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Biomedical subjects

J A Silverman

Publications and source records attributed to J A Silverman.

At least 73 records · Page 4Linked to original sources
PubMed1985

Analytical errors in measuring radioactivity in cell proteins and their effect on estimates of protein turnover in L cells.

Previous studies from this laboratory on protein turnover in 3H-labelled L-cell cultures have shown recovery of total 3H at the end of a 3-day experiment to be always significantly in excess of the 3H recovered at the beginning of the experiment. In this study we have critically reviewed a number of possible sources for this error in measuring radioactivity in cell proteins. 3H-labelled proteins, when dissolved in 0.3 M-NaOH and counted for radioactivity in a liquid-scintillation spectrometer, showed losses of 30-40% of the radioactivity; neither external or internal standardization compensated for this loss. Hydrolysis of these proteins with either Pronase or concentrated HCl significantly increased the measured radioactivity. In addition, approx. 5-10% of the cell protein is left on the plastic culture dish when cells are recovered in phosphate-buffered saline. To aggravate this latter loss further, this surface-adherent protein, after pulse labelling, contains proteins of high radioactivity that turn over rapidly and make a major contribution to the accumulating radioactivity in the medium. These combined errors can account for up to 60% of the total radioactivity in the cell culture. Similar analytical errors have been found in studies of other cell cultures. The effect of these analytical errors on estimates of protein turnover in cell cultures is discussed.

Animals↗
PubMed1985

Synthesis of protein in host-free reticulate bodies of Chlamydia psittaci and Chlamydia trachomatis.

Synthesis of protein by the obligate intracellular parasitic bacteria Chlamydia psittaci (6BC) and Chlamydia trachomatis (serovar L2) isolated from host cells (host-free chlamydiae) was demonstrated for the first time. Incorporation of [35S]methionine and [35S]cysteine into trichloroacetic acid-precipitable material by reticulate bodies of chlamydiae persisted for 2 h and was dependent upon a exogenous source of ATP, an ATP-regenerating system, and potassium or sodium ions. Magnesium ions and amino acids stimulated synthesis; chloramphenicol, rifampin, oligomycin, and carbonyl cyanide p-trifluoromethoxyphenylhydrazone (a proton ionophore) inhibited incorporation. Ribonucleoside triphosphates (other than ATP) had little stimulatory effect. The optimum pH for host-free synthesis was between 7.0 and 7.5. The molecular weights of proteins synthesized by host-free reticulate bodies closely resembled the molecular weights of proteins synthesized by reticulate bodies in an intracellular environment, and included outer membrane proteins. Elementary bodies of chlamydiae were unable to synthesize protein even when incubated in the presence of 10 mM dithiothreitol, a reducing agent which converted the highly disulfide bond cross-linked major outer membrane protein to monomeric form.

Bacterial Outer Membrane Proteins↗
PubMed1984

Deficient lung surfactant apoproteins in amniotic fluid with mature phospholipid profile from diabetic pregnancies.

An enzyme-linked immunoassay to quantitate lung surfactant apoproteins (15 to 250 ng/ml) in human amniotic fluid is described. The immunoassay was used to quantify lung surfactant in 72 samples of amniotic fluid, for which lecithin/sphingomyelin (L/S) ratios, lecithin and phosphatidylglycerol concentrations, and foam stability indices were also available. The results obtained with the immunoassay were in general agreement with those of the other methods. Measurement of the apoproteins, however, may be a better predictor of fetal lung immaturity and of respiratory distress syndrome than the L/S ratio and the concentration of lecithin. This conclusion is based on the data obtained in the analyses of samples of amniotic fluid from four diabetic and five nondiabetic pregnancies, the infants of which developed respiratory distress. In all cases, the apoprotein concentration was less than 2.1 micrograms/ml, which indicated fetal lung immaturity. In six of these cases (one diabetic and five nondiabetic pregnancies), lung immaturity was also predicted on the basis of other tests. However, in three other cases of diabetic pregnancy, the L/S ratio and lecithin concentration falsely indicated lung maturity. In addition to its being an effective predictor of fetal lung maturity in diabetic, as well as nondiabetic, pregnancies, the immunoassay is better suited for clinical use because of its high specificity, sensitivity, and ease of performance.

Amniotic Fluid↗
PubMed1984

Do maladaptive attitudes cause depression?

The Dysfunctional Attitude Scale (DAS) is an inventory of beliefs about life. These beliefs attribute happiness to external events and reflect absolute expectations for one's own behavior and that of others. Such beliefs, according to some cognitive theorists, predispose persons to depression. To test this theory, we administered the DAS to private psychiatric outpatients. Thirty-five patients were tested when they were depressed and again when they were asymptomatic. Dysfunctional thinking was found to be more prominent during depression; this finding implies that the dysfunctional thinking of depressed persons is a symptom of their illness rather than a character trait. Next, we compared DAS scores for recovered depressives with scores for other stabilized psychiatric patients and for normal persons. Bipolar patients demonstrated less maladaptive thinking than all other groups. Only the bipolars showed significantly less maladaptive thinking than the major depressives.

Adolescent↗
PubMed1984

Sources of error in estimating radioactivity in protein from cell cultures by liquid scintillation counting.

