Cryoballoon ablation of left atrial roof with a novel cryoballoon system

Introduction

A novel cryoballoon system (POLARx) has emerged and its efficacy regarding pulmonary vein isolation (PVI) has been already investigated. On the other hand, cryoballoon ablation of left atrial (LA) roof has been performed using a conventional cryoballoon system (Arctic Front Advance Pro [AFA-Pro]) in addition to PVI. However, cryoballoon ablation of LA roof with POLARx has not been investigated yet.

Methods

We performed cryoballoon ablation of LA roof with POLARx in 22 patients after we achieved PVI. After the cryoballoon ablation, complete conduction block at LA roof and isolation of all PVs were confirmed by creating an activation map during high right atrium pacing. If they could not be obtained with solely a cryoballoon, touch up ablation with radiofrequency ablation was permitted. The procedural data during ablation with POLARx was compared with those during ablation with AFA-Pro we had performed in a historical cohort of patients (n=46).

Results

Complete conduction block at LA roof without touch up ablation could be obtained in all the patients in POLARx group and 44 (95.7%) patients in AFA-Pro group. Total procedure time was almost similar in both groups (164.2±35.4 min for POLARx vs 180.3±35.4 min for AFA-Pro, p=0.10). During LA roof line ablation, nadir balloon temperature was significantly lower in POLARx group (right side: −53.6±4.4°C for POLARx vs −45.6±4.6°C for AFA-Pro, p<0.01, central part: −56.4±4.3°C for POLARx vs −46.0±3.7°C for AFA-Pro, p<0.01, left side: −55.1±3.5°C for POLARx vs −45.7±5.3°C for AFA-Pro, p<0.01), and balloon temperature reached −40°C earlier in POLARx (right side: 30.7±8.9 sec for POLARx vs 78.0±39.8 sec for AFA-Pro, p<0.01, central part: 30.6±9.3 sec for POLARx vs 65.9±33.3 sec for AFA-Pro, p<0.01, left side: 30.4±4.2 sec for POLARx vs 78.8±49.6 sec for AFA-Pro, p<0.01). Total freezing time required for LA roof line ablation was significantly shorter in POLARx group (589.3±163.6 sec for POLARx vs 877.5±191.7 sec for AFA-Pro, p<0.01).The scar area created after LA roof line ablation was similar in both groups (9.3±4.1 cm2 for POLARx vs 11.0±4.8 cm2 for AFA-Pro, p=0.23).

Conclusion

Complete conduction block at LA roof could be obtained after cryoballoon ablation with POLARx, in the same way as AFA-Pro. Lower nadir balloon temperature could be expected in shorter freezing time during LA roof line ablation in using POLARx compared with AFA-Pro.

Funding Acknowledgement

Type of funding sources: None.

How to perform effective cryoballooon ablation of left atrial roof: considerations after experiences of more than 1000 cases

Introduction

Although pulmonary vein isolation is the cornerstone of atrial fibrillation (AF) ablation, concomitant cryoballoon ablation of left atrial (LA) roof has been expected to improve clinical outcomes after ablation. We demonstrate characteristics and efficacy of cryoballoon ablation of LA roof through our experiences from a large volume of procedures.

Methods

We had performed cryoballoon ablation of LA roof in 1036 procedures including 202 redo procedures in AF patients since June 2016. Among these procedures, we analyzed 834 patients (309 paroxysmal AF) who had undergone de novo ablation for AF. We confirmed whether the complete conduction block of LA roof line was obtained after the ablation.

Results

LA roof line block was obtained in 767 patients (92.0%) without touch up ablation with a radiofrequency catheter (Group A). LA diameter (LAD) was significantly smaller (43.6±6.6mm vs 47.4±7.5mm, p<0.01) and body mass index (BMI) was significantly lower (24.9±4.0kg/m2 vs 26.3±4.6kg/m2, p=0.01) in those in Group A compared with those without LA roof line block after cryoballoon ablation (Group B). Compared with those in Group B, cryoballoon application number of LA roof (4.1±1.2 vs 4.5±1.6, p<0.01) and mean nadir of cryoballoon temperature during cryoballoon ablation of LA roof (−44.5±5.6°C vs −40.5±7.5°C, p<0.01) were significantly lower in those in Group A. Regarding cryoballoon application number, the number of the cryoballoon application in which a cryoballoon was applied to LA roof with the guiding catheter located in a left superior pulmonary vein (LSPV) was significantly lower in patients in Group A (1.3±0.8 vs 1.6±1.0, p=0.02), and when the number was less than 2, mean nadir of cryoballoon temperature was significantly lower compared with when it was 2 or more than 2 (−44.8±5.8°C vs −42.8±5.6°C, p<0.01). Among those refer to first ablation procedures, one-year Kaplan-Meier atrial arrhythmias free rate estimates, 80.6% for those in Group A and 59.0% for those in Group B (p<0.01). Multivariate analysis identified LA roof line block without touch up ablation as one of the predictors of atrial arrhythmias recurrences. Atrial tachycardia depending on LA roof occurred after cryoballoon ablation of LA roof in 8 patients, although LA roof line block without touch up ablation could be obtained in the index ablation procedure in 6 patients among them.

Conclusion

LA roof line block could be obtained by solely cryoballoon with a reasonable success rate, especially in those with smaller LAD and lower BMI. To obtaine LA roof line block, cryoballoon ablation with the guiding catheter located in LSPV is preferable. LA roof line block without touch up ablation brings better clinical outcomes in those who underwent cryoballoon ablation of LA roof.

Funding Acknowledgement

Type of funding sources: None.

Effects of antipsychotics on intravenous sedation with midazolam and propofol during dental treatment for patients with intellectual disabilities

BACKGROUND

Some patients with intellectual disabilities (ID) are prescribed antipsychotic drugs for symptomatic treatment of behavioural disorders. Nevertheless, it can still prove difficult to perform dental treatments safely for some patients with ID. In such cases, treatment under intravenous sedation (IVS) is one option. Sedative, hypnotic and α-blocking effects of antipsychotic drugs may cause adverse events, such as severe hypotension, among patients who take antipsychotic drugs regularly. This study aimed to investigate the effects of oral antipsychotic medication on cardiovascular function during IVS. Accordingly, we compared mean blood pressure (MBP) and heart rate (HR) between patients who regularly take antipsychotic drugs and patients who do not.

