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Biomedical subjects

R Schmid

Publications and source records attributed to R Schmid.

At least 217 records · Page 12Linked to original sources
PubMed1989

Effect of CCK on insulin, glucagon, and pancreatic polypeptide levels in humans.

The present study was designed to determine the effect of low doses of cholecystokinin (CCK) on insulin, glucagon, and pancreatic polypeptide (PP) secretion in the basal state and during prestimulation with amino acids and glucose alone or in combination. Two different amino acid solutions available for use in humans were employed. Aminosteril-N-Hepa was better for the imitation of the so-called "insulinogenic" amino acids while Aminoplasmal L-10 gave more comparable plasma levels of the "glucagonogenic" amino acids as observed after a protein-rich meal. In healthy volunteers, low-dose CCK infusion [Thr28,Nle31-CCK 25-33 (CCK-9)] in stepwise increasing doses of 5, 10, and 20 pmol/kg/h had no effect on basal, glucose-, or amino acid-stimulated insulin release. During the combination of Aminoplasmal + glucose, there was a small and only transient increase of plasma insulin levels that did not occur during Aminosteril + glucose. CCK did not alter glucagon levels either during i.v. amino acids alone or during combination of amino acids with glucose. CCK-stimulated PP levels in the basal state in a dose-dependent manner. This effect was enhanced during i.v. Aminosteril but not i.v. Aminoplasmal infusion. During i.v. glucose, the effect of CCK on PP levels was abolished. In conclusion, the present data demonstrate that CCK is unlikely to be a stimulus of insulin and glucagon secretion in the basal state and also during prestimulation by fairly physiological quantities of amino acid mixtures. On the other hand, the present data support a physiological role of CCK in the regulation of PP secretion.

Adult↗
PubMed1989

Applying a model of saccadic prediction to patients' saccadic eye movements.

A mathematical model of eye tracking of periodic square wave target motion has previously been proposed. In this work the model was further studied with regard to saccadic response time to symmetrical square wave target motion in 6 patients with unilateral parietal lesions following cerebrovascular accidents. Three types of saccadic response time were noted. In patients with type I, saccades contralateral to the damaged hemisphere had similar characteristics to those found in ipsilateral direction, but with longer response time. In those with type II, the saccadic response time was about the same on movement in either direction for repetitive target cycle durations of 1.2 or 2.0 s. In patients with type III, the target motion could not be predicted, in either direction.

Aged↗
PubMed1989

Circulating amino acids and pancreatic endocrine function after ingestion of a protein-rich meal in obese subjects.

We measured plasma amino acid together with insulin, glucagon, pancreatic polypeptide (PP), and glucose concentrations after the ingestion of a protein meal in lean and obese subjects. The basal plasma amino acid levels were similar in both groups. The postprandial increase in the plasma amino acid levels in the obese subjects was only 15-50% of that in the lean subjects. The mean basal and peak postprandial plasma insulin levels were significantly higher (72 and 165 pmol/L) in the obese group than in the lean group (36 and 115 pmol/L; P less than 0.05-0.01). The postprandial rise in plasma glucagon was largely attenuated in the obese subjects, and there was no difference in plasma PP and glucose levels in the 2 groups. To further evaluate the role of circulating amino acids on pancreatic endocrine function in obese and lean subjects, an amino acid mixture consisting of 15 amino acids was infused iv. During the infusion the plasma amino acid levels were comparable in both groups. Plasma insulin rose by 36 +/- 7 (+/- SE) pmol/L (5 +/- 1 microU/mL) in the lean and 129 +/- 22 pmol/L (18 +/- 3 microU/mL) in the obese subjects, whereas plasma glucagon, PP, and glucose levels were similar in both groups. In view of the 3.6-fold greater insulin responses in the obese subjects, it is likely that circulating amino acids contribute to their hyperinsulinemia in spite of the reduced postprandial rise of amino acids in this group (50-85%). Thus, under physiological conditions amino acids have to be considered as an important regulatory component of postprandial insulin release in obese subjects.

