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Biomedical subjects

R Schulz

Publications and source records attributed to R Schulz.

At least 487 records · Page 27Linked to original sources
PubMed1988

Atrial natriuretic peptide in bovine corpus luteum.

Atrial natriuretic peptide (ANP) has been demonstrated to exert endocrine functions, including the modulation of steroid synthesis. This prompted investigations to search for ANP receptors in the corpus luteum, a tissue that produces progesterone. The studies revealed a single binding site for [125I] ANP with similar characteristics (Kd, 122 pM; maximum binding, 18 fmol/mg protein) in all four stages of corpus luteum development. These receptors were demonstrated to stimulate cGMP production upon activation with synthetic ANP. Maximal cGMP synthesis was observed at 10(-7) M ANP, 5 min after activation of receptors. An acidic extract of corpus luteum contained immunoreactive ANP (approximately 220 fmol/g tissue), as indicated by gel chromatography, HPLC, and identification by means of a highly specific ANP antibody. The data do not permit definition of a specific endocrine role of ANP in the corpus luteum.

Animals↗
PubMed1988

Effects of vasospasm on levels of prostacyclin and thromboxane A2 in cerebral arteries of the monkey.

To determine whether cerebral arteries in spasm have an altered capacity to synthesize the vasoactive substances prostacyclin and thromboxane A2, we measured levels of these arachidonic acid metabolites using a primate model of vasospasm. Twenty-four cynomolgus monkeys were assigned at random to one of three groups designated sham, clot, or clot-removal. All animals underwent base line cerebral angiography and bilateral dissection of the major cerebral arteries from the arachnoid. The clot and clot-removal groups had autologous hematomas placed around the vessels to simulate subarachnoid hemorrhages. The sham group had a similar volume of saline instilled into the subarachnoid space. Twenty-four hours later, the clot-removal group underwent a second craniotomy to remove the hematomas. Seven days after the initial operation, angiography was repeated on all animals. The animals were then killed, and the cerebral arteries were removed. Basal levels of prostacyclin and thromboxane in the cerebral vessels were measured after incubation in vitro by radioimmunoassay. No detectable leukotriene C4 release by these arteries was measurable using radioimmunoassay. Angiography revealed severe cerebral vasospasm in the clot group, but not in the clot-removal or sham groups. There were no statistical differences among the groups in thromboxane release, but prostacyclin levels were significantly lower in the clot group than in the clot-removal group (P less than 0.05). It thus seems that, if an imbalance in constrictor and dilator eicosanoids occurs in association with vasospasm, this is more likely to arise from a relative lack of the vasodilator component prostacyclin than from a surplus of the vasoconstrictor thromboxane.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Comparison of [125I]beta-endorphin binding to rat brain and NG108-15 cells using a monoclonal antibody directed against the opioid receptor.

The properties of [125I]beta h-endorphin-binding sites from rat brain membranes and membranes from the NG108-15 cell line were compared using a monoclonal antibody directed against the opioid receptor and opioid peptides as probes. The binding of [125I]beta h-endorphin to both rat brain and NG108-15 membranes yielded linear Scatchard plots with Kd values of 1.2 nM and 1.5 nM, respectively, and Bmax values of 865 fmol/mg rat brain membrane protein and 1077 fmol/mg NG108-15 membrane protein. A monoclonal antibody, OR-689.2.4, capable of inhibiting mu and delta binding but not kappa binding to rat brain membranes, noncompetitively inhibited the binding of 1 nM [125I]beta h-endorphin to rat brain and NG108-15 membranes with an IC50 value of 405 nM for rat brain membranes and 543 nM for NG108-15 membranes. The monoclonal antibody also inhibited the binding of 3 nM [3H] [D-penicillamine2, D-penicillamine5] enkephalin to NG108-15 membranes with an IC50 value of 370 nM. In addition to blocking the binding of [125I]beta h-endorphin to brain membranes, the antibody also displaced [125I]beta h-endorphin from membranes. Site-specific opioid peptides had large variations in their IC50 values depending on whether they were inhibiting [125I]beta h-endorphin binding to rat brain or the NG108-15 membranes. When the peptides were tested with the monoclonal antibody for their combined ability to inhibit [125I]beta h-endorphin binding to both membrane preparations, the peptides and antibody blocked binding as though they were acting at allosterically coupled sites, not two totally independent sites. These studies suggest that mu-, delta-, and beta-endorphin-binding sites share some sequence homology with the 35,000-dalton protein that the antibody is directed against.

