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Biomedical subjects

A Betz

Publications and source records attributed to A Betz.

At least 19 recordsLinked to original sources

Quetiapine (Seroquel) shows a pattern of behavioral effects similar to the atypical antipsychotics clozapine and olanzapine: studies with tremulous jaw movements in rats.

RATIONALE: Previous studies demonstrated that clozapine and olanzapine suppressed tacrine-induced jaw movements at lower doses than those required for suppression of lever pressing. OBJECTIVE: The present studies were undertaken to evaluate the novel atypical antipsychotic quetiapine using the jaw movement model. METHODS: The effect of acute quetiapine on the suppression of tacrine-induced tremulous jaw movements was examined. To determine the relative potency of this effect compared with other behavioral effects of quetiapine, suppression of lever pressing also was studied. In other studies, rats received quetiapine for 14 consecutive days to study the effects of repeated injections of this drug. RESULTS: Acute quetiapine injections decreased tacrine-induced jaw movements and lever pressing. The ratio of the ED50 for suppression of jaw movements divided by the ED50 for suppression of lever pressing was used as an index of liability to produce motor side effects, and the present results demonstrate that quetiapine has a ratio similar to that previously shown for clozapine and olanzapine. In the repeated-administration studies, quetiapine failed to induce jaw movements. On day 14, quetiapine reduced tacrine-induced tremulous jaw movements, and in a parallel experiment quetiapine significantly suppressed lever pressing on days 1-14. Repeated injections of quetiapine reduced tacrine-induced jaw movements over a dose range lower than that required for suppression of lever pressing. CONCLUSIONS: On tests of jaw movement activity and lever pressing after both acute and repeated drug administration, quetiapine showed a profile somewhat similar to clozapine and olanzapine. A theoretical model is offered suggesting that atypical antipsychotics that act on 5-HT or muscarinic receptors have intrinsic antiparkinsonian actions that work in opposition to the motor effects produced by dopamine antagonism.

Animals↗

Behavioral effects of inhibition of cannabinoid metabolism: The amidase inhibitor AM374 enhances the suppression of lever pressing produced by exogenously administered anandamide.

Biochemical investigations have identified putative enzymatic pathways for the synthesis and metabolism of endogenous cannabinoids. Anandamide amidase is an enzyme that metabolizes anandamide into arachadonic acid and ethanolamine. Using in vitro methods, various inhibitors of amidase have been identified. The present studies were undertaken to determine if the amidase inhibitor AM 374 could enhance the effects of intraperitoneal (IP) injections of anandamide. Three studies were conducted to investigate the effects of various drug treatments on fixed ratio 5 operant lever pressing for food reinforcement. In the first study, the effects of different doses of anandamide were assessed, and it was demonstrated that 5.0 and 10.0 mg/kg anandamide IP significantly suppressed lever pressing, while 2.5 mg/kg produced very little effect. The second study tested the effects of intraventricular (ICV) injections of AM 374, and it was observed that doses up to 10.0, 20.0 and 40 microg AM 374 had no significant effect upon lever pressing. The third study investigated the combined effect of AM374 with a low dose of anandamide. Rats received two drug injections: one ICV and one IP. Four different drug treatments were assessed: 1) ICV vehicle + IP vehicle, 2) ICV vehicle + 2.5 mg/kg anandamide IP, 3) ICV 20.0 microg AM 374 + IP vehicle, and 4) ICV 20 microg AM 374 + 2.5 mg/kg anandamide IP. Combined administration of AM 374 plus anandamide led to a significant decrease in lever pressing compared to either AM374 or anandamide administered alone. Observations of the animals treated with the combination of AM374 plus anandamide indicated that the drug combination resulted in motor slowing, which is consistent with the notion that stimulation of cannabinoid receptors produced a motor deficit that interfered with lever pressing. Although AM374 produced no effect on its own, this amidase inhibitor did enhance the behavioral effect of a low dose of anandamide. These results are consistent with the notion that AM 374 inhibited the enzymatic breakdown of exogenously injected anandamide. This type of procedure can be used to assess a variety of different compounds for their ability to inhibit cannabinoid metabolism.

Amidohydrolases↗

The adenosine A2A antagonist KF17837 reverses the locomotor suppression and tremulous jaw movements induced by haloperidol in rats: possible relevance to parkinsonism.

