Search PubMed⌕ Search

Biomedical subjects

E Salinas

Publications and source records attributed to E Salinas.

At least 19 recordsLinked to original sources
PubMed2002

Effect of hypothyroidism on synaptosomal-associated protein of 25 kDa and syntaxin-1 expression in adenohypophyses of rat.

The aim of this study was to analyze the expression of SNAP-25 and syntaxin-1 in the adenohypophyses of hypothyroid rats. Rats were divided into: 1) controls; 2) thyroidectomized 40 days; and 3) thyroidectomized 40 days with replacement of T4 20 days after surgery. Adenohypophyses were studied by immunohistochemistry and immunoblot analysis using antibodies against SNAP-25, syntaxin-1 and TSH. By immunostaining, SNAP-25 and syntaxin-1 were conspicuous and were localized around cytoplasmic vacuoles of thyroidectomy cells. Immunoblot analysis shows that thyroidectomy increases adenohypophysial SNAP-25 expression and decreases syntaxin-1 levels. T4 administration for 20 days produces a recovery similar to control values. In conclusion, thyroidectomy produces changes in both expression and immunoreactivity of SNAP-25 and syntaxin-1 in adenohypophyses of rats and these effects can be reversed by T4 administration.

Animals↗
PubMed2001

Cardiac cellular actions of hydrochlorothiazide.

In long term treatment, thiazide diuretics such as hydrochlorothiazide (HCTZ) lower blood pressure by decreasing peripheral resistance rather than by their diuretic effect. This action has been attributed to the opening of Ca2+-activated K+ channels in vascular smooth muscle cells. However, little is known about their cardiac cellular actions. Here we investigated the possible actions of HCTZ on action potential and contraction of rat ventricular muscle strips and on the ionic currents of isolated rat ventricular cardiomyocytes. HCTZ depressed ventricular contraction with an IC30 of 1.85 microM (60% decrease at 100 microM). Action potential duration at -60 mV and maximal rate of depolarization were, however, only slightly decreased by 12% and 22%, respectively, at 100 microM. At the single cell level, HCTZ (100 microM) depressed the fast Na+ current (INa) and the L-type Ca2+ current (ICaL) by 30% and 20%, respectively. The effects on ICaL were not voltage-or frequency-dependent. In cells intracellularly perfused with 50 microM cyclic adenosine, monophosphate HCTZ reduced ICaL by 33%. The transient (Ito), the delayed rectifier and the inward rectifier potassium currents were decreased by 20% at 100 microM HCTZ. The effects on Ito were voltage-dependent. In conclusion, HCTZ at high concentrations possesses a negative inotropic action that could be in part due to its blocking action on INa and ICaL. The actions of HCTZ on multiple cardiac ionic currents could explain its weak effect on action potential duration.

Action Potentials↗
PubMed2001

Touch and go: decision-making mechanisms in somatosensation.

A complex sequence of neural events unfolds between sensory receptor activation and motor activity. To understand the underlying decision-making mechanisms linking somatic sensation and action, we ask what components of the neural activity evoked by a stimulus are directly related to psychophysical performance, and how are they related. We find that single-neuron responses in primary and secondary somatosensory cortices account for the observed performance of monkeys in vibrotactile discrimination tasks, and that neuronal and behavioral responses covary in single trials. This sensory activity, which provides input to memory and decision-making mechanisms, is modulated by attention and behavioral context, and microstimulation experiments indicate that it may trigger normal perceptual experiences. Responses recorded in motor areas seem to reflect the output of decision-making operations, which suggests that the ability to make decisions occurs at the sensory-motor interface.

Animals↗
PubMed2001

Neurofilament expression in cultured rat adenohypophysial cells.

