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Biomedical subjects

A Lopez

Publications and source records attributed to A Lopez.

At least 91 records · Page 5Linked to original sources
PubMed1999

Autocrine production and action of IL-3 and granulocyte colony-stimulating factor in chronic myeloid leukemia.

Primitive subsets of leukemic cells isolated by using fluorescence-activated cell sorting from patients with newly diagnosed Ph(+)/BCR-ABL(+) chronic myeloid leukemia display an abnormal ability to proliferate in vitro in the absence of added growth factors. We now show from analyses of growth-factor gene expression, protein production, and antibody inhibition studies that this deregulated growth can be explained, at least in part, by a novel differentiation-controlled autocrine mechanism. This mechanism involves the consistent and selective activation of IL-3 and granulocyte colony-stimulating factor (G-CSF) production and a stimulation of STAT5 phosphorylation in CD34(+) leukemic cells. When these cells differentiate into CD34(-) cells in vivo, IL-3 and G-CSF production declines, and the cells concomitantly lose their capacity for autonomous growth in vitro despite their continued expression of BCR-ABL. Based on previous studies of normal cells, excessive exposure of the most primitive chronic myeloid leukemia cells to IL-3 and G-CSF through an autocrine mechanism could explain their paradoxically decreased self-renewal in vitro and slow accumulation in vivo, in spite of an increased cycling activity and selective expansion of later compartments.

Base Sequence↗
PubMed1999

Enumeration of CD4(+) T-cells in the peripheral blood of HIV-infected patients: an interlaboratory study of the FACSCount system.

The aim of the present study was to assess the interlaboratory reproducibility of the FACSCount system for the enumeration of peripheral blood (PB) CD4(+) T-cells. In each of the seven participating centers, both previously stained and unstained PB samples (n = 49) were received and either analyzed or stained and then analyzed. Interlaboratory reproducibility was checked in two different groups of centers (n = 3 and n = 4) where the study was performed in parallel. In addition, both the intralaboratory precision and accuracy of this system were analyzed in comparison with results obtained with conventional flow cytometry. Accordingly, upon comparing both methods, a high degree of correlation was observed in the total number of CD3(+) T-cells (coefficient of correlation of 0.9750 +/- 0.0184, slope of the best linear fit: 0. 9214 +/- 0.0311, y-intercept of 12 +/- 47) as well as in the number of CD3(+)/CD4(+) (coefficient of correlation of 0.9794 +/- 0.1457, slope of the best linear fit: 0.9463 +/- 0.0753, y-intercept of -11 +/- 36) and CD3(+)/CD8(+) (coefficient of correlation of 0.9728 +/- 0.0192, slope of the best linear fit: 0.9682 +/- 0.0735, y-intercept of 7 +/- 95) major subsets. In addition, low coefficients of variation (CV) were obtained for replicates, indicating the method's high degree of accuracy. The present study shows that with respect to the interlaboratory reproducibility reported for most techniques used for the enumeration of PB CD4(+) T-cells, the FACSCount system results in data with much lower coefficients of variance (CVs) (mean CV of less than 10%). Upon measuring the impact on results of different variables associated with either sample preparation or data acquisition and analysis, our study clearly shows that data acquisition and analysis does not influence the results by increasing variability since the coefficients of variation obtained for samples prepared in the same laboratory under the same conditions and read in different laboratories with different instruments were identical to those obtained for the replicates of the same samples read in each individual center. In contrast, interlaboratory variability, although low, significantly increased when sample preparation was carried out in different laboratories, suggesting that pipetting still represents the major source of variability in the FACSCount system.

CD4 Lymphocyte Count↗
PubMed1999

The transmembrane protein bacterioopsin affects the polarity of the hydrophobic core of the host lipid bilayer.

