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Biomedical subjects

J M Ortiz

Publications and source records attributed to J M Ortiz.

At least 19 recordsLinked to original sources
PubMed1992

Downregulation of hepatic albumin mRNA in response to induced hypercholesterolemia in rabbits.

Albumin gene expression was studied in rabbits fed on a cholesterol-rich diet for up to 16 weeks. Livers from experimental animals showed extensive lipid deposition. Hepatic albumin mRNA abundance decreased along the treatment to very low levels after 16 weeks. An 8-fold decrease in the rate of transcription of this gene was also detected. This downregulation of albumin gene expression cannot be attributed to a general impairment of RNA synthesis, as expression of other liver-specific and housekeeping genes did not vary significantly. There was a decrease in ascitic fluid albumin levels after 10 weeks, although serum albumin levels remained unchanged throughout the treatment. Our results are discussed in view of the relationship of albumin levels with hypercholesterolemia.

Animals↗
PubMed1992

Foam cells from aorta and spleen overexpress apolipoprotein E in the absence of hypercholesterolemia.

We have studied Apo E expression in atherosclerotic lesions and spleens in rabbits after a cholesterol-rich diet is discontinued and plasma cholesterol levels return to normal values. After 16 weeks, foam cells are still present in the atherosclerotic lesions and Apo E expression persists restricted solely to the lesion as ascertained by in situ RNA hybridization and northern blot. Apo E expression is induced in spleens of hypercholesterolemic rabbits. However Apo E mRNA levels decrease in this organ parallel to the disappearance of lipid loaded macrophages. These results of in vivo studies indicate that Apo E overexpression in foam cells does not depend on high serum cholesterol levels, but is a characteristic of macrophages that have acquired the foam cell phenotype.

Animals↗
PubMed1992

Characterization and nucleotide sequence of the oriT-traM-finP region of the IncFVII plasmid pSU233.

By hybridizing the IncFVII haemolytic plasmid pSU233 with a probe containing the origin of transfer of the IncFII plasmid R1, we isolated a 1.9 kb BglII fragment containing at least the origin of transfer (oriT), and the genes traM and finP. Functional complementation analysis of deletion derivatives was used to map the origin of transfer. We also determined the nucleotide sequence of traM and finP. Comparison with similar regions of several plasmids, also belonging to the Rep-FIIA family, revelaed that pSU233 resembles the F plasmid by very close. The homology is not evenly distributed along this region, but clustered into homologous regions (TraZb-oriT, TraMb-oriT and traM separated by non-homologous regions (TraYb-oriT, finP). This organization resembles that reported for the replication region and also suggests evolution by exchange of modules. In addition, the nucleotide sequence of finP is different from those previously described for other IncF plasmids and constitutes a new allele, which we have denominated allele VI.

Amino Acid Sequence↗
PubMed1992

Hypercholesterolemia induces differential expression of rabbit apolipoprotein A and C genes.

We have compared steady-state mRNA levels of apolipoproteins AI, AII, AIV, CI, CII and CIII in liver and small intestine of rabbits fed on a cholesterol-rich diet for up to 16 weeks. Apolipoprotein (apo) AIV mRNA was detected in both liver and small intestine, while apo AII was not detected in either organ. Apo CI, apo CII and apo CIII were expressed only in liver and apo AI mRNA was detected only in small intestine. In small intestine, apo AIV and apo AI mRNA levels increased to a maximum at the 4th and 12th week of treatment, respectively. In liver there was a parallel increase in the mRNA levels of apo AIV, apo CI, apo CII and apo CIII, with maximum levels after 4 weeks of treatment. A 3-fold increase was found in apo CII and apo CIII hepatic transcription rates between hypercholesterolemic and control rabbits after 4 weeks of treatment, no longer detectable after 8 weeks. However, no changes were found in apo AIV and apo CI transcription rates. Changes in apolipoprotein mRNA levels were accompanied by changes in plasma lipoprotein levels. Overall, these changes correlate well with the variations detected in the expression of the different apolipoprotein genes. Our results indicate that dietary cholesterol plays an important role in the regulation of these genes and that this regulation is tissue dependent.

Animals↗
PubMed1991

Isolation and evolutionary analysis of a RepFVIB replicon of the plasmid pSU212.

We have isolated at least two different replication regions from pSU401, a Tn802 insertion derivative of the IncFVI plasmid pSU212. One of the replication regions (RepFVIB) is highly homologous to the RepFIIA replicon of IncFII plasmids, and thus belongs to the RepFIIA family. We have also cloned the incompatibility determinant (incFVI) and the copy number control gene (cop) from RepFVIB and determined their nucleotide sequences. The analysis of the sequences supports the idea of a modular evolution of RepFIIA plasmids.

Amino Acid Sequence↗
PubMed1991

Conjunctival synthetic and nonsynthetic fiber granulomas.

Synthetic and nonsynthetic fiber granulomas can be easily diagnosed and treated. This is a case of a child who had a granulomatous inflammation surrounding a filamentous foreign body that was removed and identified by simple histopathologic techniques. The pathologic findings are remarkably similar to the few case reports in the literature. Accurate reporting of these findings may reveal a greater incidence of synthetic and nonsynthetic fiber granulomas.

Child, Preschool↗
PubMed1990

Induction of apolipoprotein E gene expression in human and experimental atherosclerotic lesions.

Hypercholesterolemia and atherosclerosis were induced in New Zealand White rabbits by cholesterol feeding. Apolipoprotein E mRNA levels in livers were found to be slightly increased, as determined by Northern blots. Apolipoprotein E gene expression was dramatically induced in rabbit atherosclerotic aortas with respect to healthy aortas. However, apolipoprotein E mRNA levels in atherosclerotic aortas were low as compared with the hepatic mRNA levels of the same animals. Interestingly, we also found a significant increase in apolipoprotein E expression in human atheromata with respect to healthy aorta from the same individual. This is the first report on apo E gene induction in human atherosclerotic lesions.

Animals↗
PubMed1989

Analysis of IncF plasmids evolution: nucleotide sequence of an IncFIII replication region.

We determined the nucleotide sequence of RepFIII, the IncFIII replication region of the plasmid pSU316. Our data confirmed that RepFIII belongs to the RepFIIA family. The comparison of the nucleotide sequences from several RepFIIA-family plasmids revealed that pSU316 and R1 replicons are almost identical (96% similarity). Most of the differences between them are clustered in the incompatibility determinant. Analysis of the rest of the sequence suggested that the divergence between R1 and pSU316 replicons is very recent.

Base Sequence↗
PubMed1989

Characterization of the RepFVII replicon of the haemolytic plasmid pSU233: nucleotide sequence of an incFVII determinant.

We have isolated a replication region (designated RepFVII) from the IncFVII plasmid, pSU233. Hybridization experiments showed that RepFVII has high homology to the RepFIII replicon of the plasmid pSU316 and, therefore, that pSU233 is another member of the RepFIIA family. We have also located the incompatibility gene (incFVII) from RepFVII. The analysis of its sequence revealed the same organization described for several other replicons belonging to the same family.

Base Sequence↗
PubMed1987

Structure and mobilization of an ampicillin and gentamicin resistance determinant.

A DNA segment originally found in an epidemic plasmid of Escherichia coli encoding an aminoglycoside-(3)-N-acetyltransferase gene (aacC5) and a TEM-type beta-lactamase gene was characterized. The two genes were adjacent and constituted a single transcriptional unit. In addition, these genes were simultaneously mobilized through the action of an insertion sequence related to IS26, IS140, and IS15-delta. This DNA segment is a composite transposon which has been called Tn2922.

Ampicillin↗
PubMed1987

Identification and expression of a copy number control gene in the IncFIII hemolytic plasmid pSU316.

A DNA fragment carrying both the IncFIII determinant and a copy number control gene of the hemolytic plasmid pSU316 has been cloned in pBR322. Deletion derivatives of the hybrid plasmid generated by Bal 31 digestion, which no longer exhibit the IncFIII phenotype, fall into two complementation groups when tested against a pSU316 miniplasmid derivative. Type 1 mutants exhibit the copy number control (Cop+) phenotype whereas type 2 mutants do not. Restriction analysis of type 1 and type 2 mutants allowed us to locate the cop gene of pSU316 in a 700-base-pair fragment adjacent to the IncFIII determinant. Plasmid expression in a minicell system suggests that the product of the cop gene of pSU316 could be a 13,000-dalton protein.

Bacterial Proteins↗
PubMed1986

[Effect of the amplitude and frequency of sinusoidal stimulation on the harmonic distortion of the response of sensory terminations of muscle spindles].

Harmonic distortion (HD) from 1,055 responses of muscle spindles sensory endings to sinusoidal stretches (frequency range 0.0008 to 0.8333 Hz, amplitude range 0.019 to 3.09 mm) has been studied in the cat soleus muscle. Sixty-six per cent were primary afferents (Ia) and 34% secondary (II). HD mean value (0.28) did not show any significant differences between both types of endings. Analysis of variance for HD versus stimulation amplitude showed a greater HD when stretch amplitudes were beyond 1.599 mm or less than 0.031 mm on primary afferents (p less than 0.001) and less than 0.070 mm on secondary (p less than 0.001). The effect of stimulus frequency was also significant (p less than 0.01 Ia and p less than 0.001 II), however only at 0.8333 Hz and in secondary endings HD was significantly higher. The silent period in the response, at release of stretch, caused by half wave rectification could explain about 50% of measured HD.

Analysis of Variance↗
PubMed1985

Purification of alpha-hemolysin from an overproducing E. coli strain.

The genetic determinant of the alpha-hemolysin encoded by plasmid pHly152 has been cloned in both orientations in plasmid pBR322 giving rise to plasmids pSU157 and pSU158. E. coli strains carrying either of these recombinant Hly plasmids produced about 20 times more hemolysin activity than the parental plasmid pHly152, when grown in minimal medium supplemented with hemoglobin. Thus high hemolytic activity is not lethal to the cells, contrary to previous assumptions. alpha-Hemolysin was purified from culture supernatants of strain SU100 (pSU157) by ammonium sulfate precipitation and gel filtration in Sephacryl S-200 in the presence of 6 M urea. When purified alpha-hemolysin preparations were subjected to electrophoretic analysis in denaturing conditions, a single 107 kdal polypeptide was observed. This probably corresponds to the alpha-hemolysin protein, since an isogenic E. coli strain carrying plasmid pSU161, an Hly- mutant derivative of pSU157, did not synthesize the 107 kdal polypeptide.

Bacterial Proteins↗
PubMed1985

Fosfomycin-resistance plasmids determine an intracellular modification of fosfomycin.

Escherichia coli cells carrying fosfomycin-resistance plasmids modify fosfomycin intracellularly. The product of this modification (fosfomycin-derivative) differs from fosfomycin in chromatographic mobility, but the chemical nature of the modification is not yet known. Fosfomycin-derivative appears to have a cytoplasmic location and lacks antibiotic activity. The modification system can be saturated by an excess of fosfomycin in the incubation media.

Biological Transport↗