The aim of the present work was to investigate in cultured rat adenohypophysial cells: a) the presence of neurofilaments of 200 kDa (NF-H), b) the effect of thyroid hormone (T(3)) and thyrotropin releasing hormone (TRH) on the expression of NF-H and c) the possible role of NF-H on thyrotropin (TSH) secretion. The presence of NF-H was observed by immunocytochemistry in cultured rat adenohypophysial cells. The exposure to T(3) for 12 h produced a significant increase in NF-H expression; whereas incubation with TRH or T(3)+TRH resulted in no change. The cells treated with T(3) or TRH or T(3)+TRH for 24 h showed no alteration. However, incubation for 48 h with TRH or T(3)+TRH caused significant decrease in NF-H expression. Incubation with NF-H antibodies produced a significant inhibition of calcium-induced TSH release in digitonin-permeabilized adenohypophysial cells. These results provide evidence that NF-H is present in cultured rat adenohypophysial cells, and that T(3) and TRH can modify NF-H expression. It can be suggested that in cultured adenohypophysial cells, NF-H may play a role in the secretory process.

Animals↗
PubMed2001

Gain modulation in the central nervous system: where behavior, neurophysiology, and computation meet.

Gain modulation is a nonlinear way in which neurons combine information from two (or more) sources, which may be of sensory, motor, or cognitive origin. Gain modulation is revealed when one input, the modulatory one, affects the gain or the sensitivity of the neuron to the other input, without modifying its selectivity or receptive field properties. This type of modulatory interaction is important for two reasons. First, it is an extremely widespread integration mechanism; it is found in a plethora of cortical areas and in some subcortical structures as well, and as a consequence it seems to play an important role in a striking variety of functions, including eye and limb movements, navigation, spatial perception, attentional processing, and object recognition. Second, there is a theoretical foundation indicating that gain-modulated neurons may serve as a basis for a general class of computations, namely, coordinate transformations and the generation of invariant responses, which indeed may underlie all the brain functions just mentioned. This article describes the relationships between computational models, the physiological properties of a variety of gain-modulated neurons, and some of the behavioral consequences of damage to gain-modulated neural representations.

Animals↗
PubMed2001

Venlafaxine extended release (ER) in the treatment of generalised anxiety disorder: twenty-four-week placebo-controlled dose-ranging study.

BACKGROUND: Generalised anxiety disorder (GAD) has received less study than other anxiety disorders, particularly its long-term treatment. AIMS: To assess the efficacy and safety of venlafaxine extended release (ER) in patients with GAD. METHOD: A total of 541 out-patients, 18-86 years old, were recruited to this 24-week, placebo-controlled, double-blind study of three fixed doses (37.5, 75 and 150 mg/day) of venlafaxine ER. RESULTS: All doses of venlafaxine ER showed efficacy superior to placebo, apparent from week 2, that was sustained throughout the 24-week study for the two higher doses. The discontinuation rate did not differ significantly among the treatment groups. CONCLUSIONS: Venlafaxine ER is an effective and safe treatment for GAD for up to 6 months.

Adolescent↗
PubMed2001

Thyroidectomy induces neurofilament expression in adenohypophyses of rats.

We studied the effect of thyroidectomy on neurofilament expression in adenohypophyses of rats. The question of whether thyroxine (T4) administration can reduce this effect was also investigated. Rats were divided into: 1. Euthyroid controls, 2. Thyroidectomized 20 d (Tx 20 d), 3. Thyroidectomized 20 d with replacement of T4 (Tx 20 d + T4 20 d), 4. Thyroidectomized 40 d (Tx 40 d), 5. Thyroidectomized 40 d with replacement of T4 20 d after surgery (Tx 40 d + T4 20 d). Adenohypophyses were studied by immunohistochemistry and Western blot analysis using antibodies against neurofilament 200 kDa (NF-H) and thyroid-stimulating hormone (TSH). The number of thyrotrophs with immunoreactivity for NF-H was increased in Tx 20 d and Tx 40 d rats, whereas T4 administration protected the effect of thyroidectomy. In the thyroidectomized animals, thyrotrophs showed eccentric nuclei and the cytoplasm was full of NF-H immunoreactivity, whereas in T4 treated rats, the thyrotrophs were similar to control. Western blot analysis showed that NF-H expression increased in rats thyroidectomized for 20 and 40 d. T4 given immediately or 20 d after thyroidectomy caused no changes in NF-H expression. We conclude that thyroidectomy induces NF-H expression in adenohypophyses of rats and administration of T4 decreases this effect.

Animals↗
PubMed2001

Efficacy of venlafaxine extended release in patients with major depressive disorder and comorbid generalized anxiety disorder.

