Influence of the lateral ventricles and irregular skull base on brain kinematics due to sagittal plane head rotation

Two-dimensional physical models of the human head were used to investigate how the lateral ventricles and irregular skull base influence kinematics in the medial brain during sagittal angular head dynamics. Silicone gel simulated the brain and was separatedfrom the surrounding skull vessel by paraffin that provided a slip interface between the gel and vessel. A humanlike skull base model (HSB) included a surrogate skull base mimicking the irregular geometry of the human. An HSBV model added an elliptical inclusion filled with liquid paraffin simulating the lateral ventricles to the HSB model. A simplified skull base model (SSBV) included ventricle substitute but approximated the anterior and middle cranial fossae by a flat and slightly angled surface. The models were exposed to 7600 rad/s2 peak angular acceleration with 6 ms pulse duration and 5 deg forced rotation. After 90 deg free rotation, the models were decelerated during 30 ms. Rigid body displacement, shear strain and principal strains were determined from high-speed video recorded trajectories of grid markers in the surrogate brains. Peak values of inferior brain surface displacement and strains were up to 10.9X (times) and 3.3X higher in SSBV than in HSBV. Peak strain was up to 2.7X higher in HSB than in HSBV. The results indicate that the irregular skull base protects nerves and vessels passing through the cranial floor by reducing brain displacement and that the intraventricular cerebrospinal fluid relieves strain in regions inferior and superior to the ventricles. The ventricles and irregular skull base are necessary in modeling head impact and understanding brain injury mechanisms.     

Efficiency as a predictor of human jaw design in the sagittal plane

The effects of changing the direction of the bite force and of the mandibular joint reaction have been studied with a mathematical model assisted by a computer using the technique of linear programming. We conclude the following: In the sagittal plane the long axes of lower molars are each tilted in the direction that most efficiently converts muscle force into work at the bite point rather than in the direction that would maximize static bite force. These genetically determined angles are referred to as the most 'work efficient' angles. Collectively they lead to the appearance of the curve of Spee associated with the postcanines. Given the most work efficient angle of the first molar, the model indicates for bite forces generated in this direction the joint reaction is least when tilted forward from the vertical at between 20 degrees and 30 degrees. The joint reaction is normal to the articular surface of the condyle which is itself tilted forward 20-30 degrees from the occlusal plane. We conclude the condyle and articular eminence are remodelled to the angle that minimizes the joint reaction. The direction of the bite force may be controlled via neuronal circuitry connecting mechanoreceptors of the periodontal ligament with motor nerves supplying the jaw-closing muscles. The height of the occlusal plane in the molar region has little effect on jaw efficiency.     

Evaluation of a generalized model of human postural dynamics and control in the sagittal plane

A two-step identification method is used to evaluate a generalized model of human postural control in the sagittal plane. Postural dynamics are represented as a planar open-chain linkage system supported by a triangular foot. The control mechanism is modeled as a state feedback element in which the torque acting at a given link is an arbitrary function of the state variables — angles and angular velocities. To validate the approach, six normal subjects underwent two series of experiments. The first series were used to determine an appropriate model of the system dynamics. The second series were used to estimate the parameters of the feedback model. A computer simulation of the complete system shows that the model predictions closely match the observed responses. These results suggest that the proposed model provides a useful framework for analysis of postural control mechanisms.This work was supported by the National Institutes of Health under Grant NS 21363     

Immunomodulating properties of MDMA alone and in combination with alcohol: a pilot study

Cell-mediated immune response after the administration of MDMA alone and in combination with alcohol was evaluated in a randomized, double-blind, double-dummy, cross-over pilot clinical trial conducted in four healthy MDMA consumers who received single oral doses of 75 mg MDMA (n = 2) or 100 mg MDMA (n = 2), alcohol (0.8 mg/kg), MDMA and alcohol, or placebo. Acute MDMA treatment produced a time-dependent immune dysfunction associated with MDMA plasma concentrations. Although total leukocyte count remained unchanged, there was a decrease in the CD4 T/CD8 T-cell ratio as well as in the percentage of mature T lymphocytes, probably because of a decrease in both the percentage and absolute number of T helper cells. The decrease in CD4 T-cell counts and in the functional responsiveness of lymphocytes to mitogenic stimulation was dose-dependent. The correlation between MDMA pharmacokinetics and the profile of MDMA-induced immune dysfunction suggests that alteration of the immune system may be mediated by the central nervous system. Alcohol consumption produced a decrease in T helper cells, B lymphocytes, and PHA-induced lymphocyte proliferation. Combined MDMA and alcohol produced the greatest suppressive effect on CD4 T-cell count and PHA-stimulated lymphoproliferation. Immune function was partially restored at 24 hours. These results provide the first evidence that recreational use of MDMA alone or in combination with alcohol alters the immunological status.     

