Biomedical subjects

L Franco

Publications and source records attributed to L Franco.

At least 73 records · Page 4Linked to original sources

PubMed1995

Role of nitric oxide in prevention of ethanol-induced gastric damage by CuNSN a copper-chelating compound.

CuNSN a bis (2-benzimidazolyl)thiother complex with copper, has been shown to prevent the formation of acute gastric mucosal lesions induced by acetylsalicylic acid and ethanol. In the present study we have investigated the role of NO in CuNSN protection from ethanol-induced gastric damage. For this purpose we have used the inhibitor of NO biosynthesis, NG-nitro-L-arginine (L-NNA) as well as L- or D-arginine. Gastric mucosal damage caused by ethanol was dose-dependently increased by i.v. administration of graded dose of L-NNA. The effect of L-NNA was completely antagonized by the administration of L-arginine while D-arginine did not cause a reduction in the damage. Treatment with CuNSN has shown a significant protection against the damage produced by ethanol. This protection was not reversed by L-NNA and was significant as compared to the corresponding control group. The combination of L-NNA plus L-arginine potentiates this protection. These results suggest that NO synthesis is not involved in the protection afforded by CuNSN.

Amino Acid Oxidoreductases↗

PubMed1995

Eicosanoid and gastroprotection by copper derivatives and NDGA.

We investigated the effect of oral administration of graded doses of: nordihydroguaiaretic acid (NDGA), CuNSN, a bis(2-benzimidazolyl)thioether and CuCl2 on ethanol-induced gastric damage in the rat and the role of leukotrienes and prostaglandins in attenuating this damage. In the experiments we determined ex-vivo eicosanoid release in the rat gastric mucosa pretreated with the above-mentioned compounds. The results indicate that the gastric lesion is accompanied by an increase in mucosa-synthesize LTC4, while PGE2 formation remains unchanged. Pretreatment with NDGA, CuNSN and CuCl2, protects the gastric mucosa from damages and reduces the increase in LTC4 mucosal formation. CuNSN and CuCl2 increase the PGE2 release, while NDGA has no effect on this pathway. These results suggest that one of the possible mechanisms of the NDGA protective effect is related to the inhibition of LTC4 formation, while the PGE2 increase in synthesis together with the leukotriene inhibition could contribute to the protective effect of CuNSN and CuCl2.

Administration, Oral↗

PubMed1995

Essential fatty acids are antagonists of the leukotriene B4 receptor.

A series of essential fatty acids and fatty acid derivatives were evaluated for their ability to inhibit [3H] leukotriene B4 (LTB4) binding to pig neutrophil membranes. The fatty acids varied in chain length, extent of unsaturation, position of unsaturation, and isomerization. Generally, fatty acids with two or more unsaturated sites and chain lengths of 18-22 were potent inhibitors of [3H]LTB4 binding; both n-3 and n-6 fatty acids were inhibitory. The most potent compounds tested were homogammalinolenic acid and ricinelaidic acid which gave Ki values of 1 microM and 2 microM in the binding assay. Ricinelaidic acid was also tested for its ability to inhibit LTB4-mediated chemotaxis (IC50 = 10 microM) and LTB4-induced calcium fluxes (IC50 = 7 microM) in isolated human neutrophils. Ricinelaidic acid did not show agonist activity in these assays. In an in vivo model of LTB4-induced bronchoconstriction, ricinelaidic acid and homogammalinolenic acid gave 46% and 53% inhibition, respectively, at a 1 mg/kg i.v. dose. These results indicate that essential fatty acids are LTB4 receptor antagonists, which may account in part for their reported anti-inflammatory activities.

8,11,14-Eicosatrienoic Acid↗

PubMed1995

Gastric eicosanoid synthesis in normal subjects and alcoholics after ethanol stimulation.

This work studied the effect of different ethanol concentrations on the eicosanoid accumulation in human gastric incubates of healthy volunteers and chronic alcoholics, determining the in vitro eicosanoid release both in the basal condition and after different ethanol concentrations. The basal release of PGE2 and LTC4 in alcoholics is higher than in healthy volunteers. Various alcohol concentrations cause an increase in LTC4 and PGE2 in healthy volunteers; we observed no LTC4 increase in alcoholics and although PGE2 levels increased after 20% ethanol, they remained constant at higher ethanol concentrations.

Adult↗

PubMed1994

Subcellular location of enzymes involved in core histone acetylation.

