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Biomedical subjects

F Díaz

Publications and source records attributed to F Díaz.

At least 55 records · Page 3Linked to original sources
PubMed1999

Dominant lethal study of alpha-asarone in male and female mice after sub-chronic treatment.

Dominant lethal studies were conducted in male and female mice with alpha-asarone, the active hypolipidaemic component of Guatteria gaumeri Greenman, by per os sub-chronic treatment (10 and 20 mg/kg, 5 days/week, for 8 weeks) and subsequent mating. alpha-Asarone did not produce germinal mutations in either males or females. Epididymal sperm examination of male mice immediately after treatment failed to reveal any alteration in sperm count on shape. No significant alterations were observed in testicular or epididymal weights or testicular histology.

Allylbenzene Derivatives↗
PubMed1999

Ontogeny of renal renin in congenital hypothyroid rats.

In the present study we have found age-related differences between the renal renin activity (RRA) and the immunoreactive renal renin (IRR) profiles during the neonatal development of the rat. RRA was markedly greater in newborn rats than in adult ones, while IRR was low at birth and progressively increased until adulthood. These observations suggest the existence of a control mechanism operating either at the level of the translation of the template or at a post-translational level which varies throughout the development. Since thyroid hormones have been demonstrated to affect several renin-angiotensin components, the neonatal RRA and IRR profiles in congenital hypothyroid rats were evaluated to determine whether renal renin activity or its synthesis could be endogenously regulated by thyroid hormones in the early stages of life. Although significant differences were observed in the RRA profiles of congenital hypothyroid and control rats, no changes were found in the relative amount of immunoreactive protein. These findings indicate that thyroid hormone deficiency does not directly affect renal renin expression during the critical period of the normal morpho-functional development of the newborn.

Aging↗
PubMed1999

Circulating levels of immunoreactive beta-endorphin in polycystic ovary syndrome.

The plasma levels of beta-endorphin were studied in 64 women with polycystic ovarian disease (PCOD), from whom was selected a group of 23 women with normal weight and amenorrhea of < 36 days. On day 21, beta-endorphin levels were: mean 64.92 pg/ml; SD 37.32 pg/ml; 95% CI 48.38-81.47 pg/ml. It was also observed that their levels of opioid peptide were reduced, compared with women who had normal ovulatory cycles, both in the follicular phase (mean 70.93 pg/ml; SD 24.59 pg/ml; 95% CI 76.84-99.77 pg/ml) and luteal phase (mean 88.30 pg/ml; SD 31.80 pg/ml; 95% CI 76.84-99.77 pg/ml). The results were statistically significant (p < 0.05) for levels in PCOD patients compared with those of the luteal phase in women with normal ovulatory cycles. The decreased levels of beta-endorphin were negatively related to luteinizing hormone (LH) levels, which might explain the rise of LH levels in women with PCOD who control their weight and at the time of amenorrhea, although it is not clear if central opioid activity is reflected in the peripheral blood.

Adolescent↗
PubMed1999

A poroid neoplasia arising close to a seborrheic keratosis and a trichoepithelioma.

A 69-year-old woman had a well-defined, slightly raised, brownish, keratotic plaque with an eccentric group of roughly circular, bluish, dome nodules on her right scapular area. Histological study revealed the presence of an eccrine poroma demonstrating features of eccrine poroma, hidroacanthoma simplex, and dermal duct tumor and arising in a lesion of seborrheic keratosis and a trichoepithelioma. In the eccrine poroma region, an area with malignant changes was evident. The findings in this case support the view of eccrine poroma as a spectrum of histological variants and the possibility of malignant transformation from a eccrine poroma towards porocarcinoma. The association with seborrheic keratosis is most probably coincidental, and the trichoepithelioma was probably due to induction of the tumoral stroma on adjacent follicular epithelia.

Carcinoma↗
PubMed1999

Reversible cerebellar involvement in the idiopathic hypereosinophilic syndrome.

