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Biomedical subjects

A L Scott

Publications and source records attributed to A L Scott.

At least 19 recordsLinked to original sources
PubMed2005

Glufosinate herbicide-tolerant (LibertyLink) rice vs. conventional rice in diets for growing-finishing swine.

Genetically modified (GM) rice (LibertyLink, event LLRICE62) that is tolerant to glufosinate ammonium (Liberty) herbicide was compared with a near-isogenic (NI) conventional medium-grain brown rice (cultivar, Bengal) and a commercially milled long-grain brown rice in diets for growing-finishing pigs. The GM and NI rice were grown in 2000. The GM rice was from fields treated (GM+) or not treated (GM-) with glufosinate herbicide. The GM- and NI rice were grown using herbicide regimens typical of southern United States rice production practices. The four rice grains were similar in composition. Growing-finishing pigs (n = 96) were fed fortified rice-soybean meal diets containing the four different rice grains from 25 to 106 kg BW. Diets contained 0.99% lysine initially (growing phase), with lysine decreased to 0.80% (early finishing phase) and 0.65% (late finishing phase), when pigs reached 51 and 77 kg, respectively. The percentage of rice in the four diets was constant during each of the three phases (72.8, 80.0, and 85.8% for the growing, early-finishing, and late-finishing phases, respectively). There were six pen replicates (three pens of barrows and three pens of gilts) and four pigs per pen for each dietary treatment. All pigs were slaughtered at the termination of the study to collect carcass data. At the end of the 98-d experiment, BW gain, feed intake (as-fed basis), and feed:gain ratio did not differ (P > 0.05) for pigs fed the GM+ vs. conventional rice diets, but growth performance traits of pigs fed the GM+ rice diets were superior (P < 0.05) to those of pigs fed the GM- rice diet (ADG = 0.86, 0.79, 0.81, and 0.85 kg/d; ADFI = 2.41, 2.49, 2.37, and 2.45 kg/d; feed:gain = 2.80, 3.17, 2.95, and 2.89 for GM+, GM-, NI, and commercially milled rice, respectively). Carcass traits (adjusted for final BW) did not differ (P = 0.10) among treatments (hot carcass yield = 73.5, 72.6, 72.6, and 73.2%; 10th-rib backfat = 23.0, 22.7, 21.3, and 23.8 mm; LM area = 38.6, 38.0, 38.2, and 38.1 cm(2); carcass fat-free lean = 50.5, 50.5, 51.2, and 50.0%). Gilts grew slower (P < 0.05) and were leaner (P < 0.05) than barrows. Responses to type of rice did not differ between barrows and gilts, with no evidence of a diet x gender interaction (P = 0.50) for any trait. The results indicate that the glufosinate herbicide-tolerant rice was similar in composition and nutritional value to conventional rice for growing-finishing pigs.

Aminobutyrates↗
PubMed2002

Molecular characterization of a calcium binding translationally controlled tumor protein homologue from the filarial parasites Brugia malayi and Wuchereria bancrofti.

We have cloned homologues of the mammalian translationally controlled tumor protein (TCTP) from the human filarial parasites Wuchereria bancrofti and Brugia malayi. TCTP genes from B. malayi and W. bancrofti were expressed in a T7 promoter vector as histidine tagged fusion proteins. Both the recombinant B. malayi TCTP (rBm-TCTP) and recombinant W. bancrofti TCTP (rWb-TCTP) have a molecular mass of approximately 28 kDa with the histidine tag. Sequence analyses showed that there is a 98% similarity between the two filarial TCTPs at amino acid levels and are immunologically cross-reactive. Analysis of soluble proteins from various lifecycle stages of B. malayi suggested that the expression of Bm-TCTP might be differentially regulated and occurs in multimeric form. Recombinant TCTP were found to form multimers in solution under non-reducing conditions. The tendency for filarial TCTPs to become multimers was predicted by the presence of the Lupas coiled coil structure in their sequence. Despite the absence of a signal sequence, Bm-TCTP is present abundantly in the excretory/secretions (ES) of microfilariae. Characterization studies showed that both Bm- and Wb-TCTPs are calcium-binding proteins and have histamine-releasing function in vitro. When injected intraperitoneally both the filarial TCTPs induced inflammatory infiltration of eosinophils into the peritoneal cavity of mice suggesting that the filarial TCTPs may have a role in the allergic inflammatory responses associated with filarial infections.

