共查询到20条相似文献,搜索用时 31 毫秒
1.
Patricia Vel��squez Olivier Skurtys Javier Enrione Fernando Osorio 《Food biophysics》2011,6(3):349-358
Surface free energy (SFE; γ
SV) of 16 fruit epicarps present on the Chilean market was calculated by two approaches: the acid–base and Zisman. The results
show that the fruit epicarps were low surface energy since the magnitude of γ
SV falls within a narrow range, between 37 and 44 mJ m − 2. Zisman approach gave a critical surface tension values, γ
cr lower than the SFE calculated by the acid–base approach. Significant differences in SFE between the fruits may be explained
by the variation in the chemical composition of epicuticular waxes. The polar (gABSV\gamma^{\rm AB}_{\rm SV}) and apolar (gLWSV\gamma^{\rm LW}_{\rm SV}) components of the SFE were also calculated and a mathematical relation was between both values was found. Values of gABSV\gamma^{\rm AB}_{\rm SV} and gLWSV\gamma^{\rm LW}_{\rm SV} could also be associated with the fruit family and the tissue origins in the ovary region. Finally, it has been shown that
fruit epicarps exhibited predominantly electron-donator behaviour since $\gamma_{\rm SV}^- > \gamma_{\rm SV}^+$\gamma_{\rm SV}^- > \gamma_{\rm SV}^+. We believe that the results reported here can potentially impact in food engineering because the compatibility of coatings
and fruit epicarps depends on the interaction of their respective chemical and physical properties. 相似文献
2.
Beth L. Young David A. S. Rosen Martin Haulena Allyson G. Hindle Andrew W. Trites 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):105-116
The ability to use heart rate (fh) to predict oxygen consumption rates (
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established
fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed
whether fh could accurately predict
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations
to describe the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that
both feeding and physical environment are statistically relevant when deriving
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current
bioenergetic models with data gathered using these predictive fh:
[(V)\dot]\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological,
behavioral, and environmental states. 相似文献
3.
F. Scott Gayzik J. Jason Hoth Joel D. Stitzel 《Biomechanics and modeling in mechanobiology》2011,10(4):505-520
This study explores the relationship between impact severity and resulting pulmonary contusion (PC) for four impact conditions
using a rat model of the injury. The force–deflection response from a Finite Element (FE) model of the lung was simultaneously
matched to experimental data from distinct impacts via a genetic algorithm optimization. Sprague-Dawley rats underwent right-side
thoracotomy prior to impact. Insults were applied directly to the lung via an instrumented piston. Five cohorts were tested:
a sham group and four groups experiencing lung insults of varying degrees of severity. The values for impact velocity (V)
and penetration depth (D) of the cohorts were Group 1, (V = 6.0 m · s−1, D = 5.0 mm), Group 2, (V = 1.5 m · s−1,D = 5.0 mm), Group 3, (V = 6 m · s−1, D = 2.0 mm), and Group 4, (V = 1.5 m · s−1, D = 2.0 mm). CT scans were acquired at 24 h, 48 h, and 1 week post-insult. Contusion volume was determined through segmentation.
FE-based injury metrics for PC were determined at 24 h and 1 week post-impact, based on the observed volume of contusion and
first principal strain. At 24 h post-impact, the volume of high radiopacity lung (HRL) was greatest for the severe impact
group (mean HRL = 9.21 ± 4.89) and was significantly greater than all other cohorts but Group 3. The concurrent optimization
matched simulated and observed impact energy within one standard deviation for Group 1 (energy = 3.88 ± 0.883 mJ, observed
vs. 4.47 mJ, simulated) and Group 2 (energy = 1.46 ± 0.403 mJ, observed vs. 1.50 mJ, simulated) impacts. Statistically significant
relationships between HRL and impact energy are presented. The FEA-based injury metrics at 24 h post-contusion are emax·[(e)\dot]max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 94.5 s−1, ε
max exceeding 0.284 and [(e)\dot]max{\dot{\varepsilon}_{\max}} exceeding 470 s−1. Thresholds for injury to the lung still present at 1 week post-impact were also determined. They are emax·[(e)\dot]max{\varepsilon_{\max}\cdot \dot {\varepsilon}_{\max}} exceeding 149 s−1, ε
max exceeding 0.343 and [(e)\dot]max{\dot{\varepsilon}_{\max}} exceeding 573 s−1. A mesh sensitivity study found that thresholds based on strain rate were more sensitive to changes to mesh density than
the threshold based on strain only. 相似文献
4.