Multiple enzyme forms of histone deacetylase and histone acetyltransferase exist in germinating maize embryos. We analyzed the association of the different enzymes to chromatin by ion exchange chromatography of subcellular fractions from different time points of embryo germination. The vast majority of histone deacetylase HD-1A was not bound to chromatin, since it was solubilized during chromatin isolation, regardless of its phosphorylation state and the phase of embryo germination. In contrast, HD-2 was chromatin bound during the entire germination pathway. Histone deacetylase HD-1B was present in a chromatin-bound and a soluble form; the ratio between these two forms changed during germination. Both nuclear histone acetyltransferases, HAT-A1 and HAT-A2, were tightly chromatin-bound and could only be released from chromatin by salt extraction. To test whether histone acetyltransferases or deacetylases are associated with the nuclear matrix, we analyzed nuclear matrix preparations from yeast, Physarum, and maize step by step for both enzyme activities. This analysis confirmed that part of the activity is chromatin bound, but no significant enzyme activity could be found in the final nuclear matrix, regardless of the preparation protocol. This result was further substantiated by detailed analysis of histone deacetylases and acetyltransferases during cellular fractionation and nuclear matrix preparation of chicken erythrocytes. Altogether our results suggest that the participation of these enzymes in different nuclear processes may partly be regulated by a distinct location to intranuclear components.

Acetylation↗

PubMed1994

Self-aggregation of the transmembrane glycoprotein CD38 purified from human erythrocytes.

The 46 kDa human transmembrane glycoprotein CD38 is a multicatalytic enzyme exhibiting ADPribosyl cyclase, cyclic ADPribose hydrolase and NAD(+)-glycohydrolase activities at its extracellular domain. When CD38, purified to homogeneity from human erythrocyte membranes, was incubated with NAD+ or beta-mercaptoethanol, extensive aggregation took place. Addition of both compounds to CD38 led to the formation of still larger aggregates (over 300 nm), which were resistant to TCA precipitation. Extensive and stable CD38 self-aggregation was shown by, i) SDS-PAGE and autoradiography of the [32P]NAD(+)-incubated CD38, ii) SDS-PAGE followed by immunochemical detection of CD38 on the transblots, iii) direct electron microscopy on negatively stained CD38 samples. Self-aggregation of CD38 might be correlated with its putative function as a transducer of activation and proliferation signals in a number of hematopoietic cells.

ADP-ribosyl Cyclase↗

PubMed1994

[Cystic hygroma: 2 case reports and review of the literature].

Cystic hygroma, an infrequent malformation of the lymphatic system (5 cases per 1000 abortions with CRL greater than 3 cm), was observed in 2 cases which prompted the present study. The Authors also present a brief review of the literature on this topic. After reviewing the hypothetic pathogenesis of the lymphatic obstruction which underlines this pathology, the paper focuses on the association of hygroma and anatomical and chromosomic alterations. The various anatomopathological and echographical findings are then described. Special attention is drawn to the diagnosis of cystic hygroma, after which the two case studies are illustrated. The prognosis of this pathology is pessimistic and the patient and specialist have to choose between immediate abortion or waiting for the inevitable outcome of gestation.

Adult↗

PubMed1993

A single protein immunologically identified as CD38 displays NAD+ glycohydrolase, ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities at the outer surface of human erythrocytes.

The three ectoenzyme activities, NAD+ glycohydrolase, ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase were purified to homogeneity from solubilized human erythrocyte membranes. The purification procedure involved three sequential chromatography steps on hydroxylapatite, immobilized Cu++ and immobilized anti-CD38 monoclonal antibody resins. The final step yielded a single 46 kDa protein displaying all three enzymatic activities. Since the protein bound specifically to the anti-CD38 resin, it was immunologically identified as CD38, a 46 kDa surface antigen involved in activation and proliferation of lymphocyte populations.

ADP-ribosyl Cyclase↗

PubMed1993

Free ADP-ribose in human erythrocytes: pathways of intra-erythrocytic conversion and non-enzymic binding to membrane proteins.

We have previously identified free ADP-ribose (ADPR) as a normal metabolite in mature human erythrocytes. In this study the metabolic transformations of ADPR were investigated in both supernatants from erythrocyte lysates and intact erythrocytes, loaded with ADPR by means of a procedure involving hypotonic haemolysis and isotonic resealing. In both experimental systems, the main pathway was a dinucleotide pyrophosphatase-catalysed hydrolysis to yield AMP, which was readily converted into the adenylic and inosinic nucleotide pools. To a lesser extent, ADPR underwent conversion into a compound that was identified as ADP-ribulose (ADPRu), on the basis of m.s., n.m.r. spectroscopy and enzymic analysis. ADPRu was also susceptible to degradation by the dinucleotide pyrophosphatase, which was partially purified from erythrocyte lysates and characterized with respect to its substrate specificity. Isomerization of ADPR to ADPRu was markedly enhanced by ATP. Incubation of unsealed haemoglobin-free erythrocyte membranes with labelled ADPR did not cause any transformation of this nucleotide and resulted in its trichloroacetic acid- and formic acid-resistant binding to a number of membrane cytoskeletal proteins. These proteins include spectrin, glyceraldehyde 3-phosphate dehydrogenase (Ga3PDH), three proteins of molecular masses 98, 79 and 72 kDa, which apparently comigrate with bands 3, 4.1 and 4.2 respectively, and two additional proteins of molecular masses 58 and 41 kDa. Acid-resistant binding of ADPR, as well as of NAD+, to Ga3PDH was confirmed for the enzyme purified from human erythrocytes.

