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Biomedical subjects

C Lopez

Publications and source records attributed to C Lopez.

At least 19 recordsLinked to original sources
PubMed1999

The extracellular domain of the human erythropoietin receptor: expression as a fusion protein in Escherichia coli, purification, and biological properties.

We developed an efficient production system of the soluble extracellular domain of the human erythropoietin receptor (sEPO-R) and characterized the binding of erythropoietin (EPO) with the purified recombinant protein. The sEPO-R, fused to the maltose binding protein (MBP), was expressed as a soluble protein in the periplasm of Escherichia coli (E. coli) and did not accumulate in inclusion bodies. After lysis of the bacteria by an osmotic shock, the fusion protein was purified by affinity chromatography on amylose followed by size exclusion chromatography (SEC). Specific binding of 125I-labelled EPO to the sEPO-R was demonstrated by competitive and saturation binding assays. A single affinity class (Kd = 0.25 nM) of the binding site was evident by Scatchard analysis. This value is similar to the Kd observed between EPO and the EPO-R of high affinity present on human erythroid progenitors. The complex has a molecular size corresponding to a 1:1 complex of EPO and the fusion protein.

ATP-Binding Cassette Transporters↗
PubMed1998

Heat-shock protein 90 (hsp90) binds in vitro to tubulin dimer and inhibits microtubule formation.

Hsp90 interacts with steroid hormone receptors, protein kinases, and cytoskeletal proteins. The mode of action of hsp90 on microtubules and tubulin has not been investigated. Using isolated purified hsp90 and isolated tubulin, we demonstrated in vitro by difference absorption and fluorescence spectroscopy that hsp90 bound to tubulin with an apparent affinity constant of 5 x 10(5) M-1, assuming an apparent stoichiometry of 1 at 25 degrees C. Using microcalorimetry, we found a delta H of -9.8 +/- 0.8 kJ.mol-1. The binding of hsp90 to tubulin was confirmed by a sedimentation assay. Moreover, we showed that hsp90 inhibited tubulin polymerisation.

Animals↗
PubMed1998

Thermodynamic analysis of calcium and magnesium binding to calmodulin.

To elucidate some aspects still debated concerning the interaction of Ca2+ and Mg2+ with CaM, the thermodynamic binding parameters of Ca2+-CaM and Mg2+-CaM complexes were characterized by flow dialysis and isothermal microcalorimetry under different experimental conditions. In particular, the enthalpy and entropy changes associated with Ca2+ and Mg2+ binding to their sites were determined, allowing a better understanding of the mechanism underlying cation-CaM interactions. Ca2+-CaM interaction follows an enthalpy-entropy compensation relationship, suggesting that CaM explores a subspace of isoenergetical conformations which is modified by Ca2+ binding. This Ca2+-induced change in CaM dynamics is proposed to play a key role in CaM function, i.e. in its interaction with and/or activation of target proteins. Furthermore, data show that Mg2+ does not act as a direct competitor for Ca2+ binding on the four main Ca2+ binding sites, but rather as an allosteric effector. This implies that the four main Mg2+ binding sites are distinct from the EF-hand Ca2+ binding sites. Finally, Ca2+ is shown to interact with auxiliary binding sites on CaM. These weak affinity sites were thermodynamically characterized. The results presented here challenge the current accepted view of CaM ion binding.

Binding Sites↗
PubMed1998

Antiviral activity and toxicity of fialuridine in the woodchuck model of hepatitis B virus infection.

Woodchucks were used to study the antiviral activity and toxicity of fialuridine (FIAU; 1,-2'deoxy-2'fluoro-1-beta-D-arabinofuranosyl-5-iodo-uracil). In an initial experiment, groups of six chronic woodchuck hepatitis virus (WHV) carrier woodchucks received daily doses of FIAU by intraperitoneal injection for 4 weeks. At 0.3 mg/kg/d, the antiviral effect was equivocal, but at 1.5 mg/kg/d, FIAU had significant antiviral activity. No evidence of drug toxicity was observed during the 4-week period of treatment or during posttreatment follow-up. In a second experiment, groups of nine WHV carriers or uninfected woodchucks were given 1.5 mg/kg/d of FIAU orally for 12 weeks, and the results compared with placebo-treated controls. After 4 weeks, the serum WHV-DNA concentration in the FIAU-treated carrier group was two to three logs lower than that in the placebo-treated group. After 12 weeks of FIAU treatment, serum WHV DNA was not detectable by conventional dot-blot analysis, hepatic WHV-DNA replicative intermediates (RI) had decreased 100-fold, and hepatic expression of WHV core antigen was remarkably decreased. No evidence of toxicity was observed after 4 weeks, but, after 6 to 7 weeks, food intake decreased and, after 8 weeks, the mean body weights of woodchucks treated with FIAU were significantly lower than controls. Anorexia, weight loss, muscle wasting, and lethargy became progressively severe, and all FIAU-treated woodchucks died or were euthanized 78 to 111 days after treatment began. Hepatic insufficiency (hyperbilirubinemia, decreased serum fibrinogen, elevated prothrombin time), lactic acidosis, and hepatic steatosis were characteristic findings in the final stages of FIAU toxicity in woodchucks. The syndrome of delayed toxicity in woodchucks was similar to that observed previously in humans treated with FIAU, suggesting that the woodchuck should be valuable in future investigations of the molecular mechanisms of FIAU toxicity in vivo and for preclinical toxicological evaluation of other nucleoside analogs before use in patients.

