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J R Wells

Publications and source records attributed to J R Wells.

At least 55 records · Page 3Linked to original sources
PubMed1986

A unique element resembling a processed pseudogene.

We describe a unique DNA element with structural features of a processed pseudogene but with important differences. It is located within an 8.4-kilobase pair region of chicken DNA containing five histone genes, but it is not related to these genes. The presence of terminal repeats, an open reading frame (and stop codon), polyadenylation/processing signal, and a poly(A) rich region about 20 bases 3' to this, together with a lack of 5' promoter motifs all suggest a processed pseudogene. However, no parent gene can be detected in the genome by Southern blotting experiments and, in addition, codon boundary values and mid-base correlations are not consistent with a protein coding region of a eukaryotic gene. The element was detected in DNA from different chickens and in peafowl, but not in quail, pheasant, or turkey.

Amino Acid Sequence↗
PubMed1986

Transcription of the histone H5 gene is not S-phase regulated.

Levels of the tissue-specific linker histone H5 are elevated in mature erythroid cells as compared with levels in dividing cells of the same lineage. We examined levels of H5 mRNA in relation to the cell cycle in early erythroid cells transformed by avian erythroblastosis virus to determine whether the gene for this unusual histone is S-phase regulated. Northern blotting analyses revealed that during the cell cycle steady-state levels of H5 mRNA remained relatively constant in contrast to levels of the major core and H1 mRNAs which increased approximately 15-fold during S phase. In vitro pulse-labeling experiments involving nuclei isolated from synchronized cells at various stages of the cell cycle revealed that transcription of the H5 gene was not initiated at any particular stage of the cell cycle but was constitutive. In contrast, transcription of the H2A gene(s) initiated in early S phase, was present throughout the DNA replicative phase, and was essentially absent in G1 and G2 phases.

Alpharetrovirus↗
PubMed1986

Otosurgical model in the guinea pig (Cavia porcellus).

The guinea pig is a useful model for otologic research. Common problems encountered in working with individual animals include preexisting chronic middle ear disease, anesthetic deaths, and a lack of knowledge of the surgical anatomy and landmarks of the middle and inner ear. The methods detailed in this article will benefit those interested in a reliable, inexpensive, otosurgical animal model.

Anesthesia↗
PubMed1986

A technique for the placement of a long-term hyperalimentation catheter in the head and neck oncology patient.

The relative safety of silicone rubber catheters allows use of the deep brachial vein for long-term central venous access when other vascular access sites are unavailable or undesirable. After local infiltration, a small incision is made across the medial edge of the brachial biceps and the vein is isolated from the artery and median nerve. An introducer is used to aid in insertion of the catheter. Catheter position is checked with a postoperative radiograph of the chest. Sixty of our patients have had catheters in place from 14 to 200 days, with few complications. There was one catheter-related death from acute bacterial endocarditis and one case of clinical thrombosis. The surgical approach to the deep brachial vein provides a simple and safe method of long-term central venous access in the head and neck oncology patient, whereas regional therapy and treatment planning often preclude use of other more conventional access sites.

Arm↗
PubMed1985

Histone H5 and H1 cross-reacting material is restricted to erythroid cells in chicken.

Monoclonal H5 antibodies and a polyclonal antiserum, raised against the globular domain of chicken H5 (GH5) but which cross-reacts with histone H1(0) from mouse liver, were used to search for H5 or H1 (0)-like proteins in chicken embryo and adult tissue sections by indirect immunofluorescence. Chicken cell lines in culture were examined for H5 protein and H5 mRNA. Histone H5 was detected only in erythroid cells in tissue sections of chicken embryos or adult livers. H5 protein and H5 mRNA were found only in erythroid cells in culture. No cross-reacting proteins were detected in any other tissue or cell line examined.

Animals↗
PubMed1985

Inverted duplication of histone genes in chicken and disposition of regulatory sequences.

Sequence analysis of an 8.4 kb fragment containing five chicken histone genes shows that an H4-H2A gene pair is duplicated and inverted around a central H3 gene. A left and right region, each of 2.1 kb are 97% homologous and the boundaries of homology coincide with ten base pair repeats. These boundary regions also contain highly conserved gene promoter elements, suggesting that interaction of transcriptional machinery with histone genes may be connected with recombination in promoter regions, resulting in the inverted duplication structure seen in this cluster.

