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Biomedical subjects

J A Díaz

Publications and source records attributed to J A Díaz.

At least 19 recordsLinked to original sources
PubMed2003

Nucleotide sequence and infectious transcripts from a full-length cDNA clone of the carmovirus Melon necrotic spot virus.

We have studied the biological and molecular characteristics of a MNSV isolate collected in Spain (MNSV-Malpha5) and generated a full-length cDNA clone from which infectious RNA transcripts can be produced. The host range of MNSV-Malpha5 appeared to be limited to cucurbits and did not differ from that of MNSV-Dutch [4, 21]. However, differences were observed in the type of symptoms that both isolates could induce. A full-length cDNA of MNSV-Malpha5 was directly amplified by reverse-transcription polymerase chain reaction (RT-PCR) using a 5'-end primer anchoring a T7 RNA promoter sequence and a 3'-end primer, and cloned. Uncapped RNAs transcribed from this cDNA clone were infectious and caused symptoms indistinguishable from those caused by viral RNA when mechanically inoculated onto melon, cucumber or watermelon plants. The complete genome sequence of MNSV-Malpha5 was deduced from the full length cDNA clone. It is 4271 nt long and, similarly to MNSV-Dutch, consists of 5' and 3' untranslated regions (UTRs) and five open reading frames (ORFs) coding for 29, 89, 42 and two small 7 kDa proteins. One notable difference between MNSV-Malpha5 and other sequenced MNSV isolates was found, as for MNSV-Malpha5 the first of the two small ORFs, which are contiguous in the genome, terminates with a genuine stop codon, whereas for MNSV-Dutch and other sequenced MNSV isolates it terminates with an amber codon. This suggested that the putative p14 readthrough protein that could be expressed from the MNSV-Dutch and other MNSV genomes could not be expressed from the MNSV-Malpha5 genome. Also, the nucleotide and amino acid sequences comparisons showed a distant relationship of MNSV-Malpha5 with other known MNSV isolates.

Carmovirus↗
PubMed2002

Impact of induced aniseikonia on stereopsis with random-dot stereogram.

In this work, we evaluate the impact of induced aniseikonia on stereopsis. For this, we determined the disparity range (maximum disparity), a parameter related to the size of the physical region that can be perceived stereoscopically. A significant decline in the disparity range was detected with aniseikonia induced by size lenses of 3% for five of the seven observers tested; 5% was necessary for the other two observers. The data indicate the influence of aniseikonia in stereopsis and the need to minimize such impact. These results may be useful in surgical processes such as the correction of pseudophakic patients and refractive surgery in which aniseikonia can be induced to alter the binocular function of the patient.

Adult↗
PubMed2002

Binocular summation of chromatic changes as measured by visual reaction time.

We determined visual reaction times to monocular and binocular changes in the luminance of isochromatic stimuli and to monocular and binocular changes in the color of isoluminant stimuli. Two isoluminant color changes were tested: chromatic variations along the red-green axis of Boynton's (1986) two-stage color vision model and chromatic variations along the yellow-blue axis of the same model. The results indicate a greater degree of binocular summation for luminance change than for color change. This result was largely independent of the motor component of reaction time.

Adult↗
PubMed2000

Changes in stereoscopic depth perception caused by decentration of spectacle lenses.

The effect that decentered spectacle (ophthalmic) lenses exert on depth perception has been studied, evaluating stereopsis through the disparity range (maximum horizontal disparity) for random-dot stereograms (RDS). The results show that variations in fusional convergence due to increments of decentration can diminish the stereopsis in observers, reducing the region within which stereoscopic correspondence can take place. Decreases in disparity ranges were found for vertical and horizontal prismatic effects, although the prismatic effect necessary for this was less in the vertical case. A decreased disparity range has also been confirmed with figural-stimuli stereograms and using prisms for generating the prismatic effects.

Adaptation, Ocular↗
PubMed2000

[Topographical pachymetry and pachymetric topography in circumscribed posterior keratoconus].

