The respiratory responses of Carcinus maenas to declining oxygen tension

1976 ◽  
Vol 65 (2) ◽  
pp. 309-322 ◽  
Author(s):  
A. C. Taylor
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Tension ◽  
Rate Ratio ◽  
Carcinus Maenas ◽  
Level Of Activity ◽  
Wide Range ◽  
Oxygen Tensions ◽  
High Level ◽  
Respiratory Responses

The degree of respiratory independence shown by Carcinus under conditions of declining oxygen tension is dependent on the animal's level of activity. Inactive Carcinus are capable of maintaining respiratory independence down to a Po2 of 60–80 mmHg. This is achieved primarily by an increase in ventilation volume such that the amount of oxygen made available at the respiratory surfaces remains constant over a wide range of oxygen tension. The Po2 at which this can no longer be maintained corresponds closely to the Po2 at which respiratory independence is lost. Under normoxic conditions the Po2 of the post- and prebranchial blood was 97 and 18 mmHg respectively. At the high oxygen tensions prevailing in the postbranchial blood the respiratory pigment is fully saturated. Under conditions of declining oxygen tension the heart rate remains more or less constant until the Po2 reaches 60–80 mmHg, the onset of bradycardia coinciding with the loss of saturation of the haemocyanin. Although cardiac output falls during hypoxia, the capacity rate ratio remains approximately constant, which enables the effectiveness of oxygen uptake by the blood to remain at a high level.

Cardiac performance in semi-isolated heart of the crab Carcinus maenas

1994 ◽  
Vol 266 (3) ◽  
pp. R781-R789
Author(s):  
J. L. Wilkens ◽  
B. R. McMahon
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Isolated Heart ◽  
Carcinus Maenas ◽  
Ventricular Volume ◽  
Whole Body ◽  
Shore Crab ◽  
Stroke Work ◽  
Adaptive Responses

A semi-isolated, in situ heart preparation of the shore crab, Carcinus maenas, supported by its alary ligaments, pumps vigorously for hours at a mean heart rate of 49.7 beats/min and cardiac output of 30 ml.kg-1.min-1. These hearts show no adaptive responses to changes in pericardial sinus pressure, outflow resistance, or afterload. Direct perfusion-induced stretch of the heart wall causes increases in contractile force but minimal changes in heart rate. Stroke work and power are lower than comparable values for animals with myogenic hearts and closed circulatory systems. The values for heart rate and cardiac output are lower than in vivo values and may in part reflect the technique used as well as intrinsic performance of the heart without neural and neurohormonal inputs. Morphometrically the heart represents 0.2% of whole body weight, and the mean stroke volume of 0.35-0.45 ml/kg represents an ejection fraction of 27-34% of ventricular volume (1.4 ml/kg).

The effect of progressive hypoxia on respiration in the dogfish (scyliorhinus canicula) at different seasonal temperatures

1975 ◽  
Vol 63 (1) ◽  
pp. 117-130 ◽  
Author(s):  
P. J. Butler ◽  
E. W. Taylor
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Uptake ◽  
Stroke Volume ◽  
Oxygen Tension ◽  
Acclimation Temperature ◽  
Critical Oxygen Tension ◽  
Critical Oxygen ◽  
Progressive Hypoxia ◽  
Cardiac Stroke Volume

1. Dogfish were acclimated to 7, 12 or 17 degrees C and exposed to progressive hypoxia at the temperature to which they had been acclimated. During normoxia, the Q10 values for oxygen uptake, heart rate, cardiac output and respiratory frequency over the full 10 degrees C range were: 2.1, 2.1, 2.1 and 2.5 respectively. Increased acclimation temperature had no effect on cardiac stroke volume or systemic vascular resistance, although there was a decrease in branchial vascular resistance, pHa and pHv. 2. Progressive hypoxia had no effect on heart rate or oxygen uptake at 7 degrees C, whereas at 12 degrees C and 17 degrees C there was bradycardia, and a reduction in O2 uptake, with the critical oxygen tension for both variables being higher at the higher temperature. Cardiac stroke volume increased during hypoxia at each temperature, such that cardiac output did not change significantly at 12 and 17 degrees C. Neither pHa nor pHv changed significantly during hypoxia at any of the three temperatures. 3. The influence of acclimation temperatures on experimental results from poikilotherms is pointed out. Previously-published results show quantitative differences. 4. The significance of the present results with respect to the functioning and location of oxygen receptors is discussed. It is argued that as the metabolic demand and critical oxygen tension of the whole animal are increased at high acclimation temperatures the same must be the case with the oxygen receptor. This would raise the stimulation threshold and could account for the bradycardia seen during hypoxia becoming manifest at higher values of PI,O2, Pa,O2 and Pv,O2 as the acclimation temperature is raised.

