Five genetic loci involved in the synthesis of acidic exopolysaccharides are closely linked in the genome of Rhizobium sp strain NGR234

Summary R-prime plasmids were constructed from a derivative of Rhizobium strain NGR234 (ANU280) and were shown to contain overlapping genomic DNA segments involved in biosynthesis of exopolysaccharides (EPS). The R-primes originally constructed carried the mutant allele from Tn5-induced EPS-deficient (Exo^–) mutant ANU2811. This plasmid-located mutant allele was dominant to the corresponding wild-type allele as merodiploid strains were Exo^–. Exo⁺ revertants occurred at a low rate (1×10^-7) and these were shown to result from double reciprocal recombination events, which led to the isolation of R-prime plasmids carrying functional wild-type exo alleles. R-prime plasmids that carry overlapping segments of DNA from parental strain ANU280 complemented 28 of the 30 group 2 Exo^– mutants of strain ANU280. Complementation of these Exo^– mutants also restored their symbiotic abilities of effective nodulation. Subsequent in vivo recombination between the wild-type alleles located on the R-prime and the corresponding mutated allele on the genome, was used to generate a new family of R-primes, which carried mutations in the exo genes. The 30 group 2 Exo^– mutants were classified into 7 distinct genetic groups based upon complementation and physical mapping data. Five of the seven exo loci were gentically linked and located on a 15-kb region of DNA. Mutations at two loci were dominant only when the mutations were R-prime plasmid-located while a mutation at a second locus was cis-dominant to two other exo loci. At least five genes involved in the synthesis of acidic exopolysaccharide synthesis have been identified.     

Effects of pingyanymycin on chromosomes: a possible structural basis for chromosome aberration

Pingyanymycin (PYM), and antitumor-antibiotic complex which belongs to the bleomycin family can induce "G2-free chromatin" and "uncompleted-packing-mitotic figures" (UPM) at increased frequency after treatment of cultured human lymphocytes. PYM can also induce an extraordinarily high frequency of chromosomal breaks but few sister-chromatid exchanges (SCE) in the same experiment, which is similar to the action of bleomycin. To solve this remarkable contradiction we presume that the UPM is related to a basic mechanism for producing chromosomal aberrations. Our results also show that various steps of the chromosomal cycle can be affected by certain chemical agents, and these treatments lead to chromosomal aberrations. Thus, other testing systems should be used in addition to the SCE system.     

The monocyte differentiation antigen, CD14, is anchored to the cell membrane by a phosphatidylinositol linkage

CD14 is a myeloid differentiation Ag expressed primarily on peripheral blood monocytes and macrophages. Although its function is unknown, the CD14 gene maps to a region encoding several myeloid growth factors and receptors. Analysis of the CD14 protein sequence deduced from the cDNA shows that although the CD14 protein contains a characteristic leader peptide, it lacks a characteristic transmembrane region, suggesting that CD14 may be anchored to the membrane via glycosylphosphatidylinositol (PI). Treatment of monocytes as well as a CD14-expressing neuroglioma cell line with PI-phospholipase C removed CD14 from the cell surface. Furthermore, monocytes from a patient with paroxysmal nocturnal hemoglobinuria, a disease characterized by lack of expression of other PI-linked proteins, failed to express CD14. Interestingly, the CD14-expressing neuroglioma cell line, which had been transfected with a single CD14 cDNA, released a soluble form of CD14 into the supernatant. Soluble forms of CD14 have previously been observed in serum of normal individuals and in culture supernatants of CD14+ cells. Biosynthetic experiments reveal that this soluble form of CD14 (48 kDa), which is smaller than the form released from the membrane by PI-phospholipase C (53 kDa), does not contain ethanolamine, the first constitutent of the PI-anchoring system. These studies demonstrate that CD14 is a member of the family of PI-anchored proteins and suggest that soluble forms of CD14 represent molecules that completely lack the PI-anchoring system.     

Pre-lysosomal divergence of alpha 2-macroglobulin and transferrin: a kinetic study using a monoclonal antibody against a lysosomal membrane glycoprotein (LAMP-1)

We have used electron microscopic immunocytochemistry to compare the distribution of LAMP-1, a marker for lysosomal membranes, with the intracellular localization of alpha 2-macroglobulin (alpha 2-M) and transferrin at various time points after their endocytosis into cultured NIH 3T3 cells. The purposes of this study were (a) to determine how soon endocytic ligands reach lysosomal organelles, (b) to examine whether the intermediate endocytic vesicles gained lysosomal markers gradually or in a precipitous, discrete event, and (c) to examine the relationship, if any, between the pathway of recycling ligands and lysosomes. At early time points (0-5 min) after initiation of endocytosis, most structures containing alpha 2-M labeled with colloidal gold (receptosomes) were not labeled by anti-LAMP-1 detected using ferritin bridge or peroxidase immunocytochemistry. At late time points (greater than or equal to 15 min), the structures containing alpha 2-M (lysosomes) were strongly labeled by anti-LAMP-1. In contrast, transferrin that was directly labeled with ferritin was mostly located in LAMP-1-negative structures at all time points studied. The proportion of alpha 2-M-gold containing vesicles strongly labeled for LAMP-1 roughly paralleled the proportion of alpha 2-M-gold-containing structures positive for cytochemically detectable acid phosphatase. Our data indicate that ligands such as transferrin that are internalized through coated pits and receptosomes, but not delivered to lysosomes, do not traverse a lysosomal organelle compartment as marked by LAMP-1 content. Ligands such as alpha 2-M that are destined for lysosomal delivery reach a LAMP-1-positive organelle compartment only after they traverse LAMP-1-negative, non-lysosomal vesicles previously described as receptosomes.     

