bluuebunny/crossref_metadata_2025_split huggingface dataset:
MITOCHONDRIA OF PROTOZOA
Authors: Sedar Albert W. , Rudzinska Maria A. 
Published: May 2004

A study of thin sections of Paramecium multimicronucleatum, Tetrahymena pyriformis, Tokophrya infusionum, and Amoeba proteus shows that the mitochondria in all these protozoa are similar in certain aspects of their fine structure to that described in metazoan cells. As in higher organisms the mitochondrion is surrounded by a double limiting membrane and contains protrusions directed inward from the innermost of the double membranes.
There are, however, some differences. In a majority of higher organisms the internal structure of mitochondria consists of ridges or cristae mitochondriales and in a few instances only of finger-like projections, or microvilli. In all protozoa described here and elsewhere microvilli represent the dominant structure. They are characteristic therefore of protozoan mitochondria.
THE STRUCTURE OF PIGEON BREAST MUSCLE MITOCHONDRIA
Authors: Howatson Allan F. 
Published: May 2004

The structure of pigeon breast muscle mitochondria was studied both in whole muscle tissue and in mitochondrial fractions separated by differential centrifugation. No evidence was found to indicate that the mitochondria of pigeon breast muscle differ in any fundamental way from those of other tissues. In particular the absence of an enveloping membrane, claimed in recent reports, was not confirmed.
The structure of the lipide bodies present in muscle has been described, and compared with that of similar bodies in other tissues.
STUDIES ON NUCLEI USING CORRELATED CYTOCHEMICAL, LIGHT, AND ELECTRON MICROSCOPE TECHNIQUES
Authors: Moses Montrose J. 
Published: May 2004

In this paper, a procedure for correlating electron microscope and light microscope cytochemical studies using immediately adjacent serial thin and thick sections has been described and discussed. This technique, combined with the Feulgen reaction for DNA, has been of particular value in framing and answering both general and specific questions about the nucleus. The results may be summarized as follows:—
Apparent nuclear homogeneity in the electron microscope is not due to loss of DNA as evidenced by positive Feulgen reactions in such nuclei.
Arrangement of Feulgen-positive material in chromosomes, heterochromatin, perinuclear and perinucleolar chromatin, etc., is similar to that customarily observed in the light microscope but this is not necessarily reflected in a cursory survey of the electron image.
Careful comparison of light and electron images shows that fine differences in structure are associated with chromatin localization.
Primary spermatocyte prophase chromosomes of crayfish have been positively identified by their Feulgen-positive nature. Core-like axial structures in such chromosomes have been observed (9) and are described further.
A remarkable feature of spermiogenesis in the crayfish is an elaboration of the nuclear envelope of the spermatid accompanying the formation of what becomes a mass of convoluted membranes in the sperm. In the spermatid, perinuclear chromatin follows outpocketings of the nuclear envelope into the cytoplasm. In the early sperm, on the other hand, although the nuclear envelope is continuous with the system of convoluted membranes, the chromatin is distinct from it and is retained in the nucleus proper by some mechanism independent of the nuclear envelope.
None of the above observations was apparent from the electron microscope images alone; they were possible only by virtue of the correlated cytochemical and electron microscope study of adjacent sections.
The successful use of other cytochemical tests, such as the PAS reaction for certain carbohydrates, in such correlated studies is also described.
FURTHER OBSERVATIONS ON THE FINE STRUCTURE OF THE MACRONUCLEUS IN TOKOPHRYA INFUSIONUM
Authors: Rudzinska Maria A. 
Published: May 2004

In a previous paper (8) an organized structure was described in the macronuclei of certain old organisms of Tokophrya infusionum. It was found that the same honeycomb structure appears in great abundance in the macronuclei of overfed organisms. This permitted a better three-dimensional reconstruction of the described structure.
Since the defined structure may be experimentally induced, it offers an opportunity for further more detailed studies as to its nature and meaning.
THE NISSL SUBSTANCE OF LIVING AND FIXED SPINAL GANGLION CELLS
Authors: Deitch Arline D. , Murray Margaret R. 
Published: May 2004

