Exploring Heterozygosity-Survival Correlations in a Wild Songbird Population: Contrasting Effects between Juvenile and Adult Stages

The relationship between genetic diversity and fitness, a major issue in evolutionary and conservation biology, is expected to be stronger in traits affected by many loci and those directly influencing fitness. Here we explore the influence of heterozygosity measured at 15 neutral markers on individual survival, one of the most important parameters determining individual fitness. We followed individual survival up to recruitment and during subsequent adult life of 863 fledgling pied flycatchers born in two consecutive breeding seasons. Mark-recapture analyses showed that individual heterozygosity did not influence juvenile or adult survival. In contrast, the genetic relatedness of parents was negatively associated with the offspring’s survival during the adult life, but this effect was not apparent in the juvenile (from fledgling to recruitment) stage. Stochastic factors experienced during the first year of life in this long-distance migratory species may have swamped a relationship between heterozygosity and survival up to recruitment.     

Persistent At-Level Thermal Hyperalgesia and Tactile Allodynia Accompany Chronic Neuronal and Astrocyte Activation in Superficial Dorsal Horn following Mouse Cervical Contusion Spinal Cord Injury

In humans, sensory abnormalities, including neuropathic pain, often result from traumatic spinal cord injury (SCI). SCI can induce cellular changes in the CNS, termed central sensitization, that alter excitability of spinal cord neurons, including those in the dorsal horn involved in pain transmission. Persistently elevated levels of neuronal activity, glial activation, and glutamatergic transmission are thought to contribute to the hyperexcitability of these dorsal horn neurons, which can lead to maladaptive circuitry, aberrant pain processing and, ultimately, chronic neuropathic pain. Here we present a mouse model of SCI-induced neuropathic pain that exhibits a persistent pain phenotype accompanied by chronic neuronal hyperexcitability and glial activation in the spinal cord dorsal horn. We generated a unilateral cervical contusion injury at the C5 or C6 level of the adult mouse spinal cord. Following injury, an increase in the number of neurons expressing ΔFosB (a marker of chronic neuronal activation), persistent astrocyte activation and proliferation (as measured by GFAP and Ki67 expression), and a decrease in the expression of the astrocyte glutamate transporter GLT1 are observed in the ipsilateral superficial dorsal horn of cervical spinal cord. These changes have previously been associated with neuronal hyperexcitability and may contribute to altered pain transmission and chronic neuropathic pain. In our model, they are accompanied by robust at-level hyperaglesia in the ipsilateral forepaw and allodynia in both forepaws that are evident within two weeks following injury and persist for at least six weeks. Furthermore, the pain phenotype occurs in the absence of alterations in forelimb grip strength, suggesting that it represents sensory and not motor abnormalities. Given the importance of transgenic mouse technology, this clinically-relevant model provides a resource that can be used to study the molecular mechanisms contributing to neuropathic pain following SCI and to identify potential therapeutic targets for the treatment of chronic pathological pain.     

Effects of aproteic diet on hypothalamic-pituitary- gonadal regulation in the male rat

The effect of an aproteic diet (Ap) on the reproductive axis in young male rats was studied. Also the refeeding effect at different times after the aproteic diet was studied. The Ap diet was given during 21 days. In refeeding groups, the control diet was given during 2, 4 and 6 weeks after the aproteic diet. We studied the plasmatic testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels. Also the hypothalamic GnRH concentration and in vitro hypothalamic GnRH secretion in basal and induced condition was studied. The total protein deficit produced significant reduction in body, testis, seminal vesicles and prostate weights. This was accompanied with decreased levels of plasmatic testosterone (P<0.02). In this aproteic group there was a significant reduction in LH (P<0.05) and FSH (P<0.05) plasmatic levels. Refeeding with control diet reversed this situation, producing significant increment in LH (P<0.05) and FSH levels (P<0.01) at the fourth and second weeks, respectively. The basal hypothalamic GnRH secretion did not differ from the control; nevertheless the induced secretion was significantly (P<0.05) greater in the aproteic group. Also the hypothalamic GnRH concentration was increased (P<0.05) in animals fed with the aproteic diet. The minor testis, prostate, and seminal vesicles" weight, and a decreased plasmatic testosterone in rats fed with an aproteic diet, are produced by a decrease in gonadotrophin secretion. This decrease in turn is caused by a reduction in GnRH secretion, since hypothalamic GnRH concentration is increased in rats fed with the aproteic group, and induced secretion is greater in this group. All these alterations produced by an aproteic diet are reversible, since-with contol diet refeeding-the gonadotrophin secretion returned at control levels.     

