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Biomedical subjects

R Schulz

Publications and source records attributed to R Schulz.

At least 667 records · Page 37Linked to original sources
PubMedDate not supplied

Identification and verification of the anabolic steroid boldenone in equine blood and urine by HPLC/ELISA.

An enzyme linked immunosorbent assay (ELISA) was developed to detect the anabolic steroid boldenone in equine blood and urine. The polyclonal antiserum was raised in rabbits, employing boldenone-17-hemisuccinate-bovine serum albumin as antigen. Boldenone-17-hemisuccinate-horseradish peroxidase served as enzyme conjugate. Sensitivity of the assay was 26.0 +/- 3.0 pg/well. Among the endogenous steroids tested only progesterone and testosterone exhibited moderate cross-reactivities, 3.4 and 2.5%, respectively. These cross-reactivities are of no importance for the boldenone assay. For the reduction of background levels, screening for boldenone of equine serum was performed after extraction. Urine samples were determined directly after dilution, omitting hydrolysis of boldenone conjugates. Positive screening results were confirmed by means of two independent HPLC systems combined with off-line detection, employing the boldenone ELISA. Methandienone served as internal standard to ascertain retention factors. In horses treated with boldenone-17-undecylenate the presence of boldenone in serum was confirmed up to 28 days and in unhydrolyzed urine up to 56 days post applicationem.

Anabolic Agents↗
PubMedDate not supplied

Physician autonomy in the Federal Republic of Germany, Great Britain and the United States.

The concepts of 'professionalism' (including autonomy) and 'management' (involving the control of others) are logically opposed; but, in the field of health care, physicians and managers have largely co-existed without such opposition. International pressures for cost containment, however, now raise questions about the future nature of physician autonomy. This paper attempts, firstly, to conceptualize the nature of clinical autonomy as a number of independent components; secondly, to describe the nature of such autonomy in three countries in terms of these components; and, thirdly, to identify related questions for future research.

Authoritarianism↗
PubMedDate not supplied

Preventive health behaviors among spousal caregivers.

BACKGROUND: The physical and emotional burden of caring for a functionally impaired spouse may adversely affect the preventive health behavior of the caregiver. This study explores the relationship between caregiving and lifestyle health behaviors and use of preventive services. METHODS: The Caregiver Health Effects Study identified spousal caregivers among a sample of more than 3,000 married, community-dwelling older persons, from four counties in the United States, who were enrollees in the Cardiovascular Health Study. High-level caregivers were defined as having a spouse with an ADL impairment (n = 212) and moderate-level caregivers, a spouse with one or more IADL impairments (n = 222). For each caregiver, a control, matched for age and gender, was selected (n = 385). Structured interviews were conducted in the home, following enrollment. RESULTS: Being a high-level caregiver significantly increased the odds of not getting enough rest, not having enough time to exercise, not having time to rest to recuperate from illness, and forgetting to take prescription medications, compared with noncaregivers. These findings did not hold for moderate-level caregivers. The odds were not significantly different for either level of caregiver compared with noncaregivers for missing meals, missing doctor appointments, missing flu shots, and not refilling medications. Larger proportions of caregivers with a strong sense of control had good preventive health behaviors, compared with caregivers with a weak sense of control.

Activities of Daily Living↗
PubMedDate not supplied

An easy and quick implantation procedure for the measurement of myocardial wall thickness using sonomicrometry.

Ultrasonic techniques for the measurement of ventricular dimensions are widely used in acute and chronic experiments. Implantation of ultrasonic crystals is associated with reversible and irreversible myocardial damage which might limit the interpretation of the obtained results, in particular during acute experiments. We therefore developed a sonomicrometric device which can be easily and quickly implanted, and thus reduces the reversible myocardial damage induced by prolonged surgical implantation.

Animals↗
PubMedDate not supplied

Evaluation of parameters for the assessment of regional myocardial contractile function during asynchronous left ventricular contraction.

