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C Casanova

Publications and source records attributed to C Casanova.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Changes in the activity of cells in the lateral geniculate nucleus by stimulation of the abducens nucleus area in rabbits].

These investigations are aimed at studying the influence of the electrical stimulation of the VIth nucleus (abducens nucleus) on responses of lateral geniculate cells in rabbits. The animals were prepared in the usual fashion for single cell recordings at the lateral geniculate nucleus (LGN). Results show that: Electrical stimulation of the VIth nucleus always produced excitatory discharges whose latency varied from 30 to 400 ms. Interestingly, an electrical pulse applied to the abducens nucleus was capable of enhancing the light-evoked responses without altering the spontaneous rate of firing. It thus seems that the ascending influence of the VIth nucleus manifests itself when it coincides with light responses. Most cells which were sensitive to electrical activation of the abducens nucleus had their receptive field located peripherally (greater than 50 degrees). Histological reconstructions of recording electrode tracts suggest that cells which responded to electrical stimulation were located in a narrow band lying dorsally relative to the LGN. This area can be paralleled with the perigeniculate area observed in other mammals, although not identified in rabbits. It is suggested that these extraretinal impulses which reach the LGN and emerge from an area surrounding the VIth nucleus are associated with corollary discharges.

Abducens Nerve↗
PubMed1985

Reactions of the geniculate cells to extraocular proprioceptive activation in rabbits.

The aim of these investigations was to advance our knowledge of the influence of extrinsic ocular muscle (EOM) stretching on cell excitability of the retinocortical pathway. The initial goal was the lateral geniculate; however, histologic analysis indicated that most cells that responded to stretching were located near its superior edge, in an area analogous to the perigeniculate. Rabbits were anaesthetized and prepared for single-cell recordings. The extraocular muscles were detached from the eye and attached to a rigid tungsten hook. The hook was soldered to the pivot of a galvanometer that was controlled by a waveform generator. Precise and repeated length changes were obtained with extension and relaxation ramps of constant velocity. Thirty percent of the units (N = 250) responded to EOM stretching. These stimuli evoked either an excitation or a decrease of the units' spontaneous activity. Several experimental controls provided evidence that the signals that evoked the geniculate responses originated from proprioceptors belonging to the EOM. Most responding cells had their receptive fields located eccentrically (greater than or equal to 50 degrees). Also, cells that reacted to EOM stretching responded to optic nerve stimulation with a significantly shorter latency than cells that were unresponsive. Pairing the EOM stretching with light stimuli produced the following results. In about half of the units the light-evoked responses augmented, but in 28% of the cells the light-evoked discharges decreased. These effects were obtained even though EOM stretching delivered singly failed to elicit a reaction from the cell. Histologic reconstructions indicated that cells were distributed in a discrete region lying rostral and dorsomedial to the lateral geniculate nucleus. This area has been associated with the perigeniculate nucleus in cats and rats.

Animals↗
PubMed1983

The superior colliculus simultaneously modifies the responses of the lateral geniculate cells and of the oculomotor nuclei.

Descending and ascending influences of the superior colliculus (CS) were studied in the following way. In anesthetized and paralyzed rabbits two tungsten micro-electrodes were lowered in the (CS) and the Lateral Geniculate Nucleus (LGN) for single unit recordings. A third semi-micro-electrode (dia. 100 microns) was positioned in the vicinity of the oculomotor nuclei. The final position of this electrode was determined at a location which yielded an eye movement with the lowest intensity of the electrical pulse. The typical experimental procedures required that a spontaneous collicular spike triggered the flash presentation and data acquisition. Results indicated that collicular endogeneous activity may be capable of modifying simultaneously the evoked neuronal responses of the LGN and in the vicinity of the oculomotor nuclei.

Animals↗
PubMedDate not supplied

The influence of transcortical relationships on visual responses in rats.

Visual responses of the 17/18 border of one hemisphere in anesthetized rats were studied while the opposite cortex was depressed. The depression of the opposite cortex was achieved by a cryoblockade of the homotopic area or by bleaching the unstimulated eye. In the first series of experiments field potentials were recorded, whereas in the second experimental series tests were carried out on single units. Bleaching the unstimulated eye produced mostly an enhancement of long latency potentials recorded in deeper layers. Cryoblockade of the contralateral cortex depressed the responses in a more uniform fashion. Most units typically presented a weaker evoked firing after cryoblockade. However, in some neurons the reaction to the treatment depended upon the nature of the stimulus and other units lost their orientation specificity. A single explanation such as a tonic excitatory transcortical influence is insufficient to account for these results.

