Search PubMed⌕ Search

Biomedical subjects

H Simon

Publications and source records attributed to H Simon.

At least 469 records · Page 26Linked to original sources
PubMedDate not supplied

Hippocampal type I and type II corticosteroid receptors are modulated by central noradrenergic systems.

The effects of corticosteroids on various brain functions, including the negative feedback control of hypothalamo-pituitary-adrenal (HPA) axis activity, are mediated by two types of receptors (type I, or mineralocorticoid, and type II, or glucocorticoid) in the central nervous system. Although receptor numbers are thought to be regulated by circulating levels of corticosterone, there may be a direct neural control of corticosteroid receptors. In the present experiments, we demonstrate that 6-OHDA lesioning of noradrenergic (NA) ascending pathways in the pedunculus cerebellaris superior (PCS) reduces corticosterone secretion in response to novelty and increases the number of hippocampal type I corticosteroid receptors in rats 24 hr after adrenalectomy. The same lesion in adrenalectomized animals in which corticosterone levels were maintained within normal limits by corticosterone replacement implants also led to an increase in the number of type I corticosterone receptors and a decrease in the apparent affinity (Kd) of type II receptors in the hippocampus. These results suggest that the NA system may regulate HPA axis activity via a direct control of the number of type I receptors and the apparent affinity of type II receptors in the hippocampus. The possibility that there is a neural control of corticosteroid receptors may throw light on mechanisms controlling HPA axis activity and may suggest other approaches to the treatment of dysregulation of the HPA axis observed during stress and in certain psychopathological conditions.

Adrenalectomy↗
PubMedDate not supplied

Experimental approach to individual vulnerability to psychostimulant addiction.

Vulnerability to the development of drug-intake has been studied by using the acquisition of intravenous amphetamine self-administration in the rat. In a series of neurobiological experiments we provoked imbalances in the functioning of the dopaminergic (DA) network by performing lesions of the DA cell bodies in the ventral tegmental area, DA terminals in the amygdala or median raphe nucleus. These imbalances which resulted in enhanced DA transmission ratio between the nucleus accumbens and the prefrontal cortex led to an increase in the rapidity of self-administration acquisition. With a psychobiological approach, we showed that individual differences in vulnerability to develop self-administration in rats of the same strain were correlated with locomotor responses to stress and to an acute injection of amphetamine. Moreover, activation of DA transmission by repeated amphetamine injections changed animals resistant to drug-intake into vulnerable ones. It is suggested that some inherited or acquired factors, at least in part by affecting the activity of DA network, can predispose individuals to drug abuse.

Amphetamines↗
PubMedDate not supplied

Effect of aging on the basal expression of c-Fos, c-Jun, and Egr-1 proteins in the hippocampus.

In the present study the effect of aging on the basal expression of three different immediate early genes (IEGs) was investigated. The protein products of c-fos, c-jun, and egr-1 genes were visualized immunohistochemically in the rat hippocampus of young adult (4-month-old) and old rats (20-month-old). Astrocytes were quantified by GFAp immunostaining to determine whether changes in the expression of IEGs were correlated with modifications in this marker of degenerative changes. In the young adult rat brain, basal levels of c-Jun and Egr-1 but not c-Fos were detected within the hippocampal formation. Whereas very high basal levels of c-Jun were found in the dentate granule cells and in the pyramidal cells of the ventral hippocampus, Egr-1 was highly expressed in the CA1 pyramidal cells of the dorsal hippocampus. Aging was accompanied by a decrease in Egr-1 expression, by a decrease in total cell density, as well as by a loss of astrocytes in CA1 subfields. In contrast, basal expression of c-Fos and c-Jun as well as astrocyte density within the dentate gyrus were not affected by aging. No difference in these markers was observed in aged rats with or without impairment in spatial learning in a water maze. It was concluded that although these changes may reflect senescence-induced decline of brain function, they do not constitute the defect underlying the age-associated reduction in mnesic capability.

Aging↗
PubMedDate not supplied

A double-blind, placebo-controlled trial of fish oil concentrate (MaxEpa) in stroke patients.

