Sub-mm functional decoupling of electrocortical signals through closed-loop BMI learning

Volitional control of neural activity lies at the heart of the Brain-Machine Interface (BMI) paradigm. In this work we investigated if subdural field potentials recorded by electrodes < 1mm apart can be decoupled through closed-loop BMI learning. To this end, we fabricated custom, flexible microelectrode arrays with 200 µm electrode pitch and increased the effective electrode area by electrodeposition of platinum black to reduce thermal noise. We have chronically implanted these arrays subdurally over primary motor cortex (M1) of 5 male Long-Evans Rats and monitored the electrochemical electrode impedance in vivo to assess the stability of these neural interfaces. We successfully trained the rodents to perform a one-dimensional center-out task using closed-loop brain control to adjust the pitch of an auditory cursor by differentially modulating high gamma (70-110 Hz) power on pairs of surface microelectrodes that were separated by less than 1 mm.

Quantitative evaluation of diffusion-weighted imaging techniques for the purposes of radiotherapy planning in the prostate

OBJECTIVE

Diffusion-weighted imaging (DWI) is an important technique for the localization of prostate cancer, and its response assessment during treatment with radiotherapy (RT). However, it has known limitations in terms of distortions and artefacts using standard acquisition techniques. This study evaluates two alternative methods that offer the promise of improved image quality and the potential for more reliable and consistent diffusion data.

METHODS

Three DWI techniques were investigated; single-shot echoplanar imaging (EPI), EPI combined with reduced volume excitation (ZOOMit; Siemens Healthcare, Erlangen, Germany) and read-out segmentation with navigator-echo correction (RESOLVE; Siemens Healthcare). Daily measurements of apparent diffusion coefficient (ADC) value were made in a quality assurance phantom to assess the repeatability of each sequence. In order to evaluate the geometric integrity of these sequences, ten normal volunteers were scanned, and the prostate was contoured to compare its similarity with T2 weighted images.

RESULTS

Phantom ADC values were significantly higher using the standard EPI sequence than those of the other two sequences. Differences were also observed between sequences in terms of repeatability, with RESOLVE and EPI performing better than ZOOMit. Overall, the RESOLVE sequence provided the best agreement for the in vivo data with smaller differences in volume and higher contour similarity than T2 weighted imaging.

CONCLUSION

Important differences have been observed between each of the three techniques investigated with RESOLVE performing the best overall. We have adopted this sequence for routine RT simulation of prostate patients at Liverpool Cancer Therapy Centre.

ADVANCES IN KNOWLEDGE

This work will be of interest to the increasing number of centres wanting to incorporate quantitative DWI in a clinical setting.

Unique X-linked familial FSGS with co-segregating heart block disorder is associated with a mutation in the NXF5 gene

Focal segmental glomerulosclerosis (FSGS) is the consequence of a disease process that attacks the kidney's filtering system, causing serious scarring. More than half of FSGS patients develop chronic kidney failure within 10 years, ultimately requiring dialysis or renal transplantation. There are currently several genes known to cause the hereditary forms of FSGS (ACTN4, TRPC6, CD2AP, INF2, MYO1E and NPHS2). This study involves a large, unique, multigenerational Australian pedigree in which FSGS co-segregates with progressive heart block with apparent X-linked recessive inheritance. Through a classical combined approach of linkage and haplotype analysis, we identified a 21.19 cM interval implicated on the X chromosome. We then used a whole exome sequencing approach to identify two mutated genes, NXF5 and ALG13, which are located within this linkage interval. The two mutations NXF5-R113W and ALG13-T141L segregated perfectly with the disease phenotype in the pedigree and were not found in a large healthy control cohort. Analysis using bioinformatics tools predicted the R113W mutation in the NXF5 gene to be deleterious and cellular studies support a role in the stability and localization of the protein suggesting a causative role of this mutation in these co-morbid disorders. Further studies are now required to determine the functional consequence of these novel mutations to development of FSGS and heart block in this pedigree and to determine whether these mutations have implications for more common forms of these diseases in the general population.

Student perception of a new integrated anatomy practical program: does students' prior learning make a difference?

