N-(5-Nitro-1,3-thia-zol-2-yl)-4-(tri-fluoro-meth-yl)benzamide

There are two independent and conformationally dissimilar mol-ecules (A and B) in the asymmetric unit of the title compound, C11H6F3N3O3S; the dihedral angles between the benzene and thia-zole rings are 33.8 (2)° in A and 59.7 (2)° in B. The similarity of the C-N bond lengths in the amide group [1.379 (5) and 1.358 (5) Å for A, and 1.365 (5) and 1.363 (5) Å for B] indicates the presence of conjugation between the two rings. In the crystal, mol-ecules are linked by N-H⋯N hydrogen bonds, forming chains extending along [010]; weak N-H⋯Oamide inter-actions are also present in the structure.

Effect of early fluid resuscitation on the lung in a rat model of lipopolysaccharide-induced septic shock

BACKGROUND

Many clinical trials have showed that early fluid resuscitation can improve the prognosis and reduce the mortality rate of patients with septic shock. However, some experiments suggest that abundant fluid may injure the lung and other tissues.

AIM

To evaluate the protective effect of early fluid resuscitation and simultaneous norepinephrine treatment on lung function by using the rat model of lipopolysaccharide (LPS)-induced septic shock.

MATERIALS AND METHODS

Male Wistar rats were randomly divided into four groups: normal control group, septic shock control group, early fluid resuscitation treatment group, early fluid resuscitation and simultaneous norepinephrine treatment group. Blood gas, lactate, fluid volume, and dose of norepinephrine were recorded. Pathological change was observed by hematoxylin and eosin staining and transmission electron microscopy. The activities of hydroxyl radicals, MDA, SOD and MPO were detected by spectrophotometry. The expression of IL-6, IL-8, and TNF-alpha were determined with ELISA kits.

RESULTS

LPS could induce rats to suffer from acute lung injury in early stage of septic shock. Early fluid resuscitation could guarantee effective circulating blood volume and tissue perfusion pressure, improve microcirculatory derangements, increase oxygen partial pressure and oxygenation index, but have the tendency to aggravate pulmonary edema. Simultaneous norepinephrine treatment in early stage could decrease the fluid volume, alleviate the degree of pulmonary edema, reduce the expression level of pro-inflammatory mediators in the serum and BALF, and increase the oxygenation index.

CONCLUSIONS

Early fluid resuscitation and simultaneous norepinephrine treatment may be a superior alternative to protect lung injury secondary to septic shock.

Factors associated with prolonged recovery after the arterial switch operation for transposition of the great arteries in infants

This study aimed specifically to identify the predictors of prolonged recovery after the arterial switch operation for transposition of the great arteries in infants. The clinical records of all infants admitted to the surgical intensive care unit (SICU) between January 2000 and March 2011 after an arterial switch operation were retrospectively reviewed. The cohort was divided into a prolonged recovery group that included all patients who exceeded the 75th percentile for duration of SICU stay and a standard recovery group that included all the remaining patients. Of the 102 patients in the final analysis, 31 experienced prolonged recovery. The median SICU stay was 18 days (range, 14-58 days) for the patients in the prolonged recovery group and only 8 days (range, 5-13 days) for the patients in the standard recovery group. After univariate analysis, a stepwise logistic regression model analysis was used to compare the demographic data as well as the pre-, intra-, and postoperative variables between the two groups. Of all the variables analyzed, high postbypass serum lactate level [odds ratio (OR), 2.610; 95 % confidence interval (CI), 1.464-4.653; p = 0.039], need for larger volume of resuscitation fluid (OR, 3.154; 95 % CI, 1.751-5.682; p = 0.018), and noninfectious pulmonary complication (OR, 2.844; 95 % CI, 1.508-5.363; p = 0.025) were identified as independent risk factors for prolonged recovery among infants undergoing an arterial switch operation for transposition of the great arteries.

