Evaluation of a serological test for tuberculosis.

The agglutination test of Nicholls was found to be ineffective in diagnosing active tuberculosis. A positive result (titre of 1/125 or more) was found in the serum of 74 (70%) out of 105 patients with newly diagnosed, smear-positive pulmonary tuberculosis; 61 (62%) out of 98 healthy family contacts; and 19 (63%) out of 30 patients with non-tuberculous conditions. These findings were not due to faulty technique since the results obtained at Hammersmith were similar to those obtained by Nicholls''s laboratory in the same serum samples. Twenty-seven of the tuberculous patients who had a negative result before treatment were retested two months after the start of chemotherapy but showed no evidence of a rising titre.     

Cowpea Rhizobia Producing Dark Nodules: Use in Competition Studies

During a program of screening rhizobia from West Africa, it was found that some strains produced nodules of unusually dark appearance on cowpeas, but not on peanuts, soybeans, pigeon peas, or mung beans. The dark pigmentation was in the bacteroid zone, was not correlated with nodule effectiveness, and was additional to the leghemoglobin pigment. Only rhizobial strains with a nongummy (“dry”) colony morphology produced dark nodules. Visually distinguishable pink and dark nodules formed on the same root when a mixture of pink and dark strains was applied as inoculum. The dark-nodule phenotype was therefore appraised as a marker and found to be useful for studying nodulation competition with strains of the orthodox pink-nodule type. The competitiveness of 10 pink-nodule strains was examined relative to a black-nodule strain, IRc 256; a range of competitiveness was obtained of less competitive than, equally competitive to, or more competitive than IRc 256. Patterns of primary (early) nodulation were generally the same as patterns of secondary (later) nodulation. Mixed infections by dark and pink strains produced piebald nodules, the frequency of occurrence of which was much greater among primary than among secondary nodules.     

Role of phospholipids in the DDT-induced efflux of potassium in human erythrocytes

Incubation of human erythrocytes for 1–2 h at 37°C in a suspension of dipalmitoylphosphatidylcholine (DPPC) liposomes results in a phospholipid enrichment of erythrocyte membranes by 45–55% and a depletion of cholesterol by 19–24%. The enrichment by DPPC was time and concentration dependent. By contrast, dioleoylphosphatidylcholine (DOPC) liposomes were less effective in enriching the membranes with phospholipid and in depleting the membranes of cholesterol. Concomitantly, the DDT-induced efflux of K⁺ was reduced in the case of DPPC-enriched erythrocytes but enhanced in DOPC-enriched erythrocytes. These results suggest that DDT partitions more readily into the unsaturated than the saturated phospholipids of the erythrocyte membrane. It is concluded that the extent to which DDT affects the flux of K⁺ across the membrane is dependent on the fluidity of the lipid phase. We also report here a rapid method for cholesterol depletion of red blood cells in comparison to previously reported methods.     

Laser flash photolysis studies of electron transfer between semiquinone and fully reduced free flavins and the cytochrome c-cytochrome oxidase complex

Laser flash photolysis has been used to determine the rate constants for the reduction of bovine cytochrome oxidase and the cytochrome c-cytochrome oxidase complex by the semiquinone and fully reduced forms of various flavin analogues (FH. and FH-, respectively). Under the condition used, the reaction of FH. with free cytochrome oxidase is too slow to compete with FH. disproportionation whereas FH- reacts measurably. Both FH. and FH- are effective in reducing the complex. The reduction of heme a in the complex is shown to proceed via cytochrome c, and a limiting first-order rate is observed in the case of FH- at high complex concentrations. The data indicate that the interaction site for electron transfer to cytochrome c is the same in the complex as with the free protein, and although a tight complex exists, at least small reactants like the flavins are not sterically hindered in their access to the bound cytochrome c. Moreover, the results also establish that intramolecular electron transfer between cytochrome c and cytochrome oxidase within the complex occurs with a first-order rate constant of greater than 700 s-1. Thus, the presence of cytochrome c greatly enhances electron transfer from reduced flavins to cytochrome oxidase.     

Phage P22 helps phage MB78 to overcome blockage of DNA maturation in rifampicin-resistant host

Bacteriophage MB78, a virulent phage ofSalmonella typhimurium cannot grow in rifampicin-resistant mutant (rif-39) of the host having altered RNA polymerase. The temperate phage P22 which cannot multiply in presence of the virulent phage MB78 can, however, help MB78 to overcome replication inhibition in rif-39. The processing of concatemeric phage DNA to monomer is blocked in this nonpermissive host. Superinfection with P22 induces synthesis of at least five P22 specific polypeptides which help phage MB78 in the processing of the concatemeric DNA and maturation of phage particles.     

Biopharmaceutical studies of spirobishexahydropyrimidine.

Oral administration of spirobishexahydropyrimidine showed an increase in the activity of serum transaminases, lactate dehydrogenase and alkaline phosphatase. Biological half life and other pharmacokinetic parameters showed rapid absorption and slow elimination of the drug.     

Mutagenic activity of oxathiolane steroids: structural requirement for the genotoxic activity in Salmonella and E. coli.

Oxathiolanes and disulfonyl derivatives of steroids were tested for mutagenic activity in the Ames tester strains. The test compounds exhibited mutagenic activity without metabolic activation although metabolic activation markedly enhanced their activity. A significant decrease in the survival of the radiation-sensitive mutants recA, lexA and rer of E. coli was observed as compared to their wild-type counterpart in the presence of the test steroid. Structural features which appear to be crucial for the mutagenic activity in these steroidal drugs are: (i) an electron-donating group at position 3, and (ii) a bulky group anchored at the 5th and 6th positions. The test steroids appear to damage DNA which in turn initiates the SOS repair with the concomitant induction of mutation.     

Immobilization of Rhodococcus equi DSM 89-133 onto porous celite beads for cholesterol side-chain cleavage

Summary Rhodococcus equi cells immobilized onto porous celite beads were active in side-chain cleavage of cholesterol. The effect of bead size, adsorption time and washing cycles were examined. The degradation of cholesterol side-chain using adsorbed cells was studied in batch and semi-continuous systems. Compared to free cells (80 mol%), the end-product (1,4-androstadiene-3,17-dione and 4-androstene-3,17-dione) profile was lower (70 mol%) with the celite-adsorbed system. Correspondence to: B. N. Johri     

Nucleotide sequences of three different isoforms of beta-tubulin cDNA from Chinese hamster ovary cells.

The complete cDNA sequences of two clones encoding beta-tubulin isotypes and the partial sequence of a third isoform from Chinese hamster ovary cells have been determined. The deduced amino acid sequences of the three isoforms show extensive homology to each other as well as with other alpha and beta-tubulin sequences from various species. These results provide evidence for the expression of three different isoforms of beta-tubulin in Chinese hamster ovary cells.     

Mammalian pyruvate carboxylase: effect of biotin on the synthesis and translocation of apo-enzyme into 3T3-L adipocyte mitochondria

The effect of biotin on the induction (and possible requirement for uptake into mitochondria) of apopyruvate carboxylase has been examined in 3T3-L adipocytes. Cells fed biotin-sufficient medium contained only holoenzyme in mitochondria and no apoenzyme was detected. The amount of apoenzyme elaborated in biotin-deficient 3T3-L adipocytes was comparable to the holopyruvate carboxylase protein found in cells maintained on biotin-sufficient medium. Like the holoenzyme, the apoenzyme was detected exclusively in the mitochondrial fraction of 3T3-L adipocytes. This indicates that the synthesis of apopyruvate carboxylase and its translocation into mitochondria occur independently of the cofactor, biotin.