Plasminogen deficiency accelerates vessel wall disease in mice predisposed to atherosclerosis

A critical link between hemostatic factors and atherosclerosis has been inferred from a variety of indirect observations, including the expression of procoagulant and fibrinolytic factors within atherosclerotic vessels, the presence of fibrin in intimal lesions, and the cellular infiltration of mural thrombi leading to their incorporation into developing plaques. To directly examine the role of the key fibrinolytic factor, plasminogen, in atherogenesis, plasminogen-deficient mice were crossed to hypercholesterolemic, apolipoprotein E-deficient mice predisposed to atherosclerosis. We report that the loss of plasminogen greatly accelerates the formation of intimal lesions in apolipoprotein E-deficient animals, whereas plasminogen deficiency alone does not cause appreciable atherosclerosis. These studies provide direct evidence that circulating hemostatic factors strongly influence vessel wall disease in the context of a disorder in lipid metabolism.

Organization, sequence, chromosomal localization, and promoter identification of the mouse orphan nuclear receptor Nurr1 gene

We have cloned and characterized the organization of the mouse orphan nuclear receptor Nurr1 gene. The Nurr1 gene is approximately 7 kb long, contains eight exons and seven introns, and mapped to mouse chromosome 2. Although the exon/intron structure of Nurr1 is nearly identical to that of Nur77, Nurr1 possesses an additional untranslated exon. Primer extension was used to identify two major transcription initiation sites mapped 37 nucleotides apart in the first untranslated exon. Functional studies of chimeric Nurr1-luciferase reporter genes delineated the promoter region and underscored the importance of the +1 transcription start site. Sequence analysis of the 5' flanking region surrounding +1 revealed several possible response elements such as a hexanucleotide glucocorticoid binding site, a cAMP-response element, a CArG box, and two c-Jun-binding sites. These data help to explain the different response characteristics of two closely related early response genes, Nurr1 and Nur77.

Identification of downstream-initiated c-Myc proteins which are dominant-negative inhibitors of transactivation by full-length c-Myc proteins

The c-myc gene has been implicated in multiple cellular processes including proliferation, differentiation, and apoptosis. In addition to the full-length c-Myc 1 and 2 proteins, we have found that human, murine, and avian cells express smaller c-Myc proteins arising from translational initiation at conserved downstream AUG codons. These c-Myc short (c-Myc S) proteins lack most of the N-terminal transactivation domain but retain the C-terminal protein dimerization and DNA binding domains. As with full-length c-Myc proteins, the c-Myc S proteins appear to be localized to the nucleus, are relatively unstable, and are phosphorylated. Significant levels of c-Myc S, often approaching the levels of full-length c-Myc, are transiently observed during the rapid growth phase of several different types of cells. Optimization of the upstream initiation codons resulted in greatly reduced synthesis of the c-Myc S proteins, suggesting that a "leaky scanning" mechanism leads to the translation of these proteins. In some hematopoietic tumor cell lines having altered c-myc genes, the c-Myc S proteins are constitutively expressed at levels equivalent to that of full-length c-Myc. As predicted, the c-Myc S proteins are unable to activate transcription and inhibited transactivation by full-length c-Myc proteins, suggesting a dominant-negative inhibitory function. While these transcriptional inhibitors would not be expected to function as full-length c-Myc, the occurrence of tumors which express constitutive high levels of c-Myc S and their transient synthesis during rapid cell growth suggest that these proteins do not interfere with the growth-promoting functions of full-length c-Myc.

The distribution of NPY-containing nerves and the catecholamine contents of canine enteric nerve plexuses

Our previous study demonstrated that PYY was a major neuropeptide in the canine enteric nervous system, the present study defines the locations of NPY-containing enteric neurons. NPY-positive nerve cell bodies and fibers were numerous in gastric and pyloric myenteric plexuses as were positive nerve fibers in antral and pyloric muscle layers, pyloric sphincter muscle layers, and surrounding blood vessels. In contrast to findings for PYY, there were considerably fewer NPY-positive nerve cell bodies and fibers in the canine ileum and colon. Noradrenaline was the predominant catecholamine in all plexuses, the rank order of its contents being: deep muscular > submucous > myenteric plexus. The dopamine/noradrenaline ratio was constant in all plexuses; adrenaline was present in minor amounts. PYY is the more abundant neuropeptide in ileum and colon, and NPY has a greater presence in the gastric antrum, pylorus, and surrounding blood vessels. PYY and NPY may play different functional roles in the GI tract.

