Biomedical subjects

W M Muir

Publications and source records attributed to W M Muir.

At least 19 recordsLinked to original sources

PubMed2006

Genome-wide analysis of phenobarbital-inducible genes in Drosophila melanogaster.

An oligoarray analysis was conducted to determine the differential expression of genes due to phenobarbital exposure in Drosophila melanogaster (w(1118) strain) third instar larvae. Seventeen genes were observed to be induced with increased expression by a statistical analysis of microarrays approach with a q < or = 0.05. At q < or = 0.12, four more genes (Cyp12d1, DmGstd4, and two genes with unknown function) were found to be up-regulated, and 11 genes with unknown function were found to be down-regulated. Fifteen of these genes, Cyp4d14, Cyp6a2, Cyp6a8, Cyp12d1, Cyp6d5, Cyp6w1, CG2065, DmGstd6, DmGstd7, Amy-p/Amy-d, Ugt86Dd, GC5724, Jheh1, Jheh2 and CG11893, were verified using quantitative real time polymerase chain reaction. Some of these genes have been shown to be over-transcribed in metabolically DDT-resistant Drosophila strains.

Animals↗

PubMed2004

Chronic social stress differentially regulates neuroendocrine responses in laying hens: II. Genetic basis of adrenal responses under three different social conditions.

Chicken lines were divergently selected for both high (HGPS) or low (LGPS) group productivity and survivability resulting from cannibalism and flightiness in colony cages. Each line has unique characteristics in physical indexes, domestic behavior, and physiological responsiveness to stress. The differences between the selected lines could be reflected in differing regulation of the neuroendocrine system such as the hypothalamic-pituitary-adrenal axis. Change of the adrenal function is a key initial event in response to stress in animals, which differs for this trait. Comparisons between the selected lines showed that adrenal function was stable in HGPS hens but not in LGPS hens in response to chronic social stress. Social stress-induced adrenal hypertrophy and its positive correlation with plasma corticosterone concentrations were found in the LGPS hens but not in the HGPS hens. The data demonstrated that chickens selected for variations in productivity and survivability variously altered the adrenal system in response to social stressors. The results suggest that these chicken lines could be valuable animal models for biomedical investigation of the effect of genetic-environmental interactions on the neuroendocrine function in controlling stress responses.

Adaptation, Psychological↗

PubMed2003

Social stress differentially regulates neuroendocrine responses in laying hens: I. Genetic basis of dopamine responses under three different social conditions.

Effects of genetic-environmental interactions on plasma dopamine (DA) concentrations were studied in White Leghorn chickens selected for both high (HGPS) or low (LGPS) group productivity and survivability resulting from cannibalism and flightiness. Plasma DA levels were measured from chickens in three social treatments: single-, two-, or ten-hen cages. The two-hen treatment consisted of paired chickens from three genetic lines: HGPS, LGPS and a commercial strain, Dekalb XL (DXL). In HGPS/DXL and LGPS/DXL pairs, the DXL hen was used as a standardized genetic competitor. The ten-hen treatment contained only hens from the same line, which is similar to the original selection condition. After 7 weeks housing in the social environments, LGPS hens in the ten-hen treatment had greater plasma DA concentrations than HGPS hens (P<0.05). Compared to levels in the ten-hen treatment from the same line, plasma DA concentrations in both HGPS and LGPS hens were significantly lower in the two-hen treatment (average mean, 0.09 vs. 0.15 ng/ml and 0.22 vs. 0.44 ng/ml, P<0.05, respectively), but significantly higher in the single-hen treatment (average mean, 0.44 vs. 0.15 ng/ml and 1.78 vs. 0.44 ng/ml, P<0.05 and P<0.01, respectively). In the single-hen treatment, LGPS hens had greater plasma DA levels than HGPS hens (P<0.05). The results provide evidence of genetically related differences in the regulation of chickens' plasma DA concentrations in response to social stress. These differences may magnify the behavioral and physiological differences observed in the lines under basal and challenged conditions. These results suggest that these chicken lines may provide a new model for investigating effects of DA on the control of behavioral, neural and endocrine responses to stress.

Animals↗

PubMed2003

Social stress in laying hens: differential effect of stress on plasma dopamine concentrations and adrenal function in genetically selected chickens.

