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1.
We tested the hypothesis that the growth rate of Anabaena circinalis,under diurnally stratified conditions, would increase as flotationvelocity increased owing to higher light availability. An insitu experiment compared the growth of diurnally stratifiedpopulations of A. circinalis with flotation velocities of 0.5and 1.0 m h1, with neutrally buoyant populations thatwere exposed to either mixed or persistently stratified conditions.The experiment was conducted in the turbid lower Murray Riverin South Australia (vertical attenuation coefficient = 4.52± 0.36 m1). To represent the mixing patterns,A. circinalis was contained in diffusion chambers that weremoved to different positions in the water column throughoutthe day. Diurnal populations with flotation velocities of 1.0and 0.5 m h1 grew at 0.23 ± 0.01 and 0.15 ±0.01 day1, respectively. Mixed populations grew at 0.19± 0.01 day1, whereas persistently stratified populationsgrew at 0.43 ± 0.01 day1. Results were used toextend a model that predicts growth of A. circinalis when exposedto the different mixing patterns. The model showed that bloomsare unlikely to be formed when the period of diurnal stratificationis <1 week, regardless of flotation velocity. When the diurnallystratified period is >1 week, flotation velocity is importantand a bloom may form depending on values assigned to the growthperiod and maximum mixed depth (Zm). 相似文献
2.
Pith-derived calluses of Nicotiana tabacum L. cv. Wisconsinno. 38 were inoculated on an RM-1964 medium containing variousconcentrations of a morphactin, chlorflurenol (CFl) and kinetin(KIN). An addition of KIN (0.12 mg/liter) alone was effectivefor shoot formation from the calluses, but a high dose (10 mg/liter)resulted in the inhibition of growth and in no differentiation.The inhibitory effect of a high dose of KIN was counteractedwith CFl. Three combinations of KIN and CFl; CFl (0.1 mg/liter)$KIN(2.0 mg/liter); CFl (0.1 mg/liter)$KIN (10.0 mg/liter) and CFl(1.0 mg/liter) $KIN (2.0 mg/liter), were successful for 100%shoot redifferentiation in inoculated calluses. An appropriatebalance between CFl and KIN seems to be involved in shoot formation.The present results can best be interpreted by assuming thatCFl acts as an auxin in cultured tissues. (Received January 16, 1975; ) 相似文献
3.
Spherical protoplasts (3040 µm in diameter), isolatedfrom cultured tobacco cells, elongated rapidly during a cultureperiod of 3 to 8 days and finally assumed a long cylindricalform (300400 µm in length). The optimum concentrationof a-naphthaleneacetic acid and benzyladenine for the elongationwas 0.1 mg/liter and 1 mg/liter respectively. (Received August 10, 1982; Accepted November 12, 1982) 相似文献
4.
Developmental changes in electrocardiogram (ECG) andresponse to selective K+ channelblockers were assessed in conscious, unsedated neonatal (days 1, 7, 14) and adult male mice(>60 days of age). Mean sinus R-R interval decreased from 120 ± 3 ms in day 1 to 110 ± 3 ms inday 7, 97 ± 3 ms inday 14, and 81 ± 1 ms in adultmice (P < 0.001 by ANOVA; all 3 groups different from day 1). Inparallel, the mean P-R interval progressively decreased duringdevelopment. Similarly, the mean Q-T interval decreased from 62 ± 2 ms in day 1 to 50 ± 2 ms inday 7, 47 ± 8 ms inday 14 neonatal mice, and 46 ± 2 ms in adult mice (P < 0.001 byANOVA; all 3 groups are significantly different fromday 1).Q-Tc was calculated asQ- interval.Q-Tc significantly shortened from179 ± 4 ms in day 1 to 149 ± 5 ms in day 7 mice(P < 0.001). In addition, the J junction-S-T segment elevation observed in day1 neonatal mice resolved by day14. Dofetilide (0.5 mg/kg), the selective blocker ofthe rapid component of the delayed rectifier(IKr) abolished S-T segment elevation and prolonged Q-T andQ-Tc intervals in day 1 neonates but not in adult mice.In contrast, 4-aminopyridine (4-AP, 2.5 mg/kg) had no effect onday 1 neonates but in adults prolongedQ-T and Q-Tc intervals andspecifically decreased the amplitude of a transiently repolarizingwave, which appears as an r' wave at the end of the apparent QRSin adult mice. In conclusion, ECG intervals and configuration changeduring normal postnatal development in the mouse.K+ channel blockers affect themouse ECG differently depending on age. These data are consistent withthe previous findings that the dofetilide-sensitiveIKr is dominantin day 1 mice, whereas 4-AP-sensitivecurrents, the transiently repolarizingK+ current, and the rapidlyactivating, slowly inactivating K+current are the dominant K+currents in adult mice. This study provides background information useful for assessing abnormal development in transgenic mice. 相似文献
5.
