bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine Structure of the Malpighian Tubules of the Mosquito, Culex pipiens
Authors: Clifford Brendan 
Published: June 2020

An ultrastructural investigation of the Malpighian tubules of the fourth instar larva of Culex pipiens was undertaken as part of a continuing study of the fine structure of transport epithelia.Each of the five Malpighian tubules was found to be morphologically identical and regionally undifferentiated. Two distinct cell types, the primary and stellate, were found intermingled along the length of each tubule. The ultrastructure of the stellate cell was previously described in the Malpighian tubule of the blowfly, Calliphora erythrocephala by Berridge and Oschman.The basal plasma membrane of the primary cell is extremely irregular, giving rise to a complex interconnecting network of basal channels. The compartments of cytoplasm entrapped within this system of basal infoldings contain mitochondria, free ribosomes, and small amounts of rough endoplasmic reticulum. The mitochondria are distinctive in that the cristae run parallel to the long axis of the organelle.
Binding of Transfer RNA to Carbon Films for Electron Microscopy: A Quantitative Approach
Authors: Abermann Reinhard J. , Yoshikami Doju 
Published: June 2020

It is essential to establish criteria for the identification of macromolecules studied by electron microscopy. The salt solutions, or (depending on the techniques used) the grain of the shadowing or the staining material or even dirt, may limit the level of confidence with which definitive statements about the macromolecules can be made. With this in mind, we have devised preparatory procedures for the study of one macromolecule, namely tRNA, and investigated its interaction with carbon films. (See also the accompanying paper, Yoshikami and Abermann, these Proceedings.)Highly purified monomeric mixed tRNA from yeast in a buffer of 0.1 M NaCl, 10 mM MgCl2, 10 mM Na cacodylate, pH 6.6 was used throughout this investigation. Freshly evaporated carbon films were stripped from mica and mounted on grids. tRNA was mounted by floating the grid on a droplet of the tRNA solution. Removal of excess salts and dehydration were done by successive rinses of the grid in ethanol. Ethanol was selected as a rinsing agent since the constituents of the buffer were all soluble in ethanol, and ethanol precipitation and subsequent drying is a well established procedure for concentrating tRNA without destroying its biological activity.
Complementary Replicas of Bacteria
Authors: Demsey Anthony E. , Steere Russell L. 
Published: June 2020

The technique of complementary replication has emerged as a necessity for the correct interpretation of biological freeze-etchings. Pioneered by Steere, this technique consists of replicating both ‘halves’ of the fracture plane. By indicating which surfaces are apposed to one another, this process has helped to clear up misconceptions in the interpretation of biological structures.This technique has been applied to many biological materials; but until now it has not been employed successfully with bacteria because of the difficulty involved in matching complementary ‘halves’ of such a small specimen in a field of so many similar ones. The technique described herein employes avian red blood cells as ‘markers’ in a bacterial sample. By locating matching ‘halves’ of the red blood cells, the complementary bacterial ‘halves’ surrounding them may be readily observed.Avian red blood cells, used as markers, were fixed in 2% glutaraldehyde and stored in a 40% glycerol solution. A small number of these was added to the pelleted and washed bacterial specimen — untreatedStaphylococcus aureus(ATCC 12600) grown in tryptic soy broth (DIFCO), with pyruvate (0.2%) and uracil (56 mg/liter) added. This mixture of bacteria and red blood cells was placed in hinged specimen holders.
Retinal Elements Revealed by SEM Cryomicrodissection
Authors: McAlear James H. , Germinario Louis , Fucci Robert 
Published: June 2020

