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Biomedical subjects

D Templeton

Publications and source records attributed to D Templeton.

At least 37 records · Page 2Linked to original sources
PubMed1989

The relationship of intracellular free calcium activity to amylase secretion in substance P- and isoprenaline-stimulated rat parotid acini.

The relationship between intracellular free calcium activity ([Ca2+]i) and stimulated amylase secretion was investigated in rat parotid acini by measuring the effects of substance P methyl ester and isoprenaline on quin2 fluorescence and amylase release. Although both of these drugs evoked concentration-dependent increases in [Ca2+]i and amylase release, the tachykinin had a greater effect on [Ca2+]i while the catecholamine was the more effective secretagogue. Whereas isoprenaline exerted equipotent effects on amylase secretion and [Ca2+]i, the dose-response relationship for stimulation of secretion by substance P was dissociated by three orders of magnitude to the right of that for elevation of [Ca2+]i by this peptide. It is concluded that these data do not support the hypothesis that substance P-stimulated amylase secretion is mediated solely through an increase in [Ca2+]i and that other second-messengers may be involved in mediation of this secretory response.

Aminoquinolines↗
PubMed1987

Effect of parasympathetic denervation on K+ release by rat parotid slices.

1. By measuring the release of 86Rb, potassium movement was compared in parasympathectomized (Px) and contralateral control parotid gland slices three weeks following surgical denervation. 2. Carbachol and phenylephrine elicited a biphasic increase in 86Rb release that was dose related and could be blocked by atropine and phentolamine respectively. The transient phase was of 2-4 min duration and Ca independent whereas the sustained phase of 86Rb release was greatly reduced by the omission of the external Ca. 3. Denervation caused a shift to the left of the 86Rb efflux dose-response curve to carbachol and phenylephrine (3.75- and 3.37-fold respectively). Pilocarpine had similar action to carbachol but it behaved as a partial agonist. 4. Parasympathectomy (Px) increased the intrinsic activity of the partial agonist pilocarpine and converted it to a full agonist. Results of the present study indicate the possibility of an altered receptor-signal transduction mechanism between the receptor and phospholipid turnover/Ca mobilization in the denervated rat parotid gland.

Animals↗
PubMed1987

Description of an automated assay for measurement of alpha-amylase in vitro from rat parotid gland slices.

1. A modified continuous assay of alpha-amylase is detailed and its usefulness in measuring amylase secretion from rat parotid salivary gland described. 2. The alpha-amylase secretion from the rat parotid gland can be evoked by acetylcholine, substance P and isoprenaline. 3. The secretion of amylase was greatest following isoprenaline stimulation and was of a slower time course than with the other two agonists.

Acetylcholine↗
PubMed1986

The role of dopamine in salivation in the rat parotid gland.

The ability of dopamine to evoke secretion from the rat parotid gland has been investigated. The actions of dopamine were investigated alone and during carbachol mediated secretion. Dopamine increased flow rate and protein secretion in both experimental models. The increase in protein secretion is mediated via beta 1-adrenoceptors whereas the increase in flow rate may be due to activation of specific dopamine receptor.

Animals↗
PubMed1984

Substance P in the rat parotid gland: evidence for a dual origin from the otic and trigeminal ganglia.

The substance P innervation of the rat parotid was investigated using retrograde tracing with the fluorescent dye True Blue, in combination with the immunohistochemical localization of substance P. Retrogradely-labelled cells were seen in the otic, trigeminal, superior cervical and nodose ganglia. A proportion of the True Blue-labelled cells in the otic and trigeminal ganglia also contained substance P-like immunoreactivity providing direct evidence for a dual origin of substance P in the rat parotid. In addition, these results imply that in the rat otic ganglion substance P and acetylcholine coexist.

Animals↗
PubMed1984

Composition of secretion from the submandibular salivary gland in the rat.

The effects on the composition of rat submandibular saliva, of superimposing low frequency sympathetic nerve stimulation on parasympathetic nerve stimulation have been investigated. During continuous parasympathetic stimulation, additional sympathetic stimulation resulted in a frequency-dependent rise of both protein and K+ concentrations. The threshold of frequency of stimulation for the protein response was 0.1 Hz and for the K+ response 0.4 Hz. The protein secretion is presumed to be acinar in origin whilst the K+ is believed to be secreted mainly by ducts other than the main excretory duct.

