共查询到20条相似文献,搜索用时 31 毫秒
1.
The vertical distribution of a bloom-forming Microcystis population was studied based on the relevant limnological parameters obtained from the lower Nakdong River (Mulgum) during
the summer of 1994. Over three months (late June to late September), a high abundance of Microcystis population (mean ± SD, 2.9 ± 8.4 × 105 cells ml−1, n = 40) and algal biomass (mean ± SD, chlorophyll a, 131 ± 346 μg l−1, n = 31) was persistent throughout the entire water column (0–5 m, n = 11). The vertical distribution of carbon content was uneven, with a high concentration near the surface zone (mean ± SD,
total, 7.9 ± 7.8; Microcystis, 5.2 ± 8.3 μg C ml−1, n = 15). Incorporating limnological and meteorological factors, a diel study of the vertical distribution of Microcystis showed that the chlorophyll a concentration was highest near the surface zone on a calm night (wind velocity, <2 m s−1, 2300–700) but was evenly distributed on a windy day (>4 m s−1, 1100–1900). Among many possible factors, wind velocity may have played an important role in controlling the vertical distribution
of Microcystis in the lower Nakdong River.
Received: July 12, 1999 / Accepted: November 15, 1999 相似文献
2.
P. O. Vardevanyan A. P. Antonyan G. A. Manukyan A. T. Karapetyan A. K. Shchyolkina O. F. Borisova 《Molecular Biology》2000,34(2):272-276
Isotherms of the EtBr adsorption on native and denatured poly(dA)poly(dT) in the temperature interval 20–70°C were obtained.
The EtBr binding constants and the number of binding sites were determined. The thermodynamic parameters of the EtBr intercalation
complex upon changes of solution temperature 20–48°C were calculated: 1.0·106 M−1≤K≤1.4·106 M−1, free energy ΔG
o=−8.7±0.3 kcal/mol, enthalpy ΔH
o≅0, and entropy ΔS
o=28±0.5 cal/(mol deg). UV melting has shown that the melting temperature (T
m) of EtBr-poly(dA)poly(dT) complexes (μ=0.022,4.16·10−5 M EtBr) increased by 17°C as compared with the ΔT
m of free homopolymer, whereas the half-width of the transition (T
m) is not changed. It was shown for the first time that EtBr forms complexes of two types on single-stranded regions of poly(dA)poly(dT)
denatured at 70°C: strong (K
1=1.7·105 M−1; ΔG
o=−8.10±0.03 kcal/mol) and weak (K
2=2.9·103 M−1; ΔG
o=−6.0±0.3 kcal/mol).The ΔG
o of the strong and weak complexes was independent of the solution ionic strength, 0.0022≤μ≤0.022. A model of EtBr binding
with single-stranded regions of poly(dA)poly(dT) is discussed. 相似文献
3.
Nielsen P Larsen LH Ramløv H Hansen BW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(3):287-296
The oxygen consumption rate during embryogenesis of Acartia tonsa subitaneous eggs were measured at different temperatures (10, 15, 17, 21, 24 and 28°C) with nanorespirometry. The oxygen
consumption was constant during the embryogenesis but increased rapidly at hatching time. The mean ± SD oxygen consumption
rate increased exponentially with temperature and ranged from 0.09 ± 0.04 (10°C) to 0.54 ± 0.09 nmol O2 egg−1 h−1 (28°C). The mean ± SD Q10-value was 2.51 ± 0.15. Calculations of energy consumption during embryogenesis ranged from 1.86 to 18.28 mJ depending on
temperature and development time. We conclude that the effect of temperature on oxygen consumption rate was far less important
than the prolonged development time when calculating the energy consumed during embryogenesis. 相似文献
4.
