Competitive protein adsorption on polysaccharide and hyaluronate modified surfaces

Adsorption of bovine serum albumin (BSA) and fibrinogen (Fg) was measured on six distinct bare and dextran- and hyaluronate-modified silicon surfaces created using two dextran grafting densities and three hyaluronic acid (HA) sodium salts derived from human umbilical cord, rooster comb and Streptococcus zooepidemicus. Film thickness and surface morphology depended on the HA molecular weight and concentration. BSA coverage was enhanced on surfaces in competitive adsorption of BSA:Fg mixtures. Dextranization differentially reduced protein adsorption onto surfaces based on oxidation state. Hyaluronization was demonstrated to provide the greatest resistance to protein coverage, equivalent to that of the most resistant dextranized surface. Resistance to protein adsorption was independent of the type of HA utilized. With changing bulk protein concentration from 20 to 40 μg ml^?1 for each species, Fg coverage on silicon increased by 4x, whereas both BSA and Fg adsorption on dextran and HA were far less dependent on protein bulk concentration.     

The biostratigraphic and palaeoenvironmental significance of Lower Cambrian (Botomian) trilobites from the Ak-Kaya section of the Altai Mountains (southern Siberia,Russia)

The presence of one of the oldest records of polycystine Radiolaria in the Lower Cambrian sedimentary sequence of the Ak-Kaya section (Gorny Altai) requires a biostratigraphic dating. The trilobites found recently a few tens of meters below the radiolarian-bearing level belong to Calodiscus resimus Repina, Serrodiscus fossuliferus Repina and Alacephalus aff. contortus Repina; they suggest that this part of the Shashkunar Formation can be correlated with the lower part of the Botomian stage. The absence of eyes in the two former species suggests a mode of life buried in the fine pelagic sediments. Indications of the presence of a strongly developed musculature on the third species point to a palaeoenvironment characterized by a relatively high hydrodynamic regime.     

Whisker motor cortex ablation and whisker movement patterns

Previous studies, based on qualitative observations, reported that lesions of the whisker motor cortex produce no deficits in whisking behavior. We used high-resolution optoelectronic recording methods to compare the temporal organization and kinematics of whisker movements before and after unilateral lesions of whisker motor cortex in rats. We now report that while the lesion did not abolish whisking, it significantly disrupted whisking kinematics, coordination, and temporal organization. Lesioned animals showed significant increases in the velocity and amplitude of whisker protractions contralateral to the lesions, as well as a reduction in the synchrony of whisker movements on the two sides of the face. There was a marked shift in the distribution of whisking frequencies, with reduction of activity in the 5–7?Hz bandwidth and increased activity at <?2?Hz. Disruptions of the normal whisking pattern were evident on both sides of the face, and the magnitude of these effects was proportional to the extent of the cortical ablation. We suggest that the observed deficits reflect an imbalance in cortical inputs to a brainstem central pattern generator.     

Herbivory and drought interact to enhance spatial patterning and diversity in a savanna understory

The combination of abiotic stress and consumer stress can have complex impacts on plant community structure. Effective conservation and management of semi-arid ecosystems requires an understanding of how different stresses interact to structure plant communities. We explored the separate and combined impacts of episodic drought, livestock grazing, and wild ungulate herbivory on species co-occurrence and diversity patterns in a relatively productive, semi-arid Acacia savanna. Specifically, we analyzed 9 years of biannual plant community data from the Kenya long-term exclosure experiment, a broad-scale manipulative experiment that has excluded different combinations of large mammalian herbivores from 18 4-ha plots since 1995. During droughts, we observed low species diversity and random species co-occurrence patterns. However, when rain followed a major drought, areas exposed to moderate cattle grazing displayed high species diversity and evidence of significant species aggregation. These patterns were not apparent in the absence of cattle, even if other large herbivores were present. To explore possible mechanisms, we examined patterns separately for common and rare species. We found that aggregation patterns were likely driven by rare species responding similarly to the availability of open micro-sites. Our results indicate that in a productive, fire-suppressed savanna, the combination of periodic drought and moderate cattle grazing can enhance plant biodiversity and fine-scale spatial heterogeneity by opening up space for species that are otherwise rare or cryptic. Our findings also emphasize that domestic herbivores can have significantly stronger impacts on plant community dynamics than wild herbivores, even in an ecosystem with a long history of grazing.     

A closer look at the “Protopithecus” fossil assemblages: new genus and species from Bahia,Brazil

The recently extinct large-bodied New World monkey Protopithecus brasiliensis Lund 1836 was named based on a distal humerus and proximal femur found in the Lagoa Santa cave system in the southeastern Brazilian state of Minas Gerais. These bones are from an animal about twice the size of the largest extant platyrrhines. One hundred and seventy-five years later, a nearly complete skeleton was discovered in the Toca da Boa Vista caves in the neighboring state of Bahia and was allocated to the same taxon as it was the first platyrrhine fossil of comparable size found since the originals. Our detailed study of the equivalent elements, however, reveals important morphological differences that do not correspond to intraspecific variation as we know it in related platyrrhine taxa. The presence of both an expanded brachioradialis flange on the humerus and gluteal tuberosity on the femur of the Bahian skeleton distinguishes it from the Lagoa Santa fossil as well as from all other platyrrhines. Further cranial and postcranial evidence suggests a closer relationship of the former with the alouattine Alouatta, while the limited Lund material fits more comfortably with the ateline clade. Therefore, we propose to limit P. brasiliensis Lund to the distal humerus and proximal femur from Lagoa Santa and erect a new genus and species for the skeleton from Toca da Boa Vista. Cartelles coimbrafilhoi was a large-bodied frugivore with a relatively small brain and diverse locomotor repertoire including both suspension and climbing that expands the range of platyrrhine biodiversity beyond the dimensions of the living neotropical primates.     

