摘要:

AbstractOva from superovulated Swiss albino ICR mice were exposed to 1, 10, and 40 μg cytochalasin B/ml in Whitten and Biggers medium (WBM) for intervals up to 24 hours. Controls were incubated in ordinary medium or in medium containing dimethylsulfoxide (DMSO) in an amount equivalent to that used to dissolve cytochalasin B, taking dilution into account. The ova were mounted on slides in egg albumin, stained by the Feulgen method and counterstained with light green SF, or they were processed for electron microscopy. The DMSO treatment, as determined by either light or electron microscopy, had no essential effect. Eggs treated with 10 or 40 μg cytochalasin/ml did not exhibit the fragmentation observed in some of the control ova. Treated eggs contained either several spherical bodies, which sometimes reached a size of 8 to 10 μ, or as many as 20 smaller bodies, stainable with light green SF and positive for proteins when stained with mercury‐bromphenol blue. These bodies, first observed after exposure for eight hours to cytochalasin, were revealed by electron microscopy to be groups of crystalloids which occasionally entrapped microfilaments or granules. Neither the spacial relationship of crystalloids to cell organelles nor the preliminary stages of their formation could be observed. Since little protein synthesis occurs in unfertilized eggs, and the addition of 50 and 250 μg of puromycin did not prevent formation of these bodies, it is suggested that they were formed by the crystallization of proteinaceous material already present in the

ISSN:0022-104X    

DOI:10.1002/jez.1401800102

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

年代:1972

数据来源: WILEY

摘要:

AbstractL‐lactate dehydrogenase (LDH) exists as tetrameric isozymes in all vertebrates. The polypeptide subunits are encoded in at least two genetic loci, A and B. A third LDH locus, the E locus, is present only in fish. The distinctive E4isozyme encoded by this locus is synthesized in the cells of the teleost nervous tissue, particularly in the photoreceptor cells.Electrophoretic and immunochemical procedures were employed to determine which orders of fish have representatives which contain this nervous system specific LDH isozyme. In addition to the 50 species of teleostean and non‐teleostean fish examined, a compilation was made of other species reported to contain this enzyme.The LDH E gene function was not detected in Agnathans, Chondrichthyes, Dipnoans, Chondrosteans, and Holosteans. The LDH E gene appears to be restricted to the teleosts. However, some orders of teleosts, e.g., the Cypriniformes, contain many families which lack the E4isozyme. The LDH E gene appears to have arisen from a duplication of the LDH B gene near the time of the adaptive radiation of the teleosts.The immunochemical analyses of the LDH isozymes from these fish indicate that the LDH A and B loci of non‐teleostean fish have not diverged to the extent as these same loci in tel

ISSN:0022-104X    

DOI:10.1002/jez.1401800103

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

年代:1972

数据来源: WILEY

摘要:

AbstractOriented responses to linearly polarized light have been quantitatively confirmed in the marine teleostZenarchopterusstudied in underwater field experiments with the aid of SCUBA. During six successive mornings 2485 heading measurements were made on 36 untrained fish. With natural illumination spontaneous azimuth orientation is mutiply dependent on the sun's bearing and apparently on the natural polarized light of blue sky or water as well as the direction of the interisland channel where the fish were collected. When a dichroic filter is placed over the fish polarotaxis is manifest as directional preferences mainly perpendicular and less strongly, parallel to the plane of polarization. This response is most intense when the imposede‐vector differs maximally (by 60°–90°) from that predominant in the natural illumination (90° to the sun's bearing). When the sun's disc is partly or wholly obscured by clouds polarotaxis is significantly weakened even though the polarization pattern visible to the fish through the dichroic filter would be virtually unchanged. More than moderate angular turning rates by the fish swimming in the experimental vessel also weaken their response to thee‐vector. Individual fishes show different reactions: about one‐third of those in full sunlight oriented strongly parallel and perpendicular to the imposede‐vector, another smaller group appears to orient obliquely to the polarization plane while the remainder respond weakly to thee‐vector if at all. Continuing work is required to demonstrate the physiological mechanism and ecological significance of these behav

ISSN:0022-104X    

DOI:10.1002/jez.1401800104

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

年代:1972

数据来源: WILEY

摘要:

AbstractOf the many investigations reported in the past decade concerning the pattern and significance of RNA synthesis in early development, relatively few have involved mosaic embryos. These investigations have revealed a common pattern of RNA synthesis among embryos of anamniotic deuterostomes and a few have indicated that this pattern may not be shared by their protostome counterparts. The present study provides data for a thorough comparison of RNA metabolism in a mosaic embryo with that of regulative embryos.Oocytes and embryos of the coot clam,Mulinia lateralis, were pulse‐labeled with tritiated uridine and their RNA was extracted and analyzed by sucrose gradient centrifugation and MAK chromatography. Little or no RNA synthesis could be detected in oocytes before fertilization. During cleavage, newly synthesized RNA is primarily DNA‐like, heterogeneous in size and base composition and of lower average G + C content than ribosomal RNA. A prominent class of short‐lived RNA molecules sedimenting at 8–10s is also transcribed during cleavage and continues to be produced at least through gastrulation. Transfer RNA appears to be synthesized as early as mid‐ to late‐cleavage. Whereas ribosomal RNA synthesis was undetectable in these experiments prior to gastrulation, ribosomal and transfer RNA synthesis predominate in the larval stages. These results demonstrate that the temporal pattern of RNA synthesis common to embryos of the lower deuterostome phyla can be found in protostome embryos as well, and therefore that mosaic development need not entail a unique pattern of gene tr

ISSN:0022-104X    

DOI:10.1002/jez.1401800105

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

年代:1972

数据来源: WILEY

摘要:

AbstractEmbryos of the coot clam,Mulinia lateralis, have been found to synthesize the several types of RNA in essentially the same temporal pattern as observed in the regulative embryos of a variety of deuterostome organisms. Since it remained to be shown whether the RNA produced in early development of mosaic embryos such as those of the clam has the samefunctionas that synthesized by regulative embryos, a study of the entry of newly‐synthesized RNA into polyribosomes ofMuliniaembryos was carried out.Unfertilized oocytes contain a detectable number of polyribosomes, and within 45 minutes after fertilization this number has increased. The proportion of ribosomes engaged in polyribosomes continues to increase throughout development, in the absence of any change in the overall size distribution of the polyribosomes. Newly‐synthesized RNA can be found in specific association with light polyribosomes as early as the two‐cell stage, and the polyribosome classes receiving this RNA are active in protein synthesis. The RNA entering polyribosomes in late cleavage was purified and analyzed by sucrose gradient centrifugation and found to consist predominately of the 8–10s species which had been observed previously inMuliniaembryos from early cleavage through gastrulation. The similarities between this RNA and the 9–10s RNA discovered in sea urchin embryos, which is considered to include the mRNA's for chromosomal histones, suggest that early RNA synthesis in clam and sea urchin embryos fulfills basically the same function. This finding discourages speculation concerning possible differences in gene transcription patterns between early mosaic and regulativ

ISSN:0022-104X    

DOI:10.1002/jez.1401800106

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

年代:1972

数据来源: WILEY

摘要:

AbstractTo investigate electrical interaction among large cells in the lobster cardiac ganglion, electrotonic transmission between the somata of two such cells was observed by applying current pulses of two different durations and recording induced responses in the membrane potential of soma. The brief potential changes induced in one soma were transmitted to an adjacent soma through electrotonic pathways in the same way as the longer potential changes. However attenuation was greater for the shorter pulses. The amplitude of the soma spike markedly decreased compared to that of the axon spike, and the ratio was about 5.5. The soma spike was not a regenerative response of the soma membrane, but it was an electrotonic spread of the axon spike. The attenuation ratio of the soma spike was almost the same as that measured for a brief potential change such as a spike applied to the soma. These findings indicate that the soma spike spreads electrotonically to the adjacent soma through the electrical connections, while the axon spike does not. Such electrical transmission of the spike was extremely weak. The slow potential, electronic transmission of which had been observed between large cells, was restricted to the soma. The results suggest that the electrotonic pathways interconnect the somata of large cells in the anterior part of the ganglionic trunk, but not the axons. Electrical transmission of the spike through the pathways is very weak because of the inexcitable membrane of the somata. The electrotonic pathways are considered to be fibre‐like connections between dendrites arising from the somat

ISSN:0022-104X    

DOI:10.1002/jez.1401800107

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

年代:1972

数据来源: WILEY

摘要:

AbstractEndoderm movements in the chick embryo between the early short streak and head process stages were studied by tracing the migration of tritiated thymidine‐labeled grafts excised from explanted donor embryos and transplanted to identical positions in explanted recipient embryos of the same stage.During the primitive streak stages, the endoderm layer migrates in an orderly fashion away from a center of the primitive streak which is located about one fourth to one third of the distance from its anterior to its posterior end; all grafts placed in the endoderm anterior, lateral or posterior to this center migrated respectively anteriorly, laterally and posteriorly toward the outer margin of the area pellucida. During this migration, the grafts became narrowed and stretched out to conform with the rounded circumference of the area pellucida. Endoderm cells located in the endoderm center itself never completely left the streak, but spread out in all directions until they occupied a central circular area destined to form the gu

ISSN:0022-104X    

DOI:10.1002/jez.1401800108

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe reticuloendothelial system (RES) activity by the method of colloidal carbon clearance and the antibody production against heterologous erythrocytes by the method of hemagglutination were studied in hibernating hedgehogs.The organs involved in RES activity and antibody production were histologically studied.The data obtained show that the RES activity in the liver is unaffected in hibernating animals while uptake and localization of carbon particles by the spleen is impaired. The suggested hypothesis is that of a defect in the phagocytic activity of the spleen's macrophages, even if the effects of the disturbance in the handling of hibernating animals is to be considered.The antibody production is inhibited or, at least, reaches no significant values in hibernating hedgehogs.All these facts may be correlated with a general and marked involution of all the lymphoid organs. In fact we can observe a reduced white pulp and involuted follicles in the spleen, a smaller size of the thymus and its substitution by brown fat tissue, and smaller lymphnodes containing brownish material. The results are discussed in relation to the scanty and contradictory data available in the literature.

ISSN:0022-104X    

DOI:10.1002/jez.1401800109

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

年代:1972

数据来源: WILEY

摘要:

AbstractAggregates containing trypsin‐disaggregated mouse and chick embryonic liver cells were prepared, and in confirmation of Moscona's reports, no substantial sorting out was seen. While this behavior could mean that the morphogenetic properties of these cells are the same, alternative explanations have not been ruled out. Thus, additional comparisons of these cells were needed to decide whether these properties are the same, and two such tests were performed.It is known that when two pieces of chick embryonic liver are fused together, neither piece envelops the other. If mouse and chick embryonic liver cells had identical properties, no envelopment would be expected in mouse‐chick liver fusions. Such fusions were prepared, and contrary to this expectation, chick liver enveloped mouse liver almost invariably.It is known that chick embryonic liver cells sort out from chick embryonic heart ventricle cells in mixed aggregates. If mouse liver cells had properties identical to those of chick liver cells, it would be expected that they too would sort out from chick ventricle cells. Mouse liver‐chick ventricle cell aggregates were prepared, and contrary to this expectation, no substantial sorting out was found.These two tests demonstrate that the morphogenetic properties of mouse and chick embryonic liver cells are not the same. Clearly, a new explanation must be found for their lack of sorting out, and several possible explanations are disc

ISSN:0022-104X    

DOI:10.1002/jez.1401800110

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe properties of acid phosphatase from tail tissues ofXenopus laevistadpoles have been investigated by means of acrylamide gel electrophoresis and biochemical assay with alpha‐naphthyl acid phosphate as substrate. Studies were made on intact tails during development and spontaneous metamorphosis, and on isolated tail tips undergoing thyroxine‐induced regression in culture.Quantitative and qualitative changes in acid phosphatase are found to occur during the process of tail resorption. The same types of changes are found during both spontaneous metamorphosis and thyroxine‐induced regression in culture, although the magnitude of these changes is greater during spontaneous metamorphosis. Tail resorption is characterized by increases in total activity (per tail) and specific activity (per unit of protein) of acid phosphatase, as well as changes in the pH optimum and heat sensitivity of the enzyme. Electrophoresis of enzyme preparations from whole tails and different parts of the tail resolves two distinct forms of the enzyme which are both present throughout growth and regression. Densitometric tracings of these gels reveal that the ratio of one form to the other remains constant during growth and the early stages of tail regression. However during late stages of tail regression this ratio becomes significantly altered, due primarily to an increase in one form. Biochemical analysis of enzyme preparations subjected to hypotonic conditions and to Triton X‐100 indicates that there is an increase in the proportion of soluble versus bound enzyme in tail tissues undergoing advanced atrophy. Possible implications of these results are di

ISSN:0022-104X    

DOI:10.1002/jez.1401800111

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

年代:1972

数据来源: WILEY