Recipient Eggs Research Articles

Transplantations of blastula nuclei into activated eggs from the body cavity and from the uterus of Rana pipiens: I. Evidence for fusion between the transferred nucleus and the female nucleus of the recipient eggs

1. 1. Transfers of blastula nuclei were made into activated body cavity and uterine host eggs in which the female chromatin was not removed. Information obtained on the early cleavage histories, polar body formation, and ploidy of the resulting embryos indicate that in the majority of cases a fusion had occurred between the transplanted nucleus and the female pronucleus of the activated egg. 2. 2. Diploid nuclear transfers into activated body cavity and uterine eggs gave rise to larvae that varied in their chromosome number ranging from haploid to hexaploid. Mosaics were also obtained. 2.1. a. The majority of embryos were found to be triploid, and these developed only from activated eggs that cleaved on time. 2.2. b. Hexaploid embryos developed only from activated eggs whose first cleavage was delayed one cleavage interval. 3. 3. Haploid nuclear transfers into activated body cavity eggs gave rise to tadpoles possessing the following chromosome numbers: haploid, diploid, triploid, and tetraploid; a mosaic was also obtained. 3.1. a. The majority of activated eggs that cleaved on time developed into diploid embryos. 3.2. b. The tetraploids and triploids developed only from activated eggs whose first cleavage was delayed one cleavage period. 4. 4. The chromosome numbers of some of the mosaic embryos also indicate that a delayed fusion involving the transplanted nucleus may take place in activated host eggs.

Nuclear transplantation studies on the early gastrula ( Rana pipiens) : I. Nuclei of presumptive endoderm

Previously published studies showed that the nuclear changes associated with endodermal differentiation are well advanced at the late gastrula stage in Rana pipiens. In the present investigation an attempt was made to determine when in development this process of nuclear “differentiation” begins. Presumptive endoderm nuclei from the vegetal pole region of early gastrulae were tested by transplantation into enucleated eggs. For comparison, control transfers were performed with nuclei from the undetermined animal pole region of blastulae. The recipient eggs developed as follows: 1. 1. Cleavage: Control and experimental transfers gave about the same results. Approximately 60% of the transfers in each series led to the formation of complete blastulae. 2. 2. Embryonic differentiation: Eighty per cent of the complete blastulae resulting from the control transfers developed normally to larval stages. In the case of the transfers of presumptive endoderm nuclei, 52% of the blastulae developed normally. The majority of the remaining embryos displayed abnormalities in postneurula stages and failed to attain the larval stage. A few of these abnormal embryos (5) showed extreme deficiencies in the ectodermal derivatives. In the majority, however, the deficiencies were not related to the endodermal origin of the nuclei in any obvious fashion. 3. 3. Larval development: All embryos which passed through the embryonic stages normally were reared until they died or reached metamorphosis. In their larval development the nuclear-transplant animals did not differ from their normally fertilized controls. A possible exception to this conclusion is mentioned on page 261. The results summarized above are compared with those previously obtained by us in transplantation studies on nuclei from older donors; and with the results of experiments on Xenopus laevis nuclei recently reported by Fischberg et al., 1958.

Transplantation of Living Nuclei of Late Gastrulae into Enucleated Eggs of Rana pipiens

ABSTRACT In previous papers it has been shown that living nuclei of animal hemisphere cells of frog blastulae and early gastrulae can be transferred into enucleated eggs (Briggs & King, 1952,1953a). Approximately 20 per cent, to 40 per cent, of the recipient eggs cleave normally, and the majority of these develop into complete embryos, demonstrating that the transplanted nuclei are undifferentiated (i.e. still capable of participating in all types of differentiation). This result is more or less expected since the nuclei in question come from undifferentiated parts of the blastula and early gastrula.