Formation and activation of a cyclin E-cdk2 complex during the G1 phase of the human cell cycle

Human cyclin E, originally identified on the basis of its ability to function as a G1 cyclin in budding yeast, associated with a cell cycle-regulated protein kinase in human cells. The cyclin E-associated kinase activity peaked during G1, before the appearance of cyclin A, and was diminished during exit from the cell cycle after differentiation or serum withdrawal. The major cyclin E-associated kinase in human cells was Cdk2 (cyclin-dependent kinase 2). The abundance of the cyclin E protein and the cyclin E-Cdk2 complex was maximal in G1 cells. These results provide further evidence that in all eukaryotes assembly of a cyclin-Cdk complex is an important step in the biochemical pathway that controls cell proliferation during G1.

Growth-promoting activity of tissue inhibitor of metalloproteinases-1 (TIMP-1) for a wide range of cells. A possible new growth factor in serum

Human tissue inhibitor of metalloproteinases-1 (TIMP-1), but not TIMP-2, has potent growth-promoting activity for a wide range of human and bovine cells. TIMP-1 seems to be a new cell-growth factor in serum and to stimulate the cells independently of its inhibitory activity.

Loss of teratogenic response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice lacking the Ah (dioxin) receptor

BACKGROUND

The aryl hydrocarbon receptor (AhR or dioxin receptor) is a ligand-activated transcription factor that is considered to mediate pleiotropic biological responses such as teratogenesis, tumour promotion, epithelial hyperplasia and the induction of drug-metabolizing enzymes to environmental contaminants usually represented by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In contrast to the role of AhR in the regulatory mechanism of xenobiotic-metabolizing enzymes, there is no direct proof that the AhR is involved in the teratogenic effects of TCDD.

RESULTS

To gain insight into the physiological and teratogenic role of the AhR, we have used gene targeting in mice to disrupt the murine Ahr gene by homologous recombination. Ahr-null mice were viable and fertile and were apparently normal at birth, but displayed a slightly slower growth rate than wild-type mice for the first few weeks of life. When pregnant dams were administered with TCDD by gavage, at a dose of 40 microg/kg body weight at gestation day 12.5, none of the Ahr-null mutant foetuses were sensitive to the teratogenic effects of TCDD, although almost all wild-type foetuses suffered from cleft palate and hydronephrosis. In heterozygous Ahr+/- genotypes, nearly all foetuses suffered from hydronephrosis in response to TCDD treatment, while haplo-insufficiency was observed in the incidence of cleft palate.

CONCLUSION

These results clearly show that the AhR is involved in the malformation of the palate and kidney in mouse embryos caused by TCDD and suggests that the mechanism of its involvement differs between the cleft palate and hydronephrosis.

Lung nodule enhancement at CT: multicenter study

PURPOSE

To test the hypothesis that absence of statistically significant lung nodule enhancement (< or =15 HU) at computed tomography (CT) is strongly predictive of benignity.

MATERIALS AND METHODS

Five hundred fifty lung nodules were studied. Of these, 356 met all entrance criteria and had a diagnosis. On nonenhanced, thin-section CT scans, the nodules were solid, 5-40 mm in diameter, relatively spherical, homogeneous, and without calcification or fat. All patients were examined with 3-mm-collimation CT before and after intravenous injection of contrast material. CT scans through the nodule were obtained at 1, 2, 3, and 4 minutes after the onset of injection. Peak net nodule enhancement and time-attenuation curves were analyzed. Seven centers participated.

RESULTS

The prevalence of malignancy was 48% (171 of 356 nodules). Malignant neoplasms enhanced (median, 38.1 HU; range, 14.0-165.3 HU) significantly more than granulomas and benign neoplasms (median, 10.0 HU; range, -20.0 to 96.0 HU; P < .001). With 15 HU as the threshold, the sensitivity was 98% (167 of 171 malignant nodules), the specificity was 58% (107 of 185 benign nodules), and the accuracy was 77% (274 of 356 nodules).

CONCLUSION

Absence of significant lung nodule enhancement (< or = 15 HU) at CT is strongly predictive of benignity.

