No abstract

Dehydrogenase activity (DHA) in Gram-positive Staphylococcus aureus isolated from degenerated wound, Gram-negative Salmonella typhi isolated from stool, and Gramnegative Escherichia coli from a high vaginal swab were assayed. Inhibition of dehydrogenase activity of the test organisms by ethanol extract of Euphorbia hyssopifolia, and Euphorbia hirta, were determined and compared to standard antibiotics (Ciprofloxacin and Gentamycin). The total dehydrogenase assay was done using 2, 3, 5triphenyl tetrazolium chloride (TTC) as the artificial electron acceptor which was reduced to the red-coloured triphenyl-formazan (TPF). Response of the bacterial isolates varied with extract concentration. Dehydrogenase activity was progressively inhibited in a logistic dose-response fashion in the test organism by the extracts and standard drugs. All extract and standards achieved at least 70% inhibition within the tested doses (0-2000µg/ml), except for Euphorbia hirta against Staphylococcus aureus. Threshold inhibitory concentrations (IC 50 ) for Euphorbia hyssopifolia against Staphylococcus aureus, Salmonella typhi and Escherichia coli were 59.92µg/ml, 234.90µg/ml, and 492.46µg/ml respectively, while for Euphorbia hirta IC 50 against Salmonella typhi and Escherichia coli was 99.67µg/ml,and 165.90µg/ml with no significant inhibition against Staphylococcus aureus. Inhibition of dehydrogenase activity in the test organism by the extract compared well with the standard antibiotics. Euphorbia hyssopifolia was effective against Grampositive Staphylococcus aureus implicated in delayed wound healing than Gram-negative Salmonella typhi and Escherichia coli implicated in typhoid fever and urinary tract

Experiments were designed to determine whether some chemical lesions such as O6-methylguanine, N7-methylguanine, and N3-methyladenine induced in rat liver DNA by the hepatocarcinogen dimethylnitrosamine permit replication in vivo. For this purpose, [14C]dimethylnitrosamine was administered to methylate the parental strand of liver DNA. Four hours later, a time period when the carcinogen cannot be detected in either the liver or the blood, rats were subjected to partial hepatectomy in order to induce DNA replication. During the S phase, 5-bromo-2-deoxyuridine was administered to render the newly made strands heavy. The rebanded, hybrid, hepatic DNA of density 1.714 g/cm3 and greater was pooled from the neutral cesium chloride gradient, dialyzed, and lyophilized. The hybrid DNA was then treated with S1 nuclease to digest any single-stranded regions. The results obtained indicated the presence of O6-methylguanine, N7-methylguanine, and N3-methyladenine in S1 nuclease resistant, hybrid DNA. The results are interpreted to indicate that these chemical lesions permitted in vivo DNA replication.

The promoting action of four barbiturates, and their modulation of the promoting action of a choline-devoid (CD) diet was investigated by quantitating the gamma-glutamyltranspeptidase (GGT)-positive foci which developed in the liver of rats exposed to a single injection of diethylnitrosamine. Phenobarbital (PHB), pentobarbital (PTB) and amobarbital (AMB), exerted a promoting action, while barbituric acid (BA) had no effect. Addition of PHB or PTB to a CD diet resulted in a synergistic promoting action, but AMB had only an additive effect. Feeding a CD diet to rats caused a stimulation of liver DNA synthesis and of cell proliferation. These effects of the diet were markedly inhibited by addition of PHB or PTB, while addition of AMB resulted only in an inhibition of the enhanced proliferation of hepatocytes. No inhibitory effect was exerted by BA. The results indicate that the liver tumor promoting action of PHB and of barbiturates is dependent upon biological effects related to the presence of an alkyl group in their side chain. It is hypothesized that the promoting action of the agents herein studied may involve two components, a stimulation of the proliferation of initiated liver cells, and a suppression of the proliferation of non-initiated cells.

The mechanism by which amino acids increase the cellular levels of orotic acid (OA) was investigated. Administration ofglycine (2.5 mmoles/100 g) to rats resulted in a 100-fold increase in urinary OA excretion, which was inhibited by pretreatment with cycloheximide or actinomycin D. The induction of OA synthesis from NH,Cl but not from carbamoylaspartate (CA) was inhibited by cycloheximide, indicating that the cycloheximide sensitive step was after the formation of ammonia and before the formation of CA. The glycine-stimulated OA synthesis was not inhibited by acivicin, a potent inhibitor of the cytosolic carbamoylphosphate (CP) synthctase, implicating the mitochondria1 CP synthetase in supplying the CP for OA synthesis. Preliminary results indicated that cycloheximide did not inhibit glycine-induced urea synthesis to any significant extent. The results thus suggest that (i) the increased OA synthesis induced by glycine requires a transcription-translation dependent step and (ii) the regulatory step may be the transport of mitochondria1 CP to cytosol and/or the synthesis of cytosolic CA. Attempts to determine whether increased exposure of urinary bladder to high concentrations of OA will influence bladder tumorigenesis revealed that chronic administration ofglycine (2.5 mmoles/lOO g, ip, daily, 5 days a week for 20 weeks) resulted in a 44% increased incidence of hyperplastic, preneoplastic, and neoplastic lesions. Some of these rats also exhibited stones in urinary bladders. The mechanism by which glycine induces tumorigenesis in the urinary bladder is currently being explored.