A novel suppressor of ras1 in fission yeast, byr4, is a dosage-dependent inhibitor of cytokinesis

A novel gene, designated byr4, was identified in Schizosaccharomyces pombe that affects the mitotic cell cycle and shows genetic interactions with the ras1 signaling pathways. Null alleles of byr4 cause cell cycle arrest in late mitosis and permit multiple rounds of septation. The multiple septa typically divide two nuclei, but the nuclei frequently do not stain equally with 4',6-diamidino-2-phenylindole (DAPI), suggesting that byr4 is required for proper karyokinesis. Overexpression of byr4 inhibits cytokinesis, but cell cycle progression continues leading to multinucleate cells. When byr4 is overexpressed, the early steps in the cytokinesis pathway, including formation of the medial F-actin ring, occur normally; however, the later steps in the pathway, including contraction of the F-actin ring, septation, and rearrangement of the medial F-actin following mitosis, rarely occur, byr4 shows two genetic interactions with ras1. The inhibition of cytokinesis by byr4 overexpression was exacerbated by null alleles of ras1 and scd1, suggesting a link between pathways needed for cell polarity and cytokinesis. Overexpression of byr4 also partially bypasses the need for ras1 for sporulation. The electrophoretic mobility of the byr4 protein varied in response to mutants that perturb cytokinesis and karyokinesis, suggesting interactions between byr4 and these gene products. A more rapidly migrating byr4 protein was found in cells with mutations in cdc16, which undergo repeated septation, and in cdc15, which fail to form a medial F-actin ring in mitosis. A slower migrating byr4 protein was found in cells with a mutation in the beta-tubulin gene, which arrests cells at the metaphase-anaphase transition.

Elevated expression of Bcl-X and reduced Bak in primary colorectal adenocarcinomas

Expression of several members of the BCL-2 family of genes was investigated by immunohistochemical methods in 30 primary colorectal adenocarcinomas and 24 adenomatous polyps. When compared to the intensity observed in adjacent normal mucosal epithelial cells, the intensity of Bcl-X immunostaining was elevated in 18 of 30 (60%) carcinomas (P = 0.0001) and 12 of 24 (50%) adenomatous polyps (P = 0.0001). Immunoblot analysis of five pairs of tumors and adjacent normal colonic tissue indicated marked elevations in the relative levels of the anti-apoptotic Bcl-XL, protein in all cases. In contrast to the increased Bcl-X expression, the intensity of Bcl-2 immunostaining was greater than that of normal colonic mucosa in only 3 of 30 (10%) carcinomas and, in fact, was lower than that of adjacent normal epithelia] cells in 25 (83%) cases (P = 0.0001). Furthermore, the percentage of Bcl-2 immunopositive cells was generally lower in carcinomas than in adenomas (mean +/- SE, 44 +/- 6% versus 73 +/- 5%, respectively; P = 0.001) and in moderately or poorly differentiated tumors than in well-differentiated tumors (39 +/- 6% versus 70 +/- 11%, respectively; P = 0.045). In addition, the proportion of tumors in which the Bcl-2 immunointensity was more than or equal to that of normal colonic mucosa was significantly lower in carcinomas than adenomas (5 of 30 versus 15 of 24, respectively; P < 0.001), suggesting that decreases in Bcl-2 expression represent a later event associated with the progression of colorectal cancers. When compared to that of normal adjacent colonic epithelium, the intensity of Mcl-1 immunostaining was reduced in 20 of 30 (67%) of carcinomas (P = 0.0001) compared to only 1 of 24 adenomas, suggesting that decreases in Mcl-1 expression represent a later event associated with progression from a benign to a malignant phenotype or with transition to a less-differentiated state, because most of the carcinomas evaluated here (25 of 30; 83%) were not well differentiated. The intensity of immunostaining for the pro-apoptotic protein Bak was reduced compared to that of normal mucosal epithelial cells in 27 of 30 (90%) carcinomas and 22 of 24 (92%) adenomas, suggesting that reductions in Bak expression occur early in colorectal tumor progression (P = 0.0001). In contrast, the intensity of immunostaining for the pro-apoptotic protein Bax was not significantly altered in carcinomas; compared to that of normal colonic mucosa, Bax immunointensity was reduced in only 7 of 30 (23%) carcinomas and 3 of 24 (13%) adenomas, and the percentage of Bax immunopositive cells was also not significantly different in any of the histological subgroups. Taken together, these results suggest that expression of Bcl-XL is increased in undifferentiated primary colorectal cancers, often with accompanying reciprocal decreases in the anti-apoptotic proteins Bcl-2 and Mcl-1 and the pro-apoptotic protein Bak, whereas Bax expression is relatively constant. Thus, a shift from expression of the anti-apoptotic proteins Bcl-2 and Mcl-1 to the Bcl-XL protein may occur during progression of colorectal tumors.

