Biomedical subjects

K A Byrne

Publications and source records attributed to K A Byrne.

14 recordsLinked to original sources

PubMed2006

Gene expression profiling of bovine skeletal muscle in response to and during recovery from chronic and severe undernutrition.

Gene expression profiles of LM from beef cattle that underwent significant postweaning undernutrition were studied using complementary DNA (cDNA) microarrays. After 114 d of undernutrition, the RNA from LM showed 2- to 6-fold less expression of many genes from the classes of muscle structural proteins, muscle metabolic enzymes, and extracellular matrix compared with animals on a rapid growth diet. The expression levels of these genes had mostly returned to pretreatment levels after 84 d of realimentation. The gene expression changes associated with undernutrition and BW loss showed an emphasis on downregulation of gene expression specific to fast-twitch fibers, typical of starving mammals, with a preferential atrophy of glycolytic fast-twitch fibers. We also identified a small group of genes that showed 2- to 5-fold elevated expression in LM after 114 d of undernutrition. Putative roles for these genes in atrophying skeletal muscle are regulation of myogenic differentiation (CSRP3), maintenance of mesenchymal stem cells (CYR61), modulation of membrane function (TM4SF2), prevention of oxidative damage (SESN1), and regulation of muscle protein degradation (SQSTM1). A significant increase in stearoyl-CoA desaturase (SCD) gene expression was observed in atrophying muscle, suggesting either that increased fatty acid synthesis is part of the tissue response to caloric restriction, or that SCD plays another role in energy metabolism in the mixed cellular environment of bovine skeletal muscle.

Animal Feed↗

PubMed2005

Heterozygosity, inbreeding and neonatal traits in Soay sheep on St Kilda.

We investigated whether birth weight and neonatal survival, a period within which 24% of all mortalities occur, were correlated with levels of inbreeding in St Kilda Soay sheep, using pedigree inbreeding coefficients and four marker-based estimators of inbreeding. None of the inbreeding estimators, either of the offspring, or of their mothers, explained significant variation in a lamb's birth weight or probability of surviving the neonatal period, suggesting low inbreeding depression for these traits. We evaluated the correlation between the marker-based measures of inbreeding and inbreeding coefficients obtained from the Soay pedigree, where paternal links were inferred using the same panel of microsatellite markers. Even when using a relatively complete portion of the pedigree, in which all individuals had known maternal and paternal grandparents, the correlation was found to be weak (r = -0.207, where mean f = 0.0168). These results add support to the recent prediction that when the mean and variance in inbreeding are low in a population, heterozygosity-fitness correlations can be very weak or even undetectable. The pursuit of more detailed pedigrees offers the best prospect for identifying inbreeding depression within this study population.

Animals↗

PubMed2005

Maternal genetic effects set the potential for evolution in a free-living vertebrate population.

Heritable maternal effects have important consequences for the evolutionary dynamics of phenotypic traits under selection, but have only rarely been tested for or quantified in evolutionary studies. Here we estimate maternal effects on early-life traits in a feral population of Soay sheep (Ovis aries) from St Kilda, Scotland. We then partition the maternal effects into genetic and environmental components to obtain the first direct estimates of maternal genetic effects in a free-living population, and furthermore test for covariance between direct and maternal genetic effects. Using an animal model approach, direct heritabilities (h2) were low but maternal genetic effects (m2) represented a relatively large proportion of the total phenotypic variance for each trait (birth weight m2=0.119, birth date m2=0.197, natal litter size m2=0.211). A negative correlation between direct and maternal genetic effects was estimated for each trait, but was only statistically significant for natal litter size (ram= -0.714). Total heritabilities (incorporating variance from heritable maternal effects and the direct-maternal genetic covariance) were significant for birth weight and birth date but not for natal litter size. Inadequately specified models greatly overestimated additive genetic variance and hence direct h2 (by a factor of up to 6.45 in the case of birth date). We conclude that failure to model heritable maternal variance can result in over- or under-estimation of the potential for traits to respond to selection, and advocate an increased effort to explicitly measure maternal genetic effects in evolutionary studies.

Analysis of Variance↗

PubMed2005

Gene expression profiling of muscle tissue in Brahman steers during nutritional restriction.

