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Biomedical subjects

M Flores

Publications and source records attributed to M Flores.

At least 73 records · Page 4Linked to original sources
PubMed1993

HPLC purification and characterization of porcine muscle aminopeptidase B.

An aminopeptidase B from porcine skeletal muscle was successfully purified by ammonium sulphate fractionation and HPLC anion-exchange. The purified aminopeptidase B eluted at 0.18 M NaCl, had a relative molecular mass of 76,000 Da and was markedly stimulated in the presence of 0.2 M chloride anion. The enzyme exhibited maximum activity for the hydrolysis of the arginine-aminoacyl bond at pH 6.5 and 37 degrees C. Other substrates consisting of phenylalanine, proline and alanine-aminoacyl bonds were cleaved at 5.9, 5.1 and 2.5% of the maximum activity with the arginine-aminoacyl bond. The enzyme did not show endopeptidase activity and was very stable at pH above 6 and temperatures below 35 degrees C. However, the enzyme inactivated very fast when incubated at pH 5 or at 50-65 degrees C. Bestatin (50 microM) completely inhibited the aminopeptidase B activity while EDTA (5 mM) only inhibited 40% of its activity. However, 0.5 mM of E-64 did not cause any inhibition while 0.05 mM amastatin and 1 mM puromycin only inhibited 11% of the enzyme activity.

Aminopeptidases↗
PubMed1993

Opacification of Middlebrook agar as an aid in identification of Nocardia farcinica.

One hundred twenty seven human isolates of Nocardia asteroides complex were identified to the species level by drug susceptibility testing, acetamide utilization, thermotolerance studies, studies of arylsulfatase activity, and studies of acid production from rhamnose. N. asteroides complex organisms which were not identifiable as N. farcinica or N. nova were designated N. asteroides sensu stricto. All of the N. farcinica isolates and none of the other isolates produced a milky-white opacity surrounding colonies on Middlebrook 7H10 agar. This finding may facilitate the identification of N. farcinica.

Agar↗
PubMed1992

Different plasmids of Rhizobium leguminosarum bv. phaseoli are required for optimal symbiotic performance.

Rhizobium leguminosarum bv. phaseoli CFN42 contains six plasmids (pa to pf), and pd has been shown to be the symbiotic plasmid. To determine the participation of the other plasmids in cellular functions, we used a positive selection scheme to isolate derivatives cured of each plasmid. These were obtained for all except one (pe), of which only deleted derivatives were recovered. In regard to symbiosis, we found that in addition to pd, pb is also indispensable for nodulation, partly owing to the presence of genes involved in lipopolysaccharide synthesis. The positive contribution of pb, pc, pe, and pf to the symbiotic capacity of the strain was revealed in competition experiments. The strains that were cured (or deleted for pe) were significantly less competitive than the wild type. Analysis of the growth capacity of the cured strains showed the participation of the plasmids in free-living conditions: the pf- strain was unable to grow on minimal medium, while strains cured of any other plasmid had significantly reduced growth capacity in this medium. Even on rich medium, strains lacking pb or pc or deleted for pe had a diminished growth rate compared with the wild type. Complementation of the cured strains with the corresponding wild-type plasmid restored their original phenotypes, thus confirming that the effects seen were due only to loss of plasmids. The results indicate global participation of the Rhizobium genome in symbiotic and free-living functions.

Blotting, Southern↗
PubMed1992

[Characteristics of gastric cancer in the IX region of Chile].

The results of a prospective protocol for the management of patients with gastric cancer applied from May 1988 to June 1991 are reported. 123 patients were operated on and a resection performed in 55%. Only 14 patients had incipient tumor and 44 had "curative" surgery. There was a preponderance of non differentiated tumors located high in the stomach. Endoscopy and biopsy were performed in cases with positive diagnosis in 91 and 93%, respectively. The overall actuarial survival rate was 37% at 38 months, rising to 50% for patients undergoing resection and to 82% in patients with "curative" resection.

Adult↗
PubMed1991

Myocardial adaptation to chronic propranolol therapy in diabetic rats.

