bluuebunny/crossref_metadata_2025 huggingface dataset:
CYTOCHEMICAL STAINING OF MULTIVESICULAR BODY AND GOLGI VESICLES
Authors: Friend Daniel S.
Published: May 2004

To investigate the origin and nature of vesicles found within multivesicular bodies (mvb), the cytochemical staining properties of mvb vesicles were compared with those of other cytoplasmic vesicles, i.e. those associated with the Golgi complex and endocytic vesicles found near the apical cell surface. Rat epididymal tissue was stained in unbuffered OsO4 for 40–48 hr, and the distribution of stain was compared to that of reaction products for acid phosphatase (AcPase) to mark lysosomal vesicles, or thiamine pyrophosphatase (TPPase) to mark certain Golgi vesicles, or infused with peroxidase (HRPase) to demonstrate endocytic vesicles. Mvb vesicles were stained only by OsO4; AcPase, TPPase, and HRPase reaction products stained the mvb matrix. OsO4 also stained certain vesicles along the convex surface of the Golgi complex. The findings suggest that mvb vesicles in epididymal epithelium are not lysosomes and are not involved in protein uptake. The majority of these vesicles have cytochemical reactions in common with vesicles located along the convex surface of the Golgi complex and may be derived therefrom. A minority are derived from the mvb-limiting membrane.
ULTRASTRUCTURAL AND BIOCHEMICAL CHANGES IN BROWN FAT IN COLD-EXPOSED RATS
Authors: Thomson John F. , Habeck Duane A. , Nance Sharron L. , Beetham Karen L.
Published: May 2004

During the first 3 days of exposure of rats to 5°C, the nitrogen concentration of interscapular brown fat increased by 50% and remained at this elevated level for the duration of the 8-wk observation period, while the mass of tissue increased fourfold. The concentration of both DNA and RNA per unit nitrogen reached a maximum after 3 days, then declined; however, the total quantity of each continued to rise. The concentration of various respiratory enzymes decreased during the first few days and then increased, but at different rates. The morphological changes in mature brown fat cells during cold acclimation were observed to be: a reduction in fat droplet size during the first 3 days, followed by a gradual increase in size through 6 wk in the cold; a continual increase in the amount of intermitochondrial ground substance during the first 3 wk, with increased granularity and glycogen content after 1 wk; initial disappearance of glycogen between mitochondria, followed by the reappearance of a few isolated particles in the intermitochondrial ground substance after 1 wk in the cold; initial increase in the density of intramitochondrial matrix for the first 3–4 days, followed by a gradual return to the control density; loss in integrity of mitochondrial outer membranes during the first 4 days, followed by gradual but incomplete restoration; temporary loss of the dense material in lipid droplets during the first 24 hr, with return after 1 wk in the cold; and a 40% increase in mitochondrial diameter within 1 day, followed by a decrease in diameter within 1 wk to a constant value about 15% larger than the controls.
NUCLEOLAR ORTHOPHOSPHATE IONS
Authors: Tandler Carlos J. , Solari Alberto J.
Published: May 2004

Lead acetate (3–10%, pH between 4.3 and 7.0, alone or containing 2% glutaraldehyde), when used as fixative, has been demonstrated to produce an intracellular microcrystalline precipitate of lead orthophosphate, Pb5(PO4)3OH (lead hydroxyapatite). This confirms earlier work with the light microscope (6). In interphase cells the nucleoli are sharply delimited by the massive lead phosphate precipitate. Some diffuse precipitate is found in the nucleoplasm; it is always delimited by the nuclear membrane. Nucleolar localization of this orthophosphate pool is not a diffusion artifact; the pool is probably in a loosely bound state and is not retained by conventional fixatives. In maize root cells in advanced mitotic stages the lead phosphate crystals are seen distributed throughout the cytoplasm and also relatively concentrated on the late anaphase-early telophase chromosomes. This pool of inorganic phosphate anions may be involved in the mitotic cycle of chromatin condensation, and it may be partially responsible for the absence of mature ribosomes in the nucleolus through the chelation of divalent cations. It is evident that the siver-reducing component detected in the nucleoli of fixed cells (6) is a completely different substance.
HETEROGENEOUS DISTRIBUTION OF ENZYMES IN SUBMICROSOMAL MEMBRANE FRAGMENTS
Authors: Dallman Peter R. , Dallner Gustav , Bergstrand Anders , Ernster Lars
Published: May 2004

Microsomal membranes are postulated to contain either a homogeneous arrangement of individual enzymes or groupings of functionally related enzymes. In the present study we attempt to distinguish between these hypotheses in subfractions of rough microsomes from rat liver. After sonication, the individual vesicles that make up the rough-membrane fraction average less than 1/100 of their previous mass. The vesicles in the sonicated suspension are fractionated roughly according to size on a continuous sucrose gradient. Enzyme activity or concentration in fractions of the gradient is expressed on a phospholipid basis. Fractions containing primarily small vesicles differ from those containing larger vesicles in a manner suggesting a certain degree of separation of NADH-linked from NADPH-linked enzymes. NADH-ferricyanide reductase, NADH-cytochrome c reductase and cytochrome b5 are most concentrated within the large vesicles in the lowest third of the gradient. In contrast, NADPH-cytochrome c reductase and cytochrome P-450 are found in highest concentration in the small vesicles that make up the upper third of the gradient. The results suggest a nonrandom distribution of these two enzyme groups in the membranes of the endoplasmic reticulum.
ISOLATION OF PLASMA MEMBRANE FRAGMENTS FROM HELA CELLS
Authors: Boone Charles W. , Ford Lincoln E. , Bond Howard E. , Stuart Donald C. , Lorenz Dianne
Published: May 2004

