Multituberculate and other mammal hair recovered from Palaeogene excreta

Evidence of hair from several extinct mammals has been recovered from a rich accumulation of fossil excrement from the Late Palaeocene beds of Inner Mongolia, China. This highly unusual and previously undocumented depositional occurrence consists of hundreds of mammalian carnivore coprolites (fossil faeces) and a lesser number of probably raptorial bird regurgitalites (fossil pellets). The fossil hair occurs as impressions and natural casts in the extremely fine-grained, calcareous matrix that cements the skeletal remains within these faecal structures and preserves even the cuticular scale pattern on individual hair. Hair from at least four mammalian taxa, most notably the multituberculate Lambdopsalis bulla, has been identified. This record constitutes the first tangible evidence that, along with monotremes and therian mammals, multituberculates were hirsuite, and lends support for the presence of this mammalian feature in the most recent common ancestor of these three groups.

[Anesthetic management to reduce blood loose in surgical process of palatoplasty]

869 cases with palate cleft, aged from 2 to 12 years old, received palatoplasty surgery in Department of Oral Maxillofacial Surgery, West China University of Medical Science from 1987 to 1996 were reviewed. The effect of anesthetic method on blood loose during surgical procedure was analyzed specifically. It was found that the amount of blood loose was quite different with different anesthetic method. Simple method of anesthetic medication which could dramatically reduce the amount of blood loose in palatoplasty operation was recommended. The key points of anesthetic method for palatoplasty operation, especially in application for children were discussed.

A 5-lipoxygenase inhibitor at micromolar concentration raises intracellular calcium in U937 cells prior to their physiologic cell death

Micromolar MK886, a selective inhibitor of 5-lipoxygenase at nanomolar concentration, induces physiologic cell death in U937 and chronic myelogenous leukemia blast cells. When U937 cells were challenged with 10 microM MK886, an acute, biphasic and sustained rise in intracellular Ca2+ occurred, as determined with Fura-2. The initial increase was followed by a transient decline and a larger rise due to an influx of external Ca2+. The first increase and part of the subsequent rise also developed in Ca(2+)-free medium, identifying their origin from intracellular stores. The intracellular Ca2+ concentration of U937 cells that remained after culture for 24 or 48 h with 5 or 10 microM MK886 was not reliably altered from the control values of 130 +/- 8.3 nM. Under similar conditions MK886 did not increase cytosol Ca2+ of a human prostate (PC3) cell line examined in suspension. The increase in intracellular Ca2+ in response to MK886 in calcium-containing medium was confirmed with an ACAS laser spectrometer. U937 cytosol pH was measured with the fluorescent probe BCECF, but not persistent acute or chronic change was induced by MK886. The rapid and sustained rise in Ca2+ induced by MK886 is an early event in U937 cells which subsequently undergo physiologic cell death characterized in many by apoptosis.

Chronic morphine treatment of guinea pigs induces nonspecific sensitivity changes in the nucleus tractus solitarius in vitro

Chronic morphine treatment results in the development of an opioid tolerance in guinea pig myenteric S-neurons that is nonspecific among pharmacologically unrelated inhibitory agonists and the concurrent development of a nonspecific super-sensitivity to unrelated excitatory agonists. The purpose of these studies was to extend this model of opioid tolerance in the guinea pig to central neurons, specifically to the medial nucleus tractus solitarius (mnTS), the primary brainstem relay for visceroceptive information. Pharmacological responses of the guinea pig mnTS neurons were examined in an in vitro brainstem slice preparation and compared between chronically morphine-treated animals and untreated controls. The spontaneous activity of guinea pig mnTS neurons was inhibited by gamma-aminobutyric acid (GABA), the GABAA-selective agonist muscimol, 2-chloroadenosine and clonidine and was excited by glutamate and elevations in extracellular potassium. Applied alone, morphine or the GABAA-selective antagonist bicuculline inhibited and excited approximately equal proportions of nucleus tractus solitarius (nTS) neurons. However, when applied in the presence of bicuculline, morphine inhibited most neurons tested. Reduced inhibitory responses to four agonists, i.e., morphine, muscimol, 2-chloroadenosine and clonidine, were observed in mnTS neurons in slices obtained from chronically morphine-treated animals. Increased excitation of these neurons by elevated extracellular potassium was observed. It is concluded that 1) guinea pig nTS neurons respond similarly to nTS neurons from other species in vitro, 2) opioids disinhibit some proportion of guinea pig nTS neurons in vitro through a GABAergic mechanism and 3) the development of opioid tolerance in guinea pig nTS neurons is qualitatively similar to that of guinea pig myenteric S-neurons.

