Reverse engineering an amyloid aggregation pathway with dimensional analysis and scaling

Human islet amyloid polypeptide (hIAPP) is a cytotoxic protein that aggregates into oligomers and fibrils that kill pancreatic β-cells. Here we analyze hIAPP aggregation in vitro, measured via thioflavin-T fluorescence. We use mass-action kinetics and scaling analysis to reconstruct the aggregation pathway, and find that the initiation step requires four hIAPP monomers. After this step, monomers join the nucleus in pairs, until the first stable nucleus (of size approximately 20 monomers) is formed. This nucleus then elongates by successive addition of single monomers. We find that the best-fit of our data is achieved when we include a secondary fibril-dependent nucleation pathway in the reaction scheme. We predict how interventions that change rates of fibril elongation or nucleation rates affect the accumulation of potentially cytotoxic oligomer species. Our results demonstrate the power of scaling analysis in reverse engineering biochemical aggregation pathways.

Automated and semi-automated cell tracking: addressing portability challenges

Cell tracking is a key task in the high-throughput quantitative study of important biological processes, such as immune system regulation and neurogenesis. Variability in cell density and dynamics in different videos, hampers portability of existing trackers across videos. We address these potability challenges in order to develop a portable cell tracking algorithm. Our algorithm can handle noise in cell segmentation as well as divisions and deaths of cells. We also propose a parameter-free variation of our tracker. In the tracker, we employ a novel method for recovering the distribution of cell displacements. Further, we present a mathematically justified procedure for determining the gating distance in relation to tracking performance. For the range of real videos tested, our tracker correctly recovers on average 96% of cell moves, and outperforms an advanced probabilistic tracker when the cell detection quality is high. The scalability of our tracker was tested on synthetic videos with up to 200 cells per frame. For more challenging tracking conditions, we propose a novel semi-automated framework that can increase the ratio of correctly recovered tracks by 12%, through selective manual inspection of only 10% of all frames in a video.

Thin film polymer photonics: Spin cast distributed Bragg reflectors and chirped polymer structures

Polymer based photonic structures were produced by spin coating up to 50 alternating layers of polystyrene (PS) and poly(vinylpyrrolidone) (PVP) from mutually exclusive (orthogonal) solvents. The resulting thin film multi-layer structures were studied using a simple optical reflectivity apparatus and were shown to have narrow (10-20nm wide) reflectance bands in the visible region. The position of the reflectance bands was controlled by varying the spin speed used during production of the multi-layers and peak reflectance values of 55% were obtained for samples containing 50 layers. The results were shown to be in agreement with modified optical transfer matrix method calculations which include the effects of diffuse polymer interfaces. This modelling approach revealed that the width of the polymer/polymer interfaces formed by spin coating was in the range 15-20nm. Data and calculations were also obtained for chirped polymer photonic structures. These results were also shown to be in good agreement. These experiments demonstrate that simple processing methods such as spin coating can be used to produce organic photonic structures with tailored optical properties.

Polymerization and matrix physical properties as important design considerations for soluble collagen formulations

Despite extensive use of type I collagen for research and medical applications, its fibril-forming or polymerization potential has yet to be fully defined and exploited. Here, we describe a type I collagen formulation that is acid solubilized from porcine skin collagen (PSC), quality controlled based upon polymerization potential, and well suited as a platform polymer for preparing three-dimensional (3D) culture systems and injectable/implantable in vivo cellular microenvironments in which both relevant biochemical and biophysical parameters can be precision-controlled. PSC is compared with three commercial collagens in terms of composition and purity as well as polymerization potential, which is described by kinetic parameters and fibril microstructure and mechanical properties of formed matrices. When subjected to identical polymerization conditions, PSC showed significantly decreased polymerization times compared to the other collagens and yielded matrices with the greatest mechanical integrity and broadest range of mechanical properties as characterized in oscillatory shear, uniaxial extension, and unconfined compression. Compositional and intrinsic viscosity analyses suggest that the enhanced polymerization potential of PSC may be attributed to its unique oligomer composition. Collectively, this work demonstrates the importance of standardizing next generation collagen formulations based upon polymerization potential and provides preliminary insight into the contribution of oligomers to collagen polymerization properties.

Vibration as a reinforcer with a profoundly retarded child

Data are presented which indicate that lever-pressing behavior of a profoundly retarded child could be reinforced by the contingent application of vibratory stimulation for each response. With vibration available 24 hr per day, no decrement in daily rate of responding for vibration was seen over a three-week period. Suggestions are made for further use of this finding in working with the profoundly retarded.

