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M Bauer

Publications and source records attributed to M Bauer.

At least 19 recordsLinked to original sources
PubMed1995

Two heads are better than one: crystal structure of the insect derived double domain Kazal inhibitor rhodniin in complex with thrombin.

Rhodniin is a highly specific inhibitor of thrombin isolated from the assassin bug Rhodnius prolixus. The 2.6 Angstrum crystal structure of the non-covalent complex between recombinant rhodniin and bovine alpha-thrombin reveals that the two Kazal-type domains of rhodniin bind to different sites of thrombin. The amino-terminal domain binds in a substrate-like manner to the narrow active-site cleft of thrombin; the imidazole group of the P1 His residue extends into the S1 pocket to form favourable hydrogen/ionic bonds with Asp189 at its bottom, and additionally with Glu192 at its entrance. The carboxy-terminal domain, whose distorted reactive-site loop cannot adopt the canonical conformation, docks to the fibrinogen recognition exosite via extensive electrostatic interactions. The rather acidic polypeptide linking the two domains is displaced from the thrombin surface, with none of its residues involved in direct salt bridges with thrombin. The tight (Ki = 2 x 10(-13) M) binding of rhodniin to thrombin is the result of the sum of steric and charge complementarity of the amino-terminal domain towards the active-site cleft, and of the electrostatic interactions between the carboxy-terminal domain and the exosite.

Amino Acid Sequence↗
PubMed1995

X-ray structure of clotting factor IXa: active site and module structure related to Xase activity and hemophilia B.

Hereditary deficiency of factor IXa (fIXa), a key enzyme in blood coagulation, causes hemophilia B, a severe X chromosome-linked bleeding disorder afflicting 1 in 30,000 males; clinical studies have identified nearly 500 deleterious variants. The x-ray structure of porcine fIXa described here shows the atomic origins of the disease, while the spatial distribution of mutation sites suggests a structural model for factor X activation by phospholipid-bound fIXa and cofactor VIIIa. The 3.0-A-resolution diffraction data clearly show the structures of the serine proteinase module and the two preceding epidermal growth factor (EGF)-like modules; the N-terminal Gla module is partially disordered. The catalytic module, with covalent inhibitor D-Phe-1I-Pro-2I-Arg-3I chloromethyl ketone, most closely resembles fXa but differs significantly at several positions. Particularly noteworthy is the strained conformation of Glu-388, a residue strictly conserved in known fIXa sequences but conserved as Gly among other trypsin-like serine proteinases. Flexibility apparent in electron density together with modeling studies suggests that this may cause incomplete active site formation, even after zymogen, and hence the low catalytic activity of fIXa. The principal axes of the oblong EGF-like domains define an angle of 110 degrees, stabilized by a strictly conserved and fIX-specific interdomain salt bridge. The disorder of the Gla module, whose hydrophobic helix is apparent in electron density, can be attributed to the absence of calcium in the crystals; we have modeled the Gla module in its calcium form by using prothrombin fragment 1. The arched module arrangement agrees with fluorescence energy transfer experiments. Most hemophilic mutation sites of surface fIX residues occur on the concave surface of the bent molecule and suggest a plausible model for the membrane-bound ternary fIXa-FVIIIa-fX complex structure: fIXa and an equivalently arranged fX arch across an underlying fVIIIa subdomain from opposite sides; the stabilizing fVIIIa interactions force the catalytic modules together, completing fIXa active site formation and catalytic enhancement.

Amino Acid Chloromethyl Ketones↗
PubMed1995

Transgenic knockouts reveal a critical requirement for pancreatic beta cell glucokinase in maintaining glucose homeostasis.

