Effect of intravenous infusion of insulin in diabetics with acute myocardial infarction.

Diabetes mellitus is associated with a high mortality after myocardial infarction. To see whether this may be decreased by improved diabetic control the effect of an insulin infusion regimen was studied in patients with acute myocardial infarction. From April 1982 to April 1983, 33 diabetics were admitted with acute myocardial infarction. Those being treated with diet alone or oral hypoglycaemic drugs continued with this unless control was poor, when they were changed to a "sliding scale" regimen of subcutaneous insulin injections thrice daily. Those already receiving insulin were maintained on thrice daily subcutaneous injections. From April 1983 to April 1984, 29 diabetics had acute myocardial infarction. Those receiving treatment with oral hypoglycaemic drugs or insulin were changed to continuous intravenous infusion of insulin, the aim being to maintain the blood glucose concentration at 4-7 mmol/I (72-126 mg/100 ml). Those being treated with diet alone continued with this if blood glucose concentrations were acceptable. Total mortality fell from 42% in the first year to 17% in the second (p less than 0.05). Over the same period mortality among non-diabetic patients with myocardial infarction did not change significantly. There was a significant fall in cardiac arrhythmias (expressed as the percentage of patients in whom arrhythmias were recorded) from 42% to 17% (p less than 0.05). The most significant fall in the incidence of complications occurred in those who had been receiving oral hypoglycaemic drugs on entry to the study (87% to 50%, p less than 0.05).     

Antiviral activity released from Aedes albopictus cells persistently infected with Semliki forest virus.

Aedes albopictus (mosquito) cells persistently infected with Semliki Forest virus released an agent which inhibited virus production by A. albopictus cells infected with homologous virus. Inhibition of virus production was accompanied by a marked reduction in the synthesis of viral RNA and viral proteins. Expression of the antiviral effect was prevented by pretreatment of cells with actinomycin. No analogous antiviral activity was detected in culture fluids of A. albopictus cells persistently infected with a flavivirus (Kunjin virus) or a bunyavirus (Bunyamwera virus).     

Biosynthesis of penicillin N and cephalosporin C: Antibiotic production and other features of the metabolism of a Cephalosporium sp

1. The production of penicillin N and cephalosporin C by two mutants of a Cephalosporium sp. has been studied with cultures grown in a chemically defined medium and with suspensions of washed mycelium in water or a buffered salt solution. 2. Antibiotic synthesis began at an early stage of growth and its rate per unit weight of mycelium appeared to pass its maximum as morphological changes were occurring in young hyphae. This rate subsequently declined, but rapid production could continue after net growth had ceased. 3. In a series of shake-flask fermentations in the growth medium, increases in the yield of penicillin N above the mean were correlated with much smaller increases in the yield of cephalosporin C and vice versa. 4. In suspensions of washed mycelium, moderate decreases in the efficiency of aeration increased the yield of penicillin N and decreased that of cephalosporin C. A similar result normally followed the addition of methionine to the suspension fluid, and in both cases there was usually an increase in the yield of the two antibiotics combined. 5. The apparent intracellular concentrations of the antibiotics were much lower than those attained extracellularly and also much lower than those of most of the amino acids in the intracellular pool. No detectable amount of [(14)C]penicillin N added to the extracellular fluid was found to enter the mycelium. 6. Very small amounts of peptide material whose behaviour was similar to that of the sulphonic acid of delta-(alpha-amino-adipoyl)cysteinylvaline on paper electrophoresis at pH1.8 were found in extracts of the mycelium that had been oxidized with performic acid. 6-Aminopenicillanic acid and 7-aminocephalosporanic acid were not detected. 7. Ultrasonic treatment of the mycelium resulted in rapid fragmentation of mycelial chains, rupture of many individual cells, and the liberation of amino acids and other substances into the medium. 8. Ultrasonically treated preparations synthesized penicillin N and cephalosporin C rapidly after a lag of 12hr. Antibiotic synthesis was accompanied by the growth of hyphae from swollen mycelial fragments and by the re-establishment of permeability barriers resulting in the uptake of amino acids from the medium.     

