Optical measurement of osmotic water transport in cultured cells. Role of glucose transporters.

Methodology was developed to measure osmotic water permeability in monolayer cultured cells and applied to examine the proposed role of glucose transporters in the water pathway (1989. Proc. Natl. Acad. Sci. USA. 86:8397-8401). J774 macrophages were grown on glass coverslips and mounted in a channel-type perfusion chamber for rapid fluid exchange without cell detachment. Relative cell volume was measured by 45 degrees light scattering using an inverted microscope; measurement accuracy was validated by confocal imaging microscopy. The time required for greater than 90% fluid exchange was less than 1 s. In response to a decrease in perfusate osmolality from 300 to 210 mosM, cells swelled without lag at an initial rate of 4.5%/s, corresponding to a water permeability coefficient of (6.3 +/- 0.4) x 10(-3) cm/s (SE, n = 20, 23 degrees C), assuming a cell surface-to-volume ratio of 4,400 cm-1. The initial rate of cell swelling was proportional to osmotic gradient size, independent of perfusate viscosity, and increased by amphotericin B (25 micrograms/ml), and had an activation energy of 10.0 +/- 1 kcal/mol (12-39 degrees C). The compounds phloretin (20 microM) and cytochalasin B (2.5 micrograms/ml) inhibited glucose transport by greater than 85% but did not influence Pf in paired experiments in which Pf was measured before and after inhibitor addition. The mercurials HgCl2 (0.1 mM) and p-chloromercuribenzoate (1 mM) did not inhibit Pf. A stopped-flow light scattering technique was used to measure Pf independently in J774 macrophages grown in suspension culture. Pf in suspended cells was (4.4 +/- 0.3) x 10(-3) cm/s (assuming a surface-to-volume ratio of 8,800 cm-1), increased more than threefold by amphotericin B, and not inhibited by phloretin and cytochalasin B under conditions of strong inhibition of glucose transport. The glucose reflection coefficient was 0.98 +/- 0.03 as measured by induced osmosis, assuming a unity reflection coefficient for sucrose. These results establish a quantitative method for measurement of osmotic water transport in adherent cultured cells and provide evidence that glucose transporters are not involved in the water transporting pathway

Understanding of the Mole Concept Achieved by Students in a Constructivist General Chemistry Course

The purpose of this research project was to study the conceptual understanding achieved in a general chemistry course based on a constructivist approach. A group of 28 students participated in repeated measures obtained by means of conceptual maps about the mole concept prepared three times during the course: at the beginning the course, immediately after the concept was studied, and after studying other related concepts. In addition, eight students selected from the group of 28 were interviewed. The interviews were carried out focusing on their conceptual maps. The analysis of the repeated measures indicated significant differences among the three times, especially between the first two. It was evidenced, therefore, that these students obtained a significantly higher level of understanding of the mole concept. The qualitative analysis carried out with students identified a broad range of responses that represent different levels of hierarchical organization, of progressive differentiation, and of formation of significant relations of the mole concept. Some recommendations offered are to develop and implement teaching methods that promote understanding of scientific concepts, and to prepare science professors and teachers to emphasize teaching for conceptual understanding

Novice Teacher Experiences of Online Reading Instruction During the COVID-19 Pandemic

