摘要:

AbstractImmature erythrocytes of pigeons and chickens change from a spherical to a flat form following the final mitotic division during development.In vitrostudies provide evidence that initial changes in shape are influenced by conditions that affect availability of oxygen. Transformation to a flat form occurred most rapidly at 37°C, a temperature that results in deoxygenation of hemoglobin in erythrocytes of the bone marrow. The maximum rate of transformation occurred at pH 6.5, a pH which favors deoxygenated hemoglobin. Oxygen inhibited the transformation in shape at 37 °C and resulted in a reversion of shape, from flat to spherical. Flattening and deoxygenation of hemoglobin are highly correlated. Precursor erythrocytes in plasma clot culture were observed microscopically. The cell stages identified in sequence were: (1) the “n‐2” dark cells, apparently lacking hemoglobin. These cells divided to form “n‐1” cells which synthesized hemoglobin as they matured. The “n‐1” cells divided, forming spherical daughter “n” cells which flattened within 6

ISSN:0022-104X    

DOI:10.1002/jez.1401820102

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

年代:1972

数据来源: WILEY

摘要:

AbstractA histological study, involving autoradiography of tritiated thymidine labelled host: and graft, was performed in reciprocal skin grafts betweenNotophthalmus viridescensandAmbystoma mexicanum. The histoanatomical differences in the two types of skin appear to interfere in the rejection processes. The adepidermal membrane and dermal collagen, as well as the activity of the host epithelial cells, are stressed as factors playing a role in the rejection rate of the graft.

ISSN:0022-104X    

DOI:10.1002/jez.1401820103

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

年代:1972

数据来源: WILEY

摘要:

AbstractSyntheses of macromolecules, DNA, RNA, and protein, were studied in isolated presumptive epidermis ofTriturusgastrulae using radio active carbon dioxide as tracer.The explants cultured in the absence of inducing agents synthesized DNA, RNA, and protein for at least three days after explantation. Throughout the three days, DNA synthesis continued at an almost constant rate and patterns of newly synthesized proteins fractionated on polyacrylamide gel electrophoresis were similar. Activation of ribosomal RNA synthesis was observed to occur during culture. These facts suggest that, in the explants cultured in the absence of inducing agents, cell multiplication continued and the set of proteins synthesized changed little over a three‐day period.In the explants in which structures were induced by rat liver homogenate, syntheses of macromolecules differed from those in the control in some respects. There was a peak of active DNA synthesis around ten hours after induction treatment, and the phase of DNA synthesis was followed by active RNA synthesis. After three days of induction the pattern of newly synthesized proteins obtained by gel electrophoresis differed greatly from that seen earlier in the induction process and from that of control

ISSN:0022-104X    

DOI:10.1002/jez.1401820104

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

年代:1972

数据来源: WILEY

摘要:

AbstractA cyclic seasonal variation in forelimb regeneration in the newt,Notophthalmus viridescens, was noted under controlled environmental conditions at 20°C in previous experiments. Regeneration was enhanced in the summer months and reached its maximum linear growth rate in late spring‐early summer. It was suggested that this variation might be due to hormonal influences.The pituitary hormone prolactin was selected for study because it has been shown to support regeneration in hypophysectomized newts and to enhance regeneration in the intact newt, in the intact newt more effectively than growth hormone. Experiments in winter and summeri were performed to determine whether prolactin alone enhanced regeneration and what effect it might have on the seasonal variation in regeneration.The results clearly show enhancement of regeneration by intraperitoneal injections of prolactin in both summer and winter. The hormone increases the rate of linear growth and initiates early finger differentiation. The increase in linear growth rate persists throughout the 90‐day observation period. Prolactin does not enhance regeneration beyond the spontaneous optimum regenerative period in late spring‐early summer noted in previous experiments. Prolactin eliminates the seasonal variation in regeneration, and it is possible that the seasonal cycles are due to changes in output of this h

ISSN:0022-104X    

DOI:10.1002/jez.1401820105

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

年代:1972

数据来源: WILEY

摘要:

AbstractFour electrophoretic zones of trout intestinal alkaline phosphatase are described on the basis of charge and molecular weight heterogeneity. Qualitative and quantitative differences in the intestinal phosphatase complement suggest three basic phenotypes, which are exemplified by the isozyme patterns of wild brook trout, hatchery brook trout, and lake trout.The partially purified and separated trout phosphatase zones have been characterized physically and chemically. The data presented clearly place these enzymes in the category of the non‐specific alkaline phosphomonoesterases. In common with this group of enzymes, trout phosphatases catalyze the hydrolysis of a wide variety of phosphomonoesters and pyrophosphates, as well as transphosphorylation reaction

ISSN:0022-104X    

DOI:10.1002/jez.1401820106

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

年代:1972

数据来源: WILEY

摘要:

AbstractTwo fundamental physical properties of partially purified trout intestinal alkaline phosphatases which have been examined in detail are thermostability and activation energy. It has been clearly demonstrated that differences in thermostability exist between the trout isozymes, and that as a group they are more thermolabile than mammalian phosphatases. The activation energies of the two main trout phosphatase zones, however, are comparable to mammalian phosphatases.Experiments on cold‐acclimation of hatchery brook trout suggest that a fundamental reorganization of the intestinal alkaline phosphatase complement occurs. There are drastic quantitative differences in the isozyme patterns of 4° C‐acclimated fish and those acclimated to 10° C or 15° C. The 4° isozyme complement has a lower activation energy in the range of 2° C−10° C than does the 10° C isozyme complement. This finding strongly suggests that there is a reconstruction of the phosphatase isozyme complement with cold‐acclimation. This is functionally significant in that it results in the production of enzymes better suited to the new thermal regime. Three mechanisms are discussed as possible regulators o

