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Biomedical subjects

J J Reid

Publications and source records attributed to J J Reid.

At least 55 records · Page 3Linked to original sources
PubMed1991

Morphological characterization of immortalized hypothalamic neurons synthesizing luteinizing hormone-releasing hormone.

An immortalized LHRH cell line has recently been developed by genetically targeting these neurons for tumorigenesis. One of the subclones, the GT1-7 cells, was characterized at both the light and electron microscopic levels to study the cellular and subcellular organization of these cells, particularly as they relate to biosynthesis, processing, and secretion. The cells were fixed onto slides 18-36 h after plating. LHRH and GnRH-associated peptide (GAP) immunoreactivities (IR) were detected by immunocytochemistry using colloidal gold labeling. These cultured cells exhibited the classical neuronal appearance of LHRH neurons, and they established numerous interconnections. Neighboring neurons were coupled by tight junctions, while more distant cells were interconnected with neural axon-like processes and collaterals. This cellular organization is suggestive of a neural network where neuronal activity is coordinated. At the ultrastructural level, the nondividing cells possessed indented nuclei, well developed Golgi complexes, and abundant numbers of ribosomes and secretory granules. Clathrin-coated vesicles were found in fusion with the plasma membrane. The ribosomes and secretory vesicles were particularly prominent, suggestive of high rates of protein biosynthesis and secretion. All of the cells immunostained for both LHRH and GAP; however, GAP IR was always more pronounced than that for LHRH. This finding was corroborated by biochemical data reported in a companion paper. The GAP IR was associated with ribosomes and secretory vesicles. By comparison, LHRH IR was restricted mainly to the secretory vesicles. Using colloidal gold particles of different sizes to denote LHRH or GAP IR, it was determined that both GAP and LHRH IR were colocalized within the same secretory vesicle. Taken together, these data suggest that pro-LHRH is biosynthesized on the ribosomes, packaged as an intact protein into the secretory vesicles, processed to LHRH and GAP-(1-56) within these vesicles, and transported to the periphery of the cell in preparation for secretion. These morphological data emphasize the utility of using these immortalized LHRH neuronal cells to dissect the cellular and subcellular architecture involved in biosynthesis, processing, and secretion. In addition, our results provide the first detailed evidence for the intracellular pathway involved in pro-LHRH biosynthesis, processing, and secretion in these cultured neuronal cells.

Animals↗
PubMed1990

Effects of methylenedioxymethamphetamine on the release of monoamines from rat brain slices.

The effects of 3,4-methylenedioxymethamphetamine (MDMA) on monoamine release were investigated in superfused slices of rat striatum and hippocampus. MDMA (10 microM) increased the resting release of radioactivity from slices incubated in [3H]dopamine, [3H]5-hydroxytryptamine or [3H]noradrenaline. These effects of MDMA (10 microM) were blocked by the neuronal uptake inhibitors, cocaine (10 microM), fluoxetine (1 microM) and desmethylimipramine (1 microM), respectively. MDMA (10 microM) enhanced the stimulation-induced efflux of radioactivity from slices incubated in [3H]noradrenaline but not from slices incubated in [3H]5-hydroxytryptamine or [3H]dopamine. These results demonstrate for the first time a direct noradrenaline-releasing action of MDMA and differential effects of MDMA on the stimulation-induced release of noradrenaline, dopamine and 5-hydroxytryptamine from rat superfused brain slices.

3,4-Methylenedioxyamphetamine↗
PubMed1990

Effects of omega-conotoxin GVIA on autonomic neuroeffector transmission in various tissues.