The planktonic crustacean Daphnia magna was fed varying quantitiesor quality (C:N:P ratio) of phytoplankton in a flow-throughchemostat culture. Size-specific dry weight (DW) and egg productionvaried with a factor of >3, mainly governed by food quantity.A maximum was reached at 4 mg C/l. Mean C/DW was 43.96 ±4.43% and insignificant variations were recorded between thegroups of fed animals, but a decrease to 38.09 was found instarved animals. Mean N/DW was 8.18 ± 1.02% with smallvariation between the treatments, and again with the lowestvalue in starved individuals. The mean P/DW of 1.38 ±0.3% of DW, was largely unaffected by food quantity or the absoluteand relative supply of paniculate P in the food. The resultsindicate a rather constant element/DW ratio in Daphnia withinnormal ranges of food supply. This has strong implications forbiomass determinations, and is in particular important whenmodelling elemental turnover and release from Daphnia. 相似文献
6.
In situ growth and development of Neocalanus flemingeri/plumchrusstage C1C4 copepodites were estimated by both the artificial-cohortand the single-stage incubation methods in March, April andMay of 20012005 at 56°C. Results from thesetwo methods were comparable and consistent. In the field, C1C4stage durations ranged from 7 to >100 days, dependent ontemperature and chlorophyll a (Chl a) concentration. Averagestage durations were 12.414.1 days, yielding an averageof 56 days to reach C5, but under optimal conditions stage durationswere closer to 10 days, shortening the time to reach C5 (fromC1) to 46 days. Generally, growth rates decreased with increasingstage, ranging from 0.28 day1 to close to zero but weretypically between 0.20 and 0.05 day1, averaging 0.110± 0.006 day1 (mean ± SE) for single-stageand 0.107 ± 0.005 day1 (mean ± SE) forartificial-cohort methods. Growth was well described by equationsof MichaelisMenten form, with maximum growth rates (Gmax)of 0.170.18 day1 and half saturation Chl a concentrations(Kchl) of 0.450.46 mg m3 for combined C13,while Gmax dropped to 0.080.09 day1 but Kchl remainedat 0.380.93 mg m3 for C4. In this study, in situgrowth of N. flemingeri/plumchrus was frequently food limitedto some degree, particularly during March. A comparison withglobal models of copepod growth rates suggests that these modelsstill require considerable refinement. We suggest that the artificial-cohortmethod is the most practical approach to generating the multispeciesdata required to address these deficiencies. 相似文献
7.