Adenine Nucleotides↗

PubMed1993

Site specificity of pea histone acetyltransferase B in vitro.

Histone acetyltransferase B from pea embryonic axes has been purified approximately 300-fold by a combination of chromatographic procedures, including affinity chromatography on histone-agarose. The enzyme preparation has been used for the in vitro transfer of acetyl groups from [1-14C]acetyl-CoA to non-acetylated pea histone H4. Up to three acetyl groups can be introduced into the histone. The resulting mono-, di-, and triacetylated H4 isoforms were separated and sequenced to determine the acetylated sites. Only sites 5, 12, and 16 were used by histone acetyltransferase B, but no clear preference among them was observed. The absence of modification of other potentially acetylatable sites is another indication that acetylation of the different lysine residues in the N-terminal H4 tail serves as a specific signal in different nuclear processes.

Acetylation↗

PubMed1993

Production and hydrolysis of cyclic ADP-ribose at the outer surface of human erythrocytes.

Hemoglobin-free membranes from human erythrocytes are able to convert beta-NAD+ to cyclic ADP-ribose, a calcium mobilizer as potent as inositol 1,4,5-trisphosphate. Identification of cyclic ADP-ribose was based on HPLC analyses and its Ca(2+)-mobilizing activity on sea urchin egg microsomes. Erythrocyte membranes also hydrolyze cyclic ADP-ribose to ADP-ribose. By comparing the cyclic ADP-ribose-synthesizing and -hydrolyzing activities on unsealed and right-side-out resealed ghosts, it can be concluded that both are localized at the extracellular side of the membrane. This is confirmed by the demonstration of both enzyme activities on the surface of intact human red cells. Identification of the two enzymes involved in cyclic ADP-ribose metabolism might suggest some physiological role of this nucleotide in red cells.

ADP-ribosyl Cyclase↗

PubMed1993

Adenosine diphosphate ribulose in human erythrocytes: a new metabolite with membrane binding properties.

Incubation of ADPribose with yeast phosphoriboisomerase resulted in the formation of an adenylic nucleotide that was identified with ADPribulose by mass spectrometry. Synthesis of [32P]ADPribulose from [32P]NAD+ by the combined activities of commercial NAD+ glycohydrolase and phosphoriboisomerase allowed us to use it as a labeled internal standard throughout the procedure of purification from trichloroacetic acid extracts of human red blood cells. ADPribulose was purified by means of three sequential reverse phase HPLC separations and its concentration in human erythrocytes was estimated to be 0.11 +/- 0.1 microM. Unsealed erythrocyte ghosts did not transform ADPribulose, which bound to specific membrane proteins with a trichloroacetic and formic acid-resistant binding. The labeled proteins were identified as spectrin, bands 3, 4.1, 4.2 and Glyceraldehyde 3-phosphate dehydrogenase on the basis of their relative mobilities on SDS-PAGE.

Adenosine Diphosphate Ribose↗

PubMed1993

Histone deacetylase. A key enzyme for the binding of regulatory proteins to chromatin.

Core histones can be modified by reversible, posttranslational acetylation of specific lysine residues within the N-terminal protein domains. The dynamic equilibrium of acetylation is maintained by two enzyme activities, histone acetyltransferase and histone deacetylase. Recent data on histone deacetylases and on anionic motifs in chromatin- or DNA-binding regulatory proteins (e.g. transcription factors, nuclear proto-oncogenes) are summarized and united into a hypothesis which attributes a key function to histone deacetylation for the binding of regulatory proteins to chromatin by a transient, specific local increase of the positive charge in the N-terminal domains of nucleosomal core histones. According to our model, the rapid deacetylation of distinct lysines in especially H2A and H2B would facilitate the association of anionic protein domains of regulatory proteins to specific nucleosomes. Therefore histone deacetylation (histone deacetylases) may represent a unique regulatory mechanism in the early steps of gene activation, in contrast to the more structural role of histone acetylation (histone acetyltransferases) for nucleosomal transitions during the actual transcription process.

Animals↗

PubMed1993

Chromatin structure of the yeast FBP1 gene: transcription-dependent changes in the regulatory and coding regions.

