Ultrastructure of Mehlis' gland in the lung fluke, <i>Paragonimus ohirai</i> (Trematoda: Troglotrematidae)

Orido, Yasuhide

doi:10.1002/jmor.1052070103

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…In the ootype Mehlis' gland complexes of Paragonimus ohirai and O. viverrini, the distribution of cell types shows a distinct polarization (Orido 1991). Unlike Orido's observations of P. ohirai, however, our study of the ootype of O. viverrini indicated that type 1 secretions are clearly proximal and associated with formation of eggshell precursor secretions into an eggshell, whereas the location of type 2 secretions correlate with a more ordered eggshell.…”

Section: Discussioncontrasting

confidence: 80%

Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)

et al. 2011

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Eggs of most species digenean flukes hatch in the external environment to liberate larvae that seek and penetrate a snail intermediate host. Those of the human liver flukes, Opisthorchis viverrini, hatch within the gastrointestinal canal of their snail hosts. While adult parasites are primarily responsible for the pathology in cases of human opisthorchiasis, their eggs also contribute by inducing granulomata and in serving as nidi for gallstone formation. In view of the peculiar biology of O. viverrini eggs and their contribution to pathology, we investigated embryogenesis in this species by light and transmission electron microscopy. Egg development was traced from earliest stages of coalescence in the ootype until full embryonation in the distal region of the uterus. Fully mature eggs were generally impermeable to resin and could not be examined by conventional electron microscopy methods. However, the use of high-pressure freezing and freeze-substitution fixation of previously fixed eggs enabled the internal structure of mature eggs, particularly the subshell envelopes, to be elucidated. Fertilization occurs in the ootype, and the large zygote is seen therein with a single spermatozoon wrapped around its plasma membrane. As the zygote begins to divide, the spent vitellocytes are pushed to the periphery of the eggs, where they progressively degrade. The early eggshell is formed in the ootype by coalescing eggshell precursor material released by approximately six vitelline cells. The early eggs have a thinner eggshell and are larger than, but lack the characteristic shape of, mature eggs. Characteristic shell ornamentation, the "muskmelon" appearance of eggs, appears after eggshell polymerization in the ootype. Pores are not present in the shell of O. viverrini eggs. The inner and outer envelopes are poorly formed in this species, with the outer envelope evident beneath the eggshell at the opercular pole of the mature egg. The miracidium has a conical anterior end that lacks the distinctive lamellar appearance of the terebratorium of other digeneans, such as the schistosomes. The miracidium is richly glandular, containing an apical gland in the anterior end, large cephalic gland, and posterior secretory glands. Each gland contains a secretory product with different structure. The paucity of vitelline cells associating with eggs, the reduced size of eggs, and reduced complexity of the extraembryonic envelopes are interpreted as adaptations to the peculiar hatching biology of the miracidia.

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Section: Discussioncontrasting

confidence: 80%

Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)

et al. 2011

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“…Much variations in numbers, types and arrangement of these glands has been documented 1 . Most studies of Mehlis' gland have been conducted in Digenea 2,3, 4,5,6,7,8,9,10,11,12 , but ultrastructural studies of the following monogeneans have also been published: Diplozoon paradoxum and Calicotyle kroyeri 13 , Cichlidogyrus halii typicus 14 , Entobdella hipoglossi 15 and Entobdella soleae 15,16 .…”

Section: Introductionmentioning

confidence: 99%

Estudos ultraestruturais da glândula de Mehlis de Metamicrocotyla macracantha (Monogenea, Microcotylidae) parasito de Mugil liza (Teleostei)

Farias

Cohen

2005

Braz. J. Vet. Res. Anim. Sci.

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A ultraestrutura da glândula de Mehlis de Metamicrocotyla macracantha, parasita de brânquia coletado de Mugil liza do Rio de Janeiro, Brasil, foi estudado através da microscopia eletrônica de transmissão. A glândula de Mehlis consiste de dois tipos de células secretoras, S1 e S2, cada uma produzindo um corpo secretor diferente. Os corpos S1 são esféricos, em forma de lamelas e observados em diferentes estágios de desenvolvimentos no citoplasma dessas células. Os corpos S2 são esféricos a ovais com conteúdos densos, apresentando uma estrutura cristalina. O citoplasma das células da glândula de Mehlis apresenta também ribossmas livres, retículo endoplasmático granular e complexo de Golgi, organelas características de células secretoras.

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Ultrastructure of the foregut and associated glands in the lung fluke,Paragonimus miyazakii (Digenea: Troglotrematidae), with particular reference to their functional roles

et al. 1998

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The foregut and associated glands of a digenetic trematode, Paragonimus miyazakii, were examined in the forebody by transmission and scanning electron microscopy as well as by light microscopy, and their functional roles were discussed. The foregut is lined with a general tegument without spines and sensory receptors throughout its length, although it consists of the mouth, pharynx, and esophagus. This foregut tegument is regionally and intraregionally modified in appearance, suggesting the performance of auxiliary functions in digestion. This appearance is characterized by long, frequent cytoplasmic extensions of the apical tegument around the middle portion of the mouth and the anterior esophagus. Electron‐dense granules and multimembranous and multilamellar bodies are developed in the tegument to various degrees, and elaborately in the apical layer of the prepharynx. A single type of unicellular gland is embedded in the antero‐middle part of the worm in small groups. The gland cells synthesize clear secretory granules as a chief product, each granule with a pleomorphic, dense, core‐like inclusion. Mature granules are elliptical in shape, approximately 500 nm in diameter, and are subsequently discharged into the prepharyngeal foregut lumen after passing through the elongated cytoplasm of the gland cell. In the prepharynx and pharynx, host blood cells are apparently processed for digestion. In the wide lumen of the esophagus, foodstuff could undergo sufficient digestion prior to absorption by the cecal epithelium. J. Morphol. 237:43–52, 1998. © 1998 Wiley‐Liss, Inc.

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Ultrastructure of Mehlis' gland in the lung fluke, Paragonimus ohirai (Trematoda: Troglotrematidae)

Cited by 5 publications

References 13 publications

Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)

Light and electron microscopy observations of embryogenesis and egg development in the human liver fluke, Opisthorchis viverrini (Platyhelminthes, Digenea)

Estudos ultraestruturais da glândula de Mehlis de Metamicrocotyla macracantha (Monogenea, Microcotylidae) parasito de Mugil liza (Teleostei)

Ultrastructure of the foregut and associated glands in the lung fluke,Paragonimus miyazakii (Digenea: Troglotrematidae), with particular reference to their functional roles

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