N-(5-Chloro-1,3-thia-zol-2-yl)-2,4-difluoro-benzamide

The title compound, C(10)H(5)ClF(2)N(2)OS, was obtained by linking an amino heterocycle and a substituted benzoyl chloride. The dihedral angle between the two rings is 41.2 (2)° and the equalization of the amide C-N bond lengths reveals the existence of conjugation between the benzene ring and the thia-zole unit. In the crystal, pairs of N-H⋯N hydrogen bonds link mol-ecules into inversion dimers. Non-classical C-H⋯F and C-H⋯O hydrogen bonds stabilize the crystal structure.

Plasma sRAGE enables prediction of acute lung injury after cardiac surgery in children

Introduction

Acute lung injury (ALI) after cardiac surgery is associated with a high postoperative morbidity and mortality, but few predictors are known for the occurrence of the complication. This study evaluated whether elevated plasma levels of soluble receptor for advanced glycation end products (sRAGE) and S100A12 reflected impaired lung function in infants and young children after cardiac surgery necessitating cardiopulmonary bypass (CPB).

Methods

Consecutive children younger than 3 years after cardiac surgery were prospectively enrolled and assigned to ALI and non-ALI groups, according to the American-European Consensus Criteria. Plasma concentrations of sRAGE and S100A12 were measured at baseline, before, and immediately after CPB, as well as 1 hour, 12 hours, and 24 hours after operation.

Results

Fifty-eight patients were enrolled and 16 (27.6%) developed postoperative ALI. Plasma sRAGE and S100A12 levels increased immediately after CPB and remained significantly higher in the ALI group even 24 hour after operation (P < 0.01). In addition, a one-way MANOVA revealed that the overall sRAGE and S100A12 levels were higher in the ALI group than in the non-ALI group immediately after CPB (P < 0.001). The multivariate logistic regression analysis showed that the plasma sRAGE level immediately after CPB was an independent predictor for postoperative ALI (OR, 1.088; 95% CI, 1.011 to 1.171; P = 0.025). Increased sRAGE and S100A12 levels immediately after CPB were significantly correlated with a lower PaO₂/FiO₂ ratio (P < 0.01) and higher radiographic lung-injury score (P < 0.01), as well as longer mechanical ventilation time (sRAGE_N: r = 0.405; P = 0.002; S100A12_N: r = 0.322; P = 0.014), longer surgical intensive care unit stay (sRAGE_N: r = 0.421; P = 0.001; S100A12_N: r = 0.365; P = 0.005) and hospital stay (sRAGE_N: r = 0.329; P = 0.012; S100A12_N: r = 0.471; P = 0.001).

Conclusions

Elevated sRAGE and S100A12 levels correlate with impaired lung function, and sRAGE is a useful early biomarker of ALI in infants and young children undergoing cardiac surgery.

4-Allyl-2-meth-oxy-phenyl 2-acet-oxy-benzoate

In the title compound, C₁₉H₁₈O₅, the ester group is twisted with respect to the acetyl­salicylic acid and eugenol rings at dihedral angles of 22.48 (2) and 81.07 (1)°, respectively. The dihedral angle between the two benzene rings is 60.72 (1)°. The crystal packing exhibits no significantly short inter­molecular contacts.

Status epilepticus stimulates peroxisome proliferator-activated receptor γ coactivator 1-α/mitochondrial antioxidant system pathway by a nitric oxide-dependent mechanism

Peroxisome proliferator-activated receptor (PPAR) γ coactivator 1-α (PGC-1α) is a transcriptional coactivator identified as an upstream regulator of lipid catabolism, mitochondrial number and function. PGC-1α protects neurons against oxidative damage by inducing several members of the mitochondrial antioxidant system such as superoxide dismutase 2 (SOD2) and uncoupling protein 2 (UCP2). Its role in seizure-induced oxidative stress has not been studied. Here we showed that pilocarpine-induced status epilepticus (SE) stimulates the PGC-1α/mitochondrial antioxidant system signaling pathway in the rat hippocampus. Because nitric oxide (NO) is the key factor of mitochondrial biogenesis through the transcriptional induction of PGC-1α, we investigated whether NO is involved in activation of the PGC-1α/mitochondrial antioxidant system after SE. Treatment with the NO synthase (NOS) inhibitor N(G)-nitro-l-argininemethyl ester (l-NAME) attenuated the increased expression of the PGC-1α/mitochondrial antioxidant system after SE and enhanced oxidative stress. These results suggest that SE can induce the PGC-1α/mitochondrial antioxidant system signaling pathway, which may represent a protective mechanism against SE-induced oxidative stress. Furthermore, NO may positively regulate the mitochondrial antioxidant system by inducing PGC-1α in pilocarpine-induced SE.