Recent evidence indicates that adenosine A2A receptors modulate the activity of striatal neurons, and that antagonists of this receptor may have actions in various animal models related to motor function. Four experiments were conducted to study the effects of systemic injections of the adenosine A2A antagonist KF17837 on the behavioral effects produced by repeated administration of the dopamine (DA) antagonist haloperidol. In the first two experiments, it was shown that repeated 0.5 mg/kg haloperidol severely suppressed open-field locomotor activity, and that KF17837 (0.0-20.0 mg/kg) did not significantly increase open-field locomotor activity. The third experiment demonstrated that injections of KF17837 (0.0-20.0 mg/kg) completely reversed the suppression of locomotion induced by haloperidol, and also increased rearing behavior in haloperidol-treated rats. Previous research has reported that haloperidol induces tremulous jaw movements that have many of the characteristics of parkinsonian tremor. The fourth experiment demonstrated that i.p. injections of KF17837 (0.0-20.0 mg/kg) also suppressed haloperidol-induced tremulous jaw movements. Taken together, the results of these experiments indicate that adenosine A2A antagonism can reverse the locomotor suppression and tremulous movements induced by DA antagonism. This profile of activity is consistent with the hypothesis that antagonism of adenosine A2A receptors can result in an antiparkinsonian effect in animal models.

Adenosine A2 Receptor Antagonists↗

Open field locomotor effects in rats after intraventricular injections of ethanol and the ethanol metabolites acetaldehyde and acetate.

The typical response to acute peripheral administration of low to high doses of ethanol in rats is a dose-dependent depression of motor activity. Nevertheless, recent studies indicate that intraventricular (ICV) injections of ethanol can produce signs of behavioral activation. In addition, considerable evidence indicates that brain metabolism of ethanol is involved in modulating some of the behavioral effects of this drug, which suggests that ethanol may have active metabolites with central actions. The present study was undertaken to investigate the effects of ICV ethanol, and its two major metabolites acetaldehyde and acetate, on open field locomotor activity in rats. Male Sprague-Dawley rats received different doses of ethanol, acetaldehyde or acetate ICV and immediately were placed in an open field chamber in which locomotion was measured. Rats injected with ICV ethanol or acetaldehyde showed an inverted U-shaped dose-response curve, with moderate doses increasing motor activity. In contrast, acetate produced a dose-dependent decrease in motor activity. These results demonstrate that central administration of low doses of ethanol can increase locomotor activity in rats, and suggest that acetaldehyde may be an active metabolite of ethanol that also can facilitate locomotor activity. Moreover, it is possible that some of the motor suppression or sedation produced by ethanol is due to the central actions of acetate.

Acetaldehyde↗

Locomotor stimulant effects of intraventricular injections of low doses of ethanol in rats: acute and repeated administration.

RATIONALE: Low doses of ethanol stimulate locomotion in mice, but in rats the typical response to peripheral ethanol administration is a dose-dependent suppression of locomotion. Moreover, chronic ethanol administration fails to produce signs of locomotor sensitization in rats. OBJECTIVE: The present study was undertaken to determine whether intraventricular (i.c.v.) infusions of low doses of ethanol (as determined by comparisons with systemic doses, and by analyses of brain extract ethanol levels) could increase locomotor activity in rats after acute or repeated administration. METHODS: Male rats received acute doses of ethanol i.p. (0.0, 0.25, 0.5, 1.0, or 2.0 g/kg) or i.c.v. (0.0, 0.7, 1.4, or 2.8 micromol) and were tested for motor activity. In a third experiment, repeated i.c.v. vehicle or ethanol (2.8 micromol) was administered for 15 sessions over a 30-day period, and motor activity was recorded. This phase was followed by a single challenge session, in which a low dose of ethanol (0.7 micromol) was injected i.c.v. to both groups of rats. RESULTS: Rats injected with i.p. ethanol showed no increase in activity at low doses, with higher doses suppressing activity. In contrast, i.c.v. injections of low doses of ethanol increased motor activity. After repeated administration, ethanol-treated rats were more sensitive than control-treated rats to the locomotor stimulant effect of ethanol. CONCLUSIONS: These results demonstrate that central administration of low doses of ethanol can increase locomotor activity in rats and suggest that i.c.v. ethanol can produce some signs of motor sensitization, a characteristic that has been related to the potential addictive properties of many drugs.

