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Biomedical subjects

B J Morris

Publications and source records attributed to B J Morris.

At least 145 records · Page 8Linked to original sources
PubMed1990

Experimental hemiparkinsonism in the rat following chronic unilateral infusion of MPP+ into the nigrostriatal dopamine pathway--III. Reversal by embryonic nigral dopamine grafts.

In a previous study conducted over six months, we demonstrated that 1-methyl-4-phenylpyridinium ion (MPP+) the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, chronically infused (10 micrograms/24 h for seven days) into one median forebrain bundle of the rat can cause long-lasting damage to the nigrostriatal dopamine system. The present study was carried out in animals 18-19 months after MPP+ infusion to determine firstly, if the lesion was indeed permanent and secondly, if embryonic nigral dopamine suspension grafts implanted into the dopamine-denervated neostriatum can reverse the neurochemical and behavioural deficits induced by MPP+. All the animals within the MPP(+)-lesioned group showed robust contralateral and ipsilateral turning in response to apomorphine (0.05 mg/kg) and methamphetamine (2.5 mg/kg), respectively, at each time point of testing. In the grafted animals there was a progressive significant reduction in the number of rotations in response to both apomorphine and methamphetamine over the three-month test period. Autoradiographic analysis of [125I]sulpiride binding to striatal sections showed a 27% increase in dopamine D2 receptor density in the ipsilateral striatum of MPP(+)-lesioned animals. This increase in D2 receptor density was completely abolished by the dopamine grafts so that the D2 receptor density in the grafted striatum was similar to the contralateral striatum of MPP(+)-lesioned animals. This increase in D2 receptor density was completely abolished by the dopamine grafts so that the D2 receptor density in the grafted striatum was similar to the contralateral striatum of the grafted animals or the ipsilateral striatum of control non-lesioned animals. In all the animals of the lesioned and grafted groups there was a complete loss of dopamine neurons in the ipsilateral substantia nigra as demonstrated by tyrosine hydroxylase-immunohistochemistry and in-situ hybridization histochemistry. In all the animals that received nigral dopamine grafts, numerous cells were localized within the grafts which contained tyrosine hydroxylase immunoreactivity and tyrosine hydroxylase mRNA. Moreover, immunohistochemical staining showed a dense network of tyrosine hydroxylase-positive fibres within the grafted striatum. The results of the present study are important in two respects. Firstly, they demonstrate that MPP+ infusions into the rat nigrostriatal dopamine pathway can produce a permanent degeneration of nigral dopamine neurons. Thus, in animals assessed 18-19 months after the initial MPP(+)-lesion there was no significant behavioural or neurochemical compensation with time. Secondly, the results clearly show that embryonic nigral dopamine grafts implanted into the dopamine-denervated striatum can reverse the behavioural and neurochemical deficits induced by MPP+.

1-Methyl-4-phenylpyridinium↗
PubMed1990

Gene expression in striatal grafts--I. Cellular localization of neurotransmitter mRNAs.

This study utilized the technique of in situ hybridization histochemistry to identify cells expressing neurotransmitter mRNAs in embryonic striatal tissue grafts implanted into the ibotenic acid-lesioned rat neostriatum. Synthetic 32P- or 35S-labelled oligodeoxyribonucleotide probes specific for prosomatostatin, proneuropeptide Y. proenkephalin, prodynorphin and preprotachykinin mRNAs and a 32P-labelled cRNA probe specific for glutamate decarboxylase mRNA were used to study the regional and cellular changes in these mRNA levels in the normal, lesioned and grafted neostriatum. The levels of neuropeptide Y mRNA and somatostatin mRNA were substantially increased in the striatal grafts compared with the intact control striata. The levels of glutamate decarboxylase mRNA in the grafts also appeared to be slightly elevated over those in the control striata. However, the levels of proenkephalin mRNA, prodynorphin mRNA and preprotachykinin mRNA were significantly lower in the grafts. The increased levels of neuropeptide Y mRNA and somatostatin mRNA in the grafts were due both to an increase in the number of labelled cells and to an increase in the cellular levels of each neuropeptide mRNA. In contrast, the cellular levels of proenkephalin mRNA, prodynorphin mRNA and preprotachykinin mRNA in the grafts were comparable, or elevated relative, to those in the intact striata but the density of cells expressing each of these mRNAs was reduced. Since neuropeptide Y and somatostatin are known to be present in medium to large aspiny striatal neurons (interneurons) and enkephalin, dynorphin and tachykinin peptides and GABA are localized in medium spiny striatal projection neurons, the above findings would indicate that there is a divergence in the levels of activity between these two neuronal populations in the striatal grafts. Our data suggest that the levels of gene expression and hence the functional neurotransmitter-synthesizing and releasing activity in the grafted neuron are different from those in the normal mature striatum.

