Comparison Medium Research Articles

Improved biological performance of human cartilage-derived progenitors in platelet lysate xenofree media in comparison to fetal bovine serum media

Primary articular cartilage-derived cells are among the preferred contenders for cell-based therapy approaches for cartilage repair. Limited access to primary human cartilage tissue necessitates the process of in vitro cell expansion to obtain sufficient cells for therapeutic purposes. Therapeutic outcomes of such cell-based approaches become highly dependent on the quality of the in vitro culture-expanded cells. The objective of this study was to determine the differential biological effects of human platelet lysate (hPL) xeno-free defined media vs FBS containing traditional media on primary human cartilage-derived cells. Our goal in pursuing this work was to identify a preferred xenofree media alternative, that can be used as a platform for expansion of cells intended for clinical applications. Primary cartilage-derived cells obtained from five patients were simultaneously cultured in two expansion media's: (1) traditional (DMEM+10%FBS+1%P/S) and (2) defined xenofree (Nutristem® complete media+0.5%hPL). Connective tissue progenitors (CTPs) were assayed by standard colony forming unit assay, morphology, proliferation in early and late passages, expression of MSC associated cell-surface markers (CD73, CD90 and CD105) and trilineage differentiation (adipogenesis, osteogenesis and chondrogenesis) were considered for comparison of biological performance. Early biological performance of primary cartilage-derived cells was significantly improved in Nutristem® expansion media in comparison to traditional expansion media with respect to (1) Colony forming efficiency tended to be higher (p = 0.058) and (2) CTPs formed larger colonies with respect to total cells per colony and colony area (p < 0.01). In the culture expanded cell population, Nutristem® expansion media was superior to traditional expansion media with respect to: (1) overall proliferation rate through passages 1–4 (p = 0.027), (2) total cells harvested at end of passage 4 (p = 0.028) and (3) total positive stain area of CD73 (p = 0.006), CD90 (p = 0.001) and CD105 (p = 0.049). Nutristem®-hPL expanded cells when differentiated in respective xenofree serum-free defined MSCgo™ differentiated media's, also showed significant improvement in adipogenic, osteogenic and chondrogenic marker expression. Overall, we convincingly demonstrated that a low concentration of hPL in combination with defined xenofree media is an effective and economic growth supplement to culture expand primary cartilage-derived cells. It can be manufactured under cGMP conditions to improve clinical-grade cell products’ quality for therapeutic applications.

3D anisotropic TEM modeling with loop source using model reduction method

Abstract For model reduction techniques, there have been relatively few studies performed regarding the forward modeling of anisotropic media in comparison to transient electromagnetic (TEM) forward modeling of isotropic media. The transient electromagnetic method (TEM) responses after the current has been turned off can be represented as a homogeneous ordinary differential equation (ODE) with an initial value, and the ODE can be solved using a matrix exponential function. However, the order of the matrix exponential function is large and solving it directly is challenging, thus this study employs the Shift-and-Invert (SAI-Krylov) subspace algorithm. The SAI-Krylov subspace technique is classified as a single-pole approach compared to the multi-pole rational Krylov subspace approach. It only takes one LU factorization of the coefficient matrix, along with hundreds of backward substitutions. The research in this paper shows that the anisotropic medium has little effect on the optimal shift ${\gamma _{opt}}$ and subspace order m. Furthermore, as compared to the mimetic finite volume method (SAI-MFV) of the SAI-Krylov subspace technique, the method proposed in this paper (SAI-FEM) can further improve the computing efficiency by roughly 13%. In contrast to the standard implicit time step iterative technique, the SAI-FEM method does not require discretization in time, and the TEM response at any moment within the off-time period can be easily computed. Next, the accuracy of the SAI-FEM algorithm was verified by 1D solutions for an anisotropic layer model and a 3D anisotropic model. Finally, the electromagnetic characteristics of the anisotropic anomalous body of the center loop device and separated device of the airborne transient electromagnetic method were analyzed, and it was found that horizontal conductivity has a considerable influence on the TEM response of the anisotropic medium.

