Phosphatidylinositol 3-Kinase-C2β Inhibits Cisplatin-Mediated Apoptosis via the Akt Pathway in Oesophageal Squamous Cell Carcinoma

A major problem in treating oesophageal squamous cell carcinoma (ESCC) with cisplatin is the development of drug resistance. In order to determine whether phosphatidylinositol 3-kinase (PI3K)-C2β (encoded by the PIK3C2B gene) reduced the sensitivity of ESCC to cisplatin, transfected Eca109 cells that overexpressed PIK3C2B were produced. Additionally, PI3K-C2β-siRNA was used to silence endogenous PI3K-C2β in EC9706 cisplatin-resistant cells. The relationship between PIK3C2B expression and clinicopathological characteristics was also investigated in samples from 61 patients. The overexpression of PIK3C2B in Eca109 cells significantly inhibited cisplatin-induced apoptosis and cleavage of caspase-3. Knockdown of PI3K-C2β enhanced cisplatin-induced apoptosis in EC9706 cells. PIK3C2B expression was associated with an increased level of phosphorylated Akt. Based on the tumour samples, expression of PIK3C2B was associated with tumour metastasis and in vitro assay suggested that it mediated cell migration. These results indicated that PI3K-C2β, via the Akt signalling pathway, might play a key role in cisplatin resistance and that targeting this pathway might be useful in treating cisplatin-resistant tumours.

No time to lose--high throughput screening to assess nanomaterial safety

Nanomaterials hold great promise for medical, technological and economical benefits. Knowledge concerning the toxicological properties of these novel materials is typically lacking. At the same time, it is becoming evident that some nanomaterials could have a toxic potential in humans and the environment. Animal based systems lack the needed capacity to cope with the abundance of novel nanomaterials being produced, and thus we have to employ in vitro methods with high throughput to manage the rush logistically and use high content readouts wherever needed in order to gain more depth of information. Towards this end, high throughput screening (HTS) and high content screening (HCS) approaches can be used to speed up the safety analysis on a scale that commensurate with the rate of expansion of new materials and new properties. The insights gained from HTS/HCS should aid in our understanding of the tenets of nanomaterial hazard at biological level as well as assist the development of safe-by-design approaches. This review aims to provide a comprehensive introduction to the HTS/HCS methodology employed for safety assessment of engineered nanomaterials (ENMs), including data analysis and prediction of potentially hazardous material properties. Given the current pace of nanomaterial development, HTS/HCS is a potentially effective means of keeping up with the rapid progress in this field--we have literally no time to lose.

A comparison of the cytogenetic alterations and global DNA hypomethylation induced by the benzene metabolite, hydroquinone, with those induced by melphalan and etoposide

Specific cytogenetic alterations and changes in DNA methylation are involved in leukemogenesis. Benzene, an established human leukemogen, is known to induce cytogenetic changes through its active metabolites including hydroquinone (HQ), but the specific alterations have not been fully characterized. Global DNA hypomethylation was reported in a population exposed to benzene, but has not been confirmed in vitro. In this study, we examined cytogenetic changes in chromosomes 5, 7, 8, 11 and 21, and global DNA methylation in human TK6 lymphoblastoid cells treated with HQ for 48 h, and compared the HQ-induced alterations with those induced by two well-known leukemogens, melphalan, an alkylating agent, and etoposide, a DNA topoisomerase II inhibitor. We found that rather than inducing cytogenetic alterations distinct from those induced by melphalan and etoposide, HQ induced alterations characteristic of each agent. HQ induced global DNA hypomethylation at a level intermediate to melphalan (no effect) and etoposide (potent effect). These results suggest that HQ may act similar to an alkylating agent and also similar to a DNA topoisomerase II inhibitor in living cells, both of which may be potential mechanisms of benzene toxicity. In addition to cytogenetic changes, global DNA hypomethylation may be another mechanism underlying the leukemogenicity of benzene.

