Invertebrate responses to the management of genetically modified herbicide-tolerant and conventional spring crops. II. Within-field epigeal and aerial arthropods

The effects of the management of genetically modified herbicide-tolerant (GMHT) crops on the abundances of aerial and epigeal arthropods were assessed in 66 beet, 68 maize and 67 spring oilseed rape sites as part of the Farm Scale Evaluations of GMHT crops. Most higher taxa were insensitive to differences between GMHT and conventional weed management, but significant effects were found on the abundance of at least one group within each taxon studied. Numbers of butterflies in beet and spring oilseed rape and of Heteroptera and bees in beet were smaller under the relevant GMHT crop management, whereas the abundance of Collembola was consistently greater in all GMHT crops. Generally, these effects were specific to each crop type, reflected the phenology and ecology of the arthropod taxa, were indirect and related to herbicide management. These results apply generally to agriculture across Britain, and could be used in mathematical models to predict the possible long-term effects of the widespread adoption of GMHT technology. The results for bees and butterflies relate to foraging preferences and might or might not translate into effects on population densities, depending on whether adoption leads to forage reductions over large areas. These species, and the detritivore Collembola, may be useful indicator species for future studies of GMHT management.

Invertebrate responses to the management of genetically modified herbicide-tolerant and conventional spring crops. I. Soil-surface-active invertebrates

The effects of herbicide management of genetically modified herbicide-tolerant (GMHT) beet, maize and spring oilseed rape on the abundance and diversity of soil-surface-active invertebrates were assessed. Most effects did not differ between years, environmental zones or initial seedbanks or between sugar and fodder beet. This suggests that the results may be treated as generally applicable to agricultural situations throughout the UK for these crops. The direction of the effects was evenly balanced between increases and decreases in counts in the GMHT compared with the conventional treatment. Most effects involving a greater capture in the GMHT treatments occurred in maize, whereas most effects involving a smaller capture were in beet and spring oilseed rape. Differences between GMHT and conventional crop herbicide management had a significant effect on the capture of most surface-active invertebrate species and higher taxa tested in at least one crop, and these differences reflected the phenology and ecology of the invertebrates. Counts of carabids that feed on weed seeds were smaller in GMHT beet and spring oilseed rape but larger in GMHT maize. In contrast, collembolan detritivore counts were significantly larger under GMHT crop management.

Genotypic subgrouping of clinical isolates of Candida albicans and Candida dubliniensis by 25S intron analysis

AIMS

To determine the frequency, distribution and association of genotypes of Candida albicans and C. dubliniensis in invasive and noninvasive clinical isolates.

METHODS

Twenty-one invasive and 18 noninvasive isolates were examined by PCR amplification of a transposable intron region in the 25S rRNA gene. Isolates were genotyped following analysis of the size of resulting DNA amplicons. The isolates could be subdivided into four genotypes (A-D).

RESULTS

There was no significant difference between the frequency and genotype distribution of the invasive and noninvasive Candida isolates.

IMPACT OF THE STUDY

Therapeutic prophylaxis against candidal infections remains an area of controversy. Any diagnostic markers that reflect the potential of isolates to become invasive should be fully explored, so that more focused antifungal intervention should be targeted at these patients with these potential invasive markers. This study demonstrated that analysis of the transposable intron region in the 25S rRNA gene may be useful in helping to differentiate C. albicans from C. dubliniensis isolates, without the need for sequence analysis, which may not be readily available at primary diagnostic laboratories. However, employment of this genotypic assay is not a suitable locus to determine invasiveness and other more reliable markers of invasiveness should be sought.