The myocardial adaptation to chronic beta-adrenergic blockade was explored in diabetic and control female Wistar rats. Propranolol was administered by intraperitoneal injection, 30 mg/kg every 12 h. Treatment began 2 months after streptozotocin injection and at a comparable time in controls. Diabetes reduced the heart rate by 90 beats/min; propranolol decreased the heart rate by 30 beats/min further in diabetic rats. Propranolol reduced the heart rate by 100 beats/min in controls. Study of isolated ventricular papillary muscle showed qualitatively similar effects of propranolol in control and diabetic animals. Diabetes resulted in prolonged contraction duration and decreased shortening velocity; both developed tension and peak shortening were unchanged. In contrast, propranolol resulted in prolonged contraction duration but no change in shortening velocity; both developed tension and peak shortening were increased. The shortening of isometric relaxation in response to norepinephrine was exaggerated with propranolol therapy in control but not diabetic rats. These findings indicate that the myocardial adaptation to chronic beta-blockade results in increased developed tension and increased extent of muscle shortening in vitro, and differs qualitatively from the adaptation to diabetes.

Animals↗
PubMed1991

Structural complexity of the symbiotic plasmid of Rhizobium leguminosarum bv. phaseoli.

The complete physical map of the symbiotic plasmid of Rhizobium leguminosarum bv. phaseoli strain CFN42 was established. The data support the concept that Rhizobium symbiotic genes are part of a complex genomic structure which contains a large amount of reiterated DNA sequences. This plasmid is a circular structure of 390 kb with approximately 10 families of internally reiterated DNA sequences of two to three elements each. One family includes two directly oriented nitrogenase operons situated 120 kb apart. We also found several stretches of pSym that are reiterated in other replicons of the cell. Localization of symbiotic gene sequences by heterologous hybridization revealed that nodABC sequences are separated in two regions, each of which contains a nod boxlike element, and it also suggested the presence of two copies of the nifA and nodD gene sequences. We propose that the complex structure of the symbiotic plasmid allows interactions between repeated DNA sequences which, in turn, might result in frequent rearrangements.

Blotting, Southern↗
PubMed1991

Genetic variation of the glucocorticoid receptor from a steroid-resistant primate.

The neotropical cotton-top marmoset (Saguinus oedipus) is a New World primate known to have markedly increased total and free plasma cortisol concentrations when compared with Old World primates including man. The relative end-organ 'resistance' to glucocorticoids found in various New World primates has been attributed to a glucocorticoid receptor (GR) with diminished affinity for glucocorticoids. It has been demonstrated that the marmoset GR has approximately tenfold lower binding affinity for dexamethasone when compared with the human GR. We have examined the primary structure of the marmoset GR by molecular cloning and sequencing of GR functional domains. A library of cDNA clones was constructed in the phage vector gamma gt10 using poly(A)+ RNA from a marmoset-derived lymphoid cell line, and screened using the human GR cDNA. DNA sequencing determined 76 individual nucleotide substitutions in the coding region of the marmoset GR. Comparison of the marmoset GR nucleotide sequence with the human GR cDNA coding region indicated an overall sequence homology of about 97%. Thirty of the nucleotide substitutions lead to alterations in the predicted amino acid sequence (28 amino acid substitutions) of the marmoset GR. The size of the marmoset GR predicted from the 778 amino acids is approximately 90,000 which is in agreement with previous size estimates of the human and marmoset GRs. Alterations of amino acid sequence in the marmoset GR were greatest towards the amino terminus, including the tau 1 domain putatively involved in transcriptional activation. The DNA-binding domain contained an additional codon (arginine).(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

[ Taxonomic study of the yeast flora of musts and wines from "Madrid wines"].

The natural yeast flora of musts and wines elaborated in wineries of the three Madrid viticultural areas, has been taxonomically analyzed. Two hundred and seventy yeast strains belonging to eighteen species, have been isolated, and Sacch. cerevisiae strains are the most frequent. The chemical characterization of samples with enological parameters defines the yeast fermentative ecosystem.

Acids↗
PubMed1990

Physicochemical characterization of corticotrophin releasing factor receptor in rat pituitary and brain.

The physicochemical characteristics of solubilized crosslinked CRF receptor-ligand complexes were studied in the anterior and intermediate pituitary lobes and brain of the rat. In all tissues studied, there was a major labeled band with a molecular weight of 72 +2- 3.5 kDa, (n = 15), 71 +/- 1.3 (n = 6), 73 +2- 2.5 (n = 7) and 75 +2- 3.5 (n = 7) kDa in the anterior and intermediate lobes of the pituitary, amygdala and cerebral cortex, respectively. The density of this band was inhibited by CRF analogs, but not by unrelated peptides. This is consistent with the comparable binding properties of CRF in membrane preparations of these tissues. These results suggest that differences in receptor regulation and the reported ability of CRF to stimulate cAMP is due to differences in ligand receptor processing and coupling to membrane transduction systems, rather than to major differences in the binding protein.