Modulation of rat granulocyte traffic by a surface active agent in vitro and bleomycin injury

Pluronic F68 (F68) is a nonionic surfactant which has been reported to inhibit the in vitro adherence and migration of polymorphonuclear leukocytes (PMN) obtained from some species. We demonstrated similar effects on PMN obtained from rats, with diminished adherence to nylon wool and diminished chemotaxis toward zymosan-activated serum. We then examined the in vivo effects of 12-hr F68 infusion on the injury induced by intratracheal bleomycin instillation (ITB) in rats. When sacrificed 24 hr following injury, rats demonstrated neutrophilia, neutrophil-prominent lung lavage cellularity, and increased lung weights. F68 decreased lavage leukocyte counts and lung weight gain in ITB-injured animals. Lung weights of ITB-injured animals correlated (r = 0.81, P less than 0.001) with logarithmic values of lavage PMN. F68 also enhanced neutrophilia and decreased spleen weight gain in injured animals. The acute effects of F68 on circulating leukocyte counts, osmolality, and total complement were also examined. The data demonstrate that F68 can affect PMN traffic both in vitro and in vivo. The data also confirm the prominence of PMN in lavage fluid early in ITB injury, and suggest that an influx of relatively few PMN is associated with lung weight gain in this model.     

从“湖北光敏感核不育水稻”的未受精子房和花药培养出单倍体植株

采用10种诱导培养基,培养湖北光敏感核不育水稻农垦58品种的未受精子房和花药。共培养未受精子房2790个,获得胚囊愈伤组织17块,最高诱导频率达3.33%,其中2块分化出绿苗。培养花药16740个,获得花药愈伤组织15块,最高诱导频率为0.92%,其中3块分化出苗,2丛白苗,1株绿苗。胚囊植株和花粉植株经根尖染色体检查为单倍体,2n=x=12。实验证明,液体培养、2,4-D0.2-0.5 mg/1、低温预处理对诱导胚囊愈伤组织及花粉愈伤组织的形成具良好效果。     

一阶导数光谱法测定猫豆中左旋多巴的含量

川一阶导数光谱法测定猫豆中主旋多巴的含量,可以排除无关杂质吸收的干扰,省去复杂的分离提取步骤。试验结果表明:相关系数达0.9999,平均回收率101.5％,重现性较好。     

内蒙古石拐群古鳕类一新属

内蒙古石拐地区石拐群召沟组中的长腹鳍大青山鳕(新属、新种) Daqingshaniscus longiventralis gen. et sp. nov. 是在我国中侏罗世地层中发现的一比较原始的古鳕类.其头骨眶后部分短,鳃盖骨大于下鳃盖骨,背鳍位于腹鳍与臀鳍之间,腹鳍基线长,鳍条都从基部分节、远端分叉,棘鳞仅见于尾上叶,全歪型尾,鳞片呈菱形.大青山鳕既与苏联南哈萨克斯坦 Karatau 地区的 Pteroniscus 很接近,又与我国新疆的维吾尔鳕 Uighuroniscus 及西德北部的 Stadthagen 地区的 Indaginilepis 相似.     

MASTODONT REMAINS FROM THE MIOCENE OF JUNGGAR BASIN IN XINJIANG

<正> The mastodont materials described in the present paper, associated with Amblycastor tunggurensis, Amphicyon sp., Anchitherium cf. aurelianense, Brachypotherium sp., ?Chilotherium sp., Stephanocemas thomsoni, Dicrocerus grangeri, Eotragus sp., Oioceros grangeri and O. noverca, were collected from the Haramagai formation of Junggar Basin in Xinjiang by an IVPP field team in 1982. The geology of the area has already been reported by Tong (1986, 1987). The mastodont fossils found at 5 sites on the north and west banks of the Ulungur river, Junggar Basin are abundant. They comprise 5 species, among which is one new species.The author is greatly indebted to the IVPP field team (Tong, Y., the head of the 1982 Junggar field team) allocating the mastodont materials for me to study.     

大鼠应激性胃粘膜损害与eAMPCa~2及能量代谢变化的关系

本文采用放射免疫测定法、原子吸收光谱分析法和生化酶分析法,测定了大鼠在经受束缚加浸水急性应激四小时内,胃组织cAMP Ca~(2+)及在ATP、ADP、AMP和能量代谢的短期动态变化,同时观察了胃粘膜的损害程度。结果发现胃粘膜损害面积密度随着应激时间延长而逐渐增加;胃组织cAMP和Ca~(2+)则进行性降低;两者呈密切负相关;胃组织能量代谢却略有增强。若预先给以CaCl_2,再予应激,则有减轻应激性胃粘膜损害的作用。