Animals↗
PubMed1990

Localization of human cardiac beta-myosin heavy chain gene (MYH7) to chromosome 14q12 by in situ hybridization.

The genes coding for each human cardiac myosin heavy chain (alpha-MHC and beta-MHC, MYH6 and MYH7, respectively) are tightly linked and the alpha-MHC gene has been assigned to chromosome 14. In order to provide a more precise regional localization, in situ hybridization experiments were carried out using a 3H-labeled probe derived from a beta-MHC genomic clone. The results demonstrated that the human cardiac MHC genes are located within the q12 band of chromosome 14.

Chromosome Banding↗
PubMed1989

Neuronal localisation of neuropeptide Y gene expression in rat brain.

The cellular location of Neuropeptide Y (NPY) synthesis in rat brain is identified by using in-situ hybridisation histochemistry. The results show that NPY mRNA is widely distributed through the rat brain, although the levels of NPY mRNA are surprisingly low. There is a large degree of variation in the content of NPY mRNA in different regions. The highest cellular levels of NPY mRNA are found in the arcuate nucleus of the hypothalamus, in the hypothalamus, in the cerebral cortex, and in the hilar region of the hippocampus. In general, the distribution of perikarya containing NPY mRNA corresponds to the reported distribution of perikarya containing NPY-immunoreactivity. However, NPY mRNA was detected in the majority of the perikarya in the reticular nucleus of the thalamus, an area not previously known to contain NPY neurones. In many areas of the forebrain the distribution of NPY mRNA parallels that of somatostatin mRNA, supporting suggestions of their coexistence. The ability to detect NPY mRNA at the cellular level should be of considerable use in dynamic studies of the activity of NPY neurones.

Animals↗
PubMed1989

Cellular localisation of somatostatin mRNA and neuropeptide Y mRNA in foetal striatal tissue grafts.

Using in situ nucleic acid hybridisation histochemistry, we have studied the expression of somatostatin mRNA and neuropeptide Y mRNA in grafts of embryonic striatal neurones implanted into the ibotenic acid-lesioned rat neostriatum. Tissue sections of the grafted striatum were incubated with either 32P- or 35S-labelled complementary oligodeoxyribonucleotide probes specific for somatostatin mRNA and neuropeptide Y mRNA, exposed with X-ray film and dipped in Ilford K-5 emulsion. Neither somatostatin mRNA nor neuropeptide Y mRNA was detectable in the ibotenic acid-lesioned striatum indicating a pronounced degeneration of somatostatin- and neuropeptide Y-containing neurones. However, in the striatal grafts the levels of somatostatin mRNA and neuropeptide Y mRNA were substantially increased over those in the control intact striata. The results suggest that in the grafts, somatostatin mRNA and neuropeptide Y mRNA were expressed in a higher proportion of primordial striatal neurones and there was also an increased level of expression of each neuropeptide gene per individual neurone (reflecting a higher synthetic activity of such neurones) compared to the intact mature striatum. These data demonstrate the sensitivity of the in situ hybridisation technique to study patterns of gene expression in developing neuronal tissues after transplantation.

Animals↗
PubMed1989

Polymerase chain reaction for fast, nonradioactive detection of high- and low-risk papillomavirus types in routine cervical specimens and in biopsies.

