Nutritional aspects of high-altitude exposure in women.

The nutrient intake and urinary excretion characteristics of eight young university women were studied over a 4-day period at low altitude (140 m) and subsequently over a 7-day sojourn on Pikes Peak (4,300 m). High-altitude exposure was associated with a transient decrease in the consumption of protein, carbohydrate, fat, sodium, calcium, phosphorus, vitamin A, riboflavin, thiamin, and niacin and a more sustained decrease in the consumption of potassium and ascorbic acid. In most instances minimal values were observed during the first 3 days of exposure. The carbohydrate fraction of energy intake was increased at the expense of fat during this time period. Individual hypophagic responses appeared to be related to severity of acute mountain sickness. Altitude had no effect on water consumption but did lead to an average body weight loss of 1 kg. Urinary measurements revealed a marked oliguria during the entire sojourn. These measurements also showed the first 3 days to be associated with a net loss of body nitrogen and sodium. During this time period body potassium and phosphorus were conserved, and probably increased. The urea fraction of body potassium and phosphorus were conserved, and probably increased. The urea fraction of total urinary nitrogen was not affected by altitude exposure, nor was the daily excretion of uric acid and creatinine. Ammonia excretion, however, was reduced to 50% of the low-altitude value and remained at this level throughout the sojourn. With a few exceptions, the qualitative characteristics of altitude hypophagia in women were similar to those reported for men. Quantitatively, however, the responses were much more transient in women.

Somatostatin sst2 receptor knock-out mice: localisation of sst1-5 receptor mRNA and binding in mouse brain by semi-quantitative RT-PCR, in situ hybridisation histochemistry and receptor autoradiography.

The peptide hormone/neurotransmitter somatostatin (somatotropin release inhibiting factor; SRIF) and its receptors (sst(1)-sst(5)) appear to regulate many physiological functions in the CNS. Semi-quantitative analysis of the densities of mRNA expression for sst(1-5) receptors and SRIF receptor binding sites were established in sst(2) receptor knock-out (KO) mice. Patterns of sst(1-5) receptor mRNA expression were largely conserved for sst(1,3,4) and sst(5) selective oligonucleotide probes; whereas sst(2) signals were completely absent in KO mouse brain. Autoradiographic analysis demonstrated [(125)I]LTT SRIF(28), [(125)I]CGP 23996 (two radioligands known to label all five recombinant SRIF receptors) and [(125)I]Tyr(3)-octreotide (sst(2) and sst(5) receptor selective) binding in wild type (WT) mouse brain sections; yet no specific binding of [(125)I]Tyr(3)-octreotide in KO mice. In contrast, [(125)I]LTT SRIF(28) and [(125)I]CGP 23996 binding was still present in a number of brain areas in KO mice, although to a lesser degree than in those regions where [(125)I]Tyr(3)-octreotide binding was found, in WT animals. The present data suggest first, that both sst(2) receptor protein and mRNA were completely absent in the brain of these KO animals. Second, there was little evidence of compensatory regulation, at the mRNA level, of the other SRIF receptors as a consequence of the sst(2) KO. Third, the absence of any [(125)I]Tyr(3)-octreotide binding, in KO mice, suggests that this particular ligand is selective for the sst(2) receptor subtype (under the conditions utilised); or that sst(5) receptors are only marginally expressed in brain. Fourth, there were regions where the binding of [(125)I]LTT SRIF(28) and [(125)I]CGP 23996 were moderately affected by the sst(2) KO, suggesting that additional SRIF receptors may well contribute to the binding of the aforementioned radioligands. Finally, since the relative distribution of these two ligands were not entirely superimposable, it suggests that their respective selectivity profiles towards the different SRIF receptor subtypes in situ are not identical.

A role for mast cells in adenosine A3 receptor-mediated hypotension in the rat.

