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1.
Joanna Saluk-Juszczak Beata Olas Barbara Wachowicz Rafal Glowacki Edward Bald 《Cell biology and toxicology》2010,26(4):355-365
The oxidative stress induced by acute exertion may interfere with blood platelet activation. The beneficial effect of l-carnitine (γ-trimethylamino-β-hydroxybutyric acid) on oxidative stress in blood platelets has not been fully investigated;
however, different studies indicate that this compound modulates platelet functions. The aim of our study was to assess the
effects of l-carnitine on platelet activation and oxidative/nitrative protein damage (determined by the levels of protein carbonyl groups,
thiol groups, and 3-nitrotyrosine residues) in resting blood platelets or platelets treated with peroxynitrite (ONOO−, a strong physiological oxidant) in vitro. We also investigated the effects of l-carnitine on the level of platelet glutathione and on the formation of superoxide anion radicals ( O2 - · ) \left( {{\hbox{O}}_2^{ - \bullet }} \right) , lipid peroxidation measured by thiobarbituric acid reactive substances (TBARS) in blood platelets stimulated by thrombin
(a strong physiological agonist), and platelet aggregation induced by adenosine diphosphate (a strong physiological stimulator).
We have observed that carnitine decreases platelet activation (measured by platelet aggregation, the generation of O2 - · {\hbox{O}}_2^{ - \bullet } , and TBARS production). Moreover, our results in vitro demonstrate that carnitine may protect against oxidation of thiol
groups induced by ONOO−. Thus, carnitine may have some protectory effects against oxidative changes induced in blood platelets. 相似文献
2.
Donald C. Jackson Henry D. Prange 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1979,134(4):315-319
Summary Ventilation and metabolic rate were measured during exercise in adult female green turtles at Tortuguero, Costa Rica. Six turtles were studied at night on the beach while actively covering their nests. Five turtles, captured after nesting, were studied at rest, during 20 min of spontaneous activity, and during recovery from the activity. Arterial blood samples were obtained from the latter animals and analyzed for pH,
, O2 concentration and lactate concentration. Blood was obtained by heart puncture from 8 turtles immediately after nesting and analyzed for blood lactate. Active metabolism (
) in both groups was almost 10 times the standard resting value (0.024 l/kg·h). The increase in ventilation during exercise, due exclusively to higher breathing frequency, exceeded the increase in
, so that the ratio
(the air convection requirement), more than doubled. The respiratory exchange ratio,
, that averaged 0.56 in the resting turtles, increased to 1.08 during exercise in the captured turtles and was 0.90 in the nesting animals. Arterial
and O2 saturation remained unchanged during exercise, indicating efficient gas exchange in the lungs. Pre-exercise values of all variables were restored 1 h after the end of exercise. Blood acid-base changes associated with activity in the captive turtles were variable and not statistically significant, but suggested partially compensated metabolic acidosis. Lactate concentrations were significantly elevated in the nesting turtles. 相似文献
3.
Serge Thomas Joseph Poupin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,156(1):29-34
Summary The effects of two levels of water carbonate alkalinity (CA=0.3–0.5 meq·l−1 and CA=12–13.5 meq·l−1) on arterial blood acid-base status (
, pHa, [HCO
3
−
]+[CO
3
−−
]), oxygen consumption (
) and plasma ionic composition (Na+, K+, Cl−) were investigated in trout living in normoxic-normocapnic water at 15°C.
The results show that a high level of carbonate alkalinity induced a decrease in
and a situation of mixed respiratory and metabolic acidosis compared to that in low CA water.
These changes are accompanied by significant changes in ionic composition but the levels of oxygen consumption are unchanged.
The role of the different capacitance coefficients of water for CO2 and the effects of the different ionic composition of water on ionic and gascous exchanges are discussed.
Equipe de Recherche associée au CNRS N° 070622 相似文献
4.