This applied dissertation documented novice teacher experiences providing online reading instruction during the COVID-19 pandemic. Specifically, the researcher captured educators’ first-hand accounts of their experiences shifting to fully online reading instruction, adapting instructional materials that were designed for in-person instruction for online learning, confronting challenges and successes during this period of uncertainty, and transitioning back to in-person instruction amidst the then ongoing pandemic. The following research questions were posed: 1. How do novice elementary reading teachers, in a large public school district in South Florida, describe their experiences teaching reading online during a global pandemic? 2. How do novice elementary reading teachers in a large public school district in South Florida describe their experiences adapting learning resources to meet the needs of their students during online learning? 3. How do novice elementary reading teachers in a large public school district in South Florida describe challenges and/or successes encountered while providing online reading instruction to their students? 4. How do novice elementary reading teachers, in a large public school district in South Florida, describe their experiences returning to face-to-face instruction in the midst of a global pandemic? Following individual interviews with five novice teachers, the researcher analyzed the data for emerging patterns and themes. After transcribing the interviews, the researcher worked with participants to co-construct narratives of their experiences. Findings provided an understanding of the inadequate training novice teachers received for online instruction prior to the pandemic, the constraints imposed by the mandated curriculum, the extensive and time-consuming instructional planning process for online instruction, the frustration they felt during online instructional delivery, the accomplishments despite the difficulties, and the shifts in parent involvement. Future research could expand on teaching other subject areas online during the pandemic. Additional studies could include interviews with students, parents, and administrators. The results of this study have implications for educational policymakers, administrators, and other educators as this study provides insight into what novice elementary reading teachers experienced during the pandemic

La inscripción funeraria de época romana de la ermita de San Pedro. (Zegama, Gipuzkoa).

El descubrimiento de una nueva inscripción de época romana, funeraria, realizada sobre una lápida de arenisca supone una nueva fuente de conocimiento en el estudio de nuestro pasado, máxime cuando ésta se ha conservado dispuesta a los pies del altar de la ermita de San Pedro en Zegama

The kinematics of the most oxygen-poor planetary nebula PN G135.9+55.9

PN G135.9+55.9 is a compact, high excitation nebula that has been identified recently as the most oxygen-poor halo planetary nebula. Given its very peculiar characteristics and potential implications in the realms of stellar and Galactic evolution, additional data are needed to firmly establish its true nature and evolutionary history. Here we present the first long-slit, high spectral resolution observations of this object in the lines of H$\alpha$ and He II 4686. The position-velocity data are shown to be compatible with the interpretation of PN G135.9+55.9 being a halo planetary nebula. In both emission lines, we find the same two velocity components that characterize the kinematics as that of an expanding elliptical envelope. The kinematics is consistent with a prolate ellipsoidal model with axis ratio about 2:1, a radially decreasing emissivity distribution, a velocity distribution that is radial, and an expansion velocity of 30 km/s for the bulk of the material. To fit the observed line profiles, this model requires an asymmetric matter distribution, with the blue-shifted emission considerably stronger than the red-shifted emission. We find that the widths of the two velocity components are substantially wider than those expected due to thermal motions, but kinematic structure in the projected area covered by the slit appears to be sufficient to explain the line widths. The present data also rule out the possible presence of an accretion disk in the system that could have been responsible for a fraction of the H$\alpha$ flux, further supporting the planetary nebula nature of PN G135.9+55.9.Comment: accepted by Astronomy & Astrophysic

Rest In the Zebrafish

The purpose and function of sleep has been the topic of discussion for several centuries. Though our understanding of the mechanisms underlying the propagation and maintenance of rest states has undergone significant improvement, much remains to be learned with regards to the effects of disrupted sleep on diseased states. A deeper understanding of the neural circuitry and associated phenotypes would allow for the identification of sleep-related pathologies as well as the development of therapies for individuals with sleep disorders. To this end, the zebrafish (Danio rerio) pose a great advantage. Zebrafish are a diurnal animal, and the sleep rhythms of this animal are sensitive to environmental changes and pharmacological interventions. In this review, we highlight the common methods of sleep disruption, and discuss some of the effects of sleep disruption in the zebrafish. Disrupted sleep rhythms in the adult animal are linked to changes in gene and protein expression, while behavioral measures of anxiety have produced mixed results. We propose that this variation is a result of the type of sleep disruption as well as the type of anxiety test employed. This beckons the need for further study of the effects of environmental and pharmacological manipulations on the sleep rhythms of the animal. Further, researchers must not rely solely on one test as a measure of stress or anxiety as it provides only a one-dimensional insight

