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Biomedical subjects

M Diaz

Publications and source records attributed to M Diaz.

At least 19 recordsLinked to original sources
PubMed2006

[Synchronisation of the menstrual cycle and ovarian follicles: interest and benefit].

In the menstrual cycle, a slight elevation of plasma FSH levels, the inter-cycle FSH signal, initiates the 1st phase of follicular recruitment. In ovarian stimulation for IVF, exogenous FSH aims at increasing the amplitude of this signal while maintaining FSH levels elevated, in order to fool the natural mechanisms of single follicular dominance. Synchronization consists in maintaining plasma FSH levels low so that all recruitable follicles remain at a resting state, prior to inducing ovarian stimulation. Practically speaking, synchronization of ovarian follicles allows to optimize clinical efforts, reduces the risk of cyst formation and ultimately, helps improving IVF outcome.

Female↗
PubMed2006

[Urinary undiversion; Bricker to Studer. With regard of two cases].

We present two cases of urinary undiversion from an ileal loop (Bricker) to an orthotopic neobladder. Due to miss adaptation to the stoma, two patients demanded reconversion to a continent urinary diversion. We proceed to change their urinary diversion to an ileal neobladder (Studer), one by open surgery and the other by laparoscopic surgery. In both cases immediate postoperative went uneventful. Both patients are continent, satisfied with their new situation, and without metabolic complications. Urinary undiversion from an ileal conduit to an orthotopic neobladder is technically feasible by open or laparoscopic surgery. It is a valid alternative for patients with complications due to their urinary diversion or miss adaptation to the cutaneous stoma.

Humans↗
PubMed2005

Intestinal transplantation in children: differences between isolated intestinal and composite grafts.

The results of the isolated intestinal grafts were compared with those of composite grafts (intestinal graft + liver) in a series of 18 transplantations performed in 17 children; 5 isolated intestinal grafts, 12 hepatointestinal grafts, and 1 multivisceral graft. Causes of intestinal failure were short bowel syndrome (n = 13), motility disorders (n = 2) and congenital epithelial disorders (n = 2). Transplantation was indicated due to end-stage liver disease (n = 14), loss of venous access (n = 2), untreatable diarrhea (n = 1) and high morbidity associated with a poor quality of life (n = 1). Six children, all with a composite graft, died after transplantation due to lymphoma (n = 2), sepsis (n = 1); intraabdominal bleeding (n = 1); pneumonia (n = 1); and overwhelming adenoviral infection (n = 1). Digestive autonomy was achieved in 16 of 18 grafts, the 11 surviving children are free of parenteral nutrition with a reasonably good quality of life. In conclusion, intestinal transplantation is a viable therapeutic alternative for children with permanent intestinal failure. The results of transplantation with an isolated intestine are clearly better that those with a composite graft.

Adolescent↗
PubMed2004

Long-term outcome after laparoscopic splenectomy related to hematologic diagnosis.

BACKGROUND: Laparoscopic splenectomy (LS) has been demonstrated as an effective and safe treatment for hematological disorders requiring spleen removal, especially in cases of normal-sized spleens. However, although results are promising, long-term outcome data are lacking. We reviewed our clinical experience with LS in a series of 255 cases, with particular attention to the long-term outcome related to the disease process requiring LS. METHODS: From February 1993 to October 2003, LS was attempted in 255 patients (100 males and 155 females with a mean age of 45 +/- 19 years) and clinical information was recorded in a prospective database. Indications for splenectomy included idiopathic thrombocytopenic purpura (ITP) (n = 115), HIV-ITP (n = 9), Evans syndrome (n = 6), autoimmune hemolytic anemia (AIHA) (n = 13), hereditary spherocytosis (HS) (n = 19), hematologic malignancy (n = 66), thrombotic thrombocytopenic purpura (n = 1), and others (n = 26). Long-term postoperative follow-up evaluation was obtained through clinical notes, follow-up visits by the referring hematologist, and by phone interviews both with patients and with the referring hematologist. RESULTS: A total of 186 patients (73%) were available for a mean follow-up of 35 months (range, 1-104). Of the ITP patients, 87 (76%) were followed up, with a remission rate of 89% (complete remission in 75%). A similar remission rate was observed in ITP-HIV; in patients available for follow-up (78%), complete remission was achieved in 83%. In Evans, complete remission was achieved in all patients available for follow-up (67%). Clinical response for hemolytic disease ranged between 70% for AIHA and 100% for HS. In the malignant group, the late mortality rate was 22%. The mortality rate in the miscellaneous group was 5%. No cases of splenectomy-related sepsis occurred during follow-up. CONCLUSIONS: LS offers advantages for all types of splenic diseases requiring surgery. It provides not only good clinical short-term outcome but also satisfactory long-term hematological results.

