嘧肽霉素高产菌株的选育

以不吸水链霉菌辽宁变种为出发菌株,经紫外线、亚硝酸诱变和紫外线与嘧肽霉素复合诱变,选育出了嘧肽霉素的高产菌株,抑菌圈直径由原来的20.5mm提高到36.4mm。传代培养5代表明,该高产菌株遗传特性稳定。     

Effect of Donor Age on the Developmental Competence of Bovine Oocytes Retrieved by Ovum Pick Up

To study the effect of donor age on oocyte developmental competence and steroid profiles, the crossbred cow (Murray Grey × Brahman) in Yunnan province of China were selected and divided into three groups according to its age. The three groups were young cows (n = 12; 12 months old), middle‐aged cows (n = 15; parity: ≤3 calvings; age: 7–8 years old) and old cows (n = 10; parity: ≥8 calvings; age: ≥15 years old). Cumulus–oocyte complexes (COCs) were collected by 10 consecutive ovum pick up (OPU) sessions with a 4‐day interval between each session, followed by in vitro maturation, fertilization and embryo development. Results showed that cleavage rates (CR) and blastocyst rates (BR) were higher in the young cows than those in the middle‐aged and old cows (p < 0.05). CR and BR from COCs of the first and the fourth OPU sessions were lower than those from other sessions in the young cows and the middle‐aged cows (p < 0.05), whereas the similar phenomenon was not observed in the old cows. Plasma concentrations of oestradiol were higher, and plasma concentrations of progesterone were lower before and during OPU sessions in the young cows compared with those in the same period in the middle‐aged cows or the old cows (p < 0.01). In conclusion, donor age of oocytes could affect developmental competence of oocytes recovered by OPU through the action of steroid hormonal balance on follicle development.     

Animal‐Level Factors Affecting Ovarian Function in Bos indicus Heifers Treated to Synchronize Ovulation with Intravaginal Progesterone‐Releasing Devices and Oestradiol Benzoate

The primary objective of this study was to investigate the impact of animal‐level factors including energy balance and environmental/management stress, on the ovarian function of Bos indicus heifers treated to synchronize ovulation. Two‐year‐old Brahman (BN) (n = 30) and BN‐cross (n = 34) heifers were randomly allocated to three intravaginal progesterone‐releasing device (IPRD) treatment groups: (i) standard‐dose IPRD [Cue‐Mate^® (CM) 1.56 g; n = 17]; (ii) half‐dose IPRD [0.78 g progesterone (P₄); CM 0.78 g; n = 15]; (iii) half‐dose IPRD + 300 IU equine chorionic gonadotrophin at IPRD removal (CM 0.78 g + G; n = 14); (iv) and a control group, 2× PGF_2α [500 μg prostaglandin F_2α (PGF_2α)] on Day ?16 and ?2 (n = 18). Intravaginal progesterone‐releasing device‐treated heifers received 250 μg PGF_2α at IPRD insertion (Day ?10) and IPRD removal (Day ?2) and 1 mg oestradiol benzoate on Day ?10 and ?1. Heifers were managed in a small feedlot and fed a defined ration. Ovarian function was evaluated by ultrasonography and plasma P₄ throughout the synchronized and return cycles. Energy balance was evaluated using plasma insulin‐like growth factor 1 (IGF‐I) and glucose concentrations. The impact of environmental stressors was evaluated using plasma cortisol concentration. Heifers that had normal ovarian function had significantly higher IGF‐I concentrations at commencement of the experiment (p = 0.008) and significantly higher plasma glucose concentrations at Day ?2 (p = 0.040) and Day 4 (p = 0.043), than heifers with abnormal ovarian function. There was no difference between the mean pre‐ovulatory cortisol concentrations of heifers that ovulated or did not ovulate. However, heifers that ovulated had higher cortisol concentrations at Day 4 (p = 0.056) and 6 (p = 0.026) after ovulation than heifers that did not ovulate.     

马尾松半同胞家系子代林早期生长差异分析

以湖北省京山县太子山林场管理局马尾松无性系嫁接种子园半同胞8年生子代林为研究对象,在对胸径、树高、枝下高、冠幅和材积等生长因子进行实地调查的基础上进行遗传力分析.结果表明:不同半同胞家系林木各生长因子之间存在极显著性差异,显示马尾松半同胞家系林木间存在较为丰富的遗传变异,具有较大的选育潜力;8年生马尾松半同胞家系子代林树高、胸径和材积的遗传力分别为0.7436、0.6055和0.6500;采用20%的入选率时,筛选出5个优良半同胞家系且入选半同胞家系的材积、树高和胸径遗传增益分别为51.34%、17.45%和22.19%.     

