Analysis of occupant kinematics and dynamics in nearside oblique impacts.

OBJECTIVE: The objective of this article is to analyze the kinematics and dynamics of restrained postmortem human surrogates (PMHS) exposed to a nearside oblique impact and the injuries that were found after the tests. METHODS: Three male PMHS of similar age (64 ± 4 years) and anthropometry (weight: 61 ± 9.6 kg; stature: 172 ± 2.7 cm) were exposed to a 30° nearside oblique impact at 34 km/h. The test fixture approximated the seating position of a front seat occupant. A rigid seat was designed to match the pelvic displacement in a vehicle seat. Surrogates were restrained by a 3-point seat belt consisting of a 2 kN pretensioner (PT), 4.5 kN force-limiting shoulder belt, and a 3.5 kN PT lap belt. The shoulder belt PT was not fired in one of the tests. Trajectories of the head, shoulder, and hip joint (bilaterally) were recorded at 1,000 Hz by a 3D motion capture system. The 3D acceleration and angular rate of the head, T1, and pelvis, and the 3D acceleration of selected spinal locations was measured at 10,000 Hz. Seat belt load cells measured the belt tension at 4 locations. PMHS donation and handling were performed with the approval of the relevant regional ethics review board. RESULTS: Activation of the shoulder PT reduced substantially the peak forward excursion of the head but did not influence the lateral displacement of the head center of gravity (CG). In all 3 subjects, the lateral excursion of the head CG (291.1, 290, 292.1 mm) was greater than the forward displacement (271.4, 216.7, 171.5 mm). The hip joint excursion of the PMHS that was not exposed to the shoulder PT seat belt was twice the magnitude observed for the other 2 subjects. The 3 PMHS sustained clavicle fractures on the shoulder loaded by the seat belt and 2 of them were diagnosed atlantoaxial subluxation in the radiologist examination. Avulsion fractures of the right lamina of T1, T2, T3, and T4 were found when the PT was not used. The 3 PMHS received multiple fractures spread over both aspects of the rib cage and involving the posterior aspect of it. CONCLUSION: In this study of nearside oblique impact loading, the PMHS exhibited kinematics characterized by reduced torso pitching and increased lateral head excursion as compared to previous frontal impact results. These kinematics resulted in potential cervical and thoracic spinal injuries and in complete, displaced fractures of the lateral and posterior aspects of the rib cage. Though this is a limited number of subjects, it shows the necessity of further understanding of the kinematics of occupants exposed to this loading mode.

Mechanisms of blast induced brain injuries, experimental studies in rats.

Traumatic brain injuries (TBI) potentially induced by blast waves from detonations result in significant diagnostic problems. It may be assumed that several mechanisms contribute to the injury. This study is an attempt to characterize the presumed components of the blast induced TBI. Our experimental models include a blast tube in which an anesthetized rat can be exposed to controlled detonations of explosives that result in a pressure wave with a magnitude between 130 and 260 kPa. In this model, the animal is fixed with a metal net to avoid head acceleration forces. The second model is a controlled penetration of a 2mm thick needle. In the third model the animal is subjected to a high-speed sagittal rotation angular acceleration. Immunohistochemical labeling for amyloid precursor protein revealed signs of diffuse axonal injury (DAI) in the penetration and rotation models. Signs of punctuate inflammation were observed after focal and rotation injury. Exposure in the blast tube did not induce DAI or detectable cell death, but functional changes. Affymetrix Gene arrays showed changes in the expression in a large number of gene families including cell death, inflammation and neurotransmitters in the hippocampus after both acceleration and penetration injuries. Exposure to the primary blast wave induced limited shifts in gene expression in the hippocampus. The most interesting findings were a downregulation of genes involved in neurogenesis and synaptic transmission. These experiments indicate that rotational acceleration may be a critical factor for DAI and other acute changes after blast TBI. The further exploration of the mechanisms of blast TBI will have to include a search for long-term effects.

Relapsed childhood high hyperdiploid acute lymphoblastic leukemia: presence of preleukemic ancestral clones and the secondary nature of microdeletions and RTK-RAS mutations.

Although childhood high hyperdiploid acute lymphoblastic leukemia is associated with a favorable outcome, 20% of patients still relapse. It is important to identify these patients already at diagnosis to ensure proper risk stratification. We have investigated 11 paired diagnostic and relapse samples with single nucleotide polymorphism array and mutation analyses of FLT3, KRAS, NRAS and PTPN11 in order to identify changes associated with relapse and to ascertain the genetic evolution patterns. Structural changes, mainly cryptic hemizygous deletions, were significantly more common at relapse (P<0.05). No single aberration was linked to relapse, but four deletions, involving IKZF1, PAX5, CDKN2A/B or AK3, were recurrent. On the basis of the genetic relationship between the paired samples, three groups were delineated: (1) identical genetic changes at diagnosis and relapse (2 of 11 cases), (2) clonal evolution with all changes at diagnosis being present at relapse (2 of 11) and (3) clonal evolution with some changes conserved, lost or gained (7 of 11), suggesting the presence of a preleukemic clone. This ancestral clone was characterized by numerical changes only, with structural changes and RTK-RAS mutations being secondary to the high hyperdiploid pattern.

