Oral disease in free-living red squirrels (Sciurus vulgaris) in the United Kingdom

Ninety-one red squirrels (Sciurus vulgaris) found dead in the UK between January 1994 and August 1998 were necropsied at the Institute of Zoology (London, UK); their oral cavities were examined visually, and in eight cases, radiographically. Four red squirrels, which had evidence of oral disease when necropsied as part of a mortality survey, also were examined. A low prevalence (prevalence = 0.033, SE = 0.02, n = 91) of oral disease was found in free-living red squirrels. In only two cases was oral disease the probable cause of death. Attrition of the check teeth (three cases) and overgrowth of the incisors (four cases) were the most common lesions found. Partial anodontia was recorded in one squirrel.     

Regulation of telomere length and suppression of genomic instability in human somatic cells by Ku86

Ku86 plays a key role in nonhomologous end joining in organisms as evolutionarily disparate as bacteria and humans. In eukaryotic cells, Ku86 has also been implicated in the regulation of telomere length although the effect of Ku86 mutations varies considerably between species. Indeed, telomeres either shorten significantly, shorten slightly, remain unchanged, or lengthen significantly in budding yeast, fission yeast, chicken cells, or plants, respectively, that are null for Ku86 expression. Thus, it has been unclear which model system is most relevant for humans. We demonstrate here that the functional inactivation of even a single allele of Ku86 in human somatic cells results in profound telomere loss, which is accompanied by an increase in chromosomal fusions, translocations, and genomic instability. Together, these experiments demonstrate that Ku86, separate from its role in nonhomologous end joining, performs the additional function in human somatic cells of suppressing genomic instability through the regulation of telomere length.     

Further progress towards the delimitation of <Emphasis Type="Italic">Cheilanthes</Emphasis> (Cheilanthoideae,Pteridaceae), with emphasis on South American species

Cheilanthoid ferns (Cheilanthoideae sensu PPG 1 2016) constitute an important group within the Pteridaceae and are cosmopolitan in distribution. In South America, there are 155 species distributed in 13 genera, among which the largest are Adiantopsis (35), Cheilanthes (27), and Doryopteris (22). Most of the cheilanthoid species are morphologically adapted to grow in arid to semi-arid conditions and show convergent evolution, which has implied difficulties in defining the genera throughout their taxonomic history (Copeland 1947, Tryon & Tryon 1973, Gastony & Rollo 1995, 1998, Kirkpatrick Systematic Botany, 32: 504–518, 2007, Rothfels et al. Taxon, 57: 712–724, 2008). Here, we sequenced two plastid markers (rbcL?+?trnL-F) of 33 South American cheilanthoid species, most of which have not been included in phylogenetic analyses previously. The South American species were analyzed together with South African and Australasian Cheilanthes and representatives of related cheilanthoid genera. The phylogenetic analysis showed that most Cheilanthes species are related to the genus Hemionitis, constituting different groups according to their distribution; moreover, three species—C. hassleri, C. pantanalensis, and C. obducta—appear as the sister clade of Hemionitis. Cheilanthes micropteris, the type species, is strongly supported in a clade with Australasian Cheilanthes plus five South American Cheilanthes species, all of which show a reduction in the number of spores per sporangium; this feature would be a synapomorphy for core Cheilanthes s.s. We found no support uniting other South American Cheilanthes to either the group of South African Cheilanthes or to core Cheilanthes s.s. On the other hand, C. geraniifolia, C. goyazensis, and C. bradei formed a clade related to Doryopteris that, with further study, could be considered as a new genus. The phylogenetic hypotheses presented here contribute substantially to the delimitation of Cheilanthes s.s. and related groups and provide the basis for re-examining the generic taxonomy.     

Fish and limnology of a thermal water environment in subtropical South America

Two thermal sources with water temperatures from 51 to 59°C flow into a stream of 2 to 5 m width and about 0.5 m depth at Agua Caliente (23° 44′, 64° 38′) in Jujuy province, Argentina. Data from 3 years sampling show that the influence of the thermal sources maintains the water temperature of the stream section at a high and constant level (from 24 to 35°C), different from the thermal regime of other streams in the area. Composition of water (N=13) has the following mean values: pH 8.36, conductivity 1591 μS cm^-1, dominant ions (in mg l^-1) CO₃ ^-- 12.77, CO₃H^- 140.27, Cl^- 246.86, SO₄ ^-- 460.14, Na⁺ 400.45, K⁺ 2.18, Ca⁺⁺ 27.68 and Mg⁺⁺ 2.14. Mean total dissolved solids: 1.3 g l^-1. Large amounts of SO₄ ^--, Na⁺, and Cl^- Sixteen fish species (2460 specimens) were captured in the warmed reach. Dominant families were Characidae, Cichlidae and Loricariidae. New geographic distribution information is provided for eight species, some of them with restricted northwestern Argentina distributions. Most abundant species were the eurytopic characid Astyanax bimaculatus, followed by the cichlid Bujurquina vittata. These species have the highest critical thermal maximum according to field experiments. Temperature of acclimatization is closer to lethal than in fishes from ‘normal’ habitats. Agua Caliente differs from other thermal habitats in the lack of isolation, its placement in a rain forest area, a high number of species, and the lack of cyprinodontoids. The fish fauna here represents an opportunistic invasion of a habitat with water parameters strongly different from those in the area, particularly temperature and salinity. Both faunistic and limnological traits make of Agua Caliente a new type of environment within the subtropics. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cycling of NADPH by glucose 6-phosphate dehydrogenase optimizes the spectrophotometric assay of nitric oxide synthase activity in cell lysates.