Differentiation of an adult neuron cell line increases susceptibility to rabies infection

A wide variety of in vitro models have been used for studying rabies infection, however, currently, no central nervous system (CNS) adult neuron cultures are available. The current study determined the susceptibility to rabies infection in an adult CNS neuron cell line (CAD-R1). Cultures of CAD-R1 cells were held for 5 days in medium containing serum (undifferentiated CAD-R1 cells) or in serum-free medium (differentiated CAD-R1 cells). They were then infected with highly neurotropic rabies virus (RV) strain (CVS), obtained from fibroblastic cells (CVS-BHK) or from adult mouse brain (CVS-MB). Undifferentiated and differentiated cells were infected with the two RV strains, but the percentage of infected cells in differentiated cultures was significantly greater (83% and 79%, respectively) than in undifferentiated cells (51% and 60%) (Student's t test<0.05). Susceptibility to infection apparently depended on cellular differentiation state, possibly due to acquisition of additional morphological and biochemical characteristics during the differentiation process that made them more susceptible to RV infection. Therefore, CAD R1 cells may represent a good model for RV infection, making them a useful tool for studying RV neurotropism, infection pathogeny, isolation of street virus or producing safer and most potent vaccines.     

Short Term Minimum Water Temperatures Determine Levels of Infection by the Amphibian Chytrid Fungus in Alytes obstetricans Tadpoles

Amphibians are one of the groups of wildlife most seriously threatened by emerging infectious disease. In particular, chytridiomycosis, caused by the aquatic fungus Batrachochytrium dendrobatidis, is responsible for amphibian species declines on a worldwide scale. Population-level outcomes following the introduction of the pathogen are context dependent and mediated by a large suite of abiotic and biotic variables. In particular, studies have shown that temperature has a key role in determining infection dynamics owing to the ectothermic nature of the amphibian host and temperature-dependency of pathogen growth rates. To assess the temperature-dependent seasonality of infectious burdens in a susceptible host species, we monitored lowland populations of larval midwife toads, Alytes obstetricians, in Central Spain throughout the year. We found that infections were highly seasonal, and inversely correlated against water temperature, with the highest burdens of infection seen during the colder months. Short-term impacts of water-temperature were found, with the minimum temperatures occurring before sampling being more highly predictive of infectious burdens than were longer-term spans of temperature. Our results will be useful for selecting the optimal time for disease surveys and, more broadly, for determining the key periods to undertake disease mitigation.     

Molecular cloning, characterization, and chromosomal localization of the mouse homologue of CD84, a member of the CD2 family of cell surface molecules

 CD84 is a member of the immunoglobulin gene superfamily (IgSF) with two Ig-like domains expressed primarily on B lymphocytes and macrophages. Here we describe the cloning of the mouse homologue of human CD84. Mouse CD84 cDNA clones were isolated from a macrophage library. The nucleotide sequence of mouse CD84 was shown to include an open reading frame encoding a putative 329 amino acid protein composed of a 21 amino acid leader peptide, two extracellular immunoglobulin (Ig)-like domains, a hydrophobic transmembrane region, and an 87 amino acid cytoplasmic domain. Mouse CD84 shares 57.3% amino acid sequence identity (88.7%, considering conservative amino acid substitutions) with the human homologue. Chromosome localization studies mapped the mouse CD84 gene to distal chromosome 1 adjacent to the gene for Ly-9, placing it close to the region where other members of the CD2 IgSF (CD48 and 2B4) have been mapped. Northern blot analysis revealed that the expression of mouse CD84 was predominantly restricted to hematopoietic tissues. Two species of mRNA of 3.6 kilobases (kb) and 1.5 kb were observed. The finding that the pattern of expression was restricted to the hematopoietic system and the conserved sequence of the mouse CD84 homologue suggests that the function of the CD84 glycoprotein may be similar in humans and mice. Received: 1 July 1998 / Revised: 31 August 1998     

