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Biomedical subjects

O Barrera

Publications and source records attributed to O Barrera.

At least 19 recordsLinked to original sources
PubMed2002

[Influence of HIV/AIDS infection on some biochemical indicators of the nutritional status].

The main objective of this study was to analyze the influence of nutritional state among HIV-1 infected people, according to the different clinical stages referred by the CDC (Control Disease Center of the United States) in 1987, as well as the changes in the concentrations of some biochemical markers linked to nutritional state. A similar study was carried out in a control group with UltramicroELISA non-reagent healthy individuals, anthropometrically classified. Concentrations of total proteins, albumin, cholesterol, triglycerides, urea, uric acid and creatinine were analyzed by sex and clinical group, comparing the levels obtained through a variance study. When comparing HIV-1 asymptomatic infected patients to HIV-1 and HIV-2 non infected people, the results showed a non significant increase in the level of total proteins with a significant decrease of albumin and creatinine, the latter observed only in male patients. In stage IV patients, an important decrease of cholesterol and a significant increase of the triglycerides were found, as well as the lowest albumin levels. Urea and uric acid levels did not experience statistically significant changes. It was concluded that the study of biochemical markers is advisable, since it contributes to the detection by default of malnutrition marginal states in infected individuals.

Adult↗
PubMed1991

The opacity proteins of Neisseria gonorrhoeae strain MS11 are encoded by a family of 11 complete genes.

Variants of Neisseria gonorrhoeae MS11 show distinct colony morphologies because of the expression of a class of surface components called opacity (Opa, PII) proteins. Southern analyses combined with molecular cloning of genomic DNA from a single variant of MS11 has identified 11 opa genes contained in separate loci. These opa genes code for distinct opacity proteins which are distinguishable at their variable domains. The opa gene analyses were also extended to divergent variants of MS11. These studies have shown that, during in vitro and in vivo culture, 10 of the 11 opa genes did not undergo significant change in their primary sequence. However, in these variants, one gene (opaE) underwent non-reciprocal inter-opa recombinations to generate newer Opa variants. Phylogenic analysis of the opa gene sequences suggests that the opa gene family have evolved by a combination of gene duplication, gene replacement and partial inter-opa recombination events.

Amino Acid Sequence↗
PubMed1990

Piliation changes in transformation-defective gonococci.

Recombination-dependent alterations of their expressed pilin gene (pilE) enable gonococci to synthesize a myriad of structurally/antigenically different pili and to reversibly switch their pilus production on and off. These changes have been ascribed both to DNA transformation and to intragenomic recombination between pilE and silent pilin genes (pilS). We examined the pilus changes in gonococci that are incompetent for transformation because of their DNA uptake deficiency (dud) mutation, pilus- (P-) phenotype, or both. Though incompetent for DNA transformation, dud cells displayed pilus antigenic variation and underwent reversible pilus variations much like their wild-type parent. Wild-type P- with a pilE nonsense mutation were also virtually nontransformable, but they reverted to P+ at high frequencies. The pilin mRNA sequence changes that accompanied pilus transitions in these nontransformable dud and P- gonococci represent insertion of pilS stretches into their respective pilE, apparently via intragenomic recombination.

Amino Acid Sequence↗
PubMed1988

Expression of outer membrane protein II by gonococci in experimental gonorrhea.

Gonorrheal urethritis was induced in three males by intraurethral instillation of predominantly pilus+ protein II- gonococci. Virtually all gonococci reisolated from the infected men exhibited protein II+ phenotype. The reisolated gonococci expressed five distinct outer membrane protein II species. Protein IIc+ organisms predominated in urines of all three subjects, but variants expressing this particular protein II were rarely spawned in vitro by input organisms. Protein IIc+ gonococci appeared early in one man's infection; they were joined later by variants that displayed eight other protein II phenotypes, including protein II-. These results show that input protein II- gonococci are supplanted by protein IIc+ variants during incipient gonorrheal urethritis. As infection progresses, a broader variety of protein II+ variants appears.

