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Biomedical subjects

A Gibson

Publications and source records attributed to A Gibson.

At least 163 records · Page 9Linked to original sources
PubMed1983

Water drinking and the effect of angiotensin and renin in a dasyurid marsupial (Antechinus stuartii).

Marsupial mice, Antechinus stuartii, were given intraperitoneal (ip) injections of 1-30 micrograms of Val5-angiotensin II amide to determine whether it had any effect on thirst. Drinking in the first hour after injection and measured water intake over 2 and 24 hr were not substantially increased compared with controls. Intraperitoneal injection of sheep renin had no effect on water intake. Water deprivation increased 2- and 24-hr water intake. Sheep renin and Val5-angiotensin II amide elicited pressor responses after ip injection. By comparison, rats given 100 micrograms of Val5-angiotensin II amide ip increased water intake in the first 2 hr after injection compared with saline-injected and noninjected controls. The results suggest that the thirst mechanism in Antechinus is insensitive to exogenous and to low levels of endogenous circulating angiotensin II. The explanation of this difference from other mammals may be found in evidence that the thirst mechanism in species which do not normally drink water in nature is relatively insensitive to exogenous angiotensin.

Angiotensin II↗
PubMed1983

Pharmacology of postsynaptic alpha-adrenoreceptors in the mouse anococcygeus muscle.

1. The alpha-adrenoreceptor agonists noradrenaline (NA), methoxamine, phenylephrine, naphazoline, oxymetazoline, and xylazine produced contractions of the mouse anococcygeus muscle. All were full agonists. 2. Cocaine (2 microM) increased the pD2 values of NA and phenylephrine. 6-hydroxydopamine pretreatment increased the pD2 values of NA, phenylephrine, and xylazine. After both procedures the order of potency of the agonists was oxymetazoline greater than naphazoline greater than NA greater than phenylephrine greater than methoxamine greater than xylazine. 3. The order of potency of antagonists against all six agonists was prazosin greater than phentolamine greater than yohimbine. However, from differences in the pA2 values and slopes of the Schild plots of the antagonists it was possible to distinguish three distinct groups of agonists: the phenylethylamines; the imidazolines; and the thiazine derivative xylazine. 4. The results suggest that the postsynaptic alpha-adrenoreceptor of the mouse anococcygeus muscle may be broadly classified as alpha 1. However, there may be at least three drug recognition sites on the receptor which interact with agonists of differing chemical structure.

Adrenergic alpha-Agonists↗
PubMed1983

Biphasic non-adrenergic, non-cholinergic relaxations of the mouse anococcygeus muscle.

Trains of field stimulation of 60 s duration caused a biphasic relaxation of carbachol (50 microM)-induced tone in the mouse anococcygeus. The optimal pulse frequency and width were 10 Hz and 1 ms respectively. Tetrodotoxin (31, 124, and 310 nM) caused a dose-dependent reduction in the magnitude of both phases. Neither phase was affected by (+/-)-propranolol (1 microM), neostigmine (1 microM), (+)-tubocurarine (100 microM), or apamin (500 nM). Biphasic relaxations were observed in muscles from 6-hydroxydopamine pretreated mice. Haemolysed blood (10, 40, and 100 microliter/ml) reduced the magnitude of the first phase of nerve-induced relaxation to a greater extent than the second. This effect was reversible. Following a prolonged train of inhibitory nerve stimulation (10 Hz; 10 min) the magnitude of the first phase was reduced only slightly, but the second markedly. The possible relationships between the biphasic relaxation to field stimulation and putative non-adrenergic, non-cholinergic transmitters in the mouse anococcygeus are discussed.

Animals↗
PubMed1982

The effects of vasoactive intestinal polypeptide and of adenosine 5'-triphosphate on the isolated anococcygeus muscle of the mouse.

