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Biomedical subjects

S Rodríguez

Publications and source records attributed to S Rodríguez.

At least 91 records · Page 5Linked to original sources
PubMed1992

Intra-uterine long bone growth in small-for-gestational-age infants.

To better understand the intra-uterine bone modelling and remodelling process in small-for-gestational-age (SGA) newborn infants, long bone growth was studied using postmortem X-ray films in a group of such infants (n = 34). Bone length, diaphyseal diameter, medullary diameter, cortical thickness, cortical area, the Barnett-Nordin index, and the percentage of cortical area were determined in femur, tibia, and humerus. A separate group of appropriate-for-gestational-age (AGA) newborn infants (n = 146) was used as controls. Length and cortical bone mass in all three bones were significantly lower in SGA infants than in AGA infants. Decreased cortical bone mass in SGA infants was the result of decreased diaphyseal diameters and increased medullary diameters. Similar results were obtained when SGA infants were subclassified as preterm and term and compared with the control group of AGA infants. Bone lengths and diaphyseal diameters in SGA infants did not differ from those observed in a weight-matched control group of AGA infants although the latter were younger by 4 weeks' gestation. However, the cortical bone mass was lower than in the control group because of the relative greater medullary diameters in all three long bones in the SGA infants. Our present results indicate that reduced cortical bone mass in SGA infants is a mixed growth modelling and remodelling dependent process.

Bone Density↗
PubMed1992

Transverse bone growth and cortical bone mass in the human prenatal period.

The prenatal development of the normal diaphysis of the human long bone was studied through postmortem radiographs in 60 stillborns and 86 newborns of 20-41 weeks gestational age. Quantitative parameters were determined for the tibia, femur, and humerus. In all three long bones, significant positive correlations were found between the diaphyseal diameter, medullary diameter, cortical thickness, and cortical area, and the gestational age, body weight, body height, and bone length. No significant differences in any studied parameters were observed between males and females. In the tibia, the diaphyseal diameter grew more than in the femur and humerus. In these two latter bones, the medullary diameter growth rate was greater than the diaphyseal diameter growth rate, and thus the Barnett-Nordin index and percentage of cortical area showed mild but significant negative correlations with gestational age, body weight, body height, and bone length. The velocity of medullary diameter growth was similar (0.05 mm/week) in all three long bones; however, the velocity of diaphyseal diameter growth was greater in the tibia (0.161 mm/week) than in the femur (0.142 mm/week) or humerus (0.129 mm/week). The diaphyseal growth rate decreased in the second half of the period studied in all three bones. This decrease was more striking in the humerus. Observed differences in diaphyseal growth among the long bones studied may be genetically determined in relation to its different postnatal functions.

Bone Development↗
PubMed1992

[Frequency of platelet specific alloantigens HPA-1a (P1A1) and HPA-4a (Pen(a)) expression in Chilean population].

The phenotype frequency of platelet-specific alloantigens has been reported to vary with the ethnic composition of the population under study and the only two HPA-4a negative individuals found in the United States were of Hispanic origin; therefore, the aim of this work was to define the frequency of expression of these systems in the Chilean population. Using an ELISA with captured antigen by monoclonal antibodies, 604 blood donors were typed for the platelet-specific antigen systems HPA-1 and HPA-4. Eight samples typed negative for HPA-1a (1.32%) and 596 typed positive (98.68%). The calculated gene frequencies were 0.88 for HPA-1a (gene frequency > 0.99). Since these antigens are involved in thrombocytopenic disorders such as neonatal alloimmune thrombocytopenia and post-transfusion purpura, their frequency in a population is of clinical relevance. The gene frequency found for HPA-1a is higher than in Europeans (0.85) and lower than in Mapuche Indians (0.99), which is to be expected from the ethnic origin of our population. The absence of HPA-4a negatives in this study does not support our original hypothesis of a higher polymorphism of this system among hispanics.

Antigens, Human Platelet↗
PubMed1992

[An experimental evaluation of a splenic autograft in the greater omentum].

This report comprises a study of splenic autotransplantation in omental pouches in rats. Twenty six rats were operated. The spleen (50%) was transplanted after splenectomy in four different fragments. The animals were re-explored after periods between 3 and 5 1/2 months and the splenic implants retrieved for histological examination as well as size and weight evolution. In 25/26 animals a viable spleen was identified. The mean weight of the retrieved spleen fragments was 150 mg versus 525 mg weight of the implanted materials. In no case there was an increase in size of the implanted fragments. Fifty-two of the 104 implanted fragments were retrieved with weight increase in 8.65% of them.

