AN ELECTRON MICROSCOPE STUDY OF THE ENDOPLASMIC RETICULUM IN NEWT NOTOCHORD CELLS AFTER DISTURBANCE WITH ULTRASONIC TREATMENT AND SUBSEQUENT REGENERATION

Ultrasonic treatment of the tails of Triturus alpestris tadpoles, at intensities of 8 to 15 watts/cm², at 1 megacycle/sec., for 5 minutes, disrupted the epidermis and caused pycnosis in individual cells of the muscle and neural tube, but caused no damage to the notochord that could be detected by light microscopy. Electron microscopy showed that this ultrasonic treatment disordered nearly all the endoplasmic reticulum (ER) of the notochord cells into irregularly rounded vesicles, but within 3 hours after treatment some parallel arrays of normal endoplasmic reticulum were seen near, and continuous with, the outer nuclear membrane. In addition, a re-ordering of the previously disordered ER took place throughout the cytoplasm, in some cases. A classification was made of the state of the ER as shown in electron micrographs of material fixed immediately, 3, and 24 hours after treatment. This showed that more than half the total endoplasmic reticulum in notochord cells was normal again by 24 hours after treatment.     

AN ELECTRON MICROSCOPE STUDY OF THE EPITHELIUM IN THE NORMAL MATURE AND IMMATURE MOUSE CORNEA

1. An electron microscope study at high resolution of the corneal epithelium of the normal mature and immature mouse revealed new information regarding the submicroscopic appearance of these cells. 2. Two thin dense lines separated by a less dense area constituted the structure of the limiting surface membrane of epithelial cells; the thickness of this membrane was about 80 A. 3. Some differences in the appearance of the cytoplasm and mitochondria of cells from the immature mouse cornea and the appearance of the cytoplasm and mitochondria of cells from the adult mouse cornea were observed. 4. The basement membrane appeared as a dense band about 600 A wide separating the basal epithelial cells from the substantia propria. Suggestions of periodicity were seen in some phosphotungstic acid-treated specimens. 5. Round bodies believed to be bacteria were seen on the surface of the outer epithelial cells in the adult mouse cornea but not in the immature, unopened eye.     

AN ELECTRON MICROSCOPE STUDY OF THE GLAND CELLS OF THE MINK ENDOMETRIUM

Portions of mink endometrium in delayed implantation, early postimplantation, and pseudo pregnancy were fixed in buffered osmium tetroxide with sucrose, or potassium permanganate. After rapid dehydration the portions of endometrium were embedded in either methacrylate or epoxy resin. Examination of the cells from the body of the glands of the endometrium of delayed implantation revealed the presence of prominent terminal bars, numerous secretion granules, and membrane discs in the apical region of the cell. In the supranuclear and infranuclear regions, mildly dilated cisternae of the endoplasmic reticulum were present, and in many cells unusually large mitochondria were seen. Numerous changes were noted in the gland cells of the post implantation stage. The endoplasmic reticulum in the basal region was extensively dilated, and the nuclei were situated more centrally. Giant mitochondria were no longer present. The large secretion granules were not present, but smaller granules were seen, especially in the Golgi region. Some of the Golgi cisternae were dilated and the pattern of parallel membranes was consequently less distinct. It is suggested that gland cells in the postimplantation and pseudopregnancy stages exhibit evidence of greater secretory activity than those in the delayed implantation stage.     

THE ENDOPLASMIC RETICULUM OF GASTRIC PARIETAL CELLS

An electron microscopic survey has been made of the gastric parietal or oxyntic cell of the human, cat, beaver, dog, hamster, rat, mouse, and bat, and of the corresponding cell type in two species of frog, two species of toad, and the horned lizard. A feature consistently found in the parietal cells of the mammals or their equivalent in the lower vertebrates is the agranular endoplasmic reticulum, which takes the form of branching and anastomosing small tubules approximately 200 to 500 A in diameter, sometimes expanded into flattened cisternae. In mammalian parietal cells this form of the endoplasmic reticulum is found only in limited amounts, but in the corresponding secretory cells of the amphibia and reptilia the tubular agranular reticulum is abundant. It is believed to comprise a more or less continuous system of channels, but owing to their tortuous course only short profiles are seen in thin sections. Immediately subjacent to the plasmalemma at the free surface, the cytoplasm is relatively free of organelles but is occasionally traversed by the agranular reticulum, which appears to be continuous at some points with the cell surface. The possible participation of the agranular endoplasmic reticulum in hydrochloric acid secretion is discussed.     