scholarly journals Metoprolol Reduces Cerebral Tissue Oxygen Tension after Acute Hemodilution in Rats

2009 ◽  
Vol 111 (5) ◽  
pp. 988-1000 ◽  
Author(s):  
Tenille E. Ragoonanan ◽  
W Scott Beattie ◽  
C David Mazer ◽  
Albert K.Y. Tsui ◽  
Howard Leong-Poi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Cerebral Blood Flow ◽  
Oxygen Tension ◽  
Tissue Oxygen Tension ◽  
Beta Blockade ◽  
Tissue Oxygen ◽  
Cerebral Tissue ◽  
Protein Levels

Background Perioperative beta-blockade and anemia are independent predictors of increased stroke and mortality by undefined mechanisms. This study investigated the effect of beta-blockade on cerebral tissue oxygen delivery in an experimental model of blood loss and fluid resuscitation (hemodilution). Methods Anesthetized rats were treated with metoprolol (3 mg x kg) or saline before undergoing hemodilution with pentastarch (1:1 blood volume exchange, 30 ml x kg). Outcomes included cardiac output, cerebral blood flow, and brain (PBrO2) and kidney (PKO2) tissue oxygen tension. Hypoxia inducible factor-1alpha (HIF-1alpha) protein levels were assessed by Western blot. Systemic catecholamines, erythropoietin, and angiotensin II levels were measured. Results Hemodilution increased heart rate, stroke volume, cardiac output (60%), and cerebral blood flow (50%), thereby maintaining PBrO2 despite an approximately 50% reduction in blood oxygen content (P < 0.05 for all). By contrast, PKO2 decreased (50%) under the same conditions (P < 0.05). Beta-blockade reduced baseline heart rate (20%) and abolished the compensatory increase in cardiac output after hemodilution (P < 0.05). This attenuated the cerebral blood flow response and reduced PBrO2 (50%), without further decreasing PKO2. Cerebral HIF-1alpha protein levels were increased in beta-blocked hemodiluted rats relative to hemodiluted controls (P < 0.05). Systemic catecholamine and erythropoietin levels increased comparably after hemodilution in both groups, whereas angiotensin II levels increased only after beta-blockade and hemodilution. Conclusions Cerebral tissue oxygen tension is preferentially maintained during hemodilution, relative to the kidney, despite elevated systemic catecholamines. Acute beta-blockade impaired the compensatory cardiac output response to hemodilution, resulting in a reduction in cerebral tissue oxygen tension and increased expression of HIF-1alpha.

Topographical specificity of regulation of respiratory and renal sympathetic activity by the midbrain dorsolateral periaqueductal gray

2010 ◽  
Vol 299 (3) ◽  
pp. R853-R861 ◽  
Author(s):  
Kamon Iigaya ◽  
Jouji Horiuchi ◽  
Lachlan M. McDowall ◽  
Roger A. L. Dampney
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Respiratory Activity ◽  
Periaqueductal Gray ◽  
Nerve Activity ◽  
Homocysteic Acid ◽  
Behavioral Studies ◽  
Wide Range ◽  
Respiratory Responses ◽  
Renal Sympathetic

The midbrain periaqueductal gray (PAG) mediates the physiological responses to a wide range of stressors. It consists of four longitudinal columns that have different anatomical connections and functional properties. Previous anatomical and behavioral studies have led to the hypothesis that the dorsolateral PAG, but not the adjacent lateral and dorsomedial subregions, is a key center that integrates the behavioral response to acute psychological threatening stimuli. In this study, we tested whether, consistent with this hypothesis, activation of neurons in the dorsolateral PAG evokes a pattern of cardiovascular and respiratory responses that is distinct from that evoked from surrounding regions. Arterial pressure, heart rate, renal sympathetic nerve activity (RSNA), and phrenic nerve activity (PNA) were recorded simultaneously in urethane-anesthetized rats. Microinjections of very small amounts of d,l-homocysteic acid (750 pmol in 15 nl) were made in sites throughout the dorsomedial, dorsolateral, and lateral PAG subregions. Increases in RSNA of similar magnitude accompanied by small to moderate increases in arterial pressure and heart rate were evoked from all three PAG subregions. In contrast, large increases in both PNA burst rate (respiratory rate) and overall respiratory activity were evoked only from a highly circumscribed region that corresponded closely to the dorsolateral PAG subregion at an intermediate to caudal level. Within this region, the evoked increases in RSNA and respiratory activity were highly correlated ( r = 0.914, P < 0.001), suggesting the possibility that a common population of “command neurons” within the dorsolateral PAG may generate both sympathetic and respiratory responses from this region.

scholarly journals OXYGEN TENSION AND THE RATES OF MITOSIS AND INTERPHASE IN ROOTS

