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PubMed1995

Rapid screening for bacterial phenotypes capable of biodegrading anionic surfactants: development and validation of a microtitre plate method.

The Biolog microtitre plate assay, which is based on tetrazolium dye reduction as an indicator of sole-carbon-source utilization, has been evaluated as a rapid method to investigate the biodegradation of five classes of anionic surfactant by pure and mixed cultures of bacteria. The assay gave reproducible results over a fourfold range of inoculum optical density, and the surfactant concentration was selected to provide a compromise between the length of the lag period prior to colour production and the maximum colour produced. A kinetic model was developed and used to analyse the appearance of colour in the assay and was found to give rise to three biologically significant parameters describing the processes underlying the assay. No false-positives were obtained with environmental isolates. The small number of false-negatives obtained (< 8% of the total) could be explained by the methodology used to prepare the bacterial inoculum. All isolates which were positive in the Biology assay were shown to be both primary and ultimate degraders of the test surfactant. These results show that the method provides a useful means of studying the biodegradation of anionic surfactants by both pure and mixed cultures of bacteria and will find use in the rapid analysis of biodegradation kinetics and specificities of larger numbers of individual isolates than hitherto possible. In addition, an important benefit of the methodology is that it can be used for direct analysis of the biodegradation potential of whole bacterial communities without having to make an artificial selection during laboratory growth.

Bacteria↗
PubMed2001

Thermoregulatory responses of two mouse Mus musculus strains selectively bred for high and low food intake.

We examined the thermoregulatory responses of male and female mice Mus musculus that had been divergently selected on voluntary food intake, corrected for body mass, to produce a high-intake and a low-intake strain. Resting metabolic rate was determined by indirect calorimetry (at 30 degrees C, 25 degrees C, 15 degrees C and 5 degrees C). Body temperature responses were measured in a separate group of mice in a parallel protocol. High-intake mice had significantly elevated body masses compared to low-intake mice in both sexes. Lower critical temperature in both strains appeared to be around 28 degrees C. At 30 degrees C there was a significant strain effect on resting metabolic rate, with high strain mice having greater metabolism than low strain mice. Sex and body mass were not significant main effects on resting metabolic rate and there were no significant interactions. Body temperature measured at 30 degrees C, 25 degrees C, 15 degrees C and 5 degrees C differed significantly between sexes (females higher) and there was a significant sexxbody mass interaction effect, but there was no difference between strains. Thermal conductance was significantly related to strain and sex, mice from the high strain and males having greater thermal conductances than mice from the low strain and females. Artificial selection has resulted in high-intake mice having greater body masses and greater thermal conductances, which together account for up to 45% of the elevated daily energy demands that underpin the increase in food intake. The greater levels of food intake were also associated with higher resting metabolic rates at 30 degrees C.

Animals↗
PubMed2006

Sex ratio variation in Iberian pigs.

Within the area of sex allocation, one of the topics that has attracted a lot of attention is the sex ratio problem. Fisher (1930) proposed that equal numbers of males and females have been promoted by natural selection and it has an adaptive significance. But the empirical success of Fisher's theory remains doubtful because a sex ratio of 0.50 is also expected from the chromosomal mechanism of sex determination. Another way of approaching the subject is to consider that Fisher's argument relies on the underlying assumption that offspring inherit their parent's tendency in biased sex ratio and therefore that genetic variance for this trait exists. Here, we analyzed sex ratio data of 56,807 piglets coming from 550 boars and 1893 dams. In addition to classical analysis of heterogeneity we performed analyses fitting linear and threshold animal models in a Bayesian framework using Gibbs sampling techniques. The marginal posterior mean of heritability was 2.63 x 10(-4) under the sire linear model and 9.17 x 10(-4) under the sire threshold model. The probability of the hypothesis p(h(2) = 0) fitting the last model was 0.996. Also, we did not detect any trend in sex ratio related to maternal age. From an evolutionary point of view, the chromosomal sex determination acts as a constraint that precludes control of offspring sex ratio in vertebrates and it should be included in the general theory of sex allocation. From a practical view that means that the sex ratio in domestic species is hardly susceptible to modification by artificial selection.

