Diversification in the Mexican horned lizard Phrynosoma orbiculare across a dynamic landscape

The widespread montane Mexican horned lizard Phrynosoma orbiculare (Squamata: Phrynosomatidae) represents an ideal species to investigate the relative impacts of Neogene vicariance and Quaternary climate change on lineage diversification across the Mexican highlands. We used mitochondrial DNA to examine the maternal history of P. orbiculare and estimate the timing and tempo of lineage diversification. Based on our results, we inferred 11 geographically structured, well supported mitochondrial lineages within this species, suggesting P. orbiculare represents a species complex. Six divergences between lineages likely occurred during the Late Miocene and Pliocene, and four splits probably happened during the Pleistocene. Diversification rate appeared relatively constant through time. Spatial and temporal divergences between lineages of P. orbiculare and co-distributed taxa suggest that a distinct period of uplifting of the Transvolcanic Belt around 7.5-3 million years ago broadly impacted diversification in taxa associated with this mountain range. To the north, several river drainages acting as filter barriers differentially subdivided co-distributed highland taxa through time. Diversification patterns observed in P. orbiculare provide additional insight into the mechanisms that impacted differentiation of highland taxa across the complex Mexican highlands.     

Ectoparasites on reintroduced roe deer Capreolus capreolus in Israel

The ectoparasite fauna of reintroduced roe deer (Capreolus capreolus) was surveyed in a Mediterranean forest in Israel. Ectoparasites were collected from four female hand-reared deer during 2004 and 2005. Seasonality, predilection sites of infestation, and the apparent effect of the parasites are presented. This is the first study of roe deer parasites in the East Mediterranean. The ectoparasite fauna included three hippoboscid fly (Lipoptena capreoli, Hippobosca equina, and Hippobosca longipennis), four tick (Rhipicephalus sanguineus, Rhipicephalus turanicus, Rhipicephalus kohlsi, and Hyalomma marginatum), and one unidentified trombiculid mite species. For most of these ectoparasites, this is the first record on roe deer. All ectoparasite species were documented in Israel prior to the reintroduction program; exotic ectoparasites were not detected.     

Two distinct pathways for cyclooxygenase-2 protein degradation

Cyclooxygenases (COX-1 and COX-2) are N-glycosylated, endoplasmic reticulum-resident, integral membrane proteins that catalyze the committed step in prostanoid synthesis. COX-1 is constitutively expressed in many types of cells, whereas COX-2 is usually expressed inducibly and transiently. The control of COX-2 protein expression occurs at several levels, and overexpression of COX-2 is associated with pathologies such as colon cancer. Here we have investigated COX-2 protein degradation and demonstrate that it can occur through two independent pathways. One pathway is initiated by post-translational N-glycosylation at Asn-594. The N-glycosyl group is then processed, and the protein is translocated to the cytoplasm, where it undergoes proteasomal degradation. We provide evidence from site-directed mutagenesis that a 27-amino acid instability motif (27-IM) regulates posttranslational N-glycosylation of Asn-594. This motif begins with Glu-586 8 residues upstream of the N-glycosylation site and ends with Lys-612 near the C terminus at Leu-618. Key elements of the 27-IM include a helix involving residues Glu-586 to Ser-596 with Asn-594 near the end of this helix and residues Leu-610 and Leu-611, which are located in an apparently unstructured downstream region of the 27-IM. The last 16 residues of the 27-IM, including Leu-610 and Leu-611, appear to promote N-glycosylation of Asn-594 perhaps by causing this residue to become exposed to appropriate glycosyl transferases. A second pathway for COX-2 protein degradation is initiated by substrate-dependent suicide inactivation. Suicide-inactivated protein is then degraded. The biochemical steps have not been resolved, but substrate-dependent degradation is not inhibited by proteasome inhibitors or inhibitors of lysosomal proteases. The pathway involving the 27-IM occurs at a constant rate, whereas degradation through the substrate-dependent process is coupled to the rate of substrate turnover.     

Core temperature measurement by microwave radiometry

A ‘double-container model’ was used for core temperature (T_c) measurement by microwave emission radiometry (MR) of warm fluid inside a tube, placed in a container with a cooler fluid. The intensity of microwaves emitted from the warmer fluid inside the tube were measured using a MR metering device, consisting of an antenna linked to a low-noise radio frequency amplifier (bandwidth 500 MHz, centered at 4.0 GHz). Based on the MR measurements, a T_c prediction model was developed for measuring the temperature of fluid inside a tube, achieving a sensitivity of ±0.5 °C at environmental temperature of 33–37 °C.     

