[Mutant Rad50 enhances killing effects of radiation on nasopharyngeal carcinoma cell line CNE1]

Objective: To investigate the killing effects of radiation and mutant Rad50 transfection on human nasopharyngeal carcinoma cell line CNE1. Methods: The experimental groups included: control group, Ad-Rad50-GFP group, Ad-EGFP group, irradiation group, Ad-Rad50-GFP combined with irradiation group, and Ad-EGFP combined with irradiation group. CNE1 cells were transfected with recombinant adenoviral vector Ad-Rad50-GFP carrying mutant Rad50 gene. The expressions of Mre11, Rad50, Nbs1, and relevant constituents composing MRN complex were detected by Western Blot. Neutral comet assay was used to detect the effect of mutant Rad50 on restoration process of DNA damage. Cell growth curve was used to evaluate the growth inhibition of CNE1 by mutant Rad50 and radiation. Results: Expressions of Mre11, Rad50, and Nbs1 in cells of Ad-Rad50-GFP group were less significantly than those in control group when irradiation was completed (0.48 vs 0.62, 0.42 vs 0.5, and 0.53 vs 0.69, respectively, P<0.05) and 24 hours after irradiation (0.41 vs 0.69, 0.46 vs 0.58, and 0.34 vs 0.78, respectively, P<0.05). The mean tail moment (MTM) in Ad-Rad50-GFP plus irradiation group was higher than that in irradiation group when irradiation was completed (16.06 vs 14.8, P<0.05), 24 hours after irradiation (58.23 vs 15.89, P<0.05) and 48 hours after irradiation: (45.12 vs 11.42, P<0.05). Seven days after irradiation, the cells in Ad-Rad50-GFP plus irradiation group was less than those in control group or irradiation group (both P<0.05). Conclusion: Mutant Rad50 enhances killing effects of radiation on nasopharyngeal carcinoma cell line CNE1.

Scorpion Venom Heat-Resistant Peptide Protects Transgenic Caenorhabditis elegans from β-Amyloid Toxicity

Scorpion venom heat-resistant peptide (SVHRP) is a component purified from Buthus martensii Karsch scorpion venom. Our previous studies found SVHRP could enhance neurogenesis and inhibit microglia-mediated neuroinflammation in vivo. Here, we use the transgenic CL4176, CL2006, and CL2355 strains of Caenorhabditis elegans which express the human Aβ_1-42 to investigate the effects and the possible mechanisms of SVHRP mediated protection against Aβ toxicity in vivo. The results showed that SVHRP-fed worms displayed remarkably decreased paralysis, less abundant toxic Aβ oligomers, reduced Aβ plaque deposition with respect to untreated animals. SVHRP also suppressed neuronal Aβ expression-induced defects in chemotaxis behavior and attenuated levels of ROS in the transgenic C. elegans. Taken together, these results suggest SVHRP could protect against Aβ-induced toxicity in C. elegans. Further studies need to be conducted in murine models and humans to analyze the effectiveness of the peptide.

The expression and significance of WT1 in xenotransplanted ovarian carcinoma treated by paclitaxel

In this study, the authors investigated the expression and significance of WTl in xenotransplanted ovarian carcinoma cell SKOV3 of nude mice treated with paclitaxel. Xenotransplanted ovarian carcinoma was established in nude mice using the SKOV3 cell line. The mice were randomized into the treatment group with paclitaxel and control group with normal sodium. The sizes of the xenotransplanted tumors were measured and the tumor specimens were confirmed by routine hemotoxylin-eosin (H&E) staining. The apoptosis index was then assayed using flow cytometry. WTl and bcl-2 expression were detected with immunohistochemistry, and WT1 mRNA expression was determined by reverse transcriptase polymerase chain reaction (RT-PCR). The authors found that the growth of the xenotransplanted tumor was inhibited by paclitaxel therapy. Compared to the control group, the apoptosis rate was significantly increased in the treatment group (p < 0.05). At the same time, the expression of WTl, bcl-2 and WTI, mRNA were significantly decreased in the paclitaxel therapy group (p < 0.05). The authors conclude that the WTl gene may play an important role during apoptosis of ovarian carcinoma and the mechanism may be closely related to bcl-2.

Metabolic response of maize plants to multi-factorial abiotic stresses

Clarification of the metabolic mechanisms underlying multi-stress responses in plants will allow further optimisation of crop breeding and cultivation to obtain high yields in an increasingly variable environment. Using NMR metabolomic techniques, we examined the metabolic responses of maize plants grown under different conditions: soil drought, soil salinity, heat and multiple concurrent stresses. A detailed time-course metabolic profile was also performed on maize plants sampled 1, 3 and 7 days after initiation of soil drought and heat stress. The metabolic profile of maize plants subjected to soil drought was more similar to plants exposed to salt stress than to heat-stressed plants. Drought-stressed maize plants subjected to salt or heat stress showed distinct integrated metabolic profiles compared with those exposed to either stressor individually. These differences show the considerable metabolic plasticity of maize in response to different growth conditions. Moreover, glucose, fructose, malate, citrate, proline, alanine, aspartate, asparagine, threonine and one unknown compound fluctuated obviously between maize plants grown in controlled growth cabinet and a natural regime. These changes were associated with the TCA cycle and core nitrogen metabolism, and could be related to their multiple functions during plant growth. The evident stress-induced trajectory of metabolic changes in maize indicated that the primary metabolic responses to soil drought, heat and combined drought and heat stresses occurred in a time-dependent manner. Plasticity at the metabolic level may allow maize plants to acclimatise their metabolic ranges in response to changing environmental conditions.

Scorpion Venom Heat-Resistant Peptide Attenuates Glial Fibrillary Acidic Protein Expression via c-Jun/AP-1

Scorpion venom has been used in the Orient to treat central nervous system diseases for many years, and the protein/peptide toxins in Buthus martensii Karsch (BmK) venom are believed to be the effective components. Scorpion venom heat-resistant peptide (SVHRP) is an active component of the scorpion venom extracted from BmK. In a previous study, we found that SVHRP could inhibit the formation of a glial scar, which is characterized by enhanced glial fibrillary acidic protein (GFAP) expression, in the epileptic hippocampus. However, the cellular and molecular mechanisms underlying this process remain to be clarified. The results of the present study indicate that endogenous GFAP expression in primary rat astrocytes was attenuated by SVHRP. We further demonstrate that the suppression of GFAP was primarily mediated by inhibiting both c-Jun expression and its binding with AP-1 DNA binding site and other factors at the GFAP promoter. These results support that SVHRP contributes to reducing GFAP at least in part by decreasing the activity of the transcription factor AP-1. In conclusion, the effects of SVHRP on astrocytes with respect to the c-Jun/AP-1 signaling pathway in vitro provide a practical basis for studying astrocyte activation and inhibition and a scientific basis for further studies of traditional medicine.

