Effects of Caudal Elevation on Testicular Function in Rats: Separation of Effects on Spermatogenesis and Steroidogenesis

A variety of biologic processes are perturbed when exposed to microgravity (space flight) for more than 7 days, including testicular function. Suspension of rats in a special harness (caudal elevation) to induce thoracic pooling of blood fluids and remove the support function of the hind limbs is used to mimic, on earth, the effects of microgravity encountered during space flight. Typically, this induces cryptorchidism in male rats. Three experiments were conducted to differentiate the effects of caudal elevation (30 deg angle) and anatomic location of testes on spermatogenesis and steroidogenesis. Rats were subjected to caudal elevation for 7 days using either a tail harness or a whole-body harness. Testes of rats fell into the abdominal cavity when a tail harness was used, but ligation of the iguinal canal prevented this repositioning. For rats with abdominal testes, testicular weight was reduced (P less than 0.05) and histology of testes was abnormal; the number of spermatids per gram parenchyma was lower (P less than 0.05) in tail-suspended rats compared with control rats

Effects of Microgravity or Simulated Launch on Testicular Function in Rats

Testes from flight rats on COSMOS 2044 and simulated-launch, vivarium, or caudal-elevation control rats (5/group) were analyzed by subjective and quantitative methods. On the basis of observations of fixed tissue, it was evident that some rats had testicular abnormalities unassociated with treatment and probably existing when they were assigned randomly to the four treatment groups. Considering rats without preexisting abnormalities, diameter of seminiferous tubules and numbers of germ cells per tubule cross section were lower (P less than 0.05) in flight than in simulated-launch or vivarium rats. However, ratios of germ cells to each other or to Sertoli cells and number of homogenization-resistant spermatids did not differ from values for simulated-launch or vivarium controls. Expression of testis-specific gene products was not greatly altered by flight. Furthermore, there was no evidence for production of stress-inducible transcripts of the hsp7O or hsp9O genes. Concentration of receptors for rat luteinizing hormone in testicular tissue and surface density of smooth endoplasmic reticulum in Leydig cells were similar in flight and simulated-launch rats. However, concentrations of testosterone in testicular tissue or peripheral blood plasma were reduced (P less than 0.05) in flight rats to less than 20% of values for simulated-launch or vivarium controls. Thus spermatogenesis was essentially normal in flight rats, but production of testosterone was severely depressed. Exposure to microgravity for more than 2 wk might result in additional changes. Sequelae of reduced androgen production associated with microgravity on turnover of muscle and bone should be considered

Dilation of the Giant Vortex State in a Mesoscopic Superconducting Loop

We have experimentally investigated the magnetisation of a mesoscopic aluminum loop at temperatures well below the superconducting transition temperature $T_{c}$. The flux quantisation of the superconducting loop was investigated with a $\mu$-Hall magnetometer in magnetic field intensities between $\pm 100 {Gauss}$. The magnetic field intensity periodicity observed in the magnetization measurements is expected to take integer values of the superconducting flux quanta $\Phi_{0}=h/2e$. A closer inspection of the periodicity, however, reveal a sub flux quantum shift. This fine structure we interpret as a consequence of a so called giant vortex state nucleating towards either the inner or the outer side of the loop. These findings are in agreement with recent theoretical reports.Comment: 12 pages, 5 figures. Accepted for publication in Phys. Rev.

West-Central Asia: a comparative analysis of students’ trajectories in Russia (Moscow) from the 1980s and China (Yiwu) from the 2000s

Through an exploration of oral history and ethnographic material, this article makes a comparative examination of the life-trajectories of students from Yemen, Iraq, and Afghanistan who studied in Russia (Moscow) during the late 1980s, and from Tajikistan, Iran, Azerbaijan and Saudi Arabia who studied in China in the 2000s. In contrast to the cohort of students in Moscow who were mainly men from places with relatively amicable relations with the USSR, the female students of Muslim background from West and Central Asia regarded China as a place where they could pursue fulfilling forms of economic and personal autonomy. By comparing these two groups of international students, this article sheds light into the nature of historical, geographical and geopolitical connections and disconnections between West-Central Asia, Eurasia (especially Russia) and East Asia (especially China). By centring its attention to the demise of Soviet/Russian education and the emergence of China as a figure of economic prosperity, the article theorises West-Central Asia as a particular arena of interaction suitable to comprehend the networks, ‘third spaces’ or zones of interaction (e.g. Moscow and Yiwu), and forms of connection fostered by these students’ trajectories

Quantization of Superflow Circulation and Magnetic Flux with a Tunable Offset

Quantization of superflow-circulation and of magnetic-flux are considered for systems, such as superfluid $^3$He-A and unconventional superconductors, having nonscalar order parameters. The circulation is shown to be the anholonomy in the parallel transport of the order parameter. For multiply-connected samples free of distributed vorticity, circulation and flux are predicted to be quantized, but generically to nonintegral values that are tunably offset from integers. This amounts to a version of Aharonov-Bohm physics. Experimental settings for testing these issues are discussed.Comment: 5 two-column pages, ReVTeX, figure available upon request (to [email protected]

Flux transitions in a superconducting ring

We perform a numeric study of the flux transitions in a superconducting ring at fixed temperature, while the applied field is swept at an ideally slow rate. The current around the ring and its free energy are evaluated. We partially explain some of the known experimental features, and predict a considerably large new feature: in the vicinity of a critical field, giant jumps are expected

Males, but Not Females, Demonstrate Mitochondrial Dysfunction in the C26 Model of Cancer Cachexia

Cancer cachexia is characterized by progressive muscle wasting that can lead to symptoms such as anemia, severe weight loss, and fatigue. These symptoms can lead to limitations in activities of daily living and can cause resistance to chemotherapy treatments in cancer patients. There are no current treatments available to treat cancer cachexia and a critical need remains to identify mechanisms of cancer cachexia. Recently, our group identified mitochondrial disfunction precedes muscle atrophy in males but not females in a model of lung cancer induced atrophy. However, it is unknown whether this finding is replicated when studying a different type of cancer. PURPOSE: This study set out to determine if mitochondrial respiration is impaired in the plantaris muscle in a well-established colon cancer model of cachexia. METHODS: The time-course study consisted of male and female mice in four groups per sex: An age-matched control (PBS), and three groups implanted with C26 tumors. Tumor growth for 10-15 days, 20 days, and 25 days. Tumors were implanted bilaterally into the hind flank for a total of 1X106 cells PBS (one-half per each hindflank). The plantaris was weighed for wet mass then teased into small fiber bundles and permeabilized for the quantification of mitochondrial function. Mitochondrial dysfunction was classified by a decrease in the respiratory control ratio (RCR), which is the ratio of state 3 (maximal ADP stimulated respiration) to state 4 (oligomycin-induced leak respiration). Male and Female data were analyzed separately using a one-way ANOVA. RESULTS: The tumor burden increased as the number of days increased. Male RCR showed a mean difference in RCR at the early timepoint (10-15 day, p=0.058) and demonstrated significantly lower RCR at the 20 day timepoint compared to PBS control (20d= 1.170± 0.094, PBS= 2.41 ± 0.13, p=0.031). Interestingly, RCR was not significantly different between male PBS and 25 days (1.864± 0.21, p=0.084). RCR in the plantaris from females was not different among any of the groups (p=0.401). CONCLUSION: Along with our previously published data in a lung cancer model, these data indicate that the mechanisms of muscle atrophy are sex dependent. Specifically, mitochondrial dysfunction appears to play an important role in cancer-induced atrophy in male, but not female, mice

Fluxoid dynamics in superconducting thin film rings

We have measured the dynamics of individual magnetic fluxoids entering and leaving photolithographically patterned thin film rings of the underdoped high-temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, using a variable sample temperature scanning SQUID microscope. These results can be qualitatively described using a model in which the fluxoid number changes by thermally activated nucleation of a Pearl vortex in, and transport of the Pearl vortex across, the ring wall.Comment: 9 pages, 10 figures, fixed typo

A New Interpretation of Flux Quantization

We study the effect of Aharonov-Bohm flux on the superconducting state in metallic cylinders. Although Byers and Yang attributed flux quantization to the flux-dependent minimum of kinetic energies of the Cooper pairs, it is shown that kinetic energies do not produce any discernible oscillations in the free energy of the superconducting state (relative to that of normal state) as a function of the flux. This result is indeed anticipated by the observation of persistent current in normal metal rings at low temperature. Instead, we have found that pairing interaction depends on the flux, leading to flux quantization. When the flux $(\Phi$) is given by $\Phi=n\times hc/2e$ (with integer n), the pairing interaction and the free energy become unchanged (even n) or almost unchanged (odd n), due to degenerate-state pairing resulting from the energy level crossing. As a result, flux quantization and Little-Parks oscillations follow.Comment: Revtex, 10 pages, 6 figures, For more information, send me an e-mail at [email protected]