Evidence for distinct polygenic regulation of antibody responses to some unrelated antigens in lines of mice selected for high or low antibody responses to somatic antigen of Salmonella

The effect of the selective breeding of mice for high or low antibody production to complex immunogens is largely nonspecific, since it modifies the responsiveness of high (H) and low (L) lines to many antigens unrelated to the selection antigen. However, the nonspecific effect of the polygenic control operating in these lines is not a general feature. For example, the group of genes in selection IV, carried out for responsiveness to somatic antigen of Salmonella, does not modify the responses to sheep erythrocytes (SE). Despite equivalent responses in H and L mice of selection IV, a large variability was found in individual responses of F₂ interline hybrids, which demonstrates the presence of alleles with high or low effect on responses to SE. A selective breeding (Selection IV-A) was therefore initiated from this F₂ population for responsiveness to SE. A progressive interline divergence occurred during the first seven generations of selection; the interline separation was due to polygenic regulation (about four independent loci from a preliminary estimate).Equivalent responses to the s antigen of Salmonella are observed in the two lines. This constitutes additional evidence for distinct polygenic regulation of responses to SE and to somatic antigen. Moreover, the pattern of responses to several unrelated antigens (nonspecific effect) also differs between Selections IV and IV-A.Abbreviations H high responder lines - L low responder lines - s somatic antigen of Salmonella - f flagellar antigen of Salmonella - R response to selection - S selection differential - F₀ foundation population - h² heritability (realized) - RGG rabbit gamma globulin - CE chicken erythrocyte - HE human erythrocyte - PE pigeon erythrocyte - SE sheep erythrocyte     

Interaction ofH-2 and nonH-2 linked genes in the regulation of antibody response to a threshold dose of sheep erythrocytes

The antibody response to a threshold dose (¹⁰) of SE was studied in the High responder line (H) and the Low responder line (L) of mice obtained by bidirectional selective breeding for the character quantitative agglutinin response to an optimal dose of SE, and in interline hybrids: F₁, F₁ and both backcrosses. Whereas the interline difference in agglutinin responses at the optimal dose is due to the additive effect of about ten independently segregating loci, one of which isH-2 linked, the responsiveness to the threshold dose is determined by the effect of two loci. The direction of the dominance effect also varies with the antigen dose: high responsiveness is partially dominant at the optimal dose while at the threshold dose nonresponder character is partially dominant. The role of theH-2 linked locus was investigated. It has been demonstrated that on an identical background (equivalent to that of F₁ hybrids) this locus is responsible for 12% of the interline difference at the optimal antigen dose, and for 61% at the threshold antigen dose. For the two antigen doses, the quantitative effect of theH-2 locus is in agreement with the estimate of the number of loci obtained by variance analysis. The intervention of a second gene, non-H-2 linked, in the regulation of responsiveness to 10⁶ SE is demonstrated by appropriate assortative matings. The interaction between the two genes is discussed.     

Polygenic control of quantitative antibody responsiveness: restrictions of the multispecific effect related to the selection antigen

Among the differences observed between the various high (H) and low (L) antibody responder lines of mice resulting from distinct bidirectional selective breedings, one of the most puzzling is the variation in the multispecific effect, i. e., in the modification of antibody responses to antigens unrelated to those used during the selection. The best examples are the H and L lines of selection IV, selected on the basis of responses to somatic antigen of Salmonella which do not differ in their antibody responses to sheep erythrocytes (SE). However, a wide range of variability is observed in the responses of (H_IV x L_IV)F₂ hybrids to this antigen, and it was therefore hypothesized that distinct groups of genes might regulate antibody responses to SE and the somatic antigen. Indeed, a new selection (IV-A) for anti-SE responsiveness started from these (H_IV x L_IV)F₂ successfully produced a high and a low anti-SE responder line. The results of selection IV-A and the variance analysis of (H_IV-A × L_IV-A)F₂ hybrids are reported. They are roughly similar to those in selection I, also carried out for anti-SE responsiveness. In vivo attempts to identify the major regulatory mechanism which contributes to the interline difference indicate that the efficiency of macrophage accessory function has been modified in selection IV-A, as was observed in selection I, whereas this function did not differ in Hév and Lév lines. Probably in relation to the involvement of macrophage function there is a notable increase of the multispecific effect in selection IV-A when compared with selection IV. The results of selection IV-A demonstrate that responsiveness to heterologous erythrocytes and to somatic antigen of Salmonella are under separate polygenic control operating through distinct regulatory mechanisms. The choice of the selection antigen and immunization procedure is of major importance for defining the gene interaction operating in each selective breeding experiment and the extent of its multispecific effect.Abbreviations used in this paper f. ag. S. flagellar antigen of Salmonella - H high responder line (roman numeral is the selection number) - h₂ heritability - HE human erythrocytes - HoGG horse gamma globulin - L low responder line (roman numeral is the selection number) - PE pigeon erythrocytes - R response to selection - RGG rabbit gamma globulin - S selection differential - s. ag. S. somatic antigen of Salmonella - SE sheep erythrocytes     