A polymerase chain reaction (PCR) procedure capable of amplifying specific DNA sequences by up to a millionfold was developed for detection of infection by human papillomaviruses (HPVs) of low (HPV6, HPV11) or high (HPV16, HPV18, HPV33) oncogenic potential. For high-risk HPVs the region chosen was within the E6 open reading frame, which can become integrated into genomic DNA. A region corresponding to this was chosen for low-risk HPVs. After repeated cycles of specific oligonucleotide-primed extension of viral DNA with Klenow or thermophilic DNA polymerase, the type of HPV present was then determined on the basis of the size of the ethidium-bromide-stained band visible after polyacrylamide gel electrophoresis: for HPV6 or 11 the band was approximately 120 bp, for HPV 16 or 33 it was approximately 200 bp, and for HPV18 it was approximately 100 bp. Specific hybridization to the relevant band was seen using radioactive or nonradioactive (alkaline-phosphatase-linked) target oligonucleotide probes. Using the PCR method, we have determined, within as little as a few hours, the infection status of a variety of clinical specimens, including cervical scrapes and lavages, anal scrapes, and anogenital biopsies. The PCR steps can be automated, adding to the potential of PCR for widespread use in the detection of HPV, which is becoming increasingly popular in cervical screening.

Biopsy↗
PubMed1989

Localization of striatal opioid gene expression, and its modulation by the mesostriatal dopamine pathway: an in situ hybridization study.

In situ hybridization was used to study the macroscopic distribution and regulatory control of proenkephalin mRNA and prodynorphin mRNA in rat striatum. While proenkephalin mRNA was widely distributed throughout the striatum, levels of prodynorphin mRNA were highest in the medial and ventral portions of the striatum. Furthermore, in contrast to the results for proenkephalin mRNA, the levels of prodynorphin mRNA appeared higher in the nucleus accumbens than in the striatum. The mesostriatal dopaminergic pathway was destroyed by discrete, unilateral injection of 6-hydroxy-dopamine (6-OHDA) into either the substantia nigra or the neighboring ventral tegmental area (VTA). Lesions of the substantia nigra caused a dramatic ipsilateral increase in the hybridization signal for proenkephalin mRNA, but no change was observed in the hybridization signal for prodynorphin mRNA. Similar effects were seen with VTA lesions. Since destruction of the mesostriatal dopamine system elevates the levels of proenkephalin mRNA, but not of prodynorphin mRNA, in the striatal target neurons, it appears that the mesostriatal pathway exerts a tonic and selective suppression of striatal proenkephalin gene expression at the mRNA level.

Animals↗
PubMed1989

Localization of GABAA receptor alpha-subunit mRNAs in relation to receptor subtypes.

The distribution of 3 GABAA receptor alpha-subunit mRNAs in various regions of bovine brain has been investigated using in situ hybridization. Whereas the alpha 2- and alpha 3-transcripts are of low abundance in all regions except striatum, the alpha 1-transcript is considerably enriched in the inferior colliculus, olfactory bulb and substantia nigra, and appears to be correlated with benzodiazepine type I receptor localization.

Animals↗
PubMed1989

Control of opiate receptor number in vivo: simultaneous kappa-receptor down-regulation and mu-receptor up-regulation following chronic agonist/antagonist treatment.

While it is well established that opiate receptors up-regulate following chronic antagonist treatment in vivo, possible down-regulation following chronic agonist treatment remains controversial. In this study, rats received a continuous seven-day infusion of bremazocine, an opioid drug suggested to be a potent agonist at kappa receptors and an antagonist at mu and delta receptors. Opiate receptor binding was assessed in both cryostat sections and homogenates of rat brain, under conditions selective for mu, delta and kappa sites. Data from both sections and homogenates showed an increase in the capacity of mu binding sites following chronic bremazocine treatment, suggesting that up-regulation of mu receptors had occurred, and that residual ligand from the in vivo treatment had largely been removed. A significant decrease in kappa binding was observed in sections, and experiments using homogenates demonstrated a dramatic loss of high-affinity kappa binding, with an increase in low-affinity binding. There was no apparent alteration in binding to delta receptors. No significant changes were observed following acute injection of bremazocine. Quantitative light-microscopic autoradiography confirmed the results of the binding experiments, and showed that the magnitude of these effects varied between different brain regions. No decrease in kappa binding was seen following chronic administration of the partial kappa agonist nalorphine, indicating that high agonist intrinsic activity is necessary for down-regulation to occur. In addition, chronic co-administration of bremazocine with the partial agonist/antagonist diprenorphine did not cause a significant decrease in kappa binding, implying that diprenorphine can antagonize the down-regulatory effect. These results provide evidence that bremazocine possesses different degrees of intrinsic activity at mu, delta and kappa receptors. They demonstrate that, at least in the case of kappa sites, opiate receptors do show down-regulation following chronic agonist treatment in vivo.