A method for isolating plasma membrane fragments from HeLa cells is described. The procedure starts with the preparation of cell membrane "ghosts," obtained by gentle rupture of hypotonically swollen cells, evacuation of most of the cell contents by repeated washing, and isolation of the ghosts on a discontinuous sucrose density gradient. The ghosts are then treated by minimal sonication (5 sec) at pH 8.6, which causes the ghost membranes to pinch off into small vesicles but leaves any remaining larger intracellular particulates intact and separable by differential centrifugation. The ghost membrane vesicles are then subjected to isopycnic centrifugation on a 20–50% w/w continuous sucrose gradient in tris-magnesium buffer, pH 8.6. A band of morphologically homogeneous smooth vesicles, derived principally from plasma membrane, is recovered at 30–33% (peak density = 1.137). The plasma membrane fraction contained a Na-K-activated ATPase activity of 1.5 µmole Pi/hr per mg, 3% RNA, and 13.8% of the NADH-cytochrome c reductase activity of a heavier fraction from the same gradient which contained mitochondria and rough endoplasmic vesicles. The plasma membranes of viable HeLa cells were marked with 125I-labeled horse antibody and followed through the isolation procedure. The specific antibody binding of the plasma membrane vesicle fraction was increased 49-fold over that of the original whole cells.
THE SUBCELLULAR LOCALIZATION OF CALCIUM ION IN MAMMALIAN MYOCARDIUM
Authors: Legato Marianne J. , Langer Glenn A.
Published: May 2004

This study was designed to investigate the proposition that subcellular calcium is sequestered in specific sites in mammalian myocardium. 29 functioning dog papillary muscles were fixed through the intact vascular supply by means of osmium tetroxide containing a 2% concentration of potassium pyroantimonate (K2H2Sb2O7·4H2O). Tissue examined in the electron microscope showed a consistent and reproducible localization of the electron-opaque pyroantimonate salts of sodium and calcium to distinct sites in the tissue. Sodium pyroantimonate was found exclusively in the extracellular space and clustered at the sarcolemmal membrane. Calcium pyroantimonate, on the other hand, identified primarily by its susceptibility to removal by chelation with EGTA and EDTA, was consistently found densely concentrated in the lateral sacs of the sarcoplasmic reticulum and over the sarcomeric I bands. M zones were virtually free of precipitate. The implications of these findings with respect to various parameters of muscle function are discussed.
STUDIES ON CHLOROPLAST DEVELOPMENT AND REPLICATION IN EUGLENA
Authors: Carell Edgar F.
Published: May 2004

When Euglena gracilis is grown under vitamin B12 deficiency conditions, the amount of protein and of chlorophyll per cell increase with decrease of B12 in the medium and consequently in the cell. The increase in cell protein is proportional to and precedes an increase in the number of chloroplasts per cell. This replication of the chloroplasts under deficiency conditions is not accompanied by nuclear or cell division. It is concluded that chloroplast replication in Euglena gracilis is independent of nuclear and cellular replication, at least under B12 deficiency conditions. We established a graph of the growth of Euglena under different concentrations of vitamin B12 added to the growth medium, which permitted us to calculate that at least 22,000 molecules of vitamin B12 per cell are required to give normal growth.
RIBOFLAVIN AND MOUSE HEPATIC CELL STRUCTURE AND FUNCTION
Authors: Tandler Bernard , Erlandson Robert A. , Smith Archie L. , Wynder Ernest L.
Published: May 2004

Mice which had been on a riboflavin-free diet for 6–8 wk were given daily intraperitoneal injections of riboflavin. The hepatic mitochondria, which in the deficient animals were greatly enlarged, were restored to normal dimensions within 3 days. Normalization of the mitochondrial population was brought about by division of the giant organelles. Dividing mitochondria were characterized by a membranous partition separating the inner compartment into two distinct chambers. Such organelles showed varying degrees of pinching at the level of the partition. The most common site of partition formation was at the base of a small mitochondrial bud. During the 1st day of recovery, dividing mitochondria were so common that they could be easily found in mitochondrial pellets. Injection of riboflavin into normally nourished mice also produced an apparent increase in the frequency of dividing mitochondria in the liver cells.
INTRACELLULAR CENTRIFUGAL SEPARATION OF ORGANELLES IN PHYCOMYCES
Authors: Zalokar Marko
Published: May 2004

Live sporangiophores of Phycomyces blakesleeanus were centrifuged at 35,000 rpm. The cell contents sedimented into distinct layers, and each layer was studied with an electron microscope and with cytochemical methods. The following layers were found (their volumes and their densities are shown in Fig. 3): 1. polyphosphates; 2. polyphosphates and protein crystals; 3. glycogen; 4. yellow layer with ferritin; 5. ribosomes; 6. protein crystals; 7. mitochondria; 8. mitochondria and fibrils; 9. nuclei; 10. endoplasmic reticulum; 11. vesicles, membranes, and reticulum; 12. vacuole; 13. lipoproteins, membranes; 14. fat droplet. The densities of the various layers were determined by the injection of droplets of inert oils of known density into the sporangiosphores before centrifugation. Sedimented cell organelles could be isolated. Centrifuged nuclei of a lycopene-producing mutant were injected into the intact sporangiophore of an albino host where they induced color formation. The ensuing spores, when plated, gave a mixture of white and colored colonies. It was concluded that cell organelles, sedimented by centrifugation of living sporangiophores, remain alive and can be used for biochemical studies. Microspectrophotometric examination of the layers indicated the presence of cytochromes and flavines in the mitochondria and of cytochromes in the nuclei. No pigments corresponding to the action spectrum for the light growth response were found.
IMMUNOCHEMICAL STUDIES OF 22S PROTEIN FROM ISOLATED MITOTIC APPARATUS
Authors: Bibring Thomas , Baxandall Jane
Published: May 2004

