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1.
Garcia RF Gazola VA Barrena HC Hartmann EM Berti J Toyama MH Boschero AC Carneiro EM Manso FC Bazotte RB 《Amino acids》2007,33(1):151-155
Summary. Our purpose was to determine the blood amino acid concentration during insulin induced hypoglycemia (IIH) and examine if the
administration of alanine or glutamine could help glycemia recovery in fasted rats. IIH was obtained by an intraperitoneal
injection of regular insulin (1.0 U/kg). The blood levels of the majority of amino acids, including alanine and glutamine
were decreased (P < 0.05) during IIH and this change correlates well with the duration than the intensity of hypoglycemia. On the other hand,
the oral and intraperitoneal administration of alanine (100 mg/kg) or glutamine (100 mg/kg) accelerates glucose recovery.
This effect was partly at least consequence of the increased capacity of the livers from IIH group to produce glucose from
alanine and glutamine. It was concluded that the blood amino acids availability during IIH, particularly alanine and glutamine,
play a pivotal role in recovery from hypoglycemia. 相似文献
2.
Summary. Amino acids analysis in single wheat embryonic protoplast was performed using capillary electrophoresis equipped with laser-induced
fluorescence (CE-LIF), combination with tissue culture technique. Reagent fluorescein isothiocyanate (FITC) was introduced
into living protoplasts by electroporation for intracellular derivatization. A special osmotic buffer (0.6 mol/L mannitol,
5 mmol/L CaCl2) was used to keep the osmotic balance of embryonic protoplasts during the protoplasts derivatization. After completion of
the derivatization reaction in the protoplasts, a single protoplast was drawn into the capillary tip by electroosmotic flow.
Then a 0.1 M NaOH lysing solution was injected by diffusion. The derivatized amino acids were separated by capillary electrophoresis
and detected by laser-induced fluorescence detection after the protoplast was lysed Nine amino acids were quantitatively and
qualitatively determined and compared in lysate and single protoplast of wheat embryonic cells respectively, with mean concentrations
of amino acids ranging from 2.68×10−5 mol/L to 18.18×10−5 mol/L in single protoplast. 相似文献
3.
Summary. Glutamine is one of the most abundant free amino acid found in raw food. In this study, the contribution of free glutamine
to nonenzymatic browning and fluorescence was investigated using an aqueous model system with methylglyoxal. The results indicated
that glutamine contributed to the Maillard reaction via two pathways. First, the hydrolysis of the amide bond of glutamine
led to the release of ammonia which was implicated in the formation of brown color and fluorescence. Among other nitrogen
donors tested (asparagine, glutamic acid and urea) our results demonstrated that free glutamine was a major source of ammonia
during heating. When heated at 120 and 180 °C, 100% of ammonia was released from glutamine after 60 and 10 min, respectively.
The second pathway involved a direct Maillard reaction with the α-amino group of glutamine. Both pathways led to a rapid and
complete destruction of glutamine when heated in the model systems. With reference to the Maillard browning (absorbance at
420 nm) glutamine turned out to be the most reactive amine, followed by asparagine, glutamate, ammonia and urea. Maximum fluorescence
(excitation and emission wavelengths at 330 and 450 nm, respectively) was also observed with glutamine followed by urea and
ammonia. Overall this study suggested that free glutamine predominantly contributes to the color and fluorescence formations
of foodstuffs. 相似文献
4.
Summary. Accumulation of amino acids was studied in rice roots of 3-day-old seedlings subjected for 48 h to anaerobic conditions.
Alanine and Gaba were the main amino acids accumulated under anoxia. Their synthesis was strongly inhibited by MSX and AZA,
inhibitors of glutamine synthetase and glutamate synthase. These activities increased after 8 h of anaerobic treatment and,
by immunoprecipitation of 35S-labeled proteins, it was shown that glutamine synthetase and ferredoxin-dependent glutamate synthase were synthesized during
the treatment. These findings indicate that the glutamine synthetase/glutamate synthase cycle play an important role in anaerobic
amino acid accumulation.
Received April 5, 1999 相似文献
5.
