| 11179440 |
Dolastatin 11, a marine depsipeptide, arrests cells at cytokinesis and induces hyperpolymerization of purified actin |
10.1124/mol.59.3.462. |
Mol Pharmacol |
Dolastatin 11, a marine depsipeptide, arrests cells at cytokinesis and induces hyperpolymerization of purified actin
Abstract
- The successful synthesis of dolastatin 11, a depsipeptide originally isolated from the mollusk Dolabella auricularia, permitted us to study its effects on cells. The compound arrested cells at cytokinesis by causing a rapid and massive rearrangement of the cellular actin filament network. In a dose-and time-dependent manner, F-actin was rearranged into aggregates, and subsequently the cells displayed dramatic cytoplasmic retraction. The effects of dolastatin 11 were most similar to those of the sponge-derived depsipeptide jasplakinolide, but dolastatin 11 was about 3-fold more cytotoxic than jasplakinolide in the cells studied. Like jasplakinolide, dolastatin 11 induced the hyperassembly of purified actin into filaments of apparently normal morphology. Dolastatin 11 was qualitatively more active than jasplakinolide and, in a quantitative assay we developed, dolastatin 11 was twice as active as jasplakinolide and 4-fold more active than phalloidin. However, in contrast to jasplakinolide and phalloidin, dolastatin 11 did not inhibit the binding of a fluorescent phalloidin derivative to actin polymer nor was it able to displace the phalloidin derivative from polymer. Thus, despite its structural similarity to other agents that induce actin assembly (all are peptides or depsipeptides), dolastatin 11 may interact with actin polymers at a distinct drug binding site.
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| 11181894 |
Comparative specificity of platelet alpha(IIb)beta(3) integrin antagonists |
None |
J Pharmacol Exp Ther |
Comparative specificity of platelet alpha(IIb)beta(3) integrin antagonists
Abstract
- Several platelet alpha(IIb)beta(3) integrin antagonists have been designed as preventive agents against the formation of arterial thrombi. Although the potency of these compounds in inhibiting platelet aggregation is in the nanomolar range, their specificity on other integrins that can bind ligands through an arginine-glycine-aspartic acid (RGD) motif is far from being well established. For instance, some cyclic RGD peptides can also interact with alpha(v)beta(3) integrin. We used a novel pharmacological assay, based on SDS-stable interaction between (125)I-echistatin and RGD-dependent integrins, to evaluate the specificity of several RGD compounds on integrins present on rat cardiac fibroblasts and human skin fibroblasts. of the RGD peptidomimetics tested (L-734,217, lamifiban, Ro 44-3888, SR 121566A, BIBU-52, XV459) could interact with either alpha(v)beta(3) and alpha(8)beta(1) on rat fibroblasts or with alpha(v)beta(3) and alpha(v)beta(1) on human fibroblasts. Cyclic RGD peptides showed some potency (3-80 microM) on rat and human integrins with an alpha(v) subunit. We also compared the potency of these compounds on platelets. All RGD compounds demonstrated IC(50) between 0.6 and 530 nM on basal human platelets. Activation of the receptor with thrombin resulted in a 2- to 60-fold increase in potency, with L-734,217 and BIBU-52 showing the largest difference. On basal and thrombin-activated rat platelets, only eptifibatide, DMP728, and XJ735 could displace (125)I-echistatin (IC(50) approximately 0.1-1.5 microM). These results indicate that RGD peptidomimetics have a specificity limited to alpha(IIb)beta(3) integrin, whereas cyclic RGD peptides can also interact with other RGD-dependent integrins, particularly those of the alpha(v) subunit family.
|
| 11181995 |
The sequence of the human genome. |
10.1126/science.1058040 |
Science |
The sequence of the human genome.
Abstract
- A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar
Results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.
