Rheological and tribological properties of native potato starch agglomerated by fluidized bed granulator

We explored the rheological and tribological properties of potato starch agglomerated with a sugar binder (maltodextrin or lactose) at various concentrations by using a fluidized bed granulator. The magnitudes of consistency index and apparent viscosity of agglomerated potato starch (APS) decreased as the binder concentration was increased. Moreover, APS with a sugar binder showed lower viscoelastic moduli and higher tan δ values compared to APS with water as the binder (the control). The gel strength of all agglomerates decreased as the sugar concentration was increased. All samples showed anti-thixotropic behavior, and especially, APS with 20 % lactose showed a small anti-thixotropic area. Utilizing the Arrhenius equation clearly elucidated the effect of temperature on the apparent viscosity of all the samples. Although the maltodextrin concentration had little influence on the activation energy of APS, it increased as the lactose concentration was increased. APS samples with a sugar binder showed greater friction coefficient values compared to the control, with maltodextrin having a significant impact. The findings indicate that the rheological and tribological properties of APS rely on the type and concentration of sugar binder.

A comparative study on the rheological properties of concentrated xanthan gum in combination with gum arabic or gum arabic-based emulsion

A goal of this study is to explore the difference in rheological properties of xanthan gum (XG)-based mixtures with gum arabic (GA) or GA-based emulsion (GAE). The stability of GAE was improved by thickening with XG. The intrinsic viscosity of all mixtures decreased as GA concentration increased, implying an XG conformational transition from the disordered to the ordered form. All mixtures except for an XG-GA mixture at 6.0 % GA attained a higher consistency index value than XG alone, indicating synergistic interactions between the components. At a high GA concentration (>3.0 %), the XG-GAE mixture showed higher relative apparent viscosity values than the XG-GA mixture. All mixtures except for an XG-GA mixture at 6.0 % GA showed higher elastic modulus and lower viscous modulus values than XG alone. Consequently, all mixtures showed lower tan δ values (0.26-0.30) than XG alone (0.31). Moreover, with a high GA concentration (>1.5 %), the XG-GAE mixtures achieved lower relative tan δ values than XG-GA mixture. These results indicate that XG formed a higher weak gel-like network with GAE than GA. Overall, the findings demonstrate that the interaction between XG and GA is influenced by conformational changes in the latter in both aqueous and emulsion systems.

Effect of Setting Time on Viscosity Stability of Xanthan Gum- and Starch-Based Thickened Beverages for Patients with Dysphagia: Comparison of IDDSI Syringe Flow Test and Line-Spread Test

Because the viscosity of thickened beverages prepared with thickeners gradually changes before consumption, achieving their desired viscosity is important for managing dysphagia. This study aimed to investigate the viscosity changes of thickened beverages (water, orange juice, and milk) prepared with xanthan gum (XG)- and starch-based commercial thickeners over time using the syringe flow test (SFT) and line-spread test (LST). The LST values of beverages stabilized more quickly (≤1.5 h) than the SFT values (2.0∼3.5 h) at level 2 (mildly thick), whereas the opposite finding was observed at level 3 (moderately thick). After stabilization in a water system, SFT and LST yielded similar results. However, the SFT values of orange juice and milk thickened with XG-based thickener exceeded the reference values at level 2 and gradually increased at level 3. These results may be attributed to particulates interrupting fluid flow from the small tip of the syringe and the high friction force caused by the contact between the thickened sample and the syringe surface. The results suggest that the LST method is more reliable than the SFT method in clearly distinguishing between levels 2 and 3 of thickened beverages and demonstrate that the viscosity measurements of thickened beverages over time after preparation were strongly influenced by the measurement tools used for predicting the thickness level.

Rheological characteristics of concentrated ternary gum mixtures with xanthan gum, guar gum, and carboxymethyl cellulose: Effect of NaCl, sucrose, pH, and temperature

Our goal was to investigate the effects of various conditions of media (NaCl, sucrose, pH, and temperature) on the steady and dynamic shear rheological properties of a concentrated ternary gum mixture system (1.0 wt%) containing xanthan gum (XG), guar gum (GG), and carboxymethyl cellulose (CMC). Regardless of the media conditions, all gum mixtures exhibited a high shear-thinning behavior with a low flow behavior index (<0.30). NaCl addition resulted in a decrease in the consistency index (K, 32.8-16.1 Pa·sn) and apparent viscosity at 50 s-1 (ηa,50, 1.00-0.75 Pa·s), as well as the elastic modulus (G') and viscous modulus (G″) due to the charge screening effect. Similar result was observed with an increase in acidity of media. The presence of sucrose also induced the decrease in the ηa,50, K, G', and G″ values of the ternary gum, but tan δ (G″/G') decreased, indicative of higher weak gel-like properties. No effect of NaCl or sucrose addition on the temperature dependence of G' values was observed, whereas pH adjustment was impacted. These results demonstrated that the presence of co-solute, the acidity of media, and temperature influenced the rheological properties of ternary gum, and in particular acid condition gave a great impact.

