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Biomedical subjects

H Seitz

Publications and source records attributed to H Seitz.

54 records · Page 3Linked to original sources
PubMed1989

Effect of capsaicin on gastric corpus smooth muscle of the rat in vitro.

Circular strips of the rat gastric corpus muscle were mounted in Krebs solution for isometric tension recording. Addition of capsaicin usually led to either relaxation or contraction, but in some strips a biphasic response was observed. Although no clear-cut concentration-response relationship could be established, capsaicin predominantly induced contraction at 500 nM, whereas at 5 microM it mainly induced relaxation. In Krebs solution containing atropine plus guanethidine, the contraction induced by 500 nM capsaicin was significantly reduced. The contraction induced by capsaicin was abolished by spantide, a tachykinin antagonist, or by tachyphylaxis to substance P. Calcitonin gene-related peptide relaxed gastric smooth muscle, however, a dose-response relationship could not be established. This peptide contracted the muscle strips only at 1 microM. Tachyphylaxis to calcitonin gene-related peptide did not significantly influence the action of capsaicin. Vasoactive intestinal polypeptide dose dependently relaxed gastric corpus strips; however, these responses were qualitatively different from those to capsaicin. It is concluded that capsaicin contracts rat gastric smooth muscle via the release of tachykinins; cholinergic interneurones are involved. The mediator of the capsaicin-induced relaxation has yet to be determined.

Animals↗
PubMed1987

Contractile effects of substance P and neurokinin A on the rat stomach in vivo and in vitro.

Substance P and neurokinin A (substance K) were infused into the coeliac artery of anaesthetized rats at doses of 0.06-20 nmol min-1. Both tachykinins caused contractions of the stomach, the threshold dose of neurokinin A being 10 times lower than of substance P. The dose-response curve for substance P was flatter than that for neurokinin A. On circular muscle strips from the rat gastric corpus in vitro, the dose-response curves for both tachykinins were parallel, neurokinin A being 10 times more potent than substance P. The contractions in response to 10 microM neurokinin A and to 30 microM substance P were 58 and 54%, respectively, of the maximal contraction to bethanechol (1 mM). The effect of substance P was reduced by atropine both in vivo and in vitro. In vitro, the contractions to substance P were also reduced by tetrodotoxin but left unaffected by methysergide. The action of neurokinin A was not affected by these drugs. It is concluded that neurokinin A contracts rat stomach by a direct action on the circular smooth muscle, whereas the action of substance P is mediated, at least in part, by cholinergic interneurones.

Animals↗
PubMed1983

[Cytoprotection with antacids?].

Prostaglandins in very low concentrations which do not inhibit acid secretion protect the mucosa of the gastrointestinal tract against a great number of noxious agents. The protective action of various antacids is likely to be related to its acid neutralizing capacity. Antacids do not prevent lesions evoked by direct necrotising substances such as concentrated ethanol etc. It remains to be established whether the endogenous prostaglandin system is involved in the antiulcerogenic action of some antacids.

Animals↗
PubMed1982

Non-specific cell mediated immunity in patients infected with Schistosoma mansoni in Kenya.

Parameters of in vitro cell-mediated immunity (CMI) have been measured in the local Kenyan population infected with Schistosoma mansoni. Lymphocyte responses to the non-specific T cell mitogens Concanavalin A (Con A) and Phytohaemagglutinin (PHA) were reduced in about 60% of schistosomiasis patients. Lymphocytes from control uninfected, and S. mansoni-infected donors formed equal numbers of spontaneous rosettes with sheep red blood cells, indicating that there was no over-all reduction in the percentage numbers of T cells in the schistosomiasis patients.

Adolescent↗
PubMed1982

Stimulation of thymidine incorporation in isolated rat intestinal mucosal cells by feeding an ethanol-containing liquid diet.

The effect of chronic ethanol administration on the incorporation of 3H-thymidine into DNA of isolated intestinal cells in the rat was investigated. Chronic ethanol consumption increased significantly DNA synthesis in intestinal mucosal cells. Whether this enhancement of DNA synthesis as a measure for cellular regeneration is due to the local effect of ethanol via tissue injury, to a direct stimulatory effect of ethanol on enzyme activities involved in DNA metabolism or to a change in the intestinal cell population with a shift to immature crypt cells by ethanol is not known.

