Metabolic pathways from 1 alpha,25-dihydroxyvitamin D3 to 1 alpha,25-dihydroxyvitamin D3-26,23-lactone. Stereo-retained and stereo-selective lactonization

The present study was carried out in order to elucidate the metabolic pathway from 1 alpha,25-(OH)2D3 to 1 alpha,25-(OH)2D3-26,23-lactone. For that purpose, we stereospecifically synthesized the vitamin D3 derivatives 1 alpha,23(S),25-(OH)3D3, 1 alpha,23(S),25(R),26-tetrahydroxyvitamin D3, and 23(S),25(R)-1 alpha,25-dihydroxyvitamin D3-lactol. The in vitro metabolism of these compounds was examined in kidney homogenates and intestinal mucosa homogenates from 1 alpha,25-(OH)2D3-supplemented chicks. The naturally occurring 23(S),25(R)-1 alpha,25-dihydroxyvitamin D3-26,23-lactone was produced (in increasing amounts) from 1 alpha,25-(OH)2D3, 1 alpha,25(R),26-(OH)3D3, 1 alpha,23(S),25-(OH),D3, 1 alpha,23(S),25(R),26-(OH)4D3, and 23(S),25(R)-1 alpha,25-(OH)2D3-26,23-lactol. These results indicated that there are two possible metabolic pathways from 1 alpha,25-(OH)2D3 to 1 alpha,23(S),25(R),26-(OH)4D3: the major one is by way of 1 alpha,23(S),25-(OH)3D3 and the minor one is by way of 1 alpha,25(R),26-(OH)3D3. 1 alpha,23(S),25(R),26-Tetrahydroxyvitamin D3 is further metabolized to 23(S),25(R)-1 alpha,25-dihydroxyvitamin D3-26,23-lactone via 23(S),25(R)-1 alpha,25-dihydroxyvitamin D3-26,23-lactol. In the course of our studies, a new biosynthetic vitamin D3 metabolite was isolated in pure form. This metabolite was identified as 23(S),25(R)-1 alpha,25-(OH)2D3-26,23-lactol by UV spectrophotometry and mass spectrometry. Furthermore, we establish in this report that the lactonization of 1 alpha,23,25,26-(OH)4D3 and 1 alpha,25-(OH)2D3-26,23-lactol occurs in a stereo-retained and stereo-selective fashion.     

Characterization of murine monoclonal antibodies to human interferon-gamma (IFN-gamma) and their application for sandwich enzyme-linked immunosorbent assay (ELISA)

The three murine monoclonal antibodies (MAb), D1G2, D9D10, and D13C8, are specific for human interferon-gamma (IFN-gamma), but not human IFN-alpha and IFN-beta. They react weakly with heat-treated IFN-gamma. The three antibodies recognize different epitopes of the IFN-gamma molecule, as evaluated by antibody-binding inhibition experiments. We have used these three monoclonal antibodies to construct a sandwich enzyme-linked immunosorbent assay (ELISA). The best result was obtained when we used D1G2 or D9D10 MAb as a solid-phase immunosorbent and D1G2 or D9D10 MAb as a tracer. When we measured IFN-gamma in sera by a combination of D1G2 (a solid-phase) and D1G2 (a tracer), a result similar to the one by a combination of D9D10 (a solid-phase) and D1G2 (a tracer), was obtained. This may suggest that human IFN-gamma exists in oligomeric form. Recombinant human IFN-gamma expressed in E. coli is detectable at a concentration of 1 ng/ml in this sandwich ELISA. This assay can be employed for the analysis of the structural characteristics of the human IFN-gamma molecule as well as measurement of IFN-gamma in human sera and tissue culture fluids.     

D2-dopamine receptor and alpha2-adrenoreceptor-mediated analgesic response of quercetin

