Increased expression of GATA zinc finger domain containing 1 through gene amplification promotes liver cancer by directly inducing phosphatase of regenerating liver 3

We identified that GATA zinc finger domain containing 1 (GATAD1), a transcriptional factor, was significantly up-regulated in hepatocellular carcinoma (HCC) through gene amplification. We demonstrated the critical role, molecular mechanisms, and clinical implications of GATAD1 as a novel oncogenic factor in HCC. We found that GATAD1 protein was expressed in 76.6% of primary HCCs (85/111) but silenced in normal liver tissues. Gene amplification of GATAD1 was positively correlated with its overexpression in primary HCCs (R = 0.629, P < 0.0001). GATAD1 significantly increased cell proliferation, G₁ -S cell cycle transition, and migration/invasion but suppressed apoptosis in liver cell lines and promoted tumor growth and lung metastasis in both xenograft and orthotopic mouse models. Mechanistically, GATAD1 induced the transcriptional expression of phosphatase of regenerating liver 3 (PRL3) by binding to its promoter identified by RNA sequencing and chromatin immunoprecipitation-PCR analyses. PRL3 played an oncogenic role in HCC. Knockdown of PRL3 blunted the tumorigenic effect of GATAD1. In addition, GATAD1 activated Akt signaling, evidenced by increased phosphorylation levels of total Akt, Akt1, Akt2, and Akt target glycogen synthase kinase 3β, while knockdown of PRL3 abolished this effect of GATAD1. We further unveiled that PRL3 activated Akt signaling by dephosphorylating phosphatase and tensin homolog at tyrosine residue, thus reducing phosphatase and tensin homolog protein. The PRL3 inhibitor 5-[[5-bromo-2-[(2-bromophenyl)methoxy]phenyl]methylene]-2-thioxo-4-thiazolidinone significantly suppressed HCC growth by inhibiting Akt activation. Moreover, high GATAD1 nuclear protein expression was associated with poor survival of HCC patients as an independent prognostic factor.

CONCLUSION

GATAD1 plays a pivotal oncogenic role in HCC by directly inducing PRL3 transcription to activate the Akt signaling pathway. GATAD1 may serve as an independent poor prognostic factor for HCC patients. (Hepatology 2018;67:2302-2319).

Abstract 4705: Distinct gene promoter hypermethylation profile in bladder cancer patients from different Chinese populations and its implication in cancer detection using voided urine samples

Bladder cancer is the 6th most common cancer in the world and the incidence is particularly high in southwestern Taiwan. Bladder cancer patients would need to have long term follow-up and repeated urine cytology, however the sensitivity for urine cytology is known to be low. Several studies including ours had identified several tumor-related genes that are hypermethylated in bladder cancer patients and can be detected in voided urine samples (Chan et al., Clin Cancer Res 8: 464-470, 2002). However, comprehensive methylation profile of bladder cancer in Taiwan is currently unknown. On the other hand, studies also suggested that the non-random methylation profile in cancer may be related to the exposure of different environmental carcinogen in different locality. In this regard, we aim to investigate the DNA methylation profile of multiple tumor suppressor genes in bladder cancer patients from different Chinese populations including Taiwan (104 cases), Hong Kong (98 cases) and Beijing (24 cases) by methylation specific PCR (MSP). Genes showing distinct methylation in Taiwanese population will be selected as biomarkers for cancer detection in voided urine samples. Our result showed that frequent methylation was detected in p14 (84.4%), IRF8 (67.4%), sFRP1 (62.8%), and DAPK (52.2%) from cancer patients of Taiwan. While methylation was also detected in RASSF1A (37.0%), p15 (32.6%), APC (28.3%), hMLH1 (21.7%), SOCS-1 (19.6%), and CDH1 (15.2%). The methylation profile demonstrated bimodal distribution which is a characteristic of CpG island methylator phentotype (CIMP). Besides, the number of methylated genes in each patient were significantly correlated with pathological grade (P &lt;0.001) and stage (P&lt;0.05). Interestingly, methylation of CDH1, hMLH1, p14 and p15 showed obvious diversity among different Chinese populations. Importantly, the sensitivity and specificity of methylation detection of any one of the methylated gene (IRF8, p14, sFRP1 and RASSF1A) in voided urine of patients using qMSP is 89.5% and 94.4% respectively. To further identify novel targets that are epigenetically silenced in bladder cancer from Taiwan, we performed differential methylation analysis (DMH) using Agilent 244K CpG island microarray coupled with expression microarray in BFTC905 and TSGH8301 bladder cancer cell lines. ARHGEF17 and CDKN1C were identified to be concurrently methylated in these two bladder cancer cell lines as compared with SV-HUC-1 normal bladder cell line. In conclusion, our result indicated that there are distinct DNA methylation profiles among different Chinese populations. These profiles demonstrate gradual increases with cancer progression. Finally, detection of gene methylation in voided urine with these distinct DNA methylation markers is more sensitive than urine cytology.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4705.

Alterations of frizzled (FzE3) and secreted frizzled related protein (hsFRP) expression in gastric cancer

Wnt signaling pathway is important for development and carcinogenesis. Alterations of this pathway, such as mutations in adenomatous polyposis coli (APC) gene and activation mutations of beta-catenin, would result in stabilization of beta-catenin and subsequent translocation to nucleus where genes are transcribed. Recently, a receptor of Wnt, FzE3 was found to be up-regulated in esophageal carcinoma while a non-receptor antagonist of Wnt, secreted frizzled related protein (hsFRP) was found to be down-regulated in some cancer. These findings suggested that FzE3 is a potential oncogene while hsFRP is a potential tumor suppressor gene. We aimed to investigate whether FzE3 and hsFRP were altered in gastric cancer. Twelve cases of gastric cancer, including 7 cases of intestinal type, 4 cases of diffuse type and I case of mixed type, were studied. FzE3 and hsFRP mRNAs were expressed in most of the paired normal gastric tissues. FzE3 was over-expressed in 9 cases (75%) of gastric carcinoma tissues while hsFRP was down-regulated in 2 cases (16%). Beta-catenin nuclear staining was identified in 3 cases (27%) and cyclin D1 was expressed in 5 cases (41%) of cancer samples. All these cases were associated with either up-regulation of FzE3 or down-regulation of hsFRP. Our results suggested that alterations of FzE3 or hsFRP were frequent in gastric cancer. These provide alternative mechanisms leading to activation of Wnt signaling pathway in gastric carcinogenesis.

Inverse association between cyclooxygenase-2 overexpression and microsatellite instability in gastric cancer

This study examined the association between cyclooxygenase-2 (COX-2) overexpression and microsatellite instability (MSI) in gastric cancer. COX-2 expression was assessed by immunohistochemistry and scored in a semi-quantitative manner whereas MSI status was characterized by nine microsatellite markers. The clinicopathological features of cancers including survival data were analyzed. Of the 109 gastric cancers studied, COX-2 overexpression and high level of MSI (MSI-H) was detected in 64.2 and 22.0% cases respectively. Gastric tumors with MSI-H phenotypes had significantly lower level of COX-2 expression levels when compared to MSI-L and MSS tumors (P=0.002). Moreover, COX-2 overexpression was associated with tumor invasion beyond submucosa (P=0.045) and there was a trend favoring better survival in gastric cancers without COX-2 overexpression (P=0.07). The results from this study suggest that gastric cancer with microsatellite instability or COX-2 overexpression present with diverse clinicopathological features.

