André Jaylet

A genetic study of various enzyme polymorphisms in Pleurodeles waltlii (Urodele Amphibian). II. Peptidases: Demonstration of sex linkage

The existence of four peptidases was demonstrated by starch gel electrophoresis in Pleurodeles waltlii: PEP-1, PEP-2, PEP-3, and PEP-4. Peptidases-3 and -4 are monomorphic, and peptidases-1 and -2 are polymorphic. The heredity of the polymorphisms was studied using individuals arising from crosses or of gynogenetic origin. Peptidase-1 is dimeric; its polymorphism depends on a pair of codominant alleles, Pep-1A and Pep-1B, which are situated on the Z and W sex chromosomes, respectively, in close proximity to, or even within, the sex differential segment. As the differential segment is very close to the centromere, the PEP-1 locus therefore also appears to be closely linked to it. Expression of the PEP-1 locus was shown to be independent of the sex hormone environment. This locus is the first case reported in amphibians of an enzyme marker linked to the genetic sex. It allows the sex of Pleurodeles to be determined before they reach sexual maturity. Peptidase-2 is monomeric. Its polymorphism depends on a pair of codominant alleles on an autosomal PEP-2 locus. The high proportion of heterozygous animals in the gynogenetic offspring of females heterozygous for the PEP-2 locus indicates segregation which is independent of the centromere. Analysis of the offspring of doubly heterozygous females (i.e., for two of the loci—LDH-B, G6PDH, PEP-1, and PEP-2) shows that the four loci are independent.

Tétraploïdie expérimentale chez le Triton Pleurodeles waltlii Michah.

Fischbergs method, thanks to which tetraploid individuals can be obtained, has been adapted to the newt Pleurodeles waltlii. — If at the beginning of the first furrow formation, the eggs are submitted for 10 minutes to a sudden increase in temperature (37.2–37.3°C), the embryos that subsequently develop are tetraploid in 100% of the cases. The percentage obtained of viable individuals is about 30% of the number of heated eggs. — A temperature treatment between 36.2 and 36.4°C applied at the same period and for the same length of time may lead to the formation of viable animals diplo-tetraploid mosaic. — Among adult tetraploids or diplo-tetraploid mosaic males and females can be found. — The cells of tetraploids can easily be distinguished from those of diploids by their larger size. Therefore, the former can be used as cellular markers.

Modification du caryotype par une inversion péricentrique à l'état homozygote chez l'Amphibien Urodèle Pleurodeles waltlii Michahelles

A cytogenetic study on four generations of the newt Pleurodeles waltlii has resulted in a stock homozygous for a pericentric inversion in chromosomes no. 6.-The chromosomal rearrangement has first been detected at the heterozygous state in a female resulting from a cross between a normal female and a male treated with X rays. — The rearranged chromosome is very easily recognizable under direct microscopic investigation. The heterozygotes and the homozygotes for the aberration grow normally; thus, the inversion constitutes a nuclear marker which can be readily used.

Red blood cells and hemoglobin concentration in normal diploid and several types of polyploid salamanders

Abstract 1. 1. Different blood parameters were examined in both diploid and polyploid adult Pleurodeles newts. 2. 2. In 2 n, 3 n and 4 n, the hemoglobin content and hematocrit values were very close. 3. 3. The red blood cell counts decrease as the degree of polyploidy rises. 4. 4. Autotetraploid and pentaploid animals do not regulate their hemoglobin values and are slightly anaemic.

Micronucleus Test Using Peripheral Red Blood Cells of Amphibian Larvae for Detection of Genotoxic Agents in Freshwater Pollution

Increased environmental pollution can be attributed to a variety of factors resulting from new industrial and agricultural technologies together with changes in our way of life. Moreover, the nature of the pollution itself has become more diverse. Whatever the origin of the pollution it tends to find its way into the aquatic environment. Genotoxic pollutants affect the aquatic ecosystem, and their presence in the water can also have repercussions on non-aquatic species via food chains or simply from drinking the polluted water. Man is not exempt from this risk; much drinking water is derived from surface water that is more or less polluted. Before distribution to the consumer, this water is thus subjected to a number of treatments. Ironically, if the water is rich in organic matter some disinfectant treatments may in fact lead to the formation of genotoxic compounds that were not present in the initial water source. One should therefore be aware of the hidden risks stemming from potential genotoxins in the aquatic environment. Moreover, a considerable time may elapse between the action of the mutagenic agent and the outward signs of its effects. The relationship between cause and effect may thus become obscured.

A genetic study of various enzyme polymorphisms in Pleurodeles waltlii (Urodele, Amphibian). III. The relationship between sex-linked peptidase-1 expression and gene-dose effects

Erythrocyte peptidase-1 was analyzed by electrophoresis in various types of triploid Pleurodeles waltlii. Densitometric analysis of the zymograms showed (1) the existence of a gene-dose effect and (2) the presence of two Pep-1B alleles for one Pep-1A allele in heterozygous triploid females of biparental origin. Owing to the sex linkage of the PEP-1 locus (alleles Pep-1A and Pep-1B situated on the Z and W sex chromosomes, respectively), the results show that the sex genotype of these females is ZWW. In a particular line called series 103, the existence of a null allele was demonstrated. Densitometric analysis of females which were Pep-1A/Pep-10 (ZW), Pep-10/Pep-10 (WW), and Pep-1A/Pep-10/Pep-10 (ZWW) confirmed the gene-dose effect.

