Functional characterization of two S-nitroso-L-cysteine transporters, which mediate movement of NO equivalents into vascular cells

In myogenic C₂C₁₂ cells, 5 mM creatine increased the incorporation of labeled [³⁵S]methionine into sarcoplasmic (+20%, P < 0.05) and myofibrillar proteins (+50%, P < 0.01). Creatine also promoted the fusion of myoblasts assessed by an increased number of nuclei incorporated within myotubes (+40%, P < 0.001). Expression of myosin heavy chain type II (+1,300%, P < 0.001), troponin T (+65%, P < 0.01), and titin (+40%, P < 0.05) was enhanced by creatine. Mannitol, taurine, and -alanine did not mimic the effect of creatine, ruling out an osmolarity-dependent mechanism. The addition of rapamycin, the inhibitor of mammalian target of rapamycin/70-kDa ribosomal S6 protein kinase (mTOR/p70^s6k) pathway, and SB 202190, the inhibitor of p38, completely blocked differentiation in control cells, and creatine did not reverse this inhibition, suggesting that the mTOR/p70^s6k and p38 pathways could be potentially involved in the effect induced by creatine on differentiation. Creatine upregulated phosphorylation of protein kinase B (Akt/PKB; +60%, P < 0.001), glycogen synthase kinase-3 (+70%, P < 0.001), and p70^s6k (+50%, P < 0.001). Creatine also affected the phosphorylation state of p38 (–50% at 24 h and +70% at 96 h, P < 0.05) as well as the nuclear content of its downstream targets myocyte enhancer factor-2 (–55% at 48 h and +170% at 96 h, P < 0.05) and MyoD (+60%, P < 0.01). In conclusion, this study points out the involvement of the p38 and the Akt/PKB-p70^s6k pathways in the enhanced differentiation induced by creatine in C₂C₁₂ cells. protein synthesis; insulin-like growth factor; mitogen-activated protein kinase; extracellular signal-regulated kinase 1/2; 70-kDa ribosomal S6 protein kinase     

Changes in lower limb volume in humans during parabolic flight

Variations in gravity [head-to-footacceleration (G_z)] inducehemodynamic alterations as a consequence of changes in hydrostatic pressure gradients. To estimate the contribution of the lower limbs toblood pooling or shifting during the different gravity phases of aparabolic flight, we measured instantaneous thigh and calf girths byusing strain-gauge plethysmography in five healthy volunteers. Fromthese circumferential measurements, segmental leg volumes werecalculated at 1, 1.7, and 0 G_z.During hypergravity, leg segment volumes increased by 0.9% for thethigh (P < 0.001) and 0.5% for thecalf (P < 0.001) relative to1-G_z conditions. After suddenexposure to microgravity following hypergravity, leg segment volumeswere reduced by 3.5% for the thigh (P < 0.001) and 2.5% for the calf (P < 0.001) relative to 1.7-G_zconditions. Changes were more pronounced at the upper part of the leg.Extrapolation to the whole lower limb yielded an estimated 60-mlincrease in leg volume at the end of the hypergravity phase and asubsequent 225-ml decrease during microgravity. Although quantitativelyless than previous estimations, these blood shifts may participate inthe hemodynamic alterations observed during hypergravity and weightlessness.

     

Shortening velocity and myosin heavy- and light-chain isoform mRNA in rabbit arterial smooth muscle cells

In smooth muscle cells (SMCs)isolated from rabbit carotid, femoral, and saphenous arteries, relativemyosin isoform mRNA levels were measured in RT-PCR to test forcorrelations between myosin isoform expression and unloaded shorteningvelocity. Unloaded shortening velocity and percent smooth muscle myosinheavy chain 2 (SM2) and myosin light chain 17b(MLC_17b) mRNA levels were not significantly different insingle SMCs isolated from the luminal and adluminal regions of thecarotid media. Saphenous artery SMCs shortened significantly faster(P < 0.05) than femoral SMCs and had more SM2 mRNA(P < 0.05) than carotid SMCs and lessMLC_17b mRNA (P < 0.001) and higher tissuelevels of SMB mRNA (P < 0.05) than carotid and femoralSMCs. No correlations were found between percent SM2 and percentMLC_17b mRNA levels and unloaded shortening velocity in SMCsfrom these arteries. We have previously shown that myosin heavy chain(MHC) SM1/SM2 and SMA/SMB and MLC_17a/MLC_17b isoform mRNA levels correlate with protein expression for these isoforms in rabbit smooth muscle tissues. Thus we interpret these results to suggest that 1) SMC myosin isoform expression andunloaded shortening velocity do not vary with distance from the lumenof the carotid artery but do vary in arteries located longitudinally within the arterial tree, 2) MHC SM1/SM2 and/orMLC_17a/MLC_17b isoform expression does notcorrelate with unloaded shortening velocity, and 3)intracellular expression of the MHC SM1/SM2 and MLC_17a/MLC_17b isoforms is not coregulated.

