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Biomedical subjects

E Sandoval

Publications and source records attributed to E Sandoval.

At least 19 recordsLinked to original sources
PubMed2004

Energetic and kinematic consequences of weighting the distal limb.

REASON FOR PERFORMING STUDY: It is well known that adding a load to a horse's back increases its energetic costs of locomotion, but the magnitude of increase obtained by loading the most distal portion of limb has not been measured. OBJECTIVES: To measure oxygen consumption in horses with mass added to the back and hooves. Because such mass distribution alters inertial parameters of the limbs, kinematic measurements were made to quantify the magnitude of change in limb movement. METHODS: Steady-state oxygen consumption was measured in 6 horses with a load of 2.4 kg. The load was either carried on the back or distributed equally between the 4 limbs. Modified bell boots kept the mass at the level of P3. Horses trotted on a treadmill at speeds ranging from 2 to 5 m/sec (in 0.5 m/sec increments). High-speed (250 Hz) digital images were recorded in a sagittal plane and the positions of retroreflective markers located on standard positions on the limbs were digitised for kinematic analysis. RESULTS: Loading of the distal limbs produced a 6.7% increase in metabolic rate, an order of magnitude higher than when the mass was added over the back. Although the stride period was 2% longer in horses with loads on the distal limbs, time of contact and duty factor were not different. Distal limb loading increased the range of motion in hind- but not forelimbs. CONCLUSIONS: The costs of swinging the limbs in the horse are considerable and the addition of weights to the distal limb can have a profound effect on not only the energetics of locomotion but also the kinematics, at least in the hindlimb. POTENTIAL RELEVANCE: The use of weighted shoes, intended to increase animation of the gait, increases the metabolic effort of performance horses a disproportionate amount. The additional mass also increases the joint range of motion and, potentially, the likelihood of injury.

Animals↗
PubMed1999

Rapid subtyping of dengue viruses by restriction site-specific (RSS)-PCR.

Dengue is a major public health problem worldwide. It is caused by four dengue virus serotypes, each further divided into distinct genetic subtypes. Strain typing is important for understanding the epidemiology and viral factors associated with disease transmission. However, most of the existing subtyping methods are expensive and technically unwieldy for timely, practical applications in developing countries. Here we describe a simple, rapid, PCR-based subtyping method, restriction site-specific (RSS)-PCR, which we used to analyze dengue virus serotypes 2 and 3. For each serotype, four primers targeted to sequences spanning polymorphic endonuclease restriction sites in the envelope gene were used to reverse transcribe and amplify viral RNA. These RT-PCR products generated distinct electrophoretic band patterns for different strains. Analysis of 73 dengue-2 strains and 54 dengue-3 strains representing a broad geographic distribution over several decades revealed that the RSS-PCR fingerprints reproducibly fell into 7 and 3 groups, respectively. These groups correlated well with previous phylogenetic classifications. This one-step assay should be widely accessible and allow more detailed epidemiologic investigations in dengue-endemic countries. This novel PCR approach to subtyping organisms based on restriction site polymorphisms should be applicable to other pathogens.

Dengue Virus↗
PubMed1999

Application of molecular typing techniques in the 1998 dengue epidemic in Nicaragua.

This report presents the results of applying the reverse transcriptase-polymerase chain reaction (RT-PCR) to the analysis of clinical specimens during the 1998 dengue epidemic in Nicaragua. The RT-PCR was validated through comparison with viral isolation, resulting in a sensitivity of 100% and a specificity of 90%. In-country application of the RT-PCR permitted the rapid identification of dengue-3 virus as the cause of the epidemic at the beginning of 1998 and the detection of the reintroduction of dengue-2 virus in the middle of the year. Nineteen isolates of dengue-3 and one of dengue-2 were characterized using the restriction site-specific (RSS)-PCR technique. This showed that the dengue-3 strain belonged to the "Sri Lanka" subtype and that the dengue-2 strain belonged to the "Jamaica" subtype, both of which have been associated with hemorrhagic dengue in the Americas. The application of these simple PCR-based strain typing methods in a country endemic for dengue virus infections can help to characterize the transmission dynamics of this important emerging infectious disease problem and provide this information to local health authorities in a timely manner so that appropriate control measures can be implemented.

Dengue↗
PubMed1998

Carbon monoxide trend, meteorology, and three-way catalysts in Mexico City.

From the analysis of data of the Inspection/Maintenance (I/M) program, and of the long-term trend of ambient CO concentrations in Mexico City, it is inferred that three-way catalysts (TWCs) have a 45% efficiency, well below the expected 90% value. The most probable causes are sulfur poisoning, lead contamination, and ceramic breakage due to bumps and potholes on the streets. Also, we have found a ratio between the average daily peak value of atmospheric CO and gasoline consumption: (11 +/- 1) ppbCO/MLm (million liters of gasoline per month) in 1988 decaying to (10 +/- 1) in 1991 for Mexico City before the introduction of TWCs. In addition, we found a correlation between the monthly averages of CO daily peak and meteorological variables, explaining most of the seasonal changes using only the intensity of the inversion layer and surface wind speed.