Hybertson Brooks M.; Kitlowski Roger P.; Jepson Eric K.; Repine John E. 《Journal of applied physiology》1998,84(1):263-268
Hybertson, Brooks M., Roger P. Kitlowski, Eric K. Jepson,and John E. Repine. Supercritical fluid-aerosolized vitamin Epretreatment decreases leak in isolated oxidant-perfused rat lungs.J. Appl. Physiol. 84(1): 263-268, 1998.We hypothesized that direct pulmonary administration ofsupercritical fluid-aerosolized (SFA) vitamin E would decrease acuteoxidative lung injury. We previously reported that rapid expansion ofsupercritical CO2 formedrespirable particles of vitamin E and that administering SFA vitamin Eto rats increased lung vitamin E levels and decreased neutrophil-mediated lung leak. In the present investigation, we foundthat pretreatment with SFA vitamin E protected isolated rat lungsagainst the oxidant-induced lung leak caused by perfusion with xanthineoxidase (XO) and purine, an enzyme system that generates superoxideanion () and hydrogenperoxide. SFA vitamin E droplets were 0.7-3 µm in diameter, andinhalation of the airborne droplets for 30 min deposited ~55 µg ofvitamin E in rat lungs. Isolated rat lungs perfused with XO (0.02 U/ml) and purine (10 mM) gained more weight (1.75 ± 0.12 g,n = 8), retained more Ficoll(11.5 ± 1.2 mg/left lung,n = 7), and accumulated more Ficoll intheir lung lavages (700 ± 146 µg/ml,n = 8) than control lungs [0.25 ± 0.06 g (n = 10), 6.2 ± 1.2 mg/left lung (n = 9), and 141 ± 31 µg/ml (n = 8), respectively,P < 0.05]. In contrast,isolated lungs from rats that were pretreated with SFA vitamin E haddecreased (P < 0.05) weight gains(0.32 ± 0.06 g, n = 7), Ficollretentions (3.3 ± 1.1 mg/left lung,n = 7), and lung lavage Ficollconcentrations (91 ± 26 µg/ml,n = 6) after perfusion with XO andpurine compared with isolated lungs from control rats perfused with XOand purine. This protective effect was not observed in rat lungs givensham treatments (CO2 alone orvitamin E acetate aerosolized with supercriticalCO2). Our results suggest thatdirect pulmonary supplementation of vitamin E decreases susceptibilityto vascular leakage caused by XO-derived oxidants. 相似文献
8.
Sand P.; Svenberg T.; Rydqvist B. 《American journal of physiology. Cell physiology》1997,273(4):C1186
The patch-clamp technique was used to study the effects ofcarbachol (CCh) on HT-29 cells. During CCh exposure, the cells (n = 23) depolarized close to theequilibrium potential forCl(;48 mV) and the membrane potential then started to oscillate(16/23 cells). In voltage-clamp experiments, similar oscillations inwhole cell currents could be demonstrated. The whole cell conductanceincreased from 225 ± 25 pS in control solution to 6,728 ± 1,165 pS (means ± SE, n = 17). Insubstitution experiments (22 mMCl in bath solution, = 0 mV), the reversal potential changed from 41.6 ± 2.2 mV(means ± SE, n = 9) to 3.2 ± 2.0 mV (means ± SE, n = 7).When the cells were loaded with the calcium-sensitive fluorescent dye,fluo 3, and simultaneously patch clamped, CCh caused a synchronousoscillating pattern of fluorescence and membrane potential. Incell-attached patches, the CCh-activated currents reversed at arelative membrane potential of 1.9 ± 3.7 mV (means ± SE,n = 11) with control solution in thepipette and at 46.2 ± 5.3 mV (means ± SE,n = 10) with a 15 mMCl solution in the pipette.High K+ (144 mM) did not changethe reversal potential significantly (P 0.05, n = 8). In inside-out patches,calcium-dependent Clchannels could be demonstrated with a conductance of 19 pS(n = 7). It is concluded that CChcauses oscillations in membrane potential that involvecalcium-dependent Clchannels and a K+ permeability. 相似文献
9.
Protoplasts were successfully isolated from internodal callustissues of both Oxalis glaucifolia and O. rhombeo-ovata whenthey were digested in a solution containing 0.1% (w/v) MacerozymeR-10, 0.5% (w/v) cellulase Onozuka R-10 and 0.3 mmol m3sucrose. Protoplasts proliferated to give cell colonies on Gamborget al.'s B5 medium supplemented with 0.3 mmol m3 mannitol,0.5 mg dm32, 4-D, and 2.0 mg dm3 kinetin. Calluswas produced upon transfer of cell colonies to Murashige andSkoog medium containing 2.0 mg dm3 l-naphthaleneaceticacid (NAA) and 0.1 mg dm3 kinetin for O. glaucifolia,or with 5.0 mg dm3 NAA and 0.5 mg dm3 6-benzylaminopurine,for O. rhombeo-ovata. Plants were regenerated from O. glaucifoliaprotoplasts on a medium containing 0.1 mg dm3 NAA, 1.0mg dm3 kinetin and 1.0 mg dm3 gibberellic acid,but only vascular nodules were differentiated by O. rhombeo-ovataprotoplast-derived calli. Key words: Tissue culture, protoplasts, plant regeneration, Oxalis spp 相似文献
10.
