bluuebunny/crossref_metadata_2025 huggingface dataset:
FIBRILLAR DIFFERENTIATION IN MYXOMYCETE PLASMODIA
Authors: McManus Sister M. A. , Roth L. E.
Published: May 2004

Myxomycete plasmodia of four different types (not including Physarum polycephalum) were studied in thin sections viewed in the electron microscope. In the cytoplasm of the protoplasmodia of Clastoderma debaryanum and the phaneroplasmodia of Fuligo septica fixed in situ, fibrillar differentiations of three rather distinct kinds were observed. One of these is filamentous and closely resembles the filaments (or "microtubules") of the mitotic apparatus of other species. The larger phaneroplasmodia of two species belonging to the Physarales and the plasmodium of Hemitrichia vesparium showed fewer and less well defined fibrils, and no fibrils were seen in the aphanoplasmodium of Stemonitis fusca. Good stabilization of such fibrils in larger plasmodia may require fixation methods more rigidly controlled than those which succeed with microscopic protoplasmodia. The function of the observed fibrils cannot yet be determined. Their presence in cytoplasm fixed in situ, however, lends support to those theories of protoplasmic movement which are dependent on integral cross-bonding of one or a few molecular species.
THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM
Authors: Nakajima Hiromichi , Allen Robert D.
Published: May 2004

Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light.
ELECTRON MICROSCOPIC AUTORADIOGRAPHY OF GERMINAL CENTER CELLS IN MOUSE SPLEEN
Authors: Swartzendruber D. C. , Hanna M. G.
Published: May 2004

The fine structure of tritiated thymidine-labeled cells in antigen-stimulated mouse spleen germinal centers is described. In studies on the ultrastructural level, two labeled cell types found in germinal centers are observed. Large lymphocytes are characterized by their very numerous free ribosomes, a paucity of endoplasmic reticulum, relatively few mitochondria, and a poorly developed Golgi region. The nuclei are large and vesicular, and large nucleoli are present. A second labeled cell type appears to contain more mitochondria and has a higher development of the Golgi area. The nucleus contains large, numerous blocks of chromatin, indicative of a more differentiated cell type. Reticular cells, both phagocytic and non-phagocytic, were not observed to be labeled in the germinal centers.
A STUDY OF PHAGOCYTOSIS IN THE AMEBA CHAOS CHAOS
Authors: Christiansen Richard G. , Marshall John M.
Published: May 2004

The process of phagocytosis was investigated by observing the interactions between the ameba Chaos chaos and its prey (Paramecium aurelia), by studying food cup formation in the living cell, and by studying the fine structure of the newly formed cup using electron microscopy of serial sections. The cytoplasm surrounding the food cup was found to contain structures not seen elsewhere in the ameba. The results are discussed in relation to the mechanisms which operate during food cup formation.
HYDROXYPROPYL METHACRYLATE, A NEW WATER-MISCIBLE EMBEDDING MEDIUM FOR ELECTRON MICROSCOPY
Authors: Leduc Elizabeth H. , Holt S. J.
Published: May 2004

Aldehyde-fixed rat tissues were variously dehydrated and impregnated in water-miscible 2-hydroxypropyl methacrylate (HPMA) containing 3 to 20 per cent water and 0.1 per cent α,α-azobisisobutyronitrile as catalyst for subsequent polymerization with ultraviolet light. Heat polymerization was also effective. Blocks of embedded tissue readily gave ultrathin sections, which required staining by uranyl acetate and/or lead stains to give adequate contrast for electron microscopy. The ultrastructure of pancreas, kidney, muscle, and intestine was well preserved by aldehyde fixation alone. Use of postfixation in osmium tetroxide or direct osmium tetroxide fixation was unsatisfactory. The fine structure of aldehyde-fixed liver from fasted rats was well preserved, whereas that from normal rats showed considerable disorganization and collapse, apparently because of extraction of glycogen during the embedding procedure. Enzymatic extraction of proteins by pepsin and of ribonucleic acid by ribonuclease after either formaldehyde or glutaraldehyde fixation was rapidly effected by direct treatment of ultrathin sections with solutions of the enzymes. In contrast, no digestion of chromatin by deoxyribonuclease could be detected. In spite of this present limitation, HPMA appears to have several advantages over earlier water-miscible embedding media for electron microscopy and to be particularly suitable for ultrastructural cytochemistry.
THE ULTRASTRUCTURE OF GLIOSOMES IN THE BRAINS OF AMPHIBIA
Authors: Srebro Zbigniew
Published: May 2004

Small fragments of superficial neuropil and fragments of deeper layers from various regions of the brains of Xenopus laevis Daud. and Rana esculenta L. were fixed in buffered osmium tetroxide, embedded in Vestopal W or methacrylate, and studied with the electron microscope. The glial fibers and their meningeal end-feet contain numerous large mitochondrion-like dense bodies for which the term "gliosome" has been adopted. Gliosomes have a specific and constant structure characterized by the presence of a row of peripheral and circular canaliculi and an electron-opaque fibrous or finely granular matrix. Also, another less frequently found type of gliosome is present which contains regular lamellar structures. The gliosomes vary considerably in size and may be very large, up to 9 µ in length. Numerous and various intermediate forms between mitochondria and gliosomes can be seen. Gliosomes are largest and most numerous in the distal portions of the glial fibers and in the meningeal end-feet.
A COMPARISON OF THE FINE STRUCTURES OF FROG SLOW AND TWITCH MUSCLE FIBRES
Authors: Page Sally G.
Published: May 2004

