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J Vela

Publications and source records attributed to J Vela.

16 recordsLinked to original sources
PubMed2005

Dehydroepiandrosterone (DHEA) modulates GHRH, somatostatin and angiotensin II action at the pituitary level.

In view of the present controversy related to the potential beneficial effects of clinical dehydroepiandrosterone (DHEA) treatments, and considering our own previous results that reveal an influence of this steroid in pituitary hyperplasia development in vivo in rats, we decided to evaluate the role of DHEA in prolactin and GH secretion, as well as in second messengers involved, in cultured rat anterior pituitary cells. DHEA (1 x 10(-5) to 1 x 10(-7) M) did not modify basal GH or prolactin release, and a prolactin inhibitory effect was observed only for androstenediol, a metabolite of DHEA. DHEA partially prevented dopamine (1 x 10(-6) M)-induced prolactin inhibition and facilitated the prolactin-releasing effect of 10(-8) M Ang II, without modifying the resulting Ca2+(i) mobilization. Furthermore, DHEA potentiated the GH release and cAMP production induced by 1 x 10(-8) M GHRH. Finally, DHEA partially reversed the inhibitory effect of 1 x 10(-8) M somatostatin on GH, but not prolactin, release. We conclude that DHEA in vitro, directly or indirectly through conversion into metabolites, is able to modulate the hormonal response of the pituitary to hypothalamic regulators. It can enhance pituitary prolactin release and induce GH secretion. These effects could help explain some of the side effects observed in prolonged DHEA treatments in vivo and should be taken into account when considering its use in human clinical trials.

Angiotensin II↗
PubMed2001

Quantitative determination of clenbuterol, salbutamol and tulobuterol enantiomers by capillary electrophoresis.

Enantiomers of clenbuterol, salbutamol and tulobuterol were directly separated and quantitated from a spiked sample by capillary electrophoresis (CE) using sulfaited beta-cyclodextrin (SCD) as chiral selector and phosphate as running buffer. The SCD and buffer concentration, pH and field strength were the parameters studied to optimize the separation. Optimal separation was obtained using 50 mM of phosphate monobasic at pH = 2.24, 0.25% (w/w) of sulfated cyclodextrin and a field strength of 10 kV, with 20 min total time analysis. Comparison between two different injection modes (hydrodynamic and electrokinetic) was made. In the hydrodynamic mode, repeatability (expressed as relative standard deviation, RSD) was less than 1.2% for migration times for all the analyte peaks and less than 2% for peak area percentages. With respect to reproducibility, RSD was less than 3.8% for migration time and less than 3% for peak area percentages. Calibration curves were set up for two different sample concentration ranges (1 to 10 microg mL(-1) and 160-800 ng mL(-1), of each of the racemates studied). Although the electrokinetic injection mode for an aqueous sample appeared to suffer from some enantiodiscrimination, calibration curves were linear in the range between 1 and 10 ng mL(-1) with regression coefficients ranging from 0.9996 to 0.9952. As in the case of hydrodynamic injection, the method was tested with a spiked sample.

Albuterol↗
PubMed2001

Rapid PCR-mediated synthesis of competitor molecules for accurate quantification of beta(2) GABA(A) receptor subunit mRNA.

We describe a fast and easy method for the synthesis of competitor molecules based on non-specific conditions of PCR. RT-competitive PCR is a sensitive technique that allows quantification of very low quantities of mRNA molecules in small tissue samples. This technique is based on the competition established between the native and standard templates for nucleotides, primers or other factors during PCR. Thus, the most critical parameter is the use of good internal standards to generate a standard curve from which the amount of native sequences can be properly estimated. At the present time different types of internal standards and methods for their synthesis have been described. Normally, most of these methods are time-consuming and require the use of different sets of primers, different rounds of PCR or specific modifications, such as site-directed mutagenesis, that need subsequent analysis of the PCR products. Using our method, we obtained in a single round of PCR and with the same primer pair, competitor molecules that were successfully used in RT-competitive PCR experiments. The principal advantage of this method is high versatility and economy. Theoretically it is possible to synthesize a specific competitor molecule for each primer pair used. Finally, using this method we have been able to quantify the increase in the expression of the beta(2) GABA(A) receptor subunit mRNA that occurs during rat hippocampus development.

Animals↗
PubMed2001

Involvement of inducible isoforms of COX and NOS in streptozotocin-pancreatic damage in the rat: interactions between nitridergic and prostanoid pathway.