Farrell Peter A.; Fedele Mark J.; Vary Thomas C.; Kimball Scot R.; Jefferson Leonard S. 《Journal of applied physiology》1998,85(6):2291-2297
Thesestudies determined whether increases in rates of protein synthesisobserved in skeletal muscle after moderate or severe acute-resistanceexercise were blunted by insulinopenia. Rats (n = 6-9 per group) were madeinsulin deficient by partial pancreatectomy or remained nondiabetic.Groups either remained sedentary or performed acute-resistance exercise16 h before rates of protein synthesis were measured in vivo. Exerciserequired 50 repetitions of standing on the hindlimbs with either 0.6 gbackpack wt/g body wt (moderate exercise) or 1.0 g backpack wt/g bodywt (severe exercise). Insulin-deficient rats had a mean blood glucoseconcentration >15 mM and reduced insulin concentrations in theplasma. Rates of protein synthesis in gastrocnemius muscle were notdifferent in all sedentary groups. The moderate-exercised nondiabeticgroup (192 ± 12 nmol phenylalanine incorporated · gmuscle1 · h1)and moderate-exercised diabetic group (215 ± 18) had significantly (P < 0.05, ANOVA) higher rates ofprotein synthesis than did respective sedentary groups. In contrast,diabetic rats that performed severe-resistance exercise had rates ofprotein synthesis (176 ± 12) that were not different(P > 0.05) from diabetic sedentaryrats (170 ± 9), whereas nondiabetic rats that performed severeexercise had higher (212 ± 24) rates compared withnondiabetic sedentary rats (178 ± 10) P < 0.05. The present data in combination with previous studies [J. D. Fluckey, T. C. Vary, L. S. Jefferson, and P. A. Farrell. Am. J. Physiol. 270 (Endocrinol. Metab. 33): E313-E319,1996] show that the amount of insulin required for an invivo permissive effect of insulin on rates of protein synthesis can bequite low after moderate-intensity resistance exercise. However, severe exercise in combination with low insulin concentrations can ablate ananabolic response. 相似文献
11.
Moran M. M.; Roy R. R.; Wade C. E.; Corbin B. J.; Grindeland R. E. 《Journal of applied physiology》1998,85(4):1564-1571
This study was designed to determine themaximum-size subcutaneous telemeter that would enable long-term andmultichannel data collection in a 170-g rat for 90 days. Inphase 1, rats with implants weighing 5 (2.5 cm3), 15 (7.5 cm3), 25 (12.5 cm3), 35 (17.5 cm3), or 45 (22.5 cm3) g were compared withsham-operated (SOC) and nonoperated (NOC) control animals. Severe skinlesions, seromas, and lower growth rates were observed in rats havingimplants 35 g. Thus, in phase 2,rats implanted with 23.5 g (17.5 cm3; 11-g active telemeter and12.5-g implant) were compared with rats implanted with 11 g (6 cm3; telemeter only) and with theSOC and NOC groups. No differences were found among implanted groups inmean arterial pressure (MAP), heart rate (HR), subcutaneoustemperature, or spontaneous activity under standard housing conditions.All groups were more active and had a higher MAP during the dark thanthe light phase of the daily cycle. During 2 h of cold exposure(3°C), both telemetered groups exhibited similar changes in HR,MAP, temperature, and activity levels. Adrenal glands were larger inthe 23.5-g group (51 ± 1.6 mg) than in the SOC (46 ± 1.0 mg)and the NOC groups (41 ± 2.0 mg). No other significant differenceswere found in organ, muscle, or bone weights. These data verify thefeasibility of using 23.5-g (17.5 cm3) subcutaneous telemeters forchronic recordings in young adult rats. 相似文献
12.
