摘要:

AbstractIt has been previously shown that discs prepared from the tail fins of tadpoles, (R. pipiens), survivein vitrofor several weeks and respond to thyroxine by undergoing resorption. Discs cut from animals during metamorphic climax, demonstrate rapid resorption without addition of exogenous thyroxine.Discs were cut from tadpoles in early prometamorphosis and in climax and were implanted with either whole pituitary glands or the separate lobes. Controls were either implanted with cerebrum or sham‐operated. These discs were maintained in solutions of thyroxine inHanksmedium, (3 ppb or 6 ppb), or in control,Hanksmedium. In addition, discs from animals in early prometamorphosis were injected with either prolactin, GH, or control medium and discs from animals at climax were immersed in solutions of prolactin, GH, FSH and control medium.The results of these experiments demonstrates that the anterior pituitary, of the tadpole releases a factor that interferes with the action of thyroxine on tail discsin vitro.Prolactin and GH demonstrate similar activity but are less effective than the graft pituitaries. The results are interpreted to indicate that antagonism exists with respect to tail resorption between a pituitary growth factor, (possibly a prolactin‐like, or GH‐like molecule) and thyroid ho

ISSN:0022-104X    

DOI:10.1002/jez.1401690102

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe RNA of anterior and posterior regions of normal and regenerating planarians was extracted by means of a modification of the phenol procedure, and further purified. The nucleotide composition of this RNA was determined by subjecting it to alkaline hydrolysis and resolving the constituent nucleotides by thin layer electrophoresis. Contrary to older reports there was no difference in either amount or base composition of the total RNA from anterior and posterior regions or between regenerate and control worms. Resolution of the various molecular weight species of the planarian RNA by sucrose density centrifugation and gel filtration revealed a typical distribution between ribosomal and transfer RNA as well as the explanation of the negative result. Constancy of base composition of the predominate ribosomal RNA would mask any anticipated changes in base composition.

ISSN:0022-104X    

DOI:10.1002/jez.1401690103

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

年代:1968

数据来源: WILEY

摘要:

AbstractSurgically undamaged photoreceptor cells that have no connections with the central nervous system were obtained by transplanting the eye imaginal disc of third instar housefly larvae (Musca domestica) into the abdomens of host larvae and waiting for development of the host flies. Following differentiation, the photoreceptor cells of the transplants have normal cell bodies and rhabdomeres. Their axons, on the other hand, do not make synapses with higher order cells. The retinular cells, thus isolated from the optic lobe, give electrical responses to illumination that are indistinguishable from the membrane responses of normal receptor cells, and at moderate intensities of stimulation consist of an initial transient and a plateau. This graded depolarization of the soma (receptor potential) spreads electrotonically into the axon without initiating spikes. Neither CO2nor tetrodotoxin has an effect on the receptor potential of isolated photoreceptors. The transplants dark adapt at the same rate as normal retinulae, dark adaptation being slower following longer periods of light adaptation. Clearly in flies the development of the synapses of the lamina ganglionaris is not necessary for normal physiological development of the receptors, and the responses of the photoreceptors of normal eyes can be generated without significant feedback control from the optic lobe.

ISSN:0022-104X    

DOI:10.1002/jez.1401690104

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

年代:1968

数据来源: WILEY

摘要:

AbstractEmbryonic mouse kidney mesenchymes of various ages were tested for their abilities to initiate and supportureteric bud morphogenesisin vitro.Nephrogenic cord mesenchyme taken from animals before metanephros initiation (10 days) was combined with ureteric buds. The buds showed no morphogenesis. This was true for presumptive metanephric mesenchyme and for mesenchymes (pronephric and mesonephric) already undergoing nephrogenesis. These results indicate basic physiological differences between pronephric, mesonephric and metanephric regions of the cord. When entire nephric systems were cultured alone no metanephros developed. This, and the fact that presumptive metanephric mesenchyme had no influence on ureteric buds, indicates that metanephros initiation (both bud and mesenchyme) results from some activity originating outside the nephrogenic cord.When combined with metanephric mesenchyme at various stages of tubulogenesis (loose, condensed, or tubular), ureteric buds branched only in the presence of the loose mesenchyme. Branching occurred in loose mesenchyme taken from 11 to 15 day kidneys. Apparently once a given group of cells begins tubulogenesis they lose their ability to induce ureteric bud morphogenesis.As tubulogenesis proceeds, the amount of loose mesenchymes per kidney decreases sharply. Ultimate size of the metanephros may be established by depletion of loose mesenchyme resulting in its ureteric bud‐inducing potential falling below some critical leve

