Gait in Very Preterm School-Aged Children in Dual-Task Paradigms

Objective

The control of gait requires executive and attentional functions. As preterm children show executive and attentional deficits compared to full-term children, performing concurrent tasks that impose additional cognitive load may lead to poorer walking performance in preterm compared to full-term children. Knowledge regarding gait in preterm children after early childhood is scarce. We examined straight walking and if it is more affected in very preterm than in full-term children in dual-task paradigms.

Study design

Twenty preterm children with very low birth-weight (≤ 1500 g), 24 preterm children with birth-weight > 1500 g, and 44 full-term children, born between 2001 and 2006, were investigated. Gait was assessed using an electronic walkway system (GAITRite) while walking without a concurrent task (single-task) and while performing one concurrent (dual-task) or two concurrent (triple-task) tasks. Spatio-temporal gait parameters (gait velocity, cadence, stride length, single support time, double support time), normalized gait parameters (normalized velocity, normalized cadence, normalized stride length) and gait variability parameters (stride velocity variability, stride length variability) were analyzed.

Results

In dual- and triple-task conditions children showed decreased gait velocity, cadence, stride length, as well as increased single support time, double support time and gait variability compared to single-task walking. Further, results showed systematic decreases in stride velocity variability from preterm children with very low birth weight (≤ 1500 g) to preterm children with birth weight > 1500 g to full-term children. There were no significant interactions between walking conditions and prematurity status.

Conclusions

Dual and triple tasking affects gait of preterm and full-term children, confirming previous results that walking requires executive and attentional functions. Birth-weight dependent systematic changes in stride velocity variability indicate poorer walking performance in preterm children who were less mature at birth.     

Mud mounds: A polygenetic spectrum of fine-grained carbonate buildups

Summary This research report contains nine case studies (part II to X) dealing with Palaeozoic and Mesozoic mud mounds, microbial reefs, and modern zones of active micrite production, and two parts (I and XI) summarizing the major questions and results. The formation of different types ofin situ formed micrites (automicrites) in close association with siliceous sponges is documented in Devonian, Carboniferous, Triassic, Jurassic and Cretaceous mounds and suggests a common origin with a modern facies found within reef caves. Processes involved in the formation of autochthonous micrites comprise: (i) calcifying mucus enriched in Asp and Glu, this type presumably is linked to the formation of stromatolites, thrombolites and massive fabrics; (ii) protein-rich substances within confined spaces (e.g. microcavities) result in peloidal pockets, peloidal coatings and peloidal stromatolites, and (iii) decay of sponge soft tissues, presumably enriched with symbiotic bacteria, lead to the micropeloidal preservation of parts of former sponge bodies. As a consequence, there is strong evidence that the primary production of micrite in place represents the initial cause for buildup development. The mode of precipitation corresponds to biologically-induced, matrix-mediated mineralization which results in high-Mg-calcites, isotopically balanced with inorganic cements or equilibrium skeletal carbonates, respectively. If distinct automicritic fabrics are absent, the source or origin of micrite remains questionable. However, the co-occurring identifiable components are inadequate, by quantity and physiology, to explain the enhanced accumulation of fine-grained calcium carbonate. The stromatolite reefs from the Permian Zechstein Basin are regarded as reminiscent of ancestral (Precambrian) reef facies, considered the precursor of automicrite/sponge buildups. Automicrite/sponge buildups represent the basic Phanerozoic reef type. Analogous facies are still present within modern cryptic reef habitats, where the biocalcifying carbonate factory is restricted in space.     