The secretion of insulin is controlled by the rate of glucose metabolism in the pancreatic beta cells. As phosphorylation by glucokinase (GLK) appears to be the rate-limiting step for glucose catabolism in beta cells, this enzyme may be the glucose sensor. To test this possibility and to resolve the relative roles of liver and beta cell GLK in maintaining glucose levels, we have generated mice completely deficient in GLK and transgenic mice in which GLK is expressed only in beta cells. In mice with only one GLK allele, blood glucose levels are elevated and insulin secretion is reduced. GLK-deficient mice die perinatally with severe hyperglycemia. Expression of GLK in beta cells in the absence of expression in the liver is sufficient for survival. These mice demonstrate the critical need for beta cell GLK in maintaining normal glucose levels and provide a novel model for one form of noninsulin-dependent diabetes.

Alleles↗
PubMed1995

A phase II trial of human recombinant interleukin-2 administered as a 4-day continuous infusion for children with refractory neuroblastoma, non-Hodgkin's lymphoma, sarcoma, renal cell carcinoma, and malignant melanoma. A Childrens Cancer Group study.

BACKGROUND: Recombinant human Interleukin-2 (IL-2) has been effective at inducing measurable antitumor responses in adults with renal cell carcinoma and melanoma. It also is being tested as adjuvant therapy for patients with acute myeloid leukemia after autologous bone marrow transplantation. METHODS: The authors tested IL-2 in a pediatric Phase II trial using a regimen that has antitumor effects in adults and was proven to be tolerated acceptably in a prior Phase I pediatric trial. Thirty-eight patients were entered into this study of whom 36 received IL-2 and were evaluable (20 with sarcoma, 9 with neuroblastoma, 5 with renal cell carcinoma, and 1 each with melanoma and lymphoma). RESULTS: Interleukin-2 dose modifications were based on tolerance and toxicity, such that 46% of these patients received a 50% increase in IL-2 dose during the second week, and 81% of those receiving the elevated dose continued receiving this dose level during the third week of treatment. A single patient with renal cell carcinoma had a complete response that was maintained; the remaining 35 patients did not show objective evidence of tumor response sufficient to qualify as either a complete response or a partial response. CONCLUSIONS: Absolute lymphocyte counts were indicative of the immunostimulatory effect of this IL-2 regimen as observed for adults, with a median 7.2-fold increase. Nevertheless, despite immune activation, a sufficient number of patients were evaluated, indicating that IL-2 does not have measurable antitumor effects in children with large refractory sarcomas or neuroblastomas, whereas one of five children with renal cell carcinoma had a complete response, consistent with the 10-20% response rate observed in adults.

Adolescent↗
PubMed1995

Crystal structure of a complex between Serratia marcescens metallo-protease and an inhibitor from Erwinia chrysanthemi.

The crystal structure of the complex between the 50 kDa metallo-endoproteinase from Serratia marcescens (SMP), a member of the metzincin superfamily, and an inhibitor from Erwinia chrysanthemi (Inh) was solved by molecular replacement using the known structure of SMP, and refined at 2.30 A resolution to a crystallographic R-factor of 0.195. The E. chrysanthemi inhibitor folds into a compact eight-stranded antiparallel beta-barrel of simple up-down topology such as is found for members of the retinol binding protein family. It mainly interacts with the protease via its five N-terminal residues, which insert into the active site cleft, occupying the S' sites. The first N-terminal residue, SerI1, is partially cleaved off by the protease, while SerI2 makes a hydrogen bond with the catalytically active glutamic acid, Glu177, of the protease. Further interactions are made between one face of the inhibitor formed by the strands s3, s4 and s5 and the protease segment 218 to 228, which is located immediately after the characteristic "Met-turn" of the metzincins.

Amino Acid Sequence↗
PubMed1995

EPR spectroscopy of 5-DOXYL-stearic acid bound to the mitochondrial uncoupling protein reveals its competitive displacement by alkylsulfonates in the channel and allosteric displacement by ATP.

