A stereochemical model for phospholipids. II: Conformational analysis and molecular packing of phosphatidylethanolamine (PE)

A partition energy method procedure was applied to select the energetically favoured conformations of phosphatidylethanolamine (PE) as polar constituents of phospholipid molecules. The result indicated a large degree of freedom for the two torsion angles of the ester bond of the phosphate and a gauche, gauche star conformation for the ethane bond.A packing process of the molecule was carried out through a potential energy calculation by considering the conformers selected above, using previously published procedure and conventions. All the arrangements which possess the best packing energy values were characterised by an orientation of the PN dipolar segment parallel to the lattice plain. Rotation of the internal torsion angles and rotation in the eulerian space of the molecule produced differences in the charged groups that interact. An additional minimum was present in the energy packing process of those conformers which have the first torsion angle of the phosphate in a trans conformation. This minimum, which corresponds to an orientation of the molecule orthogonal to the lattice plane, requires a complete neutralisation of the point charges on the system.The results of the calculation underline the importance of changes in the behaviour of the polar group of the phospholipids in the packing process.     

The coiled-coil domain of Escherichia coli FtsLB is a structurally detuned element critical for modulating its activation in bacterial cell division

The FtsLB complex is a key regulator of bacterial cell division, existing in either an off state or an on state, which supports the activation of septal peptidoglycan synthesis. In Escherichia coli, residues known to be critical for this activation are located in a region near the C-terminal end of the periplasmic coiled-coil domain of FtsLB, raising questions about the precise role of this conserved domain in the activation mechanism. Here, we investigate an unusual cluster of polar amino acids found within the core of the FtsLB coiled coil. We hypothesized that these amino acids likely reduce the structural stability of the domain and thus may be important for governing conformational changes. We found that mutating these positions to hydrophobic residues increased the thermal stability of FtsLB but caused cell division defects, suggesting that the coiled-coil domain is a “detuned” structural element. In addition, we identified suppressor mutations within the polar cluster, indicating that the precise identity of the polar amino acids is important for fine-tuning the structural balance between the off and on states. We propose a revised structural model of the tetrameric FtsLB (named the “Y-model”) in which the periplasmic domain splits into a pair of coiled-coil branches. In this configuration, the hydrophilic terminal moieties of the polar amino acids remain more favorably exposed to water than in the original four-helix bundle model (“I-model”). We propose that a shift in this architecture, dependent on its marginal stability, is involved in activating the FtsLB complex and triggering septal cell wall reconstruction.     

Wabusk of the Omushkegouk: Cree-Polar Bear (Ursus maritimus) Interactions in Northern Ontario

In order to understand wabusk (polar bear, Ursus maritimus) behaviours and interactions with people in the Hudson Bay lowlands of northern Ontario we conducted this collaborative study of Cree kiskayndamowin/knowledge. Our findings reveal that Cree knowledge supports previously published information on polar bears, while adding further contextual findings: that male polar bears travel greater distances into the muskeg than previously recorded; that wabusk prey on amisk (beaver, Castor canadensis); that wabusk interact with muskwa (black bears, Ursus americanus); and that human-polar bear interactions occur in this region of northern Canada. Bearing in mind that Cree knowledge has been recognized in wildlife management strategies (i.e., for beaver, caribou and moose) elsewhere in Canada, this particular body of information is timely, especially since polar bears are considered threatened under the Ontario Endangered Species Act, and the province is developing a recovery strategy for the Southern Hudson Bay polar bear population. The federal government is also contemplating listing polar bears in Canada as a “species of special concern” under the Species at Risk Act (SARA). While it is unclear as to how these decisions will impact the Cree-polar interactions, the listing of polar bears by both governments, but especially the provincial government of Ontario, must recognize treaty and Aboriginal rights, acknowledge its duties to consult and properly accommodate Aboriginal people’s views, incorporate Cree kiskayndamowin/knowledge of wabusk, and re-examine the proposed Wabusk Co-Management Agreement draft developed by the Ontario Ministry of Natural Resources (OMNR) and Coastal Cree First Nations of Northern Ontario in 1994. The article provides recommendations that highlight how the Northern Cree First Nations, through the development of the Recovery Strategy for Polar Bear in Ontario, can become engaged in the management of wabusk in Ontario and throughout Canada.     