Sensitive high-performance liquid chromatographic determination of ionic drugs in biological fluids with short-wavelength ultraviolet detection using column switching combined with ion-pair chromatography: application to basic compounds

A highly sensitive and selective high-performance liquid chromatographic method with short-wavelength UV detection is described for the determination of ionic compounds in biological fluids, which was applied to two basic compounds, 2-(3-[4-(4-fluorophenyl)-1-piperazinyl]propyl)-6,7,8,9-tetrahydro-2H-nap htho [2,3-b][1,4]oxazin-3(4H)-one (I) and methyl 2-(4-diphenylmethyl-1-piperazinyl)ethyl (+/-)-1,4-dihydro-2,6-dimethyl-4-(m-nitrophenyl)-3,5-pyridinedicarboxyla te (II), in human serum. The method is based on the combination of the column-switching technique and ion-pair chromatography. In the first ODS column, the analyte is pre-separated from endogenous substances in serum by ion-pair chromatography. After column switching, in the second ODS column the heart-cut fraction containing the analyte is further separated by non-ion-pair chromatography from coeluted endogenous substances from the first ODS column. The proposed method offered high sensitivity and selectivity with UV detection at 215 nm for I and 230 nm for II. The detection limits were 0.2 ng/ml for both I and II using 1 ml of serum. The principle of the proposed method would be applicable to both acidic and basic compounds in biological fluids with a suitable ion-pair reagent.

Cell growth-promoting activity of tissue inhibitor of metalloproteinases-2 (TIMP-2)

Human tissue inhibitor of metalloproteinases-2 (TIMP-2) has a potent growth-promoting activity for wide range of human, bovine and mouse cells, having an optimal concentration (10 ng/ml, 0.46 nM) that is ten-times lower than that of TIMP-1 (Hayakawa et al. (1992) FEBS Lett. 298, 29). Neither TIMP-1 complexed with progelatinase B nor TIMP-2 complexed with progelatinase A, both of which have full inhibitory activity against active forms of matrix metalloproteinases (MMPs), showed any cell growth-promoting activity. On the contrary, both reductively alkylated TIMPs had no MMP inhibitory activity, but significantly stimulated cell proliferation. These facts clearly indicate that the cell-proliferation. These facts clearly indicate that the cell-proliferating activity of TIMPs is independent of MMP inhibitory activity. We also demonstrated that [3H]thymidine was significantly incorporated into Raji cells, a Burkitt lymphoma cell line, in the presence of either 4 ng/ml of TIMP-1 or 0.1 ng/ml of TIMP-2. Under steady-state conditions at 4 degrees C, high-(Kd = 0.15 nM) and low-(35 nM) affinity binding sites for TIMP-2 were identified on Raji cells with 20,000 and 1.4 × 10(5) sites/cell, respectively. Both high- and low-affinity binding of 125I-TIMP-2 to Raji cells were competitively inhibited by unlabeled TIMP-2 but not by unlabeled TIMP-1, suggesting the presence of receptors for TIMP-2 independent from those for TIMP-1. TIMP-2 seems to be another new TIMP cell-growth factor in serum, besides TIMP-1.

Molecular regulation of the endothelin-1 gene by hypoxia. Contributions of hypoxia-inducible factor-1, activator protein-1, GATA-2, AND p300/CBP

Endothelin-1 (ET-1) is a peptide hormone with potent vasoconstrictor properties which is synthesized and secreted predominantly by vascular endothelial cells. Its production is regulated by numerous stimuli including ischemia and hypoxia, and the enhanced levels that occur during myocardial ischemia may contribute to the progression of heart failure. We reported previously a preliminary characterization of a hypoxia-inducible factor-1 (HIF-1) binding site in the human ET-1 promoter which contributed to the activation of ET-1 expression in endothelial cells. We report here that the HIF-1 binding site alone is not sufficient for the response to hypoxia but requires an additional 50 base pairs of flanking sequence that includes binding sites for the factors activator protein-1 (AP-1), GATA-2, and CAAT-binding factor (NF-1). Mutation of any one of these sites or the HIF-1 site eliminated induction by hypoxia. Mutations of the AP-1 and GATA-2 sites, but not the HIF-1 site, were complemented by overexpressing AP-1, GATA-2, HIF-1alpha, or the activator protein p300/CBP, restoring the response to hypoxia. Binding studies in vitro confirmed physical associations among GATA-2, AP-1, and HIF-1 factors. Overexpression or depletion of p300/CBP modulated the level of ET-1 promoter expression as well as the endogenous ET-1 transcript but did not change the fold induction by hypoxia in either case. Regulation of the ET-1 promoter by hypoxia in non-endothelial cells required overexpression of GATA-2 and HIF-1alpha. The results support essential roles for AP-1, GATA-2, and NF-1 in stabilizing the binding of HIF-1 and promoting recruitment of p300/CBP to the ET-1 hypoxia response complex.