Bacterial Outer Membrane Proteins↗
PubMed1988

Differential effect of trypsin on infectivity of Chlamydia trachomatis: loss of infectivity requires cleavage of major outer membrane protein variable domains II and IV.

The initial interaction of chlamydiae with host cells is not well understood. Chlamydial cell surface components that function in attachment are key virulence factors, and their identification is critical for understanding the pathogenic strategies of this very successful parasite. We used trypsin proteolysis of chlamydiae to define surface components that function in chlamydia-host cell interactions. We found that trypsin had a differential effect on the infectivity of Chlamydia trachomatis serovars B and L2 for HeLa 229 cells. Trypsin treatment resulted in a significant loss of attachment and infectivity of serovar B but had no effect on the infectivity of serovar L2. Fluorograms of chlamydiae metabolically labeled with 14C-amino acids and treated with trypsin showed that the major outer membrane protein (MOMP) of both serovars was cleaved. Evidence for two trypsin cleavage sites was found for the serovar B MOMP. One cleavage site was located between lysine 145 and valine 146 in variable domain (VD) II of the protein. The second site was located between lysine 309 and threonine 310 in VD IV. In contrast, the serovar L2 MOMP was cleaved only at lysine 309 in VD IV. These results suggest a functional role for MOMP in chlamydial attachment and implicate VDs II and IV of MOMP in this interaction.

Amino Acid Sequence↗
PubMed1987

Gonococcal pilin variants in experimental gonorrhea.

When pilus+ Gc were introduced into a male subject's urethra, they gave rise to pilus+ variants whose pilin mRNAs differed from that of input Gc. The differences stemmed from the Gc genome's single complete pilin gene having undergone gene conversion by different partial pilin genes' sequences and by different length stretches of a single partial pilin gene. In some instances, the variant's pilin mRNA appeared to reflect two independent gene-conversion events that used sequences from two different partial pilin genes. The resulting variants' pilins exhibited antigenic differences compared with the pilin polypeptide of input Gc; these differences were discernible by immunoblotting with mAbs. Amino acid and antigenic changes occurred in a segment of the variants' pilin polypeptides that previously was thought to be conserved or constant in sequence.

Amino Acid Sequence↗
PubMed1987

Gene conversion variations generate structurally distinct pilin polypeptides in Neisseria gonorrhoeae.

Pilus+ to pilus- phenotype change occurs in Neisseria gonorrhoeae through gene conversion of the gonococcus' complete, expressed pilin gene by nucleotides homologous to the pilS1 copy 5 partial pilin gene; assembly missense pilin is synthesized but pili are not. Reversion to pilus+ occurs by a subsequent recombinational event that replaces the complete pilin gene's pilS1 copy 5-like sequence with nucleotides from a different partial gene to effect expression of an orthodox (i.e., pilus producing) pilin. Sibling pilus+ revertants of common parentage can carry different sequences in their expressed pilin genes because they have undergone nonidentical gene conversion events such as recombinations with sequences from different partial genes, or recombinations with different length nucleotide stretches of the same partial gene; either can yield structurally and antigenically variant pilin polypeptides.

Amino Acid Sequence↗
PubMed1987

Antigens that are similar in apparent molecular weight to gonococcal outer membrane protein III.

Two immunoglobulin G monoclonal antibodies (MAbs) were produced by using purified outer membranes and whole gonococci as immunogens. These MAbs recognized antigens with similar apparent sizes (30 to 31.5 kilodaltons [kDa]) in several pathogenic and nonpathogenic neisseriae. In gonococci, these 30- to 31.5-kDa components, although similar in subunit size to outer membrane protein III (P.III), are distinct due to their differences in electrophoretic migration-modification by 2-mercaptoethanol and their cellular location. The two 30- to 31.5-kDa moieties are denoted by MAb2 and MAb3, respectively, by which they are identified. The differentiating characteristic of these three antigens (P.III, MAb2, MAb3) is their change or lack of change in electrophoretic mobility in the presence versus absence of 2-mercaptoethanol; P.III migrates less rapidly, MAb2 does not change, and MAb3 migrates more rapidly. Both the epitopes that were reactive with MAb2 and MAb3 were resistant to proteolytic treatment of intact gonococci; neither epitope was detected on whole, unfixed gonococci by immunofluorescence. Both MAb2 and MAb3 epitopes were represented uniformly among pathogenic neisseriae (except group Z meningococci) and less regularly among nonpathogenic neisseriae.

