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Biomedical subjects

S Ruiz

Publications and source records attributed to S Ruiz.

At least 55 records · Page 3Linked to original sources
PubMed1998

Long-lasting remission of cytomegalovirus retinitis without maintenance therapy in human immunodeficiency virus-infected patients.

Seven AIDS patients who were receiving suppressive therapy for previously diagnosed cytomegalovirus (CMV) retinitis were offered treatment with protease inhibitors (PIs). Secondary prophylaxis for CMV was discontinued after 3 months of therapy with PIs if patients had >150 CD4 cells/mm3 and a human immunodeficiency virus (HIV) load of <200 copies/mL and if they were negative for CMV as determined by qualitative CMV polymerase chain reaction (PCR). Ophthalmologic exams were done periodically. After a median follow-up of 9 months (range, 9-12), no new episodes of CMV retinitis were observed. CD4 cell counts were >150 cells/mm3 in all cases, HIV loads were <200 copies/mL, and results for qualitative CMV PCRs remained negative. These observations suggest that for selected patients with healed CMV retinitis who have immunologic and virologic evidence of a clinical response to potent combination antiretroviral therapy, temporary discontinuation of a chronic anti-CMV suppressive therapy may not result in further retinal necrosis. However, the long-term immunologic benefit of PIs and hence the safety of prolonged withdrawal of anti-CMV therapy is unknown.

AIDS-Related Opportunistic Infections↗
PubMed1998

Prenatal malnutrition-induced functional alterations in callosal connections and in interhemispheric asymmetry in rats are prevented by reduction of noradrenaline synthesis during gestation.

Prenatal malnutrition results in increased concentration and release of central noradrenaline, a neurotransmitter that is an important regulator of normal regressive events such as axonal pruning and synaptic elimination. This suggests that some of the functional disturbances in brain induced by prenatal malnutrition could be due at least in part to increased noradrenaline activity that may enhance regressive events during early stages of development. To test this hypothesis we studied whether chronic administration of alpha-methyl-p-tyrosine, an inhibitor of tyrosine hydroxylase, to rats during gestation might prevent long-term deleterious effects of prenatal malnutrition on functional properties of interhemispheric connections of the visual cortex, and on asymmetry of visual evoked responses. The experiments were conducted on normal and malnourished rats 45-50 d of age. Prenatal malnutrition was induced by restricting the food consumption of pregnant rats to 40%, from d 8 postconception to parturition. At birth, prenatally malnourished rats had significantly greater whole-brain noradrenaline concentration as well as significantly enhanced noradrenaline release in the visual cortex. At 45-50 d of age, the malnourished group had a significantly smaller cortical area, exhibiting transcallosal evoked responses; in addition, the amplitude of these responses was significantly smaller. Malnourished rats showed a significant reduction of the normal interhemispheric asymmetry of visual evoked responses. The addition of 0.3% alpha-methyl-p-tyrosine to the diet of malnourished pregnant rats during the last 2 wk of gestation prevented functional disorders induced in the offspring by prenatal malnutrition on interhemispheric connectivity of visual areas and on interhemispheric bioelectrical asymmetry, probably by reducing the elevated brain noradrenaline activity and thereby restoring the normal trophic role of this neurotransmitter.

Animals↗
PubMed1998

Antioxidant supplementation and respiratory functions among workers exposed to high levels of ozone.

Ozone exposure has been related to adverse respiratory effects, in particular to lung function decrements. Antioxidant vitamins are free-radical scavengers and could have a protective effect against photo-oxidant exposure. To evaluate whether acute effects of ozone on lung functions could be attenuated by antioxidant vitamin supplementation, we conducted a randomized trial using a double-blind crossover design. Street workers (n = 47) of Mexico City were randomly assigned to take daily a supplement (75 mg vitamin E, 650 mg vitamin C, 15 mg beta carotene) or a placebo and were followed from March to August 1996. Pulmonary function tests were done twice a week at the end of the workday. During the follow-up, the mean 1-h maximum ozone level was 123 ppb (SD = 40). During the first phase, ozone levels were inversely associated with FVC (beta = -1.60 ml/ppb), FEV1 (beta = -2.11 ml/ppb), and FEF25-75 (beta = -4.92 ml/ppb) (p < 0.05) in the placebo group but not in the supplement group. The difference between the two groups was significant for FVC, FEV1, and FEF25-75 (p < 0.01). During the second phase, similar results were observed, but the lung function decrements in the placebo group were smaller, suggesting that the supplementation may have had a residual protective effect on the lung. These results need to be confirmed in larger supplementation studies.