PHYSIOLOGICAL AND POPULATION ECOLOGY OF INTERTIDAL AND SUBTIDAL ASCOPHYLLUM NODOSUM (PHAEOPHYTA)1

Morphological, demographic and physiological characteristics of Rhode Island intertidal and subtidal populations of Ascophyllum nodosum (L.) Le Jolis were compared in order to examine factors influencing vertical distribution. The two populations had distinctive morphologies: subtidal plants were narrower (more terete) and highly branched compared with intertidal plants. The subtidal population showed signs of necrosis and breakage, which was reflected in significantly shorter mean plant size. High survivorship and low recruitment of both population resulted in relatively constant densities, averaging 91 and 50 plants per m² in the intertidal and subtidal habitats, respectively. Intertidal plants had higher mean annual growth rates (25 cm.yr^?1) than subtidal plants (2 cm.yr^?1). In general, intertidal plants had higher photosynthetic capacity and nutrient (NO₃^?) uptake rates than the subtidal population but maintained lower light-harvesting pigment and tissue nitrogen concentrations. Although Ascophyllum nodosum is capable of survival and growth in subtidal as well as intertidal areas, results of this study suggest that different selective pressures affect persistence in each habitat. The scarcity of plants in the subtidal environment may be due to the lack of a critical balance between algal production, allocation of photosynthate, and the negative effects of grazers or competitors.     

Differential roles of ArfGAP1, ArfGAP2, and ArfGAP3 in COPI trafficking

The formation of coat protein complex I (COPI)–coated vesicles is regulated by the small guanosine triphosphatase (GTPase) adenosine diphosphate ribosylation factor 1 (Arf1), which in its GTP-bound form recruits coatomer to the Golgi membrane. Arf GTPase-activating protein (GAP) catalyzed GTP hydrolysis in Arf1 triggers uncoating and is required for uptake of cargo molecules into vesicles. Three mammalian ArfGAPs are involved in COPI vesicle trafficking; however, their individual functions remain obscure. ArfGAP1 binds to membranes depending on their curvature. In this study, we show that ArfGAP2 and ArfGAP3 do not bind directly to membranes but are recruited via interactions with coatomer. In the presence of coatomer, ArfGAP2 and ArfGAP3 activities are comparable with or even higher than ArfGAP1 activity. Although previously speculated, our results now demonstrate a function for coatomer in ArfGAP-catalyzed GTP hydrolysis by Arf1. We suggest that ArfGAP2 and ArfGAP3 are coat protein–dependent ArfGAPs, whereas ArfGAP1 has a more general function.     

New trepostome Bryozoa from the Early Triassic (Smithian/Spathian) of Nevada

Two new bryozoan species of the trepostome family Dyscritellidae,Dyscritellopsis thaynesianus n. sp. andDyscritellopsis montelloensis n. sp., are described from the Early Triassic (Smithian/Spathian) Thaynes Limestone, Nevada (USA). The bryozoan fauna documents the survival of Paleozoic lineages into the earliest Triassic on northern open shelves outside the tropics. The fauna holds paleobiogeo-graphic connections to the Early Triassic bryozoan faunas of Spitsbergen.      

Sites of ubiquitin attachment in Saccharomyces cerevisiae

Sites of ubiquitin modification have been identified by mass spectrometry based on the increase in molecular mass of a tryptic peptide carrying two additional glycine residues from the ubiquitin moiety. However, such peptides with GG shifts have been difficult to discover. We identify 870 unique sites of ubiquitin attachment on 438 different proteins of the yeast Saccharomyces cerevisiae.     

Unusual skeletal morphology and systematic description of a new Devonian cryptostome bryozoan from the Western Sahara

Palaeozoic bryozoan colonies display a large variety of skeletal elements. Various types of rod-like styles are mainly built by laminated and non-laminated (hyaline) skeleton. Typical styles consist of hyaline cores and surrounding laminated sheaths. They usually protrude on the colony surface as spines. In a new bryozoan genus from the Middle Devonian of the Western Sahara described here, styles do not protrude on the colony surface and are embedded within the laminated skeleton. They consist of fibrous material. This new type of styles, unknown from other bryozoans, is here called a “cryptostyle”. A special characteristic of these structures is their intensive reddish-brown colouration. This colouration is apparently caused by the presence of ferric iron between the individual fibres. The function of cryptostyles was apparently weight reduction and stabilising the skeleton. The general morphology of the new bryozoan, Cryptostyloecia hexapuncta gen. et n. sp., implies its systematic position within ptilodictyine cryptostomes, specifically the Family Ptilodictyidae Zittel, 1880.