1-[4-(3-Chloro-prop-oxy)-2-hydroxy-phen-yl]ethanone

The title compound, C₁₁H₁₃ClO₃, has been obtained in the reaction of 2, 4-dihydroxy­lacetonephenone, potassium carbonate and 1-bromo-3-chloro-hexane. The hydr­oxy group is involved in an intra­molecular O—H⋯O hydrogen bond. The crystal packing exhibits no significantly short inter­molecular contacts

A study of the size-dependent elastic properties of ZnO nanowires and nanotubes

We present our calculations of the Young's modulus of ZnO nanowires and nanotubes by using the empirical Buckingham-type potential. Our results indicate that the Young's moduli of ZnO nanowires increase as the diameters decrease, and the Young's moduli of ZnO nanotubes increase as the thicknesses decrease. Furthermore, we find that such size-dependent elastic properties mainly arise from the lateral facets of the nanowires and nanotubes. In particular, for a ZnO nanotube with a thin wall, the Coulomb interaction between the ions of the outer and inner atomic layers plays an important role in the Young's moduli of the surface atomic layers.

Perioperative risk factors for prolonged mechanical ventilation following cardiac surgery in neonates and young infants

BACKGROUND

Prolonged mechanical ventilation (PMV) after cardiac surgery in children is associated with a high postoperative morbidity and mortality, as well as increased ICU and hospital resource utilization. Little has been done to identify the predictors of PMV in neonates and young infants. This study was performed to evaluate the perioperative risk factors for PMV in neonates and young infants undergoing cardiac surgery.

METHODS

Clinical records of 172 consecutive children aged < or = 3 months were reviewed. PMV was defined as mechanical ventilation (MV) > or = 72 h following operation. After univariate analysis, a stepwise logistic regression analysis was used to evaluate the independent risk factors for PMV following cardiac surgery. The predictive ability of risk factors for PMV was assessed using an area under the receiver operating characteristic (ROC) curve.

RESULTS

Sixty-one patients required PMV after cardiac surgery. The median duration of MV was 150 h in PMV patients, while it was 28 h in non-PMV patients. The independent risk factors for PMV were risk adjustment for surgery for congenital heart disease (RACHS)-1 (p = 0.041), nosocomial pneumonia (p = 0.001), low cardiac output syndrome (LCOS) [p = 0.001], postoperative cumulative positive fluid balance (p = 0.032), and extubation failure (EF) [p = 0.027]. The value for the ROC curve was 0.940.

CONCLUSIONS

The present results strongly suggest that RACHS-1, nosocomial pneumonia, LCOS, fluid retention postoperatively, and EF are risk factors for PMV in neonates and young infants undergoing reparative surgery for congenital heart disease.

Resonant field emission through amorphous diamond thin films (a model study)

A model for field emission through an amorphous diamond thin film with defects is constructed. Theoretical study shows that the emission is enhanced by attractive defects which would make the resonant emission observable for films with thickness of about 10nm. The emitted current density in typical parameters is calculated as functions of thickness, field strength and defect density. The energy distribution of emitted electrons is attained.

A double cysteine trkA mutant exhibiting reduced NGF binding and delayed Erk signaling

