Role of van der Waals, Electrostatic, and Hydrogen-Bond Interactions for the Relative Stability of Cellulose Iβ and II Crystals.

Naturally occurring cellulose Iβ with its characteristic parallel orientation of cellulose chains is less stable than cellulose II, in which neighboring pairs of chains are oriented antiparallel to each other. While the distinct hydrogen-bond patterns of these two cellulose crystal forms are well established, the energetic role of the hydrogen bonds for crystal stability, in comparison to the van der Waals (vdW) and overall electrostatic interactions in the crystals, is a matter of current debate. In this article, we investigate the relative stability of celluloses Iβ and II in energy minimizations with classical force fields.

Critical current for giant Fano factor in neural models with bistable firing dynamics and implications for signal transmission.

Bistability in the firing rate is a prominent feature in different types of neurons as well as in neural networks. We show that for a constant input below a critical value, such bistability can lead to a giant spike-count diffusion. We study the transmission of a periodic signal and demonstrate that close to the critical bias current, the signal-to-noise ratio suffers a sharp increase, an effect that can be traced back to the giant diffusion and large Fano factor.

Characterization of vascular dopamine receptors in the gastric circulation of the rabbit.

An in vivo model is presented for studying the vasodilator effect of dopamine on the gastric vascular bed of the anesthetized rabbit. Dopamine was injected into the common hepatic artery simultaneously measuring the blood flow through the left gastric artery at constant perfusion pressure. The vasoconstrictor response to dopamine was blocked by pretreatment with phenoxybenzamine (0.

Blood flow redistribution by dopamine in the feline gastrointestinal tract.

The effect of intravenous infusion of dopamine (10 and 25 micrograms X kg-1 X min-1 consecutively) on visceral blood flow distribution was examined in anesthetized cats using the microsphere technique and electromagnetic flowmetry. Arterial blood pressure did not change in response to dopamine infusion, but blood flow through the superior mesenteric artery, and blood flow in the mucosa-submucosa of the gastric antrum and various gut segments increased significantly. During infusion of the high dose the increase was most marked in the mucosa-submucosa of the antrum (+355%) and distal colon (+371%).

Dopamine produces vasodilation in specific regions and layers of the rabbit gastrointestinal tract.

The effect of intravenous dopamine infusion (25 and 60 micrograms per kg and min consecutively) on blood flow distribution in the splanchnic region of anesthetized rabbits was studied applying the microsphere technique. During infusion of the low dose, blood flow increased most markedly in the stomach, less in the pancreas, jejunum and descending colon, and decreased in the spleen. In the stomach the increase was confined to the mucosa-submucosa.

Cardiovascular reflexes controlling regional sympathetic outflow during coronary artery occlusion.

In anesthetized rabbits, sympathetic activity was recorded in efferents to the skin of the ear (ESA), to the hindlimb muscles (MSA), splanchnic region (SSA), adrenals (ASA), and kidneys (KSA) in response to occlusion of the left circumflex coronary artery. Coronary occlusion caused an average decrease of mean arterial blood pressure by 18%. MSA and SSA increased, ESA decreased, and ASA, KSA, and heart rate either decreased or increased.

Regional blood flow during paraoxon infusion in rabbits.

In anaesthetized and artificially ventilated rabbits an intravenous infusion of paraoxon (0.8 mg/kg) was given over 30 min. The effects on cardiac output, blood flow to various vascular beds, and on the mass discharge of the postganglionic sympathetic efferents to the spleen and kidney were monitored.

Dopamine-induced diuresis in the cat without changes in renal hemodynamics.

The effects of intravenous (i.v.) and intraarterial (i.

Regional pre- and postganglionic sympathetic activity during experimental paraoxon poisoning.

The effects of 0.4 or 0.8 mg paraoxon/kg i.

Arterial baroreceptor function in differential cardiovascular adjustments induced by central thermal stimulation.

Dogs were anesthetized with sodium pentobarbital, relaxed with succinyl choline and were kept under artificial ventilation. Both carotid bifurcations were denervated and the Vagus nerves were cut in the neck. Regional blood flow in the skin and the intestine, cardiac output, heart rate and arterial pressure were determined before, during and after spinal cord heating and cooling.