Cyberspace Narratives for Global Interconnectivity Based on Content Analysis of Financial Media in Comparison

The paper explores the role of elite financial media in construction narratives of global interconnectivity, in a comparative framework[7]. The existing era of globalization provided us with new challenges for strategic intelligence as the virtual compression of time along with new technological achievements in shorter period of time and potentially cataclysmic threats[8]. Two globally circulated financial journals—Caijing, China’s leading financial news organization, and the Economist, with a vital influence across the globe—are chosen to manifest the diverse media discourses representing, respectively, the Chinese and Anglo-American socio- economic backgrounds. The paper aims to use the quantitative content analysis to answer the question: what are the narrative characteristics of the Caijing and the Economist in portraying China’s economic globalisation? The study are designed to tackle a specific focus on the globalised elite communication, in order to guide the investigation of China’s global interconnectivity in a hybridizing and contesting way[4]. Like other forms of mediated electronic connectivity, the Internet instead of circumscribing sovereignty has offered centralised authority new ways of conducting statecraft, by circulating ideas that represents the consensus shared by global elites.

Characterisation of extracellular vesicles surface markers and co-expression studies with single particle interferometric imaging platform

Background & Aim Extracellular vesicle (EVs)-based therapeutics have been anticipated as an alternative to cell therapies based on the premise that EVs shed by stem cells exert similar therapeutic effects. A major challenge in EV research workflow is the lack of a platform that offers characterisation at the single EV level. In light of this, we tested and validated the single particle interferometric imaging using conditioned media in comparison against purified EVs obtained using ultracentrifugation and size exclusion chromatography. We performed multiplexed measurement of typical EV surface markers (e.g. tetraspanins) and simultaneously measured the size of antigen positive EVs. Methods, Results & Conclusion Human amniotic epithelial cells (hAECs) were cultured in serum free media for 96 hours. We prepared both unpurified (conditioned media, concentrated conditioned media) and purified EV samples (ultracentrifugation and size exclusion chromatography). Single particle interferometric imaging measurement was performed using the ExoView platform (Nanoview Biosciences). CD9, CD63 and CD81-positive EVs were immunocaptured on a tetraspanin microarray chip and imaged as single particles. Co-expression of tetraspanin proteins were then assessed by labeling the captured EVs with a cocktail of fluorescence antibodies conjugated to CD81-Alexa555, CD63-Alexa647 and CD9-Alexa488. The chips were then imaged with ExoView R100 reader and analysed using ExoViewer software with sizing thresholds set to 50-200nm diameter. The label free measurement used in this study captured particles based on their expression of classical EV markers (CD9/CD63/CD81) and provided specific EV particle characterisation down to a resolution of 50nm. Further labelling the captured EVs with fluorescence antibodies proved to increase sensitivity and include particles

Abstract 5836: Activation of Wnt/beta-catenin alters the Ewing sarcoma secretome - Implications for tumor:tumor microenvironment crosstalk