The Role of Plasmalemmal-Cortical Anchoring on the Stability of Transmembrane Electropores

The structure of eukaryotic cells is maintained by a network of filamentous actin anchored subjacently to the plasma membrane. This structure is referred to as the actin cortex. We present a locally constrained surface tension model for electroporation in order to address the influence of plasmalemmal-cortical anchoring on electropore dynamics. This model predicts that stable electropores are possible under certain conditions. The existence of stable electropores has been suggested in several experimental studies. The electropore radius at which stability is achieved is a function of the characteristic radii of locally constrained regions about the plasma membrane. This model opens the possibility of using actin-modifying compounds to physically manipulate cortical density, thereby manipulating electroporation dynamics. It also underscores the need to improve electroporation models further by incorporating the influence of trans-electropore ionic and aqueous flow, cortical flexibility, transmembrane protein mobility, and active cellular wound healing mechanisms.

Quantification of electroporative uptake kinetics and electric field heterogeneity effects in cells

We have conducted experiments quantitatively investigating electroporative uptake kinetics of a fluorescent plasma membrane integrity indicator, propidium iodide (PI), in HL60 human leukemia cells resulting from exposure to 40 mus pulsed electric fields (PEFs). These experiments were possible through the use of calibrated, real-time fluorescence microscopy and the development of a microcuvette: a specialized device designed for exposing cell cultures to intense PEFs while carrying out real-time microscopy. A finite-element electrostatic simulation was carried out to assess the degree of electric field heterogeneity between the microcuvette's electrodes allowing us to correlate trends in electroporative response to electric field distribution. Analysis of experimental data identified two distinctive electroporative uptake signatures: one characterized by low-level, decelerating uptake beginning immediately after PEF exposure and the other by high-level, accelerating fluorescence that is manifested sometimes hundreds of seconds after PEF exposure. The qualitative nature of these fluorescence signatures was used to isolate the conditions required to induce exclusively transient electroporation and to discuss electropore stability and persistence. A range of electric field strengths resulting in transient electroporation was identified for HL60s under our experimental conditions existing between 1.6 and 2 kV/cm. Quantitative analysis was used to determine that HL60s experiencing transient electroporation internalized between 50 and 125 million nucleic acid-bound PI molecules per cell. Finally, we show that electric field heterogeneity may be used to elicit asymmetric electroporative PI uptake within cell cultures and within individual cells.

The costs and benefits of reforestation in Liping County, Guizhou Province, China

Reducing greenhouse gases in the atmosphere is becoming a pressing issue for the global community. Afforestation and reforestation are promoted worldwide as an effective means of sequestering carbon. For its national interest and global concerns, China has made great efforts to protect its existing forests and develop programs of afforestation and reforestation. Based on two surveys recently conducted in Liping County, Guizhou province, this paper investigates the economic changes associated with the implementation of the "Grain For Green" policy. Based on the analytical framework of benefit cost analysis, this paper concludes that the implementation of the reforestation of sloping agricultural land policy would not be possible if there were no government subsidies for the peasants. The short term economic returns of land and labour from forestation are substantially lower than those generated from grain or cash crop production on the steep slope lands. The government subsidies provide great economic incentives for peasants to take part in the project. The subsidies in fact have elevated peasant income in rural Liping. The estimated potential economic returns of plantations over the long run indicate that the removal of the government financial subsidies would not create an economic crisis for the peasants if the current market conditions continue.