[Effects of different form calcium on growth and tissue calcium level in rats]

In order to solve the problem of calcium deficiency and to look for economic and efficient source of calcium, the effects of calcium carbonate, active calcium and calcium lactate on growth, development and tissue calcium level in rats were compared. Fifty-six 3-week old weaning rats were fed with calcium deficient diet (containing vitamin D 500 IU per kg diet) for 3 weeks, and then were divided into four groups randomly with 14 rats in each group, half male and half female. The diet of control group (A) was the basic diet, while the three experiment diets were supplemented with calcium carbonate (B), active calcium (C) and calcium lactate (D) (3000 mg calcium per kg diet), respectively. The experiment term was 12 weeks. The results showed that the body weight and length of calcium supplemented group were significantly higher than that of control group (P<0.05). Among the calcium supplemented groups, no significant differences were observed except the difference of body length between the group D and the group A in female. Calcium deficiency dramatically hindered the development with reduced dietary intake and decreased food consumption efficiency. The calcium levels in plasma, red blood cells and liver were significantly higher in the supplemented groups than that in the control group (P<0.05), however, there was no difference among the supplemented groups. No significant difference of calcium levels in muscle and heart was observed among all groups. Based on needs for reaching the RDA with additional 400 mg/d from present calcium status in Chinese population, the calcium carbonate is the most economic one and the ideal calcium source for supplementation.

Emerging issues in microbiological food safety

Many microorganisms previously unrecognized as food-borne or harmful are emerging as human pathogens transmitted by food. This is a result of recent acquisition of key virulence factors, detection by newly developed isolation procedures, or astute detective-like laboratory skills of microbiologists. Six microbial pathogens, including Shiga toxin-producing Escherichia coli, Listeria monocytogenes, Arcobacter butzleri, Helicobacter pylori, Cryptosporidium parvum, and Cyclospora, have become recognized as significant causes of human illness. Although the ecology and epidemiology of illness caused by some of these pathogens have not been fully elucidated, food has the potential of being an important vehicle in their dissemination. Existing technologies and new approaches such as irradiation and hazard analysis critical control point (HACCP) programs are useful tools in the control of food-borne hazards. However, because of ever-changing products, processes, food-handling practices, societal habits, and pathogens, emerging food-borne diseases will continue to be an important public health concern.

[Bone mineral content and its influence factors of children aged 0-16 in a city and village]

The radial and ulnar bone mineral content (BMC) was measured by single-photon absorptiometry, and the effects of multiple independent variables on BMC and bone width (BW) were explored using multiple regression analysis in 332 rural and city children aged 0-16 years in Henan province from 1994 to 1995. BMC, BW, BMC/BW and forearm length increased with age increasing, and the BMC in city children aged 0-6 years was higher than that in rural children. Radial BMC was positively related to BW in the measured sites. Age, body weight and height (or length) all had significantly positive and independent effects on radial BMC in both groups. The positive correlation of radial BMC with age was observed, however, the ratio of radial BMC to body weight was negative correlation. The BW in measured site and forearm length increased with ages. After adjusted for body size, there were no significant effects of sex, age and body weight on radial BW except height (length). This study shows that overall body size rather than adiposity is the important factor for bone BMC, so that it is needed to consider several variables, for example, BMC, BMD, BMC/body weight and BMC/age.

Polymerase chain reaction for detecting Escherichia coli O157: H7

Escherichia coli O157:H7 is known as an important cause of hemorrhagic colitis and hemolytic uremic syndrome. Real-time procedures that are sensitive for detecting small populations of this bacterium in food are lacking and needed. An expression library was constructed by ligation of BamHI-EcoRI DNA fragments of E. coli O157:H7 to plasmid vector pUC19 and transformation of recombinant plasmids to E. coli JM109. A clone that contained a specific DNA fragment of E. coli O157:H7 was identified by colony immunoblot assay using monoclonal antibody MAb 4E8C12 that uniquely links to E. coli O157:H7 and a few other serotypes of verotoxin-producing E. coli. The DNA sequence of the clone consisted of 110 bp of 5' region of enterohemorrhagic E. coli (EHEC) eae gene and a 688 bp DNA fragment adjacent to 5' end of the eae gene, including an unknown function gene encoding 156 amino acids. A pair of oligonucleotide primers was synthesized based on the sequence of the 688 bp fragment. The primers were used in a polymerase chain reaction (PCR) to amplify a target DNA of 633 bp. The primers amplified 1 ng of DNA from 67 strains of E. coli O157:H7, two strains of E. coli O157:NM, and 7 of 11 E. coli O55:H7 and O55:NM strains, but not 50 ng of DNA from 34 strains of 29 other E. coli serotypes and 25 strains of 8 other bacterial species. Annealing temperatures from 60 to 63 degrees C could be used for the PCR without loss of specificity. The minimum amount of target DNA detected by the PCR was 5 pg. When a boiling method and GeneReleaser were used, the PCR was able to detect as few as 25 and 38 CFU of E. coli O157:H7, respectively, in 3 h.

