草鱼免疫应答的初步研究

研究了草鱼在不同水温条件下受抗原刺激后其中和抗体的变化。15℃培养条件下中和抗体上升缓慢,9周内滴度低于1:8;20℃时,3周后抗体可上升到1:256,最高达1:5270,而在25℃时,1周中和抗体即达到1:570,最高可达1:20000以上。并探索了从草鱼血清中提纯抗体的条件,研究其抗体的特性。草鱼血清中的抗体为大分子蛋白,容易解离为抗原性相同,分子量近似于人IgG的较小分子,含有较多的二硫键,具有类似IgM的某些特性。     

鄂西木林子种子植物区系与邻近区系的比较研究

木林子地处武陵山脉东北端,自然地理条件优越,种子植物种系饱和度大。在2100公顷的面积内有种子植物134科~1 488属、1043种(包括亚种和变种)。本文选取11个较有代表性地区的自然种子植物区系与木林子区系进行比较分析,以求深化对木林子种子植物区系性质、起源及与邻近区系关系的认识。多区系比较研究中,优势科的确立和其相似性指标是一个指示区系特征异同的重要参数,木林子种子植物区系优势科与湖北神农架、江西庐山、广东黑石顶和海南尖峰岭区系的相似性指标分别为73.3%、46.7%、33.3%和13.3%,共有优势科下辖的各种系在各区系中具明显的替代现象。在各区系种子植物属的比较中,沿用经典的分布区类型的划分和相似性指标的比较分析,并运用数量分类方法,以11个不同种子植物区系的14个分布区类型进行聚类分析,将11个种子植物区系分为3组。实践证明数量分类方法可客观地反映各区系间的异同,以及起源上的内在同一性。     

High-level expression and secretion of a lysine-containing analog of Escherichia coli heat-stable enterotoxin'

The mechanism of action of the heat-stable enterotoxin STa secreted from enterotoxigenic forms of Escherichia coli has remained elusive, in part due to a tedious, low-yield purification procedure. We report here a method for obtaining large amounts of a biologically active lysine-containing analog of STa. Initial attempts to express the toxin using an expression vector that did not encode a signal sequence resulted in no biologically active material being recovered either from lysed cells or as a secretory product. However, use of the secretion vector pJAL36, which contains the STII enterotoxin signal sequence, allowed large amounts of an STa derivative containing the additional sequence Ser-Thr-Lys at the amino terminus of the mature enterotoxin to be readily purified from culture supernatants. This enterotoxin analog, known as KSTa-1, was equal in biological and receptor binding activity to the native toxin STa. The lysine residue present in KSTa-1 promises to be useful as a reactive amino acid that is readily derivatized to allow coupling of the enterotoxin to supports for affinity chromatography and antigenic conjugates. Additionally, the insertion of the lysine residue carboxy terminal to the Ser-Thr sequence adds a reversible “handle” to the toxin sequence in that the Ser-Thr-Lys segment can be removed by treatment with trypsin, releasing the native form of STa.     