A novel fluorescence-activated cell sorter-based screen for yeast endocytosis mutants identifies a yeast homologue of mammalian eps15

A complete understanding of the molecular mechanisms of endocytosis requires the discovery and characterization of the protein machinery that mediates this aspect of membrane trafficking. A novel genetic screen was used to identify yeast mutants defective in internalization of bulk lipid. The fluorescent lipophilic styryl dye FM4-64 was used in conjunction with FACS to enrich for yeast mutants that exhibit internalization defects. Detailed characterization of two of these mutants, dim1-1 and dim2-1, revealed defects in the endocytic pathway. Like other yeast endocytosis mutants, the temperature-sensitive dim mutant were unable to endocytose FM4-64 or radiolabeled alpha-factor as efficiently as wild-type cells. In addition, double mutants with either dim1-delta or dim2-1 and the endocytosis mutants end4-1 or act1-1 displayed synthetic growth defects, indicating that the DIM gene products function in a common or parallel endocytic pathway. Complementation cloning of the DIM genes revealed identity of DIM1 to SHE4 and DIM2 to PAN1. Pan1p shares homology with the mammalian clathrin adaptor-associated protein, eps15. Both proteins contain multiple EH (eps15 homology) domains, a motif proposed to mediate protein-protein interactions. Phalloidin labeling of filamentous actin revealed profound defects in the actin cytoskeleton in both dim mutants. EM analysis revealed that the dim mutants accumulate vesicles and tubulo-vesicular structures reminiscent of mammalian early endosomes. In addition, the accumulation of novel plasma membrane invaginations where endocytosis is likely to occur were visualized in the mutants by electron microscopy using cationized ferritin as a marker for the endocytic pathway. This new screening strategy demonstrates a role for She4p and Pan1p in endocytosis, and provides a new general method for the identification of additional endocytosis mutants.

The mutation in the mitochondrial aldehyde dehydrogenase (ALDH2) gene responsible for alcohol-induced flushing increases turnover of the enzyme tetramers in a dominant fashion

Deficiency in mitochondrial aldehyde dehydrogenase (ALDH2), a tetrameric enzyme, results from inheriting one or two ALDH2*2 alleles. This allele encodes a protein subunit with a lysine for glutamate substitution at position 487 and is dominant over the wild-type allele, ALDH2*1. The ALDH2*2-encoded subunit (ALDH2K) reduces the activity of ALDH2 enzyme in cell lines expressing the wild-type subunit (ALDH2E). In addition to this effect on the enzyme activity, we now report that ALDH2*2 heterozygotes had lower levels of ALDH2 immunoreactive protein in autopsy liver samples. The half-lives of ALDH2 protein in HeLa cell lines expressing ALDH2*1, ALDH2*2, or both were determined by the rate of loss of immunoreactive protein after inhibition of protein synthesis with puromycin and by pulse-chase experiments. By either measure, ALDH2E enzyme was very stable, with a half-life of at least 22 h. ALDH2K enzyme had an enzyme half-life of only 14 h. In cells expressing both subunits, most of the subunits assemble as heterotetramers, and these enzymes had a half-life of 13 h. Thus, the effect of ALDH2K on enzyme turnover is dominant. These studies indicate that the ALDH2*2 allele exerts its dominant effect both by interfering with the catalytic activity of the enzyme and by increasing its turnover. This represents the first example of a dominantly acting allele with this effect on a mitochondrial enzyme's turnover.

Distribution of messenger RNAs for the orphan nuclear receptors Nurr1 and Nur77 (NGFI-B) in adult rat brain using in situ hybridization