An in vivo inhibitor of 5-lipoxygenase, MK886, at micromolar concentration induces apoptosis in U937 and CML cells

MK886 (Merck Frosst) is a selective in vivo inhibitor of 5-lipoxygenase, active at nanomolar concentrations. At micromolar concentrations, it inhibited the proliferation of U937 monoblastoid cells and of cultured malignant cells from patients with chronic myelogenous leukemia. These cells became morphologically apoptotic, a form of physiologic cell death. U937 cell apoptosis was assessed by flow cytometry, ultrastructure, DNA laddering and immuno-histology for free 3'OH-DNA. MK886-induced apoptosis developed over time as cells were recruited in concert with reduction in their numbers. Some CML cells exhibited cytoplasmic changes of apoptosis without typical nuclear changes. Under conditions used for measuring Ca2+ with Fura 2, 10 micromolar MK886 increased U937 intracellular Ca2+ 4-fold or more over the 8 minute period of measurement. Since MK886 inhibits the association of arachidonic acid with the 5-lipoxygenase activating protein, altered arachidonic acid metabolism may have contributed to these results.

Advanced glycation end products of the Maillard reaction in aortic pepsin-insoluble and pepsin-soluble collagen from diabetic rats

Recent immunohistological studies using antibodies against advanced glycation end products (AGEs) have demonstrated the presence of AGEs in several tissues. By an enzyme-linked immunosorbent assay using the monoclonal anti-AGE antibody, the present study aimed to determine AGEs in pepsin-insoluble collagen (PIC) as well as in pepsin-soluble collagen (PSC) from the aortas of streptozotocin (STZ)-induced diabetic rats (at 4, 16, and 28 weeks after STZ injection) and those of age-matched control rats. Addition of EDTA to the immunoassay buffer has led us to successful determination of AGEs in the aortic PIC samples with following results: 1) in diabetic rats, there was a time-related increase in the AGE contents at 28 weeks (n = 9, 226.4 +/- 13.5 ng/mg collagen [mean +/- SE]), compared with that at 4 and 16 weeks (n = 6, 79.6 +/- 9.5 ng/mg collagen, and n = 8, 149.4 +/- 30.9 ng/mg collagen at 4 and 16 weeks, respectively; both P < 0.05, between 4 and 16 weeks and 28 weeks); 2) after 28 weeks of diabetes, the AGE contents in PIC of aortas were significantly higher in diabetic rats than in controls (n = 9, 226.4 +/- 13.5 ng/mg collagen vs. n = 8, 129.6 +/- 14.9 ng/mg collagen, P < 0.01, diabetic vs. control); and 3) the level of the AGE content was strongly correlated with the PIC/total collagen (TC) ratio (n = 45, r = 0.698, P = 0.0001). By treating the samples of PSC with alkaline solution, the AGE content of PSC was also determined. In the PSC fraction, the AGE levels in the diabetic rats tended to increase with time and to be higher than those of control rats at 28 weeks although these changes were not statistically significant (diabetic: n = 4, 19.4 +/- 9.7; n = 6, 22.3 +/- 6.2; n = 6, 39.6 +/- 10.8; control: n = 4, 19.7 +/- 9.8; n = 6, 22.9 +/- 7.3; n = 7, 30.7 +/- 7.2; at 4, 16, and 28 weeks, respectively). Compared with the AGE levels of PSC, those of PIC were about four to seven times and four to five times higher in diabetic and control rats, respectively (PIC versus PSC in diabetic or control rats, all P < 0.001, at 4, 16, and 28 weeks, respectively). These findings provide the first immunochemical evidence that AGE adducts are present in the materials extracted sequentially by pepsin and collagenase and that these adducts in PIC accumulated as a function of the increase in the aortic PIC/TC ratio.