The feeding of large amounts of fish or fish oils to healthy volunteers has been shown to reduce plasma triglycerides and platelet aggregation, and prolong the skin bleeding time. To determine whether a commercially available marine oil (MaxEpa) would have similar effect in stroke patients, we performed a double-blind, placebo-controlled study in 11 patients (7 men, 4 women) with completed stroke (7) or transient ischemic attacks (TIA's) (4). Ten 1 ml opaque capsules containing either MaxEpa or olive oil were given daily for 6 weeks, and then the patients were crossed-over. Aspirin was avoided during the trial. The data were analyzed by paired-sample t-tests. A significant reduction was found in serum triglycerides, but total serum cholesterol and HDL cholesterol were unaffected. The bleeding time was modestly prolonged after 3 weeks of treatment, but the differences between MaxEpa and olive oil treatments were not significant at 6 weeks. Aside from an increase in collagen-stimulated malondialdehyde formation no other statistically significant changes in hemostatic factors were observed. We conclude that the ingestion of up to 10 MaxEpa capsules daily for 6 weeks has little influence on such established risk factors as cholesterol concentration and platelet function in patients with stroke or TIA's.

Aged↗
PubMedDate not supplied

Biochemical synthesis of stereospecifically hydrogen labeled compounds on a preparative scale, VI1-3 Synthesis of further substrates of NAD(P)-linked dehydrogenases of high specific tritium content.

The preparation of (R) and (S) [2(-3)H]lactate as well as (S) [2(-3)H] glutamate via the coupled exchange reaction catalyzed by NAD linked dehydrogenases and NADH: lipoamide oxidoreductase (diaphorase) is described. The specific radioactivity of the hydrogen ions of the 3HOH/H2O can be obtained in the substrates (100% exchange) if equilibrium isotope effects are disregarded. By the exchange procedure substrates with higher specific radioactivity are obtained from positionally [3H]labeled racemic mixtures prepared by chemical reductions with [3H]labeled hydrides. The tritium content of one of the enantiomeres is "washed out" into water. As examples are presented the preparation of (R) [2-3H] (S) [2-H]malate as well as the corresponding carnitine, glutamate and (R) and (S) lactate.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Degradation of NAD(H) by endogenous enzymes of yeasts and Clostridia.

The time courses of degradation of exogenous NAD and NADH (2.5 mM) catalyzed by endogenous enzymes present in Saccharomyces cerevisiae, Candida utilis, Clostridium spec. La 1, Clostridium kluyveri, and Clostridium sporogenes have been determined. The half lives of the pyridine nucleotides depend extremely on the organism and, for the same organism, on the growth conditions. C. spec. La 1 as well as C. kluyveri possess only negligible enzyme activities for NAD degradation. However, C. sporogenes shows activities leading to half lives of less than 2 h for NAD and 5 h for NADH. At 25 degrees C half lives in the order of 5-17 h have been observed for Candida utilis under different conditions. The half lives of NAD are roughly 5 times higher in the presence of Saccharomyces cerevisiae.

Candida↗
PubMedDate not supplied

Design and applications of sensitive enzyme immunoassays specific for clostridial enoate reductases.

Rabbit antisera raised against purified enoate reductase from Clostridium tyrobutyricum (DSM 1460) and horse-radish peroxidase-conjugated staphylococcal protein A or anti-rabbit immunoglobulin G, respectively, were used to develop enzyme immunoassays. Sensitivity limits of the assay are about 250 pg antigen if the enzyme immunoassays are performed on membrane filters and examined visually, and 20 pg for tests in aqueous solution with spectrophotometrical evaluation. The procedures were applied for dot and Western blots as well as colony lifts. Immunological distances between enoate reductases from different clostridia were determined and the amounts of antigen present in bacterial crude extracts were estimated. In crude extracts of C. thermoaceticum a protein of approximately the size of the enoate reductase and its subunits from C. tyrobutyricum was immunologically detected. Gel filtration chromatography of identically pretreated crude extracts from C. thermoaceticum and C. tyrobutyricum produced immunological signals at similar molecular weights and revealed a lesser tendency of the presumed thermophilic enoate reductase from C. thermoaceticum to disintegrate into its subunits and fragments as compared to its mesophilic counterpart.

Clostridium↗
PubMedDate not supplied

Measurements of the air conditioning capacity of the nose during normal and pathological conditions and pharmacological influence.

A simple method is introduced for measuring the air conditioning capacity of the nose. A flow of 8 1/min dry air is introduced by a catheter into the nasopharynx, while 5 1/min is sucked out from the investigated nasal cavity through a psychrometer. The additional 3 1/min passes down into the pharynx, thus reducing the intermingling with expiratory air. By using CO2 as a tracer, this error was found to be maximally 15% and often about 1%. The three different enthalpy factors: increase in enthalpy of dry air, vaporization, and increase in enthalpy of water vapour, were calculated separately and the vaporization was found to be the dominant factor. The calculated total supply of humidity showed that the method presented causes at least a slight stress on the humidifying capacity. Pharmacological studies have shown that subcutaneously injected atropine decreased the total enthalpy and that of water vapour, while nasal administration of oximetazoline also decreased the total enthalpy. Nasal administration of homatropine or pilocarpine had no effect on the air conditioning. In comparison with normal subjects, those with vasomotor rhinitis had an increased enthalpy of the air, while the same enthalpy factor was reduced in cases with atrophic rhinitis. Laryngectomized patients had no significant difference in the air conditioning capacity of the nose in relation to normal subjects, while patients operated with partial maxillectomy had a considerable reduction in vaporization and total enthalpy.

