HERG potassium channels are constitutively expressed in primary human acute myeloid leukemias and regulate cell proliferation of normal and leukemic hemopoietic progenitors.

An important target in the understanding of the pathogenesis of acute myeloid leukemias (AML) relies on deciphering the molecular features of normal and leukemic hemopoietic progenitors. In particular, the analysis of the mechanisms involved in the regulation of cell proliferation is decisive for the establishment of new targeted therapies. To gain further insight into this topic we report herein a novel approach by analyzing the role of HERG K(+) channels in the regulation of hemopoietic cell proliferation. These channels, encoded by the human ether-a-gò-gò-related gene (herg), belong to a family of K(+) channels, whose role in oncogenesis has been recently demonstrated. We report here that herg is switched off in normal peripheral blood mononuclear cells (PBMNC) as well as in circulating CD34(+) cells, however, it is rapidly turned on in the latter upon induction of the mitotic cycle. Moreover, hergappears to be constitutively activated in leukemic cell lines as well as in the majority of circulating blasts from primary AML. Evidence is also provided that HERG channel activity regulates cell proliferation in stimulated CD34(+) as well as in blast cells from AML patients. These results open new perspectives on the pathogenetic role of HERG K(+) channels in leukemias.

Gravitational unloading induces osteoclast-like differentiation of FLG 29.1 cells.

FLG 29.1 cells, cultured at 1xg, are able to switch on a differentiating process only when they are suitably induced by chemical factors. On the contrary, when FLG 29.1 cells are cultured in conditions of gravitational unloading, simulated by a Random Positioning Machine, the switching on of the differentiation process occurs in the absence of any added differentiating agent or any stimulating factor. The phenotypic characterization of the cells and quantitative measures of their bone resorption activity are consistent with a differentiation process through the osteoclastic pathway.

In vitro activity of vinorelbine on human leukemia cells.

Vinorelbine (VNR) is a semi-synthetic Vinca rosea alkaloid that has been employed both as a single agent and in combination, and has shown significant antitumor activity. As little is known about VNR activity on human leukemia, we studied its in vitro cytotoxic effect on human leukemia cell lines (FLG 29.1, HL60, K562, Balm 4, CEM and Daudi) and on fresh leukemia cells from 28 patients: 2 acute myeloid leukemia (AML); 3 chronic myeloid leukemia in blastic phase (CML-BP); 5 acute lymphoblastic leukemia (ALL); 18 B-chronic lymphatic leukemia (B-CLL), employing the colorimetric INT assay and determining the IC50. We observed that VNR exerts its cytotoxic activity on leukemic cell lines in a dose-dependent fashion. The lymphoid cell lines appear more sensitive than the myeloid ones to the VNR-dependent growth inhibition. A similar pattern was noticed for leukemia cells in primary cultures. VNR is not effective on CML-BP cells, shows variable activity on the AML and ALL cells and is very effective against B-CLL cells. VNR inhibited the growth of fresh B-CLL cells from 15 of 18 patients, the IC50 doses ranging from 4 ng/ml to 83 microg/ml (doses coinciding with the plasma levels obtained in clinics). These observations strongly suggest that VNR could be useful in clinics for the treatment of B-CLL.

HERG K+ channels activation during beta(1) integrin-mediated adhesion to fibronectin induces an up-regulation of alpha(v)beta(3) integrin in the preosteoclastic leukemia cell line FLG 29.1.

Integrin receptors have been demonstrated to mediate either "inside-to-out" and "outside-to-in" signals, and by this way are capable of regulating many cellular functions, such as cell growth and differentiation, cell migration, and activation. Among the various integrin-centered signaling pathways discovered so far, we demonstrated that the modulation of the electrical potential of the plasma membrane (V(REST)) is an early integrin-mediated signal, which is related to neurite emission in neuroblastoma cells. This modulation is sustained by the activation of HERG K(+) channels, encoded by the ether-à-go-go-related gene (herg). The involvement of integrin-mediated signaling is being discovered in the hemopoietic system: in particular, osteoclasts are generated as well as induced to differentiate by interaction of osteoclast progenitors with the stromal cells, through the involvement of integrin receptors. We studied the effects of cell interaction with the extracellular matrix protein fibronectin (FN) in a human leukemic preosteoclastic cell line (FLG 29.1 cells), which has been demonstrated to express HERG currents. We report here that FLG 29.1 cells indeed adhere to purified FN through integrin receptors, and that this adhesion induces an osteoclast phenotype in these cells, as evidenced by the appearance of tartrate-resistant acid phosphatase, as well as by the increased expression of CD51/alpha(v)beta(3) integrin and calcitonin receptor. An early activation of HERG current (I(HERG)), without any increase in herg RNA or modifications of HERG protein was also observed in FN-adhering cells. This activation is apparently sustained by the beta(1) integrin subunit activation, through the involvement of a pertussis-toxin sensitive G(i) protein, and appears to be a determinant signal for the up-regulation of alpha(v)beta(3) integrin, as well as for the increased expression of calcitonin receptor.

