Post-thaw ATP supplementation enhances cryoprotective effect of iodixanol in rat spermatozoa

BACKGROUND

Successful cryopreservation of rat spermatozoa from various strains still remains a challenge. The objective of this study was to determine if combinations of OptiPrep™ (iodixanol) and adenosine 5'-triphosphate (ATP) can improve rat sperm function during the cryopreservation procedure.

METHODS

Epididymal rat spermatozoa were frozen under different OptiPrep™ concentrations (0, 1, 2, 3 or 4 %) and were diluted with media supplemented with or without 2 mM ATP after thawing. Post-thaw sperm motility, acrosomal membrane integrity (AMI) and mitochondrial membrane potential (MMP) were then evaluated. In addition, the effect of different OptiPrep™ concentrations on fresh and cooled rat spermatozoa was tested via motility.

RESULTS

There was no effect of OptiPrep™ on motility of fresh and cooled spermatozoa. The supplementation of 1 and 2 % OptiPrep™ increased motility of frozen spermatozoa at 10 min after thawing, while it did not improve motility of spermatozoa at 3 h after thawing in the absence of ATP. During incubation of thawed spermatozoa, the ATP addition protected time-dependent decrease in motility after thawing in OptiPrep™-treated samples. OptiPrep™ had no effect on AMI and MMP in frozen-thawed spermatozoa but combinations of OptiPrep™ and ATP improved MMP in frozen-thawed spermatozoa.

CONCLUSIONS

Iodixanol has cryoprotective effects during rat sperm freezing without any toxic effect. Moreover, the combinations of iodixanol and ATP have a beneficial role in maintaining function of frozen-thawed rat spermatozoa for long period of incubation post-thaw.

Prevalence of plasma small dense LDL is increased in obesity in a Thai population

BACKGROUND

Plasma low density lipoprotein (LDL) particles vary in size, density, electrical charge and chemical composition. An increased presence of small dense LDL (sdLDL), along with raised triglyceride concentrations and decreased high density lipoprotein (HDL) cholesterol concentrations is commonly known as the atherogenic triad and has been observed in some cases of obesity, principally in Europe and America. This study examines the prevalence of sdLDL in the plasma of an obese (BMI≥25 kg/m2) Thai population.

METHODS

Plasma from fasted obese (n=48) and non-obese (n=16) Thai participants was subjected to density gradient ultracentrifugation in iodixanol to separate lipoproteins. Gradients were unloaded top-to-bottom into 20 fractions which were assayed for cholesterol, triglyceride, apo B and apo A-1 to identify lipoprotein types and subtypes.

RESULTS

LDL cholesterol was subfractionated into LDL I+II (fractions 3-6, ρ=1.021-1.033 g/ml) which was considered to represent large buoyant LDL (lbLDL), LDL III (fractions 7-9, ρ=1.036-1.039 g/ml) which was considered to represent sdLDL, and, LDL IV (fractions 10-12, ρ=1.044-1.051 g/ml) which was considered to represent very sdLDL. Concentrations of LDL III and IV were increased by 15-20% in obese participants whilst that of LDL I+II was concomitantly decreased by 10%. This was accompanied by a 50% increase in plasma triglyceride concentrations and 15% decrease in HDL cholesterol concentrations. Only 3/16 (19%) non-obese participants had a pattern B LDL cholesterol profile (peak density of >1.033 g/ml), whilst 28/48 (58%) obese participants were pattern B. When expressed as a fraction of the LDL concentration, total sdLDL (i.e. LDL III+IV) showed highly significant correlations to plasma triglyceride concentrations and the triglyceride/HDL cholesterol ratio.

CONCLUSIONS

The prevalence of sdLDL is increased in obesity in a Thai population such that they demonstrate a similar atherogenic triad to that previously observed in European and American populations.

