Substituent effects on the binding constants of arsenical-dithiol adducts

Proton nuclear magnetic resonance spectroscopy (1H NMR) was used to determine the relative binding constants for several arsenical-dithiol adducts. The compounds investigated were 2,3-dimercaptopropanol (British anti-lewisite; BAL), 1,2-ethane dithiol (ET), and 1,2-propane dithiol (PDT). It was found that PDT has a significantly higher affinity than ET or BAL for phenyldichloroarsine (PDA) in methanol.

Activation energies and formation rate constants for organic arsenical-antidote adducts as determined by dynamic NMR spectroscopy

Phenyldichloroarsine reacts with 1,3-dimercapto-2-propanol and 1,2-dimercaptopropane to form 1:1 adducts in the form of a six-membered and five-membered heteroatom rings. Two geometric isomers for each compound are present in dynamic equilibrium. Rate constants and the activation barriers for the interconversion of the geometric isomers were determined by dynamic NMR spectroscopy. The activation barriers indicate that the five-membered heteroatom ring is more stable than the six-membered heteroatom ring.

A simple method to create carotid endothelial laceration and acute platelet thrombus in vivo in guinea-pig

A simple method, named 'clamp method', was developed to create carotid endothelial laceration and produce acute platelet thrombus in vivo in guinea-pig. This method used a hemostatic forceps to clamp common carotid artery of anesthetized guinea-pig at a tangent angle. Our study included two parts. The Part one demonstrated the procedures and effects of the 'clamp method': sixteen guinea-pigs were divided equally into control and heparin-treated groups. These two groups received the same clamping procedures except that the heparin-treated group was administrated with heparin (5,000U/kg) intravenously before clamping. One hour after the clamping, carotid arteries were resected and observed under scanning electron microscopy. The results showed that large carotid mural thrombi were formed in the control group with a mean surface area of 1.75 +/- 0.63 mm2 (M +/- SD, n = 8). In the heparin-treated group, the thrombus formation was prevented and linear endothelial lacerations were seen clearly. The Part two of our study identified the histologic nature of the thrombus produced by the 'clamp method': eight guinea-pigs received same procedures as that of control group in the Part one except that the carotid arteries were resected 5 min after performing the clamping. Four of the eight specimens were prepared for observation under transmission electron microscopy. The results showed that platelets adhered onto the subendothelial substances and formed platelet thrombi in the endothelial lacerations within 5 min after the carotid clamping.

CP-82,996, a novel diglycoside polyether antibiotic related to monensin and produced byActinomadura sp

A new polyether antibiotic CP-82,996 (C50H86O16) was isolated by solvent extraction from the fermentation broth of Actinomadura sp. (ATCC 53764). Following purification by silica gel column chromatography and crystallization, the structure of CP-82,996 was determined by a single crystal X-ray analysis. The structure is closely related to monensin, but is unique in that it contains two sugar groups, whereas monensin has none. The 1H and 13C NMR chemical shifts and assignments for CP-82,996 were elucidated, and they were compared with those determined previously for monensin. CP-82,996 is active against certain Gram-positive bacteria, and is a very potent anticoccidial agent. It effectively controlled chicken coccidiosis caused by several Eimeria species at 5-10 ppm in feed, and is 10-20 times more potent than monensin.

CP-60,993, a new dianemycin-like ionophore produced byStreptomyces hygroscopicus ATCC 39305: fermentation, isolation and characterization

CP-60,993, 19-epi-dianemycin, is a novel polycyclic ether antibiotic produced by Streptomyces hygroscopicus ATCC 39305. Fermentation recovery, purification and crystallization were achieved using standard procedures. CP-60,993 was characterized as a monocarboxylic acid. Elemental analysis suggested a molecular formula of C47H78O14 for the free acid and C47H77O14 Na for the sodium salt. Crystalline from CP-60,993 sodium salt shows the following properties: m.p. 193-205 degrees C, E1%(1 cm) = 157 at 232 nm, [alpha]25 degrees C(D) + 11.0 (c 1, methanol). The structure, determined by MS, PMR and CMR, differs from dianemycin only in the stereochemistry at position 19. This was confirmed by X-ray crystallography carried out on the rubidium salt of CP-60,993. It exhibited activity in vitro against Gram-positive and anaerobic bacteria, efficacy against Eimeria coccidia in vivo in poultry, and stimulation in vitro of rumen propionic acid production.

