Effects of a Potato Spindle Tuber Viroid Tomato Strain on the Symptoms, Biomass, and Yields of Classical Indicator and Currently Grown Potato and Tomato Cultivars

The Chittering strain of potato spindle tuber viroid (PSTVd) infects solanaceous crops and wild plants in the subtropical Gascoyne Horticultural District of Western Australia. Classical PSTVd indicator hosts tomato cultivar Rutgers (R) and potato cultivar Russet Burbank (RB) and currently widely grown tomato cultivars Petula (P) and Swanson (S) and potato cultivars Nadine (N) and Atlantic (A) were inoculated with this strain to study its pathogenicity, quantify fruit or tuber yield losses, and establish whether tomato strains might threaten potato production. In potato foliage, infection caused spindly stems, an upright growth habit, leaves with ruffled margins and reduced size, and upward rolling and twisting of terminal leaflets (RB, A, and N); axillary shoot proliferation (A); severe plant stunting (N and RB); and necrotic spotting of petioles and stems (RB). Tubers from infected plants were tiny (N) or small and "spindle shaped" with (A) or without (RB) cracking. Potato foliage dry weight biomass was decreased by 30 to 44% in A and RB and 37% in N, whereas tuber yield was diminished by 50 to 89% in A, 69 to 71% in RB, and 90% in N. In tomato foliage, infection caused epinasty and rugosity in apical leaves, leaf chlorosis, and plant stunting (S, P, and N); cupped leaves (S and P); and reduced leaf size, flower abortion, and necrosis of midribs, petioles, and stems (R). Mean tomato fruit size was greatly decreased in all three cultivars. Tomato foliage dry weight biomass was diminished by 40 to 53% (P), 42% (S), and 37 to 51% (R). Tomato fruit yield was decreased by 60 to 76% (P), 52% (S), and 64 to 89% (R), respectively. Thus, the tomato strain studied was highly pathogenic to classical indicator and representative current tomato and potato cultivars, causing major losses in fruit and tuber yields. Tomato PSTVd strains, therefore, pose a threat to tomato and potato industries worldwide.

Potato spindle tuber viroid: Stability on Common Surfaces and Inactivation With Disinfectants

The length of time Potato spindle tuber viroid (PSTVd) remained infective in extracted tomato leaf sap on common surfaces and the effectiveness of disinfectants against it were investigated. When sap from PSTVd-infected tomato leaves was applied to eight common surfaces (cotton, wood, rubber tire, leather, metal, plastic, human skin, and string) and left for various periods of time (5 min to 24 h) before rehydrating the surface and rubbing onto healthy tomato plants, PSTVd remained infective for 24 h on all surfaces except human skin. It survived best on leather, plastic, and string. It survived less well after 6 h on wood, cotton, and rubber and after 60 min on metal. On human skin, PSTVd remained infective for only 30 min. In general, rubbing surfaces contaminated with dried infective sap directly onto leaves caused less infection than when the sap was rehydrated with distilled water but overall results were similar. The effectiveness of five disinfectant agents at inactivating PSTVd in sap extracts was investigated by adding them to sap from PSTVd-infected leaves before rubbing the treated sap onto leaves of healthy tomato plants. Of the disinfectants tested, 20% nonfat dried skim milk and a 1:4 dilution of household bleach (active ingredient sodium hypochlorite) were the most effective at inactivating PSTVd infectivity in infective sap. When reverse-transcription polymerase chain reaction was used to test the activity of the five disinfectants against PSTVd in infective sap, it detected PSTVd in all instances except in sap treated with 20% nonfat dried skim milk. This study highlights the stability of PSTVd in infective sap and the critical importance of utilizing hygiene practices such as decontamination of clothing, tools, and machinery, along with other control measures, to ensure effective management of PSTVd and, wherever possible, its elimination in solanaceous crops.

