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Biomedical subjects

S Espinoza

Publications and source records attributed to S Espinoza.

12 recordsLinked to original sources
PubMed2001

Depletion study of trimethoprim and sulphadiazine in milk and its relationship with mastitis pathogenic bacteria strains minimum inhibitory concentrations (MICs) in dairy cows.

Time-related concentrations in milk of a combination of trimethoprim-sulphadiazine (TMP-SDZ) intramammary formulated infusion and its relationship with pathogenic bacteria strains minimum inhibitory concentrations (MICs) isolated from clinical mastitis cows were analysed. The MICs study was performed for Escherichia coli, Staphylococcus aureus and Streptococcus sp. strains. The SDZ concentrations in milk were analysed using high-performance liquid chromatography (HPLC) and TMP using a microbiological assay. Ten lactating cows milked three times daily were used in the time-concentration studies of TMP-SDZ. Milk samples (approximately 20 mL) from the treated mammary quarters were taken at 6, 12, 24, 30 and 36 h after first administration. In order to define the withdrawal time, milk samples from the treated mammary quarters were taken at 24, 36, 48, 72, 84 and 96 h, after finishing the therapy. The MICs fluctuated between 1 and 8 microg/mL. Effective therapeutic concentrations lasted for 36 h when intramammary infusion was repeated three times every 12 h. No TMP was detected in milk for 24 h after finishing therapy. Milk SDZ concentrations were below 0.1 microg/mL in all treated cows after 84 h finishing therapy. At 96 h after finishing therapy, no SDZ milk concentrations were found in six animals, although four animals of the experimental group still had concentrations of 0.07 microg/mL.

Animals↗
PubMed2000

Vaccination against Taenia solium cysticercosis in underfed rustic pigs of México: roles of age, genetic background and antibody response.

Vaccination of pigs of mixed genetic make-up, raised as rustically as done in rural Mexico, resulted in effective protection to experimental challenge against Taenia solium cysticercosis. Maximum protection was achieved if pigs were immunized at 70 days of age. There was large variation of viable parasite load within vaccinated pigs and controls, which is suggestive of significant genetic factors influencing susceptibility, besides immunization. Our results strengthen the advisability of pig vaccination for control of T. solium cysticercosis, since it lowers the number of viable cysticerci capable of transforming into tapeworms.

Age Factors↗
PubMed1999

Deficit in the water-maze after lesions in the anteromedial extrastriate cortex in rats.

The Morris water-maze task was used to evaluate the role of the anteromedial extrastriate visual cortex in the processing of visuospatial information in rats. Six gray male rats received bilateral ibotenic acid injections targeted stereotactically to the rostral part of the anteromedial extrastriate visual cortex. These operated subjects and six other unoperated control rats were tested in the maze. Histological analysis confirmed the localization, symmetry, and depth of lesions in the rostral part of anteromedial area (AMa) in the operated subjects. In these animals, a significantly greater latency to reach the submerged platform was found (U = 0, p = 0.004). The Morris water-maze may be considered as a reference memory task. It presents a stronger demand on the use of allocentric spatial visual cues than on the use of egocentric cues for navigation. Therefore, the present data lend support to the participation of area AMa in the integration of allocentric visuospatial cues or as a link in the memory system involved in the acquisition of this task.

Animals↗
PubMed1998

Sex differences in neuropsychological functioning of first-episode and chronically ill schizophrenic patients.

OBJECTIVE: The purpose of this study was to determine whether men and women with schizophrenia demonstrate differences in cognitive abilities. METHOD: Two cohorts of patients with schizophrenia, an acute first-episode and a chronically hospitalized group, were evaluated with a neuropsychological battery and compared with a normal group of subjects. RESULTS: After adjustment for age, age at onset, and premorbid IQ, male chronic patients performed worse than female chronic patients on measures of visual memory. These differences were eliminated after control for symptom severity. No other differences were found in cognitive function between men and women in either cohort. CONCLUSIONS: Sex differences in cognitive function in schizophrenic patients are not robust findings.

Age of Onset↗
PubMed1996

Specific oncological contribution of cathepsin D and pS2 in human breast cancer: their relationship with TNM status, estradiol receptors, epidermal growth factor receptor and neu amplification.

The present study attempts to clarify the specific contribution of cathepsin D (CD) and pS2 to the progression of breast cancer (BC) by examining the relationship between these two factors and TNM status, tumour grade, estradiol receptors (ER) and the prognosis factors epidermal growth factor receptor (EGFR) and neu amplification in a group of 270 BC patients. CD and pS2 were determined by an immunoradiometric procedure in tumour cytosols obtained for ER. Neu amplifications were evaluated by dot-blot, in tumour DNA. EGFR was determined in membrane tumour preparations obtained from ER cytosols by a two-point radiometric saturation assay. CD is basically related to bad prognosis factors and has a direct correlation with tumour size (P = 0.025) and EGFR content (P = 0.007) and is associated with the presence of metastases (P = 0.000). pS2 is mostly related to good prognosis factors and showed an inverse correlation with the Scarff-Bloom Index (P = 0.011) and a direct correlation with ER content (P = 0.014). Finally, pS2 and CD also showed a strong mutual association (P = 0.009) and the fact that both correlated with ER content confirms in tumours the experimental finding that they are estrogen-induced proteins.

Adult↗
PubMed1996

The effects of clozapine on symptom reduction, neurocognitive function, and clinical management in treatment-refractory state hospital schizophrenic inpatients.

