Subcellular fractions of Brucella ovis distinctively induce the production of interleukin-2, interleukin-4, and interferon-gamma in mice.

The aim of this study was to evaluate the effect of 3 Brucella ovis subcellular protein fractions: Outer membrane (OMP), inner membrane (IMP), and cytoplasm (CP), on cellular immune response by in vitro production of interleukin (IL)-2, IL-4, and interferon (IFN)-gamma. Each fraction was inoculated 3 times into Balb/c mice, primary cultures of mice spleen cells were done, and these were then stimulated with the fractions. Culture supernatants were collected at 24, 48, 72, 96, and 120 h postinoculation. Cytokine concentration was measured by Duoset-enzyme-linked immunosorbent assay (ELISA). The OMP fraction induced highest cellular immune response of 1000 pg/mL of IL-2 at 24 h, which decreased to < 100 pg/mL by 96 h. The IL-2 response for the IMP fraction was low at 24 h, but exceeded that of the OMP fraction at 72, 96, and 120 h. The CP showed a poor IL response. Regarding the IFN-gamma production, OMP and IMP induced a high response at 120 h. These results open the possibility for the use of B. ovis outer and inner membrane proteins as a subcellular vaccine.

Antigenotoxic, antimutagenic and ROS scavenging activities of a Rhoeo discolor ethanolic crude extract.

Rhoeo discolor is a legendary plant used for treatment of superficial mycoses in Mexican traditional medicine. Despite its extended use, it is not known whether it has side-effects. An ethanolic crude extract from Rhoeo discolor was prepared, its mutagenic capacity was investigated by the Ames test, and its genotoxic activity in primary liver cell cultures using the unscheduled DNA synthesis assay. This extract was not mutagenic when tested with Salmonella typhimurium strains TA97, TA98 and TA100, and it did not elicit unscheduled DNA synthesis in hepatocyte cultures. In addition, we explored the antimutagenic and antigenotoxic activities of the extract and its ROS scavenger behaviour. Our results show that Rhoeo extract is antimutagenic for S. typhimurium strain TA102 pretreated with ROS-generating mutagen norfloxacin in the Ames test, and protects liver cell cultures against diethylnitrosamine induction of unscheduled DNA synthesis even at 1.9 ng per dish, which was the lowest dose tested. A free radical scavenging test was used in order to explore the antioxidant capacity of Rhoeo extract, as compared with three commercial well-known antioxidants quercetin, ascorbic acid and tocopherol. Rhoeo extract showed less radical scavenging effect than quercetin, but similar to that of alpha-tocopherol and more than ascorbic acid. It is important to note that this extract was neither mutagenic in S. typhimurium nor genotoxic in liver cell culture, even at concentrations as high as four- and 166-fold of those needed for maximal antimutagenic or chemoprotective activities, respectively.

Membrane vesicles released by Actinobacillus pleuropneumoniae contain proteases and Apx toxins.

Actinobacillus pleuropneumoniae serotype 1 releases vesicles containing proteases and Apx toxins into the culture medium. Vesicles were concentrated by ultracentrifugation and analyzed by electron microscopy and electrophoresis; their size ranged from 20 to 200 nm. A polyclonal antiserum raised against a purified high molecular mass secreted protease of serotype 1 recognized this protease on the surface of the vesicles by immunogold electron microscopy. Higher molecular mass polypeptides from vesicle extracts were recognized by the antiserum by Western immunoblot, indicating that the protease could form oligomers. However, these oligomers were not active against gelatin until secreted. Additionally, Apx toxins were also present in vesicles, and were recognized by Western immunoblot by an anti-serotype 1 toxins polyclonal serum. A. pleuropneumoniae antigens in vesicles were recognized by convalescent-phase pig sera from animals infected with serotype 1 or 5. The release of vesicles containing virulence factors could be a tissue damage mechanism in swine pleuropneumonia.

Secretion of proteases from Pasteurella multocida isolates.

