Central neurogenic control of cerebral blood flow

Abstract

GeneralThe preferred nitrogenous fertilizer in commercial plantations of pineapples is ammonium sulfate, according to JOHNSON (16). When sulfate of ammonia is used, the ammonium ion is oxidized to nitrate by soil microbiological activity, with an associated increase in soil acidity which renders iron more soluble. At the same time, both ammonium and nitrate ions are generally simultaneously available to the pineapple roots. Sodium nitrate is generally inferior and usually produces an atypical light-green color in leaves and unripe fruit of the pineapple. Wh-en sodium nitrate is used under dry conditions, however, there may be accumulation of sodium bicarbonate in the soil as reported by lr and THOMAS (17) caused by a greater rate of uptake of nitrate than of sodium by roots and by soil microflora, a phenomenon likely to cause precipitation of iron in the soil and associated plant chlorosis. Efficient nitrogen fertilization of pineapple plants depends greatly on an understanding of the interrelation hips of nitrate and ammonium ions with (a) the inorganic nutrient complex of the soil, that is, the relative concentrations of nutrient elements other than NO,or NH4+;(b) the activities of the microflora in the soil; and (c) shifting of pH values, and changes of temperature and moisture affecting the concentrations of these ions in the soil. It is also important to know the nitrogen requirements of plants at different growth stages on the basis of nitrogen inventories within the soil and plant tissues. This paper reports plant weights attained by one-year-old Ananas comosus grown in solution cultures with 140.0 or 2.8 mg. of nitrogen in nitrate or ammonium form and the content of ash, water, relative electrical resistance, potassium, calcium, magnesium, phosphorus and iron in the tissue.

Cholinergic Control of Blood Flow in the Cerebral Cortex of the Rat

“…10 ' n However, recent reports indicate that stimulation of discrete sites within the brain stem can induce cerebral vasodilation. 12 ' 13 On the other hand, several reports point to the idea that the cerebrovascular action of inhaled CO 2 might be indirect, as it can be blocked by transection 14 or localized lesions 15 of the brain stem. These facts suggest the existence of central neurogenic mechanisms in the control of cerebral blood flow, but little Departamento de Ciencias Fisiol6gicas, Facultad de Ciencias Medicas, Universidad de Rosario, Santa Fe 3100, Rosario, Argentina.…”

Acute Brain Swelling Complicating Insertion of Needle Electrode into Hypothalamus and Brain Stem

“…Acute transudation of water into perivascular spaces with resultant increase in CVR is another possibility, as acute increase in wa ter content of tissue within a few minutes was possible in other situa tions [6]. The location which produced brain swelling distinctly differed from previously reported centers of CBF and metabolism [1]. Lesions which produced pulmonary edema are situated more rostrally than brain swelling centers [7].…”

“…Arteriovenous difference of oxygen was moni tored with the Guyton analyzer. Arterial and cerebral venous p 0 2, pC02, and pH were analyzed by appropriate electrodes with the aid of extracorporale circulation [1], The blood pressure (BP) was recorded at the brachial artery. End-tidal C 02 was monitored by a Beckman infrared gas analyzer.…”

“…This paper deals with acute brain swelling follow ing insertion of a bipolar electrode, 0.2X2 mm in diameter, into the hy pothalamus or brain stem in four animals in a series of 360 stimulations using 25 monkeys in a stimulation study for other purposes [1]. …”

FOS Induction in Brain Associated with Seizure and Sustained Cortical Vasodilation in Anesthetized Rat

“…In contrast to the lower brainstem, which is activated in both WDSA-and GCSA-stimulated rats, the sustained cortical vasodilation elicited by GCSA cholinergic stimulation is associated with a moderate bilateral increase in c-fos expression in the posterior and anterior lateral areas of the hypothalamus, the amygdala, and the insular cortex, which does not occur during WDSA stimulation. The Fos immunoreactivity found in the hypothalamic anterior and posterior lateral areas appears to be of particular interest because previous studies, although lacking precise anatomic controls, showed that stimulation of the posterior hypothalamus may elicit a cerebral vasodilatory response (61,62). Thus it is conceivable that neurons in the lateral hypothalamic area may be implicated in maintaining adaptive long-lasting cortical vasodilation during convulsive epilepsy.…”