Correction: Aberrant iPSC-derived human astrocytes in Alzheimer's disease.

The original version of this Article contained an error in Fig. 1, in which a number of incorrect fluorescence images were inadvertently incorporated into the panel. This has been corrected in both the PDF and HTML versions of the Article.

Aberrant iPSC-derived human astrocytes in Alzheimer's disease.

The pathological potential of human astroglia in Alzheimer's disease (AD) was analysed in vitro using induced pluripotent stem cell (iPSC) technology. Here, we report development of a human iPSC-derived astrocyte model created from healthy individuals and patients with either early-onset familial AD (FAD) or the late-onset sporadic form of AD (SAD). Our chemically defined and highly efficient model provides >95% homogeneous populations of human astrocytes within 30 days of differentiation from cortical neural progenitor cells (NPCs). All astrocytes expressed functional markers including glial fibrillary acidic protein (GFAP), excitatory amino acid transporter-1 (EAAT1), S100B and glutamine synthetase (GS) comparable to that of adult astrocytes in vivo. However, induced astrocytes derived from both SAD and FAD patients exhibit a pronounced pathological phenotype, with a significantly less complex morphological appearance, overall atrophic profiles and abnormal localisation of key functional astroglial markers. Furthermore, NPCs derived from identical patients did not show any differences, therefore, validating that remodelled astroglia are not as a result of defective neural intermediates. This work not only presents a novel model to study the mechanisms of human astrocytes in vitro, but also provides an ideal platform for further interrogation of early astroglial cell autonomous events in AD and the possibility of identification of novel therapeutic targets for the treatment of AD.

Farmers' perceptions and concerns: the risks of driving farm vehicles on rural roadways in North Carolina.

This study focuses on farmers' perceptions of roadway safety and reviews specific and pertinent North Carolina rural road crash data to evaluate their perceptions and concerns. A survey was mailed to 1,357 prospective participants throughout North Carolina. Of these, 656 (48.3%) North Carolina farmers completed and returned the survey. The study revealed that while the majority of respondents took a number of specific safety measures to ensure their safety while driving their tractor on rural roads, most believed that driving their tractor on rural roads was more dangerous than it was five years ago. Few respondents believed that laws governing tractors on rural roads are well known by urban residents. While a majority of the respondents would support a law to mandate the use of a slow-moving vehicle (SMV) emblem on the back of slow-moving farm equipment, a majority also believed that a more effective way to mitigate potential crashes would be to ensure that all farm vehicles had blinking or flashing lights, that diamond-shaped caution signs depicting a tractor were posted on roadways with frequent tractor traffic, and that roadway shoulders were created or widened on roads with heavy farm traffic so that tractors could move off the roadway. Only 22% of respondents felt safe driving their tractor on rural roadways in North Carolina. Most respondents felt that the biggest problem with roadway safety was the lack of respect and increased speed of other drivers. Recent data indicate that in crashes involving farm vehicles, citations were issued to 34% of the non-farm vehicle operators and 24% to farm vehicle operators. For those driving non-farm vehicle who were deemed at fault, 66% were cited for failure to reduce speed. For those driving farm vehicles, the most frequent citation involved the lack of safe movement.

Simulation of tibial counterface wear in mobile bearing knees with uncoated and ADLC coated surfaces.

A multidirectional pin-on-plate reciprocating machine was used to compare the wear performance of UHMWPE sliding against cast cobalt chrome (CoCr) plates that were either untreated or coated with Amorphous Diamond Like Carbon (ADLC). The test conditions were based on a 1/5 scale model representative of in vivo motion at the tibial counterfaces of unconstrained mobile bearing knees. The average +/- STERR wear rates were 13.78+/-1.06 mm3/Mcycles for the ADLC counterfaces and 0.504+/-0.12 mm3/Mcycles for the control CoCr counterfaces. All of the pins run on the ADLC counterfaces exhibited the same patterns of blistering along the central axis, and severe abrasion elsewhere to the extent that all of the original machining marks were removed after just one week of testing. The average value of friction coefficient was 0.24 for the ADLC counterfaces and 0.073 for the control CoCr counterfaces. The factor of 3.5 increase was statistically significant at p < 0.05. In the tribological evaluation of ADLC coatings for tibial trays in mobile bearing knees, this study shows that this specific Physical Vapour Deposition (PVD) ADLC showed significantly poorer frictional and wear performance than uncoated surfaces which was sufficient to negate any potential benefits of improved resistance to third body damage.

Quantification of third body damage to the tibial counterface in mobile bearing knees.

