In vitro effects of trans-4-hydroxy-2-alkenals on mouse liver cytochrome P-450

Under in vitro conditions, trans-4-hydroxy-2-hexenal (t-4HH), trans-4-hydroxy-2-nonenal (t-4-HN) and trans-2-hexenal (t-2H) significantly reduced the levels of mouse liver microsomal cytochrome P-450. Incubation of trans-4-hydroxy-alkenals, under anaerobic conditions in the absence of an NADPH-generating system indicated that these compounds were converting cytochrome P-450 to cytochrome P-420. Prior activation by the mixed function oxidase system was not required for trans-4-hydroxy-alkenals to alter cytochrome P-450 concentrations. trans-4-Hydroxy-alkenals and non-hydroxylated alpha,beta-unsaturated aldehydes may be exerting their effects on cytochrome P-450 by binding to sulfhydryl groups in a similar manner as reported for sulfhydryl reagents such as p-chloromercuriphenylsulfonic acid and p-chloromercuribenzoate.     

Characterization of a Marine Bacterium Associated with Crassostrea virginica (the Eastern Oyster)

A gram-negative bacterium found to be closely associated with oysters has been isolated and characterized. The organism, designated LST, has a generation time of 106 min in Marine broth under optimal growth conditions at 25°C. During the decline phase of growth, it exhibits a morphological transition from a motile rod (ca. 1 μm in length) to an elongated, 3- to 40-μm, nonmotile, tightly coiled helix. LST synthesizes and releases a pigment in the stationary and decline phases of growth. Identified as melanin on the basis of chemical properties and UV absorbance maxima, the pigment comprises polymers of heterogeneous molecular weights, ranging from 12,000 to 120,000. The guanosine-plus-cytosine content of the LST DNA is 46%, and results of phenetic analysis and DNA-DNA hybridization indicate that this bacterium represents a new species. LST adheres to a variety of surfaces, including glass, plastics, and oyster shell, and has been shown to promote the settlement of oyster larvae.     

Coordination of flagella on filamentous cells of Escherichia coli.

Video techniques were used to study the coordination of different flagella on single filamentous cells of Escherichia coli. Filamentous, nonseptate cells were produced by introducing a cell division mutation into a strain that was polyhook but otherwise wild type for chemotaxis. Markers for its flagellar motors (ordinary polyhook cells that had been fixed with glutaraldehyde) were attached with antihook antibodies. The markers were driven alternately clockwise and counterclockwise, at angular velocities comparable to those observed when wild-type cells are tethered to glass. The directions of rotation of different markers on the same cell were not correlated; reversals of the flagellar motors occurred asynchronously. The bias of the motors (the fraction of time spent spinning counterclockwise) changed with time. Variations in bias were correlated, provided that the motors were within a few micrometers of one another. Thus, although the directions of rotation of flagellar motors are not controlled by a common intracellular signal, their biases are. This signal appears to have a limited range.     

Quantification of cytochrome P450 reductase gene expression in human tissues.

We have isolated and sequenced cDNA clones that code for a variant of human cytochrome P450 reductase. An RNase protection assay was used to quantify the corresponding mRNA in adult and fetal tissues. The results demonstrate that, in the samples analyzed, the cytochrome P450 reductase gene displays very little inter-individual variation in its expression in adult liver and is subject to little developmental or tissue-specific regulation.     

Low temperature preservation and space medicine

Cold maintenance may be an option for compromised space-borne astronauts. Contemporary aneurysm surgery can involve cooling below 20 degrees C for nearly one hour. Dogs and baboons have survived blood-substituted hypothermia for 1-3 hours. Hamsters have recovered from partial-freezing below -1 degree C, and supercooling at -5 degrees C. Laboratory frogs have survived partial-freezing from -9 degrees C, while in nature, frogs may overwinter in these states. While some invertebrates can tolerate freezing to cryogenic temperatures, no vertebrate has survived complete freezing. The following studies (hypothermia and sub-zero experiments) were conducted to explore low temperature preservation of rodents, dogs and baboons.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.