While there is evidence that science and non-science background students display small differences in performance in basic and clinical sciences, early in a 4-year, graduate entry medical program, this lessens with time. With respect to anatomy knowledge, there are no comparable data as to the impact previous anatomy experience has on the student perception of the anatomy practical learning environment. A study survey was designed to evaluate student perception of the anatomy practical program and its impact on student learning, for the initial cohort of a new medical school. The survey comprised 19 statements requiring a response using a 5-point Likert scale, in addition to a free text opportunity to provide opinion of the perceived educational value of the anatomy practical program. The response rate for a total cohort of 82 students was 89%. The anatomy practical program was highly valued by the students in aiding their learning of anatomy, as indicated by the high mean scores for all statements (range: 4.04-4.7). There was a significant difference between the students who had and had not studied a science course prior to entering medicine, with respect to statements that addressed aspects of the course related to its structure, organization, variety of resources, linkage to problem-based learning cases, and fairness of assessment. Nonscience students were more positive compared to those who had studied science before (P levels ranging from 0.004 to 0.035). Students less experienced in anatomy were more challenged in prioritizing core curricular knowledge. Clin. Anat. 24:664-670, 2011. © 2011 Wiley-Liss, Inc.

Third Order Nonlinear Optical Susceptibility of Trans-(CH)x: A Degenerate Ground State Conjugated Polymer

The promise of conducting polymers as fast response nonlinear optical materials has been recently emphasized [1,3]. Polymers such as polyacetylene, polythiophene and the soluble (and processible) poly(3-alkylthienylenes) contain a high density of x-electrons, and they are known to exhibit photoinduced absorption and photoinduced bleaching, indicating major shifts of oscillator strength upon photoexcitation [2,4]. For polyacetylene, these nonlinear effects have been studied in detail in the picosecond [5a,b] and sub-picosecond [5c] time regime and correlated with the photoproduction of charge carriers through fast photoconductivity measurements [6]. The data have demonstrated ultra-fast response with nonlinear shifts in oscillator strength occurring at times of the order of 10-13 seconds. These resonant nonlinear optical properties are intrinsic; they originate from the nonlinearity of the self-localized photoexcitations [7] which characterize this class of polymers: solitons, polarons and bipolarons [4].

Targeting the progression of Parkinson's disease

By the time a patient first presents with symptoms of Parkinson's disease at the clinic, a significant proportion (50-70%) of the cells in the substantia nigra (SN) has already been destroyed. This degeneration progresses until, within a few years, most of the cells have died. Except for rare cases of familial PD, the initial trigger for cell loss is unknown. However, we do have some clues as to why the damage, once initiated, progresses unabated. It would represent a major advance in therapy to arrest cell loss at the stage when the patient first presents at the clinic. Current therapies for Parkinson's disease focus on relieving the motor symptoms of the disease, these unfortunately lose their effectiveness as the neurodegeneration and symptoms progress. Many experimental approaches are currently being investigated attempting to alter the progression of the disease. These range from replacement of the lost neurons to neuroprotective therapies; each of these will be briefly discussed in this review. The main thrust of this review is to explore the interactions between dopamine, alpha synuclein and redox-active metals. There is abundant evidence suggesting that destruction of SN cells occurs as a result of a self-propagating series of reactions involving dopamine, alpha synuclein and redox-active metals. A potent reducing agent, the neurotransmitter dopamine has a central role in this scheme, acting through redox metallo-chemistry to catalyze the formation of toxic oligomers of alpha-synuclein and neurotoxic metabolites including 6-hydroxydopamine. It has been hypothesized that these feed the cycle of neurodegeneration by generating further oxidative stress. The goal of dissecting and understanding the observed pathological changes is to identify therapeutic targets to mitigate the progression of this debilitating disease.

Enhancing neurite outgrowth from primary neurones and neural stem cells using thermoresponsive hydrogel scaffolds for the repair of spinal cord injury

In this study, thermoresponsive xyloglucan hydrogel scaffolds were investigated as candidates for neural tissue engineering of the spinal cord. The hydrogels were optimized to provide similar mechanical properties to that of native spinal cord, although also being functionalized through the immobilization of poly-D-lysine to promote neurone adhesion and neurite outgrowth. Under 2D and 3D culture conditions, xyloglucan scaffolds supported the differentiation of primary cortical neurones. Furthermore, functionalization provided a means of controlling and optimizing the cell diameter, number, migration and the neurite density, and the direction of growth. The interaction of neural stem cells (NSCs) was also investigated on the xyloglucan scaffolds in vitro. The survival of the NSCs and the axonal extensions on the scaffolds were similar to that of the primary cortical neurones. These findings suggest that xyloglucan-based materials are suitable for providing a neurotrophic milieu.

Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols

High charge-separation efficiency combined with the reduced fabrication costs associated with solution processing and the potential for implementation on flexible substrates make 'plastic' solar cells a compelling option for tomorrow's photovoltaics. Attempts to control the donor/acceptor morphology in bulk heterojunction materials as required for achieving high power-conversion efficiency have, however, met with limited success. By incorporating a few volume per cent of alkanedithiols in the solution used to spin-cast films comprising a low-bandgap polymer and a fullerene derivative, the power-conversion efficiency of photovoltaic cells (air-mass 1.5 global conditions) is increased from 2.8% to 5.5% through altering the bulk heterojunction morphology. This discovery can potentially enable morphological control in bulk heterojunction materials where thermal annealing is either undesirable or ineffective.

Voltage-induced metal-insulator transition in polythiophene field-effect transistors

We have extensively studied the carrier transport in regio-regular polythiophene field-effect transistors (FETs) from room temperature to 4.2 K. At low temperatures, Zabrodskii plots (dlnsigma/dlnT) demonstrate that the gate voltage and source-drain voltage combine to induce the insulator-to-metal transition at a carrier density of 5x10(12) cm-2. The carrier transport in the insulating regime is well described by phonon assisted hopping in a disordered Fermi glass with Coulomb interaction between the hopping charge carrier and the opposite charge left behind, as described by Efros and Shklovskii.

Infrared imaging of the nanometer-thick accumulation layer in organic field-effect transistors

We report on infrared (IR) spectromicroscopy of the electronic excitations in nanometer-thick accumulation layers in field-effect transistor (FET) devices based on poly(3-hexylthiophene). IR data allows us to explore the charge injection landscape and uncovers the critical role of the gate insulator in defining relevant length scales. This work demonstrates the unique potential of IR spectroscopy for the investigation of physical phenomena at the nanoscale occurring at the semiconductor-insulator interface in FET devices.

Age-related changes in human blood dendritic cell subpopulations

It is well known that the human immune system is functionally less mature at birth and, within the first years of life, undergoes a process of sequential development. Two subsets of dendritic cells (DCs) were identified in the blood: plasmacytoid and myeloid DCs. DCs stain negative for CD3, CD14, CD16, CD19, CD20 and CD56, and positive for human leucocyte antigen (HLA)-DR. In addition, plasmacytoid DCs strongly express CD123 while myeloid DCs express CD11. The number of the two different subsets was measured by flow cytometry in the peripheral blood from 44 healthy infants and children, aged 8 months to 18 years. While the number of CD11c+ myeloid cells (mean 11 cells/microl) did not change with age, the proportion of CD123+ plasmacytoid DCs decreased significantly (P < 0.001) from about 20 cells/microl to 8 cells/microl with age. In addition, we found a direct correlation between the number of plasmacytoid DC and interferon (IFN)-alpha production. As the two subsets of DC preferentially recognize different pathogens, age-related changes may have an impact on the maturation of the immune response.

Singlet exciton binding energy in poly(phenylene vinylene)

The exciton binding energy (E(b)) and the band gap energy (E(g)) of poly(phenylene vinylene) are determined by high-resolution measurements of the photoconductivity excitation profile as a function of light polarization, applied electric field, and temperature. At high applied electric fields, a peak in the photoconductivity is observed when the sample is pumped at a photon energy just below the onset of the band-to-band pi-pi* absorption. This peak is interpreted as resulting from field ionization of a weakly bound exciton with E(b) approximately 60 meV. The binding energy is obtained from the energy of the exciton peak relative to the band edge and independently from analysis of the dependence of the exciton dissociation on field and temperature.