Evidence is presented that the "22S protein" of mitotic apparatus isolated from sea urchin eggs is not microtubule protein. An antibody preparation active against 22S protein is described, and immunochemical studies of the distribution of 22S protein in various cellular fractions and among morphological features of mitotic apparatus are reported. The protein is ubiquitous in the metaphase egg fractions that were tested but is not found in sperm flagella. It is immunologically distinct from proposed microtubule protein isolated from mitotic apparatus by the method of Sakai, and from proposed microtubule protein obtained after extraction with mild acid. It exists in nontubule material of isolated mitotic apparatus but is not detectable in microtubules.
QUANTITATIVE STUDIES ON ENZYMES IN STRUCTURES IN STRIATED MUSCLES BY LABELED INHIBITOR METHODS
Authors: Rogers A. W. , Darzynkiewicz Z. , Salpeter M. M. , Ostrowski K. , Barnard E. A.
Published: May 2004

Di-isopropylfluorophosphate (DFP) labeled with phosphorus-32 was applied to fragments of the diaphragm and sternomastoid muscles of the mouse, in conditions in which it saturated all available sites at the motor endplates. After adequate washing and exchange with unlabeled DFP, single endplates were obtained by microdissection and their radioactivity was found by beta track radioautography. The number of sites phosphorylated by DFP-32P per endplate was relatively constant for each muscle: in the sternomastoid, about 9 x 107 sites per endplate, in the diaphragm, about 3 x 107. Reaction with DFP-32P was abolished by prior treatment with unlabeled DFP. Labeling was unaffected by prior fixation in formaldehyde, but was inversely proportional to the time of incubation in the Koelle staining medium, when this preceded labeling. The contribution of acetylcholinesterase (AChase) to this total number of DFP-reactive sites was determined by three methods. The first involved reactivation of the phosphorylated AChase by pyridine-2-aldoxime methiodide (2-PAM), in conditions in which the reactivation of other enzymes would be insignificant. The other two methods involved protection of the active centers of AChase from phosphorylation by labeled DFP by use of 284C51, an inhibitor highly specific for this enzyme, or by use of eserine. Each of these methods indicated that about 35% of the DFP-reactive sites at endplates of the sternomastoid and diaphragm are AChase. The mean number of AChase molecules was thus found to be 3.1 x 107 and 1.1 x 107per endplate in sternomastoid and diaphragm, respectively. No significant reaction of labeled DFP with muscle and nerve was observed. Mast cells in the muscle had a concentration of DFP-reactive sites far higher than the endplates.
STUDIES ON THE HUMAN CORPUS LUTEUM
Authors: Adams Eleanor C. , Hertig Arthur T.
Published: May 2004

The ultrastructure of human corpora lutea obtained during the 6th, 10th, 16th, and 35th week of pregnancy is reported. Differences between the established luteal cell of pregnancy and the transitory luteal cell of the menstrual cycle are noted. In pregnancy the luteal cell is more compartmentalized into a peripheral mass of ER (endoplasmic reticulum) and a central area where mitochondria and Golgi complexes are concentrated. The latter area extends to a cell surface where microvilli face on a perivascular space. Long bundles of filaments are prominent within the luteal cell cytoplasm and, in contiguous cells, appear to arise from adjacent desmosomal regions. Bilateral subsurface cisternae of granular ER at lateral cell borders appear to be areas of specialized junctional surfaces. Certain luteal cells with irregular nuclear membranes are also characterized by vesicular aggregates enclosed within a single membrane. These aggregates are found within the peripheral nucleoplasm or the perinuclear cytoplasm. Their single limiting membrane often appears continuous with either the inner or outer leaflet of the nuclear membrane.
CRYSTALLINE INCLUSIONS IN THE NUCLEAR ENVELOPE AND GRANULAR ENDOPLASMIC RETICULUM OF THE FISH SPINAL CORD
Authors: Marquet Eugene , Sobel Harold John
Published: May 2004

Crystalline inclusions were found in the nuclear envelope and granular endoplasmic reticulum of spinal cord oligodendroglia of the common guppy (Poecilia reticulata) and the lungfish (Polypterus enlicheri). A considerably increased incidence of these inclusions was noted in guppies with congenital and hereditary (sex-linked, recessive) lordosis. Identical crystalline inclusions were observed in protoplasmic and fibrous astrocytes, ependymal cells, and capillary endothelial cells of the spinal cord of the lordotic fish. The oligodendroglia in these fish also revealed a prominent alteration of the endoplasmic reticulum and Golgi apparatus, with the accumulation of dense (secretion?) granules and large amounts of electron-opaque material in markedly dilated sacs of the endoplasmic reticulum. The authors postulate that this alteration is caused by a genetic defect in the control mechanism governing the elaboration of this material in the lordotic guppy, with subsequent stasis and crystallization of this material.
INTERACTION OF ESTROGEN AND PROGESTERONE IN CHICK OVIDUCT DEVELOPMENT
Authors: Oka Takami , Schimke Robert T.
Published: May 2004

