Evidence of active NADP(+) phosphatase in dormant seeds of Avena sativa L

Freshly-harvested seeds of Avena sativa L. do not germinate when imbibed at temperatures higher than 25 degrees C. This high temperature dormancy is due to the seed coats, and to the low activities of glycolysis and the oxidative pentose phosphate pathway (OPP) in the embryo. The analysis by exclusion chromatography of soluble NADP(+) phosphatase activities of embryos revealed two isoforms: a 37 kDa isoform present in both dormant and after-ripened caryopses, and a second isoform, with an apparent molecular weight of 160 kDa, five times more active in embryos of dormant seeds than in the after-ripened ones, after 6 h of imbibition at 30 degrees C. Moreover, the activity of this 160 kDa isoform was three times less in embryos from dormant caryopses when they were grown at 10 degrees C, a permissive temperature for radicle protrusion. These results suggest a correlation between the activity of the 160 kDa NADP(+) phosphatase and the dormancy state of the caryopsis. The two isoforms differed in the pH required for optimal activity: pH 5.7 and 6.5 for the 37 kDa and the 160 kDa phosphatases, respectively. Furthermore, the 160 kDa NADP(+) phosphatase displayed a strong specificity for NADP(+), whereas the 37 kDa isoform was able to hydrolyse numerous other phosphorylated compounds.     

Feeding, growth, and fecundity of Abarenicola pacifica in relation to sediment organic concentration

For marine deposit-feeding invertebrates, the distribution of species with different life history strategies has long been known to be correlated with sediment organic concentration. Large populations of opportunistic species are found in sediments with enriched organic concentration, while equilibrium species populate low organic concentration sediments. Differences in both behavioral (e.g. feeding rate) and physiological (e.g. growth rate, reproductive output) adaptations determine the ability of species to establish populations in different environments. By systematically documenting differences in the way these factors vary as sediment organic concentration varies for both opportunistic and equilibrium species, we can better understand the mechanisms underlying this correlation between sediment organic concentration and species distributions. Here, we present the results of experiments examining the interactions among food concentration, feeding rate, growth rate, and reproductive output (measured as egg number and size) for the equilibrium species Abarenicola pacifica. A. pacifica is a large, long-lived, iteroparous, sub-surface deposit-feeding polychaete. Individual worms were reared throughout most of one generation in sediments differing only in the concentration of organic matter. Juveniles (<20 mg AFDW) had higher feeding rates and growth rates in sediments of higher organic concentration throughout the range tested. These results are consistent with the predictions from optimal foraging theory. As worms grew, however, these patterns changed. Once worms reached a mean body size of approximately 50 mg AFDW, feeding rate was greater on sediments of lower organic concentration (although it took worms in the sediments with lower organic concentration longer to reach this size). Differences in growth rates among treatments decreased as worms grew. For worms >100 mg AFDW, growth rates were uniformly low ( approximately 1%/day) on all sediments, but the early advantage obtained by worms in the high organic treatments resulted in much greater body sizes after 200 days. Worms had higher tissue triacylglyceride concentrations and produced more eggs (independent of worm size) as sediment organic concentration increased. We conclude that A. pacifica alters its feeding rate in response to variations in food resources in such a way as to maximize its energy intake and thereby maximize fitness. Future studies should investigate whether opportunistic species (as well as other equilibrium species) also have this ability.     

Differential response of soybean (Glycine max (L.) Merr.) genotypes to lipo-chito-oligosaccharide Nod Bj V (C(18:1) MeFuc)

Lipo-chito-oligosaccharides (LCOs) are bacteria-to-plant signal molecules essential for the establishment of rhizobia-legume symbioses. LCOs invoke a number of physiological changes in the host plants, such as root hair deformation, cortical cell division and ontogeny of complete nodule structures. The responses of five soybean cultivars to Nod BJ: V (C(18:1) MeFuc) isolated from Bradyrhizobium japonicum strain 532C were studied with a new technique. Two distinct types of root hair deformation were evident (i) bulging, in which root hairs were swollen at the tip or at the base depending on the cultivars and (ii) curling. The nodulating capacity of B. japonicum 532C varied among cultivars. Cultivars that produced a bulging reaction when treated with LCO had fewer nodules and the roots had low phenol contents. Cultivars that produced curling had higher numbers of nodules and the roots had higher amounts of phenol. Further, the roots of cultivars that showed root hair bulging were able to degrade LCO much faster than cultivars that manifested curling. The results of the present study establish relationships among the type of LCO-induced root hair deformation, root system LCO-degrading ability and nodulation capacity of soybean cultivars.     