G. Benzi A. Gorini B. Ghigini A. Moretti F. Dagani R. F. Villa 《Neurochemical research》1996,21(1):7-18
The changes in the Mg2+-dependent V-type ATPase activity and the Mg2+-ATP-dependent H+ pumping activity of the synaptic vesicles from the cerebral cortex of rats submitted to intermittent chronic (4 weeks) mild
or severe hypoxia were evaluated. The adaptation to the chronic severe hypoxia increases both the ATPase and the H+ pumping activities which are inhibited by NEM with an exponential relationship between the IC50 values and the in vivo O2 concentration. The Mg2+-dependent increase in H+ pumping activity of synaptic vesicles from the rats subjected to in vivo chronic hypoxia may be antagonized by nigericin
(dissipating ΔpH) and by FCCP (dissipating ΔpH and ΔΨSV). In contrast, valinomycin (dissipating the ΔΨSV and facilitating an enhancement in ΔpH) increases in vitro the H+ pumping activity that is inhibited by the addition of high concentration of K gluconate (reducing the rate of K+ efflux). The preincubation of vesicles from hypoxic rats with FCCP, but not with nigericin, inhibits the valinomycin-increased
H+ pumping activity.l-glutamate increases the H+ pumping activity in synaptic vesicles from the cerebral cortex of chronic hypoxic rats, whereas other amino acids (i.e.,l-aspartate andl-homocysteate) and glutamate analogs (i.e., quisqualate and ibotenate) are ineffective. The adaptation to both chronic intermittent
severe hypoxia and in vivo treatment with posatireline causes a decrease in the Mg2+-ATPase activity consistent with the decrease in the H+ pumping one of the synaptic vesicles. The addition of nigericin into incubation medium magnifies the decrease in the H+ pumping activity, while the addition of FCCP is ineffective, suggesting that the treatment with posatireline interferes with
the ΔΨSV component in the
of the synaptic vesicles from rats submitted to chronic hypoxia. The results of the in vivo and in vitro experiments suggest
that in the synaptic vesicles from hypoxic rats the ΔΨSV component in
may be most effective in increasing the Mg2+-ATP-dependent H+ pumping activity. 相似文献
5.
Soil temperature and biotic factors drive the seasonal variation of soil respiration in a maize (Zea mays L.) agricultural ecosystem 总被引:1,自引:0,他引:1
Guangxuan Han Guangsheng Zhou Zhenzhu Xu Yang Yang Jingli Liu Kuiqiao Shi 《Plant and Soil》2007,291(1-2):15-26
The diurnal and seasonal variation of soil respiration (SR) and their driving environmental factors were studied in a maize
ecosystem during the growing season 2005. The diurnal variation of SR showed asymmetric patterns, with the minimum occurring
around early morning and the maximum around 13:00 h. SR fluctuated greatly during the growing season. The mean SR rate was
3.16 μmol CO2 m−2 s−1, with a maximum of 4.87 μmol CO2 m−2 s−1 on July 28 and a minimum of 1.32 μmol CO2 m−2 s−1 on May 4. During the diurnal variation of SR, there was a significant exponential relationship between SR and soil temperature
(T) at 10 cm depth:
. At a seasonal scale, the coefficient α and β fluctuated because the biomass (B) increased α, and the net primary productivity (NPP) of maize markedly increased β of the exponential equation. Based on this, we developed the equation
to estimate the magnitude of SR and to simulate its temporal variation during the growth season of maize. Most of the temporal
variability (93%) in SR could be explained by the variations in soil temperature, biomass and NPP of maize. This model clearly
demonstrated that soil temperature, biomass and NPP of maize combined to drive the seasonal variation of SR during the growing
season. However, only taking into account the influence of soil temperature on SR, an exponential equation over- or underestimated
the magnitude of SR and resulted in an erroneous representation of the seasonal variation in SR. Our results highlighted the
importance of biotic factors for the estimation of SR during the growing season. It is suggested that the models of SR on
agricultural sites should not only take into account the influence of soil temperature, but also incorporate biotic factors
as they affect SR during the growing season. 相似文献
6.
