Biomedical subjects

B Torres

Publications and source records attributed to B Torres.

At least 37 records · Page 2Linked to original sources

PubMed1996

Telencephalic ablation in goldfish impairs performance in a 'spatial constancy' problem but not in a cued one.

This work was aimed to study if goldfish telencephalon is involved differentially in spatial and cue learning. With this purpose, animals were assigned to two learning conditions, 'spatial constancy' and 'directly cued', and their performance was recorded before and after ablation of the telencephalon. During the presurgical acquisition period, animals of both groups learned to solve the task with accuracy, and reached the goal in transfer tests, even though they were released from new starting positions and the response requirements were changed. Ablation impaired selectively the solution of the spatial constancy problem, but had no significant effects on the cued condition. However, with additional training, performance of the ablated animals in the spatial constancy condition improved to control levels. The above data suggest that fishes can implement multiple spatial learning strategies which have different neural substrata. These results are discussed in relation to the possible nature of the representation underlying each task.

Animals↗

PubMed1996

Spatial learning and memory deficits after telencephalic ablation in goldfish trained in place and turn maze procedures.

The present work investigated whether the fish telencephalon is involved in spatial learning based on place strategies in a manner similar to mammalian hippocampus. Goldfish were trained in a 4-arm maze in a room with relevant spatial cues. Sham and to-be-ablated subjects were trained in each of 4 experimental procedures designed as follows: place, turn, place-turn, and control. After acquisition, complete ablations of both telencephalic hemispheres for the experimental groups were carried out. The results showed that ablation exclusively impaired performance in animals using place strategies; in these, accuracy fell to chance level during both postsurgery retraining and reversal periods. In the other groups, ablation of the telencephalon did not induce any significant deficit. These results suggest that the fish telencephalon plays a crucial role in complex place learning.

Animals↗

PubMed1996

Enhanced levels of wild-type versus mutant thyroid hormone receptor beta 1 messenger RNA in fibroblasts from heterozygotes of kindred S with thyroid hormone resistance.

Thyroid hormone resistance syndromes, which result from heterozygous mutations in the beta 1 thyroid hormone receptor gene, are sometimes associated with adult short stature, but more frequently with delayed bone age (BA). Primary fibroblasts from young children with both delayed BA and short stature from a kindred A have been reported to overexpress the mutant allele. However, in fibroblasts from affected members of two different kindreds with thyroid hormone resistance, S and Mf, there were equal levels of mutant and wild-type beta 1 mRNA. We investigated the ontogeny of differential allelic expression using competitive reverse transcription with PCR (RT-PCR) to measure relative mRNA levels for beta 1 and S receptor in very young affected children of kindred S. Total RNA was prepared from fibroblasts of two patients (ages 3-0.5/12 and 1-4/12 years) with delayed BA but normal growth curves. Using PCR amplimers that create an Mlu-1 site in wild-type but not mutant cDNA products from the competitive RT, we quantitated mRNA levels. Normal beta 1 mRNA was present at nearly twice the level of the mutant mRNA in cells from these patients. Relative expression of the c-erbA beta alleles thus appeared to be increased during this period of somatic growth. The relative overexpression of the normal allele potentially counteracted the potent dominant negative effect of the S receptor during early childhood ameliorating a deleterious effect on linear growth.

Age Determination by Skeleton↗

PubMed1995

Purification to homogeneity and characterisation of rat brain recombinant nitric oxide synthase.

We have previously demonstrated high expression of rat neuronal nitric oxide synthase (NO synthase) in a baculovirus system [Charles, I. G., Chubb, A., Gill, R., Clare, J., Lowe, P. N., Holmes, L. S., Page, M., Keeling, J. G., Moncada, S. & Riveros-Moreno, V. (1993) Biochem. Biophys. Res. Commun. 196, 1481-1489], where a small proportion of the expressed enzyme was soluble and active, but the majority was insoluble (approximately 15% of the total insoluble proteins). NO synthase is a complex enzyme, requiring several cofactors for full activity. These include tightly bound FAD, FMN, heme and tetrahydrobiopterin, in addition to calmodulin and NADPH. Here, we report that a substantial proportion of the total NO synthase produced becomes soluble following addition of hemin (2.5 micrograms/ml) to the culture medium. However, the enzyme purified under these conditions had very low specific activity, 50 nmol.min-1.mg-1, after ADP-Sepharose affinity purification. Full activity (approximately 800 nmol.min-1.mg-1) could, however, be obtained by including precursors for the cofactors, nicotinic acid, riboflavin, and sepiapterin in the culture medium. We demonstrate that the enzyme activity is exclusively associated with the dimeric form of the enzyme, which had the following molar ratios for the cofactors: heme, 0.92; FAD, 0.57; FMN, 0.34; H4biopterin, 0.32, with a specific activity of 1500 nmol.min-1.mg-1. The provision of substantial quantities of good quality enzyme, as described here, will facilitate the studies on the relationship between enzyme structure and its mechanism of catalysis.

