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Biomedical subjects

B Bader

Publications and source records attributed to B Bader.

At least 19 recordsLinked to original sources
PubMed2000

KT5823 inhibits cGMP-dependent protein kinase activity in vitro but not in intact human platelets and rat mesangial cells.

Many signal transduction pathways are mediated by the second messengers cGMP and cAMP, cGMP- and cAMP-dependent protein kinases (cGK and PKA), phosphodiesterases, and ion channels. To distinguish among the different cGMP effectors, inhibitors of cGK and PKA have been developed including the K-252 compound KT5823 and the isoquinolinesulfonamide H89. KT5823, an in vitro inhibitor of cGK, has also been used in numerous studies with intact cells to implicate or rule out the involvement of this protein kinase in a given cellular response. However, the efficacy and specificity of KT5823 as cGK inhibitor in intact cells or tissues have never been demonstrated. Here, we analyzed the effects of both KT5823 and H89 on cyclic-nucleotide-mediated phosphorylation of vasodilator-stimulated phosphoprotein (VASP) in intact human platelets and rat mesangial cells. These two cell types both express high levels of cGK. KT5823 inhibited purified cGK. However, with both intact human platelets and rat mesangial cells, KT5823 failed to inhibit cGK-mediated serine 157 and serine 239 phosphorylation of VASP induced by nitric oxide, atrial natriuretic peptide, or the membrane-permeant cGMP analog, 8-pCPT-cGMP. KT5823 enhanced 8-pCPT-cGMP-stimulated VASP phosphorylation in platelets and did not inhibit forskolin-stimulated VASP phosphorylation in either platelets or mesangial cells. In contrast H89, an inhibitor of both PKA and cGK, clearly inhibited 8-pCPT-cGMP and forskolin-stimulated VASP phosphorylation in the two cell types. The data indicate that KT5823 inhibits purified cGK but does not affect a cGK-mediated response in the two different cell types expressing cGK I. These observations indicate that data that interpret the effects of KT5823 in intact cells as the major or only criteria supporting the involvement of cGK clearly need to be reconsidered.

Alkaloids↗
PubMed2000

Bioorganic synthesis of lipid-modified proteins for the study of signal transduction.

Biological membranes define the boundaries of the cellular compartments in higher eukaryotes and are active in many processes such as signal transduction and vesicular transport. Although post-translational lipid modification of numerous proteins in signal transduction is crucial for biological function, analysis of protein-protein interactions has mainly focused on recombinant proteins in solution under defined in vitro conditions. Here we present a new strategy for the synthesis of such lipid-modified proteins. It involves the bacterial expression of a carboxy-terminally truncated non-lipidated protein, the chemical synthesis of differently lipidated peptides representing the C terminus of the proteins, and their covalent coupling. Our technique is demonstrated using Ras constructs, which exhibit properties very similar to fully processed Ras, but can be produced in high yields and are open for selective modifications. These constructs are operative in biophysical and cellular assay systems, showing specific recognition of effectors by Ras lipoproteins inserted into the membrane surface of biosensors and transforming activity of oncogenic variants after microinjection into cultured cells.

Animals↗
PubMed2000

[Ulnar lengthening in osteochondroma (multiple cartilagenous exostoses) of the forearm].

The osteochondroma is the most frequent bone tumor to occur during the period of growth. The multiple hereditary form often involves the forearms. Depending on localisation and size of the tumor, shortening of the bones in the forearm, angular malalignments and functional impairment of the wrist and elbow joints may result. Early diagnosis and surgery in the growing child can prevent these complications. 13 children were operated on altogether 15 forearms. In nine cases lengthening of the ulna was necessary to correct ulnar instability of the wrist as well as improving the support of the carpus and preventing dislocation of the radial head.

Adolescent↗
PubMed1999

Biochemical analysis of SopE from Salmonella typhimurium, a highly efficient guanosine nucleotide exchange factor for RhoGTPases.