     

三江平原草甸湿地土壤呼吸和枯落物分解的CO2释放

利用静态箱-碱液吸收法研究了三江平原草甸湿地土壤呼吸和枯落物分解的CO₂释放速率,讨论了影响CO₂释放的环境因素,估算了枯落物分解的CO₂释放对于总释放的贡献。结果表明,生长季,小叶章沼泽化草甸和小叶章湿草甸各部分CO₂释放均具有明显的时间变化特征,温度和水分是重要制约因素。两类草甸湿地的平均土壤呼吸速率分别为4.33g•m^-2•d^-1和6.15g•m^-2•d^-1,枯落物分解的CO₂平均释放速率分别为1.76g•m^-2•d^-1和3.10g•m^-2•d^-1,枯落物分解的CO₂释放占总释放量的31%和35%,说明在碳素由地上植物碳库转移到地下土壤碳库的过程中,湿地枯落物是一个不可忽略的碳损失源。     

Catecholaminergic modulation of respiratory rhythm in an in vitro turtle brain stem preparation

An in vitro brainstem preparation from adult turtles was used to determine effects ofdopamine (DA) and norepinephrine (NE) on the pattern of respiratorymotor output recorded from hypoglossal nerve roots (XII). Bath-appliedDA (10-200 µM) increased the frequency of respiratory bursts(peaks) from 0.9 ± 0.2 to 2.4 ± 0.3 (SE) peaks/min, resultingin a 99 ± 9% increase in neural minute activity. R[+]-SCH-23390 (10 µM,D₁ antagonist) and eticlopride (20 µM, D₂ antagonist) attenuatedthe DA-mediated increase in peak frequency by 52 and 59%,respectively. On the other hand, the DA-receptor agonists apomorphine(D₁,D₂), quinelorane(D₂), and SKF-38393 (D₁) had no effect on peakfrequency. Prazosin, an₁-adrenergic antagonist (250 nM) abolished the DA-mediated frequency increase. Although NE(10-200 µM) and phenylephrine (10-200 µM,₁-adrenergic agonist) increasedpeak frequency from 0.5 ± 0.1 to 1.2 ± 0.3 peaks/min and from0.6 ± 0.1 to 1.0 ± 0.2 peaks/min, respectively, these effectswere not as large as that with DA alone. The data suggest that bothdopaminergic and adrenergic receptor activation in the brain stemincrease respiratory frequency in turtles, but the DA receptor-mediatedincrease is dependent on coactivation of₁-adrenergic receptors.

     

Effects of N2O narcosis on breathing and effort sensations during exercise and inspiratory resistive loading

Fothergill, D. M., and N. A. Carlson. Effects ofN₂O narcosis on breathing andeffort sensations during exercise and inspiratory resistive loading.J. Appl. Physiol. 81(4):1562-1571, 1996.The influence of nitrous oxide(N₂O) narcosis on the responses toexercise and inspiratory resistive loading was studied in thirteen maleUS Navy divers. Each diver performed an incremental bicycle exercisetest at 1 ATA to volitional exhaustion while breathing a 23%N₂O gas mixture and a nonnarcoticgas of the same PO₂, density, andviscosity. The same gas mixtures were used during four subsequent30-min steady-state submaximal exercise trials in which the subjectsbreathed the mixtures both with and without an inspiratory resistance(5.5 vs. 1.1 cmH₂O ^· s ^· l¹at 1 l/s). Throughout each test, subjective ratings of respiratory effort (RE), leg exertion, and narcosis were obtained with acategory-ratio scale. The level of narcosis was rated between slightand moderate for the N₂O mixturebut showed great individual variation. Perceived leg exertion and thetime to exhaustion were not significantly different with the twobreathing mixtures. Heart rate was unaffected by the gas mixture andinspiratory resistance at rest and during steady-state exercise but wassignificantly lower with the N₂O mixture during incremental exercise (P < 0.05). Despite significant increases in inspiratory occlusionpressure (13%; P < 0.05),esophageal pressure (12%; P < 0.001), expired minute ventilation (4%;P < 0.01), and the work rate ofbreathing (15%; P < 0.001) when the subjects breathed the N₂O mixture,RE during both steady-state and incremental exercise was 25% lowerwith the narcotic gas than with the nonnarcotic mixture(P < 0.05). We conclude that the narcotic-mediated changes in ventilation, heart rate, and RE induced by23% N₂O are not of sufficientmagnitude to influence exercise tolerance at surface pressure.Furthermore, the load-compensating respiratory reflexes responsible formaintaining ventilation during resistive breathing are not depressed byN₂O narcosis.

