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Biomedical subjects

E Perez

Publications and source records attributed to E Perez.

At least 37 records · Page 2Linked to original sources
PubMed2000

Changes in REM sleep occurrence due to rhythmical auditory stimulation in the rat.

The effects of the rhythmical delivery of an auditory stimulus (1000 Hz, from 50 to 100 dB, 20 ms, every 20 s) on the pattern of rapid eye movement (REM) sleep occurrence was studied in the rat. The stimulation was simultaneously carried out on pairs of rats over 5 consecutive days (10-h recording sessions), during which a tone of increasing intensity (50, 63, 75, 88, 100 dB) was used. In each experimental session, auditory stimulation was triggered by the REM sleep occurrence of one rat (REMS-selective stimulation) whilst the other rat simultaneously received the same stimuli, but during any stage of the wake-sleep cycle (REMS-unselective stimulation). The results showed that the total amount of REM sleep in the 10-h recording session was increased over the 5 days of stimulation in the REMS-unselective group. This effect was due to an increase in the mean duration of REM sleep episodes. However, no significant changes were observed in animals under REMS-selective stimulation, nor in a third group of animals in which the spontaneous evolution of REM sleep occurrence (REMS-spontaneous) was studied. Since 86% of the stimuli under the REMS-unselective auditory stimulation fell outside REM sleep, the result would suggest that REM sleep occurrence is affected when the stimuli are delivered during a time period (i.e. during wakefulness or non-REM sleep) in which it is well known that physiological regulations are fully operant.

Acoustic Stimulation↗
PubMed2000

Effect of patient adherence to antiretroviral therapy on CD4+ cell count, HIV-1 RNA, and serum concentrations of tumor necrosis factor and its soluble receptors.

A 1-year prospective analysis of patient adherence to antiretroviral therapy (zidovudine plus zalcitabine [55 patients] or zidovudine plus zalcitabine plus saquinavir [32 patients]) was performed in human immunodeficiency virus (HIV)-infected patients attended at a tertiary care hospital. Adherence to therapy was measured jointly by pharmacy records, patients' self-recording, and an increase in mean corpuscular volume. Likewise, the effects of therapy on clinical parameters, HIV load, CD4+ cell count, and serum levels of tumor necrosis factor alpha (TNF-alpha) and its soluble receptors were analyzed. Twenty-seven patients of those on a double-agent regimen and 12 of those on a triple-agent regimen adhered to the treatment. Ten opportunistic events occurred in noncompliant patients versus none in compliant individuals. A significant increase in CD4+ cell count and a decrease in HIV viral load were observed only in patients who adhered to therapy. TNF and its soluble receptors remained elevated at the end of follow-up, even in patients in whom the HIV viral load decreased to < 400 copies/ml. In conclusion, adherence to therapy must be considered a major factor influencing the results of antiretroviral therapy. Although these treatments have been demonstrated to be efficacious, they are not able to normalize the immune activation markers. These data suggest a suboptimal effect of antiretroviral therapy on the eradication of HIV-1.

Adult↗
PubMed2000

Leptin resistance is associated with hypothalamic leptin receptor mRNA and protein downregulation.

It is well known that leptin plays a predominant role in body weight regulation. Leptin receptors are especially abundant in the hypothalamus, where the majority of leptin's biologic activity occurs. In instances where leptin has no or limited activity, it is easy to implicate leptin resistance and speculate as to the multiple levels where resistance may occur. We hypothesize that leptin resistance is associated with hypothalamic leptin receptor downregulation. Rats were randomly divided into 3 groups receiving phosphate-buffered saline (PBS) or low- or high-dose leptin continually over a 28-day period. Body weight and food intake were measured daily. Long-term leptin treatment resulted in a dose-dependent decrease in body weight for the duration of the study. It also resulted in a dose-dependent decrease in food intake, but only for the first half of the study. A test of leptin resistance was performed at week 3 demonstrating the development of resistance to the anorectic effects of leptin in both treatment groups. The results of the resistance test together with the food intake data suggest that resistance to the appetite-regulating effects of leptin developed during the final 2 weeks of the study. In addition, we show a downregulation of leptin receptor mRNA and protein in the hypothalamus, which may be one of the mechanisms by which the food-intake effects of leptin were lost.

