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Biomedical subjects

D B Taylor

Publications and source records attributed to D B Taylor.

At least 19 recordsLinked to original sources
PubMed1999

Genetic variation in geographical populations of western and Mexican corn rootworm.

Genetic variation in the nuclear rDNA ITS1 region of western corn rootworm, Diabrotica virgifera virgifera (WCR), and Mexican corn rootworm, D. v. zeae (MCR) was studied. Two sites were detected which differentiated WCR and MCR in the 642-base sequence. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the first internal transcribed spacer region (ITS1) sequence revealed no variation within or among the twelve WCR and two MCR populations. PCR-RFLP of 75% of the mitochondrial DNA genome detected one significant polymorphic site out of the approximately 190 restriction sizes observed in WCR. The polymorphism did not differentiate geographical populations of WCR and is not diagnostic for the subspecies. The low levels of variation observed in WCR suggests either high levels of gene flow or a recent geographical expansion from a relatively small base. Gene flow would facilitate the rapid spread of traits that could compromise control programmes, such as insecticide resistance or behavioural modifications. The minimal genetic differentiation between WCR and MCR raises questions about the evolutionary history of these subspecies and how the distinct phenotypes are maintained.

Animals↗
PubMed1999

Genetic similarity among pheromone and voltinism races of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae).

The genetic variability of seven European corn borer populations, Ostrinia nubilalis, from North America and Europe was assessed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis and DNA sequencing. The nuclear ribosomal internal transcribed spacer 1 (ITS-1) region (approximately 500 base pair [bp]) and four mitochondrial (mtDNA) regions (1550 bp total) were examined. The smartweed borer, Ostrinia obumbratalis, and south-Western corn borer, Diatraea grandiosella, were used for comparisons. Of 106 restriction sites identified (80 in mtDNA and 26 in ITS-1), none differentiated geographical populations, pheromone races, or voltine ecotypes of the European corn borer. The lack of variation in the ITS-1 of European corn borer was confirmed by DNA sequence analysis. The genetic similarity of European corn borer populations, despite their wide geographical range and physiological differences, may be explained by a relatively recent origin for the voltinism and pheromone races, gene flow among races, and/or expansion from genetic bottlenecks.

Animals↗
PubMed1997

The peptide LSARLAF causes platelet secretion and aggregation by directly activating the integrin alphaIIbbeta3.

A novel peptide (designed to bind to alphaIIbbeta3) caused platelet aggregation and aggregation-independent secretion of the contents of alpha-granules in an alphaIIbbeta3-dependent fashion. The agonist peptide induced secretion in the presence of prostaglandin E1. In cell-free assays, alphaIIbbeta3 bound specifically to immobilized agonist peptide and the peptide enhanced the binding of fibrinogen to immobilized alphaIIbbeta3. The agonist peptide apparently activates alphaIIbbeta3 by directly inducing a conformational change in the receptor. This change activates the platelets and causes secretion in a manner independent of fibrinogen binding.

Animals↗
PubMed1996

Variabilin, a novel RGD-containing antagonist of glycoprotein IIb-IIIa and platelet aggregation inhibitor from the hard tick Dermacentor variabilis.

A novel inhibitor of human platelet aggregation, named variabilin, was isolated from salivary glands of the hard tick Dermacentor variabilis using a combination of gel filtration and high pressure liquid chromatography. Variabilin was a potent antagonist of the fibrinogen receptor glycoprotein IIb-IIIa (GPIIb-IIIa; alphaIIbbeta3) and the vitronectin receptor alphavbeta3. Amino acid sequence analysis by Edman degradation revealed that it has 47 residues, with a molecular weight of 4968.5. Like many other naturally occurring antagonists of GPIIb-IIIa, variabilin contains the RGD (Arg-Gly-Asp) motif. However, unlike the RGD-containing antagonists of GPIIb-IIIa, the RGD sequence of variabilin is not positioned in a loop bracketed by cysteine residues. It has little sequence homology to the other known naturally occurring antagonists of GPIIb-IIIa, including the disintegrins from snakes, decorsin and ornatin from leeches, and disagregin from soft ticks. Variabilin is the first RGD-containing antagonist isolated from ticks.

Amino Acid Sequence↗
PubMed1996

Population genetics and gene variation in screwworms (Diptera: Calliphoridae) from Brazil.