Influence of the transmembrane protein bacterioopsin (the retinal-free form of bacteriorhodopsin) on the polarity of egg-phosphatidylcholine bilayers was studied by means of a steady-state and time-resolved fluorescence approach exploiting the solvatochromic properties of the 2-anthroyl fluorophore. Introduced in phosphatidylcholine molecules in the form of 8-(2-anthroyl)octanoic acid, this fluorophore probed the hydrocarbon core of the lipid bilayer. As previously shown (E. Pérochon et al., Biochemistry 31 (1992) 7672-7682), water molecules were detected in this region of the terminal part of the lipid acyl chains. Their number was considerably reduced upon addition of bacterioopsin to the lipids. This was assessed by a blue shift in the fluorescence emission spectra of the probe and a marked decrease in the fractional population of fluorophores interacting with water, to the benefit of those experiencing a hydrophobic environment. In agreement with current theories, this decrease in the hydration of the bilayer may be linked to an increase in the acyl chain order and a decrease in the lateral diffusion coefficient of lipids near the protein. The data obtained at high protein concentration accounts for a protein/lipid interface which is much less hydrated than the hydrophobic core of a protein-free lipid bilayer.

Bacteriorhodopsins↗
PubMed1999

Organization and dynamics of the proteolipid complexes formed by annexin V and lipids in planar supported lipid bilayers.

The consequences of the binding of annexin V on its lateral mobility and that of lipids were investigated by means of experimental and simulated FRAP experiments. Experiments were carried out on planar supported bilayers (PC/PS 9:1 mol/mol mixtures) in the presence of 1 mM CaCl2 in the subphase. The probes C12-NBD-PS and fluorescein-labeled annexin V were used and the data compared with that previously obtained for C12-NBD-PC [Saurel, O., Cézanne, L., Milon, A., Tocanne, J. F., & Demange, P. (1998) Biochemistry 37, 1403-1410]. At complete coverage of the lipid bilayer by the protein (Cannexin = 80 nM), the lateral mobility of C12-NBD-PC was reduced by 40% while C12-NBD-PS and bound annexin V molecules were nearly immobilized (D < 10(-)11 cm2/s). At moderate protein concentration (20 nM < Cannexin < 80 nM), best fitting of the lipid and protein probe recoveries was achieved with one single diffusion coefficient and a mobile fraction close to 100%, indicating homogeneous lipid and protein populations. In contrast, at low protein concentration (Cannexin < 20 nM), C12-NBD-PS showed a two-component diffusion. The slow PS population at Cannexin < 20 nM and the single PS population at Cannexin > 20 nM moved at the same rate that bound annexin V (mobile fraction close to 100%), indicating strong PS/protein interactions. With the aid of computer simulations of the lateral motion of PC molecules, based on the 2-D crystalline networks formed by annexin V in contact with the lipid bilayer, these FRAP results may be accounted for by considering a rather simple model of a proteolipidic complex consisting of an extended 2-D crystalline protein network facing the lipid bilayer and stabilized by strong interactions between annexin V and PS molecules. In this model, immobilization of annexin V and PS molecules originates from their mutual interactions. The slowing down of PC molecules is due to various obstacles to their lateral diffusion which can be described as: the four PS molecules bound to the protein, the tryptophan 187 which presumably interacts with the lipids at the level of their polar headgroups and probably the three other hydrophobic amino acid residues located on the AB calcium-binding loops of the protein.

Animals↗
PubMed1999

Isolation and Characterization of Twelve Microsatellite Loci for Rockfish (Sebastes).

: We describe the first microsatellites for rockfishes in the diverse genus Sebastes. Clones containing microsatellites were isolated from the genomic library of a quillback rockfish, Sebastes maliger. Twelve microsatellites are characterized; six of these are polymorphic in quillback rockfish, and eight are polymorphic in at least one rockfish species on which they were tested. The number of alleles per variable locus ranged from 4 to 15 and averaged 6.8. The expected heterozygosities ranged from 0.38 to 0.79 and averaged 0.60 in these loci. These loci should prove valuable in studies examining species identification, population genetics, hybridization, paternity, kinship, and microsatellite evolution.

Journal Article↗
PubMed1999

Malleus ankylosis: a clinical, audiometric, histologic, and surgical study of 123 cases.

