Secretory Structures in <i>Flourensia campestris</i>and <i>F. oolepis</i>: Ultrastructure, Distribution, and (-)-Hamanasic Acid A Secretion

In this work, the localization, density, morphology and ultrastructure of secretory structures in aerial organs of Flourensia campestris (FC) and F. oolepis (FO) (Asteraceae) by means of a combination of light, fluorescence, transmission (TEM) and scanning electron microscopy (SEM) were examined. The possible role of secretory structures in the production and secretion of the phytotoxic sesquiterpene (-)-hamanasic acid A ((-)HAA) in both species was also assessed. Capitate glandular trichomes were found in all reproductive organs of FC and FO, and were being reported for the first time. These glandular trichomes, typically associated to edges and veins, were of the same type as those already described for vegetative organs, and were abundant in involucral bracts and corolla of tubulose and ligulate flowers. Their density in reproductive organs of both species was similar (ca. 30/mm2) and lower than that found in leaves (ca. 100/mm2) and stems (ca. 160/mm2 in FC, and up to 650/mm2 in FO). Glandular trichomes in vegetative organs followed a species-specific pattern of distribution. TEM and SEM observations suggest that each species differs in the way in which secretory materials are released to the outside: through cracks or pores in FC, or through a loose cuticle in FO. Similar inspections of the secretory ducts revealed lipophilic vacuoles localized in subepithelial and epithelial cells, in which secretions accumulated before being transferred to the duct. The presence of wall ingrowths in subepithelial cells suggests that granulocrine secretion operates in these species. Secretory ducts varied in density and diameter among the organs in both species, with the combination being maximal in woody stems. (-)HAA was only detected in surface secreted resins of both species, and its concentration (2D-TLC, GC-FID) was intimately associated with the distribution and density of glandular trichomes in each organ (capitula, leaves, and stems with primary or secondary growth). In addition, no (-)HAA was detected internally in the resins collected from secretory ducts. The composition of these resins showed distinctive profiles for FC and FO, and only four from ca. 30 compounds detected (GC/MS) were shared by both species. In addition to the elucidation of ultrastructural traits, distribution and density of secretory structures in aerial organs of FC and FO, present findings suggest a functional role for glandular trichomes in the secretion of the putative phytotoxic allelochemical (-)HAA.

Insight on the Ultrastructure, Physicochemical, Thermal Characteristics and Applications of Palm Kernel Shells

The ultrastructure and physicochemical and thermal properties of Palm Kernel Shells (PKS) in comparison with Coconut Kernel Shells (CKS) were investigated herein. Powder samples were prepared and characterized using Surface Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Chemical and elemental constituents, as well as thermal performance were assessed by Van Soest Method, TEM/EDXA and SEM/EDS techniques. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were also performed for thermal characterization. SEM/EDS and TEM/EDXA revealed that most of the PKS and CKS materials are composed of particles with irregular morphology;these are mainly amorphous phases of carbon/oxygen with small amounts of K, Ca and Mg. The DSC data permitted to derive the materials’ thermal transition phases and the relevant characteristic temperatures and physical properties. Thermal Transition phases of PKS observed herein are consistent with the chemical composition obtained and are similar to those of CKS. Nonetheless, TGA/DTG showed that the combustion characteristics of PKS are higher than those of CKS. Taken together, our results reveal that PKS have nanopores and can be efficiently used for 3D printing and membrane filtration applications. Moreover, the chemical constituents found in PKS samples are in agreement with those reported in the literature for material structural applications and thus, present potential use of PKS in these applications.