We previously showed that activation of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) Cl− conductance (gCFTR) supports parallel activation of amiloride-sensitive epithelial Na+ channel (ENaC) in the native human sweat duct. However, it is not clear whether phosphorylated CFTR, phosphorylated ENaC,
or only Cl− -channel function is required for activation. We used basilaterally α-toxin-permeabilized human sweat ducts to test the hypothesis
that ENaC activation depends only on Cl− -channel function and not on phosphorylation of either CFTR or ENaC. CFTR is classically activated by PKA plus millimolar
ATP, but cytosolic glutamate activation of gCFTR is independent of ATP and phosphorylation. We show here that both phosphorylation-dependent (PKA) and phosphorylation-independent
(glutamate) activation of CFTR Cl− channel function support gENaC activation. We tested whether cytosolic application of 5 mM ATP alone, phosphorylation by cAMP, cGMP, G-protein dependent kinases (all in the presence of 100 μM ATP), or glutamate could support ENaC activation in the absence of gCFTR. We found that none of these agonists activated gENaC by themselves when Cl− current (
) through CFTR was blocked by: 1) Cl− removal, 2) DIDS inhibition, 3) lowering the ATP concentration to 100 μM (instead of 5 mM required to support CFTR channel function), or 4) mutant CFTR (homozygous ΔF508 CF ducts). However, Cl− gradients in the direction of absorption supported, while Cl− gradients in the direction of secretion prevented ENaC activation. We conclude that the interaction between CFTR and ENaC
is dependent on activated
through CFTR in the direction of absorption (Cl− gradient from lumen to cell). But such activation of ENaC is independent of phosphorylation and ATP. However, reversing
through CFTR in the direction of secretion (Cl− gradient from cell to lumen) prevents ENaC activation even in the presence of
through CFTR.
An erratum to this article is available at . 相似文献
7.
Viktor Reinhardt 《Primates; journal of primatology》1987,28(1):123-125
The justification for the “generalization that primate males are more aggressive than females” (Fedigan & Baxter, 1984) was tested in a troop of 24 captive rhesus monkeys. Males (N=9) were more dominant than females (N=15), i.e., they had more subordinate partners (
m=17.0 vs.
f=6.6;p<0.01); hence, their aggression rate was higher (
m=77.6 vs.
m=38.1;p<0.05). However, adjusting the rate of aggression according to the number of subordinate targets revealed no gender difference
and males directed numbers of aggressive acts against individual subordinate partners that were not higher than those of females
(
m=4.4 vs.
f=5.4;p>0.1). It was concluded that aggressiveness is an individual attribute that is (1) independent of dominance status, and (2)
independent of sex. 相似文献
8.
Didier G. Arqués Jean-Paul Fallot Christian J. Michel 《Bulletin of mathematical biology》1998,60(1):163-194
The self-complementary subset
∪{AAA,TTT} with
= {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} of 22 trinucleotides
has a preferential occurrence in the frame 0 (reading frame established by the ATG start trinucleotide) of protein (coding)
genes of both prokaryotes and eukaryotes. The subsets
∪{CCC} and
∪{GGG} of 21 trinucleotides have a preferential occurrence in the shifted frames 1 and 2 respectively (frame 0 shifted by
one and two nucleotides respectively in the 5′-3′ direction).
and
are complementary to each other. The subset
contains the subset
which has the rarity property (6 × 10−8) to be a complementary maximal circular code with two permutated maximal circular codes
and
in the frames 1 and 2 respectively.
is called a C3 code.
A quantitative study of these three subsets
in the three frames 0, 1, 2 of protein genes, and the 5′ and 3′ regions of eukaryotes, shows that their occurrence frequencies
are constant functions of the trinucleotide positions in the sequences. The frequencies of
in the frame 0 of protein genes are 49, 28.5 and 22.5% respectively. In contrast, the frequencies of
in the 5′ and 3′ regions of eukaryotes, are independent of the frame. Indeed, the frequency of
in the three frames of 5′ (respectively 3′) regions is equal to 35.5% (respectively 38%) and is greater than the frequencies
and
, both equal to 32.25% (respectively 31%) in the three frames.
