bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional differences in mesenchymal cell morphology and glycosaminoglycans in early neural-fold stage rat embryos
Authors: Morriss Gillian M. , Solursh Michael 
Published: April 2021

ABSTRACT
Rat embryos with two to four pairs of somites (day 9 of gestation) were examined by scanning electron microscopy and Alcian blue staining. The neural folds, which represent only future brain region at this stage, form a pair of elongated hemispheres with a deep neural groove between them. In transverse section the neural ectoderm is biconvex; the cranial mesenchyme cells beneath them are widely separated by extracellular matrix (ECM) and are joined to each other and to the ectodermal basement membrane by fine cytoplasmic processes and strands of ECM material. In contrast, mesenchyme cells close to the primitive streak are closely packed, having broad areas of surface contact and only small amounts of ECM.
The nature and distribution of ECM, cell surface, and basement membrane glycosaminoglycans (GAG) were investigated by staining with Alcian blue at specific pH values in combination with enzyme pretreatments, and at various critical electrolyte concentrations. The results indicate that the GAG of the ectodermal basement membrane, mesenchymal ECM and mesenchymal cell surfaces are in continuity with each other and consist largely of hyaluronate and chondroitin sulphates.
Differences in morphology and histochemistry of neural fold and primitive streak regions are discussed in relation to their possible morphogenetic significance.
The role of the cell surface in the migration of primordial germ cells in early chick embryos: effects of concanavalin A
Authors: Lee H. , Karasanyi N. , Nagele R. G. 
Published: April 2021

ABSTRACT
Effects of concanavalin A (Con A) on the morphology and migration of primordial germ cells (PGCs) in stage-6 to -12 chick embryos were investigated. Con A, at a sublethal dose (10 μg/ml), inhibited migration of PGCs from the germinal crescent area to other parts of the embryo. Affected PGCs were more rounded without the usual cytoplasmic extensions, but the integrity of other structures was unaffected. Nearly identical results were obtained with another lectin, wheat germ agglutinin (10 μg/ml). Histochemistry using Con A-horseradish peroxidase revealed that PGCs in control embryos had a thin, rather uniform layer of extracellular coat material (ECM). Con A appeared to alter the distribution of ECM on PGCs, i.e. some parts of the cell surface were devoid of any detectable ECM, while others had small, scattered patches of ECM. Con A effects were alleviated by a-methyl-D-mannoside. Overall results of the present study indicated that the observed inhibition of PGC migration in early chick embryos is a consequence of Con A-induced alterations of cell surface properties.
Cell proliferation and cell density of mesenchyme in the maxillary process and adjacent regions during facial development in the chick embryo
Authors: Minkoff Robert , Kuntz Amy J. 
Published: April 2021

ABSTRACT
Cell proliferation, as measured by DNA labeling indices was analyzed during the early development of the maxillary process. Chick embryos were labeled with [3H]thymidine for .1 h and processed for autoradiography. The percentage of labeled mesenchymal cells was determined within delineated areas in the maxillary processes and in adjacent regions. Analysis of labeling indices in each of the areas at successive stages of development demonstrated a pattern of declining rates of cell proliferation with advancing developmental age. Cell proliferation in adjacent regions declined earlier and, in some instances, faster than it did in the maxillary process.
Cell density was measured in the maxillary process and the roof of the stomodeum and was found to be higher in the maxillary process throughout the period studied. Cell density and cell proliferation data were analyzed with reference to the operation of ‘density-dependent inhibition’ of growth as a regulatory mechanism for the observed changes. ‘Density-dependent inhibition’ of growth was not a satisfactory explanation for the observed differences between the maxillary process and adjacent regions.
Ultrastructural study of the development of the auditory tympana in the cricket Teleogryllus commodus (Walker)
Authors: Ball E. E. , Cowan A. N. 
Published: April 2021