Fed-batch production of baker's yeast using millet (Pennisetum typhoides) flour hydrolysate as the carbon source

A fermentation medium based on millet (Pennisetum typhoides) flour hydrolysate and a four-phase feeding strategy for fed-batch production of baker's yeast,Saccharomyces cerevisiae, are presented. Millet flour was prepared by dry-milling and sieving of whole grain. A 25% (w/v) flour mash was liquefied with a thermostable 1,4--d-glucanohydrolase (EC 3.2.1.1) in the presence of 100 ppm Ca²⁺, at 80°C, pH 6.1–6.3, for 1 h. The liquefied mash was saccharified with 1,4--d-glucan glucohydrolase (EC 3.2.1.3) at 55°C, pH 5.5, for 2 h. An average of 75% of the flour was hydrolysed and about 82% of the hydrolysate was glucose. The feeding profile, which was based on a model with desired specific growth rate range of 0.18–0.23 h^–1, biomass yield coefficient of 0.5 g g^–1 and feed substrate concentration of 200 g L^–1, was implemented manually using the millet flour hydrolysate in test experiments and glucose feed in control experiments. The fermentation off-gas was analyzed on-line by mass spectrometry for the calculation of carbon dioxide production rate, oxygen up-take rate and the respiratory quotient. Off-line determination of biomass, ethanol and glucose were done, respectively, by dry weight, gas chromatography and spectrophotometry. Cell mass concentrations of 49.9–51.9 g L^–1 were achieved in all experiments within 27 h of which the last 15 h were in the fedbatch mode. The average biomass yields for the millet flour and glucose media were 0.48 and 0.49 g g^–1, respectively. No significant differences were observed between the dough-leavening activities of the products of the test and the control media and a commercial preparation of instant active dry yeast. Millet flour hydrolysate was established to be a satisfactory low cost replacement for glucose in the production of baking quality yeast.Nomenclature C _ox Dissolved oxygen concentration (mg L^–1) - CPR Carbon dioxide production rate (mmol h^–1) - C _s0 Glucose concentration in the feed (g L^–1) - C _s Substrate concentration in the fermenter (g L^–1) - C _s.crit Critical substrate concentration (g L^–1) - E Ethanol concentration (g L^–1) - F _s Substrate flow rate (g h^–1) - i Sample number (–) - K _e Constant in Equation 6 (g L^–1) - K _o Constant in Equation 7 (mg L^–1) - K _s Constant in Equation 5 (g L^–1) - m Specific maintenance term (h^–1) - OUR Oxygen up-take rate (mmol h^–1) - q _ox Specific oxygen up-take rate (h^–1) - q _ox.max Maximum specific oxygen up-take rate (h^–1) - q _p Specific product formation rate (h^–1) - q _s Specific substrate up-take rate (g g^–1 h^–1) - q _s.max Maximum specific substrate up-take rate (g g^–1 h^–1) - RQ Respiratory quotient (–) - S Total substrate in the fermenter at timet (g) - S ₀ Substrate mass fraction in the feed (g g^–1) - t Fermentation time (h) - V Instantaneous volume of the broth in the fermenter (L) - V ₀ Starting volume in the fermenter (L) - V _si Volume of samplei (L) - x Biomass concentration in the fermenter (g L^–1) - X ₀ Total amount of initial biomass (g) - X _t Total amount of biomass at timet (g) - Y _p/s Product yield coefficient on substrate (–) - Y _x/e Biomass yield coefficient on ethanol (–) - Y _x/s Biomass yield coefficient on substrate (–) Greek letters Moles of carbon per mole of yeast (–) - Moles of hydrogen atom per mole of yeast (–) - Moles of oxygen atom per mole of yeast (–) - Moles of nitrogen atom per mole of yeast (–) - Specific growth rate (h^–1) - _crit Critical specific growth rate (h^–1) - _E Specific ethanol up-take rate (h^–1) - _max.E Maximum specific ethanol up-take rate (h^–1)     

