Biomedical subjects

C Lopez

Publications and source records attributed to C Lopez.

At least 37 records · Page 2Linked to original sources

PubMed2001

Thermal and structural behavior of milk fat. 1. Unstable species of anhydrous milk fat.

The thermal and structural behavior of anhydrous milk fat (AMF) was studied by a technique that allowed simultaneous time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC) to be carried out in the same apparatus from the same sample. In this paper (the first of a series), the less stable crystalline structures made by triacylglycerols (TG) of bulk AMF after its liquid quenching down to -8 degrees C are addressed The coexistence of two lamellar structures characterized by sharp long spacing reflections corresponding to well-defined 3L (70 A) and 2L (47 A) longitudinal stackings but broad short spacing lines related to poorly ordered hexagonal (alpha) lateral packing is shown for the first time, The bilayered structure was very unstable, since it disappeared during a 20-min isothermal recording. Simultaneous DSC and X-ray monitoring of AMF heating in the range -8, +50 degrees C at a rate of 2 degrees C/min allows the same sample to be followed on the evolution of these unstable forms to more stable varieties. The 3L stacking transforms into a new 2L crystalline structure characterized by broad LS reflections corresponding to a ill-defined 2L (37 A) longitudinal stacking but a more compact orthorhombic (beta') lateral packing. A delimitation of the domains of existence of the crystalline structures resulted from the comparison of detailed analysis of the evolutions of positions, intensities, and widths of X-ray peaks as a function of temperature to microcalorimetry recording.

Animals↗

PubMed2001

Thermal and structural behavior of anhydrous milk fat. 2. Crystalline forms obtained by slow cooling.

The crystallization behavior of milk fat has been examined on slow cooling at 0.1 degrees C/min from 50 to -15 degrees C, to determine the variations of triacylglycerol organizations as a function of temperature. The experiments have been conducted with an instrument allowing coupled X-ray diffraction (XRD) at both small and wide angles and high-sensitivity differential scanning calorimetry (DSC) recordings from the same sample by taking advantage of the high-energy flux of a synchrotron. On slow cooling, milk fat triacylglycerols sequentially crystallize in four different lamellar structures with double-chain length of 41.5, 48.3, and 39.2 A and a triple-chain length of 62.2 A stackings. Simultaneous wide-angle XRD has shown that initial nucleation occurs in a packing of beta' type at about 24 degrees C. For temperature < 13 degrees C, triacylglycerols crystallize in an hexagonal subcell of alpha type, leading to the coexistence of the beta' + alpha polymorphic forms, which is recorded until -15 degrees C. Thermal analysis allowed to correlate the formation of the different crystalline species monitored by XRDT (XRD as a function of temperature) to the exothermal events recorded simultaneously by differential scanning calorimetry. The evolution of the species formed during crystallization was also monitored on heating at 2 degrees C/min. The absence of polymorphic evolution on heating, as well as the high final melting point observed, about 40 to 41 degrees C, confirmed that cooling at 0.1 degrees C/min leads to quasi equilibrium.

Animals↗

PubMed2001

Dietary intake of calcium, magnesium and phosphorus in an elderly population using duplicate diet sampling vs food composition tables.

The aim of this study was to estimate the dietary intake of calcium, magnesium and phosphorus in the elderly institutionalised population using duplicate diet sampling and to establish any related difference with the results obtained using food composition tables. The study was carried out on a sample group of 112 subjects in Granada (Spain). 1-week food duplicate samples offered by the elderly were studied. Calcium and magnesium were determined by AAS and phosphorus was determined by spectrophotometry. Anova showed significant differences (p<0.05) in all the minerals analyzed. These results suggest that the use of food composition tables is not suitable to evaluate the calcium, magnesium and phosphorus in nutritional trials. Moreover, the results show clearly that it is essential to consider these differences to establish the adequate intakes of calcium, magnesium and phosphorus for the elderly population in relation to the mineral bone status.