Animals↗
PubMed1989

Human renin protein and gene structures: present and future targets for renin blockade in treatment of hypertension.

The cloning of the gene for human renin has permitted remarkable advances to be made in understanding the structure of this aspartyl protease. From computer models and the determination of the actual co-ordinates of expressed recombinant human renin at 3 nm, a considerable amount of information has emerged concerning the molecular mechanism of renin activity, thus permitting the logical design and analysis of renin inhibitors suitable for use in antihypertensive medication. In addition, many of the properties of renin can now be explained in molecular terms, including the species specificity of its reaction with angiotensinogen. From the production of renin inhibitors, the next avenue of research is likely to be the design of drugs that will reduce the activity of the human renin gene and thereby curtail renin production. This may involve a 'new pharmacology' based on transacting factors. Thus cloning of the renin gene has led to elucidation of the tertiary structure of human renin for inhibitor design, and will similarly permit studies of gene-regulatory factors that may be future targets for blockade of the renin system in antihypertensive therapy.

Amino Acid Sequence↗
PubMed1989

hGK-1: a kallikrein gene expressed in human prostate.

1. Humans have three kallikrein genes: hGK-1, hRKALL (kinin-generating) and a gene encoding prostate specific antigen (PSA). 2. Using a gene-specific oligonucleotide, expression of hGK-1 was demonstrated in human prostate, but not in 10 other tissues examined. 3. The similarity in tissue specificity of expression of hGK-1 with that of the PSA gene led to an examination of putative regulatory DNA. Marked identity of greater than 90% was seen (compared with 80% for hRKALL), thus supporting a role for the operation of similar tissue-specific mechanisms for the control of hGK-1 and the PSA gene. 4. Unique structural features were observed in the protein encoded by hGK-1 suggestive of a capacity for interaction with substrate residues larger than those in kininogen. In particular it is predicted that a glycine at 186 would twist the polypeptide backbone in this crucial, highly conserved active site region and so profoundly influence interaction with substrate.

Antigens, Neoplasm↗
PubMed1989

The B subunit of coagulation factor XIII is linked to renin and the Duffy blood group to alpha-spectrin on human chromosome 1.

Family linkage studies were used to detect two linkage relationships on human chromosome 1. The B subunit of coagulation factor XIII showed significant linkage to renin with a maximum lod score of 5.071 at a distance of 10 cM. Significant linkage was also shown between the Duffy blood group and alpha-spectrin with linkage results giving a combined lod score of 3.194 at 5 cM.

Blood Group Antigens↗
PubMed1988

Opioid gene expression in rat striatum is modulated via opioid receptors: evidence from localized receptor inactivation.

The irreversible opiate antagonists beta-funaltrexamine (beta-FNA) and beta-chlornaltrexamine (beta-CNA) were injected into rat striatum. One day later, mu-opioid receptor binding, as assessed by receptor autoradiography, was abolished in the injected striatum, while [3H]spiperone binding remained largely unaffected. In situ hybridization was used to examine possible effects on striatal proenkephalin mRNA and prodynorphin mRNA content. The levels of proenkephalin mRNA were increased ipsilaterally following beta-CNA injection, but were slightly decreased following beta-FNA injection. Prodynorphin mRNA content was also increased by beta-CNA administration. The results provide evidence for a differential modulation of striatal opioid peptide gene expression via distinct opioid receptors.

