Cytology of Saprolegnia diclina Humphrey and S. terrestris Cookson ex Seymour in Relation to Congenital Oospore Abortion

In oogonia of Saprolegnia terrestris some nuclei completed twoconsecutive divisions to form small gamete nuclei, others wererestituted at intermediate division stages. Possible multiplechromosome associations were seen in some late prophase figuresof the first division. Seven to eight chromatin bodies werepresent in pro-metaphase figures. All nuclei except a smallnumber of gamete nuclei were broken down prior to formationof oospheres. Antheridial nuclei either completed divisionsto form small, gamete nuclei or were restituted to form large,torus-shaped nuclei. In oogonia of S. diclina, nuclei enteredprophase but no subsequent division stages were seen. Torus-shapednuclei, but not gamete nuclei, were seen in antheridia. Oosporenuclei of both S. terrestris and S. diclina varied both in size(about 5, 10 or 50–100 µm³) and number (0, 1 or2); 7.5 per cent of oospores of S. terrestris and 54 per centof oospores of S. diclina contained no nucleus or one smallnucleus only. The oospore abortion rate was 7.3 per cent inS. terrestris and 50.4 per cent in S. diclina. Oomycetes, Saprolegnia diclina Humphrey, Saprolegnia terrestris Cookson ex Seymour, cytology, oospores, abortion     

An Analysis of Ultrastructural Changes during Oosphere-initial Development in Oogonia from Ca2+-sufficient and Ca2+-deficient cultures of Saprolegnia terrestris Cookson ex Seymour

The central vacuole system of oogonia of Saprolegnia terrestrisfrom Ca²⁺-sufficient cultures was fully enlarged prior to theformation of oosphere initials, which did not involve cleavagevesicles. In oogonia with fully-enlarged central vacuole systems,subsidiary vacuoles at the periphery of the system sometimescontained dense bodies, and dense-body profiles were sometimespresent within sections of the central vacuole system itself.As the central vacuole system enlarged, volume densities ofdense-body vesicles, peripheral vacuoles, lipid bodies and thecytoplasmic matrix decreased relative to total oogonial volume(peripheral protoplasm volume plus central vacuole volume),while the volume density of nuclei increased and that of mitochondriaremained constant. Relative to the peripheral protoplasm only,volume densities of dense-body vesicles, lipid bodies and mitochondriaincreased and volume densities of peripheral vacuoles and ofthe cytoplasmic matrix decreased, while the volume density ofnuclei increased during central vacuole enlargement but subsequentlydecreased during formation of oosphere initials. Under conditionsof Ca²⁺ deficiency, the volume densities of mitochondria andof the cytoplasmic matrix were significantly increased, whilethat of lipid bodies was significantly decreased, at early stagesof oogonial development; the volume densities of other organelleswere not significantly altered at any stage. Saprolegnia terrestris, oogonia, development, calcium, ultrastructure, stereology     

Negative Phototropism in Vaucheria terrestris Regulated by Calcium I. Dependence on Background Blue Light and External Calcium Concentration

In the presence of 1–8 mM Ca²⁺ unilateral 10–15min irradiation with blue light can elicit negative phototropicbending in the tip-growing coenocytic fresh water alga, Vaucheriaterrestris (Xanthophyceae), when it is simultaneously irradiatedwith strong blue or green background light. By changing wavelength,fluence rate, and duration of background light and holding thoseof unilateral light (456 nm, 1.7 Wm^–2) negative phototropicresponse was analyzed: the wavelength of the background lighthad to be shorter than 540 nm; red light (660 nm) was ineffectiveeven at very high fluence rates (100W.m^–2). The negativebending was strongly and specifically dependent on the externalCa²⁺ concentration. Other divalent cations, Mg²⁺ and Ba²⁺, wereeither toxic or quite ineffective; Sr²⁺ could partly supportthe growth, but mediated neither positive nor negative phototropicbending. The rate of tip-growth was not significantly alteredbetween 10⁶M and 10^-6 mM Ca²⁺. Pre-irrradiation with the backgroundlight slightly increased the negative curvature; whereas thatwithout subsequent simultaneous irradiation does not cause negativebending, but rather increases the positive curvature. Three-mindelayed start of background light did not cause negative bendingany more. The present results strongly suggest that blue light elicitsan influx of Ca²⁺ at the apex of Vaucheria and that the increasedcytoplasmic Ca²⁺ regulates the sensitivity and direction ofphototropic response. (Received June 23, 1988; Accepted September 7, 1988)     