Abstract Ewing sarcoma is the second most common bone cancer in children and adolescents. Patients with metastatic disease have less than a 25% chance of survival making it imperative to understand the mechanisms that drive metastasis. We previously showed that activation of Wnt/β-catenin signaling in Ewing sarcoma cells alters the tumor cell transcriptome, promoting transition to a more metastatic cellular phenotype. In addition, primary tumors with high-level Wnt activation were associated with worse clinical outcomes, supporting a role for canonical Wnt signaling in metastatic progression. Significantly, extracellular matrix (ECM) protein genes were among the most affected by Wnt/β-catenin, suggesting that activation of the pathway might lead to alterations in the local tumor microenvironment (TME). Crosstalk between the TME and tumor cells regulates fundamental aspects of the metastatic cascade including invasion, migration, and angiogenesis. It is our goal to define the impact of Wnt/β-catenin signaling on the TME and elucidate how these changes contribute to metastasis. Our specific hypothesis is that activation of Wnt/β-catenin in Ewing sarcoma cells leads to changes in the tumor secretome that result in altered TME composition and tumor:TME crosstalk. To address this hypothesis, conditioned media from Ewing sarcoma cell lines cultured in the presence and absence of Wnt3a was collected for proteomic analysis. We used label-free mass spectrometry with spectral counting to quantify proteins that passed a ≤1% FDR threshold. Significance was defined as greater than 4.5 or less than 0.2 fold difference in counts between Wnt3a and control conditions. Western blot of conditioned media was used to validate identified proteins. Preliminary analysis of the TC32 cell line identified 49 proteins up regulated in Wnt3a treated media in comparison to control. Significantly, Tenascin C (TNC), was among the most significantly up regulated proteins, validating our prior data that TNC is a transcriptional target of Wnt/β-catenin and a promoter of the metastatic phenotype in vivo. Gene ontology analysis of the significantly differentially expressed proteins revealed enrichment of proteins involved in ECM-receptor signaling, ECM organization, cell adhesion, and collagen catabolism. These biologic processes all play critical roles in tumor:TME interactions and together contribute to the early steps of adhesion, migration and invasion that are responsible for initiation of metastasis. These preliminary studies confirm that Wnt/β-catenin-dependent changes in the Ewing sarcoma transcriptome are associated with changes in tumor cell secretome. We are now validating these findings in additional cell lines and updated results will be presented. These studies will elucidate how changes in tumor cells can lead to changes in the local TME and in tumor:TME crosstalk that promote metastatic progression of Ewing sarcoma. Citation Format: Allegra Hawkins, Colin Sperring, Venkatesha Basrur, Alexey Nesvizhskii, Elizabeth Lawlor. Activation of Wnt/beta-catenin alters the Ewing sarcoma secretome - Implications for tumor:tumor microenvironment crosstalk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5836. doi:10.1158/1538-7445.AM2017-5836

Hydrogen Production and Enzyme Activities in the Hyperthermophile Thermococcus paralvinellae Grown on Maltose, Tryptone, and Agricultural Waste.

Thermococcus may be an important alternative source of H2 in the hot subseafloor in otherwise low H2 environments such as some hydrothermal vents and oil reservoirs. It may also be useful in industry for rapid agricultural waste treatment and concomitant H2 production. Thermococcus paralvinellae grown at 82°C without sulfur produced up to 5 mmol of H2 L−1 at rates of 5–36 fmol H2 cell−1 h−1 on 0.5% (wt vol−1) maltose, 0.5% (wt vol−1) tryptone, and 0.5% maltose + 0.05% tryptone media. Two potentially inhibiting conditions, the presence of 10 mM acetate and low pH (pH 5) in maltose-only medium, did not significantly affect growth or H2 production. Growth rates, H2 production rates, and cell yields based on H2 production were the same as those for Pyrococcus furiosus grown at 95°C on the same media for comparison. Acetate, butyrate, succinate, isovalerate, and formate were also detected as end products. After 100 h, T. paralvinellae produced up to 5 mmol of H2 L−1 of medium when grown on up to 70% (vol vol−1) waste milk from cows undergoing treatment for mastitis with the bacterial antibiotic Ceftiofur and from untreated cows. The amount of H2 produced by T. paralvinellae increased with increasing waste concentrations, but decreased in P. furiosus cultures supplemented with waste milk above 1% concentration. All mesophilic bacteria from the waste milk that grew on Luria Bertani, Sheep's Blood (selective for Staphylococcus, the typical cause of mastitis), and MacConkey (selective for Gram-negative enteric bacteria) agar plates were killed by heat during incubation at 82°C. Ceftiofur, which is heat labile, was below the detection limit following incubation at 82°C. T. paralvinellae also produced up to 6 mmol of H2 L−1 of medium when grown on 0.1–10% (wt vol−1) spent brewery grain while P. furiosus produced < 1 mmol of H2 L−1. Twelve of 13 enzyme activities in T. paralvinellae showed significant (p < 0.05) differences across six different growth conditions; however, methyl viologen-dependent membrane hydrogenase activity remained constant across all media types. The results demonstrate the potential of at least some Thermococcus species to produce H2 if protein and α-glucosides are present as substrates.

Piezocomposite with reciprocal polarization of oriented ellipsoidal inclusions and the matrix

We consider statistically homogeneous two-phase random piezoactive structures with deterministic properties of inclusions and the matrix and with random mutual location of inclusions. We present the solution of a coupled stochastic boundary value problem of electroelasticity for the representative domain of a matrix piezocomposite with a random structure in the generalized singular approximation of the method of periodic components; the singular approximation is based on taking into account only the singular component of the second derivative of the Green function for the comparison media. We obtain an analytic solution for the tensor of effective properties of the piezocomposite in terms of the solution for the tensors of effective properties of a composite with an ideal periodic structure or with the “statistical mixture” structure and with the periodicity coefficient calculated for a given random structure with its specific characteristics taken into account. The effective properties of composites with auxiliary structures (periodic and “statistical mixture”) are also determined in the generalized singular approximation by varying the properties of the comparisonmedium. We perform numerical computations and analyze the effective properties of a quasiperiodic piezocomposite with reciprocal polarization of oriented ellipsoidal inclusions and the matrix, the layered structures with reciprocal polarization of the layers [1] of a polymer piezoelectric PVF, and find their unique properties such as a significant increase in the Young modulus along the normal to the layers and in dielectric permittivities, the appearance of negative values of the Poisson ratio under extension along the normal, and an increase in the absolute values of the basic piezomoduli.

Nicotine causes depolarization, decreased intracellular calcium concentration ([Ca2+]i) and reduced nitric oxide (NO) production in human umbilical artery endothelial cells (HUAECs)

Maternal environmental tobacco smoke (ETS) exposure has been associated with intrauterine growth retardation (IUGR) and low birth weight, both of which increase infant morbidity and mortality. Nicotine, an active component in ETS, is known to decrease birth weight and postnatal weight gain, yet the mechanism remains unclear. We hypothesized that nicotine alters membrane potential (Em)‐dependent regulation of [Ca2+]i and nitric oxide (NO) production in endothelial cells, which could cause umbilical vessel contraction, impairment of blood flow and IUGR. Fluorescent microscopy was used in HUAECs treated with nicotine (10–100ng/ml; 15m–24hr). Fura‐2 was used to measure [Ca2+]i and DiBAC4(3) was used to measure changes in Em. We found that HUAECs treated with 100ng/ml of nicotine showed depolarization and an immediate dramatic decrease in [Ca2+]i. Prolonged nicotine treatment (10 and 100ng/ml; 1–24 hr) also decreased [Ca2+]i . In addition, total nitrite levels in the cell media were measured via Griess reaction following total nitrate reduction. Treatment with nicotine (10ng/ml; 1–4hrs) reduced total nitrite levels in the media in comparison to untreated HUAECs. From these results, we conclude that nicotine, at concentrations comparable to plasma levels in non‐smokers exposed to ETS, caused decreased NO production in HUAECs, perhaps secondary to depolarization and decreased [Ca2+]i. Funded by: HL73859

Gel chromatographic characterization of proteins in mucous and serous middle ear effusions of patients with otitis media in comparison to serum proteins

