Fluorinated and iodinated dopamine agents: D2 imaging agents for PET and SPECT

A novel series of dual-labeling D2 dopamine agents (labeled with either 18F or 123I for PET or SPECT imaging, respectively) was investigated. Two desired fluorinated and iodinated dopamine agents, FIDA1, (S)-(-)-2-(2-fluoroethoxy)-5-iodo-3-methoxy-N-[(1-ethyl-2- pyrrolidinyl)methyl]-benzamide, and FIDA2, (R)-(+)-2,3-dimethoxy-5-iodo-N-[(1-(4'-fluorobenzyl)-2- pyrrolidinyl)-methyl]benzamide, were synthesized. Both compounds displayed high affinity to the D2 receptor of rat striatal membrane preparations (Kd = 0.13 and 0.02 nM for FIDA1 and FIDA2, respectively). The biodistribution study in rats exhibited high localization in the striata of the brain with the striatum/cerebellum ratio reaching 29.3 and 13.1 at 1 h post iv injection for FIDA1 and FIDA2, respectively. Imaging studies with [18F]- and [123I]FIDA2 in monkeys, with PET and SPECT, respectively, showed comparable high selective striatal uptake. These results suggest that they are potentially useful D2 dopamine receptor imaging agents for PET and SPECT.

Inhibition of HIV infection by baicalin--a flavonoid compound purified from Chinese herbal medicine

Baicalin (BA), (formulated as 7-D-glucuronic acid-5,6-dihydroxy-flavone), was purified from the plant Scutellaria Baicalensis Georgi. It has been used as a traditional Chinese herbal medicine. The inhibitory effect of BA against human immunodeficiency virus (HIV-1) infection and replication has been studied in vitro. The compound inhibits HIV-1 infection and replication as measured by: (1) a quantitative focal syncytium formation on CEM-ss monolayer cells; and (2) HIV-1 specific core antigen p24 expression and retroviral reverse transcriptase (RT) activity in the HIV-1-infected H9 cells. We have further demonstrated that the enzymatic activity of purified recombinant HIV-1/RT was inhibited by BA. In addition to lymphoid cell lines, the anti-HIV-1 activity of BA was also observed in cultures of primary human peripheral blood mononuclear cells infected with HIV-1 in vitro. Neither cytotoxic nor cytostatic effects on the indicator cells were found under the assay condition. This data suggests that BA may serve as a useful drug for the treatment and prevention of HIV infections.

Biological actions of oncogenes

Cancer, in many cases, results from multistep genetic mutation. Certain genes can have a predisposed susceptibility to mutations that lead to cancer because of chromosome location or their importance in the control of cell cycles. Mutations that deregulate the expression or activity of enzymes involved in the biochemical pathways of growth and differentiation or that suppress the expression of negative cell cycle control factors result in activation of oncogenesis. The study of oncogenes and tumor suppressor genes has greatly influenced our understanding of the molecular origins of cancer. We focus here on the normal biological action of proto-oncogenes compared with the transforming activities of oncogenes and tumor suppressor genes, and we discuss possible mechanisms of oncogenic transformation.

Characterization and purification of a novel transcriptional repressor from HeLa cell nuclear extracts recognizing the negative regulatory element region of human immunodeficiency virus-1 long terminal repeat

Cellular transcription factors play critical roles in regulating human immunodeficiency virus (HIV) gene transcription, although the precise mechanism(s) defining their roles are not well established. Primarily it has been suggested that sequence-specific interaction of trans-activating proteins with cis-acting DNA elements plays a crucial role in regulating the target genes. The negative regulatory element (NRE) of HIV-1 long terminal repeat (LTR) is one such defined region that has been reported to down-regulate LTR-directed HIV gene expression. Information regarding the role of this region in the regulation of HIV expression is lacking. Here we describe an attempt to further characterize the role of NRE cis-elements and define any sequence-specific interaction with cellular factors. Using gel mobility shift DNA-binding and Southwestern blot assays, we have mapped a distinct region of NRE (-290 to -260, a 30-base pair (bp) domain of NRE-A) sequences of HIV-1 LTR, which recognizes a specific DNA-binding protein from HeLa cell nuclear extracts. This factor is a 38-kDa polypeptide which can be affinity-purified to near homogeneity by this 30-bp specific oligonucleotide in affinity chromatography. The cellular factor from HeLa cell nuclear extract exhibits specific interaction only with the 30-bp NRE-A domain of HIV-1 LTR and acts as a strong transcriptional repressor/inhibitor molecule in the DNA-protein gel binding, as well as in vitro transcriptional studies with the nuclear extracts from cells with productive HIV-1 infection. To our knowledge, this is the first report of a factor recognizing a distinct segment within NRE that has been shown to exert an inhibitory effect on transcriptionally active DNA-protein "pre-initiation" complex formation, suggesting a possible role in HIV-1 gene regulation.

Polyoma middle T antigen or v-src desensitizes human epidermal growth factor receptor function and interference by a monensin-resistant mutation in mouse Balb/3T3 cells

Epidermal growth factor (EGF)-induced down-regulation of its receptor is an obligatory pathway for cellular regulation of EGF-specific receptor (EGF-R) in normal and malignant cells. BNER4 cells are mouse Balb/3T3 cells transfected with the human EGF-R complementary DNA (cDNA). Polyoma middle T antigen-transfectants of BNER4, B4/MT-2, B4/MT-13, B4/MT-23, and B4/MT-24, showed diminished down-regulation of cell surface human EGF-R in response to EGF relative to the parental BNER4 cells. Also, the v-src-transfectants B4/SRC-13 and B4/SRC-24 showed much less down-regulation than BNER4 cells, whereas H-ras-transfectants of BNER4, B4/RAS-24 and B4/RAS-25, showed EGF-induced down-regulation of the cell surface EGF-R similar to that of BNER4. EGF induced DNA synthesis more than 20-fold in BNER4, but induced only about a 1.5- to 6-fold increase in the middle T antigen- and v-src-transfectants. EGF-Rs of the middle T antigen-transfectants were metabolically stable in the presence of EGF in comparison with their parental BNER4 cells. EGF-Rs of BNER4 cells degraded with half-lives of about 2 h in the presence of EGF, but those of the middle T antigen transformants were found to be highly stabilized in the presence of EGF. On the other hand, transfection with polyoma middle T antigen (MTAg) cDNA causes malignant transformation of Balb/3T3 cells, but not its monensin (an ionophoric antibiotic)-resistant mutant MO-5 cells, which have no significant EGF binding activity. Transfection of human EGF-R cDNA into MO-5 leads to the expression of high levels of human EGF-R in MNER31. Unlike the polyoma MTAg transfectants of BNER4, EGF-R in polyoma MTAg cDNA-transfectants into MNER31, M31/MT-13 and M31/MT-14, were down-regulated to levels similar to those of their parental MNER31. Exposure to EGF induced a more than 10-fold increase in DNA synthesis of quiescent BNER4, MNER31, M31/MT-13, and M31/MT-14 cells. Polyoma middle T antigen or v-src appears to modulate EGF-induced down-regulation of EGF-R, possibly through interaction of the receptor with the viral oncogenes, and this interaction may be altered in the mutant.