The role of valine in the biosynthesis of penicillin N and cephalosporin C by a Cephalosporium sp

1. The production of penicillin N, but not that of cephalosporin C, was inhibited by the addition of d-valine to suspensions in water of washed mycelium of Cephalosporium sp. 8650. The production of cephalosporin C was selectively inhibited by gamma-hydroxyvaline. 2. l-[(14)C]Valine was taken up rapidly and virtually completely by suspensions of washed mycelium but d-[(14)C]valine and alpha-oxo[(14)C]-isovalerate were taken up relatively slowly. 3. Part of the l-valine was rapidly degraded in the mycelium and part was incorporated into protein. Turnover of the valine in the amino acid pool was estimated to occur in 10-17min. 4. No detectable amount of l-[(14)C]valine was converted into the d-isomer in the mycelium. alpha-Oxo[(14)C]isovalerate was rapidly converted into l-[(14)C]valine in mycelium and mycelial extracts. 5. d-[(14)C]Valine was partially converted into the l-isomer in the mycelium and (14)C from d-valine was incorporated into protein. 6. The labelling of penicillin N and cephalosporin C by (14)C from l-[(14)C]valine was consistent with the view that l-valine is a direct precursor of C(5) fragments of both antibiotics and that any intermediates involved are present in relatively small pools in rapid turnover. 7. Labelling of the antibiotics with (14)C from d-[1-(14)C]valine appeared to occur after the latter had been converted into the l-isomer. Unlabelled d-valine did not decrease the efficiency of incorporation of (14)C from l-[1-(14)C]valine. 8. Intracellular peptide material which contained, among others, residues of alpha-aminoadipic acid, cysteine and valine, was rapidly labelled by (14)C from l-[1-(14)C]valine in a manner consistent with it being an intermediate in the biosynthesis of one or both of the antibiotics. 9. Labelling of penicillin N from l-[1-(14)C]valine occurred more rapidly than that of cephalosporin C. However, the effects of d-valine and gamma-hydroxyvaline on antibiotic production and the course of labelling of the antibiotics from l-[(14)C]valine could not readily be explained on the assumption that penicillin N was a precursor of cephalosporin C.     

Unique sequences in region VI of the flagellin gene of Salmonella typhi

The H1 (now renamed fliC; lino et al., 1988) alleles specifying antigenically different Salmonella flagellins are identical at their ends but differ greatly towards the middle, where there are two hypervariable segments (regions IV and VI). The flagellar antigen, d, of Salmonella typhi, is found also as phase-1 antigen in many other Salmonella species. We cloned the H1-d gene of a strain of S. typhi and determined the nucleotide sequence of its two hypervariable regions. Comparison with gene H1-d of Salmonella muenchen showed substantial differences in region VI: four scattered amino acid differences and ten adjacent amino acids in the inferred S. typhi sequence, all of which differ from the corresponding nine amino acids in the S. muenchen sequence. The results of polymerase chain reaction amplification indicated the presence of the S. typhi version in all of 18 additional S. typhi strains and the presence of the S. muenchen version in all four non-S. typhi species with flagellar antigen d. The difference in amino acid sequence in segment VI may be responsible for the minor serological differences between antigens d of S. typhi and antigen d of S. muenchen.     

High cooperativity, specificity, and multiplicity in the protein kinase C-lipid interaction

The number of phosphatidylserine molecules involved in activating protein kinase C was determined in a mixed micelle system where one monomer of protein kinase C binds to one detergent:lipid micelle of fixed composition. Unusually high cooperativity, specificity, and multiplicity in the protein kinase C-phospholipid interaction are demonstrated by examining the lipid dependence of enzymatic activity. The rates of autophosphorylation and substrate (histone) phosphorylation are specifically regulated by the phosphatidylserine content of the micelles. Hill coefficients of 8-11 were calculated for phosphatidylserine-dependent stimulation of enzyme activity, with a maximum occurring in micelles containing greater than or equal to 12 phosphatidylserine molecules. The high specificity that exists is illustrated by the fact that phosphatidylethanolamine and phosphatidylglycerol, but not phosphatidylcholine or phosphatidic acid, can replace only some of the phosphatidylserine molecules. We propose that Ca2+ and acidic phospholipids cause the protein to undergo a conformation change revealing multiple phosphatidylserine binding sites and resulting in the highly cooperative and specific interaction of protein kinase C with phosphatidylserine. Consistent with this, the proteolytic sensitivity of protein kinase C increases approximately 10-fold in the presence of phosphatidylserine and Ca2+ compared to Ca2+ alone. The high degree of cooperativity and specificity may provide a sensitive method for the physiological regulation of protein kinase C by phospholipid.