Animals↗
PubMed1988

Long-term blockade of mu-opioid receptors suggests a role in control of ingestive behaviour, body weight and core temperature in the rat.

Chronic subcutaneous infusion with a low dose (0.5 mg/kg/h) of naloxone via minipumps blocked the antinociceptive action of the mu-agonist, morphine, without affecting that of the kappa-agonist, U50488H. This dose resulted in a transient suppression in the rate of body weight gain and a sustained reduction in daily food intake (FI) and water intake (WI): this decrease was seen in both the light and dark phases. Naloxone also resulted in a reduction in resting core temperature (TC) in the light but not the dark phase. It did not affect the weight loss or hypothermia which accompanied 24 h food and water deprivation. Naloxone did, however, suppress FI and WI following deprivation and inhibited the recovery of body weight thereafter. The influence of naloxone upon FI, WI, TC and body weight was dose-dependent over 0.05-0.50 mg/kg/h. Increasing the dose to 3.0 mg/kg/h eliminated the antinociceptive action of U50,488H revealing a blockade of kappa- (in addition to mu-) receptors. This higher dose was not more effective in reducing FI, WI, body weight and TC than 0.5 mg/kg/h. Further, treatment with MR 2266, an antagonist (or weak partial agonist) with a higher activity at kappa-receptors than naloxone, was not more effective than naloxone in reducing FI, WI and body weight: further, it did not affect TC. Moreover, chronic infusion of bremazocine, (a kappa-agonist and mu-antagonist) reduced WI, FI, body weight and TC by a magnitude comparable to that of naloxone. Finally, chronic infusion of the mu-agonist, sufentanyl, led to a sustained rise in TC. It is concluded, that: (1) mu-opioid receptors may play a major role in the modulation of daily FI and WI and of body weight in freely behaving rats: this action is expressed in both the light and dark phases of the cycle and maintained following deprivation. The data provide no evidence for (but do not exclude) a particular role of kappa-receptors. (2) mu-Receptors play a physiological role in the modulation of TC in the light but not the dark phase of the daily cycle.

Animals↗
PubMed1988

Frequency in hypertensives of alleles for a RFLP associated with the renin gene.

The genetic basis of primary hypertension is not known. Renin is important in blood pressure and volume control and a HindIII restriction fragment length polymorphism (RFLP) is present within the human renin gene locus. To examine whether there is a relationship between this RFLP and primary hypertension, DNA and renin analyses were performed on leukocytes and plasma from hypertensive and normotensive individuals. In hypertensives the frequencies of alleles for the HindIII RFLP were found to be 0.55 and 0.45, compared with 0.60 and 0.40 in the total population of 231 subjects examined, a difference that was not statistically significant. There also appeared to be no significant difference in renin activity in plasma for hypertensive patients of each genotype, nor in their pre- or post-treatment blood pressures. We thus conclude that, within the limits of the present study, the suspected genetic abnormalities associated with primary hypertension in man do not appear to be related to a HindIII RFLP in the renin gene.

Adult↗
PubMed1988

Regulation of striatal prodynorphin mRNA levels by the raphe-striatal pathway.

Peptides derived from proenkephalin and prodynorphin are known to be located in striatal projection neurones. Anatomical studies have shown the presence of a major serotonergic projection from the dorsal raphe nucleus to the striatum, although the function of this pathway is unknown. We have used in situ nucleic acid hybridization to investigate a possible role of this serotonergic innervation in the regulation of striatal opioid gene expression. The levels of proenkephalin mRNA and prodynorphin mRNA were determined in rat striatum and nucleus accumbens. Destruction of the dorsal raphe nucleus by microinjection of 5,7-dihydroxytryptamine failed to affect the levels of proenkephalin mRNA in any region. However, the levels of prodynorphin mRNA were significantly reduced in the medial nucleus accumbens and caudomedial striatum. This implies that activity in the raphe-striatal serotonin pathway mediates a tonic and selective enhancement of prodynorphin gene expression in the striatal target cells. This is in contrast to the tonic suppression of proenkephalin gene expression mediated by the mesostriatal dopamine pathway.

5,7-Dihydroxytryptamine↗