Stroke rehab down under: can Rupert Murdoch, Crocodile Dundee, and an Aboriginal elder expect the same services and care?

Australia is the world's sixth largest country, has a relatively small population of 21.5 million, and a blended (public and private) health system. In this article, we explain the stroke rehabilitation infrastructure including consumer organisations, research networks, data collection systems, and registries. This represents a complex but fledgling set of organisations showing great promise for coordination of care and research. The article goes on to expose the inequalities in service provision by describing the paths of stroke survivors in three settings - in the city, in the country, and in remote settings. The complexities and difficulties in treating indigenous stroke survivors are described in a culturally sensitive narrative. The article then discusses the outcomes of the first Australian audit of post acute stroke services completed in December 2008, which describes the journeys of 2,119 stroke survivors at 68 rehabilitation units throughout Australia's 6 states and 2 territories. It demonstrates an average length of stay of 26 days, with 18% of survivors requiring nursing home or other supported accommodation. The article concludes with future directions for stroke rehabilitation in Australia, which include hyperacute rehabilitation trials, studies in 7-days-a-week rehabilitation, and the potential use of robotics.

Measurement and modeling of pulsed microchannel plate operation (invited)

Microchannel plates (MCPs) are a standard detector for fast-framing x-ray imaging and spectroscopy of high-temperature plasmas. The MCP is coated with conductive striplines that carry short duration voltage pulses to control the timing and amplitude of the signal gain. This gain depends on the voltage to a large exponent so that small reflections or impedance losses along the striplines can have a significant impact on the position-dependent amplitude and pulse width of the gain. Understanding the pulsed gain response therefore requires careful measurements of the position- and time-dependent surface voltage coupled with detailed modeling of the resulting electron cascade. We present measurements and modeling of the time- and space-dependent gain response of MCP detectors designed for use at Sandia National Laboratories' Z facility. The pulsed gain response is understood through measurements using a high impedence probe to determine the voltage pulse propagating along the stripline surface. Coupling the surface voltage measurements with Monte Carlo calculations of the electron cascade in the MCP provides a prediction of the time- and position-dependent gain that agrees with measurements made on a subpicosecond UV laser source to within the 25% uncertainty in the simulations.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of ARQ 501 (beta-lapachone) in plasma and tumors from nu/nu mouse xenografts

A sensitive and specific LC-MS/MS method employing positive electrospray ionization for the determination of ARQ 501 (beta-lapachone) in (nu/nu) mouse plasma and tumor tissue is described. Samples were processed using protein precipitation with acetonitrile. A d6 analog of ARQ 501 was used as the internal standard (IS). The analytes were separated using a Zorbax SB8 column (30 mm x 2.1 mm i.d. 5 microm particle size) and analyzed in the multiple reaction monitoring (MRM) mode using mass transitions of 243>159 and 249>159 m/z for ARQ 501 and d6-ARQ 501, respectively. The lower limit of quantitation (LLOQ) for ARQ 501 was 3.0 ng/mL. The calibration curve was linear in the range of 3.0-2000 ng/mL with a correlation coefficient better than 0.99. Intra- and inter-batch precisions were within 8.4% for plasma and 11.8% for tumor samples. Accuracy expressed as percentage relative error (%R.E.) ranged from -9.0 to 7.7 for both plasma and tumor samples. Recovery was between 106 and 113% for both ARQ 501 and its d6 analog. Plasma pharmacokinetic data of ARQ 501 in mouse from intraperitoneal (IP) dosing at 60 mg/kg obtained using this validated method is presented along with tumor concentration data. The C(max), AUC(0-infinity), t(1/2), Cl/F, and V(d)/F were determined to be 4016 ng/mL, 4392 h ng/mL, 3.9 h, 13.7 L/h/kg, and 76.5 L/kg, respectively. Tumor tissue concentrations were in the range 1-2 microM for approximately 2 h post-dose.

Spectroscopic modeling and characterization of a collisionally confined laser-ablated plasma plume

Plasma plumes produced by laser ablation are an established method for manufacturing the high quality stoichiometrically complex thin films used for a variety of optical, photoelectric, and superconducting applications. The state and reproducibility of the plasma close to the surface of the irradiated target plays a critical role in producing high quality thin films. Unfortunately, this dense plasma has historically eluded quantifiable characterization. The difficulty in modeling the plume formation arises in the accounting for the small amount of energy deposited into the target when physical properties of these exotic target materials are not known. In this work we obtain the high density state of the plasma plume through the use of an experimental spectroscopic technique and a custom spectroscopic model. In addition to obtaining detailed temperature and density profiles, issues regarding line broadening and opacity for spectroscopic characterization will be addressed for this unique environment.

