Electron Microscope Observations of the Melanocyte of the Human Epidermis

Using standard osmium fixation and methacrylate embedding techniques, a study has been made of the melanocyte of human biopsy skin removed under general and local anaesthesia. Melanogenesis was easily observable in the melanocytes, but immature pigment granules were rarely seen in the Malpighian cells. The passage of melanin from melanocyte to Malpighian cell—cytocrine secretion—is thought to have been observed. Phagocytes near the dermal-epidermal junction seem to have their pigment granules in vacuoles, rather than surrounded directly by the cytoplasmic matrix as in the melanocytes. This, together with the failure to observe "effete" melanocytes, prompts the suggestion that the phagocytes are melanocytes which have migrated from the epidermis into the dermis. A melanin granule is shown with alternating dark and lighter transverse striations, concerning which structure little can at present be said.     

Endoplasmic Reticulum Stress Interacts With Inflammation in Human Diseases

The endoplasmic reticulum (ER) is a critical organelle for normal cell function and homeostasis. Disturbance in the protein folding process in the ER, termed ER stress, leads to the activation of unfolded protein response (UPR) that encompasses a complex network of intracellular signaling pathways. The UPR can either restore ER homeostasis or activate pro‐apoptotic pathways depending on the type of insults, intensity and duration of the stress, and cell types. ER stress and the UPR have recently been linked to inflammation in a variety of human pathologies including autoimmune, infectious, neurodegenerative, and metabolic disorders. In the cell, ER stress and inflammatory signaling share extensive regulators and effectors in a broad spectrum of biological processes. In spite of different etiologies, the two signaling pathways have been shown to form a vicious cycle in exacerbating cellular dysfunction and causing apoptosis in many cells and tissues. However, the interaction between ER stress and inflammation in many of these diseases remains poorly understood. Further understanding of the biochemistry, cell biology, and physiology may enable the development of novel therapies that spontaneously target these pathogenic pathways. J. Cell. Physiol. 231: 288–294, 2016. © 2015 Wiley Periodicals, Inc.

     

Electron Microscope Observations on the Zoospores of Pylaiella and Laminaria

The zoospores of Laminaria saccharina and Pylaiella litoralishave both been shown to possess a hairy front flagellum (Flimmergeissel).In both cases this is longer than the smooth hind flagellum.There is no proboscis. In Pylaiella it has been shown that thehairs are in two rows on the front flagellum and that they arisein pairs except at the extreme front end. Each hair has a jointedstructure and consists of a thicker basal portion which passesabruptly into a thin distal portion. There are signs of a loosetransparent skin covering the axis of the flagellum betweenthe rows of hairs. The axis has also been shown to be fibrillarin construction and to be capable of decomposing into elevenstrands, two of which are central. There is perhaps an intercalarymaterial in the axis in addition to the component fibrils.     

Electron Microscope Observations on the Fine Structure of Parietal Cells

An electron microscope study has been made of the structure of parietal cells in cats, dogs, and rats and of the cells lining the gastric glands of Bufo spinulosus. It is characteristic of all these cells to contain numerous vesicles about 0.05 to 0.3 µ in size. In the mammalian parietal cells an intracellular system of canaliculi is also observed, which is much more complex in the rat than in the cat or dog. Stimulation with histamine causes in the cat a very marked hypertrophy of the canalicular system with development of a large number of villi and a decrease in the number of vesicles. In Bufo, histamine induces the formation of a very complex system of membrane infoldings which circumscribe finger-like processes that entirely fill the glandular lumen. The cytoplasmic vesicles diminish or disappear. These experiments show that under histamine stimulation all these cells undergo a great increase in the cell membrane area. These findings provide additional circumstantial evidence that parietal cells play a role in the secretion of hydrochloric acid.     

Observations with the Electron Microscope on a Species of Saprolegnia

Electron micrographs are presented to show the morphology ofthe flagella in each of the two motile phases of Saprolegniaferax, and one visual light photograph of a stained cell ofthe second stage is added. The front flagellum of both phasesis a Flimmergeissel with hairs between 2µ and 3µlong arranged in two rows and each ending in a thin hair-point.The axis is covered by a wide transparent sheath made of somematerial which appears to liquefy after death. The hind flagellum,which is devoid of Flimmer, is covered by a similar sheath,though there are signs that this is flattened into a fin inthe hind flagellum of the second stage. Some very fine shorthairs 0?5µ long are interpreted as a possible internalframework to this fin. The axis of both flagella is fibrillar,but accurate numerical details have not yet been obtained. Theskins discarded from cysts have also been examined and shownto be covered with characteristic double-headed hooks, whichare strong enough to attach a cyst to passing objects.     

