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Biomedical subjects

D C Williams

Publications and source records attributed to D C Williams.

At least 73 records · Page 4Linked to original sources
PubMed1995

On-line fluorescence lifetime determinations in capillary electrophoresis.

A near-infrared time-correlated single-photon counting instrument was developed for on-line fluorescence lifetime determinations of components separated by capillary electrophoresis (CE). The lifetimes of the migrating components were determined using maximum likelihood estimators, which are computationally easy to perform and yield values with high precision and favorable accuracies in the limit of low photocounts within the decay profile. The laser source used in the present system was a passively mode-locked Ti-sapphire laser with a single-photon avalanche diode serving as the fast detector. The instrument response function of this system was determined to be 165 ps (fwhm). Electrophorectic separation of two near-IR dyes, DTTCI (cationic) and IR-125 (anionic), in a 95:5 methanol/water running buffer (pH = 9.5) produced electrophoretic peak widths at the base of approximately 1 -9 s, which set the integration time for collection of the decay profiles. At a loading level of 1.42 zmol for IR-125 and 49 zmol for DTTCI, lifetime values were determined to be 482 +/- 14 ps for IR-125 and 943 +/- 23 ps for DTTCI, which agreed favorably with the lifetimes determined for these dyes using static measurements at high concentrations. To minimize background resulting from scattered photons in ultradilute conditions, which introduces bias into the lifetime determination, the calculation was initiated at a fixed time delay with respect to the excitation pulse. To demonstrate the feasibility of making lifetime determinations in capillary gel electrophoresis, where the gel can produce high scattering backgrounds, the lifetimes of C-terminated fragments produced from the M13mp 18 template and labeled at the 5' end of a universal M13 sequencing primer with a near-IR fluorescent tag were determined. The collection of lifetimes for 30 different peaks in the electropherogram yielded a mean value of 581 ps and a standard deviation of +/- 9 ps.

Electrophoresis, Capillary↗
PubMed1995

Ultrasensitive near-IR fluorescence detection for capillary gel electrophoresis and DNA sequencing applications.

Electropherograms of oligonucleotides labeled with near-IR fluorescent dyes, separated by capillary gel electrophoresis and detected using an ultrasensitive near-IR fluorescence detection system, are presented. A universal M13 sequencing primer was labeled on the 5' end with a near-IR dye containing an isothiocyanate functional group. Comparison of the on-column detection limits in capillary gel electrophoresis for the near-IR dye-labeled sequencing primer to those obtained for a visible fluorescein-labeled primer indicated improved sensitivity for the near-IR case. The detection limit was found to be 3.4 x 10(-20) mol (SNR = 3) for the near-IR dye-labeled primer, while the on-column detection limit for the fluorescein analog was 1.5 x 10(-18) mol (SNR = 3). The sequence of nucleotide bases in an M13mp18 template was determined using a single lane, single dye technique. The molar concentrations of the ddNTPs used during chain extension reactions were varied to achieve a ratio of 4:2:1:0 (A:C:G:T), which allowed the identification of each terminal base via fluorescence intensity measurements. Sequencing ladders were prepared from the M13mp18 template using standard Sanger dideoxy chain-terminating techniques, the modified T7 DNA polymerase, and the near-IR dye-labeled M13 universal primer. The data indicated reliable sequence determination by the 4:2:1:0 (A:C:G:T) peak height identification method up to 250 bases from the annealing site. Comparison of the known sequence of the M13mp18 plasmid to that obtained using this protocol yielded a base-calling accuracy of 84% for the 4:2:1:0 ratio.

Base Sequence↗
PubMed1995

PK 11195 reduces the brain availability of lindane in rats and the convulsions induced by this neurotoxic agent.

