Elemental distribution of Na,P, Cl and K in different structures of myelinated nerve ofRana esculenta

Summary Measurements of the distribution of Na, P, Cl and K were performed in different structures of the myelinated nerve. Whereas the axon shows a typical intracellular distribution pattern for Na, Cl and K, the interstitial space and the myelin sheath show a typical extracellular pattern. These measurements have demonstrated that Na is present in the myelin sheath close to the node of Ranvier.     

Genetic control of LDH isozymes in the Rana esculenta complex.

Studies of LDH isozymes in the European green frogs showed that the synthesis of the B subunits is controlled by 3 alleles at a single genetic locus. The genetic evidence supports the hypothesis that Rana esculenta is the hybrid of R. lessonae X R. ridibunda.     

Biochemical variation in the Rana esculenta complex: a new hybrid form related to Rana perezi and Rana ridibunda.

Investigations of the green frogs from western Europe for electrophoretic variations at 4 enzyme loci demonstrated a new form which must be considered as a hybrid between Rana ridibunda and R. perezi. Biochemical evidence supports the hypothesis that its reproduction is hybridogenetic, as it is for R. esculenta.     

Dopamine regulation of testicular activity in intact and hypophysectomized frogs,Rana esculenta

In intact frogs, both GnRHA and L-dopa were able to increase testicular and plasma androgen levels and to induce spermiation. The dopamine antagonist pimozide inhibited both the effects of L-dopa but not those of GnRHa. Hypophysectomy reduced androgen levels, but spermiation was still induced by both GnRHa and L-dopa, suggesting that these agents can directly influence the testis through a route not involving the pars distalis. Again, pimozide antagonised spermiation induced by L-dopa but not that induced by GnRHa.This work was supported (40% and 60%) by the Italian Ministry of Education and the C.N.R. Special Project.     

Experimental gynogenesis provides evidence of hybridogenetic reproduction in the Rana esculenta complex.

The gynogenetic offspring of the hybrid frog Rana esculenta (R. ridibunda X R. lessonae) are exclusively of the ridibunda type. This is due to the premeiotic exclusion of the lessonae genome from the hybrid's germ cells.     

Radioimmunologic assay of plasma corticotropin in the green frog, Rana esculenta L.]

In the green Frog (Rana esculenta) the plasma contains a polypeptide immunologically related to human and porcine corticotropins. A radiommunoassay capable of detecting 4.10-12 g hog ACTH has been used for a direct plasma ACTH assay in the Frog. Using this method, the ACTH rate was determined both in untreated frogs and in animals under various experimental conditions.     

A gonadotropin releasing hormone analog induces spermiation in intact and hypophysectomized frogs, Rana esculenta

The sperm-releasing activity of a gonadotropin releasing hormone (GnRH) agonist, Buserelin (GnRH) and hypophysis homogenate (PD) preparations was studied in intact and hypophysectomized (PDX) frogs, Rana esculenta. In addition, human chorion gonadotropin (hCG) was tested in PDX animals, and GnRH antagonist (GnRHA) treatments were carried out in intact and PDX animals, in combination with the hormonal injections. GnRH or PD treatments were able to elicit spermiation in intact and PDX animals. While GnRH, injected 24 h later, was again effective in inducing spermiation in intact animals, this was not the case in PDX frogs. GnRHA counteracted GnRH effects in intact frogs. Moreover, in PDX animals GnRHA injections counteracted the sperm-releasing activity induced by hCG or GnRH, but failed to inhibit sperm-releasing activity induced by PD homogenate.     

Appearance of sex hormone receptors in frog (Rana esculenta) tadpole skin during metamorphosis.

In tadpole skin of Rana esculenta, a specific testosterone receptor was detected during the climax in both males and females. The Kass ranged between 1 and 2.79 x 10(9)M-1.     

An analysis of the distribution of the myelinated nerve fibers in the optic fascicle of a beagle dog

The composition of both optic fascicles of a Beagle dog was studied in topographically oriented, semithin transections of whole nerve stained with toluidine blue. About 165,000 myelinated fibers were present in each nerve, their maximum caliber reaching 11 micron; large, less densely arranged fibers occurred especially in the dorso-temporal region.