模拟酸雨对主要酸性土壤中铝的溶出及形态的影响

本文研究了模拟酸雨对主要酸性土壤中铝的溶出及形态变化的影响。结果表明,模拟酸雨对土壤酸化的影响较小,但对土壤铝的溶出却影响明显,尤其在pH<4.0时;模拟酸雨对不同类型土壤的影响是不同的,其中以高度风化的酸性土壤较为敏感。模拟酸雨对土壤游离铝形态的影响是重要的,酸处理后,交换性铝略有增加,无定形活性铝增加较多,而有机络合态铝有减少的趋势。这表明在酸雨的长期作用下,铝终将转化为交换性铝和水溶性铝而进入环境并危害生态系统。     

一种目视激光显微镜

本文介绍一种目视激光显微镜。该装置采用白炽灯和激光做光源。通过调压器衬底亮度可以调整到零。由于激光的高亮度和强相干性,与普通显微镜相比,该显微镜具有景深长,分辨率高,层次丰富的特点。使用该显微镜时能实现镜象的假色彩编码,且镜象具有立体感。文中报导了该显微镜的原理和使用效果。     

广东汉族健康人载脂蛋白AⅠ-CⅢl-AⅣ基因簇DNA多态性及其单倍型分布

本文研究了中国广东汉族健康人群apoAI-CⅢ-AIV基因簇DNA限制性内切酶PstI、SstI和EcoRI片段长度多态性。其中等位基因P_1,P_2,S_1,S_2,R_1和R_2的频率分别为0.98,0.02,0.96,0.04,0.90和0.10。经卡方检验符合Hardy-Weinbery氏遗传平衡,与其他种族比较,本文结果显示中国广东汉族人P_2等位基因频率低于日本人、亚洲印第安人和高加索人,S_2等位基因频率低于日本人、菲律宾人、沙特阿拉伯人和亚洲印第安人,而与高加索人相近,R_2等位基因频率稍高于高加索人。不同种族间apoAI-CⅢ-AIV基因簇DNA多态频率无疑存在差异,这种差异可能是由于遗传漂变和自然选择单独或联合作用所致。对P_1、P_2,S_1、S_2和R_1、R_2构成的单倍型和连锁平衡程度进行了分析,结果显示这些单倍型处于连锁不平衡状态。     

Carnivora: the primary structure of the hemoglobin from the silver fox (Vulpes vulpes var., Canidae)

The primary structure determination of the hemoglobin alpha- and beta-chains from the silver fox (Vulpes vulpes var., Canidae) is described. The separation of the chains could be achieved directly from the hemoglobin by RP-HPLC as well as by column chromatography of the globin using carboxymethyl-cellulose. Following tryptic digestion of the chains, the peptides were isolated by RP-HPLC. Amino-acid sequences were determined by Edman degradation in liquid and gas phase sequencers. The peptides could be aligned by homology with human and other Carnivora hemoglobins. Compared to human hemoglobin the alpha- and beta-chains of the silver fox exhibit 24 and 13 amino-acid exchanges, respectively. They differ by one alpha- and two beta-chain replacements from the domestic dog and the coyote. The substitutions affecting contact positions are discussed.     

Further investigation on nuclear transplantation in different orders of teleost: the combination of the nucleus of Tilapia (Oreochromis nilotica) and the cytoplasm of Loach (Paramisgurnus dabryanus).

The nucleus of a blastula cell from Tilapia (Oreochromis nilotica, family Cichlidae, order Perciformes) was transplanted into an enucleated egg of Loach (Paramisgurnus dabryanus, family Cobitidae, order Cypriniformes). From among 3747 nucleo-cytoplasmic hybrid (NCH) eggs two NCH larval fish (0.05%) were obtained; one died on the 6th day and the other died on the 12th day after the operation. Morphological examinations showed that both NCH larval fish had developed normally with an opened mouth except they could not take food after complete utilization of their egg yolk on the 5th day of development. The possible mechanisms for obtaining such inter-order NCH larval fish are discussed. This is the first report indicating that inter-order NCH larval fish can be obtained in spite of their evolutionary divergence.     