Aged↗

PubMed2000

An association study of bipolar mood disorder (type I) with the 5-HTTLPR serotonin transporter polymorphism in a human population isolate from Colombia.

The short variant of a functional length polymorphism in the promoter region of the serotonin transporter has been associated with several behavioural and psychiatric traits, including bipolar mood disorder. The same short allele has also been implicated as a modifier of the bipolar phenotype. Here we evaluate the etiologic/modifier role of this polymorphism in a case (N=103) / control (N=112) sample for bipolar mood disorder (type I) collected from an isolated South American population. We did not detect an association between bipolar disorder and the 5-HTT promoter polymorphism in this sample. However, an excess of the short allele was seen in younger cases and in cases with psychotic symptoms. When combined with data from the literature, the increased frequency of the short allele in patients with psychotic symptoms was statistically significant.

Age of Onset↗

PubMed2000

Thermal and Structural Behavior of Milk Fat.

The thermal and structural properties of unstable varieties of triacylglycerols (TGs) crystallizing in milk fat globules of cream are examined in the range -8- +50 degrees C using a new instrument allowing simultaneously time-resolved synchrotron X-ray diffraction at both wide and small angles as a function of temperature (XRDT) and high sensitivity differential scanning calorimetry (DSC). Small angle X-ray diffraction shows that the unstable alpha form first formed by cream quenching to -8 degrees C corresponds in fact to two different lamellar phases corresponding to 2L (47 Å) and 3L (70.4 Å) arrangements of TGs. The bilayered structure is very unstable since it disappears during the course of a 20-min isothermal conditioning at -8 degrees C. On fast heating, the crystalline evolution of cream TGs demonstrates the monotropic character of their polymorphism. The structural and thermal behaviors of cream which are compared to that of its anhydrous milk fat isolated from the cream (C. Lopez et al., J. Dairy Sci., submitted) show that the crystallization occurring in emulsion droplets is similar to bulk. However, the comparison of XRD peak widths indicates that the TG crystallization is more disordered in emulsion. This disorder is attributed to the constraints due to the interface curvature in emulsion droplets. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Large-scale synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.5 micrometres

Photonic technology, using light instead of electrons as the information carrier, is increasingly replacing electronics in communication and information management systems. Microscopic light manipulation, for this purpose, is achievable through photonic bandgap materials, a special class of photonic crystals in which three-dimensional, periodic dielectric constant variations controllably prohibit electromagnetic propagation throughout a specified frequency band. This can result in the localization of photons, thus providing a mechanism for controlling and inhibiting spontaneous light emission that can be exploited for photonic device fabrication. In fact, carefully engineered line defects could act as waveguides connecting photonic devices in all-optical microchips, and infiltration of the photonic material with suitable liquid crystals might produce photonic bandgap structures (and hence light-flow patterns) fully tunable by an externally applied voltage. However, the realization of this technology requires a strategy for the efficient synthesis of high-quality, large-scale photonic crystals with photonic bandgaps at micrometre and sub-micrometre wavelengths, and with rationally designed line and point defects for optical circuitry. Here we describe single crystals of silicon inverse opal with a complete three-dimensional photonic bandgap centred on 1.46 microm, produced by growing silicon inside the voids of an opal template of dose-packed silica spheres that are connected by small 'necks' formed during sintering, followed by removal of the silica template. The synthesis method is simple and inexpensive, yielding photonic crystals of pure silicon that are easily integrated with existing silicon-based microelectronics.

Journal Article↗

PubMed2000

DNA dendrimers localize MyoD mRNA in presomitic tissues of the chick embryo.