Immunohistochemical analysis of bcl-2, bax, bcl-X, and mcl-1 expression in prostate cancers

Proteins encoded by bcl-2 family genes are important regulators of programmed cell death and apoptosis. Alterations in the expression of these apoptosis-regulating genes can contribute to the origins of cancer, as well as adversely influence tumor responses to chemo- and radiotherapy. Using antibodies specific for the Bcl-2, Bax, Bcl-X, and Mcl-1 proteins in combination with immunohistochemical methods, we examined for the first time the expression of these bcl-2 family genes in 64 cases of adenocarcinoma of the prostate, including 10 Gleason grade 2 to 4 tumors, 21 grade 5 to 7 tumors, 17 grade 8 to 10 tumors, 8 lymph node metastases, and 8 bone metastases. In addition, 24 cases of prostatic intraepithelial neoplasia (PIN) or PIN coexisting with carcinoma were also evaluated. All immunostaining results were scored with regard to approximate percentage of positive tumor cells and relative immunostaining intensity. Expression of the anti-apoptotic protein Bcl-2 was present in 16 of 64 (25%) adenocarcinomas and tended to be more frequent in high grade tumors (Gleason grade 8 to 10; 41%) and nodal metastases (38%) than in lower grade (Gleason 2 to 7) primary tumors (16%; P < 0.05). Bcl-X was expressed in all 64 (100%) tumors evaluated. Bcl-X immunointensity was generally stronger in high grade primary tumors (grade 8 to 10) and metastases compared with PIN and low grade neoplasms (P < 0.0001). In addition, the proportion of specimens with > 50% Bcl-X-immunopositive tumor cells also was higher in advanced grade primary tumors (Gleason 8 to 10) and metastases than in PIN and low grade tumors (Gleason 2 to 7; P < 0.005). The anti-apoptotic protein Mcl-1 was expressed in 52 of 64 (81%) tumors, compared with only 9 of 24 (38%) cases of PIN (P < 0.001). In addition, the percentage of Mcl-1-positive cells was typically higher in Gleason grade 8 to 10 tumors and metastases than in PIN or lower grade tumors (P = 0.025). In contrast, the pro-apoptotic protein Bax was expressed in all prostate cancers evaluated, with high percentages of immunopositive cells and strong immunointensity typically occurring regardless of tumor grade. The findings suggest that expression of several anti-apoptotic members of the bcl-2 gene family, including bcl-2, bcl-X, and mcl-1 increases during progression of prostate cancers, a finding that may be relevant to the hormone-insensitive, metastatic phenotype of most advanced adenocarcinomas of the prostate.

Autoradiographic localization of active renin in the juxtaglomerular apparatus of the dog kidney: effects of sodium intake

1. The effects of dietary sodium intake on active renin binding in the juxtaglomerular apparatus (JGA) of superficial and juxtamedullary cortex of the dog kidney were examined by quantitative in vitro autoradiography using a radiolabelled renin inhibitor [125I]-H77, which has high affinity for dog renin. 2. Changes in sodium intake resulted in marked alterations of active renin binding in the radiolabelled JGA. In comparison with the control kidney (190.8 +/- 7.7 Bq/mm3), a higher density of binding occurred in the labelled JGA of sodium-depleted kidney (277.7 +/- 6.2 Bq/mm3), while a lower density of binding was found in the labelled JGA of sodium-loaded kidney (99.3 +/- 7.4 Bq/mm3). 3. Active renin binding in the labelled JGA was significantly higher in superficial JGA than in their juxtamedullary counterparts, irrespective of sodium intake. 4. Pre-incubation with trypsin (0.5 mg/mL), a procedure known to activate prorenin, markedly increased active renin binding in the labelled JGA of control (+ approximately 35%; P < 0.01) and sodium-loaded kidneys (+ approximately 75%; P < 0.01), but had little effect on binding in the labelled JGA of the sodium-depleted kidney (+/- approximately 5-10%; NS). The proportions of active renin as a percentage of total renin were 60, 75 and 95% in the labelled JGA of sodium-loaded, control, and sodium-depleted kidneys, respectively. 5. Emulsion microscopic autoradiography revealed that the binding was exclusively localized in the JGA, including the afferent and efferent arterioles, macula densa and extraglomerular mesangium. Labelling extended to the interlobular arteries in sodium depleted kidney. 6. These results indicate that autoradiography combined with the in vitro binding of radiolabelled renin inhibitors may provide a useful tool to measure active and prorenin renin and thereby study the physiological regulation of renin in the kidney.

