Biomedical subjects

G Ruiz

Publications and source records attributed to G Ruiz.

At least 19 recordsLinked to original sources

PubMed1992

Effect of histamine on signal transduction in cultured human trabecular meshwork cells.

Stimulation of cultured human trabecular meshwork cells by histamine caused time and dose related increases in inositol phosphates and intracellular free calcium. The increase in inositol trisphosphate (IP3) was immediate and calcium independent while that of inositol monophosphate (IP1) was gradual and calcium dependent. The rise in intracellular calcium was also rapid and occurred as a result of mobilization from intracellular stores and influx from external medium. Histamine also caused time and concentration related de novo synthesis of inositol phospholipids. Mepyramine but not cimetidine inhibited the action of histamine. These results indicate that histamine, via H1 receptor, evokes an early hydrolysis of inositol phospholipids and increase in intracellular free calcium, signals which may be involved with the function of the trabecular meshwork cells.

Adult↗

PubMed1992

Differentiation of endocrine myocardiocytes in the developing heart of the toad (Bufo arenarum Hensel).

The differentiation of endocrine myocardiocytes was investigated in the heart of developing toad Bufo arenarum Hensel, combining ultrastructural and immunocytochemical procedures. The distribution of immuno-reactive atrial natriuretic peptide (ANP) in the whole heart was appraised by light microscopy, applying biotin-streptavidin and immunofluorescence techniques. With the latter procedures ANP was first recognized at embryonic stage 22, in both atrium and ventricle. In the ensuing stages the ANP-reactivity became stronger in the atrium, while it became dimmer in the ventricle. At the end of the larval prometamorphic stage, atrial myocardiocytes acquired almost all the features of adult myoendocrine cells. At electron microscope level, small inclusions, about 110-120 nm in diameter, resembling secretory granules were found in myoendocrine cells beginning at embryonic stage 22. However, no immunogold labeling of ANP occurred until stage 25. The number of secretory granules diminished in the ventricles and increased in the atrium of the larval heart and at the end of the prometamorphic stage the atrial myoendocrine cells presented the ultrastructural characteristics of active secretory cells. The synthesis of ANP in larvae is enhanced at a critical period of development when the developing toad switches from an aquatic environment to terrestrial life. The cardiac hormones seem to play a key role in the regulation of the osmolarity of body fluids at this developmental stage.

Animals↗

PubMed1992

[Epidemiologic study of factors associated with hypospadias].

From August 60 to December 90, 103 male newborns with hypospadias were diagnosed among 124 588 consecutive newborns examined (8.3 per 10,000). Mortality among them was 1.94%. The annual incidence rate increased significantly over the study period (p < 0.001. Hypospadias was an isolated finding in 92% of cases, and its was associated to other non genital malformation in 8.7%. Location of hypospadias was distal in 73% and proximal in 15.5%. There was no seasonal variation in the incidence rate. Weight of affected individuals did not differ from that of controls. Older age of parents among affected individuals was not statistically significant.

Abnormalities, Multiple↗

PubMed1991

[Increase of incidence of Down syndrome and its possible relation with increased maternal age].

Among 47,458 consecutive births taking place between july 1977 and december 1989, we found 83 newborns with Down syndrome, for a 1.74/1000 live births incidence rate. This compares to a rate of 1.39 rate observed at the same maternity from 1971 to 1977 (NS). The mean age of all mothers was 25.9 years as compared to 31.87 for mothers of children with Down syndrome (p < 0.00001). The mean maternal age has increased from 24.34 in 1977 to 27.38 in 1988 (p < 0.0001), mostly due to a greater proportion of the 25 to 29 year-old group of mothers. These data support, although not conclusively, that the increased incidence of Down syndrome in our population is related to older maternal age.

Adolescent↗

PubMed1990

[Incidence of malformations of the central nervous system: 1978-1988].

During the period Jan 1978 to Dec 1988, 41,867 deliveries took place at the University of Chile Hospital. Among them, 148 babies were found to have malformations of the central nervous system, an incidence of 3.6 per 1000 live births. A longitudinal study from 1969 to 1988 suggests a yearly increment of 0.1% in the incidence rate of these malformations. The comparison of some quantitative variables, such as gestational age, birthweight, number of previous abortions and some risk factors like maternal illness, bleeding, radiation exposure, drug ingestion during the first trimester of pregnancy and instructional level of both parents show significant differences between the malformed and the control newborns. No significant differences were found for maternal age, sex nor seasonal variation.

Abnormalities, Drug-Induced↗

PubMed1989

Chronic phenytoin treatment decreases GABAA but not beta-adrenoceptors in the cerebellum of young rats.

The effects of chronic treatment with phenytoin (50 mg/kg p.o. daily, for the first 30 days after birth) on GABAA and beta-adrenoceptors in the rat cerebellum were investigated by using in vitro quantitative autoradiography and binding assays with membranes. A significant decrease in [3H]muscimol binding to GABAA sites and, to a lesser extent, [3H]flunitrazepam binding to benzodiazepine sites was observed in the granular and molecular layers of the cerebellar cortex at the end of the treatment. Scatchard analyses demonstrated that these effects were associated with a decreased Bmax for the respective binding sites in cerebellar membranes the (Kd was not changed). In contrast, [125I]cyanopindolol binding remained unaffected. These data provide further support for the involvement of GABAergic synapses in the anticonvulsant action of phenytoin.

Adrenergic beta-Antagonists↗

PubMed1989

Interspecific variations of cerebral endothelial cholinesterases in rodents and carnivores.

The cholinesterase equipment of cerebral microvessels was studied in some rodents and carnivores using the Koelle-Friedenwald histochemical method with 3 artificial substrates and specific inhibitors for butyrylcholinesterase or acetylcholinesterase. Our observations reveal a great heterogeneity in cholinesterase types and their distribution in each of the different species studied. Only in the rat, butyrylcholinesterase appears to be a marker for the microvessels provided with a blood-brain barrier.

Acetylcholine↗

PubMed1989

Altitudinal distribution and blood values in the toad, Bufo spinulosus Wiegmann.

1. Red blood cell (RBC) count, RBC size, hematocrit, cell and blood hemoglobin concentrations and plasma total solid concentration were measured in 16 lowland (from near sea level up to 2700 m) and 18 highland (3200 up to close to 4500 m) adult toads (Bufo spinulosus). 2. Lowland toads showed higher hematocrit values than highland toads, but their blood hemoglobin concentration and plasma solid concentration were not significantly different. 3. Highland toads had smaller RBC size, higher corpuscular hemoglobin concentration, a trend toward larger RBC count and a considerably smaller body size. These features may contribute to their successful life at high altitude.

Adaptation, Physiological↗

PubMed1989

Sustained decreases in systemic blood pressure do not cause ocular hypotension.

The unilateral, topical administration of certain ocular hypotensive agents, notably clonidine, is reported to result in a bilateral decrease in intraocular pressure. It has been previously proposed that such bilateral ocular hypotensive responses may be centrally mediated. However, the possible influence of blood pressure changes on intraocular pressure has remained a complicating factor in determining mechanisms of action. In order to further clarify the potential relationship between systemic blood pressure changes and intraocular pressure, the effects of two systemic antihypertensive drugs were determined in the conscious rabbit. Topical, unilateral administration of either hydralazine or prizidilol did not lower the intraocular pressure of either eye. A bolus intravenous injection of either hydralazine or prizidilol caused substantial systemic hypotension that persisted for at least 3 h, but no decreases in intraocular pressure occurred. These studies indicate that sustained decreases in systemic blood pressure of approximately 15 mm Hg do not result in ocular hypotension.

Animals↗

PubMed1989

[Incidence of congenital malformations in Chile from 1969 to 1986. Results of a Latin-American collaborative study].

At present, congenital malformations contribute more to infant mortality, given the significant decrease in overall infant mortality rate observed in Chile. A significant and steady increase in the prevalence of congenital malformations was demonstrated at the Clinical Hospital, University of Chile, from 1969 to 1986. Better epidemiologic surveillance is needed to accurately estimate the magnitude of this problem and give orientation for preventive measures.

Chile↗

PubMed1989

[Congenital malformations: a model predictive based on risk factors].

Several risk factors were studied in regard to congenital malformations. Malformed newborns (n = 1200) and controls (n = 1200) seen at the Universidad de Chile Hospital between 1969 and 1979 were examined. Their mothers were asked about possible risk factors. Parenteral age and birth order was significantly higher for malformed newborns than for controls. A family history of congenital malformations was more frequent in malformed newborns. Infertility, metrorrhagia and maternal diseases during pregnancy were more frequent in malformed newborns than in controls. A function that discriminates between controls mothers and mothers of malformed newborns was obtained by a logistic regression model. This function correctly predicted 65% of cases.

Congenital Abnormalities↗

PubMed1989

Prostaglandin F2 alpha effects on intraocular pressure negatively correlate with FP-receptor stimulation.

According to the current working classification for prostanoid receptors, the prostaglandin F2 alpha-sensitive receptor (FP-receptor) may be identified by comparing the rank order of activity of prostaglandin F2 alpha (PGF2 alpha) and its analogues. In order to further understand the pharmacology of PGF2 alpha-induced ocular hypotension, the intraocular pressure response to PGF2 alpha and selected analogues was compared with their rank order of activity in typical FP-receptor preparations such as contraction of the cat iris sphincter and affinity for corporal luteal membrane binding sites. The rank order of potency for decreasing intraocular pressure was as follows: PGF2 alpha greater than PGF1 alpha greater than 16-phenoxytetranor PGF2 alpha greater than 17-phenyltrinor PGF2 alpha = fluprostenol (inactive). For cat iris sphincter contraction, the rank order of potency appears to be fluprostenol = 17-phenyltrinor PGF2 alpha greater than 16-phenoxytetranor PGF2 alpha = PGF2 alpha greater than PGF1 alpha. The rank order of potency for PGF2 alpha analogues in decreasing intraocular pressure appears to negatively correlate with the rank order for cat iris sphincter contraction and literature values for corporal luteal membrane binding. It is concluded that the ocular hypotensive effect of PGF2 alpha is not mediated by the FP-receptor.

Administration, Topical↗

PubMed1988

The pattern of callosal connections in posterior neocortex of congenitally anophthalmic rats.

In an effort to assess the innate capacity of the central visual system to specify corticocortical connectivity in the absence of retinal afferents, we examined the tangential distribution of callosal cells and terminations in posterior neocortex of congenitally anophthalmic rats. Although our results indicate that the callosal pattern is clearly anomalous in these rats, all features of the normal visual callosal pattern are recognizable in mutant rats, indicating that central visual pathways can generate many aspects of normal interhemispheric connectivity in the absence of input from the periphery. On the other hand, the presence of anomalies in the pattern indicates that the eyes are necessary to fine-tune the distribution of callosal connections at some developmental stage. Moreover, the fact that abnormalities in the callosal pattern of mutant rats are the same as those previously described in rats enucleated at birth suggests that the eyes begin to exert their influence on callosal development after birth.

Agenesis of Corpus Callosum↗

PubMed1987

Effect of phenytoin on cytoskeletal protein phosphorylation and neuronal structure in the rat sensory cortex.

Phenytoin (PH) is commonly used as an anticonvulsant drug, and it causes several collateral effects including morphological changes in brain cortex neurons and teratogenic lesions in infants of epileptic mothers. Several lines of evidence indicate that PH may exert its action through the modification of phosphorylation patterns of neuronal polypeptides. We have studied the effects of PH on the phosphorylation of cytoskeletal proteins, because this could be related to the structural modifications induced by PH administration. The dendritic pattern of deep layers of the somatosensory cortex is clearly modified by PH but not the cell number, indicating that the drug disturbs the architecture of the neurons examined. In fact, the pattern of phosphorylation in cytoskeletal extracts of brains of 30-day-old rats is changed by PH. In vitro labeling experiments show decrease in the [32P] level of a 43-kDa polypeptide, whereas 38- and 120-kDa polypeptides show increases in their [32P] contents. The 43-kDa polypeptide has been identified as actin by in vitro experiments using a novel approach to determine cytoskeletal polypeptide behavior. We conclude that PH affects the posttranslational phosphorylation of actin and other related cytoskeletal proteins and in this manner may alter the normal morphological layout of dendritic patterns in the somatosensory cortex.

Age Factors↗

PubMed1986

Short-term stimulation by adenosine of basal and insulin-induced glycogen synthesis in rat adipose tissue.