Time-effect relationship of acupuncture on histopathology, ultrastructure, and neuroethology in the acute phase of cerebral hemorrhage

Many clinical studies have addressed the treatment of acute cerebral hemorrhage using acupuncture. However, few studies have examined the relationship between time of acupuncture and curative effect on cerebral hemorrhage. By observing the effect of acupuncture on changes in histopathology, ultrastructure, and neuroethology in a cerebral hemorrhage model of rats, we have directly examined the time-effect relationship of acupuncture. The rat model of cerebral hemorrhage was produced by slowly injecting autologous blood to the right caudate nucleus. The experimental groups were: 3-, 9-, 24-, and 48-hour model groups; and 3-, 9-, 24-, and 48-hour acupuncture groups. The sham-operation group was used for comparison. Acupuncture was performed at the Neiguan(PC6) and Renzhong(DU26) acupoints, twice a day, 6 hours apart, for 5 consecutive days. Brain tissue changes were observed by light microscopy and transmission electron microscopy. Neuroethology was assessed using Bederson and Longa scores. Our results show that compared with the sham-operation and model groups, Bederson and Longa scores were lower in each acupuncture group, with visibly improved histopathology and brain tissue ultrastructure. Further, the results were better in the 3-and 9-hour acupuncture groups than the 24-and 48-hour acupuncture groups. Our findings show that acupuncture treatment can relieve pathological and ultrastructural deterioration and neurological impairment caused by the acute phase of cerebral hemorrhage, and may protect brain tissue during this period. In addition, earlier acupuncture intervention following cerebral hemorrhage(by 3 or 9 hours) is associated with a better treatment outcome.

Aquaporin 4 expression and ultrastructure of the blood-brain barrier following cerebral contusion injury

This study aimed to investigate aquaporin 4 expression and the ultrastructure of the blood-brain barrier at 2-72 hours following cerebral contusion injury, and correlate these changes to the formation of brain edema. Results revealed that at 2 hours after cerebral contusion and laceration injury, aquaporin 4 expression significantly increased, brain water content and blood-brain barrier permeability increased, and the number of pinocytotic vesicles in cerebral microvascular endothelia cells increased. In addition, the mitochondrial accumulation was observed. As contusion and laceration injury became aggravated, aquaporin 4 expression continued to increase, brain water content and blood-brain barrier permeability gradually increased, brain capillary endothelial cells and astrocytes swelled, and capillary basement membrane injury gradually increased. The above changes were most apparent at 12 hours after injury, after which they gradually attenuated. Aquaporin 4 expression positively correlated with brain water content and the blood-brain barrier index. Our experimental findings indicate that increasing aquaporin 4 expression and blood-brain barrier permeability after cerebral contusion and laceration injury in humans is involved in the formation of brain edema.

Effects of tachyplesin on the morphology and ultrastructure of human gastric carcinoma cell line BGC-823

AIM To investigate the morphological andultrastructural changes in the human gastriccarcinoma cell line BGC-823 after being treatedwith tachyplesin.METHODS Tachyplesin was isolated from acidextracts of Chinese horseshoe crab(Tachypleustridentatus)hemocytes.BGC-823 cells and thecells treated with 2.0mg/L tachyplesin wereexamined respectively under light microscope,scanning and transmission electron microscope.RESULTS BGC-823 cells had undergone therestorational alteration in morphology andultrastructure after tachyplesin treatment.Thechanges were as follows:the shape of cells wasunanimous,the volume enlarged and cellsturned to be flat and spread,the nucleo-cytoplasmic ratio lessened and nuclear shapebecame rather regular,the number of nucleolusreduced and its volume lessened,heter-chromatin decreased while euchromatinincreased in nucleus.In the cytoplasm,mitochondria grew in number with consistentstructure relatively,Golgi complex turned to betypical and well-developed,rough endoplasmicreticulum increased and polyribosomedecreased.The microvilli at cellular surfacewere rare and the filopodia reduced whilelamellipodia increased at the cell edge.CONCLUSION Tachyplesin could alter themalignant morphological and ultrastructuralcharacteristics of human gastric carcinoma cellseffectively and have a certain inducing differen-tiation effect on human gastric carcinoma cells.