Several frequency asymmetries unexpectedly observed (e.g. the frequency difference between
and
in the frame 0), are related to a new property of the subset
involving substitutions. An evolutionary analytical model at three parameters (p, q, t) based on an independent mixing of the 22 codons (trinucleotides in frame 0) of
with equiprobability (1/22) followed by t ≈ 4 substitutions per codon according to the proportions p ≈ 0.1; q ≈ 0.1 and r = 1 − p − q ≈ 0.8 in the three codon sites respectively, retrieves the frequencies of
observed in the three frames of protein genes and explains these asymmetries. Furthermore, the same model (0.1, 0.1, t) after t ≈ 22 substitutions per codon, retrieves the statistical properties observed in the three frames of the 5′ and 3′ regions.
The complex behaviour of these analytical curves is totally unexpected and a priori difficult to imagine. 相似文献
9.
Chappell Mark A. Bucher Theresa L. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(1):129-136
Summary The effects of ambient temperature (T
a) on ventilation and gas exchange in chukar partridges (Alectoris chukar) were determined after acclimation to low and high altitute (LA and HA; 340 and 3,800 m, respectively).At both LA and HA, oxygen consumption (
) increased with decreasingT
a atT
a from 20 to –20°C. AtT
a of 35 to 40°C,
increased above thermoneutral values at HA but remained constant and minimal at LA. Water loss rates increased rapidly atT
a>30°C at both altitudes as birds began to pant. Ventilation rates (f) during panting were 5-to 23-fold greater than the minimalf at thermoneutralT
a.Increased
atT
a below thermoneutrality was supported by increased minute volume (V
i) at both altitudes. The change inV
i was primarily a function of changing tidal volume (V
t), althoughf increased slightly asT
a declined. Oxygen extraction (
) remained fairly constant atT
a below 20°C at both altitudes. BothV
t and
were considerably lower when birds were panting than at lowerT
a.Chukars showed few obvious ventilatory adaptations to HA. The 35% change in
between 340 and 3,800 m was accommodated by a corresponding change inV
i (btps), most of which was accomplished by increasedf at HA, along with a slight increase in
.Abbreviations and symbols
HA
high altitude
-
LA
low altitude
-
rate of evaporative water loss
-
oxygen extraction efficiency
-
f
respiratory frequency
-
V
t
tidal volume
-
V
i
minute volume
-
BMR
basal metabolic rate
-
MHP
metabolic heat production 相似文献
10.
During peak thermogenesis of anthesis, high rates of respiration by the sterile male florets on the spadix ofPhilodendron selloum significantly reduce the oxygen tension (PO
2) and raise CO2 tension between the florets. Nevertheless, respiration is not limited by the availability of O2 under natural conditions. At experimental PO
2 below about 17 kPa, however, florets begin to show decreased O2 consumption. A respiratory exchange ratio of 0.83 indicates that the major energy source is not starch, but is probably lipid.Abbreviations and symbols
capacitance of the gas phase for O2 (ml O2 cm-3 kPa-1)
- DO
2
binary diffusion coefficient of O2 in air (cm2 min-1)
- KO
2
Krogh's diffusion coefficient (ml O2 cm-2 min-1 kPa-1 cm)
- PO
2 PCO
2
partial pressures of O2 and CO2 (kPa)
-
rate of O2 consumption (ml O2 g-1 h-1)
- Fgas
fractional gas volume
- P80
O2 partial pressure at which
falls below 80% of maximum
- RE
respiratory exchange ratio
相似文献
11.
D. S. Robson LeRoy Powers N. S. Urquhart 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1967,37(4):205-216
Summary If genetic and environmental effects upon a quantitative phenotype X=G+E are normally and independently distributed then the probability distribution of genetic value G among individuals of fixed phenotypic value X is likewise a normal distribution. The mean of this a posteriori distribution of genetic values is
+h
2 (X−
) and the variance is σ
g
2
(1−h
2), where
is the a priori mean of X, h
2 is the heritability ratio, and σ
g
2
is genetic variance. For any fixed values of h
2 and σ
g
2
the a posteriori probability that the genetic value G associated with a given phenotype X exceeds the population mean by any specified amount can therefore be read directly from the tables of the standard normal
distribution. The expected proportion of these superior genetic deviates among individuals whose phenotypic value exceeds
some specified constant may also be calculated (by numerical analysis) and is presented here in graphical form.
