Midgut proteinase activities in larvae of Anoplophora glabripennis (Coleoptera: Cerambycidae) and their interaction with proteinase inhibitors

The major proteinase activities in the larval midgut of a common poplar tree borer, Anoplophora glabripennis, were characterised. Overall digestive capacity, as measured by casein hydrolysis, showed a pH optimum between 10 and 11.5, suggestive of serine endopeptidase activity. Trypsin, chymotrypsin, and chymotrypsin-like activities were detected using specific p-nitroanilide synthetic substrates and by use of specific serine endopeptidase inhibitors. These activities also showed pH optima in the extreme alkaline range. The absence of cysteine, aspartic, and metallo-endopeptidases were confirmed using class specific proteinase inhibitors. The dominant exopeptidase in the midgut is leucine aminopeptidase with a pH optimum of 7–9. Carboxypeptidase a and b activity were barely detectable. A large range of serine endopeptidase inhibitors were screened and were found to vary widely in their ability to inhibit casein hydrolysis. Potato proteinase inhibitor 1 (a chymotrypsin inhibitor) and wheat-germ trypsin inhibitor 1 inhibited particularly effectively in tandem and represent possible candidates for gene transformation to produce plants tolerant to this pest. © 1996 Wiley-Liss, Inc.     

银鲫受精卵中卵黄粒和线粒体的超微结构变化

电镜观察到雌性银鲫肝脏中正在形成的卵黄物质具有晶形主体结构,银鲫卵的卵黄粒内无晶形主体,第一次卵裂前的受精卵卵黄粒内有两种形式的空泡。一种是一些中空的小空泡;另一种是一个大的空泡,泡内含有线粒体和颗粒状的核糖体,泡的边缘有片层状的类脂物。受精卵中的线粒体内部结构多样,有些含有颗粒状物,有些含有片层状的类脂物。       

Overexpression of PD‐L1 causes germ cells to slough from mouse seminiferous tubules via the PD‐L1/PD‐L1 interaction

Spermatogenesis is a cyclical process in which different generations of spermatids undergo a series of developmental steps at a fixed time and finally produce spermatids. Here, we report that overexpression of PD‐L1 (B7 homolog1) in the testis causes sperm developmental disorders and infertility in male mice, with severe malformation and sloughing during spermatid development, characterized by disorganized and collapsed seminiferous epithelium structure. PD‐L1 needs to be simultaneously expressed on Sertoli cells and spermatogonia to cause spermatogenesis failure. After that, we excluded the influence of factors such as the PD‐L1 receptor and humoral regulation, confirming that PD‐L1 has an intrinsic function to interact with PD‐L1. Studies have shown that PD‐L1 not only serves as a ligand but also plays a receptor‐like role in signal transduction. PD‐L1 interacts with PD‐L1 to affect the adhesive function of germ cells, causing malformation and spermatid sloughing. Taken together, these results indicate that PD‐L1 can interact with PD‐L1 to cause germ cell detachment and male infertility.     

Prevalence and Trend of Major Transfusion-Transmissible Infections among Blood Donors in Western China, 2005 through 2010

BackgroundThe prevalence of transfusion-transmissible infections (TTIs) in blood donations is important for evaluating blood safety and potential risks to the population. This study investigated the prevalence of TTIs among blood donors in Western China and suggested measures for policy-makers.MethodsThe screening results of 66,311 donations between 2005 and 2010 from a central blood center in Western China were analyzed. The prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and syphilis infections were expressed in percentages for the entire study group as well as groups by demographic characteristics and donation frequency, with differences analyzed using Fisher''s exact or Chi-square test. Logistic regression was performed to identify the influencing factors of the detected results.Results1,769 (2.67%, 95% CI 2.55–2.79%) of the donated blood had serological evidence of infection with at least one pathogen and 44 (0.07%, 95% CI 0.05–0.09%) showed evidence of multiple infections. The seroprevalence of HBV, HCV, HIV, and syphilis infections was 0.87% (95% CI 0.80–0.94%), 0.86% (95% CI 0.79–0.93%), 0.31% (95% CI 0.26–0.35%), and 0.70% (95% CI 0.64–0.76%) respectively. Trend analysis for the prevalence of TTIs showed a significant increase from 2.44% to 3.71% (χ² = 100.72, p = 0.00) over this 6-year period. The positive rates for TTIs varied along demographic lines. The top three risk factors in test-positive donors were identified as age, education level and donation frequency. The older age group and lower educated group were linked to a higher prevalence of TTIs. A decreasing prevalence was associated with an increasing frequency of blood donations (χ2 = 562.78, p = 0.00).ConclusionsHepatitis B and C were found most, and often in conjunction with syphilis. These were the primary threats to blood safety. The high positivity rate and the increasing prevalence of TTIs among blood donors in Western China call for further actions.     

