Estrogen receptor status in breast cancer is associated with remarkably distinct gene expression patterns

To investigate the phenotype associated with estrogen receptor alpha (ER) expression in breast carcinoma, gene expression profiles of 58 node-negative breast carcinomas discordant for ER status were determined using DNA microarray technology. Using artificial neural networks as well as standard hierarchical clustering techniques, the tumors could be classified according to ER status, and a list of genes which discriminate tumors according to ER status was generated. The artificial neural networks could accurately predict ER status even when excluding top discriminator genes, including ER itself. By reference to the serial analysis of gene expression database, we found that only a small proportion of the 100 most important ER discriminator genes were also regulated by estradiol in MCF-7 cells. The results provide evidence that ER+ and ER- tumors display remarkably different gene-expression phenotypes not solely explained by differences in estrogen responsiveness.

Comparison of epinephrine with vasopressin on bone marrow blood flow in an animal model of hypovolemic shock and subsequent cardiac arrest

OBJECTIVE

The intraosseous route is an emergency alternative for the administration of drugs and fluids if vascular access cannot be established. However, in hemorrhagic shock or after vasopressors are given during resuscitation, bone marrow blood flow may be decreased, thus impairing absorption of intraosseously administered drugs. In this study, we evaluated the effects of vasopressin vs. high-dose epinephrine in hemorrhagic shock and cardiac arrest on bone marrow blood flow.

DESIGN

Prospective, randomized laboratory investigation that used an established porcine model for measurement of hemodynamic variables and organ blood flow.

SETTING

University hospital laboratory.

SUBJECTS

Fourteen pigs weighing 30 +/- 3 kg.

INTERVENTIONS

Radiolabeled microspheres were injected to measure bone marrow blood flow during a prearrest control period and during hypovolemic shock produced by rapid hemorrhage of 35% of the estimated blood volume. In the second part of the study, ventricular fibrillation was induced; after 4 mins of untreated cardiac arrest and 4 mins of standard cardiopulmonary resuscitation, a bolus dose of either 200 microg/kg epinephrine (n = 6) or 0.8 units/kg vasopressin (n = 6) was administered. Defibrillation was attempted 2.5 mins after drug administration, and blood flow was assessed again at 5 and 30 mins after successful resuscitation.

MEASUREMENTS AND MAIN RESULTS

Mean +/- sem bone marrow blood flow decreased significantly during induction of hemorrhagic shock from 14.4 +/- 4.1 to 3.7 +/- 1.8 mL.100 g-1.min-1 in the vasopressin group and from 18.2 +/- 4.0 to 5.2 +/- 1.0 mL.100 g-1.min-1 in the epinephrine group (p =.025 in both groups). Five minutes after return of spontaneous circulation, mean +/- sem bone marrow blood flow was 3.4 +/- 1.1 mL.100 g-1.min-1 after vasopressin and 0.1 +/- 0.03 mL.100 g-1.min-1 after epinephrine (p =.004 for vasopressin vs. epinephrine). At the same time, bone vascular resistance was significantly (p =.004) higher in the epinephrine group when compared with vasopressin (1455 +/- 392 vs. 43 +/- 19 mm Hg. mL-1.100 g.min, respectively).

CONCLUSIONS

Bone blood flow responds actively to both the physiologic stress response of hemorrhagic shock and vasopressors given during resuscitation after hypovolemic cardiac arrest. In this regard, bone marrow blood flow after successful resuscitation was nearly absent after high-dose epinephrine but was maintained after high-dose vasopressin. These findings emphasize the need for pressurized intraosseous infusion techniques, because bone marrow blood flow may not be predictable during hemorrhagic shock and drug therapy.

Effect of physical and chemical methods of homogenization on inflammatory mediators in sputum of asthma patients

BACKGROUND

Dithiothreitol (DTT), which is used for sputum homogenization, may split S-S bonds of the bronchial mucins as well as other proteins and, thus, may have a detrimental effect on inflammatory mediators that are present in sputum.

OBJECTIVE

To evaluate the effects of physical sputum homogenization, using ultrasonic and chemical (ie, DTT) means, on the concentrations of eosinophil cationic protein (ECP), eosinophil protein X (EPX), eosinophil peroxidase (EPO), and myeloperoxidase (MPO) in the sputum of patients with asthma.

