Non-stochastic behavior in sodium chlorate crystallization

NaClO₃ is achiral in solution. If crystallization is performed under a static set-up, it is recognized that the stochastic nucleation probability results in a racemic mixture of the conglomerate. In this paper, we report a reexamination of the crystallization of NaClO₃ from static solution in petri dishes that was conducted over a number of years and is based on the count and analysis of several thousand d- vs. l-NaClO₃ crystals. Remarkably, instead of an expected nearly 50/50 coin-tossing situation for the d/l crystal frequency, in most of our experiments a statistically significant bias in favor of d- over l-NaClO₃ crystals was found. The experiments also showed that the NaClO₃ system was relatively insensitive regarding the intentional addition of a variety of optically active agents. Only in some cases, the persisting d-bias observed in the unseeded experiments slightly increased upon the presence of such additives. Nevertheless, experiments in plastic petri dishes or in presence of fungal spores were able to reverse this bias. A literature survey shows that mainly d-directed non-stochastic behavior in the NaClO₃ system has been previously observed in other laboratory settings and by the application of different crystallization techniques. So far, the kind of chiral influence that could be at the origin of the observed bias remains unknown. After the examination of several possible chiral influences of physical, chemical and biological origin, we carefully consider the presence of bio-contaminants as most likely for the cause of this effect.     

Sodium-calcium exchange in renal epithelial cells: Dependence on cell sodium and competitive inhibition by magnesium

Summary Kinetic properties of Na⁺–Ca²⁺ exchange in a renal epithelial cell line (LLC-MK₂) were assessed by measuring cytosolic free Ca²⁺ with fura-2 and⁴⁵Ca²⁺ influx. Replacing external Na⁺ with K⁺ produced relatively small increases in free Ca²⁺ and⁴⁵Ca²⁺ uptake unless the cells were incubated with ouabain. Ouabain markedly increased cell Na⁺ and strongly potentiated the effect of replacing external Na⁺ with K⁺ on free Ca²⁺ and⁴⁵Ca²⁺ uptake.⁴⁵Ca²⁺ influx in 140mm K⁺ or N-methyl-d-glucamine minus influx in 140mm Na⁺ was used to quantify Na⁺–Ca²⁺ exchange activity of Na⁺-loaded cells. The dependence of exchange on cell Na⁺ was sigmoidal; theK _0.5 was 26±3 mmol/liter cell water space, and the Hill coefficient was 3.1±0.2. The kinetic features of the dependence of exchange on cell Na⁺ partly account for the small increase in Ca²⁺ influx when all external Na⁺ is replaced by K⁺. Besides raising cell Na⁺ ouabain appears to activate the exchanger. Magnesium competitively inhibited exchange activity. The potency of Mg²⁺ was 8.2-fold lower with potassium instead of N-methyl-d-glucamine or choline as the replacement for external Na⁺. Potassium also increased theV _max of exchange by 86% and had no effect on theK _m for Ca²⁺. The exchanger does not cause detectable²²Na⁺–Mg²⁺ exchange and does not appear to require K⁺ or transport⁸⁶Rb⁺. Although exchange activity was plentiful in the epithelial cells from monkey kidney, others from amphibian, canine, opossum, and porcine kidney had no detectable exchange activity. All of the measured kinetic properties of Na⁺–Ca²⁺ exchange in the renal epithelial cells are very similar to those of the exchanger in rat aortic myocytes.     

