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C A Parra

Publications and source records attributed to C A Parra.

18 recordsLinked to original sources
PubMed2005

Identification of five different IGHV gene families in owl monkeys (Aotus nancymaae).

In order to characterize immunoglobulin heavy-chain variable (IGHV) genes in Aotus nancymaae monkeys, different mRNAs encoded by five IGHV families in this non-human primate were molecularly analysed considering their paramount importance in antibody production in an immune response. This study reports gene products exhibiting 91% amino acid similarity with IGHV1, IGHV2, IGHV3, IGHV4 and IGHV7 human IGHV families. Our analyses suggest that the IGHV gene has several conserved characteristics in humans and A. nancymaae. Several amino acid residues that are highly conserved in all family members described in humans were also present in these families in A. nancymaae. Antibody diversity in these families has remained the same since divergence of both species. Our study continues to provide evidence supporting the use of A. nancymaae monkey as an animal model for studying antibody response.

Amino Acid Sequence↗
PubMed1995

A species-specific nucleotide sequence of Mycobacterium tuberculosis encodes a protein that exhibits hemolytic activity when expressed in Escherichia coli.

Species-specific proteins may be implicated in the unique pathogenic mechanisms characteristic of Mycobacterium tuberculosis. In previous studies, a 3.0-kb species-specific DNA fragment of M. tuberculosis was identified (C. A. Parra, L. P. Londoño, P. del Portillo, and M. E. Patarroyo, Immun. 59:3411-3417, 1991). The nucleotide sequence of this 3.0-kb fragment has been obtained. This sequence was shown to contain two open reading frames (ORFs) whose putative gene products share 68.9% identity between each other. The major ORF shows 57.8% similarity with PLC-N and 53.2% similarity with PLC-H, two phospholipase C enzymes from Pseudomonas aeruginosa. The major ORF was amplified by PCR and cloned into the pGEX-5T expression vector. Cell extracts of Escherichia coli overexpressing this glutathione S-transferase fusion protein were shown to produce beta-hemolysis suggestive of phospholipase activity. Since phospholipase C enzymes have been reported as virulence factors of P. aeruginosa and also of the intracellular pathogen Listeria monocytogenes, it is possible that the proteins identified in this study could also play a role in sustaining tuberculosis infection in humans.

Amino Acid Sequence↗
PubMed1991

Isolation, characterization, and molecular cloning of a specific Mycobacterium tuberculosis antigen gene: identification of a species-specific sequence.

A rabbit polyclonal antiserum exhibiting a specific recognition pattern for Mycobacterium tuberculosis proteins was used to screen an M. tuberculosis genomic library constructed in the expression vector lambda gt11. One clone, denominated C1:10, expressed M. tuberculosis-specific determinants as part of a large fusion protein with beta-galactosidase. The gene for this protein has been sequenced, and it encodes a protein of 134 amino acids (13.8 kDa) which did not display significant homology with any of the previously reported proteins in the data bases. Hybridization studies with restriction fragments of the cloned sequence revealed that it was not present in the genomes of related mycobacteria, namely, M. bovis, M. bovis BCG, M. flavescens, M. fortuitum, M. phlei, and M. vaccae. These findings suggest that we have detected a gene, or a fragment therefrom, unique for M. tuberculosis whose nucleotide and amino acid sequences could be useful tools in the design of an improved vaccine or a diagnostic method of greater accuracy for tuberculosis.

Amino Acid Sequence↗
PubMed1991

Identification of B- and T-cell epitopes within the MTP40 protein of Mycobacterium tuberculosis and their correlation with the disease course.