A low molecular weight outer-membrane protein of Escherichia coli O157:H7 associated with adherence to INT407 cells and chicken caeca

Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 and O26:H11 have been shown to produce a low mol.wt outer-membrane protein (OMP) that is unique to a few serotypes of E. coli. A mutant (A10) of E. coli O157:H7 strain HA1 deficient in the OMP was constructed by TnphoA mutagenesis and assayed for its adherent ability. Adherence of A10 to intestinal epithelial cells (INT407) was significantly less than that of its parent strain (HA1). Adherence of HA1 to INT407 cells was significantly decreased by treatment with a monoclonal antibody (4E8C12) that specifically binds to the OMP. When chickens were infected experimentally with E. coli O157:H7 strains, the average number of cfu of strain A10 recovered from chicken caeca was significantly less than those of strain HA1 and wild-type strain 932 at 14 and 21 days after peroral inoculation. These data suggest that the OMP of EHEC is associated with adherence of E. coli O157:H7 to epithelial cells in vitro and chicken caeca in vivo.

Line scan imaging of brain metabolites with CPMG sequences at 1.5 tesla

A line scan Carr-Purcell-Meiboom-Gill (CPMG) spectroscopic imaging sequence has been implemented on a standard 1.5 T clinical scanner to map metabolite signals at multiple echo times from voxels along selected tissue columns through the brain. The CPMG multiecho spectroscopic image data sets are used to estimate brain metabolite T2 decay parameters in a group of healthy volunteers and in one tumor patient. Inherent trade-offs between T2 decay, spectral resolution, and echo spacing prove to be important limiting factors. In particular, separate quantitation of choline and creatine resonances at 1.5 T was not achieved in the present implementation. However, the ability to collect data sets suitable for T2 decay analyses of combined choline and creatine resonances and N-acetyl aspartate resonances in under 10 minutes may prove of clinical utility in the study of brain pathology.

Binding of 14C-furazolidone metabolites to the muscular and hepatic proteins of trout

A high level of 14C was found to bind irreversibly with the liver proteins of rainbow trout (Oncorhyncus mykiss) exposed to 135 mg/kg bodyweight of 14C-labelled furazolidone (14C-FZ) in fish feed daily for 10 days. After the cessation of 14C-FZ treatment, hepatic protein-bound 14C in trout stayed high for at least 30 days. The chemical identity of protein-bound 14C remained to be elucidated. However, a part of the protein-bound 14C in the liver and muscle could be released as 3-amino-2-oxazolidinone by acid hydrolysis. The formation of protein-bound 14C in the liver was investigated further with trout dosed intravenously with different 14C-FZ doses at 10 degrees C or with 5 mg/kg FZ at different water temperatures. 14C binding to the liver proteins was found to increase with increasing FZ dose or water temperature. Results of these studies indicate that protein-bound 14C in the muscle and liver of trout is related to the formation of reactive intermediates from FZ. However, additional studies on the identities of the protein-bound FZ residues are required before they can serve as useful biomarkers to monitor FZ exposure in farm fish.

Specificity and binding affinity of an anti-crotoxin combinatorial antibody selected from a phage-displayed library

A crotoxin-specific, monoclonal, high-affinity, single-chain antibody variable region (scFv) was generated by combinatorial methods using Pharmacia's Recombinant Phage Antibody System. A high-affinity clone, designated A10G, was selected, and its DNA sequence was determined. Protein A10G showed high reaction specificity, with only the closely related rattlesnake neurotoxins, concolor toxin and Mojave toxin, showing cross-reactivity out of eleven group II phospholipase A2s (PLA2s) screened. No group I PLA2s cross-reacted in enzyme-linked immunosorbent assays. The gene coding for A10G was subcloned into an expression vector, and the resulting expressed nonfusion protein, designated A10GPE, was renatured and purified to apparent homogeneity. Dissociation constants of A10G with intact crotoxin and crotoxin basic subunit were determined to be 7 x 10(-10) and 6.8 x 10(-9) M, respectively. When A10GPE was preincubated with either the basic subunit or intact crotoxin at molar ratios of up to 5:1, no inhibition of phospholipase activity was observed. Expressed protein, however, could partially neutralize the lethality of Mojave toxin, a crotoxin homolog, in mice.

