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Biomedical subjects

J Leiva

Publications and source records attributed to J Leiva.

At least 37 records · Page 2Linked to original sources
PubMed1992

Electrophysiological relations between the superior colliculus and the red nucleus in the cat.

The electrical activity of single units located in the parvicellular part of the red nucleus (pRP) was recorded extracellularly in nitrous oxide anesthetized and C1-transected adult cats. In this area, neurons were found to respond to electrical stimulation applied to intermediate and deep layers of the right superior colliculus (SC). Forty neurons located in the pRN of both sides were studied. Three neurons out of 18 (16.6%) located in the contralateral pRN and six neurons out of 22 (27.3%) located in the ipsilateral pRN were driven by the right SC stimulation. The pRN neurons were separated into four groups according to the latency response to the SC stimulation: 1) 0.6-1.9 ms, 2) 2-4 ms, 3) 4-6 ms, 4) variable latency responses. Each of these four groups of neurons showed a particular pattern of discharge, even though their discharge frequency showed a strong consistency. Four pRN neurons, which responded to SC stimulation, showed a significant correlation with spontaneous horizontal eye movements of saccadic type. It is known that the SC represents one of the main outputs of the striato-nigral motor system. The relation between the SC and the pRN described in the present study suggest that connections exist between the cortico-rubral and the striato-nigral systems, since both have the SC as a common output structure. It is likely, therefore, that the cortico-rubral-SC system is involved in the control of oculomotor functions, and that the SC may serve to establish interactions between systems concerned with eye movements.

Animals↗
PubMed1991

[Effect of the extraction of LPS (R) on the demonstration of the serological response in acute brucellosis by immunoblotting].

In order to establish the possible influence of Brucella melitensis rough strains protein extracts contamination using LPS (R) in the immunoblotting evaluation of serologic response, we have studied sera samples from 41 patients with acute brucellosis before treatment was started and also from 62 healthy individuals (control group). A whole-cell B. melitensis 115 strain extract with an without LPS (R) was used. Extraction was carried using ether-chloroform of oil-phenol. Overall, more than 50% of patients showed an antibody response (protein bands 85, 53, 50, 47, 41, 38 and 28 kD) to both antigenic products. Less than 6.4% of the control group sera showed response to any of these protein bands. There were no significant differences in the frequency of response development against these proteins using the two antigen types. However, there was some disagreement when each individual band response was compared to its homologous band.

Acute Disease↗
PubMed1991

[Evaluation of 2 serological techniques in the diagnosis of neurocysticercosis: complement fixation reaction and Western blot].

Evaluation of two serological techniques for diagnosis cysticercosis: complement fixation reaction and Western blot. Comparative study that includes 49 sera samples and 30 CSF samples belonging to 35 patients with clinical diagnosis of cysticercosis of the CNS. As a control group we used 10 sera samples of patients with Trichinella spiralis infection, 33 sera samples of patients with hydatid cyst disease, 9 sera samples from patients with oxyuriasis, 52 sera samples of healthy blood donors and 22 additional CSF samples from patients with different CNS disorders. Thirty-one samples were positive by Western blot technique and 21 samples by complement fixation reaction technique. Agreement between both techniques was 76%. Gathering clinical and laboratory information we believe that a total of 11 patients had cysticercosis of the CNS (33 samples), and three additional patients remain with indeterminate diagnosis. We have also detected cross-reactions with Western blot techniques (reactivity to more than one band) in 43% of patients with hydatid disease and in 20% of patients with Trichinella spiralis infection, but none in oxyuriasis patients. The CFR technique had cross-reaction with 33% of sera samples from hydatid disease patients and 20% of those from oxyuriasis patients. No cross-reactions were seen in any of control patients with both techniques. The two different techniques tested can be of help, together with clinical and radiology data, in the diagnosis of cysticercosis of the CNS. However, both techniques showed strong cross-reactions with hydatid disease.

Animals↗
PubMed1991

The effects of lesioning both the superior colliculus and the substantia nigra of cats on turning behavior.

