Structural changes on Entamoeba histolytica trophozoites after cryopreservation in liquid nitrogen.

Trophozoites of Entamoeba histolytica cultures which had been deep-frozen in the presence of 5% DMSO, along with untreated cells and cells treated with DMSO (5%), were examined for fine-structural changes. After deep-freezing in liquid nitrogen only a few amoebae exhibited normal nuclear and cytoplasmic structure. One frequently observed but unspecific finding pertaining to recovered cells is the separation of the cytoplasm into large vacuolated (coarse-granular) and electron-optically fine-granular (hyaline) zones. The glycogen which normally lies in the cytoplasm is always eluted. In many cases numerous short RNP helices are scattered unevenly in the vesicular plasma, but they are also found in larger masses adjacent to the membranes of still intact and already damaged nuclei. Moderately damaged nuclei have a poorly folded membrane and their chromatin is markedly denatured. More heavily damaged nuclei have a membrane which has partly fibrillated or ruptured and then formed conspicuous folds, where the nuclear membrane has ruptured nucleoplasmic remnants of chromatin and button-like bodies appear to pour into the surrounding cytoplasm. The final destruction of the cell is marked by coalescing autolytic zones, first in the vacuolated and later in the fine-granular cytoplasm. Finally only remnants of the nuclear membrane and of the membranes of numerous vacuoles remain. It is assumed that most of the changes in the cytoplasm are of a secondary nature and are caused by the early functional disturbance of the nucleus.     

The ultrastructure of the intraerythrocytic stages of Babesia herpailuri-trophozoites and merozoites after treatment with imidocarb (3,3'-bis-2-imidazolin-2-yl)-carbanilide (author's transl)]

The fine structure of trophozoites and especially of merozoites of Babesia herpailuri is described before and after treatment with Imidocarb (Wellcome). The mostly piriform to oval merozoites possess an outer membrane and a supporting membrane below. The intratorium consists of a polar ring, rhoptries micronemes and the sperical body which lies beside the big nucleus and next to mitochondria. The endoplasmic reticulum and invaginations are not clearly formed. The cellular changes of Babesia herpailuri, observed one hour after drug treatment in trophozoites and six hours later in merozoites, concern the form and function of the parasite: widening of the subpellicular endoplasmic reticulum and of the perinuclear space; sporadic dilatation of the endoplasmic reticulum of the merozoites (9 fig.). Damaged membranes, dissolution of the cellular membrane, disintegration of the nuclei as are known effects of the Berenil treatment to Babesia herpailuri, are not noted results after the Imidocarb treatment. The original membrane systems of trophozoites as well as of merozoites, remain unaffected by the drug as long as investigations were carried on (24 h). The satisfying prophylactic effect of Imidocarb as well as the insignificant cellular damages on merozoites may be due to the small feeding of hemoglobin.     

Ultrastructural evidence for AMF mediated salt stress mitigation in Trigonella foenum-graecum

The study unveils that inoculation with arbuscular mycorrhizal fungus (Glomus intraradices Schenck and Smith) prevents salt-induced ultrastructural alterations in fenugreek (Trigonella foenum-graecum L.) plants. Mycorrhizal (M) and non-mycorrhizal (NM) fenugreek plants were subjected to four levels of NaCl (0, 50, 100, and 200 mM NaCl). Salt-induced ultrastructural changes were captured using a Transmission Electron Microscope. Effects of salt on the ultrastructure of cells include shrinkage of protoplasm, widening apoplastic space between cell wall and cell membrane, disorganization of grana in chloroplast—swelling and reduction in the number of thylakoids, disintegration of chloroplast membrane, accumulation of plastoglobules, dilation of cristae and denser matrix in mitochondria, and aggregation of chromatin in nucleus. However, the extent of salt-induced ultrastructural damage was less in M plants as compared to NM plants. Lower lipid peroxidation and electrolyte leakage in M plants also indicated less membrane damage. This reduction of ultrastructure damage is a demonstration of enhanced tolerance in M plants to salt stress. The AMF-mediated lesser damage may be due to higher osmolyte (glycinebetaine, sugars) and polyamines concentration, and more and bigger plastoglobules (higher α-tocopherol concentration) in M plants as compared to NM plants. While lower Na⁺ and Cl^? ions assures less ionic toxicity, higher osmolytes and tocopherols ensure osmotic adjustment and better capacity to scavenge free radicals generated due to salt stress, respectively.     