If phenotypic selection is practiced by choosing the best out of N phenotypes then N should be large enough to assure high probability of obtaining a superior genetic deviate. The operating characteristics
of this type of selection are displayed in tabular form, again based upon numerical integration.
Dedicated to Dr. George F. Sprague on the occasion of his 65th birthday.
Cooperative investigations of the Colorado Agricultural Experiment Station, the Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture, and the Beet Sugar Development Foundation. Approved by the Colorado Agricultural Experiment Station for publication as Scientific Series Article No. 880. Paper No. BU-78, Biometrics Unit, and Paper No. 529, Plant Breeding Department, Cornell University.
Geneticist, Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture; now deceased.
Formerly Research Assistant, Colorado State University; now Assistant Professor of Biological Statistics, Cornell University. 相似文献
Zusammenfassung Wenn genetische und umweltbedingte Effekte auf einen quantitativen Ph?notyp X=G+E von einander unabh?ngig und normal verteilt sind, dann entspricht die Wahrscheinlichkeitsverteilung des genetischen Werts G unter Individuen mit fixiertem ph?notypischem Wert X gleichfalls einer Normalverteilung. Das Mittel dieser a posteriori-Verteilung der genetischen Werte ist +h 2 (X− ) und die Varianz ist σ g 2 (1−h 2); wobei das a priori-Mittel von X, h 2 der Heritabilit?tskoeffizient und σ g 2 die genetische Varianz sind. Für jeden fixierten Wert von h 2 und σ g 2 kann daher die a posteriori-Wahrscheinlichkeit, da? der genetische Wert G das Populationsmittel in Verbindung mit einem gegebenen Ph?notyp X um einen bestimmten Wert übersteigt, direkt aus den Tabellen einer standardisierten Normalverteilung abgelesen werden. Der erwartete Anteil dieser überlegenen, genetisch bedingten Abweichung unter Individuen, deren ph?notypischer Wert einen vorgegebenen Konstantwert übersteigt, kann ebenfalls numerisch errechnet werden. Er wird im vorliegenden Fall graphisch dargestellt. Wenn eine ph?notypische Selektion zur Auswahl der besten Ph?notypen aus N Individuen erfolgt, sollte N gro? genug sein, um mit hoher Wahrscheinlichkeit eine überlegene, genetisch bedingte Abweichung zu erhalten. Die wirksamen Charakteristiken dieses Typs der Selektion werden in tabellierter Form wiedergegeben, die gleichfalls auf numerischer Integration beruht.
Dedicated to Dr. George F. Sprague on the occasion of his 65th birthday.
Cooperative investigations of the Colorado Agricultural Experiment Station, the Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture, and the Beet Sugar Development Foundation. Approved by the Colorado Agricultural Experiment Station for publication as Scientific Series Article No. 880. Paper No. BU-78, Biometrics Unit, and Paper No. 529, Plant Breeding Department, Cornell University.
Geneticist, Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture; now deceased.
Formerly Research Assistant, Colorado State University; now Assistant Professor of Biological Statistics, Cornell University. 相似文献
12.
M. -T. Linossier D. Dormois R. Fouquet A. Geyssant C. Denis 《European journal of applied physiology and occupational physiology》1996,74(5):420-427
A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5–7 s to reach
the maximal velocity (V{immax}) against different braking forces (F
B). Power was averaged during a complete crank rotation by adding the power dissipated againstF
B to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output (
) power output attained atV
max (
) calculated as the product ofV
max andF
B and the work performed to reachV
max expressed in mean power output (
). The relationships between these parameters andF
B were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken
at rest to identify muscle metabolic and morphometric properties. The
value was similar for allF
B. Therefore, the average of values was defined as corrected maximal power (
). This value was 11 higher than the maximal power output uncorrected for the acceleration. Whereas the
determination did not require high loads, the highest
value (
) was produced when loading was heavy, as evidenced by the
-F
B parabolic relationship. For each subject, the braking force (
) giving
was defined as optimal. The
, equal to 0.844 (SD 0.108) N · kg−1 bodymass, was related to thigh muscle area (r = 0.78,P < 0.05). The maximal velocity (
) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate
kinase activity). Thus, from the
determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer. 相似文献
13.