Multispectral imaging autofluorescence microscopy for the analysis of lymph-node tissues.

Although histochemical and immunohistochemical methods are the standard procedures in diagnosis of lymphoproliferative disorders, useful improvements in evidencing histopathologic manifestations can be obtained with the introduction of tissue autofluorescence analyses. We used microspectrofluorometry and a Multispectral Imaging Autofluorescence Microscopy (MIAM) technique to analyze lymph-node biopsies from patients with lymphoadenopathy of different origins. Images of tissue autofluorescence were obtained by excitation at 365 nm of lymph-node sections and sequential detection with interference filters (50 nm bandwidth) peaked at 450, 550 and 658 nm. Monochrome images were combined together in a single red-green-blue color image. Most of the fluorescence was observed within the blue spectral band because of large contributions from extracellular collagen and elastin fibers as well as from reduced form of intracellular nicotinamide adenine dinucleotide (phosphate). Autofluorescence imaging shows morphological differences between neoplastic and non-neoplastic tissues. The reactive hyperplasia samples show the typical lymph-node organization with weak fluorescent follicles separated by high fluorescent connective trabeculae. In the neoplastic lymph nodes the loss of follicle organization is observed. Consequently, MIAM permits to discriminate between non-neoplastic and neoplastic tissues on the basis of their autofluorescence pattern. Multispectral imaging of tissue autofluorescence may present some advantages with respect to standard histochemical microscopy since it (1) does not require any chemical manipulation of samples; (2) gives real-time results performing the analysis immediately upon specimen resection; and (3) supplies a representation of the biological structure organization linked to endogenous fluorophores.

Incubation of murine bone marrow cells in hypoxia ensures the maintenance of marrow-repopulating ability together with the expansion of committed progenitors.

We developed previously a hypoxic culture system in which progenitors endowed with marrow-repopulating ability (MRA), unlike committed progenitors, were selected and maintained better than in air. We report here an improvement to this system targeted at combining the maintenance of progenitors sustaining MRA with the numerical expansion of multipotent and committed progenitors. Murine bone marrow cells were incubated at 1% oxygen in liquid medium supplemented with stem cell factor, granulocyte colony-stimulating factor, interleukin-6 and interleukin-3. In day 8 hypoxic cultures, the numbers of high proliferative potential and granulocyte/macrophage colony-forming cells (HPP-CFC and CFU-GM) were increased with respect to time zero. Colonies generated by HPP-CFC derived from hypoxic cultures exhibited a high replating ability, whereas colonies generated by HPP-CFC derived from control cultures exhibited a low replating ability. MRA was fully maintained in hypoxia and markedly reduced in air. Thus, severe hypoxia is able to ensure a full maintenance of progenitors sustaining MRA, together with a significant expansion of in vitro-detectable clonogenic progenitors, including those endowed with replating ability. This system could contribute to the improvement of current techniques for the in vitro treatment of human haematopoietic cell populations before transplantation.

Activity of vinorelbine on B-chronic lymphocytic leukemia cells in vitro.

Vinorelbine (VNR) is a new semi-synthetic Vinca rosea alkaloid that has been employed both in combination and as a single agent, showing a significant antitumour activity. Since little is known about VNR in human leukemia, we studied the in vitro cytotoxic effect of VNR on peripheral blood lymphocytes from 18 patients affected by B-chronic lymphocytic leukemia (CLL), employing the INT assay. VNR inhibited fresh B-CLL cells from 15/18 patients in primary cultures, the ID50 doses ranging from 4 ng/ml to 83 micrograms/ml. These data strongly suggest that VNR could be effective in the treatment of B-CLL.

