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Biomedical subjects

A Heller

Publications and source records attributed to A Heller.

At least 91 records · Page 5Linked to original sources
PubMed1998

Hypothalamic-pituitary-gonadal axis in the mutant weaver mouse.

The weaver (wv) mutant mouse manifests severe locomotor defects, a deficiency in granule cells of the cerebellum, and cellular deficits in the midbrain dopaminergic system. The wv phenotype is associated with a missense mutation in the pore region of the G-protein-gated inwardly rectifying potassium channel, GIRK2. The homozygous male wv mouse is essentially infertile due to an inadequate level of sperm production. Females are fertile although they also manifest the neurological phenotype. Homozygotes of both sexes have reduced body weight. We have evaluated the hypothalamic-pituitary-gonadal axis in heterozygote and homozygote male and female wv mutants in comparison with wild-type controls. Testicular weight was significantly reduced in the homozygous males, due to degenerative changes of seminiferous epithelium. Serum and pituitary content of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were normal in all groups, and the normal sex differences were noted (FSH and LH higher in males, prolactin higher in females). Pituitary growth hormone (GH) concentration was normal, with control and mutant males showing higher GH than females. Serum testosterone levels were normal in the mutants, as was testicular testosterone. Testicular alpha-inhibin content was mildly reduced, but high in proportion to testicular weight. The defect in spermatogenesis appeared predominantly in the postmeiotic stages. In situ hybridization was consistent with expression of some GIRK2 mRNA isoforms in seminiferous epithelium. There were no significant differences between genotypes in the levels of dopamine, dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in the mediobasal and preoptic hypothalamic regions. Homovanillic acid levels in these two areas were, however, reduced in wv homozygotes compared to wild-type animals. In the light of normal pituitary hormone levels, normal hypothalamic monoamine concentrations and normal sex differences in gonadotropins, we conclude that the infertility in the male homozygote wv mouse lies within the tubule and is probably a primary defect in the germ cells. The hormonal data suggest that Leydig cell function, and at least some aspects of Sertoli cell function, are normal in the mutant mice.

Animals↗
PubMed1998

Lipid mediators in inflammatory disorders.

During the past few decades, intensive collaborative research in the fields of chronic and acute inflammatory disorders has resulted in a better understanding of the pathophysiology and diagnosis of these diseases. Modern therapeutic approaches are still not satisfactory and shock, sepsis and multiple organ failure remain the great challenge in intensive care medicine. However, the treatment of inflammatory diseases like rheumatoid arthritis, ulcerative colitis or psoriasis also represents an unresolved problem. Many factors contribute to the complex course of inflammatory reactions. Microbiological, immunological and toxic agents can initiate the inflammatory response by activating a variety of humoral and cellular mediators. In the early phase of inflammation, excessive amounts of interleukins and lipid-mediators are released and play a crucial role in the pathogenesis of organ dysfunction. Arachidonic acid (AA), the mother substance of the pro-inflammatory eicosanoids, is released from membrane phospholipids in the course of inflammatory activation and is metabolised to prostaglandins and leukotrienes. Various strategies have been evaluated to control the excessive production of lipid mediators on different levels of biochemical pathways, such as inhibition of phospholipase A2, the trigger enzyme for release of AA, blockade of cyclooxygenase and lipoxygenase pathways and the development of receptor antagonists against platelet activating factor and leukotrienes. Some of these agents exert protective effects in different inflammatory disorders such as septic organ failure, rheumatoid arthritis or asthma, whereas others fail to do so. Encouraging results have been obtained by dietary supplementation with long chain omega-3 fatty acids like eicosapentaenoic acid (EPA). In states of inflammation, EPA is released to compete with AA for enzymatic metabolism inducing the production of less inflammatory and chemotactic derivatives.

Animals↗
PubMed1997

Regulation of developing dopaminergic axonal arbor size in three-dimensional reaggregate tissue culture.

The role of target availability in determining axonal size of the developing dopaminergic neuron was examined in three-dimensional reaggregate culture in which these neurons undergo normal neurochemical and morphological development. The ratio of striatal target cells to dopaminergic neurons was systematically increased from 2:1 to 50:1 (striatal to mesencephalic cells). These ratios provide sufficient target for quantitative survival of dopaminergic neurons similar to that seen in vivo. After 3 weeks in culture, dopamine levels increased linearly and proportionally to dopaminergic cell number over a 25-fold relative increase in target cell availability. The amount of neurotransmitter per dopaminergic cell remained constant, suggesting that the axonal arbor did not increase as a function of target availability. This conclusion was directly tested by morphological analysis of the dopaminergic axonal arbor in single aggregates containing between 0 and 45 dopaminergic cells under conditions in which sufficient target was not a factor in dopaminergic cell survival. As was the case with respect to dopamine concentration, axonal arbor size per cell remained constant in the face of increasing target availability. Thus, availability of target cells under these conditions, is not, per se, the limiting factor on the rate of growth of the developing dopaminergic axonal arbor.