Strength cycle training: effects on muscular strength and aerobic conditioning

The strength cycle ergometer has been proposed as a method of simultaneously increasing aerobic conditioning and muscular strength, because of its unique capacity of disengaging the pedal crank, thus allowing for concurrent single-leg cycling. The purpose of this study was to assess the aerobic and muscular strength effects of strength cycle training (SCT), comparing it to similar standard cycle training. A total of 28 recreationally-trained adult subjects (9 men, 19 women) were paired for VO2peak and randomly assigned to either SCT or Monark cycle training (MCT). Subjects trained 3 days per week following a progressive interval protocol for 9 weeks under supervised conditions. Training intervals (5 minutes' duration) consisted of 3 minutes of standard cycling at an intensity of 60-85% of maximum heart rate (HRmax), and 2 minutes of either the disengaged cycling mode (SCT) or standard cycling plus 30 W (MCT). Subjects began training for a total of 25 minutes per session, progressing to 45 minutes per session by study's end. Prior to and following training, subjects were measured for VO2peak; submaximal VO2, heart rate (HR), RPE, power output, and knee and ankle isokinetic strength. Training resulted in significant (p < or = 0.05) increases in VO2peak (14.5%) and submaximal power output (11%), and significant reductions in submaximal VO2, HR, and RPE in both groups. Significant increases in bilateral isokinetic knee extension (4-6%) and left ankle plantar flexion (10.5%) were noted following training in both groups. No group differences were detected in any variable. Although the strength cycle effectively increased aerobic function and resulted in modest selected increases in lower-extremity muscular strength, these changes were not different from those seen using a similar standard cycling protocol.     

Histocytological changes and reserve accumulation during somatic embryogenesis in Eucalyptus globulus

We recently described a protocol for Eucalyptus globulus somatic embryogenesis (SE). For its immediate use at industrial levels, some stages of the process require better control. In particular, SE germination rates are variable, decreasing SE efficacy. As reserves may play a central role in embryogenic processes, we followed histocytological changes and reserve fluctuations, during SE. For SE induction, explants of mature zygotic embryos were grown on Murashige and Skoog (MS) medium with 3 mg l⁻¹ α-naphthalene acetic acid and later transferred to MS without growth regulators (MS_WH). Samples of zygotic embryo cotyledons (explants), of globular and dicotyledonar somatic embryos, and of embling leaves were analysed for reserve accumulation and histocytological profiles. Cotyledon cells of zygotic embryos were rich in lipid and protein bodies, having almost no starch. After 3 weeks of induction, starch grain density increased in differentiated mesophyll regions, while in meristematic regions their occurrence was diffuse. In globular somatic embryos, starch accumulation increased with time (in amyloplasts), but protein bodies were absent. Cotyledonary somatic embryos had lower density of starch grains and absence of lipid and protein bodies. Embling leaves showed typical histological organisation. This is the first comprehensive study on histological and cytological changes during Eucalyptus SE with emphasis in reserve accumulation. With this work we demonstrate that the presently available SE protocol for E. globulus leads to reserve fluctuations during the process. Moreover, the reserves of somatic embryo cotyledons differ from those of their zygotic embryo counterparts, which reinforce the importance of reserves in the embryogenic process and suggests that manipulating external conditions, SE may be optimised giving suitable emblings production for industrial purposes.     

Comprehensive Analysis of the 16p11.2 Deletion and Null Cntnap2 Mouse Models of Autism Spectrum Disorder

Autism spectrum disorder comprises several neurodevelopmental conditions presenting symptoms in social communication and restricted, repetitive behaviors. A major roadblock for drug development for autism is the lack of robust behavioral signatures predictive of clinical efficacy. To address this issue, we further characterized, in a uniform and rigorous way, mouse models of autism that are of interest because of their construct validity and wide availability to the scientific community. We implemented a broad behavioral battery that included but was not restricted to core autism domains, with the goal of identifying robust, reliable phenotypes amenable for further testing. Here we describe comprehensive findings from two known mouse models of autism, obtained at different developmental stages, using a systematic behavioral test battery combining standard tests as well as novel, quantitative, computer-vision based systems. The first mouse model recapitulates a deletion in human chromosome 16p11.2, found in 1% of individuals with autism. The second mouse model harbors homozygous null mutations in Cntnap2, associated with autism and Pitt-Hopkins-like syndrome. Consistent with previous results, 16p11.2 heterozygous null mice, also known as Del(7Slx1b-Sept1)4Aam weighed less than wild type littermates displayed hyperactivity and no social deficits. Cntnap2 homozygous null mice were also hyperactive, froze less during testing, showed a mild gait phenotype and deficits in the three-chamber social preference test, although less robust than previously published. In the open field test with exposure to urine of an estrous female, however, the Cntnap2 null mice showed reduced vocalizations. In addition, Cntnap2 null mice performed slightly better in a cognitive procedural learning test. Although finding and replicating robust behavioral phenotypes in animal models is a challenging task, such functional readouts remain important in the development of therapeutics and we anticipate both our positive and negative findings will be utilized as a resource for the broader scientific community.     