Lau GY Richards JG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(7):927-939
In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression
in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes
with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK
activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate (
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O2) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold
increase in eEF2 phosphorylation, and a 24% decrease in
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O2] (<40 μM O2), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O2] as assessed by estimates of cellular P50 and P90 values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects
of AICAR on
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation,
or cellular
[(M)\dot]\textO 2 \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support
for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must
be viewed cautiously because of the known off-target effects of the pharmacological agents used. 相似文献
5.
Belão TC Leite CA Florindo LH Kalinin AL Rantin FT 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(7):905-916
The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions
from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing
organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine
the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f
R) monitored and were subjected to normoxic water (PwO2 = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of
hyperactivity and maintained unchanged f
R, confirming that this species is a facultative air-breather. Its aquatic O2 uptake (
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} ) was maintained constant down to a critical PO2 (PcO2) of 60 mmHg, below which
[(V)\dot]\textO2 \dot{V}{\text{O}}_{2} declined linearly with further reductions of inspired O2 tension (PiO2). Just above the PcO2 the ventilatory tidal volume (V
T) increased significantly along with gill ventilation (
[(V)\dot]\textG \dot{V}_{\text{G}} ), while f
R changed little. Consequently, the water convection requirement
( [(V)\dot]\textG /[(V)\dot]\textO2 ) \left( {\dot{V}_{\text{G}} /\dot{V}{\text{O}}_{2} } \right) increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO2 = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher
at PiO2 tensions below the PcO2. Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath. 相似文献
6.
Guillaume Bouvignies Dmitry M. Korzhnev Philipp Neudecker D. Flemming Hansen Matthew H. J. Cordes Lewis E. Kay 《Journal of biomolecular NMR》2010,47(2):135-141
NMR relaxation dispersion spectroscopy is a powerful method for studying protein conformational dynamics whereby visible,
ground and invisible, excited conformers interconvert on the millisecond time-scale. In addition to providing kinetics and
thermodynamics parameters of the exchange process, the CPMG dispersion experiment also allows extraction of the absolute values
of the chemical shift differences between interconverting states,
| \Updelta [(w)\tilde] | \left| {\Updelta \tilde{\omega }} \right| , opening the way for structure determination of excited state conformers. Central to the goal of structural analysis is the
availability of the chemical shifts of the excited state that can only be obtained once the signs of
\Updelta [(w)\tilde] \Updelta \tilde{\omega } are known. Herein we describe a very simple method for determining the signs of 1HN
\Updelta [(w)\tilde] \Updelta \tilde{\omega } values based on a comparison of peak positions in the directly detected dimensions of a pair of 1HN–15N correlation maps recorded at different static magnetic fields. The utility of the approach is demonstrated for three proteins
that undergo millisecond time-scale conformational rearrangements. Although the method provides fewer signs than previously
published techniques it does have a number of strengths: (1) Data sets needed for analysis are typically available from other
experiments, such as those required for measuring signs of 15N
\Updelta [(w)\tilde] \Updelta \tilde{\omega } values, thus requiring no additional experimental time, (2) acquisition times in the critical detection dimension can be
as long as necessary and (3) the signs obtained can be used to cross-validate those from other approaches. 相似文献
7.
Caşcaval D Galaction AI Turnea M 《Journal of industrial microbiology & biotechnology》2011,38(9):1449-1466
Study of the distribution of the oxygen mass transfer coefficient, k
l
a, for a stirred bioreactor and simulated (pseudoplastic solutions of carboxymethylcellulose sodium salt) bacterial (P. shermanii), yeast (S. cerevisiae), and fungal (P. chrysogenum free mycelia) broths indicated significant variation of transfer rate with bioreactor height. The magnitude of the influence
of the considered factors differed from one region to another. As a consequence of cell adsorption to bubble surface, the
results indicated the impossibility of achieving a uniform oxygen transfer rate throughout the whole bulk of the microbial
broth, even when respecting the conditions for uniform mixing. Owing to the different affinity of biomass for bubble surface,
the positive influence of power input on k
l
a is more important for fungal broths, while increasing aeration is favorable only for simulated, bacterial and yeast broths.