CP-84,657, a potent polyether anticoccidial related to portmicin and produced by Actinomadura sp

A new polyether antibiotic CP-84,657 (C45H78O14) was isolated by solvent extraction from the fermentation broth of Actinomadura sp. (ATCC 53708). Following purification by column chromatography and crystallization, the structure of CP-84,657 was elucidated by spectroscopic (NMR and MS) methods. The absolute stereochemistry was determined by a single crystal X-ray analysis of the corresponding rubidium salt. CP-84,657 is among the most potent anticoccidal agents known, effectively controlling the Eimeria species that are the major causative agents of chicken coccidiosis at doses of 5 mg/kg or less in feed. It is also active in vitro against certain Gram-positive bacteria, as well as the spirochete, Treponema hyodysenteriae.

Structural determinants of the factor IX molecule mediating interaction with the endothelial cell binding site are distinct from those involved in phospholipid binding

Previous studies have indicated that Factor IX/IXa interacts in a specific and high affinity manner with a binding site on the endothelial cell surface. In this study, the contributions of the gamma-carboxyglutamic acid-containing (GLA) and growth factor domains to the finding of Factor IX to the endothelium were assessed. While GLA-containing peptides from Factors IX, X, and prothrombin were inhibitors of 125I-Factor IX-endothelial cell binding, the GLA peptide from Factor IX was about 250-800-fold more effective than those from prothrombin and Factor X, respectively. In contrast to its relative efficacy as an inhibitor of Factor IX-cell surface interaction, the Factor IX-GLA peptide neither bound to lipid vesicles nor inhibited Factor IX-lipid interaction. A synthetic peptide comprising the entire first epidermal growth factor (EGF) exon was also an inhibitor of 125I-Factor IX-endothelial cell binding, although it did not interact with lipid vesicles. Experiments with synthetic peptides comprising each of the three loops of the first EGF domain or the entire first EGF region with specific substitutions indicated the importance of determinants in both the first and probably third loops for Factor IX-endothelial interaction. In contrast, the second loop of the first EGF domain and the first loop of the second EGF exon are probably not involved in Factor IX-endothelial interaction based on their inability to block 125I-Factor IX binding to cells. These results indicate that determinants in both the GLA and the first EGF domain contribute to the specific binding of Factor IX to the endothelial cell surface and that structural requirements for Factor IX-cell surface interaction are distinct from those for Factor IX binding to lipids.

UK-69,753, a novel member of the efrotomycin family of antibiotics. I. Taxonomy of the producing organism, fermentation and isolation

UK-69,753 is a novel antibiotic structurally related to efrotomycin and factumycin, produced by a new strain of Amycolatopsis orientalis (ATCC 53550). The antibiotic potency in the fermentation broth was monitored by HPLC with diode array detection. A six tube counter current distribution was used to purify UK-69,753.

CP-78,545, a new monocarboxylic acid ionophore antibiotic related to zincophorin and produced by a Streptomyces

A new monocarboxylic acid ionophore antibiotic related to zincophorin, CP-78,545 (1), was found in the culture broth of Streptomyces sp. N731-45. CP-78,545 was extracted with organic solvents and purified by column chromatography. The metabolite, which is active in vitro against certain Gram-positive bacteria, as well as the anaerobe Treponema hyodysenteriae, and a coccidium Eimeria tenella, was isolated as a water insoluble magnesium salt (2) in 2:1 (ligand/metal) stoichiometry. The structure of CP-78,545 was elucidated by spectroscopic (NMR and MS) methods, and the relative stereochemistry was determined by single-crystal X-ray analysis of the cadmium salt (3). CP-78,545, i.e., 24-dehydrozincophorin, is unique since its molecular backbone contains a terminal double bond previously not found in other polyether ionophores.

Replication of baboon endogenous virus in human cells. Kinetics of DNA synthesis and integration

For the baboon endogenous virus to infect human cells a specific region on chromosome 6 is required for viral DNA replication and integration. In studying the kinetics of baboon endogenous virus DNA replication we show that linear DNA was synthesized as the predominant species after infection and that unintegrated DNA persisted after many cell passages. Examination of integrated DNA revealed the failure of the virus to integrate at early passages. With continuous replication, however, virus integration was observed, but at multiple sites in the host cell.

Calcium binding and putative activity of the epidermal growth factor domain of blood coagulation factor IX

The first epidermal growth factor (EGF)-like domain of human Factor IX and two chimeric analogs of this domain and EGF were synthesized unambiguously and purified to homogeneity. The synthetic EGF-like domain and its analogs showed the correct mass ions by the fission ionization mass spectrometry and similar disulfide pairings as those found in EGF, but failed to exhibit any putative EGF activity in the receptor and mitogenic assays. However, in NMR titration experiments, the EGF-like domain and one of its analogs were found to bind Ca2+ but not Mg2+. Our results therefore show that the EGF-like domain of Factor IX has the ability to bind calcium ion, shares the structural motif of EGF but does not retain the active determinants responsible for the EGF activity.

