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Biomedical subjects

A Navarro

Publications and source records attributed to A Navarro.

At least 127 records · Page 7Linked to original sources
PubMed1997

[Life tables of Blattella germanica (Dictyoptera: Blattellidae) under laboratory conditions and their importance for its control].

A study of the life tables of Blatella germanica (L.) 1767 was conducted under laboratory conditions. 3 treatments were used a according to the number of individuals in each breeding flask (A = 9 flasks with 20-25 individuals, B = 17 flasks with 30-35 individuals, and C = 30 flasks with a newly hatched nymph each). The main parameters of the population growth were calculated by the TABVID software . The respective values for treatments A and B were the following: net reproduction rate (Ro 2.23 and 2.37), natural increase finite rate (lambda = 1.06), natural increase intrinsic rate (r = 0.06), and mean generational time (T = 13.89 and 15.64). The behaviour of the survival probability by age, the fertility rate, and the mortality rate were graphically registered. Life expectancy for treatment C was 16.47 and the survival rate for this treatment was represented by a graph. Graphics of the growth curve of this species and of the survival rate for treatments A and B were shown. The latter was concave, which means that mortality is higher during the young stages. This study provides esential cuantitative basic date that allow to carry out a more efficient control if fight is directed to the period where the highest natural mortality was found, that is, at the step from nymph 6 to adult in treatments A and B.

Animals↗
PubMed1996

Ultrastructural and quantitative study of atypical age-related bodies in the hamster brain.

Atypical bodies (ABs), related to aging, are described in the central nervous system of normal aged hamsters. Our study used ultrastructural microscopy and quantitative stereology analysis to study these structures in the hypothalamus and brain stem of 3, 6, 12, 18, 24 and 30 month-old hamsters. We found that these complex bodies have an oval or a round profile with a core of fibrillar or tubular structures rounded by a cytoplasmic crown. We frequently observed accumulations of organelles displaying evidence of degeneration. We found that these structures did not appear until 12 months and their frequency increased with age from 12 to 30 months. Their size can range from 3 to 10 microns, although the median size is 6.5 +/- 0.49 microns in diameter. There is a significant correlation between the quantity of these ABs and the animal's age. Their appearance in both hamster and human normal aging can provide an appropriate animal model to yield more information about the normal aging process. This knowledge of the normal aging process in hamsters may also give new insights into which processes in the human brain occur with normal aging and which ones may be exacerbated as in Alzheimer's disease.

Age Factors↗
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

Dynamics of gametic disequilibria between loci linked to chromosome inversions: the recombination-redistributing effect of inversions.

The total gametic disequilibrium between two loci linked to polymorphic inversions can be partitioned into two types of components: within and between chromosome arrangements. The within components depend on the gametic disequilibrium within each chromosome arrangement. The between components depend on the locus-inversion disequilibria. This partitioning has practical applications and is indispensable for studying the dynamics of these systems because inversions greatly reduce recombination in the heterokaryotypes while allowing free, and sometimes different, recombination in each of the homokaryotypes. We provide equations for the per generation change of the various disequilibria for systems with two and three chromosome arrangements, and the general recursive equations predicting the disequilibria after any number of generations for the case of two arrangements. Simulation studies were carried out using different values of the recombination parameters and all possible initial conditions. The results show a complex convergence to linkage equilibrium in inversion systems. The various disequilibria can have local maxima and minima while approaching equilibrium and, moreover, their dynamics cannot be described, in general, using a single parameter, i.e. an effective recombination rate. We conclude that the effects of inversions on gametic disequilibria must be carefully considered when dealing with disequilibria in inversion systems. The formulae provided in this paper can be used for such purpose.

Alleles↗
PubMed1996

Localization of ribosomal genes in human spermatogonia by fluorescent in situ hybridization and confocal microscopy.

The distribution of ribosomal RNA genes in nucleoli is still a matter of controversy. We have investigated the nucleolus of human type A spermatogonia, which displays a single, large fibrillar center. Silver-staining was used to localize the fibrillar center by light microscopy. Fluorescent in situ hybridization was performed on the same cell, using a 5.8-kb probe specific for a transcribed region of the ribosomal genes. The fluorescent area exactly corresponded to the silver-stained area. The three-dimensional distribution of rDNA was studied in horizontal and orthogonal sections using a confocal laser scanning microscope. The presence of the fluorescent signal throughout the whole silver-stained structure demonstrated that the fibrillar center, and at least a part of the dense fibrillar component, contained most of the rDNA.

Cell Nucleolus↗
PubMed1996

The distribution of Ag-NORs proteins and ribosomal RNA genes in human spermatogonia: an original procedure associating silver-staining, fish and confocal microscopy.