RhoGTPases are key regulators of eukaryotic cell physiology. The bacterial enteropathogen Salmonella typhimurium modulates host cell physiology by translocating specific toxins into the cytoplasm of host cells that induce responses such as apoptotic cell death in macrophages, the production of proinflammatory cytokines, the rearrangement of the host cell actin cytoskeleton (membrane ruffling), and bacterial entry into host cells. One of the translocated toxins is SopE, which has been shown to bind to RhoGTPases of the host cell and to activate RhoGTPase signaling. SopE is sufficient to induce profuse membrane ruffling in Cos cells and to facilitate efficient bacterial internalization. We show here that SopE belongs to a novel class of bacterial toxins that modulate RhoGTPase function by transient interaction. Surface plasmon resonance measurements revealed that the kinetics of formation and dissociation of the SopE.CDC42 complex are in the same order of magnitude as those described for complex formation of GTPases of the Ras superfamily with their cognate guanine nucleotide exchange factors (GEFs). In the presence of excess GDP, dissociation of the SopE.CDC42 complex was accelerated more than 1000-fold. SopE-mediated guanine nucleotide exchange was very efficient (e.g. exchange rates almost 10(5)-fold above the level of the uncatalyzed reaction; substrate affinity), and the kinetic constants were similar to those described for guanine nucleotide exchange mediated by CDC25 or RCC1. Far-UV CD spectroscopy revealed that SopE has a high content of alpha-helical structure, a feature also found in Dbl homology domains, Sec7-like domains, and the Ras-GEF domain of Sos. Despite the lack of any obvious sequence similarity, our data suggest that SopE may closely mimic eukaryotic GEFs.

Bacterial Proteins↗
PubMed1999

[Polydactyly of the foot].

Polydactyly may be preaxial or tibial (hallux-side), postaxial or ulnar (side of the little toe) and central (middle toes). The duplication may appear at the distal and medial phalanges or at the whole digit. The metatarsal bone may be part wise or completely duplicated, the accessory toes may share only one metatarsal. Surgical intervention may be indicated in shoe problems, for esthetic reasons or, especially in duplication of the metatarsales, because of secondary deviation of the toes and therefore shoe problems or plantar callosities. Preoperative analysis including x-ray is of great importance to achieve good functional and cosmetic results.

Adolescent↗
PubMed1998

Expression, purification, and characterization of histidine-tagged rat and human flavoenzyme dihydroorotate dehydrogenase.

Mitochondrially bound dihydroorotate-ubiquinone oxidoreductase (dihydroorotate dehydrogenase, EC 1.3.99.11) catalyzes the fourth sequential step in the de novo synthesis of uridine monophosphate. Based on the recent functional expression of the complete rat dihydroorotate dehydrogenase by means of the baculovirus expression vector system in Trichoplusia ni cells, a procedure is described that allows the purification of baculovirus expressed enzyme protein fused to a carboxy-terminal tag of eight histidines. Extracts from mitochondria of Spodoptera frugiperda cells infected with the recombinant virus using Triton X-100 were loaded onto Ni2+-nitrilotriacetic acid agarose and histidine-tagged rat protein was selectively eluted with imidazole-containing buffer. In view of our previously published work, the quality of the electrophoretic homogenous rat enzyme was markedly improved; specific activity was 130-150 micromol dihydroorotate/min per milligram; and the stoichiometry of flavin content was 0.8-1.1 mol/mol protein. Efforts to generate mammalian dihydroorotate dehydrogenases with low production costs from bacteria resulted in successful overexpression of the carboxy-terminal-modified rat and human dihydroorotate dehydrogenase in XL-1 Blue cells. By employing the metal chelate affinity chromatography under native conditions, the histidine-tagged human enzyme was purified with a specific activity of 150 micromol/min/mg and the rat enzyme with 83 micromol/min/mg, respectively, at pH 8.0-8.1 optimum. Kinetic constants of the recombinant histidine-tagged rat enzyme from bacteria (dihydroorotate, Km = 14.6 micromol electron acceptor decylubiquinone, Km = 9.5 micromol) were close to those reported for the enzyme from insect cells, with or without the affinity tag. HPLC analyses identified flavin mononucleotide as cofactor of the rat enzyme; UV-vis and fluorometric analyses verified a flavin/protein ratio of 0.8-1.1 mol/mol. By spectral analyses of the functional flavin with the native human enzyme, the interaction of the pharmacological inhibitors Leflunomide and Brequinar with their target could be clarified as interference with the transfer of electrons from the flavin to the quinone. The combination of the bacterial expression system and metal chelate affinity chomatography offers an improved means to purify large quantities of mammalian membrane-bound dihydroorotate dehydrogenases which, by several criteria, possesses the same functional activities as non-histidine-tagged recombinant enzymes.