Pergolide: multiple-dose pharmacokinetics in patients with mild to moderate Parkinson disease

The primary objective of this study was to describe the pharmacokinetics of oral pergolide in patients with mild to moderate Parkinson disease using a new high-performance liquid chromatography-tandem mass spectrometry assay. A secondary objective was to investigate the relationship between plasma concentrations and efficacy. Fourteen patients with a diagnosis of Parkinson disease completed this multicenter, open-label, dose-escalating study. Pergolide was administered for 58 days, using increasing daily doses from 0.05 mg daily up to 1 mg three times daily and then tapering the dose. The steady-state pharmacokinetic profile and motor score were determined at dose levels of 0.25, 0.5, and 1 mg three times a day and during elimination after the last dose. Pergolide was absorbed with a median time to maximum concentration of 2 to 3 hours across the dose range. Systemic exposure appeared to increase proportionally with dose over the range of 0.25 to 1 mg three times daily within a patient, but there was a large variability in exposures between patients (interpatient coefficients of variation were 56.4% for the area under the curve). Pergolide was widely distributed (volume of distribution, approximately 14,000 L) and was eliminated with a mean half-life of 21 hours. Motor scores improved as both peak plasma pergolide concentrations and exposure increased. No unexpected safety concerns were identified. Pergolide is absorbed relatively quickly into the systemic circulation, has a large apparent volume of distribution, and has a relatively long half-life (mean, 21 hours). This prolonged half-life is of particular interest, given the current hypothesis that more continuous dopaminergic receptor stimulation may reduce motor complications in patients with Parkinson disease.

Seed Transmission of Wheat streak mosaic virus Shown Unequivocally in Wheat

Under conditions that excluded any possibility of eriophyid mite vector activity, seed transmission of Wheat streak mosaic virus (WSMV) was shown in eight different wheat genotypes at rates of 0.5 to 1.5%. Virus identification in seedlings came from characteristic symptoms in wheat, enzyme-linked immunosorbent assay with WSMV-specific antibodies, reverse-transcription polymerase chain reaction tests with WSMV-specific primers, and cDNA sequence comparisons with published sequences. Sequence comparisons of four seedborne isolates showed ≥98.6% identity with the eight Australian isolates in GenBank, indicating a common seedborne origin of WSMV. These findings warrant reconsideration of currently accepted views on WSMV epidemiology and the likelihood of introducing it to new locations through planting untested wheat seed and the movement of germplasm.

Absorption kinetics after inhalation of fluticasone propionate via the Diskhaler, Diskus and metered-dose inhaler in healthy volunteers

OBJECTIVE

The aim of this analysis was to assess the rate and extent of systemic availability of inhaled fluticasone propionate (FP) from 2 dry powder systems (Diskhaler and Diskus) and a metered-dose inhaler (MDI) by deconvolution analysis.

METHODS

The inhalation devices were evaluated in 3 separate studies with identical protocols. 12 healthy male volunteers were randomised to receive FP given as a 1000 microg inhaled dose and 250 microg by intravenous infusion according to a double-blind double-dummy crossover design. The bioavailability of FP after inhalation represents absorption of the drug from the lungs, since the bioavailability of the swallowed portion of the inhaled dose is negligible.

RESULTS

When corrected for the bioavailability (of FP) achieved by each inhalation device, the rate of absorption of FP over the first 2 hours was rapid from all devices. The mean time for absorption of 50% of the bioavailable dose was 1.6, 2.4, and 2.2 hours for the Diskhaler, Diskus and MDI, respectively. Thereafter, absorption from each device was prolonged, with approximately 10% of the dose remaining in the lungs 12 hours after inhalation.

CONCLUSION

Irrespective of the inhalation device used, the prolonged absorption of FP into the systemic circulation indicates a long residence time in the lungs.

Systemic exposure to fluticasone propionate administered via metered-dose inhaler containing chlorofluorocarbon or hydrofluoroalkane propellant

OBJECTIVE

The pharmacokinetic profile of a single dose of inhaled fluticasone propionate (FP) administered via a metered-dose inhaler (MDI), containing either a chlorofluorocarbon (CFC) or hydrofluoroalkane (HFA) propellant was investigated in healthy volunteers.

