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.

Negative cell cycle regulation and DNA damage-inducible phosphorylation of the BRCT protein 53BP1

In a screen designed to discover suppressors of mitotic catastrophe, we identified the Xenopus ortholog of 53BP1 (X53BP1), a BRCT protein previously identified in humans through its ability to bind the p53 tumor suppressor. X53BP1 transcripts are highly expressed in ovaries, and the protein interacts with Xp53 throughout the cell cycle in embryonic extracts. However, no interaction between X53BP1 and Xp53 can be detected in somatic cells, suggesting that the association between the two proteins may be developmentally regulated. X53BP1 is modified via phosphorylation in a DNA damage-dependent manner that correlates with the dispersal of X53BP1 into multiple foci throughout the nucleus in somatic cells. Thus, X53BP1 can be classified as a novel participant in the DNA damage response pathway. We demonstrate that X53BP1 and its human ortholog can serve as good substrates in vitro as well as in vivo for the ATM kinase. Collectively, our results reveal that 53BP1 plays an important role in the checkpoint response to DNA damage, possibly in collaboration with ATM.

Stable SNARE complex prior to evoked synaptic vesicle fusion revealed by fluorescence resonance energy transfer

Although it is clear that soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor (SNARE) complex plays an essential role in synaptic vesicle fusion, the dynamics of SNARE assembly during vesicle fusion remain to be determined. In this report, we employ fluorescence resonance energy transfer technique to study the formation of SNARE complexes. Donor/acceptor pair variants of green fluorescent protein (GFP), cyan fluorescent protein (CFP), and yellow fluorescent protein (YFP) are fused with the N termini of SNAP-25 and synaptobrevin, respectively. In vitro assembly of SNARE core complex in the presence of syntaxin shows strong fluorescence resonance energy transfer (FRET) between the CFP-SNAP-25 and YFP-synaptobrevin. Under the same conditions, CFP fused to the C terminus of SNAP-25, and YFP- synaptobrevin have no FRET. Adenovirus-mediated gene transfer is used to express the fusion proteins in PC12 cells and cultured rat cerebellar granule cells. Strong FRET is associated with neurite membranes and vesicular structures in PC12 cells co-expressing CFP-SNAP-25 and YFP-synaptobrevin. In cultured rat cerebellar granule cells, FRET between CFP-SNAP-25 and YFP-synaptobrevin is mostly associated with sites presumed to be synaptic junctions. Neurosecretion in PC12 cells initiated by KCl depolarization leads to an increase in the extent of FRET. These results demonstrate that significant amounts of stable SNARE complex exist prior to evoked synaptic vesicle fusion and that the assembly of SNARE complex occurs during vesicle docking/priming stage. Moreover, it demonstrates that FRET can be used as an effective tool for investigating dynamic SNARE interactions during synaptic vesicle fusion.

Differential regulation of mitogen-activated protein kinases ERK1/2 and ERK5 by neurotrophins, neuronal activity, and cAMP in neurons

Activation of the extracellular signal-regulated kinase 1 (ERK1) and ERK2 by neurotrophins, neuronal activity, or cAMP has been strongly implicated in differentiation, survival, and adaptive responses of neurons during development and in the adult brain. Recently, a new member of the mitogen-activated protein (MAP) kinase family, ERK5, was discovered. Like ERK1 and ERK2, ERK5 is expressed in neurons, and ERK5 stimulation by epidermal growth factor is blocked by the MAP kinase/ERK kinase 1 (MEK1) inhibitors PD98059 and U0126. This suggests the interesting possibility that some of the functions attributed to ERK1/2 may be mediated by ERK5. However, the regulatory properties of ERK5 in primary cultured neurons have not been reported. Here we examined the regulation of ERK5 signaling in primary cultured cortical neurons. Our data demonstrate that, similar to ERK1/2, ERK5 is activated by neurotrophins including brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and NT-4. BDNF stimulation of ERK5 required the activity of MEK5. Surprisingly, ERK5 was not stimulated by cAMP or neuronal activity induced by glutamate or membrane depolarization. In contrast to ERK1/2, ERK5 strongly activated the transcriptional activity of myocyte enhancer factor 2C (MEF2C) in pheochromocytoma 12 (PC12) cells and was required for neurotrophin stimulation of MEF2C transcription in both PC12 cells and cortical neurons. Furthermore, ERK1/2, but not ERK5, induced transcription from Elk1 and the cAMP/ Ca(2+) response element in PC12 cells. Our data suggest that mechanisms for regulation of ERK5 and downstream transcriptional pathways regulated by ERK5 are distinct from those of ERK1/2 in neurons. Furthermore, ERK5 is the first MAP kinase identified whose activity is stimulated by neurotrophins but not by neuronal activity.

Isolation and expression of the ecdysteroid-inducible angiotensin-converting enzyme-related gene in wing discs of Bombyx mori

We isolated a clone encoding a putative angiotensin-converting enzyme-related gene from the wing disc cDNA library of the silkworm, Bombyx mori (refer to as BmAcer). The predicted open reading frame encoded 648 amino acids with about 50% identities with the Drosophila melanogaster angiotensin-converting enzyme Ance and Acer. Northern analysis identified a 2.2-kilobase mRNA which was abundant in wing discs two days after the beginning of wandering. An accumulation of the transcript was observed approximately 2 h after 20-hydroxyecdysone (20E) exposure in vitro and was blocked slightly by a protein synthetic inhibitor. These data suggest that the transcription of the BmAcer gene is directly 20E-inducible.

