The use of the Chandler loop to examine the interaction potential of NXY-059 on the thrombolytic properties of rtPA on human thrombi in vitro.

BACKGROUND AND PURPOSE: Recombinant tissue-type plasminogen activator (rtPA) is the only globally approved treatment for acute ischaemic stroke. Other potential treatments might be administered with rtPA, making it important to discover whether compounds interfere with rtPA-induced lysis. We evaluated methods for examining the effect of the neuroprotectant NXY-059 on the lytic property of rtPA. EXPERIMENTAL APPROACH: Plasma clot formation and lysis in the presence of rtPA and NXY-059 was measured as the change in plasma turbidity. The effect of NXY-059 on rtPA-induced lysis was similarly assessed on preformed clots. Lysis of the thrombus formed in a Chandler loop measured release of fluorescent-tagged fibrinogen that had been incorporated during thrombus formation. Thrombi were exposed to both rtPA and NXY-059 throughout lysis in the presence of 80% autologous plasma and the release of label during lysis was measured. KEY RESULTS: Data interpretation is limited in the clot lysis experiments because either the rtPA was present during clot formation or the drug was added to a clot formed in static conditions. In contrast, thrombi were formed in dynamic flow conditions in the Chandler loop and the time course of lysis in plasma was examined. rtPA increased thrombolysis and the antifibrinolytic trans-4-(aminomethyl) cyclohexane carboxylic acid (AMCA) inhibited lysis. Lysis induced by rtPA was unaltered by NXY-059. CONCLUSIONS AND IMPLICATIONS: The Chandler loop method provides a reliable technique for examining the effect of compounds on rtPA-induced lysis in vitro and demonstrated that NXY-059 does not alter rtPA-induced lysis at clinically relevant concentrations of either drug.

Inhibition of the cortisol response to systemic angiotensin II by forebrain lesions involving the anterior wall of the third ventricle.

The influence of bilaterally narrow, medial forebrain lesions on the increase in plasma cortisol concentration normally seen in response to intravenous angiotensin II was studied in five goats. For comparison, the pre- and post-lesion cortisol responses to intravenous endotoxin were also evaluated. The cortisol response to angiotensin was extinguished in two goats, whereas a slightly attenuated response to endotoxin was still obtained post-lesioning. In these animals the lesions embraced the subfornical organ (SFO), the organum vasculosum of the lamina terminals (OVLT) and the interjacent anterior wall of the third ventricle. In two other goats, in which the SFO was completely destroyed but the OVLT remained largely intact, the lesions caused about 50% reduction of the cortisol response to angiotensin without any concomitant reduction of the response to endotoxin. It is concluded that ACTH-cortisol release in response to systemic angiotensin II is not mediated exclusively by receptors for the octapeptide confined to the SFO. Angiotensin receptors in the OVLT seem to be equally important in this respect.

Water intake and changes in plasma and CSF composition in response to acute administration of hypertonic NaCl and water deprivation in sheep.

Water intake and changes in plasma and cerebrospinal fluid (CSF) composition were measured in response to intracerebroventricular (i.c.v.) and intracarotid infusions of hypertonic NaCl solutions and after 48 h of water deprivation in sheep. Significant interindividual differences in dipsogenic sensitivity to i.c.v. NaCl were found, whereas no such differences were observed in response to intracarotid infusion of hypertonic NaCl. In the more sensitive animals, the increase in CSF [Na] at initiation of drinking during i.c.v. infusion did not differ significantly from the increase in plasma [Na] seen at the thirst threshold during intracarotid infusion of 1 M NaCl. The thirst-eliciting infusions of hypertonic NaCl into the carotid arteries were associated with a small, significant, increase in CSF [Na], which however did not differ from that caused by an i.c.v. non-dipsogenic 'control' infusion of a slightly hypertonic (0.154 M) NaCl solution. Water deprivation for 48 h induced increases in CSF and plasma [Na] similar to those observed at the onset of drinking in response to i.c.v. and intracarotid infusions of hypertonic NaCl. However, the dehydrated animals drank about four times the amount of water consumed in response to the separate treatments with hypertonic NaCl. It is concluded that significant interindividual differences in dipsogenic sensitivity to osmotic stimuli are present in sheep, and that these differences may not necessarily be simultaneously expressed on both sides of the blood-brain barrier. The thirst-eliciting effect of intravascular infusion of hypertonic NaCl may be induced without concomitant increase in CSF [Na] and/or osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)

Repeated hypotension induced by nitroprusside and haemorrhage in sheep: effects on vasopressin release and recovery of arterial blood pressure.