The effect of pretreatment with PK 11195, a ligand of the 'peripheral-type' benzodiazepine receptor (PBR), on convulsions induced by lindane (gamma-hexachlorocyclohexane, gamma-HCH) in rats was examined, to determine whether the mechanism of this convulsant activity may be mediated through the PBR. PK 11195 elicited a protective effect against the convulsant activity of orally administered lindane. It reduced the frequency of animals exhibiting convulsions and delayed the time to onset of these seizures. The concentration of lindane in the brain was found to be significantly lower in PK 11195 pretreated rats and a high correlation between blood and brain lindane concentrations was obtained. When similar experiments were repeated with alpha-HCH, a non-convulsant isomer of HCH, brain and blood concentrations were again found to be significantly reduced in PK 11195 pretreated animals. We conclude that the 'anticonvulsant' action of PK 11195 was not due to an interaction of PK 11195 and lindane on common CNS target sites, but by an action of PK 11195 on the gastrointestinal tract of the animal, delaying the absorption of lindane into the bloodstream.

Animals↗
PubMed1995

Survey of container-inhabiting mosquitoes in Clemson, South Carolina, with emphasis on Aedes albopictus.

A total of 530 oviposition trap samples were collected within a 10-km radius of Clemson University between March 30 and October 19, 1993. From 19,664 larvae reared from collected eggs, 7 species were identified: Aedes albopictus (89%), Ae. triseriatus (6.5%), Culex restuans (2.7%), Cx. territans (0.6%), Cx. pipiens complex (0.7%), Toxorhynchites rutilus septentrionalis (0.2%), and Orthopodomyia signifera (0.1%). This is the first record of Ae. albopictus in Clemson. Aedes aegypti was not found. Of the 41 ovitrap locations, 100% were positive for Ae. albopictus.

Aedes↗
PubMed1994

Activation of NF-kappa B and induction of vascular cell adhesion molecule-1 and intracellular adhesion molecule-1 expression in human glial cells by IL-1. Modulation by antioxidants.

The infiltration of leukocytes into the central nervous system is associated with many pathologic conditions of the brain. The mechanisms by which these immune cells can penetrate the blood-brain barrier and remain within the brain are not understood. However, elevated brain levels of the pro-inflammatory cytokine IL-1 appear to accompany pathogenesis. The present study provides the first evidence that IL-1 can induce the expression of adhesion molecules for leukocytes on glial cells and suggests a role for the transcription factor NF-kappa B in the induction process. Human rIL-1 alpha was found to induce the expression of the cell adhesion molecules, vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) but not E-selectin in human 1321N1 astrocytoma. Both VCAM-1 and ICAM-1 were detectable from 3 h and remained sustained for up to 72 h. Induction was inhibited by the IL-1 receptor antagonist. IL-1 alpha was also shown to induce the expression of VCAM-1 and ICAM-1 in a receptor-dependent fashion in human A172 glioblastoma. Activation of the transcription factor NF-kappa B was also observed in 1321N1 astrocytoma in response to IL-1 alpha treatment and was similarly abolished by pretreatment of cells with antagonist. Activated NF-kappa B was apparent from 20 min and remained for up to 24 h. N-acetylcysteine (NAC) and pyrollidinedithiocarbamate (PDTC), which were shown to inhibit activation of NF-kappa B in Jurkat E6.1 lymphoblasts and EL4.NOB-1 thymoma, failed to block IL-1 activation of NF-kappa B in 1321N1 astrocytoma. However, both of these antioxidants demonstrated complex modulatory effects on the induction of cell adhesion molecule expression by IL-1. The induction of VCAM-1 but not of ICAM-1 proved susceptible to inhibition by both PDTC and NAC. The expression of adhesion molecules for leukocytes on glial cells in response to IL-1 may represent an important mechanism for retention of immune cells in the central nervous system that may be a prologue to inflammatory conditions in the brain.

Antioxidants↗
PubMed1994

The peripheral-type benzodiazepine receptor is present in astrocytes but is not a primary site of action for convulsants/anticonvulsants.