Genetic selection for high or low group productivity and survivability (HGPS, LGPS) has created two phenotypically distinct chicken lines. Each line has unique characteristics in behavioral and physiological adaptability to multiple-bird cage system. The present study was designed to examine whether these differences reflect genetic variation in the control of plasma dopamine (DA) concentrations and adrenal function in response to social stress. Chickens from the HGPS and LGPS lines were randomly assigned to single- or 10-bird cages at 17 wk of age. The 10-bird cages were the same as those used in the development of the two lines. Differences in regulation of DA concentrations and adrenal function in response to different social environments were measured between the two lines when the study was conducted at 24 wk of age. In the 10-bird cages, the HGPS line had lower levels of DA (P < 0.05) and heavier adrenal glands (AG, P < 0.05) than those of the LGPS line, but concentrations of corticosterone (CORT) from the two lines were not significantly different. In the single-bird cages, DA levels in both lines were greater than in that of their siblings in the 10-bird cages, but a greater increase was found in the LGPS line (P < 0.01 and P < 0.05, 405% vs. 293%). Likewise, both lines had lower concentrations of CORT (P < 0.05) in the single- vs. 10-bird cages, but the AG were less heavy in the LGPS line but not in HGPS line in the single-bird cages (P < 0.05). The results indicated that the two strains reacted differently in terms of their stress hormone levels in the two different environments. These differences could contribute to the behavioral and physiological differences existing between the two lines.

Adrenal Glands↗

PubMed2002

Social stress in laying hens: differential dopamine and corticosterone responses after intermingling different genetic strains of chickens.

White Leghorn chickens were genetically selected for high (HGPS) or low (LGPS) group productivity and survivability. The selection resulted in two genetic lines with marked opposite changes in cannibalism and flightiness when housed in multiple-colony battery cages without beak trimming. The objective of the study was to examine whether the genetic selection differentially affected the neuroendocrine system of chickens from different strains in response to social stress. Based on the previous studies, social stress was induced by randomly pairing 17-wk-old hens from three genetic lines, i.e., HGPS, LGPS, and Dekalb XL (DXL), to form three mixed-line combinations. At 24 wk of age, the concentrations of plasma dopamine (DA) and corticosterone (CORT) showed no differences in DXL hens housed with HGPS or LGPS hens (P > 0.05). However, different regulations of DA and adrenal function were found between HGPS and LGPS hens when paired with DXL hens. Compared to HGPS hens, LGPS hens had greater levels of DA and CORT (P < 0.01 and P < 0.05, respectively). In addition, under the HGPS-LGPS social treatment, the concentrations of DA but not CORT were greater in LGPS hens than in HGPS hens (P < 0.05 and P > 0.05, respectively). The results indicated genetic selection for production and survivability differentially altered DA and CORT systems in response to social stress. The data suggested, compared to LGPS hens, HGPS hens had a better coping capability to social stress, which might have been responsible for their higher productivity and survivability.

Adrenal Glands↗

PubMed1999

Possible ecological risks of transgenic organism release when transgenes affect mating success: sexual selection and the Trojan gene hypothesis.

Widespread interest in producing transgenic organisms is balanced by concern over ecological hazards, such as species extinction if such organisms were to be released into nature. An ecological risk associated with the introduction of a transgenic organism is that the transgene, though rare, can spread in a natural population. An increase in transgene frequency is often assumed to be unlikely because transgenic organisms typically have some viability disadvantage. Reduced viability is assumed to be common because transgenic individuals are best viewed as macromutants that lack any history of selection that could reduce negative fitness effects. However, these arguments ignore the potential advantageous effects of transgenes on some aspect of fitness such as mating success. Here, we examine the risk to a natural population after release of a few transgenic individuals when the transgene trait simultaneously increases transgenic male mating success and lowers the viability of transgenic offspring. We obtained relevant life history data by using the small cyprinodont fish, Japanese medaka (Oryzias latipes) as a model. Our deterministic equations predict that a transgene introduced into a natural population by a small number of transgenic fish will spread as a result of enhanced mating advantage, but the reduced viability of offspring will cause eventual local extinction of both populations. Such risks should be evaluated with each new transgenic animal before release.

