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S Harvey

Publications and source records attributed to S Harvey.

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

Neural expression of the pituitary GH gene.

It is well established that GH-like proteins and mRNA are present in extrapituitary tissues, but it is not known whether this reflects ectopic transcription of the pituitary GH gene or the expression of a closely related gene. This possibility was, therefore, further investigated. Immunoreactive (IR) GH-like proteins were readily measured by RIA and immunoblotting in hypothalamic and extrahypothalamic brain tissues of the domestic fowl, in which GH-IR was similar in size and antigenicity to pituitary GH. RT-PCR of mRNA from these brain tissues, with oligonucleotide primers spanning the coding region of pituitary GH cDNA, also generated cDNA fragments identical in size (689 bp) to pituitary GH cDNA. The amplified brain cDNA sequences contained BamH1 and Rsa1 cleavage sites similar to those located in pituitary GH cDNA. These cDNA sequences also hybridized with a cDNA probe for chicken GH cDNA, producing moieties of expected size that were identical to the hybridizing moieties in pituitary tissue. The nucleotide sequences of the PCR products generated from hypothalamic and extrahypothalamic brain tissues, determined by a modified cycle dideoxy chain termination method, were also identical to pituitary GH cDNA. This homology extended over 594 bp of the hypothalamic cDNA fragment (spanning nucleotides 65 to 659 of the pituitary GH cDNA and its coding region for amino acids 4 to 201) and 550 bp of the extrahypothalamic cDNA fragment (spanning nucleotides 76 to 626 of pituitary GH cDNA and its coding region for amino acids 8 to 190). These results clearly establish that pituitary GH mRNA sequences are transcribed in hypothalamic and extrahypothalamic tissues of the chicken brain, in which GH-IR proteins are abundantly located. However, as GH mRNA could not be detected in the chicken brain by Northern blotting, its turnover may be more rapid than in pituitary tissue. The local production of GH within the brain nevertheless suggests that it has paracrine roles in modulating neural or neuroendocrine function.

Animals↗
PubMed1994

Enhanced calcium influx by parathyroid hormone in identified Helisoma trivolvis snail neurons.

The modulation of [Ca2+]i by parathyroid hormone (PTH) has been extensively studied in vertebrates. The present study examined the effects of PTH on [Ca2+]i in isolated invertebrate neurons B5 from buccal ganglia of the pond snail, Helisoma trivolvis, utilizing the Fura-2 fluorescence technique. Bovine PTH, bPTH-(1-84), induced a slow and sustained increase in [Ca2+]i in neurons B5. In contrast, the elevation of extracellular K+ concentration from 1.7 mM to 15 mM induced a rapid and transient increase in [Ca2+]i. Simultaneous application of 15 mM KCl and bPTH-(1-84), or application of 15 mM KCl in the presence of bPTH-(1-84) additively increased [Ca2+]i in neurons B5. An increase in [Ca2+]i in neurons B5 was also induced by a PTH agonist [bPTH-(1-34)], but not by a PTH antagonist [bPTH-(3-34)]. The absence of calcium, or the presence of lanthanum (2 mM) or omega-conotoxin (10 microM), in the bath solution abolished the effect of bPTH-(1-84) on [Ca2+]i. Furthermore, our results demonstrated that the effect of PTH on [Ca2+]i in neurons B5 was not due to the hormonal modulation of voltage-dependent Na+ or K+ channels or a Na+/Ca2+ exchanger. The results from this study show that PTH can modulate [Ca2+]i in an identified invertebrate neuron mainly by promoting extracellular calcium influx via the N-like voltage-dependent calcium channel.

Animals↗
PubMed1994

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Conflict of Interest↗
PubMed1993

Dopaminergic actions of parathyroid hormone in the rat medial basal hypothalamus in vitro.

Parathyroid hormone (PTH) modulates dopamine (DA) metabolism in the rat medial basal hypothalamus (MBH) in vivo. Direct effects of PTH on MBH DA metabolism were therefore investigated in vitro. Incubation of rat MBHs for 60 min with 10(-7)-10(-5) M human PTH1-34 consistently reduced the tissue DA content and increased the DOPAC (dihydroxyphenylacetic acid) to DA ratio. This ratio was further increased in tissues incubated in 10(-5) M PTH1-34, as a result of an increase in DOPAC content. The tissue content of DOPAC and DA was unaffected by 10(-9) M PTH. The serotonin (5HT) content of the MBH was reduced by 10(-5) M PTH1-34, but concentrations of 5HT, 5-hydroxyindolacetic acid, and norepinephrine were otherwise unaffected by 10(-9)-10(-5) M PTH1-34. Concentrations of DA in the incubation media were reduced after exposure to 10(-6) or 10(-5) M PTH1-34. The uptake of 3H-labelled DA by incubated tissues was also reduced by 10(-6) M PTH1-34, as was the metabolism of 3H-labelled DA into tissue and media DOPAC. Monoamine oxidase (MAO) activities A and B were significantly increased after the incubation of the MBH with 10(-6) or 10(-5) M PTH1-34. These results further demonstrate neuromodulatory actions of PTH on dopaminergic neurons within the rat MBH in vitro, and suggest neural and/or neuroendocrine roles of PTH of central or peripheral origin.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Life-threatening focal status epilepticus due to occult cortical dysplasia.

