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Biomedical subjects

G Ramirez

Publications and source records attributed to G Ramirez.

At least 19 recordsLinked to original sources
PubMed2002

Design and implementation of a measuring campaign to model pesticide impacts in an Ecuadorian watershed.

The first important issue in pesticide assessment for a watershed is the availability of soil and water quality information in the form of charts, maps or records. However, developing countries generally do not have enough historical data. Thus, sampling programs are crucial for the success of the evaluation, although in developing countries they always represent a controversial task between limited available budget and a precise assessment. This paper shows the steps taken to generate soil and water data to be used in a pesticide assessment project for a 34,000 ha watershed in Ecuador, South America. Sampling campaigns are still being run, so the methodology and the first results are shown here.

Ecuador↗
PubMed2001

Garlic shows promise for improving some cardiovascular risk factors.

OBJECTIVES: To summarize the effects of garlic on several cardiovascular-related factors and to note its adverse effects. METHODS: English and non-English citations were identified from 11 electronic databases, references, manufacturers, and experts from January 1966 through February 2000 (depending on the database searched). Reports of cardiovascular-related effects were limited to randomized controlled trials lasting at least 4 weeks. Reports of adverse effects were not limited by study design. From 1798 pertinent records, 45 randomized trials and 73 additional studies reporting adverse events were identified. Two physicians abstracted outcomes and assessed adequacy of randomization, blinding, and handling of dropouts. Standardized mean differences of lipid outcomes from placebo-controlled trials were adjusted for baseline differences and pooled using random effects methods. RESULTS: Compared with placebo, garlic preparations may lead to small reductions in the total cholesterol level at 1 month (range of average pooled reductions, 0.03-0.45 mmol/L [1.2-17.3 mg/dL]) and at 3 months (range of average pooled reductions 0.32-0.66 mmol/L [12.4-25.4 mg/dL]), but not at 6 months. Changes in low-density lipoprotein levels and triglyceride levels paralleled total cholesterol level results; no statistically significant changes in high-density lipoprotein levels were observed. Trials also reported significant reductions in platelet aggregation and mixed effects on blood pressure outcomes. No effects on glycemic-related outcomes were found. Proven adverse effects included malodorous breath and body odor. Other unproven effects included flatulence, esophageal and abdominal pain, allergic reactions, and bleeding. CONCLUSIONS: Trials suggest possible small short-term benefits of garlic on some lipid and antiplatelet factors, insignificant effects on blood pressure, and no effect on glucose levels. Conclusions regarding clinical significance are limited by the marginal quality and short duration of many trials and by the unpredictable release and inadequate definition of active constituents in study preparations.

Adolescent↗
PubMed2001

Rhegmatogenous retinal detachment in myopic eyes after laser in situ keratomileusis. Frequency, characteristics, and mechanism.

PURPOSE: To report the characteristics and frequency of rhegmatogenous retinal detachment (RRD) after laser in situ keratomileusis (LASIK) for the correction of myopia in a large case series. SETTING: Private practices, Caracas, Venezuela. METHODS: Five refractive surgeons and 31 739 myopic eyes that had surgical correction of a mean myopia of -6.01 diopters (D) (range -0.75 to -29.00 D) participated in this study. Laser in situ keratomileusis was performed in all eyes. Patients were followed for a mean of 36 months (range 6 to 48 months). The clinical charts of patients who developed RRD after LASIK were reviewed. RESULTS: Twenty eyes (17 patients) developed RRD after LASIK. Rhegmatogenous retinal detachments occurred a mean of 13.9 months (range 1 to 36 months) after LASIK. The mean pre-LASIK myopia in eyes that developed an RRD was -7.02 D (range -1.50 to -16.00 D). Most RRDs and retinal breaks occurred in the temporal quadrants (71.4%). Rhegmatogenous retinal detachments were managed with vitrectomy, cryoretinopexy, scleral buckling, argon laser retinopexy, or pneumatic retinopexy techniques. The frequency of RRD after LASIK was 0.06%. CONCLUSIONS: Rhegmatogenous retinal detachment after LASIK for the correction of myopia is infrequent. If managed promptly, RRD will result in good vision. Before LASIK is performed, patients should have a thorough dilated indirect fundoscopy with scleral depression and treatment of any retinal lesion predisposing to the development of an RRD.

