Neural apoptosis in the retina during experimental and human diabetes. Early onset and effect of insulin.

This study determined whether retinal degeneration during diabetes includes retinal neural cell apoptosis. Image analysis of retinal sections from streptozotocin (STZ) diabetic rats after 7.5 months of STZ diabetes identified 22% and 14% reductions in the thickness of the inner plexiform and inner nuclear layers, respectively (P < 0. 001). The number of surviving ganglion cells was also reduced by 10% compared to controls (P < 0.001). In situ end labeling of DNA terminal dUTP nick end labeling (TUNEL) identified a 10-fold increase in the frequency of retinal apoptosis in whole-mounted rat retinas after 1, 3, 6, and 12 months of diabetes (P < 0.001, P < 0. 001, P < 0.01, and P < 0.01, respectively). Most TUNEL-positive cells were not associated with blood vessels and did not colocalize with the endothelial cell-specific antigen, von Willebrand factor. Insulin implants significantly reduced the number of TUNEL-positive cells (P < 0.05). The number of TUNEL-positive cells was also increased in retinas from humans with diabetes. These data indicate that retinal neural cell death occurs early in diabetes. This is the first quantitative report of an increase in neural cell apoptosis in the retina during diabetes, and indicates that neurodegeneration is an important component of diabetic retinopathy.

Nystatin prophylaxis of fungal colonization and infection in granulocytopenic patients: correlation of colonization and clinical outcome.

Nystatin, one million units every four hours, was prospectively studied as a prophylactic antifungal agent in 164 neutropenic patients who were not initially colonized by fungi: 104 received nystatin and 60 served as controls. Fungal colonization occurred in 68/104 (65%) nystatin recipients and in 43/60 (71%) controls. However, nystatin significantly reduced multiple body site colonization and persistent oropharyngeal colonization. Despite these alterations in colonization profile, 16/104 (15%) nystatin recipients developed disseminated fungal infections, as compared to 5/60 (8%) control patients (0.5 greater than p greater than 0.1, N.S). Differences in the clinical course of colonized and non-colonized patients were observed. Eighteen of 111 (16%) colonized patients had afebrile clinical courses as compared to 16/53 (30%) non-colonized patients (p less than 0.05). Twenty-nine of 93 (31%) febrile episodes in colonized patients failed to respond to empiric antibiotic therapy as compared to 3/37 (8%) episodes in non-colonized patients (p less than 0.01). Disseminated fungal infections were diagnosed in 19/111 (17%) of colonized patients, as compared to 1/53 (2%) non-colonized patients (p less than 0.02). We conclude that colonized patients are more likely to develop febrile clinical courses, to fail to respond to empiric antibiotic therapy, and to develop disseminated fungal infection. Nystatin altered colonization patterns but did not prevent disseminated fungal infection.

Selective enrichment broth culture for detection of Clostridium difficile and associated cytotoxin.

A procedure was devised for routine examination of feces for Clostridium difficile with selective enrichment broth culture containing increased levels of carbohydrates and antibiotics to detect cytotoxin and volatile acids in broths inoculated with fecal samples. C. difficile was detected and identified with a rapidity comparable to that of conventional culture on selective cycloserine-cefoxitin fructose agar. Detection rates for C. difficile in inoculated broths (111/401 or 27%) were significantly higher than for culture on cycloserine-cefoxitin fructose agar (47/401 or 11%, P greater than 0.001). All fecal samples containing C. difficile and cytotoxin were correctly identified by the procedure. Isocaproic acid peak heights greater than 2 mm in selective enrichment broths inoculated with fecal samples indicated that C. difficile was present in the fecal sample examined. Of the positive specimens examined, 58% (64/111) produced peak heights greater than 10 mm. Peak heights less than 2 mm were not associated with C. difficile in the fecal sample. The investigated procedure provided a reliable alternative to the routine processing of feces for detecting C. difficile and associated cytotoxin in feces. Inoculated broths with isocaproic acid peak heights greater than 2 mm, after 24 to 48 h of incubation, and in which cytotoxin was detected, were subcultured to blood agar to obtain isolates of the organism as required. Broths which showed isocaproic acid peak heights less than 2 mm, and in which cytotoxin was not detected, were discarded as negative for C. difficile. The procedure was deemed potentially useful for epidemiological surveys of C. difficile.