Genetic polymorphisms involved in toxicant-metabolizing enzymes and the risk of chronic benzene poisoning in Chinese occupationally exposed populations

Benzene is a recognized haematotoxin and leukaemogen, but its mechanism of action and the role of genetic susceptibility are still unclear. Cytochrome P450 2E1 (CYP2E1) and myeloperoxidase (MPO) are involved in benzene activation; and NAD (P)H:quinine oxidoreductase 1 (NQO1), glutathione S-transferase theta 1 (GSTT1) and glutathione S-transferase mu 1 (GSTM1) participate in benzene detoxification. The common, well-studied single-nucleotide polymorphisms (SNPs) were analysed in these genes drawn from the toxicant-metabolizing pathways. A total of 100 workers with chronic benzene poisoning (CBP) and 90 controls were enrolled in China. There was a 2.82-fold (95% CI = 1.42-5.58) increased risk of CBP in the subjects with the NQO1 609C > T mutation genotype (T/T) compared with those carrying heterozygous (C/T) and wild-type (C/C). The subjects with the GSTT1 null genotype had a 1.91-fold (95% CI = 1.05-3.45) increased risk of CBP compared with those with GSTT1 non-null genotype. There was no association of CYP2E1 and MPO genotype with CBP. A three genes' interaction showed that there was a 20.41-fold (95% CI = 3.79-111.11) increased risk of CBP in subjects with the NQO1 609C > T T/T genotype and with the GSTT1 null genotype and the GSTM1 null genotype compared with those carrying the NQO1 609C > T C/T and C/C genotype, GSTT1 non-null genotype, and GSTM1 non-null genotype. The study provides evidence of an association of a gene-gene interaction with the risk of CBP.

Amplification of apoptosis through sequential caspase cleavage of the MET tyrosine kinase receptor

Activation of the MET tyrosine kinase receptor by hepatocyte growth factor/scatter factor is classically associated with cell survival. Nonetheless, stress stimuli can lead to a caspase-dependent cleavage of MET within its juxtamembrane region, which generate a proapoptotic 40 kDa fragment (p40 MET). We report here that p40 MET is in fact generated through an additional caspase cleavage of MET within its extreme C-terminal region, which removes only few amino acids. We evidenced a hierarchical organization of these cleavages, with the C-terminal cleavage favoring the juxtamembrane one. As a functional consequence, the removal of the last amino acids of p40 MET increases its apoptotic capacity. Finally, cells expressing a MET receptor mutated at the C-terminal caspase site are unable to generate p40 MET and are resistant to apoptosis, indicating that generation of p40 MET amplifies apoptosis. These results revealed a two-step caspase cleavage of MET resulting in the reshaping of this survival receptor to a proapoptotic factor.

Regulation of the Ets-1 transcription factor by sumoylation and ubiquitinylation

Sumoylation and ubiquitinylation reversibly regulate the activity of transcription factors through covalent attachment to lysine residues of target proteins. We examined whether the Ets-1 transcription factor is modified by sumoylation and/or ubiquitinylation. Among four potential SUMO motifs in Ets-1, we identified lysines 15 and 227 within the LK(15)YE and IK(227)QE motifs, as being the sumoylation acceptor sites. Using transfection of Ets-1 wildtype (WT) or its sumoylation deficient version (Ets-1 K15R/K227R), as well as WT or mutant proteins of the SUMO pathway, we further demonstrated that the E2 SUMO-conjugating enzyme Ubc9 and a E3 SUMO ligase, PIASy, can enhance Ets-1 sumoylation, while a SUMO protease, SENP1, can desumoylate Ets-1. We also found that Ets-1 is modified by K48-linked polyubiquitinylation independently of the sumoylation acceptor sites and is degraded through the 26S proteasome pathway, while sumoylation of Ets-1 does not affect its stability. Finally, sumoylation of Ets-1 leads to reduced transactivation and we demonstrated that previously identified critical lysine residues in Synergistic Control motifs are the sumoylation acceptor sites of Ets-1. These data show that Ets-1 can be modified by sumoylation and/or ubiquitinylation, with sumoylation repressing transcriptional activity of Ets-1 and having no clear antagonistic action on the ubiquitin-proteasome degradation pathway.

