Publications by authors named "Morten Zaar"

Exercise facilitates cerebral lactate uptake, likely by increasing arterial lactate concentration and hence the diffusion gradient across the blood-brain barrier. However, nonspecific β-adrenergic blockade by propranolol has previously reduced the arterio-jugular venous lactate difference (AV) during exercise, suggesting β-adrenergic control of cerebral lactate uptake. Alternatively, we hypothesized that propranolol reduces cerebral lactate uptake by decreasing arterial lactate concentration.

View Article and Find Full Text PDF

Background: To study central hypovolemia in humans, lower body negative pressure (LBNP) is a recognized alternative to blood removal (HEM). While LBNP mimics the cardiovascular responses of HEM in baboons, similarities in hemostatic responses to LBNP and HEM remain unknown in this species.

Methods: Thirteen anesthetized baboons were exposed to progressive hypovolemia by HEM and, four weeks later, by LBNP.

View Article and Find Full Text PDF
Article Synopsis
  • This study investigated how adrenaline affects blood clotting using thrombelastography (TEG) and Multiplate analyses in both splenectomized individuals and healthy controls.
  • Healthy subjects showed significant improvements in clot formation and platelet activity after adrenaline infusion, while splenectomized subjects only experienced a reduction in time to initial fibrin formation.
  • In liver transplant patients, adrenaline also enhanced clot formation during a critical surgical phase, reinforcing the idea that the spleen plays a major role in adrenaline's boost to hemostatic competence.
View Article and Find Full Text PDF

Heat stress followed by an accompanying hemorrhagic challenge may influence hemostasis. We tested the hypothesis that hemostatic responses would be increased by passive heat stress, as well as exercise-induced heat stress, each with accompanying central hypovolemia to simulate a hemorrhagic insult. In aim 1, subjects were exposed to passive heating or normothermic time control, each followed by progressive lower-body negative pressure (LBNP) to presyncope.

View Article and Find Full Text PDF

This study examined to what extent the human cerebral and femoral circulation contribute to free radical formation during basal and exercise-induced responses to hypoxia. Healthy participants (5♂, 5♀) were randomly assigned single-blinded to normoxic (21% O) and hypoxic (10% O) trials with measurements taken at rest and 30 min after cycling at 70% of maximal power output in hypoxia and equivalent relative and absolute intensities in normoxia. Blood was sampled from the brachial artery (a), internal jugular and femoral veins (v) for non-enzymatic antioxidants (HPLC), ascorbate radical (A, electron paramagnetic resonance spectroscopy), lipid hydroperoxides (LOOH) and low density lipoprotein (LDL) oxidation (spectrophotometry).

View Article and Find Full Text PDF

Cerebral non-oxidative carbohydrate consumption may be driven by a β-adrenergic mechanism. This study tested whether the 46G > A (G16R) single nucleotide polymorphism of the β-adrenergic receptor gene () influences the metabolic and cerebrovascular responses to administration of adrenaline. Forty healthy Caucasian men were included from a group of genotyped individuals.

View Article and Find Full Text PDF

Background: The mechanisms underlying red blood cell (RBC)-mediated hypoxic vasodilation remain controversial, with separate roles for nitrite () and S-nitrosohemoglobin (SNO-Hb) widely contested given their ability to transduce nitric oxide bioactivity within the microcirculation. To establish their relative contribution in vivo, we quantified arterial-venous concentration gradients across the human cerebral and femoral circulation at rest and during exercise, an ideal model system characterized by physiological extremes of O tension and blood flow.

Methods: Ten healthy participants (5 men, 5 women) aged 24±4 (mean±SD) years old were randomly assigned to a normoxic (21% O) and hypoxic (10% O) trial with measurements performed at rest and after 30 minutes of cycling at 70% of maximal power output in hypoxia and equivalent relative and absolute intensities in normoxia.

View Article and Find Full Text PDF

Objective: Sympathetic vasoconstriction regulates peripheral circulation and controls blood pressure, but sepsis is associated with hypotension. We evaluated whether apparent loss of sympathetic vasoconstrictor responsiveness relates to distended smooth muscles or to endotoxemia and/or hypoxia.

Design: Prospective descriptive study.

View Article and Find Full Text PDF

Central hypovolemia elevates hemostatic activity which is essential for preventing exsanguination after trauma, but platelet activation to central hypovolemia has not been described. We hypothesized that central hypovolemia induced by lower body negative pressure (LBNP) activates platelets. Eight healthy subjects were exposed to progressive central hypovolemia by LBNP until presyncope.

View Article and Find Full Text PDF

Mesenteric traction syndrome (MTS) manifests in 58-87% of patients undergoing upper abdominal surgery and is characterised by a triad of hypotension, tachycardia, and flushing. Prostacyclin is released from the gut mucosa following intestinal eventration and cyclooxygenase antagonists prevent the development of MTS. Also the use of remifentanil appears to increase the incidence of MTS and hypotension is aggravated by epidural analgesia.

