By V. Deckard. Alverno College. 2018.
Here we briefly review the structure of the striated muscle cells in cardiac and skeletal muscle buy omnicef 300 mg with visa antibiotics qt prolongation. The thin filaments are attached to the z- line and these filaments contain the actin purchase 300mg omnicef overnight delivery antibiotic for sinus infection and sore throat. In the center of the sarcomere is the A-band which is formed by the thick filaments containing myosin that extend to either side of the M-line. The contraction of the muscle is produced by the movement of the myosin along the actin filaments. This draws the thin filaments in towards the center of the sarcomere and thereby shortens the distance from Z-line to Z-line. The overlap of actin and myosin filaments will be a short stretch at rest but in a contracted muscle, the Z-line may be pulled in almost to the edge of the thick filaments. The diagram shows a more detailed view of the contractile proteins that compose the sarcomere. The force generated and the velocity of contraction are dependent upon the number as well as the isoform of the contractile proteins. Each of the contractile proteins that compose a sarcomere is a member of a family of isoforms of that protein. Important differences in isoforms produce significantly different contractile properties for skeletal muscle vs. Smooth muscle exhibits even greater differences in organization and physiological properties, to be discussed in a later lecture. In skeletal and cardiac muscle, the thin filament proteins are actin, tropomyosin, and troponin (troponin T,C, or I). Each thin filament is attached to the Z-line material ( actinin) of the sarcomere. The heart of the thin filament is two strands of filamentous actin that coil about one another. The troponin- tropomyosin complex is associated with the thin filament and makes the sarcomere a calcium sensitive contractile structure. This complex regulates the interaction between the heads of the myosin molecule of the thick filament and the adjacent thin filament. The tropomyosin is envisaged as lying along the actin filament, blocking the myosin binding sites. Ca2+ binding to troponin C causes a conformational change in the rest of the troponin complex (I, C and T) and this in turn moves the tropomyosin aside and thereby activates the thin filament for contraction. There are some significant distinctions between thin-filament based regulation of Ca2+ sensitivity in cardiac and skeletal muscle. Cardiac TnC has one less functional Ca2+ binding site than skeletal TnC, making the Ca2+ regulation more graded. In the case of cardiac muscle, the input output relation of log [free Ca2+] vs tension rises steeply above 0. The Ca2+ sensitivity in heart can be regulated by TnI phosphorylation, which decreases the affinity of TnC for Ca2+, thereby increasing the rate of cardiac muscle relaxation. This relative newcomer to the field is proving interesting as a likely contributor to the elasticity of the muscle. The importance of elasticity will become clearer later in the course, when we discuss the mechanical properties of muscle. Titin is an enormous (3 mega-daltons), filamentous protein that spans half the length sarcomere and interacts with both the actin thin filament and myosin thick filament. It is thought to uncoil when the muscle is stretched, eventually acting to resist over-stretching of the sarcomere, keeping the muscle in its useful working range. On the other hand, when sarcomere length becomes very short, titin may help resist over compression and provide an elastic restoring force to quickly restore the sarcomere to resting length. Force Development Thick Filament Thick Filament Force S1 Thin Filament Thin Filament B. Shortening Thick Filament Thick Filament Thin Filament Thin Filament Displacement A. Huxley & Simmons 1971 model was very influential in thinking about the nature of the conformational change in myosin.
