Proton magnetic resonance studies of lipid bilayer membranes Experimental determination of inter- and intramolecular nuclear relaxation rates in sonicated phosphatidylcholine bilayer vesicles

We have determined the relative magnitudes of the intra- and intermolecular contributions to the nuclear magnetic relaxation rates of the methylene protons of the hydrocarbon chains in phosphatidylcholine bilayer vesicles over a range of temperatures and at two NMR frequencies (100 and 220 MHz). These measurements have been made by the isotopic dilution method using deuterated phosphatidylcholines containing fully deuterated hydrocarbon chains. The results showed that both the methylene linewidths and the spin-lattice relaxation rates are dominated by intramolecular dipolar interactions. Both the intra- and intermolecular contributions to the spin-lattice relaxation rate were found to decrease with increasing temperature and to exhibit a frequency dependence, the rates being higher at the lower NMR frequency in both cases. These observations indicate that both intra- and intermolecular dipolar interactions are modulated by anisotropic motions. In the case of the intermolecular dipolar fields, it is proposed that they are modulated both by the rapid rotational isomerization of the hydrocarbon chains as well as by lateral diffusion of the lipid molecules. That the hydrocarbon chain motion must be fairly effective in effecting efficient spin-lattice relaxation is evident from the negligible intramolecular interchain contribution to the relaxation found in the present work.     

Cloning and structure of the gene for the subunits of aspartokinase II from Bacillus subtilis

A library of Bacillus subtilis DNA in lambda Charon 4A (Ferrari, E., Henner, D.J., and Hoch, J.A. (1981) J. Bacteriol. 146, 430-432) was screened by an immunological procedure for DNA sequences encoding aspartokinase II of B. subtilis, an enzyme composed of two nonidentical subunits arranged in an alpha 2 beta 2 structure (Moir, D., and Paulus, H. (1977a) J. Biol. Chem. 252, 4648-4654). A recombinant bacteriophage was identified that harbored an 18-kilobase B. subtilis DNA fragment containing the coding sequences for both aspartokinase subunits. The coding sequence for aspartokinase II was subcloned into bacterial plasmids. In response to transformation with the recombinant plasmids, Escherichia coli produced two polypeptides immunologically related to B. subtilis aspartokinase II with molecular weights (43,000 and 17,000) indistinguishable from those found in enzyme produced in B. subtilis. Peptide mapping by partial proteolysis confirmed the identity of the polypeptides produced by the transformed E. coli cells with the B. subtilis aspartokinase II subunits. The size of the cloned B. subtilis DNA fragment could be reduced to 2.9 kilobases by cleavage with PstI restriction endonuclease without affecting its ability to direct the synthesis of complete aspartokinase II subunits, irrespective of its orientation in the plasmid vector. Further subdivision by cleavage with BamHI restriction endonuclease resulted in the production of truncated aspartokinase subunits, each shortened by the same extent. This suggested that a single DNA sequence encoded both aspartokinase subunits and provided an explanation for the earlier observation that the smaller beta subunit of aspartokinase II was highly homologous or identical with the carboxyl-terminal portion of the alpha subunit (Moir, D., and Paulus, H. (1977b) J. Biol. Chem. 252, 4655-4661). A map of the gene for B. subtilis aspartokinase II is proposed in which the coding sequence for the smaller beta subunit overlaps in the same reading frame the promoter-distal portion of the coding sequence for the alpha subunit.     

