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Biomedical subjects

S Ray

Publications and source records attributed to S Ray.

At least 73 records · Page 4Linked to original sources
PubMed1988

Vitamin D, its precursors, and metabolites do not affect melanization of cultured human melanocytes.

Exposure of the skin to sunlight results in both tanning and vitamin D3 production. It has therefore been suggested that vitamin D3 or its active metabolite 1,25-dihydroxyvitamin D3 may be the mediator of UV-induced melanogenesis. To test this hypothesis, newborn foreskin-derived melanocytes were cultured in paired dishes in hormone-supplemented medium with 2% serum containing no detectable vitamin D3 or in the same medium containing 10(-8) or 10(-10) M of either provitamin D3, lumisterol, previtamin D3, vitamin D3, 25-hydroxyvitamin D3, or 1,25-dihydroxyvitamin D3. After 10 days, cell number in cultures containing vitamin D compounds was 93%-140% of unsupplemented controls and melanin content was 60%-120% of control, with no significant difference in either parameter for any compound tested. In separate experiments, human melanocytes and Cloudman S91 melanoma cells were repeatedly irradiated with physiologic doses of simulated sunlight and incubated between irradiations with provitamin D3, previtamin D3, vitamin D3, or 1,25-dihydroxyvitamin D3. Irradiated cultures had a 90%-95% inhibition of cell growth associated with a 200%-800% increase in melanin content per cell relative to controls, but there was no effect of any vitamin D compound on either cell type. Neither cultured human melanocytes nor S91 cells showed evidence of the cytosolic 1,25-dihydroxy-vitamin D3 receptor binding by sucrose density gradient analysis using radiolabeled 1,25-dihydroxyvitamin D3. The combined data strongly suggest that neither vitamin D3 nor its precursors or metabolites directly mediate melanogenesis in these cells.

Cells, Cultured↗
PubMed1988

Na+ pump in renal tubular cells is regulated by endogenous Na+-K+-ATPase inhibitor from hypothalamus.

Bovine hypothalamus contains a high affinity, specific, reversible inhibitor of mammalian Na+-K+-ATPase. Kinetic analysis using isolated membrane fractions showed binding and dissociation rates of the hypothalamic factor (HF) to be (like ouabain) relatively long (off rate = 60 min). To determine whether the kinetics of inhibition in intact cells might be more consistent with regulation of physiological processes in vivo, binding and dissociation reactions of HF in intact renal epithelial cells (LLC-PK1) were studied using 86Rb+ uptake and [3H]ouabain binding. As with membranes, a 60-min incubation with HF inhibited Na+-K+-ATPase in LLC-PK1 cells. In contrast to membrane studies, no prolonged incubation with LLC-PK1 was needed to observe inhibition of Na+-K+-ATPase. HF caused a 33% inhibition of ouabain-sensitive 86Rb+ influx within 10 min. Incubation of cells with HF followed by washout showed rapid reversal of pump inhibition and a doubling of pump activity. The dose-response curve for HF inhibition of LLC-PK1 86Rb+ uptake showed a sigmoidal shape consistent with an allosteric binding reaction. Thus HF is a potent regulator of Na+-K+-ATPase activity in intact renal cells, with binding and dissociation reactions consistent with relevant physiological processes.

Animals↗
PubMed1988

Tubuloreticular reorganization of cytomembranes in cells treated with human alpha interferons--a review.

Human alpha interferons (IFN-a) cause a reorganization of internal cell membranes into tubuloreticular inclusions (TRI). Morphogenesis and cytochemistry indicate a pre-Golgi intracisternal origin from the endoplasmic reticulum. Clinically, TRI formation in human blood mononuclear cells correlates with systemic IFN-a treatment or with endogenous overproduction of IFN-a in viral or autoimmune diseases (e.g., rubella syndrome, AIDS, systemic lupus erythematosus). In vitro, TRI formation can be produced by treatment of Daudi lymphoblasts or vascular endothelial cells with IFN-a, and is blocked by actinomycin-D. In Daudi lymphoblasts or vascular endothelial cell cultures, TRI formation parallels induction of 2'-5' A synthetase, inhibition of thymidine kinase and growth inhibition; however, heavy water treatment of Daudi cells prevented TRI formation while induction of 2'-5' A synthetase and growth inhibition persisted. TRI formation was dissociated from IFN-a antiproliferative activity in a mutant clone of Daudi lymphoblasts. Decreased glycoprotein biosynthesis and increased phospholipid biosynthesis may accompany progressive TRI accumulation.

Endothelium, Vascular↗
PubMed1987

Aminoacetone oxidase from goat liver. Formation of methylglyoxal from aminoacetone.

