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Biomedical subjects

R López

Publications and source records attributed to R López.

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

Semipreparative reversed-phase liquid chromatographic fractionation of aroma extracts from wine and other alcoholic beverages.

The suitability of reversed-phase HPLC for the semi-preparative fractionation of aroma extracts from wine and other alcoholic beverages has been explored. Aroma extracts are separated in a 250x10-mm Kromasil-C18 column using a water-ethanol gradient system as mobile phase. It has been demonstrated that the chromatographic separation does not induce any chemical change in the sample components. The maximum volume that can be injected without altering efficiency is as high as 2 ml if ethanolic extracts are injected, and slightly less in the case of less polar extracts. Aroma extracts are injected directly without the need of any pretreatment. As major compounds elute first, it is possible to fractionate all the volatiles contained in a 1-1.5-1 sample without peak distortion or mass overload problems. The usefulness of the method has been demonstrated by fractionating an extract from a Chardonnay wine to get 15 fractions that showed different aromas. The GC analysis with olfactometric and MS detection of those fractions has allowed us to identify more than 70 aroma compounds and to signal some of them as potential key aromas of Chardonnay wine.

Adult↗
PubMed1999

Heavy metal pollution of soils affected by the Guadiamar toxic flood.

Total heavy metal concentrations were determined in soil samples of seven selected areas along the Guadiamar river valley affected by the toxic flood, after removal of the deposited sludge. Mean total concentrations of nine elements (As, Au, Bi, Cd, Cu, Pb, Sb, Tl and Zn) out of the 23 (As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, In, Mn, Mo, Ni, Pb, Sb, Sc, Sn, Th, Tl, U, V, Y and Zn) analysed were higher in sludge-covered soils than in unaffected soils. Mean values of total As, Au, Pb, Sb, Tl and Zn in sludge-affected soils were higher than the upper limits for normal soils world-wide. Mean concentrations of Bi, Cd and Cu were within these ranges, although some individual values exceeded the upper limits. In all sampling areas, severe heavy metal pollution was observed in the superficial layers (0-20 cm) of most of the affected soils, which decreased downward in the soil profile. Generally, in soils with more than 25% of clay, concentration of heavy metals below the 20-cm depth decreased to values close to those of the background level of the Guadiamar valley soils, while in coarser soils, heavy metal pollution penetrated below this depth, being noticeable down to a depth of at least 50-80 cm.

Accidents, Occupational↗
PubMed1999

Accumulation of heavy metals in sunflower and sorghum plants affected by the Guadiamar spill.

The collapse of a pyrite-mining, tailing dam on 25 April 1998 contaminated approximately 2000 ha of croplands along the Agrio and Guadiamar river valleys in southern Spain. This paper reports the accumulation of chemical elements in soil and in two crops--sunflower and sorghum--affected by the spill. Total concentrations of As, Bi, Cd, Cu, Mn, Pb, Sb, Tl and Zn in spill-affected soils were greater than in adjacent, unaffected soils. Leaves of spill-affected crop plants had higher nutrient (K, Ca and Mg for sunflower and N and K for sorghum) concentrations than controls, indicating a 'fertilising' effect caused by the sludge. Seeds of spill-affected sunflower plants did accumulate more As, Cd, Cu and Zn than controls, but values were below toxic levels. Leaves of sorghum plants accumulated more As, Bi, Cd, Mn, Pb, Tl and Zn than controls, but these values were also below toxic levels for livestock consumption. In general, none of the heavy metals studied in both crops reached either phytotoxic or toxic levels for humans or livestock. Nevertheless, a continuous monitoring of heavy metal accumulation in soil and plants must be established in the spill-affected area.

Accidents, Occupational↗
PubMed1999

Spatiotemporal gradients of differentiation of chick retina types I and II cholinergic cells: identification of a common postmitotic cell population.

