A distance to the Large Magellanic Cloud that is precise to one per cent.

In the era of precision cosmology, it is essential to determine the Hubble constant empirically with an accuracy of one per cent or better1. At present, the uncertainty on this constant is dominated by the uncertainty in the calibration of the Cepheid period-luminosity relationship2,3 (also known as the Leavitt law). The Large Magellanic Cloud has traditionally served as the best galaxy with which to calibrate Cepheid period-luminosity relations, and as a result has become the best anchor point for the cosmic distance scale4,5. Eclipsing binary systems composed of late-type stars offer the most precise and accurate way to measure the distance to the Large Magellanic Cloud. Currently the limit of the precision attainable with this technique is about two per cent, and is set by the precision of the existing calibrations of the surface brightness-colour relation5,6. Here we report a calibration of the surface brightness-colour relation with a precision of 0.8 per cent. We use this calibration to determine a geometrical distance to the Large Magellanic Cloud that is precise to 1 per cent based on 20 eclipsing binary systems. The final distance is 49.59 ± 0.09 (statistical) ± 0.54 (systematic) kiloparsecs.

A combined light sheet fluorescence and differential interference contrast microscope for live imaging of multicellular specimens.

We describe a microscope capable of both light sheet fluorescence microscopy and differential interference contrast microscopy (DICM). The two imaging modes, which to the best of our knowledge have not previously been combined, are complementary: light sheet fluorescence microscopy provides three-dimensional imaging of fluorescently labelled components of multicellular systems with high speed, large fields of view, and low phototoxicity, whereas differential interference contrast microscopy reveals the unlabelled neighbourhood of tissues, organs, and other structures with high contrast and inherent optical sectioning. Use of a single Nomarski prism for differential interference contrast microscopy and a shared detection path for both imaging modes enables simple integration of the two techniques in one custom microscope. We provide several examples of the utility of the resulting instrument, focusing especially on the digestive tract of the larval zebrafish, revealing in this complex and heterogeneous environment anatomical features, the behaviour of commensal microbes, immune cell motions, and more.

Self-propelled Leidenfrost droplets.

We report that liquids perform self-propelled motion when they are placed in contact with hot surfaces with asymmetric (ratchetlike) topology. The pumping effect is observed when the liquid is in the Leidenfrost regime (the film-boiling regime), for many liquids and over a wide temperature range. We propose that liquid motion is driven by a viscous force exerted by vapor flow between the solid and the liquid.

Use of transcranial Doppler sonography to evaluate patients with cerebrovascular disease.

TCD sonography provides an instant and real-time window into the physiology of CBF in patients. Its applications are very diverse, and its utility is in specific application. The data it provides may offer key information to answer the question at hand.

Cognitive and neurologic deficits in the MRL/lpr mouse: a clinicopathologic study.

OBJECTIVES: Determine if the MRL/lpr mouse develops neurological deficits and, if so, the pathologic basis for these deficits. Antiphospholipid antibodies (aPL) are associated with ischemic stroke, multiinfarct dementia, chorea, and cardiac valvular abnormalities. The MRL/lpr mouse develops high titer anticardioplin antibodies (aCL) suggesting that it may be used as a model for the neurological complications of aPL. METHODS: We undertook a prospective clinicopathologic study comparing the MRL/lpr mouse against its congenic strain, the MRL/+ mouse. We studied 15 MRL/pr and 15 MRL/lpr and 15 MRL/+ mice at 16 to 20 weeks and a group of 16 mice of each strain at 8 to 10 weeks. aCL and anti-DNA antibodies were measured by ELISA: Cognitive and neurological deficits were assessed by a water maze and a standardized rodent neurological examination. The brains and cardiac valves of the mice were then examined pathologically. RESULTS: The MRL/lpr mice had significantly elevated aCL at both ages. Cognitive and sensorimotor deficits were apparent at 16 weeks but no correlation could be found with aCL or anti-DNA titer. Even at 8 weeks the MRL/lpr mice performed poorer on the water maze when compared to their age matched congenic strain. No evidence of cerebral infarction was found but mononuclear infiltrates were found in the choroid plexus of all the MRL/lpr mice at both 10 and 20 weeks. No evidence of cardiac valve pathology was seen at 20 weeks. CONCLUSIONS: (1) The MRL/lpr mouse develops cognitive and neurologic deficits. The etiology of these deficits is not clear but may be related to early infiltration of the central nervous system with mononuclear cells. (2) Despite the elevated aCL, evidence of cerebral infarction or mitral valve abnormalities could not be found.

Intracranial hemodynamics in sleep apnea.

Intracranial pressure changes and poor cerebral perfusion have been reported in sleep apnea syndrome (SAS), but such studies have been limited due to lack of a reliable noninvasive study method. We determined the systolic (VS), diastolic (VD), and mean (VM) cerebral blood flow velocities of the middle cerebral artery in 23 individuals (12 severe SAS patients and 11 control subjects) using transcranial Doppler sonography before sleep, during sleep (NREM and REM) and upon awakening. All three velocities (VS = 87.4 cm/s compared to 104.7 cm/s, VD = 41.6 cm/s compared to 47.7 cm/s, and VM = 57.0 cm/s compared to 67.0 cm/s) were decreased in patients with SAS and VS and VM were significantly lower than in control subjects (p = 0.005 and p = 0.033, respectively). The end-tidal CO2 (PETCO2) in the SAS patients (47.3 mm Hg) compared to the control subjects (41.8 mm Hg) was significantly higher (p = 0.003). When the VM was adjusted to normalized CO2 using the Markwalder's equation, the reduction in velocity in patients with SAS (47.5 cm/s) compared to control subjects (63.0 cm/s) became more significant (p = 0.005). This study shows that cerebral blood flow velocities are lower in patients with SAS compared to control subjects and that transcranial Doppler sonography may be useful in such evaluations.