Quercetin, a bioflavonoid (100-300 mg/kg) produced dose dependent increase in tail-flick latency, the analgesic effect being sensitive to reversal by naloxone (1 mg/kg). Prior treatment with haloperidol (1 mg/kg), D1/D2 receptor antagonist haloperidol, sulpiride (50 mg/kg), a selective D2 receptor antagonist, yohimbine (5 mg/kg), a alpha2-adrenoreceptor antagonist but not by SCH 23390 a, selective D1 receptor antagonist blocked this response. Apomorphine (1 mg/kg) a mixed D1/D2 dopamine receptor agonist, and quinpirole (0.5 mg/kg), a selective D2 receptor agonist also produced antinociception, that was reversed by haloperidol (1 mg/kg), sulpiride (50 mg/kg), but not by yohimbine (5 mg/kg). The antinociceptive action of quercetin (200 mg/kg) was potentiated by D2 agonist quinpirole (0.2 mg/kg). Dopamine D1 receptor agonist SKF38393 (10 and 15 mg/kg) failed to alter the antinociceptive effect of quercetin (200 mg/kg). Quercetin (200 mg/kg) reversed reserpine (2 mg/kg-4 hr) induced hyperalgesia, which was reversed by sulpiride but not by yohimbine. Thus, a role of dopamine D2 and alpha2-adrenoreceptors is postulated in the antinociceptive action of quercetin.     

Physiological significance of C-28 hydroxylation in the metabolism of 1alpha,25-dihydroxyvitamin D(2).

In our previous study, we indicated for the first time that C-28 hydroxylation plays a significant role in the metabolism of 1alpha, 25-dihydroxyvitamin D(2) [1alpha,25(OH)(2)D(2)] by identifying 1alpha,24(S),25,28-tetrahydroxyvitamin D(2) [1alpha,24(S),25, 28(OH)(4)D(2)] as a major renal metabolite of 1alpha,25(OH)(2)D(2) [G. S. Reddy and K-Y. Tserng Biochemistry 25, 5328-5336, 1986]. The present study was performed to establish the physiological significance of C-28 hydroxylation in the metabolism of 1alpha, 25(OH)(2)D(2). We perfused rat kidneys in vitro with 1alpha, 25(OH)(2)[26,27-(3)H]D(2) (5 x 10(-10)M) and demonstrated that 1alpha,24(R),25-trihydroxyvitamin D(2) [1alpha,24(R),25(OH)(3)D(2)] and 1alpha,24(S),25,28(OH)(4)D(2) are the only two major physiological metabolites of 1alpha,25(OH)(2)D(2). In the same perfusion experiments, we also noted that there is no conversion of 1alpha,25(OH)(2)D(2) into 1alpha,25,28-trihydroxyvitamin D(2 )[1alpha,25,28(OH)(3)D(2)]. Moreover, 1alpha,24(S),25,28(OH)(4)D(2) is not formed in the perfused rat kidney when synthetic 1alpha,25, 28(OH)(3)D(2) is used as the starting substrate. This finding indicates that C-28 hydroxylation of 1alpha,25(OH)(2)D(2) occurs only after 1alpha,25(OH)(2)D(2) is hydroxylated at C-24 position. At present the enzyme responsible for the C-28 hydroxylation of 1alpha, 24(R),25(OH)(3)D(2) in rat kidney is not known. Recently, it was found that 1alpha,25(OH)(2)D(3)-24-hydroxylase (CYP24) can hydroxylate carbons 23, 24, and 26 of various vitamin D(3) compounds. Thus, it may be speculated that CYP24 may also be responsible for the C-28 hydroxylation of 1alpha,24(R),25(OH)(3)D(2) to form 1alpha, 24(S),25,28(OH)(4)D(2). The biological activity of 1alpha,24(S),25, 28(OH)(4)D(2), determined by its ability to induce intestinal calcium transport and bone calcium resorption in the rat, was found to be almost negligible. Also, 1alpha,24(S),25,28(OH)(4)D(2) exhibited very low binding affinity toward bovine thymus vitamin D receptor. These studies firmly establish that C-28 hydroxylation is an important enzymatic reaction involved in the inactivation of 1alpha,25(OH)(2)D(2) in kidney under physiological conditions.     

Impaired renal D(1)-like and D(2)-like dopamine receptor interaction in the spontaneously hypertensive rat