Animals↗

Substantia nigra pars reticulata GABA is involved in the regulation of operant lever pressing: pharmacological and microdialysis studies.

Substantia nigra pars reticulata (SNr) is an important mesencephalic nucleus that functions as a relay area for basal ganglia output. SNr receives GABAergic inputs from the neostriatum and globus pallidus, and in turn sends projections to a variety of motor areas. Although a large number of studies have focused upon the behavioral functions of basal ganglia dopamine, much less is known about the behavioral functions of SNr GABA. The present studies were undertaken to investigate the role of SNr GABA in lever pressing behavior. In the first experiment, the GABA(A) antagonist bicuculline was infused locally into SNr to determine if blockade of GABA receptors interfered with the performance of lever pressing on a fixed ratio 5 schedule. SNr injections of bicuculline produced a dose-related suppression of operant responding. Analysis of interresponse time bins showed that SNr bicuculline produced a response slowing characterized by a relative reduction in the number of fast interresponse times, and an increase in the relative number of pauses. In an additional experiment, microdialysis methods were used to determine if extracellular GABA is elevated during the performance of fixed ratio five lever pressing. During the 30 min lever pressing session, extracellular GABA showed a significant and substantial increase relative to baseline levels. These data support the hypothesis that SNr GABA is involved in the regulation of motor output, and indicate that GABA release in this structure is increased during behavioral stimulation.

Animals↗

A Drosophila PIAS homologue negatively regulates stat92E.

Transcriptional activation by, and therefore the physiologic impact of, activated tyrosine-phosphorylated STATs (signal transducers and activators of transcription) may be negatively regulated by proteins termed PIAS (protein inhibitors of activated stats), as shown by previous experiments with mammalian cells in culture. Here, by using the genetic modifications in Drosophila, we demonstrate the in vivo functional interaction of the Drosophila homologues stat92E and a Drosophila PIAS gene (dpias). To this end we use a LOF allele and conditionally overexpressed dpias in JAK-STAT pathway mutant backgrounds. We conclude that the correct dpias/stat92E ratio is crucial for blood cell and eye development.

Alleles↗

Online reference database of European Y-chromosomal short tandem repeat (STR) haplotypes.

The reference database of highly informative Y-chromosomal short tandem repeat (STR) haplotypes (YHRD), available online at http://ystr.charite.de, represents the largest collection of male-specific genetic profiles currently available for European populations. By September 2000, YHRD contained 4688 9-locus (so-called "minimal") haplotypes, 40% of which have been extended further to include two additional loci. Establishment of YHRD has been facilitated by the joint efforts of 31 forensic and anthropological institutions. All contributing laboratories have agreed to standardize their Y-STR haplotyping protocols and to participate in a quality assurance exercise prior to the inclusion of any data. In view of its collaborative character, and in order to put YHRD to its intended use, viz. the support of forensic caseworkers in their routine decision-making process, the database has been made publicly available via the Internet in February 2000. Online searches for complete or partial Y-STR haplotypes from evidentiary or non-probative material can be performed on a non-commercial basis, and yield observed haplotype counts as well as extrapolated population frequency estimates. In addition, the YHRD website provides information about the quality control test, genotyping protocols, haplotype formats and informativity, population genetic analysis, literature references, and a list of contact addresses of the contributing laboratories.

Databases, Factual↗

DYS STR analysis with epithelial cells in a rape case.

We report here the application of Y-chromosomal DNA analysis in a rape case, which occurred in Stuttgart, Germany. Microscopic examination of the victim's vaginal swabs and her underwear showed no sperm cells. DNA was extracted from vaginal and epithelial cells and analysed with the autosomal systems SE33, THO1 (singleplex) and with the multiplex Profiler Plus (Applied Biosystems, Foster City, USA). The results of these autosomal STR analysis gave no hint at a mixed sample and failed to identify a male profile. DYS STR analysis with the systems DYS391, DYS392, DYS393, DYS19 and DYS389 I/II showed the same characteristic features as the suspect. We used this incomplete haplotype to search in the Y-STR Haplotype Reference Database via Internet. In a Caucasian population sample of 3589 minimal haplotypes we found 71 matches. The suspect confessed the crime and was finally condemned to 4 years imprisonment.

