[Effect of transfected Cx43 gene on the gap junction intercellular communication and the human glioma cells proliferation]

OBJECTIVE

To investigate the role of connexin 43 (Cx43) gene in the gap junction intercellular communication (GJIC) and the development of glioma so as to demonstrate the feasibility of using Cx43cDNA as the target of gene therapy for gliomas.

METHODS

TJ905 human glioblastoma cell line without Cx43 gene expression was transfected with Cx43cDNA mediated by lipofectamine. Northern blot, in situ hybridization and immunocytochemistry were used for examination of Cx43mRNA and its protein examination; MTT assay and silver colloid stain were used to detect cell proliferation. TUNEL method was used to determine the cell apoptosis. Scrape loading dye transfer (SLDT) was used to monitor GJIC.

RESULTS

The TJ905 transfectants resulted in dramatic upregulation of Cx43mRNA and its protein, with the GJIC of transfected glioma cells restored. Clones with high Cx43 expression also showed reduced proliferation in vitro. However, the cell apoptosis did not increase following the transfection with Cx43 gene.

CONCLUSION

These results indicate that Cx gene and gap junction intercellular communication are of crucial importance in malignant glioma cell growth and development. Cx43 gene may be a target for gene therapy of gliomas.

Alpha 1-antitrypsin and alpha 1-acid glycoprotein reduce the sensitivity of human dermal fibroblast to endotoxin

OBJECTIVE

To test the hypothesis that acute phase reactants, such as alpha 1-antitrypsin and alpha 1-acid glycoprotein, could protect mammalian cells from further damage.

METHODS

Human dermal fibroblasts (5 x 10(4)) were cultured with DMEM plus 10% FBS at 37 degrees C in a 5% CO(2) incubator. Different doses of LPS (lipo polysaccharide) and/or acute phase reactants were added. After 24 hours, the cultured supernatant was aspirated, the cells were washed, fixed and stained by methylene blue. The unbound stain was washed off. The stained cells were solubilize d in 0.1 ml of 1% Triton X-100. The absorbance of each well was measured us ing an ELISA spectrophotometer. The concentration of LPS which decreased the absorbance to 70% of the control (LPS-free) cultures was defined as LD(30).

RESULTS

In order to achieve LD(30) in the presence of acute phase proteins, it was necessary to alter the LPS concentrations. The LD(3 0) of LPS treated with 0, 0.5, 2, 10 mg/ml antitrypsin and 0, 0.5, 2, 10 mg/ml glycoprotein was 5.4, 6.5, 7.6, 14.2 mg/ml and 5.2, 5.9, 6.9, 10.5 mg/ml, respectively. Statistically, with the treatment of more than 2 mg/ml antitrypsin or glycoprotein, LD(30) increased significantly.

CONCLUSIONS

Our data show that fibroblasts are susceptible to the direct toxicity of LPS. Alpha 1-antitrypsin and alpha 1-acid glycoprotein can reduce the toxicity and/or increase the tolerance of mammalian cells to LP S.

[Screening of aberrant genes of immunocytes in severely scalded rats by inhibition of subtractive hybridization]

OBJECTIVE

To explore the relationship between the postburn changes of gene expression of immunocytes and postburn immunological functional disturbance in severely scalded rats.

METHODS

Immunocytes of female F344 rats with severe scalding were harvested and the mRNA was extracted for the inhibition of the expression of aberrant gene selected by subtractive hybridization in contrast to that before scalding. The aberrant genes were cloned and sequenced and compared to those in Genebank for homology.

RESULTS

The harvested immunocytes were identified by LM to be monocytes and lymphocytes. Multiple strips located at 200 approximately 400 bp were obtained by inhibiting subtractive hybridization and were cloned into PGEM-T easy plasmid vector. Thus the genebank of aberrant expression was constructed. Twenty clones were sequenced randomly and partial obtained known genes were in accord with postburn systemic changes. Several novel genes were accepted and registered by Genebank.

CONCLUSION

There exhibited change in the gene expression of peripheral immunocytes at early postburn stage in rats inflicted by severe burn.

