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Convertino, Victor A., David A. Ludwig, James J. Elliott, and Charles E. Wade. Evidence for central venous pressure resetting during initial exposure to microgravity. Am J Physiol Regulatory Integrative Comp Physiol 281: R2021-R2028, 2001.--We measured central venous pressure (CVP); plasma volume (PV); urine volume rate (UVR); renal excretion of sodium (UNa); and renal clearances of creatinine, sodium, and osmolality before and after acute volume infusion to test the hypothesis that exposure to microgravity causes resetting of the CVP operating point. Six rhesus monkeys underwent two experimental conditions in a crossover counterbalance design: 1) continuous exposure to 10 [degrees] head-down tilt (HDT) and 2) a control, defined as 16 h/day of 80 [degrees] head-up tilt and 8 h prone. After 48 h of exposure to either test condition, a 120-min course of continuous infusion of isotonic saline (0.4 ml.[kg.sup.-1].[min.sup.-1 iv) was administered. Baseline CVP was lower (P = 0.011) in HDT (2.3 [ + or -] 0.3 mmHg) compared with the control (4.5 [+ or -] 1.4 mmHg) condition. After 2 h of saline infusion, CVP was elevated (P = 0.002) to a similar magnitude (P = 0.485) in HDT ([DELTA]CVP = 2.7 [+ or -] 0.8 mmHg) and control ([DELTA]CVP = 2.3 [+ or -] 0.8 mmHg) conditions and returned to preinfusion levels 18 h postinfusion in both treatments. PV followed the same pattern as CVP. The response relationships between CVP and UVR and between CVP and UNa shifted to the left with HDT. The restoration of CVP and PV to lower preinfusion levels after volume loading in HDT compared with control supports the notion that lower CVP during HDT may reflect a new operating point about which vascular volume is regulated. These results may explain the ineffective fluid intake procedures currently employed to treat patients and astronauts. set point; hypovolemia; diuresis; renal function Received 8 February 2001; accepted in final form 29 August 2001

The application of N,N,N',N'-tetramethylimidazolidinium dichloride (1-lm-1 2Cl) as a model system for cation-anion interactions in the interfacial regions of Gemini micelles is reported. The crystals of 1-lm-1 2Cl consist of imidazolidinium dications linked to two apical and six equatorial chloride ions by an extensive network of C-H...Cl hydrogen bonds.

Often few alternative anesthetics for exotic species are available, due to the small numbers of these animals used in research. In this study, we evaluated the depth and duration of anesthesia in Xenopus laevis after their immersion in 3 doses of etomidate (15, 22.5, and 30 mg/L) and in 3 doses of benzocaine (0.1%, 0.5%, and 1%) compared with the 'gold standard,' tricaine methanesulfonate (MS222; 2 g/L). We then chose an optimal dose for each alternative anesthetic according to induction time, duration of surgical plane, and time to complete recovery. The optimal etomidate and benzocaine doses (22.5 mg/L and 0.1%, respectively) as well as the MS222 dose were then used to achieve a surgical plane of anesthesia, with the addition of flunixin meglumine (25 or 50 mg/kg) administered in the dorsal lymph sac at the completion of mock oocyte harvest. Efficacy of the analgesic was assessed at 1, 3, 6, and 24 h postoperatively by using acetic acid testing (AAT). Histology of the liver, kidney, and tissues surrounding the dorsal lymph sac was performed at day 3, 14, and 28 in each group of animals. Mild to moderate myocyte degeneration and necrosis were present in tissues surrounding the dorsal lymph sac at both flunixin meglumine doses after etomidate and benzocaine anesthesia. In addition, the 50-mg/kg dose of flunixin meglumine resulted in the death of 5 of the 12 frogs within 24 h, despite an otherwise uneventful anesthetic recovery. In conclusion, benzocaine and etomidate offer alternative anesthetic regimens, according to typical requirements for an anesthetic event. Flunixin meglumine at the 25-mg/kg dose provided analgesic relief at the latest time point during etomidate dosage and at all time points during benzocaine dosage, but further characterization is warranted regarding long-term or repeated analgesic administration.