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Biomedical subjects

S Ritter

Publications and source records attributed to S Ritter.

At least 73 records · Page 4Linked to original sources
PubMed1996

Feeding induced by pharmacological blockade of fatty acid metabolism is selectively attenuated by hindbrain injections of the galanin receptor antagonist, M40.

Galanin has been shown to stimulate feeding when injected intracranially in rats. Lesion and Fos studies have shown that the neural pathway for feeding stimulated by mercaptoacetate (MA)-induced blockade of fatty acid oxidation includes several structures rich in galanin cell bodies or terminals. In the present experiment, we examined the role of hindbrain galanin in feeding stimulated by MA. We found that galanin (1 nmol) stimulates feeding when injected in the nucleus of the solitary tract (NTS), a site that is crucial for MA-induced feeding, or into the fourth ventricle (4V, 1 or 5 nmol) and that NTS or 4V injections of the galanin receptor antagonist, M40 (1.5 or 5 nmol), completely blocked feeding induced by MA (68 mg/kg). The effect of the M40 appeared to be specific for MA-induced feeding, since M40 did not significantly attenuate either feeding induced by the antimetabolic glucose analog, 2-deoxy-D-glucose (2DG, 100 or 200 mg/kg), or deprivation-induced water intake. Results suggest that feeding induced by decreased fatty acid oxidation relies upon galaninergic terminals in the hindbrain. Furthermore, results indicate that hindbrain neurons involved in MA-induced feeding differ neurochemically from those important for 2DG-induced feeding.

Animals↗
PubMed1996

The effects of low-, medium-, and high-fat diets on 2-deoxy-D-glucose- and mercaptoacetate-induced feeding.

The present study examined the feeding responses stimulated by low suprathreshold and optimal doses of 2-DG and MA in three groups of rats maintained and tested on low (4.3%), medium (13.5%), or high (66.4%) fat diets. Results show that diet alters the response to 2-DG and MA. Rats on the low-fat diet significantly increased food intake after both the low and high doses of 2-DG. Rats on the medium- and high-fat diet significantly increased food intake after both the low and high doses of 2-DG. Rats on the medium- and high-fat diets significantly increased food intake only after the high dose of 2-DG. After administration of the low and high doses of MA, rats on the high-fat diet ate significantly more. However, rats on the low- and medium-fat diets significantly increased food intake only after the high dose of MA. These results suggest that diet-induced dependence of rats on fat or carbohydrate metabolism alters the sensitivity of systems controlling food intake in response to deficits in the availability of these specific metabolic fuels.

Animals↗
PubMed1996

Comparison of chromosomal damage induced by X-rays and Ar ions with an LET of 1840 keV/micrometer in G1 V79 cells.

Synchronous V79 Chinese hamster cells were exposed in G1 to either X-rays or 4.6 MeV/u Ar-ions (LET = 1840 keV/micrometer) and the induction of chromosomal damage was measured at five sampling times ranging from 14 to 30 h after treatment. To distinguish between cells in the first and second post-irradiation cycle the fluorescence-plus-Giemsa technique was applied. The experiment showed that the time-course of the appearance of damaged cells was markedly influenced by radiation-induced cell cycle delays and depended on both radiation quality and dose. The yield of aberrant metaphases and the number of aberrations per metaphase was found to increase with sampling time, but this increase was more pronounced for Ar ions. These differences in yield-time profiles of X-ray and Ar ion induced chromosomal damage are particularly important for an accurate determination of the RBE for particles. Our data clearly indicate that meaningful RBEs can only be obtained if chromosomal damage is analysed at several post-irradiation sampling times and the complete time-course of the expression of chromosomal damage is taken into account. Besides these quantitative differences, differences in the spectrum of chromosomal lesions were observed for X-rays and Ar ions. Following particle exposure more breaks and less exchange-type aberrations were formed compared with X-irradiation and, despite irradiation in G(1), a significant number of chromatid-type aberrations occurred in Ar-irradiated samples. The experimental results are interpreted on the basis of the different pattern of energy deposition by sparsely and densely ionizing radiation. In addition, a statistical analysis based on the Neyman type A distribution is performed, which takes into account the specific stochastic properties of particle irradiation.

Animals↗
PubMed1996

A model of clinical supervision for nurses undertaking short placements in mental health care settings.