ABSTRACT
The cuticle in the tympanal area of immature crickets, Teleogryllus commodus (Walker), is ultrastructurally indistinguishable from that elsewhere on the prothoracic leg. It is only in the pharate adult that changes associated with development of the tympana first appear. In pharate adults and adults the external layer of the tympana consists of a layer of electron-dense material overlying a layer where the electron-dense material is interspersed with cuticle in which the bundles of microfibrils are coarser and more loosely arranged than elsewhere in the leg. The innermost portion of the tympana consists of this same type of cuticle without the electron-dense material. Associated with the appearance of the electron-dense material in the tympana of the pharate adult is a change in the toluidine blue staining properties from blue to deep purple. The reaction of the tympana in acid and base is consistent with their being composed of chitin. There are no major deposits of resilin in the tympana. In the first few days following the imaginal ecdysis the posterior tympanum and underlying trachea come into tight apposition due to the withdrawal of the epidermal cells. The epidermal cells do not withdraw from beneath the anterior tympanum. The surrounding non-tympanal cuticle continues to thicken for several weeks with the result that in the mature adult the posterior tympanum serves as an acoustic window in the thick cuticle of the leg. The functional significance of the anterior tympanum has not been established.
The kinetic behaviour of the cranial neural epithelium during neurulation in the rat
Authors: Tuckett Fiona , Morriss-Kay Gillian M. 
Published: April 2021

ABSTRACT
The kinetic behaviour of the cranial neuroepithelial cells of rat embryos during neurulation is described. Serial transverse sections of 4-, 8-, 12- and 16-somite-stage embryos show that differential mitosis does not play a part in the mechanisms responsible for effecting cranial neural tube closure. A constant cell number is found in the midbrain/hindbrain neural epithelium during all four stages; the mitotic spindle axes are orientated parallel to the long axis of the embryo, so that increase in cell number occurs in this direction only.
Growth is only expressed by an expansion in the volume of the forebrain, which projects rostral to the notochordal tip. [3H]thymidine studies (using an in vitro culture technique) show no significant variation in the cell cycle time between the forebrain and the midbrain/ anterior hindbrain neural epithelium. It is suggested that the neural epithelium is a fluid structure whose overall shape is strictly controlled while the cells within it flow towards and into the rapidly expanding forebrain.
Development in vitro of the female germ cells of the polychaete Ophryotrocha labronica
Authors: Emanuelsson Hadar , Anehus Siw 
Published: April 2021

ABSTRACT
In the polychaete Ophryotrocha labronica each oocyte is during its growth period associated with a single nurse cell. The fact that the oocyte-nurse cell pairs occur isolated in the female coelom makes them easily removable for analysis of their developmental ability in vitro. Using Dulbecco’s modified Eagle medium supplemented with amino acids, nucleosides, foetal calf serum and sea water, we have managed to support development in vitro of germ cell pairs from early and mid-oogenesis until maturation of the oocyte, when the nurse cell degenerates and the oocyte enters meiotic metaphase. Radiolabelling of germ cells in mid-oogenesis with tritiated amino acids and uridine during the first day of incubation indicates normal development with synthesis of RNA and protein, and pulses two days later verify a continued normal protein synthesis and yolk formation. The investigation confirms autosynthesis of yolk proteins in the germ cells of this species and indicates a leading role of the nurse cell in the process.
An Investigation of Renal Function during Histogenesis in the Late Foetal and Neonatal Rat by means of the Uptake and Autoradiographic Localization of Radioactive Potassium
Authors: Bearn J. G. , Harris F. T. C. 
Published: April 2021

ABSTRACT
A technique has been developed for studying the uptake of K42 by the foetal rat kidney. Using this technique the exchange rate for K42 of the foetal and neonatal metanephros relative to the foetal and neonatal liver has been investigated. It was found that the metanephros of the 20- and 21-day foetus shows a rate of exchange which is twice that of the liver, whereas the neonatal metanephros shows a rate of exchange which is less than half that of the liver. The results of this investigation demonstrate that the ratio of K42 uptake by the metanephros of the 20- and 21-day rat foetus, relative to that of the foetal liver, is one-quarter of that reported for the adult rat. An autoradiographic study of the distribution of K42 in the foetal kidney has shown that histological localization of the isotope in the proximal and distal tubules, found in the adult, does not occur.
Half-lives of enzyme activities in an l5178y mouse leukaemic cell
Authors: Bosmann H. B. 
Published: April 2021