High density fed-batch cultures for hybridoma cells performed with the aid of a kinetic model

Hybridoma fed-batch cultures with either standard medium as feed or concentrated medium as feed and removal of toxic metabolites through dialysis were performed by using model calculations for a priori determination of process parameters. In a first step a kinetic model for specific growth and death rate, respectively as well as for substrate uptake and metabolite production rates was formulated. In a bed-batch culture with standard medium as feed the appropriate time for start of the feeding pump and the increase of feed rate were determined a priori. The glutamine concentration was controlled at 0.04 mmoll^–1. A priori calculation and course of the culture coincided rather well. A cell concentration of 3.2×10⁶ cells ml^–1, a MAb-concentration of 54 mg _MAb l^–1 and a MAb-time-space-yield of 0.53 mg _MAb l^–1h^–1 were obtained.For further increase of the efficiency a high density fed-batch process was developed, where concentrated medium is fed to the cells and the accumulating toxic low molecular weight metabolites are removed through a dialysis membrane into a dialyizng fluid. In a membrane dialysis reactor consisting of a culture chamber and a dialyzing chamber, which are separated by a cylindrical dialysis membrane, again model calculations were used to determine feed rate and exchange rate of dialyzing fluid. A viable cell density of 1.2×10⁷ cells ml^–1 and a MAb concentration of 425 mg l^–1 were reached in a culture with stepwise feeding of 10 x concentrated medium and exchange of dialyzing fluid for removal of low molecular metabolites. The course of the culture could be predicted a priori rather well. The MAb-time-space-yield was 2.47 mg _MAb l^–1h^–1, appr. 5 times higher compared to fed-batch cultures with standard medium as feed.List of Symbols A membrane area m² - c _i substrate or product concentration in culture chamber mmoll^–1 - c _a substrate or product concentration in dialyzing chamber mmoll^–1 - c _0i substrate or product concentration in the feed of culture chamber mmoll^–1 - c _0a substrate or product concentration in the feed of dialyzing chamber mmoll^–1 - c _Gln glutamine concentration mmoll^–1 - c _Amm ammonia concentration mmoll^–1 - c _MAb MAb concentration mmoll^–1 - D _a dilution rate in dialyzing chamber d^–1 - F _i feed rate during fed-batch to the culture chamber mlh^–1 - V _a volume of dialyzing chamber l - V _i volume of culture chamber l - P membrane permeability coefficient cm min^–1 - q specific substrate uptake or metabolite production rate mmol cell^–1 h^–1 - q _Gln spec. glutamine uptake rate mmol cell^–1 h^–1 - q _MAb spec. MAb production rate mmol cell^–1 h^–1 - t time h - X _v viable cell concentration cells ml^–1 - _MAb MAb-time-space-yield mgl^–1 h^–1 - specific growth rate h^–1 - _d specific death rate h^–1 Financial support from the Volkswagen-Stiftung, Germany, grand nr. I/69 359 is gratefully acknowledged.The concentrated medium was kindly provided by SERVA, Heidelberg, Germany. The hybridoma cell line was donated by Prof. fil. dr. Volker Kasche, Technische Universität Hamburg-Harburg, Germany.We express our special thanks to Andreas Schütt, Ralf Gassner, Katja Herbers and Thomas Schäfer for their help in this project.     