MyoD expression is thought to be induced in somites in response to factors released by surrounding tissues; however, reverse transcription-PCR and cell culture analyses indicate that myogenic cells are present in the embryo before somite formation. Fluorescently labeled DNA dendrimers were used to identify MyoD expressing cells in presomitic tissues in vivo. Subpopulations of MyoD positive cells were found in the segmental plate, epiblast, mesoderm, and hypoblast. Directly after laying, the epiblast of the two layered embryo contained approximately 20 MyoD positive cells. These results demonstrate that dendrimers are precise and sensitive reagents for localizing low levels of mRNA in tissue sections and whole embryos, and that cells with myogenic potential are present in the embryo before the initiation of gastrulation.

Animals↗

PubMed2000

A study of the coregulation and tissue specificity of XG and MIC2 gene expression in eukaryotic cells.

CD99, the product of the MIC2 gene, exhibits an erythroid-specific quantitative polymorphism coregulated with the polymorphism of the XG blood group gene. As a preliminary study of this phenomenon, human XG and CD99 recombinant proteins were expressed in murine RAG cells and analyzed by flow cytometry. Both proteins were expressed independently and at a similar level in single and double transfectants. Immunoprecipitation and Western blot analysis, using the murine monoclonal antibodies NBL-1 and 12E7, revealed species of 26 kd (XG) and 32 kd (CD99), respectively. A putative 28-kd intracellular precursor of CD99 was also detected, as was a 26-kd species after neuraminidase treatment of CD99-expressing cells. No evidence of association or complex formation between XG and CD99 proteins could be proven, either on transfected RAG cells or on human erythrocytes. These results were confirmed using somatic hybrids between single transfectants. These findings suggest that the phenotypic relationship between XG and CD99 is mostly regulated at the transcriptional level, but they do not formally exclude some posttranscriptional effect. Studies on the tissue specificity of XG expression showed that surface expression of the XG protein could not be restored in somatic hybrids between B-lymphoblastoid cell lines from Xg(a+) persons and fibroblasts (RAG) or erythroid (MEL) cells. RT-PCR analysis of the transcripts revealed the existence of an XG mRNA in each cell line, suggesting that the tissue-specific regulation of cell surface XG expression occurs either at a quantitative transcriptional level or is a posttranscriptional event. By Northern blot analysis, XG transcripts were detected in erythroid tissues and several nonerythroid tissues. (Blood. 2000;95:1819-1826)

12E7 Antigen↗

PubMed2000

[Importance of medicolegal data for national cause of death statistics].

OBJECTIVE: The validity of French cause of death statistics largely depends on the transmission of the medical information reported on the dedicated part of the death certificate. Data referring to death causes are collected and analyzed at the Information Department on the cause of death (INSERM SC8). In major urban areas with one or more forensic institutions, it has been observed that the proportion of death certificates indicating ìno particular cause of deathî is higher than the national average. We therefore examined deaths occurring in 1996 in the Lyons region. METHODS: This retrospective study involved 5,208 deaths recorded in Lyons France in 1996. Complementary information on these deaths was obtained from INSERM SC8 and Lyons Medicolegal Institute. RESULTS: It was observed that a large portion of violent deaths occurring in this city in 1996 (more than 30%) were not recorded appropriately in the national statistics due to a lack of communication after autopsy. CONCLUSION: Considering the importance of epidemiology and suicide prevention in the national public health strategy, improved information transmission must be developed in the near future.

Accidents↗

PubMed2000

Quantitative analysis of XG blood group and CD99 antigens on human red cells.

