Browsing by Author "GONZALEZ, A"

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    APICAL SECRETION OF HEPATITIS-B SURFACE-ANTIGEN FROM TRANSFECTED MADIN-DARBY CANINE KIDNEY-CELLS
    (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 1993) GONZALEZ, A; NICOVANI, S; JUICA, F
    Hepatitis B surface antigen (HBsAg), the major envelope component of human hepatitis B virus, during infection drives the assembly and basolateral secretion from hepatocytes of both virions and subviral lipoprotein particles into the bloodstream. We studied the sorting behavior of HBsAg in the heterologous epithelial Madin-Darby canine kidney cells permanently transformed with the hepatitis B virus S gene. These cells, forming tightly packed monolayers in permeable supports, secreted HBsAg apically through a mechanism not involving transcytosis. This suggests that molecular features acting as apical addressing information, seemingly unfunctional or less efficiently used by the exocytic machinery of hepatocytes, could be contained in short hydrophilic regions of HBsAg. Lipids also could play a role in this asymmetric sorting because HBsAg is known to be secreted by forming macromolecular lipoprotein complexes rather than as a soluble protein. Together with available data, our results would imply not only the existence of tissue-specific variations in handling constitutively secreted proteins but also that these variations are strikingly dependent on the kind of protein examined. On the other hand, pulse-chase experiments with tunicamycin showed that the expression of apical information in HBsAg particles does not require N-linked glycosylation, contrasting with the known gp80 Madin-Darby canine kidney-endogenous apical secretory marker. This is the first experimental evidence that carbohydrate moieties in secretory proteins do not hold domain-specific sorting signals, a fact previously shown exclusively for membrane proteins. Thus, HBsAg provides a novel model system for the analysis of the molecular mechanisms of constitutive apical secretion.
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    CELL-GROWTH AND NA-K-CL COTRANSPORT RESPONSES OF VASCULAR SMOOTH-MUSCLE CELLS OF MILAN RATS
    (LIPPINCOTT WILLIAMS & WILKINS, 1994) CANESSA, M; SALAZAR, G; WERNER, E; VALLEGA, G; GONZALEZ, A
    The present study examines the role of serum growth factors in the proliferative response and Na-K-Cl cotransport activity of vascular smooth muscle cells from Milan normotensive (MNS) and hypertensive (MHS) rats. Cells from thoracic aorta of both strains were cultured in 10% serum medium and made quiescent by 72 hours in 0.3% serum medium. MHS cells grown with 10% serum had a shorter population doubling time than MNS cells between passages 8 and 12 (13.8+/-1.7 versus 20.1+/-1.6 hours, P<.0l, n=4). MHS cells also exhibited a higher response of thymidine incorporation into nucleic acid to serum, epidermal, and platelet-derived growth factor BB. In MHS cells epidermal (100 ng/mL) and platelet (50 ng/mL) growth factors increased thymidine incorporation 2- and 10-fold, respectively. In MNS cells epidermal factor did not induce a significant response, and that of platelet factor was twofold lower than in MHS cells. Binding curves revealed a higher number of receptors for platelet than epidermal growth factor in both strains and a similar number of both receptors in MHS and MNS cells. Quantitative immunoblots of these receptor proteins confirmed the observation that the greater proliferation of MHS cells could not be related to a higher number of growth factor receptors. Cotransport activity (bumetanide-sensitive Rb-86 influx in nanomoles per milligram protein per 5 minutes) was found to be significantly higher in MHS cells (16+/-3, n=18) than MNS cells (8+/-3, n=15) at confluence as well as in the log phase of serum-stimulated growth. No differences were found between strains with cells in the quiescent state. However, platelet growth factor (50 ng/mL) markedly stimulated cotransport in quiescent MHS cells, whereas epidermal growth factor was without effect. In conclusion, MHS cells exhibited enhanced serum- and platelet factor-stimulated proliferation rates and cotransport activity compared with MNS cells. These results suggest that platelet factor BB plays an important role in the proliferation of hypertensive vascular cells.
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    CLINICAL EXPRESSION OF RHEUMATOID-ARTHRITIS IN CHILEAN PATIENTS
    (W B SAUNDERS CO, 1995) MASSARDO, L; AGUIRRE, V; GARCIA, ME; CERVILLA, V; NICOVANI, S; GONZALEZ, A; RIVERO, S; JACOBELLI, S
    In populations such as Northern Europeans in which the HLA-DR4 subtypes Dw14 and Dw4 show strong association with rheumatoid arthritis (RA), these alleles and the double allelic dose of the shared epitope are considered severity markers. The clinical expression of RA varies in different populations, which may be determined by variation in the prevalence of these markers. In the present study we analyzed the expression of RA in 112 consecutive Chilean patients and its relation to the prevalence of genetic factors, prompted by our previous observation that DR4 is weakly associated to RA in this population. Mean age was 50 +/- 14 years; 90% were seropositive and 87% were female, with a disease duration of 10 +/- 8 years. Extra-articular manifestations were found in 38% of patients, rheumatoid nodules in 27%, vasculitis in 8%, and Sjogren's syndrome in 29%. Functional capacity (ACR, 1991) I or II: 82%. 15% of patients stopped working. Hand radiographs scored according to Steinbrocker in 89 patients: I, 21%; II, 15%; III, 43%; IV, 21%. In this series, patients with less formal education seemed to have more benign arthritis. In 97 controls and in 65 (56%) RA patients the presence of DRB1 alleles corresponding to DR1 and DR4 serotypes, to DR4-Dw subtypes, and homozygocity, were determined by polymerase chain reaction followed by specific oligonucleotide hybridization. The shared epitope was present in 53% of RA patients and in 30% of controls (P = .0048, odds ratio [OR] = 2.64). A double allelic dose of the epitope was present in 15% of RA patients compared with 4% of controls (P = .026, OR = 4.23). In a subgroup of 31 erosive RA patients we did not find a significant association of disease severity with the shared epitope in a single or double allelic dose. None of the DR4 subtypes that associate with RA in other populations was found significantly more prevalent in our patients. The severity of RA in our study compared with published series was intermediate between British patients with severe RA and Creek patients with milder disease. This may be due to the high prevalence of Dw13*0403 in our population.
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    WEAK ASSOCIATION BETWEEN HLA-DR4 AND RHEUMATOID-ARTHRITIS IN CHILEAN PATIENTS
    (BRITISH MED JOURNAL PUBL GROUP, 1990) MASSARDO, L; JACOBELLI, S; RODRIGUEZ, L; RIVERO, S; GONZALEZ, A; MARCHETTI, R