Molecular cloning of caveolin-3, a novel member of the caveolin gene family expressed predominantly in muscle

Caveolin, a 21-24-kDa integral membrane protein, is a principal component of caveolar membranes in vivo. Caveolin interacts directly with heterotrimeric G-proteins and can functionally regulate their activity. Recently, a second caveolin gene has been identified and termed caveolin-2. Here, we report the molecular cloning and expression of a third member of the caveolin gene gamily, caveolin-3. Caveolin-3 is most closely related to caveolin-1 based on protein sequence homology; caveolin-1 and caveolin-3 are approximately 65% identical and approximately 85% similar. A single stretch of eight amino acids (FED-VIAEP) is identical in caveolin-1, -2, and -3. This conserved region may represent a "caveolin signature sequence" that is characteristic of members of the caveolin gene family. Caveolin-3 mRNA is expressed predominantly in muscle tissue-types (skeletal muscle, diaphragm, and heart) and is selectively induced during the differentiation of skeletal C2C12 myoblasts in culture. In many respects, caveolin-3 is similar to caveolin-1: (i) caveolin-3 migrates in velocity gradients as a high molecular mass complex; (ii) caveolin-3 colocalizes with caveolin-1 by immunofluorescence microscopy and cell fractionation studies; and (iii) a caveolin-3-derived polypeptide functionally suppresses the basal GTPase activity of purified heterotrimeric G-proteins. Identification of a muscle-specific member of the caveolin gene family may have implications for understanding the role of caveolin in different muscle cell types (smooth, cardiac, and skeletal) as previous morphological studies have demonstrated that caveolae are abundant in these cells. Our results also suggest that other as yet unknown caveolin family members are likely to exist and may be expressed in a regulated or tissue-specific fashion.

Mapping of angiotensin II receptor subtypes in peripheral tissues of spontaneously hypertensive rats by in vitro autoradiography

1. The regulation of angiotensin II (AII) receptor subtypes was studied in peripheral tissues of 20 week old male spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto (WKY) rats. 2. AII receptor binding was determined by a quantitative in vitro autoradiography using [125I]-[Sar1,Ile8]AII as a ligand on the kidney, adrenal gland, thoracic aorta and heart. CV-11974, a specific AT1 receptor antagonist, and CGP42112B, a specific AT2 antagonist, were used in competition with [125I]-[Sar1,Ile8]AII to differentiate AT1 and AT2 receptor binding. 3. The relative abundance of each subtype was very similar between SHR and WKY rats. In both strains of rats, the adrenal cortex contained predominantly AT1 receptors, while AT2 receptors predominated in the adrenal medulla. The kidney contained exclusively AT1 receptors over glomeruli, proximal tubules and outer medulla. AT1 receptors were predominant in the thoracic aorta and heart. 4. As for relative receptor density, important differences were observed between SHR and WKY rats. In SHR, the adrenal cortex, outer medulla of the kidney, and heart displayed higher AT1 receptor density than WKY rats. 5. These results indicate that the expression of AT1 receptors is differently regulated in some important targets of AII in SHR, and suggest that the altered regulation of AT1 receptor presented in this study should be relevant to the pathophysiological features of SHR.

