bluuebunny/crossref_metadata_2025 huggingface dataset:
LIVER PARENCHYMAL CELL INJURY
Authors: Reynolds Edward S.
Published: May 2004

The structure of the endoplasmic reticulum, plasma membrane, mitochondria, and Golgi apparatus of the liver parenchymal cell is strikingly altered within 1 hour following the administration of a single oral dose of carbon tetrachloride to rats. Progressive loss of glucose-6-phosphatase activity accompanies dispersal of the ergastoplasm. Electron microscopy reveals that these changes are associated with vacuolization of the cisternae of the granular endoplasmic reticulum, degranulation of its membranes, and the appearance of increased number of free ribosomes in the adjacent cytoplasmic matrix. Concomitantly, calcium enters the liver parenchymal cell and is sequestered by mitochondria. First increased at 30 minutes, calcium content is maximal at 1 hour and returns to normal at 2 hours. Although succinic and glutamic dehydrogenase activity patterns within the liver lobule are unaffected, liver cell mitochondria enlarge and some appear to fuse or assume cup-like configurations. Microvilli lining the space of Disse become irregularly indistinct and increasingly pleomorphic by 30 minutes when the plasma membrane becomes increasingly permeable to calcium. Golgi vesicles swell and discharge their granules during the period of poisoning studied. Although all the changes observed may be the result of direct interaction of carbon tetrachloride with the membranes of the cytoplasmic constituents of the liver parenchymal cell, the possibility that the irreversible changes observed in the granular endoplasmic reticulum may be due to the chemical interaction between the poison and this system is discussed.
CELL POPULATION KINETICS OF AN OSTEOGENIC TISSUE · I
Authors: Owen Maureen
Published: May 2004

Cell proliferation on the actively growing periosteal surface of the femur of rabbits aged 2 weeks has been investigated using autoradiographic techniques. Injections of tritiated glycine and tritiated thymidine were given simultaneously and the animals sacrificed at intervals from 1 hour to 5 days after injection. The glycine labeled the position of the bone surface at the time of injection and the thymidine labeled the cells which were synthesising DNA. The rate of increase in the cell population was determined by counting the number of cells beyond the glycine label at different times after injection. The cell kinetics of the fibroblast-pre-osteoblast-osteoblast-osteocyte system has been studied. The fibroblasts are relatively unimportant from the point of view of increase in the cell population. The main site of cell proliferation is the layer of pre-osteoblasts on the periosteal surface. The rate of movement of cells from the pre-osteoblast to the osteoblast and osteocyte compartments has been measured. The incorporation of osteoblasts into the bone is not a random process, but it appears that the osteoblast must spend a certain time on the periosteal surface before becoming either an osteocyte or a relatively inactive osteoblast lining an haversian canal. It was estimated that, on an average, an osteoblast produces 2 or 3 times its own volume of matrix during its most active period on the periosteal surface.
THE NUCLEUS OF NOCTILUCA SCINTILLANS
Authors: Afzelius Björn A.
Published: May 2004

The unicellular organism, Noctiluca, has been examined with the electron microscope. The nucleus is small compared to the very large size of the cell, but the nuclear border has an organization which indicates an active nucleocytoplasmic exchange. Whereas annuli are missing over most parts of the nuclear membrane proper, there are "annulated vesicles" in a layer inside the nuclear membrane. The hypothesis is put forth that nuclear substances move through the annuli into these vesicles, and that the annulated vesicles themselves are transported through the nuclear membrane. The various forms of the annulated vesicles are consistent with this hypothesis. An implication of this postulate is the synthesis of annulated membranes inside a closed nucleus which are physically separate from the endoplasmic reticulum. The chromosomes are in a state resembling prophase chromosomes and are surrounded by granular masses. Only a small portion of the entire nuclear volume is occupied by the chromosomes. There are many nucleolus-like bodies.
SYNTHESIS OF MESSENGER-LIKE RIBONUCLEIC ACID AND PROTEIN DURING MEIOSIS IN ISOLATED CELLS OF TRILLIUM ERECTUM
Authors: Hotta Yasuo , Stern Herbert
Published: May 2004

The synthesis of RNA and protein by cultures of isolated microsporocytes has been demonstrated. The variation in capacities of such cultures to perform syntheses is a function of meiotic stage and parallels the pattern of changes observed for microsporocytes in situ. A principal feature of this pattern is the induction of syntheses during pachytene and diplotene, stages at which the chromosomes are partly contracted. By use of Actinomycin D, chloramphenicol, pulse-labeling with P32-phosphate, and nucleotide analyses of RNA digests, part of the RNA synthesized has been shown to correspond to messenger RNA. Analysis of reaction rates and the overlappings of protein and RNA synthesis indicates that the spread of cytological events in Trillium is not purely a function of the low temperature at which it occurs but, presumably, arises from a complement of regulatory devices which govern the periodic onset of reactions within the cells. The main conclusion drawn from the whole of these studies is that the sequence of morphological changes associated with chromosome contraction and movement during meiosis is accompanied by a set of gene transcriptions. Although comparatively few genes are presumed to be active during meiosis, the action of such genes may be essential to a translation of some of the information embodying the meiotic sequence which has been stored in the genome in the course of evolution.
UPTAKE OF MAMMALIAN CHROMOSOMES BY MAMMALIAN CELLS
Authors: Choraży M. , Bendich A. , Borenfreund E. , Ittensohn O. L. , Hutchison D. J.
Published: May 2004