Nurr1 and Nur77 (NGFI-B) are orphan nuclear receptors, belonging to the steroid/thyroid hormone receptor gene superfamily. They have conserved amino acid sequence in the zinc-finger DNA binding domains and similar COOH-terminal regions, but have no known ligands. However, different expression patterns during brain development and tissue distributions of these messenger RNAs imply that they might reflect a different transcriptional role in the brain. In this study, the regional and cellular expression of messenger RNAs encoding these two proteins in rat brain has been determined by in situ hybridization. Nurr1 messenger RNA is highly expressed in the piriform and entorhinal cortices, hippocampus, medial habenular and paraventricular thalamic nuclei. Moderate labeling was detected in layers II-V of most of the cerebral cortex, and in the dorsal lateral geniculate nucleus, substantia nigra (pars compacta and reticularis) and interpeduncular nucleus. No Nurr1 hybridization signal was seen in the rhombencephalon. In the cerebellum, Nurr1 messenger RNA is present in the internal granular cell layer and Purkinje cell layer. In contrast, Nur77 has a widespread distribution, with the highest level of expression in the cerebral cortex. Moderate hybridization signals were detected in the hippocampus, the lateral dorsal and posterior nuclei, reuniens thalamic nuclei, and paraventricular and supraoptic hypothalamic nuclei. In the rhombencephalon, higher signals were present in the medial and lateral vestibular, dorsal cochlear and facial, and raphe magnus nuclei. Nur77 signal was also detected in the nucleus of the spinal tract of the trigeminal nerve. In the cerebellum, Nur77 messenger RNA is highly expressed in the Purkinje cell layer and lateral deep nucleus of the cerebellum. Our results show that Nurr1 and Nur77 messenger RNAs have both overlapping and different distribution patterns within the brain, suggesting that they might regulate different sets of responsive genes.

Gastrin-releasing peptide-like immunoreactivity is present in human maternal and fetal placental membranes

Extracts of human term amnion, placenta, and chorion/decidual tissue (n = 5) contained gastrin-releasing peptide-like immunoreactivity (GRPLI) in amounts of 4.7 +/- 2.9 (pmol/g wet wt; mean +/- SEM), 3.6 +/- 1.1 and 2.9 +/- 1.5, respectively. Using C-terminally directed antisera and gel filtration chromatography and reverse-phase high-performance liquid chromatography (HPLC), each tissue contained molecular forms consistent with the presence of GRP1-27 and GRP18-27 but also contained larger amounts of two GRPLI peaks, which apparently are novel GRP-like peptides. In contrast, tissue extracts of human fetal lung contained only GRP1-27, GRP14-27, and GRP18-27. Using RT-PCR and specific GRP primers and probes, messenger RNA encoding for GRP was readily demonstrable from 6-weeks gestation throughout pregnancy to term in full-thickness membranes, placental villi, and decidua. Positive immunohistochemical staining for GRP occurred in extravillous trophoblasts in decidual septa and fetal membranes, cytotrophoblasts, syncytiotrophoblast, and certain stromal cells in placental villi and amniotic epithelium. GRPLI and GRP messenger RNA were present from the earliest dates examined (6-9 weeks) throughout pregnancy to term. Given the proven trophic nature of GRP and related peptides, these peptides may play important roles in maternal, placental, and fetal development during human pregnancy.

Fatal embryonic bleeding events in mice lacking tissue factor, the cell-associated initiator of blood coagulation

Tissue factor (TF) is the cellular receptor for coagulation factor VI/VIIa and is the membrane-bound glycoprotein that is generally viewed as the primary physiological initiator of blood coagulation. To define in greater detail the physiological role of TF in development and hemostasis, the TF gene was disrupted in mice. Mice heterozygous for the inactivated TF allele expressed approximately half the TF activity of wild-type mice but were phenotypically normal. However, homozygous TF-/- pups were never born in crosses between heterozygous mice. Analysis of mid-gestation embryos showed that TF-/- embryos die in utero between days 8.5 and 10.5. TF-/- embryos were morphologically distinct from their TF+/+ and TF+/- littermates after day 9.5 in that they were pale, edematous, and growth retarded. Histological studies showed that early organogenesis was normal. The initial failure in TF-/- embryos appeared to be hemorrhaging, leading to the leakage of embryonic red cells from both extraembryonic and embryonic vessels. These studies indicate that TF plays an indispensable role in establishing and/or maintaining vascular integrity in the developing embryo at a time when embryonic and extraembryonic vasculatures are fusing and blood circulation begins.