Mutational analyses of fs(1)Ya, an essential, developmentally regulated, nuclear envelope protein in Drosophila

The fs(1)Ya protein (YA) is an essential, maternally encoded, nuclear lamina protein that is under both developmental and cell cycle control. A strong Ya mutation results in early arrest of embryos. To define the function of YA in the nuclear envelope during early embryonic development, we characterized the phenotypes of four Ya mutants alleles and determined their molecular lesions. Ya mutant embryos arrest with abnormal nuclear envelopes prior to the first mitotic division; a proportion of embryos from two leaky Ya mutants proceed beyond this but arrest after several abnormal divisions. Ya unfertilized eggs contain nuclei of different sizes and condensation states, apparently due to abnormal fusion of the meiotic products immediately after meiosis. Lamin is localized at the periphery of the uncondensed nuclei in these eggs. These results suggest that YA function is required during and after egg maturation to facilitate proper chromatin condensation, rather than to allow a lamin-containing nuclear envelope to form. Two leaky Ya alleles that partially complement have lesions at opposite ends of the YA protein, suggesting that the N- and C-termini are important for YA function and that YA might interact with itself either directly or indirectly.

MSX1 inhibits myoD expression in fibroblast x 10T1/2 cell hybrids

Transfer of human chromosome 11, which contains the myoD locus, from primary fibroblasts into 10T1/2 cells results in activation of myoD. In contrast, hybrids that retain human chromosome 11 and additional human chromosomes fail to activate myoD. We show that human chromosome 4 inhibits myoD activation. myoD enhancer/promoter reporter constructs show that repression is at the transcriptional level. Chromosome fragment-containing hybrids localize the repressing activity to the region of 4p that contains the homeobox gene MSX1. MSX1 is expressed in primary human fibroblasts and in 10T1/2 cells containing human chromosome 4, while parental 10T1/2 cells do not express Msx1. Forced expression of Msx1 represses myoD enhancer activity. Msx1 protein binds to the myoD enhancer and likely represses myoD transcription directly. Antisense MSX1 relieves repression mediated by chromosome 4. We conclude that MSX1 inhibits transcription of myoD and that myoD is a target for homeobox gene regulation.

Rapid genome change in synthetic polyploids of Brassica and its implications for polyploid evolution

Although the evolutionary success of polyploidy in higher plants has been widely recognized, there is virtually no information on how polyploid genomes have evolved after their formation. In this report, we used synthetic polyploids of Brassica as a model system to study genome evolution in the early generations after polyploidization. The initial polyploids we developed were completely homozygous, and thus, no nuclear genome changes were expected in self-fertilized progenies. However, extensive genome change was detected by 89 nuclear DNA clones used as probes. Most genome changes involved loss and/or gain of parental restriction fragments and appearance of novel fragments. Genome changes occurred in each generation from F2 to F5, and the frequency of change was associated with divergence of the diploid parental genomes. Genetic divergence among the derivatives of synthetic polyploids was evident from variation in genome composition and phenotypes. Directional genome changes, possibly influenced by cytoplasmic-nuclear interactions, were observed in one pair of reciprocal synthetics. Our results demonstrate that polyploid species can generate extensive genetic diversity in a short period of time. The occurrence and impact of this process in the evolution of natural polyploids is unknown, but it may have contributed to the success and diversification of many polyploid lineages in both plants and animals.

Angiotensin II receptor subtypes in the human central nervous system

The distribution of the AT1 and AT2 subtypes of angiotensin II receptor was mapped in the adult human central nervous system using quantitative in vitro autoradiography. Binding in all forebrain, midbrain, pontine, medullary and spinal cord sites where angiotensin II receptors have previously been described is of the AT1 subtype, as is binding in the small and large arteries in the adjacent meninges and in choroid plexus. By contrast, both AT1 and AT2 receptors occur in the molecular layer of the cerebellum. Angiotensin II AT1 receptors in the brain show a moderate degree of conservation across mammalian species studied so far, whereas expression of AT2 receptors is more variable, and is more restricted in the human CNS than in many other mammals. These differences between the subtype distributions in humans and other animals indicate the need for care when extrapolating the results of animal studies involving the brain angiotensin system.

Identification and characterization of a human cDNA homologous to yeast SKI2

A monoclonal antibody, 170A1, which recognizes a nucleolar peptide of molecular weight 90,000, was raised. The protein was conserved among various vertebrates. To characterize the antigen, we screened a human fetal liver expression library using the monoclonal antibody as a probe. Molecular analyses of immunopositive clones suggested the presence of a novel cDNA. It appeared to be a single-copy gene and encoded about 4- and 5-kb mRNAs. The gene appeared to be expressed in every cell tested so far. Its deduced amino acid sequence revealed an overall homology to recently described yeast SKI2. The SKI2 gene of Saccharomyces cerevisiae encoded a nucleolar protein that is involved in the antiviral system. We report here the partial human cDNA sequence and the localization of the corresponding gene on chromosome 6p21.

