bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of OsO4 Fixative for Feulgen-Stained Preparations
Authors: Rudzinska Maria A.
Published: May 2004

OsO4 has many advantages over Carnoy's fixative mixture for the Feulgen nuclear staining in the protozoan Tokophrya infusionum.

While Carnoy's fluid used prior to the Feulgen reaction produces shrinkage of the macronucleus and coarse clumping of its chromatin bodies, OsO4 preserves faithfully the size and shape of the macronucleus and its chromatin material.

This finding seems to be of special importance in view of the fact that electron microscopy relies on OsO4 fixation. The satisfactory preservation of structured detail in Feulgen-stained preparations is of importance for the correlation of histochemical and morphological information.
FINE STRUCTURAL ALTERATIONS IN CELL PARTICLES DURING CHEMICAL CARCINOGENESIS
Authors: Arcos Joseph C. , Gosch Hans H. , Zickafoose David
Published: May 2004

The previous studies on the correlation between tumor incidence and changes in microsomal and mitochondrial swelling during feeding of 3'-methyl-4-dimethylaminoazobenzene to rats have been extended to other hepatic carcinogens. Administration of 4'-fluoro-4-dimethylaminoazobenzene, 4'-ethyl-2-methyl-4-dimethylaminoazobenzene, 2-acetylam-inofluorene, ethionine, and tannic acid were found to produce drastic alterations of the swelling of rat liver mitochondria. In contrast to these compounds, feeding of the non-carcinogenic azobenzene and 4-diethylaminoazobenzene produced only small changes in swelling. Significant modification in the over-all pattern of the swelling curve was observed when the usual concentration of 3'-methyl-4-dimethylaminoazobenzene was reduced, but not when the riboflavin level in the diet was increased tenfold. Feeding of high levels of this dye to the guinea pig did not affect mitochondrial swelling which is consistent with the resistance of this species to azo-dye carcinogenesis. Hypophysectomy provides protection against the alterations, produced by feeding 3'-methyl-4-dimethylaminoazobenzene, in the characteristics of thyroxine- or mercuric chloride-induced mitochondrial swelling. Studies with citric cycle substrates on mitochondrial swelling suggest block of the glutamate ⇌ α-keto-glutarate pathway after feeding 3'-methyl-4-dimethylaminoazobenzene for 4 weeks. There is a considerable, but reversible, reduction of certain types of mitochondrial swelling in two situations associated with rapid liver growth: after partial hepatectomy and after intraperitoneal injection of 20-methylcholanthrene. Naphthacene, however, which also stimulates rapid liver growth, does not affect mitochondrial swelling.
ULTRASTRUCTURAL STUDY OF REMYELINATION IN AN EXPERIMENTAL LESION IN ADULT CAT SPINAL CORD
Authors: Bunge Mary Bartlett , Bunge Richard P. , Ris Hans
Published: May 2004

This report presents ultrastructural observations on the cytological events that attend myelin formation occurring in the wake of demyelination in adult cat spinal cord. Lesions were induced in subpial cord by cerebrospinal fluid (c.s.f.) exchange (1, 2). Tissue from eleven cats at nine intervals from 19 to 460 days was fixed in situ by replacing c.s.f. with buffered OsO4 and embedded in Araldite. After demyelination, axons are embraced by sheet-like glial processes. An occasional myelin sheath is first seen at 19 days; by 64 days, all axons are at least thinly myelinated. The cytoplasm of the myelin-forming cells, unlike that of either oligodendrocyte or fibrous astrocyte in normal cord, is dense with closely packed organelles and fine fibrils. Many of the myelinogenic cells become scarring astrocytes and at 460 days the lesion teems with their fibril-filled processes. Oligodendrocytes appear in the lesion after remyelination is under way. Phagocytes disappear gradually. A myelin sheath is formed by spiral wrapping of a sheet-like glial process around an axon. Where the first turn of the spiral is completed, a mesaxon is formed. As cytoplasm is lost from the process, the plasma membrane comes together along its outer and cytoplasmic surfaces to form compact myelin. Only a small amount of cytoplasm is retained; it is confined to the paramesaxonal region and, on the sheath exterior, to a longitudinal ridge which appears in profile as a small loop. This outer loop has the same rotational orientation as the inner mesaxon. These vestiges of spiral membrane wrapping are also found in normal adult and new-born cat cord. Nodes are present in all stages of remyelination and in normal adult cat and kitten cord. These observations suggest that myelin is reformed in the lesion in the same way it is first formed during normal development. The mechanism of myelin formation is basically similar to that proposed for peripheral nerve and amphibian and mammalian optic nerve; it does not agree with present views on the mechanism of myelinogenesis in mammalian brain and cord. This is the first demonstration of remyelination in adult mammalian central nervous tissue.
CHANGES IN THE SPERMATOZOON DURING FERTILIZATION IN HYDROIDES HEXAGONUS (ANNELIDA)
Authors: Colwin Arthur L. , Colwin Laura Hunter
Published: May 2004

