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Biomedical subjects

M Díaz

Publications and source records attributed to M Díaz.

At least 73 records · Page 4Linked to original sources
PubMed2001

[Pre-hepatic portal hypertension as a late complication of liver transplantation in children].

UNLABELLED: In the long-term after liver transplantation (LT), some children develop prehepatic portal hypertension (PPH) and raise problems not very well known yet; many of the lessons learned with the management of these patients may be useful outside the LT. AIM: 1. To analyze the incidence and risk factors of PPH after LT. 2. To evaluate the results with the different treatments used. METHODS: Retrospective study over 164 children surviving more than 1 year after LT. Univariant analysis of possible risk factors associated and multivariant (logistic regression), for those that had significance in the univariant analysis. Other factors associated are analyzed as well as the indications and results of two types of treatment: percutaneous pneumatic dilatation and surgical shunt (splenorenal and Rex shunt). RESULTS: 9 children developed symptomatic PPH (hemorrhage in 8, ascites in 1), associated to lymphoproliferative post-LT disease in 2, and to anastomotic biliary stricture in 1. The age at first LT (children under 1 year old), weight (below 10 kg), and need of retransplantation (reLT) were in the univariant analysis the associated variables with increased risk of PPH. The diagnosis (biliary atresia) and the emergency status of the LT were almost significative. In the multivariant analysis, the need of reLT is the only independent variable that increases the risk (relative risk: 4.5, confidence interval 95%: 1.29-18.87). At diagnosis 3 cases showed portal estenosis, and 5 showed absence of permeability with cavernomatous transformation. The PPH was caused in one case because of the esplenic vein disconnection (treatment not required at the moment); the three cases of portal estenosis were dilated percutaneously with success, and 2 of the 5 cases with portal thrombosis have been surgically shunted: one by an splenorenal shunt and the other by a Rex shunt (first case done in Spain); the other 3 cases are stable waiting for a surgical solution. The hepatic function is normal in the 9 cases. CONCLUSIONS: The PPH can complicate the prognostic of the pediatric LT in the long term. The treatment depends on the permeability of the portal trunk. Whenever possible, percutaneous dilatation should be attempted; should surgery be required, the Rex shunt is the best option.

Child↗
PubMed2000

6-s-cis locked analogues of the steroid hormone 1alpha, 25-dihydroxyvitamin D(3). Synthesis Of novel A-ring stereoisomeric 1, 25-dihydroxy-3-epi-19-nor-previtamin D(3) derivatives.

Efficient syntheses of A-ring synthons 24 and 32 are described from hydroxy ester 16, which is easily available on a preparative scale from (-)-quinic acid. Key features of the syntheses were (a) the ability to selectively perform desilylations in the presence of p-nitrobenzoate esters and (b) the excellent yield and complete stereospecificity with which the configuration of alcohols 16, 18, and 26 could be inverted under Mitsunobu conditions. Thus, A-ring synthons 24 and 32 were both prepared in 35-38% yield (eight steps) from the common precursor 16. The coupling of A-ring synthons 24 and 32 with the appropriate CD-ring/side chain fragment 7 provides access to novel 6-s-cis locked analogues of steroid hormone 1alpha, 25-dihydroxyvitamin D(3): 1alpha, 25-dihydroxy-3-epi-19-nor-previtamin D(3) (37) and 1beta, 25-dihydroxy-3-epi-19-nor-previtamin D(3) (38), which are unable to undergo rearrangement to the respective vitamin D form by virtue of the absence of the C-19 methyl group. Compounds 37 and 38 can be used as tools for studying the genomic and nongenomic mechanisms of action of the previtamin form of the hormone 1alpha, 25-dihydroxyvitamin D(3).

Calcitriol↗
PubMed2000

Human mtDNA haplogroups associated with high or reduced spermatozoa motility.

A variety of mtDNA mutations responsible for human diseases have been associated with molecular defects in the OXPHOS system. It has been proposed that mtDNA genetic alterations can also be responsible for sperm dysfunction. In addition, it was suggested that if sperm dysfunction is the main phenotypic consequence, these mutations could be fixed as stable mtDNA variants, because mtDNA is maternally inherited. To test this possibility, we have performed an extensive analysis of the distribution of mtDNA haplogroups in white men having fertility problems. We have found that asthenozoospermia, but not oligozoospermia, is associated with mtDNA haplogroups in whites. Thus, haplogroups H and T are significantly more abundant in nonasthenozoospermic and asthenozoospermic populations, respectively, and show significant differences in their OXPHOS performance.

