System BO Research Articles

Eclipsing Binary Systems XZ Per and BO Vul with Complex Variations in Orbital Periods

The variations in the orbital periods of the eclipsing binary systems XZ Per and BO Vul have been studied. It has been shown that the variations in the orbital period of the eclipsing binary XZ Per are equally well represented as a superposition of the secular decrease and cyclic variations or as a sum of two cyclic variations. In the first case, the monotonic component can be a consequence of the loss of angular momentum by the system due to magnetic braking, while cyclic variations can be explained by the presence of a third body in the system or by the magnetic activity of the secondary component with a convective shell. In the second case, it is possible to assume the presence of two additional bodies in the system, or to attribute one of the period oscillations to the light-time effect, and the other to the magnetic activity of the secondary component. The variations in the orbital period of the eclipsing binary system BO Vul can be represented as a superposition of the secular decrease and cyclic variations. The observed cyclic variations in the period can occur due to the presence of a third body in the system or due to the magnetic activity of the secondary component with a convective shell.

Absolute and geometric parameters of contact binary BO Arietis

We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system BO Ari from analyzed CCD (BVRI) light curves and radial velocity data. The photometric data were obtained in 2009 and 2010 at Ankara University Observatory (AUO) and the spectroscopic observations were made in 2007 and 2010 at TUBITAK National Observatory (TUG). These light and radial velocity observations were analyzed simultaneously by using the Wilson–Devinney (2013 revision) code to obtain absolute and geometrical parameters. The system was determined to be an A-type W UMa system. Combining our photometric solution with the spectroscopic data we derived masses and radii of the eclipsing system to be M1=0.995M⊙,M2=0.189M⊙,R1=1.090R⊙ and R2=0.515R⊙. Finally, we discuss the evolutionary status of the system.

Spectroscopic and photometric study of the contact binary BO CVn

We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88%. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20–24%, while the absolute parameters of components are: M1=1.16, M2=0.39, R1=1.62 and R2=1.00 (in solar units).The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt=6.3×10−8M⊙/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility).

BO Vulpeculae: Is the primary surrounded by an accretion disk?

A detailed study of the orbital period of an Algol-type eclipsing binary BO Vulpeculae is presented. Based on the analysis of the ( O– C) curve, we find that, apart from a secular decrease, several sudden jumps have occurred in the orbital period of the system BO Vul. We investigate the physical mechanisms which might underlie the variation in the orbital period of the system BO Vulpeculae, and find that the mass is transferred from the primary to the secondary with a rate of d M 1 d t = - 2.84 × 10 - 9 M ⊙ yr - 1 if the period decrease is only caused by the loss of mass and angular momentum owing to an enhanced stellar wind. It is impossible for BO Vulpeculae that the mass is transferred from the primary to the secondary because the radius of the primary is much smaller than that of its Roche lobe. This implies that an accretion disk is probably formed around the primary of BO Vulpeculae, in which the angular momentum in the transferred matter is stored. Therefore, we concluded that the secular decrease in the orbital period of BO Vulpeculae might be caused by the loss of mass and angular momentum from the system via a magnetic stellar wind (MSW) and/or by an accretion disk formed around the primary of BO Vulpeculae. The sudden jumps in the orbital period of BO Vul might be caused by the instability of the accretion disk or by the structure changes in the convective envelope of the secondary.

Nuevas observaciones de crono-paleografía ibérica levantina

This paper is the continuation of a previous study of the chronological palaeography of Iberian Levantine writing. Two signs are added to the system ( bi and bo ), and comments are made on some minor variations of other signs. The new documentation of te-1 is also revised. Finally, the distribution of the main areas demarked by variations of the signs themselves is briefly described.

