Medical Library

Reduced MMP-2 activity contributes to cardiac fibrosis in experimental diabetic cardiomyopathy.

OBJECTIVE: To evaluate the regulation of matrix metalloproteinase (MMP)-2 in diabetic cardiomyopathy. METHODS: Left ventricle (LV) function was determined by a micro-tip catheter in streptozotocin (STZ)-induced diabetic rats, 2 or 6 weeks (w) after STZ-application. LV total collagen, collagen type I and III content were immunohistologically analyzed and quantified by digital image analysis. LV collagen type I, III and MMP-2 mRNA expression was quantified by real-time RT-PCR. LV pro- and active MMP-2 levels were analyzed by zymography; Smad 7, membrane type (MT)1-MMP and tissue inhibitor metalloproteinase (TIMP)-2 protein levels by Western Blot. RESULTS: STZ-induced diabetes was associated with a time-dependent impairment of LV diastolic and systolic function. This was paralleled by a time-dependent increase in LV total collagen content, despite reduced LV collagen type I and III mRNA levels, indicating a role of post-transcriptional/post-translational changes of extracellular matrix regulation. Six weeks (w) after STZ-injection, MMP-2 mRNA expression and pro-MMP-2 levels were 2.7-fold (P < 0.005) and 1.3-fold (P < 0.05) reduced versus controls, respectively, whereas active MMP-2 was decreased to undetectable levels 6 w post-STZ. Concomitantly, Smad 7 and TIMP-2 protein levels were 1.3-fold (P < 0.05) and 10-fold (P < 0.005) increased in diabetics versus controls, respectively, whereas the 45 kDa form of MT1-MMP was undetectable in diabetics. CONCLUSION: Under STZ-diabetic conditions, cardiac fibrosis is associated with a dysregulation in extracellular matrix degradation. This condition is featured by reduced MMP-2 activity, concomitant with increased Smad 7 and TIMP-2 and decreased MT1-MMP protein expression, which differs from mechanisms involved in dilated and ischemic heart disease.

Van Linthout S, Seeland U, Riad A, Eckhardt O, Hohl M, Dhayat N, Richter U, Fischer JW, Böhm M, Pauschinger M, Schultheiss HP, Tschöpe C.

Dept. of Cardiology and Pneumology, Charité-University Medicine Berlin, Campus Benjamin Franklin Hindenburgdamm 30, 12200, Berlin, Germany.

Redox signaling triggers protection during the reperfusion rather than the ischemic phase of preconditioning.

In ischemic preconditioning (IPC) brief ischemia/reperfusion renders the heart resistant to infarction from any subsequent ischemic insult. Protection results from binding of surface receptors by ligands released during the preconditioning ischemia. The downstream pathway involves redox signaling as IPC will not protect in the presence of a free radical scavenger. To determine when in the IPC protocol the redox signaling occurs, seven groups of isolated rabbit hearts were studied. All hearts underwent 30 min of coronary branch occlusion and 2 h of reperfusion. IPC groups were subjected to 5 min of regional ischemia followed by 10 min of reperfusion prior to the 30-min coronary occlusion. The Control group had only the 30-min occlusion and 2-h reperfusion. In the second group IPC preceded the index coronary occlusion. The third group was also preconditioned, but the free radical scavenger N-2-mercaptopropionyl glycine (MPG 300 microM) was infused during the 10-min reperfusion and therefore was present in the myocardium in the distribution of the snared coronary artery during the entire reperfusion phase and also during the subsequent 30-min ischemia. In another preconditioned group MPG was added to the perfusate before the preconditioning ischemia and therefore was present in the tissue only during the preconditioning ischemia and then was washed out during reperfusion. In the fifth group MPG was added to the perfusate for only the last 5 min of the preconditioning reperfusion and therefore was present in the tissue during the last minutes of the reperfusion phase and the 30 min of ischemia. In an additional group of IPC hearts MPG was infused for only the initial 5 min of the preconditioning reperfusion and then allowed to wash out so that the scavenger was present for only the first half of the reperfusion phase. Infarct and risk zone sizes were measured by triphenyltetrazolium staining and fluorescent microspheres, resp. IPC reduced infarct size from 31.3 +/- 2.7% of the ischemic zone in control hearts to only 8.4 +/- 1.9%. MPG completely blocked IPC\’s protection in the third (39.4 +/- 2.8%) and sixth (36.1 +/- 7.7%) groups but did not affect its protection in groups 4 (8.1 +/- 1.5%) or 5 (7.8 +/- 1.1%). When deoxygenated buffer was used during IPC\’s reperfusion phase in the seventh group of hearts, protection was lost and infarct size was increased over that seen in control hearts (74.5 +/- 9.0%). Hence redox signaling occurs during the reperfusion phase of IPC, and the critical component in that reperfusion phase appears to be molecular oxygen.

Dost T, Cohen MV, Downey JM.

Dept. of Physiology, MSB 3074, University of South Alabama, College of Medicine, Mobile, AL, 36688, USA.

Slow contractions characterize failing rat hearts.

