Identified taste bud cell proliferation in the perihatching chick [published erratum appears in Chem Senses 1998 Aug;23(4):459]

Developing taste buds in the anterior mandibular floor of perihatching chicks were studied by high voltage electron microscopic autoradiography in order to identify proliferating gemmal cell types. Montaged profiles of 29 taste buds in five cases euthanized between embryonic day 21 and posthatching day 2 were analyzed after a single [3H]thymidine injection administered on embryonic day 16, 17 or 18. Results showed that dark cells comprised 55% of identified (n = 900 cells) and 62% of labeled (n = 568 cells) gemmal cells as compared with light, intermediate, basal or perigemmal bud cells. Dark cells had both a greater (P < 0.05) number of labeled cells and a greater amount of label (grains/nucleus) than the other four bud cell types, irrespective of injection day. The nuclear area (micron 2) of dark cells was not significantly larger (P > 0.05) than that of the other gemmal cell types and therefore cannot account for the greater amount for label in the dark cells. Interestingly, only dark cells showed a positive correlation (P < 0.003) between amount of label and nuclear area. Results suggest that, during the perihatching period of robust cell proliferation, dividing dark cells may give rise primarily, but not exclusively, to dark cell progeny.      

Inherited DNA Repair Defects Disrupt the Structure and Function of Human Skin

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Reduction Potentials of Imine-Substituted, Biologically Active Pyridines: Possible Relation To Activity

Cyclic voltammetry data were obtained for a number of biologically active compounds which incorporate imine substitution on the pyridine nucleus. The reductions in acid (iminium ion formation) were for the most part reversible, and in the range of—0.5 to—0.7 V. The toxic effect of these drugs is thought to be caused by the generation of reactive oxygen radicals that arise viacharge transfer, or by disruption of electron transport chains.     

A novel approach to β-lactam chemistry in vivo: Electron transfer and oxy radical formation by iminium

On binding to cell-wall enzyme, β-lactams form precursors of conjugated iminium species that apparently possess favorable reduction potentials based on studies with model compounds. The models used were iminium salts of Δ¹-pyrroline-2-carboxylic acid and Δ³-thiazoline-4-carboxylic acid. Reduction potentials of −0.76 to −0.92 V increased to −0.18 to −0.37V with decrease in pH. The potentials of the iminium species are similar to those of well-known electron transfer (ET) agents, such as quinones, nitroheterocycles, and metal complexes. Catalytic ET by these cations is discussed in relation to nephrotoxicity, antibiotic action, and cell culture redox potential. Reactions of penicillin at the binding site are addressed. We propose that the bactericidal effect involves various modes of action, including inactivation of cell-wall enzyme and electrochemical interference with normal electron transfer processes.     

The Use of a Light Visor During Night Work by Nurses

Five nurses have been investigated for the two nights of a rapidly rotating shift schedule on four occasions: once with normal ward lighting (40 lux on average) and three times while wearing a light visor (Bio-Brite Inc., MD, USA). The visor was worn for four periods of 40 minutes each, at about 2 hour intervals during each night shift, the intensity giving 400-600, 1500 and 3200 lux for the three studies. The nurses recorded subjective evaluations of mood, physical fitness, sleepiness and fatigue, and carried out some performance measures (Simple Auditory Reaction Time, Flicker Fusion Frequency, Search and Memory test) at the start, middle and end of each night shift. Plasma cortisol was measured at the end of the shift, and 6-sulphatoxymelatonin was measured in urine collected at the middle and end of each shift. Oral temperature was also recorded for 48 h covering the two shifts. No significant effects of light treatment (even at 3200 lux) upon within-shift decline in mood and performance were seen. The acceptability of the wearer of the visor was moderate since the upper visual field was impaired and, at the highest light intensity, there was difficulty in seeing clearly objects in the dimly-lit environment. Furthermore, no significant falls in melatonin excretion and cortisol excretion were noted, but there was some evidence that the circadian rhythm of oral temperature was stabilised by the light visors. This is thoroughly desirable in rapidly rotating shift systems.     

Elucidation of the Primary Events in Photosynthesis. Novel Insights Based on Enolisation and Iminium Involvement with Pheophytin in Photosystem 2

Pheophytin (Pheo) is structurally constituted as to make possible certain reactions, previously given very little attention, which appear to play crucial roles in the initial electron transfer (ET) processes. The transformations involve enolisation with subsequent formation of mono- and di-iminium cations at the Pheo core. The important impact of these ions on ET from chlorophyll (Chl) to Pheo and then to quinone are evaluated. These insights rationalise the long-standing enigmas of fast transfer, across gap ET, activation-less aspect, and essential lack of reversibility. Comparisons are made to other important areas of iminium involvement, e.g. chemistry of vision, polyaniline doping, and DNA alkylation.