OSMIUM STAINING OF ENDOPLASMIC RETICULUM AND MITOCHONDRIA IN THE RAT ADRENAL CORTEX

The zona fasciculata of the rat adrenal cortex synthesizes and secretes glucocorticoids. As observed after aldehyde fixation, the cells in this zone contain an extensive endoplasmic reticulum (ER), a small Golgi apparatus, a moderate number of lipid droplets, and abundant mitochondria with tubulovesicular cristae. Numerous areas within the endoplasmic reticulum and mitochondrial cristae appear clear. In addition, a small percentage of mitochondria encompasses large, clear areas. After immersion of finely minced adrenal cortex in unbuffered 2% OsO₄ (40–48 hr at 40°C), deposits of osmium are seen within the Golgi apparatus, the entirety of the ER, and occasionally within mitochondria. In some mitochondria, the deposits are within cristae; in others, within vacuoles; in still others, in both cristae and vacuoles. These localizations correspond best to the clear areas found in aldehyde-fixed tissue. Osmium is not deposited in lipid droplets, in bar-containing inclusions, in mitochondrial matrix inclusions, or in the peripheral, outer mitochondrial spaces. Addition of zinc-iodide to OsO₄ increases the amount of Golgi apparatus and mitochondrial staining. Adrenocorticotropin (ACTH) does not affect the localization of deposits; hypophysectomy decreases mitochondrial staining. This study (a) emphasizes the necessity for electron microscopic confirmation of osmium localization when this technique is used as a Golgi apparatus stain; and (b) suggests that the ER-staining pattern may be consistent in cells actively synthesizing steroids or steroid-like compounds.     

AN ELECTRON MICROSCOPE STUDY OF SILVER NITRATE REDUCTION IN LEAF CELLS

Brown , W. V., H. Mollenhauer , and C. Johnson . (U. Texas, Austin.) An electron microscope study of silver nitrate reduction in leaf cells. Amer. Jour. Bot. 49(1): 57–63. Illus. 1962.—As reported earlier in many studies, AgNO₃ is reduced quickly by the living chloroplasts of angiosperms. Electron microscope study has resolved the conflict of opinions concerning the exact location of the silver particles. Reduction of AgNO₃, as indicated by location of silver particles, occurs within the chloroplasts but not within the grana or pure stroma; it appears to be associated with the intergranal (also called stroma) lamellae. Silver particles are formed also at the surfaces of the cell wall, both in the middle lamella and at the inner surface, and also within plasmodesmata. It is concluded that chlorophyll is probably not involved directly in the reduction. There is some slight support for the popular hypothesis that ascorbic acid may be the chief reducing agent.     

A STUDY OF THE STRUCTURE OF SPLENIC SINUSES IN MAN AND IN THE ALBINO RAT WITH THE LIGHT MICROSCOPE AND THE ELECTRON MICROSCOPE

The splenic sinuses in the spleens of 5 human beings and 7 albino rats have been studied in the light microscope and electron microscope after fixation in Dalton's fluid and Palade's fluid and embedding in n-butyl methacrylate. Splenic sinuses are tortuous vascular channels of large but variable diameter which represent the first venous vessels in the spleen and make up almost the entire red pulp in man and in rats. These vessels are composed of reticulo-endothelial cells flattened to endothelial form and sheathed by a netted reticulum. The luminal surface of the endothelium is made highly irregular by delicate and variable cytoplasmic protrusions, slender corridors separating adjacent endothelial cells, anastomotic openings to other sinuses, bulgings of entire cells, and even thrusts of endothelium spanning the sinai lumen. The supporting reticulum presents a well developed latticed appearance in tangential sections of sinuses, but in most cuts is punctate or linear. The reticulum is composed of strands without limiting membranes, which, in substance, are amorphous and resemble basement membrane. Material identical in appearance to the substance of the reticulum may be present in the endothelium, suggesting that the reticulum is formed by endothelial cells. The endothelium also contains deposits of presumed ferritin and hemosiderin. The extreme luminal bulgings of endothelium suggest production of circulating monocytes or lymphocytes by detachment of endothelial cells. Sinuses are patent and collapsed to varying degrees. Patent sinuses are separated by collapsed sinuses and these collapsed sinuses appear to constitute splenic (Billroth) cords.     