In twenty two adult cats, distributed in four groups, stainless steel electrodes were implanted in the superior colliculus and the substantia nigra of both sides in order: 1) to find the current intensity threshold values necessary to evoke turning behavior, and record their variations after lesion of the cited structures; 2) to study the effects of lesioning two of these structures, specifically related to the direction of turning behavior, and 3) to assess the time-course of recovery from postural asymmetry after damaging two structures involved in rotation behavior, located either in the same or in the opposite side, as well as the importance of performing these lesions simultaneously or at different periods. Three main results were observed: 1) a large proportion of lesioned cats showed an increase in threshold values necessary to evoke rotation of the implanted structures located either in the same or in the opposite side; 2) the lesions induced in a significant number of cats a transient postural asymmetry. After lesioning the superior colliculus, the direction of turning was towards the damaged hemisphere. Apomorphine injected fourteen days later demonstrated the existence of an occult asymmetry, and the direction of turning was maintained. In the substantia nigra lesioned animals, the direction of turning, was towards the non-lesioned side. Apomorphine reversed the direction of turning; 3) the cats showed a remarkable capacity to recover from the postural asymmetry produced by the lesion. This experimental series further support the hypothesis of a close functional relationship between structures of both cerebral hemispheres related to turning behavior.

Animals↗
PubMed1990

Eye movement-related neurons in the red nucleus.

Extracellular unit activity of the parvocellular red nucleus (RN) and spontaneous horizontal eye movements were recorded in adult, nitrous oxide-anesthetized and C1 transected cats. It was found that 7.5% of the neurons of each RN were related to spontaneous horizontal saccadic eye movements. Three types of neurons were observed: (1) bidirectional neurons which increased their frequency of discharge in relation to any horizontal eye movement; (2) unidirectional neurons which altered their frequency of discharge in relation to a horizontal eye movement of a precise direction; and (3) neurons which increased their frequency of discharge in relation to the rapid phase of an horizontal nystagmus. These 3 types of neurons modified their frequency of discharge before the initiation of the eye movement. One pair of oculomotor neurons recorded simultaneously in both RN showed a significant correlation coefficient. These results suggest that the RN may contribute to the preparation or execution of horizontal eye movements.

Animals↗
PubMed1990

[Pattern of antibodies in acute human brucellosis defined by Western blotting].

We have evaluated with Western blotting the serologic response of 144 patients with acute brucellosis and 62 healthy controls to identify a useful antibody pattern to confirm the diagnosis of acute brucellosis. The antigen that we used was a protein extract of whole cells of the strain 115 (rough) of B. melitensis. Patients sera were obtained at the time of diagnosis and before the start of specific therapy. There was antibody response to 21 protein bands. The molecular weights (MW) and frequencies of the most significant bands were the following: 85 Kd (60.4%), 70 Kd (54.1%), 53 Kd (63.9%), 50 Kd (65.3%), 47 Kd (71.5%), 41 Kd (74.3%), 38 Kd (68.7%), 33 Kd (56.2%), 28 Kd (52.8%). At the time of diagnosis, 90.3% of the patients with acute brucellosis had antibody response to 2 or more protein bands of Mw of 47 Kd, 41 Kd, 38 Kd and 33 Kd. In none of the 62 negative control sera there was a response to more than one of the mentioned bands.

Acute Disease↗
PubMed1989

[Occupational exposure in cancer of the mouth, pharynx and larynx].

The AA. have scheduled a case-control study in order to assess the ambient hazards factors in these cancers, through the evaluation of its occupational risk. The program cover 242 cases of the epidermoid type of carcinoma (positive biopsy), and the group was parallelled with another group of 322 (after the age) admitted at the same Hospital, but affected with several processes. Were excluded the cancer of the lung, bladder, pancreas and kidney because of the causal link with tobacco smokers. In oral and pharyngeal cancer the AA. found out that the workers of high risk were butchers, blacksmiths, masons, drivers, electricians and railwaymen. Regarding the cancer of the larynx mechanics, plumbers, farmers, textile workers and drivers showed the greatest linkage. These findings are in accordance with those published in previous papers.

Adult↗
PubMed1988

Output pathway for turning behavior from the neostriatum and substantia nigra in cats.