The oldest known chironomids of the tribe Tanytarsini (Diptera: Chironomidae) indicate plesiomorphic character states

Taxonomic studies on chironomids of the tribe Tanytarsini recorded in Eocene Baltic amber from the Rovno region have revealed two new species: Archistempellina perkovskyi and Stempellinella ivanovae. Both species display interesting characters supporting evolutionary trends in the tribe. A. perkovskyi nov. sp. combines plesiomorphic characters, thus consolidating the hypothesis that the genus Archistempellina is one of the basal lineages of the tribe Tanytarsini. The antennal flagellum composed of 13 discernible segments found in S. ivanovae nov. sp. is defined as a plesiomorphic character state opposite to a reduced number of flagellomeres in extant species; the nipple-like process on the apex of the gonostylus is recognised as a unique character in the Tanytarsini and a possible homologue of the horn-like tip of the gonostylus known from several extant species of the genus Stempellinella Brundin. A key to determination of all genera and species of the Tanytarsini recorded in the Eocene is presented. Notes on evolutionary trends in the tribe are also provided.     

Middle Miocene Cephalotaxus (Taxaceae) from Yunnan,Southwest China,and its implications to taxonomy and evolution of the genus

The infrageneric taxonomy of the genus Cephalotaxus Siebold et Zuccarini ex Endlicher (Taxaceae) is controversial as morphological characters have been doubted to change coherently among species. Although the epidermal features are considered as important characters in the taxonomy of conifers, they have not been systematically studied in this genus. Neogene foliage shoots with well-preserved epidermal structure not only can provide systematic links to the extant species, but also have implications for the taxonomical definition of the extant species by their epidermal features. In this paper, the morphologies of leafy shoots combining epidermal structure of a Neogene Cephalotaxus, which was collected from the middle Miocene of Southwest China, and ten extant species (variants) were studied. Morphology as well as epidermal structures was compared among species (variants) in Cephalotaxus. Based on the comparisons, the taxonomical definition of extant species in genus Cephalotaxus are discussed. Our results indicate that leaf morphological characters in combination with the features of epidermal structure can distinguish species in genus Cephalotaxus. The fossil foliage shoots from the middle Miocene of Southwest China were assigned to a new species, C. maguanensis n. sp., which shows close affinities to the extant C. hainanensis. On the basis of leaf and epidermal information, we suggest there are seven extant species in Cephalotaxus. With global cooling and the uplift of the Qinghai-Tibet Plateau since the middle Miocene, the cooling climate induced the differentiation and southward expansions of C. maguanensis, and its extant offspring, C. hainanensis, is distributed to Hainan Island and the Indo-Chinese peninsula.     

Tooth Root Morphology in the Early Pliocene African Bear Agriotherium africanum (Mammalia, Carnivora, Ursidae) and its Implications for Feeding Ecology

Tooth root surface areas serve as proxies for bite force potentials, and by extension, dietary specialization in extant carnivorans. Here, we investigate the feeding ecology of the extinct large-bodied ursid Agriotherium africanum, by comparing its root surface areas (reconstructed with the aid of computed tomography and three-dimensional image processing) and bite force estimates, with those of extant carnivorans. Results show that in absolute terms, canine and carnassial bite forces, as well as root surface areas were highest in A. africanum. However, when adjusted for skull size, A. africanum’s canine roots were smaller than those of extant solitary predators. With teeth being the limiting factor in the masticatory system, low canine root surface areas suggest that A. africanum would have struggled to bring down large vertebrate prey. Its adjusted carnassial root sizes were found to be smaller than those of extant hard object feeders and the most carnivorous tough object feeders, but larger than those of extant omnivorous ursids and Ursus maritimus. This and the fact that it displayed its highest postcanine root surface areas in the carnassial region (rather than the most distal tooth in the tooth row) suggest that A. africanum consumed more vertebrate tissue than extant omnivorous ursids. With an apparent inability to routinely bring down large prey or to consume mechanically demanding skeletal elements, its focus was most likely on tough tissue, which it acquired by actively scavenging the carcasses of freshly dead/freshly killed animals. Mechanically less demanding skeletal elements would have been a secondary food source, ingested and processed mainly in association with muscle and connective tissue.     