Developing research capacity building for Aboriginal & Torres Strait Islander health workers in health service settings

INTRODUCTION

Aboriginal and Torres Strait Islander health workers (hereafter called health workers) can play a major role in facilitating culturally appropriate health care delivery and program development through the acquisition of improved skills in the planning, monitoring and evaluation of these programs (RCB). However, many Aboriginal and Torres Strait Islander people and communities remain concerned about research and related activities. Health workers are well placed to assist communities to not only embrace research, but to be active players and promoters of relevant, appropriate and acceptable research. One means of achieving the twin goals of RCB and community acceptance and involvement in research, is through health workers undertaking research of health priority issues and evaluation of activities, such as program delivery, that are of direct relevance to their community's aim of improving or enhancing service delivery. This article outlines the development and content of a community-based RCB framework for health workers. The focus is on the major issues that enhance a proactive service delivery model using culturally appropriate research methods. Development process: The RCB framework described here was developed, over a period of time, through community workshops and consultations aimed at deriving general consensus on the key issues and components of a culturally-appropriate, community-based training process. The framework has subsequently been reviewed by Aboriginal and Torres Strait Islander community representatives from across Australia. The overall aim of the framework is to supplement current (institutionally-based) education and training resources for health workers with community-based research training modules. These modules can be tailored to provide research and evaluation skills relevant to health workers taking a more proactive role in facilitating health and wellbeing programs in their own communities. The use of collaborative consultation and participatory methods are intended to be a two-way education process. Course content: A visual pathway is used that encompasses the impact of health and practice in the community for health workers at a grass-roots level. This enables elements of the RCB process to be divided into a series of connected modules. These are: (i 'assessing' Existing Services; (ii) methods and measures for Identifying Need at various levels; (iii) important issues in Program Development; (iv) how the former contributes to Service Improvement; (v) resultant Outcomes that will impact on community and service provision; and (vi) Evaluation Methods and applying findings to service delivery.

CONCLUSIONS

Active participation by the Aboriginal and Torres Strait Islander community is fundamental for effective research practices and outcomes. The aim is to provide health workers and community members with a working knowledge of research ethics and methods so that they can assist, monitor and steer the development of culturally appropriate research activities that will lead to provision of the highest quality services 'back' to the community. This RCB framework will enable health workers to be more proactive, self-reliant and self-sufficient within their community and healthcare settings.

Laparoscopically assisted radical vaginal hysterectomy (Coelio-Schauta): a comparison with open Wertheim/Meigs hysterectomy

The objective of this study was to compare the safety, efficacy, and short-term benefits of the Coelio-Schauta procedure with open Wertheim/Meigs radical abdominal hysterectomy. We retrospectively analyzed records of our first 35 consecutive patients undergoing laparoscopically assisted radical vaginal hysterectomy (LARVH) for early cervical cancer and 32 consecutive patients of open radical hysterectomy (ORH) performed between 1999 and 2005 in our institution. We analyzed patient age, bodyweight, previous abdominal surgery, operating time, blood loss, perioperative complications, postoperative bladder dysfunction, other postoperative complications, and histologic type. The FIGO stage, excision margins, node count and node status, follow-up, and recurrence rates were also taken into account. We excluded stage IA and stage II disease patients to reduce the impact of tumor size on the outcome of the surgery. This left 27 patients with stage IIB disease who had LARVH and 28 patients with stage IB disease who had ORH. These patients formed the study group. The cohorts were similar in age, bodyweight, previous abdominal surgery, histologic subtype, FIGO stage, resection margins, node count and node status, length of follow-up, and recurrence. There were statistically significant differences between LARVH and ORH for duration of surgery (mean 160 vs 132 min), intraoperative blood loss (479 vs 715 mL), hospital stay (mean 5 vs 9.3 days), postoperative complications (6 vs 20 patients), and duration of bladder catheterization (mean 4.4 vs 8.8 days). Four LARVH patients and no ORH patients had urinary tract injury that was repaired. None had long-term sequelae. Our data confirm that LARVH is a suitable alternative to ORH hysterectomy for small-volume stage IB1 cervical cancer with similar clinical efficacy and a superior postoperative recovery and postoperative morbidity profile. Urinary tract trauma is a clear risk in the early stages of the learning curve.

Risk of malignancy index for referral of ovarian cancer cases to a tertiary center: does it identify the correct cases?