CASE REPORT: A 29 year-old male patient presenting circumscribed posterior keratoconus in the left eye was studied. After ocular examination, corneal morphometry was studied by a computer-assisted topographic analysis and topographical ultrasonic pachymetry. Corneal thickness profile was represented by a colour-coded map from twenty-five measured points (pachymetric topography). DISCUSSION: Slit lamp biomicroscopy shows a paracentral-localized area of moderate corneal thinning with a nasal-superior concavity on posterior corneal surface. Topographical pachometry and pachometric topography allow to make precise corneal thinning evaluation and offer useful diagnostic data for this rare corneal dystrophy.

Adult↗
PubMed1999

Synthesis and anti-HIV activity of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs): a new family of HIV-1 specific non-nucleoside reverse transcriptase inhibitors.

The anti-HIV activity of a novel series of 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs) has been described. The compounds were synthesized via Curtius rearrangement of appropriate sulfamoylcarboxy azides which, in turn, were prepared from known starting materials. Several 4-substituted-2-benzyl-derivatives were found to selectively inhibit human immunodeficiency virus type 1 [HIV-1 (IIIB)] replication in MT-4 and CEM cells. These TTDs were also effective against other strains of HIV-1 (RF, HE, MN, NDK), including those that are resistant to AZT, but not against HIV-2 (ROD) or simian immunodeficiency virus [SIV(MAC251)] at subtoxic concentrations. Some of the test compounds exhibited antiviral activity against L100I RT mutant virus, but significantly lost antiviral activity against K103N, V106A, E138K, Y181C and Y188H RT mutant viruses. Compounds 6d, 6f and 6g were inhibitory to HIV-1 RT at concentrations that rank between 16.4 and 59.8 microM (nevirapine: IC50 = 4.5 microM against HIV-1 RT). Inhibition of HIV-1 RT by compound 6g was purely non-competitive with respect to the natural substrate (dGTP), which is in agreement with the nature of inhibition shown by other NNRTIs such as nevirapine and delarvidine. A structure-activity relationship was established for the anti-HIV activity of these heterocyclic compounds. TTDs represent a new chemical class of non-nucleoside HIV-1 reverse transcriptase inhibitors (NNRTIs).

Anti-HIV Agents↗
PubMed1998

Novel 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazine derivatives as non-nucleoside reverse transcriptase inhibitors that inhibit human immunodeficiency virus type 1 replication.

The 1,1,3-trioxo-2H,4H-thieno[3,4-e][1,2,4]thiadiazines (TTDs) represent a recently discovered chemical class of non-nucleoside reverse transcriptase inhibitors that selectively block human immunodeficiency virus type 1 replication. In a search for a better understanding of their mode of binding and with the aim of obtaining novel lead compounds, a second series of TTD derivatives was synthesized and evaluated for antiviral activity. The design of the new compounds was based on a variety of chemical modifications which were carried out in the original prototype 20a (QM 96521). Substitution of a halogen at the meta position of the N-2 benzyl group resulted in an improvement of the antiviral activity by 1 order of magnitude. Compounds bearing at the N-4 position a cyanomethyl, propargyl, or benzyl substituent were found to be the most potent of the series. Modifying the thieno[3,4-e] ring fused to the 1,2,4-thiadiazine moiety to other heterocyclic ring systems decreased the potency. The results obtained in this investigation have provided new indications for the design of even more effective TTDs.

Cell Line↗
PubMed1998

Biochemical characterization of the Golgi-complex proteins of Tritrichomonas foetus.

Using cell-fractionation techniques (differential and discontinuous gradient centrifugation), we obtained a highly enriched fraction containing the Golgi complex of Tritrichomonas foetus. This fraction was further subfractionated by sodium carbonate (150 mM) treatment at pH 11.5, leading to the isolation of the Golgi content and membrane subfractions. Both fractions were characterized by electron microscopy. The protein content of membrane and luminal subfractions was about 40% and 60% of the total Golgi protein, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed an enrichment of 15 protein bands in the Golgi fraction, with molecular masses varying between 15 and 116 kDa. Alkaline treatment released some proteins into the medium, but most of them were associated with the Golgi membrane.

