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PubMed2025

Selection of geographical populations suitable for artificial breeding of the Northeast China Brown Frog (Rana dybowskii).

Amphibians, as a group greatly disturbed by human activities, are at increased risk of extinction. Rana dybowskii is an anuran species with both ecological and economic significance. Due to environmental changes and human overexploitation, it has been classified as Near-Threatened. This study integrates morphological and molecular immunological approaches to identify R. dybowskii populations with greater survival and disease resistance, based on 32 morphological traits and MHC class I and II polymorphism. Morphological results showed that compared with other populations, Yichun (YC) population had the highest fatness, the lowest IOD/HW, and the largest HW/SVL, HL/SVL, HW/HL, SL/TL. It indicates that YC population shows larger body size, wider vision and stronger jumping ability. The polymorphism of MHC I gene was the highest in Shangzhi (SZ) population, and the polymorphism of MHC II gene was the highest in YC population. Moreover, duplication, selection, and recombination occurred during evolution of MHC class I and II genes. Since both SZ and YC populations scored higher in this category (the variant sites, nucleotide polymorphism, amino-acid divergence/nucleotide divergence, dN/dS, Tajima' D, etc.), they were more resistant to disease. All in all, these results indicated that YC population of the Lesser Khingan Mountains had good morphology and immune results, and R. dybowskii in the Lesser Khingan Mountains might be more suitable to be the original population of artificial breeding, which provided a theoretical basis for the realization of artificial breeding in the next step.

Ranidae↗
PubMed2002

An alternative focus in strategic research on disease vectors: the potential of genetically modified non-biting mosquitoes.

We examine the constraints and the feasibility of field experiments involving the release of genetically modified (GM) pathogen-resistant mosquitoes, and whether there are alternatives to the research line based on the production of refractory strains. The production of a GM mosquito strain characterized instead by obligate primiparous and parous autogeny and by disrupted host seeking and biting behaviour could make the release more acceptable by the general public. Genetic transformation should act in this case to reverse some of the essential steps of the evolutionary process that gave rise to hematophagy. The replacement strategy could be based on the mass release of both sexes in a well defined ecological niche made temporarily empty of the natural population, thus avoiding the problems related to the need of sexual competitiveness of the released material. This option is encouraged by the growing evidence that competitive exclusion mechanisms influence the pattern of distribution of different taxa within Anopheles gambiae s.s. and by the fact that the plesiomorphic characteristics of vitellogenesis without a blood meal (autogeny), which exploits fat body reserve accumulated during larval life and food other than blood in adult life, persist as genetic variants in various hematophagous insect groups, and it has been found secondarily fixed in others showing stable reversions to primiparous and parous autogeny. If this has been the result of natural selection, then the artificial production of non-biting mosquito strains, by selection and/or transgenesis, should be feasible.

Animals↗
PubMed2006

Sexual reproduction selects for robustness and negative epistasis in artificial gene networks.

The mutational deterministic hypothesis for the origin and maintenance of sexual reproduction posits that sex enhances the ability of natural selection to purge deleterious mutations after recombination brings them together into single genomes. This explanation requires negative epistasis, a type of genetic interaction where mutations are more harmful in combination than expected from their separate effects. The conceptual appeal of the mutational deterministic hypothesis has been offset by our inability to identify the mechanistic and evolutionary bases of negative epistasis. Here we show that negative epistasis can evolve as a consequence of sexual reproduction itself. Using an artificial gene network model, we find that recombination between gene networks imposes selection for genetic robustness, and that negative epistasis evolves as a by-product of this selection. Our results suggest that sexual reproduction selects for conditions that favour its own maintenance, a case of evolution forging its own path.

Animals↗
PubMed1993

Permeation mechanisms through artificial lipoidal membranes and effects of synthetic surfactants on xenobiotic permeability.