A simple, one-step clonal assay allows the sequential detection of committed (CFU-GM-like) progenitors and several subsets of primitive (HPP-CFC) murine progenitors.

Murine bone marrow (BM) cells were cultured in semisolid medium containing interleukin 3 (IL-3) and high doses of G-CSF. Colonies were counted twice, at day 7 and day 14, and the number of granulocyte/macrophage colony-forming units (CFU-GM) accurately estimated by the subtraction of day-14 from day-7 colonies, based on the principle that colonies detectable at day 7 and persisting beyond day 14 are generated by significantly more immature progenitors. The frequency of colonies relative to their size was determined and used to define subsets of high proliferative potential colony-forming cells (HPP-CFC). Two main groups of HPP-CFC were considered: those generating colonies of 0.6-1.8 mm of diameter or larger than 1.8 mm. The characterization of these groups showed that they correspond to different functional subsets of HPP-CFC. The replating ability of colonies was estimated. The percentage of clonogenic progenitors in the S phase of cell cycle was measured by cytosine arabinoside suicide assay. The sensitivity of colonies to 5-fluorouracil (5-FU) in vitro was determined and their survival after an in vivo treatment with 5-FU compared with that of colony-forming units in spleen (CFU-S). This technique allowed identification of: A) CFU-GM; B) relatively mature HPP-CFC, probably corresponding to CFU-S day12; C) more primitive HPP-CFC, relatively resistant to 5-FU in vivo and closely corresponding to CFU-S day 14, and D) very primitive HPP-CFC, resistant to 5-FU in vitro. This simple, rapid, and versatile method allows the detection of a broad range of hematopoietic progenitors in murine BM, from committed progenitors to largely quiescent, primitive stem cells, as well as the evaluation of the progenitors' self-renewal and proliferative potential.

Butyrate-stable monosaccharide derivatives induce maturation and apoptosis in human acute myeloid leukaemia cells.

The rapid degradation and subsequent lack of efficacy of n-butyric acid in vivo has been improved by the synthesis of monosaccharide stable pro-drugs of butyric acid. We studied the effects of D1 (O-n-butanoyl-2,3-O-isopropylidene-alpha-D-mannofuranoside), G1 (1-O-n-butanoyl-D,L-xylitol), and F1 (1-O-n-butanoyl 2,3-O-isopropylidene-D,L-xylitol) on the maturation and proliferation of AML cell lines HL 60 and FLG 29.1 and of purified blast cells from 10 cases of de novo acute myeloid leukaemia (AML). AML cell maturation was measured by surface antigen expression, morphology and cytochemistry. Toxicology in mice was also evaluated (DL50 1000 mg/kg). In HL 60 cells G1 and D1 increased the expression of CD15 and CD11a (presenting 62% of promyelo-metamyelocytes), and in 7/10 cases of primary AMLs that of CD11a, CD11b, CD15, and myeloperoxidase. D1, G1 and F1 induced a dose-dependent inhibition of tritiated thymidine uptake. Apoptosis (evaluated by flow cytometry and agarose gel electrophoresis) was induced in AML blasts by D1 and F1 (79% and 94% respectively for HL 60 cells) and, with less effect, by G1 (27%). The persistence of maturative and apoptotic activity in these new pro-drugs of butyric acid, hydrolysed only inside the tumour cell, suggests a possible use in differentiation therapy of myelodysplastic syndromes and AMLs.

Severe hypoxia enhances the formation of erythroid bursts from human cord blood cells and the maintenance of BFU-E in vitro.

