The fine structure of the cecal epithelium of Megalodiscus temperatus

1973 ◽  
Vol 51 (4) ◽  
pp. 457-460 ◽  
Author(s):  
Gerald P. Morris
Keyword(s):  
Fine Structure ◽  
Basal Lamina ◽  
Secretory Activity ◽  
Muscle Cells ◽  
Cell Types ◽  
Basal Region ◽  
Cell Type ◽  
Thorium Dioxide ◽  
Homogeneous Matrix ◽  
Mononucleate Cell

The cecal epithelium of Megalodiscus temperatus (Stafford 1905) contains two cell types. Although the major component of the epithelium is a syncytium there are also isolated, small, mononucleate cells located in the basal region. The mononucleate cells are always in contact with the underlying basal lamina and show no signs of secretory activity. The lumenal surface is extended in the form of numerous long, closely packed, cylindrical microvilli with tapering tips. Each microvillus may be up to 25 μ long and possesses a central fibrillar core. The cytoplasm of the cecal syncytium contains numerous Golgi complexes which produce membrane-delimited granules containing a dense, homogeneous matrix. These granules appear to be releasing their contents either at the lumenal surface or immediately beneath it. The base of the cecal syncytium but not that of the mononucleate cell type is penetrated by numerous projections of underlying muscle cells. No evidence of endocytotic activity by the cecum can be detected by incubation in thorium dioxide.

cAMP-dependent protein kinase differentially regulates prestalk and prespore differentiation during Dictyostelium development

Development ◽  
1993 ◽  
Vol 119 (1) ◽  
pp. 135-146 ◽  
Author(s):  
S.K. Mann ◽  
R.A. Firtel
Keyword(s):  
Protein Kinase ◽  
Spatial Localization ◽  
Cell Types ◽  
Basal Region ◽  
Cell Type ◽  
Dependent Protein Kinase ◽  
Multicellular Development ◽  
Prespore Cell ◽  
Dependent Protein ◽  
Cell Type Specific

We and others have previously shown that cAMP-dependent protein kinase (PKA) activity is essential for aggregation, induction of prespore gene expression and multicellular development in Dictyostelium. In this manuscript, we further examine this regulatory role. We have overexpressed the Dictyostelium PKA catalytic subunit (PKAcat) in specific cell types during the multicellular stages, using prestalk and prespore cell-type-specific promoters to make PKA activity constitutive in these cells (independent of cAMP concentration). To examine the effects on cell-type differentiation, we cotransformed the PKAcat-expressing vectors with reporter constructs expressing lacZ from four cell-type-specific promoters: ecmA (specific for prestalk A cells); ecmB (specific for prestalk B and anterior-like cells in the slug); ecmB delta 89 (specific for stalk cells); and SP60 (prespore-cell-specific). By staining for beta-galactosidase expression histologically at various stages of development in individual strains, we were able to dissect the morphological changes in these strains, examine the spatial localization of the individual cell types, and understand the possible roles of PKA during multicellular development. Expression of PKAcat from either the ecmA or ecmB prestalk promoters resulted in abnormal development that arrested shortly after the mound stage, producing a mound with a round apical protrusion at the time of tip formation. Prestalk A and prestalk B cells were localized in the central region and the apical mound in the terminal differentiated aggregate, while prespore cells showed an aberrant spatial localization. Consistent with a developmental arrest, these mounds did not form either mature spores or stalk cells and very few cells expressed a stalk-cell-specific marker. Expression of PKAcat from the prespore promoter resulted in abnormal morphogenesis and accelerated spore cell differentiation. When cells were plated on agar, a fruiting body was formed with a very large basal region, containing predominantly spores, and a small, abnormal sorocarp. Mature spore cells were first detected by 14 hours, with maximal levels reached by 18–20 hours, in contrast to 24–26 hours in wild-type strains. When cells were plated on filters, they produced an elongated tip from a large basal region, which continued to elongate as a tubular structure and produce a ‘slug-like’ structure at the end. The slug was composed predominantly of prestalk cells with a few prespore cells restricted to the junction between the ‘slug’ and tube. As the slug migrated, these prespore cells were found in the tube, while new prespore cells appeared at the slug/tube junction, suggesting a continual differentiation of new prespore cells at the slug's posterior.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Spiroplasma citri Movement into the Intestines and Salivary Glands of Its Leafhopper Vector, Circulifer tenellus