Proguanil metabolism is determined by the mephenytoin oxidation polymorphism in Vietnamese living in Denmark purchase omnicef 300mg mastercard antibiotic resistance who. Evidence for the polymorphic oxida- tion of debrisoquine and proguanil in a New Zealand Maori population buy 300 mg omnicef visa antibiotic honey. Evidence for the polymorphic oxidation of debrisoquine and proguanil in a Khmer (Cambodian) population. Chloro-guanide metabolism in relation to the efficacy in malaria prophylaxis and the S-mephenytoin oxidation in Tanzanians. Pharmacokinetic evaluation of proguanil: a probe phenotyping drug for the mephenytoin hydroxylase polymorphism. Proguanil metabolism in relation to S-mephenytoin oxidation in a Turkish population. Relation between chlor- oguanide bioactivation to cycloguanil and the genetically determined metabolism of mephenytoin in humans. Inherited amplification of an active gene in the cytochrome P450 2D-locus as a cause of ultrarapid metabolism of debrisoquine. Metoprolol and debrisoquin metabolism in Nigerians: lack of evidence for polymorphic oxidation. Lower prevalence of the debrisoquin oxidative poor metabolizer phenotype in American black versus white subjects. Molecular basis for rational mega- prescribing in ultrarapid hydroxylators of debrisoquine. Cytochrome P450 2D6 variants in a Caucasian population: allele frequencies and phenotypic consequences. Oxidation phenotype—a major deter- minant of metoprololol metabolism and response. Metoprolol metabolism and debrisoquine oxidation polymorphism—population and family studies. Metoprolol oxidation polymorphism in a Korean population: comparison with native Japanese and Chinese populations. Differential stereoselective of metoprolol in extensive and poor debrisoquin metabolisers. Utility of a one-point (3-hour postdose) plasma metabolic ratio as a phenotyping test using metoprolol in two East Asian pop- ulations. Polymorphic dextromethorphan metabolism: co-segregation of oxidative O-demethylation with debrisoquin hydroxylation. Dextromethorphan O-demethylation in liver microsomes as a prototype reaction to monitor cytochrome P-450 db 1 activity. Concordance of P450 2D6 (debrisoquine hydroxylase) phenotype and genotype: inability of dextromethorphan metabolic ratio to dis- criminate reliably heterozygous and homozygous extensive metabolizers. Polymorphism of dextro- methorphan metabolism: relationships between phenotype, genotype and response to the administration of encainide in humans. Prediction of phenotype for dextro- methorphan O-demethylation by using polymerase chain reaction in healthy vol- unteers. Antidepressant drug interactions and the cytochrome P450 system—the role of cytochrome P4502D6. Pharmacokinetic drug interactions of new antidepressants: a review of the effects of the metabolism of other drugs. Correlations among the metabolic ratios of three test probes (metoprolol, debrisoquine and sparteine) for genetically determined oxidation polymorphism in a Japanese population. Dissociation of co-regulatory control of debrisoquin/phenformin and sparteine oxidation in Ghanaians. Evidence for a dissociation in the control of sparteine, debrisoquine and metoprolol metabolism in Nigerians. Metoprolol alpha-hydroxylation polymorphism in the San Bushmen of Southern Africa. Polymorphism of the 4-hydroxylation of debrisoquine in the San Bushmen of Southern Africa.
Gross structural abnormal- ities of the cervix or vagina are identified in about one quarter and abnormalities of the vaginal epithelium in one-third to one-half of women whose mothers took diethylstilbe- strol during gestation (Bibbo purchase omnicef 300 mg with amex antibiotics for uti trimethoprim, 1979; Herbst et al discount 300 mg omnicef otc antibiotic resistance vertical horizontal. T-shaped uterus, constricting bands of the uterine cavity, uterine hypoplasia or paraovarian cysts also occur with increased frequency among females exposed in utero (Kaufman et al. Preterm delivery, spontaneous abortions, and ectopic pregnancy occurred with increased frequency in females whose mothers took diethylstilbestrol during gestation (Barnes et al. Progesterone is the only natural progestin and is not well absorbed by the oral route unless given in micronized form. Synthetic progestins structurally related to proges- terone are more commonly used. Low-dose progestins are used for contraception with an estrogen, and are used in the therapy of menstrual disorders at higher doses. In the 1960s and 1970s much higher doses of progesterones were used for oral contraception (Schardein, 1985), and are currently used to treat threatened abortion. In a review, female pseudohermaphroditism, including various degrees of clitoral hypertrophy with or without labioscrotal fusion, was reported in several-hundred children born to women treated with progesterone analogs in high doses during early pregnancy (Schardein, 1980, 1985). Fewer than 100 cases of male pseudohermaphroditism