Spatial and temporal patterns of intracellular calcium in colonic smooth muscle

Summary Intracellular calcium [Ca²⁺] _i measurements in cell suspension of gastrointestinal myocytes have suggested a single [Ca²⁺] _i transient followed by a steady-state increase as the characteristic [Ca²⁺] _i response of these cells. In the present study, we used digital video imaging techniques in freshly dispersed myocytes from the rabbit colon, to characterize the spatiotemporal pattern of the [Ca²⁺] _i signal in single cells. The distribution of [Ca²⁺] _i in resting and stimulated cells was nonhomogeneous, with gradients of high [Ca²⁺] _i present in the subplasmalemmal space and in one cell pole. [Ca²⁺] _i gradients within these regions were not constant but showed temporal changes in the form of [Ca²⁺] _i oscillations and spatial changes in the form of [Ca²⁺] _i waves. [Ca²⁺] _i oscillations in unstimulated cells (n = 60) were independent of extracellular [Ca²⁺] and had a mean frequency of 12.6 +1.1 oscillations per min. The baseline [Ca²⁺], was 171 ± 13 nm and the mean oscillation amplitude was 194 ± 12 nm. Generation of [Ca²⁺] _i waves was also independent of influx of extracellular Ca²⁺. [Ca²⁺] _i waves originated in one cell pole and were visualized as propagation mostly along the subplasmalemmal space or occasionally throughout the cytoplasm. The mean velocity was 23 +3 m per sec (n = 6). Increases of [Ca²⁺] _i induced by different agonists were encoded into changes of baseline [Ca²⁺] _i and the amplitude of oscillations, but not into their frequency. The observed spatiotemporal pattern of [Ca²⁺] _i regulation may be the underlying mechanism for slow wave generation and propagation in this tissue. These findings are consistent with a [Ca²⁺] _i regulation whereby cell regulators modulate the spatiotemporal pattern of intracellularly generated [Ca²⁺] _i oscillations.The authors thank Debbie Anderson for excellent technical assistance with the electron microscopy and Dr. M. Regoli for providing the NK-1 agonist [Sar⁹,Met(O₂)¹¹]-SP. This work was supported by National Institutes of Health Grants DK 40919 and DK 40675 and Veterans Administration Grant SMI.     

Nuclear magnetic tomography in the diagnosis of spinal cord cysts]

Magnetic resonance tomography (MRT) was used in examinations of 172 patients with spinal cord abnormalities. Thirty-eight cysts were detected: 25 in syringomyelia, 5 in intramedullary tumors, 4 posttraumatic and 4 postoperational ones. Based on the MRT patterns, two types of syringomyelia were distinguished, the occlusive and idiopathic ones. The size and site of cyst, as shown by the MRT, did not conform to its neurologic symptoms. A characteristic feature of tumorous cysts was a highly intensive signal originating from their contents. Traumatic cysts were detected against the background of diffuse atrophy of the cord. Computer-aided tomography did not give full-value information in such cases and therefore could not be recommended in cases with suspected intramedullary cysts.     

Reduced incidence of retained placenta with induction of parturition in the cow

Two experiments were designed to determine whether pretreatment with Opticortenol (OPT), a long-acting corticosteroid, prior to induction of parturition with 25 mg of dexamethasone (DEX) alone or in combination with 500 mug cloprostenol (CLO) would result in a reduced incidence of retained placenta. In Experiment 1, 70% of the cows pretreated with 25 mg OPT on Day 270 of gestation calved before or within 24 hours of the scheduled induction treatment on Day 277. Cows induced to calve with DEX plus CLO without OPT pretreatment had an increased rate of placental retention (P<0.05), whereas, cows that received OPT were not different from the controls. In Experiment 2, cows received either 1 mg/25 kg OPT (high dosage) or 1 mg/50 kg OPT (low dosage) on Day 270 of gestation and were induced with DEX plus CLO on either Day 274 (4 days) or Day 276 (6 days). Cows claved 29.0 to 31.8 hours after induction treatment with 95% beginning to calve between 0700 and 1900 hours. The interval from calving to placental release and the incidence of retained placenta was not different between the high dosage 6-day group (29.4+/-8.2 hours, 29%) and the non-induced control cows (16.1+/-10.7 hours, 5%). When three cows in the high dosage 6-day group that retained their placentas for 30 to 36 hours were considered as not retained, the incidence of placental retention for that group was reduced still further to 17%. First service conception rates and pregnancy rates were lower in cows with retained placentas. Differences were significant (P<0.01) in Experiment 1 but not in Experiment 2. It was concluded that pretreatment with 1 mg/25 kg OPT 6 days prior to induction of parturition with DEX plus CLO in combination results in a predictable calving time, high calf viability, and a low incidence of placental retention.     