A pioneering limnological investigation was carried out in Bhutan in a small peat bog in the Trashiyangtse district (1950 m
above sea level) from February 2000 to January 2002. The sampled pond water had low transparency (55.0–95.0 cm), was typically
acidic (pH 5.69–6.58) with soft water (alkalinity, 11.0–36.0 mg/l; total hardness, 10.0–34.0 mg/l), and had low to moderate
specific conductivity (17.0–62.0 μS/cm). Further, moderate Na (2.0–6.8 mg/l), K (1.8–13.5 mg/l), sulphate (0.85–2.99 mg/l),
and silicate (2.5–15.0 mg/l) concentrations as well as low nutrient levels such as phosphate (0.006–0.170 mg/l) and nitrate
(0.003–0.180 mg/l) characterize the water in the peat bog. The recorded net plankton comprised 27 species of phytoplankton
and 49 species of zooplankton, with the latter indicating greater homogeneity and breaking down into Rotifera (23 species)
> Cladocera (13 species) > Rhizopoda (8 species) > Copepoda (3 species) > Ostracoda = Nematoda (1 species each). On the other
hand, the net plankton density ranged between 93 and 692 number/l (n/l) with numerical dominance by phytoplankton (68.5% ±
12%), of which Chlorophyceae were predominant (90 ± 63 n/l). Zooplankton showed moderately high diversity (2.745 ± 0.293)
and evenness (0.925 ± 0.049) and exhibited almost equal abundance of four recorded groups, namely Cladocera (20 ± 15 n/l)
> Rotifera (15 ± 6 n/l) > Copepoda (14 ± 7 n/l) > Rhizopoda (14 ± 4 n/l). While no significant impact of abiotic factors was
recorded on zooplankton density, rainfall alone was the most important factor that influenced net plankton and various groups
of phytoplankton. Comments on some comparative limnological attributes are also made with similar as well as different habitats
in the nearby Himalayan countries. 相似文献
13.
Andruchov O Andruchova O Wang Y Galler S 《American journal of physiology. Cell physiology》2004,287(6):C1725-C1732
Stretch activation kinetics were investigated in skinned mouse skeletal muscle fibers of known myosin heavy chain (MHC) isoform content to assess kinetic properties of different myosin heads while generating force. The time to peak of stretch-induced delayed force increase (t3) was strongly correlated with MHC isoforms [t3 given in ms for fiber types containing specified isoforms; means ± SD with n in parentheses: MHCI 680 ± 108 (13), MHCIIa 110.5 ± 10.7 (23), MHCIIx(d) 46.2 ± 5.2 (20), MHCIIb 23.5 ± 3.3 (76)]. This strong correlation suggests different kinetics of force generation of different MHC isoforms in the following order:MHCIIb > MHCIIx(d) > MHCIIa >> MHCI. For rat, rabbit, and human skeletal muscles the same type of correlation was found previously. The kinetics decreases slightly with increasing body mass. Available amino acid sequences were aligned to quantify the structural variability of MHC isoforms of different animal species. The variation in t3 showed a correlation with the structural variability of specific actin-binding loops (so-called loop 2 and loop 3) of myosin heads (r = 0.74). This suggests that alterations of amino acids in these loops contribute to the different kinetics of myosin heads of various MHC isoforms. isoform structure-function relationship; stretch activation; muscle mechanics 相似文献
14.
Giovanni Iapichino 《In vitro cellular & developmental biology. Plant》1996,32(4):249-252
Summary Side shoots excised from underground dormant buds ofCynara scolymus L. were used as primary explants to establishin vitro cultures. A 3×3 factorial experiment with all possible combinations of three concentrations (0.5, 1.0, 2.0 mg/liter or 2.22,
4.44, 8.88 μM) ofN
6-benzyladenine (BA) and three concentrations (0, 0.1, 0.2 mg/liter or 0, 0.54, 1.07 μM) of 1-naphthaleneacetic acid (NAA) was used to determine the optimum growth regulator combination for shoot multiplication.
