X-Ray radiography for studying diffusion characteristics of sucrose in plaster of paris matrix containing yeast cells

Summary X-Ray radiography was employed to monitor the diffusion of sucrose into plaster of Paris matrix containing 20% yeast cells. It was observed that the depth of penetration of tracer P_b detected by radiography matched with the substrate penetration detected by chemical test. However electron probe microanalysis (EPMA) did not yield any conclusive evidence regarding the movements of tracer P_b and substrate to the same extent.     

A high affinity Ca2(+)-ATPase on the surface membrane of Leishmania donovani promastigote

A Ca2(+)-dependent ATP-hydrolytic activity was detected in the crude membrane ghost of the promastigote or vector form of the protozoal parasite Leishmania donovani, the pathogen responsible for kala azar. The Ca2(+)-ATPase was purified to apparent homogeneity after solubilization with deoxycholate. The enzyme consists of two subunits of Mr = 51,000 and 57,000 and has an apparent molecular weight of 215,000 +/- 12,000. The enzyme activity is exclusively dependent on Ca2+, and the pure enzyme can hydrolyze 1.6 mumol of ATP/min/mg of protein. The apparent Km for Ca2+ is 35 nM, which is further reduced to 12 nM in the presence of heterologous calmodulin. The enzyme is sensitive to vanadate, but is insensitive to oligomycin and ouabain. The enzyme is strongly associated with the plasma membrane and has its catalytic site oriented toward the cytoplasmic face. The enzyme spans across the plasma membrane as surface labeling with radioiodine shows considerable radioactivity in the completely purified enzyme. The localization and orientation of this high affinity, calmodulin-sensitive Ca2(+)-ATPase suggest some role of this enzyme in Ca2+ movement in the life cycle of this protozoal parasite.     

Acid pH-induced fusion of cells by herpes simplex virus glycoproteins gB an gD

Enveloped animal viruses enter host cells either by direct fusion at neutral pH or by endocytosis. Herpes simplex virus (HSV) is believed to fuse with the plasma membrane of cells at neutral pH, and the glycoproteins gB and gD have been implicated in virus entry and cell fusion. Using cloned gB or gD genes, we show that cells expressing HSV-1 glycoproteins gB or gD can undergo fusion to form polykaryons by exposure only to acidic pH. The low pH-induced cell fusion was blocked in the presence of monoclonal antibodies specific to the glycoproteins. Infection of cells expressing gB or gD glycoproteins with HSV-1 inhibited the low pH-induced cell fusion. The results suggest that although the glycoproteins gB and gD possess fusogenic activity at acidic pH, other HSV proteins may regulate it such that in the virus-infected cell, this fusion activity is blocked.     

Shedding of vesicular stomatitis virus soluble glycoprotein by removal of carboxy-terminal peptide.

A comparison of partial NH2-terminal sequences of vesicular stomatitis viral glycoprotein G (molecular weight, 69,000) and the soluble extracellular glycoprotein antigen Gs (molecular weight, 57,000) shows that both of the sequences are identical. Tryptic fingerprint analyses show that Gs lacks the carboxy-terminal region containing the membrane-anchoring hydrophobic domain of G. These results suggest that Gs is formed by cleavage in the carboxy-terminal region of G.     

Effect of continuous cropping and fertilizer use on the organic nitrogen fractions in a typic ustochrept soil

Summary The influence of continuous cropping and soil test based fertilizer use on the organic nitrogen fractions in the plough layer has been studied in a Typic Ustochrept soil. Seven years of multiple cropping without manuring caused marked depletion in all the hydrolysable fractions except unidentified hydrolysable N namely, hexosamine (48.8%), hydrolysable ammonium (23.9%) and amino acid (7.3%) as compared to an adjacent fallow. Fertilizer nitrogen application maintained the levels of various forms of N as in the fallow plots and nitrogen in conjunction with phosphorus raised the status of amino acid N. Phosphate improved the contents of hydrolyzable ammonium and total hydrolyzable N whereas farmyard manure enhanced the latter only. The system of intensive cropping followed with appreciably high doses of fertilizers favoured greater immobilization of N in hydrolyzable ammonium and total hydrolyzable fractions. Original not seen     

Some structural features of the d-glucan from the seed of Mirabilis jalapa

The cotyledon of the seed of Mirabilis jalapa was found to contain a d-glucan. Methylation, periodate oxidation, and graded and enzymic hydrolysis studies were conducted to elucidate its structure. For every 38 d-glucosyl residues therein, 34 are (1→4)- and 3 are (1→3)-linked; the d-glucosyl unit at the branch point is linked through O-1, O-2, and O-4. In some places in the chain, there are at least three (1→3)-linked d-glucosyl residues in a sequence. Both α- and β-d-glucosidic linkages are present in the polysaccharide, the former preponderating. The d-glucan gave with iodine a faint blue color that had λ_max 420 nm.     

Biochemical mechanism of nitrofurantoin resistance inVibrio el tor

Vibrio el tor cells contain a constitutive reductase enzyme which converts nitrofurantoin to an active principle that is responsible for the observed antibacterial activity of the drug. Acquisition of resistance of this strain towards nitrofurantoin is associated with the loss of this reductase. This enzyme is located in the periplasmic region of the nitrofurantoin-sensitive cells, and seems to play an important role in transporting the drug into the cells.