Anti-HIV plant proteins catalyze topological changes of DNA into inactive forms

GAP 31, DAP 32 and DAP 30 comprise a new class of plant proteins with potent anti-HIV activity and insignificant cytotoxicity. We report here the identification and characterization of a new DNA enzyme activity in these three proteins. They irreversibly relax and decatenate supercoiled DNA, as well as catalyze double-stranded breakage to form linear DNA. The relaxed molecules are topologically inactive and no longer serve as substrates for DNA gyrase to form supercoils, phenomena similar to those of cellular topoisomerases in the presence of topoisomerase poisons. The ability of these anti-HIV agents to interrupt essential topological interconversions of DNA may provide a novel mechanism for their antiviral and antitumor actions. The presence of this new DNA topological enzyme activity in these plant proteins also suggests that their anti-HIV activity may not be merely a consequence of ribosome inactivation previously recognized.

Iodinated tomoxetine derivatives as selective ligands for serotonin and norepinephrine uptake sites

In order to develop selective radioactive ligands for the study of presynaptic monoamine uptake sites, iodinated derivatives of tomoxetine were synthesized and evaluated in radioligand binding assays. Iodotomoxetine derivatives showed high affinity for serotonin (5-HT) uptake sites using a rat cortical membrane preparation. Compound 1R,(R)-(-)-N-methyl-3-(4-iodo-2-methylphenoxy)-3-phenylpropanamine , was the most potent and showed high stereoselectivity for 5-HT uptake sites (Ki, R isomer = 0.65 nM, S isomer = 13.9 nM). Changing the position of the methyl group or eliminating the methyl group at the phenoxy ring resulted in a loss of stereoselectivity. Substitution of the methyl group of tomoxetine with iodine gave the R and S isomers of N-methyl-3-(2-iodophenoxy)-3-phenylpropanamine 4R and 4S. These compounds displayed stereoselectivity for the norepinephrine (NE) (Ki values = 0.24 and 9.35 nM for R and S isomers, respectively). The in vitro binding data suggest that 1R and 4R are potential radioiodinated ligands for pharmacological studies of 5-HT and NE uptake sites, respectively.

Ras mediates translation initiation factor 4E-induced malignant transformation

Translation initiation factor eIF-4E binds to the eukaryotic mRNA 5' cap structure (m7 GpppN, where N is any nucleotide). eIF-4E is a limiting factor in translation and plays a key role in regulation of translation. We have shown previously that overexpression of eIF-4E in rodent fibroblasts results in tumorigenic transformation. eIF-4E also exhibits mitogenic activity when microinjected into serum-starved NIH-3T3 cells. To understand the mechanisms by which eIF-4E exerts its mitogenic property, we examined the involvement of the Ras signaling pathway in this activity. Here, we report that Ras is activated in eIF-4E-overexpressing cells, as the proportion of GTP-bound Ras is increased. Overexpression of the negative effector of cellular Ras, GTPase activating protein, causes reversion of the transformed phenotype. Furthermore, we show that neutralizing antibodies to Ras, or a dominant-negative mutant of Ras, inhibit the mitogenic activity of eIF-4E. We conclude that eIF-4E exerts its mitogenic and oncogenic activities by the activation of Ras.

EGF receptor activity and mitogenic response of Balb/3T3 cells expressing Ras and Myc oncogenes. EGF receptor activity in oncogene transformed cells

EGF receptors are found on the surface of most cells, usually with high and low binding affinities. To investigate functional relationships between EGF (EGF-like growth factors) and oncogenes we have characterized the expression of the epidermal growth factor receptor (EGFr) in H-Ras, v-Myc, and H-Ras-v-Myc transformed Balb/3T3 cells. H-Ras cells show a marked decrease in the number of EGFr molecules per cell compared to parental cells. v-Myc and H-Ras-v-Myc transformed cells express an intermediate level of receptors. The majority of the EGF receptors on the parental and oncogene transformed cells bind EGF with low affinity and this low affinity receptor is down-regulated by oncogene transformation. v-Myc expression, in the H-Ras-v-Myc transformed cells, abrogates the receptor down-regulation seen with H-Ras transformation. The mechanism of abrogation is not a result of a change in the p21-Ras concentration in the H-Ras-v-Myc transformed cells. In addition, the mitogenic response to EGF was examined. H-Ras and H-Ras-v-Myc transformed cells do not respond to EGF mitogenically. In contrast, EGF stimulates DNA synthesis in parental cells and v-Myc transfected cells; this result suggests that growth promoting signals from the EGF receptor may not be required in H-Ras transformed cells.

Components of the protein kinase C pathway induce Ia expression after injection into macrophages

Macrophages are activated by a variety of microbial and cytokine stimuli. One feature of activation is the induction of class II Ag (Ia) on the cell surface. To understand the intracellular events that occur during activation, we investigated various agents with intracellular activities, and examined their effects on the induction of Ia. We first noted that several agents that activate protein kinase C (PKC) induced Ia, and that several inhibitors of PKC inhibited Ia induction by IFN-gamma. To directly test whether PKC induced Ia, we microinjected normal peritoneal macrophages with this enzyme and other intracellular mediators, then examined Ia expression. We observed that injection of PKC itself, or of other intracellular proteins thought to participate in the PKC pathway (Ras or phospholipase C gamma) strongly induced Ia expression. The Ia-inducing activity of transforming Ras protein was blocked by kinase inhibitor treatment of cells, suggesting that Ras signal transduction requires kinase activity. On the other hand, components of the protein kinase A pathway (phospholipase A2 and protein kinase A itself) did not induce Ia. Thus, the PKC pathway can control expression of macrophage surface Ia, possibly by regulating the genes of the MHC, and may play many other roles in the activation of macrophages.

Components of the protein kinase C pathway induce Ia expression after injection into macrophages

Macrophages are activated by a variety of microbial and cytokine stimuli. One feature of activation is the induction of class II Ag (Ia) on the cell surface. To understand the intracellular events that occur during activation, we investigated various agents with intracellular activities, and examined their effects on the induction of Ia. We first noted that several agents that activate protein kinase C (PKC) induced Ia, and that several inhibitors of PKC inhibited Ia induction by IFN-gamma. To directly test whether PKC induced Ia, we microinjected normal peritoneal macrophages with this enzyme and other intracellular mediators, then examined Ia expression. We observed that injection of PKC itself, or of other intracellular proteins thought to participate in the PKC pathway (Ras or phospholipase C gamma) strongly induced Ia expression. The Ia-inducing activity of transforming Ras protein was blocked by kinase inhibitor treatment of cells, suggesting that Ras signal transduction requires kinase activity. On the other hand, components of the protein kinase A pathway (phospholipase A2 and protein kinase A itself) did not induce Ia. Thus, the PKC pathway can control expression of macrophage surface Ia, possibly by regulating the genes of the MHC, and may play many other roles in the activation of macrophages.

