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Biomedical subjects

A Artigues

Publications and source records attributed to A Artigues.

At least 19 recordsLinked to original sources
PubMed2000

Primary Sjögren's syndrome in men: clinical and immunological characteristics.

OBJECTIVE: To determine the clinical and immunological characteristics of primary Sjögren's syndrome (SS) in men from a large series of unselected patients with this condition. METHODS: We studied 223 consecutive patients (204 women and 19 men; mean age at onset 53 y, range 15-87 y, mean disease duration 77 months) with primary SS visited in our units. All these patients fulfilled 4 or more of the diagnostic criteria for SS proposed by the European Community Study Group in 1993. RESULTS: Nineteen (9%) patients were men and they represent the male group described in this paper. Extraglandular manifestations during the course of their disease were present in 10 (53%) of our male patients with primary SS: articular involvement in 4 (21%) patients, interstitial pneumopathy in 3 (16%) and peripheral neuropathy in 2 (11%). ANA were positive in 13 (68%) patients, RF in 5 (31%), anti-Ro/SS-A in 3 (16%) and cryoglobulins in 1/14 (7%). When compared with women, men with primary SS presented a lower prevalence of articular involvement (21 percent; vs 46%, P=0.03, OR 0.32, CI 0.07-0.97). CONCLUSION: Although primary SS is typically a disease of middle-aged women, clinicians should note that it may be diagnosed in male patients. Except for a lower prevalence of articular involvement, we could no find any notable differences in clinical and immunological characteristics between male and female patients with primary SS.

Adolescent↗
PubMed1999

[Validity of the notifications of red measles based on clinical diagnosis in Cataluna, Spain].

OBJECTIVE: To compare the characteristics of clinical cases of measles with confirmed cases of measles registered in Cataluña during a period of four months. PATIENTS AND METHODS: An epidemiological survey was carried out on 171 cases of measles detected by a specific system of surveillance. The survey included data on age, sex, clinical symptoms, laboratory confirmation, immunization status and probable site of transmission. The relationship between the variable case (with or without laboratory confirmation) and the rest of variables was determined by the adjusted odds ratio, using a model of logistic regression. RESULTS: The epidemiological survey showed that 30.4% (52/171) had laboratory confirmation, 12.9% (22/171) had epidemiological confirmation and the rest, 56.7% (97/171) only complied with the clinical definition. The rash had a longer duration in confirmed cases (5.9 days) than in non confirmed cases (5.2 days). The lack of laboratory confirmation was associated with age younger than 5 years (ORa = 0.1; 95% CI 0.1-0.8), but there were no differences in sex, immunization status or others clinical symptoms. CONCLUSION: In clinical cases of measles the duration of the rash was lower than confirmed cases. The proportion of cases with laboratory confirmation was low (30.4%) and should be increased in the future. History of previous immunization ought not to rule out diagnosis of measles.

Adolescent↗
PubMed1998

Divergent Hsc70 binding properties of mitochondrial and cytosolic aspartate aminotransferase. Implications for their segregation to different cellular compartments.

Cytosolic Hsc70 discriminates between the homologous mitochondrial and cytosolic isozymes of aspartate aminotransferase, binding exclusively the mitochondrial form. By screening a library of synthetic peptides spanning the sequence of the mitochondrial enzyme, we have identified binding sites in this polypeptide that interact with Hsc70. These potential binding sites are scattered over the entire sequence and map to secondary structure elements, particularly the alpha-helix, that are partly exposed on the surface of the native protein. Several peptides corresponding to analogous positions in the cytosolic enzyme sequence do not bind to Hsc70. Phylogenetic analyses suggest that Hsc70 binding sequences have diverged as a consequence of biochemical specialization ensuring differential interaction of each isozyme with the cellular machinery in charge of protein folding and translocation.

Amino Acid Sequence↗
PubMed1998

Insight into the conformation of protein folding intermediate(s) trapped by GroEL.

Many aspects of the mechanism by which the GroEL/ES chaperonins mediate protein folding are still unclear, including the amount of structure present in the substrate bound to GroEL. To address this issue we have analyzed the susceptibility to limited proteolysis and to alkylation of cysteine residues of mitochondrial aspartate aminotransferase (mAAT) bound to GroEL. Several regions of the N-terminal portion of GroEL-bound mAAT are highly susceptible to proteolysis, whereas a large core of about 200 residues containing the C-terminal half of the polypeptide chain is protected in the complex. This protection does not extend to the mAAT sulfhydryl groups which in the GroEL-mAAT complex have similar reactivity as in fully unfolded mAAT. These results suggest that the mAAT species bound to GroEL represent folding intermediates with a conformation that is substantially more disorganized than that of the native state. The N-terminal half of the molecule is more flexible and lies exposed at the mouth of the central cavity of GroEL. The more compact C-terminal section of mAAT, which contains residues located at the subunit interface in the native dimer, appears to be hidden in the central cavity of GroEL. Thus, the bulk of the interactions in the GroEL.mAAT complex seems to involve residues from the more compact C-terminal section of the substrate.

