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At least 19 recordsLinked to original sources
PubMed2005

[Genetic selection of Biomphalaria glabrata and Biomphalaria tenagophila seeking the alteration of the susceptibility and resistance to Schistosoma mansoni].

Generations of Biomphalaria glabrata and Biomphalaria tenagophila selected genetically for resistance and susceptibility to Schistosoma mansoni of strains BH and SJ were used in a study of the trematode adaptation to the intermediate host. Descendants of the planorbids were obtained by self-fertilization of the mollusks that became susceptible or resistant after exposure to the miracidia of Schistosoma mansoni. For Biomphalaria glabrata they were obtained from the following generations: Parental, F1S (Susceptible), F1R (Resistant), F2S and F2R. For Biomphalaria tenagophila the studied generations were: Parental, F1S, F1R and F50S. The comparison of the infection rates presented by the different generations showed that the increase in susceptibility was more easily obtained in both species. The difficulty in increasing the resistance of the mollusks to Schistosoma mansoni has important epidemiologic implications.

Animals↗
PubMed1995

[Comparative analysis of patterns of localization of mobile genetic elements in genetic selection experiments on Drosophila melanogaster].

A comparative selection-genetic analysis of three heterogeneous lines of Drosophila melanogaster with an interrupted longitudinal wing vein was performed. In the control line, riC, and two selection lines, riSP and riSN, overall patterns of localization of six families mobile genetic elements (MGE) (MGE) (MDG1, MDG2, MDG3, MDG4, copia, and 297) were compared. In all, the lines contained 220 sites (copies) in 153 segments of the Bridges' map. According to response to selection, six classes of sites were identified: strong positive (P), weak positive (p), neutral (n), weak negative (n), strong negative (N), and abnormal (A). More than 50% of the sites (P+N+p+n) were shown to respond to selection; the contrasting classes (P and N and p and n) counterbalanced each other. These sites are assumed to mark actual parts of the genome, where polygenes are located. In other words, more than 50% of the total number of the genome sites act as polygenes controlling this quantitative character and respond to selection. Pleiotropy of polygenes in such a system must be very high. 22.2% of sites are neutral (class 0); apparently, they do not mark polygenes. The remaining 21.8% of sites (class A) show an anomalous response to selection. They are assumed to mark the polygenes of another genetic system, which participated in the maintenance of homeostasis in the original line riC. On the basis of this evidence, the concept of oligogenes and polygenes is developed. Oligogenes and polygenes are genes that occupy respectively limiting and nonlimiting positions in systems of expression. Adaptive properties of oligogenes are evaluated first and evolve rapidly. Adaptive properties of polygenes are evaluated only with regard to their total set and are limited by oligogenes. Variation of polygenic systems is generated by polygenic combination and spontaneous transpositions and excisions of MGE.

Animals↗
PubMed1997

Genetic selection strategies--population genetics.

This paper provides an overview of the association between population genetics and selection strategies in poultry. Relationships between artificial and natural selection and among causes contributing to limits to artificial selection are discussed. Homeostasis and resource allocations at the individual and at the population level are reviewed. Examples from poultry demonstrate where human intervention has circumvented biological limits. Lastly, this paper considers the role of population genetics in future breeding strategies for poultry.

Animal Husbandry↗
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↗
PubMed1999

Genetic selection of phage engineered for receptor-mediated gene transfer to mammalian cells.

Although phage display is a powerful way of selecting ligands against purified target proteins, it is less effective for selecting functional ligands for complex targets like living cells. Accordingly, phage display has had limited utility in the development of targeting agents for gene therapy vectors. By adapting a filamentous bacteriophage for gene delivery to mammalian cells, however, we show here that it is possible to screen phage libraries for functional ligands capable of delivering DNA to cells. For example, when targeted with epidermal growth factor (EGF), M13 bacteriophage were capable of delivering a green fluorescent protein (GFP) gene to EGF receptor bearing cells in a ligand-, time-, and phage concentration-dependent manner. The EGF-targeted phage transduced COS-1 cells in a highly specific manner as demonstrated by competition with excess free EGF or alternatively with anti-EGF receptor antibodies. We further demonstrate that EGF-phage can be selected, by their ability to transduce EGF receptor bearing cells from libraries of peptide display phage. When phage were incubated with COS-1 cells, EGF ligand-encoding sequences were recovered by PCR from FACsorted, GFP-positive cells and the EGF-displaying phage were enriched 1 million-fold by four rounds of selection. These data suggest the feasibility of applying molecular evolution to phage gene delivery to select novel cell-specific DNA-targeting ligands. The same approach could be used to select genetically altered phage that are specifically designed and evolved as gene therapy vectors.