Diabetes,metformin use,and colorectal cancer survival in postmenopausal women

Background: Observational studies have associated metformin use with lower colorectal cancer (CRC) incidence but few studies have examined metformin's influence on CRC survival. We examined the relationships among metformin use, diabetes, and survival in postmenopausal women with CRC in the Women's Health Initiative (WHI) clinical trials and observational study. Methods: 2066 postmenopausal women with CRC were followed for a median of 4.1 years, with 589 deaths after CRC diagnosis from all causes and 414 deaths directly attributed to CRC. CRC-specific survival was compared among women with diabetes with metformin use (n = 84); women with diabetes with no metformin use (n = 128); and women without diabetes (n = 1854). Cox proportional hazard models were used to estimate associations among metformin use, diabetes and survival after CRC. Strategies to adjust for potential confounders included: multivariate adjustment with known predictors of colorectal cancer survival and construction of a propensity score for the likelihood of receiving metformin, with model stratification by propensity score quintile. Results: After adjusting for age and stage, CRC specific survival in women with diabetes with metformin use was not significantly different compared to that in women with diabetes with no metformin use (HR 0.75; 95% CI 0.40–1.38, p = 0.67) and to women without diabetes (HR 1.00; 95% CI 0.61–1.66, p = 0.99). Following propensity score adjustment, the HR for CRC-specific survival in women with diabetes with metformin use compared to non-users was 0.78 (95% CI 0.38–1.55, p = 0.47) and for overall survival was 0.86 (95% CI 0.49–1.52; p = 0.60). Conclusions: In postmenopausal women with CRC and DM, no statistically significant difference was seen in CRC specific survival in those who used metformin compared to non-users. Analyses in larger populations of colorectal cancer patients are warranted.     

Anti-Proliferative Effects of Evodiamine on Human Breast Cancer Cells

Endocrine sensitivity, assessed by the expression of estrogen receptor (ER), has long been the predict factor to guide therapeutic decisions. Tamoxifen has been the most successful hormonal treatment in endocrine-sensitive breast cancer. However, in estrogen-insensitive cancer tamoxifen showed less effectiveness than in estrogen-sensitive cancer. It is interesting to develop new drugs against both hormone-sensitive and insensitive tumor. In this present study we examined anticancer effects of evodiamine extracted from the Chinese herb, Evodiae fructus, in estrogen-dependent and –independent human breast cancer cells, MCF-7 and MDA-MB-231 cells, respectively. Evodiamine inhibited the proliferation of MCF-7 and MDA-MB-231 cells in a concentration-dependent manner with concentration of 1×10⁻⁶ and 1×10⁻⁵ M. Evodiamine also induced apoptosis via up-regulation of caspase 7 activation, PARP cleavage (Bik and Bax expression). The expression of ER α and β in protein and mRNA levels was down-regulated by evodiamine according to data from immunoblotting and RT-PCR analysis. Overall, our results indicate that evodiamine mediates degradation of ER and induces caspase-dependent pathway leading to inhibit proliferation of breast cancer cell lines. It suggests that evodiamine may in part mediate through ER-inhibitory pathway to inhibit breast cancer cell proliferation.     

Enhancing the Open‐Circuit Voltage of Perovskite Solar Cells by up to 120 mV Using π‐Extended Phosphoniumfluorene Electrolytes as Hole Blocking Layers

Four π‐extended phosphoniumfluorene electrolytes (π‐PFEs) are introduced as hole‐blocking layers (HBL) in inverted architecture planar perovskite solar cells with the structure of ITO/PEDOT:PSS/MAPbI₃/PCBM/HBL/Ag. The deep‐lying highest occupied molecular orbital energy level of the π‐PFEs effectively blocks holes, decreasing contact recombination. It is demonstrated that the incorporation of π‐PFEs introduces a dipole moment at the PCBM/Ag interface, resulting in significant enhancement of the built‐in potential of the device. This enhancement results in an increase in the open‐circuit voltage of the device by up to 120 mV, when compared to the commonly used bathocuproine HBL. The results are confirmed both experimentally and by numerical simulation. This work demonstrates that interfacial engineering of the transport layer/contact interface by small molecule electrolytes is a promising route to suppress nonradiative recombination in perovskite devices and compensates for a nonideal energetic alignment at the hole‐transport layer/perovskite interface.     

Complete inhibition of in vivo glioma growth by oncostatin M

We describe here the oncostatin M (OSM)-dependent inhibition of in vivo tumour formation after intracerebral inoculation of glioblastoma cells in mice. We generated human glioblastoma cells transfected with the OSM gene under the control of a tetracycline-response promoter. Upon removal of tetracycline from the medium, cells exhibited a differentiated cell morphology, while proliferation was significantly inhibited. After implantation of these cells into nude mice brains, large tumours developed in animals lacking OSM expression, whereas no tumour formation was observed in mice with induced OSM expression. Our results suggest that OSM exerts pronounced antitumorigenic effects on glioblastoma cells in vivo and provide arguments for a therapeutic application of OSM in humans.     