Antibodies, Monoclonal↗
PubMed1986

Gene conversion involving the pilin structural gene correlates with pilus+ in equilibrium with pilus- changes in Neisseria gonorrhoeae.

Gonococci (Gc) exhibit pilus+----pilus- "phase transitions" at high frequency, but only some of the pilus- Gc can revert to pilus+ phenotype. We examined reversible phase transitions between pilus+ Gc and a particular pilus- variant (P-rp+ phenotype) whose pilin mRNA carries a unique block of nucleotides encoding an "assembly missense" pilin polypeptide. The results show that Gc pilus+ in equilibrium with P-rp+ transitions can result from intragenic recombination in which there is nonreciprocal exchange of partially homologous DNA sequences from a partial pilin gene (in silent, storage form) into the expression locus' complete pilin gene. Hence Gc pilus phase variation, like pilus antigenic variation, can occur by gene conversion of the pilin structural gene expression locus.

Bacterial Adhesion↗
PubMed1985

Pilus- gonococcal variants. Evidence for multiple forms of piliation control.

Pilus+ to pilus- transitions of gonococci (Gc) that involve rearrangement of pilin gene DNA yield the P-n phenotype, which is incapable of reversion (to pilus+). Reversion to pilus+ is found for nonpiliated Gc that have undergone no apparent pilin gene rearrangement. Among the reverting, nonpiliated Gc, two distinct phenotypes (P-rp- and P-rp+) occur and are differentiated according to their synthesis (or lack) of pilin subunits; both P-rp- and P-rp+ Gc contain pilin-specific mRNA. The occurrence of these different pilus- phenotypes strongly suggests that several mechanisms can account for changes in the piliation status of Gc; one of these involves pilin gene rearrangement but the others apparently operate at posttranscriptional levels. Reverting pilus- Gc may have a pathogenic advantage in being able to reversibly alter their host cell adherence-promoting surface properties through high frequency transitions in piliation status.

Bacterial Outer Membrane Proteins↗
PubMed1984

Proteins IA and IB exhibit different surface exposures and orientations in the outer membranes of Neisseria gonorrhoeae.

Exposure of whole gonococci to proteinase K resulted in cleavage of protein I (P.I) of the organism in situ. P.I subunits in the P.IB group were cleaved into two membrane-associated fragments, whereas P.IA subunits were cleaved by proteinase K to yield a single membrane-associated fragment slightly smaller in apparent size than the intact P.IA subunit. These data suggest that P.IA and P.IB subunits are quite different in their surface exposures and orientations in the gonococcal outer membrane; P.IB subunits likely have both termini buried in the membrane, whereas P.IA subunits have one of their termini exposed on the surface of the organism.

Bacterial Outer Membrane Proteins↗
PubMed1983

Structural analysis of the variable major proteins of Borrelia hermsii.

Borrelia hermsii undergoes spontaneous antigenic variation in vivo and in vitro. Serotype specificity is associated with expression of one of a family of molecular weight-variable proteins, the pI proteins. We studied the structure of the pI proteins as well as the molecular weight-invariable pII proteins of three serotypes of B. hermsii HS1: C, 7, and 21. The techniques used were one-dimensional (1-D) mapping of Staphylococcus aureus V8 protease-generated peptides and two-dimensional (2-D) mapping of alpha-chymotrypsin-generated peptides. The pI and pII proteins were isolated by excision of polypeptides from stained polyacrylamide gel electropherograms. The 1-D peptide patterns were visualized by fluorography of intrinsically [14C]leucine-labeled proteins or by silver stain. Before 2-D mapping, polypeptides in excised gel fragments were labeled with 125I in the presence of chloramine-T. We also compared the 2-D peptide maps of pI proteins, pI7 and pI21, after their surface-exposed portions were radioiodinated using 1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril (Iodogen). The I-D and 2-D peptide maps demonstrated the following: (a) pI proteins of the three serotypes have few V8 protease- or chymotrypsin-generated peptides in common, and (b) pI proteins of each serotype appear to be identical. The findings suggest that pI protein variability derives from extensive differences in the amino acid sequences of these proteins.

