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Biomedical subjects

E Martinez

Publications and source records attributed to E Martinez.

At least 181 records · Page 10Linked to original sources
PubMed1989

Cooperative binding of estrogen receptor to imperfect estrogen-responsive DNA elements correlates with their synergistic hormone-dependent enhancer activity.

The Xenopus vitellogenin (vit) gene B1 estrogen-inducible enhancer is formed by two closely adjacent 13 bp imperfect palindromic estrogen-responsive elements (EREs), i.e. ERE-2 and ERE-1, having one and two base substitutions respectively, when compared to the perfect palindromic consensus ERE (GGTCANNNTGACC). Gene transfer experiments indicate that these degenerated elements, on their own, have a low or no regulatory capacity at all, but in vivo act together synergistically to confer high receptor- and hormone-dependent transcription activation to the heterologous HSV thymidine kinase promoter. Thus, the DNA region upstream of the vitB1 gene comprising these two imperfect EREs separated by 7 bp, was called the vitB1 estrogen-responsive unit (vitB1 ERU). Using in vitro protein-DNA interaction techniques, we demonstrate that estrogen receptor dimers bind cooperatively to the imperfect EREs of the vitB1 ERU. Binding of a first receptor dimer to the more conserved ERE-2 increases approximately 4- to 8-fold the binding affinity of the receptor to the adjacent less conserved ERE-1. Thus, we suggest that the observed synergistic estrogen-dependent transcription activation conferred by the pair of hormone-responsive DNA elements of the vit B1 ERU is the result of cooperative binding of two estrogen receptor dimers to these two adjacent imperfect EREs.

Animals↗
PubMed1989

In vitro release of endothelium-derived relaxing factor by acetylcholine is increased during the guinea pig pregnancy.

The relaxation of isolated blood vessels by acetylcholine is dependent on the presence of intact endothelium and its release of a smooth muscle relaxing nitroso-like compound. Pregnancy is associated with altered vascular responsiveness to a variety of agents. Because many of these agents stimulate the release of endothelium-derived relaxing factor, we investigated in vitro the effect of pregnancy on acetylcholine-mediated relaxation of guinea pig uterine and carotid artery rings. The presence of intact and functional endothelium was confirmed both by examination under the scanning electron microscope and by vessel relaxation after the addition of acetylcholine. The addition of acetylcholine to the vessel bath produced dose-dependent relaxation of both carotid and uterine artery segments obtained from pregnant and nonpregnant animals after they had been submaximally preconstricted with phenylephrine. There was a significant increase in both response and efficacy to acetylcholine during pregnancy for both uterine and carotid arteries (p less than 0.0001 for each). The concentrations of endothelial cells (cells per square micrometer) were similar in uterine arteries from pregnant and nonpregnant animals. We conclude that the most likely explanation for these findings is a pregnancy-mediated enhancement of endothelium-derived relaxing factor activity.

Acetylcholine↗
PubMed1989

Effect of pregnancy on uterine and carotid artery response to norepinephrine, epinephrine, and phenylephrine in vessels with documented functional endothelium.

The effect of pregnancy on arterial sensitivity to vasoconstrictors is controversial. Some of the controversy may reflect methodologic differences. Vessel reactivity in vitro is altered by both the tension placed on the segment and the presence or absence of functional endothelium. We investigated the effect of pregnancy on guinea pig uterine and carotid arteries to norepinephrine, epinephrine, and phenylephrine. Each vessel segment was stretched to the optimal point along its length-tension curve, and functional endothelium was documented by acetylcholine-stimulated relaxation. A significant dose-response relationship was observed in each vessel for each agent (each p less than 0.0001). Pregnancy was demonstrated to be associated with a significant reduction in both uterine artery response and sensitivity to norepinephrine, epinephrine, and phenylephrine. However, there was no consistent pregnancy-associated effect on carotid artery response and sensitivity.

Animals↗
PubMed1989

cis- and trans-acting elements of the estrogen-regulated vitellogenin gene B1 of Xenopus laevis.