METHODS

Thirty-seven patients with ID were enrolled in this study. All participants were outpatients of Special Care Dentistry of general hospital and received dental treatment under IVS performed with a combination of midazolam and propofol. Eighteen patients regularly took antipsychotics (medication group), and 19 patients were not currently taking antipsychotics (non-medication group). MBP, HR, dose, and effect-site concentration of intravenous sedative medications were measured at three points: 'before IVS', 'at optimal sedation', and 'during dental treatment'.

RESULTS

The magnitude of reduction of MBP was significantly smaller in the medication group than in the non-medication group (P < 0.023). However, there were no differences in MBP, HR, dose, and effect-site concentration of midazolam and propofol between groups at any point.

CONCLUSION

These results suggest that antipsychotic medication may not have clinically significant adverse effects on cardiovascular fluctuations during dental treatment under IVS for persons with ID.

Conserved HORMA domain-containing protein Hop1 stabilizes interaction between proteins of meiotic DNA break hotspots and chromosome axis

HORMA domain-containing proteins such as Hop1 play crucial regulatory roles in various chromosomal functions. Here, we investigated roles of the fission yeast Hop1 in the formation of recombination-initiating meiotic DNA double strand breaks (DSBs). Meiotic DSB formation in fission yeast relies on multiple protein-protein interactions such as the one between the chromosome axial protein Rec10 and the DSB-forming complex subunit Rec15. Chromatin immunoprecipitation sequencing demonstrated that Hop1 is colocalized with both Rec10 and Rec15, and we observed physical interactions of Hop1 to Rec15 and Rec10. These results suggest that Hop1 promotes DSB formation by interacting with both axis components and the DSB-forming complex. We also show that Hop1 binding to DSB hotspots requires Rec15 and Rec10, while Hop1 axis binding requires Rec10 only, suggesting that Hop1 is recruited to the axis via Rec10, and to hotspots by hotspot-bound Rec15. Furthermore, we introduced separation-of-function Rec10 mutations, deficient for interaction with either Rec15 or Hop1. These single mutations and hop1Δ conferred only partial defects in meiotic recombination, while the combining the Rec15-binding-deficient rec10 mutation with hop1Δ synergistically reduced meiotic recombination, at least at a model hotspot. Taken together, Hop1 likely functions as a stabilizer for Rec15–Rec10 interaction to promote DSB formation.

Replication stress induces accumulation of FANCD2 at central region of large fragile genes

During mild replication stress provoked by low dose aphidicolin (APH) treatment, the key Fanconi anemia protein FANCD2 accumulates on common fragile sites, observed as sister foci, and protects genome stability. To gain further insights into FANCD2 function and its regulatory mechanisms, we examined the genome-wide chromatin localization of FANCD2 in this setting by ChIP-seq analysis. We found that FANCD2 mostly accumulates in the central regions of a set of large transcribed genes that were extensively overlapped with known CFS. Consistent with previous studies, we found that this FANCD2 retention is R-loop-dependent. However, FANCD2 monoubiquitination and RPA foci formation were still induced in cells depleted of R-loops. Interestingly, we detected increased Proximal Ligation Assay dots between FANCD2 and R-loops following APH treatment, which was suppressed by transcriptional inhibition. Collectively, our data suggested that R-loops are required to retain FANCD2 in chromatin at the middle intronic region of large genes, while the replication stress-induced upstream events leading to the FA pathway activation are not triggered by R-loops.

Linear Regression Links Transcriptomic Data and Cellular Raman Spectra

Raman microscopy is an imaging technique that has been applied to assess molecular compositions of living cells to characterize cell types and states. However, owing to the diverse molecular species in cells and challenges of assigning peaks to specific molecules, it has not been clear how to interpret cellular Raman spectra. Here, we provide firm evidence that cellular Raman spectra and transcriptomic profiles of Schizosaccharomyces pombe and Escherichia coli can be computationally connected and thus interpreted. We find that the dimensions of high-dimensional Raman spectra and transcriptomes measured by RNA sequencing can be reduced and connected linearly through a shared low-dimensional subspace. Accordingly, we were able to predict global gene expression profiles by applying the calculated transformation matrix to Raman spectra, and vice versa. Highly expressed non-coding RNAs contributed to the Raman-transcriptome linear correspondence more significantly than mRNAs in S. pombe. This demonstration of correspondence between cellular Raman spectra and transcriptomes is a promising step toward establishing spectroscopic live-cell omics studies.

Local potentiation of stress-responsive genes by upstream noncoding transcription

It has been postulated that a myriad of long noncoding RNAs (lncRNAs) contribute to gene regulation. In fission yeast, glucose starvation triggers lncRNA transcription across promoter regions of stress-responsive genes including fbp1 (fructose-1,6-bisphosphatase1). At the fbp1 promoter, this transcription promotes chromatin remodeling and fbp1 mRNA expression. Here, we demonstrate that such upstream noncoding transcription facilitates promoter association of the stress-responsive transcriptional activator Atf1 at the sites of transcription, leading to activation of the downstream stress genes. Genome-wide analyses revealed that ∼50 Atf1-binding sites show marked decrease in Atf1 occupancy when cells are treated with a transcription inhibitor. Most of these transcription-enhanced Atf1-binding sites are associated with stress-dependent induction of the adjacent mRNAs or lncRNAs, as observed in fbp1. These Atf1-binding sites exhibit low Atf1 occupancy and high histone density in glucose-rich conditions, and undergo dramatic changes in chromatin status after glucose depletion: enhanced Atf1 binding, histone eviction, and histone H3 acetylation. We also found that upstream transcripts bind to the Groucho-Tup1 type transcriptional corepressors Tup11 and Tup12, and locally antagonize their repressive functions on Atf1 binding. These results reveal a new mechanism in which upstream noncoding transcription locally magnifies the specific activation of stress-inducible genes via counteraction of corepressors.

Functional characterization of 21 CYP2C19 allelic variants for clopidogrel 2-oxidation

Genetic variations in cytochrome P450 2C19 (CYP2C19) contribute to interindividual variability in the metabolism of therapeutic agents such as clopidogrel. Polymorphisms in CYP2C19 are associated with large interindividual variations in the therapeutic efficacy of clopidogrel. This study evaluated the in vitro oxidation of clopidogrel by 21 CYP2C19 variants harboring amino acid substitutions. These CYP2C19 variants were heterologously expressed in COS-7 cells, and the kinetic parameters of clopidogrel 2-oxidation were estimated. Among the 21 CYP2C19 variants, 12 (that is, CYP2C19.5A, CYP2C19.5B, CYP2C19.6, CYP2C19.8, CYP2C19.9, CYP2C19.10, CYP2C19.14, CYP2C19.16, CYP2C19.19, CYP2C19.22, CYP2C19.24 and CYP2C19.25) showed no or markedly low activity compared with the wild-type protein CYP2C19.1B. This comprehensive in vitro assessment provided insights into the specific metabolic activities of CYP2C19 proteins encoded by variant alleles, and this may to be valuable when interpreting the results of in vivo studies.