Animals↗

PubMed1998

Selection index updating for maximizing rate of annual genetic gain in laying hens.

Four selection strategies aimed at maximizing egg production in laying hens were compared with respect to expected annual genetic gain (GA). The selection strategies were: 1) (S1P) Traditional single-stage selection based on a single-house production system using partial records for both the individual and its ancestors, 2) Single-stage selection based on a single-house production system using full records for both the individual and its ancestors (S1F), 3) Single-stage selection based on a two-house production system using partial records for the individual and full records for its ancestors (S2P), and 4) Multistage selection based on a two-house production system using partial records for the individual and all available ancestral records (M2P). Strategy M2P resulted in the shortest generation interval (0.538 yr) and was the most efficient (deltaGA4 = 3.620 eggs per year), whereas strategy S1F generated the longest generation interval (2 yr) and was the least efficient (deltaGA2 = 1.334 eggs per year). Strategies S1P and S2P resulted in generation intervals of 1 yr, and were intermediate in efficiency (deltaGA1 = 2.232 eggs per year, deltaGA3 = 2.593 eggs per year). It was concluded that a two-house production system utilizing multistage selection was the most effective selection methodology. Further, selection based on M2P is expected to improve persistency of lay, whereas selection on S1P will not.

Animals↗

PubMed1998

Improving animal well-being through genetic selection.

This paper reviews the possibilities of adapting laying hens to cages by means of genetic selection. By selecting separately for rate of lay and longevity using a kin selection method, a strain of laying hen has been developed that shows much less feather pecking and cannibalism than a control strain, and with no decrease in productivity. This experimental strain enjoys a higher level of welfare in cages because it does not require beak trimming.

Adaptation, Physiological↗

PubMed1997

Genetic selection strategies: computer modeling.

There are four primary factors to consider in genetic selection strategies: 1) accuracy of selection, 2) selection intensity, 3) effective population size, and 4) mating system. Current theory indicates that optimum response to selection is achieved by maximizing the first three factors and using a mating systems that allows optimization of reproductive characteristics in dam lines and production characteristics in sire lines. However, with limited resources, compromises among the first three factors are needed. Simulations are useful for examining those compromises. Unrealistic simplifying assumptions are necessary for analytic theoretical results and thus do not address real world breeding problems. Using simulations, the relationship between selection accuracy, which is increased by use of family selection indices or Best Linear Unbiased Prediction (BLUP), and response to selection was examined. Results show that those procedures place a great restriction on effective population size, which offsets most of their advantage, i.e., there is too little emphasis on effective population size. A revision of the methodology and a reappraisal of the results of selection theory for optimization of genetic response is required. Another relationship that is of fundamental importance in breeding programs is that between selection intensity and effective population size. Analytical results for the additive case have been developed but have never been extended to heterotic traits. A gene level simulation program was developed to examine that relationship. Results show that the optimal selection strategy depends on the trait being selected. For additive traits and in the short term (20 generations), one should maximize selection intensity. For heterotic traits, an intermediate proportion (25% of each sex) gives optimal response. In all breeding strategies, primary attention must be given to the rate of inbreeding, which is increased by increasing either accuracy of selection or selection intensity. Inbreeding reduces response to selection in two ways. First, for both additive and nonadditive traits, inbreeding is a measure of the amount of random genetic drift that has occurred. Genetic drift causes loss of favorable alleles. Once lost, those alleles can never be recovered and thus genetic drift lowers the selection limit. Second, for heterotic traits, inbreeding results in a depression of the mean caused by directional dominance.

Animals↗

PubMed1996

Useful DNA polymorphisms are identified by snapback, a midrepetitive element in Tribolium castaneum.

The red flour bettle, Tribolium castaneum, is both a pest of stored grain products and an important experimental organism. To improve its facility as a genetic model, we are developing DNA fingerprinting methods for this insect. A Tribolium DNA fragment, snapback-1 (SBI), identified among sequences that reassociate before a Cot of 0.03 mol.s/L, was found to produce a banding pattern in restriction endonuclease digested genomic DNA that is characteristic of a midrepetitive element. DNA fingerprints of individual beetles demonstrated that unvarying inherited DNA polymorphism is revealed, and that polymorphism is inherited in a dominant Mendelian fashion. Linkage between bands was minimal. The sequence of SBI was determined, and hybridization experiments indicated that SBI is a fragment of a larger midrepetitive element. Fingerprinting individuals with known inbreeding coefficients indicated that SBI loci have relatively high mutation rates. The possibility that SBI is a fragment of a transposable element is discussed.

