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W David Wilson

Publications and source records attributed to W David Wilson.

At least 55 records · Page 3Linked to original sources
PubMed2004

DNA sequence dependent monomer-dimer binding modulation of asymmetric benzimidazole derivatives.

A number of studies indicate that DNA sequences such as AATT and TTAA have significantly different physical and interaction properties. To probe these interaction differences in detail and determine the influence of charge, we have synthesized three bisbenzimidazole derivatives, a diamidine, DB185, and monoamidines, DB183 and DB210, that are related to the well-known minor groove agent, Hoechst 33258. Footprinting studies with several natural and designed DNA fragments indicate that the synthetic compounds bind at AT sequences in the minor groove and interact more weakly at sites with TpA steps relative to sites without such steps. Circular dichroism spectroscopy also indicates that the compounds bind in the DNA minor groove. Surprisingly, Tm studies as a function of ratio indicate that the monoamidines bind to TTAA sequences as dimers, whereas the diamidine binds as a monomer. Biosensor-surface plasmon resonance (SPR) studies allowed us to quantitate the interaction differences in more detail. SPR results clearly show that the monoamidine compounds bind to the TTAA sequence in a cooperative 2:1 complex but bind as monomers to AATT. The dication binds to both sequences in monomer complexes but the binding to AATT is significantly stronger than binding to TTAA. Molecular dynamics simulations indicate that the AATT sequence has a narrow time-average minor groove width that is a very good receptor site for the bisbenzimidazole compounds. The groove in TTAA sequences is wider and the width must be reduced to form a favorable monomer complex. The monocations thus form cooperative dimers that stack in an antiparallel orientation and closely fit the structure of the TTAA minor groove. The amidine groups in the dimer are oriented in the 5' direction of the strand to which they are closest. Charge repulsion in the dication apparently keeps it from forming the dimer. It instead reduces the TTAA groove width, in an induced fit process, sufficiently to form a minor groove complex. The dimer-binding mode of DB183 and DB210 is a new DNA recognition motif and offers novel design concepts for selective targeting of DNA sequences with a wider minor groove, including those with TpA steps.

Benzimidazoles↗
PubMed2004

Characterization of a novel DNA minor-groove complex.

Many dicationic amidine compounds bind in the DNA minor groove and have excellent biological activity against a range of infectious diseases. Para-substituted aromatic diamidines such as furamidine, which is currently being tested against trypanosomiasis in humans, and berenil, which is used in animals, are typical examples of this class. Recently, a meta-substituted diamidine, CGP 40215A, has been found to have excellent antitrypanosomal activity. The compound has a linear, conjugated linking group that can be protonated under physiological conditions when the compound interacts with DNA. Structural and molecular dynamics analysis of the DNA complex indicated an unusual AT-specific complex that involved water-mediated H-bonds between one amidine of the compound and DNA bases at the floor of the minor groove. To investigate this unique system in more detail DNase I footprinting, surface plasmon resonance biosensor techniques, linear dichroism, circular dichroism, ultraviolet-visible spectroscopy, and additional molecular dynamics simulations have been conducted. Spectrophotometric titrations of CGP 40215A binding to poly(dAT)(2) have characteristics of DNA-binding-induced spectral changes as well as effects due to binding-induced protonation of the compound linker. Both footprinting and surface plasmon resonance results show that this compound has a high affinity for AT-rich sequences of DNA but very weak binding to GC sequences. The dissociation kinetics of the CGP 40215A-DNA complex are much slower than with similar diamidines such as berenil. The linear dichroism results support a minor-groove complex for the compound in AT DNA sequences. Molecular dynamics studies complement the structural analysis and provide a clear picture of the importance of water in mediating the dynamic interactions between the ligand and the DNA bases in the minor groove.

Base Sequence↗
PubMed2004

Evaluation and comparison of an indirect fluorescent antibody test for detection of antibodies to Sarcocystis neurona, using serum and cerebrospinal fluid of naturally and experimentally infected, and vaccinated horses.

