Ultrastructure of the envelopes of resistant and nonresistant Daphnia eggs

1979 ◽  
Vol 57 (9) ◽  
pp. 1773-1777 ◽  
Author(s):  
Lisa A. Seidman ◽  
John H. Larsen Jr.
Keyword(s):  
Plasma Membrane ◽  
Developmental Stage ◽  
Early Development ◽  
Outer Layer ◽  
Middle Layer ◽  
Outer Wall ◽  
Egg Envelope ◽  
Middle Component

During early development, the nonresistant egg of Daphnia had an outer wall of [Formula: see text], and an inner wall approximately the thickness of the plasma membrane. In the same genus at a comparable developmental stage, resistant eggs were surrounded by a three-layered envelope, [Formula: see text] thick. Although the outer layer [Formula: see text] of the latter appeared similar to the outer wall of the nonresistant egg, the middle layer [Formula: see text] resembled the crustacean procuticle. The outer layer developed before the formation of the middle component, and both structures were absent after development resumed. This suggests that the resistant egg envelope is characterized by an additional embryonic cuticle and molt.

Spore wall development in Sphagnum lescurii

1982 ◽  
Vol 60 (11) ◽  
pp. 2394-2409 ◽  
Author(s):  
Roy Curtiss Brown ◽  
Betty E. Lemmon ◽  
Zane B. Carothers
Keyword(s):  
Plasma Membrane ◽  
Outer Layer ◽  
Mature Spore ◽  
Outer Wall ◽  
Spore Wall ◽  
Spore Surface ◽  
Proximal Surface ◽  
Complex Development ◽  
Surface Ornamentation ◽  
Cortical System

The spore wall of Sphagnum is unique in the Bryophyta. The Sphagnum spore exine consists of two layers: an inner, lamellate layer (A layer) and a thick, homogenous, outer layer (B layer). The exine of other mosses consists of only the outermost homogenous layer and, at most, a thin ill-defined opaque layer. During development of the A-layer exine and the intine, a cortical system of evenly spaced microtubules underlies the plasma membrane. The ontogeny of the wall layers is not strictly centripetal. The A-layer exine develops evenly around the young spore immediately after cytokinesis. As the intine is deposited centripetally inside it, the homogenous B-layer exine is deposited outside the first-formed A layer. The B layer is responsible for the primary sculpturing of the spore surface. The mature spore is covered by an outermost perine, which is responsible for secondary surface ornamentation. A trilaesurate aperture develops on the proximal surface of each spore after deposition of the A layer. Ridges of the laesurae develop as a result of deposition of thick areas of intine. The ridges are eventually covered by the outer wall layers, whereas the fissure is covered only by the A layer and a very thin B-layer exine. The complex development of the trilaesurate aperture is evidence that the structure is not merely a mechanically induced "trilete mark" or "scar" resulting from compression of tetrahedrally arranged spores within a sporocyte wall.

Cell wall structures of Epicoccum nigrum (Hyphomycetes)

1973 ◽  
Vol 51 (5) ◽  
pp. 1071-1073 ◽  
Author(s):  
J. A. Brushaber ◽  
R. H. Haskins
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Outer Layer ◽  
Secondary Wall ◽  
Outer Wall ◽  
Wall Layer ◽  
Wall Material ◽  
Primary Wall ◽  
Electron Dense Material ◽  
Wall Structures

Two structurally distinct types of secondary wall layers are present in older hyphae in addition to the primary wall. A coarsely fibrous outer wall layer often becomes quite massive and frequently fuses with the outer wall layers of adjacent cells in the formation of hyphal strands. The uneven deposition of this outer layer often produces large verrucosities. The inner secondary wall layer is relatively electron transparent and contains a reticulum of electron-dense lines. The interface of the inner secondary wall with the cytoplasm is often very irregular, and sections of the plasma membrane are frequently overlain by wall material. The outer secondary wall of conidia is composed of an electron-dense material different from that of the outer wall of hyphae. Cells in the multicellular conidia tend to be polyhedral in shape with either very thick primary walls or thin primary walls having a thick inner wall deposit.

