摘要:

AbstractUrostyla weissei, a hypotrichous ciliate possessing two macronuclei and four or more micronuclei, has an inter‐division interval of about 12 hours. Macronuclear DNA replication occurs between five and ten hours after cell division, while micronuclear DNA replication takes place a short time prior to mitosis. Synchronous populations of dividing cells were isolated, provided with H3‐thymidine labelledTetrahymena, and then were equatorially transected during either G1 or macronuclear S. Regeneration was completed, with attendant micronuclear and macronuclear division, four to five hours after transection. No macronuclear DNA synthesis took place during the regeneration interval. In cells transected during macronuclear S, the replication band generally disappeared and DNA synthesis was arrested. The macronucleus then divided without mixing of replicated and un‐replicated portions, so that the replicated material generally passed to only one of the macronuclear division products, which was larger than the other. Following the completion of regeneration, a new wave of DNA synthesis commenced immediately in macronuclei of cells transected during G1, and with some delay in cells transected during S. The completion of this replication wave was not followed by cell division; instead a second replication was initiated a few hours later, and then the cells divided.Micronuclei initiated DNA synthesis prior to mitosis, which occurred whenever regeneration was completed, and regardless of the time of transection or the concurrent state of the macronucleus. Thus, in cells transected during G1, micronuclei replicated considerably earlier than in the unoperated controls.In cells subjected to repeated transection at four to five hour intervals, macronuclei became progressively smaller while micronuclei remained the same size, which is expected if macronuclear replication is suppressed due to the regeneration‐stimulus, while micronuclear replication occurs automatically prior to every

ISSN:0022-104X    

DOI:10.1002/jez.1401730102

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

年代:1970

数据来源: WILEY

摘要:

AbstractFive specimens ofVampyrum spectrumwere trained to discriminate between solid targets differing in shape or size using echolocation alone. A pair of lucite targets, one a sphere, the other a prolate spheroid, were then designed so as to produce echoes of approximately equal overall amplitude at the distance of choice by the bats, but of different frequency composition. This discrimination was successfully performed by four of the animals and the two best performers were studied in detail by photographic analysis to ascertain whether frequency or amplitude cues were actually being utilized. By manipulating the degree of frequency dependence in the echoes, it was shown that one animal seemed to rely on the availability of frequency‐dependent cues for successful discrimination while the other did not. Examination of the structure of the pulses used on these flights indicated a consistent pattern of changes as the targets were approached. Some of these changes could be correlated with the kinds of cues the two bats seemed to be using in making the discrimination

ISSN:0022-104X    

DOI:10.1002/jez.1401730103

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

年代:1970

数据来源: WILEY

摘要:

AbstractUnfertilized eggs recovered from donor rabbits at known times after injection of HCG were transferred to the oviducts of mated recipients (prevented from ovulating by having their ovaries covered with nail polish) at specific times after mating. When newly ovulated eggs (11.25–13.5 hours after HCG injection) were left in the oviducts of the recipients for 1, 1.5, 2, 2.5 and 3 hours, 15, 30, 44, 59 and 75% respectively were penetrated by spermatozoa. If the unfertilized eggs were allowed to age in the oviducts of the donor before transfer then fertilizability decreased: only 41 and 25% of eggs 15–15.5 hours and 17–17.5 hours old at time of transfer respectively were penetrated during 2.5 hours in the recipients' oviducts compared to 59% of 13–13.5 hour eggs. No beneficial effect from maturation in the donor of the unfertilized egg and its membranes was observed. When eggs with cumulus cells removed were transferred to recipients at 9–9.5 hours after mating, then a decrease in the percentage of eggs penetrated during 2.5 hours in the recipients' oviducts was found. Removal of both cumulus and corona cells had no greater effect than removal of cumulus alone. However, when eggs similarly treated were transferred to recipients at 14 hours after mating, neither removal of cumulus nor of cumulus and corona cells had any effect on the percentage of eggs penetrated during 2.5 hours. It is concluded that when conditions for fertilization are not optimal the cumulus is important for ensuring meeting of sperm and egg, but that when conditions are optimal then presence of these cellular layers is not important. Whether the products of ovulation play a role in the final stages of capacitation of sperm was tested by transferring eggs into the oviducts of rabbits unilaterally ovariectomized (more than 3 weeks previously) at 13.5–14.75 hours after mating. No difference in percentage of eggs penetrated was observed between oviducts on the ovariectomized and intact sides. The contact of the sperm with the products of ovulation in the one oviduct did not give them an advantage over the sperm in the other oviduct without such contact. It was found that although only 30% of newly ovulated eggs were penetrated in 1.5 hours following transfer to recipients at 9–9.5 hours after mating, 57 and 66% were penetrated during the same period if the transfers of similar eggs were delayed until 13.75–14.0 hours and 19.5–20.0 hours after mating of recipients respectively. It is suggested that these increases in percentages of eggs penetrated are a reflection of the presence of more sperm or of more fully capacitated sperm in the oviduct at

ISSN:0022-104X    

DOI:10.1002/jez.1401730104

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

年代:1970

数据来源: WILEY

摘要:

AbstractImplantation in the lemming occurs between the sixth and seventh days of pregnancy and is accompanied by decidualization of the stroma. The blastocyst appears to pass through the epithelium as in interstitial implantation. Alkaline phosphatase is present in the stroma along the length of the uterus before the start of implantation but becomes more intense in decidualized areas following attachment of the blastocyst.Blastocytes do not implant if animals are ovariectomized on the fourth day of pregnancy and progesterone alone is given but will implant if a small amount of oestradiol is given in addition to progesterone.A decidual cell reaction can be induced by the intrauterine injection of oil into animals mated with a vasectomized male; this reaction always occurs on the antimesometrial side of the uterus.