Reliable and global measurement of fluorescence resonance energy transfer using fluorescence microscopes

Green fluorescence protein (GFP)-based fluorescence resonance energy transfer (FRET) is increasingly used in investigation of inter- and intramolecular interactions in living cells. In this report, we present a modified method for FRET quantification in cultured cells using conventional fluorescence microscopy. To reliably measure FRET, three positive control constructs in which a cyan fluorescence protein and a yellow fluorescence protein were linked by peptides of 15, 24, or 37 amino acid residues were prepared. FRET was detected using a spectrofluorometer, a laser scanning confocal microscope, and an inverted fluorescence microscope. Three calculation methods for FRET quantification using fluorescence microscopes were compared. By normalization against expression levels of GFP fusion proteins, the modified method gave consistent FRET values that could be compared among different cells with varying protein expression levels. Whole-cell global analysis using this method allowed FRET measurement with high spatial resolutions. Using such a procedure, the interaction of synaptic proteins syntaxin and the synaptosomal associated protein of 25 kDa (SNAP-25) was examined in PC12 cells, which showed strong FRET on plasma membranes. These results demonstrate the effectiveness of the modified method for FRET measurement in live cell systems.

New spirostanol saponins from Chinese chives (Allium tuberosum)

Three new spirostanol saponins have been isolated from the seeds of Allium tuberosum. On the basis of acid hydrolysis and comprehensive spectroscopic analysis, their structures were established as tuberoside J, (25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside; tuberoside K, (25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside; and tuberoside L, 27-O-beta-D-glucopyranosyl-(25R)-5alpha-spirostan-2alpha,3beta,27-triol 3-O-alpha-D-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside.

Blocking protein geranylgeranylation is essential for lovastatin-induced apoptosis of human acute myeloid leukemia cells

Lovastatin is an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the major regulatory enzyme of the mevalonate pathway. We have previously reported that lovastatin induces a significant apoptotic response in human acute myeloid leukemia (AML) cells. To identify the critical biochemical mechanism(s) essential for lovastatin-induced apoptosis, add-back experiments were conducted to determine which downstream product(s) of the mevalonate pathway could suppress this apoptotic response. Apoptosis induced by lovastatin was abrogated by mevalonate (MVA) and geranylgeranyl pyrophosphate (GGPP), and was partially inhibited by farnesyl pyrophosphate (FPP). Other products of the mevalonate pathway including cholesterol, squalene, lanosterol, desmosterol, dolichol, dolichol phosphate, ubiquinone, and isopentenyladenine did not affect lovastatin-induced apoptosis in AML cells. Our results suggest that inhibiting geranylgeranylation of target proteins is the predominant mechanism of lovastatin-induced apoptosis in AML cells. In support of this hypothesis, the geranylgeranyl transferase inhibitor (GGTI-298) mimicked the effect of lovastatin, whereas the farnesyl transferase inhibitor (FTI-277) was much less effective at triggering apoptosis in AML cells. Inhibition of geranylgeranylation was monitored and associated with the apoptotic response induced by lovastatin and GGTI-298 in the AML cells. We conclude that blockage of the mevalonate pathway, particularly inhibition of protein geranylgeranylation holds a critical role in the mechanism of lovastatin-induced apoptosis in AML cells.

Molecular and biochemical analysis of two beta-galactosidases from Bifidobacterium infantis HL96