Daniel T. Clemens 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(1):57-66
Summary Rosy finches (Leucosticte arctoa) breed at altitudes above 3500 m in eastern California. House finches (Carpodacus mexicanus) belong to the same subfamily (Carduelinae), but breed at much lower elevations. Oxygen consumption (
) and ventilatory parameters of these two species were measured over a wide range of ambient temperatures (T
a) at low altitude (LA; 150 m) and at high altitude (HA; 3800 m).Minimal nighttime
's of rosy finches and house finches at LA (T
a=30°C) were close to allometrically predicted values for passerine birds. At both altitudes,
increased linearly with decreasingT
a betweenT
a=20 and –10°C. Resting
's were slightly higher at HA than at LA on average.In both species, minute volume (
) was inversely related toT
a.T
a-correlated increases in
resulted from significant increases in both ventilatory frequency (f) and tidal volume (V
T) at both altitudes. Oxygen extraction efficiency (
) was independent ofT
a in rosy finches at LA, but declined significantly with decreasingT
a in rosy finches at HA and in house finches at both altitudes.At a givenT
a, both species had significantly greater
(BTPS) at HA than at LA. Altitude-correlated increases in
resulted primarly from increases inf with little change inV
T.
was significantly greater at HA than at LA in both species.In spite of the difference in altitudinal distributions of rosy finches and house finches, there were few conspicuous interspecific differences in metabolic or ventilatory adaptation to altitude or lowT
a over the range of conditions examined.Symbols and abbreviations
BMR
basal metabolic rate
-
BTPS
at body temperature and pressure, saturated
-
oxygen extraction efficiency
-
f
ventilation frequency
-
h
mean coefficient of heat transfer
-
HA
high altitude
-
instantaneous oxygen consumption
-
LA
low altitude
-
RH
relative humidity
-
SMR
standard metabolic rate
-
STPD
standard temperature and pressure, dry
-
T
temperature
-
a
ambient
-
b
body
-
lc
lower critical of thermoneutral zone
-
minute volume
-
V
T
tidal volume 相似文献
14.
Evidence for four nonallelic structural genes for the γ chain of human fetal hemoglobin 总被引:4,自引:0,他引:4
T. H. J. Huisman W. A. Schroeder W. H. Bannister J. L. Grech 《Biochemical genetics》1972,7(2):131-139
An abnormal human fetal hemoglobin not only may be either aGγ- or anAγ-chain variant but also may be present in a different proportion of the total fetal hemoglobin.Gγ-Chain variants contribute either about one-fourth or one-eighth to the total production of HbF in the heterozygote, whereas
theAγ-chain variants approximate either one-eighth or one-sixteenth of the total HbF. These observations may indicate the presence
of four nonallelic Hbγ structural genes (termed
) which produce γ chains in an approximate ratio of 4 : 2 : 2 : 1. HbF Malta I is considered to be the product of a mutant
of the
locus, an undefined HbFx that of the
locus, HbF Hull and HbF Jamaica products of mutated
loci, and the newly discovered HbF Malta II a mutant of the
gene.
This work was supported in part by grants HL-05168 and HL-02558 from the National Institutes of Health, U.S. Public Health
Service. 相似文献
15.
It is considered that arteriovenous diffusive shunts of oxygen may cause inaccuracy of the oxygen Fick method as
where
is the pulmonary oxygen uptake,
is the cardiac output, and CaO2 and CvO2 are the arterial and venous oxygen contents, respectively.
