Biomedical subjects

N Amador

Publications and source records attributed to N Amador.

7 recordsLinked to original sources

PubMed2005

Effect of losartan and spironolactone on left ventricular mass and heart sympathetic activity in prehypertensive obese subjects: a 16-week randomized trial.

Obesity has been shown to be associated with increased left ventricular mass (LVM) and heart sympathetic activity even in nonhypertensive subjects. These factors are predictors of cardiovascular morbidity and mortality independent of other traditional risk factors. We evaluated the effect of losartan and spironolactone on LVM and heart sympathetic activity in prehypertensive obese subjects. A 16-week blinded randomized trial was performed in middle-aged men selected from a Health Public program. Anthropometric and clinical variables were measured at baseline and after losartan (50 mg/day; n=25) or spironolactone (25 mg/day; n=25) treatment. Heart sympathetic activity was evaluated with 60-min electrocardiograph monitoring, and spectral analysis was carried out. LVM was measured by echocardiography according to Devereux and Reicheck's formula indexed for body height (m2.7) to account for obesity. Anthropometric variables, systolic, and diastolic blood pressure levels decreased in both groups of treatment without statisticall difference between them. Losartan increased heart rate variability (from 70.0 to 82.3 ms; P=0.01), and decreased low frequency-high frequency index (from 6.6 to 4.9; P=0.001), and LVM (from 49.2 to 45.2 g; P=0.004). In the multiple regression analysis for factors associated with reduction in LVM; treatment with losartan, and decrease in SBP were the only factors included in the model (R2=0.60; P=0.003). To conclude losartan, but not spironolactone, decreased LVM and heart sympathetic overactivity in prehypertensive obese subjects after 16 weeks of treatment. Regression on LVM was associated with reduction on SBP levels.

Adult↗

PubMed2001

Renal functional reserve in patients with recently diagnosed Type 2 diabetes mellitus with and without microalbuminuria.

BACKGROUND/AIMS: During the first 10 years, two thirds of the patients with type 2 diabetes mellitus (DM) have microalbuminuria (MA). Functional renal reserve (FRR) and its relationship with proteinuria and metabolic control are unknown at the early phases of disease. We investigated the frequency of MA in recently diagnosed type 2 DM patients, and its association with FRR. METHODS: We studied 181 type 2 DM patients with less than 6 months since diagnosis. Renal volume, MA, glomerular filtration rate (GFR) and renal plasma flow (ERPF) were evaluated before and after an acute oral protein load in 28 type 2 DM patients (14 with, and 14 without MA), and in 7 healthy subjects. RESULTS: A total of 10.6% of the patients had MA. MA patients had higher cholesterol and triglyceride levels than those normoalbuminuric. Twenty recently diagnosed type 2 diabetic patients showed high basal GFR. Twelve of them had MA and insulin resistance. After the acute oral protein load, the control subjects and the patients without MA increased their GFR and their ERPF. The group with MA did not. CONCLUSIONS: Seventy-five percent of the patients were hyperfiltering. Normoalbuminuric patients had larger increase in GFR and ERRPF than MB patients. We conclude that FRR measurement can be an important tool for the diagnosis of latent diabetic nephropathy.

Adult↗

PubMed2000

Reward-predicting and reward-detecting neuronal activity in the primate supplementary eye field.

In addition to cells specifically active with visual stimuli, saccades, or fixation, the supplementary eye field contains cells that fire in precise temporal relationship with the occurrence of reward. We studied reward-related activity in two monkeys performing a prosaccade/antisaccade task and in one monkey trained in memory prosaccades only. Two types of neurons were distinguished by their reciprocal firing pattern: reward-predicting (RP) and reward-detecting (RD). RP neurons linearly increased their firing as early as 150 ms before saccade onset until the occurrence of reward, at which time they abruptly ceased firing. In contrast, RD neurons fired in phase with reward delivery, even when its duration was varied and when it was repeated at different frequencies. RD discharges were little affected or unaffected by the position of a visual cue that briefly anchored the goal at the onset of reward. The complementary firing patterns of the RP and RD neurons could provide a feedback mechanism necessary for learning and performing the task.

Animals↗

PubMed1998

Primate antisaccades. I. Behavioral characteristics.

The antisaccade task requires a subject to make a saccade to an unmarked location opposite to a flashed stimulus. This task was originally designed to study saccades made to a goal specified by instructions. Interest for this paradigm surged after the discovery that frontal lobe lesions specifically and severely affect human performance of antisaccades while prosaccades (i.e., saccades directed to the visual stimulus) are facilitated. Training monkeys to perform antisaccades was rarely attempted in the past, and this study is the first one that describes in detail the properties of such antisaccades compared with randomly intermingled prosaccades of varying amplitude in all directions. Such randomization was found essential to force the monkeys to use the instruction cue (pro- or anti-) and the location cue (peripheral stimulus) provided within a trial rather than to direct their saccades to the location of past rewards. Each trial began with the onset of a central fixation target that conveyed by its shape the instruction to make a pro- or an antisaccade to a subsequent peripheral stimulus. In one version of the task, the monkey was allowed to make an immediate saccade to the goal; in a second version, the saccade had to wait for a go signal. Analyses of the accuracy, velocity, and latency of antisaccades compared with prosaccades were performed on a sample of 7,430 pro-/antisaccades in the "immediate saccade" task (delayed saccades suffering from known distortions). Error rates fluctuated approximately 25%. Results were the same for the two monkeys with respect to accuracy and velocity, but they differed in terms of reaction time. Both monkeys generated antisaccades to stimuli in all directions, at various eccentricities, but antisaccades were significantly less accurate and slower than prosaccades elicited by the same stimuli. Interestingly, saccades to the stimulus could be followed by appropriate antisaccades with no intersaccadic interval. Such instances are here referred to as "turnaround saccades." Because they occurred sometimes with a long latency, turnaround saccades did not simply reflect the cancellation of an early foveation reflex. Consistent with human data, latencies of one monkey were longer for antisaccades than for prosaccades, but the reverse was true for the other monkey who was trained differently. In summary, this study demonstrates the feasibility of providing a subhuman primate model of antisaccade performance, but at the same time it suggests some irreducible differences between human and monkey performance.