Degradation of the Endoplasmic Reticulum by Autophagy during Endoplasmic Reticulum Stress in Arabidopsis

In this article, we show that the endoplasmic reticulum (ER) in Arabidopsis thaliana undergoes morphological changes in structure during ER stress that can be attributed to autophagy. ER stress agents trigger autophagy as demonstrated by increased production of autophagosomes. In response to ER stress, a soluble ER marker localizes to autophagosomes and accumulates in the vacuole upon inhibition of vacuolar proteases. Membrane lamellae decorated with ribosomes were observed inside autophagic bodies, demonstrating that portions of the ER are delivered to the vacuole by autophagy during ER stress. In addition, an ER stress sensor, INOSITOL-REQUIRING ENZYME-1b (IRE1b), was found to be required for ER stress–induced autophagy. However, the IRE1b splicing target, bZIP60, did not seem to be involved, suggesting the existence of an undiscovered signaling pathway to regulate ER stress–induced autophagy in plants. Together, these results suggest that autophagy serves as a pathway for the turnover of ER membrane and its contents in response to ER stress in plants.     

Further Observations with the Electron Microscope on Spermatozoids in the Brown Algae

Observations are recorded for Ascophyllum, Pelvetia, Himanthalia,and Dictyota in addition to Fucus which has already been describedin a previous paper. Fibrillar disintegration of cilia has beenobtained in all except Pelvetia, in each case to give nine peripheralstrands and a central pair. This corrects a previous error forthe hind flagellum of Fucus. Some facts are given regardingthe internal organs associated with the parts of the cilia insidethe body in Himanthalia and Dictyota. A proboscis similar tothat previously described for Fucus has been demohstrated inAscophyllum and Pelvetia, but is absent from Himanthalia andDictyota. Himanthalia differs from the other Fucoids in therelative lengths of front and hind flagella. Dictyota has onlya single flagellum. In all, the front flagellum is a Flimmergeisselwith two rows of hairs, which, in certain cases, notably Himanthalia;have very long hair points. In Himanthalia there is a largespine near the distal end of the front flagellum borne on onefibril of the peripheral series. In Dictyota there is a rowof smaller spines at the front end of the flagellum borne ina line between the two lateral rows of hairs. These spines inDictyot can be used as evidence regarding the internal symmetryof the whole cilium which is summarized in a diagram.     

Involvement of the Endoplasmic Reticulum of Chromaffin Cells of the Rat Adrenal Gland in Calcium Signaling

We studied the involvement of the endoplasmic reticulum (ER) in calcium signaling in rat chromaffin cells. For this purpose, the following agents influencing the activity of the ER were used: (i) Caffeine that activates the release of Ca²⁺ from the endoplasmic store and (ii) thapsigargin that suppresses accumulation of calcium in the ER. The intracellular Ca²⁺ concentration was measured with the help of a calcium-sensitive dye, Fura-2AM, using the microfluorescent technique. Applications of caffeine led to a rise in the level of free Ca²⁺ in the cell cytosol and also to a decrease in the amplitude of calcium transients induced by depolarization of the plasma membrane under the action of a hyperpotassium solution. Under conditions of repeated caffeine applications, the amplitude of transients decreased to 9% of its initial value, which is explained by exhaustion of the calcium stores. The action of caffeine was restored when the calcium stores were re-filled under the action of depolarization of the plasma membrane. Thapsigargin completely removed the effect of caffeine and did not influence KCl-induced transients. Therefore, our experiments are indicative of a significant importance of the ER calcium stores for calcium signaling in chromaffin cells, which allows us to hypothesize that these stores play an important role in the control of secretion of catecholamines.     

Glycoprotein Folding in the Endoplasmic Reticulum

Our understanding of eukaryotic protein folding in the endoplasmic reticulum has increased enormously over the last 5 years. In this review, we summarize some of the major research themes that have captivated researchers in this field during the last years of the 20th century. We follow the path of a typical protein as it emerges from the ribosome and enters the reticular environment. While many of these events are shared between different polypeptide chains, we highlight some of the numerous differences between proteins, between cell types, and between the chaperones utilized by different ER glycopro-teins. Finally, we consider the likely advances in this field as the new century unfolds and we address the prospect of a unified understanding of how protein folding, degradation, and translation are coordinated within a cell.     