Animals↗
PubMed1995

Restricted expression of the irreC-rst protein is required for normal axonal projections of columnar visual neurons.

The 104 kDa irreC-rst protein, a member of the immunoglobulin superfamily, mediates homophilic adhesion in cell cultures. In larval optic chiasms, the protein is found on recently formed axon bundles, not on older ones. In developing visual neuropils, it is present in all columnar domains of specific layers. The number of irreC-rst-positive neuropil stratifications increases until the midpupal stage. Immunoreactivity fades thereafter. The functional importance of the restricted expression pattern is demonstrated by the severe projection errors of axons in the first and second optic chiasms in loss of function mutants and in transformants that express the irreC-rst protein globally. Epigenesis of the phenotypes can be explained partially on the bases of homophilic irreC-rst interactions.

Animals↗
PubMed1995

Renal hemodynamics in essential hypertensives treated with losartan.

ACE-inhibitors are known to have special renal effects, i.e. they increase ERPF, decrease the filtration fraction and lower proteinuria. These effects can be due to a decrease in angiotensin II (AII) levels as well as an increase in bradykinin. New and more specific AII-receptor antagonists may help to distinguish between effects exerted by angiotensin II and those exerted by bradykinin. We investigated the effects of losartan in 9 patients with essential hypertension (sitting mean diastolic blood pressure 95-120 mmHg). Renal hemodynamics were measured by continuous inulin-and PAH-clearance (GFR and RPF) after stopping antihypertensive therapy for 1 week, followed by a 2-week placebo period and after a 4-week treatment phase with losartan (50 mg/die) followed by a therapy with an ACE-inhibitor (ramipril 5mg/die). Additionally, urine albumin excretion (UAE) was measured. Treatment of patients with essential hypertension with losartan resulted in a significant decrease of MAP after three weeks of treatment (121 +/- 8 mmHg under placebo and 114 +/- 10 mmHg under losartan; * = p < 0.05). MAP after four weeks of losartan treatment was 115 +/- 11 mmHg. Regarding changes in renal hemodynamics we could not demonstrate a significant change for neither losartan nor the ACE-inhibitor. Urine albumin excretion was reduced by both treatment regimens in correlation to the magnitude of blood pressure reduction. Our data indicate that losartan induced a significant reduction in MAP in patients with essential arterial hypertension with only moderate effects on renal hemodynamics.

Antihypertensive Agents↗
PubMed1991

Protein-metabolism kinetics and energy-substrate utilization in infants fed parenteral solutions with different glucose-fat ratios.

The relative effect of glucose and lipids on whole-body protein-metabolism kinetics was assessed in seven infants undergoing parenteral feeding. Protein intake was kept constant and nonprotein energy was either provided as glucose alone or as an isoenergetic glucose-lipid mixture according to a randomized crossover trial. Protein metabolism and energy-substrate utilization were assessed by a primed, constant L-[13C]leucine infusion, combined with indirect calorimetry. There was a significant difference in the pattern of energy-substrate utilization according to regime. Protein turnover (11.3 +/- 0.7 vs 9.8 +/- 0.4 g.kg-1.d-1; P less than 0.05), protein breakdown (8.4 +/- 0.6 vs 7.1 +/- 0.4 g.kg-1.d-1; P less than 0.05), and amino acid oxidation rates (2.7 +/- 0.4 vs 1.4 +/- 0.5 g.kg-1.d-1; P less than 0.05) were higher for the glucose than the glucose-lipid treatment, whereas protein-synthesis rates did not significantly differ. These results suggest that the nature of energy substrates delivered to parenterally fed infants may affect protein metabolism.

Calorimetry, Indirect↗
PubMed1987

Significance of ultrasound measurements of the head of the breech fetus.

