Effect of thermomechanical pre-treatment on short- and long-term Ni release from biomedical NiTi

The effect of annealing and deformation on short-term (21 days) and long-term (8 months) Ni release from biomedical NiTi wires is studied. The deformation of annealed NiTi wires causes cracking and flaking of the surface oxide layer. Flaking of oxide particles does not uncover the Ni-rich layer underneath the surface oxide layer, since at sites where flaking occurs, a thin (∼25 nm) layer of oxide remains on top of this Ni-rich layer. The number of cracks in the oxide and Ni-rich layer, respectively, increases with deformation, and intercrystalline crack propagation into the Ni-rich layer and the NiTi bulk is observed. In plastically deformed wires, the cracks may remain opened, providing access of immersion liquid to these zones. Characteristics and quantity of short-term Ni release are significantly affected by the pre-deformation, resulting in an up to 2 times higher total Ni release within the first 21 days of deformed compared to annealed wires. Pre-deformation does not significantly influence long-term Ni release; all annealed and deformed samples exhibit similar long-term Ni release rates. The source of Ni during short-term release is the Ni contained in the surface zone of the oxide layer. For high pre-deformation, the Ni-rich layer is a second source for Ni. This second source is also the cause for Ni release in long-term immersion experiments.     

Mechanism of oxide layer growth during annealing of NiTi

After annealing at 540°C, NiTi is covered by a characteristic oxide layer with an Ni-containing outer and an Ni-free inner titanium oxide region. To elucidate details of the yet unclear formation process, samples were annealed in an atmosphere containing different oxygen isotopes at a time and analyzed by nondestructive ion beam techniques at different stages of the oxidation. During the heating stage, an oxygen permeable "low Ni" titanium oxide forms, and the oxide layer grows inward. Subsequently, when the annealing temperature of 540°C is reached, Ni-free stoichiometric titanium oxide forms and inhibits the transport of oxygen toward the bulk. Thus, the oxide layer growth changes to outward, and the final location of the reaction front between O and Ti is inside the oxide layer at the transition of "low Ni" oxide to "Ni-free" oxide. Consequently, the annealing conditions during inward oxide layer growth govern the surface properties, whereas the conditions during outward oxide layer growth are uncritical with respect to the surface properties. The findings are directly applicable to set the amount of surface Ni of NiTi devices, provide basis for detailed interpretation of experimental results involving annealing of NiTi, and can further respective modeling.     

New oxidation treatment of NiTi shape memory alloys to obtain Ni-free surfaces and to improve biocompatibility

Various oxidation treatments were applied to nearly equiatomic NiTi alloys so as to form a Ni-free protective oxide on the surface. Sample surfaces were analyzed by X-ray Photoelectron Spectroscopy, and NiTi transformation temperatures were determined by differential scanning calorimetry (DSC) before and after the surface treatment. An ion release experiment was carried out up to one month of immersion in SBF for both oxidized and untreated surfaces. The results show that oxidation treatment in a low-oxygen pressure atmosphere leads to a high surface Ti/Ni ratio, a very low Ni surface concentration and a thick oxide layer. This oxidation treatment does not significantly affect the shape memory properties of the alloy. Moreover, the oxide formed significantly decreases Ni release into exterior medium comparing with untreated surfaces. As a consequence, this new oxidation treatment could be of great interest for biomedical applications, as it could minimize sensitization and allergies and improve biocompatibility and corrosion resistance of NiTi shape memory alloys.     

Ramp rate of blood pressure changes does not affect aortic afferent sensitivity in anesthetized rats

To investigate whether the rate of change in blood pressure affects the sensitivity of the aortic baroreceptor afferent response, the change in aortic nerve activity (ANA) to two different rates of ramp increase in mean blood pressure (MBP), elicited by phenylephrine administration, was determined in the rat under urethane (1.5 g kg⁻¹) anesthesia. The sensitivity of the increase in ANA following a rapid (average ramp rate, 9.14 ± 0.60 mmHg s⁻¹, n = 11) or gradual (1.78 ± 0.24 mmHg s⁻¹, n = 11) increase in MBP was 2.03 ± 0.14% and 1.81 ± 0.20% of baseline mmHg⁻¹, respectively. These values were not significantly different from each other (P = 0.16). Furthermore, we found no correlation between the rate of ramp increase in MBP and the sensitivity of the increase in ANA (r = 0.24, P = 0.29, n = 22). These results suggest that, at least within the normal physiological range of MBP, the rate of the ramp change in blood pressure does not affect aortic baroreceptor afferent sensitivity in the anesthetized rat.     