The arginine vasopressin (AVP) release in response to repeated hypotension caused by intravenous (i.v.) infusion of sodium nitroprusside (SNP) or haemorrhage was studied in conscious euhydrated sheep. Parallel determinations of renal excretion and plasma concentration of AVP were made in experiments involving two consecutive 10-min i.v. infusions of SNP (about 35 micrograms kg-1 min-1) with a 3-h interval between and repeated the next day. The AVP response to the second SNP administration was significantly reduced, but partial recovery was observed in response to the initial infusion the next day. Maximal fall in mean arterial blood pressure (MABP) and its recovery pattern did not differ in response to any of the four SNP infusions. In contrast, impaired recovery of the MABP together with markedly reduced AVP response was seen as a consequence of a hypotensive haemorrhage repeated after 3 h, but not when the interval between haemorrhages was extended to 24 h. The haemorrhage-induced increase in plasma renin activity was not affected by variations in the interval between experiments. It is concluded that the massive AVP liberation normally seen as an effect of acute isovolaemic hypotension becomes markedly reduced upon a renewed fall in the MABP occurring within 3 h. An iteration of hypotensive haemorrhage accentuates this fatigue of the hormonal response, which may contribute to the impaired recovery of the MABP.

Aldosterone secretion during acute metabolic and respiratory alkalosis in the goat.

Metabolic and respiratory alkalosis were produced in goats with the primary aim of studying possible influence of a reduced blood hydrogen ion concentration on aldosterone secretion. Metabolic alkalosis was induced by 1 h i.v. infusion of hypertonic tris(hydroxy-methyl)aminomethane (THAM) solution. The infusion was associated with a significant reduction in plasma aldosterone concentration (PA). It occurred in the absence of a detectable fall in plasma K or obvious change in plasma renin activity, but simultaneously with a moderate increase in plasma cortisol concentration and a significant reduction of plasma Na concentration. It suggests that changes of the primary aldosterone regulators were not the cause of the fall in PA, but leaves open the possibility that either the decreased blood hydrogen ion concentration as such or THAM-induced blood hypertonicity reduced the aldosterone secretion. The respiratory alkalosis was due to heat polypnoea elicited by 2 h exposure of the goats to 45 degrees C. Here, no obvious change in PA was observed during the alkalotic period, which, however, was associated with a rise in plasma K. Increased K stimulation may therefore have masked a possible inhibitory influence of the alkalosis upon the aldosterone secretion.

Intracerebroventricular and systemic saralasin used to investigate angiotensin-elicited activation of the pituitary-adrenocortical axis in the goat.

Intracerebroventricular (ICV) infusion of the competitive inhibitor for angiotensin II (AII), saralasin, (13 pmol kg-1 min-1), preceding and outlasting the intravenous (i.v.) infusion of AII (40 pmol kg-1 min-1) extinguished the elevation in plasma cortisol (PC) obtained in response to just the i.v. AII infusion. The corresponding i.v. infusion of saralasin did not visibly influence the AII-induced elevation of PC, whereas bilateral intracarotid infusions of the inhibitor tended to reduce the response. The ICV administration of the inhibitor also significantly reduced the rise in plasma aldosterone (PA) seen as an effect of the i.v. AII. Paradoxically, however, the intravascular infusions of saralasin conspicuously augmented the rise in PA obtained after the simultaneous i.v. infusion of AII. It is concluded that cerebral mediation of the ACTH-cortisol response to systemic AII occurs at sites accessible to inhibition from both sides of the blood-brain barrier, and that also the PA response to blood-borne AII may be to some extent cerebrally mediated.

Endotoxin-induced prostaglandin (PGF2 alpha) biosynthesis, fever and miosis in dexamethasone-treated goats.

Prostaglandin-releasing, adrenocortical, febrile and miotic responses to endotoxin (ET) (E. coli lipopolysaccharide; 0.25 microgram kg-1) were studied in goats with and without prolonged dexamethasone influence. The i.v. injection of ET induced a three-fold peak elevation in plasma 15-ketodihydro-PGF2 alpha at 1.5 h post-injection, that is, between the first and second phase of the temperature elevation. During the latter phase, the plasma concentration of this primary PGF 2 alpha metabolite gradually returned to basal level, which implies that the second phase of ET fever is not PG dependent. The PG response exhibited a similar pattern, but was less pronounced in the dexamethasone-ET experiments, where the duration of maximum temperature elevation and of the miosis became shortened by about 20 min, and the typical biphasic pattern of ET fever was no longer seen. The ET-induced rise in plasma aldosterone concentration was completely blocked by dexamethasone. The corresponding rise in plasma cortisol concentration was prevented for 2 h, but was later only partially inhibited in spite of the repeated dexamethasone treatment.