中国小竹鼠生态的初步研究

小竹鼠在我国仅分布于云南西部热带亚热带地区。主要生活于山坡稀树灌丛、阔叶林、橡胶园及居民点附近。在盈江县分布于海拔300-950米地带。取食、休息、繁殖主要在洞道内。洞系由洞口、取食道、趋避道、窝及“厕所”组成。食物主要有棕叶芦、芦竹及三叶橡胶等18种,尤喜食橡胶树主根,因而对橡胶树危害很大。13号标本中雌7雄6。在盈江每胎2-3只,以2只为多。成年小竹鼠过独居生活,雌雄各有自己的洞系。     

Dictyostelium discoideum lipids modulate cell-cell cohesion and cyclic AMP signaling.

During Dictyostelium discoideum development, cell-cell communication is mediated through cyclic AMP (cAMP)-induced cAMP synthesis and secretion (cAMP signaling) and cell-cell contact. Cell-cell contact elicits cAMP secretion and modulates the magnitude of a subsequent cAMP signaling response (D. R. Fontana and P. L. Price, Differentiation 41:184-192, 1989), demonstrating that cell-cell contact and cAMP signaling are not independent events. To identify components involved in the contact-mediated modulation of cAMP signaling, amoebal membranes were added to aggregation-competent amoebae in suspension. The membranes from aggregation-competent amoebae inhibited cAMP signaling at all concentrations tested, while the membranes from vegetative amoebae exhibited a concentration-dependent enhancement or inhibition of cAMP signaling. Membrane lipids inhibited cAMP signaling at all concentrations tested. The lipids abolished cAMP signaling by blocking cAMP-induced adenylyl cyclase activation. The membrane lipids also inhibited amoeba-amoeba cohesion at concentrations comparable to those which inhibited cAMP signaling. The phospholipids and neutral lipids decreased cohesion and inhibited the cAMP signaling response. The glycolipid/sulfolipid fraction enhanced cohesion and cAMP signaling. Caffeine, a known inhibitor of cAMP-induced adenylyl cyclase activation, inhibited amoeba-amoeba cohesion. These studies demonstrate that endogenous lipids are capable of modulating amoeba-amoeba cohesion and cAMP-induced activation of the adenylyl cyclase. These results suggest that cohesion may modulate cAMP-induced adenylyl cyclase activation. Because the complete elimination of cohesion is accompanied by the complete elimination of cAMP signaling, these results further suggest that cohesion may be necessary for cAMP-induced adenylyl cyclase activation in D. discoideum.     

Mechanisms of Mutagenesis by a Bulky DNA Lesion at the Guanine N7 Position

The RpII215 locus encodes the large subunit of RNA polymerase II (polII). Three of 22 RpII215 alleles cause a synergistic enhancement of the mutant phenotype elicited by mutations in the Ultrabithorax (Ubx) locus. We have recovered and analyzed three new mutations that suppress this enhancement. All three mutations map to the RpII215 locus. In addition to suppressing the Ubx enhancement of other RpII215 alleles, two of the new mutations, JH1 and WJK2, themselves enhance Ubx. RpII215 alleles can be placed into three classes based on their ability to enhance Ubx. Class I alleles, including Ubl, C4, C11, JH1, and WJK2, enhance Ubx when heterozygous with class II alleles, which include wild-type RpII215. Class III alleles, which include amorphic alleles, do not enhance Ubx. The third new mutation, WJK1, is a conditional amorphic allele, which behaves like a class III allele at 29 degrees but like a class II allele at 19 degrees. Another mutant phenotype is caused by certain RpII215 alleles, including all class I alleles. This phenotype is a synergistic enhancement of a mutant phenotype elicited by mutations at the Delta (Dl) locus. Unlike the enhancement of Ubx, the enhancement of Dl is not dependent upon antagonistic interactions between different classes of RpII215 alleles.