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Results for “Morphological Characterization”

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PubMed2006

Morphology, characterization, and distribution of retinal photoreceptors in the Australian lungfish Neoceratodus forsteri (Krefft, 1870).

The Australian lungfish Neoceratodus forsteri (Dipnoi) is an ancient fish that has a unique phylogenetic relationship among the basal Sarcopterygii. Here we examine the ultrastructure, histochemistry, and distribution of the retinal photoreceptors using a combination of light and electron microscopy in order to determine the characteristics of the photoreceptor layer in this living fossil. Similar proportions of rods (53%) and cones (47%) reveal that N. forsteri optimizes both scotopic and photopic sensitivity according to its visual demands. Scotopic sensitivity is optimized by a tapetum lucidum and extremely large rods (18.62 +/- 2.68 microm ellipsoid diameter). Photopic sensitivity is optimized with a theoretical spatial resolving power of 3.28 +/- 0.66 cycles degree(-1), which is based on the spacing of at least three different cone types: a red cone containing a red oil droplet, a yellow cone containing a yellow ellipsoidal pigment, and a colorless cone containing multiple clear oil droplets. Topographic analysis reveals a heterogeneous distribution of all photoreceptor types, with peak cone densities predominantly found in temporal retina (6,020 rods mm(-2), 4,670 red cones mm(-2), 900 yellow cones mm(-2), and 320 colorless cones mm(-2)), but ontogenetic changes in distribution are revealed. Spatial resolving power and the diameter of all photoreceptor types (except yellow cones) increases linearly with growth. The presence of at least three morphological types of cones provides the potential for color vision, which could play a role in the clearer waters of its freshwater environment.

Animals↗

PubMed1981

Induction of human malignant T-lymphoblastic cell lines MOLT-3 and jurkat by 12-O-tetradecanoylphorbol-13-acetate: biochemical, physical, and morphological characterization.

The process of induction of human malignant T-lymphoblastic cell line MOLT-3 by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) was examined. It was found that the induction process by TPA, which included increase in cells with receptors to sheep red blood cells (E--rosette positive--E+) and decrease in the levels of the marker enzyme terminal deoxynucleotidyl transferase (TdT) was not affected by the presence of DNA synthesis inhibitor arabinofuranosylcytosine (Ara-C). The exposure time to TPA required to elicit these changes was found to be short, in the order of 1 hour or less. The kinetics of the increased in E+ cells, decrease in the levels of TdT in these cells, or decrease in the ability to proliferate as measured by colony formation were similar with exposure to TPA for 1, 6, 24, or 96 hours. We have examined the effect of antitumor promoter compounds on their ability to block induction of MOLT-3 cells by TPA. Results indicated that none of these compounds, dexamethasone, antipain, retinoic acid, and L-1-tosylamide-2-phenylethylchloromethyl ketone (TPCK), was effective in reducing the number of E+ cells induced by TPA. Examination of three other leukemic T-cell lines indicated that, in addition to MOLT-3, the leukemic T-cell line Jurkat also responded to TPA, whereas two other leukemic T-cells lines CCRF-CEM and CCRF-HSB-2 did not. Certain physical and morphological changes were also observed after stimulation of MOLT-3 cells and Jurkat cells by TPA. We found that, following the addition of TPA, the cell volumes of MOLT-3 cells decreased from an average of 1150 micrometers3 to about 500 micrometers3, whereas those of Jurkat were reduced to about 700 micrometers3 from 1100 micrometers3. Electron microscopic studies of these lymphoblasts also revealed that after treatment with TPA the induced cells were generally smaller in size with increase in the density of the nuclear materials and condensation of the chromatin structures.

Cell Differentiation↗

PubMed1994

Morphological characterization of scavenger receptor-mediated processing of modified lipoproteins by rat liver endothelial cells.