     

Molecular analysis of the dhp1 + gene of Schizosaccharomyces pombe: an essential gene that has homology to the DST 2 and RAT 1 genes of Saccharomyces cerevisiae

We report here the first cloning of a chalcone flavonone isomerase gene (CHI) from maize. Northern blot experiments indicate that the maize CHI gene (ZmCHI1) is regulated in the pericarp by the P gene, a myb homologue. The ZmCHI1 gene encodes a 24.3 kDa product 55% and 58% identical to CHI-A and CHI-B from Petunia, respectively. This maize CHI gene has four exons and an intron-exon structure identical to the CHI-B gene of Petunia hybrida. RFLP mapping data indicate that some inbred lines contain two additional CHI-homologous sequences, suggesting an organization more complex than that found in Petunia or bean. The possibility that the additional CHI-homologous sequences are responsible for the lack of CHI mutants in maize will be discussed.     

Age-dependent response of the electrocardiogram to K(+) channel blockers in mice

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-T_c was calculated asQ- interval.Q-T_c 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(I_Kr) abolished S-T segment elevation and prolonged Q-T andQ-T_c 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-T_c 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-sensitiveI_Kr 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.

     

Variation in the Durations of the Photoperiod-sensitive and Photoperiod-insensitive Phases of Post-first Flowering Development in Maturity Isolines of Soyabean [Glycine max(L.) Merrill] 'Clark'

Plants of eight isolines of soyabean [Glycine max(L.) Merrill],comprising all combinations of two alleles at the three lociE₁/e₁,E₂/e₂andE₃/e₃inthe cultivar ‘Clark’ background, were transferredafter different periods following first flowering from longdays (LD, 14 h d^-1) to short days (SD, 12 h d^-1) andvice versaina reciprocal-transfer experiment in a plastic house maintainedat 30/24 °C (day/night). Photoperiod (0.10>P>0.05),transfer time (P<0.001),>isoline (P<0.001), and theirinteractions (P<0.001) all affected flowering duration, i.e.the period from first flowering until the appearance of thelast flower. The flowering duration comprised two distinct phases:a photoperiod-sensitive phase beginning at first flowering,and a subsequent photoperiod-insensitive phase. The durationof the photoperiod-sensitive phase varied much more among theisolines in LD than in SD. Only the dominant alleleE₁increasedthe sensitivity of the photoperiod-sensitive phase of floweringduration to photoperiod singly, but positive epistatic effectswere detected betweenE₁andE₂,E₁andE₃, and especially among allthree dominant alleles. The increases in flowering durationresulting from the combined effects of gene and environment(i.e. photoperiod) were associated with considerable increasesin biomass and seed yield at harvest maturity.Copyright 1998Annals of Botany Company. Glycine max(L.) Merrill, soyabean, maturity genes, flowering, photoperiod, reciprocal transfer, yield.     