Kanakis CD Tarantilis PA Polissiou MG Diamantoglou S Tajmir-Riahi HA 《Cell biochemistry and biophysics》2007,49(1):29-36
In this report we are examining how the antioxidant flavonoids can prevent DNA damage and what mechanism of action is involved
in the process. Flavonoids are strong antioxidants that prevent DNA damage. The anticancer and antiviral activities of these
natural products are implicated in their mechanism of actions. We study the interactions of quercetin (que), kaempferol (kae),
and delphinidin (del) with DNA and transfer RNA in aqueous solution at physiological conditions, using constant DNA or RNA
concentration 6.25 mmol (phosphate) and various pigment/polynucleotide(phosphate) ratios of 1/65 to 1 (DNA) and 1/48 to 1/8
(tRNA). The structural analysis showed quercetin, kaempferol, and delphinidin intercalate DNA and RNA duplexes with minor
external binding to the major or minor groove and the backbone phosphate group with overall binding constants for DNA adducts
K
que = 7.25 (±0.65) × 104 M−1, K
kae = 3.60 (±0.33) × 104 M−1, and K
del = 1.66 (±0.25) × 104 M−1 and for tRNA adducts K
que = 4.80 (±0.50) × 104 M−1, K
kae = 4.65 (±0.45) × 104 M−1, and K
del = 9.47 (±0.70) × 104 M−1. The stability of adduct formation is in the order of del>que>kae for tRNA and que>kae>del for DNA. Low flavonoid concentration
induces helical stabilization, whereas high pigment content causes helix opening. A partial B to A-DNA transition occurs at
high drug concentration, while tRNA remains in A-family structure. The antioxidant activity of flavonoids changes in order
delphinidin>quercetin>kaempferol. The results show intercalated flavonoids can make them strong antioxidants to protect DNA
from harmful free radical reactions. 相似文献
5.
Herbert R. L. Drouin 《European biophysics journal : EBJ》1999,28(7):600-604
A new ion-selective liquid membrane microelectrode, based on the neutral carrier 1,1′-bis(2,3-naphtho-18-crown-6), is described
that shows the dependence of EMF on the activity of divalent putrescine cations a
Put, with the linear slope s
Put = 26 ± 3 mV/decade (mean ± SD, N = 18), in the range 10−4–10−1 M at 25 ± 1 °C. Values of potentiometric putrescine cation selectivity coefficients of logK
Pot
Put
j
(mean ± SD, N) are obtained by the separate solution method for the ions K+ (1.0 ± 0.4, 10), Na+ (−1.2 ± 0.4, 8), Ca2+ (−2.3 ± 0.5, 10) and Mg2+ (−2.5 ± 0.5, 7). The microelectrode can be applied for the direct analysis of the activities of free divalent putrescine
cations in the range 5 × 10−4 to 10−1 M in an extracellular ionic environment. Established analytical methods, e.g. high performance liquid chromatography, determine
the total concentration of the derivatives of free and bound putrescine.
Received: 20 December 1998 / Revised version: 7 May 1999 / Accepted: 27 May 1999 相似文献
6.
Zohra Chikh Nguyêt-Thanh Ha-Duong Geneviève Miquel Jean-Michel El Hage Chahine 《Journal of biological inorganic chemistry》2007,12(1):90-100
The kinetics and thermodynamics of Ga(III) exchange between gallium mononitrilotriacetate and human serum transferrin as well
as those of the interaction between gallium-loaded transferrin and the transferrin receptor 1 were investigated in neutral
media. Gallium is exchanged between the chelate and the C-site of human serum apotransferrin in interaction with bicarbonate
in about 50 s to yield an intermediate complex with an equilibrium constant K
1 = (3.9 ± 1.2) × 10−2, a direct second-order rate constant k
1 = 425 ± 50 M−1 s−1 and a reverse second-order rate constant k
−1 = (1.1 ± 3) × 104 M−1 s−1. The intermediate complex loses a single proton with proton dissociation constant K
1a = 80 ± 40 nM to yield a first kinetic product. This product then undergoes a modification in its conformation which lasts
about 500 s to produce a second kinetic intermediate, which in turn undergoes a final extremely slow (several hours) modification
in its conformation to yield the gallium-saturated transferrin in its final state. The mechanism of gallium uptake differs
from that of iron and does not involve the same transitions in conformation reported during iron uptake. The interaction of
gallium-loaded transferrin with the transferrin receptor occurs in a single very fast kinetic step with a dissociation constant
K
d = 1.10 ± 0.12 μM and a second-order rate constant k
d = (1.15 ± 0.3) × 1010 M−1 s−1. This mechanism is different from that observed with the ferric holotransferrin and suggests that the interaction between
the receptor and gallium-loaded transferrin probably takes place on the helical domain of the receptor which is specific for
the C-site of transferrin and HFE. The relevance of gallium incorporation by the transferrin receptor-mediated iron-acquisition
pathway is discussed. 相似文献
7.
