Oxidative deficiencies and some ultrastructural features of acridine-induced male strains of Allomyces arbusculus

Summary A high proportion of small, frequently TTC^- and highly (some 100%) masculinized gametophytic colonies have been produced from meiospores of Allomyces arbusculus plated on acridine-containing media.Endogenous O₂-consumption as well as succinate dehydrogenase and cytochrome oxidase activities are reduced in the acridine-treated masculinized strains studied. Such sharp deficiencies in the oxidative metabolism are paralleled in an acridine-male strain by structural defects such as highly reduced number of cristae in the mitochondria.     

Amsacrine binds in a cooperative manner to deoxyribonucleic acid

The intercalative binding of the acridine antitumour drug 4'-(9-acridinylamino) methane-sulphonate-m-anisidine, a known inhibitor of nucleic acid synthesis, to native calf thymus DNA has been studied using optical titration method. Amsacrine (AMSA) exhibits positive cooperativity in their equilibrium binding to DNA as indicated by the positive slope in the initial region of the binding isotherms (Scatchard plots) under conditions simulating physiological ionic strengths. m-AMSA binds with a higher degree of cooperativity than o-AMSA. Although this correlates with the effectiveness of the drugs as antitumour agents, the exact relationship between the observation of cooperative binding and pharmacological activity is yet to be determined.     

Light and scanning electron microscopic studies on the effect of biocidal plant sap on the gills of a hill stream fish, Garra lamta (Ham.)

The effect of a biocidal plant sap ( Terminalia tomentosa ) on the gills of a swift-current-adapted hill-stream fish, Garra lamia , has been investigated using light and scanning electron microscopy. The biocidal plant sap affected the dissociation of the gill filament and lamellar epithelia to expose their microvasculature. Some findings on the microvasculature are discussed in the light of their probable functions. Fusion of lamellae and prominent chloride cells are further effects of the plant sap, and their impact on respiratory and osmoregulatory functions of the fish are discussed.
Use of biocidal plant sap in mass killing of hill-stream fish is considered in relation to conservation.     

Ribosomal RNA cistrons in Allomyces arbuscula

Bulk and nuclear DNA have been fractionated by preparative neutral CsCl equilibrium density gradient centrifugation and each fraction hybridized to labeled rRNA (25 + 18 S). The cistrons coding for rRNA appeared on the light side of the main peak. Hybridization of the nuclear DNA fractionated by preparative Ag+-Cs2SO4 gradients at different pHs showed that the banding profile did not change as compared to the CsCl pattern. In Hg2+-Cs2SO4 gradients, however, the peak of the fRNA-DNA hybrids shifted on the heavier side of the profile. This indicates that the ribosomal RNA cistrons in Allomyces are A-T-rich. Hybridization with homologous rRNA showed that, at saturation, 3.25% of the DNA is complementary to rRNA. With the genome size of 1.7-10(10) daltons, the multiplicity of rRNA cistrons has been found to be close to 270.     

Presence of gamma glutamyl transferase in Mycobacterium smegmatis

The presence of gamma glutamyl transferase (GGT) has been established in Mycobacterium smegmatis. The 10,000 x g supernatant demonstrated only hydrolase activity and did not exhibit any transpeptidase activity. Most of the transferase activity was recovered in 100,000 x g supernatant demonstrating that GGT is a cytosolic enzyme. Maximum activity of GGT was observed at two days of growth and the activity decreased significantly till the seventh day of growth when mycobacteria was grown as stationary culture. The km for gamma glutamyl-p-nitroanilide was found to be 0.074 mM and Vmax for the reaction approached 11.9 nmol per min per mg protein. L-serine + borate was found to be a competitive inhibitor (Ki 12.05 mM) for GGT activity. The pH optimum for GGT activity was observed between 7.5 to 8.5 and temperature above 35 degrees C rapidly inactivated the enzyme activity. To the best of our knowledge, this is the first report which unequivocally establishes the presence of GGT activity in 10,000 x g supernatant of M. smegmatis.     

Effect of body size on the dimensions of the respiratory organs of a freshwater catfish,Mystus vittatus

The data on gill and skin dimensions of 12 freshwater catfishMystus vittatus ranging from 3 g to 23 g in relation to body weight have been analysed using logarithmic transformation. The exponent value for total gill area was 0.789; corresponding values for 1st, 2nd, 3rd and 4th gill arches and skin were 0.753, 0.772, 0.816, 0.823 and 0.631 respectively. The gill diffusing capacity (0.211) was greater than that for skin (0.002).