UK-63,052 complex, new quinomycin antibiotics from Streptomyces braegensis subsp. japonicus; taxonomy, fermentation, isolation, characterisation and antimicrobial activity

UK-63,052 complex, a new group of quinomycin-like antibiotics comprising UK-63,052 (factor A), UK-63,598 (factor C), UK-65,662 (factor B) and several uncharacterised minor components, is produced by a new subspecies of the genus Streptomyces for which the name Streptomyces braegensis Dietz subsp. japonicus, is proposed. The strain, N617-29, is characterised by a negative melanin reaction, grey aerial mycelium, spiral spore chains and smooth or slightly warty spores. Structure determination has identified UK-63,052, C56H68N10O14S2, UK-63,598, C53H62N10O14S2 and UK-65,662, C55H66N10O14S2 as quinaldic acid substituted quinomycins with unusual bridgehead sulfur substitution as shown in Fig. 3.

Hydroxylation of aspartic acid in domains homologous to the epidermal growth factor precursor is catalyzed by a 2-oxoglutarate-dependent dioxygenase

3-Hydroxyaspartic acid and 3-hydroxyasparagine are two rare amino acids that are present in domains homologous to the epidermal growth factor precursor in vitamin K-dependent plasma proteins as well as in proteins that do not require vitamin K for normal biosynthesis. They are formed by posttranslational hydroxylation of aspartic acid and asparagine, respectively. The first epidermal growth factor-like domain in factor IX (residues 45-87) was synthesized with aspartic acid in position 64, replacing 3-hydroxyaspartic acid. It was used as substrate in a hydroxylase assay with rat liver microsomes as the source of enzyme and reaction conditions that satisfy the requirements of 2-oxoglutarate-dependent dioxygenases. The synthetic peptide stimulated the 2-oxoglutarate decarboxylation in contrast to synthetic, modified epidermal growth factor (Met-21 and His-22 deleted and Glu-24 replaced by Asp) and synthetic peptides corresponding to residues 60-71 in human factor IX. This indicates that the hydroxylase is a 2-oxoglutarate-dependent dioxygenase with a selective substrate requirement.

Endusamycin, a novel polycyclic ether antibiotic produced by a strain of Streptomyces endus subsp. aureus

Endusamycin formerly called CP-63,517 (C47H77O14Na), is a novel polycyclic ether antibiotic produced by a new strain of Streptomyces endus subsp. aureus (ATCC 39574). Recovery, fractionation and purification were achieved using standard procedures. Forms include the endusamycin free acid, mp 95 approximately 105 degrees C, lambda max 232 nm (log E 4.16), [alpha]25D +47.4 degrees (c 0.5, methanol) and a crystalline sodium salt, mp 215 approximately 220 degrees C, lambda max 232 nm, (log E 4.15), [alpha]25D +25 degrees (c 0.5, methanol). The structure is shown below, Fig. 1. Endusamycin exhibited; antibacterial activity, in vitro against Gram-positive and anaerobic bacteria, effectiveness against coccidia in poultry, and stimulation of propionic acid production in an in vitro system.

The dorsal protein is distributed in a gradient in early Drosophila embryos

dorsal is one of the maternally active dorsal-ventral polarity genes of Drosophila and is closely related to the vertebrate proto-oncogene c-rel. Genetic experiments suggest that dorsal represents one of the last (if not the last) steps in the maternal pathway involved in establishing dorsal-ventral polarity in the early embryo. Even though the dorsal RNA is uniformly distributed in the embryo, we have found that the dorsal protein is specifically localized in peripheral nuclei of syncytial and cellular blastoderm stage embryos, and it is distributed in a ventral-to-dorsal gradient. These findings suggest possible mechanisms for how the dorsal protein may communicate maternal positional information to the zygotic genome.

Regulation of proto-oncogenes in rat parotid acinar cells in vitro after stimulation of beta-adrenergic receptors

Stimulation of beta-adrenoreceptors in rat parotid acinar cells in vitro by the beta-adrenergic agonist isoproterenol induces steady-state levels of c-fos mRNA and c-fos protein in these cells. A dramatic increase in the steady-state levels of c-fos mRNA was observed at 60 min, followed by a decrease at 2 h with a second peak at 4 h. c-fos induction in rat parotid acinar cells in vitro seems to be mediated by cAMP. Increased levels of p53 and c-myc mRNA were detected only at 60 min. c-abl and c-sis were also induced by isoproterenol but in a pattern different from that seen with c-fos. c-abl was the only oncogene in rat parotid gland which showed increased expression after chronic isoproterenol treatment of rats. In rat parotid acinar cells we observed no correlation between DNA synthesis and c-fos induction.

