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P M Hudson

Publications and source records attributed to P M Hudson.

At least 19 recordsLinked to original sources
PubMed1996

Neurones in the midbrain periaqueductal grey send collateral projections to nucleus raphe magnus and the rostral ventrolateral medulla in the rat.

Projections to the rostral ventrolateral medulla (RVLM) and nucleus raphe magnus (NRM) appear to originate from neurones with overlapping distributions in the periaqueductal grey (PAG) as demonstrated by the retrograde transport of red and green fluorescent latex microspheres. Furthermore, double-labelling studies demonstrated collateral projections from individual neurones in the PAG to the RVLM and NRM. This anatomical arrangement may allow interactions between descending control systems during specific behaviours.

Animals↗
PubMed1996

The effects of the HIV-1 envelope protein gp120 on the production of nitric oxide and proinflammatory cytokines in mixed glial cell cultures.

Although the neurotoxicity induced by the HIV envelope protein, gp120, has been demonstrated to require the presence of glial cells (microglia/astrocytes), the mechanisms for the gp120-induced neurotoxicity are not well understood. Moreover, the neurotoxic potencies of gp120s obtained from various HIV isolates are different. Since nitric oxide (NO) and proinflammatory cytokines (TNF-alpha, IL-1, IL-6) produced by glial cells have been involved in the neuropathogenesis of various diseases, this study examined the effects of gp120 obtained from two strains, HIV-1IIIB and HIV-1SF2, of the HIV-1 virus on the production of NO, TNF-alpha, IL-1 alpha, IL-1 beta, and IL-6 in murine primary mixed glial cell cultures. The glial cells exposed to HIV-1IIIB gp120 released NO, TNF-alpha, and IL-6 in a dose-dependent manner, whereas IL-1 alpha and IL-1 beta were undetectable. The cells exposed to HIV-1SF2 gp120 increased the release of IL-6 only. The gp120-induced effects were significantly enhanced by priming glial cells with IFN-gamma. To investigate the cellular sources and mechanisms of the gp120-induced IL-6 production, in situ hybridization with mRNA for IL-6 was performed in HIV-1IIIB gp120- or HIV-1SF2 gp120-stimulated microgliaenriched or astrocyte-enriched cultures. HIV-1IIIB gp120 or HIV-1SF2 gp120 induced the expression of IL-6 mRNA in both microglia-enriched and astrocyte-enriched cultures, indicating that both microglia and astrocytes produce IL-6, and that the transcriptional regulation is involved in the gp120-induced IL-6 production. Taken together, these results demonstrate that the production of NO, TNF-alpha, IL-1, or IL-6 from glial cells is differentially regulated by HIV-1IIIB gp120 and HIV-1SF2 gp120. These results may provide insights into the roles of NO and proinflammatory cytokines in the neurotoxicity of gp120s and the neuropathology of different strains of HIV-1 viruses.

Animals↗
PubMed1996

Dexamethasone and forskolin synergistically increase [Met5]enkephalin accumulation in mixed brain cell cultures.

Possible synergistic effects of the glucocorticoid dexamethasone (DEX, 10(-7) M) and the adenylate cyclase agonist forskolin (FSK, 10(-5) M) on [Met5]enkephalin (ME) accumulation were examined in enriched rat glial cultures and in mixed neuronal/glial cultures. In enriched glial cultures, DEX and FSK each stimulated the accumulation of ME 2-3-fold over basal media levels, but there was little additional stimulation when these agonists were combined. In contrast, mixed neuronal/glial cultures showed only weak responses to DEX or FSK alone, but the combination of these agonists produced a pronounced synergistic effect on media ME accumulation (6-10-fold over basal levels). The DEX effect was mediated via a classical glucocorticoid receptor, since DEX was potent (acting over a concentration range of 10(-11)-10(-7) M), mimicked by corticosterone (10(-6) M), and blocked by the glucocorticoid receptor antagonist RU486. There was a pronounced time lag (2 days) for the synergistic effects of DEX + FSK to develop. In situ hybridization and immunocytochemical studies suggested that astrocytes were the major source for the increased ME production in all mixed neuronal/glial cultures examined. Creating a mixed culture by plating fetal neurons onto confluent, enriched P7 glial cultures inhibited accumulation of ME in the media. DEX + FSK, but neither agonist alone, overcame this neuronal inhibition and increased accumulation of media ME to levels identical to levels in stimulated enriched glial cultures. The net effect was a 6-fold increase in ME accumulation in the mixed neuronal/glial cultures relative to a 2.5-fold increase in the enriched glial cultures. Neuronal inhibition of basal glial ME production could explain the similar synergistic effects of DEX + FSK observed in all mixed neuronal/glial cultures examined, and may be important in suppressing ME production by astrocytes in the brain.