The mechanical role of the trunk and lower extremities in a seated weight-moving task in the sagittal plane

A two-dimensional, sagittally-symmetric biomechanical model was developed to analyze the joint moments required to stabilize the trunk in a seated, dynamic, weight-moving task. Kinematic and reaction force data were measured while subjects moved a hand-held weight (0-4 kgf) at shoulder level to and fro at 1 Hz. These data were then used for model input and validation purposes. A second, simpler model was used to simulate how joint loads varied with weight held, trunk inclination, and movement frequency. The results for this seated task demonstrate a) significant trunk, hip, knee, and ankle joint moments (37, 13, 4, 13 percent of maximum strength values, respectively) were required, b) considerable intersubject differences in mean joint moments (more than 66 percent) were found, which primarily were due to subtle differences in body segment kinematics and lower extremities use, and c) the important role of the lower extremities in stabilizing the trunk in the seated posture.     

Simulation of the motor units control during a fast elbow flexion in the sagittal plane.

The fact that muscles are composed of different Motor Units (MUs) is often neglected when investigating motor control by macro models of human musculo-skeletal-joint systems. Each muscle is associated with one control signal. This simplification leads to difficulties when mechanical and electrical manifestations of the muscle activity are juxtaposed. That is why a new approach for muscle modelling was recently proposed (Journal of Biomechanics 2002;35:1123-1135). It is based on MUs twitches and a Hierarchical Genetic Algorithm (HGA) is implemented for choosing the moments of activation of the individual MUs, thus simulating the control of the nervous system. Its basic benefit is obtaining the complete information about the mechanical and activation behaviour of all MUs, respectively muscles, during the whole motion. Its possibilities are demonstrated when simulating fast elbow flexion. Three flexor and two extensor muscles, each consisting of approximately real number of different types of MUs, are modelled. The task is highly indeterminate and the optimization is performed according to a fitness function that is an assessed combination of criteria (minimal deviation from the given joint moment, minimal total muscle force and minimal MUs activation). The influence of the weight of the first criterion (the one that reflects the importance of the movement accuracy on the predicted results), is investigated. Two variants concerning the muscle MUs structure are also compared: each muscle is composed of four distinct types MUs and the MUs twitch parameters are uniformly distributed.     

Isolation of glycosylated hemoglobins by a combination of ion-exchange and gel-filtration chromatographies: a pilot study

The techniques of ion exchange and gel filtration have been combined in a single chromatographic column which allows the simultaneous isolation of hemoglobins glycosylated at their beta-amino termini from other hemoglobin species as well as from molecules differing in size from the hemoglobins. This method is unique because it makes possible isolation of preparative quantities of glycosylated hemoglobins within approximately 15 min. The method works most efficiently with a dry weight-to-weight ratio of Biorex 70 to Sephadex G25 of 1.4 to 1.0. The technique was applied to the determination of the apparent first-order rate constant for the deglycosylation of the labile form of hemoglobin AIc.     

In-vitro comparison of LC-DCP- and LCP-constructs in the femur of newborn calves - a pilot study

ABSTRACT: BACKGROUND: To compare the biomechanical in-vitro characteristics of limited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) constructs in an osteotomy gap model of femoral fracture in neonatal calves. Pairs of intact femurs from 10 calves that had died for reasons unrelated to the study were tested. A 7-hole LC-DCP with six 4.5 mm cortical screws was used in one femur and a 7-hole LCP with four 5.0 mm locking and two 4.5 mm cortical screws was used in the corresponding femur. The constructs were tested to failure by cyclic compression at a speed of 2 mm/s within six increasing force levels. RESULTS: The bone-thread interface was stripped in 21 of 80 cortical screws (26.3%) before a pre-set insertion torque of 3 Nm was achieved. Only 3 corresponding intact pairs of constructs could be statistically compared for relative structural stiffness, actuator excursion and width of the osteotomy gap. Relative structural stiffness was significantly greater, actuator excursion and width of the osteotomy gap were significantly smaller in the LCP constructs. While failure occurred by loosening of the screws in the LC-DCP constructs, locking constructs failed by cutting large holes in the soft distal metaphyseal bone. CONCLUSIONS: An insertion torque sufficient to provide adequate stability in femurs of newborn calves could not be achieved reliably with 4.5 mm cortical screws. Another limiting factor for both constructs was the weak cancellous bone of the distal fracture fragment. LCP constructs were significantly more resistant to compression than LC-DCP constructs.     