Nerve growth factor stimulation of the Ras-guanine nucleotide exchange factor and GAP activities

The biological activity of Ras proteins is thought to be controlled by the guanine nucleotide exchange factor and the guanosine triphosphatase activating protein (GAP). Treatment of rat pheochromocytoma PC-12 cells with nerve growth factor (NGF) increased the amount of active Ras guanosine triphosphate complex and stimulated the activities of both the guanine nucleotide exchange factor and GAP. In PC-12 cells that overexpressed the tyrosine kinase encoded by the trk proto-oncogene (a component of the high-affinity NGF receptor), the NGF-induced activation of the regulatory proteins was potentiated. These results suggest that the NGF receptor system enhances the activities of both the guanine nucleotide exchange factor and GAP and that the activation of Ras might be controlled by the balance in activity between these two regulatory proteins.

Brefeldin A-resistant mutants of human epidermoid carcinoma cell line with structural changes of the Golgi apparatus

We have isolated brefeldin A (BFA)-resistant cell lines, KB/BF-1 and KB/BF-2, from the human epidermoid carcinoma KB cell line. The BFA-resistant phenotypes have been stably maintained for more than 3 months in the absence of BFA. KB/BF-1 and KB/BF-2 showed 10-30-fold higher resistance to cytotoxicity of BFA but were 2-3-fold more sensitive to monensin and nigericin, than KB cells. KB/BF-1 showed aberrant structures of the Golgi complex with poorly developed cisternae surrounded by many small vesicles. Immunocytochemical studies were done with antibodies against a Golgi-specific antigen (chronic rheumatoid arthritis antigen) and a coatomer subunit (beta-subunit for coat proteins of non-clathrin-coated vesicles). Golgi-specific markers were distributed into the small vesicles which were localized diffusedly in cytoplasm of KB/BF-1 cells. Such Golgi markers were observed in a strictly confined perinuclear region of the parental KB cells, whereas in the mutant cells the markers were distributed more diffusedly in dot-like structures at perinuclear regions. In addition, when exposed to BFA, the mutant and parental cells showed a different distribution of these markers. Synthesis and maturation of low density lipoprotein receptor showed apparently slower rates in processing of low density lipoprotein receptor in KB/BF-1 and KB/BF-2 cells than those observed in their parental KB cells. Protein secretion in KB/BF-1 and KB/BF-2 cells was about 30% less than that in KB cells. Much less inhibition by BFA on the secretion was observed in KB/BF-1 and KB/BF-2 cells. A BFA-resistant mutation in BFA-resistant KB cell lines appears to affect assembly of the Golgi apparatus as well as some Golgi-specific functions.

Regulation of intracellular actin polymerization by prenylated cellular proteins

Posttranslational modification by covalent attachment of polyisoprene intermediates to a carboxyterminal CAAX-box motif is required for the biologic function of proteins such as p21ras, the supergene family of ras-related proteins, nuclear lamins, and subunits of heterotrimeric G-proteins. Cells grown in the presence of lovastatin, which inhibits HMG-CoA reductase and prevents synthesis of intermediates required for protein prenylation, develop a round, refractile morphology. Our data indicate that this is due to the selective loss of actin cables without gross changes in the microtubular lattice or intermediate filament structure. Microinjection of a competitive peptide inhibitor of protein prenyltransferases into the cytoplasm of cells induces an identical change in morphology with loss of actin cables. Mevalonate (MVA) reverses the lovastatin-induced morphologic change by inducing a rapid repolymerization of actin cables with coincident reversion to the flat morphology. Furthermore, microinjection of farnesyl-pyrophosphate or geranylgeranyl-pyrophosphate into lovastatin-treated cells also results in rapid morphologic reversion. The morphologic reversion induced by MVA requires the presence of serum, and is independent of extracellular calcium. The addition of cycloheximide to the growth medium prevents lovastatin-induced loss of actin cables, and causes morphologic reversion of lovastatin-treated cells by a mechanism that is independent of MVA. A1F4- induces morphologic reversion in a manner indistinguishable from MVA. These data indicate that prenylated protein(s) play a critical role in regulating the state of intracellular actin, and that GGPP can rescue the lovastatin-induced morphologic phenotype in the absence of upstream intermediates of cholesterol biosynthesis. We have begun to dissect the signaling events that mediate this pathway.

Radioiodinated 2-hydroxy-3-(4-iodophenyl)-1-(4-phenylpiperidinyl)propane: potential radiotracer for mapping central cholinergic innervation in vitro

Radioiodinated 2-hydroxy-3-(4-iodophenyl)-1-(4-phenylpiperidinyl)propane, 5 (4-HIPP), was synthesized and evaluated as a simple vesamicol-like radiotracer for mapping cholinergic pathways in the brain. Both enantiomers of 5 exhibit significant accumulation (approx. 2% of injected dose) and prolonged retention (t1/2 greater than 3 h) within the rat brain. The accumulation of radioiodinated 5 in the rat brain was reduced by up to 70% in the presence of vesamicol and its analogs. The levorotary isomer (-)-4-[123I]HIPP exhibits significant accumulation in the monkey brain, with a half-life of about 9 h. Radioiodinated 5 may therefore be a useful tool for studying cholinergic pathways in the brain.

Activation of human leukemia protein kinase C by tumor promoters and its inhibition by N-trifluoroacetyladriamycin-14-valerate (AD 32)

N-Trifluoroacetyladriamycin-14-valerate (AD 32), a lipophilic, DNA non-binding analog of Adriamycin (ADR), was found to be a potent inhibitor of the membrane-bound enzyme, protein kinase C (PKC). PKC was isolated and purified from human leukemia ML-1 cells, and the enzyme activity was shown to be activated by the tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-dibutyrate (PDBu). AD 32, nevertheless, inhibited the activation of PKC by TPA or PDBu. The IC50 values for AD 32 inhibition of PKC activation were 0.85 microM for TPA and 1.25 microM for PDBu. Under the same assay conditions, ADR demonstrated much higher IC50 values: 550 microM for TPA and greater than 350 microM for PDBu. The inhibition of PKC by AD 32 was further shown to be competitive in nature; AD 32 inhibited the binding of [3H]PDBu to PKC. Therefore, AD 32 competes with the tumor promoter for the PKC binding site and prevents the latter from both interacting with the phospholipid and binding to PKC. These effects of AD 32 were reproduced in situ; incubation of human leukemia ML-1 cells with TPA showed an increased phosphorylation of cellular proteins, and the TPA-induced protein phosphorylation was inhibited by the addition of AD 32 to the cultured cells.

Molecular analysis of the chromosome 11p region in renal cell carcinomas

Comparative histological data suggest that papillary renal cell tumors in adults and Wilms' tumors in children develop from maturation-arrested cells of similar origin. Wilms' tumor is characterized by genetic changes at the chromosome 11p region. In the present study, we have analyzed 10 papillary and 10 non-papillary renal cell tumors and determined the allelic status of 6 loci on the short arm of chromosome 11. Only one papillary renal cell carcinoma among the 20 tumors showed a loss of constitutional heterozygosity for the chromosome 11p region. These data suggest that separate molecular events occur in the development of Wilms' tumor and papillary renal cell tumors, subsequent to the proliferation of maturation-arrested cells of the kidney.

