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Biomedical subjects

B Baur

Publications and source records attributed to B Baur.

At least 19 recordsLinked to original sources
PubMed2006

Coevolution of male and female reproductive traits in a simultaneously hermaphroditic land snail.

Inter- and intraspecific studies in gonochoristic animals reveal a covariation between sperm characteristics and the size of the female reproductive tract, indicating a rapid evolutionary divergence, which is consistent with the theory of post-copulatory sexual selection. Simultaneous hermaphrodites differ from species with separate sexes (gonochorists) in that they possess both functional male and female reproductive organs at the same time. We investigated whether in hermaphroditic animals intraspecific variation in reproductive traits results from divergent coevolution, by quantifying the variation in male and female traits among six natural populations of the snail Arianta arbustorum and examining the covariation in interacting traits. There was a significant among-population variation in spermatophore volume, number of sperm transferred and sperm length, as well as in volume of the sperm storage organ (spermatheca) and number of tubules, but not in spermatheca length. We found a positive association between sperm number transferred and spermatheca volume. This result suggests that the same post-copulatory mechanisms as in gonochorists drive the correlated evolution of reproductive characters in hermaphrodites.

Animals↗
PubMed2006

Syndromic approach for determination of reproductive tract infections among adolescent girls.

The present study shows overall prevalence (64%) of reproductive tract infection among adolescent girls, based on self-perceived symptoms. Mean age of respondents were found to be 17.8 +/- 0.82 years and mean age at marriage and mean age at first pregnancy were 17.2 years and 17.5 years respectively; 35.35% of girls in the present study were married. In addition, no significant difference was observed between unmarried (60.10%) and married (71.17%) reproductive tract infection groups. Moreover, no significant association was present in prevalence of reproductive tract infection between the Muslim (67%) and the Hindu (60%). Highest prevalence (84.06%) of reproductive tract infection was observed among illiterate girls and with improvement of educational status there was decrease in the prevalence and the association was found highly significant. Significantly, higher prevalence (72%) was observed among members of family size 7 and above.

Adolescent↗
PubMed2003

Mitochondrial differentiation in a polymorphic land snail: evidence for Pleistocene survival within the boundaries of permafrost.

The genetic differentiation of populations having colonized formerly unsuitable habitats after the Pleistocene glaciations depends to a great extent on the speed of expansion. Slow dispersers maintain their refugial diversity whereas fast dispersal leads to a reduction of diversity in the newly colonized areas. During the Pleistocene, almost the entire current range of the land snail Arianta arbustorum has repeatedly been covered with ice or been subjected to permafrost. Owing to the low potential for dispersal of land snails, slow (re)colonization of the wide range from southern refugia can be excluded. Alternatively, fast, passive dispersal from southern refugia or survival in and expansion from multiple refugia within the area subjected to permafrost may account for the current distribution. To distinguish between these scenarios we reconstructed a phylogeography based on the sequences of a fragment of the cytochrome oxidase I from 133 individuals collected at 45 localities and analysed the molecular variance. Seventy-five haplotypes were found that diverged on average at 7.52% of positions. This high degree of diversity suggests that A. arbustorum is an old species in which the population structure, isolation and the hermaphroditic nature have reduced the probability of lineage extinction. The genetic structure was highly significant with the highest variance partition found among regions. Geographic distance and mitochondrial differentiation were not congruent. Lineages had overlapping ranges. The clear genetic differentiation and the patchy pattern of haplotype distribution suggest that colonization of formerly unsuitable habitats was mainly achieved from multiple populations from within the permafrost area.

Animals↗
PubMed2003

Neurological and neuropsychological examination and outcome after use of an intra-aortic filter device during cardiac surgery.

Cerebral embolization of particles after cardiac surgery is frequently associated with neurological deficits. Aortic crossclamp manipulation seems to be the most significant cause of emboli release during cardiac surgery. The goal of this study was to demonstrate whether the use of an intra-aortic filter device has an effect on the magnet resonance imaging (MRI) and functional neurological outcome. Twenty-four patients undergoing cardiosurgical procedures using cardiopulmonary bypass (CPB) were selected: coronary artery bypass graft (CABG) surgery (n = 17), aortic valve replacement (AVR) surgery (n = 4) or combined procedures (n = 3). Patients were evaluated by diffusion weighted MRI of the brain, neurological examination and neuropsychological assessment regarding alertness as well as divided and selective attention before and five to seven days after surgery. The patients were divided into two groups. In group I, 12 patients received a filter through a modified 24 F arterial cannula immediately before the aortic crossclamp was released. Filters remained in the aorta until CPB was discontinued. Intraoperatively, bilateral middle cerebral artery transcranial Doppler (TCD) was monitored at baseline, at the beginning of CPB, at a timepoint when the aorta was crossclamped, when the filter was inserted and while the crossclamp was switched to partial clamping until the CPB was discontinued. TCD was used for detection of microembolic signals (MES). The captured material in the filter was examined histologically. Twelve patients served as controls without aortic filtration (group II). The MRI of the brain did not show any diffusion alterations in either group before or after surgery. No patient developed a focal neurological deficit or stroke. Intraoperative quantitative MES detection revealed a four to tenfold increase in patients of group I compared with group II (5-6 versus 0.5-1 MES/min) during the filter dwell time. There was no consistent pattern regarding the neurobehavioural sequelae. Filters showed arteriosclerotic debris in 75% of the patients. The use of the intra-aortic filter device did not show a positive effect on neurological, neuroradiographical and neuropsychological outcomes. The increase of the MES rate in group I patients may be due to microbubbles generated as microcavitations by the filter or the aortic filter cannula. The intra-aortic filter was able to capture atheromatous material in 75% of the patients.

Aorta, Thoracic↗
PubMed2000

A novel type of mutation in the cysteine rich domain of the RET receptor causes ligand independent activation.

Multiple endocrine neoplasia type 2A (MEN 2A) is a dominantly inherited cancer syndrome, which involves the triad of MTC, pheochromocytoma, and hyperparathyroidism. Missense mutations in one of six cysteine codons in the extracellular cysteine-rich domain of the RET proto-oncogene predispose to this disease. These mutations cause ligand-independent constitutive activation of the tyrosine kinase receptor by the formation of disulfide-bonded homodimers. We examined a different type of mutation, which results in an additional cysteine in the cysteine rich domain. A duplication of 9 bp in the first case resulted in an insertion of three amino acids between codon 633 and 634. In the second case a 12 bp duplication in exon 11 results in four additional amino acids between codon 634 and 635. Here we demonstrate that an additional cysteine causes a ligand independent dimerization of the RET receptor in transfected NIH3T3 cells, which results in an activation of the intracellular tyrosine kinase.

3T3 Cells↗
PubMed2000

Biotin and biocytin uptake into cultured primary calf brain microvessel endothelial cells of the blood-brain barrier.

The uptake of biotin and the closely related biocytin was characterized in primary cultures of calf brain microvessel endothelial (CBME) cells. Biotin uptake was found to be Na(+)-gradient dependent and independent of changes in the membrane potential. Concentration dependence revealed a single saturation mechanism with a K(m) of 47 microM and a V(max) of 101 pmol/min/mg. Inhibition studies demonstrated dependence on metabolic energy and the necessity for a free carboxyl group for transport activity. The anticonvulsants primidone and carbamazepine had no inhibitory effect. Biotin uptake into CBME cells is a secondary active, electroneutral, saturable and specific process. Biocytin which accumulates in biotinidase deficiency, a human congenital disorder, did not inhibit biotin uptake and was not transported into these cells. The presence of human serum with normal biotinidase activity significantly reduced biotin uptake by about 50%. Further, added biocytin was hydrolyzed to biotin, which accumulated intracellularly but to a lesser extent than added free biotin. Biotin uptake after addition of plasma of biotinidase-deficient patients was not different from that in the presence of normal serum. These results indicate that the absence of biotinidase activity in serum does not reduce blood-brain barrier transport of biotin.

Amidohydrolases↗
PubMed2000

Plastidic metabolite transporters and their physiological functions in the inducible crassulacean acid metabolism plant Mesembryanthemum crystallinum.

