[Collision tumor in the hypopharynx: a case report].

SummaryA collision tumor consists of two different histologically distinct and topographically independent tumors merging in the same mass. In the head and neck area, they are rare and only a few cases have been reported in the hypopharynx. It is difficult to choose to treat this disease.

[DS2, a newly synthetic ent-kaurane diterpenoid analog, inhibits proliferation and migration of human gastric cancer cell].

Objective: To investigate the effects and the underlying mechanism of DS2, a newly synthetic analog of natural ent-kaurane diterpenoid, on the proliferation and migration capabilities of human gastric cancer cells. Methods: MTT assay, colony formation assay and flow cytometry were used to measure the effects of DS2 on growth, apoptosis and cell cycle of several human gastric cancer cell lines. The function of DS2 in the migration was further detected by wound healing and transwell assays. The expression of migration related proteins were determined by western blot. Results: DS2 inhibited the growth of MGC-803, SGC-7901 and HGC-27 cells in a dose dependent manner. After treatment of DS2 at a concentration of 6.25 µmol/L for 24 h, the survival rates of MGC-803, SGC-7901 and HGC-27 cells were 53.87±3.05%, 55.91±6.97% and 32.41±2.64%, respectively. However, for the normal gastric epithelial cell GES-1, no obvious growth inhibition was observed. In addition, DS2 caused significant G(2)/M arrest and induced apoptosis in MGC-803 cells. Furthermore, compared with the negative control, the colony formation, wound healing rate as well as the number of migrating cells of MGC-803 were significantly decreased in a dose dependent manner after DS2 treatment. DS2 induced the expression of E-cadherin, whereas ß-catenin and N-cadherin levels were downregulated in MGC-803. Conclusion: The new compound DS2 has a strong anti-cancer activity, and this study will help us to design and synthesize better diterpenoids derivatives.

[Current status of nurses' perceived professional benefits and influencing factors in 3A-level hospitals in Tianjin].

Objective: To investigate the current status of nurses' perceived professional benefits in 3A-level hospitals in Tianjin, and analyze its influencing factors. Methods: A total of 421 clinical nurses from five 3A-level hospitals in Tianjin were recruited for investigation on perceived professional benefits by Nurses'Perceived Professional Benefits Scale. Results: The total score of nurses' perceived professional benefit was 110.50±14.24, the score index was 77.34%. Among five dimensions, the highest scores index was 84.80% for personal development, the lowest was 71.57% for identification by relatives and friends. Multiple linear regression analysis showed the three variables, such as department, teaching and cooperative relation between doctors and nurses entered the model, higher perceived professional benefits was observed in medical nurses, teaching nurses, and those with better cooperative relation between doctors and nurses (P<0.05) . Conclusion: The investigated nurses in 3A-level hospitals in Tianjin show upper-moderate level of perceived professional benefits. Nursing managers should develop targeted interventions based on the factors affecting the perceived professional benefits of the nurses and further enhance their perceived professional benefits.

[Jaridonin, a new diterpenoid from Isodon rubescens, induces cell cycle arrest in gastric cancer cells through activating ataxia telangiectasia mutated kinase].

OBJECTIVE: To study the effects of Jaridonin, a novel diterpenoid from isodon rubescens, on the cell cycle of human gastric cancer cells and its molecular mechanism of action. METHODS: Flow cytometry was used to analyze the cell cycle distribution and expression of ataxia telangiectasia mutated kinase (ATM) after Jaridonin treatment. Western blot was performed to detect the expression of cell cycle-related proteins. RESULTS: The results of flow cytometry showed that the percentages of MGC-803 cells in G(2)/M phase at 6 hours after 0, 10, 20 µmol/L Jaridonin-treatment were (10.8±2.2)%, (18.2±2.5)%, (27.3±3.2)%, respectively; those at 12 hours after Jaridonin-treatment were (12.0±1.5)%, (24.1±2.0)% and (39.7±5.2)%, respectively, indicating a G2/M phase arrest of MGC-803 cells was resulted in a time- and dose-dependent manner. The expressions of ATM, Chk1, Chk2, phosphorylated Cdc2 and CDK2 were up-regulated in the MGC-803 cells after Jaridonin treatment, while the levels of Cdc2 and CDK2 were decreased. KU-55933, an inhibitor of ATM, reversed the expression of relevant proteins and G(2)/M phase arrest induced by Jaridonin. CONCLUSIONS: Jaridonin can significantly induce G(2)/M arrest in gastric cancer MGC-803 cells. Its mechanism may be related to the activation of ATM and Chk1/2, and inactivation of Cdc2 and CDK2 phosphorylation.

