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J A Bixby

Publications and source records attributed to J A Bixby.

10 recordsLinked to original sources
PubMed2001

Polymorphic forms of expressed bovine interferon-tau genes: relative transcript abundance during early placental development, promoter sequences of genes and biological activity of protein products.

Multiple interferon (IFN)-tau genes exist in cattle, but it has remained unclear how many are expressed, the extent of their variation, and whether different genes exhibit similar patterns of expression and code for proteins with similar biological activities. A total of 118 complementary DNA (cDNA) were bi-directionally sequenced from reverse-transcribed bovine (bo) conceptus RNA over the period from blastocyst formation until day 25 of pregnancy. Fourteen different cDNAs, encoding eight different IFN-tau, were confirmed unique. All showed high sequence conservation (>98% nucleotide identity; >96% amino acid identity). The cDNA fell into three, recently evolved, phylogenetic groups (tau1, 2, and 3). Mean concentrations of IFN-tau messenger RNA were greater at day 17 and day 19 than at day 14 and day 25, with different genes showing comparable expression patterns, although there appeared to be a major bias in expression of two genes (for boIFN-tau1c and tau3a) in blastocysts. Genes representing members of the three boIFN-tau groups were cloned. Their promoter regions were conserved over regions considered important for transcriptional activation. Recombinant protein generated in Escherichia coli from representative genes in the three groups had similar but not identical antiviral activities. In summary, many IFN-tau genes, which are probably under similar transcriptional control, are expressed in bovine trophoblast during the peri-implantation period of development.

Amino Acid Sequence↗
PubMed2000

A classification for the interferon-tau.

An attempt has been made to provide a rational organization for the many interferon-tau (IFN-tau) sequences entered in GenBank based on phylogenetic analysis and common amino acid substitutions, which might form the basis for a universal nomenclature scheme. Over the 13 years since these genes were first discovered, large numbers of cDNA and gene sequences have been reported, and there is reason to suspect that representatives of all the major ovine and bovine forms have now been described. The data are consistent with the presence of many genes and also allelic variants in sheep and cattle analogous to what has been observed for the IFN-alpha in the human. Future variants should be easily accommodated into the scheme outlined here. A flexible system of nomenclature, based on that used for HuIFN, is needed to provide a common base for comparison between research done in different laboratories and to assign relative biologic potencies to these molecules.

Animals↗
PubMed1996

A type I ovine interferon with limited similarity to IFN-alpha, IFN-omega and IFN-tau: gene structure, biological properties and unusual species specificity.

A gene encoding a 195 amino-acid (a.a.) polypeptide with a putative 23 a.a. signal sequence that had about 60% a.a. sequence identity to ovine interferon-omega (OvIFN-omega) and 55% or less identity to BoIFN-tau, OvIFN-tau and all known IFN-alpha and -beta has been identified from an ovine genomic DNA library. Surprisingly, it shared almost complete identity to genes for rabbit IFN-omega within its coding sequence and proximal promoter region, although the two were different in their 3'-ends. This IFN (tentatively termed ovine IFN-omega variant, OvIFN-omegav), purified in recombinant form from E. coli, had normal antiviral activity when tested on sheep fetal tongue and brain cells and rabbit kidney cells, but very low activity towards bovine, goat and human cells. It competed with 125I-labeled BoIFN-tau for binding to IFN receptors on ovine cells. Expression of OvIFN-omegav was not detected by reverse transcription-PCR either in ovine peripheral blood leukocytes infected with Sendai virus, or in any other tissues examined. OvIFN-omegav may represent a previously unrecognized, non-virally inducible type I subtype distinct from IFN-alpha, -beta, -omega and -tau. The presence of a conserved gene in rabbit and sheep could reflect a recent interspecies transfer.

Amino Acid Sequence↗
PubMed1994

Selective cloning of cDNA for secretory proteins of early embryos. Identification of a transiently expressed kunitz domain protein from preimplantation sheep trophoblast.

The preimplantation ovine conceptus transiently secretes several proteins, including a type I interferon (IFN-tau), that are likely involved in establishment of pregnancy. A method has been developed to identify proteins produced simultaneously with IFN-tau. An antiserum against total ovine conceptus secretory proteins, from which IFN-tau and proteins common to maternal uterine tract secretions had first been removed, was used to immunoscreen cDNA libraries created from mRNA of days 13 and 15 ovine conceptuses. This approach has allowed several unique cDNA to be identified, including one particularly abundant transcript for a novel member of the Kunitz family of serine protease inhibitors. This cDNA encodes a 265-amino acid protein with a 20-amino acid signal sequence. A 64-amino acid Kunitz domain occupies the carboxyl terminus. It is preceded by two similar repeats of 84 residues that bear no obvious similarity to any sequences present in the protein data banks. The protein present in conceptus secretions (M(r) of approximately 14,000) represents only the carboxyl terminus of the molecule. The mRNA for this putative proteinase inhibitor was confined to trophectoderm and was highly expressed for only a few days (approximately 13-18) of development. A similar transcript was detected during the days 17-21 period in cattle embryos. Despite their high expression, no proteinase-inhibitory activity can so far be ascribed to either the ovine or bovine proteins. The P1 residue, an asparagine, is not represented in any other known Kunitz inhibitors.

Amino Acid Sequence↗
PubMed1992

Expression of interleukin-6 in porcine, ovine, and bovine preimplantation conceptuses.