The Gametophore and Sporophyte of Mittenia plumula (Mitt.) Lindb

1961 ◽  
Vol 9 (2) ◽  
pp. 124 ◽  
Author(s):  
IG Stone
Keyword(s):  
Early Development ◽  
Outer Layer ◽  
Middle Layer ◽  
Anticlinal Wall ◽  
Outermost Layer ◽  
Periclinal Walls

An account is given of the gametophore and sporophyte of Mittenia plumula, stressing those features which have not previously been described. The moss has a highly refractive lenticular protonema. There is variation in the arrangement of leaves on sterile and fertile shoots, a shoot may develop one or more side shoots at its base, and hairs are present in the axils of leaves. The capsule has a few small stomata at the base, and the inner peristome consists of 28-32 processes. The double peristome of Mittenia plumula originates from three concentric layers of cells, the two innermost layers of the amphithecium and the outermost layer of the endothecium. In all other members of the Bryales whose examination has included early development, the peristome has been found to develop from amphithecial tissue only. The 16 outer peristorno teeth are forined on the periclinwl walls separating the two outer peristome layers, thickening being laid down on the inner walls of the outer layer, which is composed of 16 cells, and in adjoining posit'ions on tho outor walls of the middle layer, which is composed of eight cells. The inner peristome processes are formed on the periclinal walls separating the middle from the inner peristome layer (the latter being endothecial in origin). Thickening is laid down on the inner walls of the middle layer at positions contiguous with the junctions of the anticlinal walls of the inner layer, which is composed of 24-28 cells. Extra processes usually develop where the anticlinal wall is part of the original quadrant wall of the embryo. A smaller amount of thickening is then contributed to the processes from the inner peristome layer. Variations in the development of the inner peristome are discussed, and a comparison is made with development of the double peristome of other members of the Diplolepideae.

A New Type of Muscle Cell from the Subumbrella of Obelia

1968 ◽  
Vol 48 (3) ◽  
pp. 667-688 ◽  
Author(s):  
David M. Chapman
Keyword(s):  
Plasma Membrane ◽  
Surface Area ◽  
Muscle Cell ◽  
Outer Layer ◽  
Close Contact ◽  
Middle Layer ◽  
Innermost Layer ◽  
New Type ◽  
Whole Mounts

The subumbrella of the hydrozoan medusa Obelia consists of three layers of cells. The innermost layer is the endodermal lamella whose broad polygonal cells are in close contact with the middle layer of polygonal myocytes which have striated myofibrils running in two layers at right angles to one another in the same cell. These myofibrils extend beyond the myocytes as plasma membrane-enclosed prongs to make contact with the prongs of neighbouring cells in such a way that whole mounts give the impression that the slender myofibrils are continuous over the subumbrella. Cross-layered myocytes can be seen to be another means of decreasing the surface area of the subumbrella, a condition necessary for medusoid locomotion. Helically banded radial myofibrils are found in the outer layer.

Review — The Orientation of Cellulose Microfibrils in the cell walls of Tracheids in Conifers

IAWA Journal ◽  
2005 ◽  
Vol 26 (2) ◽  
pp. 161-174 ◽  
Author(s):  
Hisashi Abe ◽  
Ryo Funada
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Outer Layer ◽  
Cell Walls ◽  
Secondary Wall ◽  
Middle Layer ◽  
Cellulose Microfibrils ◽  
Conifer Species ◽  
Predominant Orientation ◽  
Scanning Electron

We examined the orientation of cellulose microfibrils (Mfs) in the cell walls of tracheids in some conifer species by field emission-scanning electron microscopy (FE-SEM) and developed a model on the basis of our observations. Mfs depositing on the primary walls in differentiating tracheids were not well-ordered. The predominant orientation of the Mfs changed from longitudinal to transverse, as the differentiation of tracheids proceeded. The first Mfs to be deposited in the outer layer of the secondary wall (S1 layer) were arranged as an S-helix. Then the orientation of Mfs changed gradually, with rotation in the clockwise direction as viewed from the lumen side of tracheids, from the outermost to the innermost S1 layer. Mfs in the middle layer of the secondary wall (S2 layer) were oriented in a steep Z-helix with a deviation of less than 15° within the layer. The orientation of Mfs in the inner layer of the secondary wall (S3 layer) changed, with rotation in a counterclockwise direction as viewed from the lumen side, from the outermost to the innermost S3 layer. The angle of orientation of Mfs that were deposited on the innermost S3 layer varied among tracheids from 40° in a Z-helix to 20° in an S-helix.