Incubation in severe hypoxia (1% oxygen) increased the number of erythroid bursts generated from full-term CD34+, or premature mononucleated, human cord blood (CB) cells, in semisolid cultures containing stem cell factor (SCF), interleukin (IL)-3 and erythropoietin (EPO). Severe hypoxia also enhanced the maintenance of erythroid burst-forming units (BFU-E) in CB cell liquid cultures. These positive effects of hypoxia on the maintenance and cloning efficiency of BFU-E did not extend to the other progenitors assayed. Hypoxia, on the other hand, markedly reduced the size and level of hemoglobinization of bursts and, in liquid cultures, suppressed the growth factor-stimulated numerical increase in BFU-E and inhibited the expression of CD36, a marker of erythroid colony-forming units and maturing erythroid precursors. However, when transferred to clonal assays incubated in air, cells from liquid cultures incubated in hypoxia or in air generated fully expanded and hemoglobinized bursts, suggesting that in hypoxia the clonogenic potential of BFU-E was maintained and the development of erythroid clones reversibly inhibited. These results indicate that hypoxia inversely regulates two subsequent phases of erythropoiesis, i.e., it enhances the maintenance of BFU-E and the early development of erythroid clones but inhibits the terminal expansion and maturation of these clones. The cloning of CB cells selected for CD34 positivity, when compared with that of the total population of mononucleated CB cells, revealed that the early development of erythroid bursts was either hypoxia-enhanced or hypoxia-insensitive, reflecting the existence of two different types of BFU-E. Hypoxia-enhanced BFU-E are relatively immature, are maintained in hypoxia but not in air, and account for a large part of CD34+ BFU-E and for a high percentage of the BFU-E in premature CB. Hypoxia-insensitive BFU-E are mostly CD34- and are largely predominant in full-term CB, and most probably correspond to a more mature type of BFU-E.

Detection of bcr/abl transcripts by RT-PCR and their colorimetric evaluation in chronic myeloid leukemia patients receiving allogeneic bone marrow transplantation.

BACKGROUND: Chronic myeloid leukemia (CML) is a disease characterized by the presence of a unique molecular marker, i.e. the fusion gene bcr-abl and its mRNA and protein products. This marker permits minimal residual disease follow-up after bone marrow transplantation (BMT) through cytogenetic or molecular analysis. Although the reverse transcriptase polymerase chain reaction (RT-PCR) method is largely employed, the clinical value and impact of a positive RT-PCR as a herald of hematological relapse has not yet been definitively ascertained. METHODS: In order to verify the frequency of bcr-abl positivity in CML patients who underwent alloBMT, we performed serial two-step RT-PCR on 63 peripheral blood and bone marrow specimens obtained at different times after non T-cell-depleted BMT from 16 CML patients treated in our Institution. After amplification, RT-PCR products were always checked by liquid hybridization with a specific probe. Median molecular follow-up after BMT was 38 months (range 2-144 months). RESULTS: None of the patients studied presented clinical hematological relapse after BMT. Six out of sixteen patients were found to be positive for bcr-abl. PCR positivity appeared in 4/6 patients more than one year post-BMT and in 2/6 patients within one year post BMT. In both instances PCR was an isolated finding in 5/6 patients and reverted to negativity in subsequent analysis; only one case was PCR-positive twice. It is noteworthy that RT-PCR positivity appeared in five patients presenting acute or chronic graft versus host disease (GVHD) and in one patient who had received MUD-BMT. CONCLUSIONS: In our cohort of patients, transient bcr-abl positivity had no clinical relevance and was also found in MUD-BMT without heralding hematological relapse. Our observations further stress the importance of applying only quantitative PCR methods during the post BMT follow-up of CML patients.

Effects of fludarabine and gemcitabine on human acute myeloid leukemia cell line HL 60: direct comparison of cytotoxicity and cellular Ara-C uptake enhancement.

This study was designed to compare the effects of fludarabine and gemcitabine on cytosine arabinoside (Ara-C) uptake and retention, and their specific cytotoxicity on HL 60 human acute myeloid leukemia cells. The leukemic blasts were exposed to either drug at equimolar concentrations (10 microM) for 3 h and further incubated with Ara-C (5 microM), added immediately (day 0) or after an interval of 24 h in cells were kept in a drug free medium (day 1). On day 0, leukemic cells exposed to fludarabine 10 microM had a significant (P<0.01) increase in Ara-C uptake (297 +/- 11 pmol/10(7) cells) with respect to control cells (not pre-treated: 195 +/- 10 pmol/10 (7) cells). After treatment of leukemic cells with fludarabine, cytoplasmic Ara-C peaked after 180 min of exposure, as well as nuclear bound Ara-C. At the same time, a significant decrease in the number of S-phase leukemic cells, consistent with depressed [3 H]TdR uptake was observed. Although on day 0 gemcitabine 10 microM did not have potentiating effects on Ara-C uptake, it showed a high degree of intrinsic cytotoxicity as a single agent(clear from cell cycle distribution, [3H]TdR uptake, plating efficiency (PE) data and percentage of apoptotic cells). Cells exposed to gemcitabine, on the other hand, showed on day 1 a significant increase in Ara-C uptake (2.4 x control values in the cytoplasmic and 3x in the nuclear fractions) and a reduced number of S-phase blasts, [3H]TdR uptake and PEs, as well as an increased apoptotic cell death. Evidently, it is possible to modulate Ara-C uptake by leukemic cells with gemcitabine. Although this effect is similar to that demonstrated with fludarabine, its kinetics and time of efficacy are different and also, because of its intrinsic higher cytoxicity and lack of important side effects, gemcitabine could be considered a suitable candidate for Ara-C association therapy in acute leukemia.