Competition of fatty acids (FA) and alkylsulfonates with 5-DOXYL-stearic acid (5-SASL) binding to isolated mitochondrial uncoupling protein (UcP) is demonstrated using EPR spectroscopy. A distinct peak of the bound 5-SASL (h+1I) decreased with increasing concentration of competitors. Since alkylsulfonates are UcP substrates, it suggests that the FA binding site is located in the anion channel. Moreover, with increasing ATP the h+1I peak decreased and was smoothed with the 'micellar' peak into a single wider peak. A pH of 8.5 reversed this effect. It could reflect an allosteric release of 5-SASL from the ATP binding site which mimics the ATP gating mechanism.

Adipose Tissue, Brown↗
PubMed1995

Sequence constraints and recognition by CTL of an HLA-B27-restricted HIV-1 gag epitope.

Previous studies on the variation of an immunodominant HLA-B27-restricted HIV-1 gag p24 epitope (KRWIIL GLNK, amino acids 263-272) have demonstrated the persistence of variants recognized by CTL. Sequence comparisons of HIV isolates showed that this region is relatively conserved and as a consequence might restrict antigenic variation. To evaluate the possibility of HIV-1 to yield infectious mutants of this epitope that lack the ability to bind to HLA-B27 or escape HLA-B27-restricted CTL recognition, single-point mutations were constructed in the infectious molecular clone of HIV-1 Lai. Changes of arginine 264, the anchor amino acid for HLA-B27, to lysine or glycine resulted in infectious HIV-1 variants. The respective synthetic peptides showed reduced ability to sensitize target cells for CTL recognition and a corresponding loss of binding affinity to HLA-B27. In contrast, mutation of glycine 269 to lysine or glutamate abrogated HIV-1 infectivity. The corresponding peptides were able to bind to HLA-B27 but were not recognized by CTL. These data show that HIV-1 tolerates some genetic variation of the HLA-B27-restricted CTL epitope in gag p24 and that single-point mutations can alter quantitatively the immunologic properties. Further, it demonstrates that the mere nonrecognition of peptides derived from quasispecies analysis of small regions might simply correspond to nonviable virus variants and cannot be taken as evidence for CTL escape mutants. Together with the previously published data on the persistence of CTL epitopes, these results suggest that CTL do not play a major role in driving HIV-1 evolution in vivo.

Amino Acid Sequence↗
PubMed1995

Comparative effects of secretin (SEC) and cholecystokinin-octapeptide (CCK-8) on pancreatic microcirculation.

Using epifluorescent microscopy, we investigated the dynamic changes in pancreatic microcirculation in vivo after bolus administration of secretin (SEC) (0.1-10.0 micrograms/100 g body wt) and cholecystokinin-octapeptide (CCK-8) (0.005-1.2 micrograms/100 g body wt) in pentobarbital-anesthetized rats. Pancreatic capillary red cell velocity as a monitor for pancreatic capillary blood flow was measured in 1-min intervals from 2 min prior to 8 min following bolus infusion of SEC or CCK-8. Physiological concentrations of SEC did not increase pancreatic capillary blood flow. However, pharmacological SEC concentrations induced a dose-dependent increase in pancreatic capillary blood flow (to 162 +/- 19% of baseline; P < 0.05), due to an increase in blood flow velocity (to 153 +/- 18% of baseline; P < 0.05). In contrast, bolus administration of physiological CCK-8 concentrations, which have been proven to stimulate enzyme secretion, induced a transient and dose-dependent increase in pancreatic capillary blood flow (to 235 +/- 24% of baseline; P < 0.05), due to an increase in blood flow velocity (to 184 +/- 13% of baseline; P < 0.05) and capillary diameters (+0.63 +/- 0.15 micron; P < 0.05).

Analysis of Variance↗
PubMed1995

Concurrent agranulocytosis and acute hepatitis resulting from combination of classic neuroleptics and subsequent successful clozapine treatment.

Agranulocytosis and hepatotoxic reactions are rare but severe side-effects of neuroleptic treatment. This article presents the case of a schizophrenic patient who concurrently developed agranulocytosis and acute hepatic drug reaction as a result of a combination of chemically different neuroleptic drugs. After restoration the patient was successfully treated with clozapine for six months without the hematologic disorders recurring.

