bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF ANTIMICROTUBULAR AGENTS ON THE SECRETION OF COLLAGEN
Authors: Ehrlich H. Paul , Ross Russell , Bornstein Paul 
Published: May 2004

Embryonic chick cranial bone was cultured in the presence of the antimicrotubular agents, colchicine and vinblastine, and with a number of other compounds known from previous studies to affect the cellular handling of collagen. Secretion of procollagen, quantitated by light microscope autoradiography, was correlated with the extent of conversion of procollagen to collagen and with rates of collagen and noncollagen-protein synthesis.
Colchicine inhibited procollagen secretion and conversion to collagen and specifically inhibited collagen synthesis. Cells exposed to colchicine revealed an increased number of dilated Golgi-associated vacuoles and vesicles, some of which contained parallel aggregates of filamentous structures. These observations suggest that the pathway of at least a fraction of procollagen secretion by osteoblasts includes the Golgi complex. Disruption of microtubules may interfere with the movement of Golgi-derived vesicles, and the resulting accumulation of collagen precursors in the Golgi complex may lead secondarily to an inhibition of synthesis. Although vinblastine also inhibited both procollagen secretion and conversion to collagen, the observed reduction in general protein synthesis and striking changes in the ultrastructure of the rough endoplasmic reticulum complicated interpretation of the effects.
Interpretation of the effects of cytochalasin B was limited by the finding that the cellular response in cranial bone was markedly heterogeneous and that, contrary to some previous reports, the drug caused an inhibition in the incorporation of radiolabeled amino acids into both collagen and noncollagen protein.
ON THE ATTACHMENT OF THE NUCLEAR PORE COMPLEX
Authors: Aaronson Robert Peter , Blobel Günter 
Published: May 2004

Electron microscope examination of isolated rat liver nuclei after treatment with the detergent Triton X-100 revealed the complete removal of both the inner and outer membranes of the nuclear envelope. The envelope-denuded nuclei did not show any change in either shape or internal ultrastructure. Most strikingly, the nuclear pore complexes, which in untreated nuclei appear to be integral components of the nuclear envelope, were retained in their characteristic location at the distal ends of the channels leading through the peripheral heterochromatin.
Determination of the chemical composition of detergent-treated nuclei showed that over 95% of the nuclear phospholipid was solubilized, thus corroborating the morphological absence of nuclear membranes. Furthermore, detergent treatment also solubilized approximately 10% of the nuclear protein. Analysis of the solubilized protein by polyacrylamide gel electrophoresis in the presence of SDS indicated that these proteins belong to a few specific classes which presumably represent the major polypeptides of the nuclear membranes.
The total absence of the nuclear envelope on both morphological and biochemical grounds supports the idea that the nuclear pore complex does not require the membranes either for attachment to the nucleus or for maintenance of its own structural integrity.
GROWTH CONTROL OF DIFFERENTIATED FETAL RAT HEPATOCYTES IN PRIMARY MONOLAYER CULTURE
Authors: Leffert H. L. 
Published: May 2004

Dialyzed fetal bovine serum contains two distinct growth-controlling macromolecular fractions: one stimulates and the other inhibits proliferation of primary cultured differentiated fetal rat hepatocytes.
Both fractions are precipitated by ammonium sulfate (50% saturation, pH 7.4, 4°C). Serum fraction I (SFI, mol wt ≥ 120,000 daltons estimated by gel filtration with Bio-gel P200) appears to contain at least two factors which function, respectively, to initiate DNA synthesis (activity pH 4–10 stable) and to increase the rate at which initiated cells traverse the cell cycle (activity pH 4 and pH 10 labile). Intraperitoneal injections of SFI into adult rats have produced detectable stimulation of hepatic but not renal DNA synthesis. Serum fraction II (SFII, mol wt 40,000–80,000 daltons) suppresses in vitro incorporation of CH3-[3H]thymidine into DNA under conditions which diminish neither cell viability nor cell attachment.
Mixing experiments indicate that SFI and SFII mutually antagonize each other with respect to DNA synthesis and cell multiplication. Thus, both the relative and absolute serum levels of multiple factors control in vitro fetal hepatocyte proliferation.
GROWTH CONTROL OF DIFFERENTIATED FETAL RAT HEPATOCYTES IN PRIMARY MONOLAYER CULTURE
Authors: Leffert H. L. 
Published: May 2004