Otitis media with effusion (OME) is an inflammatory disease of the middle ear cavity that is associated with middle ear effusions (MEEs), which are frequently mucous and serous for pediatric and adult patients exhibiting low and high responsiveness to medical treatment, respectively. To assess the pathological outcomes in mucous and serous MEEs, their protein compositions were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting in comparison with those in the same patients' sera. A mucin, which is immunochemically identical with nasal mucin, was a characteristic consituent of mucous MEEs (n = 25), being present at the concentration of 59.4 mg/ml and comprising about 60% of the total proteins, but it was not detected in serous MEEs (n = 30) or sera. Serum proteins with molecular weights of less than 260 kDa were detected in serous and mucous MEEs, in which albumin was the major protein. Albumin, IgM and alpha1-acid glycoprotein, and lysozyme, IgA and IgG in MEEs were present at lower and higher concentrations than in sera, respectively. The ratios of IgA, IgG, IgM and alpha1-acid glycoprotein to albumin in mucous MEEs were 4-, 3-, 1.4- and 1.0-times higher than those in the respective pediatric sera, and those in serous MEEs were 1.7-, 1.7-, 0.6- and 0.3-times higher than those in adult sera. Also, the concentrations of lysozyme in mucous and serous MEEs were 19 and 3 microg/ml, but those in pediatric and adult sera were negligible. These results indicate that the contents of these proteins, in comparison to albumin, might be useful criteria for assessing the inflammation level in MEEs.

Role of Human Valve Interstitial Cells in Valve Calcification and Their Response to Atorvastatin

Calcific aortic valve stenosis is a common disease in the elderly and is characterized by progressive calcification and fibrous thickening of the valve, but the cellular and molecular mechanisms are not fully understood. We hypothesized that human valve interstitial cells (ICs) are able to differentiate into osteoblast-like cells through the influence of defined mediators and that this process can be modulated pharmacologically. To test this hypothesis, we treated primary cultures of human aortic valve ICs with osteogenic media, bone morphogenic proteins ([BMPs] BMP-2, BMP-4, and BMP-7), and tissue growth factor-beta ([TGF-beta] TGF-beta1 and TGF-beta3) for 21 days. These mediators induced osteoblast differentiation of valve ICs by significantly increasing the activity and expression of alkaline phosphatase ([ALP] P<0.001). A cytokine protein array revealed that atorvastatin treatment (100 micromol/L) of human valve ICs caused a downregulation in levels of expression of BMP-2, BMP-6, TGF-beta1, and TGF-beta3 after 24 hours. In addition, human valve ICs treated with atorvastatin in the presence of osteogenic media showed a significant reduction in ALP activity in comparison to cells treated with osteogenic media only (P=<0.001). This was further confirmed with immunocytochemical staining of valve ICs, whereby atorvastatin markedly reduced the expression of ALP and osteocalcin induced by osteogenic media in comparison to untreated cells. These findings suggest that human valve ICs are capable of osteoblastic differentiation, by potential mediators which can be pharmacologically targeted by atorvastatin.

Maillard Reaction between Leucine and Glucose in O/W Microemulsion Media in Comparison to Aqueous Solution

The Maillard reaction is controlled by temperature, pH, reactant nature (sugars and amino acids), and water activity. We carried out reactions between glucose and leucine in U‐type nonionic microemulsions to obtain regioselectivity and control reaction rates. Reactants were oriented at the interface and water activity was adjusted using blends of surfactant and propylene glycol (PG). U‐type microemulsions, previously studied by us, served as microreactors for the Maillard reaction. The reactions in the microemulsion media were slower than those carried out in aqueous solution and formed unique aroma compounds. Reaction rates increased when using systems richer in water, as the water activity was enhanced. The surfactant plays a key role in determining water activity and reagent reactivity in all the microemulsions. The presence of PG slows the reaction, mainly when it resides at the interface, facilitating the formation of a bicontinuous structure. Phase transitions within the U‐type microemulsions were determined by viscosity and SD‐NMR and were correlated to the interfacial presence of the reactants and their reactivity.

Investigation of the convergence of the mixed displacement-pressure formulation for three-dimensional poroelastic materials using hierarchical elements.

Recently, a mixed pressure displacement [u, P] formulation based on Biot's poroelasticity equations has been presented for porous materials. This model leads to a reduction of the number of degrees of freedom required for the modeling of three-dimensional porous media in comparison to classical displacement-displacement [u, U] formulations. In this paper, an extension of the [u, P] formulation based on hierarchical elements is presented. First, a variant of the weak integral form of the [u, P] formulation is presented and its numerical implementation using hierarchical elements is detailed, together with the application of boundary and loading conditions. Numerical results are presented to show the accuracy and performance of the present approach. In particular, the importance of correctly capturing the coupling effects between the two phases is highlighted.