Pim-2 kinase is an important target of treatment for tumor progression and bone loss in myeloma

Pim-2 kinase is overexpressed in multiple myeloma (MM) cells to enhance their growth and survival, and regarded as a novel therapeutic target in MM. However, the impact of Pim-2 inhibition on bone disease in MM remains unknown. We demonstrated here that Pim-2 expression was also upregulated in bone marrow stromal cells and MC3T3-E1 preosteoblastic cells in the presence of cytokines known as the inhibitors of osteoblastogenesis in MM, including interleukin-3 (IL-3), IL-7, tumor necrosis factor-α, transforming growth factor-β (TGF-β) and activin A, as well as MM cell conditioned media. The enforced expression of Pim-2 abrogated in vitro osteoblastogenesis by BMP-2, which suggested Pim-2 as a negative regulator for osteoblastogenesis. Treatment with Pim-2 short-interference RNA as well as the Pim inhibitor SMI-16a successfully restored osteoblastogenesis suppressed by all the above inhibitory factors and MM cells. The SMI-16a treatment potentiated BMP-2-mediated anabolic signaling while suppressing TGF-β signaling. Furthermore, treatment with the newly synthesized thiazolidine-2,4-dione congener, 12a-OH, as well as its prototypic SMI-16a effectively prevented bone destruction while suppressing MM tumor growth in MM animal models. Thus, Pim-2 may have a pivotal role in tumor progression and bone loss in MM, and Pim-2 inhibition may become an important therapeutic strategy to target the MM cell-bone marrow interaction.

Stress-induced lncRNAs evade nuclear degradation and enter the translational machinery

Long noncoding RNAs (lncRNAs) play important roles in the regulation of gene expression. In fission yeast, glucose starvation triggers a transcriptional cascade of polyadenylated lncRNAs in the upstream region of the fructose-1,6-bisphosphatase gene (fbp1(+) ), which is correlated with stepwise chromatin remodeling and necessary for the massive induction of fbp1(+) mRNA. Here, we show that these novel metabolic stress-induced lncRNAs (mlonRNAs) are 5'-capped, less stable than fbp1(+) mRNA and sensitive to a certain extent to the nuclear exosome cofactor Rrp6. However, most mlonRNAs seem to escape nuclear degradation and are exported to the cytoplasm, where they localize to polysomes precisely during glucose starvation-induced global translation inhibition. It is likely that ribosomes tend to accumulate in the upstream region of mlonRNAs. Although mlonRNAs contain an unusual amount of upstream AUGs (uAUGs) and small open reading frames (uORFs), they escape Upf1-mediated targeting to the non-sense-mediated decay (NMD) pathway. The deletion of Upf1 had no effect on mlonRNA stability, but considerably destabilized fbp1(+) mRNA, hinting toward a possible novel role of Upf1. Our findings suggest that the stability of mlonRNAs is distinctly regulated from mRNA and previously described noncoding transcripts.

Visualization of the trochlear nerve in the cistern with use of high-resolution turbo spin-echo multisection motion-sensitized driven equilibrium

BACKGROUND AND PURPOSE

The trochlear nerve is so thin that it is rarely observed with MR imaging. Therefore, we used high-resolution MSDE to reliably visualize the cisternal segments of the trochlear nerve.

MATERIALS AND METHODS

Participants were 10 healthy young adults (mean age, 24 years), and 20 trochlear nerves were examined. HR-MRC, BS-MRC, and HR-MSDE were performed. A neuroradiologist judged the visibility of the trochlear nerves as 1 of 4 grades ("Excellent," "Good," "Fair," and "Not") in each MR imaging sequence. The findings were then statistically analyzed with the χ(2) test.

RESULTS

Of all 20 trochlear nerves, 6 with HR-MRC, 13 with BS-MRC, and 18 with HR-MSDE were judged as "Excellent." CSF flow-related artifacts and vessels in the cistern and cerebellar tentorium in HR-MRC tended to prevent the neuroradiologists from identifying the trochlear nerve. Vessels in the cistern and cerebellar tentorium in BS-MRC also tended to prevent the neuroradiologists from identifying the trochlear nerve. Compared with other sequences, HR-MSDE visualized the trochlear nerve more often. The χ(2) test revealed statistically significant differences among the 3 MR imaging sequences (P < .01). The scan time of HR-MSDE was approximately 1.5-2.2 times longer than that of the other sequences.

CONCLUSIONS

HR-MSDE is able to clearly visualize the trochlear nerve and has the same or better ability to delineate the trochlear nerve compared with other MR imaging sequences, though its long scan time does not yet yield practical use.

A central coupler for recombination initiation linking chromosome architecture to S phase checkpoint

Higher-order chromosome structure is assumed to control various DNA-templated reactions in eukaryotes. Meiotic chromosomes implement developed structures called "axes" and "loops"; both are suggested to tether each other, activating Spo11 to catalyze meiotic DNA double-strand breaks (DSBs) at recombination hotspots. We found that the Schizosaccharomyces pombe Spo11 homolog Rec12 and its partners form two distinct subcomplexes, DSBC (Rec6-Rec12-Rec14) and SFT (Rec7-Rec15-Rec24). Mde2, whose expression is strictly regulated by the replication checkpoint, interacts with Rec15 to stabilize the SFT subcomplex and further binds Rec14 in DSBC. Rec10 provides a docking platform for SFT binding to axes and can partially interact with DSB sites located in loops depending upon Mde2, which is indicative of the formation of multiprotein-based tethered axis-loop complex. These data lead us to propose a mechanism by which Mde2 functions as a recombination initiation mediator to tether axes and loops, in liaison with the meiotic replication checkpoint.