Miosis and plasma prostaglandin E metabolites during endotoxin fever.

The time course and intensity of miosis accompanying endotoxin (ET) fever was studied in goats concomitant with radio-immunoassay of plasma PGE metabolites. The i.v. injection of ET (E. coli lipopolysaccharide; 0.25 micrograms kg-1) induced a biphasic miosis correlated in time with the biphasic febrile response. Plasma PGE metabolites rose from an undetectable level to a mean of 2 nmol l-1 during the early fever phase, but fell to an undetectable level during the second fever phase in spite of persisting pronounced miosis. Like light-induced pupillary constriction, the ET miosis was antagonized by corneal application of atropine. A corresponding miotic response to ET was obtained also in the sheep. It is concluded that ET-induced miosis requires cholinergic nerve conduction, and that its direct cause is not systemic liberation of PGE. It is suggested that rather some nervous or humoral stimulus developing in conjunction with ET fever acts upon the same brain stem locus as that mediating the pupillary light reflex.

ACTH-mediated aldosterone hypersecretion during endotoxin-induced fever with apparent influence upon renal sodium excretion.

Febrile, endocrine, and renal responses to i.v. injection of endotoxin (E. coli lipopolysaccharide, 0.25 microgram kg-1) were studied in hyperhydrated goats without, and after dexamethasone pre-treatment, performed with the aim of inhibiting the adenohypophyseal secretion of ACTH. As expected from previous investigations, the administration solely of endotoxin induced biphasic fever, pronounced and long-lasting (less than 4 h) elevation of plasma cortisol (PC), and a prompt inhibition of the water diuresis. Apparently the observation that endotoxin also induced a pronounced biphasic elevation of plasma aldosterone (PA) where the two rising phases coincided with the early, and respectively the second elevation in rectal temperature is original. The endotoxin had no obvious influence upon the renal Na excretion for 3 h post-injection, and did not affect plasma renin activity (PRA). After dexamethasone pre-treatment (0.02 mg kg-1, i.v. 75 min prior to endotoxin) the endotoxin-induced rise in rectal temperature initially was less steep and no biphasic pattern of the fever was observed. The PC and antidiuretic responses became delayed for about 2 h and were then much attenuated. Endotoxin-induced rise in PA was no longer observed, and a conspicuous natriuresis developed within 90 min post-endotoxin. It is concluded that endotoxin at the dose used causes liberation of ACTH to such an extent that adrenocortical hypersecretion not only of glucocorticoids, but also of aldosterone occurs. The observed differences in Na excretion suggest that this aldosterone hypersecretion may be of pathophysiological importance as a protection against inappropriate renal waste of Na during the early phase of endotoxin-induced fever.(ABSTRACT TRUNCATED AT 250 WORDS)

Atropine-antagonized miosis induced in the goat by intravenous infusions of prostaglandin E (PGE1 and PGE2).

Effects of 30 min intravenous infusions of prostaglandin (PG) E1 (total dosage 0.07 mg kg-1), E2 and F2 alpha (total dosage 0.12 mg kg-1), respectively, were studied concomitant with measurements of renal excretion of PGF metabolites in hyperhydrated goats. None of the PGs induced any rise in rectal temperature. However, the PGEs elicited pronounced, atropine-antagonized miosis and an inhibition of the water diuresis accompanied by some increase in renal excretion of arginine vasopressin (AVP). These effects were not obtained in response to PGF2 alpha. The PGF2 alpha rapidly induced a conspicuous and long-lasting increase in the renal excretion of PGF metabolites. The corresponding effect of the PGEs was more delayed, and less than 10% of the increase obtained in response to PGF2 alpha. Nevertheless, the excretion of these metabolites in response to the PGEs was of the same magnitude as that previously observed during endotoxin fever in the goat. It is concluded that endotoxin-induced miosis and stimulation of AVP secretion previously demonstrated in the goat might well have been secondary to systemic PGE production. However, this does not seem to hold true for endotoxin-induced fever.

Effects of hay-feeding on acid/base balance, renal sodium excretion, aldosterone and vasopressin secretion in the goat.

