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Biomedical subjects

F Parra

Publications and source records attributed to F Parra.

At least 55 records · Page 3Linked to original sources
PubMed1992

Identification and expression of a Fasciola hepatica gene encoding a gut antigen protein bearing repetitive sequences.

A Fasciola hepatica cDNA clone of about 2 kb was isolated from an expression library by immunological screening using blood serum from an experimentally infected calf. The cDNA clone hybridised to a RNA of about 3 kb in a Northern blot experiment. The nucleotide sequence of the cDNA revealed the presence of an open reading frame of 1636 bp which encoded 24 tandemly arranged 20-amino acid-long repeats, followed by 65 non-repeated residues preceding the stop codon. This antigen was expressed in Escherichia coli as beta-galactosidase fusion proteins which were used for the production of specific antibodies. Immunofluorescence studies using specific antifusion sera revealed that the antigen was specifically expressed in the parasite intestine epithelial cells. Due to its early appearance it might be possible to design diagnostic assays based on this repeated antigen for identification of recently infected animals.

Amino Acid Sequence↗
PubMed1992

In vitro translation of a subgenomic mRNA from purified virions of the Spanish field isolate AST/89 of rabbit hemorrhagic disease virus (RHDV).

Purified preparations of the Spanish field isolate of rabbit hemorrhagic disease virus AST/89 were found to contain the plus-stranded genomic RNA of more than 7.4 kilobases (kb) and large amounts of a subgenomic mRNA of 2.4 kb. The smaller RNA was translated in vitro and shown to code for a 60 kDa protein which was immunoprecipitated using anti-RHDV as well as anti-VP60 sera.

Caliciviridae↗
PubMed1992

Allergy to amoxicillin in patients who tolerated benzylpenicillin, aztreonam, and ceftazidime.

The usual battery of skin tests employed for determining penicillin allergy may fail to detect allergic reactions to side chain-specific beta-lactam agents. We report the cases of six patients who experienced anaphylactic reactions after treatment and challenge with amoxicillin but who tolerated parenteral challenges with benzylpenicillin, aztreonam, and ceftazidime. Results of skin tests for amoxicillin (10 mg/mL) were positive for four of the six patients.

Adolescent↗
PubMed1992

Hypersensitivity to trimethoprim.

We present two patients who experienced life-threatening immediate reactions and one patient who developed generalized urticaria following oral administration of trimethoprim (TMP) and sulfamethoxazole (SMX) combination. Skin prick tests with TMP were positive in the three patients. No patients reacted to skin prick tests with SMX. No significant levels of IgE antibodies to TMP were found by RAST in the serum of the patients. Normal subjects used as controls did not react to any of these tests. Single-blind, placebo-controlled oral challenges were positive with TMP and negative with SMX in all patients. These results suggest that the three patients developed type I hypersensitivity reactions to TMP. In our patients skin prick tests with TMP were useful in TMP hypersensitivity diagnosis.

Adult↗
PubMed1992

Changes in ribosomal proteins during colony development in Streptomyces.

The structure and functionality of the ribosomal subunits of the substrate and the aerial mycelium of Streptomyces antibioticus were compared. Using SDS-PAGE and HPLC, several differences between the ribosomal protein pattern from both stages of development were observed, including a clear decrease in the L7/L12 content of the aerial mycelium. The activity of the aerial mycelia ribosomes was also decreased when compared with that of the substrate mycelium. This effect was more pronounced in the 50S subunit. These results suggest that during cell differentiation in Streptomyces important changes occur at the ribosomal level, particularly in the transition from the substrate to the aerial mycelium.

Bacterial Proteins↗
PubMed1990

Mapping and sequence of the gene coding for protein p72, the major capsid protein of African swine fever virus.

The gene encoding protein p72, the major structural protein of African swine fever virus and one of the most immunogenic proteins in natural infection has been mapped and sequenced. The gene was mapped by using oligonucleotide probes deduced from amino acid sequences of tryptic peptides obtained from purified protein p72. This allowed the location of the gene in fragment EcoRI B of African swine fever virus DNA. The nucleotide sequence obtained from this region revealed an open reading frame encoding 646 amino acids corresponding to a protein with a calculated molecular weight of 73,096 Da. This open reading frame contains the coding information for all the sequenced tryptic peptides from protein p72. A search at the National Biomedical Research Foundation Data Bank did not reveal any significant homology with other described proteins.

African Swine Fever Virus↗
PubMed1990

Effect of ivermectin treatment on anti-hypodermin C titers of Asturiana cattle naturally infected with Hypoderma lineatum.

The collagenase (hypodermin C) from soluble crude extracts of Hypoderma lineatum 1st-instar larvae was purified by reverse-phase HPLC and used in a new indirect ELISA test. This pure protein had several advantages over the use of crude larval extracts allowing a much better discrimination between infested and non-infested cattle. The anti-hypodermin C titers of 19 Asturiana cattle were estimated over the course of a natural H. lineatum infestation cycle, in which the effect of ivermectin treatment was also investigated. The results showed differences in the onset and ending of the infestation with respect to those described for other European countries. The ivermectin treatment proved to be very effective and treated animals had relatively low anticollagenase titers.