METHODS

Two randomised, double-blind, crossover studies were conducted, each in 12 male volunteers. Both studies compared pharmacokinetic data after a single inhaled dose of FP 1000 microg from a MDI containing either CFC (CFC MDI) or HFA (HFA MDI) with a single intravenous dose of FP 250 microg.

RESULTS

The maximum plasma FP concentrations after inhalation via the 2 types of MDI were almost identical (0.56 and 0.54 microg/L for CFC MDI and HFA MDI, respectively); bioavailability values of inhaled FP from the 2 MDIs were also similar (geometric mean values: 26.4% via the CFC MDI and 28.6% via the HFA MDI). Inhalation of FP via both MDI formulations produced similar reductions in urinary cortisol excretion over 12 and 24 hours postdose.

CONCLUSION

The bioavailability values of FP after inhalation via a CFC MDI and an HFA MDI are similar. The 2 formulations deliver comparable amounts of FP, and systemic exposures to FP from the 2 devices, measured by urinary cortisol excretion, are not significantly different.

Pharmacokinetics of fluticasone propionate inhaled via the Diskhaler and Diskus powder devices in healthy volunteers

OBJECTIVE

The aim of these studies was to determine the absolute bioavailability in healthy volunteers of inhaled fluticasone propionate (FP) administered as a single dose via the Diskhaler and Diskus powder devices, and the pharmacokinetics of inhaled FP after repeated administration via the Diskhaler device.

METHODS

In 2 of the studies, single inhaled doses of FP were administered via the Diskhaler and the Diskus powder devices, and, in the third study, repeated doses of FP were administered via the Diskhaler. In the single dose studies, 12 healthy volunteers were randomised to receive FP 1000 microg by inhalation and FP 250 microg intravenously, using a double-blind crossover design. In the repeated dose study, 24 healthy volunteers received FP 1000 microg twice daily for 7.5 days.

RESULTS

Systemic exposure to FP after administration of a single 1000 microg inhaled dose of FP via the 2 powder devices was similar; the area under the plasma FP concentration-time curve (AUC) to infinite time (AUCinfinity) was 2.08 microg/L x h [95% confidence intervals (CI): 1.63-2.64] for Diskhaler and 2.49 microg/L x h (95% CI: 2.09-2.96) for Diskus. Maximum plasma FP concentration (Cmax) was 0.34 microg/L for both devices. Mean bioavailability values via the Diskhaler and Diskus were 11.9% (95% CI: 9.0-15.7%) and 16.6% (95% CI: 13.6-20.3%), respectively. No clinically significant reductions in urinary cortisol excretion were recorded in these 2 studies. After repeated administration with the Diskhaler, steady state was achieved by dose 3 (i.e. day 2) onwards. After dose 15, the AUC up to 12 hours (AUC12h) was 2.25 microg/L x h and Cmax was 0.38 microg/L. The mean steady-state to single dose accumulation ratio after twice-daily administration was 1.49 (95% CI: 1.36-1.62).

CONCLUSION

The pharmacokinetics of FP administered by the 2 powder devices are similar in healthy volunteers, although systemic bioavailability was greater with the Diskus.

Pharmacokinetics of fluticasone propionate inhaled via the Diskhaler and Diskus powder devices in patients with mild-to-moderate asthma

OBJECTIVE

The aim of these studies was to compare the pharmacokinetics of inhaled fluticasone propionate (FP) after repeated administration via the Diskus or Diskhaler dry powder inhalers (DPIs) to patients with mild-to-moderate asthma.

METHODS

Both studies evaluated the pharmacokinetics of inhaled administration of FP via a DPI to patients with mild-to-moderate asthma, according to a randomised, double-blind, placebo-controlled design. In the first study, FP 100 microg or 500 microg was administered twice daily via the Diskhaler for 6 weeks and, in the second, FP 500 microg was administered via the Diskus or Diskhaler for 12 weeks.