ISSN:0022-104X    

DOI:10.1002/jez.1401820107

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

年代:1972

数据来源: WILEY

摘要:

AbstractEarly cleavage stages, mature eggs and developing oocytes of the grass miteSiteroptes graminum(Reuter), formerlyPediculopsis graminum(Reuter), (2n = 6; males haploid), were irradiated to: (a) test the hypothesis that the chromosomes are not monokinetic, (b) determine whether the chromosomes respond differently to irradiation during oogenesis and cleavage, and (c) find out whether a special region on the chromosome is required for elaboration of its chromosomoid (Feulgen‐negative body otherwise resembling the chromosome) which is left on the equator during both the meiotic and early cleavage mitoses. Fixation occurred 1–27 hours after irradiation.Chromosomal complements of more than 160 embryos (egg through 128 cell), and a few meiotic figures, were analyzed. Clusters of cells with decipherable chromosomal complements of 8–16 elements occurred frequently, and in especially favorable embryos karyotypes of all or nearly all the blastomeres could be analyzed. Many chromosomal fragments passed through at least three to five cleavage divisions in normal or nearly normal manner. Fragments which had come through one or both meiotic divisions behaved in blastomeres in a manner similar to those induced in cleavage stages. The chromosomes, therefore, are holo‐ or polykinetic in the classical sense. The tiniest fragments and very large translocations, however, tended to missegregate or to be eliminated.Some fragments were observed en route to or at the poles in both meiotic divisions. However, aberrancies in chromosomal behavior were more frequent during the maturation divisions, especially anaphase and telophase I, than during cleavage mitoses.Differential radiosensitivity was detected during the course of oogenesis, and between oogenesis and cleavage stages, the first known case in the class Arachnida. As earlier stages were irradiated, there was a trend in blastomeres toward fewer fragments, and far morenormaland nearly normal karyotypes. Irradiation of cleavage stages yielded most fragments. Probable causes of this differential radiosensitivity are discussed.In the few cases with well‐preserved, discrete chromosomoids the relative size of the chromosomoid and its associated chromosomal elements (including very small fragments) were correlated, and in several cases more than the diploid number of each was present. Thissuggests, but does not prove, that any part of the chromosome can elaborate chromosomoidal material.Possible causes, other than restriction of the kinetochore, for aberrancies in chromosomal behavior during both somatic and meiotic mitoses are discussed. The more recent literature on holokinetic chromosomes is analyzed, and new speculations about differences between mono‐ and holokinetic chromosomes are made. Factors of importance in design of experiments to determine the location of kinetochores ar

ISSN:0022-104X    

DOI:10.1002/jez.1401820108

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe utrastructure of thein vivodeveloped late preimplantation mouse blastocyst has been compared with the fine structure of mouse blastocysts developedin vitrofor 72 and 92 hours from the late two‐cell stage, as well as those grownin vitrofor 26 hours from the late morula or early blastocyst stage. Very little difference was observed between thein vivodeveloped blastocysts and those cultured 26 hoursin vitro. The differences between 72 and 92 hour‐embryos and thein vivogrown ones were significant. Thein vivospecimen and those grown 26 hoursin vitrohad differentiated a layer of endoderm cells while the ones culturedin vitrofrom the two‐cell stage did not. Nuclear and cytoplasmic structures in thein vivodeveloped blastocysts are well‐differentiated while those of the embryos grownin vitrofrom the two‐cell stage were less advanced. Possible reasons for the apparently less differentiated stage of blastocysts developedin vitrofrom the two‐cell stage ar

ISSN:0022-104X    

DOI:10.1002/jez.1401820109

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

年代:1972

数据来源: WILEY

摘要:

AbstractTissue‐specific heterogeneity of creatine kinase (CPK) isozymes is particularly pronounced in various trout species. Several of the isozymes expressed in stomach and in skeletal muscle appeared to be identical as judged by their electrophoretic behavior, but reversible dissociation studies on single, electrophoretically pure, CPK‐isozymes isolated from these two tissues revealed significant differences between isozymes of similar electrophoretic mobility. Moreover, in contrast to trout skeletal muscle, the native and reassociated stomach CPK isozyme patterns could be accounted for by the association of the polypeptide products of two gene loci into homodimers and heterodimers, providing further evidence that the isozymes of stomach and skeletal muscle are non‐identical and thus presumably the products of distinct

ISSN:0022-104X    

DOI:10.1002/jez.1401820110

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe effects of DL‐juvenile hormone on imaginal differentiation inSarcophaga bullatawere studied with particular reference to the tissues of the abdomen. The hormone was applied topically on the pupal cuticle at the time of eversion of the head. The development of the abdomen varied considerably but a majority of the animals showed morphological abnormalities and none emerged. Histological examination of the treated animals at different periods of adult development revealed that none of them had secreted a second pupal cuticle. The most severe morphogenetic effect observed was the inhibition of the spreading of the histoblast cells. Consequently the imaginal epidermis was not formed and cuticular structures xwere completely absent. The differential sensitivity of the various cell groups derived from the histoblasts and the genital disc to JH were reflected in their developmental behaviour and are described in detail. The most conspicuous cellular effect, however, appears to be the inhibition of differentiation. Hence the JH induced abnormalities show striking similarities to those induced by x‐irradiation as well as other inhibitory agents during the metamorphosis of higher Diptera and are probably related to the highly determinate state of the ce

ISSN:0022-104X    

DOI:10.1002/jez.1401820111

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

年代:1972

数据来源: WILEY