Locations and molecular forms of gastrin-releasing peptide-like immunoreactive entities in ovine pregnancy

Large quantities of gastrin-releasing peptide-like immunoreactivity (GRP-LI) are present in ovine pregnancy fluids (allantoic fluid > fetal plasma > esophageal fluid = amniotic fluid = urine > maternal plasma) and in term endometrium (60 +/- 29 pmol.g-1) and myometrium (4.5 +/- 1.2 pmol.g-1). The larger molecular size [greater than GRP (1-27)] of this GRP-LI entity is not due to a GRP binding protein nor to a C-terminal extension of GRP. In contrast, ovine fetal colon extracts appear to contain the usual GRP (1-27) and GRP (18-27) forms. Hence, the uterus, not the fetus, is the probable source of this novel GRP-like peptide. It apparently acts as a hormone in ovine pregnancy and may play an important role in fetal-placental development.

Hormonal and chemical influences on the expression of class 2 aldehyde dehydrogenases in rat H4IIEC3 and human HuH7 hepatoma cells

We studied the effect a variety of hormones and chemical stimuli on the activity of low Km aldehyde dehydrogenase (ALDH) in rat H4IIEC3 hepatoma cells and ALDH activity in human HuH7 hepatoma cells. The low Km enzyme in H4IIEC3 cells reflects ALDH2 activity, and the ALDH activity in HuH7 likely represents ALDH5. Of the steroid hormone family, thyroid hormone, progesterone, and dihydrotestosterone increased low Km ALDH activity approximately 50%, whereas dexamethasone and estradiol had little effect. Insulin decreased the activity of low Km ALDH. None of these hormones affected the activity of ALDH in HuH7 cells. Among second messengers, 8-bromo-cAMP and A23187 increased low Km ALDH activity; HuH7 ALDH activity again was unchanged. Exposure of the cells to 22 mM ethanol reduced low Km activity by approximately 20%, whereas hydrogen peroxide, tumor necrosis factor-alpha, and interleukin-1 beta had little effect. Ultraviolet light increased the HuH7 ALDH activity. Retinaldehyde or retinolc acid reduced the HuH7 ALDH activity, but had no effect on low Km ALDH activity. These data suggest that low Km ALDH2 can be regulated by hormones and may not be constitutive as previously thought, and that the HuH7 ALDH is regulated differently.

The aldehyde dehydrogenase ALDH2*2 allele exhibits dominance over ALDH2*1 in transduced HeLa cells

Individuals heterozygous or homozygous for the variant aldehyde dehydrogenase (ALDH2) allele (ALDH2*2), which encodes a protein differing only at residue 487 from the normal protein, have decreased ALDH2 activity in liver extracts and experience cutaneous flushing when they drink alcohol. The mechanisms by which this allele exerts its dominant effect is unknown. To study this effect, the human ALDH2*1 cDNA was cloned and the ALDH2*2 allele was generated by site-directed mutagenesis. These cDNAs were transduced using retroviral vectors into HeLa and CV1 cells, which do not express ALDH2. The normal allele directed synthesis of immunoreactive ALDH2 protein (ALDH2E) with the expected isoelectric point. Extracts of these cells contained increased aldehyde dehydrogenase activity with low Km for the aldehyde substrate. The ALDH2*2 allele directed synthesis of mRNA and immunoreactive protein (ALDH2K), but the protein lacked enzymatic activity. When ALDH2*1-expressing cells were transduced with ALDH2*2 vectors, both mRNAs were expressed and immunoreactive proteins with isoelectric points ranging between those of ALDH2E and ALDH2K were present, indicating that the subunits formed heteromers. ALDH2 activity in these cells was reduced below that of the parental ALDH2*1-expressing cells. Thus, the ALDH2*2 allele is sufficient to cause ALDH2 deficiency in vitro.

The novel aldehyde dehydrogenase gene, ALDH5, encodes an active aldehyde dehydrogenase enzyme

The mRNA for the novel aldehyde dehydrogenase 5 (ALDH5) gene was detected in HuH7 hepatoma cells. The cells also expressed cytosolic aldehyde dehydrogenase (ALDH1) mRNA, but no mitochondrial aldehyde dehydrogenase (ALDH2) mRNA. Extracts of the hepatoma cells contained an enzymatic activity with an isoelectric point similar to that of ALDH1. This enzyme activity was insensitive to inhibition by disulfiram, a potent inhibitor of ALDH1. The enzyme was active with short chain aldehydes (acetaldehyde and propionaldehyde) and NAD+, but not with NADP+, and the activity was higher in the mitochondrial pellet than other cell fractions. These studies demonstrate the expression of ALDH5 mRNA in a human hepatoma and suggest that the gene product is enzymatically active and probably resides in the mitochondria.

