Properties and Microstructure Study of Polyimide Foam Plastic

Five kinds of polyimide (PI) foams were prepared from dianhydride and diamine by esterification process. The microstructure of foam was characterized by SEM and visualization methods, and many properties of material were measured, including heat resistance, fire resistance, compressive strength, heat insulation and acoustic absorption. It was shown that the cell size of foam was from 1 to 1.5 mm. The cell edge of PIBM and PIBO foam was obscure, and the cell wall was thinner than the PIBD, PIOD and PIBO-DM foam with thicker cell edge and poor cell size homogeneity. Five types of PI foams presented the trait of flexible foam plastics. All of them possess high decompose temperature, and their limiting oxygen index surpassed 40 percent, and thermal diffusion coefficients were less than 0.030 W/m·°C. In addition, PIBO, PIOD, and PIBO-DM foam had excellent acoustic absorption.

The rag locus of Porphyromonas gingivalis might arise from Bacteroides via horizontal gene transfer

Porphyromonas gingivalis is regarded as one of the risk factors of periodontitis. P. gingivalis exhibits a wide variety of genotypes. Many insertion sequences (ISs), located in their chromosomes, made P. gingivalis differentiate into virulent and avirulent strains. In this research, we investigated the prevalence of P. gingivalis in the gingival crevicular fluid (GCF) among periodontitis patients from Zhenjiang, China, detected the P. gingivalis rag locus distributions by multiplex polymerase chain reaction (PCR), and analyzed the origin of the P. gingivalis rag locus based on evolution. There were three rag locus variants co-existing in Zhenjiang. The results showed that the rag locus may be associated with severe periodontitis. This work also firstly ascertained that the rag locus might arise, in theory, from Bacteroides sp. via horizontal gene transfer.

Visualization Study of Solid Poly (Ester-Amine Salt) Precursor Foaming Process

In this research, solid poly (ester-amine salt) precursor was used to prepare polyimide foams. The foaming process was observed by microscope, and effects of particle size on bubble growth were highlighted. The results showed that the powder particles with a size between 25 and 150 μm favor to grow into single bubble mesostructure, and the ones which grow into a multi-bubble mesostructure beyond this size. On the contrary, the bubble growth terminated when the particle size below 25 μm. Sieving was an effective method to narrow size distribution and uniform the particle size, which is of benefit to the formation of polyimide foams. After filtrated with 100 mesh sieve, the retreated particles were situated in optimal band to produce polyimide foams with single bubble mesostructure.

Conversion from cyclosporin A to sirolimus retards the progression of chronic allograft nephropathy in the long term in a rat kidney transplantation model

In a rat renal allograft model, the long-term effect of conversion from cyclosporin A (CsA) to sirolimus on recipient kidneys and growth factor expression were compared with continuous use or withdrawal of CsA. Kidneys from Fisher 344 rats were orthotopically transplanted into Lewis rats. Four Fisher 344 to Lewis allograft groups were treated post-transplant as follows: (i) CsA (transplant to week 8) then sirolimus (weeks 8 - 24); (ii) CsA (transplant to week 24); (iii) CsA (transplant to week 8) then vehicle (weeks 8 - 24); (iv) control vehicle (transplant to week 24). A fifth group underwent syngeneic isograft (Lewis to Lewis) with no drug treatment. Proteinuria was measured every 4 weeks and grafts harvested at 24 weeks for morphological and immunohistochemical analysis. Conversion from CsA to sirolimus resulted in a significant decrease in proteinuria at 24 weeks, a lower Banff sum score and lower expression of transforming growth factor mRNA compared with continuous use or withdrawal of CsA. In conclusion, conversion from CsA to sirolimus retarded progression of chronic allograft nephropathy in the rat model.

Behavioral alterations associated with a down regulation of HCN1 mRNA in hippocampal cornus ammon 1 region and neocortex after chronic incomplete global cerebral ischemia in rats

It has been suggested that hyperpolarization-activated cyclic-nucleotide-gated cation non-selective channel (HCN) 1 is primarily expressed in the hippocampus and can be regulated in many pathological settings. However, little is known about its change under ischemic conditions. In the present study, we performed neurophysiological recordings of sham-operated and chronic ischemic rats with hypoperfusion during the resolution of the neurological deficits respectively. In situ hybridization methods and reverse transcriptase-polymerase chain reaction (RT-PCR) assays were used to investigate whether and how HCN1 mRNA may be altered in global incomplete chronic cerebral ischemic rat model. Our results suggested that attenuated spatial learning and memory function of rats shown by longer escape latency, shorter time spent in the target quadrant and impaired long-term potentiation (LTP) after chronic cerebral ischemia. In the in situ hybridization cytochemistry experiment, HCN1 mRNA declined to 52.00% and 46.00% of the control values in the cornus ammon 1 (CA1) regions of hippocampus and neocortex separately after chronic cerebral ischemia. HCN1 mRNA in the hippocampal CA1 region and neocortex was markedly down regulated by ischemia, reaching 48.90% and 45.80% of the control values respectively in the semi-quantitative RT-PCR experiment. The phenomenon opened new insights for further investigation of the physiological and pathological significances of HCN1 in chronic incomplete global cerebral ischemia.

Clinicopathologic risk factors for distant metastases from head and neck squamous cell carcinomas

AIMS

The aim of this study is to investigate the clinicopathologic risk factors associated with distant metastases (DMs) from head and neck squamous cell carcinomas (HNSCCs).

METHODS

Between February 1990 and February 2000, a retrospective analysis of 391 HNSCC patients was performed. The frequency and the clinicopathologic risk factors for DM were evaluated by using univariate chi(2) tests and multiple stepwise logistic regression models. Statistical analysis of overall survival was performed by using Kaplan-Meier method.