Laccase-catalyzed oxidation of N-substituted phenothiazines and N-substituted phenoxazines was investigated at pH 5.5 and
25°C. The recombinant laccase from Polyporus pinsitus (rPpL) and the laccase from Myceliophthora thermophila (rMtL) were used. The dependence of initial reaction rate on substrate concentration was analyzed by applying the laccase
action scheme in which the laccase native intermediate (NI) reacts with a substrate forming reduced enzyme. The reduced laccase
produces peroxide intermediate (PI) which in turn decays to the NI. The calculated constant (kox) values of the PI formation are (6.1±3.1)×105 M−1s−1 for rPpL and (2.5±0.9)×104 M−1s−1 for rMtL. The bimolecular constants of the reaction of the native intermediate with electron donor (kred) vary in the interval
from 2.2×105 to 2.1×107 M−1s−1 for rPpL and from 1.3×102 to 1.8×105 M-1s−1 for rMtL. The larger reactivity of rPpL in comparison to rMtL is associated with the higher redox potential of type I Cu
of rPpL. The variation of kred values for both laccases correlates with the change of the redox potential of substrates. Following outer sphere (Marcus)
electron transfer mechanism the calculated activationless electron transfer rate and the apparent reorganization energy are
5.0×107 M−1s−1 and 0.29 eV, respectively. 相似文献
8.
Culture of human hepatocytes from small surgical liver biopsies. Biochemical characterization and comparison with in vivo 总被引:4,自引:0,他引:4
M. José Gómez-Lechón Pilar López Teresa Donato Angel Montoya Amparo Larrauri Patricia Giménez Ramón Trullenque Ricardo Fabra José V. Castell 《In vitro cellular & developmental biology. Plant》1990,26(1):67-74
Summary High yields of human hepatocytes (up to 23×106 viable cells/g) were obtained from small surgical liver biopsies (1 to 3 g) by a two-step collagenase microperfusion method.
Cell viability was about 95%, attachment efficiency of hepatocytes seeded on fibronectin-coated plates was 80% within 1 h
after plating, and cells survived for about 2 wk in serum-free Ham’s F12 containing 0.2% bovine serum albumin, 10−8
M insulin, and 10−8
M dexamethasone. To evaluate the metabolism of human hepatocytes in serum-free conditions, we measured their most characteristic
biochemical functions and compared them to those reported for human liver. After 24 h in culture, glycogen content was 1250±177
nmol glucose/mg cell protein and remained stable for several days. Gluconeogenesis from lactate in hormone-free media was
(3.50±0.17 nmol glucose·mg−1·min−1) similar to that reported for human liver. Insulin at 10−8
M activated glycolysis (×1.40) and glycogenesis (×1.34), and glucagon at 10−9
M stimulated gluconeogenesis (×1.35) and glycogenolysis (×2.18). Human hepatocytes synthesized albumin, transferrin, fibrinogen,
α1-antitrypsin, α1-antichymotrypsin, α1-acid glycoprotein, haptoglobin, α2-macroglobulin, and plasma fibronectin and excreted them to the culture medium. Maximum protein synthesis was stimulated by
10−9
M dexamethasone. Basal urea synthesis oscillated between 2.5 and 3.5 nmol·mg−1 cell protein·min−1, about 5 times the value estimated for human liver. Cytochrome P-450 decreased in culture but it was still 20% of freshly
isolated hepatocytes by Day 5 in culture. In addition, ethoxycumarin-O-deethylase and aryl hydrocarbon hydroxylase could be
induced in vitro by treatment with methyl cholanthrene. Glutathione levels were similar to those reported for human liver
(35 nmol·mg−1).
The results of our work show that adult human hepatocytes obtained from small surgical biopsies and cultured in chemically
defined conditions express their most important metabolic functions to an extent that is similar to that reported for adult
human liver. 相似文献
9.
