Field experiments were conducted near Chickasha, OK, in 1999 and 2000 and near Perkins, OK, in 2000 to evaluate the effects of Palmer amaranth on harvest efficiency of grain sorghum and full-season competition with that crop. Weed densities were 0 (the weed-free check), 1, 2, 4, 6, 9, 12, and 18 plants/15 m of row. In the harvest efficiency experiments, each additional weed per 15 m of row increased grain moisture before cleaning by 0.7 and 0.2% at Chickasha in 1999 and at Perkins, respectively. After cleaning, it increased moisture by 0.2% in both the experiments for each weed. Foreign material increased 67, 2, and 3 kg/ha at Chickasha in 1999, Chickasha in 2000, and Perkins, respectively. At Chickasha in 2000, sorghum seed loss through the combine increased 11 kg/ha for each additional weed per 15 m of row. Grain grades improved at Perkins at higher weed densities. In the competition experiments, grain yield decreased by 1.8 to 3.5% for each increase of 1 weed/15 m of row. More weeds resulted in higher weed dry weight. Each kilogram of Palmer amaranth dry weight per plot reduced grain yield by 5.3 to 9.1%. In 2000, sorghum seeds per panicle were reduced by 27 to 50 for each weed. Grain grades generally decreased as weed density increased at Chickasha in 2000 but not at Perkins.

Identification of the O157 antigen is an essential part of the detection of Escherichia coli O157:H7, which is recognized as a major etiologic agent of hemorrhagic colitis. However, polyclonal antibodies produced against E. coli O157:H7 lipopolysaccharide (LPS) may react with several other bacteria including Brucella abortus, Brucella melitensis, Yersinia enterocolitica O9, Escherichia hermannii, and Stenotrophomonas maltophilia. We produced eight monoclonal antibodies (MAbs) specific for the LPS of E. coli O157. Western blots (immunoblots) of both the phenol phase (smooth) and the aqueous phase (rough) of hot phenol-water-purified LPS indicated that three of the MAbs were specific for the O antigen and five were reactive with the LPS core. The eight MAbs could be further differentiated by their reactivities to Salmonella O30 LPS (group N), which is reported to be identical to the E. coli O157 antigen. All eight MAbs reacted strongly to all of the 64 strains of E. coli O157 tested, which included 47 isolates of O157:H7 and 17 other O157 strains. None of the eight MAbs cross-reacted with any of the 38 other E. coli serotypes tested, which consisted of 29 different O-antigen serotypes, or with 38 strains (22 genera) of nonE. coli gram-negative enteric bacteria. Escherichia coli O157:H7 has been identified as a major etiologic agent of hemorrhagic colitis (31), which is occasionally accompanied by serious complications such as hemolyticuremic syndrome (18, 24) or thrombic thrombocytopenic purpura (7). Recent studies have shown that beef and dairy cattle are natural reservoirs of E. coli O157:H7 (2, 43) and that E. coli O157:H7 can be isolated from the feces of asymptomatic cattle (2, 22), from raw milk (2, 9), and from poultry, pork, and lamb (12, 30). However, undercooked ground beef is the major source of E. coli O157:H7 in food-borne outbreaks (8). The E. coli O157:H7 serotype has traditionally been identified by agglutination tests (14, 21) or immunofluorescence assays (25) with polyclonal antibodies. However, use of polyclonal antisera may result in false-positive identification of E. coli O157 (3, 20). For example, polyclonal anti-O157 E. coli antisera may cross-react with E. coli O7 and O116 (13, 27). In addition, other bacteria possess cross-reacting epitopes which mimic epitopes on the lipopolysaccharide (LPS) of E. coli

Four field experiments were conducted to measure the effects of sevenIpomoea hederacea(L.) Jacq. densities onGossypium hirsutumL. lint yield, stripper-harvest efficiency, and fiber properties. The seven densities were 0, 2, 4, 6, 8, 10, and 12 weeds 10 m−1of row. Data were used to develop prediction models to compare with those previously constructed that used fewer experiments and fewer weed densities in this range.Gossypium hirsutumlint yield in kilograms per hectare and as a percentage of the weed-free control best fit a linear regression model.Gossypium hirsutumlint yield reductions for each increase of one weed 10 m−1of row ranged from 30.7 to 36.2 kg ha−1at Chickasha and from 35.4 to 36.4 kg ha−1at Perkins. Lint yield reductions for each weed 10 m−1of row ranged from 3.8 to 6.9% at Chickasha and from 3.9 to 6.0% at Perkins. All plots could be mechanically stripper harvested, except for the 12-weed density at Chickasha in 1994 and the 10- and 12-weed densities at Perkins in 1996. Harvest efficiencies were not significantly different in any experiment. The only fiber properties to display significant differences were micronaire and strength at Chickasha in 1994. Prediction models calculated herein were highly similar to those previously constructed.

Monoclonal antibodies to K88ac and K88ab were used in enzyme-linked immunosorbent assays on Escherichia coli cultures known to produce K88 pili. A total of 415 K88-positive E. coli isolates from nine states were all found to be the K88ac variant. The cultures tested were isolated during the years 1976 to 1985.