摘要:

AbstractMorphology of chloride cells was studied in embryos, larvae and juveniles of ayu (Plecoglossus altivelis), carp (Cyprinus carpio) and flounder (Kareius bicoloratus). Chloride cells of seawater‐adapted fishes interdigitated to neighboring cells and linked each other with leaky junctions. No such interdigitation or a leaky junction was found in those of freshwater fishes. Larval ayu were able to tolerate direct transfer from fresh water to seawater even immediately after hatching. Juvenile flounder reared in seawater for 60 days were able to adapt to fresh water. Their chloride cells started developing or degenerating interdigitations and leaky junctions within 3 h after the transfer. Juvenile ayu of landlocked form caught in Lake Biwa survived in seawater for no longer than 6 h. Juvenile carp died within 12 h after transfer to 15%. seawater. Newly hatched flounder did not survive in fresh water for longer than 48 h. Their chloride cells did not show any morphological change, although the epithelial cells were severely damaged. Thus, the ability of chloride cells to modify their intercellular organization and junctional structure appears to play a critical role in salinity adaptatio

ISSN:0022-104X    

DOI:10.1002/jez.1402360202

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe actions of alkaline earth (AE) and transition element (TE) cations on Na+transport across skin of larval and adultRana catesbeianawere compared. Bathed on the outside by Ca+2‐free Ringer's, both larval and adult skins maintained a stable short‐circuit current (3–4 μAmps cm−2for larval skin and 20–30 μAmps cm−2for adult skin). Addition of Ca+2to the external bath reduced the SCC; maximal inhibition was about 36% for larval skin and 22% for adult skin. Other AE divalent cations were also inhibitory. The order of effectiveness was: Ba+2= Ca+2>Sr+2>Mg+2for larval skin and Ba+2>Ca+2= Mg+2for adult skin. Sodium influx was markedly elevated when Ca+2was removed from the external medium. Current‐voltage analysis indicated that Ca+2increases the resistance of the active pathway without affecting the shunt resistance or the electromotive force of Na+transport (ENa) in larval and adult skins.The SCC across adult skin was stimulated by TE cations (Co+2, Cd+2, La+3). These ions were inhibitory on larval skin. The transition in the response occurred at stage XXI. The inhibitory effect of TE on larvel skin resembles that seen in response to AE cations and we postulate a common mechanism. Since larval skin lacks the selective Na+channels found in apical membranes of adult skin, we infer that the mechanism of inhibition by AE cations is not on these channels. A more general phenomenon such as change in surface charge at the apical membrane seems more reasonable. The stimulatory action of TE cations in adult skin is discussed in terms of interference with the Na+‐self‐inhibition response. Apparently, larval skin lacks some component of the molecular mechanism under

ISSN:0022-104X    

DOI:10.1002/jez.1402360203

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

年代:1985

数据来源: WILEY

摘要:

AbstractAt least 20–60% of the dry weight of unionid gills occurs as inorganic calcium concretions. These concretions are a calcium store mobilized during reproduction. The concretion content in gills of reproductively active animals decreases, as determined by morphological study and chemical isolation. While mobilization is occurring, maternal blood phosphate and bicarbonate remain normal, and calcium declines. These data are consistent with the hypothesis that concretion calcium, from the gills, leaves the maternal animal and may serve as a calcium source for glochidial shell formation in the calcium poor freshwater environmen

ISSN:0022-104X    

DOI:10.1002/jez.1402360204

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

年代:1985

数据来源: WILEY

摘要:

AbstractAn examination of polypeptide synthesis during early development in the Mongolian gerbil revealed similar protein profiles up to the early 2‐cell stage, and a gradual change over a period of ∼18 h to give a distinctly different profile by the late 2‐cell stage which remained largely unchanged thereafter. The incorporation of [35S] methionine into protein was significantly reduced by the late 2‐cell stage, followed by a marked increase 24 h later. Enucleation of fertilized 1‐cell embryos and culture in vitro resulted in retention of the early 2‐cell profile. These results indicate probable transition from the initial use of stored maternal message before the onset of embryonic gene activity. Comparisons have been made with similar studies i