1. The adenosine A3 receptor agonist, N6-2-(4-aminophenyl)ethyladenosine (APNEA) induces hypotension in the anaesthetized rat. The present experiments were carried out to explore the role of mast cells in the response. 2. Intravenous injection of APNEA (1-30 micrograms kg-1 to rats in which the A3 receptor-mediated response had been isolated by pretreatment with 8-(p-sulphophenyl) theophylline (8-SPT)), induced dose-related falls in blood pressure accompanied at higher doses by small falls in heart rate. Responses to the mast cell degranulating agent, compound 48/80 (10-300 micrograms kg-1, i.v.) were qualitatively similar to those to APNEA. 3. Pretreatment with sodium cromoglycate (0.25-20 mg kg-1, i.v.) induced dose-related, although incomplete, blockade of the hypotensive responses to APNEA. At 20 mg kg-1, sodium cromoglycate also inhibited the cardiovascular response to compound 48/80 but had no effects on those to the selective A1 receptor agonist, N6-cyclopentyladenosine (CPA) or the selective A2A receptor agonist, 2-[p-(2-carboxyethyl)phenylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680). Lodoxamide (0.01-20 mg kg-1) also blocked selectively but incompletely the response to APNEA. 4. The cardiovascular responses to compound 48/80 (10-300 micrograms kg-1, i.v.) were markedly suppressed in animals which had received repeated doses of the compound by the intraperitoneal route. Similarly APNEA was essentially devoid of cardiovascular activity in such preparations. In contrast, responses to CPA were similar in animals treated repeatedly with compound 48/80 to those obtained in control animals. 5. Plasma and serum histamine concentrations were markedly increased associated with the pronounced hypotensive responses induced by intravenous injections of APNEA (30 or 100 microg kg-1) in the presence of 8-SPT, or compound 48/80 (300 microg kg-1).6. Taken together the data implicate the mast cell in a key role in adenosine A3 receptor-mediated hypotension in the anaesthetized rat.

Airway hyperresponsiveness to adenosine induced by lipopolysaccharide in Brown Norway rats.

We have explored the effects of bacterial endotoxin (lipopolysaccharide; LPS) on the response of the airways of Brown Norway (BN) rats to adenosine. Comparisons have been drawn with the effects on responses to methacholine and 5-hydroxytryptamine. In vehicle-challenged animals, adenosine, given i.v. was only a weak bronchoconstrictor. In contrast, 1 h following intratracheal administration of LPS, 0.3 mg kg-1, bronchoconstrictor responses to adenosine were markedly and selectively enhanced. At this time point, there were no significant changes in leukocyte numbers, eosinophil peroxidase and myeloperoxidase activities or protein concentrations in bronchoalveolar lavage (BAL) fluid. Twenty-four hours after challenge, the sensitivity of the airways to both adenosine and methacholine was reduced relative to the earlier time point and there were substantial increases in each marker of inflammation in BAL fluid. The bronchoconstrictor response to adenosine was blocked selectively by methysergide, disodium cromoglycate and the broad-spectrum adenosine receptor antagonist, 8-SPT, but not by DPCPX or ZM 243185, selective antagonists for the A1 and A2A receptors, respectively. Thus, the response to adenosine augmented following LPS is mast cell mediated and involves a receptor which can be blocked by 8-SPT but not by selective A1 or A2A receptor antagonists. It thus bears similarity to the augmented response to adenosine induced by allergen challenge in actively sensitized BN rats. Exposure to LPS could be a factor along with allergen in determining the increased sensitivity of the airways of asthmatics to adenosine.

Mechanism of airway hyperresponsiveness to adenosine induced by allergen challenge in actively sensitized Brown Norway rats.

