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Biomedical subjects

C Díaz

Publications and source records attributed to C Díaz.

At least 91 records · Page 5Linked to original sources
PubMed1998

[The selection of a strain of Culex quinquefasciatus resistant to lambdacyhalothrin and its spectrum of cross-resistance to other insecticides].

A field strain of Culex quinquefasciatus resistant to pyrethroid lambda-cyhalothrin insecticide was selected to be used as a reference strain in the laboratory for conducting studies of biochemistry and genetics of resistance, to evaluate the utility of this insecticide for the control of mosquitoes in Cuba, and to determine the cross resistance to organophosphate insecticides, pyrethroids and a carbamate. A high resistance to lambdacyhalothrin was obtained after 6 generations of selective pressure. Lowe or no cross resistance to other pyrethroids (deltamethrin and cypermethrin), to a carbamate (propoxur) and to the organophosphate insecticides (clorpirifos and methyl-pyrimifos) was observed. A high cross resistance to malathion (organophosphate) was detected.

Animals↗
PubMed1998

[Resistance in a strain of Culex quinquefasciatus coming from Medellín, Colombia].

The levels of susceptibility and/or resistance to 5 organophosphate insecticides (malathion, methyl-pyrimifos, clorpirifos, temephos and fenthion), 4 pyrethroids (cypermethrin, deltamethrin, permethrin and lambda-cyhalothrin), and a carbamate (propoxur) were determined in order to know the state of resistance in a strain of Culex quinquefasciatus from a locality of the city of Medellín, Colombia. Resistance to all organophosphate insecticides, though with relatively lower values for methyloirimifos and fenthion, was observed. No resistance to lambda-cyhalothrin and cypermethrin or to propoxur was found. These insecticides may be useful for the control of mosquitoes in Colombia. It was demonstrated by using the piperonil butoxide synergist that the oxidases of multiple function played an important role in the resistance to organophosphate insecticides and pyrethroids. The utilization of S.S.S. tributyl phosphotritiate revealed that the superproduction of unspecific esterases was a mechanism of resistance to organophosphate insecticides, except methyl-pirimifos and for perythroids, except lambda-cyhalothrin. This result should be taken into consideration for the strategies to be used to control Culex quinquefasciatus in Colombia. These two mechanism of resistance are not responsible for the resistance to propoxur. The electrophoretic analysis showed the presence of esterases B1, A6 and B6, which seem to have an important function in resistance.

Animals↗
PubMed1998

Ex vivo proliferation of mesothelial cells directly obtained from peritoneal effluent: its relationship with peritoneal antecedents and functional parameters.

The peritoneal membrane requires anatomico-functional integrity to guarantee long-term stability for peritoneal dialysis (PD). Since mesothelial cells (MC) are active cells and the first part of the membrane to contact the dialysate, they are important in maintaining this stability. Mesothelial cells released daily into peritoneal effluent are able to grow in culture. This growth capacity may be related to some of the anatomicofunctional characteristics of each peritoneum. Our aim was to culture mesothelial cells taken from peritoneal effluents drained by 32 PD-stable patients, and relate this growth capacity to individual peritoneal data. Cells were taken from a residual fluid after sedimentation, washed twice with phosphate-buffered saline (PBS), and seeded into 25-cm2 tissue-culture flasks. These flasks were incubated in a humidified 5%-CO2 atmosphere. After MC confluence, cells were detached by trypsinization, passaged into 24-well plates, and finally counted. Cells were identified by morphology and immuno-histochemical characteristics. Cells from 28 out of 32 patients showed an appropriate growth in culture. Mesothelial cell confluence was reached in a mean of 18.2 +/- 8 days. After 7 days of seeding in plate wells, the cell growth showed a significant and progressive increase until day 16. Mesothelial cell growth rate was inversely related to PD duration. Neither peritonitis incidence nor other demographic characteristic were related to MC growth. Creatinine and urea mass transfer coefficients (MTC), but not ultrafiltration (UF) capacity, were significantly related to MC growth rate. In conclusion, the growth in culture of MC taken directly from PD bags is certainly possible. This growth is influenced by some of the intrinsic peritoneal characteristics derived from the peritoneal dialysis process. This tool could be useful in evaluating individual peritoneal conditions and, probably, as a method for peritoneal viability follow-up, although further research is required.

Ascitic Fluid↗
PubMed1998

Consequences of peritonitis episodes appearing late during peritoneal dialysis (PD) in patients able to continue PD.