Isolation and characterisation of prolactin-releasing peptide in chicks and its effect on prolactin release and feeding behaviour

Prolactin (PRL)-releasing peptides (PrRP) have been identified in mammals, amphibians and fishes, and these animals have several PrRPs that consist of different numbers of amino acids such as 20, 31 and 37. In the present study, we identified the cDNA encoding chicken prepro-PrRP, which can generate putative PrRPs, and cloned and sequenced it. Sequences for the coding region suggested the occurrence of putative PrRPs of 20, 31 and 32 amino acid residues. The amino acid sequence of chicken PrRP20 showed 100%, 95% and 70% identity with those of PrRP20s from teleosts, Xenopus laevis and mammals, respectively. On the other hand, chicken PrRP31 showed approximately 90% and 52-55% homology to PrRP31s of X. laevis and mammals, respectively. Native chicken PrRPs were purified from an acid extract of chick brain by a Sep-Pak C18 cartridge (Waters Corp., Milford, MA, USA), affinity chromatography using anti-salmon PrRP serum, and reverse phase high-performance liquid chromatography (HPLC) on an ODS-120T column (TOSOH, Tokyo, Japan). The existence of chicken PrRP20 and PrRP31 in the brain was demonstrated by comparing them with the synthetic peptides using HPLC and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Chicken PrRP31 increased plasma PRL concentration when administered peripherally, whereas central administration decreased the concentration, suggesting that chicken PrRP31 has a distinct effect on PRL secretion between tissues in chicks. On the other hand, plasma growth hormone concentration decreased with both peripheral and central administrations of chicken PrRP31. Furthermore, central administration of chicken PrRP31 increased food intake in chicks compared to those observed in mammals and fishes. Taken together with the results indicating that chicken PrRP20 did not show endocrine and behavioural effects, we showed that chicken PrRP has a similar amino acid sequence to teleosts, Xenopus laevis and mammals, although the actions were variable among vertebrates.

Impact of superselective transarterial infusion therapy of high-dose cisplatin on maxillary cancer with orbital invasion

BACKGROUND AND PURPOSE

We have been performing the superselective transarterial infusion of high-dose cisplatin for advanced maxillary cancer since 1998 and the local control rate, disease free survival rate, and organ preservation have improved markedly compared with our former therapy. This study evaluates the effectiveness of superselective transarterial infusion therapy by using high-dose cisplatin on maxillary cancer with orbital invasion.

MATERIALS AND METHODS

We treated 23 patients with maxillary cancer by using superselective transarterial infusion therapy with high-dose cisplatin and concomitant radiation therapy for 10 years. Of all patients, 15 showed orbital invasion, with 11 of these tumors fed by both internal maxillary and ophthalmic arteries. In all patients, we performed superselective transarterial infusion therapy via the internal maxillary artery and/or the other feeding branches from the external carotid artery. After the operation, we determined whether a pCR had occurred by checking for the presence of viable cells. In addition, we calculated the overall survival rate, preservation rate of the eyeball, and disease-free survival rate.

RESULTS

For all 23 patients, pCR and overall survival rates were 95.7% and 78.4%, respectively. To date, 2 of these patients died of lung metastasis without local recurrence. For the 15 patients with orbital invasion, the respective pCR and disease-free survival rates were 93.3% and 87.5%. Eyeballs were preserved in all patients, and local recurrence occurred in only 1 patient, at the inferior wall of the maxillary sinus (not in the orbit).

CONCLUSIONS

Superselective transarterial infusion therapy with high-dose cisplatin remarkably improved the local control rate and disease-free survival rate of maxillary cancer. Even in patients with orbital invasion, a high local control rate was achieved, with preservation of the eyeball, through infusion only into branches of the external carotid artery.

Effects of ifenprodil on voltage-gated tetrodotoxin-resistant Na+ channels in rat sensory neurons

BACKGROUND AND OBJECTIVE

To examine a possible mechanism for the antinociceptive action of the N-methyl-D-aspartate receptor antagonist ifenprodil, we compared its effects with those of ketamine on tetrodotoxin-resistant Na+ channels in rat dorsal root ganglion neurons, which play an important role in the nociceptive pain pathway.

METHODS

Experiments were performed on dorsal root ganglion neurons from Sprague-Dawley rats, recordings of whole-cell membrane currents being made using patch-clamp technique.

RESULTS

Both drugs blocked tetrodotoxin-resistant Na+ currents dose dependently, their half-maximal inhibitory concentrations being 145+/-12.1 micromol (ketamine) and 2.6+/-0.95 micromol (ifenprodil). Ifenprodil shifted the inactivation curve for tetrodotoxin-resistant Na+ channels in the hyperpolarizing direction and shifted the activation curve in the depolarizing direction. Use-dependent blockade of tetrodotoxin-resistant Na+ channels was more marked with ifenprodil than with ketamine. When paired with lidocaine, these drugs produced similar additive inhibitions of tetrodotoxin-resistant Na+ channel activity.

CONCLUSIONS

The observed suppressive effects on tetrodotoxin-resistant Na+ channel activity may, at least in part, underlie the antinociceptive effects of these N-methyl-D-aspartate receptor antagonists.

Effects of alpha2-adrenoceptor agonists on tetrodotoxin-resistant Na+ channels in rat dorsal root ganglion neurons

BACKGROUND AND OBJECTIVE

When intrathecally or epidurally administered, alpha2-adrenoceptor agonists produce potent antinociception by affecting the activity of primary afferent fibres and spinal cord neurons. Recent reports have indicated that in dorsal root ganglion neurons, tetrodotoxin-resistant Na+ channels play important roles in the conduction of nociceptive sensation. We therefore investigated the effects of alpha2-adrenoceptor agonists on tetrodotoxin-resistant Na+ currents.

METHODS

Using the whole-cell patch-clamp technique, we recorded tetrodotoxin-resistant Na+ currents from rat dorsal root ganglion neurons.

RESULTS

Both clonidine and dexmedetomidine reduced the peak amplitude of the tetrodotoxin-resistant Na+ current concentration- and use-dependently. The concentration required for a half-maximal effect was significantly lower for dexmedetomidine (58.0 +/- 10.2 micromol) than for clonidine (257.2 +/- 30.9 micromol) at holding potential -70 mV. The current inhibitions induced by these agonists were not prevented by 1 micromol yohimbine, an alpha2-adrenoceptor antagonist. Both clonidine and dexmedetomidine shifted the inactivation curve for the tetrodotoxin-resistant Na+ current in the hyperpolarizing direction. The combinations clonidine with lidocaine and dexmedetomidine with lidocaine produced an additive blockade-type interaction on the tetrodotoxin-resistant Na+ current.

CONCLUSIONS

The results suggest that a direct inhibition of tetrodotoxin-resistant Na+ channels may contribute to the antinociceptive effects of clonidine and dexmedetomidine when used as additives to regional anaesthesia.