Adult↗
PubMed1989

Opiate detoxification under general anesthesia by large doses of naloxone.

For opiate detoxification 6 volunteer opiate addicts were intravenously administered 10 mg naloxone within one hour while under barbiturate anesthesia. During administration of naloxone none of the patients demonstrated significant changes in the hemodynamic parameters of heart rate, mean arterial pressure, cardiac index, peripheral resistance or in the oxygen saturation. After patients awoke from anesthesia, they experienced no or only minimal withdrawal symptoms. Possible explanations for the suppression of withdrawal symptoms are discussed.

Adult↗
PubMed1989

In vitro and in vivo studies on triclosan/PVM/MA copolymer/NaF combination as an anti-plaque agent.

A combination of triclosan, copolymer of PVM/MA and NaF has been optimized in vitro and in vivo for plaque effect. Triclosan (2, 4, 4' trichloro-2'-hydroxydiphenyl ether), a non-cationic antibacterial, was compatible with anionic surfactant, NaF and PVM/MA copolymer as evaluated by in vitro antibacterial tests. The in vitro uptake of triclosan on the saliva-coated hydroxyapatite disks, extracted human teeth and oral buccal epithelial cells was enhanced two fold in the presence of PVM/MA copolymer when compared to the uptake in the absence of the copolymer. The combination consisting of 0.3% triclosan/2% PVM/MA copolymer/1100 ppm NaF was found to be highly effective on reducing smooth and fissure caries, and plaque extent compared to to 1100 ppm/NaF by itself in rats when applied topically. The combination also showed significantly more fluoride uptake and reduction in enamel solubility than 1100 ppm/NaF. The results of these studies indicated that this optimized combination was an effective antiplaque/anticaries agent in vitro and in vivo.

Animals↗
PubMed1989

Cariostatic effects of monofluorophosphate in solutions and dentifrices in rats.

The cariostatic effectiveness of dentifrices and solutions containing sodium monofluorophosphate (MFP) was evaluated in rats. In one study using 36 CARA rats, the caries inhibiting effects of sodium fluoride and MFP solutions, at equivalent soluble fluoride concentrations (750 ppm F), were compared. Both MFP and sodium fluoride significantly (p less than 0.01) reduced smooth surface caries by 78% to 81%, respectively. No significant differences between the two treatment groups were observed. In a second study, 5 dentifrices formulated with dicalcium phosphate dihydrate (DCPD) abrasive and different amounts of MFP (0, 250, 500, 750, and 1000 ppm F) were tested for cariostatic effects in CARA rats. Compared to the control groups, the MFP/DCPD dentifrices significantly (p less than 0.01) reduced smooth surface caries incidence by 66%, 81%, 76% and 85% at the 250, 500, 750, and 1000 ppm F concentrations, respectively. In each of the studies, both enamel fluoride content and molar surface solubility were measured. A third study assessed the compatibility of MFP with different abrasives and the effect of dentifrice composition on the release of MFP from a dentifrice slurry to a saliva phase. No differences in MFP release were observed for two different silica-based formulations which differed with respect to thickener, humectants and other ingredients.

Animals↗
PubMed1988

Assessment of methods for covalent binding of nucleic acids to magnetic beads, Dynabeads, and the characteristics of the bound nucleic acids in hybridization reactions.

Dynabeads are magnetic monosized beads with high stability, high uniformity, unique paramagnetic properties, low particle-particle interaction, and high dispersibility. Different reactive groups; hydroxyl, carboxyl and amino groups can be attached to the surface. Several methods for covalent attachment of DNA or oligonucleotides to the beads were investigated. Best coupling yields were obtained by carbodiimide-mediated end-attachment of 5'-phosphate and 5'-NH2 modified nucleic acids to respectively amino and carboxyl beads. The carboxyl beads showed a low degree of non-specific binding, while a better yield of end-attached nucleic acids was obtained using the amino beads. The DNA-beads worked efficiently in hybridization experiments, and the kinetics of hybridization approach those of solution hybridization.