DNA↗

Electrostatic steering and ionic tethering in the formation of thrombin-hirudin complexes: the role of the thrombin anion-binding exosite-I.

Electrostatic interactions between the thrombin anion-binding exosite-I (ABE-I) and the hirudin C-terminal tail play an important role in the formation of the thrombin-hirudin inhibitor complex and serves as a model for the interactions of thrombin with its many other ligands. The role of each solvent exposed basic residue in ABE-I (Arg(35), Lys(36), Arg(67), Arg(73), Arg(75), Arg(77a), Lys(81), Lys(109), Lys(110), and Lys(149e)) in electrostatic steering and ionic tethering in the formation of thrombin-hirudin inhibitor complexes was explored by site directed mutagenesis. The contribution to the binding energy (deltaG(degrees)b) by each residue varied from 1.9 kJ mol(-)(1) (Lys(110)) to 15.3 kJ mol(-1) (Arg(73)) and were in general agreement to their observed interactions with hirudin residues in the thrombin-hirudin crystal structure [Rydel, T. J., Tulinsky, A., Bode, W., and Huber, R. (1991) J. Mol. Biol. 221, 583-601]. Coupling energies (delta deltaG(degrees) int) were calculated for the major ion-pair interactions involved in ionic tethering using complementary hirudin mutants (h-D55N, h-E57Q, and h-E58Q). Cooperativity was seen for the h-Asp(55)/Arg(73) ion pair (2.4 kJ mol(-1)); however, low coupling energies for h-Asp(55)/Lys(149e) (deltadeltaG(degrees)int 0.6 kJ mol(-1)) and h-Glu(58)/Arg(77a) (deltadeltaG(degrees)int 0.9 kJ mol(-1)) suggest these are not major interactions, as anticipated by the crystal structure. Interestingly, high coupling energies were seen for the intermolecular ion-pair h-Glu(57)/Arg(75) (deltadeltaG(degrees)int 2.3 kJ mol(-1)) and for the solvent bridge h-Glu(57)/Arg(77a) (deltadeltaG(degrees)int 2.7 kJ mol(-1)) indicating that h-Glu(57) interacts directly with both Arg(75) and Arg(77a) in the thrombin-hirudin inhibitor complex. The remaining ABE-I residues that do not form major contacts in tethering the C-terminal tail of hirudin make small but collectively important contributions to the overall positive electrostatic field generated by ABE-I important in electrostatic steering.

Amino Acid Substitution↗

Antithrombin binding of low molecular weight heparins and inhibition of factor Xa.

Fluorescence and stopped flow methods were used to compare clinically used heparins with regard to their ability to bind to antithrombin and to accelerate the inactivation of factor Xa. Titration of antithrombin with both low molecular weight heparin (LMWH) (enoxaparin, fragmin and ardeparin) and unfractionated heparin (UFH) produced an equivalent fluorescence increase and indicates similar affinity of all heparin preparations to antithrombin. However, relative to UFH enoxaparin, the LMWH with the smallest average molecular mass, contained only 12% material with high affinity for antithrombin. The rate of factor Xa inhibition by antithrombin increased with the concentration of the examined heparins to the same limiting value, but the concentration required for maximal acceleration depended on the preparation. According to these data the high affinity fraction of the heparin preparations increased the intrinsic fluorescence and inhibitory activity equally without additional effects by variations in chain length and chemical composition. In contrast, in the presence of Ca UFH accelerated the inhibition of factor Xa by antithrombin 10-fold more efficiently than comparable concentrations of the high affinity fractions of enoxaparin and fragmin. The bell-shaped dependence of this accelerating effect suggests simultaneous binding of both proteins to heparin. In conclusion, under physiologic conditions the anti-factor Xa activity of heparin results from a composite effect of chain length and the content of material with high affinity to antithrombin. Thus, the reduced antithrombotic activity of LMWH relative to UFH results from a smaller content of high affinity material and the absence of a stimulating effect of calcium.

