Effectiveness of Kasugamycin Against Erwinia amylovora and its Potential Use for Managing Fire Blight of Pear.

Comparative field studies on the management of fire blight were conducted in California on Asian and Bartlett pear using single-bactericide, mixture, and rotation treatments of selected compounds. Treatment efficacy was evaluated based on the natural occurrence of the disease or after inoculation with Erwinia amylovora. Kasugamycin at 100 mg/liter demonstrated similar or higher pre- and post-infection activity than the industry standards, streptomycin and oxytetracycline. Phytotoxicity caused by kasugamycin was observed only when five or six sequential weekly applications were done. In a six-spray rotation program including three bactericides (copper, kasugamycin, and oxytetracycline), with each being used twice, phytotoxicity was minor. Baseline sensitivity concentrations for kasugamycin were established for growth of 376 isolates of E. amylovora from California. Values for the lowest concentration where a reduction in growth on nutrient agar was observed ranged from 3.5 to 18.3 mg/liter, with a mean value of 8.7 mg/liter. Values for ≥95% inhibition of growth ranged from 6.9 to 46.7 mg/liter, with a mean value of 18.5 mg/liter. These inhibitory values for kasugamycin were higher than those for streptomycin or oxytetracycline. The in vitro activity of all three compounds was highly dependent on the agar medium used in the sensitivity assay. The activity of kasugamycin was also highly dependent on the pH of the medium and was significantly higher at pH 5.1 than pH 7.3. With the planned registration in the United States, kasugamycin represents the first new, highly effective bactericide for managing fire blight in over 40 years.

Effects of lasalocid on circulating concentrations of leptin and insulin-like growth factor-I and reproductive performance of postpartum Brahman cows.

Objectives were to determine effects of lasalocid on reproductive performance and serum concentrations of leptin and IGF-I, and to correlate concentrations of leptin and IGF-I with reproductive performance of beef cows. Forty-one purebred, multiparous Brahman cows were blocked to control (C; n = 20) or lasalocid (L; n = 21) treatments by BW, BCS, and predicted calving date. Treatment began 21 d before expected calving. Cows were each fed 1.4 kg daily of an 11:1 corn:soybean meal supplement, with the L group receiving 200 mg of lasalocid/cow daily. Cows and calves were weighed, and cow BCS was assessed at calving and at 28-d intervals thereafter. Blood samples were collected weekly precalving, at parturition, and twice weekly thereafter. Sterile marker bulls were maintained with cows for estrous detection. Six days after estrus, ovaries were evaluated for corpus luteum formation, and blood samples from d 6, 7, and 8 after estrus were collected. Serum samples were assayed for progesterone (P4), IGF-I, and leptin concentration. Progesterone concentrations > 1 ng/mL were considered indicative of a functional corpus luteum. Treatment ended after completion of a normal estrous cycle, and cows removed from treatment were placed with a fertile bull equipped with a chinball marker. There were no treatment differences in calving date, calf sex, cow BW, BCS, calf BW, calf ADG, or in serum concentrations of P4, IGF-I, or leptin. Prepartum cow ADG was increased (P < 0.01) in L cows and tended (P < 0.011) to be increased from calving to d 56 after calving in L cows. Postpartum interval (PPI) was not affected by treatment; however, a greater percentage (P < 0.05) of L cows conceived by 90 d after calving (43% L vs. 15% C). First-service conception rate tended (P < 0.08) to be greater in L vs. C cows (68 vs. 40%), but pregnancy rate was not different (P < 0.12; 86% for L vs. 65% for C). There were no treatment differences (P > 0.18) for serum IGF-I concentrations. At calving, leptin was positively correlated with IGF-I (P < 0.04; r = 0.32), BCS (P < 0.06; r = 0.29), and cow BW (P < 0.02; r = 0.36), and was negatively correlated with PPI (P < 0.06; r = -0.29). These results provide evidence that feeding an ionophore before calving and during the postpartum period may increase the number of cows that rebreed to maintain a yearly calving interval. Cows with higher concentrations of leptin postpartum may exhibit shorter PPI.

A Mossbauer investigation of iron-rich terrestrial hydrothermal vent systems: lessons for Mars exploration.