This, the last of a series of three papers, deals with the final events which lead to the incorporation of the spermatozoon with the egg. The material used consisted of moderately polyspermic eggs of Hydroides hexagonus, osmium-fixed at various times up to five minutes after insemination. The first direct contact of sperm head with egg proper is by means of the acrosomal tubules. These deeply indent the egg plasma membrane, and consequently at the apex of the sperm head the surfaces of the two gametes become interdigitated. But at first the sperm and egg plasma membranes maintain their identity and a cross-section through the region of interdigitation shows these two membranes as a number of sets of two closely concentric rings. The egg plasma membrane rises to form a cone which starts to project into the hole which the spermatozoon earlier had produced in the vitelline membrane by means of lysis. But the cone does not literally engulf the sperm head. Instead, where they come into contact, sperm plasma membrane and egg plasma membrane fuse to form one continuous membranous sheet. At this juncture the two gametes have in effect become mutually incorporated and have formed a single fertilized cell with one continuous bounding membrane. At this time, at least, the membrane is a mosaic of mostly egg plasma membrane and a patch of sperm plasma membrane. The evidence indicates that the fusion of the two membranes results from vesiculation of the sperm and egg plasma membranes in the region at which they come to adjoin. Once this fusion of membranes is accomplished, the egg cytoplasm intrudes between the now common membrane and the internal sperm structures, such as the nucleus, and even extends into the flagellum; finally these sperm structures come to lie in the main body of the egg. The vesiculation suggested above appears possibly to resemble pinocytosis, with the difference that the vesicles are formed from the plasma membranes of two cells. At no time, however, is the sperm as a whole engulfed and brought to the interior of the egg within a large vesicle.
SERUM FRACTIONATION AND THE EFFECTS OF BOVINE SERUM FRACTIONS ON HUMAN CELLS GROWN IN A CHEMICALLY DEFINED MEDIUM
Authors: Holmes Richard , Wolfe Sonya W.
Published: May 2004

Serum has been fractionated by curtain electrophoresis using carboxymethyl cellulose dissolved in sodium bicarbonate electrolyte. Various fractions were produced from bovine serum and added to replicate cultures of Chang's endoepithelial cells and HeLa cells grown in a chemically defined medium. The effects of each of the various fractions on the appearance of the cultures and on cell multiplication were studied. Three different fractions were obtained and two were subjected to further purification. One fraction associated with albumin promoted survival, attachment, and flattening as well as cell multiplication. A second fraction associated with the alpha globulins promoted survival and multiplication of some cells. A third fraction caused cells to aggregate and form free floating clumps. An adequate chemically defined medium for continuous growth of human cells was used throughout the study. The response of cells to alterations in their environment which simulated some of the effects produced by serum fractions is described.
AUTORADIOGRAPHIC ANALYSIS ON AGAR PLATES OF ANTIGENS FROM SUB CELLULAR FRACTIONS OF RAT LIVER SLICES
Authors: Morgan W. S. , Perlmann P. , Hultin T.
Published: May 2004

Slices of rat livers were incubated with 14C amino acids, homogenized, and subjected to differential centrifugation. The microsomes were further extracted with the non-ionic detergent Lubrol W and with EDTA. These extracts and the microsome free "cell sap," freed from the pH 5 precipitable fraction, were subsequently reacted with antisera using agar diffusion techniques. The antisera employed were obtained from rabbits injected with different subcellular fractions of rat liver or with rat serum proteins. When the agar diffusion plates were autoradiographed it was found that some of the precipitates were radioactive while others were not. Control experiments indicated that this labeling was due to the specific incorporation of 14C amino acids into various rat liver antigens during incubation of the slices rather than to a non-specific adsorption of radioactive material to the immunological precipitates. When the slices were incubated with the isotope for up to 30 minutes, the serum proteins which could be extracted from the microsomes with the detergent were strongly labeled, as were a number of additional microsomal antigens of unknown significance. In contrast, the serum proteins present in the cell sap were only weakly labeled. Most of the typical cell sap proteins, both those precipitable and those soluble at pH 5, seemed to remain unlabeled. No consistently reproducible results were obtained with the EDTA extracts of the ribosomal residues remaining after extraction of the microsomes with the detergent. Incubation of the liver slices for longer periods (up to 120 minutes) led to a strong labeling of the serum proteins in the cell sap as well as to the appearance of labeling in additional cell sap proteins. The results are discussed with regard to the subcellular site of synthesis and the metabolism of the different antigens.
FINE STRUCTURE OF THE LARVAL ANURAN EPIDERMIS, WITH SPECIAL REFERENCE TO THE FIGURES OF EBERTH
Authors: Chapman George B. , Dawson Alden B.
Published: May 2004

Small pieces of skin from 8 cm long Rana clamitans larvae were fixed in OsO4, washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU 2D. The sections showed that aggregates of fibrous material in the cells of the inner layer of epidermal cells are identical in disposition and size with the classical figures of Eberth. It is conclusively shown that these figures do not arise from an aggregation of mitochondrial filaments. The tendency of the fibrils to concentrate on attachment points, or thickenings of the basal plasma membrane, is noted. It is also observed that numerous mitochondria are located in the distal region of the cells of the outer layer of epidermis in association with the secretory vacuoles. Microvilli are seen occasionally on the free surface of the skin. Cisternae are found only in the cells of the outer epidermal layer, while vesicular endoplasmic reticulum is found in the cells of both epidermal layers.
ULTRASTRUCTURAL CYTOCHEMISTRY
Authors: Leduc Elizabeth H. , Bernhard Wilhelm
Published: May 2004

