Search PubMed⌕ Search

Biomedical subjects

J Villalobos

Publications and source records attributed to J Villalobos.

At least 37 records · Page 2Linked to original sources
PubMed1987

The differential ascending projections from the anterior, central and posterior regions of the lateral hypothalamic area: an autoradiographic study.

The ascending efferent projections of the neurons of the anterior (LHAa), central (LHAc) and posterior (LHAp) parts of the lateral hypothalamic area (LHA) have been studied using an autoradiographic analysis of the anterograde axonal transport after local injection of tritiated amino acids. Our results show that LHA regions have common projections particularly to the thalamus and to the hypothalamus. They also demonstrate the existence of differential projections: i.e. an anteroposterior gradient of projection sites according to anterior, central and posterior localisation of the LHA neurons. The LHAa neuronal projections terminate in the lateral septal area; the LHAc projections innervate the frontal cortex while LHAp neurons send their projections to the olfactory bulb and innervate both the cerebral cortex and the hippocampus. Only the LHAp neurons project measurably to the globus pallidus, the caudate putamen and the nucleus accumbens.

Animals↗
PubMed1987

The differential descending projections from the anterior, central and posterior regions of the lateral hypothalamic area: an autoradiographic study.

The descending projection sites of the anterior, central (or tuberal) and posterior regions of the lateral hypothalamic area were studied by anterograde axonal transport after local injection of tritiated amino acids. The results show that the neurons of the anterior regions project to the lateral mammillary nucleus, the ventral tegmental area, the midbrain central gray and the anterior parts of the dorsal raphe nucleus. The neurons of the central region project in the same structures and extend a projection into the dorsal tegmentum at the level of the pontine central gray, the midbrain and pontine reticular nuclei. In the ventral tegmentum region, the substantia nigra pars compacta, the interpeduncular nucleus and the anterior group of raphe nuclei were also found to be labelled. The neurons of the posterior region of the lateral hypothalamic area extend a projection to the level of the prepositus hypoglossi nucleus and to the nucleus of solitary tract. In the ventral tegmentum they project at the level of posterior group of the raphe nuclei and the inferior olivary complex.

Afferent Pathways↗
PubMed1987

Cadmium-zinc interactions in the Ehrlich cell: metallothionein and other sites.

Zinc and Cadmium metabolism in cultured Ehrlich cells has been studied. Under conditions of restriction of extracellular zinc by EDTA or chelex, zinc in basal Zn-metallothionein (Mt) is transferred from metallothionein to other sites with a rate constant of 0.35 hr-1. Current studies indicate that the rate constant for biodegradation of Mt protein is 0.07-0.11 hr-1, implying that Zn leaves the protein faster than it is biodegraded. After a 30 minute exposure of cells to 17 ng atoms Cd/mg cell protein, Cd initially displaces Zn from Mt and binds to high molecular weight species. Cell proliferation is markedly slowed, although the cells remain viable. Over time Cd shifts into newly synthesized Mt. This protein is made with an apparent rate constant four times that for basal Zn-Mt. The product contains equal amounts of Cd and Zn. However, cell proliferation is not restored for many hours after Cd is sequestered in Mt.

Cadmium↗
PubMed1987

Extratelencephalic projections of the avian visual Wulst. A quantitative autoradiographic study in the pigeon Columbia livia.

The efferent projections of the pigeon visual Wulst upon the diencephalon and mesencephalon were investigated using the autoradiographic technique following the combined injection of [3H] proline and [3H] leucine into the rostral hyperstriatum accessorium. Repeated measures of silver grain densities were performed bilaterally in different brain structures using a computer-assisted system of image analysis. The density values were compared (Mann-Whitney U-Test) with those recorded in three homolateral control structures (tractus opticus, n. rotundus, n. pretectalis principalis) and in corresponding contralateral areas and nuclei. The data showed ipsilateral projections from the visual Wulst and via the tractus septomesencephalicus upon the dorsal thalamus (n.: dorsolateralis anterior superficialis parvocellularis), ventral thalamus (n.: intercalatus, ventrolateralis, geniculatus lateralis pars ventralis--GLv), pretectum (n.: superficialis synencephali, geniculatus pretectalis, griseus tectalis, pretectalis: diffusus, pars lateralis and pars medialis, area pretectalis) as well as to the nucleus of the basal optic root, n. spiriformis medialis and optic tectum (layer 2-4, 6, 7, 12 and 13). Crossed projections were observed to pass through the supraoptic decussation and the posterior commissure, however only the contralateral n. GLv was found to be significantly labeled. Interspecies variations in the organization of descending visual Wulst projections, related to the terminal distribution and relative size of the crossed components may be linked to differences in the degree of overlap of the binocular fields. Correspondingly, this may reflect the degree of bilateralization upon the Wulst of direct input from the visual thalamus.

Animals↗
PubMed1984

Single unit activity in the nucleus of the basal optic root (nBOR) during optokinetic, vestibular and visuo-vestibular stimulations in the alert pigeon (Columbia livia).

