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Biomedical subjects

D M Bird

Publications and source records attributed to D M Bird.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of electromagnetic fields on photophasic circulating melatonin levels in American kestrels.

Birds reproduce within electromagnetic fields (EMFs) from transmission lines. Melatonin influences physiologic and behavioral processes that are critical to survival, and melatonin has been equivocally suppressed by EMFs in mammalian species. We examined whether EMFs affect photophasic plasma melatonin in reproducing adult and fledgling American kestrels (Falco sparverius), and whether melatonin was correlated with body mass to explain previously reported results. Captive kestrel pairs were bred under control or EMF conditions for one (short-term) or two (long-term) breeding seasons. EMF exposure had an overall effect on plasma melatonin in male kestrels, with plasma levels suppressed at 42 days and elevated at 70 days of EMF exposure. The similarity in melatonin levels between EMF males at 42 days and controls at 70 days suggests a seasonal phase-shift of the melatonin profile caused by EMF exposure. Melatonin was also suppressed in long-term fledglings, but not in short-term fledglings or adult females. Melatonin levels in adult males were higher than in adult females, possibly explaining the sexually dimorphic response to EMFs. Melatonin and body mass were not associated in American kestrels. It is likely that the results are relevant to wild raptors nesting within EMFs.

Animals↗
PubMed1998

The soybean cyst nematode, Heterodera glycines: a genetic model system for the study of plant-parasitic nematodes.

Despite advances in understanding plant responses to nematode infection, little information exists regarding parasitic mechanisms. Recently, it has become possible to perform genetic analysis of soybean cyst nematode. Integration of classic and reverse genetics and genomic approaches for the parasite, with host genetics and genomics will expand our knowledge of nematode parasitism.

Animals↗
PubMed1997

Behavior of captive american kestrels hatched from o,p'-dicofol exposed females.

A two-generation laboratory study was conducted on captive American kestrels (Falco sparverius) to investigate the possible behavioral alterations from the compound o,p'-dicofol. Paired females were exposed to three levels of dicofol by oral gavage. Adults of the second generation, exposed only via the maternal dose of o,p'-dicofol at 5- and 20-mg/kg, displayed negatively correlated changes in reproductive behaviors. Second generation females showed a significant difference (p < 0.05) from control birds in the miscellaneous behavior category, where more time was spent picking at the rope perch, watching flies, laying down on the perch and other such displacement activities. Second generation 5-mg/kg males completed significantly fewer copulations (p < 0.05) than the corresponding control birds. The number of attempted or failed food transfers (a pair bonding activity) was also significantly higher (p < 0.05) in the second generation 5-mg/kg male group. Trials were conducted on second generation males to determine aggressiveness of these individuals when placed in a competitive arena. Primary perch sites and food items were obtained by control birds significantly (p < 0.05) more often than dicofol-exposed males. A bird's maternal dose had a significant negative effect (p < 0.05) on its ability to achieve a high rank order position.

Animals↗
PubMed1996

Reproductive and morphological effects of o,p'-dicofol on two generations of captive American kestrels.

A two-generation laboratory study was conducted on a captive population of American kestrels (Falco sparverius) to investigate the possible reproductive and teratogenic effects of the pesticide dicofol. Paired females were exposed to three levels of dicofol: 0, 5, and 20 mg/kg. Integrity of the reproductive tract of the resulting embryos was examined. Viable eggs were hatched, and these birds were permitted to breed the following year. Breeding performance for these birds was measured based on their ability to form pair bonds and exhibit normal behavior in the presence of a mate. Clutch completion, fertility, hatchability, and number of hatchlings reared to the fledging were used as reproductive parameters. Females dosed with 20 mg/kg of dicofol laid eggs with shells that were significantly (p < 0.05) thinner than those of the control birds. Residue levels of dicofol in the form of dichlorobenzophenone were detected in the first and second clutch eggs of the 20-mg/kg dose group only. Male embryos from females dosed with 5 and 20 mg/kg of dicofol had gonads that were significantly different (p < 0.05) from the control chicks. Feminization of male embryos was confirmed by the presence of primordial germ cells in the male gonad. Second-generation adult 5-mg/kg females showed a significantly (p < 0.05) greater number of eggs and hatched chicks lost when compared to second-generation control females. Similar results were found in second-generation 5-mg/kg males paired with normal females and had a significant (p < 0.05) number of chicks die posthatching. Results of second-generation breeding parameters indicate a negative effect on reproductive behavior.