Animals↗
PubMed1998

Seasonal variation and effects of age, food availability, size, gonadal development, and parasitism on the hemogram of mytilus galloprovincialis

The study of hemogram characteristics in a population of cultured mussels through a period of 18 months revealed that the concentration of circulating Mytilus galloprovincialis hemocytes varied, following a seasonal pattern, being positively correlated with water temperature. Most mussels had between 1 and 5 x 10(6) hemocytes/ml of hemolymph. Differential counts showed that M. galloprovincialis hemolymph contained more granulocytes than hyalinocytes. The hemolymph cell concentration was not associated with size or weight of mussels. Circulating hemocyte concentration did not decrease in mussels with reabsorbing gonad, despite the hemocytic accumulation inside and around gonad follicles. No significant difference in hemolymph cell concentration was found between two groups of mussels of different ages. Nevertheless, older mussels had higher mean values of circulating granulocytes although these differences were only significant in the winter sample. Infestation by the protistan Marteilia refringens caused a significant increase of hemocytes in the hemolymph. In addition, the occurrence of some parasites induced significant changes in the proportion of circulating hemocyte types. Results suggested that a hemocytic response was detected in hemolymph when the foreign organisms are pathogenic and evoke a heavy inflammatory reaction. Mussels with large or numerous granulocytomas had a higher number of circulating granulocytes and hyalinocytes than those without granulocytomas. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

The constitutive heat shock protein-70 is required for optimal expression of myelin basic protein during differentiation of oligodendrocytes.

To further elucidate the role of the constitutive heat shock protein-70 (HSC70) as a chaperone for the synthesis of myelin basic protein (MBP), HSC70 content was decreased in oligodendrocyte precursor cells prior to MBP expression either by transfection with an antisense oligonucleotide specific for HSC70, or by exposure to low levels of quercetin, a bioflavonoid known to decrease synthesis of HSC70. As these cells underwent differentiation in vitro, antisense treatment decreased HSC70 levels to 66% of controls. At the same time, a sharp induction resulted in the stress-inducible heat shock protein-70 (HSP70). Levels of two other stress proteins increased as well, namely, the 25-kDa heat shock protein (HSP25) and the 78-kDa glucose regulated protein (GRP78). MBP synthesis proceeded over a normal time course, but at only 50% of control values. As HSC70 content returned to normal, MBP synthesis was also restored to normal levels. Quercetin reduced the expression of HSC70 to an even greater extent than transfection, and prevented the induction of HSP70. In contrast to antisense-treated cells, MBP synthesis was essentially blocked in quercetin-treated cells even though levels of HSP25 and GRP78 increased. Taken together, these observations (a) indicate that HSP70 partially compensates for decreased chaperoning of nascent MBP by HSC70 (HSC70 and HSP70 are closely related and perform similar functions); (b) preclude the involvement of HSP25 and GRP78 in MBP synthesis; and (c) emphasize the requirement of HSC70 for optimal synthesis of MBP.

Animals↗
PubMed1998

[Varicocele in adolescents. Treatment by sclerotherapy and percutaneous embolization: reflections on the method. Apropos of 23 cases].