Training-induced and electrically induced potentiation in the neocortex

Long-term potentiation (LTP) shares many properties with memory and is currently the most popular laboratory model of memory. Although it has not been proven that memory is based on an LTP-like mechanism, there is evidence that learning a motor skill can induce LTP-like effects. This evidence was obtained in a slice-preparation experiment, which precluded within-animal comparisons before and after training. In the present experiments, Long-Evans rats were unilaterally trained to acquire a forelimb reaching and grasping skill. Evoked potentials were found to be larger in motor cortex layer II/III in the trained, compared to the untrained, hemisphere in slice, acute, and chronic preparations. Consistent with previous research, the trained hemisphere was less amenable to subsequent LTP induction. Furthermore, the application of either LTP- or LTD-inducing stimulation during the training phase of the reaching task disrupted the acquisition of the skill, providing further evidence that memory may be based on an LTP mechanism.

Sensitivity and linearity of superconducting radio-frequency single-electron transistors: effects of quantum charge fluctuations

We have investigated the effects of quantum fluctuations of quasiparticles on the operation of superconducting radio-frequency single-electron transistors (rf-SETs) for large values of the quasiparticle cotunneling parameter alpha = 8EJ/Ec, where EJ and Ec are the Josephson and charging energies. We find that, for alpha > 1, subgap rf-SET operation is still feasible despite quantum fluctuations that wash out quasiparticle tunneling thresholds. Surprisingly, such rf-SETs show linearity and signal-to-noise ratio superior to those obtained when quantum fluctuations are weak, while still demonstrating excellent charge sensitivity.

[Diagnosis and treatment of congenital biliary duct cyst: twenty-year experience]

OBJECTIVE

To summarize the experience in diagnosis and treatment of congenital biliary duct cyst.

METHODS

Clinical data from 108 patients treated from 1980 to 2000 were analyzed retrospectively.

RESULTS

Abdominal pain, jaundice and abdominal mass were presented in most pediatric patients. Clinical symptoms in adult patients were non-specific, resulting in delayed diagnosis frequently. Fifty-seven patients (52.7%) had coexistent pancreatic biliary disease. Carcinoma of the biliary duct occurred in 18 patients (16.6%). Ultrasonic examination was performed in 94 patients, ERCP in 46, and CT in 71. All of the patients were correctly diagnosed before operation. Abnormal pancreatobiliary duct junction was found in 39 patients. Before 1985, the diagnosis and classification of congenital biliary duct cyst were established by ultrasonography preoperatively and confirmed during operation. The main procedure was internal drainage by cyst-enterostomy. After 1985, the diagnosis was decided with ERCP and CT, the procedure was cyst excision with Roux-en-Y hepaticojejunostomy. In 1994, we used a new and simplified operative procedure to reduce the risk of malignancy of choledochal cyst. Retrograde infection of the biliary tract the major postoperative complication, could be controlled by the administration of antibiotics.

CONCLUSIONS

The concept in diagnosis and treatment of congenital choledochal cyst has been changed greatly. CT and ERCP are of great help in the classification of the disease. Currently, cyst excision with Roux-en-Y hepaticojejunostomy is strongly recommended as the treatment of choice for patients with type I and IV cysts. Piggyback orthotopic liver transplantation is indicated for type V cysts (Caroli's disease) with frequently recurrent cholangitis, resulting in biliary cirrhosis.

[Mannose-binding lectin gene site mutations and the susceptibility of rheumatic heart disease]

OBJECTIVE

To investigate the relationship between mannose-binding lectin (MBL) gene exon 1 site mutations and chronic rheumatic heart disease (CRHD).

METHODS

Polymerase chain reaction (PCR) and restrictive fragment length Polymorphism (RFLP) were used to investigate the MBL exon 1 alleles in 36 patients with CRHD and 39 normal people.

RESULTS

No C and D alleles of MBL gene were found in both groups. Eleven patients had A/B alleles, 1 patient had B/B alleles, 15 normal people had A/B alleles but none of the 39 normal people had B/B alleles. Statistic analyses showed no significant difference between CRHD group and normal group. But when the age of heart-disease-symptom-onset (HDSO) of the CRHD group were considered, we found that the mean HDSO age of patients with B allele was 30 +/- 14 years and the mean HDSO age of patients with AA homozygous was 37 +/- 11 years. P < 0.05.

