A SENSITIVE PROTEIN ASSAY BY Co(II)-BIURET METHOD

A new and senseitive Co (II)-biuret method for determination of protein has for the first time been established. In visible wavelength region, the Co (II) -protein complexes had anabsorption peak at 360 nm. -Under the present conditions. the assay had a linear range of 0-120 μg/ml of protein with a detection limit of about 2 μg/ml, and similar calibration curves were obtained for BSA. and BγG. Compared with Cu (II) -biuret method, the present Co (II) -biuret method was more simple, sensitive, and tolerant of interferences from non-protein molecules.

Serum concentrations of insulin-like growth factor-binding protein 5 in Crohn's disease

AIM: To investigate serum insulin-like growth factor-binding protein 5 (IGFBP-5) levels and intestinal IGFBP-5 expression in patients with Crohn’s disease (CD).

Canine Distemper Virus Utilizes Different Receptors to Infect Chicken Embryo Fibroblasts and Vero cells

Inducing animal viruses to adapt to chicken embryos or chicken embryo fibroblasts(CEF) is a common method to develop attenuated live vaccines with full security.Canine distemper virus(CDV) also does this,but the mechanisms and particular receptors remain unclear.Virus overlay protein blot assays were carried out on CEF membrane proteins,which were extracted respectively with a Mem-PER TM kit,a radioimmunoprecipitation assay buffer or a modified co-immunoprecipitation method,and revealed a common 57 kDa positive band that differed from the 42-kDa positive band in Vero cells and also from those receptors reported in lymphocytes and 293 cells,indicating a receptor diversity of CDV and the possibility of the 57-kDa protein acting as a receptor that is involved in adaptive infection of CDV Kunming strain to CEF.

Safety threshold of intravitreal clonidine in rabbit's eyes

AIM： To determine the safe dose of intravitreal clonidine（IVC）, a potential drug for neuroprotection and angiogenesis inhibition in rabbits. METHODS： A total of 28 rabbits were divided into four groups. Three groups received IVC with concentrations of 15（Group A）, 25（Group B）, and 50（Group C） g/0.1 m L and the control group（Group D） received 0.1 m L balanced salt solution（BSS）. To investigate IVC safety, electroretinography（ERG） was performed at baseline, then at 1, 4 and 8 wk after injection. After last ERG, all rabbits were euthanized, their eyes were enucleated and subjected to routine histopathological evaluation, immunohistochemistry for glial fibrillary acidic protein（GFAP） and terminal deoxynucleotidyl transferase d UTP nick end labeling（TUNEL） test.RESULTS： Based on ERG, histopathology, GFAP and TUNEL assay findings, 15 g IVC was determined as the safe dose in rabbit eyes. While, the results of routine histopathology and TUNEL assay were unremarkable in all groups, toxic effects attributed to 25 and 50 g IVC were demonstrated by ERG and GFAP tests. CONCLUSION： Totally 15 g clonidine is determined as the safe dose for intravitreal injection in rabbits. Contribution of IVC in neuroprotection and inhibition of angiogenesis deserve more studies.

Site-specific recombination in Escherichia coli mediated by actinomyces phage R4 integrase

The purpose of this study was to demonstrate that actinomyces phage R4 integrase Sre protein efficiently mediate site-specific recombination in Escherichia coll. An intramolecular recombination assay system in E. coli was constructed. The plasmid pBZP contains attB and attP sites in direct orientation flanking a lacZ gene. When pBZP was introduced into E. coli cells, in which the plasmid pSREA containing sre gene was resident, Sre protein catalyzed integration of attP into attB site, resulting in excision of the lacZ gene. This integration changed bacteria colonies from blue to white on agar plates containing X-Gal, which showed that the lacZ was removed. The integrant DNAs were identified by enzyme digestion, PCR and DNA sequencing. The minimal sizes of attB and attP were 50 bp and 47 bp for 100% recombination efficiency. The phage recombinase Sre efficiently integrated attP into attB site to create attR and attL in E. coli host environment without Streptomyces specific cofactors. This intrmolecular assay system is a simple and efficient system for Sre-mediated recombination in E. coll.

Degradation and detoxification of microcystin-LR in drinking water by sequential use of UV and ozone

Microcystins （MCs） produced by cyanobacteria are strong hepatotoxins and classified as possible carcinogens. MCs pose a considerable threat to human health through tainted drinking and surface waters. Herein filtrated water from a waterworks in Harbin, China, was spiked with microcysfin-LR （MC-LR） extracted from a toxic scum of microcystis aeruginosa, and the spiked sample waters were treated using UV irradiation with consequent ozonation process （UV/O3）, compared with ozonation at a dose range commonly applied in water treatment plants, UV irradiation at 254 nm and UV irradiation combined with ozonation （UV＋O3）, respectively. The remaining of toxins were analyzed using high-performance liquid chromatography and also determined using a protein phosphatase type 2A inhibition assay, which was utilized to evaluate the reduction in toxicity. Results indicated that in comparison to other three processes （O3, UV, and UV＋O3）, UV/O3 process could effectively decrease both the concentration and toxicity of MC-LR at 100 μg/L level after 5 min UV irradiation with consequent 5 min ozonation at 0.2 mg/L （below 1 μg/L ）, while 0.5 mg/L ozone dose was required for the level below 0.1 μg/L. The addition of an UV treatment step to the existing treatment train may induce significant transformation of micropollutants and breaks down the natural organic matters into moieties unfavorable for ozone decomposition, stabilizing the ozone residual. These findings suggested that sequential use of UV and ozone may be a suitable method for the removal of these potentially hazardous microcystins from drinking water.