The inducible crassulacean acid metabolism (CAM) plant Mesembryanthemum crystallinum accumulates malic acid during the night and converts it to starch during the day via a pathway that, because it is located in different subcellular compartments, depends on specific metabolite transport across membranes. The chloroplast glucose transporter (pGlcT) and three members of the phosphate translocator (PT) family were isolated. After induction of CAM, transcript amounts of the phosphoenolpyruvate (PEP) phosphate translocator (PPT) and the glucose-6-phosphate (Glc6P) phosphate translocator (GPT) genes were increased drastically, while triose phosphate (TP) phosphate translocator (TPT) and the pGlcT transcripts remained unchanged. PPT- and GPT-specific transcripts and transporter activities exhibited a pronounced diurnal variation, displaying the highest amplitude in the light. pGlcT transcripts were elevated towards the end of the light period and at the beginning of the dark period. These findings, combined with diurnal variations of enzyme activities and metabolite contents, helped to elucidate the roles of the PPT, GPT, TPT and pGlcT in CAM. The main function of the PPT is the daytime export from the stroma of PEP generated by pyruvate orthophosphate:dikinase (PPDK). The increased transport activity of GPT in the light suggests a higher requirement for Glc6P import for starch synthesis rather than starch mobilization. Most likely, Glc6P rather than 3-phosphoglycerate or triose phosphates is the main substrate for daytime starch biosynthesis in M. crystallinum plants in which CAM has been induced (CAM-induced), similar to non-green plastids. In the dark, starch is mobilized both phosphorylytically and amylolytically and the products are exported by the GPT, TPT and pGlcT. The transport activities of all three phosphate translocators and the transcript amounts of the pGlcT adapt to changing transport requirements in order to maintain high metabolic fluxes during the diurnal CAM cycle.

Biological Transport, Active↗
PubMed1998

Sperm allocation in the simultaneously hermaphroditic land snail Arianta arbustorum.

To test the idea that individuals of the simultaneously hermaphroditic land snail Arianta arbustorum can control the number of spermatozoa in their spermatophores, we investigated whether they differentially release sperm to virgin or nonvirgin partners with respect to the potential risk of sperm competition in a given mating. The number of sperm transferred ranged from 802 620 to 3 968 800 (X= 2 185 100; N=91), but was related neither to the mating history of the partner nor to copulation duration. This indicates that individuals of A. arbustorum are not able to adjust sperm expenditure to the mating history of the partner. Furthermore, the number of sperm transferred was correlated neither with the size of the donor nor with the size of the recipient. It has been proposed that the sexual conflict between the two genders in simultaneous hermaphrodites could be resolved by gamete trading. Theory predicts that sperm trading should occur in hermaphrodites in which the female role controls fertilization, for example in gastropods with a gametolytic gland and/or sperm storage such as A. arbustorum. To see whether sperm trading occurs, we also examined whether individuals of A. arbustorum adjust the number of sperm they release to the number they receive from their mating partner. There was a high degree of reciprocity in spermatophore transfer: in 45 of the 46 mating pairs investigated both partners delivered a spermatophore that contained spermatozoa. The numbers of sperm transferred by the two mating partners were not correlated, however. This indicates that sperm trading does not occur in this simultaneously hermaphroditic land snail. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Biotin determination by three different methods: specificity and application to urine and plasma ultrafiltrates of patients with and without disorders in biotin metabolism.

A microbiological, an avidin-binding and a streptavidin-binding method for biotin determination were compared. All three methods detected biotin equally well but they exhibit different specificities for derivatives of biotin. The microbiological assay has the highest specificity and is the method of choice for biotin determination in biotinidase-deficient patients. The specificity of streptavidin-binding has not been investigated so far. Application of the three methods to urine samples of patients with and without biotin therapy indicated that only 50% of biotin equivalents measured with the avidin method correspond to authentic biotin as previously shown. The other 50% comprise mainly bisnorbiotin and biotin-d-sulfoxide. HPLC-separation of urine samples prior to assay confirmed this finding and revealed a bisnorbiotin oxidation product and an unknown compound as further biotin metabolites. The latter was measurable by all three methods and not detectable in plasma ultrafiltrate. This was the only metabolite which was able to restore deficient 3-methylcrotonyl-CoA carboxylase activity in biotin-deficient fibroblasts. The combination of the three methods together with HPLC-separation proved to be a valuable analytical tool for the identification of the main biotin metabolites in biological fluids.

Administration, Oral↗
PubMed1997

Five patients with a biotin-responsive defect in holocarboxylase formation: evaluation of responsiveness to biotin therapy in vivo and comparative biochemical studies in vitro.