The lack of specific information on the peritoneal-function consequences of late peritonitis episodes, and the concern about long-term consequences of peritoneal dialysis (PD), have prompted us to study the peritoneal function of long-term PD patients after a late peritonitis episode. The question is: Is the peritoneum more vulnerable to infections, in terms of functional effects, after a long time on PD? Forty-nine patients observed from baseline to the first year of PD with no peritonitis constituted the "early" control group; 31 other patients had one episode of peritonitis in the same period. Twenty-seven patients with no peritonitis from the fourth to fifth years comprised the "late" control group; 15 other patients had one episode during the same period. The results presented here suggest that peritoneal vulnerability to infectious episodes depends on the PD stage in which they appeared. Certainly, episodes with similar aggressive capacity in terms of inflammation duration (3-4 days) happening during the fifth year led to a loss of ultrafiltration (UF) capacity that does not appear in patients who suffer an episode during the first PD year. A remarkable feature is that this UF-capacity decrease is not accompanied by the usual creatinine mass transfer coefficient increase. This fact suggests that the dependence between peritoneal-glucose-gradient maintenance and water transport has been partially modified over time on PD. In conclusion, late mild peritonitis has distinct peritoneal-function consequences relative to early peritonitis. Patients who continue PD after one late episode showed an accentuation of the usual change which happens on long-term PD, the loss of peritoneal ultrafiltration capacity.

Creatinine↗
PubMed1998

[Transplantation of fetal dopaminergic cells simultaneously to the corpus striatum and pars reticularis of the substantia nigra in hemi-parkinsonian rats].

INTRODUCTION: Transplantation of foetal dopaminergic cells has been extensively used as restorative treatment for Parkinson's disease. OBJECTIVE: This study was carried out to determine the survival, modifications in rotatory activity induced by D-amphetamine and total content of dopamine in the striatal and nigra regions of hemiparkinsonian rats which had had foetal mesencephalic cells simultaneously transplanted to the striatum and pars reticularis of the substancia nigra. MATERIAL AND METHODS: The study was done using adult male Wistar rats weighing 200-250 gms. The following experimental groups were formed, depending on the site of transplant: St: transplant to striatum (n = 2); SNr: transplant to SNr (n = 20), ST + Snr; transplant to striatum and SNr simultaneously n = 20; and control (lesion with no transplant) n = 20. We studied the rotatory activity induced by D-amphetamine 1, 2, 3 and 6 months after transplantation. After this time the rats were deeply anaesthetized and randomly allocated for morphological study or biochemical determination of the total dopamine content in the St and SNr using the HPLC technique. RESULTS: Study of conduct showed no significant differences in rotatory activity induced by D-amphetamine between the groups with intrastriatal transplants, but there was a difference between these and the SNr and control groups. Biochemical analysis showed that striatal DA content was significantly greater in the ST for the groups with intrastriatal transplants. The content of substancia nigra DA was significantly greater in the SNr of the ST + SNr group, followed by the ST group. Morphometric study showed differences, which were not significant, between ST transplanted animals and significant differences between the SNr transplanted group with a significant increase in survival of the SNr of the ST + SNr group. CONCLUSIONS: These results suggest a positive effect due to intrastriatal transplants compared to survival following intranigral transplants.

Adrenergic Agents↗
PubMed1998

[Obtention and characterization of murine beta-NGF. Application in a model of cerebral aging].

INTRODUCTION: beta-NGF is a basic protein of 118 aminoacids which acts are a trophic factor for sensory and sympathetic neurons of the peripheral nervous system, and on cholinergic neurons of the anterior basal cerebrum. OBJECTIVES: In view of the functional effect of beta-HGF and its possibilities as a therapeutic agent in neurodegenerative disease, including Alzheimer's disease in this study our aim was to obtain, characterize and show the main results of the application of beta-NGFm in a model of cerebral ageing in rats with cognitive disorders. MATERIAL AND METHODS: For the obtention of beta-NGFm we followed Mobley's method as modified by Ebendal and used mouse submaxillary gland as a source of raw material. The characterization studies were carried out by application of seven techniques which allowed physicochemical characterization and demonstration of the biological activity of the product. Application of beta-NGF obtained under these conditions was carried out in a mode of cerebral ageing and the effects of treatment were assessed by conduct studies, measurement of the activity of the enzyme acetyl cholinesterase and study of neural plasticity. CONCLUSIONS: Characterization studies carried out on the beta-NGFm showed that the protein obtained consists of a mixture of molecules of beta-NGFm which are intact at their extreme N-Terminal, and molecules which have lost the octapeptide of the N-terminal position and show some modification increasing hydrophobicity. All these species were recognized immunologically by the specific antibody anti-NGFm and showed biological activity.

