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Biomedical subjects

E Singer

Publications and source records attributed to E Singer.

At least 37 records · Page 2Linked to original sources
PubMed1985

Angiotensin-induced hypertension in conscious dogs: biochemical parameters and baroreceptor reflex.

The effects of a continuous iv infusion (osmotic minipumps) of angiotensin II (80 ng . kg-1 . min-1) and isoprenaline (10 ng . kg-1 . min-1) lasting 28 days were studied in six normotensive, conscious dogs. The parameters measured were systolic and diastolic blood pressure, heart rate, levels of angiotensin II, renin activity, aldosterone and antidiuretic hormone in plasma, baroreceptor reflex sensitivity and body weight. The treatment resulted in an approximately sevenfold increase in plasma angiotensin II level from 62.9 +/- 24.5 pg . ml-1 to 455.3 +/- 95.6 pg . ml-1. Systolic and diastolic blood pressure, measured for the first time 2 days after implanting the minipumps, were markedly increased throughout the infusion period (pretreatment value: 123.8 +/- 5.3/68.3 +/- 3.8 mmHg; after 2 days: 159.8 +/- 12.0/100.5 +/- 9.8 mmHg; after 28 days: 159.8 +/- 7.1/98.3 +/- 6.4 mmHg, whereas the heart rate remained unchanged due to the combined effects of angiotensin II and the concomitantly given isoprenaline. A high correlation was found between angiotensin II level in plasma and mean arterial blood pressure (r = 0.846; p less than 0.001). Furthermore, plasma renin activity was markedly suppressed by the treatment, and aldosterone levels rose. Plasma antidiuretic hormone levels were found to be unchanged at the chosen sampling time. A decrease in baroreceptor reflex sensitivity accompanied the development of the hypertensive state. There was also a loss of body weight during the infusion of angiotensin II and isoprenaline. The data provide evidence for the usefulness of the presented experimental protocol as an alternative model of arterial hypertension in chronically instrumented, conscious dogs.

Aldosterone↗
PubMed1984

[Interaction of the neuropeptides substance P and neurotensin with central monoamine transmitter systems].

In the present paper, findings on two neuropeptides, substance P (SP) and neurotensin (NT), are presented and discussed with respect to a neuromodulatory role of these peptides on brain monoamine transmitter systems. Substance P: In view of the close morphological relationship of serotonin-(5-HT-) and SP-neurons in the brainstem of the rat the effect of SP was studied in vitro on the field stimulated release of 3H-5-HT from slices of medulla oblongata. Substance P enhanced the electrically induced release of 3H-5-HT without affecting the basal release. Furthermore, the immunohistochemical evidence for the coexistence of SP and 5-HT in neurons of this area was corroborated by employing neurochemical lesioning techniques. Neurotensin: Binding sites for NT in the substantia nigra and the ventral tegmentum of the rat were decreased after stereotaxic injection of the neurotoxin 6-hydroxydopamine, which specifically destroys catecholamine-containing neurons. The results indicate a localization of NT-receptors on dopaminergic neurons in these regions. In the striatum and the nucleus accumbens, the field stimulated release of 3H-dopamine in vitro was markedly and dose-dependently increased in the presence of NT, demonstrating a direct effect of the peptide on dopamine-containing nerve terminals. In the medial preoptic nucleus, a high density of NT-binding sites was measured and stereotaxically microinjected NT caused a rise in plasma levels of luteinizing hormone (LH). Concomitantly, noradrenaline levels in the injected region were significantly reduced. The results favour an interaction of NT and noradrenergic neurons in the hypothalamic control of LH secretion.

Animals↗
PubMed1980

Reduction of [3H]muscimol binding sites in rat dorsal spinal cord after neonatal capsaicin treatment.

Two-day-old rats were pretreated with 50 mg/kg of capsaicin. After 3--4 months, specific binding of [3H]muscimol and [3H]strychnine was measured in membrane preparations from dorsal spinal cord. A 20-30% decrease of the number of [3H]muscimol binding sites was observed after capsaicin treatment. In contrast, [3H]strychnine binding was unchanged. The results provide indirect evidence for a presynaptic location of GABA receptors on capsaicin-sensitive primary afferent neurons.

Animals↗
PubMed1980

[Experimental changes of GABA receptor binding in the central nervous system (author's transl)].

The effects of etazolate and cartazolate, two pyrazolopyridine derivatives with anxiolytic actions, on the receptor binding of gamma-aminobutyric acid (GABA) was studied in vitro using membrane fractions prepared from rat brain. Both compounds increased the specific GABA receptor binding. This effect was markedly enhanced in the presence of several anions, predominantly halide ions. Pyrazolopyridines appear to modulate the binding properties of GABA receptors by acting on a site closely related to the chloride ion channel of the membrane. These results indicate that activation of the GABA system is a possible mechanism of action of pyrazolopyridines. In the second part of the study binding experiments were used to provide evidence for the presynaptic localisation of GABA receptors on primary afferent terminals in the dorsal horn of the rat spinal cord. Capsaicin-induced degeneration of primary afferent fibres significantly reduced the number of GABA receptors in the dorsal spinal cord, whereas the number of benzodiazepine and glycine receptors remained unchanged. The results support the role of GABA as transmitter involved in presynaptic inhibition in the spinal cord.

Animals↗
PubMed1979

Properties of [3H]taurine release from crude synaptosomal fractions of rat cerebral cortex.

