Influence of Water Content and Temperature on Molecular Mobility and Intracellular Glasses in Seeds and Pollen1

Although the occurrence of intracellular glasses in seeds and pollen has been established, physical properties such as rotational correlation times and viscosity have not been studied extensively. Using electron paramagnetic resonance spectroscopy, we examined changes in the molecular mobility of the hydrophilic nitroxide spin probe 3-carboxy-proxyl during melting of intracellular glasses in axes of pea (Pisum sativum L.) seeds and cattail (Typha latifolia L.) pollen. The rotational correlation time of the spin probe in intracellular glasses of both organisms was approximately 10−3 s. Using the distance between the outer extrema of the electron paramagnetic resonance spectrum (2Azz) as a measure of molecular mobility, we found a sharp increase in mobility at a definite temperature during heating. This temperature increased with decreasing water content of the samples. Differential scanning calorimetry data on these samples indicated that this sharp increase corresponded to melting of the glassy matrix. Molecular mobility was found to be inversely correlated with storage stability. With decreasing water content, the molecular mobility reached a minimum, and increased again at very low water content. Minimum mobility and maximum storage stability occurred at a similar water content. This correlation suggests that storage stability might be at least partially controlled by molecular mobility. At low temperatures, when storage longevity cannot be determined on a realistic time scale, 2Azz measurements can provide an estimate of the optimum storage conditions.

Phloem Transport of Fructans in the Crassulacean Acid Metabolism Species Agave deserti1

Four oligofructans (neokestose, 1-kestose, nystose, and an un-identified pentofructan) occurred in the vascular tissues and phloem sap of mature leaves of Agave deserti. Fructosyltransferases (responsible for fructan biosynthesis) also occurred in the vascular tissues. In contrast, oligofructans and fructosyltransferases were virtually absent from the chlorenchyma, suggesting that fructan biosynthesis was restricted to the vascular tissues. On a molar basis, these oligofructans accounted for 46% of the total soluble sugars in the vascular tissues (sucrose [Suc] for 26%) and for 19% in the phloem sap (fructose for 24% and Suc for 53%). The Suc concentration was 1.8 times higher in the cytosol of the chlorenchyma cells than in the phloem sap; the nystose concentration was 4.9 times higher and that of pentofructan was 3.2 times higher in the vascular tissues than in the phloem sap. To our knowledge, these results provide the first evidence that oligofructans are synthesized and transported in the phloem of higher plants. The polymer-trapping mechanism proposed for dicotyledonous C3 species may also be valid for oligofructan transport in monocotyledonous species, such as A. deserti, which may use a symplastic pathway for phloem loading of photosynthates in its mature leaves.

Accumulation of Salicylic Acid and 4-Hydroxybenzoic Acid in Phloem Fluids of Cucumber during Systemic Acquired Resistance Is Preceded by a Transient Increase in Phenylalanine Ammonia-Lyase Activity in Petioles and Stems1

Cucumber (Cucumis sativa) leaves infiltrated with Pseudomonas syringae pv. syringae cells produced a mobile signal for systemic acquired resistance between 3 and 6 h after inoculation. The production of a mobile signal by inoculated leaves was followed by a transient increase in phenylalanine ammonia-lyase (PAL) activity in the petioles of inoculated leaves and in stems above inoculated leaves; with peaks in activity at 9 and 12 h, respectively, after inoculation. In contrast, PAL activity in inoculated leaves continued to rise slowly for at least 18 h. No increases in PAL activity were detected in healthy leaves of inoculated plants. Two benzoic acid derivatives, salicylic acid (SA) and 4-hydroxybenzoic acid (4HBA), began to accumulate in phloem fluids at about the time PAL activity began to increase, reaching maximum concentrations 15 h after inoculation. The accumulation of SA and 4HBA in phloem fluids was unaffected by the removal of all leaves 6 h after inoculation, and seedlings excised from roots prior to inoculation still accumulated high levels of SA and 4HBA. These results suggest that SA and 4HBA are synthesized de novo in stems and petioles in response to a mobile signal from the inoculated leaf.