Selective inhibitors of 5-lipoxygenase reduce CML blast cell proliferation and induce limited differentiation and apoptosis

Inhibitors of the arachidonic acid metabolizing enzyme, 5-lipoxygenase, reduce the rate of proliferation of chronic myelogenous leukemia blast cells. The inhibitory agents studied were ETYA, A63162 and SC41661A. These reagents induced differentiation of cultured chronic myelogenous leukemia cells from blast to promyelocytic morphology. Promyelocytic cells then underwent apoptosis, which was identified by nuclear and cytoplasmic morphological features and by DNA laddering. Proliferation of monoblastoid U937 and myelomonocytic HL60 cell lines, known to contain 5-lipoxygenase and synthesize leukotrienes, was reduced by these inhibitors. U937 cells cultured with ETYA, A63162 or SC41661A for 48 h exhibited apoptosis as assessed by DNA laddering and morphology. Characteristic ultrastructural changes of apoptosis were seen at 120 h. MK886, an inhibitor of 5-lipoxygenase with a mechanism of action distinct from oxidation/reduction reagents, at 20-40 microM also inhibited CML and U937 cell proliferation and induced apoptosis, as shown by DNA laddering and ultrastructure.

Cloning and nucleotide sequence of a gene upstream of the eaeA gene of enterohemorrhagic Escherichia coli O157:H7

A DNA segment located immediately upstream of the eaeA gene of enterohemorrhagic Escherichia coli O157:H7 strain HA1 was cloned and sequenced. This segment contained an open reading frame encoding a predicted protein of 156 amino acids. A database search identified similar open reading frames upstream of the eaeA gene in two other bacterial pathogens, i.e. enteropathogenic E. coli and Citrobacter freundii. The predicted amino acid sequence of the enterohemorrhagic E. coli protein shared 96.8% and 94.2% identity with the enteropathogenic E. coli and C. freundii sequences, respectively. Because the open reading frame is located within the locus of enterocyte effacement region of the E. coli chromosome, a 'hot spot' for insertion of virulence factor genes, and shares high sequence homology with attaching and effacing EPEC and C. freundii, this protein may be associated with pathogenicity of E. coli O157:H7.

Cross-reactive immunity against different strains of the hepatitis E virus transferable by simian and human sera

Monkey infection with the hepatitis E virus induces protection. We confirm the humoral nature of this immunity and show that protection is effective against the homologous strain, as well as against heterologous strains isolated from Asian and African countries. However this immunity is incomplete since only the clinical disease seems to be prevented, while the virus is still excreted in stools and can even appear in blood as well after serotherapy as previous acute or occult infections. We obtained also a preliminary evidence that convalescent human sera are also efficient for the passive protection, indicating that seroprophylaxis of HEV hepatitis in pregnant women (20% of mortality during the 3rd trimester of pregnancy) should be attempted in the case of epidemics.

Disability glare: effects of temporal characteristics of the glare source and of the visual-field location of the test stimulus

One of the main early complaints of cataract patients, even when these patients exhibit only mild glare problems as measured by standard tests, is that glare impairs their night driving. To provide a better measure of the patients' impairment, glare tests should include measurements of the glare effect in conditions more similar to those found in night driving. During night driving the ambient light is very low, and oncoming headlights present a transient temporal pattern. Furthermore, the objects of interest often appear initially in the peripheral visual field. Thus three important characteristics of glare in night driving are that the ambient illuminance is in the scotopic-mesopic range, the detection stimulus is in the periphery, and the glare source is transient. Most of the current glare testers measure glare only at photopic levels, and all the glare tests that we know of use only steady sources of glare with foveal discriminations. All these conditions are dealt with. The transient glare source raised thresholds by 0.5-0.75 log unit more than the steady glare source, and the transient glare effect was more pronounced and more long lasting in the periphery. Standard glare testers seriously underestimate disability glare effects in everyday life.

Nonenzymatic glycation and extractability of collagen in human atherosclerotic plaques

