THE HISTOCHEMISTRY AND ULTRASTRUCTURE OF JACK PINE MICROSPORANGIA DURING THE WINTER

The development of jack pine (Pinus banksiana Lamb.) microsporangia from October to April was investigated with a microdensitometer and a transmission electron microscope. DNA, RNA, and protein content of sporogenous cells was measured at monthly intervals. DNA was unreplicated (2C) until March when DNA synthesis was first noted, coinciding with a loss of heterochromatin. Protein content doubled in April. RNA staining increased in December and then decreased. Numerous whorls and stacks of rough endoplasmic reticulum and ribonucleoprotein-like granules appeared in December and may be related to the RNA increase. A fibrillar, light-staining region was found in the cytoplasm of the sporogenous cells from November to March. It was hydrolyzed in the presence of protease and may be a winter morphology of microfilament bundles or dictyosomes. Lipid bodies and vacuoles were abundant in the tapetum and sporangial wall cells during the winter. Observations substantiate reports that winter is not a time for cessation of development.     

ULTRASTRUCTURE AND HISTOCHEMISTRY OF THE POSTERIOR OESOPHAGUS OF NASSARIUS RETICULATUS (LINNAEUS)

The posterior oesophagus of N. reticulatus (Linnaeus) consistsof two histologically distinct regions. The epithelium of thethickened segment in the visceral haemocoel is virtually uniform.The cells are lipid-rich and can take up lipid from food. Inaddition, enzyme histochemistry indicates a capacity for theuptake of sugars and amino acids. The basal plasmalemma is elaboratelyinfolded and associated with numerous elongate mitochondria,features indicating an active ion pump. The physiological roleof this pump is unknown. (Received 26 March 1985; accepted 10 May 1985)     

试管棉纤维与天然棉纤维超微结构的差异(简报)

棉纤维由棉胚珠表皮细胞分化生长而成,是研究细胞分化、细胞伸长等机理的良好材料。为了更好地研究它的分化和发育,人们建立了多种实验系统:离体胚珠培养系统、胚珠来源的单细胞悬浮培养系统、胚珠愈伤组织细胞来源的细胞悬浮培养系统,并对这些实验系统的特点对纤维细胞分化和生长,如培养基的配方、激素配比、pH值、抑制剂或促进剂的影响等进行了较为系统的研究。发现棉纤维的发育     

HISTOCHEMISTRY AND ULTRASTRUCTURE OF RICE (ORYZA SATIVA) ZYGOTIC EMBRYOGENESIS

Rice embryo development was examined, histochemically and ultrastructurally, from the time of fertilization to embryo maturity. At the time of fertilization, the megagametophyte consists of an antipodal mass of 10–15 cells, parietally positioned along the placental side of the central cell, and, at the micropylar end, two partly fused polar nuclei and the egg apparatus. Hydrolysis of adjacent nucellar tissue suggests the secretion of hydrolytic enzymes by the antipodal mass. The antipodal cells stain intensely for RNA and protein, indicating that they are metabolically active. The egg, supported by two overarching synergids, occupies a small, wall ingrowth-lined pocket of the central cell that quickly fills with cellular endosperm after fertilization. The endosperm cells, initially supplied with nutrients from wall ingrowth-derived vesicles, are digested and utilized by the embryo as a nutritive source. The developing embryo is also supplied with assimilates via the nucellus at the base of the embryo until about 8 days after fertilization. After 8 days, the embryo is no longer connected to the nucellus, and the nucellar cells at the base of the embryo are crushed. The zygote is not structurally polarized and contains a central nucleus, amyloplasts, lipid bodies, dictyosomes and extensive dilated ER. The first division of the zygote is transverse and unequal and occurs about 4 hours after fertilization. Embryo development is rapid, and within 24 hr, the embryo consists of 5–8 cells. Organ development begins with scutellum emergence in the 3-day-old embryo. The shoot apex organizes and the coleoptile develops from scutellum tissue at 4 days postfertilization, the epiblast emerges at 5 days, and the vascular bundle and root apex differentiate by 6 days after fertilization. Starch begins to accumulate in the basal cells of the 3-day-old embryo and deposition proceeds acropetally over the next 9–10 days. Lipid accumulation begins in the basal scutellum in the 6-day-old embryo and also proceeds acropetally. Storage protein synthesis is first detected in 6-day-old embryos and accumulation again proceeds acropetally, reaching the apex of the scutellum of the 25-day-old embryo. The ultrastructure of the 24-hr-old embryo is distinctive. The cells are characterized by numerous vesicles, heterochromatin and extensive nuclear evaginations.     