We have studied the chromatin structure of the Saccharomyces cerevisiae FBP1 gene, which codes for fructose-1,6-bisphosphatase. A strong, constitutive, DNase I, micrococcal nuclease and S1 nuclease hypersensitive site is present close to the 3' end of the coding region. In the repressed state, positioned nucleosomes exist around this site, and subtle changes occur in this nucleosomal organization upon derepression. A DNase I hypersensitive region is located within the promoter between positions -540 and -400 and its extends towards the gene in the derepressed state, leading to an alteration of nucleosomal positioning. Psoralen crosslinking of chromatin, which is used for the first time to study the mobility of restriction fragments from an RNA polymerase II gene, revealed that part of the promoter is nucleosome-free, in accordance with the results of DNase I digestion. A model is presented that, based on the chromatin structure, puts forward the hypothesis that the promoter UAS is located between -540 and -340. Finally, psoralen crosslinking, as well as digestions with micrococcal nuclease or restriction endonucleases suggests that most if not all of the copies of the active FBP1 gene are covered by nucleosomes.

Chromatin↗

PubMed1993

Synthesis of prostaglandin E2 in rat liver.

We have investigated whether rat liver microsomes can release prostaglandins and determined the 'optimal conditions' for the in vitro synthesis of PGE2. We also studied the effect of the oral administration of indomethacin, piroxicam and ibuprofen on PGE2 release ex vivo. The drugs were administered to animals at high doses for one or three consecutive days and the animals were killed 24 h after the first or the third administration. The increased PGE2 synthesis observed for indomethacin and piroxicam (animals treated for three consecutive days) could be explained by the depression of cytochrome P-450 observed in the same animals. Cytochrome P-450 could modulate the activity of eicosanoids derived from cyclooxygenase. Moreover the different inhibition of PG synthesis exhibited by these drugs could lead to a different rise in concentration of arachidonic acid in microsome membranes and contribute to an increased PGE2 synthesis.

Animals↗

PubMed1993

Negative findings for use of coconut water as an oral rehydration solution in childhood diarrhea.

This study reports the chemical composition of coconut water during its maturation. Composition was measured at 5, 6, 7, 8, 9, 10, 11 and 12 months maturation. Concentrations of sodium and glucose, and the osmolality values showed great variation throughout maturation. The concentration of sodium remained constant between the 5th and 7th months (mean 2.9 mEq/l), but increased after the 8th month (mean 12.5 mEq/l). The concentration of glucose remained constant between the 5th and 8th months (mean 3392.4 mg%), but abruptly decreased after the 9th month (mean 820 mg%). Osmolality followed the variation of the glucose concentration averaging 377.3 mOsm/l up to the 8th month, then decreasing to 310.3 mOsm/l after the 9th month. This study showed great variability in coconut water composition during maturation of the fruit. In no instance did the coconut water contain sodium and glucose concentrations of potential value as an oral rehydration solution.

Chlorides↗

PubMed1992

Presence and turnover of adenosine diphosphate ribose in human erythrocytes.

ADP-ribose was detected in human red blood cells (RBC) at 0.45 +/- 0.1 microM concentrations. These levels could be estimated after purification of ADP-ribose by means of three sequential HPLC fractionations of RBC extracts. Extraction was performed by sonication of RBC either in trichloroacetic acid, followed by centrifugation, or in carbonate-bicarbonate buffer, pH 10.0, followed by rapid ultrafiltration. Neither procedure of extraction caused artefactual formation of ADP-ribose. Prolonged incubation of intact RBC in isotonic buffer containing labeled orthophosphate resulted in the slow incorporation of radioactivity into ADP-ribose. Identification of the labeled ADP-ribose was confirmed upon incubation of the purified metabolite with nucleotide pyrophosphatase, yielding radioactive 5'-AMP and ribose 5-phosphate, while its exposure to a nonspecific deaminase resulted in the quantitative formation of labeled inosine diphosphate ribose.

Adenosine Diphosphate↗

PubMed1992

Chromatin structure of the yeast SUC2 promoter in regulatory mutants.

We have previously suggested that two positioned nucleosomes are removed from the promoter of the Saccharomyces cerevisiae SUC2 gene upon depression by glucose starvation. To gain further insight into the changes accompanying derepression at the chromatin level we have studied the chromatin structure of the SUC2 promoter in several mutants affecting SUC2 expression. The non-derepressible mutants snf1, snf2 and snf5 present a chromatin structure characteristic of the repressed state, irrespective of the presence or absence of glucose. The non-repressible mutants, mig1 and ssn6, as well as the double mutant snfs sn6 exhibit an opened chromatin structure even in the presence of glucose. These results suggest that the DNA-binding protein encoded by MIG1 is necessary to produce the characteristic pattern of repressed chromatin and that the SNF1 protein kinase is sufficient to produce the derepressed chromatin pattern. A model is presented for the transitions that result in opening up of the chromatin structure.

Base Sequence↗