Symplasmic Constriction and Ultrastructural Features of the Sieve Element/Companion Cell Complex in the Transport Phloem of Apoplasmically and Symplasmically Phloem-Loading Species1

The ultrastructural features of the sieve element/companion cell complexes were screened in the stem phloem of two symplasmically loading (squash, [Cucurbita maxima L.] and Lythrum salicaria L.) and two apoplasmically loading (broad bean [Vicia faba L.] and Zinnia elegans L.) species. The distinct ultrastructural differences between the companion cells in the collection phloem of symplasmically and apoplasmically phloem-loading species continue to exist in the transport phloem. Plasmodesmograms of the stem phloem showed a universal symplasmic constriction at the interface between the sieve element/companion cell complex and the phloem parenchyma cells. This contrasts with the huge variation in symplasmic continuity between companion cells and adjoining cells in the collection phloem of symplasmically and apoplasmically loading species. Further, the ultrastructure of the companion cells in the transport phloem faintly reflected the features of the companion cells in the loading zone of the transport phloem. The companion cells of squash contained numerous small vacuoles (or vesicles), and those of L. salicaria contained a limited number of vacuoles. The companion cells of broad bean and Z. elegans possessed small wall protrusions. Implications of the present findings for carbohydrate processing in intact plants are discussed.

Invasion of minor veins of tobacco leaves inoculated with tobacco mosaic virus mutants defective in phloem-dependent movement.

To fully understand vascular transport of plant viruses, the viral and host proteins, their structures and functions, and the specific vascular cells in which these factors function must be determined. We report here on the ability of various cDNA-derived coat protein (CP) mutants of tobacco mosaic virus (TMV) to invade vascular cells in minor veins of Nicotiana tabacum L. cv. Xanthi nn. The mutant viruses we studied, TMV CP-O, U1mCP15-17, and SNC015, respectively, encode a CP from a different tobamovirus (i.e., from odontoglossum ringspot virus) resulting in the formation of non-native capsids, a mutant CP that accumulates in aggregates but does not encapsidate the viral RNA, or no CP. TMV CP-O is impaired in phloem-dependent movement, whereas U1mCP15-17 and SNC015 do not accumulate by phloem-dependent movement. In developmentally-defined studies using immunocytochemical analyses we determined that all of these mutants invaded vascular parenchyma cells within minor veins in inoculated leaves. In addition, we determined that the CPs of TMV CP-O and U1mCP15-17 were present in companion (C) cells of minor veins in inoculated leaves, although more rarely than CP of wild-type virus. These results indicate that the movement of TMV into minor veins does not require the CP, and an encapsidation-competent CP is not required for, but may increase the efficiency of, movement into the conducting complex of the phloem (i.e., the C cell/sieve element complex). Also, a host factor(s) functions at or beyond the C cell/sieve element interface with other cells to allow efficient phloem-dependent accumulation of TMV CP-O.

High mobility group I(Y)-like DNA-binding domains on a bacterial transcription factor.

The bacterium Myxococcus xanthus responds to blue light by producing carotenoids. It also responds to starvation conditions by developing fruiting bodies, where the cells differentiate into myxospores. Each response entails the transcriptional activation of a separate set of genes. However, a single gene, carD, is required for the activation of both light- and starvation-inducible genes. Gene carD has now been sequenced. Its predicted amino acid sequence includes four repeats of a DNA-binding domain present in mammalian high mobility group I(Y) proteins and other nuclear proteins from animals and plants. Other peptide stretches on CarD also resemble functional domains typical of eukaryotic transcription factors, including a very acidic region and a leucine zipper. High mobility group yI(Y) proteins are known to bind the minor groove of A+T-rich DNA. CarD binds in vitro an A+T-rich element that is required for the proper operation of a carD-dependent promoter in vivo.