D(1)-like (D(1), D(5)) and D(2)-like (D(2), D(3), D(4)) dopamine receptors interact in the kidney to produce a natriuresis and a diuresis. Disruption of D(1) or D(3) receptors in mice results in hypertension that is caused, in part, by a decreased ability to excrete an acute saline load. We studied D(1)-like and D(2)-like receptor interaction in anesthetized spontaneously hypertensive rats (SHR) by the intrarenal infusion of Z-1046 (a novel dopamine receptor agonist with rank order potency of D(3)> or =D(4)>D(2)>D(5)>D(1)). Z-1046 increased glomerular filtration rate (GFR), urine flow, and sodium excretion in normotensive Wistar-Kyoto rats but not in SHRs. The lack of responsiveness to Z-1046 in SHRs was not an epiphenomenon, because intrarenal cholecystokinin infusion increased GFR, urine flow, and sodium excretion to a similar extent in the two rat strains. We conclude that renal D(1)-like and D(2)-like receptor interaction is impaired in SHRs. The impaired D(1)-like and D(2)-like receptor interaction in SHRs is not caused by alterations in the coding sequence of the D(3) receptor, the D(2)-like receptor expressed in rat renal tubules that has been shown to be involved in sodium transport. Because the diuretic and natriuretic effects of D(1)-like receptors are, in part, caused by an interaction with D(2)-like receptors, it is possible that the decreased Z-1046 action in SHRs is secondary to the renal D(1)-like receptor dysfunction in this rat strain.     

强化阿托伐他汀治疗对ACS患者血脂水平的短期影响

目的:观察强化阿托伐他汀治疗对急性冠脉综合征(ACS)患者血脂水平的短期影响。方法:收集100例ACS患者,入院当天(the day of admission,D0)、入院第一天(the first day,D1)及入院第二天(The Second Day,D2)分别给予阿托伐他汀80mg治疗,入院D0立即采血化验血脂参数包括总胆固醇(total cholesterol,TC)、低度脂蛋白(LDL-cholesterol,LDL-C)、高密度脂蛋白(HDL-cholesterol,HDL-C)、甘油三酯(triglycerides,TG),分别在D1和D2晨起空腹复查。结果:总胆固醇的平均基线水平为5.24±0.07(D0),低密度脂蛋白为3.26±0.07,高密度脂蛋白胆固醇为1.07±0.07,甘油三酯为1.31±0.07。口服阿托伐他汀80毫克后第一天早晨,TC水平下降6.1%(D1)(与D0相比P0.001),第二日下降13.2%(D2)(与D0相比P0.001),LDL-C下降5.8%(D1)(DO与D1相比,P0.001)和15.6%(D2)(DO与D2相比,P0.001);HDL-C下降7.5%(D1)(DO与D1相比,P0.001)和12.1(D2)(DO与D2相比,P0.001);相反TG水平升高20.6%(D1)(DO与D1相比,P0.001)和25.5%(D2)(DO与D2相比,P0.001)。结论:强化他汀治疗对ACS患者血脂短期的影响与长期的影响是不同的,TC,LDL和HDL在短期内是下降的,而TG是升高的。     

Structural characterization of the antigenic O-chain of the lipopolysaccharide of Escherichia coli serotype O65

The antigenic O-polysaccharide moiety of the lipopolysaccharide produced by Escherichia coli serotype O65 was investigated by composition, methylation, base hydrolysis, periodate oxidation, mass spectrometric methods, and by 1D and 2D NMR spectroscopy. The O-polysaccharide had [alpha]D + 108 degrees (water) and is a high-molecular-weight unbranched linear polymer of repeating pentasaccharide units composed of 1:1:1:1:1 D-galacturonic acid (D-GalA), D-galacturonamide (D-GalANH2), 2-acetamido-2-deoxy-D-glucose (D-GlcNAc), 2-acetamido-2-deoxy-D-galactose (D-GalNAc), and 3-acetamido-3,6-dideoxy-D-glucose (D-Qui3NAc), and has the following structure: [formula: see text]     

Successful Application of Video-Projected Human Images for Signalling to Dogs

Dogs were tested (1) in a two‐way choice experiment, where the experimenter indicated a baited bowl by pointing; and (2) in a task where the owner was asked to command the dog to execute simple obedience tasks. In expt 1 dogs (n = 10) were tested at first in the presence of the experimenter (three dimensional condition, 3D), that was followed by a series of pointing trials when the life‐sized image of the experimenter was projected onto the wall by the means of a video‐projector (two dimensional condition, 2D). Dogs performed correctly more often than expected by chance in both 3D and 2D conditions. In expt 2 the commanding owner was either present in the room (3D), or her/his image was projected on the screen (2D), or only her/his voice was audible for the dog through a speaker (0D). The performance of the dogs (n = 10) decreased to great extent comparing the 3D and 0D condition, as the number of different actions the dogs obeyed was significantly less in the 0D condition. However, there was no difference in the number of different actions obeyed in the 3D and 2D conditions. Our results show that dogs readily obey life‐sized, interactive moving image in various communicative situtations. We suppose that the difference between 2D and 3D conditions can be attributed partially to the lack of some additional communicative signals as sounds (verbal cues) and odours (from the human), and to some changes in the context.     