1 Vasoactive intestinal polypeptide (VIP, 0.01- MicroM) produced dose-related relaxations of the mouse anococcygeus muscle. 2 Following incubation with indomethacin (2.8 microM 1 h) adenosine 5'-triphosphate (ATP, 0.5-10 mM) produced dose-related relaxations of the mouse anococcygeus. 3 Haemolysed blood reduced inhibitory responses of the mouse anococcygeus to field stimulation but had no effect on relaxations to VIP or ATP. 4 Apamin (0.5 microM) had no effect on the relaxation of mouse anococcygeus to field stimulation, VIP, or ATP. 5 2-2'-Pyridylisatogen tosylate (PIT, 50 microM) itself reduced muscle tone but it did not abolish inhibitory responses to field stimulation, VIP, or ATP. 6 During prolonged inhibitory nerve stimulation the relaxation of the mouse anococcygeus in response to VIP was reduced greatly while that to ATP was unaffected. 7 Bundles of VIP-immunoreactive sites were detected in sections of the mouse anococcygeus treated by the peroxidase-antiperoxidase (PAP) immunocytochemical technique. 8 The results suggest that the mechanisms underlying non-adrenergic, non-cholinergic inhibitory transmission in the mouse anococcygeus are similar to those in the bovine retractor penis and unlike those in the guinea-pig taenia caeci. 9 The possibility that VIP or ATP might be involved in inhibitory neurotransmission in the mouse anococcygeus is discussed.

Adenosine Triphosphate↗
PubMed1981

The influence of divalent cations and substrate concentration on the incorporation of myo-inositol into phospholipids of isolated bovine oligodendrocytes.

The incorporation of myo-inositol into phosphatidylinositol by two routes (CTP-independent and CTP-independent) has been investigated in homogenates prepared from isolated bovine oligodendrocyte perikarya. The CTP-dependent route has the higher maximum velocity of inositol incorporation and can utilise either Mn2+ or Mg2+ as a divalent ion cofactor. This route of inositol incorporation is also strongly inhibited by Ca2+ ions at concentrations less than 1 mM. The primary site of the inhibitory action appears to be the enzyme CDP-diglyceride inositol phosphatidyl transferase (EC 2.7.8.11) though synthesis of CDP-diacylglycerol is also inhibited by endogenous Ca2+ present in the oligodendrocyte homogenate. In contrast, CTP-independent inositol incorporation into phosphatidylinositol is only stimulated by Mn2+ (Zn2+,Cu2+, Mg2+, Ca2+ and Co2+ are ineffective) and is not inhibited by Ca2+, at least up to a concentration of 1 mM.

Animals↗
PubMed1981

Responses of the isolated anococcygeus muscle of the mouse to drugs and to field stimulation.

1. The responses of the isolated anococcygeus muscle of the mouse to drugs and to field stimulation were investigated. 2. Fluorescence micrographs of transverse sections of the muscle revealed fluorescent nerve fibres in control tissues, but not in tissues from mice pretreated with 6-hydroxydopamine. 3. The isolated muscle displayed no spontaneous tone or rhythmic activity. Field stimulation produced frequency dependent contractions which were blocked by phentolamine and by low concentrations of guanethidine (500 nM). Higher concentrations of guanethidine (30 microM) raised muscle tone and, subsequently field stimulation produced frequency dependent relaxations. In muscles from 6-hydroxydopamine pretreated mice neither field stimulation nor guanethidine produced contractions, but when muscle tone was raised by carbachol inhibitory responses to field stimulation were still observed. 4. Contractions of the muscle were produced by noradrenaline (alpha-adrenoreceptors), acetylcholine (muscarinic receptors), 5-hydroxytryptamine, and prostaglandins E1, E2, and F2 alpha. 5. Adenosine 5'-triphosphate (ATP) normally produced muscle contraction, but following incubation of the tissue with indomethacin, ATP produced relaxations of carbachol-induced tone. 6. Vasoactive intestinal polypeptide, but not bradykinin, produced relaxations of tissues in which tone had been raised by carbachol. 7. The isolated anococcygeus muscle of the mouse provides a useful preparation for the study of various aspects of autonomic neurotransmission in smooth muscle.

Animals↗
PubMed1981

Dental health and treatment needs of 5-year-old children in the health area of Lambeth, Southwark and Lewisham, England.

865 children in their first year of full-time education in the health are of Lambeth, Southwark and Lewisham were examined for dental fitness and treatment requirements. Seventy-six percent of the subjects examined required treatment for dental caries and the mean dmft was 4.85. Sixteen percent of erupted permanent first molars were carious. 404 children had marginal gingivitis. All the treatment required for gingivitis and 82% for caries could be carried out by dental auxiliaries. The need for preventive measures is discussed.

Child, Preschool↗
PubMed1980

Corticopontine visual projections in macaque monkeys.

