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Biomedical subjects

C Jimenez

Publications and source records attributed to C Jimenez.

At least 19 recordsLinked to original sources
PubMed2006

Substrate utilization during prolonged exercise with ingestion of (13)C-glucose in acute hypobaric hypoxia (4,300 m).

Energy substrate oxidation was measured using indirect respiratory calorimetry combined with tracer technique in five healthy young male subjects, during a 80-min exercise period on ergocycle with ingestion of 140 g of (13)C-labelled glucose, in normoxia and acute hypobaric hypoxia (445 mmHg or 4,300 m), at the same relative [77% V(.-)((O)(2)(max))] and absolute workload (161+/-8 W, corresponding to 77 and 54% V(.-)((O)(2)(max)) in hypoxia and normoxia). The oxidation rate of exogenous glucose was not significantly different in the three experimental situations: 21.4+/-2.9, 20.2+/-1.2 and 17.2+/-0.6 g over the last 40 min of exercise at approximately 77 and approximately 54% V(.-)((O)(2)(max)) in normoxia and in hypoxia, respectively, providing 12.5+/-1.5, 16.8+/-1.1 and 14.9+/-1.1% of the energy yield, although ingestion of glucose during exercise resulted in a higher plasma glucose concentration in hypoxia than normoxia. The contribution of carbohydrate (CHO) oxidation to the energy yield was significantly higher in hypoxia (92.0+/-2.1%) than in normoxia for both a given absolute (75.3+/-5.2%) and relative workload (78.1+/-1.8%). This greater reliance on CHO oxidation in hypoxia was entirely due to the significantly larger contribution of endogenous glucose oxidation to the energy yield: 75.9+/-1.7% versus 66.6+/-3.3 and 55.2+/-3.7% in normoxia at the same relative and absolute workload.

Adult↗
PubMed2005

Is the CAG repeat of mitochondrial DNA polymerase gamma (POLG) associated with male infertility? A multi-centre French study.

BACKGROUND: Recent data emphasized the implication of polymerase gamma (POLG) CAG repeats in infertility, making it a very attractive gene for study. A comparison of POLG CAG repeats in infertile and fertile men showed a clear association between the absence of the usual 10-CAG allele and male infertility, excluding azoospermia. It has also been suggested that the POLG gene polymorphism should be considered as a possible contributing factor in unexplained couple infertility where semen parameters are normal. In this study, we investigated the POLG CAG repeats, in a well-defined population of patients with severe male factor infertility. METHODS: We conducted a large study of POLG CAG repeats in 433 infertile and 91 fertile, normozoospermic and healthy males. In all subjects, phenotypic data, including semen parameters, hormonal status and clinical profiles, were available. RESULTS: Thirteen 'homozygous mutants' (3%) were found among the 433 idiopathic infertile patients. The follow-up of the 13 'homozygous mutant' resulted in pregnancy for more than half of the couples, through assisted reproductive techniques or even spontaneously. In addition, one 'homozygous mutant' was identified in 91 fertile men (1.1%) CONCLUSION: Under our conditions, our study does not confirm any relationship between the polymorphic CAG repeat in the POLG gene and male infertility.

Adult↗
PubMed2004

Simultaneous liver-kidney transplantation for adult recipients with irreversible end-stage renal disease.

HYPOTHESIS: Combined liver-kidney transplantation is safe (low morbidity and acceptable mortality) and effective in patients with end-stage liver disease. Although refinements in surgical technique have resulted in better patient and allograft outcomes, the negative impact of renal insufficiency on survival in patients undergoing liver transplantation has been widely reported, although some aspects are controversial. DESIGN: Analysis of the clinical characteristics and outcome in the management of patients undergoing combined liver-kidney transplantation. The end points were operative mortality, morbidity, and long-term survival. SETTING: University Hospital 12 de Octubre. PATIENTS: Between May 1986 and December 2001, 820 liver transplantations were performed. There were 16 cases (1.96%) of combined liver-kidney transplantations, which represent the sample of this study. RESULTS: Mean +/- SD follow-up of 42.2 +/- 29 months: 6 patients died (37.5% mortality rate). There were 4 (25%) hospital deaths within 6 months following surgery and 2 after 6 months (4 sepsis, 1 refractory heart failure, and 1 recurrent hepatitis C virus disease). Univariate analysis related to mortality included age, sex, etiology, preoperative creatinine level, United Network for Organ Sharing status, Child-Pugh score, type of hepatectomy (piggyback), intraoperative blood product administration, and the presence of postoperative complications. The only 2 significant factors were the presence of postoperative complications (P = .01) and the United Network for Organ Sharing status (P = .02). Crude survival rate was 62.5%. Actuarial survival rates were 80%, 71%, and 60% at 1, 3, and 5 years, respectively. CONCLUSION: Because end-stage renal disease is not a formal contraindication for liver transplantation, a combined liver-kidney transplantation for adults with end-stage renal disease can be done safely and effectively.

