The impact of trauma teams on basic surgical training

An analysis of the number of trauma teams and the extent of involvement of basic surgical trainees in these teams in the South-West region is presented.

Field trial of systemically delivered arthropod development-inhibitor (fluazuron) used to control woodrat fleas (Siphonaptera: Ceratophyllidae) and ticks (Acari: Ixodidae)

An orally delivered arthropod development-inhibitory (fluazuron) was evaluated for its potential to reduce the number of flea and tick vectors found on the dusky-footed woodrat Neotoma fuscipes Baird, a reservoir host important in disease enzootiology in northern California. Pigmented bait cubes containing fluazuron were distributed monthly to woodrat nests in a chaparral habitat for 1 yr. When compared with control woodrats, the numbers of fleas [primarily Orchopeas sexdentatus (Baker)] on treated woodrats were significantly reduced 3-4 mo after initial application, and remained so for the duration of the application period. By contrast, tick numbers were not significantly reduced on treated woodrats. After the cessation of treatments, flea indices remained lower on treated animals for up to 2 mo after application. Approximately 93% of woodrats captured in the treatment area excreted pigmented feces and 93% of distributed bait cubes were removed by woodrats, which indicates that the bait cube formulation and delivery system were highly effective. Bait cubes also were attractive to small rodents and ground-frequenting birds. The results of this study suggest that a monthly application program of fluazuron delivered by bait cube is effective in reducing woodrat flea-burdens, but is not effective, at least in the short-term, in controlling ticks.

Phylogenetic relationships of necrogenic Erwinia and Brenneria species as revealed by glyceraldehyde-3-phosphate dehydrogenase gene sequences

Recent examination of the relationships of the dry necrosis-inducing (necrogenic) erwinias using 16S rDNA sequences demonstrated that these bacteria comprise a polyphyletic group and, therefore, have been subdivided into three distinct genera, Erwinia, Brenneria and Pectobacterium, with the classical 'amylovora' group species now being distributed nearly evenly among the first two. To further assess the molecular evolutionary relationships between current necrogenic Erwinia and Brenneria species, as well as between these genera and the exclusively soft-rotting genus Pectobacterium, the glyceraldehyde-3-phosphate dehydrogenase (gapDH) genes from 57 Erwinia and Brenneria isolates along with Pectobacterium type strains were PCR-amplified, sequenced and subjected to phylogenetic analysis. Pairwise alignments of cloned gapDH genes revealed remarkably high interspecies genetic diversity among necrogenic isolates. Four evolutionary clades of necrogenic species were described that assorted more closely to known soft-rotting species than to each other. Interclade comparisons of gapDH nucleotide sequences revealed as much genetic divergence between these four necrogenic clades as existed between necrogenic and soft-rotting clades. An examination of the phylogenetic utility of the gapDH gene in light of current 16S rDNA clustering of these species revealed varying levels of taxonomic congruence between these genes for the structure of Erwinia, Brenneria and Pectobacterium. These analyses suggest that, while gapDH possesses sufficient genetic variation to fully differentiate Erwinia and Brenneria species, the gene may not accurately reflect interspecies taxonomic relatedness among all three phytopathogenic genera.

First Report of Verticillium dahliae on Stevia (Stevia rebaudiana) in North America

Stevia (Stevia rebaudiana Bertoni, Asteraceae) is the source of stevioside, a sweet, low-calorie sugar substitute. Acreage of stevia in California has been increasing in recent years. In October 1999, stevia plants in a commercial field exhibited stunting, leaf necrosis, and vascular discoloration. Verticillium dahliae was consistently isolated from diseased root and stem pieces plated on water agar and acidified potato dextrose agar (APDA). Colonies became dark with age on APDA, formed single celled conidia on hyaline verticillate condiophores, and produced dark microsclerotia. Stevia (cv. R-set 1) plants were grown from seed in soilless potting mix in 20-cm-diameter pots. Roots of eight 4-week-old stevia plants were submerged in a 10⁶ conidia per ml suspension of one of the isolates for 2 min. Eight control plants were dipped in sterile water. The plants were then repotted in soilless potting mix in 10-cm-diameter pots. Four weeks later, inoculated plants exhibited stunting, necrotic lower leaves, and discolored vascular systems. Control plants remained healthy. V. dahliae was reisolated on water agar from diseased plants. The experiment was conducted twice and the results were identical. This is the first report of V. dahliae on stevia in North America.