Genetics of resistance to Cry1C toxin from Bacillus thuringiensis in Spodoptera litura (Fab.)

The present study was undertaken to determine the genetics of Cry1C resistance in Spodoptera litura. Selection of S. litura (Fab.) with Cry1C was done for eight generations to develop resistance. Reciprocal crosses between resistant and susceptible populations were made to understand the population genetics of Cry1C resistance in S. litura. Generation wise selection with Cry1C was evaluated for resistance development in S. litura. The LC₅₀ of Cry1C was 0.14 µg/cm² for the first selected generation and it increased to 23.98 µg/cm² after eight selected generations, which is a 285.47-fold increase in resistance compared with the susceptible strain. The estimated realized heritability (h²) after eight generations of selection with Cry1C insecticidal protein was 0.44. The number of generations required for the tenfold increase in LC₅₀ (1/R) was estimated to be 3.33. Response to Cry1C selection in S. litura was 0.30, the estimated selection differential was 0.69 and the pheonotypic standard deviation (dP) was 0.24. Reciprocal crosses between Cry1C resistant and susceptible strain of S. litura showed autosomal resistance.     

Enzymatic semisynthesis of aprotinin homologues mutated in P′ positions

The replacement of amino acids in the P₁ and P₂ position of aprotinin, the bovine pancreatic trypsin inhibitor, is described. Using the modified inhibitor as starting material, with the hydrolyzed reactive-site peptide bond Lys¹⁵-Ala¹⁶, the residues P₁ (Ala¹⁶) and P₂ (Arg¹⁷) were split off by the action of aminopeptidase K. Incorporation of suitable dipeptides containing a basic residue (Lys or Arg) in the C-terminal position was carried out in a one pot reaction involving trypsin-catalyzed coupling. In this way, the native fragment Ala¹⁶-Arg¹⁷ was reintroduced and also replaced by Gly-Arg, Ala-Lys, and Leu-Arg yielding intact inhibitor molecules. The mechanism for incorporation of dipeptides was investigated by treating the aprotinin derivative with the Arg¹⁷-Ile¹⁸ peptide bond hydrolyzed with trypsin under proteosynthetic conditions. We established that only inhibitor molecules cleaved between Lys¹⁵ and Xaa¹⁶ are intermediates leading to the desired products. The inhibitory properties of the new aprotinin homologues were tested, and the significance of the P₁ residue for the inhibition of trypsin, kallikrein, and chymotrypsin was deduced.     

The mechanism of lactate transport in human erythrocytes

Summary Lactate accumulates in human erythrocytes stored at 4°C in the presence of glucose. Efflux of lactate exhibits an activation energy of 22 kcal/mole and is markedly stimulated with increasing medium pH. Lactate influx into erythrocytes that were depleted of intracellular lactate by incubation at 37° at pH 8.0 was stimulated by decreasing medium pH. Under appropriate conditions the pH-dependent lactate flux was insensitive to 4-acetamido-4-isothiocyano-2,2-disulfonic stilbene or 4,4-diisothiocyano-2,2-disulfonic stilbene, inhibitors of the inorganic anion channel, while, e.g., inorganic phosphate transport was fully sensitive. These experiments as well as measurements of H⁺ movements associated with lactate fluxes demonstrate that lactate transport takes place via a specific monocarboxylate transporter (distinct from the inorganic ion channel) by a H⁺-lactate symport mechanism.     

Temporal Genetic Variation in a Population of Aphanius fasciatus (Cyprinodontidae) from a Brackish-water Habitat at Elba Island (Italy)

