bluuebunny/crossref_metadata_2025 huggingface dataset:
Mitochondria Isolated from Rat Brown Adipose Tissue and Liver
Authors: Lever J. D. , Chappell J. B.
Published: May 2004

Mitochondrial fractions, relatively free from contamination by other cytoplasmic structures, have been isolated by differential centrifugation from homogenates of brown adipose tissue from starved rats. It was possible in such fractions to distinguish two types of mitochondria in this tissue.

Type I mitochondria, when morphologically intact, are limited by a bilaminar membrane and show regular parallel cristae. In isolated fractions, a proportion of these mitochondria are swollen, vacuolation occurring within the cristae between their limiting membranes.

Type II mitochondria are distinguished from the more numerous type I bodies by the opaque appearance of their matrix. They are limited by a membrane which is in part single, and in part double. They show a few, but crisply outlined internal membranes. Vacuolation of this type of mitochondrion has not been observed.

Vacuolation comparable to that in brown fat mitochondria was also observed between the two laminae of the enclosing membrane and within the cristae of liver mitochondria.
Factors Limiting the Number of Radiation-Induced Chromosome Exchanges
Authors: Wolff Sheldon , Atwood K. C. , Randolph M. L. , Luippold H. E.
Published: May 2004

Soaked seeds of Vicia faba were exposed to fractionated doses of x-rays or x-rays and fast neutrons. When the two-hit (exchange) chromosome aberrations were scored at the first mitosis of the root tip, it was observed that with short fractionation times the radiation-induced breaks from the two x-ray doses could rejoin with one another to form exchanges in proportion to the square of the total dose. If, however, one dose was x-rays and the second neutrons, then no quantitatively determinable interaction occurred between the breaks induced by each of the doses, and the aberration yield was simply the sum of that induced by each fraction.

The phenomenon of non-interaction as observed by these dose fractionation studies and also by the linear dose response curve for two-break aberrations induced by neutrons has led to calculations of the distance over which two breaks can rejoin. The distance is evidently much smaller than the previously accepted value of 1 µ.
Arrangement of Cellulose Microfibrils in Walls of Elongating Parenchyma Cells
Authors: Setterfield G. , Bayley S. T.
Published: May 2004

The arrangement of cellulose microfibrils in walls of elongating parenchyma cells of Avena coleoptiles, onion roots, and celery petioles was studied in polarizing and electron microscopes by examining whole cell walls and sections. Walls of these cells consist firstly of regions containing the primary pit fields and composed of microfibrils oriented predominantly transversely. The transverse microfibrils show a progressive disorientation from the inside to the outside of the wall which is consistent with the multinet model of wall growth. Between the pit-field regions and running the length of the cells are ribs composed of longitudinally oriented microfibrils. Two types of rib have been found at all stages of cell elongation. In some regions, the wall appears to consist entirely of longitudinal microfibrils so that the rib forms an integral part of the wall. At the edges of such ribs the microfibrils can be seen to change direction from longitudinal in the rib to transverse in the pit-field region. Often, however, the rib appears to consist of an extra separate layer of longitudinal microfibrils outside a continuous wall of transverse microfibrils. These ribs are quite distinct from secondary wall, which consists of longitudinal microfibrils deposited within the primary wall after elongation has ceased. It is evident that the arrangement of cellulose microfibrils in a primary wall can be complex and is probably an expression of specific cellular differentiation.
Staining of Tissue Sections for Electron Microscopy with Heavy Metals
Authors: Watson Michael L.
Published: May 2004

Heavy metals may be incorporated from solution into tissue sections for electron microscopy. The resulting increase in density of the tissue provides greatly enhanced contrast with minimal distortion. Relative densities of various structures are found to depend on the heavy metal ions present and on the conditions of staining. Certain hitherto unobserved details are revealed and some sort of specificity exists, although the factors involved are not yet understood.
An Anterior-Posterior Gradient of Refractive Index in the Ameba and Its Significance in Ameboid Movement
Authors: Allen R. D. , Roslansky J. D.
Published: May 2004

Sustained locomotion in Amoeba proteus and Amoeba dubia results in the establishment of a measureable gradient of refractive index along the anterior-posterior axis of the cell, provided thickness of the specimens is kept constant by even compression under a selected coverglass supported by quartz beams of uniform diameter.

The tail region of the ameba develops a higher refractive index, indicative of from 6 to 40 per cent more organic matter (expressed as protein) there than present in the front. This gradient fades on cessation of movement. The average protein concentrations in the crystal-free tails and fronts of 15 A. proteus were 3.9 and 3.4 per cent, respectively. In individual experiments, the tail-front difference ranged from one to eight times the accuracy of the method.

