Damage and Reproductive Potentials of Pratylenchus brachyurus and P. penetrans on soybean

Damage and reproductive potentials of Pratylenchus brachyurus and P. penetrans on soybean, Glycine max, cvs. Essex, Forrest, and Lee 68, were determined in microplot tests. Cultivar Essex was generally tolerant to P. brachyurus. Yield of Forrest was suppressed linearly with increasing P_i''s in the sandy soil (r = -0.92) and loamy sand soil (r = -0.99). Low to moderate P_i''s in the sandy clay loam gave an increase in yields as compared to plants without nematodes. Yield was not affected by this nematode in muck. Lee 68 was very sensitive to P. penetrans in microplots. Yield vs. P_i was fitted by a quadratic model (r = 0.82) with yield decreasing sharply as P_i''s were increased. The reproduction of both species decreased with increases in P_i. Lee 68 was a good host for P. penetrans, whereas Essex and Forrest were fair to poor hosts for P. brachyurus.     

Assessing the complex sponge microbiota: core,variable and species-specific bacterial communities in marine sponges

Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the world''s oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations.     

Carbohydrate and the cytokine response to 2.5h of running

Nehlsen-Cannarella, S. L., O. R. Fagoaga, D. C. Nieman, D. A. Henson, D. E. Butterworth, R. L. Schmitt, E. M. Bailey, B. J. Warren, A. Utter, and J. M. Davis. Carbohydrate and the cytokineresponse to 2.5 h of running. J. Appl.Physiol. 82(5): 1662-1667, 1997.This randomized,double-blind, placebo-controlled study was designed to determine theinfluence of 6% carbohydrate (C) vs. placebo (P) beverage ingestion oncytokine responses (5 total samples over 9 h) to 2.5 h ofhigh-intensity running (76.7 ± 0.4% maximalO₂ uptake) by 30 experiencedmarathon runners. For interleukin-6 (IL-6), a difference in the patternof change between groups was found, highlighted by a greater increasein P vs. C immediately postrun (753 vs. 421%) and 1.5 h postrun (193 vs. 86%) [F(4,112) = 3.77, P = 0.006]. Forinterleukin-1-receptor antagonist (IL-1ra), a difference in the patternof change between groups was found, highlighted by a greater increasein P vs. C 1.5 h postrun (231 vs. 72%)[F(2,50) = 6.38, P = 0.003]. No significant interaction effects were seen for bioactive IL-6 or IL-1. The immediate postrun plasma glucose concentrations correlated negatively with those of plasma cortisol (r = 0.67, P < 0.001); postrun plasma cortisol (r = 0.70, P < 0.001) and IL-6 levels(r = 0.54, P = 0.003) correlated positively withlevels of IL-1ra. Taken together, the data indicate that carbohydrateingestion attenuates cytokine levels in the inflammatory cascade inresponse to heavy exertion.

     

Alkali cation binding and permeation in the rat organic cation transporter rOCT2

Organic cation transporters of the OCT family mediate downhill transport of organic cations, compatible with carrier, pore, or gate-lumen-gate mechanisms. We studied rat OCT2 expressed in Xenopus oocytes by the two-electrode voltage-clamp technique, including membrane capacitance (C(m)) monitoring. Choline, a transported cationic substrate, elicited the expected inward currents but also elicited decreases of C(m). Similar C(m) decreases were caused by the non-transported inhibitors tetrabutylammonium (a cation) and corticosterone (uncharged). Effects on C(m) were voltage-dependent, with a maximum at -140 mV. These findings suggest that the empty rOCT2 protein can undergo an electrogenic conformation change, with one conformation highly favored at physiological voltage. Moreover, alkali cations elicited considerable inward currents and inhibited uptake of [(14)C]tetraethylammonium with a sequence Cs(+) > Rb(+) > K(+) > Na(+) approximately Li(+). Cs(+) affected current and capacitance with similar affinity (K(0.5) approximately 50 mm). Tetraethylammonium inhibited Cs(+) currents in a concentration-dependent manner. Conversely, Cs(+) inhibited tetraethylammonium uptake by a competitive mechanism. Activation energy of the currents estimated from measurements between 12 degrees C and 32 degrees C was approximately 81 kJ/mol for Cs(+) and 39 kJ/mol for tetramethylammonium, compatible with permeation of Cs(+) through rOCT2 along the same path as organic substrates and by a mechanism different from simple electrodiffusion. Rationalization of Cs(+) selectivity in terms of a pore pointed to a pore diameter of approximately 4 A. Intriguingly, that value matches the known selectivity of rOCT2 for organic compounds. Our data show that selective permeability of rOCT2 is not determined by ligand affinity but might rather be understood in terms of the ion channel concept of a distinct "selectivity filter."     

Transspecific variability of phosphohexose isomerase (E. C.: 5. 3. 1. 9) in primates

Summary The polymorphism of phosphohexose isomerase has been investigated in 428 subhuman Primates. 9 phosphohexose isomerase variants were found to be present. All of these are more negatively charged than the major band of PHI 1, the most common phenotype of human population. The distribution of the various PHI phenotypes has been estimated.

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Zusammenfassung Die Phosphohexoseisomerasen der Primaten zeigen eine genetisch determinierte Variabilität. Bei der Untersuchung von 428 subhumanen Primaten konnten wir 9 PHI-Varianten nachweisen, die stärker negativ geladen sind und daher mehr anodisch wandern als das Isoenzym PHI 1, das bei allen Menschenpopulationen weitaus am häufigsten vorkommt. Sie werden abweichend von der beim Menschen üblichen Nomenklatur als PHI B-J bezeichnet; PHI 1 des Menschen wäre als PHI A in dieses System einzuordnen.