ISSN:0022-104X    

DOI:10.1002/jez.1402360205

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe jelly canal of the unfertilized egg of the sea urchinH. pulcherrimuswas found to serve as a stable landmark of the egg axis. The eggs were bisected with a micro glass needle into two egg‐halves either equatorially or meridionally in relation to the egg axis defined by the jelly canal. The development of both egg‐halves after fertilization was observed 1 or 2 days later until the control embryos reached the gastrula stage. The embryo derived from the vegetal half formed primary mesenchyme and gastrulated while the animal half remained as the permanent blastula forming neither primary mesenchyme nor archenteron. Both embryos obtained by the meridional bisection formed primary mesenchyme and gastrulated. The presence of the female pronucleus or its adjacent cytoplasm was not a prerequisite for the occurrence of primary mesenchyme formation and gastrulation. These results indicate that unfertilized eggs already localize the cytoplasmic determinant responsible for primary mesenchyme formation and gastrulation. Localization of the cytoplasmic determinant occurs independently of formation of the cortical pigmentation polar

ISSN:0022-104X    

DOI:10.1002/jez.1402360206

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

年代:1985

数据来源: WILEY

摘要:

AbstractProtein uptake and degradation by trophotaenial cells of the viviparous goodeid fishAmeca splendenswere studied colorimetrically and ultrastructurally using horseradish peroxidase (HRP) as a tracer and acid (ACPase) and alkaline (ALPase) phosphatase cytochemistry. Trophotaeniae are ribbon‐like external projections of the embryonic gut that are equivalent to greatly hypertrophied intestinal villi. During gestation within the ovarian lumen, trophotaeniae are directly apposed to the internal ovarian epithelium (IOE) where they establish a placental association between the developing embryo and maternal organism. Trophotaenial absorptive cells possess an ALPase reactive brush border, an endocytotic apparatus, and ACPase reactive standing lysosomes. Ultrastructural studies of protein uptake indicate that cells of the trophotaenial epithelium take up HRP by micropinocytosis and degrade it within lysosomes. Initially (from 1.5–10 min), HRP is taken up in vitro at 22° C at the apical cell surface and passes via endocytotic vesicles into an apical canalicular system. From 1.5 to 10 min exposure, HRP passes passes from the apical canalicular system to a series of small collecting vesicles. After 10 min, HRP is detected within large ACPase reactive supranuclear lysosomes. Three hours after an initial 1 h exposure to HRP, most peroxidase activity within supranuclear lysosomes is no longer detected. Presence of Golgi complexes, residual bodies, and secretory granules in the infranuclear cytoplasm suggest that products of protein uptake and hydrolysis are discharged across basal and lateral cell surfaces and into the trophotaenial circulation. Trophotaeniae of embryos incubated in vitro in HRP‐saline take up HRP at an initial rate of 13.5 ng HRP/mg trophotaenial protein/min. The system becomes saturated after 3 h. Trophotaeniae incubated at 4°C show little or no uptake. In trophotaeniae continuously pulsed with HRP for 1 h, then incubated in HRP‐free saline, levels of absorbed peroxidase declined at a rate of 0.5 ng/mg trophotaenial protein/min. HRP does not appear to enter the embryo via extratrophotaenial routes. These findings are consistent with the putative role of trophotaeniae as the embryonic component of the functional placenta of goodeid fishes. Trophotaenial uptake of maternal nutrients accounts for a massive (15,000%) increase in embryonic dry weight during

ISSN:0022-104X    

DOI:10.1002/jez.1402360207

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe expansion of the quail extraembryonic epiblast is a useful system for the study of epithelial sheet locomotion. A band of cells at the epiblast edge, referred to asedge cells(EC), adheres to the vitelline membrane. The attachment side of the EC and the dorsal surface of the submarginal cells were examined with scanning electron microscopy (SEM) after different fixation procedures. Our results indicate that especially the number of the submarginal microvilli and the surface structures of the lamellipodia are affected by tissue handling before fixation. The attachment region consists of overlapping lamellipodia that are bordered by filopodia. Proximal edge cells have a smooth contour, and they are probably elongated and oriented perpendicularly to the direction of locomotion of the EC. Parts of the proximal edge are occupied by lamellipodia and threadlike extensions. The submarginal cells located nearest the EC are usually outlined by intercellular ridges and numerous blebs, whereas the more central cells are outlined by microvilli.