Evidence that the transport-related proteins BAT and 4F2hc are not specific for amino acids: induction of Na+-dependent uridine and pyruvate transport activity by recombinant BAT and 4F2hc expressed in Xenopus oocytes

Members of the BAT and 4F2hc gene family have one or, in the case of BAT, up to four transmembane domains and induce amino acid transport systems bo,+ (BAT) and y+L (4F2hc) when expressed in Xenopus oocytes. System bo,+ is a Na+-independent process with a broad tolerance for cationic and zwitterionic amino acids, whereas y+L exhibits Na+-independent transport of cationic amino acids (e.g., lysine) and Na+-dependent transport of zwitterionic amino acids (e.g., leucine). Mutations in the human BAT gene are associated with type I cystinuria, a genetic disease affecting the ability of intestinal and renal brush border membranes to transport cationic amino acids and cystine. An unresolved question is whether BAT and 4F2hc themselves have catalytic (i.e., transporting) activity or whether they operate as activators of other, as yet unidentified, transporter proteins. In this report, we have investigated the transport of representatives of four different classes of organic substrates in Xenopus oocytes following injection with rat BAT or 4F2hc RNA transcripts: leucine (a control amino acid substrate), uridine (a nucleoside), pyruvate (a monocarboxylate), and choline (an amine). Both recombinant proteins induced small, statistically significant Na+-dependent fluxes of uridine and pyruvate but had no effect on choline uptake. In contrast, control oocytes injected with transcripts for conventional nucleoside and cationic amino acid transporters (rat CNT1 and murine CAT1, respectively) showed no induction of transport of either leucine or pyruvate (CNT1) or uridine or pyruvate (CAT1). These findings support the idea that BAT and 4F2hc are transport activators and minimize the possibility that they have intrinsic transport capability. The transport-regulating functions of these proteins may extend to permeants other than amino acids.Key words: amino acid transport, uridine, pyruvate, BAT, 4F2hc, Xenopus oocytes.

Obligatory Amino Acid Exchange via Systems bo,+-like and y+L-like: A TERTIARY ACTIVE TRANSPORT MECHANISM FOR RENAL REABSORPTION OF CYSTINE AND DIBASIC AMINO ACIDS

Mutations in the rBAT gene cause type I cystinuria, a common inherited aminoaciduria of cystine and dibasic amino acids due to their defective renal and intestinal reabsorption (Calonge, M. J., Gasparini, P., Chillarón, J., Chillón, M., Gallucci, M., Rousaud, F., Zelante, L., Testar, X., Dallapiccola, B., Di Silverio, F., Barceló, P., Estivill, X., Zorzano, A., Nunes, V., and Palacín, M. (1994) Nat. Genet. 6, 420-426; Calonge, M. J., Volipini, V., Bisceglia, L., Rousaud, F., De Sanctis, L., Beccia, E., Zelante, L., Testar, X., Zorzano, A., Estivill, X., Gasparini, P., Nunes, V., and Palacín, M.(1995) Proc. Natl. Acad. Sci. U. S. A. 92, 9667-9671). One important question that remains to be clarified is how the apparently non-concentrative system bo,+-like, associated with rBAT expression, participates in the active renal reabsorption of these amino acids. Several studies have demonstrated exchange of amino acids induced by rBAT in Xenopus oocytes. Here we offer evidence that system bo,+-like is an obligatory amino acid exchanger in oocytes and in the "renal proximal tubular" cell line OK. System bo, +-like showed a 1:1 stoichiometry of exchange, and the hetero-exchange dibasic (inward) with neutral (outward) amino acids were favored in oocytes. Obligatory exchange of amino acids via system bo,+-like fully explained the amino acid-induced current in rBAT-injected oocytes. Exchange via system bo,+-like is coupled enough to ensure a specific accumulation of substrates until the complete replacement of the internal oocyte substrates. Due to structural and functional analogies of the cell surface antigen 4F2hc to rBAT, we tested for amino acid exchange via system y+L-like. 4F2hc-injected oocytes accumulated substrates to a level higher than CAT1-injected oocytes (i.e. oocytes expressing system y+) and showed exchange of amino acids with the substrate specificity of system y+L and L-leucine-induced outward currents in the absence of extracellular sodium. In contrast to L-arginine, system y+L-like did not mediate measurable L-leucine efflux from the oocyte. We propose a role of systems bo,+-like and y+L-like in the renal reabsorption of cystine and dibasic amino acids that is based on their active tertiary transport mechanism and on the apical and basolateral localization of rBAT and 4F2hc, respectively, in the epithelial cells of the proximal tubule of the nephron.

