bluuebunny/crossref_metadata_2025_split huggingface dataset:
CELL STRUCTURE AND THE METABOLISM OF INSECT FLIGHT MUSCLE
Authors: Sacktor Bertram 
Published: May 2004

The biochemical properties of insect flight muscle were investigated to ascertain the mechanisms whereby energy is made available for the contractile processes. It was found:
1. The endogenous respiration of muscle homogenates was diminished by starving the flies. The substrate for this respiration was probably glycogen.
2. To obtain the maximal rate of oxidation of glucose, the homogenate had to be fortified with inorganic phosphate, Mg ions, ATP, and cytochrome c. The nucleotides, AMP and ADP, were not as effective as ATP. The addition of DPN or TPN was not necessary for this system.
3. Flight muscle homogenates oxidized glycogen, some sugars, and amino acids, as well as the intermediates of the glycolytic and tricarboxylic acid cycles. Other evidence demonstrated the substrate specificity of the muscle.
4. By centrifugation, the muscle homogenate was divided into two fractions: one, a soluble fraction representing the sarcoplasm; the other, the particulate fraction which contained the fibrils and the sarcosomes.
5. The particulate fraction, alone, oxidized all the citric acid cycle intermediates, α-glycerophosphate, phosphopyruvate, and the amino acids, glutamic, proline, and cysteine. Regardless of the substrate, no oxygen uptake was found with the sarcoplasm by itself.
6. A recombination of the sarcoplasm and the particulate component was required for the oxidation of glycogen, the hexoses, and all the phosphorylated intermediates of glycolysis, except phosphopyruvate.
7. Isolated mitochondria accounted for all the enzymatic activity of the particulate fraction.
These results demonstrate that the enzymes of intermediate metabolism are localized in the sarcoplasm or sarcosomes. The third cytological entity, the myofibrils, plays no role in the energy-providing scheme. From a functional viewpoint, the sarcoplasm and the mitochondria, in combination, furnish the energy for the actomyosin contraction.
The results are discussed in relation to analogous findings in other insects and vertebrates.
ANTAGONISTIC EFFECTS OF 6-MERCAPTOPURINE AND COENZYME A ON MITOCHONDRIA AND MITOSIS IN TISSUE CULTURE
Authors: Biesele John J. 
Published: May 2004

The partial mitotic inhibition caused by 6-mercaptopurine in tissue cultures of Crocker mouse sarcoma 180 and embryonic mouse skin is blocked by co-enzyme A. 6-Mercaptopurine and coenzyme A also have opposite effects on mitochondrial morphology. Mitochondria in cells treated with 6-mercaptopurine become thin and fragmented. Coenzyme A blocks this effect, and alone coenzyme A makes for longer and thicker mitochondria. 6-Mercaptopurine inhibits lipogenesis in embryo skin fibroblasts, and this inhibition is partly counteracted by coenzyme A, which by itself makes for a greater accumulation of lipid droplets in the cytoplasm.
It is suggested that at least one part of the action by which 6-mercaptopurine decreases mitotic incidence in tissue cultures may be an interference on the part of 6-mercaptopurine, acting as an antimetabolite of coenzyme A, in mitochondrial function related to cell division.
A METHOD FOR ISOLATING INTACT MITOCHONDRIA AND NUCLEI FROM THE SAME HOMOGENATE, AND THE INFLUENCE OF MITOCHONDRIAL DESTRUCTION ON THE PROPERTIES OF CELL NUCLEI
Authors: Dounce Alexander L. , Witter Robert F. , Monty Kenneth J. , Pate Sidney , Cottone Mary A. 
Published: May 2004

