Effects of Phenamiphos,Methyl Bromide,and Fallowing on Pratylenchus Penetrans,Yield of Medicago sativa,and Fusarium Infections

A field study was made of the effects of a residual nematicide (phenamiphos), a fumigant (methyl bromide), and fallowing on the number of root lesion nematodes (Pratylenchus penetrans), forage yields of alfalfa, and the occurrence of Fusarium spp. in plant roots and soil. Fallowing controlled nematodes initially, but by the end of the second growing season, nematode numbers were as high as in plots which had grown a nematode-susceptible crop. Forage yield was greater in fallowed plots only for the first cut in the year after seeding. Fusarium in alfalfa roots and soil was not reduced by fallowing. Phenamiphos reduced nematode numbers, increased forage yields in 2 of 4 years, and reduced Fusarium infections of taproots. Soil fumigation with methyl bromide gave the best control of nematodes and Fusarium and gave significantly higher forage yields for the 4 years of study following fumigation. The 34% increase in alfalfa yield from fumigated plots over the 4 years indicates that the yield of alfalfa is being reduced significantly by microorganisms. The study does not establish the relative contributions of the root lesion nematodes and Fusarium spp. to the reduction.     

Effects of Pratylenchus coffeae and Scutellonema bradys Alone and in Combination on Guinea Yam (Dioscorea rotundata)

When Guinea yam, Dioscorea rotundata Poir, was inoculated with Pratylenchus coffeae and Scutellonema bradys together, there was a 53% suppression of top growth, but when plants were inoculated separately there was a 29% suppression with P. coffeae and a 21% suppression with S. bradys. The reproduction of S. bradys was greatly inhibited when both nematode species were together on the same plant in comparison with that on plants inoculated with S. bradys alone. Scutellonema bradys apparently did not affect the reproduction of P. coffeae. Storage-root quality was reduced 72% by P. coffeae but only 20% by S. bradys. The two species together resulted in a reduction in storage-root quality of 84%. Although the Guinea yam is a good host of P. coffeae and S. bradys, our results indicate that P. coffeae is responsible for most of the storage-root deterioration and dry rot of yam in Puerto Rico.     

电刺激室旁核对大鼠应激性胃粘膜损伤的影响

电刺激室旁核(PVN)有加重大鼠应激性胃粘膜损伤的作用;PVN内微量注射神经元胞体兴奋剂L-谷氨酸钠和电刺激PVN的效应相同;电解损毁双侧PVN或对其电刺激后,使应激性胃粘膜损伤明显减轻,切断膈下迷走神经或皮下注射阿托品后,可显著减轻电刺激PVN加重大鼠应激性胃粘膜损伤的效应;电刺激PVN使胃粘膜血流量减少,但对胃液量、胃酸排出量、胃蛋白酶活性及胃壁结合粘液量均无显著影响。从而表明,PVN是影响应激性胃粘膜损伤的特异性中枢部位之一,当其兴奋时,可加重应激性胃粘膜损伤,并可能是通过迷走神经胆碱能纤维起作用的,且与胃粘膜血流量的减少有关;电刺激PVN加重胃粘膜损伤似不是由胃液量、胃酸、胃蛋白酶活性及胃壁结合粘液量等因素的改变引起的。     

Competition between Heterodera glycines and Meloidogyne incognita or Pratylenchus penetrans: Independent Infection Rate Measurements

Competition on soybean between Heterodera glycines (race 3) and Meloidogyne incognita or H. glycines and Pratylenchus penetrans were investigated in greenhouse experiments. Each pair of nematode species was mixed in 3-ml suspensions at ratios of 1,000:0, 750:250, 500:500, 250:750, and 0:1,000 second-stage juveniles or mixed stages for P. penetrans. Nematodes from a whole root system were counted and infection rates standardized per 1,000 nematodes (per replication) prior to testing the null hypothesis through a lack-of-fit F-test. Although the effect of increasing H. glycines proportions on the infection rate of M. incognita was generally adverse, the rate deviated significantly from a trend of linear decline at the 75% H. glycines level in one of two experiments. All lack-of-fit F-tests for the H. glycines and P. penetrans mix were significant, indicating that infection rates for both nematodes varied considerably across inocula. The infection rate of H. glycines decreased with increasing P. penetrans proportions. The rate of P. penetrans infection increased with increasing H. glycines proportions up to the 50% level, but declined at the 75% level. Competition had no effect on nematode development. The general adverse relationships between M. incognita and H. glycines and those between P. penetrans and H. glycines showed a linear trend. The relationship between H. glycines and P. penetrans indicates that the former may be competitive when present at higher proportions than the latter. In this study we have evaluated nematode competition under controlled conditions and provide results that can form a basis for understanding the physical and physiological trends of multiple nematode interactions. Methods critical to data analyses also are outlined.     