Expression profiling using microarrays allows for the detailed characterization of the gene networks that regulate an animal's response to environmental stresses. During nutritional restriction, processes such as protein turnover, connective tissue remodeling, and muscle atrophy take place in the skeletal muscle of the animal. These processes and their regulation are of interest in the context of managing livestock for optimal production efficiency and product quality. Here we expand on recent research applying complementary DNA (cDNA) microarray technology to the study of the effect of nutritional restriction on bovine skeletal muscle. Using a custom cDNA microarray of 9,274 probes from cattle muscle and s.c. fat libraries, we examined the differential gene expression profile of the LM from 10 Brahman steers under three different dietary treatments. The statistical approach was based on mixed-model ANOVA and model-based clustering of the BLUP solutions for the gene x diet interaction effect. From the results, we defined a transcript profile of 156 differentially expressed array elements between the weight loss and weight gain diet substrates. After sequence and annotation analyses, the 57 upregulated elements represented 29 unique genes, and the 99 downregulated elements represented 28 unique genes. Most of these co-regulated genes cluster into groups with distinct biological function related to protein turnover and cytoskeletal metabolism and contribute to our mechanistic understanding of the processes associated with remodeling of muscle tissue in response to nutritional stress.

Analysis of Variance↗

PubMed2004

Joint analysis of multiple cDNA microarray studies via multivariate mixed models applied to genetic improvement of beef cattle.

In functional genomic laboratories, it is common to use the same microarray slide across studies, each investigating a unique biological question, and each analyzed separately due to computational limitations and/or because there is no hybridization of samples from different studies on one slide. However, the question of analyzing data from multiple studies is a major current issue in microarray data analysis because there are gains to be made in the accuracy of estimated effects by exploiting a covariance structure between gene expression data across studies. We propose an approach for combining multiple studies using multivariate mixed models, with the assumption of a nonzero correlation among genes across experiments, while imposing a null residual covariance. We applied this method to jointly analyze three experiments in genetics of cattle with a total of 54 arrays, each with 19,200 spots and 7,638 elements. The resulting seven-variate model contains 752,476 equations and 56 covariances. To identify differentially expressed genes, we applied model-based clustering to a linear combination of the random gene x variety interaction effect. We enhanced the biological interpretation of the results by applying an iterative algorithm to identify the gene ontology classes that significantly changed in each experiment. We found 118 elements with coordinate expression that clustered into distinct biological functions such as adipogenesis and protein turnover. These results contribute to our understanding of the mechanistic processes involved in adipogenesis and nutrient partitioning.

Animals↗

PubMed2003

A mixture model-based cluster analysis of DNA microarray gene expression data on Brahman and Brahman composite steers fed high-, medium-, and low-quality diets.

The objective of this study is to explore aspects of the statistical analysis of gene expression response at the muscle tissue level to varying levels of energy and protein in the diet. Eleven Brahman and Brahman composite steers (weighing 302 +/- 9.8 kg, on average) were allocated randomly into high- (HIGH), medium- (MED), and low- (LOW) quality forage diets for 27 d. After this period, a biopsy of the longissimus dorsi muscle was taken from each animal and total RNA was extracted to generate the labeled target for microarray experimentation. These targets were hybridized to a complementary DNA (cDNA) microarray of 9,274 probes from cattle muscle and subcutaneous fat cDNA libraries. After edits, 151,904 expression intensity levels of 4,747 genes were analyzed. Emphasis was given to the choice of power transformation of the intensity channel readings and to the consistency of readings within each diet quality group. The statistical approach to isolate differentially expressed genes was based on model-based clustering via a mixture of normal distributions estimated through maximal likelihood. The base-2 logarithm was found to be the optimal power transformation to normalize gene intensity levels. A two-sample t-statistic was defined as a measure of possible differential expression. For each of the three diet contrasts, HIGH vs. LOW, HIGH vs. MED, and MED vs. LOW, three clusters were found, two of which contained more than 94% genes with almost no altered gene expression levels, whereas the third cluster contained the remaining genes with a differential expression. Results from the HIGH vs. LOW contrast identified 27 genes with a greater than 95% posterior probability of belonging to the cluster of differentially expressed genes.

Animal Feed↗

PubMed1999

Isolation of a cDNA encoding a putative cellulase in the red claw crayfish Cherax quadricarinatus.