Signal transduction and cellular functions of the TEL/ARG oncoprotein

The TEL/ARG oncogene is formed by t(1;12)(q25;p13) reciprocal translocation and is associated with human leukemia. We have previously demonstrated that the expression of TEL/ARG in Ba/F3 cells results in prolonged viability and hyper-responsiveness to IL-3. To determine the molecular mechanisms, a series of mutants of TEL/ARG were generated, and each cDNA was expressed in Ba/F3 or CHO cells. The PNT domain in TEL and K317 in ARG were essential for both signaling and biological effects. The SH3 domain in ARG was required for hyper-responsiveness to IL-3, but not for prolonged viability. The opposite was true for the SH2 domain in ARG. Mutation of Y314 in TEL, a putative GRB2-binding site, led to reduced viability, and loss of hyper-responsiveness to IL-3. All biological functions were profoundly impaired with deletion of the C-terminus in ARG, despite maintaining high levels of its kinase activity. When expressed in CHO cells, wild-type TEL/ARG induced the formation of fillopodia, in a fashion dependent on the C-terminal portion and intact kinase activity. Thus, these results suggest several critical domains within TEL/ARG necessary for function, and indicate that the signaling pathways necessary for viability, growth factor hyper-responsiveness and cytoskeletal reorganization are likely to be separate.

Molecular cloning and characterization of a KRAB-containing zinc finger protein, ZNF317, and its isoforms

To identify zinc finger genes in human primary cultured erythroid progenitor cells, RT-PCR was performed using primers specific for the conserved sequence in zinc finger domains of mouse Friend of GATA-1. We identified a novel Krüppel-associated box (KRAB) zinc finger gene, ZNF317. Evaluation of full-length cDNA obtained by RACE showed that it encoded a protein composed of 13 Krüppel-like zinc fingers and a KRAB domain. RT-PCR analysis revealed four alternatively splicing products (ZNF317-1 through ZNF317-4). The ZNF317 gene has seven exons and is located in human chromosome 19p13. Northern analysis revealed that ZNF317-1 and ZNF317-2 transcripts were ubiquitously expressed, whereas ZNF317-3 and ZNF317-4 transcripts were detected only in lymphocytes, spleen, and lung. Competitive RT-PCR analysis showed that the expression of ZNF317 mRNA significantly decreased during erythroid maturation. In lymphocytes, ZNF317 expression was reduced in response to mitogenic stimulation. We propose that ZNF317 may play an important role in erythroid maturation and lymphoid proliferation.

Stem cell factor regulation of Fas-mediated apoptosis of human erythroid precursor cells

Multiple cytokines regulate the development of erythrocytes. Increasing attention has been directed to the possible role of Fas and its cognate ligand (Fas-L), a subject of wide interest. Documentation of in vitro data supports the role of Fas and Fas-L in erythropoiesis. Several laboratories, including ours, investigated the opposing actions of erythropoietin (EPO) and stem cell factor (SCF) on Fas-mediated cell death of the erythroid cells. Only circumstantial in vivo evidence has accumulated concerning the issue. There are several reports suggesting that Fas-mediated cell death may have a role in some pathological conditions. Results of the accumulating findings and possible implications in clinical hematology are summarized in this review.

Cysteine proteinase gene expression in the endosperm of germinating carrot seeds

A gene for carrot seed cysteine proteinase (CSCP; AB057371, AB057372) was cloned using PCR. The deduced amino acid sequence of CSCP had active sites for eukaryotic cysteine proteinases, putative signal sequences, and an endoplasmic reticulum targeting sequence. RNA gel blot analysis showed that CSCP transcripts appeared from dry seed, reached a maximum 3 days after imbibition (DAI), and disappeared by 5 DAI. In situ hybridization showed that CSCP transcripts accumulated in the endosperm of germinating seeds. This is the first report of the expression pattern of a cysteine proteinase gene in the endosperm of germinating dicotyledonous plants. The promoter of the CSCP gene had an endosperm motif and many other motifs also found in the promoters of endosperm-specific storage protein genes in monocotyledons. It is suggested that dicotyledons, like monocotyledons, have a temporal and spatial regulation system for endosperm-specific gene expression in germinating seeds.

The effects of alpha-human atrial natriuretic peptide and milrinone on pial vessels during blood-brain barrier disruption in rabbits

The effects of alpha-human atrial natriuretic peptide (HANP) and milrinone on cerebral pial vessels, especially during blood-brain barrier (BBB) disruption, are not clear. We studied topical HANP (10(-14), 10(-12), and 10(-10) M) or milrinone (10(-7), 10(-5), and 10(-3) M), and IV HANP (0.1, 0.2, and 1.0 microg. kg(-1). min(-1)) or milrinone (0.5, 5.0, and 20.0 microg. kg(-1). min(-1)) with or without hyperosmolar BBB disruption, using a rabbit cranial window preparation. At 10(-12) and 10(-10) M topical HANP produced significant arteriolar (16%, 20%, respectively), but no venular dilation. Topical milrinone (10(-3) M) produced significant arteriolar and venular dilation (21%, 8%, respectively). IV HANP produced no arteriolar or venular changes at any dose except during BBB disruption, when it caused a significant arteriolar (16%, 16%, and 17%, respectively), but no venular dilation. In contrast, IV milrinone caused small but significant arteriolar and venular dilation without BBB disruption (arterioles, 6%, 7% and 8%, respectively; venules, 6% at 20.0 microg. kg(-1). min(-1)). During BBB disruption, these responses to milrinone were similar. Although HANP and milrinone each have a direct vasodilator effect on arterioles, their systemic administration at clinical doses could induce different effects. BBB disruptive conditions could increase the response of pial vessels to systemically administered HANP.

IMPLICATIONS

Although alpha-human atrial natriuretic peptide (HANP) and milrinone each have a direct vasodilator effect on cerebral pial arterioles, their systemic administration at clinical doses could have different effects and blood-brain-barrier disruptive conditions could alter the response of pial vessels to HANP, but not to milrinone.

Leptin stimulates rat aortic smooth muscle cell proliferation and migration

Leptin, a peptide secreted from adipose tissue, plays an important role in the regulation of food intake and energy expenditure. In obese patients, plasma leptin levels are elevated and obesity is one of the major risk factors for cardiovascular diseases. Therefore, in this study, we investigated the effect of leptin on vascular smooth muscle cell (VSMC) functions. Cultured rat aortic VSMC expressed 130-kDa short form of leptin receptor. Leptin stimulated both proliferation and migration of VSMC. Leptin stimulated phosphorylation and activation of mitogen-activated protein (MAP) kinases, and also increased phosphatidylinositol (PI) 3-kinase activity. Further, two distinct PI 3-kinase inhibitors, wortmannin and LY294002 inhibited the migratory effect of leptin. These results demonstrate that leptin is a proliferative and migratory factor for VSMC, implying that leptin may play a role in the formation and development of vascular lesions.

