Factorial correspondence analysis of fear-related behaviour traits in Japanese quail

Factorial correspondence analysis was performed on 341 quails from a F2 cross between two lines divergently selected on the duration of tonic immobility over 29 generations. Several fear- or stress-related traits were recorded, i.e. tonic immobility duration, number of inductions needed to induce tonic immobility, open-field behaviour (time spent walking, latency before first movement and number of defecations), asymmetry of tibia lengths and corticosterone concentration after restraint stress. Variables were categorised in classes and analysed by factorial correspondence analysis. The first axis was mostly described by open-field behaviour, and the second by tonic immobility traits (duration of tonic immobility and number of inductions), which showed that these behaviours were almost independent. No relationship was found between axes of the factorial correspondence analysis and corticosterone concentration or asymmetry of tibia lengths, showing that these variables reflected other characteristics of stress susceptibility than those described by tonic immobility and open-field behaviour. These results show that reaction to stress of quails is a multidimensional trait and cannot be summarised by one trait.

Himalayan tectonics explained by extrusion of a low-viscosity crustal channel coupled to focused surface denudation

Recent interpretations of Himalayan-Tibetan tectonics have proposed that channel flow in the middle to lower crust can explain outward growth of the Tibetan plateau, and that ductile extrusion of high-grade metamorphic rocks between coeval normal- and thrust-sense shear zones can explain exhumation of the Greater Himalayan sequence. Here we use coupled thermal-mechanical numerical models to show that these two processes-channel flow and ductile extrusion-may be dynamically linked through the effects of surface denudation focused at the edge of a plateau that is underlain by low-viscosity material. Our models provide an internally self-consistent explanation for many observed features of the Himalayan-Tibetan system.

Differential subcellular localization of hZip1 in adherent and non-adherent cells

Two human divalent cation transporters of the ZIP family, hZip1 and hZip2, homologous to Irt1 (Arabidopsis thaliana), the first identified member, have been described. They were shown by transfection into K562 cells to be localized at the plasma membrane and to mediate zinc uptake. Here we report a differential subcellular localization of hZip1 according to cell type. By transient expressions of EGFP-hZip1, FLAG-tagged or native hZip1, we observed that hZip1 has a vesicular localization in COS-7 cells or in several epithelial cell lines, corresponding partially to the endoplasmic reticulum. Using anti-hZip1 antibodies, we confirmed the intracellular localization of the endogenous protein in PC-3, a prostate cancer cell line.

Structure of mouse L-chain ferritin at 1.6 A resolution

Cubic F432 crystals of recombinant mouse L-chain apoferritin were obtained by the hanging-drop technique with ammonium sulfate and cadmium sulfate as precipitants. The structure was refined to 2.1 and 1.6 A resolution from data obtained at room temperature and under cryogenic conditions, respectively. The structure of an eight-amino-acid loop insertion in the mouse sequence is found to be highly disordered both at room temperature and at low temperature.

[Hereditary hyperferritinemia syndrome and cataract]

Hereditary hyperferritinemia cataract is a recently described autosomal dominant syndrome, characterized by bilateral cataracts and elevated level of serum ferritin.

PATIENTS

Three members of a family were investigated for cataract and hyperferritinemia. A 30-year-old woman had elevated serum ferritin levels and bilateral cataracts. She was treated for hemochromatosis, but serum iron and transferrin saturation were normal. Her two sons, nine and five years old, also had a high ferritin level and bilateral cataracts.

RESULTS

The ferritin level was 1200 micrograms/L in the woman's serum, and respectively, 974 and 965 micrograms/L in the two boys' serum. The mother had a visual acuity of 8/10 in the right eye and 5/10 in the left eye. The cataract comprised fine crystalline cortical opacities, extending axially. The two sons had 7 to 8/10 in both eyes. No other ophthalmic abnormality was noted. These patients were heterozygous for a 16 bp deletion on the L-ferritin gene.

