Population Dynamics and Damage Potential of Meloidogyne hapla to Rose Rootstock Species

The relationship between initial population densities (Pi) of Meloidogyne hapla on growth of three rose rootstocks (Rosa corymbifera ‘Laxa’, R. multiflora and R. canina ‘Inermis’) and nematode population development was studied. Each plant species was inoculated with ranges of nematode densities of 0, 0.062, 0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 32, 64 and 128 second‐stage juvenile/g soil and were allowed to grow for 9 weeks. Seinhorst yield model was fitted to total fresh biomass data of the rootstocks. The tolerance limits (T) were 0.04, 0.09 and 0.01 J2/g soil and the minimum yield (m) 0.65, 0.47 and 0.43 for R. corymbifera ‘Laxa’, R. multiflora and R. canina ‘Inermis’, respectively. The reproductive factor (Pf/Pi) was highest at low initial nematode densities for all rootstocks and then decreased to below maintenance level with increasing initial population densities. Root gall severity consistently increased with initial nematode population density. Furthermore, number of root galling showed a strong positive relationship with final nematode population per gram root fresh weight. The relation between Pi and Pf was also fitted to the Seinhorst population model (Pf = (M*Pi)/Pi + M/a). Rosa multiflora supported the population of M. hapla to a maximum population density (M) of 27.53 J2/g soil with an estimated average maximum multiplication rate (a) of 24.39. For R. corymbifera ‘Laxa’ and R. canina, the maximum multiplication rate was 4.34 and 3.62 and the maximum population density 6.08 and 4.78 J2/g dry soil, respectively. Hence, it was demonstrated that all three rootstocks were susceptible to even low initial nematode densities and therefore are considered good hosts for M. hapla.     

Recent pulsed EPR studies of the photosystem II oxygen-evolving complex: implications as to water oxidation mechanisms

The pulsed electron paramagnetic resonance (EPR) methods of electron spin echo envelope modulation (ESEEM) and electron spin echo-electron nuclear double resonance (ESE-ENDOR) are used to investigate the structure of the Photosystem II oxygen-evolving complex (OEC), including the paramagnetic manganese cluster and its immediate surroundings. Recent unpublished results from the pulsed EPR laboratory at UC-Davis are discussed, along with aspects of recent publications, with a focus on substrate and cofactor interactions. New data on the proximity of exchangeable deuterons around the Mn cluster poised in the S(0)-state are presented and interpreted. These pulsed EPR results are used in an evaluation of several recently proposed mechanisms for PSII water oxidation. We strongly favor mechanistic models where the substrate waters bind within the OEC early in the S-state cycle. Models in which the O-O bond is formed by a nucleophilic attack by a Ca(2+)-bound water on a strong S(4)-state electrophile provide a good match to the pulsed EPR data.     

Octreotide represses secretory-burst mass and nonpulsatile secretion but does not restore event frequency or orderly GH secretion in acromegaly

Octreotide is a potent somatostatin analog that inhibits growth hormone (GH) release and restricts somatotrope cell growth. The long-acting octreotide formulation Sandostatin LAR is effective clinically in approximately 60% of patients with acromegaly. Tumoral GH secretion in this disorder is characterized by increases in pulse amplitude and frequency, nonpulsatile (basal) release, and irregularity. Whether sustained blockade by octreotide can restore physiological secretion patterns in this setting is unknown. To address this question, we studied seven patients with GH-secreting tumors during chronic receptor agonism. Responses were monitored by sampling blood at 10-min intervals for 24 h, followed by analyses of secretion and regularity by multiparameter deconvolution and approximate entropy (ApEn). The somatostatin agonist suppressed GH secretory-burst mass, nonpulsatile (basal) GH release, and pulsatile secretion, thereby decreasing total GH secretion by 86% (range 70-96%). ApEn decreased from 1.203 +/- 0.129 to 0.804 +/- 0.141 (P = 0.032), denoting greater regularity. None of GH pulse frequency, basal GH secretion rates, or ApEn normalized. In summary, chronic somatostatin agonism is able to repress amplitude-dependent measures of excessive GH secretion in acromegaly. Presumptive tumoral autonomy is inferred by continued elevations of event frequency, overall pattern disruption (irregularity), and nonsuppressible basal GH secretion.     

On-line immunoanalysis of monoclonal antibodies during a continuous culture of hybridoma cells

The monoclonal-antibody production of an immobilized hybridoma cell line cultivated in a fluidized-bed reactor was monitored on-line for nearly 900 h. The monoclonal antibody concentration was determined by an immuno affinity-chromatography method (ABICAP). Antibodies directed against the product, e.g. IgG, were immobilized on a micro-porous gel and packed in small columns. After all IgG present in the sample was bound to the immobilized antibodies, unbound proteins were removed by rinsing the column. Elution of the bound antibodies followed and the antibodies were determined by fluorescence. The analytical procedure was automated with a robotic device to enable on-line measurements. The correlation between the on-line determined data and antibody concentrations measured by HPLC was linear. A sampling system was constructed, which was based on a pneumatically actuated in-line membrane valve integrated into the circulation loop of the reactor. Separation of the cells from the sample stream was achieved by a depth filter made of glass-fibre, situated outside the reactor. Rapid obstruction of the filter by cells or cell debris and contamination of the sample system was avoided by intermittent rinsing of the sample system with a chemical solution. The intermittent rinsing of the filter, which had a surface of 4.8 cm², resulted in an operational capacity of up to 40 samples (1.0 l total sample volume). Both the sampling system and the analytical device functioned without failure during this long-term culture. The culture temperature was varied between 34 and 40 °C. Raising the temperature from 34 up to 37 °C resulted in a simultaneous increase of growth and specific antibody production rate. Specific metabolic rates of glucose, lactate, glutamine and ammonium stayed constant in this temperature range. A further enhancement of temperature up to 40 °C had a negative effect on the growth rate, whereas the specific monoclonal antibody production rate showed a small increase. The other specific metabolic rates also increased in the temperature range between 38 to 40 °C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of salt concentration and temperature on the fatty acid compositions of Ectothiorhodospira and other halophilic phototrophic purple bacteria