Animals↗
PubMed1981

Effect of intravenous ethanol on pancreatic secretion in the conscious rat.

To study whether the secretory state of the in vivo pancreas affects its response to ethanol, we administered ethanol intravenously to conscious rats in the presence and absence of exogenous secretin. In the absence of secretin when pancreatic secretion was maintained at basal levels, intravenous ethanol produced a significant stimulation of the flow rate, bicarbonate concentration, and protein concentration. This response persisted despite elimination of gastric acid production by infusion of the H2 receptor antagonist cimetidine. In contrast, intravenous ethanol inhibited the flow rate and bicarbonate concentration when pancreatic secretion was augmented by the infusion of GIH secretin. Thus, the rat pancreas responds differently to intravenous ethanol in the basal and secretin-stimulated states. These results may account for the lack of agreement regarding the pancreatic effects of systemic ethanol.

Animals↗
PubMed1980

Breath acetaldehyde: evidence of acetaldehyde production by oropharynx microflora and by lung microsomes.

After alcohol ingestion, acetaldehyde is found in expired air and is thought to originate from blood. However, we found that the ratio of acetaldehyde to ethanol was higher in dead space than in alveolar (end-expiratory) air. This observation suggested production of acetaldehyde in the airways. To study this, we washed the mouth of normal subjects with 10 ml of either saline or 5 mM ethanol. Washings with ethanol produced 5.1 +/- 1.3 nmol/ml of acetaldehyde per minute (vs none with saline). Saline mouth washings incubated with ethanol produced acetaldehyde. This reaction could be prevented by boiling or by microfiltration of the washings suggesting that it was due to microbial enzymes of the oropharynx. We also studied the possibility of pulmonary production of acetaldehyde. Rat lung slices produced 1.32 +/- 0.19 mnol of acetaldehyde/g lung (wet weight)/minute; microsomal production of acetaldehyde was also detected and this was enhanced by chronic ethanol feeding.

Acetaldehyde↗
PubMedDate not supplied

Biocompatibility of polyethylene terephthalate (Trevira hochfest) augmentation device in repair of the anterior cruciate ligament.

The biocompatibility of a 3 mm band made of polyethylene terephthalate (Trevira hochfest) has been tested in an experimental study within right knee joints of 60 sheep. After transsecting the anterior cruciate ligament (ACL), two randomized groups were formed. In group I, the ACL was repaired according to the Marshall technique whilst in group II an additional 3 mm polyethylene terephthalate (PET) augmentation band was implanted using the through-the-condyle (TTC) procedure. To assess the biocompatibility of the augmentation device the knee joints of both groups were punctured and the synovial fluids were analyzed before, as well as 2, 6, 16, 26, and 52 weeks after the operation. In addition, the histologic appearance of excised suprapatellar pouches and ipsilateral inguinal and popliteal lymphatic noduli were examined. Comparing both groups no significant differences were found neither before nor after the augmented and non-augmented ACL repair. No pathological increase in the total protein concentration occurred after operation and no significant differences versus the preoperative analysis were found. No synovitis signalling a decrease in the glucose concentration was observed. The cytological examination revealed no increase of the leukocyte cell count results. Within the synovial specimen neither free nor phagocytosed PET wearparticles could be detected. In groups I and II the histological appearance of excised popliteal and inguinal lymphatic noduli showed a normal result. In 25% of the PET augmented ACL repairs, a slight concentration of PET wearparticles and solitary, multinuclear giant foreign body cells could be seen in the histological preparations of suprapatellar pouches.

Animals↗
PubMedDate not supplied

Functional domains of DnaA proteins.

Functional domains of the initiator protein DnaA of Escherichia coli have been defined. Domain 1, amino acids 1-86, is involved in oligomerization and in interaction with DnaB. Domain 2, aa 87-134, constitutes a flexible loop. Domain 3, aa 135-373, contains the binding site for ATP or ADP, the ATPase function, a second interaction site with DnaB, and is required for local DNA unwinding. Domain 4 is required and sufficient for specific binding to DNA. We show that there are three different types of cooperative interactions during the DNA binding of DnaA proteins from E. coli, Streptomyces lividans, and Thermus thermophilus: i) binding to distant binding sites; ii) binding to closely spaced binding sites; and iii) binding to non-canonical binding sites.

Amino Acid Sequence↗