The influence of the considered factors on k
l
a were included in mathematical correlations established based on experimental data. For all considered positions, the proposed
equations for real broths have the general expression
kl a = aCXb ( \fracPa V )g vSd , k_{\rm l} a = \alpha C_{\rm X}^{\beta } \left( {{\frac{{P_{\rm a} }}{V}}} \right)^{\gamma } v_{\rm S}^{\delta } , exhibiting good agreement with experimental results (with maximum deviations of ±10.7% for simulated broths, ±8.4% for P. shermanii, ±9.3% for S. cerevisiae, and ±6.6% for P. chrysogenum). 相似文献
8.
Mammalian metallothioneins (
\textM7\textIIMTs {\text{M}}_7^{\text{IIMTs}} ) show a clustered arrangement of the metal ions and a nonregular protein structure. The solution structures of Cd3-thiolate cluster containing β-domain of mouse β-MT-1 and rat β-MT-2 show high structural similarities, but widely differing
structure dynamics. Molecular dynamics simulations revealed a substantially increased number of
\textNH - \textSg {\text{NH - }}{{\text{S}}^\gamma } hydrogen bonds in β-MT-2, features likely responsible for the increased stability of the Cd3-thiolate cluster and the enfolding protein domain. Alterations in the
\textNH - \textSg {\text{NH - }}{{\text{S}}^\gamma } hydrogen-bonding network may provide a rationale for the differences in dynamic properties encountered in the β-domains of
MT-1, -2, and -3 isoforms, believed to be essential for their different biological function. 相似文献
9.
The allometric relationships of mean tree height [`(H)]( μ [`(w)]xq ) \bar{H}( \propto \bar{w}_{\rm {x}}^{\theta } ) and of organ mass density [`(d)]x ( μ [`(w)]xd ) \bar{d}_{\rm {x}} ( \propto \bar{w}_{\rm {x}}^{\delta } ) to mean organ mass [`(w)]x \bar{w}_{\rm {x}} were studied in self-thinning Pinus densiflora Sieb. et Zucc. stands. Tree height increased significantly with increasing mean mass of organs and aboveground parts on log–log
coordinates. The value of the allometric constant θ ranged from 0.2878 to 0.3349. On the other hand, the constant value δ
was not significantly different from zero, except for leaves. The value of the allometric constant δ ranged from −0.2926 to
0.0120. According to Weller’s allometric model, the slope of the self-thinning line was calculated from the allometric constants
θ and δ. The thinning slope was estimated to be −1.51 in stem, −1.39 in branches, −1.00 in leaf and −1.41 in aboveground parts, respectively.
Mass density was high in stem, medium in branches and low in leaves. Mean leaf mass density decreased significantly with decreasing
stand density on log–log coordinates, which could be interpreted as indicating the importance of the constant final leaf biomass
in overcrowded P. densiflora stands. The self-thinning exponents of branch, stem and aboveground parts were not significantly different from 3/2, which
indicated that the 3/2 power law of self-thinning holds for stem mass, branch mass and aboveground mass in overcrowded P. densiflora stands. 相似文献
10.