Implications of Sexual Reproduction for Phytophthora infestans in the United States: Generation of an Aggressive Lineage

Phytophthora infestans isolates (n = 26) collected in the Columbia Basin of Oregon and Washington in 1993, which had been characterized previously for mating type, metalaxyl sensitivity, and alleles at the glucose-6-phosphate isomerase locus, were analyzed for nuclear restriction fragment length polymorphism (RFLP) bands detected by probe RG57 and mitochondrial haplotype. Analyses involving the larger set of markers indicated that this group of isolates satisfied expectations of a sexual progeny: they contained much greater genetic diversity than has been reported for most other epidemic populations of P. infestans in the United States and Canada (16 unique multilocus genotypes); both mating types were present in proximity; all possible combinations of alleles occurred at many pairs of polymorphic loci; and two distinct mitochondrial haplotypes were distributed among the isolates. An in vitro laboratory cross involving the putative parents (US-6 and US-7) as parental strains produced progeny with the same general characteristics as the field isolates. Among the field progeny were two genotypes, US-11 and US-16, that had been described previously but from subsequent and largely clonal collections. Isolates obtained from tomatoes (n = 40) and potatoes (n = 7) in 24 counties in California in 1998 were analyzed as described above, and all except one US-8 isolate from potatoes were of the US-11 clonal lineage, consistent with the hypothesis that the US-11 lineage is an especially fit clonal lineage that has survived over time and can dominate pathogen populations over a large area. We conclude that the 1993 Columbia Basin collection represents a sexual progeny that generated the US-11 lineage, and that this lineage is particularly fit when tomatoes are part of the agroecosystem.

Influence of Soil Saturation and Temperature on Erwinia chrysanthemi Soft Rot of Carrot

In 1998, soft rot caused by Erwinia chrysanthemi resulted in an estimated loss of 1,800 tons of carrots in California. The disease appeared to be related to unusually high temperatures and excessive irrigation. To determine the optimum conditions for development of soft rot under controlled conditions, pots of carrots inoculated with E. chrysanthemi were saturated with water and incubated at 20, 25, 30, or 35°C. Plants were harvested and examined for disease 12, 24, 36, 48, 72, and 96 h after inoculation. Negligible disease occurred after 12 h. Disease severity and incidence increased with increasing temperature and duration of saturation from 24 to 96 h. In a second experiment, carrot disks were inoculated with three isolates each of E. chrysanthemi and E. carotovora subsp. carotovora and incubated at 15, 20, 25, 30, and 35°C. After 48 h, the disks were washed to remove rotted tissue and reweighed. Neither bacterium reduced carrot disk weight at 15°C. In general, moderate weight reduction occurred at 20 and 25°C. The greatest degree of soft rot was caused by E. chrysanthemi at 30 and 35°C. E. carotovora subsp. carotovora isolates were relatively less virulent than E. chrysanthemi at 30°C and none of the E. carotovora subsp. carotovora isolates reduced carrot disk weight at 35°C. This is the first report of E. chrysanthemi causing soft rot of carrot in California. Based on these results, growers should limit the length of time carrot roots are exposed to saturated soil, especially at high soil temperatures.

