Transverse stiffness: a method for estimation of myocardial wall stress

Determination of regional ventricular wall stress would allow quantification of both regional contractile state and its interplay with global function. Current methods for quantifying regional stress include mathematical modelling and measurements with strain gauges. Both methods are difficult to validate. We hypothesized that transverse stiffness (i.e., the ratio of indentation stress to strain as the ventricular wall is indented in the direction perpendicular to the wall) would be proportional to the stresses in the plane of the wall and could be used to estimate the latter. To test this hypothesis, 6 arterially perfused canine ventricular septa were mounted in an apparatus that could exert biaxial load in the plane of the wall. A servo system maintained the central third of the septa isometric during active contractions while the septa were paced at 30-60 pulses/min. In the center of the isometric region, a probe of 7 mm diameter indented the septa while the transverse indentation stress and strain were measured. For values of peak systolic in-plane stress from 0.56 to 2.6 g/mm2, the transverse stiffness varied from 1.2 to 11.7 g/mm2 and was linearly related to the in-plane wall stress in each septum (p less than 0.001, ANOVA). After cardioplegia, the transverse stiffness also correlated with passively applied wall stress for each dog (p less than 0.001). The slopes of the individual relations between transverse stiffness and wall stress from active contractions were similar to those from passively applied stress (mean +/- SEM; 1.82 +/- 0.36 versus 1.45 +/- 0.31, NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of glutamate transporters in astrocytes: Evidence for a relationship between transporter expression and astrocytic phenotype

The astrocytic glutamate transporters, EAAT1 and EAAT2, remove released L-glutamate from the synaptic milieu thereby maintaining normal excitatory transmission. EAAT dysfunction during the excitotoxicity and oxidative stress of neurological insults may involve homoeostatic mechanisms associated with astrocytic function. We investigated aspects of EAAT function and expression in concert with astrocytic phenotype in primary cultures of cortical astrocytes and mixed cells of the spinal cord. In spinal cord mixed cultures, hydrogen peroxide (300 microM) reduced both EAAT activity and cellular viability to half of their basal values at 24 h post-treatment, but at 2 h EAAT activity was unaltered, while cellular viability was significantly decreased, suggestive of a mechanism for the maintenance of EAAT activity. Cytochemistry for MAP2, GFAP and propidium iodide revealed that neurons and astrocytes were damaged in a time-dependent manner. A change in astrocyte morphology was observed, with astrocyte cell bodies becoming larger and processes becoming more stellate and often shorter in length. EAAT1 immunoreactivity was reduced at 24 h post-treatment and a re-distribution of the protein was noted after 2 h treatment. In pure astrocytes, lipopolysaccharide (1 microg/ml, 3 d) increased [3H]D-aspartate uptake by 90%, as well EAAT1 immunoreactivity and astrocyte stellation, as shown by immunofluorescent labelling for GFAP. In both culture systems, prominent changes were noted in EAAT function and localization in conjunction with altered astrocytic phenotype. Our findings are indicative of a relationship between astrocytic phenotype and the level of EAAT activity that may be a vital component of astrocytic homeostatic responses in brain injury.     

The liver in infectious mononucleosis

Summary 1. Twenty-two patients with infectious mononucleosis were studied by liver biopsy and paper electrophoresis of the serum proteins. The findings were compared with a similar group of 30 patients with infectious hepatitis.2. The essential histologic features of infectious mononucleosis were the presence in the hepatic sinusoids and portal tracts of chronic inflammatory cells resembling small lymphocytes, with essentially no parenchymal cell damage. Admixed with this lymphocytic infiltrate, but in relatively minimal numbers, were a few plasma cells and polymorphonuclear leukocytes. In addition, in infectious mononucleosis there were, with rare exceptions, no lipochrome-containing Kupffer cells. Thus, in the majority of cases, the histologic picture was distinct from that seen in infectious hepatitis. Only in comparing a few of the more severe infectious mononucleosis cases with subsiding infectious hepatitis cases was there any tendency for the two pictures to merge, and the distinction on histologic grounds between the two entities could be made in the great majority of cases.3. The most commonly seen abnormalities in the paper electrophoretic patterns of sera obtained from patients with infectious mononucleosis were decreased albumin, increased gamma globulin, not infrequent but variable changes in alpha₂ globulin, and the presence of abnormal proteins migrating with mobilities intermediate to alpha₂ and beta, and beta and gamma globulins. The abnormalities observed in infectious hepatitis were similar to those of infectious mononucleosis, except that in hepatitis alpha₂ globulin was decreased more consistently, gamma globulin increased less frequently, and beta globulin, which was normal in practically all the cases of infectious mononucleosis, was increased in a considerable number of cases.4. Treatment of patients with infectious mononucleosis need not include prolonged bed rest and restriction of activity in an effort to avoid the development of chronic liver disease.     