An enzyme which oxidizes aminoacetone to methylglyoxal has been purified from the particulate fraction of goat liver. Polyamines, such as spermidine and spermine, are also good substrates for this enzyme. The pH optimum for aminoacetone oxidation was found to be 8.2. The apparent Km values of the enzyme for aminoacetone and spermidine were 0.009 and 0.095 mM, respectively. The subunit molecular weight of the enzyme was 93,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The apparent molecular weight of the native enzyme was 186,000 by gel filtration. The enzyme is highly sensitive to carbonyl group reagents. The enzyme is not inhibited by monoamine and diamine oxidase inhibitors.

Acetone↗
PubMed1987

Enhanced antifertility activity of non-steroidal molecules with 3-n-butylamino-2-hydroxypropyloxy side chain.

A comparative study of relative binding affinity (RBA) for estradiol-17 beta-receptors, estrogenicity and antifertility activity of compounds 2,2-dimethyl-3-phenyl-4-p-(3-n-butylamino-2-hydroxypropyloxy-pheny l)- 7-methoxycoumarin 4, 2,2-dimethyl-3-phenyl-4-p-(3-n-butylamino-2-hydroxy-propyloxyphenyl++ +)-7-methoxy chromene 5 and trans-2,2-dimethyl-3-phenyl-4-p-(3-n-butylamino-2-hydroxypropyloxyphe nyl)- 7-methoxychroman 6 with the corresponding 4-p-(beta-pyrrolidinoethoxyphenyl) compounds 1-3, is reported. It has been found that the introduction of the novel 3-n-butylamino-2-hydroxypropyloxy moiety in place of the classical tert-beta-aminoethoxy group leads to enhancement of antifertility activity.

Animals↗
PubMed1987

Neutrophil leukocyte morphology, cigarette smoking, and palmoplantar pustulosis.

Neutrophil leukocyte morphology was examined in whole blood films from 20 patients with palmoplantar pustulosis (PPP) and 32 healthy controls. In the PPP patients, there was a significant increase in the number of neutrophils having polarized morphology or membrane ruffling; however, there was no significant difference in neutrophil morphology between cigarette smokers and nonsmokers, suggesting that the epidemiologic link between smoking and PPP is not explained by increased polarization of peripheral blood neutrophils.

Cell Membrane↗
PubMed1986

Bioaccumulation of cadmium in marine organisms.

It has been established that, although Cd occurs in the marine environment in only trace concentrations, most marine organisms, especially molluscs and crustaceans, can accumulate it rapidly. Cadmium is not uniformly distributed in the body and selectively accumulates in specific organs like liver, kidney, gills, and exoskeleton. The concentrations in muscle tissues are several orders of magnitude lower. The disposition of Cd in the organisms in the laboratory studies generally parallels those in nature. A number of biotic factors like body size, maturity, sex, etc. influence bioaccumulation but extensive studies are still lacking. The chemical form of Cd in the environment is of prime importance in bioaccumulation by marine organisms. Salinity can affect the speciation of Cd, and bioaccumulation is affected by both temperature and salinity. The ultimate level of Cd in the organisms will depend not only on the biotic and abiotic factors but also on metabolism of the metal by the organisms. A few studies indicate depuration of Cd by some bivalves but other organisms show very effective retention of Cd. Metallothionein formation for detoxification and storage has been observed in a large variety of marine organisms. Recent reports indicate an alternate storage and excretion mechanism in the formation of membrane-limited vesicles or granules. There seems to be a common link between intracellular localisation of Cd in metal-binding proteins and Cd containing vesicles as detoxifying mechanisms in the marine organisms. Much of what is known about Cd bioaccumulation by marine organisms has come from laboratory studies and there are inherent dangers in trying to extrapolate the results to field situations. In spite of tremendous progress made over the years, the basic understanding of the bioaccumulation process is still very nebulous and will remain so until the uptake, storage, and elimination processes are fully understood.

Animals↗
PubMed1986

17 alpha-allyl estradiol analogues as candidates for development of high-affinity fluorescein-estradiol conjugates.

In order to develop stable, high-affinity fluorescein-estradiol conjugates, the fluorescein moiety must be leashed to the estradiol molecule at a point which interferes least with estradiol's binding to the receptor. Because of the high affinity of 17 alpha-substituted estradiol (e.g. ethynyl estradiol), we investigated a series of 17 alpha-substituted estradiol compounds to determine the optimal properties of a leash at this position. Twelve estradiol derivatives bearing a three-carbon 17 alpha side chain with or without a terminal functional group and with varying degrees of unsaturation were synthesized. Initial comparison of the receptor binding affinities of some of these derivatives suggested that three factors might reduce affinity: internal hydrogen bonding of the 17 beta-hydroxyl proton with an oxygen atom of the 17 alpha side chain; hydrophilicity of the ligand; or steric interference of the side chain with receptor binding. Further comparisons were designed to evaluate the relative contribution of these factors. The results suggest that the relative affinities of these 17 alpha-substituted estradiol derivatives are influenced primarily by the steric interference of the side chains and also by their hydrophilicity. Internal hydrogen bonding involving the 17 beta-hydroxyl proton does not seem to have a profound effect.