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Supported by the Deutsche Forschungsgemeinschaft.     

The foraging ecology of sympatric marine fish in the genus Embiotoca (Embiotocidae): Importance of foraging behavior in prey size selection

Summary Two locally sympatric temperate marine reef fishes, Embiotoca jacksoni and E. lateralis (Embiotocidae), have high taxonomic similarity in diets. Subdivision of gammarid amphipods, their principal prey, was found. E. jacksoni took more tubicolous gammarid amphipods whereas E. lateralis consumed mostly free-living individuals. The species differed considerably with respect to between-individual variability in taxonomic compositions of their diets. Each E. jacksoni closely resembled other conspecifics in this regard while individual E. lateralis displayed very high between-fish variation. The principal interspecific difference in fish diets concerned the sizes of prey items taken. E. jacksoni ate small but very common items and the mean prey weight in their guts did not differ from random collections of available prey. E. lateralis concentrated on large, rarer sizes such that the average prey weight in their guts was much heavier than available or in the diet of E. jacksoni of the same length. Disparate foraging behaviors was a much better indicator of the relative differences in diets of these two fishes than was external fish morphology. E. jacksoni, which can winnow prey items from unwanted debris, was a relatively indiscriminant forager. E. lateralis did not winnow but actively searched for prey. This species was a much more discriminating forager, but displayed much variability in foraging behavior.     

Cutting edge: TGF-beta signaling is required for the in vivo expansion and immunosuppressive capacity of regulatory CD4+CD25+ T cells

Data regarding the role of TGF-beta for the in vivo function of regulatory CD4(+)CD25(+) T cells (Treg) are controversial. A transgenic mouse model with impaired TGF-beta signaling specifically in T cells was used to assess the role of endogenous TGF-beta for the in vivo function of CD4(+)CD25(+) Treg in a murine model of colitis induced by dextran sulfate. Transfer of wild-type, but not transgenic CD4(+)CD25(+) Treg was found to suppress colitis in wild-type mice. In addition, by transferring CFSE-labeled CD4(+)CD25(+) Treg we could demonstrate that endogenous TGF-beta promotes the expansion of CD4(+)CD25(+) Treg in vivo. Transgenic mice themselves developed reduced numbers of peripheral CD4(+)CD25(+) Treg and were more susceptible to the induction of colitis, which could be prevented by the transfer of wild-type Treg. These data indicate that TGF-beta signaling in CD4(+)CD25(+) Treg is required for their in vivo expansion and suppressive capacity.     

A recessive C-terminal Jervell and Lange-Nielsen mutation of the KCNQ1 channel impairs subunit assembly

The LQT1 locus (KCNQ1) has been correlated with the most common form of inherited long QT (LQT) syndrome. LQT patients suffer from syncopal episodes and high risk of sudden death. The KCNQ1 gene encodes KvLQT1 alpha-subunits, which together with auxiliary IsK (KCNE1, minK) subunits form IK(s) K(+) channels. Mutant KvLQT1 subunits may be associated either with an autosomal dominant form of inherited LQT, Romano-Ward syndrome, or an autosomal recessive form, Jervell and Lange-Nielsen syndrome (JLNS). We have identified a small domain between residues 589 and 620 in the KvLQT1 C-terminus, which may function as an assembly domain for KvLQT1 subunits. KvLQT1 C-termini do not assemble and KvLQT1 subunits do not express functional K(+) channels without this domain. We showed that a JLN deletion-insertion mutation at KvLQT1 residue 544 eliminates important parts of the C-terminal assembly domain. Therefore, JLN mutants may be defective in KvLQT1 subunit assembly. The results provide a molecular basis for the clinical observation that heterozygous JLN carriers show slight cardiac dysfunctions and that the severe JLNS phenotype is characterized by the absence of KvLQT1 channel.     

Functional and phenotypic analysis of thymic CD34+CD1a- progenitor-derived dendritic cells: predominance of CD1a+ differentiation pathway

Whether thymic dendritic cells (DC) are phenotypically and functionally distinct from the monocyte lineage DC is an important question. Human thymic progenitors differentiate into T, NK, and DC. The latter induce clonal deletion of autoreactive thymocytes and therefore might be different from their monocyte-derived counterparts. The cytokines needed for the differentiation of DC from thymic progenitors were also questioned, particularly the need for GM-CSF. We show that various cytokine combinations with or without GM-CSF generated DC from CD34+CD1a- but not from CD34+CD1a+ thymocytes. CD34+ thymic cells generated far fewer DC than their counterparts from the cord blood. The requirement for IL-7 was strict whereas GM-CSF was dispensable but nonetheless improved the yield of DC. CD14+ monocytic intermediates were not detected in these cultures unless macrophage-CSF (M-CSF) was added. Cultures in M-CSF generated CD14-CD1a+ DC precursors but also CD14+CD1a- cells. When sorted and recultured in GM-CSF, CD14+ cells down-regulated CD14 and up-regulated CD1a. TNF-alpha accelerated the differentiation of progenitors into DC and augmented MHC class II transport to the membrane, resulting in improved capacity to induce MLR. The trafficking of MHC class II molecules was studied by metabolic labeling and immunoprecipitation. MHC class II molecules were transported to the membrane in association with invariant chain isoforms in CD14+ (monocyte)-derived and in CD1a+ thymic-derived DC but not in monocytes. Thus, thymic progenitors can differentiate into DC along a preferential CD1a+ pathway but have conserved a CD14+ maturation capacity under M-CSF. Finally, CD1a+-derived thymic DC and monocyte-derived DC share very close Ag-processing machinery.