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Biomedical subjects

N García

Publications and source records attributed to N García.

At least 19 recordsLinked to original sources
PubMed2001

Morphologic and histochemical study of blood capillaries in boar testes: effects of abdominal cryptorchidism.

BACKGROUND: Few data exist about the features of testicular microvasculature under normal and pathologic conditions. METHODS: The morphology and lectin affinity of testicular capillaries were examined in healthy boars and in unilateral and bilateral abdominal cryptorchid boars. RESULTS: The capillaries of scrotal testes contained a) the endothelial layer formed by two cells, b) the basal lamina constituted by collagen fibers and glycoconjugates with fucosyl, galactosyl, glucosyl, and neuraminic acid residues, and c) the pericyte layer formed by a single cell. These components participated in substrate exchange between blood and testicular tissue. The abdominal testes showed increased numbers of capillaries, which could exhibit a mature appearance, but also angiogenic or degenerative patterns. Angiogenesis was manifested in interstitial capillaries and was characterized by a) proliferation of endothelial cells, b) decreased thickness and decreased content of collagen fibers and glycoconjugates in the basal lamina, and c) lack of pericytes. Degenerative capillaries lay in association with seminiferous tubules and showed a) pyknotic endothelial cells; b) thickening, collagenization, and altered glycoconjugate content in the basal lamina; and c) increased development of pericytes. The angiogenesis of interstitial capillaries resulted in high vascular permeability, and the degeneration of intertubular capillaries led to defective substrate exchange between blood and seminiferous tubules. CONCLUSIONS: Unilateral abdominal cryptorchidism did not alter the morphology and function of capillaries in the scrotal testis. Unilateral and bilateral abdominal cryptorchidism resulted in increased numbers and abnormal morphology and function of capillaries in abdominal testes. The proliferation of interstitial capillaries correlated with the immaturity of Leydig cells, and the degeneration of intertubular capillaries correlated with the thickening of the lamina propria.

Animals↗
PubMed2000

Frequency modulation in the transmittivity of wave guides in elastic-wave band-gap materials.

It is shown, for the first time, that the transmittivity of wave guides created as rectilinear defects in periodic elastic band-gap materials oscillates as a function of frequency. The results are obtained using the finite difference time domain method for elastic waves propagating in two-dimensional inhomogeneous media. The oscillations of the transmittivity are due to the richness of modes in the elastic systems and, mainly, due to the periodicity of the potential in the direction of the wave propagation. Results are presented for a periodic array of Pb and Ag cylinders inserted in an epoxy host, as well as for Hg cylinders in an Al host.

Journal Article↗
PubMed2000

Negative and positive magnetoresistance manipulation in an electrodeposited nanometer Ni contact.

We show that, in a nanometric size stable electrodeposited Ni contact, it is possible to modify the magnetoresistance by applying current pulses and external magnetic fields whereby the same current path is used for detection and modification. We can pass from positive to negative magnetoresistance with values as large as 25% at room temperature, all in the same contact. We propose that the effect may be due to switching and moving domain walls in the contact region under the combination of current effects and external fields.

Electrochemistry↗
PubMed2000

Changes in the infectivity, pyruvate kinase activity, acid phosphatase activity and P-glycoprotein expression in glibenclamide-resistant Leishmania mexicana.

We previously demonstrated susceptibility of Leishmania sp. to glibenclamide, a K+ -ATP transport blocker which interacts with members of the superfamily of adenosine 5' triphosphate-binding cassette transporters. In order to characterize the molecular differences between a sensitive Leishmania strain, NR(Gs), and an experimentally selected glibenclamide-resistant strain, NR(Gr), specific biochemical and functional parameters have been evaluated both in the wild type and in the resistant strain. Most noteworthy, NR(Gr) exhibit an increased expression of P-glycoprotein and a decreased activity of functional key enzymes such as acid phosphatase, a prominent virulent factor of the parasite, and pyruvate kinase, a key control enzyme for both carbohydrate and protein metabolism. The specific biochemical, metabolic and functional changes observed in the resistant strain correlated with a reduced infectivity of stationary phase NR(Gr) in J774 macrophages and suggested a mechanism to overcome the effect of glibenclamide.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Intranasal, rectal and intraperitoneal immunization with protoxin Cry1Ac from Bacillus thuringiensis induces compartmentalized serum, intestinal, vaginal and pulmonary immune responses in Balb/c mice.

