PubMed Health⌕ Search

Biomedical subjects

Mark Cooper

Publications and source records attributed to Mark Cooper.

6 recordsLinked to original sources
PubMed2003

Advanced glycation end products activate Smad signaling via TGF-beta-dependent and independent mechanisms: implications for diabetic renal and vascular disease.

While it is thought that advanced glycation end products (AGEs) act by stimulating transforming growth factor (TGF)-beta to mediate diabetic injury, we report that AGEs can activate TGF-beta signaling, Smads, and mediate diabetic scarring directly and independently of TGF-beta. AGEs activate Smad2/3 in renal and vascular cells at 5 min, peaking over 15-30 min before TGF-beta synthesis at 24 h and occurs in TGF-beta receptor I and II mutant cells. This is mediated by RAGE and ERK/p38 mitogen-activated protein kinases (MAPKs). In addition, AGEs also activate Smads at 24 h via the classic TGF-beta-dependent pathway. A substantial inhibition of AGE-induced Smad activation and collagen synthesis by ERK/p38 MAPK inhibitors, but not by TGF-beta blockade, suggests that the MAPK-Smad signaling crosstalk pathway is a key mechanism in diabetic scarring. Prevention of AGE-induced Smad activation and collagen synthesis by overexpression of Smad7 indicates that Smad signaling may play a critical role in diabetic complications. This is further supported by the findings that activation of Smad2/3 in human diabetic nephropathy and vasculopathy is associated with local deposition of AGEs and up-regulation of RAGE. Thus, AGEs act by activating Smad signaling to mediate diabetic complications via both TGF-beta-dependent and -independent pathways, shedding new light on the pathogenesis of diabetic organ injury.

Cells, Cultured↗
PubMed2003

Ontogeny of calcitonin receptor mRNA and protein in the developing central nervous system of the rat.

In this study, the expression of receptors for calcitonin (CTR), the CTR C1a and C1b isoforms, was investigated during development of the fetal rat central nervous system (CNS) by using in situ hybridization and immunohistochemistry. Coincident expression with both techniques was evident. Immunohistochemical evidence for the expression of the C1a isoform alone was found. Expression was first observed at embryonic day 12/13 (E12/E13) within and adjacent to the ventricular zones known to include primary matrices of proliferation, in regions of the preoptic area, anterior and posterior hypothalamus, anterior and posterior pons, medulla, and spinal cord. At later times, with the decline in the density of immunoreactivity at these loci (E15), expression in primary matrices was found later at distinct loci within the ventricular zones of cerebellum (E17), and at E19, the tectum, lateral ventricle, and cortical subplate. By E19, the density of staining had increased and was widespread throughout the expanding CNS. In the rostral domains, moderate to high density was found in the external plexiform layer; the medial preoptic area and nucleus; the ventromedial, dorsomedial, and arcuate hypothalamic nuclei; and the lateral and posterior hypothalamic areas. In the midbrain, similar levels of expression were noted in the central nucleus of raphe; the deep mesencephalic, dorsal raphe, and laterodorsal tegmental nuclei; and the ventral periaqueductal gray. In the pons, positive loci included the locus coeruleus and the gigantocellular and pontine reticular nuclei. In the medulla, high expression was evident in the gigantocellular, intermediate, magnocellular, and medullary reticular, spinal trigeminal and cuneate nuclei; and the nucleus tractus solitarius. In the spinal cord, moderate to high density of staining was found in the ventral, dorsal, and lateral horns, and in the ventral, dorsal, and cuneate funiculi. On the other hand, transitory expression was found in the diagonal band, bed nucleus of the stria terminalis, amygdala, and the lateral mamillary and anterobasal nuclei of the hypothalamus. These studies indicate a role for CTR in the activation of some premigratory neuroblasts in the CNS as well as a possible role later in an undefined function associated with mature neurons of particular nuclei.

Animals↗
PubMed2003

On the determination of recombination rates in intermated recombinant inbred populations.