Comparison of API20C with molecular identification of Candida spp isolated from bloodstream infections

A study was carried out to compare the API20C technology with polymerase chain reaction amplification and direct sequencing of the short internal transcribed spacer region 2 (ITS2) for the identification of 58 isolates of invasive candida species obtained from patients with bloodstream infections over the seven year period 1994 to 2000. Overall, there was only one disagreement between the phenotypic and genotypic identification, where the API scheme identified the isolate as C albicans but the molecular method identified it as C dubliniensis. This study demonstrated that the API20C method is useful in the identification of Candida spp isolated from blood culture and that molecular methods do not enhance identifications made using the API20C scheme. However, for correct reporting of C dubliniensis, an emerging bloodborne pathogen, it is recommended that all isolates identified as C albicans by the API20C scheme are further examined phenotypically and/or genotypically.

Streptococcus pyogenes prtFII, but not sfbI, sfbII or fbp54, is represented more frequently among invasive-disease isolates of tropical Australia

Streptococcus pyogenes (group A streptococcus) strains may express several distinct fibronectin-binding proteins (FBPs) which are considered as major streptococcal adhesins. Of the FBPs, SfbI was shown in vitro to promote internalization of the bacterium into host cells and has been implicated in persistence. In the tropical Northern Territory, where group 4 streptococcal infection is common, multiple genotypes of the organism were found among isolates from invasive disease cases and no dominant strains were observed. To determine whether any FBPs is associated with invasive disease propensity of S. pyogenes, we have screened streptococcal isolates from bacteraemic and necrotizing fasciitis patients and isolates from uncomplicated infections for genetic endowment of 4 FBPs. No difference was observed in the distribution of sfbII, fbp54 and sfbI between the blood isolates and isolates from uncomplicated infection. We conclude that the presence of sfbI does not appear to promote invasive diseases, despite its association with persistence. We also show a higher proportion of group A streptococcus strains isolated from invasive disease cases possess prtFII when compared to strains isolated from non-invasive disease cases. We suggest that S. pyogenes may recruit different FBPs for different purposes.

Torquoselectivity induced by lone-pair conjugation in the electrocyclic reactions of 1-azapolyenes

Torquoselectivity in the electrocyclic interconversions of 1-azapolyenes and their heterocyclic isomers was investigated theoretically. The ring openings of 1,2-dihydroazete, 1,2-dihydropyridine, and 1,2-dihydroazocine were examined using HF, MP2, and B3LYP calculations. A large preference for inward rotation of the nitrogen lone pair and outward rotation of the N-H group was found for the four- and six-electron systems. No strong preference was observed for the eight-electron system.

Predictors of positive axillary lymph nodes after sentinel lymph node biopsy in breast cancer

OBJECTIVE

The purpose of this study was to determine the factors that predict the presence of metastasis in nonsentinel lymph nodes (SLN) when the SLN is positive.

METHODS

A prospective database was analyzed and included patients who underwent SLN biopsy for invasive breast cancer from July 1997 to August 2000 (n = 442). One hundred (22.6%) patients had one or more positive SLNs, and were analyzed to determine factors that predicted additional positive axillary nodes.

RESULTS

Of the 100 patients with a positive SLN, 40 patients (40%) had additional metastasis in non-SLNs. The only significant variables that predicted non-SLN metastasis were tumor lymphovascular invasion (P = 0.004), extranodal extension (P < 0.001), and increasing size of the metastasis within the SLN (P = 0.011). In analyzing just those patients who had lymphovascular invasion, extranodal extension, and a SLN metastasis > 2mm, 92% were found to have additional positive nodes.

CONCLUSIONS

In patients with invasive breast cancer and a positive sentinel lymph node, lymphovascular invasion, extranodal extension, and increasing size of the metastasis all significantly increase the frequency of additional positive nodes.

Selective analysis of the sentinel node in breast cancer

BACKGROUND

This study was designed to determine the minimum number of sentinel nodes necessary to accurately stage patients with breast cancer.

METHODS

Between August 1997 and February 2001, 509 consecutive patients were enrolled in a prospective sentinel node database. Nodes were characterized as either blue or hot (>2 times background), or both, and ranked based on the order harvested. Predictive value of the sentinel node based on these characteristics was evaluated to determine the minimum number necessary to stage the basin.