The effect of NO-donors on chloride efflux,intracellular Ca concentration and mRNA expression of CFTR and ENaC in cystic fibrosis airway epithelial cells

Since previous studies showed that the endogenous bronchodilator, S-nitrosglutathione (GSNO), caused a marked increase in CFTR-mediated chloride (Cl⁻) efflux and improved the trafficking of CFTR to the plasma membrane, and that also the nitric oxide (NO)-donor GEA3162 had a similar, but smaller, effect on Cl⁻ efflux, it was investigated whether the NO-donor properties of GSNO were relevant for its effect on Cl⁻ efflux from airway epithelial cells. Hence, the effect of a number of other NO-donors, sodium nitroprusside (SNP), S-nitroso-N-acetyl-dl-penicillamine (SNAP), diethylenetriamine/nitric oxide adduct (DETA-NO), and diethylenetriamine/nitric oxide adduct (DEA-NONOate) on Cl⁻ efflux from CFBE (?F508/?F508-CFTR) airway epithelial cells was tested. Cl⁻ efflux was determined using the fluorescent N-(ethoxycarbonylmethyl)-6-methoxyquinoliniu bromide (MQAE)-technique. Possible changes in the intracellular Ca^2 + concentration were tested by the fluorescent fluo-4 method in a confocal microscope system. Like previously with GSNO, after 4 h incubation with the NO-donor, an increased Cl⁻ efflux was found (in the order SNAP > DETA-NO > SNP). The effect of DEA-NONOate on Cl⁻ efflux was not significant, and the compound may have (unspecific) deleterious effects on the cells. Again, as with GSNO, after a short (5 min) incubation, SNP had no significant effect on Cl⁻ efflux. None of the NO-donors that had a significant effect on Cl⁻ efflux caused significant changes in the intracellular Ca^2 + concentration. After 4 h preincubation, SNP caused a significant increase in the mRNA expression of CFTR. SNAP and DEA-NONOate decreased the mRNA expression of all ENaC subunits significantly. DETA-NO caused a significant decrease only in α-ENaC expression. After a short preincubation, none of the NO-donors had a significant effect, neither on the expression of CFTR, nor on that of the ENaC subunits in the presence and absence of l-cysteine. It can be concluded that the effect of GSNO on Cl⁻ efflux is, at least in part, due to its properties as an NO-donor, and the effect is likely to be mediated by CFTR, not by Ca^2 +-activated Cl⁻ channels.     

Surface oxidation of NiTi shape memory alloy

Mechanically polished NiTi alloy (50 at% Ni) was subjected to heat treatment in air in the temperature range 300–800°C and characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. Thermogravimetry measurements were carried out to investigate the kinetics of oxidation. The results of thermodynamic calculations were compared to the experimental observations. It was found that NiTi alloy exhibits different oxidation behaviour at temperatures below and above 500°C. A Ni-free zone was found in the oxide layer for oxidation temperatures of 500°C and 600°C. The oxidation at 500°C produces a smooth protective nickel-free oxide layer with a relatively small amount of Ni species at the air/oxide interface, which is in favour of good biocompatibility of NiTi implants. The oxidation mechanism for the NiTi shape memory alloy is discussed.     