1. An improved type of ground glass homogenizer for soft tissues has been described which brings about a high degree of cell disruption and liberation of nuclei without causing appreciable damage to mitochondria. The gentleness and effectiveness of the new homogenizer in respect to isolation of mitochondria have been ascertained by comparing the ATP-ase activities of mitochondria isolated in 0.25 M sucrose solution without pH adjustment using a previous type of homogenizer with those of mitochondria isolated under the same conditions with the aid of the new homogenizer. In these experiments sucrose of 0.25 molarity without pH adjustment has been used in order to maintain the mitochondria in a rather sensitive state so as to make slightly deleterious effects of homogenization readily apparent.
2. A new method is described for the isolation of morphologically intact mitochondria and cell nuclei from the same homogenate. In this procedure the pH of the homogenate in 0.44 M sucrose is maintained at 6.0–6.2 with citric acid during the homogenization. An alternative method employing 0.44 M sucrose plus 0.005 M CaCl2 is given for the isolation of nuclei from tumor cells. However, the latter method does not produce unaltered mitochondria.
3. The α-ketoglutarate, malate, succinate, and hexanoate oxidases of the "intact" mitochondria isolated in 0.44 M sucrose adjusted to pH 6.0–6.2 with very dilute citric acid as described in this paper have been investigated, and it has been shown that the mitochondria compare favorably to those isolated in 0.25 M sucrose by a previously described method.
4. Mitochondria have been found to contain an enzyme which causes nuclei to lose their ability to form gels in dilute alkali. This enzyme is released from the mitochondria when the latter are disrupted.
5. Some properties of nuclei isolated by the new method have been briefly discussed.
THE NUCLEAR ENVELOPE
Authors: Watson Michael L. 
Published: May 2004

An electron microscope study of thin sections of interphase cells has revealed the following:—
Circular pores are formed in the double nuclear envelope by continuities between the inner and outer membranes which permit contact between the nucleoplasm and the cytoplasm unmediated by a well defined membrane.
The pores, seen in sections normal to the nuclear envelope, are profiles of the ring-shaped structures described by others and seen in tangential section.
The inner and outer nuclear membranes are continuous with one another and enclose the perinuclear space.
The pores contain a diffuse, faintly particulate material.
A survey of cells of the rat derived from the embryonic ectoderm, mesoderm, and endoderm, and of a protozoan and an alga has revealed pores in all tissues examined, without exception. It is concluded that pores in the nuclear envelope are a fundamental feature of all resting cells.
In certain cells, the outer nuclear membrane is continuous with membranes of the endoplasmic reticulum, hence the perinuclear space is continuous with cavities enclosed by those membranes. There are indications that this is true for all resting cells, at least in a transitory way.
On the basis of these observations, the hypothesis is made that two pathways of exchange exist between the nucleus and the cytoplasm; by way of the perinuclear space and cavities of the endoplasmic reticulum and by way of the pores in the nuclear envelope.
INTRACELLULAR DISTRIBUTION OF ALKALINE PHOSPHATASE IN RAT LIVER CELLS
Authors: Emery Arthur J. , Dounce Alexander L. 
Published: May 2004

1. Cytochemical studies of the intracellular distribution of alkaline phosphatase in rat liver have been made, using a fractionation procedure recently developed in this laboratory (8) and a similar but modified method not described previously. Aqueous media were used in both cases.
2. The alkaline phosphatase was found to consist of two forms, one of which is strongly activated by magnesium and one of which is not sensitive to this metal.
3. The form of the enzyme that is not activated by magnesium occurs mainly in the nuclear fraction, where it seems to be rather firmly bound. Some of this form of the enzyme is also found in the microsomes, but very little if any occurs in the soluble supernatant fraction.
4. The form of alkaline phosphatase which is activated by magnesium occurs mainly in the soluble supernatant fraction, but what is believed are significant amounts also occur in nuclei. A significant portion of this form of the enzyme can be extracted from the isolated nuclei with cold, isotonic saline solution. Some activity of this form of the enzyme is also found in the microsomal fraction.
5. Mitochondria appear to contain relatively little alkaline phosphatase of either kind.
6. The concept of a porous nuclear membrane has been invoked to explain some of the results obtained in this work. It is postulated that part at least of the form of the enzyme that is activated by magnesium is free to diffuse back and forth through pores in the nuclear membrane, whereas this is considered not to be possible for the form of the enzyme that is insensitive to magnesium as a result of the firm binding of the latter to nuclear substance.
STUDIES ON THE STRUCTURE OF MUSCLE
Authors: Hodge A. J. 
Published: May 2004