CP-54,883 a novel chlorine-containing polyether antibiotic produced by a new species of Actinomadura: taxonomy of the producing culture, fermentation, physico-chemical and biological properties of the antibiotic

The novel chlorine-containing acidic polycyclic ether antibiotic CP-54,883 (C41H62O12Cl2) [corrected] is produced by the fermentation of Actinomadura routienii Huang sp. nov. This report presents the taxonomy and the fermentation conditions for the antibiotic-producing culture. The antibiotic is mainly active against Gram-positive bacteria. It protects chickens against Eimeria challenge in vivo and enhances rumen propionic acid in vitro. The physico-chemical properties are also characterized.

Methylated DNA-binding protein from human placenta recognizes specific methylated sites on several prokaryotic DNAs

Methylated DNA-binding protein (MDBP) from human placenta recognizes specific DNA sequences containing 5-methylcytosine (m5C) residues. Comparisons of binding of various prokaryotic DNAs to MDBP indicate that m5CpG is present in the recognition sites for this protein but is only part of the recognition sequence. Specific binding to MDBP was observed for bacteriophage XP12 DNA, which naturally contains approximately 1/3 of its residues as m5C, and for Micrococcus luteus DNA, M13mp8 replicative form (RF) DNA, and pBR322 when these three DNAs were methylated at CpG sites by human DNA methyltransferase. Five DNA regions binding to MDBP have been localized by DNase I footprinting or restriction mapping in methylated pBR322 and M13mp8 RF DNAs. A comparison of their sequences reveals a common 5'-m5CGRm5CG-3' element or closely related sequence in which one of the m5C residues may be replaced by a T. In addition to this motif, one upstream and one downstream m5CpG as well as other common residues over an approximately 20-bp long region may be recognized by MDBP.

Identification of human N-ras as the common oncogene in NIH 3T3 cells transformed with DNAs from human primary hepatic cancer and hepatoma 7402 line

DNA was extracted from NIH 3T3 cells transformed with DNAs from human primary hepatic cancer (PHC) and Hepatoma 7402 cell line. The transformant DNA was analyzed by Southern transfer and hybridization with 32P-labeled probes of various oncogenes. The EcoRI 7.2 and 9.0 kb bands characteristic of human N-ras gene were identified in transformed NIH 3T3 cells derived both from PHC and 7402 DNA. The BamHI 6.6 kb band characteristic of human c-Ha-ras I was present only in 7402 transformants, but not in PHC transformants. Using 35S-methionine incorporation, immunoprecipitation with anti-p21 monoclonal antibodies, SDS-PAGE and autoradiography, it was demonstrated that p21 synthesis was remarkably enhanced in 7402 cells as well as in transformed cells derived from both 7402 and PHC DNA. Taking the data together, it strongly implies that N-ras is one of the transforming genes for human liver cancer.

Expression of N-ras gene in human primary hepatocarcinoma

Poly(A)+ RNA was isolated from 9 specimens of human primary hepatic carcinoma, 1 non-tumorous liver tissue adjacent to cancer and 1 normal liver tissue samples. The Oligo-dT cellulose-purified poly(A)+ RNAs were subjected to formaldehyde agarose gel electrophoresis, Northern transfer and hybridization with various oncogene probes. Two RNA species, 5.6 kb and 2.2 kb were identified by N-ras gene hybridization in 6 out of 9 mRNA samples from primary hepatic carcinoma specimen. N-ras specific mRNA was not detectable in mRNA samples from normal human liver and tumor surrounding cirrhotic tissue. No detectable hybridization of mRNA from hepatoma and normal liver with Ki-ras or Ha-ras was observed. As human N-ras gene has been identified in DNA of mouse transfectants transformed with PHC DNA, it strongly suggests that N-ras gene might be responsible for the transforming activity of part of cases of human liver cancer.