CD99, the product of the MIC2 gene, exhibits an erythroid-specific quantitative polymorphism co-regulated with the Xga blood group polymorphism. The co-expression of X-linked MIC2 and XG genes is presumably controlled at the transcriptional level by a single XGR locus in the pseudoautosomal region of sexual chromosomes. This locus is composed of two alleles, XGR(low) and XGR(high), which determine low or high CD99 levels (CD99-L, CD99-H) and the Xg(a-)/ Xg(a+) status. To test this hypothesis, the phenotypic relationship between Xga and CD99 antigens on human RBCs was investigated by quantitative flow cytometry using NBL-1 (anti-Xga) and 12E7 (anti-CD99) monoclonal antibodies and semi-quantitative estimate of membrane proteins and RNA by Western blot and Northern blot, respectively. The antibody binding capacity of RBCs, which is an estimation of the antigen density, was determined for 118 blood donors including 60 males and 58 females. Xg(a+) RBCs, which all belong to the group of CD99-H expressors, carry 159+/-13 and 960+/-50 copies of Xga and CD99 molecules/cell, respectively. Xg(a-) RBCs have no Xga antigen, but are subdivided into CD99-H (all male) and CD99-L expressors carrying 747+/-28 and 200+/-22 CD99 copies/cell, respectively, with identical CD99 levels between CD99-L males and females. However, among males, the CD99 expression was higher in Xg(a+) than in Xg(a-)/CD99-H individuals (P<0.01). In addition, CD99-H expressors in Xg(a+) males could be clearly subdivided into two categories, high and super high expressors, which are presumably heterozygous and homozygous for the XGR(high) allele, which fits the above hypothesis. This was not the case for Xg(a+) females where CD99-H subcategories were not found. Quantitative differences were confirmed by Western blot analysis of red cell membrane preparations from individuals of different Xga and CD99 phenotypes and by Northern blot analysis showing that the reticulocytes from CD99-L individuals expressed a reduced level of MIC2 transcripts compared to CD99-H donors. These findings further support the hypothesis of a single genetic control of CD99 and Xga expression by the XGR locus.

12E7 Antigen↗

PubMed2000

Mesigyna once-a-month combined injectable contraceptive: experience in Latin America.

A phase III clinical study was carried out among 534 fertile Latin American women to evaluate cycle control, side effects, and contraceptive efficacy of a once-a-month combined injectable, Mesigyna, consisting of 50 mg norethisterone enanthate and 5 mg estradiol valerate. The pregnancy rate at 1 year was 0 per 100 woman-years for a total experience of 4688 woman-months. The overall discontinuation rate at one year was 17.9%. Discontinuation rate for bleeding problems was 5.1%. The Colombian women had a significant increase (p <0.001) in bleeding problems compared to other countries. The discontinuation rate for amenorrhea was 1.1%. There were no significant differences between the groups regarding discontinuation for other medical or non-medical reasons. Mean weight gain after one year of use was 1.02 kg. Mesigyna is an appropiate once-a-month injectable contraceptive for Latin American women since it is highly effective and its perception of normal menstrual bleeding is of importance in the Latin American population.

Adolescent↗

PubMed2000

Allogeneic peripheral blood cell transplantation for hypereosinophilic syndrome with myelofibrosis.

Patients with hypereosinophilic syndrome (HES) display a very heterogeneous clinical picture ranging from asymptomatic cases to very aggressive forms. We report a 38-year-old woman with progressive HES who developed severe myelofibrosis and was treated by allogeneic stem cell transplantation, using peripheral blood (PBSCT) instead of bone marrow as the source of progenitor cells, after conditioning with cytoxan and busulphan. To the best of our knowledge, this is the first case of HES with myelofibrosis treated with PBSCT. The patient remains alive 8 months post-PBSCT, and bone marrow fibrosis has significantly decreased following transplantation. Bone Marrow Transplantation (2000) 25, 217-218.

Adult↗

PubMed2000

Determination of sevoflurane alveolar concentration for tracheal intubation with remifentanil, and no muscle relaxant.