Animals↗
PubMed1989

Altering milk composition through genetic selection.

The genetic relationships among carrier, fat, protein, and lactose will allow genetic alteration in any direction desired, although some changes would be much easier than others. Genetic parameters may vary somewhat between different populations, thus affecting the rates of different directions of change. In general, however, selection for an alteration in the fat:protein ratio would proceed rapidly, principally through alteration of fat concentration. Genetic alteration of composition is likely only if economic incentives for such change exist. Economic values, and therefore selection pressure, should be applied to amounts of components rather than concentrations. Recent developments in the theory of deriving economic weights for animal breeding indicate that selection indexes need to be reassessed. Although optimum breeding goals will vary somewhat, in most circumstances fat and protein yields and concentrations and the fat:protein ratio are likely to increase due to genetic selection. Only in the unlikely situation that fat has a very small or negative economic weight are other changes indicated. Lactose concentrations are unlikely to change much in any situation. Genetic variation in the composition of fat and protein, while of biological interest, is unlikely to be of more than minor importance in genetic improvement.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Analysis of sequences and predicted structures required for viral satellite RNA accumulation by in vivo genetic selection.

In vivo genetic selection was used to study the sequences and structures required for accumulation of subviral sat-RNA C associated with turnip crinkle virus (TCV). This technique is advantageous over site-specific mutagenesis by allowing side-by-side selection from numerous sequence possibilities as well as sequence evolution. A 22 base hairpin and 6 base single-stranded tail located at the 3'-terminus of sat-RNA C were previously identified as the promoter for minus strand synthesis. Approximately 50% of plants co-inoculated with TCV and sat-RNA C containing randomized sequence in place of the 22 base hairpin accumulated sat-RNA in uninoculated leaves. The 22 base region differed in sat-RNA accumulating in all infected plants, but nearly all were predicted to fold into a hairpin structure that maintained the 6 base tail as a single-stranded sequence. Two additional rounds of sat-RNA amplification led to four sequence family 'winners', with three families containing multiple variants, indicating that evolution of these sequences was occurring in plants. Three of the four sequence family winners had the same 3 bp at the base of the stem as wild-type sat-RNA C. Two of the winners shared 15 of 22 identical bases, including the entire stem region and extending two bases into the loop. These results demonstrate the utility of the in vivo selection approach by showing that both sequence and structure contribute to a more active 3'-end region for accumulation of sat-RNA C.

Base Sequence↗
PubMed1991

Induction of leukotriene production before antigen challenge enhances antibody affinity in genetically selected mice.

Mice genetically selected for their incapacity to produce high-affinity antibody to protein antigens in adjuvant (nonmaturing (NM) mice) were treated with indomethacin, an inhibitor of the cyclooxygenase pathway of arachidonic acid metabolism. Pretreatment with indomethacin significantly enhanced the affinity of antibodies produced 21 days after immunization with human serum albumin (HSA). Blockage of the cyclooxygenase pathway in this way was shown to induce the production of leukotrienes via the lipoxygenase pathway. The production of leukotrienes may well be responsible for the enhanced antibody affinity, since blockage of the lipoxygenase pathway in addition to the cyclooxygenase pathway reversed the effect. In an attempt to elucidate the mechanisms involved, IL-1 production and Ia expression by macrophages were examined. Ia expression by peritoneal cells from untreated NM mice was significantly lower than that by their high-affinity-producing counterparts 3 days after immunization. Indomethacin pretreatment raised inducible Ia antigen levels on macrophages of NM mice to those seen on cells from untreated high-affinity mice. Indomethacin treatment alone induced the production of IL-1 by macrophages in NM mice. However, 3 days after immunization and the withdrawal of indomethacin in NM mice, IL-1 production was significantly lower than the response of NM mice given antigen alone, suggestive of the induction of a feedback mechanism. Thus indomethacin pretreatment results in a cascade of events in macrophages which produce a decrease in IL-1 production and an increase in inducible Ia expression 3 days after antigen challenge.