1. The effects of omega-conotoxin GVIA (conotoxin), a potent inhibitor of neuronal N-type Ca2+ channels, have been examined on responses to stimulation of noradrenergic, cholinergic and non-adrenergic, non-cholinergic (NANC) nerves in a range of isolated tissues to investigate the role of conotoxin-sensitive Ca2+ channels in neurotransmission. 2. Contractions elicited by field stimulation of noradrenergic nerves in rat and mouse anococcygeus muscles, rabbit ear artery and rat vas deferens (epididymal portion) were inhibited by conotoxin. Responses to noradrenaline, and to adenosine triphosphate in the vas deferens, were not affected. 3. Positive chronotropic responses to field stimulation of noradrenergic nerves were inhibited by conotoxin in rat and mouse atria, but responses to noradrenaline and tyramine were not affected. 4. The stimulation-induced release of noradrenaline was inhibited by conotoxin in the rabbit ear artery and in rat and mouse atria. 5. Relaxations in response to stimulation of the noradrenergic perivascular mesenteric nerves were reduced or abolished by conotoxin in rat and rabbit jejunum. The response to noradrenaline in rat jejunum was not affected. 6. Contractions elicited by stimulation of cholinergic nerves were inhibited by conotoxin in rat jejunum and mouse ileum (perivascular mesenteric nerves), and in guinea-pig taenia caeci (field stimulation). Responses to acetylcholine in rat jejunum and mouse ileum were not affected. 7. Contractions elicited by stimulation of the cholinergic plus NANC pelvic nerves were inhibited by conotoxin in rabbit colon, and to a lesser extent in guinea-pig colon. The stimulation-induced contraction of the guinea-pig colon was inhibited by conotoxin by a greater proportion in the presence than in the absence of atropine. Responses to acetylcholine were not affected in the rabbit colon but were slightly reduced in the guinea-pig colon. 8. Relaxations in response to field stimulation of NANC nerves were inhibited by conotoxin in guinea-pig taenia caeci and rat gastric fundus strips, and in rat anococcygeus muscle when the tone was raised by guanethidine but not when it was raised by carbachol. The relaxations produced by sodium nitroprusside in the rat gastric fundus and anococcygeus were not affected. 9. Contractions of the rat bladder elicited by stimulation of the peri-urethral nerves, which are NANC- and cholinergically mediated, were relatively insensitive to inhibition by conotoxin. The response were almost completely abolished by tetrodotoxin. 10. The conotoxin-induced inhibitions of responses to nerve stimulation developed slowly and persisted after removal of conotoxin. The responses were almost completely abolished by tetrodotoxin. 10. The conotoxin-induced inhibitions of responses to nerve stimulation developed slowly and persisted after removal of conotoxin. 11. The inhibitory effect of conotoxin was inversely proportional to the frequency of stimulation (in several preparations) and to the Ca2+ concentration in the bathing solution (in rat vas deferens). These observations suggest that the inhibition by conotoxin of the Ca2+ influx required for excitation-secretion coupling in autonomic nerve terminals is not absolute, and can be overcome by repeated stimulation or by raising the Ca2 + concentration.

Animals↗
PubMed1989

The effect of endothelin on noradrenergic transmission in rat and guinea-pig atria.

Pre-and postjunctional effects of 10 nM endothelin have been studied in rat and guinea-pig spontaneously beating isolated atria. Endothelin increased the rate and force of contraction of atria from both species, but decreased the positive inotropic and chronotropic responses to stimulation of intramural sympathetic nerves by approximately 60% in rat and by 10-15% in guinea-pig atria. The stimulation-induced release of noradrenaline from either rat or guinea-pig atria was not significantly changed by endothelin.

Animals↗
PubMed1989

Paradoxical effects of endothelin on cardiovascular noradrenergic neurotransmission.

1. Pre- and postjunctional effects of endothelin (1-10 nmol/L) have been studied in the rabbit isolated ear artery and in rat isolated atria. 2. Endothelin produced concentration-dependent increases in arterial perfusion pressure, and had positive chronotropic and inotropic effects in rat atria. 3. Vasoconstrictor responses of the arteries to sympathetic nerve stimulation were reduced by 1 nmol/L endothelin and abolished by 10 nmol/L endothelin. In rat atria, the chronotropic responses to nerve stimulation were markedly reduced by 10 nmol/L endothelin. 4. In rabbit ear artery, vasoconstrictor responses to noradrenaline were enhanced by 1 nmol/L endothelin, but were reduced by 10 nmol/L endothelin. In rat atria, endothelin reduced the chronotropic response to isoprenaline. 5. Endothelin (10 nmol/L) increased the stimulation-induced release of radioactivity in arteries and atria labelled with [3H]-noradrenaline by 91% and 23%, respectively. 6. The pre- and postjunctional effects of endothelin persisted in both arterial and atrial preparations for at least 30 min after its removal.

Animals↗
PubMed1987

Rubella immunity in 14-18 year old females: assessment in a city practice.

