Biomedical subjects

B Schmidt

Publications and source records attributed to B Schmidt.

At least 145 records · Page 8Linked to original sources

PubMed1998

Effect of subchronic treatment with metrifonate and tacrine on brain cholinergic function in aged F344 rats.

The effects of 21-day treatment with the acetylcholinesterase inhibitors metrifonate (80 mg kg(-1) per os (p.o.)) and tacrine (3 mg kg(-1) p.o.), twice daily, on cortical and hippocampal cholinergic systems were investigated in aged rats (24-26 months). Extracellular acetylcholine levels were measured by transversal microdialysis in vivo; choline acetyltransferase and acetylcholinesterase activities were measured ex vivo by means of radiometric methods. Basal cortical and hippocampal extracellular acetylcholine levels, measured 18 h after the last metrifonate treatment, were about 15 and two folds higher, respectively, than in control and tacrine-treated rats. A challenge with metrifonate further increased cortical and hippocampal acetylcholine levels by about three and four times, respectively. Basal extracellular acetylcholine levels, measured 18 h after the last treatment with tacrine were not statistically different from those of the control rats. A challenge with tacrine increased cortical and hippocampal extracellular acetylcholine levels by about four and two times. A 75% inhibition of cholinesterase activity was found 18 h after the last metrifonate administration, while only a 15% inhibition was detectable 18 h after the last tacrine administration. The challenge with metrifonate or tacrine resulted in 90 and 80% cholinesterase inhibition, respectively. These results demonstrate that in aging rats a subchronic treatment with metrifonate results in a long-lasting, cholinesterase inhibition, and a persistent increase in acetylcholine extracellular levels which compensate for the age-associated cholinergic hypofunction. Metrifonate is therefore a potentially useful agent for the cholinergic deficit accompanying Alzheimer's disease.

Acetylcholine↗

PubMed1998

Purification and biochemical analysis of WprA, a 52-kDa serine protease secreted by B. subtilis as an active complex with its 23-kDa propeptide.

The Gram-positive bacterium Bacillus subtilis produces numerous proteases that are secreted to the extracellular milieu, and as strains are generated which lack the more prominent proteases, minor ones become detectable. We have isolated a 52-kDa secreted protease from the protease-deficient strain WB600. It is encoded by the wprA gene which encompasses a signal sequence, a 46-kDa propeptide further processed to 23 kDa, and the 52-kDa mature protease. The 52-kDa and 23-kDa polypeptides were previously detected in cell-wall preparations of a wild-type strain. We have co-purified these proteins from culture supernatant, and confirmed the same N-termini and molecular weights as the membrane-bound species. The WprA protease domain has 28.5% identity to subtilisin A, and like other subtilisins, it displays a broad substrate specificity. WprA and subtilisin A have similar pH profiles, showing optimal activity near pH 7.5 for substrates with Met, Gln, or Lys residues at P1. Using a substrate with Asp at P1, another peak of activity was observed for WprA at pH 5 and at pH 6 for subtilisin A. The pH dependence of some bacterial proteases in their interaction with substrates and inhibitors may be biologically relevant.

Amino Acid Sequence↗

PubMed1998

Centronuclear myopathy: clinical aspects of ten Brazilian patients with childhood onset.

We herein present 10 patients with the childhood onset form of centronuclear myopathy. All patients underwent a clinical and neurologic examination, and EMG/NVC. A series of ancillary examinations, consisting of muscle enzymes, EEG, EKG, echocardiogram, pulmonary function tests and head CT scan was done in most. The mean age was 16.3 years (3-25). Seven were female. There was no family history in seven and in two it was suggestive of an autosomal recessive inheritance. One patient was adopted and no history was available. Frequent gestational and neonatal abnormalities were present, namely poor fetal movements, maternal polyhydramnios, perinatal hypoxia, hypotonia at birth, and weak crying and feeding. In seven patients there was delayed motor milestones. In most patients the motor involvement was stable or slowly progressive. Upon examination the facies were myopathic and there was a global skeletal muscle involvement in all patients, with muscular hypotonia, atrophy, and areflexia. Characteristically, patients presented with ophthalmoparesis, and weakness of masticatory and facial muscles. We frequently found osteoskeletal abnormalities, namely kyphoscoliosis, tendon retractions and high-arched palate. A restrictive pulmonary function pattern was found in five patients, but only one had a cor pulmonale. CK was abnormally high in one patient, and normal in all others. EMG/NVC disclosed a myopathic pattern in nine; in three there was a mixed neurogenic picture; and in one we found myotonic discharges. A long follow-up (median 8.1 years) showed that only the patient with cor pulmonale had an unfavorable prognosis.