Chromosomes isolated from mouse leukemia L1210 cells were taken up by mouse macrophages, HeLa cells, and rat embryo fibroblasts following simple exposure in vitro. The process, which resembles pinocytosis or phagocytosis, was traced by autoradiography of chromosomes prelabeled with thymidine-H3, and by staining techniques and phase contrast microscopy. During the first six hours, the uptake of chromosomes was restricted to the cytoplasm, but there was some evidence of penetration into the nucleus after 16 and 26 hours of exposure. Treatment of rat fibroblasts with glucose and insulin markedly enhanced the uptake of chromosomes, whereas iodoacetate inhibited their penetration.
BRAIN MITOCHONDRIA
Authors: Beattie Diana S. , Sloan Howard R. , Basford R. E.
Published: May 2004

A mitochondrial fraction prepared from calf brain cortex possessed negligible glycolytic activity in the absence of the enzymes of the high speed supernatant fraction. When mitochondria were added to a supernatant system supplemented with optimal amounts of crystalline hexokinase, a 20 per cent stimulation of glycolysis was observed. The supernatant fraction produced minimal amounts of lactate in the absence of exogenous hexokinase; the addition of mitochondria doubled the lactate production. The substitution of glycolytic intermediates for glucose as substrates as well as the addition of exogenous glycolytic enzymes to the supernatant fraction or supernatant fraction plus mitochondria indicated that the mitochondria contributed mainly hexokinase and phosphofructokinase. By direct assay of all of the enzymes of the glycolytic pathway, only hexokinase and phosphofructokinase were shown to be concentrated in the mitochondrial fraction. All other glycolytic enzymes were found to exhibit higher total and specific activities in the supernatant fraction.
OBSERVATIONS ON THE VARIATIONS IN SIZE OF THE A REGION OF ARTHROPOD MUSCLE
Authors: Aronson John
Published: May 2004

The muscles of three different arthropods, a mite, a fly, and an ostracod, show variations in the length of the A region within a given individual. There is no indication that the observed differences in A band length are related to the functional state of the muscle since little, if any, decrease in the length of the A bands was noted when sarcomeres shortened. The length of the A region was determined by polarized light microscopy and in the case of the mite and the ostracod this measurement was made on intact muscles. It is concluded that the size of the A filaments in an individual can vary in a manner unrelated to immediate functional changes. The I filaments may vary in size, but this could not be clearly demonstrated.
THE FINE STRUCTURE OF EPENDYMA IN THE BRAIN OF THE RAT
Authors: Brightman M. W. , Palay S. L.
Published: May 2004

The ciliated ependyma of the rat brain consists of a sheet of epithelial cells, the luminal surface of which is reflected over ciliary shafts and numerous evaginations of irregular dimensions. The relatively straight lateral portions of the plasmalemma of contiguous cells are fused at discrete sites to form five-layered junctions or zonulae occludentes which obliterate the intercellular space. These fusions occur usually at some distance below the free surface either independently or in continuity with a second intercellular junction, the zonula adhaerens. The luminal junction is usually formed by a zonula adhaerens or, occasionally, by a zonula occludens. The finely granular and filamentous cytoplasm contains supranuclear dense bodies, some of which are probably lysosomes and dense whorls of perinuclear filaments which send fascicles toward the lateral plasmalemma. The apical regions of the cytoplasm contain the basal body complexes of neighboring cilia. These complexes include a striated basal foot and short, non-striated rootlets emanating from the wall of each basal body. The rootlets end in a zone of granules about the proximal region of the basal body, adjacent to which may lie a striated mass of variable shape. All components of the basal body complex of adjacent cilia are independent of each other.
THE CYTONUCLEOPROTEINS OF AMEBAE
Authors: Byers Thomas J. , Platt Dorothy B. , Goldstein Lester
Published: May 2004

Autoradiographs of whole Amoeba proteus host cells fixed after the implantation of single nuclei from A. proteus donors labeled with any one of 8 different radioactive amino acids showed that the label had become highly concentrated in the host cell nucleus as well as in the donor nucleus and that the cytoplasmic activity was relatively low. When these amebae were sectioned, the radioactivity was found to be homogeneously distributed throughout the nuclei. The effect of unlabeled amino acid "chaser," the solubility of the labeled material, and the long-term behavior of the labeled material gave evidence that the radioactivity was in protein. At equilibrium, the host cell nucleus contained approximately 30 per cent of the radioactivity distributed between the two nuclei. This unequal nuclear distribution is attributed to the presence of two classes of nuclear proteins: a non-migratory one that does not leave the nucleus during interphase, and a migratory one, called cytonucleoprotein, that shuttles between nucleus and cytoplasm in a non-random manner. It is estimated that between 12 per cent and 44 per cent of the cytonucleoproteins are present in the cytoplasm of a binucleate cell at any one moment. Nuclei of Chaos chaos host cells also concentrated label acquired from implanted radioactive A. proteus nuclei.
THE CYTONUCLEOPROTEINS OF AMEBAE
Authors: Byers Thomas J. , Platt Dorothy B. , Goldstein Lester
Published: May 2004