Atropine↗
PubMedDate not supplied

Central diabetes insipidus due to herpes simplex in a patient immunosuppressed by Cushing's syndrome.

OBJECTIVE: To describe a patient immunocompromised by Cushing's syndrome in whom central diabetes insipidus developed as a complication of herpes simplex involvement of the hypothalamus. METHODS: We present a case, including results of laboratory and histopathologic studies, in which herpes simplex was established as the causative agent for central diabetes insipidus. RESULTS: A woman with ectopic corticotropin-dependent Cushing's syndrome, diabetes mellitus, carcinoid tumor, and a history of thyroid cancer had the precipitous onset of seizure and fever, and hypotonic polyuria and progressive hypernatremia developed. Central diabetes insipidus was diagnosed and successfully treated with desmopressin. Nevertheless, the patient's condition deteriorated and she died. Autopsy revealed herpes simplex encephalitis involving the magnicellular neurons of the hypothalamus. CONCLUSION: Central diabetes insipidus caused by viral infections has been reported in immunosuppressed patients, such as those with acquired immunodeficiency syndrome (AIDS). To our knowledge, this is the first report of a herpes infection causing diabetes insipidus in a patient immunosuppressed by Cushing's syndrome. This case demonstrates that, in patients with Cushing's syndrome, diabetes insipidus may develop as a result of herpes simplex infection of the hypothalamus.

Cushing Syndrome↗
PubMedDate not supplied

Microleakage of Class 2 glass-ionomer-silver restorations in primary molars.

The aims of this study were to assess microleakage at the cervical margins of class 2 "sandwich" restorations placed with two glass-ionomer-silver cements in primary molars, to compare the quality of the occlusal margins of these restorations to those prepared with Miracle Mix and Ketac Silver, and to assess by scanning electron microscopy (SEM) the marginal micromorphology of those restorations. Fifty-two class 2 restorations were prepared in extracted primary molars and were restored as follows: 1) Ketac Silver + Estilux Posterior (sandwich), 2) Miracle Mix + Estilux Posterior (sandwich), 3) Ketac Silver only, and 4) Miracle Mix only. No or minimal leakage was evident in most of the occlusal margins, whereas severe leakage was observed in almost 70% of the cervical margins of the Ketac Silver groups. Scanning electron microscopy evaluation demonstrated good adaptation at the buccal and lingual margins of all the restorations. Sixty-seven percent of the Miracle Mix restorations had no defects at the cervical margins, as opposed to only 17% of those with Ketac Silver.

Cermet Cements↗
PubMedDate not supplied

[Measurement of transport in mucous membrane in the human nose with Cr-51-labeled resin beads].

The mucociliary transport of the human nasal mucosa was studied by using very small resin beads tagged with 51Cr. Several modifications of previous methods were introduced, e.g. kind of nuclide, particle size, pH, mode of application, measuring technique and reduction of local irradiation. Finally arrangements implying exact measurements of transport not only horizontally but also vertically or obliquely were obtained. No mucociliary transport was demonstrated in five of nine subjects with a common cold 10 days before or one week after the investigation. Xylometazolin as a nasal spray diminished the mucociliary transport significantly. In addition, the effects on mucociliary transport caused by homolateral or contralateral experimental nasal obstruction as well as by tobacco smoking were studied in healthy subjects. Finally, patients with various diseases: pollen allergy in free intervals, chronic rhinitis, septal deviation or perforation, and condition after laryngectomy were also investigated.

Adult↗
PubMedDate not supplied

[Image processing in pathology. IV. Age dependent changes of morphometric features of liver cell nuclei in biopsies].

PROBLEM: Several authors reported age dependent changes of single morphometric parameters on liver cell nuclei. In this study a recently developed automatic morphometry system was applied to recording of many liver cell nuclei parameters in histologic sections of liver biopsies simultaneously. The relations of the automatically generated parameters according to the age of the individuals are to be demonstrated.

Adolescent↗