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C A Murray

Publications and source records attributed to C A Murray.

36 records · Page 2Linked to original sources
PubMed1995

Generation and characterization of an antiserum reactive with a proteolytic processing site within rat procorticotrophin-releasing hormone.

In this paper we report the generation of an antibody specific for the cleavage site within procorticotrophin-releasing hormone (proCRH) at the N-terminus proCRH/CRH (1-41) junction. Using radioimmunoassay techniques were show that the antibody generated (781) cross-reacts specifically with the proCRH (137-150) Tyr fragment, corresponding to the cleavage site within the full length precursor molecule. The anti-cleavage site antibody does not crossreact with the endoproteolytic products originated from the CRH precursor molecule, i.e. CRH (1-41) or proCRH (125-151) or with any of the CRH-immunoreactive fragments tested i.e. CRH (36-41), CRH (1-20) and CRH (30-41). It also shows no cross-reactivity with CRH-related substances from other species, i.e. urotensin I (fish) and sauvagine (frog). The cleavage site antibody (781), recognizes the full length proCRH molecule in Western blotting and in liquid phase radioimmunoassay from transfected CHO-K1 cells expressing the full length pre-proCRH cDNA. Using immunofluorescence and immunoprecipitation techniques followed by SDS-PAGE and autoradiography, we confirm the presence of the intact CRH precursor molecule within the nucleus and the cytoplasm of stably transfected CHO-K1 cells expressing immunoreactive proCRH. The immunofluorescence studies using primary cultures of hypothalamic neurons, show that immunoreactive (IR) proCRH is localized within the perinuclear region and was also seen along the neuronal processes where it accumulates at their tips. Our results, therefore, show that this antibody will be an invaluable tool in the study of intracellular trafficking in relation to the endoproteolytic processing of the CRH precursor molecule.

Amino Acid Sequence↗
PubMed1995

Mitogenic effects and nuclear localisation of procorticotrophin-releasing hormone expressed within stably transfected fibroblast cells (CHO-K1).

To investigate the intracellular localisation and biological activity of procorticotrophin-releasing hormone (proCRH), we have established stably transfected CHO-K1 cells expressing the rat pre-proCRH cDNA. Using immunoblot analysis of cell lysates of transfected CHO-K1 cells, we detected a major CRH immunoreactive band with an apparent molecular weight of approximately 19 kDa. This 19 kDa band could account for full length proCRH molecule which has not undergone post-translational modifications. Metabolic labelling followed by immunoprecipitation, SDS-PAGE and autoradiography indicated that no endoproteolytic processing of proCRH takes place within the transfected CHO-K1 cells. Immunofluorescence staining localises the CRH precursor to both the cytoplasm and to the nucleus in transfected CHO-K1 cells. This result was confirmed using subcellular fractionation techniques on radiolabelled CHO-K1 cells expressing immunoreactive CRH. A major CRH-immunoreactive band of 19 kDa was detected both in the microsomal and secreted fractions, indicating the presence of proCRH within the secretory pathway of these cells. This was also evident in the nuclear fraction, therefore confirming the nuclear localisation of proCRH. Analysis of DNA concentration, cell number and DNA synthesis showed that stably transfected CHO-K1 cells expressing proCRH have a higher proliferation and DNA synthesis rate than wildtype CHO-K1 cells or CHO-K1 cells transfected with pEE14 alone. Our results therefore suggest a mitogenic role for the intact proCRH molecule within CHO-K1 cells. Furthermore, treatment of mouse corticotrophic tumour cells (AtT20/D16-16) with conditioned medium from transfected CHO-K1 cells expressing proCRH, stimulated both DNA synthesis and cell proliferation above basal levels. Our results constitute the first reported direct evidence of a mitogenic role for proCRH acting on a corticotrophic cell population.

Animals↗
PubMed1994

Neuropeptide gene transfer into neuronal and glial cell lines.

Procorticotrophin-releasing hormone (ProCRH) is the precursor to the hypothalamic neuropeptide CRH(1-41) which mediates the neuroendocrine response to stress. In neuroendocrine cells and neurones, peptide hormones and neuropeptides are targeted to the dense-core vesicles of the regulated secretory pathway. These vesicles are transported to the ends of the cellular processes where they are stored until they are released upon an external stimulus. In order to study the post-translational processing and intracellular trafficking of neuropeptides in neuronal cells we have established stably transfected Neuro2A cells and NG115-401L cells expressing proCRH. The expression vector used contains glutamine synthetase (GS) coding sequences which are used as a dominant selectable marker in cells already containing GS genes. The various clonal cell lines isolated express different levels of CRH as assessed using a specific radioimmunoassay (RIA) thus indicating that the level of expression of the exogenous gene must depend upon the site of chromosome integration. Using immunofluorescence labelling, we have demonstrated that in Neuro2A and NG115-401L cells proCRH is packaged in vesicles which accumulate at the tips of cellular processes.

Animals↗
PubMed1988

Traumatic rupture of ascending aorta and left main bronchus.