Radioactivity, apparently in cytonucleoproteins, from an amino acid-labeled nucleus implanted into a non-radioactive cell appeared in the host nucleus within 10 minutes, and the typical equilibrium ratio 70:30 donor nucleus radioactivity:host nucleus radioactivity was reached in 4 to 5 hours at 25°C. If such binucleates grew and divided, no localization of radioactivity was observable in cells fixed during mitosis, but the protein label remained concentrated in the daughter interphase nuclei for at least 4 generations. Continued migration of cytonucleoproteins was observed if these daughter nuclei were transplanted to other unlabeled cells. The Q10 (19° to 29°C) of the migration rate of radioactive cytonucleoproteins was ca. 1.3, suggesting that passage through the cytoplasm occurred by diffusion. Both non-migratory nuclear proteins and cytonucleoproteins appear to be synthesized in the cytoplasm.
ROLE OF THE GAMETE MEMBRANES IN FERTILIZATION IN SACCOGLOSSUS KOWALEVSKII (ENTEROPNEUSTA)
Authors: Colwin Arthur L. , Colwin Laura Hunter
Published: May 2004

Previous electron microscope studies of sperm-egg association in the annelid Hydroides revealed novel aspects with respect to the acrosomal region. To determine whether these aspects were unique, a comparable study was made of a species belonging to a widely separated phylum, Hemichordata. Osmium tetroxide-fixed polyspermic material of the enteropneust, Saccoglossus, was used. The acrosomal region includes the membrane-bounded acrosome, with its large acrosomal granule and shallow adnuclear invagination, and the periacrosomal material which surrounds the acrosome except at the apex; here, the acrosomal membrane lies very close to the enclosing sperm plasma membrane. After reaching the egg envelope, the spermatozoon is activated and undergoes a series of changes: the apex dehisces and around the resulting orifice the acrosomal and sperm plasma membranes form a continuous mosaic membrane. The acrosomal granule disappears. Within 7 seconds the invagination becomes the acrosomal tubule, spans the egg envelopes, and meets the egg plasma membrane. The rest of the acrosomal vesicle everts. The periacrosomal mass changes profoundly: part becomes a fibrous core (possibly equivalent to a perforatorium); part remains as a peripheral ring. The basic pattern of structure and sperm-egg association in Saccoglossus is the same as in Hydroides. Previous evidence from four other phyla as interpreted here also indicates conformity to this pattern. The major role of the acrosome is apparently to deliver the sperm plasma membrane to the egg plasma membrane.
HORMONAL CONTROL OF REVERSIBLE DEGENERATION OF FLIGHT MUSCLE IN THE COLORADO POTATO BEETLE, LEPTINOTARSA DECEMLINEATA SAY (COLEOPTERA)
Authors: Stegwee D. , Kimmel E. C. , de Boer J. A. , Henstra S.
Published: May 2004

In the hibernating (diapausing) Colorado potato beetle, Leptinotarsa decemlineata Say, the flight muscles show pronounced degeneration. The muscle fibrils are greatly reduced in diameter and the sarcosomes are virtually absent. Similar signs of degeneration could be produced by extirpation of the postcerebral complex of endocrine glands, the corpora cardiaca and corpora allata. Reimplantation of active postcerebral complexes resulted in a very rapid regeneration of the muscle fibrils and new formation of sarcosomes.
THE EFFECT OF ENUCLEATION ON THE DPN LEVEL OF AMEBA
Authors: Cohen Adolph I.
Published: May 2004

1. Amebae contain DPN at levels of from 1 to 4 x 10–13 moles per cell.

2. Following enucleation, nucleate and enucleate halves continue to have equal DPN contents over the six day period studied. Similarly, starving whole amebae maintain their DPN level over this period.

3. No reduced DPN could be detected in these aerobic animals. This remained true for whole amebae and for nucleate and enucleate halves over 5 days of starvation.

4. A method is described for the preparation and rapid separation of nucleate and enucleate ameba halves, based on a response of amebae to light.
THE ACTION OF CORTICOTROPIN (ACTH) ON NUCLEIC ACIDS AND SUBCELLULAR ELEMENTS OF THE ADRENAL CORTEX
Authors: Fiala Silvio , Sproul Edith E. , Fiala Anna
Published: May 2004

It was shown experimentally that ACTH causes an increase of cytoplasmic RNA and subcellular granules of the adrenal cortex shortly after administration. This effect was found to be concentrated primarily on the basophilic cytoplasmic granules and to be largely independent of cell division. The increase of nuclear RNA, DNA, and nuclear mass followed that of the cytoplasm. The observations indicate also that the mass increase of mitochondrial and chromidial systems is closely related to the increase in cytoplasmic, largely chromidial RNA.
ISOLATION AND PROPERTIES OF LIVER CELL NUCLEOLI
Authors: Monty K. J. , Litt M. , Kay E. R. M. , Dounce A. L.
Published: May 2004

1. The significance of the term nucleolus has been discussed.

2. A detailed method for the isolation of nucleoli from already isolated rat or cat liver nuclei has been presented.

3. The presence of DNA in isolated liver cell nucleoli has been indicated by histochemical methods.

4. The percentages of DNA and RNA in the isolated nucleoli have been determined by chemical analysis.

5. The specific activities of aldolase, arginase, and catalase have been determined for two subnuclear fractions and for the isolated nucleoli of rat and cat liver, and the relative amounts of these enzymes in the same subnuclear fractions and nucleoli of rat liver have been measured.

6. The significance of the above findings has been discussed and consideration has been given to what types of isolated nuclei might best serve as starting material for the isolation of nucleoli.

7. A new hypothesis has been presented that nucleoli of the liver cell type may function primarily in furnishing (directly or indirectly) templates for the synthesis of the particular enzymes that must govern the chemistry of mitosis.
AN ELECTRON MICROSCOPE STUDY OF SPERMATID DIFFERENTIATION IN THE TOAD, BUFO ARENARUM HENSEL
Authors: Burgos Mario H. , Fawcett Don W.
Published: May 2004

The differentiation of the spermatids of Bufo arenarum has been described from a study of electron micrographs of thin sections of testis.