Kelly M. Hare Shirley Pledger Michael B. Thompson John H. Miller Charles H. Daugherty 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(8):1173-1181
Ectotherms from low-temperature environments have higher metabolic rates at low temperatures than those from warm-temperature
environments. We predicted that nocturnal lizards, which are active at much lower environmental temperatures than diurnal
lizards, would also have higher metabolic rates at low temperatures, and by association a lower thermal sensitivity (Q
10) than diurnal and crepuscular lizards. We measured the rate of oxygen consumption (
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} ) of eight cool-temperate species of lizard (four nocturnal, three diurnal, and one crepuscular) at 13 and 26°C and analyzed
log transformations of these data using log mass as a covariate. As expected,
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} was positively correlated with temperature in all eight species, with
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} being two to four times higher at 26°C than at 13°C. As predicted, at 13°C (but not 26°C) the
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} was significantly higher in nocturnal than diurnal lizards. Species-specific differences and mass scaling factors explain
the patterns of thermal sensitivity seen among these eight lizard species. Thermal sensitivity is strongly influenced by mass,
with smaller species generally having higher thermal sensitivity of their metabolic rate, and this result deserves further
exploration among other ectotherms. We conclude that, along with the previously reported lower cost of locomotion found in
nocturnal lizards, they also partially offset the thermal handicap of activity at low body temperatures by having an elevated
[(V)\dot]\textO 2 \dot{V}{\text{O}}_{ 2} at lower temperatures. 相似文献
11.
A method for evaluating the average shear rate () in a stirred and aerated tank bioreactor has been proposed for non-Newtonian fluids. The volumetric oxygen transfer coefficient
(k
L
a) was chosen as the appropriate characteristic parameter to evaluate the average shear rate (). The correlations for the average shear rate as a function of N and rheological properties of the fluid (K and n) were obtained for two airflow rate conditions (ϕair). The shear rate values estimated by the proposed methodology lay within the range of the values calculated by classical
correlations. The proposed correlations were utilized to predict the during the Streptomyces clavuligerus cultivations carried out at 0.5 vvm and four different rotational impeller speeds. The results show that the values of the
average shear rate () varied from 437 to 2,693 s−1 by increasing with N and flow index (n) and decreasing with the fluid consistency index (K). 相似文献
12.
The synthesis of spermine derivatives (II), \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_{\rm 2} {\rm R}_{\rm 3} \mathop {\rm N}\limits^ + \left( {{\rm CH}_2 } \right)_3 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} \left( {{\rm CH}_2 } \right)_2 ]_2 \cdot 4{\rm X}^ - $\end{document}, and spermidine derivatives (III), \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_{\rm 2} {\rm R}_{\rm 3} \mathop {\rm N}\limits^ + \left( {{\rm CH}_2 } \right)_4 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} \left( {{\rm CH}_2 } \right)_3 \mathop {\rm N}\limits^ + {\rm R}_{\rm 1} {\rm R}_{\rm 2} {\rm R}_3 \cdot 3{\rm X}^ - $\end{document}, are reported. The effects of these salts on the helix–coil transition of rA–rU and rI–rC helices were examined. Increasing the size of the hydrophobic substituents, R1, R2, and R3 lowers the degree of stabilization of the helical structure. The disproportionation reaction, 2rA–rU→rA–rU2 + rA occurs readily with salts II and III, especially when the substituents, R1, R2, and R3 are small, i.e., H or Me. Spermine is found to stabilize the rA–rU2 and rI–rC helices to approximately the same extent; however, large differences between the degree of stabilization of rA–rU2 and rI-rC helices are observed when the substituents R1, R2, and R3 are large hydrophobic groups. Similar results are also obtained for the spermidine series. Finally, differences in the interactions of the salts II and III with rA–rU2 and rI–rC helices suggest that the latter helix is denser. 相似文献
13.
E J Gabbay 《Biopolymers》1967,5(8):727-747
Information concerning the structures of rA–rU, rA–rU2 rI–rC, rA–rI2, and acid rA helices in solutions is reported. Through the use of diquaternary ammonium salts of the general structure, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_2 {\rm R}_3 \mathop {\rm N}\limits^ + ({\rm CH}_2 )n\mathop {\rm N}\limits^ + {\rm R}_1 {\rm R}_2 {\rm R}_3 \cdot 2{\rm Br}^ - $\end{document} (I), it is shown that (1) the distances between adjacent negatively charged oxygen atoms on the helix increases in the following order rA–rI2 < rI–rC < rA–rU ? rA–rU2; (2) the density of the helices increases in the order. rA–rI2 < rA–rU < rA–rU2 < rI–rC; (3) there is a large hydrophobia site in rA–rI2 and possibly also in rA–rU, rA–rU2, and rI–rC helices; (4) the results of the interactions between the salts of type I and the helices may be formulated in semi-quantitative terms by the use of two parameters, α, and β which are shown to be related to the charge separation and the density of the helices, respectively; (5) the studies in solutions compare favorably with the x-ray studies on the fibers; and (6) the acid rA helix differs significantly from the other helices by the fact that the electrostatic interstrand interactions between the negatively charged oxygen atom of a phosphate group and the positively charged 10-amino group of adenine contribute significantly to the stabilization of the helix, and thus it is found that the presence of the salts, I, leads to a significant destabilization of the acid rA helix. 相似文献
14.