A simple circulation model, including the whole circulation with nine well-mixed compartments (C1, ... C9), is constructed:
the
is assigned as constant as 6000 ml min−1; the blood portions of 60 ml move at an interval of 600 ms. C1 and C2 compartments, each having 60 ml volume, represent the
blood of pulmonary microcirculation, C3 represents the arterial blood with a volume of 1500 ml, C4, ..., C8, each also having
a volume of 60 ml, represent the blood of peripheral microcirculation, whereas C9 represents the venous blood with a volume
of 3000 ml. The pulmonary oxygen uptake
, related to C1 and C2, the oxygen release
, related to C4,...,C8, as well as a “total arteriovenous diffusive shunt of oxygen”
, from the arterial blood (C3) to the venous blood (C9), are calculated simultaneously. The alveolar gas has a constant oxygen
partial pressure, and the pulmonary diffusion capacity is also constant; similar to modeling the pulmonry, oxygen diffusion,
constant partial oxygen pressures for all peripheral tissues as well as constant diffusion capacities for all peripheral oxygen
diffusion are also assigned. The diffusion capacities for the
(between C3 and C9) are arbitrarily assigned.
The Fick method gives incorrect results depending on the total arteriovenous diffusive shunt of oxygen
. But the mechanism determining the magnitude of
remains unclear. 相似文献
16.
We compared on eight dates during the ice-free period physicochemical properties and rates of phytoplankton and epipelic primary
production in six arctic lakes dominated by soft bottom substrate. Lakes were classified as shallow ( < 2.5 m), intermediate in depth (2.5 m < < 4.5 m), and deep ( > 4.5 m), with each depth category represented by two lakes. Although shallow lakes circulated freely and intermediate and
deep lakes stratified thermally for the entire summer, dissolved oxygen concentrations were always >70% of saturation values.
Soluble reactive phosphorus and dissolved inorganic nitrogen (DIN = NO3
−–N + NH4
+–N) were consistently below the detection limit (0.05 μmol l−1) in five lakes. However, one lake shallow lake (GTH 99) periodically showed elevated values of DIN (17 μmol l−1), total-P (0.29 μmol l−1), and total-N (33 μmol l−1), suggesting wind-generated sediment resuspension. Due to increased nutrient availability or entrainment of microphytobenthos,
GTH 99 showed the highest average volume-based values of phytoplankton chlorophyll a (chl a) and primary production, which for the six lakes ranged from 1.0 to 2.9 μg l−1 and 0.7–3.8 μmol C l−1 day−1. Overall, however, increased resulted in increased area-based values of phytoplankton chl a and primary production, with mean values for the three lake classes ranging from 3.6 to 6.1 mg chl a m−2 and 3.2–5.8 mmol C m−2 day−1. Average values of epipelic chl a ranged from 131 to 549 mg m−2 for the three depth classes, but levels were not significantly different due to high spatial variability. However, average
epipelic primary production was significantly higher in shallow lakes (12.2 mmol C m−2 day−1) than in intermediate and deep lakes (3.4 and 2.4 mmol C m−2 day−1). Total primary production (6.7–15.4 mmol C m−2 day−1) and percent contribution of the epipelon (31–66%) were inversely related to mean depth, such that values for both variables
were significantly higher in shallow lakes than in intermediate or deep lakes.
Handling editor: L. Naselli-Flores 相似文献
17.
Interactions between microbial growth and substrate degradation are important in determining the performance of trickle-bed
bioreactors (TBB), especially when salt is added to reduce biomass formation in order to alleviate media clogging. This study
was aimed at quantifying salinity effects on bacterial growth and substrate degradation, and at acquiring kinetic information
in order to improve the design and operation of TBB. Experiment works began by cultivating a mixed culture in a chemostat
reactor receiving artificial influent containing a mixture of benzene, toluene, and xylene (BTX), followed by using the enrichment
culture to degrade the individual BTX substrates under a particular salinity, which ranged 0–50 g l−1 in batch mode. Then, the measured concentrations of biomass and residual substrate versus time were analyzed with the microbial
kinetics; moreover, the obtained microbial kinetic constants under various salinities were modeled using noncompetitive inhibition
kinetics. For the three substrates the observed bacterial yields appeared to be decreased from 0.51–0.74 to 0.20–0.22 mg mg−1 and the maximum specific rate of substrate utilization,
declined from 0.25–0.42 to 0.07–0.11 h−1, as the salinity increased from 0 to 50 NaCl g l−1. The NaCl acted as noncompetitive inhibitor, where the modeling inhibitions of the coefficients, K
T(S), were 22.7–29.7 g l−1 for substrate degradation and K
T(μ), 13.0–19.0 g l−1, for biomass formation. The calculated ratios for the bacterial maintenance rate, m
S, to
further indicated that the percentage energy spent on maintenance increased from 19–24 to 86–91% as salinity level increased
from 0 to 50 g l−1. These results revealed that the bacterial growth was more inhibited than substrate degradation by the BTX oxidizers under
the tested salinity levels. The findings from this study demonstrate the potential of applying NaCl salt to control excessive
biomass formation in biotrickling filters. 相似文献
18.