The chick retina has three types of cholinergic amacrine cells. We have found that Types I and II differentiate from a common population of postmitotic cells temporarily located in the inner plexiform layer (IPL cells). Golgi staining and immunocytochemistry for choline acetyltransferase (ChAT) and gamma-aminobutyric acid (GABA) were used to trace the development and fate of IPL cells. Transformation of the shape of IPL cells into those typical of both conventional amacrine cells and those displaced to the ganglion cell layer are seen. All IPL cells are doubly immunoreactive, for ChAT and GABA, from the time they appear as a cell population within the inner plexiform layer (IPL) until their separation into the two amacrine cell populations. Polarization and early stages of shape differentiation of both types occur while they are in the IPL, starting in the dorsocentral area in the temporal retina and spreading to the rest of the retina. Three spatial gradients of differentiation are observed: from central-to-peripheral, dorsal-to-ventral, and temporal-to-nasal retina. Our findings suggest that the fate of both types of cells in the chick is determined locally, whereas their postmitotic precursors are within the IPL. The presence of GABA and acetylcholine in both types of amacrine cells at early stages of their morphogenesis, well before they have synaptic interactions, suggests a morphogenetic role for these molecules in inner retinal differentiation.

Acetylcholine↗
PubMed1999

A single gene (tts) located outside the cap locus directs the formation of Streptococcus pneumoniae type 37 capsular polysaccharide. Type 37 pneumococci are natural, genetically binary strains.

The molecular aspects of the type 37 pneumococcal capsular biosynthesis, a homopolysaccharide composed of sophorosyl units (beta-d-Glc-(1-->2)-beta-d-Glc) linked by beta-1,3 bonds, have been studied. Remarkably, the biosynthesis of the type 37 capsule is driven by a single gene (tts) located far apart from the cap locus responsible for capsular formation in all of the types characterized to date in Streptococcus pneumoniae. However, a cap37 locus virtually identical to the cap33f cluster has been found in type 37 strains, although some of its genes are inactivated by mutations. The tts gene has been sequenced and its transcription start point determined. Tts shows sequence motifs characteristic of cellulose synthases and other beta-glycosyltransferases. Insertion of the tts gene into the pneumococcal DNA causes a noticeable genome reorganization in such a way that genes normally separated by more than 350 kb in the chromosome are located together in clinical isolates of type 37. Encapsulated pneumococcal strains belonging to 10 different serotypes (or serogroups) transformed with tts synthesized type 37 polysaccharide, leading to the formation of strains that display the binary type of capsule. Type 37 pneumococcus constitutes the first case of a natural, genetically binary strain and represents a novel alternative to the mechanisms of intertype transformation.

Amino Acid Sequence↗
PubMed1999

Potassium ion efflux induced by cationic compounds in yeast.

Potassium efflux in yeast induced by several cationic compounds showed different characteristics. All of the observed efflux required glucose as substrate at the concentrations used. For most of them, the phenomenon required binding of the cationic compound to the cell surface and increased with the negative cell surface charge, and for all the compounds tested, it depended on a metabolizable substrate. Efflux induced with terbium chloride appeared more likely due to the function of a K+/H+ antiporter. With DEAE-dextran and dihydrostreptomycin, potassium efflux was dependent on the cell potassium content and was also sensitive to osmotic changes of the medium. DEAE-dextran-provoked efflux was not due to cell disruption. Dihydrostreptomycin seemed to activate a potassium efflux system which could not be studied in isolation, but its inhibition of potassium uptake may also be involved. Except for cells treated with ethidium bromide, no appreciable cell disruption was observed. The potassium efflux observed appears to be a membrane phenomenon reversible after washing with magnesium chloride.

Antiporters↗
PubMed1999

Effects of weak acids on cation accumulation, delta pH and delta psi in yeast.