The primary purpose of this study was to evaluate parameters used for the measurement of regional myocardial contractile function in the setting of left ventricular (LV) asynchrony. Secondarily, we tested whether the peak negative value of left ventricular dP/dt (-dP/dt) can be used to estimate global LV end-systole during asynchrony. In seven anesthetized (Isoflurane) swine the left anterior descending coronary artery was cannulated and perfused at constant blood flow rates. To produce LV asynchrony, dobutamine (D) was infused into the perfusion system. This was repeated later during coronary hypoperfusion (HYPO) sufficient to produce regional contractile dysfunction. The amount of LV wall thickening during systole (% WT, sonomicrometry) was calculated using either -dP/dt or the closure of the aortic valve (AO, electromagnetic flow probe) for estimating the timing of global LV end-systole. % WT was compared to other parameters which are not dependent upon the timing of global LV end-systole, including the amplitude of the first harmonic of the Fourier transform (AMP) and regional myocardial work (WI) estimated form the left ventricular pressure-wall thickness relationship. A close correlation between global LV end-systole defined by the AO or -dP/dt existed during control, D or HYPO. During HYPO + D no such relationship was found (r = .22, NS), and % WT calculated using -dP/dt as an estimate of end-systole was underestimated when compared to % WT calculated by use of the AO to estimate end-systole (2.9 +/- 6.8% vs 6.3 +/- 6.6%, p less than .05). % WT, AMP, and WI showed similar results during control, D and HYPO. However, During HYPO increased the AMP from .59 +/- .23 mm to .76 +/- .32 mm and WI from 67 +/- 20 mm Hg*mm to 95 +/- 24 mm Hg*mm (p less than .05), respectively. This increase in regional myocardial function, however, was not detected by % WT (10.5 +/- 6.4% vs 6.3 +/- 6.6%). Thus, during left ventricular asynchrony, the measurement of LV -dP/dt to estimate the timing of global LV end-systole is inappropriate and can lead to inaccuracies in the measurement of regional contractile function. Parameters such as AMP or WI are advantageous since global LV end-systole does not need to be accurately defined.

Animals↗
PubMedDate not supplied

Effect of coronary hyperperfusion on regional myocardial function and oxygen consumption of stunned myocardium in pigs.

The "Gregg phenomenon" implies that myocardial function and oxygen consumption (MVO2) increase when coronary perfusion is enhanced within or above the autoregulatory range. We have recently demonstrated that the "Gregg phenomenon" has no significance for regional myocardial function and MVO2 in anesthetized swine in situ. There is, however, some evidence that the "Gregg phenomenon" may exist within stunned myocardium. To test whether coronary hyperperfusion increases regional myocardial function and MVO2 in stunned myocardium, in six anesthetized swine the left anterior descending coronary artery (LAD) was cannulated and perfused at constant pressure (CAP) using an extracorporal circuit. The coronary vein which parallels the LAD was cannulated to allow measurement of regional MVO2 and regional systolic wall thickening (WT%) of the anterior myocardium was assessed using sonomicrometry. Blood flow (CBF) to the LAD was increased by increasing CAP within the extracorporal circuit or by intracoronary adenosine infusion (150 micrograms/min). In normal myocardium, increasing CBF from 71.4 +/- 19.7 (SD) to 156.7 +/- 48.8 ml/min/100 g by increasing CAP from 100 +/- 10 to 190 +/- 10 mm Hg or increasing CBF from 75.1 +/- 29.1 to 189.2 +/- 45.8 ml/min/100 g by intracoronary adenosine infusion did not increase WT% (34.3 +/- 12.2% vs 32.1 +/- 10.6% and 32.3 +/- 10.7% vs 30.1 +/- 13.2%, respectively). MVO2 was not changed during enhanced CAP (6.94 +/- 1.05 vs 8.10 +/- 1.08 ml/min/100 g) and during intracoronary adenosine infusion (6.67 +/- 1.45 vs 7.30 +/- 2.23 ml/min/100 g). Twenty min of hypoperfusion followed by 30 min of reperfusion depressed WT% by 47% (p less than 0.05). However, MVO2 was only decreased by 23% (NS). In the stunned myocardium, increasing CBF from 62.1 +/- 36.4 to 157.1 +/- 60.0 ml/min by increasing CAP was not associated with an increase in WT%. MVO2, however, increased from 5.14 +/- 1.07 to 8.88 +/- 1.83 ml/min/100 g (p less than 0.05). Comparable results were achieved when CBF was increased from 60.3 +/- 28.7 to 176.9 +/- 48.5 ml/min by intracoronary adenosine infusion. WT% was unaffected, while MVO2 increased from 4.69 +/- 0.92 to 9.46 +/- 3.39 ml/min/100 g (p less than 0.05). Thus, increasing coronary perfusion within or above the autoregulatory range increases MVO2 in stunned myocardium, but without a simultaneous increase in regional myocardial function.