RESULTS

In all, 990 sentinel nodes were harvested from 465 basins. Pathologic stage in 126 of 128 positive basins was predicted by the first or second node harvested. The remaining 2 patients were positive by immunohistochemistry only. The hottest node predicted the status in 114 of 128 basins.

CONCLUSIONS

Although all nodes should be examined, these data suggest that limiting frozen section analysis to the first two sentinel nodes identified will not compromise the accuracy of staging and may provide a vehicle for resource savings.

Determination of an arylether antiarrhythmic and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates using liquid chromatography-tandem mass spectrometry

A method was developed and validated for the quantification of (+/-)-trans-[2-morpholino-1-(1-naphthalene-ethyloxy]cyclohexane monohydrochloride (RSD1070) and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates. Chromatographic separations were achieved using reversed-phase high-performance liquid chromatography coupled with positive ion electrospray ionization and detection by tandem mass spectrometry. The assay was linear from 2.5 to 100 ng/ml and this range was used for validation. Inter- and intra-assay variability (n=6), extraction recovery, and stability in plasma were assessed. The estimated limit of quantitation was in the range 2.5-3 ng/ml for both analytes in rat plasma. The analytical method was used in a pharmacokinetic study of RSD1070 in rats after a single i.v. bolus of 12 mg/kg.

The virulence factors ofBordetella pertussis: a matter of control

Bordetella pertussis is the causative agent of whooping cough, a contagious childhood respiratory disease. Increasing public concern over the safety of whole-cell vaccines led to decreased immunisation rates and a subsequent increase in the incidence of the disease. Research into the development of safer, more efficacious, less reactogenic vaccine preparations was concentrated on the production and purification of detoxified B. pertussis virulence factors. These virulence factors include adhesins such as filamentous haemagglutinin, fimbriae and pertactin, which allow B. pertussis to bind to ciliated epithelial cells in the upper respiratory tract. Once attachment is initiated, toxins produced by the bacterium enable colonisation to proceed by interfering with host clearance mechanisms. B. pertussis co-ordinately regulates the expression of virulence factors via the Bordetella virulence gene (bvg) locus, which encodes a response regulator responsible for signal-mediated activation and repression. This strict regulation mechanism allows the bacterium to express different gene subsets in different environmental niches within the host, according to the stage of disease progression.

The common ovine Shiga toxin 2-containing Escherichia coli serotypes and human isolates of the same serotypes possess a Stx2d toxin type

Shiga toxin 2 (Stx2) has been reported as the main Shiga toxin associated with human disease. In addition, the Stx2 toxin type can have a profound impact on the degree of tissue damage in animal models. We have characterized the stx(2) subtype of 168 Shiga toxin-producing Escherichia coli (STEC) isolates of which 146 were derived from ovine sources (principally feces and meat) and 22 were isolated from humans. The ovine STEC isolates were of serotypes that have been shown to occur commonly in the gastrointestinal tract of healthy sheep. The major stx(2) subtype in the ovine isolates was shown to be stx(2d-Ount) (119 of 146 [81.5%]) and was predominantly associated with serotypes O75:H(-)/H8/H40, O91:H(-), O123:H(-), O128:H2, and OR:H2. However, 17 of 18 (94.4%) ovine isolates of serotype O5:H(-) possessed a stx(2d-O111/OX3a) subtype. Furthermore, STEC isolates of serotypes commonly found in sheep and recovered from both clinical and nonclinical human infections also contained a stx(2d) (stx(2d-Ount/O111/OX3a)) subtype. These studies suggest that a specific stx(2) subtype(s) associates with serotype and may have important epidemiological implications for tracing sources of E. coli during outbreaks of STEC-associated diseases in humans.

