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Biomedical subjects

E Díaz

Publications and source records attributed to E Díaz.

87 records · Page 5Linked to original sources
PubMed1989

Subcellular localization of the major pneumococcal autolysin: a peculiar mechanism of secretion in Escherichia coli.

The major pneumococcal autolysin (N-acetylmuramoyl-L-alanine amidase) has been localized in the cellular envelope of Streptococcus pneumoniae and Escherichia coli by using immunocytochemical labeling on ultrathin sections and whole-mounted cells. Cell fractionation experiments in E. coli confirmed the peripheral localization of the pneumococcal amidase and suggested that this enzyme is weakly bound to the outer face of the cytoplasmic membrane. This interaction does not depend on the presence of choline but represents an intrinsic property of the amidase. The autolysin, that is synthesized without any N-terminal signal sequence (García, P., García, J. L., García, E., and López, R. (1986) Gene (Amst.) 43, 265-272) was not processed during translocation. A new regulatory mechanism that might be specific for bacterial autolysins is discussed.

Amidohydrolases↗
PubMed1987

Naloxone-induced increase in blood and brain ethanol concentrations in rats.

Although a reduction in blood ethanol concentration has been proposed to mediate the ethanol antagonist activity of naloxone observed in clinical and experimental situations, an increase in this variable as well as in brain ethanol concentration has been found in rats treated with naloxone (0.5 and 2.0 mg/kg, i.p.) ten min after intragastric administration of ethanol (1 and 2 g/kg). This effect disappeared either when naloxone was administered 50 min after ethanol or when ethanol was given intraperitoneally. On the other hand, naloxone induced a slight but significant slowing in intestinal transit rate. These results suggest that naloxone may facilitate gastrointestinal absorption of ethanol when administered soon after an oral load of this drug. Therefore, mechanisms other than a pharmacokinetic interaction appear to be involved in the antagonist action of naloxone.

Animals↗
PubMed1986

Effect of ethanol on neuromuscular function in rats. Its interaction with alcuronium.

The effect of chronic ethanol intake on neuromuscular function has been analyzed by using a rat tibial muscle preparation. The time-course of single twitches, trains-of-four, tetanus and post-tetanic facilitation with and without blockade with alcuronium was evaluated. A decrease in these parameters was observed, being more pronounced in ethanol fed rats during 10 than 30 days. The twitch was the most affected parameter. After recovery of alcuronium blockade, the depressant effects of ethanol were completely reversed. These data suggest that low but sustained ethanol blood levels causes evident alterations of neuromuscular function due, probably, to a postjunctional action.

Alcoholism↗
PubMed1979

[Evaluation of the protein quality of Erythrina edulis (balú)].

The protein content (N x 6.25) of the seeds of Erythrina edulis (balú) varies between 18-21%; when the fraction corresponding to non-protein nitrogen is extracted with trichloroacetic acid (10%), this value decreases to 14-15%. Remarkable differences in the distribution of the protein fractions are observed when two schemes of extraction are assayed. The amino acid analysis shows that this legume has similar or higher amounts of most amino acids than those present in other leguminosae; the calculated chemical score and protein score show that methionine is the first limiting amino acid and tryptophan, the second. The protein efficiency ratio (PER) of thermically-treated flours has the highest value at 30 minutes of treatment (1.15).

Amino Acids, Essential↗
PubMedDate not supplied

Prenatal melatonin exposure influences the maturation of gonadotropin and prolactin estradiol-benzoate feedback system.

Gonadotropin and prolactin response to estrogen feedback in female rat offspring of control and melatonin treated (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring) were studied at these periods: infantile, prepubertal and pubertal. In controls negative or absent LH feedback developed after estradiol benzoate (EB) injection up to 30 days of age indicating that the onset of puberty had not occurred. The positive feedback was established from day 33 on. However, in MEL-offspring the first activation of gonadotropin secretion during afternoon, 31 h after EB, was observed at 25 days of age, representing the first neuroendocrine sign of the onset of puberty. This positive response disappeared on day 30 in MEL-offspring. At 33 days of age, the LH positive response to EB was found in both groups, indicating a more advanced sexual development. In controls, this response increased at 35 days of age while in MEL-offspring it was highly depressed. FSH secretion in response to EB showed a negative feedback effect from infantile to the end of prepubertal period in both groups. The positive feedback was observed earlier in MEL-offspring (at 33 days of age) than in controls (at 35 days of age), but at this age it was absent in MEL-offspring. A positive prolactin response to EB at all ages in controls was observed. The typical pulsatility with higher values in the afternoon appeared by the first time at 30 days of age. However, in MEL-offspring no pulsatile response was observed throughout any age. These data suggest that prenatal melatonin administration altered gonadotropin and prolactin response to EB inducing precocious sensitivity during prepubertal period but depressed response during the pubertal period.