1. We have explored the role of allergen sensitization and challenge in defining the response of the airways of the Brown Norway (BN) rat to adenosine. 2. In naïve animals or in rats sensitized to ovalbumin (OA) adenosine induced only weak bronchoconstrictor responses. Challenge of sensitized animals with OA induced a marked airway hyperresponsiveness to adenosine which was not seen with methacholine or bradykinin. 3. The augmented bronchoconstrictor response to adenosine was not affected by acute bivagotomy or atropine nor mimicked by an i.v. injection of capsaicin. It was, however, blocked selectively by disodium cromoglycate methysergide or ketanserin and reduced in animals treated sub-chronically with compound 48/80. 4. The augmented response to adenosine was associated with increases in the plasma concentrations of both histamine and 5-hydroxytryptamine (5-HT), which were attenuated by pretreatment with disodium cromoglycate, and degranulation of mast cells in the lung. 5. Parenchymal strips from lungs removed from sensitized rats challenged with OA gave augmented bronchoconstrictor responses to adenosine relative to strips from sensitized animals challenged with saline. Responses were inhibited by methysergide and disodium cromoglycate. 6. These data demonstrate a marked augmentation of the bronchoconstrictor response to adenosine in actively sensitized BN rats challenged with OA. The augmented response is primarily a consequence of mast cell activation, leading to the release of 5-HT, which in turn induces bronchoconstriction. Our data further suggest the involvement of a discrete lung-based population of mast cells containing and releasing mainly 5-HT and brought into play by prior exposure to allergen.

Evidence for an atypical receptor mediating the augmented bronchoconstrictor response to adenosine induced by allergen challenge in actively sensitized Brown Norway rats.

The bronchoconstrictor response to adenosine is markedly and selectively increased following ovalbumin (OA) challenge in actively sensitized, Brown Norway rats. We present a pharmacological analysis of the receptor mediating this response. Like adenosine, the broad-spectrum adenosine receptor agonist, NECA, induced dose-related bronchoconstriction in actively sensitized, OA-challenged animals. In contrast, CPA, CGS 21680 and 2-Cl-IB-MECA, agonists selective for A(1) A(2A) and A(3) receptors, respectively, induced no, or minimal, bronchoconstriction. Neither the selective A(1) receptor antagonist, DPCPX, nor the selective A(2A) receptor antagonist, ZM 241385, blocked the bronchoconstrictor response to adenosine. MRS 1754, which has similar affinity for rat A(2B) and A(1) receptors, failed to block the bronchoconstrictor response to adenosine despite blockade of the A(1) receptor-mediated bradycardia induced by NECA. 8-SPT and CGS 15943, antagonists at A(1), A(2A), and A(2B) but not A(3) receptors, inhibited the bronchoconstrictor response to adenosine. However, the degree of blockade (approximately 3 fold) did not reflect the plasma concentrations, which were 139 and 21 times greater than the K(B) value at the rat A(2B) receptor, respectively. Adenosine and NECA, but not CPA, CGS 21680 or 2-Cl-IB-MECA, induced contraction of parenchymal strip preparations from actively sensitized OA-challenged animals. Responses to adenosine could not be antagonized by 8-SPT or MRS 1754 at concentrations >50 times their affinities at the rat A(2B) receptor. The receptor mediating the bronchoconstrictor response to adenosine augmented following allergen challenge in actively sensitized BN rats cannot be categorized as one of the four recognized adenosine receptor subtypes.

Coronary flow distribution and dynamics during continuous and pulsatile extracorporeal circulation in the pig.

Four extracorporeal perfusion conditions (continuous beating, continuous fibrillating, pulsatile beating, and pulsatile fibrillating) were tested for 15 minutes each in pigs. Coronary flow, endocardial-epicardial flow ratio, phasic coronary flow, myocardial oxygen consumption, and myocardial lactate extraction were measured. No significant differences in any of these variables were found between pulsatile and continuous flow states in either fibrillating or beating hearts (p greater than 0.05). In both fibrillating conditions, significant elevations of myocardial oxygen consumption and decreases in endocardial-epicardial flow ratios were found (p less than 0.05). Lactate extraction occurred in all conditions, and phasic coronary flows were similar in both beating conditions. These data suggest caution in the expectation that pulsatile perfusion will reverse the coronary flow and myocardial oxygen consumption changes seen with fibrillation.

BW-A522 blocks adenosine A3 receptor-mediated hypotensive responses in the rat.

