The use of mitochondrial and nuclear sequence data in assessing the taxonomic status of the endangered Uluguru Bush Shrike Malaconotus alius

The endangered Uluguru Bush Shrike Malaconotus alius is a large, black-headed bush shrike, strictly endemic to the Uluguru Mountains in Tanzania. It has recently been suggested that this species has been misplaced within the genus Malaconotus and might instead be related to Malagasy Vangidae. To assess its systematic affinities, we analysed 1518 bp of sequence data obtained from a nuclear intron (myoglobin intron-2) and a mitochondrial protein-coding gene (ND2) using parsimony, maximum likelihood and Bayesian inference. Both genes strongly support the traditional placement within the genus Malaconotus , suggesting that similarities between the Uluguru Bush Shrike and the Vangidae are due to convergence. These results caution that taxonomic changes should not be made without a proper character analysis (i.e. assignment of character homology).     

Molecular phylogeny of the genus Tibicina (Hemiptera, Cicadidae): rapid radiation and acoustic behaviour

To estimate the potential contribution of ethological and ecological parameters to the mechanisms of species formation and species isolation in the Palearctic cicada genus Tibicina , we constructed a molecular phylogenetic hypothesis of extant Tibicina species. Seven mitochondrial genes and a fragment of a nuclear gene were sequenced (3046 bp). Mitochondrial genes included 547 informative sites but the nuclear gene was too conserved to be included in the analysis. The tree was characterized by a basal polytomy indicating that Tibicina species arose rapidly. Such rapid radiation might explain the low divergence in the acoustic communication observed between species. Parameters describing habitat selection and acoustic communication were mapped onto the tree. A shift in habitat selection accompanied by acoustic changes might have contributed to one speciation event. The stochastic distribution of the same acoustic characters on the other branches of the tree implies, however, that the subtle acoustic differences between species could be the result of previous speciation events and independent evolutionary histories, rather than having contributed themselves in the speciation and isolation processes.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 611–626.     

SIMS MICROSCOPY: METHODOLOGY,PROBLEMS AND PERSPECTIVES IN MAPPING DRUGS AND NUCLEAR MEDICINE COMPOUNDS

Secondary ion mass spectrometry (SIMS) microscopy, a mass spectrometry method designed in the 1960s, offers new analytical capabilities, high sensitivity (ppm to ppb region), high specificity and improved lateral resolution, thus facilitating insight into many physiological and biomedical questions. Apart from the sample preparation and the physical characteristics of the detection, the biological model must also be considered. SIMS analysis of diffusible ions and molecules requires strict cryogenic procedures which always begin by a flash-freeze fixation. Cellular integrity can be checked by mapping the major element distributions since intra and extracellular ions are redistributed only in damaged cells. Cryofixing may be followed either by a freeze-fracture methodology or by cryoembedding and dry-cutting. Chemical sample preparation is only used for ions or molecules bound to fixed cell structures. The use of scanning procedures ameliorates the lateral resolution and chromosome imaging has been reported with probe size of below 50nm. Absolute quantification can be derived for embedded specimen by using internal references included in tissue equivalent resins. The sensitivity is limited by the ionization yield of the tag element and may be further impaired when working at high mass resolution (≥5000) to eliminate interfering cluster ions. SIMS drug mapping is usually performed after in vitro administration of a molecule to cell culture systems. Drug detection is accomplished indirectly by detecting a tag isotope naturally present or introduced by labelling, mainly with halogens,¹⁵N and¹⁴C. Molecular imaging with TOF-SIMS is an appealing alternative especially for heavier compounds. We stress some biological problems through a critical review of published SIMS drug studies. SIMS proved useful in assessing the targeting specificity of nuclear medicine pharmaceutics, even after in vivo administration. The first microscopic evidence of a thionamide induced follicular blockade of the iodine organification process is presented in a human sample.     

