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Biomedical subjects

K Becker

Publications and source records attributed to K Becker.

At least 109 records · Page 6Linked to original sources
PubMed2001

Increased sensitization of acoustic startle response in spasmodic mice with a mutation of the glycine receptor alpha1-subunit gene.

The spontaneous mutant mouse spasmodic (spd) carries a missense mutation affecting the glycine receptor alpha1-subunit gene. This results in a decreased binding affinity to glycine. Spd mutants show exaggerated acoustic startle responses (ASR). The present study sought to elucidate whether this increased ASR is due to a changed auditory processing or to stronger motor output resulting from a disinhibited motor system or, alternatively, to changes in modulatory influences on the startle pathway, namely in the mechanisms underlying habituation and sensitization. We found that in homozygous spd/spd mutants the startle threshold was lower, and the recorded slope of input/output (i/o) function, which reflects the relation between sensory input and motor output, was steeper. During repetitive presentation of high sound pressure level (SPL) startle stimuli (25 dB above startle threshold), ASR amplitudes did not decrease in spd/spd mutants as they do in the wildtype. In contrast, ASR amplitudes decreased when low SPL startle stimuli were presented. Footshocks presented after high SPL startle stimuli did not cause a further increase in ASR amplitudes of spd/spd mutants as in the wildtype. In heterozygous spd/+ mutants all these parameters were between those of spd/spd mutants and wildtype mice but closer to those of the wildtype. The steeper slope of i/o function in spd/spd mutants may be caused by both an increased sensory input and an increased motor output. The altered course of ASR amplitudes during repetitive stimulation and the deficit in additional footshock sensitization, however, can only be explained by an increased sensitization level in the spd/spd mutants. In accordance with the "dual process theory" strong sensitization evoked by high SPL startle stimuli supposedly counteracts habituation, leading to a constant high ASR amplitude. Furthermore, additional footshock sensitization is prevented. The increased sensitization level may be due to a change in auditory processing leading to a stronger sensitizing effect of the startle stimuli with high SPL. Alternatively, glycinergic tonic inhibition of sensitizing structures (e.g. the amygdala) in the wildtype may be diminished in spd/spd mutants, thus leading to a high sensitization level.

Acoustic Stimulation↗
PubMed2001

The respiratory rhythm in mutant oscillator mice.

Since glycinergic inhibition is important for respiratory rhythm generation in mature mammals, we tested the hypothesis that the loss of glycine receptors during postnatal development (P17-P23) of homozygous mutant oscillator mice (spd(ot)/spd(ot)) may result in serious impairment of respiratory rhythm. We measured breathing in a plethysmographic recording chamber on conscious oscillator mice and used an in situ perfused brainstem preparation to record phrenic nerve activity, as well as membrane properties of respiratory neurones. The deletion of glycinergic inhibition did not result in failure of respiratory rhythm: homozygous mutant oscillator mice continue to generate a disturbed respiratory rhythm until death. Postsynaptic activity and membrane potential trajectories of respiratory neurones revealed a persistence of GABAergic inhibition and changes in respiratory rhythm and pattern generation.

Action Potentials↗
PubMed2001

Effects of Quillaja saponins on growth, metabolism, egg production and muscle cholesterol in individually reared Nile tilapia (Oreochromis niloticus).

The effects of supplementation of a Quillaja saponin (QS) mixture in the diets of tilapia have been studied using a respirometer system that allowed feeding and continuous measurement of oxygen consumption of individual fish. Five fish each were given control diet (C group) and control diet supplemented with 150 mg kg(-1) (S150 group) or 300 mg kg(-1) (S300 group) QS. At the end of 14 weeks the weight gain of the S300 group was significantly higher than control (P<0.05) whereas that of the S150 group had an intermediate value. The S150 group had a higher growth rate (P=0.05) after the first 3 weeks of feeding with the experimental diets, compared to the other two groups. At the end of the experiment the S300 group had significantly higher (P<0.05) average values for energy retention, apparent lipid conversion, carcass fat, energy and significantly lower (P<0.05) average values for apparently unutilised energy and carcass ash content compared to the C group. The corresponding values of the S150 group were intermediate between the C and S300 groups. One out of two female fish in the S150 group and both female fish in the S300 group never produced eggs during the entire 14-week experimental period. Contrarily, all three female fish in the control group and one out of the two female fish in the S150 group regularly produced eggs, at a rate of approximately once in every 14 days. The muscle cholesterol level in the S300 group was significantly higher than that of the C group. Possible mechanisms of action of the dietary saponins are discussed.

