Biomedical subjects

M Guerra

Publications and source records attributed to M Guerra.

At least 19 recordsLinked to original sources

PubMed1998

Elution of lipopolysaccharides from polyacrylamide gels.

A simple procedure for elution in water of bacterial lipopolysaccharides (LPS) from sodium dodecyl sulfate-polyacrylamide gels is described. It consists of the combination of three principal steps: first, highly sensitive on-gel LPS detection (1-10 ng/band) with zinc-imidazole (negative or reverse staining); second, washing of the individual LPS band in a solution of a zinc-complexing agent (e.g., 100 mM EDTA); and finally, elution of the LPS (100-200 microliters water for a 0.5-microgram LPS band) from gel microparticles for 3 h at room temperature. Using this procedure, we have successfully eluted a variety of LPS forms from Bordetella pertussis, Escherichia coli 0111:B4, E. coli K-235, Salmonella enteritidis, and Pseudomonas aeruginosa. Elution recovery of rough or semismooth LPS was about 70-80%, while that of smooth LPS was only about 10%. Eluted LPS was biologically active as tested by limulus amebocyte lysate and TNF-alpha assays.

Acrylic Resins↗

PubMed1998

Understanding the mechanism of the zinc-ion stains of biomacromolecules in electrophoresis gels: generalization of the reverse-staining technique.

We have recently shown that a few nanograms of protein separated by electrophoresis in sodium dodecyl sulfate-polyacrylamide gels can be detected by reverse-staining, exploiting the precipitation reaction between zinc(II) and imidazole. Modifications of this method have also been generated to detect gel-isolated nucleic acids and bacterial glycolipids. Because there is no recourse to chemical modifiers, the reverse-staining technique has been valuable when micropreparing these biomacromolecules for later use or characterization. The mechanism underlying the reverse-staining effect, however, remains incompletely understood and this has prevented a further generalization of the technique. Here, we have conducted physicochemical experiments and identified zinc imidazolate (ZnIm2) as the main component of the precipitate that forms along the surface of zinc-imidazole reverse-stained gels. Many staining effects observed when gels containing electrophoretically separated biopolymers are subjected to zinc-imidazole stains have been rationalized. The reverse-staining method has been vastly generalized, now allowing the detection of proteins and glycolipids as well as complexes of these macromolecules in native gels. We demonstrate the application of the reverse-staining technique in situations where Coomassie blue or silver staining was inappropriate or failed to produce detection of the species of interest. The present generalization of the reverse-staining method facilitated the characterization of biomacromolecular interaction partners in mixtures of bacterial glycolipids and human tears.

Bacteria↗

PubMed1998

Multiple locations of the rDNA sites in holocentric chromosomes of Rhynchospora (Cyperaceae).

Several cytogenetic studies have shown that representatives of the family Cyperaceae have holocentric chromosomes. Despite their interesting chromosome morphology, the chromosome organization has not been studied. This paper reports on the number and distribution of 18S-5.8S-26S ribosomal RNA sites by fluorescence in situ hybridization in eight Brazilian species of Rhynchospora. The signal of the rDNA probe was always localized in the telomeric regions. A high degree of variation was observed in the number of labelled sites, ranging from 4-8 in karyotypes with 2n = 10 to 30 sites in a karyotype with 50 chromosomes. It is possible that the same mechanism involved in the multiplication of these regions in organisms with monocentric chromosomes also plays a role in the polymorphism observed in holocentric chromosomes of Rhynchospora. An interesting feature of most hybridization sites was their diffuse state observed through to early metaphase. The decondensed state probably reflects the later transcription of this region during the cell cycle.

Chromosome Mapping↗

PubMed1998

PAF levels in saliva are regulated by inflammatory cells.

