Ultrastructural Studies of Vegetative Cells on Jaoa bullata (Jao) Fan

The present study reports the ultrastructural features of the vegetative cells in Jaoa bullata (Jao), Fan., an endemic species of Chlorophyta in China. Its thallus is composed of 3 layers of cells. Outer cells are the smallest in size, containing abundant cytoplasm, rich in various organelles; their vacuoles are smaller. The cells of mid-layer possess a large central vacuole. Their cytoplasm becomes a thin layer appressed against the cell wall; Various kinds of the organelles are still clearly visible. Inner ceils are extremely vacuolated. Their cytoplasm looks like degenerated. The cells are uninucleate, each containing a parietal, laminate chloroplast with numerous pores, which cause chloroplast a net-like appearance. The photosynthetic lamellae in a chloroplast include a number of thylakoids mainly in pairs. Chloroplast contains several pyrenoids, which are penetrated by 1 or 2 thylakoids. The present study deals with the structural characteristics of the mitochondria, plastids, endoplasmic reticulum and dictyosomes in the cells of Jaoa bullata. Two groups of intranuclear microtubules are present in a cell. Based on the similarity to Ulva mutabilis in the thylakoid arrangement and the ultrastructural features of the pyrenoids, authors suggest that daoa bullata (Jao) Fan may be closely related to Ulvaceae, among the advanced taxa in the evolution of Chlorophyta.     

Pb 在水花生愈伤组织中的超微定位及对矿质元素的影响

水体重金属污染已经成为一个日益严重的环境问题, 了解水体重金属污染原理、处理水体重金属, 已经成为一个必需解决的课题。由于重金属元素具有难降解、易积累、毒性大等特点, 另外还能被水生植物富集吸收进入食物链危害人畜健康。因此, 植物对重金属毒害的抗性机理以及提高植物抗重金属胁迫能力的探索研究越来越引起人们的关注。虽然在铅(Pb2+)胁迫下植物的抗氧化反应已经有了一些报道, 但有关于植物愈伤组织受到重金属胁迫后变化的研究报道较少。鉴于此, 研究将分布广泛的挺水植物水花生进行愈伤组织培养, 克服了光照、温度、水分及植物生长发育在自然状态下的不可控制性, 使实验数据更具重复性和科学性。经过70%酒精30s、5%次氯酸钠10min 和0.1%升汞10min 消毒后, 在激素为6-BA(3.0 mg/L)和NAA(0.2mg/L)的1/2MS 培养基中培养出水花生茎段的愈伤组织并以此作为研究对象, 以常见的污染环境的重金属离子—Pb2+为胁迫因子。研究了在不同Pb 处理浓度(0、0.2、0.4、0.8 和1.6 mmol/L)下愈伤组织对Pb 的积累、亚细胞分布、亚显微定位及矿质元素的影响。结果表明, 随着培养液中Pb 浓度的增加, (1)愈伤组织体内的Pb 含量极显著上升, 富集系数为2341—2681; (2)各亚细胞组分中的Pb 含量都呈逐渐上升的趋势, 但分配比例明显不均, 分布规律为细胞壁>细胞器>可溶性部分, Pb 胁迫与处理浓度间存在显著的剂量—效应关系, Pb在亚细胞分布与对细胞超微结构的损伤关系密切; (3)超微定位观察发现在细胞壁上分布有大量的Pb 颗粒,细胞内膜结构及基质中也都存在Pb; ⑷Pb 对各亚细胞组分中矿质元素的影响不同, 其中抑制了大量元素P、K、Mg 和微量元素Na、Zn、Mn 的吸收; Ca 在细胞壁中先升后降, 细胞器中逐渐减少, 可溶性部分中则是逐渐增加; Fe 和B 在各亚细胞组分中均表现出先升后降; Cu 在前两个组分中总体呈上升趋势, 可溶性部分中则是先升后降; Si 在细胞壁中逐渐减少, 细胞器中呈先升后降的趋势, 而可溶性部分中无法测出。可见, Pb 打乱了各亚细胞组分中离子平衡, 导致愈伤组织正常生理活动紊乱, 这些都是Pb 毒害水花生愈伤组织的主要表现。       

Influence of the enzyme equipment of white-rot fungi on the patterns of wood degradation

Abstract: In recent years a considerable amount of data have accumulated concerning the principal enzymes involved in wood decay by white-rot fungi and about their biochemical mechanism of action. Various strains of fungi and their mutants having different enzyme production were selected and the patterns of degradation resulting from their action on wood were examined by transmission electron microscopy. A correlation between the nature of the enzymes and the micromorphology of degradation was tentatively established based on a comparison between the respective patterns created by a wild-type strain and metabolic mutants in which a known activity was either enhanced or repressed. Results are illustrated with Phanerochaete chrysosporium, Dichomitus squalens and Phlebia radiata . In particular, the strong ability of manganese peroxidase and laccase to perform defibrillation of cellulose microfibrils is evidenced.     