Mühling J Burchert D Langefeld TW Matejec R Harbach H Engel J Wolff M Welters ID Fuchs M Menges T Krüll M Hempelmann G 《Amino acids》2007,33(3):511-524
Summary. We examined the effects of DON [glutamine-analogue and inhibitor of glutamine-requiring enzymes], alanyl-glutamine (regarding
its role in neutrophil immunonutrition) and alanyl-glutamine combined with L-NAME, SNAP, DON, β-alanine and DFMO on neutrophil
amino and α-keto acid concentrations or important neutrophil immune functions in order to establish whether an inhibitor of
•NO-synthase [L-NAME], an •NO donor [SNAP], an analogue of taurine and a taurine transport antagonist [β-alanine], an inhibitor
of ornithine-decarboxylase [DFMO] as well as DON could influence any of the alanyl-glutamine-induced effects. In summary,
irrespective of which pharmacological, metabolism-inhibiting or receptor-mediated mechanisms were involved, our results showed
that impairment of granulocytic glutamine uptake, modulation of intracellular glutamine metabolisation and/or de novo synthesis
as well as a blockade of important glutamine-dependent metabolic processes may led to significant modifications of physiological
and immunological functions of the affected cells. 相似文献
6.
To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending
on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 μmol m−2 s−1) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a
control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 μmol m−2 s−1. The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 μmol m−2 s−1 and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300–1600 μmol m−2 s−1). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite
content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase
and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 μmol m−2 s−1 or in the glasshouse than in plants grown at 330 μmol m−2 s−1. Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar
under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 μmol m−2 s−1 can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate.
This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase
and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate.
This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
Received: 15 November 1999 / Accepted: 27 January 2000 相似文献
7.
C. Schirlo A. Bub C. Reize A. Bührer J. Kohl E. A. Koller 《European journal of applied physiology and occupational physiology》1997,75(2):124-131
To investigate the role of fluid shifts during the short-term adjustment to acute hypobaric hypoxia (AHH), the changes in
lower limb (LV) and forearm volumes (FV) were measured using a strain-gauge plethysmograph technique in ten healthy volunteers
exposed to different altitudes (450 m, 2500 m, 3500 m, 4500 m) in a hypobaric chamber. Arterial blood pressure, heart rate,
arterial oxygen saturation (S
aO2), endtidal gases, minute ventilation and urine flow were also determined. A control experiment was performed with an analogous
protocol under normobaric normoxic conditions. The results showed mean decreases both in LV and FV of −0.52 (SD 0.39) ml · 100
ml−1 and −0.65 (SD 0.32) ml · 100 ml−1, respectively, in the hypoxia experiments [controls: LV −0.28 (SD 0.37), FV −0.41 (SD 0.47) ml · 100 ml−1]. Descent to normoxia resulted in further small but not significant decreases in mean LV [−0.02 (SD 0.11) ml · 100 ml−1], whereas mean FV tended to increase slightly [ + 0.02 (SD 0.14) ml · 100 ml−1]; in the control experiments mean LV and FV decreased continuously during the corresponding times [−0.19 (SD 0.31), −0.18
(SD 0.10) ml · 100 ml−1, respectively]. During the whole AHH, mean urine flow increased significantly from 0.84 (SD 0.41) ml · min−1 to 3.29 (SD 1.43) ml · min−1 in contrast to the control conditions. We concluded that peripheral fluid volume shifts form a part of the hypoxia-induced
acute cardiovascular changes at high altitude. In contrast to the often reported formation of peripheral oedema after prolonged
exposure to hypobaric hypoxia, the results provided no evidence for the development of peripheral oedema during acute induction
to high altitude. However, the marked increase in interindividual variance in S
aO2 and urine flow points to the appearance of the first differences in the short-term adjustment even after 2 h of acute hypobaric
hypoxia.
Accepted: 27 August 1996 相似文献
8.
John A. Hawley Garry S. Palmer Timothy D. Noakes 《European journal of applied physiology and occupational physiology》1997,75(5):407-412
This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake O2max) 4.5 (0.36)l · min−1; values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT).
Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426
(137) g · day−1 CHO [5.9 (1.4) g · kg−1 body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g · day−1 [9.3 (0.7) g · kg−1 BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol · kg−1 dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled
during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from
459 (83) to 175 (64) mmol · kg−1 d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol · kg−1 d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol · kg−1 d.w.] and total CHO oxidation [169 (20) vs 165 (30) g · h−1 for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations
during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol · l−1, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol · l−1 for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content
of their diet for 3 days from 6 to 9 g · kg−1 BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we
conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting
1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen
depletion does not determine fatigue at this exercise intensity and duration.