Oral immunization of swine with attenuated Salmonella typhimurium aroA SL3261 expressing a recombinant antigen of Mycoplasma hyopneumoniae (NrdF) primes the immune system for a NrdF specific secretory IgA response in the lungs

Salmonella typhimurium SL3261 (aroA mutant) expressing a recombinant Mycoplasma hyopneumoniae antigen was used to orally immunize swine against porcine enzootic pneumonia. This construct, designated S. typhimurium aro A SL3261 (pKF1), expressed a recombinant protein containing the carboxy-terminal 11 kDa of a 42 kDa M. hyopneumoniae NrdF ribonucleotide reductase R2 subunit protein. Here we demonstrate that this antigen is present in all seven geographically diverse strains of M. hyopneumoniae tested, and is recognized by the swine immune system after experimental infection with the virulent M. hyopneumoniae Beaufort strain. The immune response of swine orally immunized twice with S. typhimurium SL3261 (pKF1) on day 0 and day 14 was evaluated. Oral immunization with S. typhimurium SL3261 (pKF1) primed the immune system to elicit a significant (P<0.05) secretory IgA response against the 15 kDa NrdF antigen in the respiratory tract of swine, post-challenge, compared to control groups. Blood lymphocytes from swine immunized with S. typhimurium SL3261 (pKF1) proliferated significantly (P<0.05) following stimulation with M. hyopneumoniae whole-cell extracts compared to control groups 14 days post-vaccination. Following challenge with virulent M. hyopneumoniae, swine immunized with S. typhimurium SL3261 (pKF1) showed higher average daily weight gains and reduced lung pathology compared to control groups.

In vitro investigation of the hepatic extraction of RSD1070, a novel antiarrhythmic compound

PURPOSE

The hepatic extraction of a novel antiarrhythmic, RSD1070, was investigated to test the hypothesis that the poor bioavailability observed in rats is due to high hepatic metabolism.

METHODS

The pharmacokinetics of RSD1070 was examined in rats (n=8) and its metabolism was investigated using pooled rat hepatic microsomes. The free fraction in plasma and microsomal matrices was determined by equilibrium dialysis. Hepatic extraction was predicted by scaling-up of the microsomal kinetic data using the well-stirred liver model.

RESULTS

RSD1070 demonstrated tri-exponential decay following single iv bolus administration of a dose of 12 mg/kg. RSD1070 exhibited a rapid elimination, t1/2 of 25 +/- 8 min and a CL(tot) of 71 +/- 9 mL/min/kg. Renal clearance based on 24 h urinary recovery was determined to be insignificant (<< 1% of CL(tot)). A Michaelis-Menten model described the elimination of RSD1070 with a K(m) of 0.45 microg/mL and Vmax of 2.81 microg/min/mg microsomal protein. Taking the V(max)/K(m) ratio (CL(int)) as the basis for scaling, the data from the microsomal kinetic studies (75 mL/min/kg) closely approximated the apparent CL(tot). In the scale-up of the in vitro CL(int), plasma free fraction (1.5%) and microsomal free fraction (15%) were determined and incorporated into the well-stirred liver model.

CONCLUSION

RSD1070 is a high hepatic extraction compound (E = 0.94) with a predicted CL(h) value that accounted for the CL(tot) observed in rats.

Intratumoral injection of dendritic cells derived in vitro in patients with metastatic cancer

BACKGROUND

Dendritic cells (DCs) are potent initiators of immune responses, and the infiltration of DCs into tumors may confer an improved prognosis. Whether the injection of DCs directly into tumors can mediate biologic activity was examined.

METHODS

Patients with metastatic dermal or subcutaneous tumors received granulocyte-macrophage-colony stimulating factor to increase the numbers of peripheral blood monocyte precursors. DCs were then generated from monocytes obtained by phlebotomy with granulocyte-macrophage-colony stimulating factor and interleukin-4 in autologous plasma. Tumors were injected at multiple sites with 30 million autologous DCs per tumor.