HISTOCHEMISTRY AND ULTRASTRUCTURE OF THE CRYPT CELLS IN THE DIGESTIVE GLAND OF APLYSIA PUNCTATA (CUVIER, 1803)

The crypt cells lining the Aplysia punctata digestive tubulescomprise of three types ofcell; calcium, excretory, and thincells. The calcium cells play a role in osmoregulation, mineralstorage,exocrine secretion, iron detoxification, and excretion processes.They possess well-developed microvilli and a basal labyrinth,suggesting a role in absorption. The Golgi apparatusis involvedin the production of two main components of calcium spherules;the fibrillar materialand mineralized granules. Golgi complex,rough endoplasmic reticulum (RER), ribosomes, andaltered mitochondriaare involved in the formation of calcium spherules. Secretoryactivity isindicated by the formation of dense granules containingiron and calcium salts. Lipofuscinpigment has been found inlarge concretions which may arise from cytoplasmic areas surroundedbyendoplasmic reticulum, RER and Golgi tubules. There are threestages of excretory cells,called early, mature, and post-excretorycells. This study traces the development ofgranulofibrillarvacuoles up to the formation of the lipofuscin concretions andshows thatexcretory cells are in fact degenerating calciumcells. The fine structure of thin cells suggests thatthey areyoung calcium cells. (Received 29 December 1997; accepted 15 November 1998)     

己酮可可碱对非酒精性脂肪性肝炎大鼠肝脏超微结构和酶组织化学的影响

目的研究己酮可可碱(PTX)对非酒精性脂肪性肝炎(NASH)大鼠肝脏超微结构和酶组织化学的影响。方法高脂饮食建立大鼠非酒精性脂肪性肝炎模型。取SD大鼠40只,分为对照组、12w模型组、16w模型组和治疗组,每组10只。腹主动脉采血,测ALT、AST、血糖等水平。取肝组织做电镜和SDH、CCO、ATPase、LDH的酶组织化学染色。结果两个模型组均比对照组ALT、AST、血糖升高,LDL降低(P<0.05)。治疗组血糖、AST比16w模型组降低(P<0.05)。电镜显示16w模型组线粒体肿大,嵴排列紊乱,基质密度降低。治疗组结构改善。酶组织化学显示四种酶的活性16w模型组均较对照组降低(P<0.05),治疗组活性均较16w模型组升高(P<0.05)。结论NASH时存在肝细胞能量代谢障碍,经PTX治疗后能量代谢障碍得到改善。     

薏苡种子的糊粉层及亚糊粉层细胞的组织化学和超微结构

薏苡（Ｃｏｉｘｌａｃｒｙｍａ－ｊｏｂｉ）种子的糊粉层为１层细胞，径向细胞壁内含有胞间连丝，有细胞核，冰箱内浸泡的材料，未见细胞器，室温浸泡的，则观察到很多核糖体及一些嵴不明显的线粒体。细胞内充　了大量糊粉粒及脂体，糊粉粒含蛋白质，不溶性多糖，可被ＴＢＯｐＨ４．４染成绿色，基质内通常有１个球状体，球状体含有脂肪，但不被ＡＢＢ和ＰＡＳ及ＴＢＯｐＨ４．４染色。脂体大小悬殊，随机分布。亚糊粉层细胞含有许多复合淀粉粒及小形蛋白质体。蛋白质体呈弱的ＰＡＳ正反应，亦可被ＴＢＯｐＨ４．４染成绿色，并具有同心圆坏结构，中央具核心或不具，边缘具裂隙或否。内部胚乳具很多大的简单淀粉粒，蛋白质体同心圆环结构不甚明显。对薏苡与其他禾本科植物的糊粉层细胞，糊粉粒及胚乳蛋白质体的结构进行了比较。     

ULTRASTRUCTURE OF THE SUBGLANDULAR CELLS FROM THE FOLIAR NECTARIES OF COTTON IN RELATION TO THE DISTRIBUTION OF PLASMODESMATA AND THE SYMPLASTIC TRANSPORT OF NECTAR

Foliar nectaries on the midveins of 7-cm leaves from cotton (Gossypium hirsutum L., cv. Stoneville 213) were examined by light and electron microscopy. The nectaries consist of external multicellular papillae and internal subglandular tissue that extends from the bases of the papillae to the vascular tissue of the midveins. The subglandular tissue is composed of small parenchyma cells; it does not contain sieve elements or xylem vessels. The parenchyma cells are rich in mitochondria, and their walls contain numerous pit fields having a high concentration of plasmodesmata. The absence of vascular tissue and the significance of the pit fields in the subglandular tissue are discussed in relation to symplastic transport of nectar secretions.     