The objectives of this study were to evaluate the accuracy of the indirect fluorescent antibody test (IFAT) using serum and cerebrospinal fluid (CSF) of horses naturally and experimentally infected with Sarcocystis neurona, to assess the correlation between serum and CSF titers, and to determine the effect of S. neurona vaccination on the diagnosis of infection. Using receiver-operating characteristic analysis, the areas under the curve for the IFAT were 0.97 (serum) and 0.99 (CSF). Sensitivity and specificity were 83.3 and 96.9% (serum, cutoff 80) and 100 and 99% (CSF, cutoff 5), respectively. Titer-specific likelihood ratios (LRs) ranged from 0.03 to 187.8 for titers between <10 and 640. Median time to conversion was 22-26 days postinfection (DPI) (serum) and 30 DPI (CSF). The correlation between serum and CSF titers was moderately strong (r = 0.6) at 30 DPI. Percentage of vaccinated antibody-positive horses ranged from 0 to 95% between 0 and 112 days after the second vaccination. Thus, the IFAT was reliable and accurate using serum and CSF. Use of LRs potentially improves clinical decision making. Correlation between serum and CSF titers affects the joint accuracy of the IFAT; therefore, the ratio of serum to CSF titers has potential diagnostic value. The S. neurona vaccine could possibly interfere with equine protozoal myeloencephalitis diagnosis.

Animals↗
PubMed2004

Risk of transplacental transmission of Sarcocystis neurona and Neospora hughesi in California horses.

The study objective was to assess the risk of transplacental transmission of Sarcocystis neurona and Neospora hughesi in foals from 4 California farms during 3 foaling seasons. Serum of presuckle foals and serum and colostrum of periparturient mares were tested using indirect fluorescent antibody tests for S. neurona and N. hughesi. Serum antibody titers were < or =10 in 366 presuckle foals tested. There was no serologic or histologic evidence of either parasite in aborted fetuses or placentas examined. Positivity for S. neurona and N. hughesi in mares increased with age. Mares < or =9 yr that originated from Kentucky were 3.8 and 1.4 times more likely to be positive for S. neurona and N. hughesi, respectively, than mares from California. The strength of association between positivity to either parasite and state of birth decreased as age increased. Mares positive for S. neurona and N. hughesi were 2.2 and 1.7 times more likely, respectively, to have a previous abortion than negative mares, adjusted for age and state of birth. The annual mortality rate for mares was 4%. The annual incidence rate of equine protozoal myeloencephalitis was 0.2%. In conclusion, there was no detectable risk of transplacental transmission of S. neurona and N. hughesi. Prevalence of antibodies against both parasites in mares increased with age.

Abortion, Veterinary↗
PubMed2004

Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses.

OBJECTIVE: To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals. ANIMALS: 484 Thoroughbred and Warmblood foals from 4 farms in California. PROCEDURE: Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were > or = 40 and > or = 160 for S neurona and N hughesi, respectively. RESULTS: Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1 %, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM). CONCLUSIONS AND CLINICAL RELEVANCE: Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses < or = 2.5 years of age.

Age Factors↗
PubMed2004

Pharmacokinetics of a high dose of amikacin administered at extended intervals to neonatal foals.

OBJECTIVE: To determine disposition kinetics of amikacin in neonatal foals administered high doses at extended intervals. ANIMALS: 7 neonatal foals. PROCEDURE: Amikacin was administered (21 mg/kg, i.v., q 24 h) for 10 days. On days 1, 5, and 10, serial plasma samples were obtained for measurement of amikacin concentrations and determination of pharmacokinetics. RESULTS: Mean +/- SD peak plasma concentrations of amikacin extrapolated to time 0 were 103.1 +/- 23.4, 102.9 +/- 9.8, and 120.7 +/- 17.9 microg/mL on days 1, 5, and 10, respectively. Plasma concentrations at 1 hour were 37.5 +/- 6.7, 32.9 +/- 2.6, and 30.6 +/- 3.5 microg/mL; area under the curve (AUC) was 293.0 +/- 61.0, 202.3 +/- 40.4, and 180.9 +/- 31.2 (microg x h)/mL; elimination half-life (t(1/2)beta) was 5.33, 4.08, and 3.85 hours; and clearance was 1.3 +/- 0.3, 1.8 +/- 0.4, and 2.0 +/- 0.3 mL/(min x kg), respectively. There were significant increases in clearance and decreases in t(1/2)beta, AUC, mean residence time, and plasma concentrations of amikacin at 1, 4, 8, 12, and 24 hours as foals matured. CONCLUSIONS AND CLINICAL RELEVANCE: Once-daily administration of high doses of amikacin to foals resulted in high peak plasma amikacin concentrations, high 1-hour peak concentrations, and large values for AUC, consistent with potentially enhanced bactericidal activity. Age-related findings suggested maturation of renal function during the first 10 days after birth, reflected in enhanced clearance of amikacin. High-dose, extended-interval dosing regimens of amikacin in neonatal foals appear rational, although clinical use remains to be confirmed.