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| 11190346 |
Antistaphylococcal (MSSA, MRSA, MSSE, MRSE) antibiotics |
10.1016/s0025-7125(05)70302-3. |
Med Clin North Am |
Antistaphylococcal (MSSA, MRSA, MSSE, MRSE) antibiotics
Abstract
- S. aureus and coagulase-negative staphylococci such as S. epidermidis are important causes of infection of the bloodstream, cardiac valves, implanted devices, and skin, with repercussions on mortality and increased economic costs. Treatment of staphylococcal infections is made difficult by the increasing emergence of resistance to beta-lactams and other antimicrobials, including reduced susceptibility to glycopeptides. Penicillin must be used for infrequent penicillin-susceptible isolates, oxacillin and nafcillin are to be considered the major option for penicillin-resistant staphylococci, and glycopeptides are the drugs of choice for infections caused by methicillin-resistant strains. Co-trimoxazole, lincosamides, macrolides, tetracyclines, and fluoroquinolones are alternative agents, primarily in subjects allergic to beta-lactams. Newly introduced or experimental drugs, such as streptogramins (quinupristin-dalfopristin), oxazolidis (linezolid), carbapenems (LY 333328), everninomicins (SCH 27899), and derivatives of tetracyclines (glycylcyclines), could be useful for therapy of infections caused by multiresistant staphylococci.
|
| 11206551 |
Genome sequence of enterohaemorrhagic Escherichia coli O157:H7 |
10.1038/35054089. |
Nature |
Genome sequence of enterohaemorrhagic Escherichia coli O157:H7
Abstract
- The bacterium Escherichia coli O157:H7 is a worldwide threat to public health and has been implicated in many outbreaks of haemorrhagic colitis, some of which included fatalities caused by haemolytic uraemic syndrome. Close to 75,000 cases of O157:H7 infection are now estimated to occur annually in the United States. The severity of disease, the lack of effective treatment and the potential for large-scale outbreaks from contaminated food supplies have propelled intensive research on the pathogenesis and detection of E. coli O157:H7 (ref. 4). Here we have sequenced the genome of E. coli O157:H7 to identify candidate genes responsible for pathogenesis, to develop better methods of strain detection and to advance our understanding of the evolution of E. coli, through comparison with the genome of the non-pathogenic laboratory strain E. coli K-12 (ref. 5). We find that lateral gene transfer is far more extensive than previously anticipated. In fact, 1,387 new genes encoded in strain-specific clusters of diverse sizes were found in O157:H7. These include candidate virulence factors, alternative metabolic capacities, several prophages and other new functions--all of which could be targets for surveillance.
|
| 11207395 |
Somatostatin receptors on peripheral primary afferent terminals: inhibition of sensitized nociceptors |
10.1016/S0304-3959(00)00407-3. |
Pain |
Somatostatin receptors on peripheral primary afferent terminals: inhibition of sensitized nociceptors
Abstract
- Somatostatin (SST) is in primary afferent neurons and reduces vascular and nociceptive components of inflammation. SST receptor (SSTR) agonists provide analgesia following intrathecal or epidural administration in humans, but neurotoxicity in the central nervous system (CNS) has been reported in experimental animals. With the rationale that targeting peripheral SSTRs would provide effective analgesia while avoiding CNS side effects, the goals of the present study are to investigate the presence of SSTRs on peripheral primary afferent fibers and determine the behavioral and physiological effects of the SST agonist octreotide (OCT) on formalin-induced nociception and bradykinin-induced primary afferent excitation and sensitization in the rat. The results demonstrate that: (1) SSTR2as are present on 11% of peripheral primary afferent sensory fibers in rat glabrous skin; (2) intraplantar injection of OCT reduces formalin-induced nociceptive behaviors; (3) OCT reduces, in a dose-dependent fashion, responses to thermal stimulation in C-mechanoheat sensitive fibers; and (4) OCT reduces the responses of C-mechanoheat fibers to bradykinin-induced excitation and sensitization to heat. Each of these actions can be reversed following co-injection of OCT with the SSTR antagonist cyclo-somatostatin (c-SOM). Thus, activation of peripheral SSTRs reduces both inflammatory pain and the activity of sensitized nociceptors, avoids deleterious CNS side effects and may be clinically useful in the treatment of pain of peripheral origin.
|
| 11212110 |
Conformational study of a highly specific CXCR4 inhibitor, T140, disclosing the close proximity of its intrinsic pharmacophores associated with strong anti-HIV activity |
10.1016/s0960-894x(00)00664-8. |
Bioorg Med Chem Lett |
Conformational study of a highly specific CXCR4 inhibitor, T140, disclosing the close proximity of its intrinsic pharmacophores associated with strong anti-HIV activity
Abstract
- We report the solution structure of T140, a truncated polyphemusin peptide analogue that efficiently inhibits infection of target cells by T-cell line-tropic strains of HIV-1 through its specific binding to a chemokine receptor, CXCR4. Nuclear magnetic resonance analysis and molecular dynamic calculations revealed that T140 has a rigidly structured conformation constituted by an antiparallel beta-sheet and a type II' beta-turn. A protuberance is formed on one side of the beta-sheet by the side-chain functional groups of the three amino acid residues (L-3-(2-naphthyl)alanine, Tyr5 and Arg14), each of which is indispensable for strong anti-HIV activity. These findings provide a rationale to dissect the structural basis for the ability of this compound to block the interaction between CXCR4 and envelope glycoproteins from T-tropic strains of HIV-1.