Adolescent↗
PubMed2001

Microglia-astrocyte interaction in Alzheimer's disease: friends or foes for the nervous system?

Brain glial cells secrete several molecules that can modulate the survival of neurons after various types of damage to the CNS. Activated microglia and astrocytes closely associate to amyloid plaques in Alzheimer Disease (AD). They could have a role in the neurotoxicity observed in AD because of the inflammatory reaction they generate. There is controversy regarding the individual part played by the different glial cells, and the interrelationships between them. Both astrocytes and microglia produce several cytokines involved in the inflammatory reaction. Moreover, the same cytokines may have different effects, depending on their concentration and the type of cells in the vicinity. In turn, the events occurring in response to injury may lead to changes in the nature and relative concentration of the various factors involved. To learn about these putative glial interrelationships, we examined some effects of astrocytes on microglial activation.

Alzheimer Disease↗
PubMed2000

Cl(-)-dependent excitotoxicity is associated with 3H2O influx in chick embryonic retina.

The aim of this study was to show that Cl(-)-dependent excitotoxicity, with its characteristic cell swelling, involves actual water influx into the intracellular compartment. Taking advantage of the Ca2+ omission paradigm of Cl(-)-dependent excitotoxicity, in the chick embryonic neural retina ex vivo, which is associated with toxicity levels (lactate dehydrogenase (LDH) release) considerably higher than those seen after simple exposure of the retinas to glutamate agonists, we have demonstrated that an intracellular water intake of 4.2 microl into retinal cells is associated with 13.3% total retinal LDH release. The fact that mannitol blocks both water inflow and LDH release appears to link both events from a pathogenic point of view.

Animals↗
PubMed2000

Ca2+-dependent kainate excitotoxicity in the chick embryonic neural retina ex vivo.

The chick embryonic neural retina ex vivo has been singled out as a unique example of Cl(-)-dependent/Ca2+-independent excitotoxicity. However, after continuous incubation with 100 microM kainate, we have demonstrated the susceptibility of the chick retina to Ca2+-mediated damage, which becomes apparent after 12 h of exposure to the agonist in the absence of Cl-. Of the 20.8% lactate dehydrogenase released after 24 h incubation with kainate, some 11% is Cl(-)-dependent and the rest (9.8%) is presumably Ca2+-dependent. Upon omission of both Cl- and Ca2+, a 5% residual toxicity can still be detected after 24 h. This can be overcome by inclusion of EGTA in the incubation medium to neutralize Ca2+ released during incubation. A Ca2+-dependent toxicity mechanism is then operative in the embryonic chick retina ex vivo.

Animals↗
PubMed2000

Incidence of vitreoretinal pathologic conditions within 24 months after laser in situ keratomileusis.

OBJECTIVE: To report for the first time a case series of vitreoretinal pathologic conditions after laser in situ keratomileusis (LASIK) and to determine its incidence. DESIGN: Case series. PARTICIPANTS: Five refractive surgeons and 29,916 eyes that underwent surgical correction of ametropia (83.2% were myopic) ranging from -0.75 to -29.00 diopters (D; mean: -6.19 D) and from +1.00 to +6.00 D (mean: +3.23 D) participated in this retrospective study. MAIN OUTCOME MEASURES: Vitreoretinal complications after LASIK. RESULTS: The clinical findings of 20 eyes (17 patients) with LASIK-related vitreoretinal pathologic conditions are presented. Fourteen eyes experienced rhegmatogenous retinal detachments (RDs). Two eyes experienced corneoscleral perforations with the surgical microkeratome when a corneal flap was being performed (one experienced a vitreous hemorrhage and the other later experienced an RD). In four eyes, retinal tears without RDs were found. In one eye, a juxtafoveal choroidal neovascular membrane (CNVM) developed. Retinal tears were treated with argon laser retinopexy or cryotherapy. Corneoscleral perforations were sutured, and the RD was managed with vitrectomy. The remaining RDs were managed with vitrectomy, cryoretinopexy, scleral buckling, argon laser retinopexy, or pneumatic retinopexy techniques. The CNVM was surgically removed. The incidence of vitreoretinal pathologic conditions determined in our study was 0.06%. CONCLUSIONS: Serious complications after LASIK are infrequent. Vitreoretinal pathologic conditions, if managed promptly, will still result in good vision. It is very important to inform patients that LASIK only corrects the refractive aspect of myopia. Complications of the myopic eye will persist.

