摘要:

AbstractThe purpose of these investigations was to study optimal conditions for the maintenance and stimulation of division of unfertilized mouse eggs in culture after fusion with somatic cells of various species origin.When unfertilized eggs obtained from superovulated C57B1/6 virgin mice were maintained in culture in Brinster's medium for 72 hours, less than 6% of the eggs divided. Following fusion in the presence of inactivated Sendai virus with somatic cells of mouse, hamster, monkey or human origin, 10 to 60% of the eggs divided, often developing to the early morula stage (3–10 cells).Blastomeres observed at this stage of development did not differ morphologically from embryo cells dividing after fertilization. Examination of autoradiograms obtained after fusion of eggs with labeled somatic cells support the belief that fusion may be a factor which initiates egg cell division. Ultimately, nuclei of the somatic cells inside the cytoplasm undergo karyorrhexis.Mouse fibroblasts infected with Moloney sarcoma virus fused better with egg cells than did non‐infected fibrobla

ISSN:0022-104X    

DOI:10.1002/jez.1401740102

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe regeneration of appendages ofProtopterus annectensandP. aethiopicushas been studied. Both limbs and tail demonstrate a notable capacity for self‐replacement. The initial direction of growth in the regenerate depended upon the nature of the amputation plane: straight, pointed, or terminally notched cuts elicited new growth along the primary axis, whereas cuts made at an angle resulted in regenerates whose axis was perpendicular to the plane of cut. In these cases, differential growth ultimately compensated and the final form was consistent with the axis of the original appendage. Lateral notches made in the posterior margin of the pectoral limb may effect the growth of a secondary filament. Such bifidism could not be elicited from pelvic limbs or tails.Growth curves showed a lag period of up to three and one‐half weeks, a period of rapid growth lasting one or more months, and then a time of decelerating growth. For each individual fish, these phases were undergone simultaneously, regardless of appendage, direction of cut, or amputation level. Limbs cut proximally, however, showed greater and more rapid growth than those with less material removed. Total replacement was found in all but some pelvic limbs.Regeneration, if in the lag phase, was halted by estivation, but rapid growth commenced shortly after arousal.Comparisons are made with other vertebra

ISSN:0022-104X    

DOI:10.1002/jez.1401740103

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

年代:1970

数据来源: WILEY

摘要:

AbstractPhototatic orientation by the marine dinoflagellateGyrodinium dorsumwas examined using closed circuit television methods. Mono‐ and bi‐directional stimuli were used to determine directional discrimination by the cells. Cell orientation time was also measured. From the results obtained, a model is presented which proposes paired photoreceptor si

ISSN:0022-104X    

DOI:10.1002/jez.1401740104

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

年代:1970

数据来源: WILEY

摘要:

AbstractTwo isozymes of acetylcholinesterase (AChE) in the skeletal muscles of the chick embryo decrease to very low levels after hatching. These isozymes have been shown to be maintained in fast twitch muscles, the superficial pectoral and biceps brachii, of birds homozygous for inherited muscular dystrophy. Histochemical studies are presented that associate these isozymes with diffuse AChE activity in the sarcoplasm of embryonic and dystrophic muscle fibers.The hypothesis that neural activity inhibits the activity of the embryonic AChE forms in normal but not in dystrophic muscle after hatching was supported by the fact that biceps muscles of normal chicks denervated at two days still retained embryonic AChE activity when examined one month after denervation. In addition embryonic AChE forms reappeared within three days after denervation in muscles from month old chicks. One month after surgery, total AChE activity of denervated normal muscle was three to four times that of the controls. Moreover, unlike the normal, the AChE activity of dystrophic biceps muscle did not increase following denervation. Tenotomy of muscles from month old chicks had little effect on AChE activity.

ISSN:0022-104X    

DOI:10.1002/jez.1401740105

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

年代:1970

数据来源: WILEY

摘要:

AbstractTo determine whether or not various thyroxine analogues accelerate metamorphosis by acting directly upon target organs, analogue‐cholesterol pellets were prepared and implanted into the dorsal tail fins ofRana pipienslarvae. Many analogue implants caused localized fin resorption, a response attributed to the direct action of the analogue upon the fin. Analogues with acetic or propionic acid side chains or with an isopropyl group but no iodine atoms in the β ring were effective in lower concentrations than was thyroxine; on this basis, the most active compounds were triiodothyropropionic acid and isopropyldiiodothyronine. Fin resorption was not induced by implants of diiodophenoxyacetic acids or of dihalogenated methoxythyranilines. Yet, intraorbital implants of these compounds did stimulate glandular development in the skin dorsal to the eye (a region with a lower threshold of response to thyroxine than the tail fin). The causation of local metamorphic responses, either in the tail fin or in the orbital region, by various thyroxine analogues indicates the direct action of such compounds upon peripheral tissues of the tadpo

ISSN:0022-104X    

DOI:10.1002/jez.1401740106

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

年代:1970

数据来源: WILEY

摘要:

AbstractBrook trout (Salvelinus fontinales) exposed to a low environmental pH (3.0–3.3) showed a drop in mean blood pH from 7.39 to 6.97. Trout at an environmental pH of 3.5 lost 50% of their total body sodium. Control sodium influx (72.5 μmoles/100 g hours) decreased to zero between pH 3.0 and 4.9 as Na efflux increased markedly over control levels. There was no significant difference in body Na content of wild trout from three streams ranging in pH from 6.05 to 7.10. Trout survived 13.1 to 14.7 hours in a 150 mM Na solution of pH 3.5 as compared to 2.5 to 4.9 hours at 100 μM Na and the same pH. The inability of brook trout to live in waters of pH less than about five, seems to be related to a drop in blood pH caused by the high hydrogen ion concentration of the medium. The loss of body Na appears to be of secondary importance as a cause of de

ISSN:0022-104X    

DOI:10.1002/jez.1401740107

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

年代:1970

数据来源: WILEY

摘要:

AbstractYoungAmbystomalarvae were subjected to forelimb amputation followed by a series of injections of either nerve growth factor (NGF) or saline solution. The animals receiving the NGF injections showed an increase in the length of the regenerate and an acceleration of digit formation at times up to two weeks after amputation. The maximum per cent increase in length occurred at about nine days post‐amputation. By two weeks after amputation, however, the difference between NGF‐treated and control animals had diminished considerably. The nerve growth factor, by increasing the extent of sensory innervation to the stump apparently accelerated blastema formation and early stages of regeneration. The fact that the regenerative rate can be altered by changing the nerve supply implies that there is not an absolute neural threshold for regeneration. Striking differences were noted in the normal regenerative rate ofA. opacumas compared withA. macula

ISSN:0022-104X    

DOI:10.1002/jez.1401740108

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

年代:1970

数据来源: WILEY

摘要:

AbstractMammary gland anlagen from the 17‐day fetal rat were grown for six and nine days in organ culture in basal (Waymouth's agar) nutrient medium only and with added insulin, insulin and prolactin, or insulin, prolactin, and aldosterone. Prior work has shown that the three‐hormone combination is most effective in stimulating histologic differentiation and the synthesis of a casein‐like material. Cultured explants from each group were examined by electron microscopy and compared with 17‐day anlagen before culture and with the mammary gland of the newborn female rat. The 17‐day anlage is a solid mass of cells, surrounded by a basal lamina and a partially oriented sheath of mesenchyme cells; ultrastructure of the epithelial cells shows the characteristics of fetal tissue. At birth, the normal mammary gland consists of an extensively branching system of ductules with continuous lumina and a well developed sheath of connective tissue. Luminal surfaces of epithelial cells bear numerous microvilli and are ringed by continuous belts of tight junctions. Fat droplets are present in cells and lumina and the Golgi apparatus is abundant but not visibly active in protein secretion; rough endoplasmic reticulum is present in moderate quantity and occasionally is distended with low‐density, homogeneous content. Organ culture without hormones resulted in epithelial cell proliferation; however, the basal lamina disappeared, no connective‐tissue sheath developed, and the epithelial mass showed no organized growth pattern. Some small, true lumina appeared within the cell mass. With insulin added, the anlagen ramified moderately and formed true lumina that were distinct but often discontinuous; the enveloping connective and adipose tissues were well developed. Epithelial cells showed little organellar differentiation but contained many fat droplets and abundant glycogen. In the presence of insulin and prolactin, ductal organization was much improved, whereas organellar differentiation within epithelial cells was only slightly better than with insulin alone. With the three‐hormone combination, histologic organization and ultrastructural differentiation attained levels similar to those in the gland of the newborn rat; in addition, the Golgi complex in some cells was conspicuously active and many Golgi vesicles contained condensed material similar to the protein secretion products seen in pregnant and lactating

ISSN:0022-104X    

DOI:10.1002/jez.1401740109

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

年代:1970

数据来源: WILEY

摘要:

AbstractContinuous exposure of embryonic explants to thymidine‐H3was used to determine patterns of late‐replicating DNA synthesis, i.e. DNA synthesized during the last quarter of the S period, in chromosomes from different germ layers of developing frog embryos (Rana pipiens). Autoradiographic localization of silver grains over chromosomes 1, 7 and 8, as well as unkaryotyped chromosomes, revealed that patterns of late‐replicating DNA are similar in determined cells that will undergo different pathways of differentiation. In undetermined early gastrula cells and in differentiated tailbud dorsal axial cells (nerve tube, somites and notochord) more sites of DNA synthesis were late‐replicating in chromosomes 1, 7 and 8 and in unkaryotyped chromosomes than in cells of the neural plate‐dorsal mesoderm of neurulae where differentiation is occurring and in neurula endoderm where determination is tak

ISSN:0022-104X    

DOI:10.1002/jez.1401740110

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

年代:1970

数据来源: WILEY

ISSN:0022-104X    

DOI:10.1002/jez.1401740101

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

年代:1970

数据来源: WILEY