The dental awareness of nursing home staff in Singapore - a pilot study

Objective: The aim of this pilot study was to assess the oral health knowledge among staff working in a local nursing home managed by a voluntary welfare organisation. Method: A self‐administered questionnaire was completed by 53 nursing staff working in a home with 270 residents. The questionnaire was structured to assess the staff's knowledge of dental caries, periodontal disease and the care and use of dentures. Results: 99.6% of the respondents felt that oral health care of the elderly was very important. However, only 45.3% of them attributed the cause of dental caries to the frequent intake of sugar. Bacteria in dental plaque was identified by 88.7% of them as the main cause of periodontal disease while 96.2% of them indicated that dentures should be cleaned at least once a day and rinsed after every meal. Conclusion: The staff of this nursing home demonstrated positive knowledge of periodontal disease and denture care. However, their knowledge of dental caries revealed substantial room for improvement. This could signal an area for future staff training and development. Such efforts would help establish a team of caregivers who can improve the oral health and quality of life for residents in the nursing home.     

Applications of new laboratory marker assays in neurological diagnoses - a pilot study

225 consecutive patients with different neurological diseases and 101 individuals as the control were examined between 2002-2004. Cystatin C, arginase-I, tau-protein and beta-amyloid were measured. Individuals with CNS inflammation had significantly lower Cystatin-C index (CSF/serum) values. There was no diagnostic significance of the Arginase-I assay in CSF was verified. The CSF tau-protein/beta-amyloid index was shown to be a sufficient efficacy for neurodegenerative disease diagnosis.     

A molecular analysis of the isolated rat posterior frontal and sagittal sutures: differences in gene expression

Although it is one of the most commonly occurring craniofacial congenital disabilities, craniosynostosis (the premature fusion of cranial sutures) is nearly impossible to prevent because the molecular mechanisms that regulate the process of cranial suture fusion remain largely unknown. Recent studies have implicated the dura mater in determining the fate of the overlying cranial suture; however, the molecular biology within the suture itself has not been sufficiently investigated. In the murine model of cranial suture fusion, the posterior frontal suture is programmed to begin fusing by postnatal day 12 in rats (day 25 in mice), reliably completing bony union by postnatal day 22 (day 45 in mice). In contrast, the sagittal suture remains patent throughout the life of the animal. Using this model, this study sought to examine for the first time what differences in gene expression--if any--exist between the two sutures with opposite fates. For each series of experiments, 35 to 40 posterior frontal and sagittal suture complexes were isolated from 6-day-old Sprague-Dawley rat pups. Suture-derived cell cultures were established, and ribonuicleic acid was derived from snap-frozen, isolated suture tissue. Results demonstrated that molecular differences between the posterior frontal and sagittal suture complexes were readily identified in vivo, although these distinctions were lost once the cells comprising the suture complex were cultured in vitro. Hypothetically, this change in gene expression resulted from the loss of the influence of the underlying dura mater. Significant differences in the expression of genes encoding extracellular matrix proteins existed in vivo between the posterior frontal and sagittal sutures. However, the production of the critical, regulatory cytokine transforming growth factor beta-1 was equal between the two suture complexes, lending further support to the hypothesis that dura mater regulates the fate of the overlying cranial suture.     

Oscillations of upper and lower body segments in the sagittal plane during standing: Spatiotemporal relationships

The balance control in the sagittal plane during standing without visual feedback has been studied in the context of the notion that a human body can be presented as a two-segment inverted pendulum. The oscillations of the center of pressure and of the upper and lower segments were recorded for 2 min (ten records for each of seven volunteers). It is shown that the correlation coefficients and dynamic similarity between the oscillation of the upper segment and the center of pressure are significantly higher than between the lower segment and the center of pressure. The dynamic similarity between the oscillations of the upper segment in different records are higher than between the oscillations of the lower one, which is supposedly connected with the necessity of stabilizing the head in space during standing. The oscillations of the lower segment occurred with a mean delay of 16.2 ± 9.0 ms relative to those of the upper segment. At the same time, the distribution of the delays has a peak at zero, indicating that two strategies of balance control are used during quiet standing, which are described in the one-segment and the two-segment inverted pendulum models.     

Approximation of the functional kinematics of posterior stabilised total knee replacements using a two-dimensional sagittal plane patello-femoral model: comparing model approximation to in vivo measurement

Previous in vivo studies have observed that current designs of posterior stabilised (PS) total knee replacements (TKRs) may be ineffective in restoring normal kinematics in Late flexion. Computer-based models can prove a useful tool in improving PS knee replacement designs. This study investigates the accuracy of a two-dimensional (2D) sagittal plane model capable of predicting the functional sagittal plane kinematics of PS TKR implanted knees against direct in vivo measurement. Implant constraints are often used as determinants of anterior–posterior tibio-femoral positioning. This allowed the use of a patello-femoral modelling approach to determine the effect of implant constraints. The model was executed using motion simulation software which uses the constraint force algorithm to achieve a solution. A group of 10 patients implanted with Scorpio PS implants were recruited and underwent fluoroscopic imaging of their knees. The fluoroscopic images were used to determine relative implant orientation using a three-dimensional reconstruction method. The determined relative tibio-femoral orientations were then input to the model. The model calculated the patella tendon angles (PTAs) which were then compared with those measured from the in vivo fluoroscopic images. There were no significant differences between the measured and calculated PTAs. The average root mean square error between measured and modelled ranged from 1.17° to 2.10° over the flexion range. A sagittal plane patello-femoral model could conceivably be used to predict the functional 2D kinematics of an implanted knee joint. This may prove particularly useful in optimising PS designs.     