High resolution spatially extended 1D laser scattering diagnostics using volume Bragg grating notch filters

Laser light scattering systems with volume Bragg grating (VBG) filters, which act as spectral/angular filters, have often been used as a point measurement technique, with spatial resolution as low as a few hundred μm, defined by the beam waist. In this work, we demonstrate how VBG filters can be leveraged for spatially resolved measurements with several μm resolution over a few millimeters along the beam propagation axis. The rejection ring, as determined by the angular acceptance criteria of the filter, is derived analytically, and the use of the ring for 1D laser line rejection is explained. For the example cases presented,i.e., for a focused probe beam waist with a diameter of ∼150 μm, the rejection ring can provide resolution up to several millimeter length along the beam propagation axis for a 1D measurement, which is also tunable. Additionally, methods to further extend the measurable region are proposed and demonstrated, using a collimation lens with a different focal length or using multiple VBG filters. The latter case can minimize the scattering signal loss, without the tradeoff of the solid angle. Such use of multiple VBGs is to extend the measurable region along the beam axis, which differs from the commonly known application of multiple filters, to improve the suppression of elastic interferences. 1D rotational Raman and Thomson scattering measurements are carried out on pulsed and DC discharges to verify this method. The system features compactness, simple implementation, high throughput, and flexibility, to accommodate various experimental conditions.

Regulatory mechanism of fucoidan-mix AG in intestinal mucosal immune cells

Fucoidan is a series of natural sulfated polysaccharides contained in brown sea algae, and their beneficial physiological activities such as anti-tumor, anti-virus and immune regulatory effects have been reported. In previous studies, we proved that fucoidans derived from Cladosiphon okamuranus (C. okamuranus) and Undaria pinnatifida effectively improved anti-tumor immunity and tumor vaccine efficiency in combination with an Agaricus blazei mycelium extract. It is thought that the fucoidan-agaricus mix (named fucoidan-mix AG) stimulate innate immune cells to activate intestinal and mucosal immune reaction, but actual target immune tissues and cells by fucoidan have not been evidenced yet. In this study, we investigated action mechanisms of fucoidan in regulation of mucosal immune activities. At first, immune cells were isolated from Payer’s patches, mesenteric lymph node (MLN) and intestinal epithelia of Balb/c mice, then stained with fluorophore-labeled fucoidan. As the results, it was revealed that fucoidan directly interact with lymphocytes besides dendritic cells and macrophages existing in these intestinal immune tissues. Furthermore, immune cells from Payer’s patches and MLN stimulated with fucoidan from C. okamuranus and fucoidan-mix AG produced more TNF-α, IL-12 and Th1 cytokine IFN-γ. The production of an immunosuppressive cytokine IL-10 also was augmented in the fucoidan-treated immune cells, which suggesting that fucoidan balanced immune system to prevent occurrence of excessive reaction. In addition, it was newly proved that fucoidan directly stimulated T lymphocytes to induce enhanced IFN-γ production.

Ligand-aided 1H Nuclear Magnetic Resonance Spectroscopy for Non-destructive Estimation of Sulfate Content in Sulfated Saccharides

Sulfated saccharides exhibit diverse physiological activities, but a lack of any convenient assay hinders their evaluation. Herein, an assay for the analysis of sulfated saccharides is described using ¹H nuclear magnetic resonance (NMR) spectroscopy by employing ligands that can form ionic complexes with the sulfate groups. Based on the change in the chemical shift (Δδ) of the ligands by sulfated mono- to tetrasaccharide, imidazole was found to be a good ligand, showing the maximum Δδ; neutral saccharides do not show any change in the δ value. A marked and constant downfield δ value observed was changed dramatically at a molar ratio of >1:1 (imidazole:sulfated saccharides), allowing a sulfate content estimation based on the concentration of imidazole at the Δδ inflection point. By the proposed ligand-aided ¹H NMR assay, the sulfate content of natural sulfated polysaccharide, fucoidan, was non-destructively estimated to be 2.1 mmol/g-fucoidan.

Suppressive effects of fucoidan-agaricus mix (CUA-fucoidan) on angiogenesis and tumor growth in B16 melanoma-bearing mice

Fucoidan is a series of natural sulfated polysaccharides contained in brown sea algae. In previous studies, we proved that fucoidans derived from Cladosiphon okamuranus and Undaria pinnatifida effectively augmented anti-tumor immunity in combination with an Agaricus blazei mycelium extract. In this study, we evaluated dietary effects of the mixture consist of the two high-molecular weights fucoidan and the agaricus extract (named CUA-fucoidan) on tumor angiogenesis. For that purpose, C57BL/6 mice were subcutaneously injected basement membrane matrix (Geltrex) enclosing 5×104 mitomycin C-treated B16 melanoma cells or 500 ng/mL vascular endothelial growth factor (VEGF), and fed 2% CUA-fucoidan containing diet for 7 days before and after the matrix inoculation. The accumulation of hemoglobin and CD31-positive cells in the B16-enclosed Geltrex was lower in the CUA-fucoidan-fed mice than in the control mice, whereas the hemoglobin contents in the VEGF-enclosed Geltrex were not affected by the CUA-fucoidan feeding. These results suggested that CUA-fucoidan was effective in suppressing tumor angiogenesis, but did not inhibit the physiological action of VEGF. Rather, it was guessed that CUA-fucoidan suppressed VEGF production because the expression of VEGF mRNA was reduced in the matrix resected from CUA-fucoidan-fed mice. In this context, the infiltration of CD206-positive macrophages, which known to produce VEGF, were declined by the CUA-fucoidan feeding. Furthermore, CUA-fucoidan decreased accumulation of Treg in the B16-included Geltrex, and delayed B16 tumor growth. In conclusion, CUA-fucoidan was expected to be effective in inhibition of tumor angiogenesis by improving immunosuppressive tumor microenvironments.

The cooperative induction of macrophage activation by fucoidan derived from Cladosiphon okamuranus and β-glucan derived from Saccharomyces cerevisiae

The present study investigated immune stimulatory effects of Cladosiphon okamuranus-derived fucoidan to activate murine macrophage-like cell line RAW264, and the functional relationship with zymosan, a Saccharomyces cerevisiae-derived β-glucan. The production of nitric oxide (NO) and tumor necrosis factor-α (TNF-α) in RAW264 cells were remarkably enhanced in the presence of 10 μg/mL fucoidan, and the stimulatory effects of fucoidan were maximally augmented in combinational treatment with 500 ng/mL zymosan, whereas any TLR ligands had no those effects. Confocal microscopic analyses suggested that fucoidan bound on plasma membrane, and it was estimated that some cell surface molecules acted as receptor for fucoidan because cytochalasin D, an inhibitor of phagocytosis, did not affect the immune enhancing activities, whereas methyl-β-cyclodextrin (MβCD), a general agent for disruption of lipid rafts, diminished that. Furthermore, it was revealed that the additive effects of zymosan on the immune activation with fucoidan was thought to be mediated by dectin-1 based on the results with dectin-1-knockdown RAW264 cells. All of results suggested that fucoidan and some kinds of β-glucan would cooperatively reinforce the activity of innate immune cells via interactive receptor crosstalk.

NAADP receptors are present and functional in the heart

Alongside the well-studied inositol 1,4,5 trisphosphate and ryanodine receptors, evidence is gathering that a new intracellular release mechanism, gated by the pyridine nucleotide nicotinic acid adenine dinucleotide phosphate (NAADP), is present in numerous organisms, ranging from plant to mammalian cells (reviewed in [1]). Most cells have been shown to express at least two Ca(2+)-release mechanisms controlled by different messengers, and this can lead to redundancy, convergence, or divergence of responses. One exception appears to be muscle and heart contractile tissues. Here, it is thought that the dominant intracellular channel is the ryanodine receptor, while IP(3) receptors are poorly expressed and their role appears to be negligible. We now report that NAADP receptors are functional and abundant in cardiac microsomes. NAADP binds specifically and with high affinity (130 pM and 4 nM) to two sites on cardiac microsomes and releases Ca(2+) with an apparent EC(50) of 323 +/- 14 nM. Furthermore, binding experiments show that this receptor displays both positive and negative cooperativity, a peculiarity unique among intracellular Ca(2+) channels. Therefore, we show that the heart possesses multiple mechanisms to increase the complexity of Ca(2+) signaling and that NAADP may be integral in the functioning of this organ.

Molecular targets for pharmacological cytoprotection

Cell death is common to many pathological conditions. In the past two decades, research into the mechanism of cell death has characterized the cardinal features of apoptosis and necrosis, the two distinct forms of cell death. Studies using in vivo disease models have provided evidence that apoptosis is induced by an array of pathological stimuli. Thus, molecular components of the machinery of apoptosis are potential pharmacological targets. The mechanism of apoptosis can be dissected into: (i) the initiation and signaling phase, (ii) the signal amplification phase, and (iii) the execution phase. Reflecting on the diversity of apoptotic stimuli, the initiation and signaling phase utilizes a variety of molecules: free radicals, ions, plasma membrane receptors, members of the signaling kinase cascades, transcription factors, and signaling caspases. In most of the apoptotic scenarios, impairment of mitochondrial function is an early event. Dysfunctioning mitochondria release more free radicals and hydrolytic enzymes (proteases and nucleases), amplifying the primary death signal. In the final phase of apoptosis, executioner caspases are activated. Substrates of the executioner caspases include nucleases, members of the cellular repair apparatus, and cytoskeletal proteins. Partial proteolysis of these substrates leads to distinctive morphological and biochemical changes, the hallmarks of apoptosis. The first steps toward pharmacological utilization of specific modifiers of apoptosis have been promising. However, since the potential molecular targets of cytoprotective therapy play important roles in the maintenance of cellular homeostasis, specificity (diseased versus healthy tissue) of pharmacological modulation is the key to success.

Supervising trauma life support by telemedicine

The resuscitation room in a community hospital was linked with a main hospital accident and emergency department using telemedicine equipment working at 384 kbit/s. Fifteen simulated casualties replicated the 'moulage' scenarios in the Advanced Trauma Life Support Course Manual of the American College of Surgeons. Each of the 15 scenarios was broken down into three main parts: the primary survey, resuscitation and the secondary survey. While a physician in the community hospital undertook each task, a senior doctor in the accident and emergency department recorded his degree of confidence in the supervision of the task on a five-point scale. There were features of the management which the supervisor found difficult, mainly related to the camera view and the use of a proxy examiner. However, supervising major trauma management by telemedicine was feasible. The average scores were mostly above 3 and often above 4 in the assessment of the primary survey and the resuscitation. The average scores were mostly above 3 for the secondary survey but were less often above 4 than for the primary survey and the resuscitation. Trials of remote trauma management with real patients appear to be justified.

A comparison of telemedicine with face-to-face consultations for trauma management

We compared the accuracy of teleconsultations for minor injuries with face-to-face consultations. Two hundred patients were studied. Colour change, swelling, decreased movement, tenderness, instability, radiological examination, severity of illness, treatment and diagnosis were recorded for both telemedicine and face-to-face consultations. Colour change showed an accuracy of 97%, presence of swelling or deformity of 98%, diminution of joint movement of 95%, presence of tenderness of 97%, weight bearing and gait of 99%, and radiological diagnosis of 98%. The severity of illness or injury was overestimated in one case and underestimated in five cases. Treatment was over-prescribed in one case and under-prescribed in three cases. The final diagnosis was correct in all but the two cases in which mistakes were made in the teleradiology. Overall, there was good accuracy using teleconsultations.

How do teleconsultations for remote trauma management change over a period of time?

We obtained follow-up information about the new patients seen at a minor accident and treatment service (MATS) staffed by emergency nurse practitioners (ENPs). A previous study, of 150 teleconsultations in a six-month period starting in April 1996, was used for comparison. In the present series, 150 teleconsultations occurring in a four-month period starting in April 1999 were studied; the patients constituted 5.6% of the 2658 new attenders or 3.8% of the 3936 total attenders. In comparison with the study three years before, falling teleconsultation rates were partly offset by increasing numbers of attenders and an extension of the ENPs' roles and skills. Teleconsultation rates rose when the number of consultant-run clinics was curtailed and ENP-run clinics replaced some of them. Eligibility to request and report more radiographs reduced the need for teleconsultations, and subsequently teleconsultations for help with interpretation of radiographs fell as the ENPs became more experienced. Specialty residents trusted ENP judgement and accepted telephoned direct admission of cases to their wards. Fewer teleconsultations were required for soft-tissue injuries. Telemedicine is an excellent educational tool.

Nicotinic acid adenine dinucleotide phosphate triggers Ca2+ release from brain microsomes

Mobilization of Ca2+ from intracellular stores is an important mechanism for generating cytoplasmic Ca2+ signals [1]. Two families of intracellular Ca(2+)-release channels - the inositol-1,4, 5-trisphosphate (IP3) receptors and the ryanodine receptors (RyRs) - have been described in mammalian tissues [2]. Recently, nicotinic acid adenine dinucleotide phosphate (NAADP), a molecule derived from NADP+, has been shown to trigger Ca2+ release from intracellular stores in invertebrate eggs [3] [4] [5] [6] and pancreatic acinar cells [7]. The nature of NAADP-induced Ca2+ release is unknown but it is clearly distinct from the IP3- and cyclic ADP ribose (cADPR)-sensitive mechanisms in eggs (reviewed in [8] [9]). Furthermore, mammalian cells can synthesize and degrade NAADP, suggesting that NAADP-induced Ca2+ release may be widespread and thus contribute to the complexity of Ca2+ signalling [10] [11]. Here, we show for the first time that NAADP evokes Ca2+ release from rat brain microsomes by a mechanism that is distinct from those sensitive to IP3 or cADPR, and has a remarkably similar pharmacology to the action of NAADP in sea urchin eggs [12]. Membranes prepared from the same rat brain tissues are able to support the synthesis and degradation of NAADP. We therefore suggest that NAADP-mediated Ca2+ signalling could play an important role in neuronal Ca2+ signalling.