AN ELECTRON MICROSCOPE STUDY OF THE DEVELOPMENT OF A MOUSE HEPATITIS VIRUS IN TISSUE CULTURE CELLS

Samples taken at different intervals of time from suspension cultures of the NCTC 1469 line of mouse liver—derived (ML) cells infected with a mouse hepatitis virus have been studied with the electron microscope. The experiments revealed that the viruses are incorporated into the cells by viropexis within 1 hour after being added to the culture. An increasing number of particles are found later inside dense cytoplasmic corpuscles similar to lysosomes. In the cytoplasm of the cells from the samples taken 7 hours after inoculation, two organized structures generally associated and never seen in the controls are observed: one consists of dense material arranged in a reticular disposition (reticular inclusion); the other is formed by small tubules organized in a complex pattern (tubular body). No evidence has been found concerning their origin. Their significance is discussed. With the progression of the infection a system of membrane-bounded tubules and cisternae is differentiated in the cytoplasm of the ML cells. In the lumen of these tubules or cisternae, which are occupied by a dense material, numerous virus particles are observed. The virus particles which originate in association with the limiting membranes of tubules and cisternae are released into their lumen by a "budding" process. The virus particles are 75 mµ in diameter and possess a nucleoid constituted of dense particles or rods limiting an electron transparent core. The virus limiting membrane is sometimes covered by an outer layer of a dense material. In the cells from the samples taken 14 to 20 hours after inoculation, larger zones of the cell cytoplasm are occupied by inclusion bodies formed by channels or cisternae with their lumens containing numerous virus particles. In the samples taken 20 hours or more after the inoculation numerous cells show evident signs of degeneration.     

几种不同进化程度动物细胞内质网超微结构的比较研究

应用稼射电镜技术,高锰酸钾固定扫描电镜技术及生化分离技术,比较研究了家兔、家鸽、蟾蜍,鲤鱼、脉红螺肝细胞和眼虫的内质网超微结构及含量。透射电镜观察结果显示：在高等哺乳动物肝细胞内质网丰富,以扁囊结构为主,在整个细胞质内均有分布,主要存在于核周围,并伴有伴随线粒体分布的特征;蟾蜍肝细胞内质网稀少,以长管状平行排列,分布在细胞质的局部,鲤鱼肝细胞内质网呈小泡状均匀分布在细胞质中,脉红螺肝细胞及眼虫细胞     

AN ELECTRON MICROSCOPE STUDY OF THE EARLY ASSOCIATION BETWEEN TWO MAMMALIAN VIRUSES AND THEIR HOSTS

Early interaction between two animal viruses, vaccinia and adenovirus 7, which multiply readily in L strain and HeLa cells, respectively, was examined in both whole mount preparations and in thin sections. To observe the association at the surface, cells carrying adsorbed virus were swelled under controlled conditions and then "stained" with neutral phosphotungstate. Each particle of both virus types becomes attached to the cell by several capsomeres and is then ingested by phagocytosis. Within the cell, near the surface, single particles or small clumps of adenovirus are lodged within vesicles. Deeper in the cytoplasm this virus is packed in large, numerous inclusions, whereas very close to the nuclear envelope only free particles are found. Vaccinia, on the other hand, either free or in vesicles, is always found in the cytoplasm, at some distance from the nucleus (11). Adsorption and intracellular disposition of these two viruses is discussed in relation to the infectious process.     

