Cervical muscle response to trunk flexion in whiplash-type lateral impacts

The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity, whiplash-type lateral impacts when the occupant is seated out of the recommended driving position (neutral posture). Twenty healthy volunteers were subjected to left lateral impacts of 4.1, 7.7, 10.5, and 13.7 m/s² acceleration, with their trunk flexed by 45° and laterally flexed to the right and left also by 45° at the time of impact. Bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded. Under these conditions of trunk-flexed postures, in a left lateral impact, muscle responses were of generally low magnitude with the trunk flexed to either the left or right. Even at the highest acceleration of 13.7 m/s², all muscles generated less than 37% of their known maximal voluntary contraction electromyogram. Also, in these left lateral impacts, the right splenius capitis showed a greater EMG response than the left splenius capitis regardless of whether the subject was flexed to the right or left at the time of impact. The right splenius capitis (the one contralateral to the left lateral impact direction) was more active than its counterpart. Compared to what is known for EMG responses with an occupant in the neutral posture, the right sternocleidomastoid (usually the most active muscle in a left lateral collision) was significantly less-active with trunk flexion than with neutral posture conditions (P<0.01). In the absence of bodily impact, the flexed trunk posture does not produce a biomechanical response that would increase the likelihood of cervical muscle injury in low velocity lateral impacts, and may lessen the risk of injury for some muscles.     

A physical map of the linear unintegrated DNA of Visna virus

Our previous studies have shown that during the lytic infection of sheep cells in culture, visna virus produces an unintegrated viral DNA which is a linear double-stranded molecule with a molecular weight of approximately 6 × 10⁶ daltons. We have now studied this DNA using the method of Southern to locate the cleavage sites of a number of restriction endonucleases on the unintegrated visna viral DNA. Using these sites, we have constructed a physical map of the linear viral DNA. In addition, our analysis has identified two species of closed circular viral DNA in the Hirt supernatant fraction of visna virus-infected cells.     

Optimization of spray drying by factorial design for production of hollow microspheres for ultrasound imaging

A process for producing hollow microcapsules as ultrasound contrast agents was optimized using a 2(3) factorial experimental design method with two replicates. Spray drying, a conveniently scalable encapsulation technique, was used to encapsulate a volatile core material, such as ammonium carbonate, using biodegradable 50-50 poly(D,L-lactide-co-glycolide). Various effects due to changes in processing variables and their interactions were studied using the factorial grid. The high- and low-incremented variables examined included the temperature difference between the inlet and outlet of the spray dryer (5 degrees and 15 degrees C), air atomization pressure (80 and 100 psi), and polymer concentration in solvent (0.005 and 0.025 g/mL). Responses analyzed for computing the main effects and interactions were microcapsule morphology, yield, mean size, and zeta potential. Experimental results showed that polymer concentration was most important for determining microcapsule morphology. The temperature difference for drying prominently affected mean size, and atomization pressure was the main effect for microcapsule yield. Interactions among variables were not present in this case. The best conditions for producing PLGA microcapsules was a temperature difference of 5 degrees C, an initial polymer concentration of 0.005 g/mL, and an atomization pressure of 80 psi. The microcapsule zeta potentials were unaffected by spray-drying conditions.     

Waves earlier than P3 are more informative in putative subcortical Dementias: A study with mapping and neuropsychological techniques

Summary Thirty subjects (normal controls, patients with putative subcortical dementia and non-demented patient controls) were studied using advanced neurophysiological (16 scalp-electrode positions, computer-assisted brain electrical activity mapping, auditory oddball paradigm) and neuropsychological techniques. Our study suggests that waves earlier than P₃ (N₁, P₂ and N₂) are all correlated with global measures of cognitive functions. They are, however, differentially correlated with specific measures of cognitive functions, N₁ and P₂ with mental speed and N₂ with short-term memory. The abnormalities of these waves (earlier than P₃) may be an electrophysiologic marker of dementia in patients with putative subcortical states.     

Diblock Copolymers Based on 1,4‐Dioxan‐2‐one and ε‐Caprolactone: Characterization and Thermal Properties

Summary: Various poly(ε‐caprolactone‐block‐1,4‐dioxan‐2‐one) (P(CL‐block‐PDX)) block copolymers were prepared according to the living/controlled ring‐opening polymerization (ROP) of 1,4‐dioxan‐2‐one (PDX) as initiated by in situ generated ω‐aluminium alkoxides poly(ε‐caprolactone) (PCL) chains in toluene at 25 °C. 1 ¹H NMR, PCS and TEM measurements have attested for the formation of colloids attributed to a growing PPDX core surrounded by a solvating PCL shell during the polymerization of PDX promoted by ω‐Al alkoxide PCL chains in toluene. The thermal behavior of the P(CL‐block‐PDX) copolymers was studied by DSC; showing two distinct melting temperatures (as well as two glass transition temperatures) similar to those of the respective homopolyesters. Finally, the thermal degradation of the P(CL‐block‐PDX) block copolymers was investigated by TGA simultaneously coupled to a FT‐IR spectrometer and a mass spectrometer for evolved gas analysis (EGA). The degradation occurred in two consecutive steps involving a first unzipping depolymerization of the PPDX blocks followed by the degradation of the PCL blocks via both ester pyrolysis and unzipping reactions.

TEM observation of P(CL‐block‐PDX) block copolyesters ( = 11 600 and = 22 100) as formed by vaporization starting from a diluted suspension in toluene/TCE mixture solvent (50/50 v/v).     

Neutralizing antibody spectrum determines the antigenic profiles of emerging mutants of visna virus.

The visna viruses are antigenically related nononcogenic retroviruses of sheep. The original strain was isolated from the brain of a paralyzed sheep in Iceland during the 1940s. The prototype strains has been passed serially in sheep and has undergone progressive antigenic change. Previous reports have shown that such antigenic changes in visna virus can be reproduced in infected cell cultures treated with neutralizing antibody. We now show that the antigenic profiles of the emerging mutants directly reflect the nature of the selecting antibody. Mutants with minor antigenic changes were selected by "early" sera which had a limited neutralization range. Mutants with greater antigenic changes were selected by "late" sera with a wide neutralization range. Mutants selected by early sera emerged rapidly and consistently in cultures, and these were antigenically very similar to one another. Mutants rarely emerged in cultures treated with late sera, but these viruses showed major antigenic changes. The data suggest that the evolution of antigenic mutants of visna virus progresses by a series of minor mutations which accumulate under the selective pressure of antibody.     

重视儿童伤害预防 落实有效干预措施

伤害是全球儿童面临的健康威胁,也是中国1~17岁儿童的首位死因。儿童伤害预防是非常具有投入产出效益的一项公共卫生措施,国内外多年的研究和实践也证明相关儿童伤害干预措施的有效性。建议加强伤害防控工作的部门分工与协调机制,确保必要的财政经费支持,以广泛实施各项有效的干预措施,保障儿童健康成长。