BACKGROUND: A subset of patients with comorbid major depressive disorder and generalized anxiety disorder (GAD) was examined from a double-blind. placebo-controlled study comparing the efficacy and safety of venlafaxine extended release (XR) and fluoxetine. METHOD: From a total of 368 patients, 92 patients meeting DSM-IV criteria for major depressive disorder who also had comorbid GAD were identified. The comparison group comprised 276 evaluable noncomorbid patients. Patients received venlafaxine XR (75-225 mg/day), fluoxetine (20-60 mg/day), or placebo for 12 weeks. Efficacy evaluations included Hamilton Rating Scale for Depression (HAM-D), Hamilton Rating Scale for Anxiety (HAM-A), and Clinical Global Impressions (CGI) scale. RESULTS: By the final assessment at week 12, comorbid patients in the venlafaxine XR group, but not in the fluoxetine group, showed a significantly greater decrease than those in the placebo group in the primary efficacy variables of mean HAM-D and HAM-A total scores (p < .05, pairwise comparison). In comorbid patients, significant pairwise differences were noted between venlafaxine XR and placebo at week 12 for the secondary variables of HAM-D anxiety-somatization and retardation factors, HAM-D depressed mood item. HAM-A psychic anxiety factor, the Hospital Anxiety and Depression scale (HAD) anxiety subscale score, and the Covi Anxiety Scale score. Fluoxetine was significantly different from placebo only on the HAD depression subscale score. Response, defined as > or = 50% decrease in symptoms score, was achieved in 66% and 59% of the comorbid patients for HAM-D and HAM-A, respectively, in the venlafaxine XR group at week 12. This response was higher than that seen with fluoxetine (52% and 45%) or placebo (36% and 24%). Onset of efficacy appeared to be slower in comorbid than in noncomorbid patients. CONCLUSION: This is the first evidence from a controlled study of the effectiveness of pharmacotherapy in patients with comorbid major depressive disorder and GAD. The delayed improvement in comorbid patients compared with noncomorbid patients suggests that a longer treatment period may be necessary in comorbid patients.

Adult↗
PubMed2001

Pattern of symptom improvement following treatment with venlafaxine XR in patients with generalized anxiety disorder.

BACKGROUND: The efficacy of anxiolytic drugs in generalized anxiety disorder (GAD) is conventionally assessed by evaluating changes in the total score of psychometric scales such as the Hamilton Rating Scale for Anxiety (HAM-A). The purpose of this pooled analysis of data was to evaluate the efficacy of venlafaxine extended release (XR) on individual items of the HAM-A and the Brief Scale for Anxiety (BSA). METHOD: Data were pooled from 5 studies of patients with GAD who were treated with either venlafaxine XR or placebo for 8 weeks (N = 2,021) and up to 6 months (N = 767). Individual items of the HAM-A and the BSA were examined. and, using the mean changes from baseline to endpoint, an effect size for each item was calculated by dividing the difference between baseline and endpoint values for each item by the standard deviation of this difference. The effect sizes determined for the venlafaxine group were compared with those for the placebo group. Items from each scale that are concordant with the DSM-IV diagnostic criteria for GAD were selected for further examination, and the specific effect sizes of each item were expressed after controlling for placebo effects. RESULTS: The effect size of the majority of the 14 items of the HAM-A scale and the 10 items of the BSA scale associated with treatment with venlafaxine XR was greater than with placebo at both 8 weeks and 6 months. Furthermore, the effect sizes at 6 months were generally greater than at 8 weeks in venlafaxine XR-treated patients. Effect sizes associated with venlafaxine XR were greatest for the HAM-A items that were most closely related to diagnostic symptoms of GAD, namely anxious mood, tension, intellectual functioning, and behavior at interview at both 8 weeks and 6 months. Similarly, GAD-related BSA items of inner tension, worrying over trifles, hostile feelings, and muscular tension were associated with the greatest improvements with venlafaxine XR at both time-points. CONCLUSION: The HAM-A and BSA items that most closely corresponded to DSM-IV diagnostic criteria for GAD showed the largest improvement during treatment with venlafaxine XR. This indicates that the specific symptoms of GAD can be treated effectively with venlafaxine XR, both in the short and longer term.

