EXPERIMENTAL OBSERVATIONS ON THE INFLUENCE OF TEMPERATURE,LIGHT, AND SALINITY ON CELL DIVISION OF THE MARINE DIATOM,DETONULA CONFERVACEA (CLEVE) GRAN2

The influence of 116 combinations of temperature (2, 7, 12, 16 C), salinity (5–35‰ at 5‰ intervals) and light (5 levels) on the mean daily cell division rate ( K ) of the Narragansett Bay clone of Detonula confervacea was examined following appropriate preconditioning. Growth did not occur at 16 C, but was excellent (K = 1.2–1.5) under certain combinations of light and salinity at 2, 7, and 12 C, being somewhat better at the 2 highest temperature levels. At 32%, and 1100–1200 ft-c, K increased approximately 2.5 fold from 0.6 to 1.5 between 2 and 12 C. A light-temperature relationship was found which had the general trend of an increased optimal light intensity with increasing temperature. Within the optimal salinity range of 15–30‰, the optimal light intensity was 200–600 ft-c at 2 C, 600–1200 ft-c at 7 C, and 1200–1800 ft-c at 12 C. The light-temperature relationship was most pronounced at 2 and 12 C. At 2 C, K decreased with increasing light intensity, but was independent of this factor at higher temperatures. The optimal salinity range of 15–30‰ was independent of temperature negligible growth occurred at 5‰. In situ and in vitro responses of Detonula confervacea to salinity were in general agreement but its pronounced cryophilic preference in nature (usually reaching maximum abundance below 1 C) contrasts with its excellent growth at 12 C in culture. The experiments suggest that termination of the bloom of Detonula confervacea in Narragansett Bay and elsewhere is not solely temperature-dependent. Temperature does not satisfactorily account for its apparent exclusion from waters contiguous to Narragansett Bay and from other more northerly portions of the northeastern coast of the U.S, or, together with light, for its equally surprising apparent unimportance in Norwegian coastal waters.     

Changes in certain kinetic properties of hepatic microsomal aniline hydroxylase and ethylmorphine demethylase associated with postnatal development and maturation in male rats

1. Changes in certain kinetic properties (V(max.) and apparent K(m)) of hepatic microsomal mixed-function oxidases have been studied as a function of postnatal development and maturation in male rats. 2. Microsomal cytochrome P-450 content changed only slightly between 1 and 12 weeks of age. 3. Aniline hydroxylase activity (V(max.)) increased abruptly between 1 and 2 weeks of age to greater than adult activities and then returned to a plateau value between 4(1/2) and 12 weeks of age. Ethylmorphine demethylase activity remained low and relatively constant between 1 and 3 weeks of age and then increased markedly ( approximately 100%) between 3 and 4(1/2) weeks. 4. The apparent Michaelis constant (K(m)) for aniline hydroxylation increased almost linearly with time between 1 and 6 weeks of age and tended to reach a plateau value thereafter. The apparent K(m) for ethylmorphine demethylation increased between 1 and 3 weeks of age and then decreased abruptly to a constant value between 6 and 12 weeks. 5. The data indicate that developmental changes in the activity of these microsomal oxidases do not correlate temporally with each other or with changes in microsomal cytochrome P-450 content. 6. The most dramatic changes in enzyme activity were associated with early development (1-3 weeks) and weaning (3-4 weeks). 7. Changes in weight of seminal vesicle, a criterion of sexual maturation in male rats, were most prominent between 6 and 8 weeks of age and thus appeared to be separated in time from the prominent changes in enzyme activity.     