Animals↗
PubMed1996

Manipulation of host gene expression by root-knot nematodes.

Root-knot nematodes (Meloidogyne spp.) establish elaborate feeding sites in their host. Unique patterns of gene expression are induced in root cells, resulting in formation of a novel cell type called a giant cell. Based on analysis of approximately 220 giant cell expressed genes, key elements of giant cell function and regulation have been identified; examples are discussed in the context of giant cell biology and ontogeny. The potential to effect nematode control by manipulating these genes in transgenic host plants is considered, and models for giant cell induction are presented.

Animals↗
PubMed1995

Plasmodium falciparum: the adherence of erythrocytes infected with human malaria can be mimicked using pfalhesin-coated microspheres.

Infection of human erythrocytes with the malaria parasite, Plasmodium falciparum, results in the exposure of amino acid residues 542-555 of the anion-exchange protein, band 3, in a conformation that enables the cell to adhere to C32 amelanotic melanoma cells. Attempts to isolate this adhesive form from infected cells by immunoaffinity were unsuccessful, and so other approaches were utilized. Chinese hamster ovary (CHO) cells transfected with cDNA encoding the first 578 amino acid residues of human band 3 protein transiently expressed the protein efficiently. A murine monoclonal antibody (MAb) that specifically recognizes the adhesin exposed on the surface of erythrocytes bearing mature stages of P. falciparum immunostained some transfected cells, confirming that the first 578 amino residues are sufficient for the adhesive conformation. As a more efficient alternative to transgenic expression of the adhesin, microspheres with covalently bound peptides fashioned on band 3 sequences previously found to be adherent (residues 546-553 and 820-829 and called pfalhesin) were produced. The pfalhesin-coated microspheres specifically bound to C32 amelanotic melanoma cells, whereas microspheres coupled with a scrambled version of residues 546-553 had little binding capacity for melanoma cells. These results demonstrate that the previously identified band 3-related peptides that inhibit cytoadherence interact directly with target cells and suggest that microspheres with covalently coupled peptides might constitute novel 'artificial' P. falciparum-infected erythrocytes for use in in vitro and in vivo studies.

Amino Acid Sequence↗
PubMed1994

Growth of hand-reared American kestrels I. The effect of two different diets and feeding frequency.

Seventy captive-bred American kestrels (Falco sparverius) were hand-reared on diets of either day-old cockerels (Gallus domesticus) (n = 38) or laboratory mice (Mus musculus) (n = 32) at meal frequencies of 4 or 6 times per day. Ad libitum food was provided in all meals. A proximate analysis of the two diets was performed and showed that cockerels when compared to mice contained more crude protein (60.0% versus 42.7% dry matter) and less fat (28.1% versus 46.5% dry matter). Body mass of nestlings was recorded daily until fledging, while lengths of the antebrachium and 9th primary remex were measured at intervals of 2 to 5 days. Data were fitted to the Richards growth model. Cockerel-fed nestlings exhibited growth patterns similar to those found in free-ranging kestrels. Mouse-fed birds however, grew more slowly which could be related to inadequate protein intake. No effect of hand-feeding frequency (4 versus 6 times daily) on growth rates was noted under any of the two diets. Irrespective of the dietary group, female kestrels were significantly heavier at the end of the experiment, as expected from the reversed sexual size dimorphism present in adult American kestrels.

Analysis of Variance↗
PubMed1994

Growth of hand-reared American kestrels. II. Body composition and wingloading of fledglings hand-fed two different diets.

