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Biomedical subjects

J D Vincent

Publications and source records attributed to J D Vincent.

At least 163 records · Page 9Linked to original sources
PubMed1977

The effects of hypotension and hypovolaemia on the liberation of vasopressin during haemorrhage in the unanaesthetized monkey (Macaca mulatta).

Using unanaesthetized monkeys, experiments were performed to examine the effects of haemorrhage on the liberation of arginine vasopressin (AVP). Haemorrhages of 10%, 15% or 20% total blood volume were performed via a catheter with its tip in the abdominal vena cava. A catheter in the left internal jugular vein was used for blood sampling. Arterial blood pressure was monitored via a catheter whose tip resected in an iliac artery. The monkeys showed no signs of discomfort from this catheterisation. Blood samples for AVP assay were taken at different times from 0-90 min after the end of the haemorrhage. At the end of the experiment, blood removed was reinfused. Results show that haemorrhage resulted in liberation of AVP, but only if there was a fall in arterial blood pressure. AVP release occurred more readily as the total volume of blood withdrawn increased, but the absolute rise in hormone concentration was not related to the total volume of blood withdrawn. However, comparing the area under the curve of mean arterial blood pressure with that for AVP concentration showed the two to have a significant exponential relationship. It is concluded that, as in other species, haemorrhage is a potent stimulus for AVP liberation in the monkey. However, in contrast to some other species, the fall in arterial pressure seems to be the prime stimulus rather than hypovolemia per se.

Animals↗
PubMed1977

[Effect of some phosphonic amino acids on the activity of central neurons].

Microiontophoretic applications of DL-2-amino-3-phosphonopropionic, DL-3-amino-4-phosphonobutyric, aminomethylphosphonic, 2-aminoethylphosphonic and 3-aminopropylphosphonic acids in the course of extracellular recordings of central neurons in the Rat resulted in effects which appeared similar to those observed with their carboxylic analogs. The involvement of the same post-synaptic receptors is suggested.

Amino Acids↗
PubMed1976

Effects of estrogen on the electrical activity of identified and unidentified hypothalamic units.

Experiments performed on unanesthetized ovariectomized female rabbits demonstrated the effects of estradiol benzoate (EB; 20 microng i.v.) on the electrical activity of hypothalamic units which send their axons to the median eminence. Of a total of 1,840 cells recorded in hypothalamic and preoptic areas, 46 (2.5%) were antidromically activated by stimulating the median eminence. Under the present experimental conditions, EB induced a progressive diminution in the mean firing rate of these cells observed throughout the recording period (30-120 min). In addition to cells projecting to the median eminence, neurons which could not be antidromically invaded using our techniques were observed to be sensitive to estrogen. Estrogen administration produced a long-lasting inhibition of antidromically activated cells and a depression of much shorter duration (15-20 min) of unidentified nonstimulated units. These data suggest the existence of two types of hypothalamic neurons sensitive to estrogen.

Animals↗
PubMed1975

Hypothalamic supraoptic neurones: rates and patterns of action potential firing during water deprivation in the unanaesthetized monkey.

Extracellularly recorded action potentials were obtained from hypothalamic supraoptic neurones in unanaesthetized rhesus monkeys. Rates and patterns of firing were studied during an initial control period, during 5 successive days of water deprivation and during 4 further days when drinking water was again available. During water deprivation, plasma osmolarity increased progressively from about 300 mOsmoles/kg to about 340 mOsmoles/kg; control values were again reached after 3 days of rehydration. Systematic changes in action potential firing accompanied the changes in plasma osmolarity. Under control conditions, the majority of cells fire slowly and irregularly (type i), whilst a few cells exhibited phases of alternating activity and silence (type p). As dehydration progresses, the frequency of neuronal firing increase and the pattern of firing changes. By the third day the majority of cells are type p with few type i cells being found. By the fourth day, the population consists of type p cells with some others showing a high continuous rate of firing (type c). By the fifth day, these two cell types are found in approximately equal proportions. Rehydration of the animal reverses the situation. We propose that type i cells contribute little, if at all, to hormone secretion, while type p and type c cells would be in a more actively secreting state. According to this view, the three firing patterns would represent different activity states of the same functional population stimulated by the unspecific stimulus of water deprivation rather than functionally different neurones. However, the use of stimuli which selectively release either oxytocin or vasopressin may be needed to answer this problem.

Action Potentials↗
PubMed1975

Effect of ovariectomy and estradiol benzoate treatment on LH-RH induced LH and FSH release in the female rabbit.

Synthetic LH-RH (0.75 and 2.5 mug/animal) was administered to mature intact and castrated female rabbits. The animals were injected for 3 consecutive days with either 40 mug estradiol benzoate (EB) dissolved in 0.5 ml propylene glycol 60%, water 40% or with the solvent alone. LH-RH was injected i.v. on the 4th day. In intact rabbits EB priming increased the pituitary LH response while LH basal levels were lowered. In the unprimed castrated rabbits, basal FSH and LH levels and the cumulative responses to LH-RH were higher than in intact control animals; EB priming lowered basal LH levels and cumulative responses to the values of intact control rabbits while both basal FSH levels and the cumulative responses were less influenced by the treatment. It is concluded that estrogen acts at both hypothalamic and pituitary levels to modify the LH responses to endogenous LH-RH, and that the complete inhibition of FSH hypersecretion in the ovariectomized rabbit probably needs another ovarian factor.

Animals↗
PubMed1974

Firing patterns of hypothalamic supraoptic neurons during water deprivation in monkeys.

Water deprivation in monkeys caused an acceleration of action potential firing of supraoptic neurons, but not of neurons located 2 to 3 millimeters above the hypothalamic supraoptic nucleus. Whereas in the normally hydrated animal only 12 percent of the neuroendocrine cells discharged periodically, the proportion of these periodic bursters increased markedly with increasing plasma osmolarity. This finding suggests that such periodically firing supraoptic neurons are those engaged in active neurohypophyseal hormone secretion.

Action Potentials↗