Biomedical subjects

G W Hoyle

Publications and source records attributed to G W Hoyle.

26 records · Page 2Linked to original sources

PubMed1993

Expression of NGF in sympathetic neurons leads to excessive axon outgrowth from ganglia but decreased terminal innervation within tissues.

The effects of nerve growth factor (NGF) on sympathetic axon growth were investigated by generating transgenic mice in which the beta subunit of NGF was expressed in sympathetic neurons using the human dopamine beta-hydroxylase (DBH) promoter. In DBH-NGF mice, the sympathetic trunk and nerves growing to peripheral tissues were enlarged and contained an increased number of sympathetic fibers. Although sympathetic axons reached peripheral tissues, terminal sympathetic innervation within tissues was decreased in DBH-NGF mice. This effect could be reversed in the pancreas by overexpression of NGF in pancreatic islets. The observations are consistent with a model in which NGF gradients are not required to guide sympathetic axons to their targets, but are required for the establishment of the normal density and pattern of sympathetic innervation within target tissues.

Adrenal Glands↗

PubMed1992

The binding specificity of normal and variant rat Kupffer cell (lectin) receptors expressed in COS cells.

A receptor uniquely found on the surface of rat Kupffer cells was shown previously to bind oligosaccharides terminating in galactose, N-acetylgalactosamine, and fucose. To analyze further the binding specificity of the receptor, receptor-mediated adhesion of transfected COS cells to immobilized glycolipids of known structure was measured. The glycolipid Gb4Cer (GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc beta 1Cer) was the best ligand. Gb5Cer (GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc beta 1Cer) and LacCer (Gal beta 1-4Glc beta 1Cer) bound more weakly (five times less than Gb4Cer) and Gb3Cer (Gal alpha 1-4Gal beta 1-4Glc beta 1Cer), and g3Cer(GalNAc beta 1-4Gal beta 1-4Glc beta 1Cer) bound even more weakly (60 times less than Gb4Cer). Gangliosides did not support adhesion of transfected cells. The adhesion of COS cells transfected with plasmids encoding variants of the receptor was also examined. In each variant, either tryptophan 498 or 523, which are conserved in most C-type lectins, was replaced by one of several amino acids. Variants that retained binding activity had the same specificity as the normal receptor. Differences between variants were noted, however, in maximal levels of adhesion and these differences correlated with altered expression of the receptor variants in COS cells.

Acetylgalactosamine↗

PubMed1992

Alteration of neurotransmitter phenotype in noradrenergic neurons of transgenic mice.

The normal complement of neurotransmitters in noradrenergic neurons was altered by expressing the structural gene for the enzyme phenylethanolamine-N-methyltransferase (PNMT) under the control of the dopamine-beta-hydroxylase gene promoter in transgenic mice. This resulted in accumulation of large amounts of epinephrine in neurons of the sympathetic nervous system (SNS) and central nervous system (CNS) but did not reduce norepinephrine levels. Adrenalectomy reduced PNMT levels in the SNS and CNS, suggesting that the transgene is positively regulated by adrenal steroids. Epinephrine levels were unaffected by this treatment in the CNS, suggesting that PNMT is not rate limiting for epinephrine synthesis. However, catecholamines were elevated in a sympathetic ganglion and a target tissue of the SNS, perhaps due to up-regulation of tyrosine hydroxylase in response to adrenalectomy. These transgenic mice also reveal a marked difference in the ability of chromaffin cells and neurons to synthesize epinephrine.

Adaptation, Physiological↗

PubMed1991

Structure of the gene for a carbohydrate-binding receptor unique to rat kupffer cells.

The gene encoding the rat Kupffer cell receptor for fucose and galactose (Lehrman, M. A., and Hill, R. L. (1986) J. Biol. Chem. 261, 7419-7425 and Lehrman, M. A., Haltiwanger, R. S., and Hill, R. L. (1986) J. Biol. Chem. 261, 7426-7432) has been isolated and characterized. The nucleotide sequence of the 9.7-kilobase gene and of 1 kilobase of 5'-flanking sequence was determined. The 5' end of the receptor coding sequence was determined by primer extension and S1 mapping of the receptor transcript. Knowledge of the transcription start site and the 5'-flanking sequence allowed potential promoter elements to be identified. The Kupffer cell receptor coding sequence is encoded by seven exons that are split by six introns. The divisions among domains in the receptor can be correlated with divisions among exons in the gene. The carbohydrate recognition domain is encoded by three exons similar to those in the rat hepatic lectin, human Fc receptor for IgE, and rat cartilage proteoglycan core protein genes. A model for the evolution of the vertebrate lectin genes that have been analyzed is presented.

Amino Acid Sequence↗

PubMed1991

The dopamine beta-hydroxylase gene promoter directs expression of E. coli lacZ to sympathetic and other neurons in adult transgenic mice.

