Retinal accumulation of the phosducin/T beta gamma and transducin complexes in developing normal mice and in mice and dogs with inherited retinal degeneration

Rod photoreceptors of mammalian retinas contain a 33-kDa phosphoprotein, phosducin, which complexes with the beta, gamma-subunits of transducin (T beta gamma). The level of phosducin phosphorylation is modulated by light, suggesting that the phosducin/T beta gamma complex has a pivotal role in light-regulated events that occur in photoreceptors. We have investigated, in developing mouse retinas, the age at which the complex is first detected and the subsequent accumulation of the phosducin/T beta gamma complex during postnatal life. Western blot analysis detected immunoreactivity both for phosducin and T beta in retinal homogenates of 3-day-old mice. Thereafter, the level of immunoreactivity for both proteins increased steadily, to reach adult levels in the next 2 postnatal weeks. Gel filtration analysis of extracts from immature mouse retina showed that phosducin and T beta co-eluted, like the phosducin/T beta gamma complex of adult retina, as a 77-kDa complex, indicating that the phosducin/T beta gamma complex is formed when photoreceptors first synthesize the components of the complex. While the levels of the phosducin/T beta gamma complex increased steadily during the first 2 postnatal weeks, the subunits of transducin complex, T alpha together with additional amounts of T beta gamma, only started to appear around the 7-9th postnatal day, and the level of transducin complex increased sharply at 11-14 days to reach adult levels that are similar to those of phosducin/T beta gamma complex.(ABSTRACT TRUNCATED AT 250 WORDS)     

A developmental study of interphotoreceptor retinoid-binding protein (IRBP) in single and double homozygous rd and rds mutant mouse retinae

Interphotoreceptor retinoid-binding protein (IRBP) was studied using immunochemical and immunocytochemical techniques in retinae of mice with allelic combinations at the rd and rds loci at different stages of development and degeneration. Until postnatal day 7 (P7), IRBP is located intracellularly in developing retinae of the different genotypes. Thereafter, IRBP is present mainly in the interphotoreceptor matrix. As previously noted, cell death is slowest in the heterozygous +/+,rds/+ mutant with loss increasing in order in +/+,rds/rds, rd/rd, rds/rds and rd/rd,+/+ animals. The IRBP content of the total retina also approximates this pattern, with lowest amounts by far in rd/rd, rds/rds and rd/rd,+/+ mutants (after P14). Interestingly though, IRBP loss significantly precedes visual cell loss in the rd/rd,rds/rds retina. In all the mutants, the remaining rod cells in the outer nuclear layer exhibit synthesis of intracellularly located IRBP at late stages of degeneration. In the single homozygous rd/rd,+/+ and the double homozygous rd/rd,rds/rds mutants, IRBP is present intracellularly during the entire degenerative process with somewhat less intracellular IRBP in the rd/rd,rds/rds mutant. Retinae of homozygous +/+,rds/rds and heterozygous +/+,rds/+ animals exhibit a normal distribution pattern of IRBP immunoreactivity until loss of photoreceptor cells becomes pronounced at later stages of the disease. Many of the remaining cells at this time are probably cone elements although they are structurally changed. Double labeling with IRBP and S-antigen demonstrates, in many but not all, the presence of both proteins in the same cell body. Immunocytochemistry clearly demonstrated the presence of IRBP in remaining photoreceptor cells at late stages of the disease. Thus, the biochemically measured loss of IRBP appears to be a complex process neither directly dependent on the loss of photoreceptor outer segments and reduced interphotoreceptor matrix space (e.g. there is a sustained IRBP level in rodless rds mutants) nor simply due to cell death (e.g. in the rd/rd,rds/rds mutant, IRBP loss significantly precedes cell loss). That this IRBP is mainly intracellular, however, may indicate an abnormality in secretion which, combined with other factors, induces a degenerated and less differentiated phenotype.     

Chlorella virus PBCV-1 replication is not affected by cytoskeletal disruptors.

The majority, if not the entire life cycle, of the large dsDNA-containing algal virus PBCV-1 occurs in localized regions in the cytoplasm. Thirteen drugs that disrupt the cytoskeleton had no effect on PBCV-1 replication at concentrations which inhibited host growth. Therefore, host cytoskeletal elements do not appear to be important in PBCV-1 morphogenesis.     