Two genes encoding beta-galactosidase isoenzymes, beta-galI and beta-galIII, from Bifidobacterium infantis HL96 were revealed on 3.6- and 2.4-kb DNA fragments, respectively, by nucleotide sequence analysis of the two fragments. beta-galI (3,069 bp) encodes a 1,022-amino-acid (aa) polypeptide with a predicted molecular mass of 113 kDa. A putative ribosome binding site and a promoter sequence were recognized at the 5' flanking region of beta-galI. Further upstream a partial sequence of an open reading frame revealed a putative lactose permease gene transcribing divergently from beta-galI. The beta-galIII gene (2,076 bp) encodes a 691-aa polypeptide with a calculated molecular mass of 76 kDa. A rho-independent transcription terminator-like sequence was found 25 bp downstream of the termination codon. The amino acid sequences of beta-GalI and beta-GalIII are homologous to those found in the LacZ and the LacG families, respectively. The acid-base, nucleophilic, and substrate recognition sites conserved in the LacZ family were found in beta-GalI, and a possible acid-base site proposed for the LacG family was located in beta-GalIII, which featured a glutamate at residue 160. The coding regions of the beta-galI and beta-galIII genes were each cloned downstream of a T7 promoter for overexpression in Escherichia coli. The molecular masses of the overexpressed proteins, as estimated by polyacrylamide gel electrophoresis on sodium dodecyl sulfate-polyacrylamide gels, agree with their predicted molecular weights. beta-GalI and beta-GalIII were specific for beta-D-anomer-linked galactoside substrates. Both are more active in response to ONPG (o-nitrophenyl-beta-D-galactopyranoside) than in response to lactose, particularly beta-GalIII. The galacto-oligosaccharide yield in the reaction catalyzed by beta-GalI at 37 degrees C in 20% (wt/vol) lactose solution was 130 mg/ml, which is more than six times higher than the maximum yield obtained with beta-GalIII. The structure of the major trisaccharide produced by beta-GalI catalysis was characterized as O-beta-D-galactopyranosyl-(1-3)-O-beta-D-galactopyranosyl-(1-4)-D-glucopyranose (3'-galactosyl-lactose).

[Application of CT virtual bronchoscope in foreign-body in children's bronchus]

OBJECTIVE

To evaluate the clinical application of CT virtual bronchoscope in foreign-body in bonchus.

METHOD

The CT virtual bronchoscope were used in 21 cases with foreign-body in bronchus, all the images and reports were compared with the actual bronchoscopy.

RESULT

The reports and images of CT virtual bronchoscope are very agreed with that of actual bronchoscopy.

CONCLUSION

CT virtual bronchoscope is a very good complemental method in preoperative diagnosis of foreign-body in bronchus.

Quantitative (13)C NMR analysis of lignins with internal standards

Novel protocols for acquiring quantitative (13)C NMR spectra of lignins have been developed using the internal reference compounds 1,3,5-trioxane and pentafluorobenzene. Trioxane offers a convenient internal standard for collecting inverse gated proton decoupled (13)C NMR spectra for lignins, whereas pentafluorobenzene can be used to provide information on the amount of methine carbon using the DEPT experiment. In each case, the internal reference compounds provide single, un-overlapped sharp signals in the middle of the spectral region, permitting facile integration. These integrals could be used to determine the amounts of different structural features of lignins, expressed in absolute units of millimoles per gram. The optimum parameters for these experiments were validated for a variety of spectrometer platforms, and standard errors were determined for different spectral areas using lignin model compounds and "standard" lignins. In addition, the data derived for the International Round Robin "standard" lignins showed good agreement with the data from quantitative (31)P NMR spectroscopy and published data, obtained by independent laboratories using independent methods of analysis.

[Bioactivity and test grafting of acellular dermal matrix containing fibroblasts]

OBJECTIVE

To investigate the bioactivity of acellular dermal matrix with fibroblasts and its role as dermal skeleton.

METHODS

Human fibroblasts (HFs) were planted onto the surface of acellular dermal matrix (ADM) to form living dermal substitute. The IL -- 6, IL -- 8 and TGF contents in the supernatant of the culture of HF -- ADM were determined with ELISA method, and the secretion of hyaluronic acid and laminin from extracellular matrix was measured with RIA method. The speed of vascularization and the wound contracture rate were observed after the dermal substitute was grafted on the full skin loss wound of Balb/c-nu mice (nude mice).

RESULTS

HFs grew very well after being planted onto ADM so as to form a single layer of cellular membrane. Many kinds of cytokines and extra cellular matrix components were secreted. Compared with simple acellular dermal grafting, the vascularization was accelerated, and the wound contracture rate decreased, after the living dermal substitute being grafted on the wound.

CONCLUSION

The ADM seeded with HFs exhibited excellent bioactivity and might be an optimal dermal substitute.

