A rapid method of grouping beta-hemolytic streptococci using extemporaneous coagglutination

Extemporaneous coagglutination procedure for the serological grouping of beta-hemolytic streptococci is reported. Streptococcal group antigens were extracted with nitrous acid. 250 strains of groups A, B, C, F and G streptococci were tested with this method. An agreement of 100% was found between this method and the Lancefield capillary precipitation procedure. Extemporaneous coagglutination method was found to be rapid, reliable, easy and economical and could be adopted in any routine diagnostic laboratory.     

Combined effect of 2-deoxy-D-glucose and exercise on plasma catecholamine response.

2-Deoxy-D-glucose (2-DG) is a nonmetabolizable analogue of glucose that, by competitive inhibition of glucose utilization, produces a central neuroglucopenia and a peripheral hyperglycemia. This glucopenic agent was used to gain more insight into the combined effects of central glucopenia and exercise on plasma catecholamine response. This was carried out by comparing one group of exercising (26 m/min, 0% grade) rats injected with 2-DG (2-DG-EX; 250 mg/kg iv) with two control groups: one group of exercising rats injected with a saline solution (SAL-EX) and one group of resting rats injected with 2-DG (2-DG-RE). Significant (P less than 0.05) increases in blood glucose levels were observed 10 min after administration of 2-DG (7.2-13.8 and 7.3-12.4 mmol/l in 2-DG-EX and 2-DG-RE groups, respectively). These elevated blood glucose levels were maintained throughout the experiment in the 2-DG-RE condition but decreased in 2-DG-EX rats to levels observed in the SAL-EX group after 45 min of running (13.8-8.0 mmol/l). The combination of 2-DG-induced neuroglucopenia and exercise resulted in an additive response of norepinephrine (0.59 vs. 0.34 and 0.34 ng/ml; t = 12 min) and an amplified epinephrine response (1.4 vs. 0.37 and 0.31 ng/ml; t = 12 min) compared with the responses to each stimulus alone (2-DG-EX vs. 2-DG-RE and SAL-EX, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inverse identification of local stiffness across ascending thoracic aortic aneurysms

Biomechanics and Modeling in Mechanobiology - Aortic dissection is the most common catastrophe of the thoracic aorta, with a very high rate of mortality. Type A dissection is often associated with...     

Reliable simulations of the human proximal femur by high-order finite element analysis validated by experimental observations

Background: The mechanical response of patient-specific bone to various load conditions is of major clinical importance in orthopedics. Herein we enhance the methods presented in Yosibash et al. [2007. A CT-based high-order finite element analysis of the human proximal femur compared to in-vitro experiments. ASME Journal of Biomechanical Engineering 129(3), 297–309.] for the reliable simulations of the human proximal femur by high-order finite elements (FEs) and validate the simulations by experimental observations.

Method of approach: A fresh-frozen human femur was scanned by quantitative computed tomography (QCT) and thereafter loaded (in vitro experiments) by a quasi-static force of up to 1250 N. QCT scans were manipulated to generate a high-order FE bone model with distinct cortical and trabecular regions having inhomogeneous isotropic elastic properties with Young's modulus represented by continuous spatial functions. Sensitivity analyses were performed to quantify parameters that mostly influence the mechanical response. FE results were compared to displacements and strains measured in the experiments.

Results: Young moduli correlated to QCT Hounsfield Units by relations in Keyak and Falkinstein [2003. Comparison of in situ and in vitro CT scan-based finite element model predictions of proximal femoral fracture load. Medical Engineering and Physics 25, 781–787.] were found to provide predictions that match the experimental results closely. Excellent agreement was found for both the displacements and strains. The presented study demonstrates that reliable and validated high-order patient-specific FE simulations of human femurs based on QCT data are achievable for clinical computer-aided decision making.     

Development of a measles vaccine production process in MRC-5 cells grown on Cytodex1 microcarriers and in a stirred bioreactor

Measles vaccination remains the most efficient way to control the spread of the virus. This work focuses on the production of a measles vaccine using stirred conditions as an advanced option for process scale up. Non-porous Cytodex 1 microcarriers were used to support MRC-5 cell growth in suspension cultures. Virus replication was first optimized in spinner flasks, and the effects of various operational parameters were investigated. Cell infection with AIK-C measles strain at an MOI (multiplicity of infection) of 0.005, without glucose regulation and in M199 medium, resulted in a virus titer of 10^6.25 TCID₅₀ (median tissue culture infective dose)/ml. To optimize the production process in a 7-l bioreactor, we carried out various perfused cultures using minimum essential medium (MEM) + 5% FCS diluted with phosphate-buffered saline (PBS). We achieved a high cell density level (4.1 × 10⁶ cells/ml) with an efficient use of the medium when MEM + 5% FCS diluted with PBS at 25% was used during the cell amplification step. Optimization of measles production in MRC-5 cells grown on Cytodex 1 beads in a 7-l bioreactor showed that perfusion was the most efficient when compared to repeated-batch culture. Perfusion at a rate of 0.25 V (reactor volume)/day showed the highest specific productivity (1.6 IVP [infectious virus particle] cell⁻¹ day⁻¹). Testing of several stabilizers containing pharmaceutically improved components such as sugars, amino acids, and charged ions showed that the formulation composed of sucrose and MgCl₂, led to the maintenance of the infectivity of the AIK-C measles virus strain to a significant level, when stored at +28 °C, +4 °C and −60 °C.     