Ultrasound measurements of head shape and size in 451 fetuses presenting as a breech were compared to those obtained in 1,880 fetuses presenting as a cephalic between 15 and 40 weeks' gestation. No statistically significant differences were found for the biparietal diameter (BPD), head circumference (HC), or cephalic index (CI) measurements between the two groups in uncomplicated pregnancies. The mean values for the CI were found to be lower for breech presenting fetuses in complicated pregnancies, indicating a trend for these fetuses to have a more dolichocephalic head shape.

Breech Presentation↗
PubMed1986

[Medical treatment of staphylococcal epiduritis].

The authors report a case of extensive spinal epidural staphylococcal abscess responsible for spinal compression. All symptoms regressed after conservative management consisting of parenteral antibiotic therapy with Gentamycin and Vancomycin.

Abscess↗
PubMed1986

[Acquired immunodeficiency syndrome in an adolescent hemophiliac].

In an adolescent with hemophilia B, the diagnosis of AIDS was established in face of cachexia, orodigestive candidiasis, associated with lymphopenia, major decrease in T4/T8 ratio with marked decrease in T helper cells and presence of LAV-antibodies. The patient died rapidly from a cerebral infection due to Toxoplasma gondii. Difficulties in diagnosis and treatment of cerebral toxoplasmosis are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1985

[Water intoxication in children. Apropos of 2 cases].

The authors report 2 cases of water intoxication. These clinical cases show the importance of neurological signs during the acute period. Hyponatremia is constant and responsible for the clinical signs. A rapid treatment is necessary.

Adolescent↗
PubMed1983

Advanced ultrasound evaluation of fetal hydrocephaly.

Advancing technology of ultrasound imaging has unraveled numerous problems in perinatology. The 1980's is the era of high-resolution real time ultrasonography, enabling the diagnosis of fetal hydrocephaly to be made in midtrimester pregnancy even prior to the age of fetal viability. The findings obtained by full evaluation of hydrocephalic fetuses with serial ultrasounds are helpful in appropriate counseling of parents by the birth defects team and in planning the best time and management of delivery in a perinatal center. Arrest of progression of severe hydrocephaly in the second half of pregnancy prior to fetal lung maturity has been accomplished by intrauterine implantation of ventriculoamniotic shunts. The potential risk of maternal soft tissue injury from delivery of an oversized head of a severely compromised fetus can be minimized by partial and slow decompression of fetal head under ultrasound guidance using a #20 spinal needle. The influence of the recent developments on better fetal diagnosis and survival of infants with neural tube defects in 1981 was compared to that obtained during the previous five years.

Female↗
PubMed1982

T-lymphocyte subpopulations in Crohn's disease: definition by monoclonal antibodies.

Thirty-two patients with Crohn's disease (CD) and 32 age- and sex-matched controls were studied for T lymphocytes and T-lymphocyte subpopulations in the peripheral blood, using monoclonal antibodies defining the helper/inducer and the suppressor/cytotoxic compartment. T cells were reduced in patients with CD (P less than 0.05), and this reduction was more pronounced in patients with active disease (P less than 0.01). This T-cell deficiency involves helper and suppressor cells proportionally. The proportion of helper and suppressor cells in CD was independent of disease activity and therapy. We conclude that the T-cell deficiency in CD is a secondary event, and that there is no derangement in the "immunoregulatory ratio" (helper to suppressor cells) in CD which might have served as an explanation for a possible autoimmune mechanism in the pathogenesis of this disease.

Adolescent↗
PubMed1982

[Pharmacokinetic studies on plasma elimination half-life of oxipurinol (author's transl)].

In a randomized cross-over study with 10 volunteers two different commercial preparations of allopurinol (Remid and standard) were tested by reversed-phase HPLC with respect to their pharmacokinetic behaviour. After a single p.o. dose of 300 mg allopurinol plasma elimination half-life of the major metabolite oxipurinol was found to be about 40 h with both preparations, calculated from the course of the plasma levels. This result confirms that a single daily dose of 300 mg allopurinol in non-retard formulation supports therapeutically sufficient circadian plasma levels.

Adult↗