The reduced power of the failing heart can be ascribed to a combination of reduced force and slower contraction. We hypothesized that these two properties are due to different cellular mechanisms. We measured contraction parameters both in vivo and in isolated left ventricular (LV) cardiomyocytes from a rat model of post infarction congestive heart failure (CHF). ECG was measured simultaneously with echocardiography and LV pressure, respectively. Shortening and shortening velocity (SV) in isolated cardiomyocytes were measured during different stimulation protocols. LV end diastolic pressure (LVEDP) was 24.6 +/- 0.7 mmHg in CHF. LV systolic pressure was decreased by 20%, maximum rate of pressure development in the LV (+dP/dt (max)) by 36% and time in systole increased by 20% in CHF compared to sham. Electrical remodelling occurred in CHF cells, which were depolarized and had prolonged action potentials (AP) compared to sham cells. Fractional shortening (FS) was increased in CHF compared to sham independent of stimulation protocol. Larger FS was accompanied by increased sarcoplasmic reticulum (SR) Ca(2+) load and depended on the electrical remodelling. Time to peak contraction (TTP) was increased in CHF compared to sham cells, but in contrast to FS, TTP was only slightly affected when the cells were stimulated with sham APs and sham diastolic membrane potential (DMP). Contraction duration (corresponding to systolic duration) was 25% longer in CHF than in sham independent on stimulation protocol. We conclude that electrical remodelling affecting DMP and AP duration (APD) significantly affects the size of contraction, whereas the mechanism for slowing of contraction in CHF is different.

Bøkenes J, Aronsen JM, Birkeland JA, Henriksen UL, Louch WE, Sjaastad I, Sejersted OM.

Institute for Experimental Medical Research, Ullevaal University Hospital, 0407, Oslo, Norway, janny.bokenes@medisin.uio.no.

Support vector machine for classification of walking conditions using miniature kinematic sensors.

A portable gait analysis and activity-monitoring system for the evaluation of activities of daily life could facilitate clinical and research studies. This current study developed a small sensor unit comprising an accelerometer and a gyroscope in order to detect shank and foot segment motion and orientation during different walking conditions. The kinematic data obtained in the pre-swing phase were used to classify five walking conditions: stair ascent, stair descent, level ground, upslope and downslope. The kinematic data consisted of anterior-posterior acceleration and angular velocity measured from the shank and foot segments. A machine learning technique known as support vector machine (SVM) was applied to classify the walking conditions. SVM was also compared with other machine learning methods such as artificial neural network (ANN), radial basis function network (RBF) and Bayesian belief network (BBN). The SVM technique was shown to have a higher performance in classification than the other three methods. The results using SVM showed that stair ascent and stair descent could be distinguished from each other and from the other walking conditions with 100% accuracy by using a single sensor unit attached to the shank segment. For classification results in the five walking conditions, performance improved from 78% using the kinematic signals from the shank sensor unit to 84% by adding signals from the foot sensor unit. The SVM technique with the portable kinematic sensor unit could automatically recognize the walking condition for quantitative analysis of the activity pattern.

Lau HY, Tong KY, Zhu H.

Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong SAR, China, ajaxlau@yahoo.com.hk.

Tensile radial stress in the spinal cord related to arachnoiditis or tethering: a numerical model.

Spinal arachnoiditis comprises fibrous scarring of the subarachnoid space, following spinal trauma or inflammation, and is often associated with syringomyelia. We hypothesised that cord-to-dura attachments could cause transient tensile cord radial stress, as pressure waves propagate. This was tested in a fluid-structure interaction model, simulating three types of cord tethering, with \’arachnoiditis\’ confined to a short mid-section of the cord. The annular system was excited abdominally with a short transient, and the resulting Young and Lamb waves and reflections were analysed. Radial mid-section tethering was less significant than axial tethering, which gave rise to tensile radial stress locally when the cord was not fixed cranially. Simulated as inextensible string connections to the dura, arachnoiditis caused both localised tensile radial stress and localised low pressure in the cord as the transient passed. The extent of these effects was sensitive to the relative stiffness of the dura and cord. Tensile radial stress may create a syrinx in previously normal cord tissue, and transiently lowered pressure may draw in interstitial fluid, causing the syrinx to enlarge if fluid exit is inhibited. The suggested mechanism could also explain the juxtaposition of syrinxes to regions of arachnoiditis.

Bertram CD, Bilston LE, Stoodley MA.

Biofluid Mechanics Laboratory, Faculty of Engineering, University of New South Wales, Sydney, 2052, Australia, c.bertram@unsw.edu.au.

Plasma detection of NO by a catheter.

Nitric oxide (NO) released by endothelial cells in response to hemodynamic shear stress is a key controller molecule of the vascular functions and antiatherogenic mechanisms. Endothelial dysfunction is associated with increased cardiovascular events. Therefore, several indirect techniques have been employed to evaluate endothelial function or NO bioavailability. However, a growing body of evidences suggests limitations of the indirect methods for evaluation of NO bioavailability. In years, it has been considered that NO is immediately oxidized or inactivated in blood stream. However, recent studies suggest that NO remain active in blood stream, causing remote biological response. Therefore, measuring plasma NO concentration directly in the circulation will contribute to clarify the kinetics and physiological roles of NO and to evaluate endothelial function. In this article, the measurement of plasma NO concentration using a newly developed catheter-type NO sensor will be described.