Animals↗

Functional interaction of the active zone proteins Munc13-1 and RIM1 in synaptic vesicle priming.

Synaptic neurotransmitter release is restricted to active zones, where the processes of synaptic vesicle tethering, priming to fusion competence, and Ca2+-triggered fusion are taking place in a highly coordinated manner. We show that the active zone components Munc13-1, an essential vesicle priming protein, and RIM1, a Rab3 effector with a putative role in vesicle tethering, interact functionally. Disruption of this interaction causes a loss of fusion-competent synaptic vesicles, creating a phenocopy of Munc13-1-deficient neurons. RIM1 binding and vesicle priming are mediated by two distinct structural modules of Munc13-1. The Munc13-1/RIM1 interaction may create a functional link between synaptic vesicle tethering and priming, or it may regulate the priming reaction itself, thereby determining the number of fusion-competent vesicles.

Alternative Splicing↗

Efficacy of the novel selective platelet-derived growth factor receptor antagonist CT52923 on cellular proliferation, migration, and suppression of neointima following vascular injury.

Exaggerated or inappropriate signaling by the platelet-derived growth factor receptor (PDGFR) tyrosine kinase has been implicated in a wide variety of diseases. Thus, a series of piperazinyl quinazoline compounds were identified as potent antagonists of the PDGFR by screening chemical libraries. An optimized analog, CT52923, was shown to be an ATP-competitive inhibitor that exhibited remarkable specificity when tested against other kinases, including all members of the closely related PDGFR family. The PDGFRs and stem cell factor receptor were inhibited with an IC(50) of 100 to 200 nM, while 45- to >200-fold higher concentrations of CT52923 were required to inhibit fms-like tyrosine kinase-3 and colony-stimulating factor-1 receptor, respectively. Other receptor tyrosine kinases, cytoplasmic tyrosine kinases, serine/threonine kinases, or members of the mitogen-activated protein kinase pathway were not significantly inhibited at 100- to 1000-fold higher concentrations. In addition, this compound also demonstrated specificity for inhibition of cellular responses. Platelet-derived growth factor-induced smooth muscle cell migration or fibroblast proliferation was found to be blocked by CT52923 with an IC(50) of 64 and 280 nM, respectively, whereas 50- to 100-fold higher concentrations were required to inhibit these responses when induced with fibroblast growth factor. To investigate the effect of CT52923 on PDGFR signaling, in vivo studies demonstrated that CT52923 could significantly inhibit neointima formation following carotid artery injury by oral administration in the rat. Therefore, PDGFR antagonism by CT52923 could be a viable strategy for the prevention of clinical restenosis or the treatment of other human diseases involving PDGFR signaling.

Angioplasty, Balloon↗

A new method for the evaluation of matches in non-recombining genomes: application to Y-chromosomal short tandem repeat (STR) haplotypes in European males.

A 9-locus microsatellite framework (minimal haplotype), previously developed for forensic purposes so as to facilitate stain analysis, personal identification and kinship testing, has been adopted for the establishment of a large reference database of male European Y-chromosomal haplotypes. The extent of population stratification pertaining to this database, an issue crucial for its practical forensic application, was assessed through analysis of molecular variance (AMOVA) of the 20 regional samples included. Despite the notion of some significant haplotype frequency differences, which were found to correlate with known demographic and historic features of Europeans, AMOVA generally revealed a high level of genetic homogeneity among the populations analyzed. Owing to their high diversity, however, accurate frequency estimation is difficult for Y-STR haplotypes when realistic (i.e. moderately sized) datasets are being used. As expected, strong pair-wise and higher order allelic associations were found to exist between all markers studied, implying that haplotype frequencies cannot be estimated as products of allele frequencies. A new extrapolation method was therefore developed which treats haplotype frequencies as random variables and generates estimates of the underlying distribution functions on the basis of closely related haplotypes. This approach, termed frequency 'surveying', is based upon standard population genetics theory and can in principle be applied to any combination of markers located on the Y-chromosome or in the mitochondrial genome. Application of the method to the quality assured reference Y-STR haplotype database described herein will prove very useful for the evaluation of positive trace-donor matches in forensic casework.

Alleles↗

Munc13-1 acts as a priming factor for large dense-core vesicles in bovine chromaffin cells.