ABSTRACT
L5178Y cells (mouse leukaemic cell lines) were grown in Fischer’s medium and were utilized in the logarithmic phase of growth. Cells were incubated at 37 °C in 100 pg per ml of cycloheximide. This level of cycloheximide inhibited all cytoribosomal protein synthesis after 30 min incubation. After 7·0 h incubation with 100 μg per ml of cycloheximide the cell number was, in arbitrary units, 1·07 ±0·001 (control: 1·63 ±0·03), the protein content i6i±4pg per cell (control: 181 ± 1) and the percentage viable cells 17 ±2 (control: 98 ±1). Cells were removed at intervals from the incubation in 100 μg per ml of cycloheximide, extracted with 0·1% Triton X-100, and assayed for various enzyme activities. From these data half-lives, stability times, and decay rates were calculated for each enzyme activity.
Lysosomal enzyme activities, in particular the jV-acetyl hexosaminidases, were found to have long half-lives and stability and slow decay rates. Proteolytic enzyme activities were characterized by relatively long half-lives and stability times. The membrane marker enzyme activities, especially UDPase, were characterized by extremely short half-lives, rapid decay rates, and no stability time. Mitochondrial enzyme activities had relatively short stability time and half-lives and rather rapid decay rates. The decay occurring at late time intervals was thought to be a consequence of the death phase of the incubated cells as opposed to normal cellular decay.
Effect of method of cell isolation on the metabolic activity of isolated rat liver cells
Authors: Lipson L. G. , Capuzzi D. M. , Margolis S. 
Published: April 2021

ABSTRACT
Rat liver cells isolated with a tissue press, by tetraphenylboron (TPB) chelation, or by hyaluronidase and collagenase digestion were compared as to morphology, cell yield, and biosynthetic activity. The cells were intact by light microscopy; ultrastructural changes were present on electron-microscopic examination of all cell types except those prepared by a modified enzyme incubation method. TPB chelation gave the largest and enzyme techniques the smallest yield of cells. All cell types incorporated labelled amino acids into cellular protein; however, amino acid incorporation was greatest in cells isolated by the revised enzyme technique. Only enzyme and mechanical cells incorporated acetate into cellular lipid. Cofactor supplementation was not required in the modified enzyme cells. Acetate incorporation was more sensitive to preincubation than was amino acid incorporation. Calcium, which was required to prevent aggregation of enzyme cells, inhibited amino acid incorporation moderately and acetate incorporation completely in mechanical cells.
Contact-dependent transfer of a lysosomal enzyme from lymphocytes to fibroblasts
Authors: Bou-Gharios George , Moss Jill , Partridge Terry , Abraham David , Olsen Irwin 
Published: April 2021

ABSTRACT
In this study we have examined the mechanism underlying the contact-mediated transfer of a lysosomal enzyme from lymphocytes to fibroblasts in culture. We found that although antibody against the mannose 6-phosphate lysosomal targetting receptor (MPR) completely inhibited fibroblast uptake of the lysosomal enzyme β-glucuronidase (Gus) from the culture medium, it had no effect on the transfer of the enzyme from normal lymphocytes. In contrast, the presence of antibody that prevented the adhesion of the lymphocytes to the fibroblasts inhibited Gus acquisition but had no effect on endocytosis. Immunogold electron microscopy of the contact site between the two types of cell showed that the transfer of Gus involved uncoated vesicles localized near the cell surface of the fibroblast at sites of contact with the lymphocytes. The acquired lymphocyte enzyme was shown to be transported to the fibroblast lysosomes.
Different patterns of α-tubulin post-translational modification in ovarian nutritive tubes of two hemipteran insects
Authors: Harrison Alistair , Stebbings Howard , Hyams Jeremy S. 
Published: April 2021