Scavenger receptor-mediated processing by rat liver endothelial cells in vivo is studied by using acetylated and oxidized low-density lipoproteins (LDL) as ligands. The cellular localization of acetylated LDL (Ac-LDL) is visualized by both immunohistochemistry and silver enhancement of ultrasmall gold particles conjugated to Ac-LDL. Scavenger receptor-mediated internalization by the endothelial cells only involves coated vesicle formation. Subsequently, three stages of processing are noticed, as represented by (i) large electron lucent vesicles, with ligand in close association to the membrane, (ii) relatively electron-lucent structures, with Ac-LDL dispersed over the vesicular lumen, while tubular membrane extensions did not contain ligand, and (iii) electron-dense vesicles in which the nondegradable gold particles of the conjugate accumulate, while the immunoreactivity for Ac-LDL is low. Addition of chloroquine, an inhibitor of lysosomal degradation, demonstrated that the relatively electron-lucent and electron-dense structures represent subsequent stages of the lysosomal pathway of Ac-LDL, which was also verified by detection of the lysosomal enzyme cathepsin D. Evaluation of the processing of Ac-LDL and oxidized LDL, labeled with different fluorochromes, demonstrated that both ligands follow apparently the same intracellular pathway in the liver endothelial cells, since the fluorescent probes are predominantly localized in the same structures. It is concluded that the scavenger receptor-mediated processing of modified LDL by rat liver endothelial cells involves four morphologically distinguishable stages which represent a highly effective catabolic route, sustaining the important role of the liver endothelial cells in the protection against circulating atherogenic lipoproteins.

Animals↗

PubMed1995

Distribution and morphological characterization of viscerofugal projections from the large intestine to the inferior mesenteric and pelvic ganglia of the male rat.

Viscerofugal neurons are enteric neurons in the myenteric plexus of the stomach and intestine that project to the prevertebral ganglia as the afferent limb of intestino-intestinal reflexes. This study characterizes viscerofugal projections to the inferior mesenteric ganglion and investigates the possibility of similar projections to the major pelvic ganglia in the male rat. The colon and rectum were examined for retrogradely labelled neurons following the injection of retrograde tracer into the inferior mesenteric or major pelvic ganglia, or following the application of tracer to the caudal end of the cut intermesenteric nerves, or either end of the cut hypogastric nerves. All labelled viscerofugal neurons were found in the myenteric plexus and were often grouped near the mesenteric attachment. The number of viscerofugal neurons projecting to the inferior mesenteric ganglion via the lumbar colonic nerves increases along the length of the large intestine with the maximum number of viscerofugal neurons found in the rectum. Some viscerofugal neurons from the distal colon and rectum reach the inferior mesenteric ganglion via the hypogastric nerves. A similar number and distribution of viscerofugal neurons project via the inferior mesenteric ganglion into the intermesenteric nerves as terminate in the inferior mesenteric ganglion. Very few viscerofugal neurons project to the neurons of the major pelvic ganglia via the rectal nerves, and no viscerofugal neurons project caudally in the hypogastric nerves to these ganglia. The majority of labelled neurons resembled Dogiel type I morphology. Thus the inferior mesenteric ganglion receives a substantial innervation from viscerofugal neurons of the large intestine, with the greatest supply from the distal colon and rectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Morphological characterization of substance P-like immunoreactive glomeruli in the superficial dorsal horn of the rat spinal cord and trigeminal subnucleus caudalis: a quantitative study.

The aim of this work was to study the ultrastructural distribution of substance P-like immunoreactivity in laminae I and II of rat spinal cord and trigeminal subnucleus caudalis in relation to synaptic glomeruli. A bispecific monoclonal antibody directed against substance P and horseradish peroxidase was used, combining sensitive immunocytochemistry with preservation of fine ultrastructural detail. Some of the quantitative observations were carried out with an automated image analysis system. The study revealed that in lamina I of the spinal cord, almost all immunoreactive profiles counted were nonglomerular, and a considerable number of them contacted medium-size or large dendrites or were in direct contact with other vesicle-containing profiles. In ventral lamina II, 9.4% of the labeled axonal varicosities were central boutons of type I glomeruli (CI). They could be identified by their scalloped contour, number and types of peripheral profiles, reduced density of mitochondria, and localization in the dorsal horn. However, these immunoreactive glomerular CI boutons (14.1% of the total number of CI) differed statistically from the prevailing population of nonimmunoreactive CI, by being surrounded by less peripheral neuronal profiles, which established fewer synapses. In addition, they contained more than three dense-core vesicles per central profile. In the trigeminal subnucleus caudalis laminae I and II, the substance P fibers and varicosities had a plexiform orientation at the light microscopic level, which contrasted with the mainly rostrocaudal orientation of the spinal cord's lamina II plexus. However, the main ultrastructural findings were similar. These results demonstrate that substance P-like immunoreactivity occurs in a large number of type I synaptic glomeruli with specific morphological features and reinforce the current concept that the substantia gelatinosa of the spinal cord and trigeminal subnucleus caudalis are homologous structures.