Allozyme variation in New World screwworm, Cochliomyia hominivorax (Coquerel), populations from Brazil was examined. Variability was observed in 8 of 13 enzyme loci and the frequency of the most common allele was < 0.95 for seven loci. Observed and expected heterozygosities were 0.159 and 0.165, respectively. Comparisons of the Brazilian populations with previously studied populations from Costa Rica resulted in Nei's genetic distances of between 0.000 and 0.006, with the greatest distance being between populations within Brazil. Comparisons with Mexican populations using only three loci resulted in genetic distances < or = 0.031. Goodness-of-fit statistics for Hardy-Weinberg equilibrium and Wright's F statistics indicated small deviations from expected equilibrium genotype frequencies and low levels of differentiation between populations within Brazil. Differentiation among screwworm populations from Brazil, Costa Rica, and Mexico was minimal.

Alleles↗
PubMed1996

Population genetics and gene variation of stable fly populations (Diptera:Muscidae) in Nebraska.

Genetic variation in stable fly, Stomoxys calcitrans (L.), populations from Nebraska, Canada, and Texas was sampled. Four of 12 allozyme loci were polymorphic, with an average of 1.7 alleles per locus. Observed and expected heterozygosities were 0.086 and 0.070, respectively. Nei's genetic distance between populations averaged 0.001 and ranged from 0.000 to 0.005. Wright's F statistics revealed greater variation within than among populations. Allele frequencies were homogeneous among temporal samples from a single population. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of 6.4 kb of the mitochondrial DNA genome with 16 restriction enzymes revealed no variation in stable fly populations from Canada, Nebraska, and Texas. PCR-RFLP analysis of a 2.0-kb fragment of the nuclear ribosomal DNA internally transcribed spacer region also revealed no variation. The lack of genetic differentiation among stable fly populations indicates high levels of gene flow among populations. The low levels of variation observed with biochemical and molecular techniques are consistent with a genetic bottleneck during stable fly colonization of North America.

Animals↗
PubMed1996

Identification of screwworm species by polymerase chain reaction-restriction fragment length polymorphism.

Restriction fragment length polymorphisms in polymerase chain reaction amplified fragments (PCR-RFLP) of mitochondrial DNA were used to differentiate species of New World screwworms (Diptera: Calliphoridae). Twenty-seven restriction enzymes were screened on five regions of mtDNA. Eleven restriction fragment length patterns differentiated New World screwworm, Cochliomyia hominivorax (Coquerel), from secondary screwworm, Cochliomyia macellaria (F.). Five restriction fragment length patterns were polymorphic in C.hominivorax while all fragment patterns were fixed in C.macellaria. Diagnostic restriction fragment length patterns were used for species diagnosis, whereas intraspecific variable patterns were used to characterize field samples and laboratory strains. The PCR-RFLP technique is flexible with regard to developmental stage of the sample and method of preservation. We were able to characterize specimens of all life stages from egg to adult including larvae preserved in alcohol and pinned adults. PCR-RFLP is rapid and inexpensive, enabling specimens to be characterized within 24 h for less than $2.50.

Animals↗
PubMed1996

Mitochondrial DNA variation in screwworm.

Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was used to characterize mitochondrial DNA (mtDNA) variation in screwworms, Cochliomyia hominivorax, and secondary screwworm, C.macellaria, from the Caribbean, North America and South America. Four amplicons, totaling 7.1 kb, were analysed with sixteen restriction enzymes. A total of 133 restriction sites was observed in the two species, 104 in C.hominivorax, of which nineteen were variable, and ninety-five in C.macellaria, none of which was variable. Fourteen mtDNA haplotypes were observed among eighteen C.hominivorax examined. Mean divergence between C.hominivorax haplotypes (d) was 0.0064 substitutions per base-pair and genotypic diversity (G) was 0.97. Mean divergence between C.hominivorax and C.macellaria was 0.0824. Cochliomyia hominivorax haplotypes could be divided into three assemblages representing North America, South America and Jamaica, based on UPGMA clustering with d values. The assemblages did not exhibit complete geographic fidelity. These data were discordant with previously published allozyme data indicating little differentiation between screwworm populations. A scenario invoking historically isolated populations coming into contact with the introduction and movement of European livestock is proposed to explain the observed population structure of screwworm.

Animals↗
PubMed1995

Fibronectin peptide DRVPHSRNSIT and fibronectin receptor peptide DLYYLMDL arrest gastrulation of Rana pipiens.

