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PubMed1993

Cholecystokinin and bombesin inhibit ethanol and food intake in rats selectively bred for ethanol sensitivity.

Cholecystokinin octapeptide (CCK-8) and bombesin tetradecapeptide (BBS-14) are brain-gut neuropeptides shown to inhibit intake and choice of alcohol solutions and foods in a variety of species. Recently, Draski and colleagues selectively bred strains descended from N/Nih outbred Norway rats that differ in sleep time after injection of ethanol. The intake of 5% w/v ethanol, food, and water was measured in these rats with high, low, and control alcohol sensitivity (HAS, LAS, and CAS), after intraperitoneal injection of randomized sequences of doses of CCK-8 or BBS-14 (0-8 micrograms/kg). During baseline adaptation to water deprivation-induced consumption of alcohol, LAS rats consumed reliably more ethanol than HAS or CAS rats. Injection of CCK-8 or BBS-14 significantly and equivalently suppressed intake of ethanol and food at 30 min after presentation in each group of rats. Water intake and food intake at 30-60 min following alcohol access was not affected by prior injection of either neuropeptide. Large differences in alcohol neurosensitivity (HAS > CAS > LAS) were observed in these rats' resting behavior for 1 hr after intraperitoneal injection of 1 g/kg of ethanol. These selectively bred alcohol neurosensitivity differences cannot be explained by corresponding differences in sensitivity to the inhibitory behavioral effects of CCK-8 or BBS-14. However, differences in alcohol intake and resting behavior do correspond to artificially selected sensitivities to ethanol's hypnotic effect.

Alcohol Drinking↗
PubMed2000

Host hemolymph proteins and protein digestion in larval Habrobracon hebetor (Hymenoptera: braconidae).

Host plasma proteins and protein digestion in larval parasitoids were studied during trophic interactions of the ectoparasitoid Habrobracon hebetor Say (Hymenoptera: Braconidae), with a host, larvae of the Indianmeal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). We could detect no apparent differences in host hemolymph protein patterns up to 72 h after paralysation and/or parasitization by H. hebetor. A 190 kDa putative apolipophorin I present in host hemolymph could not be detected in the midguts of feeding H. hebetor larvae indicating that it is rapidly digested. The major 60 kDa storage proteins (putative hexamerins) in host hemolymph were detected in the parasitoid midgut and were completely digested 24 h after cessation of feeding and the beginning of cocoon formation. Host hemolymph had a pH of about 6.4. The pH optima of the midgut proteinases in the larval parasitoid were in the alkaline region, but midgut fluid in feeding parasitoid larvae was about pH 6. 8. Based on enzyme activity against selected artificial proteinase substrates including azocasein, N-alpha-benzoyl-L-Arg p-nitroanilide (BApNA), succinyl-Ala-Ala-Pro-Phe p-nitroanilide (SAAPFpNA), succinyl-Ala-Ala-Pro-Leu p-nitroanilide (SAAPLpNA), and inhibition by selected proteinase inhibitors, serine proteinases appear to be the predominant class of enzymes involved in protein digestion in the midguts of H. hebetor. There is also an active aminopeptidase (LpNA) associated with the microsomal fraction of midgut preparations. There was no evidence for preoral digestion or ingestion of proteinases from host hemolymph by the parasitoid larva. There was a very active BApNAase in the soluble fraction of midgut extracts. This activity increased on a per midgut basis up to 24 h after the beginning of cocoon formation but decreased rapidly by 48 h. Two major (P1 and P3) and several minor proteinases were detected in midgut extracts of H. hebetor analysed with gelatin zymograms. The apparent molecular mass of P1 varied from 95 to 49 kDa depending on protein loading. P3 had an apparent molecular mass of 39 kDa that was independent of protein loading. In summary, electrophoretic evidence indicates that host hemolymph protein patterns do not change significantly for at least 72 h after paralysation by H. hebetor. The role, if any, of envenomization in preventing breakdown of hemolymph proteins during this time remains to be determined. Because the predominant host hemolymph proteins, a putative apolipophorin I and the putative hexamerins, are readily digested by the serine proteinases present in the midguts of this parasitoid larva, these or similar proteins would provide an easily digested source of dietary amino acids that could be used for development of artificial diets for this beneficial insect.