Amino Acid Sequence↗
PubMed2001

Macrophage migration inhibitory factor (mif) transcription is significantly elevated in Caenorhabditis elegans dauer larvae.

Macrophage migration inhibitory factor (MIF) from vertebrate species is a molecule that exerts a wide-range of effects in inflammatory responses, cell activation and cell differentiation. Several species of parasitic nematodes have been shown to express genes encoding orthologues of the mammalian MIF that appear to play a key role in immune evasion by modifying the activity of host cells. In addition, MIF accumulates in nematode somatic cells where its role has not yet been defined. In order to identify the role that MIF plays in the cell biology of nematodes, we have characterized the members of the mif gene family in the free-living species Caenorhabditis elegans. Unlike the single mif gene found in humans and mice, C. elegans expresses four distinct mif genes: Ce-mif-1, Ce-mif-2, Ce-mif-3 and Ce-mif-4. The Ce-MIF proteins are between 15-30% identical to each other, 34-38% identical to the MIFs from the parasitic nematode Brugia malayi, and 22-35% identical to mammalian MIFs. The transcription of Ce-mif-2 and Ce-mif-3, but not Ce-mif-1, was upregulated >100-fold compared to L2 levels when the worms entered the dauer stage. The transcription levels of Ce-mif-2 and Ce-mif-3 fell to near baseline a few hours after exit from dauer. Ce-MIF/GFP transgenic animals and immunostaining were used to demonstrate that the main sites of MIF production are in the hypodermis, body wall muscles and in the nuclei of developing embryos. The results suggest a role for C. elegans MIF in cellular maintenance during periods of adverse conditions that lead to developmental arrest.

Amino Acid Sequence↗
PubMed2001

Immunological genomics of Brugia malayi: filarial genes implicated in immune evasion and protective immunity.

Filarial nematodes are metazoan parasites with genome sizes of> 100 million base pairs, probably encoding 15 000-20 000 genes. Within this considerable gene complement, it seems likely that filariae have evolved a spectrum of immune evasion products which underpin their ability to live for many years within the human host. Moreover, no suitable vaccine currently exists for human filarial diseases, and few markers have yet been established for diagnostic use. In this review, we bring together biochemical and immunological data on prominent filarial proteins with the exciting new information provided by the Filarial Genome Project's expressed sequence tag (EST) database. In this discussion, we focus on those genes with the highest immunological profile, such as inhibitors of host enzymes, cytokine homologues and stage-specific surface proteins, as well as products associated with the mosquito-borne infective larva which offer the best opportunity for an anti-filarial vaccine. These gene products provide a fascinating glimpse of the molecular repertoire which helminth parasites have evolved to manipulate and evade the mammalian immune response.

Animals↗
PubMed2000

The filarial genome project: analysis of the nuclear, mitochondrial and endosymbiont genomes of Brugia malayi.

The Filarial Genome Project (FGP) was initiated in 1994 under the auspices of the World Health Organisation. Brugia malayi was chosen as the model organism due to the availability of all life cycle stages for the construction of cDNA libraries. To date, over 20000 cDNA clones have been partially sequenced and submitted to the EST database (dbEST). These ESTs define approximately 7000 new Brugia genes. Analysis of the EST dataset provides useful information on the expression pattern of the most abundantly expressed Brugia genes. Some highly expressed genes have been identified that are expressed in all stages of the parasite's life cycle, while other highly expressed genes appear to be stage-specific. To elucidate the structure of the Brugia genome and to provide a basis for comparison to the Caenorhabditis elegans genome, the FGP is also constructing a physical map of the Brugia chromosomes and is sequencing genomic BAC clones. In addition to the nuclear genome, B. malayi possesses two other genomes: the mitochondrial genome and the genome of a bacterial endosymbiont. Eighty percent of the mitochondrial genome of B. malayi has been sequenced and is being compared to mitochondrial sequences of other nematodes. The bacterial endosymbiont genome found in B. malayi is closely related to the Wolbachia group of rickettsia-like bacteria that infects many insect species. A set of overlapping BAC clones is being assembled to cover the entire bacterial genome. Currently, half of the bacterial genome has been assembled into four contigs. A consortium has been established to sequence the entire genome of the Brugia endosymbiont. The sequence and mapping data provided by the FGP is being utilised by the nematode research community to develop a better understanding of the biology of filarial parasites and to identify new vaccine candidates and drug targets to aid the elimination of human filariasis.