Salicylic acid in the machinery of hypersensitive cell death and disease resistance

Although extensive data has described the key role of salicylic acid (SA) in signaling pathogen-induced disease resistance, its function in physiological processes related to cell death is still poorly understood. Recent studies have explored the requirement of SA for mounting the hypersensitive response (HR) against an invading pathogen, where a particular cell death process is activated at the site of attempted infection causing a confined lesion. Biochemical data suggest that SA potentiates the signal pathway for HR by affecting an early phosphorylation-sensitive step preceding the generation of pro-death signals, including those derived from the oxidative burst. Accordingly, the epistatic relationship between cell death and SA accumulation, analyzed in crosses between lesion-mimic mutants (spontaneous lesion formation) and the transgenic nahG line (depleted in SA) places the SA activity in a feedback loop downstream and upstream of cell death. Exciting advances have been made in the identification of cellular protective functions and cell death suppressors that might operate in HR. Moreover, the spatio-temporal patterns of the SA accumulation (non-homogeneous distribution, biphasic kinetics) described in some HR lesions, may also reveal important clues for unraveling the complex cellular network that tightly balances pro- and anti-death functions in the hypersensitive cell death.     

A single amino acid insertion in the WRKY domain of the Arabidopsis TIR-NBS-LRR-WRKY-type disease resistance protein SLH1 (sensitive to low humidity 1) causes activation of defense responses and hypersensitive cell death

In this study we characterized the sensitive to low humidity 1 (slh1) mutant of Arabidopsis ecotype No-0 which exhibits normal growth on agar plate medium but which on transfer to soil shows growth arrest and development of necrotic lesions. cDNA microarray hybridization and RNA gel blot analysis revealed that genes associated with activation of disease resistance were upregulated in the slh1 mutants in response to conditions of low humidity. Furthermore, the slh1 mutants accumulate callose, autofluorescent compounds and salicylic acid (SA). We demonstrate that SA is required for the slh1 phenotype but not PAD4 or NPR1. SLH1 was isolated by map-based cloning and it encodes a resistance (R)-like protein consisting of a domain with Toll and interleukin-1 receptor homology (TIR), a nucleotide-binding domain (NB), leucine-rich repeats (LRR) and a carboxy-terminal WRKY domain. SLH1 is identical to the R gene RRS1-R of the Arabidopsis ecotype Nd-1, a gene which confers resistance to the bacterial pathogen Ralstonia solanacearum GMI1000 and also functions as an R gene to this pathogen in No-0. We identified a 3 bp insertion mutation in slh1 that results in the addition of a single amino acid in the WRKY domain; thereby impairing its DNA-binding activity. Our data suggest that SLH1 disease resistance signaling may be negatively regulated by its WRKY domain in the R protein and that the constitutive defense activation conferred by the slh1 mutation is inhibited by conditions of high humidity.     

Wheat leaf photosynthesis loss due to leaf rust, with respect to lesion development and leaf nitrogen status

In wheat (Triticum aestivum cv. Soissons) plants grown under three different fertilisation treatments, we quantified the effect of leaf rust (Puccinia triticina) on flag leaf photosynthesis during the whole sporulation period. Bastiaans' model: Y = (1 - x)beta was used to characterize the relationship between relative leaf photosynthesis (Y) and disease severity (x). The evolution of the different types of symptoms induced by the pathogen (sporulating, chlorotic and necrosed tissues) was evaluated using image analysis. The beta-values varied from 2 to 11, 1.4-2, and 0.8-1 during the sporulation period, when considering the proportion of sporulating, sporulating + necrotic, and total diseased area, respectively. Leaf nitrogen (N) content did not change the effect of the disease on host photosynthesis. We concluded that leaf rust has no global effect on the photosynthesis of the symptomless parts of the leaves and that the large range in the quantification of leaf rust effect on the host, which is found in the literature, can be accounted for by considering the different symptom types. We discuss how our results could improve disease assessments and damage prediction in a wheat crop.     