Animals↗
PubMedDate not supplied

Effect of prenatal melatonin on the gonadotropin and prolactin response to the feedback effect of testosterone in male offspring.

The purpose of this study was to investigate the effects of prenatal melatonin administration on the sensitivity of the androgens negative feedback effect on gonadotropin and prolactin secretion in male offspring. Male offspring of control (control-offspring) and melatonin treated (MEL-treated) (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring), at infantile, prepubertal, and pubertal periods were studied. LH secretion in response to testosterone propionate (TP) in control-offspring showed the classical negative feedback effect at all ages studied. In MEL-offspring a negative response after TP was also observed in all ages studied although the magnitude of this response was altered in this group as compared to controls. FSH values were significantly lower at most ages and time points studied in MEL-offspring than in control-offspring. FSH secretion in MEL-offspring showed a delayed negative feedback action of TP injection as compared to control-offspring. This response was observed at 21 days of age in control-offspring and delayed until day 30 of life in MEL-offspring. Parallely it remain at later age in MEL-offspring than in control-offspring. Prolactin secretion in control-offspring showed increased values after TP injections from infantile to pubertal periods. This increase was blunted in MEL-offspring at 17 and 35 days of age showing significantly reduced (p<0.01; p<0.05) plasma prolactin levels. During pubertal period a prolactin positive response to TP administration was observed in MEL-offspring but with significantly lower magnitude than in control-offspring. These results indicate that prenatal melatonin exposure induced changes in the sensitivity of gonadotropin and prolactin feedback response to testosterone, indicating a delayed sexual maturation of the neuroendocrine-reproductive axis in male offspring.

Aging↗
PubMedDate not supplied

Chemical studies on Mexican plants used in traditional medicine, XV. Sesquiterpene evoninoate alkaloids from Hippocratea excelsa.

Three sesquiterpene evoninoate alkaloids, hippocrateine I [1], hippocrateine II [2], and emarginatine A have been isolated from the root and stem barks of Hippocratea excelsa. Compounds 1 and 2 are new naturally occurring substances. The structure of 1 was unequivocally established by X-ray crystallographic analysis, and the structure of the second new alkaloid was deduced by spectral analysis.

Alkaloids↗
PubMedDate not supplied

Concentrations of fluoride in wines from the Canary Islands.

Potentiometry using an ion-selective electrode has widely been used for determining fluoride because of its simplicity and rapidity. The concentration of fluoride was determined (Gran's method) in 70 wines from the main wine-producing regions of the Canary Islands. The mean concentration of fluoride in wines from a region with a high concentration of fluoride in drinking waters was significantly (p < 0.05) higher than those mean concentrations obtained in the remaining wines. Non-important differences were found among the types of wine analysed. However, the fluoride concentrations of all the Canarian wines analysed here did not present a risk for the public health.

Atlantic Islands↗
PubMedDate not supplied

[Effects of simultaneous transplant of foetal mesencephalic cells in the striatum and the subthalamic nucleus of hemiparkinsonian rats].

INTRODUCTION: The main strategy followed in neural transplants as a method of treatment for Parkinson s disease, both experimental and clinical, has been to introduce foetal mesencephalic cells into the target area: the striatum. However, when the dopaminergic cells in the substantia nigra degenerate, not only is the dopaminergic innervation of the striatum affected but also other nuclei: globus pallidus, substantia nigra, substantia nigra pars reticulata and subthalamic nucleus. A series of data from pharmacological and physiological studies offer strong evidence that the dopamine released in these nuclei may play an important role in regulating the output nuclei of the basal ganglia. AIM: To evaluate the effect of transplanting foetal mesencephalic cells on the behaviour of 6 OH DA rats when introduced into the striatum and the subthalamic nucleus. MATERIALS AND METHODS: 6 OH DA was used to induce lesions in the substantia nigra of rats, which were divided into several experimental groups. The rotating activity induced by D amphetamine (5 mg/kg, intraperitoneally) and apomorphine (0.05 mg/kg, subcutaneously) was evaluated before and three months after the transplant in all the experimental groups, except in the control group of healthy rats. The hemiparkinsonian rats received a total of 350,000 foetal ventral mesencephalic cells, which were implanted within small deposits in the striatum (8) and in the subthalamic nucleus (4). RESULTS AND CONCLUSIONS: Rotation induced by both drugs was significantly lower (p= 0.05) in animals that had had dopaminergic cells transplanted into the striatum body. No significant improvement in this behaviour was to be found when transplants were limited to just the subthalamus or, simultaneously, also to the striatum. A significant increase in rotating behaviour induced by apomorphine was observed in the group which received a transplant in just the subthalamus.

Adrenergic Agents↗