The highest rate of axillary shoots was induced on Murashige and Skoog agar medium supplemented with 0 mg NAA/liter and 1.0
mg BA/liter (4.44 μM). Other cytokinins tested (kinetin, zeatin, and 2-isopentenyl-adenine were less effective than BA in inducing axillary shoot
growth. Up to 60% of elongated microshoots rooted after 5 weeks on 1/2 MS agar medium supplemented with 2 mg/liter (11.42
μM) indole-3-acetic acid (IAA). Seventy percent of rooted plantlets were transferred successfully into soil. Plants are under
evaluation for their genetic uniformity and clonal fidelity. 相似文献
15.
Tissue factor activity is increased in human endothelial cells cultured under elevated static pressure 总被引:1,自引:0,他引:1
Silverman M. D.; Waters C. R.; Hayman G. T.; Wigboldus J.; Samet M. M.; Lelkes P. I. 《American journal of physiology. Cell physiology》1999,277(2):C233
We tested the hypothesis that elevated blood pressure, a knownstimulus for vascular remodeling and an independent risk factor for thedevelopment of atherosclerotic disease, can modulate basal andcytokine-induced tissue factor (TF; CD 142) expression in culturedhuman endothelial cells (EC). Using a chromogenic enzymatic assay, wemeasured basal and tumor necrosis factor- (TNF-; 10 ng/ml, 5 h)-induced TF activities in human aortic EC (HAEC) and vena cava EC(HVCEC) cultured at atmospheric pressure and at 170 mmHg imposedpressure for up to 48 h. Basal TF activities were 22 ± 10 U/mgprotein for HAEC and 14 ± 9 U/mg protein for HVCEC and wereupregulated in both cell types >10-fold by TNF-. Exposure topressure for 5 h induced additional elevation of basal TF activity by47 ± 16% (P < 0.05, n = 6) for HAEC and 17 ± 5%(P < 0.05, n = 3) for HVCEC. Pressurization alsoenhanced TF activity in TNF--treated cells from 240 ± 28 to 319 ± 32 U/mg protein in HAEC (P < 0.05, n = 4) and from 148 ± 25 to179 ± 0.8 U/mg protein (P < 0.05, n = 3) in HVCEC. Cytokinestimulation caused an ~100-fold increase in steady-state TF mRNAlevels in HAEC, whereas pressurization did not alter either TF mRNA orcell surface antigen expression, as determined by quantitative RT-PCRmethodology and ELISA. Elevated pressure, however, modulated the ECplasma membrane organization and/or permeability as inferred from theincreased cellular uptake of the fluorescent amphipathic dyemerocyanine 540 (33 ± 7%, P < 0.05). Our data suggest that elevated static pressure modulates thehemostatic potential of vascular cells by modifying the molecular organization of the plasma membrane. 相似文献
16.
The effect ofaddition of different dosages of caffeine (Caf) to acarbohydrate-electrolyte solution (CES) on metabolism, Caf excretion,and performance was examined. Subjects(n = 15) ingested 8 ml/kg of waterplacebo (Pla-W), 7% CES (Pla-CES), or 7% CES with 150, 225, and 320 mg/l Caf (CES-150, CES-225, and CES-320, respectively) during a warm-upprotocol (20 min) and 3 ml/kg at one-third and two-thirds of a 1-h timetrial. Performance was improved with Caf supplementation: 62.5 ± 1.3, 61.5 ± 1.1, 60.4 ± 1.0, 58.9 ± 1.0, and 58.9 ± 1.2 min for Pla-W, Pla-CES, CES-150, CES-225, and CES-320, respectively.The postexercise urinary Caf concentration (range 1.3-2.5 µg/ml)was dose dependent and always far below the doping level of theInternational Olympic Committee (12 µg/ml) in all subjects. Sweat Cafexcretion during exercise exceeded postexercise early-void urinary Cafexcretion. Caffeinated CES did not enhance free fatty acidavailability, ruling out the fact that performance improvement resultedfrom enhanced fat oxidation. It is concluded that addition ofrelatively low amounts of Caf to CES improves performance and thatpostexercise urinary Caf concentration remained low. 相似文献
17.