Stout JR Cramer JT Zoeller RF Torok D Costa P Hoffman JR Harris RC O'Kroy J 《Amino acids》2007,32(3):381-386
Summary. This study examined the effects of 28 days of β-alanine supplementation on the physical working capacity at fatigue threshold
(PWCFT), ventilatory threshold (VT), maximal oxygen consumption (
O2-MAX), and time-to-exhaustion (TTE) in women. Twenty-two women (age ± SD 27.4 ± 6.1 yrs) participated and were randomly assigned
to either the β-alanine (CarnoSyn™) or Placebo (PL) group. Before (pre) and after (post) the supplementation period, participants
performed a continuous, incremental cycle ergometry test to exhaustion to determine the PWCFT, VT,
O2-MAX, and TTE. There was a 13.9, 12.6 and 2.5% increase (p < 0.05) in VT, PWCFT, and TTE, respectively, for the β-alanine group, with no changes in the PL (p > 0.05). There were no changes for
O2-MAX (p > 0.05) in either group. Results of this study indicate that β-alanine supplementation delays the onset of neuromuscular
fatigue (PWCFT) and the ventilatory threshold (VT) at submaximal workloads, and increase in TTE during maximal cycle ergometry performance.
However, β-alanine supplementation did not affect maximal aerobic power (
O2-MAX). In conclusion, β-alanine supplementation appears to improve submaximal cycle ergometry performance and TTE in young women,
perhaps as a result of an increased buffering capacity due to elevated muscle carnosine concentrations. 相似文献
15.
B. Culik A. J. Woakes D. Adelung R. P. Wilson N. R. Coria H. J. Spairani 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(1):61-70
Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O2 consumption (
) and CO2 production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from
in lying chicks to
at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on
were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities (
), and one for walking (
). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as
, whereas mass-specific O2 consumption was related to walking speed (S, m·s-1) as
.Abbreviations
bpm
beats per minute
-
D
distance walked (m)
-
ECG
electrocardiogram
-
HR
heart rate (bpm)
-
ns
number of steps
-
RQ
respiratory quotient
-
S
walking speed (m·s-1)
-
T
time walked (s)
-
W
body mass (kg) 相似文献
16.
17.
Respiratory evaporation in panting fowl: Partition between the respiratory and buccopharyngeal pumps
John Brackenbury Peter Avery Michael Gleeson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,145(1):63-66
Summary Ventilation (V) and respiratory water loss
were measured in domestic fowlGallus gallus subjected to raised environmental temperatures (33±2°C) and breathing air, 8% O2 in N2, 3% CO2 in air or 5% CO2 in air. Birds breathing air underwent an 18.6-fold increase in respiratory frequency and a 5-fold reduction in tidal volume and panting was accompanied by vigorous gular flutter. Hypoxic and hypercapnic birds breathed more slowly and deeply and gular flutter was strongly inhibited. The
ratio was similar to that predicted on the basis of the measured ventilation assuming saturation of expired gas at measured gular mucosal temperature in hypoxic and hypercapnic birds but 54% greater than the predicted value in birds panting in air. It is concluded that the excess water loss during normal panting results from tidal airflow generated independently by the buccopharyngeal pump and that buccopharyngeal ventilation is equivalent to 54% of the respiratory ventilation. 相似文献
18.