View Article and Find Full Text PDF

A mesenteric traction syndrome manifests in some patients undergoing major abdominal surgery and is identified by flushing, accompanied by hypotension and tachycardia. We used laser speckle contrast imaging to quantify blood flow in forehead skin of patients undergoing Whipple's operation. In two patients with similar blood pressure (-50 mmHg) and profound drop in systemic vascular resistance (-40%), forehead skin perfusion increased three-fold in one patient, while it was unchanged in a patient for whom flushing was not evident.

View Article and Find Full Text PDF

The coagulation system is activated by a reduction of the central blood volume during orthostatic stress and lower body negative pressure suggesting that also a blood loss enhances coagulation. During bleeding, however, the central blood volume is supported by fluid recruitment to the circulation and redistribution of the blood volume. In eight supine male volunteers (24 ± 3 years, blood volume of 6.

View Article and Find Full Text PDF

Introduction: Frontal lobe oxygenation (Sc O2 ) is assessed by spatially resolved near-infrared spectroscopy (SR-NIRS) although it seems influenced by extra-cerebral oxygenation. We aimed to quantify the impact of extra-cerebral oxygenation on two SR-NIRS derived Sc O2 .

Methods: Multiple regression analysis estimated the influence of extra-cerebral oxygenation as exemplified by skin oxygenation (Sskin O2 ) on Sc O2 in 21 healthy subjects exposed to whole-body exercise in hypoxia (Fi O2  = 12%; n = 10) and normoxia (n = 12), whole-body heating, hyperventilation (n = 21), administration of norepinephrine with and without petCO2 -correction (n = 15), phenylephrine and head-up tilt (n = 7).

View Article and Find Full Text PDF

Lactate is shuttled between organs, as demonstrated in the Cori cycle. Although the brain releases lactate at rest, during physical exercise there is a cerebral uptake of lactate. Here, we evaluated the cerebral lactate uptake and release in hypoxia, during exercise and when the two interventions were combined.

View Article and Find Full Text PDF

Objective: Sympathetic vasoconstriction is blunted in contracting human skeletal muscles (functional sympatholysis). In young subjects, infusion of adenosine and ATP increases blood flow, and the latter compound also attenuates α-adrenergic vasoconstriction. In patients with type 2 diabetes and age-matched healthy subjects, we tested 1) the sympatholytic capacity during one-legged exercise, 2) the vasodilatory capacity of adenosine and ATP, and 3) the ability to blunt α-adrenergic vasoconstriction during ATP infusion.

View Article and Find Full Text PDF

The platelet count varies two-fold among healthy individuals. Considering the haemostatic role of platelets, this study evaluated the relation between cardiovascular and metabolic responses to uncontrolled haemorrhage and the pretrauma platelet count in pigs. A laceration liver injury was inflicted in 19 pigs (34 ± 3 kg; mean ± SD).

View Article and Find Full Text PDF

Activation-induced increase in cerebral blood flow is coupled to enhanced metabolic activity, maybe with brain tissue redox state and oxygen tension as key modulators. To evaluate this hypothesis at the onset of exercise in humans, blood was sampled at 0.1 to 0.

View Article and Find Full Text PDF

Lactate is a potential energy source for the brain. The aim of this study was to establish whether systemic lactate is a brain energy source. We measured in vivo cerebral lactate kinetics and oxidation rates in 6 healthy individuals at rest with and without 90 mins of intravenous lactate infusion (36 mumol per kg bw per min), and during 30 mins of cycling exercise at 75% of maximal oxygen uptake while the lactate infusion continued to establish arterial lactate concentrations of 0.

View Article and Find Full Text PDF

The heart of Python regius is functionally divided so that systemic blood pressure is much higher than pulmonary pressure (6.6+/-1.0 and 0.

View Article and Find Full Text PDF

Digestion is associated with gastric secretion that leads to an alkalinisation of the blood, termed the "alkaline tide". Numerous studies on different reptiles and amphibians show that while plasma bicarbonate concentration ([HCO(3)(-)](pl)) increases substantially during digestion, arterial pH (pHa) remains virtually unchanged, due to a concurrent rise in arterial PCO(2) (PaCO(2)) caused by a relative hypoventilation. This has led to the suggestion that postprandial amphibians and reptiles regulate pHa rather than PaCO(2).

View Article and Find Full Text PDF

Reptiles are ectothermic, but regulate body temperatures (T(b)) by behavioural and physiological means. Body temperature has profound effects on virtually all physiological functions. It is well known that heating occurs faster than cooling, which seems to correlate with changes in cutaneous perfusion.

View Article and Find Full Text PDF

As ectothermic vertebrates, reptiles undergo diurnal and seasonal changes in body temperature, which affect many biological functions. In conjunction with a general review regarding the effects of temperature on digestion in reptiles, we describe the effects of various temperatures (20-35 degrees C) on the metabolic response to digestion in the Burmese python (Python molurus). The snakes were fed mice amounting to 20% of their body weight and gas exchange (oxygen uptake and CO(2) production) were measured until digestion had ended and gas exchange returned to fasting levels.

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Warning

Message: fopen(/var/lib/php/sessions/ci_sessionp54jiananj0inc2pqo8jb4of0tu5cj5s): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 177

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once

A PHP Error was encountered

Severity: Warning

Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)

Filename: Session/Session.php

Line Number: 137

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once