In chromaffin cells the number of large dense-core vesicles (LDCVs) which can be released by brief, intense stimuli represents only a small fraction of the 'morphologically docked' vesicles at the plasma membrane. Recently, it was shown that Munc13-1 is essential for a post-docking step of synaptic vesicle fusion. To investigate the role of Munc13-1 in LDCV exocytosis, we overexpressed Munc13-1 in chromaffin cells and stimulated secretion by flash photolysis of caged calcium. Both components of the exocytotic burst, which represent the fusion of release-competent vesicles, were increased by a factor of three. The sustained component, which represents vesicle maturation and subsequent fusion, was increased by the same factor. The response to a second flash, however, was greatly reduced, indicating a depletion of release-competent vesicles. Since there was no apparent change in the number of docked vesicles, we conclude that Munc13-1 acts as a priming factor by accelerating the rate constant of vesicle transfer from a pool of docked, but unprimed vesicles to a pool of release-competent, primed vesicles.

Animals↗

Molecular cloning, sequencing, expression, and site-directed mutagenesis of the 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase gene from Arthrobacter spec. Rü61a.

The ring cleaving enzyme 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase (HOD)) of Arthrobacter spec. Rü61a is part of the quinaldine degradation pathway. Carbon monoxide and N-acetyl-anthranilate are the products formed by dioxygenolytic cleavage of two C-C bonds in the substrate's pyridine ring. The gene coding for HOD was cloned and sequenced. An isoelectric point of pH 5.40 and a molecular mass of 31,838 Da was deduced from the sequence. HOD is shown to be remarkably similar to 1H-3-hydroxy-4-oxoquinoline 2,4-dioxygenase (QDO) of Pseudomonas putida 33/1, but not to other dioxygenases described so far. Consensus regions indicative for any chromophoric cofactor or any catalytically relevant metal were not detected. Sequence comparisons and secondary structure predictions revealed HOD as a new member of the alpha/beta hydrolase fold family. Expression in E. coli yielded recombinant catalytically active His-tagged HOD. S101A and D233A, two mutants of HOD, were obtained by site-directed mutagenesis. Since their residual activity is 43.1% and 62.6%, respectively, they probably are of no catalytic relevance although they might play a role in the interaction between enzyme and substrate.

Amino Acid Sequence↗

Inhibition of factor Xa by a peptidyl-alpha-ketothiazole involves two steps. Evidence for a stabilizing conformational change.

Recently, peptidylketothiazoles have been shown to be potent inhibitors of proteases, but the details of the interaction have not yet been studied. In the work presented here, the interaction of factor Xa, a coagulation protease, with the transition state inhibitor BnSO(2)-D-Arg-Gly-Arg-ketothiazole (C921-78) is characterized. C921-78 is a tight and selective inhibitor of the coagulation protease factor Xa (K(d) = 14 pM). The hydrolytic activity of factor Xa was inhibited by C921-78 in a time-dependent manner. The rate-limiting step of the bimolecular combination of inhibitor and enzyme was competitive with the substrate. Conversely, the inhibitor could be displaced from the active site of the enzyme after exposure of the preformed complex to an excess of substrate or to the active site inhibitor dansyl-Glu-Gly-Arg-chloromethyl ketone (DEGR-CMK) in a slow reaction. The formation of the C921-78-factor Xa complex resulted in a 60% increase in the magnitude of the fluorescence emission spectrum. Rapid mixing of the enzyme and inhibitor produces a monophasic fluorescence increase, compatible with spectral transition in a single step. The rate constant for this reaction increased hyperbolically with the concentration of C921-78, but the amplitude remained constant. These results are consistent with the initial formation of an enzyme-inhibitor complex (EI), followed by a unimolecular conversion of EI to EI linked to a spectral transition. The rate constants of the isomerization provide an estimate of 300000-fold stabilization. Thus, the inhibition of factor Xa by C921-78 follows a mechanism similar to that described classically for slow tight binding inhibitors. However, the two steps of the reaction cannot be kinetically separated by the rapid equilibrium assumption, and therefore, the formation of EI is partially rate-limiting, too. The driving energy for the unusually fast isomerization step may result from the highly favorable interactions of the inhibitor in the primary binding site.

Amino Acid Sequence↗