Control of grasp stability in humans under different frictional conditions during multidigit manipulation

Control of grasp stability under different frictional conditions has primarily been studied in manipulatory tasks involving two digits only. Recently we found that many of the principles for control of forces originally demonstrated for two-digit grasping also apply to various three-digit grasps. Here we examine the control of grasp stability in a multidigit task in which subjects used the tips of the thumb, index, and middle finger to lift an object. The grasp resembled those used when lifting a cylindrical object from above. The digits either all contacted the same surface material or one of the digits contacted a surface material that was more, or less, slippery than that contacted by the other two digits. The three-dimensional forces and torques applied by each digit and the contact positions were measured along with the position and orientation of the object. The distribution of forces among the digits strongly reflected constraints imposed by the geometric relationship between the object's center of mass and the contact surfaces. On top of this distribution, we observed changes in force coordination related to changes in the combination of surface materials. When all digits contacted the same surface material, the ratio between the normal force and tangential load (F(n):L ratio) was similar across digits and scaled to provide an adequate safety margin against slip. With different contact surfaces subjects adapted the F(n):L ratios at the individual digits to the local friction with only small influences by the friction at the other two digits. They accomplished this by scaling the normal forces similarly at all digits and changing the distribution of load among the digits. The surface combination did not, however, influence digit position, tangential torque, or object tilting systematically. The change in load distribution, rather, resulted from interplay between these factors, and the nature of this interplay varied between trials. That is, subjects achieved grasp stability with various combinations of fingertip actions and appeared to exploit the many degrees of freedom offered by the multidigit grasp. The results extend previous findings based on two-digit tasks to multidigit tasks by showing that subjects adjust fingertip forces at each digit to the local friction. Moreover, our findings suggest that subjects adapted the load distribution to the current frictional condition by regulating the normal forces to allow slips to occur early in the lift task, prior to object lift-off.     

In ovarian neoplasms, BRAF, but not KRAS, mutations are restricted to low-grade serous tumours

Genes of the RAF family, which mediate cellular responses to growth signals, encode kinases that are regulated by RAS and participate in the RAS/RAF/MEK/ERK/MAP-kinase pathway. Activating mutations in BRAF have recently been identified in melanomas, colorectal cancers, and thyroid and ovarian tumours. In the present study, an extensive characterization of BRAF and KRAS mutations has been performed in 264 epithelial and non-epithelial ovarian neoplasms. The epithelial tumours ranged from adenomas and borderline neoplasms to invasive carcinomas including serous, mucinous, clear cell, and endometrioid lesions. It is shown that BRAF mutations in ovarian tumours occur exclusively in low-grade serous neoplasms (33 of 91, 36%); these included serous borderline tumours (typical and micropapillary variants), an invasive micropapillary carcinoma and a psammocarcinoma. KRAS mutations were identified in 26 of 91 (29.5%) low-grade serous tumours, 7 of 49 (12%) high-grade serous carcinomas, 2 of 6 mucinous adenomas, 22 of 28 mucinous borderline tumours, and 10 of 18 mucinous carcinomas. Of note, two serous borderline tumours were found to harbour both BRAF and KRAS mutations. The finding that at least 60% of serous borderline tumours harbour mutations in two members of the ERK-MAP-kinase pathway (BRAF 36%, KRAS 30%) compared with 12% of high-grade serous carcinomas (BRAF 0%, KRAS 12%) indicates that the majority of serous borderline tumours do not progress to serous carcinomas. Furthermore, no BRAF mutations were detected in the other 173 ovarian tumours in this study.     

Interpersonal callousness, hyperactivity/impulsivity, inattention, and conduct problems as precursors to delinquency persistence in boys: a comparison of three grade-based cohorts.

Boys who exhibit interpersonal callousness (IC), hyperactivity/impulsivity (HI), inattention (IN), and conduct problems (CP) may be at risk for exhibiting persistent delinquent behavior. However, few studies have established the distinctiveness of these constructs or examined their relative contributions to the prediction of delinquent behavior across different developmental periods. This study explores these issues using boys from the youngest (1st grade, N = 849), middle (4th grade, N = 868), and oldest (7th grade, N = 856) cohorts of the Pittsburgh Youth Study. Confirmatory factor analysis indicates that the 4 constructs are related, yet independent, from childhood to adolescence. After controlling for the overlap among the constructs, CP significantly predicted delinquency persistence in the youngest cohort, whereas CP and IN predicted delinquency persistence in the middle cohort. IC uniquely predicted delinquency persistence for the oldest cohort. The results suggest that the saliency of specific predictors of delinquent behavior may change from childhood to adolescence.     

