Seasonal changes in pyrethroid resistance in tarnished plant bug (Heteroptera: Miridae) populations during a three-year period in the delta area of Arkansas, Louisiana, and Mississippi.

Tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were collected from weeds at 71 locations in the delta of Arkansas, Louisiana, and Mississippi and tested with a discriminating dose bioassay for pyrethroid resistance in the spring (April-May) and again at the same locations in the fall (September-October) in 1995-1997. Percentage of mortality in the discriminating dose bioassay declined significantly (pyrethroid-resistance increased) from spring to fall by an average 18.7, 21.3, and 21.7% in Arkansas, Louisiana, and Mississippi, respectively. Pyrethroid resistance declined significantly by 26.3% from the fall of 1995 to the spring of 1996 in Mississippi, but did not significantly decline in Arkansas (4.1%) and Louisiana (13.2%). Significant decreases in resistance occurred in all 3 states from the fall of 1996 to the spring of 1997 (17.1, 38.3, and 29.8% in Arkansas, Louisiana, and Mississippi, respectively). Plant bugs from 2 locations (Indianola, MS, and Wainwright, LA) had multiple insecticide resistance to a carbamate, 2 pyrethroid, and 4 organophosphorus insecticides. However, resistance to the organophosphate acephate in plant bugs from both locations was not significant. Possible causes for the significant increases and declines in resistance from season to season are discussed.

Ablation of ventricular tachycardia associated with tetralogy of Fallot: demonstration of bidirectional block.

INTRODUCTION: Ventricular tachycardia is commonly seen in patients following surgical repair for tetralogy of Fallot. The technique of ablation for this arrhythmia is not well defined. METHODS AND RESULTS: In two patients with ventricular tachycardia following surgical repair of tetralogy of Fallot, the traditional indicators for a site for ventricular tachycardia ablation did not yield cure. Based on careful mapping, the circuit was found to involve the isthmus between the outflow tract patch and the tricuspid annulus; linear radiofrequency lesions across this isthmus resulted in cure of ventricular tachycardia. Not only was the tachycardia no longer inducible, but bidirectional block at the line of ablation confirmed interruption of the reentrant circuit. CONCLUSION: A linear radiofrequency lesion was effective in eliminating ventricular tachycardia in both patients. The demonstration of bidirectional block confirms a cure independent of inducibility of ventricular tachycardia.

Management of pterygium with surgery and radiation therapy. The North Florida Pterygium Study Group.

PURPOSE: To compare our results in the management of pterygium using a higher total dose with other reported results. METHODS AND MATERIALS: Between 1971 and 1991, 690 patients were treated with complete surgical excision followed by beta irradiation for primary or recurrent pterygium. Of these patients, 129 had two or more areas involving both eyes for a total of 825 lesions treated. Only 17 patients (2%) had temporal lesions with the rest of the patients having nasal pterygia. All patients underwent complete surgical resection of the pterygium before undergoing radiation therapy. One hundred forty-nine patients had undergone previous surgical resection alone but developed recurrence. After surgical excision, all patients were treated with Strontium-90 applicators starting immediately within 24 hr of surgery. Our standard policy was six weekly applications, each delivering a surface dose of 1000 cGy. The total dose delivered was 6000 cGy. Minimum follow-up was 1 year with a median of greater than 8 years. RESULTS: There were only fourteen recurrences (1.7%) out of a total of 825 lesions treated. Nine of the fourteen patients received suboptimal therapy undergoing less than five applications of Strontium-90. There were no major complications. CONCLUSION: The combination of surgical excision followed by adequate Strontium-90 applications is highly effective in the management of pterygium. The optimal total dose appears to be in the range of 2000 cGy to 6000 cGy.

A spacer/injector needle for 125I and other radioactive sources in permanent seed implants.

A spacer/injector needle for 125I and other radioactive sources is described. Exposure is minimized by speed, distance, and (in the case of 125I) the low energy of the source shielded within the needle. Afterloading can easily be performed using small trocars. A readily attached plunger gives the needle a syringe (injection) action, while a rapid seed loader reduces loading time as well as the number of needles required when loading is carried out in the operating room.

Surgical radiation therapy with vicryl-125I absorbable sutures.

A convenient method of interstitial radiation therapy can be quickly and easily accomplished using absorbable Vicryl-125I sutures which offer these general advantages: long shelf life, 60 day half-life; low energy, 28 kilo electron volts, permitting patients to leave the hospital; good geometric and anatomic distribution of 125I seeds which remain in place after implantation; less radiation exposure to the operating and attending personnel due to this low energy plus the reduced exposure time provided by quick implantation; removal unnecessary, reducing exposure time; implantation using minor surgical equipment; dosage determination easily calculated; hospitalization, from the standpoint of radioactivity, unnecessary.

Simplified interstitial therapy technique ("Vicryl" 125I) for unresectable lung cancer.

A simple technique of permanent radioactive implantation, originally developed for the increasing number of unresectable lung tumors, utilizes absorbable polyglactin sutures ("Vicryl") containing low intensity, long half-life 125I seeds.

Interstitial therapy suing non-absorbable (Ir192 nylon ribbon) and absrobable (I125 "Vicryl") suturing techniques.

Permanent and removable interstitial implantation techniques using absorbable and unabsorbable sutures are described. Most of these techniques can be performed in the clinic easily and quickly with basic instruments: needle holder, needle book, and hemoclips. Specifically, Ir192 (74-4 day half life, 300-610 keV, and 6.0 cm. hvl in tissue) nylon ribbon and I125 (60 day half life, 27-35 keV, and 2.0 cm. hvl in tissue) Vicryl sutures are described. A major advantage of the I125 over the Ir192 see (other than the fact that it can be permanently implanted and needs less radiation protection) is that the patient does not remain highly radioactive for as long a period due to hte extremely low I125 energy and may be allowed to leave the hospital. Both nuclides have the advantage of a long shelf life, making their use practical and economically feasible.