Animals↗
PubMed1988

Practice effect of volunteers in repeated psychometric testing. How to handle this intervening variable in clinical pharmacology studies?

Performance in psychometric tests may show a practice effect with repeated testing. Ideally, a plateau of efficiency should be reached prior to first drug intake. In order to assess the period of familiarization in a multiple choice reaction task (MCRT) 17 healthy subjects practiced the test up to 36 times in the drug free run-in period of 2 trials. A tentative "inclusion criterion" was used in 7 subjects to decide whether their learning phase could be regarded as being finished. Seven to 20 training sessions were required for a first rapid learning phase. There were remarkable differences in the absolute performance of the subjects and in the time course of their practice effect. However, the time course of the learning phase was not dependent on the absolute performance level. By means of the tentative "inclusion criterion" it was possible to reject a subject with a low but highly variable performance. However, it was not stringent enough to indicate the final plateau of efficiency. More "drug free" data concerning the practice effect should be published to enable the users of psychometric tests to make a reasonable selection according to their needs and to help them design their trials properly.

Adult↗
PubMed1988

[Correlation of the incidence of ambulatory and inpatient treatment in neurology/psychiatry in the course of a year].

There should be more out-patient treatment of neurological and psychiatric disorders. This first-ever coverage of the morbidity of out-patient treatment over a period of one year in Berlin enables appraisal in comparison to the amount of inpatient treatment, broken down according to diagnosis, age, and sex. This offers pointers for future training and capacity.

Adolescent↗
PubMed1988

Management practices, physician autonomy, and satisfaction. Evidence from mental health institutions in the Federal Republic of Germany.

Physicians are moving into organized settings where their autonomy is more constrained and where management has more responsibility for physician satisfaction. The relationship of management practices to physician autonomy and satisfaction was explored in a survey of 185 psychiatrists in the State of Hessen in the Federal Republic of Germany (FRG). Analysis revealed that controlling for physician and institutional characteristics, management practices in relationship to participative activities, supportive communication, and peer review activities were the most important predictors both of perceived clinical autonomy and of work satisfaction. Gender was also a factor in that male physicians experienced greater perceived autonomy. Perceived clinical autonomy was an important factor in explaining satisfaction, whereas a few other physician and institutional characteristics were significant in predicting satisfaction. Unexpectedly, there was more perceived clinical autonomy among psychiatrists in larger, less well funded, more managerially constrained, state institutions than in smaller, community general hospitals and private organizations. Implications for further research are discussed.

Cross-Sectional Studies↗
PubMed1988

Association of pain and physical dependency with depression in physically ill middle-aged and elderly persons.

To investigate the relationship of pain and physical dependency to depression, the authors conducted a panel survey of 133 middle-aged and elderly persons with recent exacerbations of various physical illnesses. Of the original 133 subjects, 114 participated in two in-depth personal interviews conducted about three months apart. Variables that were measured included age, income, social support, physical dependency, pain, and depression. Physical dependency was moderately associated with depression (r = .27). A multiple regression analysis performed to control for the other variables, however, revealed that physical dependency had little effect on depression (R2 change = .03). Correlation (r = .41) and regression (R2 change = .13) analyses indicated that pain was an important factor in level of depression even after controlling for all of the other variables.

Activities of Daily Living↗
PubMed1988

[Unusually early onset of Kawasaki syndrome with coronary artery aneurysms].