Animals↗
PubMed2006

Relaxation of selective constraint on dog mitochondrial DNA following domestication.

The domestication of dogs caused a dramatic change in their way of life compared with that of their ancestor, the gray wolf. We hypothesize that this new life style changed the selective forces that acted upon the species, which in turn had an effect on the dog's genome. We sequenced the complete mitochondrial DNA genome in 14 dogs, six wolves, and three coyotes. Here we show that dogs have accumulated nonsynonymous changes in mitochondrial genes at a faster rate than wolves, leading to elevated levels of variation in their proteins. This suggests that a major consequence of domestication in dogs was a general relaxation of selective constraint on their mitochondrial genome. If this change also affected other parts of the dog genome, it could have facilitated the generation of novel functional genetic diversity. This diversity could thus have contributed raw material upon which artificial selection has shaped modern breeds and may therefore be an important source of the extreme phenotypic variation present in modern-day dogs.

Animals↗
PubMed1995

High resolution mapping of genetic factors affecting abdominal bristle number in Drosophila melanogaster.

Factors responsible for selection response for abdominal bristle number and correlated responses in sternopleural bristle number were mapped to the X and third chromosome of Drosophila melanogaster. Lines divergent for high and low abdominal bristle number were created by 25 generations of artificial selection from a large base population, with an intensity of 25 individuals of each sex selected from 100 individuals of each sex scored per generation. Isogenic chromosome substitution lines in which the high (H) X or third chromosome were placed in an isogenic low (L) background were derived from the selection lines and from the 93 recombinant isogenic (RI) HL X and 67 RI chromosome 3 lines constructed from them. Highly polymorphic neutral roo transposable elements were hybridized in situ to the polytene chromosomes of the RI lines to create a set of cytogenetic markers. These techniques yielded a dense map with an average spacing of 4 cM between informative markers. Factors affecting bristle number, and relative viability of the chromosome 3 RI lines, were mapped using a multiple regression interval mapping approach, conditioning on all markers > or = 10 cM from the tested interval. Two factors with large effects on abdominal bristle number were mapped on the X chromosome and five factors on the third chromosome. One factor with a large effect on sternopleural bristle number was mapped to the X and two were mapped to the third chromosome; all factors with sternopleural effects corresponded to those with effects on abdominal bristle number. Two of the chromosome 3 factors with large effects on abdominal bristle number were also associated with reduced viability. Significant sex-specific effects and epistatic interactions between mapped factors of the same order of magnitude as the additive effects were observed. All factors mapped to the approximate positions of likely candidate loci (ASC, bb, emc, h, mab, Dl and E(spl), previously characterized by mutations with large effects on bristle number.

Abdomen↗
PubMed2005

Correlated responses to selection for stress resistance and longevity in a laboratory population of Drosophila melanogaster.

Laboratory studies on Drosophila have revealed that resistance to one environmental stress often correlates with resistance to other stresses. There is also evidence on genetic correlations between stress resistance, longevity and other fitness-related traits. The present work investigates these associations using artificial selection in Drosophila melanogaster. Adult flies were selected for increased survival after severe cold, heat, desiccation and starvation stresses as well as increased heat-knockdown time and lifespan (CS, HS, DS, SS, KS and LS line sets, respectively). The number of selection generations was 11 for LS, 27 for SS and 21 for other lines, with selection intensity being around 0.80. For each set of lines, the five stress-resistance parameters mentioned above as well as longevity (in a nonstressful environment) were estimated. In addition, preadult developmental time, early age productivity and thorax length were examined in all lines reared under nonstressful conditions. Comparing the selection lines with unselected control revealed clear-cut direct selection responses for the stress-resistance traits. Starvation resistance increased as correlated response in all sets of selection lines, with the exception of HS. Positive correlated responses were also found for survival after cold shock (HS and DS) and heat shock (KS and DS). With regard to values of resistance across different stress assays, the HS and KS lines were most similar. The resistance values of the SS lines were close to those of the LS lines and tended to be the lowest among all selection lines. Developmental time was extended in the SS and KS lines, whereas the LS lines showed a reduction in thorax length. The results indicate a possibility of different multiple-stress-resistance mechanisms for the examined traits and fitness costs associated with stress resistance and longevity.

