Attenuation of baroreflex sensitivity after domoic acid lesion of the nucleus ambiguus of rats.

The nucleus ambiguus (NA) and the dorsal motor nucleus of the vagus (DmnX) innervate distinct populations of cardiac ganglionic principal neurons. This anatomic evidence suggests that these two nuclei play different roles (Cheng Z and Powley TL, Soc Neurosci Abstr 26: 1189, 2000). However, lesion of the DmnX does not attenuate baroreflex sensitivity (Cheng Z, Guo SZ, Lipton AJ, and Gozal D, J Neurosci 22: 3215-3226, 2002). The present study tested the functional role of the NA in baroreflex control of heart rate (HR). Domoic acid (DA) was injected into the left NA of Sprague-Dawley rats to lesion the NA. The neuronal loss was assessed using retrograde labeling and confocal microscopy. HR changes induced by phenylephrine and sodium nitroprusside administration and after electrical stimulation of the left vagal trunk were measured at 15 days, and HR responses to left NA microinjection of L-glutamate were determined at 180 days postlesion. Compared with vehicle injections, DA lesions significantly reduced the population of NA motor neurons by approximately 68% (P < 0.01) and attenuated baroreflex sensitivity by approximately 83% (P < 0.01) at 15 days. Similarly, electrical stimulation of the vagal trunk of DA-lesioned animals led to attenuated decreases in HR responses. NA neuronal counts were reduced by approximately 81% (P < 0.01) and mean HR responses to l-glutamate injection into the lesioned NA were attenuated by approximately 65% (P < 0.01) at 180 days. Therefore, the NA plays a major role in baroreflex control of HR, and the integrity of the NA is critically important for the normal baroreflex control. In addition, NA lesions produce long-term anatomic and functional dysfunction of the nucleus, and thus it may provide an useful model for functional assessment of respective roles of the NA and DmnX.     

Molecular genetic linkage maps for allotetraploid Leymus wildryes (Gramineae: Triticeae).

Molecular genetic maps were constructed for two full-sib populations, TTC1 and TTC2, derived from two Leymus triticoides x Leymus cinereus hybrids and one common Leymus triticoides tester. Informative DNA markers were detected using 21 EcoRI-MseI and 17 PstI-MseI AFLP primer combinations, 36 anchored SSR or STS primer pairs, and 9 anchored RFLP probes. The 164-sib TTC1 map includes 1069 AFLP markers and 38 anchor loci in 14 linkage groups spanning 2001 cM. The 170-sib TTC2 map contains 1002 AFLP markers and 36 anchor loci in 14 linkage groups spanning 2066 cM. Some 488 homologous AFLP loci and 24 anchor markers detected in both populations showed similar map order. Thus, 1583 AFLP markers and 50 anchor loci were mapped into 14 linkage groups, which evidently correspond to the 14 chromosomes of allotetraploid Leymus (2n = 4x = 28). Synteny of two or more anchor markers from each of the seven homoeologous wheat and barley chromosomes was detected for 12 of the 14 Leymus linkage groups. Moreover, two distinct sets of genome-specific STS markers were identified in these allotetraploid Leymus species. These Leymus genetic maps and populations will provide a useful system to evaluate the inheritance of functionally important traits of two divergent perennial grass species.     

Nitrogen oxide emissions following wetting of dry soils in forest and pastures in Rondônia, Brazil

Rains at the end of the dry season can trigger increases in emissions of nitric oxide (NO) and nitrous oxide from forest and pasture soils in the Amazon Basin. The relative importance of the rain-stimulated emissions in the seasonal and annual budgets of these nitrogen gases for forests and pastures in the western Amazon is not well established. We measured soil emissions of NO and N₂O from a forest and two pastures, 11 and 26 years old, after a simulated rain event. Wetting the soil resulted in very small pulses of NO or N₂O from forest soils and no significant NO or N₂O pulses from the pastures. We estimated that in the forest, the amounts of each gas emitted from pulses during the dry to wet transition period represented 3.4% of the NO and 1.8% of the N₂O dry-season emissions, but amounted to less than 2% of the annual emissions of either gas. Total N oxide emissions of 5.6 kg N/ha/yr from the forest were nearly evenly divided between NO (42%) and N₂O (58%). The emissions of NO were evenly distributed over the wet and dry seasons, while over 84% N₂O fluxes occurred during the wet season.     

An insertion sequence unique to Frankia strain ArI5

At the genetic level, understanding of symbiotic nitrogen fixation by Frankia is limited to nif functions that are highly conserved among all organisms. The genetics and biochemistry of nodulation are largely unexplored because of a complete lack of genetic tools. In other bacteria, mobile genetic elements such as insertion sequences (IS) and transposons are commonly used to create mutations and insert new genetic material. We have characterized a 4 kbp segment of DNA from Frankia strain ArI5 that has the hallmarks of a mobile genetic element, inverted repeats flanking a gene encoding a transposase. There are at least six copies of this element in strain ArI5 but none in either strain CcI3 or CpI1. The inverted repeats are 17 nt long and separated by 2156 bp. Within that region are two, overlapping ORFs that each encode a transposase. RT-PCR analysis of RNA from Frankia ArI5 cells conclusively demonstrates the expression of one transposase gene and suggests that both may be transcribed. Numerous attempts to clone the intact IS in E. coli were unsuccessful suggesting that the element may be unstable in this context. A clone containing the complete IS was constructed in E. coli then modified by insertion of the kanamycin (KAN) resistance gene from Tn5. A fragment of DNA including the inverted repeats, transposase genes and KAN gene, was transferred to the suicide vector pJBSD1. The construct, pFRISK, was transformed into E. coli to search for transposition events.     