Accepted: 25 November 1996 相似文献
9.
C. Lydersen K. M. Kovacs M. O. Hammill 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):81-88
In this study we measured growth and milk intake and calculated energy intake and its allocation into metabolism and stored
tissue for hooded seal (Cystophora cristata) pups. In addition, we measured mass loss, change in body composition and metabolic rate during the first days of the postweaning
fast. The mean body mass of the hooded seal pups (n = 5) at the start of the experiments, when they were new-born, was 24.3 ± 1.3 kg (SD). They gained an average of 5.9 ± 1.1.
kg · day−1 of which 19% was water, 76% fat and 5% protein. This corresponds to an average daily energy deposition of 179.8 ± 16.0 MJ.
The pups were weaned at an average body mass of 42.5 ± 1.0 kg 3.1 days after the experiment was initiated. During the first
days of the postweaning fast the pups lost an average of 1.3 ± 0.5␣kg of body mass daily, of which 56% was water, 16% fat
and 28% protein. During the nursing period the average daily water influx for the pups was 124.6 ± 25.8 ml · kg−1. The average CO2 production during this period was 1.10 ± 0.20 ml · g−1 · h−1, which corresponds to a field metabolic rate of 714 ± 130 kJ · kg−1 · day−1, or 5.8 ± 1.1 times the predicted basal metabolic rate according to Kleiber (1975). During the postweaning fast the average
daily water influx was reduced to 16.1 ± 6.6 ml · kg−1. The average CO2 production in␣this period was 0.58 ± 0.17 ml · g−1 · h−1 which corresponds to a field metabolic rate of 375 ± 108 kJ · kg−1 · day−1 or 3.2 ± 0.9 times the predicted basal metabolic rate. Average values for milk composition were 33.5% water, 58.6% fat and
6.2% protein. The pups drank an average of 10.4 ± 1.8␣kg of milk daily, which represents an energy intake of 248.9 ± 39.1
MJ · day−1. The pups were able to store 73.2 ± 7.7% of this energy as body tissue.
Accepted: 15 August 1996 相似文献
10.
Summary. Our aim was to determine changes in free amino acid (FAA) and dipeptide (DP) concentrations in probable Alzheimer’s disease
(pAD) subjects compared with control (CT) subjects using liquid chromatography and electrospray ionization tandem mass spectrometry
(LCMS2). We recruited gender- and age-matched study participants based on neurological and neuropsychological assessments. We measured
FAAs and DPs in cerebrospinal fluid (CSF), plasma and urine using LCMS2 with selected reaction monitoring (SRM). Imidazole-containing FAAs (histidine, methyl-histidine), catecholamines (L-DOPA
and dopamine), citrulline, ornithine, glycine and antioxidant DPs (carnosine and anserine) accounted for the major changes
between CT and pAD. Carnosine levels were significantly lower in pAD (328.4 ± 91.31 nmol/dl) than in CT plasma (654.23 ± 100.61 nmol/dl).
In contrast, L-DOPA levels were higher in pAD (1400.84 ± 253.68) than CT (513.10 ± 121.61 nmol/dl) plasma. These data underscore
the importance of FAA and DP metabolism in the pathogenesis of AD. Since our data show changes in antioxidants, neurotransmitters
and their precursors, or FAA associated with urea metabolism in pAD compared with CT, we propose that manipulation of these
metabolic pathways may be important in preventing AD progression. 相似文献
11.