Animals↗
PubMed2000

The Wuchereria bancrofti orthologue of Brugia malayi SXP1 and the diagnosis of bancroftian filariasis.

The gene encoding the Wuchereria bancrofti orthologue of the Brugia malayi-derived diagnostic antigen SXP1 was identified from a W. bancrofti L3 cDNA library and characterized. The Wb-sxp-1 cDNA encoded a basic protein with a calculated molecular mass of 20.8 kDa. Wb-SXP-1 was 85% identical to the SXP1 protein described from B. malayi (Bm-SXP-1). The Wb-SXP-1 sequence also showed significant identity with proteins described from B. pahangi, Onchocerca volvulus, Acanthochilonema vitea, Ascaris suum, Loa loa, Litomosoides sigmodontis and Caenorhabditis elegans. The presence of a number of invariant and conserved residues in all of these nematode-derived molecules suggests that Wb-SXP-1 is a member of a new protein family. A recombinant form of Wb-SXP-1 was produced and it was determined that the anti-Wb-SXP-1 antibody response in patients with W. bancrofti infections was restricted to the IgG4 subclass. An anti-Wb-SXP-1 IgG4 ELISA was developed and this assay was found to be 100% sensitive for patients with patent W. bancrofti infection. Sera from individuals experiencing chronic pathology, endemic normals or patients with non-filarial nematode infections had no detectable IgG4 against Wb-SXP-1. While patients with patent Onchocerca volvulus infections were uniformly negative in the Wb-SXP-1 assay, 40% of sera from patent Loa loa infections were positive. When Bm-SXP-1 was used as the antigen under identical conditions, the assay was 88% specific for patent W. bancrofti infections and the antigen was recognized by antibodies from both O. volvulus and L. loa infections. The results strongly suggested that, for certain diagnostic filarial antigens, the use of same-species molecules can enhance the specificity of diagnostic tests.

Amino Acid Sequence↗
PubMed2000

Transmission of the nocturnal periodic strain of Wuchereria bancrofti by Culex quinquefasciatus: establishing the potential for urban filariasis in Thailand.

Control programmes have reduced the prevalence of Bancroftian filariasis in Thailand to low levels. Recently, there has been an influx of more than one million Myanmar immigrants into urban centres of Thailand. The prevalence of patent Wuchereria bancrofti infection in these immigrants (2-5%) has prompted concern in the public health community that the potential now exists for a re-emergence of Bancroftian filariasis in Thailand. It is possible that an urban cycle of transmission could become established. The Myanmar immigrants are infected with the nocturnal periodic (urban) type W. bancrofti for which Culex quinquefasciatus serves as the main vector. The Thai strains of Cx. quinquefasciatus have never been reported to transmit Bancroftian filariasis. Our results of feeding experiments demonstrated that the Thai Cx. quinquefasciatus are permissive for the development of Myanmar W. bancrofti to infective third-stage larvae thus establishing the potential for establishing an urban cycle of transmission in Thailand. We also adapted the SspI repeat PCR assay for the identification of infective mosquitoes that was capable of detecting a single infective stage larvae in a pool of 100 mosquitoes.

Adolescent↗
PubMed1999

Developmentally regulated expression of a unique small heat shock protein in Brugia malayi.

