A fast computational model for circulatory dynamics: effects of left ventricle–aorta coupling

The course of diseases such as hypertension, systolic heart failure and heart failure with a preserved ejection fraction is affected by interactions between the left ventricle (LV) and the vasculature. To study these interactions, a computationally efficient, biophysically based mathematical model for the circulatory system is presented. In a four-chamber model of the heart, the LV is represented by a previously described low-order, wall volume-preserving model that includes torsion and base-to-apex and circumferential wall shortening and lengthening, and the other chambers are represented using spherical geometries. Active and passive myocardial mechanics of all four chambers are included. The cardiac model is coupled with a wave propagation model for the aorta and a closed lumped-parameter circulation model. Parameters for the normal heart and aorta are determined by fitting to experimental data. Changes in the timing and magnitude of pulse wave reflections by the aorta are demonstrated with changes in compliance and taper of the aorta as seen in aging (decreased compliance, increased diameter and length), and resulting effects on LV pressure–volume loops and LV fiber stress and sarcomere shortening are predicted. Effects of aging of the aorta combined with reduced LV contractile force (failing heart) are examined. In the failing heart, changes in aortic properties with aging affect stroke volume and sarcomere shortening without appreciable augmentation of aortic pressure, and the reflected pressure wave contributes an increased proportion of aortic pressure.

     

Bioaccumulation and depuration of enteroviruses by the soft-shelled clam, Mya arenaria.

Low levels of feces-associated natural virus, simulating virus numbers estimated to exist in moderately polluted shellfish-growing waters, were used to evaluate the effectiveness of depuration as a virus depletion procedure in soft-shell clams. Depuration effectiveness depended upon the numbers of virus bioaccumulated and whether virus was solids associated. Virus uptake was greatest when viruses were solids associated and pollution levels were equivalent or greater than those likely to be found in grossly polluted growing waters. Virtually all bioaccumulated feces-associated natural virus was deposited within either the hepatopancreas or siphon tissues. Viruses usually were eliminated within a 24- to 48-h depuration period. Dependence upon depuration of clams to elimate health hazards of virus etiology involved a risk factor not measureable in the study. The greatest reduction of health risks would come from the routine depuration of clams harvested from growing waters of good sanitary quality.     

The mass culture of Dunaliella viridis (Volvocales,Chlorophyta) for oxygenated carotenoids : laboratory and pilot plant studies

The biology, and hence the mass culture, of Dunaliella viridis closely follows that of Dunaliella salina, which is successfully mass cultured for the production of -carotene. Both algae can grow at extremely high salinities and light intensities. They co-exist in the coastal salt lake, Hutt Lagoon, Western Australia. In contrast to D. salina, D. viridis does not accumulate large amounts of -carotene, producing only up to 0.7% of mixed carotenoids (lutein, zeaxathin, other oxygenated carotenoids and -carotene), compared to D. salina's ca 10% dry wt of mainly -carotene. However, in laboratory experiments, D. viridisgrew much faster and to much higher cell densities than D. salina, and attained levels of mixed carotenoids similar to those of D. salina (ca 13 mg L^–1 carotenoid). Preliminary experiments in outdoor ponds were much less promising. Harvesting by chemical flocculation was as effective as with D. salina, but extraction of carotenoids directly into vegetable oil proved inefficient. When incorporated into feed, caretonoids derived from D. viridis pigmented hen eggs acceptably. Extrapolating from laboratory results, and using costing derived from D. salina technology, the cost of production of mixed oxygenated carotenoids from D. viridis was similar to that for the production of -carotene from D. salina, at ca $A500 kg^–1.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Bioaccumulation and depuration of enteroviruses by the soft-shelled clam, Mya arenaria.

Low levels of feces-associated natural virus, simulating virus numbers estimated to exist in moderately polluted shellfish-growing waters, were used to evaluate the effectiveness of depuration as a virus depletion procedure in soft-shell clams. Depuration effectiveness depended upon the numbers of virus bioaccumulated and whether virus was solids associated. Virus uptake was greatest when viruses were solids associated and pollution levels were equivalent or greater than those likely to be found in grossly polluted growing waters. Virtually all bioaccumulated feces-associated natural virus was deposited within either the hepatopancreas or siphon tissues. Viruses usually were eliminated within a 24- to 48-h depuration period. Dependence upon depuration of clams to elimate health hazards of virus etiology involved a risk factor not measureable in the study. The greatest reduction of health risks would come from the routine depuration of clams harvested from growing waters of good sanitary quality.     

Is propagule size the critical factor in predicting introduction outcomes in passeriform birds?

Influential analyses of the propagule pressure hypothesis have been based on multiple bird species introduced to one region (e.g. New Zealand). These analyses implicitly assume that species-level and site-level characteristics are less important than the number of individuals released. In this study we compared records of passerine introductions with propagule size information across multiple regions (New Zealand, Australia, and North America). We excluded species introduced to just one of the three regions or with significant uncertainty in the historical record, as well as species that succeeded or failed in all regions. Because it is often impossible to attribute success to any single event or combination of events, our analysis compared randomly selected propagule sizes of unsuccessful introductions with those of successful introductions. Using Monte Carlo repeated sampling we found no statistical support for the propagule pressure hypothesis, even when using assumptions biased toward showing an effect.     

Age-Specific Mortality During the 1918 Influenza Pandemic: Unravelling the Mystery of High Young Adult Mortality

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.

“The war is over – and I must go” Egon Schiele, 1890–1918.