Time-sequence Observations Research Articles

Time-sequence Spectroscopy of Epsilon CrA: The 518 nm Mg i Triplet Region Analyzed with Broadening Functions

Abstract High-resolution spectroscopic observations of the W UMa-type binary ϵ CrA obtained as a time-monitoring sequence on four full and four partial nights within two weeks have been used to derive orbital elements of the system and discuss the validity of the Lucy model for description of the radial-velocity data. The observations had more extensive temporal coverage and better quality than similar time-sequence observations of the contact binary AW UMa. The two binaries share several physical properties and show very similar deviations from the Lucy model: the primary component is a rapidly rotating star almost unaffected by the presence of the secondary component, while the latter is embedded in a complex gas flow and appears to have its own rotation-velocity field, in contradiction to the model. The spectroscopic mass ratio is found to be larger than the one derived from the light-curve analysis, as in many other W UMa-type binaries, but the discrepancy for ϵ CrA is relatively minor, much smaller than for AW UMa. The presence of the complex velocity flows contradicting the assumption of solid-body rotation suggests a necessity of modification to the Lucy model, possibly along the lines outlined by Stȩpień in his concept of energy transfer between the binary components.

PHOTOSPHERIC FLOW FIELD RELATED TO THE EVOLUTION OF THE SUN'S POLAR MAGNETIC PATCHES OBSERVED BYHINODESOLAR OPTICAL TELESCOPE

We investigated the role of photospheric plasma motions in the formation and evolution of polar magnetic patches using time-sequence observations with high spatial resolution. The observations were obtained with the spectropolarimeter on board the Hinode satellite. From the statistical analysis using 75 magnetic patches, we found that they are surrounded by strong converging, supergranulation associated flows during their apparent life time and that the converging flow around the patch boundary is better observed in the Doppler velocity profile in the deeper photosphere. Based on our analysis we suggest that the like-polarity magnetic fragments in the polar region are advected and clustered by photospheric converging flows thereby resulting in the formation of polar magnetic patches. Our observations show that, in addition to direct cancellation magnetic patches decay by fragmentation followed by unipolar disappearance or unipolar disappearance without fragmentation. It is possible that the magnetic patches of existing polarity fragment or diffuse away into smaller elements and eventually cancel out with opposite polarity fragments that reach the polar region around solar cycle maximum. This could be one of the possible mechanisms by which the existing polarity decay during the reversal of the polar magnetic field.

Dynamic organization of vacuolar and microtubule structures during cell cycle progression in synchronized tobacco BY-2 cells.

In higher plant cells, vacuoles show considerable diversity in their shapes and functions. The roles of vacuoles in the storage, osmoregulation, digestion and secretory pathway are well established; however, their functions in cell morphogenesis and cell division are still unclear. To observe the dynamic changes of vacuoles in living plant cells, we attempted to visualize the vacuolar membrane (VM) by pulse-labeling tobacco BY-2 cells with a styryl fluorescent dye, FM4-64. By time-sequence observations using confocal laser scanning microscopy (CLSM), we could follow the dynamics of vacuolar structures throughout the cell cycle in living higher plant cells. We also confirmed the dynamic changes of VM structures by the observation using transgenic BY-2 cells expressing GFP-AtVam3p fusion protein (BY-GV). Furthermore, by using transgenic BY-2 cells that stably express a GFP-tubulin fusion protein [BY-GT16, Kumagai et al. (2001) Plant Cell Physiol. 42: 723], we could study the relationship between the dynamics of vacuoles and microtubules. From these observations, we identified, for the first time, some remarkable events: (1) at the late G(2) phase, tubular structures of the vacuolar membrane developed in the central region of the cell, probably in the premitotic cytoplasmic band (phragmosome), surrounding the mitotic apparatus; (2) from anaphase to telophase, these tubular structures invaded the region of the phragmoplast within which the cell plate was being formed; (3) at the early G(1) phase, some of the tubular structures expanded rapidly between the cell plate and daughter nuclei, and subsequently developed into large vacuoles at interphase.

Fate of nascent microtubules organized at the M/G1 interface, as visualized by synchronized tobacco BY-2 cells stably expressing GFP-tubulin: time-sequence observations of the reorganization of cortical microtubules in living plant cells.

Transgenic BY-2 cells stably expressing a GFP (green fluorescent protein)-tubulin fusion protein (BY-GT16) were subcultured in a modified Linsmaier and Skoog medium. The BY-GT16 cells could be synchronized by aphidicolin and the dynamics of their microtubules (MTs) were monitored by the confocal laser scanning microscopy (CLSM). We have succeeded in investigating the mode of reorganization of cortical MTs at the M/G1 interface. The cortical MTs were initially organized in the perinuclear regions and then they elongated to reach the cell cortex, forming the bright spots there. Subsequently, the first cortical MTs rapidly elongated from the spots and they were oriented parallel to the long axis towards the distal end of the cells. Around the time when the tips of the parallel MTs reached the distal end, the formation of transverse cortical MTs followed in the cortex near the division site, as we had previously suggested [Hasezawa and Nagata (1991) Bot. Acta 104: 206, Nagata et al. (1994) Planta 193: 567]. It was confirmed in independent observations that the appearance of the parallel MTs was followed by the appearance of the transverse MTs in each cell. We found that the transverse MTs spread through the whole cell cortex within about 20-30 min, while the parallel MTs disappeared. The significance of these observations on the mode of cortical MT organization is discussed.