Characterization and growth factor stimulation ofl-arginine transport in a human colon cancer cell line

Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) are potent mitogens that contribute to abnormal growth regulation in colon cancer. Growth factors have been shown to regulate transmembrane nutrient uptake as an adaptive response to support cellular proliferation. The transport of L-arginine by the SW480 primary human colon adenocarcinoma cell line was characterized by assaying the uptake of [3H]L-arginine in the presence and absence of sodium. Kinetic studies were performed over a range of L-arginine concentrations to determine transport affinity (Km) and maximal transport velocity (Vmax). To further characterize the specific transporters, [3H]L-arginine uptake was measured in the presence of selected amino acids, hormones, and under conditions of varying external pH. To investigate the effects of EGF and TGF alpha, cells were incubated with increasing doses of growth factors (1, 10, 50 ng/ml) and L-arginine transport was measured at various time intervals (8, 12, 24 h). Proliferation was assessed by the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay 3 days after growth factor stimulation. The majority of carrier-mediated L-arginine transport was via a sodium-independent process (65-70%), whereas the remainder was sodium-dependent (28-30%). Diffusion contributed a small amount to total L-arginine uptake (2%). Kinetic studies of arginine transport revealed a single high-affinity Na(+)-independent transporter with a Km = 55.8 +/- 5.8 microM and a Vmax = 710.6 +/- 87.3 pM/mg protein/30 s. Na(+)-independent arginine uptake was pH-insensitive and markedly inhibited by system y+ substrates L-homoarginine, L-lysine, and L-ornithine. A single Na(+)-dependent transporter with a Km = 19.8 +/- 2.3 microM and a Vmax = 159.1 +/- 8.9 pM/mg protein/30 s was identified. Na(+)-dependent arginine uptake was inhibited by system BO,+ substrates L-lysine, L-ornithine, L-leucine, L-cysteine, and L-glutamine, but not by 2-methylaminoisobutyric acid. In addition, Na(+)-dependent arginine uptake was pH- and hormone-insensitive. Incubation with EGF or TGF alpha had no effect on Na(+)-independent L-arginine uptake; however, Na(+)-dependent uptake was enhanced 60% by EGF (10 ng/ml, p < 0.05) and 100% by TGF alpha (10 ng/ml, p < 0.05), whereas cellular proliferation was increased 27% by EGF (10 ng/ml, p < 0.05) and 37% by TGF alpha (10 ng/ml, p < 0.01). L-arginine transport in the SW480 colon cancer cell line is principally mediated by the Na(+)-independent system y+ and to a lesser extent by the Na(+)-dependent system BO,+. Furthermore, EGF and TGF alpha preferentially stimulate L-arginine uptake via the Na(+)-dependent transporter, ostensibly to accommodate for the mitogenic stimulus.

HEPATIC Na+−INDEPENDENT AMINO ACID TRANSPORT IN ENDOTOXEMIC RATS

The effects of endotoxin on the activities of the major Na(+)-independent amino acid transporters in rat liver (Systems n, asc, L, bo,+, and y+) were studied using using hepatic plasma membrane vesicles (HPMVs). Rats were treated with a single dose of Escherichia coli endotoxin (E. coli lipopolysaccharide 0127:B8 (LPS), 7.5, 15, or 30 mg/kg BW) and HPMVs were prepared by Percoll density gradient centrifugation at various timepoints after LPS administration. Vesicle purity and integrity was established by assay of enzyme markers and identical equilibrium uptakes. The activities of the Na(+)-independent amino acid transport systems y+ and bo,+ (arginine), asc (alanine and cysteine), L (leucine), and n (glutamine) were evaluated by measuring the uptake of radiolabeled amino acids using a rapid mixing/filtration technique. Amino acid uptake by HPMVs consisted of saturable and nonsaturable components. Prior treatment with endotoxin did not alter the activities of Systems n, asc, or L but resulted in a time- and dose-dependent stimulation of saturable arginine transport. Arginine transport increased within 2 h of LPS administration and exhibited a return towards basal levels by 24 h. Nonsaturable uptake (diffusion) in HPMVs was unaltered by LPS treatment. Kinetic analysis of arginine transport demonstrated the presence of both a high affinity and a low affinity carrier. Treatment with LPS resulted in a 73% increase in the Vmax of the high affinity carrier (System y+) and a 25% increase in the Vmax of the low affinity transporter (System bo,+). The data indicate selective stimulation of Na(+)-independent arginine transport in the liver during endotoxemia which may serve to support important arginine-dependent pathways during sepsis.