Adaptation, Physiological↗
PubMed2005

Overcoming limitations of natural anticancer drugs by combining with artificial agents.

During a billion years of evolution, living creatures have perfected cytotoxic agents to kill other organisms without killing themselves, thus providing us with antibiotics to kill bacteria without killing eukaryotic (e.g. human) cells. Some natural agents inhibit specifically most vital cellular structures and functions in cancer cells. However, nature was not creating antibiotics for cancer, and natural agents kill cancer cells precisely because they share targets with normal cells. To discriminate between particular cancer cells and normal cells, we can design or select artificial agents that are not necessarily lethal but are aimed either at cancer-specific targets or at dispensable and even unavailable (in cancer cells) targets. Using rational drug combinations, such selective agents can assist natural agents to eradicate cancer cells selectively.

Antineoplastic Agents, Alkylating↗
PubMed1995

Neural network classification of infrared spectra of control and Alzheimer's diseased tissue.

Artificial neural network classification methods were applied to infrared spectra of histopathologically confirmed Alzheimer's diseased and control brain tissue. Principal component analysis was used as a preprocessing technique for some of these artificial neural networks while others were trained using the original spectra. The leave-one-out method was used for cross-validation and linear discriminant analysis was used as a performance benchmark. In the cases where principal components were used, the artificial neural networks consistently outperformed their linear discriminant counterparts; 100% versus 98% correct classifications, respectively, for the two class problem, and 90% versus 81% for a more complex five class problem. Using the original spectra, only one of the three selected artificial neural network architectures (a variation of the back-propagation algorithm using fuzzy encoding) produced results comparable to the best corresponding principal component cases: 98% and 85% correct classifications for the two and five class problems, respectively.

Alzheimer Disease↗
PubMed2003

Ontogenies in mice selected for high voluntary wheel-running activity. I. Mean ontogenies.

The evolutionary importance of postnatal ontogenies has long been recognized, but most studies of ontogenetic trajectories have focused exclusively on morphological traits. For animals, this represents a major omission because behavioral traits and their ontogenies often have relatively direct relationships to fitness. Here four replicate lines of house mice artificially selected for high early-age wheel running and their four replicate control lines were used to evaluate the effects of early-age directional selection, genetic drift, and activity environment (presence or absence of a running wheel) on variation in the ontogenies of three traits known to be genetically correlated: voluntary wheel running, body mass, and food consumption. Early-age selection significantly changed both the shape and position of the wheel-running and food-consumption ontogenies while influencing the position, but not the shape, of the body mass ontogeny. Genetic drift (as indicated by variation among replicate lines) produced significant changes in both the position and shape of all three ontogenies; however, its effect differed between the selection and control groups. For wheel running and food consumption, genetic drift only influenced the control ontogenies, whereas for body mass, genetic drift had a significant effect in both selection groups. Both body-mass and food-consumption ontogenies were significantly altered by activity environment, with the environment causing significant changes in the shape and position of both ontogenies. Overall the results demonstrate strong effects of early-age selection, genetic drift, and environmental variation on the evolution and expression of behavioral and morphological ontogenies, with selection changing only the position of the morphological ontogeny but both the position and shape of the behavioral ontogenies.

Analysis of Variance↗
PubMed1992

Sexually antagonistic genes: experimental evidence.

When selection differs between the sexes, a mutation beneficial to one sex may be harmful to the other (sexually antagonistic). Because the sexes share a common gene pool, selection in one sex can interfere with the other's adaptive evolution. Theory predicts that sexually antagonistic mutations should accumulate in tight linkage with a new sex-determining gene, even when the harm to benefit ratio is high. Genetic markers and artificial selection were used to make a pair of autosomal genes segregate like a new pair of sex-determining genes in a Drosophila melanogaster model system. A 29-generation study provides experimental evidence that sexually antagonistic genes may be common in nature and will accumulate in response to a new sex-determining gene.

Animals↗
PubMed1998

Self-evolution in a constructive binary string system.

We examine the qualitative dynamics of a catalytic self-organizing system of binary strings that is inspired by the chemical information processing metaphor. A string is interpreted in two different ways: either (a) as raw data or (b) as a machine that is able to process another string as data in order to produce a third one. This article focuses on the phenomena of evolution whose appearance is notable because no explicit mutation, recombination, or artificial selection operators are introduced. We call the system self-evolving because every variation is performed by the objects themselves in their machine form.