These experiments were designed to study the projections to the pons from visual and visual association cortex of monkeys by degeneration staining and horseradish peroxidase (HRP) methods. When lesions were made in these cortical visual areas, degenerated fibers were found in the rostral dorsolateral area of the pontine nuclei. When HRP was injected among visually responsive cells in this region of the pons, layer V cortical pyramidal cells were labeled. These labeled cells were concentrated most heavily on both banks of the superior temporal and intraparietal fissures, and on the rostral bank of the parieto-occipital fissure. The efferent targets and receptive field properties of these cortical regions are consistent with their possible role in visual guidance of movement.

Animals↗
PubMed1980

Management of chronic idiopathic urticaria by the identification and exclusion of dietary factors.

The role played by dietary chemical factors in the pathogenesis of chronic idiopathic urticaria (CIU) was assessed in seventy-six patients by challenge Stable remission was first established by using an empirically established 'exclusion diet'. A diet modified to exclude those chemicals giving a positive response to challlenge was demonstrated to be of therapeutic value for time periods of up to 18 months. Re-testing twelve patients at 12 months indicated that most patients positive to salicylate or benzoate challenge retained this pattern of reactivity.

Adolescent↗
PubMed1980

Leucine-enkephalin and methionine-enkephalin produce opposing effects on plasma corticosterone levels in ether-stressed mice.

The inhibitory effects of intracerebroventricular administration of saline on the plasma corticosterone response to ether stress in mice was reduced by Met-enkephalin and enhanced by Leu-enkephalin. When administered simultaneously the effects of the two peptides opposed each other. Met and Leu-enkephalin may subserve different physiological functions in the response of the hypothalamus-pituitary-adrenal system to stress.

Animals↗
PubMed1980

Effects of adrenalectomy and hypophysectomy on enkephalin content of the rat hypothalamus.

1 Hypothalamic content of enkephalin in rats has been measured by bioassay against methionine-enkephalin on field-stimulated mouse vas deferens after acid extraction and purification using Amberlite XAD-2 resin.2 Surgical stress lowered hypothalamic enkephalin content initially but 6 days after operation the content was higher in sham-operated than in adrenalectomized animals.3 Corticosteroid replacement therapy showed that hypothalamic enkephalin content was not related directly to circulating corticosteroid levels and that it was increased by the stress of handling and injection.4 Hypothalamic enkephalin content of rats that had undergone hypophysectomy 11 days earlier did not differ from that of intact animals but surgical stress, which lowered content in intact rats and had no effect after adrenalectomy, produced a rise in content in these hypophysectomized animals.5 The ingestion of 0.9% saline, in place of water, by sham-adrenalectomized rats altered the effect of surgical stress on hypothalamic enkephalin content without affecting the resting levels.6 Of extracts from adrenalectomized rats, 10% contained a substance that behaved atypically on the mouse vas deferens, showing a slower onset and offset of action. The mol. wt. of the substance and sensitivity to naloxone reversal appeared to be similar to enkephalin, but it was resistant to carboxypeptidase-A and protease treatment.7 It is concluded that the enkephalin content of the hypothalamus is affected by activity in the hypothalamus-pituitary-adrenal system but that it is not related in a simple manner to the levels of corticotrophin releasing hormone, corticotrophin or corticosteroids.

Adrenal Cortex Hormones↗
PubMed1980

Visual pontocerebellar projections in the cat.

1. Projections of pontine visual cells onto the cat cerebellar cortex were studied by antidromic activation and by the retrograde transport of horseradish peroxidase (HRP). 2. Cells in the medial pontine visual area, which receive visual cortex projections, were activated antidromically principally from the contralateral cerebellar hemisphere. Cells in the dorsolateral pontine visual area, which receive an input from the superior colliculus, were activated principally from the vermis and ipsilateral hemisphere. There is some overlap in the projections of these two different populations of pontine cells, which probably occurs by way of bifurcated axons. 3. The HRP technique confirmed that there is a major difference in the pattern of projections from these two pontine visual regions. Many cells in the rostral-medial portion of the pontine nuclei, which receive their input from visual cortex, were labeled following HRP injections in the contralateral cerebellar hemisphere. Far fewer of these cells were labeled following vermal injection. Cells in the dorsolateral pontine nucleus, which receive visual input from the superior colliculus, were labeled following an HRP injection in the vermis or the ipsilateral hemisphere. Cells in the region of pontine nuclei that receive input from the ventral lateral geniculate nucleus were also labeled after a vermian injection. 4. If the vermis is related to the control of whole-body movements and the hemisphere to control of ipsilateral limbs, these results suggest that the corticopontocerebellar and the tectopontocerebellar pathways may be involved in different classes of visually guided movement.

Animals↗