Natural fluorescence of white blood cells: spectroscopic and imaging study.

Autofluorescence has been proved to be an intrinsic parameter of biological substrates that may aid in both the characterization of the physiological state and the discrimination of pathological from normal conditions of cells, tissues and organs. In this work, the fluorescence properties of human white blood cells have been studied in suspension and on single cells at microscopy. The results indicate that suspensions of agranulocytes and granulocytes differ in the amplitude of the fluorescence signal on excitation at wavelengths in the range 250-370 nm. The differences are particularly enhanced when excitation is performed in the 250-265 nm range. Microspectrofluorometric analysis, performed on single cells, allows several leukocyte families to be characterized. Lymphocytes, monocytes, neutrophils and eosinophils can be distinguished according to the intensity and spectral shape of the autofluorescence emission in the visible range from 440 to 580 nm. Both the nature and extent of the differences change when the excitation wavelength is moved from 366 to 436 nm. Differences in the intrinsic metabolic engagement, rather than in the cell dimensions, seem to be responsible for the differences observed between the leukocyte populations. The results identify interesting perspectives for autofluorescence as a discriminating parameter in the differential counting of human white blood cells.

Functional and structural interactions between osteoblastic and preosteoclastic cells in vitro.

Osteoblasts are involved in the bone resorption process by regulating osteoclast maturation and activity. In order to elucidate the mechanisms underlying osteoblast/preosteoclast cell interactions, we developed an in vitro model of co-cultured human clonal cell lines of osteoclast precursors (FLG 29.1) and osteoblastic cells (Saos-2), and evaluated the migratory, adhesive, cytochemical, morphological, and biochemical properties of the co-cultured cells. In Boyden chemotactic chambers, FLG 29.1 cells exhibited a marked migratory response toward the Saos-2 cells. Moreover, they preferentially adhered to the osteoblastic monolayer. Direct co-culture of the two cell types induced: (1) positive staining for tartrate-resistant acid phosphatase in FLG 29.1 cells; (2) a decrease of the alkaline phosphatase activity expressed by Saos-2 cells; (3) the appearance of typical ultrastructural features of mature osteoclasts in FLG 29.1 cells; (4) the release into the culture medium of granulocyte-macrophage colony stimulating factor. The addition of parathyroid hormone to the co-culture further potentiated the differentiation of the preosteoclasts, the cells tending to fuse into large multinucleated elements. These in vitro interactions between osteoblasts and osteoclast precursors offer a new model for studying the mechanisms that control osteoclastogenesis in bone tissue.

In vitro structural and functional relationships between preosteoclastic and bone endothelial cells: a juxtacrine model for migration and adhesion of osteoclast precursors.

The role of vascularization in the process of bone resorption has not been clarified. The interactions between vascular endothelium and osteoclast progenitors were analyzed using clonal cell lines of bone-derived endothelial and preosteoclastic cells. Insulin-like growth factor I is a major chemotactic stimulator of preosteoclastic cell migration mediated by bone endothelial cells. Osteoclast precursors rapidly adhered to bone endothelial monolayers. This phenomenon appeared to be cell-specific and mediated through the binding of vitronectin and fibronectin receptors to fibronectin. In addition, direct contact with bone endothelial cells induced osteoclast progenitors to differentiate into more mature elements, with the tendency to cluster together to form large multinucleated cells. These findings demonstrated specific in vitro interactions between bone endothelial cells and osteoclast progenitors, offering a new model for understanding the molecular mechanisms which direct the processes of osteoclast recruitment and ontogeny.

Role for autocrine TGF-beta 1 in regulating differentiation of a human leukemic cell line toward osteoclast-like cells.

