Photodetachment of positronium negative ions.

Photodetachment of the positronium negative ion, a bound state of one positron and two electrons, has been observed. Development of a method to produce the ions efficiently using a Na coated tungsten surface has enabled the first observation of the photodetachment. The obtained lower limit of the photodetachment cross section for the wavelength of 1064 nm is consistent with the theoretical calculations reported so far. The experimental field developed in the present work gives new opportunities to explore the quantum mechanical three-body problem and to develop energy-tunable positronium beams.

Superoxide dismutase in SAS human tongue carcinoma cell line is a factor defining invasiveness and cell motility.

This article describes an apparent inverse relationship between cell motility and intracellular Cu-Zn superoxide dismutase (SOD) activity of two human squamous carcinoma-derived clones, SAS-H1 with high invasiveness and SAS-L1 with low invasiveness. Clone SAS-H1 exhibited significantly greater motility than SAS-L1 but had significantly lower levels of intracellular Cu-ZnSOD than SAS-L1 cells. We then transfected Cu-ZnSOD antisense cDNA into SAS-L1 to reduce the intracellular Cu-ZnSOD activity. Antisense cDNA transfected SAS-L-AS clones had lower Cu-ZnSOD activity than control vector-transfected SAS-L-Neo clones, and this was associated with increased motility. Invasiveness of SAS-H1 and SAS-L-AS1 was enhanced by superoxide treatment, while the invasiveness of SAS-L1 was unaffected. These findings indicate that intracellular SOD is involved in cell motility by virtue of its action in scavenging superoxide in the cells.

[Carcinomatous pericarditis successfully treated with thoracoscopic pericardial fenestration; report of a case].

We report a case of malignant pericardial effusion after lung cancer surgery treated with thoracoscopic pericardial fenestration. The patient was admitted to our hospital because of dyspnea. Computed tomography (CT) and ultrasound cardiography (UCG) revealed cardiac tamponade which was diagnosed as carcinomatous pericarditis by cytology. We attempted to inject 25 mg of cisplatin (CDDP) into the pericardial space twice. The response of the treatment was unexpectedly poor for the patient. The thoracoscopic pericardial fenestration was performed and the patient was discharged without a drainage tube on the 17th postoperative day. Malignant pericardial effusion is a common complication of advanced cancers and is often associated with significant morbidity. Thoracoscopic pericardial fenestration appears to be a safe, effective and minimally invasive treatment for patients with malignant pericardial effusion. This surgery might also have a favorable effect on the improvement of the quality of life for patients with malignant pericardial effusion resistant to chemotherapy.

Glutathione S-transferase-pi is secreted as a monomer into human plasma by platelets and tumor cells.

By employing an ELISA for detection of glutathione S-transferase-pi (GST-pi) established in our laboratory, gel filtration profiles of GST-pi in the plasma of normal subjects and patients with malignant tumors were investigated. The results showed that the plasma GST-pi for both of these groups was approximately half the molecular size of placental GST-pi used as a standard control. Similar analyses were performed on GST-pi of platelets and cultured cancer cells, which are considered to be the main sources of the GST-pi in the plasma of normal subjects and cancer patients, respectively. The results indicated that the GST-pi in both the centrifuged supernatants of aggregated platelets and in the culture medium of cancer cells was about half of the molecular size on intact GST-pi. Moreover, the GST-pi in the culture medium was shown to have an N-terminus and a C-terminus, by analysis with specific ELISA. Western blot analysis of the GST-pi in the culture medium detected a single band migrating at 23 kDa, confirming that the extracellular GST-pi was the monomer, not a cleaved form of intact GST-pi. The release of GST-pi from cancer cells was suppressed at 4 degrees C, or by sodium azide, but not suppressed by colchicine or cytochalasin B. These findings suggest that GST-pi may be released by an energy-dependent, active process, and not by a secretion mechanism.

Correlation of basal coronary artery tone with constrictive response to ergonovine in patients with variant angina.

