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Biomedical subjects

R Schmid

Publications and source records attributed to R Schmid.

At least 235 records · Page 13Linked to original sources
PubMed1988

Effect of somatostatin on skin lesions and concentrations of plasma amino acids in a patient with glucagonoma-syndrome.

A case of glucagonoma syndrome in a 58-year-old male patient who had the typical skin lesions associated with severe hypoaminoacidemia is described. The decrease in amino acids has been proposed to be causally related to the dermatosis. Furthermore, it has been shown previously that somatostatin rapidly improves skin lesions in glucagonoma patients. Therefore, plasma amino acid levels were determined before and during an infusion of somatostatin prior to surgical removal of the tumor in the tail of the pancreas. During somatostatin infusion in combination with total parenteral nutrition, 10 out of 22 amino acids were in the normal range. Thus it seems unlikely that normalization of amino acid levels is responsible for the rapid improvement in skin lesions in glucagonoma patients. On the other hand it cannot be excluded that partial normalization of amino acids contributed to the observed healing process. Nevertheless, somatostatin administered prior to surgery is a useful therapeutic regimen in these patients.

Adenoma, Islet Cell↗
PubMed1987

F0 portion of Escherichia coli ATP synthase: orientation of subunit c in the membrane.

Incubation of right-side-out oriented membrane vesicles of Escherichia coli with tetranitromethane resulted in the nitration of tyrosine residues (Tyr-10 and Tyr-73) of subunit c from the ATP synthase. Cleavage of the protein with cyanogen bromide and separation of the resulting fragments, especially of the tyrosine-containing peptides, clearly demonstrated that the distribution of the nitro groups is similar at any time and at any pH value chosen for the analysis. Furthermore, the percentage of 3-nitrotyrosine present in the two peptide fragments was in good agreement with that obtained for the intact polypeptide chain. While the modification of the tyrosine residues in subunit c with the lipophilic tetranitromethane is independent of the orientation of the membrane vesicles, the subsequent partial conversion of the 3-nitrotyrosine to the amino form only occurred when membrane vesicles with right-side-out orientation were treated with the ionic, water-soluble sodium dithionite, which at certain concentrations cannot penetrate biological membranes. Cleavage of subunit c isolated from nitrated and subsequently reduced membrane vesicles and separation of the resulting fragments by high-pressure liquid chromatography showed that the 3-nitrotyrosine in the Tyr-73-containing peptides has been completely reduced, while the nitro group in peptides containing Tyr-10 remained nearly unaffected.

Amino Acid Sequence↗
PubMed1987

Evolutionary relationship between Enterobacteriaceae: comparison of the ATP synthases (F1F0) of Escherichia coli and Klebsiella pneumoniae.

The ATP synthase complex of Klebsiella pneumoniae (KF1F0) has been purified and characterized. SDS-gel electrophoresis of the purified F1F0 complexes revealed an identical subunit pattern for E. coli (EF1F0) and K. pneumoniae. Antibodies raised against EF1 complex and purified EF0 subunits recognized the corresponding polypeptides of EF1F0 and KF1F0 in immunoblot analysis. Protease digestion of the individual subunits generated an identical cleavage pattern for subunits alpha, beta, gamma, epsilon, a, and c of both enzymes. Only for subunit delta different cleavage products were obtained. The isolated subunit c of both organisms showed only a slight deviation in the amino acid composition. These data suggest that extensive homologies exist in primary and secondary structure of both ATP synthase complexes reflecting a close phylogenetic relationship between the two enterobacteric tribes.

Biological Evolution↗
PubMed1987

Control of the Photosynthetic Apparatus of Acetabularia mediterranea by Blue Light : Analysis by Light-Saturation Curves.