Animals↗
PubMed1976

Lactation: some cardiovascular and metabolic consequences, and the mechanisms of lactose and ion secretion into milk.

Lactation causes increases in mammary blood flow, gastrointestinal blood flow and cardiac output in the rat, and the suckling-induced release of lactogenic anterior pituitary hormones probably causes these changes, directly or indirectly. Metabolic requirements of lactation in women are similar to those in other animals not artificially selected for a high milk yield but the physiological control of the relationship between milk secretion and nutrient availability is not well understood. The unusual composition of the aqueous phase of human milk (rich in lactose but poor in sodium and potassium ions) can be explained by the same basic mechanisms for secretion of lactose and ions as operate in other animals but with quantitative differences.

Animals↗
PubMed2005

A chicken consultation with ramifications.

In Madison I once worked with two postdoctoral fellows who had spent their youth in New York City and who, when asked what birds they knew both responded "why, pigeons and LBJ's!" (little brown jobbies). Despite their undoubted brilliance, they clearly had an educational deficiency not fixed by buying eggs and poultry at a grocery store. Though of enormous economic and nutritional importance to humans, turkeys and chickens constitute only a minute fraction of the disappearing avian life in our ecology. One could easily teach an entire middle or high school biology course around the reproduction, embryology, evolution, genetics, anatomy, special adaptations, virology, bacteriology, taxonomy, behavior, and extinctions of birds, as paradigmatic of all of life. Where would developmental or evolutionary biology be without the Galapagos finches, chick embryo, or neurobiology without the Zebra Finch? The modifications of the original red jungle fowl of India and South East Asia into hundreds of races through artificial selection and breeding practices provide as beautiful an example of developmental plasticity, well-known to Darwin, as the domestic dog, cat, laboratory mice, and guinea pigs. In what follows I have begun to repay my indebtedness to my mentor Emil Witschi who introduced me to developmental biology, physiology, and genetics and its historical study on the basis of birds (and amphibians); and to Mark Leppert, Professor of Human Genetics at the University of Utah for collaborative support, and bird-watching fieldtrips.

Animals↗
PubMed1984

Comparative analysis of the development of wing-flapping and flight in the fowl.

The development of wing-flapping rate, lateral flight, wing area, and the ratio of wing area to body weight are described in the Japanese quail (Coturnix coturnix japonica) and three chickens (Gallus gallus) to determine common developmental phenomena and to assess the effects of domestication. The chickens were the White Leghorn (a commercial egg producer), the Cornish X Rock (a commercial meat producer), and the Red Jungle fowl (the probable ancestor of domestic chickens). All birds performed drop-evoked wing-flapping on the day of hatching, at least 1 week before lateral flight was possible. Flapping rate of chickens doubled between hatching (approximately 4-6 Hz) and 13 days (approximately 9-12 Hz), after which it leveled off. Japanese quail (JQ) maintained a high flapping rate (approximately 11-13 Hz) during the 21 days after hatching. The Jungle fowl (JF) and JQ flapped the fastest and the White Leghorn (WL) and Cornish X Rock (CR) chickens flapped the slowest. The JF, WL, and JQ developed lateral flight at 7-9 days. The CR first flew 1-2 weeks later but subsequently became flightless. The WL, JF, and JQ had similar ratios of wing area to body weight; the ratios increased to a peak at 11-15 days and later declined. The ratio of the very heavy, essentially flightless, CR was approximately one-half that of the flighted JQ, WL, and JF. The wing-flapping frequencies of the domestic WL and CR chickens approximated that of the JF, suggesting that domestication did not affect the motor pattern generator for flight. The artificial selection of the CR for high body weight drastically diminished its flight performance by producing an unfavorable ratio of wing area to body weight. The JF and the domestic WL both flew well and had similar ratios. Domestication affected flight performance but not the neural circuitry producing wing-flapping. The central nervous system is much more conservative in its response to selection than the peripheral effector structures that it drives.

Animals↗
PubMed1991

Elevated paraquat resistance can be used as a bioassay for longevity in a genetically based long-lived strain of Drosophila.

