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Biomedical subjects

B D Smith

Publications and source records attributed to B D Smith.

At least 127 records · Page 7Linked to original sources
PubMed1982

Effects of stress and conflict difficulty on arousal and conflict resolution.

The present study was concerned with the effects of conflict type and shock stress on arousal and conflict resolution. Subjects were randomly assigned to either stress (random shock) or non-stress conditions. Each subject was exposed to three trials of each of the four Lewinian conflict types and three control trials, interspersed among additional non-conflict trials. Resolution performance was assessed in terms of speed of resolution and error frequency. Phasic electrodermal responsivity served as a measure of arousal. Results supported several hypotheses. It was found that both stress and conflict increased the magnitude of electrodermal responses and that larger responses occurred under more difficult conflicts. In addition, increased conflict difficulty produced lower speeds, and stress increased errors. Finally, stress caused a greater increase in error frequency on conflict than on control trials. Results were discussed in terms of arousal and stress hypotheses found in the theories of Lewin and Dollard & Miller.

Arousal↗
PubMed1981

Effects of the calcium-mediated enzymatic cross-linking of membrane proteins on cellular deformability.

Excess calcium binding affects the shape and dynamics of cellular deformation of human erythrocytes. It may be hypothesized that incorporation of calcium may modify cellular deformability by processes which include specific cross-linking of membrane proteins with resultant changes in cell shape and deformability. Since previous studies indicate that accumulation of calcium ions causes development of gamma-glutamyl-epsilon-lysine bridges in membrane proteins, under control of a membrane transamidating enzyme which specifically requires calcium ions for activation, experiments were devised to examine the relationship between cross-linking and deformability and to determine the effects of specific inhibitor of membrane protein cross-linking on the calcium-dependent modification of erythrocyte to the echinocytic shape. The elastic shear modulus of the membrane was not significantly affected by calcium-induced cross-linking, indicating that induced shape change, not altered elasticity, causes the observed reduction in cellular deformability. These findings support the interpretation that Ca++-induced and transamidase-catalyzed cross-linking of membrane proteins contributes to fixation of altered cellular shape and decreased cellular deformability.

Adult↗
PubMed1981

Bilateral electrodermal activity as a function of hemisphere-specific stimulation, hand preference, sex and familial handedness.

UNLABELLED: The effects of unilateral stimulation on bilaterally recorded electrodermal activity are not well understood. Factors that may contribute to bilateral response differentiation under conditions of unilateral stimulation include preferred hand, sex and familial handedness. To assess the effects of these factors, 64 subjects were each assigned to one of four cells defined by sex and preferred hand. Each subject received a counterbalanced series of 31 slides depicting objects spatially and intended to activate the right hemisphere and 31 slides depicting objects spatially and intended to activate the left hemisphere. Each condition was followed by a blank slide. Results showed smaller mean nonspecific responses on the hand contralateral to the hemisphere for which stimulation was intended. This supports the hypothesis that a contralateral inhibitory process underlies electrodermal responsiveness. Further results showed that the effects of unilateral stimulation on bilaterally differentiated electrodermal activity are mediated by familial handedness and sex. DESCRIPTORS: hemispheric processes, bilateral EDA, sex, familial handedness, preferred hand.

Adult↗
PubMed1981

Biochemical factors influencing erythrocyte deformability and capillary entrance phenomena.

Evaluation of the effects of biochemical modification of erythrocytes by low pressure filtration through Nuclepore filters of 2.8 and 3.0 micrometer pore diameter and glass micropipettes of 2.7 and 3.0 micrometer internal diameter and channel length greater than 100 micrometer indicates the relative sensitivity of the micropipette in detection of reduction of cellular deformability. In dynamic studies of erythrocyte entrance behaviour on micropipettes, the significance of induced relative sphericity on cellular deformability was evident. Reduction of intracellular ATP, cellular pH, sphere induction by bifunctional membrane protein cross-linking reagents and lead caused diminution in cellular deformability, attributable to the more spherical shape. Similarly echinocyte formation by effects of aged plasma, oleate and senscence, and stomatocyte induction by chlorpromazine caused marked decrease in capillary entry of cells having flow velocities of approximately 100 micrometer/s in contrast inhibitors of the glucose carrier, of calmodulin and manipulated decrease in membrane lipid of bilayer fluidity did not cause detectable change in cellular deformability. These data emphasize the relative importance of erythrocytic shape as a determinant of cellular deformability and suggest that necessity for adequate control of shape change is necessary when examining effects of biochemical manipulations on membrane elasticity and cellular deformability. The preliminary date from capillary entrance experiment indicate the importance of dynamic experiments in in vitro studies of microcirculation.

Adenosine Triphosphate↗
PubMed1980

Characterization of collagen synthesized by normal and chemically transformed rat liver epithelial cell lines.

A rat liver epithelial cell line (K16) and a 2-[N-(acetoxyacetyl)amino]fluorine-transformed K16 cell line (W8) [Weinstein, I.B., Yamaguchi, R., Gerbert, R., & Kaighn, M.E. (1975) In Vitro 11, 130-141] synthesize and secrete similar quantities of collagenous proteins. The transformed cells produce more total protein so that the percent collagen produced is decreased compared to that of the parent cell line. The type of collagen produced by the transformants differed from that of the parent cell line. After limited pepsin digestion, the pepsin-resistant collagen molecules synthesized by K16 cells precipitated at 2.6 M NaCl and contained both alpha 1 (I) and alpha 2 chains in a 2.5:1 ratio. The collagen synthesized by the W8 cells precipitated at higher salt concentrations, and no pepsin-resistant alpha 2 chains could be demonstrated by CM-cellulose chromatography or gel electrophoresis. The cyanogen bromide peptides of the W8 alpha 1 chains did not cochromatograph with type I rat skin collagen cyanogen bromide peptides on CM-cellulose chromatography, whereas the alpha 1 chains of the K16 cells did cochromatograph. The conversion of procollagen to collagen was also decreased in the transformant cells. Therefore, the chemical transformation of K16 produced transformants with increased protein synthesis and altered collagen metabolism.