Bromate oxidized from bromide during sonolytic ozonation

Sonolytic ozonation (US/O3) is an effective way to degrade many pollutants in drinking water as the elevated mass transfer rate of ozone gas and the enhanced forming of hydroxyl radicals (OH). This work investigated the formation of bromate (BrO3(-)) from bromide (Br(-)) in sonolytic ozonation. At neutral pH, the bromate conversion rate ([BrO3(-)]/[Br(-)]0) was increased to 60% by ultrasound at continuous ozone flow (0-0.2Lmin(-1)), much higher than that without ultrasound or without bubbling. This indicates that the promoting effect of sonolysis on BrO3(-) formation is mainly due to the sonolytic decomposition of ozone and the enhancement of gas-liquid transfer. The [BrO3(-)]/[Br(-)]0 was increased with increasing pH. In addition, the reduction of HOBr/OBr(-) with ultrasound demonstrates that bromate may be inhibited as the bromide was formed with the H2O2 generation under ultrasound. This suggests the competition between bromate and bromide during the US/O3 led to the inhibition of bromate formation at high ozone flow. Therefore, our result reveals that the bromate formation under ultrasound is improved remarkably in US/O3 in quick treatment with proper ozone flow (<0.2Lmin(-1)).

Single-photon property characterization of 1.3 μm emissions from InAs/GaAs quantum dots using silicon avalanche photodiodes

We developed a new approach to test the single-photon emissions of semiconductor quantum dots (QDs) in the optical communication band. A diamond-anvil cell pressure device was used for blue-shifting the 1.3 μm emissions of InAs/GaAs QDs to 0.9 μm for detection by silicon avalanche photodiodes. The obtained g⁽²⁾(0) values from the second-order autocorrelation function measurements of several QD emissions at 6.58 GPa were less than 0.3, indicating that this approach provides a convenient and efficient method of characterizing 1.3 μm single-photon source based on semiconductor materials.

Diabetic retinopathy in predicting diabetic nephropathy in patients with type 2 diabetes and renal disease: a meta-analysis

AIMS/HYPOTHESIS

The aim of this meta-analysis is to determine the predictive value of diabetic retinopathy in differentiating diabetic nephropathy from non-diabetic renal diseases in patients with type 2 diabetes and renal disease.

METHODS

Medline and Embase databases were searched from inception to February 2012. Renal biopsy studies of participants with type 2 diabetes were included if they contained data with measurements of diabetic retinopathy. Pooled sensitivity, specificity, positive predictive value, negative predictive value and other diagnostic indices were evaluated using a random-effects model.

RESULTS

The meta-analysis investigated 26 papers with 2012 patients. The pooled sensitivity and specificity of diabetic retinopathy to predict diabetic nephropathy were 0.65 (95% CI 0.62, 0.68) and 0.75 (95% CI 0.73, 0.78), respectively. The pooled positive and negative predictive value of diabetic retinopathy to predict diabetic nephropathy were 0.72 (95% CI 0.68, 0.75) and 0.69 (95% CI 0.67, 0.72), respectively. The area under the summary receiver operating characteristic curve was 0.75, and the diagnostic odds ratio was 5.67 (95% CI 3.45, 9.34). For proliferative diabetic retinopathy, the pooled sensitivity was 0.25 (95% CI 0.16, 0.35), while the specificity was 0.98 (95% CI 0.92, 1.00). There was heterogeneity among studies (p < 0.001), and no publishing bias was identified.

CONCLUSIONS/INTERPRETATION

Diabetic retinopathy is useful in diagnosing or screening for diabetic nephropathy in patients with type 2 diabetes and renal disease. Proliferative diabetic retinopathy may be a highly specific indicator for diabetic nephropathy.

[Spectral analysis of formation of trihalomethanes during reaction of tryptophan with disinfectants]

UV and fluorescence spectra were applied to analyze the characteristics of reaction of disinfectants (free chlorine, free bromine) with tryptophan, as well as the formation of disinfection byproduct-trihalomethanes (THMs). The results show that disinfecting reaction decrease both the intensity and FRI (fluorescence region integration) of tryptophan. A linear relationship was found between the two indexes. Increasing the ratio of free bromine led to a lowering of FRI, a decrease in UV280 and an increase in UV254. Bromine-substitution ratio of THMs also went up with increasing the ratio of free bromine, whereas the total THMs concentration didn't follow such mono-increase pattern. Those phenomena are mainly due to a higher substitution but a lower oxidation capacity of free bromine, when compared with free chlorine. A linear relationship between FRI and CHBr3 concentration was found using free bromine alone, which did not exist by dosing ammonia to change the characteristic of disinfectant.

Confined three-dimensional plasmon modes inside a ring-shaped nanocavity on a silver film imaged by cathodoluminescence microscopy

The confined modes of surface plasmon polaritons in boxing ring-shaped nanocavities have been investigated and imaged by using cathodoluminescence spectroscopy. The mode of the out-of-plane field components of surface plasmon polaritons dominates the experimental mode patterns, indicating that the electron beam locally excites the out-of-plane field component of surface plasmon polaritons. Quality factors can be directly acquired from the spectra induced by the ultrasmooth surface of the cavity and the high reflectivity of the silver (Ag) reflectors. Because of its three-dimensional confined characteristics and the omnidirectional reflectors, the nanocavity exhibits a small modal volume, small total volume, rich resonant modes, and flexibility in mode control.

Short axis contact in the chaining of ellipsoidal particles of polar molecule dominated electrorheological fluid

We simulate the effect of the chaining direction of ellipsoidal particles of polar molecule dominated electrorheological (PM-ER) fluids using commercially available COMSOL Multiphysics® software for the distribution of electric field and the total electrostatic energy. It is proved that adding ferroelectric materials to the channels parallel to the short axis would make the short axis parallel to the field direction when the ellipsoidal particles are chained under an electric field. According to our simulation, while the concentration of the channels stays constant, the greater the dielectric constant of the inserted material, the stronger the maximum local electric field will be.

Gene transfer using recombinant simian virus 40 viral vectors into mice bone marrow progenitor cells depressed the immunogenicity of keratinocyte stem cells

Hematopoietic stem cell (HSC) gene transfer has been attempted almost entirely ex vivo and has been limited by loss of self-renewal capacity and transplantation-related defects in homing and engraftment. Herein we have attempted to overcome these limitations by injecting vectors directly into the bone marrow (BM) to transduce HSCs in their native environment. Simian virus 40 (SV40)-derived gene delivery vectors were used because they efficiently transduce resting CD34+ cells. Neonatal C57BL/6 (H-2b) mice (3 days old) received SV(Nef-FLAG), carrying FLAG marker epitope directly into both femoral marrow cavities. Keratinocyte stem cells (KSCs) were purified at 7 and 14 days after SV40 injection. The KSCs from 10-day-old C57BL/6 mice were designated as controls. Flow cytometric (FCM) analyses indicated that KSCs from transgenic mice showed strong down-regulation of surface immunological molecules CD40, CD80, CD86, and human major histocompatibility complex class I chain-related antigen A (MICA). Mixed lymphocyte reaction (MLR) assays showed that transgenic KSCs depressed allogeneic T-cell proliferation. Immunofluorescence showed transgenic KSCs expressed FLAG for the entire study as well as high levels of transforming growth factor (TGF)-beta and BCL-2. Thus, direct intramarrow administration of recombinant SV40 yielded efficient gene transfer to mice BM progenitor cells. KSCs with low immunogenicity may be obtained for further investigations of skin transplantation immunity.