METHODS

The collection of sputum samples from nine patients with asthma was induced by their inhaling a sterile 3% saline solution for 10 min from an ultrasonic nebulizer. One half of the sputum sample was homogenized by ultrasound, and the other half was liquefied by DTT. The supernatant of the ultrasonically homogenized specimen was divided into the following three portions: (1) immediately frozen; (2) stored for 15 min at 37 degrees C; and (3) additionally treated with DTT. The supernatant of the sputum sample that was liquefied by DTT was divided into the following two portions: (1) immediately frozen; and (2) additionally subjected to ultrasound. The concentrations of ECP, EPO, EPX, and MPO in the sputum samples were measured using immunoassays.

RESULTS

Statistically significant differences were found between the ultrasonically homogenized specimens that had been either processed immediately or stored at 37 degrees C and those treated by DTT, but only for concentrations of EPO and MPO (p < 0.005). No effect of temperature on the mediators in the ultrasonically homogenized specimens could be detected. Ultrasonic homogenization had no influence on the mediators in the samples liquefied by DTT. However, the addition of DTT to the cell-free supernatant of the ultrasonically homogenized sputum samples caused a significant fall in measured EPO and MPO concentrations.

CONCLUSIONS

The sputum processing by DTT caused a statistically significant fall in EPO and MPO concentrations but did not significantly influence the measured concentrations of ECP and EPX.

Adsorption and desorption of chemotherapeutic drugs from a magnetically targeted carrier (MTC)

Magnetically targeted carriers (MTCs) are composite microparticles made from metallic iron and activated carbon. Particles, loaded with doxorubicin in the pharmacy (MTC-DOX), are infused intra-arterially through the artery feeding the tumor. With the aid of an externally positioned permanent dipole magnet, they can be localized and retained within a tumor mass. MTC-DOX is currently in use in a Phase I/II clinical study as a delivery vehicle for doxorubicin in primary hepatocellular carcinoma. The adsorption and desorption of doxorubicin, mitomycin C, camptothecin, methotrexate, verapamil and 9AC onto MTCs have been analyzed. Each of these chemotherapeutic agents has a different mechanism of action, suggesting that some benefit may be derived from combined delivery to a tumor using MTCs and magnetic targeting. Each drug displays different behavior with respect to adsorption and desorption. However, this behavior can be described for each drug with a non-linear thermodynamic model. The thermodynamic model predicts a controlled release rate by adjusting a number of parameters, including initial drug loading concentrations. This is confirmed with in vitro extraction experiments using human plasma as the extraction medium.

The future of optimism

Recent theoretical discussions of optimism as an inherent aspect of human nature converge with empirical investigations of optimism as an individual difference to show that optimism can be a highly beneficial psychological characteristic linked to good mood, perseverance, achievement, and physical health. Questions remain about optimism as a research topic and more generally as a societal value. Is the meaning of optimism richer than its current conceptualization in cognitive terms? Are optimism and pessimism mutually exclusive? What is the relationship between optimism and reality, and what are the costs of optimistic beliefs that prove to be wrong? How can optimism be cultivated? How does optimism play itself out across different cultures? Optimism promises to be one of the important topics of interest to positive social science, as long as it is approached in an even-handed way.

Designing clinical trials on energy healing: ancient art encounters medical science

Demand for energy healing is growing rapidly in the United States. Until recently, however, few clinical trials have been conducted to investigate its clinical efficacy, risks, and cost-effectiveness. This article discusses principles underlying the research design of clinical trials on energy healing, based on the experience of an interdisciplinary team conducting a large-sample clinical study on qigong funded by the National Institutes of Health. The first part overviews the background and contemporary practice of qigong therapy. The second addresses some difficulties and unique issues to be considered in designing a clinical trial on energy healing. These issues include research emphasis on outcome versus mechanism, randomization, control, expectations/placebo effects, staff and practitioner bias/conflict of interest, patients' belief, selection bias, intent-to-treat analysis, ethics, informed consent, sample size, and outcome report. The ultimate goal is to promote more scholarly and clinical discussion on the evaluation of energy healing.