New conformationally restricted 99mTc N2S2 complexes as myocardial perfusion imaging agents

In developing 99mTc complexes as potential myocardial imaging agents, a new series of ligands based on a conformationally restricted N2S2 system were investigated. Using piperazine or homopiperazine as the starting material, two N2S2 ligands (4a and 4b) with additional conformation restriction between the two nitrogen donor atoms were synthesized. The 99mTc complexes were prepared by a direct labeling method with tin(II) tartrate as the reducing agent for [99mTc]pertechnetate. The resulting 99mTc complexes were purified through a sulfonpropyl Sephadex column and further purified by HPLC with a reverse-phase column eluting with a solvent system of acetonitrile/buffer. Biodistribution studies in rats showed initial uptake in the heart (0.21%, 0.42% dose/order for [99mTc]4a and 4b at 2 min postinjection). Carrier-added preparation of [99mTc]4b was successful. NMR, IR, UV, crystallographic, and elemental analysis of the [99Tc]4b complex suggest that it contains a TcVO3+ center core and is 1+ charged. The results suggest that this series of 1+ charged 99mTc complexes may have potential as myocardial imaging agents, and further study of the complexes is warranted.

Characterization of radioiodinated TISCH: a high-affinity and selective ligand for mapping CNS D1 dopamine receptor

In developing CNS D1 dopamine receptor-imaging agents with improved specificity and longer brain retention, an iodinated D1 ligand was synthesized. In vitro and in vivo radiolabeling studies of a new iodinated benzazepine, TISCH [7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro-1H-3- benzazepine], an analog of SCH 23390 (7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepin e), were investigated. After an intravenous injection, the R(+) isomer of TISCH showed high brain uptake in rats (2.20 and 0.57% dose per whole brain at 2 and 60 min, respectively). The striatum/cerebellum ratio increased progressively with time (12 at 60 min). Ex vivo autoradiography of rat brain sections, after intravenous injection of R(+)-[125I]TISCH, displayed the highest uptake in striatum and substantia nigra, regions known to have a high concentration of D1 receptors, whereas the S(-) isomer displayed no specific uptake. Furthermore, the specific uptake can be blocked by pretreatment with SCH 23390. In vitro binding studies using the rat striatum tissue preparation showed high specific and low nonspecific bindings (KD = 0.21 +/- 0.03 nM). The rank order of potency exhibiting high specificity to the D1 receptor was SCH 23390 greater than (+/-)-TISCH greater than (+)-butaclamol = (+/-)-FISCH [7-chloro-8-hydroxy-1-(4'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro-1 H-3-benzazepine] much greater than WB4101 = spiperone greater than dopamine, serotonin, (+/-)-propranolol, and naloxone. Imaging studies in a monkey with the resolved isomer, R(+)-[123I]TISCH, demonstrated a high uptake in the basal ganglia and prolonged retention. The preliminary data suggest that R(+)-TISCH is selective for the CNS D1 receptor and is potentially useful for in vivo and in vitro pharmacological studies. When labeled with iodine-123, it may be suitable for noninvasive imaging in humans.

Decrease in cytokine production by HIV-infected macrophages in response to LPS-mediated activation

The capacity of human monocytes/macrophages (M/M) infected with a human immunodeficiency virus-1 (HIV-1) isolate to produce several immunomodulating cytokines including interleukin-1 alpha (IL-1 alpha), IL-1 beta, tumor necrosis factor-alpha (TNF-alpha), IL-6, IL-8, and macrophage chemoattractant and activating factor (MCAF) was examined. Although HIV infection itself induced significant increases in the level of mRNAs for IL-1 beta, TNF-alpha, IL-6, and IL-8, the levels of lipopolysaccharide (LPS)-induced mRNAs for IL-1 alpha, IL-1 beta, TNF-alpha, IL-6, IL-8, and MCAF were decreased over those of uninfected LPS-stimulated cells. In addition, HIV-infected M/M produced lower amounts of IL-8 protein, as measured by radioimmunoassay over an 18-day culture period. These results suggest that HIV infection generally suppresses the LPS-inducible cytokine production in human M/M. The impact of the role of these cytokines in the immunity and pathogenesis of HIV-1 infection is discussed.

Negative regulation of human immunodeficiency virus type 1 expression in monocytes: role of the 65-kDa plus 50-kDa NF-kappa B dimer

Although monocytic cells can provide a reservoir for viral production in vivo, their regulation of human immunodeficiency virus type 1 (HIV-1) transcription can be either latent, restricted, or productive. These differences in gene expression have not been molecularly defined. In THP-1 cells with restricted HIV expression, there is an absence of DNA-protein binding complex formation with the HIV-1 promoter-enhancer associated with markedly less viral RNA production. This absence of binding was localized to the NF-kappa B region of the HIV-1 enhancer; the 65-kDa plus 50-kDa NF-kappa B heterodimer was preferentially lost. Adding purified NF-kappa B protein to nuclear extracts from cells with restricted expression overcomes this lack of binding. In addition, treatment of these nuclear extracts with sodium deoxycholate restored their ability to form the heterodimer, suggesting the presence of an inhibitor of NF-kappa B activity. Furthermore, treatment of nuclear extracts from these cells that had restricted expression with lipopolysaccharide increased viral production and NF-kappa B activity. Antiserum specific for NF-kappa B binding proteins, but not c-rel-specific antiserum, disrupted heterodimer complex formation. Thus, both NF-kappa B-binding complexes are needed for optimal viral transcription. Binding of the 65-kDa plus 50-kDa heterodimer to the HIV-1 enhancer can be negatively regulated in monocytes, providing one mechanism restricting HIV-1 gene expression.

A new class of anti-HIV agents: GAP31, DAPs 30 and 32

Three inhibitors of human immunodeficiency virus (HIV) have been isolated and purified to homogeneity from Euphorbiaceae himalaya seeds (Gelonium multiflorum) and carnation leaves (Dianthus caryophyllus). These proteins, GAP 31 (Gelonium Anti-HIV Protein 31 kDa) and DAPs 30 and 32 (dianthus anti-HIV proteins, 30 and 32 kDa), inhibit HIV-1 infection and replication in a dose-dependent manner with little toxicity to target cells. The therapeutic indices of these compounds are in the order 10(4), suggesting that they may be clinically important agents in the treatment of AIDS. The N-terminal amino acid sequences of these proteins show little homology to those of previously described anti-HIV proteins. The structure-function features of these HIV inhibitors, based on the 40-60 amino acid residues of N-terminal sequences, are examined.

TAP 29: an anti-human immunodeficiency virus protein from Trichosanthes kirilowii that is nontoxic to intact cells

An anti-human immunodeficiency virus (anti-HIV) protein capable of inhibiting HIV-1 infection and replication has been isolated and purified to homogeneity from Trichosanthes kirilowii. This protein, TAP 29 (Trichosanthes anti-HIV protein, 29 kDa), is distinct from trichosanthin [also known as GLQ 223 (26 kDa)] in size, N-terminal amino acid sequence, and cytotoxicity. In addition to three conservative substitutions--namely, Arg-29 to Lys, Ile-37 to Val, and Pro-42 to Ser--a total difference of residues 12-16 was found. TAP 29 yielded -Lys-Lys-Lys-Val-Tyr-, whereas trichosanthin has -Ser-Ser-Tyr-Gly-Val-. Although the two proteins exhibit similar anti-HIV activity, as measured by syncytium formation, p24 expression, and HIV reverse transcriptase activity, they differ significantly in cytotoxicity, as measured by their effects on cellular DNA and protein syntheses. At the dose level of the bioassays, 0.34-340 nM, trichosanthin demonstrates a dose-dependent toxic effect on host cells. TAP 29 displays no toxic effect, even at 100 X ID50, whereas trichosanthin demonstrates 38% and 44% inhibition on cellular DNA and protein synthesis, respectively. These results indicate that the therapeutic index of TAP 29 is at least two orders of magnitude higher than that of trichosanthin. Thus TAP 29 may offer a broader safe dose range in the treatment of AIDS.