|
| 11219478 |
Quinupristin/dalfopristin: a therapeutic review |
10.1016/s0149-2918(01)80028-x. |
Clin Ther |
Quinupristin/dalfopristin: a therapeutic review
Abstract
- The proliferation of multidrug-resistant gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium (VREF), has created a pressing need for effective alternative antibiotics. Quinupristin/dalfopristin is a new combination streptogramin product with a selective spectrum of antibacterial activity, mainly against gram-positive aerobic bacteria. It has been assessed primarily in emergency-use protocols, in hospitalized patients with skin and skin-structure infections, and in patients with VREF bacteremia.
The objectives of this review were to summarize important results of in vitro microbiologic studies; to provide information on relevant pharmacokinetic parameters, drug interactions, and Y-site compatibility; and to assess efficacy and safety data from clinical studies of quinupristin/dalfopristin.
Articles included in this review were identified by a MEDLINE search of the literature published between 1966 and September 2000 using the terms Synercid, quinupristin, and dalfopristin. Additional articles were retrieved from the reference lists of articles identified in the MEDLINE search.
In vitro analysis of the spectrum of activity of quinupristin/dalfopristin has confirmed its relatively selective coverage of gram-positive aerobic bacteria. Both quinupristin and dalfopristin undergo hepatic metabolism and are extensively excreted in the feces. Combination quinupristin/dalfopristin inhibits the cytochrome P450 3A4 pathway, and caution is warranted with concomitant use of other medications eliminated via this pathway. In trials in patients with VREF infections, treatment success with quinupristin/dalfopristin varied depending on the site of infection, ranging from 51.9% in bacteremia of unknown origin to 88.9% in urinary tract infections. The results of comparative clinical trials suggest that quinupristin/dalfopristin has similar efficacy to that of commonly used antibiotics, including cefazolin, oxacillin, and vancomycin, in patients with skin and skin-structure infections or nosocomial pneumonia. The most frequently reported adverse effects with administration of quinupristin/dalfopristin were infusion-site inflammation, pain, and edema; other infusion-site reactions; and thrombophlebitis. Arthralgia, myalgia, nausea, diarrhea, vomiting, and rash occurred in 2.5% to 4.6% of patients and were the most frequently reported systemic adverse events.
Outcomes data from clinical trials indicate that quinupristin/dalfopristin has the potential to play an important role in the treatment of bacteremia, complicated skin and skin-structure infections, and nosocomial pneumonia caused by VREF. Issues of bacterial resistance to quinupristin/dalfopristin and other appropriate uses of this combination agent remain to be elucidated.
|
| 11238971 |
Plantaricin W from Lactobacillus plantarum belongs to a new family of two-peptide lantibiotics |
10.1099/00221287-147-3-643. |
Microbiology (Reading) |
Plantaricin W from Lactobacillus plantarum belongs to a new family of two-peptide lantibiotics
Abstract
- Plantaricin W (Plw) is a new two-peptide bacteriocin, from Lactobacillus plantarum, which inhibits a large number of Gram-positive bacteria. The two peptides, Plwalpha (comprising 29 residues) and Plwbeta (comprising 32 residues), were isolated from the culture supernatants and characterized. The individual peptides had low antimicrobial activity but acted synergistically, and synergism was seen at all mixing ratios tested. The data indicate that the two peptides work in a 1:1 ratio. Chemical analyses showed that both peptides are lantibiotics, but two unmodified cysteines and one serine residue were present in Plwalpha, and Plwbeta contained one cysteine residue. The Plw structural genes were sequenced and shown to encode prepeptides with sequence similarities to two other two-peptide lantibiotics, namely staphylococcin C55 and lacticin 3147. The conserved residues are mainly serines, threonines and cysteines that can be involved in intramolecular thioether bond formation in the C-terminal parts of the molecules. This indicates that these bacteriocins are members of a new family of lantibiotics with common bridging patterns, and that the ring structures play an important functional role. Based on the data a structural model is presented in which each peptide has a central lanthionine and two overlapping thioether bridges close to their C-termini.