Nicola D’Amelio Luca Fontanive Fulvio Uggeri Furio Suggi-Liverani Luciano Navarini 《Food biophysics》2009,4(4):321-330
Caffeine complexation by chlorogenic acid (3-caffeoylquinic acid, CAS Number [327-97-9]) in aqueous solution as well as caffeine–chlorogenate
complex in freshly prepared coffee brews have been investigated by high-resolution 1H-NMR. Caffeine and chlorogenic acid self-associations have also been studied and self-association constants have been determined
resorting to both classical isodesmic model and a recently introduced method of data analysis able to provide also the critical
aggregation concentration (cac). Furthermore, caffeine–chlorogenate association constant was measured. For the caffeine, the
average value of the self-association constant determined by isodesmic model (K
i = 7.6 ± 0.5 M−1) is in good agreement with the average value (K
a = 10 ± 1.8 M−1) determined with the method which permits the determination of the cac (8.43 ± 0.05 mM). Chlorogenic acid shows a slight
decreased tendency to aggregation with a lower average value of association constants (K
i = 2.8 ± 0.6 M−1; K
a = 3.4 ± 0.6 M−1) and a critical concentration equal to 24 ± 1 mM. The value of the association constant of the caffeine–chlorogenate complex
(30 ± 4 M−1) is compatible with previous studies and within the typical range of reported association constants for other caffeine–polyphenol
complexes. Structural features of the complex have also been investigated, and the complex conformation has been rediscussed.
Caffeine chemical shifts comparison (monomeric, complexed, coffee brews) clearly indicates a significant amount of caffeine
is complexed in beverage real system, being chlorogenate ions the main complexing agents. 相似文献
10.
R. Candau A. Belli G. Y. Millet D. Georges B. Barbier J. D. Rouillon 《European journal of applied physiology and occupational physiology》1998,77(6):479-485
The aim of the present study was to examine the physiological and mechanical factors which may be concerned in the increase
in energy cost during running in a fatigued state. A group of 15 trained triathletes ran on a treadmill at velocities corresponding
to their personal records over 3000m [mean 4.53 (SD 0.28) m · s−1] until they felt exhausted. The energy cost of running (C
R) was quantified from the net O2 uptake and the elevation of blood lactate concentration. Gas exchange was measured over 1 min firstly during the 3rd–4th min
and secondly during the last minute of the run. Blood samples were collected before and after the completion of the run. Mechanical
changes of the centre of mass were quantified using a kinematic arm. A significant mean increase [6.9 (SD 3.5)%, P < 0.001] in C
R from a mean of 4.4 (SD 0.4) J · kg−1 · m−1 to a mean of 4.7 (SD 0.4) J · kg−1 · m−1 was observed. The increase in the O2 demand of the respiratory muscles estimated from the increase in ventilation accounted for a considerable proportion [mean
25.2 (SD 10.4)%] of the increase in CR. A mean increase [17.0 (SD 26.0)%, P < 0.05] in the mechanical cost (C
M) from a mean of 2.36 (SD 0.23) J · kg−1 · m−1 to a mean of 2.74 (SD 0.55) J · kg−1 · m−1 was also noted. A significant correlation was found between C
R and C
M in the non-fatigued state (r = 0.68, P < 0.01), but not in the fatigued state (r = 0.25, NS). Furthermore, no correlations were found between the changes (from non-fatigued to fatigued state) in C
R and the changes in C
M suggesting that the increase in C
R is not solely dependent on the external work done per unit of distance. Since step frequency decreased slightly in the fatigued
state, the internal work would have tended to decrease slightly which would not be compatible with an increase in C
R. A stepwise regressions showed that the changes in C
R were linked (r = 0.77, P < 0.01) to the changes in the variability of step frequency and in the variability of potential cost suggesting that a large
proportion of the increase in C
R was due to an increase in the step variability. The underlying mechanisms of the relationship between C
R and step variability remains unclear.
Accepted: 15 September 1997 相似文献
11.
A microprocessor controlled apparatus is described which can measure, control and record nitrate uptake byLolium perenne in nutrient solution, comparing seven selection lines in duplicate. Nutrient solution flowed at 1 min−1, and linear response was found from 10−1 to 10−4
M NO
3
−
.
Uptake rates for Lolium were between 10−5 and 10−4
M NO
3
−
, plant−1, h−1, which agreed with previous, manually determined, rates, ‘Overshoot’ in nitrate dosing, which was a problem with manual systems,
was eliminated. Nitrate concentration was controlled (±3%) in modified Hoagland’s solution. 相似文献
12.