The organisation of the myofibrils and the sarcoplasmic reticulum in frog slow muscle fibres has been compared with that in twitch fibres. It has been found that the filaments have the same length in the two types of fibre, but that there are differences in their packing: (a) in contrast to the regular arrangement of the I filaments near the Z line in twitch fibres, those in slow fibres are irregularly packed right up to their insertion into the Z line; (b) the Z line itself shows no ordered structure in slow fibres; (c) the fine cross-links seen between the A filaments at the M line level in twitch fibres are not present in slow fibres. The sarcoplasmic reticulum in slow fibres consists of two separate networks of tubules. One set of tubules (diameter about 500 to 800 A) is oriented mainly in a longitudinal direction. The tubules of the other network (diameter about 300 A) are oriented either transversely at approximately Z line level or longitudinally, connecting the transverse tubules. Triads are very rarely found, occurring at only every 5th or 6th Z line of each fibril. The central element of these triads is continuous with the thin tubules. Slow fibres from muscles soaked in ferritin-containing solutions contain ferritin particles in the network of thin tubules, the rest of the sarcoplasm remaining free of ferritin.
CYTOLOGICAL ALTERATIONS RELATED TO STIMULATION OF THE ZONA GLOMERULOSA OF THE ADRENAL GLAND
Authors: Giacomelli Filiberto , Wiener Joseph , Spiro David
Published: May 2004

The structure of the zona glomerulosa of the rat adrenal gland stimulated by sodium restriction has been studied by light and electron microscopy. The major changes observed during the course of the experiment in stimulated glands involve cytoplasmic droplets, mitochondria, and the endoplasmic reticulum. There is a progressive decrease in the number of cytoplasmic droplets of low electron opacity. Numerous, greatly elongated mitochondria containing parallel arrays of tubules are noted. These tubules extend from within the mitochondria through gaps in the mitochondrial-limiting membranes into the cytoplasm. In addition, amorphous intramitochondrial deposits, possibly aldosterone precursors, are seen. Increased amounts of smooth-surfaced endoplasmic reticulum, often showing complex arrangements, are another feature of the stimulated zona glomerulosa. Other alterations include the presence of large numbers of dense bodies as well as cytoplasmic droplets of high electron opacity. These observations are discussed in relation to the biosynthesis of aldosterone.
THE RELATIONSHIP BETWEEN THE STRUCTURE AND ACTIVITY OF RAT SKELETAL MUSCLE MITOCHONDRIA AFTER THYROIDECTOMY AND THYROID HORMONE TREATMENT
Authors: Gustafsson R. , Tata J. R. , Lindberg O. , Ernster L.
Published: May 2004

The fine structure of rat gastrocnemius muscle fibers has been studied after changes were induced in the basal metabolic rate (BMR) by thyroidectomy and L-thyroxine administration under anabolic conditions. Biochemical analysis of skeletal muscle mitochondrial respiration and phosphorylation from the same tissue preparations has been summarized, details having been published earlier (3). As estimated from electron micrographs, the total amount of mitochondria from thyroidectomized animals was enlarged 1.5 times over that from normal controls. The total amount of mitochondria from thyroidectomized or normal animals made hypermetabolic with thyroxine was increased 2.5 to 3.5 times over that from their corresponding controls. In all cases, there was an increase in the mitochondrial population and the profile ratio of cristae to matrix was also considerably increased, thus indicating both relative and absolute enlargements of the entire surface of the cristae per unit fiber. The major structural changes persisted for at least 3 weeks after the cessation of thyroxine treatment, by which time the elevated mitochondrial respiratory and phosphorylative activity had declined to normal values. The hypertrophy and increase in mitochondrial population was more prominent in the perinuclear and subsacrolemmic regions near blood vessels than in the interstices of the fibrils. The very long interfibrillar mitochondria found in both the hypo- and hypermetabolic tissues are more likely to be derived from outgrowths of the original mitochondria rather than from a fusion of smaller ones. These findings are compatible with the ideas expressed elsewhere (see 1, 3, 10) that, under conditions close to the physiological, thyroid hormones control mitochondrial metabolic activity by a subtle alteration in mitochondrial composition with respect to their respiratory and phosphorylative constituents. The possible application of using thyroid hormones in the study of biogenesis of mitochondria and the synthesis of mitochondrial constituents are discussed.
ANTIGEN-INDUCED CHANGES IN LYMPHOID CELL HISTONES
Authors: Black Maurice M. , Ansley Hudson R.
Published: May 2004

The nuclear histones of control and antigen-affected lymphocytes and thymocytes were measured in terms of their intensity of staining with ammoniacal-silver (A-S) and alkaline fast green (FG). Subcutaneous injection of full strength and doubly concentrated tetanus toxoid into the upper forelimb was followed by an acute decrease in the intensity of the FG and A-S staining of the thymocyte nuclear histones. Such changes in staining were delayed in the nuclear histones of the regional axillary lymph nodes. In contrast, the injection of a 1:100 dilution of tetanus toxoid caused an acute decrease in staining of the nuclei of the regional lymph node lymphocytes but only minimal changes in the thymocytes. An acute decrease in staining of the lymph node lymphocytes also occurred when heterologous serum proteins were used as the antigen. Prior administration of cortisone was found to inhibit the antigen-induced changes in the staining of lymphocyte nuclear histones. No such inhibitions occurred after the administration of saline solution. The findings suggest that the nuclear histones play a significant role in the immunological competence of lymphoid cells. However, additional studies are needed to define the biochemical basis of the observed changes as well as the mechanisms whereby antigen-induced changes in nuclear histones participate in the complex cellular and serological alterations which are evoked by antigens, viz. plasma cell formation and antibody synthesis.
THE LASER AS A POTENTIAL TOOL FOR CELL RESEARCH
Authors: Rounds Donald E. , Olson Robert S. , Johnson Fred M.
Published: May 2004

