Zinc deficiency in wetland rice along a toposequence of hydromorphic soils in the Philippines

Summary Zinc deficiency in rice induced by prolonged water saturation of the soil is widespread in the Philippines. The poor drainage associated with the disorder is mostly due to upwelling of shallow artesian water in footslope areas and to ponding of water from continually flowing artesian wells common in such areas. One toposequence where no Zn deficiency occurred in the highest field and progressively severe Zn deficiency in successive lower fields, was studied in detail. With lower elevation soils showed an increase in organic matter and free carbonate, associated with increased upwelling and ponding of artesian water very high in dissolved Mg and Ca bicarbonate.     

Trichinella spiralis: Generation in the presence of rat serum of factors chemotactic for rat cells

Chemotaxis of rat peritoneal cells, of which the eosinophil was the predominant migratory cell type, toward incubates of Trichinella spiralis was studied using a modified Boyden chamber. Excysted muscle larvae, preadults, and adults were incubated in a buffered medium for 20 hr at 37 C. Worms were incubated alone or with serum or spleen cells, or both, from immune and nonimmune rats. Incubates of worm stages alone possessed no chemotactic activity as compared with incubation medium as a negative control and zymosan-activated serum as a positive control. Both normal and immune sera tested alone stimulated cell migration to the same degree. Incubates of spleen cells from either normal or immunized hosts did not show chemotactic activity. Chemotaxis caused by normal and immune sera were not altered by incubation with homologous spleen cells. Addition of larva, preadults, and adult worms to sera, however, enhanced chemotactic activity over sera alone. Chemotaxis caused by larvae plus immune sera was significantly greater than that stimulated by larvae plus normal sera. This difference decreased when preadults were substituted for larvae and was not observed when adult worms were used. Reversal of the chemical gradients showed that active cell migration caused by various incubates was due to Chemotaxis.     

Effect of restrictive temperature on cell wall synthesis in a temperature-sensitive mutant of Bacillus stearothermophilus.

A temperature-sensitive mutant of Bacillus stearothermophilus, TS-13, was unable to grow above 58 degrees C, compared to 72 degrees C for the wild type. Actively growing TS-13 cells lysed within 2 h when exposed to a restrictive temperature of 65 degrees C. Peptidoglycan synthesis stopped within 10 to 15 min postshift before a shut down of other macromolecular syntheses. Composition of preexisting peptidoglycan was not altered, nor was new peptidoglycan of aberrant composition formed. No significant difference in autolysin activity was observed between the mutant and the wild type at 65 degrees C. Protoplasts of TS-13 cells were able to synthesize cell wall material at 52 degress C, but not at 65 degrees C. This wall material remained closely associated with the cell membrane at the outer surface of the protoplasts, forming small, globular, membrane-bound structures which could be visualized by electron microscopy. These structures reacted with fluorescent antibody prepared against purified cell walls. Production of this membrane-associated wall material could be blocked by bacitracin, which inhibited cell wall synthesis at the level of transport through the membrane. The data were in agreement with previous studies showing that at the restrictive temperature this mutant is unable to alter its membrane fatty acid and phospholipid composition with temperature such that it is not able to maintain a membrane lipid composition which permits normal membrane function at the restrictive temperature.     

Ammonia overloading in hepatocytes isolated from liver of fetal and adult rats

Ammonia overloading was investigated during glucose and fructose metabolism in isolated hepatocytes under a variety of metabolic conditions. In all assay conditions, the glycolytic flux and oxygen uptake was not modified by 10 mM ammonia. In hepatocytes isolated from rats fed as libitum, the presence of ammonia caused a decrease in the production of lactate (pyruvate); this effect was not observed in anaerobic incubations, in hepatocytes isolated from starved animals, or in fetal hepatocytes. In spite of an overproduction of urea, ammonia detoxification also takes place by the synthesis of alanine, glutamate and aspartate. Addition of 1 mM aminooxyacetate, an inhibitor of aminotransferases, to the incubation medium prevents the formation of these amino acids, and also prevents the decrease of lactate in hepatocytes isolated from fed animals.     

Isolation and characterization of a trypsin inhibitor fromVigna sinensis seeds

The major trypsin inhibitor ofVigna sinensis cv. seridó was isolated and shown to be devoid of chymotrypsin inhibiting activity. It has a molecular weight of 9800 as determined by gel electrophoresis and a pI of 5.0. The activity of the inhibitor was decreased by treatment with trinitrobenzenesulfonic acid, suggesting that it isa LYS-X type trypsin inhibitor. Selfassociation of the molecule was demonstrated both in 1% sodium dodecylsulfate and inacidic (pH 2.4) conditions.     

Mutations of Chinese Hamster Somatic Cells from 2-Deoxygalactose Sensitivity to Resistance

In Chinese hamster somatic cells, the spontaneous change of phenotype from 2-deoxygalactose sensitivity to resistance was studied using fluctuation test experiments à la Luria and Delbrück (1943) for four Chinese hamster cell strains derived from V79. The results are consistent with true mutational events. The mutation rates are in the range of 1 to 3.5 X 10(-5) per cell per generation. The relationship between the 2-deoxyglactose resistance and the galactokinase markers is discussed.     

Effects of DAPI on human leukocytes in vitro.

DAPI (4'-6-diamidino-2-phenylindole), a fluorochrome specific for AT-rich DNA, was supplied for 24 h at various concentrations to human leukocytes in culture. This treatment caused the appearance on the chromosomes of specific areas lacking spiralization. In particular, the centromeric regions of chromosomes 1,9, and 16, a short region on the long arm of chromosomes 1 and 2, and the distal heterochromatic part of the long arm of the Y chromosome were despiralized. The despiralization pattern of DAPI is compared with those previously obtained with Hoechst 33258 and Distamycin A.     

Cytochemistry and freeze-fracture of membranes isolated from the electrocyte of Electrophorus electricus (L.)

Summary Membranes were isolated from the main electric organ of Electrophorus electricus and studied by means of cytochemistry and freezefracture. The membrane fractions consisted of vesicles inside-in as determined by localization of anionic sites using colloidal iron and cationized ferritin particles. The anionic sites were not homogeneously distributed on the surface of the vesicle. Freeze-fracture showed the presence of intramembranous particles associated with either protoplasmic (P) or extracellular (E) faces of the membrane. Regions of the membrane without particles were observed. The results are discussed in relation to the existence of association between intramembranous particles and membrane receptors.For all correspondence     

On the fine structure of the electrocyte of Electrophorus electricus L.

Summary The general ultrastructure of the electrocyte, the basic unit of the electric organs of Electrophorus electricus, is analyzed. Presented herein are detailed observations of the syncytial surface, its fibrillar coat, invaginations of the plasma membrane and synaptic terminals. Using Thiéry's method glycogen granules were identified in the syncytial cytoplasm and inside the synaptic terminals, their size and structure being compatible with the muscular origin of the electric organs, to which the filamentous meshwork found in the cytoplasm may be related. Among the perinuclear-organelles, are dense bodies with crystalline patterns. The mitochondrial matrix contains dense granules, their size and structure varying according to the organ to which they belong and to the fixation method used.This work has been supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Conselho de Ensino para Graduados da UFRJ and Banco Nacional de Desenvolvimento Econômico, FUNTEC-241