Animals↗
PubMed1997

Electrochemical glucose and lactate sensors based on "wired" thermostable soybean peroxidase operating continuously and stably at 37 degrees C.

Following a recent report from our laboratory on a thermostable amperometric H2O2 sensor based on "wiring" soybean peroxidase, glucose and lactate sensors maintaining stable output under continuous operation at 37 degrees C for 12 and 8 days, respectively, were built. The vitreous carbon base of the sensor was coated with four polymer layers. The first was made by cross-linking thermostable soybean peroxidase and the redox polymer formed through complexing part of the rings of poly-(vinylpyridine) with [Os(bpy)2Cl]+/2+ (bpy = bipyridine) and quaternizing part of the rings with bromoethylamine. The second was an insulating and H2O2 transport controlling cellulose acetate layer. The third was an immobilized glucose oxidase or lactate oxidase layer. The fourth was a substrate transport controlling cellulose acetate layer In the case of the glucose sensor, the current output was independent of potential between -0.2 and +0.3 V (vs SCE), and the response time (t10/90) was < 2 min when the concentration was raised from 0 to 5 mM glucose. The current was independent of the O2 partial pressure above 15 Torr. The sensor was relatively insensitive to motion and to interferants. Changing the rotation speed of the electrode from 50 to 2500 rpm increased the current by < 10%. At a glucose concentration of 4 mM, the addition of 0.1 mM ascorbate decreased the current by < 1%. The operational stability was glucose oxidase loading dependent. Though the current decreased by 85% after 100 h of operation at 37 degrees C when the 3-mm-diameter electrode was loaded with only 1.3 micrograms of glucose oxidase, it decreased by < 1% after such operation when loaded with 52 micrograms of the enzyme. Similar results were obtained for the lactate sensor, with the exception of a more noticeable oxygen concentration dependence of the lactate response at low oxygen concentrations.

Biosensing Techniques↗
PubMed1997

In vitro evidence that the reduction in mesencephalic dopaminergic neurons in the weaver heterozygote is not due to a failure in target cell interaction.

The murine weaver (wv) mutation is characterized by a genetically determined loss of several neuronal populations, which include the nigrostriatal dopaminergic neurons. Animals homozygous for the wv gene exhibit marked deficits in dopaminergic morphological and neurochemical parameters. The wv gene shows incomplete dominance in that heterozygous (wv/+) mice exhibit moderate reductions in midbrain dopaminergic neuron number. It is unclear whether the dopaminergic neuronal loss in homozygous and heterozygous animals results from an effect of the wv gene solely on the dopaminergic neurons or is due to a failure of interaction of dopaminergic neurons with target cells of the striatum. This issue has been addressed utilizing three-dimensional reaggregate tissue cultures to determine whether the wv gene acts directly on the mesencephalic dopaminergic neurons. Embryonic mesencephalon and striatum from wv/+ and wild-type (+/+) brains were dissociated and the cells recombined into four mesencephalic-striatal aggregate combinations: (1) mesencephalic(+/+)-striatal(+/+)aggregates; (2) mesencephalic(wv/+)-striatal(wv/+)aggregates; (3) mesencephalic(wv/+)-striatal(+/+)aggregates; and (4) mesencephalic(+/+)-striatal(wv/+)aggregates. At 29 days and 57 days of culture, the number of dopaminergic neurons and dopamine content from mesencephalic-striatal aggregates consisting of mixed genotype or from only wv/+ tissue were quantitated and compared with that from mesencephalic-striatal cultures prepared from +/+ tissue alone. At both culture time points, aggregates containing wv/+ mesencephalon coaggregated with either wv/+ or +/+ striatum contained fewer dopaminergic neurons than mesencephalic-striatal cultures composed of only +/+ cells. Coaggregation of +/+ mesencephalon with wv/+ striatum did not have a detrimental effect on dopaminergic cell number. The findings demonstrate that the difference in the number of mesencephalic dopaminergic neurons between wv/+ and +/+ animals seen in vivo can be reproduced in three-dimensional reaggregate culture. Since the coculture of +/+ striatum with wv/+ mesencephalon did not appear to rescue wv/+ dopaminergic neurons in the aggregates as compared to wv/+ striatum and, wv/+ striatum proved to be a perfectly adequate target for +/+ mesencephalic dopaminergic neurons, it appears that the effect of the wv gene is on the dopaminergic neurons themselves.

