Extent and mechanism of sealing in transected giant axons of squid and earthworms

Transected axons are often assumed to seal at their cut ends by the formation of continuous membrane barriers that allow for the restoration of function in the axonal stumps. We have used several electrophysiological measures (membrane potential, input resistance, injury current density) and several morphological measures (phase-contrast, video-enhanced differential interference contrast, light, and electron microscopies) of living and fixed material to assess the extent and mechanism of sealing within hours after transecting giant axons of squid (Loligo pealeiand Sepioteuthis lessoniana) and earthworms (Lumbricus terrestris). Our electrophysiological data suggest that the proximal and distal ends of transected squid giant axons do not completely seal within 2.5 hr in physiological saline. In contrast, the same set of measures suggest that proximal and distal ends of transected earthworm giant axons seal within 1 hr in physiological saline. Our morphological data show that the cut ends of both squid and earthworm axons constrict, but that a 20- 70-am-diameter opening always remains at the cut end that is filled with vesicles. Axonal transection induces the formation of vesicles that are observed in the axoplasm within minutes in standard salines and that rapidly migrate to the cut ends. These injury-induced vesicles are loosely packed near the cut ends of squid giant axons, which do not functionally seal within 2.5 hr of transection. In contrast, vesicles formed a tightly packed plug at the cut ends of earthworm medial giant axons, which do functionally seal within 1 hr of transection in physiological saline. Since we detect no single continuous membrane that spans the cut end, sealing does not appear to occur by the fusion of constricted axolemmal membrane or the formation of a membranous partition at the cut end. Rather, our data are consistent with the hypothesis that a tightly packed vesicular plug is responsible for sealing of earthworm giant axons.This work was supported in part by NIH Grant NS31256 and ONR Grant N00014-90-J-1137 to H.M.F., an NIAAA fellowship to T.L.K., and an ATP grant to G.D.B.Neuroscienc

Comparison of 99mTc-sestamibi and doxorubicin to monitor inhibition of P-glycoprotein function

P-glycoprotein (Pgp) overexpression is a well-recognized factor in resistance to chemotherapy. Doxorubicin flow cytometry is used to monitor Pgp function in haematological specimens and biopsies from other cancers, and radionuclide imaging with sestamibi has recently shown promise for non-invasive monitoring. In the present study the two methods were directly compared in single-cell suspensions of three variants of the human breast carcinoma cell line MCF7: sensitive MCF7/WT, doxorubicin-selected MCF7/AdrR, and MDR1 -gene-transfected MCF7/BC19 cells with doxorubicin resistance factors of 1, 192, and 14, respectively. Accumulation of sestamibi and mean fluorescence of doxorubicin (5.5 μM) were assessed over 60 min in the presence and absence of Pgp modulators GG918 (0.01 to 0.2 μM) and PSC833 (0.05 to 2.0 μM). Accumulation curves for sestamibi and doxorubicin differed among the cell variants under control conditions, with sestamibi showing a significantly greater difference between WT and resistant cells than doxorubicin. Both GG918 and PSC833 reversed uptake deficits to WT levels for sestamibi in MCF7/BC19 cells and doxorubicin in MCF7/BC19 and MCF7/AdrR cells, but failed to show the same effect for sestamibi in MCF7/AdrR cells (∼30% of MCF7/WT level). Thus, both methods clearly distinguished sensitive from resistant MCF7 variants, with the radionuclide method showing greater sensitivity. © 2001 Cancer Research Campaign http://www.bjcancer.co

Complete Treatment of Galaxy Two-Point Statistics: Gravitational Lensing Effects and Redshift-Space Distortions

We present a coherent theoretical framework for computing gravitational lensing effects and redshift-space distortions in an inhomogeneous universe and investigate their impacts on galaxy two-point statistics. Adopting the linearized FRW metric, we derive the gravitational lensing and the generalized Sachs-Wolfe effects that include the weak lensing distortion, magnification, and time delay effects, and the redshift-space distortion, Sachs-Wolfe, and integrated Sachs-Wolfe effects, respectively. Based on this framework, we first compute their effects on observed source fluctuations, separating them as two physically distinct origins: the volume effect that involves the change of volume and is always present in galaxy two-point statistics, and the source effect that depends on the intrinsic properties of source populations. Then we identify several terms that are ignored in the standard method, and we compute the observed galaxy two-point statistics, an ensemble average of all the combinations of the intrinsic source fluctuations and the additional contributions from the gravitational lensing and the generalized Sachs-Wolfe effects. This unified treatment of galaxy two-point statistics clarifies the relation of the gravitational lensing and the generalized Sachs-Wolfe effects to the metric perturbations and the underlying matter fluctuations. For near future dark energy surveys, we compute additional contributions to the observed galaxy two-point statistics and analyze their impact on the anisotropic structure. Thorough theoretical modeling of galaxy two-point statistics would be not only necessary to analyze precision measurements from upcoming dark energy surveys, but also provide further discriminatory power in understanding the underlying physical mechanisms.Comment: 20 pages, 5 figures, Fig.4 corrected, appendix added, accepted for publication in Physical Review