Aspartate Aminotransferases↗
PubMed1998

Opposite behavior of two isozymes when refolding in the presence of non-ionic detergents.

GroEL has a greater affinity for the mitochondrial isozyme (mAAT) of aspartate aminotransferase than for its cytosolic counterpart (cAAT) (Mattingly JR Jr, Iriarte A, Martinez-Carrion M, 1995, J Biol Chem 270:1138-1148), two proteins that share a high degree of sequence similarity and an almost identical spatial structure. The effect of detergents on the refolding of these large, dimeric isozymes parallels this difference in behavior. The presence of non-ionic detergents such as Triton X-100 or lubrol at concentrations above their critical micelle concentration (CMC) interferes with reactivation of mAAT unfolded in guanidinium chloride but increases the yield of cAAT refolding at low temperatures. The inhibitory effect of detergents on the reactivation of mAAT decreases progressively as the addition of detergents is delayed after starting the refolding reaction. The rate of disappearance of the species with affinity for binding detergents coincides with the slowest of the two rate-limiting steps detected in the refolding pathway of mAAT. Limited proteolysis studies indicate that the overall structure of the detergent-bound mAAT resembles that of the protein in a complex with GroEL. The mAAT folding intermediates trapped in the presence of detergents can resume reactivation either upon dilution of the detergent below its CMC or by adding beta-cyclodextrin. Thus, isolation of otherwise transient productive folding intermediates for further characterization is possible through the use of detergents.

Anilino Naphthalenesulfonates↗
PubMed1997

Refolding intermediates of acid-unfolded mitochondrial aspartate aminotransferase bind to hsp70.

The cytosolic (cAAT) and mitochondrial (mAAT) isozymes of eukaryotic aspartate aminotransferase share a high degree of sequence identity and almost identical three-dimensional structure. The rat liver proteins can be refolded and reassembled into active dimers after unfolding at low pH. However, refolding of the mitochondrial form after unfolding at pH 2.0 is arrested in the presence of hsp70, whereas this chaperone does not affect the refolding of the cytosolic isozyme unfolded under similar conditions. To elucidate the nature of the differential interaction between hsp70 and the two transaminase forms, we have characterized their refolding from their acid-unfolded states. The recovery of activity of the cytosolic enzyme is monophasic and can be adequately described by a single first-order reaction. By contrast, two sequential first-order rate-limiting steps can be detected for the refolding and reactivation of the mitochondrial protein. The overall refolding pathway of mAAT includes a very fast collapse to an intermediate with 80% of the secondary structure of the active dimer. This is followed by a slow isomerization to form assembly-competent monomers that rapidly associate to form an inactive dimer and a final structural rearrangement of the dimer to the native conformation. Analysis of the interaction of hsp70 with intermediates along the folding pathway of mAAT shows that the polypeptide loses its ability to bind to the chaperone after it has proceeded through the first isomerization/fast dimerization steps. Thus it appears that only the first collapsed intermediate states in the folding of mAAT bind hsp70. By contrast a faster refolding of cAAT from this collapsed state could explain, at least in part, the inability of hsp70 to bind this isozyme.

Animals↗
PubMed1996

[Fever of unknown origin in patients with HIV infection].

BACKGROUND: The aim of the study was to describe the etiology and clinical characteristics of fever of uncertain origin (FUO) among HIV-infected patients. METHODS: Prospective analysis of 35 episodes of FUO in HIV-infected patients from Balearic Islands that were studied through established guidelines. RESULTS: Most patients were at advanced stages of HIV-1 infection (mean CD4 cell count, 60/mm3). Mean duration of fever until diagnosis was 57 days. Average time of hospitalization until etiological diagnosis of FUO was 26 days (range: 8-127 days). The cause of FUO was identified in 33 cases (94%). Tuberculosis accounted for 18 cases (51%) and visceral leishmaniasis for 8 cases (23%). Other opportunistic infections were the cause of FUO in 8 cases (17%). In one patient, fever was due to Kaposi's sarcoma. Two patients died while febrile, without and identified etiology. Four patients had more than one cause that could contribute to FUO. Imaging techniques that yielded more diagnostic information were abdominal ultrasonography and serial chest X-ray. Leishmania serology and tuberculin skin test showed a high specificity but low sensitivities. Invasive procedures with a highest diagnostic field were fine needle aspirate of lymph nodes, and liver biopsy. CONCLUSIONS: FUO is more frequent in advanced stages of HIV disease. In our area, FUO is caused primarily by endemic opportunistic infections specially TB and visceral leishmaniasis, and rarely can be attributable to HIV or neoplastic diseases.