CONCLUSION

MBL gene mutations may not be a main factor of the pathogenesis of CRHD, but MBL deficiency may facilitate the development of CRHD in younger people and accelerate the progress of CRHD. This is consistent with the phenomenon that the most susceptible people of rheumatic heart disease are teenagers.

Regulation of MMP-9 production by human corneal epithelial cells

The matrix metalloproteinases, MMP-2 and MMP-9, are known to be critical extracellular-remodeling enzymes in wound healing and other diseases of the ocular surface. This study investigated the regulation of MMP-2 and MMP-9 in human corneal epithelial cells by growth factors and pro-inflammatory cytokines (IL-1beta and TNF-alpha) they are exposed to, and by doxycycline, a medication used to treat ocular surface disease. Primary human corneal epithelial cell cultures were treated with one of the following cytokines (IL-1alpha, IL-1beta, IL-6, IL-8, TNF-alpha) or growth factors (EGF, HGF, KGF, PDGF-BB, TGF-alpha, TGF-beta), with or without their corresponding inhibitors. The conditioned media were collected after 24 hr for gelatin zymography and MMP-9 activity assay. Total RNA was extracted from the cells treated for 6 hr and was subjected to RT-PCR and Northern hybridization. Between the two gelatinases, MMP-2 and MMP-9, detected by zymography, the 92 kDa MMP-9 in the conditioned medium was markedly up-regulated by the pro-inflammatory cytokines, IL-1beta and TNF-alpha. The MMP-9 protein and activity were dose-dependently stimulated by IL-1beta or TNF-alpha at 0.1, 1.0 and 10 ng ml(-1). This up-regulation was nearly abolished by neutralizing antibodies (IL-1beta and TNF-alpha) and by IL-1 receptor antagonist. Semi-quantitative RT-PCR and Northern hybridization disclosed that the MMP-9 transcript was also markedly up-regulated in a dose-dependent manner by IL-1beta and TNF-alpha. Doxycycline (10 microg ml(-1)) suppressed MMP-9 protein level and activity, but not its mRNA, that was stimulated by IL-1beta and TNF-alpha (1 ng ml(-1)). In contrast, the 72 kDa MMP-2 was not significantly modulated by any of these cytokines. In conclusion, production of MMP-9 is stimulated by the pro-inflammatory cytokines, IL-1beta and TNF-alpha. These factors may play a role in the pathogenesis of MMP-9 mediated corneal matrix degradation. The efficacy of doxycycline in treating ocular surface diseases may be related to its ability to suppress MMP-9 production in the corneal epithelium.

Suppression of interleukin 1alpha and interleukin 1beta in human limbal epithelial cells cultured on the amniotic membrane stromal matrix

AIMS

Amniotic membrane (AM) transplantation reduces inflammation in a variety of ocular surface disorders. The aim of this study was to determine if AM stroma suppresses the expression of the IL-1 gene family in cultured human corneal limbal epithelial cells.

METHODS

Human corneal limbal epithelial cells were cultured from limbocorneal explants of donor eyes on plastic or on the AM stroma. Transcript expression of IL-1alpha, IL-1beta, IL-1 receptor antagonist (RA), and GAPDH was compared with or without addition of lipopolysaccharide to their serum-free media for 24 hours using RNAse protection assay (RPA). Their protein production in the supernatant was analysed by ELISA.

RESULTS

Expression of IL-1alpha and IL-1beta transcripts and proteins was significantly reduced by cells cultured on the AM stromal matrix compared with plastic cultures whether lipopolysaccharide was added or not. Moreover, expression of IL-1 RA by cells cultured in the lipopolysaccharide-free medium was upregulated by AM stromal matrix. The ratio between IL-1 RA and IL-1alpha protein levels in AM cultures was higher than in plastic cultures.

