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The role of neurotransmitters in fat mobilization
Başlık:
The role of neurotransmitters in fat mobilization
Yazar:
Darling, Kathryn Frances, author.
ISBN:
9780438059443
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (264 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: J. D. Findlay.
Özet:
This thesis describes studies of the central neural pathways controlling fat mobilisation and metabolism in sheep, particularly during cold exposure. The introduction to the thesis contains reviews on homeothermy and its central neural control, the physiological response to cold exposure, the sources of substrate available to sheep for oxidation during cold exposure and the neural control of fat mobilisation from adipose tissue during cold exposure. The anatomy of the cerebral ventricle system of the sheep was first investigated so that chronically-prepared cannulae could be "accurately placed for the injection of putative central neurotransmitters into specific cerebro-ventricular sites. Further chronic surgical modifications of the animals were made for physiological recordings and blood sampling, some using established methods and others improving on previous methods. The first experiment was designed to find if the intracerebro-ventricular injection of transmitters that affect fat mobilisation in the body also affect blood pressure and heart rate. It was found that cholinomimetic drugs injected into the third ventricle produced, within seconds, cardiovascular effects reminiscent of peripheral sympathetic nerve stimulation as well as increasing plasma free fatty acid concentration. These results suggested that the cholinomimetics had their effect on synapses close to the third ventricle. Also, the increased circulating free fatty acid level, presumably a consequence of fat mobilisation, was directly produced by the cholinomimetic drugs and not due to reflex sympathetic activity triggered by an initial fall in blood pressure. Third-ventricle-injection of noradrenaline had the opposite effect to cholinomimetics; if the sheep were cold exposed to increase their plasma free fatty acid concentration, blood pressure and heart rate then an injection of noradrenaline produced an immediate fall in all of these measurements. These results on fat mobilisation and cardiovascular performance are consistent with previous reports of the central neural cholinergic stimulation and noradrenergic inhibition of the heat production effector pathway. An increase in plasma free fatty acid concentration is not necessarily the result of an increased rate of release of long chain fatty acid from adipose tissue into the circulation. To obtain evidence that fat mobilisation was increased experiments were carried out which involved the simultaneous measurement of free fatty acid and glycerol concentrations in the general circulation after intra-cerebroventricular injection of cholinomimetic substances. Stearic acid turnover within the circulation was also measured under similar conditions. These experiments showed that free fatty acid and glycerol concentrations increased in proportionate molecular concentrations consistent with fat mobilisation from adipose tissue triglycerides. In addition, the positive correlation found between plasma stearic acid concentration and turnover, following intracerebroventricular injection of cholinomimetic substances, was consistent with an increased mobilisation of free fatty acid, into the circulation and not a reduced rate of uptake from the circulation.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684721.1) | 684721-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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