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At least 793 records · Page 44Linked to original sources
PubMed1987

Molecular cloning of sequences from wingless, a segment polarity gene in Drosophila: the spatial distribution of a transcript in embryos.

In Drosophila the process of segmentation depends on the function of coordinate, gap, pair-rule and segment-polarity genes. Mutations in segment-polarity genes cause defects in the pattern of every segment. Here the cloning of sequences from a segment-polarity gene, wingless, and the in situ localization of a transcript in embryos are described. The transcript is first detected in the anterior and posterior regions of the blastoderm embryo at cellularization, and accumulates in a series of stripes in the extended germ band, one stripe per metameric unit. Each stripe is localized to the most posterior cells of each parasegment. The signal is predominantly epidermal, and transcript accumulates only transiently in the mesoderm and nervous system. This pattern of expression is discussed with respect to models of pattern formation in segmental units.

Journal Article↗
PubMed1987

Temporal and spatial distribution of transcripts from the Deformed gene of Drosophila.

The Deformed gene of Drosophila is necessary for the proper development of epidermal pattern elements arising from the maxillary and mandibular segments of the head. We find one major transcript (2.8 kb) homologous to Deformed (Dfd) probes which is expressed continuously from 3 h of embryogenesis into adulthood. Localized transcript accumulation is first detected just prior to the formation of the cellular blastoderm in a single circumferential band at about 65-75% egg length. The zone of Dfd expression is approximately two segment primordia in width. At later stages of embryogenesis, Dfd transcripts accumulate in the posterior ectoderm of the mandibular segment, and in the ventro-lateral ectoderm of the maxillary segment. Transcripts are also detected in the mesoderm and neuromeres of the mandibular and maxillary segments. The distribution of Dfd transcripts supports the hypothesis that Dfd functions as a homeotic selector gene in the determination of posterior head segments.

Journal Article↗
PubMed2003

Controlling the spatial distribution of ECM components in degradable PEG hydrogels for tissue engineering cartilage.

In developing a scaffold to support new tissue growth, the degradation rate and mass loss profiles of the scaffold are important design parameters. In this study, hydrogels were prepared by copolymerizing a degradable macromer, poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) endcapped with acrylate groups (PEG-LA-DA) with a nondegradable macromer, poly(ethylene glycol) dimethacrylate (PEGDM). The resulting hydrogels exhibited a range of degradation behavior and mass loss profiles. Chondrocytes were photoencapsulated in gels formulated with 50:50, 25:75, and 15:85 (mol % PEGDM: mol % PEG-LA-DA) and cultured for 6 weeks in vitro. The neocartilaginous tissue formed was examined biochemically and histologically. After 6 weeks, the DNA content in gels with 75 and 85% degradable crosslinks was nearly twice that of the DNA content in the 50% gels. The total collagen content was significantly higher in the 85% gel [2.4 +/- 0.8% wet weight (ww)] compared to the 50% gel (0.22 +/- 0.29% ww). In examining the neocartilaginous tissue with immunohistochemistry, type II collagen was localized in the pericellular region in the 50% gel; however, when increased degradation was incorporated into the gel, type II collagen was found throughout the neotissue. In summary, the important role of hydrogel degradation in controlling and influencing the deposition and distribution of extracellular matrix molecules was demonstrated and quantified.

Animals↗
PubMed2005

Temporal and spatial distribution of growth-associated molecules and astroglial cells in the rat corticospinal tract during development.

To understand better the role of growth-promoting and -inhibiting molecules in the development of the corticospinal tract (CST), temporospatial expression of embryonic neural cell adhesion molecule (E-NCAM), growth-associated protein-43 (GAP-43), and chondroitin sulfate proteoglycan (CSPG) was studied in developing rats. Transverse sections of the seventh cervical (C7), seventh thoracic (T7), and fourth lumbar (L4) segments were examined at postnatal days (P) 2, 6, 10, 14, and 28. The highest E-NCAM immunoreactivity appeared at the C7 level on P2 and shifted caudally to the T7 on P6 and L4 on P10, which correlated closely with the time course of CST development. The peak expression of GAP-43 emerged at C7 on P2 and shifted to the T7 and L4 levels at a relatively lagging pace compared with that of E-NCAM. Conversely, a transient reduction in CSPG immunoreactivity was found within the CST at the C7 level on P2, T7 level on P6, and L4 level on P10, corresponding well with the arrival of CST-leading axons at these levels. Interestingly, higher levels of CSPG were found to surround the growing CST, suggesting a repulsive environment that channels the growth of CST. Moreover, a transition from immature to mature astrocytes in a rostrocaudal direction during CST development was evidenced by anti-vimentin and anti-glial fibrillary acidic protein (GFAP) immunostaining, suggesting a guidance role of immature astroglia in axonal outgrowth. Our study thus demonstrated dynamic changes of multiple growth-related molecules and astroglial environment that contribute to postnatal development of the CST.

