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Biomedical subjects

R Schulz

Publications and source records attributed to R Schulz.

At least 379 records · Page 21Linked to original sources
PubMed1993

Family and social networks. First results of a BiB survey.

The author analyzes results from a 1990 survey of family and social networks in the former Federal Republic of Germany. "Our project...focuses on the question as to what extent the changes in the observed demographic factors do affect and modify the system of the family with its various acts of assistance and support (financial help, emotional support, rendering of services)." The questionnaire used is provided, and survey methods are described.

Behavior↗
PubMed1993

Elevated plasma prostaglandin E2 levels found in 14 patients undergoing autologous bone marrow or stem cell transplantation.

In the present study, plasma prostaglandin E2 (PGE2) levels were quantitated serially in 14 patients during the period preceding and following autologous bone marrow transplantation (ABMT) or autologous stem cell transplantation (ABSCT). In eight ABMT recipients, the pre-transplant conditioning regimen consisted of combined supralethal doses of chemo- and radiotherapy which was followed by ABMT using autografts purged in vitro either with mafosfamide or monoclonal antibodies (moAbs) plus immunomagnetic beads (IB). A further two ABMT recipients received only high-dose chemotherapy without irradiation as conditioning, followed by unpurged autologous BM. The four ABSCT recipients were also treated solely with chemotherapy followed by untreated autologous stem cell reinfusion. Elevation of plasma PGE2 levels occurred in all 14 patients, despite the difference in the pre-transplant conditioning. The peak levels of PGE2 ranged from about three times the mean value obtained with ten control individuals (29.8 +/- 3.7 pg/ml) to ten times this level. In all cases plasma PGE2 normalised with recovery of the peripheral leucocyte count.

Adult↗
PubMed1993

[Chronic myocardial ischemia--hibernating myocardium: characteristics and limits].

Myocardial ischemia has traditionally been characterized as an imbalance between energy supply and demand. In the initial seconds after a sudden reduction of coronary blood flow, myocardial energy demand most certainly exceeds the reduced energy supply. This temporary mismatch, however, is an inherently unstable condition because regional contractile dysfunction ensues. The mechanisms responsible for the rapid reduction in contractile function of the acutely ischemic myocardium are still poorly understood. If some residual blood flow exists, a state of "perfusion-contraction matching" can be maintained, at least for several hours, without the development of irreversible damage. A situation of persistent contractile failure in viable myocardium with normalizes upon reperfusion has been termed myocardial "hibernation". The metabolic status of such hypoperfused myocardium improves over the first few hours as myocardial lactate production is attenuated and creatine phosphate, after an initial reduction, returns towards control values. The "hibernating" myocardium can respond to an inotropic stimulation by dobutamine with increased function. The recruitment of an inotropic reserve implies increased energy utilization. In fact, the partially normalized lactate production is again increased, and creatine phosphate is decreased again. Apparently the inotropic challenge once again precipitates a supply-demand imbalance which had been at least partially corrected by the ischemia-induced decrease of regional contractile function. This situation of an increased regional contractile function at the expense of metabolic recovery during inotropic stimulation can be used to identify "hibernating" myocardium. The development of such a delicate balance between energy supply and energy demand is easily disturbed by unfavorable alterations in the supply/demand ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Diastolic dysfunction of stunned myocardium.

