Structures and mechanisms of Nudix hydrolases

Nudix hydrolases catalyze the hydrolysis of nucleoside diphosphates linked to other moieties, X, and contain the sequence motif or Nudix box, GX(5)EX(7)REUXEEXGU. The mechanisms of Nudix hydrolases are highly diverse in the position on the substrate at which nucleophilic substitution occurs, and in the number of required divalent cations. While most proceed by associative nucleophilic substitutions by water at specific internal phosphorus atoms of a diphosphate or polyphosphate chain, members of the GDP-mannose hydrolase sub-family catalyze dissociative nucleophilic substitutions, by water, at carbon. The site of substitution is likely determined by the positions of the general base and the entering water. The rate accelerations or catalytic powers of Nudix hydrolases range from 10(9)- to 10(12)-fold. The reactions are accelerated 10(3)-10(5)-fold by general base catalysis by a glutamate residue within, or beyond the Nudix box, or by a histidine beyond the Nudix box. Lewis acid catalysis, which contributes 10(3)-10(5)-fold to the rate acceleration, is provided by one, two, or three divalent cations. One divalent cation is coordinated by two or three conserved residues of the Nudix box, the initial glycine and one or two glutamate residues, together with a remote glutamate or glutamine ligand from beyond the Nudix box. Some Nudix enzymes require one (MutT) or two additional divalent cations (Ap(4)AP), to neutralize the charge of the polyphosphate chain, to help orient the attacking hydroxide or oxide nucleophile, and/or to facilitate the departure of the anionic leaving group. Additional catalysis (10-10(3)-fold) is provided by the cationic side chains of lysine and arginine residues and by H-bond donation by tyrosine residues, to orient the general base, or to promote the departure of the leaving group. The overall rate accelerations can be explained by both independent and cooperative effects of these catalytic components.

A validated 1H NMR method for the determination of the degree of deacetylation of chitosan

A method for the determination of the degree of deacetylation (DDA) of chitosan by 1H NMR spectroscopy has been formally validated. Chitosans with DDA ranging from 48 to 100% have been used for the validation. The method is found to be simple, rapid and more precise than other known techniques like IR or titration for %DDA measurements. The precision, ruggedness, robustness, specificity, stability and accuracy of the technique are discussed in this paper.

Osteogenic stem-cell characterization and development: potentials for cytotherapy

BACKGROUND

Primitive progenitors of bone tissue exist postnatally and exhibit stem-cell characteristics, as shown by extensive renewal potential, and capacity to differentiate into all characteristic connective tissue types, including bone, cartilage, fat, fibrous tissue, muscle and hemopoietic stroma.

METHODS

A wide variety of investigative techniques have been applied to characterize and assess differentiation of the normally non-cycling osteogenic stem cells. These include methods to assess in vitro and in vivo differentiation potentials, the production and use of Abs to identify surface markers, the expression of specific genes and, more recently, incorporation of marker genes (beta-galactosidase, green fluorescent protein) to study cell fate after implantation at tissue sites.

RESULTS

Some antigenic cell-surface molecules reactive with MAbs generated by a number of laboratories have been identified. For cell-fate studies, retroviral insertion of beta-galactosidase or green fluorescent protein genes into human marrow stromal progenitors has been accomplished with high efficiency. The stromal cell phenotype and cellular functions in vitro are not significantly altered by these genetic modifications. In vivo transplantation in immunodeficient animals demonstrates migration and persistence of marrow stromal cells to skeletal and other tissue sites.

DISCUSSION

None of the Abs generated against surface markers of early progenitors are absolutely lineage and cell-stage specific, but the respective Ags appear to participate in cell adhesion and cell-signalling mechanisms. These may be important in stem-cell activation and subsequent early osteogenic development. Studies of cell fate indicate feasibility for future uses in therapy of bone deficiency diseases and the potential for development of gene therapy procedures in these and other conditions.

