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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 649 records · Page 36Linked to original sources
PubMed1980

Localization of globin gene replication in Friend Leukemia cells to a specific interval of the S phase.

Murine erythroblastic leukemia cells, infected with Friend leukemia virus, were grown and synchronized in suspension culture by a double-block procedure involving medium depletion and treatment with excess thymidine. Replicating cultures were then caused to synthesize DNA during the early, middle, or late third of the S period with bromodeoxyuridine as a precursor. The bromodeoxyuridine density-labeled DNA and normal DNA were isolated by sedimentation in a cesium chloride density gradient and analyzed for the level of globin-specific DNA by hybridization with radioactive cDNA of the globin messenger RNA. Globin genes were found to be replicated near the end of the middle third of the S phase. The incorporation of bromodeoxyuridine into DNA also resulted in a lowered induction of hemoglobin synthesis in dimethyl sulfoxide-treated cells. In this case, the sensitivity was correlated with the introduction of bromodeoxyuridine into DNA replicated in early S phase. The possibility that this fraction of DNA, which is low in globin gene content, carries genes regulating the erythroid differentiation or the expression of globin genes is discussed.

Animals↗
PubMed1980

Bone-marrow microenvironment defect in congenital hypoplastic anemia.

An abnormal bone-marrow microenvironment has been thought to have an important role in the pathogenesis of aplastic and hypoplastic anemia in some patients, but direct evidence of such a defect has not been found. We have investigated the pathogenesis of chronic anemia in a young woman. Her bone-marrow cells, obtained by means of aspiration, showed exuberant erythroid growth in methylcellulose despite marked erythroid hypoplasia. The erythroid nature of the colony growth was further confirmed through measurement of heme synthesis and messenger RNA-globin accumulation in a liquid-culture system. In contrast, when whole bone fragments were similarly cultured, no appreciable hemoglobin synthesis was observed. The experimental evidence suggests that, in this patient, hypoplastic anemia resulted from an unfavorable microenvironment.

Adult↗
PubMed1980

Influence of hyperthyroidism on the superprecipitation response and Ca2+-sensitivity of natural actomyosin in cardiac and skeletal muscle.

In cardiac natural actomyosin prepared from hyperthyroid rabbits, the time of onset of the superprecipitation response was shortened by 58% and the rate of response was increased 4-fold compared with euthyroid animals. However, Ca2+-sensitivity of cardiac natural actomyosin prepared from either euthyroid or hyperthyroid rabbits was not changed over the range of 10(-7) to 6.6 . 10(-5) M free Ca2+ concentrations. Skeletal natural actomyosin prepared from either euthyroid or hyperthyroid rabbits showed a far higher Ca2+-sensitivity than cardiac natural actomyosin, but there was no difference in either time of onset or rate of superprecipitation response.

Actomyosin↗
PubMed1980

Size constancy fails below half a degree.

Size constance is a term used to refer to the fact that objects seem to maintain size as their distance from an observer changes, despite change in image size. It is known that size constancy has limits. People seen from the top of tall buildings look small. By observing objects, including the Moon, and after-images, we demonstrate here that size constancy holds when image size is above half a degree, and breaks down when it is less. In other words, image size is scaled for distance only when image size is above half a degree.

Figural Aftereffect↗
PubMed1980

Sleep apnea syndrome and supraglottic edema.

Obstructive sleep apnea is becoming more widely recognized. Otolaryngologists will be called upon to evaluate affected patients and offer consultation as to the appropriateness of surgical intervention. The extent to which this syndrome is attributable to edema of the larynx and hypopharynx is unknown. It may, on occasion, explain chronic fatigue, weight loss, and daytime somnolence seen in some patients following irradiation of the head and neck. Sleep apnea associated with upper airway obstruction can be confirmed by polysomnography during sleep. Monitoring the EEG, electro-oculogram, electromyogram, ECG, airflow, and respiratory effort allows differentiation of obstructive sleep apnea from central or mixed apnea. Once the diagnosis of obstructive sleep apnea is established, treatment consists of correcting the airway obstruction.

Adult↗
PubMed1980

Antibody levels in mothers colonised with group B streptococci during pregnancy and in their newborn infants, as measured by an enzyme linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was developed to measure serum antibodies to group B streptococci in 20 healthy pregnant women before delivery and in their newborn infants. The sera from 10 of these women who were colonised with group B streptococci and umbilical cord sera from their infants, had higher levels of type-specific IgG antibody than the 10 non-colonised controls and their neonates. All the babies remained well. The results demonstrate that infants from colonised mothers receive type-specific antibody. The possibility that this antibody may provide some degree of protection at birth against this potentially lethal organism warrants investigation.

Antibodies, Bacterial↗
PubMed1980

Improvement in ventricular function during exercise studied with radionuclide ventriculography after cardiac rehabilitation.