Adolescent↗
PubMed2000

Homeopathy and rheumatic disease.

Despite a growing interest in uncovering the basic mechanisms of arthritis, medical treatment remains symptomatic. Current medical treatments do not consistently halt the long-term progression of these diseases, and surgery may still be needed to restore mechanical function in large joints. Patients with rheumatic syndromes often seek alternative therapies, with homeopathy being one of the most frequent. Homeopathy is one of the most frequently used complementary therapies worldwide.

Arthritis, Rheumatoid↗
PubMed2000

Rhegmatogenous retinal detachment after laser-assisted in situ keratomileusis (LASIK) for the correction of myopia.

PURPOSE: To report a case series of rhegmatogenous retinal detachment (RRD) after laser-assisted in situ keratomileusis (LASIK) and its incidence at a mean of 24 months. METHODS: The clinical charts of patients who experienced RRD after LASIK were reviewed. Five refractive surgeons and 24,890 myopic eyes that underwent surgical correction of myopia ranging from -0.75 to -29.00 diopters (D) (mean, -6.19 D) participated in this study. RESULTS: Thirteen eyes from 12 patients developed RRD after LASIK. Rhegmatogenous RD occurred between 1 and 36 months (mean, 12.6 months) after LASIK. Eyes that developed RRD had from -1.50 to -16.00 D of myopia (mean, -6.96 D) before LASIK. Rhegmatogenous RD were managed with vitrectomy, cryoretinopexy, scleral buckling, argon laser retinopexy, or pneumatic retinopexy techniques. The incidence of RRD at a mean of 24 months after LASIK in this study was 0.05%. CONCLUSIONS: Rhegmatogenous RD after LASIK is infrequent. If managed promptly, good vision can result. No cause-effect relationship between LASIK and RD can be proved from this study, but the authors recommend that patients scheduled for refractive surgery undergo a thorough dilated indirect fundus examination with scleral depression and treatment of any retinal lesions predisposing them to the development of RRD before LASIK surgery is performed.

Adolescent↗
PubMed1999

Aquaporin-1 expression in proximal tubule epithelial cells of human kidney is regulated by hyperosmolarity and contrast agents.

Primary cells of renal proximal tubule epithelium (S1 segment) of human kidney (HRPTE cells) up-regulate aquaporin-1 (AQP-1) expression in response to hyperosmolarity. NaCl and D(+)-raffinose increased (2-2.5 fold) AQP-1 expression when medium osmolarity was 400 and 500 mOsm/kg.H2O. Urea did not have this effect. Unlike our previous findings with mIMCD-3 cells, vasopressin (10(-8)M) did not affect AQP-1 expression in HRPTE cells in isosmolar or NaCl-enriched hyperosmolar conditions. Furthermore, HRPTE cells increased (3-4 fold) AQP-1 expression when exposed to hyperosmolar Reno-60 and Hypaque-76 (diatrizoates, ionic) contrast agents at 400 and 500 mOsm/kg.H2O. Isosmolar (290 mOsm/kg H2O) Visipaque (iodixanol, non-ionic) at 10% (v/v) concentrations also increased AQP-1 expression, and 25% v/v of Visipaque rendered morphological alterations of HRPTE cells and a 3-fold increase in AQP-1 expression after 24h exposure. Finally, semi-quantitative RT-PCR of HRPTE cells subjected to various isosmolar or hyperosmolar conditions demonstrated up-regulation of AQP-1 mRNA and protein levels. Our results suggest AQP-1 up-regulation in HRPTE cells exposed to environmental stresses such as hyperosmolarity and high doses of isosmolar contrast agents.

Aquaporins↗
PubMed1999

Impact of study quality on outcome in placebo-controlled trials of homeopathy.

