High-resolution mapping of genes involved in plant stage-specific partial resistance of barley to leaf rust.

Partial resistance quantitative trait loci (QTLs) Rphq11 and rphq16 against Puccinia hordei isolate 1.2.1 were previously mapped in seedlings of the mapping populations Steptoe/Morex and Oregon Wolfe Barleys, respectively. In this study, QTL mapping was performed at adult plant stage for the two mapping populations challenged with the same rust isolate. The results suggest that Rphq11 and rphq16 are effective only at seedling stage, and not at adult plant stage. The cloning of several genes responsible for partial resistance of barley to P. hordei will allow elucidation of the molecular basis of this type of plant defence. A map-based cloning approach requires to fine-map the QTL in a narrow genetic window. In this study, Rphq11 and rphq16 were fine-mapped using an approach aiming at speeding up the development of plant material and simplifying its evaluation. The plant materials for fine-mapping were identified from early plant materials developed to produce QTL-NILs. The material was first selected to carry the targeted QTL in heterozygous condition and susceptibility alleles at other resistance QTLs in homozygous condition. This strategy took four to five generations to obtain fixed QTL recombinants (i.e., homozygous resistant at the Rphq11 or rphq16 QTL alleles, homozygous susceptible at the non-targeted QTL alleles). In less than 2 years, Rphq11 was fine-mapped into a 0.2-cM genetic interval and a 1.4-cM genetic interval for rphq16. The strongest candidate gene for Rphq11 is a phospholipid hydroperoxide glutathione peroxidase. Thus far, no candidate gene was identified for rphq16.

Pituitary grafts and behavior in mice. Effects of sex of donor and number of pituitary grafts on exploratory and learning abilities.

The effects of ectopic pituitary grafts, sex of pituitary donor, and number of isografts (one or two) were examined in intact phenotypically normal male mice of the Snell dwarf strain, using a battery of tests designed to assess exploration and learning-related behavioral processes. Results show that neither sex of pituitary donor nor number of grafts affected behavioral responses to pituitary grafts. Ectopic pituitary grafts increased the level of exploratory activities assessed in a novelty preference test and in the hole board test, facilitated the retention of a step-through type passive avoidance task--contrasting with results in rats--but did not affect spatial orientation in a spontaneous alternation and a water escape task. The results argue for a global effect of the graft, inducing increased emotional reactivity.

Prolactin similar to ectopic pituitary isograft restores responsiveness in Snell dwarf mice.

The effects of ovine prolactin (PRL) (2 x 5 IU a day) and an ectopic pituitary isograft on the responsiveness were examined using locomotor and exploratory activities as measures in PRL-growth-hormone-thyrotropin-deficient Snell dwarf mice (dw/dw). After 5 weeks of treatment, both PRL and the graft restored the two behavioural measures to normal levels. Results clearly demonstrate the involvement of PRL in global behavioural responsiveness and suggest a possible role for PRL in the changes induced by the graft.

Effect of age at the time of pituitary grafting on behavioral recovery in dwarf mice.

The effects of ectopic pituitary isograft implanted in 13- or 21-day-old Snell dwarf mice on their freely expressed behavior were examined over a 14- or 31-day period. This mutant strain has severe anterohypophyseal deficiency which causes high levels of inactivity and abnormally low exploratory activity. The graft totally normalized these behaviors. Results showed that the time necessary for inducing behavioral changes is independent of age of the animals at the time of grafting, but the age at which implantation occurs influences the speed of full behavioral normalization. The possible involvement of prolactin and growth hormone in such behavioral improvement is discussed.

Total recovery of response to novelty after ectopic pituitary isografts in Snell Dwarf mice (dw/dw).

The effects of ectopic pituitary isografts on response to novelty were studied in adult Snell Dwarf mice. Because of anterohypophyseal deficiency, these animals exhibit dwarfism, sterility and marked neurochemical and behavioural deficits. When given the opportunity to move around freely in simultaneously presented novel and familiar environments, grafted dwarf (GRAFT Dw) and sham-grafted control (SHAM C) mice showed a significant novelty preference while sham-grafted dwarf (SHAM Dw) mice exhibited no preference. Both SHAM C and GRAFT Dw mice frequently reared and covered the familiar compartment more quickly than the novel compartment, while SHAM Dw mice reared infrequently and covered the two compartments at equal speed. These data reveal in the mutant a total indifference toward its environment and show a total recovery of neotic behaviour after grafting. The literature is very vague concerning the hormonal changes induced after ectopic pituitary grafting but subsequent specific hormonal treatments and biochemical manipulations would facilitate identification of the hypophyseal hormones and/or the growth factors involved in the behavioural changes.

Recovery of exploratory capacity after ectopic pituitary homografts in Snell Dwarf mice (dw/dw).