Selective extraction of specific cell components by enzyme or acid hydrolysis is possible from ultrathin sections for electron microscopy and parallel 2 µ sections for light microscopy of tissues fixed in formalin and embedded in a water-soluble polyepoxide, product X133/2097. Normal rat tissues fixed 15 minutes in formalin at 3°C are more rapidly digested by proteinases than those fixed for the same length of time at 20°C. Trypsin selectively attacks the nuclear chromatin and the ribonucleoprotein particles of the ergastroplasm, whereas mitochondria and zymogen granules resist tryptic digestion. Pepsin rapidly attacks the mitochondria and zymogen granules. The ergastoplasm and nucleus at first resist peptic digestion, but in time the entire cytoplasm and interchromatinic portion of the nucleus are attacked. Ribonuclease abolishes cytoplasmic basophilia in 2 µ sections, but parallel ultra-thin sections, stained with uranyl acetate and examined in the electron microscope, show no change in the ribonucleoprotein particles of the ergastoplasm. Desoxyribonuclease alone had no effect, but after pretreatment of the sections with pepsin or hydrochloric acid, desoxyribonuclease specifically attacked the nuclear chromatin. Nucleic acid-containing structures in the sections are gradually disintegrated by perchloric acid or hydrochloric acid.
THE FINE STRUCTURE OF NEUROMUSCULAR JUNCTIONS AND THE SARCOPLASMIC RETICULUM OF EXTRINSIC EYE MUSCLES OF FUNDULUS HETEROCLITUS
Authors: Reger James F.
Published: May 2004

The extrinsic eye muscles of the killifish (F. heteroclitus) were fixed in OSO4 (pH 7.6) and subsequently dehydrated, embedded, and sectioned for electron microscopy. The fine structures of neuromuscular junctions and of sarcoplasmic reticulum were then observed.

The neuromuscular junction consists of the apposition of axolemma (60 to 70 Å) and sarcolemma (90 to 100 Å), with an intervening cleft space of 200 to 300 Å, forming a synaptolemma 400 to 500 Å thick. The terminal axons contain synaptic vesicles, mitochondria, and agranular reticulum. The subsynaptic sarcolemma lacks the infolding arrangement characteristic of neuromuscular junctions from other vertebrate skeletal muscle, making them more nearly like that of insect neuromuscular junctions. A comparison between the folded and non-folded subsynaptic membrane types is made and discussed in terms of comparative rates of acetylcholine diffusion from the synaptic cleft and resistances of the clefts and subsynaptic membranes. The sarcoplasmic reticulum consists of segmentally arranged, membrane-limited vesicles and tubular and cisternal elements which surround individual myofibrils in a sleeve-like arrangement. Triadic differentiation occurs at or near the A-I junction. Unit sleeves span the A and I bands alternately and consist of closed terminal cisternae interconnected across the A and I bands by tubular cisternae. The thickness of the sarcoplasmic membranes increases from 30 to 40 Å in intertriadic regions to 50 to 70 Å at the triads. The location of the triads is compared with previously described striated muscle from Ambystoma larval myotomes, cardiac and sartorius muscles of the albino rat, mouse limb muscle, chameleon lizard muscle, and insect muscle, with reference to their possible role in intracellular impulse conduction.
THE STRUCTURE OF INSECT FIBRILLAR FLIGHT MUSCLE
Authors: Smith David S.
Published: May 2004

The fine structure of fibrillar flight muscle of the mature adult beetle Tenebrio molitor is described. Although the very high frequency of contraction of fibrillar muscle has previously been in part accounted for as the result of mechanical specialization of the wing-bearing segment rather than of a correspondingly high rate of motor impulse supply, the problem of the nature of the pathway by which excitation is conducted into these large fibers remained. Therefore, particular attention has been given to the disposition and relationships of the plasma membrane and sarcoplasmic reticulum in this tissue. The invading tracheoles draw with them a sheath of plasma membrane from the surface to all depths in the fiber, and it is suggested that these sheaths, together with the extensive tubular arborisations arising from them, reduce the maximum plasma membrane-to-fibril distance from the radius of the fiber to a value of less than 2 µ. The evidence presented here confirms Veratti's contention that in fibrillar muscle the "reticulum" is associated with, though entirely distinct from the fibrils. Unlike other muscles so far examined, these flight muscle fibers contain a plasma membrane reticulum only, but it is possible that elsewhere the general "sarcoplasmic reticulum" includes a component derived from the plasma membrane, likewise acting as the pathway for inward conduction of excitation. Profiles of the internalised plasma membrane in Tenebrio showing the usual triple-layered 25-25-25 A organization are frequently seen, in sections, in close association with isolated vesicles (defined by "simple" 50 A membranes) which are here considered to represent, in vestigial form, the portion of the sarcoplasmic reticulum which in other types of muscle is complex and highly developed. Such associations, in Tenebrio, between these two dissimilar elements are here termed "dyads" and the possible morphological and functional homology between these and the "triads" of other types of fiber is considered.
DEVELOPMENT AND GERMINATION OF THE AZOTOBACTER CYST
Authors: Wyss Orville , Neumann Marilyn G. , Socolofsky M. D.
Published: May 2004