Novel soy protein wound dressings with controlled antibiotic release: mechanical and physical properties

Naturally derived materials are becoming widely used in the biomedical field. Soy protein has advantages over various types of natural proteins employed for biomedical applications due to its low price, non-animal origin and relatively long storage time and stability. In the current study soy protein isolate (SPI) was investigated as a matrix for wound dressing applications. The antibiotic drug gentamicin was incorporated into the matrix for local controlled release and, thus, protection against bacterial infection. Homogeneous yellowish films were cast from aqueous solutions. After cross-linking they combined high tensile strength and Young’s modulus with the desired ductility. The plasticizer type, cross-linking agent and method of cross-linking were found to strongly affect the tensile properties of the SPI films. Selected SPI films were tested for relevant physical properties and the gentamicin release profile. The cross-linking method affected the degree of water uptake and the weight loss profile. The water vapor transmission rate of the films was in the desired range for wound dressings (∼2300 g m⁻² day⁻¹) and was not affected by the cross-linking method. The gentamicin release profile exhibited a moderate burst effect followed by a decreasing release rate which was maintained for at least 4 weeks. Diffusion was the dominant release mechanism of gentamicin from cross-linked SPI films. Appropriate selection of the process parameters yielded SPI wound dressings with the desired mechanical and physical properties and drug release behavior to protect against bacterial infection. These unique structures are thus potentially useful as burn and ulcer dressings.     

Urethane inhibits genioglossal long-term facilitation in un-paralyzed anesthetized rats

For ∼3 decades, urethane has been (partially or solely) used as a successful anesthetic in numerous respiratory long-term facilitation (LTF) studies, which were performed on anesthetized, paralyzed, vagotomized and artificially ventilated animals of several different species. However, things become complicated when LTF of muscle activity is studied in un-paralyzed animals. For example, a commonly used acute intermittent hypoxia (AIH) protocol failed to induce muscle LTF in anesthetized, spontaneously breathing rats. But muscle LTF could be induced when hypoxic episode number was increased and/or anesthetics other than urethane were used. In these studies however, neither anesthetic nor paralysis was mentioned as a potential factor influencing AIH-induced muscle LTF. This study tested whether urethane inhibits AIH-induced genioglossal LTF (gLTF) in un-paralyzed ventilated rats, and if so, determined whether reducing urethane dose reverses this inhibition. Three groups of adult male Sprague–Dawley rats were anesthetized (Group 1: ∼1.6 g kg⁻¹ urethane; Group 2: 50 mg kg⁻¹ α-chloralose +0.9–1.2 g kg⁻¹ urethane; Group 3: 0.9 g kg⁻¹ urethane +200–400 μg kg⁻¹ min⁻¹ alphaxalone), vagotomized and mechanically ventilated. Integrated genioglossus activity was measured before, during and after AIH (5 episodes of 3-min isocapnic 12% O₂, separated by 3-min hyperoxic intervals). The AIH-induced gLTF was absent in Group 1 rats (success rate was only ∼1/7), but was present in Group 2 (in 10/12 rats) and Group 3 (in 11/11 rats) rats. The genioglossal response to hypoxia was not significantly different among the 3 groups. Collectively, these data suggest that urethane dose-dependently inhibits gLTF in un-paralyzed anesthetized rats.     

A comparative study of the cytotoxicity and corrosion resistance of nickel-titanium and titanium-niobium shape memory alloys

Nickel-titanium (NiTi) shape memory alloys (SMAs) are commonly used in a range of biomedical applications. However, concerns exist regarding their use in certain biomedical scenarios due to the known toxicity of Ni and conflicting reports of NiTi corrosion resistance, particularly under dynamic loading. Titanium-niobium (TiNb) SMAs have recently been proposed as an alternative to NiTi SMAs due to the biocompatibility of both constituents, the ability of both Ti and Nb to form protective surface oxides, and their superior workability. However, several properties critical to the use of TiNb SMAs in biomedical applications have not been systematically explored in comparison with NiTi SMAs. These properties include cytocompatibility, corrosion resistance, and alterations in alloy surface composition in response to prolonged exposure to physiological solutions. Therefore, the goal of the present work was to comparatively investigate these aspects of NiTi (49.2 at.% Ti) and TiNb (26 at.% Nb) SMAs. The results from the current studies indicate that TiNb SMAs are less cytotoxic than NiTi SMAs, at least under static culture conditions. This increased TiNb cytocompatibility was correlated with reduced ion release as well as with increased corrosion resistance according to potentio-dynamic tests. Measurements of the surface composition of samples exposed to cell culture medium further supported the reduced ion release observed from TiNb relative to NiTi SMAs. Alloy composition depth profiles also suggested the formation of calcium phosphate deposits within the surface oxide layers of medium-exposed NiTi but not of TiNb. Collectively, the present results indicate that TiNb SMAs may be promising alternatives to NiTi for certain biomedical applications.     