The effects of ectopic pituitary homografts on free behavior were studied over a period of one month in adult Snell Dwarf mice. Because of anterohypophyseal deficiency, these animals exhibit dwarfism, sterility, and marked behavioral deficits. Beginning on the 16th day after surgery, in addition to a considerable weight gain, grafts result in the total disappearance of inactivity with passive social contact--the behavior most frequently observed in the mutants--to be replaced only by exploration--the most frequently observed behavior in controls. The treatment totally restores the latter behavior. Specific hormonal treatments and biochemical manipulations at different stages would enable identification of the hypophyseal hormones and/or the growth factors involved in the behavioral and morphological changes.

[Beneficial effects of pituitary grafts under the renal capsule on behavior of dwarf mutant mice]. / Effets bénéfiques des greffes hypophysaires sous capsule rénale sur le comportement de la Souris mutante "dwarf".

The effects of pituitary grafts under the kidney capsule were studied in "dwarf" mutant mice which because of anterohypophyseal deficiency, exhibit dwarfism, sterility and important behavioral deficits. One month after grafting, the body weight was 120% in the grafted mutants while only 11 and 8% respectively in normal and sham-grafted controls. At the behavioral level, the animals were examined on 2 tasks: spontaneous alteration in a T maze and passive avoidance (step-through). Grafted mutant mice, as well as sham-grafted normal controls, were able to alternate successfully, while the sham-grafted "dwarf" mice persevered. In the step-through task, grafted animals as well as sham-grafted normal mice, avoided, entering the dark compartment, 24 h after the shock trial. On contrast, sham-grafted dwarf mice did not show passive avoidance of the shock. According to the literature, pituitary grafts under the kidney capsule secrete high levels of prolactin and very little, if any, of other pituitary hormones. It is not yet clear how the presence of only prolactin can explain the body weight and the maintenance of the behaviors we investigated.

Cerebroside and sulfatide biosynthesis in the brain of Snell dwarf mouse: effects of thyroxine and growth hormone in the early postnatal period.

Snell dwarf mice (dw/dw) and normal mice (+/?) were injected with thyroxine (T4) (1 microgram/animal, four injections) and growth hormone (GH) (20 micrograms/animal, four injections) from the 5th to the 15th day of life. In the untreated dw/dw mouse brain, the specific activities of UDP-galactose:ceramide galactosyltransferase (CGalT), PAPS:cerebroside sulfotransferase (CST), and 2', 3'-cyclic nucleotide 3'-phosphohydrolase (CNP) were decreased by 28, 25, and 37%, respectively, compared with the control untreated +/? mice. The major effect of T4 was an increase of the brain CNP in the +/? mice (+40%) and dw/dw mice (+111%). The treatment with T4 also brought to normal the level of CGalT in dw/dw brain; a somewhat less marked effect on CST was observed. The treatment with GH had a great stimulatory effect on CNP: the specific activity of this enzyme increased by 40 and 69% in +/? and dw/dw mouse brain, respectively. On the contrary, no effect of GH on the CGalT activity was observed in this study. Our results suggest that T4 and GH may have both independent and complementary actions on the myelin-associated enzymes during the early postnatal period of brain development.

Effects of post-weaning environment and apparatus dimension on spontaneous alternation as a function of phenotype in "dwarf" mice.

The spontaneous alternations of "dwarf" mice estimated in a Y maze proportioned to the size of control mice demonstrated the necessity of reducing the size of the apparatus for testing the "dwarf" mice. Tested in a maze of reduced dimension, the "dwarf" mice showed a significant deficit in this task but only in a T shaped maze, and not in a Y shaped maze. For one month after weaning, "dwarf" and control mice were reared in either an enriched or an impoverished environment. These rearing conditions did not modify the spontaneous alternation of control mice whether estimated in a T or a Y maze, but they significantly altered the behavior of "dwarf" mice, yet only when evaluated in a T maze: "isolated" "dwarf" mice alternating less than "enriched" "dwarf" mice. It is suggested that this behavioral profile displayed by "dwarf" mice in spontaneous alternation might be explained by a deficit in perceiving, integrating and/or utilizing complex spatial information.

[Effects of post-weaning rearing conditions on learning performance in "dwarf" mice (author's transl)]. / Effets des conditions d'elevage après le sevrage sur les performances d'apprentissage des souris "dwarf".

The effects of different environments on learning ability were investigated in mice homozygous for the locus "dwarf," characterized by a primary deficiency of the anterior hypophysis. Two experiments were conducted; they differed from one another in several aspects such as sex and age at entry into different environments. In both experiments, half the "dwarf" (homozygous dw/dw) and control mice of the same strain (heterozygous dw/+ or homozygous +/+) were placed in either an "enriched" or "impoverished" environment. After 31 days of rearing in these conditions, animals were then pretrained and tested with the standard 12 Hebb-Williams problems. Results from both experiments revealed that (1), independently of environment, "dwarf" mice made significantly more errors than controls (p less than 0.001); (2) mice of the "enriched" groups made significantly less errors than those of the "impoverished" groups (p less than 0.05); (3) environmental effects tended to be larger in "dwarf" mice than in controls. The results are discussed in the light of previous observations on the level of locomotor activity and on the degree of interaction of "dwarf" mice with their physical environment; they are compared to those reported for hypothyroid animals and to those of animals with hippocampal lesions.