Molecular marker analysis of genes controlling morphological variation in Brassica rapa (syn. campestris)

Construction of a detailed RFLP linkage map of B. rapa (syn. campestris) made it possible, for the first time, to study individual genes controlling quantitative traits in this species. Ninety-five F2 individuals from a cross of Chinese cabbage cv 'Michihili' by Spring broccoli were analyzed for segregation at 220 RFLP loci and for variation in leaf, stem, and flowering characteristics. The number, location, and magnitude of genes underlying 28 traits were determined by using an interval mapping method. Zero to five putative quantitative trait loci (QTL) were detected for each of the traits examined. There were unequal gene effects on the expression of many traits, and the inheritance patterns of traits ranged from those controlled by a single major gene plus minor genes to those controlled by polygenes with small and similar effects. The effect of marker locus density on detection of QTL was analyzed, and the results showed that the number of QTL detected did not change when the number of marker loci used for QTL mapping was decreased from 220 to 126; however, a further reduction from 126 to 56 caused more than 15% loss of the total QTL detected. The detection of putative minor QTL by removing the masking effects of major QTL was explored.

The human stromelysin promoter contains a previously unreported 1.0-kb sequence

Cloning and characterization of the promoter region controlling the gene encoding human stromelysin (Str) has been previously reported [Quinones et al., J. Biol. Chem. 264 (1989) 8339-8344]. We have characterized independently isolated genomic clones of the STR promoter, designated pSKStrB and 682, that are considerably different from the published sequence. Although the sequences up to an XbaI site at -480 of the 5' regions are identical, a novel 1.0-kb segment exists upstream from -480. This sequence is absent from the published clone, but its presence in the genomic DNA from twelve individuals has been confirmed by both PCR analysis and restriction mapping. Upstream of the novel 1-kb segment, the sequence of the published clone reappears, but in pSKStrB exists in inverse orientation.

A method for examining expression of homologous genes in plant polyploids

One of the essential issues regarding evolution of polyploid species is how duplicate genes are expressed. Most studies on gene expression in polyploids have been based on isozyme analyses; RNA analysis has not been widely used partially due to difficulties in distinguishing homologous transcripts which usually have the same length and similar or almost identical sequences. In this study, a method combining RT-PCR with RFLP was used to analyze transcripts of homologous genes in natural and synthetic Brassica amphidiploids. Sequences coding for several known genes were selected and used to synthesize gene-specific primers. Total RNAs were used as templates for RT-PCR to amplify homologous transcripts in three diploid parental species, three cultivated amphidiploid species and six synthetic amphidiploids. For each gene, initial PCR products amplified in all species had identical length; however, homologous transcripts in the diploid and amphidiploid species could be distinguished after digesting the PCR products with restriction enzymes. Preliminary results based on three genes indicated that both transcripts from the diploid parents were expressed in the synthetic and natural amphidiploids. This study represents the first application of RT-PCR and RFLP analysis to investigate expression of homologous genes in higher plants. The technique is a sensitive, simple and efficient method for distinguishing homologous transcripts in a mixed RNA population and can be applied to many types of studies on expression of homologous genes.

Mandibular reconstruction using computer-generated three-dimensional solid models

In mandibular reconstruction, it is necessary to know the exact, three-dimensional extent of the mandible and its defect; the bone graft must be the exact size and dimension of the defect, to assure a precise three-dimensional configuration of the mandible. Previously, the bone graft had to be reshaped during the operation by trial and error, often a time-consuming procedure. The operative procedure has been simulated in advance using three-dimensional, solid models, which has shortened the operating time required.