1. The flight muscles of blowflies are easily dispersed in appropriate media to form suspensions of myofibrils which are highly suitable for phase contrast observation of the band changes associated with ATP-induced contraction.
2. Fresh myofibrils show a simple band pattern in which the A substance is uniformly distributed throughout the sarcomere, while the pattern characteristic of glycerinated material is identical with that generally regarded as typical of relaxed vertebrate myofibrils (A, I, H, Z, and M bands present).
3. Unrestrained myofibrils of both fresh and glycerinated muscle shorten by not more than about 20 per cent on exposure to ATP. In both cases the A substance migrates during contraction and accumulates in dense bands in the Z region, while material also accumulates in the M region. It is proposed that these dense contraction bands be designated the Cz, and Cm bands respectively. In restrained myofibrils, the I band does not disappear, but the Cz and Cm bands still appear in the presence of ATP.
4. The birefringence of the myofibrils decreases somewhat during contraction, but the shift of A substance does not result in an increase of birefringence in the Cz and Cm bands. It seems therefore that the A substance, if it is oriented parallel with the fibre axis in the relaxed myofibril, must exist in a coiled or folded configuration in the C hands of contracted myofibrils.
5. The fine structure of the flight muscle has been determined from electron microscopic examination of ultrathin sections. The myofibrils are of roughly hexagonal cross-section and consist of a regular single hexagonal array of compound myofilaments the cores of which extend continuously throughout all bands of the sarcomere in all states of contraction or relaxation so far investigated.
6. Each myofilament is joined laterally with its six nearest neighbours by thin filamentous bridges which repeat at regular intervals along the fibre axis and are present in the A, I, and Z, but not in the H or M bands. When stained with PTA, the myofilaments display a compound structure. In the A band, a lightly staining medullary region about 40 A in diameter is surrounded by a densely staining cortex, the over-all diameter of the myofilament being about 120 A. This thick cortex is absent in the I and H bands, but a thinner cortex is often visible.
7. It is suggested that the basic structure is a longitudinally continuous framework of F actin filaments, which are linked periodically by the lateral bridges (possibly tropomyosin). The A substance is free under certain conditions to migrate to the Z bands to form the Cz bands. The material forming the Cm bands possibly represents another component of the A substance. The results do not clearly indicate whether myosin is confined to the A bands or distributed throughout the sarcomere.
HISTOCHEMICAL STUDIES ON MUCOPROTEINS IN NERVE CELLS OF THE DOG
Authors: Sulkin Norman M. 
Published: May 2004

Autonomic and sensory ganglion cells in the senile dog contain a deposition of PAS-positive substances which has been shown to be mucoprotein in nature.
Data are presented to show that this PAS-positive mucoprotein can be demonstrated by metachromatic staining with toluidine blue after the mucoprotein is sulfated. This procedure indicates that mucoprotein is also present in a granular form in all nerve cells in both senile and young dogs.
The evidence for this is further substantiated by the use of the aldehyde-fuchsin stain following both periodic acid oxidation and sulfation. The granular and non-granular deposition can be demonstrated by the periodic acid-aldehyde-fuchsin method due to the affinity of the aldehyde-fuchsin stain for aldehydes. It can be demonstrated following the sulfation-aldehyde-fuchsin method owing to the affinity of the stain for the sulfuric group. The evidence for this latter phenomenon has been reported by Scott and Clayton (6).
It is concluded that mucoprotein is present in a granular form in all nerve cells in both senile and young dogs but is not concentrated enough in the latter to be demonstrated by the PAS method.
STUDIES ON INFLAMMATION
Authors: Majno G. , Palade G. E. 
Published: May 2004