OBJECTIVES: This study was conducted to examine whether basal coronary artery tone is elevated at the spastic site in patients with variant angina and to determine the significance of basal artery tone in predicting provocation of coronary artery spasm. BACKGROUND: Previous data have been conflicting on whether basal coronary artery tone is elevated in patients with variant angina. METHODS: We assessed basal coronary artery tone by obtaining the percent increase in coronary artery diameter induced by nitroglycerin in 20 patients with variant angina and 24 control subjects. We also examined the correlation between basal coronary artery tone and the constrictive response to ergonovine. RESULTS: In the patients with variant angina in whom spasm was provoked by the lower doses (1 or 5 micrograms) of ergonovine, basal coronary artery tone was greater (p < 0.05) at the spastic site (54 +/- 15% or 36 +/- 16%, respectively) than at the nonspastic site (40 +/- 25% or 25 +/- 15%, respectively). Basal coronary tone at the nonspastic site in these patients was greater (p < 0.01) than that in control subjects (15 +/- 6%). In the patients with variant angina in whom spasm was provoked only by the higher doses (15 or 50 micrograms) of ergonovine, basal coronary artery tone was comparable at the spastic and nonspastic sites and was not different from that in control subjects. The diagnostic sensitivity and specificity of elevated basal coronary artery tone (> or = 40%) in predicting provocation of spasm were 26% and 98%, respectively. CONCLUSIONS: These results indicate that elevated basal coronary artery tone may be useful in predicting provocation of coronary spasm, but the normal level of basal coronary artery tone does not exclude such provocation.

Inhibitory effects of heparin, aspirin and ketanserin on coronary artery vasoconstriction after arterial balloon injury in hypercholesterolemic miniature pigs.

OBJECTIVES: The present study aimed to clarify the effects of heparin, aspirin and ketanserin on coronary artery vasoconstriction after arterial balloon injury. BACKGROUND: The mechanisms of coronary artery vasoconstriction after coronary angioplasty are not well understood. METHODS: After being fed a cholesterol-rich diet for 1 month, 71 Göttingen miniature pigs were randomly allotted to five groups: 16 pigs with no pretreatment (group A); 21 pigs pretreated with heparin, 3,000 U (group B); 13 pigs pretreated with aspirin, 50 mg/day orally for 2 days (group C); 11 pigs pretreated with ketanserin, 1 mg/kg body weight (group D); 10 pigs pretreated with aspirin, 50 mg/day for 2 days, heparin, 6,000 U and ketanserin, 1 mg/kg (group E). After this pretreatment, the left anterior descending or the left circumflex coronary artery, or both, was denuded by a 2F balloon catheter. RESULTS: The coronary vasoconstriction at the injured sites reached a peak level 6 min after the arterial injury and subsided within 30 min. The coronary vasoconstriction at the injured site 6 min after arterial injury was 56 +/- 5% in group A, which was significantly greater than that in group B (28 +/- 6%, p < 0.01), group C (25 +/- 5%, p < 0.01), group D (26 +/- 7%, p < 0.01) or group E (24 +/- 5%, p < 0.01), whereas there was no significant difference in the coronary vasoconstriction among the latter four groups. CONCLUSION: These results suggest that serotonin released from aggregating platelets plays a major part in the platelet-dependent coronary artery vasoconstriction after arterial injury.

Bradykinin-induced vasodilation of human coronary arteries in vivo: role of nitric oxide and angiotensin-converting enzyme.

OBJECTIVES: The present study aimed to determine the role of nitric oxide (NO) and angiotensin-converting enzyme (ACE) in bradykinin (BK)-induced dilation of human coronary arteries in vivo. BACKGROUND: BK, produced by way of the kinin-kallikrein system, causes endothelium-dependent vasodilation. However, little is known about the mechanism of BK-induced dilation of coronary arteries in humans in vivo. METHODS: The effects of an inhibitor of NO synthesis and of an ACE inhibitor on BK-induced coronary vasodilation were examined in 20 patients who had no significant atherosclerotic stenosis in the artery under study. Lumen diameters of the large epicardial coronary arteries and coronary blood flow (CBF) were measured by quantitative coronary arteriography and intracoronary Doppler technique. RESULTS: Intracoronary infusion of BK (0.6 and 2.0 micrograms/min) increased coronary artery diameter and CBF with no change in arterial pressure or heart rate. The BK-induced increases in coronary artery diameter and CBF were significantly reduced (p < 0.01) after pretreatment with NG-monomethyl-L-arginine (200 mumol) and were significantly increased (p < 0.01) after pretreatment with enalaprilat (50 micrograms). CONCLUSIONS: BK-induced dilation of human large epicardial and resistance coronary arteries is mediated by NO and increased by prior ACE inhibition.

Basal release of endothelium-derived nitric oxide at site of spasm in patients with variant angina.