Hiroshi Takashima Ayako Araki Keiko Takemoto Naokazu Yoshikawa Keiichi Tsukahara 《Journal of biological inorganic chemistry》2006,11(3):316-324
In order to understand the detailed mechanism of the stereoselective photoinduced electron-transfer (ET) reactions of zinc-substituted
myoglobin (ZnMb) with optically active molecules by flash photolysis, we designed and prepared new optically active agents,
such as N,N′-dimethylcinchoninium diiodide ([MCN]I2) and N,N′-dimethylcinchonidinium diiodide ([MCD]I2). The photoexcited triplet state of ZnMb, 3(ZnMb)*, was successfully quenched by [MCN]2+ and [MCD]2+ ions to form the radical pair of ZnMb cation (ZnMb·+) and reduced [MCN]·+ and [MCD]·+, followed by a thermal back ET reaction to the ground state. The rate constants (k
q) for the ET quenching at 25 °C were obtained as k
q(MCN)=(1.9±0.1)×106 M−1 s−1 and k
q(MCD)=(3.0±0.2)×106 M−1 s−1, respectively. The ratio of k
q(MCD)/k
q(MCN)=1.6 indicates that the [MCD]2+ preferentially quenches 3(ZnMb)*. The second-order rate constants (k
b) for the thermal back ET reaction from [MCN]·+ and [MCD]·+ to ZnMb·+ at 25 °C were k
b(MCN)=(0.79±0.04)×108 M−1 s−1 and k
b(MCD)=(1.0±0.1)×108 M−1 s−1, respectively, and the selectivity was k
q(MCD)/k
q(MCN)=1.3. Both quenching and thermal back ET reactions are controlled by the ET step. In the quenching reaction, the energy
differences of ΔΔH
≠(MCD–MCN) and ΔΔS
≠(MCD–MCN) at 25 °C were obtained as −1.1 and 0 kJ mol−1, respectively. On the other hand, ΔΔH
≠(MCD–MCN)=11±2 kJ mol−1 and TΔΔS
≠(MCD–MCN)=−10±2 kJ mol−1 were given in the thermal back ET reaction. The highest stereoselectivity of 1.7 for [MCD]·+ found at low temperature (10 °C) was due to the ΔΔS
≠ value obtained in the thermal back ET reaction.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
13.
Chlorogenic acid, 3’-O-caffeoyl D-quinic acid, is an inherent ligand present inHelianthus annuus L. The effect of pH on chlorogenic acid binding to helianthinin suggests that maximum binding occurs at pH 6.0. The protein-polyphenol
complex precipitates as a function of time. The association constant of the binding of chlorogenic acid to helianthinin, determined
by equilibrium dialysis, at 31°C has a value of 3.5 ± 0.1 × 104M−-1 resulting in a ΔG value of − 6.32 ± 0.12 kcal /mol. The association constantK
ais 1.0 ± 0.1 × 104M−1 as determined by ultraviolet difference spectral titration at 25°C with ΔG° of -5.46 ± 0.06 kcal/mol. From fluorescence spectral
titration at 28°C, theK
avalue is 1.38 ± 0.1 × 1 0 4M−1 resulting in a ΔG of − 5.70 ± 0.05 kcal/mol. The total number of binding sites on the protein are 420 ± 50 as calculated
from equilibrium dialysis. Microcalorimetric data of the ligand-protein interaction at 23°C suggests mainly two classes of
binding. The thermal denaturation temperature,T
mof the protein decreases from 76°C to 72°C at 1 × 10−3M chlorogenic acid concentration upon complexation. This suggests that the complexation destabilizes the protein. The effect
of temperature onK
aof chlorogenic acid shows a nonlinear increase from 10.2°C to 45°C. Chemical modification of both lysyl and tryptophanyl residues
of the protein decreases the strength of binding of chlorogenic acid. Lysine, tryptophan and tyrosine of protein are shown
to be present at the binding site. Based on the above data, it is suggested that charge-transfer complexation and entropically
driven hydrophobic interaction are the predominant forces that are responsible for binding of chlorogenic acid to the multisubunit
protein, helianthinin.
Publication No. 324. 相似文献
14.
