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Biomedical subjects

M Schuster

Publications and source records attributed to M Schuster.

At least 109 records · Page 6Linked to original sources
PubMed1992

Ochratoxin A production in Bavarian cereal grains stored at 15 and 19% moisture content.

Wheat, barley, and maize, each in 15-kg parcels at 15 and 19% initial moisture content (IMC), were kept in a Bavarian farm granary from June through November 1990. During this period, the grain at each IMC was analyzed for mycotoxins and monitored for grain temperature, carbon dioxide, seed germination, and microfloral incidence and abundance. Barley and maize stored for 20 weeks at 19% IMC contained ochratoxin A in amounts of 70 and 90 microg/kg, respectively. This mycotoxin was not detected in wheat stored at 19% IMC, nor in the grains stored at 15% IMC. Aflatoxin B1, sterigmatocystin, citrinin, and zearalenone were also assayed but not detected in grains stored at either IMC. Principal component analysis of the data indicated that ochratoxin A was produced in a damp niche in maize, when abundant metabolic activity and CO2 production by Penicillium glandicola and Aspergillus spp. were common.

Edible Grain↗
PubMed1992

Use of cisplatin for elderly patients.

The ageing of the population has resulted in a greater emphasis on cancer treatment effects in elderly patients. This population has often had arbitrary dose modification of chemotherapy owing to fear of excessive side-effects. A review was undertaken to evaluate cisplatin toxicity in patients of 70 years of age or older. Thirty-four patients were evaluated. Their mean age was 72.8 years and 85.3% were women. Fourteen of 34 (41%) patients completed the planned therapy. Treatment was terminated because of disease progression (35%), renal toxicity (9%) and non-renal toxicity (15%). Our conclusion is that cisplatin can safely be administered to elderly patients. Arbitrary dose modification or elimination of cisplatin from a treatment programme on the grounds of patient age alone is not justified.

Acute Kidney Injury↗
PubMed1992

Incidence and timing of activity parameter changes in activity responsive pacing systems.

The incidence and timing of rate response parameter reprogramming in activity responsive pacing systems during the year after implantation was evaluated in two groups of patients: 24 patients in whom a VVI,R system was implanted (Activitrax, Medtronic, Inc.), and 21 patients in whom a DDD,R system was implanted (Synchrony, Siemens Pacesetter, Inc.). Activity parameter changes in Activitrax patients were made based on the presence of symptoms, while in Synchrony patients, changes were based on objective data obtained using a sensor indicated rate histogram with a slow and fast walk protocol. No significant difference in the incidence of activity parameter reprogramming was noted at various time intervals during the first year in Activitrax patients; in Synchrony patients a greater incidence of reprogramming changes was noted at the 1-month follow-up visit compared to later follow-up visits (P less than 0.02). Further, the incidence of changes at 1 month was greater for Synchrony compared to Activitrax patients (P less than 0.001), while no difference was detected between groups at subsequent follow-up intervals. Use of the slow and fast walk protocol, by permitting serial evaluation of sensor response, demonstrated alterations in sensor drive rates with similar levels of activity over the initial 4 to 6 postimplant weeks. This may result from postoperative changes at the pacemaker insertion site. Based on this experience, predischarge programming may not predict long-term rate response requirements. We recommend evaluation of sensor function using an exercise protocol performed at 4 to 6 postimplant weeks in all rate responsive pacing systems that utilize a piezoelectric crystal.

Aged↗
PubMed1992

Effectiveness of recombinant human erythropoietin therapy in myelodysplastic syndromes.

In an attempt to determine predictors of response to recombinant human erythropoietin (r-HuEPO) therapy in 20 patients with various subtypes of myelodysplastic syndrome (MDS), plasma concentrations of transferrin receptor protein were measured before and after 4 doses of r-HuEPO. An r-HuEPO dosage of 150 U/kg was administered subcutaneously 3 times weekly and increased to 300 U/kg in patients who failed to raise plasma concentrations of transferrin receptor protein by at least one third. Ten (50%) patients had an effective clinical response to therapy by reducing (greater than 50%) or eliminating transfusion requirements, or by showing an improvement in haematocrit of greater than or equal to 6 percentage points. Changes in plasma transferrin receptor protein concentrations failed to predict which patients would eventually respond to r-HuEPO therapy. A subset of MDS patients demonstrated a delayed response to therapy in order to achieve a satisfactory clinical outcome. Precise predictors of response, either laboratory or clinical, remain to be determined. Continued research is warranted in this group of patients in order to specifically target r-HuEPO therapy. It is, however, likely that r-HuEPO therapy will have an effective and important role in this subset of MDS patients.

Anemia↗
PubMed1991

Serum amyloid A protein in very low density--and high density lipoproteins during the course of acute myocardial infarction.