The capability of Pasteurella multocida to secrete proteases to the culture medium and their characterization were studied in five animal isolates (bovine, chicken, sheep, and two from pig). All the isolates produced proteases in a wide range of molecular mass. It is suggested that they are neutral metalloproteases, since they were optimally active between pH 6 and 7, inhibited by chelating agents but not by other protease inhibitors, and reactivated by calcium. Proteases from isolates were able to degrade IgG. Several proteins from supernatants of cultures precipitated with 70% (NH4)2SO4 of all the P. multocida isolates were recognized by a polyclonal antiserum raised against a purified protease from Actinobacillus pleuropneumoniae. Protease production might play an important role during tissue colonization and in P. multocida diseases.

Purification and characterization of a protease from Actinobacillus pleuropneumoniae serotype 1, an antigen common to all the serotypes.

A high molecular-mass proteolytic enzyme of Actinobacillus pleuropneumoniae serotype 1, was purified from culture supernatants (CSN) by using DEAE-cellulose and sepharose-4B-gelatin chromatography. In 10% SDS-polyacrylamide gels copolymerized with porcine gelatin, the protease showed a single band of activity of > 200 kDa. However, minor molecular-mass proteolytic bands were observed when the protease was electrophoresed in the presence of either 5% beta-mercaptoethanol, 50 mM dithiothreitol, or 0.25 M urea. Furthermore, when the > 200-kDa purified protein was passed through a sucrose gradient, several bands with proteolytic activity were found: 62, 90, 190, and 540 kDa. The proteolytic activity was increased in the presence of calcium or zinc and was not affected after being heated at 90 degrees C for 5 min. Proteolytic activities were also observed in CSN from all A. pleuropneumoniae serotypes and biotypes. The purified protease hydrolyzed porcine IgA and IgG in vitro. In addition, by immunoblot the protease was recognized by serum of naturally infected pigs with serotypes 1 and 5, and by serum of pigs experimentally infected with serotypes 1, 2, 8, or 9. Serum of a pig vaccinated with CSN of a serotype 3 strain also recognized the protease, but not sera of pigs vaccinated with a bacterin (serotype 1). Proteins from CSN of all the serotypes, which were precipitated with 70% (NH4)2SO4, were recognized by a polyclonal antibody raised against the purified protease. Taken together these results indicate that an antigenic protease is produced in vivo by all the serotypes of A. pleuropneumoniae. The results indicate that proteases could have a role in the disease and in the immune response of pigs infected with A. pleuropneumoniae.

Entamoeba histolytica: proteinase secretion induced by collagen type I is dependent on cytoskeleton integrity.

Proteolytic activities of the protozoan parasite Entamoeba histolytica strain HM1:IMSS and the cytochalasin D-resistant mutant BG-3 were analyzed following stimulation with collagen type I and Ca2+, which induces electron-dense associated collagenase secretion. The mutant BG-3 had a protease activity of 73 kDa and secretion of total protease activity was not stimulated by collagen type I and Ca2+, which produced, in contrast, a 2-fold increase in protease secretion by the parental strain. This collagen-stimulated protease secretion was inhibited by cytochalasin D at a concentration of 1 microgram/ml. Cytochalasin D did not have any effect on the protease activity released by the mutant BG-3. These findings suggest that cytoskeleton integrity is necessary for collagen-induced protease secretion.

Kdp-like system in Salmonella typhimurium LT-2.

Salmonella typhimurium LT-2, as Escherichia coli K12, was able to grow in a potassium concentration-dependent manner, down to a very low concentration (< 5 microM). Its metabolic swelling also was [K+]-dependent. When the cells were subjected to hyperosmotic shock, this ion was uptaken rapidly, probably due to a K(+)-high affinity transport-system, similar to the E. coli Kdp system. The shrinkage in presence of 0.6 M NaCl, however, was more noticeable in S. typhimurium, which expressed a smaller level of intracellular K+ than E. coli. The genetic locus responsible for the ability of S. typhimurium to grow in low [K+], was mapped in nitrosoguanidine mutants and localized around min 18, close to the gal operon. This asseveration was confirmed by experiments of reversion, conjugation, and transduction. The mutants required considerably more [K+] to grow and to swell than the parental strain; in addition, below 1 mM [K+], they showed less internal [K+].