Increasing evidence suggests that transforming growth factor-beta (TGF-beta) is involved in bone formation during remodeling. Using a recently cloned human leukemic cell line (FLG 29.1 cells) we demonstrate that these cells synthesize and secrete TGF-beta 1 and that exogenous or autocrine TGF-beta 1 can induce the same features of osteoclastic-like cells, exerting its effects through the binding to TGF-beta specific receptors. Scatchard analysis of 125I-labeled TGF-beta 1 to FLG 29.1 cells revealed the presence of a single high affinity binding site with a Kd value of approximately 25 pM and a binding capacity of approximately 900 sites/cell. Affinity labeling experiments showed that FLG 29.1 cells express type I and type II TGF-beta receptors. Stimulation of FLG 29.1 cells with low TGF-beta 1 doses reduced cell proliferation and increased cell adhesion and tartrate resistant acid phosphatase (TRAcP) activity. Pretreatment of FLG 29.1 cells with TGF-beta 1 caused a significant and dose-dependent response to calcitonin. Northern blot of total mRNA and analysis of the conditioned media (CM) showed that TGF-beta 1 was synthesized by FLG 29.1 cells. TPA treatment, which induces partial differentiation of these cells, markedly increased TGF-beta 1 mRNA expression and growth factor release. The majority of TGF-beta 1 secreted by TPA-treated cells was in its latent form. However, anti-TGF-beta antibodies inhibited TGF-beta 1 and TPA-induced growth inhibition, calcitonin responsiveness, and TRAcP activity, suggesting that the TPA effect is mediated in part by autocrine TGF-beta 1 and indicating that the cells can activate and respond to the TGF-beta that they secrete. These findings support a potential autocrine role for TGF-beta 1 in osteoclast differentiation.

Binding and bioeffects of Ipriflavone on a human preosteoclastic cell line.

Ipriflavone, a synthetic isoflavone derivative, reduces bone resorption by inhibiting osteoclasts activity. In order to evaluate the role of Ipriflavone on osteoclast growth and differentiation, we tested Ipriflavone and its four "in vivo" main metabolites (Metabolites I, II, III, and V) on a clonal population of human osteoclast precursor cells (FLG 29.1). Pharmacological doses of Ipriflavone and Metabolite III were able to inhibit cell proliferation and interleukin 6 release. In co-cultures of FLG 29.1 cells and osteoblastic (Saos-2) cells Ipriflavone at 1 microM dose inhibited the adhesion of FLG 29.1 cells to the osteoblastic monolayer and reduced the immunocytochemical reaction of the vitronectin receptor. Binding studies with tritiated Ipriflavone showed the presence of a single specific binding site, wtih a Kd of about 70 nM and a binding capacity of 8 fmol/10(6) cells. These results demonstrate a direct effect of Ipriflavone and of Metabolite III on the human osteoclast precursor cell line FLG 29.1.

Identification of hematopoietic progenitor cells in human amniotic fluid before the 12th week of gestation.

Due to technical difficulties in performing amniocentesis before the 12th week of pregnancy, very little is known about the components of human amniotic fluid before that time. Amniocentesis was performed between the 7th-11th week of gestation in 25 informed and consenting patients, who had to undergo therapeutic interruption of pregnancy. The cells from the amniotic fluid were stained, counted on a hemocytometer, and checked for vitality. The origin of these cells was determined from cellular cultures the intracellular content of the hemoglobin and the chloroacetate esterase content of the hemoglobin and the chloroacetate esterase contents were also studied. Taking advantage of the "in vitro" adhesive properties of these cells to the bone marrow stromal feeder layer, we obtained clonal growth of an erythroid nature from 18 out of 33 samples. At the 17th week of gestation, an increased number of cells and a decrease in their vitality was found. Between the 7th and 12th week, the cellular composition of the fluid was totally different from that found later in the pregnancy. Small nucleated, round cells were identified as hematopoietic progenitor cells. At the beginning of the 11th week, a cellular population, typically used to perform prenatal diagnosis of chromosomal abnormalities from the 14th week of pregnancy appeared. Since hematopoietic progenitor cells were found in the amniotic fluid before the 12th week of gestation, these cells most probably come from the hematopoietic cells of the yolk sac through the thin membrane of the yolk sac at this time.