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Harvey Cushing and the regulation of blood pressure in giraffe, rat and man: introducing ‘Cushing’s mechanism’

The fundamental mechanism that underlies essential hypertension is a high total peripheral resistance. We review here possible origins of high total peripheral resistance in physiologically hypertensive giraffes, spontaneously hypertensive rats and humans with essential hypertension. We propose that a common link could be reduced brainstem perfusion, as first suggested by Cushing in 1901. Any tendency towards reduction of cerebral blood flow to the cardiovascular control centres in rest and sleep will be prevented by activation of a response arising in

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Kidney of Giraffes

This study focuses on certain aspects of the renal structure of the giraffe, with some implications as to its function. About 4,000 collecting ducts open at the truncated end of a curved crest that juts into the renal pelvis as the inner medulla (IM). Extensions of the pelvis pass between the medullary (MP) and vascular (VP) processes almost to the corticomedullary border. The MPs contain an IM and an outer medulla (OM) containing clusters of capillaries (vascular bundles). The VPs

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An allometric analysis of the giraffe cardiovascular system

There has been co-evolution of a long neck and high blood pressure in giraffes. How the cardiovascular system (CVS) has adapted to produce a high blood pressure, and how it compares with other similar sized mammals largely is unknown. We have measured body mass and heart structure in 56 giraffes of both genders ranging in body mass from 18 kg to 1500 kg, and developed allometric equations that relate changes in heart dimensions to growth and to cardiovascular function. Predictions

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Carotid Haemodynamics in the Giraffe

In a research letter to this journal on the physiology of the giraffe, McCalden et al. suggested that cranial blood flow in the giraffe is regulated by an autoregulatory response of the cranial vasculature. Their conclusion was based on two points: 1) that carotid flow remains constant over a wide range of carotid pressures, and 2) that the giraffe exhibits certain postural behaviour. The argument for (2) is that giraffes always remain resting sternally for a few seconds before standing

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Harvey Cushing and the regulation of blood pressure in giraffe, rat, and man: introducing ‘Cushing’s mechanism’

The fundamental mechanism that underlies essential hypertension is a high total peripheral resistance. We review here possible origins of high total peripheral resistance in physiologically hypertensive giraffes, spontaneously hypertensive rats and humans with essential hypertension. We propose that a common link could be reduced brainstem perfusion, as first suggested by Cushing in 1901. Any tendency towards reduction of cerebral blood flow to the cardiovascular control centres in rest and sleep will be prevented by activation of a response arising in

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Giraffes, Rats, and Man — What is the importance of the ‘structural factor’ in normo- and hypertensive states?

The normal structural adaptation of heart and vessels to regional changes in load or/and tissue demands is surveyed with respect to its importance for cardiovascular function in normotension as well as in physiological (giraffes) and pathophysiological (e.g. human and rat primary hypertension) variants of high pressure states. At the local level it implies an entirely appropriate adjustment of cardiovascular geometric design according to principles inherent in the LaPlace and Poiseuille laws. However, when generalized to all systemic circuits, as in

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