Effects of 30 min intense hay-feeding on acid/base and sodium homeostasis were studied in semi-starved goats during hyper- and euhydration. Parallel analyses of carotid and jugular blood samples revealed that feeding induced metabolic acidosis, which to some extent was subjected to respiratory compensation. The acidosis was accompanied by renal sodium retention and urinary acidification persisting for 2-3 h. The sodium retention was succeeded by an increase in renal Na excretion above the initial level. This natriuresis was most accentuated during hyperhydration. Blood samples taken for hormone assays during euhydration revealed a 15% increase in haematocrit and a significant rise in plasma aldosterone at termination of feeding. Inhibition of the water diuresis in hyperhydrated animals, and moderate increases in renal arginine vasopressin (AVP) excretion and plasma AVP were inconsistent effects of feeding. It is concluded, that simply jugular vein blood provides reliable information on the acid/base status of goats, but that the feeding schedule has to be considered in all experiments where small ruminants are used to investigate the integrated control of acid/base and sodium homeostasis.

The prostaglandin-analogue-9-deoxo-16,16-dimethyl-9-methylene-PGE2 inhibits the antidiuretic effect of vasopressin (AVP) in the conscious sheep.

The effects of intravenous infusions of the stable prostaglandin analogue 9-deoxo-16,16-dimethyl-9-methylene-PGE2 (9-methylene-PGE2) in a dosage of 10 or 24 micrograms/min were studied in the consicious euhydrated, dehydrated, and hyperhydrated with the simultaneous administration of exogenous arginine vasopressin (AVP), sheep. The infusions decreased urine osmolality and increased urine flow and renal free water clearance. The results indicate that 9-methylene-PGE2 exhibits its diuretic effect by antagonizing the antidiuretic action of AVP. In the hyperhydrated sheep receiving AVP the syndrome of inappropriate antidiuretic hormone release (SIADH) was simulated. As the prostaglandin analogue effectively blocked the antidiuretic effect of the AVP-administration it appears that 9-methylene-PGE2 may play a future role as a diuretic agent, especially in conditions characterized by water retention and dilutional hyponatremia such as SIADH.

Vasopressin release in response to acute hypotension induced at different time intervals in the conscious sheep.

The renal arginine vasopressin (AVP) excretion in response to acute systemic hypotension induced by intravenous infusion of sodium nitroprusside (SNP) (30-40 micrograms/kg min-1) at different experiment intervals (0, 2, 4, 7 and greater than or equal to 12 days) was studied in the conscious hyperhydrated sheep. During the first post-infusion hour, 2.5 times more AVP was excreted in response to hypotension induced at greater than or equal to 12 day intervals than that observed at intervals of 0-7 days. No interexperimental time dependence of the AVP response to SNP infusion was seen with intervals of 0-7 days. The attenuated AVP release obtained with reduced experiment intervals (0-7 days) was accompanied by shorter antidiuresis and a less accentuated natriuresis during the post-hypotensive period in comparison to what was observed with greater than or equal to 12 day experiment intervals. There were no interval-dependent differences in maximal fall of mean arterial pressure, or onset and recovery of the hypotension induced by SNP administration. It is suggested that acute systemic hypotension causes such a massive AVP release that more than one week is needed for complete restoration of a releasable neurohypophyseal pool of the hormone.

Renal excretion of prostaglandin metabolites, arginine vasopressin, and sodium during endotoxin and endogenous pyrogen induced fever in the goat.

Responses to intravenous injections of an endotoxin (E. coli-lipopolysaccharide, 1 microgram/kg b.wt.) and endogenous pyrogen were studied in euhydrated and hyperhydrated goats. The biphasic febrile response to the endotoxin was associated with a pronounced increase in the renal excretion of measured prostaglandin (PG) metabolites (11-ketotetranor PGF metabolites). This increase was time-correlated with the elevation of the rectal temperature, and (in hyperhydrated animals) with an inhibition of the water diuresis and an increase in renal excretion of arginine vasopressin (AVP). Other effects of the endotoxin were an immediate depression of renal Na and K excretion followed by the development of pronounced natriuresis, and a reduction of plasma Fe and Zn concentrations. The appearance of the febrile reactions (peripheral vasoconstriction and shivering) was accompanied by miosis. The maximum elevation of the rectal temperature was significantly greater during euhydration than during hyperhydration. Also endogenous pyrogen elicited miosis concomitant with febrile reactions, and an elevation of the renal excretion of PG metabolites which was closely correlated in time with the monophasic febrile response, and (during hyperhydration) with temporary inhibition of the water diuresis and an increase in the renal AVP excretion. However, the responses were much weaker than the corresponding endotoxin effects. No appreciable changes in renal excretion of Na and K were observed in response to the endogenous pyrogen. It is concluded that the observed effects on renal cation excretion were manifestations of direct endotoxin influences on kidney function.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation of antidiuretic response to systemic angiotensin II by elevation of CSF NaCl concentration.