U Geminorum: a test case for orbital parameters determination

High-resolution spectroscopy of U Gem was obtained during quiescence. We did not find a hot spot or gas stream around the outer boundaries of the accretion disk. Instead, we detected a strong narrow emission near the location of the secondary star. We measured the radial velocity curve from the wings of the double-peaked H$\alpha$ emission line, and obtained a semi-amplitude value that is in excellent agreement with the obtained from observations in the ultraviolet spectral region by Sion et al. (1998). We present also a new method to obtain K_2, which enhances the detection of absorption or emission features arising in the late-type companion. Our results are compared with published values derived from the near-infrared NaI line doublet. From a comparison of the TiO band with those of late type M stars, we find that a best fit is obtained for a M6V star, contributing 5 percent of the total light at that spectral region. Assuming that the radial velocity semi-amplitudes reflect accurately the motion of the binary components, then from our results: K_em = 107+/-2 km/s; K_abs = 310+/-5 km/s, and using the inclination angle given by Zhang & Robinson(1987); i = 69.7+/-0.7, the system parameters become: M_WD = 1.20+/-0.05 M_sun,; M_RD = 0.42+/-0.04 M_sun; and a = 1.55+/- 0.02 R_sun. Based on the separation of the double emission peaks, we calculate an outer disk radius of R_out/a ~0.61, close to the distance of the inner Lagrangian point L_1/a~0.63. Therefore we suggest that, at the time of observations, the accretion disk was filling the Roche-Lobe of the primary, and that the matter leaving the L_1 point was colliding with the disc directly, producing the hot spot at this location.Comment: 36 pages, 14 figures, ccepted for publication in A

Agronomic Performance and Nutritive Value of Mucuna Legume (Stilozobium Deeringianum (Bort) Merr.) as Influenced by Cutting Dates in Peruvian Central Coast

The agronomic performance and nutritive value of Mucuna legume (Stilozobium deeringianum (Bort) Merr.) in five stages were evaluated under climatic conditions of Peruvian central coast to estimate optimum stage of use. Five cutting ages were: 21, 42, 63, 84 and 105 days. Crop growing, forage yield, chemical composition, vitro dry matter digestibility and net energy for lactation of Mucuna were evaluated. The optimum cutting age was 84 days with 25633.3 kg. Ha-1 of fresh matter and 6422.6 kg-1 ha-1 of dry matter. In this age crude protein, neutral detergent fiber and acid detergent fiber and in vitro dry matter digestibility contents were 14.94%, 44.80%, 33.15% and 66.12 %. Net energy for lactation was 1.43 Mcal.kg-1. These results show that Mucuna was well adapted to Peruvian Central Coast with high forage yield and nutritive value

Erupting Cataclysmic Variable Stars in the Nearest Globular Cluster, NGC 6397: Intermediate Polars?

NGC 6397 is the closest globular cluster, and hence the ideal place to search for faint stellar populations such as cataclysmic variables (CVs). HST and Chandra observers have identified nine certain and likely CVs in this nearby cluster, including several magnetic CV candidates. We have combined our recent UV imagery with archival HST images of NGC 6397 to search for new CV candidates and especially to look for dwarf nova-like eruptive events. We find remarkable and somewhat unexpected dwarf nova-like eruptions of the two well-known cataclysmic systems CV2 and CV3. These two objects have been claimed to be {\it magnetic} CVs, as indicated by their helium emission-line spectra. Magnetic fields in CVs are usually expected to prevent the disk instability that leads to dwarf nova eruptions. In fact, most field magnetic CVs are observed to not undergo eruptions. Our observations of the dwarf nova eruptions of CV2 and CV3 can be reconciled with these objects' HeII emission lines if both objects are infrequently-erupting intermediate polars, similar to EX Hya. If this is the case for most globular cluster CVs then we can reconcile the many X-ray and UV bright CV candidates seen by Chandra and HST with the very small numbers of erupting dwarf novae observed in cluster cores.Comment: 12 pages, 3 figures. Accepted for publication in The Astronomical Journal. Two additional authors adde