Animals↗
PubMed2001

Effect of various domestic processing methods on antinutrients and in vitro protein and starch digestibility of two indigenous varieties of Indian tribal pulse, Mucuna pruriens Var. utilis.

The effect of various domestic processing methods on antinutrients and starch fractions and in vitro protein and starch digestibilities of white and black varieties of Mucuna pruriens var. utilis was studied. Cooking or autoclaving of both raw seeds and presoaked seeds in different solutions (water, tamarind extract, sodium bicarbonate, and citric acid) significantly (p < 0.05) reduced the content of total phenolics, phytic acid, trypsin inhibitor and chymotrypsin inhibitor activities, and L-dopa compared to soaking or dry heating techniques. The germination processes (24 and 48 h) were also effective in the reduction of various antinutrients, although this reduction appeared to be more pronounced in a prolonged period of germination (72 h). Water soaking followed by dehusking was found to be ineffective in the reduction of trypsin and chymotrypsin inhibitor activities in both varieties. All of the treatments were effective in significantly (p < 0.05) reducing the resistant starch content in the presently investigated samples. Cooking as well as autoclaving brought about a more significant (p < 0.05) improvement in the digestibility of protein and starch compared to germination and dry heat treatment. Moreover, among the different processing techniques, soaking in sodium bicarbonate solution followed by cooking (29.6-34.8%) or autoclaving (33.0-37.2%) seemed to be the best method for improving starch digestibility.

Cooking↗
PubMed2001

Identification of a novel mutation in 3beta-hydroxysteroid-Delta8-Delta7-isomerase in a case of Conradi-Hünermann-Happle syndrome.

The X-linked dominant Conradi-Hünermann-Happle (CDPX2, MIM 302960) syndrome belongs to the rare, heterogeneous group of diseases called chondrodysplasia punctata. The disease has been connected recently with deficiency of 3beta-hydroxysteroid-Delta8-Delta7-isomerase (also called emopamil-binding protein, EBP), catalysing an intermediate step in the conversion of lanosterol to cholesterol (1, 2). We report a case of CDPX2 with a new missense mutation (C-->G 439) in exon 4, leading to a R147G aminoacid substitution in the EBP.

Adolescent↗
PubMed2001

Enhanced T cell apoptosis in common variable immunodeficiency: negative role of the fas/fasligand system and of the Bcl-2 family proteins and possible role of TNF-RS.

CVI is a primary immunodeficiency characterized by a failure of B cell differentiation associated with an array of T cell defects, such as enhanced T cell apoptosis. In this study we investigated the mechanisms underlying CVI enhanced T cell death. We analysed both the expression of Fas using flow cytometry techniques and the expression of FasL mRNA using RT-PCR in CVI T cells. We could not find any significant differences between CVI and normal subjects with regard to Fas expression, although there was a subgroup of CVI patients with very high Fas expression which was accompanied by an up-regulation of FasL mRNA. However, attempts to induce Fas-mediated apoptosis in these high Fas expressing cells, as evaluated by propidium iodide staining and APO2.7 staining, were unsuccessful. We also investigated intracellular levels of Bcl-2, bcl-xl and bax in CD4(+) and CD8(+) CVI T cells, as well as the bax/Bcl-2 ratio, using flow cytometry techniques but could not detect any differences between CVI and normal subjects. Finally we analysed TNF-RI and TNF-RII mRNA expression in CD4(+) and CD8(+) CVI T cells using semiquantitative RT-PCR and found a significant increase in expression of both TNF-Rs in CD4(+) T cells from CVI patients. Our data suggest that the increased expression of both TNF-Rs on T cells may be one of the mechanisms responsible for the accelerated T cell apoptosis in CVI.

Adolescent↗
PubMed2001

Thioredoxin peroxidases of the malarial parasite Plasmodium falciparum.

The open reading frames of two different proteins with homologies to 2-Cys peroxiredoxins have been identified in the P. falciparum genome. Both genes, with a length of 585 and 648 bp, respectively, were amplified from a gametocyte cDNA and overexpressed in Escherichia coli. The gene products (deduced m 21.8 and 24.6 kDa) with an overall identity of 51.8% were found to be active in the glutamine synthetase protector assay. The smaller protein (named Pf-thioredoxin peroxidase 1; PfTPx1) is reduced by P. falciparum thioredoxin (PfTrx) and accepts H(2)O(2), t-butylhydroperoxide, and cumene hydroperoxide as substrates, the respective k(cat) values for the N-terminally His-tagged protein in the presence of 10 microM PfTrx and 200 microM substrate being 67, 56, and 41 min(-1) at 25 degrees C. As described for many peroxiredoxins, PfTPx1 does not follow saturation kinetics. Furthermore, in oxidizing milieu both proteins are converted to another protein species migrating faster in SDS gel electrophoresis. For PfTPx1 also this second species was found to be active, however, with different kinetic properties which might indicate a mechanism of enzyme regulation in vivo.