L. E. M. Nery M. A. da Silva A. M. Lauro Castrucci 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(8):624-630
The participation of cyclic nucleotide-dependent intracellular signalling pathways in the pigment translocation induced by
pigment-dispersing hormone (α -PDH) or pigment-concentrating hormone (PCH) was investigated in the erythrophores of the freshwater
shrimp, Macrobrachium potiuna. Cholera toxin, forskolin and dibutyryl cyclic adenosine 3′5′ monophosphate (dbcAMP) were able to induce pigment dispersion
with effective agonist concentrations for half maximal response (EC50 s) of 2.8 · 10−11 mol · l−1, 7.0 · 10−7 mol · l−1 and 3.3 · 10−7 mol · l−1, respectively. KT5720 (10−7 mol · l−1 and 10−6 mol · l−1) significantly shifted the dose response curve to α -PDH to the right. Dibutyryl cyclic guanosine 3′5′ monophosphate (dbcGMP)
was ineffective in inducing either pigment aggregation or dispersion. 2′5′ dideoxyadenosine (DDA) and SQ22,536 essentially
elicit a pigment-aggregating response in a dose-dependent manner. These effects were not due to the activation of purinergic
receptors, since concentrations up to 10−4 mol · l−1 of adenosine and adenosine triphosphate (ATP), and up to 10−3 mol · l−1 of uracil triphosphate (UTP) did not elicit pigment aggregation. In order to verify if PCH decreased cyclic adenosine 3′5′
monophosphate (cAMP) levels, cumulative dose-response curves to PCH in the absence and presence of pertussis toxin and 8-MOM-IBMX
were determined. However, neither drug significantly affected PCH activity. The levels of cAMP in the integument cells of
M. potiuna were significantly increased (P < 0.05) by α -PDH (10−7 mol · l−1) and forskolin (10−6 mol · l−1), but were not affected by PCH (10−7 or 10−10 mol · l−1). In conclusion, α -PDH seems to elicit pigment dispersion through the activation of a Gs-protein coupled receptor resulting
in cAMP increase and cAMP-dependent protein kinase (PKA) activation. Furthermore, although a decrease in cAMP was assumed
to be responsible in turn for the action of PCH, such a decrease could not be directly demonstrated.
Accepted: 11 August 1998 相似文献
12.
Inoculation and nitrate alter phytohormone levels in soybean roots: differences between a supernodulating mutant and the wild type 总被引:9,自引:0,他引:9
The levels of different cytokinins, indole-3-acetic acid (IAA) and abscisic acid (ABA) in roots of Glycine max [L.] Merr. cv. Bragg and its supernodulating mutant nts382 were compared for the first time. Forty-eight hours after inoculation with Bradyrhizobium, quantitative and qualitative differences were found in the root's endogenous hormone status between cultivar Bragg and the
mutant nts382. The six quantified cytokinins, ranking similarly in each genotype, were present at higher concentrations (30–196% on average
for isopentenyl adenosine and dihydrozeatin riboside, respectively) in mutant roots. By contrast, the ABA content was 2-fold
higher in Bragg, while the basal levels of IAA [0.53 μmol (g DW)−1, on average] were similar in both genotypes. In 1 mM NO3
−-fed Bragg roots 48 h post-inoculation, IAA, ABA and the cytokinins isopentenyl adenine, and isopentenyl adenosine quantitatively
increased with respect to uninoculated controls. However, only the two cytokinins increased in the mutant. High NO3
− (8 mM) markedly reduced root auxin concentration, and neither genotypic differences nor the inoculation-induced increase
in auxin concentration in Bragg was observed under these conditions. Cytokinins and ABA, on the other hand, were little affected
by 8 mM NO3
−. Root IAA/cytokinin and ABA/cytokinin ratios were always higher in Bragg relative to the mutant, and responded to inoculation
(mainly in Bragg) and nitrate (both genotypes). The overall results are consistent with the auxin-burst-control hypothesis
for the explanation of autoregulation and supernodulation in soybean. However, they are still inconclusive with respect to
the inhibitory effect of NO3
−.
Received: 16 April 1999 / Accepted: 13 December 1999 相似文献
13.
