Hormonal control of morphogenetic cell death of the wing hypodermis in Lucilia cuprina.

1. Cytoplasmic fragments in the haemolymph of newly emerged flies derive from the degenerating wing hypodermis. 2. At the time of eclosion, dorsal and ventral cell layers of the wing are connected by processes containing bundles of microtubules and microfilaments. Cytoplasmic fragments contain similar bundles of microtubules but few microfilaments. 3. Extensive vacuolation marks the onset of hormonally initiated fragmentation of the wing hypodermal cells. Haemocytes containing lysosomes are present in the wing at this time, but do not invade the fragmenting hypodermis.     

A Histochemical Method for the Demonstration of Diphosphopyridine Nucleotide Diaphorase

The present investigation concerning the histochemical demonstration of DPN diaphorase follows the development of a new reagent, Nitro-BT, which has already been used successfully for the cytochemical localization of the succinic dehydrogenase system. The most consistently favorable results were obtained with the lactate-lactic dehydrogenase system buffered at pH 7.4. Using sections of rat kidney and stomach, it was found that the intensity of stain was optimal after 15 minutes incubation at 37°C., conducted aerobically. By appropriate variations in the substrate mixture it was possible to selectively demonstrate the histochemical distribution of certain DPN-linked dehydrogenases in addition to DPN diaphorase. This was made possible by the special distribution of some of these dehydrogenases which distinguished them from one another. Of the dehydrogenases studied the distribution pattern of β-hydroxybutyric dehydrogenase was the most singular. In the gastric mucosa β-hydroxybutyric dehydrogenase was restricted to the cells of the mucous lining epithelium and the gland necks; and in the kidney the enzyme was limited to the cells of the proximal convoluted tubule and thick limbs of Henle's loop. In contrast, lactic dehydrogenase like DPN diaphorase was demonstrable in almost all cytologic elements of both the stomach and the kidney.     

ULTRASTRUCTURAL DEMONSTRATION OF CYTOCHROME OXIDASE ACTIVITY BY THE NADI REACTION WITH OSMIOPHILIC REAGENTS

A new method for the subcellular and cytochemical demonstration of cytochrome oxidase has been developed with the introduction of N-benzyl-p-phenylenediamine (BPDA) and the discovery that indoanilines are osmiophilic. These indoanilines produced upon oxidation of BPDA in the presence of naphthols are highly colored compounds that yield electron-opaque coordination polymers of osmium (osmium black) that are amorphous, insoluble in water, and in organic solvents. The best methods for preparing rat tissue were in decreasing order: fixation in formaldehyde solution, fresh tissue slices, and frozen sections of fresh or fixed tissue. Ultrathin sections were counterstained by bridging with the thiocarbohydrazide-osmium tetroxide (T-O) procedure for enhancing underlying membranous structures. Cytochrome oxidase activity was noted primarily in mitochondria and occasionally in sarcotubules of heart, in mitochondria and occasionally in infoldings of the plasma membrane of renal tubular cells, and in mitochondria and, to a great extent, in endoplasmic reticulum of hepatic cells. Cytochrome oxidase activity produced deposits in droplet form, whereas dehydrogenase activity resulted in uniform staining of mitochondrial cristae, as recently demonstrated with an osmiophilic tetrazolium salt. Even more recently we have succeeded in demonstrating cytochrome oxidase activity in nondroplet staining on mitochondrial cristae with an osmiophilic benzidine-type reagent that apparently polymerizes upon oxidation (to be published later).     

Thiol status in human sperm

The passage of spermatozoa along the epididymis is characterized by a gradual stabilization of intracellular organelles mainly through the oxidation of thiol groups. In this study, we examined the relationship between the thiol-disulfide status of human spermatozoa (using a specific fluorescent probe, monobromobimane) and routine semen analysis parameters. Fluorescence intensity was measured by spectrofluorimeter and its frequency distribution within samples, using a fluorescence-activated cell sorter. The mean proportion of reactive thiols SH/(SS + SH) in 29 semen samples was 29.8% +/- 2.5%. When comparing thiol labeling patterns, oligozoospermic samples differed from normozoospermic ones (P less than 0.05). However, within the normozoospermic group, no correlation was found between thiol-labeling patterns and routine sperm parameters or fertilizing capacity in vitro. No difference in thiol labeling patterns was found between "swim-up" and "whole semen" preparations.     

Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two- dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.      

Fnr (EtrA) acts as a fine-tuning regulator of anaerobic metabolism in <Emphasis Type="Italic">Shewanella oneidensis</Emphasis>MR-1

Background  

EtrA in Shewanella oneidensis MR-1, a model organism for study of adaptation to varied redox niches, shares 73.6% and 50.8% amino acid sequence identity with the oxygen-sensing regulators Fnr in E. coli and Anr in Pseudomonas aeruginosa, respectively; however, its regulatory role of anaerobic metabolism in Shewanella spp. is complex and not well understood.     

The human neonatal small intestine has the potential for arginine synthesis; developmental changes in the expression of arginine-synthesizing and -catabolizing enzymes

Background  

Milk contains too little arginine for normal growth, but its precursors proline and glutamine are abundant; the small intestine of rodents and piglets produces arginine from proline during the suckling period; and parenterally fed premature human neonates frequently suffer from hypoargininemia. These findings raise the question whether the neonatal human small intestine also expresses the enzymes that enable the synthesis of arginine from proline and/or glutamine. Carbamoylphosphate synthetase (CPS), ornithine aminotransferase (OAT), argininosuccinate synthetase (ASS), arginase-1 (ARG1), arginase-2 (ARG2), and nitric-oxide synthase (NOS) were visualized by semiquantitative immunohistochemistry in 89 small-intestinal specimens.