Amino Acid Sequence↗
PubMed2001

Effect of balloon compliance on symptomatic success of pneumatic dilation in achalasia patients.

BACKGROUND: Pneumatic dilation is the standard non-surgical treatment of achalasia. The dilation devices in use differ in their physical properties, particularly with regard to balloon compliance. PATIENTS AND METHODS: 35 achalasia patients (18male, 20-82 years, median 45 years) diagnosed by accepted criteria were prospectively and randomly assigned to 39 dilation procedures by either a low compliance dilation device (LCDD, polyethylene balloon, Rigiflex(trade mark), Microvasive Boston Scientific, USA, n = 18) or a high compliance dilation device (HCDD, latex balloon, Rüsch Inc., Germany, n = 17). Individual complaints were graded by a standardized questionnaire before treatment and prospectively after a median of 3 and 13 months. Furthermore, the patients' readiness to retrospectively re-consent (treatment satisfaction) and treatment complications were recorded. RESULTS: Patient groups did not differ with regard to age, sex, number of previous dilations, and duration of follow-up (Mann-Whitney U-test, p > 0.05). 2 patients were excluded from follow-up, with one individual (HCDD) having suffered a dilation-related perforation (2.6 %) and another subject (LCDD) having not been able to re-contact. Initial and post-treatment symptom scores as well as treatment complications were similar in both treatment groups (p > 0.05). Treatment satisfaction was 90 % for the LCDD and 82 % for the HCDD group at first control, and 89 % and 87 % at second control, respectively (p > 0.05). In both patient groups, dilation therapy best improved the symptom "dysphagia" (Wilcoxon rank sum test, p < 0.05). CONCLUSIONS: Achalasia patients' satisfaction of dilation treatment is high, with their dysphagia benefiting most from therapy. Low and high compliance balloon devices did not differ from each other with regard to symptomatic efficacy and safety in forceful dilation of these individuals.

Adult↗
PubMed2001

Effects of rumen fluid collection site on microbial population structure during in vitro fermentation of the different substrates quantified by 16S rRNA hybridisation.

Rumen fluid samples from a cow were withdrawn manually from the feed mat (solid phase) or the liquid phase below this mat and incubated in vitro with wheat straw, sorghum hay and a concentrate mixture. From the inoculum and several samples collected during in vitro incubation RNA was extracted to assess microbial population size and structure. RNA content recovered from the solid phase rumen fluid was significantly higher than from the liquid phase. The composition of the microbial population in the solid phase material was characterised by a high proportion of Ruminococci. Neither the proportion of other cell wall degrading organisms (Fibrobacter and Chytridiomycetes) nor the Eukarya and Archaea populations differed between the two sampling sites. Gas production was higher when substrates were incubated with solid phase than with liquid phase rumen fluid regardless of sampling time. However, the higher level of gas production was not accompanied by a corresponding increase in true digestibility. The RNA probes showed that during in vitro incubation with liquid phase rumen fluid, the eukaryotic population was inactive no matter which substrate was used and the activity of methanogens (Archaea) was lower than with solid phase rumen fluid. The population pattern of the cell wall degrading organisms was influenced mainly by the substrate fermented, and to a smaller extent by the inoculum used for in vitro fermentation.

Animals↗
PubMed2001

Does exposure to residential radon increase the risk of lung cancer?

In assessing the risks of exposure to ionising radiation, it is important to neither overstate nor understate the effects of the hazard. These requirements are often difficult to satisfy, especially since much of our knowledge about the effects of low levels of radiation is subject to rather large uncertainties. Our participants have given their opinions about the risk of lung cancer induction resulting from exposure to radon in residences. Each agrees that exposures to high concentrations of radon are hazardous. However, as with low level exposures to other types of ionising radiation, quantifying relatively small risks is quite difficult. The national and international standards setting bodies have recommended a fairly conservative approach that may overestimate the 'true' magnitude of deleterious effects and their dependence upon exposure, but this is to be expected given the uncertainties in the data and the need to avoid underestimates. A conservative approach can have both positive and negative consequences, and it is also important to neither overstate nor understate these consequences.