It is generally accepted that Ag-NORs proteins are associated with nucleolar components engaged in rRNA synthesis. Since conflicting results have been reported concerning the intranucleolar sites of active ribosomal genes, the relationships between the silver-stained areas and the distribution of rDNA were analyzed in human spermatogonia using confocal microscopy of fluorescent in situ hybridized preparations previously stained with silver. The fluorescent signal strictly corresponded to the silver-stained area, identified at the ultrastructural level as the fibrillar center and the surrounding dense fibrillar component. A quantitative evaluation of nucleolar activity solely based on silver-staining may be misleading, taking into account that only Ag-positive proteins located in the dense fibrillar component can be associated with transcriptional activity, while those stored in the fibrillar center are associated with non-transcribed rRNA genes.

DNA, Ribosomal↗
PubMed1996

[Endorectal echography. Its usefulness in the study of neoplasms of the rectum].

OBJECTIVE: To analyze prospectively the results of the first endorectal ultrasonographies performed at the Coloproctology Unit of the Hospital Mutua de Terrassa in patients with rectal tumors. METHODS: During the period between September 94 to June 95, 27 endorectal ultrasonographies were performed to patients with rectal tumors. The echographies were performed with a 360 degrees transducer. The ultrasound findings were compared to the histological results. RESULTS: Three patients were not treated surgically, and were excluded from the analysis. In addition, three patients with perianastomotic recurrence were excluded. Of the remaining 21 patients the level of penetration in the rectal wall was correctly identified in 17 (81%). The presence of metastatic nodes was correctly assessed in 19 of the 24 patients explored (78%). CONCLUSION: For the preoperative assessment of rectal tumors, endorectal ultrasonography offers a good accuracy even during the learning curve.

Adult↗
PubMed1996

[Biological aspects of Blatella germanica (Dictyoptera: Blattellidae) in laboratory conditions].

In a study of Blatella germanica (L) 1767 (Dictyoptera: Blattellidae) carried out in laboratory conditions, 6 nymphal stages were found in a period of 114.71 days, at 29 +/- 1 degrees C and 80-90% of relative humidity. Times of appearence and eclosion of every ovipositted ootheca, as well as the offspring average of each one, were determined. Females ovipositted up to 5 oothecas during their life. The maximum average of eggs found per ootheca was 29.22. The average longevity of males was lower that that of females (77.23 and 98.40 days, respectively) (t = 2.21; p < 0.05).

Animals↗
PubMed1996

[The performance of the Aedes aegypti eradication program in 2 towns of Ciudad de La Habana province, 1990-1992].

It is made a comparative analysis of the behaviour of the Aedes aegypti eradication program in two municipalities of Havana City with different characteristics during 1990-1992. The results show that in both municipalities the recipients with the highest positivity to mosquitoes were the following categories: other deposits, artificial deposits, and low tanks, followed by a second group that included tubs, tires, and larva tramps. The positivity of the larva tramps was observed in both municipalities and it is stressed their role in the stabilization of mosquitoes invading the urban ecosystem. There were 8 varieties of species at Plaza municipality, and 9 at the 10 de Octubre municipality. There are similar species in both municipalities.

Aedes↗
PubMed1995

[Agrobacterium radiobacter bacteremia. Study of 2 cases and review of the literature].

BACKGROUND: Agrobacteria are small gramnegative bacilli which produce tumors in different vegetal species and occasionally are human pathogens. METHODS: A retrospective review was carried out and the contribution of 2 cases of bacteremia by Agrobacterium radiobacter reported. RESULTS: Both patients developed uncomplicated bacteremia easily controlled by antimicrobian treatment without requiring removal of the intravascular device in one. CONCLUSIONS: Agrobacterium is a rare cause of bacteremic infection in immunosuppressed patients with intravenous catheters. Although the isolations are sensitive to different antibiotics some strains present resistance to cefalosporines, aminoglycosides and cloramphenicol. The mortality of these infections is slight.

Adolescent↗
PubMed1995

Ultrastructural study of a special type of ependymal cell at paraventricular level of the golden hamster third ventricle.

The present paper describes the presence of a special cell located in the ependymal wall at the level of the paraventricular nucleus. At this level, ultrastructural observation of these ependymal cells, unlike most other mammalian species, shows the presence of nucleolus-like bodies in their cytoplasm and occasionally basal processes. These processes appear perpendicular to the ependymal surface and end in contact with the basal membrane of hypothalamic capillaries. Mitochondria, endoplasmic reticulum and numerous filaments are present in the basal processes. Nucleolus-like bodies or nematosomes consist of round or ovoid unbound masses of granular appearing material of variable density located in the apical cytoplasm of the cells. Some of their ultrastructural characteristics are similar to other ependymal specialized cells which are classically termed tanycytes. These findings point out the possibility that those special cells may also be implicated in a ventricle-blood vessel communication.

Aging↗
PubMed1995

[The effect of abiotic factors on the incidence of Aedes aegypti in the town of 10 de Octobre, Ciudad de la Habana Province, 1982-1992].

An analysis of the relation among the quantity of focuses of Aedes aegypti, the rains and the temperatures in rainy and dry periods from 1982 to 1992 in 10 de Octubre municipe, at City of Havana, was carried out. No correlation was found between the number of focuses and the rains occurred in both seasons, and it was just the same between the number of focuses and temperatures. Thus, emphasis is made in the need for a strong surveillance along all year.

Aedes↗