Platelet activating factor (PAF), a powerful inflammatory phospholipid mediator, has been detected in normal human saliva and found to be increased in periodontitis. The cellular source of PAF in saliva is controversial although several data suggest an origin related to the presence of inflammatory cells. PAF levels in biological fluids are regulated by PAF-producing cells and by the PAF-degrading acetylhydrolase. Although in normal human saliva acetylhydrolase activity is very low, no information is available on the levels of this enzyme in inflammatory conditions of the mouth. The aim of our study was to assess the contribution of inflammatory cells to the levels of PAF in saliva in normal subjects and in patients with periodontitis. PAF was measured by radioimmunoassay (RIA) in mixed uncentrifuged saliva and in cell-free saliva from healthy subjects, before and after tooth brushing, and in patients with periodontitis. In healthy subjects PAF levels were significantly higher in whole saliva than in centifuged saliva (1.51 +/- 0.22 vs. 0.92 +/- 0.04 ng/ml, p < 0.0039). A significant increase in the amount of PAF was detected in whole saliva, but not in centifuged saliva, 2 h after tooth brushing. In patients with periodontitis PAF levels were not different from those of healthy individuals when using centrifuged saliva but were significantly higher when using whole, uncentrifuged saliva. Exogenous radiolabelled PAF was degraded much more rapidly by the saliva of periodontitis patients than by that of normal subjects. In conclusion, our study shows that inflammatory cells regulate the levels of PAF in saliva contributing to its production and degradation. The differential degradation of PAF in normal and inflammatory saliva highlights the absolute need of a series of methodological precautions when performing studies on salivary PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1998

Improved hematoxylin staining for algal cytogenetics.

The aceto-iron hematoxylin method of Wittmann for algal chromosomes was improved by replacing the chloral hydrate and slide heating steps with 5 N HCl hydrolysis. Squashing of the unstained material under the coverslip followed by coverslip removal and air drying allowed rapid and more homogeneous staining. Additional procedures were developed to make the method easier and quicker. Good results were obtained for all algal species analyzed. Pit-connections of red algae were also clearly differentiated.

Acetates↗

PubMed1998

Carotid endarterectomy and contralateral internal carotid artery occlusion: perioperative risks and long-term stroke and survival rates.

BACKGROUND: The aim of this article was to analyze the perioperative mortality and stroke risk rates and late benefits of carotid endarterectomy (CE) contralateral to an occluded internal carotid artery (ICA), on the basis of our surgical experience from July 1990 to June 1996. METHODS: In 57 (14.7%) of 336 patients undergoing 388 CEs, the contralateral ICA was occluded (group I). All operations were performed under general anesthesia with selective shunting based on electroencephalographic criteria. Shunting was used in 36 (63.1%) of 57 revascularizations in group I and 47 (14.2%) of 331 operations performed on the remaining 279 patients with patent contralateral ICAs (group II) (p < 0.001). RESULTS: Perioperative strokes occurred in two patients (3.5%) in group I and three patients (1%) in group II (difference not significant). The only perioperative death, which occurred in one patient (1.7%) in group I, was the result of a perioperative stroke; two patients (0.7%) in group II died within 30 days of operation (difference not significant). Life-table cumulative stroke-free rates at 1, 3, and 5 years were 95%, 95%, 95% in group I and 98.8%, 98.2%, and 98.2% in group II, respectively (p = 0.272). Life-table cumulative survival rates at 1, 3, and 5 years were 97.5%, 94.2%, and 78.1% in group I and 99.2%, 94.8%, and 71.7% in group II, respectively (p = 0.306). CONCLUSIONS: The results of this analysis indicate that CE contralateral to an occluded ICA can be performed with acceptable perioperative mortality and stroke risk rates and late stroke-free and survival rates comparable to those seen in patients without contralateral ICA occlusion who have undergone operation. Nevertheless, we think it is misleading to imply that the risks of operating on the two groups are the same. Moreover, because no late stroke-related death occurred in patients with contralateral ICA occlusion, it would appear that superior late stroke-free rates did not translate into a prolonged survival advantage.

Aged↗

PubMed1997

Results of a European randomized trial of Etanidazole combined with radiotherapy in head and neck carcinomas.