Composition and mass of the bacteriophage phi29 prohead and virion

The protein composition of the Bacillus subtilis bacteriophage phi29 prohead and virion was determined by combustion of gel bands of (3)H-labeled proteins. Copy numbers of individual proteins were calculated relative to the 12 copies of the head-tail connector protein. The mean numbers of copies of the major capsid protein in the prohead and virion were 241 and 218, respectively, approaching the 235 copies determined previously by cryoelectron microscopy. The mean numbers of copies of the dimeric head fiber on the prohead and virion were 24 and 31, respectively, demonstrating partial occupancy of the 55 fiber binding sites. Measured copies of neck and tail proteins in the virion included 11 of the lower collar, 58 of the appendage, and 9 of the tail; if the true copies of these proteins are 12, 60, and 9, respectively, the entire neck and tail of phi29 has quasi-sixfold symmetry. The mass of the fiberless prohead with pRNA was about 14.2 MDa, and the mass of the prohead determined by scanning transmission electron microscopy was consistent with the biochemical data. The mass of the fiberless virion containing the 12.8-MDa DNA genome was about 30.4 MDa. A full complement of dimeric fibers on the prohead or virion would increase the mass of the particle by about 3.2 MDa. The data complement studies relating the structure of phi29 components to dynamic functions in morphogenesis and infection.

Classification and diagnostic prediction of cancers using gene expression profiling and artificial neural networks

The purpose of this study was to develop a method of classifying cancers to specific diagnostic categories based on their gene expression signatures using artificial neural networks (ANNs). We trained the ANNs using the small, round blue-cell tumors (SRBCTs) as a model. These cancers belong to four distinct diagnostic categories and often present diagnostic dilemmas in clinical practice. The ANNs correctly classified all samples and identified the genes most relevant to the classification. Expression of several of these genes has been reported in SRBCTs, but most have not been associated with these cancers. To test the ability of the trained ANN models to recognize SRBCTs, we analyzed additional blinded samples that were not previously used for the training procedure, and correctly classified them in all cases. This study demonstrates the potential applications of these methods for tumor diagnosis and the identification of candidate targets for therapy.

Imaging of small-scale features on 433 Eros from NEAR: evidence for a complex regolith

On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks.

Exercise in 94 degrees F water for a patient with multiple sclerosis

BACKGROUND AND PURPOSE

The purpose of this case report is to describe the examination, intervention, and outcome of a patient with multiple sclerosis (MS) who participated in a comprehensive rehabilitation program that included aquatic therapy with a pool temperature of 94 degrees F. There are few descriptions of aquatic exercise programs on muscle force, exercise tolerance, and functional outcomes in individuals with MS, and most authors recommend a water temperature of less than 85 degrees F to prevent an exacerbation of symptoms.

DESCRIPTION

The patient was a 33-year-old woman. Before, during, and after the aquatic program, she was monitored for body temperature, heart rate, blood pressure, and perceived exertion. She was also assessed for muscle force and functional abilities.

OUTCOMES

The patient did not experience heat sensitivity or fatigue throughout the program, and her manual muscle test grades and mobility improved.

DISCUSSION

This patient's participation in aquatic therapy, in conjunction with land-based interventions, may have been associated with the improvement in functional abilities.

Child sexual abuse, peer sexual abuse, and sexual assault in adulthood: a multi-risk model of revictimization

This study explored the predictors and consequences of sexual assault occurring after the age of 16 years in a nonclinical sample of women. Child sexual abuse occurring before the age of 16 years was the only predictor of later sexual assault among comorbid risk factors. Peer sexual abuse, number of perpetrators, age at time of sexual abuse, and severity of sexual abuse did not increase the risk for later sexual assault. Adult sexual assault victims showed lower levels of mental health functioning than did survivors of child or peer sexual abuse. We discuss a specificity model of revictimization and the differential effects of child, peer, and adult sexual trauma on the developmental trajectory of sexual violence and psychosocial functioning.

Bioanalysis of racemic reboxetine and its desethylated metabolite in a therapeutic drug monitoring setting using solid phase extraction and HPLC

Reboxetine is a new antidepressant drug acting as a potent and selective noradrenaline reuptake inhibitor on the noradrenergic neuronal system. Because of an expected interindividual variability in drug metabolism in the clinical practice the need for therapeutic drug monitoring routines in psychiatry is always a prominent feature. In this application, the preferred bioanalytic methodology was solid phase extraction combined with reversed-phase high-performance liquid chromatography and ultraviolet detection at 210 nm. The technique proved reliable, with interday and intraday variation of less than 5% and a quantification limit for reboxetine and one of its main metabolites O-desethylreboxetine (O-reboxetine) at 5 and 30 nmol/L, respectively. The method was applied on serum samples from 38 patients treated chronically with reboxetine. These samples were drawn as trough levels in steady state with a dosage range of 2-16 mg/day. They evidenced a mean reboxetine concentration that was fairly linear and dose proportional, although the variance in concentration was large between patients, even those taking the same dosage. O-reboxetine was detected in quantifiable amounts in only 1 of the 38 patients (<3%). In conclusion, these results suggest that a routine reboxetine therapeutic drug monitoring service that is robust enough to produce reliable and reproducible results may be introduced into everyday clinical practice.