Quantitation of mitomycin C in human ocular tissues by high-performance liquid chromatography-photo-diode array detection

A chromatographic method, which can quantitate mitomycin C (MMC) along with two antiglaucoma drugs, is described. The separation of MMC, alphagan and timolol was performed on a reversed-phase C18 column with water-methanol-trifluoroacetic acid (65:35:0.01, v/v) as the mobile phase. By monitoring at 360, 248 and 296 nm, the lower limits of detection for MMC, alphagan and timolol are, respectively, 1.0, 2.0 and 5.0 ng (injection amount) at three-time S/N ratio. The dynamic ranges of quantitation for the three drugs are, respectively, 1.0 ng-10.0 microg, 2.0 ng-10.0 microg and 5.0 ng-10.0 microg with linearity being larger than 0.9960. This method was applied to the determination of MMC levels in Tenon's and trabeculum tissues of 10 glaucoma patients. MMC levels in these tissues, which were obtained from glaucoma filtering surgery, were determined following a multiple extraction with methanol. The recovery of MMC for a two-batch extraction was better than 91.2%. The reproducibility of measurement for the MMC levels in these tissues is 2.5-6.0% RSD for triplicate injections. The intra-day variation of retention times for the MMC peaks was less than 1.6% RSD (n=3). The inter-day variation of retention times for the MMC peaks was less than 4.8% RSD (n=3). MMC was detectable in three trabeculum tissues out of 10 cases (ranging from 0.8 to 25.5 ng/mg specimen), while MMC was detected in nine Tenon's tissues out of 10 cases (ranging from 0.3 to 21.1 ng/mg specimen). The results obtained show that the method is sensitive and selective for the quantitation of MMC.     

血管粘弹性对法推拿作用下血管切应力的影响

目的研究血管粘弹性对脉动血流在(扌衮)法推拿作用下切应力的影响.方法建立具有局部轴向运动狭窄的粘弹性血管中脉动血流模型.设血液为牛顿流体,血管壁为线性粘弹体.在(扌衮)法推拿作用下血管受水平外力作用形成轴向运动缓变狭窄,血流遵循线化Navier-stokes方程.结果粘弹性血管在(扌衮)法作用下,距离血管入口z=31 cm处的平均切应力、最大切应力和瞬时切应力以及最大狭窄下游血管段最大切应力随着血管粘性系数和手法频率的改变而有较大变化.结论(扌衮)法推拿作用下粘弹性血管的血管切应力有显著变化,这与中医推拿的活血化淤相吻合.     

Expression of interleukin-18 by nasopharyngeal carcinoma cells: a factor that possibly initiates the massive leukocyte infiltration

Interleukin-18 (IL-18) is a single-chain cytokine that is produced by various cells. With interleukin-12 (IL-12), it synergistically stimulates activated T cells and natural killer (NK) cells to produce interferon-gamma (IFN-gamma). Nasopharyngeal carcinoma (NPC) is the most common form of nasal and nasopharyngeal malignancy, and in NPC tumor tissues there is an intense leukocyte infiltration comprising predominantly T cells and macrophages. We previously showed an increased expression of IFN-gamma in the infiltrating T cells. To identify the cells that provide IL-12 and IL-18 for stimulating the expression of IFN-gamma in activated T cells, NPC cell lines CNE-2 and HK-1, as well as biopsies obtained from NPC and control individuals, were examined. CNE-2 and HK-1 cells were found to express messenger RNA encoding IL-18, but not IL-12. Secreted IL-18 was detected in the culture supernatant. Addition of a caspase-1 inhibitor decreased the secretion level, indicating that this IL-18 secretion was caspase-1 dependent. Moreover, the in vitro IL-18 production in NPC cell lines correlated with the NPC tumor cells in situ. NPC tumor cells in the biopsies produced IL-18, as detected by immunohistochemistry and immunofluorescent double staining. In contrast, IL-18 expression was not observed in the control biopsies. We suggest that IL-18 secreted by NPC tumor cells plays a role in initiating the leukocyte infiltration process. IL-18 stimulates T cells and NK cells to produce IFN-gamma, which consequently activates macrophages and other immune cells to secrete chemokines to start a leukocyte recruitment cascade.     

Sustained release of neurotrophin-3 and chondroitinase ABC from electrospun collagen nanofiber scaffold for spinal cord injury repair

Nerve regeneration after spinal cord injuries (SCI) remains suboptimal despite recent advances in the field. One major hurdle is the rapid clearance of drugs from the injury site, which greatly limits therapeutic outcomes. Nanofiber scaffolds represent a potential class of materials for enhancing nerve regeneration because of its biomimicking architecture. In this study, we investigated the feasibility of incorporating neurotrophin-3 (NT-3) and chondroitinase ABC (ChABC) onto electrospun collagen nanofibers for SCI treatment. By using microbial transglutaminase (mTG) mediated crosslinking, proteins were loaded onto electrospun collagen nanofibers at an efficiency of ～45-48%. By combining NT-3 with heparin during the protein incorporation process, a sustained release of NT-3 was obtained (～96% by day 28). As indicated by dorsal root ganglion outgrowth assay, NT-3 incorporated collagen scaffolds supported neuronal culture and neurite outgrowth for a longer time period than bolus delivery of NT-3. The presence of heparin also protected ChABC from degradation. Specifically, as evaluated by dimethylmethylene blue assay, bioactive ChABC was detected from collagen scaffolds for at least 32 days in vitro in the presence of heparin (～32% of bioactivity retained). In contrast, ChABC bioactivity was only ～1.9% by day 22 in the absence of heparin. Taken together, these results clearly demonstrated the feasibility of incorporating NT-3 and ChABC via mTG immobilization to produce protein-incorporated collagen nanofibers. Such biofunctional nanofiber constructs may find useful applications in SCI treatment by providing topographical signals and multiple biochemical cues that can promote nerve regeneration while antagonizing axonal growth inhibition for CNS regeneration.