The PDZ-binding domain is essential for the dendritic targeting of 5-HT2A serotonin receptors in cortical pyramidal neurons in vitro

The 5-HT(2A) serotonin receptor represents an important molecular target for atypical antipsychotic drugs and for most hallucinogens. In the mammalian cerebral cortex, 5-HT(2A) receptors are enriched in pyramidal neurons, within which 5-HT(2A) receptors are preferentially sorted to the apical dendrites. In primary cortical cultures, 5-HT(2A) receptors are sorted to dendrites and not found in the axons of pyramidal neurons. We identified a sorting motif that mediates the preferential targeting of 5-HT(2A) receptors to the dendrites of cortical pyramidal neurons in vitro. We constructed green fluorescent protein-tagged 5-HT(2A) receptors wherein potential sorting motifs were disrupted, and subsequently employed either the Semliki Forest virus or calcium phosphate for the transient expression of recombinant 5-HT(2A) receptors in cultured cortical pyramidal neurons. Using dual-labeling immunofluorescent confocal microscopy, we quantified the axonal and dendritic sorting patterns of endogenous and recombinant 5-HT(2A) receptors. We discovered that disruption of the PDZ-binding domain of the 5-HT(2A) receptor greatly attenuates the dendritic targeting of 5-HT(2A) receptors without inappropriately sorting 5-HT(2A) receptors to axons. The PDZ-binding domain is therefore a necessary signal for the preferential targeting of the 5-HT(2A) receptor to the dendritic compartment of cultured cortical pyramidal neurons, the first such role ascribed to this protein-protein interaction motif of any G protein-coupled receptor.

[Study on antifungal mechanism of alpha-pinene]

The antifungal mechanism of alpha-pinene was studied using electronic microscopy and incorporation of isotope-labelled precursor. The results demonstrated that alpha-pinene had significant roles in inhibiting and killing Candida albicans. After treatment with alpha-pinene the fungal morphology and ultrastructure showed obvious changes: their cell wall and cytoplasmic membrane ruptured; intracellular components released out and the cell residue fused to form irregular masses. In addition, the synthesis of DNA, RNA, polysaccharide of cell wall and ergosterol of cytoplasmic membrane was inhibited. It is indicated that these changes are related to antifungal mechanism of alpha-pinene.

Phosphorylation of cAMP response element-binding protein in hippocampal neurons as a protective response after exposure to glutamate in vitro and ischemia in vivo

Although accumulating evidence indicates that cAMP response element-binding protein (CREB) phosphorylation mediates not only synaptic plasticity but also survival of certain neurons, it remains uncertain whether CREB phosphorylation induced after metabolic insult leads to CRE-mediated gene transcription and is involved in cell survival or not. In the present study, we clarified that (1) CREB phosphorylation and ischemic tolerance induced after preconditioning ischemia in the hippocampal neurons was abolished by MK801 administration in gerbil global ischemia model, (2) CREB phosphorylation induced after exposure to glutamate in cultured neurons was inhibited by removal of extracellular calcium, by MK801 and by an inhibitor of calcium-calmodulin-dependent protein kinase (CaMK) II and IV, (3) inhibitor of CaMK II-IV or CRE-decoy oligonucleotide suppressed upregulation of BCL-2 expression and accelerated neuronal damage after exposure to glutamate, and (4) CREB phosphorylation induced in the hippocampal neurons after ischemia and in cultured neurons after exposure to glutamate was followed by CRE-mediated gene transcription in transgenic mice with a CRE-LacZ reporter. Our results suggest that CREB phosphorylation in neurons after ischemia and exposure to glutamate is induced by NMDA receptor-gated calcium influx and subsequent activation of CaMK II-IV and that CREB phosphorylation after metabolic stress might show a neuroprotective response through CRE-mediated gene induction.

