Cell-cell signaling during Dictyostelium development

Specific proteins and peptides, as well as cAMP, are used as intercellular signals in Dictyostelium. Our understanding of the signal transduction pathways activated by these signals has been expanded by inclusion of newly characterized proteins. cAMP-dependent protein kinase (PKA) and its associated phosphodiesterase, RegA, play multiple roles in these pathways.     

Cellular thiols as a determinant of responsiveness to menadione in cardiomyocytes

The role of intracellular thiols in menadione-mediated toxicity was studied in neonatal rat cardiomyocytes. The sensitivity of cardiomyocytes to menadione was greater than that of skeletal muscle cells and 3T3 fibroblasts. Before cell degeneration, menadione induced marked depletion of intracellular thiols and an increase of oxidized glutathione. The sensitivity of these cells to menadione correlated with the level of depletion of intracellular thiols. After incubation of cardiomyocytes with menadione, glutathione reductase activity was inhibited and lipid peroxidation was increased. Both dicumarol (an inhibitor of DT-diaphorase) and diethyldithiocarbamate (an inhibitor of superoxide dismutase) enhanced the capacity of menadione to induce cellular damage and to cause depletion of intracellular glutathione. Decreasing intracellular glutathione by pretreatment of cells with N-ethylmaleimide or buthionine sulphoximine also increased menadione-induced cell degeneration. Preincubation with cysteine or dithiothreitol suppressed the capacity of menadione to damage the cells. Menadione-induced lipid peroxidation was also suppressed by the same treatment. These results show that the oxidative stress induced by menadione in cardiomyocytes results in the depletion of glutathione and protein thiols. Both DT-diaphorase and superoxide dismutase can protect cells from the toxicity of menadione. Cellular thiols are determinants of the responsiveness to menadione.     

Clinicopathological characteristics of prostatic adenocarcinoma in men with atypical prostate needle biopsies

PURPOSE: Atypical or nondefinitive diagnoses comprise 1.5 to 10% of all prostate needle biopsies and many men with atypical biopsy have carcinoma on rebiopsy. We characterize the clinical and pathological features of these men and the tumors, and compare them to those of other men who had more than 1 biopsy. MATERIALS AND METHODS: All prostate needle biopsies done at our institution between 1989 and 1996 on men with a followup biopsy were reviewed and the clinicopathological features were correlated. RESULTS: A total of 343 men had more than 1 biopsy during this period. Of the biopsies 64 were atypical and followup (repeat biopsy) was available for 59. Men with an atypical diagnosis were more likely to have carcinoma (34%) and to be diagnosed subsequently earlier (270 days) than those with an initial negative diagnosis (22%, 603 days). No significant differences were noted in patient age, results of digital rectal examination, initial or followup serum prostate specific antigen, subsequently identified tumor size or Gleason score on needle biopsy or at resection. Although on review as many as 38% of the original atypical foci could be reclassified, this reclassification did not significantly change the results of rebiopsy. CONCLUSIONS: Men with an atypical diagnosis on prostate biopsy are significantly more likely to have carcinoma on rebiopsy than men with an initial negative diagnosis, and the second biopsy should be performed at a significantly shorter interval. The tumors that are subsequently identified in these men are similar to those identified in men without an atypical biopsy.     

Post-hoc Rasch analysis of optimal categorization of an ordered-response scale

The purpose of this study was to determine the optimal categorization of a self-efficacy ordered-response scale using the Rasch analysis and compare the performance of the Rasch statistics and parameter estimates with conventional statistics. A 50-item scale to measure psychomotor self-efficacy was administered to a total of 2,022 children, including 1,009 boys and 1,013 girls. The data analysis started by collapsing the original five adjacent categories into two, three, and four categories, and a total of 14 data sets were derived. Each of these data sets, including the original one, was analyzed using the Rasch rating scale model, and a set of Rasch model-data fit, category, and separation statistics and parameter estimates, as well as three conventional statistics, were computed and compared. It was found that, instead of the five-category construct designed, the best order of category meanings of the scale in respondents' perceptions was a three-category construct. The Rasch threshold estimates were sensitive indexes in determining the order of the categorization, and that item separation statistics were useful in determining the optimal categorization after its order was confirmed. The commonly used coefficient alpha was found not helpful at all in determining the optimal categorization. The Rasch analysis was demonstrated to be a useful post-hoc analytic approach in determining the optimal categorization of an ordered-response scale.     

Comparative analysis of antibiotic resistance, immunofluorescent colony staining, and a transgenic marker (bioluminescence) for monitoring the environmental fate of rhizobacterium

Field releases of the wild-type plant growth-promoting rhizobacterium Pseudomonas fluorescens 89B-27, its bioluminescent derivative GEM-8 (89B-27::Tn4431), and a spontaneous rifampin-resistant variant estimating the wild-type population. Seed and root samples were taken 0, 7, 14, 21, or 28, 35 or 42, and 70 days after planting in each year and processed for enumeration by spiral plating or immunofluorescent colony staining (IFC). In both years, the populations of 89B-27, R34, and GEM-8, as measured by IFC, were not significantly different (P > 0.05) from each other at each sampling time. However, the populations of R34 and GEM-8, as measured by spiral plating and differentiation based on their respective phenotypes, were significantly lower (P < 0.05) than the wild-type populations and their IFC-determined populations. These data indicate that traditional marker systems may underestimate populations and hence the survival and colonization of genetically marked bacteria.     

Expansion of transplanted hepatocytes during liver regeneration

A method for volume selective proton spectroscopy is presented based on a multiecho sequence with short refocusing interval tcp. It is demonstrated, that by appropriate choice of tcp on the order of 4-6 ms, signals from overlapping multiplets like the glutamine and glutamate (Glu/Gln) resonances in spectra of the human brain are considerably increased compared with a conventional PRESS volume selection scheme. Thus proton spectra from J-coupled multiplet signals can be acquired with TE on the order of 20-30 ms avoiding the baseline problems arising at shorter echo times due to broad resonances. This allows to selectively acquire spectra from substances with longer T2 without the confounding effects from J-coupling occurring in conventional volume selection techniques.