Prostaglandins can modify gamma-radiation and chemical induced cytotoxicity and genetic damage in vitro and in vivo

The effect of prostaglandin E1, E2, and F2 alpha on gamma-radiation, benzo(a)pyrene and diphenylhydantoin-induced cytotoxicity in vivo and genotoxicity in vitro was investigated. Prostaglandin E1 prevented both cytotoxic and genotoxic actions of all the three agents, where as both PGE2 and PGF2 alpha were ineffective. In fact, it was seen that both PGE2 and PGF2 alpha are genotoxic by themselves. Gamma-linolenic acid and dihomogamma-linolenic acid, the precursor of PGE1 were also as protective as that of PGE1, where as arachidonic acid, the precursor of 2 series PGs, has genotoxic actions to human lymphocytes in vitro. These results suggest that prostaglandins and their precursors can determine the susceptibility of cells to cytotoxic and genotoxic actions of chemicals and radiation. This study is particularly interesting since, it is known that some tumor cells contain excess of PGE2 and PGF2 alpha and many carcinogens can augment the synthesis of 2 series of PGs.     

Protective role of fructose 1,6-bisphosphate during CCl4 hepatotoxicity in rats.

Rats were injected intraperitoneally with CCl4 (2.5 ml/kg body wt.) and the hepatotoxicity was compared with that of rats receiving the same dose of CCl4 and an intraperitoneal injection of fructose 1,6-bisphosphate (2 g/kg body wt.). A 50-70% decrease in plasma aspartate aminotransferase and alanine aminotransferase activities was observed in the latter treatment, indicating a protective role of the sugar bisphosphate in CCl4 hepatotoxicity. The protection was accompanied by elevated hepatic activities of ornithine decarboxylase at 2, 6 and 24 h, S-adenosylmethionine decarboxylase at 6 h, and spermidine N1-acetyltransferase at 2 h. The increase in the enzymes involved in polyamine metabolism was shown in our previous work [Rao, Young & Mehendale (1989) J. Biochem. Toxicol. 4, 55-63] to correlate with increased polyamine synthesis or interconversion, which was related to the extent of hepatocellular regeneration. The hepatic contents of fructose 1,6-bisphosphate and ATP significantly decreased after CCl4 treatment, and administration of the sugar bisphosphate increased hepatic ATP. Fructose 1,6-bisphosphate, an intermediary metabolite of the glycolytic pathway, may decrease CCl4 toxicity by increasing the ATP in the hepatocytes. The ATP generated is useful for hepatocellular regeneration and tissue repair, events which enable the liver to overcome CCl4 injury.     

Characterization of poly(ADP-ribosyl)ated domains of rat pachytene chromatin.

Poly(ADP-ribosyl)ation of nuclear proteins was several-fold higher in the pachytene spermatocytes than in the premeiotic germ cells of the rat. Among the histones of the pachytene nucleus, histone subtypes H2A, H1 and H3 were poly(ADP-ribosyl)ated. Based on the immunoaffinity fractionation procedure of Malik, Miwa, Sugimara & Smulson [(1983) Proc. Natl. Acad. Sci. U.S.A. 80, 2554-2558] we have fractionated DNAase-II-solubilized chromatin into poly(ADP-ribosyl)ated chromatin (PAC) and non-poly(ADP-ribosyl)ated chromatin (non-PAC) domains on an anti-[poly(ADP-ribose)] IgG affinity matrix. Approx. 2.5% of the pachytene chromatin represented the PAC domains. A significant amount of [alpha-32P]dATP-labelled pachytene chromatin (labelled in vitro) was bound to the affinity matrix. The DNA of pachytene PAC domains had internal strand breaks, significant length of gaps and ligatable ends, namely 5'-phosphoryl and 3'-hydroxyl termini. On the other hand, the PAC domains from 18 h regenerating liver had very few gaps, if any. The presence of gaps in the pachytene PAC DNA was also evident from thermal denaturation studies. Although many of the polypeptides were common to the PAC domains of both pachytene and regenerating liver, the DNA sequences associated with these domains were quite different. A 20 kDa protein and the testis-specific histone H1t were selectively enriched in the pachytene PAC domains. The pachytene PAC domains also contained approx. 10% of the messenger coding sequences present in the DNAase-II-solubilized chromatin. The pachytene PAC domains, therefore, may represent highly enriched DNA-repair domains of the pachytene nucleus.     

Hydrogen peroxide permeation across liposomal membranes: a novel method to assess structural flaws in liposomes

Hydrogen peroxide permeation across large multilamellar vesicles of defined and complex lipid composition was shown to obey precise kinetic relationships for the activity of the occluded catalase. Careful assay conditions precluded simultaneous peroxidative damage to the lipids. The kinetic data was consistent with a barrier role for the bilayer for hydrogen peroxide permeation. More interestingly, hydrogen peroxide permeation across liposomes of complex lipid mixtures exhibited osmotic inhibition of permeation of hydrogen peroxide. On the other hand, purified egg lecithin vesicles did not exhibit any effect of external osmolality on hydrogen peroxide permeation in an experimentally defined non-lytic zone of external osmolarity. These results argue in favour of a heterogeneous, heteroporous structure of bilayers with complex lipid composition.     

