The plateau wave, one of the wave forms observed in patients with increased intracranial pressure, has previously been extensively investigated, but its pathophysiological aspect is as yet unclear. The authors undertook a study of cerebral hemodynamic changes while the plateau waves were observed in five brain-tumor patients. Although the number of cases studied was small, a remarkable decrease in cerebrovascular resistance was seen in all patients during the plateau waves. It is suggested that the plateau waves are caused by a marked cerebral vasodilatation. The present results support the thesis that cerebral blood volume is increased during the plateau waves. The plateau waves are closely related to the intrinsic vasomotor control of cerebral circulation, and can occur as long as cerebral vasodilating ability is maintained, irrespective of the existence of cerebral autoregulation.
Vascular architecture and the structure of the intestinal hematopoietic centers of two cyclostomes, the hagfish Eptatretus burgeri and the ammocoetes larva of Entosphenus reissneri, are compared. Blood cells of the hagfish are generated in hematopoietic nests that develop around intestinal veins established primarily for transport of absorbed nutrients. In ammocoetes, on the other hand, blood cells are generated in hematopoietic nests of the typhlosole, closely associated with venous sinusoids developing around the longitudinally oriented mesenteric artery of the typhlosole. A collateral vein of the mesenteric artery is completed in the typhlosole after metamorphosis. Since the spleen of higher vertebrates develops in relation to establishment of the collateral vein of the largest foregut artery, the intestinal hematopoietic nests of ammocoetes may be regarded as a model of the primitive form of the spleen of higher vertebrates. Hematopoiesis in the hagfish intestine is not related to establishment of a collateral vein; hence "primitive spleen" or "intestinal spleen" may be improper terms in reference to the intestinal hematopoietic tissue of the hagfish. Morphological characteristics of the hematopoietic nests of the two cyclostomes are essentially the same. Blood cells of these nests are generated in the intervenous tissue, supported by interstitial connective tissue cells and reticulin fibers. Granulated cells are the most common type in the primitive hematopoietic nests. No definitive erythrothrombocytopoiesis has been identified. Lymphocytes have not been observed in the hagfish; however, small lymphocytes have been observed in the vascular lumen of sinusoids around the hematopoietic nests of ammocoetes. These lymphocytes probably originate outside of the typhlosole.
We examined the effects of liposome-encapsulated hemoglobin, neo red cells (NRCs), on hemorrhagic shock in a canine model. The dogs were divided into the three groups according to treatment. In group 1, composed of six dogs, NRCs were substituted for blood without shock being induced; in group 2, composed of six dogs, NRCs were administered immediately after mild shock had been induced by exsanguination through the vein; and in group 3, composed of seven dogs, NRCs were administered after they had been left untreated for 30 min inducing severe shock. In group 2, administration of NRCs at a dose equivalent to the volume of exsanguinated blood improved the symptoms of shock; however, in group 3, a dose of NRCs 1.6-times the volume of exsanguinated blood was required. Peripheral vascular resistance (PVR) decreased after NRC administration in groups 1 and 2, but increased in group 3. On the other hand, the cardiac index (CI) increased in groups 1 and 2, and decreased in group 3. Concerning oxygen kinetics, there were no increases in the oxygen requirements or arteriovenous differences of the oxygen content per hemoglobin (AV/Hb) for NRCs in groups 1 and 2. Conversely, in group 3, the oxygen requirements increased and the NRCs compensated for the decrease in CI with an increase in AV/Hb by enhancing the oxygen transport efficiency to cope with the increased oxygen requirements.
We examined the effects of liposome-encapsulated hemoglobin, neo red cells (NRCs), on hemorrhagic shock in a canine model. The dogs were divided into the three groups according to treatment. In group 1, composed of six dogs, NRCs were substituted for blood without shock being induced; in group 2, composed of six dogs, NRCs were administered immediately after mild shock had been induced by exsanguination through the vein; and in group 3, composed of seven dogs, NRCs were administered after they had been left untreated for 30 min inducing severe shock. In group 2, administration of NRCs at a dose equivalent to the volume of exsanguinated blood improved the symptoms of shock; however, in group 3, a dose of NRCs 1.6-times the volume of exsanguinated blood was required. Peripheral vascular resistance (PVR) decreased after NRC administration in groups 1 and 2, but increased in group 3. On the other hand, the cardiac index (CI) increased in groups 1 and 2, and decreased in group 3. Concerning oxygen kinetics, there were no increases in the oxygen requirements or arteriovenous differences of the oxygen content per hemoglobin (AV/Hb) for NRCs in groups 1 and 2. Conversely, in group 3, the oxygen requirements increased and the NRCs compensated for the decrease in CI with an increase in AV/Hb by enhancing the oxygen transport efficiency to cope with the increased oxygen requirements.
Effects of cholinergic inhibition by atropine on cerebral circulation were studied in 15 baboons anesthetized with sodium pentobarbital. Intravertebral infusion of atropine, 0.1 mg/kg, did not cause any changes in cerebral blood flow (CBF), superior sagittal sinus wedge pressure (SSWP), epidural pressure (EDP), cerebral perfusion pressure, or cerebral vascular resistance under normal conditions. Cerebrovascular responsiveness to carbon dioxide (CO2) inhalation was not influenced by atropine. The presence of cholinergic nerve fibers has been proved in the cerebral blood vessels and the existence of cholinergic mechanism suggested in the brain stem, but it is not likely that the cholinergic nerves have tonic control of cerebral blood vessels in the resting state or affect cerebrovascular responsiveness to CO2. The changes in EDP and those in SSWP showed a very good correlation to each other. There was also a good correlation between the changes in CBF and those in EDP or SSWP.
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