Björn Lindman 《Antonie van Leeuwenhoek》1981,47(4):297-306
The initial rate ofd-glucosamine uptake by the non-halotolerant yeastSaccharomyces cerevisiae was approximately halved as the apparent half saturation constant (Km) and the apparent maximum velocity (Vmax) changed from 6.6mm to 16.4mm and from 22 μmol · g−1 · min−1 to 16 μmol · g−1 · min−1, respectively, when the salinity in the medium was increased from zerom to 0.68m NaCl. Corresponding changes in a high affinity transport system in the halotolerant yeastDebaryomyces hansenii were from 1.1mm to 4.6mm and from 3.1 μmol · g−1 · min−1 to 4.5 μmol · g−1 · min−1, implying a practically unchanged transport capacity. In 2.7m NaCl, Km and Vmax in this system were 24.5mm and 1.1 μmol · g−1 · min−1, respectively, representing a marked decrease in transport capability. Nevertheless, the degree of affinity in this extreme
salinity must still be regarded as noteworthy. In addition to the high affinity transport system inD. hansenii, a low affinity system, presumably without relevance ind-glucosamine transport, was observed. 相似文献
19.
Beatrice M. Wyse Albert Y. Chang 《In vitro cellular & developmental biology. Plant》1982,18(3):243-250
Summary [125I]Insulin (porcine) binding to an epithelial cell line established from a Chinese hamster kidney, CHK-ACE−100, showed an optimum at pH 8.0 and reached a maximum after 2.5 h incubation at 25°C. Dissociation of bound [125I]insulin was facilitated by the addition of unlabeled insulin in the dilution buffer. Porcine insulin effectively competed
for [125I]insulin binding to the cultured cells and was 30 and 90 times as potent as guinea pig insulin and porcine proinsulin in
causing 50% inhibition of [125I]insulin binding; glucagon was completely ineffective. Scatchard analysis of the binding data yielded a curvilinear plot
and a capacity of 0.6 ng/106 cells; the average affinity of the empty receptor,
, was calculated to be 1.78×108
M
−1 and that of the filled receptor,
, 0.57×108
M
−1.
Substitution of fetal bovine serum (FBS) in the culture medium with bovine calf, bovine newborn, or bobby calf serum altered
insulin binding characteristics in the cells and reduced cell growth. Insulin binding characteristics of cells grown in hormone-supplemented
medium containing 0 to 0.1% FBS were similar to those of cells grown in minimum essential medium (MEM) containing 2 to 5%
FBS. The data indicated that the established Chinese hamster kidney epithelial cell line CHK-ACE−100 possessed specific insulin receptors and the characteristics of the receptors could be manipulated by changing the serum
in culture medium. 相似文献
20.
Summary A set of three-dimensional triple-resonance experiments is described which provide
,
,
and
coupling constants. The pulse sequences generate E.COSY-like multiplet patterns and comprise a magnetization transfer from
the amide proton to the α-proton or vice versa via the directly bound heteronuclei. For residues with the 1Hα spin resonating close to the H2O signal, a modified HNCA experiment can be employed to measure the vicinal 1HN,1Hα couplings. Ambiguities associated with the conversion of
values into ϕ-angle constraints for protein structure determination can be resolved with the knowledge of the heteronuclear
3J-couplings. In favourable cases, stereospecific assignments of glycine α-protons can be obtained by employing the experiments
described here in combination with NOE data. The methods are applied to flavodoxin from Desulfovibrio vulgaris. 相似文献