Animals↗

PubMed1991

Morphological characterization of immortalized hypothalamic neurons synthesizing luteinizing hormone-releasing hormone.

An immortalized LHRH cell line has recently been developed by genetically targeting these neurons for tumorigenesis. One of the subclones, the GT1-7 cells, was characterized at both the light and electron microscopic levels to study the cellular and subcellular organization of these cells, particularly as they relate to biosynthesis, processing, and secretion. The cells were fixed onto slides 18-36 h after plating. LHRH and GnRH-associated peptide (GAP) immunoreactivities (IR) were detected by immunocytochemistry using colloidal gold labeling. These cultured cells exhibited the classical neuronal appearance of LHRH neurons, and they established numerous interconnections. Neighboring neurons were coupled by tight junctions, while more distant cells were interconnected with neural axon-like processes and collaterals. This cellular organization is suggestive of a neural network where neuronal activity is coordinated. At the ultrastructural level, the nondividing cells possessed indented nuclei, well developed Golgi complexes, and abundant numbers of ribosomes and secretory granules. Clathrin-coated vesicles were found in fusion with the plasma membrane. The ribosomes and secretory vesicles were particularly prominent, suggestive of high rates of protein biosynthesis and secretion. All of the cells immunostained for both LHRH and GAP; however, GAP IR was always more pronounced than that for LHRH. This finding was corroborated by biochemical data reported in a companion paper. The GAP IR was associated with ribosomes and secretory vesicles. By comparison, LHRH IR was restricted mainly to the secretory vesicles. Using colloidal gold particles of different sizes to denote LHRH or GAP IR, it was determined that both GAP and LHRH IR were colocalized within the same secretory vesicle. Taken together, these data suggest that pro-LHRH is biosynthesized on the ribosomes, packaged as an intact protein into the secretory vesicles, processed to LHRH and GAP-(1-56) within these vesicles, and transported to the periphery of the cell in preparation for secretion. These morphological data emphasize the utility of using these immortalized LHRH neuronal cells to dissect the cellular and subcellular architecture involved in biosynthesis, processing, and secretion. In addition, our results provide the first detailed evidence for the intracellular pathway involved in pro-LHRH biosynthesis, processing, and secretion in these cultured neuronal cells.

Animals↗

PubMed1992

Vagal afferent innervation of the rat fundic stomach: morphological characterization of the gastric tension receptor.

