Pathogenesis of arterial hypotension in cirrhotic rats with ascites: role of endogenous nitric oxide

Nitric oxide is a vasodilator tonically secreted by endothelial cells that is involved in the regulation of arteriolar tone. This study, which includes two protocols, was performed to investigate whether nitric oxide plays a role in the pathogenesis of arterial hypotension in cirrhosis with ascites. In protocol 1, the administration of increasing doses (25, 50, 250, 500 and 1,000 micrograms.kg-1.min-1) of the nitric oxide biosynthesis inhibitor N omega-nitro-L-arginine to 18 conscious rats with cirrhosis and ascites produced, at each dose tested, a significantly greater increase in arterial pressure than in 17 conscious control rats. At the lowest dose of N omega-nitro-L-arginine, arterial pressure significantly rose in cirrhotic rats but not in controls. In protocol 2, arterial pressure, estimated renal plasma flow, glomerular filtration rate and sodium excretion were measured in 12 cirrhotic rats with ascites and 10 control rats before and during the sequential infusion of previously selected doses of N omega-nitro-L-arginine (25, 50 and 250 micrograms.kg-1.min-1). Changes in arterial pressure reproduced those observed in protocol 1. In control rats, N omega-nitro-L-arginine caused a decrease in estimated renal plasma flow without affecting glomerular filtration rate or sodium excretion. In contrast, N omega-nitro-L-arginine administration to cirrhotic animals did not produce any appreciable renal vasoconstrictor effect, and it increased glomerular filtration rate and sodium excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Inactivation of propanediol oxidoreductase of Escherichia coli by metal-catalyzed oxidation

1,2-Propanediol oxidoreductase, which reduces the L-lactaldehyde formed in the fermentation of L-fucose or L-rhamnose to L-1,2-propanediol in E. coli, was inactivated by a component of E. coli cell extracts in the presence of oxygen. Pure propanediol oxidoreductase preparations were shown to be inactivated in vitro by aerobic incubations in the presence of Fe3+ and ascorbate. The Fe3+ ascorbate-mediated inactivation reaction was inhibited by catalase, although not by superoxide dismutase. Under anaerobic conditions, the presence of H2O2 strongly inactivated the enzyme. Propanediol oxidoreductase was rapidly degraded in the presence of oxygen, while the native enzyme displayed high stability as long as no oxygen was present.

Comparison of the efficacy of three different treatments with imipenem versus the classical clindamycin plus tobramycin in experimental peritonitis

This study compares the efficacy of three different treatment modalities of imipenem/cilastatin and the conventional clindamycin plus tobramycin in an experimental model of intra-abdominal sepsis. 145 Wistar rats were used. 40 served as control and 105 as study groups. A capsule with 0.5 ml of inoculum was surgically implanted in the peritoneal cavity. The inoculum was prepared from human feces of healthy volunteers, with a composition of E. coli 10(6), E. faecalis 10(6), B. fragilis, Clostridium sp 10(5) to 10(6) and anaerobic streptococci 10(5) to 10(6). Eighty animals were treated with imipenem/cilastatin and divided in 3 subgroups: "short pretreatment"--29 animals treated 1 hour prior to surgery and 3 days after; "short"--26 animals starting treatment 2 hours post-surgery and continuing it for 3 days; and "long"--25 animals treated for 10 days, starting 2 hours post-surgery. 25 animals received clindamycin plus tobramycin for 10 days. Mortality and the presence of visceral and peritoneal abscesses were the endpoints of the study. The control group had 100% mortality. There were no statistically significant differences among the treated groups although lower mortality was obtained with "short pretreatment" and "long" treatment with imipenem. The presence of abscesses were statistically significant between the imipenem and the combination group. In the imipenem groups, the "short pretreatment" and the long treatment had fewer abscesses than the short one. We conclude that imipenem may be a good alternative monotherapy to conventional therapy with clindamycin plus tobramycin. The "short pretreatment" seemed as good as the long one and better than the short treatment.