The effects of adenosine on glycogen metabolism have been studied in isolated fat-pads from epididymal adipose tissue. Adenosine caused a sustained short-term increase in the incorporation of [U-14C]glucose into glycogen, as well as a stimulation of both basal and insulin-induced [1-14C]glucose oxidation. Adenosine produced changes also in the activity of glycogen synthase and phosphorylase, these effects being apparent only when glucose was present in the incubation medium. The addition of adenosine prevented the depressed synthesis of glycogen observed in the presence of dibutyryl cyclic AMP. In the presence of adenosine deaminase, the stimulation by insulin of glycogen synthesis was markedly decreased. The results suggest that adenosine may have a regulatory role on glycogen synthesis by facilitating the glucose transport.

Adenosine↗

PubMed1986

Pharmacological characterization of beta-adrenoceptor subtype involvement in the ocular hypotensive response to beta-adrenergic stimulation.

The decrease in intraocular pressure elicited by isoproterenol in ocular normotensive animals is widely recognized. The participation of the beta-adrenoceptor subtypes in mediating this ocular hypotensive response has, however, remained unclear, because previous studies have been limited to monitoring the activity of single, supramaximal doses of relatively selective beta 2-adrenoceptor agonists. The studies herein report a relatively extensive pharmacological characterization of beta 1- and beta 2-adrenoceptor involvement in ocular hypotension associated with beta-adrenergic stimulation in the pigmented rabbit. A beta 2-adrenoceptor mechanism was indicated by the following evidence: isoproterenol and relatively selective beta 2-adrenoceptor agonists produced ocular hypotension over a similar dose range (0.001-0.1%; beta 1-adrenoceptor agonists, at doses likely to confer beta 1-adrenoceptor specificity, did not cause a similar decrease in intraocular pressure; the ocular hypotensive response to isoproterenol was abolished by topical timolol and pindolol and the relatively selective beta 2-adrenoceptor antagonist ICI 118551, whereas the relatively selective beta 1-adrenoceptor antagonists metoprolol and betaxolol were topically inactive; intravenous injection of beta 1-adrenoceptor-specific doses of metoprolol and betaxolol had little effect on isoproterenol-induced ocular hypotension, whereas the response was antagonized by a beta 2-adrenoceptor-specific i.v. dose of ICI 118551. These pharmacological results are consistent with radioligand binding and beta-adrenoceptor-linked adenylate cyclase studies which indicate a predominantly beta 2-adrenoceptor population associated with the ocular ciliary processes. None of the beta-blockers themselves altered normal intraocular pressure in the pigmented rabbit.

Adrenergic beta-Agonists↗

PubMed1986

Involvement of cyclic AMP-dependent protein kinase on the phosphorylase kinase inhibition by glucose-6-phosphate in adipose tissue extracts.

In order to achieve further clarification of the regulation of glycogenolysis in adipose tissue, we studied the effect of glucose-6-phosphate on phosphorylase activation in Sephadex G-25 filtrate of adipose tissue. The activity of phosphorylase kinase was decreased by 50% and by 75% in the presence of 0.5 mM and 2 mM of glucose-6-phosphate, respectively. This inhibition could be partially prevented by 0.5 mM AMP. Furthermore, we investigated the influence of glucose-6-phosphate on the effect of cyclic-AMP-dependent protein kinase on the activation of phosphorylase. The addition of cyclic-AMP and cyclic-AMP-dependent protein kinase caused a decrease in the inhibition of the phosphorylase activation by glucose-6-phosphate. Also, the glucose-6-phosphate at physiological concentration, decreased adipose tissue cyclic-AMP-dependent protein kinase activity.

Adenosine Monophosphate↗

PubMed1985

Membrane-bound form of acetylcholinesterase activated during postnatal development of the rat somatosensory cortex.

We are interested in the expression of synapse-specific macromolecules and its correlation with the appearance of neuronal types and synaptogenesis during development of the mammalian brain. We report here studies showing that the appearance of acetylcholinesterase (AChE) at layer IV of the rat somatosensory cortex is correlated with the expression of a membrane-bound AChE. Both its electrophoretic mobility and its sedimentation coefficient remain unaltered during maturation; however, its kinetics parameters, the heat and fixative sensitivities and the substrate inhibition changed through development. Our results suggest that an adult form of membrane-bound AChE is expressed postnatally.

Acetylcholinesterase↗