Anti-Anxiety Agents↗
PubMed2001

[Imported myiasis: 7 cases of cutaneous parasitism caused by Dermatobia hominis flie larvas].

Myiasis is the parasitism of organs and tissues of warm-blooded vertebrates by flies larvae. D hominis is a flie geographically restricted to tropical America from Mexico to northern Argentina. The adult flie, which is not hematophagous, needs to put its eggs on the abdominal surface of hematophagous arthropods which serve as carriers of future larvae which are deposited on the skin of the hosts (mammals, birds and accidentally men) when biting. Seven patients (two females) aged 7 to 35 years old, of different nationalities, recalled receiving mosquito bites, after staying in tropical American areas in the previous forty days. They presented furuncle-like lesions in exposed surfaces of the body. These lesions, 2-3 cm long, pruritic and mildly tender, broke and released a serous or serohematic fluid. Through the resulting opening, it was possible to partially observe the larva. Larvae were extracted by manual pressure (4) or surgical incision (3) and identified as D hominis larvae. Diagnosis of dermatobiasis, an imported myiasis, must be based on the characteristics of lesions and the previous residence in endemic areas of America.

Adult↗
PubMed2000

Impact of correlated synaptic input on output firing rate and variability in simple neuronal models.

Cortical neurons are typically driven by thousands of synaptic inputs. The arrival of a spike from one input may or may not be correlated with the arrival of other spikes from different inputs. How does this interdependence alter the probability that the postsynaptic neuron will fire? We constructed a simple random walk model in which the membrane potential of a target neuron fluctuates stochastically, driven by excitatory and inhibitory spikes arriving at random times. An analytic expression was derived for the mean output firing rate as a function of the firing rates and pairwise correlations of the inputs. This stochastic model made three quantitative predictions. (1) Correlations between pairs of excitatory or inhibitory inputs increase the fluctuations in synaptic drive, whereas correlations between excitatory-inhibitory pairs decrease them. (2) When excitation and inhibition are fully balanced (the mean net synaptic drive is zero), firing is caused by the fluctuations only. (3) In the balanced case, firing is irregular. These theoretical predictions were in excellent agreement with simulations of an integrate-and-fire neuron that included multiple conductances and received hundreds of synaptic inputs. The results show that, in the balanced regime, weak correlations caused by signals shared among inputs may have a multiplicative effect on the input-output rate curve of a postsynaptic neuron, i.e. they may regulate its gain; in the unbalanced regime, correlations may increase firing probability mainly around threshold, when output rate is low; and in all cases correlations are expected to increase the variability of the output spike train.

Action Potentials↗
PubMed2000

Periodicity and firing rate as candidate neural codes for the frequency of vibrotactile stimuli.

The flutter sensation is felt when mechanical vibrations between 5 and 50 Hz are applied to the skin. Neurons with rapidly adapting properties in the somatosensory system of primates are driven very effectively by periodic flutter stimuli; their evoked spike trains typically have a periodic structure with highly regular time differences between spikes. A long-standing conjecture is that, such periodic structure may underlie a subject's capacity to discriminate the frequencies of periodic vibrotactile stimuli and that, in primary somatosensory areas, stimulus frequency is encoded by the regular time intervals between evoked spikes, not by the mean rate at which these are fired. We examined this hypothesis by analyzing extracellular recordings from primary (S1) and secondary (S2) somatosensory cortices of awake monkeys performing a frequency discrimination task. We quantified stimulus-driven modulations in firing rate and in spike train periodicity, seeking to determine their relevance for frequency discrimination. We found that periodicity was extremely high in S1 but almost absent in S2. We also found that periodicity was enhanced when the stimuli were relevant for behavior. However, periodicity did not covary with psychophysical performance in single trials. On the other hand, rate modulations were similar in both areas, and with periodic and aperiodic stimuli, they were enhanced when stimuli were important for behavior, and were significantly correlated with psychophysical performance in single trials. Thus, the exquisitely timed, stimulus-driven spikes of primary somatosensory neurons may or may not contribute to the neural code for flutter frequency, but firing rate seems to be an important component of it.

Action Potentials↗
PubMed2000

Efficacy of venlafaxine extended-release capsules in nondepressed outpatients with generalized anxiety disorder: A 6-month randomized controlled trial.