DISCUSSION

Ferritin is an iron storage ubiquitous protein present in every cell. In hyperferritinemia cataract syndrome, serum iron and transferrin saturation are normal, and the elevated serum ferritin level is the consequence of an autosomal dominant disorder. The cataract is made up of the accumulation of small opacities disposed radially and more numerous on the outside edges, with relatively good visual acuity. The size of the cataract seems to be correlated to the serum ferritin level. In hemochromatosis, hyperferritinemia is related to increased iron stores and is not associated with cataracts.

H ferritin knockout mice: a model of hyperferritinemia in the absence of iron overload

Ferritin, the iron-storing molecule, is made by the assembly of various proportions of 2 different H and L subunits into a 24-mer protein shell. These heteropolymers have distinct physicochemical properties, owing to the ferroxidase activity of the H subunit, which is necessary for iron uptake by the ferritin molecule, and the ability of the L subunit to facilitate iron core formation inside the protein shell. It has previously been shown that H ferritin is indispensable for normal development, since inactivation of the H ferritin gene by homologous recombination in mice is lethal at an early stage during embryonic development. Here the phenotypic analysis of the mice heterozygous for the H ferritin gene (Fth(+/-) mice) is reported, and differences in gene regulation between the 2 subunits are shown. The heterozygous Fth(+/-) mice were healthy and fertile and did not present any apparent abnormalities. Although they had iron-overloaded spleens at the adult stage, this is identical to what is observed in normal Fth(+/+) mice. However, these heterozygous mice had slightly elevated tissue L ferritin content and 7- to 10-fold more L ferritin in the serum than normal mice, but their serum iron remained unchanged. H ferritin synthesis from the remaining allele was not up-regulated. This probably results from subtle changes in the intracellular labile iron pool, which would stimulate L ferritin but not H ferritin synthesis. These results raise the possibility that reduced H ferritin expression might be responsible for unexplained human cases of hyperferritinemia in the absence of iron overload where the hereditary hyperferritinemia-cataract syndrome has been excluded. (Blood. 2001;98:525-532)

Lack of hepcidin gene expression and severe tissue iron overload in upstream stimulatory factor 2 (USF2) knockout mice

We previously reported the disruption of the murine gene encoding the transcription factor USF2 and its consequences on glucose-dependent gene regulation in the liver. We report here a peculiar phenotype of Usf2(-/-) mice that progressively develop multivisceral iron overload; plasma iron overcomes transferrin binding capacity, and nontransferrin-bound iron accumulates in various tissues including pancreas and heart. In contrast, the splenic iron content is strikingly lower in knockout animals than in controls. To identify genes that may account for the abnormalities of iron homeostasis in Usf2(-/-) mice, we used suppressive subtractive hybridization between livers from Usf2(-/-) and wild-type mice. We isolated a cDNA encoding a peptide, hepcidin (also referred to as LEAP-1, for liver-expressed antimicrobial peptide), that was very recently purified from human blood ultrafiltrate and from urine as a disulfide-bonded peptide exhibiting antimicrobial activity. Accumulation of iron in the liver has been recently reported to up-regulate hepcidin expression, whereas our data clearly show that a complete defect in hepcidin expression is responsible for progressive tissue iron overload. The striking similarity of the alterations in iron metabolism between HFE knockout mice, a murine model of hereditary hemochromatosis, and the Usf2(-/-) hepcidin-deficient mice suggests that hepcidin may function in the same regulatory pathway as HFE. We propose that hepcidin acts as a signaling molecule that is required in conjunction with HFE to regulate both intestinal iron absorption and iron storage in macrophages.