Adolescent↗
PubMed1998

[A retrospective study of patients with epidemic optic neuropathy in a health area].

The sample of 104 patients who were diagnosed optic epidemic neuropathy at the health area of the "Rampa" Polyclinic in 1993 was reviewed. 50 of them were studied again. Visual acuity as well as the sensitivity to contrast by the Pelli Robson's method were explored. Ishihara's color-vision test was applied and an ophthalmological examination including fundus of the eye was made. All this was done by a group of experts who were searching temporary papillary paleness or lost of the bundles of papillomacular fibres, which are the diagnostic elements of the disease even in those cases that recover vision. 21 (42%) of the 50 studied patients fulfilled the criteria established for these cases by the Ministry of Public Health concerning visual acuity and color vision to diagnose optic epidemic neuropathy, although only 14 (28%) were ratified as cases. The typical alterations of the fundus of the eye were described, confirming the diagnosis. Cases were classified according to the initial state of visual acuity and to evolution. 3 had had an affectation of the visual acuity of 0.1 or worse (severe), and only one patient had a mild affectation with 0.8 of vision. The rest ranged between 0.2 and 0.6. Only one patient had a serious sequela. The low percentage of cases ratified as optic epidemic neuropathy does not represent what happened in the whole country, but it may be considered as a pattern of what took place at those units with the same conditions during the peak of the epidemic.

Color Perception↗
PubMed1997

Sphingolipids increase calcium concentration in isolated rat liver nuclei.

The sphingolipids, sphingosine (SPH), sphingosylphosphorylcholine (SPC) and psycosine induce a rapid and transient rise in nuclear free Ca2+ concentration in a dose dependent manner. To determine whether these sphingolipids act by a IP3-dependent pathway, we tested the increase of Ca2+ in the presence of heparin, an antagonist of IP3 receptor or U70122, an inhibitor of phospholipase C. Results indicate that the effect of both SPH and SPC, but not that of psychosine, is partially mediated by IP3 production. The sphingolipid-induced Ca2+ mobilization was unaffected by the inhibition of protein kinase C, but was totally abolished in the presence of nimodipine, a L-type Ca2+ channel inhibitor. The results could indicate the existence of a sphingosine-gated Ca2+-permeable channel in liver nuclei.

Animals↗
PubMed1997

Enhancement of central noradrenaline release during development alters the packing density of neurons in the rat occipital cortex.

The effect of chronic yohimbine treatment early in life on packing density of neurons was evaluated in the occipital cortex of young rats. Yohimbine administration to pups between days 5 and 16 of postnatal life (2.5 mg/kg/day i.p.) resulted at 45 days of age in significantly higher neuronal density in layers II-V of the occipital cortex, the effect being more marked in the dorsal region than in the dorsolateral and lateral ones. Results suggest a relationship between enhanced central noradrenaline activity and altered development of the neuropil in the occipital cortex.

Adrenergic alpha-Antagonists↗
PubMed1997

[Hepatoporto-appendicostomy. Our experience in 3 cases of biliary cystic disease].

This report details our preliminary experience with hepaticoporto-appendicostomy in three patients with biliary cystic disease. The surgical procedure was total resection of choledochal cyst and vascularized appendix interposition between biliary tree and duodenum. The children have been followed by clinical, ultrasonography and endoscopic (ECPR) during a period between 1-4 years. There was no episodes of ascending colangitis. All the patients remain free of jaundice and the biochemical abnormalities have become normal three months after interposition. Our results suggest that this procedure is more physiologic than the standard bilioenteric derivation Roux-in-Y, because allow bile to enter freely to duodenum and prevent reflux, stasis and ascending cholangitis. This procedure allows postoperative endoscopic valoration, not possible in another kind of bilioenteric derivations.

Appendix↗
PubMed1996

Hypothalamic-pituitary thyroid abnormalities in children after renal transplantation.