The prolonged regional contractile failure of reperfused myocardium has usually been characterized in terms of systolic function, while only few reports on its diastolic function are available. None of these studies considered changes in the isovolumic diastole and the subsequent filling phase separately. Therefore, in the present study, the velocities of wall excursion during systole (Vsys), isovolumic diastole (Viso) and filling phase (Vfill) were determined in 12 anesthetized dogs. Additionally, post-ejection thickening (Pejt), a marker of left ventricular asynchrony, was determined. Measurements were performed under control conditions, during a 15 minute left circumflex (LCX) coronary artery occlusion (CAO) and at 10 minutes, 4 and 8 hours reperfusion. Heart rate, left ventricular pressure, and Vsys, Viso, Vfill, and Pejt of the anterior myocardium remained unchanged throughout the experiments. During CAO, systolic wall-thickening of the posterior wall was reversed to systolic wall-thinning. Upon reperfusion, Vsys started to recover (2.5 +/- 3.2 mm/s at 10 minutes) and gradually improved over 8 hours of reperfusion (4.6 +/- 3.2 mm/s at 4 hours, 6.4 +/- 1.5 mm/s at 8 hours). Viso became positive during CAO (9.4 +/- 7.1 mm/s vs. -5.6 +/- 3.9 mm/s under control conditions) and was unchanged at 10 minutes reperfusion (7.9 +/- 5.2 mm/s). After 4 hours and 8 hours of reperfusion, Viso recovered to 1.2 +/- 9.2 mm/s and -0.3 +/- 10.7 mm/s, respectively. Vfill also became positive during CAO (1.5 +/- 6.2 mm/s vs. -18 +/- 8.7 mm/s under control conditions). There was a quick recovery of Vfill (-9.4 +/- 7.5 mm/s) with the onset of reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Coupling of prostaglandin E1 receptors to the stimulatory GTP-binding protein Gs is enhanced in neuroblastoma x glioma (NG108-15) hybrid cells chronically exposed to an opioid.

This study investigates the functional state of the stimulatory GTP-binding protein GS in neuroblastoma x glioma NG108-15 hybrid cells chronically exposed to an opioid. For this purpose, a novel in situ reconstitution protocol was established using membranes selectively depleted of GS function by transient exposure to low pH and then reconstituted with purified exogenous stimulatory GTP-binding proteins. With prostaglandin E1 (PGE1) receptor-stimulated adenylate cyclase activity as an indicator, reconstituted membranes of cells previously rendered tolerant to the delta-opioid [D-Ala2,D-Leu5]enkephalin (DADLE) exhibited approximately 3-fold elevated cAMP generation upon stimulation with PGE1, compared with nontolerant reconstituted cell membranes. This effect developed dose-dependently with respect to the opioid concentration used for pretreatment of the cells and was blocked by concomitant exposure to naloxone. In contrast, receptor-independent activation of GS by the stable GTP analogue guanosine-5'-O-(3-thio)triphosphate did not reveal any difference in adenylate cyclase activity between reconstituted membranes of control and chronically DADLE-pretreated cells. Furthermore, the functional activity of endogenous GS displayed no difference between control and DADLE-tolerant cells, as assessed in S49 cyc- reconstitution assays using sodium cholate extracts derived from NG108-15 membranes. The data presented suggest that the increase in PGE1 receptor-mediated adenylate cyclase activity in opioid-tolerant/dependent NG108-15 hybrid cells most likely relates to enhanced coupling efficiency between the PGE1 binding site (receptor) and GS. Moreover, our results support the concept that supersensitivity to excitatory drugs reflects an adaptive mechanism of cells chronically exposed to an opioid.

Adenylyl Cyclases↗
PubMed1993

Time course and mechanisms of contractile dysfunction during acute myocardial ischemia.

BACKGROUND: The purpose of the study was to characterize the functional and metabolic adjustments of a myocardial region subjected to low-flow ischemia. In addition, studies tested whether such myocardium retains an inotropic reserve. METHODS AND RESULTS: Anesthetized swine were studied in which the left anterior descending coronary artery was cannulated and perfused at a constant low level causing regional contractile dysfunction (sonomicrometry for wall thickness) and the appearance of metabolic indicators of ischemia (decrease in creatine phosphate and lactate production) with only slight loss of ATP and glycogen (transmural biopsies). After 85 minutes of low-flow ischemia, dobutamine was infused into the hypoperfused artery as an inotropic challenge. Coronary hypoperfusion for 5 minutes resulted in a 54% reduction of regional systolic wall thickening, reversal of lactate consumption to lactate production, and a significant decrease in creatine phosphate. Subendocardial blood flow was reduced from 0.62 +/- 0.11 (+/- SD) to 0.16 +/- 0.07 mL.min-1.g-1. Prolonged hypoperfusion for 85 minutes resulted in no further change in regional blood flow but a partial recovery of metabolic parameters. Dobutamine infusion after 85 minutes of hypoperfusion increased regional myocardial work. However, again lactate production was significantly increase and creatine phosphate was decreased. Regional coronary hypoperfusion produces a downregulation of regional contractile function in proportion to the blood flow decrease. With prolonged hypoperfusion, after the initial adjustment phase, there is little further change in function, and metabolic markers of ischemia improve. Although the ischemic downregulated myocardium retains a significant inotropic reserve, primarily anaerobic energy production is utilized. CONCLUSIONS: These data are consistent with downregulation being a protective mechanism for the ischemic myocardium to restore an energy supply-demand balance in the face of reduced blood flow. Inotropic stimulation of the downregulated myocardium enhances regional function but at the cost of worsening its metabolic status. Thus, inotropic stimulation of the hypoperfused and downregulated myocardium is probably detrimental to long-term viability.