The physiological properties of transgenic tobacco plants (Nicotiana tabacum L.) with decreased or increased transport capacities of the chloroplast triose phosphate/phosphate translocator (TPT) were
compared in order to investigate the extent to which the TPT controls metabolic fluxes in wild-type tobacco. For this purpose,
tobacco lines with an antisense repression of the endogenous TPT (αTPT) and tobacco lines overexpressing the TPT gene isolated
from the C4 plant Flaveria trinervia (FtTPT) were used. The F. trinervia TPT expressed in yeast cells exhibited transport characteristics identical to the TPT from C3 plants. Neither antisense TPT plants nor FtTPT overexpressors showed a phenotype when grown in a greenhouse in air. Contents
of starch and soluble sugars in upper source leaves were similar in TPT underexpressors and FtTPT overexpressors compared
to the wild type at the end of the photoperiod. The FtTPT overexpressors incorporated more 14CO2 in sucrose than the wild type, indicating that the TPT limits sucrose biosynthesis in the wild type. There were only small
effects on labelling of amino acids and organic acids. The mobilisation of starch was enhanced in αTPT lines but decreased
in FtTPT overexpressors compared to the wild type. Enzymes involved in starch mobilisation or utilisation, such as α-amylase
or hexokinase were increased in αTPT plants and, in the case of amylases, decreased in FtTPT overexpressors. Moreover, α-amylase
activity exhibited a pronounced diurnal variation in αTPT lines with a maximum activity after 8 h in the light. These changes
in starch hydrolytic activities were confirmed by activity staining of native gels. Activities of glucan phosphorylases were
unaffected by either a decrease or an increase in TPT activity. There were also effects of TPT activities on steady-state
levels of phosphorylated intermediates as well as total amino acids and malate. In air, there was no or little effect of altered
TPT transport activity on either rates of photosynthetic electron transport and/or CO2 assimilation. However, in elevated CO2 (1500 μl · l−1) and low O2 (2%) the rate of CO2 assimilation was decreased in the αTPT lines and was slightly higher in FtTPT lines. This shows that the TPT limits maximum
rates of photosynthesis in the wild type.
Received: 26 March 1999 / Accepted: 21 August 1999 相似文献
14.
Summary. Glutathione (reduced form GSH and oxidized form GSSG) constitutes an important defense against oxidative stress in the brain,
and taurine is an inhibitory neuromodulator particularly in the developing brain. The effects of GSH and GSSG and glycylglycine,
γ-glutamylcysteine, cysteinylglycine, glycine and cysteine on the release of [3H]taurine evoked by K+-depolarization or the ionotropic glutamate receptor agonists glutamate, kainate, 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate
(AMPA) and N-methyl-D-aspartate (NMDA) were now studied in slices from the hippocampi from 7-day-old mouse pups in a perfusion system.
All stimulatory agents (50 mM K+, 1 mM glutamate, 0.1 mM kainate, 0.1 mM AMPA and 0.1 mM NMDA) evoked taurine release in a receptor-mediated manner. Both
GSH and GSSG significantly inhibited the release evoked by 50 mM K+. The release induced by AMPA and glutamate was also inhibited, while the kainate-evoked release was significantly activated
by both GSH and GSSG. The NMDA-evoked release proved the most sensitive to modulation: L-Cysteine and glycine enhanced the
release in a concentration-dependent manner, whereas GSH and GSSG were inhibitory at low (0.1 mM) but not at higher (1 or
10 mM) concentrations. The release evoked by 0.1 mM AMPA was inhibited by γ-glutamylcysteine and cysteinylglycine, whereas
glycylglycine had no effect. The 0.1 mM NMDA-evoked release was inhibited by glycylglycine and γ-glutamylcysteine. In turn,
cysteinylglycine inhibited the NMDA-evoked release at 0.1 mM, but was inactive at 1 mM. Glutathione exhibited both enhancing
and attenuating effects on taurine release, depending on the glutathione concentration and on the agonist used. Both glutathione
and taurine act as endogenous neuroprotective effectors during early postnatal life.
Authors’ address: Prof. Simo S. Oja, Brain Research Center, Medical School, FI-33014 University of Tampere, Finland 相似文献
15.
Summary. Amino acids (AA) are components of protein and precursors of many important biological molecules. To address effects of the
genes associated with metabolism and transport of AA and their derivatives during rat liver regeneration (LR), we firstly
obtained the above genes by collecting databases data and retrieving related thesis, and then analyzed their expression profiles
during LR using Rat Genome 230 2.0 array. The LR-associated genes were identified by comparing the gene expression difference
between partial hepatectomy (PH) and sham-operation (SO) rat livers. It was approved that 134 genes associated with metabolism
of AA and their derivatives and 26 genes involved in transport of them were LR-associated. The initially and totally expressing
number of these genes occurring in initial phase of LR (0.5–4 h after PH), G0/G1 (4–6 h after PH), cell proliferation (6–66 h
after PH), cell differentiation and structure-function reconstruction of liver tissue (72–168 h after PH) were respectively
76, 17, 79, 5 and 162, 89, 564, 195, illustrating that these LR-associated genes were initially expressed mainly in initial
stage, and functioned in different phases. Frequencies of up-regulation and down-regulation of them being separately 564 and
357 demonstrated that genes up-regulated outnumbered those down-regulated. Categorization of their expression patterns into
22 types implied the diversity of cell physiological and biochemical activities. According to expression changes and patterns
of the above-mentioned genes in LR, it was presumed that histidine biosynthesis in the metaphase and anaphase, valine metabolism
in the anaphase, and metabolism of glutamate, glutamine, asparate, asparagine, methionine, alanine, leucine and aromatic amino
acid almost were enhanced in the whole LR; as for amino acid derivatives, transport of neutral amino acids, urea, γ-aminobutyric
acid, betaine and taurine, metabolism of dopamine, heme, S-adenosylmethionine, thyroxine, and biosynthesis of hydroxyproline,
nitric oxide, orinithine, polyamine, carnitine, selenocysteine were augmented during the entire liver restoration. Above results
showed that metabolism and transport of AA and their derivates were necessary in liver regeneration.
Authors’ address: Prof. Dr. C. S. Xu, College of Life Science, No. 46, Jianshe RD, Henan, Xinxiang 453007, China 相似文献
16.
Theodore J. Angelopoulos Robert J. Robertson F. L. Goss Allan Utter 《European journal of applied physiology and occupational physiology》1997,75(2):132-135
Eight fit men [maximum oxygen consumption (O2max) 64.6 (1.9) ml · kg−1 · min−1, aged 28.3 (1.7) years (SE in parentheses) were studied during two treadmill exercise trials to determine the effect of endogenous
opioids on insulin and glucagon immunoreactivity during intense exercise (80% O2max). A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order.
Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration
of naloxone (N; 1.2 mg; 3 ml) and the other after receiving a placebo (P; 0.9% NaCl saline; 3 ml). Prior to each experimental
trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately after,
each subject received either a N or P bolus injection. Blood samples were also collected after 20 min of continuous exercise
(running). Glucagon was higher (P < 0.05), while insulin was lower (P < 0.05), during exercise compared with pre-exercise values in both trials. However, glucagon was higher (P < 0.05) in the P than in the N exercise trial [141.4 (8.3) ng · l−1 vs 127.2 (7.6) ng · l−1]. There were no differences in insulin during exercise between the P and N trials [50.2 (4.3) pmol · l−1 vs 43.8 (5) pmol · l−1]. These data suggest that endogenous opioids may augment the glucagon response during intense exercise.
Accepted: 15 June 1996 相似文献
17.
Intracellular chloroplast photorelocation in the moss Physcomitrella patens is mediated by phytochrome as well as by a blue-light receptor 总被引:3,自引:0,他引:3
The light-induced intracellular relocation of chloroplasts was examined in red-light-grown protonemal cells of the moss Physcomitrella patens. When irradiated with polarized red or blue light, chloroplast distribution in the cell depended upon the direction of the
electrical vector (E-vector) in both light qualities. When the E-vector was parallel to the cross-wall (i.e. perpendicular
to the protonemal axis), chloroplasts accumulated along the cross-wall; however, no accumulation along the cross-wall was
observed when the E-vector was perpendicular to it (i.e. parallel to the protonemal axis). When a part of the cell was irradiated
with a microbeam of red or blue light, chloroplasts accumulated at or avoided the illumination point depending on the fluence
rate used. Red light of 0.1–18 W m−2 and blue light of 0.01–85.5 W m−2 induced an accumulation response (low-fluence-rate response; LFR), while an avoidance response (high-fluence-rate response;
HFR) was induced by red light of 60 W m−2 or higher and by blue light of 285 W m−2. The red-light-induced LFR and HFR were nullified by a simultaneous background irradiation of far-red light, whereas the
blue-light-induced LFR and HFR were not affected at all by this treatment. These results show, for the first time, that dichroic
phytochrome, as well as the dichroic blue-light receptor, is involved in the chloroplast relocation movement in these bryophyte
cells. Further, the phytochrome-mediated responses but not the blue-light responses were revealed to be lost when red-light-grown
cells were cultured under white light for 2 d.
Received: 7 September 1999 / Accepted: 15 October 1999 相似文献
18.