Animals↗
PubMed1997

Biocompatible, glucose-permeable hydrogel for in situ coating of implantable biosensors.

A glucose-permeable hydrogel (97% water by mass) was formed by cross-linking an 8-armed, amine-terminated poly(ethylene glycol) (PEG) derivative with a di-succinimidyl ester of an alpha,omega-dipropionic acid derivative of PEG in aqueous solution at room temperature. The gel was evaluated as a biocompatible interface between an amperometric glucose electrode and the subcutaneous tissue of a rat. Over a glucose concentration range of 0-30 mM, the loss in sensitivity to glucose caused by the application of the hydrogel was 34% and the reduction in limiting current at high glucose concentration (30 mM) was 35% at 37 degrees C for films that were approximately 0.06 mm thick, an acceptable loss. Hydrogel and Pellethane samples were subcutaneously implanted in male Sprague-Dawley rats for 7 days. The explanted samples were thin-sectioned, stained and examined under a light microscope. While the Pellethane samples were encapsulated with tissue consisting of macrophages, neutrophils, foreign body giant cells, fibroblasts and collagen, the PEG samples had very few adherent cells. The results show this system to be a good candidate for providing biocompatible interfaces for sensors, especially oxidoreductase-based sensors.

Animals↗
PubMed1997

[Effects of human i.v. immunoglobulin on bacterial clearance and granulocyte function in endotoxinemia].

PURPOSE: The therapeutic impact of intravenous immunoglobulins (ivIG) in septic patients remains controversial. Until now, the mechanisms of action have not been fully elucidated. Since polymorphonuclear neutrophils (PMN) play a key role in host defence, this study focuses on the effects of ivIG on bacterial clearance and PMN respiratory burst activity during endotoxinaemia. For this purpose, it was investigated whether ivIG improves blood clearance and organ colonisation as well as PMN functions after experimentally induced bacteraemia in rabbits. METHODS: The experiments were performed in 30 anaesthetised rabbits. To determine quantification of bacterial killing in vivo, defined numbers of exogenous Escherichia (E.) coli 1.3 x 10(8) CFU) were injected intravenously in untreated animals (n = 10) or 60 min after infusion of endotoxin (LPS: 40 micrograms/kg/h) in groups without (n = 10), and after pretreatment with ivIG (Sandoglobulin, 0.5 g/kg body weight, n = 10), respectively. Parameters monitored were rates of bacterial elimination from the blood, LPS clearance, arterial pressure, blood gases and white blood cell counts, PMN burst activity was determined using a flow cytometry assay. Samples of liver, kidney, spleen and lung were collected for bacterial counts 180 min following E. coli injection. RESULTS: Compared to controls, endotoxinaemia resulted in a prolonged elimination of the injected E. coli out of the blood associated with a significantly (p < 0.01) higher colonisation of all organs. Pretreatment with ivIG improved LPS clearance and significantly reduced bacterial colonisation of lung and kidney (p < 0.01). This was paralleled by an enhanced PMN respiratory burst activity compared to untreated animals (p < 0.05). CONCLUSION: The reduced bacterial colonisation of lung and kidney in correlation with an increased PMN bactericidal activity in endotoxinaemia suggest an improved granulocyte-dependent bacterial killing due to ivIG application.

Animals↗
PubMed1997

Systemic absorption and block after epidural injection of ropivacaine in healthy volunteers.

BACKGROUND: For local anesthetics, the process of removal from the site of administration influences the duration of anesthesia and the risk for systemic toxicity to develop. The systemic absorption of epidural ropivacaine and the time profile of sensory and motor block were studied in healthy volunteers. METHODS: Nine persons simultaneously received 150 mg ropivacaine hydrochloride (7.5 mg/ml) epidurally and 40 mg deuterium-labeled (2H3)ropivacaine hydrochloride (0.25 mg/ml) intravenously. Peripheral arterial and venous plasma samples were collected, and assessments of sensory and motor block were made. RESULTS: The arterial plasma concentrations increased faster than the venous concentrations, with 50% higher maximum concentrations after both intravenous and epidural administration. The absorption was biphasic. A correlation was seen between the duration of sensory block and the slower absorption half-life; that is, the longer the half-life, the longer the duration. The extent of spread varied among the volunteers, with the median upper block level not exceeding T12. The motor block (Bromage score 1) was of slower onset (median, 0.4 h) and of shorter duration (median, 4.1 h) than the sensory block (onset, 0.2 h; duration, 6.5 h at L2 medians). CONCLUSIONS: As much as 50% differences were seen in the arteriovenous plasma concentrations of ropivacaine during the first hour, which has implications for the interpretation of systemic toxic plasma concentrations. The absorption into the general circulation was biphasic, with a correlation between the sensory block and the slower absorption half-life. A faster onset and a longer duration of sensory compared with motor block was seen.