Inhibition of 3T3 adipogenesis by retinoic acid is not mediated by cytoplasmic retinoic acid-binding protein.

Retinoic acid (RA) inhibits 3T3 adipogenesis in a dose-dependent and reversible manner, but its mechanism of action remains unknown. 3T3-F442A cell variants obtained by mutagenesis with nitrosoguanidine and/or selection with high RA concentrations showed different resistance to RA cytotoxicity and underwent adipose conversion of various extents when they were cultured in adipogenic conditions. Commitment to adipose differentiation was also inhibited by RA in these clones. Gel filtration chromatography showed the presence of a cytosolic RA-binding activity in the parental cells but not in three of the variant clones isolated. We demonstrate that cytoplasmic RA-binding activity is not essential for the inhibitory effects of the retinoid on 3T3 adipogenesis, or for resistance to RA cytotoxicity. Other mechanisms should be involved to explain the inhibition of adipose differentiation by RA.

Secreted proteases from Actinobacillus pleuropneumoniae serotype 1 degrade porcine gelatin, hemoglobin and immunoglobulin A.

It was found that 48 hour cultures of Actinobacillus pleuropneumoniae secreted proteases into the medium. Electrophoresis in polyacrylamide gels (10%) copolymerized with porcine gelatin (0.1%), of the 70% (NH4)2SO4 precipitate from the culture supernatants, displayed protease activities of different molecular weights: > 200, 200, 90, 80, 70 and 50 kDa. They had activity over a broad range of pHs (4-8), with an optimal pH of 6-7. All were inhibited by 10 mM EDTA, and reactivated by 10 mM calcium. They were stable at -20 degrees C for more than a month. The proteases also degraded porcine IgA and porcine, human, and bovine hemoglobin, although they appeared to be less active against the hemoglobins. The IgA was totally cleaved in 48 h, using supernatants concentrated with polyvinyl pyrrolidone or the 70% (NH4)2SO4. Extracellular proteases could play a role in virulence.

Actinobacillus pleuropneumoniae: virulence and gene cloning.

Actinobacillus pleuropneumoniae is the causal agent of porcine contagious pleuropneumonia (PCP). The infection produces important economic losses in porciculture due to its high morbidity and mortality. Survivors are asymptomatic carriers infectious to other pigs and have low alimentary conversion. The causative agent possesses several virulence factors: adhesion fimbriae, lipopolysaccharide of the outer membrane, capsule, and cytolysins. In addition, our group has reported secretion proteases of a wide pH range of activity. These proteases degrade different substrates such as porcine gelatin, hemoglobin and IgA, and bovine or human hemoglobin. To control PCP dissemination, farmers require serodiagnostic tests which detect carriers and discriminate between vaccinated and infected animals. Bacterines used as immunogens are serotype specific and do not prevent the infection. Genes have been cloned that codify a cohemolysin, cytolysins, and an iron-binding protein. We have cloned A. pleuropneumoniae genes using the expression plasmids pUC19 and Bluescript, in Escherichia coli Q358 and DH5 alpha; the screening for antigen production was made in four groups of pigs (vaccinated, experimentally infected, naturally infected, and from slaughterhouses); two E. coli clones expressed polypeptides recognized by sera from all the groups.

Characterization of a cytochalasin D-resistant mutant of Entamoeba histolytica.

Characterization of a cytochalasin D-resistant mutant of the human parasite Entamoeba histolytica capable of growing at 10 microM cytochalasin is described. The mutant cells also show resistance to 5 mM colchicine and 100 microM cytochalasin B, drugs proved deleterious for wild type trophozoites. The mutants show increased osmotic fragility and electric mobility but reduced phagocytic activity, and agglutination by Concanavalin A. On the other hand pinocytic activity remains unaltered when compared with the wild type cells. Polymerized actin, seen by staining with phalloidin, often appears polarized to one end of the trophozoites and forms few of the endocytic invaginations found in wild type amebas. An altered distribution of part of the actin could explain the differences in surface properties and motility observed in the mutant amebas.

