Assertiveness predicts threat and challenge reactions to potential stress among women.

In this study assertiveness as a moderator of stress reactions among women was examined. Specifically, the experimenters examined how high and low assertive women cognitively appraised, affectively and physiologically responded to, and behaviorally coped with the stress of giving an impromptu speech. High assertive women appraised the speech stressor as challenging, whereas low assertive women appraised the stressor as threatening. High assertive women also had a challenge pattern of autonomic response during the task, compared with the threat response of low assertive women. Afterward, the high assertive women reported experiencing less stress and negative emotion and greater positive emotion than did the low assertive women. Overall, the high assertive women's stress-related reactions indicated challenge, whereas the low assertive women's reactions indicated threat (see J. Tomaka, J. Blascovich, R. M. Kelsey, & C. L. Leitten, 1993).

The effects of repeated occlusion measurement on blood pressure and pulse rate.

We examined the effects of repeated occlusion measurement on blood pressure and pulse rate during rest and during mental arithmetic stress. Participants performed two rest-and-task sequences. We took automated blood pressure readings during each minute of one rest-and-task sequence (i.e. all-minutes measurement strategy), and during every other minute for the other sequence (i.e. odd-minutes measurement strategy). Each rest-and-task period was 5 min long and we counterbalanced the two rest-and-task sequences for order. Overall, baselines, task levels and reactivity scores were highly similar across the two measurement strategies. We did, however, find small but reliable measurement strategy effects that interacted with task novelty, particularly for DBP. Specifically, DBP levels and reactivity were lower during the all-minutes measurement strategy compared to the odd-minutes strategy, particularly during the second of two repeated tasks. We observed a similar trend for systolic blood pressure, but did not for mean arterial pressure or pulse rate. Our significant effects were small, however, and they should not overshadow the high degree of similarity of results produced by the two measurement strategies.

Determination of transepithelial (mucosal and serosal) electrical potentials in toad skin. Action of chemical agents.

1. Potential differences across the mucosal or outer, and the serosal or inner, membranes of the toad skin (M and S) were recorded separately. Total potential difference across the skin (T) and the short-circuit current (SCC) were recorded by means of the classical Ussing method. 2. The independent determination of the M and the S is of importance in the elucidation of the mechanism of action of agents which alter ion fluxes across the skin. 3. The percentage values of the M and the S obtained in toad skins during the summer were similar to the percentage values obtained by microelectrode impalement of cells. 4. Angiotensin II (AII) and antidiuretic hormone (ADH) increased T with a notable rise in M and a slight increase in S. These agents act mainly by increasing mucosal membrane permeability to Na+ since M is principally affected. 5. Amiloride and ouabain reversed M, decreased T and increased S above T. The reversal of M might be explained by the flow of a cation to the mucosal aspect or of an anion to the cell interior. 6. These results show that the effects of several agents on the toad skin potential may be analysed independently across the mucosal and serosal membranes and reflect the behaviour of the entire tissue rather than of a single cell.

Diuretic, natriuretic and hypotensive effects produced by Allium sativum (garlic) in anaesthetized dogs.

Gastric administration of encapsuled garlic powder to anaesthetized dogs induced dose-dependent (2.5 to 15 mg/kg) natriuretic and diuretic responses which reached maximum 30-40 min after garlic administration and decreased to basal levels after 100-150 min. A simultaneous decrease in arterial blood pressure was observed which continued past the 250 min-mark. High garlic doses (15 and 20 mg/kg) provoked bradycardia and T-wave inversion during the first 10-15 min of the experiment with recordings returning to normal and staying normal throughout the remainder of the experiment.

Inhibitory effect of garlic (Allium sativum) on sodium transport in isolated toad skin.

