scholarly journals CHANGES IN CELL FINE STRUCTURE DURING LENS REGENERATION IN XENOPUS LAEVIS

1965 ◽  
Vol 24 (2) ◽  
pp. 211-222 ◽  
Author(s):  
Jane Overton
Keyword(s):  
Fine Structure ◽  
Xenopus Laevis ◽  
Normal Development ◽  
Low Density ◽  
Morphological Complexity ◽  
Lens Fibers ◽  
Lens Regeneration ◽  
Lens Vesicle ◽  
Rough Er ◽  
Two Phases

Changes at the level of cell fine structure have been studied during lens regeneration in the toad, Xenopus laevis, where cornea gives rise to the new lens. The transformation of these cells may be divided into three phases. (1) In the cornea, flattened cells become cuboidal and rough endoplasmic reticulum increases in amount. (2) In the new lens vesicle, cisternae of the rough ER break down into vesicles, smooth-walled vesicles and free ribosomes increase in number, and mitochondria can become enlarged and irregular, then centrally attenuated. Rudimentary cilia form. (3) As new lens fibers form, ribosomes become very numerous and low density fibrous elements and dense clumps appear in the cytoplasm. These phases are accompanied by marked nucleolar changes. The changes during the 3rd phase are similar to changes in the lens during normal development. The first two phases show an unexpected morphological complexity.

Fission yeast tmsl protein abrogates normal development in Xenopus laevis embryos

1995 ◽  
Vol 204 (3) ◽  
pp. 198-202 ◽  
Author(s):  
Peter Wagner ◽  
Michael Hoever ◽  
Katrin Appel ◽  
Walter Kn�chel ◽  
Mathias Montenarh
Keyword(s):  
Xenopus Laevis ◽  
Fission Yeast ◽  
Normal Development ◽  
Xenopus Laevis Embryos

Mitotic activity of germ cells during normal development of Xenopus laevis tadpoles

Development ◽  
1975 ◽  
Vol 34 (3) ◽  
pp. 687-694
Author(s):  
Ken-Ichi Ijiri ◽  
Nobuo Egami
Keyword(s):  
Xenopus Laevis ◽  
Germ Cell ◽  
Mitotic Activity ◽  
Germ Cells ◽  
Regional Difference ◽  
Normal Development ◽  
Uniform Value ◽  
Interesting Conclusion ◽  
Spatio Temporal ◽  
Gland Development

Data on the spatio-temporal pattern of germ cell proliferation in Xenopus laevis tadpoles were obtained, tracing the germ cells from the cloacal position forward. This spatial pattern in germ cell distribution and its change during normal development clearly coincided with histological observations of germ gland development. By application of regression lines to the analysis of this complex pattern, an interesting conclusion about the mitotic activity of germ cells was suggested. While the mitotic activity of germ cells before sexual differentiation shows a regional difference along the germ-cell-containing ridge (GCCR), the doubling time of sexually differentiated gonia seems to show a uniform value over the whole GCCR

Factors Responsible for the Abnormal Development of Embryos Obtained by Nuclear Transplantation in Xenopus laevis

Development ◽  
1960 ◽  
Vol 8 (3) ◽  
pp. 327-340
Author(s):  
J. B. Gurdon
Keyword(s):  
Xenopus Laevis ◽  
Embryo Development ◽  
Normal Development ◽  
Nuclear Transplantation ◽  
Abnormal Development ◽  
Donor Nucleus ◽  
Innate Capacity

In Xenopus the embryos derived from nuclear transplantation often develop abnormally. These abnormalities must be due to the limited potentiality for development of either the donor nucleus or the egg cytoplasm; this limited potentiality will in turn be due to technical damage during transplantation or to the innate condition of the nucleus or cytoplasm before the experiment. The extent to which these technical and innate factors are responsible for abnormalities of transplant-embryo development has been analysed by considering the effect of each factor in turn. Nuclei from early donor stages have been used, since these nuclei are believed to be undifferentiated (see p. 338) and therefore to have the innate capacity for entirely normal development. The effects of other factors have been investigated by experiments in which each factor is varied in different ways. Any correlation between variations in one factor and the resulting proportion of abnormal transplant-embryos is then recorded.