Giving hope, ticking boxes or securing services? A qualitative study of respiratory physiotherapists' views on goal-setting with people with chronic obstructive pulmonary disease.

OBJECTIVE: To explore respiratory physiotherapists' views and experiences of using goal-setting with people with chronic obstructive pulmonary disease in rehabilitation settings. PARTICIPANTS: A total of 17 respiratory physiotherapists with ⩾12 months current or previous experience of working with patients with chronic obstructive pulmonary disease in a non-acute setting. Participants were diverse in relation to age (25-49 years), sex (13 women), experience (Agenda for Change bands 6-8) and geographic location. METHOD: Data were collected via face-to-face qualitative in-depth interviews (40-70 minutes) using a semi-structured interview guide. Interview locations were selected by participants (included participants' homes, public places and University). Interviews followed an interview guide, were audio-recorded and transcribed verbatim. DATA ANALYSIS: Data were analysed using thematic analysis; constant comparison was made within and between accounts, and negative case analysis was used. RESULTS: Three themes emerged through the process of analysis: (1) 'Explaining goal-setting'; (2) 'Working with goals'; and (3) 'Influences on collaborative goal-setting'. Goal-setting practices among respiratory physiotherapists varied considerably. Collaborative goal-setting was described as challenging and was sometimes driven by service need rather than patient values. Lack of training in collaborative goal-setting at both undergraduate and postgraduate level was also seen as an issue. CONCLUSION: Respiratory physiotherapists reflected uncertainties around the use of goal-setting in their practice, and conflict between patients' goals and organisational demands. This work highlights a need for wider discussion to clarify the purpose and implementation of goal-setting in respiratory rehabilitation

Farmer-Driven Research for Developing Models of Successful Low Input Dairy Farms of Small to Medium Size in the American Midwest

The dairy industry in the upper Midwest continues to evolve with a drastic reduction in the number of dairy farms with less than 100 cows that utilise tie-stall housing. Many of the farms that do remain are at a critical point where facilities require renovation or replacement that is not economic. Rural communities have fewer residents engaged in agriculture to participate in the local economy and the rural landscape includes many farm sites that are abandoned. Low input dairies are an alternative system developed by farmers as a grass-roots movement. Low input farms may include grazing, outdoor housing throughout the year, crossbreeding, group housing of calves, etc. Barns formerly used to stable cows may be renovated to provide a milking centre. Low input dairy farmers are eager to participate in on-farm research when they determine the direction of research. We will describe one trial designed to answer questions determined by farmers and outline our research approach to designing effective reduced input dairy farms. The objective is to identify the essential components of management and organisation for low input dairy farms in the American Midwest

Endocytotic formation of vesicles and other membranous structures induced by Ca2+ and axolemmal injury

Vesicles and/or other membranous structures that form after axolemmal damage have recently been shown to repair (seal) the axolemma of various nerve axons. To determine the origin of such membranous structures, (1) we internally dialyzed isolated intact squid giant axons (GAs) and showed that elevation of intracellular Ca21 .100 uM produced membranous structures similar to those in axons transected in Ca21-containing physiological saline; (2) we exposed GA axoplasm to Ca21- containing salines and observed that membranous structures did not form after removing the axolemma and glial sheath but did form in severed GAs after .99% of their axoplasm was removed by internal perfusion; (3) we examined transected GAs and crayfish medial giant axons (MGAs) with time-lapse confocal fluorescence microscopy and showed that many injuryinduced vesicles formed by endocytosis of the axolemma; (4) we examined the cut ends of GAs and MGAs with electron microscopy and showed that most membranous structures were single-walled at short (5–15 min) post-transection times, whereas more were double- and multi-walled and of probable glial origin after longer (30–150 min) post-transection times; and (5) we examined differential interference contrast and confocal images and showed that large and small lesions evoked similar injury responses in which barriers to dye diffusion formed amid an accumulation of vesicles and other membranous structures. These and other data suggest that Ca21 inflow at large or small axolemmal lesions induces various membranous structures (including endocytotic vesicles) of glial or axonal origin to form, accumulate, and interact with each other, preformed vesicles, and/or the axolemma to repair the axolemmal damage.This work was supported by grants from National Institutes of Health (NIH; NS31256) and the State of Texas (Advanced Technology 3658-446).Neuroscienc