High-performance liquid chromatographic method development and validation for the simultaneous quantitation of naproxen sodium and pseudoephedrine hydrochloride impurities

A reversed-phase high-performance liquid chromatographic procedure for the simultaneous determination of impurities associated with pseudoephedrine hydrochloride (PSEH) and naproxen sodium (NapNa) is developed and validated. The method is developed using a Waters Spherisorb cyano column (5 microm, 250 x 4.6 mm). An isocratic elution in a water-acetonitrile-methanol-triethylamine mixture (850:75:75:5) is adjusted to a pH of 3.7 +/- 0.02 with formic acid as the mobile phase. The UV detection was set at 260 nm, and the wavelength was switched to 235 nm before the elution of the last component, 2-ethyl-6-methoxy-naphthalene (EMN). The method is shown to be linear at a concentration range of 0.24 to 1.92 microg/mL for benzaldehyde, benzoic acid, and 2-(methylamino)-propiophenone hydrochloride, which are known impurities of PSEH. The NapNa impurities, 2-(6'-hydroxy-2'-naphthyl) propionic acid, 2-hydroxy-6-methoxy-naphthalene, 1-(6'-methoxy-2'-naphthyl) ethanol, 2-acetyl-6-methoxy-naphthalene, and EMN are also demonstrated to be linear at a concentration range of 0.44 to 3.52 microg/mL. Under the chromatographic conditions of the method, all impurities are resolved from the active components.

Somatic beta-catenin mutation in gastric carcinoma--an infrequent event that is not specific for microsatellite instability

We screened 90 cases of gastric carcinoma (GCA) samples for beta-catenin exon 3 mutation and assessed its possible relationship with microsatellite instability (MSI). Three mutations were detected in two samples, including a single mutation in an intestinal type and double mutations in a diffuse type GCA. One of the mutations found in the diffuse type GCA sample was a non-sense mutation at codon 68 (CAG-->TAG). This novel mutation was predicted to disrupt the binding of beta-catenin to alpha-catenin and may be related to the diffuse type morphology. The other two mutations were missense mutations involved or related to the GSK-3beta phosphorylation site, which have been reported previously. No MSI can be demonstrated in the two cases with beta-catenin mutation. Our results suggested that beta-catenin mutation was infrequent in GCA and appeared not specific for MSI.

Exploring (novel) gene expression during retinoid-induced maturation and cell death of acute promyelocytic leukemia

During recent years, reports have shown that biological responses of acute promyelocytic leukemia (APL) cells to retinoids are more complex than initially envisioned. PML-RARalpha chimeric protein disturbs various biological processes such as cell proliferation, differentiation, and apoptosis. The distinct biological programs that regulate these processes stem from specific transcriptional activation of distinct (but overlapping) sets of genes. These programs are sometimes mutually exclusive and depend on whether the signals are delivered by RAR or RXR agonists. Furthermore, evidence that retinoid nuclear signaling by retinoid, on its own, is not enough to trigger these cellular responses is rapidly accumulating. Indeed, work with NB4 cells show that the fate of APL cells treated by retinoid depends on complex signaling cross-talk. Elucidation of the sequence of events and cascades of transcriptional regulation necessary for APL cell maturation will be an additional tool with which to further improve therapy by retinoids. In this task, the classical techniques used to analyze gene expression have proved time consuming, and their yield has been limited. Global analyses of the APL cell transcriptome are needed. We review the technical approaches currently available (differential display, complementary DNA microarrays), to identify novel genes involved in the determination of cell fate.

Genomic organization of the JEM-1 (BLZF1) gene on human chromosome 1q24: molecular cloning and analysis of its promoter region

The Jem-1 (JEM-1, HGMW-approved symbol BLZF1) gene mapping to human chromosome 1q24 codes for a ubiquitously expressed 3-kb mRNA, translated in a 45-kDa nuclear protein. Recent studies have shown a deficient expression of this gene in acute promyelocytic leukemia (APL). However, treatment with retinoids was able to upregulate JEM-1 mRNA in maturing NB4 leukemia cells. Here, we report the characterization of the structural organization of JEM-1. By hybridization screening of a human genomic library derived from blood mononuclear cells, five overlapping genomic DNA clones were isolated. These clones extend over 34 kb of the human genome and comprise the complete JEM-1 gene and a 4-kb 5'flanking region. Determination of the exon-intron structure of Jem-1 revealed seven exons whose junctions with introns exhibited typical splice sequences. A shorter transcript (Jem-1s, 1.3 kb) generated by exon 3 extension and polyadenylation was identified. Its translation generated a 23-kDa protein that exhibited a cytoplasmic localization. 5'RACE-PCR identified a major transcription start site (TSS) located at 403 nt upstream of the ATG. Computer analysis of the 1. 8-kb 5'flanking region showed that it lacks a TATA box, Inr motifs or DPE motifs, but it contains a typical CCAAT box located 95 bp upstream of the TSS. Sequencing also revealed potential cis-acting elements for multiple transcription regulators including Sp1, GATA, C/EBP, AP-1, and Pu1. No retinoic acid receptor elements or retinoic X receptor elements were detected. This 1.8-kb DNA sequence showed a strong constitutive promoter activity determined by a luciferase-reporter gene assay in transiently transfected HeLa cells. Retinoids further increased luciferase expression 2.7-fold. We demonstrated that the 1-kb distal sequence contains yet unidentified elements reducing constitutive transcription. Thus, the maximal constitutive promoter activity was assigned to a -432 + 101 region overlapping the TSS. These data support the idea of a constitutive expression of JEM-1, but a negative regulation in APL released by retinoids.

Gene expression networks underlying retinoic acid-induced differentiation of acute promyelocytic leukemia cells

To elucidate the molecular mechanism of all-trans-retinoic acid (ATRA)-induced differentiation of acute promyelocytic leukemia (APL) cells, the gene expression patterns in the APL cell line NB(4) before and after ATRA treatment were analyzed using complementary DNA array, suppression-subtractive hybridization, and differential-display-polymerase chain reaction. A total of 169 genes, including 8 novel ones, were modulated by ATRA. The ATRA-induced gene expression profiles were in high accord with the differentiation and proliferation status of the NB(4) cells. The time courses of their modulation were interesting. Among the 100 up-regulated genes, the induction of expression occurred most frequently 12-48 hours after ATRA treatment, while 59 of 69 down-regulated genes found their expression suppressed within 8 hours. The transcriptional regulation of 8 induced and 24 repressed genes was not blocked by cycloheximide, which suggests that these genes may be direct targets of the ATRA signaling pathway. A balanced functional network seemed to emerge, and it formed the foundation of decreased cellular proliferation, maintenance of cell viability, increased protein modulation, and promotion of granulocytic maturation. Several cytosolic signaling pathways, including JAKs/STAT and MAPK, may also be implicated in the symphony of differentiation. (Blood. 2000;96:1496-1504)

JEM-1, a novel nuclear co-factor: localisation and functional interaction with AP-1