RESULTS

Seven patients with melanoma and three patients with breast carcinoma were treated. Injections were well tolerated. Regression of the injected tumors, beginning as early as 4 days after injection, was observed in four patients with melanoma and in two patients with breast carcinoma. Biopsies of regressing lesions showed lymphocyte infiltration associated with DCs and necrosis. Neutrophils and macrophages were not evident. Lymphocytes expanded from the regressing tumors proliferated in response to heat shock proteins, HSP70 and gp96, derived from autologous tumor. The DCs injected produced interferon-alpha and expressed Fas ligand mRNA but did not exhibit cytolytic activity in vitro. Expression of the costimulatory molecule, B7-2 (CD86), decreased on DCs after intratumoral injection.

CONCLUSIONS

This pilot study demonstrates that DCs derived in vitro can exist viably after intratumoral injection and can mediate biologic activity in situ. Tumor-derived heat shock proteins may be involved in the antitumor activity observed.

Co-expression of the Bordetella pertussis leader peptidase I results in enhanced processing and expression of the pertussis toxin S1 subunit in Escherichia coli

Bordetella pertussis is the causative agent of whooping cough. Traditional vaccines against this disease are inherently reactogenic, thus research is currently focussed on the production of less reactive, acellular vaccines. Expression of candidate antigens for these vaccines in Escherichia coli would be preferable, however, several B. pertussis antigens undergo incorrect post-translational processing in E. coli. The leader peptidase gene (lep) of B. pertussis encodes a protein of 294 amino acid residues that shares homology with other prokaryote leader peptidase I sequences. Hydrophilicity analysis based on the predicted amino acid sequence has demonstrated a similar membrane topology to that of E. coli and Salmonella typhimurium leader peptidase I. Co-expression of the B. pertussis lep gene in E. coli strain TOPP2 expressing the pertussis toxin S1 subunit was found to markedly increase the expression and post-translational processing of the S1 protein.

Epigenetic PTEN silencing in malignant melanomas without PTEN mutation

A tumor suppressor gene at 10q 23.3, designated PTEN, encoding a dual specificity phosphatase with lipid and protein phosphatase activity, has been shown to play an important role in the pathogenesis of a variety of human cancers. Germline mutations in PTEN cause Cowden syndrome (CS), which is characterized by multiple hamartomas and a high risk of breast and thyroid cancers. Frequent loss of heterozygosity at 10q is found in both early and advanced-stage sporadic melanomas; however, mutations or deletions in PTEN are detected mainly in melanoma cell lines. In this study, we examined PTEN expression in 34 unselected sporadic melanomas (4 primary melanomas, 30 metastases) using immunohistochemistry and correlated this with the results of structural studies of this gene. Immunostaining of 34 melanoma samples revealed no PTEN expression in 5 (15%) and low PTEN expression in 17 (50%), whereas the rest of the tumors (35%) had high levels of expression. Hemizygous deletion was found in 32% of the tumors but neither intragenic PTEN mutation nor biallelic deletion was found in any of the samples. Of the 5 melanomas showing no PTEN expression, 4 had no mutation or deletion of PTEN. Of the 13 tumors having weak PTEN immunoreactivity and informative loss of heterozygosity results, 6 had evidence of hemizygous allelic loss of PTEN while the remaining 7 had intact PTEN. These results strongly support PTEN as a major tumor suppressor on 10q involved in melanoma tumorigenesis and suggest an epigenetic mechanism of biallelic functional inactivation not previously observed in other cancers where PTEN might be involved.