Base Sequence↗
PubMed2000

Analysis and description of the evolution of alginate immobilised cells systems.

Different immobilised cells models, including very simple ones, can be useful in the fitting of experimental results. However, goodness or the ability to extrapolate results needs to be in accordance with basic observations and these will also suggest models to be proposed. In this paper, observations of calcium alginate/bacteria systems are used to show the ability of basic models to fit classic observations, as well as how new observations, in this case from electronic microscopy, oblige us to think about more complex mechanisms and mathematical treatments. Nevertheless it is not only important to discuss the model type, but also the type of kinetics assumed in the interior of the beads, as well as the internal structure, the boundary conditions related to bead shredding and cell escape and finally, geometrical effects.

Alginates↗
PubMed2000

Utility of the BACTEC Myco/F lytic medium for the detection of mycobacteria in blood.

This study aims to evaluate the performance of a new vial (Myco/F Lytic) for the detection of mycobacteria from blood specimens. This vial is monitored in the BACTEC 9000 blood culture system. We compared it with the traditional method routinely used in our laboratory, which is a lysis-centrifugation based procedure. Of 275 samples tested in parallel by both methods, 23 from 20 patients grew mycobacteria (18 Mycobacterium avium complex, 4 M. tuberculosis and 1 M. simiae); 11 isolates were recovered using both systems, 12 were isolated with the Myco/F Lytic medium only, and none were isolated using the traditional method only (p < 0.05). Blood was the diagnostic sample for 12 patients with the Myco/F Lytic system and only 7 with the traditional system. The mean time to detection of mycobacteria with Myco/F Lytic medium was 17 days, whereas it was 44 days with the traditional method (p < 0.001). Identification by DNA probes was performed directly from the Myco/F Lytic bottle. Myco/F Lytic is a rapid, simple, safe and highly reliable diagnostic method for the detection of mycobacteria in blood.

Bacteremia↗
PubMed2000

In vitro activities of six fluoroquinolones against 250 clinical isolates of Mycobacterium tuberculosis susceptible or resistant to first-line antituberculosis drugs.

Two hundred fifty isolates of Mycobacterium tuberculosis were evaluated for susceptibility to ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, trovafloxacin, and gemifloxacin (SB-265805). Levofloxacin, ciprofloxacin, and grepafloxacin showed the greatest activity (MIC for 90% of strains tested [MIC(90)] 1 microg/ml), although ofloxacin also showed good activity, with an MIC(90) of 2 microg/ml. Trovafloxacin and gemifloxacin showed lower in vitro activity, with MIC(90)s of 64 and 8 microg/ml, respectively.

Anti-Infective Agents↗
PubMed2000

Heterogeneous antimicrobial resistance patterns in polyclonal populations of coagulase-negative staphylococci isolated from catheters.

Most cases of nosocomial bacteremia are catheter related, and coagulase-negative staphylococci (CoNS) are the microorganisms most frequently associated with these infections. Subtle morphological differences are frequently found among CoNS colonies cultured from infected catheters. The aim of this study was to analyze the significance of the morphological heterogeneity observed in these CoNS populations. With this purpose in mind, the clonal composition of the CoNS populations obtained from a selection of nine catheters was analyzed by two different molecular techniques, arbitrarily primed-PCR and DNA macrorestriction analysis by pulsed-field gel electrophoresis. Twenty CoNS morphotypes were included for analysis, and four single colonies representative of each morphotype were selected. Morphological differences between colonies were found to correlate in all cases with differences at the molecular level. Unique fingerprints were also obtained for some isolates which were indistinguishable from other representatives of the same morphotypes. Differences in the molecular patterns among the isolates were associated in most of the cases with differences in the antimicrobial susceptibility patterns. The frequent isolation of polyclonal CoNS populations from catheters, with heterogeneous antimicrobial susceptibility patterns, has relevant epidemiologic and therapeutic implications in the context of catheter-related infections.

Anti-Bacterial Agents↗
PubMed2000

Membrane mechanisms for electrogenic Na(+)-independent L-alanine transport in the lizard duodenal mucosa.