[Effects of scorpion venom heat-resistant protein on kainic acid induced-damage of cultured primitive rat hippocampal neuropeptide Y-nergic neurons]

AIM

To investigate the effects of scorpion venom heat-resistant protein (SVHRP) on kainic acid induced-damage of cultured primitive rat hippocampal neuropeptide Y-nergic neurons.

METHODS

We observed morphological changes, celluar vigor, NPY-immunoreactivity and NPY mRNA expression by means of Thionine staining, MTT assay, immunocytochemistry and RT-PCR, respectively, on the primitively cultured Sprague-Dawley rat hippocampal neuron treated with KA and SVHRP for 24 h.

RESULTS

MTT assay and morphologic analysis showed that SVHRP markedly increased neuron survival-rate, and protected them from kA-induced damage. The expression of NPY-immunoreactivity and NPY mRNA in SVHRP group increased obviously compared with other groups.

CONCLUSION

SVHRP protected the primitively cultured hippocampal neurons from KA-induced neuroexcitotoxicity and promoted the expression of NPY.

X-ray Flares from Postmerger Millisecond Pulsars

Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The x-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy-release time scales. Here, we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection-driven explosive events then occur, leading to multiple x-ray flares minutes after the original gamma-ray burst.

The role of microglia in paraquat-induced dopaminergic neurotoxicity

The herbicide paraquat (PQ) has been implicated as a potential risk factor for the development of Parkinson's disease. In this study, PQ (0.5-1 microM) was shown to be selectively toxic to dopaminergic (DA) neurons through the activation of microglial NADPH oxidase and the generation of superoxide. Neuron-glia cultures exposed to PQ exhibited a decrease in DA uptake and a decline in the number of tyrosine hydroxylase-immunoreactive cells. The selectivity of PQ for DA neurons was confirmed when PQ failed to alter gamma-aminobutyric acid uptake in neuron-glia cultures. Microglia-depleted cultures exposed to 1 microM PQ failed to demonstrate a reduction in DA uptake, identifying microglia as the critical cell type mediating PQ neurotoxicity. Neuron-glia cultures treated with PQ failed to generate tumor necrosis factor-alpha and nitric oxide. However, microglia-enriched cultures exposed to PQ produced extracellular superoxide, supporting the notion that microglia are a source of PQ-derived oxidative stress. Neuron-glia cultures from NADPH oxidase-deficient (PHOX-/-) mice, which lack the functional catalytic subunit of NADPH oxidase and are unable to produce the respiratory burst, failed to show neurotoxicity in response to PQ, in contrast to PHOX+/+ mice. Here we report a novel mechanism of PQinduced oxidative stress, where at lower doses, the indirect insult generated from microglial NADPH oxidase is the essential factor mediating DA neurotoxicity.

[Study on differentially expressed genes of ulcerative colitis in the rat treated by herbs-partitioned moxibustion]

OBJECTIVE

To probe the mechanism of herbs-partitioned moxibustion for treatment of ulcerative colitis.

METHODS

The rats with ulcerative colitis were randomly divided into 3 groups, normal control group, model group, and herbs-partitioned moxibustion group. The rats in the herbs-partitioned moxibustion group were treated by herbs-partitioned moxibustion at bilateral Tianshu (ST 25). BiostarR-40s gene chip was applied to detect the differentially expressed gene of their colonic tissues and fluorescence quantitative polymerase chain reaction was employed to confirm the results of the microarray analysis with interleukin-1 beta messenger RNA (IL-1beta mRNA) expression.

RESULTS

Of 174 differential expression genes identified, 28 genes (including 7 known genes) elevated in rats of ulcerative colitis were down-regulated and 146 genes (including 42 known genes) reduced in the rat of ulcerative colitis were up-regulated after herbs-partitioned moxibustion treatment.

CONCLUSION

Many abnormally expressed genes are involved in occurrence of ulcerative colitis and herbs-partitioned moxibustion can regulate expression of IL-1beta and other genes to exert therapeutic effect.

Gene cloning, expression and vaccine testing of Schistosoma japonicum SjFABP

A 600 bp DNA fragment was amplified by PCR from an adult Schistosoma japonicum cDNA library. Sequence analysis confirmed that this fragment contained an S. japonicum Chinese mainland strain fatty acid binding protein (Sj14FABP) gene. This gene was subsequently expressed in Escherichia coli (E. coli) and in Baculovirus/silkworm systems. The recombinant protein from E. coli was a 41 kDa GST fusion protein (rSj14/GST), which could be purified by glutathione agarose affinity chromatography, with a yield of 25 mg/L E. coli culture. The recombinant protein from the Baculovirus/silkworm system was an 18 kDa fusion protein (rSj14/His), which could be purified by Ni-NTA resin chromatography column with a yield of 3.5 mg per silkworm larva. Both rSj14/GST and rSj14/His could be recognized by S. japonicum-infected mouse sera and anti-rSj14/GST mouse sera in Western blotting. The purified recombinant protein was immunogenic in mice, rats and sheep, and 34.3%, 31.9% and 59.2% worm reductions, respectively, were obtained in vaccinated Kunming mice, Wistar rats and sheep vaccinated with Sj14/GST, compared to non-vaccinated control groups. Worm reductions of 48.8% and 49.0% were recorded in Balb/c mice immunized with Sj14/His, compared to non-vaccinated and BCG-vaccinated groups, respectively. These results indicate that rSj14FABP is a promising candidate vaccine for schistosomiasis japonica, particularly as in the rat and sheep vaccination experiments, no adjuvant was used.

[Studies on the sex difference in proteins between male and female adult worm of Schistosoma japonicum]

OBJECTIVE

To explore the sex difference in proteins between male and female adult worm of Schistosoma japonicum.

METHODS

Two-electrophoresis was used to analyse the difference of protein between the male and female adult worm of S. japonicum (Chinese strain).

RESULTS

Two-dimensional electrophoresis analysis revealed that at the site of 43 kDa and an isoelectric point (pI) of 5.60-5.90 the male worm exhibited a band carrying a number of spots and dots, being longer and wider than that exhibited by the female worm. The female worm exhibited 7 specific dots.

CONCLUSION

The sex differences in proteins between male and female adult worms of S. japonicum are significant.

