Intronless Pabpc6 encodes a testis-specific, cytoplasmic poly(A)-binding protein but is dispensable for spermatogenesis in the mouse†.

Besides ubiquitous poly(A)-binding protein, cytoplasmic 1 (PABPC1), testis-specific PABPC2/PABPt (in humans, referred to as PABPC3), and female and male germline-specific PABPC1L/ePAB, have been reported in the mouse testis. Recent in silico analysis additionally identified testis-specific Pabpc6 in the mouse. In this study, we characterized PABPC6 and its mutant mice. PABPC6 was initially detectable in the cytoplasm of pachytene spermatocytes, increased in abundance in round spermatids, and decreased in elongating spermatids. PABPC6 was capable of binding to poly(A) tails of various mRNAs and interacting with translation-associated factors, including EIF4G, PAIP1, and PAIP2. Noteworthy was that PABPC6, unlike PABPC1, was barely associated with translationally active polysomes and enriched in chromatoid bodies of round spermatids. Despite these unique characteristics, neither synthesis of testicular proteins nor spermatogenesis was affected in the mutant mice lacking PABPC6, suggesting that PABPC6 is functionally redundant with other co-existing PABPC proteins during spermatogenesis.

Continuous monitoring of hypothalamic neurotransmitters and thermoregulatory responses in exercising rats.

The purpose of the present study was to investigate the relationship between thermoregulation and catecholamine release in the preoptic area and anterior hypothalamus (PO/AH) during incremental treadmill running in the rat. To this aim, we combined in vivo brain microdialysis, biotelemetry and metabolic measurements for continuous monitoring of core body temperature (T(core)), neurotransmitters and thermoregulatory responses. The animals were exercised for 1h at 23°C. Treadmill speed was increased every 20 min (10, 20 and 26 m min⁻¹). T(core), oxygen consumption (V˙O2, an index of heat production) and tail skin temperature (T(tail), an index of heat loss) were simultaneously measured. Brain microdialysis samples were collected every 10 min, and these samples were analyzed for noradrenaline (NA), dopamine (DA) and serotonin (5-HT). T(core) and V˙O(2)2 significantly increased during treadmill and were exercise intensity dependent. After an initial drop T(tail) increased significantly during exercise. Both NA and DA levels in the PO/AH increased significantly during exercise. There was no effect on serotonin release. T(core), V˙O2 and T(tail) were positively correlated with the levels of NA and DA. Our data suggest that thermoregulatory responses are dependent on the intensity of the exercise and that these responses are associated with changes in NA and DA release, but not in 5-HT release in the PO/AH.

Changes in selected ambient temperatures following physical training in rats.

To clarify the mechanism of body temperature (T(b)) rise following voluntary wheel-run training in rats, we investigated the behavioral thermoregulation in female rats by means of a thermal gradient system. We performed thermal gradient tests before training, 4 weeks after training started, and 2 weeks after it stopped. We also examined the effects on the selected ambient temperature and T(b) with quantitative training activity. Nine female rats ran voluntarily in a wheel in the range of 6,545 from 1,665 revolutions/night. The higher the wheel-running activity, the higher the T(b) level rose at rest during the daytime after 4 weeks of training. The higher-activity rats selected a higher ambient temperature after the training than before, and the T(b) was maintained at a high level under this environment. Our results suggest that the rise in T(b) level during rest following the wheel-run training is a regulated body temperature change.