Animals↗

PubMed1996

Group selection for adaptation to multiple-hen cages: beak-related mortality, feathering, and body weight responses.

The hypothesis was tested that selection on the basis of family means for increased survival and hen-housed egg production, when sisters with intact beaks were kept together in multiple-bird cage, would cause adaptive changes in behavior. Specifically, it was posited that beak-inflicted injuries causing cannibalistic mortality and feather loss and damage would be reduced. Body weight effects were not predicted, but were examined. Three stocks were compared; the Selected (S), representing the seventh generation of selection, the Randombred Control (C) from which S was derived, and a commercial stock (X), known to be highly productive and peak-trimmed by commercial producers. Pullets were placed in single-bird (1H) as well as in 12-hen (12H) cages using a completely randomized block experimental design. Mortality from beak-inflicted injuries differed among stocks in total hens lost (P < 0.005). Of 576 per stock in 12H cages 287, 128, and 46 replacements were used from 17 to 44 wk in X, C, and S, respectively, to maintain group size. The C and S hens also differed from 44 to 59 wk and 17 to 59 wk. X hens were not included in comparisons of mortality beyond 44 wk. Relative incidence of mortality caused by vent-cloacal injuries differed with X > C = S (P < 0.005 for X vs C and S). For cages with > or = 1 cannibalistic death, X had twice (P < 0.025) and C 1.6 times (P < 0.10) as many with repeated losses as S. Means and variances of feather scores were different for 1H vs 12H cages, ages, and genetic stocks. Greater variances were observed in 12H cages and among older birds. Within 1H units, genetic stocks did not differ in general, but in 12H cages X and C were always more variable than S. In 12H cages, mean feather scores and body weights were decreased and S hens had better feathering than either C or X. The evidence supported the hypothesis.

Adaptation, Physiological↗

PubMed1996

Group selection for adaptation to multiple-hen cages: selection program and direct responses.

A selection experiment was initiated with a synthetic line of White Leghorns in 1982 to improve adaptability and well-being of layers in large multiple-bird cages by use of a selection procedure termed "group selection". With this procedure, each sire family was housed as a group in a multiple-bird cage and selected or rejected as a group. An unselected control, with approximately the same number of breeders as the selected line, was maintained for comparison and housed in one-third cages. Annual percentage mortality of the selected line in multiple-bird cages decreased from 68% in Generation (G)2 to 8.8% in G6. Percentage mortality in G6 of the selected line in multiple-bird cages was similar to that of the unselected control in one-bird cages (9.1%). Annual days survival improved from 169 to 348 d, eggs per hen per day (EHD) from 52 to 68%, eggs per hen housed from 91 to 237 eggs, and egg mass (EM) from 5.1 to 13.4 kg, whereas annual egg weight remained unchanged. The dramatic improvement in livability demonstrates that adaptability and well-being of these birds were improved by group selection. The similar survival of the selected line in multiple-bird cages and the control in one-bird cages suggests that break-trimming of the selected line would not further reduce mortalities, which implies that group selection may have eliminated the need to beak-trim. Corresponding improvements in EHD and EM demonstrate that such changes can also be profitable. The most surprising finding was the rate of which such improvement took place, with the majority of change in survival occurring by the third generation. However, EHD continued to improve at the rate of 4% per generation.

Adaptation, Physiological↗

PubMed1996

Group selection for adaptation to multiple-hen cages: behavioral responses.

