Search results for "Freezing"
showing 10 items of 96 documents
Numerical Solution of Foodstuff Freezing Problems Using Radial Basis Functions
2013
This work presents a novel numerical approach for the solution of time dependent non-linear freezing processes in terms of radial basis function Hermite approach. The proposed scheme is applied to a mashed potato sample during its freezing; evaluation of time evolution of the temperature profile at the core of the sample is carried out. Food thermal properties are highly dependent on temperature and the mathematical problem becomes highly non-linear and therefore particularly difficult to solve. Incorporating a Kirchhoff transformation significantly reduces the non-linearity. The robustness of the scheme is tested by comparison with experimental results available in literature.
Study and optimization of freeze-drying cycles of a model probiotic strain
2018
This work is based on the experimental study of the freeze-drying process to understand the impact of numerous factors on the survival rates of a model probiotic strain of Lactobacillus casei type. With the aim to find out if cell density in the matrix and survival rates are linked, we have studied the location of the cells after freeze drying inside a porous matrix composed of a lactose basis with a polymer, the polyvinylpyrrolidone (PVP) in various amounts. The best survival rate were obtained at slow freezing rate for a formulation containing 5% (m/V) of lactose and 5% (m/V) of PVP. Keywords: Freeze-Drying; Freezing; Probiotics; L. Casei ATCC 393
The influence of storage method on the transparency of pig crystalline lens
2019
Este artículo se ha publicado de forma definitiva en: http://www.scielo.br/pdf/abo/v82n1/0004-2749-abo-82-01-0056.pdf Purpose: The porcine eye is frequently used as a research model. This paper analyzes the effect of different storage methods on the transparency of pig crystalline lens. Methods: A spectral transmission curve (from 220 to 780 nm) for the crystalline lens was determined experimentally after storage in different conditions: saline solution, formalin, castor oil, and freezing at -80°C. The total transmission in the visible spectrum, which was used as an index of transparency, was calculated from these curves. For comparative purposes, fresh lenses were evaluated and used as con…
Negative staining and cryo-negative staining of macromolecules and viruses for TEM
2011
In this review we cover the technical background to negative staining of biomolecules and viruses, and then expand upon the different possibilities and limitations. Topics range from conventional air-dry negative staining of samples adsorbed to carbon support films, the variant termed the "negative staining-carbon film" technique and negative staining of samples spread across the holes of holey-carbon support films, to a consideration of dynamic/time-dependent negative staining. For each of these approaches examples of attainable data are given. The cryo-negative staining technique for the specimen preparation of frozen-hydrated/vitrified samples is also presented. A detailed protocol to su…
Keyhole limpet hemocyanin (KLH), II: Characteristic reassociation properties of purified KLH1 and KLH2.
1997
Subunits of the two types of keyhole limpet hemocyanin (KLH1 and KLH2), purified by gel filtration chromatography and preparative polyacrylamide gel electrophoresis from Immucothel, have been used for macromolecular reassociation studies. In-vitro reassociation has been achieved with a standardized system using a Tris-saline stabilizing buffer at pH 7.4 containing 100 mM calcium and magnesium chloride at 4 degrees C. The relatively slow progress of reassociation has been monitored and the varying oligomeric forms of KLH1 and KLH2 produced have been studied by transmission electron microscopy, using specimens negatively stained with 5% ammonium molybdate containing 1% trehalose. Specimens ha…
In vivo monitoring of alkaloid metabolism in hybrid plant cell cultures by 2D cryo-NMR without labelling
2003
Non-invasive measurements of alkaloid metabolism in plant cell suspension cultures of a somatic hybrid from Rauvolfia serpentina Benth. ex Kurz and Rhazya stricta Decaisne were carried out. When cell samples were taken sequentially from a stock feeding experiment, measuring times for in vivo NMR of 40 min were sufficient for following conversions of alkaloids at the natural abundance of 13C. Degradation of ajmaline added to the cells at 1.6 mM concentration to raumacline could be monitored after 96 h on a standard 800 MHz NMR instrument (Avance 800). Feeding vinorine an intermediate of ajmaline biosynthesis at 1.8 mM showed with a 500 MHz CryoProbe that the alkaloid enters two metabolic rou…
Influence of massed and distributed context preexposure on contextual fear and Egr-1 expression in the basolateral amygdala
2007
Preexposure to the conditioning context can influence the expression of context-conditioned fear. We used behavioral and early growth response gene (egr-1) assays in rats to study the effects of massed and distributed context preexposure on context-conditioned fear. The results demonstrated that massed context preexposure impaired acquisition of contextual fear, an effect here referred to as delayed shock deficit. Spaced context preexposure produced similar inhibitory effects. Significantly, the introduction of a brief change of context prior to conditioning completely reversed the deficit induced by massed, but not by distributed, context preexposure. This reversibility was inversely relat…
Electrolytic lesion of the nucleus incertus retards extinction of auditory conditioned fear
2013
Fear memory circuits in the brain function to allow animals and humans to recognize putative sources of danger and adopt an appropriate behavioral response; and research on animal models of fear have helped reveal the anatomical and neurochemical nature of these circuits. The nucleus (n.) incertus in the dorsal pontine tegmentum provides a strong GABAergic projection to forebrain ‘fear centers’ and is strongly activated by neurogenic stressors. In this study in adult male rats, we examined the effect of electrolytic lesions of n. incertus on different stages of the fear conditioning-extinction process and correlated the outcomes with anatomical data on the distribution of n. incertus-derive…
How to preserve and handle fish liver samples to conserve RNA integrity
2019
As transcriptomic studies are becoming more and more common, it is important to ensure that the RNA used in the analyses is of good quality. The RNA integrity may be compromised by storage temperature or freeze-thaw cycles, but these have not been well studied in poikilothermic fishes. This work studied the effects of tissue storage time and temperature, and freeze-thaw cycles of tissue and extracted RNA on RNA integrity in brown trout (Salmo trutta L.) liver. The storage time and temperature had an effect on RNA integrity, but RNA suitable for quantitative reverse transcription PCR (RT-qPCR) (RIN > 7) was still obtained from samples preserved at − 20 °C for 6 months. Freeze-thaw cycles of …
Rotarod impairment: catalepsy-like screening test for antipsychotic side effects.
2009
Extrapyramidal motoric symptoms are casual side effects under antipsychotic medication. New generation antipsychotics are expected to have a reduced risk due to different receptor affinities. Here, haloperidol and the new generation antipsychotics, risperidone, amisulpride, and aripiprazole, were examined with both catalepsy test and rotarod performance test to screen for their usability in mice. Mice treated with haloperidol, risperidone, and aripiprazole showed dose and time-dependent impairment. Amisulpride-treated mice showed no signs of catalepsy. Catalepsy test and rotarod performance test were useful methods to detect side effects of both generation antipsychotics. Catalepsy test pro…