Although the gastric tension receptor has been characterized behaviorally and electrophysiologically quite well, its location and structure remains elusive. Therefore, the vagal afferents to the rat fundus (forestomach or nonglandular stomach) were anterogradely labeled in vivo with injections of the carbocyanine dye Dil into the nodose ganglia, and the nerves and ganglia of the enteric nervous system were labeled in toto with intraperitoneal Fluorogold injection. Dissected layers and cryostat cross sections of the fundic wall were mounted in glycerin and analyzed by means of conventional and laser scanning confocal microscopy. Particularly in the longitudinal, and to a lesser extent in the circular, smooth muscle layers, Dil-labeled fibers and terminals were abundant. These processes, which originated from fibers coursing through the myenteric ganglia and connectives, entered either muscle coat and then ran parallel to the respective muscle fibers, often for several millimeters. They ran in close association with the Fluorogold-labeled network of interstitial cells of Cajal, upon which they appeared to form multiple spiny appositions or varicosities. In the myenteric plexus, two different types of afferent vagal structures were observed. Up to 300 highly arborizing endings forming dense accumulations of small puncta similar to the esophageal intraganglionic laminar endings (Rodrigo et al., '75 Acta Anat. 92:79-100) were found in the fundic wall ipsilateral to the injected nodose ganglion. They often covered small clusters of myenteric neurons or even single isolated ganglion cells (mean = 5.8 neurons) and tended to extend throughout the neuropil of the ganglia. In a second pattern, fine varicose fibers with less profuse arborizations innervated mainly the central regions of myenteric ganglia. Camera lucida analyses established that single vagal afferent fibers had separate collaterals in both a smooth muscle layer and the myenteric ganglia. Finally, Dil-labeled afferent vagal fibers were also found in the submucosa and mucosa. Control experiments in rats with supranodose vagotomy as well as rats with Dil injections directly in the distal cervical vagus ruled out the possibility of colabeling of afferent fibers of passage. In triple labeling experiments, in conjunction with Dil labeling of afferents and Fluorogold labeling of enteric neurons, the carbocyanine dye DiA was injected into the dorsal motor nucleus of the vagus to anterogradely label the efferent vagal fibers and terminals. The different distributions and morphological characteristics of the vagal afferents and efferents could be simultaneously compared. In some instances the same myenteric ganglion was apparently innervated by an afferent laminar ending and an efferent terminal.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1985

Severe congenital leukopenia (reticular dysgenesis). Immunologic and morphologic characterizations of leukocytes.

We report fatal reticular dysgenesis in a premature infant presenting with severely decreased blood and bone marrow granulocytes and lymphocytes, an absent thymic shadow by x-ray film, and generalized lymphoid hypoplasia. Immunologic and electron microscopic evaluation of his white blood cells demonstrated that, despite extremely low cell numbers, cells from all stages of both granulocytic and lymphocytic development were present. Immature bone marrow cells of both myeloid and lymphoid lineages were found in much greater proportions than were mature cells; pre-B cells outnumbered B cells by more than tenfold. Megakaryocytes and erythroid cells appeared to be present in normal numbers, and tritiated-thymidine incorporation by bone marrow nucleated cells was also normal, although it may have largely occurred in erythroblasts. These data suggest that the primary defect in reticular dysgenesis is not failure in initiation of stem cell differentiation along lymphoid and myelomonocytic lines but rather an, as yet, undefined abnormality that interferes with normal growth and maturation of immune cells committed to these differentiation pathways.

B-Lymphocytes↗

PubMed1999

Spermatogonia of rainbow trout: I. Morphological characterization, mitotic activity, and survival in primary cultures of testicular cells.

Prerequisites of developing in vitro studies for a better understanding of the control mechanisms underlying the proliferation and differentiation of spermatogonia (Go) in the teleost testis are: (1) to be able to identify the different types of Go; (2) to maintain in culture the structural relationships occurring in situ between the various testicular cell types, as intact as possible; and (3) to know how the Go survive and proliferate in culture for several days. After very gentle homogenization of trout testes treated with collagenase, a cell suspension containing mainly spermatocysts (one or several Sertoli cells enclosing one Go or a clone of germ cells) and clusters of myoid cells and Leydig cells was seeded in culture onto a laminin plus fibronectin coating. After 4.5-6 days in culture, then staining with May-Grünwald and Giemsa reagents, the determination of the nuclear and cellular size of the various Go and of the number of Go present in clones has enabled the identification of two types of large Go, in pairs or alone (Go A) and six successive types of smaller Go (Go B). Cell viability determination by staining with Rhodamine 123/propidium iodide (PI)/Hoechst 33342 and with FITC-Annexin V/PI indicated that after 5-7 days in culture, all the somatic cells and most of the Go were viable. Only some of the Go, mainly among the most differentiated ones, underwent apoptosis, as it was the case for a number of spermatocytes and spermatids increasing with the time in culture. Brdu labelling and 3H-Thymidine (3H-Tdr) incorporation indicated that the proliferative activity of Go was at a maximum after 4.5 days in culture and that the response to at least two molecules (QAYL-IGF-I and GTH-I) remained unchanged between 3 and 6 days. As only very scarce somatic cells from immature/spermatogenetic testes synthesized DNA up to 6 days in culture, the measurement of 3H-Tdr incorporation by cells from such testes reliably reflected synthesis of DNA by only the Go (and eventually also by primary spermatocytes when they are present). In conclusion, this study provides information allowing a detailed analysis of the events related with the mitotic phase of spermatogenesis in the trout and it establishes that primary cultures of testicular cells carried out in the reported conditions represent a useful tool to develop an analysis of the mechanisms participating in the control of this phase.

