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C Baumann

Publications and source records attributed to C Baumann.

At least 55 records · Page 3Linked to original sources
PubMed1998

Peritoneal mononuclear cell differentiation and cytokine production in intermittent and continuous automated peritoneal dialysis.

The long period without dialysate exchanges in nightly intermittent peritoneal dialysis (NIPD; no peritoneal filling during the day) and continuous cyclic peritoneal dialysis (CCPD; peritoneal filling during the day) might lead to an improved repopulation and functional regeneration of peritoneal macrophages (PMOs). We investigated this issue in seven stable, noninfected CCPD patients and seven stable, noninfected NIPD patients. PMO differentiation and cytokine production were measured after automated peritoneal dialysis and after a 12- to 14-hour period without dialysate exchanges. PMO maturation was evaluated by antibody staining. The proportion of "young" monocytes (positive for 27E10 and RM3/1) was decreased, whereas the proportion of mature macrophages (positive for 25F9) was significantly increased after the exchange-free interval. No differences between NIPD and CCPD were observed. The cytokine response to lipopolysaccharide was significantly increased after the exchange-free interval in both NIPD and CCPD. The interleukin-1 receptor antagonist (IL-1Ra) content of PMO lysates significantly increased after the exchange-free interval in both groups, but no changes were found in dialysate and serum IL-1Ra. We conclude that the long daytime interval without dialysate exchanges allows for additional PMO differentiation. Furthermore, the potential for cytokine release, which is inhibited (possibly by dialysate effects) after automated peritoneal dialysis, is restored after a 12- to 14-hour interval without peritoneal dialysis exchanges. The "dry" day in NIPD seems to have no important additional positive effect compared with CCPD.

Adult↗
PubMed1998

Human neurons express the polyspecific cation transporter hOCT2, which translocates monoamine neurotransmitters, amantadine, and memantine.

Recently, we cloned the human cation transporter hOCT2, a member of a new family of polyspecific transporters from kidney, and demonstrated electrogenic uptake of tetraethylammonium, choline, N1-methylnicotinamide, and 1-methyl-4-phenylpyridinium. Using polymerase chain reaction amplification, cDNA sequencing, in situ hybridization, and immunohistochemistry, we now show that hOCT2 message and protein are expressed in neurons of the cerebral cortex and in various subcortical nuclei. In Xenopus laevis oocytes expressing hOCT2, electrogenic transport of norepinephrine, histamine, dopamine, serotonin, and the antiparkinsonian drugs memantine and amantadine was demonstrated by tracer influx, tracer efflux, electrical measurements, or a combination. Apparent Km values of 1.9 +/- 0.6 mM (norepinephrine), 1.3 +/- 0.3 mM (histamine), 0.39 +/- 0.16 mM (dopamine), 80 +/- 20 microM (serotonin), 34 +/- 5 microM (memantine), and 27 +/- 3 microM (amantadine) were estimated. Measurement of trans-effects in depolarized oocytes and human embryonic kidney cells expressing hOCT2 suggests that there were different rates and specificities for cation influx and efflux. The hypothesis is raised that hOCT2 plays a physiological role in the central nervous system by regulating interstitial concentrations of monoamine neurotransmitters that have evaded high affinity uptake mechanisms. We show that amantadine does not interact with the expressed human Na+/Cl- dopamine cotransporter. However, concentrations of amantadine that are effective for the treatment of Parkinson's disease may increase the interstitial concentrations of dopamine and other aminergic neurotransmitters by competitive inhibition of hOCT2.

Amantadine↗
PubMed1997

The trp RNA-binding attenuation protein (TRAP) from Bacillus subtilis binds to unstacked trp leader RNA.

TRAP (trp RNA-binding attenuation protein) is a tryptophan-activated RNA-binding protein that regulates expression of the trp biosynthetic genes by binding to a series of GAG and UAG trinucleotide repeats generally separated by two or three spacer nucleotides. Previously, we showed that TRAP contains 11 identical subunits arranged in a symmetrical ring. Based on this structure, we proposed a model for the TRAP.RNA interaction where the RNA wraps around the protein with each repeat of the RNA contacting one or a combination of two adjacent subunits of the TRAP oligomer. Here, we have shown that RNAs selected in vitro based on their ability to bind tryptophan-activated TRAP contain multiple G/UAG repeats and show a strong bias for pyrimidines as the spacer nucleotides between these repeats. The affinity of the TRAP.RNA interaction displays a nonlinear temperature dependence, increasing between 5 degrees C and 47 degrees C and then decreasing from 47 degrees C to 67 degrees C. Differential scanning calorimetry and circular dichroism spectroscopy demonstrate that TRAP is highly thermostable with few detectable changes in the structure between 25 degrees C and 70 degrees C, suggesting that the temperature dependence of this interaction reflects changes in the RNA. Results from circular dichroism and UV absorbance spectroscopy support this hypothesis, demonstrating that trp leader RNA becomes unstacked upon binding TRAP. We propose that the bias toward pyrimidines in the spacer nucleotides of the in vitro selected RNAs represents the inability of Us and Cs to form stable base stacking interactions, which allows the flexibility needed for the RNA to wrap around the TRAP oligomer.