The fine structure of Azotobacter vinelandii has been studied by means of electron microscopy of ultrathin sections made of the encysting and germinating cells. The organisms were fixed with KMnO4 and embedded in epoxy resin. On an encystment medium the rod-shaped bacteria begin to assume an almost spherical form and then bark-like exine appears in 1½ to 2 days. The exine thickens and an electron permeable intine forms between it and the shrinking cell body. In 5 days the intine makes up more than half of the cyst volume and begins to show a definite two-layered structure. Meanwhile the peripheral bodies, which may be extensions of the cell membrane of the vegetative cell, disappear as the encystment progresses. The cell wall and membrane of the vegetative cell remain demonstrable as the confining structure of the shrinking central body of the mature cyst. In this central body lipoidal globules appear together with aggregations of nuclear material. Cyst germination begins with an increase in the size of the central body at the expense of the intine. The nuclear aggregations become more diffuse and the lipoidal globules disappear. The exine may be pushed outward and the bark-like fragments separate as the emerging vegetative cell develops. Invagination of the cell wall and membrane may occur at this stage leading to cell division. Empty exines remain as horseshoe-shaped structures.
THE FINE STRUCTURE OF INHIBITORY SYNAPSES IN THE CRAYFISH
Authors: Peterson R. Price , Pepe Frank A.
Published: May 2004

Physiological investigations have shown that the synaptic input to the sensory neuron of the stretch receptor in the abdominal muscles of the crayfish is purely inhibitory. This neuron was chosen, therefore, as a site in which to study the fine structure of inhibitory synaptic endings. It was hoped that this fine structure might (a) provide a morphological prototype for the study of more complex synaptic systems and (b) reflect the inhibitory mechanisms. Stretch receptors were fixed in situ in buffered OsO4, dehydrated, and embedded in Araldite. Both cross and longitudinal sections were examined after staining with phosphotungstic acid. The inhibitory endings were easily identified by their great similarity to previously described excitatory endings. Small circular profiles (synaptic vesicles) about 460 A in diameter and an accumulation of mitochondria were consistently observed within the presynaptic endings. An increased osmiophilia of pre- and postsynaptic membranes, where they were in apposition, was also seen. The only observed difference between these inhibitory endings and excitatory endings, described by other authors, was the variable presence of a latticework of 230 A tubules in the connective tissue immediately adjacent to the inhibitory endings. Inhibitory endings were observed on all parts of the sensory neuron except the axon.
INTRACELLULAR CRYSTALLINE ERGOSTEROL IN NEUROSPORA
Authors: Tsuda Seizo , Tatum E. L.
Published: May 2004

In the fungus Neurospora crassa, hexagonal crystalline inclusions have been observed with both the light and electron microscopes. These crystals have been enriched by differential centrifugation and found to be identical with ergosterol by the criteria of ultraviolet spectral analysis and cytochemical analysis. Observations have been made on the distribution and fine structure of the crystalline bodies in various wild type and mutant strains of N. crassa.
THE STRUCTURE OF THE YOLK OF THE HEN'S EGG AS STUDIED BY ELECTRON MICROSCOPY
Authors: Bellairs Ruth
Published: May 2004

A description of the fine structure of the yolk of the unincubated hen's egg has been provided, which will serve as a basis for further studies on yolk digestion. The gross components of the yolk (that is, free-floating lipid drops, yellow and white yolk spheres together with their enclosed lipid subdroplets, and aqueous protein fluid) could be recognized by phase contrast and low power electron microscopy. The majority of the lipid drops, whether free floating or enclosed within yolk spheres, were composed of particles about 30 to 60 A in diameter. The protein component of the yolk was found to consist of round profiles about 250 A in diameter. The surfaces of the yolk spheres were of three types, and it is difficult to decide which represents the true structure although reasons are given for believing that yolk spheres are not normally enclosed by membranes identical with cell membranes.
STUDIES ON FORMALIN FIXATION FOR ELECTRON MICROSCOPY AND CYTOCHEMICAL STAINING PURPOSES
Authors: Holt S. J. , Hicks R. Marian
Published: May 2004

A study has been made of the preservation of fine structure, phospholipids, and the activity of acid phosphatase and esterase in rat liver fixed in various solutions containing 4 per cent formaldehyde. Examination of methacrylate-embedded preparations shows that calcium-containing fixatives result in poor preservation of fine structure, whereas veronal-treated or phosphate-buffered formalin gives excellent results if the tonicity of the solutions is suitably adjusted by addition of sucrose. Formol-phosphate, to which Versene has been added, causes deterioration of cellular morphology. Phospholipids are retained almost quantitatively in tissue fixed in formol-calcium, and in phosphate-, collidine-, or triethanolamine-buffered formalin. About 50 per cent of the activity of acid phosphatase and esterase are preserved after 24 hours exposure to these fixatives at 0–2°C, and the distributions of the enzymes and of phospholipids, as judged by cytochemical staining results, are not altered by any of these formalin solutions. Consideration of the morphological and biochemical integrity of the fixed tissue suggests that 4 per cent formaldehyde, buffered at pH 7.2 with 0.067 M phosphate, and containing 7.5 per cent sucrose, is the most suitable of the fixatives for combined cytochemical staining and electron microscopical studies.
MORPHOLOGY OF ISOLATED RABBIT HEART MUSCLE MITOCHONDRIA AND THE OXIDATION OF EXTRAMITOCHONDRIAL REDUCED DIPHOSPHOPYRIDINE NUCLEOTIDE
Authors: Deshpande P. D. , Hickman D. D. , Von Korff R. W.
Published: May 2004