Aging↗
PubMed1998

[Medical negligence in Puerto Rico: 1990-1996].

The purpose of this communication is to present the statistical information of the medical and hospital professional liability situation in Puerto Rico from 1990 to 1996. The Medical Institutional liability is a topic of great relevancy and importance to the people of Puerto Rico and the leaders responsible for establishing policies for the health care services. The Reports on Medical and Hospital Professional Liability from 1991 to the 1996 produced by the Examining Physicians Board were reviewed. The liability claims from 1991 to the 1996 totaled 4054. During the seven years analyzed, 3506 cases were closed against physicians and institutions, a payment was issued in 1272 cases (36.3%), for a total compensation of $56,268,053. The risk of a legal claim is greater for the group of Plastic Surgeons and Emergency Medicine. The probability of a plaintiff receiving a compensation payment in a case of medical malpractice is approximately 36%, usually receiving a third of the total of the award as suggested by the medical literature. A thoughtful analysis of the current medical liability situation and defensive medicine should be done with the purpose of protecting the fiduciary function of the physicians with respect to the health of their patients, this is the function that guarantees a physician-patient relationship that is healthy, righteous and empathic.

Defensive Medicine↗
PubMed1998

[Epidermoid carcinoma of the nasal septum].

Squamous-cell carcinoma of the nasal septum occurs infrequently and only a few cases have been reported. Because of the small number of cases, comparisons between treatment groups have been inadequate. Five patients with this type of tumor are presented. All of them underwent surgery (4 as primary treatment and 1 for recurrence after radiation therapy). One patient had a local recurrence, 2 had cervical metastases, and 2 (40%) died as a consequence of the tumor. In the squamous cell carcinoma of the nasal septum our study supports surgical resection with wide margins combined with postoperative irradiation as the preferred treatment with prophylactic neck dissection for tumors over 2 cm or extended to adjacent areas.

Aged↗
PubMed1998

[The effects of aging on the volume of human vestibular nuclei].

Elderly persons often have balance disorders, with dizziness that sometimes leads to falls. Changes in the peripheral vestibular system with age, with loss of the hair cells and neurons of Scarpa's nucleus, have been studied for years. However, the changes in the vestibular nuclear complex with age have not been examined. We studied paraffin-embedded brainstems from nine persons of different ages in order to analyze possible changes with age. No abnormalities were observed in the volume or length of the vestibular nuclei, except for a decrease in both dimensions in the superior vestibular nucleus (SNV). All the main vestibular nuclei showed an increase in lipofuscin content with age that seemed to be less marked in the SNV. The low lipofuscin concentration in the SNV could be related with the conservation of vestibular reflexes, the center of which seems to be the SVN, in elderly persons.

Adult↗
PubMed1997

Morphometric analysis of the human vestibular nuclei.

BACKGROUND: Cytoarchitectural investigations of the vestibular nuclei have been undertaken in different species of mammals. These data provide a description of the general architecture of the nuclei but limited information about quantitative characteristics of their cell population. We have recently obtained data about the morphometric parameters of the vestibular nuclei neurons in some species. The application of quantitative image analysis techniques to the research of the cellular morphology in the vestibular area of humans might provide basic information to compare with data from animal studies, taking into account the observed correlation between physiological and morphological properties of vestibular neurons. METHODS: The characteristics of the major vestibular nuclei in humans have been studied with light microscopic techniques in serially cut sections. Camera lucida drawings of the vestibular nuclei and their neurons were made and subjected to computerized image analysis. For each vestibular nucleus, information was obtained about topography, morphological characteristics (i.e., location, volume, and length), and the number and morphometric parameters of their neurons (cross-sectional areas, maximum and minimum diameters). Morphometric data about cell parameters were statistically analyzed by comparing the populations within different parts of each nucleus and from different nuclei. RESULTS: Among the vestibular nuclei, the medial, which is the largest, has the greatest number of neurons, and the interstitial, the least. The lateral and interstitial nuclei contain the largest cells, and the descending nucleus has the smallest cells. The superior nucleus contains cells of intermediate size. The size of cells decreases in a rostrocaudal direction in the medial, lateral, and descending nuclei, the opposite trend being observed in the superior nucleus. Within the superior and medial nuclei, there are discrete areas with cells with distinctive characteristics. CONCLUSIONS: These results suggest that, just as most of the anatomical characteristics of the second-order neurons found in animals have been preserved in humans, so the physiological mechanisms observed in the vestibular system of animals should apply to humans.