The effects of 3-(3-iodo-4-aminobenzyl)-8-(4-oxyacetate)-1-propylxanthine (I-ABOPX; BW-A522), which has nanomolar affinity for the recently cloned human and sheep adenosine A3 receptor, on the putative A3 receptor mediated hypotensive response to N6-2-(4-aminophenyl)ethyl adenosine (APNEA) in the rat have been investigated. Following blockade of A1 and A2 receptors with 8-(p-sulphophenyl)theophylline, BW-A522, 10 and 40 mg/kg i.v., blocked dose-dependently and surmountable the hypotensive response to APNEA. The results provide direct evidence of an A3 receptor in the cardiovascular system of the rat which induces hypotension when activated.

Effects of wortmannin on bronchoconstrictor responses to adenosine in actively sensitised Brown Norway rats.

The bronchoconstrictor response to adenosine in the actively sensitised Brown Norway rat is markedly augmented following low level allergen (ovalbumin) challenge. The response reflects activation of the A(2B) receptor subtype and is mediated by 5-hydroxytryptamine (5-HT) released as a consequence of mast cell activation. We describe here the effects of wortmannin, a potent inhibitor of phosphatidylinositol-3-kinase and mast cell exocytosis, on the response to adenosine. Bronchoconstrictor responses to adenosine elicited 3 h following ovalbumin challenge were markedly and dose-dependently reduced by wortmannin given intratracheally (i. t.), 1 h prior to or 2 h post-allergen challenge. Responses to methacholine, which activates bronchial smooth muscle directly, and 5-HT were also reduced following wortmannin but to a lesser extent than those to adenosine. Bronchoconstrictor responses to adenosine 3 h post-challenge with vehicle were also markedly reduced by wortmannin given intratracheally (i.t.), 1 h prior to the "sham" challenge. Plasma histamine and 5-HT levels increased in response to adenosine given 3 h following ovalbumin challenge. The increases were suppressed by wortmannin given i.t., 2 h post-ovalbumin challenge. A reduction in the sensitivity of the airways to 5-HT explains in part the reduced bronchoconstrictor response to adenosine induced by wortmannin. A direct action to suppress 5-HT release from airway mast cells induced by adenosine also contributes to the reduction in the response. Inhibition of phosphatidylinositol-3-kinase is the presumed mechanistic basis for the observed effects.

Effects of wortmannin on airways inflammation induced by allergen in actively sensitised Brown Norway rats.

We have investigated the effect of wortmannin, a potent and selective inhibitor of phosphatidylinositol-3-kinase, on the immediate-type allergic response and the late phase pulmonary inflammation induced by allergen challenge in the ovalbumin-sensitised Brown Norway rat. Intratracheal (i.t.) instillation of ovalbumin induced dose-related bronchoconstrictor responses. Administration of wortmannin (1, 10 or 100 microg kg(-1) i.t., 1 h prior to challenge) induced a marked and dose-dependent inhibition of ovalbumin-induced bronchospasm (ED(50) ca. 5 microg kg(-1) i.t.). At similar doses, wortmannin also suppressed the bronchoconstrictor responses to 5-hydroxytryptamine and methacholine but the degree of blockade of these spasmogens (1.4-1.9-fold) was less than that of ovalbumin (>20-fold). Wortmannin, given intratracheally 1 h prior to allergen challenge, also suppressed the increases in bronchoalveolar lavage fluid leukocyte numbers and eosinophil peroxidase activity measured 24 h post challenge. However, relatively high doses were necessary (ED(50) ca. 100 microg kg(-1) i.t.). The potency of wortmannin was increased when dosed 1 h prior to and 24 h after allergen challenge and the readout was 48 h after challenge (ED(50) 3-5 microg kg(-1) i.t.). Thus, wortmannin is a potent inhibitor of the bronchoconstrictor response induced by allergen in the airways of actively sensitised Brown Norway rats. Inhibition of phosphatidylinositol-3-kinase, an obligatory step in mast cell activation in response to allergen, is the presumed mechanism of action. The fact that similar doses of wortmannin do not suppress the late response to allergen suggests a minimal role for the mast cell in generating the late response to allergen in this model. The striking increase in potency to inhibit the late response when dosed 1 h prior to and 24 h after allergen challenge with the readout taken at 48 h may represent an effect of wortmannin to suppress the migration of leukocytes.