Fenhexamid adsorption behavior on soil amended with wine lees

The adsorption of fenhexamid (FEN) [N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide] on vineyard soil amended with wine lees (WL) produced by vinery was studied. The adsorption extent depends on WL fraction. The addition of the centrifuged solid lees (SWL) increases the FEN adsorption on soil. Most likely, the organic insoluble fraction formed mainly by dead fermentation yeasts is responsible for the observed increase. The adsorption measured on some deactivated yeasts of wine fermentation shows that Saccharomyces cerevisiae are the most active in FEN retention. On the other hand, the soil amendment with whole WL decreases considerably the fungicide adsorption. This opposite effect may be the result of FEN hydrophobic bonds with the dissolved organic matter of lees that keeps fungicide in solution. This hypothesis is substantiated by the increased FEN solubility in the supernatant of centrifuged wine lees (LWL). The results of soil column mobility confirm that the elution with LWL increases the mobility of FEN in soil.     

Vaccination and challenge studies with psittacine beak and feather disease virus

SUMMARY: Psittacine beak and feather disease virus (PBFDV) was administered to adult galahs ( Eolophusroselcapillus ) by mouth or by intramuscular injection. Concentration of PBFDV antibodies in serum and excretion of PBFDV were monitored by haemagglutlnation inhibition (HI) and haemagglutination (HA) respectively. After oral administration, 17 of 18 galahs remained clinically normal and a small rise in antibody titre was detected in 3 of 18 birds. After intramuscular administration, antibody was detected in all birds. PBFDV was not detected in the feather dander of birds in either group. One bird developed diarrhoea and high faecal HA titres within 4 days of oral administration and then died. Adult and nestling cockatoos were vaccinated with an experimental inactivated double-oil emulsion vaccine. PBFDV antibody responses are comparable to those induced by a primary-oil emulsion vaccination regimen using Freund's adjuvants. Both vaccines protected nestlings. Three sibling wild-caught sulphur-crested cockatoos were vaccinated but died of PBFD before experimental challenge despite antibody responses in all birds. Unvaccinated control chicks developed acute PBFD within 4 weeks of challenge, probably from PBFDV-induced hepatitis since high concentrations of PBFDV were detected in their livers.     

Constant Light Exposure Causes Dissociation in Gonadotrophin Secretion and Inhibits Partially Neuroendocrine Differentiation of Leydig Cells in Adult Rats

The objective of this work was to study the changes that occur in the Leydig cells of rats exposed to continuous light. The laboratory rat is considered a non-photoperiodic species because exposure to short photoperiod has little or no effect on the reproductive status. However, exposure of adult female rats to constant light induces polycystic ovaries, indicating that extreme changes in the photoperiod affect the reproductive function seriously. Adult male rats were placed under continuous light conditions for a duration of 15 weeks. After this period, the animals were killed and testicles were dissected and processed by routine histologic protocols. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) serum levels were determined by radioimmunoassay (RIA). The visualization of antigens was achieved by the streptavidin-peroxidase immunohistochemical method. Antibodies against chromogranin A, S-100 protein, P substance, synaptofisin, neurofilament protein-200, gliofibrillary acidic protein and neurone-specific enolase were used. The mean LH serum concentration was significantly lower, while the mean FSH level was significantly higher in treated animals. The expression of S-100, NSE, CrA, SP and SYN was significantly lower in treated animals. In conclusion, the constant light exposure acting directly at the pituitary level decreases LH secretion. The increased FSH secretion may be due to a partial reduction of the negative androgen feedback in the pituitary gland. Moreover, the constant light exposure affects the expression of some immunomarkers in Leydig cells, possibly because of the changes found in the gonadotrophin level and feedback mechanism.     

玉米的不同温度和时间烘烤加工处理对泌乳奶牛瘤胃干物质和淀粉降解规律的研究

以3头安装永久性瘤胃瘘管的泌乳前期荷斯坦奶牛为试验动物，在精粗比为55：45的日粮条件下，采用In sacco法测定了不同温度和时间烘烤加工处理的玉米在奶牛瘤胃内干物质和淀粉的降解规律。结果表明，玉米经过不同温度和时间的烘烤处理，干物质和淀粉的瘤胃降解率都有不同程度的降低，随着温度逐渐升高、作用时间逐渐延长，干物质和淀粉的降解率也逐渐降低。在所有处理组中，140℃35min处理组可以明显降低玉米的瘤胃淀粉降解率（P〈O．05），比未处理玉米组降低了15．26％。淀粉在瘤胃中降解的影响因素最主要的是淀粉的快速可溶部分和降解速率。