Animals↗
PubMed1984

Electrical stimulation of the salivatory nucleus in the rat.

Unilateral electrical stimulation of the salivatory nucleus evoked a secretion from the ipsilateral parotid gland which was well maintained. Flow rate was not affected by sympathetic decentralization or by adrenoceptor antagonists but was abolished by atropine. Protein secretion was reduced by beta-adrenoceptor antagonists but not by sympathetic decentralization or adrenalectomy. In support of previous histochemical findings it is concluded that the cells of the reticular formation are the origin of the preganglionic parasympathetic fibres to the salivary glands but that a beta-adrenoceptor mechanism as yet unidentified is also involved in the protein secretion.

Adrenalectomy↗
PubMed1984

Characterization of viable mutants of polyomavirus cold sensitive for maintenance of cell transformation.

We mutagenized a cloned fragment of polyoma DNA encoding portions of the middle size (MT) and large T antigens. We regenerated infectious viral genomes containing the mutagenized DNA and tested their transforming ability at 32 and 39 degrees C. We isolated three nontransforming mutants and two mutants which were cold sensitive for the maintenance of cell transformation. The nontransforming mutants contained amber termination codons in the reading frame for the MT antigen. They synthesized truncated MT antigens which lacked MT-associated protein kinase activity. The cold-sensitive mutants synthesized MT antigens indistinguishable from wild type with regard to size, stability at 32 and 39 degrees C, intracellular location, and associated protein kinase activity. One of the mutants was shown by nucleotide sequence analysis to contain a single amino acid change in the MT antigen, located two residues upstream from the C-terminal hydrophobic region, and no changes in the large T antigen. The other mutant contained two amino acid changes in the MT antigen and two amino acid changes in the large T antigen.

Animals↗
PubMed1984

Construction and expression of a recombinant DNA gene encoding a polyomavirus middle-size tumor antigen with the carboxyl terminus of the vesicular stomatitis virus glycoprotein G.

We constructed a molecular clone encoding the N-terminal 379 amino acids of the polyomavirus middle-size tumor antigen, followed by the C-terminal 60 amino acids of the vesicular stomatitis virus glycoprotein G. This hybrid gene contained the coding region for the C-terminal hydrophobic membrane-spanning domain of the G protein in place of the C-terminal hydrophobic domain of the middle-size tumor antigen. The hybrid gene was expressed in COS-1 cells under the control of the simian virus 40 late promoter. The hybrid protein was located in cell membranes and was associated with a tyrosine-specific protein kinase activity, as was the middle-size tumor antigen. Plasmids encoding the hybrid protein failed to transform mouse NIH 3T3 or rat F2408 cells.

Antigens, Neoplasm↗
PubMed1984

N-terminal amino acid sequences of the polyoma middle-size T antigen are important for protein kinase activity and cell transformation.

We constructed deletion mutations which removed N-terminal coding sequences of various lengths from a cloned polyoma middle-size T antigen (MT antigen) gene. We introduced the MT antigen genes into a simian virus 40 expression vector so that they were expressed at high levels under the control of the simian virus 40 late promoter in COS-1 cells. The deletion mutant genes synthesized truncated MT antigens whose size was consistent with the deletion of either 70 or 106 amino acids from N termini, owing to initiation of translation at internal methionine codons in the MT antigen-coding region. The truncated MT antigens were found in cell membrane fractions but failed to show MT antigen-associated protein kinase activity. The cloned deletion mutant DNAs failed to transform rat F2408 or mouse NIH 3T3 cells. Therefore, N-terminal amino acid sequences of the polyoma MT antigen, as well as C-terminal sequences, are important for protein kinase activity and cell transformation.

Amino Acid Sequence↗
PubMed1982

The noradrenergic innervation of the excretory ducts of the parotid, mandibular and sublingual glands in the rat.

The noradrenergic innervation of the excretory ducts of the parotid, mandibular and sublingual salivary glands in the rat has been examined using fluorescence histochemistry. None of the ducts were found to be innervated directly but, in the mandibular duct, innervated blood vessels are in close proximity to the epithelial cells of the duct and it is suggested that noradrenaline may diffuse from the vascular nerve endings to receptors on the epithelial cells.

Animals↗
PubMed1982

Sites of noradrenergic innervation of the jejunal villus.