The 67-kDa laminin receptor originated from a ribosomal protein that acquired a dual function during evolution

The 67-kDa laminin receptor (67LR) is a nonintegrin cell surface receptor that mediates high-affinity interactions between cells and laminin. Overexpression of this protein in tumor cells has been related to tumor invasion and metastasis. Thus far, only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated. The finding that the cDNA for the 37LRP is virtually identical to a cDNA encoding the ribosomal protein p40 has suggested that 37LRP is actually a component of the translational machinery, with no laminin-binding activity. On the other hand, a peptide of 20 amino acids deduced from the sequence of 37LR/p40 was shown to exhibit high laminin-binding activity. The evolutionary relationship between 23 sequences of 37LRP/p40 proteins was analyzed. This phylogenetic analysis indicated that all of the protein sequences derive from orthologous genes and that the 37LRP is indeed a ribosomal protein that acquired the novel function of laminin receptor during evolution. The evolutionary analysis of the sequence identified as the laminin-binding site in the human protein suggested that the acquisition of the laminin-binding capability is linked to the palindromic sequence LMWWML, which appeared during evolution concomitantly with laminin.      

Optimal range of prey size for antlions

1. Antlions are opportunistic trap building predators that cannot control prey encounter. Their trap should ideally retain a great diversity of prey. However, building a single trap that captures many prey with varying characteristics can be challenging. 2. A series of five different ant species ranging from thin to large, of sizes ranging from 2.75 to 6.5 mm, and a mean weight ranging from 0.54 to 6.00 mg were offered in a random succession to antlions. The state of satiation of the antlions was controlled, and their mass and the depth of their pit were recorded. The reaction of antlion to the prey, the probability of capture as well as the time to escape were recorded. 3. The probability of an antlion reaction is an increasing function of the pit depth and a decreasing function of antlion mass. The probability of capture is highest for intermediate prey mass and is an increasing function of pit depth. The time to escape is a declining function of prey mass and an increasing function of pit depth. 4. There is an upper limit to prey mass given that large prey escape out of the pit. There is a lower limit to prey mass given the difficulty to apprehend the smallest, thin species. Consequently, there is a range of prey mass, corresponding to a medium‐sized ant of 2 mg, for which the pit functions best. The physics of insect locomotion on sandy slopes was identified as the key to understanding the functioning of antlion pits.     

Leptin receptor long-form splice-variant protein expression in neuron cell bodies of the brain and co-localization with neuropeptide Y mRNA in the arcuate nucleus.

Reduced leptin (Ob protein) signaling is proposed to be a stimulus for the activation of neuropeptide Y (NPY) gene activity and increased expression of mRNA for the long form of the leptin receptor (Ob-Rb) in the hypothalamic arcuate nucleus. To determine if Ob-Rb protein is expressed in arcuate nucleus NPY neurons, we developed an affinity-purified polyclonal antibody against amino acids 956-1102 of human Ob-Rb. This antibody specifically recognizes the cytoplasmic tail of Ob-Rb and does not react with shorter leptin-receptor variants. Western immunoblots of Ob-Rb-transfected COS cells showed a single 150-kD band, and immunofluorescence revealed intense perinuclear staining in the cytoplasm. A 150-kD band was also present in Western immunoblots of hypothalamus. Immunocytochemical staining of brain slices revealed immunoreactive Ob-Rb protein concentrated in many neuronal cell bodies in the same regions of the forebrain that also express Ob-Rb mRNA. In the hypothalamus, Ob-Rb-positive cell bodies were abundant in the arcuate nucleus and ventromedial nucleus, with lesser numbers in the dorsomedial nucleus and paraventricular nucleus. Immunostaining was also detected in cell bodies of pyramidal cell neurons of the pyriform cortex and cerebral cortex, in neurons of the thalamus, and on the surface of ependymal cells lining the third ventricle. The choroid plexus, which expresses the short Ob-Ra form, was negative. Combined immunocytochemistry for Ob-Rb protein and fluorescence in situ hybridization for NPY mRNA identified arcuate nucleus neurons containing both NPY mRNA and Ob-Rb protein. The present finding of Ob-Rb protein in neurons that express NPY mRNA supports the hypothesis that arcuate nucleus NPY neurons are direct targets of leptin and play an important role in regulation of food intake and body weight.