ISSN:0022-104X    

DOI:10.1002/jez.1401730105

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

年代:1970

数据来源: WILEY

摘要:

AbstractCells ofT. pyriformisstrain GL‐C synchronized in an amino‐acid‐free medium underwent synchronous oral replacement in place of cell division. This involved development of an oral primordium at the anterior end of the cell, with a concomitant rounding of the cell. The timing of this development was very similar to that of primordium development during synchronous division. In some experiments a second synchronous oral replacement was observed about 90 minutes after the first.Synchronization of oral replacement was similar to that of cell division. Prior to the heat shocks cells maintained in amino‐acid‐free medium were undergoing oral replacement asynchronously (with no concurrent macronuclear DNA synthesis). During the synchronizing treatment, development was initiated in the inter‐shock intervals but was arrested by the 34° heat shocks. As a result, cells became progressively accumulated in the earliest stage of oral replacement development. This accumulation did not take place if a single continuous heat treatment was given, or if cells were maintained in 2,4‐dinitrophenol, actinomycin D, or cycloheximide during the periodic heat shock treatment.The synchronous oral replacement which took place after the end of the synchronizing treatment (EST) could be blocked completely by actinomycin D, cycloheximide, and puromycin, and partially byp‐fluorophenylalanine. Exposure to cycloheximide (1 μg/ml) during stage 1 of stomatogenesis (10–30 minutes after EST) resulted in arrest of development, exposure during stages 3 and 4 (45 minutes) brought about primordium resorption, while exposure in stage 5 (60 minutes) permitted completion of development, with subsequent partial resorption. These responses were identical to those of synchronized dividing cells treated a

ISSN:0022-104X    

DOI:10.1002/jez.1401730106

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

年代:1970

数据来源: WILEY

摘要:

AbstractA pin‐point lens opacity can be detected at a frequency of 90% in weanling mice from inbred strain NAW‐wa‐2+− +/Sp. Defective lenses show abnormal thickening of the anterior epithelium localized over a region of persistent contact between the primary lens fiber mass and the epithelium.A morphological study of lens development indicates that the mutant strain clearly differs from normal as early as the twelfth day of embryonic life. In a lens sector associated with the naso‐ventral quadrant of the optic cup, cells undergoing the elongation characteristic of primary lens fibers are separated from the normal boundary of the anterior epithelium by a peculiar group of cells. These cells can still be detected on the following day; they do not differentiate into primary fibers. They contribute to the anterior epithelium instead, and the zone of elongation is asymmetrically displaced from the equator. Secondary fibers formed in this sector before birth do not completely displace the primary fibers from contact with the anterior epithelium. If secondary fibers formed during the neonatal period do not accomplish separation, abnormal thickening of the anterior epithelium begins around the end of the second week of postnatal life. The epithelial thickening and capsule‐like material deposited within it apparently provide the structural basis for the opacity detected upon gross

ISSN:0022-104X    

DOI:10.1002/jez.1401730107

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

年代:1970

数据来源: WILEY

摘要:

AbstractElectron microscopic examinations revealed drastic effects of actinomycin D on nucleolar formation in isolated cells ofXenopus laevisembryos. The nucleoli in newly isolated cells of early gastrulae were composed solely of a fibrous component. After culture for two to five hours in complete Stearns' solution without the antibiotic, a granular component appeared among the fibrous components in most of the nucleoli, which showed more elaborated structures. On the other hand, after being cultured for two hours in the presence of actinomycin D (l r/ml), by which inhibition of DNA synthesis was effected, all the nucleoli examined remained as spherical masses composed of fibrous component alone, lacking granular component. After five hours' treatment, inhibition of the synthesis of protein and DNA became biochemically detectable, and ultrastructural changes were observed in both the nucleoplasm and the cytoplasm: that is, fragmentation of nucleoli, condensation of chromatins and deformation of mitochondria. Relationships between the formation of nucleolar components and the RNA synthesis in amphibian embryogenesis are discussed.

ISSN:0022-104X    

DOI:10.1002/jez.1401730108

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe degree of pigment dispersal in the xanthophores and melanophores ofGillichthys mirabilismatched the animal to its background. Hypophysectomy did not affect the melanophores, which appear to be under nervous control, but did cause concentration of the pigment in the xanthophores so that the fish could no longer adapt to a yellow background. Acetyl choline had no effect on the pigment cells but epinephrine concentrated the pigment in the melanophores. Prolactin and high doses of ACTH dispersed the pigment in the xanthophores; the main effect of ACTH was indirect and probably due to stimulation of the interrenal tissue. Cortisol dispersed pigment in the xanthophores and concentrated it in the melanophores. β‐MSH also had an indirect effect in dispersing pigment in the xanthophores. Metyrapone reduced the indirect effect of β‐MSH and ACTH but had no effect on the yellowing of fish to match a yellow background. Thus prolactin, rather than the other hormones, appears to be involved in the normal response to a yellow background. The subcutaneous implantation of a single pituitary provided sufficient hormone to affect the overlying xanthophores. Reserpine resulted in pigment dispersal in the xanthophores of intactGillichthysbut had no effect in hypophysectomized fish. This suggests that the release of prolactin is normally controlled by an inhibitory factor from the

ISSN:0022-104X    

DOI:10.1002/jez.1401730109

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.1401730101

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

年代:1970

数据来源: WILEY