Doses of endothelin have natriuretic effects in conscious rats with cirrhosis and ascites

MAP, RPF, GFR, V and UNaV were measured in nine conscious control and in 11 conscious cirrhotic rats with ascites before and following two bolus injections (100 and 600 pmol/kg body wt) of endothelin (ET). PRA and plasma concentration of aldosterone and ANP were measured in basal conditions and following the high dose ET. ET induced similar increase in MAP and decrease in RPF and GFR in control and cirrhotic rats. High-dose ET produced a significant reduction in UNaV in control rats (from 2.22 +/- 0.46 to 1.14 +/- 0.28 microEq/min, P less than 0.01). By contrast, it induced marked natriuresis in cirrhotic rats (from 0.76 +/- 0.18 to 2.31 +/- 0.70 microEq/min, P less than 0.05). ET significantly increased aldosterone (control rats: 59.3 +/- 2.2 vs. 85.4 +/- 7.4 ng/dl, P less than 0.025; cirrhotic rats: 115.0 +/- 15.8 vs. 163.9 +/- 30.8, ng/dl, P less than 0.05) and ANP (control rats: 20.1 +/- 3.4 vs. 42.7 +/- 7.7, fmol/ml, P less than 0.025; cirrhotic rats: 107.5 +/- 17.3 vs. 214.2 +/- 41.1, fmol/ml, P less than 0.025) and significantly suppressed PRA (control rats: 2.5 +/- 0.5 vs. 0.2 +/- 0.04, ng/ml.hr, P less than 0.025; cirrhotic rats: 16.6 +/- 2.9 vs. 5.0 +/- 1.1, ng/ml.hr, P less than 0.01) in both groups of animals. These results indicate that ET has marked natriuretic properties in cirrhosis with ascites due to inhibition of tubular sodium reabsorption.

Oxygen regulation of L-1,2-propanediol oxidoreductase activity in Escherichia coli

Regardless of the respiratory conditions of the culture, Escherichia coli synthesizes an active propanediol oxidoreductase. Under anaerobic conditions, the enzyme remained fully active and accomplished its physiological role, while under aerobic conditions, it was inactivated in a process that did not depend on protein synthesis or on the presence of a carbon source.

Propanediol oxidoreductases of Escherichia coli, Klebsiella pneumoniae and Salmonella typhimurium. Aspects of interspecies structural and regulatory differentiation

The enzyme propanediol oxidoreductase, which converts the lactaldehyde formed in the metabolism of fucose and rhamnose into propane-1,2-diol under anaerobic conditions, was investigated in Escherichia coli, Klebsiella pneumoniae and Salmonella typhimurium. Structural analysis indicated that the enzymes of E. coli and K. pneumoniae have the same Mr and pI, whereas that of Salm. typhimurium also has the same Mr but a slightly different pI. One-dimensional peptide mapping showed identity between the E. coli and K. pneumoniae enzymes when digested with alpha-chymotrypsin, Staphylococcus aureus V8 proteinase or subtilisin. In the case of Salm. typhimurium, this held only for the subtilisin-digested enzymes, indicating that the hydrophobic regions were preserved to a considerable extent. Anaerobically, the three species induced an active propanediol oxidoreductase when grown on fucose or rhamnose. An inactive propanediol oxidoreductase was induced in Salm. typhimurium by either fucose or rhamnose under aerobic conditions, and this was activated once anaerobiosis was established. An inactive propanediol oxidoreductase was also induced in E. coli under aerobic conditions, but only by growth on fucose. The inactive enzyme was not induced by either of the sugars in K. pneumoniae.

Fermentation mechanism of fucose and rhamnose in Salmonella typhimurium and Klebsiella pneumoniae

An equimolar amount of 1,2-propanediol was detected in the medium when Salmonella typhimurium or Klebsiella pneumoniae fermented L-fucose or L-rhamnose. These metabolic conditions induced a propanediol oxidoreductase that converted the lactaldehyde formed in the dissimilation of either sugar into the diol. The enzyme was further identified by cross-reaction with antibodies against Escherichia coli propanediol oxidoreductase. This indicates that L-fucose and L-rhamnose fermentation takes place in these species by 1,2-propanediol production and excretion.