The NGF receptor trkA is a tyrosine kinase receptor comprising an extracellular domain with a ligand-binding site, a transmembrane-spanning domain (TMD), and an intracellular domain composed of a juxtamembrane region (JMR), a tyrosine kinase domain, and a short carboxy-terminal tail. Nerve growth factor (NGF) binds and activates this receptor, leading to phosphorylation of signaling substrates involved in neuronal proliferation, differentiation, and survival. Human trkA contains one cysteine residue in the TMD (C423) and another, separated by 12 residues, in the JMR (C436). We hypothesized that the removal of one or both of the cysteines would affect NGF-induced signaling of the trkA receptor. Here we show that NGF induces rapid receptor autophosphorylation in a wild-type, trkA-expressing clone (WT11), in a single cysteine trkA mutants (C423T or C436A), but lower autophosphorylation activity in a double-cysteine trkA mutant (C423T/C436A). WT11 and SM cells had similar binding affinity, but that of DM cells was lower, according to the NGF radioreceptor assay. NGF-induced Erk phosphorylation was rapid in WT11 and C423T cells, but delayed in C436A and C423T/C436A cells. NGF induced [3H]thymidine incorporation into WT11 and SM cells, but had no effect on DM cells. However, basic fibroblast growth factor (bFGF) induced rapid phosphorylation of Erk1/2, and [3H]thymidine incorporation in NIH3T3, WT11, single mutant (SM), and double mutant (DM) cells, suggesting that the impaired NGF-induced Erk phosphorylation and thymidine incorporation observed in DM cells are due to the double-cysteine mutations in the trkA receptor. Cumulatively, our findings support a model in which Cys436 of the trkA is responsible for the rapid transfer of the transmembrane occupancy signal to the SHC adaptor protein for activation of the Ras-Erk pathway and DNA synthesis.

[Determination of aluminium and barium in silicon-aluminium-barium alloy with internal standard by ICP-AES]

A method for the determination of aluminium and barium in silicon-aluminium-barium alloy with the internal standard by ICP-AES was studied. The method of melting sample, the interference of dissolved acid and coexisting elements and the working parameters were experimented. The sample was melted by appropriate acid, was changed into solution, the calculating lines were made by standard solution of aluminium and barium, then the concentrations of aluminium and barium were determined by ICP-AES. The linear rang, detection limits and RSD of the method were examined. The method was simple and the results were accurate.

Neoadjuvant chemotherapy in inoperable, locally advanced, and inflammatory breast carcinoma: a pilot study of MTT assay in vitro and outcome analysis of 10 patients

Patients with inoperable, locally advanced, and inflammatory breast carcinoma (LAIBC), whether with supraclavicular lymph nodes (SLN) or not (stage IIIB and IV), usually carry an overall poor prognosis. The current treatment for these patients is by means of combined modality, including preoperative chemotherapy. This strategy has led to a substantial improvement in clinical response, making some patients operable, and even making breast conservative surgery possible. However, the long-term results still are not promising. The aim of this pilot study was to determine the efficacy of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay in vitro in directing chemotherapy (including preoperative adjuvant chemotherapy and postoperative adjuvant chemotherapy) for these patients. Between June 1994 and March 1997, 10 patients with inoperable LAIBC, whether with SLN or not, were enrolled. During the period of the combined therapy modalities, the neoadjuvant chemotherapy was adopted for three cycles according to the results of chemosensitivity in vitro by MTT assay. Then a modified radical or radical mastectomy was performed, which was followed by radiotherapy and further postoperative adjuvant chemotherapy with the same regimen as that of neoadjuvant chemotherapy. All patients had been followed up from the beginning of neoadjuvant chemotherapy to the end of October 1999. Two patients had clinical complete response (CRs), with one having pathologic CR in both breast tumor and axillary lymph node, and the other having pathologic CR in axillary lymph node. The other eight patients had partial response. By the time of analysis, six patients had been dead of relapse or progression. Among the four patients who were still alive, one had local relapse, one had distant metastatic disease, and the other two had no evident disease. By retrieving from MEDLINE before 1999, the authors learned that this is the first pilot study of neoadjuvant chemotherapy for inoperable LAIBC using MTT assay to predict the chemosensitivity in vitro. Compared with conventional chemotherapy, the clinical response and long-term results seem to be more encouraging.