OBJECTIVES: The aim of this study was to investigate the basal release of nitric oxide at spastic sites in patients with variant angina. BACKGROUND: We previously reported that endothelium-dependent dilator responses to acetylcholine, substance P and bradykinin are preserved at the site of coronary artery spasm. However, it is not known whether the basal release of endothelium-derived nitric oxide is altered at the spastic site. METHODS: The effects of intracoronary N(G)-monomethyl-L-arginine (L-NMMA, an inhibitor of nitric oxide synthesis) at cumulative doses of 50, 100 and 200 micromol on basal coronary artery tone were investigated in eight patients with variant angina and normal coronary angiograms and in eight control subjects. The lumen diameters of large epicardial coronary arteries were assessed by quantitative coronary arteriography. RESULTS: Coronary spasm was provoked by the intracoronary administration of acetylcholine in all patients with variant angina. L-NMMA did not alter the arterial pressure and heart rate but significantly decreased the coronary artery diameter at spastic and nonspastic sites. Constrictive responses to L-NMMA were significantly greater (p < 0.01) at the spastic site (constriction by 200 micromol, 22+/-7%, mean +/- SD) than at the nonspastic site (10+/-7%). Constrictive responses to L-NMMA at the nonspastic site in patients with variant angina were comparable to those in the control subjects. CONCLUSIONS: These findings support the hypothesis that the basal release of nitric oxide may not be decreased at the spastic site in patients with variant angina.

[Metastatic carcinoma of the adrenal gland from large cell neuroendocrine carcinoma; report of a case].

A 69-year-old man had undertaken left upper lobectomy (ND 2 a) with partial resection of the left lower lobe under the diagnosis of a primary lung cancer, T2N0M0, stage IB in June, 2002. The histopathological diagnosis was large cell neuroendocrine carcinoma (LCNEC), T3N0M0, stage IIB. The patient was discharged on postoperative day 25. Abdominal computed tomography (CT) revealed an enhanced tumor in the left adrenal lesion, 3 cm in diameter, in October, 2003. Magnetic resonance imaging (MRI) showed a slightly low intensity mass on T1-weighted imaging and slightly high intensity on T2-weighted imaging without invasion to other organs. Tumor marker, NSE was slightly elevated on blood examination. Left adrenalectomy was performed with a surgical margin. Histopathologically, the tumor was diagnosed as metastasis of LCNEC. There is no evidence of recurrence for a year after surgery. Although a prognosis of LCNEC is poor in general, we should consider the resection of metastatic carcinoma of the adrenal gland from LCNEC for long-term survival expectantly.

Hyperreactivity of aortic smooth muscle to serotonin is related to the presence of atheroma in Watanabe heritable hyperlipidaemic rabbits.

OBJECTIVE: The aim was to elucidate the contribution of atheromatous plaque to alterations of smooth muscle contraction to vasoconstrictive agents, by examining vasoreactivity of vascular smooth muscle from the thoracic aorta of 10-13 month old Watanabe heritable hyperlipidaemic rabbits. METHODS: From the same vascular ring of the lower thoracic aorta, a pair of small medial smooth muscle strips was prepared from the sites beneath the atheroma (atherosclerotic medial muscle strip) and from those beneath the plaque-free intima (normal medial muscle strip), and isometric tension was measured. RESULTS: Contractions to 118 mM KCl, histamine (30 nM to 10 microM), and noradrenaline (3 nM to 0.3 microM) were similar between atherosclerotic and the normal medial muscle strip. The ED50 to serotonin was 49(SD 28) and 116(66) nM (p < 0.05, n = 7) and the maximum tension to serotonin was 125(29)% and 82(29)% of that induced by 118 mM KCl (p < 0.01, n = 7) in atherosclerotic and normal medial muscle strip, respectively. Serotonin specific hyperreactivity of the atherosclerotic strip disappeared in Ca(2+)-free solution or in the presence of 10 microM H-7, an inhibitor of protein kinase C. After incubation with 0.1 microM phorbol 12,13-dibutyrate, an activator of protein kinase C, the isometric contractions induced by Ca2+ were significantly greater in atherosclerotic than in normal medial muscle strip. CONCLUSIONS: These results indicate that medial smooth muscle located beneath the atheroma is specifically hyperreactive to serotonin and that altered protein kinase C activity may explain in part the augmented response to serotonin.

Tyrosine kinase inhibitor suppresses the (re) stenotic changes of the coronary artery after balloon injury in pigs.