Since the gradient of refractive index was shown not to result from extraction of water from the tail by the contractile vacuole, it was interpreted as displacement of water toward the anterior part of the cell during movement. It is suggested that contraction of the ectoplasm drives forward a "tide" of syncretic fluid, the anterior border of which is visible as the hyaline cap, which contains less than 1 per cent protein. The movement of the granular endoplasm into the hyaline cap would then complete the cycle by imbibition of the fluid tide. The theoretical positions of Pantin and of Dellinger have been combined in the proposal that ameba cytoplasm consists of a network of a contractile phase which is able to expel (by syneresis) a highly mobile fluid phase. Some other possible interpretations are discussed.
The Role of Carbon Dioxide as an Essential Nutrient for Six Permanent Strains of Fibroblasts
Authors: Swim H. E. , Parker R. F.
Published: May 2004

The results of these studies demonstrate that carbon dioxide is required for the growth and maintenance of strains of fibroblasts derived from human tissues, strains FS4-705 and U12-705, from mouse tissue, strain L-705, and from rabbit tissues, strains RM3-56, RS1-56, and RT-56 in a chemically defined medium containing phosphite buffer in place of bicarbonate and supplemented with dialyzed serum and dialyzed embryo extract. Under these conditions, the cells fail to proliferate at a significant rate and begin to degenerate within 5 to 10 days when the flasks are not stoppered. Sufficient carbon dioxide is produced by the cells to promote growth as indicated by the fact that maximal proliferation is obtained in the same phosphite media when stoppered flasks are employed. With the exception of RS1-56, all the remaining strains tested can be propagated serially in open flasks containing phosphite medium prepared with whole serum and embryo extract. The rate of growth under these conditions, however, is only one-half to one-third that obtained in stoppered flasks containing phosphite medium or the conventional bicarbonate medium.
Colorimetric Analysis with N,N-Dimethyl-p-phenylenediamine of the Uptake of Intravenously Injected Horseradish Peroxidase by Various Tissues of the Rat
Authors: Straus Werner
Published: May 2004

1. A method is described for the colorimetric determination of peroxidase with N,N-dimethyl-p-phenylenediamine. The amount of red pigment formed by peroxidase is proportional to the concentration of enzyme and to the time of incubation during the first 40 to 90 seconds. The influence of the concentration of enzyme, N,N-dimethyl-p-phenylenediamine, H2O2, the time of incubation, pH, the temperature, and the possible interference by oxidizing and reducing agents of tissues has been tested.

2. The method has been used to follow the uptake of intravenously injected horseradish peroxidase by 18 different tissues of the rat over a period of 30 hours. The highest concentration of the injected tracer enzyme was found in extracts of kidney, liver, bone marrow, thymus, and spleen. Considerable amounts were taken up by pancreas, prostate, epididymis, and small intestine. Lower concentrations were found in extracts of lung, stomach, heart, and skeletal muscle, aorta, skin, and connective tissue. No uptake was observed by brain and peripheral nerve tissue.

3. Tissue homogenates containing high concentrations of the injected peroxidase, in general also showed high or average activity of acid phosphatase.

4. Six hours after intravenous administration, the liver contained 27 per cent, the kidney 12 per cent, and the spleen, 1.4 per cent of the injected dose.

5. Approximately 20 per cent of the injected peroxidase was excreted in the urine during the first 6 hours, and the concentration of peroxidase in blood serum and urine fell exponentially during this time. After 6 hours, only low concentrations were excreted in the urine but low enzyme activity was still detectable after 30 hours. Approximately 6 per cent of the injected dose was excreted in the feces from 6 to 20 hours after administration.

6. After feeding through a stomach tube, low concentrations of peroxidase were found in blood serum and urine. Considerable variations in the extent of absorption from the gastrointestinal tract were observed in individual rats.
A Cytochemical Study on the Pancreas of the Guinea Pig
Authors: Siekevitz Philip , Palade George E.
Published: May 2004

DL-leucine-1-C14 was administered by intracardiac injection to guinea pigs and its in vivo incorporation into the proteins of various pancreatic cell fractions followed over a period of 2 hours.

The pancreas was homogenized in 0.88 M sucrose and fractionated by differential centrifugation to give nuclear, zymogen, mitochondrial, microsomal, postmicrosomal, and final supernatant fractions. The proteins of these fractions, obtained by precipitation with trichloroacetic acid followed by washing, were counted.

The proteins of the microsomal fraction showed the highest early specific activity and were followed by those of the zymogen and mitochondrial fractions.

The microsomal fraction was broken up into two subfractions: one consisting of detached RNP particles, the other representing mainly the microsomal content and membranes.

The incorporation of labelled leucine into the proteins of microsomal subtractions and in those of postmicrosomal fractions was studied comparatively in the pancreas of fasted and fed guinea pigs as well as in the liver and pancreas of fasted animals.

A tentative cytological picture of protein synthesis and transport based on these findings is presented.
The Arginase and Rhodanese Activities of Certain Cell Strains after Long Cultivation in Vitro
Authors: Westfall B. B. , Peppers E. V. , Evans V. J. , Sanford K. K. , Hawkins N. M. , Fioramonti M. C. , Kerr H. A. , Hobbs G. L. , Earle W. R.
Published: May 2004

The activities of the enzymes arginase and rhodanese were examined in homogenates of 13 mouse cell strains and 2 human cell strains after long cultivation of the cells in vitro. Three strains of mouse liver origin showed both high arginase and rhodanese activities in keeping with activities of the tissue of origin. Two strains of cells of human epithelial origin, HeLa and epidermis, were found to have high rhodanese activity but low arginase activity, the skin being almost devoid of it. Seven mouse fibroblast strains or substrains had moderate rhodanese activity and all except one of the strains had low arginase activity. Two of the fibroblast strains tested, NCTC 1745 and NCTC 2050, were derived from a single cell of a tumor appearing after injection of the high tumor producing strain NCTC 1742 into a mouse. The strain 1745 had 20 times and the strain 2050 had 400 times the arginase activity of the parent strain of cells. The findings imply a considerable biochemical variation in the three strains. Three mouse mammary carcinoma clones were devoid of arginase activity, but had considerable rhodanese activity.
The Fine Structure of Blastema Cells and Differentiating Cartilage Cells in Regenerating Limbs of Amblystoma Larvae
Authors: Hay Elizabeth D.
Published: May 2004