Role of mitochondrial membrane potential in the regulation of murine erythroleukemia cell differentiation

The level of cytoplasmic calcium ions appears to be important in the control of murine erythroleukemia (MEL) cell differentiation. Our interest in this study focuses on the relationship between the regulation of calcium concentration and differentiation. We used the fluorescent membrane probe DiOC₆ to examine the relationship between MEL cell mitochondria and changes in cytoplasmic calcium levels occurring at the initiation of commitment. Fluorescence microscopy reveals the selective association of DiOC₆ with MEL cell mitochondria, where an enhanced fluorescence is observed. Treatment of cells with dimethylsulfoxide (DMSO) or other inducers causes a decrease in mitochondria-associated fluorescence levels that occurs with the initiation of commitment. A decrease in DiOC₆ fluorescence is caused by agents that reduce mitochondrial membrane potential, but is only slightly affected by agents that alter plasma membrane potential. Amiloride and EGTA, agents that prevent commitment and inhibit calcium uptake, also prevent the decrease in DiOC₆ uptake caused by DMSO. The effect of DMSO on MEL cell mitochondria is mimicked by FCCP, a proton ionophore that dissipates mitochondrial membrane potential. FCCP also caused MEL cell mitochondria to release calcium into the cytoplasm. When MEL cells are treated with DMSO plus FCCP, commitment is initiated without the lag period observed when cells are treated with DMSO alone. These results are consistent with the hypothesis that mitochondrial transmembrane potential is important in the regulation of cytoplasmic calcium levels at the time of commitment of MEL cells to terminal differentiation.     

Failure of exogenous NADH and cytochrome c to support energy-dependent swelling of mitochondria

The possibility of direct oxidation of external NADH in rat liver mitochondria and of the inner membrane potential generation in this process is still not clear. In the present work, the energy-dependent swelling of mitochondria in the medium containing valinomycin and potassium acetate was measured as one of the main criteria of the proton-motive force generation by complex III, complex IV, and both complexes III and IV of the respiratory chain. Mitochondria swelling induced by external NADH oxidation was compared with that induced by succinate or ferrocyanide oxidation, or by electron transport from succinate to ferricyanide. Mitochondria swelling, nearly equal to that promoted by ferrocyanide oxidation, was observed under external NADH oxidation, but only after the outer mitochondrial membrane was ruptured as a result of the swelling-contraction cycle, caused by succinate oxidation and its subsequent inhibition. In this case, significantly accelerated intermembrane electron transport and well-detected inner membrane potential generation, in addition to mitochondria swelling, were also observed. Presented results suggest that exogenous NADH and cytochrome c do not support the inner membrane potential generation in intact rat liver mitochondria, because the external NADH-cytochrome c reductase system, oriented in the outer mitochondrial membrane toward the cytoplasm, is inaccessible for endogenous cytochrome c reduction; as well, the inner membrane cytochrome c oxidase is inaccessible for exogenous cytochrome c oxidation.     

Cd、Pb及其复合污染对烤烟叶片生理生化及细胞亚显微结构的影响

本研究以水培的烤烟给予不同浓度的Cd、Pb及其复合物处理10d后的烟叶为材料,分析了烟叶过氧化氢酶、硝酸还原酶的活性变化,测试了烟叶可溶性糖含量的变化情况,通过透射电子显微镜观察到了Cd和Pb对烟叶叶肉细胞亚显微结构的改变,特别是对叶绿体、线粒体和细胞核结构的损伤情况进行了详细观察。并探讨其毒害机理。研究结果表明：1)烟叶过氧化氢酶的活性剧烈地被Cd抑制;而随着Pb浓度的增加,其活性则表现为先增加后减弱的变化。2)Cd对硝酸还原酶活性的影响表现为先刺激增强,当Cd浓度超过50mg·L-1后,Cd剧烈地抑制其活性,当Cd浓度为200mg·L-1时,其活性几乎为零;Pb抑制烟叶硝酸还原酶的活性,仅在1000mg·L-1时出现一个低于正常活性的抗性峰。3)烟叶可溶性糖含量对Cd、Pb及其复合污染非常敏感,在较低浓度的污染处理时,其含量就明显下降,烟叶可溶性糖含量的变化可作为监测Cd、Pb污染的指标。4)Cd对烟叶叶肉细胞亚显微结构具有较强的损伤诱变作用,对细胞核、叶绿体和线粒体造成不可逆转的伤害,破坏了细胞正常生理活动所需的结构基础。电镜观察表明Cd严重地破坏细胞的膜结构。这可能是由于Cd离子与蛋白质结合而使蛋白质变性,从而使得以蛋白质为重要组成成份之一的膜的结构改变,功能丧失。5)在细胞膜的外面可以看到大量的Pb沉积粒,细胞膜可以阻止部分Pb进入原生质体内部,但在细胞质和叶绿体中仍可看到Pb沉积粒。Pb同样的损伤叶绿体、线粒体、细胞核的亚显微结构。     

