Additive incidence of developmental malformation for Xenopus embryos exposed to a mixture of ten aliphatic carboxylic acids.

A modified FETAX (Frog Embryo Teratogenesis Assay: Xenopus) protocol was used to assess the joint action of ten aliphatic carboxylic acids on Xenopus embryo development. Stock solutions of each acid alone, made up at twice the EC50 of the individual acids, were prepared for testing alone and in a mixture with an equal volume of each acid stock solution. For each treatment, five concentrations and a control dish, each with 25 embryos, were tested for 96 h, with solution renewal every 24 h. The embryos were then fixed and evaluated for gross malformations. For each dish, the number and types of malformations were recorded. An EC50 was calculated for each acid alone and this value was defined as 1.0 toxic unit (TU) for malformation induced by the acid. An EC50 was also calculated for the mixture. The concentration of each acid at the mixture EC50 and the TU values corresponding to these concentrations were then determined. A TU value of 0.990 (0.923-1.060) was obtained for the mixture by adding the TU values for each acid in the mixture. This represents a concentration additive rate of malformation. Microcephaly, TU = 1.09 (1.01-1.18), was the primary malformation, but did not completely account for the response. The concentration additive rate of malformation indicates that all ten acids are likely to induce malformation in Xenopus embryos in a similar manner. Quantitative structure-activity relationship (QSAR) analysis revealed developmental malformation induced by the acids was highly correlated (r2 = 0.979) with hydrophobicity and molar refractivity (r2 = 0.949). The approach has potential application in determining compounds that induce developmental malformations in a similar manner, when metabolism and pharmacokinetic factors are considered.     

Solubilization of active (H+ + K+)-ATPase from gastric membrane

(H+ + K+)-ATPase-enriched membranes were prepared from hog gastric mucosa by sucrose gradient centrifugation. These membranes contained Mg2+-ATPase and p-nitrophenylphosphatase activities (68 +/- 9 mumol Pi and 2.9 +/- 0.6 mumol p-nitrophenol/mg protein per h) which were insensitive to ouabain and markedly stimulated by 20 mM KCl (respectively, 2.2- and 14.8-fold). Furthermore, the membranes autophosphorylated in the absence of K+ (up to 0.69 +/- 0.09 nmol Pi incorporated/mg protein) and dephosphorylated by 85% in the presence of this ion. Membrane proteins were extracted by 1-2% (w/v) n-octylglucoside into a soluble form, i.e., which did not sediment in a 100 000 X g X 1 h centrifugation. This soluble form precipitated upon further dilution in detergent-free buffer. Extracted ATPase represented 32% (soluble form) and 68% (precipitated) of native enzyme and it displayed the same characteristic properties in terms of K+-stimulated ATPase and p-nitrophenylphosphatase activities and K+-sensitive phosphorylation: Mg2+-ATPase (mumol Pi/mg protein per h) 32 +/- 9 (basal) and 86 +/- 20 (K+-stimulated); Mg2+-p-nitrophenylphosphatase (mumol p-nitrophenol/mg protein per h) 2.6 +/- 0.5 (basal) and 22.2 +/- 3.2 (K+-stimulated); Mg2+-phosphorylation (nmol Pi/mg protein) 0.214 +/- 0.041 (basal) and 0.057 +/- 0.004 (in the presence of K+). In glycerol gradient centrifugation, extracted enzyme equilibrated as a single peak corresponding to an apparent 390 000 molecular weight. These findings provide the first evidence for the solubilization of (H+ + K+)-ATPase in a still active structure.     

The epithelial calcium channel, ECaC, is activated by hyperpolarization and regulated by cytosolic calcium.

The recently cloned epithelial Ca(2+) channel, ECaC, which is expressed in the apical membrane of 1,25-dihydroxyvitamin D(3)-responsible epithelia, was characterized in Xenopus laevis oocytes by measuring the Ca(2+)-activated Cl(-) current which is a sensitive read-out of the Ca(2+) influx. ECaC-expressing oocytes responded to a voltage ramp with a maximal inward current of -2.1 +/- 0.3 microA at a holding potential of -99 +/- 1 mV. The inward current decreased progressively at less negative potentials and at +50 mV a small Ca(2+)-induced outward current was observed. The Ca(2+) influx-evoked current at a hyperpolarizing pulse to -100 mV displayed a fast activation followed by a rapid but partial inactivation. Loading of the oocytes with the Ca(2+) chelator BAPTA delayed the activation and blocked the inactivation of ECaC. When a series of brief hyperpolarizing pulses were given a significant decline in the peak response and subsequent plateau phase was observed. In conclusion, the distinct electrophysiological features of ECaC are hyperpolarization-dependent activation, Ca(2+)-dependent regulation of channel conductance and desensitization during repetitive stimulation.     