THE ULTRASTRUCTURE OF THE STALK AND BASE OF THE ANTHERIDIUM OF POLYTRICHUM

The fluorescent boundary across the stalk of an antheridium of Polytrichum appears as a distinctive, secondary wall layer in electron micrographs. Lamellations of electron-dense and -lucent materials cause this layer to resemble the “suberized lamellae” of root endodermis and leaf bundle sheaths in grasses. The cells of the stalk below the boundary are especially rich in lipid droplets, whereas those in the base of the antheridium, above the boundary, have markedly fewer and smaller lipid droplets and abundant rough endoplasmic reticulum often in loosely parallel arrays. Cytological differences develop before the boundary appears, so that the distinctive wall layer is secreted by protoplasts that are already specialized morphologically. During maturation of an antheridium there is a secretion of a fluid into a space that forms at the bottom of the sperm chamber. However, the cells surrounding this fluid show no special morphological adaptations that would seem to relate to secretion.     

ULTRASTRUCTURE OF THE EPIDERMIS OF DEVELOPING COTTON (GOSSYPIUM) SEEDS: SUBERIN,PITS, PLASMODESMATA,AND THEIR IMPLICATION FOR ASSIMILATE TRANSPORT INTO COTTON FIBERS

The basal part of cotton fibers (Gossypium arboreum and G. hirsutum) was studied with light and electron microscopy in order to improve the understanding of assimilate transport into the fibers during the deposition of the cellulosic secondary wall. Although the distal parts of white cotton fibers are not suberized, a variable amount of suberin was found at the fiber base. This suberin is typically deposited in concentric layers, alternating with polysaccharides. Numerous pits occur in the base of cotton fibers and in ordinary epidermal cells in the periclinal and anticlinal walls. About 25% of the length of periclinal walls is occupied by pits, but only 2% of the anticlinal walls, being pitted mainly in their proximal part. In suberized walls the deposition of suberin is not reduced in the pit region. The pits, whether or not suberized, contain plasmodesmata (22 ± 2.3 and 27 ± 3.3 · μm^−-2 in the periclinal and anticlinal walls of the white lint cultivar of G. hirsutum). Transport of assimilates into the fibers through the symplast is therefore possible. This transport may occur directly from mesophyll cells to fibers, or indirectly via ordinary epidermal cells. The minimum amount of assimilates transported into individual fibers during the phase of secondary wall deposition could be estimated (1.3 pg · fiber^−-1 · sec^−-1), as well as the corresponding symplastic flux of assimilates through the periclinal cell wall, neglecting a possible transport through the anticlinal walls (10^−-3 pg · μm^−-2 · sec^−-1). It is postulated that in the green lint genotype of G. hirsutum and in wild cotton species (not studied in this paper), the uptake of assimilates into the fibers occurs through the symplast, the apoplastic pathway being excluded by the suberization of the fibers during secondary wall formation. Although cultivated, white-linted cotton species may use the same pathway, loading of assimilates from the apoplast is theoretically also possible, and the relative contribution of both pathways has to be determined experimentally.     

CAPSELLA EMBRYOGENESIS: THE SYNERGIDS BEFORE AND AFTER FERTILIZATION

The ultrastructure and composition of the synergids of Capsella bursa-pastoris were studied before and after fertilization. The synergids in the mature embryo sac contain numerous plastids, mitochondria, dictyosomes and masses of ER and associated ribosomes. Each synergid contains a large chalazal vacuole, a nucleus with a single nucleolus and is surrounded by a wall. This wall is thickest at the micropyle end of the cell where it proliferates into the filiform apparatus. At the chalazal end of the cell the wall thins and may be absent for small distances. The pollen tube grows into one of the two synergids through the filiform apparatus and extends one-third the length of the cell before it discharges. Following discharge of the pollen tube, mitochondria and plastids of the tube can be identified in the synergid as can hundreds of 0.5 μ polysaccharide spheres liberated by the tube. The method by which the sperm or sperm nuclei enter the egg or central cell is not known although an apparent rupture was found in the wall of the egg near the tip of the pollen tube. The second synergid changes at the time the pollen tube enters the first synergid. These changes result in the disorganization of the nucleus and loss of the chalazal wall and plasma membrane. Eventually this synergid loses its identity as its cytoplasm merges with that of the central cell.     

THE ULTRASTRUCTURE OF DRY AND IMBIBED COTYLEDONS OF SOYBEAN

Ultrastructural observations of parenchyma cells of cotyledons of soybean (Glycine max (L.) Merr.) indicate that a 20-min period of imbibition brings about extensive changes in membranes and organelles. The plasma membrane, which in cells of dry seeds is disorganized and disrupted, becomes relatively intact and continuous. A network of endoplasmic reticulum vesicles and tubules, no evidence of which can be discerned in dry seeds, appears extensively dispersed through the cytoplasm and around the margin of protein bodies. Mitochondria in dry tissue are distorted in shape and nearly devoid of internal structure. In imbibed cells they are round or oval and are bound by an intact membrane enclosing numerous cristae and a dense stroma. Starch grains develop in proplastids. Circular or whorled membranous structures appear in the cytoplasm. The swiftness with which membranes and organelles are structurally altered during imbibition is a reflection of their effectiveness in rapidly modifying solute loss and solvent entry.