Computational fluid dynamic analysis of bioprinted self-supporting perfused tissue models

Natural tissues are incorporated with vasculature, which is further integrated with a cardiovascular system responsible for driving perfusion of nutrient-rich oxygenated blood through the vasculature to support cell metabolism within most cell-dense tissues. Since scaffold-free biofabricated tissues being developed into clinical implants, research models, and pharmaceutical testing platforms should similarly exhibit perfused tissue-like structures, we generated a generalizable biofabrication method resulting in self-supporting perfused (SSuPer) tissue constructs incorporated with perfusible microchannels and integrated with the modular FABRICA perfusion bioreactor. As proof of concept, we perfused an MLO-A5 osteoblast-based SSuPer tissue in the FABRICA. Although our resulting SSuPer tissue replicated vascularization and perfusion observed in situ, supported its own weight, and stained positively for mineral using Von Kossa staining, our in vitro results indicated that computational fluid dynamics (CFD) should be used to drive future construct design and flow application before further tissue biofabrication and perfusion. We built a CFD model of the SSuPer tissue integrated in the FABRICA and analyzed flow characteristics (net force, pressure distribution, shear stress, and oxygen distribution) through five SSuPer tissue microchannel patterns in two flow directions and at increasing flow rates. Important flow parameters include flow direction, fully developed flow, and tissue microchannel diameters matched and aligned with bioreactor flow channels. We observed that the SSuPer tissue platform is capable of providing direct perfusion to tissue constructs and proper culture conditions (oxygenation, with controllable shear and flow rates), indicating that our approach can be used to biofabricate tissue representing primary tissues and that we can model the system in silico.     

The ant community response to the arrival of Monomorium sydneyense forel (Hymenoptera: Formicidae) at sulphur point,Tauranga, New Zealand

Abstract

Impacts of highly invasive ants in new ecosystems are well documented, but many more ant species are establishing in new ranges for which there is little or no information. We studied the effects of the recently discovered Australian ant, Monomorium sydneyense Forel, on the ant community of Sulphur Point in Tauranga, New Zealand. At the community scale, the species composition in invaded areas was significantly different from that in areas free of M. sydneyense. However, no single ant species was significantly more or less abundant in the presence of M. sydneyense. Some resident ant species categorised in the same functional group as the invader appeared to be scarcer when sympatric with M. sydneyense, but the local abundances of these species were always spatially variable, so the effects were not statistically significant Patchy distribution of M. sydneyense, and other aspects of its behaviour, such as poor foraging abilities and a lack of unicoloniality (where there is little or no aggression between conspecific ants from spatially separate nests), appear to allow resident ant species to coexist with M. sydneyense at Sulphur Point.     

The aluminium content of breast tissue taken from women with breast cancer

The aetiology of breast cancer is multifactorial. While there are known genetic predispositions to the disease it is probable that environmental factors are also involved. Recent research has demonstrated a regionally specific distribution of aluminium in breast tissue mastectomies while other work has suggested mechanisms whereby breast tissue aluminium might contribute towards the aetiology of breast cancer. We have looked to develop microwave digestion combined with a new form of graphite furnace atomic absorption spectrometry as a precise, accurate and reproducible method for the measurement of aluminium in breast tissue biopsies. We have used this method to test the thesis that there is a regional distribution of aluminium across the breast in women with breast cancer. Microwave digestion of whole breast tissue samples resulted in clear homogenous digests perfectly suitable for the determination of aluminium by graphite furnace atomic absorption spectrometry. The instrument detection limit for the method was 0.48 μg/L. Method blanks were used to estimate background levels of contamination of 14.80 μg/L. The mean concentration of aluminium across all tissues was 0.39 μg Al/g tissue dry wt. There were no statistically significant regionally specific differences in the content of aluminium. We have developed a robust method for the precise and accurate measurement of aluminium in human breast tissue. There are very few such data currently available in the scientific literature and they will add substantially to our understanding of any putative role of aluminium in breast cancer. While we did not observe any statistically significant differences in aluminium content across the breast it has to be emphasised that herein we measured whole breast tissue and not defatted tissue where such a distribution was previously noted. We are very confident that the method developed herein could now be used to provide accurate and reproducible data on the aluminium content in defatted tissue and oil from such tissues and thereby contribute towards our knowledge on aluminium and any role in breast cancer.     