Adult↗
PubMed2003

Results in split liver transplantation.

INTRODUCTION: The shortage in cadaveric grafts has prompted the development of alternative surgical techniques to expand the donor pool. OBJECTIVE: To evaluate the feasibility of split liver transplantation using an observational, retrospective, and longitudinal study. MATERIALS AND METHODS: Between April 1986 and October 2002 we performed 875 liver transplants. From April 1991 to date, we performed 18 split liver transplantations in patients of mean age 42.27+/-25.65 years; five children and 13 adults; and 83.3% women. Urgent transplants accounted for 38.9%. Mean patient weight was 52.29+/-20.87 kg. Ex situ splitting was performed in 33%. The mean cold ischemia time was 460+/-265.69 minutes with a mean warm time of 64.33+/-11.78 minutes. Mean consumption of packed blood was 5.59+/-4.87 units; of frozen fresh plasma, 11.56+/-7.42 units; and of platelets 4.89+/-4.99 units. RESULTS: After a mean follow-up of 10.83+/-12.51 months, 55.56% of the recipients are alive. Actuarial patient and graft survival rates at 1 year are 55.6% and 44.12%, respectively. Actuarial patient and graft survival rates at 1 year, excluding operative mortality were 77% and 68%, respectively. Actuarial patient and graft survival rates at 1 year, comparing urgent and elective transplantations are: 14.29 and 14%, respectively, for urgent cases and 90.91 and 90% for elective ones. Operative mortality was 16.6% while mortality during follow-up was 26.6%. The late complications included arterial thrombosis (n=2): of whom the first needed liver retransplantation 4 months after split liver transplantation; chronic rejection (n=2), recurrence of hepatitis (n=1). CONCLUSIONS: Split liver transplantation is a useful way to expand the graft pool and shows better results in elective liver transplantation.

Adult↗
PubMed2003

Live liver donation: a prospective analysis of exclusion criteria for healthy and potential donors.

INTRODUCTION: Living donor liver transplantation represents a controversial option to increase the donor pool. DESIGN: Prospective and descriptive clinical study. OBJECTIVE: (1) To identify risk factors (exclusion criteria) for live donation; (2) to determine the rate of recipients that benefit from a living donor. METHODS: Between May 1995 (first adult-to-adult living donor liver transplantation in Spain) and November 2002, we evaluated 74 healthy volunteers and performed 12 living donor liver transplants (no donor mortality). RESULTS: All actual donors and volunteers are alive and healthy. After a mean time of 3.2+/-0.5 weeks, 72% of potential donors were considered unsuitable for live donation. Exclusion criteria were grouped in three categories: (primary) donor safety reasons (68%); (secondary): ABO mismatch (17%) and (tertiary): cadaveric graft transplantation (15%). Consequently, just 43.7% of the recipients presenting to us with a potential living donor, did finally benefit from these organs. The mortality rate was 8.3% for 43 recipients presenting with a living donor in comparison to 15% for those who did not (321 recipients between May 1995 and November 2001). CONCLUSIONS: ALDLT can benefit a significant number of recipients on the waiting list (43.7% of those presenting with a donor). The most frequent exclusion criteria concern donor safety, namely, unsuspected chronic liver diseases and unsuspected thrombophilic disorders.

ABO Blood-Group System↗
PubMed2003

Muscle magnetic resonance imaging in patients with congenital muscular dystrophy and Ullrich phenotype.

The aim of this study was to evaluate muscle magnetic resonance imaging findings in patients with congenital muscular dystrophy and Ullrich phenotype. Fifteen children with congenital muscular dystrophy and Ullrich phenotype were included in the study. All patients had collagen VI studies in muscle and, when family structure was informative, linkage studies to the collagen 6 loci. Three of the 15 patients had reduced collagen in muscle. One of the three was from an informative family and linked to one of the collagen 6 loci. Another patient was linked to one of the collagen 6 loci but had normal expression of collagen in muscle. The remaining 11 all had normal collagen expression in muscle. Only two of these 11 were from informative families and linkage to collagen 6 loci was excluded in them. All patients had muscle magnetic resonance imaging of their leg muscles using transverse T1 sequences. With the exception of the two patients in whom linkage to the collagen 6 loci was excluded, the other 13 patients showed the same pattern of selective involvement on magnetic resonance imaging of thigh muscles. This consisted of relative sparing of sartorius, gracilis, adductor longus and rectus. This pattern was also found in the case linked COL6A1/A2 locus but with normal collagen. This finding, and the striking clinical and magnetic resonance imaging concordance between patients with normal and reduced collagen VI in muscle suggest that collagen VI could still be the culprit in several cases with normal collagen expression, or alternatively a primary defect in a protein that closely interacts with collagen VI. Mutation analysis of the collagen 6 genes in cases with normal collagen VI expression is needed to resolve this issue.