Streptozotocin-induced pancreatic damage involves nitric oxide (NO) and prostaglandins (PGs) overproduction. In this work we aim to evaluate a putative relationship between the elevated NO levels and the altered prostanoid production in pancreatic tissue from streptozotocin-diabetic rats. Total NOS activity and nitrate/nitrite pancreatic levels in tissues from diabetic rats are decreased when the cyclooxygenase (COX) inhibitor indomethacin (INDO) is added to the incubating medium, while the addition of PGE(2)increases nitrate/nitrite production and NOS levels. INDO and PGE(2)selectively affect Ca(2+)-dependent NOS (iNOS) activity in diabetic tissues, and they have not been able to modify nitrate/nitrite levels, iNOS or Ca(2+)-dependent (cNOS) in control tissues. When the NOS inhibitor L-NMMA was present in the incubating medium, control pancreatic [(14)C]-Arachidonic Acid ([(14)C]-AA) conversion to 6-keto PGF(1 alpha)and to TXB(2)was lower, and PGF(2 alpha), PGE(2)and TXB(2)production from diabetic tissues diminished. The NO donors, spermine nonoate (SN) and SIN-1, enhanced TXB(2)levels in control tissues, while PGF(2 alpha), PGE(2)and TXB(2)levels from diabetic tissues were increased. PGE(2)production from control and diabetic tissues was assessed in the presence of the NO donor SN plus INDO or NS398, a specific PG synthase 2 inhibitor. When SN combined with INDO or NS398 was added, the increment of PGE(2)production was abolished by both inhibitors in equal amounts, indicating that the activating effect of nitric oxide is exerted on the inducible isoform of cyclooxygenase. In the diabetic rat, prostaglandins and NO seem to stimulate the generation of each other, suggesting a lack of regulatory mechanisms that control the levels of vasoactive substances in acute phase of beta-cell destruction.

Animals↗
PubMed2000

Berberine cation: A fluorescent chemosensor for alkanes and other low-polarity compounds. An explanation of this phenomenon

Alkanes in the presence of berberine sulfate provide an enhancement of fluorescent signal, which depends on alkane concentration and structure, when the system is irradiated with monochromatic UV light. Computational analysis suggests that an ion-induced dipole between alkanes and berberine sulfate is responsible for this phenomenon. This interaction can properly model the experimentally obtained fluorescent response. The proposed explanation allows other interacting systems to be designed, which have been experimentally confirmed.

Journal Article↗
PubMed2000

GABAA and alpha-amino-3-hydroxy-5-methylsoxazole-4-propionate receptors are differentially affected by aging in the rat hippocampus.

We have investigated the age-dependent modifications in the expression of eight different subunits of the gamma-aminobutyric acid, type A (GABA(A)) receptor (alpha1, alpha2, alpha3, alpha5, beta2, beta3, gamma2S, and gamma2L) and all four subunits of the alpha-amino-3-hydroxy-5-methylsoxazole-4-propionate (AMPA) receptor (GluR1-4) in the hippocampus of 24-month-old rats. All aged hippocampi displayed a remarkable increase (aged/adult ratio, 3.53 +/- 0.54) in the mRNA levels of the short version of the gamma2 subunit in parallel with a similar increase in the gamma2 subunit protein (aged/adult ratio, 2.90 +/- 0.62). However, this increase was not observed in the mature receptor. On the other hand, the expression of the different alpha subunit mRNAs increased moderately with aging, displaying a heterogeneous pattern. The most frequent modification consisted in an increase in the expression of the alpha1 subunit mRNA (aged/adult ratio, 1.26 +/- 0.18), in parallel with a similar increase on the alpha1 protein (aged/adult ratio, 1. 27 +/- 0.12) and in the alpha1 incorporated to the assembled GABA(A) receptor (tested by immunoprecipitation; aged/adult ratio, = 1.20 +/- 0.10). However, in the same hippocampal samples, no major modifications were observed on the expression of the AMPA receptor subunits. As a whole, these results indicated the existence of an increased expression of the GABA(A) receptor subunits and a preservation of the AMPA receptor at the hippocampal formation. These modifications could reflect the existence of specific deficiencies (neuronal loss and/or deafferentiation) on the GABAergic system in the aged rats.

Age Factors↗
PubMed2000

Enhancement of fluorescence in thin-layer chromatography induced by the interaction between n-alkanes and an organic cation

Fluorescence enhancement of a broad variety of solutes has been used extensively in TLC although no thorough explanation has been proposed. In this work, we try to understand it and explore new applications to which it can be put. In this way, alkanes can be quantitatively determined by fluorescence scanning densitometry using silica gel plates impregnated with berberine sulfate. Molecular simulation and analysis of molecular orbitals allows this phenomenon to be explained in this case and lays the groundwork to explain fluorescence enhancements produced by other molecules. A ion-molecule interaction between alkanes and berberine sulfate is responsible for the enhancement of fluorescence produced by alkanes. Computational results suggest that the surrounding alkane molecules provide an apolar environment to the berberine cation, thus enhancing the intensity of the fluorescence signal. This proposed explanation has been tested by extending the fluorescence determination to other compounds. These include biologically interesting saturated and unsaturated fatty acids, steroids and derivatives, prostaglandins, ceramides, galactocerebrosides, as well as terpenes, and polypropylene glycols. In addition, according to the proposed explanation, the properties required for alternative impregnants to berberine are discussed.

Journal Article↗
PubMed2000

Pancreatic nitric oxide and oxygen free radicals in the early stages of streptozotocin-induced diabetes mellitus in the rat.