Four putative entomopathogenic fungi of armoured scale insects on <Emphasis Type="Italic">Citrus</Emphasis> in Australia

This study led to the discovery of four putative entomopathogenic fungi of armoured scale insects on citrus trees in coastal New South Wales. Two of these species belong in Podonectria as P. coccicola (Ellis & Everh.) Petch (syn. Tetracrium coccicola (Höhn.) Ellis & Everh.) and P. novae-zelandiae Dingley. Members of this genus are grown in culture for the first time. Formerly placed in the Pleosporales, Tubeufiaceae, or more recently in the Tubeufiales, these species are herein placed in the new family Podonectriaceae fam. nov., Pleosporales. Another species is placed in the Hypocreales, Bionectriaceae as Clonostachys coccicola (J.A. Stev.) H.T. Dao comb. nov. (basionym Tubercularia coccicola J.A. Stev., syn. Nectria tuberculariae Petch). The fourth species is Myriangium citri Henn. (Myriangiales, Myriangiaceae). Each fungal species is characterized and the phylogenetic placement confirmed by molecular analyses of the ITS and 28 s rDNA regions. In addition, their biology is noted, including location of the fungi within tree canopies.     

Use of a Florida Gulf Coast Barrier Island by Spring Trans-Gulf Migrants and the Projected Effects of Sea Level Rise on Habitat Availability

Barrier islands on the north coast of the Gulf of Mexico are an internationally important coastal resource. Each spring hundreds of thousands of Nearctic-Neotropical songbirds crossing the Gulf of Mexico during spring migration use these islands because they provide the first landfall for individuals following a trans-Gulf migratory route. The effects of climate change, particularly sea level rise, may negatively impact habitat availability for migrants on barrier islands. Our objectives were (1) to confirm the use of St. George Island, Florida by trans-Gulf migrants and (2) to determine whether forested stopover habitat will be available for migrants on St. George Island following sea level rise. We used avian transect data, geographic information systems, remote sensing, and simulation modelling to investigate the potential effects of three different sea level rise scenarios (0.28 m, 0.82 m, and 2 m) on habitat availability for trans-Gulf migrants. We found considerable use of the island by spring trans-Gulf migrants. Migrants were most abundant in areas with low elevation, high canopy height, and high coverage of forests and scrub/shrub. A substantial percentage of forest (44%) will be lost by 2100 assuming moderate sea level rise (0.82 m). Thus, as sea level rise progresses, less forests will be available for migrants during stopover. Many migratory bird species’ populations are declining, and degradation of barrier island stopover habitat may further increase the cost of migration for many individuals. To preserve this coastal resource, conservation and wise management of migratory stopover areas, especially near ecological barriers like the Gulf of Mexico, will be essential as sea levels rise.     

Projecting marine species range shifts from only temperature can mask climate vulnerability

Climate change is causing range shifts in many marine species, with implications for biodiversity and fisheries. Previous research has mainly focused on how species' ranges will respond to changing ocean temperatures, without accounting for other environmental covariates that could affect future distribution patterns. Here, we integrate habitat suitability modeling approaches, a high‐resolution global climate model projection, and detailed fishery‐independent and ‐dependent faunal datasets from one of the most extensively monitored marine ecosystems—the U.S. Northeast Shelf. We project the responses of 125 species in this region to climate‐driven changes in multiple oceanographic factors (e.g., ocean temperature, salinity, sea surface height) and seabed characteristics (i.e., rugosity and depth). Comparing model outputs based on ocean temperature and seabed characteristics to those that also incorporated salinity and sea surface height (proxies for primary productivity and ocean circulation features), we explored how an emphasis on ocean temperature in projecting species' range shifts can impact assessments of species' climate vulnerability. We found that multifactor habitat suitability models performed better in explaining and predicting species historical distribution patterns than temperature‐based models. We also found that multifactor models provided more concerning assessments of species' future distribution patterns than temperature‐based models, projecting that species' ranges will largely shift northward and become more contracted and fragmented over time. Our results suggest that using ocean temperature as a primary determinant of range shifts can significantly alter projections, masking species' climate vulnerability, and potentially forestalling proactive management.     