The development of the acrosome from the Golgi complex takes place in much the same manner as in mammalian spermatogenesis but no acrosome granule is formed.

A perforatorium is described for the first time in this species. It is formed by a convergence of dense filaments that arise between the nuclear membrane and the head cap.

During maturation of the spermatid the chromatin undergoes striking physicochemical alterations. Fine chromatin granules uniformly dispersed in the karyoplasm are replaced by larger and larger aggregates and these ultimately coalesce to form a very dense sperm head.

Two centrioles of cylindrical form are situated very near the base of the sperm head. The longitudinal fibrils of the tail flagellum take origin from one, and the dense fibrous substance of the undulating membrane is closely related to the other.

Phase contrast cinematographic observations on the swimming movements of living toad sperm, when considered in relation to the fine structural components of the tail, suggest that there is a contractile component in the undulating membrane as well as in the axial fibrils.

The differences in the structure of mammalian and amphibian sperm tails are discussed in relation to differences in the character of their movements.
ELECTRON MICROSCOPY OF GROWING OOCYTES OF RANA PIPIENS
Authors: Kemp Norman E.
Published: May 2004

1. In the cytoplasm of oocytes of stage Y0, prior to the appearance of yolk, one observes a few scattered profiles of endoplasmic reticulum and numerous filamentous mitochondria, usually distributed at random but sometimes clustered. As the nuclear membrane begins to bulge outward, small granules and short rods appear in the perinuclear cytoplasm and endoplasmic reticulum becomes more prominent throughout the cytoplasm.

2. Coincident with the appearance of the first yolk platelets, which are deposited in a narrow peripheral ring within the endoplasm at stage Y1, protoplasmic processes, the microvilli, push out all over the surface of the oocyte. At the same time follicle cells pull away but remain attached to the oocyte at some points through finger-like processes which interdigitate with neighboring microvilli. It is estimated that the microvilli increase the absorptive area of the surface to about thirty-five times that of a simple sphere. Just beneath the microvillous layer is the basal protoplasm of the cortex, now containing tiny granules probably synthesized from newly absorbed raw materials. Cortical granules appear and become aligned below the basal layer on the external border of the endoplasm. Both the cortical granules and the yolk platelets measure up to 1 µ in diameter at this stage.

3. By stage Y3 (yolk filling peripheral three-fourths of cytoplasm), the basal layer of the cortex is folded so that it appears in section as alternating ridges and valleys. The microvilli now extend from the summits of the cortical ridges. Small, ring-shaped granules are abundant in the cortex. Cortical granules have increased to 2 µ in diameter.

4. Yolk platelets continue to be synthesized around the cortical granules and in the subjacent endoplasm. The largest platelets measured in the interior cytoplasm at stage Y4 (cytoplasm filled with yolk) were 3.7 µ wide by 5.8 µ long. Pigment granules increase in size from 0.15 µ in diameter at stage Y3 to 0.30 µ in diameter at stage Y4.
THE STRUCTURE OF INSECT VIRUS PARTICLES
Authors: Smith Kenneth M.
Published: May 2004

Thin sections have been cut of the virus particles from four types of insect virus diseases: cytoplasmic polyhedroses of lepidopterous larvae, a nuclear polyhedrosis of Tipula paludosa (Diptera), a granulosis from Melanchra persicariae (Lepidoptera), and a new virus disease without polyhedra from T. paludosa.

The cytoplasmic polyhedral viruses are thought to have composite particles in some cases. The shape and enveloping membranes of the different virus particles are compared. In the new virus disease of T. paludosa some of the virus particles appear to be empty; inclusion bodies surrounded by complicated membranes are also demonstrated.
Sedimentation Studies of Epidermal Keratins. Keratin A and Keratin B
Authors: Matoltsy A. Gedeon
Published: May 2004

Electrophoretically homogeneous keratin A and keratin B were studied in the ultracentrifuge. Both preparations revealed two fractions: one which sedimented rapidly and another which sedimented slowly. This indicated that both preparations are heterogeneous with respect to particle size.
UPTAKE AND TRANSFER OF PARTICULATE MATTER FROM THE PERITONEAL CAVITY OF THE RAT
Authors: Odor D. Louise
Published: May 2004

1. Colloidal mercuric sulfide or thorium dioxide injected intraperitoneally passes into the cytoplasm of the mesothelium of the mesentery and of the diaphragm as early as 15 to 30 minutes after the injection.

2. Between 15 minutes and 12½ hours the number of particles within the mesothelial cells increases as the time between injection and termination of the experiment is lengthened.

3. The particulate matter is usually localized in the cytoplasm within clear vacuoles or bodies having a relatively dense matrix.

4. A greater quantity of the absorbed material is commonly observed within the cytoplasm of the diaphragmatic than of the mesenteric mesothelium.
THE GOLGI ZONE OF THE RAT SPERMATID AND ITS ROLE IN THE FORMATION OF CYTOPLASMIC VESICLES
Authors: Clermont Yves
Published: May 2004

Electron microscopic study of the Golgi zone of the rat spermatids revealed two main types of vesicular structures: flat vesicles generally accumulated in stacks and spheroidal vesicles of various sizes. The Golgi zone of young spermatids showed a predominance of flat vesicles and small spherical vesicles, while the "residual" Golgi zone of the maturing spermatids displayed an increased number of large spherical vesicles and thus became increasingly vacuolated in appearance.