Effect of ellagic acid on gastric damage induced in ischemic rat stomachs following ammonia or reperfusion

We examined the effect of ellagic acid (EA), one of the polyphenols that are abundantly contained in whisky as a nonalcoholic component, on gastric lesions induced by ammonia plus ischemia or ischemia/reperfusion in rats, in relation to the antioxidative system. Under urethane anesthesia, a rat stomach was mounted in an ex vivo chamber, and the following two experiments were performed; 1) a stomach was made ischemic (1.5 ml/100 g body weight) for 20 min, followed by reperfusion for 15 min in the presence of 100 mM HCl; 2) a stomach was made ischemic by bleeding from the carotid artery (1 ml/100 g body weight), followed by intragastric application of ammonia (NH4OH: 120 mM). EA (0.1-10 mg/ml) was applied in the chamber 30 min before the onset of ischemia. Gastric potential difference (PD) and mucosal blood flow (GMBF) were measured before, during and after 20 min of ischemia. Ischemia/reperfusion caused a profound drop in GMBF followed by a return, and resulted in hemorrhagic lesions in the stomach in the presence of 100 mM HCI. These lesions were dose-dependently prevented by EA with suppression of lipid peroxidation but no effect on GMBF, and the effect at 6 mg/ml was almost equivalent to that of superoxide dismutase (SOD: 15000 unit/kg/hr) infused i.v. during a test-period. On the other hand, application of NH4OH to the ischemic stomach produced a marked reduction in PD, resulting in severe hemorrhagic lesions. These changes were prevented with both EA and SOD. In addition, EA had a potent scavenging action against monochloramine in vitro. These results suggest that EA exhibits gastric protective action against gastric lesions induced by NH4OH or reperfusion in the ischemic stomach, probably due to its anti-oxidative activity. This property of EA partly explains the less damaging effect of whisky in the stomach and may be useful as the prophylactic for Helicobacter pylori-associated gastritis.     

Inducible expression of bacterio-opsin in transgenic tobacco and tomato plants

The development of new strategies to enhance resistance of plants to pathogens is instrumental in preventing agricultural losses. Lesion mimic, the spontaneous formation of lesions resembling hypersensitive response lesions in the absence of a pathogen, is a dramatic phenotype occasionally induced upon expression of certain transgenes in plants. These transgenes simulate the presence of a pathogen and, therefore, activate the plant anti-pathogen defense mechanisms and induce a state of systemic resistance. Lesion mimic genes have been successfully used to enhance the resistance of a number of different plants to pathogen attack. However, constitutive expression of these genes in plants is associated with the spontaneous formation of lesions on leaves and stems, reduced growth, and lower yield. We tested the possibility of using a wound-inducible promoter to control the expression of bacterio-opsin (bO), a transgene that confers a lesion mimic phenotype in tobacco and tomato plants when constitutively expressed. We found that plants with inducible expression of bO did not develop spontaneous lesions. Nevertheless, under controlled laboratory conditions, they were found to be resistant to infection by pathogens. The activation of defense mechanisms by the bO gene was not constitutive, and occurred in response to wounding or pathogen infection. Furthermore, wounding of transgenic tobacco plants resulted in the induction of systemic resistance to pathogen attack within 48 h. Our findings provide a promising initial assessment for the use of wound-inducible promoters as a new strategy to enhance pathogen resistance in transgenic crops by means of lesion mimic genes.     

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA): experience of an academic centre in the USA

S. Zhang, D. V. S. DeFrias, R. Alasadi and R. Nayar
Endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA): experience of an academic centre in the USA Objectives: Endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA) has become widely accepted as an effective modality for obtaining tissue for primary diagnosis and staging. We have been using EUS‐FNA since July 2001 and herein we summarize our experience over a 5‐year period. Methods: A computer‐based search for in‐house EUS‐FNA was performed in the pathology database from July 2001 to October 2006. To calculate the sensitivity, specificity and accuracy of EUS‐FNA, the cytology diagnosis was compared with the surgical follow‐up. Results: A total of 951 EUS‐FNAs were performed during the study period and included 279 pancreatic solid lesions, 186 pancreatic cyst lesions, 249 lymph node aspirations, 111 gastrointestinal (GI) tract submucosal lesions, and 126 miscellaneous lesions. EUS‐FNA had a very high sensitivity and accuracy for solid pancreatic lesions (94.7 and 97.7%, respectively), low sensitivity and accuracy but high specificity (47, 64.8 and 95%, respectively) for cystic lesions. Cyst fluid carcinoembryonic (CEA) levels were significantly higher in mucinous neoplasms than non‐neoplastic cysts. EUS‐FNA also had very high sensitivity and specificity for detecting metastatic carcinoma in lymph nodes (95 and 100%, respectively). GI submucosal spindle cell tumours were further classified with immunohistochemical stains performed either on a cell block or a core biopsy obtained via EUS guidance. Conclusions: EUS‐FNA has a very high sensitivity and accuracy for pancreatic solid lesions, but the sensitivity for cystic lesions is generally low. Cyst fluid chemical analysis for CEA is helpful, but the overlap between mucinous neoplasm and non‐neoplastic cysts is significant. Recognizing GI contamination is important and immunohistochemical stains are useful for GI submucosal spindle cell lesions.