Age Factors↗
PubMed2003

Cooperative dimerization of a heterocyclic diamidine determines sequence-specific DNA recognition.

In the course of a program aimed at discovering novel DNA-targeted antiparasitic drugs, the phenylfuran-benzimidazole unfused aromatic dication DB293 was identified as the first diamidine capable of forming stacked dimers in the DNA minor groove of GC-containing sequences. Its preferred binding sequence encompasses the tetranucleotide 5'-ATGA.5'-TCAT to which DB293 binds tightly with a strong positive cooperativity. Here we have investigated the influence of the DNA sequence on drug binding using two complementary technical approaches: surface plasmon resonance and DNase I footprinting. The central dinucleotide of the primary ATGA motif was systematically varied to represent all of the eight possible combinations (AXGA and ATYA, where X or Y = A, T, G, or C). Binding affinities for each site were precisely measured by SPR, and the extent of cooperative drug binding was also determined. The sequence recognition process was found to be extremely dependent on the nature of the central dinucleotide pair. Modification of the central TG step decreases binding affinity by a factor varying from 2 to over 500 depending on the base substitution. However, the diminished binding affinity does not affect the unique binding mode. In nearly all cases, the SPR titrations revealed a positive cooperativity in complex formation which reflects the ease of the dication to form stacked dimeric motifs in the DNA minor groove. DNase I footprinting served to identify additional binding sites for DB293 in the context of long DNA sequences offering a large variety of randomly distributed or specifically designed sites. The ATGA motif provided the best receptor for the drug, but lower affinity sequences were also identified. The design of two DNA fragments composed of various targeted tetranucleotide binding sites separated by an "insulator" (nonbinding) sequence allowed us to delineate further the influence of DNA sequence on drug binding and to identify a novel high-affinity site: 5'-ACAA.5'-TTGT. Collectively, the SPR and footprinting results show that the consensus sequence 5'-(A/T)-TG-(A/T) represents the optimal site for cooperative dimerization of the heterocyclic diamidine DB293.

Base Sequence↗
PubMed2003

Synthesis and antiprotozoal activity of aza-analogues of furamidine.

6-[5-(4-Amidinophenyl)furan-2-yl]nicotinamidine (8a) was synthesized from 6-[5-(4-cyanophenyl)furan-2-yl]nicotinonitrile (4a), through the bis-O-acetoxyamidoxime followed by hydrogenation. Compound 4a was prepared via selective bromination of 6-(furan-2-yl)nicotinonitrile (2a) with N-bromosuccinimide, followed by Suzuki coupling with 4-cyanophenylboronic acid. In a similar way, diamidines 8b and 8c were prepared from the dicyano derivatives 4c and 4d, respectively. N-Methoxy-6-[5-[4-(N-methoxyamidino)phenyl]-furan-2-yl]-nicotinamidine (6a) was prepared via methylation of the respective diamidoxime 5a with dimethylsulfate. Prodrugs 6b and 6c were also prepared by methylation of the respective diamidoximes 5b and 5d. The symmetrical diamidines 14a,b were synthesized through the corresponding bis-O-acetoxyamidoxime followed by hydrogenation. The key compounds 11a,b were conveniently obtained by Stille coupling between 2,5-bis(tri-n-butylstannyl)furan and the corresponding heteroaryl halides. These compounds have been evaluated in vitro for activity against Trypanosoma b.rhodesiense (T. b. r.) and P. falciparum (P. f.). The diamidines 8a, 8c, and 14b gave IC(50) values versus T. b. r. of less than 10 nM. Against P. f. 8a, 8b, and 14b exhibited IC(50) values less than 10 nM. In an in vivo mouse model for T. b. r. four compounds 6a, 6c, 6d, and 8a were curative. Compound 6a produced cures at an oral dosage of 5 mg/kg.