Estimation of the genetic parameters of meat characteristics and of their genetic correlations with growth and body composition in an experimental broiler line

Genetic parameters of breast meat characteristics [pH 15 min postmortem (pH15min), ultimate pH (pHu), CIELAB color parameters (L*, lightness; a*, redness; b*, yellowness) and drip loss (DL)] as well as their genetic correlations with BW and body composition [breast yield (BRY) and abdominal fat percentage (AFP)] were estimated in an experimental meat-type chicken line. Heritability of the pH of meat was high for pHu (0.35 +/- 0.03) and even more so for pH15min (0.49 +/- 0.01). Color parameters appeared to be the most heritable traits, with heritability values ranging from 0.50 to 0.57. Drip loss heritability was estimated at 0.39 +/- 0.04. The rate and the extent of pH decline seemed to be controlled by different genes, as shown by the extremely low estimated genetic correlation (0.02 +/- 0.04) between pH15min and pHu. The ultimate pH of the meat was genetically very strongly related to its lightness (-0.91 +/- 0.02) and water-holding capacity (-0.83 +/- 0.04). These results suggest that selection for pHu could be exploited to prevent increased incidence of pale and exudative meat. The pH15min was poorly correlated with the other meat characteristics, with estimated correlations of 0.13, -0.23, 0.05, and -0.29 for L*, a*, b*, and DL, respectively. These results may be explained by the fact that, in our experimental conditions, pH15min remained high (between 6.01 and 6.75). Body weight and BRY exhibited poor genetic correlations (ranging from -0.06 to 0.13) with the pH of the meat at 15 min and 24 h postmortem. Both of the former traits were moderately negatively correlated with a* and b* values. A significant negative genetic correlation was observed between abdominal fatness and pHu. These results do not support the idea that selection for growth and breast development has a detrimental effect on breast meat quality even if, in the long term, the color intensity could be decreased.

Iron metabolism, free radicals, and oxidative injury

Iron has the capacity to accept and donate electrons readily. This capability makes it physiologically essential, as a useful component of cytochromes and oxygen-binding molecules. However, iron is also biochemically dangerous; it can damage tissues by catalyzing the conversion of hydrogen peroxide to free-radical ions that attack cellular membranes, protein and DNA. This threat is reduced in the healthy state where, because of the fine iron metabolism regulation, there is never appreciable concentration of 'free iron'. Under pathological conditions, iron metabolism and superoxide metabolism are clearly interactive. Each can exacerbate the toxicity of the other. Iron overload may amplify the damaging effects of superoxide overproduction in a very broad spectrum of inflammatory, both acute and chronic, conditions. Furthermore, chronic oxidative stress may modulate iron uptake and storage, leading to a self-sustained and ever-increasing spiral of cytotoxic and mutagenic events. The iron chelator deferroxamine is able to chelate 'free iron' even inside the cell. Its regular clinical use is to promote the excretion of an iron overload, when phlebotomy is harmful, and the dosage varies between 2-10 g/d. In conditions where deferroxamine is used to prevent the iron-driven oxygen toxicity, i.e., acute or chronic inflammatory diseases with oxidative stress, the dosage can be extremely reduced and the addition of antioxidants could be useful.

Genetic analysis of a selection experiment on the growth curve of chickens

A selection experiment on the shape of the growth curve was performed on meat-type chickens through combined selection on juvenile and adult BW. Line X-+ was selected for low BW at 8 wk (BW8) and high BW at 36 wk (BW36). Line X+- was selected for high BW8 and low BW36. Line X++ was selected for high BW8 and BW36, and X-- was selected for low BW8 and BW36. Line X00 was maintained as an unselected control. Data on the first 14 generations (i.e., 38,693 birds) were used. The growth curve was modeled using a Gompertz function on 7,143 birds that were weighed regularly. Selection for higher BW8 increased BW from 4 to 16 wk, initial specific growth rate, and maturation rate and decreased age at inflection. Selection for higher BW36 resulted in increased BW36, asymptotic BW, and estimated BW at hatching. Body weights were more modified in Lines X++ and X--, but the growth curve parameters changed more in Lines X-+ and X-- than in Lines X++ and X+-.

