Search

Bonnet polishing has been widely used in structured surface generation, form correction and surface finishing. The inflated flexible tool is able to match the local surface to realize surface finishing. However, after surface finishing, the polishing induced form change is still not clear, especially for complex freeform surfaces with millimeter-level spatial periods. This paper presents a simulation and experimental study on form-preserving capability of bonnet polishing. The concept of form-preserving capability is discussed firstly. Subsequently, the relative surface speed and contact condition on ripple structures are calculated and analyzed. The results demonstrate that the contact condition of bonnet tool on structured surfaces has the main influence on form-preserving capability. Then, the influence of various factors on contact pressure difference is investigated. Compared with experimental results, the linear correlation between form change and the contact pressure difference is obtained, indicating that form-preserving capability can be strengthened by reducing contact pressure difference. Under optimal conditions, the form change can be controlled less than 20 nm, which proves the superior form-preserving capability of bonnet polishing.

Protease-activated receptors (PARs) are a unique family of G-protein coupled receptors. PAR4, the most recently identified PAR member, was reported to be overexpressed during the progression of colon and prostate cancers. Though PAR4 mRNA was detected in normal stomach, the role of PAR4 in gastric cancer has not been investigated. In this study, differential expression of PAR4 was measured by real-time PCR ( n = 28) and tissue microarrays ( n = 74). We showed that PAR4 was located from basal to middle portions of normal gastric mucosa. PAR4 expression was remarkably decreased in gastric cancer tissues as compared with matched noncancerous tissues, especially in positive lymph node or low differentiation cancers. Furthermore, methylation of the PAR4 promoter in cell lines was assessed by treatment with 5-aza-2′-deoxycytidine and genomic bisulfite sequencing. AGS and N87 human gastric cancer cell lines did not express PAR4, as compared to HT-29 human colon cancer cell line with significant PAR4 expression. Treatment with 5-aza-2′-deoxycytidine restored PAR4 expression in AGS and N87 cells, which exhibited significantly more 5-methylcytosines in the PAR4 promoter compared with HT-29 cells. Our results revealed that down-regulation of PAR4 expression occurs frequently in gastric cancers and exhibits association with more aggressive gastric cancer. Interestingly, the loss of PAR4 expression in gastric cancers may result from hypermethylation of the PAR4 promoter.

The king cobra (Ophiophagus hannah) is the largest venomous snake. Despite the components are mainly neurotoxins, the venom contains several proteins affecting blood system. Natriuretic peptide (NP), one of the important components of snake venoms, could cause local vasodilatation and a promoted capillary permeability facilitating a rapid diffusion of other toxins into the prey tissues. Due to the low abundance, it is hard to purify the snake venom NPs. The cDNA cloning of the NPs become a useful approach. In this study, a 957 bp natriuretic peptide-encoding cDNA clone was isolated from an O. hannah venom gland cDNA library. The open-reading frame of the cDNA encodes a 210-amino acid residues precursor protein named Oh-NP. Oh-NP has a typical signal peptide sequence of 26 amino acid residues. Surprisingly, Oh-NP has two typical NP domains which consist of the typical sequence of 17-residue loop of CFGXXDRIGC, so it is an unusual NP precursor. These two NP domains share high amino acid sequence identity. In addition, there are two homologous peptides of unknown function within the Oh-NP precursor. To our knowledge, Oh-NP is the first protein precursor containing two NP domains. It might belong to another subclass of snake venom NPs.

Platelet glycoprotein Ib (GPIb) is a primary adhesion receptor and involved in platelet-related disorders. However, it is difficult to study GPIb-specific platelet stimulation using physiological ligands in vivo. GPIb-binding snake C-type lectins (snaclecs) are useful tools for exploring GPIb in vitro because they act on platelets differently. In the present study, a novel GPIb-binding snaclec, named jerdonibitin, was purified, molecular cloned and characterized from Trimeresurus jerdonii venom. On SDS-polyacrylamide gel electrophoresis, it showed a single band with an apparent molecular weight of 25 kDa under non-reducing conditions and two distinct bands with apparent molecular weights of 15 kDa (α-subunit) and 13 kDa (β-subunit) under reducing conditions. The cDNA sequences of each subunit of jerdonibitin were identified and both deduced amino acid sequences were confirmed by N-terminal protein sequencing and trypsin-digested peptide mass fingerprinting of MALDI-TOF. Sequence alignment showed that jerdonibitin is a snaclec and has sequence similarity with TSV-GPIb-BP (a GPIb-inhibitory snaclec). Jerdonibitin dose-dependently inhibited platelet aggregation induced by ristocetin or low-dose thrombin, but not by high-dose thrombin. The GPIbα was detected by affinity chromatography on jerdonibitin. In vivo, jerdonibitin also dose-dependently induced thrombocytopenia of mice and platelet counts remained at very low level after 18 h intravenous injection. In summary, a novel GPIb-inhibitory snaclec was molecular cloned and characterized, which might provide insights into investigation of how GPIb-inhibitory snaclecs work and development of new antiplatelet agents.

Natriuretic peptides (NPs) play crucial roles in human physiology and pathophysiology through natriuresis, dieresis and vasorelaxation. NPs are also one of the important components of snake venoms. However, the low abundance in snake venom hampered the investigation. Here, a novel natriuretic peptide named Na–NP was purified from the cobra Naja atra venom. Na–NP consists of 45 amino acid residues and its molecular weight is 4618.5 Da. A full-length cDNA encoding Na–NP was obtained from the cDNA library constructed from the venom gland. The open reading frame of cloned Na–NP was composed of 498 bp and coded for a 165-amino acid residue protein precursor. The nucleotide and deduced protein sequences of Na–NP were remarkably conserved with other elapid NPs while significant different from the viperid NPs. Na–NP showed weak activity to relax the aortic rings precontracted with phenylephrine. Meanwhile, Na–NP showed cGMP-promotion activity against primary cultured rabbit endocardial endothelial cells, but had no effect on human platelet aggregation. In conclusion, this is the first report of a natriuretic peptide from the cobra N . atra venom. Na–NP might be served as a useful tool for the study of human NPs and the development of novel therapeutic drugs.