The Braincase of Eocaecilia micropodia (Lissamphibia,Gymnophiona) and the Origin of Caecilians

The scant fossil record of caecilians has obscured the origin and evolution of this lissamphibian group. Eocaecilia micropodia from the Lower Jurassic of North America remains the only stem-group caecilian with an almost complete skull preserved. However, this taxon has been controversial, engendering re-evaluation of traits considered to be plesiomorphic for extant caecilians. Both the validity of the placement of E. micropodia as a stem caecilian and estimates of the plesiomorphic condition of extant caecilians have been questioned. In order to address these issues, the braincase of E. micropodia was examined via micro-computed tomography. The braincase is considered to be a more reliable phylogenetic indicator than peripheral regions of the skull. These data reveal significant new information, including the possession of an ossified nasal septum, ossified anterior wall of the sphenethmoid, long anterolateral processes on the sphenethmoid, and paired olfactory nerve foramina, which are known only to occur in extant caecilians; the latter are possibly related to the evolution of the tentacle, a caecilian autapomorphy. A phylogenetic analysis that included 64 non-amniote taxa and 308 characters represents the first extensive test of the phylogenetic affinities of E. micropodia. The results place E. micropodia securely on the stem of extant caecilians, representing a clade within Temnospondyli that is the sister taxon to batrachians plus Gerobatrachus. Ancestral character state reconstruction confirms the braincase of E. micropodia to be largely representative of the plesiomorphic condition of extant caecilians. Additionally, the results refine the context within which the evolution of the caecilian form can be evaluated. The robust construction and pattern of the dermal skull of E. micropodia is interpreted as symplesiomorphic with advanced dissorophoid temnospondyls, rather than being autapomorphic in its robust construction. Together these data increase confidence in incorporating E. micropodia into discussions of caecilian evolution.     

Tracing the Tiger: Population Genetics Provides Valuable Insights into the Aedes (Stegomyia) albopictus Invasion of the Australasian Region

Background

The range of the Asian tiger mosquito Aedes albopictus is expanding globally, raising the threat of emerging and re-emerging arbovirus transmission risks including dengue and chikungunya. Its detection in Papua New Guinea''s (PNG) southern Fly River coastal region in 1988 and 1992 placed it 150 km from mainland Australia. However, it was not until 12 years later that it appeared on the Torres Strait Islands. We hypothesized that the extant PNG population expanded into the Torres Straits as an indirect effect of drought-proofing the southern Fly River coastal villages in response to El Nino-driven climate variability in the region (via the rollout of rainwater tanks and water storage containers).

Methodology/Principal Findings

Examination of the mosquito''s mitochondrial DNA cytochrome oxidase I (COI) sequences and 13 novel nuclear microsatellites revealed evidence of substantial intermixing between PNG''s southern Fly region and Torres Strait Island populations essentially compromising any island eradication attempts due to potential of reintroduction. However, two genetically distinct populations were identified in this region comprising the historically extant PNG populations and the exotic introduced population. Both COI sequence data and microsatellites showed the introduced population to have genetic affinities to populations from Timor Leste and Jakarta in the Indonesian region.

Conclusions/Significance

The Ae. albopictus invasion into the Australian region was not a range expansion out of PNG as suspected, but founded by other, genetically distinct population(s), with strong genetic affinities to populations sampled from the Indonesian region. We now suspect that the introduction of Ae. albopictus into the Australian region was driven by widespread illegal fishing activity originating from the Indonesian region during this period. Human sea traffic is apparently shuttling this mosquito between islands in the Torres Strait and the southern PNG mainland and this extensive movement may well compromise Ae. albopictus eradication attempts in this region.     

Sequestration of polyacetylenes by the parasite Orobanche hederae (Orobanchaceae) from its host Hedera helix (Araliaceae)

Orobanche hederae Duby and its host Hedera helix L. were collected in the North Italian Trentino-Südtirol region and analyzed for their content of polyacetylenes. Both, the host plant (Hedera) and the parasite (Orobanche) contained the polyacetylene falcarinol and two of its dehydroderivatives. The contents of polyacetylenes in Hedera decrease from roots via stems to leaves and contents in Orobanche are only about one-tenth of the contents in the Hedera roots it parasites on. Moreover, relative contents of the more polar polyacetylenes are higher in Orobanche than in Hedera, implying a bias toward the sequestration of more polar compounds.     

FINE STRUCTURE OF THE NEUROHYPOPHYSIS OF THE OPOSSUM (DIDELPHIS VIRGINIANA)

The neurohypophysis of the opossum (Didelphis virginiana) was studied by electron microscopy in order to amplify Bodian''s classic light microscopic observations in which he demonstrated a definite lobular pattern. The lobule of the opossum neurohypophysis is divided into three regions: a hilar, a palisade, and a septal zone. The hilar portion contains bundles of nerve fibers, the extensions of the hypothalamo-hypophyseal tract containing neurofilaments but few neurosecretory granules. In the opossum, pituicytes have a densely fibrillar cytoplasm. Herring bodies are prominent in the hilar region. They are large bodies packed with neurosecretory granules that have been described as end bulb formations of axons. From the hilar region, axons fan out into a palisade zone where the nerve terminals packed with neurosecretory granules, mitochondria, and microvesicles abut upon basement membranes. The neurosecretory granules are similar to those present in the neurohypophysis of other mammals, except for an occasional huge granule of distinctive type. Material morphologically and histochemically resembling glycogen occurs as scattered particles and as aggregates within nerve fibers. The septal zone, containing collagen, fibroblasts, and numerous small capillaries, is separated from the adjacent glandular tissue by a basement membrane.     