Effects of chronic hypogonadism on corticosterone secretion and cyclic AMP production in male rat adrenocortical cells

AIM: To determine the secretion of corticosterone (CCS) both in vivo and in vitro during different intervals after orchidectomy in male rats. METHODS: Three- and 12-month-old rats had been orchidectomized 0, 3, 6, or 9 months before decapitation. RESULTS: Orchidectomy increased the concentrations of plasma CCS, the basal release of CCS, and the adenosine 3', 5'-cyclic monophosphate (cAMP) production in rat zona fasciculata reticularis (ZFR) cells. The forskolin/3-isobutyl-l-methylxanthine-stimulated releases of CCS and cAMP production by ZFR cells were higher in rats with chronic hypogonadism. The CCS release from ZFR cells of orchidectomized rat was not altered by 8-bromo-cAMP treatment. Orchidectomy enhanced the stimulatory effect of deoxycorticosterone on CCS release in ZFR cells. CONCLUSION: These results suggest that orchidectomy-related increases of CCS secretion in rats are associated with an increase of adenylate cyclase activity, cAMP generation, and 11-beta-hydroxylase activity in ZFR cells.     

Arecoline excites the colonic smooth muscle motility via M3 receptor in rabbits

Arecoline is an effective component of areca (betel nuts, a Chinese medicine named pinang or binglang). The purpose of this study was to investigate the effect of arecoline on the motility of distal colon in rabbits and its mechanisms involved. Strips of colonic smooth muscle were suspended in organ baths containing Krebs solution, and their isometric contractions were examined. The response of smooth muscle to arecoline in colonic strips was recorded. The effects of atropine, gallamine and 1,1-dimethyl-4-diphenylacetoxypiperidiniumiodide (4-DAMP) on arecoline-induced contraction were also observed. Arecoline (1 nM - 1 microM) produced a concentration-dependent contraction in both the longitudinal and the circular smooth muscle of rabbit colon. Atropine (10 microM) abolished the arecoline (80 nM)--induced contraction. M3 receptor antagonist, 4 - DAMP (0.4 microM), abolished the arecoline (80 nM)--related response, whereas M2 receptor antagonist, gallamine (0.4 microM), did not affect the effect of arecoline. These results suggest that arecoline excites the colonic motility via M3 receptor in rabbits.     

A review of high-resolution X-ray computed tomography and other imaging modalities for small animal research

Dedicated high-resolution small animal systems have recently emerged as important new tools for laboratory animal research. These imaging systems permit researchers to noninvasively screen animal models for mutations or pathologies and to monitor disease progression and response to therapy. The authors survey various small animal imaging modalities, including MRI, PET, SPECT, and microCT, and discuss several representative microCT mouse imaging studies.     

Analysis of Euglena gracilis alpha-, beta- and gamma-tubulin genes: introns and pre-mRNA maturation

We have cloned and analyzed alpha-, beta- and gamma-tubulin genes from Euglena gracilis. The gamma-tubulin genes are 6-10 times longer than the alpha- and beta-tubulin genes, owing to the presence of numerous introns. These introns are all of the conventional type, whereas the alpha- and beta-tubulin genes contain both conventional and non-conventional introns. This is the first time that both types of introns have been found in the same gene. In the E. gracilis genome there are two genes for each tubulin, but the level of gamma-tubulin mRNA is 60 times lower than that of alpha- and beta-tubulin RNAs. The distinctive structure of gamma-tubulin genes prompted us to investigate the maturation of its pre-mRNA. We show that trans-splicing occurs before the cis-splicing of the first intron of the pre-mRNA and that polyadenylation occurs after the cis-splicing of the last intron of the pre-mRNA. We propose that mRNA processing is likely to play a role in regulating the amounts of different tubulins in E. gracilis.