Adult↗
PubMed2004

A re-examination of the potential impact of preventive therapy on the public health problem of tuberculosis in contemporary sub-Saharan Africa.

BACKGROUND: To estimate the effect size of tuberculosis preventive therapy (PT) on the public health problem of tuberculosis in contemporary sub-Saharan Africa. METHODS: A compartmental flow model that considers high levels of tuberculosis and human immunodeficiency virus (HIV) infection in contemporary sub-Saharan Africa was used to assess the impact of PT on the prevalence of tuberculosis and tuberculosis-associated mortality. RESULTS: Model implementation shows that giving PT to 25% of HIV-positive individuals with latent tuberculosis infection (LTBI) leads to a 3.9% reduction in the prevalence of tuberculosis in 10 years and a 5.1% reduction in 20 years. This intervention also prevents a cumulative total of 3.0% of tuberculosis-associated deaths in a decade and 5.5% in two decades. Doubling PT coverage to 50% approximately doubles the effect size, suggesting a linear relationship within the 20-year period. The effect size is slightly sensitive to changes in level of HIV transmission, level of tuberculosis transmission, and level of case detection and treatment cure rates in the population. CONCLUSIONS: Contrary to suggestions by previous authors that PT can significantly reduce the public health problem of tuberculosis in sub-Saharan Africa, this model-based analysis suggests that the impact of PT on tuberculosis in the population is likely to be small.

Africa South of the Sahara↗
PubMed2003

Pediatric living donor liver transplantation.

AIM: The aim of this study was to analyze the results of living donor in a pediatric liver transplantation program. PATIENTS: Twenty-six living donor liver transplantations were performed in children from 0.5 to 14.8 years of age. The main indication was biliary atresia (72%) followed by tumors (2 hepatoblastomas and 1 hepatocarcinoma). Left lateral segments were used in 23 (1 transformed into a monosegment), 1 left lobe was used in 1, and right lobes were used in 2. Arterial reconstruction employed saphenous venous grafts in the first 3 cases and end-to-end anastomoses with a microsurgical technique in the following 22 cases. RESULTS: There has been no major morbidity in the donors, with a median hospitalization of 6 days. Four grafts have been lost; 2 in the first 3 cases. In only 1 case, the graft loss was related to the procedure saphenous venous graft thrombosis). Early biliary complications were frequent (23%). Six month, 1 year, and 5 year graft and patient survival rates were 91%, 85%, and 85% and 100%, 96%, and 96%, respectively. CONCLUSIONS: Living donor liver transplantation is an excellent option for transplantation in children.

Adolescent↗
PubMed2003

An ICI 182,780-sensitive, membrane-related estrogen receptor contributes to estrogenic neuroprotective actions against amyloid-beta toxicity.

Although estrogen (E2)-related neuroprotection has been repeatedly demonstrated in different models, the involvement of non-classical estrogen receptors (ERs) in this activity remains unclear. Using SN56 murine cholinergic cell line from the basal forebrain, we present evidence indicating that an ER associated with the plasma membrane participates in estrogen-dependent reduction of neuronal death induced by amyloid-beta peptide (Abeta) toxicity. Exposure to either E2 or estradiol-horseradish peroxidase (E-HRP) for 15 min significantly reduced Abeta-induced cell death. This effect was decreased by the ER antagonist ICI 182,780 as well as by MC-20 antibody directed to a region neighboring the ligand-binding domain of ERa. Using MC-20 antibody in unpermeabilized SN56 cells, we detected a protein at the plasma membrane region. The binding of impermeant forms of E2, E-HRP, and E-BSA-FITC to specific sites of SN56 plasma membrane was blocked by pre-incubation with E2, ICI 182,780, and MC-20 antibody in a concentration-dependent manner. Thus, a membrane-related ER that shares some structural homologies with ERalpha may participate in estrogen-mediated neuroprotection.