Goto M, Mochizuki S.

Department of Medical Engineering, Kawasaki University of Medical Welfare, 288, Matsushima, Kurashiki, Okayama, 701-0193, Japan, goto@me.kawasaki-m.ac.jp.

Expressions of mass transfer coefficients of bubbles and free surface of culture tanks using the k-varepsilon turbulence model.

For mammalian cell culture, getting a continuous supply of oxygen and extracting carbon dioxide are primary challenges even in the most modern biopharmaceutical manufacturing plants, due to the low oxygen solubility and excessive carbon dioxide accumulation. In addition, various independent flow and mass transfer characteristics in the culture tanks vessel make scale-up extremely difficult. One method for overcoming these and providing rational optimization is solving the fluid and mass transport equations by numerical simulation. To develop a simulation program, it is decisively important to know mass transfer coefficients of gaseous species in the culture tank. In this study, oxygen mass transfer coefficients are measured using a beaker with a sparger and impellers. In order to investigate the formulation of the mass transfer coefficients, the turbulent flow statistics is calculated by a CFD code for all cases, and the expressions of the mass transfer coefficients are established as functions of the statistics. Until now, the expression by Kawase is known in this field. This expression becomes a function only of energy dissipation rate varepsilon. It does not coincide with the conventional experimental fact that mass transfer coefficient is proportional power 0.5 of impeller rotation speed. The new mass transfer coefficient is dependent on both of energy dissipation rate varepsilon and turbulent flow energy k. It satisfies the relation of power of 0.5 of impeller rotation speed.

Amano K, Haga R, Murakami S.

Power & Industrial Systems R&D Laboratory, Hitachi, Ltd., 7-2-1 Omika-cho, Hitachi, Ibaragi, 319-1221, Japan, ken.amano.yv@hitachi.com.

Diversity in antifungal activity of strains of Chromobacterium violaceum from the Brazilian Amazon.

Chromobacterium violaceum is a free-living Gram-negative bacterium found in soil and aquatic habitats; abundantly present in the Brazilian Amazon, it is an important example of exploitable microbial diversity of the tropics. In this study, 24 strains from the Brazilian Amazon and ATCC 12472(T) were investigated for biocontrol potential of seven fungi pathogenic to soybean [Glycine max (L.) Merril] seed. Both cells and the supernatants of two Brazilian strains, 07-1 and 27-1, together with ATCC 12472(T) were strongly antagonistic to six out of the seven fungi. The antifungal activity of the Brazilian strains to Fusarium sp., Phomopsis sp. and Cercospora kikuchi was consistently stronger than that of ATCC 12472(T). In addition, the two Brazilian strains, but not ATCC 12472(T), were effective against Corynespora sp., and all three strains and their supernatants were equally effective against Aspergillus sp. and Colletotrichum sp. None of the strains had antifungal activity against Botroyodiplodia sp. Three potential mechanisms related to the antibiosis were investigated: violacein toxicity, cyanide production and chitinolytic activity; however, it was not possible to associate any of them with the antifungal activity. The results highlight the biotechnological potential still to be explored within the poorly characterized microbial biodiversity of the tropics.

Barreto ES, Torres AR, Barreto MR, Vasconcelos AT, Astolfi-Filho S, Hungria M.

Embrapa Soja, Cx. Postal 231, Londrina, Paraná, 86001-970, Brazil.

Integrating biological processes to facilitate the generation of \’Biofuel\’

Singh OV, Harvey SP.

Department of Pediatrics, The Johns Hopkins School of Medicine, 600 N. Wolfe St., Park 316, Baltimore, MD, 21287, USA, osingh1@jhmi.edu.

Optimization of medium composition for actinomycin X2 production by Streptomyces spp JAU4234 using response surface methodology.

The effects of cultivation medium compositions including soybean meal, peptone, soybean oil and cornstarch for actinomycin X2 production by Streptomyces spp JAU4234 were accessed by using response surface methodology. The 2(4) full factorial designs and the paths of steepest ascent were effective in searching for the major factors of actinomycin X2 production. In this study, cornstarch and soybean oil showed negative effect on actinomycin X2 production based on the first-order regression coefficients derived from MINITAB software. Subsequently, a central composite design for optimization was further investigated. Preliminary studies showed that soybean meal and peptone were believed to be the major factors for actinomycin X2 production. Estimated optimum compositions for the production of actionmycin X2 were as follows (g/l): soybean meal 21.65 and peptone 9.41, and result in a maximum actionmycin X2 production of 617.4 mg/l. This value was closed to the 612 mg/l actionmycin X2 production from actual experimental observations. The yield of actionmycin X2 was increased by 36.9% by culturing the strain Streptomyces spp JAU4234 in the nutritionally optimized fermentation medium.

Xiong ZQ, Tu XR, Tu GQ.

College of Life Sciences and Technology, Jiangxi Agricultural University, Nanchang, 330045, People’s Republic of China.