OBJECTIVE: The authors report their experience of the treatment of varicocele in adolescents. As a result of progress in interventional radiology and embolization techniques, they have used a technique combining sclerotherapy and percutaneous embolization since 1993. MATERIAL AND METHODS: Since 1993, twenty three adolescents between the ages of 11 and and 17 years (mean = 14.5 years) were treated percutaneously for grade II and II left varicocele. The operation was performed under local anaesthesia and/or neuroleptanalgesia. Phlebography by selective catheterization of the left spermatic vein was performed for anatomical assessment (ostial incontinence, collateral vessels). Embolization was then performed under fluoroscopic control by injection of a sclerosing liquid, sodium tetradecyl sulphate (Trombovar), and systematically completed by insertion of endovascular occlusive metal coils. RESULTS: The follow-up ranged from 6 to 48 months (mean = 30 months). The follow-up clinical and ultrasound examination showed complete disappearance of the varicocele in 22 cases (95% of cases), with a persistent grade I asymptomatic left varicocele in 1 case. No complications were observed. The mean hospital stay was 48 hours. CONCLUSION: This constitutes a rapid method, which is minimally traumatic for the adolescent. Its efficacy is comparable to that of classical surgical techniques with lasting results. Insertion of coils is the endovascular equivalent of surgical ligation of the pathological vein. The liquid embolus is particularly useful as it diffuses and scleroses collateral veins, responsible for recurrence. The advantage of this method resides in a better understanding of the reflux mechanisms, allowing the procedure to be adapted to the venous anatomy. This technique ensures treatment of complex varicoceles, such as postsurgical recurrences.

Administration, Cutaneous↗
PubMed1998

[Lung resections for cancer in the elderly].

BACKGROUND: The purpose of this study is to investigate the value of surgical treatment for lung cancer in the elderly. Results are compared with findings in younger patients operated on during the same period (1985-1990). METHODS: 137 patients 70 years of age or older (range: 70 yrs-87 yrs) (group A) underwent surgical resection [pneumonectomy in 19 (13.8%), lobectomy or bilobectomy in 84 (61.3%), segmentectomy or wedge resection in 22 (16%)]. In group B (younger patients) 561 were treated by pneumonectomy in 156 (27.8%), lobectomy or bilobectomy in 294 (52.4%) and segmentectomy or wedge resection in 64 (11.4%). RESULTS: The overall 2-year survival rate was 64.6% in group A and 61.4% in B. The 5-year survival rate was 36.2% (group A) and 43.2% (group B). CONCLUSIONS: These data suggest that advanced age should not be a contraindication to curative pulmonary resections. More attention must be paid to pre-codiseases of the increasing risk of postoperative complications.

Age Factors↗
PubMed1997

Enzymes Involved in Defense Functions of Hemocytes of Mussel Mytilus galloprovincialis

Mytilus galloprovincialis hemocytes contain phosphatases, esterases, proteases, and glucosidases as revealed by a semiquantitative colorimetric method. The activity levels of some enzymes changed throughout the months of the experiment without a seasonal pattern. No differences in the enzyme levels were found between the two groups of mussels of different age (cultivated 11 and 19 months on ropes hung from the same raft). Light microscopy study of hemocyte enzymes showed that hyalinocytes and granulocytes had reaction of acid phosphatase, beta-glucuronidase, alpha-naphthyl butyrate esterase, naphthol AS-D chloroacetate esterase, and alpha-naphthyl acetate esterase. Phenoloxidase and peroxidase activities were also detected in monolayers of hemocytes. Ultrastructural study revealed that the granules of hemocytes contained acid phosphatase, beta-glucuronidase, nonspecific esterases, peroxidase, and NADH oxidase. Products of beta-glucuronidase and peroxidase reaction were also localized in the plasma membrane. Lysozyme activity level was higher in hemocytes than in serum. Comparison between the two groups of different age showed a higher activity level of lysozyme in younger mussels.

Journal Article↗
PubMed1997

Omeprazole, a specific gastric secretion inhibitor on oxynticopeptic cells, reduces gizzard erosion in broiler chicks fed with toxic fish meals.

The relation between gizzard erosion-black vomit (GE-BV) and gastric secretion is not completely understood. A pharmacological approach to reduce the presence of GE-BV in chicks due to fish meal in diets is also unknown. In this study the use of omeprazole, a H+/K+ ATPase inhibitor, and fish meals of different biotoxicological characteristics, showed that: 1) Omeprazole decreased total gastric acid content, GE scores and severe GE (SGE) cases, in a dose-dependent manner. This reduction was significant at levels higher than 20 mg omeprazole/Kg body weight (BW)/day (p < 0.01). The addition of 50 mg omeprazole/kg BW/day almost completely prevented the incidence of SGE cases and reduced in 50% GE score in chicks (p < 0.01). 2) A significant reduction in specific mortality, near 90%, was also seen with all toxic fish meals when omeprazole (50 mg/Kg BW/day) was added to experimental diets in comparison to control groups. However, no mortality was observed when omeprazole was added to diets containing non-toxic fish meals. 3) In chicks fed with toxic fish meals, addition of different amounts of omeprazole to diets changed the relative weight of proventriculus (p < 0.01) and gizzard (p < 0.05). Maximum effect was obtained with omeprazole concentration higher than 50 mg/Kg BW/day. 4) Omeprazole did not change feed intake in chicks fed with toxic fish meal. However, in some fish meal a reduction on weight gain was observed with the addition of omeprazole.

