Shot noise suppression at room temperature in atomic-scale Au junctions.

Shot noise encodes additional information not directly inferable from simple electronic transport measurements. Previous measurements in atomic-scale metal junctions at cryogenic temperatures have shown suppression of the shot noise at particular conductance values. This suppression demonstrates that transport in these structures proceeds via discrete quantum channels. Using a high-frequency technique, we simultaneously acquire noise data and conductance histograms in Au junctions at room temperature and ambient conditions. We observe noise suppression at up to three conductance quanta, with possible indications of current-induced local heating and 1/f noise in the contact region at high biases. These measurements demonstrate the quantum character of transport at room temperature at the atomic scale. This technique provides an additional tool for studying dissipation and correlations in nanodevices.

Plasma lipoprotein cholesterol concentrations in the golden-mantled ground squirrel (Spermophilus lateralis): a comparison between pre-hibernators and hibernators.

1. The concentrations of total cholesterol (free cholesterol plus cholesteryl ester) in the plasma and in two lipoprotein fractions of golden-mantled ground squirrels (Spermophilus lateralis) were measured during pre-hibernation and compared to those values measured during hibernation. 2. Hibernating ground squirrels had significantly higher (P less than 0.005) very low density lipoprotein plus low density lipoprotein cholesterol (VLDL + LDL-C) concentrations than did pre-hibernating ground squirrels. 3. Hibernating squirrels additionally exhibited significantly higher (P less than 0.005) total plasma cholesterol concentration per high density lipoprotein cholesterol concentration (TPC/HDL-C) ratios than did pre-hibernating squirrels. 4. The significant differences in the lipoprotein cholesterol concentrations observed in this study suggest that lipoprotein metabolism in pre-hibernators was significantly different from that in hibernators and was a reflection of the marked biochemical and physiological adjustments these animals must undergo during their transition from pre-hibernation to hibernation.

Gender influences the in vitro renin release responses to dopamine and adrenergic receptor blockade in the summer-active ground squirrel Spermophilus lateralis.

1. 10(-4) M Dopamine stimulated and 10(-7) M inhibited in vitro resting renin release (RR) only in the female animals. 2. Alpha- or beta-adrenergic blockade prevented the stimulation but not the inhibition of RR by dopamine in the female animals. 3. Membrane receptor mechanisms mediating these changes do not involve alterations in tissue cyclic AMP content. 4. The sensitivity of the juxtaglomerular cells to dopamine challenge is gender dependent during summer activity.

Circulating lipoprotein cholesterol concentrations in the summer-active ground squirrel (Spermophilus lateralis): a comparison with those in humans and rabbits.

1. The concentrations of total cholesterol (free cholesterol plus cholesteryl ester) in the sera and in two lipoprotein fractions of golden-mantled ground squirrels (Spermophilus lateralis) were measured and compared to those found in humans and New Zealand White rabbits (Oryctolagus cuniculus). 2. Squirrels showed significantly higher concentrations of total serum cholesterol (TSC; P less than 0.0005), high density lipoprotein cholesterol (HDL-C; P less than 0.0005), and very low density plus low density lipoprotein cholesterol (VLDL + LDL-C; P less than 0.0005) than those in rabbits. 3. Squirrels had significantly higher TSC (P less than 0.0005) and HDL-C (P less than 0.0005) concentrations than did humans. 4. Squirrels additionally exhibited significantly lower TSC/HDL-C ratios than did rabbits (P less than 0.005) or humans (P less than 0.0005). 5. The significant differences in lipoprotein metabolism observed in this study between the active hibernator and non-hibernators, may reflect the marked biochemical and physiological adjustments hibernating species make throughout their circannual cycle.

Changes in renal morphology and renin secretion in the golden-mantled ground squirrel (Spermophilus lateralis) during activity and hibernation.

Chronological changes in renal glomerular morphology and plasma renin activity were investigated during active and hibernating periods in the golden-mantled ground squirrel Spermophilus lateralis. The objective of this study was to determine whether the glomerular endothelium, visceral epithelium (podocytes), basement membrane, mesangial cells, proximal convoluted tubule cells and plasma renin activity exhibit measurable sequential differences between as well as within active and hibernating states at various time points. Limitations in the size of the experimental population prevented an evaluation of changes in these parameters during other important periods such as periodic arousal between hibernation bouts. In this study, glomerular endothelial pore number and epithelial filtration slit number significantly decreased by early hibernation when compared to those during summer activity, and then they increased back toward summer levels by late hibernation. In contrast, podocytic pedicel width along the glomerular basement membrane increased from summer activity to early hibernation, before significantly decreasing again by late hibernation. Mesangial cell and proximal convoluted tubule cell activity appeared increased during hibernation as compared to summer activity, whereas the width of the glomerular basement membrane showed no significant alterations throughout. Plasma renin activity significantly increased during early hibernation and mid-hibernation when compared to summer levels but had decreased by late hibernation toward summer values. The glomerular and plasma renin activity changes observed in this study clearly illustrate the drastic structural and functional adjustments which hibernating species make during torpor and also correlate well with the reported decrease in renal perfusion pressure and urine formation during hibernation.(ABSTRACT TRUNCATED AT 250 WORDS)