Animals↗
PubMed1996

Glutamatergic projections from the rostral hypothalamus to the periaqueductal grey.

Retrograde transport of fluorescent latex microspheres was combined with immunocytochemistry for glutamate to determine the organization of the projections from glutamate-containing neurones in the rostral hypothalamus to the different subdivisions of the periaqueductal grey (PAG). Double-labelled neurones, i.e. neurones immunoreactive for glutamate and projecting to the PAG, were found throughout the rostral hypothalamus. There were no apparent differences, however, in the origins of presumed glutamatergic projections from the rostral hypothalamus to the different subdivisions of the PAG.

Animals↗
PubMed1996

Transcription factors in primary glial cultures: changes with neuronal interactions.

Several astrocyte gene products, such as enkephalin and glial fibrillary acidic protein (GFAP), are expressed at higher levels under in vitro conditions relative to in vivo. We have observed that cultured glial cells express high basal levels of transcription factors, such as fos-related antigens (Fra), c-Jun, JunD, and cAMP responsive element binding protein (CREB). When neuronal cells are plated on top of the monolayers, the expression of Fra, c-Jun, JunD, and GFAP decreases in the astroglial cells. The DNA binding activity to the AP-1-like sites of the GFAP and proenkephalin genes was examined in these cultures. The protein complex from glial cultures which recognizes the GFAP AP-1 element contained Fra immunoreactivity while the DNA binding from mixed neuronal/glial cultures consists of CREB-immunoreactive proteins. In glial cultures, no binding occurred to the proenkephalin AP-1-like element but a CREB-immunoreactive complex recognized this sequence in the mixed cultures. Thus, with the addition of neurons, both transcription factors and target gene products decrease in astroglial cells. The proteins that compose gene modulatory complexes also change suggesting that regulation of astroglial gene expression is modulated by neurons.

Animals↗
PubMed1995

Glia-dependent neurotoxicity and neuroprotection in mesencephalic cultures.

Dopaminergic neurotoxicities of 6-hydroxydopamine (6-OHDA) and the lipopolysaccharide (LPS) were compared in rat mesencephalic cultures plated on poly-L-lysine or on glial monolayers. In the neuron-enriched cultures plated on polylysine, 6-OHDA killed 89% of the tyrosine hydroxylase (TH)-immunopositive neurons, but LPS was not neurotoxic. Conversely, in mixed neuron/glial cultures, 6-OHDA killed only 27% of the TH-immunopositive neurons while LPS killed 70%. The mixed neuronal/glial mesencephalic culture offers a better in vitro model for studying possible mechanisms involved in Parkinson's disease.

Animals↗
PubMed1995

Basal expression of 35 kDa fos-related antigen in olfactory bulb.

Recently, there have been a number of reports showing a long-term increased expression of fos-related antigens (fra), molecular weight of 35 kDa, after brain injury or chronic treatment of rats with various drugs. We report elevated basal levels of this transcription factor in the olfactory bulb relative to other brain regions. The expression of this protein is further enhanced in the olfactory bulb as long as 3 months after a single injection of kainate, an effect similar to that we previously observed in the hippocampus. The AP-1 DNA binding activity in olfactory bulb from kainate-treated rats contains fra and jun immunoreactivity suggesting that the 35 kDa fra dimerizes with jun protein, probably junD, to bind to AP-1 sites. Elevated basal levels of this transcription factor in the olfactory bulb appear to be related to the constant reinnervation and synaptogenesis which occurs in this brain region. The 35 kDa fra may be involved in long-term genomic program changes required to adapt to an altered biochemical environment.

Animals↗
PubMed1995

DNA binding activity of CREB transcription factors during ontogeny of the central nervous system.