A feasibility study on teaching evaluation system in medical education

The purpose of this study is to develop an evaluation instrument with high feasibility and acceptability, and to quantify the outcome of evaluation, in order to set up an efficient evaluation system. Teaching evaluation with questionnaire by students has been carried out in National Yang-Ming Medical College for two years. With the support of both teachers and students, the system has been established and conducted on a regular basis. The most important purpose of evaluation is to improve the quality of teaching. During the two academic years (Sep. 1986-June 1988) of the program, the overall response rate was 44.5%, the Department of Nursing had the highest response rate, followed by Dentistry, Medicine-Post Graduate, Medical Technology, and Medicine. Taking into consideration of the year and the class size, the regression analysis found that higher year or smaller size of the class had better response rate. The response rates dropped significantly after the first academic year regardless of department or year. A total of 23 classes were included in the evaluation program and 99 courses were evaluated. All questions in the questionnaire used a 0 to 4 ordinal scale, in which 0 (improvement needed) was the low end and 4 (excellent) the high end. The mean score of the seven questions of teaching evaluation was 2.47. As a whole, the students were satisfied with the teaching. As to the categories of courses, clinical courses had better mean score than basic medical courses, and basic medical courses had better mean score than common required courses. To evaluate the effectiveness of the teaching, students' achievement was used as the outcome variable. The most important predictive variable was the method of instruction, followed by the content of lecture such as degree of difficulty of the lecture and cognitiveness of the contents. The above 3 variables explained 76% of the variation of the students' achievement. However, the significant of teachers' speech, performance and attitude were not so influential. Analysis based on the characteristics of the teachers (sex, age, position, and teaching experience), the characteristics of students (department and year), teaching environments (time and place), and the 3 categories of courses (clinical, basic medical and common required courses) showed that all the above variables only explained less then 10% of the variation of the students' achievement.     

Mortality patterns among hypertensives by reported level of caffeine consumption

The effect of caffeine consumption on mortality was evaluated in a historical cohort study of 10,064 diagnosed hypertensive individuals participating in the Hypertension Detection and Follow-up Program from 1973 to 1979. Total caffeine intake level from beverages (coffee and tea) and certain medications, was estimated at the 1-year visit. No evidence was found supporting an association between increased level of caffeine consumption and increased all-cause mortality or cardiovascular disease mortality during the following 4 years. Cigarette smoking was significantly associated with mortality; the association being more pronounced among non- and low-caffeine consumers for all-cause mortality and among non-caffeine consumers for all cardiovascular mortality except cerebrovascular mortality.     

A high-resolution method for amino acid analysis of physiological fluids containing mixed disulfides

In this paper we report a high-resolution method and special buffers for the analysis for 45 common amino acids and related compounds and seven less-common components occasionally found in physiological fluids. Careful optimization of the chromatographic protocol resolves cysteine-penicillamine mixed disulfide, penicillamine disulfide, and dihydroxyphenylalanine from cystine and methionine; cysteine-homocysteine mixed disulfide is eluted between tyrosine and phenylalanine. Argininosuccinic acid is eluted before ethanolamine; glycerophosphoethanolamine is separated from taurine; glucosaminic acid is eluted between urea and aspartic acid. A Beckman Instruments System 6300 Amino Acid Analyzer was used. System performance is examined in terms of coefficient of variation (CV) over the concentration range of 1.0-5.0 nmol/50 microL; average CV for all components is better than 1.5%. Method performance is assessed through the analysis of normal and abnormal urine and plasma specimens.     

EXTERNAL CEPHALIC VERSION

External cephalic version has been used periodically for centuries to manage breech presentations. As cesarean section rates have escalated in the last two decades, ways to curb this rise have been evaluated. By reducing the number of infants that arrive in labor in a representation, it is possible to impact the overall cesarean section rate. External cephalic version is a safe, effective method when used in appropriate cases of breech presentation. A forward or backward roll can be accomplished in women at term with singleton gestations, adequate amniotic fluid, and reactive nonstress tests. Parity, fetal and placental position, and descent of the presenting part may all influence the success rate of the version.     

Immunogold localization of type IV collagen and laminin in the aging human outflow system

Tissue from the outflow system of six surgically enucleated aged eyes was used for an ultrastructural immunocytochemical study of the distribution of laminin and type IV collagen. The immunogold technique provided precise localization of laminin beneath lining endothelial cells of the inner wall of Schlemm's canal. Laminin labelling was absent in the trabecular beams. Type IV collagen was found in the basement membranes of the trabecular beams and in fine filamentous basement membrane material in the cribriform layer. Electron dense plaques in the cribriform layer labelled positively for laminin in the outer coarse fibrillar zone but not in the electron dense core. Long-spacing collagen was negative for type IV collagen.