The effect of an aqueous fraction from the bulbs of Allium sativum (GE) was investigated in toad skin. When added to the inner (serosal) solution, GE caused a maximal reversible reduction of the transepithelial potential difference and short circuit current of 38% and 45%, respectively. When added to the outer (mucosal) solution, the effect was only partially reversible. Isaacson's amiloride test showed that GE decreased sodium potential (ENa.) and sodium conductance (GNa.). The net Na+ flux decreased due principally to a fall in Na+ flux in the active direction. GE decreased Na(+)-K+ ATPase activity in vitro. Partial replacement of sodium by choline in the outer solution reduced the effect of GE on the skin and substitution of normal Ringer's solution with isethionate Ringer's solution in the outer solution significantly enhanced the effect of GE on the skin. These results indicate that GE decreases active Na transport in the toad skin.

Possible mechanism of the stimulatory effect of 4-aminopyridine on toad skin.

1. This study was undertaken to demonstrate the facilitatory effects of 4-aminopyridine on transmitter release in the toad skin preparation. 2. A dose-dependent increase in the bioelectric parameters was found. 3. This effect was blocked by propranolol and by verapamil but not by dibenamine, and was mimicked by the calcium ionophore A-23187 but not by potassium channel blockers. 4. These results support the hypothesis that 4-aminopyridine increases presynaptic nerve terminal permeability of calcium and thus the release of noradrenaline.

Comparative effects of catecholamines, angiotensin II and antidiuretic hormone on chloride transport in toad skin.

In this work we present data which show stimulation of Cl- transport in the isolated toad skin by four agonists: L-isoproterenol, L-adrenalin, angiotensin II and ADH. This response was demonstrated by raising mucosal amiloride concentration to block the sodium transport in the skin. With transepithelial sodium influx almost completely inhibited, it was likely that the response reflected transport events in the glands. Inhibition of the bioelectric parameters by removing chloride from the serosal bathing medium in the amiloride-inhibited preparation eliminated the response to all four agents, indicating that these responses are chloride dependent. The similarity of the bioelectric responses of the amiloride-treated preparation to db cAMP and to the four agents tested in this work add further evidence that this second messenger may account largely for the Cl- transport mechanism in the toad skin glands by increasing the apical membrane permeability to Cl-.

Fenoterol stimulation of sodium transport in the isolated toad skin: a beta adrenergic effect.

1. This work examines the effects of fenoterol on the isolated skin of the Chilean toad Pleurodema thaul. 2. A dose-dependent increase in the potential difference and in the short-circuit current of the skin was found. Furthermore, sodium potential (ENa) and sodium conductance (GNA) also rose. 3. The increase in bioelectric parameters was reversibly blocked by propranolol, was not significantly affected by reserpinization and was not calcium-dependent. 4. The skin response was significantly reduced in the presence of low Na+ in the outer bathing solution. Although the response was also reduced in the presence of isethionate Ringer's in the inner bathing solution, this reduction was less than the decrease in the presence of low Na+. 5. Fenoterol significantly increased toad skin oxygen consumption and net Na+ movement across the skin due to an increase in Na+ flux from mucosa to serosa. 6. These results show that fenoterol enhances active transport across the isolated toad skin probably through beta adrenergic stimulating effects which activate the sodium driving force, sodium conductance and net Na+ transepithelial flux.

Determination of the driving force for the sodium pump (ENa) and of active and passive conductances (GNa and Gsh) in isolated toad skin: influence of antidiuretic hormone.

1. Values of the sodium potential (ENa), active conductance (GNa) and passive conductance (Gsh) were measured in the isolated skin of the toad Pleurodema thaul placed in an Ussing chamber, and Isaacson's test was performed with 2,4,6-trieminopyrimidine (TAP) and with amiloride. 2. The numerical estimates obtained in the presence of TAP were ENa 122.85 +/- 15.17 mV, GNa 0.493 +/- 0.09 mS/cm2 and Gsh 1.145 +/- 0.23 mS/cm2. 3. After exposure to ADH these values were as follows: ENa 85.76 +/- 12.17 mV, GNa 1.191 +/- 0.20 mS/cm2 and Gsh 0.935 +/- 0.14 mS/cm2. 4. Addition of 0.5 x 10(2-) TAP produced a 53.90 +/- 5.10% decrease in transepithelial potential and a 37.90 +/- 4.90% fall in short-circuit current. 5. Exposure to ADH increased the transepithelial potential difference 34.20 +/- 13.20% and the short-circuit current to 78.00 +/- 20.50% above the control values. 6. Comparison of the efficiency and mechanism of action of TAP and amiloride in the determination of electrical parameters shows that both agents induce a similar decrease in Gsh, a finding which could indicate that TAP blocks toad skin apical membrane Na+ channels without affecting tight junction conductance.