The initiation of DNA synthesis has been studied in quiescent primary cultures of fetal rat hepatocytes using defined hormones and chemically defined medium.
Preparations of crystalline insulin (0.01–10 µg/ml) or 20,000-fold purified somatomedin (0.01–1 µg/ml) are stimulatory. Growth hormone (0.025 µg/ml) and hydroxycortisone (0.025 µg/ml), 3':5'-GMP! (10-5 M) fail by themselves to initiate DNA synthesis but added together with insulin, enhance the stimulatory response by 50–100%. Thyroid hormones (L-T3, L-T4, 7.5–30 ng/ml) are by themselves without effect, but when they are added to thyroid hormone-depleted serum, the reconstituted mixtures show an enhanced capacity to initiate DNA synthesis. In contrast, glucagon (0.01 µg/ml) inhibits the insulin-stimulated response by about 50% without reducing basal DNA synthesis rates.
The results described here and in the accompanying two reports indicate that environmental control over the initiation of DNA synthesis is complex, and can involve the participation of many factors. The in vitro findings are consistent with the concept that liver regeneration is hormonally controlled and raise the possibility that alterations of the intrahepatic ratio of insulin to glucagon are growth regulatory.
THE APPEARANCE AND STRUCTURE OF INTERCELLULAR CONNECTIONS DURING THE ONTOGENY OF THE RABBIT OVARIAN FOLLICLE WITH PARTICULAR REFERENCE TO GAP JUNCTIONS
Authors: Albertini David F. , Anderson Everett 
Published: May 2004

Lanthanum tracer and freeze-fracture electron microscope techniques were used to study junctional complexes between granulosa cells during the differentiation of the rabbit ovarian follicle. For convenience we refer to cells encompassing the oocyte, before antrum and gap junction formation, as follicle cells. After the appearance of an antrum and gap junctions we call the cells granulosa cells. Maculae adherentes are found at the interfaces of oocyte-follicle-granulosa cells throughout folliculogenesis.
Gap junctions are first detected in follicles when the antrum appears. In early antral follicles typical large gap junctions are randomly distributed between granulosa cells. In freeze-fracture replicas, they are characterized by polygonally packed 90-Å particles arranged in rows separated by nonparticulate A-face membrane. A particle-sparse zone surrounds gap junctions and is frequently occupied by small particle aggregates of closely packed intramembranous particles. The gap junctions of granulosa cells appear to increase in size with further differentiation of the follicle. The granulosa cells of large Graafian follicles are adjoined by small and large gap junctions; annular gap junctions are also present. The large gap junctions are rarely surrounded by a particle-free zone on their A-faces, but are further distinguished by particle rows displaying a higher degree of organization.
CHEMICAL CHARACTERIZATION OF ISOLATED EPIDERMAL DESMOSOMES
Authors: Skerrow Christine J. , Matoltsy A. Gedeon 
Published: May 2004

Desmosomes, isolated from cow nose epidermis by a method utilizing citrate buffer pH 2.6 and density gradient centrifugation, have been analyzed and found to contain approximately 76% protein, 17% carbohydrate, and 10% lipid. Nonpolar amino acids predominate in desmosomal protein, representing 456 residues per 1,000. The sialic acid content is 5 nM/mg of protein. The lipid fraction is composed of approximately 40% cholesterol and 60% phospholipids.
Desmosomes are completely solubilized by incubation with 2% sodium dodecyl sulphate and 1% ß-mercaptoethanol. Gel electrophoresis of the denatured desmosomal proteins reveals 24 bands, with mobilities corresponding to a molecular weight range of 15,000–230,000 daltons. Seven of these are considered to be major bands, together constituting 81% of the desmosomal protein. Bands 1 and 2, of molecular weights 230,000 and 210,000 daltons, together comprise 28% by weight of the desmosome. It is suggested that these protein chains are located in the desmosomal plaque. Bands 3 and 4 are PAS-positive, constitute 23% of the desmosomal protein, and have apparent molecular weights of 140,000 and 120,000 daltons, respectively. At least part of this material must originate from the carbohydrate-containing layer which is demonstrated, by histochemistry, to be present in the desmosomal interspace. The possible nature and origin of the remaining major bands, of molecular weights 90,000, 75,000, and 60,000 daltons, are discussed.
EFFECTS OF CALCIUM-CONTAINING FIXATION SOLUTIONS ON CHOLINERGIC SYNAPTIC VESICLES
Authors: Boyne Alan F. , Bohan Timothy P. , Williams Terence H. 
Published: May 2004