Freshly prepared hemoglobin solutions were successively irradiated up to five times with 1 MW (monochromatic wavelength) of green (530 mµ) laser power. Oxygenated hemoglobin showed no detectable change, but the spectral absorption of reduced hemoglobin showed a shift toward the characteristic curve for the oxygenated form. Intact human erythrocytes exposed to a power density of 110 MW/cm2 of green laser radiation showed no appreciable change in diameter or mass, but they became transparent to a wavelength range from 400 to 600 mµ. A similar power density from a ruby laser failed to produce this bleaching effect. This response in the erythrocyte demonstrates a principle which suggests the laser as a tool for cell research: specific molecular components within a cell may be selectively altered by laser irradiation when an appropriate wavelength and a suitable power density are applied.
THE NATURE OF BANDS IN PARASITIZED BOVINE ERYTHROCYTES
Authors: Simpson Charles F. , Kling J. M. , Neal F. C.
Published: May 2004

Anaplasma marginale is the etiological agent of a hemolytic disease of cattle, known as anaplasmosis. The organism appears as a marginal inclusion in parasitized erythrocytes, but certain isolates also have bands associated with the inclusion. Inclusions and associated bands in parasitized erythrocytes in the liver and peripheral circulation were studied by light microscope cytochemistry and electron microscopy. Bands were comet- and dumbbell-shaped by light microscopy and were stained by techniques used to demonstrate protein and fibrin. The same forms, as well as other shapes, were seen in infected erythrocytes which were sectioned and examined by electron microscopy. Bands had longitudinal and transverse periodicity. They did not appear to have a crystalline structure. Their appearance was collated with that of bovine fibrin. Bands were well differentiated in erythrocytes that were entensively hemolyzed by natural or artificial means, but poorly differentiated in mildly hemolyzed erythrocytes. Hemolysis methods appeared to influence the morphology of bands and their demonstration.
THE DEMONSTRATION OF THE SUCCINIC DEHYDROGENASE SYSTEM IN BACILLUS SUBTILIS USING TETRANITRO-BLUE TETRAZOLIUM COMBINED WITH TECHNIQUES OF ELECTRON MICROSCOPY
Authors: Sedar Albert W. , Burde Ronald M.
Published: May 2004

Activity of the succinic dehydrogenase system was studied in Bacillus subtilis utilizing combined techniques of cytochemistry and electron microscopy. Organisms were incubated in a medium containing tetranitro-blue tetrazolium (TNBT) which served as an electron acceptor. Enzymatic activity, as evidenced by deposition of TNBT-formazan, was found on membranous organelles associated with the cytoplasmic membrane and septal plasma membrane, the nuclear area, and the plasma membrane. Flagella, ∼190 A in diameter, with thorn-like projections protruded through the cell wall. Tangential-oblique sections of the cell wall showed many pores ∼220 A in diameter with a center-to-center spacing of ∼450 A.
ULTRASTRUCTURE OF MUCOCYSTS AND PELLICLE OF TETRAHYMENA PYRIFORMIS
Authors: Tokuyasu Kiyoteru , Scherbaum Otto H.
Published: May 2004

Tetrahymena pyriformis GL was fixed with glutaraldehyde and/or OsO4 for a study of cytoplasmic ultrastructure. Many small vacuoles 0.05 to 0.5 µ in diameter were found to contain each a dense particle enveloped by a limiting membrane. This membrane is continuous with the membrane of the vacuole. The particles are irregular in shape and size, but similar to the mucocysts in the appearance of the matrix. It is suggested that they are the first morphologically distinguishable stages in the development of mucocysts. In the course of this development, amorphous material becomes crystalline with a longitudinal period of 150 A and a lateral period of 100 A. The mature mucocysts are rather uniform in size and have a spheroidal shape. During discharge, the crystalline pattern disappears and the mucocysts assume a spherical configuration. The inner limiting membrane of a mucocyst seems to disintegrate during the process of discharge while the outer membrane becomes continuous with the outermost pellicular membrane; the inner pellicular membrane is continuous with the cytoplasmic membrane. Rows of few to 15 or more microtubules were found either between the cytoplasmic membrane and the ectoplasmic layer (longitudinal fibrils) or underneath the ectoplasmic layer (transverse fibrils). The outer and inner pellicular membranes are uniformly spaced and connected by "cross-bridges." Details of these structures are described.
STUDIES OF NATIVE GLYCOGEN ISOLATED FROM SYNCHRONIZED TETRAHYMENA PYRIFORMIS (HSM)
Authors: Barber Albert A. , Harris Warren W. , Padilla George M.
Published: May 2004

