Designing a brain computer interface for control of an assistive robotic manipulator using steady state visually evoked potentials.

An assistive robotic manipulator (ARM) can provide independence and improve the quality of life for patients suffering from tetraplegia. However, to properly control such device to a satisfactory level without any motor functions requires a very high performing brain-computer interface (BCI). Steady-state visual evoked potentials (SSVEP) based BCI are among the best performing. Thus, this study investigates the design of a system for a full workspace control of a 7 degrees of freedom ARM. A SSVEP signal is elicited by observing a visual stimulus flickering at a specific frequency and phase. This study investigates the best combination of unique frequencies and phases to provide a 16-target BCI by testing three different systems off line. Furthermore, a fourth system is developed to investigate the impact of the stimulating monitor refresh rate. Experiments conducted on two subjects suggest that a 16-target BCI created by four unique frequencies and 16-unique phases provide the best performance. Subject 1 reaches a maximum estimated ITR of 235 bits/min while subject 2 reaches 140 bits/min. The findings suggest that the optimal SSVEP stimuli to generate 16 targets are a low number of frequencies and a high number of unique phases. Moreover, the findings do not suggest any need for considering the monitor refresh rate if stimuli are modulated using a sinusoidal signal sampled at the refresh rate.

[Human papillomavirus in the aetiology of skin cancer]. / Humaan papillomavirus in de etiologie van huidkanker.

At present, human papillomavirus (HPV) infection is chiefly known for its causal relationship with cervical cancer. Apart from genital types, the papillomavirus family consists of numerous human cutaneous types. The majority belongs to the so-called epidermodysplasia-verruciformis(EV)-HPV types that are potentially involved in skin cancer development. Non-melanoma skin cancers, especially cutaneous squamous cell carcinoma contain HPV DNA (30-60%). In immune-suppressed organ transplant recipients this percentage increases up to 90. Recent epidemiological studies show a statistically significant association between EV-HPV infection and squamous cell carcinoma. In addition recent experimental studies show specific EV-HPV types have a potential to transform cells that is comparable to high-risk genital HPV types. These data indicate that cutaneous HPV infections and squamous cell carcinoma development are associated.

Human papillomavirus infection and skin cancer risk in organ transplant recipients.

Warts and squamous cell carcinomas are important cutaneous complications in organ transplant recipients. The role of infection with human papillomaviruses (HPV) in the development of cutaneous squamous cell carcinoma is still unclear. An extremely diverse group of HPV types, mainly consisting of epidermodysplasia-verruciformis (EV)-associated HPV types, can be detected in benign, premalignant, and malignant skin lesions of organ transplant recipients. Frequently, there are multiple HPV types present in single skin biopsies. Typically, the prevalence of viral warts rises steadily after transplantation and a strong association exists between the number of HPV-induced warts and the development of skin cancer. The interval between the transplantation to the development of warts is clearly shorter than the interval from transplantation to the diagnosis of the first skin cancer. A comparison of transplant recipients with and without skin cancer, however, showed an equally high prevalence of EV-HPV DNA in keratotic skin lesions in both groups of patients and the detection rate and spectrum of HPV infection in hyperkeratotic papillomas, actinic keratoses, and squamous cell carcinomas was also similar. HPV DNA can frequently be detected in patients with hyperproliferative disorders like psoriasis and antibodies against HPV in patients with regenerating skin (e.g., after extensive second degree burns). Latent infection with EV-HPV seems to be widespread. The hair follicle region might be the reservoir of EV-HPV. The E6 protein from a range of cutaneous HPV types effectively inhibits apoptosis in response to UV-light induced damage. It is therefore conceivable that individuals who are infected by EV-HPV are at an increased risk of developing actinic keratoses and squamous cell carcinomas, possibly by chronically preventing UV-light induced apoptosis.

Lipoprotein(a) changes during and after coronary artery bypass grafting: an epiphenomenon?

The lipoprotein(a) (Lp(a)) time course during and after coronary artery bypass grafting was examined in 20 caucasoid patients, in relation to the time courses of serum cholesterol and serum triglycerides. Samples were taken at eight different time points. Baseline geometric means (SD) for Lp(a), cholesterol and triglycerides were 115 (336) mg/L, 5.73 (1.10) mmol/L and 1.73 (1.21) mmol/L, respectively. Up to 10 min after cardiopulmonary bypass (CPB) and after correction for haemodilution, no observable effect of CPB on serum concentrations of Lp(a) could be demonstrated, whereas serum concentrations of total cholesterol and triglycerides showed a progressive and significant decline. Ten minutes after stopping CPB geometric means for cholesterol and triglyceride were 3.90 (0.82) and 0.90 (0.58) mmol/L, respectively. At the third post-operative day geometric Lp(a) and cholesterol means decreased to 62(90) mg/L and 2.97 (0.84) mmol/L, respectively, while triglycerides went up. It is concluded that Lp(a) levels remain constant during CPB, but mimic total cholesterol changes in the post-CABG period.

Inflamed joints of patients with rheumatoid arthritis contain T cells that display in vitro proliferation to antigens present in autologous synovial fluid. Functional analysis on the basis of synovial-fluid-reactive T-cell clones and lines.

The immunopathology of inflamed joints in patients with RA is thought to result from an antigen-driven T-cell response. The antigen(s) responsible for the activation of synovial T cells, however, are as yet unidentified. In this study, we tested SF as a potential source of (auto)antigen(s). Five of 15 IL-2-expanded T-cell lines generated from SF cells of RA patients displayed a proliferative response to autologous SF. Five CD4+CD8-alpha beta TCR+SF-reactive T-cell clones obtained from responder T-cell lines were studied in more detail. Three T-cell clones from one RA patient were found to recognize epitopes in autologous SF in the context of DR4(Dw4), and two T-cell clones of another RA patient responded to autologous SF in the context of the HLA-DPB1*0401 gene product. The two DP-restricted clones and one of the DR-restricted clones did not proliferate to 50 SF samples of other RA patients, whereas the remaining DR-restricted clones responded to one allogeneic sample. Sequence analysis demonstrated that the latter clones expressed identical V beta 6.9 + TCR beta chains. This was also found for the (V beta 19+) DP-restricted clones. Proliferation of SF-reactive T cells was not only obtained with SF of the joint that had contained the T cells, but also with autologous SF of other affected joints. Together, these findings indicate that epitopes able to stimulate synovial T cells differ among RA patients, but may be similar within multiple joints of an individual patient. The presence of T cells able to respond to SF antigens in inflamed joints suggests that these T cells play an active role in the pathogenesis of RA.