2-Deoxyribose Gene-Enzyme Complex in Salmonella typhimurium: Regulation of Phosphodeoxyribomutase

Phosphodeoxyribomutase, the enzyme which catalyzes the interconversion of 2-deoxyribose-1-phosphate to 2-deoxyribose-5-phosphate, has been partially purified from Salmonella typhimurium. The enzyme had an absolute requirement for manganese ion and was stimulated by glucose-1, 6-diphosphate. Phosphodeoxyribomutase was induced by deoxyribose-5-phosphate and was coordinately regulated with the enzymes thymidine phosphorylase and deoxyribose-5-phosphate aldolase, type II. Mutants deficient in these three enzymes were isolated and mapped close to the threonine locus in S. typhimurium. The three enzymes thymidine phosphorylase, deoxyribose-5-phosphate aldolase, type II, and phosphodeoxyribomutase are controlled by a series of linked genes and appear to constitute an operon.     

Biosynthesis of D-mannitol from D-glucose by Aspergillus candidus

Mannitol has long been known as a product of glucose metabolism by some strains of Aspergillus. Apparently no concerted effort, has been made to develop a practical fermentation process to make mannitol. Work at the Northern Laboratory has shown that nearly all strains of white Aspergillus produce significant amounts of mannitol; many strains of black Aspergillus also have this characteristic. Aspergillus candidus NRRL 305 is an exceptionally good mannitol producer. Studies on a fermentation process were conducted in 20-1, stainless steel fermentors, without baffles. Czapek-Dox medium, modified by addition of corn meal, yeast extract, and enzymatically hydrolyzed casein was the most satisfactory medium tested. Suitable increments of glucose were fed daily to the fermentors. The duration of the fermentation was from 10 to 16 days. The effects of agitation, aeration, temperature, and pH of the medium were studied. Under optimal conditions yields of mannitol approached 50% of the glucose consumed.     

The gas–liquid chromatography of carboxylic acid esters of the urinary 11-deoxy-17-oxo steroids: Determination as n-butyrates

1. The gas-liquid-chromatographic separations of the acetate, propionate, n-butyrate, isobutyrate and n-valerate esters of androsterone, aetiocholanolone and dehydroepiandrosterone were studied on a 1% neopentyl glycol sebacate column. The n-butyrate, isobutyrate and n-valerate esters were well resolved. 2. The three steroids derived from hydrolysed urinary 17-oxo steroid conjugate extracts were analysed by gas-liquid chromatography after conversion into their n-butyrate esters. The results were compared with independent determinations involving chromatography on alumina.     

Absorption and Screening in Phycomyces

In vivo absorption measurements were made through the photosensitive zones of Phycomyces sporangiophores and absorption spectra are presented for various growth media and for wavelengths between 400 and 580 mµ. As in mycelia, β-carotene was the major pigment ordinarily found. The addition of diphenylamine to the growth media caused a decrease in β-carotene and an increase in certain other carotenoids. Growth in the dark substantially reduced the amount of β-carotene in the photosensitive zone; however, growth on a lactate medium failed to suppress β-carotene in the growing zone although the mycelia appeared almost colorless. Also when diphenylamine was added to the medium the absorption in the growing zone at 460 mµ was not diminished although the colored carotenoids in the bulk of the sporangiophore were drastically reduced. Absorption which is characteristic of the action spectra was not found. Sporangiophores immersed in fluids with a critical refractive index show neither positive nor negative tropism. Measurements were made of the critical refractive indices for light at 495 and 510 mµ. The critical indices differed only slightly. Assuming primary photoreceptors at the cell wall, the change in screening due to absorption appears too large to be counterbalanced solely by a simple effect of the focusing change. The possibility is therefore advanced that the receptors are internal to most of the cytoplasm; i.e., near the vacuole.     

FINE STRUCTURE AND MORPHOGENIC MOVEMENTS IN THE GASTRULA OF THE TREEFROG, HYLA REGILLA

The blastoporal groove of the early gastrula of the treefrog, Hyla regilla, was examined with the electron microscope. The innermost extension of the groove is lined with invaginating flask- and wedge-shaped cells of entoderm and mesoderm. The distal surfaces of these cells bear microvilli which are underlain with an electron-opaque layer composed of fine granular material and fibrils. The dense layer and masses of vesicles proximal to it fill the necks of the cells. In flask cells bordering the forming archenteron the vesicles are replaced by large vacuoles surrounded by layers of membranes. The cells lining the groove are tightly joined at their distal ends in the region of the dense layer. Proximally, the cell bodies are separated by wide intercellular spaces. The cell body, which is migrating toward the interior of the gastrula, contains the nucleus plus other organalles and inclusions common to amphibian gastrular cells. A dense layer of granular material, vesicles, and membranes lies beneath the surface of the cell body and extends into pseudopodium-like processes and surface undulations which cross the intercellular spaces. A special mesodermal cell observed in the dorsal lining of the groove is smaller and denser than the surrounding presumptive chordamesodermal cells. A long finger of cytoplasm, filled with a dense layer, vesicles and membranes, extends from its distal surface along the edge of the groove, ending in a tight interlocking with another mesodermal cell. Some correlations between fine structure and the mechanics of gastrulation are discussed, and a theory of invagination is proposed, based on contraction and expansion of the dense layer and the tight junctions at distal cell surfaces.