Worcester Polytechnic Institute

About: Worcester Polytechnic Institute is a education organization based out in Worcester, Massachusetts, United States. It is known for research contribution in the topics: Computer science & Population. The organization has 6270 authors who have published 12704 publications receiving 332081 citations. The organization is also known as: WPI.

Secondary decline in apparent diffusion coefficient and neurological outcomes after a short period of focal brain ischemia in rats.

Abstract: This study was designed to characterize the initial and secondary changes of the apparent diffusion coefficient (ADC) of water with high temporal resolution measurements of ADC values and to correlate ADC changes with functional outcomes. Fourteen rats underwent 30 minutes of temporary middle cerebral artery occlusion (MCAO). Diffusion-, perfusion-, and T2-weighted imaging was performed during MCAO and every 30 minutes for a total of 12 hours after reperfusion (n = 6). Neurological outcomes were evaluated during MCAO, every 30 minutes for a total of 6 hours and at 24 hours after reperfusion (n = 8). The decreased cerebral blood flow during MCAO returned to normal after reperfusion and remained unchanged thereafter. The decreased ADC values during occlusion completely recovered at 1 hour after reperfusion. The renormalized ADC values started to decrease secondarily at 2.5 hours, accompanied by a delayed increase in T2 values. The ADC-defined secondary lesion grew over time and was 52% of the ADC-defined initial lesion at 12 hours. Histological evaluation demonstrated neuronal damage in the regions of secondary ADC decline. Complete resolution of neurological deficits was seen in 1 rat at 1 hour and in 6 rats between 2.5 and 6 hours after reperfusion; no secondary neurological deficits were observed at 24 hours. These data suggest that (1) a secondary ADC reduction occurs as early as 2.5 hours after reperfusion, evolves in a slow fashion, and is associated with neuronal injury; and (2) renormalization and secondary decline in ADC are not associated with neurological recovery and worsening, respectively.

Functional roles of metal binding domains of the Archaeoglobus fulgidus Cu(+)-ATPase CopA.

Abstract: CopA, a thermophilic membrane ATPase from Archaeoglobus fulgidus, drives the outward movement of Cu+ or Ag+ [Mandal et al. (2002) J. Biol. Chem. 277, 7201−7208]. This, as other PIB-ATPases, is characterized by a putative metal binding sequence (C380PC382) in its sixth transmembrane fragment and cytoplasmic metal binding sequences in its NH2- and COOH-terminal ends (C27AMC30 and C751HHC754). Using isolated CopA, we have studied the functional role of these three putative metal binding domains. Replacement of transmembrane Cys residues by Ala results in nonfunctional enzymes that are unable to hydrolyze ATP. However, the CPC → APA substituted enzyme binds ATP, indicating its correct folding and suggesting that enzyme turnover is prevented by the lack of metal binding to the transmembrane site. Replacement of C-terminal Cys by Ala (C751,754A) has no significant effect on ATPase activity, enzyme phosphorylation, apparent binding affinities of ligands, or E1−E2 equilibrium. In contrast, replacement of Cys in t...

Investigating the role of substrate stiffness in the persistence of valvular interstitial cell activation.

Abstract: During heart valve remodeling and in many disease states, valvular interstitial cells (VICs) shift to an activated myofibroblast phenotype characterized by enhanced synthetic and contractile activity Pronounced alpha smooth muscle actin (αSMA)-positive stress fibers, the hallmark of activated myofibroblasts, are also observed in VICs cultured on stiff substrates especially in the presence of transforming growth factor-beta1 (TGF-β1), however, the detailed relationship between stiffness and VIC phenotype has not been explored The goal of this study was to characterize VIC activation as a function of substrate stiffness over a wide range of stiffness levels including that of diseased valves (stiff), normal valves (compliant), and hydrogels for heart valve tissue engineering (very soft) VICs obtained from porcine aortic valves were cultured on stiff tissue culture plastic to activate them, then, cultured on collagen-coated polyacrylamide substrates of predefined stiffness in a high-throughput culture system to assess the persistence of activation Metrics extracted from regression analysis demonstrate that relative to a compliant substrate, stiff substrates result in higher cell numbers, more pronounced expression of αSMA-positive stress fibers, and larger spread area which is in qualitative agreement with previous studies Our data also indicate that VICs require a much lower substrate stiffness level to "deactivate" them than previously thought The high sensitivity of VICs to substrate stiffness demonstrates the importance of the mechanical properties of materials used for valve repair or for engineering valve tissue

Robotic System for MRI-Guided Stereotactic Neurosurgery

Abstract: Stereotaxy is a neurosurgical technique that can take several hours to reach a specific target, typically utilizing a mechanical frame and guided by preoperative imaging. An error in any one of the numerous steps or deviations of the target anatomy from the preoperative plan such as brain shift (up to $20$ mm), may affect the targeting accuracy and thus the treatment effectiveness. Moreover, because the procedure is typically performed through a small burr hole opening in the skull that prevents tissue visualization, the intervention is basically “blind” for the operator with limited means of intraoperative confirmation that may result in reduced accuracy and safety. The presented system is intended to address the clinical needs for enhanced efficiency, accuracy, and safety of image-guided stereotactic neurosurgery for deep brain stimulation lead placement. The study describes a magnetic resonance imaging (MRI)-guided, robotically actuated stereotactic neural intervention system for deep brain stimulation procedure, which offers the potential of reducing procedure duration while improving targeting accuracy and enhancing safety. This is achieved through simultaneous robotic manipulation of the instrument and interactively updated in situ MRI guidance that enables visualization of the anatomy and interventional instrument. During simultaneous actuation and imaging, the system has demonstrated less than $15$ % signal-to-noise ratio variation and less than $0.20\%$ geometric distortion artifact without affecting the imaging usability to visualize and guide the procedure. Optical tracking and MRI phantom experiments streamline the clinical workflow of the prototype system, corroborating targeting accuracy with three-axis root mean square error $1.38\pm 0.45$ mm in tip position and $2.03\pm 0.58^\circ$ in insertion angle.