Animals↗
PubMed1989

Site-directed deletion mutagenesis using phagemid vectors and genetic selection.

Oligonucleotide-directed mutagenesis was used along with the dut and ung genetic selection method of Kunkel to introduce large site-specific deletions into cDNAs cloned into phagemid vectors. We find that large deletions can be achieved with an efficiency equal to that of single point mutations, with a very low frequency of aberrent clones. To facilitate screening of clones, E. coli strain DH5 alpha was used as the recipient host cell to genetically select for deletion mutants. Comparisons were made to deletion mutagenesis without genetic selection, and to reactions utilizing two oligonucleotide primers simultaneously. The low frequency of deletion mutants observed without genetic selection renders random screening for deletion mutant clones cumbersome. The results provide representative expectations and a useful guide for those contemplating the construction of deletion mutants.

Base Sequence↗
PubMed2005

Molecular correlates of emotional learning using genetically selected rat lines.

The genetic contributions to active avoidance learning in rodents have been well established, yet the molecular basis for genetically selected line differences remains poorly understood. To identify candidate genes influencing this active avoidance paradigm, we utilized the bidirectionally selected Syracuse high- and low-avoidance (SHA and SLA) rat lines that markedly differ in their two-way active avoidance behavior. Rats were phenotyped, rested to allow recovery from testing stress and then hippocampi were dissected for gene expression profiling (Affymetrix U34A chips; approximately 7000 known genes), comparing SLA to SHA. Next, a subset of differentially expressed genes was confirmed by real-time PCR (RT-PCR) in hippocampi. Additional studies at the protein level were performed for some genes. Using triplicate arrays on pooled hippocampal samples, differentially expressed genes were identified by microarray suite 5.0 and robust multi-array average analyses. By RT-PCR analysis in hippocampi, eight genes were nominated as potential candidate genes consistent with the differential expression from the microarray data. Four genes, Veli1 (mlin-7B), SLC3a1, Ptpro and Ykt6p, showed higher expression in SHA hippocampi than SLA. Four genes, SLC6A4, Aldh1a4, Id3a and Cd74, showed higher expression in SLA hippocampi than SHA. The active avoidance behavioral difference between lines probably emerges from 'many small things'. These potential candidate genes generate hypotheses for future testing in human association and rodent studies. Differences in levels of a pleiotropic gene like Ptpro and SLC6A4 suggest that small differences over a lifespan may contribute to large behavioral differences.

Animals↗
PubMed1999

Effects of genetic selection and voluntary activity on the medial gastrocnemius muscle in house mice.

In a previous study, we found that in house mice both genetic selection (10 generations of artificial selection for high voluntary activity on running wheels) and access to running wheels (7-8 weeks) elicited a modest increase in maximal oxygen consumption. Based on these results, we hypothesized that genetic selection would affect the changes in endurance and oxidative capacity of the medial gastrocnemius (MG) muscle induced by wheel access (training response). Wheel access increased the isotonic endurance of the MG in both genetically selected and random-bred (control) mice. However, this exercise-induced improvement in isotonic endurance of the MG was similar between genetically selected and control mice. Wheel access also increased the succinate dehydrogenase activity of MG muscle fibers in both selected and control lines. However, this exercise-induced increase in succinate dehydrogenase activity was comparable between genetically selected and control animals. Taken together, these results indicate that the modest increase in maximal oxygen consumption associated with genetic selection is not reflected by the training-induced changes in oxidative capacity and endurance of MG muscle fibers.

Animals↗
PubMed2003

Enhancing immunity to nematode parasites in single-bearing Merino ewes through nutrition and genetic selection.