Acute Disease↗
PubMed1992

Opioid-controlled adenylate cyclase in the guinea-pig myenteric plexus is confined to nerve somata.

Previous studies with the electrically stimulated longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum suggested that opioid control of adenylate cyclase is confined to nerve somata. No indication was found for an opioid effect on the enzyme at nerve terminals of the neuro-muscular junction. The aim of the present investigation was to directly study the effect of opioids on cAMP generation in nerve fragments associated with somata or terminals of the myenteric plexus. Employing the ultracentrifugation technique an enrichment of cell organelles in fractions relating to either somata or terminals was achieved. Opioid binding studies revealed specific mu-receptors which in both fractions were regulated by GTP. Challenge of these fractions with forskolin and prostaglandin E1, respectively, resulted in an increased production of cAMP regardless of their neuroanatomical assignment. Examining the response of neuronal material to the selective mu-opioid DAMGO ([D-Ala2, MePhe4, Gly-ol5]enkephalin) revealed an inhibitory action on cAMP synthesis in somata-enriched fractions. No effect of DAMGO was observed in material linked to nerve terminals, although the presence of mu-opioid receptors and adenylate cyclase has been demonstrated. We conclude that opioid control of adenylate cyclase in the myenteric plexus of the guinea pig is confined to nerve somata.

Adenylyl Cyclases↗
PubMed1992

Detection of methandienone (methandrostenolone) and metabolites in horse urine by gas chromatography-mass spectrometry.

The metabolic transformation of methandienone (I) in the horse was investigated. After administration of a commercial drug preparation to a female horse (0.5 mg/kg), urine samples were collected up to 96 h and processed without enzymic hydrolysis. Extraction was performed by a series of solid-liquid and liquid-liquid extractions, thus avoiding laborious purification techniques. For analysis by gas chromatography-mass spectrometry, the extracts were trimethylsilylated. Besides the parent compound I and its C-17 epimer II, three monohydroxylated metabolites were identified: 6 beta-hydroxymethandienone (III), its C-17 epimer (IV) and 16 beta-hydroxymethandienone (V). In addition, three isomers of 6 beta,16-dihydroxymethandienone (VIa-c) were discovered. Apparently, reduction of the delta 4 double bond of 16 beta-hydroxymethandienone (V) in the horse yields 16 beta,17 beta-dihydroxy-17 alpha-methyl-5 beta-androst-1-en-3-one (VII). Reduction of the isomers VIa-c results in the corresponding 6 beta,16,17-trihydroxy-17-methyl-5 beta-androst-1-en-3-ones (VIIIa-c). The data presented here suggest that screening for the isomers of VI and VIII, applying the selected-ion monitoring technique, will be the most successful way of proving methandienone administration to a horse.

Animals↗
PubMed1992

Expression of atrial natriuretic peptide in thymic macrophages after dexamethasone treatment of rats.

The rat thymus represents a site of synthesis of atrial natriuretic peptide (ANP); the immunosuppressor dexamethasone strikingly increases ANP-expression in this immune organ. The presented data suggest that this increase can be attributed to macrophages. By means of immunohistochemistry and Northern blot analysis these immune cells were found to express ANP-immunoreactivity as well as mRNA coding for ANP. In contrast, macrophages of control thymi displayed only weak ANP-immunoreactivity. Thus, ANP appears to be a constituent of rat thymic macrophages, and its synthesis in the thymus is strongly elevated by acute exposure of the animals to glucocorticoids.