Cytogenetics of papillary renal cell tumors

Chromosome aberrations were determined in short-term cultures of 18 papillary renal cell tumors, as well as in the cell line ACHN, and the results were evaluated together with 20 previously published cases. We found that chromosomes 7, 17, and 16 and the Y chromosome were specifically involved in the karyotype changes, marks benign papillary renal cell adenomas (ten cases). Malignant papillary renal cell carcinomas (29 cases) were characterized by additional trisomies: trisomy 16 occurred in 20 tumors, and trisomy 12 and 20 in 8 tumors each. Loss of the Y chromosome was observed in 7 of 9 benign and in 23 of 25 malignant tumors that developed in males. None of the papillary renal cell adenomas or carcinomas showed a loss of 3p or gain of a 5q segment, both of which are characteristic of common non-papillary renal cell carcinomas.

Malignant transformation of mouse BALB/3T3 cells by polyoma middle T antigen requires epidermal growth factor receptor expression

The mouse cell line MO-5, which is defective in receptor-binding activity of epidermal growth factor (EGF), is very poorly transformed by polyoma middle T antigen or v-src gene, but activated c-H-ras and v-mos gene can induce the transformation (M. Ono, M. Yakushinji, K. Segawa, and M. Kuwano, Mol. Cell. Biol., 8: 4190-4196, 1988). We established clones of MO-5 expressing a functional EGF receptor (EGF-R) after introduction of the human EGF-R complementary DNA into MO-5 (MNER23 and MNER31), and we also established a clone (BNER4) expressing human EGF-R from the parental cell line, BALB/3T3. MNER23, MNER31, and BNER4 expressed EGF-R activity at about 2- to 6-fold higher levels than did control BALB/3T3 cells. A marked increase in DNA synthesis in response to EGF was observed in these BNER4, MNER23, and MNER31 cell lines compared to BALB/3T3 cells; however, there was little if any increase in DNA synthesis of MO-5 in the presence of EGF. Introduction of the polyoma middle T antigen gene into BALB/3T3, BNER4, MNER23, and MNER31 resulted in the appearance of transformation foci, but MO-5 again showed little response. We purified clones B4-mT-2, M23-mT-1, M23-mT-2, M23-mT-3, and M31-mT-13 from transformation foci of BNER4, MNER23, and MNER31 cells, which were respectively transfected with the middle T antigen. All of the middle T antigen-positive transfectants demonstrated abilities to form both colonies in soft agar and tumors in nude mice. The presence of EGF-R appears to be indispensable for malignant transformation by polyoma middle T antigen.

Cytogenetics of renal cell carcinomas associated with von Hippel-Lindau disease

To establish the chromosome pattern, we have analyzed short-term cultures of 24 renal cell carcinomas (RCC) from four patients with von Hippel-Lindau disease (VHL). We evaluated the results together with those for 16 RCCs from two VHL patients karyotyped previously in our laboratory and those of 6 tumors published by others. In all 46 RCCs, the cells had lost the shortest overlapping region of the 3pl3-pter chromosome segment. The rearrangement of 3p was the only karyotype change in 20 tumors. In more than 50% of the tumors, a gain of the shortest overlapping region of the 5122-qter segment was detected. Comparative analysis showed that the chromosome aberrations in RCCs associated with VHL are similar to those found in sporadic RCCs. These results indicate that non-papillary sporadic and VHL-RCCs have common genetic mechanisms that result in the loss of the 3p13-pter region containing one or more putative suppressor genes.

Modulation of the mitogenic activity of eukaryotic translation initiation factor-4E by protein kinase C

Eukaryotic initiation factor-4E (eIF-4E) binds to the cap structure of eukaryotic mRNAs and is a component of the cap-binding protein complex eIF-4F. eIF-4E is present in cells in limiting concentrations and is phosphorylated both in vivo and in vitro by protein kinase C (PKC). Recently, eIF-4E has been implicated as an intracellular transducer of extracellular growth signals; microinjection of recombinant eIF-4E into quiescent NIH 3T3 cells induced DNA synthesis. In the present report, the mitogenic activity of eIF-4E was examined after coinjection with PKC. Recombinant eIF-4E was phosphorylated by PKC at the same amino acid that is phosphorylated in cultured cells and reticulocytes in response to phorbol ester. At limiting concentrations of eIF-4E, coinjection with PKC induced a fivefold increase in the mitogenic activity of eIF-4E. Injection of PKC alone or coinjection of eIF-4E with cAMP-dependent protein kinase (PKA) or the Raf protein had no effect. These results suggest that the mitogenic activity of eIF-4E is enhanced by PKC-specific phosphorylation and that phosphate addition is a rate-limiting step in eIF-4E activity.

Cloning and characterization of a novel sequence-specific DNA-binding protein recognizing the negative regulatory element (NRE) region of the HIV-1 long terminal repeat

The present studies describe the isolation of a murine cDNA clone that encodes a novel DNA-binding protein recognizing the negative regulatory element (NRE) region of the HIV-1 long terminal repeat (LTR). This cDNA expresses a truncated protein with a functional DNA-binding domain, which is rich in glutamine/proline and serine/threonine, a characteristic of a majority of sequence-specific DNA-binding proteins and transcriptional factors. The cDNA hybridizes to a single-copy gene that is expressed as an approx. 4.2-kb mRNA in a variety of murine and human cell types, implying that this gene is expressed in an ubiquitous fashion. The NRE region has been reported to down-regulate LTR-directed gene expression [Rosen et al., Cell 41 (1985) 813-823]. This is the first sequence-specific DNA-binding protein reported to recognize the NRE region.

Synthesis and resolution of (+-)-7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro- 1H-3- benzazepine (TISCH): a high affinity and selective iodinated ligand for CNS D1 dopamine receptor

The synthesis and resolution of (+-)-7-chloro-8-hydroxy-1-(3'-iodophenyl)-3-methyl-2,3,4,5-tetrahydro-1 H-3- benzazepine, (+/-)-TISCH (8) has been achieved by resolution of intermediate 4, the O-methoxyl, 3'-bromo derivative, as the diastereomeric camphor sulfonate salt. The final products, R-(+)-8 and S-(-)-8, were prepared by treatment of R-(+)- or S-(-)-7, the 3'-tributyltin intermediates, with iodine in chloroform, followed by O-demethylation. By using HPLC with a chiral column, the optical purity (greater than 99%) of the intermediates and the final compounds was determined. Radioiodination was achieved by an iodo-destannylation reaction with sodium [125I]iodide and hydrogen peroxide. As expected, the R-(+)-[125I]-8 (the active isomer) displayed high affinity and selectivity to the CNS D-1 receptor in rat striatum tissue preparation (Kd = 0.205 nM). The rank order of potency was as follows: SCH-23390 (1a) greater than (+/-)-8 greater than (+)-butaclamol greater than spiperone, WB4101 greater than dopamine, 5-HT. After an iv injection, the R-(+)-[125I]-8 penetrated the blood-brain barrier with ease and displayed specific regional distribution corresponding to the D-1 receptor density, while the S-(-)-[125I]-8 showed no specific uptake. The data suggest that the ligand may be useful as a pharmacological tool for characterizing the D-1 dopamine receptor. When labeled with I-123, this ligand is a potential agent for in vivo imaging of CNS D-1 dopamine receptor.