Human trefoil factors (TFFs) play an important role in wound healing, epithelial restitution and anti-inflammatory effects in the gastrointestinal tract by stimulating cell migration and inhibiting cell apoptosis. In our previous study, Bm-TFF2, an amphibian trefoil factor, which is isolated from the skin secretions of frog Bombina maxima, has much stronger activities than human TFFs. We believe that the expression of the recombinant Bm-TFF2 in vitro is useful to decipher its role in amphibian skin repair. Bm-TFF2 contains 12 cysteine residues and has two TFF-domains. In this study, we expressed full-length of Bm-TFF2 and its single-domain truncations (Bm-TFF2-D1 and Bm-TFF2-D2, each contains a single TFF-domain of Bm-TFF2). The recombinant proteins, including full-length and its single-domain truncations of Bm-TFF2, can promote the migration of human epithelial AGS cells and wound healing of rat intestinal epithelial IEC-6 cells. However, only the full-length of Bm-TFF2, but not its single-domain truncations, can inhibit ceramide-induced apoptosis in AGS cells. In summary, it is the first time to use the recombinant Bm-TFF2 and its truncations to investigate its structure-function relationship. And we report that full-length and each domain of Bm-TFF2 can induce cell migration but only the full-length of Bm-TFF2 can suppress apoptosis, indicating that cell migration-promoting and apoptosis-inhibiting activities of Bm-TFF2 require distinct structure basis.

Annexin A2 is a unique member of annexin family with multi-functions in membrane physiology, implicated in inflammation and cancer progression. mRNA of Annexin A2 is abundant in the skin of some amphibians. However, no annexin A2 protein has been isolated and characterized from amphibian skin. In this report, a novel annexin A2 protein with apparent molecular weight of 33 kDa and named Bm-ANXA2, was purified from frog Bombina maxima skin, which is highly toxic to mammals, by a combination of ion exchange and gel filtration chromatography. A full-length cDNA encoding the protein was obtained from the cDNA library constructed from the frog skin. Sequence analysis indicates that Bm-ANXA2 shares 89% and 80% amino acid sequence identities with those of Xenopus and human annexin A2, respectively. Different from other annexin A2 proteins, the N-terminal 26 amino acids of Bm-ANXA2 were truncated. Bm-ANXA2 dose-dependently inhibited human platelet aggregation stimulated by various agonists in a Ca(2+)-dependent manner. It bound to activated platelets and significantly inhibited alpha(IIb)beta(3) activation and alpha-granular secretion. This is the first report that an annexin A2 protein possesses platelet aggregation-inhibiting activity, providing novel clues in the illustration of pathophysiological roles of annexin A2 proteins.

King cobra cathelicidin (OH-CATH) is composed of 34 amino acid residues having strong antibacterial and very weak hemolytic activities as reported by us recently. OH-CATH can be served as a valuable template to develop novel therapeutic drugs. In this study, OH-CATH and six of its analogs were synthesized to explore their structure-function relationships based on their bactericidal and hemolytic activities. Experimental results of OH-CATH(3-34) and OH-CATH(5-34) indicated that the N-terminal 4 amino acid residues of OH-CATH played an important role on its hemolytic activity but had weak effects on its bactericidal activity. Among OH-CATH and its analogs, OH-CATH(5-34) had the lowest hemolytic activity while maintained strong antimicrobial activity. To evaluate its potential usage, the biological activities of OH-CATH(5-34) were compared with those of pexiganan. The bactericidal activity of OH-CATH(5-34) against 5 different species (11 laboratory strains) was 2-4 times stronger than that of pexiganan (4-16 microg/ml vs 8-32 microg/ml). Hemolytic activity of OH-CATH(5-34) against human erythrocytes was 0.69% while that of pexiganan was 16.5% at the dosage of 200 microg/ml. OH-CATH(5-34) showed very weak cytotoxic activities against primary rabbit ventricular endothelial cells and four human cancer cell lines whereas pexiganan showed strong cytotoxic activity against these five cell lines (IC(50)=20-90 microg/ml). The intravenous LD(50) value of OH-CATH(5-34) on mice was 7-fold higher than that of pexiganan (175 mg/kg vs 25mg/kg). Taken together, our results suggested that OH-CATH(5-34) should be considered as an excellent candidate for developing therapeutic drugs.

The effects of temperature, NaCl, and polyethylene glycol (PEG)-6000 on the seed germination of five non-halophytic Chinese desert shrub species were investigated. The minimum temperature of germination was 10°C for all species, and the maximum temperature varied among species from 25 to 35°C. Isotonic solutions of NaCl and PEG caused different effects on seed germination in all five species. When seeds were moistened with −5·0 MPa NaCl solution for 5 days, the seeds of three species completely lost their germinability, while the seed germinability of the other two species was much less affected. These results are discussed with regard to the rehabilitation of desertified lands in China by seed dispersal.

The frequency dependent radio frequency power degradation in direct modulated microwave photonic systems employing uniform period fiber Bragg gratings (FBG) as reflective elements in investigated. Results show implications in terms of the available radio frequency bandwidth and the stability requirements for the FBG.