Direct measurement of transverse residual strains in aorta

1996 ◽  
Vol 270 (2) ◽  
pp. H750-H759 ◽  
Author(s):  
H. C. Han ◽  
Y. C. Fung
Keyword(s):  
Stress State ◽  
Outer Layer ◽  
Residual Strain ◽  
Longitudinal Axis ◽  
Outer Wall ◽  
Residual Strains ◽  
Stress States ◽  
Sectional Surface ◽  
Thoracic And Abdominal ◽  
Load State

Residual strains were measured in the porcine aorta. Segments were cut from the aorta perpendicular to its longitudinal axis. Microdots of water-insoluble black ink were sprinkled onto the transverse sectional surface of the segments in the no-load state. The segments were then cut radially, and sectional zero-stress states were approached. The coordinates of selected microdots (2-20 microns) were digitized from photographs taken in the no-load state and the zero-stress state. Residual strains in the transverse section were calculated from the displacement of the microdots. The circumferential residual strains on the inner wall and outer wall were calculated from the circumferential lengths in the no-load state and the zero-stress state. Results show that the circumferential residual strain is negative (compressive) in the inner layer of the aortic wall and positive (tensile) in the outer layer, whereas the radial residual strain is tensile in the inner layer and compressive in the outer layer. This residual strain distribution reduces the stress concentration in the aorta under physiological load. The experimental results compared well with theoretical estimations of a cylindrical model. Regional difference of the residual strain exists and is significant (P < 0.01), e.g., the circumferential residual strains on the inner wall of the ascending, descending thoracic, and abdominal regions of the aorta are -0.133 +/- 0.019, -0.074 +/- 0.020, and -0.046 +/- 0.017 (mean +/- SD), respectively. More radial cuts of a segment produced no significant additional strains. This means that an aortic segment after one radial cut can be considered as the zero-stress state.

scholarly journals The three muscle layers in the pyloric sphincter and their possible function during antropyloroduodenal motility

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mi-Sun Hur ◽  
Seunggyu Lee ◽  
Tong Mook Kang ◽  
Chang-Seok Oh
Keyword(s):  
Outer Layer ◽  
Longitudinal Muscle ◽  
Middle Layer ◽  
Comprehensive Approach ◽  
Pyloric Sphincter ◽  
Muscular Tissue ◽  
Micro Ct ◽  
Circular Layer ◽  
Korean Adult ◽  
Longitudinal Layer

AbstractThis study was conducted to determine the muscular arrangement of the human pyloric sphincter using a comprehensive approach that involved microdissection, histology, and microcomputed tomography (micro‐CT). The stomachs of 80 embalmed Korean adult cadavers were obtained. In all specimens, loose muscular tissue of the innermost aspect of the sphincter wall ran aborally, forming the newly found inner longitudinal muscle bundles, entered the duodenum, and connected with the nearby circular bundles. In all specimens, approximately one-third of the outer longitudinal layer of the sphincter entered its inner circular layer, divided the circular layer into several parts, and finally connected with the circular bundles. Anatomical findings around the sphincter were confirmed in micro-CT images. The sphincter wall comprised three layers: an inner layer of longitudinal bundles, a middle layer of major circular and minor longitudinal bundles, and an outer layer of longitudinal bundles. The stomach outer longitudinal bundles were connected to the sphincter circular bundles. The inner longitudinal bundles of the sphincter were connected to the adjacent circular bundles of the duodenum.

scholarly journals Validation of Age Estimation in the Harp Seal, Phoca groenlandica, Using Dentinal Annuli

1983 ◽  
Vol 40 (9) ◽  
pp. 1430-1441 ◽  
Author(s):  
W. D. Bowen ◽  
D. E. Sergeant ◽  
T. Øritsland
Keyword(s):  
Outer Layer ◽  
Age Estimation ◽  
Transverse Section ◽  
Age Determination ◽  
Middle Layer ◽  
Harp Seal ◽  
Growth Layer ◽  
Phoca Groenlandica ◽  
Incremental Growth ◽  
Absolute Age

