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Biomedical subjects

B J Morris

Publications and source records attributed to B J Morris.

At least 73 records · Page 4Linked to original sources
PubMed1997

Stabilization of dendritic mRNAs by nitric oxide allows localized, activity-dependent enhancement of hippocampal protein synthesis.

A small number of mRNA species are not restricted to the neuronal cell body, but are also present in neuronal dendrites. The levels of two of these dendritic mRNAs, encoding the microtubule-associated protein MAP2 and the alpha subunit of calcium/calmodulin-dependent protein kinase II (CamKIIalpha), are increased rapidly by high-frequency synaptic activity or by release of nitric oxide. To test the hypothesis that post-transcriptional mechanisms might contribute to this modulation, primary cultures of rat hippocampal neurons were exposed to s-nitroso-N-acetyl penicillamine (SNAP, 200 microM) or vehicle, and mRNA stability was determined. The stability of both CamKIIalpha mRNA and MAP2 mRNA was increased by SNAP treatment, whereas the stabilities of tubulin T26 mRNA and proenkephalin mRNA were unaffected. When the intensity of staining for MAP2 immunoreactivity and CamKIIalpha immunoreactivity was monitored in cultured hippocampal neurons, nitric oxide-releasing agents induced increases in staining intensity that were dependent on protein synthesis but not on mRNA synthesis. These results show that nitric oxide can selectively stabilize CamKIIalpha mRNA and MAP2 mRNA, leading to increased synthesis of the corresponding proteins. This demonstrates a mechanism whereby the presence of a particular mRNA in the vicinity of a synapse permits the levels of the protein product to be regulated by synaptic activity in a manner that is both prolonged and also highly localized to the region of stimulation. Thus, the dependence of sustained synaptic plasticity on de novo protein synthesis need not entail a loss of anatomical specificity.

Animals↗
PubMed1996

Effect of angiotensin-converting enzyme genotype on renin-angiotensin components in hypertensives.

Plasma angiotensin-converting enzyme (ACE) tracks with the deletion allele of an insertion/deletion (I/D) polymorphism of the ACE gene. The aim of the present study was to determine plasma renin and angiotensinogen for each ACE genotype in 54 hypertensive and 96 normotensive subjects. Plasma renin was reduced by 52 +/- 15 S.E.% in DD and by 24 +/- 12% in ID hypertensives when compared to II hypertensives (P < 0.05 by one-way ANOVA), but in the normotensive subjects, renin values were similar for each genotype. Plasma angiotensinogen did not differ across ACE genotypes, but was elevated by 25 +/- 3 S.E.% in hypertensives and showed a significant correlation with blood pressure. In conclusion, although renin does not differ significantly between ACE genotypes of normotensives, a reciprocal relationship may exist between plasma renin and plasma ACE in hypertensives.

Adult↗
PubMed1996

Molecular weight determination of plasmid DNA using electrospray ionization mass spectrometry.

Ionization and molecular weight (MW) determination of megadalton size plasmid DNA has been achieved using electrospray ionization (ESI) with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry. DNA molecules were shown to remain intact through electrospray ionization by collection on a specially prepared surface, followed by agarose gel electrophoresis. Individual highly charged ions of plasmid DNA produced by ESI were trapped in an FTICR cell for up to several hours and reacted with acetic acid to induce charge state shifts. Measurements of mass-to-charge ratios for these multiple peaks arising from charge state shifting give MW measurements of individual ions with an average accuracy of 0.2%. The MW distribution was obtained by measurements for a number of individual ions from the same sample [plasmid DNA: pGEM-5S MW(cal) = 1.946 MDa], yielding a MW(obs) of 1.95 +/- 0.07 MDa for ions clustered in the vicinity of the expected MW.

Cyclotrons↗
PubMed1996

Changes in hippocampal gene expression associated with the induction of long-term potentiation.

The expression of four genes: zif/268, c-fos, tubulin and alpha Ca2+/calmodulin-dependent protein kinase II (alpha CAMKII) was studied following the induction of LTP in Schaffer collateral CA1 neurone synapses in rat hippocampal slices maintained in vitro. Levels of c-fos mRNA and tubulin (T26) mRNA in area CA1 were unchanged after induction of LTP, however, zif/268 and alpha CAMKII mRNA levels showed a significant increase compared to non-potentiated controls. It is possible, therefore, to measure changes in gene expression using in situ hybridisation following induction of LTP in vitro and these results strengthen the theory that zif/268 and alpha CAMKII are involved in some aspect of the induction or maintenance of hippocampal LTP.

Animals↗
PubMed1996

Association analyses of NsiI RFLP of human insulin receptor gene in hypertensives.