The images presented were suggestive of a transformation of the flat vesicles into spherical vesicles by fragmentation and dilatation and also of a passage of the spherical vesicles from the Golgi zone to the surrounding cytoplasm.
THE ULTRASTRUCTURE OF STRIATED MUSCLE AT VARIOUS SARCOMERE LENGTHS
Authors: Spiro David
Published: May 2004

1. Rest and equilibrium length muscle sarcomeres are composed of thin filaments (actin) which traverse the sarcomeres from the Z membranes up to the H band; at this level the filaments are considerably thicker and less numerous.

2. Shortening of muscle is associated with a transformation of thin into thick filaments in the A band.

3. These observations are discussed in terms of interaction of actin and myosin to form a supercoiled structure as the basis of contraction.
INFOLDED BASAL PLASMA MEMBRANES FOUND IN EPITHELIA NOTED FOR THEIR WATER TRANSPORT
Authors: Pease Daniel C.
Published: May 2004

Epithelia noted for their water transport have been studied by electron microscopy with particular emphasis upon basal specializations. Epithelia of the submaxillary gland, choroid plexus, and ciliary body are described in this article, and compared with previous observations on the kidney.

The basal surface of all these epithelia is tremendously expanded by folds which penetrate deeply into the cytoplasm. In the submaxillary gland this is particularly notable in cells of the serous alveoli and in the secretory ducts. In these instances the folds have a fairly regular distribution and have a marked tendency to turn back upon themselves and so form repeating S-shaped patterns. In the choroid plexus the penetrating basal folds are limited to the lateral regions of each ependymal cell where they blend with the intercellular membranes that are also folded. In the epithelium of the ciliary body it is the inner layer that is specialized. The surface adjacent to the cavity of the eye penetrates irregularly, nearly through the full depth of the cell layer. The exposed surface is, in a fundamental sense, the basal surface of this epithelial layer.

It is apparent that the pattern of folding is quite distinctive in the different epithelia. Therefore, the specializations should be regarded as analogous rather than homologous.

Topographic considerations presumably limit the manner in which basal cell surfaces might be expanded. Penetrating folds would seem to represent almost the only possible solution.
ASPECTS OF CILIARY FINE STRUCTURE IN EUPLOTES PATELLA
Authors: Roth L. E.
Published: May 2004

1. The functional unity of cirri and membranelles can result structurally only from extensions of the ciliary membrane.

2. The pellicle is composed of an outer pellicular membrane and an inner cytoplasmic membrane.

3. The ciliary rootlets are composed of numerous filaments 120 A in diameter with central areas of low density. They have no periodic structure.

4. The ciliary membrane is a double-layered structure continuous with the pellicular membrane. The cilia show the typical arrangement of nine double, peripheral and two single, central fibrils. All fibrils pass into the basal region, the peripheral ones joining with the rootlet filaments, while the central fibrils from the extreme proximal position of the basal region turn back toward the pellicle and appear to unite just beneath the cytoplasmic membrane.

5. The cilia (300 mµ diameter) taper at their tips to a diameter at least as small as 50 mµ. At a diameter of about 150 mµ, the fibrils begin to show a reduction in number.

6. The central ciliary fibrils may determine the possible directions of ciliary beat. These fibrils show an intrafibrillar structure in their basal portion, which involves regularly spaced 40 A granules.

7. These observations on Euplotes, together with the other evidence cited, are consistent with the hypothesis that ciliary motion is produced by the contraction of the peripheral fibrils, while the central fibrils perhaps determine the plane in which the cilia can bend.
STUDIES ON THE CORNEA. II. THE FINE STRUCTURE OF DESCEMET'S MEMBRANE
Authors: Jakus Marie A.
Published: May 2004

Descemet's membrane, previously thought to be "structureless," has been found to be characterized by a fine structure of great regularity. Sections perpendicular to the plane of the membrane surface appeared to be cross-striated, with narrow dark bands separated by wide light bands traversed by fine filaments. Tangential sections showed a two-dimensional array of dark nodes and thin internodal filaments which connected each node with the six others around it to form a hexagonal figure. The average distance between nodes, and between the dark bands in transverse sections, was about 1070 A; the width of the nodes was about 270 A; and the width of the connecting filaments was less than 100 A. This pattern has been found in all species of Descemet's membrane so far examined, although it appeared to be better developed in some forms than in others. So far as is known, it has not been observed in any other type of tissue.

The differentiation of Descemet's membrane has been followed in the chick embryo. It appeared late and developed slowly but showed the characteristic fine structure from the time it could be clearly identified.

The evidence for placing Descemet's membrane in the collagen class of proteins is strongly supplemented by the results obtained from x-ray diffraction examination by Rougvie and Bear.
ELECTRON MICROSCOPY OF CARTILAGE AND BONE MATRIX AT THE DISTAL EPIPHYSEAL LINE OF THE FEMUR IN THE NEWBORN INFANT
Authors: Robinson Robert A. , Cameron D. A.
Published: May 2004

An examination of the fine structure of cartilage and bone matrix at the distal epiphyseal line of the femur of a newborn infant has revealed the following information.

Cartilage matrix is composed of a network of widely spaced fibers without obvious periodic banding. Calcification is first seen about the level of the third chondrocyte capsule distal to the furthest penetration of the capillaries. It starts as a haphazard deposition of crystals which have no obvious relationship to the location of the fibers. The process of calcification is completed before ossification commences but the central zone of matrix remains only partly mineralized.