Adolescent↗
PubMed2003

Human seminal plasma displays significant phospholipid transfer activity due to the presence of active phospholipid transfer protein.

The lipid composition of germ cell membranes is considerably modified during spermatogenesis, sperm maturation and capacitation. Some of these modifications are caused by exchanges between soluble lipid donors or acceptors and cell membranes. The aim of this study was to assess whether significant lipid transfers between lipoprotein structures are detectable in human seminal plasma. Phospholipid and cholesteryl ester (CE) transfer activities were measured by specific fluorescence and isotopic assays. Seminal plasma samples did not display significant CE transfer. Substantial levels of phospholipid transfer activity were detected in all samples studied, levels were approximately 25% of the phospholipid transfer activity measured in human blood plasma. Concordantly, CE transfer protein was not detected in seminal plasma, while the presence of the phospholipid transfer protein (PLTP) was confirmed by Western blot analysis. Enzyme-linked immunosorbent assay indicated that seminal PLTP concentrations represented 25% of the concentration measured in blood plasma. Blockade of phosphatidylcholine and phosphatidyl-ethanolamine transfer by a 60 min, 56 degrees C heating step or with anti-PLTP antibody revealed that PLTP accounts for almost 80% of the phospholipid transfer activity present in seminal plasma. As shown by gel-permeation chromatography and Western blot analysis, seminal PLTP activity was partially associated with prostasomes. Significantly higher PLTP activity levels were measured in seminal plasma samples with low seminal vesicle secretions. The latter observation may reflect the sustained secretion of active PLTP that is diluted in a variable volume of PLTP-free seminal vesicle secretion. In conclusion, human seminal plasma displays significant phospholipid transfer activity due to the presence of active PLTP.

Carrier Proteins↗
PubMed2001

Carboxyl terminal peptides derived from prepro-orphanin FQ/nociceptin (ppOFQ/N) are produced in the hypothalamus and possess analgesic bioactivities.

Orphanin FQ/nociceptin (OFQ/N), the endogenous ligand for the ORL-1/KOR-3 receptor, produces a wide variety of behavioral responses. Its precursor protein, prepro-OFQ/N (ppOFQ/N) contains several series of amino acids bounded by pairs of basic amino acids, raising the possibility that additional functional neuropeptides could be generated by proteolytic posttranslational processing. Several of these processing products have been shown to have pharmacological activity, including the 17 amino acid peptide OFQ/N (mppOFQ/N(140-157)) which is a major product of this precursor in the hypothalamus. Here we have used a newly developed radioimmunoassay and RP-HPLC to detect mppOFQ/N(160-187) in mouse hypothalamic extracts. Murine ppOFQ/N(160-187) has potent analgesic activity supraspinally (3.4 nmol, i.c.v.) and spinally (4.3 nmol, i.t.). This analgesic activity was reversed by the opioid antagonist naloxone (5 mg/kg, s.c.) and kappa(1)-selective opioid antagonist nor-BNI (60 microg, i.c.v.), despite the inability of ppOFQ/N(160-187) to compete binding in mu, delta, kappa(1), kappa(3), or OFQ/N binding assays. These findings suggest that murine ppOFQ/N(160-187) may be a physiologically relevant neuropeptide with a novel mechanism of action.

Amino Acid Sequence↗
PubMed2001

Comparison of passive heat or exercise-induced dehydration on renal water and electrolyte excretion: the hormonal involvement.

