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Biomedical subjects

A Vidal

Publications and source records attributed to A Vidal.

At least 91 records · Page 5Linked to original sources
PubMed1993

Physical interaction between Langerhans cells and T-lymphocytes during antigen presentation in vitro.

Physical interaction between Langerhans cells and T cells is an essential requirement for antigen presentation. In this study we report the ultrastructural characteristics of the antigen-specific physical interactions that occur in vitro between murine Langerhans cells and T cells. Epidermal Langerhans cells enriched to 78% purity by a panning method were pulsed with 2,4-dinitrophenyl-Limulus polyphemus hemocyanin and co-incubated with syngeneic T lymphocytes primed in vivo with the same antigen. A substantial number of conjugates constituted by Langerhans cells surrounded by three or more lymphocytes were obtained after 60 min of incubation at 4 degrees C. Electron microscopy of the conjugates revealed that Langerhans cells and T lymphocytes interacted by two type of contacts. Type I was characterized by glycocalyx-glycocalyx interaction that occurred in relation to protrusions or microvilli of both cells. Type II was characterized by wide and tight areas of close apposition between Langerhans cells and T-lymphocyte plasma membranes. In these areas there were zones with intercellular bridges and small septilaminar junctions highly suggestive of gap junctions. An electron-immunogold procedure demonstrated the presence of DNP-LPH antigen on the type I contact. Our findings suggest that type I contact may represent the locus for antigen presentation whereas the type II contact may be involved in keeping adhesiveness between Langerhans cells and lymphocytes during antigen presentation.

Animals↗
PubMed1993

[Susceptibility of Neisseria gonorrhoea strains].

The susceptibility of 45 strains of Neisseria gonorrhoea was studied measuring minimal inhibitory concentrations of five antimicrobials. Results show that 66.7% of strains are resistant to tetracycline and 11.2% to penicillin. All strains were susceptible to ciprofloxacin, ceftriaxone and cefotaxime. This results should prompt to perform surveillance in different areas of Santiago and to establish new therapeutic norms for the treatment of gonococcal infections.

Anti-Bacterial Agents↗
PubMed1993

Damage of tracer erythropoietin results in erroneous estimation of concentration in mouse submaxillary gland.

It has been previously reported that 1) plasma erythropoietin (Epo) titer during exposure to hypobaria is lower in nephrectomized rats and mice whose submaxillary glands (SMG) were either ablated or atrophied than in nephrectomized controls whose SMG were intact and 2) that the gland shows one of the highest levels of immunoreactive Epo (iEpo) in the body. The latter observation, however, was questioned recently when it was observed that SMG extracts degrade labeled Epo used as tracer antigen in the radioimmunoassay (RIA), thus giving invalid estimates of Epo. Since this interpretation was in turn questioned, the present study was conducted to obtain more information on the subject and make these conflicting points clear. Investigation of the reported/possible degradation of Epo by SMG homogenates was conducted via polyacrylamide gel electrophoresis followed by radioautography or by a RIA in solid phase in which there was no simultaneous incubation of the tracer antigen with the SMG homogenates. It was observed that 125I-labeled rhEpo was degraded when incubated with SMG homogenates. Degradation was rapid, being evident when incubation lasted 30 minutes, and occurred in the presence of a protease inhibitor. It showed a high degree of specificity since it did not occur when Epo was incubated with kidney homogenate or normal mouse serum. SMG homogenate did not degrade labeled thyrotrophic hormone and degraded alpha interferon (IFN-alpha) only partially. When estimates of iEpo in SMG homogenate were performed in conditions of simultaneous (SI-RIA) or nonsimultaneous (NSI-RIA) incubation of the homogenate with tracer Epo, it was observed that while estimates of Epo in plasma were similar in both types of RIA and somewhat higher in kidney homogenate in the SI-RIA than in the NSI-RIA, estimates of Epo in SMG were about 60 times higher in the former than in the latter. Therefore, it could be concluded that most of the Epo detected by standard RIA in SMG homogenate does not represent true Epo because of damage of tracer Epo which determines loss of the integrity of the RIA system.

Animals↗
PubMed1991

Distribution of actin, actin-binding proteins, 43K protein, and spectrin in D. tschudii electrocytes.

With a view to establishing the location of proteins related to the nicotinic cholinergic receptor (AChR), immunocytochemical studies were carried out in the electric tissue of the South American ray Discopyge tschudii. The receptor protein was localized at the innervated, ventral region of the electrocyte in cryostat sections using Texas Red-labelled alpha-bungarotoxin, a specific AChR marker. A series of antibodies against actin and actin-associated proteins (alpha-actinin, vinculin, tropomyosin and spectrin) were also employed in indirect immunofluorescence assays. Furthermore, with the aid of the monoclonal antibody 1234A, the peripheral, nonreceptor 43K protein was found to be colocated with the AChR and spectrin at the ventral surface of the electrocyte. NBD-phallacidin was used to detect the filamentous form of actin or F-actin. The anti-actin antibody recognized epitopes throughout the electrocyte cytoplasm. F-actin was mainly distributed at the dorsal, non-innervated region, where alpha-actinin, vinculin and tropomyosin were also localized. The results indicate a) the existence of a close structural relationship between the 43K protein, spectrin, and the AChR at the ventral, innervated face of the electrocyte; b) the occurrence of an actin isoform probably mono or oligomeric-throughout the electrocyte's cytoplasm, and c) the possible association of F-actin, localized at the dorsal region of the electrocyte, with alpha-actinin, tropomyosin and vinculin, as in other cellular systems.

Actins↗
PubMed1991

Serum immunoreactive erythropoietin in high altitude natives with and without excessive erythrocytosis.