Experimental kinetic data (initial rate and high conversion) on the hydrolysis of cellobiose by 1,4-β-glucosidace (Gliocladium sp.) have been analysed and a competitive inhibition by glucose has been proposed. The determination of kinetic parameters from integral data is based upon algorithms for non-linear optimization and numerical integration. The values of kinetic constants \documentclass{article}\pagestyle{empty}\begin{document}$(v_{\max } = 1.02\frac{{\mu {\rm M}_{{\rm glucose}} }}{{{\rm mg}_{{\rm protein}} \cdot \min }},K_M = 2.6{\rm mM/l, and }K_P = 1.2{\rm mM/l)}$\end{document} agree well with the initialrate results. An important distinction is the confidence limit of parameters. Linear regression analysis shows a virtual accuracy and can lead to wrong conclusions. 相似文献
19.
Effects of rheological properties and mass transfer on plant cell bioreactor performance: production of tropane alkaloids 总被引:1,自引:0,他引:1
Volumetric mass transfer coefficients, K(L)a were measured over an aeration rate range from 0.1 to 1.0 vvm in a 1.2-L draft-tube-type airlift bioreactor for different Datura stramonium cell concentrations and correlated with superficial air velocity and rheological properties of the cell suspension. The measured K(L)a values (17-40 h(-1)) for a cell volume fraction of 0.2 (v/v) were approximately 2 times higher than those for the highest cell concentrations tested (cell volume fraction 0.7-0.8 v/v). Cell suspensions exhibited yield stress and pseudoplastic behavior. This behavior was described by the Casson model. The estimated yield stress values depended upon cell concentration with an exponent of 4.0. An empirical correlation based on the data for plant cell suspensions exhibiting yield stress was developed in order to determine aeration strategy for the plant cell cultivation in draft-tube-type airlift bioreactors: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm K}_{\rm L} {\rm a} = {\rm A}({\rm U}_{{\rm gr}});{0.3} ({\rm \eta }_{{\rm eff}});{ - 0.4} $$\end{document} Aeration rates above 1.0 vvm caused a significant drop in cell yield and product content. Maximum growth and production were obtained at 0.6 vvm aeration. The cell and product yields obtained at 1.7 vvm were 2.8 times lower than the maximum values (25 g cell DW/L and 73.8 mg tropane alkaloid/L). The effects of the increased aeration rates on cell yield were also evaluated in terms of Reynolds stress. It was found that there was a relation between cell damage and the estimated Reynolds stress. The Reynolds stress estimated for the same aeration rate decreased with increasing cell concentration, suggesting that cells in the cultures at low cell concentrations are subjected to hydrodynamic damage. In the experiments with the cell cultures having a cell concentration of 0.3 (v/v), approximately 70% reduction in cell concentration was observed when the Reynolds stress was increased from 10 to 50 dyn/cm(2). (c) 1993 John Wiley & Sons, Inc. 相似文献
20.
Willis RE White CR Merritt DJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(4):477-486
Trap-building, sit-and-wait predators such as spiders, flies and antlions tend to have low standard metabolic rates (SMRs)
but potentially high metabolic costs of trap construction. Members of the genus Arachnocampa (glowworms) use an unusual predatory strategy: larvae bioluminesce to lure positively phototropic insects into their adhesive
webs. We investigated the metabolic costs associated with bioluminescence and web maintenance in larval Arachnocampa flava. The mean rate of CO2 production ([(V)\dot] \dot{V}CO2) during continuous bioluminescence was 4.38 μl h−1 ± 0.78 (SEM). The mean [(V)\dot] \dot{V}CO2 of inactive, non-bioluminescing larvae was 3.49 ± 0.35 μl h−1. The mean [(V)\dot] \dot{V}CO2 during web maintenance when not bioluminescencing was 8.95 ± 1.78 μl h−1, a value significantly lower than that measured during trap construction by other predatory arthropods. These results indicate
that bioluminescence itself is not energetically expensive, in accordance with our prediction that a high cost of bioluminescence
would render the Arachnocampa sit-and-lure predatory strategy inefficient. In laboratory experiments, both elevated feeding rates and daily web removal
caused an increase in bioluminescent output. Thus, larvae increase their investment in light output when food is plentiful
or when stressed through having to rebuild their webs. As light production is efficient and the cost of web maintenance is
relatively low, the energetic returns associated with continuing to glow may outweigh the costs of continuing to attract prey. 相似文献