Stromatoporoids: Internal Morphology

1983 ◽  
Vol 7 ◽  
pp. 149-156
Author(s):  
Carl W. Stock

There are two levels at which the internal structure of a stromatoporoid is classified. The first level includes structures which can be discerned in a thin section using low magnifications (10X); these are called macrostructures. The second level is composed of structures that are not evident unless a thin section is magnified to a higher degree (50X-100X). These smaller scale aspects are referred to as microstructures.

1964 ◽  
Vol S7-VI (1) ◽  
pp. 10-12
Author(s):  
Georgette Glacon

Abstract Radiography of the internal morphology of shells of foraminifera living on the Tunisian coast solved a number of problems by making possible examination of large numbers of individuals with an economy of time and specimens. Disadvantages encountered were structural damage resulting from X-ray flux of too great intensity, and poor visibility of internal structure in foraminifera from clay or pyritic sediments.


Author(s):  
Gregory Stump

Inflection is the systematic relation between words’ morphosyntactic content and their morphological form; as such, the phenomenon of inflection raises fundamental questions about the nature of morphology itself and about its interfaces. Within the domain of morphology proper, it is essential to establish how (or whether) inflection differs from other kinds of morphology and to identify the ways in which morphosyntactic content can be encoded morphologically. A number of different approaches to modeling inflectional morphology have been proposed; these tend to cluster into two main groups, those that are morpheme-based and those that are lexeme-based. Morpheme-based theories tend to treat inflectional morphology as fundamentally concatenative; they tend to represent an inflected word’s morphosyntactic content as a compositional summing of its morphemes’ content; they tend to attribute an inflected word’s internal structure to syntactic principles; and they tend to minimize the theoretical significance of inflectional paradigms. Lexeme-based theories, by contrast, tend to accord concatenative and nonconcatenative morphology essentially equal status as marks of inflection; they tend to represent an inflected word’s morphosyntactic content as a property set intrinsically associated with that word’s paradigm cell; they tend to assume that an inflected word’s internal morphology is neither accessible to nor defined by syntactic principles; and they tend to treat inflection as the morphological realization of a paradigm’s cells. Four important issues for approaches of either sort are the nature of nonconcatenative morphology, the incidence of extended exponence, the underdetermination of a word’s morphosyntactic content by its inflectional form, and the nature of word forms’ internal structure. The structure of a word’s inventory of inflected forms—its paradigm—is the locus of considerable cross-linguistic variation. In particular, the canonical relation of content to form in an inflectional paradigm is subject to a wide array of deviations, including inflection-class distinctions, morphomic properties, defectiveness, deponency, metaconjugation, and syncretism; these deviations pose important challenges for understanding the interfaces of inflectional morphology, and a theory’s resolution of these challenges depends squarely on whether that theory is morpheme-based or lexeme-based.


2020 ◽  
Vol 2 (1) ◽  
pp. 323-331 ◽  
Author(s):  
Pia Otto ◽  
Stephan Bergmann ◽  
Alice Sandmeyer ◽  
Maxim Dirksen ◽  
Oliver Wrede ◽  
...  

We investigate the internal structure of smart core–shell microgels by super-resolution fluorescence microscopy by combining of 3D single molecule localization and structured illumination microscopy using freely diffusing fluorescent dyes.


Author(s):  
Rolf Elofsson ◽  
Rita Walleén

Aesthetascs situated on the first antennae of crustaceans are easily recognized and distinguished from other sensilla by their hose-like appearance and thin cuticle. Their internal structure is known from decapod, mysid and isopod, i.e. malacostracan crustaceans. The aesthetasc is characterized in these animals by a large number of sensory neurons below each single aesthetasc. The neurons give rise to - from their dendrites - two cilia. The cilia protrude into the external hose-like portion of the aesthetasc splitting up into many branches. It is generally agreed that the aesthetascs are the structural base for crustacean olfaction and experiments to verify this have been performed mostly on malacostracan species.The water-flea, Daphnia, is a non-malacostracan species. It has greatly reduced first antennae and externally only nine pairs of aesthetascs remain (Figs 1, 2). The outer morphology agrees with that of malacostracan species. The internal morphology does not. Each of these aesthetascs has only four sensory cells situated deep inside the animal. The sensory cells have only one cilium (Fig. 3) extending unbranched into the external portion of the aesthetasc (Fig. 4).


Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.


Author(s):  
H.W. Deckman ◽  
B.F. Flannery ◽  
J.H. Dunsmuir ◽  
K.D' Amico

We have developed a new X-ray microscope which produces complete three dimensional images of samples. The microscope operates by performing X-ray tomography with unprecedented resolution. Tomography is a non-invasive imaging technique that creates maps of the internal structure of samples from measurement of the attenuation of penetrating radiation. As conventionally practiced in medical Computed Tomography (CT), radiologists produce maps of bone and tissue structure in several planar sections that reveal features with 1mm resolution and 1% contrast. Microtomography extends the capability of CT in several ways. First, the resolution which approaches one micron, is one thousand times higher than that of the medical CT. Second, our approach acquires and analyses the data in a panoramic imaging format that directly produces three-dimensional maps in a series of contiguous stacked planes. Typical maps available today consist of three hundred planar sections each containing 512x512 pixels. Finally, and perhaps of most import scientifically, microtomography using a synchrotron X-ray source, allows us to generate maps of individual element.


Author(s):  
E. Keyhani

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.


Author(s):  
Leo Barish

Although most of the wool used today consists of fine, unmedullated down-type fibers, a great deal of coarse wool is used for carpets, tweeds, industrial fabrics, etc. Besides the obvious diameter difference, coarse wool fibers are often medullated.Medullation may be easily observed using bright field light microscopy. Fig. 1A shows a typical fine diameter nonmedullated wool fiber, Fig. IB illustrates a coarse fiber with a large medulla. The opacity of the medulla is due to the inability of the mounting media to penetrate to the center of the fiber leaving air pockets. Fig. 1C shows an even thicker fiber with a very large medulla and with very thin skin. This type of wool is called “Kemp”, is shed annually or more often, and corresponds to guard hair in fur-bearing animals.


Author(s):  
P. Satir ◽  
J. Wais-Steder ◽  
J. Avolio
Keyword(s):  

In 1977, Sale and Satir showed that active microtubule sliding in trypsin-treated Tetrahymena axonemes is always of a single polarity. If the doublet bearing active arms is labelled N, by convention, the doublet that is pushed by those arms is N+l. In active sliding in trypsin-treated axonemes doublet N+l is always displaced tipwards with respect to N. Several different configurations of the dynein arms have been described. These include: (1) an extended configuration, where the dynein arms are tilted about 40° towards the base of the axoneme and are long enough to span the space between doublets N and Ntl completely (2) a standard, unattached image, such as is usually seen in thin section. In this configuration, the arms do not span the interdoublet gap. (3) the rigor image, where the arms always bridge the gap. This differs from the extended configuration because tilt is often absent, so that the arms often lie normal to doublets N and N+l.


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