Aging↗
PubMed1980

Spatial distribution of catecholaminergic cells in the fish retina.

The cell density, distribution pattern, and morphology of catecholaminergic (CA) cells have been studied by fluorescence microscopy of retinal flat-mounted preparations from various species of fresh water, estuary, and marine is lowest in the central region surrounding the optic disc, slightly higher in the intermediate region, and highest in the periphery. The size of CA-cells is smaller the higher their density. Following administration of L-Dopa, dompamine, or noradrenaline, the density of CA-cells approximately doubled, due to the appearance of small fluorescent cells. CA-cells are arranged in rows along radial lines which fan out from the optic disc. In large cells of the central and intermediate regions three to five processes arise from the some and extend and ramify irregularly in the inner plexiform layer, while in small cells from the intermediate and peripheral regions two processes arise from opposite poles and extend regularly in a direction perpendicular to the rows of cells and parallel to the retinal margin. In the retina of the marine fish Holocentrus sp CA-cells are fewer in number compared to other fish studied and their processes extend without any regular pattern. In the toad their size and density are homogenous throughout the retina, and their processes show a regular arrangement.

Animals↗
PubMed1991

Spatial distribution of myelin basic protein mRNA and polypeptide in quaking oligodendrocytes in culture.

In the CNS, myelin is formed from the expansion of oligodendrocyte processes. In order to study myelin assembly in the hypomyelinating mutant mouse quaking (qk), cultures of oligodendrocytes were established from affected and control animals. The cytoarchitecture of the oligodendrocytes was analyzed by performing morphometric measurements after immunostaining with antitubulin. The results indicate that the gross morphology of the processes is similar in control and mutant cells. The localization of the message for the myelin structural component, myelin basic protein (MBP), was examined by in situ hybridization. In control oligodendrocytes, 80% of MBP mRNA is found in the processes. In contrast, only 23% of MBP mRNA is localized to these structures in the mutant; the majority of MBP mRNA remains in the cell body. The mutant cells are capable of distributing mRNAs to the periphery as shown by the presence of tubulin mRNA in their processes. MBP polypeptide was visualized by immunofluorescence and found in the perikaryon, processes and membranous expansions of the control cells. In the mutant, it is largely confined to the perikaryon, reflecting the distribution of the mRNA. These results suggest that the localization of MBP polypeptide is achieved by restricting the distribution of its mRNA, and that MBP assembly into the myelin membrane occurs in the processes. This step appears to be blocked in qk oligodendrocytes in culture.

Animals↗
PubMed1993

Temporal and spatial distribution of heat shock mRNA and protein (hsp70) in the rabbit cerebellum in response to hyperthermia.

We have previously investigated the expression of hsp70 genes in the hyperthermic rabbit brain at the mRNA level by Northern blot and in situ hybridization procedures. Our studies have now been extended to the protein level utilizing Western blot and immunocytochemistry. Using an antibody which is specific to inducible hsp70, a prominent induction of hsp70 protein in glial cells of hyperthermic animals was noted. In particular, Bergmann glial cells in the cerebellum are strongly immunoreactive while adjacent Purkinje neurons are immunonegative. Extension of our in situ hybridization studies to a time course analysis revealed that the initial glial induction events were followed by a delayed accumulation of inducible hsp70 mRNA in Purkinje neurons at 10 hr post-heat shock. In control animals, high levels of constitutively expressed hsc70 mRNA and protein were observed in Purkinje neurons. Similar hsc70 and hsp70 mRNA observations were also made in neurons of the deep cerebellar nuclei and in motor neurons of the spinal cord. Our results suggest that these neuronal cell types accumulate hsp70 mRNA in response to hyperthermic treatment; however, the response is delayed when compared to the rapid response seen in glial cells. The high constitutive levels of hsc70 in certain neuronal cell types may play a role in the initial dampening of the hsp70 induction response in these cells.

Animals↗
PubMed1995

Spatial distribution of omega-agatoxin IVA binding sites in mouse brain slices.