Amygdala↗
PubMed1990

Physical map and properties of a 90-MDa plasmid of Azospirillum brasilense Sp7.

Homology was previously detected between the DNA restriction fragments containing Rhizobium meliloti nodulation genes and the 90-MDa plasmid, p90, of Azospirillum brasilense Sp7. Two DNA loci from Sp7 genome that complement mutations in the exopolysaccharide synthesis genes, exoB and exoC, of R. meliloti were also shown to be present on the plasmid. A more detailed characterization of the plasmid was undertaken to establish its physical map and to localize the nod homologies and other specific regions. Six loci were mapped, the region homologous to the nodulation genes, nodPQ, of R. meliloti, the exoB and exoC mutation-correcting loci, a locus for Ap resistance, a bla homology region different from the Ap resistance locus, and a region necessary for the maintenance of p90 as an independent replicon. Mobilization into Agrobacterium tumefaciens of p90-Tn5-Mob was obtained at a frequency of 10(-4), with the plasmid helper pJB3JI. Self-transfer of p90 was not demonstrated. Fragments of p90 hybridized with a plasmid of 90 MDa present in most A. brasilense and some A. lipoferum strains, suggesting a plasmid family in Azospirillum.

Ampicillin Resistance↗
PubMed1990

Value of the O-nitrophenyl-beta-D-galactopyranoside test to differentiate among the aerobic actinomycetes.

A comparative study to determine beta-D-galactosidase activity among 171 strains of aerobic actinomycetes (including mycobacteria and rhodococci) was performed by using two growth media and four O-nitrophenyl-beta-D-galactopyranoside (ONPG) substrates. The ONPG test was found to be a valuable screening test to differentiate between the ONPG-positive Nocardia spp. and the rapidly growing ONPG-negative mycobacteria and rhodococci. However, ONPG results varied significantly depending on the growth medium and test substrate used.

Actinomycetales↗
PubMed1988

Genomic instability in Rhizobium phaseoli.

Experience from different laboratories indicates that Rhizobium strains can generate variability in regard to some phenotypic characteristics such as colony morphology or symbiotic properties. On the other hand, several reports suggest that under certain stress conditions or genetic manipulations Rhizobium cells can present genomic rearrangements. In search of frequent genomic rearrangements, we analyzed three Rhizobium strains under laboratory conditions that are not considered to cause stress in bacterial populations. DNAs from direct descendants of a single cell were analyzed in regard to the hybridization patterns obtained, using as probes different recombinant plasmids or cosmids; while most of the probes utilized did not show differences in the hybridization patterns, some of them revealed the occurrence of frequent genomic rearrangements. The implications and possible biological significance of these observations are discussed.

Cloning, Molecular↗
PubMed1987

Reiterated DNA sequences in Rhizobium and Agrobacterium spp.

Repeated DNA sequences are a general characteristic of eucaryotic genomes. Although several examples of DNA reiteration have been found in procaryotic organisms, only in the case of the archaebacteria Halobacterium halobium and Halobacterium volcanii [C. Sapienza and W. F. Doolittle, Nature (London) 295:384-389, 1982], has DNA reiteration been reported as a common genomic feature. The genomes of two Rhizobium phaseoli strains, one Rhizobium meliloti strain, and one Agrobacterium tumefaciens strain were analyzed for the presence of repetitive DNA. Rhizobium and Agrobacterium spp. are closely related soil bacteria that interact with plants and that belong to the taxonomical family Rhizobiaceae. Rhizobium species establish a nitrogen-fixing symbiosis in the roots of legumes, whereas Agrobacterium species is a pathogen in different plants. The four strains revealed a large number of repeated DNA sequences. The family size was usually small, from 2 to 5 elements, but some presented more than 10 elements. Rhizobium and Agrobacterium spp. contain large plasmids in addition to the chromosomes. Analysis of the two Rhizobium strains indicated that DNA reiteration is not confined to the chromosome or to some plasmids but is a property of the whole genome.

Cloning, Molecular↗