Development of an optimal antigen retrieval protocol for immunohistochemistry of retinoblastoma protein (pRB) in formalin fixed,paraffin sections based on comparison of different methods

A novel protocol for antigen retrieval (AR) for immunohistochemistry (IHC) of retinoblastoma protein (pRB) in formalin fixed, paraffin embedded (FFPE) tissue sections was developed using 0.05% citraconic anhydride as the AR solution for heat treatment based on comparison of different methods. This new protocol has advantages including superior morphological preservation, greater reproducibility, and more intense staining after retrieval. Our study demonstrates the importance of comparing various AR protocols to obtain maximal IHC for standardization and for quantitative IHC.     

Insulin responsiveness of glucose transporter 4 in 3T3-L1 cells depends on the presence of sortilin

Insulin-dependent translocation of glucose transporter 4 (Glut4) to the plasma membrane of fat and skeletal muscle cells plays the key role in postprandial clearance of blood glucose. Glut4 represents the major cell-specific component of the insulin-responsive vesicles (IRVs). It is not clear, however, whether the presence of Glut4 in the IRVs is essential for their ability to respond to insulin stimulation. We prepared two lines of 3T3-L1 cells with low and high expression of myc₇-Glut4 and studied its translocation to the plasma membrane upon insulin stimulation, using fluorescence-assisted cell sorting and cell surface biotinylation. In undifferentiated 3T3-L1 preadipocytes, translocation of myc₇-Glut4 was low regardless of its expression levels. Coexpression of sortilin increased targeting of myc₇-Glut4 to the IRVs, and its insulin responsiveness rose to the maximal levels observed in fully differentiated adipocytes. Sortilin ectopically expressed in undifferentiated cells was translocated to the plasma membrane regardless of the presence or absence of myc₇-Glut4. AS160/TBC1D4 is expressed at low levels in preadipocytes but is induced in differentiation and provides an additional mechanism for the intracellular retention and insulin-stimulated release of Glut4.Adipocytes, skeletal muscle cells, and some neurons respond to insulin stimulation by translocating intracellular glucose transporter 4 (Glut4) to the plasma membrane. In all these cells, the insulin-responsive pool of Glut4 is localized in small membrane vesicles, the insulin-responsive vesicles (IRVs; Kandror and Pilch, 2011 ; Bogan, 2012 ). The protein composition of these vesicles has been largely characterized (Kandror and Pilch, 2011 ; Bogan, 2012 ). The IRVs consist predominantly of Glut4, insulin-responsive aminopeptidase (IRAP), sortilin, low-density-lipoprotein receptor–related protein 1 (LRP1), SCAMPs, and VAMP2. Glut4, IRAP, and sortilin physically interact with each other, which might be important for the biogenesis of the IRVs (Shi and Kandror, 2007 ; Shi et al., 2008 ). In addition, the IRVs compartmentalize recycling receptors, such as the transferrin receptor and the IGF2/mannose 6-phosphate receptor, although it is not clear whether these receptors represent obligatory vesicular components or their presence in the IRVs is explained by mass action (Pilch, 2008 ), inefficient sorting, or other reasons.Deciphering of the protein composition of the IRVs is important because it is likely to explain their unique functional property: translocation to the plasma membrane in response to insulin stimulation. Even if we presume that IRV trafficking is controlled by loosely associated peripheral membrane proteins, the latter should still somehow recognize the core vesicular components that create the “biochemical individuality” of this compartment. In spite of our knowledge of the IRV protein composition, however, the identity of the protein(s) that confer insulin sensitivity to these vesicles is unknown.Insulin responsiveness of the IRVs was associated with either IRAP or Glut4. Thus it was shown that Glut4 interacted with the intracellular anchor TUG (Bogan et al., 2003 , 2012 ), whereas IRAP associated with other proteins implemented in the regulation of Glut4 translocation, such as AS160 (Larance et al., 2005 ; Peck et al., 2006 ), p115 (Hosaka et al., 2005 ), tankyrase (Yeh et al., 2007 ), and several others (reviewed in Bogan, 2012 ). Results of these studies, or at least their interpretations, are not necessarily consistent with each other, as the existence of multiple independent anchors for the IRVs is, although possible, unlikely.Ablation of the individual IRV proteins has also led to controversial data. Thus knockout of IRAP decreases total protein levels of Glut4 but does not affect its translocation in the mouse model (Keller et al., 2002 ). On the contrary, knockdown of IRAP in 3T3-L1 adipocytes has a strong inhibitory effect on translocation of Glut4 (Yeh et al., 2007 ). In yet another study, knockdown of IRAP in 3T3-L1 adipocytes did not affect insulin-stimulated translocation of Glut4 but increased its plasma membrane content under basal conditions (Jordens et al., 2010 ). By the same token, total or partial ablation of Glut4 had various effects on expression levels, intracellular localization, and translocation of IRAP (Jiang et al., 2001 ; Abel et al., 2004 ; Carvalho et al., 2004 ; Gross et al., 2004 ; Yeh et al., 2007 ). Knockdown of either sortilin or LRP1 decreased protein levels of Glut4 (Shi and Kandror, 2005 ; Jedrychowski et al., 2010 ).One model that might explain these complicated and somewhat inconsistent results is that depletion of either major integral protein of the IRVs disrupts the network of interactions between vesicular proteins and thus decreases the efficiency of protein sorting into the IRVs (Kandror and Pilch, 2011 ). Correspondingly, the remaining IRV components that cannot be faithfully compartmentalized in the vesicles are either degraded (Jiang et al., 2001 ; Keller et al., 2002 ; Abel et al., 2004 ; Carvalho et al., 2004 ; Shi and Kandror, 2005 ; Yeh et al., 2007 ; Jedrychowski et al., 2010 ) or mistargeted (Jiang et al., 2001 ; Jordens et al., 2010 ), depending on experimental conditions and types of cells used in these studies. In other words, knockdown of any major IRV component may decrease vesicle formation along with insulin responsiveness. Thus, in spite of a large body of literature, the identity of protein(s) that confer insulin responsiveness to the IRVs is unknown.Here we used a gain-of-function approach to address this question. Specifically, we attempted to “build” functional IRVs in undifferentiated 3T3-L1 preadipocytes by forced expression of the relevant proteins. Undifferentiated preadipocytes do not express Glut4 or sortilin and lack IRVs (ElJack et al., 1999 ; Shi and Kandror, 2005 ; Shi et al., 2008 ). Correspondingly, IRAP, which is expressed in these cells, shows low insulin response (Ross et al., 1998 ; Shi et al., 2008 ). We found that ectopic expression of increasing amounts of Glut4 in undifferentiated preadipocytes does not lead to its marked translocation to the plasma membrane upon insulin stimulation. On the contrary, sortilin expressed in undifferentiated preadipocytes was localized in the IRVs and was translocated to the plasma membrane in response to insulin stimulation. Moreover, upon coexpression with Glut4, sortilin dramatically increased its insulin responsiveness to the levels observed in fully differentiated adipocytes. Thus sortilin may represent the key component of the IRVs, which is responsible not only for the formation of vesicles (Shi and Kandror, 2005 ; Ariga et al., 2008 ; Hatakeyama and Kanzaki, 2011 ), but also for their insulin responsiveness. It is worth noting that sortilin levels are significantly decreased in obese and diabetic humans and mice (Kaddai et al., 2009 ). We thus suggest that sortilin may be a novel and important target in the fight against insulin resistance and diabetes.Our experiments also demonstrate that undifferentiated preadipocytes lack a mechanism for the full intracellular retention of Glut4 that can be achieved by ectopic expression of AS160/TBC1D4.     

