External water transport is more important than vascular transport in the extreme atmospheric epiphyte Tillandsia usneoides (Spanish moss)

Most epiphytic bromeliads, especially those in the genus Tillandsia, lack functional roots and rely on the absorption of water and nutrients by large, multicellular trichomes on the epidermal surfaces of leaves and stems. Another important function of these structures is the spread of water over the epidermal surface by capillary action between trichome “wings” and epidermal surface. Although critical for the ultimate absorption by these plants, understanding of this function of trichomes is primarily based on light microscope observations. To better understand this phenomenon, the distribution of water was followed by its attenuation of cold neutrons following application of H₂O to the cut end of Tillandsia usneoides shoots. Experiments confirmed the spread of added water on the external surfaces of this “atmospheric” epiphyte. In a morphologically and physiologically similar plant lacking epidermal trichomes, water added to the cut end of a shoot clearly moved via its internal xylem and not on its epidermis. Thus, in T. usneoides, water moves primarily by capillarity among the overlapping trichomes forming a dense indumentum on shoot surfaces, while internal vascular water movement is less likely. T. usneoides, occupying xeric microhabitats, benefits from reduction of water losses by low‐shoot xylem hydraulic conductivities.     

Thermal Unfolding Pathway of PHD2 Catalytic Domain in Three Different PHD2 Species: Computational Approaches

Prolyl hydroxylase domain 2 containing protein (PHD2) is a key protein in regulation of angiogenesis and metastasis. In normoxic condition, PHD2 triggers the degradation of hypoxia-inducible factor 1 (HIF-1α) that induces the expression of hypoxia response genes. Therefore the correct function of PHD2 would inhibit angiogenesis and consequent metastasis of tumor cells in normoxic condition. PHD2 mutations were reported in some common cancers. However, high levels of HIF-1α protein were observed even in normoxic metastatic tumors with normal expression of wild type PHD2. PHD2 malfunctions due to protein misfolding may be the underlying reason of metastasis and invasion in such cases. In this study, we scrutinize the unfolding pathways of the PHD2 catalytic domain’s possible species and demonstrate the properties of their unfolding states by computational approaches. Our study introduces the possibility of aggregation disaster for the prominent species of PHD2 during its partial unfolding. This may justify PHD2 inability to regulate HIF-1α level in some normoxic tumor types.     

Tyrosine phosphorylation of alpha-actinin in activated platelets

The integrin alpha(IIb)beta(3) mediates tyrosine phosphorylation of a 105-kDa protein (pp105) in activated platelets. We have partially purified a 105-kDa tyrosine-phosphorylated protein from platelets stimulated with phorbol 12-myristate 13-acetate and obtained the sequence of an internal 12-mer peptide derived from this protein. The sequence was identical to human alpha-actinin sequences deposited in the Swiss Protein Database. alpha-Actinin, a 105-kDa protein in platelets, was subsequently purified from activated platelets by four sequential chromatographic steps. Fractions were analyzed by Western blotting and probed with alpha-actinin and anti-phosphotyrosine antibodies. The distribution of alpha-actinin and pp105 overlapped throughout the purification. Furthermore, in the course of this purification, a 105-kDa tyrosine-phosphorylated protein was only detected in fractions that contained alpha-actinin. The purified alpha-actinin protein was immunoprecipitated with antibodies to phosphotyrosine in the absence but not in the presence of phenyl phosphate. alpha-Actinin resolved by two-dimensional gel electrophoresis of activated platelet lysates was recognized by the antibodies to phosphotyrosine, whereas pretreatment of the platelets with bisindolylmaleimide, a protein kinase C inhibitor that prevents tyrosine phosphorylation of pp105, inhibited the reactivity of the antibodies to phosphotyrosine with alpha-actinin. Taken together, these data demonstrate that a fraction of alpha-actinin is tyrosine-phosphorylated in activated platelets.     