Bone matrix is formed over a bar of calcified cartilage. Fibers, recognizable as collagen, are deposited in a loose network in a narrow zone between the osteoblasts and cartilage. These fibers are 2 to 5 times as wide as the fibers in epiphyseal cartilage. Calcification then begins in the osteoid, crystals being first laid down irregularly on or close to the fibers. As they increase in number, the crystals tend to line up along the fibers and eventually are arranged so that the periodicity of the underlying collagen is emphasized. In such an area the fibers are more tightly packed than when uncalcified.

There is no change observed in the calcified cartilage at this level.

The extracellular matrices of this epiphyseal cartilage and bone can be distinguished from one another in the electron microscope.
OBSERVATIONS ON THE BASEMENT MEMBRANES IN RAT KIDNEY
Authors: van Breemen V. L. , Reger James F. , Cooper W. Gregory
Published: May 2004

Basement membranes in the kidney are made up of a homogeneous matrix. In argyria, silver passes from the blood in the ionic form and diffuses into the kidney basement membranes in which it is precipitated. X-ray diffraction studies of "silver-stained" rat kidneys show that most of the silver in the kidneys is combined with some form of sulfur. Histochemical staining for sulfhydryls and disulfides demonstrates the presence of these groups in basement membranes. It appears that silver ions combine with either or both the sulfhydryl or disulfide groups in the basement membranes and also in mitochondria (when the silver diffuses into a cell).
THE ULTRASTRUCTURE OF MOUSE LUNG
Authors: Karrer H. E.
Published: May 2004

The fine structure of the alveolar basement membrane of mouse lung was discussed on the basis of three electron micrographs. The basement membrane, i.e., the intercellular layer between endothelium and alveolar epithelium, was found to be of variable width. In its thin parts it appeared rather homogeneous, and did not reveal well defined layers of fibrils. In its thicker portions, some of which may be due to oblique sectioning, cell fragments could be seen lying inside the basement membrane layer. Their exact nature was not determined. In other thickened portions of the membrane bundles of slender (about 23 to 25 mµ) fibrils were found and were tentatively interpreted as collagen fibrils, in spite of the fact that a periodicity could not be observed.
THE INTERNAL ORGANIZATION OF MITOCHONDRIA
Authors: Powers E. L. , Ehret C. F. , Roth L. E. , Minick O. T.
Published: May 2004

Sections of mitochondria in Paramecium and Euplotes present a consistent pattern. The mitochondrion in these cells can be conceived of as a twisted mass of closely compacted tubules. Two general kinds of substances can be recognized: the electron-dense that borders the lumen of the tubule, and the less dense that forms the continuum. In sections of mitochondria in rat kidney and snail oviduct, tubular internal organization can be recognized. In the same organs, mitochondria with lamellar internal structure can be demonstrated. The thesis is developed that the mitochondrion is a structure capable of differentiation and change, and that developmental continuity among the different kinds may exist. Mitochondria that appear to be different may be quite similar basically; mitochondria that appear to be similar in structure may be different in other ways. The tubule is proposed as the most basic of the presently recognized mitochondrial structures.
GLOBOID STRUCTURES IN THE CYTOPLASM OF RAPIDLY GROWING HELA CELLS
Authors: Harford Carl G. , Hamlin Alice , Parker Esther , van Ravenswaay Theodore
Published: May 2004

During the course of electron microscopic study of rapidly growing uninfected HeLa cells, it was found that numerous globoid bodies occurred in the cytoplasm. Reasons are given for suspecting that these structures are mitochondria.
"MICROBODIES" AND THE PROBLEM OF MITOCHONDRIAL REGENERATION IN LIVER CELLS
Authors: Rouiller C. , Bernhard W.
Published: May 2004

The cytoplasm of the hepatic cell contains, besides the well known organelles, microbodies, characterized by a single membrane, a finely granular matrix, and average dimensions below those of mitochondria.

Microbodies, rare in normal cells, become more numerous in regenerative livers and in various pathological conditions. In these cases, they either evolve towards degenerative forms or else show structural modifications corresponding to transitional forms between them and mitochondria. This suggests to us that the microbodies can be precursors of mitochondria.
MITOCHONDRIAL STRUCTURE IN SITES OF STEROID SECRETION
Authors: Belt W. Duane , Pease Daniel C.
Published: May 2004

1. Mitochondria of the adrenal gland, corpus luteum, theca interna and granulosa of the graafian follicle, interstitial cells of the testis, and placenta of the rat have been studied with the electron microscope.

2. In most sites of steroid secretion, the internal structure of the mitochondria is in the form of tubular reflections of the internal mitochondrial membrane, rather than plate-like cristae.

3. The mitochondria of the adrenal gland have a highly variable size, even within a single cell; they may reach 2 to 3 µ in diameter, and are nearly filled with tubules.