A long-lived (L) strain of Drosophila melanogaster, derived from a normal-lived (R) strain by artificial selection, has a significantly different adult longevity. Previous work has shown that 1) the two strains age in the same manner, 2) the major genes responsible for much of the L strain's extended longevity are located on the 3rd chromosome, and 3) the extended longevity phenotype is significantly modulated by the larval environment. In this report, we investigate the resistance of the L and R strains to the lethal effects of dietary paraquat. We show that, within the limitations of our described chromosomal and environmental manipulations, the extended longevity phenotype always accompanies the phenotype of elevated paraquat resistance. In addition, reversed selection applied to the L strain results in the simultaneous decrease of both life span and paraquat resistance. Thus, the presence or absence of the latter phenotype may be used as a bioassay for the presence or absence of the extended longevity phenotype, without any necessary implication of causality. Use of this bioassay should greatly speed up the genetic analysis of this system by allowing us to identify long-lived animals at a young age. Finally, we show that the age-related loss of elevated paraquat resistance in both strains precedes all the other age-related functional decrements which we have previously noted in this system.

Animals↗
PubMed2003

Early photoperiod history and short-day responsiveness in Siberian hamsters.

Siberian hamsters exhibit seasonal, photoperiod influenced cycles of reproductive activity, body size, pelage characteristics, and thermoregulatory behavior. Laboratory populations generally exhibit inter-individual variability in expression of photoperiod responsiveness, with a subset of individuals that fail to show the species typical responses to short photoperiod. This variability is partly explained by a genetic component, as it has been possible to increase the number of short-day nonresponders by artificial selection. Responsiveness to short photoperiod is also substantially influenced by photoperiod history in this species; hamsters that have been raised under long (16L) or very long (18L) day lengths are less likely to exhibit winter-type responses to short days as compared to hamsters raised under an intermediate (14L) day length. In the present experiment, we examined effects of age and early photoperiod history in a strain of Siberian hamsters that had been selected for short-day nonresponsiveness. Hamsters transferred into short photoperiod on the day of birth were uniform in exhibiting winter-type responses. However, hamsters raised until 25 days of age in either continuous illumination or in 16L exhibited variation in responsiveness when subsequently moved into short photoperiod. We conclude that virtually all hamsters of the short-day nonresponsive strain are born responsive to short days. Subsequent development of resistance to potential short day effects is dependent on age and/or photoperiod history.

Analysis of Variance↗
PubMed2007

Do large dogs die young?

In most animal taxa, longevity increases with body size across species, as predicted by the oxidative stress theory of aging. In contrast, in within-species comparisons of mammals and especially domestic dogs (e.g. Patronek et al., '97; Michell, '99; Egenvall et al., 2000; Speakman et al., 2003), longevity decreases with body size. We explore two datasets for dogs and find support for a negative relationship between size and longevity if we consider variation across breeds. Within breeds, however, the relationship is not negative and is slightly, but significantly, positive in the larger of the two datasets. The negative across-breed relationship is probably the consequence of short life spans in large breeds. Artificial selection for extremely high growth rates in large breeds appears to have led to developmental diseases that seriously diminish longevity.

Animals↗
PubMed1998

A test of how well the repeatability of courtship predicts its heritability.

We compared repeatability and heritability estimates for courtship traits in the housefly Musca domestica L., to test the expectation that the repeatability of a behaviour is an upper-bound estimate of its heritability. The repeatabilities across and within mating partners for two courtship traits, male wing buzzing (Buzz) and female wing extension (Wing-out), were compared to heritabilities calculated from the divergence among subpopulations due to founder-flush events or artificial selection. The male's Buzz showed highly significant repeatabilities within and across female partners, but the values ranged widely (0.3-0.5). The intensity of Buzz decreased significantly with successive courtship attempts to the same female, apparently as a male strategy to optimize his efforts to gain copulation by modulating behaviour for specific females. Repeatabilities for female Wing-out within and across male partners were not significant, but this trait yielded significant heritabilities in two assessments (based on successful courtships). We attribute this contradiction to biased sampling because only the subset of reluctant females met the necessary restriction to refuse copulation throughout four successive courtships. These results demonstrate that repeatabilities are labile within individuals and may actually underestimate heritabilities when there is a genetic predisposition not to repeat performance. We concur with related studies that repeatabilities can identify evolutionary potential, but we advise caution in interpreting low values or comparing their absolute values.Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Schistosoma mansoni: continuous variation in susceptibility of the vector snail of schistosomiasis, Biomphalaria tenagophila I. Self-fertilization-lineage.