Three stocks of White Leghorns were compared for behavioral traits when kept in single-bird (1H) and 12-hen (12H) layer-house cages. Genetic stocks consisted of a commercial strain (X), a randombred control (C), and a stock derived from C and selected on the basis of kin's group performance information for increased survival and egg production over seven generations (S). Experimental units consisted of four consecutive 1H cages or a single 12H cage. All birds within a unit had intact beaks and were of the same stock. Each stock was represented by hens in 48 units of both 1H and 12H cages, and by 48 males (C and S stocks only) in 1H cages. Birds that died were replaced. Observations involved hens in their home cages except for tonic immobility (TI) and pair contests. Observations carried out soon after birds were placed in layer-house cages indicated that avoidance of the observer was essentially absent after pullets were observed on the 1st and 2nd d. Behavioral profile frequencies differed for nearly all behaviors compared in 1H and 12H environments. Following initially high crouching and low feeding frequencies, apparently normal levels were present by Days 15 and 16 posthousing. During the initial adaptation phase, genetic stock differences were not found within 1H cages and were present in only 2 of 10 categories in 12H cages. Young adult profiles also indicated no differences among stocks in 1H cages, but stock differences were found in 6 of 12 categories in 12H cages. In those cases, X strain hens differed from hens of the C and S stocks, but C and S hens did not differ from each other. Comparisons carried out between hens in 1H and 12H cages revealed that fearfulness was greater in 12H cages. Genetic stock comparisons, involving relative fearfulness and feeding and movement in a frustrating situation indicated that the X stock frequently differed from both C and S, but C and S did not usually differ from each other. However, observations of hens' agonistic activity in the 12H home cage environment revealed that the S stock had fewer agonistic acts than the C stock from which it was derived, and both C and S had less agonistic activity than the X stock. Pair contests carried out within and between C and S stocks in both sexes yielded results inconsistent with those for agonistic activity in 12H cages. The C and S hens did not differ, but S males were more aggressive and, in between-strain contests, were more dominant.

Adaptation, Physiological↗

PubMed1996

Group selection for adaptation to multiple-hen cages: hematology and adrenal function.

A selected line of White Leghorns that has shown improved survivability and productivity and reduced feather loss in multiple-hen cages was evaluated for hematological and adrenal responses under both stressed and unstressed conditions. It was hypothesized that hens selected for adaptation to multiple-bird cages would react less intensely to stressors. Three lines of chickens (selected, control, and commercial) were housed in either single-hen (1 hen) or multiple-hen cages (12 hens, social competition) at 16.7 or 17.1 wk of age. They were subsequently subjected to cold exposure at 33 wk of age and heat exposure at 44 wk of age. Genetic stock as a main effect, and the interaction of genetic stock with either a cold or heated environment or with cage size, had no effect on plasma levels of cholesterol and corticosterone. At the time of transfer to laying cages, the selected line of pullets, as indicated by a decrease in packed cell volume, appeared to adapt more quickly to the new waterer system of multiple-hen cages than did the control and commercial lines. At 33 wk of age, the control and commercial lines in multiple-hen cages experienced heterophilia and increased heterophil to lymphocyte ratios, whereas the selected line did not, when compared with these same lines in single-hen cages. This leucocytic response could be interpreted to mean that the selected line of chickens adapted better to social competition than either the control or commercial lines; however, a similar leucocytic response was not observed at 18 or 44 wk of age. In conclusion, the physiological characterization of the selected line of Leghorns showed evidence of improved adaptation to multiple-hen cages when compared to the other stocks. In some cases, the selected line responded less intensely to stress; however, trends were not always consistent.

Adaptation, Physiological↗

PubMed1996

Group selection for adaptation to multiple-hen cages: production traits during heat and cold exposures.

A selected line of White Leghorns that has shown improved survivability and productivity and reduced feather loss in multiple-hen cages was evaluated for production traits under both stressed and unstressed conditions. It was hypothesized that hens selected for adaptation to multiple-bird cages would react less intensely to stressors and therefore lay more eggs and have lower mortality under stressed conditions. Three lines of chickens (selected, control, and commercial) were housed in either single-hen (1 hen) or multiple-hen cages (12 hens, social competition) at 16.7 or 17.1 wk of age. They were subsequently subjected to cold exposure at 33 wk of age and heat exposure at 44 wk of age. The selected line of chickens in multiple-hen cages showed an increased resistance to heat exposure, as indicated by lower mortality, when compared to the control and commercial lines housed in multiple-hen cages. Egg production 8 d prior to, during, and 8 d following either cold or heat exposures indicated that the selected line of chickens withstood social, handling, and environmental stressors better than the control line and, in some cases, the commercial line of chickens. It was concluded that the selected line of Leghorns showed evidence of stress resistance through lowered mortality and improved production.

