Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 6

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
1
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Ultrastructure of the jaws of the fossil and recent Eunicida (Polychaeta)

100%
Mierzejewska G., Mierzejewski P.
Acta Palaeontologica Polonica
|
1978
|
tom 23
|
nr 3
The ultrastructure of the jaws of Ordovician, Silurian, Permian and Recent Eunicida (Polychaeta) have been studied by transmission and scanning electron microscopy. Primary and secondary zones have been distinguished in the ultrastructure of the jaws. The primary zone is formed of the pharyngeal cuticle containing an orthogonal network of collagen fibrils, while the secondary zone, underlying the primary one, is developed of inner part of the pharyngeal cuticle devoid of a regular network of collagen fibrils. The two zones are pierced by microvilli. The jaws of placognath Eunicida are structured of the primary zone only. The Eunicida with highly organized jaw apparatus have a strongly developed secondary zone underlying the primary one. A preliminary correlation of evolutionary changes in the anatomy and ultrastructure of the jaws of Eunicida has been conducted. It has also been shown that the ultrastructural studies of the scolecodonts were not very useful for taxonomic purposes.
2
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Receptaculites abhorrens n. sp. from the Upper Devonian of Poland

100%
Mierzejewska G., Mierzejewski P.
Acta Palaeontologica Polonica
|
1973
|
tom 18
|
nr 2
Receptaculites abhorrens n.sp. from the Upper Frasnian of Lower Silesia is described. The species combines in a mosaic fashion the characteristics of the Receptaculites Deshayes and Ischadites Murchison.
3
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Xenognath type of polychaete jaw apparatuses

100%
Mierzejewski P., Mierzejewska G.
Acta Palaeontologica Polonica
|
1975
|
tom 20
|
nr 3
A new type of ?eunicid jaw apparatuses designated xenognath is described; it differs from previously known jaw apparatuses in having the denticulated ridges in compound jaws perpendicular to apparatus axis. It includes the Ordovician genus Archaeoprion nov., assigned to a new family Archaeoprionidae.
4
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

The ultrastructure of ribbon - like deposits over the thecae in Orthograptus Gracilis Roemer

100%
Urbanek A., Mierzejewska G.
Acta Palaeontologica Polonica
|
1978
|
tom 23
|
nr 4
The periderm of Orthograptus gracilis has bee studied with an electron microscope (TEM and SEM). Four components have been recognized within the thecal wall: 1. endocortex, 2. fusellar layer, 3. cortex and so-called 4. taeniocortex. Taeniocortex covering the outer surface of the thecal wall consists of ribbon or sometimes roller-like elements and is produced of a peculiar material. The data obtained do not confirm Andres' belief that ribbons are made of cortical material and that entire cortex was produced by deposition of ribbon-like units.
5
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

The fine structure of zooidal tubes in Sabelliditida and Pogonophora with reference to their affinity

100%
Urbanek A., Mierzejewska G.
Acta Palaeontologica Polonica
|
1977
|
tom 22
|
nr 3
Organic tubes of Sabelliditidae are a characteristic element of Lower Cambrian faunas. They were commonly compared with tubes of sedentary polychaetes, until Sokolov (1965) suggested their close affinity with Recent pogonophores. The aim of the present paper is to verify the latter hypothesis through a better understanding of ultrastructural features of zooidal tubes in both groups considered. The ultrastructure of the tube in Sabelliditida recognized for the first time by Urbanek, 1976 (in press), reveals that the wall of the tube is composed of two almost homogenous layers - the outer one and the inner one, and of the middle distinctly laminar layer. Characteristic wrinkles on the outer surface of the tube are made solely of the outer layer which is almost homogenous or with faint traces of some lammiation. The tubes in all Pogonophora under study display an entirely laminar structure. Wrinkles observed on certain areas of the tube are due to foldings involving numerous layers of the tube wall. Earlier biochemical and ultrastructural data and results of our ultrahistochemical observations are indicative of the presence of chitin, proteins (probably sclerotins) and mucopolysaccharides in the pogonophore tubes. The above results contribute to a better knowledge of the organic skeleton in both groups in question, but the problem of sabelliditid/pogonophore affinities remains unresolved. The degree and specificity of resemblance recognized at the submicroscopic level is not sufficient to confirm or disprove the hypothesis on close relationship between both groups considered.
6
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Scanning electron microscopy of sessile graptolites

81%
Urbanek A., Mierzejewska G., Mierzejewski P.
Acta Palaeontologica Polonica
|
1980
|
tom 25
|
nr 2
The surfaces of rhabdosomes in dendroid and tuboid graptolites and in Mastigograptus were investigated with SEM. In general the surfaces are remarkably smooth and essentially featureless, even around the apertures. The only exception are subparallel rollers recognized on one specimen of Dictyonema sp., which pass at places into accumulations producing a reticulated network. The evidence available indicates a foreign nature these structures which cannot be considered units of secretion of graptolite cortex. The opinion is advanced that the recent data are suggestive of collagen fibrillogenesis occuring immediately adjacent to the surface coat of epithelial cells. The lack of bandages in sessile graptolites and the lack of foreign agglutinated material on their rhabdosomes, the intimate control of fibrillogenesis by epithelial cells in extracellular secretion of collagen are all presented as evidence in favour of the membrane model of graptolite periderm secretion.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.