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J Ros

Publications and source records attributed to J Ros.

At least 55 records · Page 3Linked to original sources
PubMed1994

Intracellular calcium concentration in vascular smooth muscle cells of rats with cirrhosis.

A decreased pressor response to endogenous vasoconstrictors, such as angiotensin II and vasopressin, is a characteristic finding in cirrhosis with ascites; this has been considered as partially responsible for the arteriolar vasodilation present in this disease. Previous investigations suggested that this abnormality is due to a post-receptor defect leading to altered intracellular Ca2+ mobilization. To assess this hypothesis, vascular responsiveness to angiotensin II (3.10(-8) M) and intracellular Ca2+ concentration in basal conditions and following angiotensin II (1-100 nM) and vasopressin stimulation (100 nM) were measured in aortic rings and in primary cultured aortic vascular smooth muscle cells, respectively. The study was carried out in 43 control rats and 40 rats with CCl4-induced cirrhosis and ascites. Cells were grown to confluence on glass cover slips and then loaded with Fura-2, a fluorescent intracellular Ca2+ indicator, for continuous monitoring of intracellular Ca2+ concentration. A decreased constrictor response to angiotensin II was detected in cirrhotic aortic rings in comparison to control rings (increase in tension: 31 +/- 5 vs 79 +/- 14 mg, p < 0.005). No differences in intracellular Ca2+ concentration between cirrhotic and control cells were observed in basal conditions (104 +/- 6 and 100 +/- 3 nM, respectively). Angiotensin II administration to cirrhotic vascular smooth muscle cells had a dose-dependent biphasic effect consisting of a rapid increase, followed by return to a sustained level significantly higher than the basal value. This response was identical to that observed in control vascular smooth muscle cells. Similar findings were obtained following vasopressin stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1994

HS-142-1, a potent antagonist of natriuretic peptides in vitro and in vivo.

To determine whether HS-142-1 (HS), a potent atrial natriuretic peptide (ANP) receptor antagonist, also inhibits the effects of brain natriuretic peptide (BNP), urodilatin (URO), and C-type natriuretic peptide, in vitro studies were carried out, demonstrating that HS inhibited production of cGMP by rat fetal lung fibroblast cells induced by ANP, BNP, URO, and C-type natriuretic peptide. Acute clearance studies were conducted in euvolemic Munich-Wistar rats under inactin anesthesia to characterize the effects of HS in vivo. In response to ANP, BNP, or URO (4 micrograms/kg priming dose plus 0.5 micrograms/kg per minute for 20 min), urine flow, absolute sodium excretion rates, and fractional sodium excretion exhibited similar increases (four- to fivefold) in vehicle-treated rats; these responses were, however, completely abolished by prior HS treatment. The tendency for GFR to rise during the infusion of natriuretic peptides (NP) was also blocked after HS. By contrast, HS did not block the renal effects of L-arginine, a precursor of nitric oxide, or of furosemide. Furthermore, the inhibition of endogenous NP by HS was associated with small but significant reductions in GFR and absolute and fractional sodium excretion in normal rats under euvolemic but not hydropenic conditions. These studies provide evidence that the observed effects of HS in vivo and in vitro are mediated exclusively by receptors of NP. Together, these data support the view that HS is a highly specific ligand for NP receptors, capable of antagonizing the renal effects not only of exogenous ANP, but also those of BNP and URO.

Animals↗
PubMed1993

Impaired responsiveness to angiotensin II in experimental cirrhosis: role of nitric oxide.

Impaired vascular responsiveness to angiotensin II is a common feature in human cirrhosis with ascites. The aim of this study was to investigate whether vascular reactivity to angiotensin II is also decreased in rats with carbon tetrachloride-induced cirrhosis and ascites and to assess the role of endogenous nitric oxide in this abnormality. Increasing doses of angiotensin II (from 31 to 500 ng.kg-1.min-1) induced significantly smaller increases in total peripheral resistance in conscious cirrhotic rats with ascites (n = 8) than in control animals (n = 9) at each dose tested. A reduced response to angiotensin II was also observed in vitro in aortic rings of rats with cirrhosis and ascites compared with that in control aortic rings (maximal response: 104 +/- 16 mg vs. 204 +/- 18 mg; p < 0.001). This in vitro hyporesponsiveness to angiotensin II in aortic rings of cirrhotic rats with ascites was reversed on endothelium denudation or nitric oxide synthesis inhibition with N omega-nitro-L-arginine but was not influenced by cyclooxygenase inhibition with indomethacin. In conclusion, this study shows reduced vascular reactivity to angiotensin II in carbon tetrachloride-induced cirrhosis with ascites and indicates that this abnormality is mediated by nitric oxide.

Angiotensin II↗
PubMed1992

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.

Alcohol Oxidoreductases↗
PubMed1992

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)

Animals↗
PubMed1991

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.

Animals↗
PubMed1991

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.

Abscess↗
PubMed1990

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.

Aerobiosis↗
PubMed1985

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.

Alcohol Oxidoreductases↗
PubMed1985

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.

Alcohol Oxidoreductases↗
PubMed1984

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.

Alcohol Oxidoreductases↗
PubMed1983

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.

Aldehyde Oxidoreductases↗
PubMed1983

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.

Alcohol Oxidoreductases↗
PubMed1982

[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.

Antineoplastic Agents↗
PubMedDate not supplied

[Characteristic times in sleep-waking electroencephalograms].

INTRODUCTION AND AIMS: EEG signals emerge from the collective behaviour of large neuronal aggregates and betrays the information processed by neocortex. This electrophysiological collective activity varies with the brain function. Thus, one can ask whether there exists any indication of that neuronal activity in the EEG record. In this work this question is considered in the particular case of sleep/awake EEG s. To this aim, the concept of lacunarity is proposed as a tool to analyse the texture of the EEG samples. From the resulting lacunarity profiles an index is defined which represents a characteristic time of each phase. PATIENTS AND METHODS: The samples analysed corresponds to 30 seconds epochs from polysomnographic night records. Essential details for the computation of lacunarity patterns and the propounded index are given. The mean values of characteristic times (in seconds) are: 0.43 (phase I); 0.73 (phase II); 1.12 (phase III/IV); 0.65 (REM); 0.12 (relaxed wakefulness). RESULTS AND CONCLUSIONS: With this criterium, the awake state is clearly distinguished from phase I and REM sleep, whereas REM sleep comes out to be similar to phase II. Finally, statistical analysis of results suggests the possibility to interpret this index as a complementary tool for reading polysomnographies as well as its application to different physiological or pathological situations of EEG records.

Electroencephalography↗