Biomedical subjects
Publications and source records attributed to M Flores.
Rhizobium sp. strain NGR234 contains three replicons: the symbiotic plasmid or pNGR234a, a megaplasmid (pNGR234b), and the chromosome. Symbiotic gene sequences not present in pNGR234a were analyzed by hybridization. DNA sequences homologous to the genes fixLJKNOPQGHIS were found on the chromosome, while sequences homologous to nodPQ and exoBDFLK were found on pNGR234b.
A myloidoma of soft tissue is rare and there have been no previously published reports of limb involvement. We describe a case in which the tumour was present in the popliteal fossa. There was no evidence of systemic amyloid disease or of malignant neoplasm one year after the diagnosis.
The Q-band (35 GHz) electron paramagnetic resonance (EPR) spectra of nitrosyl hemoglobin (HbNO) and nitrosyl myoglobin (MbNO) were studied as a function of temperature between 19 K and 200 K. The spectra of both heme proteins show two classes of variations as a function of temperature. The first one has previously been associated with the existence of two paramagnetic species, one with rhombic and the other with axial symmetry. The second one manifests itself in changes in the g-factors and linewidths of each species. These changes are correlated with the conformational substates model and associate the variations of g-values with changes in the angle of the N(his)-Fe-N(NO) bond in the rhombic species and with changes in the distance between Fe and N of the proximal (F8) histidine in the axial species.
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To select for bacterial strains with enhanced phenotypes, random fragments of a whole genome, or a defined region of the genome, are cloned in a nonreplicating vector. The resulting plasmids are integrated by recombination into the homologous DNA region of the original strain. Integration gives rise to a nontandem direct duplication of the corresponding DNA region separated by the vector moiety of the plasmid. Recombination between the direct repeats leads to tandem duplication and further amplification of the entire integrated DNA, including the vector. Bacteria harboring the amplified DNA are selected by increasing the dosage of an antibiotic corresponding to a resistance marker of the integrated vector. Pooled strains carrying amplifications are then challenged with a selective pressure for the desired phenotype. After repeated selection cycles, the most fit strains are isolated. We used this process, which we called random DNA amplification, to select Rhizobium strains with increased competitiveness for nodule formation. Derivatives containing randomly amplified DNA regions of the symbiotic plasmid of Rhizobium tropici CFN299 strain were generated. Pools of amplified strains were inoculated onto various tropical legumes. After several cycles of selection through plants, amplified derivatives showing an increased competitiveness for nodule formation with the leguminous plant Macroptilium atropurpureum were obtained.
Uremic polyneuropathy (UPNP) is a serious complication of chronic renal failure (CRF) in adults; however, its prevalence is unknown in the pediatric population. An easy-to-perform maneuver for its detection in children is the evaluation of "H" reflex. The objective of this study was to validate the usefulness of the "H" reflex maneuver for the diagnosis of UPNP in pediatric dialysis patients for CRF. Thirty-seven CRF patients were paired with healthy controls by age and sex. The patients were being treated with dialysis or one of its variants. Information was obtained regarding diagnosis, duration, and control of dialysis. Neurological examination was performed, conduction velocities in sensory and motor nerves were measured, and "H" reflex elicited bilaterally. Peripheral polyneuropathy was determined by the presence of at least two nerves with alterations in latency and/or conduction velocities. It was found that 59.4% (22/37) of the children with CRF treated with dialysis developed UPNP, 17 with ambulatory peritoneal dialysis, and 5 with hemodialysis. There was no difference in diagnosis, duration of dialysis, or control of the same in these patients from other CRF patients who did not have UPNP. All patients were clinically asymptomatic. "H" reflex showed a sensibility of 44%, a specificity of 87%, a predictive value positive of 66%, and a predictive value negative of 76%, when measured to 28 msec. With a 30 msec duration specificity rises to 95%. UPNP presents asymptomatically in pediatric patients. "H" reflex is an adequate screening test for the selection of pediatric patients to be tested further.
BACKGROUND: Colorectal carcinoma is the sixth cause of death in Chile. Half of malignant tumors in humans have genetic alterations in protoncogenes, tumor suppressing genes or both. One of the most frequent alterations is that involving p53 tumor suppressor gene. AIM: To study, using immunohistochemical methods, alterations in p53 gene expression in colorectal carcinomas and adenomas. MATERIAL AND METHODS: A random sample of 28 large bowel adenomas and 44 carcinomas was studied. Determination of p53 protein was made with an immunohistochemical method using monoclonal antibodies. Patients were followed for a mean of 36 months (range 1 to 100 months). RESULTS: p53 immunostaining was obtained in one adenoma (3.5%) and in 18 carcinomas (41%, p = 0.01). There were no differences in survival during follow up, between cancer patients that expressed or did not express p53 protein. CONCLUSIONS: About half of colorectal tumors have immunohistochemical expression of p53 protein, as published abroad. We did not find a prognostic value for this protein in our sample.
