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Biomedical subjects

A Hogan

Publications and source records attributed to A Hogan.

At least 19 recordsLinked to original sources
PubMed1992

Expression of growth factor ligand and receptor genes in the preimplantation bovine embryo.

The sensitive technique of mRNA phenotyping with the reverse transcription-polymerase chain reaction was employed to determine the patterns of gene expression for several growth factor ligand and receptor genes during bovine preimplantation development. Several thousand bovine embryos encompassing a developmental series from one-cell zygotes to hatched blastocysts were produced by the application of in vitro maturation, fertilization, and oviductal epithelial cell embryo coculture methods. Transcripts for transforming growth factor (TGF-alpha) and platelet-derived growth factor (PDGF-A) are detectable in all preimplantation bovine stages as observed in the mouse. Transcripts for TGF-beta 2 and insulin-like growth factor (IGF-II) and the receptors for PDGF-alpha, insulin, IGF-I, and IGF-II are also detectable throughout bovine preimplantation development, suggesting that these mRNAs are products of both the maternal and the embryonic genomes in the cow, whereas in the mouse they are present only following the activation of the embryonic genome at the two-cell stage. In contrast to the mouse embryo, IGF-I mRNA was detected within preimplantation bovine embryos. Basic fibroblast growth factor (bFGF) is a maternal message in the bovine embryo, since it is only detectable up until the eight-cell embryo stage. Bovine trophoblast protein (bTP) mRNA was detectable within day 8 bovine blastocysts. As was observed in the mouse, the transcripts for insulin, epidermal growth factor (EGF), or nerve growth factor (NGF) were not detectable in any bovine embryo stage. Analyses of this type should aid the development of a completely defined culture medium for the more efficient production of preimplantation bovine embryos.

Animals↗
PubMed1992

Role for the submandibular gland in modulating pulmonary inflammation following induction of systemic anaphylaxis.

Previous studies have shown that bilateral decentralization of the superior cervical ganglia (SCG; decentralization) attenuates allergen-induced pulmonary inflammatory responses in male rats sensitized to the nematode Nippostrongylus brasiliensis. The present report examines the neuronal and glandular mechanisms mediating the protection against pulmonary inflammation afforded by decentralization. Tissues and organs innervated by the SCG are responsible for this protection since, in a manner similar to decentralization, bilateral removal of the SCG (ganglionectomy) reduced anaphylaxis-induced accumulation of inflammatory cells in bronchoalveolar lavage fluid. Removal of the submandibular gland (sialadenectomy) did not modify the severity of the pulmonary inflammation, but concurrent sialadenectomy and decentralization abolished the protective effect of decentralization. Thus, we postulate that cervical sympathetic nerves tonically inhibit release of anti-inflammatory factors from submandibular glands. No relationship was found between noradrenaline and serotonin content of submandibular glands and the degree of protection against pulmonary inflammation offered by decentralization and ganglionectomy. Both decentralization and ganglionectomy appeared to increase the level of transcripts that encode immunomodulatory growth factors (nerve growth factor and epidermal growth factor) in submandibular glands, but these denervations evidently did not modify the transcripts for TGF beta 2. Systemic inflammatory events are regulated by the central nervous system at a level superior to the SCG probably through modulation of immunoregulatory factors in submandibular glands.

Anaphylaxis↗
PubMed1992

Insulin, insulin-like growth factors and glucose transporters: temporal patterns of gene expression in early murine and bovine embryos.

mRNA phenotyping by the reverse transcription-polymerase chain reaction (RT-PCR) method was used to compare the patterns of expression of insulin and insulin-like growth factor (IGF) ligand and receptor genes in preimplantation bovine embryos with those established previously for preimplantation murine embryos. In the early bovine embryo, transcripts for IGF-I, IGF-II and mRNAs encoding receptors for insulin, IGF-I and IGF-II were all detectable at all embryo stages from the 1-cell zygote to the blastocyst. In the mouse, IGF-II ligand and receptor mRNAs were not expressed until the 2-cell stage, and the insulin and IGF-I receptor mRNAs were not detectable until the 8-cell stage. Since transcriptional activation of the embryonic genome occurs at the 8- to 16-cell stage in the bovine embryo and at the 2-cell stage in the murine embryo, it is suggested that these transcripts are products of both the maternal and embryonic genomes in the bovine embryo whereas in the mouse they are present only after activation of the embryonic genome. Transcripts for insulin were not detected in preimplantation embryos of either species. Colloidal-gold immunocytochemistry with antibodies directed against the insulin receptor, IGF-I receptor and IGF-I ligand has confirmed the presence of these molecules in bovine blastocysts. RT-PCR and indirect immunofluorescence procedures demonstrated that the glucose transporter (GLUT) isoform 1 is present in murine embryos from the oocyte to blastocyst stage whereas GLUT 2 expression begins at the 8-cell stage.