Lack of evidence for cross-competition between vasoactive intestinal peptide and somatostatin at their respective receptors.

A possible cross-competition between vasoactive intestinal peptide (VIP) and somatostatin (somatotropin release inhibiting factor; SRIF) and their respective receptors, was investigated at native or recombinant SRIF and VIP/pituitary adenylate cyclase-activating polypeptide (PACAP) receptors. The activity of VIP was examined in radioligand binding assays at mouse sst(1-5), rat sst(1-2) and human sst(1-5) receptors; or at human tumours preferentially expressing each of the five SRIF receptors. Moreover, SRIF was investigated at human tumoral tissues known to exclusively express specific VIP/PACAP receptor(s). VIP had no significant effect on any of the radioligand binding sites of the SRIF receptor family of rat, mouse or human origin tested. Conversely, SRIF did not interfere with the human VIP/PACAP binding sites tested. Taken together, the results cast reservation on the claimed cross-competition between VIP and SRIF at, specifically human sst(3) receptors, or any of the cloned SRIF or VIP/PACAP receptors recognised to date.

Superiority of hypertonic saline/dextran over hypertonic saline during the first 30 min of resuscitation following hemorrhagic hypotension in conscious swine.

We compared the effectiveness of intravenously administering hypertonic saline/dextran (HSD; 7.5% NaCl in 6% Dextran-70, n = 6) to hypertonic saline (HS) alone (7.5% NaCl, n = 8) in rectifying detrimental effects of hemorrhage on cardiovascular function. Chronically instrumented conscious swine were hemorrhaged 37.5 ml/kg over 60 min. If untreated, this model is 100% lethal within 60 min. Swine received HSD or HS at 4 ml/kg. Functional variables were measured before and at 5, 15, and 30 min following treatment. HSD produced a significantly greater plasma volume expansion than HS alone (13.6 compared to 9.9 ml/kg). Over 30 min expansion was sustained in pigs receiving HSD but pigs receiving HS regressed. Cardiac index (CI) increased for both treatments, being greater with HSD, 104 ml/kg/min, compared to HS alone, 46 ml/kg/min. Neither group fully sustained these elevated values post-treatment, but remained consistently greater than values after hemorrhage; however, the difference in CI between treatments was maintained. Oxygen delivery showed a trend similar to that of CI. We conclude that resuscitation with HSD is superior to HS in improving cardiovascular function over the first 30 min after hemorrhage.

Blood acid-base curve nomogram for immature domestic pigs.

The purpose in this study was to characterize the acid-base status of arterial blood from healthy young domestic swine and to construct an acid-base curve nomogram appropriate to such animals. Accordingly, 40 immature, 20- to 31-kg domestic pigs were used to establish acid-base characteristics for arterial blood. Samples were collected from chronically implanted catheters while the animals were maintained under steady-state, near-basal conditions. At a measurement temperature of 38 C, pH averaged 7.496; PCO2, 40.6 mm Hg; [HCO3-], 31.6 mEq/L; PO2, 79.1 mm Hg; hemoglobin, 9.65 g/dl; hematocrit, 0.29; plasma albumin, 25.3 g/L; plasma globulin, 32.3 g/L; and plasma buffer base, 45.4 mEq/L. Hourly measurements over a 6-hour period in 6 of these pigs showed a small, but significant decrease in PO2 with time, but no significant change in acid-base status. The data showed that nomograms or other procedures based on blood characteristics of men were invalid when used to estimate base excess concentration of blood from young pigs. The normal pH of arterial blood was higher in immature pigs than in men; thus, reference values defining zero base excess were not equivalent in men and pigs. Constant PCO2 titrations were performed on arterial samples taken from 10 additional pigs, and the data were used to construct an acid-base curve nomogram in which zero base excess was defined for blood with a pH of 7.50 and a PCO2 of 40 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Construction of acid-base alignment nomograms to estimate buffer base and base-excess concentrations in arterial blood from immature pigs.