The goal of the present work was to study the output pathway of the information for turning behavior originating in the striatum and coursing through the substantia nigra pars reticulata (SNR). In 45 adult cats distributed in 3 groups, Ni-Cr electrodes were implanted in the caudate nucleus and substantia nigra pars reticulata and depending on the animal group in the superior colliculus (SC), nucleus ventralis lateralis/nucleus ventralis medialis (VL/VM) complex or nucleus tegmenti pedunculopontinus (TPP) of one cerebral hemisphere. The threshold current required to evoke turning behavior was determined in each animal for each implantation site. An electrolytic lesion of the superior colliculus, the VL/VM complex or the nucleus tegmenti pedunculopontinus was carried out in each group of cats. The effects of the lesions on behavior and on the electrical threshold currents were determined and compared with the prelesion values. Finally the extent of the lesions and electrode positions were analyzed. The results show that the substantia nigra pars reticulata is the structure with the lowest thresholds for turning and that the superior colliculus appears to be more relevant for carrying the information for turning than either the VL/VM complex or the nucleus tegmenti pedunculopontinus.

Animals↗
PubMed1988

Extracellular unit responses in the pulvinar-lateral posterior complex of the cat through electrical stimulation of substantia nigra reticulata and lateralis.

Extracellular single-unit responses of neurons in the ipsilateral pulvinar-lateral posterior complex were recorded in 10 encéphale isolé cats with stimulating electrodes implanted in the substantia nigra pars reticulata and pars lateralis. Fifteen percent of 101 pulvinar-lateral posterior complex thalamic neurons increased their spike discharges when the substantia nigra was stimulated and none decreased its activity. The excitatory effect of this stimulation is discussed in relation to the eventual excitatory or inhibitory character of the efferent projection from the substantia nigra pars reticulata and lateralis to the pulvinar-lateral posterior complex.

Animals↗
PubMed1988

Black tobacco, wine and mate in oropharyngeal cancer. A case-control study from Uruguay.

A case-control study of oral and pharyngeal cancer involving interviews with 108 cases and 286 controls was carried out in the University Hospital of Montevideo, Uruguay. The study was restricted to males and cases afflicted with lip, salivary gland and nasopharyngeal cancer were excluded. Point estimates of RR associated with smoking variables, alcohol variables, nutritional items and ingestion of hot infusions of the herb Ilex paraguariensis ('Mate') were obtained by logistic regression analysis. Dark tobacco smokers showed a RR 3.4 times higher than light tobacco users and heavy drinkers of wine displayed an OR of 17.2. Mate exposure showed a significant dose-response, after adjustment for age, tobacco and alcohol intake, with a fivefold increase in risk for heavy consumers. Joint exposure to black tobacco and wine displayed very high risks and no significant interactions were observed. The results suggest that the high rates of oropharyngeal cancer could be explained by the multiplicative effect of black tobacco smoking, wine drinking and mate ingestion.

Adult↗
PubMed1987

Risk factors for laryngeal cancer.

One hundred seven patients afflicted with incident laryngeal cancer and 290 controls with diseases considered not related to tobacco and alcohol exposure were interviewed in the University Hospital of Montevideo, Uruguay. The study followed a case-referent design, and epidemiologic analysis was carried out at the Louisiana State University, New Orleans. Dark tobacco smoking was the strongest risk factor, with an RR 2.5 times higher than that showed by light (flue-cured) tobacco smokers and 35 times that of non-smokers. Alcohol exposure displayed lesser effects but its interaction with tobacco smoking resulted in very high risks (more than 100 times higher). Among particular types of alcoholic beverages, red wine showed RR's similar to those displayed by hard liquor consumption. The habit of drinking a local tea called "mate" was associated with a threefold increase in risk, after controlling for the effects of age and tobacco and alcohol consumption. Infrequent consumption of vegetables and fruits showed RR on the order of 2.7, suggesting a role of diet in the causation of laryngeal cancer.

Adult↗
PubMed1987

Study of the morphological, electrophysiological and behavioral effects of unilateral kainic acid injection into the cat's substantia nigra.

Morphological, electrophysiological and behavioral studies were carried out in cats after unilateral kainic acid injection in the substantia nigra. A forced contralateral head turning and compulsive circling was observed after surgery. Fifteen days after, when asymmetry disappeared, apomorphine induced an ipsilateral head and body turning, that was blocked by haloperidol. The percentage of turning, after electrical stimulation in the superior colliculus or pulvinar-lateralis posterior complex, was affected by substantia nigra lesion. This work demonstrates that the nigro-pulvinar-lateral posterior and the nigrotectal projection modulate the capability of electrical stimulation of the target structures to elicit turning, and after unilateral substantia nigra lesion, two opposite directions of asymmetry appear, which are time-dependent and modulated by different neurotransmitters.