Biochemical Properties and Crystal Structure of a β-Phenylalanine Aminotransferase from Variovorax paradoxus

By selective enrichment, we isolated a bacterium that can use β-phenylalanine as a sole nitrogen source. It was identified by 16S rRNA gene sequencing as a strain of Variovorax paradoxus. Enzyme assays revealed an aminotransferase activity. Partial genome sequencing and screening of a cosmid DNA library resulted in the identification of a 1,302-bp aminotransferase gene, which encodes a 46,416-Da protein. The gene was cloned and overexpressed in Escherichia coli. The recombinant enzyme was purified and showed a specific activity of 17.5 U mg⁻¹ for (S)-β-phenylalanine at 30°C and 33 U mg⁻¹ at the optimum temperature of 55°C. The β-specific aminotransferase exhibits a broad substrate range, accepting ortho-, meta-, and para-substituted β-phenylalanine derivatives as amino donors and 2-oxoglutarate and pyruvate as amino acceptors. The enzyme is highly enantioselective toward (S)-β-phenylalanine (enantioselectivity [E], >100) and derivatives thereof with different substituents on the phenyl ring, allowing the kinetic resolution of various racemic β-amino acids to yield (R)-β-amino acids with >95% enantiomeric excess (ee). The crystal structures of the holoenzyme and of the enzyme in complex with the inhibitor 2-aminooxyacetate revealed structural similarity to the β-phenylalanine aminotransferase from Mesorhizobium sp. strain LUK. The crystal structure was used to rationalize the stereo- and regioselectivity of V. paradoxus aminotransferase and to define a sequence motif with which new aromatic β-amino acid-converting aminotransferases may be identified.     

Iterative Image Reconstruction for Sparse-View CT Using Normal-Dose Image Induced Total Variation Prior

X-ray computed tomography (CT) iterative image reconstruction from sparse-view projection data has been an important research topic for radiation reduction in clinic. In this paper, to relieve the requirement of misalignment reduction operation of the prior image constrained compressed sensing (PICCS) approach introduced by Chen et al, we present an iterative image reconstruction approach for sparse-view CT using a normal-dose image induced total variation (ndiTV) prior. The associative objective function of the present approach is constructed under the penalized weighed least-square (PWLS) criteria, which contains two terms, i.e., the weighted least-square (WLS) fidelity and the ndiTV prior, and is referred to as “PWLS-ndiTV”. Specifically, the WLS fidelity term is built based on an accurate relationship between the variance and mean of projection data in the presence of electronic background noise. The ndiTV prior term is designed to reduce the influence of the misalignment between the desired- and prior- image by using a normal-dose image induced non-local means (ndiNLM) filter. Subsequently, a modified steepest descent algorithm is adopted to minimize the associative objective function. Experimental results on two different digital phantoms and an anthropomorphic torso phantom show that the present PWLS-ndiTV approach for sparse-view CT image reconstruction can achieve noticeable gains over the existing similar approaches in terms of noise reduction, resolution-noise tradeoff, and low-contrast object detection.     