D. Moro S. D. Bradshaw 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):419-428
The coexistence of the Lakeland Downs short-tailed mouse Leggadina lakedownensis and house mouse Mus domesticus on Thevenard Island, in the arid north of Western Australia, prompted a study to compare their seasonal water and sodium
metabolism using tritiated water and sodium-22 as tracers. Fractional water influx rates for M. domesticus (40.3 ± 1.6% total body-water day−1) were significantly higher than those for L. lakedownensis (25.3 ± 1.2% total body-water day−1). Water effluxes were higher in both species of mouse after the passage of a cyclonic storm near the study site. Water flux
differences remained significant between species when turnover rates were scaled with body mass. A comparison of water influx
rates of M. domesticus with those predicted for field populations of other eutherian rodents showed that rates for M. domesticus on Thevenard Island were higher than expected. In contrast, water influx rates for L. lakedownensis did not differ significantly from expected values for a desert rodent. Rates of sodium influx for M. domesticus (41.7 ± 3.6 mmol kg−1 day−1) were over twice those of L. lakedownensis (19.7 ± 4.8 mmol kg−1 day−1), and were reflected in the significantly higher concentrations of sodium ingested in the diet, and excreted in the urine,
of M. domesticus. Furthermore, the rate of water influx was positively correlated with the rate of sodium influx in M. domesticus, suggesting that they were obtaining both water and sodium from the one dietary source. There was no evidence to suggest
that mice of either species were experiencing water or sodium stress, because water and sodium influxes and effluxes remained
in balance. These results suggest that M. domesticus on Thevenard Island had a higher-than-expected daily water requirement, and may represent a mesic deme of house mice that
have yet to adapt to the island environment.
Accepted: 9 May 1999 相似文献
15.
Noncovalent DIDS binding to Band 3 (AE1) protein in human erythrocyte membranes, modified by non-penetrating, water soluble
1-ethyl-3-(4-azonia-4,4-dimethylpentyl)-carbodiimide iodide (EAC), was studied at 0°C in the presence of 165 mM KCl. Under
experimental conditions applied up to (48 ± 5) % of irreversible chloride self-exchange inhibition was observed. The apparent
dissociation constant, KD, for “DIDS-Band 3” complex, determined from the chloride transport experiments, was (34 ± 3) nM
and (80 ± 12) nM for control and EAC-treated resealed ghosts, respectively. The inhibition constant, Ki, for DIDS was (35
± 6) nM and (60 ± 8) nM in control and EAC-treated ghosts, respectively. The reduced affinity for DIDS reversible binding
was not a result of negative cooperativity of DIDS binding sites of Band 3 oligomer since Hill’s coefficients were indistinguishable
from 1 (within the limit error) both for control and EAC-treated ghosts. By using tritium-labeled DIDS, 4,4’-diisothiocyanato-2,2’-stilbenedisulfonate
([3H]DIDS), the association rate constant, k+1 (M−1s−1), was measured. The mean values of (4.3 ± 0.7) × 105 M−1s−1 for control and (2.7 ± 0.7) × 105 M−1s−1 for EAC-treated ghosts were obtained. The mean values for KD, evaluated from [3H]DIDS binding measurements, were (37 ± 9) nM and (90 ± 21) nM for control and EAC-modified ghosts, respectively. The results
demonstrate that EAC modification of AE1 reduces about 2-fold the affinity of AE1 for DIDS. It is suggested that half of the
subunits are modified near the transport site by EAC. 相似文献
16.
The relationship between scale and body growth for emigrating Atlantic salmon, Salmo salar, smolts was previously not understood and therefore was examined in this study using mark-recapture techniques. The size
of smolts at time of recapture was significantly greater than when marked (P = 0.0002). The growth in length of smolts emigrating 5 km over an average of 20 days was 7.7 ± 6.1 mm per day. Instantaneous
somatic growth (G
body) ranged from 7.0 × 10−4 to 5.1 × 10−3 (mean = 2.7 × 10−3 ± 1.3 × 10−3). The mean number of plus growth circuli present per scale was significantly greater for smolts when recaptured compared
to when marked (P = 0.0014). The instantaneous growth rate of scales (G
scale) ranged from 1.4 × 10−3 to 11.5 × 10−3 (mean = 6.6 × 10−3 ± 4.3 × 10−3). The relationship between body size and scale radius showed positive allometry rather than isometry. The relationship of
G
scale with G
body showed positive allometry indicating that scales grew at a slightly faster rate than the body during the emigratory period. 相似文献
17.
