Search PubMed⌕ Search

Biomedical subjects

L Díaz

Publications and source records attributed to L Díaz.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of IGF-I on 1,25-dihydroxyvitamin D(3) synthesis by human placenta in culture.

The aim of the present study was to assess the effects of insulin-like growth factor I (IGF-I) upon the synthesis of 1, 25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] by human placenta trophoblasts in culture. Cytotrophoblastic cells obtained from normal term human placentae were cultured in Dulbecco's modified Eagle's medium with HEPES and glucose (DMEM-HG) during 72 h and further incubated in serum-free DMEM-F12 in the presence of IGF-I prior to the addition of [(3)H]-25-(OH)D(3) used as a precursor. The results showed that 2 h preincubation time with IGF-I was required for maximal production of [(3)H]-1,25-(OH)(2)D(3). Cultures in the presence of increasing concentrations of IGF-I (0-6.5 nmol/l), added 2 h before incubation with the labelled substrate, resulted in a dose-dependent response increment of [(3)H]-1,25-(OH)(2)D(3) production with a maximal conversion rate at the dose of 2.6 nmol/l. Higher doses of IGF-I did not result in further stimulatory effects. Co-incubations in the presence of cycloheximide significantly (P < 0. 0001) inhibited the IGF-I-mediated effects upon [(3)H]-1, 25-(OH)(2)D(3) production. Identity of putative [(3)H]-1, 25-(OH)(2)D(3) produced by human placenta was confirmed by spectral and receptor binding analysis. These results demonstrate the ability of cultured human syncytiotrophoblast cells to convert 25-(OH)D(3) to 1,25-(OH)(2)D(3) and suggest a local protein-dependent regulatory effect of IGF-I upon this biotransformation.

Calcifediol↗
PubMed1998

Role of the S4 segment in a voltage-dependent calcium-sensitive potassium (hSlo) channel.

We investigated the role of individual charged residues of the S4 region of a MaxiK channel (hSlo) in channel gating. We measured macroscopic currents induced by wild type (WT) and point mutants of hSlo in inside-out membrane patches of Xenopus laevis oocytes. Of all the residues tested, only neutralizations of Arg-210 and Arg-213 were associated with a reduction in the number of gating charges as determined using the limiting slope method. Channel activation in WT and mutant channels was interpreted using an allosteric model. Mutations R207Q, R207E, and R210N facilitated channel opening in the absence of Ca2+; however, this facilitation was not observed in the channels Ca2+-bound state. Mutation R213Q behaved similarly to the WT channel in the absence of Ca2+, but Ca2+ was unable to stabilize the open state to the same extent as it does in the WT. Mutations R207Q, R207E, R210N, and R213Q reduced the coupling between Ca2+ binding and channel opening when compared with the WT. Mutations L204R, L204H, Q216R, E219Q, and E219K in the S4 domain showed a similar phenotype to the WT channel. We conclude that the S4 region in the hSlo channel is part of the voltage sensor and that only two charged amino acid residues in this region (Arg-210 and Arg-213) contribute to the gating valence of the channel.

Amino Acid Sequence↗
PubMed1998

Pharmacokinetics of deflazacort in renal transplanted and hemodialyzed children.

Deflazacort (DFZ) pharmacokinetics was evaluated in fifteen pediatric patients on chronic hemodialysis or after renal transplantation, and in three normal children. After overnight fasting, oral DFZ 0.26+/-0.01 mg/kg (mean +/- SEM) was given. Serial blood samples were collected for 360 min and analyzed by HPLC for 21-hydroxy-DFZ (21-HO-DFZ). Serum concentration profiles and pharmacokinetic parameters were similar in patients on hemodialysis, renal transplant recipients and normal children. Elimination half-life was longer in the 9 cyclosporine-treated subjects (108.0+/-13.6 min) than in the other nine (71.2+/-8.3 min; p <0.02). Our finding suggests that, from a pharmacokinetic point of view, DFZ dose adjustment for renal function is not necessary in children with chronic renal failure or after renal transplantation.

Adolescent↗
PubMed1997

Biologically active steroid and thyroid hormones stimulate secretion of sex hormone-binding globulin by human term placenta in culture.