We report the estimation of blood hemoglobin (Hb), arterial blood oxygen saturation (SaO2), and serum immunoreactive erythropoietin (siEPO) in a group of Peruvian workers residing in Cerro de Pasco at 4300 m showing "excessive erythrocytosis" (EE, Monge's disease, chronic mountain sickness). These estimates were compared with those of humans residing either in Cerro de Pasco and showing "normal erythrocytosis" (NE) or in Lima (sea level, SL) to determine whether Hb and SaO2 are related to siEPO in high altitude (HA) natives with NE or EE. The three parameters showed statistically significant differences between HA and SL groups--the values in SL being lower. Significant differences were also found between NE and EE groups in Hb and SaO2. There was no statistical difference in siEPo between the two groups. The results indicate, therefore, that HA residents who develop EE are not distinguishable from residents who develop NE on the basis of estimates of siEPO. As a result, siEPO and Hb do not show a dose-response relationship in HA residents, and variation in EPO does not explain the striking variation in Hb at high altitudes.

Adult↗
PubMed1990

[The seroprevalence of Listeria infections without clinical sign in a population of pregnant women from the Reus area].

We describe the results of a study of asymptomatic Listeria monocytogenes serum prevalence in a population of pregnant women in the Reus area. The study includes newborn exam and correlation with laboratory data obtained by an indirect immunofluorescence method recently developed. The incidence of anti-Listeria antibody carriers was high (12%) but in no cases spontaneous abortions or fetal malformations were associated to high titers.

Adult↗
PubMed1990

[Paratyphoid B fever in 2 areas of Santiago. An analysis of the epidemiological significance].

Salmonella isolates from 3920 patients with typhoid fever from 2 areas in Santiago were analyzed to determine the frequency of association with S paratyphi B infection. This was demonstrated in 18.8% of subjects in both areas, a figure significantly higher than the 8-10% previously reported. The association with S paratyphi B was higher for females, especially for the younger age group. These findings suggest an infectious agent-gender-age interaction which may explain the discrepancy with previously reported rates of infection. Their possible relation to the chronic salmonella carrier state and association with biliary tract lithiasis and cancer is discussed.

Adolescent↗
PubMed1989

[Identification of group B beta hemolytic Streptococcus in infections of adults and children].

The frequency of isolation of group B beta-hemolytic streptococcus was investigated in samples from the skin, genitourinary tract and respiratory tract in adults and children, in 2 periods, 1977-79 and 1984-86. Hydrolysis of sodium hippurate or bile and sensitivity to bacitracin were used to identify the germ. Serologic group was confirmed by coagglutination. The incidence of isolation increased from 6.1% (n = 18) to 28.7% (n = 119) from the first to the second period, ranking second among all S groups. Isolation from blood and from spinal fluid in newborns was observed only in the second period.

Adolescent↗
PubMed1989

[A case of MEWDS. "The multiple evanescent white-dot syndrome"].

A young white man developed acute bilateral visual loss with no previous general illness. Ophthalmoscopic examination showed multiple small yellow-white lesions scattered throughout the posterior poles and mild periphery fundus. There was also fine granularity of two foveal areas and one optic disc margin was blurred. Fluorescein angiography showed early hyperfluorescence of the lesions and late staining of the retinal pigment epithelium. Electrophysiologic abnormalities were transient, asymmetric, more marked in photopic than in scotopic. The origin could be in retinal bipolar cells. These lesions regressed, with return of normal visual function within several weeks. These clinical findings are different from others acute inflammatory diseases primarily involving retinal pigment epithelium and photoreceptors. This aspect is usually described as "multiple evanescent white dot syndrome". The etiology of this syndrome remains unknown with no evidence of systemic disease. A history of flulike illness is rare.

Adult↗
PubMed1988

The glutathione transferase activity and tissue distribution of a cloned Mr28K protective antigen of Schistosoma mansoni.

A protective Mr28K antigen of Schistosoma mansoni, expressed from its cDNA, has been purified in a single step and shown to possess glutathione (GSH) transferase activity as predicted from sequence homologies with two mammalian GSH transferase multigene families. It is notable for its high 1-chloro-2,4-dinitrobenzene GSH transferase and linoleic acid hydroperoxide GSH peroxidase activities. The major GSH transferase of S. mansoni has been purified and its subunit is identical to this Mr28K antigen by criteria of Mr, immunochemistry, substrate specificity and peptide sequence analysis. In the parasite, the antigen is present in the tegument, protonephridial cells and subtegumental parenchymal cells. No significant immunological cross-reactivity between the S.mansoni and mammalian (human and rat) GSH transferases was observed.

Amino Acid Sequence↗
PubMed1987

[Demonstration of a pyrophosphate-fructose 6-phosphate 1-phosphotransferase in the latex from Hevea brasiliensis].

A pyrophosphate: fructose-6-phosphate 1-phosphotransferase activity (EC 2.7.1.90) has been characterized in cytosol from Hevea brasiliensis latex. It is Mg+ dependent enzyme, and the cation has an optimal effect between 2.5 to 3 mM for a concentration of 1 mM of pyrophosphate and 10 mM of fructose-6-phosphate. It is activated by catalytic content of fructose-2,6-diphosphate. Its potential activity is higher than 40% of that of ATP dependent phosphofructokinase (EC 2.7.1.11). Its optimum pH is between 7.5-7.6; then, the enzyme affinity is 0.3 mM for pyrophosphate and 3.5 mM for fructose-6-phosphate. It is suggested that the transferase plays a role in the pyrophosphate metabolism and the increasing of the energetic efficiency of glycolysis and so takes a significant part in the biochemical mechanisms involved in the latex yield.

Cytosol↗