PURPOSE: The aim of the study was to evaluate the efficacy and toxicity of Etanidazole, a hypoxic cell sensitizer, combined with radiotherapy in the treatment of head and neck squamous cell carcinoma. METHODS AND MATERIALS: A total of 374 patients from 27 European centers were included in this trial between 1987 and 1990. Treatment was either conventional radiotherapy alone (between 66 Gy in 33 fractions and 74 Gy in 37 fractions, 5 fractions per week), or the same radiotherapy dose plus Etanidazole 2 g/m2, three times weekly for 17 doses. A minimization procedure, balancing for center, site, and T stage (T1-T3 vs. T4) was used for randomization. RESULTS: Among the 187 patients in the Etanidazole group, 82% received at least 14 doses of the drug. Compliance to the radiotherapy protocol was 92% in the Etanidazole group and 88% in the control group; the main cause of deviation was acute toxicity, which was observed at an equal rate in the two treatment groups. Fifty-two cases of Grade 1 to 3 peripheral neuropathy were observed in the Etanidazole group vs. 5 cases, all of Grade 1, in the control group (p < 0.001). The 2-year actuarial loco-regional control rates were 53% in the Etanidazole group and 53% in the control group (p = 0.93), and the overall 2-year survival rates were 54% in each group (p = 0.99). CONCLUSION: Adding Etanidazole to conventional radiotherapy did not afford any benefit for patients with head and neck carcinoma. This study failed to confirm the hypothesis of a benefit for patients with N0-N1 disease, which had been suggested by the results of a previous study (10).

Adult↗

PubMed1997

Social and economic impact of neurotoxicity in hazardous waste workers in Lenoir, North Carolina.

A detailed study of workers at a hazardous waste incinerator in Lenoir, North Carolina, revealed significant financial losses resulting from health problems caused by the incinerator. The losses included approximately $3 million for 3 years of medical care for 28 workers employed at the incinerator. Future wage losses for exposed workers were projected to be from $14 million to $15 million. Loss of the incinerator as a viable employment base was a significant blow to the local economy. Third-party payers of medical costs, government and private, were also at risk of financial loss. Workers' compensation benefits ranging from $6500 to $274,000 per person were paid by insurance companies to some workers; however, these benefits did not always cover the medical expenses incurred. As a result of their illnesses, 11 of the 28 workers (39%) had to sell or give up their homes, 8 workers (36%) lost their vehicles, 19 workers (68%) began to receive Social Security Disability payments, and 11 workers (39%) obtained food stamps. One worker not included in these figures died 3 years after he settled with the state workers' compensation program. Five of the 28 interviewed workers continue to work in spite of continuing health problems. The 23 workers who cannot work will have estimated lifetime medical expenses of $25.4 million.

Air Pollutants, Occupational↗

PubMed1997

Iron stores in professional athletes throughout the sports season.

Sports anemia provoked by iron deficiency develops slowly and although the existence or reality of this condition is under discussion, the ferritin levels tend to reduce with sports practice. This paper analyzes the variations of iron metabolism, including the organism stores of this metal throughout a sports season in a group of professional sportsmen (soccer players) belonging to a team of the Spanish First Division. For the determination of the iron stores, a computer program has been developed that takes into account the ferritin concentrations, hemoglobin, and saturation of transferrin. The results show that at the end of the season, when the ferric supplementation, which had been performed at the other moments of analysis, was no longer administered the iron stores reduced significantly, as well as the serum ferritin concentration, without such decreases being considered as a prelatent (grade I) anemia.

Adult↗

PubMed1997

Carotid eversion endarterectomy and reimplantation: a safe and simple technique to prevent acute thrombosis-occlusion and/or early and late restenosis.

The purpose of this report is to consider the technical aspects of carotid eversion endarterectomy and reimplantation into the common carotid artery for surgical treatment of atherosclerotic occlusive disease, in light of previous early and late results. In the past 2 years, the authors have more frequently used carotid eversion endarterectomy and reimplantation to minimize the risk of perioperative stroke due to acute occlusion-thrombosis, and the incidence of early and late restenosis. Some 88 patients underwent 95 carotid eversion endarterectomies and reimplantation (seven bilateral): 59 internal carotid arteries were surgically corrected for ischaemic symptoms while 36 patients were symptomless but presented with a haemodynamically significant stenosis at the internal carotid artery bifurcation. The ischaemic preoperative symptoms consisted of one or more transient ischaemic attack's in 39 patients (66%), amaurosis fugax in 15 (25%) and mild stroke in five (8%). Associated elongation of the internal carotid artery beyond the end of the plaque was present in 81 cases (85%). After freeing the internal carotid artery sufficiently beyond the distal limit of the lesion, the vessel was transected obliquely to its origin, the extramedial cleavage plane opened and the endarterectomized arterial wall everted beyond the natural end of the plaque, which was gently removed. The artery was dilated distally and finally reimplanted end-to-side into the common carotid artery, 1-2 cm or more above the original site. This technique has provided excellent early and late results: no deaths, no acute thrombosis-occlusion, no minor or major stroke occurred perioperatively. No restenosis, no symptomless or symptomatic late occlusion was found during late follow-up (mean 28 (range 6-44) months). The performance of this vascular technique must be encouraged and recommended because of its speed, effectiveness and success. Carotid eversion endarterectomy and reimplantation should be performed routinely when the internal carotid artery is elongated.