Kawasaki disease is a multisystem illness that has been described throughout the world. It affects children with a peak frequency in the 6-month to 5-year group. Besides the typical clinical findings and specific laboratory changes during the initial phase of acute illness there are obligatory cardiovascular manifestations due to a generalized microvasculitis. Above all the coronary arteritis resulting in the formation of aneurysm may complicate a primarily good prognosis (causing death in 1-2% of the cases). The present case report describes a coronary artery involvement in a young 1 1/2-month-old infant with Kawasaki disease.

Cardiac Catheterization↗
PubMed1987

The effect of opioids on rat plasma atrial natriuretic peptide.

The effect of multiple opioid receptor agonists on plasma immunoreactive atrial natriuretic factor (IR-ANF) was studied in conscious non-hydrated rats. We found that mu-opioid receptor agonists, given subcutaneously, increased plasma IR-ANF, while kappa-receptor agonists did not alter the plasma levels of IR-ANF. The mu-agonist fentanyl (0.05 mg/kg) caused a 10-fold increase in the concentration of IR-ANF, maximal levels being reached within 5-10 min. U 50,488-H and ethylketocyclazocine (EKC), both selective kappa-receptor ligands, were ineffective in this respect. The effect of fentanyl upon plasma IR-ANF was completely abolished by pretreatment with the narcotic antagonist naltrexone, proving opioid receptor specificity of the fentanyl effect. The quaternary antagonist N-methylnaltrexone (1 mg/kg) failed to block the fentanyl-induced increase of ANF, suggesting that opiates bring about their action on ANF via a central mechanism.

Amino Acids↗
PubMed1987

Mechanisms of arachidonic acid-induced contractions of canine cerebral arteries.

The effects of arachidonic acid in cerebral blood vessels has been examined using rings of canine cerebral arteries. Arachidonic acid produced dose-dependent contractions of this preparation even after mechanical removal of the endothelium. The contractions were not blocked by indomethacin or acetylsalicylic acid, both of which inhibit cyclooxygenase, but were inhibited by nordihydroguaiaretic acid which is a lipoxygenase inhibitor, BW 755c which blocks both pathways, and FPL 55712 which is an antagonist at leukotriene receptors. These data imply that arachidonic acid-induced contractions are mediated by products of the lipoxygenase pathway. Leukotrienes and cyclooxygenase products are generated by this preparation as shown by HPLC and radioimmunoassay and both LTC4 and LTD4 produce contractions in cerebral arteries lending further evidence in support of this suggestion.

Animals↗
PubMed1987

Relationship between antipyrine absorption and blood flow rate in rat jejunum, ileum, and colon.

The appearance rate of antipyrine in intestinal venous blood was measured in anesthetized rats during perfusion (0.2 ml/min) of a buffered solution with 1 mmol/l labeled antipyrine through a jejunal, ileal, or colonic segment (length: 2-5 cm). When the blood flow rate was increased from 0.9-1.2 to 1.6-2.0 ml min-1 g-1 by raising the systemic blood pressure from 80 to 130 mm Hg, the absorption of antipyrine increased only in the colon. Stepwise reduction of the blood flow rate from 1.4-1.7 to 0.2-0.3 or stepwise raise from 0.2-0.3 to 1.4 ml min-1 g-1 by constriction or release of the mesenteric artery decreased or increased the absorption rate of antipyrine. The relation between absorption and flow rate can be described by curves which ascend at low and level off into a horizontal section at high flow rates. At the same blood flow rate the regional absorption rate decreased in the order jejunum, ileum, and colon with the largest step between ileum and colon. Model analysis yielded the following results for jejunum, ileum, and colon, respectively: permeability-surface area product 0.083, 0.074, and 0.037 ml min-1 g-1; fraction of absorptive site blood flow rate 0.24, 0.19, 0.08. The differences can be attributed mainly to the change of the surface area from jejunum to ileum and colon.

Animals↗
PubMed1987

Cation-mediated release and proteolytic cleavage of basic protein of isolated human myelin at acid pH.

