Actinomyces in cervical smears of women using intrauterine contraceptive devices

Cervical smears from 1,784 women who attended the family planning clinics of the Institute for Research in Reproduction were examined for the presence of Actinomyces-like organisms. Among 815 intrauterine contraceptive device (IUD) users, the repeat smears from 57 women were positive for Actinomyces-like organisms, giving a prevalence rate of 6.99%. Immunofluorescent staining using specific antisera confirmed the presence of A. israelii in all 57 women. Forty IUD users whose smears were positive for Actinomyces-like organisms underwent bacteriologic culture studies; A. israelii was isolated in 23 of these cases. The clinical findings at the time of smear collection in the 57 IUD users were within normal limits. The initial cervical smears of all IUD users and both the initial and repeat smears of all nonusers were negative for Actinomyces-like organisms. The data indicate that prolonged use (greater than 2 years) of an inert or copper intrauterine device promotes the overgrowth of Actinomyces in the vagina and that this can be detected by routine cervical cytology.     

Inhibition of cell division by interferons: Changes in the transport and intracellular metabolism of thymidine in human lymphoblastoid (Daudi) cells

The Daudi line of human lymphoblastoid cells shows a high sensitivity towards growth inhibition by human interferons. In cells pretreated with 70 reference units/ml of an interferon preparation for 48 h, the incorporation of exogenous [3H]thymidine into DNA is inhibited by as much as 85%. We are investigating the extent to which this effect reflects a true inhibition of the rate of DNA synthesis or whether it may be caused by changes in the metabolic utilization of exogenous thymidine by the cells. Interferon treatment results in a 30% inhibition of the rate of membrane transport and a 60% decrease in the rate of phosphorylation of [3H]thymidine in vivo. The latter effect is due to a decrease in V of thymidine kinase without any change in the value of Km for this enzyme. In addition to these changes, incorporation of [3H]uridine into DNA, which occurs as a result of the intracellular conversion of this precursor into thymidine nucleotides, is also inhibited by 75%, whereas RNA labelling by [3H]uridine is decreased by only 15% in interferon-treated cells. Thus several different metabolic events associated with thymidine nucleotide metabolism and DNA synthesis in Daudi cells are disrupted by interferon treatment.     

Feedback inhibition of nitrogenase.

No inhibition of nitrogenase activity by physiological levels of NH4+ or carbamyl phosphate was observed in extracts of Azotobacter vinelandii. All of the 15N2 reduced by cultures which received no NH4+ was found in the cells. By contrast, more than 95% of the 15N2 reduced by cultures which had been given NH4+ was found in the medium. Failure to examine the culture medium would lead to the erroneous conclusion that N2 fixation is inhibited by NH4+. Nitrogenase in a derepressed mutant strain of A. vinelandii was fully active in vivo in the presence of NH4+. The addition of NH4Cl to N2-fixing cultures resulted in no decrease in the N2-reducing activity of intact cells of Klebsiella pneumoniae or Clostridium pasteurianum and only a small (15%) decrease in A. vinelandii. Therefore, no significant inhibition of nitrogenase by NH4+ or metabolites derived from NH4+ exists in A. vinelandii, K. pneumoniae, or C. pasteurianum.     

Role of ascorbic acid in auxin induced cell elongation

Summary Cytochemical detection of ascorbic acid in cultured root tips of Zea mays shows that dividing cells accumulate ascorbic acid in the cytoplasm. The localization pattern alters in the root tip as the cells begin to elongate. In elongating cells ascorbic acid is distinctly localized on cell walls. Ascorbic acid content per cell inreases with the onset of cell elongation. Fully elongated cells contain fivefold more ascorbic acid than meristematic cells. Cytophotometric analysis reveals a sharp and positive correlation (r=+0.93) between percentage increase in content of ascorbic acid per cell and corresponding increase in cell size at different phases of cell elongation. IAA treatment to the roots raises the content of ascorbic acid per cell with a parallel increase in size of cell. Involvement of ascorbic acid in IAA induced cell elongation is discussed.     

UDP-glucose: ceramide glucosyltransferase of rat brain: an association with smooth microsomes and requirement of an intact membrane for enzyme activity

Subcellular distribution of rat brain UDP-glucose:ceramide glucosyltransferase, the enzyme which catalyses the first step during the sequential addition of carbohydrate moieties for ganglioside biosynthesis, was studied. The activity of the enzyme was highest in the fraction rich in microsomes. Subfractionation of crude microsomal fractions resulted in a further enrichment of the enzyme activity in the fraction which contained smooth microsomes, thus suggesting that the enzyme is associated with microsomal membranes. The enzyme does not appear to be associated with synaptosomes or myelin. Treatment of the microsomal fraction with phospholipase A and C or detergents resulted in the loss of enzyme activity. Preincubation of the microsomal fraction at 37 °C also resulted in a loss of enzyme activity. These results suggest the requirement of specific membrane structure for the activity of the enzyme UDP-glucose:ceramide glucosyltransferase of rat brain. The amount of the enzyme activity lost during preincubation was dependent on the composition of the incubation medium and the age of the rats from which microsomal fractions were obtained.     

The interaction of bacterial lipopolysaccharide with phospholipid bilayers and monolayers

The association of bacterial lipopolysaccharide with artificial membranes was studied in an attempt to understand the mechanism of binding of lipopolysaccharide to cell surfaces and to look for an effect on membrane stability. The membrane models used were phospholipid bilayers and monolayers. As measured by survival time, lipopolysaccharide was found to decrease the stability of bilayers at a concentration of 300 μg/ml. When assayed by dielectric breakdown, an effect of lipopolysaccharide was noticeable at concentrations of 50 μg/ml. In studies involving the penetration of monomolecular films of various phospholipids, native and alkali-treated lipopolysaccharide both caused increases in surface pressure, and therefore penetrated the films. However, alkali-treated lipopolysaccharide was at least ten times more efficient than the native product in penetration. Alkali-treated lipopolysaccharide had a greater degree of surface activity than native lipopolysaccharide, since alkali-treated lipopolysaccharide formed monomolecular films by itself, whereas native lipopolysaccharide did not. The changes in the surface pressure and surface potential of phospholipid films produced by lipopolysaccharide in the subsolution suggested that the interaction of lipopolysaccharide with phospholipid monolayers was by a combination of penetration and adsorption to the undersurface.     

Glycosyl transferases of microsomal fractions from brain: synthesis of glucosyl ceramide and galactosyl ceramide during development and the distribution of glucose and galactose transferase in white and grey matter

Abstract— The substrate specificity for glycosyl transferases of microsomal fractions from brain was investigated. Ceramides were found to be better acceptors than sphingosine for both glucose and galactose when a Celite dispersion of lipid substrate was used. For galactose transfer only hydroxy fatty acid ceramide served as an acceptor. For transfer of glucose both non-hydroxy and hydroxy fatty acid ceramide served as acceptors, but the hydroxy fatty acid ceramide was the more effective of the two. Glucose transferase activity was found to be highest between birth and 15 days of age and declined slowly with later development. Galactose transferase activity did not appear until the 10th day of postnatal age and reached a peak at about the 30th day. Galactose transferase activity was present principally in white matter microsomes, but glucose transferase activity was present in the microsomal fractions of both white and grey matter. The developmental alteration in the activities of galactosyl and glucosyl transferases and their distribution in white and grey matter correlated with development and distribution of cerebroside and ganglioside, respectively.