Calcium (Ca)-containing fixation solutions applied to slices of electric organ of the electric ray, Narcine brasiliensis, have been shown to have three distinct ultrastructural effects on cholinergic synaptic vesicles of the nerve terminals.
(a) An electron-dense particle (EDS) is observed within the vesicle; the particle is seen in unosmicated, unstained tissues and can be removed from thin sections by Ca-chelating agents. It is concluded that the EDS represents Ca bound by the vesicle. It is suggested that the bound ATP of the vesicle provides anionic Ca binding sites.
(b) The vesicle membrane tends to ‘crinkle’ or collapse depending on the concentration of the other components of the fixative solution. The ‘crinkling’ or collapse are largely reversed by a wash step in the absence of Ca.
(c) The presence of Ca results in the appearance of a population of vesicles which form characteristic fusions or ‘tight’ junctions with the terminal membrane. This appears to be morphological evidence for the proposal, which has been frequently put forward, that Ca facilitates such a fusion before discharge of vesicle-bound transmitter.
With the discovery that the use of Ca-containing fixatives leads to the demonstration of a subpopulation of synaptic vesicles fused to the terminal membrane, we are led to propose that this is the ultrastructural location of the newly synthesized acetylcholine which has been shown by others to be preferentially released by stimulation.
CELL CONTACT DEPENDENCE OF SURFACE GALACTOSYLTRANSFERASE ACTIVITY AS A FUNCTION OF THE CELL CYCLE
Authors: Webb Glenda C. , Roth Stephen 
Published: May 2004

Mitotic, nonmalignant Balb/c 3T3 cells exhibit endogenous, surface galactosyltransferase activity that does not require intercellular contact throughout the assay period. In this respect, mitotic 3T3 cells resemble malignant Balb/c 3T12 cells which similarly show no contact requirement for optimum transferase activity in any phase of their cell cycle.
Previously, it was shown that randomly growing populations of 3T3 cells have lower galactosyltransferase activity when assayed under conditions which decreased cell contact. This led to the conclusion that these normal (3T3) and malignant (3T12) cells differed in that intercellular contact is required for optimum activity of surface galactosyltransferases on the normal cell type.
The present data indicate that mitotic 3T3 cells may be capable of expressing enzyme activities exhibited at all times by malignant cells. That is, mitotic 3T3 cells and randomly growing 3T12 cells may readily catalyze galactosyltransferase reactions between enzymes and acceptors on the same cell. Interphase 3T3 cells, on the other hand, might require that enzymes glycosylate acceptors on adjacent cells. A model is proposed that suggests that changes in the spatial arrangement of surface enzymes and acceptors or variations in the fluidity of the cell membrane can account for this contact-related glycosylation.
The Effect of Partial Protein Extraction on the Structure of the Eggs of the Sea Urchin, Arbacia punctulata
Authors: Kane R. E. 
Published: May 2004

The structure of the eggs of the sea urchin, Arbacia punctulata, has been investigated after the removal of one-half of the cellular protein. The procedure involves treatment of the eggs with 30 per cent ethanol at -10°C. followed by extraction of the soluble proteins with water. The eggs remain intact, although all of the cytoplasmic matrix is removed. Most cell structures can still be identified, although only the membranes of most remain. The mitochondria lose all of their matrix but retain the inner membranes or cristae.
The annulate lamellae appear unaffected by this extraction procedure, remaining intact and apparently undamaged. The nuclear envelope is also retained, although it often undergoes a curious disorganization, apparently as the result of the separation of its two layers. The significance of these observations with respect to the structure of the envelope is discussed.
Epoxy Resins in Electron Microscopy
Authors: Finck Henry 
Published: May 2004

A method of embedding biological specimens in araldite 502 (Ciba) has been developed for materials available in the United States. Araldite-embedded tissues are suitable for electron microscopy, but the cutting qualities of the resin necessitates more than routine attention during microtomy. The rather high viscosity of araldite 502 also seems to be an unnecessary handicap.
The less viscous epoxy epon 812 (Shell) produces specimens with improved cutting qualities, and has several features—low shrinkage and absence of specimen damage during cure, minimal compression of sections, relative absence of electron beam-induced section damage, etc.—which recommends it as a routine embedding material. The hardness of the cured resin can be easily adjusted by several methods to suit the materials embedded in it.
Several problems and advantages of working with sections of epoxy resins are also discussed.
On the Significance of the Extractable Collagens
Authors: Jackson David S. , Bentley John P. 
Published: May 2004