The mechanism, whereby histamine and serotonin increase the permeability of blood vessels, was studied in the rat by means of the electron microscope. The drugs were injected subcutaneously into the scrotum, whence they diffused into the underlying (striated) cremaster muscle. An intravenous injection of colloidal HgS was also given, in order to facilitate the identification of leaks by means of visible tracer particles. After intervals varying from 1 minute to 57 days the animals were killed; the cremaster was fixed, embedded in methacrylate, and examined with the electron microscope.
One to 12 minutes after the injection, the blood vessels of the smallest caliber (3 to 5 micra as measured on electron micrographs) appeared intact. Numerous endothelial openings were present in blood vessels with a diameter of 7 to 8 micra or more. These gaps were 0.1 to 0.8 micra in width; portions of intercellular junctions were often present in one or both of the margins. The underlying basement membrane was morphologically intact. An accumulation of tracer particles and chylomicra against the basement membrane indicated that the latter behaved as a filter, allowing fluid to escape but retaining and concentrating suspended particulate matter of the size used.
Uptake of tracer particles by endothelial vesicles was minimal. Phagocytosis by endothelial cells became more prominent at 3 hours, but as a secondary occurrence; the pericytes were actively phagocytic at all stages. At the 3-hour stage no leaks were found.
The changes induced by histamine and serotonin were indistinguishable, except that the latter was more potent on a mole-to-mole basis. In control animals only small accumulations of tracer particles were found in the wall of a number of blood vessels.
With regard to the pathogenesis of the endothelial leaks, the electron microscopic findings suggested that the endothelial cells become partially disconnected along the intercellular junctions. Supporting evidence was provided at the level of the light microscope, by demonstrating—in the same preparation—the leaks with appropriate tracer particles1, and the intercellular junctions by the silver nitrate method. The lipid nature of the chylomicron deposits observed in electron micrographs was also confirmed at the level of the light microscope, using cremasters fixed in formalin and stained in toto with sudan red.
STUDIES ON INFLAMMATION
Authors: Majno G. , Palade G. E. , Schoefl Gutta I. 
Published: May 2004

While it is an established fact that histamine and serotonin increase the permeability of blood vessels, the exact portion of the vascular tree which is so affected has not been conclusively demonstrated. The present study was undertaken to clarify this point.
Our experiments were based on a method to which we refer as "vascular labeling," and which permits one to identify leaking vessels by means of visible accumulations of foreign particles within their walls. The mechanism of the labeling, elucidated by previous electron microscopic studies, is the following. Histamine and serotonin cause the endothelial cells of certain vessels to separate, and thus to create discrete intercellular gaps. Plasma escapes through these gaps, and filters through the basement membrane. If the plasma has been previously loaded (by intravenous injection) with colloidal particles of a black material such as carbon or mercuric sulfide, these particles—too large to pass through the basement membrane—will be retained and accumulate in visible amounts within the wall of the leaking vessel. This method is used to maximal advantage if the tissue is cleared and examined by transillumination in toto, so that leaking vessels can be accurately identified in their relationship to the vascular tree.
As a test tissue we used the rat cremaster, a laminar striated muscle which can be easily excised with its vascular supply virtually intact. The rats were prepared with an intravenous injection of carbon or HgS, and a subcutaneous injection into the scrotum of histamine, serotonin, or NaCl (as a control). The injected drug diffused into the underlying cremaster and the vessels became labeled. One hour later, when the carbon had been cleared from the blood stream, the animal was killed. The cremaster was excised, stretched, fixed in formalin, cleared in glycerin, and examined by transillumination under a light microscope.
The lesions induced by histamine and serotonin were identical. The leaking vessels, as indicated by the carbon deposits, always belonged to the venous side of the circulation. The heaviest deposits were found in venules 20 to 30 micra in diameter. The deposits decreased towards larger venules up to a maximum diameter of 75 to 80 micra, and towards the finer vessels until the caliber reached approximately 7 micra. Essentially spared by the deposits were the finest vessels, 4 to 7 micra in diameter, and constituting an extensive network oriented along the muscular fibers.
By killing animals at varying intervals after the injections, it was found that the carbon particles were slowly removed from the vascular walls by the action of phagocytic cells. After 10 months there was still enough carbon locally to be recognized by the naked eye.
A CYTOCHEMICAL DESCRIPTION OF THE MULTIPLICATION OF MENGOVIRUS IN L-929 CELLS
Authors: Franklin Richard M. 
Published: May 2004