Influence of compound aescine gel on ultrastructure of vein infused mannitol and its mechanism

Purpose: When hypertonic solution 20% mannitol solution was injected into vein, inflammatory mediators and Mitogen-activated protein kinases activated by mannitol can directly induce the fading of vascular endothelial cell, which leads to phlebitis. The study aims to observe the influences of reparil-gel N coated at the proximal parts of the puncture point and basing on this along with infusing heated mannitol to veins to the injure and ultrastructure of veins which were infused the 20% mannitol solution by indwelling needle in vein. Methodology: There are 15 adult New Zealand rabbits. We randomly divided 24 ear veins of 12 adult New Zealand rabbits into Control group, Gelatum group, Gel heated group and injected 20% mannitol solution by vein detained needle in three groups. In Gelatum group, we coated the proximal end of the puncture point with a thin layer of compound aescine gel. Based on Gelatum group, we heated 20% mannitol solution to 35oC-37oC in Gel heated group. Then we observed the intravenous parts and took the veins of each group out to observe their morphology and ultrastructural after the second day of transfusion. 6 ear veins of the rest 3 rabbits as Health group weren’t given any interventions, the veins were taken out to observe their morphology. Results: Comparison between Gelatum group and Gelatum heated group on vascular dilatation, Infiltration of inflammatory cell and Formation of thrombus had no significance, P> 0.05, while the case was different for the comparison on injury of vascular wall, perivascular edema and perivascular hemorrhage, P< 0.05). The statistical significance exists between control group and Gelatum group and Gel heated group, P< 0.05. It was observed under the electron microscope that, in control group, the membrane of endothelial cell peeled off and the mitochondria swelled and vacuolized. In Gelatum group, the membrane of endothelial cell was defective, the parts of the mitochondria were fuzzy, intercellular substance was slightly edematous. In Gel heated group, the mitochondria were clear and intercellular substance slightly swelled. It could be found that the function of phagocyte was complete. Conclusions: Compound aescine gel can prevent phlebitis or reduce the incidence of phlebitis. The combined intervention of coating with a thin layer of compound aescine gel and heating mannitol solution can produce better effect.

Effects of potassium deficiency on photosynthesis,chloroplast ultrastructure,ROS,and antioxidant activities in maize(Zea mays L.)

Potassium(K)deficiency significantly decreases photosynthesis due to leaf chlorosis induced by accumulation of reactive oxygen species(ROS).But,the physiological mechanism for adjusting antioxidative defense system to protect leaf function in maize(Zea mays L.)is unknown.In the present study,four maize inbred lines(K-tolerant,90-21-3 and 099;K-sensitive,D937 and 835)were used to analyze leaf photosynthesis,anatomical structure,chloroplast ultrastructure,ROS,and antioxidant activities.The results showed that the chlorophyll content,net photosynthetic rate(P_n),stomatal conductance(G_s),photochemical quenching(q_P),and electron transport rate of PSII(ETR)in 90-21-3 and 099 were higher than those in D937 and 835 under K deficiency treatment.Parameters of leaf anatomical structure in D937 that were significantly changed under K deficiency treatment include smaller thickness of leaf,lower epidermis cells,and vascular bundle area,whereas the vascular bundle area,xylem vessel number,and area in 90-21-3 were significantly larger or higher.D937 also had seriously damaged chloroplasts and PSII reaction centers along with increased superoxide anion(O_2^-·)and hydrogen peroxide(H_2O_2).Activities of antioxidants,like superoxide dismutase(SOD),catalase(CAT),and ascorbate peroxidase(APX),were significantly stimulated in 90-21-3 resulting in lower levels of O_2^-·and H_2O_2.These results indicated that the K-tolerant maize promoted antioxidant enzyme activities to maintain ROS homeostasis and suffered less oxidative damage on the photosynthetic apparatus,thereby maintaining regular photosynthesis under K deficiency stress.

Effects of CO_2 Enrichment on Microstructure and Ultrastructure of Two Species of Freshwater Green Algae

order to investigate the morphological response of freshwater green algae to elevated CO2 concentration, Chlamydomonas reinhardtii Dang and Scenedesmus obliquus Kutz were cultured with enriched CO2, and their microstructure and ultrastructure were examined by microscopy and electron microscopy. The effect of CO2 enrichment to 186 mumol/L, was insignificant on the shape and size of C. reinhardtii, but significant in reducing the volume of S. obliquus. High-CO2 increased the amount of chloroplast. The pyrenoids occurred in low-CO2-grown cells but not in high-CO2-grown ones and more starch granules were observed in the former.