A peptide toxin derived from funnel-web spider venom, omega-agatoxin IVA, blocks voltage-sensitive calcium channels. Many pharmacological and electrophysiological studies have shown that these channels are widely distributed in both the central nervous system (CNS) and neuromuscular junctions. However, a direct morphological demonstration of the binding sites of this toxin is still lacking. To identify which cells have the binding sites, a biologically active, biotin-conjugated omega-agatoxin IVA was applied to mouse cerebellar and hippocampal slices. Confocal microscopy revealed that omega-agatoxin IVA binding sites were distributed on the somata of Purkinje cells, cerebellar granule cells and interneurons, as well as on the dendrites of Purkinje cells. In the hippocampus, the binding sites were localized on the somata of pyramidal cells of the CA1-CA4 region and on the somata of granule cells in the dentate gyrus. A sequential competitive reaction confirmed the specificity of the binding in the cerebellum and CA1 pyramidal cells, and also suggested a difference in the binding affinity between CA1 and CA3 pyramidal cells. Since a high concentration of omega-agatoxin IVA (2 microM) was needed for the present study, the omega-agatoxin IVA binding sites presented in this study may represent "P-type" and "Q-type" calcium channels.

Animals↗
PubMed1996

Spatial distribution of CD44 and hyaluronan in the proximal tibia of the growing rat.

CD44 has been described as a cell surface hyaluronan receptor present on a variety of different cells, and it is generally assumed to be prevalent in most connective tissues that contain hyaluronan. A major aim of this study was to test that presumption by localizing CD44 and hyaluronan within several tissues of the proximal tibia of the growing rat. Comparison of these profiles would reveal whether CD44 and hyaluronan co-localize with high fidelity, as would be expected if CD44 were a major hyaluronan binding protein. Using in situ hybridization and immunohistochemistry, CD44 was identified on osteoclasts, chondroclasts, osteocytes, hematopoietic marrow cells, synovial cells, and connective tissue fibroblasts (ligaments, tendons, and fascia). Although the majority of osteocytes expressed CD44, reduced expression was observed for osteoblasts and ostcoprogenitor cells. Additionally. CD44 was not detected on chondrocytes from epiphyseal and metaphyseal growth cartilages or in meniscal fibrocartilage. Using biotinylated G1 domain from aggrecan and link protein, hyaluronan was observed in the maturational and hypertrophic zones of all growth cartilages, the synovium and other fibroblastic connective tissues, regional areas of the periosteum and endosteum (around osteoblasts, osteoprogenitor cells, and osteoclasts), osteocyte lacunae, and surrounding blood vessels. In regions of co-localization for CD44 and hyaluronan, it seems that CD44 is a likely hyaluronan binding protein in several tissues of the proximal tibia. However, it does not appear to be the predominant hyaluronan binding protein in growing cartilages of the weanling rat.

Aggrecans↗
PubMed1988

Spatial distribution of fiber types in skeletal muscle: test for a random distribution.

A statistical test is introduced for the assessment of fiber type grouping based on the number of neighboring fibers of different histochemical type. It is conceptually simple and can be applied to regular and irregular fiber patterns alike. One important feature of this test is that it has more power than existing ones, which means that deviations from a normal situation can be detected in an earlier stage than with any other method. The dependency of the outcome of the test on type-specific size differences is rather small. Moreover, a method is given to correct for this bias. With the aid of the test it is shown that in normal muscle tissue of young persons a slight segregation of fiber type is a common situation.

Humans↗
PubMed1991

Characterization and spatial distribution of the ELAV protein during Drosophila melanogaster development.

The embryonic lethal abnormal visual system (elav) gene of Drosophila melanogaster is required for the development and maintenance of the nervous system. Transcripts from this locus are distributed ubiquitously throughout the nervous system at all developmental stages. A product of this gene, the ELAV protein, has homology to known RNA binding proteins. The localization of the ELAV protein was studied in all developmental stages using antibodies that were generated against a hybrid protein made in Escherichia coli. In general, these data are consistent with previous results and demonstrate that (1) the ELAV protein is detected in the developing embryonic nervous system at a time coincident with the birth of the first neurons, (2) the ELAV protein is first detected in the majority of neurons of the central and peripheral nervous systems of embryos, larvae, pupae, and adults, (3) the ELAV protein appears to be localized to the nucleus, and (4) the ELAV protein is not detected in neuroblasts or identifiable glia. These data also provide new information concerning elav expression and show that (1) ELAV is not expressed in the ganglion mother cells (GMCs), (2) while the ELAV protein is localized to the nucleus, it is not uniformly distributed throughout this structure, and (3) other Drosophila species do express an ELAV-like antigen. We propose that the elav gene provides a neuronal-housekeeping function that is required for the successful posttranscriptional processing of transcripts from a set of genes the function of which is required for proper neuronal development and maintenance.

Animals↗
PubMed2005

Spatial distributions of desorbing products in basic catalytic processes and surface nano-structures.