Patients with a successful renal transplant may have abnormalities in thyroid function. We evaluated serum thyroid hormone levels, serum thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH), and the circadian pattern of serum TSH in 18 children aged 6.6-19.4 years (median 12.6 years), 4.0 +/- 2.9 years after renal transplantation. In 14 children, immunosuppressive therapy included methylprednisone [mean (+/-SD) 0.17 +/- 0.05 mg/ kg per day], while in 11 it included deflazacort (0.32 +/- 0.1 mg/kg per day). Seven children were studied twice, under methylprednisone and again while on deflazacort therapy. Mean total and free thyroxine (T4) values were significantly below the mean control levels (total T4 108.5 +/- 21.5 vs. 118.7 +/- 22.1 nmol/l, P < 0.05 and free T4 14.4 +/- 4.0 vs. 18 +/- 4.9 pmol/l, P < 0.001). Morning basal TSH levels were within the normal range. The mean TSH increment after TRH was 4.4 +/- 3.5 mU/l, significantly lower than that of controls (10.8 +/- 4.26, P < 0.001). Of 7 patients on methylprednisone, 4 had nocturnal TSH surges below the normal range (95% confidence limits 47%-300%); this occurred in 3 of 8 patients on deflazacort therapy. The TSH response to TRH was correlated with deflazacort dose. Patients on methylprednisone and deflazacort therapy had similar thyroid alterations. Our findings support the hypothesis that after renal transplantation some children have hypothalamic-pituitary thyroid abnormalities in which glucocorticoids may play a significant role.

Adolescent↗
PubMed1996

Effects of air pollution on the respiratory health of asthmatic children living in Mexico City.

The relation between air pollution and the exacerbation of childhood asthma was studied in a panel of 71 children (aged 5 to 7 yr) with mild asthma who resided in the northern part of mexico City. During the follow-up, ambient measures of particulate matter less than 10 microns (PM10, 24-h average) and ozone (1-h maximum) frequently exceeded the Mexican standards for these contaminants. The peak expiratory flow rate (PEFR) was strongly associated with PM10 levels and marginally with ozone levels. Respiratory symptoms (coughing, phlegm production, wheezing, and difficulty breathing) were associated with both PM10 and ozone levels. An increase of 20 micrograms/m3 of PM10 was related to an 8% increase in lower respiratory illness (LRI) among children on the same day (95% confidence interval [CI] = 1.04-1.15), and an increase of 10 micrograms/m3 in the weekly mean of particulate matter less than 2.5 microns (PM2.5) was related to a 21% increase in LRI (95% CI = 1.08-1.35). A 50 parts per billion (ppb) increase in ozone was associated with a 9% increase in LRI (95% CI = 1.03-1.15) on the same day. We concluded that children with mild asthma are affected by the high ambient levels of particulate matter and ozone observed in the northern part of Mexico City.

Air Pollutants↗
PubMed1996

Growth acceleration in children with chronic renal failure treated with growth-hormone-releasing hormone (GHRH).

Growth retardation is a prominent clinical manifestation in children with chronic renal failure (CRF). Nine children with CRF (3 on conservative treatment; 3 on dialysis and 3 after renal transplantation) aged 1.6 to 14.0 (x +/- SE: 8.1 +/- 1.4) years, were treated with twice daily subcutaneous injections of 26 +/- 2.4 micrograms/kg/day growth-hormone-releasing-hormone [GHRH (1-29) NH2 Serono (Geref)] during 3 to 6 months. Mean serum urea and creatinine remained stable, although 2 patients on conservative treatment showed a moderate increase in serum creatinine. At the start of the study, height SDS was -2.2 +/- 0.2 (x +/- SE), growth velocity was 4.5 +/- 1.0 cm/year (-2.3 +/- 0.6 DS for chronological age) and growth hormone (GH) response to acute GHRH test (1 microgram/kg IV) was 62 +/- 17.5 ng/ml. Five patients increased height velocity from 3.8 +/- 0.7 to 8.0 +/- 1.2 cm/year (paired t test, p < 0.05). The peak GH response to GHRH was significantly higher in the group of growth non-responders than in the responders (p < 0.05). In conclusion, 5 out of 9 short children with CRF, 3 on conservative treatment, 1 on dialysis and 1 post renal transplantation, showed improved growth in response to GHRH therapy. No consistent effect on renal function was detected. GHRH may be an alternative therapy to increase growth velocity in patients with CRF.

Adolescent↗
PubMed1995

Localization of the site on the complement component C1q required for the stimulation of neutrophil superoxide production.

C1q, the recognition subunit of the classical complement pathway, interacts with specific cell surface molecules via its collagen-like region (C1q-CLR). This binding of C1q to neutrophils triggers the generation of toxic oxygen species. To identify the site on C1q that interacts with the neutrophil C1q receptor, C1q was isolated, digested with pepsin to produce C1q-CLR, and further cleaved with either trypsin or endoproteinase Lys-C. The resulting fragments were separated by gel filtration chromatography and analyzed functionally (activation of the respiratory burst in neutrophils) and structurally. Cleavage of C1q-CLR with endoproteinase Lys-C did not alter its ability to trigger neutrophil superoxide production. However, when C1q-CLR was incubated with trypsin under conditions permitting optimal cleavage, the ability of C1q-CLR to stimulate superoxide production in neutrophils was completely abrogated. Fractionation of the digests obtained with the two enzymes and identification by amino acid sequencing permitted localization of the receptor interaction site to a specific region of the C1q-CLR. Circular dichroism analyses demonstrated that cleavage by trypsin does not denature the remaining uncleaved collagen-like structure, suggesting that after trypsin treatment, the loss of activity was not due to a loss of secondary structure of the molecule. However, irreversible heat denaturation of C1q-CLR also abrogated all activity. Thus, a specific conformation conferred by the collagen triple helix constitutes the functional receptor interaction site. These data should direct the design of future specific therapeutic reagents to selectively modulate this response.

Amino Acid Sequence↗
PubMed1995

Medullary responses to chemoreceptor activation are inhibited by locus coeruleus and nucleus raphe magnus.

The effect of electrical and L-glutamate stimulation of the nucleus locus coeruleus (LC) and nucleus raphe magnus (NRM) on multiunit activity evoked in the nucleus tractus solitarius (NTS) by activation of arterial chemoreceptors (15-25 micrograms kg-1 of sodium cyanoborohydride, i.v.) was studied in rats anaesthetized with urethane (1.1 g kg-1 i.p.). Multiunit discharge of NTS neurones in response to cyanide injection was composed by spikes higher than 200 microV and about 10 Hz frequency. Electrical and L-glutamate stimulation of the LC and the NRM significantly reduced the frequency of the cyanide-induced multiunit discharge. The results show that neurones of the NTS with input from arterial chemoreceptors can be inhibited by LC and and NRM cells, suggesting that these nuclei play a role in controlling chemosensory input at the NTS.

Animals↗
PubMed1995

Neuronal activity of primate putamen during categorical perception of somaesthetic stimuli.

We have studied neuronal activity in the putamen of two monkeys trained to discriminate the speed of moving tactile stimuli. Animals pressed one of two target switches to indicate whether the speed of the probe across the skin was low or high. The activity of single neurones was recorded in the putamen ipsilateral to the glabrous skin of the stimulated hand and contralateral to the responding arm. During the task, we recorded neurones in the putamen that showed responses confined exclusively to the stimulus period of all speeds. A second class of putamen neurones responded during the stimulus period but continued discharging during the reaction and movement time period. None of these two classes of putamen neurones discharged when the same set of stimuli were delivered passively. A third class of putamen neurones responded differentially in the discrimination task and predicted whether the speed of the stimulus was low or high. A number of these neurones, which responded differentially during the categorization task, were tested in a light instruction task. This tested the possibility that these differential responses were associated with the intention to move the arm to one of the two target switches. Few neurones responded in this situation. These results indicate that the putamen, in addition to its role in motor regulation, is also involved in higher order aspects of sensory-motor behaviour and in the sensory decision process in this learned somaesthetic task.

Animals↗
PubMed1995

Efficacy, safety, and immunogenicity of a meningococcal group B (15:P1.3) outer membrane protein vaccine in Iquique, Chile. Chilean National Committee for Meningococcal Disease.

A meningococcal group B (15:P1.3) outer membrane protein vaccine was tested for efficacy in a randomized, double-blind controlled study in Iquique, Chile. A total of 40 811 volunteers, ages 1-21 years, enrolled in the study. Volunteers received two doses of vaccine six weeks apart by jet injector. Both the experimental vaccine and the control vaccine (Menomune, A, C, Y and W135 meningococcal polysaccharide vaccine) were well tolerated with minor side-effects. Active surveillance for suspected cases of meningococcal disease was conducted for 20 months in Iquique. Eighteen cases of group B meningococcal disease were confirmed during the 20 months. Efficacy was estimated to be 51% (p = 0.11) for all ages combined. In children aged 1-4 no protection was evident, but in volunteers aged 5-21 vaccine efficacy was 70% (p = 0.045). The IgG antibody response by ELISA was characterized by a large booster effect after the second dose, followed by a substantial drop in antibody levels by 6 months. The youngest children had the highest responses. The bactericidal antibody response, on the other hand, was characterized by the lack of a significant booster response, higher responses in the older children, and an increase in the geometric mean titer in the later months of the study in the older children.