Acid-base characteristics of a population of immature domestic pigs were used to construct a blood acid-base alignment nomogram with scales to estimate porcine buffer base concentration. The nomogram was based on average plasma bicarbonate concentration of 31.6 mEq/L and plasma albumin and globulin values of 25.4 and 32.2 g/L, respectively. A measurement temperature of 38 C was assumed. Subsequently, this nomogram was used to construct a blood acid-base alignment nomogram with scales to estimate porcine base-excess concentration. The nomogram was based on the assignment of zero-base excess to blood with a pH of 7.50 and a PCO2 of 40 mm of Hg. Construction details, including tabular data reflecting the acid-base characteristics of porcine plasma and erythrocytes, are provided.

Arterialized capillary blood used to determine the acid-base and blood gas status of dogs.

Blood samples were collected by microhematocrit tube from posterior medial margin of the shaved, but otherwise untreated, canine ear. Acid-base and blood gas values of these samples were compared with the values of samples obtained simultaneously from the carotid artery. The arterialized nature of capillary blood from the canine ear was demonstrated under various degrees of chemical restraint and during conditions of extreme hypoxic acidosis to hyperventilatory alkalosis. Once a week determinations of acid-base and blood gas status with such arterialized capillary blood from a group of awake dogs showed within-subject variance to be significantly less (P less than 0.05) than between-subject variance; thus, uniqueness of individual dogs was reliably revealed. This technique also was used to demonstrated breed differences for acid-base and blood gas characteristics.

Body composition of mice following exposure to 4300 and 6100 meters.

Male Swiss mice were exposed for 3 and 7 d to simulated altitudes of 4300 and 6100 m. Body weight losses were enhanced at the higher elevation and after longer exposure at each elevation. Carcass analyses showed the weight losses to be attributable to decrements in body water and fat content. The water decrements were a little greater than the fat decrements after all exposure conditions. At both elevations, however, fat loss increased significantly as exposure was extended from 3 to 7 d whereas water loss remained unchanged.

Cardiovascular and pulmonary effects of morphine in conscious pigs.

Cardiovascular and pulmonary effects of morphine (1 mg/kg bolus iv) were investigated in conscious chronically instrumented pigs, a species exhibiting an excitable response. Control animals received an equivalent volume (less than 2 ml) of normal saline. Morphine induced an immediate but small increase in cardiac output and substantial increases in heart rate, mean systemic and pulmonary arterial pressure, left and right ventricular work, hematocrit, and hemoglobin concentration, but did not change stroke volume or systemic vascular resistance. Morphine administration also led to a gradual increase in ventilatory rate and rapid increases in tidal volume, expired and alveolar ventilation, ventilation-perfusion ratio, and shunt fraction. In addition, morphine administration produced substantial decrements in arterial and mixed venous PO2, hemoglobin saturation and mixed venous O2 content; no change in arterial O2 content; and a widening of the arteriovenous O2 difference. Arterial O2 transport was increased slightly. Finally, it produced substantial increments in arterial and mixed venous PCO2 and substantial decrements in arterial and mixed venous pH. It was concluded that arterial O2 delivery did not adequately rise to meet tissue O2 demand, in part because an appropriate increase in cardiac output was attenuated by morphine, and in part because morphine impaired pulmonary gas exchange.

Confounding factors in the hemorrhage of conscious swine: a retrospective study of physical restraint, splenectomy, and hyperthermia.

A retrospective study showed that variability in the responses of heart rate and mean arterial pressure to hemorrhage in conscious swine can be induced by handling procedures, hyperthermia, and splenectomy. All animals were hemorrhaged 38.5 ml/kg over 1 hour. Physical restraint caused tachycardia prior to hemorrhage, an effect that was enhanced during hemorrhage; hemorrhage had no effect on the heart rate of unrestrained animals. Animals restrained in a sling also had an attenuated fall in mean arterial pressures throughout the experiment compared to normothermic swine. Splenectomized swine had elevated heart rates compared to sham-operated animals, with the difference persisting throughout hemorrhage. No difference in mean arterial pressure was noted due to splenectomy. These sources (handling, hyperthermia, and splenectomy) of experimental variability should be considered in the design and interpretation of experiments using conscious swine.