The body composition of young American kestrels (Falco sparverius) hand-fed either a protein-rich diet (day-old cockerels Gallus domesticus) or a fat-rich diet (laboratory mice Mus musculus) was determined one day after fledging. Mouse-fed fledglings (n = 16) had significantly greater fat deposits than cockerel-fed birds (n = 15), while the crude protein content of the carcass was unaffected by the diets. At fledging, mouse-fed birds showed a significantly greater wingloading than cockerel-fed birds. Larger fat reserves (as in mouse-fed birds) might be mobilised in the event of a food shortage and thus these birds would be at an advantage in relation to fledglings with smaller reserves. On the other hand, large fat deposition, which alters wingloading, might impair the flight performance of the fledglings.

Analysis of Variance↗
PubMed1993

Rapid miniprep isolation of mitochondrial DNA from metacestodes, and free-living and parasitic nematodes.

A method, based on one to isolate supercoiled plasmid DNA from bacterial cells, has been developed to purify mitochondrial DNA (mtDNA) from cestode and nematode tissue easily and efficiently. Starting with as little as 100 mg of helminth tissue, sufficient mtDNA for electrophoretic analysis was extracted. This DNA was essentially free of nuclear DNA and readily digested by restriction endonucleases. Approximately 20% of the mtDNA in helminth tissue was recovered, which is a significant improvement over previously available techniques.

Animals↗
PubMed1992

Sequence comparison of the Caenorhabditis elegans dpy-13 and col-34 genes, and their deduced collagen products.

A 2232-nucleotide sequence spanning the col-34 gene from the nematode, Caenorhabditis elegans, is presented. This gene, which encodes a collagen protein (Clg), is transcribed from right to left with respect to the genetic map, and convergently with the nearby dpy-13 gene which also encodes a Clg. Both col-34 and dpy-13 have 5'-flanking elements in common with each other and also with other nematode Clg-encoding genes (clg). One element, variants of which are shared by col-7, col-19 and dpy-13, is predicted to be a target for a number of regulatory molecules, possibly including the ceh-18 product, a nematode POU-domain protein. The deduced amino acid sequence of Col-34 has a high degree of homology with the Dpy-13 collagen, although there are significant differences. In particular, one region of Dpy-13, which is predicted to have secondary structure different from Col-34, is altered by the recessive dpy-13(e225) mutation.

Amino Acid Sequence↗
PubMed1992

The refractive development of the eye of the American kestrel (Falco sparverius): a new avian model.

Most measures of avian visual performance are carried out on commonly available domestic species such as the chicken, and most of the data on avian induced refractive error deals with chickens. Raptors are predatory birds in which good visual resolving ability is particularly important. Behavioral studies indicate that the eyes of raptors have two to three times the resolving ability of the human eye. The domestic chicken is precocial at hatching whereas most raptors are semi-altricial. This study was an effort to determine if the effect of early visual deprivation on the refractive development of the chicken eye can be reproduced in the American kestrel, a species which is not domesticated and in which the need for acute vision is particularly important. Visual deprivation was achieved by unilaterally applying translucent plastic goggles over the eyes of kestrels two days after hatching. Refractive error was measured using a retinoscope and trial lenses. Ocular growth was monitored by A-scan ultrasonography, and frozen ocular sections of sacrificed birds. The effect of the experimental manipulation on the contralateral control eye and body weight was evaluated each day over a 42-day period. The goggles did not significantly affect the normal changes in body weight or the normal pattern of ocular growth and refractive development in the untreated eyes. An analysis of the refractive state changes as a result of form deprivation was made each week for 6 weeks after hatching on both the treated and untreated eyes in a separate group of experimental birds. Visual form deprivation caused a significant myopic shift in refractive error and a significant increase in the vitreous chamber depth in the treated eyes at 3 and 6 weeks of age. However, the amount of myopia produced is much less than that induced in chicks, and in certain cases hyperopia is produced. The kestrels recover from myopia and hyperopia within 10 days of goggle removal, after 3 to 4 weeks of deprivation. This study is the first indication that chickens may not be a representative bird model for studying form-deprivation myopia. First, myopia is not always produced in kestrels in response to form deprivation. Second, kestrels are severely myopic at hatching and therefore, the direction of emmetropization is opposite to that found in hatchling chicks.