Fluid pressure in human dermal fibroblast aggregates measured with micropipettes

Previous studies indicated that connective tissue cells in dermis are involved in control of interstitial fluid pressure (P_if). We wanted to develop and characterize an in vitro model representative of loose connective tissue to study dynamic changes in fluid pressure (P_f) over a time course of a few minutes. P_f was measured with micropipettes in human dermal fibroblast cell aggregates of varying size (<100- and >100-µm diameter) and age (days 1-4) kept at different temperatures (15, 25, and 35°C). Pressures were measured at different depths of micropipette penetration and after treatment with prostaglandin E₁ isopropyl ester (PGE₁), latanoprost (PGF₂), and ouabain. P_f was positive (more than +2 mmHg) during control conditions and increased with increasing aggregate size (day 2), age (day 4 vs. day 1), temperature, and depth of micropipette penetration. P_f decreased from 2.9 to 2.0 mmHg during the first 10 min after application of 10 µl of 1 mM PGE₁ (P < 0.001). P_f increased from 3.0 to 4.8 mmHg (P < 0.01) after administration of 10 µl of 1.4 µM ouabain and from 3.1 to 4.4 mmHg after addition of 5 µl of 1.42 mM PGF₂ (P > 0.05). In conclusion, we have developed and validated a new in vitro method for studying fluid pressure in loose connective tissue elements with the advantage of allowing reliable and rapid screening of substances that have a potential to modify P_f and studying in more detail specific cell types involved in control of P_f. This study also provides evidence that fibroblasts in the connective tissue can actively modulate P_f. micropuncture; prostaglandin E₁; prostaglandin F₂; ouabain; integrins     

Expression and regulation of parathyroid hormone-related peptide in normal and malignant melanocytes

We examined parathyroidhormone-related peptide (PTHrP) production and regulation in bothnormal human melanocytes and in a human amelanotic melanoma cell line(A375). Northern blot and immunocytochemical analysis demonstrated thatboth cultured A375 cells and normal human melanocytes express PTHrP,but A375 cells expressed much higher levels of the peptide. PTHrPsecretory rate increased at least 10-fold after treatment with 10%fetal bovine serum (100.2 ± 2.8 pmol/10⁶ cells vs.basal <15 pmol/10⁶ cells) in proliferating A375 cells butonly twofold in confluent cells. Treatment of A375 cells withincreasing concentrations of 1,25-dihydroxyvitamin D₃[1,25-(OH)₂D₃] or its low-calcemic analogEB-1089 revealed that EB-1089 was 10-fold more potent than 1,25-(OH)₂D₃ on inhibition of both cellproliferation and PTHrP expression. Furthermore, inoculation of A375cells into the mammary fat pad of female severe combinedimmunodeficiency mice resulted in the development ofhypercalcemia and elevated concentrations of plasma immunoreactivePTHrP in the absence of detectable skeletal metastases. Our study,therefore, demonstrates a stepwise increase in PTHrP expression whencells progress from normal to malignant phenotype and suggests thatEB-1089 should be further evaluated as a therapeutic agent in human melanoma.

     

Evidence for Essential Maintenance Respiration of Leaves of Xanthium Strumarium at High Temperature

Mesophyll resistance to photosynthetic carboxylation (r'_m) wasused as a criterion for leaf integrity. It was measured, at25 °C, in the light, before and after periods of high temperature(3 h at 38 °C) in the dark. During the high temperatureperiods, respiration (R_D) of attached leaves of Xanthium strumariumwas suppressed from 27%-36% by either low [O₂] (1.04% or 0.21%v.v.) or high [CO₂] (840 µl 1^–1) in the ambientair. Neither treatment affected rates of R_D or photo-respirationduring the second period at 25 °C. There was no significant increase of r'_m when R_D was not suppressedduring the high temperature treatment. When R_D was suppressedat high temperatures, r'_m increased from about 3s cm^–1before, to about 26 s cm^–1 after the high temperaturetreatment. The increase depended upon the degree of suppression. It is concluded that increased R_D at high temperature in Xanthiumleaves is partly the result of an increase of energy demandingmaintenance. The subsequent rate of carbon dioxide fixationis reduced when this increase of maintenance-induced respirationis inhibited.     

Molecular analysis of the dhp1+ gene of Schizosaccharomyces pombe: an essential gene that has homology to the DST 2 and RAT 1 genes of Saccharomyces cerevisiae

We report here the first cloning of a chalcone flavonone isomerase gene (CHI) from maize. Northern blot experiments indicate that the maize CHI gene (ZmCHI1) is regulated in the pericarp by the P gene, a myb homologue. The ZmCHI1 gene encodes a 24.3 kDa product 55% and 58% identical to CHI-A and CHI-B from Petunia, respectively. This maize CHI gene has four exons and an intron-exon structure identical to the CHI-B gene of Petunia hybrida. RFLP mapping data indicate that some inbred lines contain two additional CHI-homologous sequences, suggesting an organization more complex than that found in Petunia or bean. The possibility that the additional CHI-homologous sequences are responsible for the lack of CHI mutants in maize will be discussed.     

