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B J Morris

Publications and source records attributed to B J Morris.

At least 91 records · Page 5Linked to original sources
PubMed1995

Some physiological outcomes of renin gene studies.

1. The cloning of the renin gene has permitted studies of its physiological regulation, extrarenal expression and role in disease. 2. Marked modulation of renin mRNA concentration is seen in adrenal, heart and hypothalamus in response to sodium depletion and inhibition of AII formation, as well as in models of renal and genetic hypertension in the rat. 3. One important outcome of studies of the promoter has been the discovery of a cyclic AMP-responsive sequence. 4. Sequence variations have been detected in or near the renin gene and have been used as markers in studies of its role in cardiovascular disease aetiology. 5. In conclusion, molecular biology has, in the past decade, made a significant contribution to the understanding of renin physiology and pathophysiology.

Animals↗
PubMed1995

Renin mRNA, quantified by polymerase chain reaction, in renal hypertensive rat tissues.

To determine responses in renin gene expression in different tissues of two-kidney, one clip hypertensive Sprague-Dawley rats and the effect of NaCl loading, we developed a novel, highly sensitive quantitative polymerase chain reaction technique and measured renin mRNA at 19 and 40 days after clipping. Basal renin mRNA concentrations were 1575 +/- 127 fg/micrograms total RNA in kidney, 52 +/- 7 in hypothalamus, 7.9 +/- 0.7 in adrenal, and 4.7 +/- 0.5 in atria. In two-kidney, one clip rats, renin mRNA in the clipped kidney was increased 5.4-fold (P = .00001) and 2.3-fold (P = .001) on each respective day after clipping and in the unclipped kidney was decreased by 27% (P = .01) and 38% (P = .04). In adrenal, 3.9-fold (P = .004) and 1.7-fold (P = .02) increases were seen on days 19 and 40, respectively, and a decrease of 57% (P = .02) was found in a hypothalamic block at day 19 but not at day 40. The decrease in hypothalamus was abolished by 1% oral NaCl, which reduced renin mRNA by 37% in the clipped kidney and by 30% in the adrenal but did not lead to any change in the unclipped kidney or hypothalamus at day 40. Hypothalamic renin mRNA was also decreased by enalapril compared with increases of sixfold to ninefold in other tissues. In conclusion, we have quantified a decrease in hypothalamic renin mRNA in two-kidney, one clip rats 19 days after clipping that can be abolished by NaCl loading, whereas in the adrenal, renin mRNA was increased. Similar relative tissue-specific changes were also seen in enalapril-treated rats.

Actins↗
PubMed1995

Human renin 5'-flanking DNA to nucleotide-2750.

Renin is one of the most important factors in blood pressure and electrolyte regulation in mammals and the renin locus has been implicated in hypertension. To assist studies of promoter control we therefore determined the 5'-flanking sequence of the human gene (REN) to residue -2750 relative to the transcription start site (+1). Sites of homology to consensus sequences for binding of trans-acting factors involved in transcriptional control of other genes were identified, and functionality for two of these (a CRE and Pit-1 site) have so far been demonstrated.

Base Sequence↗
PubMed1994

Proximal 2.6 kb of 5'-flanking DNA is insufficient for human renin promoter activity in renin-synthesizing chorio-decidual cells.

In order to determine the influence of proximal 5'-flanking DNA of the human renin gene (REN) in cells that express human renin, transient expression analyses were carried out in chorio-decidual cells. Constructs containing different lengths of REN promoter DNA, extending as far as 2595 bp upstream of the transcription start site, were unable to drive transcription of a chloramphenicol acetyl transferase reporter gene in chorio-decidual cells, nor in noncognate 293 or JEG-3 cells. The tk promoter was similarly inactive in constructs containing -2595 to -453 fragments of REN 5'-flanking DNA. In each cell type, the -2595 to -1300 DNA exerted a negative influence. Additional promoter- and cell type-dependent negative influences were noted for other regions of REN 5'-flanking DNA and the -453 to -145 DNA increased tk promoter activity 2.5-fold in chorio-decidual cells. By introducing the SV40 enhancer into constructs, a weak stimulation of the REN promoter was observed in chorio-decidual cells, but not in noncognate, JEG-3 cells, although the -2595 to -1300 DNA retained its negative influence in the cognate cell type. These results show that the proximal 2.6 kb of REN 5'-flanking DNA is unable to drive reporter gene activity in renin-synthesizing, chorio-decidual cells under basal conditions and suggest that trans-acting factors unique to at least this cell type, together with enhancer(s) located outside of the proximal 2.6 kb of REN promoter DNA tested, could be required for human renin promoter activity.

