Role of the sarcoplasmic reticulum in altered action potential and contraction of myopathic human and hamster ventricle

1. The present experiments were performed in order to study the role of the sarcoplasmic reticulum (SR) in the altered action potential and contraction of ventricular myocardium obtained from myopathic Syrian hamster and explanted human hearts (n = 8). The hamsters included age-matched healthy hamsters (F1B; n = 18), young myopathic hamsters (Bio 14.6; n = 8; aged 17-27 weeks) and older myopathic hamsters (n = 10; aged 39-43 weeks). 2. Action potentials were recorded by means of a microelectrode technique and force was recorded using a transducer. Post-rest potentiation of contraction (PRPC), a measure of the SR Ca2+-pumping activity, was determined after different rest intervals (2-60 s). Furthermore, cyclopiazonic acid (10 micro mol/L), a specific blocker of SR Ca2+-ATPase, was used to unmask abnormalities in the function of the SR. 3. The relationship between PRPC and rest interval was similar in younger healthy and myopathic hamsters, but the curve of the older myopathic muscle was obviously shifted downwards. Cyclopiazonic acid decreased predominantly the ascending part of the curve in both the healthy and myopathic hamster myocardium and could induce spontaneous action potentials during drug exposure or after washout. 4. In human myopathic myocardium, the curve of the PRPC-rest interval peaked at longer intervals (40-60 s) compared with that of the hamsters (10-20 s). Cyclopiazonic acid markedly depressed the relationship and increased the diastolic force (contracture) at high driving frequency, but did not induce action potentials during the rest interval. 5. We conclude that an impaired function of the SR contributes to the progressive deterioration of ventricular function in dilated cardiomyopathy and that the electromechanical behaviour of the ventricular myocardium of patients affected by dilated cardiomyopathy shows similarity and differences with the myopathic Syrian hamster model.

Nylestriol replacement therapy in postmenopausal women. A three-year prospective study

A three-year prospective study was carried out in 283 postmenopausal women to evaluate the effects of a long-acting estriol derivative-nylestriol. The women were randomly assigned into 3 groups: group A (136 cases, nylestriol 2 mg/2 wk), group B (97, nylestriol 1 mg/2 wk) and group C (50, placebo/2wk). LDL-C decreased and HDL-C increased after 3 months of medication (P < 0.05), but TC and TG not significantly changed in any group (P > 0.05). No changes of lipids were found in group C (P > 0.05). Serum ALP, Ca/Cr and Hpr/Cr in fasting urine decreased in 3 months in both group A and B (P < 0.05), but not in group C (P > 0.05). Forearm bone mineral content loss was restrained in groups A and B (P > 0.05), but decreased markedly in group C (P < 0.01). The Kupperman index scores decreased by about 50% after 3 months and 80% in 12 months in groups A and B. Nylestriol induced mild stimulatory effect on the uterine endometrium, and addition of 6 mg of provera daily for 7-10 days every 6 months is recommended. Nylestriol exhibited no obvious effect on the breast. This study demonstrated that nylestriol can be used as an effective and acceptable estrogen replacement therapy for postmenopausal women.

Prospective double-blind study of CEE3 in peri- and postmenopausal women: effects on bone loss and lipoprotein lipids

A prospective double-blind study was carried out in 136 women 0.5 to 21 years since menopause (YSM) in order to demonstrate the effects of a long-acting estriol derivative-Nylestriol (CEE3) on bone loss and lipoprotein lipids. They were orally administered at 2 mg of CEE3 or placebo every 2 weeks. Among 90 subjects who finished 1 year of medication, 49 received CEE3 and 41 placebo. The results were: 1. Serum ALP, Ca/Cr and Hop/Cr in fasting urine decreased in 3 months (P < 0.05); 2. Menopause-related reduction of forearm bone density was restrained; 3. LDL-C decreased in 3 months and HDL-C increased in 6 months (P < 0.05), with no significant changes in TC and TG; 4. Side effects were mild. 1/3 of those with intact uterus had spotting and another 1/3 had moderate withdrawal bleeding after the addition of medroxyprogesterone acetate at the end of 12 months of CEE3 therapy. This study demonstrates that CEE3 is effective and acceptable for preventing osteoporosis and lipoprotein lipids disorder in postmenopausal women. Long-term application awaits further studies.

A glass drinking tube for small birds and mammals

A drinking tube was fabricated with a piece of 8 or 10 mm O.D. glass tubing. It gives accurate measurement of the volume of liquid consumed by small birds and mammals. The tube can be readily cleaned and autoclaved.

Alkyl chain length and acute oral toxicity of p-aminophenones

There exists a structure-toxicity relationship between the length of the alkyl chain of p-aminopropiophenone homologues and their oral LD50's in albino mice and rats. The acute oral toxicity decreased in both species with the removal of one carbon atom from the alkyl group, increased with the addition of one and two carbon atoms, and decreased again with the addition of three carbon atoms to the alkyl group.

Hepatic microsomal N-hydroxylation of p-chloroaniline and p-chloro-N-methylaniline in red-winged blackbird compared with rat

1. N-Hydroxylation of p-chloroaniline (PCA) and p-chloro-N-methylaniline (PCMA) was measured in red-winged blackbird (Agelaius phoeniceus) and rat (Rattus norvegicus) hepatic microsomes. 2. Redwing hepatic microsomes N-hydroxylated PCA slower than rat microsomes. Furthermore, redwing hepatic microsomes had marginal or no ability to N-hydroxylate PCMA, whereas rat hepatic microsomes N-hydroxylated PCMA at a higher rate than PCA. 3. The bird hepatic microsomes had only low or marginal N-demethylase activity with PCMA, whereas the rat hepatic microsomes could N-demethylate PCMA at a higher rate than they could N-hydroxylate it.

Drug metabolism in birds

Papers published over 100 years since the beginning of the scientific study of drug metabolism in birds were reviewed. Birds were found to be able to accomplish more than 20 general biotransformation reactions in both functionalization and conjugation. Chickens were the primary subject of study but over 30 species of birds were used. Large species differences in drug metabolism exist between birds and mammals as well as between various birds, these differences were mostly quantitative. Qualitative differences were rare. On the whole, drug metabolism studies in birds have been neglected as compared with similar studies on insects and mammals. The uniqueness of birds and the advantages of using birds in drug metabolism studies are discussed. Possible future studies of drug metabolism in birds are recommended.

The liver parenchyma and foreign compound metabolism in red-winged blackbird compared with rat

1. Aniline p-hydroxylase, aminopyrine N-demethylase, and p-nitroanisole O-demethylase activities were measured in liver microsomes prepared from the red-winged blackbird (Agelaius phoeniceus) and compared with analogous preparations from rat. All had lower activities in birds than in rats, when expressed in terms of microsomal protein. 2. Hepatic parenchyma of the bird was observed by electron microscopy to contain less endoplasmic reticulum than that of rat. This morphological difference may partially explain the species difference in enzyme activities. 3. Cytochrome P-450 levels were not sex-dependent in the red-winged blackbird, unlike rat, but the opposite was true for the rate of hydroxylation of aniline. 4. There was no species difference in the activity of aniline p-hydroxylase when expressed in terms of activities per unit of cytochrome P-450, but the activity of p-nitroanisole O-demethylase was higher in red-winged blackbird than in rat; the reverse may be true for the activity of aminopyrin N-demethylase.