Avshalom Hurvitz

Cloning of European eel (Anguilla anguilla) FSH-β subunit, and expression of FSH-β and LH-β in males and females after sex determination

The European eel (Anguilla anguilla) is a catadromic teleost species with a complex life cycle, both in sea and freshwater environments. The sex determination phase of gonadal development occurs in a freshwater environment. Polymorphism occurs in increasing rates with respect to gender. While males stop growing at approximately 150 g, females continue to grow to being much larger. In this study, we cloned the cDNA FSH-β subunit of the European eel (A. anguilla), and measured the mRNA levels of FSH-β and LH-β in males and females after sex determination. The FSH-β subunit cDNA consisted of 1068 bp, encoding a 127 amino acid peptide. A comparison between European and Japanese eels of the FSH-β amino acid sequence showed 98% similarity.

Cloning of Russian sturgeon ( Acipenser gueldenstaedtii ) growth hormone and insulin-like growth factor I and their expression in male and female fish during the first period of growth

In this study, the GH and IGF-I of the Russian sturgeon (rs), Acipenser gueldenstaedtii, were cloned and sequenced, and their mRNA gene expression determined. In addition, to improve our understanding of the GH function, the expression of this hormone was assessed in young males and females. Moreover, IGF-I expression was quantified in young males and compared to that in older ones. The nucleotide sequence of the rsGH cDNA was 980 bp long and had an open reading frame of 642 bp, beginning with the first ATG codon at position 39 and ending with the stop codon at position 683. A putative polyadenylation signal, AATAAA, was recognized 42 bp upstream of the poly (A) tail. The position of the signal-peptide cleavage site was predicted to be at position 111, yielding a signal peptide of 24 amino-acids (aa) and a mature peptide of 190 aa. When the rsGH aa sequence was compared with other species, the highest degree of identity was found to be with mammalians (66–70% identity), followed by anguilliformes and amphibia (61%) and other fish (39–47%). The level of rsGH mRNA was discovered to be similar in pituitaries of females and males of 5 age groups (1, 2, 3,4, and 5-yr-old). In females and males, the levels did not change dramatically during the first 5 yr of growth. The partial nucleotide sequence of the rsIGF-I was 445 bp long and had an open reading frame of 396 bp, beginning with the ATG codon at position 50. The position of the signal-peptide cleavage site was predicted to be at position 187, yielding a signal peptide of 44 aa. The highest level of IGF-I mRNA expression was recorded in the kidney of adult sturgeons. The IGF-I mRNA expression levels in the intestine, pituitary gland, and liver were not significantly different. Low levels of expression were found in the brain, heart, and muscle. In most tissues, there was no significant difference between mRNA levels of one and 5-yr-old fish. In conclusion, based on the GH-sequence analysis, A. gueldenstaedtii is genetically distant from other teleosts. The expression of the GH mRNA was similar in males and females, and its level remained constant during the first 5 yr of growth. While the IGF-I mRNA expression differed amongst various tissues, the level in each tissue was similar in 1 and 5-yr-old fish.

Gonadotropins in the Russian Sturgeon: Their Role in Steroid Secretion and the Effect of Hormonal Treatment on Their Secretion.

In the reproduction process of male and female fish, pituitary derived gonadotropins (GTHs) play a key role. To be able to specifically investigate certain functions of Luteinizing (LH) and Follicle stimulating hormone (FSH) in Russian sturgeon (Acipenser gueldenstaedtii; st), we produced recombinant variants of the hormones using the yeast Pichia pastoris as a protein production system. We accomplished to create in vitro biologically active heterodimeric glycoproteins consisting of two associated α- and β-subunits in sufficient quantities. Three dimensional modelling of both GTHs was conducted in order to study the differences between the two GTHs. Antibodies were produced against the unique β-subunit of each of the GTHs, in order to be used for immunohistochemical analysis and to develop an ELISA for blood and pituitary hormone quantification. This detection technique revealed the specific localization of the LH and FSH cells in the sturgeon pituitary and pointed out that both cell types are present in substantially higher numbers in mature males and females, compared to immature fish. With the newly attained option to prevent cross-contamination when investigating on the effects of GTH administration, we compared the steroidogeneic response (estradiol and 11-Keto testosterone (11-KT) in female and males, respectively) of recombinant stLH, stFSH, and carp pituitary extract in male and female sturgeon gonads at different developmental stages. Finally, we injected commercially available gonadotropin releasing hormones analog (GnRH) to mature females, and found a moderate effect on the development of ovarian follicles. Application of only testosterone (T) resulted in a significant increase in circulating levels of 11-KT whereas the combination of GnRH + T did not affect steroid levels at all. The response pattern for estradiol demonstrated a similar situation. FSH levels showed significant increases when GnRH + T was administered, while no changes were present in LH levels.

Vitellogenin Level in the Plasma of Russian Sturgeon ( Acipenser gueldenstaedtii ) Northern Israel

In the present study, we examined the vitellogenin (Vg) level of Russian sturgeon maintained in a relatively constant aquaculture at a water temperature of 18-22°C during growth and maturation. An increase in Vg in the blood plasma from oocytes was found in the yellow oocytes stage to the gray oocytes stage. However, no Vg was found in the pre-vitellogenic stage. Based on the present study and previous studies on hormone control reproduction and growth, we proposed a quality model that correlated between egg development and the hormones involved in controlling vitelogenesis (VTL).