RESULTS

44 patients (11.3%) developed DM in clinic. In a univariate analysis, clinical N stage, primary tumor site, level of tumor invasion, pathologic N stage and number of levels with pathologic lymph node were found to be significantly associated with the risk of DM. In a multivariate analysis, the most significant risk factors were number of levels with pathologic lymph node, level of tumor invasion, and primary tumor site. Kaplan-Meier analysis showed that overall survival rates of 44 patients with DMs in clinic were 56.8% at 1 year, 9.1% at 3 years, and 6.8% at 5 years, respectively.

CONCLUSIONS

The number of levels with pathologic lymph node, the site of primary tumor and the level of tumor invasion are decisive risk factors in determining the development of DM in head and neck SCC patients. Patients with multilevel nodal involvement in neck, with laryngeal and hypopharyngeal carcinomas, and patients with primary tumor invasion into muscular, bone or cartilage have the highest risk of developing DM.

Non-invasive bioluminescence imaging of caspase-3 activity in Breast Cancer

e14557

Background: Apoptosis is a major form of tumor cells death during cytotoxic therapy. Understanding the kinetics of apoptosis would greatly facilitate development of more effective therapeutic approaches. In order to monitor apoptosis activities in vivo, we developed a novel bioluminescence-based reporter gene to detect caspase 3 activities, which are elevated at the execution phase of apoptosis. Methods: A caspase-3 reporter system was constructed by combining two different reporter proteins; green fluorescent protein (GFP) and firefly luciferase (FL) linked through multiple polyubiquitin domains with a caspase-3 recognition site. Under normal circumstances, the reporter proteins are rapidly degraded by the proteasome system.. During apoptosis, activated caspse 3 cleaves off the multi-ubiquitin domain from the reporter protein. This enable the GFP and luciferase fusion reporter to be stabilized and achieve a significant gain in GFP protein and luciferase activities, which in turn could be monitored both in vitro and in vivo. 4T1 cells transduced with CMV-luc or Caspase-3 reporter xenografts were treated with both chemotherapy and radiation therapy and monitored for apoptosis activity. Results: In vitro experiments demonstrated increased luciferase with increasing radiation dose reflective of apoptosis with background levels nearly undetectable. Taxol was associated with a time-dependent increase from 24 to 72hrs after drug exposure, indicating that apoptosis is a gradual, heterogeneous process. EGFP signal increased from 1.85% in controls to 80.6% in cells treated with 1uM Taxol. Xenografts showed nearly undetectable luciferase background with Cytoxan therapy resulting in a 90-fold increase, 10 Gy a 24 fold increase and fractionated RT (5Gy x3) with a 46-fold increase. Conclusions: We developed a novel in vivo caspase reporter based on the ubiquitous proteosome system of protein degradation and bioluminsecence imaging. This allowed us to assess activation of apoptosis in response to chemoradiation therapy in tissue culture and breast cancer xenografts over the course of 2–3 weeks, which has not been possible with other technologies.

No significant financial relationships to disclose.

Experimental transmission of Theileria uilenbergi infective for small ruminants by Haemaphysalis longicornis and Haemaphysalis qinghaiensis

The experimental transmission of a recently designated Theileria uilenbergi pathogenic for sheep and goats in Northern China is described. Haemaphysalis qinghaiensis nymphs and adults developed from larvae and nymphs engorged on sheep infected with T. uilenbergi were able to respectively transmit the latter to sheep. However, when H. longicornis ticks picked up T. uilenbergi either at larval or nymphal, only the subsequent adult could transmit the parasites to sheep, the subsequent nymph could not transmit the parasites to sheep. This experiment suggested that the T. uilenbergi could be transmitted by at least two species of Haemaphysalis sp. ticks, H. longicornis and H. qinghaiensis, and the mode of transmission is stage to stage.

Spermatogonial stem cells: unlimited potential

Recent reports have demonstrated that adult cells can be reprogrammed to pluripotency, but mostly with genes delivered using retroviruses. Some of the genes are cancer causing; thus, these adult-derived embryonic stem (ES)-like cells cannot be used for therapy to cure human diseases. Remarkably, it has also been demonstrated recently by several groups that, in mice, spermatogonial stem cells (SSCs) can be reprogrammed to ES-like cells without the necessity of exogenously added genes. SSCs constitute one of the most important stem cell systems in the body, not only because they produce spermatozoa that transmit genetic information from generation to generation, but also because of the recent studies showing their remarkable plasticity. Very little is known about SSCs in humans, except for the earlier work of Clermont and colleagues who demonstrated that there are Adark and Apale spermatogonia, with the Adark referred to as the reserve stem cells and the Apale being the renewing stem cells. We now demonstrate that G protein-coupled receptor 125 (GPR125) may be a marker for human SSCs. Putative human SSCs can also be reprogrammed to pluripotency. We were able to achieve this result without the addition of genes, suggesting that human SSCs have considerable potential for cell-based, autologous organ regeneration therapy for various diseases.

Longitudinal spin density wave order in a quasi-1D Ising-like quantum antiferromagnet

From neutron diffraction measurements on a quasi-1D Ising-like Co2+ spin compound BaCo2V2O8, we observed an appearance of a novel type of incommensurate ordering in magnetic fields. This ordering is essentially different from the Néel-type ordering, which is expected for the classical system, and the peculiar spin structure is caused by quantum fluctuation inherent in the quantum spin chain. A Tomonaga-Luttinger liquid nature characteristic of the gapless quantum 1D system is responsible for the realization of the incommensurate ordering.