Septal pore complex morphology in the Agaricomycotina (Basidiomycota) with emphasis on the Cantharellales and Hymenochaetales

The ultrastructure of septa and septum-associated septal pore caps are important taxonomic markers in the Agaricomycotina (Basidiomycota, Fungi). The septal pore caps covering the typical basidiomycetous dolipore septum are divided into three main phenotypically recognized morphotypes: vesicular-tubular (including the vesicular, sacculate, tubular, ampulliform, and globular morphotypes), imperforate, and perforate. Until recently, the septal pore cap-type reflected the higher-order relationships within the Agaricomycotina. However, the new classification of Fungi resulted in many changes including revision of existing and addition of new orders. Therefore, the septal pore cap ultrastructure of more than 325 species as reported in literature was related to this new classification. In addition, the septal pore cap ultrastructures of Rickenella fibula and Cantharellus formosus were examined by transmission electron microscopy. Both fungi have dolipore septa associated with perforate septal pore caps. These results combined with data from the literature show that the septal pore cap-type within orders of the Agaricomycotina is generally monomorphic, except for the Cantharellales and Hymenochaetales.It appears from the fungal phylogeny combined with the septal pore cap ultrastructure that the vesicular-tubular and the imperforate type both may have arisen from endoplasmic reticulum. Thereafter, the imperforate type eventually gave rise to the perforate septal pore cap-type.     

Design and synthesis of hydroxyethylamine (HEA) BACE-1 inhibitors: Prime side chromane-containing inhibitors

The structure activity relationship of the prime region of conformationally restricted hydroxyethylamine (HEA) BACE inhibitors is described. Variation of the P1′ region provided selectivity over Cat-D with a series of 2,2-dioxo-isothiochromanes and optimization of the P2′ substituent of chromane–HEA(s) with polar substituents provided improvements in the compound’s in vitro permeability. Significant potency gains were observed with small aliphatic substituents such as methyl, n-propyl, and cyclopropyl when placed at the C-2 position of the chromane.     

Glandulocalyx upatoiensis, a fossil flower of Ericales (Actinidiaceae/Clethraceae) from the Late Cretaceous (Santonian) of Georgia, USA

Background and Aims

Ericales are a major group of extant asterid angiosperms that are well represented in the Late Cretaceous fossil record, mainly by flowers, fruits and seeds. Exceptionally well preserved fossil flowers, here described as Glandulocalyx upatoiensis gen. & sp. nov., from the Santonian of Georgia, USA, yield new detailed evidence of floral structure in one of these early members of Ericales and provide a secure basis for comparison with extant taxa.

Methods

The floral structure of several fossil specimens was studied by scanning electron microscopy (SEM), light microscopy of microtome thin sections and synchrotron-radiation X-ray tomographic microscopy (SRXTM). For direct comparisons with flowers of extant Ericales, selected floral features of Actinidiaceae and Clethraceae were studied with SEM.

Key Results

Flowers of G. upatoiensis have five sepals with quincuncial aestivation, five free petals with quincuncial aestivation, 20–28 stamens arranged in a single series, extrorse anther orientation in the bud, ventral anther attachment and a tricarpellate, syncarpous ovary with three free styles and numerous small ovules on axile, protruding-diffuse and pendant placentae. The calyx is characterized by a conspicuous indumentum of large, densely arranged, multicellular and possibly glandular trichomes.

Conclusions

Comparison with extant taxa provides clear evidence for a relationship with core Ericales comprised of the extant families Actinidiaceae, Roridulaceae, Sarraceniaceae, Clethraceae, Cyrillaceae and Ericaceae. Within this group, the most marked similarities are with extant Actinidiaceae and, to a lesser degree, with Clethraceae. More detailed analyses of the relationships of Glandulocalyx and other Ericales from the Late Cretaceous will require an improved understanding of the morphological features that diagnose particular extant groups defined on the basis of molecular data.     