Granulocyte markers in induced sputum in patients with respiratory disorders and healthy persons obtained by two sputum-processing methods

Induced sputum is increasingly used to detect and monitor airway inflammation in respiratory diseases. However, the processing of sputum has been rather laborious for clinical practice. The aim of this study was to improve the practicality of induced-sputum studies by simplifying sample processing. Eosinophil cationic protein (ECP), eosinophil peroxidase (EPO), neutrophil lipocalin (HNL) and myeloperoxidase (MPO) were used as biochemical markers of airway inflammation and the results of the study method were compared with a previously validated (reference) method. Induced sputum was obtained from 42 healthy controls, 10 subjects with acute respiratory infection, eight patients with chronic obstructive pulmonary disease (COPD) and 17 asthmatics. The sputum sample was divided into two parts and treated either: (i) by the reference method (released markers), where sputum was homogenized with dithiotreitol and centrifuged to yield cell-free supernatant and a cell pellet, or (ii) by the study method (total markers), where the cells were lysed after homogenization so that cell-associated markers were released and solubilized. For comparison, the four biochemical markers were measured in sputum supernatant and in sputum lysate. The differential cell count was performed from the cell pellet in the reference method. Repeatability was assessed in a group of 16 subjects. The effect of reagents and the recovery of assays were also evaluated. Released and total markers correlated well (ECP r(s)=0.80, P<0.0001; EPO r(s)=0.49, P<0.0001; HNL r(s)=0.87, P<0.0001; MPO r(s)=0.71, P<0.0001). Incubation with dithiotreitol and lysis reagent had no negative influence on marker assays. The within-subject variability of total ECP, MPO and HNL in both methods was small in two measurements taken I week apart. The study method, measuring total inflammatory markers, gave comparable results to the reference method, measuring released markers. In the study method the sputum processing was simplified, which may improve its applicability.

Comparison of epinephrine and vasopressin in a pediatric porcine model of asphyxial cardiac arrest

OBJECTIVE

This study was designed to compare the effects of vasopressin vs. epinephrine vs. the combination of epinephrine with vasopressin on vital organ blood flow and return of spontaneous circulation in a pediatric porcine model of asphyxial arrest.

DESIGN

Prospective, randomized laboratory investigation using an established porcine model for measurement of hemodynamic variables, organ blood flow, blood gases, and return of spontaneous circulation.

SETTING

University hospital laboratory.

SUBJECTS

Eighteen piglets weighing 8-11 kg.

INTERVENTIONS

Asphyxial cardiac arrest was induced by clamping the endotracheal tube. After 8 mins of cardiac arrest and 8 mins of cardiopulmonary resuscitation, a bolus dose of either 0.8 units/kg vasopressin (n = 6), 200 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered in a randomized manner. Defibrillation was attempted 6 mins after drug administration.

MEASUREMENTS AND MAIN RESULTS

Mean +/- SEM coronary perfusion pressure, before and 2 mins after drug administration, was 13 +/- 2 and 23 +/- 6 mm Hg in the vasopressin group; 14 +/- 2 and 31 +/- 4 mm Hg in the epinephrine group; and 13 +/- 1 and 33 +/- 6 mm Hg in the epinephrine-vasopressin group, respectively (p = NS). At the same time points, mean +/- SEM left ventricular myocardial blood flow was 44 +/- 31 and 44 +/- 25 mL x min-(1) x 100 g(-1) in the vasopressin group; 30 +/- 18 and 233 +/- 61 mL x min(-1) x 100 g(-1) in the epinephrine group; and 36 +/- 10 and 142 +/- 57 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p < .01 epinephrine vs. vasopressin; p < .02 epinephrine-vasopressin vs. vasopressin). Total cerebral blood flow trended toward higher values after epinephrine-vasopressin (60 +/- 19 mL x min(-1) x 100 g(-1)) than after vasopressin (36 +/- 17 mL x min(-1) x 100 g(-1)) or epinephrine alone (31 +/- 7 mL x min(-1) x 100 g(-1); p = .07, respectively). One of six vasopressin, six of six epinephrine, and four of six epinephrine-vasopressin-treated animals had return of spontaneous circulation (p < .01, vasopressin vs. epinephrine).

