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Abstract

In broiler chickens, the relationship between dietary supplementation of vitamin C and hepatic, cardiac and renal heat shock proteins (HSP60, HSP70 and HSP90), heat shock factors (HSF-1 and HSF-3) and enzymatic antioxidants requires further investigation. The current study aimed to investigate this relationship at cellular and molecular levels in a 42 days experiment. Two hundred, one-day-old broiler chicks (Ross 308) were allocated into four equal groups. Chicks in the first and third groups were thermo-neutral (TN; 22°C for 24 hours/day) and fed basal diet without or with vitamin C (1g/kg basal diet), respectively. Chicks in the second and fourth groups were heat stressed (HS; 34°C for 8 hours/day) and fed basal diet without or with vitamin C, respectively. Performance parameters were recorded throughout the experiment. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX), Catalase (CAT) and gene expression of heat shock proteins (HSP60, 70 and 90) and heat shock factors (HSF 1 and 3) were analyzed in liver, heart and kidney tissues of the studied groups. Heat stress induced a negative impact on performance parameters, significant reduction in activities of all examined antioxidant enzymes and a significant up-regulation in heat shock proteins and factors genes in all studied tissues. Dietary supplementation of vitamin C corrected these parameters towards the normal control values. Conclusively, dietary supplementation of the examined dose of vitamin C was efficient at ameliorating the detrimental effects of heat stress on liver, heart and kidney tissues of broilers chickens at cellular and molecular levels.
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Abstract

Biocomposite foam scaffolds of poly(ε-caprolactone) (PCL) with different porogenes were produced with batch foaming technique using supercritical carbon dioxide (scCO2) as a blowing agent. In performed experiments composites were prepared from graphene-oxide (nGO), nano-hydroxyapatite (nHA) and nano-cellulose (nC), with various concentrations. The objective of the study was to explore the effects of porogen concentration and foaming process parameters on the morphology and mechanical properties of three-dimensional porous structures that can be used as temporary scaffolds in tissue engineering. The structures were manufactured using scCO2 as a blowing agent, at two various foaming pressures (9 MPa and 18 MPa), at three different temperatures (323 K, 343 K and 373 K) for different saturation times (0.5 h, 1 h and 4 h). In order to examine the utility of porogenes, a number of tests, such as static compression tests, thermal analysis and scanning electron microscopy, have been performed. Analysis of experimental results showed that the investigated materials demonstrated high mechanical strength and a wide range of pore sizes. The obtained results suggest that PCL porous structures are useful as biodegradable and biocompatible scaffolds for tissue engineering.
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Abstract

Image-guided High Intensity Focused Ultrasound (HIFU) technique is dynamically developing technology for treating solid tumors due to its non-invasive nature. Before a HIFU ablation system is ready for use, the exposure parameters of the HIFU beam capable of destroying the treated tissue without damaging the surrounding tissues should be selected to ensure the safety of therapy. The purpose of this work was to select the threshold acoustic power as well as the step and rate of movement of the HIFU beam, generated by a transducer intended to be used in the HIFU ablation system being developed, by using an array of thermocouples and numerical simulations. For experiments a bowl-shaped 64-mm, 1.05 MHz HIFU transducer with a 62.6 mm focal length (f-number 0.98) generated pulsed waves propagating in two-layer media: water/ex vivo pork loin tissue (50 mm/40 mm) was used. To determine a threshold power of the HIFU beam capable of creating the necrotic lesion in a small volume within the tested tissue during less than 3 s each tissue sample was sonicated by multiple parallel HIFU beams of different acoustic power focused at a depth of 12.6 mm below the tissue surface. Location of the maximum heating as well as the relaxation time of the tested tissue were determined from temperature variations recorded during and after sonication by five thermo-couples placed along the acoustic axis of each HIFU beam as well as from numerical simulations. The obtained results enabled to assess the location of each necrotic lesion as well as to determine the step and rate of the HIFU beam movement. The location and extent of the necrotic lesions created was verified using ultrasound images of tissue after sonication and visual inspection after cutting the samples. The threshold acoustic power of the HIFU beam capable of creating the local necrotic lesion in the tested tissue within 3 s without damaging of surrounding tissues was found to be 24 W, and the pause between sonications was found to be more than 40 s.
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