Chemical Phenomena↗
PubMed1988

Monosized, magnetic polymer particles: their use in separation of cells and subcellular components, and in the study of lymphocyte function in vitro.

By employing the principles of "activated swelling", monosized, superparamagnetic polymer particles have been prepared ranging in size from 1-100 microns. Both during and after the swelling process, the particles can be modified to meet a series of specific demands making them potentially very interesting for many separation and assay purposes. Using monoclonal antibodies to direct the magnetic beads to their targets, immunomagnetic separation has turned out to be one of the most specific, reliable and, above all, the fastest technique available today to isolate particulate material for further studies. So far, most efforts have been concentrated on methodology for fractionation of cells in suspension, such as removal of tumour cells from bone marrow or isolation of lymphoid cells from peripheral blood. These studies have both established the parameters necessary for optimal performance and at the same time laid the groundwork for future developments making immunomagnetic separation an exciting new tool in many research areas. High speed and specificity are the most conspicuous features of immunomagnetic cell separation. These properties have been exploited in the successful development of a new technique for tissue typing of cells directly from peripheral blood specimens. Both higher sensitivity and specificity have been obtained. The same principles can be used for fast and safe quantification of cell populations and subpopulations in blood and cell suspensions. The functions of, and interactions between, peripheral blood cell populations or subpopulations in the immune response have also been studied with high precision. The significance of direct cell contact on the one hand, and soluble factors on the other, can now be established in detail. Immunomagnetic beads have also been used to study the interaction between various T lymphocyte membrane molecules in the early phases of the activation process. Finally, the usefulness of specially developed particles for the fractionation of subcellular components is described.

Antibodies, Monoclonal↗
PubMed1988

Cross-coupled effects of repeated vestibular and optokinetic stimulations on the dynamics of the vestibulo-ocular and optokinetic reflexes in the cat.

Cats were submitted to repeated step stimulations either vestibular or optokinetic. Regardless of which of the two stimuli was used, dynamic modifications were observed in both vestibulo-ocular response and optokinetic after-nystagmus (OKAN). The progressive changes in post-rotational nystagmus and OKAN were quantified by measuring the duration of their primary phase. A parallel evolution of these two parameters was found. When repeated unidirectional vestibular stimulations were used, the same asymmetry was induced in both vestibuloocular responses and OKAN. These results support the hypothesis that the vestibulo-ocular and the optokinetic reflex share a common velocity storage mechanism, although alternative hypotheses cannot be excluded.

Animals↗
PubMed1988

Transient accumulation of potassium glutamate and its replacement by trehalose during adaptation of growing cells of Escherichia coli K-12 to elevated sodium chloride concentrations.

The sequence of events following the addition of 0.5 M NaCl to cells of Escherichia coli growing in a minimal mineral medium was investigated. Immediately after upshock the cells took up a large amount of K+ and synthesized approximately half the equivalent amount of glutamate concomitantly. After 30 min the cells started to synthesize trehalose, and after 2 h they had replaced most of their initial osmoprotectants by the carbohydrate. Cell trehalose was rapidly replaced by proline, taken up from the medium when added to the osmoadapting cells. The initial rate of this proline uptake was extremely rapid, and with rates observed of up to 0.6 mmol x min-1 x g-1 of cell protein it was approximately ten times faster than that reported in the literature for non-growing cells. These results indicate that for osmoadaptation of growing cells of E. coli the uptake of proline has priority over the synthesis of trehalose, which in its turn is preferred above K+ and glutamate as osmoprotectants. We observed that two mutants with unknown lesions, but which are known to be impaired in osmoadaptation, were inhibited in replacing K+ and glutamate by trehalose, indicating that this is the basis for their defect in osmoadaptation. Further experiments revealed that neither internal pH nor the membrane potential nor the transmembrane protonmotive force are likely to be involved in osmoadaptation in E. coli. However, during osmoadaptation a high internal potassium concentration appeared to stimulate the derepression of proline-uptake systems (mainly system ProP).