OBJECTIVE: Restenosis after percutaneous transluminal coronary angioplasty (PTCA) still remains a serious late complication. Many growth factors induced in restenotic lesions may be responsible for restenosis after PTCA. Most of the receptors for such growth factors possess tyrosine kinase activity. This study was designed to determine whether or not a specific tyrosine kinase inhibitor, ST 638, can prevent (re)stenotic changes of the coronary artery after balloon injury. METHODS: A segment of the porcine coronary artery was aseptically wrapped with cotton mesh absorbing either ST 638 or vehicle, followed by balloon injury. Two weeks after the procedure, coronary stenosis and vasoconstricting responses were examined by coronary arteriography and (re)stenotic changes of the coronary artery were histologically examined. Antiphosphotyrosine immunoblotting was also performed to examine the inhibitory effects of ST 638. RESULTS: Coronary arteriography showed the development of mild stenotic lesions at the balloon-injured sites, where hyperconstrictive responses were repeatedly induced by intracoronary serotonin and histamine. Histologically, neointimal formation was noted at the balloon-injured site, where the total vessel area also tended to decrease (geometric remodeling). The treatment with ST 638 suppressed all the hyperconstrictive responses, the neointimal formation, and the geometric remodeling induced by balloon injury. Immunoblotting for phosphotyrosine proteins demonstrated the elevation of proteins at the balloon-injured site, which was suppressed by ST 638. CONCLUSIONS: These results indicate that tyrosine kinases are activated at the balloon-injured site and the inhibition of such kinase activities is effective in reducing both the (re)stenotic changes (neointimal formation and geometric remodeling) and the hyperconstrictive responses of the coronary artery after balloon injury.

Augmentation of coronary responsiveness to serotonin at the site of X-ray-induced intimal thickening in miniature pigs.

OBJECTIVE: X-irradiation is known to enhance atherosclerotic change. We tested whether coronary vasoconstrictor responses are augmented at the sites of X-ray-induced intimal thickening in Göttingen miniature pigs. METHODS: In 17 pigs, a major branch of the left coronary artery was denuded with a balloon catheter. In 10 pigs, the denuded portion of the left coronary artery was selectively irradiated with 15 Gy of X-rays twice at 3 and 4 months after denudation (group 1). The remaining 7 pigs were not irradiated (group 2). The effects of intracoronary administration of serotonin, histamine and phenylephrine on the coronary diameter were studied 3 (3M) and 5 months (5M) after denudation. After the angiographical study at 5M, the vessels were isolated and isometric tension was measured in an organ chamber. RESULTS: The percent reduction in coronary diameter evoked with 10 micrograms.kg-1 of serotonin increased from 39(s.e.m. 4)% before X-irradiation (3M) to 75(6)% after X-irradiation (5M) in group 1 (P < 0.01), while it did not differ in group 2 [39(6)% at 3M vs. 33(8)% at 5M[ [39(6)% at 3M vs. 33(8)% at 5M]. In group 1, serotonin-induced coronary constriction was frequently accompanied by ischemic ECG changes. Histamine (10 micrograms.kg-1)-induced vasoconstriction was also augmented but to a smaller degree [47(6)% at 3M vs. 62(4)% at 5M; P < 0.05] in group 1, while it remained unchanged in group 2[52(5)% at 3M vs. 44(7)% at 5M]. Phenylephrine did not cause detectable contraction in either group at 3M or 5M. Methysergide and ketanserin attenuated serotonin-induced hypercontraction in a dose-dependent fashion. In the in vitro studies, endothelium-dependent relaxation to serotonin was impaired at the denuded site with (group 1) and without (group 2) X-irradiation to a similar extent. Isometric tension of medial smooth muscle developed by serotonin was significantly greater at the denuded site with X-irradiation (group 1) than the control site and the denuded site without X-irradiation (group 2) (P < 0.05). Intimal thickening was significantly greater at the denuded sites with X-irradiation [group 1, 238(45) microns] than at the denuded sites without X-irradiation [group 2, 58(5) microns] (P < 0.05). CONCLUSIONS: These results indicate that X-irradiation augments the coronary vasoconstrictor responses to autacoids, predominantly to serotonin, and that this augmentation is accompanied by enhanced intimal thickening. Serotonin-induced hypercontraction after X-irradiation resulted mainly from the hyperreactivity of medial smooth muscle.

Nuclear accumulation of annexin A2 contributes to chromosomal instability by coilin-mediated centromere damage.