A correlation of cytochemical changes with virus production has been studied in L cells infected with Mengovirus. After a latent period of about 2 hours, virus was produced rapidly, reaching maximum titers of up to 12,000 particles per cell in 6 to 8 hours. The earliest cytological change was in the nucleus and consisted of a slight condensation of chromatin. There is no evidence, however, for the multiplication of either the viral RNA or protein in the nucleus. RNA, of high molecular weight, accumulated in the perinuclear area of the cytoplasm and was later found in inclusions. The perinuclear RNA was digestible with RNase and may be located in or on ribosomes. The inclusion RNA was resistant to RNase but could be removed by pepsin or potassium permanganate; it is probably in completed virus particles.
Viral antigen was first observed in a perinuclear location and later in the above-mentioned inclusions. Although the viral protein contains appreciable amounts of arginine and lysine, it is not a basic protein of the histone type. Phase-contrast microscopy of living cells clearly demonstrated the role of the inclusions in release of virus from infected cells. A comparison is made between these cytological changes in Mengo-infected cells and those which have been found by other workers in polio-infected cells. There are many very similar changes.
FUNCTIONAL EVIDENCE FOR THE EXISTENCE OF A THIRD CELL TYPE IN THE RENAL GLOMERULUS
Authors: Farquhar Marilyn G. , Palade George E. 
Published: May 2004

Two types of cells can be recognized on the luminal side of the glomerular basement membrane: the superficial endothelial cells which directly line the lumen and are comparable to endothelia lining the capillaries of other tissues, and the deep cells, ordinarily not in contact with the lumen, which are distinguished by their long cytoplasmic arms extending for some distance in several directions along the capillary wall, numerous spinous processes, and occasional intraluminal pseudopodia. Experiments carried out with electron-opaque tracers indicated that a functional distinction, based on extent of phagocytosis, can be made between the superficial and deep cells, thus supporting the existence of a distinctive "third" cell (in addition to endothelium and epithelium) in the renal glomerulus.
Ferritin, colloidal gold, or thorotrast was administered intravenously to normal and, in the case of ferritin, to nephrotic rats. Kidney tissue was fixed at selected intervals from 1 hour to 10 days after the injection and studied by electron microscopy. Within 1 to 4 hours after tracer administration, the particles which did not traverse the glomerular capillary wall gradually accumulated in the less compact, inner strata of the basement membrane and the large spongy areas of axial regions. After 1 day the concentration of circulating tracer declined and the peripheral areas of the capillaries became relatively free of particles while large accumulations developed in the axial regions. During this period increasing quantities of ferritin were taken up by the deep cells and were found within large and small sized invaginations of their cell membrane or concentrated within cytoplasmic vesicles, vacuoles, multivesicular and dense bodies. At the same time the deep cells showed increased numbers of intraluminal pseudopodia. Within 2 to 4 days the deposits in the spongy areas were cleared and concomitantly increased quantities of tracer appeared in the deep cells within dense cytoplasmic bodies, some of which were more compact than before. When ferritin was given to nephrotic animals the sequence of events was generally the same except that the ferritin deposits at any given period were more massive, their incorporation into the deep cells occurred primarily by means of large pockets 1 to 2 µ in diameter and their clearance from the spongy areas was slower. In normal as well as in nephrotic animals, the phagocytic activity of the superficial endothelium was negligible when compared to that of the deep cells.