Superinhibition of sarcoplasmic reticulum function by phospholamban induces cardiac contractile failure

To determine whether selective impairment of cardiac sarcoplasmic reticulum (SR) Ca(2+) transport may drive the progressive functional deterioration leading to heart failure, transgenic mice, overexpressing a phospholamban Val(49) --> Gly mutant (2-fold), which is a superinhibitor of SR Ca(2+)-ATPase affinity for Ca(2+), were generated, and their cardiac phenotype was examined longitudinally. At 3 months of age, the increased EC(50) level of SR Ca(2+) uptake for Ca(2+) (0.67 +/- 0.09 microm) resulted in significantly higher depression of cardiomyocyte rates of shortening (57%), relengthening (31%), and prolongation of the Ca(2+) signal decay time (165%) than overexpression (2-fold) of wild type phospholamban (68%, 64%, and 125%, respectively), compared with controls (100%). Echocardiography also revealed significantly depressed function and impaired beta-adrenergic responses in mutant hearts. The depressed contractile parameters were associated with left ventricular remodeling, recapitulation of fetal gene expression, and hypertrophy, which progressed to dilated cardiomyopathy with interstitial tissue fibrosis and death by 6 months in males. Females also had ventricular hypertrophy at 3 months but exhibited normal systolic function up to 12 months of age. These results suggest a causal relationship between defective SR Ca(2+) cycling and cardiac remodeling leading to heart failure, with a gender-dependent influence on the time course of these alterations.     

Tyrosine decaging leads to substantial membrane trafficking during modulation of an inward rectifier potassium channel

Tyrosine side chains participate in several distinct signaling pathways, including phosphorylation and membrane trafficking. A nonsense suppression procedure was used to incorporate a caged tyrosine residue in place of the natural tyrosine at position 242 of the inward rectifier channel Kir2.1 expressed in Xenopus oocytes. When tyrosine kinases were active, flash decaging led both to decreased K(+) currents and also to substantial (15-26%) decreases in capacitance, implying net membrane endocytosis. A dominant negative dynamin mutant completely blocked the decaging-induced endocytosis and partially blocked the decaging-induced K(+) channel inhibition. Thus, decaging of a single tyrosine residue in a single species of membrane protein leads to massive clathrin-mediated endocytosis; in fact, membrane area equivalent to many clathrin-coated vesicles is withdrawn from the oocyte surface for each Kir2.1 channel inhibited. Oocyte membrane proteins were also labeled with the thiol-reactive fluorophore tetramethylrhodamine-5-maleimide, and manipulations that decreased capacitance also decreased surface membrane fluorescence, confirming the net endocytosis. In single-channel studies, tyrosine kinase activation decreased the membrane density of active Kir2.1 channels per patch but did not change channel conductance or open probability, in agreement with the hypothesis that tyrosine phosphorylation results in endocytosis of Kir2.1 channels. Despite the Kir2.1 inhibition and endocytosis stimulated by tyrosine kinase activation, neither Western blotting nor (32)P labeling produced evidence for direct tyrosine phosphorylation of Kir2.1. Therefore, it is likely that tyrosine phosphorylation affects Kir2.1 function indirectly, via interactions between clathrin adaptor proteins and a tyrosine-based sorting motif on Kir2.1 that is revealed by decaging the tyrosine side chain. These interactions inhibit a fraction of the Kir2.1 channels, possibly via direct occlusion of the conduction pathway, and also lead to endocytosis, which further decreases Kir2.1 currents. These data establish that side chain decaging can provide valuable time-resolved data about intracellular signaling systems.     

Group I metabotropic glutamate receptors are expressed in the chicken retina and by cultured retinal amacrine cells

Glutamate is well established as an excitatory neurotransmitter in the vertebrate retina. Its role as a modulator of retinal function, however, is poorly understood. We used immunocytochemistry and calcium imaging techniques to investigate whether metabotropic glutamate receptors are expressed in the chicken retina and by identified GABAergic amacrine cells in culture. Antibody labeling for both metabotropic glutamate receptors 1 and 5 in the retina was consistent with their expression by amacrine cells as well as by other retinal cell types. In double-labeling experiments, most metabotropic glutamate receptor 1-positive cell bodies in the inner nuclear layer also label with anti-GABA antibodies. GABAergic amacrine cells in culture were also labeled by metabotropic glutamate receptor 1 and 5 antibodies. Metabotropic glutamate receptor agonists elicited Ca(2+) elevations in cultured amacrine cells, indicating that these receptors were functionally expressed. Cytosolic Ca(2+) elevations were enhanced by metabotropic glutamate receptor 1-selective antagonists, suggesting that metabotropic glutamate receptor 1 activity might normally inhibit the Ca(2+) signaling activity of metabotropic glutamate receptor 5. These results demonstrate expression of group I metabotropic glutamate receptors in the avian retina and suggest that glutamate released from bipolar cells onto amacrine cells might act to modulate the function of these cells.