Human placental DNA methyltransferase: DNA substrate and DNA binding specificity

We have partially purified a DNA methyltransferase from human placenta using a novel substrate for a highly sensitive assay of methylation of hemimethylated DNA. This substrate was prepared by extensive nick translation of bacteriophage XP12 DNA, which normally has virtually all of its cytosine residues replaced by 5-methylcytosine (m5C). Micrococcus luteus DNA was just as good a substrate if it was first similarly nick translated with m5dCTP instead of dCTP in the polymerization mixture. At different stages in purification and under various conditions (including in the presence or absence of high mobility group proteins), the methylation of m5C-deficient DNA and that of hemimethylated DNA were compared. Although hemimethylated , m5C-rich DNAs were much better substrates than were m5C-deficient DNAs and normal XP12 DNA could not be methylated, all of these DNAs were bound equally well by the enzyme. In contrast, from the same placental extract, a DNA-binding protein of unknown function was isolated which binds to m5C-rich DNA in preference to the analogous m5C-poor DNA.

Regeneration of mouse peripheral nerves in degenerating skeletal muscle: guidance by residual muscle fibre basement membrane

The part played by basement membrane in the guidance of peripheral nerve growth in vivo has been assessed by examining the capacity of degenerating mouse muscle to support the regeneration of the cut sciatic and saphenous nerves. Ethanol and formaldehyde-fixed gluteus maximus muscles were implanted around the contralateral cut nerves. The subsequent nerve growth into the degenerating muscle was assessed by silver staining after 3, 4 and 10 days. By 4 days, linear axonal growth was seen, parallel to the length of the muscle fibres, and coinciding with the onset of degeneration of the sarcoplasm. Transverse sections of the 10 day preparations showed that over 90% of linearly growing axons were located inside the remaining sheaths of muscle fibre basement membrane. This relationship was confirmed by electron microscopy of ruthenium red-stained preparations. Both motor and sensory axons were able to grow in this manner, for electrophysiological testing revealed the presence of motor axons from the sciatic nerve, while the saphenous nerve contains only sensory axons. Identical growth was seen at 10 days in muscles caused to degenerate by incubation in distilled water. However, linear growth did not occur in live-innervated and glutaraldehyde-fixed muscles, in which muscle fibre architecture was preserved. It is concluded that basement membrane derived from muscle can promote peripheral nerve regeneration. Furthermore, both motor and sensory axons show a strong preference for growth along its inner surface, the basal lamina.

A protein from human placental nuclei binds preferentially to 5-methylcytosine-rich DNA

The methylation of vertebrate DNA at the 5-position of approximately 3-10% of its cytosine residues occurs in a sequence-specific and tissue-specific manner and has been implicated in the control of transcription. How these differences are established and how they mediate the initiation or maintenance of transcription are unknown. DNA methylation might also have other roles, such as modulating DNA replication, transposition, DNA repair or chromosome configuration. These other roles suggested for DNA methylation would be consistent with the finding that tissue-specific differences in methylation of certain gene regions, highly repeated satellite DNA sequences and whole genomes often do not correlate with transcriptional activity. For DNA methylation to modulate the expression, maintenance or duplication of chromosomes, there should be effector macromolecules, presumably proteins, which specifically recognize 5-methylcytosine (m5C) residues in DNA. We describe here the first identification of a mammalian protein that binds preferentially to m5C-rich DNA sequences.

Ligation of highly modified bacteriophage DNA

After digestion by TaqI or nicking by DNAase I, five highly modified bacteriophage DNAs were tested as substrates for T4 DNA ligase. The DNAs used were from phages T4, XP12, PBS1, SP82, and SP15, which contain as a major base either glucosylated 5-hydroxymethylcytosine, 5-methylcytosine, uracil, 5-hydroxymethyluracil, or phosphoglucuronated, glucosylated 5-(4',5'-dihydroxypentyl)uracil, respectively. The relative ability of cohesive-ended TaqI fragments of these DNAs and of normal, lambda DNA to be ligated was as follows: lambda DNA = XP12 DNA greater than SP82 DNA approximately equal to nonglucosylated T4 DNA greater than T4 DNA = PBSI1 DNA much greater than SP15 DNA. Taq I-T4 DNA fragments were also inefficiently ligated by Escherichia coli DNA ligase. However, annealing-independent ligation of DNAase I-nicked T4, PBS1, and lambda DNAs was equally efficient. We conclude that the poor ligation of Taq I fragments of T4 and PBS1 DNAs was due to the hydroxymethylation (and glucosylation) of cytosine residues at T4's cohesive ends and the substitution of uracil residues for thymine residues adjacent to PBS1's cohesive ends destabilizing the annealing of the restriction fragments. Only SP15 DNA with its negatively charged, modified base was unable to serve as a substrate for T4 DNA ligase in an annealing-independent reaction; therefore, its modification directly interfered with enzyme binding or catalysis.