[Cloning and expression of gynecophoral canal protein gene of Schistosoma japonicum (Chinese strain)]

A 1949 bp cDNA fragment was amplified by RT-PCR from adult Schistosoma japonicum (Chinese strain) mRNA with 3 pair of primers that were designed according to published SmGCP gene encoding gynecophoral canal protein of Schistosoma mansoni and SjGCP1 gene encoding the conservative region of gynecophoral canal protein of Schistosoma japonicum. Sequence analysis indicated that this fragment, named SjGCP, with 85% identity to SmGCP, contained a complete open reading frame (ORF) of gynecophoral canal protein gene of Schistosoma japonicum (Chinese strain). The amino acid sequence shared 83.7% identity with gynecophoral canal protein of Schistosoma mansoni. This fragment was cloned into the expression vector pET28c(+) and subsequently expressed in Escherichia coli. SDS-PAGE revealed that the molecular weight of this expressed product was 80 kD. Western blotting showed that the recombinant protein reacted well with the rabbit serum immunized with Sj worm antigen, indicating that this expressed product had good antigenicity.

[The hemolytic site of the basic phospholipase A(2) from Agkistrodon halys pallas]

The gene of the basic phospholipase A(2) from Agkistrodon halys Pallas (BPLA(2) )was mutated site-directedly by polymerase chain reaction (PCR) and the residue Arg(34) of the encloding protein was substituted by Glu and Gln respectively. The mutant gene has been cloned into the expression vector pBLMVL2 and has been expressed in E.coli RR1 effectively. The protein was produced as insoluble inclusion bodies. After partial purification, the inclusion bodies were denatured and renatured into active form, and the renatured recombinant protein was purified by gel-filtration. The expression product has the same enzymatic activity as the denatured-refolded BPLA(2) and its hemolytic activity dropped distinctly, which suggest that the basic residue Arg(34) of BPLA(2) is a crucial amino acid residue during the process of hemolysis.

[Separation and determination of pseudoephedrine in bufferin cold tablet by capillary electrophoresis with hydropropyl-beta-cyclodextrin as chiral selective reagent]

A method for the separation and analysis of the chiral pseudoephedrine enantiomers using capillary electrophoresis was established. The buffer solution for separation was 25 mmol/L Tris-phosphate, including 38 mmol/L hydropropyl-beta-cyclodextrin with pH value of 2.65. (1S, 2S)(+) Pseudoephedrine in Bufferin Cold tablet was determined. The method has good precision, recovery and linear relationship.

[Cloning of secondary lymphoid-tissue chemokine (SLC) and its expression in prokaryotic system]

The total RNA from lymphoid tissue in Chinese was extracted, and the gene encoding the mature peptide of secondary lymphoid-tissue chemokine (SLC) was cloned by RT-PCR. Nucleotide sequence analysis showed that there is only one nucleotide different from that reported, but it doesn't alter the amino acid encoded. The SLC cDNA was inserted into an expression vector pET-28a(+) under T7 promoter and constructed recombinant plasmid pET28a-SLC. pET28a-SLC was transformed to E. coli BL21(DE3) and the expression strain was gotten. After inducing with IPTG for 3-5 hours the bacterium were sonicated. After centrifuging the supernatant was analysed by SDS-PAGE. An obvious expression band about 18 kD can be seen. The expressed product was purified by Ni2+ affinity chromatography column, and the purity is up to 90 percent.

[The new antiendotoxin strategies]

Lipopolysaccharide(LPS) is important in the pathogenesis of sepsis infected by gram-negative bacteria in humans, and part or all of this pathophysiology is mediated by a complex secondary inflammatory response. Administration of purified LPS or a variety of LPS-free recombinant mediators can reproduce much of the pathophysiology of gram-negative sepsis. There has been an explosion of new information over the last several years regarding the interactions of LPS with proteins and cells. Blocking sepsis at the bacterial toxin level is appealing because it is upstream, so that the secondary pathologic inflammatory cascade may be limited or prevented. A variety of antiendotoxin strategies have been proposed. Therapies under investigation include agents that bind and neutralize LPS, agents or systems that enhance LPS clearance, and agents that inhibit LPS interaction with serum elements or cellular receptors.

[Gene chimeric fusion and expression of nucleocapsid NS3 regions and NS4 regions of hepatitis C virus genome]

Genes encoding HCV core and NS4 antigen epitopes and C33c antigen were cloned from HCV genome by PCR, respectively. Two fused genes were constructed. One contained these three genes, another contained genes encoding C33c antigen and NS4 antigen epitopes. These fused genes were cloned into expression plasmid pET-24(a)+ and pET-22(b)+ under T7 promoter and transformed into E. coli BL21 (DE3) respectively. SDS-PAGE analysis revealed that these fused antigens CCN, CN were highly expressed after the induction by 1 mmol/L IPTG. These Expression products were detected by western blotting with anti-HCV serum.

Purification, characterization, and cDNA sequence of halysetin, a disintegrin-like/cysteine-rich protein from the venom of Agkistrodon halys Pallas

By means of DEAE-Sepharose CL-6B column chromatography, gel filtration on Sephadex G-75 and Superose 12 FPLC, halysetin, an antiplatelet protein, was purified from the venom of Agkistrodon halys Pallas with molecular mass of 29 kDa on SDS-PAGE and 23,168 Da by mass spectrometry. The p1 was about 5.0. Halysetin was devoid of phospholipase A2, fibrino-(geno)lytic, esterase, hemorrhagenic activities. Halysetin dose-dependently inhibited the aggregation of human platelet, which was stimulated by collagen with IC50 of 420 nM, but not that stimulated by ADP. The N-and C-terminal sequences of halysetin were characterized. Its full-length cDNA was cloned by RT-PCR from the total RNA extracted from the snake venom gland. It encoded a protein of 212-amino-acid residues with disintegrin-like/cysteine-rich domains and was highly homologous with SYMPs (snake venom metalloprotease).

[Fusion and expression of the gene encoding human Mn-SOD to anti-CEA single-chain antibody in Escherichia coli]

The gene encoding human manganese-superoxide dismutase (Mn-SOD) was fused to anti-carcinoembryonic antigen single-chain antibody gene to construct the fusion gene, then was ligated into prokaryotic expression vector pET-22b(+), The fusion gene was expressed in E. coli at high level, accounting for 24% of the total bacteria soluble protein; and was characterized by SDS-PAGE and Western-blot analysis; the expression product had the CEA-binding ability in RIA, and also had the SOD activity by pyrogallol autoxidation assay. So, the Mn-SOD moiety retains substantial enzymatic activity, where the ScFv moiety can deliver the fusion protein to tumor, Mn-SOD is a potential tumor-suppressor gene, maybe the fusion protein can provide a new pathway to tumor therapy.

[Cloning of the zot gene of Vibrio cholerae and its expression in Escherichia coli]

The zot gene encoding Zonula occludens toxin was amplified from classic Vibrio cholerae genomic DNA by PCR. The result of sequencing indicated that zot gene encodes 399 amino acid residues. The sequence of zot gene was a little bit different from that of reported including 14 nucleotides and four amino acid residues. The expression plasmid pET-ZOT was constructed by inserting zot gene into plasmid pET-28a(+) containing the T7 promoter. The expression plasmid was induced into E. coli BL21 (DE3) and expression strain BLZOT was selected. SDS-PAGE analysis revealed that the ZOT protein was expressed and accumulated up to above 15% of bacterial soluble protein after induced by IPTG. A protein of 47 kD was expressed as including body. Western blot analysis revealed that the expressed protein was ZOT.