Acute generalized exanthematous pustulosis induced by iodixanol (Visipaque): a serious reaction to a commonly used drug

Acute generalized exanthematous pustulosis (AGEP) is an acute sterile pustular eruption most commonly induced by medications. Although antibiotics are the most commonly accused drugs in AGEP, non-antibiotic agents may also cause this disease. We present a case of AGEP following use of iodixanol for coronary angiography in a 61-year-old woman. Given the wide use of this substance in cardiology, clinicians should be aware of this potential complication.

Hemodialysis clearance of iosimenol, a novel iso-osmolar radiographic contrast medium

BACKGROUND

Iodinated contrast media (CM) have molecular and pharmacokinetic properties likely to make them highly dialyzable. Controlled clinical studies allowing for comparisons of hemodialysis clearance between different test substances and in multiple hemodialysis filters are, however, complex and not always practically feasible. A miniaturized in vitro method was therefore developed to evaluate the dialyzability of a new CM.

PURPOSE

To evaluate hemodialysis clearance of iosimenol, a novel iso-osmolar contrast medium (CM), in a select variety of hemodialysis filters and in comparison to commercially available CM.

MATERIAL AND METHODS

Three different high-flux and one low-flux membrane were used in miniaturized dialyzers to evaluate the in vitro blood clearance of iosimenol. Commercially available CM (iodixanol and iohexol) served as control substances. In vitro dialysis parameters were then used to predict clinical hemodialysis clearances. Residual ratios of endogenous substances (inorganic phosphate, urea nitrogen, creatinine, total bilirubin, and albumin) were used as proof of reliability of the in vitro dialysis system.

RESULTS

Dialyzable small endogenous molecules were readily eliminated in all membranes. The removal ratios of iosimenol were generally similar to that of iodixanol in all membranes except the high-flux polysulfone but were consistently lower than that of iohexol. The blood clearance of iosimenol during clinical hemodialysis was predicted as, on average, approximately 85 mL/min with the high-flux membranes and 47 mL/min with the low-flux membrane.

CONCLUSION

The dialyzability of iosimenol was evaluated using a newly developed in vitro dialysis system, and iosimenol was readily cleared from blood with all four tested membranes. And it is suggested that the dialysis parameters can predict clinical hemodialysis clearance of CM.

Effects of radiographic contrast media on the micromorphology of the junctional complex of erythrocytes visualized by immunocytology

Effects of radiographic contrast media (RCM) application were demonstrated in vitro and in vivo where the injection of RCM into the A. axillaris of patients with coronary artery disease was followed by a significant and RCM-dependent decrease of erythrocyte velocity in downstream skin capillaries. Another study in pigs revealed that the deceleration of erythrocytes coincided with a significant reduction of the oxygen partial pressure in the myocardium--supplied by the left coronary artery--after the administration of RCM into this artery. Further reports showed RCM dependent alterations of erythrocytes like echinocyte formation and exocytosis, sequestration of actin or band 3 and the buckling of endothelial cells coinciding with a formation of interendothelial fenestrations leading to areas devoid of endothelial cells. Key to morphological alterations of erythrocytes is the membrane cytoskeleton, which is linked to the band 3 in the erythrocyte membrane via the junctional complex. Fundamental observations regarding the cell biological and biochemical aspects of the structure and function of the cell membrane and the membrane cytoskeleton of erythrocytes have been reported. This review focuses on recent results gained, e.g., by advanced confocal laser scanning microscopy of different double-stained structural elements of the erythrocyte membrane cytoskeleton.

Estimation of glomerular filtration rate in conscious mice using a simplified equation

To develop an expedient procedure for estimating glomerular filtration rate (GFR) in conscious mice, we first established a simple technique for repeated blood collections from the tail vein using a microcapillary tube attached to a 24-gauge needle without the hub. Then, we devised a definition equation for estimation of the GFR using the contrast medium iodixanol as a test tracer. Iodixanol was administered as a bolus injection at 1500 mg I/kg to ddY mice, and the GFR was determined by the conventional multisample strategy. Based on cumulative data from the multisample method, an equation for the single-blood-sample method including the iodixanol dose, estimated distribution volume (Vd), and plasma iodixanol concentration at 60 min later was sought. The GFR values from the multisample method were in good agreement with those calculated using the equation. In clinically healthy mice, the GFR decreased gradually with ages from 11 weeks old in both sexes, suggesting the necessity of the corresponding control in each protocol. In nephropathy mice induced by cisplatin, the GFR values decreased with rises in serum BUN and creatinine concentrations, and serum creatinine became elevated when the GFR decreased to approximately 70% of the basal value. The results suggest that the simplified equation using iodixanol, allowing for the repeated use of the same mice, is a versatile procedure for research purposes.