DNA sensing on a DNA probe-modified electrode using ferrocenylnaphthalene diimide as the electrochemically active ligand

Naphthalene diimide derivative 1 carrying ferrocenyl moieties at the termini of imide substituents binds intact calf thymus DNA 4 times more strongly than the denatured DNA, and its complex with the intact DNA dissociates 80 times more slowly than that with the denatured DNA. On the basis of these observations, ligand 1 was applied to a probe of electrochemical DNA sensing. A thiol-linked single-stranded DNA probe was immobilized through the S-Au bonding to 20-30 pmol/mm2 on a gold electrode. Following hybridization with the complementary DNA, the electrode was soaked in a solution containing 1 (intercalation step) and then washed with buffer for 5 s. The cyclic voltammogram and differential pulse voltammogram for this electrode gave an electrochemical signal due to the redox reaction of 1 that was bound to the double-stranded DNA on the electrode. Thus, dA20 and the yeast choline transport gene were quantitated at the subpicomole level. The sensitivity of DNA detection was improved to 10 zmol by reducing the amount of immobilized DNA probe and protecting the uncovered surface of the electrode with 2-mercaptoethanol.

The cdc2-related protein p40MO15 is the catalytic subunit of a protein kinase that can activate p33cdk2 and p34cdc2

Activation of the cyclin-dependent protein kinases p34cdc2 and p33cdk2 requires binding with a cyclin partner and phosphorylation on the first threonine residue in the sequence THEVVTLWYRAPE. We present evidence that this threonine residue, number 160 in p33cdk2, can be specifically phosphorylated by a cdc2-related protein kinase from Xenopus oocytes called p40MO15. Binding to cyclin A and phosphorylation of this threonine are both required to activate fully the histone H1 kinase activity of p33cdk2. In cell extracts, a portion of p40MO15 is found in a high molecular weight complex that is considerably more active than a lower molecular weight form. Wild-type MO15 protein expressed in bacteria does not possess kinase activity, but acquires p33cdk2-T160 kinase activity after incubation with cell extract and ATP. We conclude that p40MO15 corresponds to CAK (cdc2/cdk2 activating kinase) and speculate that, like p33cdk2 and p34cdc2, p40MO15 requires activation by phosphorylation and association with a companion subunit.

Endometrial cysts: diagnosis with MR imaging

The value of 1.5-T magnetic resonance (MR) imaging in diagnosing endometrial cysts and differentiating them from other gynecologic masses was prospectively evaluated in 374 female patients with clinically suspected adnexal masses. A suggestive diagnosis of endometrial cyst was made when a cyst that was hyperintense on T1-weighted images exhibited homogeneous hyperintensity on T2-weighted images. A definitive diagnosis was made when a cyst that was hyperintense on T1-weighted images exhibited hypointense signal on T2-weighted images (shading) or when the lesion consisted of multiple hyperintense cysts on T1-weighted images (multiplicity) regardless of the signal intensity on T2-weighted images. Surgery was performed in 293 patients, and confirmation was obtained in 354 lesions. MR imaging enabled accurate diagnosis of 77 of 86 endometrial cysts and exclusion of the diagnosis of endometrial cyst in 263 of 268 other gynecologic masses with or without internal hemorrhage. The overall diagnostic sensitivity, specificity, and accuracy were 90%, 98%, 96%, respectively. MR imaging seems to be an acceptable diagnostic test on which clinical decisions can be based in selecting treatment.

