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At least 739 records · Page 41Linked to original sources
PubMed1979

Overview of ventilatory control during exercise.

Practically every respiratory physiologist of the last 100 years has studied the ventilatory response to exercise. Yet we still do not know the cause of increased ventilation associated with exercise. This overview considers the problem from a broad observational point of view. Data from studies combining exercise with continuous inspired CO2 and "slug" CO2 breathing imply a feed-forward/feed-back structure for the ventilatory controller. The feed-forward stimulus is correlated to CO2 production. Feed-back senses arterial CO2 tension and acts to minimize the effects of correlation errors and correlation slope errors in the feed-forward path. This feed-forward/feed-back structure yields a regulated arterial CO2 and a tight coupling of ventilation to CO2 production. The feed-back mechanism acts via the carotid body, and indirectly via the central chemoreceptor. A variety of mechanisms are discussed that may be involved in providing the feed-forward stimulus. In particular, the intravenous loading experimental results are considered in terms of an appropriate feed-forward stimulus.

Animals↗
PubMed1977

Studies on experimental mixed infection of Schistosoma haematobium and Schistosoma mansoni in the albino mouse.

Swiss albino mice have been infected with S. haematobium and challenged with S. mansoni. No apparent disturbances as regards worm load and oviposition were observed. Yet certain deviations in the egg-distribution sites for both species were found. They were attributed to the possibility of earlier de-development of collateral circulation. Cross-pairing between the two species was met with, which might explain the extra number of S. haematobium eggs found in the small intestine. Although no major effect has been revealed, no conclusion at this stage could be put forward as regards complete absence of cross-immunity.

Animals↗
PubMedDate not supplied

Monocytogenic endothelialization in dacron grafts. Experimental studies on rats.

The cytogenetic relationship between cells of the hematopoetic system and prosthesis lining cells is still not known. The purpose of this experimental study was to determine to what degree blood monocytes may be transformed into those cells which line the inner surface of vascular grafts. Immunological identical rats (donors = 25) were pretreated with a total dose of 150 micrograms C 3H-thymidine. In 25 recipient rats of the same strain the infrarenal aorta had been replaced by a vascular graft of dacron (1.8 mm theta) by using microsurgical techniques. Arteriovenous cross-transfusion was installed in pairs of the donor and recipient animals allowing for mixing the total blood volumes of both many times. Following sacrifice of the recipients the grafts and the area of anastomosis were studied autoradiographically. In all animals labelled monocytes were found in the graft wall with a marking index (MI) running between 1.5% to 5.5%. The marking index of the prosthesis lining cells was 1.9% to 3.4%. In 6 animals the anastomotic area was labelled and the MI run from 1% to 7.5%. With this new experimental model we ascertained that blood monocytes have capability of transformation: our results would indicate the hematogenic origin of new endothelial cells on prosthetic vascular surface by transformation of blood monocytes. This appears to apply to the prosthetic wall as well as the inner surface lining cells and the neighbourhood of the anastomotic area.

Animals↗
PubMed1983

Inotropic and anesthetic potencies of etomidate and thiopental in dogs.

The effects of etomidate and thiopental on myocardial contractility were compared in 10 experiments on isolated papillary muscle preparation perfused by a conscious donor dog. Equianesthetic doses of etomidate (1.4 mg/kg) and thiopental (15.5 mg/kg) were determined separately in conscious dogs. Tension developed by the papillary muscle decreased significantly less after etomidate (17 +/- 2%) than after thiopental (33 +/- 3%) (P less than 0.002) when injected intravenously in equianesthetic doses in donor dogs. When added to arterial blood perfusing the papillary muscle, etomidate had 4-5 times more negative inotropic effect than thiopental. At the same time, the anesthetic potency of etomidate was approximately 11 times greater than that of thiopental. We conclude that both etomidate and thiopental produce a dose-dependent direct negative inotropic effect but that in equianesthetic doses, etomidate causes less pronounced depression of myocardial contractility than thiopental.

Anesthetics↗
PubMed1978

Humoral stimulation of cell proliferation in small bowel after transection and resection in rats.

Possible humoral involvement in the control of postresectional intestinal adaptation was tested in individual rats and in pairs of rats connected in vascular parabiosis for 48 hr. In individual rats, transection of the jejunum produced transient mucosal hyperplasia in the mid and distal small intestine, independent of the effect of laparotomy and of handling the bowel. Jejunal resection caused more intense and sustained distal hyperplasia, with increases in midbowel RNA content (38%), DNA content (16%), and DNA specific activity (68%) over values 48 hr after transection. In parabiotic rats, both transection and resection of the jejunum in one partner stimulated mucosal uptake of [H]TdR in the intact parabiont; increments of 59 to 128% in total radioactivity and in specific activity of DNA were found in the mid and distal small intestine of the intact parabiont. Because only rats actually undergoing abdominal operations had higher mucosal nucleic acid contents than their parabiotic partners, the transmitted response was weaker than the direct response. Systemic factors as well as local (topical) stimulators appear to be involved in adaptation of the shortened gut.

Animals↗
PubMed1981

[Inappropriate thyrotropin secretion. Part 2: non tumoral (author's transl)].

Some patients are clinically euthyroid despite high thyroid hormones levels associated with detectable but not elevated serum TSH. These patients are considered as being resistant to thyroid hormones. The resistance may be severe or partial and in most cases seems to be autosomal dominant; it affects some tissues more than others, thus giving rise to a variety of clinical symptoms. In a few patients with high TSH levels extensive studies have failed to provide evidence of pituitary tumour of resistance to thyroid hormones; the cause of TSH hypersecretion in such cases remains uncertain. Several factors (non specific serum proteins, cross-reactivity circulating antibodies) may result in falsely high T3, T4 and TSH values on radioimmune assays and must be carefully investigated in the presence of unexpectedly high serum TSH levels.

Child↗