锌胁迫下水车前叶细胞自由基过氧化损伤与超微结构变化之间关系的研究

主要研究了模拟锌污染对水车前叶细胞的自由基过氧化损伤和超微结构的变化,并对二者之间的关系作了初步探讨,随锌胁迫程度的增大,叶绿素含量,SOD（超氧化物歧化酶）活性和可溶性蛋白含量呈下降趋势;而POD（过氧化物酶）和CAT（过氧化氢酶）活性则先升后降;MDA（丙二醛）含量上升,超微结构的变化也呈现加重趋势,低浓度处理的变化为细胞核变形,叶绿体膨胀,类囊体排列紊乱,严重的超微结构的损伤是核仁散开,染色质凝集,细胞核几乎成为空核和核膜破裂,核质散出;线粒体脊突膨胀和部分溶解;叶绿体膜断裂,消失和部分类囊体溶解和散到细胞质中,实验结果表明,锌胁迫下叶细胞超微结构的变化反映了内膜系统遭到严重伤害,这可能是自由基过氧化损伤的结果。     

锌胁迫下水车前叶细胞自由基过氧化损伤与超微结构变化之间关系的研究

主要研究了模拟锌污染对水车前叶细胞的自由基过氧化损伤和超微结构的变化,并对二者之间的关系作了初步探讨。随锌胁迫程度的增大,叶绿素含量、SOD（超氧化物歧化酶）活性和可溶性蛋白含量呈下降趋势;而POD（过氧化物酶）和CAT（过氧化氢酶）活性则先升后降;MDA（丙二醛）含量上升。超微结构的变化也呈现加重趋势,低浓度处理的变化为细胞核变形、叶绿体膨胀、类囊体排列紊乱;严重的超微结构的损伤是核仁散开、染色质凝集,细胞核几乎成为空核和核膜破裂,核质散出;线粒体脊突膨胀和部分溶解;叶绿体膜断裂、消失和部分类囊体溶解和散到细胞质中。实验结果表明,锌胁迫下叶细胞超微结构的变化 反映了内膜系统遭到严重伤害,这可能是自由基过氧化损伤的结果。     

Fine Structural Observations of the Erythrocytic Stages of Plasmodium chabaudi Landau, 1965*

SYNOPSIS. Electron microscopic examination of Plasmodium chabaudi in mouse erythrocytes revealed many characteristics resembling those observed in other mammalian malarial parasites. A double unit membrane surrounds the trophozoite cytoplasm which contains many ribonucleoprotein particles, a limited amount of endoplasmic reticulum and membraned organelles including sausage-shaped vacuoles and multilaminated membraned bodies. More or less circular double membraned vacuoles, possibly cross sections of the sausage-shaped vacuoles, are common. Typical protozoan mitochondria are lacking. The limiting membrane of the merozoites is triple-layered. Paired organelles and small dense bodies are found in the merozoites along with dense granular masses in the nuclei. Trophozoites have cytostomal structures as well as invaginations of the plasma membrane at sites where no cytostomes are evident. Digestion appears to occur in single membrane-bound vesicles which contain one to several pigment grains. P. chabaudi frequently contains multiple food vacuoles and has polymorphism manifested in part by the presence of cytoplasmic extensions and of nuclei with a variety of shapes. Several apparently free forms are noted, often accompanied by a thin rim of host cytoplasm. “Appliqué” forms are common among the trophozoites as are forms in which 2 or more trophozoites are joined together. Finally, alterations in the host cytoplasm resembling the socalled Maurer's clefts are frequent. Ferritin-containing vacuoles also appear in the host cell.     