During the early postnatal period, the rat brain contains high basal levels of AP-1 DNA binding activity which declines to the low levels found in the adult by the third postnatal week. Although the individual transcription factors that comprise this AP-1 DNA binding complex had not been identified, we discovered that these proteins were immunoreactive to the cAMP responsive element binding protein (CREB) and also recognized the CRE element. The 45 kDa CREB-immunoreactive protein was detected at high levels only during the first postnatal week. CRE and AP-1 DNA binding activities were studied in the olfactory bulb, striatum, hindbrain, hippocampus, hypothalamus and cerebellum. In general, the DNA binding activity correlated with the stage of maturation of the particular brain region. However, basal AP-1 DNA binding in the olfactory bulb from adults remained slightly elevated relative to other brain regions. Interestingly, the DNA binding complex in the olfactory bulb began to include fos-related antigen as well as CREB by the third postnatal week. The fra-containing complex only recognizes the AP-1 element, while the CREB complex can bind to either CRE or AP-1 sequences. Thus, there is crosstalk between the signal transduction systems that activate CREB and AP-1 transcription factors. This elevated CREB DNA binding activity may be a sensitive index for studying the development of the brain and could be involved in modulating the genomic program in differentiating cells.

Aging↗
PubMed1995

Acute repeated nicotine injections increase enkephalin and decrease AP-1 DNA binding activity in rat adrenal medulla.

Previously we reported that a single injection of nicotine decreased AP-1 DNA binding activity in adrenal medullae, although chronic bidaily nicotine (and saline) injections increased this binding activity [15]. Repeated acute nicotine injections (3 mg/kg i.p., 7 injections equi-spaced over a 3 h period) effectively increased adrenal tyrosine hydroxylase [3] and [Met5]enkephalin levels and also profoundly decreased adrenal medulla AP-1 DNA binding activity for over 8 h.

Adrenal Medulla↗
PubMed1995

Expression of the proenkephalin A gene and [Met5]-enkephalin secretion induced by arachidonic acid in bovine adrenal medullary chromaffin cells: involvement of second messengers.

We have previously reported that arachidonic acid (AA) increases the long-term secretion of [Met5]-enkephalin (ME) and the expression of proenkephalin A (proENK) mRNA in bovine adrenal medullary chromaffin (BAMC) cells. To characterize the underlying signal transductional mechanisms for the AA-induced responses, the interactions of AA with several second messenger systems were studied. Long-term (24-h) treatment with AA (100 microM) increased both the secretion of ME and the expression of proENK mRNA. Pretreatment of BAMC cells with nimodipine (1 microM), but not with omega-conotoxin GVIA (1 microM), inhibited the secretion of ME and the expression of proENK mRNA induced by AA. Calmidazolium (1 microM), a calmodulin antagonist, also significantly inhibited AA-induced responses. However, a protein kinase C (PKC) inhibitor, sphingosine (36 microM), was ineffective in blocking AA-induced responses. In addition, the down-regulation of PKC by phorbol 12-myristate 13-acetate (0.1 microM) for 48 h did not inhibit the AA-induced responses. Forskolin (5 microM), an adenyl cyclase activator, alone increased the secretion of ME as well as proENK mRNA levels and, when coincubated with AA, showed an additive effect on the secretion of ME and the levels of proENK mRNA. The results suggest that the Ca2+/calmodulin pathway, but not the protein kinase A or PKC pathway, is partially involved in mediating the AA-induced increases of the long-term secretion of ME and the levels of proENK mRNA.

Adrenal Medulla↗
PubMed1995

Treatment of extramammary Paget's disease by radiotherapy.

Extramammary Paget's disease (EMPD) is a rare cutaneous malignancy, which usually occurs in the elderly. Wide local excision is the recommended treatment, although this may not always be feasible. We report our experience of EMPD treated by radiotherapy in five patients. The radiotherapy was well tolerated in each case, and there were no signs of recurrence during follow-up (6 months-8 years). This study shows that radiotherapy is a useful alternative therapy for EMPD, and should be considered particularly in elderly patients who may not tolerate surgery.

Aged↗
PubMed1995

Long-term stimulation of nicotinic receptors is required to increase proenkephalin A mRNA levels and the delayed secretion of [Met5]-enkephalin in bovine adrenal medullary chromaffin cells.