AIDS-Related Opportunistic Infections↗
PubMed1995

Conformational analyses on soluble and surface bound osteopontin.

Immunohistology of calvarial sections revealed that staining with monoclonal anti-osteopontin antibodies (clone MPIIIB10) is minimal unless sections are first treated with EDTA. In contrast, following treatment of sections with EDTA, strong staining of mineralizing osteoid areas and osteoblast-like cells was noted (Fig. 1B). Immunostaining for osteopontin appeared to be specific in that controls which substituted rabbit IgG or normal mouse ascites fluid for monoclonal antibody, or which omitted monoclonal antibody uniformly gave background results (Fig. 1C). In an effort to circumvent problems of antibody accessibility we examined the immunoreactivity of OP when adsorbed to plastic and hydroxyapatite surfaces. Although OP bound to plastic surfaces is reactive with MPIIIB10 antibodies, OP adsorbed to hydroxyapatite crystal surfaces is not recognized by these antibodies as assessed by two detection methods. These results demonstrate that most or all of OP bound to hydroxyapatite exhibits a different conformation than when bound to plastic surfaces. On the basis of immunohistologic results with calvarial sections, we suggest that the conformation of native OP in bone and of isolated OP adsorbed to hydroxyapatite may be similar. Finally, solution circular dichroism and Fourier-transformed infrared spectroscopic studies indicate that the conformation of bone OP is dependent upon its concentration, and, secondarily to the presence or absence of calcium ion. With both spectroscopic methods, addition of calcium appeared to increase the extent of disordered structure. We suggest that these findings support our hypothesis that bone matrix proteins exhibit a different conformation when adsorbed on hydroxyapatite crystal surfaces. Assumption of a more organized secondary structure in concentrated OP solutions (i.e., 15 mg/ml) is consistent with these results in that local concentrations of OP within a semisolid matrix may approach or exceed levels used here.

Animals↗
PubMed1994

Acid-induced reversible unfolding of mitochondrial aspartate aminotransferase.

The acid-induced reversible unfolding of several forms of the mitochondrial isoenzyme of mammalian aspartate aminotransferase, including its precursor form, has been characterized under equilibrium conditions. A minimum of two transitions can be detected for the holoenzyme (pyridoxal form). One transition takes place at pH 3.6 and corresponds to the monomerization of the dimeric protein. The second transition is centered at pH 3.3 and represents the disappearance of much of the tertiary and secondary structures. The presequence peptide in the precursor protein does not affect the equilibria nor the rate of unfolding in the pH range from 7.5 to 2.0. The presence of the cofactor, pyridoxal 5'-phosphate, stabilizes the protein against acid denaturation. At pH 2.0, the protein retains significant amounts of secondary structure (26% alpha-helix, 20% beta-structure). Increasing the ionic strength at pH 2.0 results in significant changes in the secondary structure of the unfolded protein that acquires some of the characteristics ascribed to a compact molten globule. According to the circular dichroism spectra these changes are characterized by an increase in beta-structure, although Fourier transform infrared spectroscopy analysis indicates that this increase in beta-structure is due mostly to the formation of intermolecular beta-sheet as a consequence of protein aggregation. The formation of high molecular weight aggregates has been confirmed by analytical ultracentrifugation. Following neutralization of the acid-unfolded state at low ionic strength both mature and precursor proteins refold to their native active state (> 80% yield). By contrast the compact state present at pH 2.0 and high ionic strength is unable to recover its activity following neutralization. Thus, this compact state does not appear to represent an intermediate in the folding pathway of the protein, but rather a dead end product of aggregation, which may reflect the intrinsic tendencies of the unfolded protein to oligomerize at intracellular salt concentrations unless controlled by factors such as chaperones present in the cellular environment.

Animals↗
PubMed1993

Cytosolic serine hydroxymethyltransferase. Deamidation of asparaginyl residues and degradation in Xenopus laevis oocytes.