Artificial Intelligence↗
PubMedDate not supplied

Nasal width as a guide for the selection of maxillary complete denture anterior teeth in four racial groups.

PURPOSE: Selecting artificial teeth for edentulous patients is difficult when pre-extraction records are not available. Various guidelines have been suggested for determining the width of the maxillary anterior denture teeth. This study was undertaken to evaluate the use of the nasal width as a guide for the selection of proper width maxillary anterior denture teeth in four racial groups of the Brazilian population. MATERIALS AND METHODS: One hundred and sixty subjects (40 Whites, 40 Mulattos, 40 Blacks, and 40 Asians) were selected. Using a sliding caliper, the nasal width and the intercanine distance were measured. The Pearson product-moment correlation coefficient was used to determine the relationship between the above measurements. A prediction was made of the percentage of subjects of the White, Mulatto, Black, and Asian populations in which the selection error due to the clinical application of the method of the nasal width would be within 0 to 2 mm, within 2 to 4 mm, and greater than 4 mm. RESULTS: The four racial groups showed a weak correlation between the intercanine distance and the nasal width. In 39.7% of the White, 55.7% of the Mulatto, 81.9% of the Black, and 48.2% of the Asian populations, errors greater than 4 mm would be present with the use of the nasal width. CONCLUSIONS: The correlation found between the intercanine distance and the nasal width was not high enough to be used as a predictive factor. The relationship between natural tooth width and artificial tooth width as predicted by the nasal width showed that the nasal width method is not accurate for all the studied groups.

Adolescent↗
PubMed2000

Ease of capture in lines of Japanese quail (Coturnix japonica) subjected to contrasting selection for fear or sociability.

Japanese quail (Coturnix japonica) of lines, which have been subjected to contrasting selection for duration of the tonic immobility (TI) reaction or social reinstatement (SR) behaviour over many generations show corresponding differences in underlying fearfulness and sociality. As fearfulness and sociality are particularly influential traits in domesticated species, the finding that such traits respond to artificial selection may have important implications for poultry welfare and performance. However, it is not known if or how such selection has influenced human-animal interactions. The present experiment investigated the influence of fearfulness and SR behaviour on the ease with which birds could be caught and handled. Birds of lines selected for duration of the TI response or SR behaviour were reared in mixed line groups (LTI and STI or HSR and LSR) of 491 and 346 birds, respectively, until 6 weeks of age. When the birds were 2, 4, and 6 weeks of age, they were caught one by one and their individual capture ranks noted. In the group of birds selected for duration of the TI response, birds selected of the line selected for short duration of TI were caught before those selected for long duration of the response. In the group of birds selected for SR motivation, birds of the high line were caught before their low lines counterparts. Coefficients of concordance between capture ranks were significant and capture ranks did not differ significantly across ages. These results imply that selection for low levels of fear or high levels of sociality produces animals that are less disturbed by human interventions than animals selected for the opposite traits. The greater ease of capture of low fear line birds than high fear line birds may be explained by reduced fear of humans. The fact that the birds selected for high levels of SR behaviour are easier to catch than birds selected for low levels of sociality is less readily explicable. One hypothesis is that HSR line chicks tend to be more strongly imprinted on each other and the human caretaker. However, SR behaviour is highly species specific in both lines, existing evidence for line differences in social discrimination is limited and birds of the two lines show similar duration of the TI response. Despite this, whatever their underlying causation, these results demonstrate that genetic selection can be used to reduce negative reactions to human beings and may be of value in the improvement of both animal welfare and productivity.

Journal Article↗
PubMed2005

No detectable genetic correlation between male and female mating frequency in the stalk-eyed fly Cyrtodiopsis dalmanni.

There is much interest in explaining why female insects mate multiply. Females of the stalk-eyed fly Cyrtodiopsis dalmanni can mate several times each day in a lifetime which may span several months. There are many adaptive explanations, but one hypothesis that has received little rigorous empirical attention is that female multiple mating has evolved for non-adaptive reasons as a correlated response to selection for high male mating frequency rather than because of direct or indirect benefits accruing to females. We tested this hypothesis in stalk-eyed flies by measuring the mating frequency of females from lines that exhibited a direct response in males to artificial selection for increased ('high') and decreased ('low') male mating frequency. We found that the mating frequency of high-line females did not differ from that of low-line females. Hence, there was no support for a genetic correlation between male and female mating frequency in this species. Our study suggests that the genes which influence remating may not be the same in the sexes, and that females remate frequently in this species to gain as yet unidentified benefits.