Diet and feeding habits of the small catfish,Clarias liocephalus in wetlands of Western Uganda

Clarias liocephalus is an air‐breathing catfish inhabiting wetland and river systems in East Africa. This catfish is in high demand for sale as live bait in the Nile perch fishery of Lake Victoria and equally important in the diet of local communities in the lake basin. Wetland loss and increasing fishing pressure potentially threaten the persistence of C. liocephalus; however, little information exists on the ecology of this species to permit evaluation of current threats. This study quantified dietary characteristics of C. liocephalus from heavy and lightly fished wetlands in Western Uganda using numeric, gravimetric and volumetric indices on 492 stomach samples collected over one year. Clarias liocephalus was significantly smaller in three heavily fished sites, relative to the one in‐park site, likely a reflection of a size‐selective fishery. Across sites, C. liocephalus was a generalist feeder whose diet was dominated by aquatic dipteran larvae and plant material. The broad niche gives C. liocephalus an ecological advantage to forage effectively on a wide selection of prey. The significant presence of plant material shows that the species may utilize plant protein, an important consideration of diet requirements should the species be selected for aquaculture.     

CD147, CD44, and the Epidermal Growth Factor Receptor (EGFR) Signaling Pathway Cooperate to Regulate Breast Epithelial Cell Invasiveness

The immunoglobulin superfamily glycoprotein CD147 (emmprin; basigin) is associated with an invasive phenotype in various types of cancers, including malignant breast cancer. We showed recently that up-regulation of CD147 in non-transformed, non-invasive breast epithelial cells is sufficient to induce an invasive phenotype characterized by membrane type-1 matrix metalloproteinase (MT1-MMP)-dependent invadopodia activity (Grass, G. D., Bratoeva, M., and Toole, B. P. (2012) Regulation of invadopodia formation and activity by CD147. J. Cell Sci. 125, 777–788). Here we found that CD147 induces breast epithelial cell invasiveness by promoting epidermal growth factor receptor (EGFR)-Ras-ERK signaling in a manner dependent on hyaluronan-CD44 interaction. Furthermore, CD147 promotes assembly of signaling complexes containing CD147, CD44, and EGFR in lipid raftlike domains. We also found that oncogenic Ras regulates CD147 expression, hyaluronan synthesis, and formation of CD147-CD44-EGFR complexes, thus forming a positive feedback loop that may amplify invasiveness. Last, we showed that malignant breast cancer cells are heterogeneous in their expression of surface-associated CD147 and that high levels of membrane CD147 correlate with cell surface EGFR and CD44 levels, activated EGFR and ERK1, and activated invadopodia. Future studies should evaluate CD147 as a potential therapeutic target and disease stratification marker in breast cancer.     

Identification of Biochemically Distinct Properties of the Small Ubiquitin-related Modifier (SUMO) Conjugation Pathway in Plasmodium falciparum

Small ubiquitin-related modifiers (SUMOs) are post-translationally conjugated to other proteins and are thereby essential regulators of a wide range of cellular processes. Sumoylation, and enzymes of the sumoylation pathway, are conserved in the malaria causing parasite, Plasmodium falciparum. However, the specific functions of sumoylation in P. falciparum, and the degree of functional conservation between enzymes of the human and P. falciparum sumoylation pathways, have not been characterized. Here, we demonstrate that sumoylation levels peak during midstages of the intra-erythrocyte developmental cycle, concomitant with hemoglobin consumption and elevated oxidative stress. In vitro studies revealed that P. falciparum E1- and E2-conjugating enzymes interact effectively to recognize and modify RanGAP1, a model mammalian SUMO substrate. However, in heterologous reactions, P. falciparum E1 and E2 enzymes failed to interact with cognate human E2 and E1 partners, respectively, to modify RanGAP1. Structural analysis, binding studies, and functional assays revealed divergent amino acid residues within the E1-E2 binding interface that define organism-specific enzyme interactions. Our studies identify sumoylation as a potentially important regulator of oxidative stress response during the P. falciparum intra-erythrocyte developmental cycle, and define E1 and E2 interactions as a promising target for development of parasite-specific inhibitors of sumoylation and parasite replication.     

Suppressor Analysis Reveals a Role for SecY in the SecA2-Dependent Protein Export Pathway of Mycobacteria

All bacteria use the conserved Sec pathway to transport proteins across the cytoplasmic membrane, with the SecA ATPase playing a central role in the process. Mycobacteria are part of a small group of bacteria that have two SecA proteins: the canonical SecA (SecA1) and a second, specialized SecA (SecA2). The SecA2-dependent pathway exports a small subset of proteins and is required for Mycobacterium tuberculosis virulence. The mechanism by which SecA2 drives export of proteins across the cytoplasmic membrane remains poorly understood. Here we performed suppressor analysis on a dominant negative secA2 mutant (secA2 K129R) of the model mycobacterium Mycobacterium smegmatis to better understand the pathway used by SecA2 to export proteins. Two extragenic suppressor mutations were identified as mapping to the promoter region of secY, which encodes the central component of the canonical Sec export channel. These suppressor mutations increased secY expression, and this effect was sufficient to alleviate the secA2 K129R phenotype. We also discovered that the level of SecY protein was greatly diminished in the secA2 K129R mutant, but at least partially restored in the suppressors. Furthermore, the level of SecY in a suppressor strongly correlated with the degree of suppression. Our findings reveal a detrimental effect of SecA2 K129R on SecY, arguing for an integrated system in which SecA2 works with SecY and the canonical Sec translocase to export proteins.