Animals↗
PubMed1992

Metabolism of androstenedione and 11-ketotestosterone in the kidney of the three-spined stickleback, Gasterosteus aculeatus.

Stickleback kidneys were incubated with tritiated androstenedione (A4) or 11-ketotestosterone (OT). After the A4 incubations the following steroids were found, testosterone (T), 5 beta-androstane-3,17-dione (5 beta Ad), etiocholanolone (Et), 5 beta-dihydrotestosterone (5 beta DHT), 5 beta-androstane-3 alpha,17 beta-diol (5 beta A3 alpha 17 beta diol), androsterone, 5 alpha-androstane-3,17-dione, 5 alpha-androstane-3 alpha,17 beta-diol (5 alpha A3 alpha 17 beta diol), as well as glucuronides of T, Et, 5 beta DHT, 5 beta A3 alpha 17 beta diol, and 5 alpha A3 alpha 17 beta diol. The metabolites found in the largest amounts were usually T, 5 beta Ad, Et, and the glucuronides of T, Et, and especially of 5 beta A3 alpha 17 beta diol. These results suggest the main pathway to be A4-5 beta Ad-Et-5 beta A3 alpha 17 beta diol-5 beta A3 alpha 17 beta diol-glucuronide or Et-Et-glucuronide-5 beta A3 alpha 17 beta diol-glucuronide. The formation of 5 beta-reduced compounds was larger in postbreeding males and females than in breeding males. The opposite was the case for 5 alpha-reduced compounds. The total formation of glucuronides was lower in the breeding males than in the other groups. After the OT incubations 11-ketoandrostenedione, 17 beta-hydroxy-5 beta-androstane-3,11-dione (tentatively identified), and OT-glucuronide were found. 17 beta-Hydroxy-5 alpha-androstane-3,11-dione was not present.

Androstane-3,17-diol↗
PubMed1992

Comparison of recruitment strategies and associated disease prevalence for health promotion in rural elderly.

BACKGROUND: Although interest in health promotion for the elderly is increasing, the issues of recruitment into such programs and self-selection have not been well explored. While clinical studies require high participation levels and expensive recruitment, community efforts are satisfied with recruiting small numbers of volunteers from poorly defined populations. These small samples may not be representative of the populations at risk. METHODS: As part of the Rural Health Promotion Project, a Medicare demonstration, community-based recruitment methods were evaluated and participant characteristics were compared. A total of 3,884 individuals ages 65-79 were recruited in northwestern Pennsylvania, using four sequential recruitment strategies, varying in aggressiveness. The methods were: (A) mail only, (B) mail with phone recruitment follow-up, (C) mail with phone recruitment and scheduling, and (D) mail with aggressive phone recruitment and scheduling. RESULTS: Recruitment yields were Method A, 13.5%; B, 21.1%; and C, 31.6%. The most aggressive Method (D) yielded 37.0% participation. More aggressive methods (C and D) recruited more educated individuals. No other demographic or health status differences were noted. CONCLUSION: These data show that large numbers of the elderly can be recruited into a health promotion program using aggressive methods and professional interviewers.

Aged↗
PubMed1992

Physical illness and symptoms of depression among elderly outpatients.

Elderly outpatients were assessed to clarify relations between symptoms of depression and physical illness, disability, pain, and selected psychosocial variables. Three types of assessments were made: (a) medical evaluations by physicians, (b) self-reported symptoms of depression and physical health, and (c) demographic and psychosocial data relating to participants' life circumstances. Both objective (physician-rated illness symptoms) and subjective (self-reported health, activity restriction, and use of pain medications) indicators of health accounted for independent variance in symptoms of depression. After controlling for these factors, additional variance was explained by health-related concerns (e.g., health care expenses, service needs), social support, and "other worries" (e.g., feeling useless, becoming a burden to others).

Adaptation, Psychological↗
PubMed1992

Pain, activity restriction, and symptoms of depression among community-residing elderly adults.