[Intracellular iron metabolism]

Iron is essential to life but it is poorly soluble in biological fluids and toxic in excess. Organisms have developed multiple proteins to insure iron transport and storage, and some of these have only been discovered recently. Among them, members of the Nramp family are transmembrane proteins which transport several divalent cations, including Fe2+. These proteins participate in intestinal iron absorption, erythopoiesis and microbial defence. Frataxin, which is deficient in Friedreich's ataxia, regulates iron flux through mitochondria. The intracellular labile iron pool, an intermediate form of iron between different subcellular compartments, regulates ferritin synthesis and stability of mRNA coding for proteins of iron transport. Subunit composition of ferritin plays an important role in the control of the size of this labile iron pool.

Denaturing gradient gel electrophoresis screening for mutations in the hereditary hyperferritinaemia cataract syndrome

Hereditary hyperferritinaemia cataract syndrome (HHCS) is characterized by hyperferritinaemia without iron overload. It is essential to differentiate true iron accumulation from HHCS as these patients rapidly develop iron-deficient anaemia when subjected to phlebotomies. The diagnosis of HHCS relies on the identification of point mutations or deletions present in the iron-responsive element of the first exon of the L-ferritin gene. However, many samples referred for diagnosis of putative HHCS are normal. To avoid unnecessary DNA sequencing, we have developed a diagnosis strategy based on the screening of the target DNA region by denaturing gradient gel electrophoresis. This method enabled the accurate identification of 11 different previously known mutations. This strategy will be of interest for family studies or for the screening of large series of patients.

Inactivation of iron responsive element-binding capacity and aconitase function of iron regulatory protein-1 of skin cells by ultraviolet A

The ultraviolet-A (UVA) component of sunlight produces in cutaneous cells a highly toxic oxidative stress mediated by redox cycling reactions of Fe ions. A tight regulation of cell iron uptake and storage by iron regulatory proteins (IRP) of keratinocytes and fibroblasts avoids these damaging reactions. We report here that about 40 J/cm2 of UVA are required to inactivate half of the binding capacity of apo-IRP-1 to iron responsive elements (IRE) of RNA whereas 15 J/cm2 already inhibit half of the holo-IRP-1 aconitase activity. No increase in the holo-IRP-1 activity is observed during the apo-IRP-1 photoinactivation suggesting that UVA does not trigger a shift between these two forms. As opposed to holo-IRP-1, which contains a 4Fe-4S cluster, apo-IRP-1 has no UVA chromophore. Thus it should be inactivated indirectly by reactive oxygen species generated by the UVA-induced endogenous photo-oxidative stress. The apo-IRP-1 photoinactivation is weakly prevented by the lipophilic oxyradical scavenger vitamin E but not by the hydrophilic azide anion, a singlet oxygen quencher or by diethyldithiocarbamate, a superoxide dismutase inhibitor. However, full protection against photoinactivation of the apo form is observed after incubation with N-acetylcysteine but the latter only partially protects the aconitase function of the holo-IRP-1 from photoinactivation. The marked difference in the kinetics of photoinactivation of the apo and holo forms, the light dose-independent effect of the sulfhydril group reagent, 2-mercaptoethanol and the partial protection brought by the ferric ion complexing agent desferrioxamine suggest that the photochemistry of the 4Fe-4S cluster of the holo form plays little, if any, role in the photoinactivation of the apo-IRP-1/IRE interaction. It is concluded that the apo/holo equilibrium is irreversibly destroyed by UVA irradiation.

The haptoglobin 2-2 phenotype affects serum markers of iron status in healthy males

BACKGROUND

Human iron status is influenced by environmental and genetic factors. We hypothesized that the genetic polymorphism of haptoglobin (Hp), a hemoglobin-binding plasma protein, could affect iron status.

METHODS

Reference values of serum iron status markers were compared according to Hp phenotypes (Hp 1-1, Hp 2-1, Hp 2-2; determined by starch gel electrophoresis) in 717 healthy adults. Iron storage was investigated in peripheral blood monocyte-macrophages by measuring cytosolic L- and H-ferritins and by in vitro uptake of radiolabeled ((125)I) hemoglobin-haptoglobin complexes.