Animals↗
PubMed1991

Effects of physical training during the growth on the granulation of myo-epithelioid cells of the rat kidney.

The behaviour of the granulation of the myo-epithelioid cells of the juxtaglomerular apparatus of the kidney and its relationship with the plasma concentrations of renin, sodium and potassium, and plasma osmolality have been studied in male and female Wistar rats that have been subjected to a programme of moderate physical exercise throughout their period of growth. In the trained rats a significant increase in the juxtaglomerular granulation index and a significant decrease in plasma renin concentration has been observed, the changes being more prominent in the female animals. Moreover in the trained rats significant increases in plasma sodium, potassium and osmolality have been observed.

Aging↗
PubMed1990

Single injection into the cerebrospinal fluid of antibodies against the secretory material of the subcommissural organ reversibly blocks formation of Reissner's fiber: immunocytochemical investigations in the rat.

An antibody (cf. Rodríguez et al. 1984b) raised in rabbits against the glycoproteins of the bovine Reissner's fiber (RF) was injected into the lateral brain ventricle of 38 rats with the aim to interfere with RF formation. The rats were killed 20 min; 1, 4, 8, 12 h; and 1, 2, 3, 5, and 8 days after the injection. Based on the fact that the material secreted by the subcommissural organ (SCO) into the cerebrospinal fluid (CSF) first condenses on the organ surface as a distinct layer (pre-RF material) and then becomes assembled to form RF and that both structures are distinguishable in tissue sections, three immunostaining procedures were applied. They served to visualize: (i) secretory material that had not bound the injected antibody; (ii) secretory material-antibody complexes formed in vivo; and (iii) antibody not bound to its antigen and present in the ventricles and the subarachnoid space. After a single injection of the above-mentioned antibody the following events were observed: (1) The antibody was present in the brain cavities for at least 8 h. (2) The injected antibody bound selectively to the pre-RF and RF. (3) Pre-RF displayed antibody binding during the 24 h following the injection. During the 2nd and 3rd post-injection days, the pre-RF was free of antibody, indicating that it was formed by newly released secretory material. (4) Approximately 4 h after the injection, the RF detached from the SCO and underwent fragmentation. Clusters of these fragments were found in the Sylvian aqueduct and fourth ventricle. (5) In the fragmented original RF the injected antibody against Reissner's fiber remained bound throughout the entire period of observation, i.e. for 8 days. (6) In rats of the 1-, 3-, 5- and 8-day-groups, RF was missing from the central canal of the spinal cord. (7) One day after the injection, a new RF structure started to grow from the rostral end of the SCO. This newly formed fiber could be distinguished from the original RF because of (i) its normal appearance; (ii) it did not display binding of the injected antibody. (8) At day 3, the growing RF had not yet extended to the Sylvian aqueduct. (9) At day 8, the new RF reached the fourth ventricle. Control experiments involved the intraventricular administration of (i) an antibody against the secretory material extracted from the entire bovine SCO; (ii) antivasopressin; and (iii) rabbit IgG. From these only antibody (i) bound to pre-RF and RF.

Animals↗
PubMed1990

Evaluation of the high density lipoprotein cholesterol protective effect against atherogenesis in rabbits fed cholesterol supplemented diets.

Plasma high density lipoprotein cholesterol (HDL-C) was evaluated in 15 rabbits fed cholesterol supplemented diets to assess its protective effect on the atherogenic process. From a baseline level of 29 +/- 11 mg/dl (mean +/- SD) the maximum attained for HDL-C was twofold in only three rabbits, whereas total cholesterol (TC) increased 20 fold. Plasma TC/HDL-C ratio rose 80 fold from the baseline (2.4 +/- 0.9) and it was the best parameter that correlated with aortic cholesterol accumulation and pathological scores. Aortic TC content increased 10 fold and free cholesterol/cholesterol esters ratio decreased 20 fold. Pathological studies showed that aortic lesion scores rose from 0 to 4. It can be concluded that the high correlations obtained when TC/HDL-C ratio was plotted against both aortic cholesterol deposition and lesion scores, support the theory of the reverse cholesterol transport and the effectiveness of this index to predict the degree of the atherogenic process. On the other hand, the poor response of HDL-C in this model encourages future research using drugs to increase this parameter in order to normalize TC/HDL-C ratio and avoid lesions.