Gastrulation is characterized by dramatic cell migration which is thought to require the interaction of cell adhesion molecules with extracellular molecules. We have tested two novel peptides, a fibronectin peptide and a fibronectin receptor peptide, for their effects on gastrulation of the leopard frog Rana pipiens. The fibronectin peptide DRVPHSRNSIT corresponds to residues 1373-1383 of the cell-binding domain of fibronectin; the receptor peptide DLYYLMDL corresponds to residues 124-131 of beta 1 subunit of a variety of integrins including alpha 5 beta 1. Either of these peptides significantly inhibited gastrulation after being microinjected into mid-blastulae. These results indicate that these sequences may correspond to the ligand/receptor interaction sites of fibronectin and its receptor(s).

Amino Acid Sequence↗
PubMed1994

Complementary peptides that interfere with platelet aggregation and adherence.

This article describes the application of the molecular recognition hypothesis to the critically important process of fibrinogen binding to platelets, a process that is the subject of extensive and intensive basic and clinical research. The objectives of the studies summarized below were to design, synthesize, and characterize peptides that can inhibit the binding of fibrinogen and related ligands to human platelets and thereby prevent platelet aggregation, adhesion, and clot retraction. The purpose of doing this work was twofold: first, to determine whether the molecular recognition hypothesis could serve as a useful rationale for the design of peptides that can specifically inhibit the binding of fibrinogen and related ligands to platelets; and second, to use these peptides to try to learn where fibrinogen binds to the platelet fibrinogen receptor. It was hoped that the results obtained not only would provide insight into platelet function but also might provide a rationale for the design of a clinically useful anti-thrombotic agent. Although our studies are not complete, they have resulted in the design of a variety of peptides that can inhibit platelet aggregation, adhesion, and clot retraction as a consequence of specifically inhibiting the binding of fibrinogen and related ligands to the platelet fibrinogen receptor. Although none of these peptides appears to be ligand specific, one or two of them may be specific for platelets.

Amino Acid Sequence↗
PubMed1994

Carcinoma of the breast with sarcomatous metaplasia.

Carcinoma of the breast with sarcomatous metaplasia (CSM) is a rare and interesting tumour with a poorer prognosis than the usual breast malignancies. The mammographic appearances of this lesion have only previously been described once in the literature. A case of CSM is presented with mammographic-pathological correlation and review of the literature.

Breast Neoplasms↗
PubMed1994

Antibodies to GPIIb alpha (300-312) inhibit Fg binding, clot retraction, and platelet adhesion to multiple ligands.

We previously reported that a peptide with the sequence Gly-Ala-Pro-Leu (GAPL) found as residues 309-312 in glycoprotein IIb alpha (GPIIb) comprises at least part of a Fg binding site on GPIIb (1). Subsequent studies demonstrated that a peptide corresponding to residues 300-312 of GPIIb alpha can bind to Fg and Vn, and is a potent inhibitor of platelet aggregation and the adhesion of activated platelets to at least four adhesive ligands: Fg, Fn, Vn, and vWf (2). Here, the production and initial characterization of polyclonal antibodies against this peptide are described. ELISAs and dot-blot assays reveal the specificity of the antibodies for the peptide immunogen. In immunoblots, the antibodies recognize GPIIb under reducing conditions. The binding of Fg to immobilized GPIIb/IIIa, the rate of clot retraction and the adhesion of stimulated platelets to Fg, fibronectin (Fn), vitronectin (Vn), and von Willebrand factor (vWf) were inhibited by these antibodies, but not by a control IgG. These results together with our earlier published data indicate that GPIIb alpha (300-312) comprises at least part of a common ligand binding site within the integrin alpha IIb subunit.

Amino Acid Sequence↗
PubMed1993

Characterization of adhesion of "resting" and stimulated platelets to fibrinogen and its fragments.

Adhesion of resting and stimulated platelets to immobilized fibrinogen (Fg) was characterized using various forms of Fg, receptor peptide mimics, and antibodies to glycoprotein (GP) IIb/IIIa and Fg. Resting platelets adhered to Fg, but to less than half the extent of the same platelets stimulated with epinephrine/ADP. The adhesion of resting and stimulated platelets to Fg was inhibited by a receptor peptide mimic (G13, a peptide corresponding to residues 300-312 of GPIIb), anti-GPIIb/IIIa antibodies, and a monoclonal antibody (4A5) against the carboxyl terminus of the gamma chain of Fg. The results presented here demonstrate that the alpha chain RGD platelet recognition sites are not required to mediate the adhesion of either stimulated or resting platelets to immobilized Fg. Although stimulated platelets can adhere extensively to monomeric Fg containing one functional gamma chain, resting platelets require bivalent Fg containing two functional gamma chains to mediate irreversible adhesion to Fg.