The sevoflurane alveolar concentration needed for tracheal intubation with remifentanil was studied in 26 adult patients premedicated with 100 mg hydroxyzine. Anaesthesia was induced with sevoflurane in oxygen. The concentration was determined by Dixon's up-and-down method. The first patient was tested at 4.5%. One minute after obtaining the preselected value, remifentanil 1 microg.kg-1 was injected for 60 s followed by an infusion of 0.25 microg.kg-1. min-1. Ventilation was then manually assisted for 2 min and tracheal intubation was attempted. Tracheal intubation conditions and responses to intubation were noted. Heart rate and mean arterial pressure were recorded before induction, before remifentanil injection, and before and 3 min after tracheal intubation. The concentration for acceptable intubating conditions was 2.5 +/- 0.7%. From logistic regression, ED50 and ED95 were 2.0% (95% CI 1.3-2.5) and 3.2% (95% CI 2.6-5.6), respectively. With sevoflurane 2.5%, heart rate and mean arterial pressure decreased by 18% and 15%, respectively, after remifentanil administration and increased slightly after tracheal intubation.

Adolescent↗

PubMed2000

Kikuchi-Fujimoto necrotizing lymphadenitis associated with cutaneous lupus erythematosus: a case report.

Histiocytic necrotizing lymphadenitis or Kikuchi-Fujimoto disease is a rare entity, and even more rarely, it is associated with other diseases. In a few cases, the condition is associated with cutaneous lupus erythematosus (CLE). Histiocytic necrotizing lymphadenitis predominantly affects young women, who present with solitary or multiple cervical lymphadenopathy accompanied by symptoms such as fever, weight loss, sweating, or, in exceptional cases, hepatosplenomegaly. Laboratory examinations show normal or nonspecific results. The disease is of unknown origin, although a viral origin has been suggested, with the suspected agents including Epstein-Barr virus, herpesvirus type 6, and cytomegalovirus (CMV). Although the first and most of the more recent cases have been reported in Oriental patients, the disease has a wide geographic distribution. The clinical evolution is favorable, with spontaneous remission in less than 4 months in almost all cases. We present a case of a 37-year-old woman from Peru who presented with cervical adenopathies on two occasions. Biopsy of a lymph node revealed a histopathologic picture compatible with Kikuchi-Fujimoto histiocytic necrotizing lymphadenitis. The adenopathy disappeared in a few months. A year later, she presented with a maculopapular rash in the nasal and malar regions. The results of the skin biopsy and immunofluorescence examination were compatible with chronic CLE. The results of the serology testing for CMV were positive. Treatment with chloroquine was initiated, with almost complete recovery by 5 months. No manifestations of systemic lupus erythematosus have occurred since. The epidemiologic, clinical, and anatomopathologic aspects as well as the differential diagnosis of this entity are reviewed.

Adult↗

PubMed2000

Multifractal structure of chaotically advected chemical fields

The structure of the concentration field of a decaying substance produced by chemical sources and advected by a smooth incompressible two-dimensional flow is investigated. We focus our attention on the nonuniformities of the Holder exponent of the resulting filamental chemical field. They appear most evidently in the case of open flows where irregularities of the field exhibit strong spatial intermittency as they are restricted to a fractal manifold. Nonuniformities of the Holder exponent of the chemical field in closed flows appears as a consequence of the nonuniform stretching of the fluid elements. We study how this affects the scaling exponents of the structure functions, displaying anomalous scaling, and relate the scaling exponents to the distribution of local Lyapunov exponents of the advection dynamics. Theoretical predictions are compared with numerical experiments.

Journal Article↗

PubMed2000

Bulk dynamics for interfacial growth models

We study the influence of the bulk dynamics of a growing cluster of particles on the properties of its interface. First, we define a general bulk growth model by means of a continuum Master equation for the evolution of the bulk density field. This general model just considers an arbitrary addition of particles (though it can be easily generalized to consider subtraction) with no other physical restriction. The corresponding Langevin equation for this bulk density field is derived where the influence of the bulk dynamics is explicitly shown. Finally, when a well-defined interface is assumed for the growing cluster, the Langevin equation for the height field of this interface for some particular bulk dynamics is written. In particular, we obtain the celebrated Kardar-Parisi-Zhang equation. A Monte Carlo simulation illustrates the theoretical results.