RESULTS

In males but not in females, the Hp 2-2 phenotype was associated with higher serum iron (P <0.05), transferrin saturation (P <0.05), and ferritin (P <0.01) concentrations than Hp 1-1 and 2-1, whereas soluble transferrin receptor concentrations were lower (P <0.05). Moreover, serum ferritin correlated with monocyte L-ferritin content (r = 0.699), which was also highest in the male Hp 2-2 subgroup (P <0.01). In vitro, monocyte-macrophages took up a small fraction of (125)I-labeled hemoglobin complexed to Hp 2-2 but not to Hp 1-1 or 2-1.

CONCLUSIONS

The Hp 2-2 phenotype affects serum iron status markers in healthy males and is associated with higher L-ferritin concentrations in monocyte-macrophages because of a yet undescribed iron delocalization pathway, selectively occurring in Hp 2-2 subjects.

Genetic analysis of growth curve parameters for male and female chickens resulting from selection on shape of growth curve

The objectives of this research were to evaluate gender differences and selection on body weight as they affect growth curves of chickens. Marginal posterior densities of growth curve parameters were studied by Gibbs sampling on 10,671 male and female chickens originating from five lines. Line X-+ was selected on low body weight at 8 wk (BW8) and high body weight at 36 wk (BW36), line X+- on high BW8 and low BW36, X++ on high BW8 and BW36, X-- on low BW8, and BW36, and X00 was an unselected control line. Growth was modeled by a Gompertz function. Heritabilities and genetic correlations among parameters of the Gompertz curve were estimated. Marginal posterior densities were drawn for parameters of the growth curve and for sexual dimorphism at ages ranging from hatching to 1 yr. Lines selected for a higher BW8 had higher initial specific growth rates (L), higher maturation rates (K), and lower ages at inflection (T(I)). Lines selected for a higher BW36 had higher asymptotic body weights (A). Estimates of A, L, and T(I) were higher in males and K was higher in females. Difference between sexes for A was greater in the line selected for a lower BW8 and a higher BW36. Dimorphism for L and K was the lowest in lines X++ and X--, respectively. The greatest difference in T(I) was observed in the line selected for lower BW8 and BW36. Sexual dimorphism of body weight was lower at most ages in the lightest line. Before 15 wk, sexual dimorphism in X++ line was lower than in the line selected for higher BW8 and lower BW36. The increase in sexual dimorphism with body weight could be reduced by selecting animals on body weight at two ages instead of one, as is usually done in commercial lines.

Crystallization and preliminary X-ray diffraction data of mouse L-chain apoferritin crystals

Crystals of recombinant mouse L-chain apoferritin were obtained by the hanging-drop technique using ammonium sulfate as precipitant. Two crystal forms were observed in the same drop. The crystals belong to either the P2 monoclinic or to the P42(1)2 tetragonal space group. The monoclinic crystals diffracted to beyond 2.4 A resolution but were systematically twinned, while the tetragonal crystals diffracted to beyond 2.9 A. These crystallization conditions in the absence of metal salts should facilitate the study of the interaction between L-chain ferritins and heavy metals, particularly the iron core.

Early embryonic lethality of H ferritin gene deletion in mice

Ferritin molecules play an important role in the control of intracellular iron distribution and in the constitution of long term iron stores. In vitro studies on recombinant ferritin subunits have shown that the ferroxidase activity associated with the H subunit is necessary for iron uptake by the ferritin molecule, whereas the L subunit facilitates iron core formation inside the protein shell. However, plant and bacterial ferritins have only a single type of subunit which probably fulfills both functions. To assess the biological significance of the ferroxidase activity associated with the H subunit, we disrupted the H ferritin gene (Fth) in mice by homologous recombination. Fth(+/-) mice are healthy, fertile, and do not differ significantly from their control littermates. However, Fth(-/-) embryos die between 3.5 and 9.5 days of development, suggesting that there is no functional redundancy between the two ferritin subunits and that, in the absence of H subunits, L ferritin homopolymers are not able to maintain iron in a bioavailable and nontoxic form. The pattern of expression of the wild type Fth gene in 9.5-day embryos is suggestive of an important function of the H ferritin gene in the heart.