In this study, several common sample preparation techniques for liquid scintillation counting were critically reviewed. It has been shown that techniques such as NaOH or formic acid solubilization of trichloroacetic acid (TCA)-precipitated proteins led to underestimation of the radioactivity by 20-40%; this loss was not corrected by either internal or external standardization. Hydrolysis of the proteins with 6 N HCl or Pronase significantly increased the recovery of the labeled proteins. Also, 10% of the labeled cell proteins remained on the dish when cells were scraped into buffer; these labelled proteins could be recovered either by in situ hydrolysis with Pronase or by solubilization and scraping in 0.3 N NaOH. These techniques increased the recovered radioactivity by 50-60%, allowing quantitative measurements to be made over a 3-day chase period. A possible mechanism and the implications of this observation were discussed.

Animals↗
PubMed1983

Amniotic fluid lecithin, phosphatidylglycerol, L/S ratio, and foam stability test in predicting respiratory distress in the newborn.

Amniotic fluid phospholipids (lecithin, sphingomyelin, phosphatidylglycerol) were extracted and separated by the method of Gluck and associates. In addition, these lipids were quantified against standards that were concurrently developed in three adjacent thin layer chromatography (TLC) channels. A log-log transformation of the reflectance and concentration values provided rectilinear plots for quantification. A foam stability assay (FS) of 0.48 or greater was associated with high values of L/S ratio and lecithin concentration, and values of 0.44 or less almost always were associated with low values. Lecithin values of 12 micrograms/mL or more were associated with L/ S ratios of 2.0 or greater. Phosphatidylglycerol was detected consistently only when lecithin levels were 40 micrograms/mL or greater and L/S ratios 4.0 or greater. Case reviews indicated that: (1) FS test of 0.48 almost always was associated with pulmonary maturity in the newborn; (2) that a pulmonary maturity index combining the lecithin concentration and L/S ratio was a better predictor of pulmonary maturity in the newborn then either one alone; (3) that phosphatidylglycerol added little to this discrimination; and (4) that these assays showed no significant interpretative differences between diabetic and non-diabetic mothers.

Amniotic Fluid↗
PubMed1982

Adenine nucleotide and lysine transport in Chlamydia psittaci.

Isolated reticulate bodies of Chlamydia psittaci were found to transport ATP and ADP by an ATP-ADP exchange mechanism. ATP uptake activity was not detected in elementary bodies. The apparent Km of transport for both ATP and ADP was approximately 5 microM, and the calculated Vmax for both was about 1 nmol of nucleotide transported per min per mg of protein. ADP competitively inhibited ATP transport with a Ki of 4.5 microM. Other nucleotides tested had no effect on the uptake of ATP. A magnesium-dependent, oligomycin-sensitive ATPase (ATP phosphohydrolase, EC 3.6.1.3) was associated with reticulate bodies, and most of the transported ATP was hydrolyzed to ADP, which was exchanged for additional, extracellular nucleotide. Some ADP was hydrolyzed to AMP, which exited the cells slowly. Lysine was transported against the electrochemical gradient by reticulate bodies in the presence of ATP. Oligomycin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone inhibited ATP-dependent lysine transport. Lysine exited reticulate bodies when the reticulate bodies were incubated in the presence of ADP, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, or a reduced concentration of ATP. The results support the concept that chlamydiae are energy parasites which are capable of drawing upon the adenine nucleotides of their hosts, hydrolyzing ATP, and establishing an energized membrane.

Adenosine Diphosphate↗
PubMed1982

Liquid-chromatographic estimation of saturated phospholipid palmitate in amniotic fluid compared with a thin-layer chromatographic method for acetone-precipitated lecithin.

The "high-performance" liquid-chromatographic method we report for measuring palmitate derived from saturated phospholipids in amniotic fluid is sensitive and precise and possesses a wide dynamic range. Palmitate from nonsurfactant sources is largely excluded. The procedure involves oxidation of the chloroform/methanol-extracted lipids with osmium tetroxide, precipitation of the resulting phosphatides with cold acetone, mild alkaline hydrolysis, derivatization of the liberated fatty acids to phenacyl esters, and reversed-phase chromatography. The method is no less convenient or more time-consuming than measurement of the lecithin/sphingomyelin ratio by thin-layer chromatography. The clinical usefulness of the procedure is indicated by results of a correlative study of 26 amniotic fluids evaluated by "lung profile" tests in a second laboratory. A value for dipalmitoyl lecithin of 13 mg/L or greater indicates fetal lung maturity.

Acetone↗
PubMed1979

Body image and perfectionism of ballerinas: comparison and contrast with anorexia nervosa.

The authors studied a group of young ballerinas through responses to a questionnaire and intensive interviews. The young women described a life characterized by complete dedication in which academics, social life, and pleasures were sacrificed and a program of intensive exercise and practice became their main activity. They tended to feel overweight in spite of being thin and continued to diet or to employ other means to become even thinner. Two heuristic conclusions were reached: (a) the goal of thinness was in part a flight from conflicts about adult sexuality that arose at puberty; and (b) repetitive practice was engaged in for its own sake, not for career advancement, in an attempt to lose themselves in a transcendental quest for perfection. A comparison was made between this group and girls of the same age with anorexia nervosa. Several similarities but many more differences were found. Findings are based on a very small sample and must be interpreted cautiously, but directions for further studies are implied.

Adolescent↗
PubMed1977

Anorexia nervosa - the paucity of radiologic findings in more than fifty patients.

Anorexia nervosa is a self-imposed progressive starvation based on a psychiatric disorder. More than fifty patients (mainly adolescent girls) have had extensive radiologic evaluation. The radiographic findings are an absence of subcutaneous fat, with reduced muscle mass; the gastrointestinal findings are limited to moderate non-obstructive dilatation of small bowel loops with minimal effect on transit. These findings reflect the cachexia and in no way are diagnostic of anorexia nervosa per se.

Adolescent↗