Regulation by irradiance level of the mechanism for dissolved inorganic carbon (DIC) acquisition was examined in the red
macroalga Gracilaria tenuistipitata Zhang et Xia. For this purpose, affinity for external DIC, carbonic anhydrase (CA; EC 4.2.1.1) activity and content of ribulose-1,5-bisphosphate
carboxylase/oxygenase (Rubisco; EC 4.1.1.39) were determined in thalli grown at 45 and 500 μmol photons m−2 s−1. Oxygen evolution rates declined by 50% when the medium pH was changed from 8.1 to 8.7, and the pH compensation point attained
was ca. 9.2. These characteristics were unaffected by the light treatments. In contrast, photosynthetic conductance for DIC
at pH 8.7 was doubled in thalli grown at high irradiance compared with those grown at low irradiance (to 0.74 × 10−6 from 0.33 × 10−6 m s−1). Photosynthetic rates at saturating DIC concentration were also higher by 60% in thalli grown at high irradiance. These
differences could not be attributed to changes in the use of external DIC, since external CA activity did not vary. Although
the irradiance level did not modify the pool size of Rubisco, Rubisco content expressed on a chlorophyll a basis was almost doubled at high irradiance. These results likely indicate that the internal transport of DIC towards the
active-site of Rubisco, rather than the external use of DIC, is enhanced in the thalli grown at high irradiance.
Received: 7 June 1999 / Accepted: 16 October 1999 相似文献
19.
M. D. Baustian S. Q. Wang K. W. Beyenbach 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):61-70
Plasma and urine of toadfish (Opsanus tau) in sea water and 10% sea water were analyzed to assess responses of an aglomerular fish to hypoosmotic challenge. Following
transfer to 10% sea water, plasma osmotic pressure decreased slowly from 318 to 241 mmol · kg H2O−1, over a period of 10–15 days. Urine osmotic pressure decreased in parallel from 299 to 207 mmol · kg H2O−1, leaving urine/plasma ratios of osmotic pressure essentially unchanged. In contrast, the volume and composition of urine
changed rapidly following transfer to 10% sea water. Urine flow rate increased 110% from 3.0 to 6.3 μl · 100g−1 · h−1 and Na+ excretion increased 346%, while excretion of Mg2− and SO4
2− decreased 81% and 90%, respectively. Excretion rates for Cl− were low in seawater toadfish and decreased further in 10% sea water. An unknown sulfur-containing anion, present in the
urine of seawater toadfish, contributed significantly to the composition and ionic balance in urine of toadfish in 10% sea
water. These results suggest that the inability to produce strongly dilute urine obliges toadfish to lose salt in order to
excrete water, in hypoosmotic media. The decrease in plasma osmotic pressure may be both a strategy to reduce osmotic and
ionic gradients in dilute media and a consequence of the kidney's inability to excrete water without salt.
Accepted: 22 August 1996 相似文献
20.
Hilde Spielvogel Armando Rodriguez Brigitte Sempore Esperanza Caceres J.-M. Cottet-Emard Laurent Guillon R. Favier 《European journal of applied physiology and occupational physiology》1997,75(5):400-406
The present study was undertaken to determine the haematological and cardiovascular status, at rest and during prolonged
(1 h) submaximal exercise (approximately 70% of peak oxygen uptake) in a group (n = 12) of chronic coca users after chewing approximately 50 g of coca leaves. The results were compared to those obtained
in a group (n = 12) of nonchewers. At rest, coca chewing was accompanied by a significant increase in heart rate [from 60 (SEM 4) TO 76 (SEM 3)
beats · min−1], in haematocrit [from 53.2 (SEM 1.2) to 55.6 (SEM 1.1)%] in haemoglobin concentration, and plasma noradrenaline concentration
[from 2.8 (SEM 0.4) to 5.0 (SEM 0.5) μmol · l−1]. It was calculated that coca chewing for 1 h resulted in a significant decrease in blood [−4.3 (SEM 2.2)%] and plasma [−8.7 (SEM 1.2)%]
volume. During submaximal exercise, coca chewers displayed a significantly higher heart rate and mean arterial blood pressure.
The exercise-induced haemoconcentration was blunted in coca chewers compared to nonchewers. It was concluded that the coca-induced
fluid shift observed at rest in these coca chewers was not cumulative with that of exercise, and that the hypovolaemia induced
by coca chewing at rest compromised circulatory adjustments during exercise.
Accepted: 29 October 1996 相似文献