Localised micro-mechanical stiffening in the ageing aorta

Age-related loss of tissue elasticity is a common cause of human morbidity and arteriosclerosis (vascular stiffening) is associated with the development of both fatal strokes and heart failure. However, in the absence of appropriate micro-mechanical testing methodologies, multiple structural remodelling events have been proposed as the cause of arteriosclerosis. Therefore, using a model of ageing in female sheep aorta (young: <18 months, old: >8 years) we: (i) quantified age-related macro-mechanical stiffness, (ii) localised in situ micro-metre scale changes in acoustic wave speed (a measure of tissue stiffness) and (iii) characterised collagen and elastic fibre remodelling. With age, there was an increase in both macro-mechanical stiffness and mean microscopic wave speed (and hence stiffness; young wave speed: 1701 ± 1 m s⁻¹, old wave speed: 1710 ± 1 m s⁻¹, p < 0.001) which was localized to collagen fibril-rich regions located between large elastic lamellae. These micro-mechanical changes were associated with increases in both collagen and elastic fibre content (collagen tissue area, young: 31 ± 2%, old: 40 ± 4%, p < 0.05; elastic fibre tissue area, young: 55 ± 3%, old: 69 ± 4%, p < 0.001). Localised collagen fibrosis may therefore play a key role in mediating age-related arteriosclerosis. Furthermore, high frequency scanning acoustic microscopy is capable of co-localising micro-mechanical and micro-structural changes in ageing tissues.     

Microstructure,nickel suppression and mechanical characteristics of electropolished and photoelectrocatalytically oxidized biomedical nickel titanium shape memory alloy

A new surface modification protocol encompassing an electropolishing pretreatment (EP) and subsequent photoelectrocatalytic oxidation (PEO) has been developed to improve the surface properties of biomedical nickel titanium (NiTi) shape memory alloy (SMA). Electropolishing is a good way to improve the resistance to localized breakdown of NiTi SMA whereas PEO offers the synergistic effects of advanced oxidation and electrochemical oxidation. Our results indicate that PEO leads to the formation of a sturdy titania film on the EP NiTi substrate. There is an Ni-free zone near the top surface and a graded interface between the titania layer and NiTi substrate, which bodes well for both biocompatibility and mechanical stability. In addition, Ni ion release from the NiTi substrate is suppressed, as confirmed by the 10-week immersion test. The modulus and hardness of the modified NiTi surface increase with larger indentation depths, finally reaching plateau values of about 69 and 3.1 GPa, respectively, which are slightly higher than those of the NiTi substrate but much lower than those of a dense amorphous titania film. In comparison, after undergoing only EP, the mechanical properties of NiTi exhibit an inverse change with depth. The deformation mechanism is proposed and discussed. Our results indicate that surface modification by dual EP and PEO can notably suppress Ni ion release and improve the biocompatibility of NiTi SMA while the surface mechanical properties are not compromised, making the treated materials suitable for hard tissue replacements.     

In vitro bioactivity and osteoblast response of porous NiTi synthesized by SHS using nanocrystalline Ni-Ti reaction agent