Bacillus subtilis↗
PubMed1997

Alanine-scanning mutagenesis of Bacillus subtilis trp RNA-binding attenuation protein (TRAP) reveals residues involved in tryptophan binding and RNA binding.

In Bacillus subtilis, expression of the trp genes is negatively regulated by an RNA binding protein called TRAP (trp RNA-binding Attenuation Protein), which is activated to bind RNA by binding l-tryptophan. TRAP contains 11 identical subunits assembled in a symmetric ring. We have used alanine-scanning mutagenesis to analyze the functions of surface amino acid residues of TRAP. The in vivo regulatory activity of each mutant TRAP was analyzed in a B. subtilis reporter strain containing a trpE'-'lacZ fusion. Mutant TRAP proteins with defective in vivo regulatory activities were characterized in vitro by measuring their tryptophan binding and RNA binding activities. Most of the mutant proteins with altered tryptophan binding, either affinity or cooperativity, contained substituted residues located on two loops formed by residues 25 to 33 and residues 49 to 52, as well as on the beta-strand and beta-turn contiguous with these loops. Substitution of three residues (Lys37, Lys56 and Arg58) with alanine resulted in significant decreases in the RNA binding activity of TRAP without altering tryptophan binding. Structural analysis shows that these three residues are directly aligned on the outer edge of TRAP. Further mutagenic analysis of these three residues revealed that only lysine or arginine residues at positions 37 or 58 allow proper TRAP function, whereas at position 56, only lysine is functional. Residue Asn20 is the only other residue in TRAP that is located on the line formed by residues 37, 56 and 58, and virtually any amino acid residue is functional at position 20. We propose that RNA wraps around TRAP by interacting with residues Lys37, Lys56 and Arg58.

Alanine↗
PubMed1997

Cloning and characterization of two human polyspecific organic cation transporters.

Previously we cloned a polyspecific transporter from rat (rOCT1) that is expressed in renal proximal tubules and hepatocytes and mediates electrogenic uptake of organic cations with different molecular structures. Recently a homologous transporter from rat kidney (rOCT2) was cloned but not characterized in detail. We report cloning and characterization of two homologous transporters from man (hOCT1 and hOCT2) displaying approximately 80% amino acid identity to rOCT1 and rOCT2, respectively. Northern blots showed that hOCT1 is mainly transcribed in liver, while hOCT2 is found in kidney. Using in situ hybridization and immunohistochemistry, expression of hOCT2 was mainly detected in the distal tubule where the transporter is localized at the luminal membrane. After expression in Xenopus laevis oocytes, hOCT1 and hOCT2 mediate tracer influx of N-1-methylnicotinamide (NMN), tetraethylammonium (TEA), and 1-methyl-4-phenylpyridinium (MPP). For cation transport by hOCT2 apparent K(m) and K(i) values were determined in tracer flux measurements. In addition, electrical measurements were performed with voltage-clamped oocytes. Similar to rOCT1, cation transport by hOCT2 was pH independent, electrogenic, and polyspecific; however, the cation specificity was different. In voltage-clamped hOCT2-expressing oocytes, inward currents were induced by superfusion with MPP, TEA, choline, quinine, d-tubocurarine, pancuronium, and cyanine863. Cation transport in distal tubules is indicated for the first time. Here hOCT2 mediates the first step in cation reabsorption. hOCT1 may participate in hepatic excretion of organic cations.

Amino Acid Sequence↗
PubMed1997

Sendai virus efficiently infects cells via the asialoglycoprotein receptor and requires the presence of cleaved F0 precursor proteins for this alternative route of cell entry.

Biochemical evidence suggests that the asialoglycoprotein receptor (ASGP-R) can be used as an alternative receptor for a temperature-sensitive Sendai virus (SV) mutant. We now have investigated this possible alternative route of infection for SV wild-type (SV-wt) strain Fushimi by using a pair of cell lines which differ only with regard to ASGP-R expression. Infection studies after enzymatic destruction of conventional sialic acid-containing SV receptors (SA-R) revealed that only ASGP-R-expressing cells could be infected by SV-wt. This alternative route of cell entry could be completely blocked by incubation of cells with ASGP-R-specific antibodies prior to infection. Furthermore, cleavage of SV-F0 precursor protein into the subunits F1 and F2 was necessary to establish infection via ASGP-R, suggesting a fusion-mediated cell entry after binding of SV-wt to the ASGP-R on host cells. Interestingly, infection via ASGP-R was found to be nearly as efficient as infection via conventional sialic acid-containing SV receptors. A possible physiological role of the ASGP-R-mediated route of SV infection is discussed.

