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J Mallol

Publications and source records attributed to J Mallol.

At least 55 records · Page 3Linked to original sources
PubMed1996

Inefficacy of collagen shields in the rabbit corneal wound-healing process.

A controlled study in the rabbit eye was performed to clarify the suitability of collagen shields in accelerating the wound healing process in damaged cornea. After a standardized bilateral keratectomy, the spontaneous evolution of the healing process in the right eye (control eye) was compared with the evolution in the left eye, treated with a collagen shield (a shield of the 12- or 24-h type). The healing area was measured by planimetry after fluorescein staining at 0, 24, 48, and 72 h after keratectomy. Histological and immunohistochemical analysis of the healing process was also performed. Reepithelization of the damaged cornea was almost complete at 72 h, and there were no differences in the time course of the healing process between control and treated eyes. There was an important polymorphonuclear infiltration in treated eyes, mainly composed of eosinophiles, which was not present in control eyes. This indicates a subacute inflammatory immunological reaction. It is concluded that the usefulness of collagen shields should be reappraised, especially in injured corneas.

Animals↗
PubMed1996

Corneal wound healing in the rabbit eye: activity of a fibronectin-splitting product.

The corneal wound-healing properties of fibronectin (FN) and a fibronectin hydrolysate (FNH) have been evaluated in comparison with commonly used drugs. Nonpenetrating bilateral surgical keratectomy was performed in male albino rabbits. The left eye was treated with the active product, whereas the right eye served as a control (vehicle). The healing area was measured by planimetry after fluorescein staining at 0, 24, 48, and 72 h after keratectomy. Histological and immunohistochemical analysis of the healing process was also performed. Results were as follows: (a) Nandrolone (p < 0.005) and asiaticoside (p < 0.001), both at 10 mg/ml, in eyedrops delayed the healing process. (b) An ointment containing vitamin A and amino acids also delayed the process but at the limit of statistical significance (p = 0.055). (c) FNH (20-80 mg prot/ml) significantly improved the quality and shortened the time of the healing process at 60 mg prot/ml and above. (d) Human FN (100-800 micrograms/ml) did not affect the healing process. Immunohistochemical analysis demonstrated that FNH accelerated the appearance of endogenous FN in the damaged cornea earlier than in the control eyes. It is concluded that FNH may be useful in the management of corneal wounds, whereas the effectiveness of FN is doubtful.

Animals↗
PubMed1996

Glutathione, glutathione S-transferase and reactive oxygen species of human scalp sebaceous glands in male pattern baldness.

We investigated the contribution of reactive oxygen species to the development of sebaceous gland hyperplasia and the characteristics of the glutathione S-transferase/glutathione system in male pattern baldness. Glutathione S-transferase, glutathione, and thiobarbituric acid-reactive substances were determined in sebaceous gland-enriched scalp skin of men affected by male pattern baldness and were subjected to hair autotransplantation. In comparison with the hairy occipital-donor areas, the following results were obtained in alopecic frontoparietal samples: glutathione S-transferase-specific activity increased 7-fold (p < 0.001); enzyme affinity towards 1-chloro-2,4-dinitrobenzene decreased 2-fold (p = 0.009); glutathione content decreased 2.5-fold (p = 0.017); and thiobarbituric acid reactive substances increased 2-fold (p = 0.006). Chromatofocusing analysis, bromosulfophthalein IC50 values, enzyme-linked immunosorbent assay, and immunohistochemistry with polyclonal antibodies raised against glutathione S-transferases alpha, mu, and pi demonstrated the presence of alpha, pi, and probably the 5.8 alpha isoenzymes in the sebaceous gland. These results support the hypothesis that reactive oxygen species are involved in the pathogenesis of sebaceous gland hyperplasia in male pattern baldness.

Adult↗
PubMed1995

Immunological identification of A1 adenosine receptors in brain cortex.