The antidiuretic effect of the simultaneous intracerebroventricular (ICV) infusion of 0.24 M NaCl (0.02 ml/min) and intravenous (i.v.) infusion of angiotensin II (12 ng/kg X min) was studied in hydrated goats, and was compared to the antidiuretic effects of the separate infusions. The combined infusions inhibited the water diuresis for 30 min, whereas the separate infusions only reduced the water diuresis by 25% (ICV NaCl) and by 50% (i.v. angiotensin). The combined infusions increased the urine osmolality on the average by 415%. Corresponding increases induced by ICV NaCl and by i.v. angiotensin were 100 and 160%. The results suggest that systemic angiotensin II and elevated CSF NaCl concentration interact and potentiate each other as stimuli for antidiuretic hormone secretion. It is postulated that this synergism may help to preserve body water in hypovolemic conditions associated with hyperactivity of the renal renin-angiotensin system.

Oro-gastro-intestinal inhibition of hypernatremia-induced drinking in the goat.

Reduction of drinking by slow (5 ml/min) administration for 20 min of nearly body-warm (35 degrees C) and cold (15 degrees C) water into the mouth, the abomasum, or the duodenal bulb was studied in goats made thirsty by the simultaneous i.v. infusion of hypertonic (2 M) NaCl at 2 ml/min. During the control experiments the drinking response to corresponding infusion of 1.7 M NaCl was recorded. This in order to eliminate the possible influence on the results of a postabsorptive thirst inhibition which would occur if the administered water was completely absorbed already during the saline infusion. The entrance of warm water into the mouth or into the abomasum caused about 20%, and into the duodenal bulb about 30% reduction of drinking during the infusion of hypertonic NaCl. The corresponding reduction for cold water was when introduced into the mouth and duodenal bulb about 50% and into the abomasum about 60%. Cold water also considerably delayed the onset of drinking. The inhibition obtained during cold water administration was partially compensated for by increased post-infusional drinking. As regards the sensory input underlying preabsorptive inhibition of thirst, it is concluded that (regardless of distension, swallowing, and other mechanical factors) the entrance of pure water into various parts of the alimentary tract contributes to reduce the thirst drive. In addition, stimulation of oral, gastric, and duodenal cold receptors obviously diminish the urge to drink considerably.

Drinking in goats as effect of simultaneous intravenous infusions of angiotensin (I or II) and hypertonic NaCl or mannitol.

Drinking during the simultaneous intravenous infusion of angiotensin I (AI) or II (AII) and hypertonic NaCl or mannitol was studied in the goat, and was compared to the dipsogenic responses to the separate infusion of each of these four factors. Approximately the same amount of water was drunk during the infusion of AI/NaCl, AI/mannitol and AII/NaCl. The amount was roughly equal to the sum of the amounts taken when each of two paired stimuli was infused separately. Significantly less water was drunk in response to AII/mannitol. Somewhat more water was drunk during the separate AI than during the separate AII infusion. Administration of an AI converting enzyme inhibitor completely abolished the AI contribution to drinking during the AI/NaCl infusion but did not reduce AII/NaCl drinking, indicating that the response to AI was entirely due to its conversion into AII. The possibility is discussed that the considerable difference between AI/mannitol and AII/mannitol drinking might have been the result of choroidal and/or ependymal AI converting enzyme activity.

Postoperative evaluation after correction of oesophageal hiatus hernia.

This is mainly a postoperative study of 33 male and female patients operated on for oesophageal hiatus hernia with the same technique, at the same hospital, by four different surgeons over a 5-year period. All the patients were followed up for a mean period of 2.8 years (range 11 months to 4 years 11 months). The patients were personally interviewed about the clinical (subjective) results of the operation and the outcome is compared with pre-operative symptoms. All underwent postoperative radiological examination with barium meal and the results are given. Further investigations on all available patients, who still had symptoms postoperatively, were carried out by oesophagogastroscopy, pH oesophageal reflux and acid perfusion tests. The result of these investigations are presented, evaluated and compared with clinical symptoms.