Myelin from human brain was incubated at pH 4.4 with metal salts, including KCl, NaCl, CaCl2, and MgSO4, to elicit cation-dependent autoproteolysis of myelin proteins. Incubation of myelin resulted in soluble proteolytic breakdown products of Mr smaller than those of the three original myelin basic proteins (MBPs). Comparable polypeptides were essentially absent from residual myelin. Proteolysis was strongly stimulated by increasing millimolar concentrations of K+, Na+, and Mg2+ and only moderately by Ca2+. Breakdown products were traced to MBP by immunostaining. Their origin from MBP was also indicated by identical electrophoretic cleavage patterns from endogenous myelin protein and exogenous MBP. All four metal salts, in addition to activating endogenous proteolysis, also caused a biphasic extraction of MBP. Electrophoresis of myelin revealed a quick initial and a slow further loss of protein, eventually leading to the removal of up to 78% of original MBP. The results are consistent with a concurrent extraction of MBP and activation of latent-bound acid protease activity by metal cations. It is therefore suggested that, in particular disease states, unfavorable changes in electrolytes and pH of white matter may cause a selective loss and proteolytic cleavage of MBP.

Acids↗
PubMed1987

Evidence for the expression of peptides derived from three opioid precursors in NG 108CC15 hybrid cells.

Five opioid peptides (immunoreactivity) derived from their respective opioid precursors were measured in neuroblastoma-glioma hybrid cells (NG 108CC15; pmol/g protein): heptapeptide (Tyr-Gly-Gly-Phe-Met-Arg-Phe), 13.0 +/- 2.6; alpha-neoendorphin, 6.6 +/- 0.8; dynorphin A, 4.4 +/- 1.5; dynorphin A 1-8, 1.3 +/- 0.29; beta-endorphin, 0.3 +/- 0.13. These peptides originate from preproenkephalin A (heptapeptide), prodynorphin (alpha-neonedorphin, dynorphin A, dynorphin A 1-8) and proopiomelanocortin (beta-endorphin). The data suggest the expression of all three known opioid precursors in a single hybrid cell line, permitting a simultaneous investigation of the processing of different opioid peptides under identical experimental conditions.

Animals↗
PubMed1987

Gonadotropin stimulated androgen secretion of rainbow trout (Salmo gairdneri Richardson) testis in vitro.

1. The secretion of five androgens was quantified from trout testes under GTH-stimulation in vitro before and after the onset of milt production, and a general increase of basal and GTH stimulated androgen secretion was recorded during this period. 2. 11-Ketotestosterone, testosterone, and in spermiating males, 11 beta-hydroxytestosterone as well showed GTH dependent concentration increases, while androstenetrione and 11 beta-hydroxyandrostendione were found in highly variable amounts. 3. 17 beta-Hydroxyandrogen glucuronides in the medium (with the exception of testosterone) and tissue androgens were by far exceeded by the free androgens in the medium.

Androgens↗
PubMed1987

Origins of stereotypes of the elderly: an experimental study of the self-other discrepancy.

An experiment using young and old subjects was carried out to test two different explanations for the Harris survey data showing that elderly persons rate their own lives much more positively than they rate the lives of similarly aged others. The informational bias explanation suggests that the old (and young) are passive recipients and mediators of widely disseminated information concerning the life problems of the elderly. The negative evaluations of the elderly in general reflect in part the objective conditions of the lives of the elderly and the tendency of the media to focus on the problems of the elderly. In contrast, self-evaluations are relatively positive because generalized views of growing old are attenuated by lowered expectancies regarding living conditions in late life. The motivational bias explanation assumes a self-enhancing cognitive bias among the elderly that causes them to devalue the lives of similarly aged others. The first explanation is supported by replicating the Harris poll data and demonstrating that the self-other discrepancy can be systematically manipulated by varying, in theoretically relevant ways, the instructions given to subjects.

Adolescent↗