JEM-1 is a novel gene whose mRNA expression in acute promyelocytic leukemia (APL) is induced by retinoid treatments. The gene product, a 45 kDa basic nuclear factor containing a leucine repeat, was transiently expressed in HeLa or COS-7 cells and immunocharacterized within the nuclei in fine punctuated structures which increase in size after cell transfection. Jem-1 was not expressed in the nucleoli. Experimental deletion of peptide domains of Jem-1 (JemDelta331-400 and Jem DeltaL179-206) showed that its C-terminal sequence (Thr331 --> Leu400) is required for nuclear translocation, while the leucine repeat domain (Arg179 --> Glu206) has no influence on subcellular localization. The Jem-1 protein was not detected in the PML-containing nuclear bodies or in speckled structures containing the splicing factor SC-35. In contrast it was localized in the nucleus in structures containing activator protein-1 (AP-1). DNA mobility shift assays showed that the in vitro translated Jem protein interacts neither with the DNA binding site of AP-1, nor directly with in vitro co-translated c-Fos or/and c-Jun proteins bound to this specific sequence. Interestingly, Jem-1-1 increased substantially the transcriptional activity of c-Jun (three-fold) and more strongly that of ectopically co-expressed c-Fos and c-Jun (five- to six-fold), as measured by a CAT reporter gene driven by a heterologous promoter containing the AP-1 binding site of the human collagenase gene. These synergistic effects were strongly Jem-1 dose-dependent. However, Jem-1 alone showed no activity on the collagenase promoter. A deletion of the leucine repeat of Jem-1 (Arg179 --> Glu206) did not diminish the enhancer capacity of Jem-1 on AP-1 activity. In contrast, the enhanced AP-1 activity was abrogated when Jem-1 was deleted of its C-terminus (Thr331 --> Leu400). We conclude that the 45 kDa nuclear product of the JEM-1 gene has features of a novel transcription cofactor, which is enhancing AP-1 activity without directly interacting with c-Jun or c-Fos proteins. Possible implications of these findings for APL cell maturation are discussed.

Genomic sequence, structural organization, molecular evolution, and aberrant rearrangement of promyelocytic leukemia zinc finger gene

The promyelocytic leukemia zinc finger gene (PLZF) is involved in chromosomal translocation t(11;17) associated with acute promyelocytic leukemia. In this work, a 201-kilobase genomic DNA region containing the entire PLZF gene was sequenced. Repeated elements account for 19.83%, and no obvious coding information other than PLZF is present over this region. PLZF contains six exons and five introns, and the exon organization corresponds well with protein domains. There are at least four alternative splicings (AS-I, -II, -III, and -IV) within exon 1. AS-I could be detected in most tissues tested whereas AS-II, -III, and -IV were present in the stomach, testis, and heart, respectively. Although splicing donor and acceptor signals at exon-intron boundaries for AS-I and exons 1-6 were classical (gt-ag), AS-II, -III, and -IV had atypical splicing sites. These alternative splicings, nevertheless, maintained the ORF and may encode isoforms with absence of important functional domains. In mRNA species without AS-I, there is a relatively long 5' UTR of 6.0 kilobases. A TATA box and several transcription factor binding sites were found in the putative promoter region upstream of the transcription start site. PLZF is a well conserved gene from Caenorhabditis elegans to human. PLZF paralogous sequences are found in human genome. The presence of two MLL/PLZF-like alignments on human chromosome 11q23 and 19 suggests a syntenic replication during evolution. The chromosomal breakpoints and joining sites in the index acute promyelocytic leukemia case with t(11;17) also were characterized, which suggests the involvement of DNA damage-repair mechanism.

Human endothelin-1 clearance kinetics revealed by a radiotracer technique

Levels of endothelin-1 (ET-1) are elevated in many disease states, although its total body kinetics of elimination are poorly understood. Therefore, it remains uncertain whether the presence of elevated levels of ET-1 in the setting of disease are secondary to changes in production or clearance or some combination thereof. Using a 125I-labeled ET-1 infusion technique, the volume of distribution and kinetics of clearance of endothelin were described in five normal volunteers. Heart rate, blood pressure, right atrial pressure, and arterial blood samples for the counting of 125I and the measurement of ET-1 were obtained at multiple time points before and up to 45 h after the start of the infusion. The radiotracer infusion had no effect on heart rate, blood pressure, right atrial pressure, or endogenous ET-1 levels. ET-1 clearance was best described by a three-compartment model, which revealed that ET-1 has a much longer terminal half-life and volume of distribution than was previously reported. This suggests extensive uptake of ET-1 in various organ systems and slow clearance. These new findings have important implications for the understanding of the pathophysiology of ET-1 in disease states as well as for the understanding and development of ET-1 receptor blockers and endothelin-converting enzyme inhibitors.

Expression patterns of the JEM-1 gene in normal and tumor cells: ubiquity contrasting with a faint, but retinoid-induced, mRNA expression in promyelocytic NB4 cells

The JEM-1 gene, recently identified in acute promyelocytic leukemia (APL) cells, codes for a novel nuclear factor (Duprez et al Oncogene 1997; 14: 1563-1570). JEM-1 is kept silent in the APL cell line NB4, but up-regulated (3 kb transcript) during cell maturation. Here, we show that retinoic acid (RA)-induced JEM-1 expression is biphasic (peaks at 6 h and 48 h) and associated with the later stages of maturation. Retinoids, which cooperates with cAMP to induce maturation, also cooperates with cAMP to up-regulate JEM-1, either in maturation-responsive NB4 cells or in NB4-R1 resistant subclones. APL patients showed a low, yet variable, level of JEM-1 mRNA in bone marrow. RA treatment induced an increase in the level of JEM-1 mRNA, as detected by a semi-quantitative PCR. This increase can result from both gene up-regulation or replacement of leukemia cells by differentiated ones. Analysis of JEM-1 expression patterns in normal and tumor cells revealed that JEM-1 expression was ubiquitous. Cell lines derived from monocytic and erythroid leukemias, expressed low and high amounts of JEM-1 mRNA, respectively. Using a JEM cDNA probe, distinct profiles of expression and different transcript sizes (4 kb, 3 kb and 2 kb) were also identified in tumour and normal non-hematopoietic tissues, while interestingly only the 3kb transcript was up-regulated in NB4 cells. This work identifies JEM-1 as a novel ubiquitous gene whose expression is low in APL cells, but can be restored by RA treatment, concomitant with cell maturation.

Comparative protection against oxyradicals by three flavonoids on cultured endothelial cells

Oxygen-derived free radicals are known to injure the endothelium of aorta in diverse disorders. In this study we compared the cytoprotective effects of three flavonoids against oxyradical damage to porcine aortic endothelial cells in vitro. Cultured porcine aortic endothelial cells were exposed to oxyradicals generated by xanthine oxidase--hypoxanthine (XO-HP). The cytoprotective activities of morin, quercetin, and catechin on these systems were compared using established morphologic criteria. The results in the XO-HP system showed that morin at 0.125, 0.25, and 0.5 mM delayed cell necrosis to 27.4 +/- 1.3, 46.8 +/- 1.8, and longer than 70 min, respectively, compared with 12.0 +/- 1.3 min in the control group. These degrees of protection were significantly stronger than those provided by quercetin and catechin at corresponding concentrations (p < 0.01). Morin and quercetin were moderate inhibitors of xanthine oxidase on the basis of the oxygen consumption rate, whereas catechin at the same concentrations had little inhibitory effect. The data from uric acid formation and cytochrome c reduction were consistent with the oxygen consumption measurement for the three flavonoids.