4. It is suggested that while mitochondria in many places have a tubular component, those in the adrenal gland are highly specialized by virtue of their giant size and their internal structure.
SMALL GRANULES IN THE AMPHIBIAN OOCYTE NUCLEUS AND THEIR RELATIONSHIP TO RNA
Authors: Gall Joseph G.
Published: May 2004

Small particles (100 to 300 A in diameter) are seen in sections of nucleoli, the loops of the amphibian lampbrush chromosomes, and the Balbiani-ring regions of dipteran salivary-gland chromosomes. All of these structures contain cytochemically demonstrable RNA. Furthermore, the annuli seen on the nuclear envelope are composed of small particles which are similar to or identical with those commonly associated with the endoplasmic reticulum. It seems likely that ribonucleoproteins are organized as small particulates in the nucleus as well as in the cytoplasm.
FINE STRUCTURE OF CHROMOSOMES
Authors: Kaufmann Berwind P. , De Deepesh N.
Published: May 2004

Electron micrographs of staminate hair cells of Tradescantia reflexa indicate that early prophase chromosomes are composed of a number of helically arranged chromonemata. Favorable preparations reveal as many as 64 identifiable subsidiary strands, assumedly arranged as intertwined pairs to form a hierarchy of pairs of pairs. The helices of the smallest discernible units have a diameter of about 125 A, with highly electron-scattering material disposed peripherally around a less dense "core." The wall of this peripheral ring has a thickness of about 40 A, and apparently represents another pair of coiled threads surrounding a 40 A central axis. The implications of the findings are discussed briefly.
THE CHEMICAL FRACTIONATION OF LYMPHATIC ORGANS
Authors: Hess Eugene L. , Lagg Saima E.
Published: May 2004

A method for chemically fractionating lymphatic organs has been described. The method has been shown to be applicable to bovine palatine tonsils, sheep palatine tonsils, and bovine thymus. Approximately 50 per cent of the dry weight of tonsils and about 30 per cent of thymus has been found to be soluble in the 0.15 M NaCl extract. Four components have been isolated which together account for 65 per cent by weight of the material in the extracts. Four other components have been identified and partially defined by means of electrophoretic mobility, solubility, or some other chemical or physical property.
A POSSIBLE MECHANISM FOR THE MORPHOGENESIS OF LAMELLAR SYSTEMS IN PLANT CELLS
Authors: Hodge A. J. , McLean J. D. , Mercer F. V.
Published: May 2004

A mechanism for the formation of lamellar systems in the plant cell has been proposed as a result of electron microscope observations of young and mature cells of Nitella cristata and the plastids of Zea mays in normal plants, developing plants, and certain mutant types. The results are compatible with the concept that lamellar structures arise by the fusion or coalescence of small vesicular elements, giving rise initially to closed double membrane Structures (cisternae). In the chloroplasts of Zea, the cisternae subsequently undergo structural transformations to give rise to a compound layer structure already described for the individual chloroplast lamellae.

During normal development, the minute vesicles in the young chloroplast are aggregated into one or more dense granular bodies (prolamellar bodies) which often appear crystalline. Lamellae grow out from these bodies. In fully etiolated leaves lamellae are absent and the prolamellar bodies become quite large, presumably because of inhibition of the fusion step which appears to require chlorophyll. Lamellae develop rapidly on exposure of the plant to light, and subsequent development closely parallels that seen under normal conditions. The plastids of white and very pale green mutants of Zea similarly lack lamellae and contain only vesicular elements. A specialized peripheral zone immediately below the double limiting membrane in Zea chloroplasts appears to be responsible for the production of vesicles. These may be immediately converted to lamellae under normal conditions, but accumulate to form a prolamellar body if lamellar formation is prevented, as in the case of etiolation and chlorophyll-deficient mutation, or when the rate of lamellar formation is slower than that of the production of precursor material (as appears to be the case in the early stages of normal development).
CYTOCHEMICAL STUDIES OF MITOCHONDRIA
Authors: Siekevitz Philip , Watson Michael L.
Published: May 2004

1. Mitochondria isolated from rat liver were disrupted with 0.3 per cent deoxycholate and a number of subfractions were isolated from this preparation by differential centrifugation.

2. The protein N, RNA and phospholipide content, as well as the succinoxidase, cytochrome c oxidase, adenylate kinase, and DPNH-cytochrome c reductase of these fractions were determined.

3. Two of these subfractions, found to consist of mitochondrial membranes (2), contained ∼ 12 per cent of the protein N and ∼ 35 per cent of the phospholipide of the whole mitochondria and accounted for ∼ 70 per cent of the succinoxidase and cytochrome c oxidase activity of the original mitochondrial preparation. There was no discernible adenylate kinase, DPNH-cytochrome c reductase, or phosphorylating activities in these fractions, nor could they oxidize other substrates of the Krebs's cycle.

4. The most active fraction (60 minutes at 105,000 g pellet) had a higher phospholipide/protein value than the whole mitochondria and showed a seven-to elevenfold concentration of succinoxidase and cytochrome c oxidase activities.

5. Evidence has been given to indicate that the various components of the succinoxidase complex are present in this membrane fraction in the same relative proportions as in the whole mitochondria.

6. The implications of these findings are discussed.
ELECTRON MICROSCOPIC AND HISTOCHEMICAL OBSERVATIONS OF MUSCLE DEGENERATION AFTER TOURNIQUET
Authors: Moore Dan H. , Ruska Helmut , Copenhaver Wilfred M.
Published: May 2004

As an experimental model for the different forms of muscle degeneration, injury caused by 2 hours' ischemia has been studied from 20 minutes to 16 hours after release of the tourniquet.

Discoid degeneration developed in stretched fibers by dissolution of the I bands (Z substances and actin). The discs represented the Q bands (A-H-A). In fibers which passively maintained contraction lengths during degeneration, the Z substances were dissolved, but the continuity of the fibrils was preserved, since the filaments are continuous over all sarcomeres under these conditions. Mitochondria and the tubules of the endoplasmic reticulum swelled, ruptured, and disintegrated. Granular degeneration developed in fibers where mitochondria were abundant. Unstretched degenerating fibers with few mitochondria gave a homogeneous or hyaline appearance. The different forms of degeneration therefore were dependent on the status of stretch and the fiber type. The extent of degeneration was not a function of time after ischemia, there being both nearly normal and severely damaged fibers at 20 minutes and 16 hours after the release of tourniquets. When degeneration occurred, however, the basic alterations were the same in all fibers; there was mitochondrial and reticular swelling, dissolution of the Z substances, and finally disintegration of the contractile material. Some damage developed in the sarcolemmas and capillaries.

