Search PubMed⌕ Search

Biomedical subjects

G Schmidt

Publications and source records attributed to G Schmidt.

At least 865 records · Page 48Linked to original sources
PubMedDate not supplied

Histaminergic effects on the isolated rat ovarian artery during the estrous cycle.

Histamine may play a role in many of the events occurring in the ovarian tissue and leading to ovulation. To elucidate the histaminergic influence on the ovarian vasculature, the mechanical response of the isolated rat ovarian artery to histamine and histamine agonists was investigated. Histamine relaxed the precontracted vessel segments in a concentration-dependent way, amounting to 82.7 +/- 4.3% of the papaverine-induced relaxation. This relaxant effect was counteracted by both the H1 antagonist, pyrilamine, and the H2 antagonist, cimetidine. That the effect of histamine was mediated by both histamine receptor subtypes was further confirmed by the relaxant effect produced in the presence of either of the H1-specific agonists, 2-pyridylethylamine and 2-methylhistamine on the one hand, and the H2-specific agonists, impromidine and 4-methylhistamine on the other. The H1 receptor-induced relaxation was mediated via an effect on the endothelium, whereas the H2 receptor-mediated relaxation was mostly a direct effect on the smooth musculature in the vessel wall. No major differences in the mechanical response of the rat ovarian artery were seen during the different stages of the estrous cycle, although at late proestrus, just before ovulation, the maximum relaxation induced by histamine was particularly high, in spite of a low sensitivity of the receptors for the amine.

Acetylcholine↗
PubMedDate not supplied

Mitral valve reconstruction and mitral valve replacement for ischemic mitral insufficiency.

BACKGROUND: Patients with ischemic mitral incompetence have a high operative risk whether the valve is repaired or replaced. The advantage of repair over replacement is unclear in this group of patients. METHODS: Between April 1986 and December 1994, 232 patients underwent surgery for ischemic mitral valve insufficiency; mitral valve replacement was performed in 98 of them. Operative mortality was 13.3%. The actuarial survival rate after 5 years was 73.3%. The surgical risk in patients whose left ventricular ejection fraction (LVEF) was 10%-30% (operative mortality 50.0%) was higher than in those whose LVEF was greater than 30%. Valve reconstruction was performed in 102 patients. Operative mortality in this patient group was 14.7%. The surgical risk in patients whose LVEF was < or = 30% was higher (operative mortality 42.9%). RESULTS: The total actuarial survival rate of all patients was 64.4% after 5 years. Mortality during follow-up was higher in patients with residual mitral valve insufficiency greater than grade I after mitral valve reconstruction. Twenty-four patients with severely impaired left ventricular function underwent heart transplantation. Operative mortality in this group was 12.5%. Eight patients received left ventricular aneurysmectomy in addition to valve surgery, three of them died early. CONCLUSIONS: We conclude that patients with highly impaired left ventricular function and ischemic mitral insufficiency are at too great a risk for either valve reconstruction or replacement. Cardiac transplantation should be considered for this patient group. However, patients with ischemic mitral insufficiency and moderately impaired left ventricular function can undergo valve reconstruction or replacement with an acceptable prognosis. The goal of mitral valve reconstruction should be reducing mitral valve insufficiency to at least grade I. If this is not achieved, the prognosis after repair is worse than after valve replacement, therefore, the surgeon should replace the valve without delay.

Aged↗
PubMedDate not supplied

Nutritional support by intraperitoneal dialysis in the rat: maintenance of body weight with normal liver and plasma chemistries.

A rat model was developed to study intraperitoneal (ip) dialysis as a means of total nutritional support. Rats (200 g) were implanted ip with a catheter device and connected to a rodent infusion assembly. An automated system exchanged 10-ml volumes of a 37 degrees C solution containing 10% dextrose, 2% amino acid solution plus micronutrients. Rats were adapted over 3 days to a schedule of 16 1-hr cycles/day, and continued on this regimen for another 4 days. Rats subjected to this program maintained similar body weight, nitrogen balance, plasma chemistries, and liver tests in comparison to control animals fed per os in isocaloric and isonitrogenous amounts. Efficiency of peritoneal absorption for both glucose and amino acid was 95%. Histological examination of intraabdominal organs revealed only mild inflammation. This model is applicable to studies involving nutritional support via the peritoneal cavity, a technique which may be of value in patients with sensitive fluid balances (cardiac, renal, or pulmonary failure).