Allozyme electrophoresis was used to assess temporal genetic variation in three successive generations of the Mediterranean killifish, Aphanius fasciatus. Samplings were carried out in 1995, 1996 and 1997 in a brackish-water habitat at Elba Island, Italy and a total of 212 specimens were collected. The five loci for which polymorphism has been detected in a previous study were assayed. Mean expected heterozygosity values [H=0.397 (SE 0.077), H=0.336 (SE 0.092) and H=0.313 (SE 0.092) in 1995, 1996 and 1997, respectively] were not significantly different by ANOVA test. Deviations from Hardy–Weinberg equilibrium were minimal, with only one out of the 15 probability tests showing a significant departure from the equilibrium; whereas genotypic linkage disequilibrium was not detected. Values of Nei's genetic distance were lower than 0.04. Temporal genetic variation in the A. fasciatus population at Elba Island was observed, with F-statistics indicating significant genetic divergence among samples (=0.035, SE 0.027, p<0.001). Genetic drift acting on two loci (GPD-1 ^* and LDH-3 ^*) is presumably the main force determining the temporal genetic heterogeneity observed; however, the occurrence of selection on individual loci and/or sampling error cannot be excluded. The observed allelic variation among generations in a single population of A. fasciatus is much less than levels observed among geographically discrete samples in previous studies.     

Heritability and quantitative genetic divergence of serotiny,a fire-persistence plant trait

Background and Aims

Although it is well known that fire acts as a selective pressure shaping plant phenotypes, there are no quantitative estimates of the heritability of any trait related to plant persistence under recurrent fires, such as serotiny. In this study, the heritability of serotiny in Pinus halepensis is calculated, and an evaluation is made as to whether fire has left a selection signature on the level of serotiny among populations by comparing the genetic divergence of serotiny with the expected divergence of neutral molecular markers (Q_ST–F_ST comparison).

Methods

A common garden of P. halepensis was used, located in inland Spain and composed of 145 open-pollinated families from 29 provenances covering the entire natural range of P. halepensis in the Iberian Peninsula and Balearic Islands. Narrow-sense heritability (h²) and quantitative genetic differentiation among populations for serotiny (Q_ST) were estimated by means of an ‘animal model’ fitted by Bayesian inference. In order to determine whether genetic differentiation for serotiny is the result of differential natural selection, Q_ST estimates for serotiny were compared with F_ST estimates obtained from allozyme data. Finally, a test was made of whether levels of serotiny in the different provenances were related to different fire regimes, using summer rainfall as a proxy for fire regime in each provenance.

Key Results

Serotiny showed a significant narrow-sense heritability (h²) of 0·20 (credible interval 0·09–0·40). Quantitative genetic differentiation among provenances for serotiny (Q_ST = 0·44) was significantly higher than expected under a neutral process (F_ST = 0·12), suggesting adaptive differentiation. A significant negative relationship was found between the serotiny level of trees in the common garden and summer rainfall of their provenance sites.

Conclusions

Serotiny is a heritable trait in P. halepensis, and selection acts on it, giving rise to contrasting serotiny levels among populations depending on the fire regime, and supporting the role of fire in generating genetic divergence for adaptive traits.     

Selective uptake of high density lipoproteins cholesteryl ester in the dog, a species lacking in cholesteryl ester transfer protein activity; An in vivo approach using stable isotopes

Amongst the processes involved in the reverse cholesterol transport (RCT) from organs to liver, including high density lipoproteins-apolipoprotein AI (HDL-apoAI) dependent tissue uptake and cholesteryl ester transfer protein (CETP)-mediated transfers, the selective uptake of cholesteryl ester (CE) is of increasing interest through its antiatherogenic role. The purpose of this report is to develop a simple protocol allowing study of this process in an animal model with easier quantification of CE selective uptake. The dog was chosen essentially because this animal has a low CETP activity and an appropriate size to conduce a kinetic study. Tracer kinetics were performed to estimate in vivo the contributions of the pathways involved in HDL-CE turnover in dogs. Stable isotopes, ¹³C-acetate and D₃-leucine as labeled precursors of CE and apoAI, were infused to fasting dogs. Isotopic enrichments were monitored in plasma unesterified cholesterol and in HDL-CE and apoAI by mass spectrometry. Kinetics were analyzed using compartmental modeling. Results concerned the measurement of the activity of cholesterol esterification (0.13±0.032 h⁻¹), rate of HDL-apoAI catabolism (0.024±0.012 h⁻¹), HDL-CE turnover (0.062±0.010 h⁻¹) and CE selective uptake (0.038±0.014 h⁻¹). Our results show that CE in dogs is mainly eliminated by selective uptake of HDL-CE (60% of HDL-CE turnover), unlike in other species studied by similar methods in our laboratory. This study shows that among species used to analyze cholesterol metabolism, the dog appears to be the animal in whom HDL-CE selective uptake represents the largest part of HDL-CE turnover.     

