Thiol-disulfide redox buffers maintain a structure of immunoglobulin A that is essential for optimal in vitro binding to secretory component

We have shown that human secretory component (SC) binds in vitro to different samples of human and murine dimeric immunoglobulin A (IgA). The binding ratio in the IgA/SC complex is 1:1. IgA which is stably bound to SC is separated from unreacted IgA by anion exchange chromatography. A part of IgA/SC complexes formed in vitro is unstable to this elution; the proportion varies between different samples of IgA; it increases following prolonged incubation of IgA at 37 degrees C. Incubation of IgA with glutathione/glutathione disulfide (GSH/GSSG) redox buffers increases the proportion able to form a stable complex with SC to approximately 90%. The presence of bound SC is not essential for this process but does allow it to occur at a lower GSH/GSSG concentration. The stable IgA/SC complex consists of a structure with a disulfide bond between IgA and SC apparently in equilibrium with a structure in which this bond is absent. The proportion bound covalently is similar for different samples of IgA and is insensitive to incubation with GSH/GSSG. It is significantly greater for secretory IgA (sIgA) and for IgA and SC incubated together with a starting mixture of cysteine/cystine. Monoclonal, antigen-specific IgA, all of which is optimally bound to SC in essentially the same way as in native sIgA, can be isolated in high yield. Our results support a mechanism for optimal binding of IgA to SC, that can occur both in vitro and in vivo, in which a thiol disulfide interchange occurs between a free IgA thiol and a sensitive SC disulfide following the initial non-covalent interaction.

One hundred liver resections including comparison to non-resected liver-mobilized patients

BACKGROUND

Factors of liver resection associated with postoperative recovery and survival, the modalities that affect survival with resected colorectal carcinoma liver metastases, the comparison of liver function of liver-resected to liver-mobilized but not resected patients, and observation of early liver regeneration volume over time have not been studied prospectively. This study aimed to prospectively analyse these factors.

METHODS

Data were collected prospectively on 100 consecutive liver resections, and 10 liver-mobilized but not resected patients by the Hepatobiliary Unit, University of Melbourne, Austin Campus. Follow-up of patients was 100%.

RESULTS

The factors associated with blood loss were the type of liver resection (P = 0.0001), the length of the operation (P = 0.0001) and a central venous pressure greater than 5 cm of water (P = 0.0008). An inverse correlation existed between blood loss and long-term survival (P = 0.003). The only predictor for a postoperative complication was the length of the operation (P = 0.03): a correlation of moderate significance existed between blood loss and a complication (P = 0.052; confidence interval 0.19-1.17). The 5-year cumulative survival for hepatic resection for colorectal carcinoma Dukes A + B was 55%; there was a significantly better survival of Dukes A + B compared to Dukes C (P = 0.03) and also for those 50 years or older, but this did not depend on whether there were one or more lesions present. Resected patients had a significantly higher alanine transaminase (ALT), total bilirubin and international normalized ratio than non-resected patients, but not albumin, total protein, alkaline phosphatase or aspartate aminotransferase. The serum albumin fall was similar in both groups, which indicated that loss of liver tissue was not the cause. The re-resection rate was 8% without mortality and with low morbidity. Liver volume was restored by 64% (510 +/- 170 cc) by 7 days postoperatively.

CONCLUSIONS

Major hepatic resection can be performed with low mortality, morbidity and short hospital stay, with a 5-year survival for colorectal carcinoma better than 50%. Resection needs to be considered more frequently for curative management. Serum albumin fall is not caused by loss of liver tissue and blood loss can be controlled by central venous pressure manipulation and vascular isolation. Re-resection is a safe and rewarding treatment and needs to be planned at the first resection.