Adult↗
PubMed1997

Age-specific prevalence of Escherichia coli with localized and aggregative adherence in Venezuelan infants with acute diarrhea.

To evaluate the epidemiological significance of HEp-2 cell-adherent Escherichia coli isolates in diarrheal disease, we performed a study with 513 Venezuelan infants with diarrhea and 241 age-matched controls to determine the prevalence of enteropathogenic E. coli (enteroadherent E. coli, enterotoxigenic E. coli, enteroinvasive E. coli, and enterohemorrhagic E. coli) and their correlation with O:H serotypes. E. coli isolates exhibiting localized and aggregative adherence in the HEp-2 cell assay were significantly more frequently isolated from the patients (8.5 and 26.9%, respectively) than from the controls (1.7 and 15%, respectively). This difference was significant for the group 0 to 2 months of age but for older infants. Regardless of age, E. coli isolates with diffuse adherence were found at similar frequencies in both the patients and the controls. A striking correlation between classic O serogroups and localized adherence was also observed. These findings confirm the pathogenic role of E. coli with localized and aggregative adherence in diarrheal disease, as well as the epidemiological importance of O:H serotyping for characterizing localized-adhering E. coli.

Acute Disease↗
PubMed1997

Primary Sjögren's syndrome and associated lung disease: CT findings in 50 patients.

OBJECTIVE: We prospectively evaluated the high-resolution CT findings in 50 nonsmoking patients with proven primary Sjögren's syndrome. CONCLUSION: High-resolution CT is a sensitive technique in assessing pulmonary involvement in patients with primary Sjögren's syndrome. Interstitial lung disease and bronchiolar inflammatory changes are common abnormal findings seen on CT scans in primary Sjögren's syndrome.

Adult↗
PubMed1997

Isolation, identification and antimicrobial activity of ombuoside from Stevia triflora.

From aerial parts of Stevia triflora DC the flavonol glycoside ombuoside (7,4'-di-O-methylquercetin-3-O-beta-rutinoside) has been isolated and identified on the basis of spectral data. Ombuoside and the synthetic derivatives octa-acetylombuoside, ombuine and retusine were tested for antimicrobial activity against several strains of Gram-positive and Gram-negative bacteria and the yeast Candida albicans, using the agar diffusion method. The flavonol glycoside ombuoside and the respective aglycone ombuine, both exhibited moderated activity against Corynebacterium diphtheria, Staphylococcus aureus, Escherichia coli and Candida albicans. To a lesser degree, octaacetylombuoside and retusine showed activity against the Gram-positive bacteria C. diphtheria and S. aureus, but proved to be inactive against Gram-negative bacteria and Candida albicans. These results indicate that the presence of free hydroxyl groups, either alcoholic or phenolic, is an important chemical feature for the expression of flavonol antimicrobial activity. It is worth noting that this is the first study reported on the antibacterial and antifungal activity of these substances.

Anti-Bacterial Agents↗
PubMed1997

[Determination of insecticide resistance and its biochemical mechanisms in 2 strains of Culex quinquefasciatus from Santiago de Cuba].

It was analyzed the behavior of the resistance of 3 organophosphated insecticides (malathion, clorpirifos and methyl-pyrimifos), 3 pyrethroids (deltamethrin, lambda-cyhalothrin and cypermethrin), and 1 carbamate (propuxur) in populations of Culex quinquefasciatus from 2 municipalities of the province of Santiago de Cuba. The values of the resistance factor proved that there is resistance to malathion and clorpirifos. However, in spite of the existence of a high frequency of the mechanisms of elevated esterases and altered acetylcholinesterase no resistance to methylpymirifos, was observed which demonstrated that this insecticide is not affected by these mechanisms selected in our populations of Culex quinquefasciatus. There was resistence to deltamethrin, and lambda-cyhalothrin in Santiago de Cuba, whereas it was moderate to cypermethrin in Santiago and San Luis. Resistance to deltamethrin was also found in San Luis, but it was mild to lambda-cyhalothrin. The results obtained from the use of the synergists S,S,S tributyl phosphotritiade (DBF) and piperonyl butoxide (PB) indicated that the mechanisms of resistance of unspecific esterases and oxidases of multiple function are involved in the resistance to pyrethroids in both strains from Santiago de Cuba and San Luis. It was determined by the biochemical tests that there existed a high frequency of the mechanisms of esterases and altered acetylcholinesterase. The results of the polyacrylamide gel electrophoresis (PAGE) showed that esterase B1 appears more frequently associated with esterases A6 and B6. It was inferred that this association could be connected with the resistance to pyrethroids.