Natural selection on the plant-water relations of Cleome serrulata growing along natural moisture gradients

Summary I investigated the extent and adaptive importance of genetically-based variation in plant water relations in two populations of the annual plant Cleome serrulata found growing along relatively short (<30 m) and mild soil moisture gradients. Field measurements of predawn plant water potentials showed that plants at the dry end of the moisture gradients had consistently lower _Plant in May and June of 1984; differences up to 0.9 MPa were seen along the gradients. Seeds were collected from maternal plants growing along the moisture gradients and then grown under well-watered conditions in the greenhouse. Pressure-volume curves were constructed for a total of 92 seedlings from 25 maternal plants when the seedlings were four weeks old.Considerable genetic variation in the four highly correlated water potential components was seen in both populations, suggesting relatively high heritabilities (h²0.5). A partial correlation analysis revealed that cell wall elasticity was higher in seedlings from maternal plants which grew in the dry portions of each site. This suggested that natural selection had acted on this character during one or more previous generations. It appears that slight variations in the physiological genotype can significantly affect overall fitness in C. serulata.     

Membrane adenosine triphosphatase of Micrococcus lysodeikticus. Isolation of two forms of the enzyme complex and correlation between enzymatic stability,latency and activity.

Summary Two new forms of the plasma membrane ATP-ase ofMicrococcus lysodeikticus NCTC 2665 were isolated from a sub-strain of the microorganism by polyacrylamide gel electrophoresis. One of them had a mol.wt of 368,000 and a very low specific activity (0.80 µ mol.min^–1.mg protein^–1) that could not be stimulated by trypsin. This form has been called B^I (strain B, inactive). If the electrophoresis was carried out in the presence of reducing agents (i.e., dithiothreitol) and the pH of the effluent maintained at a value of 8.5 another form of the enzyme was obtained. This had a mol.wt of 385,000 and a specific activity of 2.5–5.0 µ mol.min^–1.mg protein^–1 that could be stimulated by trypsin to 5–10 µ mol.min^–1.mg protein^–1. This preparation of the ATPase has been called form B_A (strain B, enzyme active). The subunit composition of both forms has been studied by sodium dodecyl sulphate and urea gel electrophoresis and compared to that of the enzyme previously purified from the original strain (form A). The three forms of the enzyme had similar and subunits, with mol.wt of about 50,000 and 30,000 dalton, respectively. They also had in common the component(s) of relative mobility 1.0, whose status as true subunit(s) of the enzyme remains yet to be established. However, subunit, that had a mol.wt of about a 52,500 in form A (Andreu et al. Eur. J. Biochem. (1973) 37, 505–515), had a mol.wt similar to in form B_I and about 60,000 in form B_A. Furthermore B_A usually showed two types of this subunit ( and) and an additional peptide chain () with a mol.wt of about 25,000 dalton. This latter subunit seemed to account for the stimulation by trypsin of form B_A.Forms B_A could be converted to B_I by storage and freezing and thawing. Conventional protease activity could not be detected in any of the purified ATPase forms and addition of protease inhibitors to form B_A failed to prevent its conversion to form B_I. The low activity form (B_I) was more stable than the active forms of the enzyme and also differed in its circular dichroism. These results show thatM. lysodeikticus ATPase can be isolated in several forms. Although these variations may be artifacts caused by the purification procedures, they provide model systems for understanding the structural and functional relationships of the enzyme and for drawing some speculations about its functionin vivo.     