M. E. Forster W. Davison M. Axelsson L. Sundin C. E. Franklin S. Gieseg 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):345-352
Two species of Antarctic fish were stressed by moving them from seawater at −1 °C to seawater at 10 °C and holding them for
a period of 10 min. The active cryopelagic species Pagothenia borchgrevinki maintained heart rate while in the benthic species Trematomus bernacchii there was an increase in heart rate. Blood pressure did not change in either species. Both species released catecholamines
into the circulation as a consequence of the stress. P. borchgrevinki released the greater amounts, having mean plasma concentrations of 177 ± 54 nmol · l−1 noradrenaline and 263 ± 131 nmol · l−1 adrenaline at 10 min. Plasma noradrenaline concentrations rose to 47 ± 14 nmol · l−1 and adrenaline to 73 ± 28 nmol · l−1 in T. bernacchii. Blood from P. borchgrevinki was tonometered in the presence of isoprenaline. A fall in extracellular pH suggests the presence of a Na+/H+ antiporter on the red cell membrane, the first demonstration of this in an Antarctic fish. Treatment with the β-adrenergic
antagonist drug sotalol inhibited swelling of red blood cells taken from temperature-stressed P. borchgrevinki, suggesting that the antiporter responds to endogenous catecholamines.
Accepted: 22 January 1998 相似文献
18.
Julio C. Davila Chandrasekara G. Reddy Patrick J. Davis Daniel Acosta 《In vitro cellular & developmental biology. Plant》1990,26(5):515-524
Summary The present study was undertaken to assess and compare the toxic effects of papaverine hydrochloride and its metabolites.
Primary cell cultures of rat hepatocytes were treated with papavarine (papaver), 3′-O-desmethyl (3′-OH), 4′-O-desmethyl (4′-OH),
and 6-O-desmethyl (6-OH) papaverine at 1×10−5, 1×10−4, and 1×10−3
M for 4,8, 12, and 24-h periods. Cell injury was determined by: a) cell viability using the trypan blue exclusion test; b)
cytosolic enzyme leakage of lactate dehydrogenase and aspartate aminotransferase; c) morphologic alterations; and d) lactate:
pyruvate (L:P) ratios. Cell cultures showed concentration-and time-dependent responses. For example, a decrease in cell viability
and an increase in enzyme leakage were observed after cell treatment with 1×10−4 and 1×10−3
M papaver for 8 h; 1×10−3
M 6-OH papaverine for 8 h and 1×10−4
M for 24 h; and 1×10−3
M 4′-OH papaverine for 24 h (P<0.05). Furthermore, changes in morphology correlated to cell viability and enzyme release in those cultures treated with
papaver, 4′-OH and 6-OH papaverine. Some of these changes included size deformation, cell detachment from the dishes, and
cell necrosis. On the other hand, an increase in L:P ratios (P<0.05) was detected with papaver as early as 8 h with 1×10−4 and 1×10−3
M and 12 h with 1×10−5
M; 6-OH showed an increase, in L:P ratios at 8 h with 1×10−3
M and 12 h with 1×10−4
M; these changes were evident with 4′-OH at 12 h with 1×10−3
M. In contrast, cells treated with 3′-OH papaverine did not show significant damage with any time period and concentration
used in this study. The results of this study indicate that papaverine-derived metabolites are less cytotoxic than its parent
compound, papaver. The toxicity was ranked as follows: papaver>6-OH>4′-OH>−3′-OH.
This work was supported in part by grant ES04200-02 from the National Institute of Environmental Health Sciences, Bethesda,
MD.
Presented in part at the fall ASPET meeting in Salt Lake City, August, 1989. Daniel Acosta is a Burroughs Wellcome Scholar
in Toxicology. 相似文献
19.
R. E. Anderson J. W. Kemp W. S. S. Jee D. M. Woodbury 《In vitro cellular & developmental biology. Plant》1984,20(11):847-855
Summary Na+,K+-ATPase, HCO
3
−
-ATPase, Ca2+,Mg2+,-ATPase, Ca2+-ATPase, and alkaline phosphatase activities were measured in cultures of osteoblastlike cells treated with fluoride and cortisol
separately and in combinations. Low concentrations of cortisol increased HCO
3
−
-ATPase (10−11 to 10−18
M cortisol) and alkaline phosphatase (10−11 to 10−9
M cortisol) activities, but higher cortisol concentrations reduced these activities. Na+,K+-ATPase, Ca2+,Mg2+-ATPase, and Ca2+-ATPase activities tended only to be reduced by cortisol.
Fluoride (10−6 and 5×10−6
M) increased HCO
3
−
-ATPase and alkaline phosphatase activities, but these activities were similar to controls in the presence of 10−5
M fluoride. Ca2+,Mg2+-ATPase activity was decreased and Na+,K+-ATPase activity was increased as the concentration of fluoride increased (10−6 to 10−5
M). Preliminary experiments with fluoride indicated that lower concentrations (10−7
M) were without effect.