CONCLUSIONS

AM stromal matrix markedly suppresses lipopolysaccharide induced upregulation of both IL-1alpha and IL-1beta. These data may explain in part the effect of AM transplantation in reducing ocular surface inflammation, underscoring the unique feature of the AM as a substrate for tissue engineering.

Five new insecticidal sesquiterpenoids from Celastrus angulatus

Five new sesquiterpene polyol esters were isolated from the root bark of Celastrus angulatus by bioassay-guided fractionation. Their structures were determined by spectral data interpretation as 1alpha,2alpha,6beta,8beta,13-pentaacetoxy-9beta-benzoyloxy-4beta-hydroxy-beta-dihydroagarofuran (1), 1alpha,2alpha,6beta-triacetoxy-8alpha-(beta-furancarbonyloxy)-9beta-benzoyloxy-13-isobutanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (2), 1alpha,2alpha,6beta-triacetoxy-8beta-isobutanoyloxy-9beta-(beta-furancarbonyloxy)-13-(alpha-methyl)butanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (3), 1alpha,2alpha,6beta-triacetoxy-8alpha,13-diisobutanoyloxy-9beta-benzoyloxy-4beta-hydroxy-beta-dihydroagarofuran (4), and 1alpha,2alpha,6beta-triacetoxy-8alpha-isobutanoyloxy-9beta-benzoyloxy-13-(alpha-methyl)butanoyloxy-4beta-hydroxy-beta-dihydroagarofuran (5). Compounds 1-5 exhibited insecticidal activity against the larval of Mythimna separata.

A new bonded porous polymer PLOT U column with increased polarity

The separation features of a new type of PLOT U column are presented through many applications. This type of PLOT U column is coated with a divinylbenzene-ethylene glycol dimethacrylate copolymer. It has an increased polarity when compared with a conventional PLOT Q type column. The stationary phase of the PLOT U column is truly bonded, thus providing column rinsability and low column bleed.

Doxycycline inhibition of interleukin-1 in the corneal epithelium

PURPOSE

To evaluate the effect of doxycycline on the regulation of interleukin (IL)-1 expression and activity in human cultured corneal epithelium.

METHODS

Human corneal limbal epithelium (HLE) was cultured from explants prepared from limbal rings of donor corneas. Primary cultured limbal epithelial cells were treated with either 10 microg/ml lipopolysaccharide (LPS), LPS with 10 microg/ml doxycycline, or LPS with 0.1 mg/ml methylprednisolone (MP) for 24 hours. The intracellular and supernatant protein amounts of IL-1alpha, the precursor and mature forms of IL-1beta, IL-1 receptor antagonist (IL-1 RA), and the intracellular level of IL-1beta-converting enzyme (ICE) were measured with enzyme-linked immunosorbent assays (ELISAs). Western blot analysis was performed to evaluate IL-1 RA protein. mRNA steady state amounts were determined by RNase protection assay (RPA) for IL-1alpha, IL-1beta, IL-1 RA, and ICE.

RESULTS

LPS increased the mRNA and protein amounts of intracellular and released IL-1alpha, mature IL-1beta, and IL-1 RA. Doxycycline inhibited the LPS-induced IL-1beta increase in the mRNA and protein amounts in the corneal epithelium and upregulated the expression of the anti-inflammatory IL-1 RA protein. In addition, doxycycline reduced the steady state level of the cellular ICE protein but did not affect the level of ICE transcripts. IL-1beta secreted to the conditioned media of HLE was functionally active in inducing matrix metalloproteinase (MMP)-1 and MMP-3 in cultured corneal fibroblasts. Doxycycline significantly decreased IL-1beta bioactivity in the supernatants from LPS-treated corneal epithelial cultures. These effects were comparable to those induced by the corticosteroid, MP.

CONCLUSIONS

Doxycycline can suppress the steady state amounts of mRNA and protein of IL-beta and decrease the bioactivity of this major inflammatory cytokine. These data may partially explain the clinically observed anti-inflammatory properties of doxycycline. The observation that doxycycline was equally potent as a corticosteroid, combined with the relative absence of adverse effects, makes it a potent drug for a wide spectrum of ocular surface inflammatory diseases.