Native glycogen was isolated from Tetrahymena pyriformis (HSM) by isopycnic centrifugation in cesium chloride density gradients. A density of 1.62 to 1.65 was isopycnic for glycogen. Most of the banded glycogen existed as 35 to 40 mµ particles which had a sedimentation coefficient of 214. These particles were composed of aggregates of 2 to 3 mµ spherical particles. Extraction of glycogen with hot alkali reduced the sedimentation coefficient of native glycogen from 214 to 64.7 and the particle diameter from approximately 40 to 20 mµ and smaller. Cell division was synchronized by a repetitive 12-hour temperature cycle, and glycogen was measured at several times during the cell cycle. The temperature cycle consisted of 9.5 hours at 12°C and 2.5 hours at 27°C. Approximately 90 per cent of the cells divided during the last 1.5 hours of the warm period. The carbohydrate/protein ratio of cells at the end of the cold period was 0.27 and was reduced slightly during the warm period. Glucose was incorporated into glycogen during both periods, although the rate of incorporation was greater during the warm period. No preferential incorporation on the basis of particle size was noted. Incorporation was measured in both native glycogen and KOH-extracted glycogen. Tetrahymena glycogen is compared with rat liver glycogen previously isolated by similar procedures, and the significance of using combined rate-zonal and isopycnic centrifugation for isolating native glycogen is discussed.
THE EFFECT OF ACTIDIONE ON MITOSIS IN THE SLIME MOLD PHYSARUM POLYCEPHALUM
Authors: Cummins J. E. , Brewer E. N. , Rusch H. P.
Published: May 2004

Actidione, reportedly a specific inhibitor of protein synthesis, was found to reduce the incorporation of labeled amino acids into proteins of the slime mold Physarum polycephalum without drastically inhibiting the incorporation of nucleic acid precursors into RNA. This inhibitor was found to completely block the ensuing mitosis if it was added at any time between telophase and late prophase. Plasmodia given Actidione in late prophase (about the time of nucleolar dissolution) went on through telophase to reconstruction even though nuclear amino acid incorporation was drastically reduced during that period.
PATHWAYS OF CELLULAR MORPHOGENESIS
Authors: Green Paul B.
Published: May 2004

Evidence is presented to show that a given change in cell form or size may generally be brought about by a variety of patterns of local surface distortion and expansion. Structural and chemical features of the cell which are important in morphogenesis may thus be expected to relate not to form per se but to the kinetics of surface behavior which establish form. These kinetics evaluate both the rate at which local regions of cell surface expand and the directed character (anisotropy) of this expansion. These variables have been studied in model systems and, through marking experiments, in growing cells of various shapes in Phycomyces, Clypeaster, and particularly Nitella. In the latter plant, prominent "giant internodes" display a well defined longitudinal anisotropic expansion devoid of sizeable gradients in expansion rate. These cells have their origin, however, in apical cells which have a pronounced gradient in area expansion rate (maximal at the tip). The great part of the expansion in the apical cell is apparently isotropic (equal in all directions), but the basal region often shows predominant expansion laterally. This transverse stretching in the apical cell could align cell wall texture and possibly fibrous cytoplasmic constituents, such as microtubules, into configurations significant in later morphogenetic stages, including the elongation of the internodes.
LEBENDNACHWEIS VON EINZELELEMENTEN DES ENDOPLASMATISCHEN RETIKULUMS
Authors: Girbardt Manfred
Published: May 2004

By means of a special selective preparation technique, it is possible to investigate in thin sections, by electron microscopy, areas of a cell that have been observed in the living state, by phase-contrast microscopy, up to the time of fixation. Structures recorded in the living state can thus be compared to structures seen in electron micrographs. In cells of the fungus Polystictus versicolor, aggregates of membrane systems as well as single cisternae with a diameter of approximately 200 to 300 A can be detected with phase optics. It can be shown, by calculation, that these structures, which are far below the limit of resolution of the light optical system, give enough contrast to be discernible by phase optics. Thus a basis is provided for observing the dynamics of membrane systems which perhaps may contribute to the analysis of the functional significance of these cell components.
THE PERMEABILITY OF RAT TRANSITIONAL EPITHELIUM
Authors: Hicks R. M.
Published: May 2004

Permeability barriers must exist in transitional epithelium to prevent the free flow of water from underlying blood capillaries through the epithelium into the hypertonic urine, and such a barrier has now been demonstrated in isolated bladders. This barrier is passive in function and can be destroyed by damaging the luminal surface of the transitional epithelium with sodium hydroxide and 8 M urea solutions, by digesting it with trypsin, lecithinase C, and lecithinase D, or by treating it with lipid solvents such as Triton x 100 and saponin. From this it is concluded that the barrier depends on the integrity of lipoprotein cell membranes. The barrier function is also destroyed by sodium thioglycollate solutions, and electron microscope investigations show that sodium thioglycollate damages the thick asymmetric membrane which limits the luminal face of the superficial squamous cell. Cytochemical staining shows the epithelium to contain disulfide and thiol groups and to have a concentration of these groups at the luminal margin of the superficial cells. It thus appears that the permeability barrier also depends on the presence of disulfide bridges in the epithelium, and it is presumed that these links are located in keratin. Because of the effect of thioglycollates, both on the barrier function and on the morphology of the membrane, it is suggested that keratin may be incorporated in the thick barrier membrane. It is proposed that the cells lining the urinary bladder and ureters should be regarded as a keratinizing epitheluim.
THE EFFECT OF STRYCHNINE AND LIGHT ON PIGMENTATION IN BLEPHARISMA UNDULANS STEIN
Authors: Kennedy John R.
Published: May 2004