Biochemical studies in five patients with a defect in biotin-responsive holocarboxylase synthesis are reported. The age of onset (2 d to 6 y) as well as the severity of illness varied considerably. In all patients diagnosis was established by the finding of organic aciduria typical for multiple carboxylase deficiency in a catabolic state. In four patients the response to biotin therapy was evaluated by measurement of mitochondrial carboxylase activities in lymphocytes and by monitoring urinary organic acid excretion. In three patients clinical symptoms disappeared with 10-20 mg biotin/d, whereas normalization of the biochemical parameters required higher doses (20-40 mg/d). The fourth patient required a dose of 100 mg biotin/d before her skin rash disappeared. She remains mentally retarded and shows slightly elevated urinary organic acid excretion. Carboxylase activities were clearly deficient in fibroblasts grown in the commonly used medium which contains 10 nmol/L biotin (contributed by FCS in medium) in two patients. Fibroblasts of the other three patients became deficient only in a low biotin medium (0.1 nmol/L). Reactivation of deficient carboxylase activities in relation to time and biotin concentration correlated well with the severity and age of onset of illness in four patients. In one patient, however, carboxylase reactivation followed a more complex pattern requiring the longest incubation time but only a moderately increased biotin concentration of 19 nmol/L compared with 3-5 nmol/L in normal cells and 34-4000 nmol/L in the other four patients. The results in the five patients are in accordance with a primary defect of holocarboxylase synthetase due to a decreased affinity for biotin, in one patient combined with a decreased Vmax.

Acetyl-CoA Carboxylase↗
PubMed1996

Genetic transformation in freshwater: Escherichia coli is able to develop natural competence.

Until now, Escherichia coli was thought to be unable to develop natural competence, i.e., genetic transformation could be achieved only artificially with the aid of nonphysiological concentrations of calcium ions or by other treatments. We have tested the competence development of E. coli through transformation under natural conditions in river water, springwater, and mineral water which contained between 0 and 11 mM Ca2+, using pUC18 DNA. The presence of calcium ions at concentrations as low as 1 to 2 mM was sufficient to obtain transformants. Variations in the temperature of incubation were not required for competence development but had an influence on the transformation frequency. Using water from mineral springs originating from calcareous regions, we have obtained transformation frequencies with laboratory strains of E. coli similar to those reported for other gram-negative bacteria known to develop natural competence. The competence development of E. coli is most probably internally regulated (as for the other gram-negative bacteria), and inadequate conditions chosen for the transformation tests in the laboratory might impair the detection of higher natural transformation frequencies. The results will enhance our knowledge about the fate of laboratory or production strains of E. coli cells reaching natural aquatic ecosystems.

Calcium↗
PubMed1995

An agarose slide method to follow the fate of bacteria within digestive vacuoles of protozoa.

A method to follow the fate of ingested bacteria within digestive vacuoles of protozoa is presented. Tetrahymena pyriformis, previously fed with bacteria, is deposited onto glass microscope slides covered with a film of nutritive agarose. The protozoa lyse and the digestive vacuoles containing the bacteria stay undamaged and can be observed microscopically. After incubation, microcolonies reveal those vacuoles which contained living bacteria. The method can be used to study the survival ability of the ingested bacteria. It is a potentially valuable technique for studies on digestion efficacy, virulence ability, or escape mechanisms of bacteria from digestion.

Animals↗
PubMed1993

Na(+)-dependent biotin transport into brush-border membrane vesicles from human kidney cortex.

Renal reabsorption of biotin was investigated in human kidney by means of the isolated brush-border membrane vesicle technique. Biotin uptake into the vesicles was sodium-dependent producing a typical overshoot when incubated under sodium-gradient conditions (external concentration greater than internal). This effect was not observed in the presence of gradients of KCl, LiCl or choline-chloride, nor in the absence of any salt. Using the K+/valinomycin voltage-clamp method biotin uptake remained uninfluenced, i.e. was electroneutral, whereas glucose uptake (which is known to be electrogenic in kidney of other species) was greatly increased. When biotin transport was investigated as a function of external sodium concentration a stoichiometic coupling factor of 1 for the Na(+)-biotin- cotransport was determined. Increasing the biotin concentration in the incubation medium up to 200 mumol/l led to saturation with the kinetic parameters of 31 mumol/l for the apparent Michaelis constant and 82 nmol g protein-1 30 s-1 for the maximal transport rate. Uptake was not saturable in the concentration range of 0.001-1 mumol/l. Inhibition of the biotin uptake (25 mumol/l) was observed in the presence of 250 mumol/l dethiobiotin, bisnorbiotin, thioctic acid, and probenecid, whereas biocytin, propionic acid, lactic acid, succinic acid, citric acid, ascorbic acid, primidone and carbamazepine had no effect. We conclude that renal biotin reabsorption in human kidney is specifically sodium-dependent, saturable and electroneutral. It therefore fulfills the requirements for a secondary active carrier-mediated transport system. The results suggest that biocytin is not an inhibitor of renal biotin reabsorption.

Biomarkers↗
PubMed1992

Regulatory protein phosphorylation of phosphoenolpyruvate carboxylase in the facultative crassulacean-acid-metabolism plant Mesembryanthemum crystallinum L.