|
| 11258796 |
Complete genome sequence of enterohemorrhagic Escherichia coli O157:H7 and genomic comparison with a laboratory strain K-12 |
10.1093/dnares/8.1.11. |
DNA Res |
Complete genome sequence of enterohemorrhagic Escherichia coli O157:H7 and genomic comparison with a laboratory strain K-12
Abstract
- Escherichia coli O157:H7 is a major food-borne infectious pathogen that causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome. Here we report the complete chromosome sequence of an O157:H7 strain isolated from the Sakai outbreak, and the results of genomic comparison with a benign laboratory strain, K-12 MG1655. The chromosome is 5.5 Mb in size, 859 Kb larger than that of K-12. We identified a 4.1-Mb sequence highly conserved between the two strains, which may represent the fundamental backbone of the E. coli chromosome. The remaining 1.4-Mb sequence comprises of O157:H7-specific sequences, most of which are horizontally transferred foreign DNAs. The predominant roles of bacteriophages in the emergence of O157:H7 is evident by the presence of 24 prophages and prophage-like elements that occupy more than half of the O157:H7-specific sequences. The O157:H7 chromosome encodes 1632 proteins and 20 tRNAs that are not present in K-12. Among these, at least 131 proteins are assumed to have virulence-related functions. Genome-wide codon usage analysis suggested that the O157:H7-specific tRNAs are involved in the efficient expression of the strain-specific genes. A complete set of the genes specific to O157:H7 presented here sheds new insight into the pathogenicity and the physiology of O157:H7, and will open a way to fully understand the molecular mechanisms underlying the O157:H7 infection.
|
| 11260230 |
Identification of novel C253Y missense and Y864X nonsense mutations in the insulin receptor gene in type A insulin-resistant patients |
10.1034/j.1399-0004.2001.590309.x. |
Clin Genet |
Identification of novel C253Y missense and Y864X nonsense mutations in the insulin receptor gene in type A insulin-resistant patients
Abstract
- Mutations in the insulin receptor gene have been reported in cases of type A insulin resistance. We report herein two cases of type A insulin resistance, which involve some novel mutations. Case 1 is a heterozygote of the C253Y missense mutation and case 2 is a heterozygote of the Y864X nonsense mutation. In the C253Y missense mutation in exon 3, a cysteine residue is replaced with tyrosine in the cysteine-rich domain of the alpha subunit. The Y864X in exon 13 results in a truncated receptor, which is devoid of most of the beta subunit. This mutant receptor could not be expressed on a cell membrane since the transmembrane domain is missing. Other significant mutations were not found for the entire coding regions and splice/donor sites.
|
| 11266082 |
Polymorphism of the ABC transporter genes, MDR1, MRP1 and MRP2/cMOAT, in healthy Japanese subjects |
10.1097/00008571-200103000-00008. |
Pharmacogenetics |
Polymorphism of the ABC transporter genes, MDR1, MRP1 and MRP2/cMOAT, in healthy Japanese subjects
Abstract
|
| 11277744 |
Pitipeptolides A and B, new cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula |
10.1021/np000456u. |
J Nat Prod |
Pitipeptolides A and B, new cyclodepsipeptides from the marine cyanobacterium Lyngbya majuscula
Abstract
- Two new cyclodepsipeptides have been isolated from a population of the marine cyanobacterium Lyngbya majuscula collected at Piti Bomb Holes, Guam. They appear to be unique to this particular Guamanian collection and have been named pitipeptolides A (1) and B (2). Their structures have been elucidated by spectroscopic techniques and by characterization of degradation products. Distinctive features include the presence of a 2,2-dimethyl-3-hydroxy-7-octynoic acid residue in 1 and a 2,2-dimethyl-3-hydroxy-7-octenoic acid residue in 2, previously shown to be biosynthetic signatures of cyanobacterial metabolites. Pitipeptolides A (1) and B (2) exhibit weak cytotoxicity against LoVo cancer cells, but possess moderate antimycobacterial activity and stimulate elastase activity.
|
| 11278596 |
Identification of an amino acid residue in multidrug resistance protein 1 critical for conferring resistance to anthracyclines. |
10.1074/jbc.m010008200 |
J. Biol. Chem. |
Identification of an amino acid residue in multidrug resistance protein 1 critical for conferring resistance to anthracyclines.