Positron emission tomography using fluorine-18 deoxyglucose in evaluation of coronary artery bypass grafting

To assess the clinical value of positron emission tomography (PET) in the evaluation of coronary artery bypass grafting (CABG), PET perfusion and metabolic imaging using nitrogen-13 ammonia and fluorine-18 deoxyglucose (FDG) was performed before and 5 to 7 weeks after CABG in 22 patients with coronary artery disease. Postoperative improvement in hypoperfusion was observed more often in the metabolically active segments (62%) than in the inactive segments (27%) on the preoperative PET study (p less than 0.05). Similarly, the postoperative lessening of wall motion abnormality was observed more often in the metabolically active segments (78%) than in the inactive segments (22%) (p less than 0.001). Of 19 asynergic segments showing increased FDG uptake before operation, the postoperative PET revealed a decrease in FDG uptake in 13 (68%) and persistent uptake in 6 (32%). The improvement in asynergy was observed in all the segments that showed a postoperative decrease in FDG uptake, but in only 50% of those with persistent uptake (p less than 0.01). On the other hand, 4 of 5 segments showing a new FDG uptake after operation revealed further wall motion abnormality. Furthermore, the segments metabolically active before operation were more likely to have patent grafts (95%) than the metabolically inactive segments (70%) (p less than 0.05). Thus, preoperative metabolic imaging using PET appears to be useful for predicting the response to CABG. Improvement in metabolic derangement was associated with improvement in regional function after CABG.

Total arch replacement using aortic arch branched grafts with the aid of antegrade selective cerebral perfusion

BACKGROUND

We report our clinical experience with total arch replacement using aortic arch branched graft in an attempt to determine the independent predictors of both in-hospital mortality and neurologic outcome.

METHODS

We studied 220 consecutive patients who underwent total arch replacement using aortic arch branched graft between May 1990 and June 1999. All operations were performed with the aid of hypothermic extracorporeal circulation, antegrade selective cerebral perfusion, and open distal anastomosis.

RESULTS

The overall in-hospital mortality rate was 12.7%. Multivariable analysis showed independent determinants of in-hospital mortality to be chronic renal failure, long pump time, participation in early series, and shock. Postoperative permanent neurologic dysfunction was 3.3%. On multivariable analysis, old cerebral infarct and pump time were independent determinants of permanent neurologic dysfunction. The selective cerebral perfusion time had no significant influence on in-hospital mortality or neurologic outcome. The 5-year survival rate including in-hospital deaths was 79% +/- 6%.

CONCLUSIONS

Selective cerebral perfusion allows increased ease of performance of total arch replacement, a complex and time-consuming procedure, and helps reduce periprocedural mortality and morbidity in patients with aortic arch aneurysm and those with acute aortic dissection.

Enlarged uterus: differentiation between adenomyosis and leiomyoma with MR imaging

The potential of magnetic resonance (MR) imaging in differentiation of adenomyosis from leiomyoma was evaluated in 93 patients who had a palpable enlarged uterus that was suspect for leiomyoma or adenomyosis. In all cases, MR images were correlated with surgical/pathologic findings. Pathologic findings showed that 71 enlarged uteri were due to leiomyoma, including one leiomyosarcoma, and 16 were due to adenomyosis. The other six patients were shown to have an enlarged uterus attributable to simultaneous involvement of both lesions. On T2-weighted images, adenomyosis appeared as an ill-defined, relatively homogeneous low-signal-intensity area embedded with sparse high-intensity spots. In contrast, leiomyomas were well-circumscribed masses with a spectrum of signal intensity. The cause of uterine enlargement was correctly diagnosed with MR images in 92 of the 93 cases. It is concluded that MR imaging is highly accurate in helping to distinguish between adenomyosis and leiomyoma in cases of enlarged uterus.