Synthetic peptides derived from the amino acid sequence of MTP40, a recently characterized Mycobacterium tuberculosis protein, were tested by two different immunological assays in 91 individuals. For the purposes of this study, the population was distributed in four groups: active tuberculosis (TBC) patients with elevated bacillus loads (BK+), active TBC patients with low bacillus loads (BK-), healthy individuals living in the same household with tuberculous patients (HH), and normal individuals, who had presumably never been in contact with the bacilli (control). We found that T cells of individuals belonging to the HH group showed the highest and most frequent recognition of these peptides in a T-cell proliferation assay, while their antibodies showed the lowest recognition of these peptides when tested by enzyme-linked immunosorbent assay. In contrast, TBC patients revealed an inverse pattern of immune response. Interestingly, one of these peptides (P7) was recognized by T cells of 64% of the HH individuals and by 4.5% of normal donors. Another peptide (P4) was recognized by 55% of sera from BK+ patients and by 5.5% of normal donors. The results presented here indicate the existence of T- and B-cell epitopes within the MTP40 protein. Given the particular recognition pattern of this protein, added to the fact that it appears to be a species-specific antigen of M. tuberculosis, a detailed study of the immune response to it may be useful in the design of more accurate diagnostic tests and an improved vaccine against human TBC.

Amino Acid Sequence↗
PubMed1989

Structural homology of complement protein C6 with other channel-forming proteins of complement.

The amino acid sequence of the amino-terminal half of the complement protein C6 has been found to show overall structural homology with the homologous regions of the channel-forming proteins C7, C8 alpha, C8 beta, and C9. In addition, two specific cysteine-rich segments common to the amino-terminal regions of C7, C8 alpha, C8 beta, and C9 also occur in their expected positions in C6, suggesting functional significance. Two cDNA clones encoding C6 were isolated from a human liver library in the bacteriophage vector lambda gt11. The predicted protein sequence contains an apparent initiation methionine and a putative signal peptide of 21 residues, as well as a site for N-glycosylation at residue 303. The sequence of the C6 protein reported here has 47-52% similarity with C7, C8 alpha, C8 beta, and C9, as well as 31-38% similarity with thrombospondin, thrombomodulin, and low density lipoprotein receptor. The sequence data have been interpreted by using computer algorithms for estimation of average hydrophobicity and secondary structure.

Amino Acid Sequence↗
PubMed1988

[Congenital ischemic onychodystrophy (Iso-Kikuchi syndrome) and chronic lupus erythematosus].

We report a patient with nail and bone disorders of the index and middle fingers (Iso and Kikuchi syndrome) associated with chronic discoid lupus erythematosus. Angiographic studies showed filiform arteries of the fingers and slow blood circulation. Since a vascular pathogenic mechanisms is probable, the designation "Congenital ischemic onychodystrophy" seems more suitable. The association with chronic discoid lupus erythematosus has not previously been reported.

Adult↗
PubMed1987

[Infantile acropustulosis. Considerations on 11 cases].

Eleven patients with infantile acropustulosis, 10 from Mendoza and one from Buenos Aires, are presented. Remarkably was a blood eosinophilia in 4 cases and the prompt improvement with dapsone in 2 cases. The differential diagnosis with other dermatosis, specially with scabies, are discussed.

Diagnosis, Differential↗
PubMed1979

Diameter of the collagen fibrils in the sclerodermatous skin of porphyria cutanea tarda.

The diameter of collagen fibrils was studied in a patient with porphyria cutanea tarda in a specimen obtained from the sclerodermatous skin of the back. A bimodal distribution of the diameter of the fibrils was observed with maxima at 33.5 nm and 68.7 nm. The mean diameter was 67 nm with a standard deviation of 10.6 nm. These results are similar to those obtained previously in localized scleroderma (morphoea).

Aged↗
PubMed1979

[Bullous pemphigoid and lymphoblastic lymphoma].

We present a 66 years old patient with bullous pemphigoid which appeared two years before a lymphoblastic lymphoma. According to the bibliography, there appear to be a causal relationship between lymphoma and pemphigoid.

Aged↗
PubMed1977

Transepithelial elimination in necrobiosis lipoidica.

Elimination of necrotic material through the hair follicle as a means of excretion has been observed in three cases of necrobiosis lipoidica. Clinically this process presents as comedo-like plugs localized mainly in the periphery of the lesions.

Adult↗