Extracellular recordings were performed in the nucleus of the basal optic root (nBOR) of alert pigeons during optokinetic nystagmus (OKN), vestibulo-ocular reflex (VOR) and combined visuo-vestibular stimulation. Cell identification was assessed either by histological control or by electrophysiological testing (antidromic response to vestibulo-cerebellar or oculomotor complex stimulation). 1) OKN was induced in 8 directions by a binocular stimulation. During the fast phase of OKN, optokinetic after nystagmus (OKAN) or reversed OKAN, most cells showed an inhibition which varied in magnitude independent of the direction of stimulation. A few cells however showed a phasic discharge for some OKN directions. 2) During the slow phase of OKN induced by a binocular stimulation, cells displayed either a tonic activation or a more or less strong inhibition according to the direction of the OKN. Cells were classified in 4 groups, according to their degree of directional specificity. The best OKN direction (slow phase) for maximal cell activation was upwards and naso-upwards, and next to best, naso-temporal and downwards. Maximal cell inhibition occurred during downward, and for some cells during upward, directions. 3) During OKN induced by stimulating the eye contralateral to the recorded nBOR, cell responses resembled those obtained during binocular stimulation, but, during ipsilaterally induced OKN, the cells lost their directional specificity. As a result of binocular integration, neuronal activation seems to originate from contralateral input whereas cell inhibition would mainly come from ipsilateral input. 4) During sinusoidal optokinetic stimulation induced in the temporo downward-naso upward axis, cells showed a more or less marked modulation (according to their directional selectivity) that was closely in phase with the stimulation velocity, and therefore probably with retinal slip. 5) nBOR cells appeared generally unaffected during both the slow phase and the fast phase of the VOR. However, some cells showed a slight but irregular modulation which might imply a weak vestibular input. During visuo-vestibular stimulation, the response resembled that obtained with sinusoidal optokinetic stimulation but the fast phase inhibition was often strengthened in the downwards direction (fast phase).

Animals↗
PubMed1983

Efferent projections of the visual Wulst upon the nucleus of the basal optic root in the pigeon.

Efferent projections of the visual Wulst upon the nucleus of the basal optic root (nBOR) were investigated using various neuroanatomical approaches: optical and EM orthograde degeneration methods (following visual Wulst ablation), radioautographic and HRP techniques (following injection of various tracers within the visual Wulst). The radioautographic and electron microscope degeneration experiments clearly demonstrated a visual Wulst projection upon the ipsilateral nBORl and the lateral portions of nBORd and nBORp. The pigeon's hyperstriato-nBOR projection is compared to a similar descending visual cortico-accessory optic pathway in mammals and its possible role in the control of oculomotor function is discussed.

Animals↗
PubMed1983

Optokinetic nystagmus in the pigeon (Columba livia). II. Role of the pretectal nucleus of the accessory optic system (AOS).

In birds, the accessory optic system (AOS) includes two nuclei: the nucleus ectomamillaris (nEM) and the pretectal nucleus superficialis synencephali (nSS). The role of the nSS in the production of a horizontal optokinetic nystagmus (OKN) was studied in the pigeon, by comparing the OKN before and after a unilateral lesion of this nucleus. The lesions were performed either by electrolysis or by local application of kainic acid (KA); the KA lesions gave more stable modifications of the OKN than the electrolytic lesions. A quantitative analysis of the slow-phase velocity (V) of the OKN was carried out on the animals receiving KA lesions. Lesion of the nSS provokes the almost total disappearance of the OKN for stimulation of the contralateral eye in the temporo-nasal direction, and a reduction of the OKN for stimulation in the naso-temporal direction. Thus, the nSS is essential for the production of the OKN in the temporo-nasal direction, but it also participates in the production of the OKN in the naso-temporal direction (slow-phase direction). The same lesion produces a large increase of the OKN (V) when the ipsilateral eye is stimulated in the temporo-nasal direction, and a smaller increase following stimulation in the naso-temporal direction. These increases suggest some kind of inhibitory (or disfacilitatory) interactions between the nSS (or the associated system) on one side, and the contralateral optokinetic centers. The lesion of one nSS does not provoke a deficit when the stimulation is binocular. This result probably reflects the combined effect of both monocular inputs. After a pretectal KA injection, a spontaneous nystagmus of the contralateral eye, in the naso-temporal direction, can be seen for several hours. The mechanism is still unknown, but it might be related to a reverse optokinetic after nystagmus (R-OKAN). The anatomical and physiological data so far available consistently support the hypothesis of a functional equivalence between the nSS in birds and the nucleus of the optic tract in mammals.

Animals↗
PubMed1983

Optokinetic nystagmus in the pigeon (Columba livia). III. Role of the nucleus ectomamillaris (nEM): interactions in the accessory optic system (AOS).

