Responses to water stress of apoplastic water fraction and bulk modulus of elasticity in sunflower (Helianthus annuus L.) genotypes of contrasting capacity for osmotic adjustment

The responses to water stress of the bulk modulus of elasticity () and the apoplastic water fraction were examined using six sunflower cultivars of differing capacity for osmotic adjustment (OA). Water stress did not affect the partitioning of water between apoplastic (ca. 20%) and symplastic fractions in leaves which expanded during the exposure to stress in any genotype. Hence, no genotype-linked effects on either the buffering of cell water status during stress or on the estimates of bulk leaf osmotic potential could be expected. Genotypes differed in the degree of change in (estimated from pressure/volume [P/V] curves) and OA (estimated using both ln RWC/ ln o plots and P/V curves) induced by exposure to stress. In three genotypes increased significantly (p=0.05) as a consequence of stress, in another three change were small. OA was the only attribute of the three examined that could have contributed to turgor maintenance under stress. There was a strong negative association between leaf expansion and degree of OA across genotypes (r=–0.91) and a strong positive one between OA and (r=0.94). However all genotypes evidenced some degree of OA. These results are consistent with part of the genotype differences in OA being attributable to variations in leaf expansion during exposure to stress.     

Patterns of short-term amino acid accumulation and loss in the root-zone of liquid-cultured forage rape (Brassica napus L.)

Amino acid release from roots of sterile and non-sterile, solution-grown, 7-, 21- and 60-days-old forage rape plants (Brassica napus L.), was measured over periods of up to 6 hours. With sterile plants, release of amino acids into a fixed volume of collection medium (6, 12, 70 mL) was concentration-limited, giving rise to similar convex accumulation profiles for individual acids. In contrast, amino acid accumulation in continuously circulating collection medium was not concentration limited, giving a linear accumulation pattern. The compositions of accumulating amino acids, which were similar to those measured in root extracts, did not change significantly. However, the proportions of ALA, GABA, GLU and ILE in both root extracts and root-derived amino acids increased as plants aged. Older plants released more amino acids per plant, while younger plants released more amino acids g^-1 root DW. Using non-sterile plants, the patterns of change in amino acid concentration and composition in the collection medium were completely different from those determined with sterile plants. In general, with 7-days-old plants, and 60-days-old plants that had recently become non-sterile, an initial rise in the concentration of all acids was followed by a fall to low levels. The loss of amino acids was apparently due to microbial consumption. Individual amino acids attained maximum concentration at different times during the collection process. This is attributed mainly to concentration-dependent differential assimilation of amino acids, since those with the highest initial concentrations, the major components of the mixtures released from roots, declined the earliest. When calculated rates of amino acid release from roots (R_r) and microbial consumption of amino acids (R_c) were compared (for 7-days-old plants), the highest ratios of R_c/R_r were found for ASN, ARG, GLU, GLN, and LYS. This suggests a degree of selectivity for glutamate and nitrogen-rich acids on the part of the consuming micro-organisms. With 21-days old plants and 60-days old plants grown entirely under non-sterile conditions, fluctuations in amino acid concentration were similar for all acids.     

Changes in populations of soil microorganisms,nematodes, and enzyme activity associated with application of powdered pine bark

Evaluation of enzyme activities in combination with taxonomic analyses may help define the mechanisms involved in microbial decomposition of orgaic amendments and biological control of soilborne pathogens. In this study, powdered pine bark was added to nematode-infested soil at rates of 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 g kg^–1. Total fungal populations did not differ among treatments immediately after application of pine bark. After 7 days, fungal populations were positively correlated with increasing levels of pine bark. This increase was sustained through 14 and 21 days.Penicillium chrysogenum andPaecilomves variotii were the predominant fungal species isolated from soil amended with pine bark. Total bacterial populations did not change with addition of pine bark at 0, 7, and 14 days after treatment. At 21 and 63 days, total bacterial populations declined in soil receiving the highest rates of pine bark. Addition of pine bark powder to soil caused a shift in predominant bacterial genera fromBacillus spp. in nonamended soil, toPseudomonas spp. in amended soil. Soil enzyme activities were positively correlated with pine bark rate at all sampling times. Trehalase activity was positively correlated with total fungal populations and with predominant fungal species, but was not related to bacterial populations. The number of non-parasitic (non-stylet bearing) nematodes andMeloidogyne arenaria in soil and roots were not correlated with pine bark rate. However,Heterodera glycines juveniles in roots, and the number of cysts g^–1 root, declined with increasing levels of pine bark.Journal Series Series No. 18-933598 Alabama Agricultural Experiment Station     

Divergent ecology of sympatric clones of the asexual gecko,Lepidodactylus lugubris