A 14-year-old male pedestrian was hit by a truck and admitted with respiratory distress and subcutaneous emphysema. Aortography revealed disruption of the ascending aorta. Bronchoscopy revealed rupture of the left main bronchus at the carina. Both lesions were repaired using a median sternotomy, cardiopulmonary bypass, and a transpericardial approach for the bronchial repair. To our knowledge, this is the first report of successful repair of a combined rupture of a major bronchus and the ascending aorta.

Adult↗
PubMed1988

Role of glutathione in the toxicity of the sesquiterpene lactones hymenoxon and helenalin.

Hymenoxon and helenalin are toxic sesquiterpene lactones present in the toxic range plants Hymenoxys odorata and Helenium microcephalum. Helenalin (25 mg/kg) or hymenoxon (30 mg/kg) administered to immature male ICR mice caused a rapid decrease in hepatic glutathione levels and were lethally toxic to greater than 60% of the animals within 6 d. L-2-Oxothiazolidine 4-carboxylate (OTC), a compound that elevates cellular glutathione levels, administered to mice 6 or 12 h before either helenalin or hymenoxon protected against hepatic glutathione depletion and the lethal toxicity of these toxins. OTC administered at the same time as the sesquiterpene lactones was not protective, suggesting that the critical events against which glutathione is protective occur within the first 6 h. In primary rat hepatocyte cultures, hymenoxon and helenalin (4-16 microM) caused a rapid lethal injury as determined by the release of lactate dehydrogenase. Cotreatment of cultures with N-acetylcysteine at high concentrations (4 mM) afforded significant protection against lethal injury by both toxins. In contrast, BCNU, which inhibits glutathione reductase, or diethylmaleate, which depletes hepatocellular glutathione, potentiated the hepatotoxicity of helenalin and hymenoxon in monolayer rat hepatocytes. These studies suggest that the in vivo and in vitro toxicity of hymenoxon and helenalin is strongly dependent on hepatic glutathione levels, which hymenoxon and helenalin rapidly deplete at very low concentrations.

Acetylcysteine↗
PubMed1986

Influences of glutathione status on different cytocidal responses of monolayer rat hepatocytes exposed to aflatoxin B1 or acetaminophen.

In short-term primary monolayer cultures of rat hepatocytes, aflatoxin B1 (AFB1) causes a characteristic prelethal cytomorphological response in which peripheral attached cytoplasm contracts segmentally to form finger-like blebs. This response precedes lethal injury as detected by release of lactate dehydrogenase (LDH) into culture medium. We compared the influences of various modifiers of cellular glutathione (GSH) status on cytocidal responses of Fischer 344 rats hepatocytes exposed to AFB1 or acetaminophen (AAP), a hepatotoxin which does not produce segmental cytoplasmic contraction. N-Acetylcysteine (4 mM) reduced the degree of LDH release by AAP (4 to 16 mM) but was not protective against cell killing by AFB1, although it slightly reduced the percentage of hepatocytes with segmental cytoplasmic contraction at 6 hr. BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) at 40 microM markedly inhibited glutathione reductase and also strongly potentiated cell killing by AAP but did not significantly influence segmental cytoplasmic contraction or LDH release in response to AFB1. Diethylmaleate (40 to 160 microM), a depletor of hepatocellular GSH, and buthionine-D,L-sulfoximine (4 mM), an inhibitor of GSH synthesis, each did not alter hepatocyte killing by AFB1 but were strong potentiators of toxicity of AAP. AAP inhibited glutathione reductase but AFB1 did not. Total GSH concentrations at 6 and 18 hr were reduced by AAP and to a lesser extent by AFB1 in comparison with control cultures. These findings demonstrate that, in contrast to AAP toxicity, the characteristic mode of hepatocyte killing by AFB1 in monolayer cultures is substantially independent of induced alterations in GSH. These results indicate that GSH-dependent detoxification mechanisms do not play a major role in removing necrogenic metabolites of AFB1 in Fischer 344 rat hepatocytes. They further suggest that prelethal responses of AFB1-injured hepatocytes are not affected by GSH-dependent cytoprotective mechanisms.

Acetaminophen↗
PubMed1983

Lipoma of the myocardium.

A case of myocardial lipoma is presented which was diagnosed by computed tomography (CT). The resultant distortion of the cardiac chambers was well delineated by CT.

Adult↗
PubMed1977

The treatment of esophageal perforation with delayed recognition and continuing sepsis.

Five patients, recently treated for esophageal ruptures, provided a spectrum of "late" perforations. Treatment was individualized for each patient and ranged from suture closure of the perforation to esophagectomy. Four of the 5 patients survived and now have no dietary restrictions. The goals of treatment should be: (1) elimination of sources of chemical and bacterial soilage; (2) drainage of infected areas; (3) augmentation of host defenses by antibiotics; and (4) provision of adequate nutrition. Several treatment adjuncts, alone or in combination, may be used to accomplish these goals. The selection of treatment methods should be influenced by the site of perforation, the extent of local inflammation, the status of the residual esophagus, the overall status of the patient, and the chronicity of the perforation. As the risk of uncontrolled sepsis increases, the surgeon should take more aggressive and definitive steps, up to and including esophagectomy in certain cases, to prevent further soilage.