Cloning of a gene (RIG-G) associated with retinoic acid-induced differentiation of acute promyelocytic leukemia cells and representing a new member of a family of interferon-stimulated genes

In a cell line (NB4) derived from a patient with acute promyelocytic leukemia, all-trans-retinoic acid (ATRA) and interferon (IFN) induce the expression of a novel gene we call RIG-G (for retinoic acid-induced gene G). This gene codes for a 58-kDa protein containing 490 amino acids with several potential sites for post-translational modification. In untreated NB4 cells, the expression of RIG-G is undetectable. ATRA treatment induces the transcriptional expression of RIG-G relatively late (12-24 hr) in a protein synthesis-dependent manner, whereas IFN-alpha induces its expression early (30 min to 3 hr). Database search has revealed a high-level homology between RIG-G and several IFN-stimulated genes in human (ISG54K, ISG56K, and IFN-inducible and retinoic acid-inducible 58K gene) and some other species, defining a well conserved gene family. The gene is composed of two exons and has been mapped by fluorescence in situ hybridization to chromosome 10q24, where two other human IFN-stimulated gene members are localized. A synergistic induction of RIG-G expression in NB4 cells by combined treatment with ATRA and IFNs suggests that a collaboration exists between their respective signaling pathways.

JEM-1, a novel gene encoding a leucine-zipper nuclear factor upregulated during retinoid-induced maturation of NB4 promyelocytic leukaemia

Retinoid-induced proliferation causing hyperleukocytosis is a severe complication of retinoid therapy in t(15;17) acute promyelocytic leukaemia. The molecular basis of this phenomenon is unknown. It is possible that the transiently enhanced cell proliferation results from RA-induction of growth regulatory genes. Using Differential Display of cDNAs from NB4 cells we have identified Jem, a novel gene transcript which is upregulated by retinoids during the early proliferative response in maturating cells but not in resistant cells. A 2.7 kb cDNA was cloned and sequenced. The open reading frame contains a 400 amino acid sequence corresponding to a novel 45 kDa basic protein (pI 8.9). The JEM DNA sequence is detected by FISH on human chromosome 1 at q24. The Jem peptide sequence shows a 'leucine-zipper' dimerisation motif with limited homology to Fos/Jun and ATF/CREB proteins and several putative phosphorylation sites. An atypical basic region may correspond to an unknown DNA-binding domain. The C-terminal end of Jem spans a long stretch featuring a PEST motif. After transfection into COS cells, the Jem protein shows a ponctuated nuclear localisation. We hypothesise that this novel nuclear factor may act as a transcription factor, or a coregulator, involved in either cell growth control and/or maturation.

Digoxin reduces cardiac sympathetic activity in severe congestive heart failure

OBJECTIVES

This study evaluated the effect of digoxin on cardiac sympathetic activity in patients with congestive heart failure.

BACKGROUND

Digoxin favorably alters autonomic tone in heart failure. Whether it reduces cardiac sympathetic drive in the setting of heart failure is unknown.

METHODS

Digoxin (0.25 mg intravenously) was administered to 12 patients with severe heart failure and elevated left ventricular end-diastolic pressure (> 14 mm Hg, Group A), 5 patients with less severe heart failure who had normal left ventricular end-diastolic pressure (> 14 mm Hg, Group B) and 6 patients with normal ventricular function. Seven additional patients with heart failure were studied as a time control group. Cardiac and total body norepinephrine spillover, systemic arterial pressure, left ventricular filling pressure and peak positive first derivative of left ventricular pressure were all assessed before and 30 min after administration of digoxin.

RESULTS

In Group A there were no changes in hemodynamic variables or total body norepinephrine spillover after digoxin administration; however, there was a significant reduction in cardiac norepinephrine spillover (263 +/- 70 to 218 +/- 62 pmol/min, mean +/- SEM, p < 0.001). In contrast, in Group B, digoxin caused a significant increase in cardiac norepinephrine spillover that was not associated with any hemodynamic changes or a change in total body spillover. There were no hemodynamic changes or a change in total body spillover. There were no hemodynamic or spillover changes in the time control or normal ventricular function group.

CONCLUSIONS

Digoxin, in the absence of detectable inotropic or hemodynamic effects, caused a reduction in cardiac norepinephrine spillover in patients with heart failure who had elevated filling pressures. This finding suggests a potentially beneficial primary autonomic action of digoxin in patients with severe heart failure.

RIG-E, a human homolog of the murine Ly-6 family, is induced by retinoic acid during the differentiation of acute promyelocytic leukemia cell

In vivo all-trans-retinoic acid (ATRA), a differentiation inducer, is capable of causing clinical remission in about 90% of patients with acute promyelocytic leukemia (APL). The molecular basis for the differentiation of APL cells after treatment with ATRA remains obscure and may involve genes other than the known retinoid nuclear transcription factors. We report here the ATRA-induced gene expression in a cell line (NB4) derived from a patient with APL. By differential display-PCR, we isolated and characterized a novel gene (RIG-E) whose expression is up-regulated by ATRA. The gene is 4.0 kb long, consisting of four exons and three introns, and is localized on human chromosome region 8q24. The deduced amino acid sequence predicts a cell surface protein containing 20 amino acids at the N-terminal end corresponding to a signal peptide and an extracellular sequence containing 111 amino acids. The RIG-E coded protein shares some homology with CD59 and with a number of growth factor receptors. It shares high sequence homology with the murine LY-6 multigene family, whose members are small cysteine-rich proteins differentially expressed in several hematopoietic cell lines and appear to function in signal transduction. It seems that so far RIG-E is the closest human homolog of the LY-6 family. Expression of RIG-E is not restricted to myeloid differentiation, because it is also present in thymocytes and in a number of other tissues at different levels.

Retinoic acid regulatory pathways, chromosomal translocations, and acute promyelocytic leukemia

Retinoic acids (RAs) exert a broad range of physiologic actions during embryonic development and adult life. Two families of RA receptors, retinoic acid receptor (RAR) and retinoid X receptor (RXR), have been identified. The therapeutic effect of all-trans-RA (ATRA) in induction of remission for acute promyelocytic leukemia (APL) has largely been proved, and this has, over the past 10 years, greatly stimulated research on oncogenesis and RA-regulated differentiation pathways. In APL, one of the RAR genes, RARA, is fused to PML in the great majority of patients as a result of the chromosomal translocation t(15; 17). However, a small subset of APL patients have a different fusion gene, PLZF-RARA, resulting from the variant translocation t(11;17). A third translocation, t(5;17), in which the NPM gene is fused to RARA, has been described. Current data suggest that PML-RAR alpha and PLZF-RAR alpha fusion receptors may play an important role in the development of APL and that PML-RAR alpha could be the target of ATRA differentiation therapy. Characterization of the genes regulated by retinoic acid may open up new prospects for an understanding of the mechanisms of ATRA differentiation therapy for APL and may help to extend the concept of cancer-targeting treatment to other types of leukemias or solid tumors.