Purification of white spot syndrome virus by iodixanol density gradient centrifugation

Up to now, only a few brief procedures for purifying white spot syndrome virus (WSSV) have been described. They were mainly based on sucrose, NaBr and CsCl density gradient centrifugation. This work describes for the first time the purification of WSSV through iodixanol density gradients, using virus isolated from infected tissues and haemolymph of Penaeus vannamei (Boone). The purification from tissues included a concentration step by centrifugation (2.5 h at 60,000 g) onto a 50% iodixanol cushion and a purification step by centrifugation (3 h at 80,000 g) through a discontinuous iodixanol gradient (phosphate-buffered saline, 5%, 10%, 15% and 20%). The purification from infected haemolymph enclosed a dialysis step with a membrane of 1,000 kDa (18 h) and a purification step through the earlier iodixanol gradient. The gradients were collected in fractions and analysed. The number of particles, infectivity titre (in vivo), total protein and viral protein content were evaluated. The purification from infected tissues gave WSSV suspensions with a very high infectivity and an acceptable purity, while virus purified from haemolymph had a high infectivity and a very high purity. Additionally, it was observed that WSSV has an unusually low buoyant density and that it is very sensitive to high external pressures.

Intravascular radiocontrast iodixanol increases permeability of proximal tubule epithelium: a possible mechanism of contrast-induced nephropathy

PURPOSE

To investigate the effect of Iodixanol on kidney proximal tubular cell line human kidney 2 (HK-2).

METHODS

The HK-2 cells were treated with Iodixanol. A Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay was used to evaluate apoptosis. Cell viability was measured by proliferation assay kit. Cell permeability changes were assessed by transwell assay and intercellular gaps measurement. Expression of claudin-2 was assessed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blot.

RESULTS

Iodixanol reduced tubule cell viability (P < .01) but did not cause apoptosis. The intercellular gap formation (P < .01) and transwell (P < .05) assays revealed that cell permeability significantly increased after Iodixanol treatment of monolayer cells. Western blot and qRT-PCR showed significant upregulation of claudin-2 protein (P < .05) and messenger RNA expression (P < .01).

CONCLUSIONS

Our in vitro data do not support the hypothesis that direct kidney cell death from Iodixanol is a major mechanism of contrast-induced nephropathy (CIN). However, increased permeability of proximal tubule epithelium caused by Iodixanol may play an important role in CIN.

Glomerular filtration rate in Holstein dairy cows estimated from a single blood sample using iodixanol

The isotonic, nonionic, contrast medium iodixanol, as a test substance, was compared with the conventional glomerular filtration rate (GFR) tracer inulin to establish a simplified procedure for estimating the GFR in Holstein dairy cows. First, inulin and iodixanol were coadministered as a bolus intravenous injection to clinically healthy cows at 30 mg/kg and 10mg of I/kg of body weight, respectively, followed by blood collection for multisample strategies. Serum iodixanol and inulin concentrations were separately determined by using HPLC and colorimetry, respectively, and blood urea nitrogen and creatinine concentrations in sera were measured. In the multisample method, the GFR values estimated by iodixanol were consistent with those estimated by inulin. No effects of body weight, age, or parity on GFR estimates were noted with either protocol used. No difference was observed between the GFR values obtained from nonlactating and lactating cows, suggesting that no transfer of iodixanol to milk occurred. An equation for calculating the GFR in the single-sample method was derived from the injected dose, sampling time, serum concentration, and estimated volume of distribution based on data from the multisample method in clinically healthy cows and cows with reduced renal function. The GFR values estimated by the single-sample method were in good agreement with those calculated by using the multisample method. These results demonstrate that the single-sample method using iodixanol can be applied as an alternative procedure for screening GFR in dairy cows.