Adaptation, Physiological↗

PubMed1996

Group selection for adaptation to multiple-hen cages: humoral immune response.

A selected line of White Leghorns, which has shown improved survivability and reduced feather loss in large multiple-hen cages, was evaluated for humoral immune response to SRBC under both stressed and unstressed conditions. Three lines of chickens (selected, control, and commercial) were housed in either single- (1 hen) or multiple-hen cages (12 hens, social competition) and subjected to a cold ambient temperature (0 C) at 33 wk of age and to two heating episodes (38 C) at 44 wk of age. Each hen was challenged intravenously with 1 mL of a 7% saline suspension of SRBC at the time that cold exposure was initiated. Hens subjected to high ambient temperatures had been exposed previously to a cold temperature, but were not challenged with SRBC until 16 to 18 h following the end of the second heating episode. Exposure to cold caused immunosuppression in single-caged hens, but not in hens in colony cages. Single- vs colony-caged hens of the control environment challenged with SRBC at 33 wk of age had similar primary hemagglutinin responses to SRBC. Hens subjected to heat experienced immunosuppression at 9 and 12 d following challenge to SRBC when compared to the controls. Hens of multiple-bird cages challenged with antigen at 44 wk of age had a significantly lower hemagglutinin response to SRBC than those reared in single-bird cages. The three lines of genetic stock had similar primary hemagglutinin responses to SRBC; the interactions of genetic stock with cage size or environmental temperature were not significant. It was concluded that genetically selecting hens for survival in multiple-hen cages did not affect their humoral immune response to SRBC.

Adaptation, Physiological↗

PubMed1995

Multistage selection for maximum economic return with an application to beef cattle breeding.

Methodology for selection index updating was developed to allow multistage selection. The program determines truncation points for each stage of selection that will maximize either profit or the ratio of aggregate economic gain to cost (R = delta H/C). Either maximum profit or R may be attained by reducing the cost of performance testing in later stages of a multistage program. In order to eliminate the need for multiple integration and assure convergence, a piecewise algorithm was developed. Examples of beef bull selection compared single-stage selection at 1 yr of age, two-stage selection at birth and 1 yr, two-stage selection at 205 d and 1 yr, and three-stage selection at birth, 205 d, and 1 yr. Selection based on three traits (birth weight, gain birth to 205 d, and gain 205 to 365 d) was compared with selection based on four traits (the above three plus ultrasound fat depth) and selection based on five traits (the above four plus feed:gain ratio). Five scenarios were used that allowed variation in proportion of candidates selected for breeding, number of progeny per selected bull, and proportion of profit returned to the nucleus herd. General conclusions based on the examples were 1) multistage selection reduced aggregate economic gain relative to that attained by single-stage selection, 2) inclusion of feed conversion in the index of traits resulted in reduced profit and aggregate economic gain, 3) measurement of feed conversion could be justified when selected bulls produced a large number of progeny, and 4) three-trait selection produced greater profit in all five scenarios than did four- or five-trait selection. Use of the selection updating program described here provides a new source of information that can be used in developing economically sound performance testing and selection programs.

Aging↗

PubMed1991

Multistage selection for genetic gain by orthogonal transformation.

An exact transformed culling method for any number of traits or stages of selection with explicit solution for multistage selection is described in this paper. This procedure does not need numerical integration and is suitable for obtaining either desired genetic gains for a variable proportion selected or optimum aggregate breeding value for a fixed total proportion selected. The procedure has similar properties to multistage selection index and, as such, genetic gains from use of the procedure may exceed ordinary independent culling level selection. The relative efficiencies of transformed to conventional independent culling ranged from 87% to over 300%. These results suggest that for most situations one can chose a multistage selection scheme, either conventional or transformed culling, which will have an efficiency close to that of selection index. After considering cost savings associated with multistage selection, there are many situations in which economic returns from use of independent culling, either conventional or transformed, will exceed that of selection index.

Animals↗