A New Equation to Estimate Muscle Mass from Creatinine and Cystatin C

Background

With evaluation for physical performance, measuring muscle mass is an important step in detecting sarcopenia. However, there are no methods to estimate muscle mass from blood sampling.

Methods

To develop a new equation to estimate total-body muscle mass with serum creatinine and cystatin C level, we designed a cross-sectional study with separate derivation and validation cohorts. Total body muscle mass and fat mass were measured using dual-energy x-ray absorptiometry (DXA) in 214 adults aged 25 to 84 years who underwent physical checkups from 2010 to 2013 in a single tertiary hospital. Serum creatinine and cystatin C levels were also examined.

Results

Serum creatinine was correlated with muscle mass (P < .001), and serum cystatin C was correlated with body fat mass (P < .001) after adjusting glomerular filtration rate (GFR). After eliminating GFR, an equation to estimate total-body muscle mass was generated and coefficients were calculated in the derivation cohort. There was an agreement between muscle mass calculated by the novel equation and measured by DXA in both the derivation and validation cohort (P < .001, adjusted R² = 0.829, β = 0.95, P < .001, adjusted R² = 0.856, β = 1.03, respectively).

Conclusion

The new equation based on serum creatinine and cystatin C levels can be used to estimate total-body muscle mass.     

Scalar coupling between 31P and spin-1/2 metal nuclides in 31P NMR of complexes with a ligand containing phosphonate donor groups.

Scalar couplings between ³¹P and $\text{spin-}\text{1}\text{2}$ isotopes of cadmium, mercury, lead, and tin are reported for the respective metal complexes with the chelating agent (ethylenedinitrilo) - tetramethylenephosphonic acid.     

Mass transfer and biochemical reaction with semipermeable microcapsules

Enzymes can be encapsulated within a semipermeable membrane which allows reactants to enter and the products to diffuse out. The mass transport from the external fluid to the membrane and the combined mass transport and biochemical reaction from the membrane inwards can be modeled with recognized formulations; measurements of the overall reaction rate lead then to estimates of the permeability of the membrane itself. With capsules enclosing catalase, the permeability of collodion membranes to H₂O₂ is found to be large (<2 × 10^?2cm/sec) in comparison to rates in the other two diffusion zones. For this first-order reaction system, an analytical solution to the transient case of the well-stirred finite bath is found using the Laplace transform. With capsules enclosing urease, the nonlinear Michaelis-Menten kinetics apply to the enzymatic step. The steady-state operation of a column packed with urease microcapsules is analyzed with the aid of numerical computation and the membrane permeability for urea is found to be 10^?3cm/sec.     

Effect of Chelate-Assisted Hexavalent Chromium on Physiological Changes,Biochemical Alterations,and Chromium Bioavailability in Crop Plants—An In Vitro Phytoremediation Approach

This study revealed heavy metal–induced physiological and biochemical alterations in crop seedlings by supplementing chelating agents in the nutrient solution. Hexavalent chromium (Cr⁺⁶) induces several toxic effects in hydroponically grown rice, wheat, and green gram seedlings. A noticeable decrease was observed in root length, shoot length, biomass content, and chlorophyll biosynthesis of the seedlings grown in the nutrient solutions supplemented with Cr⁺⁶ at 100 μM. The seedling growth was stimulated with supplement of chelating agents such as EDTA, DTPA, and EDDHA. An increase in proline content was noticed with the application of Cr⁺⁶ (100 μM) in nutrient solutions. Stimulated activities of antioxidant enzymes such as catalase and peroxidase were noticed with increasing concentrations of chromium. Cr bioaccumulation was significantly high in roots of seedlings treated with Cr⁺⁶ at 100 μM in nutrient solution. Shoot translocation of Cr as depicted by transportation index (Ti) values for different crops were enhanced with the application of chelating agents. The total accumulation rate (TAR) for Cr was enhanced with the supplementation of DTPA in rice and wheat, whereas the application of EDDHA was found effective for increasing the accumulation rate of Cr in green gram seedlings. This study demonstates the role of chelating agents in lessening the toxic effects of Cr⁺⁶. The chelating agents supplemented with Cr⁺⁶ in the culture medium enhanced the Cr bioavailability in plants.     

Mass spectrometry label-free quantitative analysis of proteins

The dependence of the intensity of a mass spectrometric signal on protein concentration has been investigated using individual purified proteins and complex protein mixtures. Linearity of this dependence has been determined within the concentration ranges from 1 nM to 1 μM. In this range the dependence of the mass spectrometric signal intensity on concentration possesses a slope (tangent) characteristic for each protein studied. The efficacy of the method has been evaluated using the other methods (AQUA and ¹⁸O-labelling) employed in quantitative proteomics.     

Distribution of Foliar-applied Boron Measured by Spark-source Mass Spectrometry and Laser-probe Mass Spectrography

The distribution of foliar-applied boron ([¹⁰B]boric acid) in radish (Raphanus sativus L.) was studied using for analysis of the stable isotopes a technique allowing a high sensitivity: spark-source mass spectrometry. Boron was recovered in the nontreated aerial parts and in the roots; however, the greatest fraction was in the treated leaf. It was possible with a laser-probe mass spectrograph to show that boron was not superficially located in the treated area but was present in tissues at all levels of depth considered.     

An Industry-Scale Mass Marking Technique for Tracing Farmed Fish Escapees

Farmed fish escape and enter the environment with subsequent effects on wild populations. Reducing escapes requires the ability to trace individuals back to the point of escape, so that escape causes can be identified and technical standards improved. Here, we tested if stable isotope otolith fingerprint marks delivered during routine vaccination could be an accurate, feasible and cost effective marking method, suitable for industrial-scale application. We tested seven stable isotopes, ¹³⁴Ba, ¹³⁵Ba, ¹³⁶Ba, ¹³⁷Ba, ⁸⁶Sr, ⁸⁷Sr and ²⁶Mg, on farmed Atlantic salmon reared in freshwater, in experimental conditions designed to reflect commercial practice. Marking was 100% successful with individual Ba isotopes at concentrations as low as 0.001 µg. g^-1 fish and for Sr isotopes at 1 µg. g^-1 fish. Our results suggest that 63 unique fingerprint marks can be made at low cost using Ba (0.0002 – 0.02 $US per mark) and Sr (0.46 – 0.82 $US per mark) isotopes. Stable isotope fingerprinting during vaccination is feasible for commercial application if applied at a company level within the world’s largest salmon producing nations. Introducing a mass marking scheme would enable tracing of escapees back to point of origin, which could drive greater compliance, better farm design and improved management practices to reduce escapes.     

Stimulation of the activity of prolyl hydroxylase in 3T3 fibroblasts by 1,10-phenanthroline

In confluent cultures of 3T3 fibroblasts, incubated for 24 h with 1,10-phenanthroline at 10^?5–10^?9 M, the activity of prolyl hydroxylase was significantly increased. 1,10-Phenanthroline was inhibitory at concentrations greater than 10^?4 M. The stimulatory effect of 1,10-phenanthroline manifets itself after 6 h inhubation and increased with time up to 48 h. 2,2′-dipyridyl and 5,6-dimethyl-1-1,10-phemamthroline were also stimulatory; a nonchelating analog, 1,7-phenanthroline had no effect.Cycloheximide did not modify the 1,10-phenanthroline effect. The stimulatory effect does not seem to depend on the shift of an inactive precursor of prolyl hydroxylase to an active form because 1,10-phenanthroline was shown to be ineffective in logarithmically growing cells.While dialysis of washed and homogenized cells significantly increased prolyl hydroxylase activity in cell extracts, undialyzed 1,10-phenanthroline treated samples exhibited higher prolyl hydroxylase activity than dialyxed controls.These data suggested to us that 1,10-phenanthroline and other chelating agents may be forming complexes with certain metal ions or protein-metal ions which are inhibitory towards prolyl hydroxylase.     

A chelate complex‐enhanced luminol system for selective determination of Co(II), Fe(II) and Cr(III)

A determination method for Co(II), Fe(II) and Cr(III) ions by luminol‐H₂O₂ system using chelating reagents is presented. A metal ion‐chelating ligand complex with a Co(II) ion and a chelating reagent like ethylenediaminetetraacetic acid (EDTA) produced highly enhanced chemiluminescence (CL) intensity as well as longer lifetime in the luminol‐H₂O₂ system compared to metals that exist as free ions. Whereas free Cu(II) and Pb(II) ions had a strong catalytic effect on the luminol‐H₂O₂ system, significantly, the complexes of Cu(II) and Pb(II) with chelating reagents lost their catalytic activity due to the chelating reagents acting as masking agents. Based on the observed phenomenon, it was possible to determine Co(II), Fe(II) and Cr(III) ions with enhanced sensitivity and selectivity using the chelating reagents of the luminol‐H₂O₂ system. The effects of ligand, H₂O₂ concentration, pH, buffer solution and concentrations of chelating reagents on CL intensity of the luminol‐H₂O₂ system were investigated and optimized for the determination of Co(II), Fe(II) and Cr(III) ions. Under optimized conditions, the calibration curve of metal ions was linear over the range of 2.0 × 10^‐8 to 2.0 × 10^‐5 M for Co(II), 1.0 × 10^‐7 to 2.0 × 10^‐5 M for Fe (II) and 2.0 × 10^‐7 to 1.0 × 10^‐4 M for Cr(III). Limits of detection (3σ/s) were 1.2 × 10^‐8, 4.0 × 10^‐8 and 1.2 × 10^‐7 M for Co(II), Fe(II) and Cr(III), respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Chelates of tetracycline with first row transition metal perchlorates

2:1 adducts of tetracycline (tc) with 3d metal perchlorates (M = Cr ³⁺, Mn ²⁺, Fe ²+, ^Fe3+, ^Co2+, Ni ²⁺, Cu ²⁺, Zn ²⁺) are synthesized by boiling under reflux mixtures of tc free base and metal salt in ethanol— triethyl orthoformate. Characterization studies suggest that the new complexes are monomeric chelates involving bidentate tetracycline ligands, chelating via the amide group oxygen and the C3O oxygen of the ring A tricarbonylmethane. The complexes also contain unidentate coordinated −OClO ₃ ligands, as weil as ionic ClO ₄^-. The M ³⁺ (Cr, Fe) complexes are hexacoordinated of the [M(tc) ₂(OClO ₃)2 ₃]ClO ₄ type (MO ₆ chromophores), with two bidentate chelating tc and two unidentate perchlorato ligands in the first coordination sphere of the central metal ion. In the M2+ (Mn, Fe, Co, Ni, Cu, Zn) complexes, the inner coordination sphere of the metal ion is occupied by two bidentate chelating tc and only one −OClO ₃ ligand, and the coordination number is five, i.e. [M(tc) ₂OClO ₃]ClO ₄ (MO ₅absorbing species).     

Tracking the Fate of Stem Cell Implants with Fluorine-19 MRI

Background

In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (¹⁹F) agent. ¹⁹F-MRI offers unambiguous detection and in vivo quantification of labeled cells.

Methods

We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. ¹⁹F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using ¹⁹F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty.

Results

Immediately following transplantation, ¹⁹F-MRI quantification correlated very well with the expected cell number in both models. The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model. By endpoint, only 2/7 syngeneic mice had any detectable ¹⁹F signal. In the xenograft model, all mice had detectable signal at endpoint. Fluorescence microscopy and immunohistochemistry were used to show that the ¹⁹F signal was related to the presence of bystander labeled macrophages, and not original MSC.

Conclusions

Our results show that ¹⁹F-MRI is an excellent tool for verifying the delivery of therapeutic cells early after transplantation. However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells.     

Metal-ion effects on proteolysis and stability in secondary lysosomes of mouse kidney

In previous studies, in vitro digestion of [^{1 2 5}I] ribonuclease by lysosomes of mouse kidney was limited because breakdown, which was rapid at first slowed markedly so that most of the labeled protein escaped degradation. We now describe incubation conditions which allow digestion to proceed until approximately 70% of the exogenous protein label is released in acid-soluble from, after 30–45 min at 37°C. Such activity is seen with either the addition of EDTA or incubation of concentrated cell particle suspensions. EDTA is effective in low concentrations and shows the same stimulation of digestion over a range of approximately 10⁻⁶−10⁻³ M. Other chelating agents have similar effects; dipyridyl and hydroxquinoline are as effective as EDTA, o-phenanthroline and diethyldithiocarbamate are slightly less effective. When the incubation medium had been treated with a chelating resin, Chelex 100, dilute suspensions of lysosomes were as active as those in EDTA. These results lead to the conclusion that metal ions, present as contaminants in very small concentraions, inhibit the activity of mouse kidney lysosomes.The effect of the metal ions is to diminish lysosomal stability, leading to release of intact labeled ribonuclease in non-sedimentable form. Interaction between lysosomes and metal, leading to inhibition of digestion upon heating occurs at low temperature, but breakdown requires incubation at 37°C and may be autolytic. In contrast to chelators, mercaptoethanol is without marked effect on stability; the stimulation in digestion rate caused by this agent is due either to a direct effect on the lysosomal enzymes or to a non-destructive influence on the lysosomal structure.     

Engineering of Mesoscale Pores in Balancing Mass Loading and Rate Capability of Hematite Films for Electrochemical Capacitors

Design and synthesis of metal oxide‐based pseudocapacitive materials to simultaneously achieve high mass loading (e.g., up to 10 mg cm^?2) and excellent rate capability for electrochemical capacitors is a long‐lasting challenge. These two characteristics are usually mutually exclusive due to the poor ion diffusion kinetics of most metal oxides. Here, a glucose‐assisted hydrothermal method to prepare thick hematite film (>1 µm) with engineerable mesopore size through controlled variation of glucose concentration is demonstrated. The capability of controlling the size of mesopores offers a unique opportunity to investigate for the first time the interplay between mesopore size and electrochemical performance of hematite films. The hematite film with an average mesopore size of 3 nm at an ultrahigh loading of 10 mg cm^?2 exhibits an areal capacitance of 1502 mF cm^?2 at 1 mA cm^?2, and retains 871.2 mF cm^?2 at 50 mA cm^?2. Such performance, to the best of the authors' knowledge, is at the top of the reported hematite electrodes with comparable or even lower mass loadings. The strategy demonstrated herein may be extended to fabricate diverse types of mesoporous metal oxide architectures with improved ion diffusion kinetics, which is critical for a broad range of devices for energy storage and conversion.     

Exploration of Inorganic C and N Assimilation by Soil Microbes with Time-of-Flight Secondary Ion Mass Spectrometry

Stable C and N isotopes have long been used to examine properties of various C and N cycling processes in soils. Unfortunately, relatively large sample sizes are needed for accurate gas phase isotope ratio mass spectrometric analysis. This limitation has prevented researchers from addressing C and N cycling issues on microbially meaningful scales. Here we explored the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) to detect ¹³C and ¹⁵N assimilation by individual bacterial cells and to quantify N isotope ratios in bacterial samples and individual fungal hyphae. This was accomplished by measuring the relative abundances of mass 26 (¹²C¹⁴N⁻) and mass 27 (¹³C¹⁴N⁻ and ¹²C¹⁵N⁻) ions sputtered with a Ga⁺ probe from cells adhered to an Si contact slide. TOF-SIMS was successfully used to locate and quantify the relative ¹⁵N contents of individual hyphae that grew onto Si contact slides in intimate contact with a model organomineral porous matrix composed of kaolin, straw fragments, and freshly deposited manure that was supplemented with ¹⁵NO₃⁻. We observed that the ¹⁵N content of fungal hyphae grown on the slides was significantly lower in regions where the hyphae were influenced by N-rich manure than in regions influenced by N-deficient straw. This effect occurred over distances of tens to hundreds of microns. Our data illustrate that TOF-SIMS has the potential to locate N-assimilating microorganisms in soil and to quantify the ¹⁵N content of cells that have assimilated ¹⁵N-labeled mineral N and shows promise as a tool with which to explore the factors controlling microsite heterogeneities in soil.     

Investigation of mechanisms of synaptic transmission in ampullae of Lorenzini in the skate

The effect of magnesium ions, L-glutamate (L-GLU), and the diethyl ester of glutamic acid (DEE-GLU) on temperature and electrical sensitivity of the ampullae of Lorenzini in skates was studied by the method of perfusion of the basal membrane of electroreceptor cells and recording spike activity from single nerve fibers. Addition of 10^–4–10^–5 M L-GLU to the solution was shown to cause an increase in the spontaneous discharge frequency of receptors with low initial level of activity (8–20 spikes/sec) and a decrease in receptors with spontaneous activity of 22–42 spikes/sec. In solution with an increased magnesium ion concentration (15–50 mM) both spontaneous and evoked receptor activity was blocked, Under these conditions the addition of L-GLU to the solution caused partial recovery of spontaneous receptor activity. Reversible blocking of spontaneous and evoked receptor activity was observed in a solution containing 10^–4–10^–3 M DEE-GLU. It is suggested that L-GLU is the synaptic transmitter in the ampullae of Lorenzini of the skate.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 292–298, May–June, 1981.     

Proteolytic activity within lysosomes and turnover of pinocytic vesicles a kinetic analysis

In previous studies, in vitro digestion of [^{1 2 5}I] ribonuclease by lysosomes of mouse kidney was limited because breakdown, which was rapid at first slowed markedly so that most of the labeled protein escaped degradation. We now describe incubation conditions which allow digestion to proceed until approximately 70% of the exogenous protein label is released in acid-soluble from, after 30–45 min at 37°C. Such activity is seen with either the addition of EDTA or incubation of concentrated cell particle suspensions. EDTA is effective in low concentrations and shows the same stimulation of digestion over a range of approximately 10⁻⁶−10⁻³ M. Other chelating agents have similar effects; dipyridyl and hydroxquinoline are as effective as EDTA, o-phenanthroline and diethyldithiocarbamate are slightly less effective. When the incubation medium had been treated with a chelating resin, Chelex 100, dilute suspensions of lysosomes were as active as those in EDTA. These results lead to the conclusion that metal ions, present as contaminants in very small concentraions, inhibit the activity of mouse kidney lysosomes.The effect of the metal ions is to diminish lysosomal stability, leading to release of intact labeled ribonuclease in non-sedimentable form. Interaction between lysosomes and metal, leading to inhibition of digestion upon heating occurs at low temperature, but breakdown requires incubation at 37°C and may be autolytic. In contrast to chelators, mercaptoethanol is without marked effect on stability; the stimulation in digestion rate caused by this agent is due either to a direct effect on the lysosomal enzymes or to a non-destructive influence on the lysosomal structure.     

Quinidine blocking of sodium and potassium channels in myelinated nerve fibers

Experiments by the voltage clamp method showed that external application of quinidine (5 × 10^–5 M) to the Ranvier node membrane of the frog nerve fiber inhibitis both sodium and potassium currents. Blocking of the sodium current is considerably intensified by repetitive depolarization of the membrane (1–10 Hz); the rate of development of the block increases with an increase in stimulation frequency. After the end of stimulation the sodium current gradually returns to its initial level (with a time constant of the order of 30 sec at 12°C). Unlike repetitive depolarization with short (5 msec) stimuli, a prolonged shift (1 sec) of potential toward depolarization has no significant effect on quinidine blocking of the sodium current. Analysis of the current-voltage characteristic curves showed that quinidine blocks outward sodium current more strongly than inward. Batrachotoxin protects sodium channels against the blocking action of quinidine in a concentration of 10^–5 M. Inhibition of the outward potassium currents by quinidine is distinctly time-dependent in character: Initially the potassium current rises to a maximum, then falls steadily to a new stationary level. The results agree with the view that quinidine, applied externally, penetrates through the membrane in the basic form and blocks open sodium and potassium channels from within in the charged (protonated) form. The similarity in principle between the action of quinidine and local anesthetics on the sodium suggests that these compounds bind with the same receptor, located in the inner mouth of the sodium channel.A. V. Vishnevskii Institute of Surgery, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 14, No. 3, pp. 324–330, May–June, 1982.     

Apoptosis-Promoting Effects of Hematoporphyrin Monomethyl Ether-Sonodynamic Therapy (HMME-SDT) on Endometrial Cancer

Objective

The aim of the present study was to examine the apoptosis-promoting effects and mechanisms of hematoporphyrin monomethyl ether (HMME)-sonodynamic therapy (SDT) on endometrial cancer cells in vitro.

Methods

Endometrial cancer cell samples were divided into four groups: 1) untreated control group, 2) HMME group, 3) pure ultrasound group, and 4) HMME combined with ultrasound, i.e. SDT group. CCK-8 method was utilized to assess the inhibiting effect of SDT on the proliferation of endometrial cancer cells. Optical microscope and field emission transmission electron microscopy were used to characterize the morphology changes of the cancer cells induced by the treatments. Apoptosis rate, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were examined by flow cytometer. Fluorescence intensity measured by laser scanning confocal microscopy was used to explore the variation of intracellular calcium ion (Ca²⁺) concentration. Apoptosis-related proteins involved in both intrinsic and extrinsic apoptosis signallings were analyzed by western blot.