Amyloid beta-Peptides↗
PubMed2003

Quantitation of red cell-bound IgG, IgA, and IgM in patients with autoimmune hemolytic anemia and blood donors by enzyme-linked immunosorbent assay.

This paper describes an enzyme immunoassay for the quantitative determination of IgG, IgA, and IgM immunoglobulins on RBCs. Ether eluates made from RBCs were followed by an enzyme-linked immunosorbent assay of immunoglobulin concentration. Calibration curves were derived from immunoglobulin standards and the number of molecules of each isotype per RBC was calculated. The assay was carried out in 200 healthy blood donors and 62 patients with warm autoimmune hemolytic anemia (AIHA), two of them with a negative DAT. For healthy blood donors, mean values were 58 IgG, 16 IgA, and 3 IgM molecules per RBC. For patients with a positive DAT, the mean values were 3435 IgG, 157 IgA, and 69 IgM molecules per RBC. An increased level of IgA was found in 12 patients without IgA autoantibodies demonstrable in RBC eluates. Increased IgG levels were also observed in patients with a negative DAT and, in one case, an increased level of IgA was also found. The enzyme-linked immunosorbent assay using ether eluates is a sensitive method for quantitating RBC autoantibodies in patients with AIHA as well as immunoglobulins bound to RBCs in healthy individuals.

Journal Article↗
PubMed2001

Okadaic acid-sensitive activation of Maxi Cl(-) channels by triphenylethylene antioestrogens in C1300 mouse neuroblastoma cells.

1. The regulation of Maxi Cl(-) channels by 17beta-oestradiol and non-steroidal triphenylethylene antioestrogens represents a rapid, non-classical effect of these compounds. In the present study we have investigated the signalling pathways used for the regulation of Maxi Cl(-) channel activity by oestrogens and antioestrogens in C1300 neuroblastoma cells. 2. Whole-cell Maxi Cl(-) currents were readily and reversibly activated by tamoxifen, toremifene and the membrane-impermeant ethyl-bromide tamoxifen, only when applied to the extracellular medium. 3. Pre-treatment of C1300 cells with oestrogen or cAMP prevented the antioestrogen-induced activation of Maxi Cl(-) channels. The inhibitory effect of 17beta-oestradiol and cAMP was abolished by the kinase inhibitor staurosporine. 4. Current activation was unaffected by the removal of intracellular Ca(2+) and Mg(2+), but was completely abolished in the presence of okadaic acid. These results are consistent with the participation of an okadaic acid-sensitive serine/threonine protein phosphatase in the activation of Maxi Cl(-) channels. However, neither oestrogen or antioestrogen treatment modified the total activity of the two major serine/threonine phosphatases, PP1 and PP2A, in C1300 cells. 5. Although the role of these Maxi Cl(-) channels remains unknown, our findings suggest strongly that their modulation by oestrogens and antioestrogens is linked to intracellular signalling pathways.

Animals↗
PubMed2001

Photodegradation of natural organic matter exposed to fluctuating levels of solar radiation.

Irradiation of natural water samples with natural or artificial UVR typically results in a progressive loss of color and decreased absorbance; a process often referred to as photobleaching. In a typical photobleaching experiment, samples are exposed to a relatively constant level of artificial or natural UVR. However, under most natural situations, the vertical mixing of the water within the upper mixed layer results in strong and periodic fluctuations in UV irradiance. In this paper, we present the results of an experiment in which natural lake water was exposed to solar radiation in quartz tubes that were incubated either at fixed depths or rotating within the water column. We found differences between rotating and fixed samples in (i) photobleaching, (ii) nutrient release, and (iii) subsequent use by algae and bacteria. The evidence presented in this study demonstrated that photochemical processes might be affected by vertical water motion. The reasons for such differences remain largely unknown. Although we offer a potential explanation for such differences, our proposed mechanism is based on a post-hoc analysis of the data and should be taken solely as a working hypothesis for future research.

Biological Assay↗
PubMed2001

Decreased frequency of somatic hypermutation and impaired affinity maturation but intact germinal center formation in mice expressing antisense RNA to DNA polymerase zeta.