Animals↗
PubMed1991

Glucose transporter gene expression in early mouse embryos.

The glucose transporter (GLUT) isoforms responsible for glucose uptake in early mouse embryos have been identified. GLUT 1, the isoform present in nearly every tissue examined including adult brain and erythrocytes, is expressed throughout preimplantation development. GLUT 2, which is normally present in adult liver, kidney, intestine and pancreatic beta cells is expressed from the 8-cell stage onward. GLUT 4, an insulin-recruitable isoform, which is expressed in adult fat and muscle, is not expressed at any stage of preimplantation development or in early postimplantation stage embryos. Genetic mapping studies of glucose transporters in the mouse show that Glut-1 is located on chromosome 4, Glut-2 on chromosome 3, Glut-3 on chromosome 6, and Glut-4 on chromosome 11.

Amino Acid Sequence↗
PubMed1990

Expression of genes for insulin and insulin-like growth factors and receptors in early postimplantation mouse embryos and embryonal carcinoma cells.

The expression of genes for insulin and insulin-like growth factors (IGFs) and their receptors was examined in early postimplantation mouse embryos and differentiating F9 embryonal carcinoma cells using mRNA phenotyping. Messenger RNA phenotyping involves the reverse transcription of RNA followed by amplification of specific target cDNA sequences using the polymerase chain reaction (PCR). The identities of the resulting PCR fragments were confirmed using at least two of the following methods: 1) size determination by agarose gel electrophoresis, 2) the presence of diagnostic restriction sites, 3) hybridization with radiolabeled cDNA probes, 4) sequencing of the PCR fragment. Transcripts for insulin receptors, IGF-I receptors, and IGF-II receptors were detected in RNA samples from day 7.5 to day 9.5 mouse embryos and in F9 cells, although the level of insulin receptor mRNA in F9 cells was very low. Transcripts for both IGF-I and IGF-II ligands were also detectable in the embryo and F9 RNA samples, but transcripts for insulin ligand were undetectable in either set of material. The results suggest that insulin does not act as a paracrine or autocrine growth factor in early postimplantation embryos or F9 cells but that both embryos and F9 cells have the potential to respond to exogenous (e.g., maternal) sources of insulin. Both IGF-I and IGF-II could act as paracrine or autocrine growth factors, and IGF-II is the more abundant growth factor in differentiating F9 cells.

Amino Acid Sequence↗
PubMed1989

The Drosophila hairy protein acts in both segmentation and bristle patterning and shows homology to N-myc.

The Drosophila segmentation gene, hairy (h), acts to regulate embryonic segmentation and bristle pattern. We present the DNA sequence of the h gene and of h cDNAs, thereby deducing the organization of the h transcripts. The h gene encodes a 337 amino acid protein that acts in both embryonic segmentation and adult bristle patterning. The h protein includes a domain that shows extensive similarity to a domain of the proto-oncogene N-myc that may be involved in DNA binding and/or protein dimerization. We discuss mechanisms of h action as a transcriptional regulator.

Amino Acid Sequence↗
PubMed1989

Evaluating managerial efficiency of Veterans Administration medical centers using Data Envelopment Analysis.

This study applied the methodology of Data Envelopment Analysis (DEA) to the set of VA medical centers to evaluate their relative managerial efficiencies. Each VAMC was viewed as a producer of multiple outputs and a consumer of multiple inputs. DEA uses linear programming to identify resources that were underutilized and services that were inefficiently produced. Managerial strategies based on the dual variables were constructed to indicate the manner in which inefficient VAMCs may be made efficient. The analysis showed that relative inefficiency existed in about one third of the VAMCs nationwide. Elimination of this inefficiency would save the VA over $300 million annually on personnel, equipment, drugs, and supplies, without reducing the level of services provided. A subsequent analysis of co-variance revealed that VAMCs affiliated with a university were generally less efficient than those without such an affiliation. A similar finding was obtained for larger VAMCs relative to smaller medical centers. In neither case, however, should these results be construed to imply that VAMCs should terminate their university affiliations or that VAMCs should be made smaller since factors other than relative efficiency are clearly as or more important in such decisions.

Cost Control↗
PubMed1989

An in situ transgenic enzyme marker for the midgestation mouse embryo and the visualization of inner cell mass clones during early organogenesis.