The effects of hydromineral hormones and catecholamines on renal water and electrolyte excretion were examined during and after dehydration induced by either passive heat or exercise. Eight healthy young Caucasian subjects participated in three separate trials, each including three consecutive phases. Phases 1 and 3 involved a 90-min period at rest in a thermoneutral environment, while phase 2 involved a 120-min period designed to provide: (1) euhydration (control trial), (2) passive heat-induced dehydration of 2.8% body mass, or (3) exercise-induced dehydration of 2.8% body mass. During the two dehydration procedures, the decreases in urine flow and sodium excretion were more marked during exercise (P < 0.05). An increase in plasma catecholamines occurred only during exercise, together with a reduction in creatinine clearance and more marked increases in plasma renin and aldosterone than during passive heat exposure (P < 0.05). Although plasma vasopressin was elevated during the two dehydration procedures, urine osmolality did not change and, moreover, free water clearance increased during exercise (P < 0.05). Plasma levels of atrial natriuretic peptide increased markedly only during exercise compared to the other trials (P < 0.05). After the dehydration procedures, urine flow decreased again and urine osmolality increased markedly (P < 0.05), while plasma vasopressin remained elevated. These results suggest that sympathoadrenal activation during exercise plays a major role in the more marked reduction in diuresis and natriuresis than during passive heat exposure. Despite high plasma vasopressin concentrations during the two dehydrating events, the observed antidiuresis was not due to an increased renal concentrating ability, and the vasopressin was more effective after the dehydration procedures.

Adult↗
PubMed2001

Detection of human papillomavirus DNA in benign oral squamous epithelial lesions in Venezuela.

The polymerase chain reaction (PCR) was applied to the detection of human papillomavirus (HPV) infection in biopsies taken from clinically normal oral mucosa of 20 subjects and clinical lesions of 40 patients. PCR for HPV-DNA amplification was performed using consensus primers MYO9/MYO11 and subsequent typing for HPV of high and low oncogenic risk HPV types were identified by restriction enzyme analysis (restriction fragment length polymorphism, RFLP). The HPV viral genome was present in 55% (22/40) of the oral benign lesions (OBL) and in 10% (2/20) of the control samples. In the PCR+ OBL, we observed 90.9% of low oncogenic risk types (HPV-6 -13 and -32) and 9.1% of the samples had a mixed infection with low and high oncogenic types (HPV-6 and -16). In the control samples, we observed one patient with HPV-6 and another with HPV-6 and -16 in the same sample. All of the eight focal epithelial hyperplasia cases were positive for low risk HPV types (88% HPV-13 and 12.5% HPV-32). In conclusion, this study demonstrates a high incidence of HPV in oral benign lesions from Venezuelan patients.

Adolescent↗
PubMed2001

Poststreptococcal reactive arthritis in adults: long-term follow-up.

BACKGROUND: Poststreptococcal reactive arthritis (PSReA) is a recognized inflammatory articular syndrome that follows group A streptococcal infection in persons not fulfilling the Jones criteria for the diagnosis of acute rheumatic fever. Characteristic features include nonmigratory arthritis, lack of response to aspirin or nonsteroidal anti-inflammatory agents, and the presence of extra-articular manifestations, including vasculitis and glomerulonephritis. Whether or not patients with PSReA develop carditis is a point of contention. METHODS: We analyzed the clinical features, laboratory findings, response to therapy, and outcome in patients diagnosed with PSReA between 1983 and 1998 and observed through April 2000. All patients were contacted, reexamined, and repeat antistreptolysin, rheumatoid factor, C3 and C4 complement components, and echocardiograms were performed. RESULTS: Seventeen patients (4 men and 13 women) were included. All were of low socioeconomic status. All patients had acute severe arthritis that began shortly after a sore throat episode. Extra-articular involvement including tenosynovitis, vasculitis, and glomerulonephritis was relatively common. More importantly, none exhibited clinical and/or echocardiographic evidence of cardiac involvement. Longterm antibiotic therapy was not given. CONCLUSION: Cardiac involvement did not occur in this group of patients with PSReA. Prolonged prophylactic antibiotic therapy may not be required for adult patients presenting with PSReA.

Adolescent↗
PubMed2000

Temporal lobe focal cortical dysplasia: MRI imaging using FLAIR shows lesions consistent with neoplasia.

Focal cortical dysplasia (FCD), a form of neuronal migration disorder, is a malformative lesion of the neocortex that occurs during development of the brain. It can cause partial and generalized epilepsy. Seizures occur at an early age and are often resistant to medication. Surgical resection has been found to be beneficial in these patients. Dual pathology, in the form of mesial temporal sclerosis, has been associated with FCD. At the Children's Hospital of Eastern Ontario, four patients with temporal lobe FCD have recently, been identified. This paper discusses how these children presented and how they were managed, with particular emphasis on their MRI findings and differential diagnoses. In three of the four patients neuroimaging studies showed lesions consistent with a neoplastic process because of the large volume and mass effect. Radiologically, FCD may mimic the MRI appearance of tumors, such as dysembryoplastic neuroepithelial tumors, primitive neuroectodermal tumors, gangliogliomas, oligodendrogliomas, and astrocytomas. These lesions are best visualized on fluid-attenuated inversion recovery (FLAIR) imaging, a technique that has recently become applicable in the clinical setting, as we help demonstrate in this series. With better MRI capability, milder forms of FCD and microdysplasia may be distinguished.