The effects of nicotine on the transcriptional activity of the proENK gene, proenkephalin A (proENK) mRNA levels, and the secretion of [Met5]-enkephalin (ME) were studied in bovine adrenal medullary chromaffin (BAMC) cells. Nicotine (10 microM) caused an immediate secretion (within 1 hr) of ME followed by a delayed secretion (12-24 hr after treatment) into the medium. Posttreatment with the cholinergic antagonists, hexamethonium (1 mM) and atropine (1 microM), up to 6 hr after the nicotine treatment significantly inhibited the delayed secretion of ME induced by nicotine. However, nicotine-induced long-term secretion of ME was not affected when cholinergic antagonists were added 9 or 12 hr after the nicotine treatment. Long-term (24 hr) stimulation of BAMC cells with nicotine also increased proENK mRNA level. This nicotine-induced response was inhibited by posttreatment with cholinergic antagonists 0.5, 1, 3 and 6 hr after the nicotine treatment. As with the secretion experiments, these cholinergic antagonists did not affect the nicotine-induced responses when they were added at 9 and 12 hr. Posttreatment with nimodipine (1 microM), calmidazolium (1 microM) or KN-62 (5 microM) up to 6 hr after the nicotine treatment significantly inhibited the increases of the long-term secretion of ME and proENK mRNA level induced by nicotine. However, these agents were ineffective in blocking the long-term secretion of ME and proENK mRNA level induced by nicotine when BAMC cells were posttreated after 9 and 12 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Regulation of tyrosine hydroxylase in olfactory bulb cultures: selective inhibition of depolarization-induced increase by endogenous opioids.

Regulation of tyrosine hydroxylase (TH) by second messenger pathway activators was examined in rat olfactory bulb cell cultures. The number of TH-immunoreactive neurons was increased 2-3-fold by 36 h treatments with forskolin (Fsk, 10(-6) M) or phorbol myristate acetate (PMA, 10(-7) M), but was not significantly increased by a depolarizing concentration of KCl (45 mM). In contrast, KCl increased media [Met5]enkephalin (ME) immunoreactivity 2-fold in these cultures, equivalent to stimulation with Fsk or PMA. The possibility was examined that ME or another opioid produced by the cultures selectively inhibited the TH response to KCl. Pretreatment with the opioid receptor antagonist naloxone (10(-6) M) greatly increased the number of TH-immunoreactive neurons observed in response to KCl treatment, but had no effect on basal or Fsk-stimulated TH immunostaining, nor on basal or stimulated ME release. The increase in TH-immunoreactivity observed with combined KCl plus naloxone treatment was prevented by pretreating the cultures with the calcium channel blocker nimodipine (10(-6) M), which had no effect on Fsk stimulation or basal TH immunostaining. These data suggest that endogenous opioids selectively inhibit KCl-stimulated Ca2+ entry and thus TH induction in olfactory bulb cell cultures. These cultures offer a simple model system for further study of TH regulation in dopaminergic neurons.

Animals↗
PubMed1994

Role of a 35 kDa fos-related antigen (FRA) in the long-term induction of striatal dynorphin expression in the 6-hydroxydopamine lesioned rat.

D1 dopamine (DA) receptor agonists induce the expression of the opioid peptide dynorphin (DYN) in the striatum, an effect accentuated several fold by removing the dopaminergic innervation to the striatum (e.g., by lesioning the DA cell bodies in the substantia nigra [SN]). D1 receptor-mediated effects are thought to involve cAMP and/or phosphoinositides as second messengers. However, it is unclear what third messengers are involved in the regulation of DYN expression. The present experiments evaluated the possible role of two families of immediate-early gene (IEG) proteins, Fos and Jun, in the induction of DYN biosynthesis following repeated treatment with DA agonists. In addition, the role of N-methyl-D-aspartate (NMDA) receptors in modulating DA-induced changes in DYN and IEG protein expression was assessed. Adult male rats received unilateral 6-hydroxydopamine (6-OHDA) or sham lesions of the SN. Following a recovery period, animals were injected twice daily with the DA agonist, apomorphine (APO; 5 mg/kg), for 4 or 7 days. As expected, APO induced DYN biosynthesis, at both the peptide and mRNA level, several fold more in the striatum ipsilateral to the 6-OHDA lesion than in the contralateral control side (or a sham lesioned striatum). These effects appeared to be mediated by D1 receptors since the D1 agonist, SKF 38393 (5 mg/kg), caused the same changes in DYN expression as APO whereas a D2 agonist, quinpirole (1 mg/kg), had no effect. Paralleling the increase in DYN expression, APO also induced the expression of c-Fos and Fos-related antigens (FRA's), in particular a 35 kDa FRA, but had no effect on the expression of various Jun-related IEG proteins (i.e., c-Jun, Jun B, Jun D). Consistent with the notion that Fos and FRA proteins alter transcriptional activity by binding to AP-1 (or AP-1-like) DNA sequences in the promoter regions of target genes, we found that repeated APO treatment caused large increases in AP-1 binding activity in striata ipsilateral to 6-OHDA lesions. These data indicate that repeated activation of D1 receptors increases both the expression of a 35 kDa FRA and AP-1 binding, events which may mediate the large increases in DYN expression in the DA denervated striatum. While co-administration of the NMDA receptor antagonist, MK-801, inhibited APO-induced increases in DYN and Fos/FRA expression in the intact striatum, its only effect in the DA-denervated striatum was a partial (35%) inhibition of the APO-induced increase in DYN-ir concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

Biphasic generation of diacylglycerol by angiotensin and phorbol ester in bovine adrenal chromaffin cells.

