Cloning of the PYR4 gene encoding orotidine-5′-phosphate decarboxylase in Cephalosporium acremonium

Summary We have cloned the Cephalosporium acremonium pyr4 gene by cross-hybridization with the equivalent gene from Neurospora crassa, the closest relative from which this gene is available. The C. acremonium pyr4 gene complements an E. coli pyrF mutant lacking orotidine-5-phosphate decarboxylase (OMPdecase), and most probably does not contain introns. Maxicell analysis in E. coli shows that it encodes a 46 kDa polypeptide. The C. acremonium OMPdecase contains a highly conserved pentadecapeptide characteristic for this category of enzyme. Extensive sequence comparison suggests an important role of this region in enzymatic activity.     

General morphology and capsid fine structure of African swine fever virus particles

The structure of African swine fever virus particles has been examined by electron microscopy. The analysis of virions prepared by negative staining, thin sectioning, and freeze-drying and shadowing showed that the virus particle was composed of several concentric structures with an overall icosahedral shape. The inner region of the virus particles was a nucleoid that was surrounded by a membrane covered by the capsid. The capsid had side-to-side dimensions of 172 to 191 nm and was built up by capsomers arranged in an hexagonal lattice. Computer-filtered electron micrographs of either negatively stained or freeze-dried and shadowed capsids revealed capsomers with a hexagonal outline and a hole in the center. The intercapsomer distance ranged from 7.4 to 8.1 nm. The triangulation number of the capsid was estimated to be 189 to 217, indicative of 1892 to 2172 capsomers. Extracellular African swine fever virus particles had an external membrane that resembled the cytoplasmic unit membrane.     

C3 binds with similar efficiency to Fab and Fc regions of IgG immune aggregates

The covalent binding reaction of the third component of complement (C3) with rabbit IgG immune aggregates has been studied by enzymic digestion of C3b-IgG adducts. In these adducts C3b was radioactively labeled in the free thiol group generated during activation of the internal thioester of C3. Trypsin digestion of ¹⁴C-labeled C3b-IgG adducts degrades C3b to a small antibody-bound ¹⁴C-labeled C3 fragment (¹⁴C-C3frg), whereas the antibody remains unaltered. Papain digestion of trypsin-treated ¹⁴C-C3frg-IgG complexes generated Fc and Fab fragments bearing equivalent amounts of covalently bound ¹⁴C-C3frg (43% and 40%, of the total C3 present in the aggregates, respectively). Hydroxylamine treatment of the ¹⁴C-C3frg-Fab and ¹⁴C-C3frg-Fc complexes released a ¹⁴C-C3frg of similar size (about 3–4 kDa) in which the N-terminal residue was the radiolabeled Cys¹⁰¹⁰. A fragment with the same radioactive N terminus and characteristics was obtained by sequential trypsin and papain digestion of purified C3 labeled with iodo–[¹⁴C] acetamide. Affinity-purified ¹⁴C-C3frg-Fc complexes digested with pepsin generated a mixture of radioactive peptides, most probably complexes formed by ¹⁴C-C3frg and Cγ2 or the hinge digestion products, and ¹⁴C-C3frg-pFc' complexes. The latter was also immunoprecipitated with anti-Fc-Sepharose from the pepsin digestion supernatants of ¹⁴C-labeled-C3b-IgG complexes. Taken together these data indicate that, during complement activation through the alternative pathway by IgG immune aggregates, C3 is not bound to a single site on the antibody molecule. Both Fab and Fc regions of IgG are equally efficient targets for C3 anchorage. In addition, the data confirm the pFc' as a region of C3 attachment within the Fc portion, and strongly suggest that C3b is bound either to the Cγ2 domain or the hinge or both.     