Animals↗

PubMed1987

Morphological characterization of a granulocytosis/hypercalcemia-inducing murine mammary carcinoma cell line.

A newly established cell line of a granulocytosis/hypercalcemia-inducing murine mammary carcinoma (CE mammary carcinoma) grown in serum-free culture medium secretes factors that stimulate proliferation of granulocytes and embryonal bone cells. These cultured cells retain the ability to produce granulocytosis and hypercalcemia when they are transplanted back into mice. In culture these cells form clusters of organized cells. Studies by scanning, transmission, and freeze-fracture electron microscope techniques reveal that these in vitro tumor cells retain the structural epithelial characteristics of mammary epithelia. They maintain cellular polarity, microvilli, and complete tight junctions. Both the in vivo and in vitro tumor cells produce viral particles with the ultrastructural features of murine mammary tumor viruses. In both in vivo and in vitro conditions, A-type particles are present intracellularly. B viral particles are present predominantly in the intercellular spaces. Since the structural characteristics of the cultured tumor cells are consistent with the features of mammary adenocarcinomas, this is a prime culture system for studying the tumor-derived soluble factors.

Animals↗

PubMed1989

Primary cell culture and morphological characterization of ventricular myocytes from the adult newt, Notophthalmus viridescens.

Previous work has demonstrated that adult newt cardiac myocytes possess a proliferative ability in response to an experimentally induced injury, in vivo. This study describes an in vitro model in which the proliferative events of the adult cardiac myocyte may be studied. Ventricles were minced and then enzymatically dissociated in a Ca++- and MG++-free salt solution containing 0.5% trypsin and 625 U/ml of CLS II collagenase for 8 to 10 hours at 25 degrees C. Enzyme digests were preplated and then cultured on bovine corneal endothelial-derived basement membrane "carpets" in either serum-free or serum-supplemented modified Leibovitz's medium for up to 30 days. Light and transmission electron microscopic characterization demonstrated that a majority of the myocytes underwent an initial period of disorganization characterized by a "rounding up" of the cell and a loss of myofibrillar organization. Once the myocytes had attached to the culture substratum they began to spread out, underwent a reassembly of their contractile elements, resumed spontaneous contractions, and demonstrated ultrastructural evidence of protein synthesis. Mitosis was observed in several myocytes 8 to 15 days following isolation. In 15-day serum-supplemented and serum-free cultures, 6.5% +/- 0.9% and 8.1% +/- 1.4% of the myocytes were binucleated, respectively. These results demonstrate that adult newt ventricular myocytes can be successfully placed into primary culture and are capable of undergoing mitosis. This work may be considered as a foundation for future investigations which will focus on the mechanisms which control cardiac myocyte proliferation.

Animals↗

PubMed2003

Morphologic characterization of green fluorescent protein in embryonic, neonatal, and adult transgenic rats.

Transgenic (Tg) animals with reporter genes are useful models in which to study cell lineage and the process of differentiation into tissues. We developed the green fluorescent protein (GFP)-Tg rat, which is more suitable for transplantation and stem cell research because it is larger than mice. We found that marker gene expression was dependent on each organ and developmental stage. In this study we describe GFP expression in various tissues from embryonic, neonatal, and adult animals. GFP expression in brain, lung, liver, and islet tissues was restricted to early developmental stages, but it was continuously strong in the exocrine pancreas, kidney, and cardiac and skeletal muscles. The CAG promoter that was presumed to induce ubiquitous protein expression might be responsible for the differences in expression.