Through the use of permeation/lipophilicity correlations, the mechanisms of permeation of selected test compounds across artificial lipoidal membranes of the polysiloxane type, in the absence and in the presence of a nonionic surfactant (Polysorbate 80), are investigated, in order to design "in vitro" conditions and features suitable for reproducing "in vivo" intestinal absorption tests, as well as to validate some conclusions arising from "in situ" rat gut experiments about the effects of the synthetic surfactants on drug and xenobiotic absorption processes. Six 4-alkylanilines showing a perfect homology were used as test compounds. The reported results clearly show that the in situ biophysical absorption (diffusion) models are completely reproduced by in vitro tests, provided that perfect sink conditions are achieved. Further selection of artificial membrane polarity should be necessary, however, in order to exactly equalize in vitro and in situ permeation rates. As far as the synthetic surfactant action on permeability is concerned, our conclusions are similar to those drawn from in situ studies, except that the effect of the surfactant on membrane polarity is much smaller and the micelle-solubilizing effect somewhat larger. The disruption of the aqueous stagnant diffusion layers adjacent to the membranes by the surfactant has been conclusively demonstrated. A clear first-element deviation for aniline, which prevents its inclusion as a term of the tested series, has been observed; this feature should be borne in mind whenever any in vivo/in vitro correlation has to be established.

Absorption↗
PubMed2001

[Use of matroclinous haploid plants in recurrent selection in corn].

Two cycles of recurrent selection were performed in maize with the use of matroclinous haploids. Two synthetic populations, SP and SA, were improved. Each cycle consisted of two stages: (1) isolation of haploids from the synthetic populations and (2) growth of the haploids, pollination with pollen from diploid plants, and selection. The selection was performed for ear size in haploid plants. The mean gain in productivity in the synthetic populations SP and SA the per cycle was 16.48 and 20.98%, respectively. It is suggested that the high value of this index is related to the fact that haploid plants reveal useful genes with additive and epistatic effects. Natural selection may have played a part, too. The combination of artificial and natural selection in haploids resulted in a considerable gain in productivity in the synthetic populations to be improved.

Epistasis, Genetic↗
PubMed1994

A yeast artificial chromosome clone map of the Drosophila genome.

We describe the mapping of 979 randomly selected large yeast artificial chromosome (YAC) clones of Drosophila DNA by in situ hybridization to polytene chromosomes. Eight hundred and fifty-five of the clones are euchromatic and have primary hybridization sites in the banded portions of the polytene chromosomes, whereas 124 are heterochromatic and label the chromocenter. The average euchromatic clone contains about 211 kb and, at its primary site, labels eight or nine contiguous polytene bands. Thus, the extent as well as chromosomal position of each clone has been determined. By direct band counts, we estimate our clones provide about 76% coverage of the euchromatin of the major autosomes, and 63% coverage of the X. When previously reported YAC mapping data are combined with ours, euchromatic coverage is extended to about 90% for the autosomes and 82% for the X. The distribution of gap sizes in our map and the coverage achieved are in good agreement with expectations based on the assumption of random coverage, indicating that euchromatic clones are essentially randomly distributed. However, certain gaps in coverage, including the entire fourth chromosome euchromatin, may be significant. Heterochromatic sequences are underrepresented among the YAC clones by two to three fold. This may result, at least in part, from underrepresentation of heterochromatic sequences in adult DNA (the source of most of the clones analyzed), or from clone instability.

Animals↗
PubMed2005

Impact of genetic selection on management of boar replacement.