Role of phosphoglucomutase of Bordetella bronchiseptica in lipopolysaccharide biosynthesis and virulence

The phosphoglucomutase (PGM)-encoding gene of Bordetella bronchiseptica is required for lipopolysaccharide (LPS) biosynthesis. An insertion mutant of the wild-type B. bronchiseptica strain BB7865 which disrupted LPS biosynthesis was created and characterized (BB7865pgm). Genetic analysis of the mutated gene showed it shares high identity with PGM genes of various bacterial species and forms part of an operon which also encompasses the gene encoding phosphoglucose isomerase. Functional assays for PGM revealed that enzyme activity is expressed in both bvg-positive and bvg-negative strains of B. bronchiseptica and is substantially reduced in BB7865pgm. Complementation of the mutated PGM gene with that from BB7865 restored the wild-type condition for all phenotypes tested. The ability of the mutant BB7865pgm to survive within J774. A1 cells was significantly reduced at 2 h (40% reduction) and 24 h (56% reduction) postinfection. BB7865pgm was also significantly attenuated in its ability to survive in vivo following intranasal infection of mice, being effectively cleared from the lungs within 4 days, whereas the wild-type strain persisted at least 35 days. The activities of superoxide dismutase, urease, and acid phosphatase were unaffected in the PGM-deficient strain. In contrast, the inability to produce wild-type LPS resulted in a reduced bacterial resistance to oxidative stress and a higher susceptibility to the antimicrobial peptide cecropin P.

Ischaemia selectivity confers efficacy for suppression of ischaemia-induced arrhythmias in rats

Eight novel and three reference antiarrhythmics were investigated in anaesthetised rats for antiarrhythmic actions, as well as for effects on the electrocardiogram (ECG) under normal and "simulated ischaemic" conditions. In rats subjected to coronary artery occlusion lidocaine, (+/-)-trans-[2-(4-morpholinyl)-cyclohexyl]naphthyl-1-acetate, RSD1000 and (+/-)-trans-[2-(4-morpholinyl)-cyclohexyl]-2-(1-naphthyl)propionate, RSD1030, (Group A) produced dose-related and complete antiarrhythmic protection. Group B compounds, such as (+/-)-trans-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-3, 4-dichlorocinnamamide, RSD995, produced complete antiarrhythmic protection but had aberrant dose-response curves. Group C compounds, such as quinidine and flecainide, failed to give full antiarrhythmic protection and had shallow dose-response curves. The potency of Group A compounds, but not Group B or C compounds, for ECG actions indicative of Na(+) channel blockade (prolongation of PR and QRS intervals) were significantly increased under "simulated ischaemic" conditions ([K(+)] 10 mM and pH 6.4) in isolated rat hearts. Thus, compounds with ischaemia-selective actions provided superior protection against ischaemia-induced arrhythmias in rats.

Expression and purification of recombinant human indoleamine 2, 3-dioxygenase

Indoleamine 2,3-dioxygenase, the first and rate-limiting enzyme in human tryptophan metabolism, has been implicated in the pathogenesis of many diseases. The human enzyme was expressed in Escherichia coli EC538 (pREP4) as a fusion protein to a hexahistidyl tag and purified to homogeneity in terms of electrophoretic and mass spectroscopic analysis, by a combination of phosphocellulose and nickel-agarose affinity chromatography. The yield of the fusion protein was 1.4 mg per liter of bacterial culture with an overall recovery of 56% from the crude extract. When the culture medium was supplemented with 7 microM hemin, the purified protein contained 0.8 mol of heme per mole of enzyme and exhibited an absorption spectrum consistent with the ferric form of hemoprotein. The pI value of the recombinant enzyme was 7.09 compared with 6.9 for the native enzyme. This was as expected from the addition of the hexahistidyl tag. Similar to the native enzyme, the recombinant enzyme required methylene blue and ascorbic acid for enzyme activity and oxidized not only l-tryptophan but also d-tryptophan and 5-hydroxy-l-tryptophan. The molecular activities for these substrates and their K(m) values were similar to those of the native enzyme, indicating that the addition of the hexahistidyl tag did not significantly affect catalytic activity. The recombinant protein can therefore be used to investigate properties of the native enzyme. This will aid the development of specific inhibitors of indoleamine 2,3-dioxygenase, which may be effective in halting disease progression.