This paper presents a model of supervision developed from the experience of supervising undergraduate general nursing students undertaking clinical experience in psychiatric wards. Supervision structures and methods are presented and the theoretical under-pinnings of the supervision model are discussed. Our experience of using the model over the past 5 years suggests that it has the potential to allow students to gain a good understanding of individual patients within a short time span and to engage with them as active collaborators in care. The supervision model can also assist students to develop the knowledge and insights needed to gain the respect of senior colleagues, and the confidence to challenge the professional conservatism that often characterizes psychiatric wards.

Clinical Competence↗
PubMed1996

Diagnostic and prognostic value of cerebral 31P magnetic resonance spectroscopy in neonates with perinatal asphyxia.

The impact of depressed neonatal cerebral oxidative phosphorylation for diagnosing the severity of perinatal asphyxia was estimated by correlating the concentrations of phosphocreatine (PCr) and ATP as determined by magnetic resonance spectroscopy with the degree of hypoxic-ischemic encephalopathy (HIE) in 23 asphyxiated term neonates. Ten healthy age-matched neonates served as controls. In patients, the mean concentrations +/- SD of PCr and ATP were 0.99 +/- 0.46 mmol/L (1.6 +/- 0.2 mmol/L) and 0.99 +/- 0.35 mmol/L (1.7 +/- 0.2 mmol/L), respectively (normal values in parentheses). [PCr] and [ATP] correlated significantly with the severity of HIE (r = 0.85 and 0.9, respectively, p < 0.001), indicating that the neonatal encephalopathy is the clinical manifestation of a marred brain energy metabolism. Neurodevelopmental outcome was evaluated in 21 children at 3, 9, and 18 mo. Seven infants had multiple impairments, five were moderately handicapped, five had only mild symptoms, and four were normal. There was a significant correlation between the cerebral concentrations of PCr or ATP at birth and outcome (r = 0.8, p < 0.001) and between the degree of neonatal neurologic depression and outcome (r = 0.7). More important, the outcome of neonates with moderate HIE could better be predicted with information from quantitative 31P magnetic resonance spectroscopy than from neurologic examinations. In general, the accuracy of outcome predictability could significantly be increased by adding results from 31P magnetic resonance spectroscopy to the neonatal neurologic score, but not vice versa. No correlation with outcome was found for other perinatal risk factors, including Apgar score.

Asphyxia Neonatorum↗
PubMed1995

2-Deoxy-D-glucose but not 2-mercaptoacetate increases Fos-like immunoreactivity in adrenal medulla and sympathetic preganglionic neurons.

2-Deoxy-D-glucose (2DG) and 2-mercaptoacetate (MA) are drugs that competitively inhibit metabolism of glucose and fatty acids, respectively. Both 2DG and MA stimulate food intake. In addition, 2DG-induced glucoprivation is a known stimulus for adrenomedullary secretion. However, very little is known about the effects of MA on the sympathoadrenal system. In the present study, we examined effects of 2DG and MA on the activity of preganglionic neurons and the adrenal medulla, as indicated by expression of Fos-like immunoreactivity (Fos-li). 2DG, MA, or saline was administered using a stress-attenuated paradigm incorporating remote drug infusion. Expression of Fos-like immunoreactivity (Fos-li) was subsequently examined in the adrenal medulla and in preganglionic sympathetic neurons throughout the intermediolateral column (IML) of the thoracic and lumbar spinal cord. We found that 2DG increased Fos-li in the adrenal medulla and in the IML primarily at spinal cord segments T7-T10, where adrenomedullary preganglionic neurons reside. In contrast, MA did not induce Fos-li either in the adrenal medulla or in sympathetic preganglionic neurons at any cord level. Results support the hypothesis that decreased fatty acid oxidation is not a stimulus for adrenal medullary secretion and provide evidence for a highly selective stimulation of adrenal medullary preganglionic neurons by 2DG.

Adrenal Medulla↗
PubMed1995

Glucose homeostasis and sympathoadrenal activity in mercaptoacetate-treated rats.