Recovery of Trichuris tenuis Chandler, 1930, from camelids (Lama glama and Vicugna vicugna) in Argentina

A survey of whipworms was conducted in llamas and vicu?as in northwestern Argentina. Fecal examinations of a group of 14 llamas (April 1995-March 1996) and 69 vicu?as (November 1996) indicated a high prevalence (usually >50%) of Trichuris sp. in these hosts. Prevalence was highest during July-November 1995 that also coincided with the highest mean fecal egg count. During postmortem examinations of 1 llama and 1 vicu?a, specimens of Trichuris tenuis were recovered from the cecum/large intestine of each camelid. This is the first report of T. tenuis in South America, and the first report in the vicu?a. It is suggested that T. tenuis is the typical whipworm of aboriginal camelids.     

The life cycle of Amblyomma neumanni Ribaga, 1902 (Acari: Ixodidae) in the laboratory

A colony of Amblyomma neumanni was started with engorged females collected from cattle in the province of Salta (24° 51S, 65° 33W), Argentina. The larvae and nymphs were fed on rabbits and the adults on calves. The non-parasitic stages were maintained in darkness at 27 ± 1°C and 83–86% RH. The life cycle (pre-feeding period not tested) had a mean duration of 205.7 days. The mean time (days) for the different phases of the cycle were as follows: feeding of females 8.8, pre-oviposition 23.8, oviposition 41.4, minimum egg incubation 76.1, feeding of larvae 8.5, pre-moult to nymphs 16.4, feeding of nymphs 7.9 and pre-moult to adults 22.8. The mean recovery rates of larvae, nymphs and females were 83.8, 85.6 and 89.3%, respectively. The nymphs moulting to females were heavier (8.1 ± 2.34 mg) than those moulting to males (6.0 ± 2.34 mg; p < 0.01), but their range of engorgement weight showed overlap (2.3–16.2 versus 2.2–12.8 mg, respectively). Two gynandromorphs were detected between the nymphs. A comparison of biological parameters of A. neumanni with other American Amblyomma species from mammals is presented. © Rapid Science Ltd. 1998     

What is the protein design alphabet?

Selecting a protein sequence that corresponds to a specific three-dimensional protein structure is known as the protein design problem. One principal bottleneck in solving this problem is our lack of knowledge of precise atomic interactions. Using a simple model of amino acid interactions, we determine three crucial factors that are important for solving the protein design problem. Among these factors is the protein alphabet-a set of sequence elements that encodes protein structure. Our model predicts that alphabet size is independent of protein length, suggesting the possibility of designing a protein of arbitrary length with the natural protein alphabet. We also find that protein alphabet size is governed by protein structural properties and the energetic properties of the protein alphabet units. We discover that the usage of average types of amino acid in proteins is less than expected if amino acids were chosen randomly with naturally occurring frequencies. We propose three possible scenarios that account for amino acid underusage in proteins. These scenarios suggest the possibility that amino acids themselves might not constitute the alphabet of natural proteins.     

Coralline algae indicate Pleistocene evolution from deep,open platform to outer barrier reef environments in the northern Great Barrier Reef margin

Coralline algae from a drill core in Ribbon Reef 5 have been used to interpret changes in the depositional palaeoenvironments in the northern Australian Great Barrier Reef over the last 790 ka. Three main coralline algal assemblages, each dominated by members of a particular subfamily, have been distinguished by quantitative analysis: (1) mastophoroid assemblages, usually occurring as crusts on corals, are typical of the shallowest reef settings; (2) lithophylloid assemblages within algal nodules may represent shallow-water, cooler environments or deeper reef subenvironments; and (3) melobesioid assemblages are characteristic of deeper-water platform areas. The algal assemblages between 96 and 210 m b.s.f. (metre below sea floor) record a fluctuating but progressive shallowing-upwards from deep, outer-platform to shallower, non-reefal depositional environments. Two intervening episodes dominated by mastophoroids represent two phases of reef growth. The section above 96 m b.s.f. comprises several stacked reefs in which mastophoroid crusts similar to the present-day shallow-water assemblages predominate.Electronic Supplementary Material Supplementary material is available for this article at .Communicated by: Geological Editor P.K. Swart