Tissue steroid sulfatase levels, testosterone and blood pressure

The objective of this study was to examine the response of tissue steroid sulfatase (STS) levels in hypertensive rat strains, when blood pressure (BP) was lowered by different techniques at an early age. A 4×3 factoral design was used, in which males (n=6–8) from four rat strains (WKY, SHR, SHR/a, SHR/y) at 4 weeks of age, were randomly assigned to one of three treatment groups: a hydralazine group, a castration group and a control group. BP was measured by the tail cuff technique and verified by tail catheter at the end of the experiment. BP was significantly reduced by both treatments in the hypertensive strains (SHR, SHR/a, SHR/y) compared to respective control groups. At 15–17 weeks of age, animals were euthanized and heart, kidney, adrenal glands and liver were assayed for STS levels. The major trend in tissue STS was that castration significantly lowered: adrenal, heart and liver STS in specific strains. In conclusion, castration and hydralazine significantly lowered the BP in the hypertensive rat strains, but only castration consistently lowered STS levels across strains implicating testosterone as a regulator of tissue STS.     

A non-invasive method for measuring preimplantation embryo physiology

The physiology of the early embryo may be indicative of embryo vitality and therefore methods for non-invasively monitoring physiological parameters from embryos could improve preimplantation diagnoses. The self-referencing electrophysiological technique is capable of non-invasive measurement of the physiology of individual cells by monitoring the movement of ions and molecules between the cell and the surrounding media. Here we use this technique to monitor gradients of calcium, potassium, oxygen and hydrogen peroxide around individual mouse preimplantation embryos. The calcium-sensitive electrode in self-referencing mode identified a region of elevated calcium concentration (approximately 0.25 pmol) surrounding each embryo. The calcium gradient surrounding embryos was relatively steep, such that the region of elevated calcium extended into the medium only 4 microns from the embryo. By contrast, using an oxygen-sensitive electrode an extensive gradient of reduced dissolved oxygen concentration was measured surrounding the embryo and extended tens of micrometres into the medium. A gradient of neither potassium nor hydrogen peroxide was observed around unperturbed embryos. We also demonstrate that monitoring the physiology of embryos using the self-referencing technique does not compromise their subsequent development. Blastocyts studied with the self-referencing technique implanted and developed to term at the same frequency as did unexamined, control embryos. Therefore, the self-referencing electrode provides a valuable non-invasive technique for studying the physiology and pathophysiology of individual embryos without hindering their subsequent development.     

KGF pretreatment decreases B7 and granzyme B expression and hastens repair in lungs of mice after allogeneic BMT

We investigated keratinocyte growth factor (KGF) as a pretreatment therapy for idiopathic pneumonia syndrome (IPS) generated as a result of lung damage and allogeneic T cell-dependent inflammatory events occurring in the early peri-bone marrow (BM) transplant (BMT) period. B10.BR (H2(k)) recipient mice were transplanted with C57BL/6 (H2(b)) BM with spleen cells after lethal irradiation with and without cyclophosphamide conditioning with and without subcutaneous KGF pretreatment. KGF-pretreated mice had fewer injured alveolar type II (ATII) cells at the time of BMT and exhibited ATII cell hyperplasia at day 3 post-BMT. The composition of infiltrating cells on day 7 post-BMT was not altered by KGF pretreatment, but the frequencies of cells expressing the T-cell costimulatory molecules B7.1 and B7.2 and mRNA for the cytolysin granzyme B (usually increased in IPS) were decreased by KGF. Sera from KGF-treated mice had increases in the Th2 cytokines interleukin (IL)-4, IL-6, and IL-13 4 days after cessation of KGF administration (i.e., at the time of BMT). These data suggest that KGF hinders IPS by two modes: 1) stimulation of alveolar epithelialization and 2) attenuation of immune-mediated injury as a consequence of failure to upregulate cytolytic molecules and B7 ligand expression and the induction of anti-inflammatory Th2 cytokines in situ.     

Glutathione depletion inhibits IL-1 beta-stimulated nitric oxide production by reducing inducible nitric oxide synthase gene expression

L-buthionine-S,R-sulfoximine (BSO), an inhibitor of GSH synthesis, decreased IL-1 beta-induced nitrite release in rat islets and purified rat beta cells, nitrite formation and iNOS gene promoter activity in insulinoma cells, and iNOS mRNA expression in rat islets. The thiol depletor diethyl maleate (DEM) and an inhibitor of glutathione reductase 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) reduced IL-1 beta-stimulated nitrite release in islets. We conclude that GSH regulates IL-1 beta-induced NO production in islets, purified beta cells and insulinoma cells by modulation of iNOS gene expression.     

Preliminary X-ray crystallographic and NMR studies on the exonuclease domain of the epsilon subunit of Escherichia coli DNA polymerase III

The structured core of the N-terminal 3'-5' exonuclease domain of epsilon, the proofreading subunit of Escherichia coli DNA polymerase III, was defined by multidimensional NMR experiments with uniformly (15)N-labeled protein: it comprises residues between Ile-4 and Gln-181. A 185-residue fragment, termed epsilon(1-185), was crystallized by the hanging drop vapor diffusion method in the presence of thymidine-5'-monophosphate, a product inhibitor, and Mn(2+) at pH 5.8. The crystals are tetragonal, with typical dimensions 0.2 mm x 0.2 mm x 1.0 mm, grow over about 2 weeks at 4 degrees C, and diffract X-rays to 2.0 A. The space group was determined to be P4(n)2(1)2 (n = 0, 1, 2, 3), with unit cell dimensions a = 60.8 A, c = 111.4 A.