With glucose as carbon source, as reported by other authors (Conway et al., 1950), yeast cells accumulated large amounts of CO2, carbonic acid, bicarbonate and K+ than when grown with ethanol. The addition of propionic acid to the cells produced an increase in the potassium ion accumulation when cells were incubated with ethanol as substrate, but not when incubated with glucose. In disagreement with Ryan et al. (1971) and Ryan and Ryan (1972), the internal pH of the cells with ethanol was lower than with glucose, eliminating this factor as the limiting factor for potassium accumulation. When the membrane potential difference was estimated, it was found that it was higher with glucose as substrate than with ethanol. In addition, with ethanol the addition of propionic acid produced an increase of the membrane potential, in agreement with the idea of an accumulation of the anions of monoprotic acids, which, being not diffusible, increase the negative membrane potential inside, which can drive the accumulation of larger amounts of monovalent cations. It was also found that the addition of propionic acid to cells incubated with glucose as substrate produced an efflux of CO2 from the cells, so that an exchange of the acid appears to take place.

Bicarbonates↗
PubMed1999

Immunomagnetic bone marrow (BM) and peripheral blood progenitor cell (PBPC) purging in follicular lymphoma (FL).

Twenty-nine B cell follicular lymphoma (FL) patients had their BM (n = 12) or PBPC (n = 17) purged using a panel of monoclonal antibodies and immunomagnetic beads (IMB). The median recovery of nucleated cells (NC) and CD34+ cells was 59.3% (40.5-74) and 56.1% (30.8-82.9) in BM and 77.2% (64.7-88.3) and 73.5% (61.5-98.6) in PBPC (P<0.0005). A median of >1.62 and >1.02 log of target cell depletion was achieved as judged by flow cytometry analysis in BM and PBPC, respectively. Of 29% of initial harvests that had a bcl2 PCR-amplified signal, 37.5% became PCR negative in the final purged products. Absorbed cells containing IMB-target cell complexes gave bcl2 rearrangement signal in 20% of samples in which the start and final purged components were negative. Twenty-three of 26 patients receiving an autologous purged product are evaluable for engraftment. Median time to reach an ANC >0.5x10(9)/l and platelet count >20x10(9)/l was 21 (11-43) and 41 days (13-70) for BM (n = 9) and 14 (10-31) and 14 (8-37) for PBPC (n = 14) autografted patients (P = 0.01 and 0.001). One patient did not engraft and was rescued with a back-up BM. These data demonstrate that this indirect immunomagnetic technique is able to achieve a high grade of lymphoma cell depletion in BM and PBPC and that these purged products are capable of rapid engraftment after autologous transplantation.

Adult↗
PubMed1999

First molecular characterization of a uridine diphosphate galacturonate 4-epimerase: an enzyme required for capsular biosynthesis in Streptococcus pneumoniae type 1.

Uridine diphosphate galacturonate 4-epimerases (UDPGLEs) are enzymes that convert UDP-glucuronate into UDP-galacturonate. Although the presence of UDPGLEs has been reported in prokaryoic and eukaryotic organisms, the genes coding for these enzymes are completely unknown. The galacturonic acid-containing capsular polysaccharide of Streptococcus pneumoniae type 1 is synthesized through the action of a specific UDPGLE. We have constructed a defined deletion mutant in the cap1J gene (one of the 15 cap1 genes responsible for the synthesis of the type 1 capsule) that exhibited an unencapsulated phenotype. This mutant was unable to synthesize UDPGLE, suggesting that Cap1J was the type 1-specific UDPGLE of S. pneumoniae. Escherichia coli cells harbouring the recombinant plasmid pRMM38 (cap1J) overproduced a 40 kDa protein, characterized as Cap1J on the basis of the N-terminal amino acid sequence analysis, and expressed high levels of enzymatically active Cap1J epimerase. Cap1J was partially purified, although purification to electrophoretic homogeneity inactivated the enzyme irreversibly. The enzyme has the following characteristics: K(m) for UDP-glucuronate, 0.24 mM; pH optimum, 7.5; equilibrium constant (in the direction of UDP-galacturonate formation), 1.3; and an approximate M(r) of 80,000 for the active form. The Cap1J protein exhibited a fluorescence emission spectrum similar to that of NADH. Upon inactivation with p-hydroxymercuribenzoate, the addition of NAD+ and 2-mercaptoethanol were sufficient to reactivate the enzyme. Among several compounds tested, UDP-galactose and UDP-xylose exhibited the highest inhibition of the UDPGLE activity. Inactivation of UDPGLE activity was also observed in the presence of UMP and several reducing sugars. To our knowledge, this is the first example of a thoroughly molecular characterization of a UDPGLE.