取食转Bt基因水稻对稻纵卷叶螟幼虫中肠的组织病理学效应

利用透射电镜观察了稻纵卷叶螟 Cnaphalocrocis medinalis（Guenée）幼虫取食转Bt基因水稻后中肠的组织病理变化。结果表明：稻纵卷叶螟幼虫取食转cry1Ab基因水稻后,中肠上皮细胞的线粒体先发生形态变化,随连续取食时间的延长线粒体出现凝聚、内嵴稀疏、空泡化等,在后期还呈凝聚态随突起脱落或沿杯腔边沿单一排列。内质网的变化也很明显,病变过程中伴随着粗糙内质网的肿胀、核糖体脱落,粗糙内质网增多等现象。细胞核的变化较小,在处理后期出现细胞核拉长、核仁聚集等变化。组织病变程度不一,有的细胞在病变早期就出现了空泡化。     

Histopathological changes in susceptible corn inoculated with Helminthosporium maydis race O

Seedlings of a susceptible inbred line of male-fertile corn were inoculated with conidia of Helminthosporium maydis race O. Histological and ultrastructural observations of mesophyll, bundle sheath and phloem were made over a period of 8 days. Histological observations at 1 day revealed that lesions were comprised of several dead mesophyll cells bordered by a pair of vascular bundles. By 3 days lesions had developed their characteristic appearance caused by mesophyll collapse and had increased to a width of 10–12 bundles. At the ultrastructural level, the first signs of mesophyll cell change were rupture of the tonoplast and swelling of the mitochondrial matrix followed by a disintegration of the cytoplasm and swelling of the chloroplast stroma. Following these changes the cytoplasm became filled with an electron dense material and the plasmalemma ruptured leaving only partial remnants of chloroplasts as recognizable organelles. All of these changes occurred by 1 day. Bundle sheath cells were more resistant and intact cells could be observed in 3-day-old lesions. Phloem showed signs of degeneration by 1 day with distortion of the sieve-tube element membranes and disintegration of the companion cell cytoplasm. By 4 days the phloem had disintegrated.     

Cytoplasmic Ultrastructural Changes During Microsporogenesis of Gossypium hirsutum:With Emphasis on

Conspicuous cytoplasmic changes took place during the microsporogenesis of Gossypium hirsutum L. These changes mainly involved in the ribosomes, plastids and mitochondria. During meiotic prophase 1, the ribosome population of the cytoplasm diminished and reached to aminimum during pachytene--diplotene interval, and the membrane structures of both plastids and mitochondria turned unclear. In metaphase I, cytoplasmic ribosome population restored to premeiotic level; plastids and mitochondria also regained their normal structures. The disintegration of nucleoloids from nucleus was the main mechanism for the restoration of ribosome population in metaphase I cytoplasm. Endoplasmic reticulum may play an important role in the elimination and protection of part of cytoplasmic ribosomes during prophase I. These obvious cytoplasmic changes are considered to be relevant to sporophyte-gametophyte transition.     

荔枝雄花性别决定过程中细胞超微结构的变化

荔枝雄花雌蕊原基在大孢子母细胞减数分裂后开始衰退.内质网历经增生扩展,穿壁相连,同心缠绕,多条平行弯曲,不规则堆叠.内质网和高尔基体产生许多囊泡,囊泡在细胞内含物的降解和运输过程中起着重要的作用.线粒体在雌蕊原基细胞衰败的前、中期数量增加,后期分批降解.过氧化物酶体在雌蕊原基细胞衰败的中期紧挨核短暂出现.细胞核的染色质凝集断裂;核周腔扩大,形成胀泡;染色质趋边,外泄.细胞原生质表现出有序的、在膜包裹下的降解,首先是核糖体,而后依次是:过氧化物酶体、内质网、高尔基体、线粒体、核.雌蕊原基的衰败历程可能是一种程序性细胞死亡的过程.     