Results

SDT can effectively induce the apoptosis of endometrial cancer cells. Compared with ultrasound which is known as an effective anti-tumor method, SDT leads to a significant improvement on suppression of cell viability and induction of apoptosis, together with more remarkable modifications on the morphology and substructure in both ultrasound sensitive and resistant endometrial cancer cells. Further studies reveals that SDT promotes ROS production, induces loss of MMP and increases intracellular Ca²⁺ concentration more efficiently than HMME or ultrasound alone. SDT groups also show a rather high expression of apoptosis-promoting proteins, including Bax, Fas and Fas-L, and a significant low expression of apoptosis-suspending proteins including Bcl-2 and Survivin. Meanwhile, both cleaved caspse-3 and caspase-8 are dramatically enhanced in SDT groups. Multiple pathways has been proposed in the process, including the intrinsic activation by excessive ROS and overloaded Ca²⁺, silencing survivin gene, and the extrinsic pathway mediated by the death receptor.

Conclusion

Given its considerable effectivity in both ultrasound sensitive and resistant cells, SDT may therefore be a promising therapeutic method for treating endometrial cancers.     

Immune Adjuvant Activity of Pre-Resectional Radiofrequency Ablation Protects against Local and Systemic Recurrence in Aggressive Murine Colorectal Cancer

Purpose

While surgical resection is a cornerstone of cancer treatment, local and distant recurrences continue to adversely affect outcome in a significant proportion of patients. Evidence that an alternative debulking strategy involving radiofrequency ablation (RFA) induces antitumor immunity prompted the current investigation of the efficacy of performing RFA prior to surgical resection (pre-resectional RFA) in a preclinical mouse model.

Experimental Design

Therapeutic efficacy and systemic immune responses were assessed following pre-resectional RFA treatment of murine CT26 colon adenocarcinoma.

Results

Treatment with pre-resectional RFA significantly delayed tumor growth and improved overall survival compared to sham surgery, RFA, or resection alone. Mice in the pre-resectional RFA group that achieved a complete response demonstrated durable antitumor immunity upon tumor re-challenge. Failure to achieve a therapeutic benefit in immunodeficient mice confirmed that tumor control by pre-resectional RFA depends on an intact adaptive immune response rather than changes in physical parameters that make ablated tumors more amenable to a complete surgical excision. RFA causes a marked increase in intratumoral CD8⁺ T lymphocyte infiltration, thus substantially enhancing the ratio of CD8⁺ effector T cells: FoxP3⁺ regulatory T cells. Importantly, pre-resectional RFA significantly increases the number of antigen-specific CD8⁺ T cells within the tumor microenvironment and tumor-draining lymph node but had no impact on infiltration by myeloid-derived suppressor cells, M1 macrophages or M2 macrophages at tumor sites or in peripheral lymphoid organs (i.e., spleen). Finally, pre-resectional RFA of primary tumors delayed growth of distant tumors through a mechanism that depends on systemic CD8⁺ T cell-mediated antitumor immunity.

Conclusion

Improved survival and antitumor systemic immunity elicited by pre-resectional RFA support the translational potential of this neoadjuvant treatment for cancer patients with high-risk of local and systemic recurrence.     

Activation of NADP-specific isocitrate dehydrogenase by chelating agents.

The effects of different metal chelating agents on the activity of the NADP-linked isocitrate dehydrogenase from pig heart have been studied. Addition of ethylene glycolbis(β-aminoethyleter) N,N′-tetraacetic acid, N-hydroxyethylenediamine triacetic acid, and ethylenediamine tetraacetic acid (EDTA) under certain conditions could enhance the activity by a factor of nearly 3. Moreover, the time lag occurring before the reaction rate approached a constant value at suboptimal metal-ion concentrations was abolished by the metal chelating agents. S^0.5 for isocitrate increased slightly in the presence of the metal-chelating agents. The substrate inhibition occurring at high NADP concentrations was abolished by the activator. The pH optimum was the same in the absence and presence of EDTA. The extent of activation increased on a relative basis with increasing pH. Studies of the sedimentation behavior of the enzyme under different conditions suggested that the effect of the metal-chelating agents could not be accounted for by aggregation or depolymerization of the enzyme. NADPH affects the enzyme activity in a similar way, although less efficiently than the metal chelating agents. The results indicate that most organic metal complexes can activate the enzyme. It has previously been suggested that isocitrate complexed with a metal ion is the real substrate for the enzyme. If this holds true, the activation found with other organic metal complexes can be accounted for by a reduction in the apparent K_m for the isocitrate metal complex and by an increase in the maximum rate of the reaction by removal of the substrate inhibition at high NADP concentrations.