Amino Acid Sequence↗
PubMed1999

The molecular characterization of the first autolytic lysozyme of Streptococcus pneumoniae reveals evolutionary mobile domains.

A biochemical approach to identify proteins with high affinity for choline-containing pneumococcal cell walls has allowed the localization, cloning and sequencing of a gene (lytC ) coding for a protein that degrades the cell walls of Streptococcus pneumoniae. The lytC gene is 1506 bp long and encodes a protein (LytC) of 501 amino acid residues with a predicted M r of 58 682. LytC has a cleavable signal peptide, as demonstrated when the mature protein (about 55 kDa) was purified from S. pneumoniae. Biochemical analyses of the pure, mature protein proved that LytC is a lysozyme. Combined cell fractionation and Western blot analysis showed that the unprocessed, primary product of the lytC gene is located in the pneumococcal cytoplasm whereas the processed, active form of LytC is tightly bound to the cell envelope. In vivo experiments demonstrated that this lysozyme behaves as a pneumococcal autolytic enzyme at 30 degrees C. The DNA region encoding the 253 C-terminal amino acid residues of LytC has been cloned and expressed in Escherichia coli. The truncated protein exhibits a low, but significant, choline-independent lysozyme activity, which suggests that this polypeptide adopts an active conformation. Self-alignment of the N-terminal part of the deduced amino acid sequence of LytC revealed the presence of 11 repeated motifs. These results strongly suggest that the lysozyme reported here has changed the general building plan characteristic of the choline-binding proteins of S. pneumoniae and its bacteriophages, i.e. the choline-binding domain and the catalytic domain are located, respectively, at the N-terminal and the C-terminal moieties of LytC. This work illustrates the natural versatility exhibited by the pneumococcal genes coding for choline-binding proteins to fuse separated catalytic and substrate-binding domains and create new and functional mature proteins.

Amino Acid Sequence↗
PubMed1999

Isolation of a proliferation inhibitor factor from uterine myomatosis fibroblasts.

In this work, we report the isolation of a factor from the culture supernatant of confluent fibroblasts from human cervix with the diagnosis of uterine myomatosis. This factor possesses the capacity to inhibit the proliferation of normal fibroblasts. The proliferation inhibitor factor (PIF) was purified from the culture supernatant by precipitation with 80% ammonium sulfate, and by molecular sieve chromatography. Our results indicate that PIF is a protein of 23 kDa, which is highly sensitive to trypsin treatment, and is thermolabile, since temperatures equal to, or above, 60 degrees C eliminate the protein activity in 15 to 20 min. Western blot analyses identified no cross reactions of the purified PIF with TGF-alpha, TNFalpha, IFNgamma, or IL-1beta, suggesting that PIF is a new protein belonging to the group of factors secreted by fibroblasts able to inhibit cellular proliferation.

Blotting, Western↗
PubMed1999

Impaired kidney transplant survival in patients with antibodies to hepatitis C virus.