Vitamin D(3) and analogues modulate the expression of CSF-1 and its receptor in human dendritic cells

The active vitamin D(3)-metabolite 1,25(OH)(2)D(3) inhibits the interleukin 4/granulocyte-macrophage colony-stimulating factor (IL-4/GM-CSF)-induced differentiation of human monocytes into dendritic cells without altering survival. Colony-stimulating factor 1 (CSF-1) is an important survival factor for cells of the monocytic lineage. We therefore investigated whether the inhibitory activity of 1,25(OH)(2)D(3) is paralleled by a regulation of CSF-1 and its receptor. Purified human monocytes were cultured together with IL-4/GM-CSF in the presence of 1,25(OH)(2)D(3), its analogue tacalcitol, the low-affinity vitamin D receptor ligand 24,25(OH)(2)D(3), or the solvent ethanol for up to 5 days. Expression of CSF-1, CSF-1R, and GM-CSF mRNA was measured by RT-PCR. Protein secretion for CSF-1 was measured by ELISA, expression of CSF-1R by flow cytometry. The results showed that 1,25(OH)(2)D(3) and tacalcitol significantly up-regulated CSF-1 mRNA-expression and protein secretion in a dose-dependent manner. The effect of 1,25(OH)(2)D(3) occurred already after 1h of pre-treatment. In contrast, CSF-1R mRNA- and cell surface-expression was down-regulated simultaneously. The solvent ethanol and 24,25(OH)(2)D(3) were without effect. GM-CSF mRNA expression was not modulated in 1,25(OH)(2)D(3)-treated cells. These data point towards a distinct and specific regulation of CSF-1 and its receptor by 1,25(OH)(2)D(3) and its analogue tacalcitol in human monocytes which parallels the inhibition of differentiation into dendritic cells without altering survival.     

1Alpha,25-dihydroxyvitamin D3-mediated stimulation of steroid sulphatase activity in myeloid leukaemic cell lines requires VDRnuc-mediated activation of the RAS/RAF/ERK-MAP kinase signalling pathway

1Alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) stimulates the activity of steroid sulphatase (STS) in myeloid cells [Hughes et al., 2001, 2005]. This was attenuated by inhibitors of phospholipase D (PLD) (n-butanol, 2,3-diphosphoglyceric acid, C(2)-ceramide) and phosphatidate phosphohydrolase (PAP) (propranolol and chlorpromazine), but was unaffected by inhibitors of phospholipase C. The 1alpha,25(OH)(2)D(3)-induced STS activity was also attenuated by inhibitors of protein kinase Calpha and protein kinase Cdelta (Go 6976, HBDDE and rottlerin), but not by an inhibitor of protein kinase Cbeta (LY379196). Additionally, 1alpha,25(OH)(2)D(3)-induced STS activity was attenuated by inhibitors of RAS (manumycin A), RAF (GW5074), MEK (PD098059 and U1026) and JNK (SP600125), but not p38 (PD169316). 1alpha,25(OH)(2)D(3) produced a rapid and long lasting stimulation of the ERK-MAP kinase signalling cascade in HL60 myeloid leukaemic cells. This 'non-genomic' effect of 1alpha,25(OH)(2)D(3) blocked by pharmacological antagonists of nuclear vitamin D receptors (VDR(nuc)) and does not appear to require hetero-dimerisation with the retinoid-X receptor (RXR). Inhibitors of the Src tyrosine kinase (PP1), RAS (manumycin A), RAS-RAF interactions (sulindac sulphide and RAS inhibitory peptide), RAF (GW5074 or chloroquine), and protein kinase Calpha (HBDDE) abrogated the 1alpha,25(OH)(2)D(3)-stimulated increase in ERK-MAP kinase activity. Taken together, these results show that 1alpha,25(OH)(2)D(3)/VDR(nuc) activation of the RAS/RAF/ERK-MAP kinase signalling pathway plays an important role in augmenting STS activity in human myeloid leukaemic cell lines.     