Daily administration of estrogen to immature female chicks results in marked oviduct growth and appearance of characteristic tubular gland cells which contain lysozyme. Although a rapid increase in total DNA and RNA content begins within 24 hr, cell specific protein, lysozyme, is first detectable after 3 days of estrogen. Progesterone administered concomitantly with estrogen antagonizes the estrogen-induced tissue growth as well as appearance of tubular gland cells and their specific products, lysozyme and ovalbumin. When the initiation of progesterone administration is delayed for progressively longer periods (days) during estrogen treatment, proportionally greater growth occurs with more lysozyme and tubular gland cells after 5 days of total treatment. Progesterone does not inhibit the estrogen-stimulated increase in uptake of α-aminoisobutyric acid and water by oviduct occurring within 24 hr or the estrogen-induced increase in total lipid, phospholipid, and phosphoprotein content of serum. The above results of progesterone antagonism can best be explained by the hypothesis that progesterone inhibits the initial proliferation of cells which become tubular gland cells but does not antagonize the subsequent cytodifferentiation leading to the synthesis of lysozyme and ovalbumin once such cell proliferation has occurred.
THE ULTRASTRUCTURE OF THE CAT MYOCARDIUM
Authors: Fawcett Don W. , McNutt N. Scott
Published: May 2004

The ultrastructure of cat papillary muscle was studied with respect to the organization of the contractile material, the structure of the organelles, and the cell junctions. The morphological changes during prolonged work in vitro and some effects of fixation were assessed. The myofilaments are associated in a single coherent bundle extending throughout the fiber cross-section. The absence of discrete "myofibrils" in well preserved cardiac muscle is emphasized. The abundant mitochondria confined in clefts among the myofilaments often have slender prolongations, possibly related to changes in their number or their distribution as energy sources within the contractile mass. The large T tubules that penetrate ventricular cardiac muscle fibers at successive I bands are arranged in rows and are lined with a layer of protein-polysaccharide. Longitudinal connections between T tubules are common. The simple plexiform sarcoplasmic reticulum is continuous across the Z lines, and no circumferential "Z tubules" were identified. Specialized contacts between the reticulum and the sarcolemma are established on the T tubules and the cell periphery via subsarcolemmal saccules or cisterns. At cell junctions, a 20 A gap can be demonstrated between the apposed membranes in those areas commonly interpreted as sites of membrane fusion. In papillary muscles worked in vitro without added substrate, there is a marked depletion of both glycogen and lipid. No morphological evidence for preferential use of glycogen was found.
THE HISTOGENESIS OF RAT INTERCOSTAL MUSCLE
Authors: Kelly A. M. , Zacks S. I.
Published: May 2004

Intercostal muscle from fetal and newborn rats was examined with the electron microscope. At 16 days' gestation, the developing muscle was composed of primary generations of myotubes, many of which were clustered together in groups. Within these groups, the membranes of neighboring myotubes were interconnected by specialized junctions, including tight junctions. Morphologically undifferentiated cells surrounded the muscle groups, frequently extended pseudopodia along the interspace between adjacent myotubes, and appeared to separate neighboring myotubes from one another. At 18 and 20 days' gestation, the muscle was also composed of groups of cells but the structure of the groups differed from that of the groups observed at 16 days. Single, well differentiated myotubes containing much central glycogen and peripheral myofibrils dominated each group. These large cells were interpreted as primary myotubes. Small, less differentiated muscle cells and undifferentiated cells clustered around their walls. Each cluster was ensheated by a basal lamina. The small cells were interpreted as primordia of new generations of muscle cells which differentiated by appositional growth along the walls of the large primary myotubes. All generations of rat intercostal muscle cells matured to myofibers between 20 days' gestation and birth. Coincidentally, large and small myofibers diverged from each other, leading to disintegration of the groups of muscle cells. Undifferentiated cells frequently occurred in the interspaces between neighboring muscle cells at the time of separation. Myofibers arising at different stages of muscle histogenesis intermingled in a checkerboard fashion as a result of this asynchronous mode of development. The possibility of fusion between neighboring muscle cells in this developing system is discussed.
ANNULATE LAMELLAE AND "YOLK NUCLEI" IN OOCYTES OF THE DRAGONFLY, LIBELLULA PULCHELLA
Authors: Kessel R. G. , Beams H. W.
Published: May 2004

Annulated membranes in the form of single and short lamellae are present adjacent to and parallel to the nuclear envelope in oogonia and early oocyte (synaptene) stages of the dragonfly, Libellula pulchella. These solitary and short annulate lamellae are usually continuous with long, part rough- and part smooth-surfaced cisternae which extend into more distal areas of the oogonial ooplasm. These particular annulate lamellae then either disappear or decrease in number to be replaced by a much more extensive system of annulate lamellae in the cortical ooplasm of previtellogenic oocytes. The differentiation of extensive stacks of annulate lamellae is consistently observed to be restricted to large cytoplasmic areas of considerable electron density. These cytoplasmic regions consist of material which stains basophilic and contains RNA but differs structurally from the large number of ribosomes which surround the dense masses. The cytoplasmic dense masses, in terms of their formation and staining reactions, are comparable to the "yolk nuclei" or "Balbiani bodies" described in insect oocytes in earlier studies. The results of the present study thus provide evidence that the appearance of cortical ooplasmic stacks of annulate lamellae in the dragonfly oocyte is specifically limited to cytoplasmic areas of high electron density which contain RNA but which do not have a ribosomal morphology.
ULTRASTRUCTURE OF SARCOPLASMIC RETICULUM PREPARATIONS
Authors: Deamer D. W. , Baskin R. J.
Published: May 2004