Profiling with structural elucidation of the neutral and anionic O-linked oligosaccharides in the egg jelly coat of Xenopus laevis by Fourier transform mass spectrometry

A strategic method with high speed and sensitivity is outlined for the analysis of mucin-type oligosaccharide from the jelly coat of Xenopus laevis. The method relies primarily on mass spectrometric techniques, in this case matrix-assisted laser desorption/ionization Fourier-transform mass spectrometry (MALDI-FTMS) and collision-induced dissociation (CID). Separation with isolation of the oligosaccharides was streamlined to couple well with mass spectrometry allowing the rapid determination of all detectable components from both neutral and anionic species. Partial structures of anionic components, composed primarily of sulfate esters, were obtained with CID. For neutral species, a method that allowed the complete structural determination using mass spectrometry was used. The method builds on the structure of small number of known compounds to determine unknown structures from the same biological source. In this example, a small number of oligosaccharides, elucidated previously by NMR, were used to develop a set of substructural motifs that were characterized by CID. The presence of the motifs in the CID spectra were then used to determine the structures of unknown compounds that were in abundances too small for NMR analysis.     

β-Chemokines Are Produced in Lungs of Mice with Mycoplasma Respiratory Disease

The abilities of Bacillus polymyxa and Bacillus thuringiensis to survive on the rice phyllospere were compared; it was found that B. polymyxa colonizes the crop better. This study also showed that B. polymyxa inoculation to rice plants increased the shoot and the root growth of the crop. Efforts were made to introduce the cry1Ac gene of B. thuringiensis subsp. kurstaki into B. polymyxa so that the application of such transgenic B. polymyxa strains would prove to be dually beneficial to rice crops both as a biopesticide and as a biofertilizer. Immunoblot analysis of the recombinant organism containing the cry1Ac gene, strain BP113, indicated efficient expression of this gene in the heterologous host. Bioassays with the first instar larvae of the yellow stem borer of rice (Scirpophaga incertulas) revealed that the protein preparations from BP113 were toxic. Received: 12 August 1998 / Accepted: 25 September 1998     

大麦初生叶中质外体的蛋白、酯酶和苹果酸脱氢酶同工酶(英文)

把6天株龄的大麦(Hordeum vylgare L.)初生叶的下表皮剥去后,以含pH6.5的200mmol/L NaCl缓冲液真空渗洗叶片36min,获得的细胞间隙洗液含有水溶性或弱离子结合态的质外体蛋白质和酶。渗洗过的叶片用缓冲液磨成匀浆和离心后,上清液含原质体蛋白质和酶。用1mmol/L NaCl可溶解离子结合态的质外体蛋白质和酶,两条(25和31kD)和7条(22,28,30,51,55,60和71kD)蛋白质带只分别在含有200mmol/L和1mmol/L NaGl的质外体提取液中测得。机械创伤诱导两条(32和33kD)可溶于200mmol/L NaCl的质外体蛋白带,在质外体还测到3条可溶于200mmol/L NaCl和4条可溶于1mmol/L NaCl的苹果酸脱氢酶同工酶。在质外体和共质体两部分均发现有酯酶Ⅰ同工酶,但移向阴极的酯酶同工酶Ⅰ只见于溶在200mmol/L NaCl的质外体中。移向阳极的酯酶Ⅱ同工酶仅见于共质体中。     

Immunomodulatory effects of Streptococcus suis capsule type on human dendritic cell responses, phagocytosis and intracellular survival

Streptococcus suis is a major porcine pathogen of significant commercial importance worldwide and an emerging zoonotic pathogen of humans. Given the important sentinel role of mucosal dendritic cells and their importance in induction of T cell responses we investigated the effect of different S. suis serotype strains and an isogenic capsule mutant of serotype 2 on the maturation, activation and expression of IL-10, IL-12p70 and TNF-α in human monocyte-derived dendritic cells. Additionally, we compared phagocytosis levels and bacterial survival after internalization. The capsule of serotype 2, the most common serotype associated with infection in humans and pigs, was highly anti-phagocytic and modulated the IL-10/IL-12 and IL-10/TNF-α cytokine production in favor of a more anti-inflammatory profile compared to other serotypes. This may have consequences for the induction of effective immunity to S. suis serotype 2 in humans. A shielding effect of the capsule on innate Toll-like receptor signaling was also demonstrated. Furthermore, we showed that 24 h after phagocytosis, significant numbers of viable intracellular S. suis were still present intracellularly. This may contribute to the dissemination of S. suis in the body.     

Ascorbic acid catabolism by gut microflora: studies in germ-free and conventional guinea pigs

The role of gut microflora in ascorbic acid catabolism was investigated in both conventional and germ-free guinea pigs. In vitro studies demonstrated extensive degradation of the vitamin by fresh feces, cecal, and colonic contents of conventional guinea pigs. Direct injection of [1-¹⁴C] ascorbic acid into the cecum of conventional guinea pigs in vivo yielded a 70% recovery of the label as respiratory ¹⁴CO₂ within 6 hr compared with only 5% recovery following injection into the virtually sterile peritoneum in a comparable group of conventional guinea pigs. Thus, ascorbic acid not absorbed prior to reaching the lower gastrointestinal tract stands to be extensively decarboxylated by microflora in the cecum. In a companion study of germ-free guinea pigs, 10% of an administered dose of [1-¹⁴C] ascorbic acid was expired as ¹⁴CO₂ within 36 hr post-injection following intraperitoneal injection compared with 16% recovery in a matched group of conventional animals injected at the same site. Results of this series of studies suggest that hepatic decarboxylation and gut microflora, in tandem, contribute to ascorbic acid decarboxylation in this species.