Spinal canal narrowing during simulated frontal impact

Between 23 and 70% of occupants involved in frontal impacts sustain cervical spine injuries, many with neurological involvement. It has been hypothesized that cervical spinal cord compression and injury may explain the variable neurological profile described by frontal impact victims. The goals of the present study, using a biofidelic whole cervical spine model with muscle force replication, were to quantify canal pinch diameter (CPD) narrowing during frontal impact and to evaluate the potential for cord compression. The biofidelic model and a sled apparatus were used to simulate frontal impacts at 4, 6, 8, and 10 g horizontal accelerations of the T1 vertebra. The CPD was measured in the intact specimen in the neutral posture (neutral posture CPD), under static sagittal pure moments of 1.5 Nm (pre-impact CPD), during dynamic frontal impact (dynamic impact CPD), and again under static pure moments following each impact (post-impact CPD). Frontal impact caused significant (P<0.05) dynamic CPD narrowing at C0-dens, C2-C3, and C6-C7. The narrowest dynamic CPD was observed at C0-dens during the 10 g impact and was 25.9% narrower than the corresponding neutral posture CPD. Interpretation of the present results indicate that the neurological symptomatology reported by frontal impact victims is most likely not due to cervical spinal cord compression. Cord compression due to residual spinal instability is also not likely.     

How does prosthesis head size affect vibration transmission in ossiculoplasty?

OBJECTIVES: The transmission of vibrations from the tympanic membrane to the stapes footplate by an ossicular reconstruction prosthesis is affected by the size of the prosthesis head. We sought to determine if augmenting or reducing the head size of prosthesis had a systematic effect on transmission of vibrations to the stapes. STUDY DESIGN: We conducted a fresh cadaveric temporal bone middle ear study. METHODS: The incus was replaced with a prosthesis using a tympanic membrane to stapes head (TASH)-type hydroxyapatite prosthesis in nine fresh cadaveric temporal bones. Three prosthesis head sizes were created: unaltered, reduced, and augmented. Stapes vibrations were measured with a laser Doppler vibrometer in response to acoustic frequency chirps at 90 dB SPL. RESULTS: All three head size prostheses resulted in smaller stapes vibrations than the intact ear. There was no difference in the vibration transmission between the three different head sizes. All prostheses showed a vibration loss of 10 to 15 dB compared to the intact ear. CONCLUSIONS AND SIGNIFICANCE: Within the range of sizes tested, prosthesis head size had little impact on vibration transmission to the stapes footplate.     

Use of in vivo-induced antigen technology for identification of Escherichia coli O157:H7 proteins expressed during human infection

Using in vivo-induced antigen technology (IVIAT), a modified immunoscreening technique that circumvents the need for animal models, we directly identified immunogenic Escherichia coli O157:H7 (O157) proteins expressed either specifically during human infection but not during growth under standard laboratory conditions or at significantly higher levels in vivo than in vitro. IVIAT identified 223 O157 proteins expressed during human infection, several of which were unique to this study. These in vivo-induced (ivi) proteins, encoded by ivi genes, mapped to the backbone, O islands (OIs), and pO157. Lack of in vitro expression of O157-specific ivi proteins was confirmed by proteomic analysis of a mid-exponential-phase culture of E. coli O157 grown in LB broth. Because ivi proteins are expressed in response to specific cues during infection and might help pathogens adapt to and counter hostile in vivo environments, those identified in this study are potential targets for drug and vaccine development. Also, such proteins may be exploited as markers of O157 infection in stool specimens.     

Murine splenic hematopoietic subpopulations: the enlarged undifferentiated subset in New Zealand black mice is multipotent stem cells.