UTP经PLC-IP3信号通路调控猪冠状动脉平滑肌细胞自发性瞬时外向电流

本文采用全细胞穿孔膜片钳技术研究uTP对急性酶分离的猪冠状动脉平滑肌细胞(coronary artery smooth muscle cells,CASMCs)自发性瞬时外向电流(spontaneous transient outward currents,STOCs)的作用,探讨细胞内Ca2 释放在UTP产物三磷酸肌醇(inositol 1,4,5.trisphosphate,IP3)调控STOCs过程中的作用机制.结果显示:(1)UTP(40 gmol/L)可明显激活CASMCs的STOCs,使其幅度和频率分别增~0(57.54±5.34)%和(77.46±8.42)%(P<0.01,n=38).(2)磷脂酶C(phospholipase C,PLC)阻断剂U73122(5 gmol/L)可明显抑制STOCs的活性,使其幅度和频率分别降低(31.04±7.46)%和(41.65±16.59)%(P<0.05,,n=10);细胞外再加入UTP小能再次激活STOCs(n=7).(3)L型电压依赖性钙通道(L-type voltage-dependent Ca2 channels,L-VDCCs)阻断剂verapamil(20 gmol/L)和CdCl2(200 gmol/L)几乎不影响UTP对STOCs活性的调节(n=8).(4)1 gmol/L的bisindolylmaleimide I[Bisl,蛋白激酶C(protein kinase C,PKC)的特异性阻断剂]可明显激活STOCs,使其幅度和频率分别增加(65.44±24.66)%和(61.35±21.47)%(P<0.01,n=12),细胞外再加入UTP(40 gmol/L)可使STOCs的幅度及频率进一步明显增加(P<0.05,P<0.01,n=12),细胞外继续加入ryanodine(50 gmol/L)则可完全阻断STOCs.(5)UTP(40 gmol/L)预处理细胞后,IP受体(IP3 receptors,IP3Rs)阻断剂2-aminoethoxydiphenyl borate(2-APB,40 gmol/L)可使STOCs的幅度降低(24.08±3.97)%(P<0.05,n=8),对其频率的影响较小(n=8);而80 gmol/L的2-APB则可明显抑制STOCs的活性,使其幅度和频率分别降低(31.43±6.34)%和(40.59±19.01)%(P<0.05,P<0.01,n=6),细胞外继续加入高浓度的ryanodine(50 Bmol/L)可完全抑制STOCs(n=6).用2-APB(40 gmol/L)或ryanodine(50 gmol/L)预处理细胞后,UTP(40 gmol/L)不能再次激活STOCs.以上结果提示:UTP主要通过PLC-IPl信号通路激活急性酶分离的猪CASMCs的STOCs,IP3Rs和ryanodine受体(ryanodine receptors,RyRs)介导的细胞内Ca2 释放在此过程中发挥重要作用.     

Detection of two Zn-finger proteins ofXenopus laevis,TFIIIA, and p43, by probing western blots of ovary cytosol with65Zn2+,63Ni2+, or109Cd2+

Two Zn-finger proteins, TFIIIA (a constituent of 7S RNP particles) and p43 (a constituent of 42S RNP particles), were detected in ovary extracts of juvenile Xenopus laevis females by in vitro binding of radiolabeled divalent metals. Proteins fractionated by SDS-PAGE (sodium dodecylsulfate-polyacrylamide gel electrophoresis) were transferred by Western blotting onto nitrocellulose membranes, probed with 65Zn2+, 63Ni2+, or 109Cd2+, and visualized by autoradiography. Detection limits for TFIIIA were approx 0.07 micrograms/well by 109Cd(2+)-probing, 0.13 micrograms/well by 65Zn(2+)-probing, and 0.26 mu/well by 63Ni(2+)-probing. Protein p43 was more clearly visualized by probing with 63Ni2+ than with 65Zn2+ or 109Cd2+. After purified TFIIIA was cleaved with cyanogen bromide, 65Zn2+, 109Cd2+, and 63Ni2+ distinctly labeled the 22 kDa middle fragment; 65Zn2+ and 109Cd2+ also labeled the 11 kDa N-terminal fragment, but did not label the 13 kDa C-terminal fragment. These results are consistent with the notion that the radioligands were bound to finger-loop domains of TFIIIA, which occur in the middle and N-terminal fragments. Based on the abilities of nonradioactive metal ions to compete with 65Zn2+ for binding to TFIIIA on Western blots, the relative affinities of the metals for TFIIIA were ranked as follows: Zn2+ = Cu2+ greater than or equal to Hg2+ greater than Cd2+ greater than Co2+ greater than or equal to Ni2+. Even at a 1000-fold molar excess, Mn2+ did not compete with 65Zn2+ for binding to TFIIIA. Probing Western blots with the radiolabeled metal ions greatly facilitates the detection, isolation, and quantitation of TFIIIA and p43.     

Purification and characterization of a DNase γ-like endonuclease from Xenopus laevis liver

We recently found that two apoptotic DNase γ-like endonucleases (36 and 38kDa DNases) were present in Xenopus laevis larval and adult liver cell nuclei and that their activities increased in metamorphic climax. Here, we purified the main DNase γ-like endonuclease from Xenopus laevis liver cell nuclei and characterized its physical and enzymatic properties in detail. The molecular mass of Xenopus liver nuclear endonuclease was 38,000 daltons as determined by SDS-polyacrylamide gel electrophoresis. A native molecular mass of 35,000 was estimated by gel filtration. The purified Xenopus liver endonuclease was a neutral one and required both Ca2+ and Mg2+ for DNase activity. Unlike the mammalian DNase γ, the Ca2+/Mg2+ requirement could not be supplied by Mn2+. The inhibition profiles by aurintricarboxylic acid, sodium citrate and divalent metal ions such as Co2+, Ni2+, Cu2+ and Zn2+ were similar to those of mammalian DNase γ. These results suggest that this endonuclease is a Xenopus laevis homolog of the mammalian apoptotic endonuclease DNase γ. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of long-term nickel ingestion on insulin binding and antilipolytic response in rat adipocytes

Male Wistar rats of the third generation of rats drinking 200 micrograms Ni2+/mL as NiCl2 in their drinking water were studied. Basal plasma glucose and insulin levels were unchanged. Epididymal adipocytes from Ni2(+)-fed rats showed an increased insulin binding with a slight increase in apparent insulin affinity (ED50: Ni2(+)-fed rats 2.8 x 10(-9) M and controls 5 x 10(-9) M) with no change in insulin receptor numbers (Ni2(+)-fed rats 143,000 +/- 12,000 (6) receptors/cell and controls 126,000 +/- 13,000 (5]. Moreover, a decreased sensitivity to the antilipolytic response of insulin was also observed in adipocytes from Ni2(+)-fed rats. These events could represent actions of Ni2+ both at the receptor and post-receptor insulin levels. Several possible mechanisms involved in the process are suggested.     

Extracts from plants used in Mexican traditional medicine activate Ca(2+)-dependent chloride channels in Xenopus laevis oocytes.

The two-electrode voltage-clamp technique was employed to investigate the effects of chloroform-methanol (1:1) extracts derived from five medicinal plants on Xenopus laevis oocytes. When evaluated at concentrations of 1 to 500 microg/ml, the extracts prepared from the aerial parts of Baccharis heterophylla H.B.K (Asteraceae), Chenopodium murale L. (Chenopodiaceae), Desmodium grahami Gray (Leguminosae) and Solanum rostratum Dun (Solanaceae) produced concentration-dependent oscillatory inward currents in the oocytes, while the extract of Gentiana spathacea did not induce any response. The reversal potential of the currents elicited by the active extracts was -17 +/- 2 mV and was similar to the chloride equilibrium potential in oocytes. These ionic responses were independent of extracellular calcium. However, they were eliminated by overnight incubation with BAPTA-AM (10 microM), suggesting that the currents were dependent on intracellular Ca2+ increase. Thus the plant extracts activate the typical oscillatory Ca(2+)-dependent Cl- currents generated in the Xenopus oocyte membrane more probably via a mechanism that involves release of Ca2+ from intracellular reservoirs. These observations suggest that Xenopus oocyte electrophysiological recording constitutes a suitable assay for the study of the mechanisms of action of herbal medicines.     