1999 ◽  
Vol 89 (12) ◽  
pp. 1144-1151 ◽  
Author(s):  
Myoung-Ok Kwon ◽  
Astri C. Wayadande ◽  
Jacqueline Fletcher
Keyword(s):  
Salivary Gland ◽  
Salivary Glands ◽  
Basal Lamina ◽  
Muscle Cells ◽  
Cell Types ◽  
Cell Periphery ◽  
Spiroplasma Citri ◽  
Circulifer Tenellus ◽  
Gland Cells ◽  
Salivary Gland Cells

Spiroplasma citri, a helical, wall-less prokaryote in the class Molli-cutes, is transmitted by the beet leafhopper, Circulifer tenellus. Invasion of leafhopper tissues and cytopathological effects by S. citri were investigated by transmission electron microscopy. All eight cell types of the principle salivary glands, as well as the adjacent muscle cells and the cells of the accessory salivary glands, were colonized by the spiroplas-mas. In both midgut epithelia and salivary gland cells, spiroplasmas usually occurred in membrane-bound cytoplasmic vesicles that often were located near the cell periphery. In several salivary gland cells, spiroplas-mas were also observed within membranous pockets apparently formed by invagination of the plasmalemma beneath intact basal lamina. These observations are consistent with spiroplasma entry into the insect cells by receptor-mediated endocytosis. Cytopathological effects of spiroplasma infection in salivary cells included loss of membrane and basal lamina integrity, presence in some cells of irregular inclusion-like structures containing dense matrices of filamentous material that labeled with anti S. citri antibodies, and apparent disorganization of the endoplasmic reticulum. Compared to the tightly aligned fiber bundles in healthy muscle cells, bundles in spiroplasma-containing muscle cells appeared fragmented and loosely arranged. Such symptoms could contribute to the reduction in longevity and fecundity that has been previously reported for S. citri-infected C. tenellus.

scholarly journals Single-Cell Epigenomics and Functional Fine-Mapping of Atherosclerosis GWAS Loci

2021 ◽  
Author(s):  
Tiit Örd ◽  
Kadri Õunap ◽  
Lindsey Stolze ◽  
Rédouane Aherrahrou ◽  
Valtteri Nurminen ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Cell Types ◽  
Regulatory Elements ◽  
Chromatin Accessibility ◽  
Cell Type ◽  
Atherosclerotic Lesions ◽  
Genome Wide ◽  
Single Nucleus

Rationale: Genome-wide association studies (GWAS) have identified hundreds of loci associated with coronary artery disease (CAD). Many of these loci are enriched in cis-regulatory elements (CREs) but not linked to cardiometabolic risk factors nor to candidate causal genes, complicating their functional interpretation. Objective: Single nucleus chromatin accessibility profiling of the human atherosclerotic lesions was used to investigate cell type-specific patterns of CREs, to understand transcription factors establishing cell identity and to interpret CAD-relevant, non-coding genetic variation. Methods and Results: We used single nucleus ATAC-seq to generate DNA accessibility maps in > 7,000 cells derived from human atherosclerotic lesions. We identified five major lesional cell types including endothelial cells, smooth muscle cells, monocyte/macrophages, NK/T-cells and B-cells and further investigated subtype characteristics of macrophages and smooth muscle cells transitioning into fibromyocytes. We demonstrated that CAD associated genetic variants are particularly enriched in endothelial and smooth muscle cell-specific open chromatin. Using single cell co-accessibility and cis-eQTL information, we prioritized putative target genes and candidate regulatory elements for ~30% of all known CAD loci. Finally, we performed genome-wide experimental fine-mapping of the CAD GWAS variants using epigenetic QTL analysis in primary human aortic endothelial cells and STARR-Seq massively parallel reporter assay in smooth muscle cells. This analysis identified potential causal SNP(s) and the associated target gene for over 30 CAD loci. We present several examples where the chromatin accessibility and gene expression could be assigned to one cell type predicting the cell type of action for CAD loci. Conclusions: These findings highlight the potential of applying snATAC-seq to human tissues in revealing relative contributions of distinct cell types to diseases and in identifying genes likely to be influenced by non-coding GWAS variants.

Hymenolepis nana: the fine structure of the ‘penetration gland’ and nerve cells within the oncosphere

Parasitology ◽  
1981 ◽  
Vol 82 (3) ◽  
pp. 445-458 ◽  
Author(s):  
I. Fairweather ◽  
L. T. Threadgold
Keyword(s):  
Fine Structure ◽  
Secretory Granules ◽  
Polar Filament ◽  
Secretory Activity ◽  
Muscle Cells ◽  
Neurosecretory Cells ◽  
Nerve Cells ◽  
Epithelial Layer ◽  
Hymenolepis Nana ◽  
Penetration Gland