Regenerating forelimbs of larval salamanders, Amblystoma punctatum, were fixed in OsO4 at various intervals after amputation and were sectioned for study with the electron microscope. The dedifferentiated cells comprising the early blastema were found to have a fine structure similar to that of other undifferentiated cells and to have lost all of the identifying morphological features of their tissues of origin. The cytoplasm of such cells is characterized by numerous free ribonucleoprotein granules and a discontinuous vesicular endoplasmic reticulum. The cells have more abundant cytoplasm and are in closer contact with each other than was previously realized. The layer of condensed ground substance investing most differentiated cell types is lacking. After a period of rapid cell division, the morphology of the blastema cell changes. Cytoplasm is now sparse and contains a high concentration of free ribonucleoprotein granules, but little endoplasmic reticulum. The differentiating cartilage cell, however, develops an extensive, highly organized endoplasmic reticulum and the Golgi apparatus also appears to become more highly differentiated and more extensive at this time. Small vesicles appear throughout the cytoplasm at the time the new cisternae originate and may contribute to their formation. These and other changes in the cytoplasmic organelles are discussed.
The Fine Structure of the Adipose Cell of the Leech Glossiphonia complanata
Authors: Bradbury S. , Meek G. A.
Published: May 2004

The two distinct types of cytoplasm seen with the light microscope in the adipose cell of the leech Glossiphonia complanata have been identified in the electron microscope image of this cell.

One of these, the basophil cytoplasm, contains many well oriented, paired membranes which are much more clearly evident when calcium ions are added to the fixative. The membranes sometimes appear as concentric arrays of lamellae and are thought to represent sections through a phospholipide-containing body. The paired membranes and the concentric lamellae have granules attached to them and resemble in size and structure the membranes of the endoplasmic reticulum encountered in many mammalian cells.

Small dense cytoplasmic particles are present throughout the cell; they may be ferritin molecules, derived from the breakdown of haemoglobin taken in as food.

On the basis of a previous histochemical study and the present electron microscope investigation, it is suggested that these paired membranes are similar to the organized type of mammalian ER and the results seem to confirm the belief that these membranes are composed of layers of phospholipoprotein together with attached particles of ribonucleoprotein.
Cellular Mechanism of Myelination in the Central Nervous System
Authors: De Robertis Eduardo , Gerschenfeld Hersch M. , Wald Flora
Published: May 2004

A study of myelination with electron microscopy has been carried out on the spinal cord of young rats and cats. In longitudinal and transverse sections the intimate relationship of the growing axons with the oligodendrocytes was observed. Early naked axons appear to be embedded within the cytoplasm and processes of the oligodendrocytes from which they are limited only by the intimately apposed membranes of both elements (axon-oligocytic membrane). In a transverse section several axons are observed to be in a single oligodendrocyte.

The process of myelination consists in the laying down, within the cytoplasm of the oligodendrocyte and around the axon, of concentric membranous myelin layers. The first of these layers is deposited at a certain distance (200 to 600 A or more) from the axon-oligocytic membrane. This and all the other subsequently formed membranes have higher electron density and are apparently formed by the coalescence and fusion of vesicles (of 200 to 800 A) and membranes found in large amounts within the cytoplasm of the oligodendrocytes.

At an early stage the myelin layers may be discontinuous and some vesicular material may even be trapped among them or between the myelin proper and the axon-oligocytic membrane. Then, when the 8th to 10th layer is deposited, the complete coalescence and alignment of the lamellae leads to the characteristic orderly multilayered organization of the myelin sheath.

Myelination in the central nervous system appears to be a process of membrane synthesis within the cytoplasm of the oligodendrocyte and not a result of the wrapping of the plasma membranes as postulated in Geren's hypothesis for the peripheral nerve fibers. The possible participation of Schwann cell cytoplasm in peripheral myelination is now being investigated.
Electron Microscope Study of DNA-Containing Plasms
Authors: Kellenberger Edouard , Ryter Antoinette , Séchaud Janine
Published: May 2004

The nucleoids of Escherichia coli, independently of the physiological state of the bacteria, are shown to be preserved as a fine-stranded fibrillar nucleoplasm by an OsO4 fixation under defined conditions: acetate-veronal buffer pH 6, presence of Ca++ and amino acids, stabilization with uranyl-acetate before dehydration. The same fixation procedure applied to the DNA of vegetative phage reveals a pool of homogeneous fibrillar structure very similar to the nucleoplasm. The "versene test," which produces a coarse coagulation of these plasms, emphasizes the similar behaviour of the pool and the nucleoids.

The heads of mature phage are preserved in their true polyhedral shape by the standard fixation procedure, although they may be badly distorted when fixed under different conditions. Lanthanum nitrate and uranyl-acetate are shown to increase markedly the contrast of both phage and cytoplasm.