Fragmented sarcoplasmic reticulum (FSR) from rabbit muscle was examined by positive staining, negative staining, and freeze-etch electron microscopic techniques in the absence and presence of calcium transport conditions. The existence of 30–40 A particles covering the outer surface of FSR vesicles was confirmed by two different negative stains in unfixed, glutaraldehyde-fixed and osmium tetroxide-fixed material. Freeze-etch microscopy revealed a second type of particle, 80–90 A in diameter, on the fractured surfaces of FSR vesicles. Following calcium oxalate accumulation, negative and positive staining techniques provided evidence for large nodular deposits within FSR vesicles which probably correspond to calcium oxalate crystals and are responsible for increments in turbidity during calcium oxalate accumulation. The most probable configuration of FSR vesicles in solution is spherical. "Tadpole" or tubular configurations were not seen by freeze-etch microscopy, positive staining, or in prefixed negatively stained material.
THE ULTRASTRUCTURE OF THE CAT MYOCARDIUM
Authors: McNutt N. Scott , Fawcett Don W.
Published: May 2004

The ultrastructure of the cells specialized for contraction in the atrium and ventricle of young adult cats are compared. The cells specialized for conduction are not included. In addition to possessing distinctive atrial granules, the cells of the atrium are smaller in diameter (5–6 µ) than ventricular cells (10–12 µ) and have strikingly fewer T tubules. These latter differences are discussed in terms of their possible significance for the rate of conduction of the action potential. It is suggested that the very small number of T tubules in atrial cells may compensate for the small cell diameter, and thus permit rapid conduction of the action potential across the surface of the atrium. Coated dense vesicles found in association with the sarcoplasmic reticulum at the level of the Z line in ventricular muscle are more evident in atrial cells. In the virtual absence of T tubules in atrial cells, the sub-sarcolemmal cisternae of the sarcoplasmic reticulum are almost exclusively at the cell periphery. The ends of the cells and their processes in ventricular muscle are rectilinear with the interdigitated portions of the intercalated discs oriented transversely, whereas those of the atrium are often oblique to the myofilament axis. This difference may be related to the lower mechanical tension on atrial cells.
CORRELATED MORPHOMETRIC AND BIOCHEMICAL STUDIES ON THE LIVER CELL
Authors: Stäubli Willy , Hess Robert , Weibel Ewald R.
Published: May 2004

The changes occurring in rat hepatocytes during a 5 day period of treatment with phenobarbital were determined by morphometric and biochemical methods, particular attention being paid to the endoplasmic reticulum. The hepatocytic cytoplasm played an overwhelming part in the liver hypertrophy, while the hepatocytic nuclei contributed to only a moderate extent. The endoplasmic reticulum accounted for more than half of the increase in cytoplasmic volume. The increase in the volume and number of hepatocytic nuclei in the course of phenobarbital treatment was associated with changes in the ploidy pattern. Until the 2nd day of treatment both the rough-surfaced endoplasmic reticulum (RER) and the smooth-surfaced endoplasmic reticulum (SER) participated in the increase in volume and surface of the whole endoplasmic reticulum (ER). Subsequently, the values for RER fell again to control levels, whereas those for SER continued to increase, with the result that by the 5th day of treatment the SER constituted the dominant cytoplasmic element. The specific volume of mitochondria and microbodies (peroxisomes) remained constant throughout the duration of the experiment, while that of the dense bodies increased. The specific number of mitochondria and microbodies displayed a significant increase, associated with a decrease in their mean volume. The phenobarbital-induced increase in the phospholipid and cytochrome P-450 content of the microsomes, as well as in the activities of microsomal reduced nicotinamide-adenine dinucleotide phosphate-cytochrome c reductase and N-demethylase, was correlated with the morphometric data on the endoplasmic reticulum.
EARLY STAGES OF INTESTINAL ABSORPTION OF SPECIFIC ANTIBODIES IN THE NEWBORN
Authors: Kraehenbuhl J. P. , Campiche M. A.
Published: May 2004

In mammals, passive immunity is transferred from mother to offspring by transplacental passage or by intestinal absorption. The rabbit receives antibodies exclusively across the placenta, whereas intestinal absorption is the principal source of antibodies for the new-born pig. In the rat, passive immunity is transferred by both pathways. The role of the jejunal absorptive cells was investigated in these three species, by the use of specific immune globulins as tracers of protein absorption. Rabbit anti-peroxidase and anti-ferritin antibodies were injected into the jejunum of newborn pigs, rats, and rabbits, and absorption was studied over the first 2 hr. The specific antibodies were detected in glutaraldehyde-fixed tissues after in vitro treatment with the antigens, and in sera by immunological methods. Intact antibodies are transferred into the circulation of the pig and the rat, but not into that of the rabbit. In the three species, the jejunal absorptive cells take up antibodies by endocytosis. In the pig, the antibodies are transported across the epithelium in vacuoles. In the rabbit, the endocytosis of antibodies triggers a lysosomal response and all absorbed antibodies are trapped in lysosomes. In the rat, both situations are found; there is no evidence of transfer of antibody fragments into the circulation.
BIOGENESIS OF MITOCHONDRIA
Authors: Kellerman G. M. , Biggs D. R. , Linnane Anthony W.
Published: May 2004