Boars in an artificial insemination centre have been selected for their superior genetic potential, with 'superior' being defined as having traits the customer wants transmitted to his herd. The ability to meet the customers' needs depends on the heritability of the trait, the geneticist's success in devising a selection scheme for the trait in balance with other economically important traits, and the boar's ability to produce sperm that can fertilise oocytes. Genetic evaluation research over the past 20 years has greatly increased the number of traits for which a boar can be selected: currently in the Canadian national program, these include age at 100 kg, backfat at 100 kg, feed efficiency, lean yield and litter size. In the near future, traits that are very likely to be added to this selection list include piglet survival, marbling, loin eye area and structure traits. In Canada, sires are ranked on two estimated breeding value (EBV) indices; one, focused on development of terminal sire lines, is based on the growth and yield traits and another, primarily focused on maternal line development, de-emphasises these traits and incorporates litter size. Boars that are in Canadian AI centres because of their excellent growth traits are typically in the top 5-10% of the national population for terminal sire line index, but they may be only average or substandard for litter size. Conversely, boars selected to be in the top 5-10% for conveying such reproductive traits as litter size may only be in the top 33% for growth traits. The more offspring from a superior boar in either of these indices, the faster the population average for the trait improves. The original sire gets knocked out of the elite group, is culled and replaced by a higher ranked young boar from the now improved general population. Although genetic superiority should govern an AI centre's selection and culling of boars, decision-making in real life is seldom that simple. Selection criteria may be contradictory as above, or a boar with truly superior traits may be excluded because a newly-developed molecular genetics test determines he carries an undesirable gene such as PSS, RN or others being developed. Selection for terminal sire or maternal line traits can ignore important practical factors that affect an AI centre--boars with superior genetics may not produce good semen because skeletal or penile problems prevent ejaculation, or because sperm production is poor due to a genetic flaw, disease, or some other cause. Interestingly, selection pressure for one trait may inadvertently select for a trait that is linked but whose linkage is unrecognised, and such unintentionally selected genes could benefit, harm, or have no effect on production traits. An AI centre serving a variety of customers must select boars in anticipation of their customers' needs (including new, foreign and niche markets). A centre should also review its genetic evaluation results and progeny records, both to critique its own selection success and to try to detect unexpected linkages. Finally, an AI centre needs to predict its own future, selecting not just for production traits for the swine producer, but also for factors that enhance the centre's efficiency including boar conformation and temperament, and sperm quantity, quality and hardiness. Can we select for efficiency? Our colleagues in dairy cattle AI evaluate bull performance--should the swine industry consider evaluation of male fertility traits?

Animals↗
PubMed1982

Diet versus average Danish food in insulin-dependent diabetes mellitus. An evaluation during treatment with an artificial betacell.

Ten randomly selected insulin-dependent diabetics with minimal betacell function were studied during treatment with an artificial betacell during two consecutive 24-hour periods. Patients were randomly served diabetic diet for one 24-hour period and average Danish food during the other 24-hour period. No significant (P greater than 0.05) difference was found between the mean blood glucose concentrations, nor insulin requirements on average Danish food compared to diet. However, the mean amplitude of glucose excursions was significantly higher on average Danish food than on diabetic diet (median 3.6 versus 2.7 mmol/l, P less than 0.05). Thus insulin-dependent patients not following their diabetes diet will show increased blood glucose fluctuations.

Adolescent↗
PubMed2006

Air versus ground transportation of artificially ventilated neonates: comparative differences in selected cardiopulmonary parameters.

OBJECTIVE: To assess if cardiopulmonary interventions and abnormal CO2 tension are more likely in intubated neonates transported by air versus ground. METHODS: We reviewed the transport records of all ventilated neonates retrieved to a pediatric teaching hospital in the United States within a 12-month period. Demographic data, underlying diagnosis, pretransport and posttransport ventilation settings and blood gas data, and transport data were recorded. RESULTS: Seventy-five intubated neonates were transported by ground (n = 43), helicopter (n = 29) and by fixed-wing aircraft (n = 3). Thirty-nine patients (52%) received interventions, including adjustments of ventilator settings (36 patients) and increase in the rate of dopamine infusion or boluses infusion (volume expanders or sodium bicarbonate) in 9 patients. There were no overt pneumothoraces, endotracheal tube complications, arrhythmias, or cardiopulmonary resuscitation en route. The posttransport blood gas analysis revealed 7 patients with hypercapnia greater than 55 mm Hg and 17 patients with hypocapnia of less than 30 mm Hg. When compared with patients with Pco2 30 to 55 mm Hg, all patients with posttransport Pco2 greater than 55 mm Hg had interventions en route (P = 0.01). No significant difference between the mode of transport and stabilization time, return time, diagnostic groups, interventions, or the occurrence of hypercapnia and hypocapnia was identified. Additional adjustments of ventilatory settings were retrospectively considered necessary in many of these patients with Pco2 greater than 55 mm Hg or less than 30 mm Hg. CONCLUSIONS: There were no cardiopulmonary disasters (such as overt pneumothoraces, endotracheal tube complications, arrhythmias, or cardiopulmonary resuscitation en route) in the various modes of neonatal transport. Adjustments of ventilation, inotropes, and volume infusion are often required for stabilization of patients during the dynamic process of transport. When compared with ground transport, there is no increase in the risk of cardiopulmonary interventions or abnormal CO2 tension in air transport of intubated neonates. Additional adjustments of ventilatory settings were retrospectively considered necessary in many of these patients with significant hypercapnia or hypocapnia.