The consequences of the fibrillar structure of the genetic material are discussed in relation to the probable division process.
Electron Microscope Studies of the Human Epidermis The Clear Cell of Masson (Dendritic Cell or Melanocyte)
Authors: Clark Wallace H. , Hibbs Richard G.
Published: May 2004

The human epidermis has been studied by electron microscopy following osmium tetroxide and potassium permanganate fixation. An anatomically distinct cell in the human epidermis has been demonstrated with features similar to the melanocyte of the hair bulb described by Barnicot, Birbeck and Cuckow (3). It is dendritic in form and does not contain tonofilaments. "Intercellular bridges" are not formed. The mitochondria are larger and more numerous than those of other epidermal cells and the endoplasmic reticulum is more complex. Some of these cells contain melanin but others are melanin-free. The cell has been interpreted as being identical with the dopa-positive, clear cell of Masson (dendritic cell of Bloch or melanocyte). We have found that many membranous structures in the human epidermis are better preserved by permanganate fixation than by osmium tetroxide fixation.
A Comparison of Scanning and Two-Wavelength Microspectrophotometry
Authors: Mendelsohn Mortimer L. , Richards Brian M.
Published: May 2004

Because of the absence of suitable standards, microspectrophotometry suffers from a lack of objective verification. An approach to this problem is suggested which is based on the comparison of results obtained when different techniques or instruments are applied to the same objects. The application of this approach to scanning versus two-wavelength photometry has been justified by the widely different bases of these two methods. A group of ascites tumor cells stained with gallocyanin-chrome alum was measured successively with both methods and a high degree of proportionality between the two sets of results was found. This suggests that the two methods measure the same quality of the cells within a standard deviation of 3.39 per cent. This degree of correlation is a verification of the accuracy of both of the methods and shows that either one is suitable for resolving differences in stain content between cell nuclei of the order of 10 per cent.
The Cytochemical Localization of Oxidative Enzymes
Authors: Scarpelli D. G. , Hess R. , Pearse A. G. E.
Published: May 2004

Cytochemical methods involving metal chelation of the formazan of an N-thiazol-2-yl tetrazolium salt are described for the localization of diphosphopyridine nucleotide diaphorase (DPND) and triphosphopyridine nucleotide diaphorase (TPND) in mitochondria. These methods utilize the reduced coenzymes DPNH or TPNH as substrate. The reaction involves a direct transfer of electrons from reduced coenzyme to the respective diaphorase which in turn transfers the electrons to tetrazolium salt, reducing it to the insoluble formazan. Competition for electrons by preferential acceptors in the respiratory chain was prevented by various inhibitors. In the presence of respiratory inhibitors the rate of tetrazolium reduction was markedly increased. The greatest reduction was observed when amytal was used.

Sites of diaphorase activity appeared as deposits of blue-black metal formazan chelate measuring 0.2 to 0.3 µ in diameter. Small mitochondria contained 2 deposits, while larger ones contained up to 6.

Considerable differences were observed in the rate of tetrazolium reduction and cellular localization of diaphorase activity when DPNH was used as substrate as compared to TPNH. In each instance DPNH was oxidized more rapidly by tissues than TPNH. These findings support the concept that the oxidation of coenzymes I and II is mediated through separate diaphorases.
A Cellophane-Strip Technique for Culturing Tissue in Multipurpose Culture Chambers
Authors: Rose George G. , Pomerat C. M. , Shindler T. O. , Trunnell J. B.
Published: May 2004

A new technique for the cultivation of living tissues in the multipurpose culture chamber is described. This procedure employs strips of cellophane as the agent for anchoring tissue explants to the coverslip walls of the chamber and disposes of the time-honored plasma-clot technique. The primary advance embodied in this procedure lies in the fact that cells emigrating from so-cultured explants manifest themselves in a highly differentiated manner comparable to the cells of origin, whereas the outgrowth from the same types of tissue in plasma clots results in a more undifferentiated type of growth. Comparisons of outgrowths from embryonic thyroid, bone, and muscle (chicken) are photographically documented, and attention is called to certain cytochemical methods which further corroborate the differentiated quality obtained with the cellophane-strip technique.
Adenosinetriphosphatase Activity in the Cell Membranes of Kidney Tubule Cells
Authors: Spater Herman W. , Novikoff Alex B. , Masek Bertha
Published: May 2004

This cytochemical study demonstrates high levels of apparent ATPase activity in the infolded cell membranes of the proximal tubules (dog, rat, human, mouse, monkey, and opossum) and ascending loops of Henle (dog, rat, human and, to a variable degree, mouse). Electron microscopy has shown (see Rhodin (1)) that these membranes separate adjacent cells where they interlock with one another by multiple cytoplasmic lamellae containing oriented mitochondria. The significance of the high ATPase activity is considered in relation to possible movements of the membranes and to "active transport" believed to occur there.

In the rat, enzyme activity in the proximal tubule membranes does not survive formol-calcium fixation, and it is therefore necessary to use unfixed sections for its demonstration. However, in edematous rats with experimental nephrosis (induced by the injection of aminonucleoside or with antikidney serum) marked ATPase activity is exhibited in these membranes even after formol-calcium fixation.