Reviews of recent progress in angle-resolved measurements of desorbing surface reaction products are discussed. The angular and velocity distributions of desorbing products deliver information about the reaction site as well as the reaction mechanism when the products are repulsively desorbed. These distribution measurements can yield symmetry and orientation information of the reaction site for associative processes whereas, in dissociative desorption, the collimation of fragment desorption is related to the orientation of the intermediate species immediately before dissociation. These different collimations provide information on desorption steps whenever any step becomes rate determining.

Journal Article↗
PubMed1998

Analysis of spatial distributions of cellular molecules during mechanical stressing of cell surface receptors using confocal microscopy.

Confocal laser scanning microscopy represents a suitable technique to study the localization of cellular components in three dimension. The authors used this technique to analyse cellular events related to mechanical stimulation of integrin receptors on the cell surface. By performing optical sections the distribution of integrin receptors on the apical surface of an osteoblastic cell was determined. Concerning intracellular compartimentalization of signal transduction events, it was demonstrated that mechanical stimulation of integrins induced their linkage to the cytoskeleton. Cytoskeletally associated proteins like vinculin and talin accumulated in the vicinity of the site where the mechanical stress was applied to integrins on the cell surface. Optical sections revealed that clustering of these proteins proceeded to the base of the cell with gradually decreasing extent. In summary, it was demonstrated that the local distribution of cellular components is an important factor in mechanically induced signal transduction.

Humans↗
PubMed2002

Spatial distribution of mDLG6 mRNA in embryonic and adult mouse brain.

We have isolated mouse DLG6 (mDLG6) cDNA clones by RT-PCR and then by using the RT-PCR products to screen a mouse brain cDNA library. The deduced amino acid sequence of mDLG6 shows 79.2% and 82.7% overall identity to human (hDLG6) and rat DLG6 (rDLG6), respectively. In situ hybridization revealed that mDLG6 mRNA is predominantly expressed in embryonic and adult brain.

Animals↗
PubMed1996

Different temporal and spatial distribution of TGF-beta 1 and TGF-beta 2 in rabbit vascular tissue: potential role in normal vessel growth and maturation.

The expression of transforming growth factor beta 1 and beta 2 (TGF-beta 1 and beta 2) in aortic and venous tissue from male New Zealand White rabbits, at selected time intervals after birth, was examined by the reverse transcriptase polymerase chain reaction. Stable levels of TGF-beta 1 were found in all segments derived from the aortic arch and descending aorta at each time interval. However, increasing amounts of TGF-beta 2 transcripts were observed for the aortic arch from day 4, with peaks occurring between 1 and 6 months of age, followed by progressively decreasing levels thereafter. TGF-beta 2 transcripts in the descending aorta generally did not change significantly over time. TGF-beta transcripts manifested a significantly lower expression in the vena cava than in aortic segments. Histological analysis of the vascular tissue showed cellular hyperplasia (2.5-fold greater prevalence of nuclei per field) in the aortic arch media at 1 month of age as compared with nuclei per field at 12 months and increasing thickness of the aortic arch media with time. No significant differences in relative collagen concentrations were observed among the aortic and vena cava segments. These results suggest that these TGF-beta isoforms may participate in the physiological induction and differentiation of arterial and venous tissue during early normal vascular maturation.

Actins↗
PubMed2000

Spatial distribution and differentiation potential of stem cells in hatchlings and adults in the marine platyhelminth macrostomum sp.: a bromodeoxyuridine analysis.

Stem cells (neoblasts) in Platyhelminthes are pluripotent, and likely totipotent, undifferentiated cells which retain throughout adult life the capacity to proliferate and from which all somatic cells as well as the germ cells derive. However, basic data on the pool and heterogeneity of neoblasts, their rates of differentiation into sets and subsets of differentiated cells, and their migration to different body regions are still lacking. To fill this gap, S-phase cells in the macrostomid Macrostomum sp. were labeled with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU). S-phase cells were found to be neoblasts and to be distributed in two bands along the lateral sides of the body leaving unlabeled the median axis of the body and the region anterior to the eyes. This distribution is parallel to that of mitotic cells demonstrated using an antibody to phosphorylated histone H3. At different chase times, clusters of BrdU-labeled cells appear, labeled cells migrate to formerly unlabeled areas, and they differentiate into several somatic cell types and into germ cells. Finally, continuous exposure to BrdU shows an extensive renewal of the epithelial cells. Altogether, these results strengthen the idea of platyhelminth neoblasts as an unparalleled stem-cell system within the Animal Kingdom calling for further investigation.

Animals↗