Acute administration of alpha-methyl-para-tyrosine alters levels of norepinephrine transporter mRNA in the rat brainstem

This study investigated whether rat norepinephrine transporter (NET) mRNA levels would be altered by alpha-methyl-p-tyrosine (alpha-MPT), a tyrosine hydroxylase inhibitor. While NE levels decreased at 1 and 3 days but recovered at 7 days after alpha-MPT, NET mRNA levels decreased at 3 and 7 days but not at 1 day after alpha-MPT. The results indicate that acute treatment with alpha-MPT led to a delayed time response in its effects on NET mRNA and NE levels in the rat brain.

Regulation of the interferon-inducible protein kinase PKR and (2'-5')oligo(adenylate) synthetase by a catalytically inactive PKR mutant through competition for double-stranded RNA binding

The interferon-inducible double-stranded RNA-dependent protein kinase PKR has been suggested to function as a tumour suppressor gene product. Catalytically inactive mutants of PKR give rise to a tumorigenic phenotype when overexpressed in NIH-3T3 fibroblasts and this has been attributed to a dominant negative effect on the activity of the wild-type enzyme. Here we show that the mutant with Lys296 replaced by Arg, [K296R]PKR, not only inhibits the protein kinase activity of wild-type PKR but is also inhibitory towards another double-stranded RNA-dependent enzyme, the 40-kDa form of (2'-5')oligo(adenylate) synthetase. Inhibition of both wild-type PKR and (2'-5')oligo(adenylate) synthetase is reversed by adding higher concentrations of double-stranded RNA. These results suggest competition between [K296R]PKR and wild-type PKR or (2'-5')oligo(adenylate) synthetase for limiting amounts of double-stranded RNA. Moreover, the data imply that the tumorigenic effect of this PKR mutant could be due to inhibition of additional pathways requiring low levels of double-stranded RNA for activation and cannot be unambiguously attributed to inhibition of endogenous PKR itself.

[The clinical role of appendectomy in surgical procedures for ovarian cancer]

To assess the clinical role of appendectomy in the surgical procedures for ovarian cancer. We have evaluated retrospectively 96 cases of epithelial ovarian cancer treated from Aug. 1986 to Aug. 1993. In 19 cases the appendiceal involvement was pathologically confirmed (19.8%). All of the patients with appendiceal metastases were found in stages III-IV, with an incidence of 33.3%. There was no significant statistical difference between either the histologic type of ovarian cancer or the side (left or right) of the ovarian involvement and the incidence of metastasis in the appendix. We conclude, with these results, that the appendix was not a primary site involved in the early stages. Appendectomy is not to be regarded as a routine surgical procedures in the early I-II stages of ovarian cancer, but it may help to reduce residual disease in advanced patients.

Lipofectin-aided cell delivery of ribozyme targeted to human urokinase receptor mRNA

A 37-mer hammerhead ribozyme has been designed to efficiently cleave the 1.4 kb mRNA of the urokinase plasminogen activator receptor (uPAR). Under in vitro conditions, the chemically synthesized ribozyme cleaved uPAR mRNA and inhibited its translation in a concentration-dependent fashion. The ribozymes were 5'-[35S]thiophosphorylated and used as a model to analyze conditions for RNA delivery in a cultured human osteosarcoma cell system. Ribozymes degraded immediately in cell-conditioned medium but ribozymes complexed with lipofectin were protected from RNases for up to 22 h. Lipofectin rapidly transported ribozyme into the cell, where it accumulated almost exclusively in the cytoplasm. Thus, lipofectin dramatically enhances stability and cytoplasmic delivery of ribozymes, potentially enabling targeting of mRNA in vivo.