Analysis of Variance↗
PubMed1994

Selective hydrolysis of tRNA by ethylenediamine bound to a DNA oligomer.

A sequence-selective artificial ribonuclease was prepared by attaching ethylenediamine to the 5'-end of a DNA oligomer as the sequence-recognizing moiety. The hybrid, incorporating a 19-mer DNA which is complementary with the A44-A62 sequence of tRNA(Phe), hydrolyzed the tRNA selectively at the 3'-side of C63.

Base Sequence↗
PubMed2003

Functional trade-offs in the limb muscles of dogs selected for running vs. fighting.

The physical demands of rapid and economical running differ from those of physical fighting such that functional trade-offs may prevent simultaneous evolution of optimal performance in both behaviours. Here we test three hypotheses of functional trade-off by measuring determinants of limb musculoskeletal function in two breeds of domestic dogs that have undergone intense artificial selection for running (Greyhound) or fighting performance (Pit Bull). We found that Greyhounds differ from Pit Bulls in having relatively less muscle mass distally in their limbs, weaker muscles in their forelimbs than their hindlimbs, and a much greater capacity for elastic storage in the in-series tendons of the extensor muscles of their ankle joints. These observations are consistent with the hypothesis that specialization for rapid or economical running can limit fighting performance and vice versa. We suggest that functional trade-offs that prevent simultaneous evolution of optimal performance in both locomotor and fighting abilities are widespread taxonomically.

Agonistic Behavior↗
PubMed1979

Some models of genetic selection.

This paper begins with a description of the classical theory of viability selection in which probabilities that individuals of various genotypes survive are in proportions that do not change with time and are independent of population structure. Salient features of viability selection with one and two loci are reviewed. This theory is intimately connected with the usual theory of mass selection in quantitative genetics. It is well known that the mean of the relative viabilities does not necessarily increase if there is viability selection at more than one locus. It also turns out that if there is selection for fecundity with one locus, the mean fecundity may steadily decrease or oscillate rather than increase. This and the fact that a Hardy-Weinberg structure may no longer exist at any stage of life may have a bearing on predicting progress from artificial selection on reproductive characters. Classical viability selection theory does not completely describe natural selection. Other possibilities are discussed. Among these is the density and frequency dependent selection induced when the population lives in a limited habitat. Implications in quantitative genetics are discussed.

Alleles↗
PubMed2000

Sex-limited mutations and the evolution of sexual dimorphism.

Although the developmental and genetic mechanisms underlying sex differences are being elucidated in great detail in a number of species, there remains a breach between proximate and evolutionary studies of sexual dimorphism. More precisely, the evolution of sex-limited gene expression at autosomal loci has not been well reasoned using either theoretical or empirical methods. Here, I show that a Mendelian genetic model including elementary details of sexual differentiation provides novel insight into the evolution of sex differences via sex limitation. This model indicates that the nature of allelic effects and the pattern of selection must be known in both sexes to predict the evolution of sex differences. That is, selection interacts with genetic variation for sexual dimorphism to produce unanticipated patterns of trait divergence or convergence between the sexes. Ultimately, this model may explain why previous models for the evolution of sexual dimorphism do not predict the erratic behavior of the sex difference during artificial selection experiments.

Alleles↗
PubMed2000

Direct and correlated responses to individual selection for large adult weight in the edible snail Helix aspersa Muller.

A selection experiment for large adult weight based on individual performance was conducted for three generations in Helix aspersa aspersa. A second line was kept as an unselected control line. Direct response measured as deviation from the control line was 3.55 g after three generations of artificial selection, which averaged 13%. Realized heritability was 0.38 +/- 0.04. Correlated responses to selection showed a significant increase in weight after hibernation, mean egg weight and mean weight of newly-hatched snails with selection. For adult age, egg number, and hatching rate, no significant change correlated to selection was found, but this is to be confirmed.

Animals↗