Recently we discovered that the Cry1Ac protoxin of Bacillus thuringiensis administered to Balb/c mice intraperitoneally (i.p.) or intragastrically is a systemic and intestinal immunogen as potent as cholera toxin. To further characterize the mucosal immunogenicity of Cry1Ac we additionally tried the intranasal (i.n.) and rectal routes and used enzyme-linked immunoassays to determine anti-Cry1Ac antibody responses in the serum as well as in vaginal and tracheobronchial washes and in the fluids of the large and the small intestine. Immunization by the i.p., i.n. and rectal routes induced IgM, IgG and IgA antibodies in all the mucosal surfaces analyzed, but the magnitude and predominant isotype of each response depended on the route used and the mucosal site analyzed. These data extend our findings on the striking mucosal immunogencity of Cry1Ac and provide additional evidence on the compartmentalization of the mucosal immune system.

Administration, Intranasal↗
PubMed2000

Possible involvement of the adenine nucleotide translocase in the activation of the permeability transition pore induced by cadmium.

Low levels of cadmium induce a rapid calcium efflux in energized rat kidney mitochondria. This is accompanied by the collapse of the transmembrane gradient in a partial CSA-sensitive fashion. The binding of 109Cd2+ to mitochondria is a saturable function; in the presence of NEM, the binding of 2.5 nmol 109Cd2+/mg of protein suffices to induce the opening of the permeability transition pore. It was found that cadmium bound mainly to proteins of molecular weight between 30 and 50 kDa. In the presence of the monothiol reagent NEM, the label is concentrated in the 30 kDa protein. Following the addition of the reducing agent dithiothreitol, calcium is reaccumulated and the membrane potential restored. This correlates with a significant loss of label in the 30 kDa protein region. The 30 kDa protein was identified as the adenine nucleotide translocase by labelling experiments with eosin 5-maleimide and experiments of reconstitution.

Animals↗
PubMed2000

Copper sensitizes the mitochondrial permeability transition to carboxytractyloside and oleate.

Addition of 5 microM copper to rat kidney mitochondria enhances the effect of carboxyatractyloside and oleate on pore opening, in a cyclosporin A-sensitive fashion. The effects of the pair copper-carboxyatractyloside were observed on matrix Ca2+ efflux, mitochondrial swelling and on the transmembrane electric gradient. The effect of Cu2+ emphasizes the importance of membrane thiol groups located, probably, in the ADP/ATP translocase (ANT), on permeability transition. It was also found that Cu2+ does not block the fluorescent label of ANT by eosin 5-maleimide, but abolishes the inhibition by CAT on the labeling. This suggests that the binding of Cu2+ to cysteine residues of ANT promotes a conformational change in the carrier, strengthening the effect of CAT and oleate on membrane leakage.

Animals↗
PubMed2000

A meta-analysis of short versus long therapy with a proton pump inhibitor, clarithromycin and either metronidazole or amoxycillin for treating Helicobacter pylori infection.

BACKGROUND: Although triple therapies with a proton pump inhibitor, clarithromycin and either amoxycillin or metronidazole are the most widely accepted treatment for Helicobacter pylori infection, there is no consensus on how long treatment should be maintained for. AIM: To evaluate whether increasing the length of triple therapies beyond 7 days improves treatment efficacy. METHODS: An extensive search of the literature was performed. Reports of randomized trials comparing different lengths of therapy were selected. Short (7-day) vs. long (10/14-day) therapies were compared, and three-way comparison of 7-day vs. 10-day, 10-day vs. 14-day and 7-day vs. 14-day therapies was performed. Meta-analysis was conducted using conventional shareware (Review Manager 4.0). The Peto Odds Ratio using a fixed model analysis was calculated for each comparison. RESULTS: Thirteen studies were identified. Pooled 10- to 14-day therapies achieved better results than 7-day schedules. In head-to-head comparisons, only 14-day therapies were significantly better than 7-day treatments. Improvement in cure rates ranged from 7 to 9%. Comparisons of 7-day vs. 10-day and 10-day vs. 14-day also showed a non-significant trend towards better cure rates with longer therapies. CONCLUSIONS: Fourteen-day, proton pump inhibitor-based triple therapy achieves better results than 7-day schedules. Additional data are necessary to evaluate 10-day therapies.

Amoxicillin↗
PubMed2000

Proton pump inhibitor, clarithromycin and either amoxycillin or nitroimidazole: a meta-analysis of eradication of Helicobacter pylori.