Regulation of indoleamine 2,3-dioxygenase, the first enzyme in UV filter biosynthesis in the human lens. Relevance for senile nuclear cataract

3-Hydroxykynurenine (3OHKyn), the precursor of UV filters in human lens, is highly autooxidizable, generates H2O2, and binds to lens proteins, yielding a tanned/yellow product resembling senile nuclear cataractous materials. Thus, if 3OHkyn can be shown to be the causative agent in cataract, it may be possible to prevent the disease by lowering the level of 3OHKyn. To this end, indoleamine 2,3-dioxygenase, the first enzyme in UV filter synthesis, was studied using lens epithelial cell lines. The results indicated that the IDO expression is mediated by IFN-gamma. Immuno-suppressants which inhibit production of IFN-gamma may act as anti-cataract agents. Another way to lower the level of 3OHKyn is to use specific inhibitors for IDO. A recombinant human IDO was expressed to develop the inhibitors.

Pharmacology--a unique discipline for unique questions?

This article discusses the nature and responsibilities of the biomedical subject known as pharmacology. It will attempt to show how pharmacology is a very special subject that is uniquely positioned to ask fundamental questions about drugs, such as how they produce their actions, and how they may be used more effectively in man. Furthermore, pharmacology is a most important subject to the pharmaceutical industry as it is pharmacology, combined with medicinal chemistry and toxicology, that is responsible for the introduction of the vast majority of new drugs. Thus, pharmacologists are to be found in universities, research institutes and industry. In universities, pharmacologists are concerned more with discovering new drug-like entities in the body and natural world and in understanding how current drugs work. In industry, pharmacologists seek new drugs. Over the last decade there have been many discoveries in molecular biology, the new biology. The enthusiasm and revolutionary spirit which greets such discoveries leads to an assumption by some that pharmacology in its present form has been rendered redundant. This article refutes such a conclusion and shows how pharmacology has unique attributes and approaches that are as important now as they always were. Indeed, it argues for improvements in the understanding of pharmacology and how it remains a unique and special subject that should be nurtured.

Cardiac transplantation does not effect ischaemia-induced arrhythmias in rats

OBJECTIVE

In many species arrhythmias induced by myocardial ischaemia appear to be in part dependent upon cardiac sympathetic nerves. However, previous experiments in rats did not suggest that myocardial or other catecholamines are involved in ischaemic arrhythmogenesis in this species. The aim of this study was to investigate this further using transplanted hearts.

METHODS

We transplanted 'donated' hearts onto the abdominal aorta of recipient rats and, at varying periods after transplantation, subjected donated and recipient hearts to occlusion of the left anterior descending (LAD) coronary artery. Donated and recipient hearts were tested at various times after transplantation for responsiveness to drugs acting upon aspects of the autonomic nervous system. The intention of this latter study was to assess the status of innervation and receptors simultaneously in both donated and recipient hearts.

RESULTS

Donated (transplanted) hearts showed responses consistent with denervation and receptor supersensitivity. Changes varied with the duration of the transplant. Over the same period recipient hearts did not change in responsiveness to drugs. When subjected to coronary artery occlusion, transplanted hearts responded to occlusion with the same frequency and severity of arrhythmias as recipient and other control hearts, regardless of the duration of transplant, or sensitivity to drugs.

CONCLUSIONS

The results of these experiments suggest that cardiac innervation is not an important factor in the genesis of ischaemia-induced arrhythmias in rats.

Expression of urease does not affect the ability of Bordetella bronchiseptica to colonise and persist in the murine respiratory tract

To investigate the role played by urease during the Bordetella bronchiseptica infection process, the ability to colonise and persist in the mouse respiratory tract of a urease-negative B. bronchiseptica BB7865 and a BB7865 derivative constitutively expressing urease was compared with that of the wild-type strain. The results obtained showed that neither constitutive expression nor abolishment of urease activity had any significant effect on the course of B. bronchiseptica infection. Therefore, under our experimental conditions, urease is not essential for B. bronchiseptica to colonise and persist within the murine host.