CONTEXT: Generalized anxiety disorder (GAD) is a chronic disorder that is associated with debilitating psychic and somatic symptoms. Venlafaxine extended-release (XR) capsules have been shown to be effective in short-term treatment of patients with GAD without major depressive disorder (MDD), but long-term data are needed to establish whether this agent confers persistent benefits. OBJECTIVE: To compare the 6-month efficacy and safety of a flexible dosage of venlafaxine XR in outpatients with GAD without associated MDD. DESIGN: Six-month, randomized, double-blind, placebo-controlled, parallel-group trial conducted May 1996 to October 1997. SETTING: Fourteen outpatient clinics and private psychiatric practices in the United States. PARTICIPANTS: A total of 251 outpatients aged 18 years or older who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for GAD, had sufficient symptoms to require treatment, and did not have coexisting MDD. INTERVENTIONS: Participants were randomly assigned to receive either placebo (n=127) or venlafaxine XR (75, 150, or 225 mg/d, as required to control symptoms; n=124) for 28 weeks. MAIN OUTCOME MEASURES: Changes from baseline in the Hamilton Rating Scale for Anxiety (HAM-A) total score, the HAM-A psychic anxiety factor score, and the Clinical Global Impressions (CGI) scale Severity of Illness and Global Improvement scores, compared by intervention group. RESULTS: During weeks 6 through 28, response rates in the venlafaxine XR group were 69% or higher compared with rates of 42% to 46% in the placebo group (P<.001). By an evaluable-patient analysis, venlafaxine XR compared with placebo significantly improved anxiety scores from week 1 or 2 through week 28 on all primary efficacy measures, including the HAM-A total (P<.001), the HAM-A psychic anxiety factor (P<.001), and the CGI scale scores (P<.001). Adjusted mean changes from baseline to week 28 using last-observation-carried-forward methods were for HAM-A, venlafaxine XR -13.4, placebo -8.7 (P<.001); for HAM-A psychic anxiety score, venlafaxine XR -7.4, placebo -4.2 (P<.001); and for CGI-Improvement, venlafaxine XR 2.2, placebo 3.0 (P<.001). The most common treatment-emergent adverse event was nausea, followed by somnolence and dry mouth. CONCLUSIONS: This study is the first placebo-controlled demonstration of the long-term efficacy of any drug class in treating outpatients with DSM-IV-diagnosed GAD. Venlafaxine XR is an effective, rapidly acting, safe, once-daily agent for both the short- and long-term treatment of anxiety and may provide an important alternative to currently available anxiolytics. JAMA. 2000.

Adult↗
PubMed2000

Zaleplon shortens subjective sleep latency and improves subjective sleep quality in elderly patients with insomnia. The Zaleplon Clinical Investigator Study Group.

Insomnia is a frequent complaint in the elderly population. Hypnotic agents, including benzodiazepines, with longer pharmacological half-lives have been associated with side effects, including residual sedation, memory impairment, and discontinuation effects. Zaleplon is a short-acting (elimination half-life of 1 hour), non-benzodiazepine hypnotic that acts on the benzodiazepine type 1 site of the gamma-aminobutyric acid type A (GABA(A)) receptor complex. The pharmacology and pharmacokinetics of Zaleplon suggest a safety profile that is improved over other hypnotics. The objective of this placebo-controlled study was to evaluate the efficacy and safety of Zaleplon (5 and 10 mg) in elderly (> or =65 years) outpatients with primary insomnia. This was a multicenter, double-blind, randomised, placebo-controlled 2-week outpatient study. Postsleep questionnaires were used to record subjective sleep variables: sleep latency, sleep duration, number of awakenings, and sleep quality. Zaleplon significantly reduced subjective sleep latency during both weeks of the study with both 5- and 10-mg doses. Subjective sleep quality was improved for significantly more patients treated with zaleplon 10 mg than those treated with placebo during both weeks of treatment. There was a weak indication of rebound insomnia after discontinuation of treatment with the 10-mg dose, but no significant difference in common treatment-emergent adverse events across treatment groups. Zaleplon is an effective and safe hypnotic for the treatment of insomnia in the elderly.

Acetamides↗