兔膀胱出口不同梗阻时间对逼尿肌功能和超微结构的影响

目的 观察兔膀胱出口部分梗阻不同时间后逼尿肌功能改变及其超微结构变化。方法 新西兰雄性白兔 2 4只 ,分为A组 (对照组 ) ,B组 (梗阻 5周组 )和C组 (梗阻 2周组 ) ,各 8只。梗阻组手术建成膀胱出口部分梗阻兔模型 ,分别饲养 5周和 2周后解剖膀胱。①测定膀胱重量、容量 ;②检测逼尿肌功能 ;③观察膀胱逼尿肌细胞超微结构。对照组仅行下腹部切口而不建成梗阻模型。结果 (1 )A、B、C组膀胱重量分别为 (3.83±0 .71 )、(1 2 .6 5± 4 .0 1 )、(1 5 .6 3± 4 .0 0 ) g。A、B、C组膀胱容量分别为 (98.1 3± 1 8.1 1 )、(6 9.5 0± 1 0 .2 1 )、(48.1 3± 1 7.1 5 )mL ;(2 )A组单位重量逼尿肌最大张力及最大收缩速度均明显大于B组及C组 (P <0 .0 5或 0 .0 1 ) ;C组单位重量逼尿肌最大张力及最大收缩速度 (除高K+ 液外 )均大于B组 ,但差异无显著性 (P >0 .0 5 ) ;(3)B组和C组兔逼尿肌细胞中粗面内质网明显扩张 ,线粒体水肿。结论 膀胱出口部分梗阻可引起逼尿肌功能障碍并在短时间内进入失代偿期 ,这一变化有其超微结构形态学基础。

猪雌性生殖道黏膜显微和超微结构观察

应用组织学方法和电镜技术研究了雌性成年猪生殖道黏膜显微和超微结构的特征。试验选用成年长白×大约克夏二元杂交母猪20头,通过光镜和透射电镜分别观察了母猪的输卵管、子宫和阴道的黏膜结构特征。结果显示成年母猪的生殖道黏膜由上皮、固有膜和黏膜肌层等构成,输卵管、子宫角、子宫体和子宫颈黏膜的上皮为单层柱状上皮,上皮的游离面含有纤毛和微绒毛,固有膜和上皮间含有丰富的淋巴细胞。淋巴细胞在上皮内移行过程中由胞质伸出许多伪足,淋巴细胞的胞质中主要含有线粒体和高尔基体。母猪生殖道黏膜内的淋巴细胞在某些部位聚集形成淋巴细胞群,特别是子宫角和子宫颈黏膜中较多,淋巴细胞向子宫腔内移行呈现“腔排”现象。结果显示猪雌性生殖道黏膜中含有较多的淋巴细胞,生殖道黏膜可能是黏膜免疫的诱导位点。

Seasonal Changes in the Ultrastructure of the Vascular Cambium in Shoots of Populus tomentosa

Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.

Effects of Doubled_CO_2 Concentration on Ultrastructure, Supramolecular Architecture and Spectral Characteristics of Chloroplasts from Wheat

Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.

Effects of hydrogen peroxide on ultrastructure and cellular permeability of Candida albicans

The changes of the ultrastructure and the cellular permeability of Candida albicans were ob-served after the fungus was exposed to 3%～10% hydrogen peroxide.Damages on the fungus cellsespecially cytoplasm leakage were found under transmission electron microscopy and morphologicalchanges with small hole-like structures under scanning dectron microcopy.Radioactivity assay ofthe leakage of [~3H]-TdR-DNA of C.albicans further proved the existence of cellular permeabilitydamage.There was negative correlation between the amount of [~3H-TdR-DNA leakage and thenumber of the survival fungus cells,which indicates that the damage on cellular permeability andDNA leakage caused by hydrogen peroxide of certain concentration is one of the important factorsto kill the fungus.