Animals↗
PubMed1992

The effect of dietary sodium fluoride on internal organs, breast muscle, and bones in captive American kestrels (Falco sparverius).

In 1982, 29 7-day-old American kestrel (Falco sparverius) chicks from captive stock were randomly assigned to one of three dietary regimens: (1) 10 birds were fed daily with cockerel mash (0 ppm of F-: control birds); (2) 10 birds were fed daily with cockerel mash containing 1,120 ppm of F-; (3) 9 birds were fed daily with cockerel mash containing 2,240 ppm of F-. Growth of the kestrels was not significantly affected by NaF in their diet. No significant differences were found among the 3 groups for length of duodenum, jejunum and ileum. Rectum was longer as more fluoride was added to the diet. Weights of adrenals, brain, gizzard, spleen, heart, kidneys, liver, pancreas, and pectoral muscle were not significantly affected by treatment, although kidneys, spleen and adrenals tended to become lighter. Percent bone ash was significantly (P less than 0.05) increased, while bone breaking strength was significantly (P less than 0.05) decreased by treatment.

Animals↗
PubMed1992

Chronic sulfonylurea therapy augments basal and meal-stimulated insulin secretion while attenuating insulin responses to sulfonylurea per se.

OBJECTIVE: To examine changes in glycemia and insulin secretion in response to SU per se and in response to a standard diet plus OD or TD SU therapy during chronic GP and GB therapy. RESEARCH DESIGN AND METHODS: Randomized (between agents and in order of dosing regimens), prospective, open, crossover study among 14 NIDDM patients to compare glucose, insulin, and C-peptide responses to a standard diet and to 10 mg of oral GP or GB taken without food 1) after 2 wk without therapy, 2) after 4 wk of either GP (n = 7) or GB (n = 7) treatment OD, and 3) after 4 wk of TD therapy with the same agent. Each patient received the same drug for maintenance therapy and for assessment of the response to the drug alone. RESULTS: We observed a comparable reduction in overall glycemia with both agents, with more marked postprandial effects for GP. Similar glucose, insulin, and C-peptide profiles for both agents during OD and TD therapy. Augmented insulin secretion in response to meals contrasting with reduced insulinotropic effects of the drugs per se with chronic therapy. CONCLUSIONS: Therapeutic equivalence of OD and TD dosing with GP and GB during chronic therapy. In view of the improved insulin secretion in response to nutrient stimuli, the attenuation of responses to SU per se during chronic therapy does not imply impairment of beta-cell secretory capacity or represent a therapeutic disadvantage.

Adult↗
PubMed1991

Secondary poisoning hazard of fenthion to American kestrels.

The possibility that fenthion, an organophosphorus pesticide, could represent a secondary poisoning hazard to birds of prey was tested, using American kestrels (Falco sparverius) and house sparrows (Passer domesticus) as representative models of a naturally occurring predator-prey interaction. Fourteen kestrels were presented with live sparrows exposed previously to perches containing Rid-A-Bird 1100 solution (11% fenthion active ingredient). Eleven kestrels died within twenty-four h after consuming one fenthion-exposed sparrow. Two kestrels died after consumption of a second fenthion-exposed sparrow on day 2, and a final kestrel died after partially consuming a third fenthion-exposed sparrow on day 3. Brain cholinesterase (ChE) activity in kestrels was depressed to levels diagnostic of poisoning by a ChE-inhibiting compound. The majority of fenthion contamination of sparrows was external, with the highest amounts measured on the feet. The detection of fenthion residues in kestrel gastro-intestinal tracts confirmed secondary fenthion poisoning.

Animals↗
PubMed1991

Metformin increases insulin sensitivity and basal glucose clearance in type 2 (non-insulin dependent) diabetes mellitus.