Cortisol concentrations of 10−9 and 10−8
M were chosen for studies with combinations of cortisol and fluoride because the effects of these concentrations on alkaline
phosphatase activity were opposite, i.e. 10−9
M increased whereas 10−8
M decreased activity. Fluoride concentrations of 10−6, 5×10−6, and 10−5
M were chosen because a peak of alkaline phosphatase activity occurred at 5×10−6
M fluoride. Higher (10−4
M) and lower (10−7
M) fluoride concentrations were without effect.
The effects of combinations of cortisol and fluoride depend on the enzyme activity measured. Fluoride (10−6
M) combined with cortisol (10−9
M) produced a peak of Na+,K+-ATPase activity. The increased activity obtained with all concentrations of fluoride alone was preserved when fluoride was
combined with 10−8
M cortisol, although the activity tended to be reduced at 5×10−6 and 10−5
M fluoride. HCO
3
−
-ATPase activity was increased by fluoride combined with 10−8
M cortisol and decreased by fluoride combined with 10−9
M cortisol compared to the activities obtained with fluoride alone. The decrease in Ca2+,Mg2+-ATPase activity caused by fluoride alone was prevented by 10−9 and enhanced by 10−8
M cortisol, although all treatments produced the same activity at 10−5
M fluoride. Ca2+-ATPase activity tended to be increased by combinations of fluoride and cortisol, but significantly so only at 10−5
M fluoride in combinations with 10−8 and 10−9
M cortisol. Alkaline phosphatase activity was increased by fluoride combined with 10−9
M cortisol and decreased by fluoride combined with 10−8
M cortisol compared to the activities obtained with fluoride alone.
These results suggest that the abilities of bone cells to regulate ion transport (as reflected in their ion-transporting ATPase
activities) are modulated by glucocorticoids and fluoride. Inasmuch as these cells may regulate the ionic composition and
concentrations of the bone extracellular fluid (ECF) in vivo, the modulation of their activities by cortisol and fluoride
may result in altered bone ECF composition.
This work was supported by Grant NAG-2-108 from the National Aeronautics and Space Administration, D.C., and Grant PO1 NS15767
from the National Institute of Neurological and Communicative Disorders and Stroke, Bethesda, MD. 相似文献
20.
Allison A. Welder Roberta Grant June Bradlaw Daniel Acosta 《In vitro cellular & developmental biology. Animal》1991,27(12):921-926
Summary Tricyclic antidepressants (TCAs) are currently used in the treatment of mental depression and nocturnal enuresis. Clinically,
these drugs are useful; however, cardiotoxicity can occur even with therapeutic dosages. For example, TCAs are known to alter
myocardial function, induce arrhythmias, and produce heart block in individuals with a normal cardiovascular history. The
present study was undertaken to establish a culture system of spontaneously contracting adult primary myocardial cells for
toxicologic testing and to examine their contractility, morphology, and lactate dehydrogenase release (LDH) after treatment
with one of the most cardiotoxic TCAs, amitriptyline. Primary myocardial cell cultures were obtained from approximately 60-
to 90-day-old Sprague-Dawley rats. After the cells had been grown in culture for 11 days, they were treated with amitriptyline
(1 × 10−3, 1 × 10−4, and 1 × 10−5
M) for 2 to 24 h. The highest concentration of amitriptyline (1 × 10−3
M) completely destroyed the cardiac muscle cells. In addition to moderate and severe vacuole, granule, and pseudopodia formation,
all contractile activity was inhibited as early as 2 h after exposure to the intermediate concentration of 1 × 10−4
M amitriptyline. Significant LDH release did not occur until 8 h after treatment with this intermediate concentration. Even
though there was no significant LDH release at all 3 time points tested, there was a 50% decrease in beating activity (154±9
to 77±5 beats/min) and initiation of vacuole formation by 2 h with the lowest concentration of amitriptyline (1 × 10−5
M). This study presents a new apparatus for the isolation of adult cardiac myocytes for the establishment of primary cell cultures
for toxicologic testing. Furthermore, these data demonstrate that amitriptyline induces a concentration- and time-dependent
cardiotoxic profile in a model of spontaneously contracting adult cardiac muscle cells in culture. 相似文献