29,51). If sebaceous fatty acids were to penetrate into the follicular epithelial cells and compete with linoleic acid from the circulation for incorpora- tion into lipids, a localized essential fatty acid deﬁciency could be produced. The resulting scaling could lead to comedo formation, and the defective barrier func- tion would facilitate exchange of materials between the follicle and surrounding tissue. This would include an inﬂux of water and nutrients into the follicle to support bacterial growth as well as the eﬂux of inﬂammatory mediators. This can be achieved by oral administration of retinoids (52,53), estrogen (54,55), or antian- drogens (55,56). Estrogen is thought to act by reducing production of testoster- one, and antiandrogens act by blocking the androgenic receptors on sebocytes, thereby preventing binding of androgens. Orally administered 13-cis-retinoic acid is an effective treatment for moder- ate-to-severe acne vulgaris (52,53). Although the retinoids probably act through speciﬁc receptors (57), details of their mechanisms of action remain uncertain (58). Determination of density of follicles on various regions of the face by cyanoacrylate biopsy: correlation with sebum output. Les Methodes d’evaluation quantitative des lipides de surface chez l’homme: Presentation d’une nouvelle procedure. The fatty acids of wax esters and sterol esters from vernix caseosa and from human skin surface lipid. Endocrinologic control of the development and activity of the human sebaceous gland. Age- Sebum 55 related changes in sebaceous wax ester secretion rates in men and women. Identiﬁcation of a fatty acid in human skin surface lipids apparently associated with acne vulgaris. Further studies of the saturated methyl branched fatty acids of vernix caseosa lipid. Possible genetic control of the propor- tions of branched-chain fatty acids in human sebaceous wax esters. The skin surface lipids of man compared with those of eighteen species of animals.