RBAT, related to L-cysteine transport, is localized to the microvilli of proximal straight tubules, and its expression is regulated in kidney by development.

We have recently isolated a renal cDNA clone (rBAT) that induces amino acid transport in oocytes either as a component or as a specific activator of a system bo,(+)-like transporter. (Bertran, J., Werner, A., Moore, M. L., Stange, G., Markovich, D., Biber, J., Testar, X., Zorzano, A., Palacín, M., and Murer, H. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 5601-5605. In order to obtain additional information on the rBAT protein, we have investigated the cellular localization of rBAT and its expression during development in rat kidney. A polyclonal antibody raised against rBAT recognizes a specific protein band of approximately 90 kDa, which is highly enriched in rat renal brush border membranes. Immunofluorescence and immunoelectron microscopy studies demonstrated that rBAT is expressed in the microvilli domain of S3 epithelial cells (i.e. straight tubules). The onset of rBAT mRNA expression in kidney was detected during late fetal life. In keeping with this, induction in oocytes of L-cystine uptake due to fetal rBAT-related mRNA was approximately 10% of the induction obtained with rBAT-related mRNA from adult kidneys. rBAT mRNA levels were low in early postnatal life, and only at the end of lactation did they increase steeply, attaining approximately 50% of adult values after weaning. rBAT protein was undetectable in total membrane preparations of kidneys from fetuses and early neonates, weakly detected during lactation, and represented < 15% of adult values after weaning. The postnatal expression of rBAT and its specific location in the microvilli of epithelial cells from the S3 segment of the proximal tubule coincide with postnatal maturation of cystine resorption and with the site of high affinity resorption of cysteine in kidney. This is consistent with the involvement of rBAT in a b(o,+)-like high-affinity resorption system for cysteine in the proximal straight tubule of the nephron.

Characterization of L-arginine transport by pulmonary artery endothelial cells

The transport of L-arginine by porcine pulmonary artery endothelial cells (PAECs) was characterized. Uptake of 50 microM L-arginine was time dependent and linear in the presence and absence of sodium, with approximately 70% of uptake occurring via a carrier-mediated Na(+)-independent process. Kinetic studies of saturable Na(+)-independent transport revealed two transport components: a high-affinity transporter [Michaelis constant (Km) = 304 +/- 23 microM, maximal transport velocity (Vmax) = 679 +/- 34 pmol.mg protein-1.30 s-1], and a low-affinity carrier (Km = 3.9 +/- 1.0 mM, Vmax = 2.8 +/- 0.7 nmol/mg protein-1.30 s-1). Saturable Na(+)-independent uptake of 50 microM L-arginine transport showed no significant variation in uptake between pH 6.0 and 8.0 and was blocked by the system y+ substrates L-arginine, L-homoarginine, L-lysine, and L-ornithine. Na(+)-dependent L-arginine transport occurred via a single high-affinity system (Km = 62 +/- 3 microM, Vmax = 211 +/- 24 pmol.mg protein-1.30 s-1) which was significantly inhibited by L-arginine, L-lysine, L-ornithine, L-leucine, L-alanine, L-cysteine, and L-glutamine, but not by 2-methylaminoisobutyric acid. Na(+)-dependent arginine uptake was pH and hormone insensitive, and lithium did not substitute effectively for sodium. These data are consistent with mediation of high-affinity arginine transport by PAECs via Na(+)-independent system y+ and Na(+)-dependent system BO,+.

PHOTOMETRIC OBSERVATION AND ANALYSIS OF THE CLOSE BINARY SYSTEM BO PEGASI.

ABSTRACT Photoelectric BV light curves of the close binary system BO Peg (P = 0d.580) are obtained and analyzed with a synthesis method to determine the photometric elements. It is found that the components of BO Peg are not in contact with each other but almost fill their respective Roche lobes. Two spectrograms of the system (A7 IV-V) have also been obtained, and a brief discussion on physical quantities of the components is made.