[Expression of human GDNF in methyltrophic yeast Pichia pastoris and silkworm larvae]

The cDNA encoding glial cell derived neurotrophic factor (GDNF) was cloned into the Pichia expression vector pPIC9K and then transformed into his4 mutant yeast GS115 by electroporation. Multicopy transformants were screened by various G418 concentrations and induced by methanol. The human GDNF gene was cloned into the baculovirus transfer vector pBacPAK8. The recombinant transfer vector pBacPAK-GDNF was coinfected with linear Bm-BacPAK6 DNA into BmN cells. The recombinant virus was screened and plaque-purified. The silkworm larvae were infected with the recombinant virus and collected 5 days later. SDS-PAGE and Western blot confirmed that GDNF was expressed in Pichia culture medium and silkworm larvae hemolymph. The GDNF protein expressed in Pichia and silkworm larvae could significantly promote the survival and neurite outgrowth of dopaminergic neurons.

Preparation of recombinant human GDNF by baculovirus expression system and analysis of its biological activities

Recombinant human glial cell line-derived neurotrophic factor (GDNF) has been expressed at high levels and produced in large quantities in baculovirus-infected Trichoplusia ni cells (Tn-5B1-4). The glycosylated protein was purified using immunoaffinity chromatography and gel filtration. Pure, recombinant human GDNF promoted the survival and morphological differentiation of embryonic dopaminergic neurons and enhanced axonal regeneration after sciatic nerve transection. Because recombinant bioactive human GDNF can be obtained in large quantities, and purified to near homogeneity, they are suitable for evaluation in animal models.

High-dose and long-term therapy with interferon-alfa inhibits tumor growth and recurrence in nude mice bearing human hepatocellular carcinoma xenografts with high metastatic potential

Postoperative recurrence of human hepatocellular carcinoma (HCC) is the major issue that must be addressed to further improve prognosis. This study was undertaken to investigate the effects of interferon-alfa-1b (IFN-alpha-1b) on recurrent tumor and metastasis after curative resection in nude mice bearing an HCC xenograft with high metastatic potential. Tumor tissues from LCI-D20, a metastatic model of HCC in nude mice, were orthotopically implanted in 105 nude mice. Eleven days later, 64 mice underwent curative resection of liver tumors. IFN-alpha at different doses was administered subcutaneously to mice with or without resection. In mice without resection, when comparison was made among control, IFN 7.5 x 10(6) U/kg/day, 1.5 x 10(7) U/kg/day for treated groups, and 3 x 10(7) U/kg/day; tumor volume was 8,475 mm(3) +/- 2,636 mm(3), 7,963 mm(3) +/- 3,214 mm(3), 769 mm(3) +/- 287 mm(3), and 13 mm(3) +/- 9 mm(3); incidence of lung metastasis being 100%, 80%, 40%, and 0%; life span was 45 +/- 4 days, 53 +/- 8 days, 81 +/- 6 days, and 105 +/- 24 days, respectively. In mice with curative resection, when comparison was made among control, IFN 5 x 10(5) U/kg/day, 1 x 10(6) U/kg/day, 4 x 10(6) U/kg/day, 7.5 x 10(6) U/kg/day, 1.5 x 10(7) U/kg/day, and 3 x 10(7) U/kg/day for treated groups; incidence of recurrent tumor was 100%, 100%, 87.5%, 100%, 87.5%, 62.5%, and 12.5%; lung metastasis being 100%, 75%, 87.5%, 50%, 62.5%, 0%, and 0%, respectively. IFN-alpha inhibited neovascularization induced by LCI-D20 tumor specimens implanted into the micropocket of nude mice corneas. In conclusion, high-dose and long-term therapy with IFN-alpha dose-dependently inhibits tumor growth and recurrence after resection of HCC. The effect of IFN-alpha may be attributed to antiangiogenesis in this experiment. These results provide potential clinical implication, particularly for the prevention of recurrence after curative resection of HCC.

Expression of isolated C-type carbohydrate recognition domains

A galactose-binding lectin from the venom of the snake Trimeresurus stejnegeri consists of isolated carbohydrate recognition domains, belonging to group VII of the C-type animal lectins. As a first step toward determining the tertiary structure of the galactose-specific lectin, we produced the lectin in Escherichia coli. By in vitro refolding and affinity chromatography, modest amounts (8 mg/liter) of active recombinant proteins were obtained. The recombinant protein was homogeneous, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry. Its amino acid sequence without the initiated methionine at the N-terminus was also characterized by mass spectrometry. The data of hemagglutination and enzyme-linked lectin binding assays demonstrated that the recombinant lectin showed similar sugar-binding activity as the native protein. In addition, fluorescence spectroscopy and circular dichroism also showed obviously their structural similarity.

Human glial cell-line-derived neurotrophic factor: a structure-function analysis

Glial cell-line-derived neurotrophic factor (GDNF) is a protein known to enhance the survival of dopaminergic and motor neurons. It has been shown to have therapeutic potential in the treatment of Parkinson's disease and other neurodegenerative diseases. GDNF gene was modified by deletion and insertion mutagenesis using PCR methods. The various mutants were all highly expressed in Escherichia coli. The recombinant proteins were purified and their survival-promoting activities were determined by motor neurons. The result showed that the C-terminus was critical for structure stability of GDNF, and the alpha-helix, finger1 and finger2 regions were involved in receptor binding, while the N-terminus was not essential for the biological functions of GDNF.

[Expression of Bacillus thuringiensis (Bt) crystal toxin gene in the chloroplast of tobacco]

The 3.5 kb wild-type Bt Cry I A(c) gene and its 3' truncated forms (2.1 kb, 1.8 kb) were placed under the control of plastid expression signals consisting of the strong light-induced psbA promoter and its 3' untranslated region with the aadA cassette (Prrn, aadA and psbA3') as a selectable marker. The resulting vectors pBT3, pBT8 and pBT22 also contain flanking tobacco plastid DNA homology regions to direct insertion of the Bt transgene into the tobacco plastid genome between psbA and trnK by homologous recombination. Transformed plastid genomes were selectively amplified by growing the cells on spectinomycin medium. Several independently transformed lines were obtained at last. The results of Southern and Western blot demonstrated that these three kinds of Bt genes had been introduced into tobacco plants, and their filial generations are resistant to spectinomycin. Insecticidal activity assay with transgenic tobacco leaves indicate that some plants have strong toxicity to cotton bollworm. This is the first report in China that Bt gene has been introduced and successfully expressed in the chloroplast of higher plants.

