Ultrastructure of Sieve Elements in Secondary Phloem of Dalbegia odorifera During Leaf-Bearing and Leaf-Absent Period

Ultrastructures of sieve elements of secondary phloem of 1–2 year old branchlet of tropical deciduous tree Dalbegia odorifera T. Chen growing on Hainan Island were studied under transmission electron microscope and a comparation was made between the sieve elements in leaf-bearing and leaf-absent period. During the leaf-bearing period, there was a tailed spindleshaped P-protein body in each mature sieve element. The main part of the P-protein body con sisted of a disordered fine fiber mass with two crystalline tails. The sieve elements had horizontal end walls with simple sieve plate. The inner layers of the wall near the sieve plate appeared intumescent, protruding into the sieve element lumen. During the leaf-absent period, a functional phloem remained about the same thickness as that during the leaf-bearing period. The sieve elements in the leaf-absent period contained normal protoplasts and the P-protein and the sieve plate pores had the same structures as those during the leaf-bearing period. More starch grains and vesicles were found in sieve elements in the leaf-absent period.     

观察导管和筛管的两种简便方法

采用将徒手切片煮沸透明的方法改进了两种观察导管和筛管的方法     

Growth and development of conifer pollen tubes

Conifer pollen tubes are an important but underused experimental system in plant biology. They represent a major evolutionary step in male gametophyte development as an intermediate form between the haustorial pollen tubes of cycads and Ginkgo and the structurally reduced and faster growing pollen tubes of flowering plants. Conifer pollen grains are available in large quantities, most can be stored for several years, and they grow very well in culture. The study of pollen tube growth and development furthers our understanding of conifer reproduction and contributes towards our ability to improve on their productivity. This review covers taxonomy and morphology to cell, developmental, and molecular biology. It explores recent advances in research on conifer pollen and pollen tubes in vivo, focusing on pollen wall structure, male gametophyte development within the pollen wall, pollination mechanisms, pollen tube growth and development, and programmed cell death. It also explores recent research in vitro, including the cellular mechanisms underlying pollen tube elongation, in vitro fertilization, genetic transformation and gene expression, and pine pollen tube proteomics. With the ongoing sequencing of the Pinus taeda genome in several labs, we expect the use of conifer pollen tubes as an experimental system to increase in the next decade.     

纳米银水凝胶涂膜干预气管导管表面铜绿假单胞菌黏附及生物膜形成的实验研究

目的研究纳米银水凝胶涂膜对气管导管（endotracheal tube,ETT）表面铜绿假单胞菌粘附及细菌生物膜（biofilm,BF）形成的干预作用。方法实验共设6组,分别为空白对照组,涂纳米银3．5、7．0、10．5、14．0和17．5μg／cm^2组。参考Brown平板法,制备ETT、表面铜绿假单胞菌BF模型。通过超声振荡-平板菌落计数法检测体外培养6、12、18h时各组ETT表面BF中的活细菌粘附数量。借助激光共聚焦显微镜观察BF中的活死菌分布情况,并测量BF厚度。结果（1）与空白对照组相比,最小量涂膜组（3．5μg／cm^2）体外培养6h时,导管表面活细菌的粘附量显著减少（P〈0．05）,12h时差异无显著性（P〉0．05）;最大量涂膜组（17．5μg／cm^2）体外培养6h时,ETT表面几乎未见细菌粘附（P〈0．05）,18h时BF中的活菌数量及BF厚度均显著减少（P〈0．05）。（2）激光共聚焦显微镜观察可见,培养6h时,空白对照组ETT表面粘附的死活菌呈不规则散点样分布,未见明显的细菌菌落形成,而各实验组ETT表面仅有细菌零星分布,其数量少于空白组。18h时空白对照组表面可见大量活死菌堆积粘连,有小菌落形成并相互交通成地图状,可见典型BF结构,而此时最大量涂膜组（17．5μg／cm^2）表面仅见数量不等的菌落形成,菌落周围可见数量不等的细菌分布。结论纳米银水凝胶涂膜可有效减少ETT表面铜绿假单胞菌的粘附数量,延缓导管表面细菌BF形成,其作用强弱随培养时间及单位面积中的纳米银剂量的变化而变化。     

Comparison of the growth patterns and morphological characteristics of mechanically and enzymatically isolated fallopian tube epithelial cells

This study set out to compare the growth patterns and morphological characteristics of human fallopian tube epithelial cells isolated: (1) mechanically; and (2) enzymatically. Cells were cultured in medium supplemented with fetal bovine serum and antibiotics and their epithelial nature was established by immunocytochemistry for cytokeratins. Primary cultures were polygonal in shape with centrally located nuclei, irrespective of the isolation method. Cells isolated enzymatically exhibited a higher growth rate, but the survival rate was poor after more than 2-3 passages. Mechanical isolation gave a lower yield of cells, but had a higher survival rate when sub-cultured, even beyond 8 passages. Thus, mechanically isolated cells might be useful for longer term cultures, whereas enzymatically isolated cells are best only for short-term work.     