Time-sequence observations of microtubule dynamics throughout mitosis in living cell suspensions of stable transgenic Arabidopsis--direct evidence for the origin of cortical microtubules at M/G1 interface.

Transgenic Arabidopsis thaliana, stably expressing a GFP-TUA6 fusion protein, were subcultured in B5 medium supplemented with 2,4-D and BA. In the cell suspensions, the microtubular changes in the mitotic cells could be monitored by time-sequence observations using a time-lapse system of fluorescence microscopy. We have succeeded in following the microtubule (MT) dynamics in living cells throughout mitosis, from the late G2 phase to early G1 phase, and found that, at the M/G1 interface, the cortical MTs were firstly reorganized in the perinuclear regions and then in the cortex, as we had previously suggested (Hasezawa and Nagata 1991, Nagata et al. 1994). The significance of this observation on the origin of cortical MTs is discussed.

Epigenesis in developing avian scales: III. Stage-specific alterations of the developmental program caused by 5-bromodeoxyuridine

As an approach to the study of a developmental program, 5-bromodeoxyuridine (BrdU) was administered to chick embryos in ovo at various stages of avian scale formation. This brought about stage-specific alterations in morphogenesis in the anterior tarsometatarsus such as feathered scales, from Day 6 through Day 6 1 2 ; feathers only, from Day 6 3 4 through Day 7 1 4 ; scalelessness and rudimentary scales, from Day 7 7 8 through Day 8 1 8 ; and partial ridge scales, from Day 8 1 8 through Day 10. The effects of BrdU were completely nullified by an excess dose of thymidine which instantly suppressed BrdU incorporation into nuclear DNA. Effects of BrdU causing scalelessness were further examined. The percentage of BrdU labeled cells was immunohistochemically detected. It increased linearly in both the epidermis and dermis, reaching nearly 100% 24 hr following its injection on Day 8. However, scale forming potency, as assayed by the area of scale epidermis on Day 11, decreased with the duration of BrdU incorporation into the cells and disproportionately dropped at 15 hr when about 50% of the cells had incorporated BrdU. Scalelessness was also produced when the period of the incorporation of BrdU exceeded 15 hr. Time sequence observations demonstrated epidermal cell shape, polarity, alignment, and packing density to be remarkably disordered so that the placode and interplacode failed to develop on Day 9 1 4 . Epidermal-dermal recombinations were carried out by exchanging normal tissues with those treated with BrdU in the anterior tarsometatarsus. The results clearly showed defects in the dermis at the time of reassociation, giving rise to scalelessness.

A minibead method to study cell surface receptors for various proteins coupled to latex particles

A method is described in which various proteins are linked covalently to amide-modified polystyrene latex minibeads (0.345 μ m). The minibeads are then used as markers to identify, quantitate, and delineate the topography of the protein receptors on the cell surface in scanning electron microscopy (SEM) and to make time sequence observations on their internalization in transmission electron microscopy (TEM). The beads are first activated by glutaraldehyde and then coupled to the protein. Optimal conditions were determined by coupling human serum albumin to the minibeads. Bead activation was best at 37°C when incubated for 24–48 hr with 5% glutaraldehyde. Coupling of the activated beads to the test protein occurred optimally at 22°C and at an incubation time of 6 hr. The recommended protein concentration is 200 μ g/mg minibeads. Using this method, transcobalamin II, transferrin, or insulin linked to minibeads was, respectively, incubated with mouse L1210 cells, rat reticulocytes, and adipocytes. Covalently bound proteins retained their biological activities and from TEM and SEM findings, evidence for receptor-mediated transport process was also obtained. This method provides advantages over the previously used protein markers for localization and delineation of the topography of cell surface receptors, in that (a) it permits covalent binding between protein and the marker, (b) the derivatized protein is structurally stable and retains its biologic activity, (e) the beads are submicrometer in size and permit the delineation of topography of receptors in SEM, and (d) the small size of the beads also permits observations on their internalization in TEM.

A Clinical Index of Disability Due to Chronic Asthma Tested During a Trial of Cromolyn Sodium Treatment

An ordinal ranking system for clinically grading disability due to chronic asthma is described, by which to quantitate the changing course of individual patients during time-sequence observations. Experience over two years with 47 asthmatic patients undergoing various trials of disodium cromoglycate therapy indicates this index is very sensitive, reasonably reproducible in the hands of clinicians trained in its use, and specific for asthma rather than for coexisting chronic obstructive lung disease in this patient population. Duplicate scoring by trained observers is recommended. Correlations between disability and daily asthma symptom scores were generally statistically significant, but coefficients were low. Correlations of disability with pulmonary function parameters (measured fortnightly) were not significant. Statistically significant improvement was evident in most asthma indices after a month of disodium cromoglycate treatment. Disability scores improved a great deal, which implies that the observed “statistically significant” improvement in the asthma patient after disodium cromoglycate treatment represents a real clinical advantage.