The effect of the fatty acid oxidation inhibitor, sodium mercaptoacetate (MA, 600 mumol/kg) on peripheral energy substrate metabolism was investigated in rats with permanent heart catheters. Rats were either fed, 48-h food deprived, or exercising for 30 min. Before and after intravenous MA injection, stress-free blood samples were taken for measurement of blood glucose, plasma free fatty acids (FFA), insulin, epinephrine (E), and norepinephrine (NE) concentrations. In fed animals, MA increased blood glucose, plasma FFA, and NE and decreased insulin concentrations. Plasma E levels did not change. In 48-h-deprived animals, MA elevated low baseline glucose concentrations to levels observed in MA-treated fed animals. Plasma insulin concentrations decreased to almost undetectable levels. Plasma catecholamines and FFA were increased compared to fed rats. In exercising rats, MA caused an exaggerated increase of blood glucose and a pronounced reduction of plasma insulin without affecting exercise-induced FFA and catecholamine responses. The data revealed that the mechanisms that regulate blood glucose concentrations during MA treatment are dependent on the nutritional state and ambient energy expenditure.

Adrenal Glands↗
PubMed1995

Mercaptoacetate-induced feeding is impaired by central nucleus of the amygdala lesions.

Systemic administration of mercaptoacetate (MA) blocks beta oxidation of fatty acids and stimulates food intake. The present experiment examined MA-induced feeding in rats with bilateral lesions of the central nucleus of the amygdala (CNA) and sham-operated controls. Food intake was measured for 6 h immediately following i.p. injection of 400, 600, or 800 mumol/kg of MA or saline. Feeding was also measured in these rats in response to 2-deoxy-D-glucose (2DG) (100, 200, and 300 mg/kg, SC), a glucose analogue that competitively inhibits glucose utilization. We found that CNA lesions blocked feeding in response to all three doses of MA. Feeding in response to 2DG was significantly reduced, but not abolished, by the lesion. These findings suggest that the CNA is a crucial component of the neural pathway for feeding in response to MA and may also participate in 2DG-induced feeding.

Amygdala↗
PubMed1994

Induction of Fos-like immunoreactivity (Fos-li) and stimulation of feeding by 2,5-anhydro-D-mannitol (2,5-AM) require the vagus nerve.

The antimetabolic fructose analogue, 2,5-anhydro-D-mannitol (2,5-AM), stimulates feeding. Selective hepatic branch vagotomy has been shown to block feeding induced by low 2,5-AM doses. However, hepatic vagal fibers are not the sole mediators of 2,5-AM-induced feeding, since hepatic branch vagotomy does not impair feeding induced by higher doses of 2,5-AM. To further evaluate the role of the vagus in the response to 2,5-AM, we examined the effect of total subdiaphragmatic vagotomy on feeding induced by a high 2,5-AM dose (500 mg/kg). In addition, we assessed the ability of 2,5-AM (300 and 500 mg/kg) to induce Fos-like immunoreactivity (Fos-li) in the brain in sham-operated (SHAM), hepatic branch vagotomized (HBV) and total subdiaphragmatic vagotomized (TSDV) rats. Both doses of 2,5-AM, but not control solutions, induced Fos-li in the area postrema (AP), nucleus of the solitary tract (NTS) and lateral parabrachial nucleus (1PBN). Very weak immunoreactivity was present in the central nucleus of the amygdala and none was observed in the locus coeruleus or paraventricular nucleus of the hypothalamus. The effect of the lower 2,5-AM dose on Fos-li was blocked by HBV. The high dose effect was blocked by TSDV but not by HBV. Feeding induced by the high dose of 2,5-AM was also blocked by TSDV. Results are consistent with the hypothesis that stimulation of feeding by 2,5-AM is dependent on the vagus nerve. Hepatic branch fibers may have the lowest threshold for activation, but fibers in other vagal branches independently mediate induction of c-fos and stimulate food intake at higher doses of the analogue.

Animals↗
PubMed1994

2-Mercaptoacetate and 2-deoxy-D-glucose induce Fos-like immunoreactivity in rat brain.

2-Deoxy-D-glucose (2-DG) and 2-mercaptoacetate (MA) are antimetabolic drugs that selectively antagonize glucose and fatty acid utilization, respectively, and stimulate feeding. Fos immunohistochemistry was employed to identify brain neurons activated by these drugs and to assess the role of the vagus nerve in the drug effects. Remote intravenous infusions of both MA and 2-DG induced Fos-like immunoreactivity (Fos-li) in specific brain sites, but the pattern was different for the two drugs. Mercaptoacetate induced Fos-li in the nucleus of the solitary tract (NTS), the central subnucleus of the lateral parabrachial nucleus (1PBN), the central nucleus of the amygdala (CNA, lateral part) and the dorsal motor nucleus of the vagus (DMV). Induction of Fos-li in the brain by MA was totally abolished by vagotomy. 2-Deoxy-D-glucose also induced Fos-li in the NTS, CNA (lateral part) and DMV, as well as in the external 1PBN subnucleus, locus coeruleus, paraventricular and supraoptic hypothalamic nuclei, and in scattered cells throughout the diencephalon. Induction of Fos-li by 2-DG was not blocked by vagotomy. Results suggest that 2-DG's effects on Fos-li are mediated by a direct central action, whereas MA's effects are mediated by peripheral sensory neurons. Thus, availability of glucose and fatty acids influences the activity of specific brain sites by different neural mechanisms. The correlation of Fos-immunoreactive sites with sites where lesions have been shown to cause deficits in MA- and 2-DG-induced feeding indicates that c-fos expression defines in part the central pathways involved in the metabolic control of feeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Differential effects of infused nutrients on 2-deoxy-D-glucose- and 2-mercaptoacetate-induced feeding.

