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Thaxtomin A production in culture, potato common scab severity (percentage of tuber surface infected or number of lesions per tuber), and fatty acid profiles were determined for 78 Streptomyces isolates. Only pathogenic Streptomyces spp. (n = 17) produced thaxtomin A in culture. Thaxtomin A production in culture (microgram/mL) was significantly positively correlated with the percentage of tuber surface infected (R = 0.60; p = 0.017) but not with the number of lesions per tuber (R = 0.37; p = 0.17). An increase of 1 microgram/mL in thaxtomin A production corresponded to an 11% increase in disease severity (percentage of tuber surface infected). The data indicate that quantitative information on the ability of a particular pathogen isolate or population to produce thaxtomin A may be critical to understanding and predicting the disease potential of that population. Using cluster analysis of fatty acid data, 94% of 67 unknown field isolates grouped with other field isolates having the same pathogenicity (plus or minus).

Analysis of cellular fatty acid profiles was used to distinguish among introduced pathogen- suppressive strains and indigenous strains of Streptomyces spp. isolated from soil of field plots established to test the efficacy of Streptomyces strains PonSSII and PonR in the biological control of potato scab. Reference libraries of fatty acid profiles were developed for a collection of known pathogenic strains and the introduced suppressive strains. Population densities of pathogen-related, suppressive, and saprophytic Streptomyces strains were determined from the relationship of field isolates to mean library profiles using cluster analysis and the unweighted pair-group method using arithmetic averages. Community diversity was similarly determined. Streptomyces strains PonSSII and PonR were distinguished from each other and from the pathogen group (which clustered together) based on fatty acid profiles. The introduced, suppressive strains successfully colonized the soil and represented 2-19% of the isolates sampled over 2 years. The introduction of the suppressive strains inhibited the population of strains related to the pathogen library at each sample date; the pathogen population was substantially lower in soil from treatments where the suppressive strains were introduced compared with the nonamended control. At harvest, the pathogen-related population was suppressed 85-93 and 36-44% in 1991 and 1992, respectively, in treatments with the suppressive strains compared with the nonamended control. Diversity of the community was not affected by the introduced strains, and diversity and equitability indices were similar among treatments at any sample time. The inhibition of the pathogen-related population was correlated with a reduction of scab symptoms observed in the field plots into which the suppressive strains were introduced. Implications of a fundamental shift in the pathogen-related population in response to the introduction of the suppressive strains for long-term biological control of potato scab are encouraging.

Lasers have been used for endoscopic gastrointestinal surgery at our institution since 1977. The argon and Nd-YAG lasers are valuable for coagulating upper gastrointestinal hemorrhage, arteriovenous malformations, and benign and malignant lesions, as well as a variety of anatomic anomalies. Between December 1977 and September 1983, 222 procedures were performed in 122 patients. Hospital charts were reviewed and a scale constructed to assess the results of treatment. When information was available, a comparison of transfusion requirements before and after laser therapy was made. Success was achieved in 84 percent of the patients regardless of initial diagnosis. Laser therapy was not effective in 12 patients (10 percent). In 27 patients with gastrointestinal atrioventricular malformations, transfusion requirements fell from a mean of 17 +/- 5.9 units in the year before laser therapy to 1 +/- 0.8 units in the year after laser phototherapy (p less than 0.01). Complications rarely occurred (6 percent of all procedures). There were no perforations of the gastrointestinal tract and only one death (0.8 percent) partially attributable to laser application. Endoscopic laser surgery is minimally invasive and can be performed on an outpatient basis without anesthesia. It is especially valuable in patients with a high operative risk.

Anisotropine methyl bromide, an anticholinergic, 80 mg given orally at 8 P.M., suppresses gastric acid secretion through the night without significant side effects. Thirty patients with endoscopy-proved symptomatic duodenal ulcer disease completed a randomized, double-blind, placebo-controlled trial of nighttime anisotropine methyl bromide therapy. Eleven (69 per cent) of 16 anisotropine methyl bromide-treated and six (43 per cent) of 14 placebo-treated subjects healed their ulcers within two weeks of starting treatment. The anisotropine methyl bromide-treated subjects averaged 0.63 +/- 0.27 (mean +/- S.E.) episodes of nocturnal pain during the treatment period versus 2.71 +/- 1.08 episodes in the placebo group (P = 0.06). This is the first reported study of this type designed to evaluate the efficacy of an anticholinergic agent in the healing of duodenal ulcers. Although not conclusive, the results suggest nighttime anisotropine methyl bromide therapy may be useful in the treatment of duodenal ulcer disease. Further studies seem warranted.

Nutrition is an antegral part of medical management and patient care. The goal of nutritional therapy is to provide nutrients in form and amount appropriate to patients' needs. Dietary modification and application of available nutritional supplements in digestive disorders should be based upon an appreciation of the fundamental pathophysiological derangements and tailored to restore optimal gastrointestinal function.