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tetraploid chimeric mice
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CHANGES IN MEMBRANE PROPERTIES OF CELLS ISOLATED FROM THE ANLMAL POLE OF XENOPUS BLASTULAE: AN ELECTROPHYSIOI.OG[CAL STUDY. C. BAUD. Laboratoire de Neurobiologie Cellulaire et Mol~culaire, CNRS, 91190 Gif-sur-Yvette, France.
PRENATAL AND POSTNATAL DEVELOPMI~FP OF DIPLOID/TETRAPLOID CHIMERIC ~LICE. M. Bauernfeind, M. Leipoldt. Institute of Human Genetics, University of C45ttingen, 3400 C~ttingen, FRG
The electrical properties of blastomeres isolated from the animal pole of Xenopus blastulae have been investisated, uslng conventional electrophysiologlcal technique, as a preliminary study to possible membrane signaling during differenciation. The following characteristics appear: i) all blastomeres at all stages have high specific resistances, much higher than differenciated cells; 2) at stage 6-7 t~e membrane is poorly selective to K , and is very sensitive to external pH; at stage 9, sensitivity to pH has disappeared ~nd the membrane seems more selective to K ; 3) activity of the Na-K ATPase decreases between stage 7 and 9, as the blastocoelic cavity reaches its maximum vSlume; 4) st the time of each division and a few minutes before the onset of contraction, a slight hyperpolarization occurs with an increase of input resistance; as membrane is added during furrowing, the input resistance decreases slowly; no electrical uncoupling between daughter cells is observed in such in vitro divisions; 5) all cells reach--~ ~tate of high K conductance a few minutes after impalement with a microelectrode, this increase in K conductance seems to be due to the increase of ionic content of the cell.
Diploid/tetraploid chimer<].< were produced by aggregating 4n embryos of F I (BALB/c x DBA) with 2n embryos of C57BL/6J mice. Preimplantation, postimplantation and prenatal development of the chimeras were investigated. By karyotype ~ a l y s i s ~ i s Q z y m e typing, quantification of 4n cells and by the use of fur color we could d~nonstrate that a few of our newborn mice are indeed 2n/4n chimeras. Due to the fact that we could find 4n cells in a low percentage in different tissues, the chimeras showed a normal development postnatally. The rate of 4n cells in the implants of day I0.5 is also very low, indicating that a low nt~nber of 4n cells in the inner cell mass enhances the probability of normal development. The proportion of mitotic and meiotic cells in the testis in cc~parison to the control suggests that tetraploid cells contribute to the keimbahn and probably tetra% ]oid spermatogonia are capable of entering and passing meiosis.
314
315
WOUND HEALING IN THE UPPER LAYER OF TIIE CHICKEN BLASTODERM. H. Bortier and L. Vakaet, Laboratory of Anatomy and Embryology, Rijksuniversiteit Gent, Godshuizenlaan, 4, B-9000 Ghent, Belgium.
VIDEOMICROGRAPHY IN THE STUDY OF MORPHOGENETIC MOVEMENTS IN THE EARLY CHICKEN BLASTODERM. H. Bortier and L. Vakaet. Laboratory of Anatomy and Embryology. Rijksuniversiteit Gent, Godshuizenlaan, 4, B-9000 Ghent, Belgium.
We have studied wound healing in the upper layer of the chicken blastoderm in New culture, using videomicrography, scanning electron microscopy, and autoradiography. Wound healing is a process that has to counteract the radial tension exerted by the margin of overgrowth. Square wounds made with a needle (0,25 mm x 0,25 mm) in the upper layer do not heal unless covered with deep layer (Gallera and Castro-Correia, C.R.Soc.Biol., 154, 17281732, 1960). The direct effect of the presence of this layer is flattening of the wound lips. Circular holes punched with a glass pipette (0,2 mm to 0,25 mm diameter) heal without being covered with deep layer, but need more time to do so (4-6 hr vs + 2 hr). Although -the deep layer facilitates healing of wounds in the upper layer, healing does not require it. Healing of the upper layer seems to be intrinsic to the layer itself, and is not depending on a burst of mitotic activity.
Videomicrography is used increasingly in the study of cell movements, advantageously replacing cinemicrography. Morphogenetic movements in the early chicken blastoderm during normal development in New culture are demonstrated. Some are made without marking; in others vital marking or xenografting of homologous fragments of quail upper layer was performed. From these observations, the disposition~ of anlage fields can be deduced. The preneural plate extends its wings more caudally at Vakaet stage 6 (Arch.Biol., 81, 387-426, 1970) than proposed by Spratt (J.Exp.Zool., 120, 109-130, 1952). This is correlated with the situation of the limit of ingression of the pre-mesoblast. Ingression through the streak is not proven directly by videomicrography. However, ingression is suggested by the bilateral presence of quail mesoblast cells from a unilateral graft of upper layer in the ingression area of a chicken blastoderm. 114S
313
CHANGES IN MEMBRANE PROPERTIES OF CELLS ISOLATED FROM THE ANLMAL POLE OF XENOPUS BLASTULAE: AN ELECTROPHYSIOI.OG[CAL STUDY. C. BAUD. Laboratoire de Neurobiologie Cellulaire et Mol~culaire, CNRS, 91190 Gif-sur-Yvette, France.
