Formation of Nitrate from 3-Nitropropionate by Aspergillus flavus

Extracts of the hyphae of a nitrifying strain of Aspergillus flavus formed nitrite and nitrate from 3-nitropropionate. Nicotinamide adenine dinucleotide phosphate and nicotinamide adenine dinucleotide enhanced the production of nitrate but not nitrite, whereas cysteine and diethyldithiocarbamate increased nitrite but diminished nitrate synthesis. Quinacrine reduced the extent of conversion of the nitro compound to nitrite and nitrate, but only the inhibition of nitrite formation was completely reversed by flavine coenzymes. Molecular oxygen was essential for this part of the nitrification sequence. 3-Chloropropionate stimulated the oxidation of nitrite by hyphae or enzyme preparations. Although the fungus contained a noncytochrome-linked nitrite-oxidizing enzyme, partially purified preparations free of this enzyme formed both nitrite and nitrate from 3-nitropropionate. Possible mechanisms of this latter stage of heterotrophic nitrification are discussed.     

Microdensitometric analysis for study of skeletal growth and aging in the living subject

Microdensitometric analysis of a radiographic image of mineralized tissue offers information on the morphologic characteristics of the specimen examined. The use of microstructure (such as individual trabecula of bone) and macrostructure (such as Harris lines of arrest) as in vivo bone markers allows for assessment of gross skeletal changes in nondestructive fashion. This technique is also applicable to the study of the interrelationship of tooth and bone. In addition, microdensitometry offers precise information on the fine structure of bone as regards the trabecular elements. This technique is applicable in determining the size and quantity of trabeculae, their persistence over long periods of time, and the factors responsible for change or lack of change in trabeculae during growth and aging.     

Effect of carbohydrates on the growth ofRhizoctonia solani Kühn

The growth OfRhizoctonia solani in different carbohydrates was studied. The rate of growth of the fungus was traced by taking the dry weights of mycelia obtained from the carbohydrate medium at regular intervals and shifts in the pH were recorded. Different carbohydrate sources had different effects on the growth of the organism. The exoenzymes from the organism were capable of cleaving carbohydrates irrespective of whether the fungus grew in them or not.     

Efficiency of Chlorine Dioxide as a Bactericide

We found chlorine dioxide to be a more effective disinfectant than chlorine in sewage effluent at pH 8.5. Chlorine dioxide was also found to be a more stable bactericide in relation to pH in the range studied.     

Expression of class I histocompatibility antigens in neuroectodermal tumors is independent of the expression of a transfected neuroblastoma myc gene

We have evaluated the relationship between the neuronal myc gene (NMYC) and class I major histocompatibility complex (MHC) expression in human neuroblastoma (NB) tumor cell lines. Class I MHC surface Ag expression in NB cell lines varied from nearly undetectable to levels nearly as high as in a lymphoblastoid cell line. Class I MHC mRNA levels in NMYC-amplified NB cell lines were lower than levels observed in single copy NMYC NB cell lines. However, considerable variation in class I MHC surface Ag and mRNA expression was evident in NMYC-amplified cell lines. To determine directly whether NMYC might modulate class I MHC expression in NB, we transfected a plasmid containing a recombinant NMYC gene into two tumor cell lines derived from a NB and a related neuroepithelioma tumor. Constitutive overexpression of the recombinant NMYC gene produced no consistent change in class I MHC surface Ag or mRNA levels. To determine whether class I MHC expression might be developmentally regulated in adrenal medullary cells, the precursor cells of adrenal NB tumors, beta 2-microglobulin expression was measured in fetal and adult adrenal glands. beta 2-Microglobulin expression was not evident in the neuroblasts of a 24-wk-old fetal adrenal gland, whereas beta 2-microglobulin expression was present in the adult adrenal medulla. These data suggest that variation in class I MHC expression among NB cells may reflect the developmental stage at which neuroblasts were arrested during tumorigenesis.     

Sodium and calcium currents in action potentials of rat somatotrophs: their possible functions in growth hormone secretion

We report that both Na+ and Ca2+ currents are involved in the action potentials and in the hormone release from rat somatotrophs in primary culture. Single somatotrophs were identified by reverse hemolytic plaque assay (RHPA) and transmembrane voltage and currents were recorded using the whole-cell mode of the patch-clamp technique. Somatotrophs displayed a mean resting potential of -80mV and an average input resistance of 5.7G omega. Most of the cells showed spontaneous or evoked action potentials. Single action potentials or the initial spike in a burst were characterized by their high amplitude and short duration. Tetrodotoxin (TTX, 1 microM) blocked single action potentials and the initial spikes in a burst, whereas action potentials of long duration and low amplitude persisted. Cobalt (2 mM) plus TTX (1 microM) blocked all the action potentials. Voltage-clamp experiments confirmed the presence of both a TTX-sensitive Na+ current and Co2(+)-sensitive Ca2+ currents. TTX or Na(+)-free medium slightly decreased the basal release of GH but did not markedly modify hGRF-stimulated GH release. However, Co2+ (2 mM), which partially decreased the basal release, totally blocked hGRF-stimulated release. We conclude that (1) Na+ currents which initiate rapid action potentials may participate in spontaneous GH release; (2) Ca2+ currents, which give rise to long duration action potentials and membrane voltage fluctuation, are probably involved in both basal and hGRF-stimulated GH releases.     

Cloning and nucleotide sequence of human liver cDNA encoding for cystathionine gamma-lyase.

We have cloned and sequenced a full-length cDNA (1083 bp) encoding the human liver cystathionine-gamma-lyase enzyme (cystathionase). The human cystathionase sequence presented a substantial deletion of 132 bases (44 amino acids) compared to that reported for rat cystathionase, and of 135 bases (45 amino acids) compared to that reported for yeast cystathionase. After re-alignment for the missing nucleotides, the human cDNA sequence shows significant amino acid homology to that for the rat enzyme (85%) and the yeast enzyme (50%). A search for an undeleted cDNA, by the polymerase chain reaction, yielded a second clone which contained the missing 132 bases. Flanking nucleotides in the latter clone were identical to those in the cDNA clone containing the deletion. The two forms of human cystathionase deduced from the two cDNA clones may be derived from two different genes or may be splice variants.