PERIZONIUM AND INITIAL VALVE FORMATION IN THE DIATOM NAVICULA CUSPIDATA (BACILLARIOPHYCEAE)1

This paper describes the perizonium and initial valve formation in Navicula cuspidata Kütz., based on light microscope (LM) and scanning electron microscope (SEM) observations. The perizonium consists of concentric over-lapping bands, laid down sequentially at the tips of the expanding biconical auxospore during its elongation. The central perizonial band has fimbriate edges and is considerably more rigid than the more distal bands. During auxospore elongation and the band secretion, the chloroplasts continuously oscillate between the two ends of the cell; this oscillation ceases once the elongation is complete. The initial valves, formed within the perizonium, are molded into the basically biconical shape of the perizonium except for a central flattening of each valve face. In contrast to the raphes in gametangial and vegetative valves which are surrounded by a smooth axial area, the raphes in initial valves lie within a raised ridge running along the apical axis of the valve. The regular pattern of apically oriented ridges on the outer surface of vegetative valves is also lacking on initial valves. Comparison of pore–pore spacing within striae of gametangial valves, initial values and post-initial valves (first division and vegetative cells) reveals that the pore–pore distance within striae is conserved at all sexual stages. However, the distance between striae is considerably larger in initial valves than in gametangial and post-initial valves. Vegetative interstriae spacing as well as the planar morphology of the valve face is regained at the first division of the initial cell. This suggests that the spacing between striae is dependent on the sexual stage of the cell during valve formation (i.e. not directly dependent on the cell size) and can be altered independently of the pore–pore spacing.     

Design and applications of a self-aligning liquid junction-electrospray interface for capillary electrophoresis-mass spectrometry

A simple self-aligning liquid junction-electrospray interface for coupling a capillary electrophoresis (CE) system to an atmospheric pressure ionization (API) mass spectrometer (CE-MS) was developed. In contrast to previous liquid junction interfaces, the self-aligning liquid junction interface simplifies the precise alignment of the CE capillary and the sprayer needle and uses a positive make-up flow. Several capillary CE-MS applications were run using both the self-aligning liquid junction interface and the widely used sheath flow interface for comparison purposes. The electrospray stability of the self-aligning liquid junction interface is consistently better even when non-volatile electrolyte solutions are used. At first, some band broadening was obtained with the self-aligning liquid junction interface. Experiments with different CE buffer systems suggested that this band broadening was caused by the materials used in constructing the interface. By using a more inert material for the sprayer needle, the self-aligning liquid junction exhibits excellent electrophoretic resolution, comparable sensitivity, and higher signal-to-noise ratios when run under the same conditions as the sheath flow interface.     

Detection of a 65 kDaras binding protein in rat and sheep brain cytosol using a chemical cross linking agent

The ability of aras protein to associate with proteins present in rat brain cytosolin vitro was investigated using chemical cross-linking agents and the¹²⁵I-labelled v-H-ras protein. Two iodinated protein complexes with apparent molecular weights of 40 and 85 kDa were observed when a mixture of rat brain cytosol and [¹²⁵I]ras was treated with the cross-linking agent disuccinimidyl suberate and subjected to SDS-PAGE. Formation of the [¹²⁵I] 85 kDa complex was enhanced by a high concentration of EDTA while generation of the 40 kDa species was abolished by this treatment. Formation of the [¹²⁵I] 85 kDa complex was inhibited by unlabelledras protein, GTP, GTPS, and GDP but not by ATPS and GMP.Chromatography of the cross-linked brain cytosol-[¹²⁵I]ras mixture on DEAE cellulose partially resolved the [¹²⁵I] 85 kDa complex from the [¹²⁵I]ras protein. The [¹²⁵I] 85 kDa complex (formed using ethyleneglycolbis (succinimidylsuccinate) as the cross-linking agent) could be immunoprecipitated using a rabbit anti-ras polyclonal antibody. Treatment of the immunoprecipitate with hydroxylamine to cleave the cross-link yielded [¹²⁵I]-labelledras. A substantial enrichment of the proportion of the [¹²⁵I] 85 kDa complex in the cross-linked extract was achieved by preparative SDS-PAGE. It is concluded that thein vitro chemical cross-linking approach employed here has detected tworas binding proteins in rat brain cytosol: a 65 kDa heat-sensitive and a 20 kDa heat-stable protein. The possibility that the 65 kDaras binding protein is aras regulatory orras effector protein which has not so far been characterised is briefly discussed.Abbreviations DSS disuccinimidyl suberate - EGS ethyleneglycolbis (succinimidylsuccinate) - GTPS guanosine 5-[-thio] triphosphate - ATPS adenosine 5-[-thio] triphosphate     