Porous NiTi with an average porosity of 55 vol % and a general pore size of 100-600 microm was synthesized by self-propagating high temperature synthesis (SHS) with the addition of mechanically alloyed nanocrystalline Ni-Ti as the reaction agent. The SHS of porous NiTi using elemental powders was also performed for comparison. To enhance the bioactivity of the metal surface, porous NiTi synthesized by nanocrystalline Ni-Ti was subjected to chemical treatment to form a layer of TiO(2) coating. The porous NiTi with TiO(2) coating was subsequently immersed in a simulated body fluid (SBF) to investigate its apatite forming ability. The effects of the addition of nanocrystalline Ni-Ti as reaction agent and the application of apatite coating on osteoblastic behavior were studied in primary cultures of human osteoblast cells. Results showed that the main phases in porous NiTi synthesized by elemental powders were NiTi, Ti(2)Ni, and unreacted free Ni. By using nanocrystalline Ni-Ti as reaction agent, the secondary intermetallic phase of Ti(2)Ni was significantly reduced and the free Ni was eliminated. TiO(2) coating with anatase phase was formed on the surface of porous NiTi after the chemical treatment. A layer consisting of nanocrystalline carbonate-containing apatite was formed on the surface of TiO(2) coating after soaking in SBF. The preliminary cell culture studies showed that the porous NiTi synthesized with the addition of nanocrystalline Ni-Ti attracted marked attachment and proliferation of the osteoblast cells. This gives the evidence of the potential biomedical applications of the porous NiTi.     

Biocompatilibity-related surface characteristics of oxidized NiTi

In the present study, we examined the effect of NiTi oxidation on material surface characteristics related to biocompatibility. Correspondence between electron work function (EWF) and adhesive force predicted by electron theory of adsorption as well as the effect of surface mechanical stress on the adhesive force were studied on the nonoxidized and oxidized at 350, 450, and 600 degrees C NiTi alloy for medical application. The adhesive force generated by the material surface towards the drops of alpha-minimal essential medium (alpha-MEM) was used as a characteristic of NiTi adsorption properties. The study showed that variations in EWF and mechanical stress caused by surface treatment were accompanied by variations in adhesive force. NiTi oxidation at all temperatures used gave rise to decrease in adhesive force and surface stress values in comparison to the nonoxidized state. In contrary, the EWF value revealed increase under the same condition. Variations in surface oxide layer thickness and its phase composition were also followed. The important role of oxide crystallite size in EWF values within the range of crystallite dimensions typical for NiTi surface oxide as an instrument for the fine regulation of NiTi adsorption properties was demonstrated. The comparative oxidation of pure titanium and NiTi showed that the effect of Ni on the EWF value of NiTi surface oxide is negligible.     

Slower eating rate is independent to gastric emptying in obese minipigs

The aim of our study was to investigate whether the altered eating behavior observed in the context of a diet-induced metabolic syndrome is related to changes of the gastric emptying and autonomic balance. Eight adult male Göttingen minipigs were subjected during 5 months to ad libitum Western diet (WD). Several factors were compared between the lean (before WD) and obese conditions: general activity and eating behavior, gastric emptying, adiposity, glycemia and insulinemia during IVGTT, and heart rate variability (HRV). In our model, obesity did not alter the gastric emptying (258 ± 26 vs. 256 ± 14 min, P > 0.10) but induced insulin resistance: increased basal insulinemia (12.6 ± 0.8 to 36.6 ± 6.1 mU/l, P < 0.02) and reduced insulin sensitivity (4.5E−4 ± 0.7E−4 to 2.5E−4 ± 0.2E−4 min⁻¹ per mU.l⁻¹ of insulin, P < 0.05). The HRV and sympathovagal balance were not significantly modified (P > 0.10). Fed ad libitum with WD, animals overate durably (P < 0.001). During a 30-min meal test though, the ingestion speed, the food ingested (1076 ± 48 vs. 520 ± 52 g) and energy intake decreased in the obese condition (P < 0.05), which can be explained by the fragmentation of the daily caloric intake. These data suggest that the slower eating rate and increased number of meals observed in obese minipigs without neuropathy is independent to gastric emptying. The explanation may be sought rather in central modifications induced by obesity that might modify the food perception and/or motivation.     