Changes in Menaquinone Concentration During Growth and Early Sporulation in Bacillus subtilis

In two strains of Bacillus subtilis, menaquinone-7 has been shown to reach maximal cellular concentrations during early stationary phase. These concentration changes closely parallel the previously reported concentration changes in the cytochromes.     

Effect of Sodium Chloride Concentration in an Agar Medium on Growth of Heat-Shocked Staphylococcus aureus

The numbers of Staphylococcus aureus 196E surviving heat treatment in milk for various times at 60 C were determined by plate count with normal and modified Staphylococcus Medium No. 110 (S-110), with Plate Count Agar (PCA), and by milk enrichment techniques. Portions of specific heated samples appeared to contain lower populations of S. aureus 196E when the survivors were enumerated with normal S-110 than with PCA. Similarly, the times at 60 C needed for total destruction of the culture suspension in the test milk appeared to be shorter when survival was determined with normal S-110 agar. The apparently lower thermal death times were found to be related to the NaCl content of the S-110 medium, because use of S-110 agar containing lesser concentrations of NaCl resulted in growth of larger numbers of heat-shocked S. aureus 196E.     

The Effect of Calcium Chloride on Growth,Photosynthesis, and Antioxidant Responses of Zoysia japonica under Drought Conditions

Few attempts have been made to study the alleviating effects of signal molecules on zoysiagrass ( Zoysia japonica ) under drought stress. Calcium chloride has been shown to ameliorate the adverse effects of drought stress on many plants. It is necessary to investigate how to enhance drought tolerance of zoysiagrass using calcium chloride. The study elucidated the effects of calcium chloride on zoysiagrass under drought conditions by investigating the following parameters: biomass, chlorophyll (Chl) content, net photosynthetic rate (Pn), chlorophyll fluorescence, antioxidant enzymes, proline content, and malondialdehyde (MDA) content. Experimental conditions consisted of an aqueous CaCl₂ solution at 5, 10, and 20 mM sprayed on zoysiagrass leaves for 3 d, following by an inducement of drought conditions by withholding water for 16 d. Under drought conditions, all CaCl₂ pretreatments were found to increase the above-ground fresh biomass, as well as below-ground fresh and dry biomass. The resulting Chl (a, b, a+b) contents of the 5 and 10 mM CaCl₂ pretreatment groups were higher than those of the control. In the later stages of drought conditions, the chlorophyll fluorescence parameter Fv/Fm was higher in leaves treated with 10 mM CaCl₂ than in the leaves of the other two treatment groups. Zoysiagrass pretreated with 10 mM CaCl₂ possessed both the maximum observed Pn and antioxidant enzyme activities. Meanwhile, lower MDA and proline contents were recorded in the plants pretreated with 5 and 10 mM CaCl₂ under drought conditions. As a whole, the drought tolerance of zoysiagrass was improved to some extent by the application of a moderate calcium concentration.     

MS培养基不同碳源和矮壮素浓度对马铃薯试管苗农艺性状的影响

选用马铃薯脱毒试管苗(大西洋,滇薯6号),MS培养基碳源(蔗糖,白砂糖)、MS培养基矮壮素浓度(0 mg·L~(-1)、100mg·L~(-1)、150mg·L~(-1)、200mg·L~(-1)、250mg·L~(-1)、300mg·L~(-1))进行3因素完全随机试验,观察处理后各试管苗生长的农艺性状。结果表明:以白砂糖作为碳源的MS培养基比以蔗糖作为碳源的MS培养基有利于大西洋和滇薯6号脱毒试管苗生长。矮壮素浓度为200mg·L~(-1)对马铃薯脱毒试管苗的壮苗效果较好。     