Choice of anaesthetic regimen influences haemodynamic response to cemented arthroplasty

Haemodynamic changes during bilateral cemented arthroplasty (BCA) were compared in dogs anaesthetized with isoflurane/N2O (ISOF) or diazepam/fentanyl (100 microg x kg(-1))N2O(FENT). Eight animals were anaesthetized with each regimen. After establishing monitoring and recording baseline values, BCA was performed. Haemodynamic measurements included aortic blood pressure (ABP), pulmonary artery pressure (PAP), right and left atrial pressures, and cardiac output. These were recorded at 30, 60, 180 and 300 sec after BCA. Lungs were removed and examined postmortem using quantitative morphometry. Groups demonstrated similar increases in PAP (ISOF 15 +/- 2 to 32 +/- 7, FENT 19 +/- 4 to 38 +/- 13; P> 0.05 between groups, P< 0.05 vs baseline). The proportion of lung vasculature occluded by fat was not different between groups (ISOF 9.63 +/- 3.38%, FENT 8.85 +/- 2.20%). Stroke volume decreased similarly in both groups (P> 0,05 between groups, P< 0.05 vs baseline). However, ABP decreased within one minute of BCA in ISOF (111 +/- 17 to 55 +/- mmHg, P< 0.05 and two of eight dogs died. All FENT dogs survived and hypotension (118 +/- 20 to 102 +/- 24 mmHg) was transient and less severe (P< 0.05 vs ISOF). Increased heart rate (HR) was noted in FENT following BCA (73 +/- 8 to 108 +/- 25 beats x min(-1); P< 0.05). Baseline HR was higher in ISOF (P< 0.05) and no increase in HR was noted. Systemic vascular resistance decreased in ISOF (P< 0.05), but not FENT (P> 0.05 vs baseline, P< 0.05 vs ISOF). To assess the role of slower baseline HR in FENT (73 +/-8) versus ISOF (131 +/- 5), six FENT dogs were paced (130 beats x min(-1)) with epicardial leads and an AV sequential pulse generator to simulate the ISOF group's baseline HR. Haemodynamic stability was maintained in this group in spite of a more rapid baseline HR. The choice of anaesthetic regimen strongly influenced acute haemodynamic changes in response to BCA.

Effect of retinoic acid isomers on proliferation, differentiation and PML relocalization in the APL cell line NB4

Retinoic acids exert a wide physiological role in development and differentiation. Retinoic acids have also been used in the treatment of human cancers, particularly in acute promyelocytic leukemia (APL). A structure-function relationship of the RA isomers in terms of clinical effect has been observed since all-trans retinoic acid (ATRA) induces a high complete remission rate while 13-cis retinoic acid (13-cis RA) shows much poorer effect. In this study, we examined the effect of RA isomers, including ATRA, 13-cis RA and 9-cis RA, on the proliferation and differentiation of NB4 cells. A number of parameters such as cell growth curve, dynamics of cell cycle, expression of clusters of differentiation and reduction of nitro blue tetrazolium (NBT) as well as immunofluorescence staining of PML were used to evaluate the effects of three isomers at two concentrations (10(-8) M and 10(-7) M). It has been shown that during the first 48 h of RA treatment, the APL cell differentiation was coupled with the cell proliferation. Although similar effects of proliferation inhibition and differentiation induction were observed among the three isomers at 10(-7) M, significant differences appeared at a concentration of 10(-8) M, 9-cis RA showed a higher activity than that of ATRA, while ATRA showed better results than 13-cis RA. Our results provide further evidence that 9-cis RA could be a promising molecule in differentiation induction of malignant cells.

AML-1 gene rearrangement and AML-1-ETO gene expression as molecular markers of acute myeloblastic leukemia with t(8;21)

Rearrangements of the AML-1 gene on chromosome 21 as well as transcriptional expression of AML-1-ETO fusion gene were studied in 35 leukemic patients with t(8;21)(q22;q22). A panel of probes generated from the AML-1 gene regions flanking the breakpoint on chromosome 21 allowed us to detect the rearrangement in 24 out of 29 patients. A specific nested reverse transcriptase/polymerase chain reaction (RT/PCR) was developed to detect the t(8;21), either at diagnosis or as minimal residual disease. PCR amplification products were obtained in ten out of 11 patients investigated, and the sensitivity of the reaction was estimated to be between 1 x 10(4) and 1 x 10(-5) cell. An AML-1 rearrangement was also detected in one patient with 8q- and only one chromosome 21, but without 21q+. This indicated that the molecular rearrangement of the der(8) chromosome is more important than the reciprocal one in the malignant process.

Poor response to all-trans retinoic acid therapy in a t(11;17) PLZF/RAR alpha patient

All-trans retinoic acid (ATRA) is a potent inducer of differentiation and cell death in malignant cells. Its effect is known to be mediated through binding to specific nuclear (RARs and RXRs) or cytoplasmic (CRABP) proteins. ATRA is strikingly effective in acute promyelocytic leukemia (the AML3 subtype) inducing a high incidence of complete remissions. Paradoxically, most AML3 cells harbor an abnormal retinoic acid receptor (PML/RAR alpha) resulting from the t(15;17) translocation. Though few AML3 patients do not respond to ATRA therapy, individualization of these cases is of practical importance. Recently the RAR alpha gene has been demonstrated to be involved in a novel fusion transcript (PLZF/RAR alpha) through a t(11;17) translocation. We describe here the second case of such a patient with a t(11;17)-PLZF/RAR alpha leukemic clone. Southern analysis revealed that the breakpoint in the RAR alpha gene was within the second intron (as for PML/RAR alpha) and the intron separating the second and third zinc finger of the PLZF gene. In vitro, the leukemic cells did not show increased NBT reduction or loss of self-renewal after incubation with ATRA. After therapy with ATRA, only partial remission was obtained. These results suggest that the t(11;17) (PLZF/RAR alpha) case of this study was less responsive to ATRA therapy than t(15;17) (PML/RAR alpha) cases and raises the question of the definition of this novel AML subtype.

Gamma and delta chain gene rearrangement of T cell receptor in acute lymphoblastic leukemia

The immunophenotype, rearrangements of T cell receptor (TCR) gamma and delta chain genes as well as the immunoglobulin heavy chain (IgH) gene were studied in 37 cases of morphologically defined acute lymphoblastic leukemia (ALL). According to the expression of differentiation antigens, 8 cases were classified as T-ALL, 26 B lineage ALL, 2 acute undifferentiated leukemia (AUL) and myeloid phenotype. An order of TCR gene rearrangements was observed in T-ALL, with the rearrangement of delta gene preceding that of gamma gene. Both genes were also found frequently rearranged and/or deleted in high proportions of the ALL of B cell lineage. However, the patterns of gene rearrangements were somewhat different between the T and B lineage ALLs. In contrast, the IgH gene rearrangements were observed only in the B lineage ALL. The immunogenotype analysis of ALL proved to be a useful marker of the clonality and provided us with important information on early human lymphoid differentiation. We conclude that the determination of TCR gamma gene V-J junctional sequence can be used as clonal marker for detecting the minimal residual disease during clinical remission.