SUMMARYThe fine structure of the oncosphere of Hymenolepis nana has been investigated by transmission and scanning electron microscopy, together with light microscope observations of JB–4 embedded material. The outer surface of the oncosphere is covered by an epithelial layer, termed the embryonic epithelium. Cell types present within the oncosphere include the penetration gland cell, oncoblast, or hook-forming cells, nerve cells, muscle cells (both somatic and hook), and undifferentiated ‘stem’ cells. The penetration gland is a large, U-shaped structure, situated in the anterior region of the oncosphere, and filled with secretory granules of 2 distinct morphological types. Histochemically, the secretory material yields reactions characteristic of an acid mucopolysaccharide. A proteinaceous-substance and small amounts of glycogen are also present. Up to 4 pairs of ducts from the penetration gland have been observed. They pass through the basal lamina and the epithelial layer to open against the polar filament layer at the anterior end of the oncosphere. Nerve cells are described in a cestode oncosphere for the first time. The cells are paraldehyde-fuchsin-positive and show a high level of secretory activity, as evidenced by the large numbers of dense-cored vesicles produced by the Golgi apparatus in the perikarya; consequently, they are tentatively regarded as possible neurosecretory cells. The vesicles are transported down the axon to be stored in specialized swollen axon terminals, which form definite junctions with the muscle cells.

scholarly journals Acetylcholinesterase Clustering at the Neuromuscular Junction Involves Perlecan and Dystroglycan

1999 ◽  
Vol 145 (4) ◽  
pp. 911-921 ◽  
Author(s):  
H. Benjamin Peng ◽  
Hongbo Xie ◽  
Susanna G. Rossi ◽  
Richard L. Rotundo
Keyword(s):  
Neuromuscular Junction ◽  
Basal Lamina ◽  
Acetylcholine Receptors ◽  
Muscle Cells ◽  
Cell Types ◽  
Specific Form ◽  
Lateral Migration ◽  
Extracellular Matrix Molecules ◽  
A Cell ◽  
Nerve Muscle

Formation of the synaptic basal lamina at vertebrate neuromuscular junction involves the accumulation of numerous specialized extracellular matrix molecules including a specific form of acetylcholinesterase (AChE), the collagenic-tailed form. The mechanisms responsible for its localization at sites of nerve– muscle contact are not well understood. To understand synaptic AChE localization, we synthesized a fluorescent conjugate of fasciculin 2, a snake α-neurotoxin that tightly binds to the catalytic subunit. Prelabeling AChE on the surface of Xenopus muscle cells revealed that preexisting AChE molecules could be recruited to form clusters that colocalize with acetylcholine receptors at sites of nerve–muscle contact. Likewise, purified avian AChE with collagen-like tail, when transplanted to Xenopus muscle cells before the addition of nerves, also accumulated at sites of nerve–muscle contact. Using exogenous avian AChE as a marker, we show that the collagenic-tailed form of the enzyme binds to the heparan-sulfate proteoglycan perlecan, which in turn binds to the dystroglycan complex through α-dystroglycan. Therefore, the dystroglycan–perlecan complex serves as a cell surface acceptor for AChE, enabling it to be clustered at the synapse by lateral migration within the plane of the membrane. A similar mechanism may underlie the initial formation of all specialized basal lamina interposed between other cell types.

scholarly journals THE FINE STRUCTURE OF MOTOR ENDPLATE MORPHOGENESIS

1969 ◽  
Vol 42 (1) ◽  
pp. 154-169 ◽  
Author(s):  
A. M. Kelly ◽  
S. I. Zacks
Keyword(s):  
Fine Structure ◽  
Schwann Cells ◽  
Basal Lamina ◽  
Plasma Membranes ◽  
Muscle Cells ◽  
Motor Endplate ◽  
Intercostal Muscle ◽  
Motor Endplates ◽  
Terminal Axon ◽  
Small Muscle

The fine structure of the developing neuromuscular junction of rat intercostal muscle has been studied from 16 days in utero to 10 days postpartum. At 16 days, neuromuscular relations consist of close membrane apposition between clusters of axons and groups of myotubes. Focal electron-opaque membrane specializations more intimately connect axon and myotube membranes to each other. What relation these focal contacts bear to future motor endplates is undetermined. The presence of a group of axons lying within a depression in a myotube wall and local thickening of myotube membranes with some overlying basal lamina indicates primitive motor endplate differentiation. At 18 days, large myotubes surrounded by new generations of small muscle cells occur in groups. Clusters of terminal axon sprouts mutually innervate large myotubes and adjacent small muscle cells within the groups. Nerve is separated from muscle plasma membranes by synaptic gaps partially filled by basal lamina. The plasma membranes of large myotubes, where innervated, simulate postsynaptic membranes. At birth, intercostal muscle is composed of separate myofibers. Soleplate nuclei arise coincident with the peripheral migration of myofiber nuclei. A possible source of soleplate nuclei from lateral fusion of small cells' neighboring areas of innervation is suspected but not proven. Adjacent large and small myofibers are mutually innervated by terminal axon networks contained within single Schwann cells. Primary and secondary synaptic clefts are rudimentary. By 10 days, some differentiating motor endplates simulate endplates of mature muscle. Processes of Schwann cells cover primary synaptic clefts. Axon sprouts lie within the primary clefts and are separated from each other. Specific neural control over individual myofibers may occur after neural processes are segregated in this manner.