Array-based genotype-phenotype correlation in a case of supernumerary ring chromosome 12.

Supernumerary ring chromosomes (SRC) account for approximately 10% of prenatal marker chromosomes and 60% of these SRCs are associated with an abnormal phenotype of the patient carrying them. SRCs have, with few exceptions, not been characterized at the molecular genetic level. Here, we present the first case of a SRC 12 thoroughly investigated with tiling resolution array-based comparative genomic hybridization (array CGH); multicolor, centromere, subtelomeric and whole chromosome painting fluorescence in situ hybridization. In addition, to be able to correlate phenotypic manifestations with a possible pathogenetic outcome of the SRC 12, we retrospectively compared and reviewed all 14 cases of SRC 12 reported, including our present case. Our analyses revealed that the SRC comprised 25.53-46.40 Mb of chromosome 12, a region known to harbor 47 annotated genes of which nine were of putative pathogenetic relevance. Reviewing the previously described cases of SRC 12, we could not establish any specific recurrent features associated with this type of SRC. This most probably reflects heterogeneity in break-point distribution among the reported cases, resulting in differently sized ring chromosomes and hence varying phenotypic traits of the patients. Detailed genomic evaluation, by array CGH or similar techniques may thus be of importance to predict the clinical course in individual cases.

Visualizing photochemical dynamics in solution through picosecond x-ray scattering.

A photoexcited state of molecular iodine in solution is observed using diffuse x-ray scattering at a synchrotron source. The measured changes in the diffuse scattering profile were consistent with earlier models of iodine's photodissociation and geminate recombination reaction, for which the recombined A/A(') state has a 0.4 A greater interatomic spacing than the resting state and has a lifetime of 500 ps in CH2Cl2. This technique should find application in the study of increasingly complicated photochemical systems which undergo structural rearrangements following rapid photolysis.

Neck injuries in car collisions--a review covering a possible injury mechanism and the development of a new rear-impact dummy.

A review of a few Swedish research projects on soft tissue neck injuries in car collisions is presented together with some new results. Efforts to determine neck injury mechanisms was based on a hypothesis stating that injuries to the nerve root region in the cervical spine are a result of transient pressure gradients in the spinal canal during rapid neck bending. In experimental neck trauma research on animals, pressure gradients were observed and indications of nerve cell membrane dysfunction were found in the cervical spinal ganglia. The experiments covered neck extension, flexion and lateral bending. A theoretical model in which fluid flow was predicted to cause the transient pressure gradients was developed and a neck injury criterion based on Navier-Stokes Equations was applied on the flow model. The theory behind the Neck Injury Criterion indicates that the neck injury occurs early on in the rearward motion of the head relative to the torso in a rear-end collision. Thus the relative horizontal acceleration and velocity between the head and the torso should be restricted during the early head-neck motion to avoid neck injury. A Bio-fidelic Rear Impact Dummy (BioRID) was developed in several steps and validated against volunteer test results. The new dummy was partly based on the Hybrid III dummy. It had a new articulated spine with curvature and range of motion resembling that of a human being. A new crash dummy and a neck injury criterion will be very important components in a future rear-impact crash test procedure.

[Nerve cell damages in whiplash injuries. Animal experimental studies]. / Nervenzellschäden bei Schleudertraumen. Tierexperimentelle Untersuchungen.

Mechanical loading of the cervical spine during car accidents often lead to a number of neck injury symptoms with the common term Whiplash Associated Disorders (WAD). Several of these symptoms could possibly be explained by injuries to the cervical spinal nerve root region. It was hypothesised that the changes in the inner volume of the cervical spinal canal during neck extension-flexion motion would cause transient pressure changes in the CNS as a result of hydro-dynamic effects, and thereby mechanically load the nerve roots and cause tissue damage. To test the hypothesis, anaesthetised pigs were exposed to experimental neck trauma in the extension, flexion and lateral flexion modes. The severity of the trauma was kept below the level where cervical fractures occur. Transient pressure pulses in the cervical spinal canal were duly recorded. Signs of cell membrane dysfunction were found in the nerve cell bodies of the cervical spinal ganglia. Ganglion injuries may explain some of the symptoms associated with soft-tissue neck injuries in car accidents. When the pig's head was pulled rearward relative to its torso to resemble a rear-end collision situation, it was found that ganglion injuries occurred very early on in the neck motion, at the stage where the motion changes from retraction to extension motion. Ganglion injuries did not occur when pigs were exposed to similar static loading of the neck. This indicates that these injuries are a result of dynamic phenomena and thereby further supports the pressure hypothesis. A Neck Injury Criterion (NIC) based on a theoretical model of the pressure effects was developed. It indicated that it was the differential horizontal acceleration and velocity between the head and the upper torso at the point of maximum neck retraction that determined the risk of ganglion injuries.