MFGE8 protects against CCl4-induced liver injury by reducing apoptosis and promoting proliferation of hepatocytes

Milk fat globule-EGF factor 8 (MFGE8) has been reported to play various roles in acute injury and inflammation response. However, the role of MFGE8 in liver injury is poorly investigated. The present research was designed to clarify the expression and function of MFGE8 in carbon tetrachloride (CCl₄)-induced liver injury. Using serum cytokine arrays, we selected a promising cytokine MFGE8 as the candidate in the process of hepatitis-fibrosis-hepatocellular carcinoma (HCC) progression, based on the elevated expression in both hepatic fibrosis and HCC models. We validated the increased expression of MFGE8 in liver tissues and serum samples of acute and chronic CCl₄-induced mice. Immunohistochemistry staining of mouse liver tissues indicated that elevated MFGE8 expression was mainly derived from the injured hepatocytes. In addition, MFGE8 expression in the supernatant of primary hepatocytes was accumulated with prolongation of culture time, and CCl₄ treatment further increased the expression of MFGE8. Moreover, a strong correlation between serum MFGE8 expression and liver transaminase activities suggested that MFGE8 may be a novel candidate in liver injury. Intriguingly, mice pretreated with MFGE8 were protected from CCl₄-induced liver injury through antiapoptosis role in the early stage and proproliferation role in the late stage. MFGE8 reduced apoptosis by inhibiting the activation of IRE1α/ASK1/JNK pathway and promoted proliferation by phosphorylation of ERK and AKT. Moreover, serum MFGE8 expression was increased in hepatitis patients while decreased in liver cirrhosis patients. All the results suggest MFGE8 as a novel marker and promising therapeutic agent of liver injury.     

The presence of PEG-lipids in liposomes does not reduce melittin binding but decreases melittin-induced leakage.

Poly(ethyleneglycol) (PEG), anchored at the surface of liposomes via the conjugation to a lipid, is commonly used for increasing the liposome stability in the blood stream. In order to gain a better understanding of the protective properties of interfacial polymers, we have studied the binding of melittin to PEG-lipid-containing membranes as well as the melittin-induced efflux of a fluorescent marker from liposomes containing PEG-lipids. We examined the effect of the polymer size by using PEG with molecular weights of 2000 and 5000. In addition, we studied the role of the anchoring lipid by comparing PEG conjugated to phosphatidylethanolamine (PE) which results in a negatively charged PEG-PE, with PEG conjugated to ceramide (Cer) which provides the neutral PEG-Cer. Our results show that interfacial PEG does not prevent melittin adsorption onto the interface. In fact, PEG-PE promotes melittin binding, most likely because of attractive electrostatic interactions with the negative interfacial charge density of the PEG-PE-containing liposomes. However, PEG-lipids limit the lytic potential of melittin. The phenomenon is proposed to be associated with the change in the polymorphic tendencies of the liposome bilayers. The present findings reveal that the protective effect associated with interfacial hydrophilic polymers is not universal. Molecules like melittin can sense surface charges borne by PEG-lipids, and the influence of PEG-lipids on liposomal properties such as the polymorphic propensities may be involved in the so-called protective effect.     

A micro potentiometric immunosensor for hemoglobin-A1c level detection based on mixed SAMs wrapped nano-spheres array

A micro potentiometric immunosensor based on mixed SAMs wrapped nano-spheres array for the detection of hemoglobin-A1c level is presented in this paper. Nano-spheres array is prepared by wrapping nano-gold particle with mixed SAMs on the surface of micro immunosensor. Mixed SAMs make the nano-gold particles distribute uniformly without aggregation and render the signal less susceptible to noise. Based on this nano-spheres array, antibody is covalently immobilized on the immunosensor surface. The micro immunosensor, consisting of ISFET integrated chip and MEMS electrodes array is applied to measure hemoglobin-A1c level by detecting the concentration of hemoglobin-A1c and hemoglobin simultaneously. The responses of the immunosensor are linear over the concentration range of 166.7-570 ng/ml hemoglobin and 50-170.5 ng/ml HbA1c. Whole blood sample obtained from hospital was also examined using this immunosensor. The low relative deviation shows that this micro immunosensor may provide an alternative tool for the determination of HbA1c level.