Adolescent↗

PubMed1998

Pressure-induced dissociation of carbamoyl-phosphate synthetase domains. The catalytically active form is dimeric.

Carbamoyl-phosphate synthetase consists of an amidotransferase domain or subunit (GLN) that hydrolyzes glutamine and transfers the ammonia to the synthetase component (CPS) where the biosynthetic reaction occurs. The CPS domain is composed of two homologous subdomains, CPS.A and CPS.B, that catalyze different ATP-dependent reactions involved in carbamoyl phosphate synthesis. When the individual CPS.A and CPS.B subdomains were individually cloned and expressed in Escherichia coli (Guy, H. I., and Evans, D. R. (1996) J. Biol. Chem. 271, 13762-13769), they were found to be functionally equivalent and could each independently catalyze carbamoyl phosphate synthesis. The proposal was advanced that, although the monomers could catalyze the individual partial reactions, overall synthesis of carbamoyl phosphate required a homodimer of CPS.A or CPS.B. To test this hypothesis, the GLN-CPS.B dimer was reversibly dissociated at 1500 bar in a high pressure cell. Dissociation was accompanied by a loss of both glutamine- and ammonia-dependent CPSase activity. Activity was recovered once the protein was returned to atmospheric pressure. If the sample was cross-linked before exposure to high pressure, there was no dissociation and no loss of biosynthetic activity. In contrast, the bicarbonate-dependent ATPase and the carbamoyl phosphate-dependent ATP synthetase activities were largely unaffected by pressure-induced dissociation. These experiments confirmed the hypothesis that the synthesis of carbamoyl phosphate requires the concerted action of the two active sites within the homodimer.

Adenosine Triphosphate↗

PubMed1998

Prion protein fragment interacts with PrP-deficient cells.

A fragment of the prion protein (PrP106-126) induces cell death in cultures of wild-type embryonic day (E)16 mouse cortical neurons but not cells derived from mice devoid of cellular PrP(PrPo/o). Two common binding partners for PrP106-126 expressed in both wild-type and PrPo/o mouse brain were isolated and their sequences determined. The two proteins were found to be alpha and beta tubulin. Further evidence that tubulin binds PrP106-126 within cells comes from cell culture experiments. Colchicine toxicity on PrPo/o mouse cortical cells is enhanced by PrP106-126 and taxol enhances toxicity of PrP106-126 on wild-type mouse cortical cells. Our evidence shows that a fragment of PrP can bind a cellular protein and in so doing, alters the metabolism of cells even when they do not express native PrP. This indicates that PrP106-126 is nontoxic to PrPo/o cells, not because of an inability to interact with these cells but because of the loss of some aspect of a PrP expression-dependent phenotype.

Amino Acid Sequence↗

PubMed1998

Apamin improves spatial navigation in medial septal-lesioned mice.

We investigated the effects of acute i.p. injections of the Ca2+-dependent K+ channel blocker, apamin, on water maze spatial navigation, Y-maze and passive avoidance behavior in intact and medial septal-lesioned mice. Apamin 0.02, 0.06 or 0.2 mg/kg (i.p.) administered 30 min before or immediately after the training did not affect the performance of intact mice. Apamin 0.02 or 0.06 mg/kg (i.p.) administered immediately after the daily training did not affect the performance of medial septal-lesioned mice. Apamin 0.02 and 0.06 mg/kg (i.p.) administered 30 min before daily training reversed the navigation failure present in medial septal-lesioned mice during the initial and reversal learning stages of the water maze task. Apamin had no effect on the cognitive performance in Y-maze or passive avoidance tests. The results indicate that blockade of Ca2+-dependent K+ channels may facilitate acquisition of spatial navigation performance, but has no effect on consolidation, inhibitory avoidance and spontaneous alternation behavior in mice.

Animals↗

PubMed1998

Sulfatases, trapping of the sulfated enzyme intermediate by substituting the active site formylglycine.