The effects of ultraviolet radiation on antibiotic-resistant bacteria in vitro

Wound infections produced by antibiotic-resistant bacterial strains are particularly difficult to manage. This study examined the effectiveness of ultraviolet (UV) light treatment in killing antibiotic-resistant strains of Staphylococcus aureus and Enterococcus faecalis in vitro. Between 2 and 5 replications of each organism at 10(8) organisms/ml were prepared and plated on sheep blood agar medium and treated with UV light (254 nm, 15.54 mW/cm2 output). Irradiation times were 0, 2, 5, 8, 15, 30, 45, 60, 90 or 120 seconds. Bacterial cultures were then incubated at 35 degrees C for 24 hours. Kill rates were 99.9 percent for the methicillin-resistant strain of S. aureus (MRSA) at 5, 8, 15, 30, 45, 60 seconds and 100 percent at 90 and 120 seconds. Kill rates were 99.9 percent at 5, 8, 15, 30 seconds for vancomycin-resistant E. faecalis (VRE) and 100 percent at 45, 60, 90, 120 seconds. Similar results were found with UV light treatment of the antibiotic-susceptible strains of S. aureus and E. faecalis. A significant difference in kill rates at 30 seconds of UV exposure was detected between the antibiotic-resistant strain of S. aureus and the antibiotic-resistant strain of E. faecalis (Student's t test, p < 0.01). Significant differences were also detected in the kill rates at 30 second exposure times for the antibiotic-susceptible strains of S. aureus and E. faecalis. These findings suggest that the Enterococcal bacteria is more susceptible to the killing effects of UV. This data also suggests that UV light at 254 nm is bactericidal for antibiotic-resistant strains of S. aureus and E. faecalis at times as short as 5 seconds and that the enterococcal bacteria is more susceptible to the killing effects of UV. With recommended patient treatment times for infected wounds being significantly longer than 5 seconds, this data indicates that patient treatment times need to be re-examined.

Comparative pathology: radiation-induced coronary artery disease in man and animals

The occurrence of coronary artery disease following mediastinal radiation for malignancies has long been debated. However, the development of coronary pathology in young individuals following radiation who lack risk factors for atherosclerosis is highly suggestive of a cause-and-effect relationship. By far the most convincing pathologic changes are adventitial scarring and medial atrophy with severe intimal atherosclerotic disease consisting of necrotic core, fibrous tissue, and calcification. Initial clinical studies in patients with coronary atherosclerosis treated with intraluminal radiation following stenting hold great promise in the treatment and prevention of restenosis. There are little or no data, however, on long-term effects of intra-coronary radiation therapy in man. Therefore, it may be important to study the chronic effects of radiation in animal models in order to predict what is likely to occur in humans. We evaluated the effects of varying doses (0.15-23.0 microCi of 32P) of beta-particle-emitting radioactive stents in pig coronary arteries at 1 and 6 months. At 1 month, there were dose-dependent changes in the morphology of the intima and media. High activities (>3 microCi) caused medial necrosis with fibrin deposition in the media and intima, with interspersed red cells most marked in regions surrounding the stent struts. Only rare smooth muscle cells (SMCs) and inflammatory cells were seen away from the stent struts. In the intermediate (1 microCi) stent activity group, the neointima was expanded by SMCs and a proteoglycan-rich matrix with focal endothelialization of the luminal surface. Neovascular capillaries and extravascular red cells were present adjacent to stent struts. At low activities (<0.5 microCi), the neointima was significantly smaller than control stents and consisted of SMCs and matrix with complete endothelialization of the luminal surface. The neointimal cell density of the media and intima decreased with increasing doses of radiation. In pigs 6 months after radioactive stenting (activities ranging from 0.5-12 microCi 32P), >3.0 microCi radioactive stents induced marked neointimal thickening, with changes similar to atherosclerosis, consisting of necrotic debris containing cholesterol clefts surrounded by macrophage collections, fibrosis, and focal calcification. There was increased adventitial thickening in the radiated vs non-radiated arteries. The intermediate stent activity (1.0 microCi) also showed greater neointimal thickening (vs control stents) and consisted mostly of SMCs in a proteoglycan-rich matrix. At <1.0 microCi, there were minimal differences seen between radiated and control non-radiated stented arteries. The media was unevenly injured in all stent activities and varied from less than to significantly greater than controls. These data suggest that radiation-induced coronary atherosclerosis seen in man is partially simulated in normal porcine coronary arteries 6 months following high-dose beta-particle-emitting radioactive stent placement. There is greater fibrosis and thickness of the adventitia and focal attenuation of the media in man and severe luminal narrowing in pig coronary arteries treated with high doses of radiation. Only long-term clinical follow up and careful autopsy studies will determine if endoluminal or intra-arterial radiation is a viable means of reducing restenosis in man.

Central venous pressure and its effect on blood loss during liver resection

BACKGROUND

Any strategy to reduce blood loss in liver resection and decrease blood transfusion would be of benefit to the patient and surgeon. This study evaluates the association of central venous pressure (CVP) with blood loss and blood transfusion during liver resection.

METHODS

One hundred consecutive hepatic resections in the period 1986-1996 were studied prospectively concerning CVP, volume of blood lost, and volume of blood transfused. Blood loss volume and blood transfusion were analysed for those with a CVP less than or equal to 5 cmH2O, and greater than 5 cmH2O. A multivariate analysis assessed potential confounding factors in the comparison.