Journal Article↗

PubMed2000

[Diabetes and urination disorders].

Diabetic neuropathy of can induce multi-organ dysfunction. The diabetes simultaneously has profound repercussions on gastrointestinal, sexual and erectile functions. One of the main sequelae of diabetic neuropathy is autonomic neuropathy affecting the vesicosphincteric control. The objective of this study was to review the epidemiological, clinical, laboratory and therapeutic data concerning voiding disorders observed in diabetes. Although the therapeutic management of an isolated voiding disorder in diabetics still remains symptomatic, it raises aetiological problems due to the comorbidity, particularly prostatic obstructive syndromes in men, pelvic dysfunction in women and ageing. Diabetic patients in renal failure also present specific vesicosphincteric disorders which are reviewed. Diabetic patients should be more systematically screened for the development of diabetic bladder disease, especially for associated factors which participate in its clinical expression. This implies extreme caution in the management of benign prostatic hyperplasia in the case of comorbidity, to avoid deteriorating a sometimes fragile detrusor-sphincter equilibrium. Diabetic detrusor hyperactivity must be better known in order to be more effectively detected. Pharmacological treatment of this condition raises problems related to detrusor hypocontractility also related to diabetic bladder disease. Clinical examination should be able to select those patients requiring further urodynamic studies in order to assess the individual detrusor-sphincter equilibrium. These investigations are required when surgical treatment of an associated urological or gynaecological disorder is considered.

Diabetes Complications↗

PubMed2000

[Lower pole pedicle in a series of 84 pyelo-ureteral junction syndromes surgically treated in children].

OBJECTIVE: To evaluate the involvement and consequences of the lower pole pedicle (LPP) associated with ureteropelvic junction syndrome. MATERIAL AND METHOD: Retrospective study in 81 children presenting a total of 84 ureteropelvic junction syndromes operated consecutively between 1994 and 1998. Urinary tract ultrasound and cystography were systematically performed. Renal scintigraphy (DTPA or MAG 3) was performed in 80 children. Preoperative intravenous urography was performed in 60 children. LPP was considered to be present when its participation in the obstruction was confirmed intraoperatively (Anderson Hynes technique with uncrossing of the vascular pedicle). RESULTS: Group I: a LPP was revealed in 24 kidneys (28.5% of cases), 17 left kidneys and 7 right kidneys, in 14 boys and 10 girls, with a mean age of 4 years (range: 2 months-14 years). Group II: 60 kidneys without LPP (71.5% of cases), 32 left kidneys and 28 right kidneys, in 40 boys and 17 girls, with a mean age of 2 years (range: 1 month-15 years). The most frequent presenting complaint was recurrent low back pain in 58% of cases in group I (14/24) and 5% of cases in group II (3/60). The mean age at diagnosis was 6 years. Hydronephrosis was detected by antenatal ultrasound in 33% of cases in group I (8/24) and in 72% of cases in group II (43/60). Kidney function in group I was greater than 40% in 19 patients, between 20 and 39% in 2 patients and less than 20% in 2 patients. These results were not influenced by age at diagnosis and were not significantly different from those observed in group II. Renal malrotation was observed in 2 cases in group I and in 12 cases in group II. Histology of the junction revealed nonspecific fibrosis in the same percentage of cases (91%) in the two groups. The mean follow-up was 15 months (range: 2 months-5 years). No surgical failure was observed. CONCLUSION: Ureteropelvic junction syndrome associated with a LPP appears to present later with recurrent low back pain in older children. It does not worsen the functional prognosis of the affected kidney. LPP can be visualized by duplex ultrasound. It may act as an inducer of obstruction by aggravating a pre-existing abnormality of the ureteropelvic junction. When LPP is associated with isolated dilatation of the pyelocaliceal cavities, the risk of subsequent decompensation requires closer ultrasound surveillance, until puberty.

Adolescent↗