OBJECTIVE: Neuronal migration disorders are usually, but not necessarily, demonstrated by magnetic resonance imaging. Preoperative suspicion of these anomalies in the presence of normal magnetic resonance studies has important practical implications. This study delineates some clinical features that permit early suspicion of focal cortical dysplasia localized in the central and precentral regions. DESIGN: In a retrospective case series, we studied the clinical presentation of four consecutive patients with normal preoperative magnetic resonance images in whom focal cortical dysplasia was found in the surgical specimen. SETTING: Patients were seen in three referral centers specializing in epilepsy surgery. PATIENTS: Four patients (three female), between the ages of 4 and 21 years, had intractable partial seizures leading to resective brain surgery. INTERVENTION: Three patients had corticectomies in the central (two patients) or frontal (one patient) regions. One underwent an en bloc resection of the central area after two unsuccessful corticectomies and cortical transection. RESULTS: Three patients presented with life-threatening focal motor status epilepticus necessitating intubation, and one had epilepsia partialis continua. All had had seizures previously, and the attacks progressed to intractability after 1 1/2 to 3 years. Surgery led to control of the seizures, but only two patients became seizure free (mean follow-up, 15.7 months). All but one developed a postoperative deficit, which eventually improved. CONCLUSIONS: Focal cortical dysplasia should be suspected when life-threatening focal motor status epilepticus or epilepsia partialis continua occur in children or young persons without another obvious cause. Normal magnetic resonance studies do not exclude neuronal migration disorders.

Adolescent↗
PubMed1993

Expression of parathyroid hormone-related peptide gene in the rat hypothalamus.

1. Parathyroid hormone-related peptide (PTHrP), originally isolated from human malignant tumors, is present in a variety of normal mammalian tissues, including the brain. 2. The expression and translation of the PTHrP gene within the rat hypothalamus was demonstrated in this study by the specific hybridization of a 1.8 kb mRNA product with a PTHrP cDNA probe and by the crossreactivity of rat hypothalamic extracts in a PTHrP radioimmunoassay. 3. These results suggest roles for PTHrP in neural or hypophysiotropic regulation.

Animals↗
PubMed1993

The genesis of a phenomenological approach to advanced nursing practice.

This paper describes how participation, as a co-investigator, in a phenomenological study of the high-risk perinatal experience led to the development of a new approach to advanced nursing practice for a maternity clinical nurse specialist. Prior to implementation of the study, nursing was practised based in a structured, conceptual framework, but, as a result of conducting interviews with study subjects, analysing data with a research team and gaining a better understanding of the high-risk perinatal experience, a new style of nursing practice based in a phenomenological approach emerged, which permeated all aspects of clinical nurse specialist practice.

Adaptation, Psychological↗
PubMed1993

Neural effects of parathyroid hormone: modulation of the calcium channel current and metabolism of monoamines in identified Helisoma snail neurons.

Neuronal effects of parathyroid hormone (PTH) have been reported in vertebrates. The effect of PTH on invertebrate central neurons within the buccal ganglion of Helisoma trivolvis snails was examined in the present study. By using a vibrating probe, PTH was found to induce a transient calcium-dependent inward current in intact buccal ganglia. Intracellular microelectrode recording revealed that PTH broadened the spontaneous action potential in buccal B5 neurons in situ. By using the whole-cell configuration of the patch-clamp technique, PTH was demonstrated to increase the N-like calcium channel currents in isolated B5 neurons in a concentration-dependent manner. This effect of PTH on the N-like calcium channel currents depended on the activation of a G protein insensitive to pertussis toxin, but was unlikely to be mediated by the cyclic AMP dependent protein kinase. Furthermore, the release of gamma-glutamyl conjugate of dopamine from buccal ganglia was selectively increased in the presence of PTH. These results represent the first demonstration that a vertebrate peptide hormone, PTH, selectively modulates the N-like voltage-dependent calcium channel currents in identified invertebrate neurons. Therefore, a novel role of PTH in the regulation of invertebrate central neural functions is indicated.

Action Potentials↗