摘要:

The purpose of this paper is to describe the development of the amebocytes in the testicular cavities and epididymal ducts ofDina lineata.The samples used in this study were healthy and sexually mature. Testicular amebocytes are found to enter the testicular cavities arising from the submesothelial connective tissue, and they proceed towards the spermatogonial morulae, to which they attach by means of tight junctions. When the amebocytes come out of the morulae, they increase in size and develop the cellular features of a macrophage. These cells remove residual cytophores and can eventually fuse to enclose entire morulae.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672162

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Spermducts of H. virescens increased in length and developmental state after injection of 20HE into early pupae. Spermducts culturedin vitrodid not change in the absence of 20HE. incorporated into tissue culture medium induced changes which depended on the amount of time diapausing pupae maintained at 10°C were exposed to warmth and light. Spermducts from diapausing pupae did not respond to 20HE, and spermducts from pupae warmed for two days at LD increased in length but lost visible structure. Spermducts from pupae warmed for four days at LD differentiated to myogenically contracting organs resembling the seminal vesicles of adult moths. Thus, the degree to which post-diapause spermducts developedin vitroin the presence of 20HE depended on the developmental age of the donor.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672163

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Oocytes of the European lancelet (Branchiostoma lanceolatum) were fixed for transmission electron microscopy at Banyuls (French Mediterranean) in mid spring, which is just before the spawning season. Special attention is given to the growth stage (= diplotene) oocytes and to their relations with non-germinal cells of the ovary. At the time of year studied, the ovaries contain both relatively small (7–57 μm) and relatively large (97–127 μm) oocytes, but none of medium-size. In addition to the usual cell organelles (like free ribosomes, mitochondria, and endoplasmic reticulum), the oocytes include a number of more specialized structures. Nuage is present throughout the growth stage, both adjacent to the nucleus and scattered elsewhere in the cytoplasm. Other specialized structures do not begin to appear until the oocytes attain a certain diameter. The following structures are first detected at the following oocyte diameters: cortical granules, always in close association with Golgi complexes (20 μm); vacuoles containing presumed precursors of the vitelline layer (30 μm); yolk granules (35 μm); and a central vacuole within the nucleolus (50 μm). The cytoplasm of the largest oocytes includes a few annulate lamellae and some very unusual striated fibers resembling ciliary rootlets. These fibers, which are banded with a 70-nm periodicity (but are evidently not associated with centrioles), occur only at the animal pole of the oocyte, and their functional significance is unknown. The smaller oocytes have relatively smooth plasma membranes, except where endocytotic pits are abundant, whereas the larger oocytes bear abundant microvilli and are covered by a vitelline layer of dense, granular material. During oocyte growth, areas of contact between the oocytes and neighboring non-germinal cells shrink progressively. In the large oocytes, such contacts are limited to the animal pole, where a few processes from non-germinal cells pass through the vitelline layer and terminate on the oocyte plasma membrane at adhaerens type junctions (perhaps mixed with gap junctions). The possible functions and phylogenetic significance of such junctions are discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672164

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Symbiont bacteroids were found in the cytoplasm ofSciara ocellariseggs. At the posterior pole of the eggs symbiont agregates are seen from oviposition up to the stage of pole cells formation. These agregates disappear at later stages and the symbionts are included in the two formed pole cells. In somatic regions the symbionts, which were scattered throughout the cytoplam, start to aggregate at the anterior pole of 1 h embryos and there remain up to 2.5 h of development. At later stages the aggregates disappear and the symbionts are once again scattered in the egg endoplasm. Analysis of germ cells during gonadal development in embryonary life (30 and 96 h) and in developed ovary of later 4th instar larva, has showed that the symbionts persist in the germ cells throughout development. No symbionts were found in somatic cells at germ band stage (30 h) as well as at later stages. These findings indicate a transovarian mode of transmission of the symbiont bacteroids inSciara.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672165

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In1(3) ecdysone-1tsmutants ofD. melanogaster, multiform ovarian dysfunctions appear within a few days when mature flies are transferred from 21 to 29°C. (i) In germana, abnormal organization of the germ-line cells may be expressed by the lack of oocytes and/or aberrant numbers of nurse cells, (ii) In previtellogenic egg chambers, the fate of somatic cells (follicular epithelium) is varied, some of them become very thin, whereas others degenerate, (iii) In more advanced chambers, vitellogenin incorporation and yolk deposition fail to start in some oocytes whereas associated nurse cells continue growing.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672166

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The hatching synchrony of embryos within individual egg masses was examined in order to understand the factors that influence the rate of embryonic development ofLymnaea.When reared at 25°C, individual embryos from single egg masses hatch at various times from 9–16 days after first cleavage. The peak time for eclosion is on the 11th day of embryonic development, when approximately 30% of the embryos hatch. Hatching time correlates with the position of the embryo within the egg mass; embryos near the center of the mass hatch later than those on the periphery. This spatio-temporal pattern of hatching does not reflect any pattern of initial differences in the sizes of the individual egg capsules or in the sequence of eggs undergoing first cleavage. Instead the pattern of hatching appears to correlate with the relative exposure of the embryos to the external environment. Furthermore, isolation of eggs from the mass results in shorter times to peak hatching and much greater synchrony in hatching: i.e. 90% of the embryos hatch over a 2-day period (from 9 to 10 days after first cleavage). Together these findings suggest that the pattern of hatching observed in intact egg capsules results from positional differences of the embryos for the exchange of substances with the environment.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672167

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A method for the isolation ofSpisulaoocyte membranes was developed. 5-hydroxytryptamine (5-HT) receptors in the isolated oocyte membranes were determined by measuring the binding of [3H]5-HT. The dissociation constant of [3H]5-HT binding to the membrane receptor was estimated to be 17.5 nM and the maximum binding capacity was 7.9 pmoles/mg protein. Inhibition study of [3H]5-HT binding with site selective 5-HT analogs was performed. The results suggest that the 5-HT receptors in oocyte membranes contain sites that interact with 5-HT1and 5-HT3selective analogs.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672168

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

SEM was used to study the external morphology of spermatozoa from two species ofMacrobiotus(Eutardigrada). In both species, the spermatozoon consists of 4 parts: (1) a rod-shaped acrosome; (2) a helical nucleus; (3) an elongated, swollen middle piece, with lateral vesicles; (4) a tail ending in a tuft of thin and long filaments (probably microtubules). Observations madein vivoand on fresh preparations of sperm cellstotoconfirm the SEM images. Moreover, light microscopy findings also showed that spermatozoa in the testes and gonoducts have a folded-back acrosomal-nuclear region, joined to the middle piece. Artificially extracted spermatozoa appeared in some cases straight-headed.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672169

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A better understanding of the mechanisms underlying growth and degrowth in freshwater planarians, and the control systems associated with them, requires a thorough investigation at the cellular and molecular levels. As a first step towards this goal, we have measured the body volume, plan area, number of cells, percentage of different cell types and mean cell area and volume in growing and degrowing organisms from five species of planarians with sexual, asexual, semelparous and iteroparous reproduction.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672170

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672171

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor