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Biomedical subjects

O Hess

Publications and source records attributed to O Hess.

At least 19 recordsLinked to original sources
PubMed2000

Protein disulfide isomerase mediates integrin-dependent adhesion.

Cell adhesion is mediated by the integrin adhesion receptors. Receptor-ligand interaction involves conformational changes in the receptor, but the underlying mechanism remains unclear. Our earlier work implied a role for sulfhydryls in integrin response to ligand binding in the intact blood platelet. We now show that non-penetrating blockers of free sulfhydryls inhibit beta(1) and beta(3) integrin-mediated platelet adhesion regardless of the affinity state of the integrin. Removal of the inhibitors prior to adhesion fully restores adhesion despite the irreversible nature of inhibitor-thiol interaction, indicating sulfhydryl exposure in response to adhesion. We further show that blocking protein disulfide isomerase (PDI) inhibits adhesion. These data indicate that: (a) ecto-sulfhydryls are necessary for integrin-mediated platelet adhesion; (b) disulfide exchange takes place during this process; (c) surface PDI is involved in integrin-mediated adhesion.

4-Chloromercuribenzenesulfonate↗
PubMed2000

alpha-adrenergic coronary vasoconstriction and myocardial ischemia in humans.

The use of quantitative coronary angiography, combined with Doppler and PET, has recently been directed at the study of alpha-adrenergic coronary vasomotion in humans. Confirming prior animal experiments, there is no evidence of alpha-adrenergic coronary constrictor tone at rest. Again confirming prior experiments, responses to alpha-adrenoceptor activation are augmented in the presence of coronary endothelial dysfunction and atherosclerosis, involving both alpha(1)- and alpha(2)-adrenoceptors in epicardial conduit arteries and microvessels. Such augmented alpha-adrenergic coronary constriction is observed during exercise and coronary interventions, and it is powerful enough to induce myocardial ischemia and limit myocardial function. Recent studies indicate a genetic determination of alpha(2)-adrenergic coronary constriction.

Coronary Vessels↗
PubMed2000

Assessment of prosthetic aortic valve performance by magnetic resonance velocity imaging.

OBJECTIVES: Magnetic resonance (MRI) velocity mapping was used to evaluate non-invasively the flow profiles of the ascending aorta in normal volunteers and in patients with an aortic (mechanical) valve prosthesis. BACKGROUND: In patients with artificial aortic valves the flow profile in the ascending aorta is severely altered. These changes have been associated with an increased risk of thrombus formation and mechanical hemolysis. METHODS: Velocity profiles were determined 30 mm distal to the aortic valve in six healthy volunteers and seven patients with aortic valve replacement (replacement within the last 2 years) using ECG triggered phase contrast MRI. Peak flow, mean flow and mean reverse flow were measured in intervals of 25 ms during the entire heart cycle. Systolic reverse flow, end-systolic closing and diastolic leakage volume were calculated for all subjects. RESULTS: Peak flow velocity during mid-systole was significantly higher in patients with valvular prosthesis than in normals (mean + SD, 1.9 +/- 0.4 m/s vs. 1.2 +/- 0.03 m/s, P < 0.001) with a double peak and a zone of reversed flow close to the inner (left lateral) wall of the ascending aorta of the patients. Closing volume was significantly larger in patients than in controls (-3.3 +/- 1.2 ml/beat vs. -0.9 +/- 0.5 ml/beat; P < 0.001). There was reverse flow during systole in valvular patients amounting to 15.7 +/- 6.7% of total cardiac output compared to 2.3 +/- 1.2% in controls (P < 0.001). Diastolic mean flow was negative in patients after valve replacement but not in controls (-11.0 +/- 15.2 ml/beat vs. 6.8 +/- 3.2 ml/beat; P < 0.01). CONCLUSIONS: The following three major quantitative observations have been made in the present study: (1) Mechanical valve prostheses have an increased peak flow velocity with a systolic reverse flow at the inner (left lateral) wall of the ascending aorta. (2) A double peak flow velocity pattern can be observed in patients with bileaflet (mechanical) prosthesis. (3) The blood volume required for leaflet closure and the diastolic leakage blood volume are significantly higher for the examined bileaflet valve than for native heart valves.

Adult↗
PubMed1998

Systolic and diastolic function with alternate and combined site pacing in the right ventricle.

UNLABELLED: We hypothesized that pacing at two ventricular sites simultaneously would activate the myocardium more rapidly and improve ventricular function. We studied the effect of pacing at the right ventricular outflow tract (RVOT) and the RV apex (RVA) on systolic and diastolic function. In 14 patients with a reduced systolic ejection fraction < 40% (mean EF 32% +/- 4%) we measured RV pressures, left ventricular pressures, EF, cardiac output, peak dP/dt, peak negative dP/dt, and the time constant of relaxation, Tau, during intrinsic rhythm, atrial pacing and DVI pacing at the RVA, the RVOT, and both RV sites combined in random order. Repeated measures analysis of variance showed no significant differences in any of these parameters. The highest absolute values of dP/dt were observed during sinus rhythm and the lowest with RVA pacing. This parameter tended to improve progressively with pacing in the RVOT and at both sites. Peak negative dP/dt showed a similar nonsignificant trend. CONCLUSION: These data suggest that in patients with poor LV function, there may be subtle improvements in diastolic and systolic function with pacing in the RVOT and at combined sites in the RV compared to traditional RVA pacing.

Analysis of Variance↗
PubMed1998

Expression of CRISP proteins in the male equine genital tract.

Cysteine rich secretory proteins (CRISPs) have been detected immunochemically in the equine male genital tract. CRISPs are secretory products of the epididymis, the ampulla and the seminal vesicle. A particular feature of the horse is the abundance of CRISPs in seminal plasma. CRISPs can also be detected in extracts of testicular, epididymal and ejaculated spermatozoa in increasing amounts. Unlike other seminal plasma proteins, they cannot be removed completely from spermatozoa by high salt treatment. The remaining CRISP antigens are localized on the midpiece, and the postacrosomal and equatorial region of the sperm head. Tissue distribution and localization of CRISPs on equine spermatozoa point to a role of these proteins in epididymal sperm maturation and equine reproduction.

Animals↗
PubMed1994

Fetal responses to maternal exercise: effect on fetal breathing and body movement.

This study was conducted to determine the impact of maternal exercise on fetal breathing and fetal body movement, which are commonly used for assessing fetal well-being. Twelve healthy patients with a range of gestational ages of 26 to 36 weeks, who actively exercised throughout pregnancy, participated in the study. The patients walked on a motorized treadmill using a modified Bruce protocol until the maternal heart rate reached 75% of the age-predicted maximal heart rate. Fetal activities (fetal breathing and fetal body movement) were continuously monitored with real-time ultrasonography for 20 minutes before and after the standardized exercise test. Our results demonstrate that there is a significant increase in maternal heart rate and blood pressure associated with exercise. In addition, there is a significant decrease in the total duration and frequency of fetal breathing and fetal body movements following acute maternal exercise.

Adult↗