Absorption↗
PubMedDate not supplied

Rho GTPases as targets of bacterial protein toxins.

Several bacterial toxins target Rho GTPases, which constitute molecular switches in several signaling processes and master regulators of the actin cytoskeleton. The biological activities of Rho GTPases are blocked by C3-like transferases, which ADP-ribosylate Rho at Asn41, but not Rac or Cdc42. Large clostridial cytotoxins (e. g., Clostridium difficile toxin A and B) glucosylate Rho GTPases at Thr37 (Rho) or Thr35 (Rac/Cdc42), thereby inhibiting Rho functions by preventing effector coupling. The 'injected' toxins ExoS, YopE and SptP from Pseudomonas aeruginosa, Yersinia and Salmonella ssp., respectively, which are transferred into the eukaryotic target cells by the type-III secretion system, inhibit Rho functions by acting as Rho GAP proteins. Rho GTPases are activated by the cytotoxic necrotizing factors CNF1 and CNF2 from Escherichia coli and by the dermonecrotizing toxin DNT from B. bronchiseptica. These toxins deamidate/transglutaminate Gln63 of Rho to block the intrinsic and GAP-stimulated GTP hydrolysis, thereby constitutively activating the GTPases. Rho GTPases are also activated by SopE, a type-III system injected protein from Salmonella ssp., that acts as a GEF protein.

Bacterial Toxins↗
PubMedDate not supplied

Structure of the ATP-synthase from chloroplasts and mitochondria studied by electron microscopy.

The structure of the ATP-synthase, F0F1, from spinach chloroplasts and beef heart mitochondria has been investigated by electron microscopy with negatively stained specimens. The detergent-solubilized ATP-synthase forms string-like structures in which the F0 parts are aggregated. In most cases, the F1 parts are arranged at alternating sides along the string. The F0 part has an approximate cylindrical shape with heights of 8.3 and 8.9 nm and diameters of 6.2 and 6.4 nm for the chloroplast and mitochondrial enzyme, respectively. The F1 parts are disk-like structures with a diameter of about 11.5 nm and a height of about 8.5 nm. The F1 parts are attached to the strings, composed of F0 parts, in most cases, with their smallest dimension parallel to the strings. The stalk connecting F0 and F1 has a length of 3.7 nm and 4.3 nm and a diameter of 2.7 nm and 4.3 nm for the chloroplast and mitochondrial enzyme, respectively.

Animals↗
PubMedDate not supplied

Characterization of histamine receptors mediating contraction and relaxation of the ovarian follicle wall.

Histamine is known to be present in ovarian tissue and may play a role in the ovulation process. The effect of histamine on the follicular smooth musculature was investigated using strips from the protruding part of mature bovine follicles, mounted in vitro for registration of isometric motor activity. Histamine contracted the preparation in a concentration-dependent manner. The response was inhibited competitively by the specific H1 receptor antagonist pyrilamine while the adrenergic alpha-receptor antagonist phentolamine had no clear-cut effect. A Schild plot revealed a pA2 value of 8.81, corresponding to a mean KB value (dissociation constant for receptor-antagonist complex) of (7.5 +/- 3.2) X 10(-9) M. After potassium depolarization and blockade of the contractile H1-receptors with pyrilamine, histamine induced a concentration-dependent relaxation of the follicle wall preparation. This response could be inhibited by the H2-receptor antagonist cimetidine (which also potentiated the contractile effect in the absence of pyrilamine). The pA2 value for the cimetidine-induced inhibition was 6.25, and KB was found to be (6.5 +/- 3.0) X 10(-7) M. The beta-receptor antagonist propranolol was effective only in very high concentrations. It is suggested that a possible role for histamine during follicle rupture is mediated via specific receptors in the follicular smooth musculature.

Animals↗
PubMedDate not supplied

Why some patients prefer to become manic-depressive rather than schizophrenic.

This paper reports the authors' observations on fifteen families in which a young adult member had been diagnosed as manic-depressive. All families were seen in systemic family therapy, with intervals of four to six weeks between sessions. The circular questioning method developed by Selvini-Palazzoli [1] and her team was widely employed. All families could be described as extremely rigid and bound-up systems characterized by a "restrictive parental complementarity," typical dynamics of reciprocal delegation, and certain cognitive features and shared assumptions. These "manic-depressive" families show similarities as well as differences when compared with families with schizophrenic members (i.e., "schizo-present" families). Finally, some therapeutic implications of this view and approach are developed.

Bipolar Disorder↗