Cell contact induces multiple types of electrical excitability from ascidian two-cell embryos that are cleavage arrested and contain all cell fate determinants

2007 ◽  
Vol 293 (5) ◽  
pp. R1976-R1996
Author(s):  
Motoko Tanaka-Kunishima ◽  
Kunitaro Takahashi ◽  
Fumiyuki Watanabe
Keyword(s):  
Stem Cells ◽  
Cell Fate ◽  
Single Cells ◽  
Muscle Cells ◽  
Cell Types ◽  
Specific Cell ◽  
Cell Type ◽  
Cell Pair ◽  
Fate Determinants ◽  
Cell Fate Determinants

Ascidian early embryonic cells undergo cell differentiation without cell cleavage, thus enabling mixture of cell fate determinants in single cells, which will not be possible in mammalian systems. Either cell in a two-cell embryo (2C cell) has multiple fates and develops into any cell types in a tadpole. To find the condition for controlled induction of a specific cell type, cleavage-arrested cell triplets were prepared in various combinations. They were 2C cells in contact with a pair of anterior neuroectoderm cells from eight-cell embryos (2C-aa triplet), with a pair of presumptive notochordal neural cells (2C-AA triplet), with a pair of presumptive posterior epidermal cells (2C-bb triplet), and with a pair of presumptive muscle cells (2C-BB triplet). The fate of the 2C cell was electrophysiologically identified. When two-cell embryos had been fertilized 3 h later than eight-cell embryos and triplets were formed, the 2C cells became either anterior-neuronal, posterior-neuronal or muscle cells, depending on the cell type of the contacting cell pair. When two-cell embryos had been fertilized earlier than eight-cell embryos, most 2C cells became epidermal. When two- and eight-cell embryos had been simultaneously fertilized, the 2C cells became any one of three cell types described above or the epidermal cell type. Differentiation of the ascidian 2C cell into major cell types was reproducibly induced by selecting the type of contacting cell pair and the developmental time difference between the contacting cell pair and 2C cell. We discuss similarities between cleavage-arrested 2C cells and vertebrate embryonic stem cells and propose the ascidian 2C cell as a simple model for toti-potent stem cells.

Embryonic Stem Cells Differentiated in Vitro as a Novel Source of Cells for Transplantation

1996 ◽  
Vol 5 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Jonathan Dinsmore ◽  
Judson Ratliff ◽  
Terry Deacon ◽  
Peyman Pakzaba ◽  
Douglas Jacoby ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Es Cells ◽  
Embryonic Stem ◽  
Muscle Cells ◽  
Cell Types ◽  
Cell Type ◽  
Skeletal Myoblasts ◽  
Muscle Cell Type

The controlled differentiation of mouse embryonic stem (ES) cells into near homogeneous populations of both neurons and skeletal muscle cells that can survive and function in vivo after transplantation is reported. We show that treatment of pluripotent ES cells with retinoic acid (RA) and dimethylsulfoxide (DMSO) induce differentiation of these cells into highly enriched populations of γ-aminobutyric acid (GABA) expressing neurons and skeletal myoblasts, respectively. For neuronal differentiation, RA alone is sufficient to induce ES cells to differentiate into neuronal cells that show properties of postmitotic neurons both in vitro and in vivo. In vivo function of RA-induced neuronal cells was demonstrated by transplantation into the quinolinic acid lesioned striatum of rats (a rat model for Huntington's disease), where cells integrated and survived for up to 6 wk. The response of embryonic stem cells to DMSO to form muscle was less dramatic than that observed for RA. DMSO-induced ES cells formed mixed populations of muscle cells composed of cardiac, smooth, and skeletal muscle instead of homogeneous populations of a single muscle cell type. To determine whether the response of ES cells to DMSO induction could be further controlled, ES cells were stably transfected with a gene coding for the muscle-specific regulatory factor, MyoD. When induced with DMSO, ES cells constitutively expressing high levels of MyoD differentiated exclusively into skeletal myoblasts (no cardiac or smooth muscle cells) that fused to form myotubes capable of spontaneous contraction. Thus, the specific muscle cell type formed was controlled by the expression of MyoD. These results provided evidence that the specific cell type formed (whether it be muscle, neuronal, or other cell types) can be controlled in vitro. Further, these results demonstrated that ES cells can provide a source of multiple differentiated cell types that can be used for transplantation.