Influence of Gibberellic Acid on Carrot Growth and Severity of Alternaria Leaf Blight

Applications of gibberellic acid (GA) to carrot foliage consistently reduced the percentage of leaf area affected by Alternaria dauci compared with nontreated plants. The degree of leaf blight reduction with two applications of GA was similar to that achieved with four applications of the fungicide iprodione. At the rates examined (GA at 2.5 to 250 mg/liter), foliage dry weights were generally increased by GA. Although root weight was significantly reduced by rates of 250 mg/liter, applications of lower rates (40 mg/liter or less) reduced leaf blight severity without affecting root quality. Applications of GA usually resulted in plants with longer leaves, wider petioles, and a more upright growth habit. In one trial, leaf length and petiole diameter increased linearly with increasing rates (20, 30, and 40 mg/liter). When applied twice at 30 mg/liter, GA did not affect cuticle, epidermal, or leaf thickness. In general, the initial timing of two applications of 20 to 40 mg/liter (4, 6, or 8 weeks after plant emergence) did not influence the effects of GA. However, in one trial, there was a greater incidence of core separation from the root cortex when 40 mg/liter was applied initially at 4 weeks. GA at 30 mg/liter slightly but significantly decreased inner root color in one of two trials.

Outbreak of Eremothecium coryli Fruit Rot of Tomato in California

A ripe fruit rot of tomato (Lycopersicon esculentum) associated with stink bug (Euschistus conspersus) feeding caused extensive losses in the Sacramento Valley of California in 1998. Portions of several fields were abandoned at harvest due to fruit rot levels >30%. Symptoms included a soft, water-soaked rot often surrounding a firm, dark green island. Entire fruit sometimes became watery and soft. The ascomycetous yeast, Eremothecium coryli, characterized by spindle-shaped ascospores with long, thin, whip-like terminal appendages (1), was consistently isolated from diseased tissue plated on V8 or potato dextrose agar amended with tetracycline. Ripe tomato fruit were inoculated with a 0.1-ml suspension of 1.5 × 10⁵ ascospores per ml injected to a depth of ≈4 mm to simulate stink bug probing. Fruit were placed in plastic containers and, in initial tests, were held at room temperature. In subsequent tests, inoculated fruit were maintained at constant temperatures of 20, 25, 30, or 35°C. Controls included inoculum either placed on the fruit surface or injected with sterilized water. Each treatment consisted of one to four fruit in two to four replications. All experiments were repeated. Lesions were visible within 5 days after inoculation and were >25 mm in diameter after 7 days. Progression of rot occurred at all temperatures but was fastest at 30 and 35°C. Controls remained symptomless. E. coryli was reisolated from infected fruit. This is the first documentation of field-level losses caused by E. coryli associated with stink bug feeding. Isolates are maintained in the Herman J. Phaff Collection of Yeast and Yeast-like Microorganisms at the University of California, Davis. Reference: (1) G. S. de Hoog et al. 1998. Eremothecium Borzi emend. Kurtzman. Pages 201-208 in: The Yeasts-A Taxonomic Study. C. P. Kurtzman and J. W. Fell, eds. Elsevier Scientific Publishers, Amsterdam.

First Report of Pseudomonas syringae pv. tomato Race 1 on Tomato in California

Symptoms of bacterial speck have occurred sporadically in California since 1993 on tomato (Lycopersicon esculentum) cultivars that possess the PTO gene for resistance to Pseudomonas syringae pv. tomato race 0. In 1998, the disease was found on numerous cultivars resistant to race 0 in fields throughout the Sacramento Valley. In several fields, it caused severe defoliation of tomato seedlings. Symptoms included dark brown to black leaf and stem lesions surrounded by yellow halos. Seven isolates were identified as P. syringae pv. tomato based on analysis of whole cell fatty acids (MIDI, Newark, DE; similarity indices of 0.746 to 0.710), carbon utilization profile (Biolog, Hayward, CA; similarity indices of 0.556 to 0.840), and LOPAT results: levan production (+), oxidase reaction (-), potato soft rot (-), arginine dihydrolase production (-), and tobacco hypersensitivity (+) (2). The isolates were identified as race 1 by inoculating greenhouse-grown tomato plants of cv. Ontario 7710, which possesses the PTO gene, and cv. H1916, which is susceptible to both known races of P. syringae pv. tomato. At least eight plants of each cultivar were inoculated with each isolate. Plants were inoculated by spraying leaves with a bacterial suspension mixed with Carborundum or puncturing leaves with needles dipped in the bacterial suspension (10⁷ cells per ml). Controls were inoculated with water. All plants inoculated with the bacteria developed speck symptoms in 6 days. The bacteria were reisolated from all inoculated plants and confirmed as strains of P. syringae pv. tomato. This is the first documentation of P. syringae pv. tomato race 1 in California. This race was previously reported in Canada in 1986 (1). References: (1) M. B. Lawton and B. H. MacNeill. Can. J. Plant Pathol. 8:85, 1986. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966.