The effect of strychnine sulfate and light on pigmentation in the ciliate protozoan Blepharisma undulans has been determined. Upon exposure of cells to strychnine, the pigment granules become loosened from their surrounding membranes. Eventually these membranes break and the granules are simultaneously released from the cell. At the cell surface, a fusion occurs between adjacent membraneless granules with the incorporation of membrane fragments. This fusion of granules and membrane fragments results in the formation of a pigmented "capsule" around the organism. After elimination of the pigment, the granule membranes remaining in the cytoplasm fuse to form apparently empty vesicles. Other cell organelles are generally undisturbed. A similar situation occurs upon exposure of cells to artificial light for 12 to 18 hr, however, the slow elimination of granules from the cells under these conditions does not result in the formation of a pigmented "capsule." The possible mechanisms of these reactions are discussed.
THE SYNTHESIS OF DNA, RNA, AND NUCLEAR PROTEIN IN NORMAL AND TUMOR STRAIN CELLS
Authors: Seed John
Published: May 2004

Interferometric and photometric measurements have been made on replicating embryo mouse cell cultures. From a study of the relations between successive physical measurements on individual cells, it was found that the net syntheses of DNA, nuclear RNA, nuclear protein, and cytoplasmic RNA are closely associated during interphase. In auxiliary experiments, an inhibition of the onset of DNA synthesis (produced by a dose of X-rays) was found to block the majority of the accumulation of nuclear protein and nuclear RNA. These results are consistent with others previously reported in dividing cell cultures freshly prepared from normal tissues.
FRACTIONATION OF SPINACH CHLOROPLASTS BY FLOW SEDIMENTATION-ELECTROPHORESIS
Authors: Packer Lester , Nobel Park S. , Gross Elizabeth L. , Mel Howard C.
Published: May 2004

A separation of spinach chloroplasts in vitro into fractions according to size (volume) and activity (light-dependent shrinkage and NADP reduction) has been achieved by stable-flow free boundary sedimentation-electrophoresis. The salient features of this chloroplast study are: (a) separation is achieved within 30 min; (b) only small density gradients are required, thus minimizing osmotic effects; (c) the fractions are collected continuously, with size fractionation being evidenced; and (d) particles are separated into fractions of higher and lower activities as compared with the control population.
THE EFFECT OF DEPRIVATION OF GLUCOSE ON THE ULTRASTRUCTURE AND FUNCTION OF THE SUPERIOR CERVICAL GANGLION OF THE RAT IN VITRO
Authors: Nicolescu P. , Dolivo M. , Rouiller C. , Foroglou-Kerameus C.
Published: May 2004

The superior cervical sympathetic ganglion of the rat kept in vitro in a bicarbonate-buffered Krebs' solution retains its capacity for synaptic transmission and axonal conduction during more than 36 hr. After glucose withdrawal, synaptic transmission is lost in 2½ hr and this loss is irreversible; on the other hand, axonal conduction can still be measured on the postganglionic nerve for more than 24 hr after glucose deprivation. Electrophysiological measurements as well as electron microscope studies revealed specific changes at the level of the presynaptic terminal processes, while the ganglion cells and the satellite cells remained relatively unaltered. The presynaptic lesion due to lack of glucose can be prevented by keeping the preparation in vitro at 6°C. This strongly suggests that this lesion results from a major disturbance of the metabolism of the presynaptic fibers.
SECRETION OF α-AMYLASE BY THE EMBRYONIC CHICK PANCREAS IN VITRO
Authors: Kulka R. G. , Yalovsky U.
Published: May 2004

Pancreases taken from chick embryos secrete amylase in vitro when stimulated by cholinergic drugs. Rates of secretion increase with developmental age. The pancreas isolated together with the duodenal loop from the 8 day embryo is already capable of secretion in vitro. It is therefore concluded that the pancreas acquires the ability to secrete digestive enzymes more than 10 days before the beginning of the prominent biochemical and morphological changes associated with the maturation of the gland.
THE ULTRASTRUCTURE OF THE SENSORY HAIRS AND ASSOCIATED ORGANELLES OF THE COCHLEAR INNER HAIR CELL, WITH REFERENCE TO DIRECTIONAL SENSITIVITY
Authors: Duvall Arndt J. , Flock Åke , Wersäll Jan
Published: May 2004

From the apical end of the inner hair cell of the organ of Corti in the guinea pig cochlea protrude four to five rows of stereocilia shaped in a pattern not unlike the wings of a bird. In the area devoid of cuticular substance facing toward the tunnel of Corti lies a consistently present centriole. The ultrastructure of this centriole is similar to that of the basal body of the kinocilium located in the periphery of the sensory hair bundles in the vestibular and lateral line organ sensory cells and to that of the centrioles of other cells. The physiological implications of the anatomical orientation of this centriole are discussed in terms of directional sensitivity.
THE MEMBRANE CAPACITANCE OF THE SEA URCHIN EGG
Authors: Rothschild Lord
Published: May 2004

1. The surface of the unfertilized sea urchin egg is folded and the folds are reversibly eliminated by exposing the egg to hypotonic sea water. If the plasma membrane is outside the layer of cortical granules, unfolding may explain why the membrane capacitance per unit area decreases (and does not increase) when a sea urchin egg is put into hypotonic sea water.