Adolescent↗
PubMed1995

Radioprotection of DNA by polyamines.

Putrescine, spermidine and spermine are natural polyamines bearing at neutral pH the net electrical charges +2, +3 and +4 respectively. We report here the radioprotective effect of these polyamines on the radiolysis of pBR322 plasmid DNA. We observe a very efficient protection against fast neutron-induced single and double-strand breakage in the presence of spermine and spermidine, and a significantly less efficient protection in the presence of putrescine. An ionic strength dependence is observed for spermidine and spermine, but not for putrescine. Circular dichroism measurements show spermidine- and spermine-induced structural modifications of DNA, i.e. the formation of tightly packaged condensates in the concentration range corresponding to radioprotection. No structural change is observed for concentrations of putrescine affording radioprotection. We explain the radioprotection by: (1) the scavenging of OH radicals in the bulk, essentially observed in the case of putrescine; (2) a local scavenging at the sites of binding of polyamines; and (3) the reduced accessibility of the attack sites in the condensed structures induced by spermine or spermidine.

Biogenic Polyamines↗
PubMed1995

Representation of moving tactile stimuli in the somatic sensory cortex of awake monkeys.

1. We have studied how neurons of primary somatic sensory (SI) cortex encode the direction and speed of moving tactile stimuli delivered to the glabrous skin of the contralateral hand. 2. From a total of 178 neurons recorded in SI cortex of 3 awake Macaca mulatta monkeys, 103 were selected for quantitative analysis. Forty-six neurons had slowly adapting (SA) responses, 43 quickly adapting (QA), and 14 mixed SA-QA properties. All possessed cutaneous receptive fields on the distal segments of digits 2, 3, or 4. Receptive fields were scanned with a metal probe (2 mm diam, hemispheric tip) in four different directions (0, 90, 180, and 270 degrees), over a fixed traverse distance of 6 mm, at a variety of speeds (4-100 mm/s), and with a static normal force of 20 g by means of a computer-controlled tactile stimulator. 3. Most neurons gave statistically significant differences in mean impulse rate during the moving stimuli (Wilcoxon, P < 0.01), in at least one of the four directions, compared with the control (nonstimulus) period. The Kruskal-Wallis test (P < 0.01) and the direction index (DI > 35%) determined that about one-half of SI cortical neurons showed significant differences in mean impulse rates associated with the direction of the stimuli at the speeds of 23, 50, and 100 mm/s, and about one-third at 4 mm/s. 4. We determined how the temporal covariance of the neural activity was associated with the parameters of the moving stimuli by calculating the coefficients of the Karhunen-Loève (KL) transform for each set of stimulus responses. Decomposition of the neural activity into principal components indicated that approximately 85% of the impulse train variance during the stimulus responses was contained in the 1st 10 coefficients of the KL transform for the speeds of 23, 50, and 100 mm/s, and approximately 75% at the speed of 4 mm/s. The line spectra calculated from the coefficients of the KL transform showed that the variance contained in the impulse trains in about one-half of the neurons is related to the stimuli. 5. We investigated how the temporal covariance of the neuronal activity was correlated with the direction of the stimulus, by fitting the first coefficient of the KL transform to a weighting function model. This analysis showed that the first coefficient of the KL transform varied as an orderly function of the direction of the moving stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Central noradrenergic hyperactivity early in life: a hypothesis on the origin of morpho-functional brain disorders induced by malnutrition.

Many studies have revealed that malnutrition, caused either by insufficient or unbalanced diet, during early stages of growth and development could result in a variety of morpho-functional brain disturbances, whose severity depends on the time of onset, duration and intensity of the nutritional injury. Nevertheless, little is known about the intimate mechanisms by which early malnutrition impairs brain structure and function. This article reviews evidence showing that (i) developmental malnutrition induces central noradrenergic hyperactivity, (ii) noradrenaline exerts a trophic role during brain development, and (iii) pharmacological reduction of central noradrenergic hyperactivity prevents malnutrition-induced functional brain disturbances.

Animals↗