Search PubMed⌕ Search

Biomedical subjects

C Bell

Publications and source records attributed to C Bell.

At least 307 records · Page 17Linked to original sources
PubMed1973

Oestrogen-induced sensitization of the uterine artery of the guinea-pig to acetylcholine.

1. It has been shown previously that a dilatation of the uterine artery of the guinea-pig in response to acetylcholine or to stimulation of cholinergic vasodilator nerves occurs only during pregnancy. Experiments have now been performed to determine the hormonal basis of this change in responsiveness.2. Chronic treatment of virgin guinea-pigs with oestradiol, either by intramuscular injection or by subcutaneous implantation, caused the development of a responsiveness of the uterine artery to acetylcholine which was similar in degree to that occurring during pregnancy.3. Simultaneous administration of progesterone did not significantly inhibit this oestrogen effect. In contrast the characteristic actions of oestrogen on uterine growth and fat catabolism were completely antagonized by progesterone.4. The time course of the development of responsiveness to acetylcholine of the uterine arteries during pregnancy was parallel to the rises in oestrogen production and placental blood flow as determined by other workers. This supports the concept that cholinergic dilator nerves participate in uterine hyperaemia during pregnancy and that their functioning is regulated by the maternal blood oestrogen level.

Acetylcholine↗
PubMed1971

Eression of allelic immunoglobulin in homozygous rabbits injected with RNA extract.

Ribonucleic acid extracts obtained from lymph nodes of immunized rabbits homozygous for the b(4)or b(5)allele of light chain immunoglobulin allotypes were injected intravenously into nonimmunized rabbits homozygous for the alternate allele. Approximately 30 percent of the plaque-forming cells in the spleen yielded plaques with immunoglobulin M antibody possessing the allotype of the RNA donor. The allotype of the RNA donor was also found in the IgG immunoglobulin of lymphoid cell lysates as well as in the IgG isolated from the serum. These results suggest that the injected RNA has an informational role in the in vivo synthesis of immunoglobulins by host lymphoid cells.

Alleles↗
PubMed1971

Release of endogenous noradrenaline from an isolated muscular artery. Release of endogenous noradrenaline from an isolated muscular artery.

1. The release of noradrenaline by field stimulation of vasoconstrictor nerves has been studied in isolated preparations of the main uterine artery of the guinea-pig.2. In preparations from virgin animals stimulation with trains of 3000 square pulses at 5 and 25 pulses/sec resulted in mean overflows of 0.56 ng/g.pulse and 1.53 ng/g.pulse respectively.3. Inhibition of monoamine oxidase and catechol-O-methyltransferase had no consistent effect on overflow at either stimulation frequency.4. Desmethylimipramine (10(-5)M) caused, on the average, a 2.4-fold increase in overflow following stimulation at 5 pulses/sec while phenoxybenzamine (10(-5)M) caused a 3.8-fold increase. Neither of these drugs caused a significant alteration of the overflow during stimulation at 25 pulses/sec.5. Treatment of the tissues with desmethylimipramine plus normetanephrine (4.5 x 10(-4)M) caused no more increase in overflow than treatment with desmethylimipramine alone.6. It is concluded that enzymatic metabolism of noradrenaline at the synapse is of little functional importance in this tissue, and that the most important mechanism of transmitter inactivation is by nervous re-uptake. Although phenoxybenzamine was more effective than desmethylimipramine in increasing transmitter overflow, no evidence was obtained to support the view that this effectiveness was due partly to blockade of ;Uptake 2'.7. There was sometimes very low overflow of noradrenaline from arteries taken from animals in the last week of pregnancy. In these instances overflow following stimulation at 5 pulses/sec was not increased by phenoxybenzamine treatment of the tissue.8. Methylene blue and fluorescence microscopic techniques indicated that the terminal adrenergic axons in each artery possess approximately 8.74 x 10(5) varicosities. The mean tissue content of noradrenaline was found to be 9.6 mug/g or 29 ng/artery. These results have been correlated with known morphological and electrophysiological data to derive a peak post-junctional concentration of noradrenaline during transmission of about 4 x 10(-4)M.9. The fraction of total noradrenaline content of the artery released per pulse (under the influence of phenoxybenzamine) had a mean value of 2.2 x 10(-4).

Animals↗