When proximal tubule or Henle loop cells of the dog acquire an altered metabolism, as indicated by accumulated lipide spheres or by "droplets," the infolded ATPase-rich membranes are no longer demonstrable.
Structure and Mode of Formation of the Nucleolus in Meristematic Cells of Vicia faba and Allium cepa
Authors: Lafontaine J. G.
Published: May 2004

Interphase nucleoli from Vicia faba and Allium cepa meristematic cells are roughly classified into two categories: (a) those that commonly show a rather homogeneous texture (except for small light spaces of various sizes) and frequently contain dense particles 140 A in diameter; (b) those found more frequently in Vicia characterized by a very sharp boundary between a dense outer cortex and a much lighter central core. The dense particles are not found in such nucleoli. In Allium the boundary is more irregular and dense particles are sometimes observed in the outer layer. Many nucleoli show a structure intermediate between these two types. They are characterized by a gradient of increasing density from the center to the periphery and occasionally contain dense 140 A granules.

During interphase, certain nucleoli are closely associated with segments of chromatin strands which undoubtedly represent nucleolar organizing regions.

The dense 140 A granules are followed during the mitotic cycle. In Allium, they are first seen in loose clusters between arms of late anaphase chromosomes where they become more concentrated in early telophase. The substance within which they are scattered slowly increases in density during that time until finally, the particles are limited to small bodies of distinctive character. Evidence is presented suggesting that these small prenucleolar bodies fuse during telophase to give rise to the mature interphase nucleoli.

Similar events are described in Vicia material except that a coating of dense substance appears around telophase chromosomes before the formation of prenucleolar bodies.
Fine Structure and Function in Stentor polymorphus
Authors: Randall J. T. , Jackson Sylvia Fitton
Published: May 2004

The fine structure of the ciliate Stentor has been studied by means of the electron microscope and the results have been correlated with observations made on the living organism by means of light microscopy; special reference has been made to structural features which may be responsible for contraction and extension in Stentor.

Descriptions have been given of the structure of the macronucleus, the vacuolated cytoplasm, mitochondria and the pellicle; a detailed study has also been made of the adoral membranelles. About 250 membranelles encircle the peristomal cap and each is composed of 3 rows of cilia, with 20 to 25 cilia in each row; a fibrillar root system connected with the membranelles depends into the endoplasm for about 20 µ and each is essentially in the shape of a fan, the terminal ends of each root bifurcating to connect to neighbouring roots. The membranelles thus form a cohesive unit and this morphological arrangement may have a bearing on the motion and coordination of the whole system.

Two structural features extending throughout the length of the animal have been identified per cortical stripe in the body wall of Stentor; first, km fibres lying just beneath the pellicle are composed of stacks of fibrillar sheets and are identical with the birefringent fibres observed in the living animal. The individual fibrils of the sheets are in turn connected to the kinetosomes of the body cilia; thus the km fibres are homologous to kinetodesmata. Secondly, M bands lie beneath the km fibres and form an interconnected system in contact with the surrounding vacuolated cytoplasm; the thickness of the M bands is greatest at the base of a contracted animal. The contractile and extensile properties of these organelles have been discussed in the light of experimental results and theoretical considerations.
THE ANATOMIC SITE OF THE TRANSEPITHELIAL PERMEABILITY BARRIERS OF TOAD BLADDER
Authors: DiBona Donald R. , Civan Mortimer M. , Leaf Alexander
Published: May 2004

An examination of the mucosal epithelium of the urinary bladder of the toad reveals that the two major cell types which abut on the urinary surface, the granular and mitochondria-rich cells, also contact the basement membrane. Thus, the epithelium functions as a single cell layer. Although basal cells are interpolated between the granular cells and the basement membrane over a large portion of the epithelium, they do not constitute an additional continuous cell layer. This finding is consistent with extensive physiological data which had assumed that the major permeability barriers of this epithelium were the apical and basal-lateral plasma membranes of a single layer of cells.
A FIBRILLAR INTERCELLULAR MATERIAL BETWEEN REAGGREGATING EMBRYONIC CHICK CELLS
Authors: Overton Jane
Published: May 2004

Lanthanum staining of embryonic chick cell reaggregates reveals an intercellular material composed of fibrils. Fibrillar arrays may be composed of parallel fibrils with a 35 A center-to-center spacing. Fibrils may also be disoriented, long, and tortuous. Newly dissociated cells show little lanthanum staining surface material, but appreciable amounts are present after 6 hr of reaggregation. Examination of intact tissue does not give the same clear evidence of a fibrillar matrix surrounding the cells, but treatment with a number of agents permits observation of intercellular fibrils, and in some cases there is evidence of orientation. Thus fibrillar material must be taken into account in considering mechanisms of cell aggregation.
STUDIES ON STREAMING
Authors: Nachmias Vivianne T.
Published: May 2004

In Chaos chaos streaming, motility, and cytokinesis were inhibited nearly 100% for several hours by 2.5–5 mM sodium adenosine triphosphate (ATP)1 added to culture fluid. All three effects were completely prevented by the addition of equimolar Mg++ or Ca++ ions but not Na+ to the ATP/culture fluid solution. The effects of ATP were not reproduced by EDTA, EGTA, colchicine, or AMP. Sodium pyrophosphate produced about 50% inhibition at 5 mM. Studies with 14C-ATP showed that 5 x 10-5 to 5 x 10-4 mmole of ATP was firmly associated with each milliliter of packed cells after an hour's incubation at 24°C. Labeling studies also showed that prevention of the ATP effects by Mg++ ions was not due to a decrease in the amount of ATP associated with the cells.
PROTEOLYTIC MICRODISSECTION OF SMOOTH-SURFACED VESICLES OF LIVER MICROSOMES
Authors: Ito Akio , Sato Ryo
Published: May 2004