Mechanistic studies to evaluate the enhanced antiproliferation of human keratinocytes by 1alpha,25-dihydroxyvitamin D(3)-3-bromoacetate, a covalent modifier of vitamin D receptor, compared to 1alpha,25-dihydroxyvitamin D(3).

1alpha,25-Dihydroxyvitamin D(3)-3-bromoacetate (1, 25(OH)(2)D(3)-3-BE), an affinity labeling analog of 1alpha, 25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), displayed stronger antiproliferative activities than 1,25(OH)(2)D(3) at 10(-10)-10(-6) M dose levels in cultured human keratinocytes (CHK). Additionally, preincubation of the cells with 10(-6) M 1,25(OH)(2)D(3), followed by treatment with various doses of 1,25(OH)(2)D(3)-3-BE, resulted in a significantly stronger antiproliferative activity by the mixture than individual reagents at every dose level. To search for a mechanism of this observation, we determined that [(14)C]1, 25(OH)(2)D(3)-3-BE covalently labeled human recombinant 1alpha, 25-dihydroxyvitamin D(3) receptor (reVDR) swiftly (<1 min) with a 1:1 stoichiometry and induced conformational changes (in VDR) that are different from 1,25(OH)(2)D(3), by limited tryptic digestion. Furthermore, a protein band, corresponding to reVDR, was specifically labeled by [(14)C]1,25(OH)(2)D(3)-3-BE in CHK extract, indicating that VDR is the main target of [(14)C]1, 25(OH)(2)D(3)-3-BE. The above-mentioned observations suggest that a rapid covalent labeling of VDR in CHK might alter the interaction between the holo-VDR and 1,25(OH)(2)D(3)-controlled genes. Furthermore, we observed that 1,25(OH)(2)D(3)-3-BE significantly decreased the binding of VDR to human osteocalcin vitamin D responsive element (hOCVDRE), as well as the dissociation rate of VDR from hOCVDRE, compared with 1,25(OH)(2)D(3) in COS-1 cells, transiently transfected with a VDR construct. Additionally, 1, 25(OH)(2)D(3)-3-BE was found to be more potent in inducing 1alpha, 25-dihydroxyvitamin D(3)-24-hydroxylase (24-OHase) promoter activity and mRNA expression in keratinocytes. The accumulation of 24-OHase message was also prolonged by the analog. Collectively these results indicated that rapid covalent labeling of VDR in keratinocytes (by 1, 25(OH)(2)D(3)-3-BE) might result in the conversion of apo-VDR to a holo-form, with a conformation that is different from that of the 1, 25(OH)(2)D(3)-VDR complex. This resulted in an enhanced stability of the 1,25(OH)(2)D(3)-3-BE/VDR-VDRE complex and contributed to the amplified antiproliferative effect of 1,25(OH)(2)D(3)-3-BE in keratinocytes.     

Synergistic anticancer activity of 1,25-dihydroxyvitamin D(3) and immune cytokines: the involvement of reactive oxygen species

It was previously shown that 1,25-dihydroxyvitamin D(3) (1, 25(OH)(2)D(3)) enhances the cytotoxic activity of tumor necrosis factor alpha (TNFalpha), doxorubicin and menadione. A feature shared by these anticancer agents is the involvement of reactive oxygen species (ROS) in their action. In this work we found that 1, 25(OH)(2)D(3) acted synergistically with interleukin 1 beta (IL-1beta) or interleukin 6 (IL-6) to inhibit the proliferation of MCF-7 breast cancer cells. The extent of the synergism was maximal at 1 nM, a concentration at which 1,25(OH)(2)D(3), acting singly, only marginally reduced the cell number. The thiol antioxidant, N-acetylcysteine (NAC) abolished the synergism between IL-1beta or IL-6 and 1,25(OH)(2)D(3), but had only a small protective effect when the cytokines acted alone. NAC and reduced glutathione (GSH) protected MCF-7 cells from cytotoxicity induced both by TNFalpha alone and by TNFalpha and 1,25(OH)(2)D(3). A two-day exposure to TNFalpha caused a 27.7+/-3.1% (mean +/- SEM) reduction in GSH content. This effect increased to 46.4+/-5.5% by co-treatment with 1, 25(OH)(2)D(3) which did not affect GSH levels on it own. We conclude that 1,25(OH)(2)D(3) can act synergistically with anticancer cytokines present in the tumor milieu and that ROS plays a mediatory role in this interaction.     