The morphology of rabbit heart muscle mitochondria isolated in several media has been compared by electron microscopy. The internal structure of isolated mitochondria differs from that of in situ mitochondria, with the type and degree of alteration depending on the isolation medium. Examination of the isolated mitochondria after incubation revealed that additional morphological changes occurred during incubation, but these changes were less pronounced when the incubation was conducted in a complete medium containing substrate. The isolated mitochondria have been shown to be capable of catalyzing a slow aerobic oxidation of extramitochondrial reduced diphosphopyridine nucleotide. The rate of DPNH oxidation observed is sufficient to account for the ability of the mitochondria to oxidize lactate in the presence of catalytic amounts of DPNH. The suspensions used were essentially free of mitochondrial fragments, which are known to oxidize DPNH. Possible relationships of these findings to metabolism in situ are discussed. The results indicate the desirability of correlating biochemical activities with the morphology of isolated mitochondria.
METHODS FOR THE USE OF INDIUM AS AN ELECTRON STAIN FOR NUCLEIC ACIDS
Authors: Watson Michael L. , Aldridge William G.
Published: May 2004

Methods are presented for the staining of blocks of tissue with trivalent indium so that good contrast and good specificity for nucleic acids is achieved for the electron microscope. The tissue is fixed in organic fixative, dehydrated, subjected to reduction by lithium borohydride, acetylated by acetic anhydride, stained with trivalent indium dissolved in organic solvent, and embedded. The embedding material may be either Vestopal or butyl methacrylate especially handled to eliminate the "explosion" phenomenon. Numerous new problems encountered are discussed and a brief description of the findings is included.
TRANSIENT PHOSPHORYLATION OF DEOXYRIBOSIDES AND REGULATION OF DEOXYRIBONUCLEIC ACID SYNTHESIS
Authors: Hotta Yasuo , Stern Herbert
Published: May 2004

Microspores isolated from Lilium longiflorum and Trillium erectum were studied with respect to their capacities for phosphorylating deoxyribosides in vitro. It was found that such capacities are manifest only during brief intervals of time adjacent to periods of DNA synthesis, and that none of the neighboring cells in the anther acquire them. The observed patterns of behavior are interpreted in terms of enzyme induction as a device for regulating DNA synthesis.
MATURATION OF THE RAT FETAL THYROID
Authors: Feldman Joseph D. , Vazquez Jacinto J. , Kurtz Stanley M.
Published: May 2004

Maturation of the rat fetal thyroid was studied with the aid of I131 and of fluorescence and electron microscopy. The I131 concentration of the fetal gland increased exponentially from day 17 to day 20 of gestation and was related to the weight of the fetus (and presumably the weight of the thyroid) and also to the quantity of I131 accumulated by the fetus. In the 17-day gland, thyroglobulin or immunologically similar material was sparsely present in the incipient lumens of some cell clusters. With maturation, this material increased and was also observed within follicular cells on days 18 to 19 of gestation. On day 20, the specifically reacting material was present in the follicular lumens and was absent from the cytoplasm of follicular epithelium. Ultrastructurally, the earliest thyroid cells examined were replete with all the organelles found in the more mature epithelium. No direct correlation could be made between the cytoplasmic structures and the presence of thyroglobulin, although the granular endoplasmic reticulum was most likely the organelle responsible for synthesis of thyroglobulin. Thyroglobulin or a precursor was found in fetal thyroid cells before measurable quantities of I131 were concentrated and before cytoplasmic droplets appeared.
FINE STRUCTURE OF THE PHOTOSYNTHETIC BACTERIUM RHODOMICROBIUM VANNIELII
Authors: Boatman Edwin S. , Douglas Howard C.
Published: May 2004

The fine structure of the photosynthetic bacterium Rhodomicrobium vannielii was studied by the ultra thin sectioning technique. Cells were fixed in buffered osmium tetroxide and embedded in Epoxy resin. The feature most common to nearly all cells was an array of intracellular membranes situated in a concentric manner at the periphery of the cell. The membranes were mostly paired and quite often five pairs were seen aligned together. Calculations from densitometric tracings showed the average width of a "unit" membrane to be 65 A. Sections of material from disrupted cells after passage through a sucrose gradient revealed vesicular forms composed of membranes similar in width to those in the intact cell. Absorption spectra of both intact cells and isolated membranes were very similar in the bacteriochlorophyll regions. Septa and membranes were demonstrated in the filaments that join mature cells. No evidence for chromatophores was obtained although the methods used were adequate for their demonstration in Rhodospirillum rubrum.
THE TWO-WAVELENGTH METHOD OF MICROSPECTROPHOTOMETRY
Authors: Mendelsohn Mortimer L.
Published: May 2004

In connection with the potential development of automatic two-wavelength microspectrophotometry, a new version of the two-wavelength method has been formulated. Unlike its predecessors, the Ornstein and Patau versions, the new method varies the area of the photometric field seeking to maximize a relationship between distributional errors at the two wavelengths. Stating this distributional error relationship in conventional photometric terms, the conditions at the maximum are defined by taking the first derivative with respect to field size and setting it equal to zero. This operation supplies two equations; one relates the transmittances at the two wavelengths, and a second states the relative amount of chromophore in the field in terms of transmittance at one wavelength. With the first equation to drive a servomechanism which sets the appropriate field size, the desired answer can then be obtained directly and continuously from the second equation. The result is identical in theory with those of the earlier methods, but the technique is more suitable for electronic computing.
THE USE OF SPECIFIC ANTIBODY IN ELECTRON MICROSCOPY
Authors: Pepe Frank A. , Finck H.
Published: May 2004

