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Biomedical subjects

A Lehmann

Publications and source records attributed to A Lehmann.

At least 109 records · Page 6Linked to original sources
PubMed1990

In vivo substitution of choline for sodium evokes a selective osmoinsensitive increase of extracellular taurine in the rat hippocampus.

Recent investigations have demonstrated that taurine and phosphoethanolamine (PEA) are the amino acids most sensitive to microdialysis-perfusion with reduced concentrations of NaCl. The aim of the present work was to assess the importance of Na+ deficiency in evoking this response. Further, the previously described selectivity of replacement of Cl- with acetate with respect to amino acid release was reinvestigated. The hippocampus of urethane-anesthetized rats was dialyzed with Krebs-Ringer bicarbonate buffer, and amino acid concentrations of the perfusate were determined. Choline chloride was then stepwise substituted for NaCl, and, in some cases, mannitol (122 mM) was included in low sodium-containing media. In other experiments, NaCl was replaced with sodium acetate. The dialysate levels of taurine increased selectively in response to Na+ substitution. The elevation of taurine was linearly related to the increase in choline chloride, and maximal levels amounted to 335% of basal levels. The increase in extracellular taurine was not inhibited by perfusion with medium made hyperosmotic with mannitol. Replacement of Cl- with acetate stimulated the release of taurine to 652% of resting levels. In addition, PEA levels increased to 250% of control concentration. Other amino acids were unaffected by Cl- substitution. The results show that taurine transport is considerably more sensitive to Na+ depletion than glutamate transport, which also is known to be Na+ dependent. The taurine increase evoked by low Na+ is not caused by cellular swelling as it was unaffected by hyperosmolar medium. Finally, substitution of acetate for Cl- causes a specific elevation of extracellular taurine and PEA, possibly as a result of cytotoxic edema.

Animals↗
PubMed1990

[Reference values of Na(+) and Cl(-) concentrations in adult sweat].

The results of the investigations to reference values for Na(+)- and Cl(-)-concentrations in sweat of adults are as follows: The normal range of electrolyte values in sweat in adults is up to 70 mmol/l (Na+) and 55 mmol/l (Cl-) respectively in infants (40 mmol/l for Na+ and Cl-). There are no sex and age differences. Adults with chronical bronchitis and bronchiectasis don't show different results in comparison with healthy persons. Adults with cystic fibrosis have significantly increased sweat electrolyte concentrations (90-120 mmol/l). Variations in the electrolyte values of a day or of a month are important and much higher than the analytical one.

Adult↗
PubMed1990

[Measurement of epidemiological facts in dentistry].

Recent epidemiological investigations about caries report about phenomenons like "caries increase" or "caries decline". This kind of observation bases on prevalence-studies. But describing such phenomenons does not give the opportunity to explain the observations. For that purpose the modern methodology of epidemiology should be used. Despite of the fact that epidemiology differs exactly between incident and prevalent cases, the use of incidence studies seems to be extremely seldom in stomatology. This paper discusses the problems, which occur in incidence-studies about caries and especially in cohort-studies. The authors show the difficulties to adopt terms like incidence density and cumulative incidence to studies about caries. A proposal is given in order to adopt the modern methodology of epidemiology to the special problem of caries.

Cohort Studies↗
PubMed1989

Effects of 2-guanidinoethane sulfonate on glutamate uptake in primary astroglial cultures from the rat cerebral cortex.

The competitive taurine uptake inhibitor 2-guanidinoethane sulfonate (GES) is frequently used to deplete cerebral pools of taurine. Previous work has revealed that extracellular glutamate increases during GES administration. In view of this, accumulation of glutamate in the absence or presence of 10 or 100 microM GES was measured in primary astroglial cultures from the rat cerebral cortex. At 100 microM, GES reduced Km as well as Vmax for glutamate uptake. A similar tendency was seen at 10 microM GES, but this was not statistically significant. The data suggest that GES is an uncompetitive inhibitor of reuptake of glutamate in astrocytes, which may underlie the previously noted GES-induced elevation of extracellular glutamate in vivo.

Animals↗
PubMed1989

Calcium dependency of N-methyl-D-aspartate toxicity in slices from the immature rat hippocampus.