The scanning electron microscope was used to study the surface of a frozen and then fractured mouse eye. The frozen fractured surface was microdissected in the scanning electron microscope and the freshly fractured surface thus exposed was observed in the microscope.In order to study the frozen surface it was necessary to develop a cold stage for the Cambridge Stereoscan microscope. This was achieved by fashioning a platform which rests on the standard stage and makes contact with it at three points, two on top and the third below on the back of the stage. It is connected by a braided copper cable to a 1/2-inch by 3-inch brass bar which hangs in front of the stage in the vacuum. The stage functions as a sort of cold block. It is demounted from the microscope and placed in liquid nitrogen and the vitriously frozen sample is attached by means of a set screw in a hole. The cold stage with specimen attached is moved quickly onto the waiting microscope stage. It is necessary to back the specimen chamber with dry N2 gas and to use a liquid N2 trap in the vacuum system in order to minimize ice formation on the stage and to facilitate pumpdown. The stage warms up to the etching temperature (approx -100°C) in 20 to 30 minutes and the ice contamination disappears gradually to reveal the underlying fractured surface. There is no problem in charging up of these samples.
SEM Examination of a Used Diamond Knife
Authors: Black J. Temple 
Published: June 2020

Since its introduction by Fernandez-Moran, the diamond knife has gained wide spread usage as a common material for cutting of thin sections of biological and metallic materials into thin films for examination in the transmission electron microscope. With the development of high voltage E.M. and scanning transmission E.M., microtomy applications will become increasingly important in the preparation of specimens. For those who can afford it, the diamond knife will thus continue to be an important tool to accomplish this effort until a cheaper but equally strong and sharp tool is found to replace the diamond, glass not withstanding.In Figs. 1 thru 3, a first attempt was made to examine the edge of a used (β=45°) diamond knife by means of the scanning electron microscope. Because diamond is conductive, first examination was tried without any coating of the diamond. However, the contamination at the edge caused severe charging during imaging. Next, a thin layer of carbon was deposited but charging was still extensive at high magnification - high voltage settings. Finally, the knife was given a light coating of gold-palladium which eliminated the charging and allowed high magnification micrographs to be made with reasonable resolution.
High Voltage Electron Microscope Study of Living Materials
Authors: Nagata F. , Ishikawa I. 
Published: June 2020

During these thirty years, some experiments have been made to observe living materials in an electron microscope. Observation of living things will prove whether biological tissues found in microscope images of sectioned specimens are same as that of living material, and also will enable us to observe organic functions dynamically.The authers studied the possibility of the observation of living materials. There are three important subjects for the accomplishment; (1) development of environmental cell, (2) specimen injury with electrons irradiation, (3) improvement of image contrast for wet specimen.It is generally expected that injury to living material will be reduced as an accelerating voltage of irradiating electrons is increased. But neither the rate nor the effects has been studied precisely. In this studies, dry spores of Bacillus megaterium were irradiated with electrons in a specimen chamber of an electron microscope. The accelerating voltage was in the region of 25 to 750 kV and electron quantity was 1x10-7 to 1xl0-2 coulombs/cm2 on a specimen. After the irradiation, the specimens were incubated in the culture fluid and then they were observed with an electron microscope. It is found that as electron number increase, new vegetable cells cease to exist, moreover monsters occur and then spores do not swell. They are similar in tendency at each accelerating voltage but different in amount of irradiation.
Method for Processing of Periodic Images at Reduced Levels of Electron Irradiation
Authors: Glaeser Robert M. , Kuo Ivy , Budinger Thomas F. 
Published: June 2020

Meaningful high resolution microscope of specimens that are sensitive to radiation damage is limited in resolution by considerations of statistics and contrast in the image. The product of contrast, C, and resolution, d, must satisfy the inequalitywhere S/n is the minimum acceptable ratio of real contrast to statistical fluctuations in intensity, f is the fraction of electrons incident upon the specimen that actually contribute to image formation, and Dmin is the minimum dose or exposure that causes structural disorder at the resolution, d. While the value of S/N must be approximately 5 for visual perception of structure, a very much smaller value can be made acceptable by spatial superposition or “averaging” of similar images. In most circumstances this is practical only for objects with a determinable spatial redundancy. We report here on the construction of an experimental system for (1) recording statistically noisy images, (2) determining the image redundancy, and (3) executing the desired spatial averaging.
The Formation, Structure, Distribution and Frequency of Nuclear Pores
Authors: Maul G. G. 
Published: June 2020

