ISSN:0022-104X    

DOI:10.1002/jez.1402320202

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

年代:1984

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1402320203

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

年代:1984

数据来源: WILEY

摘要:

AbstractIt has been suggested that formation of the shoulder in the embryonic chick is caused by caudal movement of the pleural coelom (Yander and Searls, '80a,b; Searls, '83). The cells of the somatopleure over the pleural coelom move into the base of the wing causing a thickening at the cranial base of the wing (the shoulder). In the previous work cited what caused the pleural coelom to move in a caudal direction could not be determined.It has now been observed that part of this movement is due to increase in the cranial‐caudal width of the hyoid arch. The mandibular arch does not move relative to the base of the wing or the somites. The caudal margin of the hyoid arch on the surface of the neck moves caudally at a rate of four to six somites per day, overgrowing the cervical sinus in the process. The aortic arches move in the same direction at a rate of 2 to 3 somites per day. It is suggested that the more medial elements of the hyoid arch are increasing in size, displacing the cervical sinus in a caudal direction. Part of the caudal movement of the cranial margin of the pleural coelom is also due to increase in length of the trachea. The trachea branches from the larynx ventral to about the eighth somite from 4 to 7 days of development. The distance from the cranial end of the trachea to the bifurcation that produces the left and right bronchi increases so that the bronchi become medial to the shoulder at 5.5 days, and the distance from the cranial end of the trachea to the pleural coelom increases so that the pleural coelom becomes medial to the shoulder at 4.5 day

ISSN:0022-104X    

DOI:10.1002/jez.1402320204

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

年代:1984

数据来源: WILEY

摘要:

AbstractA nerve‐conditioning lesion induced sustained acceleration of limb regeneration. Newt limb nerves were subjected to a conditioning lesion by unilateral axotomy at the elbow 2 weeks prior to amputating both limbs above the elbows. Limbs on the side that had received a conditioning lesion began the regeneration process 3–4 days earlier than contralateral controls and this difference was observed up to recognizable digit formation. Limb buds on the conditioned sides had a twofold greater axonal density than contralateral counterparts at 2 weeks after amputation. Since limb bud formation is dependent on a sufficient quantity of axonal regrowth, accelerated limb regeneration is apparently due to accelerated reinnervat

ISSN:0022-104X    

DOI:10.1002/jez.1402320205

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe squid cornea is derived from epithelial tissue behind the eyeball. The future cornea is pulled over the developing eyeball by contraction of muscle cells which develop just behind the leading edge. Treatment with cytochalasin B or colchicine does not stop this embryonic tissue movement, suggesting that the muscle is the main motive force in corneal closure.

ISSN:0022-104X    

DOI:10.1002/jez.1402320206

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

年代:1984

数据来源: WILEY

摘要:

AbstractDuring the early stages of somitogenesis in the chick embryo the presomitic cells in the segmental plate undergo compaction. The aggregation of segmental plate cells is stimulated by fibronectin. The stimulation of segmental plate cells to aggregate and undergo compaction can be effected in isolated segmental plate cells, in isolated segmental plates, and in intact embryos removed from the yolk. The fact that the segmental plate cells react with greater vigor to cellular fibronectin than to plasma fibronectin suggests a specific molecular mechanism in the initiation of somitogenesis.

ISSN:0022-104X    

DOI:10.1002/jez.1402320207

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe effects of retinoic acid on the regeneration of double anterior lower arms in the adult newt,Notophthalmus viridescens, were investigated. Normally, double anterior lower arms regenerate a hypomorphic, symmetrical pattern of structures, which are distally complete; and double anterior upper arms regenerate a hypomorphic, symmetrical butdistally incompletepattern of structures. In limbs with a normal anteroposterior axis, the major effect of retinoic acid is to alter the proximodistal (PD) positional value of cells local at the amputation level to a much more proximal value, thereby creating duplications in the regenerate of structures proximal to the amputation plane (Thoms and Stocum, '84). Therefore, we predicted that double anterior lower arms treated with retinoic acid would regenerate like double anterior upper arms. However, in a substantial number of cases, each half of these double anterior lower arms regenerated a limb that was complete in the anteroposterior (AP) axis, with asymmetry corresponding to the half of origin. In addition, these regenerates were serially duplicated in the PD axis. These results indicate that retinoic acid can posteriorize the positional value of midline cells, leading to restoration of normal AP pattern, when the set of posterior‐half positional values is removed from the cross section of the lim

ISSN:0022-104X    

DOI:10.1002/jez.1402320208

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

年代:1984

数据来源: WILEY

摘要:

AbstractLimbs were amputated through the thigh in stages from V onward inRana pipiens, R. sylvatica, andPseudacris nigritatadpoles to establish regenerative capacity. Normal regenerates were produced through stages XII, XI, and XIII, respectively, for the three species. However, hypomorphic forms with reduced toe numbers or a single spikelike spur, or nonregeneration, could appear as early as stages VII or VIII, and increased in frequency thereafter.Pseudacrisproduced the largest fraction of hypomorphs andR. sylvaticathe smallest. Regenerated limbs of various stages were reamputated just distad of the initial transection level and produced regenerates with almost the same frequency as did the initial amputees. InR. pipiensreamputation and regeneration was followed for up to six sequences, with but little change in frequency or quality of regeneration, even when the contralateral control limbs were in stages XIV–XVII, well beyond the possibility of regeneration after transection through the thigh. Clearly, the hormonal milieu did not limit regeneration, though rate of regeneration accelerated as metamorphic climax was approached. Foot sizes were measured inR. pipiens, and were seen in control animals to be correlated to both stage and to tadpole length. Regenerated feet tended to be slightly larger than control feet of the same stage, showed comparable relationships between length and width, but correlated more poorly with tadpole lengt

ISSN:0022-104X    

DOI:10.1002/jez.1402320209

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe normal timing and appearance of feather germs was per‐turbed by injecting the dye Janus Green B into the amniotic fluid of chick embryos at late stage 28, prior to the first appearance of feather germs. This treatment prevented feather germ morphogenesis in some regions while else‐where it delayed normal morphological development. The Janus Green B effect lasted for approximately 98 hours. Feather regions, which normally form epidermal placodes during the period of treatment, showed the longest delays in subsequent feather germ formation and were the most likely to remain featherless. These results suggest that the epidermal placode stage is critical for feather germ formation. Janus Green B appears to prevent feather germ morphogenesis by interfering with development prior to this critical stage. Since severely affected regions fail to recover their capacity to form feather germs, even after the period of sensitivity to the dye, a limited period of competence is suggested for feather germ format

ISSN:0022-104X    

DOI:10.1002/jez.1402320210

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

年代:1984

数据来源: WILEY

摘要:

AbstractWe have examined the fate of cultured stage 20 and 25 dorsal and ventral wing bud epithelia and have found evidence that the requirements of apical ectodermal ridge and nonridge limb ectoderms for in vitro survival are different. As previously reported for the apical ectodermal ridge (Boutin and Fallon, '84), dorsal and ventral ectoderms were extensively necrotic after 12 hours of culture in serum‐containing medium. The survival of dorsal and ventral limb epithelia at 18 hours was not improved by a collagen substratum, 10% Nuserum, epidermal growth factor, nerve growth factor, multiplication‐stimulating activity, insulin, or insulin, transferrin, and selenium. This is in contrast to our observations on the ridge which remains vital for at least 24 hours in insulin or insulin, transferrin, and selen

ISSN:0022-104X    

DOI:10.1002/jez.1402320211

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

年代:1984

数据来源: WILEY