scholarly journals Ultrastructure of Feline Mammary Hypertrophy

1983 ◽  
Vol 20 (3) ◽  
pp. 254-264 ◽  
Author(s):  
D. W. Hayden ◽  
K. H. Johnson ◽  
H. K. Ghobrial
Keyword(s):  
Basal Lamina ◽  
Plasma Membranes ◽  
Secretory Activity ◽  
Cell Types ◽  
Myoepithelial Cells ◽  
Mammary Tissue ◽  
Stromal Fibroblasts ◽  
Cell Layers ◽  
Multiple Cell ◽  
One Year

The ultrastructure of feline mammary hypertrophy was studied in a five-month-old female which had aborted recently, a ten-year-old female which was one month postestrus, and a four-year-old progestin-treated neutered male. Morphologic comparisons were made to normal mammary tissue from a one-year-old female cat. Hypertrophied mammary tissue had the same cell types and spatial relationships as did the normal gland. Major differences included a more highly developed duct system composed of metabolically active cells which often were arranged in multiple cell layers, and periductular stroma with increased fibroblasts and vascularization. Hypertrophied epithelial cells were characterized generally by smooth-contoured nuclear membranes, more evenly dispersed heterochromatin, prominent nucleoli, increased polyribosomes, and elongated mitochondria. Secretory activity was developed significantly only in the cat that had aborted recently. Modifications in myoepithelial cells included: more evenly dispersed nuclear heterochromatin, thicker bundles of cytoplasmic filaments, more straight plasma membranes along the basal lamina, and elongated hemidesmosomes. Multilayering of the basal lamina was accentuated. Stromal fibroblasts had nuclear heterochromatin distributed similarly to that of epithelial and myoepithelial cells, and increased rough endoplasmic reticulum. Myoepithelial cells did not contribute to the increased stromal cellularity. No significant ultrastructural differences were noted between mammary hypertrophy in young, old, and progestin-treated cats.

scholarly journals Featured Article: Temporal responses of human endothelial and smooth muscle cells exposed to uniaxial cyclic tensile strain

2015 ◽  
Vol 240 (10) ◽  
pp. 1298-1309 ◽  
Author(s):  
Alexandra M Greiner ◽  
Sarah A Biela ◽  
Hao Chen ◽  
Joachim P Spatz ◽  
Ralf Kemkemer
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Actin Cytoskeleton ◽  
Focal Adhesion ◽  
Tensile Strain ◽  
Muscle Cells ◽  
Cell Types ◽  
Cell Type ◽  
Cyclic Tensile Strain ◽  
Cell Type Specific

The physiology of vascular cells depends on stimulating mechanical forces caused by pulsatile flow. Thus, mechano-transduction processes and responses of primary human endothelial cells (ECs) and smooth muscle cells (SMCs) have been studied to reveal cell-type specific differences which may contribute to vascular tissue integrity. Here, we investigate the dynamic reorientation response of ECs and SMCs cultured on elastic membranes over a range of stretch frequencies from 0.01 to 1 Hz. ECs and SMCs show different cell shape adaptation responses (reorientation) dependent on the frequency. ECs reveal a specific threshold frequency (0.01 Hz) below which no responses is detectable while the threshold frequency for SMCs could not be determined and is speculated to be above 1 Hz. Interestingly, the reorganization of the actin cytoskeleton and focal adhesions system, as well as changes in the focal adhesion area, can be observed for both cell types and is dependent on the frequency. RhoA and Rac1 activities are increased for ECs but not for SMCs upon application of a uniaxial cyclic tensile strain. Analysis of membrane protrusions revealed that the spatial protrusion activity of ECs and SMCs is independent of the application of a uniaxial cyclic tensile strain of 1 Hz while the total number of protrusions is increased for ECs only. Our study indicates differences in the reorientation response and the reaction times of the two cell types in dependence of the stretching frequency, with matching data for actin cytoskeleton, focal adhesion realignment, RhoA/Rac1 activities, and membrane protrusion activity. These are promising results which may allow cell-type specific activation of vascular cells by frequency-selective mechanical stretching. This specific activation of different vascular cell types might be helpful in improving strategies in regenerative medicine.

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