CrkL is an adapter for Wiskott-Aldrich syndrome protein and Syk

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia are caused by mutations of the WAS protein (WASP) gene. WASP may be involved in the regulation of podosome, an actin-rich dynamic cell adhesion structure formed by various types of cells. The molecular links between WASP and podosomes or other cell adhesion structures are unknown. Platelets express an SH2-SH3 adapter molecule, CrkL, that can directly associate with paxillin, which is localized in podosomes. The hypothesis that CrkL binds to WASP was, therefore, tested. Results from coprecipitation experiments using anti-CrkL and GST-fusion proteins suggest that CrkL binds to WASP through its SH3 domain and that the binding was not affected by WASP tyrosine phosphorylation. The binding of GST-fusion SH3 domain of PSTPIP1 in vitro was also not affected by WASP tyrosine phosphorylation, suggesting that the binding of the SH3 domains to WASP is not inhibited by tyrosine phosphorylation of WASP. Anti-CrkL also coprecipitates a 72-kd protein, which was identified as syk tyrosine kinase, critical for collagen induced-platelet activation. CrkL immunoprecipitates contain kinase-active syk, as evidenced by an in vitro kinase assay. Coprecipitation experiments using GST-fusion CrkL proteins suggest that both SH2 and SH3 domains of CrkL are involved in the binding of CrkL to syk. WASP, CrkL, syk, and paxillin-like Hic-5 incorporated to platelet cytoskeleton after platelet aggregation. Thus, CrkL is a novel molecular adapter for WASP and syk and may potentially transfer these molecules to the cytoskeleton through association with cytoskeletal proteins such as Hic-5.

Effect of fluvoxamine on the pharmacokinetics of mexiletine in healthy Japanese men

BACKGROUND AND OBJECTIVES

Fluvoxamine, a selective serotonin reuptake inhibitor, is known to inhibit several hepatic cytochrome P450 (CYP) isozymes, in particular CYP1A2. Mexiletine is mainly catalyzed by CYP2D6 and partially catalyzed by CYP1A2. Our objective was to study the potential pharmacokinetic interaction between fluvoxamine and mexiletine.

METHODS

A randomized crossover design with two phases was used. A 7-day washout period separated the two treatment conditions. In the one phase, 6 healthy Japanese men received an oral dose of 200 mg of mexiletine alone (study 1); in the other phase, the men received fluvoxamine (50 mg twice a day) for 7 days, and on the eighth day they received oral mexiletine (200 mg) and fluvoxamine concomitantly (study 2). The concentrations of mexiletine were measured with HPLC.

RESULTS

The area under the concentration-time curve and serum peak concentration of mexiletine in study 2 were significantly increased compared with those in study 1 (10.4 +/- 4.85 versus 6.70 +/- 3.21 microg x h/mL, P =.006 and 0.623 +/- 0.133 versus 0.536 +/- 0.164 microg/mL, P =.008, respectively).

CONCLUSION

The effect of fluvoxamine on the mexiletine disposition is comparatively large, and when mexiletine and fluvoxamine are coadministered careful monitoring of mexiletine is needed.

Stem cell factor prevents Fas-mediated apoptosis of human erythroid precursor cells with Src-family kinase dependency

The Fas ligand (Fas-L) expressed on mature erythroblasts may induce apoptosis of more immature erythroid cells that express Fas, whereas stem cell factor (SCF) may prevent Fas-mediated cell death in hematopoietic progenitor cells. The manner in which SCF prevents Fas-mediated cell death still is unclear. Given the essential role of SCF and the potentially important involvement of the Fas/Fas-L system in the development of erythrocytes, we studied mechanisms related to SCF prevention of Fas-mediated apoptosis. We used primary cultured human erythroid colony-forming cells (ECFC) derived from CD34+ cells and enriched glycophorin A positive (GPA+) c-kit+ cells in ECFC. Apoptosis of ECFC was induced by an Fas-L mimetic monoclonal antibody CH11. DNA fragmentation and the activation of caspase-3 and caspase-8 were measured using commercially available kits. Characterization of expanded cells was performed using multiparameter flow cytometry. Lyn kinase activity was measured by enolase kinase assays. SCF inhibited the CH11-induced DNA fragmentation of ECFC as well as enriched GPA+ c-kit+ cells in ECFC, but not those of GPA+ c-kit- cells. SCF also inhibited the activation of caspase-3 and caspase-8, without downregulation of the surface expression of Fas, suggesting that SCF prevents apoptosis through uncoupling of Fas ligation from subsequent caspase activation. PP2, a specific inhibitor of Src-family kinases, antagonized the effects of SCF in preventing Fas-mediated apoptosis. We propose that SCF prevents Fas-mediated apoptosis of erythroid progenitor cells in a manner dependent on the activity of Src-family tyrosine kinases. We also identified active Lyn in erythroid cells. These data suggest the presence of a novel Src-family-dependent function of SCF in the development of erythrocytes.

Wiskott-Aldrich syndrome protein and platelets

Wiskott-Aldrich syndrome (WAS) and X-linked thrombocy topenia (XLT) are caused by mutations of the WAS protein (WASP) gene. The manifestations of the classic WAS phenotype consist of immunodeficiency, eczema and thrombocytopenia. However, thrombocytopenia and small platelets are the only consistent features of WAS and XLT. The exact mechanisms of the development of thrombocytopenia in patients with WAS or XLT are unknown. To date, platelets are the only primary cells in which inducible tyrosine phosphorylation of WASP has been consistently demonstrated. This review focuses on the recent progress in dissecting the causes of thrombocytopenia and the emerging understanding of WASP phosphorylation.

Thrombopoietin and interleukin-2 induce association of CRK with STAT5

Crk (Crk I and II) proteins and closely related CrkL are adapters which are commonly involved in various signaling processes in various cells, and these proteins share many ligands. Whether they have redundant or distinct physiologic roles is unclear. By coprecipitation and far Western blotting analysis, we demonstrate that Crk (I/II) binds to tyrosine phosphorylated STAT5 in cells stimulated by cytokines such as thrombopoietin (TPO) and interleukin-2 (IL-2). The association did not require nuclear elements and can be observed in primary cells as this was also demonstrated in TPO-stimulated platelets. Using a beta-casein promoter STAT5 binding site as a probe, we have also demonstrated that CrkL (a close relative of Crk) antiserum, but not Crk antiserum, supershifted the STAT5-DNA complex by an electrophoretic mobility shift assay, suggesting that CrkL, but not Crk, is the major component of the complex. Thus, Crk and CrkL may have distinct roles in the regulation of STAT5.

