摘要:

AbstractDividing eggs ofEchinarachnius parma, Hydractinia echinata, Cerebratulus fuscusandMytilus eduliswere subjected to experiments designed to yield additional information concerning the cytoplasm in the cleavage plane. Answers to the following questions were sought: (1) Will the base of the furrow cut itself upon a needle placed in its path at right angles to the cleavage plane? (2) What part of the surface is responsible for the constricted shape of the partly divided egg? (3) Does completion of furrowing depend upon a specific subsurface cytoplasmic arrangement? It was found that in no case could the base of the furrow cut itself upon a needle. The constricted shape of the partly dividedEchinarachniusegg depends on the integrity of the surface at the base of the furrow. The eggs of all four species completed division despite drastic stirring and mixture of subsurface cytoplasm which was begun during early stages of furrowing and continued until the blastomeres were separated.

ISSN:0022-104X    

DOI:10.1002/jez.1401610102

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe duodenal progenitor population has been investigated with tritium thymidine (H3‐T) and autoradiography in male Swiss albino mice to characterize the role that individual cell types (principal, goblet, and Paneth) have in the proliferative activity of the duodenal crypt of Lieberkühn.Incorporation of H3‐T into newly synthesized DNA of all three cell types was observed by one‐half after injection of the isotope. Labeled principal and goblet cells were distributed from the first cell of the cryptal mouth to the last cell at the cryptal base. The majority of labeled cells was found in the central region of the crypt Labeled Paneth cells were restricted to the last four cells at the cryptal base.Analysis of the percentage of labeled metaphase and mitotic figures after H3‐T administration showed that the progenitor cycle duration of principal and goblet cells was about 15 hours, while that of Paneth cells was approximately 80 hours. The mean S‐phase duration was 7.4, 7.4 and 8.7 hours for principal, goblet, and Paneth cells, respectively. Thus, the G1portion of the cell cycle was considerably longer for Paneth cells, while all phases of the progenitor cycle were of the same duration for principal and goblet cells.It appears from the data that the three cell types of the adult duodenal crypt comprise independent populations capable of self‐renewal. Our observations also suggest the existence of causal relationships between the positioning of the proliferative cells types in the duodenal microenvironment and their respective cyc

ISSN:0022-104X    

DOI:10.1002/jez.1401610103

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

年代:1966

数据来源: WILEY

摘要:

AbstractEggs ofBufo punctatus, B. cognatus, B. valliceps, B. luetkeni, a hybrid combination (maleB. vallicepsX femaleB. luetkeni), Scaphiopus couchi, Microhyla olivacea, Acris crepitans, Pseudacris clarki, andHyla cinereawere exposed to a range of temperatures to determine the developmental temperature tolerance of each species.When comparing closely related species, the species with the most northern distribution has the lowest lethal minimum temperature, while the species with the most southern distribution has the highest lethal maximum temperature.Temperatures of water in which anurans breed are found to be within the temperature tolerance range of the particular species, and usually near that temperature most favorable for optimum development.

ISSN:0022-104X    

DOI:10.1002/jez.1401610104

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe time to maturation of a free‐living, protandrous, self‐fertilizing nematode,Caenorhabditis briggsae, was used to assay preparations of a proteinaceous growth factor and the effects of different treatments. Development was measured as time of the production of F1offspring against concentration of growth factor. The data were transformed to the reciprocal of F1time against logarithm of the dose and analyzed by regression analysis. Estimates were made of the dose of growth factor required for maturation in seven days, and relative potencies were determined for assays whose regression coefficients did not significantly differ from one another. The dose of growth factor required for maturation in seven days fell within the range from 8 μg/ml to 28 μg/ml. The methods of treatment for activation of growth factor studied were freezing overnight at —23°C, dialysis to low phosphate, and addition of the sucrose polymer, FICOLL. Reproducibility of results was shown for controls made for each experiment and for assays repeated at different times. Inocula of various numbers of larvae per tube, 1 through 30, were compared; significant increase in maturation time occurred when inocula were large

ISSN:0022-104X    

DOI:10.1002/jez.1401610105

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

年代:1966

数据来源: WILEY

摘要:

AbstractMaleDrosophila melanogasterembryos inheriting deficiencies of theNotchseries on the X‐chromosome fail to hatch from the egg, and are characterized in part by almost complete lack of differentiation of the mesoderm. In order to determine the developmental capacities of these tissues, male embryos containing N8 and N264‐40 deficiencies were culturedin vivoin the hemocoeles of wild‐typeD. melanogasterlarvae and adults. After periods of five and 12 days, theNotchembryos were compared with similarly cultured wild‐type control embryos. The deficient embryos of both types revealed considerable growth. The mesodermal derivatives muscle, fat, and gonad sheath were well differentiated. In every case, embryos of the short deficiency, N264‐40, grew to a greater size than did those of the much longer deficiency, N8. They generally did not exceed the size attained by normal embryos cultured for the same length of time. The growth of transplants in larval hosts always exceeded that seen in adult hosts in the same period of time. Neither of the types of deficient embryos was able to molt in either type of host, although control embryos always molted in larval hosts. The results indicate that the mesodermal tissues ofNotchembryos are capable of further differentiation than they are able to exhibit in their own environment, and that the genetic materal within the extent of the N8 deficiency may be involved in their capacity to grow i

ISSN:0022-104X    

DOI:10.1002/jez.1401610106

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

年代:1966

数据来源: WILEY

摘要:

AbstractBy grafting and other micrurgical operations, cells and cell‐systems bearing two oral regeneration primordia initially in different phases of development can be produced. There is a strong tendency for the two anlagen to synchronize their developments and complete the later stages of oral differentiation together. The minority of cases, which failed to synchronize the developing primordia, indicated the limits of this coordination and always revealed prominent interaction between the graft components. A simple substrate hypothesis will probably not explain the results. Conclusions are that the oral primordium, once initiated, does not develop autonomously at its own intrinsic rate, and that a cell or fusion of cells performing the same process (elaboration of feeding organelles) in two different places within the system, strongly tends not to do so out of phase but synchronousl

ISSN:0022-104X    

DOI:10.1002/jez.1401610107

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe effects of β‐mercaptoethanol on cell division, nuclear division, and oral morphogenesis were investigated in two strains ofTetrahymena pyriformis, WH‐6 (micronucleate) and GL (amicronucleate). Mercaptoethanol inhibited division in both strains. In exponentially growing cell cultures, cell multiplication stopped after a 30 minute lag (strain WH‐6); in synchronized cultures, division was prevented or very greatly delayed if the agent was added during the first 60% of the interval between the end of the last synchronizing shock and the synchronous division.In both strains, mercaptoethanol brought about an arrest of oral primordium development in cells which had not yet begun to form visible membranelles at the time of addition of the drug. In cells arrested just prior to the onset of membranelle development the oral primordia became disorganized and in many cases were gradually resorbed. In these cells micronuclear division was generally arrested (strain WH‐6) and macronuclear and cell division did not occur at all (strain WH‐6), or were resumed after a long delay (strain GL).Cells which were in stages of visible membranelle development at the time of addition of mercaptoethanol continued to develop. In strain WH‐6, all of these cells completed oral development and divided, while in strain GL about 40% of these cells were arrested in the course of membranelle development. In these arrested cells, the oral primordia were resorbed, and division did not take place.In the situations in which oral morphogenesis was completed and cell division took place in mercaptoethanol, micronuclear division (in strain WH‐6) was in all cases normally completed. Macronuclear division in strain WH‐6 was also normal at the minimum concentration (4 × 10−2M) which affected morphogenesis when added at earlier stages. However, at a somewhat higher concentration (5 × 10−2M) in strain WH‐6, and at the lowest concentration employed (1.5 × 10−2M) for strain GL, macronuclear division was either prevented (in both strains) or else rendered highly abnormal (in strain GL).These data suggest that mercaptoethanol blocks some process required for the initial organization of oral structures and for the division of the macronucleus. The nature o

ISSN:0022-104X    

DOI:10.1002/jez.1401610108

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

年代:1966

数据来源: WILEY

摘要:

AbstractNine groups of experiments on 537 eyes of adult newts,Triturus v. viridescens, examined conditions under which lens regeneration is inhibited or released from dorsal iris tissue. The lens is quite vulnerable for it degenerates when the lens capsule is injured and when the neural retina degenerates following a temporary loss of blood supply. Degeneration of neural retina in lentectomized eyes delays lens regeneration from both implanted and host dorsal iris. If degeneration of neural retina is induced after lens regeneration begins its further development is temporarily retarded until the neural retina proceeds to regenerate.If one of two large lens regenerates in a single eye is removed, one from the host eye or one from an implanted segment of dorsal iris, the surviving lens inhibits further lens regeneration from any dorsal iris tissue present. Two dorsal halves of eyes can be fused into one normal appearing unit which regenerates two lenses, one from each half. When one lens is removed the remaining lens inhibits lens regeneration from either half in the environment of a normal amount of neural retina.If a plastic membrane is implanted to divide the upper and lower halves of the eye into two separate chambers, each with its own aqueous humor and half of the neural retina, lens regeneration from the isolated iris above is no longer inhibited by the intact normal lens below.

ISSN:0022-104X    

DOI:10.1002/jez.1401610109

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

年代:1966

数据来源: WILEY

摘要:

AbstractDevelopment of the protractor lentis muscle and the vestige of the choroid fissure, the ventral iris cleft, was studied inAmblystoma punctatumembryos, larvae and young adults. One hundred twenty‐three embryonic eyes in various stages of development were excised, rotated 180° and reimplanted to determine when in development the cleft and muscle become ventrally polarized. In Amblystoma, as the optic cup forms and the ventral region closes, the choroid fissure becomes a deep notch at the mid‐ventral rim of the cup. It remains as a cleft in the iris near the retina as the outgrowing iris obliterates the rest of the fissure. InTriturus v. viridescensthe cleft becomes located in the middle of the ventral iris membrane some distance from the ora serrata. The protractor lentis muscle arises from mesenchyme cells at the inner surface of the cornea near the cleft which it enters. InA. punctatum, the polarity of the cleft and muscle is not yet established up to stage 29. From stages 29+ to 33, when the early optic cup is forming, their polarity is labile. Polarity is permanently established soon after at stage 34.After complete ventral iridectomy the cleft reappeared in the regenerated iris. The muscle reappeared in some cases also. Retinal pigment cells locally regenerate the ventral iris and restore to it the capacity to replace a cleft which is similar to the vestigeal structure derived from the choroid fissure.This is another example where dedifferentiated retinal pigment cells restore locally to regenerating tissue the ability to form special structures normal to that re

ISSN:0022-104X    

DOI:10.1002/jez.1401610110

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

年代:1966

数据来源: WILEY

摘要:

AbstractVegetalization was produced in sea urchin embryos by treatment with D‐ and L‐p‐tyrosine, o‐tyrosine, and m‐tyrosine, for 2 to 6 hours during cleavage. Glycine was without effect on development; phenylalanine produced general effects represented by reduction of both animal and vegetal structures. The vegetalizing action of tyrosine was synergistic with that of lithium or dinitrophenol. However, unlike the latter compounds, tyrosine had no effect on respiratory rate of the embryos.The uptake and the incorporation of algal hydrolysate‐C‐14 and leucine‐C‐14, added to the sea water medium, were lower in sea urchin embryos in the presence of tyrosine or phenylalanine than in untreated control embryos. Inhibition of incorporation caused by phenylalanine was about twice that by tyrosine, and it was postulated that the different effects of these substances on development are related to the degree of inhibition. Neither glycine nor lithium inhibited amino acid uptake.When embryos were treated with tyrosine in the presence of a full complement of those free amino acids normally found in the egg, the vegetalizing effect of tyrosine was annulled. Since the sea urchin depends upon endogenous amino acids for protein synthesis during cleavage, it is suggested that in some way tyrosine limits the endogenous supply of amino acids available for synthesis of the proteins associated with animal structures by inhibiting their release fro

ISSN:0022-104X    

DOI:10.1002/jez.1401610111

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

年代:1966

数据来源: WILEY