Plasma angiotensinogen is elevated in essential hypertensives and shows a strong correlation with blood pressure. Patients with hypertension often display insulin resistance and we have found previously an association of a RsaI RFLP in intron 9 of the insulin receptor gene (INSR) with hypertension. Since insulin resistance is accompanied by hyperinsulinaemia and insulin can stimulate angiotensinogen production, we hypothesized that hypertension-associated genotypes of INSR may be associated with elevation in plasma angiotensinogen. We used PCR to detect a NsiI RFLP in exon 8 of INSR and examined its relationship with plasma angiotensinogen, as well as hypertension, in 134 Caucasian hypertensives with two hypertensive parents and in 126 normotensives. Plasma angiotensinogen tracked weakly with the major allele of the NsiI RFLP in hypertensives (p = 0.08). Moreover, the frequency of this allele was higher in lean hypertensives than in lean normotensives (p < 0.05) and in normolipidaemic hypertensives than normolipidaemic normotensives (p < 0.02). The present study thus suggests that there could be a relationship of plasma angiotensinogen with INSR genotype, and of each with hypertension.

Alleles↗
PubMed1996

Hypothesis: glucagon receptor glycine to serine missense mutation contributes to one in 20 cases of essential hypertension.

1. A missense mutation leading to reduced ligand affinity in the glucagon receptor (GCG-R) has been found recently to be five-fold more common in essential hypertensives than normotensives. The present paper provides additional information on patients that harbour this variant and proposes a possible mechanism by which this may lead to hypertension. 2. The seven hypertensives with the mutation were all female, had a later age of onset of the disease and a slightly higher body mass index. 3. Glucagon is involved in the regulation of fluid and electrolyte excretion. Mutant GCG-R results in reduced ligand affinity and cAMP response which, in the kidney, would reduce the normal natriuretic effect of glucagon. This could lead to enhanced fluid reabsorption, expansion of extracellular fluid volume and hypertension via long-term autoregulation of blood pressure.

Adult↗
PubMed1996

Transcriptional and posttranscriptional mechanisms regulate human renin gene expression in Calu-6 cells.

We have recently identified a human pulmonary carcinoma cell line (Calu-6) that expresses human renin (hREN) mRNA endogenously, and we use it herein as a model to examine the regulation of the hREN gene. Transfection analysis of a deletion series (-2750 to -149) of hREN promoter-luciferase fusion constructs revealed the presence of multiple weak regulatory elements within the first 1,301 bp of the 5'-flanking region and a classic silencer element within the first intron (intron A) of the gene. The 5'-flanking regulatory domain consisted of three closely linked elements, two negative and one positive, each contributing a cell-specific threefold modulation of transcriptional activity. Treating Calu-6 cells with forskolin caused a 100-fold increase in steady-state endogenous hREN mRNA but no increase in hREN promoter activity in transient transfections or in nuclear runoff transcription assays. Nevertheless, de novo transcription and translation were necessary for adenosine 3',5'-cyclic monophosphate (cAMP)-mediated induction. Our results suggest that multiple regulatory elements regulate basal transcriptional activity of the hREN gene and the increase in hREN mRNA by cAMP may be mediated by posttranscriptional mechanisms.

Base Sequence↗
PubMed1996

Hypothesis: an angiotensin converting enzyme genotype, present in one in three caucasians, is associated with increased mortality rate.

1. This review argues that the deletion (D) allele of an insertion (I)/deletion polymorphism of the angiotensin I-converting enzyme (ACE) gene is a marker for a variant associated with increased ACE expression, as well as myocardial infarction (MI) and other life-threatening conditions. 2. By examination of I/D frequency in different age groups of individuals having well-known risk factors, it appears that homozygosity for the D allele may be associated with an increased risk of premature death in subjects at high-risk of cardiovascular events. For the risk factor hypertension, the odds ratio for DD vs II in patients aged > or = 60 years was 6.6. 3. Besides in MI itself, the DD genotype appears to be also more prevalent in MI patients who develop restenosis several months after balloon angioplasty, patients with various forms of heart failure, those with ventricular hypertrophy and diabetic patients who develop nephropathy. 4. Particular genotypes of other components of the renin-angiotensin system may add to the risk conferred by the ACE DD genotype. 5. Emerging evidence therefore suggests that the ACE genotype may eventually be placed on the list of common, well-known risk factors for fatal cardiovascular events.

Adult↗
PubMed1995

Stimulation of immediate early gene expression in striatal neurons by nitric oxide.