We have undertaken a pilot study to assess the rubella immunity status of 88 females aged 14-18 years in a Dunedin suburban general practice. According to practice records, only 60% were found to have a record of immunisation. The low response rate of only 58% of those requested to participate was of concern given the publicity about the dangers of the congenital rubella syndrome. All the girls who responded were shown to be immune against rubella. While 40% of the study group apparently escaped immunisation recording, they nonetheless acquired immunity. One explanation for this finding may be incomplete record keeping and transmission of the vaccination history of the patient. These results remind us that we should not be complacent as to the efficiency of our present immunisation efforts and to be alert to opportunities for ensuring protection in the patient population.

Adolescent↗
PubMed1987

Evaluation of the addition of cromolyn sodium to bronchodilator maintenance therapy in the long-term management of asthma.

Three hundred ninety-seven patients, aged 5 to 63 years, took part in a year-long international multicenter, double-blind, placebo-controlled trial. The patients, whose asthma was considered not adequately controlled, were divided into two groups according to their principal medication at entry (group A, oral and/or inhaled beta 2-bronchodilators; group B, methylxanthines, with or without beta 2-agonists) and randomly allocated to additional treatment with cromolyn sodium (metered-dose inhaler, 2 mg, four times a day, or capsules, 20 mg, four times a day) or matching placebo. A 2-month baseline preceded 10 to 12 months of treatment. After 4 to 8 weeks of treatment, patients were encouraged to reduce bronchodilator usage. Patients used diary cards to record asthma severity, sleep difficulty, morning and evening peak expiratory flow rates, days of disruption of normal activity, use of test treatments, and concomitant medication. Significant differences favoring cromolyn sodium (p less than 0.05 and better) were observed for most of the treatment period in respect to (1) asthma severity, (2) morning and evening peak expiratory flow rates, and (3) days of disruption of normal activity. Patients receiving cromolyn sodium experienced fewer exacerbations and tended to use less concomitant medication than patients receiving placebo. Patients' opinions of treatment significantly favored cromolyn sodium. These results demonstrate the value of the addition of cromolyn sodium to existing therapy in the long-term management of asthma and endorse its use as a first-line treatment.

Adolescent↗
PubMed1987

A histological method for studying the effects of drugs on mediator-induced airway microvascular leakage in rodents.

Methods are described for studying the effects of drugs on increases in tracheobronchial microvascular permeability (leakage) induced by inflammatory mediators. A model in conscious guinea pigs (in which the leakage effects resulted from circulating mediator) and a model in anesthetized rats (in which the leakage effects resulted from application of the mediator to the airway lumen) are described. Inhibitor drugs were given i.v. 2 min before the mediator. In guinea pigs either histamine or leukotriene D4 (LTD4) and colloidal carbon (C, the tracer molecule for leakage) were administered together iv.; in rats 5-hydroxytryptamine (5-HT, 100 micrograms) was injected intratracheally followed by i.v. colloidal carbon. Tracheal and bronchial tissues were removed 15 min later from the killed animals and prepared for histology, and the number of C-labeled microvessels in the mucosal/submucosal region of 7-micron sections was counted. In guinea pigs, leakage produced by LTD4 or histamine was related to the dose administered and the relative potency of LTD4:histamine was approximately 123:1, on a molar basis. Leakage caused by histamine, but not by LTD4, was prevented by mepyramine (1 mg/kg) and LTD4-induced leakage was prevented by FPL 55712 (1 mg/kg). Terbutaline (1 mg/kg) attenuated leakage to both mediators but never abolished it. In rats, leakage was also seen to 5-HT, which was prevented by methysergide (1 mg/kg) and markedly attenuated by ketanserin (1 mg/kg) or by terbutaline (1 mg/kg). It is suggested that the colloidal carbon tracer technique has application to pharmacological studies designed to examine the effects of drugs on mediator-induced permeability to macromolecules in the tracheobronchial microcirculation.

Animals↗
PubMed1987

Recording of monophasic action potentials in the horizontally perfused guinea pig heart. An in vitro method to study drug-induced changes in cardiac electrophysiology.