Amino Acid Oxidoreductases↗

PubMed1995

Distribution of neurons projecting to the trochlear nucleus in goldfish (Carassius auratus).

The distribution of neurons projecting to the trochlear nucleus of goldfish (Carassius auratus) was studied by the electrophoretic injection of horseradish peroxidase into the nucleus. The location of the injection site was electrophysiologically determined by the antidromic field potential elicited from the trochlear nucleus after the electrical stimulation of its nerve. Retrogradely labeled neurons were observed in the following structures: (1) anterior, tangential and descending nuclei of the octaval column--afferents to these nuclei were mainly ipsilateral for the former and exclusively contralateral for the other two; (2) cerebellum; (3) rhombencephalic reticular formation, near the abducens nucleus; and (4) nucleus of the medial longitudinal fasciculus. In addition, a few stained neurons were scattered in the nucleus of the posterior commissure and in nucleus pretectalis superficialis pars magnocellularis. These results are compared with the afferent sources to trochlear nucleus in mammals and with the set of structures projecting to the oculomotor and abducens nuclei in goldfish. It is suggested that the neuronal pathways involved in the compensatory vestibular and optokinetic reflexes, as well as in the saccadic system, are similarly organized in vertebrates but that the relative importance of some of the components of these pathways varies.

Abducens Nerve↗

PubMed1993

Competitive polymerase chain reaction quantitation of c-erbA beta 1, c-erbA alpha 1, and c-erbA alpha 2 messenger ribonucleic acid levels in normal, heterozygous, and homozygous fibroblasts of kindred S with thyroid hormone resistance.

Mutations in the T3-binding domain of the thyroid hormone receptor gene c-erbA beta result in dominant negative proteins and thyroid hormone resistance syndromes. Variable clinical manifestations of resistance to thyroid hormones have been reported, including short stature and neuropsychological abnormalities. The molecular bases for heterogeneity of phenotype among and within kindreds have not been fully elucidated. Recent investigations have considered differential expression of mutant and wild-type beta 1-receptor alleles and the regulation thereof as a mechanism to explain differential sensitivity to thyroid hormones. We used reverse transcription-competitive polymerase chain reaction (PCR) to measure c-erbA beta 1, c-erbA alpha 1, and c-erbA alpha 2 mRNAs in skin fibroblasts cultured from normal subjects, heterozygotes, and a severely affected homozygous mutant of kindred S. The homozygous mutant of kindred S had severe growth and mental retardation. After reverse transcription with primers specific for each of the c-erbA mRNAs, first strand cDNAs were amplified by PCR using subtype-specific amplimers. Primer design allowed simultaneous detection of wild-type and mutant messages in heterozygous fibroblasts and showed an approximately 1:1 ratio of these mRNAs in three patients. Inclusion of competitive standard cDNAs of known concentration in the PCR reactions allowed quantitation of the absolute levels of the beta 1-, alpha 1-, and alpha 2 mRNAs by comparison of products on ethidium bromide-stained agarose gels. These studies showed no effect of the presence of the mutant beta 1-allele, as fibroblast RNA from normal subjects, heterozygotes, and the homozygote gave values of 56-184, 2.8-12, and 23-40 attomol/5 micrograms total RNA for beta 1-, alpha 1-, and alpha 2 mRNAs, respectively. We conclude that these sensitive methods allow the detection of molecular species present at levels as low as 10 molecules/cell, and that this potent dominant negative receptor does not disrupt c-erbA expression at the level of mRNA. The neuropsychological sequelae of the kindred S mutation are not due to relative overexpression of the mutant allele.

