Rotational motions of macro-molecules by single-molecule fluorescence microscopy

Several complementary techniques have been developed to determine average orientation, dynamics on multiple time scales, and concerted rotational motions of individual fluorescent probes bound to biological macromolecules. In both protein domains and nucleic acids, tilting and wobble are relevant to their functional mechanisms. Here we briefly review methods to detect angles and rotational motions of single fluorophores and give an example of three-dimensional, total internal reflection, single-molecule fluorescence polarization applied to actin as it is translocated by conventional muscle myosin.     

Modified Pound-Drever-Hall scheme for high-precision free spectral range measurement of Fabry-Perot etalon

Improvement of two orders of magnitude of the Pound-Drever-Hall based free spectral range (FSR) measurement method is reported. The improved technique results in 1 part in 10⁶ precision. This is believed to be the most precise measurement of FSR.     

A Prototypical Small‐Molecule Modulator Uncouples Mitochondria in Response to Endogenous Hydrogen Peroxide Production

A high membrane potential across the mitochondrial inner membrane leads to the production of the reactive oxygen species (ROS) implicated in aging and age‐related diseases. A prototypical drug for the correction of this type of mitochondrial dysfunction is presented. MitoDNP‐SUM accumulates in mitochondria in response to the membrane potential due to its mitochondria‐targeting alkyltriphenylphosphonium (TPP) cation and is uncaged by endogenous hydrogen peroxide to release the mitochondrial uncoupler, 2,4‐dinitrophenol (DNP). DNP is known to reduce the high membrane potential responsible for the production of ROS. The approach potentially represents a general method for the delivery of drugs to the mitochondrial matrix through mitochondria targeting and H₂O₂‐induced uncaging.     

Task constraints and visual feature binding

Tel.: 00 44 1904 433135; fax: 00 44 1904 433181; e-mail: ptql@york.ac.uk. Experimental variations on the paradigm described by Kahneman, D., Treisman, A., Gibbs, B.J., 1992. Cognitive Psychology 24, 175-219 are reported. With these techniques two coloured letters are briefly presented, in a preview field. Following a short blank interval, a single coloured letter (the target) is presented. In the first experiment, reported here, subjects named the target letter, and in the second they named the target's colour. In neither of the experiments did the colour relationships between the target and preview items influence performance, but in both cases the shape relationships were important. Further experiments explored the notion that performance in the tasks was only an imperfect reflection of underlying perceptual processes because of the constraint of having to name the letters. When subjects were presented with unfamiliar characters and named the target's colour, then the colour relationships in the displays were important; residual effects of shape preview were also found. In final studies visually similar letters were used and different groups of subjects either named the target letter or the colour of the target. Of main interest was that the colour relations between the items exerted an effect when subjects named the target's colour. The theoretical and methodological implications of these results are discussed and the limitations of the original experiments are considered in the light of the reported findings.     

Role of interleukin 8 in the genesis of acute respiratory distress syndrome through an effect on neutrophil apoptosis

OBJECTIVE: To evaluate the role of interleukin 8 (IL-8) in the regulation of neutrophil (PMN) apoptosis in normal plasma and plasma from patients with early, fulminant acute respiratory distress syndrome (ARDS). DESIGN: Experimental study using cultured human PMNs. SETTING: University hospital, level I trauma center. PARTICIPANTS: Plasma was obtained from 6 patients with early, fulminant posttraumatic ARDS (mean Injury Severity Score, 26). All samples were drawn within 24 hours after injury. Plasma was also taken from 13 healthy control subjects. These controls were also used as sources of PMNs. MAIN OUTCOME MEASURES: Effect of early, fulminant ARDS and normal plasma on spontaneous apoptosis, CD16, and CD11-b expression in PMNs in vitro; levels of IL-8 in plasma; correlation of extracellular IL-8 concentration with rate of PMN apoptosis; and effect of IL-8 blockade on PMN apoptosis, CD16, and CD11-b expression in ARDS and normal plasma. RESULTS: Plasma from patients with early, fulminant ARDS inhibited spontaneous PMN apoptosis at 24 hours (35%+/-5% vs 54%+/-5%; P=.01). Neither CD16 nor CD1l-b differed significantly between the 2 groups. The mean plasma level of IL-8 in patients with early, fulminant ARDS was 359+/-161 pg/mL vs 3.0+/-0.4 pg/mL in healthy controls (P<.05). Interleukin 8 inhibited apoptosis in plasma-free medium at low doses (1-50 pg/mL) but had no significant effect at higher doses (100-5000 pg/mL) (P<.05). Interleukin 8 blockade with monoclonal antibody suppressed apoptosis in normal plasma (28%+/-5% with monoclonal antibody vs 51%+/-5% without monoclonal antibody; P=.008) but not in plasma from patients with early, fulminant ARDS (29%+/-5% with monoclonal antibody vs 34%+/-6% without monoclonal antibody; P=.67). It had no effect on CD16 or CD11-b expression in either plasma. CONCLUSIONS: Plasma from patients with early, fulminant ARDS contains soluble factors that inhibit PMN apoptosis in vitro. Low levels of IL-8 inhibit PMN apoptosis in normal plasma. Although plasma levels of IL-8 are markedly elevated in early, fulminant ARDS, IL-8 is not directly responsible for the antiapoptotic effect of plasma from patients with early, fulminant ARDS.     

Neoadjuvant chemoradiotherapy for esophageal cancer: is it worthwhile?

BACKGROUND: With promising results from several institutions, many centers began treating patients with esophageal cancer with neoadjuvant chemoradiotherapy (NC) followed by esophagectomy. This approach is demanding for the patient and has not been proved to be better than esophagectomy alone. OBJECTIVE: To assess survival time and measures of quality of life associated with NC. DESIGN: A retrospective review during 1990 to 1996. SETTING: The 3 tertiary academic hospitals affiliated with the University of Massachusetts Medical School, Worcester. PARTICIPANTS: All patients (N=51) with cancer of the middle or lower esophagus who were treated with NC followed by esophagectomy during this period. MAIN OUTCOME MEASURES: Median and 1-, 2-, and 3-year survival times; median preoperative treatment time (first office visit for surgical consultation before beginning NC to the date of surgery), median hospital stay, and postoperative swallowing function. RESULTS: The median survival time of all patients was 16.3 months; 1-, 2-, and 3-year overall survival rates were 67%, 46%, and 39%, respectively. The median hospital stay was 12 days. The median postoperative treatment time was 3.3 months, which was 20% of the median survival time. Of the 51 patients, 19 were alive with a median follow-up time of 2.5 years. Twenty-nine percent of the patients had a complete pathological response with median and 1-, 2-, and 3-year survival rates of 17.5 months, 73%, 57%, and 57%, respectively. Palliation of dysphagia was excellent, with 44 (93%) of 47 operative survivors taking either a soft diet (18 [38%]) or a regular (26 [55%]) diet by the first postoperative visit. CONCLUSIONS: Median survival time with NC followed by esophagectomy for resectable cancer of the esophagus does not appear to be significantly better than that reported for esophagectomy alone. Further, treatment time with NC consumed 20% of survival time. Examining only these outcome variables suggests that NC is not worth-while. However, examining a longer-term outcome survival variable, such as 3-year survival time, suggests that NC followed by esophagectomy may result in greater long-term survival than that reported for esophagectomy alone. We conclude that further randomized, controlled studies are necessary before NC followed by esophagectomy is considered superior to esophagectomy alone for the treatment of resectable esophageal cancer.     

A simple method for synthesis of acicular β-Si3N4 seed crystals

Acicular silicon nitride (β-Si₃N₄) seed crystals have been synthesized using a moderately low temperature heat-treatment process, with the aid of a low volume fraction of multiple sintering aids (i.e. MgO and CaO, in combination with either Y₂O₃ or Nd₂O₃). The effects of the heat-treatment cycle and the additive composition on the α- to β-Si₃N₄ phase transformation were examined, for both cold-isostatically pressed pellets and simple packed powder. In the case of the packed powder, full transformation was achievable following heat-treatment at 1625 °C for four hours, in ∼0.1 MPa nitrogen. The use of multiple oxide additives allows seed liberation from the heat-treated materials using a simple dilute HF soak at room temperature. The resulting β-Si₃N₄ seed crystals exhibit a narrow size distribution, with mean aspect ratios of ∼4:1.