ABSTRACT
Usage of the tyrosinated, detyrosinated and acetylated forms of α-tubulin in ovarian nutritive tube microtubules of the hemipterans Oncopeltus fasciatus and Notonecta glauca glauca was investigated by immunofluorescence microscopy of frozen sections of ovarioles with isotype-specific antibodies. In Oncopeltus, nutritive tubes at all stages of development contained tyrosinated α-tubulin and showed only a weak reaction to antibodies to the detyrosinated and acetylated forms. In Notonecta, tyrosinated β-tubulin was confined to a zone around the periphery of functional nutritive tubes; the body of these tubes, and the older, redundant, nutritive tubes stained strongly for both the detyrosinated and acetylated isotypes. The difference in isotype usage between the two species was confirmed by immunoblotting of 2-D gels of ovariole extracts. The results are consistent with the different time-course of oogenesis, and hence the longevity of the nutritive tube microtubules, in the two insects. A model for the insertion of new microtubules into nutritive tubes as they grow is proposed.
Organization of talin and vinculin in adhesion plaques of wet-cleaved chicken embryo fibroblasts
Authors: Feltkamp Constance A. , Pijnenburg Marian A. P. , Roos Ed 
Published: April 2021

ABSTRACT
We have studied the fine structure of adhesion plaques in chicken embryo fibroblasts (CEF) and visualized the localization of vinculin and talin using immunoelectron microscopy on CEF opened by ‘wetcleaving’. This procedure, performed with nitrocellulose on cells grown on electron microscope grids, cleaved the CEF close to the inner face of the ventral membrane or at a slightly higher level through the cytoplasm. In the resulting preparations, adhesion plaques were identified by their localization at the end of microfilament bundles and by their density of vinculin and talin. The plaques showed a substructure of moderately electron-dense parallel bands that were interconnected. Both the parallel bands as well as the interconnecting threads showed a high density of vinculin and talin labels, whereas neither the surrounding membrane cytoskeleton nor the overlaying bundled microfilaments were labeled. In stereomicrographs, we observed no difference between the distances from vinculin or talin label, respectively, to the plasma membrane. In early spreading cells, vinculin and talin were found to be deposited simultaneously in fine radiating streaks that covered rather large parts of the ventral membrane at areas of close contact with the substratum. These streaks, which were initially over-layed by an isotropic cytoskeletal network without filament bundles, were the apparent precursors of later formed adhesion plaques. These observations suggest that there are no separate layers of talin and vinculin, but rather that adhesion plaques consist of a dense network of talin and vinculin. The observations strongly support the model proposed by Bendori et ?l. (1989), J. Cell Biol. 108, 2383-2393, that was based on the location of vinculin- and talin-binding sites in the vinculin molecule.
Ectopic expression of an A-type lamin does not interfere with differentiation of lamin A-negative embryonal carcinoma cells
Authors: Peter M. , Nigg E. A. 
Published: April 2021

ABSTRACT
The nuclear lamina is an intermediate filament-type network underlying the inner nuclear membrane. It is believed to be important for nuclear envelope integrity and the organization of interphase chromatin. On the basis of biochemical properties and sequence criteria, vertebrate lamin proteins are classified as either A- or B-type. While B-type lamins are expressed in almost all cell types, no A-type lamins are present in early vertebrate embryos or undifferentiated embryonal carcinoma cell lines. Intriguingly, expression of A-type lamins occurs concomitant with cell differentiation and embryonic development. These findings have led to the hypothesis that A-type lamins might play a role in establishing or stabilizing cell-type specific differences in nuclear organization, which in turn might relate to the developmental potential of a cell. To test this hypothesis, we have stably expressed chicken lamin A in undifferentiated murine embryonal carcinoma (P19) cells, and examined the consequences of ectopic lamin A expression for the differentiation state and potential of these cells. Our results demonstrate that the P19 cells, although normally devoid of lamin A, properly incorporate and process chicken lamin A. Moreover, the stably transfected cell lines maintain the properties of undifferentiated cells, demonstrating that expression of lamin A does not directly induce differentiation. Conversely, when exposed to retinoic acid, an inducer of differentiation, lamin A-expressing P19 cells are able to differentiate normally. Taken together, our results suggest that unscheduled expression of A-type lamins is not sufficient to deregulate cell differentiation programs. The implications of these findings for the possible role for lamin A expression during development are discussed.
Arrangement of cellular fibronectin in noncollagenous fibrils in human fibroblast cultures
Authors: Dzamba Bette J. , Peters Donna M. Pesciotta 
Published: April 2021

ABSTRACT
The assembly of fibronectin into fibrils was examined by high-voltage immunoelectron microscopy in subconfluent cultures of ascorbate-treated human skin fibroblasts. Cells grown in the presence of ascorbic acid for 24, 48 or 72 h were labeled with Ist-9, a monoclonal antibody specific for the EIIIA site in fibronectin, and polyclonal antibodies to type I collagen. Cells were then labeled with goat antimouse IgG and goat anti-rabbit IgG coupled to 5 or 18 nm colloidal gold beads. Our results show that by 24 h, fibronectin is observed in fibrils in the extracellular matrix. The majority of fibronectin in fibrils does not co-localize with type I collagen. Morphometric analysis of the distance between EIIIA sites in fibronectin fibrils (&lt;l2nm in diameter) show that the EIIIA sites appear to be spaced approximately 84 nm apart. The distance of 84 nm suggests that fibronectin is fully extended in fibrils and that the amino termini of adjacent fibronectin dimers overlap by 20 nm. As fibronectin fibrils become thicker, the average distance between EIIIA sites in fibronectin dimers decreases to 42 nm. This decrease in the distance between EIIIA sites may be due to a staggering of fibronectin dimers within the fibril as the fibril matures.
Changes in relative concentrations of the hemoglobin components in Paramecium caused by cell growth and temperature of the culture
Authors: Usuki Itaru , Hino Akihiro 
Published: April 2021

ABSTRACT
The Hb (hemoglobin) content of Paramecium has been known to maintain a constant level even when the cells are exposed to different conditions. However, the relative concentrations of the Hb components in the stocks of P. caudatum, P. multimicro-nucleatum and P. jenningsi were found to change during cell growth from logarithmic young phase to stationary growth phase even when the culture was maintained at a constant temperature of 18 or 27°C. The temperature of the culture also affected the relative concentrations of the Hb components in a cell. A large part of the growth-dependent and temperature-dependent change was attributable to a variation in the amounts of two or three major Hb components, and the variation in other minor components was almost negligible. At the time of cell growth and of a shift in temperature, the major Hb components in a cell respond in opposite ways from each other. These components differed in several properties: one of them showed a faster migration by PAGE, a smaller molecular mass and a lower pl value than another.
Altered response of progeria fibroblasts to epidermal growth factor
Authors: Colige A. , Nusgens B. , Lapiere CH. M. 
Published: April 2021

ABSTRACT
The Hutchinson-Gilford syndrome (progeria) is a rare disorder in childhood characterized by premature and accelerated aging. This study reports the effect of a potent growth factor, EGF, on the proliferative capacities and extracellular matrix macromolecules and collagenase expression of two strains of progeria skin-derived cells. At low population doubling levels (PDL&lt;IO), confluent cultures of progeria fibroblasts made quiescent by lowering the concentration of serum in the medium did not respond to EGF while the mitotic activity of normal PDL-matched fibroblasts was almost maximally restored upon addition of EGF. No obvious difference between normal and low PDL progeria fibroblasts was observed in the number and in the affinity of the receptors measured by [125I]EGF binding. The synthesis of collagen and non-collagen proteins was similar in normal and affected cells at low and high serum concentration and both types of cells re sponded to EGF by a specific inhibition of collagen synthesis. Besides a normal level of mRNA coding for type I and type III collagens, collagenase and laminin, progeria fibroblasts expressed a high level of elastin and type IV collagen mRNA. Like normal fibroblasts, progeria cells responded to EGF by a decrease in the level of mRNA for fibrillar collagens and elastin. In contrast, a complete lack of response to EGF was observed for collagenase mRNA whereas the expression of this enzyme was strikingly induced by EGF in normal PDL-matched cells. The abnormal expression of type IV collagen was not significantly modified by EGF. At PDL&gt;IO, progeria cells exhibited features of senescence. A significant reduction of collagen synthesis was observed and no further inhibition by EGF was recorded.