Supported planar bilayers in studies on immune cell adhesion and communication

Supported planar bilayers have been used extensively in immunology to study molecular interactions at interfaces as a model for cell-cell interaction. Examples include Fc receptor-mediated adhesion and signaling and formation of the immunological synapse between T cells and antigen-presenting cells. The advantage of the supported planar bilayer system is control of the bilayer composition and the optical advantages of imaging the cell-bilayer or bilayer-bilayer interface by various types of trans-, epi- and total internal reflection illumination. Supported planar bilayers are simple to form by liposome fusion and recent advances in micro- and nanotechnology greatly extend the power of supported bilayers to address key questions in immunology and cell biology.     

Engagement of gaze in capturing targets for future sequential manual actions

We investigated the role of saccadic gaze fixations in encoding target locations for planning a future manual task consisting of a sequence of discrete target-oriented actions. We hypothesized that fixations of the individual targets are necessary for accurate encoding of target locations and that there is a transfer of sequence information from visual encoding to manual recall. Subjects viewed four targets presented at random positions on a screen. After various delays following target extinction, the subjects marked the remembered target locations on the screen with the tip of a hand-held stick. When the targets were presented simultaneously among distracting elements, the overall accuracy of marking increased with presentation time and total number of targets fixated because the subjects had to serially fixate the individual targets to locate them. Without distractors, the marking accuracy was similarly high regardless of duration of target presentation (0.25-8 s) and number of targets fixated; it was comparable to that with distractors when all four targets had been fixated. This indicates parallel encoding of target locations largely based on peripheral vision. Location memory was stable in these tasks over the delay periods investigated (0.5-8 s). With parallel encoding there was a "shrinkage" in the visuomotor transformation, i.e., the distances between the markings were systematically smaller than the corresponding inter-target distances. When the targets were presented sequentially without distractors, marking accuracy improved with the total number of targets fixated and shrinkage in the visuomotor transformation occurred only with parallel encoding, i.e., when subjects did not fixate the targets. In all experimental conditions for trials in which targets were fixated during encoding, there was little correspondence between the marking sequence and the sequence in which the targets were fixated. We conclude that subjects benefit from fixating targets for subsequent target-oriented manual actions when the targets are presented among distractors and when presented sequentially; when distinct targets are presented simultaneously against a blank background, they are efficiently encoded in parallel largely by peripheral vision.     

Managing people: the breakfast menu

Discusses an exploratory study of the impact of NHS reforms on the management of staff. Argues that "management" has moved from a view that staff should be provided with a secure and comfortable working environment to "labour" being viewed simply as a factor of production. The result seems to be an unprecedented sense of alienation among significant numbers of NHS staff. Proposes possible ways forward. The first focuses on the "means", accepting that the "ends" of the NHS will, for the foreseeable future, be dominated by the market. The second examines more closely the market-driven, business "end" or purpose and challenges the unitary view of the NHS Trust as a coherent business entity. Beyond these short- to medium-term responses, concludes that a return to a somewhat more flexible and less hard-edged human resources philosophy is a longer-term investment as the labour market tightens and skilled staff become scarcer in the later 1990s.     

Pseudocyesis in an adolescent using the long-acting contraceptive Depo-Provera.

A case report documents a Hispanic adolescent, 17 years of age, with pseudocyesis, who became amenorrheic using Depo-Provera to prevent a second pregnancy. Pseudocyesis includes classic symptoms of pregnancy such as nausea, breast enlargement and pigmentation, abdominal distention, and amenorrhea in nonpregnant women. It demonstrates the to control one's physical aspect at the level of hypothalamus. The involvement that contributed to her pseudocyesis--in this case, of her mother and boyfriend -- was not unusual. The abrupt resolution was brought on by normal menstrual period that began after she voluntarily missed her Depo-Provera injection. However, her ambivalence about a pregnancy became clear after she and her family received counseling. While the agenda had been to help her prevent a pregnancy, hers had not been as clear and uncomplicated. Her subsequent conception was a very positive one for her and her family, which helped to resolve the situation.