Adenosine↗
PubMedDate not supplied

The bidirectional hydrogenase of Synechocystis sp. PCC 6803 works as an electron valve during photosynthesis.

The activity of the bidirectional hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 was found not to be regulated in parallel to respiration but to photosynthesis. A mutant with a deletion in the large hydrogenase subunit gene (hoxH), which contains the active site, was impaired in the oxidation of photosystem I (PSI) when illuminated with light, which excites either PSI alone or both photosystems. The fluorescence of photosystem II (PSII) of this mutant was higher than that of wild-type cells. The transcript level of the photosynthetic genes psbA, psaA and petB was found to be different in the hydrogenase-free mutant cells compared to wild-type cells, which indicates that the hydrogenase has an effect on the regulation of these genes. Collectively, these results suggest that the bidirectional hydrogenase functions as a valve for low-potential electrons generated during the light reaction of photosynthesis, thus preventing a slowing down of electron transport. This conclusion is supported by growth curves demonstrating that the mutant cells need more time to adapt to changing light intensities. Investigations of the wild-type and deltahoxH strains strongly suggest that Synechocystis contains only the bidirectional hydrogenase, which seems to be essentially insensitive to oxygen.

Blotting, Northern↗
PubMedDate not supplied

Regulation of luteinizing hormone secretion in prepubertal male and female rats.

The effect of naloxone or clonidine, on serum levels of luteinizing hormone (LH) was investigated in immature male and female rats. After birth, naloxone progressively increased serum LH concentrations in females, reaching maximal effects on the 10th to the 16th day of life. Males failed to respond to naloxone during this period. Clonidine only moderately increased LH in immature female rats. However, immature males displayed a high sensitivity to this alpha 2-adrenoceptor agonist. The secretion pattern of LH caused by clonidine during the first two weeks of life resembled that evoked by naloxone in females. Thus, regulation of LH secretion of immature female rats involves endorphins, while in males control of LH-release is by adrenergic mechanisms.

Animals↗
PubMedDate not supplied

The development of opiate tolerance may dissociate from dependence.

Experiments on opiate sensitive peripheral tissue preparations such as the mouse vas deferens and the guinea-pig ileum have demonstrated the ability to induce very high degrees of selective tolerance towards particular opiate agonists. Interestingly, the highly tolerant mouse vas deferens failed to display any sign of dependence as judged by the inability of naloxone to precipitate a withdrawal sign. In analogy, the present studies on the guinea-pig ileum revealed a striking dissociation in the degree of tolerance and dependence developed. Opiate receptor binding studies on both tissues point to distinct differences in the opiate-induced effector mechanisms. It is concluded that adaptational changes upon chronic opiate receptor activation may occur at multiple sites within the effector system of the opiate receptor.

Animals↗
PubMedDate not supplied

Measurement of five androgens in the blood of immature and maturing male rainbow trout, Salmo gairdneri (Richardson).

Antisera for radioimmunoassay (RIA) against testosterone, 11-oxo-testosterone, 11 beta-hydroxytestosterone, 11-oxo-androstenedione, and 11 beta-hydroxyandrostenedione were raised in female rabbits. The RIAs were tested for their suitability for quantification of the steroids after thin layer chromatography of ether extracts from plasma pools of immature and maturing male rainbow trout. Results from control experiments of the RIAs (buffer blanks, sensitivity, cross reactivity, intra- and inter-assay coefficients of variation, accuracy) were all within a normal range. These RIAs should be helpful tools to test the significance of the hypothesis concerning the "interrenal-liver-gonad axis" which has been proposed to account for the high androgen levels in male trout during high reproductive activity.

Androgens↗