The release of previously accumulated [3H]taurine and [14C]GABA from crude synaptosomal (P2) fractions isolated from rat cerebral cortex was studied using a superfusion system. The spontaneous efflux of [3H]taurine and [14C]GABA was stimulated by elevated concentrations of K+ (15--133 mM) in a concentration-dependent manner. This K+-stimulated relase of [14C]Gaba but not of [3H]taurine was enhanced in the presence of Ca2+. However, addition of 3 mM Ca2+ to the superfusion medium in the presence of the ionophore A 23187 resulted in a stimulation of the release of both [3H]taurine and [14C]GABA. These results are discussed in connection with the cellular localization of taurine in the central nervous system.

Animals↗
PubMed1977

[Effect of the beta-adrenergic blocking agent bupranolol on the plasma renin activity in normotensive rats].

The effects of the beta-adrenergic blocking agent 3-tert.-butyl-amino-1-(6'-chloro-3'-methylphenoxy)-propan-2-ol hydrochloride (bupranolol; KL 255; Betadrenol) on the plasma renin activity (PRA) of normotensive rats were studied in comparison to propranolol. Bupranolol (10--100 microgram/kg) reduced basal PRA and inhibited the isoproterenol as well as dihydralazine induced increase of PRA in a dose dependent fashion. Bupranolol exhibited an effect 2--4 times stronger than that of propranolol. The PRA inhibiting effects of bupranolol seem to be linked to its beta-receptor blocking properties.

Adrenergic beta-Antagonists↗
PubMed1976

Mepiprazole, a new psychotropic drug: effects on uptake and retention of monoamines in rat brain synaptosomes.

The influence of mepiprazole (EMD 16,923), a new pyrazol-ylalkyl-piperazine derivative, on the uptake of 3H-norepinephrine (NE), 3H-dopamine (DA), and 3H-serotonin (5-HT) into rat brain synaptosomes from cerebral cortex, corpus striatum, and hypothalamus was investigated in comparison with several psychotropic drugs, including oxypertine, d-amphetamine, imipramine, desipramine, chlorimipramine, amitriptyline, and chlorpromazine in vitro. Mepiprazole was a relatively weak inhibitor of monoamine uptake and exhibited its strongest action on the hypothalamic 5-HT uptake, being almost equipotent with desipramine (IC50 = 0.9 MUM). Furthermore, the influence of the drugs on the retention of 3H-amines previously taken up by whole rat brain synaptosomes was studied. Unlike the tricyclic antidepressants, mepiprazole as well as oxypertine and d-amphetamine markedly increased the efflux of radioactivity during a 20-min incubation at 37 degrees C at low concentrations (10(-6) to 10(-5) M), whereas at 10(-4) M all drugs greatly enhanced the efflux. The ability of mepiprazole to increase 5-HT concentration at the receptor level by a combination of neuronal uptake inhibition and release is discussed in relationship to the central actions of the drug.

Animals↗
PubMed1976

Replicating psychiatric ratings through multiple regression analysis: The Midtown Manhattan Restudy.

This paper examines three related questions: First, can psychiatrists' judgments be successfully predicted by multiple regression techniques? Second, assuming that they can, are such ratings a valid measure of mental health for the same sample at a later point in time? Third, what is the relation between mental health ratings made in 1954 and such subsequently reported behavioral outcomes as nervous breakdown, mental hospitalization, or seeking professional help for emotional problems? The evidence presented warrants two conclusion. (1) The computer-derived mental health ratings are an adequate substitute for the original ratings. The regression equation accounts for 69 percent of the variance in those ratings; and the computer-derived ratings behave in the same way as the psychiatrists' ratings in relation to other variables. (2) However, neither the psychiatrists' ratings nor the computer-derived ratings are very accurate in predicting subsequent self-reported behavior indicative of mental impairment.

Adult↗
PubMed1976

Sociopsychological factors influencing response to levodopa therapy for Parkinson's disease.

This article examines the effect of a series of physical and sociopsychological variables on the response shown by Parkinson patients to levodopa therapy. Of the ten major variables examined, six measure relatively enduring personality adaptations: suggestibility, passivity, self-expectations, stigma, attitudes toward illness, and the perception of the expectations of others. Four are illness-related characteristics: diagnosis (primary or secondary parkinsonism); the existence of health problems in addition to Parkinson's disease; whether or not the patient was hospitalized at the beginning of treatment; and symptom improvement as rated by the patient's physician. Age, sex, severity and duration of disease, and use of anti-Parkinson drugs in addition to levodopa were controlled in all of the analyses. The effect of levodopa therapy was assessed in four major areas: activity, social participation, depression, and enjoyment of life. Findings can be summarized as follows: Five of the six personality variables do, in fact, modify the amount of social or psychological change shown by Parkinson patients treated with levodopa. The only one which fails to have such an effect is passivity; this may reflect a measurement problem. However, only two of the four illness-related characteristics which were examined made a difference in treatment outcome: diagnosis and symptomatic improvement, as rated by the patient's physician.

Adaptation, Psychological↗
PubMed1976

[Change of a releasing mechanism involved in pre-catching behavior during the development of Salamandra salamandra (L.)].

Preycatching behaviour in salamanders (Salamandra salamandra L.) was studied before (60 larvae) and after metamorphosis (50 juveniles) to find out whether there are differences in releasing mechanisms depending on the developmental stage. Responses to prey dummies of different size, shape and orientation were recorded. With advancing age salamanders respond more selectively, preferring "wormlike" dummies. The releasing mechanism is narrowed down during 10 months after metamorphosis. This is not caused by learning processes.

Animals↗