In this study, the influence of steroid and thyroid hormones and epidermal growth factor on the production of SHBG by placental tissue explants was investigated. Explants of trophoblastic tissue obtained from normal term placentas were cultured for 48 h in serum free culture medium, and then for an additional 24 h period in the presence or absence of various concentrations of either estradiol (0.25-5 nM), testosterone (0.5-500 nM), triiodothyronine (0.01-100 nM) or EGF (2-40 microM), respectively. Human SHBG concentration in culture media was estimated on each day by specific two-site time-resolved fluoroimmunometric assay and the results expressed as pmol/mg tissue protein. Binding characteristics and molecular structure of secreted SHBG were determined by [3H]5 alpha-DHT binding assays and Western blot analysis, respectively. Estradiol and triiodothyronine but not testosterone increased significantly (p < 0.05 vs. control) the secretion of SHBG into the culture media. Addition of EGF did not significantly change the production of SHBG at the various concentrations studied. [3H] 5 alpha-DHT binding assays and Western blot analysis of placental SHBG resulted in identical binding affinities (Kd 2.0 +/- 0.16 x 10(-9)M) and molecular structure to those obtained in serum from normal pregnant women. These findings support and extend previous observations by our laboratory indicating that SHBG gene is expressed in the placenta and provide further evidence on the hormonal regulatory characteristics of this steroid-binding protein in cultured placenta.

Epidermal Growth Factor↗
PubMed1997

[Follow-up study of the evolution of the quantitative EEG in intraventricular infusion of nerve growth factor in an aged baboon].

The animal model of aged monkeys is a good homologue of Alzheimer's disease in humans, in which it has been shown that there is disproportionate slowing of the EEG when compared with healthy subjects paired for age. This is found both on the conventional EEG and quantitatively. In the latter, relative energy has been the measurement most commonly used for diagnosis and follow-up with various treatments. The follow-up parameters evaluated in this study were: absolute and relative energy of the quantitative EEG (EEGq) obtained in an aged (39 year old) baboon (Papio hamadryas) before and after infusion of intraventricular nerve growth factor (NGF). These findings were compared with those of a young animal (6 year old) of the same species, treated in the same way. Since the animals were first anaesthetized with ketamine and diacepam so as to be able to carry out the study, we used a cerebral function analyzer which allowed us to ascertain that the changes found on analysis of the EEGq were not due to the depth of anaesthesia. The analyzer evaluated the tendencies of amplitude and frequency of the EEG, which is a method widely used for the indirect evaluation of the level of anaesthesia.

Aging↗
PubMed1996

Compression of the median nerve by an anomalous palmaris longus tendon: a case report.

A report on compression of the median nerve in distal forearm and wrist by an accessory muscle (the palmaris bitendinous) is described. Its position, deep to the palmaris longus, and distal insertion on the deep surface of the superficial aponeurosis were similar to palmaris profundus. Nevertheless, both its tendinous-musculo-tendinous structure and the origin from the dorsal epimysium of the palmaris longus muscle belly were unlike palmaris profundus.

Carpal Tunnel Syndrome↗
PubMed1996

[Nocardiosis in a renal transplant recipient].

We report a unilateral pulmonary nocardiosis in a 51 years old male that received a renal allograft. The clinical picture appeared 68 days after transplantation and the culture of a bronchoalveolar lavage showed the presence of Nocardia asteroides. Cyclos-porine and azathioprine were discontinued and trimethoprim-sulphamethoxazole was started with a good clinical response. Afterwards, azathioprine was restarted and the patient is asymptomatic at the present moment.

Azathioprine↗
PubMed1995

Lidocaine reduces the hypoxia-induced release of an excitatory amino acid analog from rat striatal slices in superfusion.

1. Lidocaine has been extensively investigated as a potential neuroprotective drug against ischemia-induced neurodegeneration without reaching any satisfactory conclusion. 2. The present work evaluates the effect of lidocaine -17 microM- on the hypoxia-induced release of tritiated D-aspartate from rat striatal slices in superfusion. 3. Hypoxia resulted in a significant increase in the amount of D-aspartate released from striatal slices preloaded with the tritiated excitatory amino acid analog. 4. The addition of lidocaine to the superfusion solution resulted in a drastic reduction in the amount of D-aspartate release evoked by hypoxia, rendering it close to normal values.

Animals↗
PubMed1995

Vaginal melanoma. Report of two cases and review of the literature.

Two cases of primary vaginal melanoma were treated between 1984 and 1986 at the Asturias Central Hospital, University Centre. Radical surgery was carried out in the first case--the patient surviving six months--and irradiation in the second case--living for only four months. Genital melanoma is a rare tumor--accounting for 3 per cent of female melanomas--with only 125 patients having been reported in the literature concerning vaginal melanoma. There is great disagreement as to the optimal treatment although radical surgery is the most frequently used. Primary vaginal melanoma is a lesion of poor prognosis, even more serious than cutaneous localizations, such as vulvar melanoma.

Aged↗
PubMed1994

[Evolution of child undernutrition in Chile and some of its conditioning factors: a time series analysis].