Anti-Bacterial Agents↗
PubMedDate not supplied

Interleukin-1 beta inhibits glutamate release in hippocampus of young, but not aged, rats.

The proinflammatory cytokine, interleukin-1, is synthesized in neuronal and glial cells and is released in response to stress/injury. IL-1 exerts profound effects on the central nervous system, which include an inhibitory effect on synaptic activity in hippocampus, a brain area expressing a high density of IL-1 receptors. We report that IL-1 beta has an inhibitory effect on KCl-stimulated release of glutamate and KC1-stimulated [45Ca] influx in synaptosomes prepared from hippocampus of 4-month-old rats. These effects were inhibited by the endogenous receptor antagonist, IL-1ra, and by the phospholipase A2 (PLA2) inhibitor, quinacrine, suggesting that IL-1 receptor activation is coupled to PLA2. An inhibitory effect of IL-1 beta on protein kinase C activity was also observed. KC1-induced calcium-dependent release and calcium influx, and protein kinase C activity were significantly decreased in hippocampal synaptosomes prepared from 22-month-old compared to 4-month-old animals. In contrast to the inhibitory effect of IL-1 beta in synaptosomes prepared from young adult animals, no effect was observed on release, calcium influx, or protein kinase C activity in synaptosomes prepared from aged animals. We report that there is an age-related increase in expression of IL-1 beta in hippocampus and propose that this change may underlie the attenuated responses to IL-1 beta in hippocampus of aged animals.

Age Factors↗
PubMedDate not supplied

Age-related changes in oxidative mechanisms and LTP are reversed by dietary manipulation.

Aged rats exhibit an impaired ability to sustain long-term potentiation in dentate gyrus which correlates with a decrease in arachidonic acid concentration. Here we confirm the previous finding that dietary supplementation with arachidonic acid and its precursor, gamma-linolenic acid, reversed the impairment in LTP in aged rats and report that there is a significant correlation between membrane arachidonic acid concentration and response to tetanic stimulation. We observed that age was associated with decreases in the concentration of vitamins C and E and increased activity of superoxide dismutase, indicative of a compromise in antioxidative defenses; these changes were paralleled by increases in interleukin-1beta (IL-1beta) concentration and lipid peroxidation. Dietary manipulation restored polyunsaturated fatty acid concentrations to values observed in tissue prepared from young rats and reversed the age-related changes in vitamins E and C, IL-1beta concentration and superoxide dismutase activity. We propose that these changes reverse the increase in lipid peroxidation and thereby the age-related change in polyunsaturated fatty acids.

Aging↗
PubMedDate not supplied

Interleukin-1 induces lipid peroxidation and membrane changes in rat hippocampus: An age-related study.

BACKGROUND: The proinflammatory cytokine, interleukin-1, is traditionally associated with the immune response but recent evidence indicates that it plays a role in neuronal function. Its expression is increased in neurodegenerative conditions and preliminary evidence suggests that it is also increased with increasing age. Receptors for interleukin-1 are differentially distributed in the brain with a high density in the hippocampus, where interleukin-1beta exerts inhibitory effects on release and calcium channel function. OBJECTIVE: The aim of this study was to investigate the possibility that interleukin-1 might lead to age-related changes in membrane composition. METHODS: Lipid peroxidation was assessed in the presence or absence of interleukin-1beta in hippocampal tissue prepared from 4- and 22-month-old rats. These data were analysed in parallel with age-related changes in arachidonic acid and interleukin-1beta concentrations in the hippocampus. RESULTS: We report that interleukin-1beta increased lipid peroxidation in hippocampal tissue prepared from 4- but not 22-month-old rats, and that this effect was inhibited by alpha-tocopherol. The attenuated response to interleukin-1beta in tissue prepared from aged rats correlated with increased expression of endogenous interleukin-1beta. Thus, using an ELISA, we have demonstrated an age-related increase in the concentration of interleukin-1beta, which is accompanied by an age-related decrease in membrane arachidonic acid. CONCLUSION: We propose that increased interleukin-1beta expression impacts on membrane composition and therefore contributes to age-related impairments in neuronal function.

Aging↗
PubMedDate not supplied

Trends in viral meningitis hospitalisations and notifications in the North Eastern Health Board (1997 - 2001): a cause for concern?

This study aimed to compare trends in both hospital admissions and notifications of viral meningitis in the North Eastern Health Board (NEHB). Hospital admissions from 1997 to 2001, involving NEHB residents with an infectious disease diagnosis, were examined and viral meningitis cases were analyzed. During this period 265 NEHB residents were admitted to hospital with viral meningitis--an increase of 429% between 1997 and 2001 with the bulk of this increase during 2000 and 2001. A total of 1,234 bed days were taken up by this cohort and the mean length of stay was 4.5 days (95% CI 4.2 - 4.9). The number of viral meningitis notifications in the NEHB was 38 (ranging from 4 in 1997 to 11 in 2001). This number is much lower than expected given the corresponding number of hospital admissions for the same period. Thus, most cases were not notified which means that current surveillance systems under-estimate the disease burden of viral meningitis. Such under-reporting has implications for infectious disease policy in Ireland.

Adolescent↗