Ni ion release, osteoblast-material interactions, and hemocompatibility of hafnium-implanted NiTi alloy

Hafnium ion implantation was applied to NiTi alloy to suppress Ni ion release and enhance osteoblast-material interactions and hemocompatibility. The auger electron spectroscopy, x-ray photoelectron spectroscopy, and atomic force microscope results showed that a composite TiO(2)/HfO(2) nanofilm with increased surface roughness was formed on the surface of NiTi, and Ni concentration was reduced in the superficial surface layer. Potentiodynamic polarization tests displayed that 4 mA NiTi sample possessed the highest E(br) - E(corr), 470 mV higher than that of untreated NiTi, suggesting a significant improvement on pitting corrosion resistance. Inductively coupled plasma mass spectrometry tests during 60 days immersion demonstrated that Ni ion release rate was remarkably decreased, for example, a reduction of 67% in the first day. The water contact angle increased and surface energy decreased after Hf implantation. Cell culture and methyl-thiazol-tetrazolium indicated that Hf-implanted NiTi expressed enhanced osteoblasts adhesion and proliferation, especially after 7 days culture. Hf implantation decreased fibrinogen adsorption, but had almost no effect on albumin adsorption. Platelets adhesion and activation were suppressed significantly (97% for 4 mA NiTi) and hemolysis rate was decreased by at least 57% after Hf implantation. Modified surface composition and morphology and decreased surface energy should be responsible for the improvement of cytocompatibility and hemocompatibility.     

Scalable production of microbially mediated zinc sulfide nanoparticles and application to functional thin films

A series of semiconducting zinc sulfide (ZnS) nanoparticles were scalably, reproducibly, controllably and economically synthesized with anaerobic metal-reducing Thermoanaerobacter species. These bacteria reduced partially oxidized sulfur sources to sulfides that extracellularly and thermodynamically incorporated with zinc ions to produce sparingly soluble ZnS nanoparticles with ∼5 nm crystallites at yields of ∼5 g l⁻¹ month⁻¹. A predominant sphalerite formation was facilitated by rapid precipitation kinetics, a low cation/anion ratio and a higher zinc concentration compared to background to produce a naturally occurring hexagonal form at the low temperature, and/or water adsorption in aqueous conditions. The sphalerite ZnS nanoparticles exhibited narrow size distribution, high emission intensity and few native defects. Scale-up and emission tunability using copper doping were confirmed spectroscopically. Surface characterization was determined using Fourier transform infrared and X-ray photoelectron spectroscopies, which confirmed amino acid as proteins and bacterial fermentation end products not only maintaining a nano-dimensional average crystallite size, but also increasing aggregation. The application of ZnS nanoparticle ink to a functional thin film was successfully tested for potential future applications.     

Highly efficient large-scale lentiviral vector concentration by tandem tangential flow filtration

Large-scale lentiviral vector (LV) concentration can be inefficient and time consuming, often involving multiple rounds of filtration and centrifugation. This report describes a simpler method using two tangential flow filtration (TFF) steps to concentrate liter-scale volumes of LV supernatant, achieving in excess of 2000-fold concentration in less than 3 h with very high recovery (>97%). Large volumes of LV supernatant can be produced easily through the use of multi-layer flasks, each having 1720 cm² surface area and producing ∼560 mL of supernatant per flask. Combining the use of such flasks and TFF greatly simplifies large-scale production of LV. As a demonstration, the method is used to produce a very high titer LV (>10¹⁰ TU/mL) and transduce primary human CD34+ hematopoietic stem/progenitor cells at high final vector concentrations with no overt toxicity. A complex LV (STEMCCA) for induced pluripotent stem cell (iPSC) generation is also concentrated from low initial titer and used to transduce and reprogram primary human fibroblasts with no overt toxicity. Additionally, a generalized and simple multiplexed real-time PCR assay is described for lentiviral vector titer and copy number determination.     

Gz- and not Gi-proteins are coupled to pre-junctional μ-opioid receptors in bovine airways