Amino Acid Sequence↗
PubMed1985

An H1 histone gene-specific 5' element and evolution of H1 and H5 genes.

In previous studies we have shown that the H5 gene is not closely linked to the dispersed clusters of core and H1 histone genes. Here we emphasise features of H1 and H5 genes relevant to their expression in the chicken genome. Of particular note is an H1 gene-specific 5' element, 5' AAACACA 3' found upstream of all H1 genes studied to date. This "H1-box" is not found in the related H5 gene, which is expressed only in erythroid cells. A second aspect relates to generation of histone mRNA 3' termini. The H5 gene is shown to contain a remnant of the dyad symmetry element (as well as other conserved sequences) associated with core and H1-histone gene transcript 3' processing. However, it appears as if H5 has evolved a different mechanism in which the mRNA terminus (which is polyadenylated) is displaced downstream from the dyad element. The two clear differences noted here have the potential to affect transcriptional (H1-box) and post-transcriptional (3' terminus processing) regulation of H1 and H5 gene expression.

Animals↗
PubMed1985

Changes in the H-1 histone complement during myogenesis. II. Regulation by differential coupling of H-1 variant mRNA accumulation to DNA replication.

We have shown that changes in proportions of the four chicken H-1's during in vitro myogenesis are primarily the result of differential coupling of their synthesis to DNA replication (see the previous paper). We show here that the four major chicken H-1's are encoded by distinct mRNAs which specify primary amino acid sequence variants. Accumulation of the H-1-variant mRNAs is coupled to DNA replication to different extents. The level of mRNA encoding H-1c (the H-1 variant that increases relative to the other H-1's in nondividing muscle cells) is completely uncoupled. In contrast, the level of mRNAs encoding H-1's a, b, and d (which have levels that decrease in nondividing muscle cells) are more tightly coupled. Polyadenylation is not involved in uncoupling H-1c mRNA accumulation from DNA replication.

Amino Acid Sequence↗
PubMed1985

Separation by velocity sedimentation of human haemopoietic precursors forming colonies in vivo and in vitro cultures.

Cells which give rise to granulocyte-macrophage colonies under the influence of peripheral blood white cells (CFU-c (WBC] and Mo T cell conditioned medium (CFU-c (Mo] sedimented at a faster rate than the cells which form mixed erythroid-granulocytic colonies in methylcellulose in vitro (CFU-mix) and granulocytic (CFU-dg) and megakaryocytic (CFU-dm) colonies in diffusion chambers in mice. Despite identical peak sedimentation rate for the two CFU-c populations, sedimentation profiles suggest that they are heterogeneous with respect to size. A proportion of CFU-c (Mo) may be identical with CFU-dg and CFU-mix. Sedimentation profiles for cells which give rise to mixed colonies in vitro (CFU-mix) and to granulocytic colonies in diffusion chambers in cyclophosphamide pretreated mice (CFU-dg (CY] and in Mo conditioned medium treated mice (CFU-dg (Mo] were similar. On the average CFU-dm sedimented somewhat slower than CFU-dg. These and other observations suggesting a close relationship between CFU-dg and multipotential haemopoietic precursors are discussed.

Bone Marrow Cells↗
PubMed1985

Chromosomal organization of chicken histone genes: preferred associations and inverted duplications.

We present a detailed picture of the disposition of core and H1 histone genes in the chicken genome. Forty-two genes were located within four nonoverlapping regions totalling approximately 175 kilobases and covered by three cosmid clones and a number of lambda clones. The genes for the tissue-specific H5 histone and other variant histones were not found in these regions. The longest continuous region mapped was 67 kilobases and contained 21 histone genes in five dissimilar clusters. No long-range repeat was evident, but there were preferred associations, such as H1 genes with paired, divergently transcribed H2A-H2B genes and H3-H4 associations. However, there were exceptions, and even when associations such as H1-H2A-H2B we maintained, the order of those genes within a cluster may not have been. Another feature was the presence of three (unrelated) clusters in which genes were symmetrically ordered around central H3 genes; in one such cluster, the boundaries of a duplicated H2A-H4 gene pair contained related repeat sequences. Despite the dispersed nature of chicken histone genes, the number of each type was approximately equal, being represented as follows: 6 H1, 10 H2A, 8 H2B, 10 H3, and 8 H4.