The La antigen inhibits the activation of the interferon-inducible protein kinase PKR by sequestering and unwinding double-stranded RNA

The La (SS-B) autoimmune antigen is an RNA-binding protein that is present in both nucleus and cytoplasm of eukaryotic cells. The spectrum of RNAs that interact with the La antigen includes species which also bind to the interferon-inducible protein kinase PKR. We have investigated whether the La antigen can regulate the activity of PKR and have observed that both the autophosphorylation of the protein kinase that accompanies its activation by dsRNA and the dsRNA-dependent phosphorylation of the alpha subunit of polypeptide chain initiation factor eIF-2 by PKR are inhibited in the presence of recombinant La antigen. This inhibition is partially relieved at higher concentrations of dsRNA. Once activated by dsRNA the protein kinase activity of PKR is insensitive to the La antigen. We have demonstrated by a filter binding assay that La is a dsRNA binding protein. Furthermore, when recombinant La is incubated with a 900 bp synthetic dsRNA or with naturally occurring reovirus dsRNA it converts these substrates to single-stranded forms. We conclude that the La antigen inhibits the dsRNA-dependent activation of PKR by binding and unwinding dsRNA and that it may therefore play a role in the regulation of this protein kinase in interferon-treated or virus-infected cells.

[Effects of beta-endorphin on blood pressure and heart rate in rats]

The present work was undertake to investigate the mechanism of changes of blood pressure and heart rate induced by beta-endorphin (beta-End) after microinjection into the Nucleus Amygdaloideus Centralis (AC) of anaesthetized rats. The results were as follows: (1) beta-End (100, 250 pg/microliters) injected into AC decreased both blood pressure and heart rate. (2) Both these effects could be antagonized by naloxone and beta-End anti-serum. (3) The effects of beta-End could also be reversed by phentolamine and propranolol. The results showed that the cardiovascular effects on beta-End were mediated by opioid receptors and through the intervention of adrenergic neurons.

The primary structure of phosphofructokinase from Lactococcus lactis

The primary amino acid sequence of phosphofructokinase (EC2.7.1.11) from Lactococcus lactis, obtained by Edman analysis of peptides obtained from proteolytic digestions, is MKRIAVLTSGGDAPGMNAAIRAVVRKAISEGIEVYGINHGYAGMVAGDIF PLTSASVGDKIGRGGTFLYSARYPEFAQVEGQLAGIEQLKKFGIEGVVVI GGDGSYHGAMRLTEHGFPAVGLPGTIDNDIVGTDFTIGFDTAVSTVVDAL DKIRDTSSSHNRTFVVEVMGRNAGDIALNAGIAAGADDISIPELEFKFEN VVNNINKGYEKGKNHHIIIVAEGVMTGEEFATKLKEAGYKGDLRVSVLGH IQRGGSPTARDRVLASRMGARAVELLRDGIGGVAVGIRNEELVESPILGT AEEGALFSLTTEGGIKVNNPHKAGLELYRLNSALNNLNL.

Reversal of the double-stranded-RNA-induced inhibition of protein synthesis by a catalytically inactive mutant of the protein kinase PKR

The interferon-inducible double-stranded-RNA(dsRNA)-dependent protein kinase PKR has been implicated in both the antiviral and cell growth-regulatory effects of the interferons. Over-expression of the wild-type form of this protein inhibits cell proliferation, whereas over-expression of inactive mutant forms transforms cells to a tumourigenic phenotype. It has been suggested that mutant PKR exerts a dominant negative effect on the activity of the wild-type protein kinase. We have investigated this possibility using the rabbit reticulocyte cell-free translation system in which protein synthesis is inhibited by dsRNA due to activation of PKR and phosphorylation of initiation factor eIF-2. Addition of a highly purified inactive PKR mutant, synthesised in a baculovirus-infected insect cell system, rescues protein synthesis from inhibition by low concentrations of dsRNA in a dose-dependent manner. The PKR mutant has no effect on protein synthesis in the absence of dsRNA or in the presence of another inhibitory protein kinase, the haem-controlled repressor. Inhibition of translation can be re-established in the presence of the mutant PKR by adding a higher concentration of dsRNA. These results suggest that inactive mutant PKR does exert a dominant negative effect on wild-type PKR and that this may be due to competition for dsRNA binding.

Inhibitory effect of arginine restriction on hepatoma growth

The potential effects of arginine depletion on promotion of hepatocarcinogenesis and the proliferation of hepatoma cells was investigated. A promotional effect of an arginine-free diet on tumor incidence in liver and kidney was not detected in rats and mice treated with N-nitrosodimethylamine. Inhibitory effects of an arginine-deficient diet on the growth of transplanted hepatomas were observed. Relative to the effect on body weight, the inhibition was greater in mice than rats. The inhibitory effects of an arginine-deficient diet were not correlated with the arginase activity in the tumors. Studies with hepatoma cells treated with polyethyleneglycol-modified arginase indicated that the inhibitory effects of arginine-deprivation on DNA synthesis need not be related to depletion of polyamine precursors.