Glycerinated chicken muscle was stained with antimyosin antibody conjugated with mercury and fluorescein. The antibody was visualized in both the electron and the fluorescence microscope by using adjacent thin and thick sections. In order to make this possible, Araldite was used as the embedding medium. The mercury was reduced to metallic mercury in the electron beam and either migrated in the section or was sublimated in the vacuum. Therefore special techniques of carbon filming had to be used to prevent this. Some nonspecific staining occurred because of the binding of mercury to available sulfhydryl groups in the tissue. The available sulfhydryl groups were blocked by pretreating the tissue with iodoacetic acid and formaldehyde. The non-specific staining which occurred after this treatment was easily removed by brief washing with a buffered solution of thioglycolic acid.
THE FINE STRUCTURE OF BONE CELLS
Authors: Dudley H. Robert , Spiro David
Published: May 2004

An electron microscopic study of Araldite-embedded, undecalcified human woven and chick lamellar bone is presented. The fine structure of the cells of bone in their normal milieu is described. Active osteoblasts possess abundant granular endoplasmic reticulum, numerous small vesicles, and a few secretion droplets. Their long cytoplasmic processes penetrate the osteoid. The transition of osteoblasts into osteoid osteocytes and then into osteocytes is traced and found to involve a progressive reduction of cytoplasmic organelles. Adjoining the osteocytes and their processes is a layer of amorphous material which is interposed between the cell surfaces and the bone walls of their respective cavities. Osteoclasts contain numerous non-membrane-associated ribosomes, abundant mitochondria, and little granular endoplasmic reticulum, thus differing markedly from other bone cells. The brush border is a complex of cytoplasmic processes adjacent to a resorption zone in bone. No unmineralized collagen is seen at resorption sites and it appears that collagen is removed before or at the time of mineral solution. All bone surfaces are covered by cells, some of which lack distinctive qualities and are designated endosteal lining cells. The structure of osteoid, bone, and early mineralization sites is illustrated and discussed.
ELECTRON MICROSCOPIC AND HISTOCHEMICAL COMPARISON OF THE TWO TYPES OF ELECTROPLAQUES OF NARCINE BRASILIENSIS
Authors: Wachtel Allen , Mathewson Robert , Grundfest Harry
Published: May 2004

The torpedine electric fish Narcine brasiliensis has two morphologically distinct electric organs (main and accessory) which also differ with respect to a number of electrophysiological properties. The fine structure of the electroplaques of these organs has been examined by electron microscopy and by a histochemical method for localizing esterase activity with a high degree of resolution. In both kinds of electroplaques the innervated surface (ventral in those of the main organ, dorsal in those of the accessory) is the only site of esterase activity. The latter is further confined to the regions of synaptic contact between vesicle-containing axon terminals and the electroplaque membrane. The synaptic apparatus is similar to, but less elaborate than, that of neuromuscular junctions. The axon terminals and electroplaque membranes are free of connective tissue envelopments. The membrane of the uninnervated surfaces forms a continuum with a dense canalicular network which penetrates deeply into the 7 µ thick electroplaques of the main organ. The canalicular network has about the same thickness in the 20 µ electroplaques of the accessory organ. Except for this difference, the two kinds of cells appear to have the same fine structure. This finding is discussed in relation to the electrophysiological data on functional differences.
THE ULTRASTRUCTURE AND HISTOCHEMISTRY OF A NEMATODE-INDUCED GIANT CELL
Authors: Bird Alan F.
Published: May 2004

The development of giant cells induced by the nematode Meloidogyne in tomato roots has been followed under controlled growth conditions and the ultrastructure and histochemistry of these structures have been examined. Entry of the nematode larvae into the roots took place within 24 hours; giant cell formation started on the 4th day and involved breakdown of the cell walls accompanied by thickening of a surrounding giant cell wall and an increase in density and area of the cytoplasm. The nuclei increased in number by simultaneous mitosis throughout a single giant cell. The peak of cytoplasmic density was reached after moulting and during egg production. The rate of protein synthesis in the giant cell is correlated with the rate of growth of the nematode. The giant cell wall is a thick, irregularly surfaced structure which contains all the normal polysaccharide components of a cell wall. The cytoplasm is rich in protein and RNA and contains mitochondria, proplastids, Golgi bodies, and a dense endoplasmic reticulum. The nuclei are large and irregular in shape and contain large nucleoli and a number of Feulgen-positive bodies scattered irregularly along the nuclear envelope. The nucleolus contains RNA and fat as well as Feulgen-positive granules which are revealed after treatment with ribonuclease. It consists of a dense outer cortex surrounding a much lighter central core and is connected at times with the Feulgen-positive bodies in the nucleus. Speculation is provided on the role of these bodies in cytoplasmic protein synthesis.
ON THE PERSISTENCE OF OOCYTE NUCLEI FROM FETUS TO MATURITY IN THE LABORATORY MOUSE
Authors: Rudkin George T. , Griech Helen A.
Published: May 2004

Tritiated thymidine injected intraperitoneally into female mice midway through the gestation period was demonstrated by autoradiographic methods to be incorporated into the nuclei of oocytes of female embryos, observed at the pachytene stage of meiosis 2 to 4 days after the injection. The tritium label was also demonstrated in the oocyte nuclei of the daughters of similarly treated females at maturity (6 weeks post partum). It was also found that some follicle cells, likewise labeled with H3-thymidine in mid-fetal life, persisted to maturity with few or no intervening mitoses. The observations are presented in support of the prevailing view that individual oocytes which arise from germ cell primordia in fetal stages become the egg cells of the adult female mammal.
ISOLATION OF SMOOTH VESICLES AND FREE RIBOSOMES FROM RAT LIVER MICROSOMES
Authors: Chauveau J. , Moulé Y. , Rouiller C. , Schneebeli J.
Published: May 2004