The chromatin of eukaryotic cells is separated from the cytoplasm by a double membrane. One obvious structural specialization of the nuclear membrane is the presence of pores which have been implicated to facilitate the selective nucleocytoplasmic exchange of a variety of large molecules. Thus, the function of nuclear pores has mainly been regarded to be a passive one. Non-membranous diaphragms, radiating fibers, central rings, and other pore-associated structures were thought to play a role in the selective filter function of the nuclear pore complex. Evidence will be presented that suggests that the nuclear pore is a dynamic structure which is non-randomly distributed and can be formed during interphase, and that a close relationship exists between chromatin and the membranous part of the nuclear pore complex.Octagonality of the nuclear pore complex has been confirmed by a variety of techniques. Using the freeze-etching technique, it was possible to show that the membranous part of the pore complex has an eight-sided outline in human melanoma cells in vitro. Fibers which traverse the pore proper at its corners are continuous and indistinguishable from chromatin at the nucleoplasmic side, as seen in conventionally fixed and sectioned material. Chromatin can be seen in octagonal outline if serial sections are analyzed which are parallel but do not include nuclear membranes (Fig. 1). It is concluded that the shape of the pore rim is due to fibrous material traversing the pore, and may not have any functional significance. In many pores one can recognize a central ring with eight fibers radiating to the corners of the pore rim. Such a structural arrangement is also found to connect eight ribosomes at the nuclear membrane.
Sites of Insulin Action Using Ferritin Labeling
Authors: Silver Burton B. , Nelson Ronald S. 
Published: June 2020

Some investigators feel that insulin does not enter cells but exerts its influence in some manner on the cell surface. Ferritin labeling of insulin and insulin antibody was used to determine if binding sites of insulin to specific target organs could be seen with electron microscopy.Alloxanized rats were considered diabetic if blood sugar levels were in excess of 300 mg %. Test reagents included ferritin, ferritin labeled insulin, and ferritin labeled insulin antibody. Target organs examined were were diaphragm, kidney, gastrocnemius, fat pad, liver and anterior pituitary. Reagents were administered through the left common carotid. Survival time was at least one hour in test animals. Tissue incubation studies were also done in normal as well as diabetic rats. Specimens were fixed in gluteraldehyde and osmium followed by staining with lead and uranium salts. Some tissues were not stained.
Cytopathology of Cardiac Tissue from Daunomycin-Treated Mice
Authors: Liss Robert H. , Cotton Frances A. 
Published: June 2020

Daunomycin, an antibiotic used in the clinical management of acute leukemia, produces a delayed, lethal cardiac toxicity. The lethality is dose and schedule dependent; histopathologic changes induced by the drug have been described in heart, lung, and kidney from hamsters in both single and multiple dose studies. Mice given a single intravenous dose of daunomycin (10 mg/kg) die 6-7 days later. Drug distribution studies indicate that the rodents excrete most of a single dose of the drug as daunomycin and metabolite within 48 hours after dosage (M. A. Asbell, personal communication).Myocardium from the ventricles of 6 moribund BDF1 mice which had received a single intravenous dose of daunomycin (10 mg/kg), and from controls dosed with physiologic saline, was fixed in glutaraldehyde and prepared for electron microscopy.
Effect of Estrogen and Progesterone on Oviduct Smooth Muscle: An Ultrastructural and Cytochemical Study
Authors: Nayak R. K. , Wu A. S. H. 
Published: June 2020

The smooth muscle cells of the Fallopian tube, although similar in structure to those of other organs are unique in their response to the action of steroid hormones. To our knowledge few studies have as yet been published about the fine structure of oviduct smooth muscle cell. This fact has induced us to study the influence of estrogen and progesterone upon the ultrastructure of oviduct smooth muscle cells in an attempt to elucidate the action of hormones on the cellular level. Attempts were also made to demonstrate the presence of adenosine triphosphatase (ATP-ase) in these cells at subcellular level.In Experiment I, prepubertal rabbits (8 weeks old) were given 7 daily intramuscular injections of estradiol benzoate (5 μg/day) and progesterone (2 mg/day) in propylene glycol. In Experiment II, rabbits were ovariectomized at 8 weeks of age and received hormone treatment same as that given in Experiment I, starting 40 days after surgery.
The Differences in Lung Ultrastructural Response of Small and Large Rats to Hyperoxia
Authors: Harrison Gladys A. 
Published: June 2020