氯化钙对非洲菊切花的保鲜作用

以 1 0mg ml的CaCl2 溶液作为保鲜液 ,对非洲菊切花进行瓶插试验 ,通过外部形态观察和生理指标测定 ,结果表明 :用CaCl2 溶液瓶插非洲菊切花可以增强花枝的吸水能力 ,增加花枝的鲜重 ,保持切花的水分平衡 ,减少溶质外渗 ,维持膜结构的相对稳定性 ,从而使切花的瓶插寿命比对照延长 3 3d。     

盐酸胍浓度对变性溶菌酶复性的影响

研究了复性液中盐酸胍浓度对变性溶菌酶复性的影响。变性酶的复性收率与复性液中盐酸胍度浓度紧密相关,获得高复性收率所需的盐酸胍浓度随酶浓度提高而增大。当酶浓度较低时（0．06－0．21g/L）,0．7mol/L的盐酸胍即可溶菌酶完全复性;当酶浓度较高时（0．6－1．05g/L）,提高盐酸胍浓度至1．0－1．5mol/L才可使复性收率达到95％以上。另外,酶的复性速率随盐酸胍浓度增大而下降。因此,根据酶浓度选择最佳盐酸胍浓度是提高蛋白质复性收率的关键。     

Effect of Ethyl Picolinate on Germination, Growth and Sporulation of Bacillus spp.

Ethyl picolinate inhibited outgrowth and sporulation of Bacillus cereus T and laboratory isolates of B. megaterium AH2 and AV1 and B. brevis AG4. The outgrowth-inhibition was relieved by supplementing the medium before inoculation with any of the following: aspartate, asparagine, leucine, lysine, phenylalanine, tyrosine and vitamin-free casamino acids. The uptake of radioactive precursors in the synthesis of proteins, ribonucleic acid and deoxyribonucleic acid was prevented when ethyl picolinate was added before inoculation. Cultures incubated for a short period before the addition of ethyl picolinate assimilated radioactive precursors, outgrew and divided after a lag. None of the cultures containing ethyl picolinate sporulated. Growth was not inhibited when a portion of vegetatively growing culture was transferred to medium containing ethyl picolinate.     

Synchronous Growth and Sporulation of Bacillus megaterium

Filtration of late log-phase cultures of Bacillus megaterium ATCC 19213 grown on defined sucrose salts medium (SS) or SS plus glutamate medium (SSG) through nine layers of Whatman no. 40 filter paper in a fritted-glass disc Büchner funnel resulted in filtrates containing cells which showed synchronous growth and proceeded to sporulation. SS cells completed one synchronous division after filtration; sporulation ensued after the cessation of growth. SSG cells completed two synchronous divisions and sporulation occurred during the second division. A high degree of synchrony of vegetative growth of SSG cells was evident by the stepwise pattern of growth, by the doubling of cell numbers at each division, the high division index, and by the rapid formation of sporulation cell types and homogeneity of cell types in the filtered cultures when compared with asynchronous cultures. Because the described system gives both good growth and sporulation synchrony, the method should be useful in delineating early events in sporulation and their regulation.     

钙离子对293细胞结团和生长的影响

分别在有血清和无血清条件下、方瓶和转瓶中考察了Ca²⁺ 对2 93细胞结团和生长的影响。通过实验发现,Ca²⁺ 浓度在0 1～1 0mmol L范围内对2 93细胞的贴壁和结团性质有显著影响,而对生长影响不大。结果表明:有血清贴壁培养时,较高的Ca²⁺ 浓度有利于细胞贴壁;无血清悬浮培养中,Ca²⁺ 浓度越高,细胞结团越严重,细胞结团达到平衡后的平均粒径(D ,μm)与Ca²⁺ 浓度(c,mmol L)在0.1～0.5mmol L范围内可用一次函数D =58.65c +16.96描述,细胞结团尺寸是可调控的;而细胞在不同的Ca²⁺ 浓度下有相似的生长规律。     