Most human cancers show chromosomal instability (CIN), but the precise mechanisms remain uncertain. Annexin A2 is frequently overexpressed in human cancers, and its relationship to tumorigenesis is poorly understood. We found that annexin A2 is overexpressed in the nuclei of CIN cells compared with cells with microsatellite instability (MIN). Ectopic annexin A2 expression in MIN cells results in a high level of aneuploidy and induces lagging chromosomes; suppression of annexin A2 in CIN cells reduces such CIN signatures with apoptosis of highly aneuploid cells. Ectopic expression of annexin A2 in MIN cells reduces the expression of centromere proteins. Conversely, annexin A2-knockdown in CIN cells increases the expression of centromere proteins. Moreover, the endogenous expression levels of centromere proteins in CIN cells were greatly reduced compared with MIN cell lines. The reduced expression of centromere proteins likely occurred due to aberrant centromere localization of coilin, a major component of the Cajal bodies. These results suggest that nuclear accumulation of annexin A2 has a crucial role in CIN by disrupting centromere function.

Fibronectin fragment-facilitated retroviral transfer of the glutathione-S-transferase pi gene into CD34+ cells to protect them against alkylating agents.

To protect bone marrow cells from the toxicity of chemotherapy, a multidrug resistant gene or a dihydrofolate reductase gene has been introduced into stem cells. These genes, however, are not capable of conferring refractoriness to alkylating agents (AA), which are some of the most commonly used agents in chemotherapy regimens. In the present study, an attempt was made to endow human stem cell (CD34+ cells) with resistance to cyclophosphamide, a well-known AA, and adriamycin (ADM) by transducing the glutathione-S-transferase pi (GST-pi) gene whose product is thought to detoxify AA by conjugating them with glutathione and to remove a toxic peroxide formed by ADM. The gene transduction was carried out retrovirally with a virus titer of 1 x 10(5) FFU/ml, employing a recombinant fibronectin fragment; transduction efficiency was extremely low without the fragment. Incubation with interleukin-6 and stem cell factor enhanced the expression of fibronectin ligands VLA4 and VLA5 on CD34+ cells. This enhanced expression of VLA4 and VLA5 was considered to facilitate a close contact of the CD34+ cell to the retroviral vector via fibronectin fragments and the subsequent transduction process. The GST-pi gene-transduced CD34+ cells formed almost 3- and 2.5-fold more CFU-GM than neo gene-transduced CD34+ cells in the presence of 2.5 microg/ml of 4-hydroperoxycyclophosphamide (4-HC), an active form of cyclophosphamide, and 30 ng/ml ADM, respectively. The transfectants formed an appreciable number of colonies, even at higher concentrations of these drugs (5.0 microg/ml of 4-HC, 50 ng/ml of ADM) whereas neo gene-transduced or nontransduced CD34+ cells formed no colonies at all, indicating the possibility of selecting out the transfectants by exposing them to these anticancer drugs. Thus, we were able to demonstrate that transduction of the GST-pi gene confers resistance to cyclophosphamide as well as to ADM, and therefore this approach can be applied clinically for high-dose chemotherapy.

GST-pi gene-transduced hematopoietic progenitor cell transplantation overcomes the bone marrow toxicity of cyclophosphamide in mice.

Autologous transplantation of bone marrow cells (BMCs) transduced with the multidrug resistance 1 (MDR1) gene or dihydrofolate reductase (DHFR) gene has already been applied in clinical chemoprotection trials. However, anticancer drugs frequently used in high-dose chemotherapy (HDC), such as alkylating agents, are not relevant to MDR1 or DHFR gene products. In this context, we have previously reported that glutathione S-transferase-pi (GST-pi) gene-transduced human CD34(+) cells showed resistance in vitro against 4-hydroperoxicyclophosphamide, an active form of cyclophosphamide (CY). In the present study, a subsequent attempt was made in a murine model to evaluate the effectiveness of transplantation of GST-pi-transduced BMCs to protect bone marrow against high-dose CY. The gene transfection was carried out retrovirally, employing a recombinant fibronectin fragment. Transfection efficiency into CFU-GM was 30%. After the transplantation, recipient mice (GST-pi mice) received three sequential courses of high-dose CY. As the chemotherapy courses advanced, both shortening of recovery period from WBC nadir and shallowing of WBC nadir were observed. In contrast to the fact that three of seven control mice died, possibly due to chemotoxicity, all seven GST-pi mice were alive after the third course, at which point the vector GST-pi gene was detected in 50% of CFU-GM derived from their BMCs and peripheral blood mononuclear cells. When BMCs obtained from these seven mice were retransplanted into secondary recipient mice, 20% of CFU-GM from BMCs showed positive signals for vector GST-pi DNA after 6 months. These data indicate that the GST-pi gene can confer resistance to bone marrow against CY by being transduced into long-term repopulating cells.