OBJECTIVE: Malleus ankylosis is a cause of conductive hearing loss that can be difficult to assess, particularly in association with otosclerotic stapes fixation. The aim of this study is to seek the clinical and audiometrical features unique to this pathology. STUDY DESIGN: The study design was a review of malleus ankylosis cases and an analysis of functional results after ossiculoplasty. SETTING: The study was performed at Jean Causse Clinic in France. PATIENTS: The authors reviewed a series of 123 ears in 112 patients who underwent surgery for incudo-mallear ankylosis from January 1991 to September 1997. INTERVENTION: The surgical technique depends on the type of pathology encountered. In case of associated stapedial fixation, a stapedotomy with vein graft interposition and reconstruction with a total prosthesis will be performed during a same step. MAIN OUTCOME MEASURES: Clinical evaluation, preoperative and postoperative audiometrical evaluation, operative findings, histologic examination, and postoperative functional results. RESULTS: In our series, a postoperative air-bone gap smaller than 10 dB was obtained in 77% of cases. These results confirm the possibility of managing both pathologies in a single surgical step. CONCLUSION: Incudo-mallear ankylosis remains an unusual pathology but should be systematically assessed during surgery and preferably after separation of the incudo-stapedial joint. A preoperative diagnosis is difficult to ascertain; some audiometrical features allow a suspicion. In this series, it is shown that otosclerosis can be responsible for ankylosis as seems to be confirmed by the two cases presented in this study.

Adolescent↗
PubMed1998

Effect of age and dietary restriction on expression of heat shock protein 70 in rat alveolar macrophages.

Dietary restriction (DR) is the only effective experimental manipulation known to retard aging in rodents, and this manipulation has been shown to alter a variety of processes that change with age. However, there is no information on the effect of DR on macrophage Function. In the present study, the effect of aging and DR on the ability of alveolar macrophages (AMs) to express the heat shock gene, hsp70 was studied. AMs were isolated by lavage from the lungs of young (4-6 months) and old (24-26 months) rats fed either ad libitum (AL) or a restricted diet (60% of AL). There was no age-related change in the number of cells recovered from young and old rats fed AL. However, the number of cells recovered from the lungs of the DR rats was reduced, and this decrease was statistically significant in young rats. The expression of heat shock protein 70 (hsp70) was measured by the level of the hsp70 mRNA transcript in total RNA isolated from AMs cultured under two conditions: in suspension and after adherence to plastic. When AMs were incubated at 37 degrees C in suspension, no detectable hsp70 expression was observed; however, hsp70 expression was induced at 37 degrees C when the AMs adhered to the plastic culture dishes. Hsp70 mRNA levels were rapidly induced by heat shock (43 degrees C, 1 h) in AMs cultured both in suspension and on plastic. The induction of hsp70 expression did not change significantly with either age or DR in AMs cultured in suspension. In contrast, the induction of hsp70 mRNA levels by AMs adherent to plastic culture plates decreased approximately 70% with age, and hsp70 induction was greater in AMs isolated from DR rats; this difference was statistically significant in young rats. The induction of hsp70 by heat shock (43 degrees C, 1 h) also decreased with age in the adherent AMs, and DR increased the induction of hsp70 expression three- to fourfold in adherent AMs from both young and old rats.

Aging↗
PubMed1998

Fracture of coronary guidewire during rotational atherectomy with coronary perforation and tamponade.

We present the case of a calcified right coronary artery lesion with a 90-degree exit angle. Attempts at rotational atherectomy led to wire transection and vessel wall perforation necessitating emergent pericardiocentesis and bypass surgery. We review the literature on complications of rotational atherectomy and the management of coronary perforations and retained guidewire fragments.

Atherectomy, Coronary↗
PubMed1998

Evaluation of the toxicity of guarana with in vitro bioassays.

A natural stimulant, Paullinia cupana, commonly called guarana, was tested for its ability to induce in vitro toxicity in Chinese hamster ovary (CHO) cells and bacterial cells (Photobacterium phosphoreum). The cytotoxic effects of aqueous guarana extracts were evaluated by three endpoint systems: neutral red (NR) uptake assay, total protein content [kenacid blue (KB)] assay, and tetrazolium (MTT) assay. The Microtox test was also used. Results indicated that the lowest concentration of guarana tested was not toxic and that the IC50 values calculated with the NR, KB, and MTT assays were lower than the highest concentration tested (40 mg/ml). There was no significant difference in cytotoxicity between the three test systems. The EC50 values obtained with the Microtox assay were consistent with these data. The present in vitro analysis suggests that the concentration of guarana is of critical importance in its cytotoxic activity and high doses could be harmful to human health.