Blockade by intravenous losartan of AT1 angiotensin II receptors in rat brain, kidney and adrenals demonstrated by in vitro autoradiography

1. The in vivo inhibition of angiotensin II (AII) receptor binding in the rat brain, kidney and adrenal was investigated after intravenous administration of the AT1-selective AII receptor antagonist losartan. 2. Male Sprague-Dawley rats were administered intravenously either vehicle, or losartan at doses of 1, 3 or 10 mg/kg. Plasma samples were collected and tissues removed at 1, 2, 8 or 24 h after administration of the antagonist. The effects of losartan on AII receptor binding were assessed by quantitative in vitro autoradiography. 3. Losartan significantly increased plasma renin activity (PRA) by six-fold and nine-fold at doses of 1 and 10 mg/kg, respectively (P < 0.05). Plasma losartan concentrations rose from 0.83 micrograms/mL at 1 mg/kg to 46.5 micrograms/mL at 10 mg/kg 1 h after administration of the drug. Plasma renin activity returned to control, whilst losartan was undetectable 24 h after injection of the antagonist. 4. In the brain, losartan produced a dose-dependent inhibition of AII receptor binding to the brain structures which express exclusively, or predominantly, AT1 receptors both outside and within the blood brain barrier. By contrast, losartan did not affect binding to the nuclei which contain exclusively, or predominantly, AT2 receptors. 5. In the kidney, losartan blocked AII receptor binding to all anatomical sites in a dose-dependent manner. The inhibition peaked at 1 h and persisted beyond 24 h despite the fact that PRA had returned to control, and losartan was not detectable in the circulation. In the adrenal gland, where AT1 and AT2 receptors occur in both the cortex and medulla, losartan caused partial inhibition at both regions. 6. These results indicate that losartan, administered intravenously at these doses, and/or its active metabolites, partially penetrate the blood brain barrier to selectively inhibit central AT1 receptors, and exert selective and prolonged blockade at AT1 receptors in peripheral target tissues.

Localization and quantitation of active renin in monkey kidney by radioinhibitor binding and in vitro autoradiography

We developed an in vitro autoradiographic method to localize and quantify active renin in primate tissues. Active renin in monkey kidney sections was labeled with the primate specific renin inhibitor, 3H-CGP29287, and quantitated with autoradiography and computerized densitometry. Microscopic emulsion autoradiography was carried out to clarify the detailed localization of the binding. Non-specific binding to aspartyl proteases other than renin was blocked using 1 mumol/L of N-acetyl-pepstatin. To assess the usefulness of this procedure, binding of 3H-CGP29287 was examined both by film and emulsion autoradiography in the kidneys of monkeys (Macaca fuscata) that were given chronically either an angiotensin converting enzyme inhibitor (trandolapril), an angiotensin II receptor antagonist (E4177), or vehicle. 3H-CGP29287 was found to bind very selectively to the juxtaglomerular apparatus (JGA) under control conditions. In monkeys treated with trandolapril or E4177, 3H-CGP29287 binding was increased in proportion to the increase in renal renin concentration determined enzymatically; in these kidneys, emulsion autoradiography revealed radioinhibitor binding extending far from the JGA. The potency of a series of unlabeled renin inhibitor in competing for 3H-CGP29287 binding in the autoradiographic system closely paralleled their potencies, as determined in inhibiting renin by an enzymatic assay. This technique permits specific labeling of the catalytic site of renin in the monkey kidney sections.

The Drosophila fs(1)Ya protein, which is needed for the first mitotic division, is in the nuclear lamina and in the envelopes of cleavage nuclei, pronuclei, and nonmitotic nuclei

The Drosophila melanogaster fs (1) Ya gene encodes a nuclear envelope protein needed to initiate embryonic cleavage divisions. In cleavage stage embryos the fs (1) Ya gene product is localized to the nuclear envelope in a cell cycle dependent manner. We show here that fs(1)Ya protein is also present in polar bodies of early cleavage stage embryos as well as in endoreplicating yolk nuclei. This observation suggests that the fs(1)Ya protein is necessary but not solely responsible for embryonic mitosis. Furthermore, cell cycle stage dependent nuclear localization is also seen for ectopically produced fs(1)Ya protein in tissue culture cells, neuroblasts, and male accessory glands, which are free of maternal products. We therefore conclude that cell cycle dependent nuclear localization does not require any exclusively maternal products. Finally, our immunoelectron microscopy shows that the fs(1)Ya protein distribution parallels that of lamin, indicating that it is a nuclear lamina protein.

