Cytological and Morphological Changes during Amphibian Metamorphosis

Fox, H.

doi:10.1007/978-1-4613-3246-6_10

Cited by 39 publications

(27 citation statements)

References 29 publications

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“…The fine structural alterations observed in the involuting ventral velum shared features with those of the metamorphosing tail (Weber, 1964 ;Kerr et al 1974 ;Yoshizato, 1989), gills (Houdry, 1974 ;Michaelis et al 1969, 1971), pronephros (Fox, 1981, intestine (Houdry & Dauca, 1977 ;Ishizuya-Oka, 1996 ;Ishizuya-Oka & Ueda, 1996), nervous system (Fox, 1981), skin (Fox, 1981 ;Yoshizato, 1989), and epidermal tissue homeostasis (Budtz & Spies, 1989).…”

Section: mentioning

confidence: 96%

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

Bartel¹,

Lametschwandtner²

2000

Journal of Anatomy

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Structural changes of the ventral velum of Xenopus laevis tadpoles from late prometamorphosis (stage 58) to the height of metamorphic climax (stage 62) were examined by light and transmission electron microscopy. Special emphasis was given to the blood vessel regression. Early changes of velar capillaries were formation of luminal and abluminal endothelial cell processes, vacuolation, and cytoplasmic and nuclear chromatin condensation. At the height of metamorphic climax, transmission electron microscopy revealed apoptotic endothelial cells with nuclear condensation and fragmentation, intraluminal bulging of rounded endothelial cells which narrowed or even plugged the capillary, and different stages of endothelial cell detachment ('shedding') into the vessel lumen. These changes explain the 'miniaturisation' of the velar microvascular bed as well as the typical features found in resin-casts of regressing velar vessels which have been observed in a previous scanning electron microscopy study of the ventral velum.

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Section: mentioning

confidence: 96%

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

Bartel¹,

Lametschwandtner²

2000

Journal of Anatomy

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“…Metamorphosis in amphibians is a time of fasting due to the extensive reorganization of the digestive tract (reviewed in Fox, 1981). In Xenopus, tadpoles are fasting after stage 62 but their glucose levels in body fluids do not decrease (Hanke and Leist, 1971).…”

Section: Amp Protection Of Naïve Juvenile Frogs Exposed To B Dendrobmentioning

confidence: 99%

Skin peptides protect juvenile leopard frogs (Rana pipiens) against chytridiomycosis

Pask

Cary

Rollins‐Smith

2013

Journal of Experimental Biology

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SUMMARYOne issue of great concern for the scientific community is the continuing loss of diverse amphibian species on a global scale. Amphibian populations around the world are experiencing serious losses due to the chytrid fungus, Batrachochytrium dendrobatidis. This pathogen colonizes the skin, leading to the disruption of ionic balance and eventual cardiac arrest. In many species, antimicrobial peptides secreted into the mucus are thought to contribute to protection against colonization by skin pathogens. Although it is generally thought that antimicrobial peptides are an important component of innate immune defenses against B. dendrobatidis, much of the current evidence relies on correlations between effective antimicrobial peptide defenses and species survival. There have been few studies to directly demonstrate that antimicrobial peptides play a role. Using the northern leopard frog, Rana pipiens, we show here that injection of noradrenaline (norepinephrine) brings about a long-term depletion of skin peptides (initial concentrations do not recover until after day 56). When peptide stores recovered, the renewed peptides were similar in composition to the initial peptides as determined by MALDI-TOF mass spectrometry and in activity against B. dendrobatidis as determined by growth inhibition assays. Newly metamorphosed froglets depleted of their peptide stores and exposed to B. dendrobatidis died more rapidly than B. dendrobatidis-exposed froglets with their peptides intact. Thus, antimicrobial peptides in the skin mucus appear to provide some resistance to B. dendrobatidis infections, and it is important for biologists to recognize that this defense is especially important for newly metamorphosed frogs in which the adaptive immune system is still immature.

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“…Most amphibian larval organs and tissues undergo metamorphic changes in a temporally regulated manner (For reviews , Etkin 1968;Dodd & Dodd 1976;Fox 1981). The molecular basis for the temporal regulation of metamorphosis remains to be elucidated.…”

Section: Introductionmentioning

confidence: 99%

Role of type III iodothyronine 5‐deiodinase gene expression in temporal regulation of Xenopus metamorphosis

1999

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To elucidate the role of type III iodothyronine 5-deiodinase (5-D) in the temporal regulation of amphibian metamorphosis, the regulation of gene expression of 5-D and thyroid hormone receptor ␤ (TR␤) in organs of Xenopus laevis was investigated. High levels of TR␤ mRNA in the respective organs were observed at the times of their major morphological changes. Expression of the 5-D gene was highly regulated among the organs during metamorphosis, including up-regulation in the tail and down-regulation in the liver. The tail and liver expressed 5-D gene before their metamorphic changes. These precocious expressions correlated with the lower responsiveness to exogenously added triiodo-L-thyronine (T3) for inducing a high level of TR␤ mRNA expression. However, the same organs responded to lower doses of T3 to regulate 5-D gene expression as seen in spontaneous metamorphosis. The induction of 5-D gene expression was considerably delayed in the intestine, even at an excess dose of T3. Thus, the two genes in a given organ appeared to respond to T3 either with different dose dependencies or with different timetables. The results obtained are also discussed in respect to recent findings in Rana catesbeiana.

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Cytological and Morphological Changes during Amphibian Metamorphosis

Cited by 39 publications

References 29 publications

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

Skin peptides protect juvenile leopard frogs (Rana pipiens) against chytridiomycosis

Role of type III iodothyronine 5‐deiodinase gene expression in temporal regulation of Xenopus metamorphosis

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