Alleles↗

PubMed1992

Afferents to the oculomotor nucleus in the goldfish (Carassius auratus) as revealed by retrograde labeling with horseradish peroxidase.

The goal of this work was to compare the distribution and morphology of neurons projecting to the oculomotor nucleus in goldfish with those previously described in other vertebrate groups. Afferent neurons were revealed by retrograde labeling with horseradish peroxidase. The tracer was electrophoretically injected into the oculomotor nucleus. The location of the injection site was determined by the antidromic field potential elicited in the oculomotor nucleus by electrical stimulation of the oculomotor nerve. Labeled axons whose trajectories could be reconstructed were restricted to the medial longitudinal fasciculus. In order of quantitative importance, the afferent areas to the oculomotor nucleus were: (1) the ipsilateral anterior nucleus and the contralateral tangential and descending nuclei of the octaval column. Furthermore, a few labeled cells were found dorsomedially to the caudal pole of the unlabeled anterior octaval nucleus; (2) the contralateral abducens nucleus. The labeled internuclear neurons were arranged in two groups within and 500 microns behind the caudal subdivision of the abducens nucleus; (3) a few labeled cells were observed in the rhombencephalic reticular formation near the abducens nucleus, most of which were contralateral to the injection site. Specifically, stained cells were found in the caudal pole of the superior reticular nucleus, throughout the medial reticular nucleus and in the rostral area of the inferior reticular nucleus; (4) eurydendroid cells of the cerebellum, located close to the contralateral eminentia granularis pars lateralis, were also labeled; and (5) a small and primarily ipsilateral group of labeled cells was located at the mesencephalic nucleus of the medial longitudinal fasciculus. The similarity in the structures projecting to the oculomotor nucleus in goldfish to those in other vertebrates suggests that the neural network involved in the oculomotor system is quite conservative throughout phylogeny. Nevertheless, in goldfish these projections appeared with some specific peculiarities, such as the cerebellar and mesencephalic afferents to the oculomotor nucleus.

Afferent Pathways↗

PubMed1992

A morphological study of abducens nucleus motoneurons and internuclear neurons in the goldfish (Carassius auratus).

The location and distribution of abducens (ABD) nucleus motoneurons (Mn) and internuclear neurons (Int) were determined in the goldfish (Carassius auratus) by means of horseradish peroxidase and fluorochrome retrograde labeling. ABD Mn were labeled following tracer injection into the ipsilateral lateral rectus muscle. These Mn were arranged in two ventrolateral clusters along the rostro-caudal axis of the posterior brainstem. Both groups of neurons showed a similar number of cells, and their axons ran ventrally to their respective nerve roots. ABD Int were labeled following the injection of the tracer into the contralateral oculomotor nucleus. They also formed two distinct groups in the rostro-caudal axis. The rostral group of Int formed a dorso-lateral cap around the caudal motoneuronal pool, with little if any intermingling. The caudal group of Int was located at the same position in the dorso-ventral and medio-lateral axis as the rostral group, but 500 microns behind it. Both groups of ABD Int had a similar number of neurons. Int axons ascended dorso-medially, then crossed the midline through the internal arcuate fibers, and entered the contralateral medial longitudinal fasciculus. The soma diameters of both ABD Mn and Int were not significantly different. The relative location of both types of neurons is discussed.

Animals↗

PubMed1992

Effects of diazepam and D-amphetamine on rhythmic pattern of eye movements in goldfish.

The effects of diazepam and D-amphetamine on spontaneous, vestibular- and visually-induced eye movements were studied in the restrained goldfish. These animals showed a stereotyped pattern of spontaneous eye movements that scanned the visual field in the horizontal plane. Fourier analysis of these eye movements revealed a rhythmic pattern of about 5 cycles per minute, whose frequency increased to double and decreased to half following treatment with diazepam and D-amphetamine, respectively. However, the fast and slow components of vestibulo-ocular and optokinetic reflexes, as well as peculiar blink-like movements, remained unchanged at the same drug doses. These results suggest the presence of a central pattern generator for spontaneous eye movements in the goldfish, whose oscillation frequency is pharmacologically modifiable.

Animals↗

PubMed1992

Activities of daily functioning and community adjustment of veterans in the VA residential care program.