Kanaley J. A.; Weltman J. Y.; Veldhuis J. D.; Rogol A. D.; Hartman M. L.; Weltman A. 《Journal of applied physiology》1997,83(5):1756-1761
Kanaley, J. A., J. Y. Weltman, J. D. Veldhuis, A. D. Rogol,M. L. Hartman, and A. Weltman. Human growth hormone response torepeated bouts of aerobic exercise. J. Appl.Physiol. 83(5): 1756-1761, 1997.We examinedwhether repeated bouts of exercise could override growth hormone (GH)auto-negative feedback. Seven moderately trained men were studied onthree occasions: a control day (C), a sequential exercise day (SEB; at1000, 1130, and 1300), and a delayed exercise day (DEB; at 1000, 1400, and 1800). The duration of each exercise bout was 30 min at 70%maximal O2 consumption (O2 max) on a cycleergometer. Standard meals were provided at 0600 and 2200. GH wasmeasured every 5-10 min for 24 h (0800-0800). Daytime(0800-2200) integrated GH concentrations were ~150-160% greater during SEB and DEB than during C: 1,282 ± 345, 3,192 ± 669, and 3,389 ± 991 min · µg · l1for C, SEB, and DEB, respectively [SEB > C(P < 0.06), DEB > C(P < 0.03)]. There were nodifferences in GH release during sleep (2300-0700). Deconvolutionanalysis revealed that the increase in 14-h integrated GH concentrationon DEB was accounted for by an increase in the mass of GH secreted perpulse (per liter of distribution volume,lv): 7.0 ± 2.9 and 15.9 ± 2.6 µg/lv for C and DEB,respectively (P < 0.01). Comparisonof 1.5-h integrated GH concentrations on the SEB and DEB days (30 minexercise + 60 min recovery) revealed that, with each subsequentexercise bout, GH release apparently increased progressively, with aslightly greater increase on the DEB day [SEB vs. DEB: 497 ± 162 vs. 407 ± 166 (bout 1), 566 ± 152 vs. 854 ± 184 (bout2), and 633 ± 149 vs. 1,030 ± 352 min · µg · l1(bout 3),P < 0.05]. We conclude thatthe GH response to acute aerobic exercise is augmented with repeatedbouts of exercise. 相似文献
18.
Rosker C Lohberger B Hofer D Steinecker B Quasthoff S Schreibmayer W 《American journal of physiology. Cell physiology》2007,293(2):C783-C789
The blocking efficacy of 4,9-anhydro-TTX (4,9-ah-TTX) and TTX on several isoforms of voltage-dependent sodium channels, expressed in Xenopus laevis oocytes, was tested (Nav1.2, Nav1.3, Nav1.4, Nav1.5, Nav1.6, Nav1.7, and Nav1.8). Generally, TTX was 40–231 times more effective, when compared with 4,9-ah-TTX, on a given isoform. An exception was Nav1.6, where 4,9-ah-TTX in nanomole per liter concentrations sufficed to result in substantial block, indicating that 4,9-ah-TTX acts specifically at this peculiar isoform. The IC50 values for TTX/4,9-ah-TTX were as follows (in nmol/l): 7.8 ± 1.3/1,260 ± 121 (Nav1.2), 2.8 ± 2.3/341 ± 36 (Nav1.3), 4.5 ± 1.0/988 ± 62 (Nav1.4), 1,970 ± 565/78,500 ± 11,600 (Nav1.5), 3.8 ± 1.5/7.8 ± 2.3 (Nav1.6), 5.5 ± 1.4/1,270 ± 251 (Nav1.7), and 1,330 ± 459/>30,000 (Nav1.8). Analysis of approximal half-maximal doses of both compounds revealed minor effects on voltage-dependent activation only, whereas steady-state inactivation was shifted to more negative potentials by both TTX and 4,9-ah-TTX in the case of the Nav1.6 subunit, but not in the case of other TTX-sensitive ones. TTX shifted steady-state inactivation also to more negative potentials in case of the TTX-insensitive Nav1.5 subunit, where it also exerted profound effects on the time course of recovery from inactivation. Isoform-specific interaction of toxins with ion channels is frequently observed in the case of proteinaceous toxins. Although the sensitivity of Nav1.1 to 4,9-ah-TTX is not known, here we report evidence on a highly isoform-specific TTX analog that may well turn out to be an invaluable tool in research for the identification of Nav1.6-mediated function, but also for therapeutic intervention. sodium channel; tetrodotoxin 相似文献
19.