H-ferritin subunit overexpression in erythroid cells reduces the oxidative stress response and induces multidrug resistance properties

The labile iron pool (LIP) of animal cells has been implicated in cell iron regulation and as a key component of the oxidative-stress response. A major mechanism commonly implied in the downregulation of LIP has been the induced expression of ferritin (FT), particularly the heavy subunits (H-FT) that display ferroxidase activity. The effects of H-FT on LIP and other physiological parameters were studied in murine erythroleukemia (MEL) cells stably transfected with H-FT subunits. Clones expressing different levels of H-FT displayed similar concentrations of total cell iron (0.3 +/- 0.1 mmol/L) and of reduced/total glutathione. However, with increasing H-FT levels the cells expressed lower levels of LIP and reactive oxygen species (ROS) and ensuing cell death after iron loads and oxidative challenges. These results provide direct experimental support for the alleged roles of H-FT as a regulator of labile cell iron and as a possible attenuator of the oxidative cell response. H-FT overexpression was of no apparent consequence to the cellular proliferative capacity. However, concomitant with the acquisition of iron and redox regulatory capacities, the H-FT-transfectant cells commensurately acquired multidrug resistance (MDR) properties. These properties were identified as increased expression of MDR1 mRNA (by reverse transcription polymerase chain reaction [RT-PCR]), P-glycoprotein (Western immunoblotting), drug transport activity (verapamil-sensitive drug efflux), and drug cytotoxicity associated with increased MDR1 or PgP. Although enhanced MDR expression per se evoked no significant changes in either LIP levels or ROS production, it might be essential for the survival of H-FT transfectants, possibly by expediting the export of cell-generated metabolites.

The identification of ferritin in the nucleus of K562 cells, and investigation of a possible role in the transcriptional regulation of adult beta-globin gene expression

We studied the subcellular distribution of ferritin in K562 cells by immunofluorescence techniques and have made a reappraisal of a direct binding interaction between ferritin and the proximal promoter region of the human beta-globin gene, as previously mentioned in the literature. Confocal microscopy indicates that ferritin, the iron-storage protein, is present in the nucleus of K562 cells, in addition to its expected cytoplasmic localisation. The stain distribution suggests that it is not directly associated with the nuclear matrix. Using a gel mobility shift assay, a protein that cross-reacts with monoclonal ferritin antibodies competitively binds to a double-stranded oligonucleotide spanning the region situated 150 base pairs upstream from the beta-globin transcription start site. Despite this antibody cross-reactivity, the protein is unlike cytosolic ferritin as it appears to be highly sensitive to both temperature and freeze-thaw cycles, and UV-crosslinking experiments indicate that the molecular mass of the protein factor lies between 90 and 100 kDa. In conclusion, while the intranuclear location of ferritin is described in the present study, ferritin is not in direct contact with the beta-globin promoter region.