Molecular study on the chromosome 15 breakpoints in the translocation t(15; 17) in acute promyelocytic leukemia (APL)

Chromosomal translocation t(15; 17) is a specific marker of acute promyelocytic leukemia (APL). In this study, molecular cloning of the t(15; 17) breakpoint was carried out in a Chinese APL patient. It has been shown that the retinoic acid receptor alpha (RARA) gene, normally located on chromosome 17, was fused with a new transcription unit PML, normally localized on chromosome 15. We have subsequently cloned a portion of the PML gene and generated a panel of probes. A PML gene rearrangement was detected in 33 out of 36 APL cases studied. 24 rearrangements were clustered in a 4.4 kb region, designated here as PMLbcr1 whereas 9 rearrangements were concentrated in a 6.5 kb region, defining another breakpoint cluster region (PMLbcr2). These two types of rearrangement constitute the basis for the heterogeneity of the PML-RARA fusion gene and its possible biological significance remains to be explored.

Rearrangements of the retinoic acid receptor alpha and promyelocytic leukemia zinc finger genes resulting from t(11;17)(q23;q21) in a patient with acute promyelocytic leukemia

Cytogenetic study of a patient with acute promyelocytic leukemia (APL) showed an unusual karyotype 46,xy,t(11;17) (q23;21) without apparent rearrangement of chromosome 15. Molecular studies showed rearrangements of the retinoic acid receptor alpha (RAR alpha) gene but no rearrangement of the promyelocytic leukemia gene consistent with the cytogenetic data. Similar to t(15;17) APL, all-trans retinoic acid treatment in this patient produced an early leukocytosis which was followed by a myeloid maturation, but the patient died too early to achieve remission. Further molecular analysis of this patient showed a rearrangement between the RAR alpha gene and a newly discovered zinc finger gene named PLZF (promyelocytic leukemia zinc finger). The fusion PLZF-RAR alpha gene found in this case, was not found in DNA obtained from the bone marrow of normals, APL with t(15;17) and in one patient with AML-M2 with a t(11;17). Fluorescence in situ hybridization using a PLZF specific probe localized the PLZF gene to chromosomal band 11q23.1. Partial exon/intron structure of the PLZF gene flanking the break point on chromosome 11 was also established and the breakpoint within the RAR alpha gene was mapped approximately 2 kb downstream of the exon encoding the 5' untranslated region and the unique A2 domain of the RAR alpha 2 isoform.

Breakpoint clusters of the PML gene in acute promyelocytic leukemia: primary structure of the reciprocal products of the PML-RARA gene in a patient with t(15;17)

DNA studies of the translocation t(15;17) in acute promyelocytic leukemia (APL) have shown that the retinoic acid receptor alpha (RARA) gene on chromosome 17 is juxtaposed to the promyelocytic leukemia (PML) gene on chromosome 15. The PML breakpoints have been mapped to 3 clusters: bcr1, bcr2, and bcr3. We have examined the PML breakpoint distribution in a series of 33 Chinese patients with APL. Twenty-two patients fell within bcr1, 2 within bcr2, and 9 within bcr3. The primary structure of the reciprocal chromosome translocation joints of one patient and that of their normal counterparts have been determined and compared to those of 2 previously reported cases. These studies revealed possible topoisomerase II cleavage sites close to the breakpoints and suggested implications of DNA attachment sites to nuclear matrix. We propose that these features are relevant to the process of illegitimate recombination generating the translocation.

Fusion between a novel Krüppel-like zinc finger gene and the retinoic acid receptor-alpha locus due to a variant t(11;17) translocation associated with acute promyelocytic leukaemia

We have identified a unique case of acute promyelocytic leukaemia (APL) with a t(11;17) reciprocal chromosomal translocation involving the retinoic acid receptor alpha (RAR alpha) and a previously uncharacterized zinc finger gene. As a result of this translocation, mRNAs containing the coding sequences of the new gene, fused in-frame either upstream of the RAR alpha B region or downstream from the unique A1 and A2 regions of the two major RAR alpha isoforms, are expressed from the rearranged alleles. The above gene, which we have termed PLZF (for promyelocytic leukaemia zinc finger), encodes a potential transcription factor containing nine zinc finger motifs related to the Drosophila gap gene Krüppel and is expressed as at least two isoforms which differ in the sequences encoding the N-terminal region of the protein. Within the haematopoietic system the PLZF mRNAs were detected in the bone marrow, early myeloid cell lines and peripheral blood mononuclear cells, but not in lymphoid cell lines or tissues. In addition, the PLZF mRNA levels were down-regulated in NB-4 and HL-60 promyelocytic cell lines in response to retinoic acid-induced granulocytic differentiation and were very low in mature granulocytes. Our results demonstrate for the first time the association of a variant chromosomal translocation involving the RAR alpha gene with APL, further implicating the RAR alpha in leukaemogenesis and also suggesting an important role for PLZF as well as retinoic acid and its receptors in myeloid maturation.

Localization of the chromosome 15 breakpoints and expression of multiple PML-RAR alpha transcripts in acute promyelocytic leukemia: a study of 28 Chinese patients

Translocation (15;17)(q22;q12-q21) is a chromosome aberration specifically found in acute promyelocytic leukemia (APL), that generates a chimeric gene between the promyelocytic leukemia (PML) gene on chromosome 15 and the retinoic acid receptor alpha (RARA) gene, on chromosome 17. In the course of molecular investigations of a series of 28 Chinese patients with APL, we have simultaneously used Southern blot and reverse transcriptase polymerase chain reaction (RT-PCR) analysis to characterize the PML gene breakpoints on chromosome 15 and identify PML-RARA fusion transcripts. Our results confirmed the existence of the three recently described bcr1, bcr2, and bcr3 breakpoint cluster regions. In addition, structural data provided by PML-RARA transcripts allowed us to more accurately locate the 3' borders of clusters bcr1 and bcr3. Moreover, our data suggest a preferential localization of the breakpoints within bcr1 and bcr3. The primary structure of a 1.4 kb DNA segment flanking the 5' part of the PML gene and that of the bcr3 cluster (2.1 kb) were also established.

Occurrence of distinct PML-RAR-alpha fusion gene isoforms in patients with acute promyelocytic leukemia detected by reverse transcriptase/polymerase chain reaction

A specific 'nested' reverse transcriptase/polymerase chain reaction (RT/PCR) procedure was used to characterize the expression patterns of PML-RAR-alpha chimeric mRNAs in 32 patients with acute promyelocytic leukemia (APL). The sensitivity of the technique was such that the fusion gene transcript could be detected from as little as 2.5 pg of total leukemic cell RNA against a background of 1 microgram of cellular RNA lacking the PML-RAR-alpha fusion gene transcript(s). In 19 cases the PML-RAR-alpha isoform referred to here as long was identified. A short isoform, which in comparison with the long form lacks three PML exons, was detected in 11 other cases. A third PML-RAR-alpha mRNA isoform, in which the most 3' PML exon present in the long-type isoform was truncated in its sequences lying immediately upstream of RAR-alpha B region, was found and characterized in a single patient. In one APL patient with a variant translocation t(11;17), the PCR product corresponding to PML-RAR-alpha chimeric mRNAs could not be amplified despite the presence of RAR-alpha gene rearrangement. Genomic and PCR analysis showed that the different PML-RAR-alpha isoforms found in APL patients arise as a result of distinct translocation breakpoints. In each case the exons encoding the B-F regions of RAR-alpha are expressed and are spliced downstream from variable PML gene exons. The 'nested' RT/PCR analysis of the PML-RAR-alpha fusion gene proved to be a rapid and sensitive tool for the diagnosis of the APL and for monitoring the residual APL chimeric mRNA expression during complete remission.