Rabbit liver cytosolic serine hydroxymethyltransferase exists as a set of subforms which exhibit different isoelectric points. Previous studies have shown that deamidation of an asparagine residue at position 5 of the amino acid sequence accounted for some of the charge heterogeneity (Artigues, A., Birkett, A., and Schirch, V. (1990) J. Biol. Chem. 265, 4853-4858). The present study has also identified asparagine 220 as being partially deamidated. An estimated 25-30% of the purified enzyme contains an isoaspartyl residue at position 220. This suggests that deamidation of asparagine 220 occurs by the beta-aspartyl shift mechanism. Western blot analysis of purified cytosolic serine hydroxymethyltransferase, after isoelectric focusing under reducing and denaturing conditions, showed four subforms of the individual subunits with respect to isoelectric point. Extracts from 3-day- and 3.5-year-old rabbit livers showed the presence of these same four subunit subforms. Purified cytosolic serine hydroxymethyltransferase was found to be degraded in 24 h after mechanical injection into Xenopus laevis oocytes. However, when the first 14 amino acid residues are removed from the enzyme by digestion with chymotrypsin, leaving a fully catalytically active enzyme, the rate and extent of degradation of the truncated enzyme in oocytes were significantly reduced. One of the deamidated asparagine residues is at position 5, suggesting that this deamidation site may be a signal for degradation of the enzyme.

Amino Acid Sequence↗
PubMed1991

[Yield of health exam in a rural school population].

The yield of the health status examination and associated factors in schoolchildren was assessed in the Primary Health Care center at Les Borges Blanques (Lérida), by means of the detection of abnormalities unknown by the parents receiving treatment. A self-administered questionnaire before the examination permitted to identify the already known abnormalities. Subsequently, a personal interview evaluated the follow-up. A total of 252 schoolchildren were evaluated, and 327 abnormalities were detected; 111 of these were unknown to the parents (33.94%); less than one half (48) presented for confirmation of the diagnosis. The diagnosis was confirmed in 44, treatment being prescribed in 36. In 33 schoolchildren (13.09%) the examination could have been useful. The observed low yield may be accounted for by the small rate of families that present for confirmation of the diagnosis. The personal communication of the diagnosis to the parents and the follow-up of cases might improve the yield.

Adolescent↗
PubMed1990

Evidence for the in vivo deamidation and isomerization of an asparaginyl residue in cytosolic serine hydroxymethyltransferase.

Rabbit liver cytosolic serine hydroxymethyltransferase exists in several subforms which have different isoelectric points. Incubation of the purified enzyme with chymotrypsin cleaves the enzyme at Trp14. The released amino-terminal 14-mer peptide was shown to exist in three forms of equal concentration. The peptides differ in structure only at the asparaginyl residue at position 5. In addition to asparagine at this position we found both aspartyl and isoaspartyl residues. The deamidation of Asn5 does not appear to occur during the purification of the enzyme. The in vitro rate of deamidation of Asn5 in the enzyme is more than 5-fold slower than the rate of deamidation of this residue in the free 14-mer peptide. The isoaspartyl residue at position 5 serves as a substrate for protein carboxyl methyltransferase both in the free 14-mer peptide and the native enzyme. The enzyme which has had the amino-terminal 14 residues removed by digestion with chymotrypsin still exists in several forms with different isoelectric points. Reaction of peptides from this enzyme with carboxyl methyltransferase suggests that there is at least one more asparaginyl residue in this enzyme other than Asn5 which has undergone deamidation with the formation of isoaspartyl bonds.

Amino Acid Sequence↗
PubMed1988

Phospholipase A2 hydrolysis of membrane phospholipids causes structural alteration of the nicotinic acetylcholine receptor.

Thermal perturbation techniques have been used to probe structural alteration of the nicotinic acetylcholine receptor as a function of perturbations of its native membrane environment. Differential scanning calorimetry and a technique involving heat inactivation of the alpha-bungarotoxin-binding sites on the receptor protein reveal that there is a profound destabilization of the acetylcholine receptor structure when receptor-containing membranes are exposed to phospholipase A2. The characteristic calorimetric transition assigned to irreversible denaturation of the receptor protein and the heat inactivation profile of alpha-bungarotoxin-binding sites are shifted to lower temperatures by approx. 7 and 5 C degrees, respectively, upon exposure to phospholipase A2 at a phospholipase/neurotoxin binding site molar ratio of about 1:100. The effects of phospholipase A2 on receptor structure can be (i) reversed by using bovine serum albumin as a scavenger of phospholipase hydrolysis products of membrane phospholipids, and (ii) stimulated by incorporation into the membranes of free, polyunsaturated fatty acids. In particular, linolenic acid (18:3(n-3] causes detectable destabilization of the alpha-bungarotoxin binding sites on the receptor at free fatty acid/receptor molar ratios as low as 10:1. Furthermore, alteration of receptor structure by added phospholipase occurs very rapidly, which is consistent with the observation of rapid in situ phospholipase A2 hydrolysis of membrane phospholipids, particularly highly unsaturated phosphatidylethanolamine and phosphatidylserine. Based on previously published data on the inhibition of acetylcholine receptor cation-gating activity caused by the presence of either phospholipase A2 or free fatty acids (Andreasen T.J. and McNamee M.G. (1980) Biochemistry 19, 4719), we interpret our data as indicative of a correlation between structural and functional alterations of the membrane-bound acetylcholine receptor induced by phospholipase A2 hydrolysis products.