Sulfatases contain an active site formylglycine residue that is generated by post-translational modification. Crystal structures of two lysosomal sulfatases revealed significant similarity to the catalytic site of alkaline phosphatase containing a serine at the position of formylglycine. To elucidate the catalytic mechanism of sulfate ester hydrolysis, the formylglycine of arylsulfatases A and B was substituted by serine. These mutants upon incubation with substrate were covalently sulfated at the introduced serine. This sulfated enzyme intermediate was stable at pH 5. At alkaline pH it was slowly hydrolyzed. These characteristics are analogous to that of alkaline phosphatase which forms a phosphoserine intermediate that is stable at pH 5, but is hydrolyzed at alkaline pH. In wild-type sulfatases the hydroxyl needed for formation of the sulfated enzyme intermediate is provided by the aldehyde hydrate of the formylglycine. The second, non-esterified hydroxyl of the aldehyde hydrate is essential for rapid desulfation of the enzyme at acidic pH, which most likely occurs by elimination. The lack of this second hydroxyl in the serine mutants explains the trapping of the sulfated enzyme intermediate. Thus, in acting as a geminal diol the formylglycine residue allows for efficient ester hydrolysis in an acidic milieu.

Alanine↗

PubMed1998

Arylsulfatase from Klebsiella pneumoniae carries a formylglycine generated from a serine.

Eukaryotic sulfatases share an unusual posttranslational protein modification, which converts a cysteine into alpha-formylglycine. The alpha-formylglycine is essential for the catalytic activity. Klebsiella pneumoniae expresses an inducible arylsulfatase for which the DNA predicts a serine at the position occupied by the alpha-formylglycine residue in eukaryotic sulfatases. Structural analysis showed that the majority of the arylsulfatase polypeptides from K. pneumoniae carries the alpha-formylglycine, whereas the remaining arylsulfatase polypeptides contain the predicted serine residue. This demonstrates the evolutionary conservation between prokaryotes and eukaryotes of this novel protein modification that so far has been found only in sulfatases. alpha-Formylglycine in Klebsiella is generated from a serine and not from a cysteine as in eukaryotes.

Alanine↗

PubMed1998

Conversion of cysteine to formylglycine in eukaryotic sulfatases occurs by a common mechanism in the endoplasmic reticulum.

Sulfatases undergo an unusual protein modification leading to conversion of a specific cysteine residue into alpha-formylglycine. This conversion is essential for catalytic activity. In arylsulfatase A the alpha-formylglycine is generated inside the endoplasmic reticulum at a late stage of protein translocation. Using in vitro translation in the presence of transport-competent microsomes we found that arylsulfatase B is also modified in a similar way by the formylglycine-generating machinery. Modification depended on protein transport and on the correct position of the relevant cysteine. Arylsulfatase A and B did not compete for modification, as became apparent in co-expression experiments. This could argue for an association of the modification machinery with the protein translocation apparatus.

Alanine↗

PubMed1998

Stability of reconstituted indomethacin sodium trihydrate in original vials and polypropylene syringes.

The stability of reconstituted indomethacin sodium trihydrate 0.5 mg/mL in sterile water for injection for 14 days at either 2-6 degrees C or room temperature (21-25 degrees C) in the drug's original vial and in polypropylene syringes was studied. Twenty 1-mg vials of indomethacin sodium trihydrate were reconstituted with 2 mL of Sterile Water for Injection, USP. Solution from 10 vials was drawn into 20 1-mL disposable polypropylene syringes. Five vials and 10 syringes were stored at 21-25 degrees C, and the other 5 vials and 10 syringes were stored at 2-6 degrees C. Samples were taken on days 0, 1, 2, 4, 5, 7, 9, 12, and 14 and analyzed by liquid chromatography. Physical inspections and pH determinations were made as well. Throughout the study period, all solutions stored at 2-6 degrees C retained more than 95% of the initial indomethacin concentration. At room temperature, solutions stored in syringes retained more than 95% of the initial indomethacin concentration. Solutions stored in glass vials contained only 89.7% of the initial concentration on day 14. Solutions stored at room temperature in either syringes or vials had greater amounts of degradation products than solutions stored at 2-6 degrees C. Reconstituted indomethacin sodium trihydrate 0.5 mg/mL was stable for 14 days when stored in polypropylene syringes at 2-6 or 21-25 degrees C and in its original glass vials at 2-6 degrees C. When stored in the glass vials at 21-25 degrees C, the reconstituted drug was stable for 12 days.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1998

Congenital melanocytic nevi with placental infiltration by melanocytes: a benign condition that mimics metastatic melanoma.