We report a patient with cerebellar manifestations due to the idiopathic hypereosinophilic syndrome, in whom magnetic resonance imaging (MRI) showed hyper-intense lesions in both cerebellar hemispheres. Following steroids and hydroxyurea administration, the lesions on MRI disappeared, suggesting that the pathogenetic mechanism was reversible and did not cause significant structural damage. To our knowledge, the resolution of the abnormal MRI findings have not been reported to date in the idiopathic hypereosinophilic syndrome.

Aged↗
PubMed1998

Effects of aging on middle-latency auditory evoked potentials: a cross-sectional study.

BACKGROUND: The results of previous studies comparing the middle-latency auditory evoked potentials (MAEPs) of young and elderly subjects have suggested that thalamic inhibitory deficits underlie age-related increases in MAEP amplitudes. METHODS: MAEPs were recorded from 73 healthy subjects aged between 20 and 86 years. The latencies of MAEPs recorded at Fz were subjected to two-way analyses of variance for the effects of age group and sex. Amplitude data were subjected to analyses of covariance with age group and sex as between-subjects factors, electrode position as within-subject factor, and individual perceptual thresholds as covariates. Variables exhibiting significant effects of age group were further investigated by regression analysis. RESULTS: Age correlated positively with Na, Na-Pa, and Nb-Pb amplitudes. The distribution of Na-Pa amplitude over the scalp varied with age. CONCLUSIONS: The observed age-related increases in amplitude are believed to reflect diminished capacity of subcortical and related cortical systems to inhibit the response to repetitive auditory stimuli that require no attentional effort. Possible age-related changes in the cortical distribution of MAEPs are also discussed.

Acoustic Stimulation↗
PubMed1998

Automatic and effortful processes in auditory memory reflected by event-related potentials. Age-related findings.

Mismatch negativity (MMN) and N2b were elicited during a selective dichotic-listening task in 16 young (Y), 16 middle-aged (M) and 19 elderly (E) subjects to evaluate automatic and effortful memory comparison of auditory stimuli. Sequences of standard (80%) and deviant (20%) tones were dichotically presented to subjects in two runs. In each run, subjects were instructed to give a button-press response to the deviant (target) tones in the ear designated as attended and to ignore the input to the other ear. Peak latencies, peak amplitudes and mean amplitudes were calculated for MMN and N2b components in each subject. MMN latency and amplitude were quite stable regardless of age, while N2b latency was significantly longer in M and E subjects than in Y subjects. These results are interpreted as reflecting that automatic processes of comparison in auditory memory of stimuli presented at short interstimulus intervals remain quite stable from 23 to 77 years of age; however, those requiring attentional effort decline with age.

Acoustic Stimulation↗
PubMed1998

Aging-related changes in processing of non-target and target stimuli during an auditory oddball task.

A total of 73 healthy subjects aged 20-86 years performed an auditory 'oddball' task. The age-dependence of N1 and P2 elicited by non-target stimuli, of N2 and P3 elicited by target stimuli and of N2a and N2b components (target minus non-target difference waves) was investigated across 20 electrodes to detect any aging-related changes in the psychophysiological processing of such stimuli during the task. Aging-related differences in within-task changes in non-target ERPs were also investigated. In non-target ERPs, it was found that P2 amplitude at Fz increased linearly with advancing age and the analysis of within-task changes indicated that P2 amplitude decreased during the task in young subjects at Pz, but remained unchanged in middle-aged and elderly subjects. These results suggest the existence of aging-related inhibitory deficits that may hinder the disengagement of attentional resources from irrelevant stimuli during the task. In the target ERPs, the latencies of N2 and P3 increased linearly at Fz, Cz and Pz. The increases in N2 were mainly due to linear increases in N2b latency at Fz, Cz and Pz, indicating that the aging-related slowing begins at controlled memory comparison of non-target/target stimuli. P3 amplitude presented a more uniform scalp distribution in middle-aged and in elderly subjects and pnly decreased significantly with advancing age in men, which may explain the divergent results in the literature on aging-related changes of P3 amplitude.

Adult↗
PubMed1998

Relation between RNA content and ageing in neurons of the dorsal lateral geniculate nucleus.