have been reported, and the anomaly is usually isolated hypospadias (Aarskog, 1979; Mau, 1981; Schardein, 1985). Exposure to progestational agents during embryogenesis, therefore, seems not to increase substantially the risk for nongenital congenital anomalies in infants born to treated women. Among more than 100 94 Endocrine disorders, contraception, and hormone therapy during pregnancy infants born to women who took norethindrone during the first trimester, congenital anomalies were not increased in frequency, or in more than 100 infants whose mothers took this drug after the first trimester (Heinonen et al. Two case–control stud- ies of 365 infants with congenital anomalies yielded similar results (Kullander and Kallen, 1976; Spira et al. Several cases were reported in which use of norethin- drone during pregnancy, at doses that were much greater than those used in contempo- rary practice, was associated with masculinization of the external female genitalia (cli- toral hypertrophy with or without labioscrotal fusion), but internal genitalia and subse- quent pubertal development were normal (Schardein, 1980, 1985). The genital anom- alies observed include various degrees of masculinization (Wilkins et al. Clitoral hypertrophy may occur in exposures any time after the 8th embryonic week, but labio- scrotal fusion is limited to exposure during the 8th to 13th embryonic weeks. The risk for pseudohermaphroditism among female infants born to women who took norethin- drone during pregnancy is probably less than 1 percent (Bongiovanni and McPadden, 1960; Ishizuka et al. No increased risk of fetal sexual malformation was reported in a meta-analysis of published reports of women exposed to sex hormones after conception (Ramin-Wilms et al. Masculinized external female genitalia were observed in several species of experimental animals, including nonhuman primates, following maternal treatment with high doses of norethindrone during pregnancy (Hendrickx et al. Nongenital malformations were not increased in frequency among three species of nonhuman primates given up to 100 times the oral contraceptive dose of norethindrone during pregnancy in combination with ethinyl estradiol (Hendrickx et al. Contemporary low-dose therapy with norethindrone is not a risk factor for genital mal- formations, and probably poses no increased risk for congenital anomalies in general. Congenital anomalies were not increased in frequency among more than 150 infants born to women who took norethynodrel during the first trimester, or among more than 150 women who took the drug after the first trimester (Heinonen et al. Virilization of female fetuses has not been reported in the human; however, female rat fetuses born to mothers that received several-hundred times the human contraceptive dose had masculinized external genitalia (Kawashima et al. Treatment of human pregnancy within the low-dose range presently employed for contraception and for menstrual irregularity will not cause female virilization. There are no controlled studies of congenital anom- alies among infants born to women who used norgestrel during pregnancy. Although no human reports have associated the use of norgestrel during pregnancy with masculiniza- tion of external female genitalia, large doses administered in the latter two-thirds of pregnancy would be expected to produce virilization based upon clinical experience with other closely related compounds. The frequency of congenital anomalies was not General hormonal therapy 95 increased among mouse and rabbit litters born to females treated with very large doses of norgestrel during pregnancy (Heinecke and Kohler, 1983; Klaus, 1983). Major congen- ital anomalies were not increased in frequency among almost 500 infants born to women treated with medroxyprogesterone during the first trimester, or among 217 infants whose mothers took the drug after the first trimester of pregnancy (Heinonen et al. Claimed associations between maternal use of high-dose progestins early in pregnancy and masculinization of the genitalia in female children, feminization of the genitalia in male children, a variety of malformations of other organ systems and certain behavioral alterations (Hines, 1982; Schardein, 1980, 1985; Wilson and Brent, 1981) are appar- ently not true. A large study that included 1274 cases where medroxyprogesterone was taken for first-trimester bleeding failed to reveal an increased rate of malformations when compared to 1146 control infants (Katz et al. Although ambiguous external genitalia occurred among both sons and daughters of women who were treated with high doses of medroxyprogesterone to prevent miscar- riage during pregnancy, these abnormalities were isolated and very rare (Schardein, 1985; Yovich et al. Growth, sexual maturation, and sexually dimorphic behav- ior were unaltered among 74 teenage boys and 98 teenage girls whose mothers had taken medroxyprogesterone during pregnancy (Jaffe et al.