We investigated the validity and accuracy of age estimation in harp seals, Phoca groenlandica, using a sample of 155 known-age teeth from seals age 3 mo to 10 yr. Under transmitted light, transverse sections of harp seal canine teeth showed distinct incremental growth layers (IGLs) in the dentine. The first growth-layer group (GLG), representing Ist-year growth, consists of two IGLs: an outer layer of opaque dentine, bounded by the neonatal line, and an inner layer of translucent dentine. Subsequent GLGs, each representing 1 yr of growth, generally consist of three IGLs: an outer layer of interglobular dentine deposited during the annual molt in April, a middle layer of opaque dentine formed during the northward spring migration (May–June), and an inner layer of translucent dentine formed from July to March. We show that dentinal GLGs can be used to estimate the absolute age of harp seals. The accuracy of the method decreases with age. Only 72.4% of estimates of 0-group seals were correct using only transverse sections. These errors were virtually eliminated (99.0% correct age determination) when the tooth root was examined. Based on a single examination of a transverse section, the probabilities of correctly estimating age are 0.983, 0.889, 0.817, and 0.553 at ages 1, 2, 3, and 4 + yr, respectively, when clearly inaccurate tag-tooth associations are omitted. The respective probabilities are only slightly higher when age is based on the average of five blind readings, being 1.0, 0.889, 0.833, and 0.625. Beyond age 3 yr, existing data are insufficient to estimate reliably the accuracy of age determined by counting GLGs.

Influence of Heat Insulation Material on Thermal Stress of Long Nozzle

2012 ◽  
Vol 535-537 ◽  
pp. 1609-1614 ◽  
Author(s):  
Hui Min Liu
Keyword(s):  
Thermal Stress ◽  
Layer Thickness ◽  
Outer Layer ◽  
Heat Insulation ◽  
Outer Wall ◽  
Symmetric Model ◽  
Insulation Material ◽  
Axially Symmetric ◽  
Coefficient Of Thermal Conductivity ◽  
Heat Insulation Material

To prevent a long nozzle (LN) of non-preheating from rupture caused by thermal shock, heat insulation material (HIM) with a lower coefficient of thermal conductivity (CTC) was compounded in the inner hole (inner layer) or around the outer wall (outer layer), and the thermal stress was investigated. The two-dimension axially symmetric model of LN was proposed by simplifying the structure and boundary conditions. The influences of the HIM to the thermal stress of LN were analyzed by finite element method. The results show that the thermal stress suffered by LN can be drastically reduced by the inner layer, making the slow variation, but when its thickness increases from 2 mm to 3 mm, it almost has no influence on the thermal stress. The maximum thermal stress at the neck of LN reduces with the depression of the CTC at the inner layer thickness of 2 mm. The maximum thermal stress of LN can’t be reduced by outer layer, but the lasting time of higher stress can be shortened, and the thermal stress at the later period of steel-irrigating can be lowed. When the outer layer thickness is more than 2 mm, the increase of it has little influence on the thermal stress of LN, and the change of its CTC has little influence on the thermal stress either. The LN with tri-layer has lower thermal stress during all the period of steel-irrigating.

The Cuticle of Cysticerci of Taenia Saginata, T. Hydatigena, and T. Pisiformis

1963 ◽  
Vol s3-104 (65) ◽  
pp. 141-144
Author(s):  
E. H. SIDDIQUI
Keyword(s):  
Electron Microscopy ◽  
Outer Layer ◽  
Middle Layer ◽  
Taenia Saginata ◽  
Optical And Electron Microscopy

The structure of the cuticle of the cysticerci of 3 species of Taenia was studied by means of optical and electron microscopy. In all 3 species the cuticle is composed of 3 layers and covered with hair-like processes. The middle layer, which comprises the bulk of the cuticle, varies in thickness from head to bladder, but there are no differences in thickness between the species studied. The hairs are composed of a core representing an extension of the middle layer and are covered by a continuation of the outer layer. The arrangement of these hairs varies in the species studied.

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