Interleukin-6 levels in the conjunctival epithelium of patients with dry eye disease treated with cyclosporine ophthalmic emulsion

PURPOSE

To evaluate interleukin-6 (IL-6) levels in the conjunctival epithelium of patients with moderate to severe dry eye disease before and after treatment with cyclosporin A ophthalmic emulsion (CsA) or its vehicle.

METHODS

Conjunctival cytology specimens were obtained from a subset of patients enrolled in a 6-month randomized, double-masked clinical trial of the efficacy and safety of topical CsA at baseline and after 3 and 6 months of B.I.D. treatment with 0.05% cyclosporine emulsion (n = 13), 0.1% cyclosporine emulsion (n = 8), or vehicle (n = 10). RNA was extracted and a competitive reverse transcriptase polymerase chain reaction (RT-PCR) was used to evaluate the levels of mRNA encoding the inflammatory cytokine IL-6 and a housekeeping gene, G3PDH. Levels of IL-6 and G3PDH were measured and compared.

RESULTS

There was no change from baseline in the level of G3PDH after 3 or 6 months in any group. IL-6 normalized for G3PDH (IL-6/G3PDH ratio) was not different from baseline at 3 months but showed a significant decrease from baseline in the group treated with 0.05% CsA (p = 0.048) at 6 months. No significant between-group differences were noted and no correlation was observed between the change in IL-6/G3PDH and corneal fluorescein staining.

CONCLUSIONS

This preliminary, small-cohort study showed a decrease in IL-6 in the conjunctival epithelium of moderate to severe dry eye patients treated with 0.05% CsA for 6 months. The observed decrease suggests that dry eye disease involves immune-mediated inflammatory processes that may be decreased by treatment with topical ophthalmic cyclosporine.

Inactivation of alpha7 ACh receptors and activation of non-alpha7 ACh receptors both contribute to long term potentiation induction in the hippocampal CA1 region

Acute and chronic nicotine exposure differentially facilitate the induction of long-term potentiation (LTP), a synaptic model of learning and memory, in the hippocampal CA1 region. The mechanisms underlying these effects of nicotine, however, are unknown. In the present study, both nicotinic acetylcholine receptor (nAChR) agonists and an alpha7 nAChR antagonist facilitated the induction LTP in the hippocampal CA1 region of naive rat. Furthermore, chronic nicotine treatment lowered the threshold for induction of LTP, and acute application of nicotinic agonists, but not an alpha7 antagonist, further facilitated LTP induction in the chronic-nicotine-treated hippocampus. These results suggest not only that both activation of non-alpha7 nAChRs and inactivation of alpha7 nAChRs contribute to LTP induction, but also that chronic-nicotine-mediated facilitation of LTP induction is due to chronic-nicotine-induced desensitization of alpha7 nAChRs.

[Purification and characterization of cuticle-degrading protease from entomopathogenic fungus, Metarhizium anisopliae]

The cuticle-degrading proteases from entomopathogensis fungus, Melarhizium anisopliae, were induced by adding cicada exuviae, colloidal chitin, shrimp cuticle, maggot cuticle, horsefly cuticle and silkworm chrysalis cuticle into minimal medium. After ultrafiltration, Ultrogel AcA 54 column and IEF, a protease designated as MAP-21 with Mr 27 kD, and pI 7.6 were purified. It was shown that the recognition site of MAP-21 was Arg, PMSF and TLCK could inhibited the activity of this protease, indicating that there were Ser and His residues in the active center. The inhibitors to trypsin, leupeptin antipain and STI also repressed the activity of MAP-21, while chymostatin, TPCK and elastatinal TEI were shown no inhibition to its activity, demonstrating that, MAP-21 was a trypsin-like protease. Other properties of MAP-21 were also reported.