ISSN:0022-104X    

DOI:10.1002/jez.1402710402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA molecular characterization of tubulin and microtubule‐associated proteins (MAPs) along with their intracellular pool distributions in both unfertilized and fertilized oocytes of the troutOncorhynchus mykisswas carried out. In vitro assembly of microtubular proteins was obtained by cycles of assembly‐disassembly and by taxol‐induced polymerization, thus allowing identification of the protein components of isolated microtubules from the oocyte. Extraction procedures were developed in order to separate molecular components of the egg vitelum prior to purification steps. The use of antibodies that specifically tag tubulin and a set of site‐directed probes against repetitive binding sequences on MAPs provided data on the presence of tubulins and enabled the identification of an 85‐kDa protein that shares common functional epitopes with mammalian MAPs. An enzyme‐linked immunosorbent assay analysis of the free soluble tubulin pools revealed a significant decrease in the pool extent during fertilization as compared with unfertilized oocytes controls. Interestingly, this decrease in free tubulin in the fertilized trout oocyte appeared to be accompanied with a concomitant increase of the assembled tubulin pools. Within the context of the known effects of heat shock in oocyte fertilization, temperature changes from 4 to 26.5°C of fertilized eggs resulted in a transient increase in the soluble tubulin pools during the initial 5‐min heat incubation, decaying after 10 min treatment, to reach at 15 min the levels of soluble tubulin pools of untreated controls. Total tubulin pools remained constant during the heat incubations of fertilized eggs. The distribution of MAPs pools in the oocyte was also investigated using the specific immunological probes. In contrast to tubulin no major differences were found between free MAPs pools of the fertilized oocytes as compared with unfertilized controls. However, heat shock treatment of fertilized oocytes also induced a transient increase in free MAP pools during the first 5 min followed by a mobilization of immunoreactive MAP components from the soluble to the assembled pools. © 1995

ISSN:0022-104X    

DOI:10.1002/jez.1402710403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe body wall epithelium of starfish gastrulae change the barrier property of the septate junction against large molecules in response to hypertonic environment caused by small molecules such as glycine, arabinose, urea, and NaCl. Ultrastructural obesrveations reveal that the septal portion of the junction either becomes diffuse or disappears altogether while the opposing junctional membranes remain unaltered. Under such conditions, Molecules as large as IgG and IgM can penetrate the body wall without causing morphological abnormalities to the embryo. We have devised a method to detect the paracellular permeation by applying fluorescein‐labeled IgG into the stimulation medium and monitoring the fluorescence which penetrated into the blastocoel. Micropreciptiates of LaCl3were found, in thin sections of embryos treated with glycine, to lie along the intercelluar spaces, showing, although indirectly, that macromolecules flow through this pathway instead of a transcellular one.The possible role of the septal plates in the barrier function of the septate junction is discussed. © 1995 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402710404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIsolated hepatoctes from the marine vertebrateRaja erinacea(the little skate) retain their structural and functional integrity as clusters of cells formed around a single tubular bile canaliculus, and therefore can be used as a model of polarized hepatocytes in situ. In this study we used confocal and conventional epifluorescence microscopy in conjunction with fluorescent markers and immunocytochemistry to examine the structure and function of the cytoskeleton in these cells. Actin filaments in the hepatocyte clusters were found cortically and also concentrated in a pericanalicular array, while microtubules disrupting agent, nocodazole, resulted in the microtubules depolymerizing from the basolateral surfaces towards the apical surface, indicating that the microtubules were oriented with their plus ends at the basolateral surface and their minus ends at the apical surface. Nocodazole was also found to disrupt the ability of clusters to transcytose a fluorescent bile salt derivative into their canalicular lumens. We detected cytoplasmic dynein in skate hepatocyte homogenates by Western blotting using an anti‐dynein intermediate chain anti‐body, and immunofluorescent staining of intact hepatocytes revealed a punctate vesicular pattern. The polarized arrangement of microtubules, the presence of cytoplasmic dynein, and the inhibition of bile salt secretion by nocodozole are consistent with the microtubule cytoskeleton playing a fundamental role in the mediation of transcytosis, endocytosis, and bile excretory function in these hepatocytes. These polarized isolated skate hepatocytes represent an excellent experimental model for the in vitro study of hepatic transport, and allow for important comparative studies aimed at elucidating the evolutionarily conserved nature of various hepatocyte structures amongst the vertebrates. © 1995 Wiley‐Lis

