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Biomedical subjects

E Rivera

Publications and source records attributed to E Rivera.

At least 73 records · Page 4Linked to original sources
PubMed1997

Correlation of the suppressive activity of a biological response modifier on the proliferation of peripheral blood mononuclear cells and the reduction of HIV titer.

Activation of CD4+ cells is a prerequisite for infection by the human immunodeficiency virus (HIV). Thus, any agent capable of suppressing CD4+ cell proliferation could create a refractory stage that would impede viral infection. We have reported, in a previous publication, that a biological response modifier (BRM), polyantigenic immunomodulator (PAI) substantially reduces HIV-1 titer (from 20 to 100%) in peripheral mononuclear cells (PBMC) cultures with high viral titer (p24 = 10(2)-10(5) pg/ml). We are presenting data suggesting that the reported reduction in virus titer seems to be associated with a suppressive activity of PAI on the proliferation of PBMC from intravenous drug users (IVDU) infected and non-infected with HIV-1. PAI, a well characterized BRM, is a mixture of inactivated bacterial and influenza virus vaccines. PBMC from healthy donors and IVDU individuals were exposed to PAI, phytohemagglutinin (PHA), interleukin-2 (IL-2) and to combinations of PAI with either PHA or IL-2. Appropriate controls were included. 3H-thymidine pulsing was used as indicator of cell proliferation. The stimulation index and the difference between mean cpm of test sample and control were used to measure proliferative activity. There was a low proliferative response in the PBMC cultures from IVDU and HIV-1 positive patients, but it was substantially lower in the later group. When PBMC cultures from the same group of individuals were exposed to PAI, PHA and IL-2, and to the combination of either PAI plus PHA or IL-2, the response observed in the PAI treated group was uniformly lower than in the other treated cultures. Moreover, when PAI was combined with PHA, it exerted a significant reduction in the measured parameters. The effect of PAI on IL-2 activity was negligible. A suppressive effect of a PAI has been detected on the proliferation of PBMC from IVDA and HIV-1 positive individuals. This activity may be associated with the capacity of PAI to reduce HIV titers in infected PBMC cultures.

Adjuvants, Immunologic↗
PubMed1997

[Balo concentric sclerosis. Report of one case].

We report a 50 years old woman admitted to the hospital due to progressive dysphagia and disarthria of there weeks duration. On admission a right hemiparesis was noted. CSF examination showed a protein of 9 mg/dl and no cells. A brain CAT scan showed rounded bilateral subcortical frontoparietal hypodense zones peripheral contrast material enhancement. Pseudobulbar palsies and hemiparesis worsened and the patient required nasoenteral feeding. She was discharged after four months, with severe disabilities, with the diagnosis of Balo concentric, a progressive demyelinating disease.

Diffuse Cerebral Sclerosis of Schilder↗
PubMed1996

Effect of tamoxifen on intraperitoneal N-nitroso-N-methylurea induced tumors.

The effect of tamoxifen (TAM) was evaluated on a mammary tumor model induced in Sprague-Dawley rats by intraperitoneal administration of three N-nitroso-N-methylurea (NMU) doses. Animals received TAM (1 mg/kg per day) from 10 days before the first NMU dose up to 140 days later. Thereafter, treatment was discontinued and the observation period was extended 60 days longer. Mean overall latency period, tumor number per rat and tumor incidence were recorded. Significant differences between treated and control batches were observed in tumor number per rat (1.8 +/- 1.1 versus 5.2 +/- 1.6; P < 0.05) and in tumor incidence (50% versus 100%; P < 0.05), respectively. No significant difference in latency period between both batches was recorded. All lesions induced in the control batch were malignant, whereas only 45% of those induced in TAM-treated animals were malignant and the remaining 55% were preneoplastic. At 60 days after treatment discontinuance, tumor incidence increased to 90% and also tumor number per rat increased to 4.6 +/- 1.5. TAM effect was also evaluated in rats with NMU-induced tumors by treatment with 1 mg/kg per day during 60 days starting when tumors reached a 1.5-cm diameter. Regression to less than 80% of initial size in 49% of the tumors was observed, while in ovariectomized rats, 33% of tumors regressed. Estrogen receptor content, ER (fmol/mg protein) and Kd (nM) in control tumors were: 56 +/- 10 and 0.5 +/- 0.1. In tumors of TAM-treated animals, ER was less than 5 fmol/mg protein. Findings demonstrate that TAM significantly decreased the appearance of tumors induced in rats by i.p. injection of NMU and when TAM treatment was initiated after tumor induction, some tumors failed to respond to hormonal manipulation. Differential tumor growth response after TAM or oophorectomy in each tumor indicates that in the same rat it is possible to distinguish hormone-dependent and hormone-autonomous tumor populations. Hormonal regulation of tumor growth can be under intrinsic control, regardless of the hormonal status of the whole organism.