Dopamine receptor-mediated regulation of striatal cholinergic activity: positron emission tomography studies with norchloro[18F]fluoroepibatidine

Large numbers of in vitro studies and microdialysis studies suggest that dopaminergic regulation of striatal acetylcholine (ACh) output is via inhibitory dopamine D2 receptors and stimulatory dopamine D1 receptors. Questions remain as to the relative predominance of dopamine D2 versus D1 receptor modulation of striatal ACh output under physiological conditions. Using positron emission tomography, we first demonstrate that norchloro[18F]fluoroepibatidine ([18F]NFEP), a selective nicotinic ACh receptor (nAChR) ligand, was sensitive to changes of striatal ACh concentration. We then examined the effect of quinpirole (D2 agonist), raclopride (D2 antagonist), SKF38393 (D1 agonist), and SCH23390 (D1 antagonist) on striatal binding of [18F]NFEP in the baboon. Pretreatment with quinpirole increased the striatum (ST) to cerebellum (CB) ratio by 26+/-6%, whereas pretreatment with raclopride decreased the ST/CB ratio by 22+/-2%. The ratio of the distribution volume of [18F]NFEP in striatum to that in cerebellum, which corresponds to (Bmax/K(D)) + 1 (index for nAChR availability), also showed a significant increase (29 and 20%; n = 2) and decrease (20+/-3%; n = 3) after pretreatment with quinpirole and raclopride, respectively. However, both the D1 agonist and antagonist had no significant effect. This suggests that under physiological conditions the predominant influence of endogenous dopamine on striatal ACh output is dopamine D2, not D1, receptor-mediated.     

Pulsed high-field gradient in vivo NMR spectroscopy to measure diffusional water permeability in Corynebacterium glutamicum

Pulsed high-field gradient in vivo NMR spectroscopy was used to measure diffusional water permeability in cell suspensions of the Gram-positive bacterium Corynebacterium glutamicum. Two different regions of H2O mobility were detected. One was characterized by the apparent coefficient of self-diffusion, D(1 app) = (4.6-12.7)x10(-8) cm(2) s(-1), depending on the observation time t. The other region was characterized by D(2) = 1.4x10(-5) cm(2) s(-1). The value of D(2) was similar to the diffusion coefficient of H2O in free water and in extracellular biological fluids. Restricted diffusion could be demonstrated for the slower process (D(1)). It was attributed to the cytoplasm of the cells. The membrane permeability, P(d H2O), for C. glutamicum was (4.8+/-0.4)x10(-3) cm s(-1). It compared favorably with values reported for human erythrocytes and was higher by a factor of about 100 compared to the diffusional permeability for ethanol, P(d ethanol), in Zymomonas mobilis. Addition of HgCl2, a water channel inhibitor in eukaryotes, decreased P(d H2O) in C. glutamicum by a factor of approximately 8. To our knowledge, these are the first functional studies of water transport in prokaryotes that yielded quantitative data, viz., transmembrane water permeability expressed through D(H2O) and P(d H2O).     

拔节期与开花期测墒补灌对小麦旗叶荧光特性和水分利用效率的影响

为研究依据不同土层的土壤质量含水量进行测墒补灌对小麦(Triticum aestivum)拔节期与开花期旗叶荧光特性和水分利用效率的影响, 2011-2012和2012-2013年度两个小麦生长季, 设置0-20 (D1)、0-40 (D2)、0-60 (D3)和0-140 cm (D4) 4个土层进行处理, 测定土壤质量含水量, 以各土层平均土壤相对含水量在拔节期为65%和在开花期为70%为目标相对含水量进行补灌, 全生育期不灌溉为对照(D0)。结果表明: (1) D2处理拔节至开花期40-100 cm土层和开花至成熟期40-140 cm土层的土壤贮水消耗量高于其他处理, 开花至成熟期是小麦贮水消耗的最大时期。(2)开花后旗叶水分利用效率、PSII潜在活性(F_v/F_o)、PSII电子传输活性(F_m/F_o)、相对电子传递速率(ETR)和光化学猝灭系数(q_P) D2处理最高, D3次之, D0最低。(3)两个小麦生长季, 各处理的籽粒产量为D2 > D3 > D1 > D4 > D0, D2的水分利用效率分别为20.19 kg·hm^-2·mm^-1和21.92 kg·hm^-2·mm^-1, 高于D0、D3和D4处理, 与D1处理间无显著差异。综合分析, 小麦拔节期和开花期依据0-40 cm土层的土壤质量含水量进行测墒补灌可兼顾高产和高水分利用效率。     