Growth efficiencies of freshwater bacterioplankton

The growth efficiency of freshwater bacteria was examined in continuous cultures. One series of experiments was carried out using generation times from 50 to 200 hours and aged, normal, and enriched media, all of natural origin. Another series of experiments examined the bacterial growth efficiency during the growth season in eutrophic Frederiksborg Slotssø, in relation to changes in the planktonic communities and to factors controlling the bacterial incorporation of ³H-thymidine. Attachment of bacteria to the inner surfaces of the experimental flasks was examined using various types of bottles, adding glass tubes to the bottles, and measuring ³H-thymidine incorporation and direct cell counts of attached and free-living bacteria. Attachment of bacteria varied, and in one example up to 36% of the thymidine incorporation was by attached bacteria after 4 days. It was calculated that 36% of attached bacteria caused an underestimation of the growth efficiency of 11%. The mean growth efficiency tended to decrease with generation time using enriched medium (47 to 19%) and aged medium (35 to 12%), and tended to decrease with medium quality (enriched > normal > aged media) from 37% to 27%. The only significant difference in growth efficiency occurred in relation to generation time, in samples with enriched medium (unpaired t-test, P < 0.05). The overall mean value for all generation times and media was 30% (SEM = 3%, n = 24). From April to October, the growth efficiency was determined 5 times in samples from Frederiksborg Slotssø. The overall mean value was 31% (SEM = 3%, n = 30), and there was no significant change in the growth efficiency during the period measured. In June, three bioassay experiments revealed that carbon limitation controlled bacterial incorporation of ³H-thymidine, whereas additions of phosphate and nitrate did not change the incorporation rates. The narrow range of growth efficiencies obtained in this study (mean 31%, SEM = 2%, n = 54) suggests that changes in substratequality in the media applied and in the eutrophic samples examined causes only subtle changes in the growth efficiency.     

Triglyceride interesterification by lipases. 3. Alcoholysis of pure triglycerides

Lipase-catalyzed alcoholysis of triolein dissolved in ethanol or isopropanol for the formation of ethyl and isopropyl esters was investigated. Of 16 lipases screened, Amano lipase from P. fluorescens was selected for investigation of the effects of basic reaction conditions on alcoholysis yields. Ethanolysis yields were only slightly affected by water additions to immobilized lipase preparations. Isopropyl ester yields decreased with water addition. Good operational stability was observed over 17 days. Changes in initial triolein concentration in the range 5–50 mM had very little effect on ester yields. The ionic strength of the phosphate buffer used in lipase immobilization affected ethanolysis and isopropanolysis yields in opposite ways. The highest ethanolysis yields were obtained with lipases immobilized from 250 mM buffer, while isopropyl ester yields were highest with lipases immobilized from water. In addition, the quantities and isomers of monoglyceride intermediates in ethanolysis were affected by the immobilization buffer strength. Larger quantities of 2-monoglycerides were formed in ethanolysis reactions with lipase preparations immobilized from water.     

不同叶色水稻叶绿体密度及基粒结构的计算机图象分析

水稻叶绿体计算机图象分析表明,随着叶片色级的提高,叶绿体表面积密度、体积密度以及两者的比值都相应增加。深色稻叶基粒堆直径与高度、类囊体垛叠数与类囊体厚度、叶绿素与类胡萝卜素含量、气孔导度与净光合率均大于浅色叶片。深色叶片基粒堆密集,有些基粒类囊体出现沿叶绿体长轴方向排列整齐现象;浅色叶片基粒堆稀疏,其中较大的基粒类囊体与长轴呈倾斜排列。     

多效唑连用其它植物激素对水稻试管苗生长的影响

本实验采用继代多年的花培体细胞无性系Hu18再生绿芽(0.5mm)为起始材料,研究多效唑(MET)与其它激素配合使用对试管苗的调控作用,结果指出:(1)单独使用MET对绿芽生长有毒害作用,除2,4-D、GA,外,MET与适宜浓度的其它激素配合使用才能发挥增苗、壮苗作用,其中以MET与BA配合使用的培养效果最好,MET与NAA,C_2H_4配合使用的效果次之;(2)MET与其他激素配合使用不但能降低植株高度,促进根系发育,而且可以延长试管苗的保存时间;(3)MET与乙烯利配合使用能加速绿芽成苗速度,而与其他激素配合使则延缓绿芽成苗速度,如与2,4-D配合使用则延缓2,4-D对绿芽的脱分化进程;(4)在本实验条件下,以MET 2.5mg/L+BA 2mg/L+NAA 0.2mg/L配合使用有利根芽的协调生长。本文还从植株干物质累积,叶细胞结构,细胞活力等方面进行了探讨。