The effectiveness of protein supplementation and genetic selection to enhance the resistance of periparturient Merino ewes to infection from gastrointestinal parasites was tested in a replicated grazing experiment. One hundred and twenty ewes from lines selected for increased resistance (R) to Haemonchus contortus or at random (C) were subjected to one of the three supplement groups that provided 0 or 250 g per day cottonseed meal for 5 weeks prior to, or for 6 weeks after the start of lambing. Faecal egg counts (FEC) of R ewes were consistently lower than those of C ewes but both groups exhibited a periparturient rise in FEC. Supplementation during the pre-partum period reduced FEC and increased ewe body weight gain. The benefits of pre-partum supplementation in reducing FEC continued to be apparent up to 10 weeks after supplementation ceased. There was a strong suggestion that the benefits to parasite resistance from protein supplementation were greatest in C ewes. Wool growth rates (15%) and birth weights (5%) were greater for C ewes but differences between the lines for lamb body weight had disappeared by day 97. The greatest benefit to resistance from protein supplementation was observed when ewes were experiencing a loss of maternal body weight. Conversely, no benefits to resistance were observed when ewes had moderate (78-107 g per day) rates of maternal weight gain. These results suggest that increased resistance as a result of protein supplementation is dependent on the prevailing supply and demand for scarce nutrients such as metabolisable protein (MP). Both genetic selection and protein nutrition are effective strategies to enhance host resistance to nematode infection during the periparturient period.

Aging↗
PubMed2004

Effects of Lonomia obliqua (lepidoptera, saturniidae) toxin on clotting, inflammatory and antibody responsiveness in genetically selected lines of mice.

Lines of mice genetically selected for high (H) or low (L) antibody response and for maximal (AIRMAX) or minimal (AIRMIN) acute inflammatory reaction, in which the opposite extreme potentialities have been clearly defined, offer an appropriate model for investigating the environmental and genetic factors acting on innate and adaptative immunobiological functions. This model has been successfully employed to study the resistance or susceptibility against pathogens and/or toxins. It had been demonstrated that the skin contact with Lonomia obliqua caterpillar bristles induces local inflammation and may elicit severe hemorrhagic disorders. In the present study, blood coagulation time, and the acute inflammatory reaction were scored 24 h after injection of the Lonomia bristles crude extract in a subcutaneous dorsal air pouch. The acute inflammation was determined by the leukocyte concentration in the local exudates. The highest interline differences were observed between the AIRMAX (10(6) cells/ml) and AIRMIN (2 x 10(5) cells/ml) and this distinct expression involves the number of monocytes, eosinophils and mainly neutrophils. Regarding coagulation, the highest interline difference was observed between the HIII and LIII mice, and the F1)[LIII x HIII] hybrids showed the overdominance of the fast clotting character. The adaptative immune response was evaluated by comparing the anti-Lonomia bristle extract IgG titer among the lines: the antibody titers were higher in the H lines than in the L ones and equivalent in the AIRMAX and AIRMIN mice, in accordance to the phenotype profiles generated by the distinct selective processes. The genetically selected mice lines-AIRMAX, AIRMIN, HI, HIII, HG, LIII and LG-showed an almost continuous distributions for inflammation, coagulation time and IgG antibody titers, being the interline variances always higher than the intraline ones for the individually measured phenotypes. Altogether, these results suggest the independent polygenic regulation of these traits, being indicative of the genetic control to Lonomia toxin innate and adaptative sensitivity in humans.

Analysis of Variance↗
PubMed1978

Trichinella spiralis infection in mice. Mechanism of the resistance in animals genetically selected for high and low antibody production.

Mice genetically selected according to their capacity to produce antibody were orally infected with fifty muscle larvae. After 1 month, the number of larvae found in low responder mice was twice the number found in high responder mice. Following a second infection, low responder mice were completely protected while high responder mice showed only partial protection. It is suggested that the better resistance of high responder mice after a primary infection is due to their high and rapid antibody production. However, at the time of a secondary infection both lines of mice possess enough antibody to act on the effector cells (macrophages, eosinophils, etc.) and resistance is then dependent on the metabolic activity of these cells, which is more intense in the low responder mice.

Animals↗
PubMed1988

A genetic selection for temperature-sensitive variants of the gene V protein of bacteriophage f1.