ISSN:0022-104X    

DOI:10.1002/jez.1402360208

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

年代:1985

数据来源: WILEY

摘要:

AbstractAggregations of Con A binding sites that occur on the surface of preconjugant cells have been studied in order to reveal their possible functions in the conjugation process. By means of a newly adapted horseradish peroxidase method, they can be visualized in distinctly shaped oval fields (OF) as soon as 10–15 min after mixing cells of opposite mating types. Cycloheximide (CHX) prevents establishment of new OFs but does not effect preexisting ones. In the absence of previously developed OFs, cells cannot form pairs. However, even if OFs are fully present, pairing still can be inhibited by CHX, high K+concentrations (≥ 60 mmol/liter), or the K+‐channel blocker tetraethyl‐ammonium (TEA, 10 mmol/liter). A doublet cell with OFs on both halves normally binds to one singlet. This partner, after a stay of 10 min in an angled agglutination position, quickly rotates into the parallel pairing position. At this moment, the doublet suddenly loses its affinity for complementary cells at its free OF. This behavior explains why many doublets pair only with one singlet. The Con A binding sites themselves seem not to be active in cell pairing; they are regarded as a marker for a region of the cell surface whose contact with a complementary cell subsequently results in the unmasking of unidentified compounds that serve as adhesive agents and/or the hinge for the quick rotation of agglutinate

ISSN:0022-104X    

DOI:10.1002/jez.1402360209

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

年代:1985

数据来源: WILEY

摘要:

AbstractDiploid F1 hybrids betweenRana ridibundafrom Adriatic SW Yugoslavia and PolishR. lessonae, and between PolishR. ridibundaand an unnamed species from SW Yugoslavia are shown by electrophoresis and examination of lampbrush chromosomes to contain both parental genomes in their diploid oocytes I. In contrast, central EuropeanR. ridibundagenomes in diploid hybrids, whether F1s or from natural hemiclonal lineages, induce exclusion of the lessonae genome in the germ line, only ridibunda translation products and endoreduplicated ridibunda chromosomes being detected in their diploid oocytes I. The data demonstrate geographic variation ofR. ridibundain the ability of its genomes to induce clonal gametogenesis in interspecies hybrids. They also suggest that genomes of the unnamed Yugoslavian species may be resistant to such exclusion.

ISSN:0022-104X    

DOI:10.1002/jez.1402360210

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

年代:1985

数据来源: WILEY

摘要:

AbstractDuring fertilization inLimulus, the spermatozoa first attach to the egg and then undergo an acrosomal reaction. In this reaction, the acrosomal vesicle exocytoses, and a long, preformed acrosomal filament is extruded (and subsequently penetrates the egg chorion). The egg surface component that triggers the acrosome reaction has not yet been solubilized; therefore, previous studies have examined either spontaneous acrosome reactions or acrosome reactions that were triggered by eggs (or insoluble egg fragments), elevated extracellular Ca2+, or Ca2+ionophores. In this study, we report a new method for initiating acrosome reactions inLimulussperm. When theLimulussperm motility‐initiating peptide (SMI) is added to sperm in K+‐free sea water, greater than 90% acrosome reactions are initiated within 5 min. However, less than 5% acrosome reactions occur either in K+‐free sea water lacking SMI or when SMI is added to sperm in either normal sea water or K+‐and Ca2+‐free sea water. Experiments with K+ionophores (nigericin and valinomycin), a K+channel blocking agent (tetraethyl ammonium), an Na+ionophore (monensin), and reagents that increase the intracellular pH (monensin, nigericin, and NH4Cl) indicate that changes in intracellular K+, Na+, or H+do not mediate SMI‐initiated acrosome reactions. The K+/Ca2+ratio determines whether or not SMI will initiate acrosome reactions, with>50% acrosome reactions being initiated when this ratio is below 0.3. In that K+movement does not appear to be the critical event, possibly the K+/Ca2+ratio either determines the rate of Ca2+entry or controls the conformation of sperm surface molecules to allow SMI to initiate acrosome reaction

ISSN:0022-104X    

DOI:10.1002/jez.1402360211

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

年代:1985

数据来源: WILEY