Expression of the thyroid sodium/iodide symporter in Xenopus laevis oocytes

Poly(A+) RNA isolated from FRTL-5 cells (a continuous line of cultured and fully functional rat thyroid cells (Ambesi-Impiombato, F. S., Parks, L. A. M., and Coons, H. G. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 3455-3459] was injected into Xenopus laevis oocytes, and the expression of the Na+/I- symporter in the plasma membrane was assayed by measuring the Na+-dependent ClO4--sensitive uptake of 125I. Expression of the Na+/I- symporter was detected as a 7-fold average increase in transport over background, 5-6 days after injection. Poly(A+) RNA was subsequently fractionated by sucrose gradient centrifugation, and fractions were assayed for their ability to induce I- transport activity. The poly(A+) RNA encoding the Na+/I- symporter was found in a fraction containing messages of 2.8-4.0 kilobases in length.     

Effect of antikeratin microinjection on the embryonic development of Xenopus laevis

Anti-keratin monoclonal antibody AF5 was introduced into fertilized eggs of Xenopus laevis.,and its effects on embryonic development were studied.Survival rate of the antikeratin-injected embryos was much lower(only 35.67% at gastrula)than that of the control(74.85% at gastrula),in which embryos were injected with mouse IgG.Most of survivors in the experimental series showed aberrant external appearance.On the other hand,in cleavage stage,ie 2-7h after fertilization,immunohistochemical staining of embryos showed that the expermental embryos were mostly keratin negative,while embryos of the control ones were keratin positive.When introducing this antikeratin into one cell of a 2-cell embryo,only the uninjected half of the embryo continued its development while the other half could not develop at all.These results suggested that intact keratin cytoskeleton in early embryos is indispensable to the embryonic development of Xenopus laevis.     

Activation of Mg-ATPase (spectrin-dependent ATPase) by Ca2+.

The dependence of saponin-stimulated Mg-ATPase activity in the erythrocyte membrane on Ca2+ concentration was studied. In the membrane of freshly sampled human erythrocytes we found for this enzyme and Ca2+ an apparent dissociation constant of 0.611 mumol/l (SE +/- 0.106 mumol/l) and Hill coefficient of 0.93 (SE +/- 0.05). The enzyme is in most probability identical with Ca,Mg-ATPase of high affinity to Ca2+ described also as spectrin-dependent Ca,Mg-ATPase.     

Presence of a Ca2+-sensitive CDPdiglyceride-inositol transferase in canine cardiac sarcoplasmic reticulum

Sarcoplasmic reticulum (SR) and plasma membranes from canine left ventricle were used to evaluate the presence of the enzyme CDPdiglyceride-inositol transferase in these membranes. (K+,-Ca2+)-ATPase activity, a marker for SR, was 79.2 +/- 5.0 (SE) and 11.2 +/- 2.0 mumol.mg-1.h-1 in SR and plasma membrane preparations, respectively, and (Na+,K+)-ATPase activity, a marker for plasma membranes, was 5.6 +/- 1.2 and 99.2 +/- 8.0 mumol.mg-1.h-1, respectively. Contamination of SR and plasma membrane preparations by mitochondria was estimated to be 2% and 8%, respectively, and by Golgi membranes, 0.9% and 1.8%, respectively. Transferase activity, measured at pH 6.8, was 1.32 +/- 0.04 (SE) and 0.28 +/- 0.04 nmol of [3H]phosphatidylinositol ([3H]PtdIns).mg-1.min-1 in three SR and plasma membrane preparations, respectively. The transferase activity detected in the plasma membrane preparation could be accounted for largely, but not entirely, by contaminating SR membranes. The pH optimum for the SR transferase activity was between 8.0 and 9.0; little or no activity was detectable at pH 6.3 and 5.5, the lowest pH tested. Ca2+ inhibited the enzyme, half-maximal inhibition occurring at about 10 microM Ca2+; removal of the Ca2+ by addition of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid restored activity. No loss of [3H]PtdIns could be detected when membranes were incubated in the presence or absence of Ca2+. The Ca2+ inhibition of the transferase was noncompetitive with respect to CDP-dipalmitin while that with respect to myo-inositol was slightly noncompetitive at low [Ca2+] and became uncompetitive at higher [Ca2+].(ABSTRACT TRUNCATED AT 250 WORDS)     