A heterogeneous group of 19 consecutive patients with coronary artery disease were studied with radionuclide ventriculography before and after a mean of 6 months of exercise training. Ejection fraction was measured at rest, at matched submaximal supine work loads and during maximal supine bicycle exercise. After training there was no change in mean ejection fraction at rest or during maximal exercise, but a higher maximal mean systolic blood pressure, heart rate and work load were achieved. At equivalent submaximal work loads after training, similar levels of mean heart rate and systolic blood pressure were reached but a statistically greater mean ejection fraction was obtained. These preliminary results suggest that exercise training may improve cardiac function during exercise in selected patients with coronary disease. A randomized study using similar techniques has been initiated.

Adult↗
PubMed1980

Oscillations and efficiency in glycolysis.

We suggest that temporal oscillations of concentrations of intermediates in biochemical reaction systems may enhance the efficiency of free energy conversion (reduce dissipation) in those reactions. Experiments on glycolysis are used to estimate the Gibbs free energy changes along the glycolysis mechanism, and to postulate a construct for the glycolysis "machine" which involves: the PFK reaction as the primary oscillophor; the GAPDH reaction as a phase-shifting device; and the PK reaction with the property of intrinsic oscillatory response at resonance with the driving frequency. Analysis of a simple reaction mechanism with these postulated properties shows that the conversion of free energy from reactants to products is more efficient in an oscillatory than a steady state operation. The efficiency of free energy conversion in glycolysis from glucose + ADP to products + ATP is estimated to be increased by 5--10% due to oscillations. This may have been relevant for the evolutionary development of oscillations such as in glycolysis, especially in anaerobic cells.

Glyceraldehyde-3-Phosphate Dehydrogenases↗
PubMed1980

Processing of human beta-globin mRNA precursor to mRNA is defective in three patients with beta+-thalassemia.

Nucleated bone marrow cells from normal individuals and from three patients with homozygous beta+-thalassemia were pulse-labeled with tritiated nucleosides. The processing of the newly synthesized globin mRNA precursors was monitored by inhibiting additional transcription with actinomycin D for 30 min. Human beta-globin mRNA is derived from its precursor via a series of reactions that generate processing intermediates. In nonthalassemic cells the precursor is processed efficiently to mature mRNA during the chase. In contrast, in beta+-thalassemic cells the processing of beta-globin RNA is defective. In one patient the beta-globin mRNA precursor turns over during the chase, but some of the intermediate RNAs accumulate and are not processed to mRNA. In two other patients a large fraction of the precursor and intermediate RNAs is not processed to mRNA. The alpha-globin mRNA precursor and intermediates are processed efficiently to mRNA-sized molecules in thalassemic and normal cells. The reduction in the rate of beta-globin but not alpha-globin RNA processing accounts for the alpha/beta globin mRNA imbalance in thalassemic erythroid cells. We discuss the possibility that the genetic lesions in beta+-thalassemia are at splicing signal sites within intervening sequences of the beta-globin gene.

Bone Marrow↗
PubMed1980

Detection of latent coronary stenosis in conscious dogs: regional functional and electrocardiographic responses to isoprenaline.

A conscious animal model was developed in which coronary stenosis could be produced while regional myocardial function and local surface electrocardiograms were measured. Responses to isoprenaline stress in the presence of mild (latent) coronary stenosis were then examined. In the absence of coronary stenosis, isoprenaline produced increases in regional function and no change in the surface VCG; at higher doses, increases in the endocardial ST segments occurred. After partial coronary stenosis, which produced no apparent regional dysfunction or electrocardiographic changes, isoprenaline infusion for 3 min (0.02 microgram . kg-1 . min-1) rapidly produced decreases in percentage wall thickening (average 17 +/- 4%, mean +/- SE, P < 0.01) and increases in the mean sum of VCG ST segments by 0.23 +/- 0.06 mV (P < 0.05). 1 min after stopping isoprenaline, most dogs showed further significant deterioration of both measures of ischaemia, but by 5 min there was no significant mean change from control. We conclude that in the presence of latent partial coronary stenosis, stress due to mild sympathomimetic stimulation alone can rapidly induce regional myocardial ischaemia. Deterioration of regional myocardial contractile function during such stress can provide as sensitive means of detecting latent coronary obstruction.

Animals↗
PubMed1980

Improvement by isosorbide dinitrate of exercise-induced regional myocardial dysfunction.

Sonomicrometry was used in 10 conscious dogs to measure regional segment length and dynamic wall thickness by telemetry in a zone supplied by the left circumflex coronary artery after implantation of an ameroid constrictor. When coronary obstruction was nearly complete and collaterals had developed (24-42 days), control exercise and exercise runs after oral isosorbide dinitrate were carried out. During control runs, significant increases occurred in hemodynamic parameters, and percent shortening in normal segments increased (P < 0.01). During the repeat runs after isosorbide dinitrate, there were smaller increases in left ventricular systolic and end-diastolic pressures and significantly reduced end-diastolic dimensions. In addition, percent wall thickening and percent segment shortening in the ischemic zone did not deteriorate significantly during exercise. In this animal model, which appears to mimic chronic single-vessel coronary heart disease, isosorbide dinitrate can prevent exercise-induced deterioration of regional myocardial function.

Animals↗