Dopamine beta-hydroxylase (DBH) catalyzes the final step in the biosynthesis of norepinephrine, the principal classic neurotransmitter of peripheral sympathetic neurons. We have shown that 5.8 kb of 5' upstream region from a cloned human DBH gene promoter is sufficient to direct expression of the E. coli lacZ gene in transgenic mice to neurons of the locus ceruleus and other classic noradrenergic brain stem nuclei, sympathetic ganglion neurons, and adrenal chromaffin cells. lacZ expression was also observed in neurons of the enteric system, the retina, some sensory and all cranial parasympathetic ganglia, and some diencephalic and telencephalic brain nuclei. The expression pattern of the transgene in DBH-immunonegative sites overlapped with many sites where expression of tyrosine hydroxylase or phenylethanolamine N-methyltransferase, two other catecholamine biosynthetic enzymes, has been reported.

Animals↗

PubMed1991

Some neuronal cell populations express human dopamine beta-hydroxylase-lacZ transgenes transiently during embryonic development.

The 5' flanking region from the human dopamine beta-hydroxylase gene directs expression of bacterial beta-galactosidase reporter genes to a subset of adult neurons and adrenal chromaffin cells of transgenic mice. In this paper, we examine the spatial and temporal patterns of expression of these transgenes during embryogenesis. Expression begins at embryonic day 9 in the developing central and peripheral nervous systems and persists in cell populations in which expression is observed in adult transgenic mice. However, transient embryonic expression occurs in presumptive neuroblasts in developing sensory ganglia and ventrolateral neural tube that are destined to synthesize neurotransmitters other than catecholamines. These observations support the concept that some cells fated to become "non-catecholaminergic" neurons exhibit transient catecholaminergic features during their differentiation.

Animals↗

PubMed1988

Molecular cloning and sequencing of a cDNA for a carbohydrate binding receptor unique to rat Kupffer cells.

cDNA comprising the entire length of the rat Kupffer cell receptor (Mr = 88,000 and 77,000) for carbohydrates with an affinity for fucose and galactose was isolated, and its nucleotide sequence was determined. Receptor cDNA encoded a protein containing 550 amino acid residues with a Mr = 61,104. This Mr was consistent with the size of the deglycosylated receptor which was found to contain two polypeptides by gel electrophoresis with Mr = 58,000 and 52,000, respectively. Edman degradation of the receptor yielded a sequence which corresponded to amino acid residues 83-104 of the sequence derived from the cDNA. This confirmed that the cDNA which had been isolated corresponded to mRNA for the receptor and suggested that the smaller polypeptide in receptor preparations arises by proteolysis of the intact receptor. Amino acid composition of the receptor was nearly identical to that predicted by the cDNA. The Kupffer cell receptor was found to be homologous to other carbohydrate binding proteins including the hepatic receptors with different binding specificities. The Kupffer cell receptor also contained a series of 18 contiguous, homologous sequences with an average length of 14 residues.

Amino Acid Sequence↗

PubMedDate not supplied

Expression of TNF and the necessity of TNF receptors in bleomycin-induced lung injury in mice.

Bleomycin (BLM) induction of lung fibrosis in mice is an established model to study the mechanism of pulmonary fibrosis. Cytokine secretion has been implicated as a fundamental component of the lung fibrotic process observed in response to BLM. Among the cytokines implicated in lung fibrosis, Tumor necrosis factor (TNF) alpha has been considered to play a fundamental role. In the present study, we characterized the cellular sources of TNF during BLM-induced lung injury and examined the importance of TNF receptors in this process. To characterize the expression of TNF, we utilized two strains of mice, one sensitive (C57BL/6) and one resistant (BALB/c) to BLM-induced lung injury. Mice received BLM (120 mg/kg total) or saline, as control, by multiple subcutaneous injections. BLM induced the development of inflammation in subpleural areas only in the lungs of BLM-sensitive mice. These subpleural areas were characterized by infiltration of CD68-positive macrophages and increased collagen deposition. BLM enhanced the expression of TNF mRNA in BLM-sensitive, but not in BLM-resistant, mice. In situ hybridization studies localized the expression of TNF in the areas of BLM-induced inflammation in 6% and 27% of macrophages at 14 and 21 days post BLM treatment. In addition to TNF, BLM exposure resulted in the upregulated expression of transforming growth factor (TGF)-beta 1, but not interleukin (IL)-1, mRNA in the lungs of both murine strains at 14 and 21 days. This upregulated expression of TGF-beta 1 mRNA was greater in the lungs of BLM-sensitive mice. In separate experiments, double TNF receptor knockout mice were exposed to BLM. These animals demonstrated an increased expression of TNF, but not TGF-beta 1, mRNA in response to BLM and did not exhibit histologic evidence of lung injury following BLM exposure. In summary, the upregulation of TNF mRNA in macrophages correlated with the appearance of inflammation following BLM exposure and was limited to the BLM-sensitive strain. Furthermore, in addition to the release of the TNF ligand, it appears that the presence of TNF receptors is necessary for the development of BLM-induced lung injury, and signaling through these receptors may contribute to the regulation of the TGF-beta 1 mRNA expression observed in response to bleomycin. These results provide further support for a role of macrophages and TNF in the induction of lung inflammation.

Animals↗