RESULTS

In the first study, plasma FP concentrations could be detected consistently only with the higher dose; the lower dose produced concentrations close to or below the 0.025 microg/L quantification limit of the radioimmunoassay used. From detailed analysis of a subgroup of patients receiving the 500 microg dosage, steady-state plasma FP concentrations were attained within one week of commencing treatment. After 4 weeks, the maximum plasma FP concentration (Cmax) in this subgroup was 0.096 microg/L [95% confidence interval (CI) 0.066-0.141] and the area under the plasma FP concentration-time curve up to the last quantifiable concentration (AUClast) was 0.491 microg/L x h (95% CI: 0.256-0.940). The steady-state to single dose accumulation ratio for FP after twice-daily administration varied between patients: a ratio of approximately 1.7 was recorded after comparison of Cmax at week 4 and day 1. In the second study, the point estimate of the Diskus to Diskhaler ratio for Cmax in all patients was 0.91 (90% CI: 0.76-1.10) after 4 weeks' treatment. From a detailed analysis of a subgroup of patients, the corresponding ratio for AUClast at the same time point was 1.15 (90% CI: 0.69-1.94), indicating no significant difference in systemic exposure to FP between the 2 devices. Steady-state kinetics were achieved by week 1: the point estimate ratios of Cmax and AUClast at week 4 compared with week 1 were 0.88 (90% CI: 0.66-1.16) and 0.95 (90% CI: 0.66-1.36), respectively. Administration of FP via either DPI had no effect on plasma cortisol levels over the 12-hour postdose period.

CONCLUSION

In patients with asthma receiving repeated inhaled doses of FP, the systemic exposure (AUC) after inhalation from the Diskus was similar to that from the Diskhaler, with no difference between the DPIs in the effects on cortisol suppression. The 2 DPIs therefore have very similar pharmacokinetic profiles.

The relationship between systemic exposure to fluticasone propionate and cortisol reduction in healthy male volunteers

OBJECTIVE

The aim of this analysis was to assess the pharmacokinetic/pharmacodynamic relationship between systemic exposure to fluticasone propionate (FP) and reductions in the plasma cortisol level and urinary cortisol excretion.

METHODS

A total of 122 healthy male volunteers participating in 7 different studies received either oral (5 to 40 mg), inhaled (500 to 2000 microg) or intravenous (250 to 1000 g) single morning doses of FP or placebo. Data on systemic exposure to FP, expressed in terms of the area under the FP concentration-time curve up to 24 hours (AUC(24h,FP)) for the 3 different routes of administration were pooled, together with corresponding data on the 24-hour plasma cortisol level or urinary cortisol excretion. The data were used to develop a pharmacokinetic/pharmacodynamic model, from which parameter estimates and 95% confidence intervals (CI) for the estimates could be derived.

RESULTS

The intercept in the absence of drug (E0) was -0.5% (95% CI: -0.6, -0.3%) and the maximum drug-induced reduction in mean plasma cortisol levels (Emax) was 72% (95% CI: 64, 79%). The systemic exposure to FP that resulted in half the maximum possible reduction in plasma cortisol levels (AUC50) was 3.2 microg/L x h (95% CI: 2.8, 3.7 microg/L x h); this equates approximately to the plasma FP concentration obtained after administration of a 1000 microg inhaled dose. A similar relationship was seen between AUC50 and urinary cortisol excretion, although the variability in AUC50 for urinary cortisol was much greater than for plasma cortisol.

CONCLUSION

A pharmacokinetic/pharmacodynamic model has been established which relates systemic exposure to FP (after a single morning dose) to the percentage reduction in urinary or plasma cortisol. The relationship is independent of both dose and route of administration.