1962 ◽  
Vol 13 (3) ◽  
pp. 365-371 ◽  
Author(s):  
J. E. Amoore
Keyword(s):  
Oxygen Tension ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Root Tips ◽  
Pea Root ◽  
Wide Range ◽  
Oxygen Tensions ◽  
Mitotic Figures

The object of this work was to determine the influence of a wide range of oxygen tensions upon the relative rates of respiration, mitosis, and interphase in pea root tips, compared with the normal rates of these processes in air. From the rates of disappearance of mitotic figures in excised tips kept in various oxygen tensions, the relative rates of mitosis were found to decrease gradually from 122 per cent in 100 per cent oxygen to 24 per cent in 0.0007 per cent oxygen. From the mitotic indices of intact seedlings, the relative rates of interphase were found to decrease sharply from 82 per cent in 10 per cent oxygen to 6 per cent in 5 per cent oxygen. The data on relative rates of respiration, mitosis, and interphase in root tips were compared, and it was shown that the three processes are perfectly distinct in their quantitative relationships to low oxygen tensions.

LOCAL INDUSTRY PARTICIPATION-OPPORTUNITIES AND CHALLENGES

1997 ◽  
Vol 37 (1) ◽  
pp. 687
Author(s):  
W.S. Sashegyi
Keyword(s):  
Western Australia ◽  
Life Support ◽  
Petroleum Industry ◽  
Fully Integrated ◽  
Life Project ◽  
Industrial Estate ◽  
Level Of Activity ◽  
Wide Range ◽  
High Level ◽  
Australian Industry

The current high level of activity in the resources sector within Western Australia offers opportunities for local industry to participate in a wide range of major construction, manufacturing and service opportunities. At the same time, however, local industry has again been expressing concern about their involvement in these projects.Challenges arise from the rapid technological change occurring within the petroleum industry, the availability of skilled labour, the increasing size and complexity of tender packages and the move to modularisation, the availability of the necessary industrial infrastructure and changes in purchasing practices. On the other hand project developers remain dependent on local industry to assure through-life project support.There is a need for the upgrading of infrastructure and the development of a fully integrated heavy engineering facility based in Western Australia. The Jervoise Bay/Henderson Industrial Estate has been identified as the most suitable base for such activity. The opportunity also exists for the establishment of an Indian Ocean based gas turbine overhaul and refurbishment facility.The challenge for the petroleum industry is to foster Australian industry involvement. The opportunity is to thereby strengthen through life support for projects. For its part, Australian industry must be able to meet specification, quality, price and delivery criteria.In today's procurement environment, addressing the challenges facing local industry participation and capitalising on the available opportunities requires the cooperation of the complete purchasing chain. Project proponents, however, still play a pre-eminent role in ensuring the necessary cooperation and the early involvement of local industry at all levels of that purchasing chain.

Optimal contractility and minimal oxygen consumption for constant external work of heart

1988 ◽  
Vol 254 (6) ◽  
pp. R933-R943
Author(s):  
N. Tanaka ◽  
Y. Yasumura ◽  
T. Nozawa ◽  
S. Futaki ◽  
M. Uenishi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Consumption ◽  
Good Predictor ◽  
Left Ventricular ◽  
Middle Level ◽  
O2 Consumption ◽  
Ventricular Contractility ◽  
External Work ◽  
Wide Range

We theoretically considered the relation between left ventricular O2 consumption (MVO2) and a contractility index (Emax), searching for an optimal Emax that minimizes MVO2 for a given external mechanical work. We used one equation relating Emax with ventricular pressure and volume and another equation relating MVO2 with pressure-volume area (PVA). PVA is theoretically and experimentally a good predictor of MVO2 with Emax as a parameter. Then we could theoretically show the existence of the optimal Emax. For example, MVO2 was minimized to 8.9 ml O2.min-1.100 g-1 at an Emax of 6.3 mmHg.ml-1.100 g when cardiac output was 1.2 l/min, afterload pressure was 100 mmHg, and heart rate was 150 beats/min. These values can be observed experimentally in a 10- to 15-kg dog. Optimal Emax values for a wide range of external work fall in the middle of the normal working range of Emax. Thus our MVO2-PVA-Emax relationship supports the contemporary concept of the optimal contractility that MVO2 for a given cardiac external work is minimum at a middle level of ventricular contractility.