Digestion of rabbit liver microsomal smooth vesicles with Bacillus subtilis protease released proteins and peptide fragments from the vesicles, without solubilizing phospholipids and cholesterol. The proteolysis was, however, limited when about 30% of the protein had been solubilized. The same limitation was observed when the vesicles were treated with trypsin, chymotrypsin, or their combinations with the bacterial protease. The limited proteolysis was accompanied by selective solubilization of cytochrome b5 and microsomal NADPH-specific flavoprotein, leaving the CO-binding hemoprotein and some other enzymes still attached to the vesicular membranes. Sucrose density gradient centrifugation of protease-treated vesicles indicated that all the vesicles had been attacked by the protease to similar extents. The behavior of intact and digested vesicles in dextran density gradient centrifugation suggested that the vesicles, even after proteolytic digestion, existed in the form of closed sacs which were impermeable to macromolecules such as dextran and proteases. It was concluded that only the outside surface of the vesicles is susceptible to the proteolytic action and that cytochrome b5 and the NADPH-specific flavoprotein are located in the susceptible area.
ESTABLISHMENT OF A CLONAL STRAIN OF HEPATOMA CELLS WHICH SECRETE ALBUMIN
Authors: Richardson U. Ingrid , Tashjian Armen H. , Levine Lawrence
Published: May 2004

A clonal strain of epithelial cells (designated MH1C1) has been established from the transplantable Morris hepatoma No. 7795. The cells have maintained distinctive morphology throughout more than 20 subcultures (split 1:5) at 2- to 4-week intervals in supplemented Ham's F 10 medium. They contain many highly refractile, round, cytoplasmic bodies which stain bright red with Oil Red O. The population doubling time was 2 wk when the clonal strain was first established. It has gradually decreased to 1 wk. The cells synthesize rat serum albumin and secrete it into the culture medium as determined immunologically by microcomplement fixation and double diffusion. Albumin secretion (3–6 µg albumin/mg cell nitrogen/24 hr) occurs throughout the logarithmic phase of cell proliferation and has not diminished during serial propagation since the strain was initiated 15 months ago.
SOURCES OF LARVAL SALIVARY GLAND SECRETION IN THE DIPTERAN CHIRONOMUS TENTANS
Authors: Doyle D. , Laufer H.
Published: May 2004

The soluble proteins in the hemolymph, the salivary gland, and the salivary secretion of fourth instar Chironomus tentans were examined by disc electrophoresis in acrylamide gels. Of the 11 protein fractions detected in buffered saline extracts of the gland, 10 are present also in the hemolymph. Amino acid isotope incorporation experiments indicate that the protein fractions shared by the salivary gland and the hemolymph are not synthesized in the gland but are synthesized in other larval tissues. Immunochemical studies show that most of these proteins eventually are secreted from the gland. The salivary gland in vivo and in vitro is active in de novo protein synthesis. The protein synthesized tends to form large molecular weight aggregates. As demonstrated by radioautography, at least 80% of this protein is secreted from the 30 large cells forming most of the gland. The proteins synthesized in the salivary gland cannot be detected in the hemolymph. The results of this investigation are consistent with a mechanism of secretion formation involving both de novo synthesis of some secretion proteins and the selective uptake, transport, and secretion of hemal proteins by the salivary gland.
USE OF POTASSIUM PYROANTIMONATE IN THE LOCALIZATION OF SODIUM IONS IN RAT KIDNEY TISSUE
Authors: Bulger Ruth Ellen
Published: May 2004

Potassium pyroantimonate added to fixative solutions has been used in tissue localization of sodium ions. The distribution and specificity of the resulting precipitate in rat kidney is described in this study. Two reproducible patterns of precipitate were obtained in control tissues. The first pattern, which occurred after fixation in solutions containing aldehyde, showed the precipitate to be mainly extracellular. The second pattern, showing the precipitate in both intracellular and extracellular locations, occurred after aldehyde fixation in those experimental situations favoring cellular swelling or after fixation with solutions containing osmium tetroxide. It appeared that sodium ions could move after fixation but that sodium pyroantimonate precipitate could not. Since model systems demonstrated that dense precipitate formed when potassium pyroantimonate was added to solutions containing certain biological amines or some divalent cations, it appeared likely that the reagent did not provide specific tissue localization for sodium ions.
MICROTUBULAR CRYSTALS IN MAMMALIAN CELLS
Authors: Bensch Klaus G. , Malawista Stephen E.
Published: May 2004

Periwinkle alkaloids in very low concentrations cause an intracytoplasmic sequestration of microtubule protein in the form of symmetrical, microtubular bodies. These crystals, which may measure up to 8 µ in length, appear within 30 min in L-strain fibroblasts in vitro, but they increase in incidence and size with time of exposure to the alkaloids. Similarly, if exposed to these compounds, human leukocytes in vitro contain identical crystalline structures. Neither colchicine nor puromycin prevents the formation of these bodies; the latter compound, however, retards crystal growth.
THE DEVELOPMENT OF SURFACE SPECIALIZATION IN THE SECRETORY EPITHELIUM OF THE AVIAN SALT GLAND IN RESPONSE TO OSMOTIC STRESS
Authors: Ernst Stephen A. , Ellis Richard A.
Published: May 2004