The relationship between the extractability of collagen by enzymatic digestion and the degree of nonenzymatic glycation of collagen was examined in the aorta and skin from 38 subjects without diabetes mellitus (mean age: 62.3 +/- 20.2 years). Samples were obtained from the aortic media (M), lesion-free intima (I), atherosclerotic intima (A) and dermis of the skin (S). Collagen was extracted first by incubation with 1/50 (enzyme/substrate weight ratio) pepsin at 4 degrees C for 24 h (P-fraction) and then by incubation with 1/10 (enzyme/substrate weight ratio) pepsin at room temperature for 24 h (EP-fraction). The pepsin-insoluble precipitates were digested by incubation with 270 units of bacterial collagenase at 37 degrees C for 24 h (PIS-fraction). Collagen contents, ketoamines and collagen-linked fluorescence (CLF) were measured in each fraction. The amount of ketoamines and the level of CLF correlated inversely with the susceptibility of collagen to pepsin digestion in various tissues, including M, I, A and S. These values were highest in both the P- and EP-fractions of M, which contained the least amount of collagen extracted by pepsin digestion. In contrast, they were lowest in S, where the concentration of collagen extracted by pepsin digestion was greatest among all of the tissue samples. Atherosclerotic intima (A) and aortic media (M) showed an age-related increase in the total amount of collagen digested with pepsin and collagenase, which depended mainly on an increase in the content of pepsin-insoluble collagen. Although the total amount of collagen did not increase with advancing age in I or S, collagen in I and S became progressingly resistant to pepsin digestion. These results suggest that the age-related decrease in the susceptibility of collagen to pepsin digestion may be due to nonenzymatic glycation in atherosclerotic lesions as well as normal tissues, including the aortic media, lesion-free intima and skin. The level of CLF significantly increased with age in the P-fraction and/or EP fraction of M, I and S. However, there was no relationship between the level of CLF and the subject's age in A. Thus, the accumulation of advanced glycation endproducts (AGEs) on collagen fibers may be partially responsible for the increase in collagen matrix in atherosclerotic lesions of subjects without diabetes mellitus.

[Aging of aorta and atherosclerosis--role of nonenzymatic glycation of collagen]

In order to clarify the role of the nonenzymatic glycation of the collagen matrix in aging of the aorta and atherogenesis, we studied the relation between ketoamine or advanced glycation end-products (AGEs) and the solubility of collagen in human skin and aorta. AGEs were measured as a collagen-linked fluorescence (excitation wavelength: 370 nm. emission wavelength: 440 nm). There was a positive correlation between the level of AGEs and subjects' age in skin and aortic media. Collagen became more insoluble with increase in the amount of ketoamine and AGEs. Collagen was more resistant to pepsin digestion in atherosclerotic intima than in other tissues including aortic media, lesion-free intima and skin. Diabetic rats showed an accumulation of collagen in aortic media at 28 weeks after an injection of streptozotocin. Moreover, they increased the percentage of insoluble collagen to total collagen and the amount of AGEs binding to insoluble collagen in aortic media. In contrast, the amount of ketoamine of insoluble collagen was increased in diabetic rats at 16 weeks as compared to control. There was no difference in DNA contents of cultured smooth muscle cells between glycolaldehyde-modified and non-modified matrices. However, the activity of type I collagenase (inactive form) of smooth muscle cells decreased on glycolaldehyde-modified type I collagen as compared to that on non-modified collagen. These results suggest that AGEs contribute to the accumulation of collagen in atherosclerotic lesions and aged aorta through the insolubility of collagen and the inhibition of collagenase activity of smooth muscle cells.

Molecular characterisation of Escherichia coli O157:H7 isolates by pulsed-field gel electrophoresis and plasmid DNA analysis

Foods of bovine origin have been identified as sources of Escherichia coli O157:H7. Genomic DNA of E. coli O157:H7 isolates from patients (six isolates), food samples (18 isolates from ground beef and six isolates from raw milk) and calf faecal samples (31 isolates) were characterised by pulsed-field gel electrophoresis (PFGE) and plasmid DNA analysis. These isolates originated from different locations in the USA during 1992 and 1993. Twenty-one distinct genomic profiles were generated from the 61 isolates by PFGE after digestion with the endonuclease XbaI. Four genomic profiles were identified among five patient isolates and the remaining patient isolate was not typable. Five different profiles were detected amongst the isolates from ground beef, one of which was associated with 13 ground beef isolates from an outbreak in the Pacific Northwest of the USA in 1993. The PFGE profile of five calf isolates from Washington and Wisconsin was identical to the profile of the ground beef isolates from the outbreak, suggesting that these isolates were related. Similarly, one PFGE profile accounted for three isolates from calf faeces and one from ground beef. Six raw milk isolates from Georgia were indistinguishable both from each other and from one isolate from calf faeces. Fourteen genomic profiles were identified among 31 calf faecal isolates from 18 different herds in 11 states. Only five plasmid profiles were identified among the 61 isolates. PFGE was shown to be a useful typing technique for E. coli O157:H7.