The effect of sleep on intracranial hemodynamics: a transcranial Doppler study.

The effect of sleep on intracranial blood flow velocities has not been reported in children or adults, even though blood flow velocities are evaluated for clinical purposes during both sleep and wakefulness. We report the effect of sleep on intracranial blood flow velocities of 11 healthy individuals (five children and six adults) who were monitored by polysomnography and transcranial Doppler sonography (TCD). Thirty-three TCDs were obtained on middle cerebral arteries. Before sleep, during non-rapid-eye-movement sleep, and after sleep, measurements of systolic, end diastolic, and mean flow velocities were obtained by TCD. Pulse oximetry and end tidal carbon dioxide were monitored during each 8-hour polysomnogram. The before-sleep blood flow velocity values were compared to sleep and after-sleep values in children and adults separately using ANOVA. A significant decrease in the blood flow velocities was noted during sleep compared to before-sleep values in both children (P less than .05) and adults (P less than .01). The blood flow velocities after sleep were also decreased compared to before-sleep values. This study shows that sleep reduces blood flow velocities in both children and adults. A decrease in blood flow velocities during normal sleep should be taken into account when interpreting TCDs in patients.

Detection of cell surface and intracellular antigens by human monoclonal antibodies. Hybrid cell lines derived from lymphocytes of patients with malignant melanoma.

This study represents an initial attempt to analyze the humoral immune reactions of patients with malignant melanoma by hybridoma methodology. Using lymphocytes from regional lymph nodes, peripheral blood and tumor infiltrates, 158 fusions were performed with SKO-007 (human myeloma line), LICR-LON-HMy2 (LICR-2), GM 4672 (human lymphoblastoid lines), or NS-1 (mouse myeloma line). Fusion of lymph node lymphocytes with NS-1 resulted in a 3-4 times higher frequency of clones than fusion with LICR-2, and a 10 times higher frequency than fusion with SKO-007 or GM 4672. In the case of peripheral blood lymphocytes, fusion with NS-1 gave greater than 25 times higher frequency of clones than fusion with LICR-2 or SKO-007. Production of human mu, gamma, or alpha heavy chains was detected in 50-80% of wells containing growing clones, and the levels of immunoglobulin ranged from 0.3 micrograms to 40 micrograms/ml. NS-1-derived clones could be easily subcultured, while LICR-2 and SKO-007 clones grew more slowly on subculturing. In this study, Ig secretion appeared to be a more stable property of LICR-2-derived clones than NS-1-derived clones. A panel of 20 human cancer cell lines was used to screen 771 Ig-secreting cultures for antibody to cell surface or intracellular antigens. Reactivity with cell surface antigens was found infrequently (6 cultures), whereas reactivity with intracellular antigens was more common (27 cultures). A new cell surface antigen with properties of a glycolipid was defined with an IgM monoclonal antibody secreted by a tetraploid cell derived from a fusion of LICR-2 with lymphocytes from the axillary lymph node of a patient with melanoma. The hybrid cell line has been subcloned four times and secretes 5 micrograms IgM/ml. The antigen detected by this IgM antibody was found on 5 of 23 melanoma cell lines and 12 of 30 epithelial cancer cell lines. No reactions were found with 11 cultures derived from normal cells. Stable cell lines secreting human antibody that detected nuclei, nucleoli, cytoskeletal elements, Golgi complex, or other cytoplasmic components were also isolated in this study. One of these antibodies detected an intracellular antigen that is restricted to cells of neuroectodermal derivation, and a second antibody reacted primarily with cells of epithelial origin. Using these methods to isolate and analyze human monoclonal antibody, it should now be possible to define the repertoire of the humoral immune response to melanoma.

Serological survey of normal humans for natural antibody to cell surface antigens of melanoma.

Sera of 106 normal adult men were tested for antibodies reacting with cell surface antigens of three established lines of cultured malignant melanoma. Positive reactions with a protein A assay for IgG antibodies were extremely rare (1-2%). The frequency of positive reactions with assays for IgM antibodies was higher: 5-15% in immune adherence assays and 55-82% in anti-C3 mixed hemadsorption assays. After low-titered sera and sera reacting with fetal calf serum components, conventional alloantigens, and widely distributed class 3 antigens were excluded, sera from seven individuals (one with IgG antibody and six with IgM antibodies) were selected for detailed analysis. The serum containing the IgG antibody came from a healthy 65-year-old Caucasian man; titers of antibody in his serum ranged from < 1/10 to 1/40,000 in tests with different melanoma cell lines. This IgG antibody identifies a differentiation antigen of melanocytes, provisionally designated Mel 1, that distinguishes two classes of melanomas: 22 melanoma cell lines typed Mel 1+ and 17 types Mel 1-. Mel 1 is expressed by fetal fibroblasts but not adult fibroblasts and can be found on a proportion of cultured epithelial cancer cell lines (5 out of 23) but not on glioma or B-cell lines. The melanoma antigens detected by the naturally occurring IgM antibodies are serologically unrelated to Mel 1 but, like Mel 1, appear to be differentiation antigens that distinguish subsets of melanoma. These IgM antibodies detect antigens that are identical or closely related to the AH antigen, a melanoma surface antigen that was initially defined by autologous antibody in a patient with melanoma. In view of the immunogenicity of both Mel 1 and the AH antigens in humans and their occurrence on more than 50% of melanomas, it remains to be seen whether antibody to these antigens can be elicited by specific vaccination of seronegative melanoma patients and whether this will have an influence on the clinical course of the disease.