In the work with oxygen exposed animals, it is readily apparent that there are great differences in the responses of young and old animals. Young rats are far more resistant to oxygen poisoning than are older rats. The younger animals, weighing 90-110 grams (about four weeks old) will live in 100% oxygen at one atmosphere for long periods of time, many surviving for four to six weeks. On the other hand, larger rats, 300-350 grams (12-16 weeks old) live only about three days in the same atmosphere. Obviously, changes must occur at a greater rate, they may be more damaging and may even be different in character.Rats in the 90-110 gram range and in the 300-350 gram range were exposed for 48 hours to pure oxygen at one atmosphere. The animals were sacrificed, the tissue removed, cut into small blocks and fixed in glutaraldehyde, followed by osmium post-fixation.
Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver
Authors: Elfont E. A. , Tobin R. B. , Colton D. G. , Mehlman M. A. 
Published: June 2020

5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred dally for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biochemical analyses, while the rest was prefixed in buffered 3.5% glutaraldehyde (390 mOs) and post-fixed in buffered I% OsO4 (376 mOs). Tissues were embedded in Araldite 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.
High Voltage Electron Microscopy at Berkeley
Authors: Thomas G. 
Published: June 2020

A Hitachi 650kV electron microscope was installed at Berkeley in May 1969. (fig. 1) The fourier resolution test showed 4A° (fig. 2). The research program is centered around three principal advantages which open up new areas of microscopic analyses. These advantages are: a) the gain in transmission power with increasing voltage enabling thick specimens to be examined (up to about 6μ at 650kV depending on material) b) increased stability of roganic solids to radiation damage c) the disappearance voltage effect and fundamental advantages arising from many beam contrast phenomena at high energies.The increase in transmission enables materials to be examined for which preparation of thin foils is difficult. It also enables specimens to be examined in some cases without any preparation. In the study of fossils it is particularly important to minimize preparation methods since material which has been imbedded in rocks for millions of years are usually brittle and difficult to section. Fig. 3 shows an example of the fibious structure of part of a graptolite specimen, which is 4 × 108 years old. Another example is a study of damage in as-received lunar surface particles (fig. 4).
Human Interphase Nuclei; Dry Mass and Fiber Diameter
Authors: Golomb H. M. , Engler W. F. , Mikel U. , Bahr G. F. 
Published: June 2020

Dry mass determinations of human male chromosomal homologues in each group (A through G) have previously been reported. In this report whole intact interphase nuclei present with the chromosome preparation are studied. The relationship of the dry mass of interphase nuclei to the total chromosomal complement dry mass (46, X, Y karyotype) and their respective fiber diameter is investigated.Interphase nuclei were photographed quantitatively with a Siemens Elmiskop IA, and measured with the intergrating photometer (Carl Zeiss IPM-2). Absolute dry mass was determined using latex spheres as standards. Fibers of both interphase nuclei and individual metaphase chromosomes were photographed at 19.000X and their diameters measured on a Nikon profile projector.
The Observation of Channeling Patterns in Silicon Single Crystals at 200-500 kv
Authors: Geiss R. H. , Lawless K. R. 
Published: June 2020

Transmission electron channeling patterns, the complement to the backscattered electron blocking patterns seen by Coates in the scanning electron microscope, have been observed in near perfect single crystals of silicon with the 500 kV electron microscope at the University of Virginia. Such channeling patterns, which are thought to be associated with the anomalous absorption and transmission of the Block waves describing the electrons inside a crystal, have all the characteristics of Kikuchi patterns and are but another example of the convergent beam phenomena first demonstrated by Kossel and Möllenstedt in 1939.The difference between the work discussed here and that of Kossel and Möllenstedt and others using convergent beam techniques is that in our experiments the sample is placed near the center of a single field condenser-objective lens. The pre-field of the lens forms a convergent beam with an angular spread of approximately 10−2 radians and gives rise in the channeling pattern, while the post-field acts as an ordinary objective lens and enables defects in the sample to be imaged. The simultaneous action of these fields therefore yields images wherein defects are seen superimposed on the channeling pattern.
Different Pathways of Food Transportation in the Intestinal Cells of Larvae and Adult Rana Pipiens
Authors: Giaquinta R. , Hayat M. A. 
Published: June 2020

