The reflex decrease in blood volume of the spleen, the liver, and the intestine of vagotomized dogs was measured by plethysmographic techniques during bilateral carotid occlusion and moderate and severe hemorrhage. The volume of blood mobilized from each organ during carotid occlusion and moderate hemorrhage was from 6 to 30% of their respective blood volumes and from 55 to 81% during severe hemorrhage. In each experimental situation the spleen exhibited the greatest ability to release blood and the intestine, the least. During moderate hemorrhage (9 ml/kg) the spleen yielded a volume equal to 35% of the blood lost, the liver 14% and the intestine 7%. Comparable figures for severe hemorrhage were 26, 13, and 5%, respectively. This order of ranking the component regions of the splanchnic circulation with regard to function as a blood reservoir may be specific for the dog.

SUMMARY A mean decrease of 60% in liver blood volume was recorded by a plethysmographic technique during electrical stimulation of the hepatic nerves in anesthetized, vagotomized dogs. A decrease in pressure in the vascularly isolated carotid sinus to 40 mm Hg, from a mean control of 144 mm Hg, decreased liver blood volume by a mean of 16%; arterial blood pressure increased by a mean of 77 mm Hg. Carotid sini's hypotension was accompanied by respective mean increases of 16% and 1.4% in hepatic arterial and portal venous blood flows, and of 45% and 22% in arterial and portal resistances. Increase in sinus pressure to 240 mm Hg increased liver blood volume by a mean of 20%; arterial blood pressure decreased by 90 mm Hg. Sinus hypertension was accompanied by respective mean decreases of 10% and 1.5% in hepatic arterial and portal venous blood flows, and of 44% and 18% in arterial and portal resistances. Interruption of afferent vagal traffic from cardiopulmonary receptors was maximally effective in decreasing liver blood volume at a carotid sinus pressure of 40 mm Hg and was ineffective at carotid sinus pressures greater than 160 mm Hg. Combined withdrawal of carotid and cardiopulmonary vasomotor inhibition decreased liver blood volume by 42%; of this 37% was due to the cardiopulmonary and 63% to the carotid baroreflex. The study showed the canine liver to function as a blood reservoir by active mobilization of a portion of its blood volume.THE ABILITY of the sympathetic adrenergic system to modify reflexly splanchnic blood flow and blood volume is well documented. "5 Francois-Frank and Hallion 6 used a plethysmographic technique to demonstrate a decrease in liver blood volume in response to direct and reflex stimulation of hepatic sympathetic nerves in the dog. The technique was modified for use in the cat by Griffith and Emery.7 Liver blood volume decreased during pressor reflexes and increased during depressor reflexes; hemorrhage induced a reduction in liver blood volume. The reactions were abolished on cutting the postganglionic fibers of the hepatic plexus. Further evidence for a reflex control of hepatic capacitance vessels was provided by the studies of Heymans et al., 8 who demonstrated a reduction in liver blood volume during bilateral carotid occlusion in the dog. There is thus considerable evidence for a reflex control of hepatic blood volume mediated through alteration in sympathetic adrenergic nerve activity. However, quantitative measurements could not be made in the above studies.Recently, Greenway and Oshiro 9 reported quantitative measurements of the decrease in liver blood volume during direct stimulation of hepatic nerves in the cat and the dog. Maximal responses were obtained at frequencies of about 6 Hz when 50% of the liver blood volume was expelled. The hepatic capacitance therefore was large and, in contrast to the autoregulatory escape that occurred in the hepatic arterial resistance vessels, the contraction of the capacitance vessels was well sustained through the period of stimulation....

Rev Bras Otorrinolaringol. V.67, n.6, 845-51, nov./dez. 2001 Palavras-chave: emissões otoacústicas, ototoxicidade, detecção precoce.

For years teeth of tetraodontoid fishes generally have been considered coalescent even though "coalescence," which also is found in fishes of other families, has never been well defined. This paper deals with some aspects of coalescence of the teeth in tetraodontoids and attempts to define this condition. The sites of osteodentinogenesis and the mechanisms by which hard tissues are formed, reabsorbed, and abraded during feeding were analyzed from semiserial decalcified sections and from ground sections, as well as from autoradiographs of the premaxilla and dentary bones of Sphoeroides greeleyi. The observations reported here, taken together with other data we have obtained on members of the Tetraodontoidei, permit clear definitions of "tooth" and "supporting bone," and consequently the structural meaning of coalescence. From these data we hypothesize how coalesced masticatory structures may have evolved in this group.

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