Animals↗
PubMed1998

Improvement of the print-capture polymerase chain reaction procedure for efficient amplification of DNA virus genomes from plants and insect vectors.

A rapid and simple procedure is described to amplify efficiently geminivirus DNA genomes by improving the print-capture polymerase chain reaction (PCR) procedure reported recently for RNA viruses. This method, termed print-PCR (P-PCR), allows direct amplification of DNA from infected plant or whitefly tissues printed directly on Whatman 3MM paper, without the need of any grinding, incubation, or washing steps previous to the amplification reaction. P-PCR reduces sample manipulation and avoids previous extraction of nucleic acids, thereby diminishing the possibilities of cross-contamination between samples. P-PCR has been successfully applied to whiteflies and various plant species infected by two different tomato yellow leaf curl viruses, TYLCV-Sr and TYLCV-Is, and for the amplification of the full-length genome of TYLCV-Is from infected plants.

Animals↗
PubMed1997

Purification and biochemical characterization of the hydrogenosomes of the flagellate protozoan Tritrichomonas foetus.

A highly purified hydrogenosomal fraction was obtained from Tritrichomonas foetus by differential and Percoll gradient centrifugations. Transmission electron microscopy and assay of the malic enzyme activity were used to evaluate the isolation method and the integrity of the organelle. The isolated hydrogenosomes showed the same morphology as observed in intact cells, including the presence of a peripheral vesicle with an electron-dense content. SDS-PAGE revealed the presence of several protein bands, with those of 120, 66, 60, 59, 48, 45, and 35 kDa as the major ones. The hydrogenosome membrane was solubilized with Triton X-100 leaving a fraction containing its matrix attached to the peripheral vesicle. Further treatment with proteinase K solubilized the matrix components, leaving a pure peripheral vesicle fraction. Enzymatic assay during all procedures suggested that malate dehydrogenase was localized in the hydrogenosomal membrane. SDS-PAGE showed that proteins of 66, 45 and 32 kDa were localized in the peripheral vesicle. Western blot analysis of all fractions using alkaline phosphatase-conjugated wheat germ agglutinin revealed the presence of glycoproteins, with a major one of 45 kDa, in the peripheral vesicle of the hydrogenosome.

Animals↗
PubMed1996

Tritrichomonas foetus: isolation and characterization of the Golgi complex.

An effective methodology to isolate and characterize the Golgi complex of Tritrichomonas foetus is described in this work. Using sucrose density gradient centrifugation, two highly enriched Golgi fractions (GF1 and GF2) were obtained. Enzymatic assays of GF1 and GF2 showed a strong enrichment in galactosyltransferase activity (20- and 7-fold, respectively), with minimal contamination with other organelles. The GF fraction was further subfractionated by alkaline treatment, which resulted in the production of Golgi content and membrane subfractions. Electron microscopic observations of intact cells or Golgi fractions fixed in solutions containing glutaraldehyde and tannic acid, as well as of deep-etched replicas of isolated fractions, revealed the presence of discrete bridges only between closely apposed cisternae.

5'-Nucleotidase↗
PubMed1996

Isolation and biochemical characterization of the plasma membrane of Tritrichomonas foetus.

A fraction containing plasma membrane-enriched vesicles has been prepared from Tritrichomonas foetus. Cells were ruptured using a Potter type homogenizer, under well controlled conditions, and membranes were isolated by differential centrifugation and in discontinuous sucrose gradient. This fraction was enriched 8 and 10-fold in the plasma membrane marker enzymes 5'-nucleotidase and (Na+ + K+)-dependent, ouabain-sensitive ATPase, respectively. Determination of Glucose-6-phosphatase and NADPH cytochrome c reductase activities in this fraction, indicates a minimal contamination with endoplasmic reticulum membranes. Analysis by Sodium Dodecyl Sulfate-Polyacrylamide (SDS-PAGE) gradient gel showed that the plasma membrane fraction contains several proteins with major bands corresponding to apparent molecular weights of 48, 45, 39, 37, 32, 30, 27, 23, 20, 19, 17, and 15 kDa.