FORMATION OF SOLID PARTICLES IN BLOOD STREAM AND EFFECTS ON PULMONARY ULTRASTRUCTURE DURING CARDIOPULMONARY BYPASS IN CHILDREN

An electronic particle size analyzer (Coulter Counter ZM) was utilized to quantitate the particulate microemboli, varying from 15 to 80μin size, during cardiopulmonary bypass. We confirmed the main causes of microemboli were banked blood, cardiotomy reservoirs and oxygenators. Electronic microscopic examination showed that a large number of solid particles more than 20μin size were formed during heart-lung bypass, which obstructed microcirculation and damaged the pulmonary capillary endothelial and alveolar epithelial cells. The degree of histological damage was related to the number and size of microemboli and time of pulmonary microcirculatory obstruction.

Physiology and Ultrastructure of Azolla imbricata as Affected by Hg 2+ and Cd 2+ Toxicity

The toxic effects of different gradient concentrations of Hg2+ and Cd2+ on chlorophyll content, chlorophyll a/b value, photosynthetic O-2 evolution, respiration rate, anti-oxidase system (superoxide dismulase (SOD), catalase (CAT), peroxidase (POD)) and ultrastructure of the cells of Azolla imbricata (Roxb.) Nakai were studied. The results showed that with Hg2+ and Cd2+ increase, chlorophyll content and chlorophyll a/b value, photosynthetic O-2 evolution decreased drastically; respiration rate peaked at 2 mg/L pollutant and declined afterwards. The activities of SOD, CAT and POD increased first and decreased afterwards except the activity of POD, which decreased with the increasing of Cd2+ concentration. Ultrastructural observation showed that the extent of ultrastructural damage was much more serious with higher pollutant concentration and longer time of stress. This resulted in swelling of chloroplast, disruption and disappearance of chloroplast membrane and disintegration of chloroplasts; swelling of cristae of mitochondria, deformation and vacuolization of mitochondria; condensation of chromatin in nucleus, dispersion of nucleolus and disruption of nuclear membrane. The experimental results showed: (1) Hg2+ and Cd2+ pollution not only destroyed physiological activities, but also caused irreversible damage to its ultrastructure, thus leading the cells to death; (2) With increase in the stress of Hg2+ and Cd2+, ultrastructural damage was related to the changes of plant physiology; (3) The toxic symptoms of plant showed an evident correlation between dose and effect; (4) The toxicity of Cd2+ on A. imbricata is heavier than that of Hg2+ under the same treatment time and concentration. The lethal concentration of Hg2+ to A. imbricata ranged from 3.5 to 4 mg/L, and that of Cd2+ ranged from 3 to 3.5 mg/L. The damage of cell ultrastructure on Anabaena azollae Strasburger was observed. The results indicated that tolerance of Azolla imbricata for Hg2+ and Cd2+ was higher than that of A. imbricata.

Evidence of Ultrastructure and Physiology of F-actin as Component of Plasmodesmata

The characters and ultrastructure of the intercellular connection were revealed in the outer epidermis of the garlic clove sheath by means of fluorescent probe TRITC_Phalloidin (TRITC_Ph) labeling combined with confocal laser scanning microscopy (CLSM), immuno_gold labeling and transmission electron microscopy. These results show that transcellular channel is a complex of rod_like cytoplasm channel and grouped plasmodesmata (PDs) in pit. The former remains a portion of the cell protoplast. The diameter of PD is normally 60-70 nm. The PDs are the real intercellular symplasmic connections of the cells. The transcellular fibers labeled with the TRITC_Ph obviously become narrow in the primary pit fields, which is the same as the characters observed under the electron microscope. The bright fluorescent spot in the primary wall reflects the grouped PDs in pit, and hence the presence of F_actin in the PDs can be confirmed. In immuno_gold labeling experiment, a lot of gold particles were massively distributed in the rod_like cytoplasm channel and grouped PDs. The result provides effective support that these fluorescent filaments possibly are the existing form of F_actin.