Calcium efflux from amphibian sciatic nerve

Eight Xenopus laevis were injected intraperitoneally with 45CaCl2 and 16-18 h later an unbranched section from each sciatic nerve was removed. Efflux measurements of nerve from which the perineurial sheath had been removed could be described by three compartments of approximately equal size with half-lifes of 2.37 +/- 0.76 (SD), 30.3 +/- 17.3 and 196 +/- 61 min, the shortest lived compartment representing diffusion from the extracellular space with a coefficient of diffusion of 2.1 +/- 0.7 X 10(-6) cm2/s. Efflux from nerve in which the perineurium remained intact was characterized by a half-life of 862 +/- 399 min resulting from the sheath acting as a diffusion barrier of permeability 3.4 +/- 1.6 X 10(-7) cm/s. The perineurium was found to bind or sequester a quantity of calcium 1-2 times that contained in an equal volume of plasma.     

Effects of ethanol on the primitive streak stage mouse embryo

Recent studies of mouse models have suggested that malformations associated with the fetal alcohol syndrome (FAS) are caused by the effects of ethanol on early embryos during gastrulation and neurulation. A study of Xenopus laevis embryos showed that exposure of gastrula stage amphibian embryos to ethanol inhibits migration of the mesodermal cells, causes formation of small neural plates, and subsequently causes hypoplastic craniofacial malformations in tadpoles. We now report effects of ethanol on the primitive streak stage mouse embryos. An ethanol solution (25%) was injected intraperitonealy twice into mice of 6.5-7.0 days of pregnancy at a dose of 0.015 ml/gm of body weight. Histological and morphometric examinations of 7.5-day embryos, 20 hr after the second injection, showed that the epiblast layer was disorganized and shrunk with formation of many blebs. In addition, formation of the mesodermal cell layer was retarded in the ethanol-treated embryos, suggesting that exposure of gastrula stage embryos to ethanol causes similar abnormalities in mouse and Xenopus embryos. These results suggest that the inhibition of the morphogenetic movements during gastrulation may be the primary effect of ethanol in causing major craniofacial malformations of FAS.     

Zn2+对爪蟾卵母细胞表达鲫鱼脑GABA受体的调制作用

爪蟾卵母细胞注射鲫鱼脑ｍＲＮＡ后表达的ＧＡＢＡ受体中约８５％为ＧＡＢＡＡ受体。约１５％的成分为ＧＡＮＡＣ受体。本文利用双电极电压箝方法结合药物灌流研究了Ｚｎ６２＋对这两型受体的作用。我们观察到了Ｚｎ＾２＋对它们的调制都是可抑制性的,可逆的。     

Asymmetries in H+/K+-ATPase and cell membrane potentials comprise a very early step in left-right patterning

A pharmacological screen identified the H+ and K+ ATPase transporter as obligatory for normal orientation of the left-right body axis in Xenopus. Maternal H+/K+-ATPase mRNA is symmetrically expressed in the 1-cell Xenopus embryo but becomes localized during the first two cell divisions, demonstrating that asymmetry is generated within two hours postfertilization. Although H+/K+-ATPase subunit mRNAs are symmetrically localized in chick embryos, an endogenous H+/K+-ATPase-dependent difference in membrane voltage potential exists between the left and right sides of the primitive streak. In both species, pharmacologic or genetic perturbation of endogenous H+/K+-ATPase randomized the sided pattern of asymmetrically expressed genes and induced organ heterotaxia. Thus, LR asymmetry determination depends on a very early differential ion flux created by H+/K+-ATPase activity.     