Effects of antidiuretic hormone on the electrical properties of canine tracheal epithelium.

The canine tracheal epithelium causes net transport of Cl- from serosa to mucosa and of Na+ from mucosa to serosa. These processes are manifested by the short-circuit current which represents the algebraic sum of both fluxes. Antidiuretic hormone (ADH) alters the permeability of several epithelia. This work examines the effect and possible mechanism of action of ADH on the potential difference (PD), short-circuit current (ISC) and conductance (G) of canine tracheal epithelium. The epithelium was mounted in Ussing-type chambers containing Krebs-Henseleit solution at 37 degrees C (pH 7.4) and bubbled with 95% O2 and 5% CO2. PD was recorded on an Cole-Parmer recorder by means of the classical technique and ISC was recorded automatically using a voltage clamp. ADH (mucosal surface) significantly decreased PD, ISC and G in a dose-dependent fashion. Similar doses of ADH applied to the serosal side did not produce a significant effect. Angiotensin II (Agt II, serosal side) and amphotericin B (mucosal side) reversed the depressor effect of mucosal ADH. The effect of ADH was less when the Cl- serosa to mucosa movement was blocked by pretreatment with serosal furosemide. It is considered that ADH blocks apical membrane Cl-channels and that angiotensin reverses this effect by increasing apical membrane permeability to Cl-. Amphotericin B reverses the effect of ADH possibly by increasing Na+ absorption.

Effect of bovine heart atrial natriuretic and diuretic fractions on sodium transport in isolated toad skin.

The effects of two bovine heart atrial fractions (AF I and AF II) were investigated in toad skin. When added to the inner (serosal) solution, AF I caused a maximal reversible depression of the transepithelial potential and short-circuit current of about 60% and AF II induced maximal decline of these parameters of only 35%. When added to the outer (mucosal) solution, the effect of both fractions was often only partially reversible. Isaacson's amiloride test showed that AF I decreased the numerical estimates of all the components in the electrical equivalent circuit. The net Na+ flux decreased due to a fall in Na+ flux in the active direction. Incubation with Ca2+-free Ringer's solution decreased and Ca2+ ionophore A 23187 increased the effect of AF II. Partial replacement of sodium by choline in the outer solution slightly reduced the effect and substitution of normal Ringer's solution with sulfate or isethionate Ringer's solution in the outer solution significantly enhanced the effect of the AF. These results indicate that bovine heart atrial natriuretic fractions decrease the sodium potential (ENa), sodium conductance (GNa) and passive conductance (Gsh). The fall in net Na+ transport measured with sodium tracer fluxes confirms the decrease in ENa and GNa.

Effects of a low concentration of ethanol on the potential difference of mucous-secreting glands of the toad Pleurodema thaul.

The effect of noradrenaline on the bioelectric activity of the mucous glands of 9 toads was studied by means of intraglandular recording. Noradrenaline induced a transient increase in glandular secretion and a simultaneous two-phase increase in the potential difference of the glands. Perfusion with 0.043 mM ethanol-Ringer's reversibly reduced this response. Ouabain, in concentrations which block Na+K+-activated ATPase, markedly reduced the slow phase of the response of the 'isolated skin to noradrenaline. The results suggest that ethanol acts in two ways: first by increasing the electrical resistance of the skin and secondly by partially inhibiting the active transport of sodium due to a decrease in permeability of the apical membrane of the transporting cells.