Animals↗
PubMed2000

Utility of tissue culture for detection of Toxoplasma gondii in vitreous humor of patients diagnosed with toxoplasmic retinochoroiditis.

Laboratory recovery and confirmation of the etiologic agent in necrotizing retinochoroiditis are problematic. Tissue culture and intraocular antibody titers were compared as adjuncts to clinical diagnosis for toxoplasmic retinochoroiditis: the correlations were 91 and 67%, respectively. Isolation of Toxoplasma gondii may establish a definitive diagnosis in patients with toxoplasmic retinochoroiditis.

Animals↗
PubMed2000

A simple severity index for pressure ulcers.

The aim of this study was to design and test a pressure ulcer severity score based on assessment by experienced clinicians. Fifty pressure ulcers were each evaluated independently by seven experienced clinicians, using a scale that ranged from 0 (mildest damage) to 10 (most severe). Ulcer characteristics were analysed to determine which factors related to the assessments. A second set of 50 ulcers was used to test the validity of the resulting scoring system. Inter- and intra-observer reliability were tested in a further 10 pressure ulcers. A multivariate linear model was produced, based on the following three variables: colour (CO-matched-matched) in the wound base; depth (DE) of the ulcer; and mean diameter (D) of the wound ('CODED'). The coefficients for each variable were rounded to yield points in an additive equation, the CODED score. This score had a high correlation (r = 0.92, P < 0.001) with the second set of evaluations, used to test the score performance. The CODED score is a simple and valid tool to quantify the progress of a pressure ulcer. It has a high correlation with the severity assessment of experienced clinicians and is reliable when used by non-experienced observers.

Humans↗
PubMed1999

Spectroscopic limits on the distance and energy release of GRB 990123

An optical spectrum of the afterglow from the unusually bright gamma-ray burst GRB 990123 obtained on 24.25 January 1999 universal time showed an absorption system at a redshift of z = 1.600. The absence of a hydrogen Lyman alpha forest sets an upper limit of z < 2.17, whereas ultraviolet photometry indicates an upper limit of z < 2.05. The probability of intersecting an absorption system as strong as the one observed along a random line of sight out to this z is at most a few percent, implying that GRB 990123 was probably at z = 1. 600. Currently favored cosmological parameters imply that an isotropic energy release equivalent to the rest mass of 1.8 neutron stars (4.5 x 10(54) erg) was emitted in gamma rays. Nonisotropic emission, such as intrinsic beaming, may resolve this energy problem.

Journal Article↗
PubMed1999

Identification of a virulence gene cluster of Mycobacterium tuberculosis by signature-tagged transposon mutagenesis.

Tuberculosis remains the greatest cause of death worldwide due to a single pathogen. In order to identify the genes required for the pathogenicity of Mycobacterium tuberculosis, a functional genomic approach was developed. A library of signature-tagged transposon mutants of this bacterium was constructed and screened for those affected in their multiplication within the lungs of mice. From 1927 mutants tested, 16 were attenuated for their virulence. The insertions harboured by the selected mutants were mapped on the M. tuberculosis genome and most of the mutated loci appeared to be involved in lipid metabolism or transport across the membrane. Four independent mutations identified a cluster of virulence genes located on a 50 kb chromosomal region. These genes might be involved in the production of phthiocerol and phenolphthiocerol derivatives, a group of molecules restricted to eight mycobacterial species, seven of them being either strict or opportunistic pathogens. The interaction of five mutant strains with mouse bone marrow macrophages was investigated. These five mutants were still able to multiply in this cell type. However, in three cases, there was a growth defect in comparison with the wild-type strain. The other two strains exhibited no clear difference from the virulent strain, MT103, in this model. This study, which is the first global research of virulence factors of M. tuberculosis, opens the way to a better understanding of the molecules that are key players in the interaction of this pathogen with its host.

Animals↗
PubMed1999

Survey of three bacterial louse-associated diseases among rural Andean communities in Peru: prevalence of epidemic typhus, trench fever, and relapsing fever.