Okadaic acid, a potent inhibitor of type 1 and type 2A protein phosphatases, activates cdc2/H1 kinase and transiently induces a premature mitosis-like state in BHK21 cells

When BHK21 cells synchronized in early S phase were exposed to okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A, mitosis specific events such as premature chromosome condensation, the production of MPM-2 antigens, dispersion of nuclear lamins and the appearance of mitotic asters were induced, and then disappeared upon further incubation. These mitosis specific events occurred even in the presence of cycloheximide. Within 1 h of exposure to OA, cdc2/histone H1 kinase activity rose 10-fold compared with untreated controls, but returned to the control level upon further incubation. Using antibodies against either p34cdc2 or cyclin B it was found that p34cdc2 complexed with cyclin B was dephosphorylated after OA treatment concomitant with the activation of cdc2 kinase, and that cyclin B was subsequently degraded concomitant with a decrease in cdc2 kinase activity, as in normal mitosis. In contrast, when cells in G1 phase were treated with OA no increase in cdc2 kinase activity was observed. Moreover when cells in pseudo-metaphase induced by nocodazole were treated with OA, cdc2 kinase was inactivated. These results suggest that OA sensitive protein phosphatases control both the activation and inactivation of the p34cdc2 kinase.

Aberrant promoter methylation and tumor suppressive activity of the DFNA5 gene in colorectal carcinoma

To identify novel methylated gene promoters, we compared differential RNA expression profiles of colorectal cancer (CRC) cell lines with or without treatment of 5-aza-2'-deoxycytidine (5-aza-dC). Out of 1776 genes that were initially 'absent (that is, silenced)' by gene expression array analysis, we selected 163 genes that were increased after 5-aza-dC treatment in at least two of three CRC cell lines. The microarray results were confirmed by Reverse Transcription-PCR, and CpG island of the gene promoters were amplified and sequenced for examination of cancer-specific methylation. Among the genes identified, the deafness, autosomal dominant 5 gene, DFNA5, promoter was found to be methylated in primary tumor tissues with high frequency (65%, 65/100). Quantitative methylation-specific PCR of DFNA5 clearly discriminated primary CRC tissues from normal colon tissues (3%, 3/100). The mRNA expression of DFNA5 in four of five colon cancer tissues was significantly downregulated as compared to normal tissues. Moreover, forced expression of full-length DFNA5 in CRC cell lines markedly decreased the cell growth and colony-forming ability whereas knockdown of DFNA5 increased cell growth in culture. Our data implicate DFNA5 as a novel tumor suppressor gene in CRC and a valuable molecular marker for human cancer.

Perfusion imaging of brain tumors using arterial spin-labeling: correlation with histopathologic vascular density

BACKGROUND AND PURPOSE

We investigated the relationship between tumor blood-flow measurement based on perfusion imaging by arterial spin-labeling (ASL-PI) and histopathologic findings in brain tumors.

MATERIALS AND METHODS

We used ASL-PI to examine 35 patients with brain tumors, including 11 gliomas, 9 meningiomas, 9 schwannomas, 1 diffuse large B-cell lymphoma, 4 hemangioblastomas, and 1 metastatic brain tumor. As an index of tumor perfusion, the relative signal intensity (SI) of each tumor (%Signal intensity) was determined as a percentage of the maximal SI within the tumor per averaged SI within normal cerebral gray matter on ASL-PI. Relative vascular attenuation (%Vessel) was determined as the total microvessel area per the entire tissue area on CD-34-immunostained histopathologic specimens. MIB1 indices of gliomas were also calculated. The differences in %Signal intensity among different histopathologic types and between high- and low-grade gliomas were compared. In addition, the correlations between %Signal intensity and %Vessel or MIB1 index were evaluated in gliomas.

RESULTS

Statistically significant differences in %Signal intensity were observed between hemangioblastomas versus gliomas (P < .005), meningiomas (P < .05), and schwannomas (P < .005). Among gliomas, %Signal intensity was significantly higher for high-grade than for low-grade tumors (P < .05). Correlation analyses revealed significant positive correlations between %Signal intensity and %Vessel in 35 patients, including all 6 histopathologic types (rs = 0.782, P < .00005) and in gliomas (rs = 0.773, P < .05). In addition, in gliomas, %Signal intensity and MIB1 index were significantly positively correlated (rs = 0.700, P < .05).

CONCLUSION

ASL-PI may predict histopathologic vascular densities of brain tumors and may be useful in distinguishing between high- and low-grade gliomas and in differentiating hemangioblastomas from other brain tumors.