Differential cardiovascular effects mediated by mu and kappa opiate receptors in hindbrain nuclei

To further investigate the role of opioid peptides and specific opiate receptor subtypes in central cardiovascular regulation by hindbrain nuclei, mu (D-Ala²,MePhe⁴,Gly-ol⁵ enkephalin, DAGO), delta (D-Ala²,D-Leu⁵ enkephalin, DADL) or kappa (MRZ 2549) agonists were microinjected into hindbrain nuclei of spontaneously or artificially respired, pentobarbital-anesthetized rats. In the nucleus tractus solitarius (NTS), DAGO and DADL (0.3 nmol) elicited pressor responses and tachycardia. MRZ (3.0–16 nmol) depressed blood pressure in spontaneously breathing rats, but accelerated heart rate in artificially ventilated animals. Blood pressure and heart rate of spontaneously breathing animals were not altered following nucleus ambiguus (NA) injection of DAGO or DADL (0.3 nmol), but were elevated in artificially respired animals; MRZ (3.0–10 nmol) injected into the NA depressed blood pressure in both groups. These data suggest that in the absence of respiratory depression, NTS and NA mu receptors mediate pressor responses and tachycardia; kappa receptors in the NA mediate a decrease in blood pressure but cardioacceleration in the NTS.     

Cardiodynamic response to psychological and cold pressor stress: Further evidence for stimulus response specificity and directional fractionation

In the present study 36 police officers were exposed to a psychological stressor (IQ quiz) and to cold pressor stress while several cardiovascular variables were monitored. Impedance cardiography was used to provide measures of heart rate, stroke volume, cardiac output, myocardial contractility, and total peripheral resistance. In addition, measures of systolic and diastolic blood pressure and peripheral skin temperature were obtained. A multivariate analysis of variance (MANOVA) indicated that significant increases in diastolic and systolic blood pressure during the cold pressor test were mediated by large increases in total peripheral resistance, whereas blood pressure elevation during the IQ quiz were accompanied by significant increases in heart rate and, to a lesser extent, cardiac output. Peripheral skin temperature decreased in response to each stressor. Additional analysis indicated a degree of stimulus specificity for several variables. For example, diastolic blood pressure showed greater increases to cold pressor than quiz, whereas systolic blood pressure increased more with the psychological than the physical stressor. Directional fractionation occurred for both myocardial contractility and cardiac output.     

Changes of intraocular pressure in patients with open-angle glaucoma in relation to the passage of atmospheric fronts and environmental contamination

Effects of atmospheric frontal passages on intraocular pressure (IOP) in patients with open-angle glaucoma are statistically investigated to show the meteorotropism of this disease. Changes in IOP caused by frontal passages are evident; the response is not identical in all the patients near the day of the passage of a warm front, while on the third day following the passage of the front a well pronounced drop in IOP occurs. Anomalous increases of IOP over several months' duration occurred in the years 1986–7. This finding is explained in relation to the hypothesis of environmental contamination in Central Europe by radioactive cesium nuclides due to the Chernobyl accident.     

Drug-Induced Changes in Blood Pressure Lead to Changes in Extracellular Concentrations of Epinephrine, Dihydroxyphenylacetic Acid, and 5-Hydroxyindoleacetic Acid in the Rostral Ventrolateral Medulla of the Rat

Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter and 500 microns in length was stereotaxically implanted in the RVLM of the urethane-anesthetized rat. Sterile physiological Ringer's solution was perfused at a rate of 1.5 microliter/min. The perfusate was collected under ice-cold conditions every 15 min for the assay of epinephrine, dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), ascorbic acid, and uric acid. After stable baseline neurochemical concentrations were achieved, animals were infused with phenylephrine or nitroprusside intravenously to raise or lower the blood pressure. Increasing blood pressure 50 mm Hg above the baseline value by phenylephrine led to a significant reduction in heart rate and a reduction in extracellular epinephrine and DOPAC concentrations. The 5-HIAA concentration was increased during the hypertensive drug infusion. There were no changes in the concentrations of ascorbic acid or uric acid. Hypotension produced by nitroprusside (-20 mm Hg) led to neurochemical changes which were the reciprocal of those seen during hypertension. During hypotension, heart rate increased as did the extracellular fluid epinephrine concentration. The 5-HIAA concentration fell with hypotension and remained depressed following the nitroprusside infusion. Ascorbic acid and uric acid concentrations did not change during hypotension but ascorbic acid did increase after the nitroprusside infusion stopped. These data provide direct evidence that epinephrine release in RVLM is linked to changes in systemic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hydrostatic pressure mimics gravitational pressure in characean cells

Summary Hydrostatic pressure applied to one end of a horizontalChara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca²⁺ concentrations, osmotic pressure, neutral red, TEA Cl^–, and the Ca²⁺ channel blockers nifedipine and LaCl₃. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.     