Regional deposition of inhaled particles in human lungs: comparison between men and women

We measured detailed regional depositionpatterns of inhaled particles in healthy adult male(n = 11; 25 ± 4 yr of age) and female (n = 11; 25 ± 3 yr of age)subjects by means of a serial bolus aerosol delivery technique formonodisperse fine [particle diameter(D_p) = 1 µm] and coarse aerosols(D_p = 3 and 5 µm). The bolus aerosol (40 ml half-width) was delivered to a specificvolumetric depth (Vp) of the lung ranging from 100 to 500 ml with a50-ml increment, and local deposition fraction (LDF) was assessed for each of the 10 local volumetric regions. In all subjects, the deposition distribution pattern was very uneven with respect to Vp,showing characteristic unimodal curves with respect to particle sizeand flow rate. However, the unevenness was more pronounced in women.LDF tended to be greater in all regions of the lung in women than inmen for D_p = 1 µm. For D_p = 3 and 5 µm, LDF showed a marked enhancement in the shallow region of Vp  200 ml in women compared with men(P < 0.05). LDF in women wascomparable to or smaller than those of men in deep lung regions of Vp > 200 ml. Total lung deposition was comparable between men and womenfor fine particles but was consistently greater in women than men forcoarse particles regardless of flow rates used: the difference rangedfrom 9 to 31% and was greater with higher flow rates(P < 0.05). The results indicatethat 1) particledeposition characteristics differ between healthy men and women undercontrolled breathing conditions and2) deposition in women is greaterthan that in men.

     

p38 mitogen-activated protein kinase inhibits calcium-dependent chloride secretion in T84 colonic epithelial cells

We havepreviously shown that Ca²⁺-dependent Clsecretion across intestinal epithelial cells is limited by a signalingpathway involving transactivation of the epidermal growth factorreceptor (EGFR) and activation of ERK mitogen-activated protein kinase (MAPK). Here, we have investigated a possible role for p38 MAPK inregulation of Ca²⁺-dependent Cl secretion.Western blot analysis of T₈₄ colonic epithelial cells revealed that the muscarinic agonist carbachol (CCh; 100 µM)stimulated phosphorylation and activation of p38 MAPK. The p38inhibitor SB-203580 (10 µM) potentiated and prolonged short-circuitcurrent (I_sc) responses to CCh acrossvoltage-clamped T₈₄ cells to 157.4 ± 6.9% of thosein control cells (n = 21; P < 0.001).CCh-induced p38 phosphorylation was attenuated by the EGFR inhibitortyrphostin AG-1478 (0.1 nM-10 µM) and by the Src family kinaseinhibitor PP2 (20 nM-2 µM). The effects of CCh on p38phosphorylation were mimicked by thapsigargin (TG; 2 µM), whichspecifically elevates intracellular Ca²⁺, and wereabolished by the Ca²⁺ chelator BAPTA-AM (20 µM), implyinga role for intracellular Ca²⁺ in mediating p38 activation.SB-203580 (10 µM) potentiated I_sc responses toTG to 172.4 ± 18.1% of those in control cells (n = 18; P < 0.001). When cells were pretreated withSB-203580 and PD-98059 to simultaneously inhibit p38 and ERK MAPKs,respectively, I_sc responses to TG and CCh weresignificantly greater than those observed with either inhibitor alone.We conclude that Ca²⁺-dependent agonists stimulate p38 MAPKin T₈₄ cells by a mechanism involving intracellularCa²⁺, Src family kinases, and the EGFR. CCh-stimulated p38activation constitutes a similar, but distinct and complementary,antisecretory signaling pathway to that of ERK MAPK.

     

Effects of alpha1D-adrenergic receptors on shedding of biologically active EGF in freshly isolated lacrimal gland epithelial cells