Influence of biological, environmental and technical factors on phenolic content and antioxidant activities of Tunisian halophytes

Halophyte ability to withstand salt-triggered oxidative stress is governed by multiple biochemical mechanisms that facilitate retention and/or acquisition of water, protect chloroplast functioning, and maintain ion homeostasis. Most essential traits include the synthesis of osmolytes, specific proteins, and antioxidant molecules. This might explain the utilization of some halophytes as traditional medicinal and dietary plants. The present study aimed at assessing the phenolic content and antioxidant activities of some Tunisian halophytes (Cakile maritima, Limoniastrum monopetalum, Mesembryanthemum crystallinum, M. edule, Salsola kali, and Tamarix gallica), depending on biological (species, organ and developmental stage), environmental, and technical (extraction solvent) factors. The total polyphenol contents and antioxidant activities (DPPH and superoxide radicals scavenging activities, and iron chelating and reducing powers) were strongly affected by the above-cited factors. Such variability might be of great importance in terms of valorising these halophytes as a source of naturally secondary metabolites, and the methods for phenolic and antioxidant production.     

The effect of a daytime 60-min nap opportunity on postural control in highly active individuals

Although napping is commonly used as a strategy to improve numerous physical and cognitive performances, the efficacy of this strategy for improving postural balance has not yet been elucidated. Thus, the aim of this study was to conduct a comprehensive examination of the effect of a 60 min nap opportunity (N60) on different components of postural control. Ten highly active individuals (age = 27 ± 3.5 y, height = 1.75 ± 0.52 m, weight = 66.02 ± 8.63 kg) performed, in a randomized order, two afternoon test sessions following no nap (NN) and N60. Postural balance was assessed using the sensory organisation test (SOT), the unilateral stance test (UST), and the limits of Stability Test performed on NeuroCom^® Smart Balance Master. The subjective rating of sleepiness before and after the nap conditions was also assessed. Compared to NN, N60 improved the composite balance score (p < 0.05, ES = 0.75, Δ = 5.3%) and the average and maximum percentage balance in the most challenging postural conditions of the SOT (p < 0.05 for SOT-4 and 5 and p < 0.0005 for SOT-6; ES range between 0.58 and 1.1). This enhanced postural balance in N60 was accompanied with improved visual (p < 0.05; ES = 0.93; Δ = 8.9%) and vestibular (p < 0.05; ES = 0.81; Δ = 10.5%) ratios and a reduced level of sleepiness perception (p < 0.001, ES = 0.87). However, no significant differences were found in any of the UST and LOS components’ scores (p > 0.05). Overall, a 60 min post lunch nap opportunity may be viable for improving static balance, although further work, involving larger samples and more complex motor activities, is warranted.     

A novel animal-component-free medium for rabies virus production in Vero cells grown on Cytodex 1 microcarriers in a stirred bioreactor

Vero cells growth and rabies production in IPT-AF medium, a property animal-component-free medium are described in this work. Kinetics of cell growth and rabies virus (strain LP 2061) production were first conducted in spinner flasks. Over eight independent experiments, Vero cell growth in IPT-AF medium, on 2 g/l Cytodex 1 was consistent. An average Cd (cell division number) of 3.3 ± 0.4 and a specific growth rate μ of 0.017 ± 0.006 h⁻¹ were achieved. Such performances were comparable to those obtained in serum-containing medium (MEM + 10% FCS). Rabies virus production on Vero cells in IPT-AF medium was also optimised in spinner flasks. The effects of multiplicity of infection (MOI), regulation of glucose level at 1 g/l and cell washing step, were investigated. The highest virus titer was achieved when the cells were infected at an MOI of 0.1; this level was equal to 10⁷ FFU/ml. The step of medium exchange before cell infection can be omitted; nevertheless in this case glucose level should be maintained at 1 g/l to avoid a decrease of specific virus productivity. Process optimisation in a 2-l stirred bioreactor pointed out that the aeration mode was the prominent parameter that affected cell growth in IPT-AF medium and on Cytodex 1 microcarriers. An acceptable level of cell density (cell density level of 1.5 × 10⁶ cells/ml) was achieved when cells were grown in batch mode and using headspace aeration. Nevertheless, this aeration mode is not optimal for large-scale culture. The addition of Pluronic F68 at 0.1% at 24 h post inoculation as well as the switch from surface aeration mode to the sparged mode, 2 days after the start of the culture, had markedly improved cell growth performance. A cell density level of 5.5 × 10⁶ cells/ml was reached when cells were grown in a 2-l bioreactor, on 3 g/l Cytodex 1 in IPT-AF medium and using the recirculation culture mode. Cell infection at an MOI of 0.1 and using perfused culture, resulted in a maximal virus titer of 3.5 × 10⁷ FFU/ml. The activity of the pooled inactivated rabies virus harvests showed a protective activity that meets WHO requirements.