THYMIDINE-3H ELECTRON MICROSCOPE RADIOAUTOGRAPHY OF OSTEOGENIC CELLS IN THE FETAL RAT

The proximal tibial epiphyses of 18–21-day-old fetal rats have been studied by thymidine-³H radioautography. The results reveal that the label is incorporated into two types of osteogenic cells: (a) a spindle cell type (A cells) with characteristics generally associated with matrix production, including an extensive development of the endoplasmic reticulum and the presence of large intracellular accumulations of a dense, finely granular material, morphologically identifiable as glycogen; and (b) a rounded cell type (B cells) with morphological features similar in degree and kind to those of the developing neutrophilic leukocyte, including an abundance of free ribosomes and mitochondria and a complex Golgi apparatus associated with dense specific granules, morphologically identifiable with primary lysosomes. These results, along with the occurrence of recognizable, labeled, immature, perivascular forms of both of these A and B type cells, lead to the conclusion that the specialization of osteogenic cells into osteoclasts and osteocytes may involve separate pathways of cytodifferentiation.     

A LIGHT AND ELECTRON MICROSCOPE STUDY OF THE MORPHOLOGICAL CHANGES INDUCED IN RAT LIVER CELLS BY THE AZO DYE 2-ME-DAB

The cytological changes induced in rat liver cells by the aminoazo dye 2-Me-DAB have been examined by light and electron microscopy. It is observed that this non-carcinogenic compound duplicates most of the morphological alterations produced by other hepatotoxins, some of which, such as the closely related aminoazo dye 3'-Me-DAB, are potent carcinogens. These non-specific effects involve both the granular and agranular forms of the endoplasmic reticulum as well as the glycogen content of hepatic cells. The arrays of cisternal profiles of the granular reticulum in normal hepatic cells become disorganized and the dispersed cisternae often appear fragmented and irregular. Large cytoplasmic inclusions, consisting of loosely organized tubules and vesicles, are also observed which result from a hypertrophy of the agranular reticulum. The glycogen in the cells progressively decreases in amount. The most specific effect of 2-Me-DAB is to induce an increase in the number of mitochondria per cell. Many of these organelles are characterized by the presence of a median double membrane continuous with the inner limiting membrane of the mitochondrial envelope. Evidence is presented in favor of the view that this partition is directly related to the phenomenon of mitochondrial division. It was noted also in the course of the experiment that an increasing number of cells appear which stain quite intensely with methylene blue and appear denser than normal under electron microscopy. The significance of these cells is not known.     

中华绒螯蟹神经细胞和胶质细胞的光镜及电镜观察

中华绒螯蟹神经节存在神经细胞和胶质细胞两类细胞。神经细胞膜为３层,细胞质由内质网和核蛋白体的聚合体的所构成的尼氏体,高尔基体,线粒体,液泡等细胞器组成,核膜双层,核仁明显,胶质细胞内含有似神经细胞的细胞器结构,根据细胞核的形态及核内染色质的分布情况,可把胶质细胞分成３类：星形胶质细胞核最大,卵圆形,少突胶质细胞核较小,圆形;小胶质细胞核最小,呈三角形或卵圆形,神经细胞的数量与附肢的生理活动强弱有一     

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。     

AN ELECTRON MICROSCOPE STUDY OF RADIATION DAMAGE IN THE MOUSE OOCYTE

Cytological changes occurring in young oocytes of the mouse, following whole-body x-irradiation, have been examined by light and electron microscopy. Two minutes after a dose of 200 r, a drop occurs in the number of mitochondria per oocyte. The normal number of mitochondria is restored in the next few minutes. Five to 6 hours after a dose of 7 r, and 30 to 45 minutes following a dose of 200 r, all the oocytes are markedly contracted. In the next 2 hours (at a dose of 7 r), some cells shrink further and become pycnotic, while others expand and show signs of karyolysis. Of the expanded cells, some (about 50 per cent of total young oocytes) become morphologically normal. In both pycnotic and karyolytic nuclei, the nucleolus was contracted but without loss of its fibrillar structure. The contracted nucleolus appeared similar to those seen in some nearly mature normal oocytes (these oocytes have a high natural death rate). No other cell type in the ovary was affected by doses of x-rays up to 200 r. Observations on the nucleus of the normal oocyte are included. In the dictyate stage of meiotic prophase the chromosomes were dispersed into bundles of 100 A microfibrils. The main component of the nucleolus was found to be tightly coiled fibrils of 60 to 100 A, which appear to have a close relationship with the microfibrils of the chromosomes.