Stimulation of angiotensin receptors in bovine adrenal medullary cells with Sar1-angiotensin II increased diacylglycerol levels in a biphasic fashion. An initial peak occurred at 3 min and an increase was observed again at 60 min and even at 18 hrs. Phorbol 12-myristate 13-acetate produced a similar pattern of increase in diacylglycerol levels. Both the angiotensin analog and the phorbol ester also increased the release of (3H)choline into the culture medium from prelabelled cells. The long-term diacylglycerol production could be derived from phosphatidylcholine rather than from the phosphoinositides. The latter may be the source of the angiotensin stimulated initial production of diacylglycerol and activation of PKC. Activated PKC then turns on the continuous production of DAG which maintains PKC in an active state for long periods of time in the presence of the peptide.

Adrenal Medulla↗
PubMed1993

Developmental changes in rat adrenal enkephalin precursor: peptide ratio.

Developmental changes in rat adrenal [Met5]enkephalin (ME) immunoreactivity and [Met5]enkephalinargininephenylalanine (MERF) immunoreactivity (which presumably reflects proenkephalin) were examined. The concentration of MERF appeared highest at the end of the first week postnatally and decreased fourfold to near adult values by day 21, while ME levels decreased only about twofold. This indicates a fall in the adrenal proenkephalin:ME ratio during the transition from the suckling to the weanling period in the rat. The elevated MERF levels during the suckling period may result from deficient processing of proenkephalin to free ME. An increase in the activity of the processing enzyme carboxypeptidase E was observed at day 15, which may contribute to the developmental fall in the adrenal proenkephalin to free ME ratio. Mimicking sympathetic activity by nicotine treatment (3 mg/kg i.p. twice daily from birth) produced a precocious decrease in the MERF:ME ratio at day 8, and also increased the activity of the processing enzyme. Denervation at day 10 markedly decreased adrenal ME and produced a three-fold increase in MERF:ME ratio when measured at day 30. Adrenal carboxypeptidase E activity was also decreased after denervation. In summary, these results suggest that increasing preganglionic sympathetic nerve activity during the third week postnatally stimulates proenkephalin processing and leads to the developmental decrease in MERF:ME ratio in the rat adrenal.

Adrenal Glands↗
PubMed1993

Role of omega-conotoxin GVIA-sensitive Ca2+ entry in angiotensin II-stimulated [3H]phorbol 12,13-dibutyrate binding in bovine adrenal medullary cells.

The relative contributions of Ca2+ influx and intracellular Ca2+ mobilization were examined for angiotensin II-stimulated [3H]phorbol 12,13-dibutyrate binding, which reflects the level of activated protein kinase C in bovine chromaffin cells. Angiotensin II receptors activate phospholipase C in chromaffin cells, leading to a short-lived mobilization of intracellular Ca2+. Angiotensin II-stimulated [3H]phorbol 12,13-dibutyrate binding was largely blocked in Ca(2+)-free buffer and by pretreatment with the Ca(2+)-channel blocker omega-conotoxin GVIA. The [3H]phorbol 12,13-dibutyrate binding response to [Sar1]angiotensin II also appeared to be voltage sensitive, as no additivity was observed with the response to the depolarizing agent 4-aminopyridine (3 mM). Threshold sensitivities of the extra- and intracellular Ca(2+)-mobilizing pathways to angiotensin II were similar, and all examined effects of angiotensin II in these cells were apparently mediated by losartan-sensitive (AT1-like) receptors. The dependence of angiotensin II-stimulated [3H]phorbol 12,13-dibutyrate binding on extracellular Ca2+ entry, in contrast to stimulation by other phospholipase C-linked receptor agonists (bradykinin and methacholine), suggests that angiotensin II preferentially stimulates protein kinase C translocation to the plasma membrane, rather than to internal membranes, in bovine adrenal medullary cells.

Adrenal Medulla↗