AA1, a newly synthesized monovalent lipophilic cation, expresses potent in vivo antitumor activity

Certain lipophilic cations have been reported to display anticarcinoma activities because of their selective uptake and retention by mitochondria of cancer cells. Thus, these agents may comprise a unique class of agents directed against carcinoma. After screening more than 1000 lipophilic cations, we found that the monovalent lipophilic cation, 2,6-bis(4-amino-phenyl)-4-[4-(dimethylamino)phenyl]thiopyrylium chloride (AA1), displayed remarkable anticarcinoma activity both in vitro and in vivo. Unlike most other lipophilic cations, AA1 is stable and displays minimal light sensitivity. In vitro testing showed that AA1 was 10 times more toxic to the carcinoma cell line CX-1 than to the normal epithelial cell line CV-1. In vivo animal experiments showed that AA1 significantly prolonged the survival of mice implanted with tumors. For C57BL x DBA/2 F1 mice implanted with the mouse bladder carcinoma cell line, MB49, the treated:control ratio was 344%. For Swiss nu/nu mice implanted i.p. with the human melanoma cell line, LOX, the treated:control ratio was 341%. The most significant observation was obtained with Swiss nu/nu mice that were implanted i.p. with the human ovarian cell line, OVCAR-III. The treated:control ratio in this situation was greater than 450%. In all these tumor models, AA1 produced minimal toxicities. AA1 exhibited little inhibition of electron transport in isolated rat liver mitochondria; however, it inhibited mitochondrial ATPase with 50% inhibitory concentration of 6 microM. Compared with previously reported anticarcinoma lipophilic cations such as rhodamine 123 and dequalinium chloride, AA1 appeared to display more effective in vivo anticarcinoma activity. Thus, AA1 could be considered for further clinical development as a candidate for anticarcinoma chemotherapy.

Development of synthetic Brassica amphidiploids by reciprocal hybridization and comparison to natural amphidiploids

In a previous study we proposed that cytoplasmic genomes have played an important role in the evolution of Brassica amphidiploid species. Based on this and other studies, we hypothesized that interactions between the maternal cytoplasmic genomes and the paternal nuclear genome may cause alterations in genome structure and/or gene expression of a newly synthesized amphidiploid, which may play an important role in the evolution of natural amphidiploid species. To test this hypothesis, a series of synthetic amphidiploids, including all three analogs of the natural amphidiploids B. napus, B. juncea, and B. Carinata and their reciprocal forms, were developed. These synthetic amphidiploids were characterized for morphological traits, chromosome number, and RFLPs revealed by chloroplast, mitochondrial, and nuclear DNA clones. The maternal transmission of chloroplast and mitochondrial genomes was observed in all of the F1 hybrids examined except one hybrid plant derived from the B. rapa x B. oleracea combination, which showed a biparental transmission of organelles. However, the paternal chloroplast and mitochondrial genomes were not observed in the F2 progeny. Nuclear genomes of synthetic amphidiploids had combined RFLP patterns of their parental species for all of the nuclear DNA clones examined. A variation in fertility was observed among self-pollinated progenies of single amphidiploids that had completely homozygous genome constitutions. Comparisons between natural and synthetic amphidiploids based on restriction fragment length polymorphism (RFLP) patterns indicated that natural amphidiploids are considerably more distant from the progenitor diploid species than the synthetic amphidiploids. The utility of these synthetic amphidiploids for investigating the evolution of amphidiploidy is discussed.

In vitro pharmacology of a novel non-peptide angiotensin II-receptor antagonist, E4177

E4177, 3-[(2'-carboxybiphenyl-4-yl)methyl]-2-cyclopropyl-7-methyl-3H- imidazo[4,5-b]pyridine, was characterized by in vitro autoradiography and by examining functional antagonism upon angiotensin II (Ang II)-induced contraction of isolated vessels. In rat adrenal cortex and liver, E4177 competitively inhibited the specific binding of 125I-[Sar1,Ile8]Ang II, with IC50 being (5.2 +/- 1.0) x 10(-8) M for the adrenal cortex and (1.2 +/- 0.3) x 10(-7) M for the liver. These IC50 values were similar to those for losartan, which showed an IC50 of (6.0 +/- 0.9) x 10(-8) M for the adrenal cortex and (1.3 +/- 0.5) x 10(-7) M for the liver. In contrast, E4177 and losartan had little effect on the binding to rat adrenal medulla where AT2-receptors predominate. These results indicate that E4177 is AT1-specific as is losartan. E4177 and losartan competitively antagonized the Ang II-induced contraction of human and rabbit arterial strips without any agonistic action. The obtained IC50 values indicated that E4177 was twice as potent as losartan in human arteries and three times more so in rabbit aortic strips. Responses to norepinephrine, serotonin, histamine or KCl were not affected by E4177. In addition, E4177 (10(-5) M) had no effect on angiotensin-converting enzyme activity. These data indicate that E4177 is a potent AT1 Ang II-receptor antagonist that may be clinically useful for the treatment of cardiovascular diseases such as hypertension.