ISSN:0022-104X    

DOI:10.1002/jez.1402710405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDuring larval development in instar IV brine shrimp, segment 1 grew by cell replication and cell differentiation. Cell cycle analysis revealed that the cell cycle was synchronized with the molt cycle. Mitosis occurred late in the instar and S phase began at hr 6 of the following instar. Three populations of cells comprised the dorsal integument. The medial‐dorsal region did not grow. Cell enlargement occurred in the dorsal‐lateral population while cell replication took place in the lateral population. The limb bud (ventral surface) grew in width by replication in the distal population, and in height by enlargement of the general epidermal cells in the proximal population. Expansion of each region of the integument was proportional to the cell growth in that region. Moreover, both growth processes were dependent on the level of nutrients and were enhanced by diets enriched in polyunsaturated fatty acids. A nutrient‐dependent growth control point occurred in the G1 period. The commitment to replication and differentiation occurred by hr 2 of instar IV. The findings show that integumental growth is a result of regionspecific cell growth processes which are controlled by nutrients during the G1 period. © 1995 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402710406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe formation, structure, and rearrangements of the notochord were studied inPleurodeles waltliiandXenopus laevisembryos. We measured length and cross‐sectional area and calculated volume of the notochord at different stages of development. In both species, the notochord emerges as a condensation and a columnarization of dorsal mesoderm along the midsagittal plane in the midgastrula. InP. waltliiembryos, the notochord segregates from archenteron roof by apical cell surface shrinking. The wave of shrinkage begins in the middle of the rudiment and simultaneously extends cranially and caudally. InX. laevisembryos, the notochord elongates in two directions also, but the mode of notochord formation is not identical in anterior and posterior parts of embryo. While anterior development looks similar to that found inP. waltlii, posterior development features closer binding of the notochord rudiment to ectoderm within existing delaminating boundaries from somite mesoderm. Rates of elongation in the different directions are approximately the same in the two species studied: It is 45–47% for the anterior and 53–55% for the posterior direction compared to total length of the notochord. © 1995 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402710407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractBased on its amino acid composition and N‐terminal sequence, a polypeptide (HRP‐B) has been identified as a member of the avian histidine‐rich protein (HRP) family. An antiserum against HRP‐B has been used to localize this polypeptide in developing feathers and scales of chick embryos. HRP‐B was first detectable in the barb ridge cells of feathers at 13 days of incubation and progressively appeared in the distal/proximal and peripheral/central gradients observed previously for the feather‐type β keratins in developing feathers. The HRP‐B polypeptide was detected only in the embryonic layers of scutate scales. It first appeared at 16 days of incubation and not found in the differentiated beta strata of these scales. At no time during the development of reticulate scales or apteric skin regions did the epidermal cells or cells of the embryonic layers express HRP‐B. The transient expression of HRP‐B by the embryonic layers of the scutate scale epidermis is discussed in light of the feather‐forming potential of the presumptive epidermis of the scutate scale‐forming region.

ISSN:0022-104X    

DOI:10.1002/jez.1402710408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMembrane fractions from homogenized adultSchistosoma mansoniare known to lyse host red blood cells (RBC's), Which serve as an important nutrient source for the parasite, In order to learn more about the homolytic process, we investigated the effects of pH and temperature on the steps involved in the hemolytic process. For maximum schistosome induced hemolysis to occur the worm lytic agent must be in the contact with RBCs in a low pH (pH 5.1), high temperature (37°C) environment for a short time (30 min), after which hemolysis occurs at both pH 7.5 and 5.1 At pH 7.5 the hemolytic process is relatively temperature independent and highly concentration dependent. Dose‐response experiments suggest that a multi‐hit process of hemolysis is probably involved. Temperature and dextran experiments suggest that a pore is formed in the RBC membrane at pH 7.5 At pH 5.1 hemolysis is temperature dependent and not very concentration dependent. Dose‐response data suggest that a single‐hit process of hemolysis is utilized at low pH. The hemolytic process at pH 7.5, the pH of the host blood, and pH 5.1, the approximate pH of the worm gut, appears to be very different. © 1995 Wiley

ISSN:0022-104X    

DOI:10.1002/jez.1402710409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractCheetahs (Acinonyx jubatus) produce poor quality ejaculates that can limit the efficiency of standard assisted reproduction including artificial insemination (AI) and in vitro fertilization (IVF). The purpose of this study was to: (1) further study sperm‐oocyte interaction in this teratospermic species by examining the ability of malformed sperm to interact with various oocyte barriers; and (2) assess the potential of zona piercing for assisting IVF in a teratospermic felid. Zonae of salt‐stored (SS), domestic cat oocytes were mechanically pierced (ZnPd) three times each. Semen was collected by electroejaculation from six male cheetahs and ejaculates were processed for IVF. Sperm aliquots from each ejaculate were assessed for a sperm motility index (SMI) over time. Zona‐intact (ZnIn‐SS) oocytes (n=78) and ZnPd‐SS oocytes (n=74) were coincubated with spermatozoa in vitro for 6 h. The proportion of morphologically abnormal spermatozoa per ejaculate was high for all males (range 81.5% to 95.9% ). SMI values at 0 and 6 h were variable, ranging from 50 to 75 and 0 to 40, respectively. Spermatozoa from all ejaculates bound to and penetrated the outer zona pellucida of ZnIn‐SS and ZnPd‐SS oocytes similarly (P>0.05). The proportion of oocytes containing spermatozoa within the inner zona layer and the average number of spermatozoa per oocyte in this region were greater (P0.05) in pleiomorphic spermatozoa penetrating the inner zona pellucid or PVS. Penetration of both ZnIn‐SS and ZnPd‐SS oocytes was positively correlated (P0.05). In summary, altering the integrity of the zona pellucida by creating artificial channels increases the number of cheetah spermatozoa entering the inner zona region, but not the PVS. This phenomenon occurs without increasing the number of pleiomorphic sperm entering the zona/oocyte interface, reinforcing the role of the zona pellucida, especially the inner region, as a powerful filter for malformed sperm.

ISSN:0022-104X    

DOI:10.1002/jez.1402710410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1402710401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY