Nanotechnology and protein mechanics

The atomic force microscope is currently used in our and many other laboratories to measure the mechanical response of polypeptide and proteins against tensile forces applied to well defined positions in their chemical structures. The resulting force vs. extension (F-E) curves are analyzed in relation to their known conformations under various conditions. The method can be extended to study the mechanical responses of other, often much larger biological structures, and extract the component proteins and DNAs from cell membranes and chromosomes.

IL-6 and TNF-alpha expression in, and release from, contracting human skeletal muscle

The aim of the present study was to examine whether IL-6 and TNF-alpha are expressed in, and released from, human skeletal muscle during exercise. We hypothesized that the skeletal muscle will release IL-6, but not TNF-alpha, during exercise because of previous observations that TNF-alpha negatively affects glucose uptake in skeletal muscle. Six healthy, male subjects performed 180 min of two-legged knee-extensor exercise. Muscle samples were obtained from the vastus lateralis of one limb. In addition, blood samples were obtained from a femoral artery and vein. Plasma was analyzed for IL-6 and TNF-alpha. We detected both IL-6 and TNF-alpha mRNA in resting muscle samples, and whereas IL-6 increased (P < 0.05) approximately 100-fold throughout exercise, no significant increase in TNF-alpha mRNA was observed. Arterial plasma TNF-alpha did not increase during exercise. Furthermore, there was no net release of TNF-alpha either before or during exercise. In contrast, IL-6 increased throughout exercise in arterial plasma, and a net IL-6 release from the contracting limb was observed after 120 min of exercise (P < 0.05).

Decreased synthesis of matrix metalloproteinase-7 and adhesion to the extracellular matrix proteins of human colon cancer cells treated with troglitazone

PURPOSE

In the present study, we investigated the effect of troglitazone, a selective ligand and agonist of PPAR-gamma, on the metastatic potential of human colon cancer cells.

METHODS

High- and low-PPAR-gamma expression clones of the colon cancer cell line, HT29, namely clones 21 and 3 respectively, were used. We investigated the effect of troglitazone on the proliferation, on the adhesion to extracellular matrix proteins and on the synthesis of matrix metalloproteinases (MMPs) of colon cancer cells.

RESULTS

Troglitazone inhibited the proliferation of both subclones, in a dose-dependent manner, and the inhibitory effect correlated with the level of PPAR-gamma expression. Troglitazone strongly inhibited the production of MMP-7, an enzyme associated with invasiveness of cancer cells, by both subclones. In addition, troglitazone caused a strong decrease in the adhesion of clone 21 to extracellular matrix (ECM) proteins, laminin and type IV collagen. This effect was independent of beta1-integrins expression

CONCLUSION

In addition to inhibition of cancer cell growth, troglitazone had an inhibitory effect on two important events associated with the metastatic potential of cancer cells, production of MMPs and adhesion to ECM proteins. Consequently, troglitazone is a promising agent for the treatment and prevention of colon cancer metastasis.

Blood flow and oxygen uptake increase with total power during five different knee-extension contraction rates

Controversies exist regarding quantification of internal power (IP) generated by the muscles to overcome energy changes of moving body segments when external power (EP) is performed. The aim was to 1) use a kinematic model for estimation of IP during knee extension, 2) validate the model by independent calculation of IP from metabolic variables (IP(met)), and 3) analyze the relationship between total power (TP = EP + IP) and physiological responses. IP increased in a curvilinear manner (5, 7, 13, 21, and 34 W) with contraction rate (45, 60, 75, 90, and 105 contractions/min), but it was independent of EP. Correspondingly, IP(met) was 5, 7, 10, 19, and 28 W, supporting the kinematic model. Heart rate, pulmonary oxygen uptake, and leg blood flow plotted vs. TP fell on the same line independent of contraction rate, and muscular mechanical efficiency as well as delta efficiency remained remarkably constant across contraction rates. It is concluded that the novel metabolic validation of the kinematic model supports the model assumptions, and physiological responses proved to be closely related to TP, supporting the legitimacy of IP estimates.

Effects of nitrite and ammonium on methane-dependent denitrification

For effective application of methane-dependent denitrification (MDD) in the treatment of wastewater containing NO(2)(-) or NH(4)(+), the effect of these inorganic nitrogen compounds on MDD activity needs to be clarified. The MDD activity of sludge acclimatized with CH(4) and O(2) was determined with mineral media of different nitrogen-compound compositions in the presence of 0.21 atm CH(4) and 0.20 atm O(2). Incubations with media containing only NO(2)(-) or two of the three inorganic nitrogen compounds (NO(3)(-)+NO(2)(-), NO(2)(-)+NH(4)(+) or NH(4)(+)+NO(3)(-)) resulted in MDD activity equal to or higher than that with media containing only NO(3)(-). However, there was no MDD activity in media containing NO(2)(-) at 10 degrees C, probably because of serious inhibition of NO(2)(-) on methane oxidation. MDD occurred in media containing only NH(4)(+), although the total nitrogen removal efficiency was very low. These results show that NO(2)(-) and NH(4)(+), in the presence of NO(x)(-), do not inhibit but rather promote MDD. Consequently, NH(4)(+) does not need to be completely oxidized to NO(3)(-) in the nitrification reactor before MDD. However, under psychrophilic conditions, NO(2)(-) seriously inhibited MDD. Therefore, the nitrification reactor must not discharge effluent containing NO(2)(-) under psychrophilic conditions.

Muscle glycogen content and glucose uptake during exercise in humans: influence of prior exercise and dietary manipulation

There are many factors that can influence glucose uptake by contracting skeletal muscle during exercise and although one may be intramuscular glycogen content, this relationship is at present not fully elucidated. To test the hypothesis that muscle glycogen concentration influences glucose uptake during exercise, 13 healthy men were studied during two series of experiments. Seven men completed 4 h of two-legged knee extensor exercise 16 h after reducing of muscle glycogen by completing 60 min of single-legged cycling (Series 1). A further six men completed 3 h of two-legged knee extensor exercise on two occasions: one after 60 min of two-legged cycling (16 h prior to the experimental trial) followed by a high carbohydrate diet (HCHO) and the other after the same exercise followed by a low carbohydrate diet (LCHO) (Series 2). Muscle glycogen was decreased by 40 % when comparing the pre-exercised leg (EL) with the control leg (CL) prior to exercise in Series 1. In addition, muscle glycogen was decreased by the same magnitude when comparing LCHO with HCHO in Series 2. In Series 1, glucose uptake was 3-fold higher in the first 60 min of exercise, in the presence of unchanged pre-exercise GLUT4 protein in EL compared with CL, suggesting that the lower glycogen, and not the exercise the day before, might have provided the stimulus for increased glucose uptake. Despite the same magnitude of difference in pre-exercise glycogen concentration when comparing Series 1 with Series 2, neither direct-nor isotopic tracer-determined glucose uptake was higher in LCHO compared with HCHO in Series 2. However, arterial concentrations of insulin and glucose were lower, while free fatty acids and adrenaline were higher in LCHO compared with HCHO. These data suggest that pre-exercise glycogen content may influence glucose uptake during subsequent exercise. However, this is only the case when delivery of substrates and hormones remains constant. When delivery of substrates and hormones is altered, the potential effect of glycogen on glucose uptake is negated.

Quantitative effects of respiration on venous return during single knee extension-flexion

Respiration and the muscle pump play major roles in increasing venous return. However, the relative contribution of each of these factors remains unclear. The present study investigates the quantitative effects of interaction between respiration and the muscle pump on femoral venous blood flow (FVBF) during a single voluntary knee extension-flexion (KEF) using duplex-Doppler ultrasound. During various respiration modes, which consisted of arrested respiration, normal respiration and deep respiration (inspiration or expiration), eight subjects performed a supine one-legged voluntary KEF. FVBF was measured during respiration only (Protocol A) and during KEF synchronized with respiration (Protocol B). The difference between FVBF values obtained in Protocol B and Protocol A was defined as DeltaFVBF. When KEF was synchronized with normal or deep respiration, FVBF with inspiration was significantly lower than that with expiration. However, DeltaFVBF was significantly higher with inspiration than with expiration during deep respiration but was not significant during normal respiration. Furthermore, DeltaFVBF was significantly higher at both normal and deep respiration than at arrested respiration. The effects upon the venous return during KEF differed between inspiration and expiration. The present findings indicate that during a single supine KEF, respiration might promote venous return to a range of 1.5- to 2.3-fold DeltaFVBF during arrested respiration.

Intramuscular fatty acid metabolism in contracting and non-contracting human skeletal muscle

The present study was undertaken to investigate the fate of blood-borne non-esterified fatty acids (NEFA) entering contracting and non-contracting knee extensor muscles of healthy young individuals. [U-(13)C]-palmitate was infused into a forearm vein during 5 h of one-legged knee extensor exercise at 40 % of maximal work capacity and the NEFA kinetics, oxidation and rate of incorporation into intramuscular triacylglycerol (mTAG) were determined for the exercising and the non-exercising legs. During 4 h of one-legged knee extensor exercise, mTAG content decreased by 30 % (P < 0.05) in the contracting muscle, whereas it was unchanged in the non-contracting muscle. The uptake of plasma NEFA, as well as the proportion directed towards oxidation, was higher in the exercising compared to the non-exercising leg, whereas the rate of palmitate incorporation into mTAG was fourfold lower (0.70 +/- 0.14 vs. 0.17 +/- 0.04 micromol (g dry wt)(-1) h(-1); P < 0.05), resulting in fractional synthesis rates of 1.0 +/- 0.2 and 3.8 +/- 0.9 % h(-1) (P < 0.01) for the contracting and non-contracting muscle, respectively. These findings demonstrate that mTAG in human skeletal muscle is continuously synthesised and degraded and that the metabolic fate of plasma NEFA entering the muscle is influenced by muscle contraction, so that a higher proportion is directed towards oxidation at the expense of storage in mTAG.

Femoral artery inflow in relation to external and total work rate at different knee extensor contraction rates

Whether limb blood flow is directly regulated to match the work rate, independent of the rate of contraction, remains elusive. This study therefore investigated the relationship between femoral arterial blood flow (FABF; Doppler ultrasound) and "external" (applied load) as well as "total" [external + "internal" (potential and kinetic energy changes of the moving lower leg)] work rate, during steady-state one-legged, dynamic, knee extensor exercise (1L-KEE) in the sitting position at different contraction rates. Ten subjects performed 1L-KEE at 30, 60, and 90 contractions/min (cpm) 1) at constant resistive loads of 0.2 and 0.5 kg inducing incremental external work rates (study I) and 2) at different relative resistive loads inducing constant external work rates of 9 and 18 W (study II). Moreover, 3) six subjects performed 1L-KEE at 60 and 100 cpm at incremental total work rates of 40, 50, 60, and 70 W (study III). In study I, FABF increased (P < 0.001) with increasing contraction frequency and external work rate, for each resistive load. In study II, FABF increased (P < 0.001) with increasing contraction frequency for each constant external work rate. Of major importance in study III, however, was that FABF, although increasing linearly with the total work rate, was not different (P = not significant) between contraction rates, at the total work rates of 40, 50, 60, and 70 W, respectively. Furthermore, FABF correlated linearly and positively with both the external and total work rate for each contraction frequency. In conclusion, the findings support the concept that leg blood flow during 1L-KEE in a normal knee extensor ergometer is matched directly in relation to the total work rate and metabolic activity, irrespective of the contraction frequency. The rate of contraction seems erroneously to influence the results only when it is related to the external work rate without taking into account the internal work component.

Dendritic cells cultured in anti-CD40 antibody-immobilized plates elicit a highly efficient peptide-specific T-cell response

The function of dendritic cells (DCs), antigen-presenting cells that can initiate and regulate cellular and humoral responses, is highly influenced by their level of maturation. Immature DCs may be harmful in anti-tumor immunotherapy, because they can induce immunotolerance rather than immunostimulation. In this study, the authors sought to determine the optimal culture conditions for obtaining fully mature DCs. When DCs were cultured in agonistic anti-CD40 monoclonal antibody-immobilized plates, they showed a higher expression of the maturation marker CD83 than DCs cultured without CD40 ligation or those cultured in medium supplemented with anti-CD40 monoclonal antibody. In addition, when interferon-gamma (IFN-gamma) was added to the medium, additive up-regulation of CD83 expression was observed. These DCs treated with both maturation signals showed a higher secretion of interleukin-12. To evaluate the capacity of antigen presentation, specific cytotoxic T lymphocytes were generated using autologous DC pulsed with a human lymphocyte antigen-A24-restricted peptide epitope derived from carcinoembryonic antigen. Interferon-gamma-secreting CD8+ T cells were analyzed by flow cytometry using the cellular affinity matrix technology. Dendritic cells, matured with CD40 ligation and IFN-gamma, were more efficient at eliciting an antigen-specific T-cell response in vitro than DCs stimulated with anti-CD40 monoclonal antibody or IFN-gamma alone. A cytotoxicity assay using carcinoembryonic antigen-expressing tumor cell lines also showed that DCs matured with both signals were more efficient at inducing cytotoxic T lymphocytes. These results demonstrate that DC culture in an anti-CD40 monoclonal antibody-immobilized plate in medium supplemented with IFN-gamma has a positive impact on DC maturation and may be optimal for eliciting an antigen-specific T-cell response without the need for CD4+ T-helper epitopes.

Transcriptional activation of the IL-6 gene in human contracting skeletal muscle: influence of muscle glycogen content

In humans, the plasma interleukin 6 (IL-6) concentration increases dramatically during low-intensity exercise. Measurements across the working limb indicate that skeletal muscle is the source of IL-6 production. To determine whether energy availability influences the regulation of IL-6 expression during prolonged exercise, six male subjects completed two trials consisting of 180 min of two-legged dynamic knee extensor with either normal or low (~60% of control) pre-exercise muscle glycogen levels. Increases in plasma IL-6 during exercise were significantly higher (P<0.05) in the low-glycogen (16-fold) trial verses the control (10-fold) trial. Transcriptional activation of the IL-6 gene in skeletal muscle was also higher in the low-glycogen trial; it increased by about 40-fold after 90 min of exercise and about 60-fold after 180 min of exercise. Muscle IL-6 mRNA followed a similar but delayed pattern, increasing by more than 100-fold in the low-glycogen trial and by about 30-fold in the control trial. These data demonstrate that exercise activates transcription of the IL-6 gene in working skeletal muscle, a response that is dramatically enhanced when glycogen levels are low. These findings also support the hypothesis that IL-6 may be produced by contracting myofibers when glycogen levels become critically low as a means of signaling the liver to increase glucose production.

Interleukin-6 production in contracting human skeletal muscle is influenced by pre-exercise muscle glycogen content

1. Prolonged exercise results in a progressive decline in glycogen content and a concomitant increase in the release of the cytokine interleukin-6 (IL-6) from contracting muscle. This study tests the hypothesis that the exercise-induced IL-6 release from contracting muscle is linked to the intramuscular glycogen availability. 2. Seven men performed 5 h of a two-legged knee-extensor exercise, with one leg with normal, and one leg with reduced, muscle glycogen content. Muscle biopsies were obtained before (pre-ex), immediately after (end-ex) and 3 h into recovery (3 h rec) from exercise in both legs. In addition, catheters were placed in one femoral artery and both femoral veins and blood was sampled from these catheters prior to exercise and at 1 h intervals during exercise and into recovery. 3. Pre-exercise glycogen content was lower in the glycogen-depleted leg compared with the control leg. Intramuscular IL-6 mRNA levels increased with exercise in both legs, but this increase was augmented in the leg having the lowest glycogen content at end-ex. The arterial plasma concentration of IL-6 increased from 0.6 +/- 0.1 ng x l(-1) pre-ex to 21.7 +/- 5.6 ng x l(-1) end-ex. The depleted leg had already released IL-6 after 1 h (4.38 +/- 2.80 ng x min(-1) (P < 0.05)), whereas no significant release was observed in the control leg (0.36 +/- 0.14 ng x min(-1)). A significant net IL-6 release was not observed until 2 h in the control leg. 4. This study demonstrates that glycogen availability is associated with alterations in the rate of IL-6 production and release in contracting skeletal muscle.

Peripheral blood dendritic cells, but not monocyte-derived dendritic cells, can augment human NK cell function

Dendritic cells (DCs) are essential antigen-presenting cells with a wide variety of functions relating to both adaptive and innate immunity. Recently, interactions of DCs with natural killer (NK) cells and NK1.1-positive T cells have been reported in mice. However, in humans, this interaction is not well understood. Here we report the use of a coculture method to analyze the modulation of NK cell function in antitumor immunity by DCs. We found that peripheral blood DCs (PDCs) enhanced NK cell activity in cytotoxicity assay, even without direct contact between DC and NK cells. In contrast, neither monocyte-derived DCs (MoDCs), nor TNF-alpha-treated MoDCs, stimulated NK lytic activity. Secretion of IL-12 and TNF-alpha into the PDC-NK coculture supernatant was increased. However, blocking antibodies against these cytokines could not completely abolish the upregulation of NK activity, suggesting the presence of other soluble factor(s) that affect DC-NK cell interaction. To summarize, this study demonstrates for the first time the direct activation of human NK cells by DC-NK cell interaction in vitro, suggesting that DCs may have a central role linking the innate and adaptive immune responses. Moreover, in stimulating NK cell function, PDCs appear to have a different potential from MoDCs.

Clustered cancer cells show a distinct adhesion behavior from single cell form under physiological shear conditions

It remains a question whether hematogeneous metastasis arises from a single cancer cell attached to the local endothelium or from a cluster of cancer cells trapped in the vascular bed in the target organ. Adhesive interaction of the single cell form and the clustered form of cancer cells was examined under flow conditions, using two subclones of mouse colon adenocarcinoma Colon 26. A subclone NL17, but not NL14, formed many clusters composed of tumor cells and platelets just after the addition of platelet rich plasma (PRP). Under the shear of 1.0 dyn/cm3, the clustered form of NL17 tethered on laminin or mouse endothelial cell line in hepatic sinusoids (HSE) more frequently than the single cell form of NL17 and NL14. However, all of the clusters showed only transient attachment and never underwent stable arrest on coated laminin, while the single cell form of NL14 and NL17 underwent immediate arrest under shear conditions. On HSE stimulated with TNF-alpha, a small number of NL17 clusters made stable adhesion, although all the clusters detached if the shear stress was increased above 4.0 dyn/cm2. In contrast, the single form of arrested NL17 as well as NL14 remained adherent even at shear of 8.0 dyn/cm2. Compared with single cell, binding of cancer cell clusters to laminin and HSE showed lower resistance to shear stress, although they had adhesive interactions more frequently in flow condition. Since NL17 cells form significantly more metastases by intravenous injection in vivo, our data suggest that "stable adhesion" observed in our flow assay system is not always a prerequisite for clustered cancer cells to develop into metastatic lesions.

Male reproductive defects caused by puromycin-sensitive aminopeptidase deficiency in mice

Male reproductive performance is composed of two principal elements, copulation and spermatogenesis. A wealth of literature has described the intricate web of endocrine events underlying these biological processes. In the present study we show that puromycin-sensitive aminopeptidase (Psa)-deficient mice are infertile, lack copulatory behavior, and have impaired spermatogenesis. The reproductive deficits of the mutants are not restored by androgen administration, although no aberrant localization of the sex steroid receptors was detectable in their brains and testes. Considering the strong expression of the Psa gene in the brain and Sertoli cells and the degenerative morphology of Sertoli cells in Psa-deficient mice, Psa may participate in testosterone-mediated reproductive signal pathways in the brain and testis.

Puromycin-sensitive aminopeptidase is essential for the maternal recognition of pregnancy in mice

Maternal recognition of pregnancy in rodents requires semicircadian surges of hypophyseal PRL secretion during early gestation, which are required for the formation of the corpus luteum of pregnancy (CLP). Here we show that puromycin-sensitive aminopeptidase (Psa)-deficient mice display female infertility that results from impaired formation of CLP. Transplantation of mutant ovaries into normal females restored fertility but not vice versa. Psa-deficient females revealed no semicircadian surges of PRL induced after mating stimuli. Pregnancy in the mutant females was restored by grafting intact pituitaries to elevate circulating levels of PRL. Psa is thus required for the appearance of the semicircadian surges of PRL secretion that are crucial for maintaining pregnancy in rodents.