Stimulation of nodulation and plant growth of chickpea ( Cicer arietinum L . ) by Pseudomonas spp. antagonistic to fungal pathogens

Two strains of Pseudomonas MRS23 and CRP55b showed antagonistic activity towards the pathogenic fungi Aspergillus sp., Fusarium oxysporum f. sp. ciceri, Pythium aphanidermatum and Rhizoctonia solani under culture conditions. Larger growth inhibition zones were obtained on nutrient agar (NA) and King's B media in comparison to potato dextrose agar and pigment production media. Both the strains produced siderophore in agar plates as well as in liquid cultures. Fungal inhibition zones were reduced in size and abolished in iron-supplemented NA medium by Pseudomonas strains MRS23 and CRP55b, respectively, indicating that some other metabolites along with siderophores are involved in growth inhibition of fungi by strain MRS23, whereas CRP55b produced only siderophores. Only Pseudomonas strain MRS23 was found to produce hydrocyanic acid (HCN). Seed bacterization with Pseudomonas strains of two chickpea (Cicer arietinum L.) cultivars, H8618 and C235, showed root-stunting effects at 5 days, whereas this inhibitory effect was overcome at 10 days of seedling growth in cv. H8618. Coinoculation of chickpea with Pseudomonas strains MRS23 and CRP55b, and Mesorhizobium sp. Cicer strain Ca181 resulted in the formation of 68.2–115.4% more nodules at 80 and 100 days after planting as compared to single inoculation with the Mesorhizobium strain under sterile conditions. The shoot dry weight ratios of coinoculated treatments at different stages of plant growth varied from 1.18 to 1.35 times that of Mesorhizobium-inoculated and 3.25 to 4.06 times those in uninoculated controls. The plant N contents were also increased significantly on coinoculation. Coinoculation effects of HCN-producing strain MRS23 were significantly lower than those of non-HCN-producing strain CRP55b in terms of shoot dry weight and shoot N. The results demonstrated the potential benefits of using rhizosphere bacteria as coinocula in nodule promotion and plant growth in chickpea.

The association between iron-deficiency anemia and recurrent acute otitis media

Purpose: This study was designed to examine the association between iron-deficiency anemia and the frequency of recurrent acute otitis media in children, and to evaluate the effect of restoring normal hemoglobin levels on the frequency of acute otitis media attacks. Materials and Methods: A total of 680 children with frequent episodes of acute otitis media were enrolled in the study. The levels of the hemoglobin were measured in both these children and in 200 healthy children with no history of infections. The correlation between hemoglobin level and the frequency of middle ear infections was studied and analyzed. All children with hemoglobin levels lower than 9.5 g/dL received iron supplementation until they reached a level of at least 11 g/dL, and the subsequent frequency of middle ear infections was recorded. Results: The 680 children had an average of 8.3 ± 2.7 episodes of acute otitis media per year per child, and an average hemoglobin level of 11.4 ± 2.7 g/dL, whereas the controls had an average hemoglobin level of 13.1 ± 2.5 g/dL. Twenty percent had hemoglobin levels below 9.5 g/dL. These children had more episodes of acute otitis media when compared with children with average levels. By increasing the hemoglobin level in these children, the frequency of the episodes of acute otitis media decreased significantly. Conclusions: This study confirms that anemic children have higher prevalence of episodes of acute otitis media in comparison to healthy, nonanemic children, and shows that there is a direct relationship between the degree of the anemia and the number of the episodes. (Am J Otolaryngol 2001;22:391-394. Copyright © 2001 by W.B. Saunders Company)

A method for the preparation of high purity lead titanate zirconate solid solutions by carbonate–gel composite powder precipitation

