Sampling for pod rot of peanut Wheeler, T A; Woodward, JE; Russell, SA ...
Phytopathology,
06/2010, Letnik:
100, Številka:
6
Journal Article
Recenzirano
Two peanut fields with a history of pod rot were sampled weekly at 101 randomly chosen locations. Each sample location covered 0.5 m of row. The objective was to determine a sampling intensity which ...would adequately estimate pod rot for three treatment thresholds. Low, medium, and high treatment thresholds were chosen at .1%, .2.5%, and .5.5% pod rot. Pythium pod rot was the primary disease at both sites. From the sampled locations, 5, 10, 15, 20, 25, 35, and 50 sample points were selected at random from the data sets, with 10 simulations for each sampling intensity. In general, when a threshold number was close to the average pod rot, there were more wrong threshold decisions than when the average pod rot was far away from a threshold number. There were more wrong decisions for the high threshold, compared with the moderate and low thresholds. It was more difficult to be accurate at the higher percentage of pod rot than the lower disease levels when sampling up to 50 locations (of the 101 sampled points). For the low and moderate thresholds, 15 sampling points was as likely to be accurate as higher sampling intensity, and more likely to be accurate in terms of being over or under threshold than with lower sampling intensity. Crop consultants must determine how intensive to sample to identify disease problems timely, but must also maintain profitability while scouting fields, by minimizing time spent in a field. This project is aimed at assisting consultants.
After infusion of cryoprecipitate, the very prolonged bleeding time of patients with severe von Willebrand disease (vWD) is shortened but not always normalized in spite of normalization of plasma von ...Willebrand factor (vWF) levels. Therefore treatments that further improve primary hemostasis in severe vWD patients are needed. Since DDAVP shortens the bleeding time in a variety of bleeding disorders, we investigated in a double-blind, placebo-controlled crossover study the effects of the intravenous (IV) infusion of DDAVP (0.3 µg/kg) on the bleeding times of 10 patients with severe vWD treated with cryoprecipitate. Their very prolonged bleeding times (>30 minutes), partially corrected by the infusion of cryoprecipitate (14 ± 2 minutes, mean ± SEM), were further shortened by the administration of DDAVP (9 ± 2 minutes, P < .01) but not of saline (15 ± 3 minutes, ns). Plasma vWF levels, raised from unmeasurable to normal values by cryoprecipitate, were not changed after DDAVP or saline. The defective deposition of platelets from eight patients onto human umbilical artery subendothelium was increased but not normalized by cryoprecipitate and was not significantly affected by DDAVP or saline. Therefore the infusion of DDAVP after cyroprecipitate may be of clinical benefit for management of bleeding episodes in severe vWD patients. Since severe vWD patients do not have releasable tissue stores of vWF, DDAVP must shorten their prolonged bleeding times independently of released vWF.
During September–October 1997, 21 three‐component broadband seismometers were deployed on Stromboli Volcano at radial distances of 0.3–2.2 km from the active crater to investigate the source ...mechanisms of Strombolian explosions. In the 2–50 s band, the very‐long period (VLP) signals associated with explosions are consistent with two stationary sources repeatedly activated in time. VLP particle motions are essentially linear and analyses of semblance and particle motions are consistent with a source centroid offset 300 m beneath and 300 m northwest of the active vents. Similar VLP waveforms are observed at all 21 stations, indicating that the seismograms are source‐dominated. The VLP ground displacement response to each explosion may be qualitatively interpreted as: (1) pressurization of the conduit associated with the ascent of a slug of gas; (2) depressurization of the conduit in response to mass withdrawal during the eruption; and (3) repressurization of the conduit associated with the replenishment of the source with fluid.
