The Late Triassic Schilderia Adamanica and Woodworthia Arizonica Trees of the Petrified Forest National Park, Arizona, Usa

Two fossil tree species, both with unusual characteristics, occur in the Upper Triassic of the Petrified Forest National Park, Arizona, USA and adjacent areas. The first, Schilderia adamanica , has a highly idiosyncratic secondary xylem structure which contains normal uniseriate and broad complex multiseriate 'herring-bone' rays. The trunk cross-section of the secondary xylem may be either of a normal pycnoxylic type with a central pith and rays radiating from that or it may consist of appressed 'xylem masses' with rays curving towards one another at their extremities. The second, Woodworthia arizonica , has narrow, horizontal vascular traces traversing the entire radial width of the secondary xylem. By analogy with extant tree species, these traces would have terminated on preventitious buds deeply embedded in the bark which, in the case of these fossil trunks, have failed to be silicified. Such buds have the capacity to develop into epicormic shoots when the crown foliage of the tree is damaged. A further specimen of W. arizonica is recorded for the first time from the Permian of southern Brazil. Reconstruction drawings of both trees are produced.     

Spermatological characters of monozoic tapeworms (Cestoda: Caryophyllidea), including first data on a species from the Indomalayan catfish

The ultrastructure of spermiogenesis and mature spermatozoon in Lytocestus indicus (Cestoda: Lytocestidae) is described; this is the first representative of this group of monozoic, presumably most basal, tapeworms (Eucestoda) from the Indomalayan region to be documented in this manner. Similarly, as in other caryophyllideans, its spermiogenesis involves the formation of a conical differentiation zone with 2 centrioles associated with striated roots and an intercentriolar body. In the course of the process, 1 of the centrioles develops a free flagellum, which fuses with a cytoplasmic protrusion, whereas the other remains oriented in a cytoplasmic bud. Spermiogenesis is also characterized by the presence of electron-dense material in the early stages of spermiogenesis and a slight rotation of the flagellar bud. The mature spermatozoon of L. indicus is a filiform cell tapered at both extremities that lacks mitochondria; its nucleus has parallel disposition to the axoneme and does not reach up to the posterior extremity of the spermatozoon, which is typical for spermatozoa of the type III pattern. The new data confirm that caryophyllideans share the same type of spermiogenesis that is considered to be plesiomorphic in the Eucestoda. The existing information on spermatological ultrastructure of 8 members for 3 of 4 caryophyllidean families from different host groups (cyprinids and catostomids, both Cypriniformes, and mochokids and clariids, both Siluriformes) from 4 zoogeographical regions (Palearctic, Neotropic, Ethiopian, and Indomalayan regions) demonstrates great uniformity in spermiogenesis and sperm ultrastructure, which does not reflect different taxonomic position of the species studied.     

GTfold: Enabling parallel RNA secondary structure prediction on multi-core desktops

ABSTRACT: BACKGROUND: Accurate and efficient RNA secondary structure prediction remains an important open problem in computational molecular biology. Historically, advances in computing technology have enabled faster and more accurate RNA secondary structure predictions. Previous parallelized prediction programs achieved significant improvements in runtime, but their implementations were not portable from niche high-performance computers or easily accessible to most RNA researchers. With the increasing prevalence of multi-core desktop machines, a new parallel prediction program is needed to take full advantage of today's computing technology. FINDINGS: We present here the first implementation of RNA secondary structure prediction by thermodynamic optimization for modern multi-core computers. We show that GTfold predicts secondary structure in less time than UNAfold and RNAfold, without sacrificing accuracy, on machines with four or more cores. CONCLUSIONS: GTfold supports advances in RNA structural biology by reducing the timescales for secondary structure prediction. The difference will be particularly valuable to researchers working with lengthy RNA sequences, such as RNA viral genomes.     