The objective of the present study was to explore the regulatory mechanisms of free radicals during streptozotocin (STZ)-induced pancreatic damage, which may involve nitric oxide (NO) production as a modulator of cellular oxidative stress. Removal of oxygen species by incubating pancreatic tissues in the presence of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) (1 U/ml) produced a decrease in nitrite levels (42%) and NO synthase (NOS) activity (50%) in diabetic but not in control samples. When NO production was blocked by N(G)-monomethyl-L-arginine (L-NMMA) (600 microM), SOD activity increased (15.21 +/- 1.23 vs 24.40 +/- 2.01 U/mg dry weight). The increase was abolished when the NO donor, spermine nonoate, was added to the incubating medium (13.2 +/- 1.32). Lipid peroxidation was lower in diabetic tissues when PEG-SOD was added (0.40 +/- 0.02 vs 0.20 +/- 0.03 nmol/mg protein), and when L-NMMA blocked NOS activity in the incubating medium (0.28 +/- 0.05); spermine nonoate (100 microM) abolished the decrease in lipoperoxide level (0.70 +/- 0.02). We conclude that removal of oxygen species produces a decrease in pancreatic NO and NOS levels in STZ-treated rats. Moreover, inhibition of NOS activity produces an increase in SOD activity and a decrease in lipoperoxidation in diabetic pancreatic tissues. Oxidative stress and NO pathway are related and seem to modulate each other in acute STZ-induced diabetic pancreas in the rat.

Analysis of Variance↗
PubMed1996

[Continuous domiciliary oxygen therapy in Zaragoza: a cross-sectional home study].

To assess use of long-term domiciliary oxygen therapy (LDOT) in Saragossa by means of home interviews. We conducted a cross-sectional study of patients undergoing LDOT, interviewing 312 of the 614 patients who used O2 at home in January 1993 (103/100,000 h). Health care workers visited the patients at home and collected all available information related to indications, pattern of use of O2 and complementary tests done. The interviewer also took spirometric readings, SaO2 readings breathing room air and after 30 min breathing O2, and administered a quality of life questionnaire (only to patients with pneumopathies). All patients selected were assessed; 195 (62.5%) suffered from chronic obstructive pulmonary disease (COPD), 33 (10.6%) from asthma, 31 (9.9%) from other pneumopathies, and 53 (17%) from a variety of conditions that were not primarily bronchopulmonary. Thirty-six (11.5%) were active smokers. Only 101 of the 184 patients for whom arterial gasometric readings were available met the criteria for prescribing LDOT. SaO2 without O2 was > or = 92% in 89 (28.5%) patients and > or = 90% in 193 (61.8%). Only 96 (31%) patients reported using O2 more than 15 hours/day and there was a weak inverse relation (p = 0.04) between hours of use and FEV1 in the COPD group. Quality of life for patients with pneumophaties depended entirely on degree of lung function deterioration and was unrelated to use of O2. The rate of use of LDOT Saragossa is one of the highest in Spain. In an estimated 28.5-46% of cases, the indications are inappropriate, mainly due to infrequent use of arterial gas measurement and the prescription of LDOT for patients without COPD. This situation largely explains why patients hardly ever use LDOT on a daily basis.

Aged↗
PubMed1996

[Hypothyroidism as a complication of the treatment of hepatitis C with interferon].

Interferon is becoming the most important therapy for chronic hepatitis due to hepatitis C virus. Secondary effects are frequent and sometimes so important to stop the therapy. Autoimmune disorders, specially autoimmune thyroid diseases may occur. We report two out of 69 chronic hepatitis C patients treated with interferon who developed hypothyroidism, that required definitive substitutive therapy.

Adult↗
PubMed1983

Self-mutilation.

Explore the source record for details and available documents.

Abdomen↗
PubMedDate not supplied

Determination of hydrocarbon types in petroleum and coal-derived products by thin-layer chromatography/densitometry.

Different methodologies based on thin-layer chromatography (TLC)/densitometry were used to separate and quantitate hydrocarbon types in middle distillates (gas oil), heavy distillates (lubricant) from petroleum, and coal-derived products. Thus, petroleum products were separated into saturates and aromatics by development, using n-hexane (9 min) followed by dichloromethane (4.5 min), of silica gel plates impregnated with berberine sulfate. Detection of saturates and aromatics was performed by fluorescence scanning using 365 nm as the excitation wavelength. Alternative detection of aromatics can be performed on either silica gel or berberine-impregnated plates by using ultraviolet (UV) densitometry at 250 nm. On the other hand, polar coal-derived products were separated into aromatics, polar compounds, and uneluted components by using silica gel plates and development with toluene (12 min), followed by dichloromethane-methanol (95 + 5, v/v), with detection by UV densitometry at 250 nm. In all cases, external standard calibration was used for quantitation. Results were validated by using standard methods or well-established techniques of the petrochemical industry. The potential usefulness of TLC/densitometry is discussed.

Chromatography, Thin Layer↗