Activation by ADP of both P2Y1 and P2Y12 receptors in platelets contributes to platelet aggregation, and antagonists at these receptor subtypes have antithrombotic properties. In an earlier ...publication, we have characterized the SAR as P2Y1 receptor antagonists of acyclic analogues of adenine nucleotides, containing two phosphate groups on a symmetrically branched aliphatic chain, attached at the 9-position of adenine. In this study, we have focused on antiaggregatory effects of P2Y antagonists related to a 2-chloro-N6-methyladenine-9-(2-methylpropyl) scaffold, containing uncharged substitutions of the phosphate groups. For the known nucleotide (cyclic and acyclic) bisphosphate antagonists of P2Y1 receptors, there was a significant correlation between inhibition of aggregation induced by 3.3 μM ADP in rat platelets and inhibition of P2Y1 receptor-induced phospholipase C (PLC) activity previously determined in turkey erythrocytes. Substitution of the phosphate groups with nonhydrolyzable phosphonate groups preserved platelet antiaggregatory activity. Substitution of one of the phosphate groups with O-acyl greatly reduced the inhibitory potency, which tended to increase upon replacement of both phosphate moieties of the acyclic derivatives with uncharged (e.g., ester) groups. In the series of nonsymmetrically substituted monophosphates, the optimal antagonist potency occurred with the phenylcarbamate group. Among symmetrical diester derivatives, the optimal antagonist potency occurred with the di(phenylacetyl) group. A dipivaloyl derivative, a representative uncharged diester, inhibited ADP-induced aggregation in both rat (K I 3.6 μM) and human platelets. It antagonized the ADP-induced inhibition of the cyclic AMP pathway in rat platelets (IC50 7 μM) but did not affect hP2Y1 receptor-induced PLC activity measured in transfected astrocytoma cells. We propose that the uncharged derivatives are acting as antagonists of a parallel pro-aggregatory receptor present on platelets, that is, the P2Y12 receptor. Thus, different substitution of the same nucleoside scaffold can target either of two P2Y receptors in platelets.
In essential hypertension, captopril attenuates forearm vasoconstriction reflexly induced by deactivation of cardiopulmonary and arterial baroreceptors, thus exerting a sympathomoderating effect. We ...investigated whether this is a common effect of angiotensin converting enzyme (ACE) inhibitors.
Cardiopulmonary and arterial baroreceptors were deactivated by progressively reducing central venous pressure (CVP) through progressively greater lower body negative pressures in eight untreated mild essential hypertensives on a moderately low-sodium diet (50 mmol/l per day). This deactivation was performed after oral administration of the non-sulphidrylic ACE inhibitor benazepril (10 mg) and placebo according to a double-blind randomized crossover experimental design.
After placebo, the reduction in CVP increased forearm vascular resistance (FVR; mean arterial pressure: plethysmographic forearm blood flow ratio). After benazepril, baseline blood pressure (beat-to-beat finger pressure) and FVR were significantly reduced whilst plasma angiotensin II was suppressed and PRA increased (both measured by radioimmunoassay). The FVR increases induced by progressive CVP reduction were less than after placebo administration, and the overall difference was statistically significant. Benazepril did not affect the reflex FVR reduction observed by increasing CVP through leg raising, nor the reflex changes in plasma norepinephrine measured by high-performance liquid chromatography accompanying the changes in FVR.
Benazepril attenuates sympathetic vasoconstriction as does captopril. This effect (which is mainly operative during an increased sympathetic drive and exerted through a reduction of adrenoceptor responsiveness) is thus likely to be a class- rather than a compound-related feature.
Animal studies have shown that vasopressin secretion is modulated by arterial baroreceptors and cardiopulmonary volume receptors. Whether this is the case also in humans is controversial, however. To ...determine whether vasopressin is reflexly modulated by cardiac volume receptors, we studied the effect on plasma vasopressin (venous blood, radiolmmunoassay) of reducing venous return and left ventricular end-diastolic diameter (echocardiography) by producing a 20-minute lower body negative pressure in 14 healthy subjects (aged 49.3±3.8 years, mean±SEM). The data were compared with those of 14 age-matched heart-transplant recipients, i.e., subjects with cardiac denervation. In healthy subjects, lower body negative pressure at −15 mm Hg caused a modest reduction in left ventricular end-diastolic diameter (−5±3.4%) and no change in vasopressin, whereas lower body negative pressure at −37.5 mm Hg caused a more marked reduction in left ventricular end-diastolic diameter (−12±2.5%) and a small, variable, but overall statistically significant (p<0.05) increase in vasopressin (+145±46%, p<0.01). The left ventricular end-diastolic diameter changes induced by the two lower body negative pressure stimuli were similar in heart-transplant recipients, but the vasopressin increase seen with the lower body negative pressure at −37.5 mm Hg was abolished. The marked increase in plasma renin activity and forearm vascular resistance induced by lower body negative pressure in healthy subjects was also abolished or drastically attenuated in heart-transplant recipients. The abolition of the responses was not due to a generalized hyporeactivity because, in heart-transplant recipients, vasopressin, plasma renin activity, and forearm vascular resistance increased normally when stimulated by hyperosmolarity, angiotensin converting enzyme inhibition, and cold, respectively. Thus, in humans vasopressin is modulated reflexly by cardiac volume receptors, although to a limited degree and only for large changes in central blood volume. The reflex influence of cardiac receptors extends to plasma renin activity and vascular resistance, indicating a role of these receptors in both blood volume and blood pressure control.
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