Dendritic cells activate antitumor immunity for malignant intracranial germ cell tumor: a case report

We report a 22-year-old male patient with a history of intracranial malignant germ cell tumor (GCT) who had undergone tumor resection twice, followed by radiation and chemotherapy. The tumor had rapidly recurred along the entire ventricular wall with extensive invasion into the brain parenchyma. The serum level of human beta-chorionic gonadotropin (beta-hCG) was 232.3 ng/ml on admission. Although tissue samples of the recurrent tumor could not be obtained, the previous histological diagnosis of germinoma and elevated serum beta-hCG levels suggested recurrence of malignant GCT. The patient declined chemotherapy but accepted dendritic cell (DC)-based immunotherapy. DC inoculation five times resulted in rapid tumor shrinkage and a significant decrease in the serum level of beta-hCG. Here we discuss the effectiveness of immunotherapy using DCs for recurrent intracranial malignant GCTs.

Hofstadter butterfly and integer quantum hall effect in three dimensions

For a three-dimensional (3D) lattice in magnetic fields we have shown that the hopping along the third direction, which normally smears out the Landau quantization gaps, can rather give rise to a Hofstadter's butterfly specific to 3D when a criterion is fulfilled by anisotropic (quasi-one-dimensional) systems. In 3D the angle of the magnetic field plays the role of the field intensity in 2D, so that the butterfly can occur in much smaller fields. We have also calculated the Hall conductivity in terms of the topological invariant in the Kohmoto-Halperin-Wu formula, and each of sigma(xy),sigma(zx) is found to be quantized.

Thoracic empyema associated with recurrent colon cancer: report of a case and review of the literature

Many types of infections associated with colorectal cancer have been reported. Here, we describe a rare case of thoracic empyema that was observed during immunotherapy for recurrent colon cancer. Culture of the pleural fluid yielded Streptococcus bovis, which is known to be associated with gastrointestinal lesions, especially colorectal malignancies. The possible correlation between these two clinical entities-empyema and colon cancer-is discussed.

Development of a new dynamic chamber system for measuring harmful gas emissions from composting livestock waste

A dynamic chamber system consisting of a chamber covering a composting mixture (3 m in diameter, 2.2 m in height, 13 m3), a ventilator for suction of air into the chamber, and equipment to measure the gas composition and indicate temperature, was developed for evaluation of harmful gas emissions from such livestock waste composting. Fresh air was introduced through the space between the floor and the lower edge of the chamber, and exhaust gas was removed through an outlet placed on top of the chamber. NH3, CH4 and N2O concentrations in exhaust air from the chamber were measured by Infrared Photoacoustic Detector (IPD, multi gas monitor type 1312, INNOVA, Copenhagen, Denmark) at 5 minutes intervals. The system was evaluated with standard gas of NH3, CH4 and N2O. High recoveries of 98.5% (NH3, SD 6.25), 96.6% (CH4, SD 4.03) and 99.5% ( N2O, SD 2.68) were obtained for each gas emission in the chamber over 17-20 min. The measured values of those gases obtained by the IPD method and conventional method at the time of a composting examination of swine waste were measured, and the differences were only a few percent of the total emissions.

Entropy and holography constraints for inhomogeneous universes

We calculated the entropy of a class of inhomogeneous dust universes. Allowing spherical symmetry, we proposed a holographic principle by reflecting all physical freedoms on the surface of the apparent horizon. In contrast to flat homogeneous counterparts, the principle may break down in some models. We refined fractal parabolic solutions to have a reasonable entropy value for the present observable universe and found that the holographic principle always holds in the realistic cases.

Implications of mechanical stretch on wound repair of gastric smooth muscle cells in vitro

Gastric smooth muscle cells continually receive repetitive physical stretching by food storage, peristalsis and fasting contraction; therefore mechanical stretch can not be disregarded in gastric events. The aim of this study was to clarify the effects of mechanical stretch on wound repair using a rabbit gastric smooth muscle cell sheet. Mechanical stretch was imposed on adherent cells on a flexible membrane in order to increase elongation by an average of 5% and 10%, respectively, at 5 cycles per minute after artificial wounding. Adherent cells not subjected to mechanical stretch served as controls. The restoration process was monitored by measuring wound size for 48 h. Proliferation was assessed by BrdU staining and the influence on the cytoskeletal system was assessed by actin staining. The speed of restoration was highest in controls and lowest in the 10% stretch groups. Proliferation was almost equal to that of controls in the stretch groups. Under the condition of mechanical stretch, stress fibers appeared weakened and the direction of fibers was not consistent but random. In conclusion, mechanical stretch inhibited the migration of gastric smooth muscle cells, leading to cytoskeletal dysfunction. It is suggested that physical stretch, such as mechanical stretch, might be an important factor in the process of gastric wound repair.

Production of interleukin-6 in contracting human skeletal muscles can account for the exercise-induced increase in plasma interleukin-6

1. Plasma interleukin (IL)-6 concentration is increased with exercise and it has been demonstrated that contracting muscles can produce IL-The question addressed in the present study was whether the IL-6 production by contracting skeletal muscle is of such a magnitude that it can account for the IL-6 accumulating in the blood. 2. This was studied in six healthy males, who performed one-legged dynamic knee extensor exercise for 5 h at 25 W, which represented 40% of peak power output (Wmax). Arterial-femoral venous (a-fv) differences over the exercising and the resting leg were obtained before and every hour during the exercise. Leg blood flow was measured in parallel by the ultrasound Doppler technique. IL-6 was measured by enzyme-linked immunosorbent assay (ELISA). 3. Arterial plasma concentrations for IL-6 increased 19-fold compared to rest. The a-fv difference for IL-6 over the exercising leg followed the same pattern as did the net IL-6 release. Over the resting leg, there was no significant a-fv difference or net IL-6 release. The work was produced by 2.5 kg of active muscle, which means that during the last 2 h of exercise, the median IL-6 production was 6.8 ng min-1 (kg active muscle)-1 (range, 3.96-9.69 ng min-1 kg-1). 4. The net IL-6 release from the muscle over the last 2 h of exercise was 17-fold higher than the elevation in arterial IL-6 concentration and at 5 h of exercise the net release during 1 min was half of the IL-6 content in the plasma. This indicates a very high turnover of IL-6 during muscular exercise. We suggest that IL-6 produced by skeletal contracting muscle contributes to the maintenance of glucose homeostasis during prolonged exercise.

Distribution and serum concentration of sisomicin released from fibrin glue-sealed dacron graft in the rat and human

We investigated whether or not fibrin glue (FG) used as a sealant in vascular prostheses to prevent leakage might be useful as a carrier of antibiotics for the prevention of local graft infection. Sisomicin (SISO) was incorporated into fibrin glue (SISO-FG) and evaluated as to its safety and pharmacokinetics. SISO (1.75 mg) -FG Dacron grafts were implanted subcutaneously in the anterior abdominal region of Sprague-Dawley rats, and then the changes in SISO concentrations in the serum and in the tissue around the implantation sites were compared with those same sites in rats that had had intravenous injection of SISO (1.75 mg). The serum SISO concentrations were significantly lower in the SISO-FG Dacron graft group than they were in the intravenous injection group. However, until 4 h after implantation the SISO concentrations in the tissues around the implantation sites were significantly higher in the SISO-FG Dacron group than they were in the iv injection group, and the peak concentrations during that time were 5.8 times higher for the SISO-FG Dacron group than they were for the intravenous injection group. The ratio of the area under the tissue concentration time curve of SISO (AUC tissue) after implantation of the SISO-FG Dacron graft to that after intravenous injection of SISO was 13.08. Therefore, FG was considered to control the release of SISO into the serum and to maintain a high SISO concentration in the tissue around the implantation site. Clinically, SISO (45 mg) -FG was applied directly to the Dacron grafts implanted in 10 patients who underwent prosthetic vascular reconstruction. No graft infection was observed in any of the patients who received SISO-FG Dacron grafts. The mean serum concentration of SISO was 0.65+/-0.17 microg/mL after 1 h and 0.33+/- 0.21 microg/mL after 3 h. The results of these clinical applications are in close correlation with those of the animal experiment and suggest that FG is useful as a carrier of SISO, allowing its controlled release for the prevention of local infection.