Light microscopy and computer three-dimensional reconstruction of the blood capillaries of the enamel organ of rat molar tooth germs

We performed a light microscope and a computer three-dimensional reconstruction study of serial sections of the molar enamel organ of 3- and 5-day-old rats perfused with Indian ink through the arterial system. The tooth germs were fixed in Bouin's solution, embedded in paraffin, sectioned and stained with haematoxylin and eosin. For the three-dimensional reconstruction, light micrographs of the serial sections were digitized, and aligned using the serial EM Align software downloaded from http://synapses.bu.edu/tools/. After alignment, the boundaries of the India-ink-filled blood vessels were manually traced with a mouse using the software IGL trace (version 1.26b), also downloaded from the above website. After tracing, a three-dimensional representation of the blood vessel contours was generated in a VRML format and visualized with the help of the software Cortona Web3D viewer (version 4.0) downloaded from http://www.parallelgraphics.com/products/cortona. Our results showed that in regions where ameloblasts are polarized the capillaries are arranged in three distinct levels: (1) penetrating and leaving capillaries in relation to the outer enamel epithelium; (2) capillaries crossing and branching inside the stellate reticulum; and (3) capillaries branching and anastomosing profusely within the stratum intermedium, thereby forming an extensive capillary plexus intimately associated with the cells of the stratum intermedium. The existence of a conspicuous capillary plexus intermingled with cells of the stratum intermedium, as shown in our results, suggests that some molecules produced by cells of the stratum intermedium could be released into the capillary plexus and thereafter carried to the dental follicle.

Effects of subtypes alpha- and beta-adrenoceptors of the lateral hypothalamus on the water and sodium intake induced by angiotensin II injected into the subfornical organ

The present experiments were conducted to investigate the role of the alpha (1A)-, alpha (1B), beta (1),- and beta (2)-adrenoceptors of the lateral hypothalamus (LH) on the water and salt intake responses elicited by subfornical organ (SFO) injection of angiotensin II (ANG II) in rats. 5-methylurapidil (an alpha (1A)-adrenergic antagonist), cyclazosin (an alpha (1B)-adrenergic antagonist) and ICI-118,551 (a beta (2)-adrenergic antagonist) injected into the LH produced a dose-dependent reduction, whereas efaroxan (an alpha (2)-antagonist) increased the water intake induced by administration of ANG II into the SFO. These data show that injection of 5-methylurapidil into the LH prior to ANG II into the SFO increased the water and sodium intake induced by the injection of ANG II. The present data also show that atenolol (a beta (1)-adrenergic antagonist), ICI-118,551, cyclazosin, or efaroxan injected into the LH reduced in a dose-dependent manner the water and sodium intake to angiotensinergic activation of SFO. Thus, the alpha (1)- and beta -adrenoceptors of the LH are possibly involved with central mechanisms dependent on ANG II and SFO that control water and sodium intake. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Interaction between the lateral preoptic area and the subfornical organ in the control of water ingestion caused by cellular dehydration, hypotension, hypovolemia, and deprivation

Water intake was studied in albino rats with lesions in the lateral preoptic area, in the subfornical organ, and in both the lateral preoptic area and the subfornical organ. Drinking was induced by cellular dehydration, hypovolemia, hypotension (isoproterenol or caval ligation), and water deprivation. The animals with lesions in both areas showed a significant reduction in their water intake in response to cellular dehydration. Drinking due to extracellular dehydration was reduced in the animals that received only subfornical organ lesions, and was reduced even further in the animals with both areas ablated. The lesions in the subfornical organ were sufficient to reduce the thirst induced by caval ligation. The lesions in both areas inhibit water intake induced by caval ligation. Water intake induced by deprivation was reduced when both areas were destroyed. These findings demonstrate that both the lateral preoptic area and the subfornical organ are necessary for normal drinking in response to cellular dehydration, hypovolemia, and hypotension. There is further evidence that the lateral preoptic area and subfornical organ interact in the control of water intake induced by a variety of thirst challenges.

Effect of cholinergic and adrenergic stimulation of the subfornical organ on water intake

Cholinergic and adrenergic agonists and antagonists were injected directly into the subfornical organ (SFO), via implanted cannulae, and the volume of water ingested was recorded over a period of 1 hour after injection. Application of 2 nmol carbachol caused intense water intake in 100% of the animals (8.78±0.61 ml), with a very short intake latency. When the 2 nmol carbachol dose was preceded by increased doses of atropine, a progressive reduction in water intake was observed, with complete blockage of the thirst-inducing response to carbachol at the 20 nmol dose level with atropine. Followed by several doses of hexamethonium, the water intake caused by application of 2 nmol carbachol was reduced, although the response was not totally blocked. Injection of 80 nmol of nicotine had a significant thirst-inducing inducing effect in 50% of the animals studied (1.06±0.18 ml) and increase in water intake was further reduced by application of increased doses of hexamethonium. Raising the dose levels of noradrenaline into th SFO caused an increase in water intake although to a lesser degree than was observed after carbachol injection. When the 40 nmol dose of noradrenaline was preceded by increased doses of propranolol (5 to 40 nmol), there was a gradual reduction in water intake, with total blockage at the 40 nmol dose. Application of phentolamine in doses of 10 to 80 nmol caused no reduction in water intake after 40 nmol of noradrenaline. Application of isoproterenol at doses from 20 to 160 nmol into the SFO caused a dosedependent increase in water intake which was blocked by previous applications of propranolol. These results support the hypothesis that the water intake caused by chemical stimulation of the SFO is mainly due to muscarinic cholinergic receptors, although the influence of nicotinic receptors or participation of adrenergic mediation should not be ruled out. © 1984.

Effects of the alpha antagonists and agonists injected into the lateral hypothalamus on the water and sodium intake induced by angiotensin II injection into the subfornical organ

The subfornical organ (SFO) and the lateral hypothalamus (LH) have been shown to be important for the central action of angiotensin II (ANG II) on water and salt regulation. Several anatomical findings have demonstrated neural connections between the SFO and the LH. The present experiments were conducted to investigate the role of the α-adrenergic antagonists and agonists injected into the LH on the water and salt intake elicited by injections of ANG II into the SFO. Prazosin (an α1-adrenergic antagonist) injected into the LH increased the salt ingestion, whereas yohimbine (an α2-adrenergic antagonist) and propranolol (a β-adrenergic antagonist) antagonized the salt ingestion induced by administration of ANG II into the SFO. Previous administration of clonidine (an α2-adrenergic agonist) or noradrenaline into the LH increased, whereas pretreatment with phenylephrine decreased the sodium intake induced by injection of ANG II into the SFO. Previous treatment with prazosin and propranolol reduced the water intake induced by ANG II. Phenylephrine increased the dipsogenic responses produced by ANG II, whereas previous treatment with clonidine injected into the LH reduced the water intake induced by ANG II administration into the SFO. The LH involvement with SFO on the excitatory and inhibitory mechanisms related to water and sodium intake is suggested.

Caring for organ donors: The intensive care unit nurses' view

The nursing care for patients who are pronounced brain-dead but kept alive to serve as organ donors demands technical-scientific skills and the ability to handle situations that are often in conflict with the traditional concepts of nursing care. Based on the phenomenological approach in this article, essential themes of the lived experience of caring for these patients, including the technical and specific nursing care, the relationship with organ donors and their families, and the nurses' perception of themselves in this professional situation are described. The results point to the contradictions and ambiguities of this type of nursing, especially in regards to the affective and philosophical aspects.

Free diet selection by broilers as influenced by dietary macronutrient ratio and corticosterone supplementation. 1. Diet selection, organ weights, and plasma metabolites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)