The recurrent intermating of F(2) individuals for some number of generations followed by several generations of inbreeding produces an intermated recombinant inbred (IRI) population. Such populations are currently being developed in the plant-breeding community because linkage associations present in an F(2) population are broken down and a population of fixed inbred lines is also created. The increased levels of recombination enable higher-resolution mapping in IRI populations relative to F(2) populations. Herein we derive relationships, under several limiting assumptions, for determining the expected recombination fraction in IRI populations from the crossover rate per meiosis. These relationships are applicable to situations where the inbreeding component of IRI population development is by either self-fertilization or full-sib mating. Additionally, we show that the derived equations can be solved for the crossover rate per meiosis if the recombination fraction is known for the IRI population. Thus, the observed recombination fraction in any IRI population can be expressed on an F(2) basis. The implications of this work on the expansion of genetic maps in IRI populations and limits for detecting linkage between markers are also considered.

Chromosome Mapping↗
PubMed2002

Effects of lerisetron, a new 5-HT3 receptor antagonist, on ipecacuanha-induced emesis in healthy volunteers.

The purpose of these studies was to evaluate the effect of lerisetron (1-phenyl-methyl-2-piperazinyl-1H-benzimidazole hydrochloride, CAS 143257-98-1, F-0930-RS2), a new 5-HT3 receptor antagonist, on ipecacuanha-induced nausea and vomiting. The ipecacuanha model of emesis has been used to test the anti-emetic activity of several different 5-HT3 antagonists and the anti-emetic doses that were effective in the ipecacuanha model have been found to correlate well with the clinically effective doses. Study 1 investigated oral doses of lerisetron from 4 mg to 40 mg. Study 2 evaluated the duration of effect of a single dose of 20 mg oral lerisetron. Study 3 evaluated intravenous doses of 18 mg and 12 mg lerisetron. In Study 1, the 40 mg dose of oral lerisetron inhibited emesis in all test subjects. The percentage of subjects who experienced an emetic episode increased as the dose of lerisetron decreased. At the lowest dose level tested five of six subjects had an emetic episode compared with four out of five in the placebo group. In Study 2, 20 mg oral lerisetron was effective up to 12 h after administration. When ipecacuanha was administered at 18 h post-dose three of seven subjects had an emetic episode and at 24 h post-dose the incidence of emesis was similar to the placebo treatment groups in the previous study. Study 3 demonstrated the effectiveness of intravenous doses of lerisetron. The 18 mg intravenous dose reduced the number of patients experiencing emetic episodes by 75% compared with placebo, doses below 12 mg i.v. were not evaluated because of the reduced efficacy of the compound at this dose level. In conclusion, lerisetron has been shown to be effective in the treatment of ipecacuanha-induced nausea and vomiting at intravenous doses of 18 mg and at oral doses of 20 mg for up to 12 hours.

Administration, Oral↗
PubMed2002

The GP problem: quantifying gene-to-phenotype relationships.

In this paper we refer to the gene-to-phenotype modeling challenge as the GP problem. Integrating information across levels of organization within a genotype-environment system is a major challenge in computational biology. However, resolving the GP problem is a fundamental requirement if we are to understand and predict phenotypes given knowledge of the genome and model dynamic properties of biological systems. Organisms are consequences of this integration, and it is a major property of biological systems that underlies the responses we observe. We discuss the E(NK) model as a framework for investigation of the GP problem and the prediction of system properties at different levels of organization. We apply this quantitative framework to an investigation of the processes involved in genetic improvement of plants for agriculture. In our analysis, N genes determine the genetic variation for a set of traits that are responsible for plant adaptation to E environment-types within a target population of environments. The N genes can interact in epistatic NK gene-networks through the way that they influence plant growth and development processes within a dynamic crop growth model. We use a sorghum crop growth model, available within the APSIM agricultural production systems simulation model, to integrate the gene-environment interactions that occur during growth and development and to predict genotype-to-phenotype relationships for a given E(NK) model. Directional selection is then applied to the population of genotypes, based on their predicted phenotypes, to simulate the dynamic aspects of genetic improvement by a plant-breeding program. The outcomes of the simulated breeding are evaluated across cycles of selection in terms of the changes in allele frequencies for the N genes and the genotypic and phenotypic values of the populations of genotypes.

Computer Simulation↗