The effects of metformin on glycaemia, insulin and c-peptide levels, hepatic glucose production and insulin sensitivity (using the euglycaemic, hyperinsulinaemic clamp) were evaluated at fortnightly intervals in 9 Type 2 diabetic patients using a stepwise dosing protocol: Stage 1--no metformin for four weeks; stage 2--metformin 500mg mane; stage 3--metformin 500mg thrice daily; stage 4--metformin 1000mg thrice daily. Results are expressed as Mean +/- SEM. Fasting blood glucose decreased from basal values (9.7 +/- 1.0 mmol/L) by 13% at stage 2, 34% at stage 3 and 41% at stage 4 (p less than 0.02 vs basal for all stages; p less than 0.02 stage 2 vs stage 3). Post-prandial glycaemia was significantly improved only with metformin 3000mg/day (p less than 0.05). Fasting, meal-stimulated and total insulin and c-peptide levels showed no change. Hepatic glucose output did not change significantly with metformin. Insulin sensitivity, measured as total glucose utilisation during hyperinsulinaemia, increased from stage 1 (10.3 +/- 2.1 mumoL/kg/min) by 23% at stage 3 (p less than 0.05) and by 29% at stage 4 (p less than 0.02). Basal metabolic clearance of glucose increased compared to stage 1 (1.69 +/- 0.16 mL/kg/min) by 30% at stage 2, 53% at stage 3 and 44% at stage 4 (all p less than 0.02). This study demonstrates that improved efficiency of glucose utilisation, both basally and under conditions of euglycaemic hyperinsulinaemia, is the basis of metformin's antihyperglycaemic action.

Adult↗
PubMed1989

Theory of zone axis electron diffraction.

The theory of high-energy electron diffraction is reviewed, with an emphasis on methods that help most in understanding the form of zone axis convergent-beam patterns. A Bloch wave description is used throughout the paper, and the theory is formulated in real space, leading to general expressions for both zero-layer and higher-order Laue zone (HOLZ) diffraction amplitudes. HOLZ diffraction is discussed in detail, and it is shown that first-order perturbation theory is usually applicable and provides a clear picture of the diffraction. The computation of diffracted intensities is discussed with reference to the many-beam equations. Diffraction at the [0001] axis in 1T-VSe2 is analysed both to illustrate the theory and to provide an example of the special effects that occur at well defined string zone axes.

Crystallography↗
PubMed1989

Molecular cloning and sequencing of ama-1, the gene encoding the largest subunit of Caenorhabditis elegans RNA polymerase II.

Two genomic sequences that share homology with Rp11215, the gene encoding the largest subunit of RNA polymerase II in Drosophila melanogaster, have been isolated from the nematode Caenorhabditis elegans. One of these sequences was physically mapped on chromosome IV within a region deleted by the deficiency mDf4, 25 kilobases (kb) from the left deficiency breakpoint. This position corresponds to ama-1 (resistance to alpha-amanitin), a gene shown previously to encode a subunit of RNA polymerase II. Northern (RNA) blotting and DNA sequencing revealed that ama-1 spans 10 kb, is punctuated by 11 introns, and encodes a 5.9-kb mRNA. A cDNA clone was isolated and partially sequenced to confirm the 3' end and several splice junctions. Analysis of the inferred 1,859-residue ama-1 product showed considerable identity with the largest subunit of RNAP II from other organisms, including the presence of a zinc finger motif near the amino terminus, and a carboxyl-terminal domain of 42 tandemly reiterated heptamers with the consensus Tyr Ser Pro Thr Ser Pro Ser. The latter domain was found to be encoded by four exons. In addition, the sequence oriented ama-1 transcription with respect to the genetic map. The second C. elegans sequence detected with the Drosophila probe, named rpc-1, was found to encode a 4.8-kb transcript and hybridized strongly to the gene encoding the largest subunit of RNA polymerase III from yeast, implicating rpc-1 as encoding the analogous peptide in the nematode. By contrast with ama-1, rpc-1 was not deleted by mDf4 or larger deficiencies examined, indicating that these genes are no closer than 150 kb. Genes flanking ama-1, including two collagen genes, also have been identified.

Amino Acid Sequence↗