Genetic and structural evidence for the presence of propanediol oxidoreductase isoenzymes in Escherichia coli

The synthesis of propanediol oxidoreductase, an enzyme permitting the anaerobic metabolism of fucose and rhamnose, has been described as being controlled by the prd locus closely linked to the fuc locus in wild-type cells of Escherichia coli. However, strain AA-787, deleted in the fuc and prd loci, grew anaerobically on rhamnose, displaying propanediol oxidoreductase activity. From the deleted strain we derived a constitutive producer of propanediol oxidoreductase able to grow on 1,2-propanediol by oxidizing the diol to lactaldehyde which was further metabolized to lactate. Transduction experiments showed that this ability to use propanediol was closely linked to the rha locus. Peptide mapping of fucose- and rhamnose-induced propanediol oxidoreductase of wild-type cells established structural differences between the two enzymes, indicating two structural genes, one for each sugar metabolizing system.

Use of operon fusions to examine the regulation of the L-1,2-propanediol oxidoreductase gene of the fucose system in Escherichia coli K12

Escherichia coli K12 growing anaerobically on L-fucose excretes L-1,2-propanediol as a fermentation product whose formation is catalysed by an inducible NAD-linked oxidoreductase. The activity of this enzyme is highly induced only during anaerobic growth. Three bacterial strains bearing a hybrid operon with the structural genes for lactose utilization (lacZYA) fused to the promoter of the propanediol oxidoreductase gene (fucO) were constructed to test whether or not transcriptional control was involved. In contrast to propanediol oxidoreductase of wild-type cells, beta-galactosidase in the phi(fuc-lac) strains was induced by fucose to high levels both aerobically and anaerobically. Data from this work are in accord with the previous report that the enzyme protein (assayed by specific antibodies) was induced both aerobically and anaerobically, but that only in anaerobically grown cells was the oxidoreductase catalytically active. In the present study, we found that the oxidoreductase induced anaerobically in wild-type cells remained enzymically active during aerobic growth in the absence of fucose. On the other hand, wild-type cells grown aerobically in the presence of fucose and then allowed limited anaerobic growth on glucose did not gain any oxidoreductase activity. The mechanism of this post-transcriptional control remains to be discovered.

Identification of lactaldehyde dehydrogenase and glycolaldehyde dehydrogenase as functions of the same protein in Escherichia coli

Lactaldehyde dehydrogenase is an enzyme involved in the aerobic metabolism of fucose in wild type Escherichia coli, and glycolaldehyde dehydrogenase is an enzyme involved in the metabolism of ethylene glycol in mutant cells able to utilize this glycol. Both enzyme sources display oxidative activity on either substrate with a constant ratio between these activities. We have found that both enzymatic activities present the same electrophoretic mobility when crude extracts were electrophoresed in polyacrylamide gels and the gels stained for enzyme activities. Furthermore, both enzymatic activities co-chromatograph in a DEAE-Sephadex column. If lactaldehyde dehydrogenase of wild type cells is purified near homogeneity and the purification procedure is screened for both aldehydes as substrates, only one enzyme is apparent, giving again a constant ratio between lactaldehyde and glycolaldehyde dehydrogenase activities. Genetic evidence of the fact that both activities are functions of the same protein is provided by the observation that mutation to thermosensitivity for the production of lactaldehyde dehydrogenase affected in the same way the production of glycolaldehyde dehydrogenase. Glycolaldehyde dehydrogenase from mutant cells is purified in a procedure coincident with the lactaldehyde dehydrogenase purification, yielding a single enzyme electrophoretically indistinguishable from the purified lactaldehyde dehydrogenase. Peptide mapping of the purified preparation after digestion with chymotrypsin or Staphylococcus aureus protease V8 gives an indistinguishable band pattern between both enzymes.

[Rhabdomyosarcoma of the bile ducts]

Two children of two and three years old affected with biliary tract rhabdomyosarcoma are presented. In both cases the diagnostic was confirmed by anatomopathologic studies of the tumoural piece obtained by surgical extraction. Clinic evolution, surgical technic and cytostatic treatment are described been noticeable a favourable clinic development in both cases. Authors had made a bibliographic revision on the subject, pointing a minor incidence of the biliary tract in comparison with other tumour locations.