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At least 991 records · Page 55Linked to original sources
PubMed1979

[Cytological study of the hemopoietic organ in the crab: Carcinus maenas (L.) (Crustacea, Decapoda). (author's transl)].

A cytological observation, using conventional fixing and staining, is made on the hemopoietic tissue in the crab, Carcinus maenas. The hemopoietic organ is formed by nodules grouping different cell types; nodules are surrounded by a limiting layer including collagenous filaments and material looking like basal lamina. Some fibrocytes and semi-granulous hemocytes are lining this limited layer. These hemocytes, more or less flattened, are transforming in fibrocytes. Fibroblast-like cells, with well developed intercellular junctions, are the first cell type: their dedifferentiation gives rise to isolated mitoting cells. We have named these mitoting cells "hemocytoblast". They are stem cells for hyaline hemocytes. Fibroblast-like cells can be compared with "reticular cells" in Insects. Uncertainty exists as to the formation and evolution of nodules.

Animals↗
PubMed1977

[Ultrastructure of the testicular germinal zone and of the secondary spermatogonia in normal and destalked brachyuran decapod crustacea].

Ultrastructural study of gonia of various species of male crabs shows that these cells belong to two types : primary and secondary gonia; these are discriminated according to their location inside or outside germinative islets, i. e. by the presence or absence of surrounding somatic tissue. The most original feature of the primary spermatogonia concerns the extrusion of gonial material under the shape of lamellar bodies or granules engulfed by the contiguous mesodermic cells; the latter degenerate when they are full of germ cell remnants. Poorly differentiated, the primary gonia have no great variety of cytoplasmic organelles. However two characteristic structures can be recognized in juxtanuclear position : nuage material (electron dense bodies more or less associated with gonia) and chromatoid bodies. Lipid droplets, the significance of which is unknown occur sometimes. Secondary spermatogonia divide synchronously although they are placed side by side without any connection such as cytoplasmic bridges. No ultrastructural modification has been noticed among the two types of gonia in crabs deprived of eyestalks. Mesodermic tissue distributed between primary gonia probably has a double role : inhibition of the onset of gametogenesis (as in Amphipods) and prevention of gonia cytolysis by collecting of altered elements.

Animals↗
PubMed1980

Cytochemistry of the neurosecretory cells in the crab Menippe rumphii (Fabricius, Crustacea: Brachyura).

In Menippe rumphii five types of neurosecretory cells are found in the cerebral, commissural and thoracic ganglia. Detailed cytochemical observations on the neurosecretory cells revealed that they have responded strongly to saliva resistant PAS staining. Among proteins those rich in disulfides and sulhydryl groups are observed. Greater amounts of cytoplasmic RNA are observed in the reproductive season. Considerable amounts of lipids and phospholipids are also observed in the AS cells. The cytochemical differences between the NS cells and the nonsecretory neurons are also discussed.

Animals↗
PubMed1981

Cellular interactions and pattern formation in the development of the visual system of Daphnia magna (Crustacea, Branchiopoda). II. Induced retardation of optic axon ingrowth results in a delay in laminar neuron differentiation.

Groups of embryonic photoreceptors in one side of the compound eye of Daphnia were irradiated with an ultraviolet microbeam at a stage when the cells were postmitotic but had yet to elaborate axons. Immediately after irradiation, the embryos were placed under fluorescent illumination. On the average, 16 of the irradiated photoreceptors were killed by the exposure. Previous observations suggest that an approximately equal number were rescued by the post-irradiation fluorescent illumination. The schedule of differentiation of the rescued photoreceptors was affected such that their axons arrived at the target region in the optic lamina from 2 to 10 hr after they would have normally. Serial section electron microscopic analysis showed that differentiation of laminar neurons contacted by the delayed axons also was delayed by a length of time corresponding to the delay in axon arrival. These and previous observations indicate that the differentiation of laminar neurons is triggered by contact with optic axons and can be initiated over a period of several hours after these cells become postmitotic.

Animals↗
PubMedDate not supplied

[Artemia sp. (Crustacea, Anostracea) as intermediate host of Eurycestus avoceti Clark, 1954 (Cestoda, Cyclophyllidea) (author's transl)].

Examination of Artemia sp. (Crustacé, Anostracé) for natural infection by cysticercoids of Flamingolepis liguloides, Cestode of the Flamingo (Phoenicopterus ruber) shows the presence of three other cysticercoids of cestode parasites of the Flamingo in the hemocoele of the Branchiopode. A fourth one is reported as the cysticercoid of Eurycestus avoceti, Clark, 1954, which parasitizes the Avocet (Recurvirostra avosetta). The systematic position of this Cestode is always unknown. This report shows the importance of Artemia in the life cycle of Cestodes of Anseriforms and Charadriiforms birds in saline lagoons.

Animals↗
PubMed1994

Characterization of insulin receptor from the muscle of the shrimp Penaeus japonicus (Crustacea: Decapoda).

The beta-subunit of the insulin receptor from the muscle of the shrimp Penaeus japonicus exists as multiple subtypes with M(r) of 79,000, 77,000 and 75,000. Only the subunit of M(r) 79,000 is autophosphorylated after the addition of insulin. The autophosphorylation occurred specifically at Tyr residues, as demonstrated by the specific subsequent dephosphorylation by the phosphotyrosyl protein phosphatase from the human placenta. The detergent, Triton X-100, and the metal ion, Mn2+, caused a noticeable enhancement of the autophosphorylation of shrimp insulin receptors from the muscle. Okadaic acid activated the kinase activity of the insulin-stimulated insulin receptor, but not the basal activity of the insulin receptor without the addition of insulin. Further studies comparing the insulin binding of the shrimp insulin receptor in the regulation of kinase activity of the multiple beta-subunit subtypes from the shrimp muscle are under way.

Amino Acid Sequence↗
PubMedDate not supplied

A new bopyrid isopod Athelges neotenuicaudis (Crustacea: Isopoda: Epicaridea) parasitic on Pagurus kulkarnii from Visakhapatnam Coast, India.

A new bopyrid isopod Athelges neotenuicaudis is reported. The new isopod is collected from the crab Pagurus kulkarnii as ectoparasite. They are found in the intertidal region of Mukkam, Visakhapatnam Coast. Andhra Pradesh, India. Athelges neotenuicaudis n. sp. is compared with A. paguri Rathke, 1843; A. tenuicaudis Rathke, 1843; and A. bilobus Rathke.

Animals↗
PubMed1975

[Vesicles of the smooth endoplasmic reticulum in the Y organ of Carcinus maenas L. (Crustacea, Decapoda)].

The smooth endoplasmic reticulum in the Y organ cells consists of vesicular and tubular elements containing a slightly electron dense substance. The contents of these vesicles are released either at the gland surface or within the intercellular spaces. These processes which are concomitant with the hormonal activity preparatory to the molting, may represent the release of crustecdysone or of one of its precursors.

Animals↗