Acetylcholinesterase↗
PubMed1996

Rostrocaudal and ventrodorsal change in neuronal cell size in human medial vestibular nucleus.

BACKGROUND: The present paper describes the cytoarchitectonic, morphometric, and three-dimensional characteristics of the human medial vestibular nucleus (MVN). We also studied the regional distribution, in size, of the different neurons and its possible relationship with a functional polarization of the different regions of the nucleus. METHODS: Nine adult human brainstems (30-50 years of age) without neurological problems were used. Specimens were obtained from necropsy and fixed in 4% paraformaldehyde and 5% acetic acid in distilled water. After fixation, blocks were washed, dehydrated, and embedded in paraffin and serial sectioned at 20 microns. Sections were stained with formaldehydethionin, dehydrated, cleared in eucalyptol, and mounted with Eukitt. MVN neurons were drawn with the aid of a camera lucida at 200-micron intervals at 390 x magnification. Serial 50-micron frozen sections were used to determine the volume of the MVN. The three-dimensional reconstruction of MVN was accomplished with a drawing program in a Macinthosh II computer and an AVS on a Stardent workstation computer. RESULTS: In the three-dimensional reconstruction, the human MVN shows a pyramidal form. The base of this pyramid constitutes the rostral limit, and its vertex forms the caudal border of the MVN. The estimated volume is 30.44 +/- 0.85 mm3, with a neuronal population of 127,737 cells and 4,136 neurons/mm3 in density. The average neuronal cross-section changes from one minimum at caudal level (212.46 +/- 2.04 microns 2) to one maximum at rostral level (491.47 +/- 5.08 microns 2). Four cell types, small (< 200 microns 2), medium (200-500 microns 2), large (500-1000 microns 2), and giant (> 1,000 microns 2) cells, were observed. Medium cells constitute 66%, small cells 18%, and large and giant cells 15% and 1% of the neuronal population. CONCLUSIONS: The MVN shows a variation in neuronal size, and it has the highest neuronal density of all the human vestibular nuclei. Large cells predominate in rostral regions of the MVN, with significant differences in the area and diameter of the cells among rostral, central, and caudal regions. Furthermore, the largest cells are grouped in the ventrolateral part of the nucleus, close to its boundaries with the inferior and the lateral vestibular nuclei. The morphological polarization, with respect to the neuronal size of the MVN, can be related to a functional polarization of rostral and caudal regions of this nucleus.

Adult↗
PubMed1996

Appropriate pattern formation following regulative regeneration in the hindbrain neural tube.

Patterns of neuronal differentiation and axon outgrowth were examined in regenerated neural tissue of the hindbrain of the chicken embryo. Specific regions of the hindbrain neural tube corresponding to identified rhombomeres were selectively removed unilaterally by microsurgery. Of the embryos that survived, about 35% exhibited regulative regeneration, wherein the missing hemi-rhombomere was reconstituted to normal size and morphology through compensatory proliferation and migration from adjacent tissue. The capacity for regeneration depended on the embryonic stage at which the ablation was performed and on whether the midline floor plate was included in the ablation. Ablations performed prior to the formation of morphologically overt rhombomere boundaries led to significantly lower frequencies of regulative regeneration than ablations performed after the formation of boundaries. Ablations that included the floor plate led to significantly lower frequencies of regulative regeneration than ablations sparing the floor plate. Regulative regeneration was also observed at low frequency following excision of an entire rhombomere. Within the regenerated hemi-rhombomere, identified neuron groups appeared in their normal positions and differentiated normal patterns of migration and axon outgrowth. The fidelity of this patterning, however, depended on the mediolateral position of the neuron group, being more reliable for neuron groups in the basal plate than in the alar plate. These results confirm the extensive regulative potential of the neural tube and demonstrate the capacity for appropriately patterned cellular differentiation within the regenerated tissue.

Animals↗
PubMed1996

Bilateral blindness in Takayasu's disease.

We report the case of a 61-year-old woman who presented bilateral blindness at the age of nineteen. Although she did not receive any treatment, she did not present any other symptoms through 40 years of follow-up. After reviewing the literature, we have not found any case of bilateral blindness as the first manifestation of TD without further progression of the disease despite the absence of treatment.

Aorta, Thoracic↗