The A1 adenosine receptor from pig brain cortex has been identified by means of two antipeptide antibodies against two domains of the receptor molecule: PC/10 antiserum was raised against a part of the third intracellular loop, and PC/20 antiserum was raised against a part of the second extracellular loop. PC/10 antibody was able to recognize a 39-kDa band that corresponded to the A1 receptor, as demonstrated by immunoblotting and by immunoprecipitation of the molecule cross-linked to [125I](R)-2-azido-N2-p-hydroxy(phenylisopropyl)adenosine. Besides the 39-kDa band, PC/20 also recognized a 74-kDa form that does not seem to correspond to a receptor-G protein complex. The occurrence of the two bands was detected and analyzed in samples from different species and tissues showing a heterogeneous distribution of both. The 74-kDa form can be converted into the 39-kDa form by treatment with agonists or antagonists of A1 adenosine receptors. These results suggest that A1 adenosine receptor can occur in dimers and that the dimer-monomer conversion might be regulated by adenosine as the physiological ligand. Since the 74-kDa aggregates were not recognized by PC/10, it is likely that part of the third intracellular loop participates in the protein-protein interaction.

Animals↗
PubMed1994

Solubilization and molecular characterization of the nitrobenzylthioinosine binding sites from pig kidney brush-border membranes.

The nitrobenzylthioinosine binding sites from luminal membranes of proximal tubule of pig kidney were solubilized by treatment of the brush-border membrane vesicles with the zwitterionic detergent CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate) in 2% solution. The high yield solubilization of a stable form of the transporter took place in the presence of adenosine in the medium of incubation with the detergent and the additional presence of glycerol as stabilizer. The solubilization of the NBTI-sensitive nucleoside transporter from pig kidney brush-border membranes did not change the nitrobenzylthioinosine (NBTI) binding characteristics; the only major change was a 3-fold decrease in the affinity. The carrier molecule was cross-linked to [3H]NBTI and by electrophoretic characterization under reducing conditions it displayed a molecular mass of 65 kDa. Treatment of the samples at low temperature prior to electrophoresis gave rise to the appearance of further bands corresponding to dimeric and tetrameric forms which interacted non-covalently. The removal of the N-linked oligosaccharides by treatment with endoglycosidase F shifted the molecular mass to 57 kDa. The chromatographic behaviour of the solubilized transporter was similar to that of human erythrocytes and differed from that found in pig erythrocytes. Since the molecular mass of the monomer before and after treatment with endoglycosidase F is the same for pig erythrocytes and pig kidney luminal membranes, the different chromatographic behaviour might result from tissue differences due to transcriptional variations or to posttranscriptional modifications of the transporter molecule.

Affinity Labels↗
PubMed1994

Phosphorylation of adenosine in renal brush-border membrane vesicles by an exchange reaction catalysed by adenosine kinase.

Uptake of [3H]adenosine in brush-border membrane (BBM) vesicles from either rat or pig kidney leads to an accumulation of intravesicular [3H]AMP. The lack of significant levels of ATP and the presence of AMP in BBM indicated that a phosphotransfer between [3H]adenosine and AMP occurs. The phosphotransfer activity is inhibited by iodotubercidin, which suggests that it is performed by adenosine kinase acting in an ATP-independent manner. The existence of a similar phosphotransferase activity was demonstrated in membrane-free extracts from pig kidney. From the compounds tested it was shown that a variety of mononucleotides could act as phosphate donors. The results suggest that phosphotransfer reactions may be physiologically relevant in kidney.

Adenine Nucleotides↗
PubMed1994

Influence of duration of occlusion time on respiratory mechanics measured with the single-breath technique in infants.

To determine the effect of the length of end-inspiratory occlusion on the values of respiratory system compliance (Crs) and resistance (Rrs) calculated from the single-breath technique, 6 infants with cystic fibrosis were studied. End-inspiratory occlusions lasted between 0.3 and 1.2 seconds, and between 8 and 32 separate occlusions were made in each infant. Examination of the individual data showed a systematic tendency for Crs to decrease as the length of the airway occlusion increased, with statistical significance reached in two subjects. Using a random effects model, it was demonstrated that there was a decrease of 0.15 mL/cmH2O in Crs for each 0.1 s increase in occlusion time. The influence of length of plateau time for Crs was similar to that of total occlusion time. No such tendency was seen for Rrs. These data reinforce the current emphasis on greater standardization in the methodologies used for infant lung function testing and for more fully reporting methodological details.

Airway Resistance↗
PubMed1994

A1 adenosine receptors can occur manifesting two kinetic components of 8-cyclopentyl-1,3-[3H]dipropylxanthine ([3H]DPCPX) binding.

The results described in this paper show, for the first time, that A1 adenosine receptors can have two kinetic components for the binding of the antagonist [3H]DPCPX. At low ionic strength (< or = 42 mmol/l), dissociation of [3H]DPCPX bound to A1 receptors fitted better to a two kinetic components model than to a one kinetic component model. The kinetic constants were consistent with comparable Kd values for the two components of the antagonist binding, and therefore these two components cannot be distinguished by saturation isotherm analysis.