Linkage studies of the h gene with plant weight in flax genotrophs

Summary The association of the H-h (hairy-hairless septa) character with plant weight was studied in the coupling and repulsion phases in F₂ of reciprocal crosses between large (L) and small (S) genotrophs of flax variety Stormont Cirrus. F₂ plants of reciprocal crosses in coupling (L^H x S^h) and in repulsion (L^h x S^H) giving H-h segregations were grown with their parents at two sowing times. Significant positive and negative associations between h and plant weight were obtained. A model is proposed based on the hypothesis that the H phenotype had changed to the h phenotype at the time of induction by a heterochromatic region extending over this locus. In the heterozygote, stable equilibria of the homozygotes are destroyed and transfer of heterochromatin, or number of reiterated sequences, or a decrease in one homologue and an increase in the other, occur in this region between homologous chromosomes. The amount and direction of the association is dependent upon the frequency of transfer: 0% transfer gives complete positive association; 50% transfer, no association; 100% transfer, complete negative association. This mechanism or heterochromatic transfer preserves the Mendelian ratio of 31 of Hh in the F₂. It is also supposed that there must be other controlling elements present as well.     

Effect of genomic prediction on response to selection in forest tree breeding

Through stochastic simulations, estimates of breeding values accuracies and response to selection were assessed under traditional pedigree-based and genomic-based evaluation methods. More specifically, several key parameters such as the trait’s heritability (0.2 and 0.6), the number of QTLs underlying the trait (100 to 200), and the marker density (1 to 10 SNPs/cM) were evaluated. Additionally, impact of two contrasting mating designs (partial diallel vs. single-pair mating) was investigated. Response to selection was then assessed in a seed production population (seed orchard consisting of unrelated selections) for different effective population sizes (N_e?=?5 to 25). The simulated candidate population comprised a fixed size of 2050 individuals with fast linkage disequilibrium decay, generally found in forest tree populations. Following the genetic/genomic evaluation, top-ranked individuals were selected to meeting the predetermined effective population size in target production population. The combination of low h², high N_e, and dense marker coverage resulted at maximum relative genomic prediction efficiency and the most efficient exploitation of the Mendelian sampling term (within-family additive genetic variance). Since genomic prediction of breeding values constitutes the methodological foundation of genomic selection, our results can be used to address important questions when similar scenarios are considered.     

Ethanol-induced alterations in human erythrocyte shape and surface properties: Modulatory role of prostaglandin E1

Summary Exposure of human erythrocytes to ethanol (1 to 20% by vol) in Ca²⁺ and Mg²⁺-free phosphate-buffered saline, pH 7.4, transformed biconcave discs into spiculated echinocytes within 3 min at 25°C. The effects of ethanol were concentration- and time-dependent, but reversible by washing in the incubation buffer system within 60 min of initial exposure to ethanol. After prolonged ethanol exposure (180 min), washing of cells resulted in the formation of stomatocytes (cup-forms). Ethanol-induced echinocytosis was also accompanied by a 30% enhancement in the agglutinability of erythrocytes by ligands with high affinity for negative surface charge (poly-l-lysine and wheat germ agglutinin, 20 l/ml) without any alterations in surface charge topography. Concomitant exposure of erythrocytes to prostaglandin E₁ (100nm) selectively prevented the enhancement of ligand-mediated agglutinability, but did not modify cell shape. These data indicate that certain erythrocyte surface properties may not be directly influenced by cell shape and suggest a unique modulatory action of prostaglandin E₁ on shape-transformed cells.     

Association between line per se and testcross performance for eight agronomic and quality traits in winter rye

Key message

We investigated associations between line per se and testcross performance in rye and suggested that selection for per se performance is valuable for several traits in multi-stage selection programs.

Abstract

Genotypic correlation between line per se and testcross performance is an important quantitative-genetic parameter for optimizing hybrid breeding programs. The main goal of this survey was to study the association of line per se and testcross performance at the phenotypic level. We used experimental data from the line per se and testcross performance of two segregating winter rye populations (A, B) with each of 220 progenies tested in six environments for eight agronomic and quality traits. Genotypic variances were considerably larger for per se than for testcross performance of all investigated traits resulting in higher heritabilities of the former in most instances. Genotypic correlations (r _g) between testcross and line per se performance decreased with increasing complexity of the trait as shown by the respective heritabilities. They were highest (r _g ≥ 0.7) for plant height and test weight in population B, and thousand-kernel weight, falling number and starch content in both populations. A selection of these traits for line per se performance in early generations will save field plots in further testing testcross performance and increase efficiency of hybrid breeding.     