Exposure of primary cultures of embryonic rat striatal neurons to agents releasing nitric oxide (NO), including sin-1 molsidomine, S-nitroso-n-acetyl-penicillamine (SNAP), and S-nitrosoglutathione, resulted in an increase in the levels of expression of the immediate early genes c-fos and zif/268 in the cultured neurons. The membrane-permeable cGMP analogue, 8-bromo-cGMP, did not significantly affect c-fos and zif/268 mRNA levels, and the highly selective inhibitor of cGMP-dependent protein kinase, KT5823, was unable to inhibit the elevation in c-fos and zif/268 mRNA levels induced by SNAP. The induction of c-fos by the calcium ionophore A23187 was reduced by treatment with SNAP or 8-bromo-cGMP. Inhibitors of ADP-ribosyltransferases attenuated the stimulation of c-fos expression by SNAP. These results demonstrate for the first time that NO can induce immediate early gene expression in neurons, suggesting that NO may act as a mediator of neuronal plasticity via alterations in the expression of downstream genes. In addition, the results suggest that NO may exert these effects through a pathway that does not involve guanylate cyclase and cGMP-dependent protein kinase.

Animals↗
PubMed1995

Fourier transform infrared spectroscopy of dysplastic, papillomavirus-positive cervicovaginal lavage specimens.

To assess the utility of a new, rapid, economical procedure that may prove valuable in cervical screening, Fourier transform infrared (ir) spectroscopy was performed on 25 cervicovaginal lavage specimens from women referred for colposcopy on the basis of a cytological abnormality detected on their Pap smear and whose lavage specimen was positive for human papillomavirus. Of the 18 classed as CIN I or less by histopathology, 11 showed band frequencies that deviated only slightly from spectra that characterize normal cervical cells and 3 of 5 "atypia" specimens had spectra identical to normal. Two of 3 classed as CIN II had spectra only slightly more abnormal to these 11. In the case of 2 graded as CIN I, several bands were similarly altered in the direction of the pattern seen for 4 CIN III specimens. A further CIN I sample gave a spectrum that was even further shifted toward the latter and the remaining CIN I sample had a pattern that matched the 4 CIN IIIs. The most obvious change in each of the CIN IIIs was an additional peak at 972 cm-1 and this has been suggested as a key indicator for malignancy. One of the 3 CIN IIs had this peak. Other characteristic spectral changes were seen as well in the CIN III samples. High-risk HPV18 was present in 3 of the CIN III samples, as well as in one specimen classed as atypia, but having an abnormal ir spectrum. Low-risk HPV 6 or 11 was seen along in samples with a normal or slightly abnormal ir spectrum, but never in those that showed an ir pattern that was abnormal. The current study has therefore shown complete concordance between ir spectral findings and histopathology result in the case of CIN III specimens, but less precise matching for other grades of CIN. The spectral differences revealed by ir spectroscopy are likely to characterize molecular abnormalities in cervical cells during progression to cancer and may therefore have potential in assisting with clinical decision making. More studies will, however, be required to establish the place of this technique in cervical screening.

Colposcopy↗
PubMed1995

Stimulation of zif/268 gene expression by basic fibroblast growth factor in primary rat striatal cultures.

The presence of basic fibroblast growth factor (bFGF) in the basal ganglia, and its known neurotrophic activity, has created interest in its possible role as an agent to attenuate striatal neurodegeneration. However, little information is available on the mechanisms through which bFGF might exert a long-term influence on striatal function. Primary cultures of embryonic rat striatal neurones were used to ascertain whether bFGF can alter the pattern of striatal gene expression. Treatment of cultures with bFGF (500 pM) resulted in a dramatic increase in the levels of zif/268 mRNA within 45 min. This induction was attenuated by the tyrosine kinase inhibitor genistein (100 microM), but not by its inactive structural analogue genistin (100 microM). The induction of zif/268 mRNA was found to occur in non-neuronal cells, with no increase in mRNA levels being observed in neurones. A similar induction was noted for another putative transcription factor, jun B, although no induction of the related factor jun D could be detected. These results show that bFGF can induce immediate-early gene expression in striatal cultures, and therefore that this may provide a mechanism, mediated by non-neuronal cells, which allows bFGF to cause a long-term change in striatal neurochemistry.

Animals↗
PubMed1995

A role for hippocampal opioids in long-term functional plasticity.

In the granule cells of the hippocampus, glutamate coexists with opioid peptides derived from the proenkephalin and prodynorphin genes. The functional significance of this coexistence has been unclear but recent evidence suggests that the dynorphins and enkephalins play a crucial role in regulating the efficiency of neurotransmission at granule-cell synapses. Together with evidence that the level of opioid activity in this pathway can change dramatically according to the physiological or pathological state of the tissue, this information focuses attention on granule-cell opioids as primary mediators of hippocampal plasticity.

Animals↗
PubMed1995

N-methyl-D-aspartate and nitric oxide regulate the expression of calcium/calmodulin-dependent kinase II in the hippocampal dentate gyrus.