Growth under conditions of oxygen restriction results in a generalized decrease in the definition of the mitochondrial membranes, a decrease in the mitochondrial cytochromes, and a decrease in citric acid cycle enzymes of the obligate aerobic yeast Candida parapsilosis. Addition of unsaturated fatty acids and ergosterol to cultures exposed to limited oxygen results in improved definition of the mitochondrial membranes and an increase in the total mitochondrial cytochrome content of the cells. Euflavine completely inhibits mitochondrial protein synthesis in vitro. Its in vivo effect is to cause the formation of giant mitochondrial profiles with apparently intact outer membranes and modified internal membranes; the cristae (in-folds) appear only as apparently disorganized remnants while the remainder of the inner membrane seems intact. Cytochromes a, a3, b, and c1 are not synthesized by the cells in the presence of euflavine. Ethidium appears to have effects identical to those of euflavine, whereas chloramphenicol, lincomycin, and erythromycin have similar effects in principle but they are less marked. The effects of all the inhibitors are freely reversible after removal of the drugs. The results are discussed in terms of a functionally three-membrane model of the mitochondrion. In addition, the phylogenetic implications of the observed differences between this organism and the facultative anaerobic yeasts are considered.
DISTRIBUTION OF PEROXISOMES (MICROBODIES) IN THE NEPHRON OF THE RAT
Authors: Beard Margaret E. , Novikoff Alex B.
Published: May 2004

The distribution of peroxisomes (microbodies) in the rat nephron was studied cytochemically, using glutaraldehyde- or formaldehyde-fixed tissue, by means of α-hydroxy acid oxidase activity in light microscopy or oxidation of 3,3'-diaminobenzidine (DAB) at pH 9 in both light and electron microscopy.The two cytochemical methods show peroxisomes to be nearly sperical particles found only in cells of the proximal convoluted tubule. Lysosomes were identified in the same or parallel sections, with ß-glycerophosphate or 5'-cytidylic acid as substrate. They are found in all cells of the nephron. These cytochemical methods visualize the two organelles for light microscopy; they also permit unequivocal differentiation of all kidney peroxisomes from lysosomes in electron micrographs. Peroxisomes are larger and more reactive in the cells of the pars descendens (P3 segment) of the proximal convolution, located in the outer medulla and medullary rays, than in the cells of the pars convoluta (P1 and P2 segments), situated in the cortex. In contrast, lysosomes are much smaller in the P3 segment and larger and more reactive in the P1 and P2 segments. In all cells of the proximal convolution, peroxisomes tend to be concentrated nearer the base of the cells than do lysosomes. Mitochondria in P3 cells also show low levels of DAB oxidation at pH 6, in contrast to those in P1 and P2 cells. The possibility is discussed that P3 cells possess an extramitochondrial means of oxidation in which peroxisome oxidases play an important role.
NEGATIVE STAINING AND ADENOSINE TRIPHOSPHATASE ACTIVITY OF ANNULATE LAMELLAE OF NEWT OOCYTES
Authors: Scheer Ulrich , Franke Werner W.
Published: May 2004

Semi-isolated annulate lamellae were prepared from single newt oocytes (Triturus alpestris) by a modified Callan-Tomlin technique. Such preparations were examined with the electron microscope, and the negative staining appearance of the annulate lamellae is described. The annulate lamellae can be detected either adhering to the nuclear envelope or being detached from it. Sometimes they are observed to be connected with slender tubular-like structures interpreted as parts of the endoplasmic reticulum. The results obtained from negative staining are combined with those from sections. Especially, the structural data on the annulate lamellae and the nuclear envelope of the very same cell were compared. Evidence is presented that in the oocytes studied the two kinds of porous cisternae, namely annulate lamellae and nuclear envelope, are markedly distinguished in that the annulate lamellae exhibit a much higher pore frequency (generally about twice that found for the corresponding nuclear envelope) and have also a relative pore area occupying as much as 32% to 55% of the cisternal surface (compared with 13% to 22% in the nuclear envelopes). The pore diameter and all other ultrastructural details of the pore complexes, however, are equivalent in both kinds of porous cisternae. Like the annuli of the nuclear pore complexes of various animal and plant cells, the annuli of the annulate lamellae pores reveal also an eightfold symmetry of their subunits in negatively stained as well as in sectioned material. Furthermore, the annulate lamellae are shown to be a site of activity of the Mg-Na-K-stimulated ATPase.
ELECTRICAL AND MECHANICAL CHARACTERISTICS OF A VERY FAST LOBSTER MUSCLE
Authors: Mendelson Martin
Published: May 2004

The remotor muscle of the second antenna of the American lobster is functionally divided into two parts. One part produces slow, powerful contractions and is used for postural control. The other part produces very brief twitches, can follow frequencies over 100/sec without fusion and is probably used for sound production. This great speed is due, in part, to synchronous arrival of nerve impulses at multiple terminals, a very brief membrane electrical response and electrical continuity throughout large volumes of sarcoplasm. Calculations indicate that the very extensive sarcoplasmic reticulum is probably responsible for the rapid decline of tension in this muscle.
ENDOTHELIAL CONTRACTION INDUCED BY HISTAMINE-TYPE MEDIATORS
Authors: Majno Guido , Shea Stephen M. , Leventhal Monika
Published: May 2004

