Impact of Magnetic Field Configuration on Heat Transport in Stellarators and Heliotrons.

We assess the magnetic field configuration in modern fusion devices by comparing experiments with the same heating power, between a stellarator and a heliotron. The key role of turbulence is evident in the optimized stellarator, while neoclassical processes largely determine the transport in the heliotron device. Gyrokinetic simulations elucidate the underlying mechanisms promoting stronger ion scale turbulence in the stellarator. Similar plasma performances in these experiments suggests that neoclassical and turbulent transport should both be optimized in next step reactor designs.

Recovery from disturbance requires resynchronization of ecosystem nutrient cycles.

Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance.

Development of new experimental setup focusing on long-pulse magnetic reconnection by using rotating magnetic field technique.

A new closed-type experimental setup to achieve a long-pulse magnetic reconnection in weakly ionized plasmas was developed by using a rotating magnetic field (RMF) technique. The experimental setup has a cylindrical vacuum vessel in which two sets of four antennas are equipped to generate RMF which drives steady azimuthal electron current in two torus plasmas. This device provided a quasi-steady magnetic reconnection condition in weakly ionized plasmas with ionization fraction of less than 1%. The proposed experimental setup will extend the research area of laboratory reconnection experiments and be helpful to comprehend the reconnection process in weakly ionized plasmas such as solar chromosphere.

Effects of pituitary graft and 2-bromo-alpha-ergocryptine on mammary DNA synthesis in mice in relation to mammary tumorigenesis.

3H-thymidine incorporation into mammary DNA as an index of mammary DNA synthesis in C3H/He virgin females was significantly higher at proestrus than at estrus and diestrus. The rise in incorporation at proestrus was completely blocked by the administration of 2-bromo-alpha-ergocryptine (Bromocriptin) 1 day before proestrus. The incorporation was maintained at a higher level than that at proestrus by pituitary grafts. The results supported the view that mammary DNA synthesis, which is stimulated by prolactin, is an important factor for mammary tumorigenesis.

Two-way selection of a stock of Swiss albino mice for mammary tumorigenesis: establishment of two new strains (SHN and SLN).

Two mouse strains (SHN and SLN) with high and low incidences, respectively, of mammary tumors were established from the same basal stock of Swiss albino mice that were unrelated in origin to other mouse strains with mammary tumors. In the breeders, mammary tumor incidence and average age of the mice when they developed mammary tumors were 97.2 % and 6.6 months for SHN, and 5.57% and 10.1 months for SLN, respectively...

Suppression by Nocardia rubra cell wall skeleton mammary DNA synthesis, plasma prolactin level, and spontaneous mammary tumorigenesis in mice.

The effects of the cell wall skeleton of Nocardia rubra on mammary gland DNA synthesis, plasma prolactin levels, and spontaneous mammary tumorigenesis in mice were studied. Female SHN mice received s.c. injections of 100 microgram N. rubra cell wall every 7 days between 2 and 12 months of age. The treatment resulted in the marked inhibition of mammary tumorigenesis; incidence was significantly lower in the experimental mice than in the controls except at 9 and 12 months of age. The age of onset of mammary tumors was significantly higher in the former than in the latter. In association with these findings, the treatment also reduced normal mammary gland DNA synthesis and prolactin levels in the circulation, both of which are primary factors for mammary tumorigenesis.

Long-term effects of prenatal and neonatal administration of 5beta-dihydrotestosterone on normal and neoplastic mammary development in mice.

The long-term effects on mammary glands of 5beta-dihydrotestosterone, considered to be biologically inactive, were studied in female SHN mice with mammary tumor, virus. 5beta-Dihydrotestosterone was adminstered to mothers for 4 days from Day 12 to Day 15 of pregnancy (prenatal treatment) and to pups for 5 days of postnatal life (neonatal treatment) at daily doses of 1 mg and 200 mug, respectively. Neonatal treatment resulted in marked stimulation of spontaneous mammary tumorigenesis; all neonatally treated mice had palpable mammary tumors by 6.2 months of age, when mammary tumor incidences in the control mice and in mice treated prenatally with 5beta-dihydrotestosterone were 21.1 and 6.3 percent, respectively. Furthermore, neonatal treatment promoted normal and preneoplastic mammary growth and pituitary prolactin secretion and induced ovarian anovulatory syndrome in all mice. Prenatal treatment also increased the number of mammary hyperplastic alveolar nodules and induced an delayed anovulatory syndrome. These results have demonstrated that perinatal treatment with 5beta-dihydrotestosterone can induce such irreversible changes in the mammary glands, pituitary gland, ovaries, and genital tracts as those seen with other biologically active steroid hormones.

Importance of mammary gland DNA synthesis on carcinogen-induced mammary tumorigenesis in rats.