Marked species-difference in the vascular angiotensin II-forming pathways: humans versus rodents

Using isolated arteries, we demonstrated a marked difference in the angiotensin II-forming systems between human and rodent vessels. In human arteries, only 30-40% of the conversion of angiotensin I to angiotensin II depended on the angiotensin-converting enzyme (ACE), and the rest of the angiotensin II formation was ascribed to chymostatin-sensitive angiotensin II-generating enzyme (CAGE). On the contrary, angiotensin II formation in rodent arteries totally depended upon ACE, without any sign of CAGE involvement. Such a marked species-difference can be relevant to the reported difference between humans and rodents in the ACE inhibitor effects on the myointimal hyperplasia after intimal balloon injury.

Distribution of angiotensin II receptor subtypes in the rabbit brain

We have determined the distribution of angiotensin II receptor subtypes in rabbit brain using in vitro autoradiography. AT1 receptors were found in very high concentrations in the forebrain circumventricular organs--the subfornical organ, organum vasculosum of the lamina terminalis, and the median eminence as observed in other mammals. However, there was very little labeling in the area postrema. In the paraventricular nucleus, median preoptic nucleus, supraoptic nucleus there were high levels of predominantly AT1 receptors. High densities of AT1 receptors were also found in the nucleus of the solitary tract and the rostral and caudal ventrolateral medulla. All of these regions have putative roles in the regulation of blood pressure and fluid and electrolyte balance. In the rabbit brain there is less AT2 receptor binding than the rat, with most AT2 binding found in the molecular layer of the cerebellum and in the septohypothalamic nucleus. In the subthalamic nucleus, the mediodorsal and ventroposterior nuclei of the thalamus, locus coeruleus and inferior olivary nuclei, areas containing mostly AT2 receptors in the rat, no binding was detected in the rabbit except in the locus coeruleus which contains moderate levels of AT1 receptors. Taken in conjunction with our previous results in the rat and human brains, these results reveal that AT1 receptors predominate in rostral forebrain, hypothalamus and autonomic control centers of the medulla oblongata in all three species. However, the distribution and density of AT2 bearing sites in regions such as the septum, thalamus subthalamic nuclei, locus coeruleus, cerebellum and inferior olivary nuclei show marked species differences.

m-Calpain requires DNA for activity on nuclear proteins at low calcium concentrations

m-Calpain (calpain II, m-CANP), which normally requires millimolar Ca2+ for activity in vitro, was capable of proteolyzing a number of matrix proteins in isolated rat liver nuclei at Ca2+ concentrations as low as 3 microM (Mellgren, R. L. (1991) J. Biol. Chem. 266, 13920-13924). Treatment of nuclei with deoxyribonuclease I eliminated the activity of m-calpain at low Ca2+ concentrations, while ribonuclease A and phospholipase C had no effect. Addition of DNA to DNase-treated nuclei restored m-calpain activity at low Ca2+. RNA had little if any effect. Eukaryotic and prokaryotic DNA were equally effective, and synthetic polydeoxyribonucleotides were also activators. m-Calpain did not bind to a DNA-cellulose column in the presence of 200 microM Ca2+, and m-calpain preincubated in the presence of DNA and 200 microM Ca2+ was not activated at low Ca2+ concentrations following removal of the DNA. DNA did not alter the Ca2+ requirement for m-calpain-catalyzed cleavage of casein. These results demonstrate that the Ca2+ requirement for proteolysis of nuclear matrix proteins by m-calpain can be dramatically decreased in the presence of DNA. Activation did not seem to be a result of DNA binding directly to calpain but appeared to require interaction of DNA, calpain, and calpain substrates in the nuclear matrix.