Studies of hCG binding and endocytosis in rat ovary by ultrastructural immunocytochemistry

Summary Localization of hCG binding sites and the process of endocytosis in pseudopregnant rat ovaries were investigated by indirect electron-microscopic immunocytochemistry. Immature female rats were treated with pregnant-mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) to induce ovarian luteinization. Eight days after priming with PMSG-hCG and 1–6 h before sacrifice the animals were given another injection of hCG to bind the receptors. Receptor sites to hCG localized by reaction product were present in most luteal cells, but not in primary follicular cells. The receptor sites were distributed on luteal cell surfaces facing interstitial spaces. Endocytotic pits containing hCG binding sites were rarely seen 1 h after hCG injection. At 2 h, hCG and presumably its receptor were taken up within endocytotic vesicles with the evidence of reaction product coated on the vesicle wall. With time, fusion of endocytotic vesicles with lysosome occurred and the reaction product appeared in phagolysosomes. The reaction product was localized on phagolysosomal inner surface or in free granular form. These findings suggest that hCG and its receptors were internalized through endocytotic pits and endocytotic vesicles and delivered to lysosomes probably for degradation. An additional experiment for localization of acid phosphatase was also performed to delineate the lysosomes and phagolysosomes.     

The ultrastructure of nerve endings containing pigment-dispersing hormone (PDH) in crustacean sinus glands: Identification by an antiserum against a synthetic PDH

Summary A high-liter antiserum has been obtained from two rabbits immunized with a glutaraldehyde conjugate of synthetic pigment-dispersing hormone (PDH) from Uca pugilator and bovine thyroglobulin. The antiserum blocked melanophore-dispersing activity of the peptide in vivo. In sinus glands (SG) of Carcinus maenas, Cancer pagurus, Uca pugilator and Orconectes limosus, electron-microscopic immunocytochemistry revealed sparsely distributed axon endings containing a distinct PDH-immunoreactive type of neurosecretory granules (diameter 90–130 nm). Exocytotic figures indicating release of the content of these granules into hemolymph lacunae were occasionally observed. Preservation of fine structure and antigenicity of the PDH granules were markedly dependent on the fixation procedure used. A preliminary experiment with C. maenas showed that preterminal axon dilatations near the basal lamina seemed to accumulate PDH-granules when animals were kept in complete darkness for three days. Immunodot blotting of fractions after high pressure liquid chromatography (HPLC) of extracts from SGs of C. maenas and O. limosus revealed a strongly immunoreactive substance at a retention time very similar to those of synthetic PDHs of Uca pugilator and Pandalus borealis. It is also coincident with a zone of biological activity. Thus, the antigen demonstrated by immunocytochemistry is identical or very similar to one of the known PDHs.     

Structural alterations inEuglena gracilis exposed to the herbicide isopropyl-N-phenylcarbamate (IPC)

Summary Ultrastructural abnormalities of various kinds and severity appeared inEuglena gracilis green cells after a 48-hour exposure to 4 × 10^–4M of isoprophyl-N-phenylcarbamate (IPC), a widely used herbicide thought to affect microtubules and/or microtubule organizing centers in susceptible plant and animal species.A high proportion of cells contained nuclei in the G 2 phase of the cycle; in a significant percentage of organisms, however, structural aberrations of the nucleolus and chromosomes were evident. The pellicle outline, chloroplasts, mitochondria, and dictyosomes were also affected. The cytoplasm was rich in dense bodies which sometimes showed granular, fibrillar or tubular materials. Furthermore IPC partially inhibited flagellum regeneration after mechanical amputation.The mechanism by which IPC causes these responses remains unclear. Nevertheless, some indications suggest that the herbicide acts primarily on microtubule organizing centers. However, mitochondria, chloroplasts and nuclear constituents appear as possible additional targets of the compound.The study was supported by a grant from Italian Research Council (CNR), contract No. 80.00420.04.     