Metabolic disorder in myocardiac intracellular free calcium after thermal injury

Cutaneous burn trauma causes functional inhibition of the heart, but the mechanism is unclear. Using a high dissociation constant (K(D)) calcium indicator TF-BAPTA and 19F MR spectroscopy, the relationship between the changes of cytosolic free calcium and cardiac function after burn trauma was examined. Sprague-Dawley rats received scald (43% TBSA) or sham burns. Twenty-four hours later, the hearts were excised and perfused by the Langendorff method with a modified phosphate-free Krebs-Henseleit bicarbonate buffer. Left ventricular developed pressure (LVDP) was recorded through a catheter attached to an intraventricular balloon. At the same time, 31P and 19F nuclear magnetic resonance (NMR) spectroscopy was perforined before and after TF-BAPTA loading. LVDP of the heart from burned rats was 40% less than in sham burn rats (65+/-6 vs 110+/-12 mmHg, P<0.01). Cytosolic free calcium increased about four-fold in those hearts from the burn group compared to the sham burn group (0.807+/-0.192 vs 3.891+/-0.929 microM). Loading TF-BAPTA in those hearts only caused about a 15-20% decrease in LVDP. PCr/Pi ratio also decreased significantly with this loading, but ATP signals were not affected. In conclusion, the inhibition of cardiac contractility caused by burn trauma correlated with the overload of cytosolic free calcium in the heart.

Arsenic induces apoptosis in rat cerebellar neurons via activation of JNK3 and p38 MAP kinases

Primary cultures of rat cerebellar neurons were used to study mechanisms of arsenic neurotoxicity. Exposure to 5, 10, or 15 microM sodium arsenite reduced cerebellar neuron viability and induced nuclear fragmentation and condensation as well as DNA degradation to oligonucleosome fragments. Exposure to 1 or 5 mM dimethylarsinic acid caused similar changes. Therefore, both inorganic arsenite and organic dimethylarsinic acid induce apoptosis in cerebellar neurons, with the inorganic form being more toxic. Cotreatment with cycloheximide or actinomycin D, inhibitors of protein or RNA synthesis, respectively, or with the caspase inhibitor zVAD, completely blocked arsenite-induced cerebellar neuron apoptosis. This implies that arsenite-induced cerebellar neuron apoptosis requires new gene expression and caspase activation. Interestingly, sodium arsenite selectively activated p38 and JNK3, but not JNK1 or JNK2 in cerebellar neurons. Blocking the p38 or JNK signaling pathways using the inhibitors SB203580 or CEP-1347 protected cerebellar neurons against arsenite-induced apoptosis. These data suggest that arsenite neurotoxicity may be due to apoptosis caused by activation of p38 and JNK3 MAP kinases.

Cerivastatin triggers tumor-specific apoptosis with higher efficacy than lovastatin

The statin family of drugs inhibits 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, the rate-limiting enzyme of the mevalonate pathway, and is used clinically as a safe and effective approach in the control of hypercholesterolemia. We have shown previously (Dimitroulakos, J., Nohynek, D., Backway, K. L., Hedley, D. W., Yeger, H., Freedman, M. H., Minden, M D., and Penn, L. Z. Increased sensitivity of acute myelogenous leukemias to lovastatin-induced apoptosis: a potential therapeutic approach. Blood, 93: 1308-1318, 1999) that lovastatin, a prototypic member of the statin family, can induce apoptosis of human acute myeloid leukemia (AML) cells in a sensitive and specific manner. In the present study, we evaluated the relative potency and mechanism of action of the newer synthetic statins, fluvastatin, atorvastatin, and cerivastatin, to trigger tumor-specific apoptosis. Cerivastatin is at least 10 times more potent than the other statins at inducing apoptosis in AML cell lines. Cerivastatin-induced apoptosis is reversible with the addition of the immediate product of the HMG-CoA reductase reaction, mevalonate, or with a distal product of the pathway, geranylgeranyl pyrophosphate. This suggests protein geranylgeranylation is an essential downstream component of the mevalonate pathway for cerivastatin similar to lovastatin-induced apoptosis. The enhanced potency of cerivastatin expands the number of AML patient samples as well as the types of malignancies, which respond to statin-induced apoptosis with acute sensitivity. Cells derived from acute lymphocytic leukemia are only weakly sensitive to lovastatin cytotoxicity but show robust response to cerivastatin. Importantly, cerivastatin is not cytotoxic to nontransformed human bone marrow progenitors. These results strongly support the further testing of cerivastatin as a novel anticancer therapeutic alone and in combination with other agents in vivo.