3T3 Cells↗
PubMed1996

Kinetic and thermodynamic analysis of the interaction between TRAP (trp RNA-binding attenuation protein) of Bacillus subtilis and trp leader RNA.

In Bacillus subtilis, expression of the tryptophan biosynthetic genes is regulated in response to tryptophan by an RNA-binding protein called TRAP (trp RNA-binding attenuation protein). TRAP has been shown to contain 11 identical subunits arranged in a symmetrical ring. Kinetic and thermodynamic parameters of the interaction between tryptophan-activated TRAP and trp leader RNA were studied. Results from glycerol gradients and mobility shift gels indicate that two TRAP 11-mers bind to each trp leader RNA. A filter binding assay was used to determine an apparent binding constant of 8.0 +/- 1.3 x 10(9) m-1 (Kd = 0.12 +/- 0.02 nM) for TRAP and an RNA containing residues +36 to +92 of the trp leader RNA in 1 mM L-tryptophan at 37 degrees C. The temperature dependence of Kapp was somewhat unexpected demonstrating that the delta H of the interaction is highly unfavorable at + 15.9 kcal mol-1. Therefore, the interaction is completely driven by a delta S of +97 cal mol-1 K-1. The interaction between tryptophan-activated TRAP and trp leader RNA displayed broad salt and pH activity profiles. Finally, the rate of RNA dissociation from the RNA-TRAP.tryptophan ternary complex was found to be very slow in high concentrations of tryptophan (> 40 microM) but increased in lower tryptophan concentrations. This suggests that dissociation of tryptophan from the ternary complex is the rate-limiting step in RNA dissociation.

Bacillus subtilis↗
PubMed1996

Increased paternal age in CHARGE association.

The acronym CHARGE refers to a non-random clustering of congenital malformations whose cause remains unknown. Here, we report on a series of 41 patients and find a significant increase in mean paternal age of birth of CHARGE patients (33.7 +/- 8 years) compared with the control population (30.8 +/- 5 years). In contrast, maternal age was not statistically different in patients and controls. These data suggest the possible role of a dominant mutation or, less likely, a subtle chromosomal abnormality in CHARGE association.

Abnormalities, Multiple↗
PubMed1995

Interaction of the 11-subunit trp RNA-binding attenuation protein (TRAP) with its RNA target.

The trp RNA-binding attenuation protein (TRAP) regulates expression of the B. subtilis trp operon by binding to an RNA target composed of 11 G/UAG repeats in the trp leader transcript. TRAP contains 11 identical subunits arranged in a ring. The binding of 11 molecules of L-tryptophan to sites formed between adjacent subunits activates TRAP to bind trp leader RNA. We propose that the trp leader RNA forms a matching circle on the surface of TRAP when it binds. RNA binding is relatively insensitive to changes in ionic strength and pH, and is apparently driven by changes in entropy. Two lysine residues on the surface of TRAP have been shown to be important for RNA binding.

Bacillus subtilis↗
PubMed1994

[Treatment of bacterial meningitis in newborn infants and children].

Third generation cephalosporin as cefotaxime or ceftriaxone is the best first line treatment. Duration of treatment is 7 to 10 days in uncomplicated disease. Dexamethasone used very early--before or at the same time of the antibiotic injection--seems to decrease sensorial sequelae. Amikacin by IV route, decreases short term complications. For bacterial meningitis due to intermediate penicillin pneumococci, an increase in daily dose of beta-lactamin is recommended; for resistant pneumococci, vancomycin by continuous infusion and with large doses is used. Chemoprophylaxis by rifampicine is effective for both Meningococcus and Haemophilus. Haemophilus influenzae b vaccination will decrease systemic infection due to this pathogen. In newborns, morbidity is higher, due in part to brain abscesses. Therapeutic choice is not the same for materno-foetal and postnatal infection. Antibiotherapy duration is, at least, 15 days and 21 days for gram-negative bacteria.

Age Factors↗
PubMed1994

Configuration of light responses in isolated retinal rods. A patch-clamp study.

The whole-cell patch-clamp technique was employed to investigate the light responses of single retinal rods of the frog (Rana esculenta and R. temporaria). In the majority of experiments, completely isolated cells were studied. Coupling with neighboring cells gave rise to a more complex response configuration. Responses were recorded under voltage-clamp and under current-clamp conditions. Stimulus response curves were measured in experiments with local stimuli illuminating only parts of the outer segment. Metabolic factors such as cGMP, GTP and ATP were also tested and were found to have specific and different influences on the response configurations. When the recording pipette was filled with an intracellular medium devoid of nucleotides, a retardation in the recovery of the light responses was observed during the course of an experiment. Addition of 1 mM ATP to the pipette medium prevented the larger part of the retardation, while 1 mM GTP accelerated the response recovery at the beginning of an experiment but did not prevent a subsequent retardation. Micromolar concentrations of cGMP were sufficient to elicit both a depolarization of the photoreceptor membrane and an increase in the response duration. These results show that, in single photoreceptors, the configuration of light responses not only depends on the stimulus parameters but also on those properties of the cells that are directly controlled by their nucleotide metabolism.