The literature on ionic requirements for excitotoxicity is largely contradictory. Depending on the experimental paradigms, it has been concluded that either Ca2+ or Na+ and Cl- mediate excitotoxicity. In the present study, the dependence on Ca2+ of N-methyl-D-aspartate-induced damage to neurons in immature rat hippocampal slices was investigated with light microscopy. In addition N-methyl-D-aspartate-induced cell damage was followed by measurement of release of lactate dehydrogenase from slices. When incubated in N-methyl-D-aspartate-containing (100 microM) buffer for 30 min, hippocampal neurons displayed fine chromatin aggregation and swelling of neuronal nuclei and neuropil. Slices incubated in standard medium for 90 min after exposure to N-methyl-D-aspartate contained a large number of neurons that failed to recover from the initial lesion. The acute edema was at least as severe in slices incubated in N-methyl-D-aspartate-containing, Ca2+-free buffer. In contrast, clumping of the chromatin could not be observed. CA1 neurons recovered completely from the acute changes, and granule cells recovered to some extent. While omission of Ca2+ had no obvious morphological effects on the tissue in its own right, the efflux of lactate dehydrogenase was significantly increased after incubation in Ca2+-free medium. Slices exposed to N-methyl-D-aspartate released approximately twice as much lactate dehydrogenase as controls 1-5 h after the exposure, and the same rate of release was seen if Ca2+ was absent during N-methyl-D-aspartate treatment. The morphological results suggest that N-methyl-D-aspartate toxicity is Ca2+-dependent in pyramidal cells whereas the toxicity in granule cells is partly Ca2+-independent.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Effects of microdialysis-perfusion with anisoosmotic media on extracellular amino acids in the rat hippocampus and skeletal muscle.

Changes in the levels of amino acids have been implicated as being important in osmoregulation both within and outside the CNS. The present study addressed the question of whether changes in osmolarity affect the extracellular concentration of amino acids in the rat hippocampus and femoral biceps muscle (FBM). Microdialysis probes were implanted in these tissues and perfused with standard physiological saline. Amino acid concentrations in the dialysate were determined with HPLC separation of o-phthaldialdehyde derivatives and fluorescence detection. The osmolarity of the perfusion buffer was gradually decreased by reduction of the concentration of NaCl from 122 to 61 to 0 mM. In other experiments, the osmolarity was increased by elevation of the NaCl level from 122 to 183 to 244 mM or by addition of mannitol. Glutamate, aspartate, gamma-aminobutyrate, and alanine levels in dialysate from the hippocampus increased when the concentration of NaCl was decreased by 61 mM, and they were further elevated when NaCl was omitted. Taurine and phosphoethanolamine (PEA) levels were maximally elevated at the intermediary decrease of NaCl concentration, and glutamine in particular but also methionine and leucine were suppressed by perfusion with hypoosmolar medium. The amino acid response of the FBM differed substantially from that of the hippocampus. The aspartate content increased slightly, and there was a marginal transient increase in PEA level. Perfusion with media containing high concentrations of NaCl induced diminished dialysate levels of taurine, PEA, and glutamate, whereas levels of other amino acids were either unaffected or increased. Mannitol administration via the perfusion fluid led to reduced levels of taurine, PEA, glutamate, and aspartate. In contrast to the effects of high NaCl levels, hyperosmotic mannitol did not induce increases in level of any of the amino acids detected. The results suggest that taurine and PEA are involved in osmoregulation in the mammalian brain. From a quantitative viewpoint, taurine seems to be most important. Transmitter amino acids may also be involved in the maintenance of the volume of neural cells subjected to severe disturbances in osmotic equilibrium.

Amino Acids↗
PubMed1989

[Immediate breast reconstruction: indications and technics. Apropos of 120 cases treated at the Institut Gustave-Roussy].

From 1976 to 1986 one hundred and twenty immediate breast reconstructions (IBR) were performed at the Gustave-Roussy Institut. 90% of these cases were treated for in situ or infiltrating carcinomas, while only 10% had prophylactic mastectomy. Over recent decades indications for IBR have progressively changed. In the first period they were reserved for prophylactic mastectomies and in situ carcinomas. Over the last several years IBR has also been proposed to patients with infiltrating carcinomas (30%). Although the adequate treatment for small invasive carcinomas is a radiosurgical conservative procedure, a mastectomy is still indicated in stage II, over three centimeters multifocal carcinomas, and local recurrence after conservative treatment. In our series, this procedure seems safe and advisable as it does not interfere with the treatment of primary and secondary disease. The low incidence of surgical complications reported in our series did not increase the hospital stay of our patients. Indications, surgical techniques including myocutaneous flaps, and results of IBR will be discussed.

Breast↗
PubMed1989

[Long-term results following breast reconstruction].