BACKGROUND: Placental metastases from cutaneous malignant melanoma from both the mother and the fetus have been reported. The finding of benign-appearing melanocytes in the placenta in association with congenital melanocytic nevi (CMN) is more exceptional, with only 6 reports in the literature. Clinically, the finding of melanocytes in the placenta in this setting can be alarming and might erroneously lead to the diagnosis of metastatic melanoma. OBSERVATIONS: Herein, we describe 3 additional patients with CMN with placental infiltration by melanocytes with a benign phenotype. In the results of immunoperoxidase stains, the melanocytic cells were positive for S-100 protein and HMB-45 in the 2 lesions available for study. Staining of placental vessels with Ulex europaeus agglutinin I (Vector Laboratories, Burlingame, Calif) failed to show intravascular melanocytes in the 1 lesion available for study. We report for the first time DNA diploidy in 2 lesions available for study, which were analyzed by DNA image cytometry. We describe the first patient with a relatively small, nongiant CMN. CONCLUSIONS: We support the notion of the aberrant migration of melanocytes from the neural crest during fetal development as the most likely explanation of this phenomenon and note the similarity to the association of CMN and leptomeningeal melanocytosis. However, the precise histogenesis of this process remains uncertain. Most importantly, our data provide further evidence for the benign nature of this condition. Awareness of this entity is of vital importance in avoiding overdiagnosis of melanoma in this clinical setting.

Adolescent↗

PubMed1998

A novel protein modification generating an aldehyde group in sulfatases: its role in catalysis and disease.

In multiple sulfatase deficiency, a rare human lysosomal storage disorder, all known sulfatases are synthesized as catalytically poorly active polypeptides. Analysis of the latter has shown that they lack a protein modification that was detected in all members of the sulfatase family. This novel protein modification generates a 2-amino-3-oxopropanoic acid (C alpha-formylglycine) residue by oxidation of the thiol group of a cysteine that is conserved among all eukaryotic sulfatases. The oxidation occurs in the endoplasmic reticulum at a stage when the nascent polypeptide is not yet folded. The aldehyde is part of the catalytic site and is likely to act as an aldehyde hydrate. One of the geminal hydroxyl groups accepts the sulfate during sulfate ester cleavage leading to the formation of a covalently sulfated enzyme intermediate. The other hydroxyl is required for the subsequent elimination of the sulfate and regeneration of the aldehyde group. In some prokaryotic members of the sulfatase gene family, the DNA sequence predicts a serine residue, and not a cysteine. Analysis of one of these prokaryotic sulfatases, however, revealed the presence of the C alpha-formylglycine indicating that the aldehyde group is essential for all members of the sulfatase family and that it can be generated from either cysteine or serine.

Aldehydes↗

PubMed1998

A method for a simulation of continuous intracranial pressure curves.

The study introduces a method to simulate continuously an intracranial pressure (ICP) wave form. In a system analysis approach the intracranial compartment was viewed as a black box with arterial blood pressure (ABP) as an input signal and ICP as an output. A weight function was used to transform the ABP curve into the ICP curve. The output ICP waveform was generated using a weight function derived from the transcranial Doppler blood flow velocity (FV) and ABP curves. In order to establish the relationship between TCD characteristics and weight functions simultaneous recordings of FV, ABP, and ICP curves of a defined group of patients were used. A linear function between the TCD characteristics and the weight functions was obtained by calculating a series of multiple regression analyses. Given examples demonstrate the procedure's capabilities in predicting the mean ICP, the pulse and respiratory waveform modulations, and the trends of ICP changes.

Computer Simulation↗

PubMed1998

A prion protein fragment primes type 1 astrocytes to proliferation signals from microglia.

Giliosis is a hallmark of prion disease. A neurotoxic prion peptide (PrP106-126) induces astrocyte proliferation in the presence of microglia. This peptide also directly enhances microglial proliferation in culture. We have investigated this further to understand the method by which factors released by microglia and PrP106-126 work together to enhance astrocyte proliferation. PrP106-126 in the presence of microglia specifically enhanced type 1 astrocyte proliferation but not Type 2. Astrocytes that do not express the prion protein were more sensitive to oxidative stress and the toxicity of cytosine arabinoside. In the presence of cytosine arabinoside, PrP106-126 was toxic to pure astrocyte cultures. Using conditioned medium from microglia we have shown that PrPc-expressing astrocytes proliferate in response to factors released by microglia stimulated by granulocyte/macrophage colony-stimulating factor. This response is enhanced in the presence of PrP106-126. PrPc-deficient astrocytes do not show this response. These results suggest that astrocytes are primed by PrP106-126 to respond more to factors released by proliferating microglia. Astrocytes may proliferate in this system to escape entering the cell suicide pathway.

Animals↗

PubMed1998

[Large Brunner adenoma in the duodenal bulb--a case report].