[The effects of ZMS on learning and memory ability and brain choline acetyltransferase in scopolamine-induced mouse model]

OBJECTIVE

To observe the effects of ZMS on learning and memory ability and on brain choline acetyltransferase activity.

METHODS

A single intraperitoneal injection of scopolamine was used to establish a dementia mouse model. The learning and memory ability was detected by step-through and sted-down tests. And the choline acetyltransferase activity in brain was determined by 3H-acetyl-CoA incorporation analysis.

RESULTS

ZMS could significantly reduce wrongness frequences, prolong incubation period of scopolamine-induced dementia mice in step-through and step-down tests (P < 0.01). ZMS could also significantly improve the activity of brain choline acetyltransferase (ChAT) (P < 0.01).

CONCLUSION

ZMS could improve the learning and memory ability and the activity of brain ChAT in scopolamine-induced dementia mice. However, ZMS had no significant dose-response effect on improving the activity of brain ChAT, and the effect of Tacrine was similar to that of ZMS, it seemed unlikely that ZMS had a direct action on the ChAT. More probably, ZMS exerted its effect on ChAT activity and on learning and memory ability via elevating brain M receptor density.

Taxol induces apoptosis in cortical neurons by a mechanism independent of Bcl-2 phosphorylation

Bcl-2, an antiapoptotic protein, protects cells against many but not all forms of apoptosis. For example, Bcl-2 does not protect non-neuronal cells against taxol, a microtubule-stabilizing agent. The underlying mechanism for the ineffectiveness of Bcl-2 against taxol has been the subject of intense interest. Data from non-neuronal cells indicate that taxol-induced apoptosis requires activation of N-terminal c-Jun protein kinase (JNK) that phosphorylates and inactivates Bcl-2. This suggests the interesting possibility that the apoptotic activity of JNK may be caused by phosphorylation of Bcl-2 and inhibition of the antiapoptotic activity of Bcl-2. Here we report that taxol induces apoptosis in cortical neurons but by a mechanism significantly different from that in non-neuronal cells. In contrast to human embryonic kidney 293 cells, expression of wild-type Bcl-2 in cortical neurons protected against taxol-induced apoptosis, and taxol did not induce Bcl-2 phosphorylation. Furthermore, cortical neurons express high basal JNK activity, and taxol did not stimulate total JNK activity. However, taxol activated a subpool of JNK in the nucleus and stimulated c-Jun phosphorylation. JNK inhibition or expression of a dominant-negative c-Jun abrogated taxol-induced apoptosis in cortical neurons, suggesting a role for JNK and JNK-mediated transcription in taxol-stimulated apoptosis. Furthermore, taxol-induced apoptosis in cortical neurons required inhibition of phosphatidylinositol 3-kinase signaling. These data suggest that taxol induces apoptosis in neurons by a mechanism quite distinct from that of non-neuronal cell lines and emphasize the importance of elucidating apoptotic mechanisms specific for neurons in the CNS.

DNA elements of the type 1 adenylyl cyclase gene locus enhance reporter gene expression in neurons and pinealocytes