The Wilms' tumor gene product WT1 mediates the down-regulation of the rat epidermal growth factor receptor by nerve growth factor in PC12 cells

Recently, we characterized the rat epidermal growth factor receptor (EGFR) promoter and demonstrated that TCC repeat sequences are required for the down-regulation of EGFR by nerve growth factor (NGF) in PC12 cells. In this study, we report that the Wilms' tumor gene product WT1, a zinc finger transcription factor, is able to enhance the activity of the rat EGFR promoter in cotransfection assays. Gel mobility shift assays demonstrate that WT1 binds to the TCC repeat sequences of the rat EGFR promoter. Overexpression of WT1 resulted in up-regulation of the expression levels of endogenous EGFR in PC12 cells. Interestingly, NGF down-regulated the expression levels of WT1 and EGFR in PC12 cells, but not in the p140(trk)-deficient variant PC12nnr5 cells or in cells expressing either dominant-negative Ras or dominant-negative Src. Most importantly, we evaluated the inhibitory effect of antisense WT1 RNA on EGFR expression, and we found that antisense WT1 RNA could substantially reduce EGFR repression in either histochemical staining study or immunoblot analysis. These results indicate that NGF-induced down-regulation of the EGFR in PC12 cells is mediated through WT1 and that WT1 may play an important role in the differentiation of nerve cells.

PI-3 kinase and IP3 are both necessary and sufficient to mediate NT3-induced synaptic potentiation

Signaling mechanisms underlying neurotrophic regulation of synaptic transmission are not fully understood. Here we show that neurotrophin-3 (NT3)-induced potentiation of synaptic transmission at the neuromuscular synapses is blocked by inhibition of phosphoinositide-3 kinase, phospholipase C-gamma or the downstream IP3 receptors of phospholipase C-gamma, but not by inhibition of MAP kinase. However, neither stimulation of Ca2+ release from intracellular stores by photolysis of caged IP3, nor expression of a constitutively active phosphoinositide-3 kinase (PI3K*) in presynaptic motoneurons alone is sufficient to enhance transmission. Photo-uncaging of IP3 in neurons expressing PI3K* elicits a marked synaptic potentiation, mimicking the NT3 effect. These results reveal an involvement of PI3 kinase in transmitter release, and suggest that concomitant activation of PI3 kinase and IP3 receptors is both necessary and sufficient to mediate the NT3-induced synaptic potentiation.

Local attenuation of systemically mediated splanchnic vasoconstriction during shock due to cholera

Hypovolemic shock, most often due to hemorrhage, is typically associated with intense splanchnic vasoconstriction. This can be severe enough to impair the functional and structural integrity of the gastrointestinal tract. Paradoxically, with cholera the structure of the gastrointestinal tract is preserved, and the intestine continues to secrete fluid delivered to it in the circulating blood in spite of severe hypovolemic shock. This suggests that splanchnic blood flow is maintained at higher levels in hypovolemic shock due to cholera than in hypovolemic shock due to hemorrhage. Our hypothesis is that cholera toxin in the intestinal lumen activates local mechanisms that attenuate systemically mediated splanchnic vasoconstriction. Blood flow to an isolated ileal segment in situ in the anesthetized rabbit was measured continuously (ultrasound transit-time volume flow probe) for 5 to 6 h after instillation of cholera toxin into the isolated intestinal lumen. Norepinephrine was infused selectively into the mesenteric artery supplying the segment to elicit local responses uncomplicated by compensatory changes secondary to systemic effects of norepinephrine. Baseline vascular conductance increased gradually and became significantly greater in cholera toxin experiments than in vehicle experiments 5 h after treatment (P < 0.035). Animals treated with cholera toxin were less responsive to norepinephrine than vehicle treated animals were (P < 0.05) and became more so over time (P < 0.001). Our conclusion is that cholera toxin activates local mechanisms that attenuate systemically mediated splanchnic vasoconstriction, at least in part by reducing vascular responsiveness to a systemic vasoconstrictor, norepinephrine.