Animals↗
PubMed1985

Sodium-amino acid cotransport by type II alveolar epithelial cells.

Type II alveolar epithelial cell monolayers have been shown to actively transport sodium (Na+). Coupling to amino acid uptake could be an important mechanism for Na+ entry into these cells. This study demonstrates the presence of such a coupled cotransport mechanism in the plasma membrane of isolated type II cells by use of the nonmetabolizable amino acid analogue alpha-methylaminoisobutyric acid (MeAIB). Transport of MeAIB in 137 mM Na+ is saturable, with the uptake constant (Vmax) equaling 13.9 pmol X mg prot-1 X s-1 and the Michaelis-Menten constant (Km) equaling 0.13 mM. In the presence of Na+, MeAIB is accumulated against a concentration gradient. MeAIB uptake in the absence of Na+ is linear with MeAIB concentration, as expected for simple diffusion. The Hill coefficient for Na+-MeAIB cotransport is 1.11, suggesting a 1:1 stoichiometry. Proline inhibits Na+-MeAIB cotransport, with Ki equaling 0.5 mM. These findings suggest that Na+-amino acid cotransport may be an important pathway for Na+ (and/or amino acid) uptake into type II alveolar epithelial cells.

Aminoisobutyric Acids↗
PubMed1984

Clustering of human H1 and core histone genes.

An H1 histone gene was isolated from a 15-kilobase human DNA genomic sequence. The presence of H2A, H2B, H3, and H4 genes in this same 15-kilobase fragment indicates that mammalian core and H1 histone genes are clustered.

Animals↗
PubMed1984

Ribosomal gene reiteration in a marsupial species with an X-linked nucleolar organizer.

The number of ribosomal cistrons in somatic cells of males and females of Macropus eugenii have been estimated using RNA/DNA hybridization in 70% (v/v) formamide. The male has one X-linked active nucleolar organizer and the female two and while the number of ribosomal cistrons is variable between the four males examined (31-65 copies), it is substantially less than the number present in the three females (94-103 copies). There is, therefore, no evidence of dosage compensation by amplification.

Animals↗
PubMed1983

Analysis of histone H5 and globin mRNAs in chick-embryo development.

Transcripts from histone H5 and alpha and beta chicken globin genes were analysed in total RNA extracted from 2-6-day-old chick embryos. Denatured RNA, separated on gels, was transferred to either aminophenylthioether (APT) paper or to nitrocellulose and was detected with 32P-labelled recombinant DNA probes. Good resolution was achieved with methyl mercury hydroxide gels and aminophenylthioether transfer, allowing estimation of H5 and alpha and beta globin mRNA sizes. With glyoxal gels and nitrocellulose transfer, alpha and beta globin mRNAs were not resolved, but an increased sensitivity of detection of at least 10-fold was achieved. Levels of H5 and alpha globin mRNAs increased in parallel over 2-6 days. The appearance of definitive red cells in 6-day embryos was indicated by detection of adult beta globin transcripts at this stage.

Animals↗
PubMed1983

The chicken H5 gene is unlinked to core and H1 histone genes.

An H5 cDNA clone was used to select H5 genomal recombinants from a chicken Charon 4A library. DNA sequence analysis shows that the H5 gene contains no introns. Putative 5' promoter elements and a 3' polyadenylation site are present within the 1.8 kb of DNA examined. Analysis of 41 kb of DNA surrounding the H5 gene shows that it is not closely linked to either H1 or core histone genes.Images

Amino Acid Sequence↗
PubMed1983

Enhancement of human myeloid stem cell growth in vitro.

Human myeloid stem cell growth in agar was enhanced by the addition of human plasma, red-cell lysate, hemin, and beta-mercaptoethanol to the culture system. Using conditioned media from a human T-cell or leukocyte-conditioned media as a source of colony-stimulating activity, the number of colonies was increased due to enhancement by an average of 54%. Analysis of colony types indicated that over 80% of the increase in colony number at eight days was due to granulocytic colony growth. Light density marrow cells cultured with enhancing agents produced colony levels of approximately 12-27 CFU-C/2 x 10(3) cells.

Clone Cells↗