We investigated the influence of indicators of methodological quality on study outcome in a set of 89 placebo-controlled clinical trials of homoeopathy in three different ways: (1) The results of studies meeting single criteria (explicit statement of random allocation, allocation concealment, double-blinding, completeness of follow-up) of methodological quality were compared with those of studies not meeting the criteria in univariate and multivariate analyses; (2) The results of studies scoring above and below predefined scores in two quality assessment scales were compared; (3) Primary studies were consecutively entered into a cumulative meta-analysis according to the summary scores derived from the quality assessment scales. All analyses were performed using meta-regression methods. Studies that were explicitly randomized and were double-blind as well as studies scoring above the cut-points yielded significantly less positive results than studies not meeting the criteria. In the cumulative meta-analyses, there was a trend for increasing effect sizes when more studies with lower-quality scores were added. However, there was no linear relationship between quality scores and study outcome. We conclude that in the study set investigated, there was clear evidence that studies with better methodological quality tended to yield less positive results. Because summarizing disparate study features into a single score is problematic, meta-regression methods simultaneously investigating the influence of single study features seem the best method for investigating the impact of study quality on outcome.

Analysis of Variance↗
PubMed1999

Mayaro virus disease: an emerging mosquito-borne zoonosis in tropical South America.

This report describes the clinical, laboratory, and epidemiological findings on 27 cases of Mayaro virus (MV) disease, an emerging mosquito-borne viral illness that is endemic in rural areas of tropical South America. MV disease is a nonfatal, dengue-like illness characterized by fever, chills, headache, eye pain, generalized myalgia, arthralgia, diarrhea, vomiting, and rash of 3-5 days' duration. Severe joint pain is a prominent feature of this illness; the arthralgia sometimes persists for months and can be quite incapacitating. Cases of two visitors from the United States, who developed MV disease during visits to eastern Peru, are reported. MV disease and dengue are difficult to differentiate clinically.

Adult↗
PubMed1999

High altitude living: genetic and environmental adaptation.

High altitude (HA) living produces physiological changes for adaptation to chronic hypobaric-hypoxemic conditions. Although much is known about these physiologic adaptations, no clear separation has been made regarding what is "native" or "genetic" adaptation and what is "acquired." In this review, we describe the genetic vs. acquired adaptation and only include studies performed in a population native to HA and not in an acclimatized population or trekkers. The changes encountered in animals and humans living at HA in terms of hematology, muscular, respiratory, cerebral, cardiovascular, hormonal, fluid and electrolytes and reproduction, strongly suggest that genetics play a very important role in HA adaptation. Unfortunately, the characteristic physiology of HA natives has not been systematically defined to established specific measurable parameters of adaptation in comparison to the acquired ambient adaptation of the non-native population. Once the parameters are established, we can compare non-native populations exposed to HA that must emulate the HA physiology for a definite adaptation to be present. With measurable parameters, especially in the management of fluids and electrolytes, we can define how long it will take for a sea level native to adapt to an HA altitude. Until these studies are performed, speculation will continue and no rational medical intervention can be offered to HA newcomers who may experience HA difficulties.

Adaptation, Physiological↗
PubMed1998

Aquaporin-1: an osmoinducible water channel in cultured mIMCD-3 cells.

The expressions of aquaporin-1 (AQP-1) in cultured mIMCD-3 cells were studied. There was no detectable AQP-1 in cells grown in serum-containing growth medium (SM, 297 +/- 2 mOsm/kg. H2O). When SM was supplemented with NaCl (406 +/- 2 mOsm/kg. H2O), cellular AQP-1 was induced. A further increase in medium osmolarity with NaCl (493 +/- 3 mOsm/kg. H2O) had conferred cells an 2.5 to 3-fold increase of AQP-1 expression over those grown in the 406 +/- 2 mOsm/kg. H2O medium. Moreover, AQP-1 was found to be translocated from cytosol to membrane. In addition, exposing the mIMCD-3 cells to vasopressin (AVP, 10(-8) M) and/or NaCl-supplemented serum-free media (496 +/- 3 mOsm/kg. H2O) for 6h did not render them to produce AQP-1. However, AQP-1 was induced after 24h of incubation, with an 1.5-fold additive effect by AVP. Our RT-PCR data had confirmed the NaCl inducibility and AVP synergism in AQP-1 expression at both mRNA and protein levels. This suggests a new role for cellular AQP-1 and AVP in overcoming osmotic stress in an in vitro system.

Animals↗