The Frequent 5,10-Methylenetetrahydrofolate Reductase C677T Polymorphism Is Associated with a Common Haplotype in Whites, Japanese, and Africans

The common 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism causes decreased activity of this enzyme and can be associated with mild-to-moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with vascular dementia, arterial thrombosis, venous thrombosis, neural-tube defects, and fetal loss. When folic acid intake is sufficient, homozygotes for MTHFR 677T appear to be protected against colon cancer and acute lymphatic leukemia, and fetuses bearing this genotype have an augmented survival. The distribution of MTHFR 677T is worldwide, but its frequency in different populations varies extensively. In the present study, we addressed the question of whether the MTHFR 677T alteration has an ancestral origin or has occurred repeatedly. We analyzed the frequency distribution of the previously described polymorphism A1298C in exon 7 and of three intronic dimorphisms, in white Israelis (Jews and Arabs), Japanese, and Ghanaian Africans. The 677T allele was, remarkably, associated with one haplotype, G-T-A-C, in white and Japanese homozygotes. Among the Africans, analysis of maximum likelihood also disclosed an association with the G-T-A-C haplotype, although none of the 174 subjects examined was homozygous for MTHFR 677T. These results suggest that the MTHFR 677T alteration occurred on a founder haplotype that may have had a selective advantage.     

A Pro-Nerve Growth Factor (proNGF) and NGF Binding Protein, α2-Macroglobulin,Differentially Regulates p75 and TrkA Receptors and Is Relevant to Neurodegeneration Ex Vivo and In Vivo

Nerve growth factor (NGF) is generated from a precursor, proNGF, that is proteolytically processed. NGF preferentially binds a trophic tyrosine kinase receptor, TrkA, while proNGF binds a neurotrophin receptor (NTR), p75^NTR, that can have neurotoxic activity. Previously, we along with others showed that the soluble protein α₂-macroglobulin (α₂M) is neurotoxic. Toxicity is due in part to α₂M binding to NGF and inhibiting trophic activity, presumably by preventing NGF binding to TrkA. However, the mechanisms remained unclear. Here, we show ex vivo and in vivo three mechanisms for α₂M neurotoxicity. First, unexpectedly the α₂M-NGF complexes do bind TrkA receptors but do not induce TrkA dimerization or activation, resulting in deficient trophic support. Second, α₂M makes stable complexes with proNGF, conveying resistance to proteolysis that results in more proNGF and less NGF. Third, α₂M-proNGF complexes bind p75^NTR and are more potent agonists than free proNGF, inducing tumor necrosis factor alpha (TNF-α) production. Hence, α₂M regulates proNGF/p75^NTR positively and mature NGF/TrkA negatively, causing neuronal death ex vivo. These three mechanisms are operative in vivo, and α₂M causes neurodegeneration in a p75^NTR- and proNGF-dependent manner. α₂M could be exploited as a therapeutic target, or as a modifier of neurotrophin signals.     

Functional Diversity of Culturable Bacterial Communities in the Rhizosphere in Relation to Fine-root and Soil Parameters in Alder Stands on Forest, Abandoned Agricultural, and Oil-shale Mining Areas

Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing the functional diversity and activity of microbial communities in the soil–root interface and in the bulk soil in relation to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine community-level physiological profiles (CLPP) of culturable bacteria in soil–root interface and bulk soil samples. CLPP were summarized as AWCD (average well color development, OD 48 h⁻¹) and by Shannon diversity index, which varied between 4.3 and 4.6 for soil–root interface. The soil–root interface/bulk soil ratio of AWCD was estimated. Substrate-induced respiration (SIR) and basal respiration (BAS) of bulk soil samples were measured and metabolic quotient (Q = BAS/SIR) was calculated. SIR and Q varied from 0.24 to 2.89 mg C g⁻¹ and from 0.12 to 0.51, respectively. Short-root morphological studies were carried out by WinRHIZO^TM Pro 2003b; mean specific root area (SRA) varied for grey alder and black alder from 69 to 103 and from 54 to 155 m² kg⁻¹, respectively. The greatest differences between AWCD values of culturable bacterial communities in soil–root interface and bulk soil were found for the young alder stands on oil-shale mining spoil and on abandoned agricultural land. Soil–root interface/bulk soil AWCD ratio, ratio for Shannon diversity indices, and SRA were positively correlated. Foliar assimilation efficiency (FOE) was negatively correlated with soil–root interface/bulk soil AWCD ratio. The impact of soil and alder species on short-root morphology was significant; short-root tip volume and mass were greater for black alder than grey alder. For the investigated microbiological characteristics, no alder-species-related differences were revealed.     

A Unified Approach to Linking Experimental,Statistical and Computational Analysis of Spike Train Data

A fundamental issue in neuroscience is how to identify the multiple biophysical mechanisms through which neurons generate observed patterns of spiking activity. In previous work, we proposed a method for linking observed patterns of spiking activity to specific biophysical mechanisms based on a state space modeling framework and a sequential Monte Carlo, or particle filter, estimation algorithm. We have shown, in simulation, that this approach is able to identify a space of simple biophysical models that were consistent with observed spiking data (and included the model that generated the data), but have yet to demonstrate the application of the method to identify realistic currents from real spike train data. Here, we apply the particle filter to spiking data recorded from rat layer V cortical neurons, and correctly identify the dynamics of an slow, intrinsic current. The underlying intrinsic current is successfully identified in four distinct neurons, even though the cells exhibit two distinct classes of spiking activity: regular spiking and bursting. This approach – linking statistical, computational, and experimental neuroscience – provides an effective technique to constrain detailed biophysical models to specific mechanisms consistent with observed spike train data.