Amino acid sequences of cellulases have been determined in insects, nematodes, plants, slime moulds and bacteria but not in crustaceans. However, cellulase activity has been demonstrated in the hepatopancreas of the red claw crayfish, Cherax quadricarinatus. In order to obtain information on the nature of this cellulase, a C. quadricarinatus hepatopancreas cDNA library was screened with a PCR product generated using degenerate oligonucleotide primers derived from conserved regions of known cellulases. Two identical 1.56kb cDNAs with sequence similarities to known cellulases, particularly the termite endoglucanases, were identified and sequenced. The clones contain the complete cDNA open reading frame for an endo-1, 4-beta-glucanase of 469 amino acids termed Cherax quadricarinatus endoglucanase (CqEG). The endogenous origin of the gene was confirmed by PCR amplification and sequencing of a 1012bp PCR product from genomic DNA. This fragment contains four exon sequences identical to the cDNA and is interrupted by three introns of 371, 102, 194bp respectively, with one intron exhibiting typical eukaryotic splice sites. The isolation of an endo-1,4-beta-glucanase encoding cDNA from the crayfish C. quadricarinatus provides the first endogenous cellulase sequence in a crustacean species.

Amino Acid Sequence↗

PubMed1997

Genome organization and transcription strategy in the complex GNS-L intergenic region of bovine ephemeral fever rhabdovirus.

A 1622 nucleotide region of the bovine ephemeral fever virus (BEFV) genome, located between the second glycoprotein (GNS) gene and the polymerase (L) gene, has been cloned and sequenced in Australian (BB7721) and Chinese (Beijing-1) isolates of the virus. In the Australian isolate, the region contains five long open reading frames (ORFs) organized into three coding regions (alpha, beta and gamma), each of which are bound by a consensus transcription initiation and transcription termination-polyadenylation-like sequences. The alpha coding region contains three long ORFs (alpha 1, alpha 2 and alpha 3). The alpha 1 ORF encodes a 10.6 kDa polypeptide which contains hydrophobic and highly basic regions characteristic of a viroporin. The alpha 2 ORF encodes a 13.7 kDa polypeptide and overlaps the alpha 3 ORF which encodes a 5.7 kDa polypeptide. The beta coding region contains a single long ORF encoding a polypeptide of 12.2 kDa. The gamma coding region, which does not occur in Adelaide River virus (ARV), contains a single long ORF encoding a polypeptide of 13.4 kDa. The Chinese isolate shares 91% nucleotide sequence identity with the Australian isolate. The organization of the alpha, beta and gamma coding regions is preserved and the sequences of the encoded polypeptides are similar to those of BB7721. The major transcription products of the region were identified in BB7721 as polycistronic alpha (alpha 1-alpha 2-alpha 3) and beta-gamma mRNAs. Sequence similarities in the BEFV alpha-beta and beta-gamma gene junctions, and the gamma-L and beta-L gene junctions of BEFV and ARV, suggest that the gamma gene may have evolved from the beta-gene by sequence duplication.

Amino Acid Sequence↗

PubMed1994

Effective vaccination of cattle using the virion G protein of bovine ephemeral fever virus as an antigen.

In a series of experiments, the envelope glycoprotein (G protein) of bovine ephemeral fever virus (BEFV) induced immunity against challenge with virulent virus. Protection correlated with the level of specific serum antibodies to G protein measured by a blocking ELISA test and with the level of neutralizing antibody. The optimum vaccination regimen consisted of two injections given 21 days apart at a dose rate of 0.32 microgram per cow of purified G protein emulsified in the adjuvant Quil A. This schedule conferred immunity for the duration of the preliminary experiment (46 days). Immunity to severe disease, but not to infection, remained for at least 12 months after vaccination, although BEFV could not be reisolated from vaccinated cattle following challenge. Unvaccinated cattle used as controls exhibited typical signs of clinical ephemeral fever and BEFV was recovered from all control animals following challenge.

Animals↗

PubMed1992

Fungal keratitis in Saudi Arabia.

We studied a total of 27 cases of fungal keratitis is Saudi Arabia. History of trauma was found in 9 patients, and previous use of topical steroids in 6 patients. In the majority of patients the onset of the disease was in fall and spring. The most frequent cause of fungal keratitis was found to be Aspergillus spp., and these were isolated from 11 cases (41%). Eight of the 11 isolates were Aspergillus flavus. Other causes of keratomycosis included: Fusarium, Candida, and Mycelia sterilia. All patients were treated with antifungal therapy and 18 patients required surgical intervention. Vision improved among 11 patients, remained the same in 4 patients, and deteriorated after treatment in 6 patients. (6 patients failed to return for follow-up.) Four of the 27 patients developed fungal endophthalmitis. The high prevalence of Aspergillus spp. may be due to the fact that spores of Aspergillus can survive the hot and dry weather of Saudi Arabia.