In a preceding paper we reported on the detection and characterization of human serum amyloid A protein (SAA) in very low density lipoproteins (VLDL) and high density lipoproteins (HDL) of patients after acute myocardial infarction. Here we describe the time course of the occurrence of SAA in VLDL and HDL in the postinfarction period. SAA reached its maximum in VLDL and HDL approximately 53 h after the acute event. At the peak of the acute-phase response, SAA comprised as much as 38% of the total apoproteins of VLDL and HDL. SAA appeared at the same points in time and with nearly the same concentrations in VLDL and HDL. We conclude that SAA is not exchanged in plasma between lipoproteins of different densities and that this protein is secreted on its own by hepatocytes and not as a part of an already constituted lipoprotein particle.

Adult↗
PubMed1991

Nucleophile specificity in papain-catalyzed acyl transfer reactions.

The ratio of hydrolysis to aminolysis product in papain-catalyzed acyl transfer reactions using various nucleophiles was determined. The data are interpreted in terms of binding specificity. The acyl transfer reactions were performed using the acyl donor Mal-Phe-Ala-OEtCl. The analysis of the structure-activity relationships of the hydrophobic S1'-P1' contact indicates that the S1' subsite can accommodate maximally three methyl(ene) groups. Hydrophilic amino acid side chains are better bound to S1' than can be explained by their hydrophobicities. The S2' as well as the S3' binding subsite exhibits a preference for space-filling hydrophobic amino acid residues.

Acylation↗
PubMed1991

Protease-catalyzed peptide synthesis in frozen aqueous systems: the "freeze-concentration model".

Freezing of the aqueous reaction mixtures can cause dramatically increased peptide yields in protease-catalyzed kinetically controlled peptide synthesis reactions. The "Freeze-concentration model" which implies that the enzymic reaction within a macroscopically frozen system takes place in an unfrozen liquid phase is presented as a reasonable basis for the understanding of the effect of freezing. It is shown that L-amino acid esters are effective nucleophiles in alpha-chymotrypsin-catalyzed acyl transfer reactions when these are performed in frozen state.

Amino Acid Sequence↗
PubMed1991

S'-subsite mapping of endoproteinase Glu/Asp-C from Actinomyces sp.

The S'-subsite specificity of the endoproteinase Glu/Asp-C from Actinomyces sp. was studied by acyl transfer reactions using amino-acid- and peptide-derived nucleophilic amino components. The following results were obtained: 1. The enzyme prefers amino acid amides with hydrophobic side chains in P'i position. In addition, positively charged functions in this position favour S'-P' interactions significantly. 2. Stereospecific binding is a prerequisite for nucleophilic efficiency. 3. Dipeptide amides are more efficient amino components in comparison to free dipeptides whereas oligoglycines show a poor nucleophilic behaviour independent of chain length.

Actinomyces↗
PubMed1991

Therapy of refractory/relapsed acute leukemia with cytosine arabinoside plus tetrahydrouridine (an inhibitor of cytidine deaminase)--a pilot study.

Thirty two patients with refractory or recurrent acute leukemia or blast crisis of chronic myelocytic leukemia were treated with 1-beta-D-arabinofuranosylcytosine (Ara-C), 100 mg/m2 [group I (n = 15)] or 200 mg/m2 [group II (n = 18)], and tetrahydrouridine (THU) 350 mg/m2, given concurrently as a 3 h continuous intravenous infusion at 12 h interval for eight doses. Two of 13 (15.3%) evaluable patients in group I achieved a complete response, both of whom had acute myelocytic leukemia. In group II, seven of 14 evaluable patients (50%) obtained objective responses--six with complete responses (42.8%) and one with partial response (7%). Myelosuppression was seen in all patients with a median duration of 32.5 days (group I) and 36.3 days (group II), respectively. Non-hematologic toxicity consisted of nausea, vomiting, diarrhea, conjunctivitis, skin rash, hepatocellular toxicity, hemorrhage, and renal toxicity. Pharmacokinetic studies revealed, for group I, mean peak plasma Ara-C levels at 3 h (Cp3h) of 1254 ng/ml, area under the curve (AUC) 4651 ng x h/ml, total body clearance (TBC) 32.65 l/h/m2, renal clearance (RC) 7.04 l/h/m2 with a mean of 12.36% of the injected amount of Ara-C excreted unchanged in urine over the first 24 h. The corresponding mean values for group II are Cp3h 3305 ng/ml, AUC 15080 ng x h/ml, TBC 20.48 l/h/m2, RC 7.02 l/h/m2 and 26.23%. Ara-C 200 mg/m2 combined with THU gave serum Ara-C levels and response rates comparable to those achieved with high dose Ara-C (HiDAC) (greater than or equal to 1 g/m2). Central nervous system toxicity associated with HiDAC was not seen. Pharmacokinetics for uracil arabinoside (Ara-U) in patients treated with Ara-C 200 mg/m2 plus THU, were comparable to values seen with Ara-C for Cp3h, AUC and 24 h urine, amounting to 3160 ng/ml, 21717 ng x h/ml and 23.62% whereas TBC was significantly lower (p less than 0.001) for Ara-U than for Ara-C (3.02 versus 20.48 l/h/m2).