This study was designed to identify the level of function in Activities of Daily Living (ADL) of veterans placed in the Personal Care Home Program (PCH) of the Department of Veterans Affairs Medical Center in Puerto Rico. At the same time, we explored how community adjustment was related to the veterans ADL functioning. It was an exploratory, descriptive, cross-sectional study of a random sample of 60 veterans placed in (32) Personal Care Homes. The Functional Independence Measure (FIM) was used to evaluate the veteran and determined his level of independence in ADL. The Community Adjustment Scale was used to assess adjustment behavior patterns of veterans at the personal care homes. Findings indicate the majority of veterans in the PCH program were elderly with a mean age of 64 years. They were functioning in a modified dependence level in ADL. They had made good to excellent community adjustment. No relationship between ADL level of functioning and community adjustment was found.

Activities of Daily Living↗

PubMed1991

In vitro activity of loracarbef (LY163892), a new oral carbacephem antimicrobial agent, against respiratory isolates of Haemophilus influenzae and Moraxella catarrhalis.

The in vitro activity of a new orally administered carbacephem analog of cefaclor, loracarbef (LY163892), was compared with those of cefaclor and several other oral antimicrobial agents against recent clinical isolates of Haemophilus influenzae and Moraxella catarrhalis. Loracarbef was found to be slightly more active than cefaclor against H. influenzae and had activity essentially equivalent to that of cefaclor for M. catarrhalis. Resistance to loracarbef was uncommon and was noted only with rare beta-lactamase-producing strains of H. influenzae. On the basis of these observations, loracarbef may be of utility in the management of localized, non-life-threatening infections caused by H. influenzae and M. catarrhalis.

Anti-Bacterial Agents↗

PubMed1991

Discharge characteristics of medial rectus and abducens motoneurons in the goldfish.

1. The discharge of antidromically identified medial rectus and abducens motoneurons was recorded in restrained unanesthesized goldfish during spontaneous eye movements and in response to vestibular and optokinetic stimulation. 2. All medial rectus and abducens motoneurons exhibited a similar discharge pattern. A burst of spikes accompanied spontaneous saccades and fast phases during vestibular and optokinetic nystagmus in the ON-direction. Firing rate decreased for the same eye movements in the OFF-direction. All units showed a steady firing rate proportional to eye position beyond their recruitment threshold. 3. Motoneuronal position (ks) and velocity (rs) sensitivity for spontaneous eye movements were calculated from the slope of the rate-position and rate-velocity linear regression lines, respectively. The averaged ks and rs values of medial rectus motoneurons were higher than those of abducens motoneurons. The differences in motoneuronal sensitivity coupled with structural variations in the lateral versus the medial rectus muscle suggest that symmetric nasal and temporal eye movements are preserved by different motor unit composition. Although the abducens nucleus consists of distinct rostral and caudal subgroups, mean ks and rs values were not significantly different between the two populations. 4. Every abducens and medial rectus motoneuron fired an intense burst of spikes during its corresponding temporal or nasal activation phase of the "eye blink." This eye movement consisted of a sequential, rather than a synergic, contraction of both vertical and horizontal extraocular muscles. The eye blink could act neither as a protective reflex nor as a goal-directed eye movement because it could not be evoked in response to sensory stimuli. We propose a role for the blink in recentering eye position. 5. Motoneuronal firing rate after ON-directed saccades decreased exponentially before reaching the sustained discharge proportional to the new eye position. Time constants of the exponential decay ranged from 50 to 300 ms. Longer time constants after the saccade were associated with backward drifts of eye position and shorter time constants with onward drifts. These postsaccadic slide signals are suggested to encode the transition of eye position to the new steady level. 6. Motoneurons modulated sinusoidally in response to sinusoidal head rotation in the dark, but for a part of the cycle they went into cutoff, dependent on their eye position recruitment threshold. Eye position (kv) and velocity (rv) sensitivity during vestibular stimulation were measured at frequencies between 1/16 and 2 Hz. Motoneuronal time constants (tau v = rv/kv) decreased on the average by 25% with the frequency of vestibular stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

Comparison of therapeutic regimen of anticysticercal drugs for parenchymal brain cysticercosis.

