D-Amino acids in mouse tissues are not of microbial origin

Summary Neutral free D-amino acid contents in the serum, kidney, liver, brain, small intestine and urine in germ-free mice and those in specific pathogen-free mice were compared. No significant difference was found. This strongly suggests that the free D-amino acids which were shown to be present in mice in our previous work^{1, 2} did not originate from the enteric microbial flora.     

Identification of hemolytic granules isolated from human myocardial cells

Summary Human myocardial cells from fresh autopsy material contained granules which possessed hemolytic activity against guinea pig and rabbit erythrocytes. The hemolytic granules, which had a density of 1.02 and a diameter of 200–300 nm, were recovered as a microsome fraction from subcellular homogenates of human myocardial cells by differential centrifugation in 300 mM sucrose containing 0.1 mM PMSF and 10 mM EDTA. The membrane lesions caused by the granules were ring-like structures with an internal diameter of about 10–17 nm, analogous to that caused by perforin- and complement-induced lysis. However, the requirement for divalent cation differed from that for perforin-induced lysis, since the microsome-mediated lysis occurred in the presence of EDTA.     

Retention of topical liposomal formulations on the cornea

The ability of liposomes composed of different kinds of phospholipid materials to adhere to the surface of the cornea was studied in the rabbit. The liposomes were labelled with tracer amounts of an I125-labelled phosphatidylethanolamine derivative and were instilled in 10 microliters drops onto the cornea. The retention of radioactivity was monitored. The results show that liposomes containing positively charged phospholipids are better retained than an albumin control. Thus, it may be possible to develop a drug delivery liposome system which would permit long-term sustained release of ophthalmic drugs onto the cornea.     

Mammalian pineal melatonin: a clock for all seasons

The central role of the pineal gland and its hormone melatonin (MEL) in mammalian photoperiodic responses is discussed in terms of: 1) evidence for the involvement of MEL in photoperiodism, 2) which feature of the MEL secretion profile might be most important for regulating photoperiodic responses, 3) evidence for the modulation of responses to changes in daylength based on previous photoperiod exposure (i.e., photoperiodic history) and 4) how the MEL signal might be processed at its target sites to elicit physiological responses.     

Cryopreservation of Drosophila melanogaster embryos

There is an urgent need to preserve the ever-increasing number (greater than 30,000) of different genetic strains of D. melanogaster that are maintained in national and international stock centres and in the laboratories of individual investigators. In all cases, the stocks are maintained as adult populations and require transfer to fresh medium every two to four weeks. This is not only costly in terms of materials, labour and space, but unique strains are vulnerable to accidental loss, contamination, and changes in genotype that can occur during continuous culture through mutation, genetic drift or selection. Although cryopreservation of Drosophila germ-plasm would be an enormous advantage, many attempts using conventional procedures have been unsuccessful. D. melanogaster embryos are refractory to conventional cryopreservation procedures because of the contravening conditions required to minimize mortality resulting from both intracellular ice formation and chilling injury at subzero temperatures. To overcome these obstacles, we have developed a vitrification procedure that precludes intracellular ice formation so that the embryos can be cooled and warmed at ultra-rapid rates to minimize chilling injury, and have recovered viable embryos following storage in liquid nitrogen. In a series of 53 experiments, a total of 3,711 larvae emerged from 17,280 eggs that were cooled in liquid nitrogen (18.4 +/- 8.8%). Further, using a subset from this population, approximately 3% of the surviving larvae (24/800) developed into adults. These adults were fertile and produced an F1 generation.     

Comparison of retinal pigment epithelium cell preparations from the bovine eye

Summary Retinal pigment epithelium (RPE) cells were collected from, bovine eyes using a new method. The cells were harvested by vortexing the RPE and underlying choroid in 0.05 M citrate phosphate buffer, pH 5. RPE cells recovered by this method were compared to a standard method by microscopic examination of cell integrity, estimation of total protein, and assay of 11-cis and all-trans retinyl ester hydrolase (REH) activities. Results suggest that this method collects RPE cells of good integrity and with a significantly higher protein yield than the conventional method. Additionally, a much higher retinyl ester hydrolase activity was noted. Therefore we propose that this procedure offers a new and convenient method in the collection of RPE proteins for certain purposes such as enzyme purification.     

Organophosphate-mediated inhibition of choline acetyltransferase activity in rat brain tissue

Administration of the organophosphate compound soman in rats resulted in an inhibition of choline acetyltransferase activity in almost all brain regions examined. Enzyme activity was inhibited by 20-50% in various brain regions 30 min after soman injection (94-120 micrograms/kg). Enzyme activity in two regions decreased with time to a near zero level by 3 h after injection.     

Regional distribution of thiamin pyrophosphokinase in rat brain

Summary The highest specific activity of thiamin pyrophosphokinase was found in the cerebellum, and lower activity in cerebral cortex and midbrain. The regional difference in the enzyme activity was similar to that in thiamin content and the influx rate in rat brain, suggesting that the enzyme is involved in the thiamin transport.     

Indoxyl derivatives of drug metabolites

Indoxyl derivatives were detected as minor products among the urinary metabolites of two trial drugs, a benzodiazepine (GP 55 129) and a benzophenone (CGP 11 952). Their structures were elucidated by NMR and mass spectroscopy. Presumably, metabolites containing potential aldehyde functions react spontaneously with endogenous indoxyl. Such derivatives have not hitherto been encountered in drug metabolism.