Mascara, D., Kawano, T., Magnanelli, A. C., Silva, R. P. S., Sant' Anna, O. A., and Morgante, J. S. 1999. Schistosoma mansoni: continuous variation in susceptibility of the vector snail of schistosomiasis, Biomphalaria tenagophila I. Self-Fertilization-Lineage. Experimental Parasitology 93, 133-141. Artificial selection of Biomphalaria tenagophila snails for susceptibility to infection by Schistosoma mansoni (Brazilian SJ strain) was carried out from natural populations. After five self-fertilization generations, two lineages were isolated and were designated as SUSC (highly susceptible 93-100%) and RES (nonsusceptible 5-0%). Length of the prepatent period, cercarial production, and mortality of the hosts in postexposure were determined in all generations (F(1)-F(8)) and were analyzed as quantitative traits related to host susceptibility. Distribution patterns of frequencies were observed within snail families (samples derived from one F(0) snail), these traits showing a significant influence by selection applied to susceptibility. The multiple quantitative classes were described in terms of continuous variation. During the selection of SUSC lineage, classes with higher values of prepatent length and lower cercarial production were eliminated, and the heritability calculated for these two traits was 0.811 and 0.709, respectively. Experimental results were correlated with an increase in the level of susceptibility in the generations selected and are discussed in relation to inheritance patterns as well as the quantitative variation of susceptibility.

Animals↗
PubMed1977

Quantitative electron microscopic analysis of the epithelium of normal human alveolar mucosa.

The epithelium of normal human alveolar mucosa originating from the anterior vestibulum was subjected to stereologic analysis. Eight biopsies were collected half-way between the muco gingival junction and the vestibular fornix from 20 to 50 year-old females, and processed for light and electron microscopy. At two levels of magnification, electron micrographs were sampled from four artificially selected strata in regions of epithelial ridges. Stereologic point counting based on a computer-aided system for analyzing stratified epithelia served for examining a total of about 860 electron micrographs. The alveolar epithelium was 0.26 mm thick, occasionally interdigitated by short, slender connective tissue papillae, and consisted of (1) a narrow basal and suprabasal, and (2) a broad spinous and surface compartment. It displayed a differentiation pattern which, in most subjects studied, was similar to that of normal human buccal epithelium, however, on the average, produced less mature surface cells. This pattern was expressed mainly by a density increase of cytoplasmic filaments (98 A in diameter), a concomitant decrease of the cytoplasmic ground substance, the formation of dark-cored membrane coating granules, and invividually variable amounts of glycogen deposition. In some subjects, a mixed differentiation pattern was found. The structural organization of alveolar epithelium, in analogy to cheek epithelium, was compatible with the function of distensibility.

Adult↗
PubMed1984

The role of lipid and antioxidant exchanges in cell division synchronization (mathematical model).

Cell-cycle synchronization of two diffuse-coupled cells has been studied in the framework of the membrane model for the cell division cycle, proposed by Chernavskii et al. (1977). It has been shown semi-analytically (using the averaging principle) and by computer stimulation that a) if the duration of the G1-phase (TG1) for two identical cells is comparable with the duration of the remaining cycle (TS + G2 + M), the lipid (L)-exchange results in a synchronization with phase difference phi = 0. The antioxidant (A)-exchange leads to a phase-locking with phi = T0/2 (where T0 is the cell cycle period; b) if TG1 much greater than TS + G2 + M (or TG1 much less than TS + G2 + M) the L-exchange makes synchronization possible both with phi = 0 and phi = T0/2 while the A-exchange results in phase-locking with phi confined to the region 0 to T0/2; c) for non-identical cells differing in the values of kinetic parameters, the locking band narrows as the population density increases (when some model parameters are close to the bifurcation thresholds). We expect that the cells selected artificially at a definite phase of cycle might maintain the synchronous division for a long time if the lipid exchange between cells were stimulated.

Antioxidants↗
PubMed1991

Electrophoretic variation at flight-related enzyme loci and its possible association with flight capacity in Epiphyas postvittana.