Giardia muris: ultrastructural analysis of in vitro excystation

Giardia muris cysts were examined by transmission electron microscopy before treatment, after induction, and at timed intervals during the incubation phase of in vitro excystation. Untreated G. muris cysts had a thick cyst wall composed of a fibrous outer wall and a thin, electron-dense inner membrane which extended from the trophozoite plasma membrane. The cytoplasm was devoid of endoplasmic reticulum, Golgi bodies,and mitochondria. Numerous large vacuoles were present within the ectoplasm just beneath the plasma membrane in untreated cysts. Following induction these cysts lacked ectoplasmic vacuoles. Concurrently, numerous membrane bound vesicles were seen in the peritrophic space closely adhering to the surface of the trophozoite. These vesicles appear to be of cytoplasmic origin. The cytoplasm of fully excysted trophozoites lacked ectoplasmic vacuoles but displayed well-developed ribbons of microtubular bodies, probably precursors of ventral disk, lateral flange, and median bodies and also contained extensive granular endoplasmic reticulum. No more than two nuclei were observed within each organism. The earliest excysted organisms were observed 0-5 min after incubation had begun and most organisms had excysted within 10 min. Cytokinesis occurred only after excystation was complete.     

六价铬污染对水车前叶片生理生化及细胞超微结构的影响

以培养在铬 ( VI)浓度梯度的污水中 6 d的水车前为实验材料 ,分析了叶绿素含量和抗氧化酶系统的变化 ,并用透射电镜观察了叶细胞超微结构的损伤。实验结果表明 :( 1 )叶绿素含量在 0 .1 mg/L浓度达到最高 ,而后下降。而可溶性蛋白则一直成下降趋势 ;( 2 ) SOD(超氧化物歧化酶 )、POD(过氧化物酶 )、CAT(过氧化氢酶 )活性影响明显 :三者分别在 0 .1 mg/L、1 0 mg/L、和 1 mg/L处理浓度有抗性峰出现 ,随处理浓度的继续增大则下降 ;( 3)对超微结构造成不可逆损伤 ,特别是对叶绿体、线粒体和细胞核 :叶绿体膨胀 ,被膜破裂和消失 ,叶绿体解体 ;线粒体脊突膨胀和空泡化 ;细胞核变形 ,染色质凝集和核质解体 ,核膜破裂。并根据实验结果初步讨论了重金属对植物的毒害机制     

Effects of Purified Helminthosporium maydis Race T Toxin on the Structure and Function of Corn Mitochondria and Protoplasts

A toxin preparation from Helminthosporium maydis Race T containing several closely related molecules with apparently identical biological activities was highly active against mitochondria and protoplasts from Texas male-sterile (T) cytoplasm corn (T mitochondria and T protoplasts, respectively) but had no effect on their male-fertile (N) cytoplasm counterparts. The toxin preparation caused multiple changes in isolated T mitochondria, including uncoupling of oxidative phosphorylation, stimulation of succinate and NADH respiration, inhibition of malate respiration, increased swelling, loss of matrix density, and unfolding of the inner membrane. Only 6 to 7 nanograms toxin per milligram mitochondrial protein (1.8 nanogram per milliliter) were required to fully uncouple oxidative phosphorylation and to completely inhibit malate respiration in isolated T mitochondria. Similar low concentrations of toxin caused collapse of T protoplasts after several days of culture. Severe ultrastructural damage to mitochondria in T protoplasts was observed within 20 minutes; no changes in other cellular components were observed at this time. These observations on the cytoplasmic specificity, multiple effects, and high activity of the toxin at the mitochondrial and cellular levels highlight its biological significance and potential usefulness in determining the molecular basis of southern corn leaf blight disease.     

Vahlkampfia sp: structural observations of cultured trophozoites

Some structural observations on cultured Vahlkampfia sp. trophozoites are reported. Trophozoites are active and pleomorphic, producing large cell protrusions related to locomotion such as lamellipodia, filopodia and endocytic structures formed by hyaline cytoplasm, in which actin provides a framework that allows rapid changes in morphology. As observed by transmission electron microscopy, the cytoplasm is highly granular masking some cell organelles and the major cytoplasmic membrane systems. The structure of cell organelles such as the nucleus, endoplasmic reticulum, and digestive vacuoles is described. A common finding was the presence of 50 nm electron-dense round granules that are not limited by a membrane and that appear scattered in the cytoplasm, and whose function remains unknown. Apparently, the cell reserve material is glycogen, since complete trophozoites were positive to Schiff periodic-acid technique.     