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The presence of HIV antibodies was screened in 241 paired samples of serum and saliva from seronegative subjects with risk factors for human immune deficiency virus (HIV) infection (n = 99), asymptomatic and symptomatic HIV-seropositive patients (n = 104) and healthy blood donors (n = 38) as negative controls, in order to assess the reliability of two saliva tests for the detection of HIV antibodies. These results were confirmed by Western blot. The saliva samples were collected using an oral device (Salivette) maintained in the lateral gingival fold until the individual perceived that it was becoming less rigid due to hydration with saliva. The two tests were a rapid one (Test Pack) and a conventional one (GACELISA). The results for antibody detection in saliva show 99% specificity and 99% sensitivity for the rapid test versus 100% sensitivity and 81% specificity for the conventional test. All results for the saliva samples which were positive in the rapid test were confirmed by Western blot (WHO criteria), and there were no indeterminate Western blot results among the samples which were false-positive in the conventional enzyme immunoassay. No statistically significant differences were observed between the absorbance values of HIV-infected symptomatic and asymptomatic patients. The correlation for the results of the HIV-antibody analysis in the paired sera was 98%. This method of saliva sampling in combination with a rapid and sensitive test for HIV-antibody detection may be applicable in studies conducted with limited technical resources or insufficiently trained health personnel or where blood sample collection is difficult.
We report on identical traumatic injuries in a pair of monozygotic (identical) twins treated at the same unit, one year apart. Both had sustained a complete tear of the patellar tendon and were treated surgically.
Serological (Western blot) detection of bovine immunodeficiency-like virus (BIV) in Holstein dairy herds is reported in Costa Rica for the first time, as well as the isolation of the virus, from a seropositive bovine, by cocultivation of peripheral blood mononuclear cells (PBMC) with embryonic rabbit epithelial (EREp) cells. The isolated strain, BIVCR1, reacted similarly in Western blot as the reference strain BIV R29 and is clearly distinguishable from bovine leukaemia virus (BLV). The data suggest an association between BIV infections and BLV infections, as it has been reported elsewhere. From these results it can be concluded that BIV is present in Costa Rica and it is suggested that these viral infections will probably follow the epidemiological parameters of BLV infections in Costa Rica, reaching high infection rates in dairy herds.
Frequent tandem amplification of defined regions of the genome, called amplicons, is a common characteristic in the genomes of some Rhizobium species, such as Rhizobium etli. In order to map these zones in a model Rhizobium replicon, we undertook an analysis of the plasticity patterns fostered by amplicons in the pSym (390 kb) of R. etli CFN42. Data presented in this article indicate the presence of four amplicons in pSym, used for the generation of tandem amplifications and deletions. The amplicons are large, ranging from 90 to 175 kb, and they are overlapping. Each amplicon is usually flanked by specific reiterated sequences. Formation of amplifications and deletions requires an active recA gene. All the amplicons detected are concentrated in a zone of roughly one-third of pSym, covering most of the symbiotic genes detected in this plasmid. No amplicons were detected in the remaining two-thirds of pSym. These data support the idea that most of the known symbiotic genes in this plasmid are located in a genomic region that is prone to the formation of frequent tandem amplification.
The tartrate-resistant acid phosphatase (TRAP) of skeletal osteoclasts was found to partially dephosphorylate the bone matrix phosphoproteins osteopontin (OPN) and bone sialoprotein (BSP). TRAP also partially dephosphorylated metabolically [32P]PO4-labeled OPN as well as BSP, whereas comparable amounts of either alkaline phosphatase or prostatic acid phosphatase, at their respective pH optima, were ineffective, indicating a certain preference of TRAP for these phosphoprotein substrates. It has previously (Flores, M., Norgärd, M., Heinegård, D., Reinholt, F. P., and Andersson, G. (1992) Exp. Cell Res. 201, 526-530) been shown that osteoclasts bind to OPN as well as to BSP coated onto glass. We can now show that the partially dephosphorylated proteins no longer support osteoclast binding. These results indicate that the secretion of TRAP from osteoclasts into the resorption area could exert a regulatory influence on the attachment of the cells to the bone surface. This could imply roles in the development of ruffled borders and/or in the regulation of osteoclast motility on the bone surface.
The case of a patient with systemic lupus erythematosus who developed pneumonia caused by Aspergillus fumigatus is described. She was treated with itraconazole 200 mg twice daily, with a rapid response. After a follow-up period of 5 years no recurrence of the infection has been detected. To our knowledge this is the first report on the use of itraconazole in patients with systemic lupus erythematosus. Considering the poor prognosis associated with Aspergillus pneumonia in patients with systemic lupus erythematosus, we believe that itraconazole constitutes a safe and effective alternative to amphotericin B in these patients.
Nocardia asteroides complex organisms derived from human specimens between 1979 and 1992 were identified to the species level. Of 117 N. asteroides complex organisms, 34 (29%) were N. farcinica, 28 (24%) were N. nova, and 55 (47%) were N. asteroides sensu stricto. An analysis of the specimen sites from which the organisms were derived showed that isolates derived from blood, brain, or bone marrow were more likely to be N. farcinica than the other two species. A study of the virulence of ten strains of each species was undertaken, using a mouse model with intravenous inoculation. The 50% lethal doses (LD50) for N. farcinica were significantly lower than those of the other two species. LD50 values for N. nova and N. asteroides were not significantly different. The above data confirming the greater virulence of N. farcinica support the identification of species within the N. asteroides complex.
A genetic element that allows the positive selection of different genomic rearrangements was used to analyze DNA amplification in Rhizobium leguminosarum biovar phaseoli. Discrete amplifiable DNA regions (amplicons) were detected in different regions of the genome of the model strain CFN42, including the chromosome and several large plasmids. Amplicons were mobilized into Escherichia coli using a genetic approach that involves the introduction of an origin of replication active in E. coli and an origin of conjugal transfer into the amplifiable DNA regions of the Rhizobium genome. The strategy can be a valuable tool for studies on genome organization and function. We propose that amplicons define a structural characteristic of the genome that may play an important biological role.