Genetic parameters of growth curve parameters in male and female chickens

1. Individual growth curves of 7143 chickens selected for the form of the growth curve were fitted using the Laird form of the Gompertz function, BW4=BW0xe(L/K)(1-e-Kt) where BWt is the body weight at age t, BW0 the estimated hatching weight, L the initial specific growth rate and K the maturation rate. 2. Line and sex effects were significant for each parameter of the growth curve. In males, L, BW0, age and body weight at inflection (T(I)and BWI) were higher whereas K was lower than in females. Lines selected for high adult body weight had higher BW0 and BW(I) whereas lines selected for high juvenile body weight had larger estimates of L and lower estimates of T(I). 3. Data from 38,474 animals were included in order to estimate the genetic parameters of growth curve parameters in males and females, considering them as sex-limited traits. Genetic parameters were estimated with REML (REstricted Maximum Likelihood) and an animal model. Maternal genetic effects were also included. 4. Heritabilities of the growth curve parameters were moderate to high and ranged between 0.31 and 0.54, L, BW0 in both sexes and BW(I) in males exhibited significant maternal heritability. Heritabilities differed between males and females for BWI and T(I). Genetic correlations between sexes differed significantly from one for all parameters. L, K and T(I) were highly correlated but correlations involving BW0 and BW(I) were low to moderate. 5. Sexual dimorphism of body weight at 8 and 36 weeks and of L, K and T(I) was moderately heritable. Selection on growth curve parameters could modify the difference between sexes in precocity and thus in body weight at a given age.

Genetic parameters of body weight of broiler chickens measured at 22 degrees C or 32 degrees C

1. Male broilers (n = 1521) from 247 families were reared from 4 to 6 weeks of age at 22 degrees or 32 degrees C. 2. Genetic correlations between measurements recorded at 22 degrees C and 32 degrees C were 0.73 +/- 0.12 for weight gain between 4 and 6 weeks and 0.74 +/- 0.08 for food conversion ratio (FCR). Genes controlling weight gain at both temperatures differed to some extent. 3. Heritability of weight gain from 4 to 6 weeks was much lower at 32 degrees C than at 22 degrees C (0.13 +/- 0.03 vs 0.24 +/- 0.04): selection for increased body weight will thus be much less efficient at 32 degrees C than at 22 degrees C. 4. Conversely, heritabilities of the FCR were very similar at the 2 temperatures (0.28 +/- 0.04 at 22 degrees C and 0.27 +/- 0.04 at 32 degrees C). Selecting for FCR would thus be efficient at 32 degrees C too. 5. These results justify, at least under our experimental conditions, selecting broiler lines for improved growth performance at 22 degrees C. However, it could be more efficient if broilers are to be reared in hot climates to select for improved FCR rather than for increased body weight.

Physiological responses of hens divergently selected on the number of chicks obtained from a single insemination

A series of experiments was conducted in domestic fowl to investigate the consequences of five generations of divergent selection for increased (L+) or decreased (L-) numbers of hatched chicks. After artificial insemination with pooled ejaculates within the same line (L+ males x L+ hens or L- males x L- hens), significant differences were observed between L+ and L- hens for mean fertility rates (L+ 94.8%, L- 70.2%, P < 0.0001) and for effective and maximum duration of fertility (P < 0.00001). A comparison of the overall laying performance and shell quality between the two selected lines showed that L- hens laid fewer eggs than L+ hens (P < 0.00001) and L- eggs had poorer shell quality (shell breaking strength) than L+ eggs (P < 0.00001). These observations were associated with significantly higher percentages of early embryo death in eggs from L- hens compared with L+ hens. Another series of experiments revealed the presence of larger initial populations of spermatozoa in the sperm storage tubules as well as in the perivitelline layer of eggs from L+ hens. The populations of spermatozoa in the sperm storage tubules of commercial laying hens inseminated with pooled semen samples from L+ males was compared with those in hens inseminated with samples from L- males to determine whether the variations in oviductal sperm storage between the two lines were male dependent. No significant differences between the populations of spermatozoa present in the sperm storage tubules of either group of hens could be detected at any of the intervals examined after insemination (days 1, 3 and 10). Finally, an experiment conducted on hens originating from the two selected lines indicated that the utero-vaginal junction of L+ hens contained significantly more sperm storage tubules compared with L- hens (P < 0.01). It is concluded that selection based on overall reproductive performance modifies the number of eggs capable of developing viable embryos and also influences the efficacy of initial sperm storage by increasing or altering the population of sperm storage tubules located in the utero-vaginal junction. Such changes have major consequences on the duration of the fertile period, which in avian species is directly dependent on both the actual population of spermatozoa stored in the oviduct and on their rate of release from the storage sites.