Air Pollutants, Radioactive↗
PubMed2001

A 46,XX fetus with external female and internal male genitalia, facial dysmorphic features and mildly dilated lateral ventricles of the brain: a new syndrome?

The clinical features of a 46,XX fetus with dysmorphic facial features, mild dilatation of the lateral ventricles of the brain, and female external and male internal genitalia are described. This combination of abnormalities does not appear to have been reported previously, and may represent a new syndrome.

Abnormalities, Multiple↗
PubMed2001

Enterotoxigenic potential of Staphylococcus intermedius.

Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In contrast to Staphylococcus aureus, a systematic screening for the enterotoxins has not yet been performed on the genomic level for the coagulase-positive species S. intermedius. Therefore, the enterotoxigenic potential of 281 different veterinary (canine, n = 247; equine, n = 23; feline, n = 9; other, n = 2) and 11 human isolates of S. intermedius was tested by using a multiplex PCR DNA-enzyme immunoassay system targeting the staphylococcal enterotoxin genes sea, seb, sec, sed, and see. Molecular results were compared by in vitro testing of enterotoxin production by two immunoassays. A total of 33 (11.3%) S. intermedius isolates, including 31 (12.6%) canine isolates, 1 equine isolate, and 1 human isolate, tested positive for the sec gene. In vitro production of the respective enterotoxins was detected in 30 (90.9%) of these isolates by using immunological tests. In contrast, none of 65 veterinary specimen-derived isolates additionally tested and comprising 13 (sub)species of coagulase-negative staphylococci were found to be enterotoxigenic. This study shows on both molecular and immunological levels that a substantial number of S. intermedius isolates harbor the potential for enterotoxin production. Since evidence for noninvasive zoonotic transmission of S. intermedius from animal hosts to humans has been documented, an enterotoxigenic role of this microorganism in SFP via contamination of food products may be assumed.

Animals↗
PubMed2001

Analogs of Eap protein are conserved and prevalent in clinical Staphylococcus aureus isolates.

Map and Eap are secreted Staphylococcus aureus proteins that interact with various extracellular matrix molecules. PCR analysis using map primers yielded positive reactions in 97.9% of S. aureus isolates but not in Staphylococcus epidermidis isolates. Cloning and sequencing of the conferring genes revealed a high degree of overall homology combined with size variability of the gene product due to various repeat numbers and early translation termination in a poly(A) region. Thus, Map and Eap may provide a potential novel tool for S. aureus identification and typing.

Amino Acid Sequence↗
PubMed2001

Identification and characterization of a novel 38.5-kilodalton cell surface protein of Staphylococcus aureus with extended-spectrum binding activity for extracellular matrix and plasma proteins.

The ability to attach to host ligands is a well-established pathogenic factor in invasive Staphylococcus aureus disease. In addition to the family of adhesive proteins bound to the cell wall via the sortase A (srtA) mechanism, secreted proteins such as the fibrinogen-binding protein Efb, the extracellular adhesion protein Eap, or coagulase have been found to interact with various extracellular host molecules. Here we describe a novel protein, the extracellular matrix protein-binding protein (Emp) initially identified in Western ligand blots as a 40-kDa protein due to its broad-spectrum recognition of fibronectin, fibrinogen, collagen, and vitronectin. Emp is expressed in the stationary growth phase and is closely associated with the cell surface and yet is extractable by sodium dodecyl sulfate. The conferring gene emp (1,023 nucleotides) encodes a signal peptide of 26 amino acids and a mature protein of a calculated molecular mass of 35.5 kDa. Using PCR, emp was demonstrated in all 240 S. aureus isolates of a defined clinical strain collection as well as in 6 S. aureus laboratory strains, whereas it is lacking in all 10 S. epidermidis strains tested. Construction of an allelic replacement mutant (mEmp50) revealed the absence of Emp in mEmp50, a significantly decreased adhesion of mEmp50 to immobilized fibronectin and fibrinogen, and restoration of these characteristics upon complementation of mEmp50. Emp expression was also demonstrable upon heterologous complementation of S. carnosus. rEmp expressed in Escherichia coli interacted with fibronectin, fibrinogen, and vitronectin in surface plasmon resonance experiments at a K(d) of 21 nM, 91 nM, and 122 pM, respectively. In conclusion, the biologic characterization of Emp suggests that it is a member of the group of secreted S. aureus molecules that interact with an extended spectrum of host ligands and thereby contribute to S. aureus pathogenicity.

Adhesins, Bacterial↗