Responses of vertebrates to pastoralism,military land use and landscape position in an Australian tropical savanna

Despite the hegemony of pastoralism over most of Australia’s tropical savannas, its impacts upon biodiversity are poorly known. There is even less knowledge about the impacts of military training, a recent, but rapidly expanding, alternative land use. We compare impacts of these land uses upon mammals, birds, reptiles and frogs at a site in north‐eastern Australia, with sampling from 24 quadrats stratified by four landscape positions (upper slope to riparian) and three current land‐use types (pastoralism, military training and undisturbed). Prior to exclusion in 1967, the whole study area had been subjected to grazing over the course of approximately 100 years, so differences observed strictly reflect responses to changed land use (largely cessation from grazing) over the period of 32 years subsequent to the imposition of the present regime. The four classes of vertebrates showed contrasting responses. Frog distribution was unrelated to land use, but strongly associated with landscape position. Reptiles showed a very strong response to land‐use type but not to landscape position. The total abundance and richness of reptiles was greater in ungrazed (i.e. military and undisturbed) than in grazed quadrats. The total abundance and species richness of birds varied strongly with landscape position but was unrelated to land use. However, many individual bird species showed significant responses to land‐use type, and bird species composition was significantly related to both land‐use type and landscape position. The richness of the mammal fauna was weakly related to landscape position and not related to land‐use type. A few individual mammal species showed significant responses to either or both factors, but mammal species composition was significantly (albeit weakly) related only to land‐use type. With due regard to some interpretative constraints in the study design, and the history of the site prior to this study, these results suggest that pastoralism leads to a substantial rearrangement of the vertebrate fauna, and particularly so for reptiles and those mammals and birds associated with the ground and understorey layers. Given the extent of pastoralism across the tropical savannas, these results suggest that this industry has contributed to major and widespread change in the savanna fauna. In contrast to pastoralism, military land use (at least at the relatively low intensity examined here) produced little change in vertebrate assemblages.     

The ultrastructure of mouse testicular interstitial tissue containing plutonium-239 and its significance in explaining the observed distribution of plutonium in the testis.

The technique of autoradiography with Araldite-embedded sections was used to study the distribution of 239Pu in mouse testis at various times post-injection. Adjacent sections were examined with both the light microscope and electron microscope. The autoradiographs showed that from 1 week to 3 months postinjection, most 239Pu in located in interstitial tissue. The major change in distribution observed was that the early diffuse deposit in interstitial tissue is concentrated in macrophages with increasing time post-injection. This is a real change of distribution as the amount of 239Pu in mouse testis remains constant from 1 week to 3 months post-injection. Study of the ultrastructure of interstitial tissue indicated that the accumulation of 239Pu in macrophages may be brought about in two ways. First, there may be phagocytosis of dead cells containing 239Pu. Second, 239Pu may follow the transfer of waste products of hormone synthesis from Leydig cells into macrophages. The significance of these observations is discussed with regard to the deposition of 239Pu in human testis.     

Heavy meromyosin binding to microfilaments involved in cell and morphogenetic movements

Certain microfilaments found in migratory single cells and in morphogenetically-active epithelial cells are shown to bind heavy meromyosin prepared from skeletal muscle. This ‘actin-like’ feature of the filaments is compatible with the hypothesis that such filaments are components of contractile systems in these cells.     

CHEMOSENSING: SELECTIVITY, SENSITIVITY AND ADDITIVE EFFECTS ON A STIMULANT-INDUCED ACTIVITY OF OLFACTORY PREPARATIONS

Stimulant-induced changes in soluble preparations from rabbit olfactory epithelium were monitored by ultraviolet difference spectroscopy. A time-dependent decrease of absorbance, maximum at 267 nm, was generated when specific stimulants were mixed with the olfactory preparations. Only seven of the 37 organic chemicals tested generated the absorbance change at 267 nm. The olfactory preparations exhibited a high degree of selectivity and sensitivity; measurable absorbance changes were observed when the active stimulant concentrations were 1 × 10^?5m . The experimental results suggest a complex mechanism of conformational change for the initial stimulant-induced molecular interactions in biological chemosensing.     

Nematodirus battus: development of cold hardiness in dormant eggs

Thermistors and an amplified bridge were used to detect supercooling points of Nematodirus battus eggs weighing ca. 1 microgram wet weight. A cooling rate of about 1 C min-1 was achieved with a manually controlled cold stage using the Peltier effect. The supercooling point of eggs fell during chilling at 5 +/- 1 C for up to 8 weeks from -34.48 +/- 0.49 C to -37.17 +/- 0.76 C. Juveniles freed from these eggs were less cold hardy than intact eggs but chilling improved their supercooling to a greater extent from -19.33 +/- 1.38 C to -32.10 +/- 0.68 C. These results were obtained with eggs showing the characteristic hatching response for this species after transfer from chilling at 5 C to higher temperatures (5-37 +/- 1 C). The results indicate eggs of N. battus acclimate to chilling at a time when previous work had established an increase in their trehalose content.