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In female Podarcis s. sicula, D-Aspartic acid (D-Asp) is present in the ovary and significantly increases in females engaged in vitellogenesis. It, moreover, induces, either in vivo or in vitro, a decrease of testosterone level and an increase of 17beta-estradiol level, both in ovary and plasma. These findings let to assign an interesting regulatory role to D-Asp in lower vertebrate gonad's control. D-Asp, in fact, seems to act by inducing an enhancement of ovarian aromatase activity and, therefore, favours the conversion of testosterone into 17beta-estradiol. During reproduction, female lizard liver synthesised paramount amounts of vitellogenin, a process induced by ovarian 17beta-estradiol. Therefore, D-Asp helps to sustain an additional 17beta-estradiol availability, useful to lizard reproductive physiology.D-Asp, finally, is proposed as a new regulatory agent of steroidogenesis in vertebrates.

In the green frog, Rana esculenta, a peculiar feature of female reproductive endocrinology is an high level of circulating testosterone. Although several hypotheses have been set out to explain this phenomenon, the testosterone specific roles in female anuran have not been yet fully explored. This study results propose a testosterone implication in liver vitellogenin synthesis control, since in ovariectomized frogs the hormone induces an increase of circulating vitellogenin. The testosterone action could depend on its local conversion to 17beta-estradiol by aromatase which is present in frog liver tissue. Liver aromatase activity ranges from 7.5 to 26 fmoles E2 formed/mg protein/h and results higher as long as liver is engaged in vitellogenin synthesis. Aromatase activity seems depend on testosterone since it decreases after ovariectomy and is restored by testosterone injection in ovariectomized frogs. In green frog liver, testosterone binding molecules are present both in cytosol and nuclei. These molecule binding properties (Kd and Bmax in nM range; t 1/2 = 85 min; specificity) are in line with those of testosterone receptor of other lower vertebrate target tissue. In liver nuclei, testosterone receptor level undergoes modification throughout the sexual cycle which almost coincides with that of plasma testosterone level and liver aromatase activity. This could indicate that the testosterone induction of liver aromatase in frogs is via the testosterone receptor, as reported for aromatase of mammalian brain tissues.

Alburnus albidus is an endangered and little known cyprinid fish species endemic m southern Italy. Histological characteristics of testes and plasma steroids levels of A albidus from River Alento, Campania Region, were analysed every month berween January-July 1996 Depending on the relative abundance of spermatogonia, spermatocytes, spermatides and spermatozoa in the testes and the sex steroids levels in plasma, we defined the gonadal cycle of A. albidus

Marine phytoplankton are known to produce surface-active materials as part of their metabolism. The surface tension gradient due to the presence of plankton-produced surfactants leads to a surface shear stress, commonly known as Marangoni stress. In this work we try to gain some understanding on these complex phenomena while, at the same time, obtaining some information on the order of magnitude of the surface stress and the resulting velocity in the bulk flow. As the direct modelling of the surfactants is extremely difficult due to the complexity (and uncertainty) of their chemical composition and to the absence of information on the rate of production by marine phytoplankton, we have formulated a model of their effects based on the data of surface activity of seawater samples as they are presented by ?uti? et al. (1981) [?uti?, V., ?osovi?, B., Mar?enko, E., Bihari, N., 1981. Surfactant production by marine phytoplankton. Mar. Chem. 10, 505-520] and ?uti? and Legovic (1990) [?uti?, V., Legovic, T., 1990. Relationship between phytoplankton blooms and dissolved organic matter in the Northern Adriatic. In: Final reports on research projects dealing with eutrophication and plankton blooms (activity h). Mediterranean Action Plan (MAP) Technical Reports Series No. 37. United Nations Environment Program (UNEP), Athens]. Using satellite data and a chlorophyll concentration profile reported in the literature we predict a Marangoni stress whose maximum order of magnitude is 10- 6 N m- 2. We also present the results of a numerical test, where we evaluate the Marangoni stress caused by horizontal variations of the plankton distribution due to the converging flows in a thermal bar, obtaining a Marangoni stress of order of magnitude 10- 5 N m- 2 and a corresponding velocity in the bulk that is at most equal to 10- 4 m s- 1, with values of film pressure within the range of the data available in the literature.

Prostaglandin F2alpha (PGF2alpha), prostaglandin E2 (PGE2), progesterone, androgens, and estradiol-17beta in vitro basal release by follicles of the oviparous lizard, Podarcis s. sicula was studied; in addition, the in vitro effect of PGF2alpha and PGE2 on sex steroid release was evaluated. Follicles were divided according to the different vitellogenic developmental stages: pre-vitellogenic, early-vitellogenic, mid-vitellogenic and fully-grown. PGF2alpha and progesterone basal release was highest in fully-grown follicles; PGE2 and estradiol basal release was highest in early-vitellogenic follicles; androgens basal release was detectable in mid-vitellogenic and fully-grown vitellogenic follicles only. PGF2alpha increased progesterone release by fully-grown follicles; PGE2 increased estradiol release by all follicle types, except by early-vitellogenic ones. The present data suggest that PGF2alpha and PGE2 exert different roles on follicles: PGF2alpha seems to induce ovulation through the mediation of progesterone, while PGE2 seems to be implied in the start and the sustaining of oocyte vitellogenic development through the mediation of estradiol.

Author(s): V. Botte, F.E Corcione, M Costa, F.M. Denaro & G. De Stafano Abstract: Modem software design is largely based on the object-oriented programming that is being increasingly adopted also for specific scientific calculations. This paper has the goal of applying such an approach in the field of the computational fluid dynamic, and focuses on the numerical simulation of 3D incompressible flows. One of the more attractive features of the object programming is its intrinsic unstructured structure, particularly suitable to be associated to an unstructured tessellation of the computational domain. The design of the code is detailed and preliminary results are addressed for a laminar test case.

Progesterone (P), 17-OH-progesterone (17-OH-P), androstenedione (A), dehydroepiandrosterone (DHEA), testosterone (T), 5 alpha-dihydrotestosterone (5 alpha-DHT), and 17 beta-estradiol (E2) were measured by RIA in plasma and testes of 114 males of the oviparous lizard Podarcis s. sicula raf, a species that displays annual hibernating cycles. Hormones were determined each month from January until December, except for August. Testosterone peaked at 174.8 ng/ml of plasma after emergence (March), while 5 alpha-DHT and A peaked in April. Plasma DHEA increased during hibernation. During the refractory period there were progressive increases in P and E2 plasma levels. The testicular peak of T, in March, coincided with that observed in plasma. The striking increases in testicular T and A in early July occurred at a time when plasma androgen concentrations were low. 5 alpha-DHT increased in April when spermatogenesis with spermiation occurred and then decreased alongside a second peak of T. There is an apparent separation of plasma and testicular androgen concentrations during the reproductive cycle.