We report differences in the thermal biology, elevational, temporal and geographic distributions of sympatric clones of the widespread asexual house gecko, Lepidodactylus lugubris. The two most common L. lugubris clones in Fiji, clones 2NA and 2NB, differ significantly in preferred temperature as measured in a laboratory heat gradient, but were similar in critical thermal maximum and minimum. Significant differences were found in the relative frequency of clones 2NA, 2NB, and a third Fijian clone, clone 3NB, at seven sites along an elevational gradient in Fiji. Clone 2NB was not collected at sites above 235 m, consistent with its higher preferred temperature, whereas clone 2NA was captured as high as 835 m. Clone 3NB was extremely rare at sealevel (1% of all individuals at three sites below 100 m), but predominated at the two highest-elevation sites (42% and 100%). Clones 2NA and 2NB did not differ significantly in their activity time or ambient activity temperature at low-elevation sites. Clone 3NB however, was active on significantly cooler nights at two of those sites. These significant inter-clonal differences in spatial and temporal distribution should allow a more complete utilization of resources by the assemblage of clones than by any single clonal genotype, and may promote coexistence of clones at a within-island and within-site scale. Clone 2NA, which is the most common clone in Fiji and has the broadest elevational distribution, also has the widest geographic distribution. It was the predominant clone at 27 of 34 sites surveyed in nine Pacific archipelagoes. This suggests that the ecological attributes that favor this clone in Fiji also favor it elsewhere in the Pacific despite differing environmental conditions and clonal composition in those areas.     

Identification and inter-relationship analysis of Bradyrhizobium japonicum strains by restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD)

Genomic DNA of 13 Bradyrhizobium japonicum strains was prepared and analysed by restriction fragment length polymorphism (RFLP) with nif and nod probes, and by random amplified polymorphic DNA (RAPD) with 11 primers of arbitrary nucleotide sequence. Polymorphism was observed in both analyses. The RFLP and RAPD banding patterns of different strains were used to calculate genetic divergence and to construct phylogenetic trees, allowing studies on the relationships between the strains. RFLP with nif and nod probes permitted the separation of the strains into two divergent groups, whereas RAPD separated them into four main groups. RAPD allowed closely related strains to be distinguished.     

Cell Lysis Due to Ultrasound Gel In Fine Needle Aspirates; an Important New Artefact In Cytology

An important new artefact in cytopathology is described. the initial observation of the artefact followed contamination of a breast fine needle aspiration (FNA) sample by ultrasound gel which was used to localize the lesion. the changes proved reproducible ex vivo. the changes varied depending on the conditions and degree of contamination, and ranged from cell swelling to leakage of nuclear chromatin and cell lysis. This artefact is discussed in the context of other major sources of cytology artefact. Pathologists and radiologists should beware of the detrimental effects of ultrasound gel on cytology specimens.     

Scrape cytology in the diagnosis of Paget's disease of the breast

Eczema of the nipple is an important symptom presenting to the general surgeon in the out-patient department. the diagnosis of Paget's disease of the nipple has traditionally been made by incision biopsy necessitating at least a local anaesthetic. We present 14 patients with nipple skin change, in whom the technique of scrape cytology was used to identify patients with Paget's disease. In our series eight cases of Paget's disease were successfully identified by scrape cytology with no false negatives or positives. We suggest that this is a quick, easy, non-invasive method of screening eczema of the nipple in the out-patient clinic.     

Reflections on biosystems motivating supramolecular engineering

Some goals of bioelectronics—interfacing biology and electronics — are the understanding of supramolecular bioprocesses and the construction of supramolecular devices. The principles for the design and fabrication of machineries with functional components of molecular size are inspired by reflecting on biosystems, and it seems important to consider such principles. We first discuss attempts to construct supramolecular machines, and then we consider the bacterial reaction centre as an example where supramolecular engineering helps to elucidate a bioprocess. We then discuss possible mechanisms leading to the emergence of life-like systems in the light of the basic principles used to design supramolecular devices. Finally, we reflect on prospects in molecular engineering inspired by studying the emergence of life-like systems.     

Receptor interactions of the position 4 side chains of angiotensin II analogues: Importance of aromatic ring quadrupole

A triad of interacting group (TyrOH? His$ \underline\ominus$O₂C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr⁴ residue in [Sar¹]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar¹ Nva(δ-OH)⁴]ANG II, [Sar¹ Nva(δ-OCH₃)⁴]ANG II, [Sar¹ Met⁴]ANG II, [Sar¹ Gln⁴]ANG II, [Sar¹ Glu⁴]ANG II and [Sar¹ DL -Alg⁴]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar¹ Nal⁴]ANG II, [Sar¹ Pal⁴]ANG II, [Sar¹ DL -Phg(4′-F)⁴]ANG II, [Sar¹ Phe(4′-F)⁴]ANG II, [Sar¹ Phe(F₅)⁴]ANG II and [Sar¹ His⁴]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar¹] Phe(4′-F)⁴ ANG II (pA₂ = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA₂) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity.     

Bats of the Gulf of Guinea islands: faunal composition and origins

The present study compares the bat faunas of the islands of the Gulf of Guinea. Species composition. endemism and hypothetical origins are discussed. All families present in the mainland region are found in Bioko, a typical landbridge island. Foliage gleaning guild species (Nycteridae) show limited colonization abilities. This is also true of the family Rhinolophidae, but not for the closely related family Hipposideridae. The majority of the oceanic island species are African bats which show a widespread distribution and, therefore, have a high ecological plasticity. The continental relatives of the two endemic species Myonycteris brachycephala and Chaerephon tomensis are restricted to relatively small forested areas. Bioko's bat fauna is the result of the recent isolation from a formerly land-connected community. The oceanic bat faunas originated from the establishment of incomers from other areas. Nevertheless, extinction appears in both vicariant and dispersal processes, as an important factor in modelling the current bat communities of the Gulf of Guinea islands.