Linear estimates of disease progression predict survival in patients with amyotrophic lateral sclerosis

We have shown that linear estimates of rates of disease progression (LEP), derived from isometric myometry [grip or foot dorsiflexion (FD) strength] and forced vital capacity (FVC%), are clinically and statistically significant predictors of survival of patients with amyotrophic lateral sclerosis (ALS) from date of disease onset and, except those based on grip strength, of survival from the date of measurement. We tested these results in 2 additional groups of patients: 1) those who participated in a previously reported Protropin (GH) study; and 2) those enrolled in two other clinical trials (group 2). The LEP were derived and tested as predictors of survival. In a Cox proportional hazards model, LEP based on all measures predicted survival from disease onset in both groups of patients. Using cutoff points determined within the original group to stratify patients in the validation groups into faster and slower progressing subgroups resulted in statistically significant separation of survival curves from disease onset in group 2 for all LEP and in group 1 (the GH group) for LEP derived from FD strength; and, for survival from date of measurement in group 2, when stratified by LEP based on FD strength or FVC%. LEP based on data generated by myometry or pulmonary function studies have now been shown to predict survival in 3 unrelated groups of patients with ALS entering clinical trials. Their precise use in clinical trial design needs to be explored further.

Linear estimates of rates of disease progression as predictors of survival in patients with ALS entering clinical trials

Maximal voluntary isometric grip and foot dorsiflexion (FD) strength and forced vital capacity (FVC) were obtained in 62 patients with ALS at or close to enrollment into two clinical trials. The agents tested did not slow disease progression. Isometric strength data were standardized, and the worse side was taken. FVC was expressed as a percentage of the predicted value (FVC%). We derived linear estimates of rates of disease progression based on the isometric myometry and FVC measures and on disease duration. Forty one patients were known to have died or to have undergone tracheostomy for ventilatory support. Probability of tracheostomy-free survival was calculated using the Kaplan-Meier method. The measured values, the linear estimates for rates of decline of these values, gender, age at onset, bulbar vs. spinal onset, height and weight were tested as risk factors within the Cox proportional hazards model, using regression techniques. When tested individually, estimates of rates of decline based on all three measures (FD, grip and FVC%) were the only statistically significant risk factors (P<0.005). Multivariate analysis resulted in a 3-variable model (chi-square=75.3, P<0.00001) in which estimated rates of decline of FD strength and of FVC%, and bulbar onset were independently significant (P<0.0001, P<0.0007 and P<0.05, respectively). We conclude that linear estimates of the rate of disease progression till enrollment into a clinical trial may be better predictors of patient survival than demographic data or discrete biologic measures.

A large-scale program in laparoscopic intrauterine insemination with frozen-thawed semen in Australian Merino sheep in Argentine Patagonia

This report shows the results of a large-scale laparoscopic intrauterine insemination program on a flock of Australian Merino sheep in Argentine Patagonia. The study was carried out on a total of 1824 ewes (3-to-7-yr-old) and 480 ewe hoggets (19-20 months old) on 2 farms in the southeastern region of Santa Cruz Province, in April and May 1996. The animals, divided into 15 groups, were synchronized with vaginal sponges containing 60 mg medroxyprogesterone acetate for 14 d and injected with 200 IU PMSG upon sponge removal. Estrus was screened every 12 h by means of vasectomized marker rams. The animals were inseminated laparoscopically by the intrauterine route using 2 schemes: 1) at a fixed time (12 h) after estrus detection, or 2) at a fixed time (60 h) after sponge removal irrespective of estrus. Pregnancy was determined at 30 d by transrectal ultrasound imaging. The results showed that 1) the onset of estrus occurs most often between 24 and 48 h after sponge removal, 2) ewe hoggets undergo estrus significantly earlier than sexually mature ewes, 3) in those animals showing estrus, there appears to be no relationship between fertility (as assessed by pregnancy outcome) and time of estrus, 4) there is a significant association between the percentage of estrus occurrence and pregnancy rate, 5) fertility is significantly higher in ewes than in hoggets, 6) for practical purposes insemination at a fixed time after the onset of estrus has no advantage over that of to insemination at a fixed time after sponge removal. It is concluded that large-scale laparoscopic intrauterine insemination can be successfully applied in Australian Merino ewes and ewe hoggets in low-productivity areas such as that of Argentine Patagonia and that estrus detection is unnecessary when insemination is performed at 60 h after sponge removal.

