Four new species of Cayaponia (Cucurbitaceae) from Brazil and Bolivia

Four new species ofCayaponia are described and illustrated: three from Brazil (C. cogniauxiana, C. nitida andC. rugosa) and one from Brazil and Bolivia (C. ferruginea).     

Uncoupling of mitochondrial oxidative phosphorylation by thallium.

The mechanism of integration of λ$\text{bio}$ll, which is deleted of all the known λ recombination genes, was studied using $\text{bio}$ deleted hosts as recipients. The presence of $\text{rec}$BC DNase and $\text{exo}$I in the recipient cells affected the fate of λ$\text{bio}$ll DNA. In nine of ten $\text{imm}\text{λ}{}^{\mathrm{+}}$ transductants, insertion of the λ$\text{bio}$ll genome took place somewhere between J and N and the remaining one had abnormally permuted prophage λ. In this lysogen (#42), the sequence of prophage genes was similar to that of vegetative phage λ. The properties of lysogen #42 were compared with those of other lysogens.     

Identification of a phosphorylated form of phosphoenolpyruvate carboxykinase from the yeast Saccharomyces cerevisiae

A phosphoprotein of 65 kDa, as determined by SDS-gel electrophoresis, has been isolated from yeast crude extracts. This phospho form copurifies with phosphoenolpyruvate carboxykinase in the enzyme purification procedure worked out in our laboratory (Tortora, P., Hanozet, G.M. and Guerritore, A. (1985) Anal. Biochem. 144, 179-185). Moreover, both proteins bind strongly to 5'AMP-Sepharose 4B in the presence of Mn2+, whereas a substantially lower binding occurs if Mn2+ is replaced by Mg2+. This binding pattern is consistent with the well-known Mn2+-dependence of yeast phosphoenolpyruvate carboxykinase. These data suggest that the 65-kDa protein might be a phosphorylation product of the native enzyme. Furthermore, although the phospho form is not immunoprecipitated by anti-phosphoenolpyruvate carboxykinase antibodies, addition of Protein A-Sepharose CL-4B to crude extracts preincubated with the antibodies results in the binding to the resin of the phospho form, thus providing immunological evidence for its identification as a modified form of native enzyme. The same 65-kDa phosphoprotein is detectable in extracts from cells grown in the presence of [32P]Pi, as well as in cell extracts incubated with [gamma-32P]ATP. Moreover, digestion of the phosphoprotein with BrCN or with Staphylococcus aureus V8 proteinase, yields two and three fragments, respectively, which appear parallel to digestion products of phosphoenolpyruvate carboxykinase, again supporting the proposed identification. Finally, analysis of the phosphorylated amino acids in the 65-kDa protein shows that phosphoserine is the only labelled phosphoamino acid.     

Evaluation of structural and secretory glycoconjugates in normal human jejunum by means of lectin histochemistry

Summary The labelling pattern of eight lectins was studied in jejunal samples from ten normal subjects, in order to define the normal distribution of structural and secretory glycoconjugates in the small bowel.The following lectins were studied by means of a peroxidase technique on formalin-fixed samples: Arachis hypogaea, Ricinus communis, Canavalia ensiformis, Lens culinaris, Phaseolus vulgaris, Triticum vulgaris, Ulex europaeus, Dolichos biflorus. Phaseolus vulgaris reacted with goblet cell mucus throughout the villus-crypt axis.Conversely Ulex europaeus, Dolichos biflorus and Triticum vulgaris lectin labelling of globet cells appeared to be confined to the upper part of the villi. This finding suggests that during cell migration from crypt to villus tip, the continuing maturation of goblet cells is associated with the differentiation of secretory carbohydrates, which probably parallels the cell maturation cycle. Lectin histochemistry appears to be a reliable tool for the study of structural and secretory glycoconjugates in the jejunal mucosa, and might be of value in the study of diseases in which the cell-maturation cycle in the small bowel is altered.     

DNA repair after gamma irradiation in lymphocytes exposed to low-frequency pulsed electromagnetic fields

The effect of exposure to extremely low-frequency pulsed electromagnetic fields (EMFs) on DNA repair capability and on cell survival in human lymphocytes damaged in vitro with gamma rays was studied by two different micromethods. In the first assay, which measures DNA repair synthesis (unscheduled DNA synthesis, UDS), lymphocyte cultures were stimulated with phytohemagglutinin (PHA) for 66 h and then treated with hydroxyurea (which blocks DNA replication), irradiated with 100 Gy of 60Co, pulsed with [3H]thymidine ([3H]TdR), and then exposed to pulsed EMFs for 6 h (the period in which cells repaired DNA damage). In the second assay, which measures cell survival after radiation or chemical damage, lymphocytes were first irradiated with graded doses of gamma rays or treated with diverse antiproliferative agents, and then stimulated with PHA, cultured for 72 h, and pulsed with [3H]TdR for the last 6 h of culture. In this case, immediately after the damage induced by either the radiation or chemicals, cultures were exposed to pulsed EMFs for 72 h, during which cell proliferation took place. Exposure to pulsed EMFs did not affect either UDS or cell survival, suggesting that this type of nonionizing radiation--to which humans may be exposed in the environment, and which is used for both diagnostic and therapeutic purposes--does not affect DNA repair mechanisms.     