Thirty chronically hospitalized, refractory schizophrenic patients were evaluated while on typical neuroleptics and again after 12 weeks of clozapine treatment. Patients demonstrated small but statistically significant reductions in total Brief Psychiatric Rating Scale (BPRS) symptoms, need for seclusion and restraint, and PRN medications, and they frequently were transferred to a less restrictive treatment environment. Neuropsychological test data from a subset of patients suggested improvement on measures of verbal fluency and graphomotor speed, but deterioration on measures of visual memory and executive/frontal ability. Clozapine's different effects on multiple neurotransmitter systems may be responsible for its mixed effects on cognitive abilities. No significant relationships were found between symptom reduction, cognitive improvement, and transfer to a less restrictive environment.

Adult↗
PubMed1996

On the origin of extracellular glutamate levels monitored in the basal ganglia of the rat by in vivo microdialysis.

Several putative neurotransmitters and metabolites were monitored simultaneously in the extracellular space of neostriatum, substantia nigra, and cortex and in subcutaneous tissue of the rat by in vivo microdialysis. Glutamate (Glu) and aspartate (Asp) were at submicromolar and gamma-aminobutyric acid (GABA) was at nanomolar concentrations in all brain regions. The highest concentration of dopamine (DA) was in the neostriatum. Dynorphin B (Dyn B) was in the picomolar range in all brain regions. Although no GABA, DA, or Dyn B could be detected in subcutaneous tissue, Glu and Asp levels were 5 and approximately 5 and approximately 0.4 microM, respectively. Lactate and pyruvate concentrations were approximately 200 and approximately 10 microM in all regions. The following criteria were applied to ascertain the neuronal origin of substances quantified by microdialysis: sensitivity to (a) K+ depolarization, (b) Na+ channel blockade, (c) removal of extracellular Ca2+, and (d) depletion of presynaptic vesicles by local administration of alpha-latrotoxin. DA, Dyn B, and GABA largely satisfied all these criteria. In contrast, Glu and Asp levels were not greatly affected by K+ depolarization and were increased by perfusing with tetrodotoxin or with Ca2+-free medium, arguing against a neuronal origin. However, Glu and Asp, as well as DA and GABA, levels were decreased under both basal and K+-depolarizing conditions by alpha-latrotoxin. Because the effect of K+ depolarization on Glu and Asp could be masked by reuptake into nerve terminals and glial cells, the reuptake blocker dihydrokainic acid (DHKA) or L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) was included in the microdialysis perfusion medium. The effect of K+ depolarization on Glu and Asp levels was increased by DHKA, but GABA levels were also affected. In contrast, PDC increased only Glu levels. It is concluded that there is pool of releasable Glu and Asp in the rat brain. However, extracellular levels of amino acids monitored by in vivo microdialysis reflect the balance between neuronal release and reuptake into surrounding nerve terminals and glial elements.

Amino Acids↗
PubMed1993

[Attitude and behavior regarding breast self examination among health professionals in Chile].

This study was carried out from April to December 1990 in the commune of Valdivia, Chile and involved 207 physicians, nurses, midwives, and nurse-midwives. The objective was to determine the relationship between subjective attitude and personal behavior on the part of these health professionals with regard to the practice of monthly breast self-examination (BSE). The data were collected by means of an instrument designed to measure attitudes, which was prepared by Victoria Lee Champion (1984) on the basis of the health beliefs model of Becker, et al. (1974). Also included were questions aimed at ascertaining the personal and sociodemographic background of the professionals surveyed and their knowledge of several aspects of breast cancer and BSE. The information collected was subjected to the following tests of validity and reliability: Person product-moment correlation coefficient r, split half method, Spearman-Brown R coefficient, Cronbach alpha coefficient, and the Chi-square test to determine the degree of association between the variables. The results showed that although 79% of the women studied had ample knowledge of many aspects of breast cancer and 82% were aware of the benefits of BSE, only 28% practiced it on a monthly basis. It is alarming that health professionals, who are responsible for teaching prevention measures to other people, have yet to assume responsibility for protecting their own health insofar as early detection of breast cancer is concerned.

Adult↗
PubMed1978

Threshold spectral sensitivity of single neurons in the lateral geniculate nucleus and of performing monkeys.

A technique is described for controlling fixation within central mascular fields and locating and determining thresholds for single neural units in the afferent pathways on the same awake, performing monkey for the same stimuli and at the same retinal loci from which behavioral thresholds are obtained. Comparison of preliminary neural unit and behavioral thresholds appears to reject the hypothesis that the color-opponent LGN units can serve threshold detection. A type of broad-band LGN unit is described which could serve that function, having its absolute threshold within the variability of the behavioral threshold (+/- 1 standard deviation) for all wavelengths successfully tested.

Afferent Pathways↗
PubMed1972

Further steps in the research of cortico-hypothalamic interactions in cats.

The cerebral cortex of the cat was systematically stimulated with electric shocks, and the recording of the evoked potentials in the hypothalamus was performed with macro- and microelectrodes stereotaxically guided. Stimulation of definite cortical loci evoked potentials in several hypothalamic nuclei studied. Three focuses were found, coincident with the so called "primary sensory area" of the neocortex. Hypothalamic responses elicited by stimulation of the ipsilateral cortex have greater amplitude and shorter latency than those evoked by contralateral stimulation. The "uconditioning" stimulus given on the cortex produces on the "test" stimulus response an inhibitory effect if the interstimulus delay is shorter than 0.6 sec, and a facilitatory if it is greater than 0.6 sec.

Animals↗