Animals↗
PubMed1987

Thermal perturbation studies of membrane-bound acetylcholine receptor from Torpedo: effects of cholinergic ligands and membrane perturbants.

Thermal perturbation techniques have been used to probe structural features of the nicotinic acetylcholine receptor (AcChR). The information obtained from differential scanning calorimetry (DSC) of AcChR membranes (M.C. Farach and M. Martinez-Carrion (1983) J. Biol. Chem. 258, 4176) in the absence and in the presence of cholinergic ligands and local anesthetics, is comparable to that obtained from a simpler technique of heat inactivation of the alpha-bungarotoxin (alpha-Bgt) binding sites on the AcChR protein in similar samples. When AcChR membranes are heated at approximately 1 degree C/min, heat inactivation of toxin binding sites has a characteristic T50 value (temperature at which 50% of the initial capacity to bind alpha-Bgt remains) of approximately 60 degrees C. When heated at a constant temperature during increasing periods of time, the rate at which heat inactivation occurs is also characteristic of the temperature chosen for the experiment. The above thermal parameters are also sensitive to perturbation of the AcChR membrane matrix by the presence of subsolubilizing concentrations of detergents. Moreover, elimination of detergents by dialysis allows us to evaluate the reversibility or irreversibility of AcChR thermal destabilization induced by detergents or other membrane perturbants. Under the experimental conditions used, structural destabilization induced by octylglucoside or cholate can be fully reversed by detergent dialysis, while that exerted by deoxycholate cannot. "Thermal gel" analysis of the aggregation of AcChR subunits induced by heat (G. Soler, J. R. Mattingly, and M. Martinez-Carrion (1984) Biochemistry 23, 4630) has also been used to assess the effects of detergent presence on the AcChR protein. When deoxycholate is used as the perturbing agent, there is a particularly effective sulfhydryl-mediated aggregation of the gamma-delta subunit group, which appears to correlate with the irreversible destabilization of alpha-Bgt binding sites induced by that detergent.

Animals↗
PubMedDate not supplied

[Risk factors associated to tuberculosis patients with positive sputum microscopy].

OBJECTIVE: The main factor responsible for producing new cases of tuberculosis by exogen transmission is the existence of Mycobacterium tuberculosis in the sputum of tuberculosis patients. The objective of this study was to determine the risk factors associated to positive smear tuberculosis cases in Lleida (Spain). METHODS: We studied new cases of tuberculosis over the period 1992-1998. The variables considered were: age, gender, coinfection with HIV, injection drug use (IDU), consumption of alcohol, existence of caverns in thorax X-ray, and laboratory results of direct smear examination. We calculated the incidence rates for 100,000 persons-year. The association between the dependent variable case of tuberculosis with positive Mycobacterium tuberculosis smear and the remaining independent variables were assessed obtaining odds ratios (OR) and 95% confidence intervals (CI) (crude cOR and adjusted aOR by non conditional logistic regression). RESULTS: We detected 905 new cases of tuberculosis. The rates in the period 1992-1998 decreased from 38.8 to 30.8. 44.9% of cases (n = 406) presented a positive direct smear. There was a positive association between the risk of being a positive smear patient and having caverns in thorax x-ray (aOR = 6.8; 95% CI, 4.8-95), being male (aOR = 1.8; 95% CI, 1.3-2.6) and consuming alcohol (aOR = 1.6; 95% CI,1.1-2.3) and this risk was significant lower in those under 15 years old (aOR = 0.2; 95% CI, 0.1-0.5), and coinfection with HIV (aOR = 0.5; 95% CI, 0.3-0.9). CONCLUSIONS: HIV infection implies a reduced impact in endemecity of tuberculosis. Study of contacts and the implementation of directly observed treatment must be considered not only for coinfected HIV cases and IDU but also for adult males, especially those who consume alcohol, particularly when they have caverns.

AIDS-Related Opportunistic Infections↗