Inactivation and dissociation of rice ribulose-1,5-bisphosphate carboxylase/oxygenase during denaturation by sodium dodecyl sulfate.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a key enzyme in photosynthesis and photorespiration. The inactivation and subsequent conformational changes and dissociation of rice Rubisco by SDS have been studied. At low SDS concentrations (0.4 mM), Rubisco completely lost its carboxylase activity and most of its sulfhydryl groups became exposed. Dissociation of small subunits and significant conformational changes occurred at higher SDS concentrations. Increasing SDS concentrations caused only slight changes in CD spectrum, indicating no significant effect of SDS on the secondary structure of the enzyme. The results prove that the active site of Rubisco is more fragile to denaturants than the protein as a whole. The results also suggest that small subunits are more liable to SDS denaturation and thus dissociate first, while the more hydrophobic large subunits remain complexed. The naturally existing hydrophobic surface of Rubisco may be an important factor in the interaction of Rubisco with other macromolecules.

Properties and biocompatibility of chitosan films modified by blending with PEG.

Chitosan (beta-1,4-D-glucosamine), a polysaccharide with excellent biological properties, has been widely used in biomedical fields, but many barriers still exist to its broader usage due to its chemical and physical limitations. Further work is needed to improve these properties, but changes of the chemical and physical properties will influence its biocompatibility, so the biological attribute of modified chitosan must be evaluated. In this study, the biocompatibility of chitosan modified by several methods was carefully evaluated at the cellular and protein levels using different physical and biological methods. The results provide a theoretical basis for screening biomaterials. We studied the properties of five kinds of materials made by blending chitosan with different types of polyethylene glycol (PEG). The properties included physical and chemical properties, such as mechanical strength, static contact angle, spectroscopy, thermodynamic attributes and so on. The mechanical properties were slightly improved with the proper amount of PEG, but the improvement was not obvious and was destroyed by the wrong proportion of PEG. Cultures of the cells and amounts and structures of the adsorbed proteins on different materials showed that the PEG effectively improved the biocompatibility of the materials. The PEG enhanced the protein adsorption, cell adhesion, growth and proliferation, but the effects were impaired by excessive PEG. The experiments also demonstrated that the optimum PEG concentration helped to maintain the natural structure of the protein adsorbed on the materials and that maintaining the natural structure benefited cell growth. Analysis of the results based on the intramolecular and intermolecular interaction forces leads to a basic theory for the modification of biomaterials.

Strong-light photoinhibition treatment accelerates the changes of protein secondary structures in triton-treated photosystem I and photosystem II complexes.

Changes in the protein secondary structure and electron transport activity of the Triton X-100-treated photosystem I (PSI) and photosystem II (PSII) complexes after strong illumination treatment were studied using Fourier transform-infrared (FT-IR) spectroscopy and an oxygen electrode. Short periods of photoinhibitory treatment led to obvious decreases in the rates of PSI-mediated electron transport activity and PSII-mediated oxygen evolution in the native or Triton-treated PSI and PSII complexes. In the native PSI and PSII complexes, the protein secondary structures had little changes after the photoinhibitory treatment. However, in both Triton-treated PSI and PSII complexes, short photoinhibition times caused significant loss of alpha-helical content and increase of beta-sheet structure, similar to the conformational changes in samples of Triton-treated PSI and PSII complexes after long periods of dark incubation. Our results demonstrate that strong-light treatment to the Triton-treated PSI and PSII complexes accelerates destruction of the transmembrane structure of proteins in the two photosynthetic membranes.

Molecular cloning and expression of a phospholipid hydroperoxide glutathione peroxidase homolog in Oryza sativa.

A cDNA encoding putative phospholipid hydroperoxide glutathione peroxidase (PHGPX) was isolated from rice using rapid amplification of cDNA ends. This cDNA, designated ricPHGPX, includes an open reading frame encoding a protein of 169 amino acids which shares about 60% and 50% amino acid sequence identity with plant and mammalian PHGPXs, respectively. The gene is expressed at a relative high level in flag leaves and the expression can be markedly induced by oxidative stress, suggesting that the product of the gene plays a key role in defense against oxidative damage in rice.

[Pharmacokinetics of topically applied in-situ-forming gels of fluconazole in rabbit eyes].

AIM: To study the pharmcokinetics of fluconazole (FCZ) in the aqueous humors and tears of New Zealand white rabbits following topically applied in-situ-forming gels of 0.5% FCZ (ISG-FCZ) and 0.5% FCZ eye drops to rabbit eyes. METHODS: The rabbit tears and aqueous humors were obtained and quantified at different times after topically applying single dose of ISG-FCZ and FCZ eye drops to the rabbit eyes. The drug levels were assayed by megabore capillary gas-liquid chromatography with nitrogen-selective detector. The pharmacokinetic parameters were calculated with nonlinear least square method with computer. RESULTS: FCZ concentrations in rabbit tears within 180 min after applying ISG-FCZ were found to be significantly higher compared with those of FCZ eye drops. The FCZ levels in the aqueous at 10, 30, 60, 90 and 120 min after applying ISG-FCZ are significantly higher compared with FCZ eye drops. The time for arriving peak concentration (Tmax) and the area under concentration (AUC)-time curve as well as the half-life (T1/2) of FCZ in rabbit aqueous humors were markedly higher after application of ISG-FCZ. The peak levels in the aqueous humors showed no difference between the two groups. CONCLUSION: The ISG-FCZ, which upon exposure to physiological conditions will shift the gel phase, can significantly extend FCZ release and increase the precorneal residence time of the drug, thus enhance ocular bioavailability compared with FCZ eye drops.