Animals↗

PubMed2005

Morphological characterization of point patterns.

A triplet of function s for the statistical characterization of planar point patterns is introduced. They are related to the integral-geometric quantities area, boundary length and Euler number of patterns of discs centred at the given points. These functions are able to give information on the distribution of a given point pattern which the traditional summary statistics of point process theory do not offer and so can lead to an improved statistical description. The paper describes the statistical estimation of the new characteristics. Some examples illustrate their application in the exploratory analysis of point patterns of tree positions in forests, in comparison to results obtained by means of second-order and distance characteristics.

Agriculture↗

PubMed1990

Variability of light-evoked response pattern and morphological characterization of amacrine cells in goldfish retina.

Amacrine cells of the goldfish retina were characterized electrophysiologically and subsequently labelled by intracellular injection of horseradish peroxidase. An attempt was made to broaden the electrophysiological classification of the cells. Light-evoked sustained amacrine cell responses were divided into two subtypes depending on colour opponency. Colour-coded responses (red/depolarizing and green/hyperpolarizing) were found to arise in amacrine cells possessing highly polarized dendritic fields; the dendrites were monostratified in the proximal half (sublamina b) of the inner plexiform layer. Non-colour-opponent sustained responses also arose in monostratified units, but the level of dendritic ramification was in sublamina a or b (hyperpolarizing or depolarizing units, respectively). Transient (ON-OFF) responses were associated mainly with bi- or multi-stratified or diffuse amacrine cells. Some variability was observed in the sizes of the dendritic fields in different sublaminae. There was a tendency for units with brisk components of responses to be narrowly stratified in the inner plexiform layer. Some units possessed "distant" dendrites. Several aspects of structure-function correlation in amacrine cells are discussed.

Animals↗

PubMed2006

Mechanical and morphological characterization of homogeneous and bilayered poly(2-hydroxyethyl methacrylate) scaffolds for use in CNS nerve regeneration.

Homogeneous and bilayered macroporous poly(2-hydroxyethyl methacrylate), p(HEMA), hydrogel scaffolds were examined as possible matrices for nerve regeneration in the CNS. An important issue to consider for a CNS scaffold is that it must be able to closely mimic the natural tissue it is replacing, while remaining intact, and mechanically stable enough to allow for regenerating axons to elongate through it. Phase-separated homogeneous and bilayered p(HEMA) scaffolds were fabricated, by varying water, crosslinking, and initiating agents; all of which directly affected the mechanical properties of the polymer. An increase in water concentration resulted in a decrease in the modulus for a given crosslinking and initiating concentration for all homogenous scaffolds, but the same result was not evident in the bilayered scaffolds. The distinct regions within the bilayered scaffolds generate a matrix, containing both a highly porous region with modulus values representative of spinal cord tissue, as well as a nonporous region that provides overall mechanical stability to the entire implant. The overall result is a composite matrix for possible use in CNS nerve regeneration, which mimics the mechanical properties of spinal tissue, but can withstand the forces that it will be subjected to in the injury site.

Biocompatible Materials↗

PubMed1988

Biochemical and morphological characterization of growth and differentiation of normal human neonatal keratinocytes in a serum-free medium.