The objective of this study was to determine the evolution of the nutritional status of the population under five years of age during the period 1975-1990. Several conditioning factors were also assessed. The information was evaluated through time series analysis by using the AREG procedure. This procedure allows for the estimation of a regression model correcting by the autocorrelation of errors. Results indicates a significant trend to decreased undernutrition rates (p < 0.0001). A seasonal effect on undernutrition was observed, being higher the prevalences in summer. Analysis of selected conditioning factors, as well as the familiar buying capacity remained stable during the period. An exception to the lack of association among undernutrition and the conditioning factors evaluated, was seen during the period 1975-1982 when clear inverse relationship was evidenced. In conclusion, the decrease of infant undernutrition in Chile during the period 1975-1990 was not related to the changes observed in certain socioeconomic indices.

Child Nutrition Disorders↗
PubMed1994

[The short-term results and angiographic predictors of subacute thrombosis in the coronary implantation of the Palmaz-Schatz endoprosthesis].

INTRODUCTION AND OBJECTIVES: Intracoronary stenting has been proposed as an adjunct to balloon angioplasty in order to improve the immediate and long-term results. The purpose of this study was evaluate the short-term results, subacute closure rate and to try to identify angiographic predictors of subacute thrombotic after Palmaz-Schatz stent implantation. METHODS: Through a prospective registry, we have evaluated in 500 patients the safety and efficacy of Palmaz-Schatz stent implantation (580 in total) in coronary arteries and saphenous vein grafts. The identification of clinic and angiographic predictors of subacute closure have been evaluated with the assistance of a BMDP statistical software using an univariate and multivariate statistical analysis (logistic regression). The determination of diameter and stenosis has been achieved by electronic caliper. RESULTS: The stent was implanted successfully in 98.6% of the patients. There was no abrupt closure (< or = 1 day), however 36 patients (7.2%) developed subacute thrombotic closure (among 2nd-21st day after stenting). The major complications were: death 9 patients (1.8%), bypass surgery 7 patients (1.4%) and myocardial infarction 21 patients (4.2%). The predictors of subacute thrombotic closure through univariate statistical were: stenting for bail-out (S.T.: 27%; p < or = 0.0001), multiple stenting (S.T.: 24.1%; p < or = 0.0001), final diameter stent < or = 3.25 mm (S.T.: 12.6%; p < or = 0.013), and left ventricular ejection fraction < or = 45% (S.T.: 15.7%; p < or = 0.022). We showed with logistic regression that final diameter stent < or = 3.25 mm; p < or = 0.0030, left ventricular ejection fraction < or = 45%; p < or = 0.0012, stenting for bail-out; p < or = 0.0195 and multiple stenting; p < or = 0.0252, were predictors of subacute thrombotic closure. CONCLUSIONS: The Palmaz-Schatz coronary stenting will preferably realize in those arteries bigger than 3.25 mm and left ventricular ejection fraction > 45%, showing multiple stenting and stenting for bail-out greater subacute thrombotic closure rate.

Acute Disease↗
PubMed1993

Evidence that human placenta is a site of sex hormone-binding globulin gene expression.

The presence of an androgen-binding component in placenta was investigated in vitro using a tissue culture system of human placental explants. Explants of trophoblastic tissue from normal term placentas were kept in culture under appropriate conditions for at least 48 h in a serum-free medium. The existence of an androgen-binding protein was explored by binding assays, immunohistochemistry studies and Northern blot analyses of placental mRNA. Steady-state polyacrylamide gel electrophoresis and Scatchard plot analyses revealed the presence of a high affinity specific binding component for 5 alpha-dihydrotestosterone in cultured placenta. Immunohistochemical studies performed on intact placenta and on Percoll-gradient purified trophoblastic cells demonstrated the presence of specific immunoreactivity in the cytoplasm of syncytial cells. Northern blot analyses of placental mRNA showed a single hybridizable 32P-labeled human sex hormone-binding globulin (SHBG) cDNA band of approx. 1.6 kb which was identical in size to that obtained with liver mRNA. The results strongly suggest the placenta as an origin of SHBG and point out this tissue as an additional site of SHBG synthesis during pregnancy.

Blotting, Western↗
PubMed1992

Polarographic study of the photodecomposition of nimodipine.

Nimodipine, a calcium antagonist belonging to the dihydropyridine family, produces a well-defined polarographic peak due to the four-electron reduction of the nitro group. This peak was used to track the photodecomposition of nimodipine induced by UV light and daylight. Nimodipine was modified by UV irradiation with degradation following first-order kinetics. A degradation rate constant of 0.099 min-1, with a half-life of 7.78 min, for UV irradiation without a filter was obtained. Furthermore, a quantum yield of 1.32 x 10(-3) molecules/quantum absorbed was measured with a chemical actinometer. The UV degradation product, which was isolated and identified, showed that irradiation of nimodipine causes oxidation of the dihydropyridine ring and transmutation of the nitro group in the nitrobenzene moiety.