Previous work has shown that endogenous chemical mediators, of which histamine is the prototype, increase the permeability of blood vessels by causing gaps to appear between endothelial cells. In the present paper, morphologic and statistical evidence is presented, to suggest that endothelial cells contract under the influence of mediators, and that this contraction causes the formation of intercellular gaps. Histamine, serotonin, and bradykinin were injected subcutaneously into the scrotum of the rat, and the vessels of the underlying cremaster muscle were examined by electron microscopy. To eliminate the vascular collapse induced by routine fixation, in one series of animals (including controls) the root of the cremaster was constricted for 2–4 min prior to sacrifice, and the tissues were fixed under conditions of mild venous congestion. Electron micrographs were taken of 599 nuclei from the endothelium of small blood vessels representing the various experimental situations. Nuclear deformations were classified into four types of increasing tightness (notches, foldsl closing folds, and pinches. In the latter the apposed surfaces of the nuclear membrane are in contact). It was found that: (1) venous congestion tends to straighten the nuclei in al groups; (2) mediators cause a highly significant increase in the number of pinches (P < 0.001), also if the vessels are distended by venous congestion; (3) fixation without venous congestion causes vascular collapse. The degree of endothelial recoil, as measured by nuclear pinches, is very different from that caused by mediators (P < 0.001). (4) Pinched nuclei are more frequent in leaking vessels, and in cells adjacent to gaps (P < 0.001); (5) mediators also induce, in the endothelium, cytoplasmic changes suggestive of contraction, and similar to those of contracted smooth muscle; (6) there is no evidence of pericyte contraction under the conditions tested. Occasional pericytes appeared to receive fine nerve endings. Various hypotheses to explain nuclear pinching are discussed; the only satisfactory explanation is that which requires endothelial contraction.
PRESERVATION OF THE ULTRASTRUCTURE OF BACILLUS SUBTILIS BY CHEMICAL FIXATION AS VERIFIED BY FREEZE-ETCHING
Authors: Nanninga N.
Published: May 2004

The present study on the ultrastructure of Bacillus subtilis was undertaken in order to examine by means of the freeze-etching technique possible structural changes occurring during the chemical fixation procedure (Ryter-Kellenberger (R-K) fixation). Three stages were followed by freeze-etching, viz.: (a) fixation in osmium tetroxide, (b) fixation in osmium tetroxide and posttreatment with uranyl acetate, and (c) fixation in osmium tetroxide, posttreatment in uranyl acetate, and dehydration in a graded series of acetone. Preparations were made after each stage in the presence of 20% glycerol. Good preservation of ultrastructure was observed, after any of the three treatments, of the outer surface of the plasma membrane, and the inner surface of the plasma membrane. No alteration in fracturing properties could be observed. However, if we are to judge by the results of freeze-etching, any of the successive steps of the chemical fixation procedure achieve strong contrast between the nucleoplasmic region and the cytoplasm. Dependent on the quality of fixation, very delicately preserved DNA fibrils or strongly aggregated ones were seen. It appears that R-K fixation is capable of producing more or less distinctly visible changes in the native state of the nucleoplasm in young cells of B. subtilis.
ULTRASTRUCTURAL STUDIES OF RADIATION-INDUCED CHROMOSOME DAMAGE
Authors: Humphrey Ronald M. , Brinkley B. R.
Published: May 2004

The fine structure of radiation-induced chromosomal aberrations in Potorous tridactylis (rat kangaroo) cells was examined in situ by electron microscopy. The observations on the structure of terminal deletions (acentric fragments), anaphase bridges and "gaps," sidearm bridges, and specialized regions, such as the nucleolus organizer, are discussed in detail. Conclusions based on these observations are the following: (a) damage is physically expressed only at anaphase; (b) a gap region is composed of two subunits, each of which is about 800–1000 A in diameter and may correspond to a half-chromatid structure; (c) the ends of acentric fragments are structurally similar to normal chromosome ends, except where the break occurs in a specific region such as the secondary constriction; (d) at metaphase the fragment and the main portion of the chromosome move as a single unit to the equator, and the two units are disconnected only at the onset of anaphase; (e) sidearm bridges appear to be exchanges, involving a subchromatid unit. The interpretation of this evidence is consistent with the hypothesis that the chromosome is a multistranded structure.
LIPIDS OF ACANTHAMOEBA CASTELLANII
Authors: Ulsamer Andrew G. , Smith Frank Rees , Korn Edward D.
Published: May 2004

The lipids of Acanthamoeba castellanii (Neff) consist of 52% neutral lipids and 48% polar lipids. Triglycerides account for 75% and free sterols for 17% of the neutral lipids. The major phospholipids are phosphatidylcholine (45%), phosphatidylethanolamine (33%), phosphatidylserine (10%), a phosphoinositide (6%), and diphosphatidylglycerol (4%). The phosphoinositide is unique in that it contains fatty acids, aldehyde, inositol, and phosphate in the ratio of 1.4:0.5:1.1, but it contains no glycerol. Sphingomyelin, cerebrosides, psychosine, and glycoglycerides were not detected, but small amounts of unidentified long chain bases and sugars are present. The rates of uptake of palmitate-1-14C and of its incorporation into glycerides and phospholipids were not affected by the phagocytosis of polystyrene latex beads. Although phagocytosis usually decreased the uptake by amebas of phosphate-32P, serine-U-14C, and inositol-2-3H, their subsequent incroporation into phospholipids was not demonstrably stimulated or inhibited by phagocytosis. Phagocytosis did seem to increase the incorporation into ameba phospholipids of phosphatidylcholine-1 ,2-14C but not that of phosphatidylethanolamine-1 ,2-14C. These experiments, in which the incorporation of radioactive precursors into total cell lipids was measured, do not, of course, eliminate the possibility that localized effects may occur.
ACTIVATION IN VITRO OF RAT LIVER POLYRIBOSOMES
Authors: von der Decke Alexandra
Published: May 2004