Stories and photographs of William A. Arnold (1904–2001), a pioneer of photosynthesis and a wonderful friend

William A. Arnold discovered many phenomena in photosynthesis. In 1932, together with Robert Emerson, he provided the first experimental data that led to the concept of a large antenna and a few reaction centers (photosynthetic unit); in 1935, he obtained the minimum quantum requirement of 8–10 for the evolution of one O₂ molecule; in 1951, together with Bernard L. Strehler, he discovered delayed fluorescence (also known as delayed light emission) in photosynthetic systems; and in 1956, together with Helen Sherwood, he discovered thermoluminescence in plants. He is also known for providing a solid-state picture of photosynthesis. Much has been written about him and his research, including many articles in a special issue of Photosynthesis Research (Govindjee et al. (eds.) 1996); and a biography of Arnold, by Govindjee and Srivastava (William Archibald Arnold (1904–2001), 2014), in the Biographical Memoirs of the US National Academy of Sciences, (Washington, DC). Our article here offers a glimpse into the everyday life, through stories and photographs, of this remarkable scientist.     

The arterial depressor response to chronic low-dose angiotensin II infusion in female rats is estrogen dependent

The complex role of the renin-angiotensin-system (RAS) in arterial pressure regulation has been well documented. Recently, we demonstrated that chronic low-dose angiotensin II (ANG II) infusion decreases arterial pressure in female rats via an AT(2)R-mediated mechanism. Estrogen can differentially regulate components of the RAS and is known to influence arterial pressure regulation. We hypothesized that AT(2)R-mediated depressor effects evident in females were estrogen dependent and thus would be abolished by ovariectomy and restored by estrogen replacement. Female Sprague-Dawley rats underwent ovariectomy or sham surgery and were treated with 17β-estradiol or placebo. Mean arterial pressure (MAP) was measured via telemetry in response to a 2-wk infusion of ANG II (50 ng·kg(-1)·min(-1) sc) or saline. MAP significantly decreased in females treated with ANG II (-10 ± 2 mmHg), a response that was abolished by ovariectomy (+4 ± 2 mmHg) and restored with estrogen replacement (-6 ± 2 mmHg). Cardiac and renal gene expression of components of the RAS was differentially regulated by estrogen, such that overall, estrogen shifted the balance of the RAS toward the vasodilatory axis. In conclusion, estrogen-dependent mechanisms offset the vasopressor actions of ANG II by enhancing RAS vasodilator pathways in females. This highlights the potential for these vasodilator pathways as therapeutic targets, particularly in women.     

The Parallel Worm Tracker: a platform for measuring average speed and drug-induced paralysis in nematodes

Background

Caenorhabditis elegans locomotion is a simple behavior that has been widely used to dissect genetic components of behavior, synaptic transmission, and muscle function. Many of the paradigms that have been created to study C. elegans locomotion rely on qualitative experimenter observation. Here we report the implementation of an automated tracking system developed to quantify the locomotion of multiple individual worms in parallel.

Methodology/Principal Findings

Our tracking system generates a consistent measurement of locomotion that allows direct comparison of results across experiments and experimenters and provides a standard method to share data between laboratories. The tracker utilizes a video camera attached to a zoom lens and a software package implemented in MATLAB®. We demonstrate several proof-of-principle applications for the tracker including measuring speed in the absence and presence of food and in the presence of serotonin. We further use the tracker to automatically quantify the time course of paralysis of worms exposed to aldicarb and levamisole and show that tracker performance compares favorably to data generated using a hand-scored metric.

Conclusions/Signficance

Although this is not the first automated tracking system developed to measure C. elegans locomotion, our tracking software package is freely available and provides a simple interface that includes tools for rapid data collection and analysis. By contrast with other tools, it is not dependent on a specific set of hardware. We propose that the tracker may be used for a broad range of additional worm locomotion applications including genetic and chemical screening.