The Ca2+-stimulated type 1 adenylyl cyclase (AC1) contributes to several forms of synaptic plasticity and is the only known neurospecific adenylyl cyclase. Furthermore, the protein and mRNA levels of AC1 undergo a circadian oscillation in the pineal gland, and AC1 may play a pivotal role in regulating nocturnal melatonin synthesis. To better understand the expression of AC1, we isolated mouse genomic DNA clones of AC1. The transcription and translation start regions of mouse AC1 share extensive homologies with the bovine counterpart. The upstream proximal region has potential binding sites for transcription factors, including the steroid receptor family, the E-box factors, and Sp1. A 280-bp fragment that contains the transcription start site directed reporter gene expression in cultured cortical neurons and pinealocytes functioning as a basal neuro- and pineal-directed promoter. Interestingly, pinealocyte expression of the reporter gene was inhibited by increases in cAMP. This cAMP sensitivity may explain why AC1 mRNA in the pineal is low at night when cAMP is elevated and high during the day when cAMP signals drop. An adjacent 330-bp fragment interacted specifically with nuclear factor(s) that we designate binary E-box factor (BEF). Methylation interference and DNase I footprinting identified the BEF-binding site sequence as 5'-CCAAGGTCACGTGGC-3'. When linked to the basal tissue-directed promoter, this 15-bp sequence further enhanced reporter expression in neurons and pinealocytes. We propose that this 15-bp sequence may contribute to increased expression of AC1 in neurons and pinealocytes relative to other cells.

Truncated STAT proteins are prevalent at relapse of acute myeloid leukemia

Signal transducer and activator of transcription (STAT) proteins are implicated in the control of cell survival, proliferation and differentiation in response to hematopoietic cytokines. C-terminally truncated STAT isoforms (STATbeta), as opposed to the full length form (STATalpha), have a competitive or even transdominant negative effect on gene induction mediated by the STAT pathway. We have previously demonstrated that while constitutively active STAT proteins were detected in ten of 36 (28%) for STAT3 and eight of 36 (22%) for STAT5 in pretreatment samples from newly diagnosed acute myeloid leukemia (AML) patients, a significantly larger fraction of samples [21 of 27 (78%)] expressed STATbeta proteins. To determine whether STATbeta expression was maintained or increased after relapse in AML, we compared STAT activity and isoform expression at diagnosis and at relapse in 17 patients. In this selected group, constitutively active STAT3 was detected in 13 of 17 (76%) AML samples at diagnosis but was detected in only four of these patients at relapse. Constitutively active STAT5 was detected in three of 17 (18%) AML samples at diagnosis; but only two at relapse. In contrast, STATbeta protein expression was observed in 12 of the 17 pretreatment samples (71%) and in 16 of 17 samples at relapse. Only one patient did not express STATbeta at relapse. Our results suggest that STATbeta isoform expression, rather than level of constitutive activity, may be involved in disease progression in AML.

Total Synthesis of Dendroamide A, a Novel Cyclic Peptide That Reverses Multiple Drug Resistance

Dendroamide A (1) was isolated from a blue-green alga on the basis of its ability to reverse drug resistance in tumor cells that overexpress either of the transport proteins, P-glycoprotein or MRP1. Because of this activity, methods for the synthesis of analogues of this oxazole- and thiazole-containing cyclic peptide have been developed, and the total synthesis of 1 has been completed. Highlights of the synthetic strategy are as follows: (1) a dicyclohexylcarbodiimide coupling of D-Ala and L-Thr, followed by reaction with Burgess reagent and DBU-assisted oxidation to form D-Ala-oxazole; (2) formation of D-Val-thiazole and D-Ala-thiazole via modified Hantzsch reactions; and (3) use of molecular modeling to select the preferred precursor for the final cyclization of the peptide analogue. Synthetic 1 demonstrated spectral properties identical to those of the natural product and reversed P-glycoprotein-mediated drug resistance more effectively than MRP1-mediated resistance. Certain of the synthetic precursors had biological activity, indicating that cell permeability and peptide cyclization are necessary for optimal activity. Thus, the structure and the biological activities of the natural product are confirmed, and methods for the synthesis of analogues for further structure-activity explorations are defined.

The preparation of rat heme oxygenase-1 mutant to reduce the level of bilirubin

OBJECTIVE

To prepare rat heme oxygenase-1 (HO-1) mutants and to determine the activity and inhibition of this mutated enzyme.

METHODS

pcDNA3HO1 containing truncated native rat HO-1 cDNA and pcDNA3HO1 delta 25 carrying mutated rat HO-1 cDNA (His25Ala) were constructed, respectively. COS-1 cells transfected with pcDNA3HO1 and pcDNA3HO1 delta 25 were collected and their activities were analyzed.