Renal safety in pediatric imaging: randomized, double-blind phase IV clinical trial of iobitridol 300 versus iodixanol 270 in multidetector CT

BACKGROUND

It is debated whether iso-osmolar and low-osmolar contrast media are associated with different incidences of contrast medium-induced nephropathy (CIN) in patients with renal insufficiency.

OBJECTIVE

To compare the incidence of CIN in children undergoing contrast-enhanced multidetector computer tomography (MDCT) with intravenous injection of low-osmolar (iobitridol, Xenetix® 300) or an iso-osmolar (iodixanol, Visipaque® 270) iodinated contrast medium.

MATERIALS AND METHODS

One hundred forty-six children with normal renal function were included in this multicenter trial and underwent contrast-enhanced MDCT. The primary endpoint was the relative change in creatinine clearance from 48 h pre- to 72 h postcontrast medium administration using a noninferiority analysis in the intent-to-treat (ITT, n = 128) and per protocol (n = 68) populations. Secondary endpoints were incidence of CIN, global image quality, diagnostic efficacy and clinical safety.

RESULTS

In the ITT population, the noninferiority of iobitridol over iodixanol was demonstrated. CIN incidence was 4.8% (three cases) with iobitridol and 10.6% (seven cases) with iodixanol (not significant). No statistically significant differences were observed for the secondary endpoints.

CONCLUSION

Comparable satisfactory safety profiles were confirmed for both contrast media, with no significant difference in the incidence of CIN in children with normal renal function.

Purification of islets of Langerhans from porcine pancreas

Flotation through a slightly hyperosmotic discontinuous gradient iodixanol achieves a much higher recovery of islets of an improved viability than the customary method using sedimentation on to a diatrizoate/polysaccharide barrier. Flotation techniques achieve an enhanced separation of the islets from any residual digestive enzymes and from acinar cells. The method has been extended to human pancreas.

Purification of lipid rafts from cultured cells

Lipid-rich lipid rafts are microdomains of the plasma membrane that are resistant to low concentrations of nonionic detergent. This forms the basis for their isolation. Either a microsomal fraction or a postnuclear supernatant are loaded beneath a discontinuous iodixanol gradient. If all the solutions contain 0.5-1.0% Triton X-100, the intact lipid rafts float to the top of the gradient while all of the other detergent-solubilized membranes remain at the bottom.

Isolation of peripheral blood mononuclear cells from macaques on a density barrier

The standard techniques for the isolation of human peripheral blood mononuclear cells (PBMCs) using commercial "lymphocyte isolation media" cannot be satisfactorily extended to experimental animals without manipulating either the density or the osmolality of the medium. PBMCs from Macaques can also be isolated from whole blood by sedimentation on to a density barrier containing approx. 10% iodixanol, polysucrose (Ficoll) with a density of approx 1.074 g/ml.

Separation of human monocytes from a leukocyte-rich plasma

Human peripheral blood monocytes are isolated by flotation from a dense leukocyte-rich plasma (LRP) through two lower-density barriers prepared from OptiPrep. The separation from lymphocytes depends on the more rapid rate of flotation of the monocytes because of their slightly lower density and larger size. The method works optimally only with fresh (within 2 h of drawing) EDTA-anticoagulated blood.

Purification of parietal and chief cells from the gastric mucosa

Acid-secreting parietal cells from the gastric mucosa are widely studied as a model in studies on ion transport. A discontinuous gradient of iodixanol has been found to be superior to earlier protocols using Nycodenz and this method, which removes a significant amount of contaminating cells and mucus is a very useful prelude to further purification by elutriation.