Time-Lapse Microscopy of Streptomyces coelicolor Growth and Sporulation

Bacteria from the genus Streptomyces are among the most complex of all prokaryotes; not only do they grow as a complex mycelium, they also differentiate to form aerial hyphae before developing further to form spore chains. This developmental heterogeneity of streptomycete microcolonies makes studying the dynamic processes that contribute to growth and development a challenging procedure. As a result, in order to study the mechanisms that underpin streptomycete growth, we have developed a system for studying hyphal extension, protein trafficking, and sporulation by time-lapse microscopy. Through the use of time-lapse microscopy we have demonstrated that Streptomyces coelicolor germ tubes undergo a temporary arrest in their growth when in close proximity to sibling extension sites. Following germination, in this system, hyphae extended at a rate of ~20 μm h⁻¹, which was not significantly different from the rate at which the apical ring of the cytokinetic protein FtsZ progressed along extending hyphae through a spiraling movement. Although we were able to generate movies for streptomycete sporulation, we were unable to do so for either the erection of aerial hyphae or the early stages of sporulation. Despite this, it was possible to demonstrate an arrest of aerial hyphal development that we suggest is through the depolymerization of FtsZ-enhanced green fluorescent protein (GFP). Consequently, the imaging system reported here provides a system that allows the dynamic movement of GFP-tagged proteins involved in growth and development of S. coelicolor to be tracked and their role in cytokinesis to be characterized during the streptomycete life cycle.     

微激光照射肥大细胞对胞内钙离子浓度的影响

目的:研究850 nm波长微激光对肥大细胞照射后胞内钙离子浓度的影响。方法:实验前12 h,将肥大细胞接种于激光共聚焦专用培养皿中,然后用D-Hank’s液洗涤3次,加入2 m L D-Hank’s液,按照照射时间不同共分六组(Control,1 min,2 min,2.5 min,3 min,4 min),其中,空白对照组不进行激光照射处理;激光照射后,弃去D-Hank’s液,加入含有Fluo-3/AM的D-Hank’s液1 m L,放入培养箱中孵育30 min后,用D-Hank’s液洗涤3次去除胞外多余的Fluo-3/AM,再加入含有10%FBS的D-Hank’s液2 m L,置激光扫描共聚焦显微镜检测。结果:空白对照组中细胞内未见荧光,说明此时胞内无钙离子,但从1 min开始在细胞中发现荧光,而且发现随着照射时间的加长,其荧光强度越来越强,这可能与微激光照射时间越长从而刺激胞内出现更多的钙离子有关。从上面的实验说明850 nm微激光能作为仿灸仪器的光源。     

Effects of m-Tyrosine on Growth and Sporulation of Bacillus Species.

Aronson, John N. (Arizona State University, Tempe), and Gerald R. Wermus. Effects of m-tyrosine on growth and sporulation of Bacillus species. J. Bacteriol. 90:38-46. 1965.-The aromatic amino acid analogue, dl-beta-(3-hydroxyphenyl)alanine (m-tyrosine), reduced sporulation of a strain of Bacillus subtilis to less than 5% of that of control cultures in a glucose-salts minimal medium. The mass-doubling time increased twofold, but maximal growth equivalent to that of control cultures was eventually attained. A decreased growth rate could be maintained in the presence of the analogue for more than 10 doublings, despite incorporation of m-tyrosine-2-C(14) in place of some of the protein phenylalanine. The organism proliferated to chain lengths of 10 to 15 cells. These cells persisted for many hours after maximal growth had been reached, in contrast to normal cultures which had begun to autolyze and sporulate. The response to m-tyrosine of strains of B. cereus, B. thuringiensis, and B. megaterium was like that of B. subtilis. In addition, B. thuringiensis and B. cereus converted m-tyrosine to dihydroxyphenylalanine, which was further oxidized to a melaninlike substance. Growth of a strain of B. stearothermophilus was not slowed by m-tyrosine, but a strain of Escherichia coli grew at a reduced rate.