Equivalent induction of telomerase-specific cytotoxic T lymphocytes from tumor-bearing patients and healthy individuals

Although high frequencies of T lymphocytes specific for certain tumor-associated antigens have been detected in some cancer patients, increasing evidence suggests that these T cells may be functionally defective in vivo and fail to induce meaningful clinical responses. One strategy to overcome this limitation is to target novel antigens that are ignored during the natural antitumor immune response but are nevertheless capable of triggering effector T-cell responses against tumors after optimal presentation by antigen-presenting cells. Here, we show that the telomerase catalytic subunit (hTERT)-a nearly universal tumor antigen identified by epitope deduction rather than from patient immune responses-is immunologically ignored by patients despite progressive tumor burden. Nevertheless, HLA-A2-restricted CTLs against hTERT are equivalently induced ex vivo from patients and healthy individuals and efficiently kill human tumor cell lines and primary tumors. Thus, telomerase-specific T cells from cancer patients are spared functional inactivation because of immunological ignorance. These findings support clinical efforts to target the hTERT as a tumor antigen with broad therapeutic potential.

[A study on the myocardial contractile function and intracellular free calcium in scalded rats]

OBJECTIVE

To explore the relationship between postburn myocardial function and intracellular free calcium concentration.

METHODS

Sprague-Dawley (SD) rats were employed as the model in which 7 were inflicted with 43% TBSA degree scalding (S group) and 7 as sham scalding control group (C group). The hearts of the injured rats were isolated and perfused in vitro by Langendorff method after 24 postburn hours (PBHs). The hearts were connected to a cardiac function monitor, and the dynamic changes in left ventricular develop pressure (LVDP) were continuously monitored. The cardiac 19F and 31P NMR spectroscopy was determined before and after and TF-BAPTA was added to the perfusate.

RESULTS

When compared with those in C group, the LVDP of scalded rat heart decreased by 40% (P < 0.01), and the myocardial cytoplasmic free calcium concentration was four times above that in C group (P < 0.01). After TF-BAPTA was taken by myocytes, cardiac LVDP only decreased by 15% to 20%, and the PCr/Pi ratio decreased, while there was no change in ATP.

CONCLUSION

Myocardial contractile function could be inhibited after burn injury, which might be related to the increase of myocardial cytoplasmic free calcium concentration.

Construction and analysis of mouse strains lacking the ubiquitin ligase UBR1 (E3alpha) of the N-end rule pathway

The N-end rule relates the in vivo half-life of a protein to the identity of its N-terminal residue. In the yeast Saccharomyces cerevisiae, the UBR1-encoded ubiquitin ligase (E3) of the N-end rule pathway mediates the targeting of substrate proteins in part through binding to their destabilizing N-terminal residues. The functions of the yeast N-end rule pathway include fidelity of chromosome segregation and the regulation of peptide import. Our previous work described the cloning of cDNA and a gene encoding the 200-kDa mouse UBR1 (E3alpha). Here we show that mouse UBR1, in the presence of a cognate mouse ubiquitin-conjugating (E2) enzyme, can rescue the N-end rule pathway in ubr1Delta S. cerevisiae. We also constructed UBR1(-/-) mouse strains that lacked the UBR1 protein. UBR1(-/-) mice were viable and fertile but weighed significantly less than congenic +/+ mice. The decreased mass of UBR1(-/-) mice stemmed at least in part from smaller amounts of the skeletal muscle and adipose tissues. The skeletal muscle of UBR1(-/-) mice apparently lacked the N-end rule pathway and exhibited abnormal regulation of fatty acid synthase upon starvation. By contrast, and despite the absence of the UBR1 protein, UBR1(-/-) fibroblasts contained the N-end rule pathway. Thus, UBR1(-/-) mice are mosaics in regard to the activity of this pathway, owing to differential expression of proteins that can substitute for the ubiquitin ligase UBR1 (E3alpha). We consider these UBR1-like proteins and discuss the functions of the mammalian N-end rule pathway.

[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.