BACKGROUND: With a few exceptions, most published studies do not show an influence of antibodies to the hepatitis C virus (HCV) on the success of a kidney transplant. METHODS: We studied all our renal transplant recipients who had received kidneys from cadaver donors (n = 335) and had been treated with quadruple immunosuppression (steroids, azathioprine, and antilymphocyte antibodies, followed by cyclosporin). We had information on the status of the hepatitis C antibodies before and/or after the transplant in 320 cases (95.5%; in 300, pre-transplant). Patients with HCV antibodies before and/or after the transplant were considered to be HCV positive (HCV+). RESULTS: The HCV+ patients had more time in dialysis and a greater number of transfusions, hyperimmunized cases, and re-transplants. The evolution in the first post-transplant year was similar in both groups, but afterwards, the HCV+ patients had proteinuria more often as well as worse kidney function. The survival rate of the graft was significantly less in the HCV+ cases: 90.6, 68.3 and 51.0% at respectively 1, 5 and 10 years, compared with 91.5, 84.7 and 66.5% in HCV-patients (P<0.01). The patient survival rate was: 96.4, 87.0, and 71.9% in the HCV+ patients at 1, 5, and 10 years, compared with 98.2, 96.0 and 90.0% in the HCV- cases respectively (P<0.01). The differences remained the same in stratified studies according to time spent in dialysis or pre/post-transplant evolution of HCV antibodies, even when immunologically high-risk patients were excluded. In multivariant analysis, the presence of HCV antibodies acted as a independent prognostic factor for the survival of the kidney and the patient: 3.0 (1.8-5.0) and 3.1 (1.2-7.8) odds-ratio (95% of the confidence interval), respectively. The main cause of death among HCV+ patients was cardiovascular; there was no apparent increase in mortality rate due to infections or chronic liver disease. The loss of organs was mainly due to chronic nephropathy or death with a functioning kidney. CONCLUSION: The presence of hepatitis C antibodies, before or after transplantation, is associated with a worse long-term survival rate for both the patient and the transplanted kidney in our patients treated with quadruple therapy.

Adult↗
PubMed1999

Zygomatic-transmandibular approach for giant tumors of the infratemporal fossa and parapharyngeal space.

OBJECTIVE: The surgical anatomy of the infratemporal fossa and parapharyngeal space is often not properly understood by neurosurgeons, because these areas are more related to other medical disciplines. This article provides a detailed description of the infratemporal fossa and parapharyngeal space anatomy in cadaveric specimens and offers a neurosurgical perspective on a surgical approach that allows wide exposure and complete resection of giant tumors in this location. METHODS: Ten cadaveric specimens were prepared for anatomic study. Dissections were performed to emphasize the relationship between bone, muscles, and neurovascular structures and to simultaneously expose the middle cranial fossa, the infratemporal fossa, and the parapharyngeal space. Ten patients with giant lesions in these areas (with maximum tumor diameter >8 cm) were treated via this approach. RESULTS: The main obstacles to approaching the infratemporal fossa and the parapharyngeal space are the zygomatic arch, the parotid gland, the facial nerve, and the ascending ramus of the mandible. Thus, by combining a pterional-zygomatic craniotomy with transmandibular access, working up and down the parotid gland, the exposure is wider and safer. Among the 10 patients treated, tumors were totally resected in 7, subtotally resected in 2, and partially resected in 1. Morbidity was unremarkable, and, in 8 patients, clinical status improved dramatically. CONCLUSION: The zygomatic-transmandibular approach allows resection of giant lesions in the middle cranial base, when they are invading the infratemporal fossa and parapharyngeal space, with a low morbidity rate.

Adolescent↗
PubMed1999

Characterization of the type 8 capsular gene cluster of Streptococcus pneumoniae.

The complete nucleotide sequence of the capsular gene cluster (cap8) responsible for the biosynthesis of the capsular polysaccharide of Streptococcus pneumoniae type 8 has been determined. The cap8 gene cluster, located between the genes dexB and aliA, is composed of 12 open reading frames. A 14.7-kb DNA fragment embracing the cap8 genes was sufficient to transform an unencapsulated type 3 S. pneumoniae strain to a strain with the type 8 capsule. A possible scenario for the evolution of pneumococcal types 2 and 8 is outlined.

Base Sequence↗