To examine a role of DNA polymerase zeta in somatic hypermutation, we generated transgenic mice that express antisense RNA to a portion of mouse REV3, the gene encoding this polymerase. These mice express high levels of antisense RNA, significantly reducing the levels of endogenous mouse REV3 transcript. Following immunization to a hapten-protein complex, transgenic mice mounted vigorous Ab responses, accomplished the switch to IgG, and formed numerous germinal centers. However, in most transgenic animals, the generation of high affinity Abs was delayed. In addition, accumulation of somatic mutations in the V(H) genes of memory B cells from transgenic mice was decreased, particularly among those that generate amino acid replacements that enhance affinity of the B cell receptor to the hapten. These data implicate DNA polymerase zeta, a nonreplicative polymerase, in the process of affinity maturation, possibly through a role in somatic hypermutation, clonal selection, or both.

Animals↗
PubMed2001

Human ClC-3 is not the swelling-activated chloride channel involved in cell volume regulation.

Volume regulation is essential for normal cell function. A key component of the cells' response to volume changes is the activation of a channel, which elicits characteristic chloride currents (I(Cl, Swell)). The molecular identity of this channel has been controversial. Most recently, ClC-3, a protein highly homologous to the ClC-4 and ClC-5 channel proteins, has been proposed as being responsible for I(Cl, Swell). Subsequently, however, other reports have suggested that ClC-3 may generate chloride currents with characteristics clearly distinct from I(Cl, Swell). Significantly different tissue distributions for ClC-3 have also been reported, and it has been suggested that two isoforms of ClC-3 may be expressed with differing functions. In this study we generated a series of cell lines expressing variants of ClC-3 to rigorously address the question of whether or not ClC-3 is responsible for I(Cl, Swell). The data demonstrate that ClC-3 is not responsible for I(Cl, Swell) and has no role in regulatory volume decrease, furthermore, ClC-3 is not activated by intracellular calcium and fails to elicit chloride currents under any conditions tested. Expression of ClC-3 was shown to be relatively tissue-specific, with high levels in the central nervous system and kidney, and in contrast to previous reports, is essentially absent from heart. This distribution is also inconsistent with the previous proposed role in cell volume regulation.

Amino Acid Sequence↗
PubMed2001

A shark antibody heavy chain encoded by a nonsomatically rearranged VDJ is preferentially expressed in early development and is convergent with mammalian IgG.

In most vertebrate embryos and neonates studied to date unique antigen receptors (antibodies and T cell receptors) are expressed that possess a limited immune repertoire. We have isolated a subclass of IgM, IgM(1gj), from the nurse shark Ginglymostoma cirratum that is preferentially expressed in neonates. The variable (V) region gene encoding the heavy (H) chain underwent V-D-J rearrangement in germ cells ("germline-joined"). Such H chain V genes were discovered over 10 years ago in sharks but until now were not shown to be expressed at appreciable levels; we find expression of H(1gj) in primary and secondary lymphoid tissues early in life, but in adults only in primary lymphoid tissue, which is identified in this work as the epigonal organ. H(1gj) chain associates covalently with light (L) chains and is most similar in sequence to IgM H chains, but like mammalian IgG has three rather than the four IgM constant domains; deletion of the ancestral IgM C2 domain thus defines both IgG and IgM(1gj). Because sharks are the members of the oldest vertebrate class known to possess antibodies, unique or specialized antibodies expressed early in ontogeny in sharks and other vertebrates were likely present at the inception of the adaptive immune system.

Amino Acid Sequence↗
PubMed2001

Evolution and the molecular basis of somatic hypermutation of antigen receptor genes.

Somatic hypermutation of immunoglobulin genes occurs in many vertebrates including sharks, frogs, camels, humans and mice. Similarities among species reveal a common mechanism and these include the AGC/T sequence hot spot, preponderance of base substitutions, a bias towards transitions and strand bias. There are some differences among species, however, that may unveil layers of the mechanism. These include a G:C bias in frog and shark IgM but not in nurse shark antigen receptor (NAR), a high frequency of doublets in NAR hypermutation, and the co-occurrence of somatic hypermutation with gene conversion in some species. Here we argue that some of the similarities and differences among species are best explained by error-prone DNA synthesis by the translesion synthesis DNA polymerase zeta (Pol zeta) and, as suggested by others, induction of DNA synthesis by DNA breaks in antigen receptor variable genes. Finally, targeting of the variable genes is probably obtained via transcription-related elements, and it is the targeting phase of somatic hypermutation that is the most likely to reveal molecules unique to adaptive immunity.

Animals↗