Transient viral replication during analytical treatment interruptions in SIV infected macaques can alter the rebound-competent viral reservoir

Analytical treatment interruptions (ATIs) of antiretroviral therapy (ART) play a central role in evaluating the efficacy of HIV-1 treatment strategies targeting virus that persists despite ART. However, it remains unclear if ATIs alter the rebound-competent viral reservoir (RCVR), the virus population that persists during ART and from which viral recrudescence originates after ART discontinuation. To assess the impact of ATIs on the RCVR, we used a barcode sequence tagged SIV to track individual viral lineages through a series of ATIs in Rhesus macaques. We demonstrate that transient replication of individual rebounding lineages during an ATI can lead to their enrichment in the RCVR, increasing their probability of reactivating again after treatment discontinuation. These data establish that the RCVR can be altered by uncontrolled replication during ATI.     

A comparison of the kinetics of aluminum (Al) uptake and distribution in roots of wheat (Triticum aestivum) using different aluminum sources. A revision of the operational definition of symplastic Al

The lack of information about the movement of aluminum (Al) across the plasma membrane presents a significant barrier to the elucidation of resistance mechanisms which may involve exclusion of Al from the symplast. An understanding of mechanistic aspects of exclusion requires the estimation of symplastic Al levels. Such measurements may be achievable through the use of a kinetic approach. A kinetic protocol was developed to characterize the accumulation and distribution of Al in various cellular compartments in roots of wheat (Triticum aestivum L.). The kinetics of uptake and desorption were similar when Al was supplied as AIK(SO₄)₂ or as AlCl₃. When both salts were supplied at low concentration (50 μM), Al bound to a purified cell wall fraction could be reduced to less than 10–20% of non-exchangeable Al, if roots were washed for 30 min in citric acid following exposure. In contrast, when AlK(SO₄)₂ was supplied at a high concentration (200 μM), a strong linear phase of uptake into cell wall material was observed, which accounted for approximately 48% of non-exchangeable Al in roots. These results suggest that the use of low concentrations of Al in simple salt solutions is required to minimize accumulation of non-exchangeable Al in the apoplasm. A series of multiple-desorption experiments confirmed that citric acid was effective in removing Al from the cell wall compartment of roots exposed to Al for short periods (3 h). However, long exposures (48 h) appeared to create conditions conducive to the accumulation of non-exchangeable Al in the cell wall. In experiments where uptake from solutions containing 50 μM AlCl₃ was followed by desorption in citric acid, non-exchangeable Al in microsomal membrane fractions represented less than 4% of total non-exchangeable Al. Thus, we can exclude the plasma membrane and cell wall as major sites for accumulation of non-exchangeable Al in short exposure studies. Although we cannot provide unequivocal evidence for the localization of Al within the symplast, use of simple salt solutions followed by desorption in citric acid provides the best kinetic technique currently available for the quantitation of Al in the symplasm.     

The subsistence technology of capuchins

Via Oswalt’s system of classification, I compare the tool-kits of wild and captive capuchins with those of Tanzanian chimpanzees and Tasmanian aborigines. The results indicate that capuchins have tool-kits that are smaller, and have lower ratios of artifacts to naturefacts, than those of Tanzanian chimpanzees and Tasmanian aborigines. Accordingly, Oswalt’s system can be used productively to assess the relative technological skills of monkeys versus those of apes and humans.     

Chirally dimorphic male genitalia in praying mantids (Ciulfina: Liturgusidae)

Although male polymorphisms occur widely in nature and have received considerable recent attention from studies of alternative mating strategies, male genital polymorphisms are less well known. Here, we describe a dimorphism in the orientation of the male genitalic complex of the praying mantid genus Ciulfina. Populations of Ciulfina species vary in the proportion of males with dextral (right‐oriented) and sinistral (left‐oriented) genitalia, ranging from directional asymmetry (single orientation only) to apparent antisymmetry (equal proportions of both orientations). The proportion of dextral males varied between species (C. baldersoni: 46%; C. rentzi: 24%; C. klassi: 100%; C. biseriata: 83%) and between populations. We used elliptic Fourier analysis to quantify shape and size variation between the genitalia of dextral and sinistral males and determined that the two forms were mirror images of one another in two species. We found that the level of mechanical reproductive isolation between heterospecific populations of opposite genital orientation was no greater than that between heterospecific populations with the same orientation or of mixed orientation. Genital orientation therefore did not influence premating isolation between these species, despite complete postmating isolation. The geographic proximity of populations to heterospecifics also showed no particular pattern with respect to genital orientation. These results suggest that reversible trait asymmetry in Ciulfina is not driven by reproductive isolation, and add to the growing evidence against the species isolation hypothesis for rapid genital evolution. J. Morphol. 271:1176–1184, 2010. © 2010 Wiley‐Liss, Inc.     

Placental specializations of the mountain spiny lizard Sceloporus jarrovi

The lizard Sceloporus jarrovi (Phrynosomatidae) is one of the most widely studied viviparous reptiles of North America. Past research has assumed that placentation in this species is relatively simple and functions mainly in gas exchange. Our examination of the late stage placenta via transmission electron microscopy reveals that S. jarrovi has a unique combination of placental characteristics, with unusual specializations for secretion and absorption. In the chorioallantoic placenta, chorionic and uterine tissues are directly apposed through eggshell loss, and their epithelia are greatly attenuated, enhancing gas exchange; this placenta shows evidence of both nutrient transfer and endocrine function. Contrary to past inferences, a yolk sac placenta forms from the avascular omphalopleure and persists through the end of gestation. The uterine epithelium is enlarged and secretory, and the fetal omphalopleure shows branching absorptive channels and other specializations for uptake. Elsewhere, the omphalopleure develops elongated folds that protrude into a coagulum of degenerating shell membrane and other organic material. Uterine tissue in this region shows specializations for absorption. Placental features in S. jarrovi have unexpected functional implications, and challenge assumptions that specializations for nutrient transfer are confined to matrotrophic species. J. Morphol. 271:1153–1175, 2010. © 2010 Wiley‐Liss, Inc.     

BIOLOGICAL AVAILABILITY OF IRON TO THE FRESHWATER CYANOBACTERIUM ANABAENA FLOS‐AQUAE1

Iron acquisition from various ferric chelates and colloids was studied using iron‐limited cells of Anabaena flos‐aquae (Lyng.) Brèb UTEX 1444, a cyanobacterial strain that produces high levels of siderophores under iron limitation. Various chelators of greatly varying affinity for Fe³⁺ (HEDTA, EDDHA, desferrioxamine mesylate, HBED, 8‐hydroxyquinoline) were assayed for the degree of iron acquisition by iron‐limited cyanobacterial cells. Iron uptake rates (measured by graphite furnace atomic absorption spectrometry) varied approximately inversely with calculated [Fe³⁺] (calculated as pFe) and decreased with increasing chelator‐to‐iron ratio. No iron uptake was observed when Fe³⁺ was chelated with HBED, the strongest of the tested chelators. Iron‐limited Anabaena cells were able to take up iron from 8‐hydroxyquinoline (oxine or 8HQ), a compound sometimes used to quantify aquatic iron bioavailability. Iron bound to purified humic acid was poorly available but did support some growth at high humic acid concentrations. These results suggest that for cyanobacteria, even tightly bound iron is biologically available, including to a limited extent iron bound to humic acids. However, iron bound to some extremely strong chelators (e.g. HBED) is likely to be biologically unavailable.