Ewing's sarcoma of the maxilla.

Ewing's sarcoma is an uncommon malignancy that occurs usually in childhood. In most reported cases, the occurrence of this tumor is more in the mandible than the maxilla. A case of Ewing's sarcoma of the maxilla together with its associated structures is presented and discussed with complete clinical, radiographic, and histological evaluation. Although the prognosis remains poor, an increased rate of survival is now associated with early diagnosis and combined therapy.

Nitrification and simultaneous denitrification by Azospirillum brasilense 12S.

Azospirillum brasilense, an associative diazotrophs from sorghum roots grows autotrophically on NH + 4 and CaCO3. NH + 4 a is also oxidized to NO – 2 and then denitrified. Addition of malate to the autotrophic medium enhances both NH + 4 oxidation as well as NO – 2 dissimilation. The incomplete nitrification linked denitrification results in a rapid loss of nitrogen from the growth medium. The bacterium also shows assimilatory NO3− and NO 2 reductases and fixes nitrogen at < 50 μg N/ml of NH + 4 , NO−3 or NO-2.

Sequential release of cellulose enzymes during germination of Trichoderma reesei spores.

The pattern of release of extracellular cellulase during the germination of Trichoderma reesei spores has been examined. The four enzymes namely, filter paper degrading enzyme, β-1,4 endoglucanase, β-glucosidase and xylanase appear sequentially in the culture broth during germination of the spores. The order of enzyme appearance is not altered by the type of carbon source in the germination medium. Measureable quantities of filter paper degrading enzyme is detected only after the outgrowth has occurred. A possible mechanism of spore germination and induction of the enzymes by insoluble cellulose is suggested.

Mechanism of action of carboxin and the development of resistance in yeast.

Carboxin prevents the growth of yeast by inhibiting protein synthesis; the resumption of growth in the presence of this chemical appears to be primarily due to a cellular alteration affecting carboxin entry into the cells.

In vitro and in vivo nitrogenase activity of Rhizobium mutants and their symbiotic effectivity.

A slow growing nitrogen-fixing strain of Vigna radiata var. aureus (mung bean) Rhizobium which expressed nitrogenase activity in a synthetic medium was isolated from its native population. Mutants with decreased and increased nitrogenase activity were derived from this strain by treatment with acridine orange and ethidium bromide. These mutants were tested for symbiotic effectivity in vivo. The effectivity of mutants with decreased nitrogenase activity in the culture medium was lower than the parent strain; however, the effectivity of mutants with higher nitrogenase activity did not increase above that of the parent. This suggests that the plant is perhaps a limiting factor in the full expression of rhizobial nitrogenase in the nodules.