Transactivation of EGF receptors by G protein-coupled receptors is a well-known phenomenon. This process involves the ectodomain shedding of growth factors in the EGF family by matrix metalloproteinases. However, many of these studies employ transformed and/or cultured cells that overexpress labeled growth factors. In addition, few studies have shown that EGF itself is the growth factor that is shed and is responsible for transactivation of the EGF receptor. In this study, we show that freshly isolated, nontransformed lacrimal gland acini express two of the three known ₁-adrenergic receptors (ARs), namely, _1B- and _1D-ARs. _1D-ARs mediate phenylephrine (an ₁-adrenergic agonist)-induced protein secretion and activation of p42/p44 MAPK, because the _1D-AR inhibitor BMY-7378, but not the _1A-AR inhibitor 5-methylurapidil, inhibits these processes. Activation of p42/p44 MAPK occurs through transactivation of the EGF receptor, which is inhibited by the matrix metalloproteinase ADAM17 inhibitor TAPI-1. In addition, phenylephrine caused the shedding of EGF from freshly isolated acini into the buffer. Incubation of freshly isolated cells with conditioned buffer from cells treated with phenylephrine resulted in activation of the EGF receptor and p42/p44 MAPK. The EGF receptor inhibitor AG1478 and an EGF-neutralizing antibody blocked this activation of p42/p44 MAPK. We conclude that in freshly isolated lacrimal gland acini, ₁-adrenergic agonists activate the _1D-AR to stimulate protein secretion and the ectodomain shedding of EGF to transactivate the EGF receptor, potentially via ADAM17, which activates p42/p44 MAPK to negatively modulate protein secretion. epidermal growth factor ectodomain shedding; protein secretion; signal transduction     

Prostaglandin production contributes to exercise-induced vasodilation in heart failure

Lang, Chim C., Don B. Chomsky, Javed Butler, Shiv Kapoor,and John R. Wilson. Prostaglandin production contributes toexercise-induced vasodilation in heart failure. J. Appl. Physiol. 83(6): 1933-1940, 1997.Endothelial release of prostaglandins may contribute toexercise-induced skeletal muscle arteriolar vasodilation in patientswith heart failure. To test this hypothesis, we examined the effect ofindomethacin on leg circulation and metabolism in eight chronic heartfailure patients, aged 55 ± 4 yr. Central hemodynamics and legblood flow, determined by thermodilution, and leg metabolic parameterswere measured during maximum treadmill exercise before and 2 h afteroral administration of indomethacin (75 mg). Leg release of6-ketoprostaglandin F₁ was alsomeasured. During control exercise, leg blood flow increased from 0.34 ± 0.03 to 1.99 ± 0.19 l/min(P < 0.001), legO₂ consumption from 13.6 ± 1.8 to 164.5 ± 16.2 ml/min (P < 0.001), and leg prostanoid release from 54.1 ± 8.5 to267.4 ± 35.8 pg/min (P < 0.001).Indomethacin suppressed release of prostaglandinF₁(P < 0.001) throughout exercise anddecreased leg blood flow during exercise(P < 0.05). This was associated witha corresponding decrease in leg O₂ consumption (P < 0.05) and a higher level offemoral venous lactate at peak exercise(P < 0.01). These data suggest thatrelease of vasodilatory prostaglandins contributes to skeletal musclearteriolar vasodilation in patients with heart failure.

     

Differential Effects of Day and Night Temperature on Development to Flowering in Rice

There are conflicting reports with regard to difference in effectsof day temperature (T_D) and night temperatures (T_N) on plantdevelopment. The objective of this study is to determine whetherthere are different effects ofT_DandT_Non development from sowingto flowering in rice (Oryza sativaL.). Plants of 24 rice cultivars were grown in naturally-lightedgrowth chambers at five diurnally constant (22, 24, 26, 28 and32 °C) and four diurnally fluctuating temperatures (26 /22,30 /22, 22 /26 and 22 /30 °C forT_D/T_Nwith 12hd^-1each) witha constant photoperiod of 12hd^-1. The treatments were selectedto enable the separation of effects ofT_DandT_Non developmentrate (DR). The response of DR to constant temperatures was typically nonlinear.This nonlinearity could not explain the difference in floweringdates between fluctuating temperatures with the same mean dailyvalue but oppositeT_D/T_Ndifferences. Differential effects ofT_DandT_NonDR to flowering were detected in all but one cultivar. In mostcases,T_Dexerted a greater influence thanT_N, in contrast withmany previous reports based on the assumption of a linearitybetween DR and temperature. The data were further analysed bya nonlinear model which separated effects ofT_DandT_N. The estimatedvalue for the optimumT_Nwas generally 25 –29 °C, about2 –4 °C lower than the estimated optimumT_Din mostcultivars. The effects ofT_DandT_Non DR were found to be interactivein some cultivars. These results form a new basis for modellingflowering dates in rice. Oryza sativa; rice; flowering; development; day and night temperature; thermoperiodicity