Forward and reverse response to artificial selection

Summary The effect of t generations of reverse selection after t generations of forward selection can be described by expressing the change in the metric mean resulting from reverse selection (R) interms ofthe change in the metric mean due to the previous forward selection (x). An additive model of artificial selection in a population of effective size N with no natural selection has been considered.If reverse selection is continued for as many generations as the previous forward selection (t=t), then the ratio R/x equals 1 – F where F is the inbreeding coefficient for a neutral locus at generation t and is estimated as [1–(1–1/2N)^t]. The result of a single generation of reverse selection (t=1) following t generations of forward selection can be described in terms of the ratio NR₁/Dx where R₁ is the response to the first generation of reverse selection. The value of NR₁/x is expected to be (1–F) /2F.For any period of reverse selection following any period of forward selection, the value of R/x never exceeds t /t, and tends to decrease exponentially from this value as t increases.     

Heritable variation for female remating in Lobesia botrana, a usually monandrous moth

The occurrence of heritable variation for polyandry in the usually monandrous moth Lobesia botrana Den. and Schiff. (Lepidoptera: Tortricidae) was studied in the laboratory, using isofemale lines, a selection experiment and F₁ and F₂ crosses between the selected line (S) and an unselected control line (C). We assessed polyandry by observing the frequency of recalling in once mated females (i.e. the frequency of females resuming calling after mating). Polyandry differed significantly between isofemale lines, ranging from 0 to 100% in a normal distribution. Heritability of polyandry ±SE, estimated as a threshold trait using a full-sib design, wash² =0.40±0.12. Artificial selection for polyandry resulted in a significant increase from 32 to 65% in which a plateau occurred. Realized heritability in the first and second generations of selection yielded estimates ofh² =0.41 and h²=0.53, respectively. We also found a concomitant, significant increase in matings per female. In the sixth generation (S line), when only females that had mated more than twice were used as parents, polyandry rose again from 65 to 80%. Results from F₁ crosses supported the hypothesis that polyandry was recessive and autosomally inherited. Cavalli's joint scaling test confirmed these results, yielding values ±SE ofd =0.18±0.03 and h=−0.16±0.05. Observed and expected frequencies of polyandry in F₂ fitted significantly under the hypothesis of a two-loci model. The underlying implications of heritable variation in polyandry in a usually monandrous species are outlined, from an evolutionary perspective, in the context of the adaptive significance of this aspect of insect mating systems. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Characterization of the hydrogen bond network in guanosine quartets by internucleotide 3hJNC′ and 2hJNN scalar couplings

Scalar coupling correlations across hydrogen bonds with carbonyl groups as acceptors have been observed in a variety of proteins, but not in nucleic acids. Here we present a pulse scheme that allows such an observation and quantification of trans-hydrogen bond ^3hJ_NC correlations in nucleic acid base pairs, between the imino nitrogen ¹⁵N1 and the carbonyl ¹³C6 nuclei within the guanine quartets of the Oxy-1.5 DNA-quadruplex. Intra- and internucleotide N-H···O=C connectivities can be traced around each guanine quartet, allowing the hydrogen bonding partners to be unambiguously assigned. Absolute values of the ^3hJ_NC couplings are approximately 0.2 Hz as quantified by a selective long-range H(N)CO experiment and are thus on average smaller than the analogous ^3hJ_NC couplings observed in proteins. In addition, an improved version of the pseudo-heteronuclear H(N)N-COSY [Majumdar et al. (1999) J. Biomol. NMR, 14, 67–70] is presented which allows simultaneous detection of the ¹⁵N-donor and ¹⁵N-acceptor resonances connected by ^2hJ_NN couplings in hydrogen bonds involving amino groups. Using this experiment, values ranging between 6 and 8 Hz are determined for the ^2hJ_NN couplings between ¹⁵N2 and ¹⁵N7 nuclei in the guanine quartet. These values are not strongly influenced by the presence of a significant amount of chemical exchange broadening due to amino group rotations.