Adolescent↗

PubMed1992

The genome of bovine ephemeral fever rhabdovirus contains two related glycoprotein genes.

A 3789 nucleotide region of the bovine ephemeral fever virus (BEFV) genome, located 1.65 kb downstream of the N gene, has been cloned and sequenced. The region contains two long open reading frames (ORFs) which are bounded by putative consensus (AACAGG) and polyadenylation (CATG[A]7) sequences and are separated by an intergenic region of 53 nucleotides. Discrete mRNAs corresponding to each ORF have been identified. The first ORF encodes a polypeptide comprising 623 residues which was identified by peptide sequencing as the virion G protein. The deduced amino acid sequence of the G protein includes putative signal and transmembrane domains and five potential glycosylation sites. The second ORF encodes a polypeptide of 586 amino acids which also has characteristics of a rhabdovirus glycoprotein, including putative signal and transmembrane domains and eight potential glycosylation sites, and appears to correspond to a 90-kDa nonstructural glycoprotein (GNS) identified in BEFV-infected cells (Walker et al. [1991] J. Gen. Virol. 72, 67-74). A database search indicated that both the G and GNS proteins share significant amino acid sequence homology with other rhabdovirus G proteins and with each other. Highest homology scores for each protein were with sigma virus and vesicular stomatitis virus serotypes.

Amino Acid Sequence↗

PubMed1991

Proteins of bovine ephemeral fever virus.

The proteins of bovine ephemeral fever virus (BEFV) were examined in purified virions and in infected BHK-21 cells. Five structural proteins were named L (180K), G (81K), N (52K), M1 (43K) and M2 (29K). The 81K G protein incorporated [3H]glucosamine, was removed from virions by treatment with Triton X-100 and bound monoclonal antibodies which were both neutralizing and protective. Treatment of virions with Triton X-100 and 0.2 to 1.0 M-NaCl progressively released L, M1 and M2. The N protein remained associated with nucleocapsids in up to 2.5 M-NaCl. The glycoprotein (G), nucleoprotein (N) and matrix protein (M2) were phosphorylated. In BEFV-infected BHK-21 cells, five virus-induced proteins were detected from 12 h post-infection. The L, N, M1 and M2 proteins corresponded to those detected in virions whereas the G protein existed in two forms. In tunicamycin-treated cells these occurred as 67K and 71K non-glycosylated precursors. In the absence of tunicamycin, 77K and 79K glycosylated forms were further modified to produce the 81K virion G protein and a 90K cell-associated form. Five viral proteins were also detected in cells infected with the closely related Berrimah virus; the Berrimah virus G protein was also present in two forms.

Animals↗

PubMed1990

Mapping of antigenic sites on the bovine ephemeral fever virus glycoprotein using monoclonal antibodies.

Monoclonal antibodies (MAbs) were produced against the G, M2 and N proteins of bovine ephemeral fever virus (BEFV) and 29 were selected for further study. Thirteen neutralizing MAbs were assigned to one conformation-independent and at least two conformation-dependent antigenic sites on the G protein by a competitive binding ELISA. The panel of MAbs were tested by neutralization and immunofluorescence with three strains of BEFV and three BEFV-related viruses. The results indicated that BEFV strains from different sources were not identical and that the M2 protein was the least variable of the proteins investigated. Passive protection studies in mice showed that the correlation between neutralizing titre and resistance to challenge was 0.85 (P less than 0.001).

Animals↗

PubMed1988

Goblet cell population among patients with inactive trachoma.

Trachoma is a chlamydial disease that affects millions of people each year, particularly in developing countries. In the chronic phase, inflammation causes scarring of the conjunctiva followed by dry eye which can result in blindness. Trachoma may cause dryness of the eye by decreasing mucus production and aqueous secretions. Conjunctival impression cytology was carried out to determine the goblet cell population among patients with trachoma. We performed impression cytology on 32 patients with inactive trachoma and 31 age and sex matched controls. Impression cytology showed that the nasal conjunctiva contains the greatest number of goblet cells. Trachoma patients with severe scarring had significantly less goblet cell counts than those with mild scarring (p less than 0.05). In the group of ten patients with severe trachoma and keratinization, there was marked reduction or absence of goblet cells. Trachoma appears to initiate a viscious cycle of conjunctival scarring, mucus deficiency, and chronic conjunctival inflammation.

Cell Count↗