Electron Microscope Observations on in Vitro Cultures of the Isolated Fowl Embryo Otocyst

In vitro cultures of isolated fowl embryo otocysts were studied with the electron microscope. Hair cells of the developing organ of Corti and crista ampullaris have been examined with particular reference to the structure of the cilia and of the cell membrane. Two types of hair cells could be distinguished on the basis whether or not they possessed a "kinocilium" and "stereocilia," or "stereocilia" only. The cytoplasmic membranes were simple and there were no multiple vesicular layers in any of the hair cells. The supporting elements consisted of supporting cells flanking the hair cells, fibroblasts, and the cartilaginous otic capsule. Both the cochlear and vestibular sensory area showed rich innervation by mainly non-myelinated fibers with partial myelinization in others. There were well developed ganglion cells present. Bare axons penetrated the basement membrane and spread, amongst the supporting cells sheltering them, to the base of the hair cells where they formed bud-shaped nerve endings but, at the stage of development examined, no calyces. These in vitro cultures of the isolated fowl embryo otocyst provided convenient and suitable material for the electron microscope study of the sensory epithelium of the ear and revealed further that the isolated fowl embryo otocyst possesses great powers of self-differentiation also at the ultrastructural level.     

Electron Microscope Observations on Spore Formation in the True Slime Mold Didymium nigripes

SYNOPSIS. Developing and mature sporangia of the true slime mold Didymium nigripes were studied with the electron microscope to follow the course of spore formation. The sporangium forms from the plasmodium as a protoplasmic bleb which differentiates into a stalk and an apical sphere containing a mass of protoplasm. Nuclei within this protoplasmic mass undergo synchronous division (presumably meiosis). The division spindle forms within the nuclear membrane which is retained intact throughout the division; centrioles have not been observed at the spindle poles. At the same time the nuclei are dividing, the protoplasm cleaves to give ultimately uninucleate spheres—the incipient spores. Capillitial threads come to lie in the furrows created by the cleaving protoplasm. A wall consisting of an inner thick component and an outer thin component forms about each sphere. Cyto-chemical tests suggest that the inner wall of the spore is cellulose-containing and that the outer component might contain chitin.     

Observations with the Electron Microscope on Biciliate and Quadriciliate Zoospores in Green Algae

Quadriciliate zoospores of Draparnaldia and biciliate zoosporesof Chaetomorpha have been examined using our previous methods.New features have been seen in both, chiefly in connexion withthe basal organs which attach the cilia to the cytoplasm ofthe parent cell.     

Electron Microscope Study of the Human Neuromuscular Junction

A preliminary electron microscope study of human neuromuscular junction is presented. The biopsy material was taken from the palmarus longus, and fixed routinely in osmium tetroxide and embedded in methacrylate. The structure of the motor endings and the relationship of the synaptic vesicles to the axolemmal membrane are described. The synaptic clefts are filled with an homogeneous material in continuity with the basement membrane covering the muscle fiber. The subneural apparatus is described, and special attention is paid to a vesicular component present in the sarcoplasm of the junctional area, which differs from synaptic vesicles and is presumed to be a derivate of the sarcoplasmic reticulum.     

植物内质网胁迫研究进展

内质网是蛋白质折叠和蛋白质糖基化修饰的重要场所。在内质网中存在多种调控机制来确保其中的蛋白质被正确地折叠、修饰和组装,以维持内质网稳态,这对于细胞正常的生理活动十分重要。然而,多种物理、化学因素均可使内质网稳态失衡,即在应激条件下,错误折叠和未折叠蛋白质的大量积累将导致内质网胁迫(endoplasmic reticulum stress, ERS),进而会引起未折叠蛋白质响应(unfolded protein response, UPR),极端情况下还会启动细胞程序性死亡(program cell death, PCD)。目前,植物内质网胁迫方面的研究较酵母和动物滞后,因此,从内质网质量控制系统和未折叠蛋白质响应2个方面对植物内质网胁迫现有研究进行了综述,以期为进一步理解内质网胁迫与植物逆境胁迫的关系提供参考。     