Isolation of rat and human hippocampal neuron fractions in a discontinuous density gradient

The plating efficiency of neurons in culture is highly dependent on the concentration of cells used to establish the monolayer. A discontinuous iodixanol gradient permits both the production of a viable concentrated suspension of neurons and purification from other brain tissue elements. The gradient that is described in this Protocol Article is applicable to brain tissue from rat and also from human biopsy specimens.

Purification of gastric mucosal ECL cells from a crude elutriation fraction

Acid-secreting parietal cells from the gastric mucosa are widely studied as a model in studies on ion transport and the endocrine/paracrine ECL cells effectively control parietal cell function. Discontinuous gradients of iodixanol for the purification of ECL cells were subsequently simplified to the use of a density barrier. This technique is now commonly used following initial centrifugal elutriation.

Isolation of human platelets (thrombocytes)

Platelets from human blood can be isolated in high yield by centrifugation of whole blood over an iodixanol density barrier of 1.063 g/ml. The separation from all of the blood cells (which form a pellet) is based on the slower sedimentation velocity of the smaller platelets.

Separation of membrane vesicles and cytosol from yeast, cultured cells, and bacteria in a small volume self-generated gradient in a fixed-angle rotor

There are many situations when it is necessary to separate rapidly and efficiently a cytosolic and a membrane vesicle fraction from yeast, cultured cells, or from bacteria. This Protocol Article describes the flotation of the vesicles through a self-generated gradient from a dense sample zone using the low-viscosity medium iodixanol. As the sample is exposed to the gmax the tendency of the proteins to sediment overcomes any diffusion in the opposite direction and are therefore completely separated from the vesicles.

Purification of peroxisomes in a preformed iodixanol gradient in a fixed-angle rotor

In iodixanol, peroxisomes are the densest organelle in the light mitochondrial fraction and are therefore easily separated from the other components (lysosomes, mitochondria, etc.) in a preformed isosmotic continuous gradient. The resolution of the peroxisomes is far superior than that in sucrose and, unlike in Percoll there is no contamination from endoplasmic reticulum.

OptiPrep density gradient solutions for macromolecules and macromolecular complexes

Any density gradient for the isolation of mammalian cells should ideally only expose the sedimenting particles to an increasing concentration of the gradient solute. Thus they will experience only an increasing density and viscosity, other parameters such as osmolality, pH, ionic strength and the concentration of important additives (such as EDTA or divalent cations) should remain as close to constant as possible. This Protocol Article describes the strategies for the dilution of OptiPrep in order to prepare such solutions for mammalian cells.

Separation of membrane vesicles and cytosol from cultured cells and bacteria in a preformed discontinuous gradient

There are many situations when it is necessary to separate rapidly and efficiently a cytosolic and a membrane vesicle fraction from either cultured cells or from bacteria. Flotation of the vesicles through a low-density barrier from a dense sample zone using the low viscosity medium iodixanol allows complete separation of these compartments. As the sample is exposed to the gmax the tendency of the proteins to sediment overcomes any diffusion in the opposite direction.

Rapid purification of nuclei from animal and plant tissues and cultured cells

Nuclei are isolated by buoyant density banding in a discontinuous iodixanol gradient, under isoosmotic conditions. The low viscosity of the gradient allows the purification to be carried out at 10,000g in only 20 min. The method avoids possible damage to nucleoprotein complexes caused by hyperosmotic sucrose gradients. Although developed for mammalian liver the method can be applied (with or without minor modifications) to any tissue or cell type.

Purification of peroxisomes in a self-generated gradient

In iodixanol, peroxisomes are the densest organelle in the light mitochondrial fraction and are therefore easily separated from the other components (lysosomes, mitochondria, etc.) in a self-generated gradient. Self-generated gradients make sample handling very easy and are highly reproducible but need to be formed in either a vertical, near-vertical, or small volume high-performance fixed-angle rotor. The resolution of the peroxisomes is far superior than that in sucrose and, unlike in Percoll there is no contamination from endoplasmic reticulum.