A novel MT gene of rice plants is strongly expressed in the node portion of the stem.

We identified a cDNA encoding a metallothionein (MT)-like protein from a cDNA library of rice endosperm. This cDNA (ricMT) encoded an open reading frame of 80 amino acids, with two cysteine-rich domains at the amino-terminus and carboxy-terminus, respectively. The deduced amino acid sequence was homologous to those of class I MT-like proteins. Southern blot analysis revealed that the gene exists at one locus in the rice genome. Northern blot analysis with rice seedlings showed that the transcript level in shoots was elevated by the addition of metal ions, such as Cu, Zn, Cd, Fe, Pb and A1, whereas in roots it was reduced in the presence of metal ions other than copper. The expression level of ricMT in mature rice plants was extremely high in stems relative to leaf blades, leaf sheaths, endosperm and roots. In the first nodes, the yield of the transcript was 150-times higher than that in leaf blades. These results suggest that ricMT protein may play an important role in the metabolism of metal elements in the stem.

Effects of muscle electrical activity on the transmission of developing neuromuscular junction.

Miniature endplate potentials (MEPPS) caused by the spontaneous release of ACh from the growth cone of cholinergic neurons, are recorded by the whole-cell patch-clamp technique on a large number of 1-day cultured myoballs which have contact neurites of co-cultured neurons. Both muscle cell and neuron are dissociated from the 1-day-old (about stage 20) Xenopus embryo. Frequency and/or amplitude of MEPPs can obviously increase after the repetitive high-level depolarization caused by the stimuli on muscle cells. No detectable changes of single ACh receptor channel property are observed by using the single-channel recording technique. These results suggest that the mechanism of the increase of MEPPs after electrical activity of postsynaptic muscle cells probably involve some alteration of presynaptic membrane.

The effects of glutamate and GABA (gamma-amino-butyric-acid) on spontaneous acetylcholine release at the neuromuscular junction in Xenopus laevis embryo cell cultures.

The miniature endplate currents (MEPC's) were recorded at the neuromuscular junction of Xenopus laevis embryo neuron-muscle co-cultured cells. These MEPC's were due to the spontaneous release of acetylcholine from the nerve terminal. After perfusion with glutamate (10 mumol/L), both frequency and amplitude of the MEPC's increased. After washing away of glutamate, this effect persisted. We named this phenomena "Long-Term Facilitation". GABA (20 mumol/L) on the other hand had an inhibitory effect on both frequency and amplitude of the MEPC's. After washing away of GABA, the MEPC frequency and amplitude increased. We named this effect "Post-Potentiation". Local perfusion experiments furthermore indicated that the effect of glutamate was restricted to the neuromuscular junction, the effect of GABA was restricted to the soma.

Small-angle neutron scattering study of the structure of protein/detergent complexes.

Small-angle neutron scattering (SANS) was used to study the structure of protein/sodium dodecylsulfate complexes. Two water soluble proteins, bovine serum albumin (BSA) and ovalbumin (OVA), were used. The protein concentration was kept constant at 1 wt %, and protein/detergent wt ratio varied between 1/1, 1/1.5, 1/2 and 1/3. Absolute intensities of SANS distributions were analyzed by a fractal model. Analyses of large Q portions of SANS distributions established that sodium dodecylsulfate (SDS) molecules bound to a protein/SDS complex form micelle-like clusters. On the other hand, analyses of small Q portions of SANS distributions clearly showed that the arrangement of micelle-like clusters resembles a fractal packing of spheres. We showed that a protein/SDS complex can be characterized by four parameters extracted from the scattering experiment, namely, the average micelle size and its aggregation number, the fractal dimension characterizing the conformation of the micellar chains, the correlation length giving the extent of the unfolded polypeptide chains, and the numbers of micelle-like clusters in the complex.

Electrofusion of IBRS2 cells and the study of their fusion process.

IBRS2 epithelial cells in monolayer culture fused at a very high frequency when exposed to high-voltage electric pulsing fields. Exposure to four repetitive electric pulses of about 1.7 kilovolts per centimeter with a duration of 100 microseconds caused more than 90 percent of the cells to become fused (multinucleate) when 1 millimolar magnesium was present in the pulsing medium. Magnesium and calcium ions in the pulsing medium had a very strong effect on the electrofusion of IBRS2 cells. Magnesium could increase not only the electrofusion yield but also the stability of the cells under the conditions of electrofusion. In contrast, calcium inhibited electrofusion and decreased the stability of the cells. Careful microscopic observation revealed the electrofusion of IBRS2 cells to be very complex, dynamic process undergoing many interesting changes. A possible explanation for the process and mechanism of electrofusion of IBRS2 cells was proposed in agreement with the experimental observation.