Methodology to geometrically age human body models to average and subject-specific anthropometrics, demonstrated using a small stature female model assessed in a side impact

The aged population has been associated with an increased risk of injury in car-crash, creating a critical need for improved assessment of safety systems. Finite element human body models (HBMs) have been proposed, but require representative geometry of the aged population and high mesh quality. A new hybrid Morphing-CAD methodology was applied to a 26-year-old (YO) 5^th percentile female model to create average 75YO and subject-specific 86YO HBMs. The method achieved accurate morphing targets while retaining high mesh quality. The three HBMs were integrated into a side sled impact test demonstrating similar kinematic response but differing rib fracture patterns.

Sex, Age and Stature Affects Neck Biomechanical Responses in Frontal and Rear Impacts Assessed Using Finite Element Head and Neck Models

The increased incidence of injury demonstrated in epidemiological data for the elderly population, and females compared to males, has not been fully understood in the context of the biomechanical response to impact. A contributing factor to these differences in injury risk could be the variation in geometry between young and aged persons and between males and females. In this study, a new methodology, coupling a CAD and a repositioning software, was developed to reposture an existing Finite element neck while retaining a high level of mesh quality. A 5th percentile female aged neck model (F05_75YO) and a 50th percentile male aged neck model (M50_75YO) were developed from existing young (F05_26YO and M50_26YO) neck models (Global Human Body Models Consortium v5.1). The aged neck models included an increased cervical lordosis and an increase in the facet joint angles, as reported in the literature. The young and the aged models were simulated in frontal (2, 8, and 15 g) and rear (3, 7, and 10 g) impacts. The responses were compared using head and relative facet joint kinematics, and nominal intervertebral disc shear strain. In general, the aged models predicted higher tissue deformations, although the head kinematics were similar for all models. In the frontal impact, only the M50_75YO model predicted hard tissue failure, attributed to the combined effect of the more anteriorly located head with age, when compared to the M50_26YO, and greater neck length relative to the female models. In the rear impacts, the F05_75YO model predicted higher relative facet joint shear compared to the F05_26YO, and higher relative facet joint rotation and nominal intervertebral disc strain compared to the M50_75YO. When comparing the male models, the relative facet joint kinematics predicted by the M50_26YO and M50_75YO were similar. The contrast in response between the male and female models in the rear impacts was attributed to the higher lordosis and facet angle in females compared to males. Epidemiological data reported that females were more likely to sustain Whiplash Associated Disorders in rear impacts compared to males, and that injury risk increases with age, in agreement with the findings in the present study. This study demonstrated that, although the increased lordosis and facet angle did not affect the head kinematics, changes at the tissue level were considerable (e.g., 26% higher relative facet shear in the female neck compared to the male, for rear impact) and relatable to the epidemiology. Future work will investigate tissue damage and failure through the incorporation of aged material properties and muscle activation.

Importance of the cervical capsular joint cartilage geometry on head and facet joint kinematics assessed in a Finite element neck model

Finite element human neck models (NMs) aim to predict neck response and injury at the tissue level; however, contemporary models are most often assessed using global response such as head kinematics. Additionally, many NMs are developed from subject-specific imaging with limited soft tissue resolution in small structures such as the facet joints in the neck. Such details may be critical to enable NMs to predict tissue-level response. In the present study, the capsular joint cartilage (CJC) geometry in a contemporary NM was enhanced (M50-CJC) based on literature data. The M50-CJC was validated at the segment and full neck levels and assessed using relative facet joint kinematics (FJK), capsular ligament (CL) and intervertebral disc (IVD) strains, a relative vertebral rotation assessment (IV-NIC) and head kinematics in frontal and rear impact. The validation ratings at the segment level increased from 0.60 to 0.64, with improvements for modes of deformation associated with the facet joints, while no difference was noted at the head kinematic level. The improved CJC led to increased FJK rotation (188%) and IVD strain (152.2%,) attributed to the reduced facet joint gap. Further enhancements of the capsular joint representation or a link between the FJK and CL injury risk are recommended. Enhancements at the tissue level demonstrated a large effect on the IVD strain, but were not apparent in global metrics such as head kinematics. This study demonstrated that a biofidelic and detailed geometrical representation of the CJC contributes significantly to the predicted joint response, which is critical to investigate neck injury risk at the tissue level.