During growth, Acetabularia mediterranea requires the action of blue light to maintain high rates of photosynthesis. In the present study, blue light-dependent alterations of the photosynthetic apparatus, which can be detected by analysis of light-saturation curves and by measurements of partial reactions of the photosynthetic electron transport chain, are described. Light-saturation curves of photosynthesis in vivo were measured with a new closed oxygen electrode system after culture of Acetabularia in continuous red or blue light. These curves were compared to those of 2,6-dichlorophenol-indophenol reduction by isolated chloroplast membranes. The analysis lead to the following statements: (a) only one reaction limits electron transport rates in vitro (dichlorophenol-indophenol reduction) at all light intensities irrespective of the light quality during growth, and (b) the limiting step is light driven and located in the reaction center of photosystem II. Presumably, this same reaction determines the flow of electrons under low light intensities in vivo in cells from white, blue, and red light. In addition to photosynthesis, the rates of dark respiration changed due to the action of blue light. Concomitantly, the light compensation point of apparent photosynthesis was shifted during monochromatic irradiations.

Journal Article↗
PubMed1987

[Current computerized support for vestibular function tests. II. An expert system for the classification of vertigo].

A computerized system (VERTIGO) aimed to the classification and diagnosis of different types of vertigo has been developed. It is based on the shell EXPERT (Weiss and Kulikowski, 1979). At present only the findings arising from patient history are considered as input data and the diagnostic possibilities of the system have been limited to the differential diagnosis of vertigo due to peripheral vestibular disorders. About thirty different forms of vertigo are taken into account. They are clustered in two groups, true vertigo and dizziness. Data are collected through a computer controlled questionnaire. Using the facilities offered by EXPERT, the sequence of the questions can be modified according to the flow of information in order to reproduce different diagnostic strategies. After history taking, the system presents a summary of the available findings followed by its diagnostic conclusions. Different conclusions can be proposed with different degrees of certainty. Conclusions can be justified by the system when required.

Adult↗
PubMed1987

[Current computerized support for vestibular function tests.I. Expert systems and their clinical applications].

Expert Systems are a new method developed by the branch of Computer Science known as Artificial Intelligence in order to make available the knowledge and the expertise of the specialists in a certain domain of the science to other operators in the same field. Most of their applications belong to the medical domain. In this paper the main features of the expert systems are briefly described. As an example the structure and the characteristics of the shell EXPERT (Weiss and Kulikowski, 1979) are presented in detail. This shell has already been used to develop several expert systems. It is the tool by which we constructed a consultation system (VERTIGO) aimed to classify different types of vertigo.

Expert Systems↗
PubMed1986

Very long chain fatty acids in genetic peroxisomal disease fibroblasts: differences between the cerebro-hepato-renal (Zellweger) syndrome and adrenoleukodystrophy variants.

Very long chain fatty acids were investigated by gas chromatography in fibroblasts of patients with genetic peroxisomal diseases (cerebro-hepato-renal (Zellweger) syndrome, childhood adrenoleukodystrophy, adrenomyeloneuropathy, neonatal adrenoleukodystrophy) and of controls. Concentrations of C 26:0 were increased to about the same extent in all disorders investigated. C 26:1 concentrations, on the other hand, were considerably elevated only in the cerebro-hepato-renal syndrome. In all control, adrenoleukodystrophy, and adrenomyeloneuropathy cases the C 22:0 concentration was higher than the respective C 26:0 concentration; the reverse was found in the cerebro-hepato-renal syndrome. These differences seem to reflect different impairment of peroxisomes in the cerebro-hepato-renal syndrome and adrenoleukodystrophy variants, respectively. Additional experiments to characterize C 26:1 by thin layer chromatography, gas chromatography and mass spectrometry revealed the presence of two straight-chain C 26:1 isomers with similar fragmentation patterns.

Abnormalities, Multiple↗
PubMed1986

Velocity characteristics of smooth pursuit eye movements to different patterns of target motion.