The active Na(+)-independent transport of L-alanine across the duodenal mucosa of the lizard Gallotia galloti was studied in Ussing-type chambers using a computer-controlled voltage clamp. Addition of L-alanine to the Na(+)-free bathing solutions resulted in a significant L-alanine absorption (J(net)) that was paralleled by an increase in transepithelial short-circuit current (I(sc)) and potential difference (PD) without apparent changes in the tissue conductance. The concentration dependence of J(net), PD, and I(sc) displayed Michaelis-Menten kinetics. L-alanine-induced electrical changes were completely inhibited by external alkaline pH or by the H(+)-ionophore carbonyl cyanide m-chlorophenyl-hydrazone in the bathing solution. The alanine-induced electrogenicity was dependent on the presence of extracellular K(+) and could be blocked by serosal Ba(2+) or mucosal orthovanadate. These results suggest the existence of an H(+)-coupled L-alanine cotransport at the apical membrane of enterocytes. The favorable H(+) driving force is likely to be maintained by an apical vanadate-sensitive H(+)-K(+)-ATPase, allowing the extrusion of H(+) in an exchange with K(+). Potassium exit through a basolateral barium-sensitive conductance provides the key step for the electrogenicity of L-alanine absorption.

Alanine↗
PubMed2000

Effect of interleukin-6 and tumor necrosis factor-alpha on GABA release from mediobasal hypothalamus and posterior pituitary.

The release of cytokines during infection, inflammation and stress induces brain-mediated responses, including alterations of neuroendocrine functions. We examined the effect of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on release of gamma-aminobutyric acid (GABA) from mediobasal hypothalamic (MBH) explants and posterior pituitaries (PP) of male rats. IL-6 (10 ng/ml) did not modify basal GABA release from MBH and PP, but significantly increased GABA release under depolarizing conditions (40 mM K(+)). This effect was abolished by incubation of the tissue with indomethacin, an inhibitor of cyclooxygenase activity, indicating that prostaglandins could mediate the stimulation of GABA release induced by IL-6. On the contrary, TNF-alpha (50 ng/ml) significantly decreased K(+)-evoked GABA release from both MBH and PP. This inhibitory effect was not modified by indomethacin. Neither IL-6 nor TNF-alpha affected nitric oxide synthesis, as measured by [(14)C]citrulline production. The current results indicate that IL-6 stimulates GABA release from both hypothalamus and posterior pituitary by a mechanism mediated by prostaglandins. On the contrary, TNF-alpha inhibits GABA release from both tissues. These results suggest the possibility that GABAergic activity in the hypothalamic-pituitary axis could be involved in neuroendocrine responses to cytokines.

Animals↗
PubMed2000

[Congenital fibrosarcoma. Diagnostic-therapeutic implications].

Most of the soft tissue sarcomas of childhood other than rabdomyosarcoma, have as final diagnosis fibrosarcoma, specially in the first months of life. Overlapping features between infantile myofibromatosis and congenital fibrosarcoma, hemangiopericytoma and fibrohistiocytoma have seen noted. Five patients with congenital fibrosarcoma were operated since 1991. Anatomical sites included lower limb, hand and forearm, and three of them had previous diagnoses of hemangiopericytoma, fibrohistiocytoma and myofibromatosis, with provocated non radical surgery and reoperation. The postoperative course was satisfactory and all are live one to eight years later. In our experience accurate histological diagnosis must be achieved to perform radical surgery on these cases.

Fibrosarcoma↗
PubMed2000

[Complex and complicated syndactylia. Review and treatment progress].

Complex syndactyly is generally defined as abnormal digital interconnection by bone, but sometimes simple syndactyly with complicated cutaneous, musculotendinous or neurovascular interconnections should be considered complex as well. Additionally, complex syndactyly involving anomalous bones (delta phalanx, brachiphalangism...) falls in different category called "complicated". 35 patients with complex or complicated congenital syndactyly are studied and 58 children with cutaneous syndactyly due to burns and epidermolysis bullosa are analyzed as well.

Child↗
PubMed2000

[Impact of complete resection on survival of patients with large neuroblastoma].

UNLABELLED: The aim of our study is to assess the role of complete resection after chemotherapy in stage 3 and 4 (INSS) neuroblastoma. MATERIAL AND METHODS: We treated in the period 1990-1997 a group of 71 infants and children with neural tumors. There were 63 neuroblastomas (median age: 24.8 +/- 25 months, median 18). 47 were abdominal, 13 thoracic, 2 pelvic and 1 cervical. Survival rate (Kaplan-Meier) in patients with or without complete resection of the tumor were assessed (Mantel Cox). RESULTS: 14 of 17 patients with stage 3 tumors and only 8 of 23 with stage 4 survive. All patients with stage 3 undergoing complete resection are alive, whereas only 4 of 7 with incomplete resection survive (p < 0.01). In contrast, the effort and risk of resection do not appear to be worth in stage 4. Two kidneys, one spleen and a portion of the pancreas were removed to perform complete tumor removal. CONCLUSIONS: Complete resection in stage 3 neuroblastoma after chemotherapy improves survival, and radical surgery seems justified even if neighboring structures have to be removed. Radical surgery does not seem to be useful in stage 4 neuroblastoma.