Vitellogenin genes are expressed under strict estrogen control in the liver of female oviparous vertebrates. Gene transfer experiments using estrogen-responsive cells have shown that the 13 bp perfect palindromic element GGTCACTGTGACC found upstream of the Xenopus laevis vitellogenin gene A2 promoter mediates hormonal stimulation and thus, was called the estrogen-responsive element (ERE). In the Xenopus vitellogenin genes B1 and B2 there are two closely adjacent EREs with one or more base substitutions when compared to the consensus ERE GGTCANNNTGACC. On their own, these degenerated elements have only a low or no regulatory capacity at all but act together synergistically to form an estrogen-responsive unit (ERU) with the same strength as the perfect palindromic 13 bp element. Analysis of estrogen receptor binding to the gene B1 ERU revealed a cooperative interaction of receptor dimers to the two adjacent imperfect EREs which most likely explains the synergistic stimulation observed in vivo. Furthermore, a promoter activator element located between positions --113 and --42 of the gene B1 and functional in the human MCF-7 and the Xenopus B3.2 cells has been identified and shown to be involved in the high level of induced transcription activity when the ERE is placed at a distance from the promoter. Finally, a hormone-controlled in vitro transcription system derived from Xenopus liver nuclear extracts was exploited to characterize two additional novel cis-acting elements within the vitellogenin gene B1 promoter. One of them, a negative regulatory element (NRE), is responsible for repression of promoter activity in the absence of hormone. The second is related to the NF-I binding site and is required, together with the ERE, to mediate hormonal induction. Moreover, we detected three trans-acting activities in Xenopus liver nuclear extracts that interact with these regions and demonstrated that they participate in the regulation of the expression of the vitellogenin promoter in vitro.

Animals↗
PubMed1989

Direct evidence for acute and massive norepinephrine release in the hippocampus during transient ischemia.

Recent studies suggest the norepinephrine (NE) may play a regulatory role in neuronal cell death in the hippocampus after transient ischemia. However, ischemia-induced changes in extracellular NE release have not been demonstrated. In the present study, we utilized the microdialysis technique to measure extracellular NE levels in the hippocampus before, during, and after 20 min of global ischemia induced by two-vessel occlusion combined with systemic hypotension in the rat. Stable basal concentrations of extracellular NE were detected in three consecutive samples collected prior to ischemia (1.86 +/- 1.21 pmol/ml of perfusate mean +/- SEM). During ischemia, NE levels increased to 30.1 +/- 5.5 pmol/ml, representing an 18-fold increase. The levels gradually returned to baseline by 40 min of reperfusion. These results are the first to demonstrate that acute and massive extracellular release of NE occurs in the hippocampus during ischemia and early recirculation. These results support the hypothesis that the activation of the noradrenergic system may play a significant role in modulating the development of ischemic neuronal damage.

Animals↗
PubMed1989

Effect of mild hypothermia on ischemia-induced release of neurotransmitters and free fatty acids in rat brain.

We have demonstrated previously that mild intraischemic hypothermia confers a marked protective effect on the final histopathological outcome. The present study was carried out to evaluate whether this protective effect involves changes in the degree of local cerebral blood flow reductions, tissue accumulation of free fatty acids, or alterations in the extracellular release of glutamate and dopamine. Rats whose intraischemic brain temperature was maintained at 36 degrees C, 33 degrees C, or 30 degrees C were subjected to 20 minutes of ischemia by four-vessel occlusion combined with systemic hypotension. Levels of local cerebral blood flow, as measured autoradiographically, were reduced uniformly in all experimental animals at the end of ischemia by gas chromatography after tissue extraction and separation by thin layer chromatography. A massive ischemia-induced accumulation of individual free fatty acids was observed in animal groups whose intraischemic brain temperature was maintained at either 36 degrees C or 30 degrees C. Extracellular neurotransmitter levels were measured by microdialysis; the perfusate was collected before, during, and after ischemia. In rats whose intraischemic brain temperature was maintained at 36 degrees C, dopamine and glutamate increased significantly during ischemia and the early period of recirculation (by 500-fold and sevenfold, respectively). In animals whose brain temperature was maintained at 33 degrees C and 30 degrees C, the release of glutamate was completely inhibited, and the release of dopamine was significantly attenuated (by 60%). These results suggest that mild intraischemic hypothermia does not affect the ischemia-induced local cerebral blood flow reduction or free fatty acid accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Exocrine pancreatic function in Sjögren's syndrome.

Pancreatic function testing was carried out in 19 patients with Sjögren's syndrome (SS) (nine primary type, ten secondary) by the N-benzoyl-tyrosil-p-aminobenzoic acid (PABA) test, serum immunoreactive trypsin (IRT) levels, and stool fat measurements to evaluate the incidence and type of exocrine pancreatic alterations in this disease. Exocrine pancreatic impairment was found to be present in 63% of the patients. Three types of secretory patterns were observed: (1) normal PABA test results and normal IRT levels (37% [7/19] of the patients); (2) normal PABA test results and elevated IRT levels (42% [8/19]; and (3) low PABA test results and elevated IRT levels (21% [4/19]), including two patients with steatorrhea. Functional pancreatic impairment tended to be more severe in patients with longer disease duration and it was related to the degree of alteration of salivary flow but not to labial salivary gland histologic changes or the type of SS. Inasmuch as hypertrypsinemia was the common marker of pancreatic dysfunction in all patients, we suggest a periodic measurement of serum IRT levels in the follow-up of patients with SS to detect early stages of pancreatic involvement.