Novel transcripts of the estrogen receptor alpha gene in channel catfish

Complementary DNA libraries from liver and ovary of an immature female channel catfish were screened with a homologous ERalpha cDNA probe. The hepatic library yielded two new channel catfish ER cDNAs that encode N-terminal ERalpha variants of different sizes. Relative to the catfish ERalpha (medium size; 581 residues) previously reported, these new cDNAs encode Long-ERalpha (36 residues longer) and Short-ERalpha (389 residues shorter). The 5'-end of Long-ERalpha cDNA is identical to that of Medium-ERalpha but has an additional 503-bp segment with an upstream, in-frame translation-start codon. Recombinant Long-ERalpha binds estrogen with high affinity (K(d) = 3. 4 nM), similar to that previously reported for Medium-ERalpha but lower than reported for catfish ERbeta. Short-ERalpha cDNA encodes a protein that lacks most of the receptor protein and does not bind estrogen. Northern hybridization confirmed the existence of multiple hepatic ERalpha RNAs that include the size range of the ERalpha cDNAs obtained from the libraries as well as additional sizes. Using primers for RT-PCR that target locations internal to the protein-coding sequence, we also established the presence of several ERalpha cDNA variants with in-frame insertions in the ligand-binding and DNA-binding domains and in-frame or out-of-frame deletions in the ligand-binding domain. These internal variants showed patterns of expression that differed between the ovary and liver. Further, the ovarian library yielded a full-length, ERalpha antisense cDNA containing a poly(A) signal and tail. A limited survey of histological preparations from juvenile catfish by in situ hybridization using directionally synthesized cRNA probes also suggested the expression of ERalpha antisense RNA in a tissue-specific manner. In conclusion, channel catfish seemingly have three broad classes of ERalpha mRNA variants: those encoding N-terminal truncated variants, those encoding internal variants (including C-terminal truncated variants), and antisense mRNA. The sense variants may encode functional ERalpha or related proteins that modulate ERalpha or ERbeta activity. The existence of ER antisense mRNA is reported in this study for the first time. Its role may be to participate in the regulation of ER gene expression.

A clinical investigation on garlicin injectio for treatment of unstable angina pectoris and its actions on plasma endothelin and blood sugar levels

To investigate the therapeutic effects and mechanisms of garlicin for treatment of unstable angina pectoris (UAP), garlicin injectio was intravenously dripped 60 mg/day in 34 cases for 10 days. Nitroglycerine was used in 21 cases of the control group. The results showed that the total effective rates in improving symptoms and electrocardiogram after garlicin treatment were respectively 82% and 62%, and that the plasma endothelin and blood sugar levels were markedly lowered in cases with hyperglycemia.

[Effects of Salvia miltiorrhiza compound injection on serum endothelin, prostaglandin I2/thromboxane A2 ratio alteration following myocardial ischemia-reperfusion in patients undergoing intracardiac surgery]

OBJECTIVE

To investigate the effects of Salvia miltiorrhiza compound injection (SMCI) on serum endothelin (ET), prostaglandin I2(PGI2), thromboxane A2(TXA2), and PGI2/TXA2 ratio following myocardial ischemia-reperfusion in patients undergoing intracardiac surgery.

METHODS

Twenty patients, scheduled for selective surgery, were randomly divided into the SMCI group (group A, 10 cases) and the control group (group B, 10 cases). SMCI 200 mg/kg was given intravenously in group A before starting the operation and at the time of rewarming respectively, and equivalent volumes of normal saline were administered to group B. The central venous blood samples were collected to measure the serum concentration of ET, PGI2, TXA2, and PGI2/TXA2 ratio.

RESULTS

ET significantly reduced, while PGI2 and TXA2 obviously raised in both groups at the beginning (T1) of extracorporeal cardiopulmonary bypass (CPB) (P < 0.05). After cardiac ischemia-reperfusion, ET in group B increased rapidly and significantly (P < 0.05) and evidently higher than the corresponding value in group A 30 min after reperfusion (T3) till 24 hrs after reperfusion (T5). During reperfusion, PGI2 and TXA2 in group A decreased more rapidly than that of group B, while group A maintained higher PGI2/TXA2 ratio than that of group B. At T5, PGI2 and TXA2 in group A were significantly lower than those in group B, while PGI2/TXA2 ratio was higher than that in group B (P < 0.05). The serum ET level was obviously negatively correlated to PGI2/TXA2 ratio. The postoperative cardiac function recovered much better in group A than in that group B.

CONCLUSION

SMCI can significantly reduce serum ET level, raise PGI2/TXA2 ratio, thus facilitate the postoperative cardiac function recovery following intracardiac surgery under CPB.