Cardiovascular and renal effects of eel and rat atrial natriuretic peptide in rainbow trout,Salmo gairdneri

Summary The renal and in vitro vascular effects of atrial natriuretic peptides have been examined in seveal species of fish. However, comparatively few investigations have described the effects of these peptides on the cardiovascular system in vivo. In the present experiments the dorsal aorta and urinary bladder were cannulated and the effects of atrial natriuretic peptides from rat and eel were monitored in conscious trout during bolus injection or continuous atrial natriuretic peptide infusion. The results show that the initial pressor effect of atrial natriuretic peptides is independent of environmental salinity adaptation (fresh or seawater) and the chemical form of atrial natriuretic peptide injected, but it is affected by the rate of atrial natriuretic peptide administration. This pressor response, and the accompanying diuresis, are mediated through -adrenergic activation. Continuous infusion of either rat or eel atrial natriuretic peptide produces a steady fall in mean arterial blood pressure, which is temporally preceded by an increase in heart rate and a decrease in pulse pressure. Diuresis induced by atrial natriuretic peptides is only partially sustained during continuous infusion. Propranolol partially blocks the increase induced in heart rate by atrial natriuretic peptides, but does not affect either pulse pressure or mean arterial pressure. Propranolol significantly increases urine flow in saline-infused animals but has no apparent effect on animals subjected to infusions of atrial natriuretic peptides. These results indicate that there are multiple foci for the action of atrial natriuretic peptides in trout and that in many instances the effects of atrial natriuretic peptides are mediated through secondary effector systems.Abbreviations ANP atrial natriuretic peptide - bw body weight - PBS phosphate-buffered saline     

Chronopharmacokinetics and Cardiovascular Effects of Nifedipine

Orcadian phase dependency in pharmacokinetics and hemodynamic effects on blood pressure and heart rate of different galenic formulations of nifedipine (immediate-release, sustained-release, and i.v. solution) were studied in healthy subjects or in hypertensive patients. Pharmacokinetics of immediate-release but not sustained-release and i.v. nifedipine were dependent on time of day: immediate-release nifedipine had higher C_max (peak concentration) and shorter t_max (time-to-peak concentration) after morning than evening application, and bioavailibility in the evening was reduced by about 40%. Orcadian rhythm in estimated hepatic blood flow as determined by indocyanine green kinetics may contribute to these chronokinetics. A circadian time dependency was also found in nifedipine-induced effects on blood pressure and heart rate as monitored by 24-h ambulatory blood pressure measurements. In conclusion, the dose response relationship of oral nifedipine is influenced by the circadian organization of the cardiovascular system as well as by the galenic drug formulation.     

不同发育时期中华绒螯蟹血淋巴渗透压的分析

中华绒螯蟹血淋巴渗透压随不同的生长阶段而异;不论是在淡水中,还是在不同盐浓度的海水中,都具有保持血淋巴高渗调节控制的能力。青春期前,6—9月份,血淋巴渗透压自390mOsm/Kg H_2O升至560mOsm/Kg H_2O;青春期后,9—12月份,自555mOsm/Kg H_2O升至656mOsm/Kg H_2O,但12月到翌年3月份却明显下降。雌蟹从淡水移入海水后的血淋巴渗透压调升速度,青春期后是青春期前的三倍左右。     

The effect of high hydrostatic pressure on eukaryotic protein synthesis

The pressure response of two eukaryotic protein synthesizing systems has been characterized. The rabbit reticulocyte system has been tested, both in vivo and in vitro, using endogenous polysomes and polyuridylic acid (poly U). In addition, the poly U-directed polyphenylalanine synthesizing system obtained from wheat germ was utilized. The effect of pressure on eukaryotic protein synthesis has been found to be basically similar to that observed in prokaryotic systems, although the response of the eukaryotic protein synthesizing system is somewhat more complex signifying a greater influence of overlapping reactions. Magnesium was found to affect eukaryotic systems in much the same way as has been reported for prokaryotic systems, i.e., increasing the Mg²⁺ concentration in a protein synthesizing system increases the barotolerance exhibited by that system. Under conditions of high Mg²⁺ concentration, however, extreme (up to 160%) stimulation of protein synthesis at lower pressure levels was observed in the eukaryotic systems. Such high stimulation is not apparent in prokaryotic systems. The poly U-directed wheat germ system exhibited the most barotolerant polypeptide synthesis ever seen in our laboratory. This extreme barotolerance was only slightly decreased when the system was tested at reduced concentrations of magnesium.     

Water balance in Collembola and its relation to habitat selection: Water content,haemolymph osmotic pressure and transpiration during an instar

In the two collembolan species Orchesella cincta and Tomocerus minor the water content, haemolymph osmotic pressure and transpiration rate fluctuate with the feeding rhythm during each instar. The changes in water content, however, are due to changes in dry weight, because the absolute water weight stays constant during the instar.The intake of food is probably the cause of the increase in haemolymph osmotic pressure. Increase of osmotically active substances in the blood and/or blood volume reduction may be responsible for the rise in osmotic pressure. This change in osmotic pressure in turn may affect the responsiveness of the animals to water as well as their feeding behaviour.Changes in the epicuticle and in epidermal cell membranes may cause changes in the rate of transpiration. The high rate observed during ecdysis and during the mid-instar may explain the behaviour of the animals in varied water conditions.Dehydration during the instar causes an equivalent rise in osmotic pressure for both Tomocerus minor and Orchesella cincta. The water loss appears to involve the haemolymph. The physiological state of the animal does not influence the rise in osmotic pressure. There are no signs of any osmoregulation in the two species.