4-Aminobenzoic Acid↗
PubMed1988

Cerebral phosphoinositide, triacylglycerol and energy metabolism during severe hypoxia and recovery.

The cerebral concentrations of phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP), phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidic acid (PA), triacylglycerol (TAG) and free fatty acids (FFA), as well as cerebral metabolites, were measured in rats subjected to 10 min of hypoxia and subsequent recovery of 7 or 30 min duration. The experiments were carried out with control of physiological variables. Hypoxia (paO2 values of about 15 mm Hg) caused a decrease in PI, whereas PIP and PIP2 did not change significantly. A two-fold increase of total FFA was noted, mainly comprising stearic and arachidonic acids. TAG-arachidonate tended to increase, but the other species in TAG decreased. Adenosine triphosphate (ATP) and energy charge (EC) decreased slightly and there was a marked lactate accumulation. PA did not change throughout the experiment. With recovery of 7 min duration, PI decreased further and total FFA continued to increase. TAG-arachidonate increased significantly. ATP remained depressed but EC recovered to the control range. Both tissue and plasma glucose increased. Tissue lactate remained elevated and systemic acidosis occurred. After a recovery period of 30 min, all lipids normalized and the energy state returned toward control. The data suggest that the phosphoinositide alterations during hypoxia are metabolically linked to changes in FFA and the lipid changes are accompanied by alterations in cerebral energy and carbohydrate metabolism. The selective increase in TAG-arachidonate may represent an incorporation of arachidonic acid into TAG, which may serve to reduce the free arachidonic acid level in the brain.

Animals↗
PubMed1988

Intra-ischemic extracellular release of dopamine and glutamate is associated with striatal vulnerability to ischemia.

We have previously described a marked attenuation of postischemic striatal neuronal death by prior substantia nigra (SN) lesion, and have shown that lowering the brain temperature by only a few degrees during ischemia also confers a marked protective effect. The present study was carried out to evaluate whether the protective effect of these manipulations involves changes in extracellular release of striatal dopamine (DA) and glutamate (Glu) during ischemia. Four animal subgroups were investigated, including unilateral SN-lesioned rats whose intra-ischemic brain temperature was maintained at 36 degrees C, and non-lesioned animals whose brain temperature was not regulated, or was maintained at 33 or 36 degrees C during ischemia. Striatal extracellular sampling was performed by a microdialysis probe in rats subjected to 20 min of ischemia by 4-vessel occlusion. In rats whose intra-ischemic brain temperature was 36 degrees C, both DA and Glu increased significantly. In SN-lesioned rats no changes were found in extracellular levels of DA. However, significant increases in Glu were measured. In animals whose brain temperature was not regulated (the intra-ischemic brain temperature fell to 30 degrees C) or maintained at 33 degrees C there was a significant increase of DA release, but no changes were found in extracellular levels of Glu. These results, taken together with the neuropathological findings, suggest that release of both DA and Glu during ischemia is necessary for the development of postischemic striatal damage.

Animals↗
PubMed1988

pACYC184-derived cloning vectors containing the multiple cloning site and lacZ alpha reporter gene of pUC8/9 and pUC18/19 plasmids.

A new series of vectors, pSU2716, pSU2717, pSU2718, and pSU2719, has been constructed. The plasmids contain (i) the P15A replicon, (ii) the chloramphenicol acetyl transferase (CAT)-coding gene from Tn9, and (iii) the HaeII fragment which carries the multiple cloning site and the lacZ alpha reporter gene of pUC8, pUC9, pUC18 and pUC19, respectively. These vectors allow rapid and simple transfer of inserts from pUC plasmids, have an intermediate copy number (which allows regulated expression from the lac promoter), and are compatible with ColE1-derived vectors (and, therefore, can be used in studies requiring the joint expression of two genes, for example, in genetic complementation analysis). Furthermore, the accumulation of CAT instead of beta-lactamase, allows an easy visualization in sodium dodecyl sulfate-polyacrylamide-gel electrophoresis of proteins of 28-35 kDa, which can otherwise be obscured by the beta-lactamase.

Base Sequence↗
PubMed1988

Ultrasound scanning as a screening technique for hydatidosis in developing countries.

This study presents new evidence as to the usefulness of ultrasound scanning in field conditions, to screen out hydatidosis in endemic areas, and to compare its detection capability with serological methods. It also intends to demonstrate that for an efficient rural ultrasound screening, neither an experienced ultra sonographer nor expensive and sophisticated equipment is necessary, it can be done by suitably trained personnel (eg, nurse, public health worker), using basic equipment, without public health installations or electricity, thus making it a feasible, simple, fast, and cheap screening method for hydatidosis.

Argentina↗
PubMed1988

Transposon Tn21 encodes a RecA-independent site-specific integration system.