Adult↗
PubMed1995

Absolutely therapy-resistant depression and mixed movement disorder in an unusual case of polycythemia vera.

This report presents a 64-year-old female patient with unusual psychiatric and neurological complications in polycythemia vera. Six years after onset of the hematologic disorder the patient succumbed to an absolutely therapy-resistant depression, from which she has been suffering for the past four years--intensive and broad--spectrum drug and electroconvulsive treatment has failed to ameliorate the condition. In addition, the patient has developed a mixed movement disorder with rhythmical movements, mainly affecting the trunk, akathisia, hyperventilation, and pleurothotonus ("Pisasyndrome"). The paper discusses a possible link between hypoxic cerebral damage, caused by hyperviscosity of the blood due to polycythemia vera, and the therapy resistance of the depression. The case confirms that organic factors may cause therapy resistance in depressive disorders.

Depressive Disorder↗
PubMed1995

[Effects of desflurane on liver microcirculation in comparison with isoflurane and pentobarbital. An intravital microscopy study in the rat].

OBJECTIVE: It is well known that the volatile anaesthetics halothane, enflurane and isoflurane alter hepatic blood flow in a dose-dependent manner. However, there are only a few studies investigating the effect of the new anaesthetic desflurane on the hepatic blood flow. In particular no information is available about the influence of desflurane on liver microcirculation. Therefore, the aim of this study was to evaluate the effects of desflurane in comparison to isoflurane and pentobarbital on microcirculation of the liver in vivo using intravital fluorescence microscopy. MATERIALS: 18 female Sprague-Dawley rats were anaesthetised with pentobarbital sodium, tracheotomised and mechanically ventilated using a rodent ventilator. A midline laparotomy was performed for later intravital microscopy of the liver. At the beginning of the one-hour ventilation period the animals were assigned to one of the following groups: isoflurane 0.75 MAC, desflurane 0.75 MAC and pentobarbital group. Animals of the pentobarbital group received additionally 25 mg/kg pentobarbital intravenously. After 60 min of ventilation and continuous monitoring of the systemic circulation the hepatic microcirculation was investigated by intravital fluorscence microscopy. RESULTS: Mean arterial blood pressure decreased slightly in the isoflurane and the desflurane groups compared to the pentobarbital group. Neither isoflurane nor desflurane did affect the sinusoidal diameters or the sinusoidal blood flow compared to the pentobarbital group. CONCLUSION: Hepatic microcirculation is not affected by one-hour anaesthesia with 0.75 MAC isoflurane or desflurane in comparison to pentobarbital.

Anesthetics, Inhalation↗
PubMed1995

Attenuation of shock-induced hepatic microcirculatory disturbances by the use of a starch-deferoxamine conjugate for resuscitation.

OBJECTIVE: To determine the effects of a hydroxyethyl starch-deferoxamine conjugate on hepatic microcirculation in an isobaric, anesthetized rat model of hemorrhagic shock and asanguineous resuscitation. DESIGN: Prospective, randomized, controlled study. SETTING: Laboratory at a university hospital. SUBJECTS: Twenty-three female, inbred Lewis rats (190 to 215 g). INTERVENTIONS: After anesthesia (pentobarbital-sodium; 50 mg/kg), tracheotomy, and cannulation, animals were assigned to a hemorrhagic shock (mean arterial pressure at 40 +/- 3 mm Hg for 45 mins) or a time-matched sham protocol. Rats in the shock groups received either hydroxyethyl starch or a starch-deferoxamine conjugate for resuscitation. Liver microcirculation was assessed in vivo 60 mins after onset of volume therapy by epifluorescence microscopy. MEASUREMENTS AND MAIN RESULTS: Conventional resuscitation with the starch-vehicle failed to restore sinusoidal blood flow compared with either time-matched controls (71% of control value; p < .01) or the starch-deferoxamine-treated animals (89% of control value; p < .05 compared with starch-vehicle), although a comparable restoration of central hemodynamics was achieved with both starch preparations. Additionally, treatment with the starch-deferoxamine conjugate resulted in a significant attenuation of sinusoidal leukocyte margination (sham 72.4 +/- 11.0/mm2; starch-vehicle 194.5 +/- 19.0/mm2 [p < .01 compared with controls]; starch-deferoxamine conjugate 135.9 +/- 12.1/mm2 [p < .02 compared with sham and starch-vehicle]). CONCLUSIONS: Asanguineous resuscitation with conventional hydroxyethyl starch failed to restore hepatic microvascular blood flow, despite otherwise effective resuscitation. In contrast, the starch-deferoxamine conjugate improved volumetric blood flow and attenuated leukocyte margination in hepatic sinusoids compared with starch-vehicle, suggesting involvement of iron-dependent, oxygen-derived radicals in shock-induced hepatic microcirculatory disturbances.