Detection of a global aquatic invasive amphibian, Xenopus laevis, using environmental DNA

2016 ◽  
Vol 37 (1) ◽  
pp. 131-136 ◽  
Author(s):  
Jean Secondi ◽  
Tony Dejean ◽  
Alice Valentini ◽  
Benjamin Audebaud ◽  
Claude Miaud
Keyword(s):  
Invasive Species ◽  
Xenopus Laevis ◽  
Dna Amplification ◽  
Control Program ◽  
Environmental Dna ◽  
Climatic Conditions ◽  
Low Density ◽  
African Species ◽  
A Site ◽  
And Control

Detection is crucial in the study and control of invasive species but it may be limited by methodological issues. In amphibians, classical survey techniques exhibit variable detection probability depending on species and are often constrained by climatic conditions often requiring several site visits. Furthermore, detection may be reduced at low density because probability capture (passive traps), or activity (acoustic surveys) drop. Such limits may impair the study of invasive species because low density is typical of the onset of colonisation on a site. In the last few years, environmental DNA (eDNA) methods have proved their ability to detect the presence of aquatic species. We developed here an eDNA method to detectXenopus laevisin ponds. This austral African species is now present worldwide because of its use in biology and as a pet. Populations have settled and expanded on several continents so that it is now considered as one of the major invasive amphibians in the World. We detected the presence ofX. laevisat density as low as 1 ind/100 m2and found a positive relationship between density in ponds and rate of DNA amplification. Results show that eDNA can be successfully applied to survey invasive populations ofX. laeviseven at low density in order to confirm suspected cases of introduction, delimit the expansion of a colonized range, or monitor the efficiency of a control program.

Cardiac output in Xenopus laevis tadpoles during development and in response to an adenosine agonist

1996 ◽  
Vol 270 (5) ◽  
pp. R997-R1004
Author(s):  
Y. Y. Tang ◽  
C. M. Rovainen
Keyword(s):  
Cardiac Output ◽  
Xenopus Laevis ◽  
Cardiac Cycle ◽  
Normal Development ◽  
Volume Overload ◽  
Adenosine Agonist ◽  
Video Frames ◽  
Blood Pressures ◽  
Aquarium Water ◽  
Accelerated Growth

We test the hypothesis that the heart and arteries enlarge with increased cardiac output (CO) during development and volume overload. Transparent albino tadpoles of Xenopus laevis at stages 43-50 were anesthetized in 0.3-0.5 mM benzocaine. Areas and radii [maximum and minimum radius (Rmax and Rmin, respectively)] of the ventricle were measured in digitized video frames during the cardiac cycle. Stroke volume (SV) and CO were calculated from Rmax and Rmin. Maximal velocities of 3.4-microns fluorescent beads were measured in the aortic arches. Arterial pressure was estimated by the Landis method. During normal development, the radii of the ventricle and aortic arch diameters increased with lengths of tadpoles, and SV (0.7 microliters/g) and CO (70 microliters.g-1.min-1) with wet weights. Volume overload was induced by a vasodilatory adenosine agonist 5'-N-ethylcarboxamidoadenosine (NECA) in the aquarium water. Acute (0.5-4 h) NECA significantly increased Rmax and heart rate. Chronic (> 1 wk) NECA significantly increased both Rmax and Rmin. SV and CO increased more than two times, blood pressures decreased, and specific vascular conductances increased more than five times. It is concluded that NECA increases CO in Xenopus tadpoles through a combination of increased filling and accelerated growth.

The fine structure of the leucocytes of the holothurian, Cucumaria miniata

1977 ◽  
Vol 55 (9) ◽  
pp. 1530-1544 ◽  
Author(s):  
A. R. Fontaine ◽  
Philip Lambert
Keyword(s):  
Stem Cells ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Rough Endoplasmic Reticulum ◽  
Acid Mucopolysaccharide ◽  
Rough Er

The fine structure of amoebocytes, lymphocytes, and morula cells is described and related to their functions. Three morphological phases (bladder, transitional, and filiform) of the amoebocyte are distinguished. Their surface protrusions and activities are based on microtubule and microfilament systems and the transitional-filiform phases are functionally involved in coelomocyte aggregation. The bladder phase is phagocytic; bladder formation and activities are also microfilament based. Morula cells contain spherules composed of acid mucopolysaccharide and protein. Dilated rough endoplasmic reticulum (ER) cisternae apparently synthesize spherule material which is added by accretion. Lymphocytes have little cytoplasm and relatively few organelles, except for abundant rough ER and free ribosomes. Lymphocytes are probably stem cells for amoebocytes and morulas. These cells are compared with the leucocytes of other echinoderms.

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