Fourteen pairs of explanted low contact stress (LCS) tibial interface components: six rotating platform (RP), six meniscal (MN) and two anterior-posterior (AP) glide designs, have been analysed with particular attention paid to the condition of the tibial counterfaces. The average surface roughness, Ra, for the tibial trays ranged from 0.01 to 0.087 micron, significantly greater than the unworn control measurement of 0.008 micron. The scratch geometry analysis showed that the scratch peaks were found to be consistently of a lower aspect ratio than the scratch valleys and under 1 micron in height (average asperity height Rp = 0.52 micron, aspect ratio delta p = 0.01, average asperity depth Rv = 1.10 microns, delta v = 0.05). The largest scratches were 3-4 microns in both Rp and Rv. In vitro tests have shown that ultra-high molecular weight polyethylene (UHMWPE) wear increases in the presence of counterface scratches perpendicular to the direction of motion. In these explants, the unidirectional motion produced scratches parallel to the direction of sliding which is predicted to produce a smaller increase in UHMWPE wear. Other designs in mobile bearing knees have less constrained motion at the tibial counterface and this has been shown to accelerate wear; it may also lead to a further increase in wear in the presence of third body scratches. It may be possible in future knee designs to reduce this type of wear damage by introducing alternative materials or coatings which are more resistant to scratching and surface roughening.

Drug targeting Mycobacterium tuberculosis cell wall synthesis: genetics of dTDP-rhamnose synthetic enzymes and development of a microtiter plate-based screen for inhibitors of conversion of dTDP-glucose to dTDP-rhamnose.

An L-rhamnosyl residue plays an essential structural role in the cell wall of Mycobacterium tuberculosis. Therefore, the four enzymes (RmlA to RmlD) that form dTDP-rhamnose from dTTP and glucose-1-phosphate are important targets for the development of new tuberculosis therapeutics. M. tuberculosis genes encoding RmlA, RmlC, and RmlD have been identified and expressed in Escherichia coli. It is shown here that genes for only one isotype each of RmlA to RmlD are present in the M. tuberculosis genome. The gene for RmlB is Rv3464. Rv3264c was shown to encode ManB, not a second isotype of RmlA. Using recombinant RmlB, -C, and -D enzymes, a microtiter plate assay was developed to screen for inhibitors of the formation of dTDP-rhamnose. The three enzymes were incubated with dTDP-glucose and NADPH to form dTDP-rhamnose and NADP(+) with a concomitant decrease in optical density at 340 nm (OD(340)). Inhibitor candidates were monitored for their ability to lower the rate of OD(340) change. To test the robustness and practicality of the assay, a chemical library of 8,000 compounds was screened. Eleven inhibitors active at 10 microM were identified; four of these showed activities against whole M. tuberculosis cells, with MICs from 128 to 16 microg/ml. A rhodanine structural motif was present in three of the enzyme inhibitors, and two of these showed activity against whole M. tuberculosis cells. The enzyme assay was used to screen 60 Peruvian plant extracts known to inhibit the growth of M. tuberculosis in culture; two extracts were active inhibitors in the enzyme assay at concentrations of less than 2 microg/ml.

An experimental model of tibial counterface polyethylene wear in mobile bearing knees: the influence of design and kinematics.

Current designs of mobile bearing knees have different kinematics at the tibial counterface articulation; unidirectional represented by linear tracks and rotating platform designs, and multidirectional represented by reduced constraint designs with motion of the tibial surface in A-P and M-L directions simultaneously. One fifth scale experimental models of the tibial counterface articulation have been developed with mean contact stresses of 0.6 MPa. The unidirectional model had a linear reciprocating motion with a 10 mm stroke, the multidirectional model had a reciprocating motion with a 10 mm stroke and simultaneous rotation of +/- 7.5 degrees. Six specimens of GUR415 polyethylene were tested for each model, sliding on polished cobalt chrome counterfaces with Ra < 0.01 micron in 25% bovine serum lubricant. The mean +/- STERR wear rates were: unidirectional 0.045 +/- 0.015 mm3/million cycles and multidirectional 0.44 +/- 0.15 mm3/million cycles. Applying the scaling factor of 5, the predicted wear rates in actual knee prostheses were: unidirectional 0.23 mm3/million cycles and multidirectional 2.2 mm3/million cycles. The order of magnitude increase in wear rate was statistically significant (p = 0.05).

Determining transthoracic impedance, delivered energy, and peak current during defibrillation episodes.

A simplified method has been developed to determine peak current, transthoracic impedance, and delivered energy during a damped sinusoidal defibrillation pulse. The discharge waveform information is generated from sampling the peak discharge current through a current transformer and measuring the voltage stored on the energy storage capacitor. For a given defibrillator circuit a unique relationship exists between the peak discharge current IM and the unknown external impedance Rext presented to the defibrillator by the patient; hence, measurement of IM allows calculation of Rext. A microprocessor-controlled algorithm provides delivered energy information using known internal resistance, capacitance, and inductance parameters. The benefit of this method of delivered energy calculation is that the current and voltage waveforms need not be digitized and then integrated to provide the desired information. This method also keeps defibrillation circuitry ground isolated and simplifies operation through the high electromagnetic fields generated during the discharge. The delivered energy information, along with time, date, and other patient parameters, is documented automatically with an annotation strip-chart recorder.