Animals↗
PubMed1995

Interleukin-1 receptor antagonist attenuates leukocyte-endothelial interactions in the liver after hemorrhagic shock in the rat.

OBJECTIVE: To evaluate the influence of interleukin-1 on leukocyte-endothelial cell interactions and the microcirculation in the liver after hemorrhagic shock by means of intravital microscopy using an interleukin-1 receptor antagonist (IL-1ra). DESIGN: Prospective, randomized, blinded, controlled study. SETTING: University research laboratory. SUBJECTS: Anesthetized female Sprague Dawley rats weighing 200 to 230 g. INTERVENTIONS: Hypovolemic shock was induced and maintained for 1 hr (mean arterial pressure 40 mm Hg; cardiac output 50% of baseline). After adequate resuscitation and 5 hrs of reperfusion (mean arterial pressure > 100 mm Hg; cardiac output > 120% of baseline), the microcirculation in liver sinusoids was examined by intravital fluorescence microscopy. Continuous administration of IL-1ra (5 mg/kg/hr) was started at different times in a prospective, randomized, blinded fashion, either as pretreatment 5 mins before shock induction (n = 6), or as therapy at the time of resuscitation (n = 6). An additional bolus injection of 5 mg/kg of IL-1ra was given to the latter group. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure, cardiac output, heart rate, and blood gases were comparable in all shock groups during the experiments. The percentage of permanently adherent leukocytes (adhesion time of > 20 secs) in the pretreated group was significantly decreased in comparison with the control group (pretreatment group 16.9 +/- 1.9% vs. control group 42.1 +/- 5.4%; p < .001 by analysis of variance; sham group 9.1 +/- 1.1%). Administration of IL-1ra at the time of resuscitation also reduced firm adhesion of leukocytes to sinusoidal endothelium (treated group 28.8 +/- 3.6%, p < .01). Temporary adhesion rates of leukocytes (adhesion time of < 20 secs) were unaffected by pretreatment or treatment with IL-1ra with respect to control values. Liver microcirculation was impaired after hemorrhagic shock but not improved by IL-1ra. CONCLUSIONS: The results show that adhesion of leukocytes to hepatic sinusoidal endothelium is at least partly regulated by interleukin-1. Adherence was attenuated by the application of IL-1ra, which might be due to diminished expression of adhesion receptors by endothelial cells or leukocytes. Even administration of IL-1ra at the time of resuscitation reduces the early inflammatory response in the liver after shock, thus offering a potentially important therapeutic approach.

Animals↗
PubMed1995

Vessel- and target cell-specific actions of endothelin-1 and endothelin-3 in rat liver.