A screen of an expression library from the fourth larval stage (L4) of the parasitic nematode Brugia malayi resulted in the identification of a 727 bp full-length cDNA with 29-40% identity to members of the small heat shock family of proteins (Bm-hsp-s1). The open reading frame encoded a protein of approximately 18 kDA (Bm-HSP-s1). An alignment of the Bm-HSP-s1 sequence with the sequences of small HSPs from vertebrate and invertebrate species demonstrated that a majority of the identity was concentrated in the central alpha-crystallin domain. Bm-HSP-s1 was constitutively produced by L4 and adult parasites and at low levels by third-stage larvae (L3), but not by first-stage larvae (microfilariae). In adult parasites, Bm-HSP-s1 was localized to the body wall muscle cells and to the cells of the hypodermis/lateral cord. Bm-HSP-s1 production was induced in adult and L3 incubated at 42 degrees C and in L3s during the developmental transition from vector-stage to vertebrate-stage parasites at 37 degrees C. Neither increased nor decreased temperatures induced Bm-HSP-s1 production in microfilariae. Nitric oxide induced low-level, transient Bm-HSP-s1 synthesis in adults, but not in microfilariae. Bm-HSP-s1 did not function as a molecular chaperone to prevent heat-induced aggregation of a test substrate. The developmentally regulated expression and inducable nature of Bm-HSP-s1 suggests that it may have a stage-restricted role in maintaining parasite homeostasis.

Amino Acid Sequence↗
PubMed1999

Antibody levels to recombinant tick calreticulin increase in humans after exposure to Ixodes scapularis (Say) and are correlated with tick engorgement indices.

The antibody responses of subjects who presented with a definite Ixodes scapularis (Say) tick bite were measured to determine the utility of the antibody response against recombinant tick calreticulin (rTC) as a biologic marker of tick exposure. Subjects bitten by I. scapularis evidenced an increase in anti-rTC antibody levels between visit 1 and visit 2 from 24.3 to 27.1 ng/microl serum (n = 88, p = 0.003), and levels remained elevated at visit 3 (p = 0.005). These anti-rTC antibody levels during visits 2 and 3 were significantly higher than those in four non-exposed controls. Tick engorgement indices, measured on the biting ticks, were found to be correlated with anti-rTC antibody levels (e.g., for visit 3: Pearson's r = 0.357, p = 0.001). Tick engorgement index (TEI), ratio of body length to scutal width, was identified to be the only independent predictor of anti-rTC antibody levels in linear regression models. Logistic regression revealed that a bite from an I. scapularis tick that became engorged (TEI >3.4) was a risk factor for anti-rTC antibody seropositivity (adjusted odds ratio for age and bite location = 7.4 (95% confidence interval 2.1-26.4)). The anti-rTC antibody test had a sensitivity of 0.50 and a specificity of 0.86 for a bite from I. scapularis that became engorged. Immunoblotting revealed that subjects made a specific anti-rTC antibody response.

Adult↗
PubMed1999

Calgranulin C has filariacidal and filariastatic activity.

The calgranulins are a family of calcium- and zinc-binding proteins produced by neutrophils, monocytes, and other cells. Calgranulins are released during inflammatory responses and have antimicrobial activity. Recently, one of the calgranulins, human calgranulin C (CaGC), has been implicated as an important component of the host responses that limit the parasite burden during filarial nematode infections. The goal of this work was to test the hypothesis that human CaGC has biologic activity against filarial parasites. Brugia malayi microfilariae and adults were exposed in vitro to 0.75 to 100 nM recombinant human CaGC. Recombinant CaGC affected adult and larval parasites in a dose-dependent fashion. Microfilariae were more sensitive to the action of CaGC than were adult parasites. At high levels, CaGC was both macrofilariacidal and microfilariacidal. At lower levels, the percentage of parasites killed was dependent on the level of CaGC in the culture system. The larvae not killed had limited motility. The filariastatic effect of low-level CaGC was reversed when the CaGC was removed from the culture system. Immunohistochemical analysis demonstrated that human CaGC accumulated in the cells of the hypodermis-lateral chord of adult and larval parasites. The antifilarial activity of CaGC was not due to the sequestration of zinc. Thus, the cellular and molecular mechanisms that result in the production and release of CaGC in humans may play a key role in the regulation of filarial parasite numbers.

Animals↗
PubMed1999

Chemiluminescent detection of sequential DNA hybridizations to high-density, filter-arrayed cDNA libraries: a subtraction method for novel gene discovery.