2. The degree of surface folding markedly increases after fertilization, which provides an explanation for the increase in membrane capacitance per unit area observed after fertilization.

3. The percentage reduction in membrane folding in fertilized eggs after immersion in hypotonic sea water is probably sufficient to explain the decrease in membrane capacitance per unit area observed in these conditions.
THE STRUCTURE AND CONCENTRATION OF SOLIDS IN PHOTORECEPTOR CELLS STUDIED BY REFRACTOMETRY AND INTERFERENCE MICROSCOPY
Authors: Sidman Richard L.
Published: May 2004

Fragments of freshly obtained retinas of several vertebrate species were studied by refractometry, with reference to the structure of the rods and cones. The findings allowed a reassessment of previous descriptions based mainly on fixed material. The refractometric method was used also to measure the refractice indices and to calculate the concentrations of solids and water in the various cell segments. The main quantitative data were confirmed by interference microscopy.

When examined by the method of refractometry the outer segments of freshly prepared retinal rods appear homogeneous. Within a few minutes a single eccentric longitudinal fiber appears, and transverse striations may develop. These changes are attributed to imbibition of water and swelling in structures normally too small for detection by light microscopy. The central "core" of outer segments and the chromophobic disc between outer and inner segments appear to be artifacts resulting from shrinkage during dehydration. The fresh outer segments of cones, and the inner segments of rods and cones also are described and illustrated.

The volumes, refractive indices, concentrations of solids, and wet and dry weights of various segments of the photoreceptor cells were tabulated. Rod outer segments of the different species vary more than 100-fold in volume and mass but all have concentrations of solids of 40 to 43 per cent. Cone outer segments contain only about 30 per cent solids. The myoids, paraboloids, and ellipsoids of the inner segments likewise have characteristic refractive indices and concentrations of solids.

Some of the limitations and particular virtues of refractometry as a method for quantitative analysis of living cells are discussed in comparison with more conventional biochemical techniques. Also the shapes and refractive indices of the various segments of photoreceptor cells are considered in relation to the absorption and transmission of light. The Stiles-Crawford effect can be accounted for on the basis of the structure of cone cells.
DISTRIBUTION OF ENZYMES CLEAVING PYRIDINE NUCLEOTIDES IN ANIMAL TISSUES
Authors: Jacobson K. Bruce , Kaplan Nathan O.
Published: May 2004

1. The distribution of DPN and DPNH pyrophosphatases and DPNase in centrifugally prepared fractions of organs of several species of animals is reported.

2. A DPNH pyrophosphatase was found in the soluble fraction of pigeon and of rabbit liver. This enzyme did not split DPN but accounted for over 50 per cent of the DPNH pyrophosphatase activity of the whole homogenates.

3. All the organs tested, including the pigeon liver and rabbit liver, contained a microsomal pyrophosphatase that attacked both DPNH and DPN. This microsomal enzyme split DPNH faster than DPN in all cases.

4. DPN pyrophosphatase and DPNase activity were generally concentrated in the microsomal fraction of liver, of kidney, and of brain.

5. The DPNase of hamster liver was virtually inactive at pH 7.5 but was optimally active at pH 5.5. Considerable difference was found with respect to pH on the activity of DPNase from organs of different animals.

6. The inhibition of mitochondrial and microsomal DPNH oxidation by nicotinamide was noted during the course of these experiments.

7. The significance of some of the distribution patterns is discussed.
THE STRUCTURE OF SOME CYTOPLASMIC COMPONENTS OF PLANT CELLS IN RELATION TO THE BIOCHEMICAL PROPERTIES OF ISOLATED PARTICLES
Authors: Hodge A. J. , Martin E. M. , Morton R. K.
Published: May 2004

1. Electron micrographs of thin sections of material fixed with buffered osmium tetroxide have been used for comparison of the fine structure of isolated cytoplasmic particles from silver beet petioles and roots of germinating wheat with that of the cytoplasm of the intact cells.

2. Mitochondria of wheat roots have an external double membrane and poorly oriented internal double membranes. As compared with the structures seen in situ, the isolated mitochondria showed evidence of some disorganisation of the fine internal structure, probably due to osmotic effects. The possible influence of such changes on the enzymic properties of the isolated mitochondria is discussed.

3. The isolated plant microsomes are mainly spherical vesicular structures consisting of (a) an outer membrane enclosing (b) either an homogeneous slightly dense material (wheat root microsomes) or some granular dense material (silver beet microsomes) and (c) small dense particles, mostly associated with the vesicle membranes.

4. The cytoplasm of the wheat root cells does not contain any structures similar to the isolated microsomes but has a very dense reticular network, consisting of membranes with associated small dense particles, here called the endoplasmic reticulum. The observations indicate that the isolated microsomes arise mainly by rupture and transformation of the membranes of this structure. The effects of such extensive changes in the lipoprotein membranes on the enzymic activities of the endoplasmic reticulum, as studied in isolated microsomes, is discussed.