Molecular rearrangements of the MYL gene in acute promyelocytic leukemia (APL, M3) define a breakpoint cluster region as well as some molecular variants

Genomic DNA probes generated from the retinoic acid receptor alpha (RARA) gene located on chromosome 17 and from the MYL gene located on chromosome 15 were used to study the chromosome 15 breakpoints resulting from the t(15; 17) translocation in 26 patients with acute promyelocytic leukemia (APL). In 20 out of 22 patients with a detectable MYL rearrangement, the breakpoints were clustered within a 4.4 kb segment designated MYLbcr. The two remaining patients exhibited a more 5' rearrangement at about 10 kb upstream of the MYLbcr region, implying the lack of at least one MYL gene exon in the resulting MYL-RARA fusion gene. The variation of chromosome breakpoints within the MYL gene may explain size heterogeneity previously observed in some MYL-RARA fusion transcripts expressed in APL cells.

Rearrangements in the second intron of the RARA gene are present in a large majority of patients with acute promyelocytic leukemia and are used as molecular marker for retinoic acid-induced leukemic cell differentiation

Chromosome 17 breakpoints in translocation t(15;17), a hallmark for acute promyelocytic leukemia (APL), have been shown to disrupt the retinoic acid receptor-alpha (RARA) gene. In this study, DNA probes around the second exon of the RARA gene showed rearrangements not previously detected. Analysis of 25 Chinese APL cases showed that RARA gene rearrangements were present in 23 cases (92%). The breakpoints were mapped unequivocally in 22 cases within the second intron of the gene. Therefore, the RARA gene rearrangement provides us with a specific marker of the disease. Simultaneous molecular and cytologic studies showed that the RARA gene rearrangements persisted during the first 2 to 3 weeks of all-trans retinoic acid (ATRA) therapy when differentiated granulocytes predominated in bone marrow, while these rearrangements disappeared after achieving complete remission. These data indicate that ATRA induces differentiation of APL cells.

The retinoic acid alpha receptor gene is frequently disrupted in its 5' part in Chinese patients with acute promyelocytic leukemia

The t(15;17)(q22;q11-q21) translocation, a hallmark for acute promyelocytic leukemia (APL), has recently been shown to disrupt the retinoic acid-alpha receptor (RARA) gene localized on band 17q21. Leukemic cell DNAs from 16 Chinese patients with APL were analysed by Southern blot hybridization with probes covering the 5' and the 3' parts of the gene. In ten patients, the breakpoints were concentrated within a 5.5 kb EcoRI fragment containing part of intron 1, whereas no rearrangement was detected in the six remaining patients. Genomic amplification of the RARA gene was observed in one case. When RNA was available (six patients), abnormal-sized RARA gene transcripts were observed. Interestingly, no rearranged transcript was found in cells from a patient during a 6-day treatment with all-trans retinoic acid, while bone marrow cells still possessed the translocation.

Uptake of 17 beta-estradiol and its conjugates by isolated rabbit liver nuclei

The present study compares the uptake and metabolism of 17 beta-estradiol, 17 beta-estradiol 3-glucoside, and 17 beta-estradiol 3-glucuronide by a highly purified preparation of rabbit liver nuclei. The uptake of the three estrogens was rapid and equilibration was reached within 60 s. The order of uptake was 17 beta-estradiol (64 fmol X mg protein -1) greater than 17 beta-estradiol 3-glucoside (10 fmol X mg protein -1) greater than 17 beta-estradiol 3-glucuronide (6.5 fmol X mg protein -1). Thin-layer chromatography of the estrogens taken up by rabbit liver nuclei indicated the presence of a beta-glucosidase activity associated with the nuclear preparation. The apparent Km value of this enzyme for 17 beta-estradiol 3-glucoside (3.5 microM) was about 10-fold higher when compared with the cytosolic enzyme. The uptake of the three estrogens was linearly proportional to the substrate concentration from 1 to 100 nM. No competition for uptake was observed among the steroids and the presence of diethylstilbestrol did not reduce the uptake of the steroids. These findings suggest that 17 beta-estradiol, 17 beta-estradiol 3-glucoside, and 17 beta-estradiol 3-glucuronide are taken up by nuclei by a nonsaturable diffusion process. The effect of cytosol on the uptake of estrogens by purified nuclei was also investigated. It was observed that cytosol reduced the uptake o 17 beta-estradiol but had little effect on that of its conjugates.

Comparative studies of the 17 beta-estradiol receptors in rabbit liver, kidney and uterus

The cytosol 17 beta-estradiol receptors from rabbit kidney, liver and uterus, compared under identical experimental conditions, were similar in terms of their pH-activity profiles, dependence on incubation temperature, sensitivity to sulfhydryl reagents and steroid specificity. 17 beta-[3H]-Estradiol binding was saturable with all three tissues, having an apparent dissociation constant of 4 X 10(-10)M. The binding of 17 beta-[3H]-estradiol in kidney, liver and uterus was inhibited by estrogens, including estrogen conjugates, but not by testosterone, progesterone or cortisol. The 17 beta-estradiol receptors of liver, kidney and uterus exhibited significant differences with respect to their chromatographic behaviour on heparin-Sepharose. Furthermore, a comparison of their sucrose density gradient centrifugation patterns showed that the 17 beta-[3H]-estradiol-receptor complex of liver and kidney sedimented at 3-4 S in both low and high ionic strength media, while the uterine receptor sedimented at 7-8 S in low ionic strength media and at 4-5 S in high ionic strength media. When the liver and uterine cytosol fractions were combined the uterine receptor was altered and sedimented at 3-4 S in low ionic strength media.

On the characteristics of mitochondrial monoamine oxidase in pancreas and adipose tissues from genetically obese mice

The substrate specificity of mitochondrial monoamine oxidase (MAO) in pancreatic and adipose tissues of obese mice and their lean counterparts was determined. The pancreatic MAO of obese mice had a greater specific activity than that of the lean mice. The white adipose tissue MAO was found to be more active than the brown adipose MAO in both groups of mice. While there was no appreciable difference in the MAO activities of brown adipose tissues between obese and lean mice, the enzyme from the white adipose tissue of obese mice had a higher specific activity than that of the lean mice. The higher MAO activity in white adipose tissue was observed when tyramine or serotonin was employed as substrate but not with benzylamine. Examination of mitochondrial MAO from epididymal adipocytes revealed marked differences in the properties of the enzyme between whole adipose tissue and isolated adipocytes. The inhibition characteristics of MAO from these tissues were studied with the specific inhibitors clorgyline and deprenyl.