Cell surface specialization, a characteristic common to most ion-transporting epithelia, was studied in the salt (nasal) gland of the domestic duck in relation to osmotic stress. Three days after hatching, experimental ducklings were given 1% NaCl to drink for 12 hr and freshwater for the remainder of each day. Control ducklings were maintained exclusively on freshwater. The fine structure of the secretory epithelium was examined on various days of the regimen. The nasal gland epithelium of the secretory lobule is composed of several types of cells. Peripheral cells, lying at the blind ends of the branched secretory tubules, are similar in both control and experimental animals at all stages of glandular development. These generative cells contain few mitochondria and have nearly smooth cell surfaces. Partially specialized secretory cells predominate in the secretory tubules of control animals and appear as transitional cells in the tubular epithelium of salt-stressed animals. These cells contain few mitochondria and bear short folds along their lateral cell surfaces. Fully specialized cells dominate the secretory epithelium of osmotically stressed ducklings. The lateral and basal surfaces of these cells are deeply folded, forming complex intra- and extracellular compartments. This vast increase in absorptive surface area is paralleled by an increase in the number of mitochondria that pack the basal compartments. The development of this fully specialized cell is correlated with the marked increase in (Na+-K+)-ATPase activity in the glands of osmotically stressed birds.
DETECTION OF COMPLEX CARBOHYDRATES IN THE GOLGI APPARATUS OF RAT CELLS
Authors: Rambourg A. , Hernandez W. , Leblond C. P.
Published: May 2004

Two methods used for the electron microscopic detection of glycoproteins were applied to a variety of cell types in the rat; one involved successive treatment of sections with periodic acid, chromic acid, and silver methenamine; and the other, a brief treatment with a chromic acid-phosphotungstic acid mixture. The results obtained with the two methods were identical and, whenever the comparison was possible, similar to those obtained with the periodic acid-Schiff technique of light microscopy. In secretory as well as in nonsecretory cells, parts of the Golgi apparatus are stained. The last saccule on one side of each Golgi stack is strongly reactive (mature face), and the last saccule on the other side shows little or no reactivity (immature face); a gradient of reactivity occurs in between these saccules. The more likely explanation of the increase in staining intensity is that carbohydrate is synthesized and accumulates in saccules as they migrate toward the mature face. In many secretory cells, the mature face is associated with strongly stained secretory granules. Other structures stained are: (1) small vesicles, dense and multivesicular bodies, at least some of which are presumed to be lysosomal in nature; (2) cell coat; and (3) basement membrane. The evidence suggests that the Golgi saccules provide glycoproteins not only for secretion, but also for the needs of the lysosomal system as well as for incorporation into the cell coat and perhaps basement membrane.
RESOLUTION OF GRANULES FROM RABBIT HETEROPHIL LEUKOCYTES INTO DISTINCT POPULATIONS BY ZONAL SEDIMENTATION
Authors: Baggiolini Marco , Hirsch James G. , de Duve Christian
Published: May 2004

Postnuclear supernates from homogenates of essentially pure rabbit heterophil leukocytes were fractionated by means of zonal differential centrifugation through a discontinuous sucrose gradient at various speeds. Three distinct groups of granules were characterized biochemically and morphologically. They were, in order of decreasing sedimentation coefficient: (a) Large, relatively dense granules, identified morphologically as the azurophil or primary granules, and containing essentially all of the myeloperoxidase activity of the preparations, about one-third of their lysozyme activity, and between 50 and 80% of their content in five acid hydrolases typically associated with lysosomes in other cells; (b) smaller, less dense granules, with the morphological appearance of the specific or secondary granules, and carrying most of the alkaline phosphatase and the remainder of the lysozyme activity of the preparations; (c) a second group of lysosome-like particles, associated with a morphologically heterogeneous fraction, and containing the remainder of the acid hydrolases, but little or no myeloperoxidase. When p-nitrophenyl phosphate was used instead of ß-glycerophosphate for the assay of acid phosphatase, only small proportions of the total activity accompanied the two main lysosomal bands, and considerable activity was found in a zone slightly retarded with respect to the slowly moving band of acid hydrolases.
THE OXIDATION OF EXOGENOUS AND ENDOGENOUS CYTOCHROME C IN MITOCHONDRIA
Authors: Muscatello Umberto , Carafoli Ernesto
Published: May 2004

The effect of the nonionic detergent Lubrol on the oxidation of endogenous and exogenous cytochrome c by cytochrome oxidase in intact and fragmented mitochondria was studied. Mitochondria and mitochondrial fragments from liver, kidney, heart, and skeletal muscle have been used. Negatively stained preparations of intact mitochondria showed the particles of Fernández-Morán on the matrix side of their inner membrane system: under these conditions, the oxidation rate of externally added cytochrome c was very high, and it was stimulated very poorly by Lubrol. Mechanical fragmentation of liver mitochondria yielded vesicles with a smooth external profile: also under these conditions, the oxidation of externally added cytochrome c was very high, and poorly stimulated by Lubrol. The oxidation of endogenous cytochrome c was also unaffected by Lubrol. On the other hand, fragmentation of heart and skeletal muscle mitochondria yielded vesicles having numerous particles of Fernández-Morán on their external profiles. Under these conditions, the oxidation of exogenous cytochrome c was low and was markedly stimulated by Lubrol. On the contrary, no activation of the oxidation of endogenous cytochrome c was induced by the detergent. The results indicate a difference in the permeability properties of the two faces of the inner mitochondrial membrane: a permeability barrier for cytochrome c is suggested to exist at the inner face.
STUDIES ON THE ORIGIN OF RIBOSOMES IN AMOEBA PROTEUS
Authors: Craig Nessly , Goldstein Lester
Published: May 2004