Aged↗

PubMed1997

Results of electroencephalographic monitoring during 369 consecutive carotid artery revascularizations.

A continuous intraoperative EEG monitoring was performed in 369 consecutive carotid artery revascularizations (CARs) (321 patients) to minimize the intraoperative neurological morbidity. There were 227 carotid endarterectomies and patch graft angioplasty (198 patients), 79 carotid eversion endarterectomies (70 patients) and 58 internal carotid artery reimplantations into the common carotid artery (48 patients). Indications for CARs were TIAs (141, 43.9%), amaurosis fugax (60, 18.6%) and fixed or partial nonprogressing stroke (14, 4.3%). One hundred and six patients (33.1%) were asymptomatic. EEG abnormalities consistent with cerebral ischemia occurred in 97 (26.3%) operations. The indwelling shunt (IS) was used in 73 cases; in the remaining 24 (24.7%), IS was not used on purpose because the surgical procedure was carried out successfully within 5-6 min after the appearance of EEG changes. All patients awoke from the anesthesia without any neurological deficit. Five patients presented with a major stroke within postoperative day 1 and 2, and 1 patient died on postoperative day 10. In 2 of these cases, the intraoperative EEG monitoring was absolutely normal and the IS was not used: the carotid occlusion was due to technical errors. The most striking finding of this series is the absence of false-negative results in continuous EEG monitoring. EEG monitoring appears an available and useful method for the detection of cerebral ischemia secondary to carotid cross-clamping and contributes to put at zero the intraoperative complications of the surgical procedure.

Adult↗

PubMed1997

Phenotype expression of gingival fibroblasts cultured on membranes used in guided tissue regeneration.

Human gingival fibroblasts were cultured in vitro using as substrates an extracellular matrix (matrix) and polytetrafluoride (PTFE) membranes, which are used in guided tissue regeneration. To test the degree of biocompatibility of these membranes, the cellular proliferation and the accumulation of extracellular matrix (ECM) macromolecules were considered as parameters. The fibroblasts were cultured in vitro for 24 and 48 hours without serum on plastic, matrix, and PTFE membranes in the presence of 3H-thymidine, 3H-glucosamine, and 3H-proline to study the neo-synthesis of DNA, glycosaminoglycans (GAG), and collagen proteins, respectively. Studies on cell proliferation showed that fibroblasts grown on matrix membrane significantly increased 3H-thymidine incorporation, while fibroblasts grown on PTFE membrane decreased 3H-thymidine incorporation, compared to plastic used as a control. Moreover, the PTFE membrane induced a marked decrease of collagen and GAG accumulation both in the cellular and extracellular pool, while the matrix membrane provoked a decrease of the two macromolecules in the cellular pool and an increase in the extracellular one, compared to the control. The data we obtained demonstrate that matrix membranes are the most suitable to stimulate both cellular proliferation and ECM macromolecule accumulation.

Adult↗

PubMed1997

[Etiopathogenic hypotheses on dental ankylosis].

The authors review the literature about the different etiopathogenetic hypotheses of tooth ankylosis. They classified the ankylosis in three big groups: traumatic ankylosis due to direct and indirect injuries to the tooth, iatrogenic ankylosis due to unadvised maneuvers made by the dentist, and atraumatic ankylosis. The last is the most important group caused by metabolic problems and with family characteristics. Furthermore they underline the important role played by GAG and corresponding lytic enzymes in the development of atraumatic ankylosis. They described, the therapeutical procedures to be used in the different cases. The clinical cases presented are representative of the different therapeutical approaches.

Ankylosis↗

PubMed1997

[Preservation of the anal sphincter in low rectal lesions].