An in vitro technique has been developed for the recording of monophasic action potentials to enable the measurement of changes in the duration of repolarization and in rise time produced by known concentrations of drugs and ions. Guinea pig hearts were perfused horizontally at constant pressure (60 cm H2O) and temperature (37 degrees C) with Krebs-Henseleit buffer. Epicardial monophasic action potentials were recorded from the right ventricular base using a bipolar Ag/AgCl electrode to which a suction pressure of 400 mm Hg was applied. The monophasic action potential signals had smooth depolarization and repolarization phases with amplitudes of 25-65 mV; repeated measurements of monophasic action potential duration at the 50, 75, and 90% repolarization levels (MAPD 50, 75, and 90) and rise time, determined by computer analysis, were reproducible for at least 150 min of perfusion. There was an excellent linear correlation between heart rate and monophasic action potential duration. The ability of the method to detect drug-induced changes was confirmed using clofilium (10(-9) to 10(-5) M), which significantly prolonged monophasic action potential duration 50, 75, and 90 in a concentration-dependent manner, and tocainide (3 x 10(-4) M), which significantly decreased monophasic action potential duration 50, 75, and 90 and increased rise time.

Action Potentials↗
PubMed1986

Cardiac arrest and heart attack: an evaluation of lay knowledge.

Random samples of Dunedin residents were interviewed before and after the publication in the telephone directory of an information sheet on cardiac arrest and heart attack. Most subjects had heard of both cardiac arrest and heart attack but almost half of the samples were either wrong in identifying which was the more serious or they did not know. One-third of the post-publication sample had looked at the information sheet. Results indicate limited awareness of all but the most elementary medical facts and the existence of a variety of confusions and misconceptions in the two samples. Problems of comprehension and remembering are discussed in the context of the communication of medical information by doctors and health educators.

Adult↗
PubMed1986

Characterization of the O-methylation of catechol oestrogens by intact rabbit thoracic aorta and subcellular fractions thereof.

In the present study we investigated the O-methylation of catechol oestrogens by intact rabbit thoracic aorta and subcellular fractions thereof. The O-methylation of 2-hydroxyoestradiol (2OHE2) and 2-hydroxyoestriol (2OHE3) displayed saturation kinetics in the intact tissue. The apparent Km and Vmax values for the O-methylation of 2OHE2 were determined to be 0.91 mumol/l and 104 pmol g-1 min-1, respectively, when 2OHE2 was used as substrate; and 1.14 mumol/l and 188 pmol g-1 min-1 when 2OHE3 was used as substrate. The inhibitors of the extraneuronal uptake process (viz; phenoxybenzamine 33 mumol/l; normetanephrine, 46 mumol/l; and deoxycorticosterone acetate 27 mumol/l) failed to inhibit the O-methylation of either 2OHE2 (3.4 mumol/l) or 2OHE3 (3.4 mumol/l) in intact segments of the rabbit thoracic aorta. (-)-Isoprenaline (40 mumol/l) abolished the O-methylation of 2OHE2 (3.4 mumol/l) and markedly reduced that of 2OHE3 (3.4 mumol/l). Pretreatment of tissues with phenoxybenzamine (33 mumol/l) partially restored the O-methylation of 2OHE2 and 2OHE3 in the presence of (-)-isoprenaline (40 mumol/l). The O-methylation of 2OHE2 (5 mumol/l) was significantly reduced in segments of aorta in which the endothelium was removed. The latter reduction could not be attributed to damage to components of the vessel media. The O-methylation of 2OHE2 and (-)-isoprenaline by subcellular fractions of the rabbit aorta also was examined. Both the microsomal and cytosolic fractions were shown to O-methylate 2OHE2 and (-)-isoprenaline, providing evidence for the existence of membrane-bound and soluble forms of COMT in the rabbit aorta. The O-methylation of 2OHE2 by cytosolic and microsomal fractions of the aorta was determined and compared to that of (-)-isoprenaline. The kinetic constants for the O-methylation of 2OHE2 by cytosolic (Km: 0.27 mumol/l; V max: 112 pmol g-1 min-1) and microsomal (Km: 0.15 mumol/l; Vmax: 161 pmol g-1 min-1) fractions were similar. In contrast, the kinetic constants for the O-methylation of isoprenaline by cytosolic (Km: 121 mumol/l; Vmax: 174 pmol g-1 min-1) and membranal (Km: 0.91 mumol/l; Vmax: 105 pmol g-1 min-1) fractions were very different. It is concluded that catechol oestrogens are excellent substrates for catechol-O-methyltransferase (COMT) in the rabbit aorta. Their O-methylation can occur in endothelial structures as well as in the smooth muscle-containing medial sections of the vessel.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Evidence that 6-hydroxydopamine is an inhibitor of catechol-O-methyltransferase in intact tissue.