Biochemical analysis of point mutations in the 5'-3' exonuclease of DNA polymerase I of Streptococcus pneumoniae. Functional and structural implications

To define the active site of the 5'-3' exonucleolytic domain of the Streptococcus pneumoniae DNA polymerase I (Spn pol I), we have constructed His-tagged Spn pol I fusion protein and introduced mutations at residues Asp(10), Glu(88), and Glu(114), which are conserved among all prokaryotic and eukaryotic 5' nucleases. The mutations, but not the fusion to the C-terminal end of the wild-type, reduced the exonuclease activity. The residual exonuclease activity of the mutant proteins has been kinetically studied, together with potential alterations in metal binding at the active site. Comparison of the catalytic rate and dissociation constant of the D10G, E114G, and E88K mutants and the control fusion protein support: (i) a critical function of Asp(10) in the catalytic event, (ii) a role of Glu(114) in the exonucleolytic reaction, being secondarily involved in both catalysis and DNA binding, and (iii) a nonessential function of Glu(88) for the exonuclease activity of Spn pol I. Moreover, the pattern of metal activation of the mutant proteins indicates that none of the three residues is a metal-ligand at the active site. These findings and those previously obtained with D190A mutant of Spn pol I are discussed in relation to structural and mutational data for related 5' nucleases.

Cloning and molecular characterization of the citrate utilization citMCDEFGRP cluster of Leuconostoc paramesenteroides

The citMCDEFGRP cluster from Leuconostoc paramesenteroides involved in citrate utilization was cloned and its nucleotide sequence determined. Homology of the inferred gene products with characterized enzymes reveals that citP encodes the citrate permease P, citC the citrate ligase and citDEF the subunits of the citrate lyase of Leuconostoc. Moreover, it suggests that citM encodes a Leuconostoc malic enzyme. Analysis of citrate consumption by and citrate lyase activity of Lc. paramesenteroides J1[pCITJ1] showed that its citrate permease and its citrate lyase are induced by the presence of citrate in the growth medium. Southern blot analysis demonstrated that the citMCDEFGRP cluster is located in a plasmid.

[Severe acute hepatitis due to allopurinol in a patient with asymptomatic hyperuricemia and kidney failure. A review of the literature and an analysis of the risk factors]

The case of a 39-year-old female with mild renal failure and asymptomatic hyperuricemia who developed generalized exanthema, fever and eosinophilia followed by progressive jaundice and worsening of renal function 19 days after the initiation of treatment with alopurinol (300 mg/day) is reported. Liver biopsy showed a combination of mixed inflammatory infiltrate with abundant eosinophils and periportal necrosis and bridging, together with cholestasis and moderate steatosis. A review of the literature is made providing detailed analysis of other cases with preexisting renal failure and the role of renal dysfunction as a risk factor is discussed.

Comparative analysis of gene expression in Streptococcus pneumoniae and Lactococcus lactis

The pFL10 plasmid vector for translational fusions was constructed. pFL10 is based in the promiscuous pLS1 replicon and contains the pC194 cat gene deprived of its transcriptional promoter and Shine-Dalgarno (SD) sequence. Three promoters (Pcit, PpolA and PtetL) from Gram-positive bacteria, inserted in pFL10, were tested for their ability to drive transcription in Lactococcus lactis and Streptococcus pneumoniae. These promoters were coupled to the SD sequence of the lactococcal citP gene fused to the cat gene. Determination of the 5' ends of the three mRNAs by primer extension revealed the same start sites in both bacterial systems. However, it was observed a differential efficiency of promoter utilization by the RNA polymerases from the two hosts. The transcriptional behavior correlates with expression of the cat gene measured by determinations of chloramphenicol acetyltransferase (CAT) activity. Substitution of the SD of citP by that of the T7 phi 10 gene rendered a similar decrease of the CAT production in both bacterial systems.