Phosphoenolpyruvate PyrP carboxylase (PyrPC) and PyrPC kinase were copurified from dark-adapted leaves of the common ice plant Mesembryanthemum crystallinum L. with crassulacean-acid metabolism (CAM). Purification by (NH4)2SO4 fractionation, chromatography on Fractogel-DEAE and hydroxylapatite resulted in a PyrPC preparation with a specific activity of 23-25 U/mg protein and a protein kinase activity of 255 mumol Pi.mol-1 PyrPC.s-1. After in vitro phosphorylation, the most prominently phosphorylated polypeptide was identified as PyrPC by immunoblotting and sequencing. Phosphorylation of PyrPC in vitro by incubation with 400 microM MgATP decreased its sensitivity towards malate. When purified in the absence of the protease inhibitor chymostatin, PyrPC lost an N-terminal sequence of 128 amino acids. Although the carboxylation reaction was unaffected, the truncated PyrPC could neither be phosphorylated in vitro nor inhibited by malate. This result and data obtained by limited proteolysis concur with the hypothesis [Jiao, J.A. & Chollet, R. (1989) Arch. Biochem. Biophys. 283, 300-305] that Ser11 is the phosphorylation site of the CAM PyrPC of M. crystallinum. At pH 7.0, the Km for ATP of the protein kinase was 25 microM; phosphorylation of PyrPC was maximal after 30 min at pH 7.0. The kinase showed also activity with histone III-S but not with dephosphorylated casein. It was inhibited by malate. The results show, that reversible protein phosphorylation is an important factor in the regulation of PyrPC in the facultative CAM plant M. crystallinum, similar to C4 and constitutive CAM plants.

Adenosine Triphosphate↗
PubMed1990

Na(+)-dependent biotin transport into brush-border membrane vesicles from rat kidney.

The mechanisms of biotin reabsorption in rat kidney cortex were investigated using isolated brush-border membrane vesicles. An inwardly directed Na+ gradient specifically stimulated a transient biotin overshoot. Biotin transport was not affected by a valinomycin-induced K(+)-diffusion potential, and biotin(-)-Na+ stoichiometry was found to be 1:1. As a function of concentration, the uptake showed saturation in the presence of a Na+ gradient with an apparent Michaelis constant (Km) of 55 microM and Vmax of 217 pmol.mg protein-1.25 s-1. Desthiobiotin, 250 microM, norbiotin, bisnorbiotin, thioctic acid, valeric acid, probenecid, and nonanoic acid inhibited the transport of 30 microM biotin, whereas other biotin derivatives, as well as biocytin and organic acids found in the urine of biotinidase-deficient patients, did not. Preloading of the vesicles with biotin, desthiobiotin, norbiotin, and thioctic acid in the presence of Na+ increased initial uptake of biotin from the incubation medium (trans-stimulation). Our results indicate that biotin absorption in rat kidney fulfills the criteria for a specific carrier-mediated and electroneutral Na(+)-biotin- cotransport in a 1:1 ratio. The results are discussed in context with congenital biotinidase deficiency in humans.

Animals↗
PubMed1989

[Visual EEG analysis in controlling intravenous anesthesia using propofol].

Since the discovery of brain waves by Berger, repeated efforts have been made to use the electroencephalogram EEG for monitoring and controlling anesthesia. Owing to its susceptibility to failure and the high expenditure regarding technology and personnel, the technique has not yet been adopted in routine anesthesia, however. In the study now reported an attempt was made to apply the positive experience with the recording and interpretation of EEG in the development of new anesthetic agents in the experimental laboratory, during routine clinical operations. The anesthetic used in the study was Propofol, an induction hypnotic that has only recently been introduced, together with nitrous oxide and repeated doses of fentanyl. Propofol is distinguished by its fast onset of action and short inactivation time; it is therefore suitable for induction and maintenance of anesthesia. The aim of the study was to maintain predetermined stages of sleep during anesthesia with the aid of visual on-line analysis of the EEG and to establish the dose of Propofol required for this purpose. The operations-general and orthopedic surgery-lasted 70-190 min (average duration: 120 min). In accordance with the randomization plan, the maintenance dose of Propofol was controlled in such a way that in ten patients light sleep levels (C0 to D1) and in the other ten deep sleep levels were maintained. The EEG was recorded via five active scalp electrodes (FP2, F4, C4, P4, O2) with reference to a joint electrode (A2). The stages of sleep were classified according to Kugler.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