The effect of in-vitro sympathetic denervation on the O-methylation of 2-hydroxyoestradiol was examined using the rabbit thoracic aorta. Aortic segments were exposed to 6-hydroxydopamine (400 mg litre-1, 10 min), incubated in 2-hydroxyoestradiol (5 microM, 60 min), and the 2-methoxyoestradiol formed was quantified using HPLC with electrochemical detection. Pre-exposure to 6-hydroxydopamine reduced O-methylation by 90% in intact aortic strips. However, O-methylation was also reduced (81%) in rabbit aorta that had been surgically denervated before exposure to 6-hydroxydopamine. Furthermore, the O-methylation of 2-hydroxyoestradiol (20 microM, 15 min) by partially purified soluble catechol-O-methyltransferase was inhibited by 6-hydroxydopamine (400 mg litre-1) by 95% and 51% in the absence and presence of antioxidant, respectively. These results suggest that the inhibition of catechol-O-methyltransferase by 6-hydroxydopamine reported for the purified enzyme, applies to the intact tissue and that the inhibition is dependent on oxidation of the 6-hydroxydopamine. Subsequent experiments using dialysis techniques demonstrated that the inhibition of soluble catechol-O-methyltransferase by 6-hydroxydopamine was irreversible in part, but the degree of irreversibility was influenced by pH and by the extent of in-vitro oxidation of 6-hydroxydopamine.

Animals↗
PubMed1985

HPLC-ECD procedure for the measurement of O-methylation of catechol estrogens by vascular tissue.

A precolumn extraction procedure combined with high-performance liquid chromatography with electrochemical detection (HPLC-ECD) has been developed for the identification and quantitation of catechol estrogens, their immediate precursors (estrogens), and their 0-methylated metabolites. These compounds were isolated from Krebs solutions and from perchloric acid tissue extracts or whole tissues by simple solvent extraction prior to quantitation. The optimal conditions for detection by HPLC-ECD were those employing a radial compression module, a C18 Bondapak cartridge, and an isocratic mobile phase of ammonium phosphate (pH 3.0) combined with 30-70% acetonitrile. A biological application of this procedure includes the investigation of the 0-methylation of catechol estrogens by vascular tissue. In the present study, the 0-methylation of 2-hydroxyestradiol by rabbit aorta has been examined. The 0-methylation in segments of thoracic aorta was significantly less than that in abdominal aortic segments, but was reproducible along the length of the thoracic aorta.

Animals↗
PubMed1984

Kinetic constants of isoprenaline and corticosterone for extraneuronal uptake in different cell types from various tissues.

Extraneuronal uptake of isoprenaline was studied in a number of different, histologically identified, cell types: trachealis smooth muscle cells, vascular smooth muscle cells and myocardial cells. Segments of cat, rat or rabbit trachea, dog coronary artery or cat atria were incubated in isoprenaline, in the presence of U-0521 (100 mumol l-1) to inhibit catechol-O-methyltransferase. The intensities of formaldehyde-induced fluorescence (due to accumulation of isoprenaline) were measured, using microphotometry, in the appropriate cells in histological sections of the tissue. Endogenous fluorescence in adrenergic nerves was removed by pretreatment of rats with 6-hydroxydopamine and of cats and rabbits with reserpine. Segments of dog coronary artery were incubated with 6-hydroxydopamine in vitro to remove neuronal fluorescence. This treatment was also shown to be effective in guinea-pig trachea without any influence on the determination of the kinetic parameters of isoprenaline uptake in the trachealis smooth muscle cells. Fluorescence in all cell types studied was shown to represent isoprenaline which had accumulated by extraneuronal uptake, in that fluorescence was reduced by drugs which inhibit extraneuronal uptake (corticosterone, normetanephrine, metanephrine and/or phenoxybenzamine), by exposure to a K+-Krebs solution and by incubating tissues in isoprenaline at 0 degree C rather than 37 degrees C. In each cell type, isoprenaline uptake obeyed Michaelis-Menten saturation kinetics, both in the absence and presence of corticosterone. Corticosterone was a competitive inhibitor of isoprenaline uptake in all the cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