Variations at three flight-related enzyme loci, delta-glycerophosphate dehydrogenase (delta-Gpdh), glucose-6-phosphate dehydrogenase (G6pd), and phosphoglucomutase (Pgm), of Epiphyas postvittana (Walker) moths were investigated using starch gel electrophoresis. Among the three enzyme loci, delta-Gpdh and G6pd were found to be monomorphic, but Pgm was polymorphic, with a total of seven different genotypes and five alleles identified in this study. Comparisons of allozyme variability at the Pgm locus showed significant differentiation among five natural populations sampled from geographically distinct localities in New Zealand and Australia and between laboratory populations differentiated by artificial selection on flight capacity. The Pgm polymorphism was shown to be associated with the variation of flight capacity, but the role of the enzyme locus in the evolution of flight behavior is to be demonstrated in this species.

Animals↗
PubMed1989

Genetic analyses of photoresponsiveness in the Djungarian hamster, Phodopus sungorus.

Endotherms living at temperate and arctic latitudes must adjust their physiology and behavior in order to survive seasonal change. The Djungarian hamster uses photoperiod to cue annual cycles of reproduction and thermoregulation, and its responses to short photoperiod include loss of body weight and change in pelage color. Some individuals do not exhibit these responses when exposed to short days. In this study individual variation in photoresponsiveness is quantified, and four lines of evidence for a genetic component to that variation are provided. First, two separate breeding stocks differed in both the percent of animals responding to a short-day lighting regimen (SD) and in the degree and timing of their response. Second, analysis of variance within and between families of full sibs for a photoresponsive index, PI (body weight loss +2 (molt index -1] following 12 weeks in SD demonstrated a significant family resemblance (intraclass correlation of 0.36 +/- 0.03). Third, heritability estimates from regression of offspring scores on parent scores for body weight loss, molt index and PI after 12 weeks in SD were 0.34 +/- 0.13, 0.36 +/- 0.10 and 0.37 +/- 0.12, respectively, indicating a strong additive genetic component for the three characters. Finally, a significant response occurred after one generation of artificial selection for and against photoresponsiveness.

Animals↗
PubMed1993

Sources of behavioral deviation modeled by early color preferences in quail. III. Developmental stability and normative canalization.

Successful artificial selection of quail (C. coturnix japonica) for divergent early approach preferences for, and imprintabilities to, the wavelength characteristics of otherwise identical visual stimuli decreased the trait's developmental stability. The developmental error that resulted from selecting for extreme initial preferences was associated with enhanced imprintabilities. Conversely, the developmental error that resulted from selecting for extreme imprintabilities was associated with enhanced expression of directional gene effects in extreme initial preferences. The data are attributed to selectively relaxed normative canalization of trait development, and to related enhanced expression of genetic, environmental, and stochastic influences in trait deviations.

Animals↗
PubMed1975

A genetic analysis of phototactic behavior in Drosophila melanogaster. II. Hybridization of divergent populations.

Artificial selection has produced populations of Drosophila melanogaster which show either positive or negative phototactic behavior. Selection was carried out in the presence of various marked multiple inversions used to suppress genetic recombination. Reciprocal hybridizations between photopositive and photonegative populations of flies have revealed the X chromosome of D. melanogaster to be important in phototactic behavior regardless of conditions which restricted genetic recombination during selection.

Animals↗
PubMed1992

Sources of behavioral deviation modeled by early color preferences in quail. II. Diathetic genes and the leftover variance "V(e)".

The sources of deviation from population-typical norms of variability were studied in relation to early approach preferences between colors in newly hatched Japanese quail chicks (Coturnix coturnix japonica). Subjects were drawn from an unselected genetic control line, two genetic lines that were artificially selected for extreme blue and red preferences, their hybrids, and a large set of backcross and assortatively derived generations. Large progressive increases were observed with selection in the leftover (V(e)) component of F1 variance and consistent additional variance increases in F2 hybrids. Backcross generations exhibited greater than expected expression of the blue and red preference genes. Discussion differentiates between diathetic and normative influences in preference deviations and relates the increased Ve to relaxed normative canalization of preference development by directional selection.

Animals↗