Adult↗
PubMed1990

Characterization of the S'-subsite specificity of V8 proteinase via acyl transfer to added nucleophiles.

The S'-subsite specificity of endoproteinase Glu-C (V8 proteinase) was studied by acyl transfer reactions using Z-Glu-OMe as acyl donor and a series of amino acid- and peptide-derived nucleophiles. The partition constant, which characterizes specificity, was determined by a method based on the integrated rate equation. V8 proteinase prefers amino acid residues with hydrophobic side chains in the P'1 position. Di- and tripeptide amides are more efficient nucleophilic amino components than amino acid amides.

Binding Sites↗
PubMed1990

Synthesis and kinetic characterisation of omega-guanidinocarbonic acid ethyl esters as trypsin substrates.

Aliphatic omega-guanidinocarbonic acid ethyl esters of different chain length (C3-C6) were synthesized and characterized as 4-toluenesulfonates. The kinetic parameters of the trypsin-catalyzed hydrolysis indicate that the ethyl ester of delta-guanidinovaleric acid is the most effective substrate in this series. The Km value of this compound is in the same order of magnitude as those of arginine-containing ester substrates like N alpha-benzoylarginine ethyl ester (BAEE). However, kcat is decreased by approximately two orders of magnitude.

Amino Acids, Dicarboxylic↗
PubMed1989

A survey on the occurrence of Fusarium mycotoxins in Bavarian cereals from the 1987 harvest.

Bavarian cereals and wheat flour from the 1987 harvest were analysed for nivalenol (NIV) and deoxynivalenol (DON) using high performance liquid chromatography (HPLC) and for T-2 toxin and zearalenone (ZEA) by enzyme-linked-immunosorbent assay (ELISA). The study included 190 field samples of wheat, barley, rye and oat with visibly damaged ears, 45 samples of wheat intended for feed production and two series of wheat flour (type 550) and whole wheat flour collected in October 1987 and June 1988. The field samples examined showed a high DON contamination of wheat (87%) with an average of 3.96 mg/kg and a maximum of 43.8 mg/kg. Mean levels between 0.33 mg/kg and 0.27 mg/kg DON could be detected in barley, rye and oat. Of the wheat samples, 58% contained ZEA with a maximum of 1.560 mg/kg. The highest levels of ZEA were detected in samples which also showed high concentrations of DON. The NIV and T-2 toxin levels were comparatively low. Thirty percent of the samples showed NIV concentrations between 0.04 mg/kg and 0.29 mg/kg and 38% contained between 0.005 and 0.60 mg/kg of T-2. In the wheat samples for feed production, only DON was detected with an average of 0.190 mg/kg and a maximum of 0.75 mg/kg. The highest DON levels (0.58 mg/kg) from October 1987 were found in the wheat flour samples which were lower than the highest DON concentration (3.24 mg/kg) detected in the samples collected during June 1988. This fact was probably due to a substantial amount of non-contaminated wheat from 1986. The toxin concentrations in the whole wheat flour were not higher than in the type 550 flour.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1988

Temperature dependence of anion transport in the human red blood cell.

Arrhenius plots of chloride and bromide transport yield two regions with different activation energies (Ea). Below 15 or 25 degrees C (for Cl- and Br-, respectively), Ea is about 32.5 kcal/mol; above these temperatures, about 22.5 kcal/mol (Brahm, J. (1977) J. Gen. Physiol. 70, 283-306). For the temperature dependence of SO4(2-) transport up to 37 degrees C, no such break could be observed. We were able to show that the temperature coefficient for the rate of SO4(2-) transport is higher than that for the rate of denaturation of the band 3 protein (as measured by NMR) or the destruction of the permeability barrier in the red cell membrane. It was possible, therefore, to extend the range of flux measurements up to 60 degrees C and to show that, even for the slowly permeating SO4(2-) in the Arrhenius plot, there appears a break, which is located somewhere between 30 and 37 degrees C and where Ea changes from 32.5 to 24.1 kcal/mol. At the break, the turnover number is approx. 6.9 ions/band 3 per s. Using 35Cl- -NMR (Falke, Pace and Chan (1984) J. Biol. Chem. 259, 6472-6480), we also determined the temperature dependence of Cl- -binding. We found no significant change over the entire range from 0 to 57 degrees C, regardless of whether the measurements were performed in the absence or presence of competing SO4(2-). We conclude that the enthalpy changes associated with Cl- - or SO4(2-)-binding are negligible as compared to the Ea values observed. It was possible, therefore, to calculate the thermodynamic parameters defined by transition-state theory for the transition of the anion-loaded transport protein to the activated state for Cl-, Br- and SO4(2-) below and above the temperatures at which the breaks in the Arrhenius plots are seen. We found in both regions a high positive activation entropy, resulting in a low free enthalpy of activation. Thus the internal energy required for carrying the complex between anion and transport protein over the rate-limiting energy barrier is largely compensated for by an increase of randomness in the protein and/or its aqueous environment.

Anion Exchange Protein 1, Erythrocyte↗