We recently reported that a significant population of the murine splenic non-T, non-B "null" cell compartment consists of non-lineage-specific, undifferentiated cells which are in the G0 and G1 phases of the cell cycle and that their numbers are particularly high in the spleens of New Zealand Black mice. A highly enriched population of these non-lineage-specific cells obtained by successive elimination of differentiated cells was further purified to homogeneity by fluorescence-activated cell sorting. The morphologic, phenotypic, and histochemical characteristics of this purified population suggest that these cells may be primitive hematopoietic stem cells. The germ line configuration of the genomic DNA establishes that these are uncommitted stem cells. In vivo, these cells form day 12 colonies in the spleen and liver of lethally irradiated recipients and confer radioprotection. These cells also differentiate into T- and B-cell lineages and reconstitute the immunodeficiency in mice with severe combined immunodeficiency. In response to a combination of a very few early-acting lymphokines and/or stromal cell-conditioned medium in vitro, these cells differentiate into both myeloid and lymphoid cell types. More of these cells are obtained from the enlarged spleens of New Zealand Black mice than from those of BALB/c mice. The presence of a comparatively higher number of stem cells in the spleen than in the marrow or fetal liver provides an alternative, and possibly superior, source of uncommitted stem cells for a variety of experimental investigations or therapeutic manipulations.     

Hydrophobically Modified Poly(acrylic acid) Using 3‐Pentadecylcyclohexylamine: Synthesis and Rheology

Summary: Hydrophobically modified poly(acrylic acid) was synthesized using 3‐pentadecylcyclohexylamine (3‐PDCA), which was in turn synthesized from 3‐pentadecylphenol, one of the components of cashew‐nut shell liquid (CNSL), a renewable resource material. ¹H NMR spectra confirmed the incorporation of 3‐PDCA onto PAA and a series of HMPs with three different molar concentrations, viz ? 3, 5 and 7 mol‐% of 3‐PDCA, were synthesized. An increase in viscosity with increasing hydrophobic content was observed by rheological measurements. The critical association concentrations were determined using an Ubbelohde viscometer and a controlled stress rheometer. The stability of HMPs towards temperature and shear was studied. Rheological measurements showed that there was a steady increase in viscosity with increase in hydrophobe content due to the formation of reversible networks. These polymers exhibited gel‐like behavior at low concentrations (≥2 wt.‐%) with an apparent yield stress (ca. 10 Pa) and showed shear thinning properties (non‐Newtonian). However, below a critical concentration, c [η], they showed Newtonian behavior.

η_sp of unmodified and modified PAA‐Na at various polymer concentrations.     

Acute hypervolemia does not improve arterial oxygenation in maximally exercising thoroughbred horses

Recently, it was reported that acute hypervolemia improves arterial oxygen tension in human athletes known to experience exercise-induced arterial hypoxemia. Since exercise-induced arterial hypoxemia is routinely observed in racehorses and is known to limit performance, we examined whether pre-exercise induction of acute hypervolemia would similarly benefit arterial oxygenation in maximally exercising thoroughbred horses. Two sets of experiments, namely, placebo [intravenous (IV) physiological saline] and acute hypervolemia (IV 7.2% NaCl, causing an 18.2% expansion of plasma volume) studies were carried out in random order on 13 healthy, exercise-trained thoroughbred horses, 7 days apart. An incremental exercise protocol leading to 120 s of galloping at 14 m s^–1 on a 3.5% uphill incline was used. Galloping at this workload elicited maximal heart rate and induced pulmonary hemorrhage in all horses in both treatments. In the placebo study, arterial oxygen tension decreased to 76.1 (2) mmHg (P<0.0001) at 30 s of maximal exertion, but further significant changes did not occur as exercise duration increased to 120 s [arterial oxygen tension 72.4 (2) mmHg]. A significant arterial hypoxemia also developed in galloping horses in the acute hypervolemia study [arterial oxygen tension at 30 and 120 s was 76.7 (1.7) and 71.9 (1.6) mmHg, respectively], but significant differences between treatments could not be demonstrated. In both treatments, a similar desaturation of arterial hemoglobin was also observed at 30 s of maximal exercise, which intensified with increasing exercise duration as hyperthermia, acidosis and hypercapnia intensified. Thus, acute expansion of plasma volume did not benefit arterial oxygenation in maximally exercising thoroughbred horses.