Influences of the salt concentration on the fatty acid composition of Ectothiorhodospira species and other phototrophic purple bacteria have been analysed. Major fatty acids in bacteria of the genera Rhodobacter, Rhodopseudomonas, Chromatium, and Ectothiorhodospira were straight chain saturated and monounsaturated C-16 and C-18 fatty acids. Salt-dependent responses of all investigated bacteria revealed relations to their salt optima. Minimum values of C-16 and saturated fatty acids and maximum values of C-18 and unsaturated fatty acids were found at or close to the salt optima. Responses of Ectothiorhodospira mobilis upon changes in salinity were nearly identical, whether cells were grown in batch culture or in continuous culture with identical dilution rates at all salt concentrations. With increasing temperature, the fatty acid composition of Ectothiorhodospira mobilis and Ectothiorhodospira halophila strains showed decreasing portions of C-18 and of unsaturated fatty acids, while the contents of C-16 and saturated fatty acids increased. The results are discussed with respect to bilayer stabilisation and membrane fluidity.Abbreviations PC phosphatidylcholine - PG phosphatidylglycerol - CL cardiolipin - PE phosphatidylethanolamine     

Scavenger receptor CD36 mediates uptake of high density lipoproteins in mice and by cultured cells

The mechanisms of HDL-mediated cholesterol transport from peripheral tissues to the liver are incompletely defined. Here the function of scavenger receptor cluster of differentiation 36 (CD36) for HDL uptake by the liver was investigated. CD36 knockout (KO) mice, which were the model, have a 37% increase (P = 0.008) of plasma HDL cholesterol compared with wild-type (WT) littermates. To explore the mechanism of this increase, HDL metabolism was investigated with HDL radiolabeled in the apolipoprotein (¹²⁵I) and cholesteryl ester (CE, [³H]) moiety. Liver uptake of [³H] and ¹²⁵I from HDL decreased in CD36 KO mice and the difference, i. e. hepatic selective CE uptake ([³H]¹²⁵I), declined (–33%, P = 0.0003) in CD36 KO compared with WT mice. Hepatic HDL holo-particle uptake (¹²⁵I) decreased (–29%, P = 0.0038) in CD36 KO mice. In vitro, uptake of ¹²⁵I-/[³H]HDL by primary liver cells from WT or CD36 KO mice revealed a diminished HDL uptake in CD36-deficient hepatocytes. Adenovirus-mediated expression of CD36 in cells induced an increase in selective CE uptake from HDL and a stimulation of holo-particle internalization. In conclusion, CD36 plays a role in HDL uptake in mice and by cultured cells. A physiologic function of CD36 in HDL metabolism in vivo is suggested.     

Pulsation of nuclei in insect oocytes is reversibly inhibited by cytochalasin B

Oocyte nuclei of the dipteran insect Heteropeza pygmaea display swift pulsating movements during in vitro follicle formation in the ovaries. Low doses of cytochalasin B (CB) completely inhibit the nuclear movements within a few minutes and cause the nuclei to assume spherical shapes. If the drug is removed, nuclear pulsation is resumed within 5–10 min. Phalloidin and colchicine do not affect the nuclear movements. Actin is shown by indirect immunofluorescence microscopy to be present in considerable amounts all over the cytoplasm of the oocytes. It is concluded that microfilaments are responsible for pulsation of the oocyte nuclei, whereas microtubules are not involved.     

Dissimilatory iron reduction in Escherichia coli: identification of CymA of Shewanella oneidensis and NapC of E. coli as ferric reductases

Over geological time scales, microbial reduction of chelated Fe(III) or Fe(III) minerals has profoundly affected today's composition of our bio- and geosphere. However, the electron transfer reactions that are specific and defining for dissimilatory iron(III)-reducing (DIR) bacteria are not well understood. Using a synthetic biology approach involving the reconstruction of the putative electron transport chain of the DIR bacterium Shewanella oneidensis MR-1 in Escherichia coli , we showed that expression of cymA was necessary and sufficient to convert E. coli into a DIR bacterium. In intact cells, the Fe(III)-reducing activity was limited to Fe(III) NTA as electron acceptor. In vitro biochemical analysis indicated that CymA, which is a cytoplasmic membrane-associated tetrahaem c -type cytochrome, carries reductase activity towards Fe(III) NTA, Fe(III) citrate, as well as to AQDS, a humic acid analogue. The in vitro specific activities of Fe(III) citrate reductase and AQDS reductase of E. coli spheroplasts were 10× and 30× higher, respectively, relative to the specific rates observed in intact cells, suggesting that access of chelated and insoluble forms of Fe(III) and AQDS is restricted in whole cells. Interestingly, the E. coli CymA orthologue NapC also carried ferric reductase activity. Our data support the argument that the biochemical mechanism of Fe(III) reduction per se was not the key innovation leading to environmental relevant DIR bacteria. Rather, the evolution of an extension of the electron transfer pathway from the Fe(III) reductase CymA to the cell surface via a system of periplasmic and outer membrane cytochrome proteins enabled access to diffusion-impaired electron acceptors.