DNA synthesis in mammary gland estimated by [3H]thymidine incorporation was significantly higher on the day of proestrus than on the second day of diestrus in 50-day-old female Sprague-Dawley rats. The percentage of progressive mammary tumors, tumor growth rate, and the number and the weight of tumors per tumor-bearing rat were significantly higher in the animals given a single i.v. injection of 5 mg 7,12-dimethylbenz(a)anthracene at proestrus than in the animals given it at diestrus. Inhibition of DNA synthesis at proestrus by 2-bromo-alpha-ergocryptine also suppressed mammary tumorigenesis by the carcinogen. In 90-day-old rats in which little difference was found in mammary gland DNA synthesis between proestrus and diestrus, there was no difference in mammary tumorigenesis between animals given the carcinogen at proestrus and animals given it at diestrus. On the other hand, the prestimulation of mammary gland DNA synthesis by prolactin increased the growth, the number, and the weight of carcinogen-induced mammary tumors. These results demonstrate the importance of mammary DNA synthesis at the time when a carcinogen acts on the glands in mammary tumorigenesis.

Effects of oestrogen and/or pituitary grafts on nucleic acid synthesis in the mammary glands of lactating mice.

The mammary gland synthesizes little DNA during lactation in mice. The effects of daily injections of oestradiol benzoate (OB) between days 9 and 11 of lactation, and/or grafting with three isologous anterior pituitary glands on day 1, on the growth of the litter and the development and function of mammary glands were studied on day 12 of lactation in C3H/He mice. The level of prolactin in the plasma of mice with pituitary grafts was raised, but mammary gland function was not affected. The synthesis and content of mammary gland RNA was depressed after injection of 0.5 microgram OB/day; at a dose of 10 microgram/day, OB also depressed litter growth and mammary DNA content, but increased the synthesis of DNA and the level of prolactin in the plasma. Pituitary grafting enhanced the effect of 10 microgram OB/day on DNA synthesis. These findings suggest that one of the causes of the low level of DNA synthesis in the mammary gland during lactation in mice is a low level of oestrogen in the circulation.

Oestrogenic effects of catechol oestrogens on secretion of prolactin by the pituitary gland and synthesis of DNA by the mammary gland in ovariectomized rats.

The effects of 2-hydroxyoestradiol-17 beta and 2-hydroxyoestriol (2OH-OE3) on levels of serum prolactin, DNA synthesis by the mammary gland and the weight of the uterus were examined in ovariectomized Sprague-Dawley rats. 2-Hydroxyoestradiol-17 beta had a potent oestrogenic activity in stimulating the secretion of prolactin by the pituitary gland, the synthesis of DNA by the mammary gland and in increasing the weight of the uterus. On the other hand, 2OH-OE3 increased the weight of the uterus only.

Mammary nucleic acids and pituitary prolactin secretion during prolonged lactation in mice.

Lactation was prolonged until 61 days by repeated renewal of litters every week after day 12 in primiparous C3H/He strain mice. On days 12, 19, 40, and 61 of lactation, litters were removed for 5 h and after 1 h of resuckling the synthesis of DNA and RNA in the mammary gland was estimated by the incorporation of (3H)thymidine and (14C)uridine into mammary DNA and RNA in vitro respectively. Mammary nucleic acid content and pituitary and plasma levels of prolactin were also assayed. Nulliparous mice were similarly treated on day 19 of pregnancy. The percentage gain in litter weight per week was highest between days 5 and 12 of lactation, declined until days 26-33 and became steady thereafter. Mammary DNA synthesis was extremely high on day 19 of pregnancy, decreased on day 12 of lactation to less than one-fifteenth of that on day 19 of pregnancy and increased linearly therafter. Changes in mammary DNA content were not so marked, but DNA content was high on days 12 and 19 of lactation. RNA synthesis was highest on day 19 of pregnancy, abruptly decreased on days 12 and 19 of lactation and increased again with the advance of lactation. Mammary RNA content, RNA:DNA and 14C:3H ratios increased from day 19 of pregnancy to days 12-19 of lactation and decreased on days 40 and 61. While the pituitary levels of prolactin were almost constant during lactation, they were significantly higher than those on day 19 of pregnancy. There were only slight differences in plasma prolactin levels at any stage.

Inhibition of pituitary prolactin secretion by human placental lactogen in rats.

Intact female rats given twice daily injections of 1 mg human placental lactogen (HPL) showed continued dioestrous vaginal smears and their ovarian corpora lutea were found to be hypertrophied and functiona. The serum prolactin level was significantly lower in these rats than in the controls at dioestrus as well as at pro-oestrus. Twice-daily injections of 0.5 or 2 mg HPL to ovariectomized rats decreased serum and pituitary levels of prolactin and increased hypothalamic activity of prolactin inhibiting hormone, although the effect was less at the lower dose. Human placental lactogen had no direct effect on pituitary prolactin secretion in vitro. These findings have demonstrated that HPL, like prolactin itself, inhibits prolactin secretion by actin