ISSN:0022-104X    

DOI:10.1002/jez.1401690105

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe early development of the zebra fish embryo,Brachydanio rerio(Hamilton) was studied under thermostatically controlled temperatures ranging from 13° to 35°C. Regular and successive cleavages and a distinct continuity of morphological features proceed regularly between 23° and 34°C. Embryos kept at temperatures above or below these limits did not complete embryogenesis. Embryogenesis up to late high blastula proceeded at the same rate of development over the temperature range of 24°C to 32°C.Time‐lapse cinephotomicrography was utilized in a study of development from the one‐celled blastodisc to the closure of the blastopore, incubated in a modified Rose culture chamber. The number of abnormal embryos was constant over the range of temperatures from 23

ISSN:0022-104X    

DOI:10.1002/jez.1401690106

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

年代:1968

数据来源: WILEY

摘要:

AbstractIndividual sites of ATP synthesis were studied in the Minute(2)z mutant ofDrosophila melanogasterby supplying appropriate substrates to isolated mitochondria and determining the ratio of phosphorus esterifield to oxygen consumed at each locus. In this manner it was determined that the terminal locus of phosphorylation in the Minute is comparable to control, but the first two sites of ATP synthesis and possibly the substrate level phosphorylation are aberrant.The significance of these data and their relation to the Minute effect are discussed.

ISSN:0022-104X    

DOI:10.1002/jez.1401690107

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

年代:1968

数据来源: WILEY

摘要:

AbstractMale 129/Re mice were castrated at 18–24 days of age. At 20 weeks of age they were sacrificed and the body weights and the weights of the anterior tibialis, biceps brachii, extensor digitorum longus, soleus and sternomastoideus were recorded. These muscles were also examined cytologically for total fiber number and fiber diameter distributions. The differences between the muscle weights of castrates and controls were correlated with different levels of fiber growth. The level of fiber growth in the phasic anterior tibialis, biceps brachii and extensor digitorum longus (i.e. muscles bringing about body movements) was concluded as being under the indirect control of the pituitary growth hormone, in that it acts on the body as a whole thereby increasing the work load of these muscles. Whereas for the sternomastoideus there appears to be a more direct effect of testosteron

ISSN:0022-104X    

DOI:10.1002/jez.1401690108

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

年代:1968

数据来源: WILEY

摘要:

AbstractDugesia dorotocephalaandD. tigrinawere sectioned transversely, imbedded in agar, and exposed to alternating current in a rectangular chamber. At field strengths of from 310 to 418.4 rms mv/mm potential fall, functional bipolar, regressive bipolar and permanent bipolar regenerants were produced. No regenerants showed reversal of polarity. The similarity in field strength for the three groups was primarily due to the extreme motility of imbedded pieces. The results were independent of absolute healing time and duration of exposure to the field, and of body level of regenerate origin. No significant differences were found between the species with respect to mortality or response to the AC field. AC field action is non‐polar, but its direction must coincide with the regenerant axis to be effective. The field operates to reduce the normal antero‐posterior polar

ISSN:0022-104X    

DOI:10.1002/jez.1401690109

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe number of mitotic figures in the optic tectum of the chick increases from just over 20, 000 on the fourth day of incubation (stages 25 and 26) to a peak of approximately 45, 000 on the fifth and sixth days (stages 28 and 29). Thereafter, the number declines sharply to about 10, 000 and 2, 000 on the eighth and ninth days respectively and to as few as 100 and 18 on the eleventh and twelfth days. The dividing cells are not uniformly distributed throughout the tectum but show a clear rostral to caudal gradient such that at every stage the number of mitoses in the caudal half of the tectum exceeds that in its rostral half. In addition the number of mitotic figures in the ventrolateral half of the tectum exceeds that in its dorsomedial half between the fourth and seventh days of incubation, but this pattern is reversed during the last few days of mitotic activity.The process of cell proliferation in the optic tectum appears to be completely independent of the developing eye since there is no significant change in either the total number of mitotic figures in the tectum, or in their spatial distribution, after complete removal of the optic vesicle towards the end of the second day of incubation.

ISSN:0022-104X    

DOI:10.1002/jez.1401690110

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

年代:1968

数据来源: WILEY

摘要:

AbstractThis investigation describes the autotomy and regeneration of the metapodium in the mollusc,G. varia, a species inhabiting infratidal habitats along the Red Sea littoral. It was shown that in this species there is a histologically prominent autotomy line that separates the metapodium from the propodium and enables autotomy. The animals can regenerate the dropped‐off part of the foot and at new irritation, they can reautotomize and re‐regenerate new metapodia.The histological development of the regenerate is described in detail, especially the development of the neural net and the musculat

ISSN:0022-104X    

DOI:10.1002/jez.1401690111

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

年代:1968

数据来源: WILEY