Characterization of adnexal masses to identify patients with malignant ovarian tumors preoperatively for referral to a cancer center for treatment has been extensively studied. A simple algorithm called "risk of malignancy index" (RMI) reported by Jacobs incorporated the serum CA125 level, menopausal status, and ultrasound morphologic features. This algorithm has subsequently been tested on retrospective and prospective data with encouraging results. However, these studies did not include cases that had had both their serum CA125 measurements and ultrasound examinations from a diverse range of laboratories and sonographers. The purpose of this study was to determine the effectiveness of the RMI algorithm for identifying cases of ovarian malignancy presenting at cancer units for subsequent referral to a cancer center. All cases of suspected ovarian malignancy referred to the Northern Gynaecological Oncology Centre (NGOC) during an 18-month period were identified from the NGOC database. A case note review was performed, and the following data were extracted: patient demographics, the referring physician and the operating surgeon, ultrasound morphology, serum CA125 levels, and menopausal status. All patients had their ultrasound performed by sonographers at the peripheral unit according to local protocols. A total of 182 patients with a pelvic mass were referred to the center for surgery. A total of 24% patients had benign tumors, 6% had tumors of borderline malignancy, and 70% had invasive tumors. A total of 145 cases had an RMI >200; 125 of these had ovarian or peritoneal cancers. An RMI >200 had a sensitivity of 88.5% for diagnosing invasive lesions. The overall sensitivity of this algorithm for diagnosing all borderline, invasive ovarian, or primary peritoneal lesions was 87.4%, and the positive predictive value was 86.8%. Our data confirm the effectiveness of the RMI algorithm in clinical practice for the identification and subsequent referral to cancer centers of cases of potential ovarian malignancy. We therefore recommend its continued use.

Stage III and IV ovarian cancer in the South West of England: five-year outcome analysis for cases treated in 1998

This study evaluates the 5-year outcome data for the management of advanced ovarian cancer in the South West of England. Anonymized data for 361 stage III and IV ovarian cancers registered between January 1, 1998, and December 31, 1998, were obtained from the central gynecological tumor database. The following data were identified: age at diagnosis, FIGO stage, American Society of Anesthesiologists (ASA) grade, tumor differentiation, treating network and surgeon, amount of residual disease after debulking surgery, current life status, and date of death if applicable. Survival analysis was performed using Kaplan-Meier crude survival for univariate analysis, and multivariate analysis was performed by Cox regression. In our data the 5-year survival for patients with stage III was 16% and with stage IV was 10%. Survival analysis demonstrated that patients in whom the disease was debulked to less than 1 cm were more likely to be alive 5 years after diagnosis than those with a 2-cm residuum (P < 0.0001). There was no significant survival difference for those patients operated on by subspecialist surgeons despite these surgeons being twice as likely to achieve optimal debulking. Therefore, there must be other variables influencing survival apart from cytoreductive surgery. While there is near-complete data collection about ovarian cancer surgery, our database on chemotherapy is incomplete. This is clearly crucial for a complete view of cancer care in our region.

Gut transport of a molybdenum/ascorbic acid complex

BACKGROUND

Relatively little work has been done on the absorption of trace elements in the mammalian small intestine. Recently, studies have demonstrated that a molybdenum/ascorbic acid complex has shown some promise as a potentially orally administered insulin-mimetic agent. However, the transport mechanism of the molybdenum/ascorbic acid complex is unknown. In this study we examine some aspects of the movement of the complex across the intestinal wall using measurements of elemental molybdenum as an indicator because it is not possible to measure the complex directly.

METHODS

Everted rat small intestine sacs were used to determine some aspects of the transport of the complex across the intestine. Intestinal sacs from five rats were incubated in a medium containing 1 g/L of the molybdenum complex. Sacs from a further five rats had 1 mmol/L of 2,4-dinitrophenol, a known inhibitor of oxidative phosphorylation, added to the incubation medium. In a second experiment, everted sacs from five rats were also incubated in media containing one of six concentrations of the molybdenum complex (0.5, 1, 2, 4, 8 or 10 g/L).

RESULTS

There was no significant difference between transport rates of groups with or without 2,4-dinitrophenol in the incubation medium, suggesting that the predominant mechanism of molybdenum transport is energy-independent. There was a significant positive, linear increase in the transport rate with increasing concentration of the molybdenum complex.

CONCLUSION

These data suggest that the predominant mechanism of this molybdenum/ascorbic acid complex transport in the small intestine is non-saturable and therefore not protein-mediated.