We studied the sinusoidal and extrasinusoidal constrictor response of hepatic microcirculation to endothelin-1 (ET-1) and endothelin-3 (ET-3) and the possible role of Ito cells vs. Kupffer cells or endothelial cells in mediating this response, using isolated rat livers under high-power intravital microscopy. Rats were pretreated by injection of 2.6 x 10(8) fluorescent latex beads (1 micron) intravenously to label Kupffer cells. Three hours later livers were isolated and perfused before and during the infusion of 1 nM ET-1 or ET-3 with or without the endothelin type A (ETA) receptor antagonist BQ-123 or ETB antagonist IRL-1038. Alternatively, the perfused livers were infused with the ETB agonist sarafotoxin 6c (S6c, 1 or 5 nM). Sinusoid diameters were quantitated at the sites of Ito cells (identified by vitamin A fluorescence) or Kupffer cells (phagocytosed fluorescent latex beads) or where neither cell type was found (endothelial cells). ET-1 was found to induce significant sinusoid constriction at the sites of Ito cells (13.21 +/- 0.58 microns control vs. 10.47 +/- 0.48 microns during ET-1 infusion) but not at the sites of Kupffer cells or endothelial cells (13.26 +/- 0.79 vs. 12.92 +/- 0.61 microns and 12.20 +/- 0.71 vs. 11.98 +/- 0.40 microns, respectively), whereas neither ET-3 nor S6c had any effect on sinusoid narrowing, despite a 1.8-fold (ET-3) or 5.6-fold (5 nM S6c) greater increase in total portal resistance compared with ET-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Localization of the undulin gene (UND) to human chromosome band 8q23.

Undulin, a large extracellular matrix (ECM) mosaic glycoprotein related to collagen type XIV, is associated with dense collagen matrices in soft tissues and is likely to be involved in the supramolecular organization of interstitial collagens. By fluorescence in situ hybridization (FISH), we have assigned the undulin locus (UND) to band q23 of human chromosome 8.

Chromosome Mapping↗
PubMed1995

Chronic ethanol consumption increases hepatic sinusoidal contractile response to endothelin-1 in the rat.

Recent evidence suggests that hepatic stellate cells function as liver-specific pericytes that are highly contractile in response to endothelin-1 (ET-1). Liver injury has been shown to lead to "activation" of stellate cells producing a phenotypic change to a more myofibroblastic cell type including loss of vitamin A and increased contractility. The present study was undertaken to test the effects of short-term chronic ethanol consumption (36% of total calories for 5 weeks according to the Lieber-DeCarli protocol) on hepatic vitamin A storage, expression of smooth muscle alpha-actin, and sinusoidal contractility in Sprague-Dawley rats. Using in vivo epifluorescence video microscopy, we quantified the number of sites of vitamin A fluorescence (purportedly stellate cells) and assessed sinusoidal microhemodynamics at baseline and during a 20-minute infusion period of ET-1 (1 pmol * 100 g body weight [bw]*1*min-1). Retinol and retinyl palmitate were measured after the experiment by means of high-pressure liquid chromatography (HPLC). A highly significant decrease in liver retinyl palmitate level (control: 622.5 +/- 50.9; ethanol: 273.0 +/- 38.0 microgram/g liver; P< .001) was found that correlated with a decrease in sites of vitamin A fluorescence (control: 531.4 +/- 76.1; ethanol: 141.1 +/- 30.2* mm-2; r = .82, P <.001). Concomitantly scattered expression of smooth muscle alpha-actin in sinusoids was observed. Although sinusoidal hemodynamics were not affected at baseline, a significant increase in sinusoidal contractility on endothelin-1 infusion (e.g., sinusoidal resistance [% of baseline value]: control: 10 minutes: 288.7 +/- 71.7, 20 minutes: 200.5 +/- 46.9; ethanol: 10 minutes: 1,916.0 +/- 701.7, 20 minutes: 656.8 +/- 103.3; P < .05 and .01, respectively) was observed. These data indicate that chronic ethanol consumption in this moderate model initiates stellate cell activation. Increased sinusoidal responsiveness to the vasoconstrictor ET-1 in vivo may contribute to the increased susceptibility of ethanol-fed rats to secondary stresses that increase ET-1 expression, such as endotoxemia.

Actins↗