Modulation by ellagic acid of DCA-induced developmental toxicity in the zebrafish (Danio rerio)

The ability of ellagic acid (EA) to modulate dichloroacetic acid (DCA)-induced developmental toxicity and oxidative damage was examined in zebrafish embryos. Embryos were exposed to 20 mM EA administered concomitantly with 32 mM DCA at 4 hours postfertilization (hpf) and 20 h later. Embryos were observed through 144 hpf for developmental malformations, and production of superoxide anion (SA) and nitric oxide (NO) was determined in embryonic homogenates. DCA was shown to produce developmental abnormalities and significant levels of SA and NO in zebrafish embryos. EA exposure alleviated the developmental malformations observed in treated embryos and decreased the levels of SA and NO in those same embryos. Less than 10% of DCA + EA exposed embryos showed developmental malformations compared to 100% of embryos treated with DCA alone. Animals in this group that developed malformations were shown to have fewer defects than those treated with DCA only. Taken together, the results confirm the involvement of oxidative stress in the developmental toxicity of DCA in zebrafish embryos, and suggest possible protection against those effects with the use of antioxidants.     

Myofibril and sarcoplasmic reticulum changes with exercise and growth

The intent of this study was to observe the effects of different treadmill running programs upon selected biochemical properties of soleus muscle from young rats. Young 10 day litter-mates were assigned to endurance (E), spring (S) and control (C) groups. Each was partitioned into either 21 or 51 day exercising groups and 10 day controls. For C the myofibril ATPase activity at 21 and 51 days were lower than 10 day activity (p less than or equal to 0.05). In the 51 day E group ATPase activity (0.378 +/- 0.009 mumol Pi X mg-1 X min-1) was greater than at 10 and 21 days (0.307 +/- 0.006 and 0.323 +/- 0.008 mumol Pi X mg-1 X min-1) (p less than or equal to 0.05). No change occurred in the S group from 10 to 21 and 51 days (p greater than or equal to 0.05). Both the 21 and 51 day S (0.318 +/- 0.011 and 0.399 +/- 0.010 mumol Pi X mg-1 X min-1) and E (0.323 +/- 0.008 and 0.378 +/- 0.009 mumol Pi X mg-1 X min-1) groups had higher activity compared to the C group (0.193 +/- 0.029 and 0.172 +/- 0.031 mumol Pi X mg-1 X min-1) (p less than or equal to 0.05). Maturation (10--51 day) resulted in a lowered sarcoplasmic reticulum (SR) yield and Ca2+ binding (p less than or equal to 0.05) while Ca2+ uptake ability did not change (p greater than or equal to 0.05). SR yield, Ca2+ binding and uptake were not altered with S training (p greater than or equal to 0.05). The E training resulted in greater Ca2+ uptake at 51 days compared to C and S (p less than or equal to 0.05), with no change in Ca2+ binding (p greater than or equal to 0.05). The data suggest that E training alters the normal development pattern of young rat soleus muscle.     

Brain glutamate metabolism during hypoxia and peripheral chemodenervation

Glutamate stimulates resting ventilation by altering neural excitability centrally. Hypoxia increases central ventilatory drive through peripheral chemoreceptor stimulation and may also alter cerebral perfusion and glutamate metabolism locally. Therefore the effect of hypoxia and peripheral chemodenervation on cerebrospinal fluid (CSF) transfer rate of in vivo tracer amidated central nervous system glutamate was studied in intact and chemodenervated pentobarbital-anesthetized dogs during normoxia and after 1 h of hypoxia induced with 10 or 12% O2 in N2 breathing at constant expired ventilation and arterial CO2 tension. Chemodenervation was performed by bilateral sectioning of the carotid body nerves and cervical vagi. CSF transfer rates of radiotracer 13NH4+ and [13N]glutamine synthesized via the reaction, glutamate + NH4(+)----glutamine, in brain glia were measured during normoxia and after 1 h of hypoxia. At normoxia, maximal glial glutamine efflux rate jm = 103.3 +/- 11.2 (SE) mumol.l-1.min-1 in all animals. After 1 h of hypoxia in intact animals, jm = 78.4 +/- 10.0 mumol.l-1.min-1. In denervated animals, jm was decreased to 46.3 +/- 4.3 mumol.l-1.min-1. During hypoxia, mean cerebral cortical glutamate concentration was higher in denervated animals (9.98 +/- 1.43 mumol/g brain tissue) than in intact animals (7.63 +/- 1.82 mumol/g brain tissue) and corresponding medullary glutamate concentration tended to be higher in denervated animals. There were no differences between mean glutamine and gamma-aminobutyric acid concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)