Animals↗
PubMed1996

[Lipoprotein(a) concentrations in type I diabetes mellitus].

OBJECTIVES: To determine the distribution of lipoprotein(a) levels and prevalence of hyperLp(a) in diabetes mellitus type I (IDDM). To analyze the effect of glycemic control and microalbuminuria on Lp(a) levels. METHODS: Cross-sectional study of 263 subjects with IDDM with a mean age of 19.2 +/- 11.6 years and an evolutive course of 6.3 +/- 6.5 years. Apart from Lp(a), measurements were obtained from serum levels of lipids, apolipoproteins AI and B, fructosamine, glycosilated hemoglobin (HbA1c), and albuminuria in all patients. RESULTS: Mean serum concentrations of Lp(a) were 16.5 +/- 18.1 mg/dl and 18.5% of patients had Lp(a) levels > 30 mg/dl [hyperLp(a)]. With a multivariate regression analysis, the only variable correlated with Lp(a) levels was cholesterol LDL (p < 0.001). Patients with hyperLp(a) did not differ from the other patients in any of the other variables analyzed, and patients with HbA1c higher and lower than 8% had similar mean serum Lp(a) concentrations (14.0 +/- 16 vs. 17.9 +/- 20). Lp(a) concentration was also similar among patients with albuminuria higher and lower than 20 micrograms/min (16.6 +/- 20 vs. 17.7 +/- 16). CONCLUSIONS: Control of glycemia and microalbuminuria have no effect on Lp(a) concentrations in diabetes mellitus type I. HyperLp(a) is not indicative of a poor glycemic control.

Adolescent↗
PubMed1995

Influence of the luminance signal and red-green and yellow-blue opponent chromatic signals in figural-stimuli stereograms.

The influence of color signals on stereopsis has been studied using figural-stimuli stereograms with variations introduced according to the opponent chromatic channels (red-green and yellow-blue), derived from Boynton's color-vision model. We used wallpaper stereograms, which enable the rank-order disparity ranges of the chromatic and luminance signals to be compared with the rank-order disparity range of proximity, a particular spatial configuration of the stereogram in which there are no variations in chromaticity and/or luminance. The results indicate that both chromatic signals contribute to stereopsis as does the luminance signal, contradicting the model of Hubel and Livingstone. The results also show there are no clear dependencies upon the kind of signal processed, as luminance and chromatic variations are processed with the same efficiency.

Color Perception↗
PubMed1992

Differences in antidiabetic drug utilisation between three different health systems in the same national region.

The consumption of antidiabetic drugs in a Spanish region (Extremadura) in the period 1986-1987 has been investigated by the "defined daily dose" (DDD) method. The study was done in three health care systems in the region: civil servants ("Mutualidad de Funcionarios Civiles del Estado: MUFACE") armed forces group ("Instituto Social de las Fuerzas Armadas: ISFAS") and the national system ("Instituto Nacional de la Salud: INSALUD"). The total consumption of antidiabetic drugs varied three-fold, ranging from 5,73 DDD per 1000 inhabitants per day (3,71 DDD per 1000 inhabitants per day for oral antidiabetic drugs and 2,02 DDD per 1000 inhabitants per day for insulin) in the civil servant group to 15,82 DDD per 1000 inhabitants per day (12 DDD per 1000 inhabitants per day for oral antidiabetic drugs and 3,82 DDD per 1000 inhabitants per day for insulins) in the armed forces. The differences were more pronounced for oral antidiabetics than for insulins. The utilization of insulin among the civil servants was about half of that by the two other groups. Of oral antidiabetics, sulphonylureas were the most frequently used by the three groups, and within them glibenclamide accounted for more than half of the DDDs, while biguanides were scarcely used in any group. The differences are difficult to assess, since they could be due to several factors, such as age-differences in the population studied, different prescribing habits, and differences in sociocultural level. The results justify further comparative studies of drug utilization in different health systems within the same region.

Drug Utilization↗