Cloning of an auxin-responsive 1-aminocyclopropane-1-carboxylate synthase gene (CMe-ACS2) from melon and the expression of ACS genes in etiolated melon seedlings and melon fruits

Two cDNA fragments (pCMe-ACS2 and 3) encoding auxin-responsive 1-aminocyclopropane-1-carboxylate synthase (ACS; EC.4.4.1.14) have been isolated from melon, and the expression patterns of the genes in etiolated melon seedlings and melon fruit have been determined by RT-PCR analysis. The deduced amino acid sequences of pCMe-ACS2 and 3 were homologous to those of AT-ACS6 and 4, which were auxin-responsive ACS genes of Arabidopsis. Both CMe-ACS2 and 3 were auxin-responsive ACS genes and their expressions in roots and hypocotyls were induced by treatment with indole acetic acid (IAA, 100 µM). The mRNA level of CMe-ACS2 in the fruit increased after pollination. Those of both CMe-ACS2 and 3 temporarily increased in the mesocarp tissues at the preclimacteric stage (from day 3 to day 5 after harvest) during ripening, while that of CMe-ACS3 was lower than that of CMe-ACS2. The increase in the mRNA level of CMe-ACS1 (wound- and ripening-induced gene, T. Miki, M. Yamamoto, N. Nakagawa, O. Ogura, H. Mori, H. Imaseki, T. Sato, Nucleotide sequence of a cDNA for 1-aminocyclopropane-1-carboxylate synthase from melon fruits, Plant Physiol. 107 (1995) 297-298.) in the mesocarp tissue was not observed until 5 days after harvest. A genomic DNA encoding CMe-ACS2 was isolated and its nucleotide sequence was determined. Nucleotide sequences resembling the auxin-responsive elements (AuxRE) D1 and D4 (the TGTCTC element) in the GH3 gene from soybean, and the auxin-responsive domain (AuxRD) B in PS-IAA4/5 from pea were found in the 5'-flanking region of the CMe-ACS2 gene.

Characteristics of ropivacaine block of Na+ channels in rat dorsal root ganglion neurons

When used for epidural anesthesia, ropivacaine can produce a satisfactory sensory block with a minor motor block. We investigated its effect on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) Na(+) currents in rat dorsal root ganglion (DRG) neurons to elucidate the mechanisms underlying the above effects. Whole-cell patch-clamp recordings were made from enzymatically dissociated neurons from rat DRG. A TTX-S Na(+) current was recorded preferentially from large DRG neurons and a TTX-R Na(+) current preferentially from small ones. Ropivacaine shifted the activation curve for the TTX-R Na(+) channel in the depolarizing direction and the inactivation curve for both types of Na(+) channel in the hyperpolarizing direction. Ropivacaine blocked TTX-S and TTX-R Na(+) currents, but its half-maximum inhibitory concentration (IC(50)) was significantly lower for the latter current (116 +/- 35 vs 54 +/- 14 microM; P: < 0.01); similar IC(50) values were obtained with the (R)-isomer of ropivacaine. Ropivacaine produced a use-dependent block of both types of Na(+) channels. Ropivacaine preferentially blocks TTX-R Na(+) channels over TTX-S Na(+) channels. We conclude that because TTX-R Na(+) channels exist mainly in small DRG neurons (which are responsible for nociceptive sensation), such selective action of ropivacaine could underlie the differential block observed during epidural anesthesia with this drug.

IMPLICATIONS

Whole-cell patch-clamp recordings of tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neurons showed ropivacaine preferentially blocked tetrodotoxin-resistant Na(+) channels over tetrodotoxin-sensitive Na(+) channels. This could provide a desirable differential sensory blockade during epidural anesthesia using ropivacaine.

Patient anxiety scores after low-dose ketamine or fentanyl for epidural catheter placement

PURPOSE

To compare the effect of low-dose ketamine with that of low-dose fentanyl on patient anxiety during the identification of the epidural space and catheterization.

METHODS

Sixty patients were randomly assigned to one of three groups: saline group (n=20), saline 2 ml; ketamine group (n=20), 5 mg ketamine; or fentanyl group (n=20), 50 microg fentanyl. Each drug was administered intravenously (iv) five to ten minutes before the epidural procedures began. After epidural catheter placement had been accomplished, anxiety and pain were rated using a visual analog scale.

RESULTS

The anxiety scores given for ketamine(20.2 +/- 18.5, mean +/- SD) and fentanyl (24.6 +/- 20.3) were similar, and both were lower than that for saline (44.1 +/- 32.7) (P=0.0034 and 0.0153 vs saline group, respectively). Pain scores were similar for all three groups. A decrease in hemoglobin oxygen saturation during the procedure was only observed in the fentanyl group, and two patients in fentanyl group had SpO2 <90%.

CONCLUSION

Ketamine, 5 mg iv, is as effective as 50 microg fentanyl, iv, in alleviating patient anxiety and in providing adequate sedation during the procedures necessary for epidural catheter placement, without inducing severe complications.

Signal transduction in primary cultured human erythroid cells

Development of erythrocytes is a complex process governed by multiple cytokines. Colony assays have revealed the physiologic importance of these cytokines, although biochemical studies of highly purified human colony-forming unit-erythroid (CFU-E) generated in vitro from CD34+ cells have only recently begun. Studies from our groups and others suggested that signal transduction in primary erythroid cells differs considerably from that in cell lines or primary cells from other species. In this review, we summarize results of these studies with emphasis on possible implications for hematotherapy.

