Development beyond the gastrula stage and digestive organogenesis in the apple-snail Pomacea canaliculata (Architaenioglossa, Ampullariidae).

Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenteron's lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.

Development beyond the gastrula stage and digestive organogenesis in the apple-snail Pomacea canaliculata (Architaenioglossa, Ampullariidae)

Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenterons lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.(AU)

Development beyond the gastrula stage and digestive organogenesis in the apple-snail Pomacea canaliculata (Architaenioglossa, Ampullariidae)

Development of Pomacea canaliculata from the gastrula stage until the first day after hatching is described. Trochophore embryos are developed after gastrulation, showing the prototroch as a crown of ciliated orange-brownish cells. However, no true veliger embryos are formed, since the prototroch does not fully develop into a velum. Afterward, the connection between the fore- and midgut is permeated and the midgut becomes full of the pink-reddish albumen, which is stored into a central archenteron's lake, from where it is accumulated into the large cells forming the midgut wall ("giant cells"). Electron microscopy of giant cells in late embryos showed that albumen is engulfed by large endocytic vesicles formed between the irregular microvilli at the top of these cells. By the end of intracapsular development, giant cells become gradually replaced by two new epithelial cell types which are similar to those found in the adult midgut gland: the pre-columnar and the pre-pyramidal cells. Pre-columnar cells have inconspicuous basal nuclei and are crowned by stereocilia, between which small endocytic vesicles are formed. Pre-pyramidal cells have large nuclei with 2-3 nucleoli and show a striking development of the rough endoplasmic reticulum. The genesis of the three cell lineages (giant, pre-columnar and pre-pyramidal cells) is hypothetically attributed to epithelial streaks that occur at both sides of the midgut since early stages of development.

Acantholytic ectodermal dysplasia: clinicopathological study of a new desmosomal disorder.

We describe two boys with curly hair, palmoplantar keratoderma and skin fragility who presented clinical and histological features similar, but not identical, to those exhibited by patients with ectodermal dysplasia-skin fragility syndrome (McGrath syndrome) and other genetic desmosomal defects such as Carvajal syndrome and Naxos disease. Clinical features included trauma-induced blisters and erosions, palmoplantar keratoderma and hyperkeratotic, fissured plaques with perioral involvement. The patients had abundant curly scalp hair, and normal eyebrows and eyelashes. Sweating was normal. Nails were normal at birth but subsequently showed secondary dystrophy. Histopathological analysis of the skin demonstrated acantholysis and intercellular widening of the spinous and granular layers in involved regions. No involvement of scalp skin was seen. Desmosomes were markedly reduced in number and poorly developed with no clear insertions of the keratin filaments. The latter were clumped around the nuclei. Immunostaining of patient skin with antibodies raised against key desmosomal proteins demonstrated disrupted expression of desmoplakin, plakoglobin and desmoglein 1. Additional studies of the family history and of the desmoplakin, plakoglobin and desmoglein 1 genotype for both patients may help further elucidate the molecular cause of this variation on ectodermal dysplasia-skin fragility syndrome.

Cerebriform plantar hyperplasia: ultrastructural study of two cases.

In the present work we report the histopathological features of the cerebriform plantar hyperplasia observed in two patients with a mild form of the Proteus syndrome. Light microscopy revealed increased fibro-adipose tissue and adnexal structures in the dermis. Ultrastructurally, densely packed collagen fibrils variable in diameter and configuration, described as composite fibrils and unraveled fibrils, as well as a few fragmented elastic fibrils presenting an altered ratio between the elastin and the microfibrillar components were the major features observed. We consider that these histopathological findings will contribute to further delineate cerebriform plantar hyperplasia and also to establish clues for the early diagnosis of the Proteus syndrome.

Ultrastructural changes during nuclear maturation in Bufo arenarum oocytes.

During progesterone-induced nuclear maturation the oocytes of Bufo arenarum undergo a series of nuclear and cytoplasmic changes. The breakdown of heterocellular communications between the follicular cell projections and the oocyte microvilli, and the consequent enlargement of the perivitelline space, were observed at the animal pole. The more evident cytoplasmic feature during nuclear maturation comprised the gathering of glycogen granules in clusters, some phagocytosed by empty vesicles. With respect to the location of these vesicles, some were observed in close proximity to the oolemma and others were freely suspended in the perivitelline space, extruded from the oocyte. Other visible events were the disruption of the annulate lamellae, the formation of an elaborate cortical endoplasmic reticulum and the rearrangement of the cortical granules in a monolayer immediately beneath the oolemma together with aggregates of endoplasmic reticulum cisternae. Our results show that during nuclear maturation the nuclear oocyte changes include a flattening of the spherical oocyte nucleus, its migration towards the surface of the animal pole, the disappearance of the nucleoli and the dissolution of the nuclear envelope.

Wrinkly skin syndrome: ultrastructural alterations of the elastic fibers.

We report the clinical and pathologic features of a patient with wrinkly skin syndrome. The essential clinical features were wrinkly skin with poor elasticity over the abdomen and on the dorsum of the hands and feet, increased palmar and plantar creases, and a prominent venous pattern over the chest. On light microscopy, histopathologic findings included appreciable heterogeneity in the structure, amount, and distribution pattern of elastic fibers. Agglutination and fragmentation of the microfibrillar component and a remarkable decrease in elastin were the major ultrastructural features. The differential diagnosis with other connective tissue disorders is discussed.

Juvenile hyaline fibromatosis: ultrastructural study.

Juvenile hyaline fibromatosis is a multisystemic disorder characterized by a triad of cephalic fibrous outgrowths, gingival hyperplasia, and flexion contractures. The aim of this study was to find new ultrastructural features that could be useful for differentiating this entity from other types of fibromatosis. Mucosal lesions processed for light and electron microscopy by routine techniques showed hyperactive-appearing spindle-shaped fibroblasts and dysplastic mesenchymal cells. Dilated rough endoplasmic reticulum, prominent Golgi complexes, and multivesicular bodies as well as single membrane vesicles filled with fibrillogranular material were seen within the cytoplasm of dysplastic mesenchymal cells. Many fibrillogranular vesicles contained smaller vesicles. There were also invaginations of the cell membrane that contained fibrillogranular material similar to that seen in the single membrane vesicles, suggesting engulfment of an extracellular substance. The stroma contained both normal and serrated collagen fibrils, microfibrils, and two types of fibrillogranular material, one of them with a characteristic banding pattern. Our clinical and histopathologic findings resemble those previously described in cases of infantile systemic hyalinosis and juvenile hyaline fibromatosis. So many features of these two conditions overlap that it is difficult not to consider them as parts of a spectrum of the same disorder.