Air Movements↗
PubMed1998

Typing of dengue viruses in clinical specimens and mosquitoes by single-tube multiplex reverse transcriptase PCR.

In recent years, dengue viruses (serotypes 1 to 4) have spread throughout tropical regions worldwide. In many places, multiple dengue virus serotypes are circulating concurrently, which may increase the risk for the more severe form of the disease, dengue hemorrhagic fever. For the control and prevention of dengue fever, it is important to rapidly detect and type the virus in clinical samples and mosquitoes. Assays based on reverse transcriptase (RT) PCR (RT-PCR) amplification of dengue viral RNA can offer a rapid, sensitive, and specific approach to the typing of dengue viruses. We have reduced a two-step nested RT-PCR protocol to a single-tube reaction with sensitivity equivalent to that of the two-step protocol (1 to 50 PFU) in order to maximize simplicity and minimize the risk of sample cross-contamination. This assay was also optimized for use with a thermostable RT-polymerase. We designed a plasmid-based internal control that produces a uniquely sized product and can be used to control for both reverse transcription or amplification steps without the risk of generating false-positive results. This single-tube RT-PCR procedure was used to type dengue viruses during the 1995 and 1997-1998 outbreaks in Nicaragua. In addition, an extraction procedure that permits the sensitive detection of viral RNA in pools of up to 50 mosquitoes without PCR inhibition or RNA degradation was developed. This assay should serve as a practical tool for use in countries where dengue fever is endemic, in conjunction with classical methods for surveillance and epidemiology of dengue viruses.

Aedes↗
PubMed1997

Postprandial hypotension in Alzheimer's disease.

The degree of postprandial hypotension in patients with Alzheimer's disease (AD) is not known. We therefore studied ten AD patients and 23 controls before and after a meal. Seven AD patients but only six controls showed a fall in blood pressure (BP) of 20 mmHg or more. Maximum BP fall in AD patients was observed between 20 and 120 min after food ingestion. This differed from the time course in other groups with primary chronic autonomic failure. Postural hypotension occurred in two controls, but not in AD patients. Abnormalities in cardiac vasomotor regulation, gut peptide liberation or both could be responsible for postprandial hypotension in AD.

Aged↗
PubMed1997

[Wernicke's encephalopathy as a complication of chronic hemodialysis: report of one case].

Wernicke encephalopathy, due to the depletion of thiamine, can be a complication of chronic hemodialysis. We report a 43 years old diabetic male in chronic hemodialysis, who two weeks after an infra-condyleal amputation of his left leg, was admitted to the hospital due to an episode of vomiting and abdominal pain lasting 5 days, where confusion and ocular motor signs appeared. Parenteral thiamine administration was started and the confusional state abated. Dialysis can be a predisposing factor for Wernicke encephalopathy and this diagnosis must be considered in confused patients.

Adult↗
PubMed1997

[Balo concentric sclerosis. Report of one case].

We report a 50 years old woman admitted to the hospital due to progressive dysphagia and disarthria of there weeks duration. On admission a right hemiparesis was noted. CSF examination showed a protein of 9 mg/dl and no cells. A brain CAT scan showed rounded bilateral subcortical frontoparietal hypodense zones peripheral contrast material enhancement. Pseudobulbar palsies and hemiparesis worsened and the patient required nasoenteral feeding. She was discharged after four months, with severe disabilities, with the diagnosis of Balo concentric, a progressive demyelinating disease.

Diffuse Cerebral Sclerosis of Schilder↗
PubMed1990

Prevention of high altitude-induced testicular disturbances by previous treatment with cyproheptadine in male rats.

Male rats were exposed to 4,340 m altitude for 4 days. At this time histological alteration in the testes were observed. There were tubules with pyknotic primary spermatocytes and spermatids, necrosis of numerous cells, and sloughing of primary spermatocytes. The damaged areas were limited by normal tissue. Serum testosterone increased significantly after 4 days of exposure. Administration of an anti-serotoninergic compound, cyproheptadine (10 mg/kg body weight), prevented the high altitude-induced changes in both spermatogenesis and serum testosterone. These observations suggest that serotonin is involved in the testicular changes that occurred when rats are acutely exposed to high altitude.

Altitude Sickness↗
PubMed1989

Hemodynamic and gas exchange alterations during Intralipid infusion in patients with adult respiratory distress syndrome.