Relations among physical illness, functional disability, pain, and symptoms of depression were investigated in a sample of community-residing elderly outpatients. As expected, physical illness, functional disability, and pain were correlated with depressive symptomatology. It was further hypothesized that functional disability (but not physical illness per se) would attenuate the relation between depressed affect and pain. The data supported these predictions by showing that functional disability (but not physical illness) accounted for differences in reported pain between nondepressed subjects and those at risk for developing clinical depression. Additional analyses revealed that functional disability mediated relations between pain and depressed affect and also between illness and depressed affect. These results indicate that both pain and illness are important contributors to functional disability, which in turn contributes to symptoms of depression. Secondary analyses revealed that restriction of certain activities associated with physical mobility and independence were strong individual factors in attenuating the relation between pain and depressed affect. An important implication of this research is that neither pain nor activity restriction should be treated in isolation. Maximal effects are likely to be achieved when both are targeted simultaneously.

Activities of Daily Living↗
PubMed1992

Induction and potential biological relevance of a Ca(2+)-independent nitric oxide synthase in the myocardium.

1. We have investigated whether the myocardium and isolated cardiac myocytes can express a Ca(2+)-independent NO synthase after treatment with endotoxin or cytokines. Nitric oxide synthesis was measured in cytosols from the left ventricular wall from rats treated with endotoxin, or from freshly isolated myocytes from adult rats treated in vitro with cytokines. 2. Cytosols from the ventricle of saline-treated control animals showed only Ca(2+)-dependent NO synthesis. After treatment with endotoxin, the expression of an inducible, Ca(2+)-independent NO synthase was observed. The activity of this enzyme was maximal at 6 h and returned towards control levels by 18 h; no alterations occurred in the Ca(2+)-dependent NO synthase activity. Parallel to this enzyme induction there was an increase in myocardial guanosine 3':5'-cyclic monophosphate (cyclic GMP) and plasma nitrite and nitrate (NOx-). All these changes were prevented by pretreatment of the rats with dexamethasone. 3. Myocytes possessed Ca(2+)-dependent NO synthase activity and expressed, after treatment with tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta), a Ca(2+)-independent NO synthase, the induction of which was prevented by dexamethasone and cycloheximide. 4. Since increases in cyclic GMP levels in the heart are associated with reduced myocardial contractility, it is possible that the enhanced production of NO by a Ca(2+)-independent enzyme accounts, at least in part, for the depression of myocardial contractility seen in septic shock, cardiomyopathies, allograft rejection, burn trauma, as well as during anti-tumour therapy with cytokines.

Amino Acid Oxidoreductases↗
PubMed1992

Lysoplasmenylethanolamine accumulation in ischemic/reperfused isolated fatty acid-perfused hearts.

Lysophospholipid accumulation has been implicated in the pathogenesis of irreversible injury during myocardial ischemia and reperfusion. Plasmalogens (phospholipids with a vinyl-ether bond in the sn-1 position) account for more than 50% of total myocardial sarcolemmal and sarcoplasmic reticulum phospholipids. Accumulation of plasmalogen choline and ethanolamine lysophospholipids (lysoplasmenylcholine and lysoplasmenylethanolamine) or the effects of exogenous fatty acids on lysoplasmalogen accumulation during ischemia and reperfusion have not been examined. Isolated working rat hearts perfused with buffer containing either 11 mM glucose or 11 mM glucose plus 1.2 mM palmitate were subjected to aerobic, ischemic, or ischemia/reperfusion protocols. Levels of lysoplasmenylcholine and lysoplasmenylethanolamine were quantified using a two-stage high-performance liquid chromatographic technique. In hearts perfused with glucose alone, no significant differences in levels of lysoplasmenylcholine or lysoplasmenylethanolamine were seen during ischemia or reperfusion. In fatty acid-perfused hearts, however, significant accumulation of lysoplasmenylethanolamine occurred during reperfusion but not during ischemia (723 +/- 112, 734 +/- 83, and 1,394 +/- 193 nmol/g dry wt for aerobic, ischemic, and ischemic/reperfused hearts, respectively; p less than 0.05 for ischemic/reperfused hearts versus aerobic or ischemic hearts). Lysoplasmenylcholine levels after ischemia and reperfusion did not differ significantly from aerobic values, regardless of whether fatty acids were present or absent from the perfusate. Aerobic and ischemic/reperfused rabbit hearts, in the presence of fatty acid, showed a similar profile in their lysoplasmalogen content. We conclude that differential lysoplasmenylethanolamine accumulation occurs during myocardial reperfusion when exogenous fatty acid concentrations are high. This may reflect the selective action of fatty acid intermediates on the metabolism of lysoplasmenylethanolamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Recruitment of an inotropic reserve in moderately ischemic myocardium at the expense of metabolic recovery. A model of short-term hibernation.