AIM: To perform a meta-analysis of studies comparing twice daily, one-week triple therapy with a proton pump inhibitor, clarithromycin (C) and amoxycillin (A) (PCA) vs. those using proton pump inhibitor, clarithromycin and a nitroimidazole (N) (PCN) for H. pylori eradication. REVIEW METHODS SELECTION CRITERIA: Comparative randomized trials of PCA vs. PCN were included. DATA SOURCES: PubMed database and abstracts from congresses until September 1999. STATISTICS: Meta-analysis was performed combining the Odds Ratios (OR) of the individual studies in a global OR (Peto method) both on an intention-to-treat (ITT) and on a per protocol (PP) basis. RESULTS: Twenty-two studies fulfilled the inclusion criteria. Eighteen studies reported ITT and 20 PP analysis. Mean H. pylori eradication rates were 81% (95% CI: 79-83%) ITT, and 84% (82-86%) PP with PCA, and 81% (78-83%) ITT and 84% (82-86%) PP with PCN; the odds ratio for the effect of PCA vs. PCN was 1 (0.83-1.22) on an ITT, and 0.98 (0.8-1.2) on a PP basis. Subanalysis showed that mean H. pylori eradication efficacy with PC(250 b.d.)A was 81% (78-85%) ITT, vs. 86% (83-89%) with PC(250 b.d.)N. The odds ratio for this comparison was 0.68 (0.48-0.98). Finally, when comparing PC(500 b.d. )A against PC(250 b.d.)N ITT cure rates were 77% (74-80%), and 75% (72-78%) with an odds ratio of 1.18 (0.93-1.5). CONCLUSION: Overall, one-week combination regimens of PCA and PCN present similar H. pylori eradication efficacy. Nevertheless, the PCN regimen obtains significantly better results when using low doses of C (250 mg b.d.).

Amoxicillin↗
PubMed2000

Four-day, twice daily, quadruple therapy with amoxicillin, clarithromycin, tinidazole and omeprazole to cure Helicobacter pylori infection: a pilot study.

BACKGROUND: The best regimen for the treatment of Helicobacter pylori infection has yet to be defined. Four-day quadruple therapy with tetracycline, metronidazole, bismuth, and a proton pump inhibitor has been shown to obtain a very high cure rate. However, the fact that it must be taken four times daily may interfere with compliance. The objective of the study was to test the efficacy and tolerability of a new 4-day therapy with 4 drugs taken every 12 hours to cure H. pylori infection. Patients and Methods. Fifty-six consecutive patients with peptic ulcer disease and H. pylori infection were treated with an oral 4-day course with omeprazole (20 mg/12 hours), clarithromycin (500 mg/12 hours), amoxicillin (1 g/12 hours) and tinidazole (500 mg/12 hours). Efficacy of the treatment was determined at least 2 months after therapy either by biopsy (in the case of gastric ulcer) or by 13C-urea breath test. A second breath test was performed at least 6 months after therapy. RESULTS: Two patients were lost to follow-up. Forty-nine of the remaining 54 patients were cured at the first control [intention-to-treat cure rate: 87.5% (CI 95% 75-94%); per protocol cure rate: 90.7% (CI 95% 81-98%)]. Forty-three of these 49 cured patients returned for a second 13C urea breath-test at 6-12 months. Two of them were not cured, giving a long-term cure rate of 85.5% per protocol and 73.2% by intention-to-treat. Compliance was good, although 25 patients had mild side effects. CONCLUSION: This particular four-day therapy is well tolerated, easy to follow, and achieves an acceptably high cure rate.

Adult↗
PubMed1999

A complete human pelvis from the Middle Pleistocene of Spain.

The Middle Pleistocene site of Sima de los Huesos in Sierra de Atapuerca, Spain, has yielded around 2,500 fossils from at least 33 different hominid individuals. These have been dated at more than 200,000 years ago and have been classified as ancestors of Neanderthals. An almost complete human male pelvis (labelled Pelvis 1) has been found, which we associate with two fragmentary femora. Pelvis 1 is robust and very broad with a very long superior pubic ramus, marked iliac flare, and a long femoral neck. This pattern is probably the primitive condition from which modern humans departed. A modern human newborn would pass through the birth canal of Pelvis 1 and this would be even larger in a female individual. We estimate the body mass of this individual at 95 kg or more. Using the cranial capacities of three specimens from Sima de los Huesos, the encephalization quotients are substantially smaller than in Neanderthals and modern humans.

Adult↗
PubMed1999

Characterization of the semen quality of postpuberal boars with spontaneous unilateral abdominal cryptorchidism on the right side.