Animals↗
PubMed1996

Preoperative chemotherapy for stage IIIa non-small cell lung cancer.

About 20% of patients with non-small cell lung cancer are stage IIIa at diagnosis. The treatment of stage IIIa tumors has been discouraging. Long-term disease control and cure rates with a single modality approach with surgery or radiotherapy have been poor; this is particularly so for N2 tumors, which account for the majority of stage IIIa disease. In the past decade there has been interest in multimodality treatment of stage IIIa non-small cell lung cancer using preoperative induction chemotherapy with or without radiotherapy followed by surgery. Several phase II studies and two small phase III trials have shown that a strategy of induction chemotherapy with or without radiotherapy is feasible and probably does offer some survival advantage over surgery or radiotherapy alone. The next issue to be tackled is to determine whether the results achieved with induction chemoradiation followed by surgery are equivalent to those of chemoradiation without surgery. A phase III intergroup trial is underway to answer this question.

Antineoplastic Agents↗
PubMed1996

Delayed full-thickness grafting of lower leg defects following removal of skin malignancies.

BACKGROUND: Closure of wounds on the lower leg can be difficult. If primary closure of local flap repair cannot be accomplished, grafting is usually the next option. Full-thickness grafts are, generally superior to split-thickness grafts, but may not survive immediate postoperative grafting on the lower leg. OBJECTIVE: The purpose of this report is to demonstrate another approach to treatment of lower leg wounds. METHODS: Thirteen patients with lower leg wounds were successfully closed with a delayed full-thickness skin graft. CONCLUSION: This study demonstrates that delayed full-thickness grafting of the lower extremities may have advantages over other methods.

Adolescent↗
PubMed1996

The uvrB gene of Pseudomonas aeruginosa is not DNA damage inducible.

The uvrB gene of Pseudomonas aeruginosa has been isolated from a genomic library by complementation of an Escherichia coli uvrB mutant. The complete nucleotide sequence of P. aeruginosa uvrB consists of 2,013 bp, encoding a polypeptide of 670 amino acids. A P. aeruginosa SOS consensus region, which functions as a binding site for the LexA repressor molecule, is not present in the upstream region of the uvrB gene isolated. By transcriptional fusions with a reporter gene, it has been demonstrated that, contrary to what happens with the homologous gene of E. coli, the P. aeruginosa uvrB gene is not DNA damage inducible. Nevertheless, the UvrB protein must be functional in P. aeruginosa cells because a uvrB-defective mutant is extremely sensitive to UV radiation.

Amino Acid Sequence↗
PubMed1996

Identification of a pKM101 region which confers a slow growth rate and interferes with susceptibility to quinolone in Escherichia coli AB1157.

The effect of plasmid pKM101 on the survival of Escherichia coli AB1157, growing in minimal medium, in the presence of a 4-quinolone DNA gyrase inhibitor was investigated. The presence of this plasmid decreased susceptibility to the quinolone ciprofloxacin, whereas mucAB genes present in a multicopy plasmid did not. The same effect of pKM101 was detected in a recA430 mutant, confirming that it was not really related to the SOS response. In contrast, when survival assays were performed under amino acid starvation conditions, pKM101 did not confer protection against ciprofloxacin. All of these results indicated that the synthesis of a product(s), different from MucAB, which was encoded by the plasmid pKM101 increased the rate of survival of the AB1157 strain in the presence of quinolone. To identify the gene(s) responsible for this phenotype, several plasmid derivatives carrying different portions of pKM101 were constructed. The 2.2-kb region containing korB, traL, korA, and traM genes was sufficient to decrease susceptibility to quinolone. This plasmidic fragment also made the AB1157 host strain grow more slowly (the Slo phenotype). Moreover, the suppression of the Slo phenotype by addition of adenine to the cultures abolished the decreased susceptibility to quinolone. These results are evidence that the protection against quinolone conferred by this region of pKM101 in strain AB1157 is a direct consequence of the slow growth rate.

Anti-Infective Agents↗
PubMed1995

Origin and molecular changes associated with emergence of a highly pathogenic H5N2 influenza virus in Mexico.