Benign, proliferative changes of the Brunner's gland are very rare and account for about 10% of duodenal bulb neoplasias. The authors present a case of Brunner's gland adenoma of unusual dimensions (12 x 5 x 2.5 cm). The patient presented with vague epigastric discomfort as isolated symptoms. In this case we performed surgical treatment, including a duodenotomy and polypectomy. Because they are localized in the submucosa small, superficial endoscopic biopsies may fail to confirm the diagnosis. Malignancy seems to occur only very rarely, with only 14 cases reported in the literature. As the majority of Brunner's adenomas are quite small, endoscopic polypectomy will confirm the diagnosis and cure the condition in most cases. Large symptomatic adenomas may require surgical resection.

Adenoma↗

PubMed1998

Down-regulation of surface monocyte lipopolysaccharide-receptor CD14 in patients on cardiopulmonary bypass undergoing aorta-coronary bypass operation.

OBJECTIVES: Major operative trauma like aorta-coronary bypass operation may lead to postoperative immunodisturbance, putting the patient at an increased risk for infection and sepsis. The monocyte/macrophage system and the endotoxin receptor CD14 are important in the early recognition and elimination of invading bacteria. The aim of this study was to analyze changes in membrane-associated CD14 and soluble CD14 during and after cardiac involving cardiopulmonary bypass. METHODS: We studied numbers of leukocytes, monocytes, and monocyte subpopulations, expression of monocyte membrane-associated CD14 and plasma levels of soluble CD14 in 10 patients (63 +/- 8 years of age), who underwent elective cardiopulmonary bypass. RESULTS: Cardiopulmonary bypass induced marked postoperative monocytosis, which was maximal 20 hours after the operation (485 +/- 242 cells/microl before, 1080 +/- 264 cells/microl 20 hours after surgery). Expression of membrane-associated CD14 on classical CD14++ monocytes decreased significantly by 40%, reaching a nadir 20 hours after surgery (p < 0.05). At the time of maximal membrane-associated CD14 suppression, the levels of soluble CD14 measured by enzyme-linked immunosorbent assay were clearly increased (3.2 +/- 1.0 microg/ml before versus 5.6 +/- 1.0 microg/ml 20 hours after, p < 0.001). No significant change of the percentage of small (alpha) and large (beta) forms of soluble CD14 was found. CONCLUSIONS: Cardiopulmonary bypass leads to reduced membrane-associated CD14 expression on peripheral blood monocytes and increased levels of soluble CD14 through shedding or secretion of membrane-associated CD14 from the cell surface. These findings indicate that bypass is associated with significant monocyte activation.

Blotting, Western↗

PubMed1998

Plasma homocysteine concentrations are regulated by acute hyperinsulinemia in nondiabetic but not type 2 diabetic subjects.

An association between hyperhomocysteinemia and premature atherosclerosis in patients with non-insulin-dependent diabetes mellitus (NIDDM) has recently been described. Little is known about the role of insulin in homocysteine [H(e)] metabolism. We measured plasma H(e) concentrations in the fasting state and during a hyperinsulinemic-euglycemic clamp in normal subjects and patients with NIDDM. Plasma H(e) decreased significantly from 7.2 +/- 2.6 to 6.0 +/- 2.7 mmol/L (P < .01) in normal subjects, but did not change in patients with NIDDM (6.0 +/- 2.7 to 5.9 +/- 2.5 mmol/L, respectively). These data suggest that plasma H(e) concentrations are regulated by acute hyperinsulinemia in normal subjects, but not in insulin-resistant NIDDM subjects. These abnormalities may have implications for the pathogenesis of premature vascular disease associated with NIDDM.

Acute Disease↗

PubMed1998

Ragweed allergy: correlation between skin reactivity and in vitro complement activation.

Recently we have reported on several observations which indicate that allergen-induced complement activation contributes to the development of the symptoms of ragweed allergy. In the present paper a new finding that supports this assumption is summarized. In 48 ragweed-allergic patients individual skin reactivity to ragweed allergen extract (RWA) was assessed using dilution skin prick testing. Sera of these patients were incubated with 20, 100, and 400 U/ml RWA and generation of two complement activation products, alternative pathway C3-convertase (C3bBbP) and terminal pathway activation complex (C5b-9) was measured by ELISA methods. A strong positive correlation (Spearman correlation coefficient r = 0.495, P = 0.0004, and r = 0.454, P = 0.0012, respectively) was found between individual skin reactivity to RWA and C3bBbP generation induced by 20 and 100 A allergological units/ml (U/ml) RWA. This finding further supports the role of complement activation products in the aggravation of the basic IgE-mediated immunopathology of ragweed allergy.

Complement Activation↗