Animals↗
PubMed1990

Purification and characterization of a calicivirus as the causative agent of a lethal hemorrhagic disease in rabbits.

The causative viral agent of a lethal rabbit hemorrhagic disease has been purified and characterized. In negative-stained preparations, the virions were icosahedral, measured 27 to 35 nm in diameter, were without an envelope, and showed 10 peripheral cup-shaped depressions. The major structural protein was 60 kilodaltons, which constitutes a unique characteristic of the Caliciviridae.

Animals↗
PubMed1989

Sequence of the coding regions from the 3.0 kb and 3.9 kb mRNA. Subgenomic species from a virulent isolate of transmissible gastroenteritis virus.

Subgenomic mRNA from a virulent isolate of porcine transmissible gastroenteritis virus (TGEV) was used to produce cDNA clones covering the genome region from the 3' end of the peplomer gene to the start of the integral membrane protein gene. The nucleotide sequence of this area was determined using clone pTG11 and a previously reported cDNA clone pTG22. Three open reading frames (ORFs) were identified encoding putative polypeptides of relative molecular masses (Mr) 6,600, 27,600, and 9,200. The sequence encoding the Mr 9,200 polypeptide was found to be present on the "unique" 5' region of the 3.0 kb mRNA species whereas the other two ORFs mapped on the 3.9 kb mRNA species. Differences between the ORFs from this strain of TGEV and those from a previously reported avirulent strain of TGEV were compared.

Amino Acid Sequence↗
PubMed1988

Sequence of the nucleoprotein gene from a virulent British field isolate of transmissible gastroenteritis virus and its expression in Saccharomyces cerevisiae.

Subgenomic mRNA from a virulent isolate of porcine transmissible gastroenteritis virus (TGEV) was used to produce cDNA which was sequenced. Two non-overlapping open reading frames (ORFs) were identified. The largest, encoding a polypeptide of 382 amino acids (relative molecular mass (Mr) 43,483), was shown to be the viral nucleoprotein gene. The second ORF, found 3' to the larger ORF, encodes a polypeptide of 78 amino acids (Mr 9068) which has yet to be assigned to a viral product. The nucleoprotein gene was expressed in yeast cells under the control of two types of yeast promoters: the constitutive PGK promoter, and the inducible GAL1 promoter. Yeast cells containing recombinant plasmids, with the nucleoprotein gene in the correct orientation, produced a polypeptide of Mr 47,000, identical to the viral product, that reacted with a specific monoclonal antibody.

Amino Acid Sequence↗
PubMed1987

Perceptions of mental illness in Mexico: a descriptive study in the city of Chihuahua.

This work is a study of perceptions toward mental illness among respondents from the city of Chihuahua in Mexico. A non-probability sample of forty-seven respondents was taken during a two-week stay in the summer of 1985. To tap respondents' perceptions of mental illness, vignettes characterizing people normally thought to have symptoms of mental illness were employed. The study reveals that men and women perceive mental illness differently. In three out of four vignettes, women perceive mental disorder than men. It is argued that the reason for the disparity in perceptions between the sexes is the result of the sexual differentiation that exists in Mexico. With regard to whom the respondents would refer the person for help, the majority of the respondents recommended that, whether or not the person in the vignette is characterized as mentally ill or simply "sick", the person should seek professional help.

Adult↗
PubMed1986

Trehalase activation in yeasts is mediated by an internal acidification.

It has been reported that the addition of glucose, uncouplers and nystatin to yeast cells grown in a sugarfree medium causes trehalase activation; it has been postulated that this activation might be mediated by the depolarization of the plasma membrane. In this article the values of membrane potential and pH gradient across the plasma membrane of Saccharomyces cerevisiae have been determined under the same conditions as those in which trehalase is activated. Membrane potential was evaluated from the distribution of triphenylmethylphosphonium, the pH gradient from the distribution of benzoic acid across the plasma membrane. When the effect of several agents on the two components of the electrochemical proton gradient across the plasma membrane of ethanol-grown yeast cells were studied, under trehalase activation conditions, the following observations were made. (a) The addition of glucose activated trehalase and caused internal acidification of the cells, but had practically no effect on the membrane potential. (b) The addition of 200 mM KCl depolarized the cell membrane but did not affect the internal pH, nor trehalase activity. (c) Although carbonyl cyanide m-chlorophenylhydrazone depolarized the cells at external pH 6.0 and 7.0, it only activated trehalase at an external pH 6.0, leading to the acidification of the internal medium at this pH. (d) Nystatin caused an increase in the triphenylmethylphosphonium accumulation at external pH 6.0 and 7.0, but only activated trehalase at external pH 6.0, causing acidification of the cell interior at this pH. (e) Activation of trehalase was also observed when the internal acidification was caused by addition of a weak acid such as acetate. It is concluded that trehalase activation is mediated by an intracellular acidification and is independent of the membrane potential.