We carried out a study to establish ribonucleic acid (RNA) content in the nucleus and cytoplasm of single neuronal cells from the dorsal lateral geniculate nucleus (dLGN) of 3-30 month-old rats. Mean RNA content was calculated as the product of RNA concentration and nuclear or cytoplasmic surface. The analysis of neuronal nuclei revealed no significant differences in RNA concentration, nuclear area, and RNA content from 3-18 months. However, a significant decrease in RNA concentration (18.73%) was found from the 18th-24th month, although no changes were observed in nuclear area and RNA content. The oldest rats, 24-30 months old, presented a significant increase in nuclear area and RNA content. As regards to the neuronal cytoplasm, no significant differences were found in any of the parameters at the ages from 3-18 months and 18-24 months. In contrast, a significant increase in RNA concentration (26.26%), cytoplasm area (18%), and RNA content (52%) takes place from the 24th-30th month. The increase in RNA content could be related to neuronal hypertrophy.

Aging↗
PubMed1998

Ageing effects on flash visual evoked potentials (FVEP) recorded from parietal and occipital electrodes.

The effects of ageing on flash visual evoked potentials (FVEP) recorded from 6 posterior parietal and occipital sites were studied in a sample of 73 healthy subjects of between 20 and 86 years of age. Latencies of components P1, N1 and P2, and amplitudes of components P1 and P3 increased linearly with age at all emplacements. The results obtained from occipital electrodes are in line with previous reports and additionally show that i) the effects of age constantly increase over time, and ii) age affects not only the early but also the later components (> 150 ms) of the FVEP. The overall pattern of results suggests that elderly subjects show slower transmission of visual information and deficiencies in the inhibitory regulation of activity generated during the arrival of repetitive non-attended visual stimulation. The findings with parietal electrodes show that ageing effects are more marked at these emplacements than at occipital electrodes. Furthermore, this raises the question of a possible differential involvement of primary and nonprimary visual cortex by age, but this hypothesis can only be explored with high-intensity multichannel recordings and dipolar modelling.

Adult↗
PubMed1998

Subclavian vascular access stenosis in dialysis patients: natural history and risk factors.

Stenosis of the subclavian vein (SVS) after cannulation occurs in 15 to 50% of chronic hemodialysis patients, and impedes the placement of an arteriovenous fistula in the ipsilateral arm. Its natural history and pathogenic mechanisms are not well established. This study examined 42 consecutive chronic renal failure patients (28 men and 14 women; 46+/-19 yr) in whom subclavian catheters had been placed as the initial vascular access for hemodialysis. All patients underwent sequential venography studies: at baseline (24 to 48 h after removal of the catheter) and 1, 3, and 6 mo thereafter. Venograms were considered abnormal when there was evidence of unequivocal strictures (more than 30% narrowing), with or without collateral circulation. At baseline, 52.4% (n=22) of patients showed stenotic vein lesions (n=19) or total thrombosis (n=3), and identical lesions were also observed after 1 mo. Surprisingly, 10 of 22 patients with initial SVS (45.4%) showed spontaneous recanalization of venous lesions in the venographies performed 3 mo after removal. The patients with normal baseline venograms (n=20) showed no change during follow-up. Patients with definitive stenosis at 6 mo (n=12) had a higher number of inserted catheters (1.58+/-0.6 versus 1.2+/-0.48; P < 0.05), longer time in place (49.08+/-32.2 versus 29.03+/-26.6 d; P < 0.05), and higher number of dialysis sessions (21+/-13.8 versus 12.4+/-11.4; P < 0.05) than those without SVS or with spontaneous recanalization of venous lesions during follow-up. Furthermore, a higher number of catheter-related infections were observed in patients with definitive SVS (66.6% versus 33.3%; P < 0.05). In summary, SVS is observed in more than half of patients 24 to 48 h after catheter removal and 1 mo later. Even when recanalization occurs in many cases, a definitive stenosis is seen in 28% of patients by the third month. Thus, the creation of an ipsilateral vascular access is possible provided that venography is normal at this time. Finally, mechanical factors and catheter-related infections are the major risk factors for the development of late SVS.

Adult↗
PubMed1998

Can digital examination substitute anorectal manometry for the evaluation of anal canal pressures?