The effect of osmotic pressure on oligomycin-sensitive ATPase activity and the liberation of Mg2+ from liver mitochondria of rats of various ages]

The influence of osmotic pressure of the incubating medium (25-500 mM sucrose) on oligomycin--sensitive, 2,4-dinitrophenyl-stimulated ATP-ase-activity, Mg2+ release and swelling of the liver mitochondria in 1-, 3-, 12-, 24-months Wistar rats is, investigated to determine age changes of structurally functional state of mitochondria. An increase in the sucrose concentration in the medium from 150 to 500 mM causes almost equal and practically absolute inhibition of ATP-ase-activity in different-age groups of rats, regardless of the presence or absence of Mg2+ ions in the medium A fall of the sucrose concentration to 150-25 mM induces a decrease in mitochondria ATP-ase-activity in Mg2+ free medium in 12- and 24-months rats (to 30 and 22%, respectively). No changes are observed in 1- and 3-months animals. Differences in rates of exogenous NADH oxidation by mitochondria of 1- and 12-months rats as a reflection of inner membrane damage degree are not observed under these conditions. Relative changes in ATP-ase-activity in a Mg2+ free medium with sucrose concentration of 25 mM (compared with 150 mM) correlate (r = 0.82) with those of optical density of mitochondria, measured at light wave length of 520 nm. It is obvious that the liver mitochondria of young and old rats sufficiently differ in spontaneous swelling rate in the media with different osmotic pressure: mitochondria of 1-month rats swell much faster than those of old rats. Considerable age differences of osmotic dependence of Mg2+ output from mitochondria are observed. They depend also on peculiarities of spontaneous organelle swelling dynamics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Trypanosoma cruzi: ultrastructural changes produced by an anti-trypanosomal factor from Pseudomonas fluorescens

Trypomastigotes and amastigotes of Trypanosoma cruzi exhibited distinct ultrastructural alterations when treated with an extracellular lytic substance (anti-trypanosomal factor) produced by Pseudomonas fluorescens. Marked swelling of the parasites and detachment of the plasma membrane from the subjacent cytoplasm were observed after 15 min of treatment. After 3 hr, the nucleus was extensively damaged, the kinetoplast was indistinguishable, the mitochondrion was markedly swollen, the cytoplasm was disrupted, and the plasma membrane showed extensive blebbing and focal loss of subpellicular microtubules. These changes were progressive, as shown by the occurrence of parasite ghosts after 10 hr. Amastigotes exhibited an extremely swollen mitochondrion with disrupted internal structure, widening of the perinuclear space, and blebbing of the external nuclear membrane. The kinetoplast, however, remained clearly discernible. The drugs used today in controlling Chagas' disease are toxic. Therefore, there is a need for new anti-trypanosomal agents such as the Pseudomonas fluorescens antibiotics. The observations described in this study indicate the potential chemotherapeutic usefulness of these compounds for this disease.     

Regulation of mitochondrial matrix volume

Mitochondrial volume homeostasis is a housekeeping cellular function essential for maintaining the structural integrity of the organelle. Changes in mitochondrial volume have been associated with a wide range of important biological functions and pathologies. Mitochondrial matrix volume is controlled by osmotic balance between cytosol and mitochondria. Any dysbalance in the fluxes of the main intracellular ion, potassium, will thus affect the osmotic balance between cytosol and the matrix and promote the water movement between these two compartments. It has been hypothesized that activity of potassium efflux pathways exceeds the potassium influx in functioning mitochondria and that potassium concentration in matrix could be actually lower than in cytoplasm. This hypothesis provides a clear-cut explanation for the mitochondrial swelling observed after mitochondrial depolarization, mitochondrial calcium overload, or opening of permeability transition pore. It should also be noted that the rate of water flux into or out of the mitochondrion is determined not only by the osmotic gradient that acts as the driving force for water transport but also by the water permeability of the inner membrane. Recent data suggest that the mitochondrial inner membrane has also specific water channels, aquaporins, which facilitate water movement between cytoplasm and matrix. This review discusses different phases of mitochondrial swelling and summarizes the potential effects of mitochondrial swelling on cell function. potassium homeostasis; depolarization; mitochondrial swelling