摘要:

Accelerated spiculogenesis in the sea urchin,Stomopneustes variolaris(Lamarck), was followed during embryonic development. The results indicated that primary mesenchyme cells migrated into the blastocoel in the blastula stage embryo, extended spicules formed in the early gastrula, and a pair of much more elaborate spicules was constructed in the prism stage. In addition, an Okazaki type of micromere-derived primary mesenchyme cell (PMC) culture was employed to induce spicule formationin vitro.Micromeres, which were isolated from 16-cell stage embryos and cultured in seawater containing 3% horse serum, readily differentiated into primary mesenchyme cells. They extended filopodia and formed spicules at 24 h and 48 h after fertilization, respectively. When sera from various organisms were used in the micromere-derived PMC culture, goat and porcine sera produced spicules 10 times greater in number than calf, horse, and rabbit sera. The results suggest thatS. variolaris, with its accelerated development of embryonic spicules and the ability to produce spicules in micromere-derived PMC culturein vitro, is an ideal system to study the mechanisms regulating spiculogenesis.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652372

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The midgut epithelium of larval Lepidoptera consists of a monolayer of mature columnar and goblet cellsin vivowith loosely bound stem cells at its base. Cultures ofHeliothis virescensmidgut contained quiescent and dividing stem cells, differentiating and mature cells as well as small rows of attached cells, randomly distributed in the culture vessel. Fixed cultures were immunostained with polyclonal antibodies to fibronectin and integrin β1. Many stem cells stained darkly; lighter staining stem cells imply that some stem cells can become less adhesive. Developing cells were pale, lacking integrin and fibronectin epitopes on their surfaces, and were probably poorly adhesive. During a moltin vivo, differentiating stem cells insert between existing epithelial cells, increasing gut size; lack of stickiness would enable them to do so. As pre-columnar cells differentiatedin vitro, stainability reappeared. Mature columnar cells were decorated with a pattern of intense surface immunostaining material. Small immature columnar and goblet cells adhered to the distal ends of mature columnar cells by their proximal areas near a fibronectin positive area. Goblet cells, seldom found togetherin vivoorin vitro, lacked prominent fibronectin or integrin-like surface proteins. Cells were joined to each other in the same orientation and cell pattern observed in intact midguts. The pattern was achievedin vitroby cell-cell adhesion without basal membrane or existing midgut as guides.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652373

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The general organization of the vitellocytes inAllostomasp. is described. In all the species of prolecithophorans studied, and therefore also inAllostomasp., the eggshell globules have the same ultrastructure consisting of highly electron-dense granules embedded in a medium-electron-lucent grey matrix (multigranular pattern) and mainly contain polyphenols. The type of yolk bodies principally characterized by membrane whirls inAllostomasp. is unknown for the other neoophoran taxa. This peculiar yolk originates from Golgi-derived vesicles, presumably containing lysosomal enzymes, which fuse with membrane-bound substrates. This characteristic is hypothesized as an autapomorphy of the Prolecithophora.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652374

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The study shows that the regenerating pharynx ofGirardia tigrinaforms a simple and valuable model system for studies of pattern formation in the nervous system and its relationship to the developing muscles. Immunocytochemistry was used, with antisera raised against 5-HT and the native planarian neuropeptide GYIRFamide. We studied the sequential development of the innervation in the regenerating pharynx, and using TRITC-labelled phalloidin we followed the corresponding differentiation and maturation of pharynx musculature. The peptidergic and aminergic neuronal cell types develop according to different time schedules and different modes. Throughout the process, the GYIRFamide-IR elements are in contact with the old parts of the nervous system, while the apical 5-HT-IR elements developde novo.In the regenerating pharynx the GYIRFamide-IR nerves develop in a proximodistal direction. The first 5-HT-IR cell bodies appear in the tip of the pharynx and are symmetrically placed. They have no contact to the rest of the nervous system. From these cell bodies processes grow disto-proximally and fasciculate with fibres from the proximal part. A striking parallelism between the appearance of GYIRFamide-IR nerves and muscle fibres stained with TRITC-phalloidin was observed. The GYIRFamide-IR nerves cling to the muscle fibres. These results suggest that the contact between muscle fibres and GYIRF-IR nerves is essential for the function of pharynx. The delayed appearance of 5-HT-IR nervous elements is discussed in terms of the influence of 5-HT on sprouting of nerve fibres and synapse formation. The development of the pharynx in tail parts after fission is compared with that after pharynx amputation. The faster rate observed for pharynx regenerating after amputation in comparison with that in regenerating tail parts indicates the importance of the remains of the old nervous system in the pharynx structure.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652375