Basal release of nitric oxide is decreased in the coronary circulation in patients with heart failure.

It is unknown whether basal release of endothelium-derived nitric oxide in the coronary artery is altered in heart failure in humans. The aim of the present study was to evaluate the effect of inhibition of nitric oxide synthesis on basal tone of the conduit and resistance coronary arteries in awake patients. Coronary blood flow velocity (Doppler guide wire) and coronary arterial diameter (quantitative coronary angiography) were measured in 14 patients with heart failure caused by nonischemic left ventricular dysfunction (7 idiopathic dilated cardiomyopathy and 7 valvular insufficiency) and 7 patients with normal ventricular function (controls). Intracoronary N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide synthesis, at graded doses decreased coronary blood flow in both groups. However, the magnitude of flow reduction was smaller in patients with heart failure than in control patients (P<.0001). The magnitude of coronary blood flow reduction in response to L-NMMA inversely correlated to indexes of left ventricular contractile function (P<.01) but was not affected by the cause of heart failure. Constriction of the large epicardial coronary artery with L-NMMA also tended to be attenuated in patients with heart failure. In summary, vasoconstricting response to L-NMMA was blunted in the coronary resistance artery in heart failure in vivo. These findings suggest that basal release of nitric oxide in the coronary circulation is decreased in patients with heart failure.

Expression of human T-cell leukemia virus type I envelope protein in Saccharomyces cerevisiae.

The entire envelope gene of human T-cell leukemia virus type I (HTLV-I) was inserted into an expression vector and expressed under the control of the repressible acid phosphatase promoter in yeast (Saccharomyces cerevisiae). The product in yeast cells was glycosylated into heterodisperse proteins.

Wideband squeezing in photon number fluctuations from a high-speed light-emitting diode.

Wideband, highly noise-suppressed squeezing was observed by using a high-speed, high-quantum-efficiency light-emitting diode. The squeezing bandwidth extended over 200 MHz. We also have investigated the dependence of the squeezing bandwidth on the pump-current at low temperature. The experimental result was compared with the theoretical predictions based on a unified model of the pump and recombination process and was well explained by the model at the thermionic emission limit.

Ulcerative colitis after autologous peripheral blood stem cell transplantation for non-Hodgkin's lymphoma.

A 54-year-old woman with peripheral T cell lymphoma in second complete remission (CR) received an autologous peripheral blood stem cell transplant (PBSCT). Antibiotic-resistant bloody diarrhea, and fever developed 110 days after transplant. Blood and stool cultures were negative. Skin rash was not observed. Barium enema and colonoscopy showed typical features of pancolonic-type ulcerative colitis (UC). Endoscopic biopsies confirmed the diagnosis of UC. Mesalazine and immunosuppressive therapy improved symptoms dramatically. We detected serum antibodies against synthetic tropomyosin (TM) peptide when UC was diagnosed. We postulate that autoimmunity including autoreactive anti-TM antibodies may be involved in the pathogenesis of UC after autologous PBSCT in this patient.

Co-administration of IL3 with G-CSF increases the CFU-S mobilization into peripheral blood.

In an attempt to establish an efficient method of collecting peripheral blood stem cells and to utilize them for allogeneic peripheral blood stem cell transplantation, the effect of a combined administration of recombinant murine interleukin-3 (IL3) and recombinant human granulocyte colony-stimulating factor (G-CSF) to mobilize bone marrow stem cells into the circulation was examined in C57BL/6 mice. Some appreciable numbers (796 +/- 112/ml) of CFU-GM were recovered 6 days after G-CSF administration (500 micrograms/kg per day), while by IL3 administration (100,000 units/kg per day), the CFU-GM count was much lower (61 +/- 9/ml) with a small peak at day 4. By a combined administration of IL3 (100,000 units/kg per day) and G-CSF (500 micrograms/kg per day), the CFU-GM count at the peak of day 5 was significantly augmented (1178 +/- 277/ml) as compared to that of G-CSF or IL3 alone (P < 0.05). The CFU-S counts at day 5 (168 +/- 12/ml) and at day 6 (172 +/- 27) were also significantly higher than those of IL3 alone (day 5, 30 +/- 15/ml; day 6, 20 +/- 10/ml) or G-CSF alone (day 5, 114 +/- 14/ml; day 6, 112 +/- 19/ml). Thus the combined administration of IL3 and G-CSF appears to be promising for high yield collection of peripheral blood stem cells.