Microsporogenesis and male gametophyte development in Prunus mahaleb Linn.

Microsporogenesis and male gametophyte development in Prunus mahaleb Linn. were assessed using a method combined of scanning electron microscopy (SEM) and paraffin sections. The results showed the following: (1) the anther underwent normal development and is tetrasporangiate. The tapetum was glandular; (2) cytokinesis occurred simultaneously with meiosis in the microspore mother cell, and the tetrads were tetrahedral; (3) after meiosis, microspores generated by microsporogenesis were more or less irregular in shape during the contraction period. As the microspore increased in size, mature three cell types pollen grains finally developed in the chambers; (4) mature pollen grains were observed by SEM. The shape of the pollen was nearly flat and triangular. There were three germinal furrows in the exine of the pollen with horizontal stripes. These findings provide a scientific basis for explaining the reproductive biological characteristics of the breeding resources of Prunus mahaleb, and microspore vacuolization is considered to be the main explanation for the low fruit set.     

Diversity and community pattern of sulfate-reducing bacteria in piglet gut

Background: Among the gut microbiota, sulfate-reducing bacteria(SRB) is a kind of hydrogen-utilizing functional bacteria that plays an important role in intestinal hydrogen and sulfur metabolism. However, information is lacking regarding diversity and community structure of SRB in the gut of piglets. Middle cecum contents were collected from 6 Yorkshire and 6 Meishan piglets at postnatal days(PND) 14, 28 and 49. Piglets were weaned at PND28. Real-time quantitative PCR was performed to detect the number of SRB in the cecum based on dissimilatory sulfite reductase subunit A(dsrA) gene. Prior to real-time PCR, plasmid containing the dsrA gene was constructed and used as external standard to create a standard curve, from which the gene copies of dsrA were calculated. H_2S concentration in the cecal contents was measured. Illumina PE250 sequencing of dsrA gene was used to investigate SRB diversity in cecum contents.Results: The qPCR results showed that the number of SRB at PND49 was significantly higher than that at PND28 in Meishan piglets. The concentration of H_2S has no significant difference between piglet breeds and between different ages. The Illumina sequencing analysis revealed that the Chao1 richness index was significantly higher at PND49 than that at PND14 and PND28 in Yorkshire piglets. Based on dsrA gene similarities, Proteobacteria, Actinobacteria, and Firmicutes were identified at the phylum level, and most sequences were classified as Proteobacteria. At the genus level, most of sequences were classified as Desulfovibrio. At the species level, Desulfovibrio intestinalis was the predominant SRB in the piglet cecum. The relative abundance and the inferred absolute abundance of Faecalibacterium prausnitzii at PND49 were significantly higher than that at PND14 in Yorkshire piglets. Pig breeds did not affect the dsrA gene copies of SRB, diversity index and community pattern of SRB.Conclusions: Sulfate-reducing bacteria are widely colonized in the cecum of piglets and D. intestinalis is the dominant SRB. The age of piglets, but not the pig breeds affects the diversity and community pattern of SRB.     

黑加伦果汁奶茶的加工技术研究

黑加伦果汁奶茶是一种新型蛋白保健饮料，具有动物性营养和植物性营养成分综合互补作用，利于人体消化吸收，常饮可提神醒脑，抗病，强身，使人保持旺盛精力。本试验运用正交试验法确定了其最佳配方及工艺，并应用模糊数学对产品的质量进行了综合评判，提高了试验结果的可靠性。     

Small diameter Polyurethane vascular graft reinforced by elastic weft-knitted tubular fabric of polyester/spandex

Small diameter vascular grafts were fabricated from pure Polyurethane (PU) as well as PU reinforced with a tubular weft-knitted fabric. The tensile properties of the reinforced composite vascular grafts were compared with that of the tubular fabric itself and the pure PU vascular grafts. The elasticity and strength of the reinforced vascular grafts were improved compared with the tubular fabric. Strength of the reinforced vascular grafts was 5–10 times of the strength of the pure PU vascular grafts. Expanding the tubular fabric to increase the inner diameter of the reinforced vascular graft reduced the graft’s strength and initial modulus, but the difference was reduced as the PU content was increased. For grafts of the same inner diameter, increasing the PU content increased the thickness and strength of the graft wall, which led to a general increase in the strength and initial modulus of the composite vascular grafts.     