The measurement of nitric oxide synthase activity in cell lysates is often performed by radiochemical assay that quantifies the conversion of L-[3H]arginine to L-[3H]citrulline. We have developed a spectrophotometric procedure which continuously recycles NADPH through the addition of glucose 6-phosphate dehydrogenase to the cell lysate. This allows nitric oxide synthase to operate linearly for hours, so that nitric oxide-derived nitrite accumulates at amounts sufficient to be detected with the Griess assay. The incorporation of cycling of NADPH also improves the radiochemical assay for nitric oxide synthase activity.     

HIV-1 Matrix Protein Interactions with tRNA: Implications for Membrane Targeting

The N-terminally myristoylated matrix (MA) domain of the HIV-1 Gag polyprotein promotes virus assembly by targeting Gag to the inner leaflet of the plasma membrane. Recent studies indicate that, prior to membrane binding, MA associates with cytoplasmic tRNAs (including tRNA^Lys3), and in vitro studies of tRNA-dependent MA interactions with model membranes have led to proposals that competitive tRNA interactions contribute to membrane discrimination. We have characterized interactions between native, mutant, and unmyristylated (myr-) MA proteins and recombinant tRNA^Lys3 by NMR spectroscopy and isothermal titration calorimetry. NMR experiments confirm that tRNA^Lys3 interacts with a patch of basic residues that are also important for binding to the plasma membrane marker, phosphatidylinositol-4,5-bisphosphate [PI(4,5)P₂]. Unexpectedly, the affinity of MA for tRNA^Lys3 (K_d = 0.63 ± 0.03 μM) is approximately 1 order of magnitude greater than its affinity for PI(4,5)P₂-enriched liposomes (K_d(apparent) = 10.2 ± 2.1 μM), and NMR studies indicate that tRNA^Lys3 binding blocks MA association with liposomes, including those enriched with PI(4,5)P₂, phosphatidylserine, and cholesterol. However, the affinity of MA for tRNA^Lys3 is diminished by mutations or sample conditions that promote myristate exposure. Since Gag–Gag interactions are known to promote myristate exposure, our findings support virus assembly models in which membrane targeting and genome binding are mechanistically coupled.     

Localization by restriction fragment length polymorphism mapping in potato of a major dominant gene conferring resistance to the potato cyst nematode Globodera rostochiensis

Summary A major dominant locus conferring resistance against several pathotypes of the root cyst nematode Globodera rostochiensis was mapped on the linkage map of potato using restriction fragment length polymorphism (RFLP) markers. The assessment of resistance versus susceptibility of the plants in the experimental population considered was based on an in vivo (pot) and an in vitro (petri dish) test. By linkage to nine RFLP markers the resistance locus Gro1 was assigned to the potato linkage group IX which is homologous to the tomato linkage group 7. Deviations from the additivity of recombination frequencies between Gro1 and its neighbouring markers in the pot test led to the detection of a few phenotypic misclassifications of small plants with poor root systems that limited the observation of cysts on susceptible roots. Pooled data from both tests provided better estimates of recombination frequencies in the linkage interval defined by the markers flanking the resistance locus.     

Protein turnover,synthesis and secretion of albumin in hepatocytes isolated from rats bearing walker 256 carcinoma

Summary Hepatocytes isolated from rats bearing line A of Walker 256 carcinoma (WA) were used to study the turnover of total liver protein and the synthesis of albumin in comparison with ad libitum (AL) and pair-fed (PF) healthy controls. The rates of total protein synthesis by hepatocytes of WA animals were 40 and 90% higher than in AL and PF controls, respectively. The degradation of fast-turnover proteins was not affected by nutrition or by the tumor, whereas the degradation of slow-turnover proteins was slightly but significantly increased—about 24% higher in hepatocytes from WA rats than in PF controls. The combination of the two processes, synthesis and degradation, was in favor of an increased synthesis which explains the increase in liver protein content observed in vivo in WA rats. Dietary restriction did not affect the synthesis and secretion of albumin, whereas the tumor significantly reduced its synthesis by about 30%. The plasma concentration of albumin in WA rats dropped by about the same percentage compared with AL and PF animals.