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Biomedical subjects

A M Ryan

Publications and source records attributed to A M Ryan.

At least 37 records · Page 2Linked to original sources
PubMed1996

Renal and neuronal abnormalities in mice lacking GDNF.

Glial cell-line derived neurotrophic factor (GDNF) is a potent survival factor for embryonic midbrain dopaminergic, spinal motor, cranial sensory, sympathetic, and hindbrain noradrenergic neurons, and is available to these cells in vivo. It is therefore considered a physiological trophic factor and a potential therapeutic agent for Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. Here we show that at postnatal day 0 (P0), GDNF-deficient mice have deficits in dorsal root ganglion, sympathetic and nodose neurons, but not in hindbrain noradrenergic or midbrain dopaminergic neurons. These mice completely lack the enteric nervous system (ENS), ureters and kidneys. Thus GDNF is important for the development and/or survival of enteric, sympathetic and sensory neurons and the renal system, but is not essential for catecholaminergic neurons in the central nervous system (CNS).

Animals↗
PubMed1996

A karyotypic analysis of the lesser Malay chevrotain, Tragulus javanicus (Artiodactyla: Tragulidae).

Chevrotains are small forest-dwelling ruminants of the family Tragulidae. The chromosome number of the lesser Malay chevrotain was determined to be 2n = 32, NF = 64, G- and Q-banding allowed the identification of homologous chromosomes, and C-banding demonstrated the presence of pericentromeric, telomeric and interstitial constitutive heterochromatin. Q-band comparisons with domestic cattle revealed relatively few monobrachial chromosome band homologies. However, the smallest biarmed autosome of the chevrotain, chromosome 15, was determined to be cytogenetically homologus with the acrocentric chromosome 19 of cattle. A molecular cytogenetic analysis confirmed this putative chromosomal homology. In fact, molecular cytogenetic analyses indicate complete conservation of synteny among mouse deer chromosome 15, domestic cattle chromosome 19, domestic pig chromosome 12 and human chromosome 17. In the light of these molecular cytogenetic data and since mouse deer chromosome 15 is submetacentric and appears homologous in banding to submetacentric chromosome 12 of the domestic pig, these outgroup comparisons indicate that the acrocentric condition of cattle chromosome 19 has been derived by inversion. Since this derivative condition is present in the Antilocapridae, Bovidae, Cervidae and Giraffidae, it is a chromosomal synapomorphy that unites these advance ruminant families within the Artiodactyla.

Animals↗
PubMed1995

Golfer's nails.

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Adult↗
PubMed1995

Induction of liver growth in normal mice by infusion of hepatocyte growth factor/scatter factor.

Hepatocyte growth factor/scatter factor (HGF/SF) is a potent stimulator of DNA synthesis in a variety of epithelial cells, including hepatocytes, and has been implicated in liver regeneration. We show here that combining dextran sulfate with HGF/SF markedly increases the plasma concentrations of HGF/SF that are achieved during intraperitoneal infusion. Three days of administration of HGF/SF by this mechanism caused a dose-dependent increase in liver wet weight. Mitotic figures were rarely observed in control livers but were abundant in livers exposed to HGF/SF, and liver DNA content was elevated. Serum levels of triglycerides, cholesterol, total protein, and albumin were also dose dependently increased, whereas alkaline phosphatase was reduced. From these data we conclude 1) that combining HGF/SF with dextran sulfate provides a novel method for delivering HGF/SF in a continuous manner, 2) that HGF/SF can induce liver growth in an intact animal, and 3) that HGF/SF-induced liver enlargement is associated with changes in serum biochemistry.

Animals↗
PubMed1994

Neutrophil and B cell expansion in mice that lack the murine IL-8 receptor homolog.