The mitochondrial disintegration was not linked with inactivation of the succinic dehydrogenase system.
THE CONTENT AND RELATIVE BASE RATIOS OF RIBONUCLEIC ACID IN AMOEBA
Authors: Iverson Ray M.
Published: May 2004

The amount and relative base ratios of ribonucleic acid (RNA) in the nucleus and cytoplasm of Amoeba proteus and A. dubia, and of homospecies cells obtained by nuclear transfer with A. proteus, have been determined by microelectrophoresis. In A. proteus the average amounts of RNA in the nucleus and the cytoplasm were 134. micromicrograms and 2520. micromicrograms; in A. dubia the averages for the nucleus and cytoplasm were 67. micromicrograms and 1427. micromicrograms. The relative base ratio of RNA of the nucleus is similar to that of the RNA of the cytoplasm within a species, but the two species differed in this respect. Homospecies nuclear transfer did not affect the relative base ratio or amount of RNA.
LAMINATED MEMBRANE SURFACE AND OSMIOPHILIC INCLUSIONS IN AVIAN LUNG EPITHELIUM
Authors: Tyler W. S. , Pangborn J.
Published: May 2004

A study of the fine structure of the avian lung revealed the presence of a unique laminated membrane surface and associated osmiophilic inclusions in epithelial cells of the tertiary bronchi and atria. These structures were not found in the air-capillary epithelium. Each lamination of the membrane surface had the appearance and dimensions of the unit membrane. It is suggested that the laminated membrane surface is associated with the formation of the osmiophilic inclusions and that these inclusions compare with those described in mammalian alveolar epithelium. It is further suggested that the laminated membrane surface is lipoprotein or phospholipid in composition and is responsible for the surface-tension-reducing properties of avian lung extracts.
THE RELATION BETWEEN THE INTRACELLULAR RIBONUCLEIC ACID DISTRIBUTION AND AMINO ACID INCORPORATION IN THE LIVER OF THE DEVELOPING CHICK EMBRYO
Authors: Duck-Chong Coral , Pollak J. K. , North R. J.
Published: May 2004

The RNA-P and DNA-P content of the nucleus and the RNA-P content of the whole cell of the livers of 8- to 20-day chick embryos and of adult fowls have been determined. The DNA-P content of the liver nuclei was slightly higher in the 8- and 10-day embryo than in all the other stages examined. A significant decrease in the RNA content of the cell occurred during embryonic development. The RNA content of the adult cell was the same as that of the 14- to 16-day embryo. The proportion of the cellular RNA contributed by the nucleus also decreased during development. In respect to both nuclear RNA content and distribution of RNA between nucleus and cytoplasm, the adult resembled the 8- to 12-day embryo. Examination of the fine structure of the cell showed that, as development progressed, free ribosomes decreased in number and the rough membranes increased. Slices of 8-, 14-, and 20-day embryonic livers and of adult livers were incubated with 14C-leucine, and the amount of labeled amino acid incorporated into whole tissue protein and into the proteins of the subcellular fractions was measured. Embryonic liver incorporated 14C-leucine 15 to 30 times more rapidly than adult liver. The microsomal protein was always more highly labelled than the protein in any other subcellular fraction; however, in the 8-day embryonic and the adult liver the proportion of total counts found in the nuclear fraction was considerably higher than in the 14- or 20-day embryonic liver. The significance of an apparent correlation between the proportion of the cell's RNA contributed by the nucleus and the proportion of total counts in the nuclear fraction is discussed.
THE MECHANISM OF ADHESION OF CELLS TO GLASS
Authors: Curtis A. S. G.
Published: May 2004

An optical technique for measuring the thickness of thin films has been adapted and evaluated for studying the structure of the adhesion of cells to glass in tissue culture. This technique, which is termed interference reflection microscopy, has been used to study embryonic chick heart fibroblasts. These findings have been observed: in normal culture medium the closest approach of the cell surface to substrate in its adhesions is ca. 100 A, much of the cell surface lying farther away; chemical treatments which bring the cell surface to near its charge reversal point reduce the closest approach of adhesions to <50 A, probably to <30 A; chemical treatments which increase surface charge increase the nearest approach of cell and substrate in adhesions from ca. 100 A; high osmotic concentration of a non-polar substance, i.e. sucrose, does not affect the distance between cell and substrate in the adhesions. In addition, optical evidence indicates that there is no extracellular material between cell and glass in the adhesions. When cells de-adhere from glass, they appear not to leave fragments behind. The adhesive sites in these fibroblasts appear to be confined to the edge of the side of the cell facing the substrate and to the pseudopods. The significance of this is discussed in relation to the phenomenon of contact inhibition. Evidence is presented that the mechanism of cell adhesion does not involve calcium atoms binding cells to substrate by combining with carboxyl groups on cell surface, substrate, and with a cement substance. Osmium tetroxide fixation results in a final separation of 100 to 200 A between cell and substrate: there are reasons for thinking that this fairly close approach to the condition in life is produced as an artefact. The results can be accounted for only in terms of the action of electrostatic repulsive forces and an attractive force, probably the van der Waals—London forces. Biological arguments suggest that these results are equally applicable for cell-to-cell adhesions.