Development of an enzymatic procedure to produce high-protein amaranth flour

Summary A basic procedure was developed to produce high-protein amaranth flour (HPAF) using a commercial preparation of heat-stable alpha-amylase. Slurries (20%, w/v) of gelatinized whole flour were liquefied at 70 and 90°C, pH 6.5, 0.1% (w/v) enzyme concentration and 30 min hydrolysis time. Protein content of raw flour was increased from 15 to 29.6 or 39.3% at liquefaction temperatures of 70 or 90°C, respectively. Some physicochemical and functional properties of HPAF were assessed. HPAF might be used as a dry milk extender.     

A physico-chemical approach to the study of the binding interaction between S-adenosyl-L-methionine and polyanions: binding constants and nature of the interaction with sodium poly(styrene sulfonate)

The interaction between S-adenosyl-L-methionine (AdoMet) and sodium poly(styrene sulfonate) NaPSS) was studied by means of ultrafiltration and ultraviolet absorption spectroscopy at several pH values and sodium sulfate concentrations. The results obtained are interpreted mainly in terms of electrostatic interactions and permit the evaluation of the binding constants under different experimental conditions. Furthermore, ultraviolet absorption spectroscopy data show a specific short-range interaction between the aromatic electronic system of AdoMet and the NaPSS aromatic ring. The results indicate that the binding strength is greatly affected by the AdoMet positive charge on the adenine ring. The other positive charges on both the sulfonic pole and the amino acidic group of AdoMet contribute only weakly to the binding to the polyanionic matrix, thus assuring some stability of AdoMet even at physiological pH.     

Developmental and Dimensional Changes in the Cambial Fusiform Initials ofHoloptelea integrifolia (Roxb.) Planch.

Divisional activity, intrusive growth of the cell wall and loss of fusiform initials have been studied in Holoptelea integrifolia. The dimensional changes in relation to mean length, length frequency, mean width and length variation in relation to fibre length have also been analysed.     

Effects of nucleotide bromination on the stabilities of Z-RNA and Z-DNA: a molecular mechanics/thermodynamic perturbation study

The structures of ZI- and ZII-form RNA and DNA oligonucleotides were energy minimized in vacuum using the AMBER molecular mechanics force field. Alternating C-G sequences were studied containing either unmodified nucleotides, 8-bromoguanosine in place of all guanosine residues, 5-bromocytidine in place of all cytidine residues, or all modified residues. Some molecules were also energy minimized in the presence of H2O and cations. Free energy perturbation calculations were done in which G8 and C5 hydrogen atoms in one or two residues of Z-form RNAs and DNAs were replaced in a stepwise manner by bromines. Bromination had little effect on the structures of the energy-minimized molecules. Both the minimized molecular energies and the results of the perturbation calculations indicate that bromination of guanosine at C8 will stabilize the Z forms of RNA and DNA relative to the nonbrominated Z form, while bromination of cytidine at C5 stabilizes Z-DNA and destabilizes Z-RNA. These results are in agreement with experimental data. The destabilizing effect of br5C in Z-RNAs is apparently due to an unfavorable interaction between the negatively charged C5 bromine atom and the guanosine hydroxyl group. The vacuum-minimized energies of the ZII-form oligonucleotides are lower than those of the corresponding ZI-form molecules for both RNA and DNA. Previous x-ray diffraction, nmr, and molecular mechanics studies indicate that hydration effects may favor the ZI conformation over the ZII form in DNA. Molecular mechanics calculations show that the ZII-ZI energy differences for the RNAs are greater than three times those obtained for the DNAs. This is due to structurally reinforcing hydrogen-bonding interactions involving the hydroxyl groups in the ZII form, especially between the guanosine hydroxyl hydrogen atom and the 3'-adjacent phosphate oxygen. In addition, the cytidine hydroxyl oxygen forms a hydrogen bond with the 5'-adjacent guanosine amino group in the ZII-form molecule. Both of these interactions are less likely in the ZI-form molecule: the former due to the orientation of the GpC phosphate away from the guanosine ribose in the ZI form, and the latter apparently due to competitive hydrogen bonding of the cytidine 2'-hydroxyl hydrogen with the cytosine carbonyl oxygen in the ZI form. The hydrogen-bonding interaction between the cytidine hydroxyl oxygen and the 5'-adjacent guanosine amino group in Z-RNA twists the amino group out of the plane of the base. This may be responsible for differences in the CD and Raman spectra of Z-RNA and Z-DNA.     

Structure dynamics of the hemoglobin mutants Hb H?tel Dieu, HbG Philadelphia, HbJ Mexico, Hb St. Mandé and Hb San Diego, studied by nanosecond-laser-flash photolysis

The kinetics of the change from the carboxy to the deoxy conformation of the mutated hemoglobins mentioned in the title and of normal human adult hemoglobin were determined from measurements of light absorption changes occurring up to 50 microseconds after nanosecond-laser photodissociation of the corresponding CO complexes. The spectral evolution of the mutated hemoglobins was found to be similar in its main features to that of normal hemoglobin. The kinetics could be decomposed into two phases with rates 1.1-1.8 x 10(6) s-1 and 0.17-0.34 x 10(6) s-1 (except Hb St. Mandé which displayed only the faster phase). Study of the mutated subunits of HbJ Mexico (alpha subunit) and Hb H?tel Dieu (beta subunit) showed that they convert exponentially to the stable deoxy state after photodeligation at the same rates as the corresponding subunits of normal Hb: 1.1 x 10(6) s-1 (alpha) and 0.3 x 10(6) s-1 (beta). The results indicate that there is no direct correlation between the kinetics of spectral relaxation in the time range studied and the oxygenation properties for these hemoglobins. However, there is some indication that the kinetics are dependent upon the region of mutation.