Animals↗
PubMed2003

Trisubstituted acridine derivatives as potent and selective telomerase inhibitors.

The synthesis and evaluation for telomerase-inhibitory and quadruplex DNA binding properties of three related series of rationally designed trisubstituted acridine derivatives are described. These are substituted on the acridine ring at the 2,6,9; 2,7,9; and 3,6,9 positions. The ability of several of the most potent compounds to interact with and stabilize an intramolecular G-quadruplex DNA was evaluated by surface plasmon resonance methods, and affinities were found to correlate with potency in a telomerase assay. The interactions of a number of compounds with a parallel quadruplex DNA structure were simulated by molecular modeling methods. The calculated interaction energies were compared with telomerase activity and showed generally consistent correlations between quadruplex affinity and telomerase inhibition. These data support a model for the action of these compounds that involves the stabilization of intermediate quadruplex structures that inhibit the elongation of telomeric DNA by telomerase in tumor cells.

Acridines↗
PubMed2003

The activity of diguanidino and 'reversed' diamidino 2,5-diarylfurans versus Trypanosoma cruzi and Leishmania donovani.

The in vitro activity of 20 dicationic molecules containing either diguanidino or reversed amidine cationic groups were evaluated versus Trypanosoma cruzi and Leishmania donovani. The most active compounds were in the reversed amidine series and six exhibited IC(50) values of less than 1 micro mol versus T. cruzi and five gave similar values versus L. donovani.

Amidines↗
PubMed2003

Selective recognition of G-qQuadruplex telomeric DNA by a bis(quinacridine) macrocycle.

The interaction of G-quadruplex DNA with the macrocyclic compound BOQ1, which possesses two dibenzophenanthroline (quinacridine) subunits, has been investigated by a variety of methods. The oligonucleotide 5'-A(GGGT(2)A)(3)G(3), which mimics the human telomeric repeat sequence and forms an intramolecular quadruplex, was used as one model system. Equilibrium binding constants measured by biosensor surface plasmon resonance (SPR) methods indicate a high affinity of the macrocycle for the quadruplex conformation (K > 1 x 10(7) M(-)(1)) with two equivalent binding sites. The affinity of BOQ1 for DNA duplexes is at least 1 order of magnitude lower. In addition, the macrocycle is more selective than the monomeric control compound (MOQ2), which is not able to discriminate between the two DNA structures (K(duplex) approximately K(quadruplex) approximately 10(6) M(-)(1)). Strong binding of BOQ1 to G4 DNA sequences was confirmed by fluorometric titrations with a tetraplex-forming oligonucleotide. Competition dialysis experiments with a panel of different DNA structures, from single strands to quadruplexes, clearly established the quadruplex binding specificity of BOQ1. Fluorescence resonance energy transfer (FRET) T(m) experiments with a doubly labeled oligonucleotide also revealed a strong stabilization of the G4 conformation in the presence of BOQ1 (DeltaT(m) = +28 degrees C). This DeltaT(m) value is one of the highest values measured for a G-quadruplex ligand and is significantly higher than observed for the monomer control compounds (DeltaT(m) = +10-12 degrees C). Gel mobility shift assays indicated that the macrocycle efficiently induces the formation of G-tetraplexes. Strong inhibition of telomerase was observed in the submicromolar range (IC(50) = 0.13 microM). These results indicate that macrocycles represent an exciting new development opportunity for targeting DNA quadruplexes.