The storage of pure ram semen at room temperature results in capacitation of a subpopulation of spermatozoa

We investigated whether storage of pure ram semen at room temperature would facilitate the sperm capacitation process, as assessed by means of the chlortetracycline method. Objective motility, membrane integrity and ability of spermatozoa to undergo acrosome reaction induced by A23187 for 15 min were simultaneously evaluated to gain further insight into this process. Storage for 4 h at room temperature had a clear capacitating effect in approximately 50% of spermatozoa and increased their ability to respond to A23187. Beyond that time, the percentage of motility and membrane integrity remained unchanged. Moreover, storage did not alter the ability of those spermatozoa that remained noncapacitated under these conditions to become capacitated in SOF-m medium. Storage for 4 h increased the percentage of spermatozoa showing swelling of the apical ridge from 3 to 13%. In conclusion, storage of ram semen at room temperature for 4 h in the dark has a marked capacitating effect on a subpopulation of spermatozoa, without changes in motility or membrane integrity, and a low effect on the appearance of the acrosome. Since semen storage is generally included in different IVF protocols, the results presented here contribute toward a clearer understanding of its role in these procedures.

Changes in sperm-bound amidase activity suggest subtle damage to ram sperm acrosomes by freezing/thawing, not detected by light microscopy

We have measured sperm-bound amidase activity in fresh, cooled and frozen/thawed ram spermatozoa, in order to study if freezing and thawing led to some degree of acrosome damage of motile/viable spermatozoa not detected by optical methods. This assay was based on the fact that membrane damage would result in an increased access of the enzyme substrate to the sperm acrosome. Semen was collected from adult Australian Merino rams, and spermatozoa were washed by centrifugation through a Ficoll solution. Sperm-bound amidase activity was measured in whole spermatozoa using the protease substrate benzoyl-arginyl-p-nitroanilide (BAPNA). Acrosomal status was also assessed by light microscopy after Giemsa staining. Most amidase activity was shown to be sperm-bound, as only a minor fraction of the enzyme activity was release into the medium after induced damage. Simultaneous assessment of sperm-bound amidase activity and the percentage of spermatozoa with microscopically evident acrosomal damage, after mild sonication for different times, showed a high correlation between both parameters (r = 0.97, p < 0.001). In separate experiments, fresh, cooled and frozen/thawed semen samples were filtered through Sephadex G-10 to obtain a subpopulation of motile, mostly acrosome-intact spermatozoa. As controls, spermatozoa from the same samples to which extensive acrosome damage was induced were evaluated. Slow cooling to 4 degrees C had no effect on amidase activity or percent acrosomal damage with respect to fresh samples. Freezing and thawing resulted in a sperm population that, after filtration through Sephadex, had a low percentage of acrosome damage (9.4%, vs. 2.1% for fresh filtered controls), which was 11% of that obtained after extensive acrosome damage (83%). However, amidase activity in these samples was markedly increased, showing values of activity that were 56% of those obtained in extensively damaged spermatozoa. This effect was not due to an alteration in the enzyme kinetics. We conclude that sperm-bound amidase activity is useful to detect subtle changes, provoked by a standard freezing/thawing procedure, in the permeability of acrosomes from ram spermatozoa which are not detected by direct observation of the acrosomes after Giemsa staining.

Mosaicism for trisomy 12: four cases with varying outcomes

Trisomy 12 observed in chorionic villus sampling (CVS) may reflect generalized mosaicism or indicate mosaicism confined to only the placenta. In this report, four cases of trisomy 12 observed in CVS or cultured placental biopsies with varying outcomes are presented. Seven dinucleotide repeat polymorphisms for chromosome 12 were used to determine the chromosome 12 origins in the fetus or child and to delineate the mechanism(s) that gave rise to the trisomy. In two cases (cases A and C), the mosaicism was confined to the placenta, resulting in normal liveborns. Although, in one case, the molecular results suggested an apparent duplication of one paternal chromosome 12 in the placenta, normal biparental inheritance was found in the diploid fetal cell line in both cases. In two other cases (cases B and D), trisomy 12 was observed in both extraembryonic and fetal tissues. In one of these pregnancies, a child was born by Caesarean section at 37 weeks because of intrauterine growth retardation and oligohydramnios, and resulted in neonatal death. Molecular markers and fluorescence in situ hybridization (FISH) revealed low-level trisomy 12 mosaicism in the spleen. In the fourth case, fetal abnormalities were detected on ultrasound and low-level trisomy 12 mosaicism was observed in amniotic fluid cells using conventional cytogenetics and FISH. Molecular markers revealed a maternal meiosis I non-disjunction of chromosome 12 in DNA from a cultured placental biopsy. Although predicting the outcomes of pregnancies involving confined placental mosaicism remains difficult, molecular techniques are valuable tools for distinguishing uniparental from biparental disomy and mechanisms of mosaicism.