A novel wet chemical route for the preparation of perovskite titanates (ABO 3 type, where A is a divalent cation and B is a tetravalent cation) such as PbTiO 3 and its solid solutions, is described. The method involves the coprecipitation of the divalent cations (A) as fine particles of carbonates with hydrated gels of titania or zirconia (BO 2 xH 2 O, 12<x<130; B=Ti 4+ , Zr 4+ ) by the addition of ammonium carbonate. Such coprecipitation is possible because of the instability of the carbonates and oxycarbonates of Ti and Zr in aqueous media in comparison to the polymerised hydroxides, whereas lead carbonate is precipitated readily. The method gives rise to composite powders in which the submicron crystalline particles of the carbonates, crystalline to X-ray diffraction, are embedded within amorphous gels of BO 2 xH 2 O. The composite nature of the precipitate is confirmed by transmission electron microscopy. The precipitate is dried and calcined at elevated temperatures. Upon heating to 350–400 °C, the reaction between the carbonate and the amorphous dry gel proceeds via the formation of the intermediate PbOzTiO 2 (z<0.09) solid solution which then converts to a defect pyrochlore phase (A 2 B 2 O 7-δ , δ=1). Above 450 °C, the latter converts to an isocompositional perovskite phase. The process is superior to ceramic methods because of the high purity, uniform chemical homogeneity and lower particle size of the final product.

Some further pertinent considerations regarding the comparative toxicity of contrast materials for the dog kidney.

In an earlier study (1) reported from this laboratory, note was made of varying degrees of nephropathy occurring in conjunction with injections into the canine renal artery of certain specific contrast media in equal quantities in their market concentrations. The amount of each contrast material under these test circumstances (10 c.c.) was thought to be approximately ten times the amount necessary for renal angiography. In the preliminary study a purposeful attempt was made to determine whether available media, in their shelf concentrations, might exhibit sufficient disparities in their toxic potential to point to major identifying chemical characteristics that could be related to observed clinical differences. The present study, on the other hand, was designed to probe somewhat more extensively into basic physiochemical mechanisms. Certain media (and some analogues) found previously to be polar in their effects on the kidney were adjusted for molarity and test injected into the dog's renal artery in an attempt better to delineate the portion or portions of the contrast radical responsible for the histologic alterations detected by means of light and electron microscopy. A small-bore polyethylene catheter was inserted into the femoral artery of an anesthetized, laparot-omized dog and guided up the aorta into the left renal artery under direct vision. Equal molar quantities (10 to 13 c.c.) of each test material were then injected over a five- to eight-second period. Roentgenograms of the kidney were obtained three seconds after the completion of the injection, and again at five minutes. For every material, injected kidneys were examined after nephrectomy at five-minute, twenty-four-hour, and ten-day intervals post-injection. The test media were as follows: A. Media for comparison with 70 per cent Urokon: (a) 54 per cent sodium iodide; (b) 24 per cent 3-acetamidobenzoic acid (nonhalogenated Urokon) ; (c) 53 per cent 3-acetamido 2,4,6-tribromobenzoic acid (brominated Urokon); (d) 26 per cent 3,5-diacetamidobenzoic acid (nonhalogenated Hypaque) ; (e) 46 per cent 3,5-diacetamido 2,4,6-tribromobenzoic acid (brominated Hypaque). B. Media for comparison with 60 per cent Reno-grafin: (a) 34 per cent sodium iodide; (b) 44 per cent 3-acetamido 2,4,6-triiodobenzoic acid (Urokon); (c) 39 per cent diethanolamine salt of 3,5-diiodo-4-pyridone-N-acetic acid (Diodrast); (d) 47 per cent 5 - acetamido - N - methyl - 2,4,6 - triiodoisophtha-lamic acid (M.I.-216); (e) 49 per cent methyl-glucamine salt of 3,5-dipropionamido-2,4,6-triiodo-benzoic acid (Unipaque). Results The pertinent findings for the dogs in each contrast material group are summarized in the following tables along with the calculated equivalent amounts of injected halogen. The tabulated values are averages of 6 dogs in all but the M.I.-216 and Unipaque groups where injections were made into only 3 dogs.