Oxidative inactivation of brain ecto-5'-nucleotidase by thiols/Fe2+ system

5'-Nucleotidase, responsible for the conversion of adenosine-5'-monophosphate into adenosine, was purified from bovine brain membranes, and subjected to oxidative inactivation. The 5'-nucleotidase activity decreased slightly after the exposure to either glutathione or Fe2+. The glutathione-mediated inactivation of 5'-nucleotidase was potentiated remarkably by Fe2+, but not Cu2+, in a concentration-dependent manner. Similarly, glutathione exhibited a concentration-dependent enhancement of the Fe2+-mediated inactivation. In comparison, the glutathione/Fe2+ system was much more effective than the ascorbate/Fe2+ system in inactivating the enzyme. In support of an intermediary role of superoxide ions or H2O2 in the action of glutathione/Fe2+ system, superoxide dismutase and catalase expressed a substantial protection against the inactivation by the glutathione/Fe2+ system. Meanwhile, hydroxyl radical scavengers such as mannitol, benzoate or ethanol were incapable of preventing the inactivation, excluding the participation of extraneous hydroxyl radicals. Whereas adenosine 5'-monophosphate as substrate exhibited a modest protection against the glutathione/Fe2+ action, a remarkable protection was expressed by divalent metal ions such as Zn2+ or Mn2+. Structure-activity study with a variety of thiols indicates that the inactivating action of thiols in combination with Fe2+ resides in the free sulfhydryl group and amino group of thiols. Overall, thiols, expressing more inhibitory effect on the activity of 5'-nucleotidase, were found to be more effective in potentiating the Fe2+-mediated inactivation. Further, kinetic analyses indicate that Fe2+ and thiols inhibit the 5'-nucleotidase in a competitive or uncompetitive manner, respectively. These results suggest that ecto-5'-nucleotidase from brain membrane is one of proteins susceptible to thiols/Fe2+-catalyzed oxidation, and the oxidative inactivation may be related to the selective association of Fe2+ and thiols to the enzyme molecule.

Dual effect of heparin and low molecular weight heparin on cultured smooth muscle cells

The effects of heparin and low molecular weight heparin (LMWH) on the growth of cultured human aortic smooth muscle cells (hASMCs) were studied. The fourth-passage hASMCs were planted onto a 24-well plate (5 wells for each concentration of heparin or LMWH) and cultured by DMEM containing 5% either old or fresh human serum (HS), 10% fetal calf serum (FCS), and differing concentrations of heparin or LMWH (heparin and LMWH were presented as hexuronic acid) together with corresponding control groups (without heparin or LMWH) for 24h. hASMCs growth was estimated both morphologically and by 3H-TdR incorporation. The results revealed that both heparin and LMWH inhibited the proliferation of healthy growth hASMCs, but promoted the proliferation of weak growth hASMCs. These results suggest for the first time that heparin and LMWH have a dual regulative role (inhibition and promotion) in hASMCs growth and indicate that they may play an important role in controlling the proliferation of vascular smooth muscle cells and maintaining the integrity of vascular structure.

Cloning and characterization of the promoter region of the rat epidermal growth factor receptor gene and its transcriptional regulation by nerve growth factor in PC12 cells

Our previous studies have shown that treatment of PC12 cells with nerve growth factor (NGF) causes a profound down-regulation of the epidermal growth factor receptor (EGFR) mRNA and protein. Further, the NGF-induced down-regulation of the EGFR is under transcriptional control. To elucidate the molecular mechanism of this down-regulation we have cloned a 2.7-kilobase sequence from the promoter region of the rat EGFR from a rat P1 library. Six transcriptional start sites were identified by 5'-rapid amplification of cDNA ends and primer extension. Sequence analysis showed a 62% overall homology with the human EGFR promoter region. To investigate its transcription, 1.1 kilobases of the 5'-flanking sequence were fused to a luciferase reporter gene. This sequence exhibited functional promoter activity in transient transfection experiments with PC12, C6, and CV-1 cells. Treatment of PC12 cells with NGF inhibited promoter activity. By transfection of promoter deletion constructs, a silencer element was found between nucleotides -260 and -181, and TCC repeat sequences appeared to be at least partially responsible for the down-regulation of the EGFR by NGF. Supportive evidence for the relevance of this sequence was obtained from gel mobility shift assays and by transfection of TCC mutation constructs. Our results demonstrate that TCC repeat sequences are required for the down-regulation of rat EGFR by NGF in PC12 cells and may lead to the identification of the NGF-responsive transcription factors.