CONCLUSIONS

Administration of epinephrine, either alone or in combination with vasopressin, significantly improved left ventricular myocardial blood flow during cardiopulmonary resuscitation. Return of spontaneous circulation was significantly more likely in epinephrine-treated pigs than in animals resuscitated with vasopressin alone.

Differential processing of UV mimetic and interstrand crosslink damage by XPF cell extracts

We have recently developed a mammalian cell free assay in which interstrand crosslinks induce DNA synthesis in both damaged and undamaged plasmids co-incubated in the same extract. We have also shown using hamster mutants that both ERCC1 and XPF are required for the observed incorporation. Here, we show that extracts from an XPF patient cell line differentially process UV mimetic damage and interstrand crosslinks in vitro. XPF extracts are highly defective in the stimulation of repair synthesis by N:-acetoxy-N:- acetylaminofluorene, but are proficient in the stimulation of DNA synthesis by psoralen interstrand crosslinks. In addition, we show that extracts from the hamster UV140 mutant, which has high UV sensitivity, but moderate mitomycin C sensitivity, are similar in both assays to XPF cell extracts. These findings support the hypothesis that the activities of XPF in nucleotide excision repair (NER) and crosslink repair are separable, and that mutations in XPF patients result in the abolition of NER, but not recombinational repair pathways, which are likely to be essential as has been observed in ERCC1 homozygous -/- mice.

Pyrogenic reactions associated with single daily dosing of intravenous gentamicin

OBJECTIVE

To identify risk factors associated with an unexpected outbreak of pyrogenic reactions (PR) following intravenous gentamicin.

DESIGN

We conducted two cohort studies. PRs were defined as chills, rigors, or shaking within 3 hours after initiating the gentamicin infusion during the preepidemic (December 1, 1997-January 15, 1998) or epidemic (May 1-June 15, 1998) periods. We tested gentamicin vials for endotoxin using the limulus amebocyte lysate assay.

SETTING

Inpatient services of a large community hospital in Los Angeles, California.

RESULTS

During the epidemic period, 22 (15%) of 152 patients developed documented PRs following intravenous gentamicin. PRs were more likely among patients receiving single daily dosing (SDD) than multiple daily dosing gentamicin (20/73 [27%] vs. 2/79 [3%]; relative risk, 10.8; 95% confidence interval, 2.6 44.7). Laboratory analysis of gentamicin vials found endotoxin levels that were higher among Fujisawa-brand gentamicin (implicated brand) than gentamicin used after the outbreak terminated (non-implicated brand). Although endotoxin levels in the vials did not exceed US Pharmacopeia limits (1.7 endotoxin units/mg gentamicin), the use of SDD gentamicin may place patients at greater risk of receiving doses of endotoxin above the threshold for PRs in humans.

CONCLUSIONS

Reassessment of the acceptable amounts of endotoxin in gentamicin and other parenteral products should be considered when dosing intervals used in clinical practice change.

Strengths and limitations of molecular subtyping in a community outbreak of Legionnaires' disease

An epidemiological and microbiological investigation of a cluster of eight cases of Legionnaires' disease in Los Angeles County in November 1997 yielded conflicting results. The epidemiological part of the investigation implicated one of several mobile cooling towers used by a film studio in the centre of the outbreak area. However, water sampled from these cooling towers contained L. pneumophila serogroup 1 of another subtype than the strain that was recovered from case-patients in the outbreak. Samples from two cooling towers located downwind from all of the case-patients contained a Legionella strain that was indistinguishable from the outbreak strain by four subtyping techniques (AP-PCR, PFGE, MAb, and MLEE). It is unlikely that these cooling towers were the source of infection for all the case-patients, and they were not associated with risk of disease in the case-control study. The outbreak strain also was not distinguishable, by three subtyping techniques (AP-PCR, PFGE, and MAb), from a L. pneumophila strain that had caused an outbreak in Providence, RI, in 1993. Laboratory cross-contamination was unlikely because the initial subtyping was done in different laboratories. In this investigation, microbiology was helpful for distinguishing the outbreak cluster from unrelated cases of Legionnaires' disease occurring elsewhere. However, multiple subtyping techniques failed to distinguish environmental sources that were probably not associated with the outbreak. Persons investigating Legionnaires' disease outbreaks should be aware that microbiological subtyping does not always identify a source with absolute certainty.