RESULTS

Native rat HO-1 was highly expressed in transfected cells and its activity was 13,688-15,600 U/mg protein per hour. However, the enzyme activity of mutated HO-1 declined and the value was 1948-2160 U/mg protein per hour. When an equal amount of mutant was added to the enzyme reaction system, the level of bilirubin decreased by 42%.

CONCLUSION

The His25Ala mutant reduced the formation of bilirubin, suggesting that the mutant could completely bind the heme with native enzyme.

[Modeling research about bioremediation of organic pollutants in soil-water-microbes system]

A new Theory, organic pollutant sequestration inside soil particles, was applied in the research in order to explain the persistence of residual chemicals in remediation sites. Based on this theory, a mathematical model which simulates organic pollutant bioremediation process in soil-water-microbes system was developed. In the model, diffusion is represented by Fick's second law, reversible sorption-desorption by a linear isotherm, irreversible sequestration by a pseudo-first order kinetics, and biodegradation by Monod kinetics. Model results match successfully with experimental data. Model simulations are performed in the study. It is noteworthy that the mathematical model will be useful in quantitatively predicting the time and degradation extend of organic pollutant in remediation sites.

[Researches on high frequency inverter in X-ray machine]

This paper mainly explicates the high frequency inverter circuit and its features and deliberates the question of how to prevent the short circuit of inverter.

A novel serine-dependent proteolytic activity is responsible for truncated signal transducer and activator of transcription proteins in acute myeloid leukemia blasts

Hematopoietic cytokine receptor signaling involves activation of signal transducer and activator of transcription (STAT) proteins that are thought to control cellular differentiation. Truncated STAT isoforms (beta forms, rather than the normal alpha forms) have been described and found to block the normal signaling function of the alpha isoforms. We recently demonstrated STATbeta isoforms in bone marrow samples from 21 of 27 (78%) acute myeloid leukemia (AML) patients. We sought to determine the mechanism by which the STATbeta forms were generated. Samples from eight newly diagnosed AML patients were studied; four expressed predominantly STATalpha, and four expressed predominantly STATbeta. The reverse transcription-PCR generated identical products in the two groups, suggesting that alternate mRNA splicing is not responsible for the genesis of STATbeta. Extracts from cells expressing predominantly STATbeta incubated with cell extracts from the MO7E cell line, which expresses predominantly STATa, caused a decrease of the alpha isoforms and an increase of the beta isoforms, suggesting the presence of proteolytic activity. This proteolytic activity was: (a) specific for STAT3 and STAT5, but not for STAT6; (b) serine dependent; (c) equally present in nuclear and cytoplasmic fractions of the leukemic blasts; and (d) different than the activity detected in a murine hematopoietic cell line. The cleaved beta isoforms retained their DNA-binding activity. Because expression of truncated STATs may be involved in blocking differentiation of AML blasts, elucidation of the regulation of the proteolytic activity may contribute to our understanding of leukemogenesis.

Pregnancy after tubal sterilization with silicone rubber band and spring clip application

OBJECTIVE

To determine risk factors for pregnancy after tubal sterilization with silicone rubber bands or spring clips.

METHODS

A total of 3329 women sterilized using silicone rubber bands and 1595 women sterilized using spring clips were followed for up to 14 years as part of a prospective cohort study conducted in medical centers in nine US cities. We assessed the risk of pregnancy by cumulative life-table probabilities and proportional hazards analysis.

RESULTS

The risk of pregnancy for women who had silicone rubber band application differed by location of band application and study site. The 10-year cumulative probabilities of pregnancy varied from a low of 0.0 per 1000 procedures at one study site to a high of 42.5 per 1000 procedures in the four combined sites in which fewer than 100 procedures per site were performed. The risk of pregnancy for women who had spring clip application varied by location of clip application, study site, race or ethnicity, tubal disease, and history of abdominal or pelvic surgery. The probabilities across study sites ranged from 7.1 per 1000 procedures at 10 years to 78.0 per 1000 procedures at 5 years (follow-up was limited to 5 years at that site).

CONCLUSION

The 10-year cumulative probability of pregnancy after silicone rubber band and spring clip application is low but varies substantially by both clinical and demographic characteristics.