Chorion↗
PubMed1994

Selective regulation of dendritic MAP2 mRNA levels in hippocampal granule cells by nitric oxide.

Application of NMDA, or agents releasing nitric oxide (NO), onto the dendrites of hippocampal granule cells increased the levels of the mRNA encoding MAP2, a cytoskeletal component induced during periods of neurite outgrowth. Furthermore, local increases in the hybridisation signal in the molecular layer, representing dendritic MAP2 mRNA, occurred independently of changes in MAP2 mRNA levels in the cell body layer. The selective modulation of MAP2 mRNA in dendrites reveals a mechanism allowing a sustained stimulation of dendritic outgrowth to be confined to those regions of a neuron's dendritic arbour local to glutamate receptor stimulation.

Animals↗
PubMed1994

zif/268 does not mediate increases in proenkephalin mRNA levels after NMDA receptor stimulation.

THE immediate-early gene zif/268 is induced in the hippocampal dentate gyrus by stimuli leading to long-term potentiation (LTP), and is though then to alter the rate of transcription of other genes involved in hippocampal plasticity, such as the proenkephalin (Penk) gene. Injection of 50 microM NMDA in vivo on to the granule cells of the dentate gyrus results in a highly localized increase in Penk mRNA levels 24 h later, while vehicle has no effect. In contrast, there is a widespread induction of zif/268 mRNA throughout the dentate gyrus, after injection of either NMDA or vehicle. This suggests that zif/268 induction in the hippocampal dentate gyrus is not sufficient to increase Penk gene expression.

Animals↗
PubMed1994

Isolation and structure of cat superfast myosin light chain-2 cDNA and evidence for the identity of its human homologue.

A full-length cDNA clone coding for superfast myosin light chain-2 (MyLC2) was isolated from an expression cDNA library prepared from cat masseter muscle and was fully characterized. The deduced amino acid sequence shares 58% overall identity with limb fast MyLC2, whereas homologies of the latter among higher vertebrates show 90% identity, indicating that superfast MyLC2 has diverged considerably from limb fast MyLC2 during evolution. Superfast MyLC2 cDNA has 89% nucleotide homology and 93% amino acid homology with a published novel human MyLC2 (MYL5), suggesting that MYL5 is a human homologue of the cat superfast MyLC2. Hybridization of a superfast MyLC2 isoform-specific probe reveals that expression of superfast MyLC2 in cat is confined to jaw-closing muscles. In conclusion, the present paper describes for the first time the cloning of a superfast myosin light chain coding sequence.

Amino Acid Sequence↗
PubMed1994

Identification of cyclic AMP response element in the human renin gene.

In order to identify the mechanism by which cyclic AMP stimulates expression of the human renin gene (REN), the effect of forskolin was tested in transient expression analyses of REN 5'-flanking DNA-chloramphenicol acetyltransferase (CAT) reporter gene constructs in secondary cultures of human chorio-decidual cells, a major site of renin synthesis. Forskolin induced a mean 5-fold stimulation which was localized to DNA in the region -249 to -162 with respect to the transcription start site (+1). Such DNA also mediated a response to forskolin in heterologous (HSV thymidine kinase) promoter constructs. Strong cAMP-response element (CRE) homology at -222 to -218 resembled the target for members of the CRE binding protein (CREB) family. Gel shift assays demonstrated similarly migrating nucleoprotein complexes for oligonucleotides containing the putative REN CRE as for a canonical CRE, in chorio-decidual, JEG-3 and HeLa nuclear extracts. Mutation of residues critical for CREB attachment reduced binding. In conclusion, a CRE was identified at -222 to -218 that appears critical for cAMP-induced human renin gene transcription.

Animals↗
PubMed1994

Basic fibroblast growth factor induces c-fos expression in primary cultures of rat striatum.

Basic fibroblast growth factor (bFGF) is present in the rat striatum in vivo, where evidence suggests it may have a long-term trophic role in supporting the survival of striatal neurones. To examine the possibility that these effects of bFGF might be mediated by induction of neuronal gene expression, we have investigated the ability of bFGF to stimulate expression of the immediate-early gene c-fos in primary cultures of embryonic rat striatum. The basal levels of c-fos mRNA were low in both neurones and glia in culture. Application of 500 pM bFGF resulted, within 45 min, in a 11-fold increase in the c-fos hybridisation signal in the non-neuronal cells. No significant induction of c-fos mRNA was detected in the striatal neurones at this time. The induction in non-neuronal cells was blocked by the tyrosine kinase inhibitor genistein (100 microM), but not by its inactive structural analogue genistin (100 microM). These results represent a novel mechanism whereby bFGF can exert prolonged effects on striatal function, and indicate that the increases in striatal c-fos gene expression induced by bFGF occur primarily in non-neuronal cells.

Animals↗
PubMed1994

Neuronal expression of protease-nexin 1 mRNA in rat brain.

Protease-nexin 1 (PN1), also known as glia-derived nexin, is a protease inhibitor secreted by cultured fibroblasts and glioma cells, with postulated roles in regeneration and the regulation of neurite outgrowth. In this study we have localised the sites of PN1 gene expression in rat brain using in situ hybridisation. As expected, cultured cortical astrocytes contained relatively high levels of PN1 mRNA. However, the mRNA localisation in rat brain suggested that the primary sites of synthesis in the CNS are neuronal. Relatively high levels of PN1 mRNA were found in the olfactory nerve layer of the olfactory bulb, in layer V of the cerebral cortex, in magnocellular neurones of the basal forebrain, and in scattered neurones of the striatum. The results show that PN1 gene expression occurs in discrete populations of neurones in the brain, and suggest that these neurones may therefore play a role in the local regulation of neurite outgrowth.

Amyloid beta-Protein Precursor↗
PubMed1994

Phenotypic characterisation of rat striatal neurones in primary culture.

The aim of this study was to determine to what extent the neuronal phenotypes present in primary cultures of rat striatal neurones correspond to those present in vivo. A large percentage of cultured striatal neurones contained relatively high levels of proenkephalin mRNA. In addition, a high level of expression was found for the prosomatostatin mRNA. Protachykinin mRNA and proneuropeptide Y mRNA were also expressed, but at a comparatively low level. No prodynorphin mRNA could be detected. Considerable numbers of neurones were also found to express NADPH-diaphorase activity, while a smaller number of neurones were positive for acetylcholinesterase. The NADPH-diaphorase and the acetylcholinesterase could be detected both in cell bodies, and in neuronal processes contacting groups of neighbouring neurones. Since nitric oxide does not require synaptic specialisations to exert its intercellular actions, this provides strong evidence that NADPH-positive neurones communicate with other cells in primary culture. These observations demonstrate that when striatal neurones are grown in primary culture, a range of neurochemical phenotypes are present which correspond closely to those present in the mature striatum in vivo. Together with the evidence for cell-cell interactions, this suggests that primary striatal cultures will provide a suitable model to study the molecular mechanisms controlling striatal function.

Animals↗
PubMed1994

Induction of c-fos gene expression is not responsible for increased proenkephalin mRNA levels in the hippocampal dentate gyrus following NMDA stimulation.

The increased levels of proenkephalin mRNA in the dentate gyrus following hippocampal stimulation have been assumed to be a consequence of the transient induction of c-fos. Injection of 50 microM NMDA in vivo onto the dendrites of a small number of granule cells causes a pronounced but highly localised elevation in proenkephalin mRNA levels 24 h later, whereas vehicle has no effect. In contrast, there is a widespread induction of c-fos mRNA throughout the dentate gyrus, 45 min after injection of either vehicle or NMDA, suggesting that induction of c-fos expression is unrelated to the subsequent, anatomically discrete, increase in proenkephalin mRNA levels.

Animals↗
PubMed1994

Nitric oxide alters proenkephalin and prodynorphin gene expression in hippocampal granule cells.

Application of N-methyl-D-aspartate on to the dendrites of hippocampal granule cells dramatically decreased prodynorphin messenger RNA levels in the affected cells while increasing proenkephalin messenger RNA levels. Sin-1 molsidomine (an agent which releases nitric oxide) and 8-bromo-cyclic GMP were similarly effective, and the actions of sin-1 molsidomine were blocked by inhibition of cyclic GMP-dependent protein kinase. Since, in this region, dynorphins act to inhibit potentiation of synaptic transmission, while enkephalins have excitatory effects, this switch in opioid gene expression is likely to have a prolonged effect on the efficiency of the mossy fibre synapses. In addition, the results demonstrate a powerful role for nitric oxide in the long-term regulation of hippocampal excitability.

2-Amino-5-phosphonovalerate↗
PubMed1994

Function of human renin proximal promoter DNA.

An understanding of the mechanisms involved in the control of the human renin promoter have been hampered and confounded in work to date because of deficiencies in material available and experimental design. The promoter appears to be weak and a good cell model is lacking. Chorio-decidual cultures have been used since these have high renin synthesis, are readily available and grow well in culture. They suffer, however, from phenotypic variability and do not transfect well in transient expression analyses. Recent evidence suggests that 2.6 kb of proximal 5'-flanking DNA is unable to induce native promoter activity under basal conditions. Experiments in which an exogenous enhancer was introduced have raised the possibility that an endogenous enhancer residing outside of the 2.6 kb 5'-flanking region could be required. Cell-type specific factors also appear to be needed. The proximal flanking DNA does, however, appear to be capable of conferring activity on the promoter in chorio-decidual cells under stimulated conditions, suggesting that factors so activated may have considerable importance. Evidence suggests that forskolin-responsive signal transduction pathways may lead cyclic AMP responsive element (CRE) binding protein (CREB) to act on a CRE at -222 in the proximal REN promoter DNA. Activation of the mouse promoter by cAMP appears to involve a different element, however. Furthermore, overall control of renin synthesis is likely to involve post-transcriptional mechanisms as well. Thus, despite being the first cardiovascular gene to be cloned, much more work is required before the control of the human renin gene is fully understood.

Animals↗
PubMed1994

Significant relationships of plasma lipids and body mass index with polymorphisms at the linked low-density-lipoprotein receptor gene and insulin receptor gene loci (19p13.2) in essential hypertensive patients.