Horizontal smooth pursuit eye movements were recorded in normal subjects in response to different patterns of target motion that was either periodic or not. Periodic patterns were triangular and sinusoidal waves. Non-periodic patterns were ramps with either constant or sinusoidally varying velocity. In both cases, several different amplitudes and peak velocities were considered. The experimental results indicate that (a) the performance of the smooth pursuit system depends on the spatio-temporal characteristics of target motion, (b) the relationship between smooth pursuit eye velocity and target velocity during the tracking of constant velocity ramps is strongly nonlinear with a saturation depending on the amplitude of target excursion, (c) in the remaining experimental conditions, there is a linear behaviour up to target velocities of 75 deg/s with a gain of about 0.9.

Adult↗
PubMed1986

Effect of insulin on secretion of bombesin-like immunoreactivity and gastrin from the isolated rat stomach in response to acetylcholine, VIP and leucine-enkephalin.

Bombesin-like immunoreactivity (BLI), a putative peptidergic neurotransmitter of the gastrointestinal intrinsic nervous system is released from the isolated perfused rat stomach in response to the classical neurotransmitter acetylcholine and in response to other putative peptidergic neurotransmitters such as vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI) or growth hormone releasing factor (GRF). The secretion of BLI is modulated not only by gastric factors such as the intragastric pH but also by changes of perfusate glucose concentrations indicating that alterations of carbohydrate metabolism might have an effect on gastric neuroendocrine regulation. Since previous studies have shown that insulin, the major regulatory hormone of glucose metabolism, reduces gastric somatostatin and glucagon secretion it was of interest to determine the effect of insulin on gastric BLI and gastrin secretion. The experiments were performed in the isolated perfused rat stomach model. The addition of porcine insulin to the perfusate at concentrations of 50 and 100 microU/ml had no effect on basal BLI and gastrin secretion. The infusion of acetylcholine (2 X 10(-6)M and 4 X 10(-6)M) elicited a stimulation of BLI and gastrin secretion which was not altered by the addition of insulin (100 microU/ml). On the other hand, significant effects of insulin were observed during administration of the two putative peptidergic neurotransmitters VIP and leu-enkephalin. The infusion of VIP at 10(-11)M and 10(-8)M had no effect on BLI and gastrin secretion in the absence of insulin, however, with the addition of insulin (100 microU/ml) the higher dose of VIP (10(-8)M) elicited a significant stimulation of BLI secretion while both doses of VIP (10(-11)M and 10(-8)M) significantly increased gastrin release. Similar to VIP the infusion of leu-enkephalin at doses of 10(-9)M and 10(-6)M had no effect on BLI and gastrin secretion in the absence of insulin. When insulin was added to the perfusate both doses of leu-enkephalin elicited a significant stimulation of BLI secretion while gastrin remained unchanged. The addition of the specific opiate receptor antagonist naloxone (10(-5)M) did not block the effect of leu-enkephalin in the presence of insulin. In addition the effect of naloxone was also examined during cholinergic stimulation. The addition of naloxone (10(-5)M) during the infusion of acetylcholine abolished the stimulatory effect on BLI secretion in the absence of insulin, whereas in the presence of insulin naloxone did not alter cholinergically-induced BLI secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1986

Glycated plasma proteins in normal and diabetic mothers and their offsprings.

Glycated plasma proteins (GPP) and glycated hemoglobin (G Hb) has been evaluated in 134 non-diabetics (ND), 299 women with potential abnormality of glucose tolerance (pot.AGT), 75 with impaired glucose tolerance (IGT) and 34 insulin dependent diabetics (IDDM) during pregnancy or postpartum including 94 cord blood determinations. Mean HbA1c levels were significantly elevated in IDDM (6.6 +/- 1.3% M +/- SD) compared to ND (5.1 +/- 0.7%; P less than 0.01), but were similar for the other groups studied. Mean GPP were increased for the IDDM (0.58 +/- 0.29 nmol 5- HMF/mg protein; M +/- SD) and the IGT-group (0.53 +/- 0.22) over ND (0.3 +/- 0.13; P less than 0.01) and the Pot.AGT group (0.37 +/- 0.14; P less than 0.01). 6% of the ND, 15% of the Pot AGT-, 52% of the IGT- and 62% of the IDDM group were found to have GPP values exceeding the 97% confidential limit of the ND. However, the large overlap of individual values from patients with different degrees of glucose intolerance with the normal range of pregnancy precludes the use of GPP as a screening parameter for IGT during pregnancy. A 30-35% reduction of fetal hemoglobin- and plasma protein glycosylation relative to maternal values was observed.