Ultrastructure of freeze-substituted pollen tubes ofLilium longiflorum

Summary In view of the importance of the lily pollen tube as an experimental model and the improvements in ultrastructural detail that can now be attained by the use of rapid freeze fixation and freeze substitution (RF-FS), we have reexamined the ultrastructure of these cells in material prepared by RF-FS. Several previously unreported details have been revealed: (1) the cytoplasm is organized into axial slow and fast lanes, each with a distinct structure; (2) long, straight microtubule (MT) and microfilament (MF) bundles occur in the cytoplasm of the fast lanes and are coaligned with every organelle present; (3) the cortical cytoplasm contains complexes of coaligned MTs, MFs, and endoplasmic reticulum (ER); (4) the cortical ER is arranged in a tight hexagonal pattern and individual elements are closely appressed to the plasma membrane with no space between; (5) mitochondria and ER extend into the extreme apex along the flanks of the pollen tube, and vesicles and ER are packed into an inverted cone-shaped area at the center of the apex; (6) MF bundles in the tip region are fewer, finer, and in random orientation in comparison to those of the fast lanes; (7) the generative cell (GC) cell wall complex contains patches of plasmodesmata; (8) The GC cytoplasm contains groups of spiny vesicles that are closely associated with and seem to be fusing with or pinching off from mitochondria, and (9) the vegetative nucleus (VN) contains internal MT-like structures as well as numerous cytoplasmic MTs associated with its membrane and also located between the VN and GC.Abbrevations CF chemical fixation - ER endoplasmic reticulum - GC generative cell - MF microfilament - MT microtubule - PD plasmodesmata - PM plasma membrane - RF-FS rapid freeze fixation-freeze substitution - VN vegetative nucleus     

Endoplasmic reticulum derived decorated tubules in the sieve elements ofNymphaea

Summary Bundles of decorated tubules found in the sieve elements ofNymphaea have been studied with the transmission electron microscope. Comparatively straight tubules (100 nm in diameter) arise from the endoplasmic reticulum during early stages of sieveelement development and subsequently associate into bundles of up to 100 tubules that parallel the longitudinal cell axis. From the start of their formation the tubules are structurally distinct from other ER profiles due to their dense decoration with particles. High magnifications reveal an orderly array of the particles (about 24 surround a 100 nm tubule) and suggest a modification of their membrane so that it is no longer dissolvable into a regular three-layered structure. Later during sieve-element ontogeny the decorated tubules get invaginated by smooth ER membranes, thereby squeezing out the intratubular (extracytoplasmic) space. As a result a double mantle is formed that surrounds a plasmatic cylinder. Decorated 100 nm tubules with inner membranes are present in enucleate mature sieve elements ofNymphaea alba andN. tuberosa. Considerably larger tubules (about 200 nm in diameter) were found inN. Candida andN. tetragona and occasionally also inNuphar and Barclaya, two other genera from the same family. The decoration of the tubules and their subsequent invagination by smooth membranes are discussed with respect to the controlled autolysis of sieve elements.Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Growth inhibition and recovery in freeze-substitutedLilium longiflorum pollen tubes: structural effects of caffeine

Summary In an attempt to correlate structural effects with the known dissipation of the tip-focused Ca²⁺ gradient caused by caffeine, we have examined the ultrastructure of caffeine-treated lily pollen tubes prepared by rapid freeze fixation and freeze substitution. We show that treatment with caffeine results in a rapid rearrangement of secretory vesicles at the pollen tube tip; the normal cone-shaped array of vesicles is rapidly dispersed. In addition, microfilament bundles appear in the tip region, where they had previously been excluded. Delocalized vesicle fusion continues in the presence of caffeine but tube extension ceases. Removal of caffeine from the growth medium initially causes tip swelling, delocalized vesicle fusion and presence of microfilaments well into the tip before normal structure and growth resume, concurrent with the previously reported return to a normal Ca²⁺ gradient.Abbreviations ER endoplasmic reticulum - MES 2-[N-morpholino] ethanesulfonic acid - MFs microfilaments