Ontogeny of Amphibian Hemopoietic Cells

The developmental origin of lymphoid cells of vertebrates continues to be a fascinating, perplexing problem. Historically, the disputable issues have revolved around two fundamental aspects: the origin of the precursors of the various types of differentiated blood cells and the lineal relationships among these different cell types. There are special features of amphibians that make them suitable for clarifying the embryogenesis of hemopoietic cells. An array of microsurgical techniques from experimental embryology can be used to marked advantage. In this chapter, we will review the contributions made by investigators who have used the tools of experimental embryology to gain insight into the ontogeny of vertebrate blood cells.

Mécanisme cytologique de la tétraploïdie expérimentale chez le Triton Pleurodeles waltlii

When the eggs of the newt Pleurodeles waltlii, at the beginning of the first furrow formation, are submitted for 10 minutes to a sudden increase in temperature (37.2 to 37.3 degrees C), the subsequently developing embryos are tetraploid. The percentage obtained of viable individuals is about 30% of the number of treated eggs. A temperature between 36.2 and 36.4 degrees C applied at the same period and for the same length of time may lead to viable animals diplo-tetraploid mosaics as previously reported.--Cytological examination showed that at the formation of the first furrow the egg contains two interphase nuclei. During heat treatment, cytoplasmic cleavage regresses resulting in an uncleaved egg with two interphase nuclei. About 2 1/2 hours after heat treatment the egg divides again into two cells. Tetraploidy results from doubling of chromosomes of both nuclei instead of the second mitotic division. The mechanism which leads to tetraploidy consists in inhibition of the movement of the two asters and aberration of spindle formation.--The mosaic animals develop from eggs in which only one of the nuclei became tetraploid while the other one divided normally.When the eggs of the newt Pleurodeles waltlii, at the beginning of the first furrow formation, are submitted for 10 minutes to a sudden increase in temperature (37.2 to 37.3°C), the subsequently developing embryos are tetraploid. The percentage obtained of viable individuals is about 30% of the number of treated eggs. A temperature between 36.2 and 36.4°C applied at the same period and for the same length of time may lead to viable animals diplo-tetraploid mosaics as previously reported. — Cytological examination showed that at the formation of the first furrow the egg contains two interphase nuclei. During heat treatment, cytoplasmic cleavage regresses resulting in an uncleaved egg with two interphase nuclei. About 21/2 hours after heat treatment the egg divides again into two cells. Tetraploidy results from doubling of chromosomes of both nuclei instead of the second mitotic division. The mechanism which leads to tetraploidy consists in inhibition of the movement of the two asters and aberration of spindle formation. — The mosaic animals develop from eggs in which only one of the nuclei became tetraploid while the other one divided normally.

A genetic study of various enzyme polymorphisms in Pleurodeles waltlii (Urodele Amphibian). I. Lactate dehydrogenase-B and glucose-6-phosphate dehydrogenase

On starch gel electrophoresis of erythrocyte hemolysates of Pleurodeles waltlii (Urodele Amphibian), both lactate dehydrogenase-B (LDH-B) and glucose-6-phosphate dehydrogenase (G6PDH) show polymorphism that depends on a pair of autosomal codominant alleles, confirmed by analysis of gynogenesis progeny. Diploid gynogenesis results from fusion of the female pronucleus with the second polar body. The heterozygous state of a female for a given character is maintained in certain progeny when crossing-over occurs between the locus in question and the centromere. So the high proportion of heterozygotes (45.7% for LDH-B and 76% for G6PDH) indicates the high frequency of crossing-over and hence the large distance between each of the loci and the centromere.

Une triple translocation chez le Triton Pleurodeles waltlii

A cytogenetic study has lead us to a stock of fertile heterozygotes for a triple translocation. The chromosomal rearrangement has first been detected in a female resulting from a cross between a normal female and a male submitted to X ray-irradiation. The aberration consists of rearrangements between a chromosome 3, a chromosome 6 and a chromosome 7. Abnormal chromosomes have the following constitution: 7q−: the terminal portion of the long arm is lost and replaced by the end of the short arm of the chromosome 3. 6 q+: the terminal portion of the long arm is lost and replaced by the end of the long arm of the chromosome 7. 3p+: the terminal portion of the short arm is lost and replaced by the end of the long arm of the chromosome 6. On the analogy of the human chromosome standardization, the formula of heterozygotes is 24, t (3p+, 6q+, 7q−). The first meiotic division shows both in the female and in the male 9 bivalents and one hexavalent. The formulae of the gametes are the same in both sexes. When a heterozygote is bred with a normal individual the offspring is composed of phenotypically normal or abnormal animals, depending on their karyotypes. The unbalanced karyotypes are lethal or semilethal. The importance of the malformations depends on the temperature of the water where the animals grow. The study of the meiotic slides brings a cytological confirmation of the results obtained from the study of the phenotypes and karyotypes which appear in the offspring.