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To appraise the physiological pattern(s) of episodic testosterone and FSH release in man, we withdrew blood samples at 10-min intervals for 24-36 h in a total of 15 normal men. We subjected the resulting FSH (15 men) and testosterone (5 men) time series to 3 statistically based and mathematically independent procedures for detecting hormone pulsatility, viz. Cluster analysis, the Detect program, and Fourier transformation. The Cluster technique disclosed discrete testosterone and FSH peaks occurring at mean (+/- SEM) interpulse intervals of 112 +/- 14 and 85 +/- 3.4 min, respectively. These values were not significantly different from the mean LH interpulse interval of 95 +/- 11 min. The average durations of the testosterone and FSH pulsations were 90 +/- 11 and 59 +/- 3 min, respectively. The mean testosterone pulse amplitude reached a maximal value of 910 +/- 92 ng/dL (31.5 +/- 3.2 nmol/L), which represented a mean increase of 242 +/- 26 ng/dL (8.4 +/- 0.9 nmol/L) above the preceding nadir. FSH pulses had a maximum of 7.2 +/- 0.3 IU/L, and an incremental amplitude of 1.3 +/- 0.1 IU/L. An independent pulse detection procedure. Detect, yielded a testosterone pulse frequency of 12.3 +/- 0.8 pulses/day [P = NS vs. Cluster program (13 +/- 1.9 pulses/day)]. The Cluster and Detect estimates of FSH pulse frequency were also similar, viz. 16 +/- 1.9 and 16 +/- 0.6 pulses/day. Further analysis by Fourier transformation revealed significant circadian periodicities for serum testosterone, FSH, and LH, which had mean nyctohemeral amplitudes of 185 ng/dL (6.4 nmol/L), 0.38 IU/L, and 1.3 IU/L, respectively. Cross-correlation analyses disclosed significantly positive uncorrected cross-correlations between LH and testosterone that were maximal at a testosterone lag of 60 min (range, 50-70 min). To eliminate high intrinsic autocorrelations within the testosterone and LH time series, stepwise autoregressive fitting was employed. The resulting partial cross-correlation matrices indicated that LH concentrations at any given instant were significantly positively correlated to testosterone concentrations lagged by 10 and 20 min. Similarly, contemporaneous LH and FSH concentrations were significantly positively correlated (r = 0.40-0.89; P less than 0.001). Moreover, autoregressive modeling disclosed significantly positive partial cross-correlations between LH and FSH at a FSH lag of 10 min. In summary, we have identified significant pulsatile as well as circadian (24-h) patterns of testosterone and FSH release in normal men.(ABSTRACT TRUNCATED AT 400 WORDS)

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N e a r -a n d F a r -F ie ld s : S o u r c e C h a r a c te r is tic s a n d th e C o n d u c tin g M e d iu m in N e u r o p h y s io lo g y

Across the Upper Missouri River Basin, the recent drought of 2000 to 2010, known as the “turn-of-the-century drought,” was likely more severe than any in the instrumental record including the Dust Bowl drought. However, until now, adequate proxy records needed to better understand this event with regard to long-term variability have been lacking. Here we examine 1,200 y of streamflow from a network of 17 new tree-ring–based reconstructions for gages across the upper Missouri basin and an independent reconstruction of warm-season regional temperature in order to place the recent drought in a long-term climate context. We find that temperature has increasingly influenced the severity of drought events by decreasing runoff efficiency in the basin since the late 20th century (1980s) onward. The occurrence of extreme heat, higher evapotranspiration, and associated low-flow conditions across the basin has increased substantially over the 20th and 21st centuries, and recent warming aligns with increasing drought severities that rival or exceed any estimated over the last 12 centuries. Future warming is anticipated to cause increasingly severe droughts by enhancing water deficits that could prove challenging for water management.