新疆褐家鼠种群生命表及其在干旱区的生存能力分析

从2000年至今,曾于野外捕捉的褐家鼠3 837只,其中雌鼠2 685只,雄鼠1 152只,经鉴定划分为幼年组(Ⅰ)、亚成年组(Ⅱ)、成年Ⅰ组(Ⅲ)、成年Ⅱ组Ⅳ、老年组(Ⅴ)等5个年龄组,其年龄结构探讨种群数量动态,结果表明,种群中Ⅱ龄的平均生命期望值最高1.0357,其次为Ⅲ龄0.9488。该种群中1龄个体占优势地位,种群属于增长性种群,种群内禀增长率rm为0.2789/年,年周限增长率λ为1.3217,世代时间T为2.623年,种群经一世代的净增殖率R0为2.0782。     

Alterations in dihydropyridine receptors in dystrophin-deficient cardiac muscle

The deficiency of dystrophin, a critical membrane stabilizing protein, in the mdx mouse causes an elevation in intracellular calcium in myocytes. One mechanism that could elicit increases in intracellular calcium is enhanced influx via the L-type calcium channels. This study investigated the effects of the dihydropyridines BAY K 8644 and nifedipine and alterations in dihydropyridine receptors in dystrophin-deficient mdx hearts. A lower force of contraction and a reduced potency of extracellular calcium (P < 0.05) were evident in mdx left atria. The dihydropyridine agonist BAY K 8644 and antagonist nifedipine had 2.7- and 1.9-fold lower potencies in contracting left atria (P < 0.05). This corresponded with a 2.0-fold reduction in dihydropyridine receptor affinity evident from radioligand binding studies of mdx ventricular homogenates (P < 0.05). Increased ventricular dihydropyridine receptor protein was evident from both radioligand binding studies and Western blot analysis and was accompanied by increased mRNA levels (P < 0.05). Patch-clamp studies in isolated ventricular myocytes showed no change in L-type calcium current density but revealed delayed channel inactivation (P < 0.05). This study indicates that a deficiency of dystrophin leads to changes in dihydropyridine receptors and L-type calcium channel properties that may contribute to enhanced calcium influx. Increased influx is a potential mechanism for the calcium overload observed in dystrophin-deficient cardiac muscle.     

In vitro anti-mutagenic effect of magnolol against direct and indirect mutagens

Magnolol, a component of the bark of Magnolia obovata, has been reported to possess various biological activities, such as anti-carcinogenicity, anti-promotion activity and anti-oxidative activity. These findings suggest potential for this compound in cancer chemoprevention. Interestingly, there have been no reports to date on the potential anti-mutagenic activity of magnolol, involving inhibition of initiation processes of the primary stage of carcinogenicity. In this study, anti-mutagenic activity of magnolol against mutagenicity induced by direct mutagens [1-nitropyrene (1-NP), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG)] and indirect mutagens [2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2), benzo(a)pyrene (B(a)P), 2-aminoanthracene (2-AA) and 7,12-dimethylbenz[a]anthracene (DMBA)] were investigated using the bacterial mutagenicity test (Ames test). Results show that magnolol strongly inhibits mutagenicity induced by indirect mutagens, but does not affect direct mutagens. To elucidate the mechanism of this effect against indirect mutagens, effect of magnolol on CYP1A1- and CYP1A2-related enzyme activities of ethoxyresorufin-O-deethylase (EROD) and methoxyresorufin-O-demethylase (MROD) were investigated. Magnolol strongly and competitively suppressed these enzyme activities, suggesting it inhibited mutation induced by indirect mutagens through suppression of CYP1A1 and CYP1A2 activity.     