Tuberculosis: a current problem

Tuberculosis is a public health problem. If the current trends continue, is expected to arrive to 10.2 million of new cases in 2005. There are three studies accomplished in 1995 in Mexican patients. The results show important difficulty in the application and the follow-up of the program of control of the tuberculosis, what has caused accumulation of chronic cases, moderate rate of primary resistance and alarming levels of primary and secondary multiresistance (23%). Mechanism of protective immunity against mycobacterium tuberculosis (MTB) in humans have not been clarified. Different subpopulations of lymphocytes CD4, CD8 and other populations as well as macrophages, and monocytes, have an important role. In industrialized countries, the managing of the MDRTB is based on the use of individualized treatments with second line drugs according to susceptibility test, however the foregoing has not been possible to apply it middle or low income countries. WHO has launches the initiative "DOTS plus" that consist in the administration of a standarized regimen on the basis of epidemiology of resistance in the country or region.     

Seroprevalence of human herpesvirus-8 in blood donors from different geographical regions of Argentina, Brazil, and Chile

Human herpesvirus-8 (HHV-8) causes Kaposi's sarcoma (KS) and lymphoproliferative disorders in both HIV-infected and uninfected patients. HHV-8 has a worldwide occurrence but infection rates vary according to a combination of geographic and behavioral risks. The main transmission route seems to be sexual, nevertheless, nasal secretions, saliva, blood, and organ graft have been proposed. HHV-8 was postulated as a new infectious agent for screening in blood donors. The aim of this study was to evaluate the prevalence of antibodies against HHV-8 antigens in blood donors of South America. Serum samples from 2,470 blood donors from Argentina, Brazil, and Chile corresponding to five geographic regions were studied by indirect immunofluorescence assay (IFA). Seroprevalence rate was 3.7% (92/2,470; 95% CI 2.9-4.5) in the entire blood donor population distributed as follows: Argentina, 4.0% (Buenos Aires city, 4.3%; Bahia Blanca, 2.4%; and Córdoba, 4.0%), Campinas (Brazil), 2.8%; and Santiago de Chile, 3.0%. There was no difference (P>0.05) between men and women or age related, except in Brazil where positive cases were 30-49-year-old males. The present study, which includes different geographical areas of multiple countries from South America, has not been done before. The results show similar prevalence rates among the studied zones corresponding to low-prevalence regions. South America is a large sub-continent with a wide spectrum of population and geographical characteristics, thus, more HHV-8 prevalence studies should be necessary to establish possible regional differences.     

A Complementary Method for the Detection of Osteoblastic Metastases on Digitized Radiographs

Purpose This study was conducted to evaluate the diagnostic usefulness of gray level parameters in order to distinguish healthy bone from osteoblastic metastases on digitized radiographs. Materials and methods Skeletal radiographs of healthy bone (n = 144) and osteoblastic metastases (n = 35) were digitized using pixels 0.175 mm in size and 4,096 gray levels. We obtained an optimized healthy bone classification to compare with pathological bone: cortical, trabecular, and flat bone. The osteoblastic metastases (OM) were classified in nonflat and flat bone. These radiological images were analyzed by using a computerized method. The parameters (gray scale) calculated were: mean, standard deviation, and coefficient of variation (MGL, SDGL, and CVGL, respectively) based on gray level histogram analysis. Diagnostic utility was quantified by measurement of parameters on healthy and pathological bone, yielding quantification of area under the receiver operating characteristic (ROC) curve, AUC. Results All three image parameters showed high and significant values of AUC when comparing healthy trabecular bone and nonflat bone OM, showing MGL the best discriminatory ability (0.97). As for flat bones, MGL showed no ability to distinguish between healthy and flat bone OM (0.50). This could be achieved by using SDGL or CVGL, with both showing a similar diagnostic ability (0.85 and 0.83, respectively). Conclusion Our results show that the use of gray level parameters quantify healthy bone and osteoblastic metastases zones on digitized radiographs. This may be helpful as a complementary method for differential diagnosis. Moreover, our method will allow us to study the evolution of osteoblastic metastases under medical treatment.