Effects of tetracyclines on the production of extracellular proteins by members of the propionibacteriaceae

The effect of tetracyclines on the synthesis of proteins in Propionibacterium avidum and P. acnes was examined. Synthesis of an extracellular lipase by P. avidum was slightly more sensitive to inhibition by tetracycline than total (cellular and extracellular) protein synthesis. The effect of tetracycline and other analogues on the synthesis of secreted proteins was also examined in P. avidum and P. acnes by protein radiolabelling experiments. In all cases the synthesis of secreted proteins was only about 2-fold more sensitive to inhibition by tetracyclines than total protein synthesis. These results contrast with previously published findings in Escherichia coli which show that synthesis of secreted proteins is highly susceptible to inhibition by tetracycline. The implications of these findings in relation to inhibition of membrane bound ribosomes by tetracyclines are discussed.     

Lignocaine Therapy after Acute Myocardial Infarction

Thirty-five patients with ventricular dysrhythmias and seven with other dysrhythmias after acute myocardial infarction were treated with intravenous lignocaine.Satisfactory initial suppression of ventricular ectopic beats was achieved in 27 (82%) of 33 patients after either a 50-mg. bolus or a 50-mg. bolus followed by a 100-mg. bolus of intravenous 2% lignocaine. Continuous suppression of ventricular ectopic beats was accomplished in 21 (78%) of these 27 patients by continuous intravenous lignocaine infusions of 1 to 2 mg. per minute. Recurrence of ventricular ectopic beats occurred in four patients despite lignocaine infusion rates of up to 6 mg. per minute. Six patients with ventricular ectopic beats developed ventricular fibrillation despite satisfactory initial suppression of their dysrhythmia by lignocaine. In three of them ventricular fibrillation supervened while they were receiving a lignocaine infusion and two subsequently died. Unheralded ventricular fibrillation occurred in three other patients between four and seven days after completing the full course of lignocaine therapy.Toxic effects of lignocaine were minimal in patients receiving 1 to 2 mg. per minute.     

Mutual relationships among bacterioids,leghaemoglobin and nitrogen content of Egyptian clover (Trifolium alexandrinum) and gram (Cicer arietinum)

Summary The mutual relationships among bacteroids, leghaemoglobin and nitrogen content of Egyptian clover (Trifolium alexandrinum) and gram (Cicer arietinum) at different age levels were studied. The relationships among the three factors were found to be positive and significant in both the plants.Part of a thesis by the Senior author approved for M.Sc. degree of Post-Graduate School, I.A.R.I., New Delhi.     

Origin of tetracycline efflux proteins: conclusions from nucleotide sequence analysis

The sequences of six tetracycline efflux proteins and three transport proteins which have some resemblance to them were compared. The tetracycline efflux proteins fall into three families: (i) those encoded by pBR322, RP1, and Tn10 (Escherichia coli); (ii) pT181 (Staphylococcus aureus) and pTHT15 (Bacillus subtilis); and (iii) tet347 (Streptomyces rimosus). There is global sequence homology within each of the first two families, but there is none between the families. The pT181/pTHT15 family shares close homology with the N-terminal half of the methylenomycin A efflux protein (Streptomyces coelicor), while tet347 resembles the C-terminal half. Portions of the N-terminal half of the Tn10-encoded protein show significant resemblance to portions in the N-terminal half of the pT181/pTHT15 family, but this sometimes occurs among transport proteins which do not have a common substrate. Tetracycline efflux proteins, therefore, appear to have arisen on at least two, or possibly three, separate occasions, probably from other transport proteins.     

Plasmodium falciparum activates endogenous Cl(-) channels of human erythrocytes by membrane oxidation.

Intraerythrocytic survival of the malaria parasite Plasmodium falciparum requires that host cells supply nutrients and dispose of waste products. This solute transport is accomplished by infection-induced new permeability pathways (NPP) in the erythrocyte membrane. Here, whole-cell patch-clamp and hemolysis experiments were performed to define properties of the NPP. Parasitized but not control erythrocytes constitutively expressed two types of anion conductances, differing in voltage dependence and sensitivity to inhibitors. In addition, infected but not control cells hemolyzed in isosmotic sorbitol solution. Both conductances and hemolysis of infected cells were inhibited by reducing agents. Conversely, oxidation induced identical conductances and hemolysis in non-infected erythrocytes. In conclusion, P.falciparum activates endogenous erythrocyte channels by applying oxidative stress to the host cell membrane.     

Short-chain organic acids at ph 5.0 kill Escherichia coli and Salmonella spp. without causing membrane perturbation

When strains of Escherichia coli K12 and Salmonella spp. were incubated with 0.5-0.7 mol/l formic or propionic acid at pH 5.0, propionic acid was more active than formic acid. It killed 90% of the cell population within 60 min compared with over 3 h for formic acid. Cell death was not associated with a reduction in culture turbidity or a loss of membrane integrity since morphologically normal membranes were observed by electron microscopy and only a small proportion of the cytoplasmic enzyme beta-galactosidase leaked into the supernatant fluid of acid-treated E. coli K12 cultures.