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Biomedical subjects

S Thompson

Publications and source records attributed to S Thompson.

At least 325 records · Page 18Linked to original sources
PubMed1978

Ultrastructure of the foveal glands of the ticks, Dermacentor andersoni Stiles and D. variabilis (Say).

The foveal glands of Dermacentor variabilis appear to consist of 2 cell types. The outer cells (Type I) are active, with large areas of abundant finely granular material, apparently precursors of the mature secretory granules. The inner cells (Type II) are apparently storage cells. They are highly vacuolated and contain coarsely granular material as well as presumably mature secretory granules. The foveal glands of D. andersoni contain only Type II cells with extensive accumulations of presumably mature secretory granules.

Animals↗
PubMed1977

Osmotic properties of human lymphocyte.

The osmotic properties of human lymphocytes isolated from 15 ml of venous blood were examined. Measurements of the permeability of the membrane to water under an osmotic gradient were also made. The Boyle-Van't Hoff relation held very well for the human lymphocyte when the cells were shrunken in hyperosmotic media to concentrations twice isosmotic. The volume of osmotically inactive material or "b" value averaged 32% of the mean corpuscular volume. These values were independent of temperature. Ponder's R ranged between 0.8 and 0.9. The average value for Lp, the hydralic coefficient was 0.46 mu/min atm +/- 0.02 (S.E.M.) at 25 degrees C. No significant effect of age, sex, or race was noted. The effect of temperature between 10 degrees C and 37 degrees C was measured and heats of activation between 11.1 and 17.4 kcal/mole were calculated with a mean of 14.1 kcal/mole +/- 1.6 (S.E.M.). Concanavalin A at 10 microgram/1.5 X 10(6) lymphocytes produced blastogenesis of 25% or more of the lymphocytes without clumping, agglutination, or toxicity. The mean corpuscular volume increased by 21% after 72 hours due to an increase in the "b" value which increased by 80%. The volume of free water remained constant. Histograms of the distribution of cell volumes showed that volume changes were uniform throughout the population with no evidence of agglutination of clumping. The significance of these results is discussed in the context of membrane fluidity and the state of intracellular water.

Cell Membrane Permeability↗
PubMed1977

The effects of benzoflavones on polycyclic hydrocarbon metabolism and skin tumor initiation.

The effects of benzoflavones on skin tumor initiation by polycyclic hydrocarbons and epidermal aryl hydrocarbon hydroxylase were investigated. 7,8-Benzoflavone (7,8-BF) was found to be a potent inhibitor of the inhibition of skin tumors by 3-methylcholanthrene (MC) as well as 7,12-dimethylbenz(a)anthracene (DMBA). 5,6-Benzoflavone(5,6-BF) inhibited tumor initiation by MC and DMBA, but to a lesser degree than 7,8-BF. Dose-response studies of the capacity of 7,8-BF to inhibit DMBA tumor initiation revealed that 7,8-BF was an effective inhibitor at 2.5 microgram and a maximum inhibition of 90% occurred at 100 microgram of 7,8-FB. The tumor initiating ability of 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHMe-12MeBA) was not inhibited by 7,8-BF. Epidermal aryl hydrocarbon(benzo(a)pyrene hydroxylase(AHH) was increased by 5,6-BF and either had no effect or was slightly inhibited by 7,8-BF when given either topically or i.p. Both flavones when added directly to the assay tubes inhibited the in vitro epidermal AHH activity from control and MC pretreated mice by greater than 75%. When added in vitro, 7,8-BF and 5,6-BF inhibited epidermally mediated covalent binding of radioactive DMBA and dibenz(a,h)anthracene to DNA by 50% or more. The inhibition of skin tumor initiation by 7,8-BF and 5,6-BF appears to be partially related to its ability to inhibit the formation of electrophilic intermediates.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1977

Mutagenicity of anti-cancer nitrobenzofuroxans.

Anti-leukaemically active benzofuroxans were tested for mutagenicity in Salmonella typhimurium. Mutagenicity was not found to be correlated to the previously established anti-leukaemic activity. One anti-leukaemically inactive compound after exposure to liver microsomal enzymes proved the most mutagenic of the derivatives for TA100, whereas after similar treatment, the mutagenicity of the most potent anti-leukaemic compound was reduced. All twelve derivatives tested were mutagenic in a base-substitution strain which was defective in excision-repair and also carried a plasmid-linked repair deficiency. Mutagenicity of five dervatives was undetectable in strains proficient for one or the other of the above repair pathways. Nine of the benzofuroxans could also be detected as mutagens in the frameshift tester strain TA98.

Animals↗
PubMed1977

Binding of dexamethasone by the subcellular fractions of mouse epidermis and dermis.

The binding of the potent anticarcinogenic agent, dexamethasone, to mouse epidermal and dermal subcellular fractions was investigated. When applied to mouse skin, 3H-labeled dexamethasone remained associated, after extensive dialysis, with epidermal and dermal cytosol, microsomes, microsomes, mitochondria, and chromatin. The specific activity of dexamethasone binding to these fractions was from 2 to 5 times as high in the epidermis as in the dermis. Epidermal chromatin had the highest specific activity fo binding. Dexamethasone was not associated with the cytosol protein receptor which was previously found to specifically bind tumor promoters and polycyclic hydrocarbon carcinogens.

Animals↗
PubMed1977

Cobb syndrome.

