Christian Cayrol

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.

Comparative plasma levels of androgens and 17β-estradiol in the diploid and triploid newt, Pleurodeles waltl

Seasonal changes in the plasma levels of androgens (testosterone plus dihydrotestosterone) and 17 beta-estradiol in diploid and triploid adult newts, Pleurodeles waltl were studied. In both male and female diploid individuals, large variations were reported with highest levels being found during breeding periods. In triploid newts seasonal variations were also found, similar to the diploid ones, but the plasma concentrations of the 17 beta-estradiol and androgens in triploid females and androgens in triploid males were lower throughout the year than those reported for the diploids. This difference is discussed in relation to the genetic sexual constitution.

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.

Identification of the vitellogenin proteins in the newt Pleurodeles waltl (Urodele amphibian)

Vitellogenin derived from the blood of estrogen-treated Pleurodeles waltl was identified by immunochemical and electrophoretic analyses, using an antiserum against plasma vitellogenin isolated by dimethylformamide precipitation. Pleurodeles vitellogenin migrates as four bands on native PAGE, designated alpha-, beta-, gamma- and delta- VTG, with apparent mol. wts of 250,000, 270,000, 280,000 and 520,000 respectively. In the plasma, from estrogen-treated males like from ovariectomized estrogen-treated females, an additional band (mu-VTG) was found by native PAGE, never observed in estrogen-treated female plasma. It has a mol. wt of about 380,000 and shows complete immunological cross-reactivity with the vitellogenin antiserum. At least two polypeptides, termed VTG-I and VTG-II (mol. wt = 180,000 and 210,000) were identified by SDS-PAGE. Rocket immunoelectrophoresis displays three distinct precipitate lines indicating major immunological differences between the plasma vitellogenins.

Effects of thyroxine on the ontogeny of the vitellogenic response in Pleurodeles waltli of both sexes

SummaryIn the newt, Pleurodeles waltli, vitellogenin synthesis can be induced by oestrogen prior to metamorphosis and well before vitellogenin synthesis is normally observed in females. Vitellogenin indicubility has been shown to occur during normal development at stage 53 in both sexes. Immersion of young larvae in thyroxine at concentrations that did not result in early morphological metamorphosis led to a precocious acquisition of liver responsiveness to oestrogen. Treatment of larvae with thiourea greatly diminished the ability of oestradiol to induce vitellogenin synthesis, although it did not abolish the hormonal response.

Nuclear estrogen binding sites in the liver of the newt Pleurodeles waltl

Previous investigations of the liver estrogen-specific binding in the newt, Pleurodeles waltl, have identified in the cytosol fraction, only from normal males, a new middle-affinity estrogen-binding component (MEBC) displaying the properties of type II sites reported in various tissues of vertebrates. The present work demonstrates that MEBC sites are not unique to the male but are also present in the nuclei of female animals. However, comparative study between males and females of liver nuclear sites under various extraction conditions shows sex-linked differences in the subnuclear localization. The relationships between the association states of MEBC in the nuclear compartment according to sex and their presence or absence in the cytosol fraction are discussed.

A comparative study of the levels of glucose-6-phosphate dehydrogenase in the erythrocytes of diploid and polyploid salamanders (Pleurodeles waltlii)

Abstract 1. 1. The level of glucose-6-phosphate dehydrogenase is determined in the red blood cells of diploid and polyploid adult Pleurodeles newts. 2. 2. Large variations in the cell enzyme content are reported for 2n animals. 3. 3. Triploid and autotetraploid animals show different dosage effects when the G-6-PDH activity is expressed on a per cell basis.