Child, Preschool↗
PubMed2000

Apolipoprotein D expression in benign and malignant prostate tissues.

BACKGROUND: Apolipoprotein D (ApoD), a protein component of the human plasma lipid transport system, is an androgen regulated protein in both breast and prostate cancer cell lines. METHODS: Here we examined, by immunohistochemical assay, the ApoD expression in normal, benign and malignant prostate tissues. RESULTS: ApoD was detected in the two analyzed normal prostate tissues, in 16 (94.1%) of 17 benign prostatic hyperplasias, and in 36 (63.1%) of 57 prostate carcinomas. In prostate carcinomas, ApoD immunostaining values did not show significant relationship neither with age of the patients, stage and histologic grade of the tumors, nor with preoperative serum levels of prostatic specific antigen (PSA). However, ApoD-negative immunostaining predicted shorter survival duration in the subgroup of 46 patients with nonresectable prostate cancer (p = 0.02). CONCLUSIONS: Our results led us to consider that Apo D expression by prostate carcinomas migth be of clinical usefulness for identificating lesions with different evolution.

Adult↗
PubMed1999

Functional uncoupling between intracellular calcium dynamics and secretion in the alphaT3-1 gonadotropic cell line.

Gonadotropin releasing hormone (GnRH) stimulates both transcription and secretion of the alpha subunit of the gonadotropins in a Ca2+-dependent fashion. In this study, we examined the role of Ca2+ as the signal coupling agonist occupancy of GnRH receptors to hormone secretion using the gonadotropic cell line alphaT3-1. Treatment of alphaT3-1 cells for 60 min with GnRH (0.1-100 nM), veratridine (50 microM) or high K+ (56 mM) was completely ineffective in stimulating secretion. The lack of effect occurred in spite of a robust, specific, and dose-dependent biphasic [Ca2+]i response consisting of a rapid peak sensitive to thapsigargin (200 nM) followed by a smaller plateau sensitive to the extracellular application of EGTA (5 mM). On the other hand, treatment of alphaT3-1 cells with the Ca2+ ionophore ionomycin resulted in a significant dose-dependent stimulation of secretion and [Ca2+]i responses comparable to those elicited by GnRH. Binding assays revealed the presence of Ins(1,4,5)P3 receptors (Kd = 3.2 nM, Bmax = 50.5 fmol/mg protein) but not ryanodine receptors in alphaT3-1 cell membranes. Together, these results show a functional uncoupling between the [Ca2+]i response and secretion in this cell line, suggesting that the increase in [Ca2+]i triggered by GnRH and depolarization may be necessary but not sufficient to stimulate exocytosis.

Calcium↗
PubMed1999

Characterization of a basic phospholipase A2-homologeu myotoxin isolated from the venom of the snake Bothrops neuwiedii (yarará chica) from Argentina.

A basic protein was isolated by CM-Sephadex C-25 chromatography from the venom of Bothrops neuwiedii from Argentina, and named B. neuwiedii myotoxin I. This protein exerted local myotoxic and edema-forming effects in mice, with potencies comparable to other myotoxins isolated from Bothrops spp. venoms. When injected by i.v. route at doses up to 4.7 mg/kg of body weight, the toxin was not lethal. In vitro, the toxin had no detectable phospholipase A2 activity on egg yolk phospholipids. B. neuwiedii myotoxin I appeared as a homodimer in sodium dodecylsulphate-polyacrylamide gel electrophoresis, with a subunit molecular weight of 15 kD. Gel immunodiffusion revealed a pattern of partial antigenic identity between the newly isolated myotoxin and myotoxin II from Bothrops asper venom. The sequence of B. neuwiedii myotoxin I was determined for the first 40 amino acid residues, showing high homology to several class II phospholipase A2 myotoxins of the Lys-49 family from crotalids. Altogether, results suggest that this toxin is a new member of the Lys-49 phospholipase A2-homologues with myotoxic, cytolytic, and edema-inducing activities.

Amino Acid Sequence↗