Night shift work and osteoporosis among female blue-collar workers in Poland - a pilot study

ABSTRACT

Osteoporosis is an important public health problem worldwide. Although a number of factors that affect bone structure have been described; thus far, the current knowledge of occupational factors that may have an influence on bone tissue metabolism is strongly limited. Published studies indicate night shift work and the related circadian rhythm disruption may be considered as plausible underlying factors. The aim of the present study was to assess the potential association between night shift work and bone mineral density (BMD) among female blue-collar workers in Poland. A cross-sectional study was carried out among 194 female blue-collar workers >40 years of age employed in industrial plants. The operating system of work consisted of three work shifts clockwise rotation: morning (06:00–14:00 h), afternoon (14:00–22:00 h), and night (22:00–06:00 h), with five consecutive shifts per week followed by a free weekend. A questionnaire survey, based on a Polish version of The European vertebral osteoporosis study (EVOS) questionnaire, a validated instrument, was administered. Data on current job characteristics, job seniority, and lifetime duration of night shift work were also collected. BMD of the lumbar spine and hip (both total femur and femoral neck) was measured using dual-energy X-ray absorptiometry. Multivariate linear regression models were run, with bone mineralization parameters as dependent variables, as well as night work characteristics and important confounders. Statistical analysis was performed separately for premenopausal and postmenopausal women. The analyses adjusted for confounders did not reveal any significant differences between current or lifetime experience of night shift work and BMD among both premenopausal and postmenopausal women. However, the outcomes supported the well-established correlation with factors, such as age, BMI, and menopausal status. BMD at the three sites measured was significantly associated with BMI (p < .001) and inversely associated with age (p < .001) in the total study population. Postmenopausal women had significantly lower BMD than did premenopausal women (p < .001). The study findings indicate that in the population of Polish female blue-collar workers, the system of work does not seem to be associated with the development of osteoporosis.     

Cervical spine motion in the sagittal plane (I) range of motion of actually performed movements, an X-ray cinematographic study

A fast method has been developed to determine the position of the outlines of bony structures on X-ray photographs of the cervical spine movements in the sagittal plane (105 mm spot film camera; 4 frames per second; about 10 seconds per complete anteflexion-retroflexion or vice versa). This method corrects for incongruity of the vertebral contours on consecutive frames due to motion in another than the sagittal plane. It also automatically corrects erroneously marked points. This method has been used to determine segmental range of motion (SROM) and total range of motion of the head with respect to the seventh cervical vertebra (TROM). It is shown that SROM may be larger when frames of intermediate instead of extreme positions of the film are considered. In ten test persons without cervical complaints the interindividual variability of SROM turned out to be comparable to the ones found with older methods. Intraindividual variability of SROM and TROM was determined by registration at three different measuring sessions (0, 2 and 10 weeks). This intraindividual variability is high, especially in the cranial and caudal parts of the cervical spine. It is concluded that SROM and TROM are unsuitable to be used as a parameter of cervical spine mobility.     

Kinematic and kinetic features of normal level walking in patellofemoral pain syndrome: More than a sagittal plane alteration

Patients with patellofemoral pain syndrome (PFPS) often report discomfort and pain during walking. To date, most of the studies conducted to determine gait alterations in PFPS patients have focused on sagittal plane alterations. Physiological and biomechanical factors, however, suggest that frontal and transverse plane alterations may be involved in PFPS. We therefore decided to conduct a kinematic and kinetic evaluation on all three planes in 9 PFPS subjects and 9 healthy sex- and age-matched controls. General gait characteristics were similar in patients and controls, with the exception of swing velocity, which was lower in PFPS patients. Patients also displayed an increased knee abductor and external rotator moments in loading response, and reduced knee extensor moment both in loading response and in terminal stance. We speculate that these findings may be linked both to a pain-avoiding gait pattern and to alterations in the timing of activation of different components of the quadriceps muscle, which is typical of PFPS. The relevance for clinicians is this gait pattern may represent a biomechanical risk factor for future knee osteoarthritis. We therefore recommend that treatments aimed at PFPS should also attempt to restore a correct walking pattern.