皂苷类药物的制剂研究进展

皂苷类药物普遍分子量比较大,水溶性好,但不易透过细胞膜难以被人体吸收,因此口服制剂体内生物利用度较低.近年来对单体皂苷及总皂苷类药物制剂方面的研究越来越多,随着新型的给药系统和新辅料的出现,皂苷类药物在体内的生物利用度大大提高.本文主要介绍以单体皂苷或总皂苷活性部位为主药的制剂研究进展,以期为该类成分的进一步研究提供思路.     

Bone morphogenetic protein 9 overexpression reduces osteosarcoma cell migration and invasion

Transforming growth factor-β (TGF-β) is known to promote tumor migration and invasion. Bone morphogenetic proteins (BMPs) are members of the TGF-β family expressed in a variety of human carcinoma cell lines. The role of bone morphogenetic protein 9 (BMP9), the most powerful osteogenic factor, in osteosarcoma (OS) progression has not been fully clarified. The expression of BMP9 and its receptors in OS cell lines was analyzed by RT-PCR. We found that BMP9 and its receptors were expressed in OS cell lines. We further investigated the influence of BMP9 on the biological behaviors of OS cells. BMP9 overexpression in the OS cell lines 143B and MG63 inhibited in vitro cell migration and invasion. We further investigated the expression of a panel of cancer-related genes and found that BMP9 overexpression increased the phosphorylation of Smad1/5/8 proteins, increased the expression of ID1, and reduced the expression and activity of matrix metalloproteinase 9 (MMP9) in OS cells. BMP9 silencing induced the opposite effects. We also found that BMP9 may not affect the chemokine (C-X-C motif) ligand 12 (CXCL12)/C-X-C chemokine receptor type 4 (CXCR4) axis to regulate the invasiveness and metastatic capacity of OS cells. Interestingly, CXCR4 was expressed in both 143B and MG63 cells, while CXCL12 was only detected in MG63 cells. Taken together, we hypothesize that BMP9 inhibits the migration and invasiveness of OS cells through a Smad-dependent pathway by downregulating the expression and activity of MMP9.     