湿地松人工林矿质营养循环的研究

利用一块天然集水区 ,研究了湿地松人工林内K、P、Ca、Mg、Zn、Cu、Fe、Mn等矿物质元素。 1998～ 1999年通过降雨输入、地表径流输出以及积累、归还和吸收等循环过程。湿地松人工林有较高的生产力 (生物生产量为 2 0 349t·hm-2 ·a-1、材积生长量为 9 40 8m3·hm-2 ·a-1) ,原因在于它对矿物质元素有较高的利用率。林分矿质元素支出大于收入 ,并且归还量少 ,林分矿质元素循环效率低。建议采用阔叶树混交等方法调控湿地松林 ,以提高林分生产力 ,建立良性循环的生态系统     

四川西部亚高山暗针叶林生态系统定位研究 --卧龙地区木本植物区系分析

通过对四川卧龙地区木本植物类群的详细调查资料和已有研究资料进行系统收集及统计分析。结果表明：卧龙地区有木本植物８３科、２２４属和６８４种（含种以下等级,不含栽培种）;卧龙地区以温带成分为主,占总属数５８．３３％,热带成分占３６．５６％;卧龙地区稀有濒危植物、单种属、少种属、中国特有属均占较大比例,说明其历史起源的古老性;卧龙林区木本植物地理成分复杂。联系广泛,分布交错,特别是热带、亚热带科,属中耐     

连云港市水土流失加剧的成因及其防治对策初探

随着连云港市东方桥头堡位置的确立,区域开发建设的速度愈来愈快。由于有关部门忽视城市水土保待工作及诸多人为和自然因素的影响,造成水土流失状况加剧.不仅恶化了生态环境,而且带来了巨大经济损失和灾难性的影响。为此我们在调查和研究的基础上,提出了相应的对策。     

高效氯氟氰菊酯不同抗性基因型甜菜夜蛾相对适合度研究

在室内相同条件下 ,构建了甜菜夜蛾高效氯氟氰菊酯抗性种群 (R)、敏感种群(S)、正交 F1代 (RS)、反交 F1代 (SR)和对照种群 (CK)的生命表 ,研究了各种群的产卵量、卵孵化率、幼虫和成虫发育历期和蛹重等主要生物学特性。抗高效氯氟氰菊酯基因型甜菜夜蛾在生活力和繁殖力上与其它基因型比较均存在一定程度的不利性 ,杂合子的大部分生物学特性与敏感基因型比较差异不显著。在经过一个完整世代后 ,R、S、RS、SR和 CK种群的净增殖率(R0 )分别为 117.8、624.7、589.1、642 .3、218.8。以敏感种群为参比 ,S、RS、SR、R和 CK种群的相对适合度分别为 1、0 .934、1.028、0.188和 0 .368。与敏感品系 S相比 ,SR和 RS品系的相对适合度无变化 ,抗高效氯氟氰菊酯种群适合度明显降低。     

Antihyperglycemic, Antihyperlipidemic and Antiglycation Effects of Byrsonima crassifolia Fruit and Seed in Normal and Streptozotocin-Induced Diabetic Rats

The hypoglycemic effects of hexane, chloroform and methanol extracts from fruits and seeds of Byrsonima crassifolia were evaluated by oral administration to normoglycemic and streptozotocin-induced severe diabetic rats (SD). The anti-diabetic effect was examined by blood glucose, triglycerides, lipid peroxidation, total cholesterol levels in the serum, glycogen content of liver and skeletal muscles, superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and oxidized glutathione (GSSG) levels. The most active extracts were obtained with hexane. Hexane and chloroform extracts from fruits and seeds of Byrsonima crassifolia increased the levels of SOD, GSH, GSSG and CAT, hepatic glycogen content, glucose-6-phosphatase (G6Pase) and the plasma insulin levels. They also decreased glucokinase (GK) and TBAR (thiobarbituric acid assay). In conclusion, Byrsonima crassifolia possesses significant antihyperglycemic properties after 4 h of a single oral dose. It can also improve hyperlipidemia and hyperinsulinemia in streptozotocin-induced diabetic rats. Both extracts exhibited significant inhibitory activity against AGEs (advanced glycation end products) formation with IC₅₀ values ranging from 94.3 to 138.7 μg/ml. Therefore, B. crassifolia can be considered as a potential safe anti-diabetic agent.     

Tilapia fisheries in Guangdong Province,China: Socio‐economic benefits,and threats on native ecosystems and economics

Tilapia is one of the groups of fish species most widely cultured globally. China has been the largest producer of tilapia in the world since 1990s. Guangdong Province produces almost 40% of all tilapia in China because of its suitable geography and weather conditions, and tilapia culture has brought considerable economic benefits. Unfortunately, many of the biological traits that make tilapia popular for culture also contribute to its success as an invader. Tilapia has invaded natural waters and has become the dominant fish in many rivers of Guangdong Province, causing economic loss in capture fisheries, and affecting native fish species, biodiversity and aquatic ecosystems. Poor fishery management, water quality degradation and biodiversity loss have all facilitated the tilapia invasion. Tilapia have filled the niches left vacant by now locally extinct native species resulting from environmental changes in freshwater ecosystems of the province. The introduction of tilapia has both advantages and disadvantages, which should be managed to use effectively the various tilapia species in aquaculture while controlling their spread in natural waters.