Localization of the rat immunoglobulin heavy chain locus to chromosome 6

We have previously used rat/mouse somatic cell hybrids to localize the rat c-myc gene to chromosome 7 (Sümegi et al. 1983) and the rat immunoglobulin kappa locus to chromosome 4 (Perlmann et al. 1985). We now report that by utilizing rat/mouse somatic cell hybrids, we have localized the rat immunoglobulin heavy chain locus to chromosome 6.     

Vagus nerve stimulation in children with mitochondrial electron transport chain deficiencies

We retrospectively investigated outcome data for vagus nerve stimulation (VNS) in children less than 12 years of age with intractable seizures and mitochondrial disease. Five children with a mitochondrial disease, due to electron transport chain deficiency, were studied. Information was collected from clinic visits prior to, and subsequent to, VNS implantation. Data were collected by type and frequency of seizures, encephalogram and neuroimaging findings, and medication history. Four of the children had predominantly myoclonic seizures, while the other child had focal seizures with secondary generalization and myoclonic seizures. All five children did not have significant reduction in seizure frequency with VNS. VNS may not be an effective method to control myoclonic seizures in children with electron transport chain disorders.     

Plant neighborhood influences colonization of Brassicaceae by specialist and generalist aphids

A plant's own characteristics, but also those of its neighbors, might have an impact on its probability of being colonized by herbivorous insects. A plant might be less colonized and experience associational resistance when it grows near repellent neighbors. In contrast, it might be more colonized and experience associational susceptibility near attractive neighbors. To date, mechanisms that drive associational defense are not really understood. In order to gain insights into the occurrence of associational resistance versus associational susceptibility under field conditions, we conducted an experiment to determine the influence of neighboring plants on the colonization of a focal plant by aphids. The focal plant was always Brassica oleracea. The neighbors were B. oleracea (control), B. napus, B. nigra, or Solanum lycopersicum, which represent contrasting levels of physical and chemical defenses. The focal plant, B. oleracea, was more colonized by the specialist aphid Brevicoryne brassicae, and experienced associational susceptibility when it was surrounded by B. nigra or B. napus. In contrast, B. oleracea was less colonized by the generalist aphid Myzus persicae, and experienced associational resistance when it was surrounded by S. lycopersicum, B. nigra or B. napus. Neighboring plants had no significant impact on host plant choice by the generalist aphid Macrosiphum euphorbiae. In conclusion, attraction or repulsion of the specialist aphid B. brassicae and the generalist aphid M. persicae by B. nigra, B. napus, and S. lycopersicum resulted in associational susceptibility or associational resistance for B. oleracea.     

An experimental manipulation of life-history trajectories and resistance to oxidative stress

Optimal investment into life-history traits depends on the environmental conditions that organisms are likely to experience during their life. Evolutionary theory tells us that optimal investment in reproduction versus maintenance is likely to shape the pattern of age-associated decline in performance, also known as aging. The currency that is traded against different vital functions is, however, still debated. Here, we took advantage of a phenotypic manipulation of individual quality in early life to explore (1) long-term consequences on life-history trajectories, and (2) the possible physiological mechanism underlying the life-history adjustments. We manipulated phenotypic quality of a cohort of captive zebra finches (Taeniopygia guttata) by assigning breeding pairs to either an enlarged or a reduced brood. Nestlings raised in enlarged broods were in poorer condition than nestlings raised in reduced broods. Interestingly, the effect of environmental conditions experienced during early life extended to the age at first reproduction. Birds from enlarged broods delayed reproduction. Birds that delayed reproduction produced less offspring but lived longer, although neither fecundity nor longevity were directly affected by the experimental brood size. Using the framework of the life-table response experiment modeling, we also explored the effect of early environmental condition on population growth rate and aging. Birds raised in reduced broods tended to have a higher population growth rate, and a steeper decrease of reproductive value with age than birds reared in enlarged broods. Metabolic resources necessary to fight off the damaging effect of reactive oxygen species (ROS) could be the mechanism underlying the observed results, as (1) birds that engaged in a higher number of breeding events had a weaker red blood cell resistance to oxidative stress, (2) red blood cell resistance to oxidative stress predicted short-term mortality (but not longevity), and (3) was related with a parabolic function to age. Overall, these results highlight that early condition can have long-term effects on life-history trajectories by affecting key life-history traits such as age at first reproduction, and suggest that the trade-off between reproduction and self-maintenance might be mediated by the cumulative deleterious effect of ROS.     

Anatomical evidence for glutamatergic transmission in primary sensory neurons and onto postganglionic neurons controlling penile erection in rats: an ultrastructural study with neuronal tracing and immunocytochemistry

In male rats, the dorsal penile nerve (DPN) conveys sensory information from the genitals to the lumbosacral spinal segments of the spinal cord. DPN is the afferent limb of a reflex loop that supports reflexive erections, and that includes a network of spinal interneurons and autonomic and somatic motoneurons to the penis and perineal striated muscles. Autonomic efferent pathways to the penis relay in the major pelvic ganglion (MPG). Glutamate (Glu) is a likely candidate as a neurotransmitter of reflexive erections. Both AMPA and NMDA glutamatergic receptor subunits are present in the lumbosacral spinal cord, and AMPA and NMDA receptor antagonists block reflexive erections. In the present study, we used tract-tracing experiments combined with immunohistochemical and immunocytochemical techniques to ascertain the presence of Glu at two different levels of the network controlling reflexive erections. DPN afferents were localized in the dorsal horn of the lumbosacral cord and displayed the characteristics of either C-fibers or Aδ fibers. DPN terminals (some of them glutamatergic) were mainly distributed in the medial edge of the dorsal horn in the L6 spinal segment. GluR1 subunits were present in some DPN afferents, suggesting that they could be autoreceptors. DPN fibers were also present in the MPG, as were Glu terminals and GluR4 subunits. The results reveal the presence of Glu in DPN fibers and terminals and suggest that both the spinal cord and the MPG use glutamatergic transmission to control reflexive erections. This work was supported by grant no. 5R01MH059811–03 from the NIH and by an institutional grant from the Institut National de la Recherche Agronomique.