Hydrothermal spring systems may well have been present on early Mars and could have served as a habitat for primitive life. The integrated instrument suite of the Athena Rover has, as a component on the robotic arm, a Mossbauer spectrometer. In the context of future Mars exploration we present results of Mossbauer analysis of a suite of samples from an iron-rich thermal spring in the Chocolate Pots area of Yellowstone National Park (YNP) and from Obsidian Pool (YNP) and Manitou Springs, Colorado. We have found that Mossbauer spectroscopy can discriminate among the iron-bearing minerals in our samples. Those near the vent and on the surface are identified as ferrihydrite, an amorphous ferric mineraloid. Subsurface samples, collected from cores, which are likely to have undergone inorganic and/or biologically mediated alteration (diagenesis), exhibit spectral signatures that include nontronite (a smectite clay), hematite (alpha-Fe2O3), small-particle/nanophase goethite (alpha-FeOOH), and siderite (FeCO3). We find for iron minerals that Mossbauer spectroscopy is at least as efficient in identification as X-ray diffraction. This observation is important from an exploration standpoint. As a planetary surface instrument, Mossbauer spectroscopy can yield high-quality spectral data without sample preparation (backscatter mode). We have also used field emission scanning electron microscopy (FESEM), in conjunction with energy-dispersive X ray (EDX) fluorescence spectroscopy, to characterize the microbiological component of surface sinters and the relation between the microbiological and the mineralogical framework. Evidence is presented that the minerals found in these deposits can have multi-billion-year residence times and thus may have survived their possible production in a putative early Martian hot spring up to the present day. Examples include the nanophase property and the Mossbauer signature for siderite, which has been identified in a 2.09-billion-year old hematite-rich chert stromatolite. Our research demonstrates that in situ Mossbauer spectroscopy can help determine whether hydrothermal mineral deposits exist on Mars, which is significant for exobiology because of the issue of whether that world ever had conditions conductive to the origin of life. As a useful tool for selection of samples suitable for transport to Earth, Mossbauer spectroscopy will not only serve geological interests but will also have potential for exopaleontology.

Nitric oxide modulates the activity of the hemoproteins prostaglandin I2 synthase and thromboxane A2 synthase.

Nitric oxide modulates the activity of the hemoprotein isomerase enzymes that transform prostaglandin H2 into prostaglandin I2 and thromboxane A2. Two nitric oxide donors, 1-hexanamine, 6-(2hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-nitroso- hydrazine (MMNN) and 1,1-diethyl-2-hydroxy-2-nitrosohydrazine, modulated prostaglandin I2 synthase activity in a bidirectional manner. At moderate concentrations, they increased enzyme activity irreversibly and at higher concentrations they inhibited enzyme activity reversibly. We confirmed that these effects originated from nitric oxide. First, we showed that hemoglobin, a substance that sequesters nitric oxide, prevented both the activation and the inhibition of catalysis, stoichiometrically. Second, we showed that solutions depleted of nitric oxide had no effect on catalysis. Nitric oxide also modulated thromboxane A2 synthase activity; however, its effects on thromboxane A2 synthase differed from its effects on prostaglandin I2 synthase in three ways: (i) It inhibited thromboxane A2 synthase in a concentration-dependent manner. The IC50 = 4.2 +/- 0.8 microM MMNN corresponded to an IC50 congruent with 0.1-0.3 microM nitric oxide. (ii) It did not increase thromboxane A2 synthase activity at any concentration tested. (iii) Its irreversible inhibition of thromboxane A2 synthase contrasted with its reversible inhibition of prostaglandin I2 synthase. Nitric oxide also inhibited cellular formation of thromboxane A2 by intact platelets in a concentration-dependent manner. The IC50 = 267 +/- 26 microM MMNN corresponded to an IC50 congruent with 6-18 microM nitric oxide. We conclude that nitric oxide can modulate certain hemoprotein enzymes in the biosynthetic cascade that governs the formation of eicosanoid mediators of thrombosis and hemostasis.

"Suicide" inactivation of prostaglandin I2 synthase: characterization of mechanism-based inactivation with isolated enzyme and endothelial cells.

"Suicide" inactivation accompanied catalysis by isolated prostaglandin I synthase. Inactivation occurred via a saturable, pseudo-first-order process with an apparent binding constant Ki = 8 microM prostaglandin H2 and an inactivation rate constant ki = 0.06 s-1. Enzymatic activity declined as an exponential function of substrate concentration and a linear function of product formation. A competitive inhibitor, 9,11-(methanoepoxy)-15(S)-hydroxy-prosta-5Z,13E-dienoic acid, protected the enzyme from inactivation. Prostaglandin H1, an endoperoxide which is not a substrate, inactivated the enzyme less effectively than prostaglandin H2. The differences between inactivation by prostaglandin H2 and H1, the protective effect of the competitive inhibitor, the quantitative similarity between Km and Ki, and the dependence on catalysis all suggest that inactivation originates primarily from a transition-state intermediate, not from malondialdehyde formed by hydrolysis of prostaglandin endoperoxides. Collectively, the data conform to criteria for a specific, mechanism-based process in which a common enzyme-substrate complex participates in two parallel reactions, one leading to turnover and the other to suicide inactivation. Inactivation accompanying catalysis by prostaglandin I synthase in intact endothelial cells was transient, consistent with the cellular capacity for de novo protein synthesis. Enzyme activity returned to the initial steady-state level within 15-20 min, suggesting that prostaglandin I synthase has a half-life < or = 5 min.

Tomographic evaluation of temporomandibular joints following discoplasty or placement of polytetrafluoroethylene implants.

A retrospective comparison was made of tomographic change in the temporomandibular joint (TMJ) of patients who had been treated by either discoplasty or discectomy with polytetrafluoroethylene (PTFE) disc replacement. Fifty-five PTFE- and 18 discoplasty-treated joints were evaluated. More than 60% of the PTFE-treated joints showed severe, destructive osseous change, whereas none of the discoplasty joints showed such change. Histologic examination of the tissues surrounding removed PTFE implants showed a foreign body giant cell reaction. The severity of radiographic change raises questions about the propriety of PTFE as a disc replacement material.