Nimodipine↗
PubMed1991

Incidence and prevalence of HIV-positive patients on chronic hemodialysis at the University and San Juan City Hospital.

There is controversy on whether or not patients with End Stage Renal Disease (ESRD) on chronic hemodialysis (HD) should be routinely tested for the presence of HIV-antibody (HIV-Ab) in their blood. Several reports have appeared in the literature reporting incidence from 0 to 11%. A total of 227 patients receiving chronic HD; at the University and San Juan City Hospital, from January to December 1987 were screened for the presence of HIV-Ab by the ELISA method. Those reported as positive were confirmed by the Western Blot method. HIV-Ab presence was reported and confirmed in 9 patients (4%). Five of these patients (2%) were IV drug abusers, 2 (0.9%) homosexual, 1 (0.4%) had history of sexual promiscuity and 1 (0.4%) had been exposed to multiple blood transfusion (MBT) prior to HIV testing of blood. Our prevalence was 7%. However when risk factors other than MBT were excluded the prevalence was 0.4%. The incidence and prevalence of HIV positive cases in our hemodialysis population is comparable to that previously reported.

Age Factors↗
PubMed1990

[Testicular microlithiasis: echographic diagnosis of a new cause of orchialgia and infertility].

Five patients who consulted for orchialgia in whom the diagnosis of testicular microlithiasis was made by means of scrotal sonography, are reported. Four of them showed oligo or azoosperm and also four had their testis diminished in size. The echographic findings are characteristic and they consist of multiple small echogenic non shadowing images, randomly distributed within both testis. Pathology was available in three cases. Atrophy of the germinal epithelium with impairment of the spermiogenesis associated with intratubular calcic microspheres was demonstrated. There are few reports in the literature regarding testicular microlithiasis and until now we have not heard about an association between testicular microlithiasis, orchialgia and oligo or azoosperm. The diagnosis can be done by means of scrotal sonography. This imaging method should be considered in the work-up of male infertility.

Adult↗
PubMed1989

[Carcinoma and fibroadenoma of the breast].

Eight cases of breast carcinoma coexisting with fibroadenoma were retrieved from the files of the Division of Pathology from 1957 to 1987. In 3 patients (Group I) the lesion was within the fibroadenoma and in the remaining 5 patients, adjacent to it (Group II: synchronic carcinomas). All patients were females. During the same period, 987 fibroadenomas and 2004 carcinomas were diagnosed: 0.30% of the fibroadenomas developed carcinoma within the epithelial component and 0.15% of the carcinomas originated in the fibroadenoma's epithelium. The mean age was 39 years for in situ lesions and 45.5 years for infiltrating carcinoma with a general mean age of 43.3 years, 20 years older than the peak age of fibroadenoma. In Group I, there were 3 in situ lesions, 1 lobular and 3 ductal (Table 1). Two of the three patients had another coexisting gynecologic malignancy. In Group II all cases had infiltrating carcinomas, one lobular, 3 ductal and 1 mixed lobular and ductal (Table 1). The adjacent breast tissue showed associated pathology in all cases: multiple fibroadenomas, fibrocystic diseases, sclerosing adenosis, infiltrating ductal carcinoma and/or lobular hyperplasia. Different hypotheses from the literature were analysed concerning an association between carcinoma and fibroadenoma. A casual association is suggested by the low percentage of carcinomas developing in fibroadenomas as well as the low percentage of carcinomas originating from fibroadenomas.

Adenofibroma↗
PubMed1988

Thirty-five years of Tropical biology: a quantitative history.

Citation indices are inappropriate measures of scientific output and impact. For that reason, nonparametric statistics were preferred to analyze 35 years of publication on Tropical biology in the Revista de Biología Tropical. The most frequent subjects are animal taxonomy, human biology-including medicine- ecology and animal behavior. Botany papers are less frequent and mainly deal with morphology and taxonomy. Applied studies are not predominant. In that period, only one case of unethical experimentation with humans was discovered in a paper of Mexican origin. The proportion of foreign institutions publishing in the journal has increased from 23% (1953-1963) to 50% in the last decade; similarly, the number of studies done in the Neotropics is on the rise. English and Spanish are equally frequent, although English is the basic language of ethology and evolution and Spanish predominates in papers on animal morphology and parasitology. Most Costa Rican authors publish in Spanish, in contrast with many of their Latin American colleagues. In recent years, there is a tendency to publish shorter papers written by more than one author. The Revista de Biología Tropical, covered by 18 data bases, accounts for most exchanges and sales in the Universidad de Costa Rica and has worldwide distribution.

Biology↗