Typhus and other louse-transmitted bacterial infections in Peruvian sierra communities are known to occur but have not recently been assessed. In this study, 194 of 1,280 inhabitants of four villages in Calca Province in the Urubamba Valley were included. Thirty-nine (20%) of the 194 volunteers had antibodies to Rickettsia prowazekii, whereas 24 (12%) had antibodies to Bartonella quintana and 2 against Borrelia recurrentis. There was a significant correlation between the presence of infesting ectoparasites and antibodies to R. prowazekii, as well as between antibodies to R. prowazekii and ectoparasite infestation and fever in the previous 6 months. The proportion of inhabitants infested with ectoparasites was significantly higher in the highest-altitude village than in the other three villages. Two volunteers' antibody levels suggested a recent typhus infection, but only B. quintana DNA was amplified from lice. Epidemic typhus remains extant in the area, and B. quintana infections were encountered and documented for the first time in South America.

Adult↗
PubMed1999

Field evaluation of the Determine rapid human immunodeficiency virus diagnostic test in Honduras and the Dominican Republic.

Rapid detection of human immunodeficiency virus (HIV) infection can result in improved patient care and/or faster implementation of public health preventive measures. A new rapid test, Determine (Abbott, Abbott Park, Ill.), detects HIV type 1 (HIV-1) and HIV-2 antibodies within 15 min by using 50 microl of serum or plasma. No specialized equipment or ancillary supplies are required, and results are read visually. A positive result is noted by the appearance of a red line. An operational control (red line) indicates proper test performance. We evaluated the Determine rapid HIV detection test with a group of well-characterized serum samples (CD4 counts and viral loads were known) and serum samples from HIV-positive individuals at field sites in Honduras and the Dominican Republic. In the field evaluations, the results obtained by the Determine assay were compared to those obtained by local in-country HIV screening procedures. We evaluated serum from 100 HIV-positive patients and 66 HIV-negative patients. All samples gave the expected results. In a companion study, 42 HIV-positive samples from a Miami, Fla., serum bank were tested by the Determine assay. The samples had been characterized in terms of CD4 counts and viral loads. Fifteen patients had CD4 counts <200 cells/mm(3), while 27 patients had CD4 counts >200 cells/mm(3). Viral loads ranged from 630 to 873,746 log(10) copies/ml. All samples from the Miami serum bank were positive by the Determine test. Combined results from the multicenter studies indicated that the correct results were obtained by the Determine assay for 100% (142 of 142) of the HIV-positive serum samples and 100% (66 of 66) of the HIV-negative serum samples. The Determine test was simple to perform and the results were easy to interpret. The Determine test provides a valuable new method for the rapid identification of HIV-positive individuals, especially in developing countries with limited laboratory infrastructures.

AIDS Serodiagnosis↗
PubMed1999

Evaluation of the MRL diagnostics dengue fever virus IgM capture ELISA and the PanBio Rapid Immunochromatographic Test for diagnosis of dengue fever in Jamaica.

We evaluated two new commercial dengue diagnostic tests, the MRL Diagnostics Dengue Fever Virus IgM Capture ELISA and the PanBio Rapid Immunochromatographic Test, on serum samples collected during a dengue epidemic in Jamaica. The MRL ELISA method correctly identified 98% (78 of 80) of the samples as dengue positive, while the PanBio test identified 100% (80 of 80). Both tests were 100% (20 samples of 20) specific.

Adolescent↗
PubMed1999

Effects of neonatal undernutrition and binaural ear occlusion on neuronal development of the superior olivary complex of rats.

Golgi-Cox-impregnated neurons of the superior olivary complex were investigated in control, binaural ear-occluded control, undernourished, and binaural ear-occluded undernourished Wistar rats of 12, 20, and 30 days of age. In neonatally undernourished and binaural ear-occluded animals, a significant reduction in the number of dendrites and dendritic intersections in the medial trapezoid body neurons was observed. Inconsistent effects upon the dendritic arbor lateral superior olivary cells were also detected. Control and undernourished rats with binaural ear occlusion exhibited a significant increase in the dendritic arbor measurements of lateral superior olivary neurons as compared with the cells of the medial trapezoid body. The cytoarchitectonic imbalance between the modulatory efferent control of these systems and the sensory auditory input to the cochlea may be important for the integration of complex auditory physiological phenomena.