Growth and differentiation of keratinocytes in a serum-free medium (keratinocyte growth medium or KGM) was studied and compared to that under conditions in which serum and feeder cell layers were used. Cells were grown in KGM containing 0.1 mM calcium (KGM/low calcium), KGM containing 1.2 mM calcium (KGM/normal calcium), or Dulbecco's modified Eagles medium containing 5% fetal calf serum and 1.8 mM calcium in presence of mitomycin treated 3T3 M cells (DMEM/5% FCS). Plating efficiency and rate of growth were similar in the three media till confluence. In postconfluent cultures, protein and DNA content of cells attached to the plate in KGM/low-calcium dishes decreased as an increased number of cells were shed into the medium. Cell shedding was much less evident in the presence of normal calcium. Cells grown in KGM/low calcium had a higher rate of cell proliferation (3H-thymidine incorporation into cellular DNA) than cells grown in normal calcium. Transglutaminase activity, involucrin content, and cornified envelope formation were greatest in cells grown in KGM/normal calcium, intermediate in cells grown in DMEM/5% FCS, and least in cells grown in KGM/low calcium. Keratin profiles from cells grown in KGM/low calcium showed a lower percentage of high molecular weight bands compared to the keratin profiles from cells grown in the presence of normal calcium. Keratinocytes in KGM/low calcium grew as a monolayer of cuboidal cells with few features of differentiation, whereas cells grown in KGM/normal calcium stratified into multilayered islands (3-5 layers) surmounted by 2-4 layers of enucleated cells with thickened cornified envelopes. Cells grown in KGM/normal calcium also contained tonofilaments and lamellar bodies unlike cells grown in KGM/low calcium. Cells grown in DMEM/5% FCS also formed stratified layers comparable to cells grown in KGM/normal calcium but lacked cornified cells, keratohyalin granules, tonofilament bundles, and lamellar bodies. These studies indicate the usefulness of serum-free conditions for the culture of human keratinocytes and confirm the importance of extracellular calcium in keratinocyte differentiation.

Cell Differentiation↗

PubMed1996

Functional and morphological characterization of immunomagnetically selected CD34+ hematopoietic progenitor cells.

We evaluated the potential of immunomagnetically selected (miniMACS) progenitor cells to give rise to colony-forming cells and their precursors, detected as long-term culture-initiating cells (LTC-IC), as well as their capacity to expand in liquid cultures. A 90% mean purity, a 43.2% yield and a 55.8-fold enrichment were achieved from normal bone marrow. When corrected for enrichment, the mean number of committed progenitor cells and the frequency of LTC-IC (evaluated by means of limiting dilution assay [LDA]) were not statistically different in low density mononuclear cells or in the CD34-enriched fractions. In five cases CD34+ selected cells grown in a stroma-free long-term bone marrow culture system with the addition of stem cell factor, interleukin 3, interleukin 6 and GM-CSF every 48 h, showed a 15 (+/- 15) and 31 (+/- 21) mean colony forming unit-granulocyte/macrophage fold increase on cultures at days 7 and 14. However, when corrected for enrichment, the expansion capability of these cells was significantly lower than that of the unseparated fraction, particularly after the first week. Immediately after separation, electron microscopy revealed that the CD34+ selected fraction contained more than 45% of well-differentiated myeloid cells (MPO+), with iron beads preferentially clustered at one pole of the cell surface and sometimes already endocytosed in pinocytic vesicles. After 24 h and 48 h incubation at 37 degrees C, the majority of the cells showed no iron particles, but about 30% of the cells were iron-labeled phagocytic cells. The percentage of apoptotic cells with internalized iron was negligible. These data show that immunomagnetically separated CD34+ cells may have a slightly impaired short-term expansion capability, but give rise to both committed and more primitive progenitor cells. During the separation, the iron beads are internalized, rapidly processed in the cytoplasm and do not seem to interfere with in vitro growth.

Adult↗

PubMed1999

Morphological Characterization of the Molecular Superstructure of Polyphenylene Ethynylene Derivatives.

Two different polyphenylene ethynylene derivatives, one partly hydrophobic and one hydrophilic, were investigated with a combination of X-ray and light scattering techniques and hydrodynamic techniques, as well as scanning force microscopy and transmission electron microscopy to elucidate their molecular structure and aggregation behavior in tetrahydrofuran and water, respectively. It turns out that both polymers possess a rod-like molecular architecture which, however, is the basis of a cascade of aggregation steps. Both, electron microscopy and X-ray analysis support the concept of a primary back-to-back aggregation of polymer chains into cylindrically shaped aggregates with high anisometry. The thickness of these aggregates was between 4.0 and 4.5 nm. The aggregates of the hydrophobic polymer further associate into fibrils and these fibrils form clusters of globular shape, though with high internal anisometry. Copyright 1999 Academic Press.

Journal Article↗