1. It has been demonstrated that the upper region of the jejunal villus is supplied with noradrenergic nerves. 2. These nerves are in close proximity to the capillary network underlying the epithelial cells and the lacteal. 3. Hitherto sympathetic innervation of the gut had not been demonstrated to extend further than the crypt region. 4. This evidence allows the proposal that the vasculature and epithelial cells may be involved in the control of absorption from the gastrointestinal tract.

Animals↗
PubMed1982

Non-specific supersensitivity in rat parotid salivary glands following parasympathectomy.

1 The effect of parasympathetic denervation (Px) of the rat parotid salivary glands has been studied. 2 Px produced a significant reduction in wet and dry weight of the parotid gland compared with the intact contralateral control gland. The DNA content per gland was not reduced indicating that cell death had not occurred but that individual cells were smaller. 3 Supersensitivity to both cholinoreceptor and beta-adrenoreceptor stimulation resulted following Px and was observed as a decrease in the threshold dose and an increase in the maximum secretory response. 4 The supersensitivity to beta-adrenoreceptor stimulation was not accompanied by a change in cyclic AMP production but there was an increase in the density of beta-adrenoreceptor binding sites/mg membrane protein. 5 The relationship of this increased density of receptors to the observed supersensitivity is discussed.

Animals↗
PubMed1982

The effect of carbachol and isoprenaline on cell division in the exocrine pancreas of the rat.

The effect of muscarinic cholinergic receptor stimulation on pancreatic acinar cell division has been investigated. Muscarinic receptor stimulation, in addition to causing a 50% depletion of amylase in the pancreas after 4 h, resulted in a 400% increase in the incorporation of [6(-3)H]thymidine 27 h after drug administration. This increase in incorporation was dose-dependent. Autoradiography showed this increase to be due to an increased acinar cell labelling. Isoprenaline also increased the incorporation of [6(-3)H]thymidine into the pancreas but did not reduce enzyme levels. However, with isoprenaline there was no increase in acinar cell labelling. The possibility of a relationship between secretion and hyperplasia of acinar cells in the rat pancreas is discussed.

Amylases↗
PubMed1982

Mutation causing premature termination of the polyoma virus medium T antigen blocks cell transformation.

We used site-specific mutagenesis to introduce a termination codon, TGA, into the reading frame for the polyoma virus medium T antigen. We induced this mutation in a region of the polyoma genome in which the overlapping coding regions for the large and medium TE antigens are translated in different reading frames. Therefore, the mutation terminated translation of the medium T antigen, but it caused only a single amino acid substitution in the large T antigen and did not affect the small T antigen. Cells infected by the mutant virus produced normal-size small and large T antigens. The infected cells produced a 28,000-dalton fragment of the 48,000-dalton medium T antigen, whose size and tryptic peptide map were consistent with its being a truncated N-terminal fragment terminating at the new termination codon of the mutant. Immunoprecipitates of mutant-infected cell extracts did not show medium-T-antigen-associated protein kinase activity. The mutant virus replicated normally in mouse 3T6 cells and induced cellular DNA synthesis in resting mouse 3T3 cells, but it failed to transform rat or hamster cells, as judged by focus formation and growth in agar. The mutant complemented a tsA mutant which affects the large T antigen for transformation, implying that the mutant defect for transformation was in the medium T antigen. These results imply that the small T antigen and the large T antigen together are insufficient to cause transformation and support the conclusion that the medium T antigen is essential for cell transformation by polyoma virus.

Animals↗
PubMed1981

Na+ and K+ concentration of rat parotid saliva. Comparison of carbachol and auriculo-temporal stimulation.

The effects of carbachol and auriculo-temporal stimulation on the Na+ and K+ concentrations of rat parotid saliva have been compared. The main duct perfused in situ, does not transport Na+ or K+ and is water impermeable. The Na+ concentration of secretion evoked by either stimulus is flow dependent, increasing with increasing flow rate and plateauing at near plasma Na+ levels. At low flow rate the carbachol evoked secretion has a higher Na+ concentration. This is not due to the release of catecholamines since neither sympathectomy nor adrenoceptors block altered the nature of the secretion. The K+ concentration, whilst flow dependent, decreasing with increasing flow rate, was the same for both stimuli.

Animals↗