Impact of primary breast cancer therapy on energetic capacity and body composition

PURPOSE: This observational study was designed to measure baseline energy parameters and body composition in early-stage breast cancer patients, and to follow changes during and after various modalities of treatment. This will provide information to aid in the development of individualized physical activity intervention strategies. METHODS: Patients with newly diagnosed stage 0-III breast cancer were enrolled into three cohorts: A (local therapy alone), B (endocrine therapy), or C (chemotherapy with or without endocrine therapy). At baseline, 6 months, and 12 months, subjects underwent a stationary bicycle protocol to assess power generation and DEXA to assess body composition. RESULTS: Eighty-three patients enrolled. Patients had low and variable levels of power generation at baseline (mean power per kilogram lean mass 1.55 W/kg, SD 0.88). Power normalized to lean body mass (W/kg) decreased significantly, and similarly, by 6 months in cohorts B (1.42-1.04 W/kg, p = 0.008) and C (1.53-1.18 W/kg, p < 0.001). In all cohorts, there was no recovery of power generation by 12 months. Cohort C lost lean body mass (- 1.5 kg, p = 0.007), while cohort B maintained lean body mass (- 0.2 kg, p = 0.68), despite a similar trajectory in loss of power. Seven patients developed sarcopenia during the study period, including four patients who did not receive any chemotherapy (cohort B). CONCLUSIONS: The stationary bike protocol was feasible, easy, and acceptable to patients as a way to measure energetic capacity in a clinical setting. Early-stage breast cancer patients had low and variable levels of power generation, which worsened following primary therapy and did not show evidence of 'spontaneous recovery' by 12 months. Effective physical activity interventions will need to be personalized, accounting for both baseline ability and the effect of treatment

Climate-associated tundra thaw pond formation and range expansion of boreal zooplankton predators

© 2015 Nordic Society Oikos. Most of the freshwater component of the Earth's surface is composed of shallow tundra ponds. These high latitude ecosystems have been exposed to a variety of abiotic disturbances associated with recent environmental change. However, the biological significance of these changes remains poorly understood. Here, we characterize the abiotic disturbance to the shallow tundra ponds of northwest Alaska. We used historical aerial imagery to determine that up to 53% of the sampled ponds have formed during the recent warmer decades (since the 1970s). We discovered that two top predator species (phantom midges of the genus Chaoborus) of the freshwater zooplankton have recently undergone range expansion, forming widespread (a scale of hundreds of km) stable tundra populations. We assessed the population persistence of these boreal predators by longitudinal sampling over 14 yr. Recent thaw ponds had significantly dissimilar zooplankton communities to communities of ponds that formed before 1950. Both predator and herbivore species differed by age of pond. Younger pond ages and warmer surface temperatures were the significant predictors of the presence of temperate Chaoborus americanus in tundra ponds. Ponds containing tundra populations of C. americanus and C. cf. flavicans were associated with recent formation (83-90%). Recent ponds in river valleys appeared more important than recent ponds near roads as colonization corridors for C. americanus. Only 24% of the tundra keystone predator, Heterocope septentrionalis, populations were from recent ponds. Our results suggest that climate-associated disturbance can lead to a widespread stable range expansion of boreal species despite the propinquity of older ponds with top-down control exerted by an endemic keystone predator

Lessons learned on closed cavity thermophotovoltaic system efficiency measurements

Previous efficiency measurements have highlighted that to accurately measure and predict thermophotovoltaic (TPV) integrated cell or array efficiencies, a thorough understanding of the system is required. This includes knowledge of intrinsic diode and filter characteristics, radiative surface properties of all materials used within the cavity, and an intimate knowledge of the radiator/photon source. As a result of these and other lessons learned, the cavity test fixture used in earlier experiments was redesigned. To reduce radiator temperature gradients, the radiator was oversized and thickened, cavity walls were eliminated, the diode heat sink and shielding material were separated, and the cold side was redesigned to incorporate a steady state heat absorbed measurement technique. This redesigned test fixture provides an isothermal radiator and significantly enhances calorimetry capabilities. This newly designed cavity test fixture, in conjunction with the Monte Carlo Photon Transport code RACER-X, was used to improve and demonstrate the understanding of in-cavity TPV diode/module system efficiency testing. A single TPV diode was tested in this new fixture and yielded good agreement between measurements and predictions