[High expression of human EPO gene in the larvae and pupae of the silkworm, Bombyx mori]

Erythropoietin (EPO) is a glycoprotein hormone produced primarily by the kidney, and is principal factor regulating red blood cell poduction. The synthesized EPO cDNA was inserted into the transfer vector pBlueBac III to generate the recombinant transfer plasmid pBlueBacEPO. Cotransfection of BmN cells with pBlueBacEPO DNA and Wild BmNPV DNA generated the recombinant virus rBmNPVEPO carrying EPO gene driven by the strong promoter of AcNPV polyhedrin gene. The results of Southern blot and PCR reaction confirmed that EPO gene had been correctly inserted in the target position in the BmNPV genome. ELISA assay showed that the EPO gene was expressed with high level in the larvae and pupae of the silkworm. The larvae and pupae produced as high as 62,800 u and 74,000 u in 1 mL hemolymph on the 4th day (larve) and the 5th day(pupae) after infection with the recombinant virus rBmNPVEPO, respectively. Western blot analysis showed the molecular weight of rhEPO produced in the lavae or pupae was about 26 kD. Biologic assay showed the rhEPO had high activity (about 63,000 u in per milliliter of hemolymph) in vitro.

Cloning of a galactose-binding lectin from the venom of Trimeresurus stejnegeri

A galactose-binding lectin isolated from the venom of Trimeresurus stejnegeri is a homodimer C-type lectin. The cloned cDNA encoding the monomer of Trimeresurus stejnegeri lectin (TSL) was sequenced and found to contain a 5'-end non-coding region, a sequence which encodes 135 amino acids, including a typical 23 amino acid signal peptide followed by the mature protein sequence, a 3'-end non-coding region, a polyadenylation signal, and a poly(A) region. To completely characterize the deduced amino acid sequence, on-line HPLC-MS and tandem MS were used to analyse the intact monomer and its proteolytic peptides. A modified peptide fragment was also putatively identified by HPLC-MS analysis. The deduced amino acid sequence was found to contain a carbohydrate-recognition domain homologous with those of some known C-type animal lectins. Thus TSL belongs to group VII of the C-type animal lectins as classified by Drickamer [(1993) Prog. Nucleic Acid Res. Mol. Biol. 45, 207-232]. At present, a number of C-type lectins have been purified from snake venom, but most of them have been characterized only at the protein level. To our knowledge, this is the first known cDNA sequence of a true C-type lectin from snake venom.

The gene expression of coagulation factor VIII in mammalian cell lines

Both the full-length and B domain-deleted cDNA of factor VIII were constructed in plasmid pcDNA3, respectively, and successfully expressed in Cos-7 cells. The yield of recombinant factor VIII-deltaB (0.4 U/mL/10(6) cells/day) was approximately four times higher than that of the recombinant factor VIII. In addition, it was indicated that the gene expression of factor VIII is specific for cells from different tissues. The highest expression level was found in the hepatocellular carcinoma line SMMC-7721, followed by kidney, ovary, and lung cell lines. To compare the efficiency of gene expression of recombinant factor VIII, the factor VIII-deltaB gene was further reconstructed in different forms in the expression plasmid pCMV-dhfr for transient gene expression in Chinese hamster ovary cells. The redundant 5'- and 3'-untranslated sequences of factor VIII-deltaB were deleted. The cDNA encoding the heavy and light chains of factor VIII were constructed, respectively. Among them the high yield of the recombinant factor VIII was found in the coexpression of the heavy and light chain cDNA fragments of factor VIII. The deletion of the redundant 5'-untranslated sequence of factor VIII-deltaB was also beneficial for gene expression. As expected, the gene coexpression of factor VIII-deltaB and von Willibrand Factor cloned by the long-polymerase chain reaction method was also helpful for enhancing the expression level of recombinant factor VIII. A monoclonal antibody raised against factor VIII was prepared and used for the specific assay of recombinant factor VIII by the competitive ELISA method, the assay results were consistent with those determined by the one-stage bioassay.

[Expression of chimeric single-chain antibody with specificity for HBsAg in E. coli]

The Vk gene of MAb with specificity for HBsAg and human Ck gene have been combined to form chimeric light chain (Vk-Ck) by recombinant PCR, which has combined with VH to construct chimeric single-chain antibody(ScFv-Ck) by a linker encoding a flexible peptide[(Gly3 Ser)3]. The ScFv-Ck has been expressed in the heat-induced expression system and secreted expression system of E. coli respectively. Analysis by Western-blot and indirect ELISA shows that the ScFv-Ck product in two systems both have HBsAg-binding ability, and ScFv-Ck has been secreted from E. coli in the direction of secretion peptide.

Cloning of a cDNA encoding a nerve growth factor precursor from the Agkistrodon halys Pallas

Based on the high conservation in the 5' and 3' untranslated regions of NGF cDNAs, oligonucleotides complementary to all these known sequences were synthesized. By RT-PCR, we successfully isolated the complementary DNA encoding NGF precursor from the Agkistrodon halys Pallas (a Chinese snake strain). The nucleotide sequence which presents 90.5%, 88.6% and 63.4% homology to that of Krait Bungarus multicinctus, cobra and human NGF respectively, encoded a prepro-NGF molecule with 241 amino acids and a mature NGF molecule with 119 amino acids. The NGF cDNA inserts were subcloned into pCDNA3 expression vector and then transfected into COS-7 cells. The supernatant of the transfected cells turned out NGF biological activity as assayed by the survival rate of PC12 pheochromocytoma cells.

Diversity of cDNAs encoding phospholipase A2 from Agkistrodon halys pallas venom, and its expression in E. coli

As a step toward understanding the structure and function of phospholipase A2(PLA2), we isolated several novel cDNAs encoding Agkistrodon halys Pallas PLA2 isoenzymes including B-PLA2, Asn49-PLA2, A-PLA2, A'-PLA2 and BA1-PLA2 by polymerase chain reaction with oligonucleotide primers corresponding to the N- and C-terminus of these enzymes. The amino acid sequences of A-PLA2 deduced from cDNA are consistent with that isolated from venom except for four residues. Asn49-PLA2 and B-PLA2 are highly similar (> 95%), but the critical residue Asp49 in the active centre of B-PLA2 is replaced by Asn49 in Asn49-PLA2. The N-terminal residues (1-24) of BA1-PLA2 shows high similarity to that of B-PLA2 which has strong ability to hemolyze erythrocytes, while its C-terminal residues (72-125) are the same as that of A-PLA2 which can inhibit platelet aggregation. The successful cloning of these isoenzymes not only provide excellent native material to study the structure-function relationship of PLA2s, but also to disclose the genesis of structural diversity of PLA2s, namely DNA modification and gene rearrangement. The cloned cDNA for A-PLA2 has been expressed in E. coli. By Q-Sepharose column chromatography, denaturation-renaturation and FPLC, we obtained the active recombinant protein with the initiator Met. This is the first report of the production of an active recombinant PLA2 with the initiator Met.