We have discussed the surgical options to save the anorectal sphincter in lesions within the lower 2/3 of the rectum. We presented four clinical cases: two villous adenomas, one adenocarcinoma and one benign tumor, probably of embryonic origin. We discussed the surgical options in order to avoid a permanent colostomy. There is not a single surgical procedure that we can count on to preserve the anal sphincter, either in benign or malignant lesions. The surgeons treating this pathology should consider all options and be able to select the most adequate, the less complicated and yet be able to preserve continence. The surgeons should remember that in treating malignant lesions "a curative resection is worth a colostomy".

Adenocarcinoma↗

PubMed1996

Immunocompetence of T lymphocytes during whole-blood storage.

In WB stored for 28 days at 4 degrees C the pattern of peripheral T-cell CD25 (IL-2R) expression after polyclonal in vitro stimulation was examined. Flow cytrometic analysis was performed with lymphocytes after 72 h in culture with and without ConA using antibody against CD3 and CD25. In culture supernatants IL-2 was determined. T-cells bearing the CD25 marker decreased with storage time, the mean fluorescence (i.e., number of IL-2R molecules per cell) remained rather stable. IL-2 concentrations peaked with stimulated cells which have been stored for 6 days. The low detectable levels of IL-2 in cultures of T-cells which have not been stored may reflect a much more efficient interplay of IL-2/IL-2R. Thus, even after longer periods of blood storage there are sufficient numbers of T-cells which can be stimulated to excite preprogrammed effector functions, i.e. also a GVHD.

Blood Preservation↗

PubMed1996

Linkage of frontotemporal dementia to chromosome 17: clinical and neuropathological characterization of phenotype.

Frontotemporal dementia is a behavioral disorder of insidious onset and variable progression. Clinically, its early features reflect frontal lobe dysfunction characterized by personality change, deterioration in memory and executive functions, and stereotypical and perseverative behaviors. Pathologically, there is degeneration of the neocortex and subcortical nuclei, without distinctive features such as plaques, neurofibrillary tangles, or Pick or Lewy bodies. Within-family variation in neuropathology and clinical phenotype is observed. In cases where family aggregation is observed, it is inherited as an autosomal dominant, age-dependent disorder. Family studies recently have identified two dementia loci: chromosome 17 for disinhibition-dementia-parkinsonism-amyotrophic complex and pallido-ponto-nigral degeneration and chromosome 3 for familial nonspecific dementia. We describe a family (DUK1684) with clinically and neuropathologically confirmed, autosomal dominant, non-Alzheimer disease dementia. Linkage analysis of this family showed evidence for linkage to chromosome 17q21, with a multipoint location score (log10) of 5.52. A comparison of the clinical and pathological features in DUK1684 with those of the other chromosome 17-linked families, together with the linkage data, suggests that these families are allelic. These studies emphasize that genetic linkage analysis remains a useful tool for differentiating disease loci in clinically complex traits.

Age of Onset↗

PubMed1996

[Color loss evaluation of a dietary formulation in function of temperature, storage time and packaging].

Color loss of a dietetic formulae based on pumpkin (Cucurbita maxima), rice, hen and vegetable oils was evaluated. The product was under an accelerated test at temperatures of 40, 50 and 70 degrees C for a month. The kinetic reaction of color loss (quality loss indicator) was obtained with n = 1 and Ea = 11.5 Kcal/mol. The product was also stored for sixth months at temperatures of 25, 30, 35 and 40 degrees C using glass containers, laminated and composite cans (non metallic). The color was measured by a colorimetric method and by sensory evaluation under the defined conditions of time, temperature and package. The statistical analyses of the color loss measured by instrument was performed by a randomized block design with a significance level of p < 0.05. The results obtained both by the instrument and by the sensory evaluation method, showed that the temperature and storage time has significant effect (p < 0.05) on the other hand, the package does not have a significant effect. It was concluded from this study that the product could be stored for 6 months at temperatures below 35 degrees C without changes in color.

Color↗

PubMed1996

[Knowledge about AIDS prevention among professionals and students in health care].

This work is a exploratory research based on the analysis of the answers to the questionnaires of 52 students and health care professionals knowledge about AIDS sexual prevention, biosecurity, diagnosis tests, patients and workers rights and the modifications of nursing and medical care to this kind of disease.

Acquired Immunodeficiency Syndrome↗