A kit formulation for preparation of iodine-123-IBZM: a new CNS D-2 dopamine receptor imaging agent

A method for the preparation of iodine-123IBZM, a central nervous system D-2 imaging agent, is reported. By using a rapid filtration technique to remove the unreacted iodide, the preparation can be completed in less than 20 min (overall yield greater than 60%). The product, with high purity (greater than or equal to 95%) and specific activity, is suitable for human use.

Overview of radiopharmaceuticals for diagnosis of central nervous disorders

There are two types of imaging instruments, single-photon emission computed tomography (SPECT) and positron emission tomography (PET) that use radiopharmaceuticals for the diagnosis of brain disorders. Brain perfusion imaging agents, labeled either with 123I or 99mTc, are useful in detecting various cerebral vascular abnormalities, such as stroke and transient ischemia with SPECT. The management of other neurological disorders (i.e., in Alzheimer's, epilepsy, schizophrenia, and head trauma patients) may also be benefitted by these agents. The exact trapping mechanisms and their relationships with potential clinical applications still remain to be elucidated. Imaging studies using 18F fluorodeoxyglucose with PET is currently the most promising diagnostic tool for the evaluation of local glucose metabolism related to various disease states, such as Alzheimer's disease, brain tumor, and epilepsy. In the past few years significant progress has been made in the design and characterization of new CNS neuronal and postsynaptic receptor imaging agents for PET and SPECT. The new diagnostic agents are aimed at measurements of localization and changes of neuronal function. It is likely that these types of agents have potential for clinical application, especially in the diagnosis of psychiatric disorders that do not involve morphological changes.

Synthesis and biodistribution of a new class of 99mTc-labeled fatty acid analogs for myocardial imaging

A series of 99mTc-bis(aminoethanethiol)-fatty acid (99mTc-BAT-fatty acid) analogs were synthesized and evaluated as potential tracers of myocardial metabolism. The BAT-fatty acid precursors were prepared using a new synthetic route that avoids the use of strong reducing agents such as lithium aluminum hydride. Biodistribution studies of the no-carrier-added 99mTc-complexes were conducted in rats using [125I]IPPA as an internal standard. The myocardial uptake of the 99mTc-BAT-fatty acid analogs was significantly less than that of [125I]IPPA and indicates the 99mTc analogs are not suitable candidates for SPECT-based myocardial imaging studies.

Acute toxicity and mutagenicity of the copper complex of pyruvaldehyde-bis (N-4-methylthiosemicarbazone), Cu-PTSM

Cu-PTSM is a potential imaging agent for the heart and brain when labeled with either 64Cu or 62Cu. Unlabeled Cu-PTSM was evaluated for its acute toxicity and mutagenicity. Cu-PTSM had an i.v. LD50 of 26 mg kg-1 in the rat and 2 mg kg-1 in the rabbit. At necropsy, rats exhibited severely hemorrhagic lungs, histological findings of acute pulmonary congestion, hemorrhage and edema, and mild congestion in kidney, liver and brain. The rabbit displayed marked polymorphonuclear infiltration in alveoli, peribronchial and periarterial areas with marked macrophage hyperplasia, congestion and mild hemorrhage into alveolar spaces. No effects were found in kidney, liver, testes or brain. Administration of 2.16 micrograms kg-1 day-1 for 5 days per week for 2 weeks resulted in no changes in histopathology, hematology or clinical chemistry parameters. This daily dose is at least 300 times the diagnostic dose intended for use in man. Cu-PTSM was not mutagenic when tested in the absence of S9 supernatant, but elicited a weakly mutagenic response in the presence of S9. Since acute effects in the lung occur at doses approaching 300,000 times the diagnostic dose, it is highly unlikely that the clinical use of Cu-PTSM would result in any acute adverse effects.

Synthesis and applications of an aldehyde-containing analogue of SCH-23390

SCH-23390 is a high-affinity antagonist selective for D1 dopamine receptors (Ki = 2.5 nM). It does not contain a functional group that can be conveniently coupled to commercially available resins for affinity chromatography or to prepare photolabels for photoaffinity labeling of receptors. To construct an affinity resin for purification of dopamine D1 receptors, an aldehyde analogue of SCH-23390, (+/-)-7-chloro-8-hydroxy-1-(4'-formylphenyl)-3-methyl-2,3,4,5-tetrahydro -1H- 3-benzazepine (ASCH), was synthesized. 8-Methoxy-1-(4'-bromophenyl)-SCH-23390 was lithiated, formylated, and O-demethylated to form the aldehyde. NMR and IR analyses were performed to characterize the product. Assays were performed with the radioligand [125I]SCH-23982 to define the biological activity of the aldehyde. ASCH displaced [125I]SCH-23982 binding from caudate membranes with a Ki value of 7.1 nM. ASCH has been coupled through the aldehyde group on the phenyl ring to diaminodipropylamine-agarose for affinity chromatography. After solubilization of caudate membranes in 1% digitonin, the affinity resin retained binding sites for [125I]SCH-23982 that were eluted with 10 mM SCH-23390. The aldehyde was also covalently coupled to biotin hydrazide for fluorescence labeling of dopamine D1 receptors. The biotin-conjugated aldehyde of SCH-23390 displaced [125I]SCH-23982 binding from caudate membranes with a Ki value of 9.3 nM.

MAP 30: a new inhibitor of HIV-1 infection and replication

A new inhibitor of human immunodeficiency virus (HIV) has been isolated and purified to homogeneity from the seeds and fruits of the Momordica charantia. This compound, MAP 30 (Momordica Anti-HIV Protein), is a basic protein of about 30 kDa. It exhibits dose-dependent inhibition of cell-free HIV-1 infection and replication as measured by: (i) quantitative focal syncytium formation on CEM-ss monolayers; (ii) viral core protein p24 expression; and (iii) viral-associated reverse transcriptase (RT) activity in HIV-1 infected H9 cells. The doses required for 50% inhibition (ID50) in these assays were 0.83, 0.22 and 0.33 nM, respectively. No cytotoxic or cytostatic effects were found under the assay conditions. These data suggest that MAP 30 may be a useful therapeutic agent in the treatment of HIV-1 infections. The sequence of the N-terminal 44 amino acids of MAP 30 has been determined.