Animals↗
PubMedDate not supplied

[Hospitalizations due to ambulatory care sensitive conditions: selection of diagnostic codes for Spain].

BACKGROUND: Hospitalisations due to Ambulatory Care Sensitive Conditions (ACSC) are considered an indicator to measure the use of hospital services because of health conditions that could have been prevented and controlled by primary health care. The objective of this study is to select the list of diagnostic codes to assess the performance of primary health care in Spain. METHODS: The five criteria proposed by Weissman and Solberg, to select an appropriate indicator, were applied to a first list of 87 ACSC diagnostic codes identified through bibliographic search. Information on two main criteria-whether care for a health condition was a primary health care role and whether hospitalisation was needed once the health problem occurred was obtained by means of the Delphi technique. A group of 44 experts gathered together for the study. For the remaining criteria, information came from the results of the Pilot study on hospitalisations due to ACSC in Catalonia, Spain. Meeting the five criteria was the criterion selected to evaluate the solving ability of primary health care. RESULTS: a) from the Delphi group: 42 (95.4%) participants completed the three rounds. The question on whether the care of the selected health conditions was responsibility of primary health care reached a high level of consensus (between 86.1 and 100%). The consensus on the need for hospitalisation was lower, from 75.7 to 88.6%, moreover, 5 diagnostic codes did not reach the established consensus, and b) from the ACSC selection process: five diagnostic codes did not meet the criteria and were excluded. Out of the remaining 82, all them were considered as health problems to be cared for at primary level and in 37 cases hospitalisation was considered always as necessary. Thirty-five diagnostic codes, that met the five criteria, represented the set of ACSC diagnostic codes in our setting. CONCLUSIONS: A set of 35 diagnostic codes of ACSC, adapted to our setting, is proposed to evaluate primary health care performance. The selected codes reduce significantly the limitations that stem from hospital admission criteria due to patient clinical characteristics, variations in hospital medical practice, and hospital admission policies.

Ambulatory Care↗
PubMedDate not supplied

Effects of angiotensin II on visual evoked potentials in the superior colliculus of juvenile rats.

There are age-related changes in the relative expression of the AT(1)and AT(2)receptors of angiotensin II (Ang II) in brain regions such as the superior colliculus, a midbrain visual structure where both receptor subtypes are found. We investigated the effects of Ang II on gross visual activity in the colliculus of anesthetized rats aged between 15 and 35 post-natal days. Microinjection of Ang II in the superficial layers yielded a strong reduction in the amplitude of visual evoked potentials in a dose-related manner. Injection of the peptide in more ventral collicular layers did not modify the potential confirming the discrete localization of the angiotensinergic receptors in the superficial layers. Preliminary data indicated that the co-injection of Ang II with Losartan or PD 123319 yielded a partial blockade of Ang II suppressive effects, indicating that both AT(1)and AT(2)receptors are likely to be involved in mediating these responses. Overall, this study shows that the inhibitory nature of Ang II action is similar in juvenile and adult animals (Merabet et al. 1994 and Merabet et al. 1997)

Aging↗
PubMedDate not supplied

Connections between areas 17 and 18 depend on orientation and cell type.

The functional relationships between areas 17 and 18 are still incompletely understood; many experiments indicate that cells sharing like properties are linked together, whereas other studies suggest a deviation from this principle. Here we report the effect of using GABA to block circumscribed area 17 neuronal populations with known orientation preferences. We studied the interaction of this treatment on the responses of simple and complex neurons in area 18. The data suggest that these interactions follow different rules for simple and complex cells: specifically, an iso-orientation linkage appears to hold for simple cells while a cross-orientation linkage appears to hold for complex cells.

Animals↗
PubMedDate not supplied

[Sandflies (Diptera, Psychodidae) from the transmission area for American cutaneous leishmaniasis in the town of Itupeva, the southeastern region of São Paulo state, Brazil].

The present study was effected aiming the verification of the seasonal, spatial and hourly of the phlebotominic species found in the county of Itupeva. Captures were performed fortnightly and 864 sand flies were collected between april/94 and march/95. 81.3% of the captured specimens belonged to 4 species: L. migonei (32.4%), L. whitmani (26.0%), L. intermedia (12.0%) e L. fischeri (10.9%). Such species showed larger densities during the cold and dry season of the year (from april to september/94) and were more active between the second and the fifth hour after twilight. L. migonei predominated almost in all the investigated surroundings being followed by L. whitmani and L. longipalpis in the domestic environments. In conclusion it is thought that in conjunction with L. intermedia, a suspect vector in the State of São Paulo, L. migonei and L. whitmani may have an important role in the transmission of cutaneous leishmaniasis in the area under study.

Animals↗