N-Linked Protein Glycosylation in the Endoplasmic Reticulum

The attachment of glycans to asparagine residues of proteins is an abundant and highly conserved essential modification in eukaryotes. The N-glycosylation process includes two principal phases: the assembly of a lipid-linked oligosaccharide (LLO) and the transfer of the oligosaccharide to selected asparagine residues of polypeptide chains. Biosynthesis of the LLO takes place at both sides of the endoplasmic reticulum (ER) membrane and it involves a series of specific glycosyltransferases that catalyze the assembly of the branched oligosaccharide in a highly defined way. Oligosaccharyltransferase (OST) selects the Asn-X-Ser/Thr consensus sequence on polypeptide chains and generates the N-glycosidic linkage between the side-chain amide of asparagine and the oligosaccharide. This ER-localized pathway results in a systemic modification of the proteome, the basis for the Golgi-catalyzed modification of the N-linked glycans, generating the large diversity of N-glycoproteome in eukaryotic cells. This article focuses on the processes in the ER. Based on the highly conserved nature of this pathway we concentrate on the mechanisms in the eukaryotic model organism Saccharomyces cerevisiae.The presence of glycans on proteins is known to influence their stability and solubility and the glycan core can contribute to folding processes (Shental-Bechor and Levy 2008; Hanson et al. 2009; Culyba et al. 2011). N-glycans also influence the function and activity of proteins (Skropeta 2009). The terminal residues of N-glycans play a key role in the quality control of protein folding in the ER. Ultimately the glycan signals whether a protein is correctly folded and can leave the ER to continue its maturation in the Golgi or whether the protein is not correctly folded and is degraded (Helenius and Aebi 2004; Aebi et al. 2010). It is therefore of great importance that the oligosaccharide to be transferred to proteins is complete. This “quality control” of the oligosaccharide is mediated by the substrate specificity of oligosaccharyltransferase.     

藏红花素诱导人胶质瘤U251细胞内质网应激性凋亡的研究

目的:研究藏红花素对人胶质瘤U251细胞的促凋亡作用和可能的机制。方法:不同浓度藏红花素处理U251细胞后,MTT法检测细胞活力,TUNEL染色观察细胞凋亡情况。结果:①藏红花素显著抑制U251细胞的增殖,并诱导其发生凋亡。②藏红花素增加了U251细胞胞浆内钙离子的含量,并上调了内质网分子伴侣GRP78的表达。③藏红花素处理后的U251细胞内质网相关凋亡分子CHOP,Caspase-4,JNK活性明显增高。结论:藏红花素通过诱导内质网应激性凋亡抑制人胶质瘤U251细胞的增殖。     

建兰类原球茎体生长、发育过程中扫描电镜观察

建兰(Cymbidium ensifolium)类原球茎体(PLB)培养在含3％蔗糖和不含蔗糖的1/2 MS_0培养基中生长,比较连续光照、8h光照和黑暗条件下原球茎生长发育的动态进程。扫描电镜观察表明:原球茎表面布满密集的发育程度不同的分生区,随继代培养进程,形成分株更多的丛生形原球茎,连续光照促进分生区的增殖,黑暗不利于分生区的发育,在无糖源培养基中生长的PLB,分生区的细胞伸长,发育呈管状结构,这种结构丧失分生能力。在原球茎顶端分化叶原基,并可分化类似气孔的保卫细胞。     

Studies on Cartilage: Electron Microscope Observations on Normal Rabbit Ear Cartilage

Normal rabbit ear cartilage studied with the light and electron microscope shows chondrocytes in which large lipide spherules, and an abundance of glycogen, a few small mitochondria, and relatively few elements of the endoplasmic reticulum can be identified. The chondrocytes contain, in addition, a material which stains strongly with acid fuchsin and appears in the electron microscope as a relatively dense felt-work. In electron micrographs, the matrix of normal rabbit ear cartilage consists of two components: a uniformly distributed moderately dense substance which appears as a fine meshwork without any particular pattern extending from cartilage cell border to cartilage cell border; and a three-dimensional anastomotic network of more dense material, which is best described as "felt-like" lying between the cells. The similarity between the felt-like material of the matrix and the elastic fibers described in previous electron microscope observations is discussed.     

藏红花素诱导人胶质瘤U251细胞内质网应激性凋亡的研究

目的：研究藏红花素对人胶质瘤U251细胞的促凋亡作用和可能的机制。方法：不同浓度藏红花素处理U251细胞后,MTT法检测细胞活力,TUNEL染色观察细胞凋亡情况。结果：①藏红花素显著抑制U251细胞的增殖,并诱导其发生凋亡。②藏红花素增加了U251细胞胞浆内钙离子的含量,并上调了内质网分子伴侣GRP78的表达。③藏红花素处理后的U251细胞内质网相关凋亡分子CHOP,Caspase-4,JNK活性明显增高。结论：藏红花素通过诱导内质网应激性凋亡抑制人胶质瘤U251细胞的增殖。