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Platyhelminths possess a unique stem cell system that is claimed to be totipotent. It is supposed to be competent for the renewal of all cell types, including germ cells, during postembryonic development and regeneration. A connection to stem cells in the embryo has been postulated repeatedly. This cell type is now most frequently termed “neoblast”. Light microscopy can reveal only a few neoblast characters, and ultrastructural studies have shown additional characters for discriminating possible types andlor stages. While some progress has been made in this respect for triclad turbellarians (freshwater planarians), rather little is known about the microturbellarians. We have investigated the fine structure of neoblasts of hatchlings and adults ofMacrostomum hystricinum marinurn, a member of a primitive taxon in the “Turbellaria”-Rhabditophora (a paraphyletic group giving rise to the main parasitic flatworm taxa). InMacrostomum, one population of neoblasts is located in lateral bands along the main longitudinal nerve cords within the body cavity. Another population is found in the gastrodermis in a basi-epithelial position. Based on their cytoplasmic and nuclear organization, three stages in neoblast differentiation have been distinguished. The first and second stages are characterized by cytoplasm lacking organelles except free ribosomes and scattered mitochondria, a finding identical with the picture known from the “classical” planarian neoblast. In the first stage, heterochromatin is scattered over the nucleus in isolated clumps in a typical speckled (checkerboard) appearance; a nuclear lamina is weakly developed. In stage 2 the heterochromatin forms strands and clumps connected to each other. In stage 3 the nucleus is characterized by more prominent heterochromatin strands and by heterochromatin attachments to the well developed nuclear lamina. In this last stage a rough endoplasmic reticulum (rER) and Golgi complex are also present, indicating the entrance into cytoplasmic differentiation. Early epidermal replacement cells are located baso-epithelially, which show a nuclear organization similar to stage 3 neoblasts. Observations of stem cells in regenerating specimens and on isolated neoblasts are reported briefly. The data show that from the three types of differentiating cells distinguished recently in regenerative blastemas of planarians, the first stage (“undifferentiated cells”) resembles stage 2 neoblasp described here for postembryonic development. The results are compared with observations that have been published for neoblasts in other free-living platyhelminths.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652376

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Photoperiod has a profound influence on the life cycleof Nereis (Neanthes) virenscoordinating the transition from somatic growth to reproductive development. Here we report on a rapid method to characterize the diel component of the photoperiodic response and characterize the photoperiodic response curve. The diel emergence activity of the semelparous polychaeteNereis (Neanthes) virensSars has been investigated by means of an automated actograph. Emergence events were recorded for every second of real time and the number of events per hour analyzed over periods of up to 5 consecutive days under a variety of photoregimes. There is a marked nocturnal pattern of activity. The number of excursions from the burrow system is high during the night reaching near zero shortly after dawn. Excursions from the burrow system during daylight hours were much less frequent. The total number of emergence events per 24 h was significantly higher under LD 16:8 than under LD 8.16 even though the period of dark, when spontaneous emergence mainly occurs, was longer. The actographic records suggest that under LD 8:16 the feeding behaviour of the animals is substantially reduced compared with that observed under LD 16:8. A photoperiodic response curve has been obtained where there is a critical LD cycle around LD 11:12 and a progressive increase in emergence rate between LD 12:12 and LD 16:8. The mean number of emergence events per day is directly related to the duration of the photophase and inversely related to the scotophase duration although emergence mainly occurs during the night.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652377

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

During spermiogenesis in the sea urchinsDiadema setosumandSalmacis bicolor, two pattems of flagellum development were shown. For both species a significant proportion of spermatids examined possessed an axoneme that remained associated with the nucleus during development, and this results in the formation of sperm cells with an anteriorly directed flagellum, whereas the majority of spermatids gave rise to sperm cells with a posterior flagellum which is typical of multicellular animals. The morphology ofD. setosumandS. bicolorsperm cells was generally similar to that of other echinoids.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652378

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Copulation in the acoelOtocelis luteolamay result in mutual or one-sided insemination. Fifty specimens cultured with a species ofNaviculawere allowed to mate in pairs for a period of 6 h, 50 were allowed to mate in pairs for 24 h, and nine were allowed to mate freely for 24 h. All wows were then isolated in separate containers that were examined at frequent intervals in order to record the number of eggs and young. The number of progeny produced by worms that had been inseminated ranged from 1 to 65, and one worm had progeny as late as 55 days after mating. This study shows thatO. luteolais able to store viable sperm in its seminal bursa for several weeks.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652379

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

We conducted a series of experiments designed to investigate the regulation of regeneration following implantations of limb tissues in crabs. Autotransplantation (transplantation within the same crab) of the fourth walking leg tissues into claw stumps regenerated either a walking leglike limb, bifurcated limbs, a composite limb with claw and walking leg characteristics, or a normal claw. Interspecies experiments consisted of claw tissues fiom the crabCancer productustransplanted into the autotomized stump of the fourth walking leg ofCancer gracilis.The resulting regenerates appeared as either a claw-like limb, a walking leg with a toothed dactyl, a walking leg with two dactyls and two pollexes, or a normal walking leg. Reciprocal interspecies transplants of donor walking leg tissues into host claw stumps were able to induce the regeneration of walking leg-like limbs. Most of the regenerates had characteristics of both host and donor limbs. Our results suggest that both donor and host cells participate in limb regeneration. In the host claw stumps that produced the bifurcations, we propose that two distal organizers were generated. The identity of the limb fields generated by the distal organizers may be dependent upon the cells adjacent to the distal organizers, such that varying interactions between the two limb fields in the host stumps resulted in the formation of a range of regenerate morphologies.

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652380

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1999.9652381

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor