Low Glycerol Concentrations Research Articles

Combination of trehalose and low boron in presence of decreased glycerol improves post-thawed ram sperm parameters: A model study in boron research.

Sperm cryopreservation has been widely used in the field of reproductive biotechnology. It applies to certain males of economic and scientific values, including livestock breeds or endangered animal species. The development of a semen extender with a low cryoprotectant concentration and an appropriate amount of trehalose and boron can prevent the deterioration of sperm parameters. The main goal of this study is to establish a suitable ram extender model, by examining different combinations of high (5%) and low (3%) glycerol concentrations (to reduce its toxic effects on sperm freezing), a fixed amount of trehalose and an increased dose of boron to prevent the deterioration of sperm parameters, and investigate the levels of gene expressions. The Merino ram ejaculates were collected. The collected ejaculates providing the defined criteria were pooled. The pooled ejaculates were divided into eight aliquots and diluted with the Tris extender including different combinations of glycerol (5% and 3%) and boron (0.25, 0.5, and 1mm) concentrations and a fixed amount of trehalose, then frozen. After freeze-thawing process, sperm motility, mitochondrial membrane activity, plasma membrane integrity, acrosomal membrane integrity, DNA damage (single cell gel electrophoresis (COMET) and TUNEL assays) as well as NAD(P)H quinone oxyreductase (NQO1), glutamate-cycteine ligase (GCLC), and glutathione S-transferase (GSTP1) for molecular mechanisms of sperm cell response to oxidative stress were assessed for different extender groups following freeze-thawing process: 5% glycerol+0mm boron (G5B0.00), 5% glycerol+0.25mm boron (G5B0.25), 5% glycerol+0.5mm boron (G5B0.50), 5% glycerol+1mm boron (G5B1.00), 3% glycerol+0mm boron (G3B.00), 3% glycerol+0.25mm boron (G3B0.25), 3% glycerol+0.5mm boron (G3B0.50), and 3% glycerol+1mm boron (G3B1.00). G3B0.25 presented higher percentages of subjective motility, mitochondrial activity, and viability of spermatozoa comparing with G5B0.00 and groups with boron. Supplementation of 0.25mm boron with and without trehalose (G3B0.25 and G5B0.25) showed higher acrosome integrity, compared with G5B0.00, G5B1.00, G3B0.50, and G3B1.00. For TUNEL analysis, G3B1.00 showed the highest DNA integrity among the experimental groups which was statistically significant only with G5B0.50 (p<0.05). The mRNA levels of NQO1 were significantly decreased in G5B1.00, G3B0.50, and G3B1.00, when compared to G5B0.00. In comparison with G5B0.00, supplementation of 1mm boron with and without trehalose had significantly lower expression of GCLC. The level of GSTP1 gene was significantly lower (approximately threefold) in G3B1.00, compared to G5B0.00 (p<0.05). It can be assumed that the increase of the boron concentration in the extender may have important adverse effects on sperm parameters and antioxidant gene expression after thawing. The results obtained from this study will help to understand the toxicity limits of boron and eliminate the toxicity of glycerol in studies of gametes and tissue freezing. Therefore, it can be concluded that the use of sufficient boron can decrease cryodamages of cryopreservation of mammalian spermatozoa as well tissue engineering.

Computing the Structural Dynamics of RVFV L Protein Domain in Aqueous Glycerol Solutions.

Many biological and biotechnological processes are controlled by protein–protein and protein–solvent interactions. In order to understand, predict, and optimize such processes, it is important to understand how solvents affect protein structure during protein–solvent interactions. In this study, all-atom molecular dynamics are used to investigate the structural dynamics and energetic properties of a C-terminal domain of the Rift Valley Fever Virus L protein solvated in glycerol and aqueous glycerol solutions in different concentrations by molecular weight. The Generalized Amber Force Field is modified by including restrained electrostatic potential atomic charges for the glycerol molecules. The peptide is considered in detail by monitoring properties like the root-mean-squared deviation, root-mean-squared fluctuation, radius of gyration, hydrodynamic radius, end-to-end distance, solvent-accessible surface area, intra-potential energy, and solvent–peptide interaction energies for hundreds of nanoseconds. Secondary structure analysis is also performed to examine the extent of conformational drift for the individual helices and sheets. We predict that the peptide helices and sheets are maintained only when the modeling strategy considers the solvent with lower glycerol concentration. We also find that the solvent-peptide becomes more cohesive with decreasing glycerol concentrations. The density and radial distribution function of glycerol solvent calculated when modeled with the modified atomic charges show a very good agreement with experimental results and other simulations at .

Exploring the application and mechanism of sodium hyaluronate in cryopreservation of red blood cells.

The cryopreservation of red blood cells (RBCs) is essential for transfusion therapy and maintaining the inventory of RBCs units. The existing cryoprotectants (CPAs) have many defects, and the search for novel CPAs is becoming a research hotspot. Sodium hyaluronate (SH) is polymerized from sodium glucuronate and N-acetylglucosamine, which has good water binding capacity and biocompatibility. Herein, we reported for the first time that under the action of medium molecular weight sodium hyaluronate (MSH), the thawed RBCs recovery increased from 33.1 ​± ​5.8% to 63.2 ​± ​3.5%. In addition, RBCs functions and properties were maintained normally, and the residual MSH could be removed by direct washing. When MSH was used with a very low concentration (5% v/v) of glycerol (Gly), the thawed RBCs recovery could be increased to 92.3 ​± ​4.6%. In general, 40% v/v Gly was required to achieve similar efficiency. A mathematical model was used to compare the performance of MSH, PVA and trehalose in cryopreservation, and MSH showed the best efficiency. It was found that MSH could periodically regulate the content of intracellular water through the “reservoir effect” to reduce the damages during freezing and thawing. Moreover, MSH could inhibit ice recrystallization when combined with RBCs. The high viscosity and strong water binding capacity of MSH was also conducive to reducing the content of ice. This works points out a new direction for cryopreservation of RBCs and may promote transfusion therapy in clinic.

Carbon catabolite repression occurrence in photo fermentation of ethanol-rich substrates

The paper investigates the phenomenon of Carbon Catabolite Repression occurring during photo fermentation of ethanol-rich effluents, which usually contain ethanol as main carbon source, and glycerol as secondary one. The study was conducted using mixed phototrophic cultures, adopting, as substrate, the effluent produced by the alcoholic fermentation of sugar cane bagasse. In order to elucidate the phenomenon, experimental tests were carried out using two different ethanol to glycerol ratios. Results were compared with those resulting from pure ethanol and glycerol conversion. According to the obtained data, as a result of Carbon Catabolite Repression occurrence, the presence of glycerol negatively affects hydrogen production. Indeed, part of the ethanol source is converted to biomass and polyhydroxybutyrate rather than to hydrogen. In more details, the presence of glycerol determines a drop of the hydrogen production, which goes from 12 % to 32 %, according to the ethanol/glycerol ratio, compared to the production obtained from fermentation of ethanol alone. Therefore, to promote the hydrogen production, it is advisable to apply strategies to produce low glycerol concentrations in the ethanol production stage.

Biodegradable films from fishing industry waste: Technological properties and hygroscopic behavior

The objective was to evaluate the effect of glycerol on functional properties and sorption behavior of films elaborated with myofibrillar proteins of fish. Analyses of solubility, water vapor permeability (WVP), tensile strength (TS), elongation, and moisture sorption isotherms were performed. Films with lower glycerol concentrations (5, 10, and 15%) showed lower (p ≤ 0.05) permeability when compared to films with 30 and 40%. The increase in the glycerol concentration decreased the TS and increased the elongation of the lyophilized myofibrillary protein films (p ≤ 0.05). Glycerol significantly affected the solubility properties, with an increase of 95.96%. In the sorption process, the films presented curves types II and III, in which high concentrations of glycerol increased their water content. The sorption hysteresis decreased when the concentration of glycerol increased up to its disappearance in films with 40% glycerol. The GAB model was adequate to represent the sorption process of biodegradable films in the relative humidity range of 10–85% under the studied conditions. Films based on fish myofibrillar proteins in the presence of glycerol increase the water's binding capacity to mono and multilayers, and depending on the packaged food, like fresh produce, can preserve the moisture in the food, prolonging its shelf-life.

Self-Assembling Metabolon Enables the Cell Free Conversion of Glycerol to 1,3-Propanediol

Cell free biocatalysis is showing promise as a replacement or complement to conventional microbial biocatalysts due to the potential for achieving high yields, titers, and productivities. However, there exist several challenges that need to be addressed before its broader industrial adoption is achieved. New paradigms and innovative solutions are needed to overcome these challenges. In this study we demonstrate high levels of glycerol conversion to 1,3-propanediol using a self-assembling metabolic pathway leveraging the arraying strategy (protein scaffolds) used by thermophilic cellulolytic bacteria to assemble their biomass degrading enzymes. These synthetic metabolons were capable of producing 1,3-PDO at a yield more than 95% at lower glycerol concentration and close to 70% at higher concentrations at a higher productivity rate than the equivalent microbial strain. One of the benefits of our approach is the fact that no enzyme purification is required, and that the assembly of the complex is accomplished in vivo before immobilization, while product formation is conducted in vitro. We also report the recovery of enzymatic activity upon fusion enzymes binding to these protein scaffolds, which could have broader applications when assembling arrayed protein complexes.

Mathematical modelling of Love waves propagation in viscoelastic waveguide loaded with complex fluids

Love waves propagation in a viscoelastic waveguide loaded on its surface with viscoelastic fluids of finite thickness is investigated in this paper. The Maxwell and Kelvin-Voigt constitutive equations are employed in order to describe the fluid viscoelasticity. By solving the equations of motion in the different media (viscoelastic fluid, viscoelastic waveguide and elastic substrate) and imposing the suitable boundary conditions, an accurate and simple generalized complex dispersion equation is established for Love waves. Subsequently, a comparison is made with the published complex dispersion equations in the literature in some particular cases, and a very good agreement is showed. A detailed study was conducted by varying key parameters such as operating frequency, waveguide thickness and fluid thickness. The waveguide surface was subjected to various glycerol concentrations, with a wide range of dynamic viscosity, representing both Newtonian and viscoelastic behaviors. Theoretical analysis shows that to reasonably predict the characteristics responses of Love waves, the Maxwell fluid is more appropriate for low glycerol concentration and, the Kelvin-Voigt fluid is more suitable for high glycerol concentration and at high frequency. Results also evaluated the influence of layer thickness on the dispersion curves. The obtained results can be very useful in the design and optimization of Love wave fluid sensors.

Fine-tuned dehydration by trehalose enables the cryopreservation of RBCs with unusually low concentrations of glycerol.

The clinical transfusion of red blood cells (RBCs) has provided the greatest number of cryobiology applications in the case of rare blood groups and antibody problems, as well as civil and military disasters. The main technical difficulty with the current clinical technique is the removal of high concentration glycerol (20% or 40%) after thawing. Reducing the probability of intracellular ice formation (IIF) as well as preventing the solution effect are crucial to ensure RBCs avoid cryoinjury. Here, the non-permeating cryoprotectant trehalose was used to dehydrate RBCs before freezing. Furthermore, with the substitution of the low concentration glycerol (5% or 7.5%) for the intracellular remaining water, the bulk of RBCs were successfully cryopreserved to obtain a nearly 95% high survival rate with rapid cooling via EP tubes. Additionally, the washed RBCs after cryopreservation maintained their morphology, deformability, ATP, and 2-3 DPG levels, and all of them met the clinical standards for transfusion safety. Moreover, the whole addition and washing process was simple and easy to operate and could be completed within 30 min, which is crucial for emergency uses. This method will provide more potential for current clinical RBCs cryopreservation practices.

Glycerol dehydrogenation steps on Au/C surface in alkaline medium: An in-situ ATR-FTIR approach

The glycerol oxidation reaction (GLYOR) was evaluated using an Au/C electrocatalyst under alkaline conditions and varying glycerol (GLY) concentration. This electrocatalyst was synthesized by the borohydride reduction method. Au/C was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrochemical techniques associated with in situ attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR). XRD diffractograms showed the presence of Au (fcc). Cyclic voltammetry assisted by ATR-FTIR in situ measurements revealed that GLY oxidation on gold leads to the formation of a high amount of glyceraldehyde (GLYAD) for low GLY concentrations, while a lower amount of GLYAD was observed and the formation of dihydroxyacetone (DHA) was prevalent for high GLY concentrations. For high GLY concentrations DHA is almost stable, whereas for low GLY concentration DHA is fast oxidized to hydroxypyruvate. The excellent GLYOR activity of the Au/C catalyst in low GLY concentrations leads to the formation of deeper oxidized C1 species.

Physicochemical composition and fermentation kinetics of a novel Palm Sap-based Kefir Beverage from the fermentation of Borassus aethiopum Mart. fresh sap with kefir grains and ferments

Palm sap collected (sugary juice) from palm trees is very widespread in the intertropical regions of Asia, America and Africa. This study aimed to evaluate the use of kefir grains and ferments as starters for the fermentation of fresh palm sap (PS) from Borassus aethiopum Mart. to produce new kefir-like beverages (KLBs). The batch fermentation was performed statically at room temperature (22 °C) during 48 h. Physicochemical analysis were performed using standard and HPLC methods. The KLBs (kefir-like beverages) from PS showed low ethanol and glycerol contents ranging from 0.84 ± 0.14 to 17.30 ± 2.06 g/L (0.07 to 1.38% v/v) and 0 to 0.67 g/L respectively. The pH value decreased significantly during 24 h of fermentation and ranging from 3.98 to 4.40 at the end of fermentation. The organic acids (lactate, acetate, propionate, citrate, succinate and pyruvate) were detected in KLBs from PS. There was an increase in the content of lactate, acetate, propionate and succinate during fermentation process, except citrate content. Lactate and acetate content reached maximum values ranging between 5.18 and 9.31 g/L, 0.94 and 1.69 g/L respectively. Sucrose concentration decreased significantly and reached a value ranging from 0 to 0.84 g/L, except in KLBs fermented using milk ferments (9.45 g/L). The study showed that water and milk kefir grains as well as kefir ferments were well adapted to ferment Borassus aethiopum Mart. fresh sap for KLBs production. Palm sap could be an ideal alternative base substrate to produce non-dairy probiotic fermented beverage with low ethanol and sugar contents.

Morphology Modulation of Ionic Surfactant Micelles in Ternary Deep Eutectic Solvents.

Deep eutectic solvents (DES) are potentially greener solvents obtained through the complexation of simple precursors which, among other applications, have been investigated in recent years for their ability to support the self-assembly of amphiphilic molecules. It is crucial to understand the factors which influence surfactant solubility and self-assembly with respect to the interaction of the surfactant molecule with the DES components. In this work, small-angle neutron scattering (SANS) has been used to investigate the micellization of cationic (CnTAB) and anionic (SDS) surfactants in a ternary DES comprising choline chloride, urea, and glycerol, where the hydrogen bond donors are mixed in varying molar ratios. The results show that in each case either globular or rodlike micelles are formed with the degree of elongation being directly dependent on the composition of the DES. It is hypothesized that this composition dependence arises largely from the poor solubility of the counterions in the DES, especially at low glycerol content, leading to a tighter binding of the counterion to the micelle surface and giving rise to micelles with a high aspect ratio. This potential for accurate control over micelle morphology presents unique opportunities for rheology control or to develop templated syntheses of porous materials in DES, utilizing the solvent composition to tailor micelle shape and size, and hence the pore structure of the resulting material.

Characterization and properties of non-granular thermoplastic starch—Clay biocomposite films

Biocomposite films were prepared using as raw materials non-granular normal maize starch plasticized with glycerol and Na-montmorillonite clay particles in various concentrations. The physicochemical properties of films were studied, and their structure and morphology were investigated using XRD analysis, Thermal analysis, Scanning Electron Microscopy combined with Element Microanalysis. The mechanical characteristics were investigated through tensile test. The results indicated that the presence of clay particles in the starch matrix reduced the water absorption rate of films in comparison to starch films containing glycerol but not clay particles. The biocomposite films exhibited enhanced tensile properties at low glycerol and high clay contents. Best results were obtained for films containing 20 wt% glycerol and 10–20 wt% clay content. It is suggested that the non-granular maize starch, is a suitable raw material for the preparation of biocomposite films with improved structural and mechanical characteristics in comparison to films prepared using granular starch.

Viscous Media Slow Down the Decay of the Key Intermediate in Bacterial Bioluminescent Reaction.

The effects of medium viscosity on the decay rate of the 4a-hydroperoxyflavin intermediate of the bioluminescent reaction was investigated. It was found that at low concentrations of glycerol or sucrose (viscosity 1.1-1.3 cP) the decay rate rises, whereas a further increase in viscosity to 6.2 cP leads to a decrease in the decay rate following a power function with an exponent of 0.82-0.84. Using molecular dynamics methods, it was shown that the presence of glycerol and sucrose molecules causes a change in the mobility of the amino acid residues in the active center of luciferase, particularly those responsible for binding of flavin. The results obtained are indicative of two opposite effects of viscous media with glycerol and sucrose: (1) destabilization of 4a-hydroperoxyflavin due to a change in the structural and dynamic properties of the protein and (2) stabilization of this intermediate by the decrease in the diffusion rate of its decay products.

Self-recording the skin hydration and Trans-Epidermal Water Loss parameters: A pilot study.

To evaluate the reliability of data self-recorded by subjects enrolled in a study for skin surface hydration and Trans-Epidermal Water Loss (TEWL). A connected device, previously described, simultaneously records both the hydration status and the TEWL on the same skin site. The effects of a Xanthane-based gel containing low concentrations of glycerol (3% or 7%) applied on both face and forearms of Caucasian women, were self-recorded at various times for 24hours, outside of Research facility. In the first-hour post application, the skin hydration and TEWL values show a sharp increase and decrease, respectively. They progressively recover their initial values 24hours post washing, on both skin sites. A significant dose effect of glycerol (ie, 3% vs 7%) was obtained on both skin sites. The repeatability of data was found acceptable in both parameters, although more precise on arms than face, probably linked to an easier handling of the device. The use of this skin measuring connected device outside of Research facility, following a training of subjects, leads to reliable data. Such approach could be extended to other connected devices.

Molecular velocity auto-correlations in glycerol/water mixtures studied by NMR MGSE method

Molecular dynamics in binary mixtures of water and glycerol was studied by measuring the spectrum of water velocity auto-correlation in the frequency range from 0.05−10 kHz by using the NMR method of modulated gradient spin echo. The method shows that the diversity of diffusion signature in the short spin trajectories provides information about heterogeneity of molecular motion due to the motion in the micro-vortexes of hydrodynamic fluctuation, which is especially pronounced for the mixtures with low glycerol content. As concentration of glycerol increases above 10vol%, a new feature of spectrum appears due to interaction of water molecules with the clusters formed around hydrophilic glycerol molecules. New spectrum exposes a rate thickening of molecular friction, according to Einstein–Smoluchowski–Kubo formula, which inhibits rapid molecular motions and creates the conditions for a slow process of spontaneously folding of disordered poly-peptides into biologically active protein molecules when immersed in such a mixture.

Microtubule Seeded-assembly in the Presence of Poorly Nucleating Nucleotide Analogues.

Microtubule dynamic instability is driven by the hydrolysis of the GTP bound to the β-subunit of the α-β tubulin heterodimer. Nucleotide analogues are commonly used to mimic the different steps of the tubulin GTPase cycle, but most of them are poor microtubule nucleators. Usually, microtubule assembly is seeded by guanylyl-(α, β)-methylene-diphosphonate (GMPCPP) or glycerol that can be limiting factors in monitoring the effect of other nucleotide analogs on their polymerization. Here, we describe a protocol that allows the assembly of microtubules in the presence of nucleotide analogues without the need of heterogeneous seeds and at a low final glycerol concentration. Microtubules are first assembled in the presence of the analogue of interest and glycerol to promote assembly. These microtubules are then sonicated to produce seeds that will be used to assemble microtubules in the absence of glycerol. This strategy produces homogeneous nucleotide-bound microtubules that can be further analyzed by biochemical or structural methods such as cryo-electron microscopy.

Electrochemical Valorization of Glycerol on Ni-Rich Bimetallic NiPd Nanoparticles: Insight into Product Selectivity Using in Situ Polarization Modulation Infrared-Reflection Absorption Spectroscopy

Glycerol partial electrooxidation was studied on NixPd1–x (x = 100, 95, 90, and 80 atom %) nanoparticles synthesized using a polyol method. The shape-controlled urchin-like monometallic Ni and spherical NixPd1–x catalysts were synthesized. The morphology, crystal structure, and composition of Ni-rich catalysts were characterized using a number of physicochemical techniques. Detailed electrochemical characterizations showed that Ni and NixPd1–x NPs are active for GEOR and that the reaction follows either the direct electron transfer mechanism at low glycerol concentrations or the indirect electron transfer mechanism at high concentration. Among all investigated electrocatalysts, Ni80Pd20 exhibited the highest current density at lower overpotentials due to both a synergetic effect of Ni and Pd and the smaller particle size of Ni80Pd20. In situ polarization modulation infrared-reflection absorption spectroscopy (PM-IRRAS) at various anodic potentials allowed discriminating the reaction products and intermediates directly on the electrode surface and in the electrolyte solution. PM-IRRAS showed that the main reaction products on NixPd1–x are glyceraldehyde, carbonyl groups for mesoxalate and tartronate ions, carboxylate ions, and traces of carbon dioxide. NixPd1–x catalysts are promising anode materials for glycerol oxidation to value added products and could be potentially combined with cathodic hydrogen production or CO2 electro-reduction processes in alkaline media.

Effect of the degree of acetylation, plasticizer concentration and relative humidity on cassava starch films properties

Abstract The objective of this study was to develop films with reduced hygroscopicity and improved mechanical properties from acetylated cassava starch. For that, an acetylation procedure using acetic anhydride as the esterification reagent was performed, resulting in starch acetates with degrees of substitution (DS) of 0.6 (S0.6) and 1.1 (S1.1). Twelve films formulations were studied: native cassava starch (S), starch acetate S0.6 and S1.1, with two glycerol concentrations (0.25 g.100 g-1 (25) and 0.30 g.100 g-1 (30)). The films were conditioned at the relative humidities (RH) of 58% and 75% for 96 h before characterization. Water vapor permeability, water solubility, water sorption isotherms, microstructural analyses, and mechanical properties in different relative humidity and different glycerol concentration were performed. Starch acetate films (S1.1) resulted in lower water vapor permeability (2.35 ± 0.26 × 10-7g/m.s.Pa) and water solubility (21.2 ± 0.16 g.100 g-1) than native starch films (3.79 ± 0.26 × 10-7 g/m.s.Pa and 25.46 ± 0.12 g.100 g-1). S0.6 films showed higher tensile strength (8.42 ± 0.84 MPa) than S1.1 films (6.93 ± 0.55 MPa). The results indicated that acetylated starch can be used to produce films with improved mechanical properties, with less water solubility and permeability to water vapor, especially when starch acetate with 0.6 DS and low glycerol concentration are used. Chemical compounds used in this article: Starch, acetate (PubChem CID: 24832118); Acetic acid (PubChem CID: 176); Acetic anhydride (PubChem CID: 7918); Sulfuric acid (PubChem CID: 1118); Glycerol (PubChem CID: 753).

Comparison of the Effects of Five Semen Extenders on the Quality of Frozen-Thawed Equine Epididymal Sperm

Cryopreservation of epididymal sperm allows the saving of genetic material in case of unexpected death or emergency castration. The aim of the present study was the comparison of five different combinations of extenders commercially available for equine frozen semen processing for cryopreservation of epididymal sperm. Epididymal sperm were harvested from gonads of 10 healthy stallions after routine castration by retrograde flush technique. Then, samples were split and diluted with (1) INRA96 + INRA Freeze, (2) BotuSemen + BotuCRIO, (3) EquiPlus + Gent Freeze, (4) EquiPlus + EquiPlus Freeze, and (5) Gent + Gent Freeze. Extenders 1 and 2 showed higher values for total and progressive motility after thawing compared with extender 4 (P < .05). Extender 3 was in between 1 and 2 (P > .05), and extender 5 resulted in the lowest values (P < .05). The subpopulation of viable frozen-thawed sperm with high mitochondrial membrane potential and low intracellular calcium content was higher using extender 1 compared with extenders 3, 4, and 5 (P < .05) and higher in extender 2 compared with extenders 4 and 5 immediately after thawing (P < .05). After 1 hour of incubation, this subpopulation yielded the highest values in extender 2 (P < .05). Immediately after thawing, extender 1 yielded higher values for percentage of DFI and mean DFI than extenders 3, 4, and 5 (P < .05). Following 1 hour of incubation after thawing, sperm processed with extender 1 resulted in the highest values for percentage of DFI and mean DFI (P < .05). Using extender 2, mean DFI values were lower than those in extender 1 and higher than the extenders 3, 4, and 5 (P < .05). The study revealed that according to the examined sperm quality parameters, freezing extenders (extender 1, extender 2) using low concentrations of glycerol either combined with or without methylformamide were beneficial for cryopreservation of stallion epididymal sperm. For processing of stallion epididymal sperm, an extender containing milk proteins (extenders 1–4) for initial dilution after sperm harvesting is preferable to an extender including egg yolk (extender 5).

Improved Oxidative Biostability of Porous Shape Memory Polymers by Substituting Triethanolamine for Glycerol.

While many aromatic polyurethane systems suffer from poor hydrolytic stability, more recently proposed aliphatic systems are oxidatively-labile. The use of the renewable monomer glycerol as a more oxidatively-resistant moiety for inclusion in shape memory polymers (SMPs) is demonstrated here. Glycerol-containing SMPs and the amino alcohol control compositions are compared, with accelerated degradation testing displaying increased stability (time to complete mass loss) as a result of the inclusion of glycerol without sacrificing the shape memory, thermal transitions, or the ultralow density achieved with the control compositions. Gravimetric analysis in accelerated oxidative solution indicates that the control will undergo complete mass loss by approximately 18 days, while lower concentrations of glycerol will degrade fully by 30 days and higher concentrations will possess approximately 40% mass at the same time. In real time degradation analysis, high concentrations of glycerol SMPs have 96% mass remaining at 8 months with 88% gel fraction remaining that that time, compared to less than 50% mass for the control samples with 5% gelation. Mechanically, low glycerol-containing SMPs were not robust enough for testing at three months, while high glycerol concentrations displayed increased elastic moduli (133% of virgin materials) and 18% decreased strain to failure. The role of the secondary alcohol, as well as isocyanates, is presented as being a crucial component in controlling degradation; a free secondary alcohol can more rapidly undergo oxidation or dehydration to ultimately yield carboxylic acids, aldehydes, carbon dioxide, and alkenes. Understanding these pathways will improve the utility of medical devices through more precise control of property loss and patient risk management through reduced degradation.