The increase in the incorporation of amino acids into protein in vitro by preparations obtained from protein-fed rats as compared with preparations obtained from carbohydrate-fed rats has been described previously. After molecular sieving through Sephadex G-25 of cell-free preparations, the difference in incorporating activity between the two types of rats was diminished in systems containing ATP, phosphoenolpyruvate, pyruvate kinase, GTP, and a mixture of amino acids. When, after molecular sieving, a mitochondrial (15,000 g) supernatant was incubated for 4 min at 35°C the polysomal pattern of the preparations was unchanged. In the presence of ATP, phosphoenolpyruvate, and pyruvate kinase the polysomal incorporating activity was low and the polysomal pattern was only slightly changed. Addition of GTP increased the activity markedly, and a more pronounced activity was observed when a mixture of amino acids was added as well. As the amino acid incorporation ability increased, monosomes were formed from the polyribosomes. The activity of the polyribosomes was severalfold higher than that of non-Sephadex-treated preparations, indicating an activation of polysomal aggregates which under the usually applied conditions of incubation and prior to molecular sieving show little or insignificant activity. It was possible to activate polyribosomes from carbohydrate-fed and protein-fed rats to almost the same extent.
A COMPARISON OF CHLOROPLAST MEMBRANE SURFACES VISUALIZED BY FREEZE-ETCH AND NEGATIVE STAINING TECHNIQUES; AND ULTRASTRUCTURAL CHARACTERIZATION OF MEMBRANE FRACTIONS OBTAINED FROM DIGITONIN-TREATED SPINACH CHLOROPLASTS
Authors: Arntzen C. J. , Dilley R. A. , Crane F. L.
Published: May 2004

Spinach chloroplast lamellae were washed free of negatively staining surface particles (carboxydismutase and coupling factor protein) and the resulting smooth-surfaced lamellae still showed the usual large (175 A) and small (110 A) particles seen by freeze-etching. Therefore, the freeze-fracture plane probably occurs along an internal surface of the chloroplast membrane.

Fractions obtained by differential centrifugation of digitonin-treated chloroplast membranes were studied by negative staining, thin sectioning, and freeze-etching techniques for electron microscopy. The material sedimenting between 1,000 g and 10,000 g, enriched in photosystem II activity, was shown to consist of membrane fragments. These freeze-etched membrane fragments were found to have large particles on most of the exposed fracture faces. The large particles had the same size and distribution pattern as the 175 A particles seen in intact chloroplast membranes. The material sedimenting between 50,000 g and 144,000 g, which had only photosystem I activity, was found to consist of particles in various degrees of aggregation. Freeze-etching of this fraction revealed only small particles corresponding to the 110 A particles seen in intact chloroplasts. A model is presented suggesting that chloroplast lamellar membranes have a binary structure, which digitonin splits into two components. The two membrane fragments have different structures, revealed by freeze-etching, and different photochemical and biochemical functions.
A SIMPLE MODEL OF A STEADY STATE DIFFERENTIATING CELL SYSTEM
Authors: Rubinow S. I.
Published: May 2004

A simple theoretical model is hypothesized to describe the steady state behavior of a differentiating cell system as exemplified by blood cells. The cell system consists of several morphologically distinguishable cell classes which develop sequentially. Each cell class except the last one is mitotically capable. Mitosis is assumed to be either heteromorphogenic, homomorphogenic, or asymmetric. Some algebraic equations are derived which are conservation equations describing the flux of cells from one class to another. The theoretical considerations have been applied to some experimental observations in humans concerning neutrophil production, particularly in reference to relative cell numbers and mitotic fractions of the myeloblast, promyelocyte, and myelocyte cell classes. These observations are utilized to help determine the values of the parameters which characterize the model. Among these parameters are the generation times of the various cell classes, and the predicted values of the generation times are found to be in excellent agreement with observed grain-count halving times. However, the predicted mitotic times are in disagreement with their observed values.
ISOLATION AND CHARACTERIZATION OF GOLGI MEMBRANES FROM BOVINE LIVER
Authors: Fleischer Becca , Fleischer Sidney , Ozawa Hidehiro
Published: May 2004

Zonal centrifugation has been used to isolate a fraction from bovine liver which appears to be derived from the Golgi apparatus. Morphologically, the fraction consists mainly of sacs and tubular elements. Spherical inclusions, probably lipoproteins, are occasionally seen in negative stains of this material. The preparation is biochemically unique. UDP-galactose:N-acetyl glucosamine, galactosyl transferase activity is concentrated about 40-fold in this fraction compared to the homogenate. Rotenone- or antimycin-insensitive DPNH- or TPNH- cytochrome c reductase activities are 60–80% of the level of activities found in microsomes. Purified organelles from bovine liver such as plasma membranes, rough microsomes, mitochondria and nuclei have negligible levels of galactosyl transferase. Some activity is present in smooth microsomes but at a level compatible with the possible presence of Golgi membranes in this fraction. The Golgi fraction does not contain appreciable amounts of enzymes such as ATPase, 5'-nucleotidase, glycosidase, glucose-6-phosphatase, acid phosphatase, or succinate-cytochrome c reductase. Similar fractions isolated from bovine epididymis also have very high levels of galactosyl transferase. The fraction is heavily osmicated when incubated for long periods of time at elevated temperatures, a characteristic property of Golgi membranes.