Administration, Oral↗
PubMed1997

Multiple sclerosis: altered expression of 70- and 27-kDa heat shock proteins in lesions and myelin.

Recent studies have implicated heat shock proteins (HSP) in the pathogenesis of the multiple sclerosis (MS) lesion. Expression of the 73 kDa constitutive HSP (HSC70), the 72 kDa stress-inducible HSP (HSP70), and the 27 kDa small HSP (HSP27) was analyzed in white matter and myelin from central nervous system (CNS) tissue of MS and normal subjects using a combination of immunocytochemistry and quantitative immunoblotting. Plaques of all types were sharply defined by reduced immunostaining for HSC70, and shown by immunoblotting to contain 30 to 50% less HSC70 than surrounding white matter or normal tissue. In contrast, HSP27 was markedly enhanced 2.5- to 4-fold in plaque regions, especially in fibrous astrocytes and in hyperplastic interfascicular oligodendrocytes at the lesion edge. HSP70 was less abundant than HSC70, and no significant differences in HSP70 levels were noted between MS and normal white matter. Myelin isolated from active plaques contained 3- to 4-fold more HSC70 than normal myelin. Pronounced expression of HSP70 and HSP27 was also found in MS myelin, although neither protein was detected in normal myelin. Thus, white matter undergoing immune-mediated destruction in MS was associated with altered distribution and expression of HSC70 and HSP27. These changes may initially serve to protect myelin from further destruction and facilitate repair; however, enhanced expression of HSC70, HSP70, and HSP27 in myelin may subsequently present as additional immune targets involved in the progression of disease.

Astrocytes↗
PubMed1997

[Pigmented villonodular synovitis of the wrist. Apropos of a case].

The authors presented a case of pigmented villonodular synovitis of the wrist with extrinsic bony defects on opposing articular surfaces, seen after two recurrences following excision surgery. They performed a total synovectomy followed by curettage and autogenous bone grafting of the carpal and radiocubital bone lesions. Four years after the procedure, the patient-a woman aged 44-was symptom-free and there was no objectivable evidence of recurrence. Pigmented villonodular synovitis (PVNS) is an uncommon, benign, chronic process that causes synovial proliferation. Its etiology is unknown. The majority of patients is young to middle-aged adults. Especially the knee but other joints are involved including the hip, ankle, wrist, hand, and foot. Both soft tissue and bone abnormalities occur in PVNS. Magnetic resonance imaging (MRI) shows a heterogenous synovial mass with intermediate and low signal intensity areas on T1 and T2-weighted images, consistent with hemosiderin deposition. Computed tomography defines clearly the extrinsic bone erosions and excavations, which usually exhibit a sclerotic margin, produced by intraosseous invasion of the expanding synovia. After excision recurrence is common, leading eventually to arthrodesis, arthroplasty and even radiation therapy. The etiology of PVNS is controversial. First approach is conservative surgical treatment with total synovectomy and curettage of the osteolytic foyers. Bone grafts are employed for filling the sites of osteolysis. The sensitivity of MRI permits early detection of the process and may obviate the need for radical management options in PVNS.

Adult↗
PubMed1997

[Evaluation of 20 years' experience of enuresis in children].

The clinical and urodynamic approach to enuretic children over a period of more than 20 years has allowed the authors to develop a multifactorial pathophysiological concept of this disorder. The main factors involved are psychological, familial, genetic, vesical, due to bladder immaturity, hormonal, due to a defect of nocturnal ADH secretion, hygiene and dietary habits, etc. The sleep factor is predominant in the majority of cases. Although nocturnal enuresis is apparently isolated in many cases, it is often associated with a state of bladder immaturity, sometimes latent during the day, but occurring at night with episodes of detrusor hyperactivity, occurring during various phases of sleep. In practice, the recognition, in children, of these factors, some of which require specific treatments, implies a management combining several of these therapeutic modalities.

