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J Walter

Publications and source records attributed to J Walter.

302 records · Page 17Linked to original sources
PubMedDate not supplied

The effect of pH and oxygen concentration on the formation of 3-ketodisaccharides by Agrobacterium tumefaciens.

The further optimization of 3-ketodisaccharide formation with sucrose, leucrose and iso maltulose was studied with special regard to pH and oxygen concentration in the reaction mixture with resting cells of Agrobacterium tumefaciens. It was found that the optimal pH values for the highest reaction rate and highest yield were different as the pH affected the stability of the 3-keto derivatives formed. A pH shift to 5.0 clearly reduced the enzymatic degradation of the 3-keto derivatives thus stabilizing them. The influence of constant oxygen concentrations on 3-ketosucrose formation was tested showing results not explicable with normal Michaelis-Menten kinetics. For each substrate a maximum of reaction rate and yield were obtained at very low oxygen concentrations.

Agrobacterium tumefaciens↗
PubMedDate not supplied

Posttransplantation hemodynamics and exercise function are not affected by body-size matching of donor and recipient.

Because the number of heart transplantations performed is limited by the number of available donor hearts, many centers have expanded the acceptable criteria for donor hearts in an attempt to provide a sufficient number of donors for the number of patients awaiting heart transplantation. Traditionally, body-size matching has been an important criteria for matching donors with potential heart transplant recipients. Although initially thought to be detrimental, studies have shown no difference in survival of patients who receive hearts from smaller donors, but heart performance in this subset of patients who receive undersized hearts has not been extensively examined. We assessed exercise capacity and 1-year posttransplantation hemodynamics in 72 consecutive adult orthotopic heart transplant recipients, grouped according to donor-recipient weight ratio and the ratio of donor to recipient body surface area. Total exercise time and relative oxygen consumption were not significantly different among three groups of patients grouped according to donor-recipient body weight ratio as follows: low, 0.60 to 0.79; mid, 0.80 to 1.0; high, more than 1.0. No difference was noted among the three donor-recipient weight ratio groups with respect to 1-year posttransplantation hemodynamics. Similarly, 1-year posttransplantation hemodynamics were not different between patients with a body surface area ratio of less than 1.0 versus those with a body surface area ratio of 1.0 or more. Differences in pretransplantation hemodynamics or graft preservation did not affect our results. Neither donor-recipient weight ratio nor body surface area ratio correlated with any posttransplantation hemodynamic measurement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Analysis of DNA methylation processes related to the inhibition of DNA synthesis by 5-azacytidine in Streptomyces antibioticus ETH 7451.

5-Azacytidine inhibits DNA synthesis and to a lesser proportion RNA synthesis in S. antibioticus. The biosynthesis of proteins is not affected. The main inhibitory effect of 5-azacytidine on DNA and RNA synthesis is probably caused by its incorporation into newly synthesized DNA or RNA and the formation of covalent complexes between cytosine-specific methyltransferases and the modified DNA or RNA templates. To analyze whether such effects could occur at the oriC region of S. antibioticus we analyzed the methylation status of this region using the bisulphite assisted genomic sequencing method. One of the cytosine residues found to be partially methylated was contained within an unique NaeI sequence (GCCGGC) in oriC. Subsequent analysis shows chromosomal DNA from S. antibioticus to be resistant to R.NaeI restriction indicating that this strain contains a NaeI-specific cytosine C5-methyltransferase activity. Following 5-azacytidine treatment the NaeI site within the oriC region becomes partially demethylated. Our results suggest that some of the 5-azacytidine effects on DNA and RNA synthesis might indeed be related to the complex formation and inhibition of a cytosine-specific DNA methyltransferase.

Azacitidine↗