Animals↗
PubMed1994

Modifications of glutathione S-transferase (GST) activity in the last period of pregnancy in rats treated with benzo(a)pyrene (BP).

Pregnant rats were treated with benzo(a)pyrene (BP) (50 mg/kg every 2 days) from day 7 of pregnancy and killed at day 16 or day 19. Km of erythrocyte glutathione S-transferase (GST) decreased during pregnancy in control rats (1.29 x 10(-3) M at day 16; 1.02 x 10(-3) M at day 19) and even more in treated rats at day 19 (0.71 x 10(-3) M). Vmax was lower in treated rats at day 19 (0.56 mumol/min/g haemoglobin) than in control rats (0.88 mumol/min/g haemoglobin) suggesting inhibition of the enzyme. Placental weight diminished in treated rats at day 19 but was not affected at day 16. Chromatofocusing of placental GST showed a single peak (pH 8.3-8.6) in control and treated rats on day 16 and an additional peak (pH 7.0-7.4) in treated rats on day 19. An increase in Km (2.84 x 10(-3) M) and Vmax (69 nmol/min/mg protein) in placental GST was observed in treated rats at day 16 (Km = 1.61 x 10(-3) M; Vmax = 43.3 nmol/min/mg protein, in control rats) followed by a decrease in these parameters in rats treated until day 19 (Km = 1.63 x 10(-3) M; Vmax = 48.7 nmol/min/mg protein). These results suggest that BP, initially, stimulates GST synthesis in placenta, followed by an inhibition of the enzyme at day 19. Fetal weight was also affected by BP treatment, especially at day 16. Km and Vmax values of fetal GST were higher in treated rats at day 16 than in control rats but these differences were not detectable at day 19. This may be explained by the more protective role of the placenta at day 19 than at day 16. Glutathione content in erythrocytes, placenta and fetus was not affected by BP.

Animals↗
PubMed1994

Regulation of nitrobenzylthioninosine-sensitive adenosine uptake by cultured kidney cells.

The effect of nitrobenzylthioinosine (NBTI) on [3H]adenosine uptake and the characterization of the [3H]NBTI binding in cell (primary cultures and LLC-PK1 cell line) plasma membrane and brush-border membrane (BBM) vesicles from pig renal cortices and LLC-PK1 cells was analyzed. [3H]adenosine uptake was strongly inhibited by NBTI in nonconfluent cells, whereas it was totally insensitive to the reagent in BBM. The concentration dependence of [3H]adenosine uptake in BBM was linear, suggesting simple diffusion. In both cell membranes and BBM high-affinity [3H]NBTI binding was observed. [3H]NBTI binding as well as NBTI-sensitive [3H]adenosine uptake was strongly reduced when cells grew to confluence. Both reduction effects were reproduced by treatment of nonconfluent cells with chlorophenyl adenosine 3',5'-cyclic monophosphate (cAMP), which indicates that the transporter is regulated by a cAMP-dependent protein kinase. To confirm this hypothesis, the binding of [3H]NBTI was analyzed in pig kidney BBM obtained in the presence of orthovanadate and alkaline phosphatase. With respect to control membranes, BBM obtained in the presence of orthovanadate showed a lower maximum number of binding sites (Bmax), whereas those obtained in the presence of alkaline phosphatase showed a slight increase in Bmax for [3H]NBTI binding. Taken together, these results suggest that the reduction in both [3H]NBTI-binding capacity and NBTI-sensitive [3H]adenosine uptake takes place by a mechanism that involves phosphorylation of the transporter molecule or of a protein that interacts with it.

Adenosine↗
PubMed1994

Glutathione S-transferase in normal human anagen hair follicles.

Glutathione S-transferase (GST) has been quantified and characterized in healthy human anagen hair follicles obtained from 36 men and 36 women (26 +/- 7 years of age). GST activity was determined using 1-chloro-2,4-dinitrobenzene as a substrate, and the values in men were: 0.5 +/- 0.2 mU/follicle, significantly different from women (0.36 +/- 0.2 mU/follicle); 196 +/- 98 mU/mg protein and 309 +/- 158 mU/mg DNA without significant differences from women. Enzyme activity showed a high degree of inter-individual variability (23.5-fold when expressed per follicle, 18.29-fold expressed per mg of protein and 22.75-fold per mg of DNA) in the whole population and this variability was higher in women. Ion-exchange chromatography by KCl and enzyme immunoassay suggest that the GST present in hair follicles corresponds with the acidic form. The percentage of anagen hairs in each subject showed a positive correlation with the following parameters: GST/hair, GST/DNA and DNA/hair. It is concluded that GST may contribute to the maintenance of the hair growth cycle.