5. Meristematic wheat root cells contain structures which consist of smooth membranes with associated vacuoles and are similar to the Golgi zones of animal cells. The membranes of these zones probably contribute to the microsomal fraction under the conditions of preparation used for the enzymic and chemical studies previously reported.
THE ELECTRON MICROSCOPY OF THE HUMAN HAIR FOLLICLE
Authors: Birbeck M. S. C. , Mercer E. H.
Published: May 2004

1. The three cylinders of cells, each one cell thick, which together constitute the inner root sheath, arise from the peripheral portions of the undifferentiated matrix. These cells, like the hair cuticle, are stabilised by the spread of adhesive contacts between their plasma membranes which occurs in the mid-bulb and upper bulb of the hair follicle.

2. The characteristic intracellular product of all three cell layers is trichohyaline. This substance is formed in the first place as amorphous droplets which subsequently transform into a birefringent form.

3. This transformation, involving the formation of a birefringent product from an amorphous precursor, is in contrast to the formation in the cortex of keratin which originates in a fibrous form.

4. Trichohyaline appears first and transforms first in the cells of Henle which are nearest the outer sheath and the dermal supply vessels. This transformation occurs at the level of the neck of the follicle. Synthesis and transformation in the cells of Huxley and the sheath cuticle lag behind the similar events in the cells of Henle. The transformation does not begin until the lower prekeratinous zone in the Huxley and cuticle cells.

5. The amorpous-fibrous transformation occurs rapidly cell by cell and involves the conversion of all the trichohyaline droplets. In longitudinal sections the birefringent modification can be seen extending from the droplets in both directions parallel to the axis of the hair. In cross-sections the images of the transformed material are difficult to interpret. They may be seen as sections of corrugated sheets (∼100 A thick) or condensed fibrils ∼100 A in width.

6. At the same time that the trichohyaline transforms, the spacing between the cell membranes increases and a dark deposit appears centrally between them. This membrane complex, and the similar complex of the hair cuticle cells described in Part 2, may be specialised formations whose purpose is to hold the hardened cells together.
Electron Microscopic Evidence Suggesting Secretory Granule Formation within the Golgi Apparatus
Authors: Farquhar Marilyn G. , Wellings S. Robert
Published: May 2004

Secretory granules have been seen within components of the Golgi bodies of rat pituitary acidophils and mouse pancreatic acinar cells. The fact that secretory granules are much more frequently encountered within Golgi components under conditions of increased secretory activity suggests that granule formation may occur within the Golgi apparatus in these two types of cells.
A CYTOLOGICAL STUDY OF THE ALBUMIN-SECRETING CELLS OF THE HEN OVIDUCT
Authors: Hendler Richard W. , Dalton Albert J. , Glenner George G.
Published: May 2004

1. The electron and light microscope have been employed in a cytological study of the albumin-secreting cells of the hen oviduct and of fractions of this tissue obtained after homogenization and differential centrifugation.

2. These studies confirm the observation that in this tissue material corresponding to liver "microsomes" in amino acid-incorporating ability and ribonucleic acid content sediments in relatively low centrifugal fields.

3. The electron microscope studies suggest that the protein secretion of the gland is formed in intimate association with the ergastoplasm.
ELECTRON MICROSCOPY OF THE PACINIAN CORPUSCLE
Authors: Pease Daniel C. , Quilliam T. Andrew
Published: May 2004

The Pacinian corpuscle has a framework of cytoplasmic lamellae arranged concentrically in the outer zone, and bilaterally in the core. Between these is an intermediate growth zone.

The inner core shows an unexpected complexity in that its component lamellae are arranged in two symmetrical groups of nested cytoplasmic sheets. Longitudinal tissue spaces form clefts separating the two groups. The perikarya of the core lamellae lie in or near the intermediate growth zone, and send arms into the clefts. The arms then branch and terminate as lamellae which interdigitate with those of neighboring cells.

The single nerve fiber loses its myelin sheath just before it reaches the inner core but retains its Schwann cell cytoplasmic covering for a short additional distance. The Schwann sheath is not continuous with the lamellae of the inner core. Inside the core the fiber contains a striking circumferential palisade of radially disposed mitochondria. The fiber does not arborize.

Vascular capillaries penetrate the hilar region of the corpuscle only as far as the myelinated sheath of the nerve, and they have not been seen elsewhere in the corpuscle. There is direct continuity between the clefts of the core and tissue spaces in the vicinity of the capillaries. It is likely that this provides a route whereby metabolites reach the active nerve ending, as well as the cells of the growth zone.

The outer zone consists of at least 30 flattened concentric cytoplasmic lamellae separated from one another by relatively wide fluid-filled spaces. Collagenous fibrils are present, particularly on the outer surface of lamellae, and tend to be oriented circularly.

The girdle of proliferating cells constituting the growth zone, which is prominent in corpuscles from young animals, is the layer from which the outer lamellae are derived. Osmotic forces probably elevate the lamellae, and maintain turgor pressure.
THE MICROSTRUCTURE OF THE COMPOUND EYES OF INSECTS
Authors: Goldsmith Timothy H. , Philpott Delbert E.
Published: May 2004

The apposition eyes of two diurnal insects, Sarcophaga bullata (Diptera) and Anax junius (Odonata), have been examined with the electron microscope. In the latter case only the rhabdom is described.

The rhabdom of the fly consists of a central matrix and seven rhabdomeres, one for each retinula cell. The rhabdomeres show an ordered internal structure built up of transverse tubes, hexagonal in cross-section. These slender compartments running the width of the rhabdomere are 370 A in diameter. After fixation with osmium tetroxide the walls of the compartments are more electron dense than the interiors. The retinula cells contain mitochondria, and pigment granules smaller than those found in the pigment cells. These granules tend to cluster close behind the membranes which separate the retinula cells from their rhabdomeres.