Clinical orodental abnormalities in Mexican children.

A total of 32,022 Mexican children (16,473 boys, 15,549 girls) were examined for several congenital oral and paraoral anomalies. The findings for commissural lip pits (boys 53.1, girls 52.4 per 1000) are less than those reported for adults. This may indicate that pits become accentuated with age. Fordyce granules were seen with a prevalence of 1.2 per 1000. This is in contrast to the reported 85.6% prevalence for the adult population, also possibly reflecting increased manifestation with increased age. Our data for exogenous tooth pigmentation show increased prevalence with age (group I [5 to 10 1/2 years], 9.8%, versus group II [10 1/2 to 14 1/2 years], 12.9%), possibly indicating decrease in attention to oral hygiene. The prevalence of talon cusp was found to be 0.6 per 1000, and for ankyloglossia 8.3 per 1000. Prevalence values for bifid tongue are reported for the first time, indicating one affected per 187 children examined. The prevalence of fissured tongue (15.7%) shows a statistically significant difference between boys (16.8%) and girls (14.5%). The prevalence of geographic tongue (1.9%) shows a marked difference between group I (2.2%) and group II (1.2%).

Pelvic exenteration for carcinoma of the cervix: analysis of 252 cases.

We present the results of 252 pelvic exenterations for primary and recurrent carcinoma of the cervix at the Hospital General de Mexico, a tertiary-care institution for the indigent. Emphasis is placed on the morbidity and mortality of the procedure in relation to patient selection. In underdeveloped countries, where early detection of cervical cancer is a rare event, pelvic exenteration must continue in the armamentarium of physicians; it can be associated with gains in the quality of life, with long-term survival, with effective rehabilitation, and possibly with cures.

[Preventive and social aspects in medical education, Mexico]. / Aspectos preventivos y sociales en la carrera de medicina, México.

The subject of the article is medical education in Mexico, particularly in the area of preventive and social medicine. It emphasizes the impact on this instruction of the country's economic and cultural dependence. It then presents some important qualitative data such as those on the existence of the administrative academic body responsible for the area, the names of the academic subjects in the area of preventive and social medicine, the educational objectives and study plan of this area; its connection with undergraduate internship and social service; agreements with other institutions for instructions; the semester in which the subjects in the area are taught and the faculty members teaching them. Finally, on the basis of the information presented, several conclusions are reached which make it possible to asseverate that the teaching of preventive and social medicine is not given the importance it merits, in the study plan of any medical school in the country.

[Mitral valve replacement, results in 160 patients]. / Reemplazo valvular mitral, resultados en 160 pacientes.

The results of 163 mitral valve replacement from 160 patients since August 1972 til August 1977 are presented, this is the second communication in Mexico related to mechanical mitral prosthesis. 95 patients were females and 55 males. With ages from 8 to 57 years, average 34; the 13% were child or teenagers. In 67% there were a clear background of rheumatic fever; 50% cardiac insufficiency and 19% previous mitral surgery from 8 months to 12 years before. 94% were class III or IV (N.Y.H.A.) and only 6% in I or II. Surgery was indicated according symptoms and hemodynamic data, 98% were catheterized. 26 Starr-Edwards and 137 Bjork-Shiley prosthesis were implanted in mitral position; in 112 cases only the mitral valve was substituted, in 41 cases a tricuspid procedure was done and in another 10 cases the aortic valve was also changed. The postoperative complications were: arrhythmies 32%; low cardiac output in 21%; infections 9%. Operative mortality in the isolated mitral replacement was 12%; in those cases with mitral-aortic or mitro-tricuspic lesions have been 33% in the first three years and 25% in the last three years. The long-term follow-up in 130 survivors is 29 months; 81% of them are actually in class I, 16% in class II and 3% in class III. The literature is reviewed and the facts responsive for the improved results are analyzed; special importance is given to the temporal external cardiac pacing in the management of the postoperative arrhythmies. Mitral valve replacement is considered as a good palliative procedure to the functional and socio-economical long-term rehabilitation in the survivors.