Changes in the glucose-6-phosphatase complex in hepatomas

Hepatomas tend to have a decreased glucose-6-phosphatase activity. We have observed phenotypic stability for this change in Morris hepatomas transplanted in rats. To determine if this decrease is selective for translocase functions or the hydrolase activity associated with glucose-6-phosphatase, we have compared activities in liver and hepatomas with glucose-6-phosphate or mannose-6-phosphate as substrates and with intact or histone-disrupted microsomes. In five out of seven subcutaneously transplanted rat hepatoma lines, the microsomal mannose-6-phosphatase activity was lower than in preparations from liver of normal or tumor-bearing rats. With liver microsomes and with most hepatoma microsomes, preincubation with calf thymus histones caused a greater increase in mannose-6-phosphatase than in glucose-6-phosphatase activity. In studies with liver and hepatoma microsomes there were similar increases in mannose-6-phosphatase activity with total calf thymus histones and arginine-rich histones. A smaller increase was seen with lysine-rich histones. The effect of polylysine was similar to the action of lysine-rich histones. There was only a small effect with protamine at the same concentration (1 mg/ml). Rat liver or hepatoma H1 histones gave only about half the activation seen with core nucleosomal histones. Our data suggested that microsomes of rat hepatomas tend to have decreased translocase and hydrolase functions of glucose-6-phosphatase relative to activities in untransformed liver.

[Clinical significance of changes in plasma renin-angiotensin aldosterone system in patients with high altitude pulmonary edema]

Plasma levels of renin activity, angiotensin II and aldosterone were determined in 16 patients with high altitude pulmonary edema (HAPE) with radioimmunoassay and compared with those in the controls including 9 patients with high altitude acute response (HAAR) and 14 health subjects. All of them arrived recently in Lhasa, a place with an altitude of 3,658 m. The results showed that the concentration of plasma renin activity, angiotensin II, and aldosterone was significantly increased (P < 0.05-0.001) in patients with HAPE and higher than that in the controls. It is suggested that the increase plays a role in the development of pulmonary edema in patients with HAPE.

Inhibitory effects of tea extracts and (-)-epigallocatechin gallate on DNA synthesis and proliferation of hepatoma and erythroleukemia cells

Polyphenols extracted from green or black tea with ethyl acetate were strongly inhibitory for DNA synthesis in HTC rat hepatoma cells and DS19 mouse erythroleukemia cells at concentrations of 0.1-0.2 mg/ml. There was less inhibition with a subsequent black tea fraction extracted with butanol and with the residual water-soluble fraction. Although cell proliferation was inhibited by (-)-epigallocatechin gallate and the tea extracts, there were only marginal effects on differentiation of DS19 cells as judged by hemoglobin synthesis.

Butyramide and monobutyrin: growth inhibitory and differentiating agents

Butyramide and monobutyrin were chosen for study as neutral compounds that might exhibit some of the growth inhibitory and differentiating effects of butyrate. Inhibitory effects on DNA synthesis in hepatoma cells and on cellular proliferation in mouse erythroleukemia cells were observed. Induction of differentiation by butyramide and monobutyrin was seen in mouse erythroleukemia cells as monitored by increased synthesis of hemoglobin and H1 zero histone. Butyramide and monobutyrin were less effective inducers of hemoglobin synthesis than butyrate but their neutral character may offer an advantage in the induction of tumor cell differentiation.

dUTP pyrophosphatase and uracil-DNA glycosylase in rat liver and hepatomas

1. The activity of dUTP pyrophosphatase (dUTPase) was similar in rat liver and hepatomas of slow or moderate growth rate but was increased several fold in three rapidly growing hepatomas. 2. There was an approx three-fold increase in the activity of uracil-DNA glycosylase in Morris hepatoma 7800 but there was little change in activity in other hepatomas that were examined. 3. The activities of dUTPase and uracil-DNA glycosylase were not significantly affected by two diets that may be promotional for hepatocarcinogenesis, a high orotate diet and an arginine-deficient diet.