Dynamic modeling of cortisol reduction after inhaled administration of fluticasone propionate

Fluticasone propionate (FP) is a new corticosteroid that has been developed for the treatment of asthma. The compound has a very high receptor affinity, 18 times that of dexamethasone. After inhalation, FP is systemically available because of inhaled bioavailability. In healthy subjects this may lead to measurable systemic effects, such as cortisol reduction. A clinical study was conducted in 12 healthy volunteers to determine the systemic effects after inhaled administration of single 500-micrograms, 1,000-micrograms, and 2,000-micrograms doses of FP. Blood samples were collected over a 24-hour period after administration. Concentrations of FP and cortisol were measured in plasma by immunoassay. Cortisol reduction was chosen as the pharmacodynamic parameter. A novel linear release rate model was used to parameterize the cortisol data. The pharmacokinetics of FP were linear over the dose range studied. The cortisol release parameters were determined from baseline data (before drug administration). Based on these results, the E50 values for cortisol reduction were then determined for each dose of FP. The average E50 was 0.134 ng/mL for total FP concentrations and 0.013 ng/mL for unbound FP concentrations; these results were not dose dependent. These in vivo pharmacodynamic values measured in healthy subjects are in good agreement with the relatively high receptor affinity of FP.

Pharmacokinetics of intravenous fluticasone propionate in healthy subjects

1. Fluticasone propionate (FP) is a potent glucocorticoid used in the treatment of asthma. Prior to reporting the pharmacokinetics following the inhaled and oral routes, the pharmacokinetics need to be established following intravenous dosing. The present study determines the intravenous pharmacokinetics of FP, using non-compartmental analysis, in healthy male subjects over the 250 to 1000 micrograms dose range. 2. The pharmacokinetics of FP can be regarded as being linear over this dosing range. FP was extensively distributed within the body (Vss 3181), rapidly cleared (CL 1.1 l min-1) with a terminal elimination half-life of 7.8 h and a mean residence time of 4.9 h. 3. In order that future pharmacokinetic/pharmacodynamic and other modelling can be carried out, the plasma concentration-time profiles were parameterized using a model based on sums of exponentials, the appropriateness of this model was justified as the secondary kinetic parameters from the model were similar to those obtained using non-compartmental analysis.

Glucocorticoids and the cell surface of human glioma cells: relationship to cytostasis

The glucocorticoid hormones methyl prednisolone and dexamethasone were shown to be cytostatic, but not cytotoxic, at high cell densities for early passage and continuous cell lines from human glioma at 0.25 microM and above, in the presence or absence of serum. In the absence of serum both steroids at 2.5 nM increased the saturation density close to the level reached in serum. Examination of the iodinated glycoproteins of the cell surface by gel electrophoresis did not reveal any consistent change. However, gel exclusion chromatography of protease digests of the cell surface and of material released into the medium showed an increase in incorporation of 3H-glucosamine in pronase digests after treatment with methyl prednisolone. Ion exchange chromatography showed that sulphated glycosaminoglycans, particularly heparan sulphate, increased and hyaluronic acid decreased in response to steroids, and there was increased retention of GAGs on the cell surface relative to the released fraction. It was concluded that glucocorticoid hormones modify the cell surface of human glioma cells and that this may contribute to enhanced cell intraction and lead to increased density limitation of cell proliferation.

Phenotypic modification of human glioma and non-small cell lung carcinoma by glucocorticoids and other agents

Glucocorticoids are cytostatic for human glioma grown at a high cell density in cell culture. The effect is not cytotoxic, appears to involve a modification of the cell surface, and has been detected with methyl prednisolone, dexamethasone, and beta-methasone. Glucocorticoids were also found to reduce malignancy-associated properties (plasminogen activator and endothelial mitogenesis) and enhance differentiation (glutamyl synthetase activity and high affinity GABA uptake). Cytostasis was also seen at high cell densities in non-small cell lung carcinoma with a concomitant reduction in plasminogen activator activity and endothelial mitogenesis. Preliminary data on surfactant production in A549 cells suggests that the repression of malignancy-associated properties is accompanied by an increase in cell differentiation. Treatment of the WIL adenocarcinoma gown as a xenograft in nude mice caused total cessation of growth and massive central necrosis in the tumor.