Intracerebral malignant lymphoma in a patient with long-standing multiple sclerosis

We present a patient with long-standing MS who developed a malignant intracerebral lymphoma, suspected on MRI and verified by brain biopsy. This raises the interesting question about whether the coexistence of the two conditions is explained by cause or is just coincidental. Our case report also illustrates that other pathological conditions may develop in MS patients and demand attention in the individual patient. Copyright 1998 Lippincott Williams & Wilkins

Inhibition of cADPR-Hydrolase by ADP-ribose potentiates cADPR synthesis from beta-NAD+

Cyclic adenosine 5'-diphosphate ribose (cADPR) is a potent Ca2+ releasing agent in a number of tissues. A particular bifunctional NAD+ glycohydrolase is responsible for both the cyclase and hydrolase activity necessary for its synthesis from beta-NAD and degradation to ADPR. We now report that ADPR, the end-product of this enzyme, releases Ca2+ at high concentrations (above 100 microM), and at lower concentrations (10-100 microM) inhibits the hydrolysis of cADPR and potentiates the production of cADPR from NAD+. This evidence suggests that ADPR may be an important modulator of the NAD+ glycohydrolase responsible for the production of cADPR.

Paraganglioma of the cauda equina. A case report and review of the literature

A 59-year-old man presented with clinical evidence of a primary tumor of the cauda equina region. It was well circumscribed and was completely removed by neurosurgery. Routine staining showed that it had structural similarities to an ependymoma, but immunohistochemistry with antisera to synaptophysin, NSE, chromogranin-A and PGP 9.5 proved it to be a neuroendocrine tumor, i.e. a paraganglioma. We propose the use of endocrine markers in cases with tumors of the cauda equina to differentiate a paraganglioma from an ependymoma. Paragangliomas appear to have a better clinical outcome than ependymomas. Recurrence after surgery for a paraganglioma in the cauda equina region, especially if it is encapsulated, is rarely encountered.

Heterogeneity of the cardiac calcium release channel as assessed by its response to ADP-ribose

ADP-ribose (ADPR) was found to decrease the rate of Ca2+ release from isolated cardiac sarcoplasmic reticulum (SR) vesicles, which was limited to a maximum of 46 +/- 8% inhibition and was in accordance with our results obtained with single cardiac ryanodine receptor Ca2+ release channels (RyRC) incorporated into planar lipid bilayers: Out of 23 separate single channels, 9 responded to ADPR by a complete closure, while 14 channels showed no response at all, resulting in a reduction in overall open probability in the presence of ADPR (relative to control channels) by 39.7%. Although the ADPR-responsive and unresponsive single channels showed no differences in their respective open times, current amplitudes or relative occurrences of dwell levels, the bare existence of two types of response to ADPR together with the 50%-limited inhibition of cardiac SR Ca2+ release by ADPR indicates a heterogeneity of RyRCs in cardiac SR, which is likely due to protein(s) that interact(s) with the channel and are present in substoichiometric mole ratios.

Augmented effect of short-term pulsatile versus continuous insulin delivery on lipid metabolism but similar effect on whole-body glucose metabolism in obese subjects

The present study was designed to examine the effect of pulsatile versus continuous insulin delivery on glucose and lipid metabolism in insulin-resistant subjects. Six obese women (body mass index, 40.0 +/- 2.8 kg/m2) underwent a euglycemic glucose clamp (plasma glucose, 90 mg/dL) twice. In random order, insulin was infused intravenously for 375 minutes either at a constant rate (0.4 mU/kg/min) or in a pulsatile manner (2.4 mU/kg/min for 2 minutes followed by an off interval of 10 minutes). Endogenous insulin release was suppressed by infusion of somatostatin (250 micrograms/h). Mean circulating insulin concentrations were similar during the two protocols (pulsatile v continuous infusion, 60 +/- 10 v 56 +/- 9 mU/L), but pulsatile infusion was accompanied by oscillations with an amplitude of 120 mU/L. After 6 hours of pulsatile versus continuous insulin, isotopically determined total glucose disposal (3-3H-glucose) and hepatic glucose production (HGP) were comparable (pulsatile v continuous, 2.80 +/- 0.56 v 2.82 +/- 0.51 and 0.37 +/- 0.14 v 0.32 +/- 0.17 mg/kg/min). However, the rate of glucose oxidation (indirect calorimetry) was augmented (P < .05), whereas lipid oxidation tended to be diminished (.10 > P > .05) following pulsatile infusion. In addition, blood glycerol was more suppressed with pulsatile (31 +/- 9 nmol/L) than with continuous infusion (36 +/- 10 nmol/L, P < .05), whereas blood lactate, alanine, and 3-hydroxybutyrate were similar in the two infusion protocols.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic ADP-ribose as an endogenous regulator of the non-skeletal type ryanodine receptor Ca2+ channel

The skeletal and cardiac isoforms of the ryanodine receptor Ca2+ channel (RyRC) constitute the Ca2+ release pathway in sarcoplasmic reticulum of skeletal and cardiac muscles, respectively. A direct mechanical and a Ca(2+)-triggered mechanism (Ca(2+)-induced Ca2+ release) have been respectively proposed to explain the in situ activation of Ca2+ release in skeletal and cardiac muscle. In non-muscle cells, however, where the RyRC also participates in Ca2+ signalling, the mechanism of RyRC activation is unknown. Cyclic adenosine 5'-diphosphoribose (cADPR), which is present in many mammalian tissues, has been reported to induce Ca2+ release from ryanodine-sensitive intracellular Ca2+ stores in sea urchin eggs. Here we provide evidence that cADPR directly activates the cardiac but not the skeletal isoform of the RyRC. This, together with results on sea urchin eggs, suggests that cADPR is an endogenous activator of the non-skeletal type of RyRC and may thus have a role similar to inositol 1,4,5-trisphosphate in Ca2+ signalling.

Influence of short-term dexfenfluramine therapy on glucose and lipid metabolism in obese non-diabetic patients

In a short-term (eight days) double-blind crossover study involving 10 obese patients, the effects of dexfenfluramine on glucose and lipid metabolism were examined. The protocol comprised whole body in vivo measurements (hyperinsulinemic euglycemic clamp in combination with indirect calorimetry) and in vitro studies of isolated adipocytes (lipolysis and glucose transport). All study participants were weight stable during the study period (103.1 +/- 3.2, placebo vs 103.3 +/- 3.1 kg, dexfenfluramine, NS). The following parameters were significantly reduced after dexfenfluramine treatment: fasting levels of plasma glucose (6.2 +/- 0.2 vs 5.7 +/- 0.2 mmol/l, p < 0.01), serum insulin (168.0 +/- 14.5 vs 138.9 +/- 7.9 pmol/l, p < 0.05), serum C-peptide (0.68 +/- 0.03 vs 0.58 +/- 0.02 nmol/l, p < 0.05) and total serum cholesterol (6.07 +/- 0.41 vs 5.48 +/- 0.38 mmol/l, p < 0.01). In the basal state glucose oxidation rate was significantly reduced by 36% (p < 0.001), whereas non-oxidative glucose disposal was significantly increased by 41% (p < 0.01), following dexfenfluramine treatment. Insulin-stimulated (2 mU.kg-1 x min-1) glucose disposal rate tended to be increased (18%, p = 0.10) after dexfenfluramine. In conclusion, dexfenfluramine possesses beneficial regulatory effects on glucose and lipid metabolism in non-diabetic obese patients, independently of weight loss.

Simultaneous internalization and binding of calcium during the initial phase of calcium uptake by the sarcoplasmic reticulum Ca pump

The kinetics of Ca2+ transport mediated by the sarcoplasmic reticulum (SR) Ca-ATPase were investigated by rapid kinetic techniques that either measure the disappearance of Ca2+ from the medium [stopped-flow photometry of Ca2+ indicators or rapid filtration (method 1)] or directly detect the changes in the accessibility of Ca2+ to the exterior of the membrane, i.e., occlusion of Ca2+ within the Ca pump and Ca2+ transport into the lumen of SR vesicles [EGTA quench (method 2)]. SR vesicles were preincubated in micromolar Ca2+ to form the E.2Cacyt intermediate of the Ca-ATPase, and then Ca2+ transport was initiated by addition of ATP. It was found that Ca2+ uptake measured by method 1 began with no lag phase, in spite of the prediction of kinetic models of the Ca-ATPase. Instead, the time course of Ca2+ uptake was found to have two components: a fast and a slow phase, similar to that obtained using method 2, although the rate constant of the fast phase determined by method 1 was considerably lower than that measured by method 2. The fast phase of Ca2+ uptake measured by method 1 was not influenced by either Ca2+ ionophore or detergent treatment, whereas the slow phase was diminished.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sulfonylureas on adipocyte and skeletal muscle insulin action in patients with non-insulin-dependent diabetes mellitus

The effect of glibenclamide treatment on insulin action in isolated fat cells was studied in eight moderately obese patients with non-insulin-dependent diabetes mellitus (NIDDM). Insulin receptor binding and the effect of insulin on glucose transport and lipogenesis were determined before and after 3 months of glibenclamide therapy. At the end of the treatment period, mean daytime plasma glucose concentrations were reduced (10.8 +/- 0.4 versus 7.0 +/- 0.3 mmol/L, p less than 0.001) whereas mean daytime plasma insulin level was increased (40 +/- 12 versus 71 +/- 9 mU/L, p less than 0.001). Adipocyte insulin receptor binding as well as basal glucose transport and metabolism were unaffected by drug treatment. In contrast, insulin-stimulated glucose transport and lipogenesis were both significantly enhanced (p less than 0.05). These findings are comparable to those of another study involving seven moderately obese subjects with NIDDM who had biopsies of the lateral vastus muscle taken for measurement of insulin receptor function and glycogen synthase activity before and during 2 months of gliclazide treatment. In that study insulin receptors purified with wheatgerm agglutinin showed unchanged insulin binding and receptor kinase activity. Moreover, gliclazide had no impact on maximal glycogen synthase activity. However, under physiologic hyperinsulinemic conditions gliclazide therapy was associated with an increased sensitivity of glycogen synthase for its allosteric activation by glucose-6-phosphatase (p less than 0.04). In conclusion, sulfonylurea treatment of NIDDM enhances insulin-stimulated peripheral glucose utilization in part through a potentiation of insulin action on adipose tissue glucose transport and lipogenesis and skeletal muscle glycogen synthase.

The effects of metformin on adipocyte insulin action and metabolic control in obese subjects with type 2 diabetes

To investigate the mechanisms of action of metformin, insulin receptor binding and the activity of several insulin-controlled metabolic pathways were measured in adipocytes taken from 10 obese Type 2 diabetic patients treated for 4 weeks with either metformin (0.5 g x 3 daily) or matching placebo using a double-blind crossover design. Metformin therapy was associated with a significant fall in serum fructosamine levels (3.1 +/- 0.4 vs 2.8 +/- 0.4 mmol l-1, p less than 0.02) as well as fasting (10.8 +/- 2.4 vs 9.4 +/- 2.1 mmol l-1) and daytime (11.5 +/- 2.4 vs 10.0 +/- 2.2 mmol l-1) plasma glucose concentrations (p less than 0.05). Fasting and postprandial plasma levels of C-peptide and insulin were unchanged. While fasting plasma lactate concentrations remained unaltered after metformin, a rise was noted in response to meals (from 1.4 +/- 0.1 to 1.8 +/- 0.2 mmol l-1, p less than 0.05). Adipocyte insulin receptor binding was unaffected by drug treatment. Moreover, no insulin-like effects or post-binding potentiation of insulin action could be found on adipocyte glucose transport, glucose oxidation, lipogenesis, glycolysis or antilipolysis. A complementary in vitro study using adipocytes from non-obese healthy volunteers failed to show any direct effect of metformin on adipocyte insulin binding or glucose transport and metabolism, at media drug concentrations corresponding to therapeutic plasma levels.

A mixed meal potentiates the insulin sensitivity of glucose transport and metabolism in adipocytes from patients with type 2 diabetes mellitus

Post-glucose enhancement of insulin action may represent a physiological mechanism for the acute regulation of insulin sensitivity of target tissues. To clarify whether a similar mechanism is operative in the insulin-resistant diabetic state we have investigated the effects of a mixed meal on adipocyte insulin action in eight patients with Type 2 diabetes mellitus. Ninety minutes after ingestion of breakfast insulin binding to fat cells increased by 21% (p less than 0.05). In the fasting state 6 patients had a significant response of glucose transport and lipogenesis to insulin whereas two exhibited non-responsiveness. In the 6 responders insulin sensitivity, as estimated by the insulin concentration at which half-maximal effect was achieved, increased for glucose transport (before, 260 +/- 46 pmoll-1; after, 105 +/- 21 pmol l-1; p less than 0.05) and for lipogenesis (before, 36 +/- 9 pmol l-1; after, 9 +/- 2 pmol l-1; p less than 0.05). No significant changes occurred in basal or maximal glucose transport or lipogenesis. In the two primary non-responders intake of the meal was associated with average increase in maximal insulin responsiveness of 52% for glucose transport and 28% for lipogenesis. Intake of a mixed meal is associated with a slight increase of insulin binding to adipocytes from patients with Type 2 diabetes mellitus but a marked increase of adipocyte insulin sensitivity at the post-binding levels of glucose transport and metabolism.