CFTR modulates programmed cell death by decreasing intracellular pH in Chinese hamster lung fibroblasts 总被引:4,自引:0,他引:4
Barrière H Poujeol C Tauc M Blasi JM Counillon L Poujeol P 《American journal of physiology. Cell physiology》2001,281(3):C810-C824
To study the potentialinfluence of cystic fibrosis conductance regulator (CFTR) onintracellular pH regulation during apoptosis induction, we usedPS120 Chinese hamster lung fibroblasts devoid of theNa+/H+ exchanger (NHE1 isoform) transfectedwith constructs, allowing the expression of CFTR and/or NHE1. Kineticsof lovastatin-induced apoptosis were measured by orceinstaining, double staining with Hoechst-33258, propidium iodide, DNAfragmentation, and annexin V labeling. In PS120 control cells, thepercentage of apoptotic cells after 40 h of lovastatintreatment was 23 ± 3%, whereas in PS120 CFTR-transfected cells,this percentage was 40 ± 4%. In PS120 NHE1 cells, thetransfection with CFTR did not modify the percentage of apoptoticcells after 40 h (control: 19 ± 3%, n = 8;CFTR: 17 ± 1%, n = 8), indicating that blockingintracellular acidification by overexpressing theNa+/H+ exchanger inhibited the enhancement ofapoptosis induced by CFTR. In all cell lines, the initial pHvalues were identical (pH = 7.46 ± 0.04, n = 9), and treatment with lovastatin led to intracellular acidification.However, the pH value after 40 h was lower in PS120 CFTR-transfected cells (pH = 6.85 ± 0.02, n = 10) than in PS120 cells (pH = 7.15 ± 0.03, n = 10). To further investigate the origin of thisincreased intracellular acidification observed in CFTR-transfected cells, the activity of the DIDS-inhibitableCl/HCO exchanger was studied.8-Bromoadenosine 3',5'-cyclic monophosphate incubation resulted inCl/HCO exchanger activation in PS120 CFTR-transfected cells but had no effect on PS120 cells. Together, ourresults suggest that CFTR can enhance apoptosis in Chinese hamster lung fibroblasts, probably due to the modulation of the Cl/HCO exchanger, resulting in a more efficient intracellular acidification. 相似文献
20.
The mummichog, Fundulus heteroclitus, was first used in thelaboratory as a source of ripe eggs and sperm to provide developingbony-fish eggs. These in turn were used mostly to study embryologicalprocesses and responses to various chemicals. Other investigationsat the end of the nineteenth and beginning of the twentiethcenturies dealt with regeneration, developmental genetics andhybridization, osmoregulation, behavior, and pigmentation, especiallycolor change. Except for experiments on chromatophore control,endocrinological studies did not get underway until the 1930s.They have included the functioning of the thyroid, adrenal,and pineal glands, and the endocrine control of reproduction,growth, osmoregulation, and calcium metabolism. Among more recentlystudied subjects are survival at subzero temperatures, adaptationto stress, weightless orientation in space, circadian rhythms,and the bioassay of the exophthalmos-producing substance ofman as well as other physiologically active factors. The singleattribute of the mummichog that has been most responsible forits remarkable popularity as a laboratory animal is its hardinessin captivity. Despite the fact that it is not widely availablelike the goldfish, is not easily bred in aquaria like the livebearingguppy, and has no value as a food or game fish like the trout,the mummichog has made a most substantial contribution to experimentalbiology 相似文献