Child↗
PubMed1996

Antisense oligonucleotide to the 70-kDa heat shock cognate protein inhibits synthesis of myelin basic protein.

Transfection of rat oligodendrocytes with an oligonucleotide sequence complementary to the mRNA encoding the initial ten amino acids of the rat 70-kDa heat shock cognate protein (HSC70) resulted in a rapid (within 24 h) and significant reduction in HSC70 synthesis (69% of control cells transfected with sense oligonucleotide). A further decrease to approximately 44% of controls was detected after 2 days. At that time, HSC70 protein content fell to approximately 49% of controls, and a significant reduction in the synthesis of myelin basic protein (MBP) was first detected (66% of controls). After 5 days, HSC70 synthesis returned to control levels. As HSC70 protein content recovered, so did the synthesis of MBP. Throughout the 5-day experimental period, only minor changes were detected in cell morphology, overall pattern of protein synthesis and the synthesis and content of proteolipid protein (PLP) and the pi isoenzyme of glutathione-S-transferase (pi). These data show that when HSC70 protein content is sufficiently reduced by antisense oligonucleotide, synthesis of MBP (but not PLP or pi) is correspondingly down-regulated, and provide evidence consistent with the role of HSC70 as a chaperone for MBP.

Animals↗
PubMed1996

The deleterious effects of human erythropoietin gene driven by the rabbit whey acidic protein gene promoter in transgenic rabbits.

Human erythropoietin (EPO) gene and cDNA associated with the rabbit whey acidic protein (WAP) gene promoter were used to tentatively produce the recombinant protein in milk of transgenic mice and rabbits. Several gene constructs showed good efficiency in the mouse mammary cell line HC11. None of them was able to direct the expression of the hormone at a concentration higher than 50 micrograms/mL in mouse and rabbit milk. With one of the construct, the rabbits had an abnormally high amount of red blood cells irrespectively of their sex, they could not reproduce and no milk could be obtained from them. These animals died prematurely. In these animals, the EPO gene was therefore expressed at a low but supraphysiological level in organs other than the mammary gland. These experiments show that transgenic animals obtained with gene constructs which do not contain insulators cannot be used as living fermentors to produce human erythropoietin in their milk at an industrial scale.

Animals↗
PubMed1996

1,000 consecutive ultrasounds for blunt abdominal trauma.

Diagnostic peritoneal lavage (DPL) and computed tomography (CT) are the primary diagnostic modalities used in the evaluation of patients with suspected blunt abdominal trauma (BAT). DPL is fast and accurate but is associated with complications. CT is also accurate, yet requires stability and transportability of the patients. Ultrasound (US) has been suggested as an aid in evaluating BAT. We evaluated US in the initial assessment of BAT in 1000 patients. Patients were eligible for the study if they met specified trauma criteria and had suspected BAT. We then followed the outcome of the patients and their further work-up. US showed a sensitivity of 88%, a specificity of 99%, and an accuracy of 97% for detecting intraabdominal injuries. We conclude that emergency ultrasound may be used as the initial diagnostic modality for suspected blunt abdominal trauma.

Abdominal Injuries↗
PubMed1995

Incorporation of sulphonated cyclodextrins into polypyrrole: an approach for the electro-controlled delivering of neutral drugs.

The electro-controlled delivery of drugs based on the doping-dedoping mechanism of Electro-Conducting Polymers is restricted to charged substances acting as dopants. In order to overcome this limitation, this study presents an approach where the trapping/delivering is based on host-guest interaction. As an example of a neutral guest, the molecule N-methylphenothiazine (NMP) is encapsulated in the host, heptasulphonated beta-cyclodextrin (beta-CDSO3-), which is tailor-made to dope PPy. The original synthetic method for beta-CDSO3- is based on sulphonation of the periodated beta-CD in the phase transfer medium. As a consequence of their size and of their multicharged character, beta-CDSO3-s are fixed dopants. The stability of the beta-CDSO3- entrapment is checked by Optical Beam Deflection (mirage effect) measurements. The ionic movements associated with the switching of the beta-CDSO3- doped PPy (PPy+, beta-CDSO3-) film appear to be mainly due to cations with this technique. Cyclic voltammetry experiments confirm the entrapment of neutral NMP by simply dipping the PPy+, beta-CDSO3- film in a CH3CN solution containing NMP. Repeated electrochemical cycling of such a reservoir electrode indicates the progressive elimination of NMP from the (PPy+, beta-CDSO3- [NMP]) film.

Cyclodextrins↗