Voltage-sensitive calcium currents are acutely increased by nerve growth factor in PC12 cells

Whole cell calcium currents were recorded from PC12 cells with the perforated patch technique. Currents were evoked by step depolarization from a holding potential of -90 mV. Nerve growth factor (NGF) increased calcium currents through L-type calcium channels by >75% within 3-5 min. This increase was inhibited by K-252a, by nifedipine, and by inhibition or down-regulation of kinase C. Brain-derived neurotrophic factor (BDNF) also increased calcium current, but to a smaller extent. Thus increases in calcium current can be linked to activation of either the high- or the low-affinity nerve growth factor receptor. Increases in presynaptic calcium uptake appear to be a crucial element in the short-term actions of the neurotrophins on neurotransmitter release leading to long-term potentiation. Also, the control of calcium uptake is likely to be an important factor in the long-term actions of the neurotrophins on neuronal survival and neuronal protection. The present data indicate that the PC12 cell may be a useful model for studying the effect of the neurotrophins on calcium uptake.

Regulation and inactivation of brain phosphocholine-phosphatase activity

Regulation of phosphocholine-hydrolyzing phosphatase (phosphocholine-phosphatase) activity, purified from bovine brain, was examined under physiological conditions. Various endogenous phosphomonoesters, which were utilized as substrate, inhibited the phosphocholine-phosphatase activity competitively (Ki, 5.5-82.0 microM); among phosphomonoesters tested, there was a similar order of capability between the binding affinity of substrate and the inhibitory potency. In addition, phosphate ions also inhibited the phosphatase activity competitively with a Ki value of approximately 167 microM. Although leucine or theophylline inhibited the phosphatase activity at pH 9.0, their inhibitory action decreased greatly at pH 7.4. The pH-Km and pH-Vm profiles indicate that ionizable amino acids are involved in substrate binding as well as catalysis, alluding that the phosphatase activity may be highly dependent on the intracellular pH. Amino acid modification study supports the existence of tyrosine, arginine or lysine residue in the active site, and the participation of tyrosine residue in the catalytic action may be suggested positively from the susceptibiliy to the action of tetranitromethane or HOI-generator. Separately, the oxidative inactivation of phosphocholine-phosphatase activity was investigated. Of oxidants tested, HOONO, HOCl, HOI and ascorbate/Cu2+ system were effective to inactivate the phosphatase activity. Noteworthy, a remarkable inactivation was accomplished by 30 microM HOCl in combination with 1 mM KI. In addition, Cu2+ (3 microM) in combination with ascorbate at concentrations as low as 0.1-0.3 mM reduced the phosphatase activity to a great extent. From these results, it is proposed that the phosphocholine-phosphatase activity may be regulated endogenously and susceptible to the various oxidant systems in vivo.

Nerve growth factor (NGF)-induced calcium influx and intracellular calcium mobilization in 3T3 cells expressing NGF receptors

The neurotrophins have been implicated in the acute regulation of synaptic plasticity. Neurotrophin-stimulated presynaptic calcium uptake appears to play a key role in this process. To understand the mechanism of neurotrophin-stimulated calcium uptake, the regulation of calcium uptake and intracellular mobilization by nerve growth factor (NGF) was investigated using NIH 3T3 cells stably transfected with either the high affinity NGF receptor p140(trk) (3T3-Trk) or the low affinity NGF receptor p75(NGFR) (3T3-p75). In 3T3-Trk cells, NGF increased both calcium uptake and intracellular calcium mobilization. In 3T3-p75 cells, NGF increased calcium uptake but not intracellular calcium mobilization. K-252a alone increased intracellular calcium in 3T3-Trk cells but not in 3T3-p75 cells. Nifedipine, an inhibitor of calcium uptake through L-type calcium channels, inhibited the action of NGF on both 3T3-Trk cells and 3T3-p75 cells, indicating that both p140(trk) and p75(NGFR) receptors are linked to nifedipine-sensitive L-type calcium channels. These studies show that either NGF receptor will support increases in intracellular calcium but that p140(trk) does so by increasing both uptake and mobilization, whereas p75(NGFR) does so by increasing uptake only.