Injection of small volumes of N-methyl-D-aspartate (NMDA) or Sin-1 molsidomine (a nitric oxide releasing agent) onto the dendrites of granule cells in the hippocampal dentate gyrus leads to changes in the level of expression of a number of genes. There is a fall in prodynorphin mRNA levels with a corresponding increase in proenkephalin mRNA levels. Similar changes in opioid gene expression occur following the induction of long-term potentiation (LTP). We report here that at short time periods (1-6 h) after injections of NMDA or sin-1 molsidomine, there is an increase in the levels of the mRNA encoding the alpha subunit of Ca2+/calmodulin-dependent protein kinase II (CaMKII alpha), consistent with a report of elevated CaMKII alpha mRNA in postsynaptic neurons in the CA1 region of the hippocampus following LTP induction [54]. However, we also report that 24 h after injection of NMDA or sin-1, there is a dramatic decrease in CaMKII alpha mRNA levels in the vicinity of the injection. This effect is specific for CaMKII alpha mRNA, in that many other mRNA species are not affected, and occurs in the dendritic population of CaMKII alpha mRNA as well as in the pool of mRNA in the granule cell bodies. The effect is blocked by an inhibitor of cGMP-dependent protein kinase. The biphasic regulation of CaMKII alpha mRNA may be of considerable functional importance for the long-term response of granule cells to local stimulation of NMDA receptors or NO release.

Animals↗
PubMed1995

Induction of c-fos and zif/268 gene expression in rat striatal neurons, following stimulation of D1-like dopamine receptors, involves protein kinase A and protein kinase C.

Changes in the level of dopaminergic activity in the rat striatum lead to the induction of a number of immediate-early genes, including c-fos and zif/268. These immediate-early genes are thought in turn to alter the rate of transcription of downstream genes. There is evidence that the dopaminergic activation of the c-fos and zif/268 genes in the striatum in vivo is linked to stimulation of D1-like dopamine receptors. We have used primary cultures of embryonic rat striatal neurons to identify the intracellular pathways involved in this response. Dopamine (10 nM-5 microM) caused a marked increase in the levels of c-fos mRNA and zif/268 mRNA in cultured striatal neurons, an effect that was reproduced by the D1-like dopamine receptor agonist SKF38393 (10 nM-5 microM). These actions were attenuated by the D1-like antagonist SCH23390 (1 microM) but not by the D2-like antagonist eticlopride (1 microM). The D2-like agonist quinpirole did not increase zif/268 mRNA above basal levels at concentrations up to 5 microM, but caused a slight increase in the levels of c-fos mRNA. The stimulation of c-fos mRNA levels caused by 1 microM SKF38393 was reduced by 45% following pretreatment with the selective protein kinase A inhibitor KT5720, and by 87% following pretreatment with the selective protein kinase C inhibitor calphostin C. The stimulation of zif/268 mRNA levels caused by 1 microM SKF38393 was reduced by 90% following pretreatment with KT5720, but was not significantly affected by pretreatment with calphostin C. In addition, the actions of SKF38393 to stimulate the expression of both immediate-early genes were attenuated by coadministration of quinpirole. These results suggest that SKF38393 acts on striatal neurons to stimulate c-fos expression predominantly through protein kinase C, but also partially through protein kinase A. Conversely, SKF38393 induces zif/268 expression through protein kinase A. The ability of quinpirole to antagonize the actions of SKF38393 on cultured neurons is consistent with the presence of both D1-like receptors on the same neuronal population.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1995

Association of HincII RFLP of low density lipoprotein receptor gene with obesity in essential hypertensives.

Obese (BMI > or = 26 kg/m2; n = 51) and lean (BMI < 26 kg/m2; n = 61) Caucasian patients with severe, familial essential hypertension, were compared with respect to genotype and allele frequencies of a HincII RFLP of the low density lipoprotein receptor gene (LDLR). A similar analysis was performed in obese (n = 28) and lean (n = 68) normotensives. A significant association of the C allele of the T-->C variant responsible for this RFLP was seen with obesity (chi 2 = 4.6, P = 0.029) in the hypertensive, but not in the normotensive, group (odds ratio = 3.0 for the CC genotype and 2.7 for CT). Furthermore, BMI tracked with genotypes of this allele in the hypertensives (P = 0.046). No significant genotypic relationship was apparent for plasma lipids. Significant linkage disequilibrium was, moreover, noted between the HincII RFLP and an ApaLI RFLP (chi 2 = 33, P < 0.0005) that has previously shown even stronger association with obesity (odds ratio 19.6 for cases homozygous for the susceptibility allele and 15.2 for heterozygotes). The present study therefore adds to our previous evidence implicating LDLR as a locus for obesity in patients with essential hypertension.

Alleles↗