Orientation and penetration depth of monolayer-bound p40phox-PX

X-ray reflectivity was used to study the interaction of the PX domain of p40(phox) protein (p40(phox)-PX) with a Langmuir monolayer of a mixture of SOPC (1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine), SOPS (1-stearoyl-2-oleoyl-sn-glycero-3-phosphoserine), and DPPtdIns(3)P (1,2-dipalmitoylphosphatidylinositol 3-phosphate) lipids supported on a buffered aqueous solution. The reflectivity is analyzed in terms of the known crystallographic structure of the p40(phox)-PX domain and a slab model that represents the lipid layer, yielding an electron density profile of the lipid layer and bound PX domains. This analysis determines the angular orientation and penetration depth of the p40(phox)-PX domain bound to the SOPC/SOPS/DPPtdIns(3)P monolayer. The best fit orientation is characterized by the following angles: theta = 30 +/- 10 degrees and phi = 140 +/- 30 degrees. These angles describe rotations, about axes in a coordinate system fixed to the domain, that are required to orient the domain with respect to the lipid layer at the interface. The protein penetrated into the lipid layer by 9 +/- 2 A, indicating that the protein penetrated into the headgroup region, but not deeply into the hydrocarbon region of the monolayer. In this analysis, polar Tyr(94) and hydrophobic Val(95) penetrated deepest into the lipid monolayer. The backbone of these residues was approximately 5 A above the headgroup-buffer interface, i.e., at the level of the SOPC/SOPS lipid phosphates. Positively charged Lys(92) and Lys(98) were also near the SOPC/SOPS lipid phosphates. This position of the protein allows for a favorable electrostatic contribution to binding.     

Additive roles of XPA and MSH2 genes in UVB-induced skin tumorigenesis in mice

We have made xeroderma pigmentosum group A gene (XPA)-knockout mice (XPA(-/-) mice). The XPA(-/-) mice had no detectable activity for nucleotide excision repair (NER) and showed a high incidence of UVB-induced skin tumorigenesis. We have also found that cell lines derived from skin cancers in UVB-irradiated XPA(-/-) mice become tolerant to UV-irradiation and showed abnormal UV-induced cell cycle checkpoints and decreased mismatch repair (MMR) activity. These results suggested that the MMR-downregulation may help cells escape killing by UV-irradiation and thus MMR-deficient clones are selected for during the tumorigenic transformation of XPA(-/-) cells. In this report, we examined whether the incidence of UVB-induced skin tumorigenesis is enhanced in XPA(-/-)MSH2(-/-), XPA(-/-) and MSH2(-/-) mice when compared with that in wild-type mice. Our results indicate that the MSH2-deficiency caused a high incidence of spontaneous and UVB-induced skin tumorigenesis and the XPA and MSH2 genes have additive roles in the UV-induced skin tumorigenesis.     

Traits and selection strategies to improve root systems and water uptake in water-limited wheat crops

Wheat yields globally will depend increasingly on good management to conserve rainfall and new varieties that use water efficiently for grain production. Here we propose an approach for developing new varieties to make better use of deep stored water. We focus on water-limited wheat production in the summer-dominant rainfall regions of India and Australia, but the approach is generally applicable to other environments and root-based constraints. Use of stored deep water is valuable because it is more predictable than variable in-season rainfall and can be measured prior to sowing. Further, this moisture is converted into grain with twice the efficiently of in-season rainfall since it is taken up later in crop growth during the grain-filling period when the roots reach deeper layers. We propose that wheat varieties with a deeper root system, a redistribution of branch root density from the surface to depth, and with greater radial hydraulic conductivity at depth would have higher yields in rainfed systems where crops rely on deep water for grain fill. Developing selection systems for mature root system traits is challenging as there are limited high-throughput phenotyping methods for roots in the field, and there is a risk that traits selected in the lab on young plants will not translate into mature root system traits in the field. We give an example of a breeding programme that combines laboratory and field phenotyping with proof of concept evaluation of the trait at the beginning of the selection programme. This would greatly enhance confidence in a high-throughput laboratory or field screen, and avoid investment in screens without yield value. This approach requires careful selection of field sites and years that allow expression of deep roots and increased yield. It also requires careful selection and crossing of germplasm to allow comparison of root expression among genotypes that are similar for other traits, especially flowering time and disease and toxicity resistances. Such a programme with field and laboratory evaluation at the outset will speed up delivery of varieties with improved root systems for higher yield.     

Semi-synthesis and bio-evaluation of polybrominated diphenyl ethers from the sponge Dysidea herbacea

The sponge Dysidea herbacea was collected from the Mandapam Coast, Tamilnadu, India. Isolated gram quantities of hydroxylated polybrominated diphenyl ether (HO-PBDE) and semi-synthesized a series of new PBDEs derivatives and tested them for antibacterial and cytotoxic activities.