Downregulation of telomerase reverse transcriptase mRNA expression by wild type p53 in human tumor cells

The p53 tumor suppressor protein inhibits the formation of tumors through induction of cell cycle arrest and/or apoptosis. In the present study we demonstrated that p53 is also a powerful inhibitor of human telomerase reverse transcriptase (hTERT), a key component for telomerase. Activation of either exogenous temperature-sensitive (ts) p53 in BL41 Burkitt lymphoma cells or endogenous wild type (wt) p53 at a physiological level in MCF-7 breast carcinoma cells triggered a rapid downregulation of hTERT mRNA expression, independently of the induction of the p53 target gene p21. Co-transfection of an hTERT promoter construct with wt p53 but not mutant p53 in HeLa cells inhibited the hTERT promoter activity. Furthermore, the activation of the hTERT promoter in Drosophila Schneider SL2 cells was completely dependent on the ectopic expression of Sp1 and was abrogated by wt p53. Finally, wt p53 inhibited Sp1 binding to the hTERT proximal promoter by forming a p53-Sp1 complex. Since activation of telomerase, widely observed in human tumor cell lines and primary tumors, is a critical step in tumorigenesis, wt p53-triggered inhibition of hTERT/telomerase expression may reflect yet another mechanism of p53-mediated tumor suppression. Our findings provide new insights into both the biological function of p53 and the regulation of hTERT/telomerase expression.

Aspects of delayed chemotherapy-induced nausea. Dexamethasone and adrenal response patterns in patients and healthy volunteers

Delayed chemotherapy-induced nausea is still a clinical problem, and the underlying mechanisms are poorly understood. Previous studies have suggested that corticosteroids are involved, although the mechanisms by which corticosteroids exert their antiemetic effect are largely unknown. We have previously found impaired control of delayed nausea after injection of dexamethasone. The possibility of differences in the recovery of the hypothalamic-pituitary-adrenal (HPA) axis after injection of dexamethasone was investigated in patients (n = 5) with gynaecological cancer being treated with platinum-based chemotherapy and in healthy female volunteers (n = 10). Urinary free cortisol was used to assess the levels of endogenous cortisol. Results showed that in both patients and controls injections of dexamethasone led to a significant decline in endogenous cortisol levels in 24 h and a subsequent significant recovery in the next 24 h. We conclude that the recovery of the HPA axis is rapid after a single dose of dexamethasone in patients and controls. The absence of an abnormal response pattern in patients makes it probable that the suppression and recovery of the HPA axis after injection of dexamethasone does not influence the corticosteroid-induced rebound effect on delayed platinum-induced nausea.

Molecular cloning and characterization of a lipid phosphohydrolase that degrades sphingosine-1- phosphate and induces cell death

Sphingosine and sphingosine-1-phosphate (SPP) are interconvertible sphingolipid metabolites with opposing effects on cell growth and apoptosis. Based on sequence homology with LBP1, a lipid phosphohydrolase that regulates the levels of phosphorylated sphingoid bases in yeast, we report here the cloning, identification, and characterization of a mammalian SPP phosphatase (mSPP1). This hydrophobic enzyme, which contains the type 2 lipid phosphohydrolase conserved sequence motif, shows substrate specificity for SPP. Partially purified Myc-tagged mSPP1 was also highly active at dephosphorylating SPP. When expressed in yeast, mSPP1 can partially substitute for the function of LBP1. Membrane fractions from human embryonic kidney HEK293 cells transfected with mSPP1 markedly degraded SPP but not lysophosphatidic acid, phosphatidic acid, or ceramide-1-phosphate. Enforced expression of mSPP1 in NIH 3T3 fibroblasts not only decreased SPP and enhanced ceramide levels, it also markedly diminished survival and induced the characteristic traits of apoptosis. Collectively, our results suggest that SPP phosphohydrolase may regulate the dynamic balance between sphingolipid metabolite levels in mammalian cells and consequently influence cell fate.

Clustering ECG complexes using hermite functions and self-organizing maps

An integrated method for clustering of QRS complexes is presented which includes basis function representation and self-organizing neural networks (NN's). Each QRS complex is decomposed into Hermite basis functions and the resulting coefficients and width parameter are used to represent the complex. By means of this representation, unsupervised self-organizing NN's are employed to cluster the data into 25 groups. Using the MIT-BIH arrhythmia database, the resulting clusters are found to exhibit a very low degree of misclassification (1.5%). The integrated method outperforms, on the MIT-BIH database, both a published supervised learning method as well as a conventional template cross-correlation clustering method.