Adult↗
PubMed1993

Adenine nucleotides and adenosine metabolism in pig kidney proximal tubule membranes.

Exogenous adenosine triphosphate (ATP) added to brush-border membrane vesicles was rapidly degraded mainly to inosine according to the high ecto-nucleotidase activities in these vesicles. In the absence of phosphate, inosine was slowly transformed into hypoxanthine, and xanthine oxidase and dehydrogenase activities were not detected. The presence of ecto-adenosine deaminase and ecto-adenosine monophosphate (AMP) nucleotidase was shown. The ecto-adenosine deaminase was inhibited by deoxycoformycin and was also detected in rat renal brush-border membrane vesicles. Using orthovanadate, levamisole, and alpha, beta-methylene adenosine diphosphate as possible inhibitors, alkaline phosphatase was shown to be the main agent responsible for ecto-AMP nucleotidase activity. In pig renal basolateral membrane vesicles and in whole cell extracts from pig renal cortex, ecto-AMP nucleotidase was the limiting factor in ATP degradation. Comparing the ATP catabolism in the whole cell cortical extract with the catabolism in the same sample precleared of membranes, it was shown that ectonucleotidase activity is mainly bound to the membranous components. It is also shown that the whole cell extract of pig renal cortex has hypoxanthine phosphoribosyl transferase activity, and it seems probable that the rapid and specific formation of luminal inosine and its transport into the cell in competition with adenosine may start the purine salvage pathway through the synthesis of IMP from hypoxanthine.

Adenine Nucleotides↗
PubMed1993

International comparison of asthma prevalence in children: Australia, Switzerland, Chile.

The aim of the study was to determine if the prevalence of symptoms suggestive of asthma in school-age children was similar in three countries with differing language and culture. To answer this question, we used the same instrument, translated appropriately, for schoolchildren in Melbourne, Australia, St. Gallen, Switzerland, and La Serena, Chile. A three page respiratory symptoms questionnaire was issued to schools for distribution to children for completion by parents and return to the school. Three age groups were selected for study, based on the average age of the school grade. Grades were used with average ages of 7, 12, and 15 years, respectively. A total of 26,628 questionnaires were issued to parents (Australia, 10,981; Switzerland, 4,464; Chile, 11,183). The response rates for each country were 89% for Australia, 97.5% for Switzerland, and 71% for Chile. The prevalence of wheezing in the last 12 months for 7 year olds was 23.1% in Melbourne, 7.4% in St. Gallen, and 26.5% in La Serena; for 12 year olds it was 20.9% in Melbourne, 6.0% in St. Gallen, and 21.1% in La Serena; for 15 year olds it was 18.6% in Melbourne, 4.5% in St. Gallen, and 17.7% in La Serene. A history of wheezing was more common in boys than girls at age 7 in Melbourne and St. Gallen, but not La Serena. This difference was less at age 12 and was not seen at age 15. Among those who had reported wheezing in the last 12 months, bronchodilator use was reported by 83% (1,611/1,948) from Melbourne, 46% (118/259) from St. Gallen, and 47% (538/1,140) from La Serena.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Enhanced glutathione S-transferase activity and glutathione content in human bladder cancer. Followup study: influence of smoking.

Glutathione content and glutathione S-transferase activity have been studied in human bladder specimens obtained from controls and from patients with superficial transitional cell carcinoma (tumor samples and peri-tumor normal tissues from the same patient). After combining an earlier study from our laboratory with the additional material presented (9 healthy controls and 25 transitional cell carcinoma patients), it can be observed that glutathione S-transferase activity was significantly greater in tumor than in peri-tumor normal tissue (34 patients, p < 1 x 10(-7)) or in normal mucosa (17 controls, p < 1 x 10(-3)). Glutathione content was significantly greater in tumor than in peri-tumor normal tissue (p < 5 x 10(-3)) or in normal mucosa (p < 2 x 10(-2)), with this increase being evident only in smokers. When comparing normal mucosa and peri-tumor samples no significant differences were found either for glutathione S-transferase activity or for glutathione content. Results demonstrate the relationship between the glutathione S-transferase/glutathione system and development of transitional cell carcinoma, as well as its role in cellular resistance to chemotherapy.