Living chick embryo spinal ganglion neurons grown from 1 to 4 weeks in vitro were studied under the phase contrast microscope. In the peripheral cytoplasm of the earliest stages studied, a homogeneous, phase-dense material is seen which corresponds in location to the cytoplasmic basophil material of the same stages. As maturation proceeds, this material increases in extent, and becomes separated by lighter channels into discrete bodies.
Short fixation by 1 per cent buffered osmium tetroxide followed by post-fixation with neutral buffered formalin does not significantly alter the size, shape, or distribution of any of the cytoplasmic components, and the fixed, hydrated cell is almost indistinguishable from the living cell. Dehydration causes some shrinkage of the fixed preparations, but if the photographs of the stained preparations are enlarged to correspond with those of the living cell, excellent correspondence can be made between at least the larger basophil masses and the larger dark masses seen with phase contrast. Fixation by a formalin-mercuric chloride procedure also results in satisfactory correspondence between the stained Nissl bodies and the phase-dark homogeneous areas. It is concluded that discrete Nissl bodies preexist in the living neuron and are essentially unchanged after good cytological fixation.
Evidence is also presented of the presence of neurofibrils in the living state.
EVIDENCE FROM ELECTRON MICROGRAPHS FOR THE PASSAGE OF MATERIAL THROUGH PORES OF THE NUCLEAR MEMBRANE
Authors: Anderson Everett , Beams H. W. 
Published: May 2004

1. The nurse cells of Rhodnius possess nucleoli that stain with Heidenhain's hematoxylin but give a negative Feulgen reaction. In localized positions adjacent to the nuclear membrane are seen masses of material both within the nucleus and the adjoining cytoplasm that stain with Heidenhain's hematoxylin, but, like the nucleolus, give a negative Feulgen reaction.
2. Electron micrographs of the nurse cells of Rhodnius reveal the nuclear membrane to contain pores approximately 400 A in diameter.
3. In electron micrographs the nucleolus is seen to be composed of a reticulum containing tightly packed granules. Between the centrally located nucleolus and the nuclear membrane are observed relatively small bunches of granules of the same relative size as those occurring in the nucleolus. Aggregated at certain positions adjacent to the nuclear membrane both within the nucleus and in the adjoining cytoplasm are irregularly shaped masses of granules. Certain of these masses within the nucleus are seen to be continuous with those in the cytoplasm through narrow isthmuses of material extending through pores of the nuclear membrane. Other masses of granules show evidence of preparing to enter the pores by projecting tongues of material toward and into them. In the adjacent cytoplasm pear-shaped masses of granules are seen in front of and in contact with the pores which suggests that they were fixed in the process of or just after completing passage through the pores.
THE ELECTRON MICROSCOPY OF THE CHOROID PLEXUS
Authors: Maxwell David S. , Pease Daniel C. 
Published: May 2004

1. The choroid plexus of the rat has been studied in detail by electron microscopy. Samples from the frog, rabbit, and cat have also been examined without noting significant differences.
2. The surface of the ependymal epithelium is covered by pedicels of variable size. There is reason for thinking of these structures as labile. They may actually pinch off and contribute to the secretory product. In any case, the surface area is vastly increased by their presence. Polypoid border seems an apt term to apply to this type of surface.
3. There is also a great expansion of the basal surface of ependymal cells. In the vicinity of cell junctions this surface is deeply infolded, and continuous with elaborate interdigitations of the lateral intercellular surfaces. Analogous infolding of the basal cell surface is known to exist in other epithelia also noted for their water transport (kidney tubules, salivary gland, and ciliary body).
4. Pretreatment of rats with diamox, an agent known to block cerebro-spinal fluid production, did not produce an important morphological change in the features of the ependyma, or any other part of the choroid plexus.
5. Capillaries of the choroid plexus have a very attenuated endothelium. This is seen to be fenestrated. It is thought this probably represents the condition in life, and is not simply a fixation artefact.
6. Pial cells tend to interpose sheets of cytoplasm between the capillaries and ependyma. The sheets are not continuous, however, and so would not constitute a serious diffusion barrier. These cells belong to the reticuloendothelial system, and undergo shape changes, and probably increase in number, when the system is stimulated by the repeated injection of trypan blue.
POLARIZATION AND ELECTRON MICROSCOPE STUDY OF FROG NERVE AXOPLASM
Authors: Thornburg Wayne , De Robertis Eduardo 
Published: May 2004

1. The submicroscopic organization of nerve axons from R. pipiens and R. catesbiana has been studied by means of polarizing and electron microscopes.
2. In measurements on a series of 85 fresh myelinated axons from which the sheaths had been removed average values were obtained for the total birefringence, +2.5 x 10–4, the form birefringence, +1.4 x 10–4, and the refractive index of the oriented component, 1.523. The average partial volume occupied by axially oriented filaments was computed to be 0.69 per cent.
3. Electron micrographs of fixed myelinated axons demonstrate an average of 93 axially oriented neuroprotofibrils per square micron of cross-section. The neuroprotofibrils are approximately 90 A in diameter, of indefinite length, and occupy a computed partial volume of 0.59 per cent.
4. Mitochondria, neuroprotofibrils, endoplasmic reticulum, and dense particles are seen in electron micrographs of both myelinated and unmyelinated nerve axons.
5. It is concluded that the neuroprotofibrils are present in the living nerve, that they play an important but undetermined role in nerve function, and that these structures are not an artifact of osmium tetroxide fixation.
CLOSE TOPOGRAPHICAL RELATIONSHIP BETWEEN MITOCHONDRIA AND ERGASTOPLASM OF LIVER CELLS IN A DEFINITE PHASE OF CELLULAR ACTIVITY
Authors: Bernhard W. , Rouiller C. 
Published: May 2004

1. In most rat liver cells, no special topographical relationship between mitochondria and ergastoplasmic lamellae is to be observed. In some cells, nevertheless, the two organelles are grouped together in dense zones clearly separated from the hyaloplasm.
2. Such an association can be produced at will in the livers of animals refed after prolonged fasting, or in the regenerative phases after partial hepatectomy and intoxication with carbon tetrachloride. In all these cells, the ergastoplasm, after having disappeared, suddenly reappears in the cytoplasm, either along the nucleus or cell membranes, where the mitochondria are grouped.
3. It may be supposed that these topographical relationships between mitochondria and ergastoplasm during a definite period of cellular activity indicate a close functional link between chondrioma and basophilic structures. Mitochondria seem to play an important part in the elaboration of hepatic ergastoplasm.
QUANTITATIVE ESTIMATION OF LYO- AND DESMOENZYMES IN TISSUE SECTIONS WITH AND WITHOUT FIXATION
Authors: Nachlas Marvin M. , Prinn William , Seligman Arnold M. 
Published: May 2004

1. Tissue sections eight microns thick were exposed to various experimental conditions used in histochemistry, and the effect upon the activities of esterase, the phosphatases, leucine aminopeptidase, ß-glucuronidase, and arylsulfatase was determined colorimetrically.
2. Significant differences were found in the amounts of the lyo and desmo fractions of these enzymes. The desmo components were found to be for esterase, alkaline phosphatase, leucine aminopeptidase, acid phosphatase, ß-glucuronidase, and arylsulfatase, ⅓, 2/3, 2/3, ½, ⅛, and ⅛ of the total enzymatic activity respectively.
3. Variations in the time and in the temperature at which diffusion was studied and of the pH and salt concentration of the solution into which the sections were placed, resulted in differences in the amount of enzymatic activity which remained in the tissue section. Some enzyme loss by diffusion was noted even after fixation of the tissue section.
4. The significance of the findings with respect to some of the concepts of localization of enzymes in tissue sections was discussed.
CONCENTRATION OF ACID PHOSPHATASE, RIBONUCLEASE, DESOXYRIBONUCLEASE, ß-GLUCURONIDASE, AND CATHEPSIN IN "DROPLETS" ISOLATED FROM THE KIDNEY CELLS OF NORMAL RATS
Authors: Straus Werner 
Published: May 2004

1. Three fractions of "droplets" having diameters of 1 to 5 µ (fraction I), 0.5 to 1.5 µ (fraction II), and 0.1 to 1.0 µ (fraction III) were isolated from the kidney cells of normal rats.
2. All three "droplet" fractions showed 10 to 15 times higher activities of acid phosphatase, ß-glucuronidase, ribonuclease, desoxyribonuclease, and cathepsin than the total homogenate and the mitochondrial fraction.
3. After a rough fractionation of the total homogenate, approximately 50 per cent of the 5 enzymes was found in the fractions which contained the "droplets" and approximately 30 per cent in the supernatant fluid.
4. The similarities between the enzymatic properties of the "droplets" from kidney cells and of the fractions isolated from liver cells by other investigators have been discussed.
FACTORS AFFECTING THE PRODUCTION OF CHROMOSOME ABERRATIONS BY CHEMICALS
Authors: Kihlman B. A. 
Published: May 2004

In the present paper, the results of a study on the influence of temperature, hydrogen ion concentration, and oxygen tension on the production of chromosome aberrations in Vicia root tips by maleic hydrazide (MH), di-(2, 3-epoxypropyl)ether (DEPE), and 8-ethoxycaffeine (EOC), are described.
Variations in the hydrogen ion concentration of the treatment solutions did not significantly influence the effect of EOC and DEPE. In contrast, the MH effect was considerably diminished by raising the pH from 4.7 to 7.3.
A marked increase in the frequencies of aberrations produced by DEPE and MH was obtained by raising the temperature from 3° to 25°C. The effect of EOC increased with rising temperature up to 12°C. With a further rise in temperature the effect of EOC decreased, so that at 25°C. it was of about the same magnitude as at 3°C.
The effect of EOC was completely inhibited, and that of MH partly so, when during the treatment (1) oxygen was excluded from the solution, (2) respiration was inhibited by azide or cyanide, or (3) phosphorylation was uncoupled from respiration by 2, 4-dinitrophenol (DNP). Pretreatments with DNP had a similar effect, but posttreatments did not influence the frequencies of aberrations. The effect of DEPE was unchanged by anoxia. Pre- or posttreatments with DNP did not change the total number of aberrations produced by DEPE, but the appearance of the effect was considerably delayed.
The results are discussed.
THE NUTRITION OF ANIMAL TISSUES CULTIVATED IN VITRO
Authors: Morton Helen J. , Pasieka Arthur E. , Morgan Joseph F. 
Published: May 2004

1. Cultivation of freshly explanted chick embryonic heart tissues in Hanks's salt solution for 3 to 4 days has been shown to create a general state of nutritional deficiency in the cultures. Provided the depletion is not prolonged beyond 4 days, the cultures subsequently revive and survive to a normal period in synthetic medium M 150.
2. Paper chromatographic studies on the culture medium have shown that the amino acid metabolism of the depleted cultures is restored to a normal pattern within a few days in medium M 150.
3. By the use of the nutritional deficiency technique, a coenzyme A requirement for this type of culture has been established.
4. The application of these findings to tissue cell nutrition and the possible hazards of using serum, or other uncharacterized additions, either to establish cultures, or as part of the experimental medium, are discussed.
PANCREATIC MICROSOMES
Authors: Palade G. E. , Siekevitz P. 
Published: May 2004

The pancreatic exocrine cell of the guinea pig has a voluminous endoplasmic reticulum distinguished by extensive association with small, dense particles, and by its orderly disposition in the basal region of the cell.
In addition to the small, (∼15 mµ), dense particles attached to the limiting membrane of the endoplasmic reticulum, numerous particles of similar appearance are found freely scattered in the cytoplasmic matrix.
The various cell structures of pancreatic exocrine cells can be satisfactorily identified in pancreatic homogenates.
The microsome fraction consists primarily of spherical vesicles (80 to 300 mµ), limited by a thin membrane (7 mµ) which bears small (∼15 mµ) dense particles attached on its outer surface. The content of the microsomal vesicles is usually of high density. Pancreatic microsomes derive by extensive fragmentation mainly from the rough surfaced parts of the endoplasmic reticula of exocrine cells. A few damaged mitochondria and certain dense granules (∼150 mµ) originating probably from islet cells, contaminate the microsome fraction.
Pancreatic microsomes contain RNA, protein, and a relatively small amount of phospholipide and hemochromogen. They do not have DPNH-cytochrome c reductase activity. In six experiments the RNA/protein N ratios were found grouped around two different means, namely 0.6 and 1.3.
Pancreatic microsomes are more labile than liver microsomes but react in a similar way to RN-ase-(loss of the particulate component and RNA), and deoxycholate treatment (loss of the membranous component and of phospholipide, hemochromogen, and most of the protein).
Postmicrosomal fractions consisting primarly of small (∼15 mµ), dense particles of ribonucleoprotein (RNA/protein N ratio = 1 to 2) were obtained by further centrifugation of the microsomal supernatant.
The small nucleoprotein particles of these fractions are frequently found associated in chains or clusters.
THE EFFECT OF CORTISONE ON DNA CONTENT OF RAT HEPATOCYTES
Authors: Lowe Charles U. , Rand Royden N. 
Published: May 2004