High-affinity binding sites for [3H]PK 11195 and [3H]Ro 5-4864 with the properties of the peripheral-type benzodiazepine receptor were detected in primary cultures of both mouse neocortical and cerebellar astrocytes. The binding sites were enriched in mitochondrial fractions on differential centrifugation. An 18-kDa polypeptide was specifically photolabelled in cerebellar astrocytes by [3H]PK 14105, a photolabel for the peripheral-type benzodiazepine receptor. However, this polypeptide did not show any reactivity with an antiserum previously raised against the corresponding polypeptide from rat adrenal gland. Various anticonvulsant and convulsant agents were tested for their ability and potency at inhibiting [3H]Ro 5-4864 binding to neocortical astrocytes. Many of these compounds previously reported to be inhibitors of diazepam binding to neocortical astrocytes, proved ineffective in this study. No correlation was observed between convulsant/anticonvulsant potency and ability to inhibit [3H]Ro 5-4864 binding to the peripheral-type benzodiazepine receptor in these cells. Thus, whereas some convulsants and anticonvulsants might interact with this astrocytic receptor, such a system has no validity as a general screening method for these agents.

Animals↗
PubMed1994

Raloxifene (LY139481 HCI) prevents bone loss and reduces serum cholesterol without causing uterine hypertrophy in ovariectomized rats.

There is a medical need for an agent with the positive effects of estrogen on bone and the cardiovascular system, but without the negative effects on reproductive tissue. Raloxifene (LY139481 HCI) is a benzothiophene derivative that binds to the estrogen receptor and inhibits the effects of estrogen on the uterus. In an ovariectomized (OVX) rat model we investigated the effects of raloxifene on bone loss (induced by estrogen deficiency), serum lipids, and uterine tissue. After oral administration of raloxifene for 5 wk (0.1-10 mg/kg per d) to OVX rats, bone mineral density in the distal femur and proximal tibia was significantly greater than that observed in OVX controls (ED50 of 0.03-0.3 mg/kg). Serum cholesterol was lower in the raloxifene-treated animals, which had a minimal effective dose of 0.1 mg/kg and an approximate oral ED50 of 0.2 mg/kg. The effects of raloxifene on bone and serum cholesterol were comparable to those of a 0.1-mg/kg per d oral dose of ethynyl estradiol. Raloxifene diverged dramatically from estrogen in its lack of significant estrogenic effects on uterine tissue. Ethynyl estradiol produced a marked elevation in a number of uterine histologic parameters (e.g., epithelial cell height, stromal eosinophilia). These data suggest that raloxifene has promise as an agent with beneficial bone and cardiovascular effects in the absence of significant uterine effects.

Administration, Oral↗
PubMed1994

Emergency control of Aedes aegypti in the Dominican Republic using the Scorpion 20 ULV forced-air generator.

In an effort to develop a more effective measure for use in emergency control of the dengue vector Aedes aegypti. applications of a combination of a larvicide (Bacillus thuringiensis israelensis [B.t.i.]) and an adulticide (permethrin) were made using a truck-mounted forced-air generator (Scorpion 20) and evaluated in the Dominican Republic. This method has the potential to simultaneously control adults and larvae. In bioassay cages placed in household water containers at the time of application, larval mortalities were 95.1 and 100% for 2 application rates of permethrin mixed with B.t.i. Adult mortalities were not as impressive, probably because of resistance to permethrin. Higher adult mortality in caged specimens (78.5%) and a substantial reduction in the natural population (68.4%) of Ae. aegypti were obtained following a 2.1-g AI/ha application of deltamethrin alone.

Aedes↗
PubMed1994

Malathion resistance in mosquitoes from Charleston and Georgetown counties of coastal South Carolina.