In order to study the deployment of cells during gastrulation and early organogenesis, it is necessary to have an in situ cell marker which can be used to follow cell fate. To create such a marker a transgenic mouse strain, designated Tg(Act-lac Z)-1, which carries 6 copies of the Escherichia coli lac Z gene under the control of the rat beta-actin promoter, was made by pronuclear injection of DNA. Staining early postimplantation hemizygous mouse conceptuses, during gastrulation and early organogenesis, for beta-galactosidase activity shows that lac Z expression is ubiquitous and constitutive in all epiblast derivatives of the 10th day conceptus. No activity is seen in trophectoderm and primitive endoderm derivatives. Postimplantation grafts of [3H]thymidine-labelled transgenic cells establish the cell autonomy of this transgenic marker. Preliminary observations on the distribution of inner cell mass (ICM) descendant clones, identified in situ in midgestation conceptuses, confirm the pluripotency of individual ICM cells. The implications regarding patterns of cell growth in nascent fetal primordia are discussed.

Animals↗
PubMed1986

Nonhomologous recombination in the parvovirus chromosome: role for a CTATTTCT motif.

The mechanism of nonhomologous recombination in murine cells infected with the parvovirus minute virus of mice (MVM) has been investigated by analysis of DNA sequences at recombination junctions in naturally occurring deletion variants of the virus. We report here that nonhomologous recombination in the MVM chromosome is characterized by short homologies, by insertion at recombination junctions of foreign DNA sequences that are enriched for preferred eucaryotic topoisomerase I cleavage sites, and by an association with a common DNA sequence motif of the type 5'-CTATTTCT-3'. Additional analyses of broken MVM chromosomes provided evidence for specific enzymatic cleavage within 5'-CTTATC-3' and 5'-CTATTC-3' sequences. The results indicate that the 5'-CTATTTCT-3' motif is an important genetic element for nonhomologous recombination in the parvovirus chromosome.

Animals↗
PubMed1984

Short direct repeats mediate spontaneous high-frequency deletions in DNA of minute virus of mice.

Previous work (E. A. Faust and D. C. Ward, J. Virol. 32:276-292, 1979) revealed a remarkably high rate of spontaneous deletion in viral DNA during lytic infection of cultured murine cells with minute virus of mice (MVM), an autonomous parvovirus. In the present study, we have isolated plasmid and phage recombinants containing MVM DNA inserts bearing deletions and we have determined the DNA sequence spanning three deletion junctions. The deletions, which average 3 kilobases in length, occur between pairs of perfectly homologous 4- to 10-base-pair direct repeats, such that one copy of the repeated sequence is lost, whereas the other remains behind at the deletion junction. When compared, the three sets of direct repeats exhibit no apparent sequence homology and have an A + T content of between 50 and 80%. These results indicate that 4- to 10-base-pair homologies mediate spontaneous deletion formation in the MVM genome and highlight parvoviruses as novel model systems for studies of this ubiquitous pathway of genetic variation.

Base Sequence↗
PubMed1984

Aggregation patterns of bile salts: crystal structure of calcium cholate chloride heptahydrate.

Crystals of calcium cholate chloride heptahydrate, CaC24H39O7Cl . 7H2O, are monoclinic, space group P2(1), with a = 11.918(2), b = 8.636(1), c = 15.302(3) A, beta = 97.93(3) degrees, V = 1559.9(8) A3, and Z = 2. A trial structure was obtained by Patterson and Fourier techniques and was refined by full-matrix least-squares calculations using absorption corrected CuK-alpha diffractometer data. The final R index is 0.047. The crystal structure contains bilayer-type arrangements, with hydrophobic portions of cholate rings sandwiched between layers of polar groups that are interacting with calcium ions and water molecules. The calcium ion is coordinated to five water molecules and to the two carboxylate oxygen atoms of the cholate residue. Two additional water molecules are involved only in crystal packing through the formation of hydrogen bonds. Cholate-cholate hydrophobic interactions involve contacts between the hydrocarbon portions of the carboxylate sidechains and the A and B rings. This results in a staggered packing pattern that is nearly identical to that found in crystals of sodium cholate and rubidium deoxycholate. Similar bilayer aggregation patterns may also be involved in the formation of bile salt micelles in aqueous media. The characteristic bilayer packing arrangement can accommodate a variety of cation-binding patterns, as evidenced by the finding that calcium, sodium, and rubidium ions interact with the polar faces of the bilayers in different ways. The carboxylate sidechain displays two different conformations in the crystal structure of calcium cholate chloride heptahydrate. Variation in sidechain conformation may be of importance in the adjustment required to accommodate different cation coordination schemes.

Bile Acids and Salts↗