We examined the effects of glucose, lipid, or fructose infusion on 2-deoxy-D-glucose (2DG)- and 2-mercaptoacetate (MA)-induced feeding. Rats with chronic intra-atrial catheters were infused for 15 min with one of the above nutrients and then injected with 2DG or MA. The nutrient infusion continued for the next 2 h and food intake was simultaneously measured. For control conditions, equitonic saline was infused, and 2DG, MA, or saline was injected. We found that glucose was the only nutrient source capable of significantly reducing 2DG-induced feeding. Equicaloric infusions of lipid or fructose did not significantly reduce 2DG-induced feeding. However, feeding induced by MA was similarly and significantly reduced by glucose, lipid, and fructose. These results suggest that 2DG-induced feeding is mediated by receptor cells that are selectively responsive to glucose availability, and MA-induced feeding is mediated by receptor cells that are responsive to a wider range of metabolic fuels.

Animals↗
PubMed1994

Cell cycle delays induced by heavy ion irradiation of synchronous mammalian cells.

Cell cycle delays in V79 Chinese hamster cells induced by heavy ion exposure have been investigated using flow cytometry. Synchronous cell populations in G1, S and late-S G2/M phase were used, which were prepared by centrifugal elutriation. Cells were irradiated with particles from Z = 10 (neon) up to 96 (uranium) in the energy range from 2.4 to 17.4 MeV/u and the LET range from 415 to 16,225 keV/micron at the UNILAC at GSI, Darmstadt. For comparison, experiments with 250 kV X-rays were performed. For light particles like neon, cell cycle perturbations comparable with those after X-ray irradiation were found, and with increasing LET an increasing delay per particle traversal was observed. For the highest LET values extended delavy in G1, S and G2/M phase were detected immediately after irradiation. A large fraction of the cells remained in S or G2/M phase up to 48 h or longer after irradiation: they probably died in interphase. The prolongation of delays with increasing LET is in contrast with inactivation cross section measurements, where cross sections reach a plateau at LET values > 500 keV/micron. No significant cell age dependence of cycle delays was detected for the very high LET values. In addition to cell cycle delays, two effects related to the DNA content as determined by flow cytometry were found after irradiation with very high LET particles, that were attributed to cell fusion and drastic morphological changes of the cells. Estimations based on the dose deposited by a single particle hit in the cell nucleus and the actual number of hits show that the basic trend of the experimental results can be explained by the stochastic properties of particle radiation.

Animals↗
PubMed1994

Influence of radiation quality on the expression of chromosomal damage.

The amount of chromosomal damage induced in synchronous V79 cells by either 250 kV X-rays or 4.6 MeV/u Ar ions (LET: 1850 keV/microns) was determined at five successive sampling times. The experiments show that the time course of the appearance of damaged cells is strongly influenced by radiation-induced cell cycle perturbations and mitotic delay and depends on radiation quality and dose. The yield of chromosomal damage was found to increase with sampling time, but this increase was more pronounced for Ar ions. Because of the observed differences in the yield time profiles induced by sparsely and densely ionizing radiation the contribution of each sample to the overall damage was considered, i.e. the total (time integrated) amount of damage was determined. The obtained data are interpreted in terms of differences in the spatial energy deposition by sparsely and densely ionizing radiation.

Animals↗
PubMed1994

Contaminated collection media as a cause of pseudoinfection.

Following the appearance of positive Gram's stains from sterile surgical cases, an investigation was begun. Nonviable but stainable bacteria were found in the gel-based transport media. The use of a cause-and-effect diagram helped to show the numerous items that affected the problem.

Bacteria↗