Respiratory Gas Exchange in the Resting Starry Flounder, Platichthys Stellatus: A Comparison with Other Teleosts

1979 ◽  
Vol 78 (1) ◽  
pp. 167-179
Author(s):  
CHRIS M. WOOD ◽  
B. R. McMAHON ◽  
D. G. McDONALD
Keyword(s):  
Cardiac Output ◽  
Rate Ratio ◽  
Peripheral Vascular ◽  
High Cardiac Output ◽  
Starry Flounder ◽  
Content Difference ◽  
Platichthys Stellatus ◽  
Wide Range ◽  
Ventilation Perfusion Ratio

A wide range of respiratory, ventilatory, and cardiovascular parameters have been recorded under completely resting conditions in the starry flounder (Platichthys stellatus), a generally inactive benthic teleost. The results differ in a number of important respects from those of a previous study on the same species. The present data have also been compared with those reported for the active pelagic rainbow trout (Salmo gairdnen) and for other teleost species. Of particular note in the flounder, relative to the trout, are low arterial and venous Poo2's, a low arterial-venous O2 content difference, a low transfer factor and high diffusion gradient for O2 across the gills, a high in vivo blood O2 affinity, a high cardiac output and stroke volume accompanied by a low peripheral vascular resistance, a low ventilation volume, a low ventilation-perfusion ratio, and a low capacity-rate ratio for O2 exchange at the gills. Parameters of CO2 transport and acidbase regulation appear conventional, though blood CO2 contents and lactate concentrations are low. The respiratory strategies of inactive versus active, and benthic versus pelagic teleosts are discussed. Note: Present address: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4K1.

Role of impaired myocardial relaxation in the production of elevated left ventricular filling pressure

2005 ◽  
Vol 288 (3) ◽  
pp. H1203-H1208 ◽  
Author(s):  
Ilan Hay ◽  
Jonathan Rich ◽  
Paul Ferber ◽  
Daniel Burkhoff ◽  
Mathew S. Maurer
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Diastolic Pressure ◽  
Left Ventricular ◽  
Myocardial Relaxation ◽  
End Diastolic Volume ◽  
Wide Range

Although present in many patients with heart failure and a normal ejection fraction, the role of isolated impairments in active myocardial relaxation in the genesis of elevated filling pressures is not well characterized. Because of difficulties in determining the effect of prolonged myocardial relaxation in vivo, we used a cardiovascular simulated computer model. The effect of myocardial relaxation, as assessed by τ (exponential time constant of relaxation), on pulmonary vein pressure (PVP) and left ventricular end-diastolic pressure (LVEDP) was investigated over a wide range of τ values (20–100 ms) and heart rate (60–140 beats/min) while keeping end-diastolic volume constant. Cardiac output was recorded over a wide range of τ and heart rate while keeping PVP constant. The effect of systolic intervals was investigated by changing time to end systole at the same heart rate. At a heart rate of 60 beats/min, increases in τ from a baseline to extreme value of 100 ms cause only a minor increase in PVP of 3 mmHg. In contrast, at 120 beats/min, the same increase in τ increases PVP by 23 mmHg. An increase in filling pressures at high heart rates was attributable to incomplete relaxation. The PVP-LVEDP gradient was not constant and increased with increasing τ and heart rate. Prolonged systolic intervals augmented the effects of τ on PVP. Impaired myocardial relaxation is an important determinant of PVP and cardiac output only during rapid heart rate and especially when combined with prolonged systolic intervals. These findings clarify the role of myocardial relaxation in the pathogenesis of elevated filling pressures characteristic of heart failure.

scholarly journals Isolation and Biochemical Characterization of Two Novel Metagenome-Derived Esterases

2006 ◽  
Vol 72 (5) ◽  
pp. 3637-3645 ◽  
Author(s):  
C. Elend ◽  
C. Schmeisser ◽  
C. Leggewie ◽  
P. Babiak ◽  
J. D. Carballeira ◽  
...  
Keyword(s):  
Biochemical Characterization ◽  
Biotechnological Applications ◽  
Temperature Optimum ◽  
Ph Optimum ◽  
Level Of Activity ◽  
Wide Range ◽  
Soil Metagenome ◽  
Ph Range ◽  
High Level

ABSTRACT The metagenomes of uncultured microbial communities are rich sources for novel biocatalysts. In this study, esterase EstA3 was derived from a drinking water metagenome, and esterase EstCE1 was derived from a soil metagenome. Both esterases are approximately 380 amino acids in size and show similarity to β-lactamases, indicating that they belong to family VIII of the lipases/esterases. EstA3 had a temperature optimum at 50�C and a pH optimum at pH 9.0. It was remarkably active and very stable in the presence of solvents and over a wide temperature and pH range. It is active in a multimeric form and displayed a high level of activity against a wide range of substrates including one secondary ester, 7-[3-octylcarboxy-(3-hydroxy-3-methyl-butyloxy)]-coumarin, which is normally unreactive. EstCE1 was active in the monomeric form and had a temperature optimum at 47�C and a pH optimum at pH 10. It exhibited the same level of stability as EstA3 over wide temperature and pH ranges and in the presence of dimethyl sulfoxide, isopropanol, and methanol. EstCE1 was highly enantioselective for (+)-menthylacetate. These enzymes display remarkable characteristics that cannot be related to the original environment from which they were derived. The high level of stability of these enzymes together with their unique substrate specificities make them highly useful for biotechnological applications.

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