INTRODUCTION: Anorectal manometry provides objective information on the sphincter function of the anal canal. However, in many centers sphincter function is evaluated by digital examination, due to the unavailability of manometry. OBJECTIVE: A study is made to correlate the sensitivity and specificity of a quantitative digital examination in the analysis of sphincter tone with the pressures recorded by manometry, and to examine the capacity of both techniques to discriminate continent subjects and incontinent patients. PATIENTS AND METHODS: A total of 191 patients were divided into three groups: control (C), obstructive defecation (OD) and fecal incontinence (FI). Subjective quantitative digital evaluation of anal tone was performed on a scale of 0 to 5 points at rest, and 0 to 10 points at squeeze. A correlation analysis was performed, and the sensitivity and specificity of each fecal incontinence diagnostic test was determined. RESULTS: Digital examination found rectal tone to be diminished in elderly patients. A significant correlation was established between the digital and manometric tone readings, both at rest and at squeeze. Both techniques showed a low anal sphincter pressure in the FI group versus the C and OD groups. Differences in tone were recorded between the C and OD groups with manometry, but not with digital examination. The latter was in turn found to be more sensitive but less specific than manometry in differentiating between fecal continence and incontinence. CONCLUSIONS: Although digital examination does not substitute anorectal manometry, a good correlation exists between the two techniques. In this sense, digital examination may afford an approximate clinical evaluation of some fecal continence mechanisms in those centers where manometry is not available.

Adolescent↗
PubMed1998

[Urinary obstruction in fetal rabbits. An experimental model].

An original model of urethral ligation on 23 gestational-day fetal rabbits is described, that can be applied in studies of both urinary obstruction and oligohydramnios. The surgical technique is detailed and subsequent urinary obstruction is assessed, as well as the lung weight. In conclusion, this is an easy, mildly aggressive, inexpensive and fast model that can be used to investigate the pathophysiology of urinary obstruction and that of oligohydramnios.

Animals↗
PubMed1997

The effect of ageing on RNA content in neurons from the thalamic reticular nucleus visual sector.

In this paper we investigate nucleic acid content in neurons from the dorsocaudal region of the thalamic reticular nucleus in ageing Wistar rats. Nucleic acid per surface unit was analysed by calculating mean extinction using cytophotometric methods. Once the mean extinction and nuclear and cytoplasmic areas were known, nucleic acid total content was calculated. There was an increase in nucleic acid total content and in nuclear and cytoplasmic areas from the age of 3 months onwards. We interpreted these findings as a compensatory response, by 'neuronal hypertrophy', to the deterioration process occurring in the ageing rats. Between the 24th and 30th month, i.e. old age, nucleic acid per surface unit and total content in the cytoplasm exhibited a considerable decrease.

Aging↗
PubMed1997

Identification of a cysteine protease responsible for degradation of sperm histones during male pronucleus remodeling in sea urchins.

We have identified a 60-kDa cysteine protease that is associated with chromatin in sea urchin zygotes. This enzyme was found to be present as a proenzyme in unfertilized eggs and was activated shortly after fertilization. At a pH of 7.8-8.0, found after fertilization, the enzyme degraded the five sperm-specific histones (SpH), while the native cleavage-stage (CS) histone variants remained unaffected. Based on its requirements for reducing agents, its inhibition by sulfhydryl blocking compounds and its sensitivity to the cysteine-type protease inhibitors (2S,3S)-trans-epoxysuccinyl-L-leucyl-amido-3-methylbutane-ethyl-es ter (E-64 d), cystatin and leupeptin, this protease can be defined as a cysteine protease. Consistently, this protease was not affected by serine-type protease inhibitors phenylmethylsulfonyl fluoride (PMSF) and pepstatin. The substrate selectivity and pH modulation of the protease activity strongly suggest its role in the removal of sperm-specific histones, which determines sperm chromatin remodeling after fertilization. This suggestion was further substantiated by the inhibition of sperm histones degradation in vivo by E-64 d. Based on these three lines of evidence, we postulate that this cysteine protease is responsible for the degradation of sperm-specific histones which occurs during male pronucleus formation.

Animals↗