The efficacy of different regimens of therapy for parenchymal brain cysticercosis either with praziquantel (PZQ) or with albendazole (ALB) was compared in 114 patients. Four schemes of treatment were used: PZQ 50 mg/kg per day for 15 days, PZQ 50 mg/kg per day for 8 days, ALB 15 mg/kg per day for 30 days, and ALB 15 mg/kg per day for 8 days. Three months after therapy, it was apparent that both PZQ and ALB were effective, as shown by the disappearance of cystic lesions in computed tomographic scans. Thirty-three control patients followed for a mean of 11 months had no spontaneous remission of lesions. When comparing PZQ with ALB, the latter was found to be more effective than the former for both the full and the short course of treatment: 85% vs 60% and 85% vs 48% disappearance of lesions, respectively (P less than 0.001). Comparison of the full vs the short course of PZQ showed that the short course had a further 12% reduction in drug effectiveness. In contrast, the length of ALB therapy could be shortened without lessening its efficacy. Based on these results, an 8-day course of ALB is recommended as treatment for parenchymal brain cysticercosis; a 15-day course of PZQ could be subsequently used in those patients who show only partial response to ALB.

Adolescent↗

PubMed1988

Behavioral and morphological effects of oculomotor nucleus lesion on abducens internuclear neurons in the cat.

The activity of identified control and injured abducens internuclear neurons was recorded during spontaneous eye movements in the alert cat. From 2 days following the electrocoagulation of the contralateral oculomotor nucleus, abducens internuclear neurons showed a quick fatigability during eye fixations not observed in controls. Discharge rate during saccades started after the beginning of the eye movement and showed a fast exponential-like decay. These abnormal responses were not further recorded from 20 days following the lesion. Morphological studies indicated that 90% of the abducens internuclear neuron population disappeared 2 months following the lesion and showed no sign of recovery one year later.

Abducens Nerve↗

PubMed1988

Cytodifferentiation of mouse visceral endoderm: study with a teratocarcinoma antiserum.

In this work we separated homogeneous embryoid bodies (EB); this population is composed of only endodermal vesicles of a visceral type. These EB were used to immunize rabbits. After absorption, the antisera were analyzed immunohistochemically in sections of 7.5- and 9-day-old mouse embryos, which showed a selective reaction to visceral endoderm. The cytodifferentiation of the visceral endoderm was studied.

Animals↗

PubMed1987

Cysticercotic encephalitis: a severe form in young females.

Clinical and computerized tomography findings in patients with miliary infestation of cysticerci in brain parenchyma are presented. Cysticercotic encephalitis produces a severe and frequently fatal neurological disorder. Although parenchymal cysticercosis is common in endemic areas, in the cases reported here, the pathology is induced by a severe inflammatory response in brain parenchyma rather than by the physical presence of multiple cysts. As a result of diffuse brain edema, all cases develop subacute severe intracranial hypertension and compromise of visual function. One important feature of this form of neurocysticercosis is that it particularly affects young women.

Adolescent↗

PubMed1986

Analysis of the fluctuations in the interspike intervals of abducens nucleus neurons during ocular fixation in the alert cat.

The behavior of abducens nucleus motoneurons and internuclear neurons was recorded during eye fixation in the alert cat. The interspike interval (ISI) values during a given fixation followed a normal distribution, with coefficients of variation for motoneurons and interneurons ranging from 4.6 to 16% and 5.7 to 21.7%, respectively. The ISI mean was linearly related to its standard deviation and to the coefficient of variation. The power spectral density of ISI fluctuations did not reveal any relevant peak. The autocorrelation function of ISI fluctuations was flat except at the origin. Results suggest the presence of a gaussian white noise superimposed on the clock-like firing of the activity of abducens neurons during ocular fixation. Some physiological implications of the results are discussed.

Abducens Nerve↗

PubMed1986

A quantitative analysis of abducens motoneuron behavior during saccadic eye movements in the alert cat.

The activity of identified abducens motoneurons has been recorded during spontaneous eye movements in the alert cat. Abducens motoneurons showed a burst of activity during saccades in the abducting direction. However, peak frequency during the burst was reached on the 4th-7th intervals. Instantaneous frequency of the first 5 intervals during the burst was linearly related to peak saccadic velocity and to peak frequency. Functional implications of reported findings are discussed in the text. These results favor the view that firing in abducens motoneurons during saccades is predetermined from the beginning of saccades, and do not provide evidence for possible modification of abducens motoneurons firing through internal feedback of motor error signals.

Abducens Nerve↗