Susceptibility tests were conducted using the World Health Organization diagnostic test procedure on strains of Aedes taeniorhynchus, Aedes sollicitans, Aedes vexans, and Culex nigripalpus collected from several localities in Charleston and Georgetown counties of South Carolina. Aedes taeniorhynchus was resistant to malathion (mortality 1.0-54.4%) but not to propoxur, permethrin, or fenitrothion. There also were indications that Ae. sollicitans and Cx. nigripalpus were resistant to malathion, but to a lesser extent than Ae. taeniorhynchus (mortalities: 72.1-81.0%, and 46.2%, respectively). Aedes vexans was susceptible to malathion (mortality 98.6%). In field tests using ULV application of malathion and field-collected Ae. taeniorhynchus, and susceptible Ae. aegypti and Ae. taeniorhynchus, a noticeably lower mortality also was obtained in the wild mosquitoes.

Aedes↗
PubMed1993

Interleukin-1 and phorbol myristate acetate modulate the peripheral-type benzodiazepine receptor in lymphocytes and glial cells.

High affinity "peripheral-type" benzodiazepine binding sites were detected in an interleukin-1 (IL-1) responsive murine thymoma cell line EL4.NOB-1. Exposure of these cells to IL-1 over a period of at least 24 hr resulted in down-regulation of the binding sites. This effect was inhibited by the IL-1 receptor antagonist (IL-1RA) which in these cells inhibits IL-1 binding to the type I IL-1 receptor. Phorbol myristate acetate (PMA), another activator of EL4.NOB-1 cells, had an opposite effect to IL-1 in that it increased binding site expression dramatically suggesting different mechanisms of action for these two effectors. IL-1 produced a similar response in the rat glioma cell line C6 whereas PMA was ineffective. Such modulation of the peripheral-type benzodiazepine receptor may provide an insight into its physiological role and its possible participation in IL-1 actions in different cells.

Animals↗
PubMed1993

Interleukin-1 activates transcription factor NF kappa B in glial cells.

Recombinant human interleukin-1 (IL-1) alpha and beta were found to activate a latent cytosolic form of the transcription factor NF kappa B in rat C6 glioma. IL-1 beta was 10 times more potent than IL-1 alpha for this activity and both were inhibited by the IL-1 receptor antagonist. The activation was detectable from 20 min and remained sustained for up to 24 h. The electrophoretic mobility of the activated complex was shown to be different from that of the corresponding complexes in another IL-1-responsive cell line, the murine thymoma line EL4.NOB-1. C6 cells, when transiently transfected with five NF kappa B consensus sequence repeats linked to the reporter gene chloramphenicol acetyltransferase (CAT), demonstrated increased CAT activity in response to IL-1 beta treatment. The activation of NF kappa B in glial cells may thus represent an early step in IL-1 signalling in brain and is likely to have consequences for IL-1-induced gene expression in these cells.

Animals↗
PubMed1993

Barrier spraying to control the malaria vector Anopheles albimanus: laboratory and field evaluation in the Dominican Republic.

To develop a new strategy for control of exophilic/exophagic malaria vectors which rest on peridomestic foliage, Anopheles albimanus was used for laboratory bioassays of mosquito adulticides applied to various vegetation types. Of the three classes of insecticide tested, the pyrethroid (permethrin at 112 g/ha) showed greater foliar persistence than either the carbamate (bendiocarb at 340 g/ha) or the organophosphorus compound (malathion at 277 g/ha). Field evaluation of barrier spraying against An.albimanus was evaluated in rural villages of southwest Dominican Republic during 1989. The pyrethroid deltamethrin was sprayed aerially for ultra-low volume application at treatment rates of 17-19 g a.i./ha in a radius of 500 m around two villages. An.albimanus were monitored by light-traps and human bait collections at both treated villages, compared with two similar untreated villages, up to 9 nights posttreatment. Densities of female An.albimanus were significantly reduced in the sprayed villages for at least 8 or 9 nights. Further evaluation of barrier spraying is recommended to determine optimal pyrethroid formulations and applications rates, their impact on non-target fauna and efficacy against malaria transmission.

Analysis of Variance↗