Effect of redox-responsive DTSSP crosslinking on poly(l-lysine)-grafted-poly(ethylene glycol) nanoparticles for delivery of proteins

Therapeutic proteins are utilized in a variety of clinical applications, but side effects and rapid in vivo clearance still present hurdles. An approach that addresses both drawbacks is protein encapsulation within in a polymeric nanoparticle, which is effective but introduces the additional challenge of destabilizing the nanoparticle shell in clinically relevant locations. This study examined the effects of crosslinking self-assembled poly(l -lysine)-grafted-poly(ethylene glycol) nanoparticles with redox-responsive 3,3′-dithiobis(sulfosuccinimidyl propionate) (DTSSP) to achieve nanoparticle destabilization in a reductive environment. The polymer-protein nanoparticles (DTSSP NPs) were formed through electrostatic self-assembly and crosslinked with DTSSP, which contains a glutathione-reducible disulfide. As glutathione is upregulated in various cancers, DTSSP NPs could display destabilization within cancer cells. A library of DTSSP NPs was formed with varying copolymer to protein (C:P) and crosslinker to protein (X:P) mass ratios and characterized by size and encapsulation efficiency. DTSSP NPs with a 7:1 C:P ratio and 2:1 X:P ratio were further characterized by stability in the presence proteases and reducing agents. DTSSP NPs fully encapsulated the model protein and displayed 81% protein release when incubated with 5 mM dithiothreitol for 12 hr. This study contributes to understanding stimulus-responsive crosslinking of polymeric nanoparticles and could be foundational to clinical administration of therapeutic proteins.     

An isothermal titration calorimetric method to determine the kinetic parameters of enzyme catalytic reaction by employing the product inhibition as probe.

An isothermal titration calorimetric (ITC) method was developed to measure the kinetic parameters of ribonuclease A catalytic hydrolysis of cytidine 2',3'-cyclic monophosphate. Employing the inhibition of product as a probe, the K(m), K(i), k(c), and DeltaH(m) can be determined by two simple calorimetric measurements. First, the substrate was titrated into the cell containing high concentration of enzyme. The molar reaction heat was calculated from the titration peak area divided by substrate moles per titration, and the initial catalytic reaction rate in the presence of various concentrations of product can be calculated from the peak height and the molar reaction heat. From Michaelis-Menten function in the presence of inhibitors, the relationship between K(m) and K(i) can be obtained. Then, the dissociation constant, which is equal to K(i), was measured by a regular ITC experiment. Thus, K(m) and k(c) can be calculated. The method developed here can be applied in other enzyme catalytic systems with inhibitive products.     

Selected contribution: effects of ischemia-reperfusion on vascular contractility and alpha(1)-adrenergic-receptor signaling in the rat tail artery.

To determine the effects of ischemia-reperfusion (I/R) on alpha(1)-adrenergic-receptor (alpha(1)-AR) functions, alpha(1)-AR-mediated contraction, inositol phosphate (IP) accumulation, and alpha(1)-AR-G protein coupling were examined in the tail arteries of anesthetized rats after 60 min of ischemia and 60 min of reperfusion. The contractile response to norepinephrine (NE) was significantly increased after I/R, whereas the contractile response to KCl remained unchanged. This was accompanied by a 69% increase in NE-stimulated IP accumulation. Furthermore, receptor-stimulated coupling of alpha(1a)-AR to G alpha(q/11) proteins was increased, whereas the coupling of alpha(1b)-AR or alpha(1d)-AR to their G proteins was not altered by I/R. These changes in vascular alpha(1)-AR function occurred without concurrent alteration in expression levels of membrane alpha(1)-AR subtypes or in the associated G proteins. These data demonstrate that I/R increases alpha(1a)-AR-G(q/11) protein coupling and alpha(1)-AR-stimulated IP accumulation in the tail artery. The alterations in alpha(1)-AR signaling are associated with and may underlie the enhanced contractile response of the tail artery to adrenergic stimulation after I/R.     

BJ-HCC-20, a potential novel cancer-testis antigen.

In an effort to identify novel Cancer-Testis genes, we analyzed the sequence in the q26-28 region of human X chromosome by several on-line tools. The candidate sequences were then confirmed by experiments. We have obtained a novel Cancer-Testis gene, BJ-HCC-20. In vivo, it was found to have two isoforms. In samples of liver, colon, gastric and lung cancer tested, the expression frequency of BJ-HCC-20 is 25%, 17%, 21% and 15%, respectively. Full-length cDNAs of both BJ-HCC-20 isoforms were isolated and their gene structures and promoter regions were characterized. BJ-HCC-20 might have implications in theoretical and practical tumor biology.     

五种雀形目鸟类核型的比较研究

染色体核型的比较研究,对于了解物种的特性,探索物种的遗传、进化、系统发育及分类地位都有一定的意义。有关鸟类的核型研究,国外已有不少报道(Castrovicja,1969; Hammar,1966,1975; Ray-Chaudhuri et al.,1969;Shidds,1982;Ta—kagi,1972等)国内在这方面的工作开展较迟,已作过核型分析的鸟类为数不多,仅见王应祥等(1982)的报道。迄今,作过核型研究的鸟类已达500多种,其中雀形目有200种。本文比较分析了五种野生雀形目鸟类的核型,它们是黑头蜡嘴雀,斑鸫,黄腹山雀,红尾伯劳和灰背椋鸟。     

Microcalorimetric measurements of tissue cells in vitro

A culture flask was designed for the microcalorimetric measurements of tissue cells by an MS 80 standard calvet microcalorimeter. Tissue cells cultured in this flask behaved in the same manner as in the common culture flask used in cytobiological studies. The thermograms of human adenocarcinoma gastric cells (SGc 7901) and HeLa cells were obtained. The heat output power of SGc 7901 cells continuously increased for 70 h with an initial cell number of 3.0 X 10(5). The thermogram was reproducible under strictly controlled conditions. The relationship between the heat output power and the number of SGc 7901 cells within 48 h was obtained. The heat output power was 40 pW/cell to 49 pW/cell when the cell number was in the range 4.5 X 10(5) to 10.4 X 10(5). It was 62.3 +/- 2.9 pW/cell for HeLa cells when the cell number was 6 X 10(5).     

Beta-thalassemia mutations in Indonesia and their linkage to beta haplotypes.

A total of 72 chromosomes from 36 Indonesian patients, 23 with beta-thalassemia major and 13 with Hb E-beta-thalassemia, were analyzed by specific oligonucleotide hybridization after DNA amplification. Thirteen had the beta E mutation (codon 26 GAG----AAG). Of the 59-beta-thalassemic chromosomes, 32 were of the variant IVS-1 nt5 (G----C). Seven had the mutation IVS-2 nt654 (C----T), one had the mutation codon 41/42 (deletion CTTT), and one had the mutation codon 17 (AAG----TAG). Another six with the mutation IVS-1 nt1 (G----T), one with the mutation IVS-1 nt1 (G----A), four with the mutation codon 15 (TGG----TAG), one with a mutation codon 30 (AGG----ACG), and one with a mutation codon 35 (deletion C) were first identified by direct sequencing of a patient's genomic DNA followed by further hybridizing other patients' DNA with the appropriate oligonucleotide probes. Five did not carry the common mutations previously described in Asian populations. The four most prevalent mutations encountered made up 83% of the total number of beta-thalassemic chromosomes studied. The most common mutation, IVS-1 nt5 (G----C), was mostly associated with two different haplotypes.