Hypoxia as a risk factor for doxorubicin-induced cardiotoxicity: a NMR evaluation

Previous studies suggested that one possible mechanism of doxorubicin (DXR)-induced cardiomyopathy involves the depletion of high-energy phosphate stores. In this study, we used 31P nuclear magnetic resonance to assess the high-energy phosphate content in Langendorff perfused rat hearts. Hearts were perfused in normoxic conditions (spontaneous flow) or in partially hypoxic conditions obtained by perfusing at 50% of the spontaneous flow. DXR was used at the subtoxic conditions of 50 mg/l for 15 min and at the cardiotoxic concentration of 100 mg/l for 60 min. Left ventricular pressure (dP/dt), heart rate, myocardial ATP and PCr levels and PCr/ATP ratio were measured. We found that, in normoxic conditions, DXR (50 mg/l, 15 min) does not impair cellular high-energy phosphate metabolism. However, in mild hypoxic conditions, DXR induces a significant decrease in PCr/ATP ratio, due to a decrease in PCr and to a simultaneous increase in ATP. Similar results are obtained after 60 min perfusion with the cardiotoxic dose of DXR. This study suggests that hypoxia may represent a risk factor for the development of DXR-induced acute cardiotoxicity.     

Characterization of genetic transformation in Streptococcus oralis NCTC 11427: Expression of the pneumococcal amidase in S. oralis using a new shuttle vector

Summary We have worked out conditions for the study of competence development and genetic transformation in Streptococcus oralis NCTC 11427 (type strain), a species that contains choline in the cell wall. The peak of competence was found at the early exponential phase of growth and the optimal conditions for transformation were achieved with shuttle plasmids prepared from S. pneumoniae or from Escherichia coli serving as donor DNA. Transformation with dye-bouyant density gradient purified plasmid preparations followed first-order kinetics. The pneumococcal amidase can be expressed in S. oralis harbouring a plasmid carrying the lytA gene. This enzyme lysed the cell wall of the transformed cell in the presence of detergents.     

Direct detection of paramagnetic species in adriamycin perfused rat hearts

Direct detection of paramagnetic species in control and adriamycin-perfused rat hearts has been carried out. Depending on the flow rate of the perfusion solution (8,4,2 and 1 ml/min) different paramagnetic species were observed: Fe(III)(g = 2.12) at 4 ml/min; three types of oxygen centered radicals of which two in control hearts (g = 2.05 g = 2.038 g = g = 2.008) and the third one (g = 2.03 g = 2.005) in adriamycin perfused hearts, at 2 ml/min. The latter radical was the only one observed at perfusion rate of 1 ml/min both in control and adriamycin treated systems. A relationship between the intracellular enzymatic reductive activation of the anthracycline and the occurrence of ischemic conditions (4,2 and 1 ml/min) in myocardial tissues is proposed basing on the relative amounts of the paramagnetic species above mentioned.     

Polyamine-sensitive protein kinase from chick intestinal mucosa

Summary A cyclic nucleotide-independent protein kinase which phoshorylates preferentially acidic proteins such as casein or phosvitin was isolated from cytosol of chick duodenal mucosa. The enzyme was purified more than 633 fold to apparent homogeneity by ammonium sulfate fractionation, column chromatography on DEAE-cellulose, phosphocellulose, hydroxylapatite and by sucrose density gradient centrifugation. The native enzyme has a molecular weight of 131000 as measured by gel filtration. The enzyme is a complex protein containing three polypeptides of molecular weight of 39 000, 36 000 and 27 000. It behaves as a complex throughout its purification and gel filtration but its components are readily separated by electrophoresis in denaturing buffer. The 27 000 molecular weight band was selectively autophosphorylated when the enzyme was incubated in the presence of [-³²P]ATP.When casein was used as substrate, physiological concentrations of naturally occurring polyamines such as spermine and spermidine markedly stimulated enzyme activity. However with phosvitin as substrate polyamines were strong inhibitors of the enzyme activity. This contrasting effect on intestinal kinase activity was also apparent using cytoplasmic proteins as endogenous phosphate acceptors. A characterization of this differential effect is presented and some possible physiological implications are discussed.