Amino acid uptake in the peripheral nerve of the rat

When rat sciatic nerves were incubated with C¹⁴l-lysine, l- or d-glutamate, or d-l γ-aminoisobutyrate, the labeled compounds penetrated the nerve, and the level of lysine and leucine after 1 hr was higher in the nerve than in the medium. The level increased with time, and at 24 hr glutamate levels also were higher in the nerve than in the medium. Lowering the temperature strongly inhibited uptake, while other conditions such as absence of glucose, absence of sodium, or the presence of cyanide inhibited uptake by nerve less than uptake by brain slices. The uptake against a concentration gradient, and inhibitions of this uptake by metabolic inhibitors and by structural analogs, were interpreted as showing the presence of transport processes for amino acids in peripheral nerves with characteristics similar to such transport processes in the central nervous system.     

Generic Identification of L-Forms by Polyacrylamide Gel Electrophoretic Comparison of Extracts from Parent Strains and Their Derived L-Forms

A polyacrylamide gel electrophoretic method was used for identification of L-forms in the genera Streptococcus, Staphylococcus, and Proteus, by comparing phenol-acetic acid-water extracts of homologous parent L-form pairs to one another and to other pairs. The method requires only milligram quantities of material for analysis. The standard patterns for the strains used in this study are shown as pictures of the gels and as densitometric tracings of appropriate gels. They show that, despite occasional minor differences in some organisms, the gel electrophoretic patterns of homologous L-forms and bacterial pairs are sufficiently similar-as well as sufficiently dissimilar from patterns of other genera-to permit generic identification of an unknown L-form by reference to patterns derived from possible parental bacteria.     

Rapid Sulfonamide Disc Sensitivity Test for Meningococci

Minimal inhibitory concentrations (MIC) of 90 strains of Neisseria meningitidis were determined by a plate dilution technique that employed twofold changes in concentrations of sulfadiazine. The geometric mean of three MIC determinations on each strain was correlated with inhibition zones produced by a 300-mug sulfathiazole disc. The linear relationship between the logarithm of the geometric mean MIC values and the zone diameters was highly significant. Strains were separated into sensitive and resistant populations by both test procedures. Quantitative criteria for interpreting the sensitivity of a strain by the disc test were established.     

The submicrosomal distribution of hepatic uridine diphosphate glucuronyltransferases in the rabbit

1. Rabbit liver microsomes were subfractionated into rough- and smooth-surfaced types, and glucuronyltransferase activity in each microsomal subfraction was determined with p-nitrophenol, o-aminophenol and phenolphthalein as substrates. The glucuronyltransferase activity measured with p-nitrophenol and o-aminophenol as substrates was localized predominantly in rough-surfaced microsomes. Glucuronyltransferase measured with phenolphthalein as substrate was equally present in rough- and smooth-surfaced microsomes. 2. Phenobarbital pretreatment of rabbits did not stimulate any of the glucuronyltransferase activities measured in either rough- or smooth-surfaced microsomes. 3. Preincubation of rabbit liver microsomes for 30-60min. at 37 degrees under oxygen did not cause any loss of glucuronyltransferase activity. Such preincubation caused either no change or increased enzyme activity in both submicrosomal fractions. The relative distribution of transferase activity in rough- and smooth-surfaced microsomes was not affected by preincubation.     

DISTRIBUTION QUANTITATIVE DES DIVERS PHOSPHO-LIPIDES DANS LES NEURONES ET LES CELLULES GLIALES ISOLES DU CORTEX CEREBRAL DE RAT ADULTE

Resumé–— On décrit une méhode de préparation de neurones et de cellules gliales à partir du cortex cérébral, basée sur la dissociation du tissu à travers un tamis en nylon suivie ď une ultracentrifugation différentielle sur gradients de sucrose et de Ficoll.
On a dosé le DNA, ľazote protéque et les divers phospholipides. II ressort que le taux ď DNA par cellule est identique dans les neurones et les cellules gliales. Par contre, la quantité absolue ďazote protéique est 2.8 fois plus élevée dans les cellules gliales, celle des lipides totaux et des divers phospholipides 5-6 fois plus élevée.
La proportion de chacun des phospholipides dérminée par rapport aux phospholipides totaux est similaire dans les deux types cellulaires.