2-Acetylaminofluorene↗
PubMed1979

Collagen synthesis in normal BHK cells and temperature-sensitive chemically transformed BHK cells.

Collagen synthesis in normal BHK 21/cl 13 and chemically transformed temperature sensitive BHK 21/cl 13 cells (Me2N4) was assessed by examination of hydroxyproline formation and collagenase-susceptible protein. The Me2N4 cells lost their ability to synthesize collagen at both permissive and nonpermissive temperatures for transformation. These conclusions were confirmed by polyacrylamide-gel eletrophoresis and CM-cellulose chromatography. Prolyl hydroxylase activity was present in both normal and transformed cells even when no collagen could be demonstrated. The production of noncollagen protein, although decreased in the transformed cell, did not change as drastically as the collagen synthesis.

Animals↗
PubMed1979

Parallel decrease of erythrocyte membrane deformability and spectrin solubility at low pH.

Reduction of pH over the range 6.0-4.5 results in a decrease of erythrocyte deformability in parallel with the induced progressive sphericity of cells. At low deformation rates employed, increase of hemoglobin viscosity was not significant. A decrease of membrane elasticity was detected in cells when sphering, the major determinant of cellular deformability, was prevented at pH 5.0 by hyperosmotic medium. The pronounced change of deformability and the reduced elasticity occurred at calculated intracellular pH values at which solubility in vitro of extracted erythrocyte spectrin is also markedly reduced. The parallel decrease of deformability and spectrin solubility supports the hypothesis that spectrin aggregation may contribute to regulation of erythrocyte deformability through effects on shape and membrane elastic characteristics.

Erythrocyte Membrane↗
PubMed1978

Drug usage as determined under conditions of anonymity and high questionnaire return rate.

The present study had three principal purposes: (1) to collect, on one sample, information concerning lifetime usage of major drugs, overall frequency of usage, places and situations of initial usage, and exposure to drug usage through social group contacts; (2) to assure subjects of absolute anonymity in order to avoid biases introduced by identification of subjects; and (3) to obtain high questionnaire return rates in order to assure reduction of sample biases. A drug survey questionnaire dealing with marijuana, amphetamines, heroine, hallucinogens, tranquilizers, and antidepressants was administered in classroom settings to a total of 332 college students. Subjects did not record their names and thus were assured of complete anonymity. The return rate for questionnaires was 99.4%. Data were subgrouped for analysis to differentiate freshmen and upperclassmen and to differentiate males and females. For various subgroups, lifetime usage of marijuana and LSD ranged from 55 to 80.6% and from 14 to 30%, respectively. Current use ranged from 30.1 to 62.5% for marijuana and from 2.5 to 9.1% for hallucinogens. Sex differences were minimal, and usage levels were generally higher in upperclassmen than in freshmen.

Amphetamines↗
PubMed1977

Characterization of collagen precursors found in rat skin and rat bone.

Two genetic types of collagenous proteins, type I and type III, were isolated by extraction and differential salt precipitation from rat skin. The yield of collagen precursors was increased by injecting animals with colchicine 30 min before sacrifice to inhibit secretion of collagen. DEAE-cellulose chromatography was used to separate collagen from collagen precursors. Although these preparations contained more type I collagen than type III collagen, there were always more type III than type I precursors. The precursor chains of type I fractions were separated on CM-cellulose chromatography after denaturation. Three precursor forms were found for each collagen alpha chain, a complete chain (proalpha chain), and a precursor chain with only an amino-terminal (pNalpha chain) and carboxy-terminal extension (pCalpha chain). Species differences were demonstrated between rat collagen precursors and other species using rat calvaria (frontal and parietal) bones extracted with either 0.5 N acetic acid or neutral salt buffers containing protease inhibitors. Native rat procollagen elutes earlier than chicken or human procollagen on DEAE-cellulose chromatography and does not separate significantly from the pC collagen form. The collagenase resistant amino terminal peptides of rat pNalpha1 and pNalpha2 were the same size (16 000) but could be separated by DEAE-cellulose chromatography.

Animals↗
PubMed1977

Psychological differentiation, event uncertainty, and heart rate.

Psychological differentiation and uncertainty about receiving a painful noise were examined for their effects on heart rate during the anticipatory, impact and recovery phases of the tone presentation. Psychologically differentiated and nondifferentiated subjects were randomly assigned to three event uncertainty conditions (5 percent, 50 percent, 95 percent probability of noise). Subjects were informed of the probability of receiving the noise, as well as the time of occurrence as indicated by a sequentially numbered visual display. Subjects received the noise on the second of the experiment's two trials. Cognitive style and event uncertainty interacted during the anticipatory phase--i.e., differentiated subjects showed a monotonic increase in heart rate with increasing probability of receiving the noise that represents preparation for instrumental activity. Results are consistent with the theory that meaningful personality-stress relationships may be obtained when examining stimulus-oriented dispositions.

Acoustic Stimulation↗