We investigated the signal transmission pathway by which activation of μ-opioid receptors attenuates acetylcholine (ACh) release in bovine trachealis. Electrical stimulation (ES)-induced [³H]-ACh release was determined in bovine tracheal smooth muscle strips pre-incubated with either the Gi-protein inhibitor pertussis toxin (PTX, 500 ng/ml and 1 μg/ml) or the Gz-protein specific inhibitor arachidonic acid (AA, 10⁻⁶ M and 10⁻⁵ M) and then treated with DAMGO (D-Ala²,N-MePhe⁴,Gly-ol⁵-enkephalin) 10⁻⁵ M. Indomethacin 10⁻⁵ M was used to block AA cascade. The inhibitory effect of DAMGO on ES-induced [³H]-ACh release was PTX-insensitive, but, by contrast, ablated by AA in a concentration-dependent manner. AA 10⁻⁵ M alone reduced [³H]-ACh release, an effect that was prevented by iberiotoxin 10⁻⁷ M, suggesting an involvement of Ca²⁺-activated K⁺-channels. Western blot analysis consistently showed immunoreactive bands against a specific antibody anti-Gz-α subunit at ∼40 kDa, consistent with the presence of Gz-protein. The present findings suggest that in isolated bovine trachealis, activation of μ-opioid receptors inhibits ACh-release through a signal transmission pathway involving Gz-protein rather than Gi-protein.     

The role of Cɛ2, Cɛ3, and Cɛ4 domains in human and canine IgE and their contribution to FcɛRIα interaction

The C?2 and C?4 domains are considered as scaffolds, allowing C?3 domains to assume an appropriate orientation to interact with Fc?RI (0130 and 0050). Human/canine IgE chimeric antibodies were expressed to assess the nature of the contribution of C?2 and C?4 domains to bind to and induce target cell degranulation via Fc?RIα. Our results indicate that for (1) C?3 domains in IgE of canine and human origin are the only necessary region for binding to Fc?RIα. (2) The interaction of canine IgE with human sFc?RIα is significantly enhanced by contributions from both C?2 and C?4 domains of dog origin. (3) The canine/human IgE chimeric antibody construct rapidly dissociates from its the receptor when the canine C?2 and C?4 domains are replaced by the homologous human Fc domains which do not confer a conformation on the C?3 domain to facilitate stable interaction with canine Fc?RIα. Kinetic constants for the binding of this chimera to the soluble extracellular domain of the receptor indicate an approximate 120-fold decrease in the affinity for canine sFc?RIα (k_a = 5.30 × 10² M⁻¹ s⁻¹) and a 330-fold increase in the dissociation from canine sFc?RIα (K_D = 6.9 × 10⁻⁶ M⁻¹), compared to the wild type IgE kinetic constants (K_a = 6.30 × 10⁴ M⁻¹ s⁻¹; K_D = 2.1 × 10⁻⁸ M⁻¹). Although canine IgE does engage human Fc?RIα, canine C?2 and C?4 do not contribute to the high-affinity of interaction with human Fc?RIα. Upon replacement of human C?2 and C?4 domain by the canine homologues, human IgE C?3 only retains a low affinity for the human receptor, which shows that C?2 and C?4 domains in human IgE Fc contribute significantly to the interaction with its cognate receptor.     

Effects of the glucose-lowering rate on cTnI and hs-CRP serum levels in type 2 diabetics

Objectives

The current objective is to evaluate the effect of intensive glycemic control on serum levels of both Cardiac Troponin I (cTnI) and high sensitivity C-reactive protein (hs-CRP) in subjects with type 2 diabetes. Hence, we are trying to find a reasonable glucose-lowering rate associated with type 2 diabetics with and without coronary heart disease.

Methods

A total of 132 type 2 diabetes mellitus without coronary heart disease (T2DM) cases and 135 type 2 diabetes mellitus with coronary heart disease (T2DM+CHD) cases received intensive glycemic control. Serum cTnI and hs-CRP levels were tested before and after intensive glycemic control.

Results

There was no significant difference in the changing amplitude of cTnI and hs-CRP serum levels variation between four glucose-lowering rates in T2DM group (P > 0.05), while this difference was observed in T2DM+CHD group(P < 0.05). During the follow-up, cTnI and hs-CRP serum levels were lower than those before glycemic control in both T2DM and T2DM+CHD groups (P < 0.05).

Conclusions

The glucose-lowering rate in T2DM+CHD group should be no more than 4 mmol L⁻¹ d⁻¹ and the appropriate glucose-lowering rate in T2DM group is no more than 6 mmol L⁻¹ d⁻¹. Serum levels of cTnI and hs-CRP will be increased if the glucose-lowering rate is over this range, which means that cardiovascular endpoints might be induced.