Occurrence and Pathogenicity of Fungi Associated with Melon Root Rot and Vine Decline in California

The occurrence of fungi associated with root rot and vine decline of melon (Cucumis melo) in commercial fields in California was surveyed over 3 years. The fungi most frequently isolated from discolored vascular tissue or root rot were Acremonium cucurbitacearum, Rhizopycnis vagum, Monosporascus cannonballus, Fusarium solani, Macrophomina phaseolina, Pythium spp., and Verticillium dahliae. The frequency of isolation of the various fungi varied with root symptomology. Pythium spp., and M. phaseolina were frequently associated with a wet, brownish root rot, while A. cucurbitacearum, R. vagum, and Rhizoctonia solani were generally associated with a dry, corky root rot. Presence of Monosporascus cannonballus was associated both with a wet, brownish rot as well as with discrete, reddish, corky lesions. The frequency of isolation of a given pathogen varied with geographic location, with M. cannonballus present only in the southern production areas, while A. cucurbitacearum and Rhizopycnis vagum were most common in the northern production areas. In pathogenicity tests in field microplots, M. cannonballus caused vine collapse and severe root rot of cantaloupe, reducing root length density by 93%. California isolates of R. vagum and A. cucurbitacearum, although only weakly pathogenic in field microplots, caused root discoloration and reduced vine growth in greenhouse tests. Reduction in dry weight of greenhouse-grown cantaloupe was 40, 23, and 39% for R. vagum, A. cucurbitacearum, and M. cannonballus, respectively.

Active variants of human parathyroid hormone (1-34) with multiple amino acid substitutions

We used site-directed mutagenesis to construct 55 single-site variants of rhPTH, a recombinantly-expressed form of human parathyroid hormone (1-34) containing three amino acid changes compared to the natural sequence (ML8, ML18 and FY34). We identified several mutations, at residues Lys(13), Glu(19), Val(21), Glu(22), Lys(27) and Asp(30), that increase biological activity by up to 2. 5-fold, as measured by stimulation of adenylate cyclase activity in rat UMR-106 cells. We constructed a series of 15 variants in which two to eight substitutions at these positions were combined, and found that the mutations behaved additively, leading to peptides with significantly enhanced potency. The most active combination variant, with six substitutions (KS13, ES19, VQ21, ES22, KQ27 and DN30), is 15 times more active than the parent molecule. However, the extent to which such combinations increase the activity of the peptide depends critically on the identity of the residues at positions 8 and 18. We constructed two of the combination variants in a variety of sequence backgrounds containing different combinations of leucine, methionine and norleucine at positions 8 and 18. Enhancements in potency were significantly reduced when Met or Nle was present at either of these positions, both in UMR-106 cells and human SaOS-2 cells. A corresponding non-additivity was observed in direct measurements of receptor binding affinity on UMR-106 cells. These results suggest that interactions, either direct or indirect, between certain PTH side chains prevent these mutations from behaving in an additive manner.

Wound healing following anterior keratectomy and lamellar keratoplasty in the pig

PURPOSE

To examine corneal wound healing in an animal model of two types of mechanical lamellar keratectomy.