Purification, cDNA cloning and molecular characteristic of a fibrinolytic enzyme from the venom of Agkistrodon acutus

A nonglycoprotein-like fibrinolytic enzyme ((FIB-I) was purified from the crude venom of Agkistrodon acutus by CM-Sepharose CL-6B and DEAE-Sepharose CL-6B ion exchange chromatography and then by FPLC through Superose 12 gel filtration. Its molecular weight is about 23 kDa and isoelectric point is near 6.0. It not only has fibrinolytic and caseinolytic activity, but also can hydrolyze BAEE. The local hemorrhagic activity was found in mice after the subcutaneous injection of this enzyme. EDTA can inhibit its fibrinolytic activity completely, but PMSF and arrowhead proteinase inhibitor have no such obvious inhibitory effect, thus implying that FIB-I is a metalloproteinase. The N-terminal ten amino acid residues 'STEFQRYMEI' of FIB-I was elucidated. A full-length cDNA gene of this enzyme was cloned by using RT-PCR from the total RNA extracted from the snake venom gland and FIB-I was expressed in E. coli. Having analyzed the sequence, we found that it had a typical zinc-chelating characteristic as 'HEXXHXXGXXHD.'

Preparation of highly purified hemoglobin by affinity elution

The large scale production of recombinant hemoglobin (Hb) from microorganism or transgenic hosts for Hb-based blood substitutes places utmost emphasis on purity. In the present study, a high-resolution, convenient and inexpensive purification method is developed for purification of Hb from mixtures containing E. coli extract and bovine serum. This method is based on affinity elution by pyrophosphate (PPi) of Hb adsorbed on an FPLC column of the anion exchanger Toyopearl DEAE-650M. Compared to pH elution or NaCl elution, PPi elution makes possible the preparation of Hb of much higher purity. A procedure combining pH elution and PPi elution sequentially using a single column proves particularly valuable. The purification method is also applicable to the purification of cyanomet-Hb (CNHb+).

[Expression of human 17 beta-hydroxysteroid dehydrogenase gene in BmNPV expression system]

Estrogenic 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) plays a crucial role in the synthesis of estrogens, but it also produces negative action of estrogens in promoting the growth of hormone-sensitive cancers, especially in breast and prostate. The high specific activity can be taken as an important signal for the diagnosis of cancers. Recombinant rAcBm-NPV/17 beta-HSD virus which contains the human 17 beta-HSD cDNA under the control of polyhedron gene promoter is generated by cotransfection of the BmN cells with the transfer plasmid pVL/17 beta-HSD and wild BmNPV genomic DNA. 17 beta-HSD is maximally expressed 72 h and 120 h post infection in BmN cells and the 5th instar silkworm larvae respectively. At those time interval, intracellular and hemolymphic enzymatic activity reach 0.12 U/mg and 0.15 U/mg of protein which produced total activity of 0.97 U/1.5 x 10(6) cells and 4.7 U/larva. The expressed quantities in female larvae are a little higher than that in male larvae. The present data shows that Silkworm/BmNPV expression system can express 3-5 times higher than that of the richest human placenta. It also indicates that there is an apparent band with a molecular mass of 35 kDa using SDS-PAGE method, the size of which is similar to that of the crude enzyme from placenta.

Reconstruction and expression of chimeric anti-HBx antibody in Escherichia coli

The variable regions of murine monoclonal anti-HBx immunoglobulin and the constant region of human antibody were cloned by reverse transcript-polymerase chain reaction (RT-PCR). The heavy-chain and light-chain variable regions were connected and coexpressed with human constant region C-r3 and C-k3 in the reconstructed vector of E. coli. The products showed high specificity and binding ability with HBx. Which is closely associated with hepatocarcinogenesis. This makes it possible to humanize the mouse monoclonal antibodies and express the fusion protein in E.coli for potential radioimmunotherapy in patients with hepatocellular carcinoma.

Reconstruction and expression of chimeric anti-HBx antibody in Escherichia coli

The variable regions of murine monoclonal anti-HBx immunoglobulin and the constant region of human antibody were cloned by reverse transcript-polymerase chain reaction (RT-PCR). The heavy-chain and light-chain variable regions were connected and coexpressed with human constant region C-r3 and C-k3 in the reconstructed vector of E. coli. The products showed high specificity and binding ability with HBx. Which is closely associated with hepatocarcinogenesis. This makes it possible to humanize the mouse monoclonal antibodies and express the fusion protein in E.coli for potential radioimmunotherapy in patients with hepatocellular carcinoma.

Survival of cells with bleomycin-induced chromosomal lesions in the cultured lymphocytes of lung cancer patients

In a previous study of lung cancer, we showed that bleomycin, a radiomimetic agent, induced breaks preferentially on chromosomes 4 and 5. The molecular cytogenetic study reported here, using chromosome painting and G banding, was designed to assess whether the chromatid breaks induced by bleomycin could survive as chromosome-type aberrations after treated lymphocyte populations were allowed to recover in a drug-free medium for one or two cell generations and whether the survival rates of lesions on chromosomes 4 and 5 differed in cases with lung cancer and controls. The findings from 16 cases and 14 controls showed that in samples allowed to recover for 48 h, most aberrations were of the chromosome type. The proportion of chromosome 5 abnormalities surviving as chromosome-type aberrations was significantly higher in the cells of lung cancer cases (13.4%) than in controls (4.6%; P < 0.0001). However, no significant differences in survival of chromosome 4 abnormalities were detected between cases and controls. The proportions of chromosome 5q13-q22 abnormalities were 5.3% in the cases and 0.6% in the controls (P < 0.0001). 5q13-q22 regions encompassed 38.4% of all abnormalities on chromosome 5 in the cases but only 14.5% in the controls. Therefore, the survival rate of chromosome 5 lesions (especially those at 5q13-q22) in lymphocytes might be used as a biomarker to identify populations at high risk for lung cancer.