Identification and preliminary characterization of protein-cysteine farnesyltransferase

Ras proteins must be isoprenylated at a conserved cysteine residue near the carboxyl terminus (Cys-186 in mammalian Ras p21 proteins) in order to exert their biological activity. Previous studies indicate that an intermediate in the mevalonate pathway, most likely farnesyl pyrophosphate, is the donor of this isoprenyl group. Inhibition of mevalonate synthesis reverts the abnormal phenotypes induced by the mutant RAS2Val-19 gene in Saccharomyces cerevisiae and blocks the maturation of Xenopus oocytes induced by an oncogenic Ras p21 protein of human origin. These results have raised the possibility of using inhibitors of the mevalonate pathway to block the transforming properties of ras oncogenes. Unfortunately, mevalonate is a precursor of various end products essential to mammalian cells, such as dolichols, ubiquinones, heme A, and cholesterol. In this study, we describe an enzymatic activity(ies) capable of catalyzing the farnesylation of unprocessed Ras p21 proteins in vitro at the correct (Cys-186) residue. This farnesylating activity is heat-labile, requires Mg2+ or Mn2+ ions, is linear with time and with enzyme concentration, and is present in all mammalian cell lines and tissues tested. Gel filtration analysis of a partially purified preparation of protein farnesyltransferase revealed two peaks of activity at 250-350 kDa and 80-130 kDa. Availability of an in vitro protein farnesyltransferase assay should be useful in screening for potential inhibitors of ras oncogene function that will not interfere with other aspects of the mevalonate pathway.

Current and future radiopharmaceuticals for brain imaging with single photon emission computed tomography

Development of radiopharmaceuticals for functional brain imaging has progressed rapidly in recent years. Measurement of regional cerebral blood flow in humans can be achieved by using [123I]-iodoamphetamine or [99mTc]-HMPAO. Several other lipid-soluble [99mTc]-technetium complexes are currently undergoing clinical trials. New 123I-labeled agents designed to measure central nervous system receptors, including D1 and D2 dopamine, serotonin, muscarinic, and benzodiazepine receptors, have been developed. In conjunction with single photon emission computed tomography, they may provide useful tools to evaluate brain function related to changes in receptor concentration.

Purification of a factor capable of stimulating the guanine nucleotide exchange reaction of ras proteins and its effect on ras-related small molecular mass G proteins

We have previously identified a membrane factor capable of stimulating guanine nucleotide exchange activity for ras p21 proteins. The ras guanine nucleotide exchange factor (rGEF) was purified from bovine brain to near homogeneity by successive chromatographies on DE52 DEAE-cellulose, Sepharose 6B, hydroxylapatite, and FPLC phenyl-Superose resins. SDS/polyacrylamide gel electrophoresis of the purified rGEF showed a single major protein with a molecular mass of 35 kDa. rGEF increased the exchange rate of GDP in normal [Gly12]p21 or oncogenic [Val12]p21 up to 30- to 40-fold under physiological concentrations of Mg2+. Since the factor was free from GDP/GTP binding activity and nonspecific GDP hydrolytic activity, we propose that rGEF may regulate GDP/GTP exchange reaction of ras proteins in response to external growth signals. Moreover, rGEF enhanced the dissociation of bound GDP from some of ras-like G proteins, R-ras, rap1-A, rab1-B, and rho proteins, raising the possibility that rGEF may affect the activities of these proteins.

A new myocardial imaging agent: synthesis, characterization, and biodistribution of gallium-68-BAT-TECH

In order to develop a new myocardial perfusion agent for positron emission tomography (PET), a new lipid-soluble gallium complex was evaluated. Synthesis, radiolabeling, characterization, and biodistribution of a unique gallium complex, [67Ga]BAT-TECH (bis-aminoethanethiol-tetraethyl-cyclohexyl), are described. The complex formation between Ga+3 and BAT-TECH ligand is simple, rapid, and of high yield (greater than or equal to 95%). This process is amenable to kit formulation. The complex has a net charge of +1 and a Ga/ligand ratio of 1:1. Biodistribution in rats shows high uptake in the heart as well as in the liver. When [68Ga] BAT-TECH was injected into a monkey, the heart and liver are clearly delineated by PET imaging, suggesting that this complex may be a possible tracer for myocardial perfusion imaging.

I-123 hydroxyiodobenzyl propanediamine (HIPDM) cerebral blood flow imaging demonstrating transtentorial diaschisis

To assess the clinical significance of transtentorial diaschisis (TTD) as demonstrated by I-123 HIPDM brain imaging, SPECT and/or planar images of 35 patients with stroke, 26 patients with Alzheimer's disease (AD), 2 patients with Creutzfeldt-Jakob disease (CJD), and 1 patient with a schizoaffective disorder were analyzed. TTD was observed in 21 of the 35 patients with strokes. In 13 stroke patients, TTD was associated with large infarcts in the middle cerebral artery (MCA) territory; in the remaining 8 stroke patients, TTD was associated with internal capsule and/or basal ganglia infarcts. TTD was not associated with small occipital or parietal infarcts. Despite cortical perfusion decrements, TTD was not seen in the AD patients, the CJD patients, or the patient with schizoaffective disorder. It is concluded that 1) TTD frequently occurs following cerebral infarct of the MCA territory (60% of the patients in this sample); 2) absence of TTD in the presence of a large cerebral perfusion abnormality may represent neuronal dysfunction of the cerebral cortex; and 3) the presence of TTD without a significant cortical perfusion abnormality may indicate basal ganglia and/or internal capsule infarct.

Antibodies with high affinity for spiroperidol--II. Cross reactivity with iodobenzamide and domperidone

Three radioligands, 3H-spiroperidol (3H-SPD), 3H-domperidone (3H-DOMP) and 125I-iodobenzamide (125I-IBZM), were used to investigate the antibody response to two haptens, aminospiroperidol (NH2SPD) and N-aminophenethylspiroperidol (NAPS). Although structurally different, these three radioligands each bind with high affinity to the D2 dopamine receptor. Antibodies with high affinity for 3H-SPD were elicited in rabbits following immunization with the hapten NH2SPD covalently linked to keyhole limpet hemocyanin (KLH). In addition, antibodies in the rabbit anti-NH2SPD antisera bound 125I-IBZM or 3H-DOMP. Rabbit anti-NH2SPD antibodies that bound 125I-IBZM or 3H-DOMP were found to have higher affinity for IBZM or DOMP, respectively, than for SPD. The binding properties of the anti-NH2SPD antibodies that bound 3H-SPD, 125I-IBZM and 3H-DOMP were characterized using a panel of competitive inhibitors and each radioligand appeared to bind to a distinct subpopulation of anti-NH2SPD antibodies. BALB/c mice were immunized with NH2SPD-KLH or NAPS-KLH. A population of antibodies that bound 3H-SPD and a population of antibodies that bound 3H-DOMP were detected. The population of antibodies that bound 3H-DOMP was found to be heteroclitic for DOMP, since DOMP was a more effective competitive inhibitor than SPD. Binding sites for 125I-IBZM were not detected in either the anti-NH2SPD or the anti-NAPS BALB/c antisera. However, two anti-NAPS monoclonal antibodies, N6-24 and N6-29, that bind 3H-SPD with high affinity (Kd = 10(-9) M), were also found to bind IBZM (Ki = 2 x 10(-7) M) and DOMP (Ki = 2 x 10(-6) M). Although anti-NH2SPD and anti-NAPS antibodies were identified that appeared to bind 3H-SPD, 3H-DOMP or 125I-IBZM with high affinity, none of the populations of polyclonal antibodies or monoclonal antibodies bound all three ligands with high affinity.