Aging↗
PubMed1999

Control of REM sleep: an aspect of the regulation of physiological homeostasis.

Since REM sleep is characterized by a suspension of the hypothalamic integration of homeostatic regulations, it has been assumed that the duration of both REM sleep episodes and of the time interval between the end of one episode and the beginning of the following episode may be regulated according to sleep related processes and the homeostatic needs of the organism. A series of studies performed on the rat has shown that REM sleep episodes occur as two basic types: single REM sleep episodes, that are separated by intervals > 3 min and sequential episodes, that are separated by intervals < or = 3 min and appear in a cluster. Moreover, it has been observed that, in this species, a change in REM sleep occurrence is caused by a modification in the number of episodes and not in their duration. With respect to this, sleep deprivation and recovery are characterized by a decrease and an increase, respectively, in the number of sequential REM sleep episodes, but the number of single episodes tends to be kept constant. The central aspects of this kind of regulation have been examined biochemically in the preoptic-anterior hypothalamus, an area involved in the control of autonomic and sleep related processes. The results show that the accumulation of adenosine 3':5'-cyclic monophosphate (cAMP) is impaired, in this region, during sleep deprivation and appears to return to the control levels, during the recovery, with a rate inversely related to the degree of the previous deprivation. Moreover, it has been observed that the systemic administration of DL-propranolol and LiCl reduces cAMP accumulation mainly in the preoptic-anterior hypothalamus; this condition is concomitant with a reduction in REM sleep occurrence.

Animals↗
PubMed1998

Prospective study for the detection of Anaplasma marginale Theiler, 1911 (Rickettsiales: Anaplasmataceae) in Costa Rica.

A prospective study was conducted to assess the dynamics of the infection and host response to Anaplasma marginale in one closed herd in the dry tropical forest of Costa Rica. The study subjects were the dams and their calves born during 1 breeding season (1995-1996). All cows were sampled at 3 month intervals for antibody detection using a competitive ELISA (cELISA) and for antigen detection using PCR/nonradioactive probe assay. All 24 calves born during the study were individually identified at birth and subsequently sampled each month for PCR and cELISA. Ticks were identified from all animals throughout the entire study period. The results from this study confirmed that the cELISA is a reliable assay for identifying new and carrier infections and that carrier infections can exist at levels below that detectable by PCR. In addition, it was demonstrated that calves born in this region will most likely be exposed to Anaplasma within the first 6 months of age.

Anaplasma↗
PubMed1998

The influence of a heavy thermal load on REM sleep in the rat.

This study was carried out in order to further test the hypothesis that the occurrence of REM sleep in the rat in the form of episodes separated by long intervals (single REM sleep episodes) and by short intervals (sequential REM sleep episodes) is differently influenced by changes in both sleep and ambient related processes. Rats were studied during the exposure to Ta -10 degrees C for 24 or 48 h and during a 12 h recovery period at laboratory Ta (23 degrees C) following either the first or the second 24 h of cold exposure. The exposure to such a low Ta induced an almost complete abolition of REM sleep which was followed, during recovery, by a marked REM sleep rebound. However, in spite of the larger REM sleep deprivation, the REM sleep rebound was weaker following the 48 h-exposure than that following the exposure for 24 h. The increase in the amount of REM sleep during the recovery period was due to an increase in the amount of that occurring in the form of sequential episodes, whilst that in the form of single episodes did not change with respect to control levels. However, the occurrence of REM sleep in the form of sequential episodes was partially impaired during the REM sleep rebound observed in the recovery period following the 48 h-exposure. These results would suggest that the homeostatic regulation of physiological variables may conflict with that of REM sleep occurrence and that the degree of such a contrast is indicated, at low Ta, by the amount of REM sleep in the form of single episodes and, during the following recovery, by the amount of REM sleep in the form of sequential episodes.

Animals↗