An epidemiological study of risk factors for lung cancer in Guangzhou, China

Lung cancer has been on a rapid rise worldwide during the last three or four decades, in part due to modern social habits and unhealthy lifestyles. Although smoking, air pollution, and certain types of occupational exposure have been recognized as the major risk factors for lung cancer, the significance of each of these factors appears to vary with sex, country, and with region within a given country. In the case of nonsmoking females, some risk factors for lung cancer remain to be identified. In the city of Guangzhou, lung cancer is one of the five leading tumors and the rate has been increasing steadily in both males and females since the 1970s. In this report, more than 6000 cases of lung cancer deaths, accumulated over the past 9 years, were analyzed. The severity of air pollution and cigarette smoking were positively correlated with the incidence of lung cancer deaths. Analysis of levels of SO2 and NOx suggests that the major source of indoor air pollution came from cooking. Two studies were performed in order to determine the relative contribution and importance of smoking, indoor air pollution and occupational exposure as risk factors for the rising incidence of lung cancer. The first was a population-based case-control study involving 849 subjects (566 males and 283 females). The second study was based on the data made available by the Third National Census survey, in which the standardized mortality rate (SMR) and population attributable risk (PAR) for lung cancer due to occupational exposure for the population in Guangzhou were analyzed. Results of these two studies show that: in females, indoor air pollution, derived primarily from burning coal, was found to be a highly significant risk factor for lung cancer. In males, however, cigarette smoking and occupational exposure were significantly associated with lung cancer. To further elucidate the contribution of indoor air pollution as a risk factor for lung cancer in nonsmoking females, two additional case-control studies were performed in 1985 and 1986. The 1985 study involved 120 nonsmokers (28 males, 92 females) in which the influence of such lifestyle factors as: personal history of nonmalignant respiratory diseases, fresh vegetable consumption, lifetime occupation and occupational exposure histories, exposure to environmental tobacco smoke (ETS), degree of indoor air pollution, general conditions of home residence, cooking practices and environments, and family history of cancer were first individually assessed and then collectively subjected to multiple conditional regression analysis for evaluation as risk factors for lung cancer. The 1986 study involved 75 cases of never-smoking females in which the aim was to investigate the influence of exposure to spousal smoke as a risk factor for lung cancer. These studies suggest that consumption of fresh vegetables was a "protective" factor for lung cancer in both males and females. In females, indoor air pollution and size of the kitchen were risk factors for lung cancer, whereas ETS exposure, respiratory disease history, family history of cancer, living conditions, use of cooking fuel, and participation in cooking, were not statistically associated with female lung cancer deaths. Occupational exposure was also correlated with the incidence of female lung cancer deaths. In males, chemists had the highest SMR, whereas in females, homemakers had the highest SMR. In males, the most common lung cancer cell type was squamous cell carcinoma, whereas in females adenocarcinoma was the most predominant type. The factors affecting the distribution of histologic lung cancer cell types were also investigated and discussed.

mRNA levels of nm23 in murine ascites hepatoma (H22) clones with different lymphatic metastatic potential

Levels of expression of the nm23 gene inversely correlated with metastatic potential in several rodent tumor model systems and human breast carcinoma. In the present study, we examined nm23 mRNA levels in two murine ascites hepatoma models (H22-16A3-F and H22-A2-P) with different metastatic potentials. Metastatic H22-16A3-F (80% metastatic rate) and non-metastatic H22-A2-P clones were both derived from murine ascites hepatoma (H22). We found that a 0.8-kb nm23 transcript was expressed in both cell clones. The nm23 gene was expressed at a higher level in non-metastatic H22-A2-P: approximately 8.6-fold higher than in metastatic H22-16A3-F. The present data suggest that the expression of nm23 mRNA might be associated with metastasis of murine ascites hepatoma (H22), though heterogeneity of nm23 steady-state expression levels among the H22 clones remains to be investigated.

Failure of blood-island formation and vasculogenesis in Flk-1-deficient mice

The receptor tyrosine kinase Flk-1 (ref. 1) is believed to play a pivotal role in endothelial development. Expression of the Flk-1 receptor is restricted to endothelial cells and their embryonic precursors, and is complementary to that of its ligand, vascular endothelial growth factor (VEGF), which is an endothelial-specific mitogen. Highest levels of flk-1 expression are observed during embryonic vasculogenesis and angiogenesis, and during pathological processes associated with neovascularization, such as tumour angiogenesis. Because flk-1 expression can be detected in presumptive mesodermal yolk-sac blood-island progenitors as early as 7.0 days postcoitum, Flk-1 may mark the putative common embryonic endothelial and haematopoietic precursor, the haemangioblast, and thus may also be involved in early haematopoiesis. Here we report the generation of mice deficient in Flk-1 by disruption of the gene using homologous recombination in embryonic stem (ES) cells. Embryos homozygous for this mutation die in utero between 8.5 and 9.5 days post-coitum, as a result of an early defect in the development of haematopoietic and endothelial cells. Yolk-sac blood islands were absent at 7.5 days, organized blood vessels could not be observed in the embryo or yolk sac at any stage, and haematopoietic progenitors were severely reduced. These results indicate that Flk-1 is essential for yolk-sac blood-island formation and vasculogenesis in the mouse embryo.

Structural characterization of a homophilic binding site in the neural cell adhesion molecule

We have previously used synthetic peptides to identify a homophilic binding site between Lys-243 and Glu-252 (KYSFNYDGSE) in the third immunoglobulin-like domain of the chick neural cell adhesion molecule (NCAM). In this report, we show that the deletion of this decapeptide sequence from chick NCAM or the scrambling of the first 5 amino acid residues led to the abolition of the homophilic binding activity of NCAM, thus confirming the role of this sequence in NCAM-NCAM binding. To investigate the involvement of individual residues of this decapeptide in NCAM binding, competition experiments were carried out using peptide analogues with various amino acid substitutions. Substitution of both Lys-243 and Asp-249 with Ala or of the 3 aromatic residues with Ala led to a total loss of activity, highlighting the importance of these residues in NCAM binding. Site-directed mutagenesis was then employed to substitute individual amino acids within the decapeptide sequence with Ala. The homophilic binding activity of mutant NCAMs transiently expressed in COS-1 cells was determined using the NCAM-Covasphere binding assay. Substitution of the charged residues with alanine decreased NCAM binding activity, implicating electrostatic interactions in NCAM binding activity. Substitution of the aromatic residues Tyr-244 and Phe-246 with Ala abolished NCAM binding activity, suggesting that hydrophobic and/or aromatic interactions may play an important role in NCAM homophilic binding. Substitution of amino acids in the predicted beta-strand portion of the decapeptide with Pro, which would tend to disrupt beta-strand conformation, led to a substantial loss of activity. Thus, NCAM-NCAM binding may also depend on the beta-backbone structure of this site. These results are consistent with the involvement of multiple amino acids within the decapeptide sequence in NCAM homophilic interaction.

Identification of a peptide sequence involved in homophilic binding in the neural cell adhesion molecule NCAM

The neural cell adhesion molecule NCAM is capable of mediating cell-cell adhesion via homophilic interactions. In this study, three strategies have been combined to identify regions of NCAM that participate directly in NCAM-NCAM binding: analysis of domain deletion mutations, mapping of epitopes of monoclonal antibodies, and use of synthetic peptides to inhibit NCAM activity. Studies on L cells transfected with NCAM mutant cDNAs using cell aggregation and NCAM-covasphere binding assays indicate that the third immunoglobulin-like domain is involved in homophilic binding. The epitopes of four monoclonal antibodies that have been previously shown to affect cell-cell adhesion mediated by NCAM were also mapped to domain 3. Overlapping hexapeptides were synthesized on plastic pins and assayed for binding with these monoclonal antibodies. One of them (PP) reacted specifically with the sequence KYSFNY. Synthetic oligopeptides containing the PP epitope were potent and specific inhibitors of NCAM binding activity. A substratum containing immobilized peptide conjugates also exhibited adhesiveness for neural retinal cells. Cell attachment was specifically inhibited by peptides that contained the PP-epitope and by anti-NCAM univalent antibodies. The shortest active peptide has the sequence KYSFNYDGSE, suggesting that this site is directly involved in NCAM homophilic interaction.