Animals↗

PubMed1997

Antisaccade performance predicted by neuronal activity in the supplementary eye field.

The voluntary control of gaze implies the ability to make saccadic eye movements specified by abstract instructions, as well as the ability to repress unwanted orientating to sudden stimuli. Both of these abilities are challenged in the antisaccade task, because it requires subjects to look at an unmarked location opposite to a flashed stimulus, without glancing at it. Performance on this task depends on the frontal/prefrontal cortex and related structures, but the neuronal operations underlying antisaccades are not understood. It is not known, for example, how excited visual neurons that normally trigger a saccade to a target (a prosaccade) can activate oculomotor neurons directing gaze in the opposite direction. Visual neurons might, perhaps, alter their receptive fields depending on whether they receive a pro- or antisaccade instruction. If the receptive field is not altered, the antisaccade goal must be computed and imposed from the top down to the appropriate oculomotor neurons. Here we show, using recordings from the supplementary eye field (a frontal cortex oculomotor centre) in monkeys, that visual and movement neurons retain the same spatial selectivity across randomly mixed pro- and antisaccade trials. However, these neurons consistently fire more before antisaccades than prosaccades with the same trajectories, suggesting a mechanism through which voluntary antisaccade commands can override reflexive glances.

Animals↗

PubMed1995

[Mortality of women of child-bearing age in Costa Rica, 1987-1989].

The purpose of this descriptive study was to detect regional differences in the mortality of women 15 to 44 years of age, especially mortality due to preventable causes. The regions studied corresponded to the health regions of Costa Rica. The deaths of women 15 to 24, 25 to 34, and 35 to 44 recorded from 1987 to 1989 in the National Deaths Register were classified as due to preventable causes or nonpreventable causes and grouped by region. The nationwide mortality rate for women 15 to 44 years of age was 6.9 per 10,000 women. The highest rates were recorded in the Huetar Atlántica (10.05) and Brunca (8.29) regions, and the lowest in the West Central region (4.38). Some 44.4% of the deaths were preventable, mainly by secondary prevention measures or a mix of measures. The lowest proportions of preventable mortality were found in the North Central and Brunca regions (35.2% and 36.7%, respectively), and the highest in the West Central (64.7%). The nonpreventable deaths mostly corresponded to causes not easily avoided and to the remainder of causes not included under other headings of the Taucher International Classification. Ill-defined causes represented 1.2% of total deaths in the study period. Almost all the peripheral regions showed higher mortality than the central plateau, which may be because of their lesser degrees of socioeconomic and infrastructure development and of access to health services. Another influence may be the more subordinate status of women in rural areas. This situation can be changed by making better use of available resources and improving the quality of services. It is recommended that this type of study be continued in order to monitor trends in women's mortality.

Adolescent↗

PubMedDate not supplied

[Comparison of HOMA IR with the minimal model for measuring insulin sensitivity in polycystic ovary syndrome].

BACKGROUND: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of premenopausal women. These women have insulin resistance independent of obesity; and insulin resistance is now recognized as a risk factor for the development of type 2 diabetes mellitus, hypertension and cardiovascular disease. PURPOSE: We sought, therefore, to assess whether there was correlation between a simple fasting measure of insulin sensitivity (Homeostatic Model) and the Minimal-Model in this syndrome. METHODS: Thirty-three PCOS women (aged 22.7 +/- 6.2 years and body mass index (BMI) 29.1 +/- 5.4) underwent frequently sampled i.v. glucose tolerance test (Minimal-Model). RESULTS: Seventeen patients (51.5%) had insulin sensitivity < 1.5 x 10(-4) min.-1.microU-1.mL-1. Patients with BMI > de 27 was more resistant than the BMI < or = de 27 (p = 0.004). The correlation in PCOS between Si (insulin sensitivity) and HOMA IR was found significant for all the group (p = 0.0001; RRANK = -0.76) and those women with BMI > de 27 (RRANK = -0.77; p = 0.00006), but not significant correlation was found in those with BMI < or = de 27 (RRANK = -0.43; p = 0.13). CONCLUSIONS: We conclude that the HOMA IR may be useful as a screening test for insulin resistance in overweight and obese Mexican PCOS women but not in the lean ones.

Adipose Tissue↗