Autoradiography↗
PubMed1983

Gonococcal pilus subunit size heterogeneity correlates with transitions in colony piliation phenotype, not with changes in colony opacity.

The apparent subunit sizes for pili of gonococci (Gc) have been visualized by using either Iodogen 125I-labeled whole Gc or immunoblotting with antipilus antiserum. These methods permitted definition of pilus subunit sizes for Gc of a given strain that had undergone changes either in piliation phenotype or in colonial opacity/protein II phenotype. The results indicate that pilus subunit size does not change coincident with changes in colony opacity/protein II phenotypes; but change in pilus subunit size is seen after a change in piliation phenotype (P+ leads to P++, and vice versa). Marked diversity in pilus subunit sizes is found for Gc of individual strains when P+ derivatives of P- colonies are compared. This diversity extends to pilus subunits of Gc found in single colonies; two distinct pilus forms were demonstrated for Gc residing in several single colonies. These findings show that Gc of a given strain are able to express any of a number of different pilus subunit size forms.

Bacterial Proteins↗
PubMed1983

Immunological characteristics of gonococcal outer membrane protein II assessed by immunoprecipitation, immunoblotting, and coagglutination.

Immunoprecipitation or coagglutination with whole gonococci and immunoblotting have been used to assess the comparative antigenicities of 11 different protein II (P.II) moieties from four different strains. Rabbit antisera used for these studies include both anti-whole gonococcal sera and antisera raised by immunization with "isolated" P.II preparations. The results show that: (a) immunization with gonococci possessing a single P.II elicits formation of antibodies directed mainly at the homologous P.II when assessed by either immunoprecipitation or immunoblotting; and (b) immunization with isolated P.II material elicits formation of antibodies that are cross-reactive with all (or nearly all) P.II species in immunoblots; these antibodies recognize mainly the homologous P.II by immunoprecipitation. These results have been interpreted as showing the following: (a) all gonococcal outer membrane P.II moieties share antigenic determiners, but these common antigens are not generally accessible on the organisms' surfaces for interaction with antibody molecules; and (b) the surface-exposed antigens of different P.II constituents are, in general, different from one another.

Agglutination↗
PubMed1980

Preparation, characterization, and immunogenicity of Haemophilus influenzae type b polysaccharide-protein conjugates.

A method is presented for covalently bonding Haemophilus influenzae type b capsular polysaccharide (HIB Ps) to several proteins. The method is efficient and relies upon the use of adipic dihydrazide as a spacer between the capsular polysaccharide and the carrier protein. In contrast to the poor immunogenicity of the purified HIB Ps in mice and rabbits, the HIB Ps-protein conjugates induced serum anti-type b antibodies having bactericidal activity at levels shown to be protective in humans when low doses were injected subcutaneously in a saline solution. The antibody response in mice was related to the dose of the conjugates, increased with the number of injections, and could be primed by the previous injection of the carrier protein. The HIB Ps-protein conjugates were immunogenic in three different mouse strains. The importance of the carrier molecule for the enhanced immunogenicity of the HIB Ps-protein conjugates was shown by the failure of HIB Ps hybrids prepared with either the homologous polysaccharide or pneumococcus type 3 polysaccharide to induce antibodie in mice. Rabbits injected with the HIB Ps-protein conjugates emulsified in Freund's adjuvant produced high levels of serum anti-type b antibodies which induced a bactericidal effect upon H. influenzae type b organisms. It is proposed that the HIB Ps component of the polysaccharide protein conjugates has been converted to a thymic-dependent immunogen. This method may be used to prepare protein-polysaccharide conjugates with HIB Ps and other polysaccharides to be considered for human use.

Animals↗