A porcine interleukin-6 (pIL-6) cDNA has been cloned from pig spleen cDNA library to provide information that would allow us to study IL-6 mRNA expression during pregnancy of several domestic Artiodactyla. The cDNA is 1058 bp long and with a single open reading frame that encodes a 212 amino acid polypeptide with 28-residue signal sequence. It shares 61% and 43% amino acid sequence identity with human and mouse IL-6, respectively. PCR procedures with primers designed from regions of sequence conserved between human and pig have been used to identify IL-6 cDNA in lambda gt11 libraries constructed from day 15-16 (sheep), day 17 (cattle), and day 13-17 (pig) conceptus mRNA. The presence of IL-6 mRNA in elongating preimplantation ovine (days 13-25), porcine (days 13-21), and bovine (days 16-20) conceptuses was also demonstrated by PCR after reverse transcription of total ribonucleic acid with reverse transcriptase and by solution hybridization with a pIL-6 cRNA probe. These observations suggest that IL-6 is a product of these early conceptuses and may be involved in early maternal responses to the presence of an embryo within the uterus.

Amino Acid Sequence↗
PubMed1991

The genes for the trophoblast interferons and the related interferon-alpha II possess distinct 5'-promoter and 3'-flanking sequences.

The genes for trophoblast interferons (IFN) bovine trophoblast protein-1 (bTP-1) and ovine trophoblast protein-1 (oTP-1) are expressed massively in the trophectoderm of preimplantation bovine and ovine concepti during the period of maternal recognition of pregnancy. These 172-amino acid IFN are closely related to the IFN-alpha II, a family of "long" IFN expressed in virus-induced leukocytes. Genomic Southern blotting with a full-length bTP-1 cDNA revealed about 15 genes that bind the probe with varying intensities. By using more specific probes for the 3'-ends of the cDNA, we have shown that only four to five of these represent bTP-1 genes, whereas no more than another four are IFN-alpha II. Genes for bTP-1 and IFN-alpha II, all of which are intronless, have been isolated from bovine genomic libraries, and their nucleotide sequences were compared. Additional bTP-1 genes and two distinct oTP-1 genes have been isolated from bovine and ovine genomic DNA by using the polymerase chain reaction procedure in conjunction with specific 3'- and 5'- primers (derived from the bTP-1 gene sequences determined above). The promoter region up to 100 bases upstream from the transcription start sites of the trophoblast IFN are almost completely conserved across different genes and across species, yet show only limited sequence identity with IFN-alpha II. Two putative binding regions for interferon regulatory factor-1 as well as several GAAANN motifs (where N is any nucleotide) that have been implicated in viral responsiveness of alpha 1- and beta-IFN genes are retained at identical positions in all of the trophoblast genes. Putative interferon regulatory factor-1-binding nucleotide hexamers and GAAANN motifs are also present in the IFN-alpha II genes, but these are organized very differently than in the trophoblast IFN genes. A GAAATG motif is present in IFN-alpha II promoters but is absent in trophoblast IFN genes. Based on the evidence presented, it is proposed that the trophoblast interferons constitute a separate subclass of IFN-alpha distinct from IFN-alpha II and IFN-alpha I.

Animals↗
PubMed1991

The polypeptides and genes for ovine and bovine trophoblast protein-1.

Ovine and bovine trophoblast protein-1 (oTP-1 and bTP-1) have been strongly implicated as antiluteolytic agents and responsible for maternal recognition of pregnancy in sheep and cattle, respectively. Both are interferons (IFN) belonging to the IFN-alpha family, but their length (172 residues versus 166 for most IFN-alpha) places them in an unusual subclass (the IFN-alpha II). The various isoforms of oTP-1 and bTP-1 produced by trophoblast tissue appear to arise in part from translation of multiple mRNAs which are themselves the products of distinct genes. These genes, like those for other IFN-alpha, are without introns. However, the genes for oTP-1 and bTP-1 form a distinct subgroup within the IFN-alpha II on the basis of their overall primary sequences and the high conservation of the 3'-untranslated ends of their transcription units. The bTP-1 genes also differ from the bovine IFN-alpha II in the organization of the promoter regions upstream from the transcription start site. Nevertheless, computer-aided analysis of the primary polypeptide sequences of oTP-1 and bTP-1 indicates that the molecules are likely to have approximately the same shapes and dimensions as all other IFN-alpha molecules. It remains to be determined whether they have unique biological properties which distinguish them from other IFN-alpha molecules.

Amino Acid Sequence↗
PubMed1977

The quantitative histologic distribution of pyridoxal phosphate in the rat stomach, effects of drugs influencing secretion.

The quantitative histologic distribution of pyridoxal phosphate (PLP), the coenzyme of histidine decarboxylase in the biosynthesis of histamine as well as the coenzyme of other enzyme systems, was established in the rat glandular stomach in different secretory states. This was accomplished by analyzing PLP with an improved fluorometric microprocedure in histologically identified fresh-frozen microtome tissue sections cut serially through the stomach wall of fed and 24-hr fasted rats, and of the latter injected with drugs that stimulate (histamine, theophylline and urecholine) or inhibit (atropine) secretion. In fasted compared with fed rats, and in fasted rats injected with histamine (low dose) or theophylline, compared with saline injected controls, the PLP level was reduced not only in the chief cell region where PLP is utilized in histamine production, but also in the parietal and mucous neck cell region, indicating PLP function in other enzyme systems in these sites. No change in PLP level occurred when histamine was injected at a high dose known to suppress histidine decarboxylase activity. Administration of urecholine or atropine had negligible effect on the PLP levels, indicating a lack of vagal stimulatory or inhibitory influence.

Animals↗