Ambulances↗
PubMedDate not supplied

Evolvability of Hsp70 expression under artificial election for inducible thermotolerance in independent populations of Drosophila melanogaster.

To test whether expression of the inducible heat-shock protein Hsp70 increases under selection for inducible thermotolerance in Drosophila melanogaster, we performed artificial selection on replicate sets of Drosophila lines founded from two independent populations. Selection entailed pretreatment at 36 degrees C to induce thermotolerance and Hsp70 expression, followed by a more severe heat shock, whose temperature varied between sexes and among generations to achieve 50% mortality. Inducible thermotolerance increased slowly and continuously in selected lines and was 37%-50% greater than in controls after 10-11 generations. Lines founded from the two populations differed in their coevolution of Hsp70 expression. In lines founded from Evolution Canyon, Israel, Hsp70 level initially increased and thereafter was unchanged; replicate lines exhibited two temporal patterns of response to selection. In lines founded from Australia, Hsp70 levels increased throughout selection. In both cases, however, the increase in Hsp70 level averaged only 15%, suggesting that pleiotropy in Hsp70 function constrains evolutionary increase in its expression.

Adaptation, Physiological↗
PubMed1993

Influence of selective decontamination of the digestive tract on microbial biofilm formation on endotracheal tubes from artificially ventilated patients.

The effect of selective decontamination of the digestive tract on the nature and incidence of microbial biofilm formation on endotracheal tubes was assessed. Thirty endotracheal tubes were obtained post-extubation from patients in the intensive care unit who had been ventilated for a 1 to 15 day period and who did or did not receive the antibiotic regimen. Extensive biofilm formation was identified by scanning electron microscopy on 97% of tubes examined. Endotracheal tube biofilm in tubes obtained from patients who received selective decontamination of the digestive tract showed a high prevalence of colonization with yeast (4 of 15 tubes) and gram-positive bacteria (streptococci, staphylococci and diphtheroids) (14 of 15 tubes). Staphylococcus aureus was isolated only from this group. Pseudomonas spp. were isolated from 2 of 15 tubes in both patient groups. Enteric gram-negative organisms (coliforms, Klebsiella and Proteus spp.) were isolated only from tubes of patients who did not receive the antibiotic regimen (4 of 15 tubes). Yeasts, however, were not isolated from these tubes. Group D streptococcal isolates were resistant to tobramycin as were half of the Staphylococcus aureus isolates. For gram-negative bacteria, the MIC of tobramycin was in the range 1-64 micrograms/ml and the MIC of polymyxin in the range 0.5-16 micrograms/ml. Although a reduction was observed in the incidence of gram-negative microorganisms, this antibiotic regimen does not inhibit biofilm formation on the endotracheal tube by other pathogens associated with pneumonia in ventilated patients. This persistent nidus may be a factor in the pathogenesis of nosocomial pneumonia.

Adolescent↗
PubMed2006

Site-selective hydrolysis of huge DNA by artificial restriction DNA cutter.

Genomic DNAs of lambda phage (48.5 kbp) and E. coli (4.6 Mbp) were successfully cleaved at the target site by artificial restriction DNA cutter (ARCUT), which we recently developed by combining Ce(IV)/EDTA and PNA (peptide nucleic acid). PNA satisfactorily invaded the target site in such huge DNAs and activate there for Ce(IV)/EDTA-induced scission.

Bacteriophage lambda↗