Histological factors of 1-h biopsy influencing the delayed renal function and outcome in cadaveric renal allografts

The morphological characteristics of a kidney biopsy specimen taken 1 h after reperfusion of blood into the graft (1-h biopsy) during a cadaveric transplant operation were studied. The aim of the 1-h biopsy is to evaluate the pre-transplant risk factors for the delayed graft function, assess the renal function of the graft, and predict long-term graft survival. The total number of 1-h biopsies was 113, consisting of 86 male and 27 female donors. The mean age of the donors is 39.5 +/- 17.3 yr. Arteriosclerosis (AS) and tubulo-interstitial injury (TI) were both estimated using a semi-quantitative scale. AS score was graded into four categories, according to the severity of the thickening of interlobular artery: 0: none, 1: mild, 2: moderate and 3: severe. No biopsy revealed severe AS of grade 3. The TI score was graded from 0 to 5, according to the morphological injury: 0: none, 1-2 non-specific tubulo-interstitial injury (NSTI), and 3-5 compatible with acute tubular necrosis (ATN) in terms of pathological diagnosis. The mean ages of donors showing as AS of score 0, 1, and 2 were 30.6 +/- 14.6, 49.7 +/- 13.5, and 56.9 +/- 6.30, respectively. The mean donor age of the AS 1 group and AS 2 group was significantly lower than for the AS 0 group. The lowest serum creatinine values after operation (best Cr) of recipients with AS scores of 0, 1, and 2 were 1.31 +/- 0.45, 1.60 +/- 0.70, and 1.84 +/- 0.71 mg/dL, respectively; the best Cr of AS scores of 1 and 2 was significantly higher than in the AS score 0 group. The mean creatinine level at the final point of the AS 0 group was significantly lower than in the combined AS 1 and AS 2 group (serum creatinine 1.44 +/- 1.03 vs 1.87 +/- 1.53 mg/dL: p < 0.01). The duration of severe hypotension less than 50 mmHg or 80 mmHg was significantly shorter in the NSTI group than in the ATN group (less than 50 mmHg was 29.7 +/- 124 vs 72.5 +/- 174, less than 80 mmHg 105 +/- 234 vs 193 +/- 261 min: p < 0.01). The post-operative (po) day expressing diuresis in excess of 1000 mL of urine per d was 8.28 +/- 17.5 and 13.7 +/- 23.3 (p < 0.01) in the NSTI and ATN group, respectively. The po-d of the last hemodialysis and the po-d showing serum creatinine less than 2.0 mg/dL in NSTI and ATN group was 7.74 +/- 17.4 and 13.3 +/- 23.2 (p < 0.01), and 25.0 +/- 30.5 and 38.0 +/- 35.2 (p < 0.01), respectively. We concluded that 1-h renal biopsy is useful for assessing the outcome of renal allograft. AS of a donor kidney is one of the most important risk factors for both short and long-term outcome of the graft. The TI score was useful to predict the outcome of delayed graft function.

Rapid tyrosine phosphorylation and activation of Bruton's tyrosine/Tec kinases in platelets induced by collagen binding or CD32 cross-linking

Stimulation of the platelet nonintegrin collagen receptor, glycoprotein VI, evokes a signaling response similar to that induced by antigen receptor activation in B and T lymphocytes. A key transducer of the lymphocyte signaling pathways is the Bruton's tyrosine kinase (Btk)/Tec kinase family, which connects receptors to the elevation of intracellular-free calcium levels. An important signaling function for Btk in collagen-induced platelet activation in vitro was recently demonstrated by other researchers using Btk-deficient platelets from patients with X-linked agammaglobulinemia (XLA). Since Btk-deficiency does not induce an overt platelet-based bleeding disorder in vivo, collagen receptor responses may include other Btk/Tec kinase family members in normal platelets. Both Btk and Tec had increased tyrosine following stimulation of collagen receptors or CD32 cross-linking. Data from kinetic analyses and inhibitor studies and the use of phosphopeptide-specific antibodies recognizing 2 Btk regulatory phosphorylated tyrosine residues suggest a mechanism for coordinate recruitment of Btk and Tec through the immunoreceptor tyrosine-based activation motif, Src family kinases, and phosphatidylinositol 3-kinase. In XLA platelets, collagen treatment increased tyrosine phosphorylation of Tec and several other signaling proteins, including Lyn, Fyb, Slp-76, and the Wiskott-Aldrich syndrome protein. This indicates that important elements of the collagen signaling pathway proximal and distal to Btk and Tec are preserved despite the lack of functional Btk. The results are consistent with the conclusion that activation of Tec may sustain XLA platelet function in vivo, while some in vitro assays of nonintegrin collagen receptor signaling through the Btk/Tec kinase family reflect the additive dosage of the transducers. (Blood. 2000;95:1663-1670)

A method of measuring finger force with the Kin-Com dynamometer

The purpose of this study was to determine whether the force of a finger could be measured with a new system based on an attachment to the Kin-Com dynamometer, and to define the reproducibility of the finger force measurement. Eleven male subjects (age, 27.6 +/- 6.12 years) took part. All were free of orthopedic problems in the tested hand. Mean forces of the index and little finger for concentric and eccentric motion were measured using the new system. Overall coefficients of variation (OCVs) were calculated as an index of reproducibility. The reproducibility of force curves was considered good when an OCV was less than 20%. The OCVs for mean force of the index finger and for eccentric motion of the little finger were less than the 20% standard, at 10.7 and 14.0, respectively. The OCV for concentric motion of the little finger was greater than 20%. The findings suggest that measurement of finger force is feasible with the new Kin-Com attachment.

Phosphatidylinositol 3-kinase is involved in the protection of primary cultured human erythroid precursor cells from apoptosis

Little is known about the physiologic role of phosphatidylinositol 3-kinase (PI-3K) in the development of erythrocytes. Previous studies have shown that the effects of the PI-3K inhibitor wortmannin on erythropoietin (EPO)-dependent cell lines differed depending on the cell type used. Wortmannin inhibited EPO-induced differentiation of some cell lines without affecting their proliferation; however, the EPO-induced proliferation of other cell lines was inhibited by wortmannin. In neither case were signs of apoptosis observed. We have previously reported that signaling in highly purified human colony forming units-erythroid (CFU-E), generated in vitro from CD34(+) cells, differed from that in EPO-dependent cell lines. In the current study, we examined the effects of a more specific PI-3K inhibitor (LY294002) on human CFU-E. We found that LY294002 dose-dependently inhibits the proliferation of erythroid progenitor cells with a half-maximal effect at 10 micromol/L LY294002. LY294002 at similar concentrations also induces apoptosis of these cells, as evidenced by the appearance of annexin V-binding cells and DNA fragmentation. The steady-state phosphorylation of AKT at Ser-473 that occurs as a result of PI-3K activation was also inhibited by LY294002 at similar concentrations, suggesting that the effects of LY294002 are specific. Interestingly, the acceleration of apoptosis by LY294002 was observed in the presence or absence of EPO. Further, deprivation of EPO resulted in accelerated apoptosis irrespective of the presence of LY294002. Our study confirms and extends the finding that signaling in human primary cultured erythroid cells is significantly different from that in EPO-dependent cell lines. These data suggest that PI-3K has an antiapoptotic role in erythroid progenitor cells. In addition, 2 different pathways for the protection of primary erythroid cells from apoptosis likely exist: 1 independent of EPO that is LY294002-sensitive and one that is EPO-dependent and at least partly insensitive to LY294002.