The origin of cytoplasmic RNA and ribosomes was studied in Amoeba proteus by transplantation of a radioactive nucleus into an unlabeled cell followed by examination of the cytoplasm of the recipient for the presence of label. When a RNA-labeled nucleus was used, label appeared in the ribosomes, ribosomal RNA, and soluble RNA. Since the kinetics of appearance of labeled RNA indicates that the nucleus was not injured during the transfer, and since the transferred nuclear pool of labeled acid-soluble RNA precursors is inadequate to account for the amount of cytoplasmic RNA label, it is concluded that cytoplasmic ribosomal RNA is derived from acid-insoluble nuclear RNA and is probably transported as an intact molecule. Likewise, cytoplasmic soluble RNA probably originated in the nucleus, although labeling by terminal exchange in the cytoplasm is also possible. The results were completely different when a protein-labeled nucleus was grafted into an unlabeled host. In this case, label was found only in soluble proteins in the host cell cytoplasm, and there were no (or very few) radioactive ribosomes. This suggests that the nuclear pool of ribosomal protein and ribosomal protein precursors is relatively small and perhaps nonexistent (and, furthermore, shows that there was no cytoplasmic ribosomal contamination of the transferred nucleus).
THE ENDOCRINE CELLS IN THE EPITHELIUM OF THE GASTROINTESTINAL MUCOSA OF THE RAT
Authors: Forssmann W. G. , Orci L. , Pictet R. , Renold A. E. , Rouiller C.
Published: May 2004

The authors of this study examine the question of whether the so-called enterochromaffin or argentaffin cells of the gastrointestinal tract should be considered as a single cell type. The systematic application of purely morphologic methods has led to the conclusion that the epithelium of the gastrointestinal mucosa comprises endocrine cells of several types. This conclusion is primarily based on the uneven and characteristic distribution of the various cell types along the intestinal tract, an observation precluding the interpretation that the different types correspond to diverse functional stages of the same cell. A specific endocrine function may be attributed to each of the given cell types recognized so far on account of their appearance and their localization in characteristic areas of the gastrointestinal tract. It is acknowledged, however, that a purely morphological study leaves room for doubt. The first cell type is probably responsible for the formation of 5-hydroxytryptamine. Cells of type II are morphologically comparable to the pancreatic A cells and may, therefore, be called intestinal A cells. Cell type III comprises intestinal D cells since their appearance corresponds to that of pancreatic D cells. Cell type IV might well be responsible for catecholamine production, whereas gastrin is in all probability produced in endocrine cell type V. As yet, the thorough morphological study of the gastrointestinal epithelium does not provide information as to additional distinct cellular sites of production of the several other hormones isolated from different parts of the gut.
MEASUREMENT OF THICKNESS WITHIN SECTIONS BY QUANTITATIVE ELECTRON MICROSCOPY
Authors: Silverman Lloyd , Schreiner Berit , Glick David
Published: May 2004

To apply the method of quantitative electron microscopy to the measurement of mass in thin sections, the thickness of the section at or very near the structure to be studied must be known. Dowex anion exchange resin AG 1 x 2, stained with phosphotungstic acid (PTA) at pH 6.4, was used as a thickness standard which could be embedded and sectioned. The sectioned PTA-Dowex appeared uniformly stained and exhibited suitable electron opacity. The stoichiometry of the reaction between PTA and the Dowex resin was measured by three independent methods based on gravimetric, colorimetric, and nitrogen determinations whose results showed close agreement. From the PTA uptake, the density of the stained spheres was calculated. Mass of a defined area of PTA-Dowex was measured by quantitative electron microscopy, and from this mass and density, the volume and then the thickness were calculated. The values for thickness were compared to those obtained by interference microscopy on the embedding medium alone in the same sections.
MEASUREMENT OF PROTEIN CONCENTRATION BY QUANTITATIVE ELECTRON MICROSCOPY
Authors: Silverman Lloyd , Glick David
Published: May 2004

The method of quantitative electron microscopy was applied to the measurement of protein concentration in thin sections. The human erythrocyte was selected as a model because of its apparently uniform protein concentration. Phosphotungstic acid (PTA) in aqueous solution was used as a reversible stain for protein, and PTA-stained Dowex resin spheres were embedded along with the red cells as standards for measurement of section thickness. The mass of stain removed from a given area of sectioned red cell by buffer (pH 7.4) was measured by quantitative electron microscopy. From the stoichiometry of the reaction between PTA and red cell protein established in this study, the amount of protein present in the measured area was calculated. From this amount of protein and the measured thickness, the concentration of protein was calculated and expressed as g/100 ml, for comparison with the clinical laboratory value for hemoglobin. Groups of red cells from the same sample were measured on 3 different days and their mean values (g/100 ml ± SD) were 29 ± 3.9, 30 ± 2.7, and 33 ± 4.6, compared to the clinical laboratory value of 32.1 g/100 ml packed cells, after correction for volume change and protein loss during fixation.