The regional, functional as well as metabolic consequences of inotropic stimulation on myocardium subjected to prolonged moderate ischemia were investigated. In 35 enflurane-anesthetized swine the left anterior descending coronary artery was cannulated and perfused at constant flow. The vein paralleling the left anterior descending coronary artery was cannulated for measurement of lactate and oxygen content. Transmural biopsies from the anterior myocardium were taken for the measurement of ATP, creatine phosphate, and glycogen. After control measurements, flow was adjusted to reduce regional contractile function (expressed as a work index, determined by sonomicrometry) by approximately 50%. After either 5, 25, 40, or 85 minutes of moderate ischemia, dobutamine was infused for 5 minutes into the ischemic region. In a separate group of five swine also subjected to 85 minutes of ischemia followed by infusion of dobutamine and 2 hours of reperfusion, triphenyltetrazolium chloride staining and light microscopy were used to identify infarcted tissue. Moderate ischemia (regional myocardial blood flow, 0.21 +/- 0.07 ml.min-1.g-1, determined by radiolabeled microspheres) was associated with a reduction of creatine phosphate after 5 minutes (from 9.35 +/- 2.54 to 6.43 +/- 1.06 mumol/g wet wt, p less than 0.05) and a further reduction after 25 minutes (3.18 +/- 0.69 mumol/g wet wt, p less than 0.05). Thereafter, creatine phosphate recovered despite continued ischemia (after 40 minutes, 4.95 +/- 1.37 mumol/g wet wt; after 85 minutes, 5.78 +/- 2.27 mumol/g wet wt). Lactate consumption during control conditions was reversed to production after 5 minutes of ischemia, which moderated during more prolonged ischemia. Without changing regional myocardial blood flow, infusion of dobutamine increased the work index significantly at any time point but also caused worsening of metabolic markers of ischemia. Nevertheless, even after 85 minutes of ischemia followed by the infusion of dobutamine and 2 hours of reperfusion, there was no evidence of necrosis. This experimental model provides a means of characterizing the mechanisms of short-term hibernation.

Animals↗
PubMed1992

[Poor reproducibility of parameters of heart rate variations].

The analysis of heart rate variability is supposed to be a marker of autonomic cardiac activity and is used for risk stratification of post-infarction patients. Analysis of heart rate variability in the frequency domain may permit a differentiation of vagal and sympathetic control; for such analyses only short time intervals characterized by a steady-state autonomic balance can be used. Yet, it is unclear whether single determinations of heart rate variability indices derived from short time intervals yield reproducible results. Therefore, the reproducibility of heart rate variability indices was studied with weekly measurements in 10 healthy volunteers under the following defined conditions: 13 min supine rest, 10 min standing, 13 min sitting, and 15 min cycle ergometry followed by a 14 min recovery period. Heart rate variability was determined in the frequency domain (fast Fourier transformation) and in the time domain. The reproducibility was estimated by the coefficient of variation (CV). Additionally, the reproducibility of heart rate, blood pressure, and the expiratory-inspiratory ratio of heart rate was determined. The reproducibility of the frequency domain indices (36.6-74.9% CV) and of the time domain indices (19.6-32.8% CV) was considerably worse than that of heart rate (5.2-8.2% CV), blood pressure (5.1-8.2% CV) and the expiratory-inspiratory ratio of heart rate (4.6% CV). The reproducibility of heart rate variability indices was not improved by orthostatic or ergometric challenge. This poor reproducibility does not permit a reliable interpretation of heart rate variability on the basis of single measurements in healthy volunteers. Given the wide range and scatter of the measured parameters, the diagnostic and prognostic value of heart rate variability indices derived from short recording periods appears questionable.

Arrhythmias, Cardiac↗