A ten-year experience of breast reconstruction (BR) at the Gustave-Roussy Institute (Paris) provides material for a long-term analysis of carcinologic and cosmetic results. Carcinologic results have been studied in a group of 120 breast reconstructions which was matched to a group of 120 mastectomies without BR. No statistical difference was observed both for the overall survival and the disease-free survival in both groups. The percentage of local recurrences in the reconstructed breast was inferior, but not statistically, to the percentage observed in the controls providing a good argument in favour of the BR inocuity. Cosmetic results were analyzed on photographs according to a previously defined scale. They show a 55% percentage of satisfactory results when all the techniques of BR are mixed. A comparison between the cosmetic results according to the technique of BR demonstrates the superiority of the rectus abdominis flap which provides a higher rate of satisfactory results (63%) as compared to the results observed after simple reconstruction (53%) or latissimus dorsi (44%). A psychologic study of 150 BR shows that every patient underwent a specific psychological process called mourning work. The degree of satisfaction is not linked to objective results. Overall, 93% of the groups were satisfied, would do it again and would advise it for others; 7% were dissatisfied for surgical or emotional reasons.

Breast↗
PubMed1988

The excitatory amino acid antagonist kynurenic acid administered after hypoxic-ischemia in neonatal rats offers neuroprotection.

The neuroprotective effect of kynurenic acid, an unspecific antagonist of excitatory amino acid receptors, was evaluated in a model of hypoxic-ischemia in neonatal rats. One-week-old rats were subjected to ligation of the left carotid artery and exposure to 7.7% O2/92.3% N2 for 2 h. Kynurenic acid (300 mg/kg) was administered i.p. immediately after the period of hypoxic-ischemia in one group (n = 32) and compared with saline-treated (n = 27). After 2 weeks the rats were sacrificed and the brain damage evaluated by comparing the weight of the lesioned and unlesioned hemispheres. In rats receiving kynurenic acid the reduction in weight of the lesioned hemisphere was 25.4 +/- 3.3% as compared to 37.8 +/- 3.6% in saline-treated controls (P less than 0.001). The results suggest that excitatory amino acids are involved in the development of postischemic damage in the immature brain.

Animals↗
PubMed1988

[The professional field of the psychologist in vocational training--results of a survey].

A questionnaire inquiry was carried out with the Psychological Services of the Vocational Training Centres in the Federal Republic of Germany, directed at their fields of work and their position within the facility. The Psychological Services invariably are involved in the admission procedure, and counselling as well as therapeutic work, individual and in groups, have become a firmly established focus alongside their traditional diagnostic tasks. Aspects of supervision are increasingly being used as new methods of personnel development. Though staffing has improved since 1977, great variations still exist between the various centres, and our findings clearly point out the gaps in service provision related with lower client/psychologist ratios. Following introduction and consolidation of the Psychological Services, a phase of re-orientation seems to be under way, with special attention to focus on interactional processes within the facilities, on implementation of rehabilitation objectives, and on entry of clients with chronic mental impairment.

Adolescent↗
PubMed1987

Neurotoxicity of calcium ionophore A23187 in immature rat cerebellar slices.

The causal role of Ca2+ in neuronal necrosis is controversial and it has been suggested that neuronal Ca2+ uptake is only a secondary effect to cell death. Here, I address this question directly by studying the morphological effects of calcium ionophore A23187 on immature cerebellar slices. Parasagittal slices were prepared and incubated for 30, 90 or 120 min in physiological saline with or without A23187. In some cases Ca2+ was omitted from the incubation medium. Slices were processed for light microscopy. A23187 produced nuclear changes indicative of cell death that encompassed cells of the external granule cell layer at short incubation times (30 min) and more deeply situated cells at longer times (120 min). This indicates that A23187 diffusion is limited in the slice. The histological changes produced by 30 min exposure to the ionophore could not be reversed by incubation for 90 min in normal medium. Necrosis was never observed when slices were exposed to A23187 in Ca2+-free medium. The results demonstrate that influx of excessive amounts of Ca2+ kills cells of the central nervous system.

Animals↗
PubMed1987

Analysis of amino acids: neurochemical application.

For high sensitivity analysis of neuroactive amino acids, liquid chromatography employing precolumn derivatisation with o-phthalaldehyde (OPA) is suitable for several reasons. The OPA reagent is non-fluorescent per se, the reaction occurs rapidly in alkaline aqueous solutions and forms highly fluorescent derivatives with primary amines.

Amino Acids↗