The accessory optic system (AOS) in birds is composed of two structures: the nucleus Superficialis Synencephali (nSS), essential for the production of an optokinetic nystagmus (OKN) in the temporo-nasal direction (slow phase) for the eye contralateral to the nucleus, and the nucleus Ectomamillaris (nEM), or nucleus of the basal optic root (nBOR). The objectives of the present work were: (1) to study the importance of the nEM for the horizontal OKN, (2) to study the interactions between the nSS and the nEM. Experiments were realized by combining different kinds of lesion. (1) Results show that the nEM is essential for the production of an OKN in the naso-temporal direction (direction of the slow-phase), but it also participates in the temporo-nasal response. (2) After bilateral lesion of the nEM or the nSS, only a residual nystagmic response remains. (3) Synergic effects exist between (I) the homolateral nEM and nSS, or between the systems related to them; we call this relation "homolateral synergy", (II) a nEM and the contralateral nSS (or systems related to these nuclei). The synergic effect exerted by one nEM upon the contralateral nSS appears to be stronger than the reciprocal effect. (4) The effects obtained after combined lesions, either homolateral (nEM and nSS on the same side) or heterolateral (nEM and nSS on opposite sides) confirm the previous results and show that heterolateral interactions are stronger than homolateral interactions. (5) For all the lesions studied, the results obtained from binocular stimulation are compatible with a model of convergence of monocular inputs. The role of the nuclei of the AOS in birds is discussed in terms of existing anatomical and physiological data.

Animals↗
PubMed1982

[Single unit activity in the nucleus ectomamillaris (nem) during optokinetic nystagmus, in the pigeon].

Extra-cellular recordings of single units were obtained in the nucleus ectomamillaris (nEM) in waking Pigeons, during optokinetic nystagmus (OKN). OKN was obtained for 8 directions of stimulation (horizontal, vertical and oblique) in monocular and binocular vision. For half of the units the responses were synchronized, showing activation during the slow-phase and inhibition during the fast phase of the OKN. This response pattern was more common for the horizontal OKN, both in the Nasal to Temporal (N-T) and in the Temporal-to-Nasal (T-N) directions. With contralateral stimulations, most cells showed directional selective responses for upwards and backwards directions, the activity being inhibited for the other directions. Some units showed a less marked directional selectivity or were unaffected by the stimulations. Ipsilateral stimulations provoked no directional selectivity, but rather a reduction of the firing level. With binocular stimulation, responses were very close to those obtained with contralateral stimulation, with an increase of the directional selectivity. The nEM seems to be involved in the control of OKN, specially for the N-T and upwards directions, and less significantly for the T-N direction.

Animals↗
PubMed1980

[Horizontal optokinetic nystagmus in the pigeon: role of accessory optical system].

Some characteristics of the horizontal optokinetic nystagmus (OKN) have been studied in the pigeon using monocular and binocular stimulations. The OKN is asymmetrical, temporal to nasal stimulation eliciting a larger response than a nasal to temporal one. The role of the accessory optic system (AOS) was studied by means of unilateral or bilateral lesions of the primary relays, nuclei ectomamillaris (nEM) and superficialis synencephali (nSS). Results show the existence of a synergy between nEM and nSS on the same side and between nEM and nSS on opposite sides, whereas each nucleus has an inhibitory effect upon its contralateral homologue. Some evidence was obtained which suggests the existence of an ipsilateral retinal projection to the nEM.

Animals↗
PubMed1980

Computerized information system for ICU patient management.

To solve the problem of data management, a digital computer was introduced in this ICU in 1977. Data are manually entered at the bedside alpha-numeric keyboards; two beds are directly connected to the computer. The system was especially designed to work in the 11-bed ICU; its functions are: (1) admission, discharge, and transfer data of patients; (2) management of doctors' and nurses' notes in a free text form; (3) management of the problem-oriented record; (4) management of physical and bio chemical variables, medical disorders, and fluid balance; and (5) diagnostic and therapeutic decision-making. Since 1977, the authors have computerized over 2600 patients and now conclude: (1) data management and communication have improved, thus, allowing nurses more time for direct patient care; (2) teaching of the residents and nurses has been facilitated and minimizes disparities from their diverse experience; (3) it has contributed to the development of protocols for many of the procedures; and (4) it has led to a more systematic approach to patient care. The assistance of a professional computer programmer and continuous maintenance of the software are essential.

Computers↗
PubMed1979

[Neurophysiological study of 36 patients with cerebral vascular processes treated with nicergoline (author's transl)].

The results obtained from a group of 36 patients with non-acute cerebral vascular disturbances of various forms were evaluated. The clinical course and additional examinations are reported: electroencephalography, visually evoked potentials and cerebral rheography for the assessment of different cerebral regions and an interhemispherical comparison. The determination of the data obtained by rheography can be applied to the whole patient group. All tests were carried out before treatment and after a period of treatment with 15-20 mg 10-methoxy-1,6-dimethyl-ergoline-8 beta-methanol-(5-bromonicotinate) (nicergoline, Sermion) administered daily p.o. On the basis of the therapeutic results conclusions can be drawn as to clinical improvement and EEG normalisation and visually evoked potentials. The changes in the amplitude and the changes in the systolic gradient recorded by the rheogramme as well as the tendency to correction of dyssymmetry can be described as the result of nicergoline on the cerebral vascular system, on the oxygen supply and on the metabolism of the brain tissue.

Adult↗