Amino Acid Sequence↗
PubMed1992

A peptide corresponding to GPIIb alpha 300-312, a presumptive fibrinogen gamma-chain binding site on the platelet integrin GPIIb/IIIa, inhibits the adhesion of platelets to at least four adhesive ligands.

The platelet fibrinogen (Fg) receptor (GPIIb/IIIa) is an integrin which plays a critical role in hemostasis by recognizing at least the four adhesive ligands: Fg, fibronectin (Fn), vitronectin (Vn), and von Willebrand factor (vWf). We reported that residues 309-312 of GPIIb alpha appear to comprise at least part of a Fg binding site on the Fg receptor (Gartner, T. K., and Taylor, D. B. (1990) Thromb. Res. 60, 291-309). Here we report that the peptide GPIIb alpha 300-312 (G13) inhibits platelet aggregation and binds Fg and Vn. Significantly, this peptide inhibits the adhesion of stimulated platelets to Fg, Fn, Vn, and vWf, but not the adhesion of resting platelets to Fn. Thus, GPIIb 300-312 may constitute a specific but common recognition site on GPIIb/IIIa for both LGGAKQAGDV- and RGD-containing ligands.

Amino Acid Sequence↗
PubMed1991

The peptides APLHK, EHIPA and GAPL are hydropathically equivalent peptide mimics of a fibrinogen binding domain of glycoprotein IIb/IIIa.

The anticomplementarity hypothesis predicted that the peptides APLHK, EHIPA, GAPL and LGVPPR would be functional mimics of a fibrinogen binding domain(s) in the fibrinogen receptor. The peptides APLHK and EHIPA were derived by translation of the cRNA of vitronectin m-RNA. The peptides GAPL and LGVPPR result from translations of the cRNA of von Willebrand factor m-RNA. The peptides APLHK, EHIPA, and GAPL, but not LGVPPRT, are hydropathically equivalent and inhibit fibrinogen binding to platelets. APLHK and EHIPA are hydropathic retromers. Thus for one pair of these peptides, the direction of their backbones did not affect function.

Amino Acid Sequence↗
PubMed1991

Gelled diet for screwworm (Diptera: Calliphoridae) mass production.

A rearing system based on a diet gelled with Water-Lock G-400, a synthetic superabsorbent (poly(2-propenamide-co-2-propenoic acid, sodium salt)) (WL), was compared with the standard rearing system (liquid diet suspended in acetate fibers) for the mass production of screwworms, Cochliomyia hominivorax (Coquerel). The WL rearing system yielded 2% heavier pupae, 32% higher egg to pupa survival, and required 54% less diet and 88% less labor than the standard rearing system. Other advantages of the WL system include reduced susceptibility to suboptimal environmental conditions and labor practices and characteristics conducive to centralization and mechanization of rearing procedures.

Animals↗
PubMed1991

Reproductive compatibility and mitochondrial DNA restriction site analysis of New World screwworm, Cochliomyia hominivorax, from North Africa and Central America.

The reproductive compatibility of New World screwworms, Cochliomyia hominivorax (Coquerel), from North Africa and a strain being mass produced for the Mexican eradication programme was examined to assess the feasibility of using flies from the Mexican screwworm mass production facility for a sterile insect technique eradication programme in North Africa. Males from the production strain mated randomly with females from North Africa and from the production strain when both were present. Neither strain of males discriminated between cuticular extracts of North African and production strain females containing a contact sex pheromone. Interstrain crosses between North African flies and production flies were fertile and produced fertile progeny. Chromosome morphology did not differ significantly between the two strains and homologue pairing was normal in hybrid meiotic and polytene nuclei. Mitochondrial DNA restriction site analyses indicated that the genetic divergence of the North African strain from Mexican and Central American strains was within the range of the diversity observed in Central American, Mexican and Caribbean populations. Test results indicate that New World screwworms from North Africa are reproductively compatible with the strain currently being mass produced in Mexico. Mating barriers should not impede the progress of an eradication programme using the sterile insect technique in North Africa with sterile screwworms from the Mexican mass production facility.

Africa, Northern↗