Thermal expansion measurements of frozen biological tissues at cryogenic temperatures.

Thermal expansion data are essential for analyses of cryodestruction associated with thermal stresses during cryopreservation protocols as well as during cryosurgery. The present study tests a commonly used hypothesis that the thermal expansion of frozen tissues is similar to that of pure water ice crystals. This study further provides insight into the potential effect of the presence of cryoprotectants on thermal expansion. A new apparatus for thermal strain measurements of frozen biological tissues within a cryogenic temperature range is presented. Results are presented for fresh tissue samples taken from beef muscle, chicken muscle, rabbit muscle, rabbit bone, and pig liver. Pilot studies of the effect of cryoprotectants on thermal expansion are further presented for rabbit muscle immersed in dimethyl sulphoxide (2 mols/l) and glycerol (2 mols/l), and for pig liver perfused with dimethyl sulphoxide (2 mols/l). Thermal expansion of frozen soft biological tissues was found to be similar to that of water ice crystals in the absence of cryoprotectant. Thermal expansion of the rabbit bone was found to be about one half of that of frozen soft tissues. A significant reduction in the thermal expansion at higher temperatures was observed in the presence of cryoprotectants. A rapid change of thermal strain near -100 degrees C was also observed, which is likely to be associated with the glass transition process of the cryoprotectant solutions.     

Morphogenic Regulation of Pathotoxin Synthesis in Cochliobolus carbonum

The fungus Cochliobolus carbonum causes leaf spot disease of maize. Highly virulent isolates of the pathogen produce a host-selective, peptide toxin that is active against susceptible genotypes of maize. Prior to infection, spores must germinate and differentiate appressoria, structures specialized for leaf penetration. Analysis of spore germination fluids by plasma desorption mass spectrometry, which allowed detection of as little as 0.5 ng toxin, revealed that spores induced to form appressoria in vitro synthesized and released the toxin at a time coincident with maturation of appressoria. Spores incubated under conditions that did not induce appressorium formation failed to produce toxin. These observations indicate that synthesis of the host-selective toxin, which is essential for successful pathogenesis of maize by C. carbonum, is regulated by infection-related morphogenesis.     

Large scale preparation and purification of apo-D-aminoacid oxidase for use in novel amplification assays

Summary Dissociation of FAD from D-aminoacid oxidase occurred most rapidly at pH 6.0 in the presence of 1 M KBr. Diafiltration of 0.6 g of enzyme under these conditions yielded apoenzyme containing 1.3% of residual holoenzyme activity, which was subsequently reduced to less than 0.01% by chromatography on Blue Sepharose and ion exchange, giving material containing <1 ppb of contaminating phosphatase and nucleotidase.     

Morphometric study of hepatic ultrastructure in alcoholic hepatitis. Veterans Administration Cooperative Study Group on Alcoholic Hepatitis

We undertook a morphometric analysis of hepatocellular organelles in an attempt to correlate their changes with the clinical stages of patients with alcoholic hepatitis. Although hepatic ultrastructural alterations did not correlate with disease severity, we found significant differences between patient and control groups in the measured parameters of non-organelle cytoplasm, mitochondria, SER, RER, glycogen, and lipid.     

NRAS transforming gene maps to region p11----p13 on chromosome 1 by in situ hybridization

The human transforming gene NRAS, cloned from SK-N-SH neuroblastoma cells, has been mapped to region p11----p13 on chromosome 1 by in situ hybridization.