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Biomedical subjects

R Duncan

Publications and source records attributed to R Duncan.

At least 253 records · Page 14Linked to original sources
PubMed1981

Phosphorylation of ribosomal protein S6. Relationship to protein synthesis in HeLa cells.

The time course of S6 phosphorylation and several aspects of protein synthesis have been studied in suspension cultures of HeLa cells, following transfer to fresh medium and serum. The phosphorylation of S6 is not temporally correlated with changes in polypeptide initiation and elongation rates, as judged from polysome profiles. Phosphorylation of S6 can be maximal within 30 min after transfer; elongation and initiation rates increase coordinately and more slowly, becoming maximal about 6 h after transfer, a time at which the net phosphorylation of protein S6 is greatly reduced or negligible. Recruitment of messenger RNA into polysomes is another response to fresh medium and serum; this response occurs almost as rapidly as the phosphorylation of S6. We suggest that the phosphorylation of S6 may play a role in messenger RNA recruitment.

HeLa Cells↗
PubMed1981

Ethylenediaminetetraacetic acid (disodium salt)-labile bovine immunoglobulin M Fc binding to Brucella abortus: a cause of nonspecific agglutination.

It was demonstrated by a radioimmunoassay procedure that Brucella abortus agglutinins from noninfected cattle sera, absorbed to B. abortus antigen and eluted with ethylenediaminetetraacetic acid (EDTA), was immunoglobulin M that bound to that bacterium by its Fc portion. The EDTA-eluted immunoglobulin M agglutinated intact B. abortus cells but not erythrocytes treated with B. abortus lipopolysaccharide. The specificity of the EDTA-eluted immunoglobulin was for B. abortus, although a small titer to Yersinia enterocolitica serotype O:9 was observed. In contrast, immunoglobulin M purified from the serum of a cow injected 7 days previously with heat-killed B. abortus bound to the antigen by its Fab portion, was not labile to EDTA treatment, cross-reacted extensively with Y. enterocolitica serotype O:9, and agglutinated various other bacterial antigens and normal erythrocytes.

Animals↗
PubMed1981

Behavioural action of androgen in the dove: effects of long-term castration on response specificity and brain aromatization.

Differences in the effectiveness of oestradiol-17 beta and testosterone on male courtship and vocal behaviour were examined in long-term castrated doves. Nest-orientated behaviour was restored by intramuscular injection of oestradiol-17 beta. Testosterone was effective in restoring aggressive courtship and vocal behaviour, but not for the nest-orientated behaviour. The effects of these hormones were separable, therefore, under conditions of prolonged androgen deficit, suggesting differences in their specificity of action. In-vitro assay of brain enzyme activity indicated that aromatization of testosterone to oestradiol-17 beta occurred in the preoptic area of long-term castrated doves. Preoptic aromatase activity of long- and short-term castrated doves did not differ. The ineffectiveness of testosterone in restoring nest-orientated behaviour in long-term castrated doves did not appear, therefore, to be due to a difference between the groups in the basal rate of testosterone aromatization in the preoptic area.

Animals↗
PubMed1979

Mechanism of polycation stimulation of pinocytosis.

Synthetic polycations cause a stimulation in the rate of tissue accumulation of colloidal 198Au by the rat visceral yolk sac (at 17.5 days of gestation) and rat peritoneal macrophages cultured in vitro. The mechanism of stimulation has been elucidated in these two cell types by using a dual-substrate technique, and by examining the differential effects of poly(D-lysine) and poly(L-lysine) and of metabolic and cytoskeletal inhibitors. Polycations cause aggregation of colloidal 198Au in the culture medium and increase its affinity for the plasma membrane. In the rat peritoneal macrophage this polycation-colloidal gold complex is pinocytosed, thus enhancing the intracellular accumulation of the radio-labelled substrate. In contrast, the rat visceral yolk sac cannot internalize this complex, and so the substrate accumulates extracellularly. This mechanism of polycation modification affords the opportunity for differential uptake of a substrate into distinct cell types.

Animals↗
PubMed1978

Pinocytosis in the rat visceral yolk sac. Effects of temperature, metabolic inhibitors and some other modifiers.

Low temperature,2,4-dinitrophenol and moniodoacetate could each completely abolish the pinocytic uptake of 125I-labelled polyvinylpyrrolidone, 125I-labelled bovine serum albumin or colloidal 198 Au by 17.5-day rat visceral yolk sac cultured in vitro. Cytochalasin B and colchicine caused a partial and dose-dependent inhibition. It is concluded that the mechanism of pinocytic uptake of these substrates is not micropinocytosis as conventionally defined. Removal of extracellular calcium or the presence of theophylline inhibited liquid-phase pinocytosis by the rat yolk sac, whereas addition of ouabain caused a biphasic response: a slight stimulation of pinosome formation at a low concentration, and an inhibitory effect at a higher concentration.

Animals↗
PubMed1978

Spontaneous 51Cr release by isolated rat hepatocytes: an indicator of membrane damage.

Radiochromium uptake and release by isolated rat hepatocytes in suspension was monitored under continuous-labeling conditions. Cell protein remained unchanged during the absorption phase, whereas the release of 51Cr correlated well with the loss of cell viability and release of cytoplasmic protein. The results suggest that under equilibrium conditions, 51Cr release represents an efflux of label from damaged or dying preparations and not an elution of radioisotope from intact cells.

Ammonium Chloride↗
PubMed1970

Wringer injuries.

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Accidents, Home↗
PubMedDate not supplied

The chemotherapy of colon cancer.

Despite extensive clinical trials, mortality from colon cancer has remained essentially unchanged since the 1950s. However, the increasing numbers of complete and partial responses seen in clinical trials suggest that colon cancer can be successfully treated by chemotherapy, but only if the antitumour selectivity can be increased by a substantial amount. This will be possible by the introduction of new drugs with more precise mechanisms of action, such as those acting specifically on signalling or cell cycle control pathways shown to be aberrant in colon cancer. Alternatively, the selectivity of present day agents may be increased considerably by the selective activation of prodrugs in tumours (ADEPT) or by targeting them to tumours using polymers. Other new approaches using vaccines or some form of gene therapy will potentiate present chemotherapy, while the introduction of positron emission tomography (PET) scanning will allow the rapid detection of agents with activity that would have been missed by conventional measurements of response.

Antineoplastic Agents↗