Absorption↗
PubMed1997

Treatment of gingival Crohn's disease with laser therapy.

Crohn's disease is an inflammatory disease of unknown etiology. Oral manifestations appear most frequently on the lips, gingival tissue and buccal mucosa. The case presented here shows how a patient with oral lesions resulting from Crohn's disease can be treated by laser therapy and obtain optimal esthetic results.

Adolescent↗
PubMed1996

Statistics for critical clinical decision making based on readings of pairs of implanted sensors.

Low error rates are essential if lives of patients are to depend on readings of implanted sensors, such as glucose sensors in insulin-dependent diabetic patients. To verify the operation and to calibrate on demand an implanted sensor, it is necessary that calibration through a single, independent measurement involving withdrawal of only one sample of blood and its independent analysis be feasible. Such a one-point calibration must be accurate. Borrowing from nuclear reactor safety assurance, where a likelihood ratio test is applied to readings of pairs of pressure sensors for shutdown/no shutdown decisions, we apply a similar test to sensor pairs implanted in rats. We show, for five sets of glucose sensor pairs, calibrated in vivo by withdrawal of a single sample of blood, that application of the likelihood ratio test increases the fraction of the clinically correct readings from 92.4% for their averaged readings to 98.8%.

Algorithms↗
PubMed1996

Glial-derived neurotrophic factor (GDNF) induced morphological differentiation of an immortalized monoclonal hybrid dopaminergic cell line of mesencephalic neuronal origin.

Monoclonal hybrid cell lines derived from either mesencephalic or striatal neuronal parents were screened for the effects of glial-derived neurotrophic factor (GDNF) on morphological differentiation. The mesencephalic dopaminergic MN9D cell line responded to GDNF with a 3- to 4-fold increase in the number of differentiated solitary cells and provides an unlimited source of monoclonal cells for studies on the mechanism of action of GDNF and the nature of its receptor.

Animals↗
PubMed1996

[Association of chronic urticaria with Helicobacter pylori-induced antrum gastritis].

In spite of its high incidence, not much is known about the etiology of chronic urticaria. We performed gastroscopic evaluation of 10 patients in whom no cause for chronic urticaria had been found. In 8 of these 10 patients, Helicobacter pylori was identified in the gastric mucosa. The chronic urticarial lesions disappeared within a few days after starting therapy with amoxicillin and omeprazol.

Adult↗
PubMed1996

Amperometric biosensors.

Over the past 18 months, our understanding of the chemistry and engineering principles of amperometric biosensors, including bioaffinity sensors, has deepened. In addition, several novel amperometric biosensors have been commercialized and progress has been made in the design of subcutaneous sensors, particularly those for glucose.

Biosensing Techniques↗
PubMed1996

Alteration of n-3 fatty acid composition in lung tissue after short-term infusion of fish oil emulsion attenuates inflammatory vascular reaction.

OBJECTIVES: To investigate whether modulation of the fatty acid profile can be achieved by the short-term infusion of a fish oil emulsion which may attenuate the pulmonary response to inflammatory stimulation. Changes of fatty acid pattern in-lung tissue and perfusate were analyzed and correlated with physiologic data after a 3-hr infusion of fish oil in comparison with a soybean oil preparation. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Forty standard breed rabbits of either gender. INTERVENTIONS: Isolated lungs from anesthetized rabbits were ventilated and recirculation-perfused (200 mL/min) with 200 mL of cell-free buffer solution to which either 2 mL of saline (control, n = 6), 2 mL of a 10% soybean oil preparation (n = 6), or 2 mL of a 10% fish oil emulsion (n = 6) were added. Samples of perfusate and lung tissue were collected for analysis of fatty acid composition. Tissue and perfusate fatty acid composition were analyzed by capillary gas chromatography. To study metabolic alterations in states of inflammatory stimulation, lungs of each group were stimulated with small doses of the calcium ionophore, A23187 (10(-8) M), during the 180-min lipid perfusion period and again after washing out the lipids by exchanging the perfusion fluid. Pulmonary arterial pressure and lung weight gain were monitored, and eicosanoids were analyzed in the perfusate. MEASUREMENTS AND MAIN RESULTS: Free eicosapentaenoic acids increased several-fold in lung tissue and perfusate during a 3-hr infusion with fish oil. The intravenously administered n-3 fatty acids were rapidly hydrolyzed, as indicated by the appearance of substantial quantities of eicosapentaenoic acid in the perfusate free fatty acid fraction. This increase of perfusion levels of eicosapentaenoic acid was paralleled by an attenuated pressure increase and edema formation due to calcium ionophore challenge and an altered eicosanoid spectrum determined in the perfusate compared with soybean oil-treated lungs. CONCLUSION: Short-term n-3 lipid application (fish oil emulsion) exerts anti-inflammatory effects on lung vasculature, which may be due to the metabolism of eicosapentaenoic acid resulting in the generation of less potent inflammatory eicosanoids.