Aged↗
PubMed1993

Role of histidine residues in agonist and antagonist binding sites of A1 adenosine receptor.

The influence of pH on the equilibrium dissociation constant and on kinetic association and dissociation constants was studied for adenosine receptor agonist L-N6-[adenine-2,8-3H, ethyl-2-3H]phenylisopropyladenosine ([3H]R-PIA) and antagonist 8-cyclopentyl-1,3-[3H]-dipropylxanthine ([3H]DPCPX). Two ionizable groups, of pK 7.0 and pK 7.4, are involved in the [3H]R-PIA associations with high- and low-affinity states of the receptor, and another group, of pK 6.0, is involved in the association with the low-affinity state. No ionizable group is involved in the dissociation process for the high-affinity state, whereas two ionizable groups, of pK 6.0 and 6.5, are involved in the low-affinity state. For [3H]DPCPX, three ionizable groups (pK 6.0, 7.4, and 8.0) are involved in the association process and only one group, (pK 6.0), is involved in the dissociation step. The apparent pK values obtained agree with histidine residues. We thus studied the effect of diethylpyrocarbonate (DEP), which reacts irreversibly with histidine residues, on agonist and antagonist binding to A1 adenosine receptors from pig brain cortical membranes. DEP treatment of membrane reduced the affinity (KD) and the total binding (R) of the agonist and the antagonist. Membrane preincubation with unlabeled ligand (R-PIA or DPCPX) prevented the effect of DEP modification observed when the same ligand, but with label, is added to the same membranes, but did not prevent the DEP modification on different, labeled ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Guanylate cyclase activity in male pattern baldness. Stimulating effect of 3-beta-androstanediol.

Guanylate cyclase (GC) activity was measured in the cytosolic fraction of sebaceous gland-enriched skin samples obtained from alopecic and non-alopecic areas of subjects affected by male pattern baldness. GC activity was significantly higher in alopecic scalp (7.13 +/- 2.7 pmol/min/mg prot; n = 22) than in non-alopecic samples (3.91 +/- 0.48 pmol/min/mg prot; n = 8). 3-beta-androstanediol was able to increase GC activity up to 15% when added to the incubation medium (1 x 10(-5) M). The regional differences observed should be due to the larger size of the sebaceous glands in alopecic areas. The higher production of dihydrotestosterone and 3-beta-androstanediol in alopecic areas may also contribute to determine the level of GC in scalp skin. The role of second messenger systems in sebaceous glands to understand certain aspects of the action mechanism of androgens is discussed.

Alopecia↗
PubMed1993

Thermodynamic analysis of agonist and antagonist binding to membrane-bound and solubilized A1 adenosine receptors.

The thermodynamic properties of the agonist [Adenine-2,8-3H, ethyl-2(3)-H]-N6-phenylisopropyladenosine ([3H]R-PIA) and the antagonist 8-Cyclopentyl-1,3-[3H]dipropylxanthine ([3H]DPCPX) binding to membrane-bound and 3-3[-(choloamidopropyl)-dimethylammoniol-1-propanesulfonate/ digitonin- solubilized A1 adenosine receptors from pig brain cortex were evaluated. Rate constants for [3H]R-PIA and [3H]DPCPX association (k+1) and dissociation (k-1) processes to this receptor subtype were measured from association-dissociation experiments at six different temperatures. The values for equilibrium association constant (KA = 1/KD) were derived from rate constant values (k+1/k-1). The antagonist binding to membrane-bound receptors, the agonist binding to fast kinetic component membrane-bound receptors and the agonist binding to soluble receptors showed a linear temperature-dependence of the standard free-energy change. The first two processes are enthalpy- and entropy-driven, and the third process is enthalpy-driven with entropy working against it. On the other hand, a curvilinear temperature-dependence appears in the agonist binding to slow kinetic component membrane-bound receptors and in the antagonist binding to soluble receptors, but analyzing the semireactions (association-dissociation) involved in each case reveals that the thermodynamic behavior is very different. The thermodynamic similarities and differences are discussed in terms of receptor--G protein interaction.

Animals↗