Hemodynamic and pulmonary gas exchange consequences of 20 percent intravenous fat emulsion infusion (3.0 +/- .3 mg/kg/min) were evaluated in 19 patients who demonstrated ARDS. Lipid infusion precipitated a significant reduction in PaO2/FIO2 from 241 +/- 50 to 184 +/- 41 (mean +/- SD) and increased MPAP from 26.0 +/- 5.1 to 31.8 +/- 4.8 mm Hg, pulmonary vascular resistance from 149 +/- 78 to 179 +/- 61 dyne.s/cm5 and pulmonary venous admixture (Qva/Qt) from 20.7 +/- 15.2 to 30.6 +/- 8.6 percent. Further analysis revealed that the magnitude of increased Qva/Qt was greater in patients who manifested septicemia (N = 10) compared to those who did not (N = 9): 12.3 vs 7.3 percent, respectively. We conclude that intravenous lipid administration was associated with increased MPAP and Qva/Qt in patients with ARDS, particularly when accompanied by septicemia. Although these alterations resolved after the lipid infusion was terminated, we suggest that prudent measures should be taken to guarantee adequate oxygenation during intravenous fat emulsion therapy in patients suffering from ARDS.

Fat Emulsions, Intravenous↗
PubMed1988

Cardiopulmonary effects of Intralipid infusion in critically ill patients.

Cardiopulmonary effects of 500 ml of 20% iv fat emulsion (Intralipid) infusion in two groups of patients who required mechanical ventilation were evaluated in our Critical Care Center. Group 1 included ten patients void of signs or symptoms of sepsis. Group 2 consisted of ten patients exhibiting clinical and laboratory signs and symptoms of sepsis. Data were measured before and immediately after Intralipid infusion and when serum lipemia cleared. Intralipid infusion precipitated a significant increase in venous admixture (Qsp/Qt) from 13.7 +/- 3.6 (SEM) to 18.0 +/- 6.5% and from 22.0 +/- 4.8 to 25.8 +/- 7.0% in groups 1 and 2, respectively. Mean pulmonary artery pressure (MPAP) increased from 22.7 +/- 4.2 to 29.2 +/- 8.1 mm Hg and 26.4 +/- 6.8 to 28.0 +/- 4.0 mm Hg in groups 1 and 2, respectively. When serum lipemia cleared, Qsp/Qt and MPAP returned to preinfusion levels. We conclude that Intralipid infusion increases pulmonary artery pressure and venous admixture in critically ill patients. These changes are temporary and coincidental with serum lipemia rather than presence or absence of sepsis. Adequate levels of oxygenation should be confirmed during Intralipid infusion in patients with borderline oxygenation.

Aged↗
PubMed1979

Glutamate as a CNS transmitter. II. Regulation of synthesis in the releasable pool.

Slices of the molecular layer of the dentate gyrus of rat hippocampus were used to study the regulation of glutamate synthesis and release. Net glutamate synthesis increased dramatically during conditions which stimulated the release of glutamate. The rate of glutamine incorporation into glutamate released into the medium was increased almost immediately upon stimulation with a 56 mM KCl, 3 mM CaCl2 medium. Synthesis appeared to be regulated both by glutamine uptake and the activity og glutaminase. Glutamine uptake was stimulated in the presence of 56 mM KCl and 3 mM CaCl2. The increased glutamine uptake was not due to a decrease in efflux, was unrelated to tissue glutamate levels, and could be dissociated from the rate of glutamate biosynthesis. The presence of Ca2+ ions and depolarization seemed necessary. Glutaminase activity was regulated by end product inhibition: increased levels of tissue glutamate resulted in a decrease in glutamate synthesis. Glutamine in the presence of 56 mM KCl increased the rate of glucose incorporation into glutamate over that seen without glutamine.

Animals↗
PubMed1979

Endotoxin shock in the beagle dog.

The hemodynamic and metabolic responses to endotoxemia were assessed in seven splenectomized, chronically instrumented, conscious but lightly sedated beagle dogs. Measurements included: cardiac output (CO), right and left atrial pressures (RAP, LAP), systemic and pulmonary arterial pressures (SAP, PAP), and heart rate (HR). Arterial blood samples were measured for blood gas tensions, pH, lactate, and pyruvate. After a brief control period, 1 mg/kg endotoxin (Difco 026:B6) was given as an intravenous bolus. Two hours later, each animal was treated with low-molecular weight dextran (LMDX), 2 ml/kg/min for 15 minutes. Endotoxin initially produced a precipitate decline in CO, HR, RAP, LAP, and SAP with concurrent pulmonary hypertension; both pulmonary and systemic vascular resistance increased significantly, then declined to control values as the animal partially recovered. A progressive metabolic acidosis with excess lactate accumulation developed. LMDX produced a significant increase in CO, SAP, PAP, and LAP with a decrease in HR; RAP increased slightly. With hydration, hemodilution was noted along with relief of the metabolic acidosis and the oxygen debt. We conclude (1) neither pulmonary nor systemic vasconstriction persisted in the shocked dog, (2) the response of the pulmonary and systemic vascular beds to endotoxin was qualitatively similar, and (3) oncotic fluid therapy appeared to restore the hemodynamic and metabolic parameters to preshock values.

Animals↗