Animals↗
PubMed1996

Somatic sex-determining signals act on XX germ cells in Drosophila embryos.

In Drosophila, the enhancer-trap line mgm1 is already specifically expressed in male germ cells. Staining is first detected in 10-hour-old embryos and it is found in later stem cells. This line, which reveals the earliest sex-specific gene expression in the germline known so far, is a useful molecular marker to assess the sexual pathway that germ cells have entered before any overt sexual dimorphism is apparent. XY germ cells that develop in feminized animals express mgm1, which shows that this marker is autonomously expressed in XY germ cells. However, XX germ cells that develop in masculinized animals also express mgm1. Therefore, somatic sex-determining signals have already acted on XX germ cells in 10-hour-old embryos.

Animals↗
PubMed1996

Interferon-independent activation of (2'-5') oligoadenylate synthetase in Friend erythroleukemia cell variants exposed to HMBA.

To provide evidence for the implication of interferon (IFN)-induced proteins in the regulation of cell growth during differentiation, the activation of (2'-5') oligoadenylate synthetase (2-5A synthetase) as well as of PKR, two IFN-induced proteins, during differentiation of Friend erythroleukemia cells, was studied. Two cell variants were used. The first (FL) was completely susceptible to hexamethylene bis-acetamide (HMBA)-treatment and responded in both growth-retardation and hemoglobin synthesis. The second (R1) failed to synthesize hemoglobin in response to HMBA although cell growth was still inhibited. In both cell variants, 2-5A synthetase enzyme activity was induced in a similar fashion, reaching a peak at 26 hours after treatment with HMBA. However, the down regulation of activity thereafter was not identical in both cases. In R1 cells, the reduction was much slower compared to FL cells. A similar pattern was observed with the appearance of the 43 kDa isoform of 2-5A synthetase in immunoblots. An analysis of 2-5A synthetase gene expression revealed the presence of 1.7 kb transcripts which peaked at 16 hours after HMBA-treatment in both cell variants. Again, the down-regulation in expression was slower in R1 than in FL cells. Addition of anti-murin alpha/beta-IFN antibodies did not reduce the level of either 2-5A synthetase expression or enzyme activity in either cell variant. Interestingly, the presence of antibodies also did not affect the pattern of pRb phosphorylation in the cell variants exposed to HMBA. In both cell variants, an increase in the amount of the phosphorylated form (ppRb) was observed in immunoblots after 4 hours. This form was gradually transformed to the underphosphorylated molecule (pRb) with time in culture, even in the presence of antibodies. This further substantiates the notion that IFN-induced regulation of pRb phosphorylation is mediated by IFN-induced proteins. The basal level of either expression or ezymatic activity of PKR detected in untreated FL or R1 cells, was relatively high. Treatment with HMBA did not result in further induction of PKR in either cell variant.

2',5'-Oligoadenylate Synthetase↗
PubMed1995

Detection of basal acetylcholine in rat brain microdialysate.

A liquid chromatography-electrochemistry (LC-EC) method is described for the determination of basal acetylcholine (ACh) in microdialysate from the striatum of freely moving rats. This method is based on the separation of ACh and choline (Ch) by microbore liquid chromatography followed by passage of the effluent through a post-column immobilized enzyme reactor (IMER), containing acetylcholinesterase (AChE) and choline oxidase (ChO), and then the electrochemical detection of the hydrogen peroxide produced. Instead of the conventional platinum electrode generally used for the anodic detection of hydrogen peroxide, a peroxidase-redox polymer modified glassy carbon electrode operated at + 100 mV vs. Ag/AgCl has been used to detect the reduction of hydrogen peroxide. With this method, a detection limit of 10 fmol (injected) for ACh (S/N = 3:1) was obtained and the basal ACh concentration in striatal microdialysate was determined without using esterase inhibitors.

Acetylcholine↗