Microsomes, isolated from rat liver homogenate in 0.88 M sucrose, have been fractionated by differential centrifugation. The 2nd microsomal fraction, sedimented between 60 minutes at 105,000 g and 3 hours at 145,000 g, consists mainly of smooth vesicles, free ribosomes, and ferritin. By utilizing the differences in density existing between the membranes and the granular elements it has been possible to separate the smooth membranes from the free ribosomes and ferritin. The procedure is to resuspend the 2nd microsomal fraction in a sucrose solution of 1.21 or 1.25 density and centrifuge it at 145,000 g for 20 or 40 hours. A centripetal migration of membranes and a centrifugal sedimentation of granular elements are obtained. Phospholipids, as well as the enzymatic activities DPNH-cytochrome c reductase, glucose-6-phosphatase and esterase are localized in the membranes. The free ribosomes have been purified by washing. A concentration of 200 µg RNA per mg nitrogen has been reached. RNA is also present in the membranes. These results are discussed in relation to current views on microsomal structure and chemistry.
THE MITOTIC APPARATUS: ISOLATION BY CONTROLLED pH
Authors: Kane R. E.
Published: May 2004

The isolation of the mitotic apparatus (MA) from the echinoderm egg was studied in detail, with particular attention given to the factors governing its stability. Successful isolation depends mainly on the pH of the isolation solution, slightly acid values being required. The use of a 1 M solution of hexanediol, buffered at pH 6.0 to 6.4, gives high yields of stable MA, while MA of poorer quality can be isolated in water buffered at pH 5.5 to 5.8. Isolation is possible only over a very narrow range of pH, as the cells become more difficult to break at lower values and the MA becomes unstable at higher values. Within this range the fibrous structure of the MA varies with the pH. The isolated MA disintegrates slowly when transferred to water at pH 7 and dissolves rapidly in solutions of high ionic strength.
SOME ELECTRON MICROSCOPICAL OBSERVATIONS ON LIQUID-CRYSTALLINE PHASES IN LIPID-WATER SYSTEMS
Authors: Stoeckenius Walther
Published: May 2004

OsO4 fixation preserves some liquid-crystalline phases of soaps and phospholipids to an extent that it is possible to observe their structure in electron micrographs of thin sections. Good agreement exists between the structure observed directly and that deduced from x-ray diffraction studies of the same systems.
THE FINE STRUCTURAL LOCALIZATION OF ACETYLCHOLINESTERASE AT THE MYONEURAL JUNCTION
Authors: Barrnett Russell J.
Published: May 2004

A study of the cytochemical localization of acetylcholiriesterase activity, combining histochemistry with electron microscopy, showed that the final product of the reaction, which was deposited at or near enzyme sites, occurred at four places in the myoneural junction. These included: plasma membrane of the muscle covering the junctional folds, the primary and secondary synaptic clefts, parts of the plasma membrane covering the axon terminal, and vesicular structures in the terminal axoplasm. No reaction occurred in the presence of 10-4 eserine or DFP, whereas 10-5 DFP inhibited the reaction at all sites except in the vesicles of the terminal axon. These findings are discussed with reference to the histochemical method used and to the occurrence of esterolytic activity in the vesicles, as well as to some of the current hypotheses concerning the relationship of the site of acetylcholinesterase and synaptic transmission.
FIXATION OF NEURAL TISSUES FOR ELECTRON MICROSCOPY BY PERFUSION WITH SOLUTIONS OF OSMIUM TETROXIDE
Authors: Palay Sanford L. , McGee-Russell S. M. , Gordon Spencer , Grillo Mary A.
Published: May 2004

This paper describes in detail a method for obtaining nearly uniform fixation of the nervous system by vascular perfusion with solutions of osmium tetroxide. Criteria are given for evaluating the degree of success achieved in the preservation of all the cellular components of the nervous system. The method permits analysis of the structural relations between cells at the electron microscopic level to an extent that has not been possible heretofore.
ACROSOME FORMATION IN THE HOUSE CRICKET
Authors: Kaye Jerome S.
Published: May 2004

Acrosome formation during spermatogenesis in the house cricket was studied with the electron microscope. In the early spermatid there is a single Golgi body, called the acroblast, which is cup-shaped, the walls being composed of a number of parallel membranes. A pro-acrosomal granule then appears within the acroblast. Next, the granule migrates to the nucleus, where it becomes attached. The acroblast then migrates away from the attached granule and is eventually sloughed off. In the first stage of acrosome differentiation the granule assumes the shape of a blunt cone and its base invaginates deeply so that it becomes hollowed. Within the space created by the invagination a new structure forms which, from the first, has the shape of a hollow cone. The two cones constitute the mature acrosome. Both have a biconvex cross-section.
THE REVERSAL OF MITOCHONDRIAL MEMBRANE
Authors: Chandra Satish
Published: May 2004