The rhabdom of the dragonfly is a single structure which appears to be composed of three fused "rhabdomeres," each similar to a rhabdomere of Sarcophaga.

Reasons are given for believing that the rhabdom may be the site of photoreception, as well as the organ for analyzing plane-polarized light, as suggested by other workers.
REDUCTION OF HEATING ARTIFACTS IN THIN SECTIONS EXAMINED IN THE ELECTRON MICROSCOPE
Authors: Watson Michael L.
Published: May 2004

Certain phenomena affecting contrast obtained from tissue sections with the electron microscope have been investigated and a technique is described for reducing destruction by the electron beam of fine details in sections. It has been concluded that loss of embedding material is slightly higher at exposed surfaces of sections than it is at surfaces covered by substrate film. Covering of both surfaces of sections with thin films of formvar, collodion, or carbon materially improves the general appearance, reduces distortion, and sometimes reduces loss of tissue mass from the section as result of exposure to the electron beam. This improvement is considered to result from the relatively high melting-point of the covering films which serve to eliminate or reduce surface-tension or other forces operating in methacrylate softened by the electron beam.
THE FINE STRUCTURE OF ELASTIC FIBERS
Authors: Greenlee Theodore K. , Ross Russell , Hartman Jerry L.
Published: May 2004

The fine structure of developing elastic fibers in bovine ligamentum nuchae and rat flexor digital tendon was examined. Elastic fibers were found to contain two distinct morphologic components in sections stained with uranyl acetate and lead. These components are 100 A fibrils and a central, almost amorphous nonstaining area. During development, the first identifiable elastic fibers are composed of aggregates of fine fibrils approximately 100 A in diameter. With advancing age, somewhat amorphous regions appear surrounded by these fibrils. These regions increase in prominence until in mature elastic fibers they are the predominant structure surrounded by a mantle of 100 A fibrils. Specific staining characteristics for each of the two components of the elastic fiber as well as for the collagen fibrils in these tissues can be demonstrated after staining with lead, uranyl acetate, or phosphotungstic acid. The 100 A fibrils stain with both uranyl acetate and lead, whereas the central regions of the elastic fibers stain only with phosphotungstic acid. Collagen fibrils stain with uranyl acetate or phosphotungstic acid, but not with lead. These staining reactions imply either a chemical or an organizational difference in these structures. The significance and possible nature of the two morphologic components of the elastic fiber remain to be elucidated.
THE INTRACELLULAR DISTRIBUTION OF CALCIUM IN THE MUCOSA OF THE AVIAN SHELL GLAND
Authors: Hohman Wayne , Schraer Harald
Published: May 2004

The intracellular distribution of calcium has been studied in the mucosa of the avian shell gland, a tissue which transports large quantities of calcium during discrete time intervals. Ca45 was administered to hens either in a single dose followed by sacrifice 5 min later or in repeated doses over an extended period followed by sacrifice 2 hr or 24 hr after the last injection. Subcellular fractions were isolated by differential centrifugation and analyzed for Ca45. The Ca45 was located principally in the particulate fractions; the concentration (CPM Ca45/mg N) was highest in the mitochondrial fraction. Comparisons of (1) the Ca45 distribution in shell gland cells with that of liver cells, (2) the alterations which occur due to the phase of the egg laying cycle, (3) the effects due to the time elapsed since the last injection of Ca45, and (4) the Ca45 distribution of the short term experiments with that of the long term experiments revealed that the mitochondrial fraction of the shell gland appeared to be active in the movement of calcium. The microsomal fraction showed increased values in CPM Ca45/mg N when calcification was occurring, which may indicate that the subcellular components of this fraction have a role in calcium transport. The nuclear and supernatant fractions did not seem to be involved in the transport process. The implications of these results concerning the manner by which calcium may be controlled on a cellular level in this system are discussed.
AN IMPROVED CHEMICALLY DEFINED BASAL MEDIUM (CMRL-1415) FOR NEWLY EXPLANTED MOUSE EMBRYO CELLS
Authors: Healy George M. , Parker Raymond C.
Published: May 2004

An improved chemically defined medium, CMRL-1415, has been devised by testing the response of trypsinized, newly explanted mouse embryo cells in stationary cultures to various modifications of an earlier medium, CMRL-1066. The improvements are attributed to changes in amino acid levels, in the vitamin-coenzyme composition, and to an enhanced buffering capacity resulting from the use of free base amino acids, galactose and pyruvate, together with greatly reduced levels of glucose and sodium bicarbonate and the inclusion of both monobasic and dibasic sodium phosphate in the ratio 1:4. When the medium is equilibrated with 5% CO2 in air, an initial pH of 7.2–7.4 is achieved, with excellent buffering capacity. CMRL-1415 contains 50 ingredients (9 fewer than CMRL-1066) and is prepared from six stable stock concentrates. By omitting sodium bicarbonate (to give CMRL-1415-ATM), the medium may be used in unsealed cultures in free gas exchange with air. CMRL-1415 and CMRL-1415-ATM are intended for use with and without serum protein and other supplements; and by preparing them double strength they may be combined with agar or other gelling agents to provide a semi-solid substrate.