Cellular characteristics of immunolabeled luteinizing hormone releasing hormone (LHRH) neurons

This study utilized the preembedding immunocytochemical technique in order to identify LHRH-containing neurons in rat brain and define their ultrastructural characteristics. LHRH-containing neurons in the vertical limb of the diagonal band of Broca, medial septum, triangular nucleus of the septum and other regions were studied by taking ultrathin serial sections. These neurons had scant cytoplasm surrounding a centrally-located, spheroid, euchromatic nucleus. Neurosecretory granules were evenly distributed throughout the cell, but many tended to lie directly under the plasmalemma. The cytoplasm was organized in such a way that the most extensive portion of the rough endoplasmic reticulum was polar opposite to areas having high concentrations of Golgi complex, lysosome-like bodies, smooth endoplasmic reticulum and ribosomes. The perikarya had no axosomatic synapses but functional interaction via unspecialized appositions to the plasmalemma cannot be discounted. Many of the perikarya bore at least one cilium. Processes from immunonegative cells were occasionally observed to penetrate the cytoplasm of the LHRH perikaryon or its processes. At their points of origin, dendrites were found to be broadened processes containing many elements common to the cytoplasm: ribosomes, smooth endoplasmic reticulum, cristal and lamellar mitochondria, neurotubules, and an occasional alveolate caveola. Infrequently, some of the LHRH axons were partially myelinated. This method of studying serial-sectioned immunocytochemically-identified cells is suggested as a means of describing the cellular and subcellular characteristics of other specific peptide-containing cells.     

低温和超低温保存对中国大鲵成熟精子的影响

中国大鲵Andrias davidianus是中国特有的一种濒危有尾两栖类动物,为了保护这一珍稀物种并且为中国大鲵人工辅助繁育建立一套可靠的技术,对中国大鲵的精子在0—4℃下低温短期保存和在液氮中超低温长期保存进行了研究。研究表明中国大鲵精子原液在常温下一般仅存活3—5h,4℃下能存活6d,0℃下存活时间可达9d。精子原液中添加Ringer氏液或Holtferter氏液,精子存活率比原液保存显著降低。在改良的超低温冻存条件下,中国大鲵精子在液氮中保存两周后解冻,精子复苏率可达10%—15%。利用扫描和透射电镜观察冻融前后中国大鲵精子的超微结构,发现受冷冻损伤精子质膜出现膨胀、破裂;精子穿孔器和轴丝显著弯曲,甚至断裂;波动膜明显脱落或膜结构损坏;精子线粒体嵴变形。结果表明,超低温冻存导致部分中国大鲵精子超微结构发生变化而产生冻伤,进而导致精子活力、复苏率下降。研究为建立规范化的中国大鲵精液保存程序和中国大鲵规模化人工繁育提供重要参考。     

Effect of c-myc on the ultrastructural structure of cochleae in guinea pigs with noise induced hearing loss

Noise over-stimulation may induce hair cells loss and hearing deficit. The c-myc oncogene is a major regulator for cell proliferation, growth, and apoptosis. However, the role of this gene in the mammalian cochlea is still unclear. The study was designed to firstly investigate its function under noise condition, from the aspect of cochlear ultrastructural changes. We had established the adenoviral vector of c-myc gene and delivered the adenovirus suspension into the scala tympani of guinea pigs 4 days before noise exposure. The empty adenoviral vectors were injected as control. Then, all subjects were exposed to 4-kHz octave-band noise at 110 dB SPL for 8 h/day, 3 days consecutively. Auditory thresholds were assessed by auditory brainstem response, prior to and 7 days following noise exposure. On the seventh days after noise exposure, the cochlear sensory epithelia surface was observed microscopically and the cochleae were taken to study the ultrastructural changes. The results indicated that auditory threshold shift after noise exposure was higher in the ears treated with Ad.EGFP than that treated with Ad.c-myc-EGFP. Stereocilia loss and the disarrangement of outer hair cells were observed, with greater changes found in the Ad.EGFP group. Also, the ultrastructure changes were severe in the Ad.EGFP group, but not obvious in the Ad.c-myc-EGFP group. Therefore, c-myc gene might play an unexpected role in hearing functional and morphological protection from acoustic trauma.     

大鼠粒细胞内质网的电镜细胞化学反应

本实验用电镜细胞化学方法观察了大鼠骨髓粒细胞发育过程中内质网的髓过氧化物酶(MPO)反应和葡萄糖-6-磷酸酶(G-6-P)反??应。结果表明:MPO除定位于内质网、核膜,还出现在高尔基体和颗粒,它是粒细胞内质网的合成产物。G-6-P只在内质网、核膜中出现,它是内质网膜的结构成分。MPO反应的超微结构定位随粒细胞发育而变,利用这种变化作标志可以划分不同发育阶段的粒细胞;G-6-P反应定位不随发育而变,但反应强度与内质网的多寡、功能状态相对应。实验还表明核膜与内质网在结构、功能上的一致性;尤其在成熟粒细胞内质网很少的情况下,核膜可能代替了内质网的功能。