Biological Transport, Active↗
PubMed1988

Uptake and catabolism of gamma-aminobutyric acid by the isolated perfused rat liver.

Serum concentrations of gamma-aminobutyric acid (GABA) are increased in liver failure, possibly because of decreased hepatic GABA catabolism. To study in detail the role of the liver in GABA metabolism, uptake and catabolism of GABA by isolated perfused liver from normal rats and rats with galactosamine- or carbon tetrachloride-induced liver failure were measured. Hepatic GABA uptake was almost complete at GABA concentrations of up to 10 microM and approached saturation at a concentration of 50 microM. The apparent affinity of hepatic GABA uptake was 38 microM and the apparent maximal velocity was 158 nmol/g.min. Hepatic GABA uptake was sodium-dependent. gamma-Aminobutyric acid taken up by the liver was rapidly catabolized as measured by 14CO2 formation from [U-14C]GABA. Aminooxyacetic acid, a GABA transaminase inhibitor, completely and irreversibly inhibited hepatic GABA catabolism and thereby also inhibited hepatic GABA uptake. Although uptake of GABA by livers of carbon tetrachloride- or galactosamine-treated rats was decreased (apparent maximal velocity, 103 and 98 nmol/g.min, respectively), at physiologic GABA concentrations in the perfusate GABA uptake and catabolism was not different from that of untreated controls. The observed impairment of hepatic GABA uptake or catabolism by the diseased liver would be expected to contribute to increased GABA levels in peripheral blood plasma in liver failure. However, the magnitude of the observed impairment would be insufficient to account for a 10-fold increase in such levels.

Animals↗
PubMed1988

Modulatory effect of glucose on VIP-induced gastric somatostatin release.

The present study was designed to examine the effect of increasing perfusate glucose concentrations on vasoactive intestinal peptide (VIP)-induced somatostatin (SLI) release from the isolated rat stomach. The stomach of overnight-fasted rats was perfused with Krebs-Ringer buffer containing 100, 150, or 200 mg/dl glucose, respectively. VIP was administered at 10(-12), 10(-11), 10(-9), and 10(-8) M. At a normal glucose concentration of 100 mg/dl, VIP at doses of 10(-12), 10(-11), and 10(-9) M elicited a small inhibitory effect on SLI release by 200-300 pg/min (P less than 0.01). As reported previously at 10(-8) M, VIP stimulated gastric SLI secretion by 500 pg/min (P less than 0.01). Increasing perfusate glucose to 150 mg/dl resulted in a stimulation of SLI release by all four concentrations of VIP with a maximal effect at 10(-9) M. During 200 mg/dl glucose, VIP had no effect in concentrations below 10(-9) M, and only the two highest doses (10(-9) and 10(-8) M) stimulated SLI release significantly. In the absence of VIP, glucose had no effect on gastric SLI release. In conclusion, the present data demonstrate for the first time that at normal glucose levels VIP has not only stimulatory but also inhibitory effects on gastric SLI, and second, a modest elevation of glucose has a modulatory effect on gastric D-cell function.

Animals↗
PubMed1988

Cariogenicity of traditional African foodstuffs (maize, beans, sorghum, brown bread) on rat caries.

The cariogenicity of the following traditional African foods was tested in a rat model system: cooked maize and beans, cooked maize and spinach, uncooked and cooked sorghum, both plus 20% sucrose and brown bread, as well as a control (wheat starch plus 50% sucrose). Plaque extent was low in all the test groups and caries incidence was almost zero in all groups except for the cooked wheat starch and 50% sucrose group. Comparison to earlier results suggests a possible cariostatic effect of sorghum but not for the other traditional foods.

Animals↗