Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.      

Persistently modified h-channels after complex febrile seizures convert the seizure-induced enhancement of inhibition to hyperexcitability

Febrile seizures are the most common type of developmental seizures, affecting up to 5% of children. Experimental complex febrile seizures involving the immature rat hippocampus led to a persistent lowering of seizure threshold despite an upregulation of inhibition. Here we provide a mechanistic resolution to this paradox by showing that, in the hippocampus of rats that had febrile seizures, the long-lasting enhancement of the widely expressed intrinsic membrane conductance Ih converts the potentiated synaptic inhibition to hyperexcitability in a frequency-dependent manner. The altered gain of this molecular inhibition-excitation converter reveals a new mechanism for controlling the balance of excitation-inhibition in the limbic system. In addition, here we show for the first time that h-channels are modified in a human neurological disease paradigm.     

Homeostatic plasticity studied using in vivo hippocampal activity-blockade: synaptic scaling, intrinsic plasticity and age-dependence

Homeostatic plasticity is thought to be important in preventing neuronal circuits from becoming hyper- or hypoactive. However, there is little information concerning homeostatic mechanisms following in vivo manipulations of activity levels. We investigated synaptic scaling and intrinsic plasticity in CA1 pyramidal cells following 2 days of activity-blockade in vivo in adult (postnatal day 30; P30) and juvenile (P15) rats. Chronic activity-blockade in vivo was achieved using the sustained release of the sodium channel blocker tetrodotoxin (TTX) from the plastic polymer Elvax 40W implanted directly above the hippocampus, followed by electrophysiological assessment in slices in vitro. Three sets of results were in general agreement with previous studies on homeostatic responses to in vitro manipulations of activity. First, Schaffer collateral stimulation-evoked field responses were enhanced after 2 days of in vivo TTX application. Second, miniature excitatory postsynaptic current (mEPSC) amplitudes were potentiated. However, the increase in mEPSC amplitudes occurred only in juveniles, and not in adults, indicating age-dependent effects. Third, intrinsic neuronal excitability increased. In contrast, three sets of results sharply differed from previous reports on homeostatic responses to in vitro manipulations of activity. First, miniature inhibitory postsynaptic current (mIPSC) amplitudes were invariably enhanced. Second, multiplicative scaling of mEPSC and mIPSC amplitudes was absent. Third, the frequencies of adult and juvenile mEPSCs and adult mIPSCs were increased, indicating presynaptic alterations. These results provide new insights into in vivo homeostatic plasticity mechanisms with relevance to memory storage, activity-dependent development and neurological diseases.     

Metamorphosis in the Cirripedia Rhizocephala and the homology of the kentrogon and trichogon

The Rhizocephala are considered to be monophyletic due to several synapomorphies in the ontogeny of the cndoparasitic phase. The various types of metamorphosis described in the Rhizocephala are discussed and compared to metamorphosis in the Cirripedia Thoracica and Acrothoracica. In males and females of the suborder Kentrogonida. the cyprid settles and metamorphoses into a new instar, in males the trichogen and in females the infective kentrogon. The kentrogon goes through yet another. incomplete moult associated with the development of the stylet. Within the three kentrogonidan families. the Iernaeodiscid-peltogastrid type of kentrogon differs from the sacculinid type in the mode of attachment to the host. in the complexity of internal anatomy. in the position and penetration of the stylet, and in whether or not the cyprid carapace must be shed prior to penetration of the stylet. In the Akentrogonida metamorphosis never results in a new instar. Where observed (Clistosaccidae and Thompsoniidae). both male and female cyprids settle and penetrate into their substrate (female parasite or new host) with one of the antennules. Using the antennule as a syringe. male cyprids inject spermatogonia while female cyprids injects embryonic cells developing into an endoparasite. By comparison with metamorphosis in the Cirripedia Thoracica and Acrothoracica it is concluded that the presence of a metamorphic moult leading to a post-cyprid instar is plesiomorphic and that the trichogon and kentrogon are homologous with the first metamorphosed juvenile in these outgroups. The abbreviated ontogeny in the Akentrogonida without metamorphic moult and post-cyprid larval instars is considered apomorphic. This contradicts the long-held supposition that the Akentrogonida are the most‘primitive’Rhizocephala and dovetails with new information that this suborder contains many advanced traits. Within the Kentrogonida. the lernacodiseid-peltogastrid type of kentrogon is considered more plesiomorphic than the sacculinid type, which resembles the clistosaccidthompsoniid type in having the antennules involved in the penetration process. The homologization of the kentrogon with a juvenile barnacle indicates that presence of a kentrogon is plesiomorphic within the Rhizocephala and that the Kentrogonida is paraphyletic.     

