Modeling the euglycemic hyperinsulinemic clamp by stochastic differential equations

The Euglycemic Hyperinsulinemic Clamp (EHC) is the most widely used experimental procedure for the determination of insulin sensitivity. In the present study, 16 subjects with BMI between 18.5 and 63.6 kg/m² have been studied with a long-duration (5 hours) EHC. In order to explain the oscillations of glycemia occurring in response to the hyperinsulinization and to the continuous glucose infusion at varying speeds, we first hypothesized a system of ordinary differential equations (ODEs), with limited success. We then extended the model and represented the experiment using a system of stochastic differential equations (SDEs). The latter allow for distinction between (i) random variation imputable to observation error and (ii) system noise (intrinsic variability of the metabolic system), due to a variety of influences which change over time. The stochastic model of the EHC was fitted to data and the system noise was estimated by means of a (simulated) maximum likelihood procedure, for a series of different hypothetical measurement error values. We showed that, for the whole range of reasonable measurement error values: (i) the system noise estimates are non-negligible; and (ii) these estimates are robust to changes in the likely value of the measurement error. Explicit expression of system noise is physiologically relevant in this case, since glucose uptake rate is known to be affected by a host of additive influences, usually neglected when modeling metabolism. While in some of the studied subjects system noise appeared to only marginally affect the dynamics, in others the system appeared to be driven more by the erratic oscillations in tissue glucose transport rather than by the overall glucose-insulin control system. It is possible that the quantitative relevance of the unexpressed effects (system noise) should be considered in other physiological situations, represented so far only with deterministic models.The work was supported by grants from the Danish Medical Research Council and the Lundbeck Foundation to S. Ditlevsen.     

Increases in 1H-NMR mobile lipids are not always associated with overt apoptosis: evidence from MG-63 human osteosarcoma three-dimensional spheroids exposed to a low dose (2 Gy) of ionizing radiation

The metabolic changes that occur in MG-63 osteosarcoma three-dimensional tumor spheroids exposed to 2 Gy of ionizing radiation, a dose that is comparable to radiation therapy, were studied using high-resolution proton nuclear magnetic resonance ((1)H-NMR) spectroscopy. Specifically, the (1)H-NMR spectra of control and exposed MG-63 spheroids were compared. Small spheroids (about 50-80 microm in diameter) with no hypoxic center were used. The spectra of whole MG-63 spheroids as well as the perchloric acid extracts of these systems were evaluated. Cell damage was also examined by lactate dehydrogenase release and changes in cell growth. No cell damage was observed, but numerous metabolic changes took place in spheroids after exposure to ionizing radiation. In particular, significant increases in both CH(2) and CH(3) mobile lipids, considered by many authors as markers of apoptosis and also present in MG-63 spheroids undergoing overt apoptosis, were observed in spheroids irradiated with 2 Gy. However, the chromatin dye Hoechst 33258 and DNA fragmentation assays showed no overt apoptosis up to 7 days after irradiation with this low dose. Thus it is evident that increases in mobile lipids do not always indicate actual cell death. A detailed analysis of the other metabolic changes observed appears to suggest that the cell death program was initiated but not completed. In fact, the completely different behavior of two important cellular defense mechanisms, reduced glutathione and taurine, in spheroids irradiated with 2 Gy and in those undergoing overt apoptosis seems to indicate that these systems are protecting spheroids from actual cell death. In addition, these data also suggest that (1)H-NMR can be used to examine the effects of low doses of ionizing radiation in spheroids, a cell model of great complexity that closely resembles tumors in vivo. The importance of this possibility in relation to reaching the ultimate goal of a better evaluation of the outcome of radiotherapy protocols should not be ignored.     

Regio and stereoselective oxidations of unsaturated steroidal compounds with H2O2 mediated by CH3ReO3

We have investigated the oxidative behavior of sterols such as cholesteryl acetate (1), 7-dehydrocholesteryl acetate (2), ergosteryl acetate (3), cholecalciferol acetate (Vitamin D(3) acetate) (4) and ergocalciferol acetate (Vitamin D(2) acetate) (5) with the oxidant system methyltrioxorhenium/H(2)O(2)/pyridine in order to check potential parameters controlling the selectivity. The reactions, performed in CH(2)Cl(2)/H(2)O at 25 degrees C, have shown good regio- and stereoselectivity. All oxidation products were isolated by high-performance liquid chromatography (HPLC) and characterized by MS(EI) or FAB, (1)H NMR, (13)C NMR, APT, COSY, HSQC, HMBC, ROESY and NOEDS measurements. Seven new oxygenated compounds were also obtained. Under the experimental conditions adopted in this work, only the diene steroids, i.e. 7-dehydrocholesteryl acetate and ergosteryl acetate, undergo hydrolytic oxirane ring opening, whereas Vitamin D(2) and D(3) acetates, containing the triene system and cholesteryl acetate yield only epoxides. The selectivity seems to be controlled by the nucleophilicity of double bonds and by stereoelectronic and steric effects.     

Analysis of the periprosthetic femoral bone reaction after uncemented total hip arthroplasty with computertomography assisted osteodensitometry in vivo: 6-year follow-up]

AIMS: We prospectively analyzed the cancellous and cortical periprosthetic femoral bone reaction after implantation of a cementless total hip arthroplasty with computertomography assisted osteodensitometry after a mean of 1 and 6 years. MATERIALS AND METHODS: Twenty-one patients (? age at implantation: 52 years) with osteoarthrits of the hip joint received 21 cementless hip prostheses with a three-dimensionally tapered design. All patients were analyzed clinically, with CT-osteodensitometry and plain radiography after a mean of 10 days, at 1 and 6 years postoperatively. Cancellous and cortical bone density was evaluated automatically using a special software tool. RESULTS: The proximal region of the stem showed progessive cortical (? -15% 1 year, -25% 6 years post-OP) and cancellous (? -26% 1 year, -49% 6 years post-OP) bone density loss. Cortical bone density loss was lower and non-progressive at the diaphysis (? -7% 1 year, -9% 6 years post-OP) and the distal region (? -6% 1 year, -4% 6 years post-OP) of the stem. All stems showed no signs of loosening on plain radiography and good clinical results according to the Harris hip score. CONCLUSION: Computertomography assisted osteodensitometry is the only method which allows discrimination between periprosthetic cortical and cancellous bone density changes in vivo. The analyzed uncemented stem fixates at the diaphysis and distal region. Due to the changed biomechanical loading after stem implantation, progressive proximal cancellous bone density loss was measured for the first time in vivo. Its role in the pathogenesis of implant loosening is still unknown and needs to be further elucidated.     

Comparative Study of Alkaline, Saline, and Mixed Saline–Alkaline Stresses with Regard to Their Effects on Growth, Nutrient Accumulation, and Root Morphology of Lotus tenuis

Both saline and alkaline conditions frequently coexist in nature; however, little is known about the effects of alkaline and salt?Calkaline stresses on plants. We performed pot experiments with four treatments, control without salt addition and three stress conditions??neutral, alkaline, and mixed salt?Calkaline??to determine their effects on growth, nutrient accumulation and root architecture in the glycophytic species Lotus tenuis. Neutral and alkaline salts produced a similar detrimental effect on L. tenuis growth, whereas the effect of their combination was synergistic. Neutral salt addition, alone or mixed with NaHCO₃, led to significant leaf Na⁺ build up and reduced K⁺ concentration. In contrast, in plants treated with NaHCO₃ only, Na⁺ levels and the Na⁺/K⁺ ratio remained relatively unchanged. Proline accumulation was not affected by the high pH in the absence of NaCl, but it was raised by the neutral salt and mixed treatments. The total root length was reduced by the addition of NaCl alone, whereas it was not affected by alkalinity, regardless of the presence of NaCl. The topological trend showed that alkalinity alone or mixed with NaCl turned the root more herringbone compared with control roots, whereas no significant change in this index was observed in the treatment with the neutral salt only. The pattern of morphological changes in L. tenuis root architecture after the alkaline treatment (in the absence of NaCl) was similar to that found in the mixed salt?Calkaline treatment and different from that observed in neutral salt. A unique root morphological response to the mixed salt?Calkaline stress was the reduction in the ratio between xylem vessels and root cross-sectional areas.     

Solution NMR structure of the ribosomal protein RP-L35Ae from Pyrococcus furiosus

The ribosome consists of small and large subunits each composed of dozens of proteins and RNA molecules. However, the functions of many of the individual protomers within the ribosome are still unknown. In this article, we describe the solution NMR structure of the ribosomal protein RP-L35Ae from the archaeon Pyrococcus furiosus. RP-L35Ae is buried within the large subunit of the ribosome and belongs to Pfam protein domain family PF01247, which is highly conserved in eukaryotes, present in a few archaeal genomes, but absent in bacteria. The protein adopts a six-stranded anti-parallel β-barrel analogous to the "tRNA binding motif" fold. The structure of the P. furiosus RP-L35Ae presented in this article constitutes the first structural representative from this protein domain family.     

RAGE binds C1q and enhances C1q-mediated phagocytosis

RAGE, the multiligand receptor of the immunoglobulin superfamily of cell surface molecules, is implicated in innate and adaptive immunity. Complement component C1q serves roles in complement activation and antibody-independent opsonization. Using soluble forms of RAGE (sRAGE) and RAGE-expressing cells, we determined that RAGE is a native C1q globular domain receptor. Direct C1q-sRAGE interaction was demonstrated with surface plasmon resonance (SPR), with minimum K(d) 5.6 μM, and stronger binding affinity seen in ELISA-like experiments involving multivalent binding. Pull-down experiments suggested formation of a receptor complex of RAGE and Mac-1 to further enhance affinity for C1q. C1q induced U937 cell adhesion and phagocytosis was inhibited by antibodies to RAGE or Mac-1. These data link C1q and RAGE to the recruitment of leukocytes and phagocytosis of C1q-coated material.