This investigation has sought to determine the significance of the wide range of extractable collagen fractions which appear to exist in growing connective tissues and to determine their position in the process of fibrogenesis.
Carrageenin granulomata were induced in guinea pigs and, after injection of 14C-glycine, this tissue and skin from the same animal were subjected to successive extractions with neutral salt solutions of increasing ionic strength, citrate buffer pH 3.6, and to gelatinization. The specific activity of these fractions was determined at various time intervals. At 8 hours it was found that the specific activity decreased with increasing ionic strength of the neutral salts and was still lower in the citrate extracts and gelatin. At 36 hours the situation was almost completely reversed except that the citrate extract and gelatin still had the lowest activities. The data from skin were more clear cut than that from the granuloma and the reasons for this are discussed.
It is concluded that at any given time in developing connective tissue, there is a continuous spectrum of collagen aggregates of varying degrees of strength of cross-linkage, dependent upon the time that has elapsed since their constituent molecules were synthesized. The various extraction media used remove a particular cross-section of these aggregates depending upon their disaggregating power. These extracts will thus be biologically heterogeneous. The fraction extracted with 0.14 M NaCl will contain the collagen molecules most recently synthesized and in this respect can be considered the earliest form of extracellular collagen.
Effects of 5-Fluorodeoxyuridine and Related Halogenated Pyrimidines on the Sand-Dollar Embryo
Authors: Karnofsky David A. , Basch Ross S. 
Published: May 2004

The embryo of the sand-dollar (Echinarachnius parma) was exposed to various concentrations of fluorinated pyrimidines immediately after fertilization. FUDR (5-fluorodeoxyuridine) was most active, and a concentration of 2 to 4 mγ/10 cc. (0.8 to 1.6 x 10-6 m.eq./liter) blocked development at the early blastula stage. Larger doses interrupted development at the same stage. This effect was prevented by thymidine (TDR) and thymine (T); and these pyrimidines protected against many times the minimal lethal concentration of FUDR. TDR was active as a protective agent if added just before early blastula formation.
The other fluorinated pyrimidines, 5-fluorouracil (FU), 5-fluorouridine (FUR), 5-fluorocytidine (FCR), 5-fluorodeoxycytidine (FCDR), and 5-fluoroorotic acid (FO), were also studied. These drugs produced effects on embryonic development similar to those seen with FUDR. The effective concentrations, however, varied greatly. T and TDR provided protection against these drugs, but in most cases they were not so effective as against FUDR.
5-Bromodeoxyurdine (BrUDR), beginning at the early blastula stage, caused a random pattern of embryonic death up to the pluteus stage. This drug has been shown to be incorporated into bacterial DNA. BrUDR protected embryos against the early lethal effects of FUDR presumably acting as a thymidine substitute, but the embryos died subsequently in a pattern similar to that seen with BrUDR alone.
FUDR and BrUDR appear to inhibit the formation and alter the structure of DNA, respectively, distinctive effects whch may provide a means for studying the role of DNA in embryonic development.
Spermatogenesis in Animals as Revealed by Electron Microscopy
Authors: Yasuzumi G. 
Published: May 2004

Testes of Eriocheir japonicus were fixed in buffered (pH 7.2) 1 per cent osmium tetroxide and thin sections of the methacrylate-embedded tissue were studied with the electron microscope. Spermatozoa from the vasa deferentia and spermatids from the testes were examined in smear preparations and sections. The most useful stainings proved to be the Feulgen, Unna-Pappenheim, and PAS reactions.
The present paper covers one of the late stages of spermatogenesis. At the late stage of differentiation of the spermatid, the nucleus shows a concave disc-like contour in longitudinal sections and the karyoplasm is finely alveolar in appearance. A vesicle with a fibrillar or granular content appears situated between the cytoplasm and the nucleus. In an advanced spermatid, a large vacuole develops between the nucleus and this vesicle. As development of the spermatid proceeds, the cytoplasm is sloughed off. Thus, the advanced spermatid consists of an ovoid vesicle surrounded by a flattened nuclear disc. The former corresponds to the "capsule" or the "head," and the latter to the "pseudopodia." Concurrently with the sloughing off of the cytoplasm, a lamellar structure appears at the periphery of the head. It is composed of thin plates imbricated like the leaves of an onion. Each plate consists of triple layers, two dense layers separated by a lighter space. Each layer measures about 7 mµ in diameter.
At the distal pole of the head, a depression develops into a tubule which reaches the proximal pole of this structure. The lumen of the tubule is occupied by a dense substance part of which arises from the limiting membrane of the vacuole. The dense material begins to fill the tubule from the distal towards the proximal end. It finds its way till the middle of the tubule, leaving its proximal half unfiled. Thus, the proximal portion of the mature sperm head has a straight tubule whlich opens on its surface. The latter is covered by a dense membrane about 60 mµ in width.
Cytochemical analysis reveals that the pseudopodia contain DNA, and the head a carbohydrate component as well as PNA. The classical concept that the head becomes the male pronucleus after fertilization can no longer be accepted on the basis of the cytochemical analysis. The present study came to no definite conclusions concerning the functional significance of the head.
Succinic Dehydrogenase and Cytochrome Oxidase Activities in Cell Cultures
Authors: Leslie I. , Yarnell Margaret 
Published: May 2004