The IncW plasmid R388 and the DNA region of Tn21 containing the Smr and the Sur genes are capable of RecA-independent recombination. This recombination occurs at a relatively high frequency (up to 10(-4) recombinants per recipient molecule) and results in integration of the two plasmids. No detectable repeats are formed in the process. The crossover points have been confined to a 0.4-kb homologous segment in both plasmids which contains a 59-bp DNA sequence presumably involved in the acquisition of new genes by Tn21 and its relatives (Cameron et al. 1986). It is likely that the recombination occurs precisely at this point. At least one trans-acting function (an integrase) is required for the site-specific recombination. It has been localized to a 1456-bp BstEII-BamHI fragment of Tn21 and can efficiently complement the integration of plasmids containing the integration site.

DNA Transposable Elements↗
PubMed1988

Effect of ischemia on the in vivo release of striatal dopamine, glutamate, and gamma-aminobutyric acid studied by intracerebral microdialysis.

We have previously described a marked attenuation of postischemic striatal neuronal death by prior substantia nigra (SN) lesioning. The present study was carried out to evaluate whether the protective effect of the lesion involves changes in the degree of local cerebral blood flow (ICBF) reduction, energy metabolite depletion, or alterations in the extracellular release of striatal dopamine (DA), glutamate (Glu), or gamma-aminobutyric acid (GABA). Control and SN-lesioned rats were subjected to 20 min of forebrain ischemia by four-vessel occlusion combined with systemic hypotension. Levels of ICBF, as measured by the autoradiographic method, and energy metabolites were uniformly reduced in both the ipsi- and contralateral striata at the end of the ischemic period, a finding implying that the lesion did not affect the severity of the ischemic insult itself. Extracellular neurotransmitter levels were measured by microdialysis; the perfusate was collected before, during, and after ischemia. An approximately 500-fold increase in DA content, a 7-fold increase in Glu content, and a 5-fold increase in GABA content were observed during ischemia in nonlesioned animals. These levels gradually returned to baseline by 30 min of reperfusion. In SN-lesioned rats, the release of DA was completely prevented, the release of GABA was not affected, and the release of Glu was partially attenuated. However, excessive extracellular Glu concentrations were still attained, which are potentially toxic. This, taken together with the previous neuropathological findings, suggests that excessive release of DA is important for the development of ischemic cell damage in the striatum.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1988

Genetic diversity and relationships among isolates of Rhizobium leguminosarum biovar phaseoli.

Fifty-one isolates of Rhizobium leguminosarum biovar phaseoli from various geographic and ecological sources, largely in Mexico, were characterized by the electrophoretic mobilities of 15 metabolic enzymes, and 46 distinctive multilocus genotypes (electrophoretic types [ETs]) were distinguished on the basis of allele profiles at the enzyme loci. Mean genetic diversity per enzyme locus among the 46 ETs was 0.691, the highest value yet recorded for any species of bacterium. The occurrence of strong nonrandom associations of alleles over loci suggested a basically clonal population structure, reflecting infrequent recombination of chromosomal genes. Multilocus genotypic diversity was unusually high, with the most strongly differentiated pairs of ETs having distinctive alleles at all 15 loci and major clusters of ETs diverging at genetic distances as large as 0.89. This great diversity in the chromosomal genome raises the possibility that R. leguminosarum biovar phaseoli is a polyphyletic assemblage of strains. As other workers have suggested, the inclusion of all strains capable of nodulating beans in a single biovar or species is genetically unrealistic and taxonomically misleading. A biologically meaningful classification of Rhizobium spp. should be based on assessment of variation in the chromosomal genome rather than on phenotypic characters, especially those mediated for the most part or wholly by plasmid-borne genes, such as host relationships.

Alleles↗
PubMed1988

Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris.

Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix phenotype to the Agrobacterium transconjugants. A Fix phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris.

Journal Article↗
PubMed1988

Place of cystectomy in superficial bladder cancer.

Between January 1978 and June 1985, 44 patients underwent cystectomy for clinically diagnosed superficial bladder cancer. Operative mortality was 13.6%. Early and late complications were observed in 34 and 55% patients, respectively. Clinical understaging was seen in 23%, and stage reduction in 18% of the patients. Clinical staging was correct in 59% of the patients. The mean follow-up was 40 months (range, 24-84 months). Five patients presented local recurrence (13%) of the tumor and 10 patients showed distant metastases (26%). Urethral and upper urinary tract recurrences were observed in 7 and 4 patients, respectively. Fourteen patients (39%) died of cancer after a mean follow-up of 24 months. The actuarial 5-year survival was achieved by 77% of the patients with PTo-PTa-PTis and by 67% of the patients with PT1 (p, not significant).

Adult↗