PRENATAL AND POSTNATAL DEVELOPMI~FP OF DIPLOID/TETRAPLOID CHIMERIC ~LICE. M. Bauernfeind, M. Leipoldt. Institute of Human Genetics, University of C45ttingen, 3400 C~ttingen, FRG
The electrical properties of blastomeres isolated from the animal pole of Xenopus blastulae have been investisated, uslng conventional electrophysiologlcal technique, as a preliminary study to possible membrane signaling during differenciation. The following characteristics appear: i) all blastomeres at all stages have high specific resistances, much higher than differenciated cells; 2) at stage 6-7 t~e membrane is poorly selective to K , and is very sensitive to external pH; at stage 9, sensitivity to pH has disappeared ~nd the membrane seems more selective to K ; 3) activity of the Na-K ATPase decreases between stage 7 and 9, as the blastocoelic cavity reaches its maximum vSlume; 4) st the time of each division and a few minutes before the onset of contraction, a slight hyperpolarization occurs with an increase of input resistance; as membrane is added during furrowing, the input resistance decreases slowly; no electrical uncoupling between daughter cells is observed in such in vitro divisions; 5) all cells reach--~ ~tate of high K conductance a few minutes after impalement with a microelectrode, this increase in K conductance seems to be due to the increase of ionic content of the cell.
Diploid/tetraploid chimer<].< were produced by aggregating 4n embryos of F I (BALB/c x DBA) with 2n embryos of C57BL/6J mice. Preimplantation, postimplantation and prenatal development of the chimeras were investigated. By karyotype ~ a l y s i s ~ i s Q z y m e typing, quantification of 4n cells and by the use of fur color we could d~nonstrate that a few of our newborn mice are indeed 2n/4n chimeras. Due to the fact that we could find 4n cells in a low percentage in different tissues, the chimeras showed a normal development postnatally. The rate of 4n cells in the implants of day I0.5 is also very low, indicating that a low nt~nber of 4n cells in the inner cell mass enhances the probability of normal development. The proportion of mitotic and meiotic cells in the testis in cc~parison to the control suggests that tetraploid cells contribute to the keimbahn and probably tetra% ]oid spermatogonia are capable of entering and passing meiosis.
314
315
WOUND HEALING IN THE UPPER LAYER OF TIIE CHICKEN BLASTODERM. H. Bortier and L. Vakaet, Laboratory of Anatomy and Embryology, Rijksuniversiteit Gent, Godshuizenlaan, 4, B-9000 Ghent, Belgium.
VIDEOMICROGRAPHY IN THE STUDY OF MORPHOGENETIC MOVEMENTS IN THE EARLY CHICKEN BLASTODERM. H. Bortier and L. Vakaet. Laboratory of Anatomy and Embryology. Rijksuniversiteit Gent, Godshuizenlaan, 4, B-9000 Ghent, Belgium.
We have studied wound healing in the upper layer of the chicken blastoderm in New culture, using videomicrography, scanning electron microscopy, and autoradiography. Wound healing is a process that has to counteract the radial tension exerted by the margin of overgrowth. Square wounds made with a needle (0,25 mm x 0,25 mm) in the upper layer do not heal unless covered with deep layer (Gallera and Castro-Correia, C.R.Soc.Biol., 154, 17281732, 1960). The direct effect of the presence of this layer is flattening of the wound lips. Circular holes punched with a glass pipette (0,2 mm to 0,25 mm diameter) heal without being covered with deep layer, but need more time to do so (4-6 hr vs + 2 hr). Although -the deep layer facilitates healing of wounds in the upper layer, healing does not require it. Healing of the upper layer seems to be intrinsic to the layer itself, and is not depending on a burst of mitotic activity.
Videomicrography is used increasingly in the study of cell movements, advantageously replacing cinemicrography. Morphogenetic movements in the early chicken blastoderm during normal development in New culture are demonstrated. Some are made without marking; in others vital marking or xenografting of homologous fragments of quail upper layer was performed. From these observations, the disposition~ of anlage fields can be deduced. The preneural plate extends its wings more caudally at Vakaet stage 6 (Arch.Biol., 81, 387-426, 1970) than proposed by Spratt (J.Exp.Zool., 120, 109-130, 1952). This is correlated with the situation of the limit of ingression of the pre-mesoblast. Ingression through the streak is not proven directly by videomicrography. However, ingression is suggested by the bilateral presence of quail mesoblast cells from a unilateral graft of upper layer in the ingression area of a chicken blastoderm. 114S