Animals↗
PubMed1998

Characterization of membrane domains by FRAP experiments at variable observation areas.

In this paper we show that FRAP experiments at variable beam radii provide an experimental approach for investigating membrane organization and dynamics, with great potential for identifying micrometer-sized domains and determining their size and the diffusion coefficient of the lipid and protein molecules they contain. Monte Carlo simulations of FRAP experiments at variable beam radii R on models of compartmentalized membranes have allowed us to establish the relationships (i) between the mobile fraction M of a diffusing particle and the size r of the domains, and (ii) between the apparent diffusion coefficient Dapp and the real diffusion coefficient DO of this particle inside the domains. Furthermore, in its present stage of development, this approach allows us to specify whether these domains are strictly closed or not. This approach was first validated on an experimental model of a strictly compartmentalized membrane consisting of a monolayer of apposed spherical phospholipid bilayers supported by silica beads of known radius (0.83 micron). To prevent fusion between the spherical bilayers 5 mol% of a polymer-grafted phospholipid was added to the lipids. Analysis of the M versus R data yielded a radius r of 0.92 +/- 0.09 microns for the spherical bilayers, close to that of the supporting silica beads. When applied to the experimental data available for lipids and proteins in the plasma membrane of living cells, this approach suggests the existence of domains within these membranes with a radius of about 0.4-0.7 microns for the lipids and 0.25 micron for the proteins. These domains are not strictly closed and they are believed to be delineated by fluctuating barriers which are more or less permeable to lipid and protein molecules.

Animals↗
PubMed1998

Prolonged pneumoperitoneum at 15 mmHg causes lactic acidosis.

BACKGROUND: Acute increases in intraabdominal pressure (IAP) induce systemic and regional circulatory changes. Besides, mechanical compression on the capillary beds may decrease oxygen availability to the tissues. The purpose of this clinical study was to analyze the effects of increased IAP on acid-base disturbances and plasma lactate levels during prolonged carbon dioxide pneumoperitoneum. METHODS: Twenty-eight patients undergoing laparoscopic sigmoidectomy were included in this study. Fourteen of them (group A) had IAP of 15 +/- 1 mmHg while the remaining 14 (group B) had IAP of 10 +/- 1 mmHg. The control group included six patients undergoing conventional sigmoidectomy. RESULTS: A progressive significant increase in PaCO2 was observed in the laparoscopic groups (p < 0.01). Plasma lactate levels in group A significantly increased 90 min after insufflation (p < 0.05) and reached the highest value 1 h after deflation (9.9 +/- 1 vs 31.9 +/- 2.5 mg/dl, p < 0.005). Simultaneously, arterial pH decreased in all groups; however, at 1 h after surgery, it was significantly lower (p = 0.02) in group A. There was a significant correlation between acid concentration due to lactate and lactate concentration (GA: R2 = 0.717, p = 0.03; GB: R2 = 0.879, p = 0.006 and GC: R2 = 0.853, p = 0.008). CONCLUSION: High IAP causes lactic acidic accumulation in patients undergoing prolonged laparoscopic procedures.

Acidosis, Lactic↗
PubMed1998

Surgical treatment for neuroblastoma: complications during 15 years' experience.

BACKGROUND/PURPOSE: Surgery plays an important role in neuroblastoma treatment. Although influence of resectability in survival has been studied deeply, reports about surgical complications are scant. The authors analyze retrospectively their experience in neuroblastomas (NB) diagnosed from 1980 to 1995. METHODS: Clinical variables such as age, stage, location, presurgical chemotherapy, type, and extent of surgery were studied. Complications were classified according to the following criteria: time, type of surgery, and extent of resection. RESULTS: Seventy-eight NB patients had surgery performed in our hospital. Mean age at diagnosis was 2.4 years (range, 0 to 11 years); 33 patients were under 1 year of age. Sixty-eight percent of the patients had advanced disease. Abdominal tumors were predominant. Sixty-three percent of the patients had chemotherapy before surgery, with shrinkage of the tumor in most of the cases (88%). Eighty-six surgical procedures were performed, 29 initially and 57 delayed. Complete resection was reached in 52 patients, partial in 19 patients, and seven patients underwent biopsy only. There were 42 surgical complications. Three of them were considered extremely serious (one death caused by cardiac arrest, one tumoral rupture, and one great vessel injury). Nephrectomies (n = 12) were the most frequent intraoperatory complications. Bernard-Horner syndrome (n = 5) and pleural effusions (n = 5) predominated in the postoperative period. CONCLUSIONS: (1) Surgery in NB can be performed safely. (2) Nephrectomies can be necessary to achieve complete resection in some abdominal tumors. (3) Nephrectomies, Bernard-Horner syndrome, and pleural effusions were the most frequent complications in our patients. (4) Presurgical chemotherapy can lead to a wider and safer removal of locally advanced tumors.