Brain Diseases↗
PubMed2000

Increased phosphoinositide 3-kinase activity induces a lymphoproliferative disorder and contributes to tumor generation in vivo.

Alterations in the cell division:cell death ratio induce multiple autoimmune and transformation processes. Phosphoinositide 3-kinase (PI3K) controls cell division and cell death in vitro, but its effect on the function of the cellular immune system and on tumor formation in mammals is poorly characterized. Here we show that transgenic mice expressing in T lymphocytes an active form of PI3K derived from a thymic lymphoma, p65(PI3K), developed an infiltrating lymphoproliferative disorder and autoimmune renal disease with an increased number of T lymphocytes exhibiting a memory phenotype and reduced apoptosis. This pathology was strikingly similar to that described in mice exhibiting heterozygous loss of the tumor suppressor PTEN, a lipid and protein phosphatase. We show that overexpression of PTEN selectively blocks p65(PI3K)-induced 3T3 fibroblast transformation. Moreover, the early development of T cell lymphomas in p65(PI3K) Tg p53(-/-) mice indicated that PI3K contributes to tumor development. These observations demonstrate that constitutive activation of PI3K extends T cell survival in vivo, affects T cell homeostasis, and contributes to tumor generation, supporting a model in which selective increases in one type of PTEN substrate, the PI3K-derived lipid products, induce tumorigenesis. PI3K thus emerges as a potential target in autoimmune disease and cancer therapy.

Animals↗
PubMed2000

Determination of the velocity associated with VO2max.

PURPOSE: The theoretical velocity associated with VO2max (vVO2max) defined by Daniels (1985) is extrapolated from the submaximal VO2-velocity relationship. VO2 is generally determined by assuming that the aerobic response reacts like a linear first-order system at the beginning of square-wave exercise with a steady-state reached by the 4th minute. However, at supra-ventilatory threshold work rates, the steady state in VO2 is delayed or not attained. METHODS: The present study was carried out to compare three values for vVO2max determined with Daniels' method, but with VO2 either measured at the 4th minute (vVO2max4), the 6th minute (vVO2max6), or after the attainment of the true steady-state (vVO2maxSS). The metabolic response during square-wave exercise at each of the three vVO2max were also assessed. RESULTS: These velocities were significantly different (P < 0.05), but vVOmaxSS and vVO2max6 were highly correlated (r = 0.98; P < 0.05). Blood lactate concentrations measured after exercise at velocities very close to the three vVO2max were similar and the end-exercise VO2 were not different from VO2max, but the time required to elicit 95% VO2max during these three square-wave tests were significantly different. CONCLUSION: Therefore, when vVO2max is determined by extrapolation from the submaximal VO2-velocity relationships, submaximal VO2 should be measured beyond the 6th minute of square-wave exercise (at least if it takes 30 s to reach the desired velocity) to ensure that all vVO2max reported in future studies describe a similar quantitative index.

Adult↗
PubMed2000

Use of bioelectrical impedance analysis to estimate body fluid compartments after acute variations of the body hydration level.

Physiological measurements including body mass, plasma osmolality, natremia, plasma volume measured by Evans Blue dilution, and total body water (TBW) and extracellular water (ECW) volumes estimated by bioelectrical impedance analysis (BIA) were recorded in eight healthy young Caucasian subjects before and after acute variations of their body hydration state on four separate occasions: 1) euhydration or control trial (C); 2) heat-induced dehydration of 2.8% body mass (D); 3) exercise-induced dehydration of 2.8% body mass (E); and 4) glycerol-hyperhydration (H). Heart rate, rectal and mean skin temperatures were also recorded throughout the experiment. The main result of the study is that BIA only half predicted the body water loss after exercise, although conditions were standardized (electrode placement, side of the body, limb position, posture, and ambient temperature). Differences in body temperatures cannot explain such an unexpected result, nor did the study of plasma osmolality and sodium concentration. If BIA appears to adequately predict changes in TBW after heat-induced dehydration and glycerol hyperhydration, further studies including measures of TBW and ECW by dilution tracer methods would be necessary to establish the validity of using the BIA method to measure such changes and to interpret ECW variations.

Adult↗