Culture Media↗
PubMed1985

Social tolerance of the mentally ill in the Mexican American community.

This work is a comparative study of social tolerance toward mental illness. The central concern is with the orientation of the Chicano toward these phenomena. The aim is to determine whether or not attitudes that Mexican Americans hold toward mental illness differ from those of other Americans. Survey research methods are used to conduct a comparative study of two ethnically distinct groups - Anglo and Mexican American. Attitudes toward mental illness are measured by a social distance scale. High to low tolerance toward the mentally ill is measured. The questions range from close personal to more distant association, such as whether or not one would mind having his or her children marry someone considered to be mentally ill, to whether or not one would mind working with such a person. We have found that sex, age and education are the primary variables associated with attitudes towards mental illness. Better educated Chicanos are clearly more tolerant of the mentally disabled than the little schooled. The gender of the respondents also appears significant in determining the extent of their tolerance. Older Chicanas with less education are the least tolerant of the mentally ill, while younger women are more tolerant than the older. And the Chicano tends to be tolerant whatever his educational level. There is little difference in tolerance between Chicanos and Anglos.

Adolescent↗
PubMed1984

Location on the Escherichia coli genome of a gene specifying O-acetylserine (thiol)-lyase.

The plasmid pAB65, derived from a specialized transducing phage carrying DNA from about 52 min on the Escherichia coli genome, coded for two polypeptides of Mr approx. 34 000. The expression of one was regulated by cyst(e)ine and the cysB gene product and the other by the cysB gene product only. One of these polypeptides was a subunit of O-acetylserine (thiol)-lyase (EC 4.2.99.8); the other, associated with the E. coli membrane, was the N-terminus of the product of the lambda ben gene. The pattern of peptide synthesis directed by plasmids carrying smaller DNA fragments indicated that the gene for O-acetylserine (thiol)-lyase was transcribed clockwise. The spectrum, amino acid composition and subunit number of the enzyme were determined. The enzyme appears homologous with the Salmonella typhimurium cysK gene product. This provides further evidence for the inversion of this region of the genome.

Amino Acids↗
PubMed1983

Phosphotransferase-mediated regulation of carbohydrate utilization in Escherichia coli K12: the nature of the iex (crr) and gsr (tgs) mutations.

Mutants of Escherichia coli K12 defective in the gene iex (crr) no longer utilize glucose or N-acetylglucosamine in preference to lactose, but competition between either of these sugars and another that also enters by a phosphotransferase (PT) mechanism is not affected. In this they differ from gsr (tgs) mutants. In gsr mutants, glucose does not exclude any other sugar, though N-acetylglucosamine still does so. In gsr mutants that are also ptsM the phosphoenolpyruvate-dependent phosphorylation of glucose or methyl alpha-glucoside is reduced by 90%: N-acetylglucosamine phosphorylation is not affected. The iex mutation does not affect the phosphorylation of either of these compounds. The wild-type alleles iex+ and gsr+ are dominant in lambda heterozygotes. Glucose inhibits the lactose permease of wild-type cells, but only when the permease is present in low amounts. The inhibition is also relieved (1) by induction of another transport system that is subject to regulation by the iex system or (2) by an iex mutation. We suggest that the iex gene specifies a protein that, in cells transporting certain sugars by a PT mechanism, acts to inhibit active transport systems. The protein is present in limiting concentration in the cell, sufficient only to inhibit the basal, uninduced, level of the active transport systems. In consequence the inducer (or its precursor) may be excluded from the cell and induction thus prevented.

Acetylglucosamine↗
PubMed1983

Phosphotransferase-mediated regulation of carbohydrate utilization in Escherichia coli K12: location of the gsr (tgs) and iex (crr) genes by specialized transduction.

A lysogen of Escherichia coli K12 with lambda cI857 S7 xis6 nin5 b515 b519 integrated into ptsI was induced and the lysates plated on a Pel- host [on which lambda strains with less than the wild-type amount of DNA form plaques at low frequency (Cameron et al., 1977)]. All of the 40 plaques examined contained phage able to transduce at least two of the genes known from bacteriophage P1 transduction experiments to be closely linked to ptsI. Assuming that each specialized transducing phage arose by a single illegitimate recombination event, the distribution of phage types showed that the gene order is cysA gsr ptsI (ptsH, iex) cysZ lig; both gsr+ and iex+ were dominant. Analysis of restriction endonuclease digests of the transducing phage confirmed that no unexpected DNA rearrangements had taken place and allowed the construction of a map of the sites of action of the restriction endonucleases EcoRI, HindIII, BamI and Kpn for over 20 kilobases of E. coli DNA. In an Appendix, we show cysA and cysZ mutants to be deficient in sulphate assimilation.

Carbohydrate Metabolism↗