Dynamic changes in renal sodium handling during sympathetic stimulation in healthy human males.

The temporal response of changes in renal sodium reabsorption during increased renal sympathetic nerve activity has not been investigated. Central hypovolemia by application of lower-body negative-pressure (LBNP) elicits baroreceptor mediated sympathetic reflexes to maintain arterial blood pressure. We hypothesized, that during 90 min LBNP, the renal sodium retention would increase rapidly, remain increased during intervention, and return to baseline immediately after end of intervention. METHODS: 30 young, healthy, sodium loaded, non-obese males were exposed to -15 mmHg LBNP, -30 mmHg LBNP, -15 mmHg LBNP + renin blockade or time-control (0 mmHg LBNP) for 90 min. Urine was collected every 15 min during 90 min of intervention and 60 min of recovery to identify a possible relation between time of intervention and renal response. RESULTS: All intervention groups exhibited a comparable reduction in distal sodium excretion at the end of the intervention (P = 0.46 between groups; -15 mmHg: -3.1 ± 0.9 %, -30 mmHg: -2.9 ± 0.6 %, -15 mmHg + aslikiren: -1.8 ± 0.6 %). -15 mmHg+Aliskiren resulted in a slower onset, but all groups exhibited a continued reduction in sodium excretion after 1 h of recovery despite return to baseline of renin, aldosterone, diuresis and cardiovascular parameters. CONCLUSION: Sympathetic stimulation for 90 min via LBNP at -30 mmHg LBNP compared to -15 mmHg did not result in a greater response in fractional Na+ excretion, suggesting that additional baroreceptor unloading did not cause further increases in renal sodium reabsorption. Changes in distal Na+ excretion were linear with respect to time (dose) of intervention, but seem to exhibit a saturation-like effect at a level around 4 %. The lack of recovery after 1 h is also a new finding that warrants further investigation.

Postural influence on intracranial and cerebral perfusion pressure in ambulatory neurosurgical patients.

We evaluated postural effects on intracranial pressure (ICP) and cerebral perfusion pressure [CPP: mean arterial pressure (MAP) - ICP] in neurosurgical patients undergoing 24-h ICP monitoring as part of their diagnostic workup. We identified nine patients (5 women, age 44 ± 20 yr; means ± SD), who were "as normal as possible," i.e., without indication for neurosurgical intervention (e.g., focal lesions, global edema, abnormalities in ICP-profile, or cerebrospinal fluid dynamics). ICP (tip-transducer probe; Raumedic) in the brain parenchyma (n = 7) or in the lateral ventricles (n = 2) and cardiovascular variables (Nexfin) were determined from 20° head-down tilt to standing up. Compared with the supine position, ICP increased during 10° and 20° of head-down tilt (from 9.4 ± 3.8 to 14.3 ± 4.7 and 19 ± 4.7 mmHg; P < 0.001). Conversely, 10° and 20° head-up tilt reduced ICP to 4.8 ± 3.6 and 1.3 ± 3.6 mmHg and ICP reached -2.4 ± 4.2 mmHg in the standing position (P < 0.05). Concordant changes in MAP maintained CPP at 77 ± 7 mmHg regardless of body position (P = 0.95). During head-down tilt, the increase in ICP corresponded to a hydrostatic pressure gradient with reference just below the heart, likely reflecting the venous hydrostatic indifference point. When upright, the decrease in ICP was attenuated, corresponding to formation of a separate hydrostatic gradient with reference to the base of the skull, likely reflecting the site of venous collapse. ICP therefore seems to be governed by pressure in the draining veins and collapse of neck veins may protect the brain from being exposed to a large negative pressure when upright. Despite positional changes in ICP, MAP keeps CPP tightly regulated.

Clocking the melting transition of charge and lattice order in 1T-TaS2 with ultrafast extreme-ultraviolet angle-resolved photoemission spectroscopy.

We use time- and angle-resolved photoemission spectroscopy with sub-30-fs extreme-ultraviolet pulses to map the time- and momentum-dependent electronic structure of photoexcited 1T-TaS(2). This compound is a two-dimensional Mott insulator with charge-density wave ordering. Charge order, evidenced by splitting between occupied subbands at the Brillouin zone boundary, melts well before the lattice responds. This challenges the view of a charge-density wave caused by electron-phonon coupling and Fermi-surface nesting alone, and suggests that electronic correlations play a key role in driving charge order.

Polaronic conductivity in the photoinduced phase of 1T-TaS2.

The transient optical conductivity of photoexcited 1T-TaS2 is determined over a three-order-of-magnitude frequency range. Prompt collapse and recovery of the Mott gap is observed. However, we find important differences between this transient metallic state and that seen across the thermally driven insulator-metal transition. Suppressed low-frequency conductivity, Fano phonon line shapes, and a midinfrared absorption band point to polaronic transport. This is explained by noting that the photoinduced metallic state of 1T-TaS2 is one in which the Mott gap is melted but the lattice retains its low-temperature symmetry, a regime only accessible by photodoping.

Wavelength calibration of a fiber-optical spectrum analyzer: temperature dependence.

Optical spectrum analyzers are of increasing importance in fiber-optic laboratories. To perform reliable measurements with these devices, one must calibrate them with respect to wavelength, resolution bandwidth, power, etc. and know the temperature dependence of such calibrations. We have constructed a temperature-controlled chamber that can contain a spectrum analyzer and that can be regulated to within +/-0.1 degrees C. We report the temperature dependence of wavelength calibration and compare the various calibration results performed under temperature control with those previously obtained at ambient nonregulated temperature. For these studies we have used a compact calibration artifact based on absorption spectroscopy of acetylene.

Infrared radio-frequency double resonance of (13)CH(3)OH.

Infrared radio-frequency double-resonance spectroscopy has been carried out for (13)CH(3)OH. Four K-type doublet transitions have been observed below 1 GHz, using the 9P(10) and 9P(12) CO(2) laser lines. The results confirm previously proposed assignments of infrared absorption transitions and far-infrared laser emission lines observed in this molecule. Measurements of the A-state splittings have permitted the determination of the asymmetry splitting parameters S(O)(K) and S(CO)(K) for (n, K) = (0, 4) and (1, 3).

Mammography in women under age 30: is there clinical benefit?

With the increasing utilization of mammography, young women under age 30 are being referred for mammographic examination more frequently. A review of the mammograms of 76 patients, aged 18-29 years, was conducted to evaluate the clinical utility of the examination in this age group, for whom the probability of malignancy is quite low and the risk of radiation carcinogenesis may not be negligible. In 74% of patients referred for study of a palpable mass, no mass was evident on mammograms. When a mass was seen, the radiographic features did not influence clinical management. Radiologists should inform their clinical colleagues regarding the risks and limitations of mammography in women under age 30 and encourage more frequent utilization of ancillary diagnostic procedures including sonography and diagnostic aspiration.

Rapid immunoelectrophoretic assay for detection of serum antibodies to Aspergillus fumigatus catalase in patients with pulmonary aspergillosis.

A rapid immunoelectrophoretic assay was developed to detect antibodies to Aspergillus fumigatus catalase. The method's diagnostic sensitivity for pulmonary aspergillosis was 88% (72-97%, 95% confidence limits) in 33 patients presenting with either aspergilloma or Aspergillus lung infiltrate. The diagnostic specificity was 94% (90-97%) as judged from 191 patients with other infiltrative lung diseases, including infections and neoplasia. None of the 185 healthy subjects had catalase antibodies. The highest titres (ranging up to 256) were found in aspergillosis patients with cavitary lesions. Catalase antibody titres increased in two patients with concomitant development of lung cavities and mycetomas. In patients with resected or stable Aspergillus lung disorders catalase antibody titres declined by less than one dilution step per year.

Taking laetrile: conversion to medial deviance.

For members of the CCS, laetrile use occurs in a self-help social context where users derive substantial social and emotional support from fellow members. We are convinced that much of the appeal of laetrile results from this social context in which it is frequently used. The CCS and the extensive network of similar organizations are fulfilling unmet needs in cancer patients and those fearful of cancer. Until conventional cancer therapy deals more successfully with the social and psychological needs of cancer patients, promoters of laetrile will till fertile ground.