In October of 1993, there was decreased egg production and increased mortality among Mexican chickens, in association with serologic evidence of an H5N2 influenza virus. First isolated from chickens in May of 1994, after spreading widely in the country, the virus caused only a mild respiratory syndrome in specific pathogen-free chickens. Because eradication of the virus by destruction of infected birds posed major obstacles to the poultry industry in Mexico, we were able to conduct a "field experiment" to determine the fate of an avirulent virus after repeated cycles of replication in millions of chickens. By the end of 1994, the virus had mutated to contain a highly cleavable hemagglutinin (HA), but remained only mildly pathogenic in chickens. Within months, however, it had become lethal in poultry. Nucleotide sequence analysis of the HA cleavage site of the original avirulent strain revealed R-E-T-R, typical of avirulent viruses and unlike the K-K-K-R sequence characterizing viruses responsible for the 1983 outbreak in poultry in the United States. Both mildly and highly pathogenic isolates contained insertions and a substitution of basic residues in the HA connecting peptide, R-K-R-K-T-R, which made the HA highly cleavable in trypsin-free chicken embryo fibroblasts. Phylogenetic analysis of the HA of H5 avian influenza viruses, including the Mexican isolates, indicated that the epidemic virus had originated from the introduction of a single virus of the North American lineage into Mexican chickens. This sequence of events demonstrates, apparently for the first time, the stepwise acquisition of virulence by an avian influenza virus in nature.

Amino Acid Sequence↗
PubMed1995

Non-reciprocal regulation of Rhodobacter capsulatus and Rhodobacter sphaeroides recA genes expression.

The Rhodobacter capsulatus recA gene has been isolated and sequenced. Its deduced amino acid sequence showed the closest identity with the Rhodobacter sphaeroides RecA protein (91% identity). However, the promoter regions of both R. capsulatus and R. sphaeroides recA genes are only 64% similar. An Escherichia coli-like LexA binding site was not present in the upstream region of the R. capsulatus recA gene. Nevertheless, the R. capsulatus recA gene is inducible by DNA damage in both hetero- and phototrophically growing conditions. The R. capsulatus recA gene is poorly induced when inserted into the chromosome of R. sphaeroides, indicating that the recA gene of both bacteria possess different control sequences despite their phylogenetically close relationship.

Amino Acid Sequence↗
PubMed1995

Acute outbreak of porcine parvovirus infection in Mozambique.

Investigations were made to determine the causal agent of an acute outbreak of abortions recorded in a swine herd in Mozambique. Isolation of porcine parvovirus and demonstration of its specific antibodies accomplished by using enzyme-linked immunosorbent assay, haemagglutination inhibition and immunofluorescent tests, indicated that porcine parvovirus was the causal agent of the abortions. Other pathogenic agents causing reproductive failure, e.g. pseudorabies virus, Leptospira or Brucella species, were ruled out because investigations of these agents proved to be negative.

Abortion, Veterinary↗
PubMed1995

Inadvertent use of ionic contrast material in myelography: case report and management guidelines.

A 38-year-old man with chronic low back pain underwent myelography and was inadvertently injected with ionic contrast medium. Within minutes, he started complaining of muscle spasms in his lower extremities, followed by respiratory distress and myoclonus. Immediate intravenous treatment with fluids, antihistamines, and supplemental oxygen was started. Within 1 hour after the myelogram, he was intubated and paralyzed with a neuromuscular blocking agent. Shortly thereafter, he began receiving triple anticonvulsant therapy and a lumbar drain was inserted to allow for the evacuation of cerebrospinal fluid. Electroencephalographic monitoring, which initially showed that the patient was in status epilepticus, subsequently showed no more episodes of seizure activity. Massive rhabdomyolysis, renal failure, and metabolic derangement were prevented. He was then extubated and regained full consciousness. He was discharged on the 13th day of hospitalization with mild amnesia and some cognitive dysfunction. A review of the literature reveals descriptions of 9 of 15 patients who survived similar episodes. We conclude that prompt identification of the contrast medium error and prompt intervention are crucial to increase significantly the chances of survival. Elective paralysis, anticonvulsant therapy, and cerebrospinal fluid drainage are the recommended modes of treatment.

Adult↗
PubMed1994

Evaluation of protein A and protein G as indicator system in an ELISA for detecting antibodies in mink to Pseudomonas aeruginosa.

A modified, indirect enzyme-linked immunosorbent assay (ELISA) was developed and applied in the detection of mink antibodies to Pseudomonas aeruginosa. In this assay, peroxidase conjugated protein A and protein G were evaluated as indicator systems for detecting antigen-antibody complexes. It was found that protein A has a strong affinity for mink immunoglobulins. In contrast, protein G showed no such affinity. The affinity of protein A for mink immunoglobulins was further demonstrated by immunoprecipitation assays.

Animals↗