Complementary negative and positive genetic selections based on the activity of a plasmid-encoded bacteriophage f1 gene V are developed. The negative selection is based on an activity of the gene V protein in E. coli cells which markedly reduces the infection of those cells by f1-related viruses. In order to select against cells expressing active gene V protein, the cells are infected with the p'age R386, a derivative of f1 which confers resistance to chloramphenicol, and are plated in the presence of the antibiotic. Those cells which contain gene V protein are infrequently infected with the virus and are unable to grow in the presence of chloramphenicol; those which do not contain the gene V protein are readily infected and can grow in the presence of the antibiotic. The positive genetic selection consists of excising the gene V sequences from the plasmids and using them to replace the gene V of a bacteriophage f1 derivative containing an amber mutation in gene V. Only those genes which encode an active gene V protein can support phage growth and yield plaques. The two genetic selections can be combined in order to yield a substantial enrichment for genes encoding temperature-sensitive gene V proteins.

Cloning, Molecular↗
PubMed1993

Molecular cloning of the olfactory neuronal transcription factor Olf-1 by genetic selection in yeast.

A novel genetic selection in yeast has been used to isolate a complementary DNA for the transcriptional activator, Olf-1, which binds to the regulatory sequences of several olfactory-specific genes. The Olf-1 protein, expressed exclusively in the olfactory receptor neurons and their precursors, contains a new helix-loop-helix motif and functions as an apparent homodimer. Olf-1 may be the first member of a family of related proteins that may direct cellular differentiation in a variety of neuronal tissues.

Amino Acid Sequence↗
PubMed2003

Chemical complementation: small-molecule-based genetic selection in yeast.

Protein and metabolic engineering would greatly benefit from a general system linking the presence of a small molecule to the power of genetic selection. We use nuclear receptors to link the survival of Saccharomyces cerevisiae to the presence of small molecules through genetic selection, extending classical genetic complementation to a new "chemical complementation." In this system the Gal4 DNA-binding domain is fused to ligand-binding domains from two nuclear receptors, expressed in the strain PJ69-4A, and grown on plates containing known ligands for the receptors. Yeast survive on selective plates only in the presence of a nuclear receptor and the corresponding ligand. Mutagenesis can increase the sensitivity of chemical complementation. This system may be extended to engineer nuclear receptors for practically any small molecule through directed evolution coupled to genetic selection, and for performing metabolic engineering in yeast.

Antineoplastic Agents↗
PubMed1982

Muscle and adipose tissue lipoprotein lipase in fetal and neonatal swine as affected by genetic selection for high or low backfat.

The effect of genetic selection for backfat accumulation on adipose tissue and muscle lipoprotein lipase (LPL) in fetal and neonatal pigs was investigated. Fetal pigs at 110 d of gestation were taken surgically from sows of either a high backfat (High) or low backfat (Low) line of Yorkshire pigs selected over 18 generations on the basis of backfat thickness at 80 kg live weight. Fetuses of Yorkshire (Control) and Ossabaw (Obese) sows were used for comparison. Activities of LPL/mg cytoplasm protein in subcutaneous adipose tissue were 2.23 +/- .19, 3.98 +/- 1.06, 6.37 +/- .83 and 7.57 +/- .66 nmol FFA released/min and LPL/g tissue was 34.80 +/- 4.06, 58.36 +/- 14.23, 99.55 +/- 15.15 and 159.94 +/- 9.7, for Low, Control, High and Obese 110-d fetuses, respectively. Muscle (semimembranous) LPL/mg protein was 1.06 +/- 1.17 and 1.39 +/- .20 and LPL/g tissue was 50.11 +/- 6.9 and 59.07 +/- 9.12 for High and Low line fetuses, respectively. Fetal body composition was not different for High and Low lines. In 14 d-old suckling pigs, adipose tissue LPL/mg protein had increased to 18.09 +/- 3.48 and 17.76 +/- 3.98 and LPL/g tissue was 291.12 +/- 56.60 and 308.45 +/- 64.43 in High and Low line pigs, respectively. Muscle LPL/mg protein had decreased to .83 +/- .08 in High and 1.25 +/- .13 in Low line pigs, while LPL/g muscle was similar between these lines. These effects of genetic selection on muscle and adipose tissue suggest that early in development, the partitioning of nutrients to lean of fat tissues may be altered, eventually leading to a marked difference in body composition.

Adipose Tissue↗