An electron microscope study of mitochondria in hamster liver and kidney cells has revealed that at some points the outer membrane of these organelles is continuous with the inner membrane. Also, at such points the discontinuous components of the membrane pairs have free endings. The outer and the inner membranes of a mitochondrion, therefore, may not be two different and distinct entities, as has been conventionally assumed, but may rather be a part of the same unit. Such a morphological structure would make the intramitochondrial substance accessible to the cytoplasmic substance through the intermembrane channel. This structure would also facilitate the swelling of a mitochondrion either by an unfolding of the cristae, or a sliding of the two membranes, or by both these processes occurring simultaneously.
THE SARCOPLASMIC RETICULUM OF THE BAT CRICOTHYROID MUSCLE
Authors: Revel J. P.
Published: May 2004

The bat cricothyroid muscle is believed to participate in the production of the short bursts of frequency modulated ultrasound which these animals use as an echolocation device. The evidence seems to indicate that this muscle must be extremely fast acting. It possesses a very well developed sarcoplasmic reticulum, consisting of intercommunicating longitudinal and transverse tubular elements. The transverse elements, situated at the level of the junction between the A and the I bands, are tripartite complexes of tubules called triads, and these are sometimes replaced by more complex structures, the pentads. The intermediate element of the triad appears as a slender continuous tubule, which can be shown to come into close contact with the sarcolemma and also to share with it certain common staining properties. The longitudinal components of the reticulum consist of very numerous tubules which link successive triads to each other and anastomose to form multiple layers of close-meshed reticula in the interfibrillar sarcoplasm. Both the longitudinal and the transverse elements of the sarcoplasmic reticulum form a continuous network across the muscle fiber. It is suggested that the extraordinary development of the sarcoplasmic reticulum in the bat cricothyroid is related to the unusual physiological properties of this muscle.
AN ELECTRON MICROSCOPE STUDY OF THE FINE STRUCTURE OF FEATHER KERATIN
Authors: Filshie B. K. , Rogers G. E.
Published: May 2004

Thin sections of the rachis of regenerating follicles of pigmented fowl feathers and of mature non-pigmented seagull feather rachis, embedded in methacrylate and Araldite respectively, were studied in the electron microscope. The late stages of development of keratin fibrils were examined in OsO4-fixed follicle material, and after poststaining with lead hydroxide the keratin aggregates were found to be composed of fine microfibrils approximately 30 A in diameter apparently embedded in a matrix material which had absorbed the lead stain. The centre-to-centre separation of the microfibrils was of the order of 35 A. After bulk treatment by reduction with thioglycollic acid, OsO4 staining, and poststaining with lead hydroxide, a similar microfibrillar fine structure was observed in mature rachis. Only after lead staining could the microfibrils be delineated, and their diameter and separation were similar to that found in the keratin of the follicle. It is suggested that feather keratin resembles α-keratins in consisting of microfibrils embedded in an amorphous protein matrix. However, in comparison with α-keratins, the microfibrils are much smaller in diameter, their arrangement is less orderly, and on the basis of the reactions towards the electron staining procedures, the cystine content of the matrix appears to be not greatly different from that of the microfibrils. The significance of a microfibrillar constitution of feather keratin is discussed in relation to current structural models for this fibrous protein deduced from x-ray diffraction studies. The boundaries between the component cells of feather rachis are desmosomal in character and similar to those of related keratinous structures and a number of different types of cells; the melanin granules are dissimilar to those of mammalian epidermis in their apparent lack of melanin-protein lamellae.
AN ELECTRON MICROSCOPIC STUDY OF THE DEVELOPMENT OF THE CLEAVAGE FURROW IN MAMMALIAN CELLS
Authors: Buck Robert C. , Tisdale James M.
Published: May 2004

The process of cytoplasmic cleavage has been studied in thin sections of rat erythroblasts and the cells of mouse leukemia and Walker 256 carcinoma of the rat. The development of the cleavage furrow begins in relation to the mid-body, which, earlier, appears on the equatorial plane in association with the continuous fibers of the spindle. The earliest evidence of a cleavage furrow is the presence of a vesicle or vesicles close to the mid-body. Subsequently, many smaller vesicles are seen in the equatorial plane. The cleavage furrow probably develops by the fusion of these vesicles so that a new plasma membrane is formed between the daughter cells, and extends from the telophase intercellular bridge to the cell margin. During the stage of formation of the vesicles, cisternae, believed to be part of the endoplasmic reticulum, assume an intimate relationship with the cleavage plane, and they may perhaps be involved in the formation of the vesicles.
DNA CONTENT OF PLACENTAL NUCLEI
Authors: Galton Michael
Published: May 2004

The DNA content of individual nuclei in four immature human placentas was determined by microspectrophotometric analysis of Feulgen-stained sections. The absence of mitosis in the syncytiotrophoblast, taken together with the finding of a diploid unimodal distribution, at a time of rapid placental growth, indicated that the syncytiotrophoblast possessed little or no intrinsic reproductive capacity. In contrast, the cytotrophoblast displayed considerable mitotic activity and was found to contain a high proportion of nuclei with DNA values in excess of the diploid amount, corresponding to DNA synthesis in interphase nuclei preparatory to division. From the complementary behavior of the two layers of trophoblast, with respect to evidence of reproductive ability, it is concluded that the rapid accumulation of nuclei in the syncytiotrophoblast, during the early development of the placenta, is accounted for by cell proliferation within the cytotrophoblast followed by alignment and coalescence of some daughter cells in the syncytiotrophoblast.