Abstract
- Murine multidrug resistance protein 1 (mrp1), unlike human MRP1, does not confer resistance to anthracyclines. Previously, we have shown that a human/murine hybrid protein containing amino acids 959-1187 of MRP1 can confer resistance to these drugs. We have now examined the functional characteristics of mutant proteins in which we have converted individual amino acids in the comparable region of mrp1 to those present at the respective locations in MRP1. These mutations had no effect on the drug resistance profile conferred by mrp1 with the exception of converting glutamine 1086 to glutamate, as it is in the corresponding position (1089) in MRP1. This mutation created a protein that conferred resistance to doxorubicin without affecting vincristine resistance, or the ability of mrp1 to transport leukotriene C(4) (LTC(4)) and 17beta-estradiol 17-(beta-d-glucuronide) (E(2)17betaG). Furthermore, mutation Q1086D conferred the same phenotype as mutation Q1086E while the mutation Q1086N did not detectably alter the drug resistance profile of mrp1, suggesting that an anionic side chain was required for anthracycline resistance. To confirm the importance of MRP1 E1089 for conferring resistance to anthracyclines, we mutated this residue to Gln, Asp, Ala, Leu, and Lys in the human protein. The mutation E1089D showed the same phenotype as MRP1, while the E1089Q substitution markedly decreased resistance to anthracyclines without affecting LTC(4) and E(2)17betaG transport. Conversion of Glu-1089 to Asn, Ala, or Leu had a similar effect on resistance to anthracyclines, while conversion to a positive amino acid, Lys, completely eliminated resistance to anthracyclines and vincristine without affecting transport of LTC(4), E(2)17betaG, and the GSH-dependent substrate, estrone-3-sulfate. These
Results demonstrate that an acidic amino acid residue at position 1089 in predicted TM14 of MRP1 is critical for the ability of the protein to confer drug resistance particularly to the anthracyclines, but is not essential for its ability to transport conjugated organic anions such as LTC(4) and E(2)17betaG.
|
| 11278867 |
Mutation of a single conserved tryptophan in multidrug resistance protein 1 (MRP1/ABCC1) results in loss of drug resistance and selective loss of organic anion transport. |
10.1074/jbc.m011246200 |
J. Biol. Chem. |
Mutation of a single conserved tryptophan in multidrug resistance protein 1 (MRP1/ABCC1) results in loss of drug resistance and selective loss of organic anion transport.
Abstract
- Multidrug resistance protein 1 (MRP1/ABCC1) belongs to the ATP-binding cassette transporter superfamily and is capable of conferring resistance to a broad range of chemotherapeutic agents and transporting structurally diverse conjugated organic anions. In this study, we found that substitution of a highly conserved tryptophan at position 1246 with cysteine (W1246C-MRP1) in the putative last transmembrane segment (TM17) of MRP1 eliminated 17beta-estradiol 17-(beta-d-glucuronide) (E(2)17betaG) transport by membrane vesicles prepared from transiently transfected human embryonic kidney cells while leaving the capacity for leukotriene C(4)- and verapamil-stimulated glutathione transport intact. In addition, in contrast to wild-type MRP1, leukotriene C(4) transport by the W1246C-MRP1 protein was no longer inhibitable by E(2)17betaG, indicating that the mutant protein had lost the ability to bind the glucuronide. A similar phenotype was observed when Trp(1246) was replaced with Ala, Phe, and Tyr. Confocal microscopy of cells expressing Trp(1246) mutant MRP1 molecules fused at the C terminus with green fluorescent protein showed that they were correctly routed to the plasma membrane. In addition to the loss of E(2)17betaG transport, HeLa cells stably transfected with W1246C-MRP1 cDNA were not resistant to the Vinca alkaloid vincristine and accumulated levels of [(3)H]vincristine comparable to those in vector control-transfected cells. Cells expressing W1246C-MRP1 were also not resistant to cationic anthracyclines (doxorubicin, daunorubicin) or the electroneutral epipodophyllotoxin VP-16. In contrast, resistance to sodium arsenite was only partially diminished, and resistance to potassium antimony tartrate remained comparable to that of cells expressing wild-type MRP1. This suggests that the structural determinants required for transport of heavy metal oxyanions differ from those for chemotherapeutic agents. Our
Results provide the first example of a tryptophan residue being so critically important for substrate specificity in a eukaryotic ATP-binding cassette transporter.
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