Animals↗
PubMed1986

Androgen receptor affinity chromatography: synthesis and properties of 17 alpha-epoxypropyl-dihydrotestosterone Sepharose.

We have prepared a new affinity chromatography reagent, 17 alpha-epoxypropyl-dihydrotestosterone linked to Thiopropyl-Sepharose, with potential for use in purification of androgen receptor and other specific androgen binding proteins. The linkage is stable, and the ligand has reasonably high affinity for the receptor. Starting with 5 alpha-androstane-3 beta-ol-17-one, we synthesized in two steps 17 alpha-allyl-dihydrotestosterone, which was then oxidized to 17 alpha-epoxypropyl-DHT yielding 2 diastereomers in about a 4:1 ratio. The 17 alpha-allyl-DHT had about 50% of DHT's affinity for rat uterine androgen receptor, while the affinity of the major epoxide isomer was 9% and that of the minor isomer was 4%. Reaction of the epoxides with Thiopropyl-Sepharose-6B gave about 7 mumol of covalently bound DHT per ml of beads. These beads took up 83% of the androgen receptor from a rat uterine cytosol in a preliminary study, which more than equalled the performance of identically prepared estradiol beads successfully used for estrogen receptor purification. The use of the new DHT beads in purifications of the androgen receptor and other binding proteins is now being explored by other laboratories.

Animals↗
PubMed1986

Studies in antifertility agents. 50. Stereoselective binding of d- and l-centchromans to estrogen receptors and their antifertility activity.

Centchroman [dl-3,4-trans-2,2-dimethyl-3-phenyl-4-[p-(beta-pyrrolidinoethoxy)phenyl] - 7-methoxychroman hydrochloride], an antifertility agent under clinical evaluation, has been resolved into its optical enantiomers. The cytosol estrogen receptor binding affinity and estrogenic, antiestrogenic and antiimplantation activities of the two enantiomers have been determined. The enantiomers display a 7-fold difference in receptor affinity, and a corresponding difference in stimulation of the uterine growth and antiimplantation activity was observed in rats.

Animals↗
PubMed1986

Stimulation of human neuroblastoma DNA polymerase alpha and primase activities by a protein factor isolated from rat liver chromatin.

Nuclear protein factor type 1 (NPF-1) that simulates IMR-32 primase-associated DNA polymerase alpha 1 and alpha 2 activities has been purified from a high-salt extract of liver chromatin from 6-month-old rats. The final purified factor lacks DNA polymerase alpha, RNA polymerase, and DNA-unwinding or topoisomerase type I activities. The stimulatory activity is destroyed by trypsin (60 min at 37 degrees C), DNase II (60 min at 37 degrees C), and heat treatment (2 min at 68 degrees C). The 125I-labeled NPF-1 does not bind to activated calf thymus DNA or poly(dC). However, it forms a ternary complex with DNA in the presence of DNA polymerase alpha-primase complex (alpha 1 and alpha 2). The ternary complex sediments on sucrose density gradient as a heavier band (11S). The NPF-1 also stimulates (2.5-fold) primase-catalyzed incorporation of GMP and dGMP from the corresponding triphosphates on poly(dC) template even in the presence of a high concentration of alpha-amanitin (400 micrograms/ml). The labeled duplex containing the poly(dC) template, [32P]-GTP, and [3H]dGTP loses 80% of the 32P label and 70% of the 3H label after treatment with 0.3 M KOH and DNase I, respectively. The products were isolated from reaction mixtures incubated with and without NPF-1 and subjected to alkaline sucrose-density-gradient sedimentation analysis. The results suggest that the rate of synthesis of DNA short chains is increased in the presence of NPF-1 without a concomitant increase in the chain length of the newly synthesized products.

Animals↗
PubMed1986

Electrical conduction in bone in frequency range 0.4-1.3 GHz.

Dielectric permittivity and conductivity of bone in different physiological conditions and collagen, a major component of bone are measured in the frequency range 400-1300 MHz using a Network analyzer. The dielectric dispersion observed in each cases are explained in terms of the relaxation of 'bound water' in this frequency range. The relaxation frequency as well as distribution parameter are computed in each case, under certain simplifying conditions, hydration as well as static dielectric permittivity of bound water attached with bone in different physiological conditions and collagen are also calculated. The effect of ultraviolet light irradiation on the dielectric properties of bone in this frequency range is also examined. The change in dielectric properties due to radiation is attributed to the breakage of hydrogen bonds in the ring structure. A consistent physical model in line with other data is presented.

Animals↗