Although the ultrastructural changes in the intestinal epithelium during amphibian metamorphosis have been reported (Bonneville, 1963), little information is available on the pathways of food transportation in the intestinal epithelium of various metamorphic stages of Rana pipiens. This report describes two different pathways of food transportation in the intestinal epithelium of larvae and adult frog. Possible physiological significance of the proposed pathways has been discussed.Tadpole and adult Rana pipiens were fed herbivorous and carnivorous diets respectively, and 48 hr after feeding, thve animals were dissected and segments of the small intestine were collected for electron microscopy. The tissue specimens were processed according to standard procedures (Giaquinta and Hayat, 1970; Hayat, 1970).
Fine Structural Alterations in Fallopian Tube Epithelium
Authors: Horbelt D. V. , Roberts D. K. 
Published: June 2020

The epithelium of the uterus and fallopian tube undergo cyclic ultrastructural changes as the levels of feminine hormones fluctuate during the menstrual cycle. Other changes occur when pregnancy ensues. Marked alterations in the hormonal levels occur between term pregnancy and 72 hours post-partum. The ultrastructure of the fallopian tube reflects this change in hormone level. Specimens were obtained from human females at term pregnancy and 72 hours post-partum. The specimens were fixed with osmium tetroxide and embedded in Araldite. They were evaluated with a Philips 200 electron microscope.Ciliated and secretory cells were considered from the distal and proximal end of each pregnant and post-partum female.
Fine Structure of Interdental Cells in the Mouse Cochlea
Authors: Bruck Roberta M. 
Published: June 2020

An unusual structure in the cochlea is the spiral limbus; this periosteal tissue consists of stellate fibroblasts and collagenous fibers embedded in a translucent ground substance. The collagenous fibers are arranged in vertical columns (the auditory teeth of Haschke). Between the auditory teeth are interdental furrows in which the interdental cells are situated. These epithelial cells supposedly secrete the tectorial membrane.The fine structure of interdental cells in the rat was reported by Iurato (1962). Since the mouse appears to be different, a description of the fine structure of mouse interdental cells' is presented. Young adult C57BL/6J mice were perfused intervascularly with 1% paraformaldehyde/ 1.25% glutaraldehyde in .1M phosphate buffer (pH7.2-7.4). Intact cochlea were decalcified in .1M EDTA by the method of Baird (1967), postosmicated, dehydrated, and embedded in Araldite. Thin sections stained with uranyl acetate and lead citrate were examined in a Phillips EM-200 electron microscope.
Freeze-Etch Replication of the Microvasculature in Loose Connective Tissue of the Chick Embryo and Young Chick
Authors: Sanderson Margaret H. , Steamer S. Phyllis 
Published: June 2020

The extra-embryonic membrane of the 3-day chick embryo and the mesentery of the 3-week chick, tissues of similar structure, were studied in conventional thin sections and freeze-etch replicas. The ultrastructure of the microvasculature and the surrounding interstitial region of the two tissues is compared.In the 3-day chick embryo, there is no differentiation into vessel types. Small vessels in the area pellucida have a continuous endothelium (E) surrounded by processes of mesenchymal cells(M) (Fig. 1). The lumen(L) often contains erythrocytes (R). No continuous basement lamina(BL) is seen, and the interstitial spaces(IS) contain a few collagen fibers(C). In freeze-etch replicas, the endothelium is thin, with numerous cytoplasmic processes (Fig.2). The cytoplasmic matrix has some randomlyspaced particles, a few pinocytotic vesicles(PV), and other organelles. The interstitial space beneath the endothelium has a uniform vacuolar appearance. No basement lamina can be identified.