A chemiluminescent approach for sequential DNA hybridizations to high-density filter arrays of cDNAs, using a biotin-based random priming method followed by a streptavidin/alkaline phosphatase/CDP-Star detection protocol, is presented. The method has been applied to the Brugia malayi genome project, wherein cDNA libraries, cosmid and bacterial artificial chromosome (BAC) libraries have been gridded at high density onto nylon filters for subsequent analysis by hybridization. Individual probes and pools of rRNA probes, ribosomal protein probes and expressed sequence tag probes show correct specificity and high signal-to-noise ratios even after ten rounds of hybridization, detection, stripping of the probes from the membranes and rehybridization with additional probe sets. This approach provides a subtraction method that leads to a reduction in redundant DNA sequencing, thus increasing the rate of novel gene discovery. The method is also applicable for detecting target sequences, which are present in one or only a few copies per cell; it has proven useful for physical mapping of BAC and cosmid high-density filter arrays, wherein multiple probes have been hybridized at one time (multiplexed) and subsequently "deplexed" into individual components for specific probe localizations.

Animals↗
PubMed1998

Design and synthesis of N-alkylated saccharins as selective alpha-1a adrenergic receptor antagonists.

Benign prostatic hyperplasia can be managed pharmacologically with alpha-1 adrenergic receptor antagonists. Agents that demonstrate selectivity for the alpha-1a receptor subtype may offer advantages in clinical applications with respect to hypotensive side effects. The N-alkylated saccharins reported here represent a new class of subtype selective alpha-1a adrenergic receptor antagonists which demonstrate potent effects on prostate function in vivo and are devoid of blood pressure side effects.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1998

Thioredoxin peroxidases from Brugia malayi.

Parasite-derived antioxidant proteins have been implicated in playing an important role in protection against the oxygen radicals that are generated during aerobic metabolism and in defense against host immune cell attack. Here we report that filarial nematodes include the thioredoxin peroxidase/thiol-specific antioxidant (TPx/TSA) family of antioxidant proteins as part of their complex defense against radical-mediated damage. At the protein level, the TPx/TSA from Brugia malayi (Bm-TPx-1) was approximately 50% identical and approximately 60% similar to TPx/TSAs from mammals, amphibians and yeast. Bm-TPx-1 was also approximately 60% identical to putative TPx proteins from a related filarial nematode, Onchocerca volvulus, and from the free-living nematode Caenorhabditis elegans. That B. malayi may express multiple forms of molecules with TPx/TSA activity was indicated by the identification of a B. malayi gene encoding a second, distinct member of the TPx/TSA family (Bm-tpx-2). Bm-tpx-1 was found to be transcribed in all stages of the parasite present in the mammalian host and the 25 kDa translation product was present in all of the developmental stages studied. The results of immunohistochemical, immunofluorescent and immunoprecipitation studies showed Bm-TPx-1 to be localized in the cells of the hypodermis/lateral chord in adult parasites and not to be present at the surface or in excretory/secretory products. The distribution in the parasite suggests that Bm-TPx-1 may play its major role in countering radicals produced within cells. A recombinant form of Bm-TPx-1 was biologically active and capable of protecting DNA from oxygen radical-mediated damage. Thioredoxin peroxidases may prove to be a critical component in the parasite's defense against injury caused by oxygen radicals derived from endogenous and exogenous sources.

Amino Acid Sequence↗
PubMed1998

3-(1-piperazinyl)-4,5-dihydro-1H-benzo[g]indazoles: high affinity ligands for the human dopamine D4 receptor with improved selectivity over ion channels.

3-(4-Piperidinyl)-5-arylpyrazoles, such as 1, were selective for the cloned human dopamine D4 receptor (hD4), but also showed affinity at voltage sensitive calcium, sodium and potassium ion channels. A combination of substituent changes to reduce the basicity of the piperidine nitrogen and conformational restriction to give 4,5-dihydro-1H-benzo[g]indazoles reduced this ion channel affinity at the expense of selectivity for hD4 over other dopamine receptors. Incorporation of piperazine into the 4,5-dihydro-1H-benzo[g]indazoles in place of piperidine gave a novel series of high affinity, selective, orally bioavailable hD4 ligands, such as 16, with improved selectivity over ion channels.

Administration, Oral↗