Animals↗
PubMed1987

Evidence for a nigro-pulvinar-lateralis posterior complex projection in the cat using horseradish peroxidase neuronal retrograde technique.

The possible existence of a direct projection from the substantia nigra to the pulvinar-lateral posterior complex (Pul-LP) was investigated in the cat by using the horseradish peroxidase technique. In particular horseradish peroxidase was injected in the Pul-LP of 8 animals, either unilaterally or bilaterally. Tissue sections obtained from the cat's brain 24-48 hrs. after injection were prepared according to Mesulam's method as slightly modified by the authors. Retrogradelly labelled neurons were observed in substantia nigra pars lateralis and reliculata ipsilaterally to the injected pulvinar-lateral posterior complex. A small number of labelled cells were also found in the contralateral substantia nigra. These findings demonstrate the existence of a close connection between two system which are involved in turning behavior: the nigrostriatal and the pulvinar-lateral posterior complex-superior colliculus.

Animals↗
PubMed1986

Simultaneous unitary neuronal activity in both superior colliculi and its relation to eye movements in the cat.

The analysis of simultaneous unitary neuronal activity related to eye movement and recorded in both superior colliculi has shown a mirror-functioning image. Increase of the frequency discharge in a collicular unit, was associated with a decrease of the frequency discharge in the contralateral superior colliculus unit. This unitary neuronal reciprocal behaviour was observed each time a horizontal or oblique eye movement was produced. It is possible that this reciprocal functioning between neurones in both superior colliculi could exert an important influence on oculomotor brainstem structures. These results give a better idea of the role played by both superior colliculi in the control of conjugate eye movements.

Animals↗
PubMed1986

Electrophysiological projections of pulvinar-lateralis posterior complex (P-LP) upon superior colliculus units in the cat.

The effect of Pulvinar-Lateral Posterior (P-LP) electrical stimulation on superior colliculus unitary responses and eye movements is analyzed in 17 encéphale isolé cats. Twelve of them were curarized. Out of a total of 190 recorded units, 117 were localized in the superior colliculus and 73 units in the Mesencephalic Reticular Formation (MRF) below the superior colliculus. Thirty eight per cent (n = 45) of the collicular units modified their discharge frequency when the ipsilateral P-LP was electrically stimulated. The current intensity thresholds of transynaptic activation had a range between 0.5 and 2.0 mA. Most of the orthodromic responses were produced by ipsilateral P-LP stimulation and were localized in the intermediate and deep layers of the superior colliculus. Three types of responses were obtained: short latency responses between 2 and 10 ms (57%); intermediate latency responses between 15 and 40 ms (29%), and long latency responses between 50 and 200 ms (14%). Thirty one per cent (n = 18) of the units recorded in the MRF responded to P-LP stimulation with 10 ms pulse-trains duration. In the MRF 3 types of responses were observed: 1) a decrease or blockade in the resting discharge during 20 to 100 ms after stimulation (20%); simple responses with a latency between 25 and 150 ms (40%), and complex responses with an early response and a latency between 15-40 ms, and a late response with a latency between 150 and 200 ms (40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Correlation between pulvinar-lateralis posterior complex unit activity and eye movements in the cat.

In 15 encéphale isolé cats, 130 units were recorded in the pulvinar-lateralis posterior complex (P-LP); 19 units responded in relation to horizontal eye movements (15%), 9 of which discharged when ipsiversive movements were recorded and the remaining 10 to contraversive movements. Three units discharged during spontaneous nystagnoid eye movement. All units always responded after initiation of the eye movement, with a latency range between 50 and 250 ms. The eye movement-related units were preferentially located (80%) in the border between the pulvinar and the lateralis posterior complex. Our results show the presence of eye movement-related units in the cat's P-LP, and their probable participation in ocular motility.

Animals↗
PubMedDate not supplied

Subdermal contraceptive implants in nurse-midwifery practice.

Subdermal contraceptive implants have only recently been approved for use in the United States. At present, only one subdermal contraceptive implant, Norplant, is approved in the United States. This article describes the development of Norplant, its efficacy and safety, a description of the system, education for clients, side effects, indications and contraindications, insertion and removal, incorporation into midwifery practice, and education for health professionals regarding its use.

Drug Implants↗