Studies on amikhellin. II.-Inhibition of dna-polymerase from murine sarcoma leukemia virus.

We have previously reported that amikhellin binds to double-stranded DNA by an intercalation process (1). We now report that this drug inhibits the DNA-polymerase from murine sarcoma leukemia virus. The extent of inhibition was found to vary with the nature of the primer-template used : maximum with poly(rA)n-oligo(dT)10 (nucleotide ratio 20:1), minimum with poly(rA)n-poly(dT)n and intermediate with native calf thymus DNA. Experiments performed with synthetic templates of the (rA)-(dT) type have led to the following conclusions as to the mechanism of inhibition: 1) Amikhellin acts at an early stage of the synthesis reaction because the drug is no longer inhibitory when a limited extension of the oligo(dT) primers has been allowed to occur. However, mere incubation of the enzyme with the template in the absence of dTTP is not sufficient to confer resistance to the drug. 2) Progression of enzyme molecules actively engaged in polymerization is stopped when they reach downstream duplex regions to which amikhellin is bound.     

Studies on biologically active complexes of cobalt(II) and nickel(II) with dithiooxamide-derived ligands.

A number of cobalt(II) and nickel(II) complexes with novel dithiooxamide ligands derived from precursors such as benzonitrile, benzosulfonamide, benzaldehyde, benzoic acid, and phenol have been synthesized and characterized on the basis of their elemental analysis molar conductance, magnetic moment, H NMR and electronic and IR spectral data. These ligands and their complexes have been screened for their antibacterial activities against bacterial species Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, and Tuberculi bacilli. The studies indicate that in comparison to the ligands their metal complexes are more potent and antibacterial.     

Studies on organomercury(II) complexes of isoniazid

A number of organomercury(II) complexes involving isoniazid (I), of the type RHgCl(L)(II) [R = phenyl(C6H5), o-hydroxyphenyl (o-HOC6H4), p-hydroxyphenyl (p-HOC6H4), p-acetoxyphenyl (p-AcOC6H4), 2-furyl (2-C4H3O); L = isoniazid] have been synthesized and characterized. Conductance measurements indicate that the complexes are nonelectrolytes. From IR and UV studies, it is concluded that isoniazid acts as a bidentate ligand, coordinating through hydrazinic nitrogen and carbonyl oxygen. 1H and 13C NMR support the stoichiometry of the complexes. From fluoroscence studies a number of photochemical parameters have been elucidated. For the C6H5HgCl(L), p-HOC6H4HgCl(L), and p-AcOC6H4HgCl(L) complexes, thermogravimetric studies have been carried out and relevant kinetic and thermodynamic parameters for thermal degradation have been enumerated. In addition, the fragmentation pattern of the complexes has been analyzed on the basis of mass spectra. The C6H5HgCl(L) and p-HOC6H4HgCl(L) complexes have been screened for tuberculosis activity.     

Studies on the seasonal histocytological changes in the internal and chromaffin cells of male Puntius sophore (Ham) in relation to its reproductive cycle.

An attempt has been made to correlate the activities of interrenal and chromaffin cells with the reproductive cycle of Puntius sophore. Chromaffin cells do not have any significant bearing while interrenal cells undergo qualitative and quantitative changes which have been correlated with the various phases in the reproductive cycle of this fish. These cells undergo degranulation and vacuolisation during spawning phase, disorganisation during regression phase, and reorganisation and gradual growth during resting and prespawning phases. These cells thus appear to play an important role in the reproductive physiology of this fish.     

The influence of weather on the seasonal incidence of coffee berry moth,Prophantis smaragdina (Butler)

The seasonal incidence of the coffee berry moth, Prophantis smaragdina (Butler) (Lepidoptera: Pyralidae), was investigated on Coffea arabica L. in Jimma, Ethiopia. Our results showed that; the coffee berry moth was present throughout the study period except during November and December. The average incidence was 24.5% and the peak incidence (61%) was in September. Multiple correlation analysis was used to estimate the strength of association between weather variables and the incidence of the pest, and stepwise (both forward and backward) regression analysis was used to select the best explanatory variable. There were strong associations among the explanatory weather variables, indicating the potential problem of multicollinearity in the regression analysis. Relative humidity had a highly significant regression coefficient of 2.228 and was selected in the stepwise regression analysis as the best explanatory variable. The results of the study can be used in designing an integrated pest management strategy against the coffee berry moth.     

Studies of Zn(II) and Co(II) complexes of imidazole and n-methylimidazole with regard to the activity related ionization in carbonic anhydrase.

Mixed aquo-N-methylimidazole complexes of Co(II) have been studied as a function of pH to gain a fuller understanding of the metal-binding site in Co(II)-carbonic anhydrase. The inherent affinity of N-methylimidazole for Co(II) has been calculated along with a species distribution for the stepwise addition of ligand to the metal ion. From these studies, it is apparent that the occurrence of Zn(II) rather than Co(II) in native carbonic anhydrase can be explained by the stronger affinity of Zn(II) for imidazole and the preference of Zn(II) for a tetrahedral geometry as offered by the enzyme. Octahedral Co(II) fails to ionize metal bound water. However, at high pH, Co(II)-N-methylimidazole complexes interact directly with the hydroxide ion, generating species with visible spectra very similar to that of Co(II)-carbonic anhydrase. Tentative structures have been proposed for these species.     

Fungal Parasites of the Phytoplankton. II (Studies on British Chytrids, XII)

This paper brings together the species of Chytrid fungi recordedfrom large bodies of water in the British Isles. Four new speciesare described.     

Studies on new types of haustoria in some Central EuropeanRhinanthoideae (Scrophulariaceae)

Two new types of haustoria have been found in many representatives ofRhinanthoideae. Metahaustoria are stimulated by host roots but lack contact with them. They develop a massive haustorial core with a large- and a smalled-celled portion, but little vascular core. In very old metahaustoria the vascular core is much enlarged and numerous tracheal elements develop in the reduced haustorial core and cortex. Warthaustoria are very small, occur only in the upper portions of the root system, and have host contacts. Vascular and haustorial core, and the endophyte are lacking, the intrusive cells are usually not endogenous, but rather roothair-like. Wart-haustoria may represent reduced and partly inhibited normal haustoria.