In recent studies, we found that the ectopic testis from postpuberal boars with unilateral abdominal cryptorchidism does not produce sperm. Therefore, in these males, the seminal characteristics can be used as indicators of the activity of the scrotal testis and its epididymis and also the accessory glands. The semen quality (ejaculate volume, cell-rich fraction volume, sperm concentration, sperm vitality, sperm motility, sperm morphology and cephalic stability of spermatozoa) was evaluated in healthy postpuberal boars and in postpuberal boars with unilateral abdominal cryptorchidism on the right side. In comparison with the healthy boars, the unilateral abdominal cryptorchid boars showed a significant decrease of the ejaculate volume, sperm concentration and sperm motility. The low sperm concentration indicated that unilateral abdominal cryptorchidism severely impairs the sperm production of the scrotal testis. The decrease of ejaculate volume was attributed to an abnormal activity of the accessory glands. The alterations in sperm motility develop as a result of dysfunctions in the epididymal epithelium and/or the accessory glands. The sperm vitality, sperm morphology and cephalic stability of spermatozoa maintained normal values; therefore, at testicular level, despite the low sperm production, the germ cell differentiation is not disturbed. At epididymal level, the morphological maturation of spermatozoa is not altered.

Animals↗
PubMed1999

Carboxyatractyloside increases the effect of oleate on mitochondrial permeability transition.

Addition of a low concentration of carboxyatractyloside (0.075 microM) renders mitochondria susceptible to the opening of the non-specific pore by 5 microM oleate, in a cyclosporin A-sensitive fashion. Matrix Ca2+ efflux as well as collapse of the transmembrane potential reveal permeability transition. The effect of oleate is reached after the titration, by carboxyatractyloside, of 38 pmol of adenine nucleotide translocase per mg mitochondrial protein. We propose that permeability transition may result from an additive action of carboxyatractyloside plus oleate on the ADP/ATP carrier.

Animals↗
PubMed1999

The hairless gene of the mouse: relationship of phenotypic effects with expression profile and genotype.

Various mutations of the hairless (hr) gene of mice result in hair loss and other integument defects. To examine the role of the hr gene in mouse development, the expression profile of hr has been determined by in situ hybridisation and correlated to the nature of genetic changes and morphological abnormalities in different mutant animals. Four variant alleles have been characterised at the molecular level. hr/hr mice produce reduced, but significant, levels of hr mRNA whereas other alleles contain mutations which would be expected to preclude the synthesis of functional product, demonstrating a correlation between allelic variation at the hr locus and phenotypic severity. hr expression was shown to be widespread and temporally regulated. It was identified in novel tissues such as cartilage, developing tooth, inner ear, retina, and colon as well as in skin and brain. Analysis of mice homozygous for the rhino allele of hairless revealed that, although no morphological defects were detectable in many tissues normally expressing hr, previously undescribed abnormalities were present in several tissues including inner ear, retina, and colon. These findings indicate that the hairless gene product plays a wider role in development than previously suspected. Dev Dyn 1999;216:113-126.

Animals↗
PubMed1999

Assessment of biliary bicarbonate secretion in humans by positron emission tomography.

BACKGROUND & AIMS: Positron emission tomography (PET) allows imaging and quantitative analysis of organ functions in basal and stimulated conditions. We have applied this method to the study of biliary bicarbonate secretion in humans. METHODS: PET was performed in 5 healthy subjects and 13 patients with hepatobiliary disorders after intravenous injection of NaH11CO3. In each case the study was performed in basal conditions and after secretin stimulation. Positron emission from the hepatic area was scanned, and normalized uptake values for parenchymal and hilar regions were estimated. RESULTS: In healthy individuals, the injection of NaH11CO3 resulted in a peak uptake of the label in parenchymal and hilar regions 2-3 minutes after the injection. In both normal and cirrhotic subjects, secretin administration increased bicarbonate uptake in the parenchymal region, followed by accumulation of the label in the perihilar area. Normal basal uptake with absent response to secretin was registered in extrahepatic biliary obstruction and in untreated primary biliary cirrhosis (PBC). The secretin response was present in patients with PBC undergoing treatment with ursodeoxycholic acid. CONCLUSIONS: PET allows investigation of biliary bicarbonate secretion in humans. An impaired response to secretin was observed in cholestatic conditions. Preliminary data suggest that ursodeoxycholic acid might improve the response to secretin in PBC.

Adult↗