1. Recent molecular genetic studies have implicated the low-density-lipoprotein receptor gene locus (LDLR, at chromosome 19p13.2) in obesity in essential hypertensive patients and in the atherogenic lipoprotein phenotype. The present study examined genotypes for the obesity-associated ApaLI restriction fragment length polymorphism of LDLR, and genotypes for a hypertension-associated RsaI restriction fragment length polymorphism at the insulin receptor gene (INSR) locus, which is linked to LDLR, in relation to plasma lipids, body mass index and blood pressure in 27 obese and 57 non-obese Caucasians with severe essential hypertension, selected on the basis of having parents who were both hypertensive, and in 25 obese and 45 non-obese normotensive subjects selected on the basis of having parents who were both normotensive after the age of 50 years. 2. Plasma triacylglycerol and low-density-lipoprotein-cholesterol were elevated in hypertensive patients, but did not differ between the obese and non-obese hypertensive groups. Significant positive correlations were seen between body mass index and triacylglycerol and low-density-lipoprotein-cholesterol in the obese and non-obese hypertensive patients, respectively. In addition, obese hypertensive patients had significantly higher diastolic blood pressure than non-obese hypertensive patients. 3. The eight obese hypertensive patients who were homozygous for the obesity-associated 6.6 kb allele of the ApaLI restriction fragment length polymorphism of LDLR ('6.6. kb homozygotes') had a significantly higher body mass index [34 +/- 6.0 (SD) kg/m2] than the 18 heterozygotes (29 +/- 2.7 kg/m2) and the single subject who was homozygous for the 9.4 kb allele (29 kg/m2) (P = 0.012 by one-way analysis of variance). The body mass index of the eight hypertensive 6.6 kb homozygotes was also greater than the body mass index of 29 +/- 2.4 kg/m2 observed for the eight obese normotensive 6.6 kb homozygotes. In addition, the eight obese hypertensive 6.6 kb homozygotes had a higher plasma triacylglycerol [4.2 +/- 0.77 (SEM) mmol/l] than the 18 obese hypertensive heterozygotes (2.4 +/- 0.33 mmol/l; P = 0.045). Non-obese hypertensive patients showed no significant genotypic differences in relation to the LDLR restriction fragment length polymorphism. 4. In the normotensive group, however, the frequency of the 6.6 kb allele of the LDLR ApaLI restriction fragment length polymorphism in obese subjects (0.54) was not significantly greater than in non-obese subjects (0.48) [cf. the significantly (P = 0.004( different values of 0.63 and 0.39, respectively, in obese and non-obese hypertensive patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

NMDA and nitric oxide increase microtubule-associated protein 2 gene expression in hippocampal granule cells.

Microtubule-associated protein 2 (MAP2), a component of the neuronal cytoskeleton, has attracted attention as a possible cellular substrate linking hippocampal N-methyl-D-aspartate (NMDA) receptor stimulation to alterations in cellular morphology. We show here that microinjection of NMDA, 8-bromo-cyclic GMP, or sin-1 molsidomine (which spontaneously releases nitric oxide), onto the molecular layer of the hippocampal dentate gyrus, increased the levels of MAP2 mRNA in the affected granule cells. No changes were observed in the levels of mRNAs encoding several other cytoskeletal components. This shows that hippocampal NMDA receptor stimulation can potentially initiate a long-term alteration in dendritic structure by affecting MAP2 gene expression and provides the first evidence that nitric oxide release in vivo, acting through cyclic GMP-dependent protein kinase, can cause long-term changes in neuronal function by modulating gene expression.

Animals↗
PubMed1994

Modulation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) binding sites by nitric oxide.

Nitric oxide release is reported to be involved in physiological processes associated with altered sensitivity of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) class of glutamate receptor. A series of compounds liberating nitric oxide were therefore tested for their ability to modulate in vitro the characteristics of [3H]AMPA binding to sections of rat brain. Pretreatment of forebrain or cerebellar sections with sodium nitroprusside (1 mM), S-nitroso-N-acetylpenicillamine (SNAP, 200 microM), glyceryl trinitrate (1 microM), or isosorbide dinitrate (0.5 mM) all increased the binding of 3 nM [3H]AMPA by 15-30%. These actions were reproduced by 8-bromo-cyclic GMP (200 microM) in the cerebellum but not in the forebrain. In a similar manner, the effect of SNAP was attenuated by an inhibitor of cyclic GMP-dependent protein kinase in the cerebellum but not in the forebrain. The elevated [3H]AMPA binding observed after pretreatment with SNAP was caused by an increase in binding affinity, but the capacity of the sites was unchanged. Autoradiographic analysis showed that forebrain binding was enhanced in the cerebral cortex and hippocampus but not in the striatum. Nitric oxide therefore appears to be able to increase the affinity of AMPA binding sites via two distinct mechanisms in different brain areas. This action may contribute to synaptic plasticity associated with nitric oxide release.

Animals↗