Liver monoamine oxidase in the obese-hyperglycaemic (ob/ob) mouse

1. The specific activity of monoamine oxidase was found to be greater in liver mitochondria from ob/ob mice than from lean mice. The activities of marker enzymes were similar in both tissues. 2. Experiments with various substrates (5-hydroxytryptamine, benzylamine and tyramine) and inhibitors (clorgyline and deprenyl) indicated that, unlike rat liver mitochondria, mouse liver mitochondria contain a predominance of the B-form of monoamine oxidase. 3. The Km values for lean and ob/ob mice were the same for any given substrate and were in the increasing order 5-hydroxytryptamine less than tyramine less than benzylamine. Vmax. was approximately 50% greater in obese than in lean mice. 4. Extraction of liver mitochondria with acetone/water or acetone/water/NH3 to remove lipids decreased the enzyme activity relatively more in obese- than in lean-mice preparations, but residual activity was the same in both preparations.

In vivo studies on the conversion of m-tyrosine to 3,4-dihydroxyphenylalanine in the rat

The question whether m-tyrosine can give rise to catechols in vivo has been investigated using labelled precursor. DL-[2-14C]m-tyrosine (38 muCi/mmol (1 Ci = 37 GBq)) was synthesized from [2-14C]glycine. Radioactive catechols in rat brain, liver, and kidneys were examined 15 min after intraperitoneal administration of DL-[2-14C]m-tyrosine (100 mg/kg). The kidney was the only organ which showed demonstrable amounts of radioactive catechols, and about 14% of the catechols formed was identified as 3,4-dihydroxyphenylalanine (dopa), 22% as 3,4-dihydroxyphenylacetic acid, and 56% as dopamine. However, when the animals were pretreated with dopa decarboxylase inhibitor, labelled catechols were also observed in liver and brain, and dopa accounted for over 95% of the catechols formed in all three organs examined. Thus it is clear that m-tyrosine can by hydroxylated in vivo. Results from experiments using [2-14C]m-tyrosine enantiomers and specific enzyme inhibitors suggest that phenylalanine hydroxylase could be the enzyme catalyzing this reaction.

Solubilization and partial purification of particulate catechol-O-methyltransferase from rat liver

Particulate catechol-O-methyltransferase (COMT) from rat liver has been solubilized by acetone treatment and partially purified. Results from the present study demonstrate that the solubilized, partially purified enzyme is similar to the cytosol COMT with respect to molecular weight, pH profile, sensitivity toward inhibitors, Mg2+ requirement, and substrate affinities. However, a comparison of the crude particulate COMT and the solubilized enzyme shows that there is a significant difference in their affinity for catechol substrates. This finding suggests that membrane protein and (or) lipid components may play an important role in catecholamine metabolism. The relationship of particulate COMT to [3H]norepinephrine binding was investigated. No correlation between the COMT and [3H]norepinephrine binding activities was observed in vitro.

Studies on the depletion of brain amines by m-tyrosine

The biochemical basis of the well-known physiological and pharmacological actions of m-tyrosine was examined by a detailed study of its effect on the brain biogenic amines. m-Tyrosine was injected i.p. and rat brain monoamine levels were measured. Endogenous levels of dopamine, norepinephrine and serotonin all showed approximately 50% reductions 1 h after the administration of L-m-tyrosine at 150 mg/kg. These actions of L-m-tyrosine could be blocked by the inhibition of the central dopa decarboxylase. Depletion of brain monoamines was also observed with the D-isomer of m-tyrosine, although this effect was less pronounced than that of the L-isomer. In vitro experiments with rat brain homogenates showed that L-m-tyrosine, m-tyramine and m-octopamine enhanced in efflux of exogenous labeled monamines from brain particles, whereas D-m-tyrosine was completely ineffective. From these results it is concluded that the observed decreased in brain monamine levels by L-m-tyrosine may be due to a m-tyramine-enhanced release of the amines which are quickly metabolized in vivo.

Differential effects of L-thyroxine on cardiac and hepatic monoamine oxidase activity toward benzylamine and serotonin

Male and female rats of 2 age groups were given subcutaneous injections of L-thyroxine (500 mug/kg) at 12 h intervals for a period of 10 days. The activity of monoamine oxidase (MAO) in normal and thyrotoxic rats was studied with two substrates: benzylamine and serotonin. The results showed that a thyroxine effect on cardiac and liver MAO activity is dependent on the substrate used in the assay. Kinetic studies of cardiac and liver MAO after thyroxine-treatment showed an unaltered Km for benzylamine but a change in Km for serotonin. Both findings may indicate a discriminative action of thyroid hormones on different forms of MAO. The possible presence of a soluble activator and inhibitor for MAO was investigated.

Tryptophan hydroxylase. Purification and some properties of the enzyme from rabbit hindbrain

Tryptophan hydroxylase from rabbit hindbrain has been extensively purified. It is estimated that the enzyme is between 85 and 90% pure and has a molecular weight of 230, 000. Sodium dodecyl sulfate gel electrophoresis shows that the enzyme is composed of two subunits very close in molecular weight (57, 500 and 60, 900). The substrate specificity and the reaction stoichiometry catalyzed by the enzyme in the presence of 6, 7-dimethyltetrahydropterin, 6-methyltetrahydropterin, and tetrahydrobiopterin have been determined. The effect of some natural occurring phospholipids on the purified enzyme was investigated.

Transamination of ring-substituted L-phenylalanines by an extract from rat liver mitochondria

The L- and D-isomers of m-tyrosine, o-tyrosine, p-chlorophenylalanine (p-CP), and p-fluorophenylalanine (p-FP) were tested as substrates for the soluble tyrosine aminotransferase and a mitochondrial extract of rat liver by measuring the amino acids formed with 2-oxoglutarate, oxaloacetate, and pyruvate as acceptors. None of the above were substrates for the soluble enzyme. L-m-Tyrosine, L-p-CP, and L-p-FP were transaminated at substantial rates (16–25% of the rate for L-tyrosine) by the mitochondrial enzyme with all three keto acids as amino group acceptors. A slow but definite transamination of L-o-tyrosine by the mitochondrial enzyme was demonstrated using labeled 2-oxoglutarate as acceptor.

The effects in vivo of L- and D-para-chlorophenylalanine on the aromatic hydroxylating activity of rat liver

Injections of D- or L-p-chlorophenylalanine into rats resulted in identical decreases in the phenylalanine hydroxylase activities of their livers. Similar effects were produced on the ability of the livers to convert L-m-tyrosine to 3,4-dihydroxyphenylalanine. No effects on the tyrosine hydroxylase activities of the brain and adrenals could be detected.

Resolution of ring-substituted phenylalanines by the action of alpha-chymotrypsin on their ethyl esters

The D- and L-isomers of the following ring-substituted phenylalanines have been prepared from the racemates in 60–80% yield: tyrosine, o-tyrosine, m-tyrosine, p-chlorophenylalanine, p-fluorophenylalanine, and 3,4-dihydroxyphenylalanine. The resolutions were effected by digestion of the racemic ethyl esters with α-chymotrypsin at pH 5.0 (pH-stat). The L-isomers were crystallized from the concentrated digests; the D-isomers were obtained by saponification of the remaining D-esters after extraction into ethyl acetate. Analysis of the isomers by column chromatography indicated optical purities greater than 99.5%. The racemic esters were prepared with ethanol/hydrogen chloride and were used without isolation.