METHODS

One eye from each of 28 pigs was studied. Using a motorized keratome, corneas were subjected to an anterior lamellar keratectomy with removal of anterior stroma and epithelium, or to automated lamellar keratoplasty (ALK) with reapposition of a corneal flap. The exposed stromal surfaces were labeled intraoperatively with a fluorescent dye (DTAF) to assess deposition of stromal components during subsequent wound healing. Examination before surgery and enucleation included measurement of corneal curvature and intraocular pressure, and assessment of corneal haze. Eyes were prepared for histological examination, fluorescence microscopy, and for fibronectin immunohistochemistry.

RESULTS

Both keratectomy procedures produced flattening of corneas by up to 3.80 diopters, 28 days after surgery. Corneal haze was more pronounced in eyes from which epithelium was removed (anterior lamellar keratectomy group). The increased haze in this group was associated histologically with appearance of many reactive keratocytes and inflammatory cells, deposition of new stromal material, and more widespread appearance of fibronectin immunoreactivity. In the lamellar keratoplasty group, only the edges of the corneal wound showed significant reactivity, and included keratocyte activation and epithelial ingrowth.

CONCLUSIONS

The pig provides a useful model for studies of refractive surgical techniques using procedures and instruments designed for use in humans. Mechanized keratectomy procedures that minimize disruption of the epithelium and Bowman's layer produce a less reactive corneal wound than procedures in which an expanse of epithelium and anterior stroma are removed.

Use of orally administered chitin inhibitor (lufenuron) to control flea vectors of plague on ground squirrels in California

The efficacy of orally administered lufenuron, a chitin inhibitor, to control fleas on California ground squirrels, Spermophilus beecheyi (Richardson), was evaluated during a 2-yr study in Santa Barbara County, CA. Results demonstrated that use of a host-targeted feed cube containing lufenuron was effective in significantly reducing the burden of Oropsylla montana (Baker) and Hoplopsyllus anomalus (Baker) fleas on ground squirrels. A flea index that indicated a mean number of fleas per squirrel of 10.0 decreased to 1.3 after 2 treatments in season 1, and to 0.7 and 0.2 after the 3rd and 4th treatments, respectively, in season 2. A cost comparison of this new method compared with a traditional reactive, emergency, insecticide-based plague control program demonstrated a cost reduction of approximately 90%. The results of this study indicated that a lufenuron feed cube was an effective, cost-saving, and proactive technique for controlling fleas on California ground squirrels, and thus reducing the risk of disease transmission in plague endemic regions.

Corneal wound-associated glycoconjugates analyzed by lectin histochemistry

PURPOSE

To examine changes in corneal glycoconjugates during wound healing in a pig model of refractive surgery.

METHODS

Pig corneas were wounded using a mechanized microkeratome. Lamellar keratectomy, without replacement of a corneal cap, or automated lamellar keratoplasty, with replacement of a corneal cap, was performed. Corneas were prepared for microscopy 1, 7, or 28 days after surgery. Cryosections of corneas were probed with lectins recognizing a variety of carbohydrate moieties. Glycoconjugates were characterized by glycosidase digestion and chemical extraction.

RESULTS

Of the lectins used, only that from Dolichus biflorus (DBA), specific for terminal N-acetylgalactosamine, exhibited a dramatic change in staining pattern after wounding. In unwounded corneas, DBA labeled the superficial epithelium, Bowman's layer, and occasional keratocytes. After wounding, DBA intensely labeled exposed stromal surfaces and keratocytes near wound sites. RESULTS of glycosidase treatments indicated that the DBA-binding material contains alpha-linked N-acetylgalactosamine. After extraction with lipid solvents, stromal DBA labeling was unchanged, while that of keratocytes was greatly diminished.

CONCLUSIONS

Corneal wounding results in the accumulation of specific glycoconjugates at surfaces and in keratocytes. After keratectomy, the exposed stromal surface is infiltrated with ocular surface components, including DBA-binding glycoproteins. The presence of these components may influence the course of wound healing. In addition, changes in keratocyte glycoconjugates may accompany their mobilization to the wound-repair phenotype.