The Iberian record of the puma-like cat Puma pardoides (Owen, 1846) (Carnivora,Felidae)

Fossil puma-like cats (Puma pardoides) are recorded from several Late Pliocene to Early Pleistocene Eurasian localities, but the interpretation of the phylogenetic relationships between them and the extant puma (Puma concolor) remains controversial. In the past, extinct puma-like cats have been classified into several genera and species, and a close relationship with both pumas (Puma concolor) and snow leopards (Uncia uncia) has been suggested. Here, we describe the fossil remains of puma-like cats from the Iberian Peninsula. These remains (from the localities of La Puebla de Valverde, Cueva Victoria and Vallparadís) cover the whole known chronological distribution of this species in Eurasia. Although there are dentognathic similarities with U. uncia, the Iberian remains of P. pardoides most closely resemble the extant P. concolor. It is concluded that P. pardoides is closely related to living pumas, which supports a likely Eurasian origin of the puma lineage.     

Significance of the polar lobe for the determination of dorsoventral polarity in Dentalium vulgare (da Costa)

The development of dorsoventral polarity in Dentalium dentale has been analyzed after inhibiting first polar lobe formation with cytochalasin B and bisecting the egg into two equal parts at an early trefoil stage. Cleavage pattern and morphogenesis have been studied in both in vivo and permanent cytological preparations. After bisecting the egg, each blastomere may fuse with its adhering polar lobe half and subsequently behave as a CD blastomere. The polar lobe substance may induce both halves to develop an apical tuft and probably also a posttrochal region. Cytochalasin B embryos which pass through an equal first cleavage form a four-cell stage in which the two D blastomeres are situated opposite or adjacent to each other (CDCD or CCDD embryos, respectively). During further development the larvae show a duplication of lobe-dependent structures. It is concluded that dorsoventral polarity originates epigenetically by fusion of the polar lobe with one of the first two blastomeres and is not preformed in the uncleaved egg.     

A new ground sloth (Mammalia: Xenarthra) from the Quaternary of Brazil

The record of South-American Pleistocene Megalonychidae is scarce. Of the species described for intertropical Brazil, including Megalonyx sp., Ocnopus gracilis, Valgipes deformis, Xenocnus cearensis and Ahytherium aureum, only the last, recently described, is valid. The new megalonychid species described here was recovered from the same locality as Ah. aureum. The latter is apparently more closely linked to the North-American Pleistocene forms whereas Australonyx aquae may be more closely related to the Antillean sloths. The fossil remains of extant taxa recovered in association with the new sloth species suggest that the region, currently within the Caatinga biome, was a mosaic of the Atlantic Forest and Savannah biomes during the final stages of the Pleistocene.     

A new sexually dimorphic mantidfly species of Allomantispa Liu et al., 2015 from China (Neuroptera: Mantispidae)

Allomantispa Liu et al., 2015 is the only extant genus of the mantidfly subfamily Drepanicinae from Eurasia, being endemic to the Oriental region. It currently consists of only two species from southeastern Tibet and northern Myanmar, respectively. Here we describe a new species of this rarely observed mantidfly genus, namely Allomantispa coniprocessa sp. nov. from Yunnan, China. Interestingly, the new species displays distinctive sexual dimorphic characters on the pronotum. The molecular identification reveals obvious genetic divergence between the allopatric individuals of the new species. Their morphological variations are illustrated and compared. In addition, some characters with taxonomic or phylogenetic significance present on the pronotum, the abdomen and the genitalia in Allomantispa are also discussed. Our finding updates the morphological and distributional information on Allomantispa and implies a more diverse fauna of this genus in the Oriental region than previously assumed.     

Europrotomus (Mollusca: Caenogastropoda: Strombidae): a new Middle Miocene European strombid genus (Revision of Euprotomus Gill, 1870. Part 4)

The medium-sized, strongly ornamented nominal species Strombus schroeckingeri H?rnes in Hoernes & Auinger, 1884 is well known from Langhian deposits of the Paratethys Sea. Its traditional generic affiliation in the literature with Euprotomus Gill, 1870, implicated a biogeographic relation of the Paratethys and the proto-Mediterranean with the Neogene Indo-West-Pacific region. This relation, however, is problematic because the Tethys Seaway was already closed or a very shallow, strongly evaporitic passage at that time. Despite its superficial similarity with extant genera of the IWP region, the genus is unrelated to all known strombid genera and represents a new genus, which is introduced herein as Europrotomus nov. gen. The genus comprises only one or maybe two species, which occur in the European Middle Miocene geological record. No ancestors are known so far. This sudden occurrence is discussed as immigration from an adjacent bioprovince rather than as a result of autochthonous evolution. Hypothetically, such a biogeographic source area might have been established along the coasts of tropical West Africa??a scenario that is already documented for Pleistocene times.