Animals↗
PubMed1989

Light- and electron-microscopic investigation of the rat subcommissural organ grafted under the kidney capsule, with particular reference to immunocytochemistry and lectin histochemistry.

There is increasing evidence that, in the rat, a serotonin-mediated neural input may have an inhibitory influence on the secretory activity of the subcommissural organ (SCO). In the present investigation the rat SCO was studied 7, 30 and 90 days after transplantation under the kidney capsule, an area devoid of local serotonin-containing nerves. The grafted tissue was examined by use of immunocytochemistry employing a series of primary antisera, lectin histochemistry and transmission electron microscopy. The grafted SCO survived transplantation and contained, in addition to secretory ependymal and hypendymal SCO-cells, also elements immunoreactive with antisera against glial fibrillary acidic protein or S-100 protein. In transplants, SCO-cells produced a material displaying the characteristic immunocytochemical and lectin-binding properties of SCO-cells observed under in-situ conditions. The ependymal cells lined 1-3 small cavities, which contained secretory material. A fully developed structural equivalent of Reissner's fiber was, however, never found. The immunocytochemical and ultrastructural study of the grafted SCO showed an absence of nerve fibers within the graft and suggested a state of enhanced secretory activity. A network of protruding basal lamina structures connected the secretory cells to the newly formed capillaries revascularizing the SCO. One week after transplantation, long-spacing collagen started to appear in expanded areas of such laminar networks and also in the perivascular space. It is suggested (i) that the formation of long-spacing forms of collagen is triggered by factors provided by the SCO-secretory cells, and (ii) that secretory material of the ependymal and hypendymal cells may reach the reticular extensions of the basal lamina. In contrast to the SCO in situ, the grafted SCO-cells showed a positive immunoreaction for neuron-specific enolase. They became surrounded by a S-100-immunoreactive glial sheath that separated them from other transplanted cell types and the adjacent kidney tissue of the host.

Animals↗
PubMed1989

[Peritoneal hydatidosis with fistulization into the sigmoid colon].

A case is presented of peritoneal hydatidosis with fistulization into the sigmoid in a patient who had previously undergone surgery for hepatic hydatidosis. The clinical picture made its debut as an alteration in intestinal habit followed by the appearance of diarrheic syndrome and expulsion of hydatid membranes. The natural history of peritoneal hydatidosis, its complications and therapeutic guidelines are discussed.

Aged↗
PubMed1986

Light- and electron-microscopic immunocytochemistry and lectin histochemistry of the subcommissural organ: evidence for processing of the secretory material.

The subcommissural organ (SCO) of the rat was investigated by use of histochemical and immunocytochemical methods at the light- and electron-microscopic levels. Consecutive thin methacrylate sections were stained with the pseudoisocyanin (Psi), immunoperoxidase (IMC; employing an antiserum against Reissner's fiber, AFRU), periodic acid-Schiff (PAS) and periodic acid-silver methenamine (SM) techniques, and reacted with six types of lectins. Psi, SM, concanavalin A (Con A) and IMC were also used for double and triple sequential staining of the same section. Increasing dilutions of AFRU (from 1:1000 to 1:200 000) were used for immunostaining of serial paraffin sections. In addition, ultrastructural localization of (i) Con A-binding sites and (ii) immunoreactive secretory material was performed. Some of these procedures were also applied to the ophidian and canine SCO. Con A-positive, Psi-positive and immunoreactive materials coexisted within the same cisternae of the rough endoplasmic reticulum. The Golgi apparatus lacked Con A-positive and immunoreactive substances. Apical secretory granules and secreted material lying on the surface of the SCO showed (i) the highest affinity for AFRU, but were (ii) Con A-negative, and (iii) wheat-germ agglutinin-, PAS- and SM-positive. Reissner's fiber displayed a low affinity for AFRU. It is suggested that the SCO secretes N-linked glycoproteins, the carbohydrate and protein moieties of which undergo (i) a maturation process before being released, and (ii) some kind of modification(s) after their release into the ventricle. The perivascular secretory cells of the dog SCO might secrete a material different from that secreted by the ependymal cells.

Animals↗