Interleukin-8 (IL-8) is a proinflammatory cytokine that specifically attracts and activates human neutrophils. A murine gene with a high degree of homology to the two known human IL-8 receptors was cloned and then deleted from the mouse genome by homologous recombination in embryonic stem (ES) cells. These mice, although outwardly healthy, had lymphadenopathy, resulting from an increase in B cells, and splenomegaly, resulting from an increase in metamyelocytes, band, and mature neutrophils. Thus, this receptor may participate in the expansion and development of neutrophils and B cells. This receptor was the major mediator of neutrophil migration to sites of inflammation and may provide a potential therapeutic target in inflammatory disease.

Animals↗
PubMed1994

Localization of uridine monophosphate synthase (UMPS) gene to river buffalo chromosomes by FISH.

Uridine monophosphate synthase plays an important role in pyrimidine synthesis, converting orotic acid to uridine 5' monophosphate. In cattle, UMPS deficiency is inherited as a monogenic autosomal recessive trait. While heterozygous carriers are phenotypically normal, homozygotes are lethal in utero (Shanks et al. 1992). UMPS has been mapped to human chromosome 3q13 (Qumsiyeh et al. 1989), sheep chromosome 1q (Burkin et al. 1993) and cattle chromosome 1q31 (Ryan et al. 1994). In the present study we used a cattle genomic probe to localize UMPS to river buffalo chromosomes by fluorescence in situ hybridization.

Animals↗
PubMed1994

A genetic linkage map of the bovine genome.

A cattle genetic linkage map was constructed which marks about 90% of the expected length of the cattle genome. Over 200 DNA polymorphisms were genotyped in cattle families which comprise 295 individuals in full sibling pedigrees. One hundred and seventy-one loci were found linked to one other locus. Twenty nine of the 30 chromosome pairs are represented by at least one of the 36 linkage groups. Less than a 50 cM difference was found in the male and female genetic maps. The conserved loci on this map show as many differences in gene order compared to humans as is found between humans and mice. The conservation is consistent with the patterns of karyotypic evolution found in the rodents, primates and artiodactyls. This map will be important for localizing quantitative trait loci and provides a basis for further mapping.

Animals↗
PubMed1994

Polymorphism analysis of the prion gene in BSE-affected and unaffected cattle.

Polymerase chain reaction (PCR) primers designed to amplify the octapeptide repeat region of the bovine prion gene were used to test the association of genotypes with bovine spongiform encephalitis (BSE) in 56 BSE-affected and 177 unaffected animals. Three alleles (A,B,C) were detected as single-strand conformation polymorphisms (SSCPs) and two alleles (1,2--representing six or five copies of the octapeptide repeat respectively) were detected as amplified double-strand fragment length polymorphisms (AMFLPs). Observed genotypes of SSCPs and AMFLPs were analysed by chi-square. The SSCP genotypes of nuclear family members of animals with BSE and BSE-affected animals were different (P < 0.001, P < 0.01) from unrelated animals of the same breed without BSE. No genotypic differences were found between the BSE-affected animals and their relatives (P > 0.469). No AMFLP genotypic differences were detected between BSE-affected animals, their relatives, unrelated animals of the same breed or animals of different breeds (P > 0.05). These data suggest that BSE-affected animals and their relatives are more likely to have the AA SSCP genotype than unrelated animals of the same breed or animals of different breeds.

Alleles↗
PubMed1994

Psychophysiological measures of workload during continuous manual performance.

Twelve subjects (six female) participated in an experiment designed to separate the effects of perceptual/central and physical demands on psychophysiological measures of peripheral nervous system activity. The difficulty of a single-axis continuous manual tracking task was varied in two ways: order of control was manipulated to vary perceptual/central processing demand, and disturbance amplitude was manipulated to vary physical demand. Physiological measures were sensitive to the imposition of a task and were more sensitive to physical than to perceptual/central demands. A principal components analysis identified five factors (three of them physiological) that accounted for 83.1% of the observed variance. Perceptual/central processing demands specifically affected the component identified with sympathetic cardiovascular control, whereas physical demands were reflected in the component identified with parasympathetic cardiovascular control. This finding suggests that dissociations observed among cardiovascular measures in manual performance tasks are attributable to differential activation of the autonomic control systems.

Adolescent↗