Intercellular mobility and homing of an archaeal rDNA intron confers a selective advantage over intron- cells of Sulfolobus acidocaldarius.

Some intron-containing rRNA genes of archaea encode homing-type endonucleases, which facilitate intron insertion at homologous sites in intron- alleles. These archaeal rRNA genes, in contrast to their eukaryotic counterparts, are present in single copies per cell, which precludes intron homing within one cell. However, given the highly conserved nature of the sequences flanking the intron, homing may occur in intron- rRNA genes of other archaeal cells. To test whether this occurs, the intron-containing 23S rRNA gene of the archaeal hyperthermophile Desulfurococcus mobilis, carried on nonreplicating bacterial vectors, was electroporated into an intron- culture of Sulfolobus acidocaldarius. PCR experiments demonstrated that the intron underwent homing and spread through the culture. By using a double drug-resistant mutant of S. acidocaldarius, it was shown that spreading resulted partly from a selective advantage of intron+ cells and partly from intercellular mobility of the intron and homing.

Structure and function of a human transcription factor TFIIIB subunit that is evolutionarily conserved and contains both TFIIB- and high-mobility-group protein 2-related domains.

Transcription factor TFIIIB plays a central role in transcription initiation by RNA polymerase III on genes encoding tRNA, 5S rRNA, and other small structural RNAs. We report the purification of a human TFIIIB-derived complex containing only the TATA-binding polypeptide (TBP) and a 90-kDa subunit (TFIIIB90) and the isolation of a cDNA clone encoding the 90-kDa subunit. The N-terminal half of TFIIIB90 exhibits sequence similarity to the yeast TFIIIB70 (BRF) and the class II transcription factor TFIIB and interacts weakly with TBP. The C-terminal half of TFIIIB90 contains a high-mobility-group protein 2 (HMG2)-related domain and interacts strongly with TBP. Recombinant TFIIIB90 plus recombinant human TBP substitute for human TFIIIB in a complementation assay for transcription of 5S, tRNA, and VA1 RNA genes, and both the TFIIB-related domain and the HMG2-related domain are required for this activity. TFIIIB90 is also required for transcription of human 7SK and U6 RNA genes by RNA polymerase III, but apparently within a complex distinct from the TBP/TFIIIB90 complex.

Coherent electron dynamics in a two-dimensional random system with mobility edges

We study numerically the dynamics of a one-electron wavepacket in a two-dimensional random lattice with long-range correlated diagonal disorder in the presence of a uniform electric field. The time-dependent Schrodinger equation is used for this purpose. We find that the wavepacket displays Bloch-like oscillations associated with the appearance of a phase of delocalized states in the strong correlation regime. The amplitude of oscillations directly reflects the bandwidth of the phase and allows us to measure it. The oscillations reveal two main frequencies whose values are determined by the structure of the underlying potential in the vicinity of the wavepacket maximum.

Mobility and Aging in Denver, Colorado: Travel Behavior, Mobility Barriers, and Perceptions of Transit

The number of seniors in the U.S. today is growing rapidly because of longer life expectancies and the aging Baby Boomer generation. This age groups' travel behavior will have substantial impacts on transportation, economics, safety, and the environment. This research used a mixed-methods approach to address issues of mobility and aging in Denver, Colorado. A quantitative approach was used to answer broad questions about travel behavior and the effects of age, gender, work status, disability, residential location and socio-economic status on mobility. Qualitative interviews with seniors in the Denver metro area were conducted to identify barriers to mobility, decision-making processes and travel decisions, and seniors' perceptions of public transit. The results of the quantitative and qualitative analyses show that residential location is an important variable for determining seniors' travel behaviors and transportation options. Perceptions of public transit were positive, but accessibility and information barriers exist that prevent older adult from using transit. The findings of this study will help to provide transportation and service recommendations to policymakers and planners in the Denver area as well as to inform studies of other North American cities with large aging populations.