The effect of sudden failure of a rotary blood pump on left ventricular performance in normal and failing hearts

We investigated the hemodynamic effect of regurgitation (or back-flow) due to sudden failure of a rotary blood pump (diagonal pump). Seven healthy sheep (Group C) and 7 with chronic heart failure (Group F) were studied. Chronic heart failure was obtained by intracoronary injection of microspheres several weeks earlier. Left ventricular function and ventricular efficacy were assessed by the pressure-volume relationship. The back-flow through the stopped pump was significantly lower in Group F (2.3 +/- 0.34 L/min) than in Group C (2.8 +/- 0.33 L/min). Mean aortic blood pressure dropped significantly from 68.3 +/- 9.65 to 61.9 +/- 9.75 mm Hg in Group C and from 62.5 +/- 9.12 to 51.5 +/- 9.08 in Group F but remained stable during the 15 min period of pump stop. Parameters of left ventricular contractility (preload recruitable stroke work) dropped significantly in both groups, remained stable during the pump stop, and returned to baseline values 30 min after the end of back-flow. The ventricular efficacy (in terms of energy transfer) was tolerant against this acute volume overload even in the failing hearts. Sudden pump failure of a rotary blood pump leads to an acute depression of the hemodynamic state and myocardial contractility. However, this depression remained stable over 15 min, did not lead to further deterioration of the animals, and was completely reversible.

Regulation of the yeast transcriptional factor PHO2 activity by phosphorylation

The induction of yeast Saccharomyces cerevisiae gene PHO5 expression is mediated by transcriptional factors PHO2 and PHO4. PHO4 protein has been reported to be phosphorylated and inactivated by a cyclin-CDK (cyclin-dependent kinase) complex, PHO80-PHO85. We report here that PHO2 can also be phosphorylated. A Ser-230 to Ala mutation in the consensus sequence (SPIK) recognized by cdc2/CDC28-related kinase in PHO2 protein led to complete loss of its ability to activate the transcription of PHO5 gene. Further investigation showed that the Pro-231 to Ser mutation inactivated PHO2 protein as well, whereas the Ser-230 to Asp mutation did not affect PHO2 activity. Since the PHO2 Asp-230 mutant mimics Ser-230-phosphorylated PHO2, we postulate that only phosphorylated PHO2 protein could activate the transcription of PHO5 gene. Two hybrid assays showed that yeast CDC28 could interact with PHO2. CDC28 immunoprecipitate derived from the YPH499 strain grown under low phosphate conditions phosphorylated GST-PHO2 in vitro. A phosphate switch regulates the transcriptional activation activity of PHO2, and mutations of the (SPIK) site affect the transcriptional activation activity of PHO2 and the interaction between PHO2 and PHO4. BIAcore(R) analysis indicated that the negative charge in residue 230 of PHO2 was sufficient to help PHO2 interact with PHO4 in vitro.

SNAP-25 functional domains in SNARE core complex assembly and glutamate release of cerebellar granule cells

Synaptosomal associated protein of 25 kDa (SNAP-25) is a member of the SNARE protein complex that has been implicated in synaptic vesicle docking and fusion. In this report, we have generated SNAP-25 mutants and assayed their functions in SNARE complex formation and glutamate release from cultured rat cerebellar granule cells. In vitro binding studies show that a deletion mutant lacking the C-terminal 181-206 amino acid sequence inhibits the formation of the SNARE core complex. Additional deletion of an N-terminal 1-31 amino acid sequence abolished this inhibitory activity. Adenovirus-mediated gene transfer is used to overexpress wild-type and mutant SNAP-25 in cerebellar granule cells. Neurons overexpressing the wild-type protein show slight reductions in glutamate release, ranging from 10 to 15% in both the developing and mature granule cells. A 30-35% inhibition is obtained with the C-terminal deletion mutant, and the inhibitory effect is abolished in the N- and C-terminal double deletion mutant. These results demonstrate that the SNARE core complex exists in a dynamic and reversible state, and the formation of the core complex is necessary for neurotransmitter release in neurons.

SRF-dependent gene expression is required for PI3-kinase-regulated cell proliferation

Recent evidence indicates that phosphatidylinositol 3-kinase (PI3K) is a central regulator of mitosis, apoptosis and oncogenesis. Nevertheless, the mechanisms by which PI3K regulates proliferation are not well characterized. Mitogens stimulate entry into the cell cycle by inducing the expression of immediate early genes (IEGs) that in turn trigger the expression of G(1) cyclins. Here we describe a novel PI3K- regulated transcriptional cascade that is critical for mitogen regulation of the IEG, c-fos. We show that PI3K activates gene expression by transactivating SRF-dependent transcription independently of the previously described Rho and ETS TCF pathways. PI3K-stimulated cell cycle progression requires transactivation of SRF and expression of dominant- negative PI3K blocks mitogen-stimulated cell cycle progression. Furthermore, dominant-interfering SRF mutants attenuate mitogen-stimulated cell cycle progression, but are without effect on MEK-stimulated cell cycle entry. Moreover, expression of constitutively active SRF is sufficient for cell cycle entry. Thus, we delineate a novel SRF-dependent mitogenic cascade that is critical for PI3K- and growth factor-mediated cell cycle progression.