Adrenal Gland Neoplasms↗
PubMed1998

Rectal drainage: unusual evolution of a psoas abscess.

We report two cases of primary psoas abscess in two patients of 15 months and 4 years of age. As the first case showed the natural history of this process the second one was large enough to produce a huge ureterohydronephrosis and to drain through the rectal wall to the rectum spontaneously, although this natural way did not achieve complete drainage. Both were treated by open drainage and systemic antibiotics with good response. They were discharged at the 7th and 12th postoperative day. 5 months later no complication has come up. Etiological, clinical and therapeutic aspects of this unusual pathology are reviewed.

Child, Preschool↗
PubMed1998

Comparison of black fly species (Diptera: Simuliidae) on an Amerindian reservation with a high prevalence of fogo selvagem to neighboring disease-free sites in the State of Mato Grosso do Sul, Brazil. The Cooperative Group on Fogo Selvagem Research.

Fogo selvagem is an autoimmune blistering skin disease that principally occurs among rural Brazilians living in geographically clumped disease foci. Exposure to hematophagous black flies possibly is related to the cause of the disease. We compared the occurrence, proportions, and richness of simuliid species immatures and the biting activity of adult females within a recently discovered, high prevalence focus of fogo selvagem, the Limão Verde Terena Reservation, to that of neighboring regions with no reported cases of fogo selvagem. Nine black fly species were collected from 12 stream sites during 5 trips to the fogo selvagem focus. The species showed longitudinal (upstream-downstream) trends in occurrence, proportions, and richness, and the abundance of simuliid immatures was greater at downstream sites. The most prevalent species at the focus, Simulium nigrimanum (Macquart), dominated the stream sites with highly abundant simuliid assemblages, and was the most common black fly in human bait collections. This species was absent or in very low numbers in neighboring valleys and villages that did not have cases of fogo selvagem.

Animals↗
PubMed1998

DNA aneuploidy by flow cytometry is an independent prognostic factor in gastric cancer.

In the present study the prognostic value of both DNA ploidy and the proliferative activity of tumour cells were studied in a series of 76 consecutive patients suffering from gastric tumours. DNA ploidy and the proliferative index (as measured by the percentage of S-phase cells) were determined by flow cytometry using fresh tumour specimens. The presence of DNA aneuploid clones by flow cytometry was detected in 62% of the cases (mean DNA index of 1.63 +/- 0.46; range 1.08-2.92), the mean proportion of S-phase cells being of 18.4 +/- 11.5%. In comparison with diploid cases, aneuploid tumours showed a higher proliferative activity (cases with more than 15% S-phase cells: 18.4% versus 6.1%, p = 0.0001) as well as a higher incidence of node involvement (95% versus 68%, p = 0.001). By contrast, no significant differences were detected with respect to sex, age, histologic grade and type, clinical stage, tumour size and the incidence of extranodal involvement. Upon grouping the patients according to the proportion of S-phase cells no significant differences were observed for the clinical and biological parameters explored except for an association between a high percentage of S-phase cells and the presence of DNA aneuploidy (40% versus 96%, p = 0.0001). Regarding survival the presence of DNA aneuploidy was significantly associated with poor outcome as compared to the diploid cases (median of 15 versus 26 months, p = 0.005). By contrast, the proportion of S-phase cells did not predict patients's outcome. Multivariate analysis of prognostic factors showed that the presence of DNA aneuploidy (p = 0.003) together with the histologic type (p = 0.03) and the existence of extranodal metastases (p = 0.05) were the best combination of prognostic factors for survival prediction.

Aged↗