Structural change in wood by brown rot fungi and effect on enzymatic hydrolysis

The effects of biological pretreatment on Pinus radiata and Eucalyptus globulus, were evaluated after exposure to two brown rot fungi Gloephylum trabeum and Laetoporeus sulphureus. Changes in chemical composition, structural modification, and susceptibility to enzymatic hydrolysis in the degraded wood were analyzed. After eight weeks of biodegradation, the greatest loss of weight and hemicellulose were 13% and 31%, respectively, for P. radiata with G. trabeum. The content of glucan decreased slightly, being the highest loss of 20% for E. globulus with G. trabeum. Consistent with degradation mechanism of these fungi, lignin was essentially undegraded by both brown rot fungi. Both brown rot fungi cause a sharp reduction in the cellulose degree of polymerization (DP) in the range between 58% and 79%. G. trabeum depolymerized cellulose in both wood faster than L. sulphureus. Also, structural characteristic of crystalline cellulose were measured by using two different techniques - X-ray diffraction (XRD) and infrared spectroscopy (FT-IR). The biological pretreatments showed an effect on cellulose crystallinity structure, a decrease between 6% and 21% was obtained in the crystallinity index (CrI) calculated by IR, no changes were observed in the XRD. Material digestibility was evaluated by enzymatic hydrolysis, the conversion of cellulose to glucose increased with the biotreatment time. The highest enzymatic hydrolysis yields were obtained when saccharification was performed on wood biopretreated with G. trabeum (14% P. radiata and 13% E. globulus). Decreasing in DP and CrI, and hemicellulose removal result in an increase of enzymatic hydrolysis performance. Digestibility was better related to DP than with other properties. G. trabeum can be considered as a potential fungus for biological pretreatment, since it provides an effective process in breaking the wood structure, making it potentially useful in the development of combined pretreatments (biological-chemical). A viable alternative to pretreatment process that can be used is a bio-mimetic system, similar to low-molecular complexes generated by fungi such as G. trabeum combined pretreatments (biological-chemical).     

Enzymes produced by <Emphasis Type="Italic">Ganoderma australe</Emphasis> growing on wood and in submerged cultures

Enzymes produced by Ganoderma australe in solid-state fermentation and submerged cultures were evaluated. Strain A464 produced laccase activity in liquid medium and in solid-state cultures containing Drimys winteri or Eucalyptus globulus wood chips, while MnP and LiP activities were not detected. On the other hand, strain A272 cultured for 75 days on E. globulus presented MnP activity of 719 IU/kg of wood. The suitability of D. winteri wood as a substrate enabling MnP production was checked with a well-documented MnP-producing basidiomycete, Ceriporiopsis subvermispora, which produced MnP activity of 327 IU/kg of wood in 9-day-old cultures. Data from two different G. australe strains (A272 and A464) indicated that MnP secretion depended on strain origin as well as on culture conditions.     

An evolving neural network for the interpretation of gene expression patterns

It is of central interest in biology to understand how gene activity networks are coordinated and integrated in the cell. Within the field of genomics, microarray technologies have become a powerful technique for monitoring simultaneously the expression patterns of thousands of genes under different sets of conditions. A main task now is to propose analytical methods that can suggest which groups of genes are activated by similar conditions. We review several techniques based on self-organizing map and clustering algorithms but implemented through a network of units controlled by biologically inspired functions (see Table 1). The computer tool, named NBIA, permits a categorization that generates a set of gene groups with coordinated expression patterns.     

Understanding ribosome assembly: the structure of in vivo assembled immature 30S subunits revealed by cryo-electron microscopy

Four decades after early in vitro assembly studies demonstrated that ribosome assembly is a controlled process, our understanding of ribosome assembly is still incomplete. Just as structure determination has been so important to understanding ribosome function, so too will it be critical to sorting out the assembly process. Here, we used a viable deletion in the yjeQ gene, a recognized ribosome assembly factor, to isolate and structurally characterize immature 30S subunits assembled in vivo. These small ribosome subunits contained unprocessed 17S rRNA and lacked some late ribosomal proteins. Cryo-electron microscopy reconstructions revealed that the presence of precursor sequences in the rRNA induces a severe distortion in the 3' minor domain of the subunit involved in the decoding of mRNA and interaction with the large ribosome subunit. These findings suggest that rRNA processing events induce key local conformational changes directing the structure toward the mature assembly. We concluded that rRNA processing, folding, and the entry of tertiary r-proteins are interdependent events in the late stages of 30S subunit assembly. In addition, we demonstrate how studies of emerging assembly factors in ribosome biogenesis can help to elucidate the path of subunit assembly in vivo.