Translation initiation factors induce DNA synthesis and transform NIH 3T3 cells

Several polypeptide factors that are essential for the initiation of protein synthesis bind to eukaryotic mRNAs and facilitate the formation of ribosome initiation complexes. Purified mRNA-binding translation initiation factors were microinjected into quiescent NIH 3T3 cells to study the possible growth-promoting role of these factors in living cells. We report that recombinant eIF-4E and rabbit reticulocyte eIF-4F induce a dose-dependent increase of DNA synthesis and morphologically transform NIH 3T3 cells. These results suggest that polypeptides involved in activating the rate-limiting step of protein synthesis (initiation complex formation) can be mitogenic and oncogenic when overexpressed in a cell by direct injection. Thus, eIF-4E and eIF-4F represent a class of proto-oncogenic proteins that is cytoplasmic, is involved in protein synthesis initiation, and is distinct from the proto-oncogenes that have been identified previously.

Induction of transformation and DNA synthesis after microinjection of raf proteins

Full-length and N-terminal deletion mutants of human c-raf-1 cDNA were cloned into Escherichia coli expression plasmids. Bacterially expressed c-raf proteins were purified by anion-exchange, gel filtration, and affinity chromatography. Microinjection of mutant c-raf proteins into G0-arrested NIH 3T3 cells induced DNA synthesis and morphological transformation, whereas microinjection of full-length c-raf had no effect. The amino terminus of the raf protein has an important negative regulatory influence; alteration of this region resulted in increased kinase activity and oncogenicity.

Iodine-123-HIPDM lung imaging in pulmonary vein-banded pulmonary hypertension

To evaluate the use of N,N,N'-trimethyl-N,-[2-hydroxy-3-methyl-5 iodobenzyl-1, 3 propanediamine iodine-123 (HIPDM) in lung imagings for the diagnosis of individual pulmonary vein stenosis, 14 single-pulmonary vein-banded rats underwent lung imaging. After i.v. injection of 250-300 microCi [123I]HIPDM lung images were recorded at 2 min by a gamma camera interfaced with a PDP computer. Banded lung demonstrated higher [123I]HIPDM radioactivity than that of nonbanded lungs. The activity ratio of banded-to-nonbanded lungs ranged from 4.0 to 1.22 (average 1.62). Technetium-99m-macroaggregated albumin (MAA) lung images showed decreased perfusion in banded lung, and normal perfusion in the nonbanded lung. Postmortem microscopic changes in pulmonary arteries and veins were compatible with the elevated pulmonary artery and venous pressure in vein-banded lung. Whether the high uptake of [123I]HIPDM in banded lungs relates to endothelial receptors for HIPDM is unknown. Nevertheless, the finding of high lung uptake in banded lung in [123I]HIPDM lung imaging may be potentially used to diagnose individual pulmonary vein stenosis.

The characterization of IBF as a new selective dopamine D-2 receptor imaging agent

The in vivo and in vitro studies of a new iodinated benzamide analog, [125I]IBF,5-iodo-7-N-[(1-ethyl-2-pyrrolidinyl)methyl]carboxamido-2,3- dihydrobenzofuran as a potential central nervous system (CNS) D-2 dopamine receptor imaging agent were investigated. In vivo biodistribution of IBF in rat indicated that this agent concentrated in the striatum region and displayed a remarkably high target-to-nontarget ratio (striatum/cerebellum = 48 at 120 min post-injection). The in vitro binding studies suggested that IBF binds selectively to D-2 dopamine receptors with high affinity and low nonspecific binding (Kd = 0.106 +/- 0.015 nM, Bmax = 448 +/- 18.2 fmole/mg protein). Ex vivo autoradiography results in rats further confirmed the high uptake and retention of this agent in the basal ganglia region. The planar images of monkey brains (lateral view of the head) after i.v. injection of [123I]IBF clearly demonstrated that D-2 dopamine receptors can be visualized. With the excellent in vivo stability to deiodination and high target-to-nontarget ratio, [123I]IBF may be useful as a CNS D-2 dopamine receptor imaging agent for single photon emission computed tomography (SPECT) in humans.

In vivo SPECT imaging of CNS D-2 dopamine receptors: initial studies with iodine-123-IBZM in humans

Iodobenzamide (IBZM) is a D-2 dopamine receptor antagonist. In this paper the results of Phase I clinical studies of iodine-123-(123I)IBZM in humans are reported. Preliminary imaging studies, both planar and single-photon emission tomography (SPECT), of no-carrier added [123I]IBZM in humans show specific localization in the basal ganglia of the brain. At 2 hr after an i.v. injection, the brain uptake was 3.72% of the dose, and at 20 hr later the uptake diminished to 0.7%. Radiation dosimetry calculation indicated that the radiation dose to the brain was minimum, 0.039 rad/mCi, while the large intestine wall received the highest dose, 0.28 mrad/mCi. The radiation dosimetry and pharmacology data suggest that this agent is safe for human use.

Negative regulation of human immune deficiency virus replication in monocytes. Distinctions between restricted and latent expression in THP-1 cells

In THP-1 monocytoid cells infected with HIV, viral expression can be regulated in several ways: (a) latency (no viral expression); (b) restricted expression (chronic low-level viral expression with little or no detectable virus released); and (c) continuous production. In cells with restricted HIV expression, nuclear factor(s) were found that blocked tat-associated DNA binding complex formation, suggesting that initiation of transcription was negatively regulated. Also, viral particles were seen budding into and accumulating within intracytoplasmic vacuoles with little virus released, suggesting multiple levels of regulation. These cells with restricted expression had no detectable viral antigens on the cell surface and were not lysed by IL-2-activated large granular lymphocytes. However, they could cause viral-mediated T cell cytolysis in cell-cell assays, suggesting viral transmission through cell contact. In addition, cells with latent HIV were identified and could still produce infectious virus after 5-azacytidine exposure 10 mo later. LPS and other treatments could increase viral production in cells with restricted but not latent expression, suggesting they occur by distinct mechanisms. These infected cells provide a reservoir for viral transmission to uninfected T cells that itself is not detected by immune surveillance mechanisms.

Inhibition of human immunodeficiency virus infectivity by chloroquine

The effect of chloroquine, a drug known to affect intracellular exocytic pathways, was studied in two retroviral systems: human immunodeficiency virus (HIV-1) and avian reticuloendotheliosis virus (REV-A). With chloroquine treatment of virus-infected cells, significant size reduction of the cell- and virus-associated surface glycoproteins, gp90 of REV-A and gp120 of HIV-1, was observed. In the case of HIV-1, extracellular virions derived from treated cells contained very little gp120. Infectivity and reverse transcriptase assays of HIV-1 demonstrated that by chloroquine treatment the majority of the virions released was noninfectious and the total virus yield was also reduced. The data suggest that chloroquine inhibition of infectious virus production is most likely due to interference with terminal glycosylation in the trans-Golgi network.