Movements of sodium and potassium into ejaculated boar spermatozoa suspended in seminal plasma and a biological salt solution

Uptake of 22Na and 42K into ejaculated boar spermatozoa was measured in vitro. Cells were suspended either in seminal plasma or in a biological salt solution of essentially the same composition as boar seminal plasma. Samples were incubated at 30 degrees C. Correction was made for extracellular space in the centrifuged sperm pellet. This was determined as 22Na-space, which was less (P less than 0.001) than [14C] carboxyinulin space. Large differences were observed among individual ejaculates. The half-time for potassium uptake into the spermatozoa averaged 11.5 min, which is much faster than that for leukocytes or erythrocytes. When the spermatozoa were suspended in the biological salt solution, the initial rate of 42K uptake was significantly decreased. This may be due to disturbances of the protein components of the sperm membrane. The uptake of 22Na into the spermatozoa was slow. Sodium and potassium transport appeared not to be coupled in the 3/2 ratio which has been reported for erythrocyte membranes. The average concentration of sodium was 108 mM in seminal plasma and 26 mM in the spermatozoa (112 mmol/kg water and 38 mmol/kg water, respectively). The corresponding figures for potassium were 26 mM and 51 mM (27 mmol/kg water and 74 mmol/kg water). The random error for a single determination for the various methods used varied between 2.4 and 13.3% of the mean.     

Salt intake, blood pressure, and cardiovascular structure

Epidemiologic data revealed that a low sodium intake might have a favorable influence on blood pressure throughout an individual's lifetime. Sodium restriction was reported to lead to a modest fall in blood pressure in some studies, although a few groups of hypertensive patients experienced a rise in blood pressure. Left ventricular hypertrophy has been demonstrated to be related to cardiovascular morbidity and mortality independent of other risk factors. Dietary salt intake participates in the hypertrophic process independent of other determinants. Thus, 24-hour urinary sodium excretion has been reported to correlate with left ventricular mass independent of levels of arterial pressure. Three different mechanisms may link dietary salt intake to myocardial hypertrophy: the renin-angiotensin-aldosterone system, the sympathetic nervous system, and fluid volume homeostasis. Whether salt restriction reduces cardiovascular structural damage independent of arterial pressure has not been determined.     

Widespread integration and survival of adult-derived neural progenitor cells in the developing optic retina

Adult rat hippocampus-derived neural progenitor cells (AHPC) show considerable adaptability following grafting to several brain regions. To evaluate the plasticity of AHPCs within the optic retina, retrovirally engineered AHPCs were grafted into the vitreous cavity of the adult and newborn rat eye. Within the adult eye, AHPCs formed a uniform nondisruptive lamina in intimate contact with the inner limiting membrane. Within 4 weeks of grafting to the developing eye, the AHPCs were well integrated into the retina and adopted the morphologies and positions of Müller, amacrine, bipolar, horizontal, photoreceptor, and astroglial cells. Although the cells expressed neuronal or glial markers, none acquired end-stage markers unique to retinal neurons. This suggests that the adult-derived stem cells can adapt to a wide variety of heterologous environments and express some but not all features of retinal cells when exposed to the cues present late in retinal development.