hybridlab (version 1.0): a program for generating simulated hybrids from population samples

We present the computer program hybridlab 1.0 for simulating intraspecific hybrids from population samples of nuclear genetic markers such as microsatellites, allozymes or SNPs (single nucleotide polymorphisms). The program generates a user‐specified number of multilocus F1 hybrid genotypes between any pair of potentially hybridizing populations included in a standard input‐file of multilocus genotypes for population genetic analysis. This simple, user‐friendly program has a wide range of applications for studying natural and artificial hybridization; in particular, for evaluating the statistical power for individual assignment of parental and hybrid individuals. An example of application for Atlantic cod populations is given.     

Immunocytochemical localization of alpha2,3(N)-sialyltransferase (ST3Gal III) in cell lines and rat kidney tissue sections: evidence for golgi and post-golgi localization

Sialylation is a biosynthetic process occurring in the trans compartments of the Golgi apparatus. Corresponding evidence is based on localization and biochemical studies of alpha2, 6(N)-sialyltransferase (ST6Gal I) as previously reported. Here we describe generation and characterization of polyclonal antibodies to recombinant rat alpha2,3(N)-sialyltransferase (ST3Gal III) expressed as a soluble enzyme in Sf9 cells or as a beta-galactosidase-human-ST3Gal III fusion- protein from E.coli , respectively. These antibodies were used to localize ST3Gal III by immunofluorescence in various cell lines and rat kidney tissue sections. In transiently transfected COS cells the antibodies directed to soluble sialyltransferase or the sialyltransferase portion of the fusion-protein only recognized the recombinant antigen retained in the endoplasmic reticulum. However, an antibody fraction crossreactive with beta-galactosidase recognized natively expressed ST3Gal III which was found to be colocalized with beta1, 4-galactosyltransferase in the Golgi apparatus of several cultured cell lines. Antibodies affinity purified on the beta- galactosidase-ST3Gal III fusion-protein column derived from both antisera have then been used to localize the enzyme in perfusion-fixed rat kidney sections. We found strong staining of the Golgi apparatus of tubular epithelia and a brush-border-associated staining which colocalized with cytochemical staining of the H+ATPase. This subcellular localization was not observed for ST6Gal I which localized to the Golgi apparatus. These data show colocalization in the Golgi apparatus and different post-Golgi distributions of the two sialyltransferases.      

Evidence for Functional Diversity between the Voltage-Gated Proton Channel Hv1 and Its Closest Related Protein HVRP1

The Hv1 channel and voltage-sensitive phosphatases share with voltage-gated sodium, potassium, and calcium channels the ability to detect changes in membrane potential through voltage-sensing domains (VSDs). However, they lack the pore domain typical of these other channels. Na_V, K_V, and Ca_V proteins can be found in neurons and muscles, where they play important roles in electrical excitability. In contrast, VSD-containing proteins lacking a pore domain are found in non-excitable cells and are not involved in neuronal signaling. Here, we report the identification of HVRP1, a protein related to the Hv1 channel (from which the name Hv1 Related Protein 1 is derived), which we find to be expressed primarily in the central nervous system, and particularly in the cerebellum. Within the cerebellar tissue, HVRP1 is specifically expressed in granule neurons, as determined by in situ hybridization and immunohistochemistry. Analysis of subcellular distribution via electron microscopy and immunogold labeling reveals that the protein localizes on the post-synaptic side of contacts between glutamatergic mossy fibers and the granule cells. We also find that, despite the similarities in amino acid sequence and structural organization between Hv1 and HVRP1, the two proteins have distinct functional properties. The high conservation of HVRP1 in vertebrates and its cellular and subcellular localizations suggest an important function in the nervous system.     

Activation of morphogenesis and proliferation by low specificity chemical effectors

Activation of highly specific biochemical processes by simple chemical agents is demonstrated for morphogenesis (anlage and development of female gametophyte in cereal) and mitosis (in cell cultures and animal and plant tissues). The effects of these agents are tissue-specific. Structure--activity relationship is analyzed in this group of compounds. Thus, the phenomenon reveals the exact pathways of the influence of allelopathic and anthropogenic chemical agents on evolution of plant biocenoses.