体外培养牛腔前卵泡卵母细胞的超微结构

直径约100μm牛腔前卵泡在无血清下体外培养15d。超微结构研究显示,培养前腔前卵泡卵母细胞微绒毛短小,分布均匀。胞质内细胞器致密而均匀,线粒体多为长或圆形,嵴较少,高尔基体、脂滴稀少,未见有皮质颗粒出现。培养6d时,微绒毛略变粗长,但数量减少。胞质内细胞器,由近核分布向胞质中央区转移,线粒体形态丰富,基质电子密度极高。培养15d腔前卵泡卵母细胞微绒毛增多,变长,斜向或垂直插入已经形成的透明带中。线粒体增多,大小不等,形态各异,胞质中区有溶酶体样物质及零星的皮质颗粒出现。电镜研究表明,体外培养与体内正常发育腔前卵泡卵母细胞超微结构变化规律基本相似。

THE SECRETORY STIGMAS IN POPULUS: DEVELOPMENT, CYTOCHEMISTRY, ULTRASTRUCTURE AND THEIR RELATION TO INTERSECTIONAL INCOMPATIBILITY *

The stigmas of five species, Populus euphratica Oliv., P. alba L., P. simonii Carr., P. lasiocarpa Oliv. and P. nigra L. have been studied. Scanning electron microscopy re veals that exudates are present in the intercellular spaces, in the clefts between the multicel lular papillae and on the receptive surface. Release and movement of exudates can be visual ized when the fresh stigmas are stained with sudan Ⅲ and auramine O. Paraffin and semi thin resin sections of stigmas after glutaraldehyde osmium fixation evidence the lipidic nature of the exudates. Transmission electron microscopy reveals the glandular features of the stigmatic papillae cells, such as abundance of rough and smooth endoplasmic reticulum, polyribosomes, and well developed dictyosomes with secretory vesicles. Pellicle and epicuticular lamellate layers which have been considered as typical features of the dry type stigmas are also present in the species where stigmas appear extremely wet. It is concluded that stigmas in all of the five species are secretory at the receptive stage. Well developed generative and sperm cells were observed in the pollen tubes penetrating through the deep layers of the stigmatic tissue in the reciprocal crosses between P. euphratica and P. simonii, which indicated that there is no significant barrier in the stigma.

Nanomechanics and Ultrastructure of Bone:A Review

In this review,a brief presentation is first given to the hierarchical structure and mechanical behavior of bone.Then,the recent advancements in nanoscale characterization of bone ultrastructure and ingredients are discussed based on an extensive quantity of references in the literature.Moreover,computational and analytical bone mechanics at ultrastructure levels are critically reviewed with the growing body of knowledge in the field.The computational and analytical models are summarized in several categories for ease of understanding bone nanomechanics and their applicability/limitations.This review is expected to provide a well-informed foundation for the researchers interested in interrogating the complex biomechanical response of bone at its nanoscale hierarchy.

Influence of lanthanum on chloroplast ultrastructure of soybean leaves under ultraviolet-B stress

In order to investigate the effects of lanthanum（Ⅲ） on cell ultrastructure of soybean leaves under elevated ultraviolet-B irradiation （UV-B, 280-320 nm）, the chloroplast ultrastructure of soybean seedlings was studied by hydroponics under laboratory conditions. The resuits showed that the thylakoid in chloroplast was orderly and clearly as soybean leaves were pretreated by La（Ⅲ）. The thylakoid was indis- tinctly disordered, expanded and even indiscoverable in the chloroplast under UV-B stress. The impact on the thylakoid by the high intensity UV-B irradiation （T2） was bigger than that by the low intensity UV-B irradiation （T1）. However, the destruction of the chloroplast structure caused by UV-B stress was alleviated by La（Ⅲ）, and the arrangement of the thylakoid in the chloroplast became orderly and clearly. The effect of the alleviation by La（Ⅲ） under the low intensity UV-B irradiation （T1） was better than that under the high intensity UV-B irradiation （T2）.