Characterization of the insulin resistance of glucose utilization in adipocytes from patients with hyper- and hypothyroidism

Insulin action on glucose utilization was characterized in adipocytes from 10 thyrotoxic patients, 6 hypothyroid patients and 10 age- and sex-matched control subjects. In thyrotoxic patients insulin binding at low insulin concentrations was reduced (P less than 0.05) and accompanied by impaired insulin sensitivity of glucose transport (P less than 0.02), glucose oxidation (P less than 0.05) and lipogenesis (P less than 0.05). Glucose transport and glucose oxidation rates also exhibited depressed maximal insulin responsiveness (P less than 0.05). In hypothyroid patients insulin binding was reduced, too, (P less than 0.05) and associated with impaired sensitivity to insulin of glucose transport (P less than 0.05). Both glucose transport and lipogenesis rates showed decreased maximal insulin responsiveness (P less than 0.05).

IN CONCLUSION

In man, both hyper- and hypothyroidism are characterized by insulin resistance of adipocyte glucose utilization localized to insulin binding as well as to insulin-stimulated glucose transport and metabolism.

Insulin action and insulin secretion in identical twins with MODY. Evidence for defects in both insulin action and secretion

To evaluate the pathogenetic mechanisms responsible for development of diabetes in the genetically inherited disease maturity-onset diabetes of the young (MODY), we have investigated a pair of identical twins (19 yr old) from a MODY family. One twin had nondiabetic fasting plasma glucose values but impaired glucose tolerance (IGT), whereas the other suffered from frank diabetes (fasting plasma glucose 12.5 mM). Differences in insulin secretion pattern and/or insulin action between the twins is supposed to be responsible for development of hyperglycemia in MODY. On the other hand, identical defects in insulin secretion and action in the twins may point to the primary genetic defect in MODY. Therefore, our aim was to investigate insulin secretion and insulin action in the twins to find these differences and similarities. We found that fasting plasma insulin and C-peptide values were slightly increased in the twins, whereas the responses of insulin and C-peptide to oral glucose tolerance tests (OGTT) and meals were similar in the twins and within normal range. The insulin responses to OGTT were, however, lower than expected from the glucose values, indicating a beta-cell defect. Despite elevated plasma insulin levels, basal hepatic glucose output (HGO) was normal in the IGT twin but increased by 75% in the diabetic twin. The maximally inhibitory effect of insulin on HGO, when estimated at euglycemia, was normal in the IGT twin but reduced by 60% in the diabetic twin. Furthermore, the maximal insulin-mediated glucose uptake in peripheral tissues was reduced by 40% in the diabetic twin.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced hepatic insulin sensitivity, but peripheral insulin resistance in patients with type 1 (insulin-dependent) diabetes

Sensitivity to insulin in vivo was studied in 8 normal weight C-peptide negative Type 1 (insulin-dependent) diabetic patients (age 23 +/- 1 years, diabetes duration 6 +/- 2 years), and in 8 age, weight and sex matched healthy subjects, using the euglycaemic clamp and 3-3H-glucose tracer technique. Prior to the study diabetic patients were maintained normoglycaemic overnight by a glucose controlled insulin infusion. Sequential infusions of insulin in 3 periods of 2 h resulted in mean steady state insulin levels of 12 +/- 2 versus 11 +/- 1, 18 +/- 2 versus 18 +/- 2 and 28 +/- 3 versus 24 +/- 2 microU/ml in diabetic patients and control subjects. Corresponding glucose utilization rates were 2.4 +/- 0.2 versus 2.4 +/- 0.1, 2.4 +/- 0.2 versus 3.0 +/- 0.3 and 2.9 +/- 0.3 versus 4.6 +/- 0.6 mg.kg-1.min-1, p less than 0.02. Portal insulin values in the three periods were calculated to 12 +/- 2 versus 25 +/- 3, 18 +/- 2 versus 32 +/- 3 and 28 +/- 3 versus 37 +/- 3 microU/ml in the diabetic patients and control subjects using peripheral insulin and C-peptide concentrations and assuming a portal to peripheral insulin concentration gradient of 1 in diabetic patients and of 2.4 in control subjects. Corresponding glucose production rates were 2.5 +/- 0.2 versus 2.4 +/- 0.1, 1.6 +/- 0.1 versus 0.9 +/- 0.2 and 0.7 +/- 0.1 versus 0.4 +/- 0.2 mg.kg-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased insulin binding is not involved in the improved insulin effectiveness of gestational diabetics after hypoenergetic dieting

125I-Insulin binding to monocytes from 14 gestational diabetics was measured before and after 6 weeks of treatment with a 5500 kJ, low-fat, low-sucrose diet. After the hypoenergetic feeding of gestational diabetics, fasting plasma concentrations of glucose (P less than 0.01) and insulin (P less than 0.05) decreased significantly, whereas insulin binding was unaltered. Provided the monocyte insulin receptor reflects insulin receptors of more determinant tissues for insulin action, our data indicate that an increased insulin receptor binding is not involved in the improved insulin effectiveness of gestational diabetics after hypoenergetic dieting.