Acridines↗
PubMed2003

Cutaneous and ocular habronemiasis in horses: 63 cases (1988-2002).

OBJECTIVE: To describe clinical manifestations of cutaneous and ocular habronemiasis in horses and evaluate outcome of treatment. DESIGN: Retrospective study. ANIMALS: 63 horses. PROCEDURE: The diagnosis was made on the basis of history, clinical signs, and identification of calcified concretions (sulfur granules) in lesions. Histologic examination of biopsy specimens was used to confirm the diagnosis. Case horses were compared with a control population of 12,720 horses examined during the same period. RESULTS: Arabians, gray horses, and horses with diluted coat colors were overrepresented; Thoroughbreds were underrepresented. Lesions were identified most often during the summer and early fall. The medial canthus of the eye, male genitalia, third eyelid, and distal portions of the extremities were the most commonly affected locations. Twenty-five lesions were biopsied, and results of histologic examination were consistent with a diagnosis of habronemiasis. However, nematode larvae were seen in only 11 (44%) biopsy specimens. Treatment consisted of surgical removal (7 horses) or medical treatment (56) consisting of debulking granulation tissue and topical, intralesional, or systemic treatment with corticosteroids. All horses were treated with ivermectin. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cutaneous and ocular habronemiasis should be considered when examining a horse during the summer months with a proliferative, moist, granulomatous lesion. Treatment should be aimed at decreasing the size of the lesion, reducing inflammation, and preventing recurrence. In general, the prognosis was good, and healing occurred within a few weeks. Fly control and regular deworming with ivermectin are recommended to reduce the incidence of habronemiasis.

Age Distribution↗
PubMed2003

Bis-4-aminoquinolines: novel triple-helix DNA intercalators and antagonists of immunostimulatory CpG-oligodeoxynucleotides.

Six dimeric 2-(2-naphthyl)quinolin-4-amines with a linker between the amino groups and eight dimeric 2-(4-anilino)quinolin-4-amines linked between the anilino groups were synthesized and evaluated for their interaction with duplex/triplex DNA's and as antagonists of immunostimulatory oligodeoxynucleotides with a CpG-motif (CpG-ODN). The most powerful triple-helix DNA intercalator known to date, with high affinity toward T.A.T triplets and triplex/duplex selectivity, was found. The potent antagonism of immunostimulatory CpG-ODN by several bis-4-aminoquinolines is not related to their DNA interactions.

Adjuvants, Immunologic↗
PubMed2003

Sequence-specific minor groove binding by bis-benzimidazoles: water molecules in ligand recognition.

The binding of two symmetric bis-benzimidazole compounds, 2,2-bis-[4'-(3"-dimethylamino-1"-propyloxy)phenyl]-5,5-bi-1H-benzimidazole and its piperidinpropylphenyl analog, to the minor groove of DNA, have been studied by DNA footprinting, surface plasmon resonance (SPR) methods and molecular dynamics simulations in explicit solvent. The footprinting and SPR methods find that the former compound has enhanced affinity and selectivity for AT sequences in DNA. The molecular modeling studies have suggested that, due to the presence of the oxygen atom in each side chain of the former compound, a water molecule is immobilized and effectively bridges between side chain and DNA base edges via hydrogen bonding interactions. This additional contribution to ligand-DNA interactions would be expected to result in enhanced DNA affinity, as is observed.

Base Sequence↗
PubMed2003

Malignant Sertoli cell tumor in the retained abdominal testis of a unilaterally cryptorchid horse.

A 13-year-old Morgan gelding was evaluated because of a mass in the caudal region of the abdomen. The horse had been presumed to be a gelding, but necropsy findings revealed a retained testis in the right retroperitoneal space. Histologically, the retained testis contained neoplastic cells; metastases were identified in the liver, spleen, lungs, and sublumbar lymph nodes. Immunohistochemical examination of the testis and metastatic tissues confirmed the diagnosis of malignant Sertoli cell tumor. Testicular neoplasms are infrequently reported in stallions. Seminomas are most commonly reported, whereas Sertoli cell tumors are considered to be rare. Typical biological behavior of Sertoli cell tumors in horses is unknown. To the authors' knowledge, there have been 2 reports of Sertoli cell tumors in horses; the tumors developed in descended testes, and 1 tumor was malignant.