Validation of a mobility item bank for older patients in primary care

Background: To develop and validate an item bank to measure mobility in older people in primary care and to analyse differential item functioning (DIF) and differential bundle functioning (DBF) by sex. Methods: A pool of 48 mobility items was administered by interview to 593 older people attending primary health care practices. The pool contained four domains based on the International Classification of Functioning: changing and maintaining body position, carrying, lifting and pushing, walking and going up and down stairs. Results: The Late Life Mobility item bank consisted of 35 items, and measured with a reliability of 0.90 or more across the full spectrum of mobility, except at the higher end of better functioning. No evidence was found of non-uniform DIF but uniform DIF was observed, mainly for items in the changing and maintaining body position and carrying, lifting and pushing domains. The walking domain did not display DBF, but the other three domains did, principally the carrying, lifting and pushing items. Conclusions: During the design and validation of an item bank to measure mobility in older people, we found that strength (carrying, lifting and pushing) items formed a secondary dimension that produced DBF. More research is needed to determine how best to include strength items in a mobility measure, or whether it would be more appropriate to design separate measures for each construct.

What do older people understand by mobility-related difficulties?

Despite the centrality of the difficulty concept in the study of disability, there has been little research on its significance from the point of view of people with functional limitations. The main objective of this study was to describe what older people understand when asked about difficulty in undertaking mobility activities. As a secondary objective, we considered whether there are any differences depending on the type of activities, according to the International Classification of Functioning (ICF) mobility domains. Methods: Seventeen community-dwelling men and women aged 70 years old or over were interviewed by means of a questionnaire containing 55 items covering the ICF mobility domains. The participants responded to the items while thinking aloud, saying what led them to give a specific answer about their level of difficulty. Inductive content analysis was conducted and categories, subthemes and themes were identified. Results: Causes of difficulty (pathologies, impairments, symptoms) and accommodations (task modifications and use of aids) were the two themes identified; and their importance (and that of the subthemes included) varied across the types of activity. All the participants said that they had no difficulty in at least one task, despite mentioning changes in the way they performed them. Conclusions: Older people's opinions were consistent with theoretical models of disability and with the standard practice of measuring functional limitations by asking about the degree of difficulty; however, the design of these measures needs to be improved in order to detect perceptions of no difficulty in the presence of task modification.

'A Kind of Logic, A Kind of Dominant Logic': Navigating Colonialism, Honoring Black Mobility, and Thinking on Moving Through

My thesis thinks through the ways Newtonian logics require linear mobility in order to produce narratives of progress. I argue that this linear mobility, and the resulting logics, potentially erases the chaotic and non-linear motions that are required to navigate a colonial landscape. I suggest that these non-linear movements produce important critiques of the seeming stasis of colonial constructs and highlight the ways these logics must appear neutral and scientific in an attempt to conceal the constant and complex adjustments these frameworks require. In order to make room for these complex motions, I develop a quantum intervention. Specifically, I use quantum physics as a metaphor to think through the significance of black life, the double-consciousness ofland, and the intricate motions of sound. In order to put forth this intervention, I look at news coverage of Hurricane Katrina, Du Bois’s characterization of land in Souls of Black Folks, and the aural mobilities of blackness articulated in an academic discussion and interview about post- humanism.

Three types of transnational players: differing women's football mobility projects in core and developing countries

Mobile players in men's football are highly skilled professionals who move to a country other than the one where they grew up and started their careers. They are commonly described as migrants or expatriate players. Due to a much less advanced stage of professionalism and production of the game in women's football mobility projects are different. At describing the cases of Brazil, Equatorial Guinea, Mexico, Colombia and Portugal, the aim of this paper is to conceptualise an umbrella category for mobile players that can include current realities in the women's game, namely the transnational player who has gained and displays transnational football experience in different countries and socio-culturally contexts. Furthermore, analyses allow introducing two new subcategories besides the “expatriate”, namely diaspora players and new citizens.