Mutations of Thr169 affect substrate specificity of pyranose 2-oxidase from Trametes multicolor

Site-directed mutagenesis was used to enhance the catalytic activity of pyranose 2-oxidase (P2Ox) from Trametes multicolor with different substrates. To this end, threonine at position 169 was replaced by glycine, alanine and serine, respectively. Using oxygen as electron acceptor the mutant T169G was equally active with d-glucose and d-galactose, whereas wild-type recombinant P2Ox only showed 5.2% relative activity with the latter substrate. When d-galactose was used as electron donor in saturating concentrations, T169G showed a 4.5-fold increase in its catalytic efficiency k_cat/K_M for the alternative electron acceptor 1,4-benzoquinone and a nine-fold increased k_cat/K_M value with the ferricenium ion compared with wt recP2Ox. Variant T169S showed an increase in its catalytic efficiency both with 1,4-benzoquinone (3.7 times) as well as with the ferricenium ion (1.4 times) when d-glucose was the substrate.     

A computational study of the EN 1078 impact test for bicycle helmets using a realistic subject-specific finite element head model

Abstract

In the present study, the free fall impact test in accordance with the EN1078 standard for certification of bicycle helmets is replicated using numerical simulations. The impact scenario is simulated using an experimentally validated, patient-specific head model equipped with and without a bicycle helmet. Head accelerations and intracranial biomechanical injury metrics during the impacts are recorded. It is demonstrated that wearing the bicycle helmet during the impact reduces biomechanical injury metrics, with the biggest reduction seen in the metric for skull fracture.     

Left ventricular wall stress compendium

Left ventricular (LV) wall stress has intrigued scientists and cardiologists since the time of Lame and Laplace in 1800s. The left ventricle is an intriguing organ structure, whose intrinsic design enables it to fill and contract. The development of wall stress is intriguing to cardiologists and biomedical engineers. The role of left ventricle wall stress in cardiac perfusion and pumping as well as in cardiac pathophysiology is a relatively unexplored phenomenon. But even for us to assess this role, we first need accurate determination of in vivo wall stress. However, at this point, 150 years after Lame estimated left ventricle wall stress using the elasticity theory, we are still in the exploratory stage of (i) developing left ventricle models that properly represent left ventricle anatomy and physiology and (ii) obtaining data on left ventricle dynamics. In this paper, we are responding to the need for a comprehensive survey of left ventricle wall stress models, their mechanics, stress computation and results. We have provided herein a compendium of major type of wall stress models: thin-wall models based on the Laplace law, thick-wall shell models, elasticity theory model, thick-wall large deformation models and finite element models. We have compared the mean stress values of these models as well as the variation of stress across the wall. All of the thin-wall and thick-wall shell models are based on idealised ellipsoidal and spherical geometries. However, the elasticity model's shape can vary through the cycle, to simulate the more ellipsoidal shape of the left ventricle in the systolic phase. The finite element models have more representative geometries, but are generally based on animal data, which limits their medical relevance. This paper can enable readers to obtain a comprehensive perspective of left ventricle wall stress models, of how to employ them to determine wall stresses, and be cognizant of the assumptions involved in the use of specific models.     

Physiological control of an in-series connected pulsatile VAD: numerical simulation study

This paper investigates ventricular assist device (VAD)-assisted cardiovascular dynamics under proportion–integration–differentiation (PID) feedback control. Previously, we have studied the cardiovascular responses under the support of an in-series connected reciprocating-valve VAD through numerical simulation, and no feedback control was applied in the VAD. In this research, we explore the contribution of the VAD control on the circulatory dynamics assisted by the reciprocating-valve VAD, in response to the changing physiological conditions. The classical PID control algorithm is implemented to regulate the VAD stroke beat-to-beat, based on the error signal between the expected and the realistic mean aortic pressures. Simulation results show that under the PID VAD control, physiological variables such as left atrial, ventricular and systemic arterial pressures, cardiac output and ventricular volumes are satisfactorily maintained in the physiological ranges. With the online PID feedback control, operation of the reciprocating-valve VAD can be satisfactorily regulated to accommodate metabolic requirements under various physiological conditions including normal resting and exercise situations.     

Reducing oxidative/nitrosative stress: a newly-discovered genre for melatonin

The discovery of melatonin and its derivatives as antioxidants has stimulated a very large number of studies which have, virtually uniformly, documented the ability of these molecules to detoxify harmful reactants and reduce molecular damage. These observations have clear clinical implications given that numerous age-related diseases in humans have an important free radical component. Moreover, a major theory to explain the processes of aging invokes radicals and their derivatives as causative agents. These conditions, coupled with the loss of melatonin as organisms age, suggest that some diseases and some aspects of aging may be aggravated by the diminished melatonin levels in advanced age. Another corollary of this is that the administration of melatonin, which has an uncommonly low toxicity profile, could theoretically defer the progression of some diseases and possibly forestall signs of aging. Certainly, research in the next decade will help to define the role of melatonin in age-related diseases and in determining successful aging. While increasing life span will not necessarily be a goal of these investigative efforts, improving health and the quality of life in the aged should be an aim of this research.