Animals↗
PubMed2002

Distribution of furamidine analogues in tumor cells: targeting of the nucleus or mitochondria depending on the amidine substitution.

Diphenylfuran diamidines represent an important class of DNA minor groove binders of high therapeutic interest as antiparasitic or antitumor agents depending on the compounds structures. To exert their cytotoxic action, the compounds must first get into the cell and reach the nuclear compartment where the main target, DNA, is located. The forces that drive the drugs into cell nuclei, as well as the influence of the molecular structures on the cell distribution, are not known. To address these issues, we took advantage of the fluorescence of the molecules to analyze their intracellular distribution profiles in tumor cells of different origins (B16 melanoma, MCF7 mammary adenocarcinoma, A549 lung carcinoma, HT29 colon carcinoma, LNCaP, and PC3 prostatic carcinoma) by epifluorescence and confocal microscopy. A homogeneous series of synthetic bis-substituted alkyl or phenyl amidine and reverse amidine derivatives of furamidine was used to dissect the molecular mechanisms that control the distribution of the drugs into the cytoplasm or the nucleus of the cells. The amidine (DB75) and the various N-alkyl derivatives were found to accumulate selectively in the cell nuclei. This is also the case for a guanidine derivative but not for the phenyl-substituted compound DB569, which essentially localizes in cytoplasmic granules. Similar cytoplasmic patterns were observed with a reverse amidine analogue and a pyridine-substituted compound indicating that the presence of aromatic rings on the terminal side chain is the limiting factor that restricts the uptake of the compounds in the nuclear compartment. The use of different organelle-selective fluorescent probes, such as JC-1 and chloromethyl-X-rosamine, both specific to mitochondria and neutral red considered as a lysosome-selective probe, suggests that DB569 preferentially accumulates in mitochondria. Competition experiments with the antitumor drug daunomycin reveal that the diphenylfurans are attracted into the nuclei by the DNA. The DNA minor groove-drug interactions provide the driving force that permits massive accumulation of the fluorescent molecules in the nuclei. The DNA binding properties of the diphenylfuran derivatives were investigated by DNase I footprinting and surface plasmon resonance biosensor experiments to measure sequence selectivity and binding affinities, respectively. Furamidine and its phenyl-substituted analogue that accumulate in the cell nuclei and mitochondria, respectively, share a common selectivity for AT sites and bind equally tightly to these sites. Therefore, it is possible to modulate the intracellular distribution of the furamidine derivatives without affecting their DNA binding and sequence recognition properties. The introduction of aromatic substituents on diphenylfuran diamidines represents a novel strategy to control the intracellular compartmentalization of these DNA binding agents and directs them to mitochondria. This drug design strategy may prove useful to trigger drug-induced apoptosis.

Adenocarcinoma↗
PubMed2002

Tight binding of the antitumor drug ditercalinium to quadruplex DNA.

The structural selectivity of the DNA-binding antitumor drug ditercalinium was investigated by competition dialysis with a series of nineteen different DNA substrates. The 7H-pyridocarbazole dimer was found to bind to double-stranded DNA with a preference for GC-rich species but can in addition form stable complexes with triplex and quadruplex structures. The preferential interaction of the drug with four-stranded DNA structures was independently confirmed by electrospray mass spectrometry and a detailed analysis of the binding reaction was performed by surface plasmon resonance (SPR) spectroscopy. The BIAcore SPR study showed that the kinetic parameters for the interaction of ditercalinium with the human telomeric quadruplex sequence are comparable to those measured with a duplex sequence. Slow association and dissociation were observed with both the quadruplex and duplex structures. The newly discovered preferential binding of ditercalinium to the antiparallel quadruplex sequence d(AG(3)[T(2)AG(3)](3)) provides new perspectives for the design of drugs that can bind to human telomeres.

Antineoplastic Agents↗