Blood Proteins↗
PubMed1986

Modulatory glucose effect on bombesin-like immunoreactivity and gastrin secretion from isolated perfused rat stomach.

Previous studies have demonstrated mostly inhibitory effects of elevated plasma glucose levels on gastric exo- and endocrine as well as motor functions. Because increased plasma glucose levels reduce vagal activity via the central nervous system, it remains unclear if glucose exerts a direct effect on gastric functions. Therefore, our study was designed to determine the effect of acute changes in glucose concentrations on the release of gastrin and bombesin-like immunoreactivity (BLI) from the isolated perfused rat stomach. Acute elevations of perfusate glucose from 100 to 200 mg/dl or from 100 to 300 mg/dl augmented BLI secretion significantly without affecting gastrin release. During an acute decrease from 200 to 30 mg/dl, the secretion of both peptides remained unchanged. When acetylcholine was administered to stimulate BLI and gastrin secretion, the elevation of perfusate glucose to 200 mg/dl and the decrease to 30 mg/dl attenuated BLI secretion, whereas gastrin secretion remained unchanged compared with the control experiments at 100 mg/dl glucose. On the other hand, the perfusion of vasoactive intestinal peptide (VIP) and Leu-enkephalin had no effect on BLI and gastrin secretion during 100 mg/dl glucose perfusion, but both peptides elicited a significant stimulatory effect on BLI secretion during a perfusate glucose concentration of 200 mg/dl without affecting gastrin secretion. In conclusion, our study demonstrates first that an acute increase of glucose augments basal BLI secretion. Second, cholinergically induced BLI secretion is attenuated by hypo- and hyperglycemia. Third, hyperglycemia augments BLI secretion in response to the neuropeptides VIP and Leu-enkephalin. Fourth, basal and stimulated gastrin secretion remains unchanged during acute alterations of perfusate glucose levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1986

Physiological and pathophysiological aspects of somatostatin.

Somatostatin is found in the D-cells of organs that are exclusively responsible for the digestion, absorption, and metabolism of ingested nutrients. D-cells apparently release their secretory products both into the interstitial space (paracrine action) and into the circulation (endocrine action). Ingestion of all three basic nutrients--fat, carbohydrate, and particularly protein--elicits a significant increase in peripheral vein plasma somatostatin levels in dogs and humans. Acidification of a meal stimulates somatostatin release in dogs. Vagal, cholinergic, and adrenergic mechanisms exert a species-dependent effect on somatostatin release. Gut hormones also participate in the regulation of postprandial somatostatin release, and endogenous opioids have an effect that depends on the composition of the meal. Stimulation of postprandial somatostatin release by H2-receptor agonists and prostaglandins has been reported. Insulin inhibits and glucagon stimulates somatostatin release. Elevated levels of circulating glucose reduce the somatostatin response, an effect that cannot be entirely explained by the parallel augmentation of insulin secretion. Circulating nutrients also modify the effect of gut hormones on D-cell function. The physiological action of somatostatin is an inhibitory effect on virtually all gastrointestinal and pancreatic exocrine and endocrine functions. Secretory and/or motor activities are attenuated, thereby preventing an exaggerated and overshooting response. Alterations of tissue somatostatin content and plasma somatostatin levels have been observed in obesity and suggest that somatostatin deficiency may be a pathogenic factor. The observed changes of somatostatin may be secondary to alterations of other functions; nevertheless, hyposomatostatinaemia might facilitate nutrient assimilation.

Animals↗