Succinic dehydrogenase and cytochrome oxidase have been assayed in permanent cell lines (HEP 1, HEP 2, and HLM), in short-term cultures of chick embryo heart cells, and in various tissues. Their activities in different cells are compared by relating them to deoxyribonucleic acid. They are very low in HEP 1, HEP 2, and HLM cells by comparison with the activities in any normal tissues examined. All the succinic dehydrogenase was shown to be located in the mitochondria of the permanent cell lines by staining with tetrazolium derivatives. Both enzymes were more active in tissues of 19-day chick embryos than in those of 11- or 14-day embryos. The increasing activities found during normal development were quickly curtailed or reversed when heart cells were grown as monolayer cultures.
Digitonin-treated mitochondria produced preparations with much higher activities of cytochrome oxidase than untreated samples. Activities measured in this way were again very much lower in HEP 1, HEP 2, and HLM cells than in the normal tissues. From the derived ratio of cytochrome oxidase:succinic dehydrogenase, it was apparent that cytochrome oxidase is diminished to a greater extent than succinic dehydrogenase in both permanent cell lines and short-term cultures, by comparison with the corresponding activities in embryonic and adult tissues. The features common to the metabolism of proliferating cells in vitro and malignant cells are discussed.
Some Characteristics of DNA Synthesis and the Mitotic Cycle in Ehrlich Ascites Tumor Cells
Authors: Edwards Joshua L. , Koch Arthur L. , Youcis Pauline , Freese Herbert L. , Laite Melville B. , Donalson J. Thomas 
Published: May 2004

In vivo studies of Ehrlich ascites tumor cells during the first 5 days of growth in peritoneal cavities of mice consisted of the following:
1. Determination of growth curves by direct enumeration of cells.
2. Estimation of the duration of each phase of the mitotic cycle based on incidence of cells in different phases.
3. Radioautographic studies to determine the proportion of cells in different phases of the mitotic cycle that incorporate tritiated thymidine during a single brief exposure to this precursor of DNA.
4. Estimation of the rate of incorporation of tritiated thymidine at different times during the period of DNA synthesis by comparison of mean grain counts over nuclei in radioautographs at different times following exposure to tritiated thymidine.
The assumptions underlying these experiments and our observations concerning the duration of the period of DNA synthesis and its relation to the mitotic cycle are discussed. It is concluded that DNA synthesis is continuous, occupying a period of 8.5 hours during the interphase and that the average rate of synthesis is approximately constant.
Incorporation and Rate of Loss of S35-Methionine by Adult Rat Trachea in Organ Cultures and in Living Animals
Authors: Crocker T. Timothy , Pelc S. R. 
Published: May 2004

Full-thickness pieces of adult rat trachea were supported on rayon on the surface of clotted medium in watch glasses. Differentiated epithelium was reduced in height during 25 days of cultivation because basal cells and some columnar cells migrated to cover exposed parts of the explants and because some differentiated cells died and were shed.
S35-methionine was (a) placed on explants in vitro and (b) injected intraperitoneally in living rats. Cultured tissues and tissues of living rats were examined by autoradiography at 4 and 24 hours and 4, 7, and 11 days after labeling.
Although migratory undifferentiated epithelial cells appeared in cultured trachea, all living epithelial cells in vitro incorporated and subsequently lost S35-methionine to the same extent as did epithelium of intact rats. The biologic half-life of methionine in rat tracheal epithelium in vivo and in vitro was about 5 days.