Adenosine Triphosphate↗
PubMed1994

Pre- and postnatal diagnosis of succinic semialdehyde dehydrogenase deficiency using enzyme and metabolite assays.

We report our cumulative experience for the prenatal diagnosis of succinic semialdehyde dehydrogenase (SSADH) deficiency in seven 'at-risk' pregnancies from four unrelated families. Prenatal diagnosis was performed by determination of 4-hydroxybutyric acid (4-HBA) concentration in amniotic fluid using isotope-dilution gas chromatography-mass spectrometry in conjunction with assay of SSADH activity in biopsied chorionic villus and/or cultured amniocytes. In three of four pregnancies predicted as affected, confirmation was obtained by demonstration of deficient SSADH activity in fetal tissues. Our results suggest that determination of 4-HBA concentration in amniotic fluid combined with enzyme determination in cultured or biopsied tissue represents a reliable method for the prenatal diagnosis of SSADH deficiency.,

Aldehyde Oxidoreductases↗
PubMed1993

Myasthenia gravis with polyhydramnios in the fetus of an asymptomatic mother.

Transient myasthenia gravis was observed in an infant whose mother had no signs of neuro-muscular disease. The case presented with severe polyhdramnios at 31 weeks. Sonographic and invasive work-up showed only an absence of fetal swallowing. At birth, the infant had severe muscle weakness and respiratory distress. He had high titres of anti-acetylcholine receptor (anti-AChR) antibodies of maternal origin. Anti-AChR antibodies were also found in stored samples of fetal serum and amniotic fluid. To our knowledge, this is the first case of neonatal myasthenia gravis for which neither past nor present evidence of disease could be obtained in the mother. Anti-AChR antibody testing should be considered in cases of unexplained polyhydramnios.

Abnormalities, Multiple↗
PubMed1993

[Atrioventricular block complicating the use of diphemanil (Prantal) in 2 premature newborn infants].

BACKGROUND: Diphemanil can be useful in some neonates presenting with bradycardia due to vagal hyperreflectivity. Paradoxically, this drug may induce atrio-ventricular (AV) block in premature babies. CASE REPORTS: Case no 1. A premature neonate suffering from acute respiratory distress from birth required respiratory support, antibiotics and caffeine. Despite this treatment, he underwent many episodes of apnea, and bradycardia that appeared on day 4 and did not respond to IV doxapram (1 mg/kg/h). He was given diphemanil on day 9 (10 mg/kg/d) and permanent bradycardia with complete AV block and a normal QT interval appeared 2 days later. Cessation of diphemanil and administration of IV isoprenaline led to a normal sinusal rhythm, but there were bladder, intestinal and ocular signs of atropinic intoxication. A complete definitive recovery occurred 5 days after cessation of diphemanil. Case no 2. A premature neonate developed episodes of apnea 2 days after birth. These episodes persisted and were complicated by bradycardia on day 4 despite administration of caffeine. Vagal stimulation on day 7 was positive and the infant was then given diphemanil (10 mg/kg/d). Permanent bradycardia occurred 2 days later, with partial AV block and a normal QT interval. The child recovered a normal sinusal rhythm 2 days after cessation of diphemanil. CONCLUSIONS: Anticholinergic therapy may cause permanent bradycardia due to AV block in premature infants. This therapy should not be given to premature infants without a prior ECG. Doses lower than those used in infants are recommended.

Bradycardia↗
PubMed1992

Size and chirality of intracellularly applied anions affect the function of isolated photoreceptors.

The effect of intracellularly applied anions on the function of retinal rods of the frog Rana esculenta was investigated by means of the whole-cell patch-clamp technique. When the recording pipette contained a medium based on potassium chloride, a slow spontaneous hyperpolarization was observed presumably due to a diffusional loss of the photoreceptor's internal transmitter cyclic guanosine monophosphate (cGMP) and its precursor guanosine triphosphate (GTP). When chloride was replaced by organic anions such as acetate, aspartate, or gluconate the speed of hyperpolarization diminished and the dark voltage of the rods was stabilized. The extent of stabilization correlates with the molecular weight of the anions. A significant difference in the stabilizing effect was found for L-aspartate and D-aspartate, suggesting an additional influence of the chirality. Effects of some of the anions on the configuration of the light responses were also observed.

Animals↗