Serum aminoglycoside monitoring by enzyme immunoassay, biological, and fluorescence immunoassay procedures.

Aerobic gram-negative infections are treated with aminoglycosides, but it is difficult to achieve safe yet effective dosages in individual patients using a standard dosing formula. Serum aminoglycoside levels are monitored to determine dosage adjustments. We compared enzyme immunoassay, bioassay, and fluorescence immunoassay procedures for measuring gentamicin and tobramycin levels in patients' sera, and in pooled human sera containing added gentamicin and tobramycin. The enzyme immunoassay procedure provided the most acceptable method for monitoring serum aminoglycoside levels on the bases of precision, cost, and turnaround time.

Clinical laboratory evaluation of a reverse CAMP test for presumptive identification of Clostridium perfringens.

Ninety-six percent of Clostridium perfringens isolates from clinical specimens were reverse CAMP test positive, whereas several other Clostridium species tested were reverse CAMP test negative. C. perfringens was detected by direct inoculation of clinical specimens to reverse CAMP plates, and the reverse CAMP procedure provided reliable presumptive identification of this organism.

The effects of various incubation temperatures, particulate isolation, and possible role of calmodulin on the activity of the base exchange enzymes of rat brain.

The involvement of calmodulin in the choline, ethanolamine, and serine exchange activities of rat brain microsomes was investigated. Calmodulin stimulated choline exchange activity to a greater extent than ethanolamine and serine exchange activities. The three base exchange activities were inhibited by antipsychotic drugs believed to prevent calmodulin interaction, but not by calmodulin-binding protein. The solutions employed for tissue homogenization and subsequent isolation of microsomes greatly influenced the base exchange activities. The process of resuspending isolated microsomes and recentrifugation, or "washing," produced major losses of detectable activity. The base exchange enzyme activities were maximal at 45 degrees, and Arrhenius plots revealed a common transition temperature of 31 degrees. The activation energies for the base exchange reactions decreased at temperatures above the observed transition temperature. Kinetic data, Km and Vmax, for the base exchange activities at 27, 37, and 45 degrees are presented.

Superoxide dismutase from nitrogen-fixing Azotobacter chroococcum: purification, characterization, and intracellular location.

Superoxide dismutase (SOD, EC 1.15.1.1) from nitrogen-fixing Azotobacter chroococcum was purified and identified as being similar to the manganese SOD of other procaryotes. The enzyme was relatively thermostable and insensitive to cyanide. A molecular weight of approximately 33 000 was estimated. Superoxide dismutase was found to be cytoplasmic (not bound to cell membranes) in A. chroococcum, but some enzyme was released by sonication of membrane vesicles.

The response of Azotobacter chroococcum to oxygen: superoxide-mediated effects.

Nitrogenase in Azotobacter chroococcum whole cells was inhibited by enzymically generated superoxide anion (O2-), hydrogen peroxide, and ethyl hydrogen peroxide. The degree of inhibition produced by O2- was related to the quantity of oxygen supplied to the organisms in continuous cultures. O2- also inhibited oxygen uptake by whole cells. These O2- mediated inhibitions were prevented by bovine superoxide dismutase. The quantities of superoxide dismutase (SOD), and catalase associated with cells grown under varying oxygen concentrations were determined. The role of hydrogen peroxide, and of the hydroxyl radical (.OH) in nitrogenase inhibition was examined. The response of Azotobacter chroococum to oxygen was evaluated with respect to the observed effects of O2- on the organism, and some explanation is given to account for nitrogenase sensitivity to oxygen.

The effects of pH and temperature on the assay of superoxide dismutase.

A simple and reliable method for the measurement of superoxide dismutase (EC 1.15.1.1) activity is described. The method is based on a linear inhibition of the reduction of acetylated cytochrome c by superoxide dismutase.