Fatty Acid Methyl Ester Profiles for Characterization of Glomalean Fungi and Their Endomycorrhizae

Arbuscule-forming fungi in the order Glomales form obligate endomycorrhizal associations with plants that make them difficult to quantify, and taxonomy of the group is only beginning to be objectively understood. Fatty acid methyl ester (FAME) profiles were analyzed to assess the diversity and quantity of fatty acids in 53 isolates of 24 glomalean species. Spores and endomycorrhizal roots of sudan grass (Sorghum sudanense) and the citrus rootstock Carrizo citrange (Poncirus trifoliata x Citrus sinensis) were examined. Spores yielded reproducible FAME profiles from replicate spore collections extracted from soil pot cultures despite being grown in association with a host plant and with contaminating microorganisms present. Unweighted pair group analysis revealed relatively tight clusters of groups at the intraspecific, specific, and generic levels; however, lipid profiles at the family level were convergent. Thus, FAME profile comparisons provided a robust measure of similarity below the family level. FAME profiles in sudan grass roots containing vesicles and/or spores of Glomus intraradices were more similar to spore profiles than to profiles from nonmycorrhizal roots. The FAME profiles for Gigaspora species, which do not form vesicles or spores in roots, were less distinct from nonmycorrhizal roots. G. intraradices and G. rosea produced fatty acids in roots that were distinguishable from each other as well as from the host root. Production in citrus roots of the fatty acid 16:1(inf(omega)5) cis by two Glomus species was correlated with the development of mycorrhizal colonization as measured by clearing and staining procedures and by estimates of total incidence and vesicle intensity. FAME analysis of roots not only provided a measure of colonization development but also served as an index of carbon allocated to intraradical fungal growth and lipid storage.     

A distance geometry program for determining the structures of small proteins and other macromolecules from nuclear magnetic resonance measurements of intramolecular1H−1H proximities in solution

DISGEO is a new implementation of a distance geometry algorithm which has been specialized for the calculation of macromolecular conformation from distance measurements obtained by two-dimensional nuclear Overhauser enhancement spectroscopy. The improvements include (1) a decomposition of the complete embedding process into two successive, more tractable calculations by the use of “substructures”, (2) a compact data structure for storing incomplete distance information on a structure, (3) a more efficient shortest-path algorithm for computing the triangle inequality limits on all distances from this information, (4) a new algorithm for selecting random metric spaces from within these limits, (5) the use of chirality constraints to obtain good covalent geometry without the use ofad hoc weights or excessive optimization. The utility of the resultant program with nuclear magnetic resonance data is demonstrated by embedding complete spatial structures for the protein basic pancreatic trypsin inhibitor vs all 508 intramolecular, interresidue proton-proton contacts shorter than 4.0 Å that were present in its crystal structure. The crystal structure could be reproduced from this data set to within 1.3 Å minimum root mean square coordinate difference between the backbone atoms. We conclude that the information potentially available from nuclear magnetic resonance experiments in solution is sufficient to define the spatial structure of small proteins.     

Studies with a human plasma-derived immunosuppressive,anti-lymphoma factor

Summary A low-molecular-weight (1,400) factor isolated from a human plasma -globulin concentrate by acid-salt dissociation and ultrafiltration inhibits proliferation of mitogen-stimulated T cells and L1210 leukemia cells. The factor (UM05R) inhibits DNA, RNA, and protein synthesis in sensitive cells, acts in G1 of the cell cycle, and appears to suppress mitogen-responsive T cells without an accessory cell requirement. UM05R activity is enhanced by known cAMP-elevating agents and by sulfhydryl compounds. The results of the present study are consistent with the hypothesis that the plasma-derived agent inhibits lympho-proliferation as a result of elevation of intracellular cAMP.     

On the optimal harvesting of persistent age-structured populations

Summary This paper discusses optimal harvesting policies for age-structured populations harvested with effort independent of age.