Effect of 1,25-dihydroxyvitamin D3 on cytokine-induced thymocyte proliferation

To clarify the mechanism of the inhibitory effect of 1,25(OH)2D3 on lymphocyte proliferation, the effect of 1,25(OH)2D3 on murine thymocyte proliferation induced by interleukin 1 (IL-1), or 2 (IL-2) was examined. Physiological concentrations of 1,25(OH)2D3 inhibited thymocyte proliferation induced by IL-1 and IL-2 in similar fashion suggesting an inhibition of the response to IL-2 by this hormone. In addition, cortisone-resistant thymocytes (including a majority of medullary thymocytes), which proliferate more vigorously in response to IL-1 than do untreated thymocytes, were more sensitive to 1,25(OH)2D3 inhibition. Therefore, the inhibition of IL-2 production of the mature medullary thymocyte by this hormone was also suggested.     

Metabolism of vitamin D(3) by human CYP27A1

Human vitamin D(3) 25-hydroxylase (CYP27A1) cDNA was expressed in Escherichia coli, and its enzymatic properties were revealed. The reconstituted system containing the membrane fraction prepared from the recombinant E. coli cells was examined for the metabolism of vitamin D(3). Surprisingly, at least eight forms of metabolites including the major product 25(OH)D(3) were observed. HPLC analysis and mass spectrometric analysis suggested that those metabolites were 25(OH)D(3), 26(OH)D(3), 27(OH)D(3), 24R,25(OH)(2)D(3), 1alpha, 25(OH)(2)D(3, )25,26(OH)(2)D(3) (25,27(OH)(2)D(3)), 27-oxo-D(3) and a dehydrogenated form of vitamin D(3). These results suggest that human CYP27A1 catalyzes multiple reactions and multiple-step metabolism toward vitamin D(3). The K(m) and V(max) values for vitamin D(3) 25-hydroxylation and 25(OH)D(3) 1alpha-hydroxylation were estimated to be 3.2 microM and 0.27 (mol/min/mol P450), and 3.5 microM and 0.021 (mol/min/mol P450), respectively. These kinetic studies have made it possible to evaluate a physiological meaning of each reaction catalyzed by CYP27A1.     

Acute and long-term effects of Roux-en-Y gastric bypass on glucose metabolism in subjects with Type 2 diabetes and normal glucose tolerance

Our aim was to study the potential mechanisms responsible for the improvement in glucose control in Type 2 diabetes (T2D) within days after Roux-en-Y gastric bypass (RYGB). Thirteen obese subjects with T2D and twelve matched subjects with normal glucose tolerance (NGT) were examined during a liquid meal before (Pre), 1 wk, 3 mo, and 1 yr after RYGB. Glucose, insulin, C-peptide, glucagon-like peptide-1 (GLP-1), glucose-dependent-insulinotropic polypeptide (GIP), and glucagon concentrations were measured. Insulin resistance (HOMA-IR), β-cell glucose sensitivity (β-GS), and disposition index (D(β-GS): β-GS × 1/HOMA-IR) were calculated. Within the first week after RYGB, fasting glucose [T2D Pre: 8.8 ± 2.3, 1 wk: 7.0 ± 1.2 (P < 0.001)], and insulin concentrations decreased significantly in both groups. At 129 min, glucose concentrations decreased in T2D [Pre: 11.4 ± 3, 1 wk: 8.2 ± 2 (P = 0.003)] but not in NGT. HOMA-IR decreased by 50% in both groups. β-GS increased in T2D [Pre: 1.03 ± 0.49, 1 wk: 1.70 ± 1.2, (P = 0.012)] but did not change in NGT. The increase in DI(β-GS) was 3-fold in T2D and 1.5-fold in NGT. After RYGB, glucagon secretion was increased in response to the meal. GIP secretion was unchanged, while GLP-1 secretion increased more than 10-fold in both groups. The changes induced by RYGB were sustained or further enhanced 3 mo and 1 yr after surgery. Improvement in glycemic control in T2D after RYGB occurs within days after surgery and is associated with increased insulin sensitivity and improved β-cell function, the latter of which may be explained by dramatic increases in GLP-1 secretion.