Cobb syndrome consists of a vascular skin nevus associated with an angioma in the spinal cord. We describe a young man with this condition. To our knowledge, this is the 28th case reported. Cobb syndrome must be differentiated from other syndromes characterized by vascular cutaneous lesions associated with central nervous system abnormalities, such as Sturge-Weber, Osler-Weber-Rendu, Fabry-Anderson, von Hippel-Lindau, and ataxia telangiectasia.

Adolescent↗
PubMed1976

Mouse epidermal aryl hydrocarbon hydroxylase.

Mouse skin contains a NADPH-dependent, aryl hydrocarbon hydroxylase (AHH), which is inducible by polycyclic aromatic hydrocarbons. In general, unsubstituted polycyclic hydrocarbons caused a greater induction of epidermal AHH than substituted one (1,2,3,4-dibenzanthracene greater than 1,2,5,6-dibenzanthracene greater than benz (a)anthracene equal 3-methylcholanthrene greater than 7,12-dimethlbenz (a)anthracene) which did not correlate with their ability to initiate tumors in mouse skin. Two different techniques were used to isolate epidermis and similar results were obtained with both. However, the technique of isolating epidermis using a mild heat treatment required that the temperature be maintained at 52 degrees C for 30 sec. If the temperature was raised to 54 degrees C or above, there was a large reduction in the AHH activity. Isolated epidermis has 4 to 5 times the AHH activity as dermis and about twice that of whole skin. This was true for control mice or mice in which AHH was induced by pretreatment with benz(a)anthracene.

Animals↗
PubMed1976

The effect of nursing intervention on a program of behavior modification by parents in the home.

The purpose of the study was to determine if nursing intervention affects a program of behavior modification for neurologically impaired children carried out by parents in the home. Nine neurologically impaired subjects between the ages of two and four years were selected for programs of behavior modification by their parents at home. The nine subjects were randomly divided into an experimental and control group. The groups were generally matched for age and socioeconomic status. The four subjects in the experimental group were visited bi-weekly for a two-month period after the initial program was set up with changes, assessments and/or alterations made in the programs as necessary. The five subjects in the control group were visited at the beginning of the study to establish the programs of behavior modification the parents would implement. This group was not revisited until the end of the two-month period. The findings indicated a marked change in the subjects of the experimental group. This difference was significant on the basis of Wilcoxin Matched Pairs p. greater than .00003. In the control group only one child had any appreciable change in the specific target behavior, and it was not the desired goal.

Activities of Daily Living↗
PubMed1975

Correlation of structural changes at different levels of the jejunal villus with positive net water transport in vivo and in vitro.

Experiments were done for indentification and localization of certain structural changes at different levels of jejunal villus of the hamster during positive and negative water transport across the intestine in vivo and in vitro. Positive transport occurred when the mucosal surface of the intestine was bathed (in vitro experiments) or perfused (in vivo experiments) with isotonic Krebs-Ringer bicarbonate solution containing 10 mM glucose, and negative water transport was achieved by rendering this solution hypertonic with 150 mM mannitol. Results indicate that during positive net water transport the intestine in vivo transported more fluid and exhibited a more conspicuous dilatation of the lateral intercellular spaces (L.I.S.) than did the in vitro preparation. Dilatation of the L.I.S. in both preparations was present only in the apical part of the villus, suggesting that this is the principal site of water absorption. When the mucosal solution was made hypertonic with mannitol, the L.I.S. in the in vivo intestine totally collapsed, whereas in the in vitro intestine these spaces remained open very slightly. These morphological changes correspond well with our finding that in the presence of the hypertonic mucosal solution there was a greater net negative water transport in vivo than in vitro. Incubation of the intestine in the isotonic mucosal solution produced subnuclear swelling of the mid-villus epithelial cells, and this morphological change was associated with an increase in the water content of the tissue. Perfusion of the in vivo intestine with the isotonic solution produced neither the swellings nor the increase in water content of the tissue. In the presence of hypertonic mucosal solution there was a water loss from the tissue both in vivo and in vitro, and these swellings were not observed. These results are discussed in relation to intestinal sugar transport and to the maturity of the epithelial cells, and it is concluded that transport studies on in vitro preparations may provide valid information on a qualitative basis, if not on a strictly quantitative basis.

Animals↗
PubMed1975

Prolonged inhibition of mouse epidermal DNA synthesis by dexamethasone.

The effect of dexamethasone, an anti-inflammatory agent that inhibits skin carcinogenesis, on DNA, RNA, and protein synthesis in mouse epidermis was investigated. Within 1 hour after the topical application of 75 mug dexamethasone to the skin of mice, epidermal DNA synthesis was inhibited drastically and lasted for approximately 5 days, followed by a biphasic stimulation at 7 and 10 days after treatment. Histologically, the skin after dexamethasone treatment revealed only subtle quantitative changes. The dermis was not altered. The epidermal thickness was unchanged, but the nuclei of the epidermal cells were more densely stained and the chromatin was more densely clumped. These changes were present by 12 hours and persisted for 10 days. Both epidermal RNA and protein syntheses were stimulated early, reached a peak of around 180% of controls at 1 hour, but returned to control levels by 3 hours. They were slightly inhibited between 3 and 12 hours after treatment and then returned to control levels. This prolonged inhibition of DNA synthesis by dexamethasone may be related to its anticarcinogenic effect.

Administration, Topical↗