Rats were treated with cortisone, x-radiation, and both agents in combination, and the effect noted on the DNA content of hepatocytes. Nuclei were enumerated both in whole liver homogenates and following isolation. The incorporation of P32 into DNA was also studied in relation to these agents. The following observations were made:—
1.The DNA content of nuclei fell both during cortisone administration and following x-radiation. In the former instance, the fall was progressive with continuing administration of hormone; in the latter instance, there was a return to normal 5 days after radiation.
2. Cortisone administration to x-radiated rats caused a fall in DNA/nucleus and prevented the return to normal at 5 days.
3. There was no evidence that the effects of cortisone and x-rays were additive in reducing DNA/nucleus.
4. These data indicate an alteration in DNA/nucleus, but simple changes in ploidy cannot be excluded. Either explanation requires that the agents used affect the DNA of non-regenerating nuclei.
5. Cortisone interfered with the incorporation of P32 into the DNA of regenerating liver. Only a small effect on DNA synthesis in resting liver was observed with cortisone or x-radiation.
6. DNA content of nuclei returned to normal 5 days after x-radiation and 3 days after discontinuance of cortisone. Slight increase in the incorporation of P32 by DNA was observed during recovery phases.
7. The hypothesis is proposed that the apparent losses and increases in DNA/nucleus were due to depolymerization and repolymerization of DNA. Following x-radiation and/or cortisone administration, it is proposed that some DNA is depolymerized and becomes cold acid-soluble and dissociated from organized chromatin. Later, conditions are such that this degraded DNA is repolymerized.
8. These data might be interpreted to indicate that a portion of the DNA is not essential to cell integrity; alternatively, there may be two or more species of DNA, one of which is more readily affected by the agents investigated in the present report.
ELECTRON MICROSCOPE OBSERVATIONS ON INTRACELLULAR VIRUS-LIKE PARTICLES ASSOCIATED WITH THE CELLS OF THE LUCKÉ RENAL ADENOCARCINOMA
Authors: Fawcett Don W. 
Published: May 2004

The common renal adenocarcinoma of the leopard frog was studied in thin sections with the electron microscope.
Approximately a third of the tumors examined were found to contain spheroidal bodies of uniform size and distinctive morphology that are believed to be virus particles. These consist of hollow spheres (90 to 100 mµ) having a thick capsule and a dense inner body (35 to 40 mµ) that is eccentrically placed within the central cavity (70 to 80 mµ). Virus particles of this kind occur principally in the cytoplasm but occasionally they are also found in the nucleus and in the extracellular spaces of the tumor.
The intranuclear inclusion bodies that are visible with the light microscope are largely comprised of hollow, spherical vesicles with thin limiting membranes. These are embedded in a finely granular matrix. A few of the thin walled vesicles contain a dense inner body like that of the cytoplasmic virus particles. This suggests that they may be immature virus particles. The inclusion bodies are believed to be formed in the course of virus multiplication but they usually contain very few mature virus particles.
Bundles of dense filaments and peculiar vacuolar inclusions also occur in the cytoplasm of the tumor cells. These seem to be related in some way to the presence of virus but their origin and significance remain obscure.
These findings are discussed in relation to previous work suggesting that the Lucké adenocarcinoma is caused by an organ-specific filtrable agent. It is concluded that the "virus particles" found in electron micrographs of the tumor cells may be the postulated tumor agent. On the other hand, the possibility remains that the particles described here are not those that are causally related to the tumors.