RESULTS

The median blood loss in patients with a CVP of 5 cmH2O or less was 200 ml (n=40) and that in those with a CVP above 5 cmH2O was 1000 ml (n=52) (P=0.0001). Only two of 40 patients with a CVP of 5 cmH2O or less had a blood transfusion whereas 25 of 52 patients with a CVP greater than 5 cmH2O required a transfusion (P=0.0008). A multivariate analysis did not show confounding factors.

CONCLUSION

The volume of blood lost during liver resection correlates with the CVP. Lowering the CVP to less than 5 cmH2O is a simple and effective way to reduce blood loss during liver surgery.

The cuffed oropharyngeal airway. Its clinical use in 100 patients

We studied the efficacy of the cuffed oropharyngeal airway in 100 patients. Insertion of the airway after induction of anaesthesia with propofol was easy in 95 of 100 patients, moderately difficult in four patients and failed in one patient. Complications, such as coughing, gagging or body movement, occurred during induction and insertion in 15 patients. Insertion of the airway was not associated with tachycardia or hypertension. Manual ventilation through the airway was easy in less than 30% of patients immediately after insertion. Manual ventilation became easier after adjusting the position of the patient's head, neck or jaw. During spontaneous breathing, adjustment of the head, neck or jaw was required in 30% of patients. Complete airway obstruction occurred in one patient after insertion of the device and in two patients during maintenance of anaesthesia. The airway was left in place during emergence from anaesthesia in the remaining 97 patients. No complications occurred in 91 patients and coughing occurred in the remaining six patients before or during removal of the airway. No regurgitation, vomiting or laryngospasm occurred in any patient at any time. Therefore, the cuffed oropharyngeal airway has a potential use in anaesthetised patients who are breathing spontaneously.

Anaesthetic organ toxicity: is it really a problem?

The hepatotoxicity of halothane is now well known, but only became apparent after several years of use. The nephrotoxicity of methoxyflurane was not realized immediately, but once identified, led to its withdrawal from use. Therefore, when new agents that appear to offer significant advantages over established drugs become available, exhaustive testing and monitoring is necessary to ensure their safety. Sevoflurane, recently available in the UK and the USA but used for some time in Japan, has been subjected to considerable scrutiny.

Comparison of remifentanil in combination with isoflurane or propofol for short-stay surgical procedures

There are few data in the literature that describe the use of remifentanil when administered as a component of an inhalation or total i.v. anaesthetic (TIVA) technique. We studied 251 male and female patients, aged 18-75 years, ASA I-II, undergoing inguinal hernia repair, arthroscopic knee surgery or varicose vein surgery of at least 30 min duration without premedication. Patients were randomized to receive a remifentanil loading dose of 1.0 microgram kg-1 followed by a continuous infusion of 0.5 microgram kg-1 min-1 in combination with isoflurane (end-tidal concentration 0.6%), (Group I, n = 115) or propofol (initial infusion rate 9 mg kg-1 h-1 reduced to 6 mg kg-1 h-1 after 10 min), (Group P, n = 118). The remifentanil infusion rate was reduced by 50%, 5 min after tracheal intubation. Intraoperative stresses were treated with a remifentanil bolus (1 microgram kg-1) followed by an increase in the remifentanil infusion rate. At the insertion of the last suture, the remifentanil infusion and concomitant anaesthetic were switched off simultaneously. Times to spontaneous respiration, adequate respiration and tracheal extubation were significantly shorter in group I compared with group P (6.4 min vs 7.6 min, P < 0.01; 7.6 min vs 9.3, P < 0.003; 7.8 min vs 9.5 min, P < 0.015). Overall mean systolic blood pressures during surgery were greater in group P compared with group I (P < 0.05) but the absolute differences were clinically insignificant (4-5 mm Hg).

Effects of toothbrush design and brushing proficiency on plaque removal

A single-blind, short-term cross-over clinical trial compared the plaque removal performance of three commercially available manual toothbrushes. A sample of 25 dental hygiene students, 19 to 42 years old, served as participants. On 3 separate occasions, participants were instructed to refrain from toothbrushing or flossing for 24 hours before clinical trials. A prebrushing plaque index using disclosing solution was performed on each participant. One of the 3 test brushes was then randomly dispensed to each participant, and they were allowed to brush for 90 seconds without the aid of a mirror. A postbrushing plaque index was then performed on each participant. This procedure was repeated 2 more times at 2-week intervals so that each participant was tested with all 3 toothbrushes. Previous studies of this kind using random participant samples have suggested that brush design does indeed affect the efficacy of plaque removal. This study used participants who were well versed on efficient toothbrushing technique to determine if improved brushing skills would overshadow advantages in toothbrush design. No significant differences in performance were detected between the test brushes for any of the three scored areas.

Identification and mechanism of formation of potentially genotoxic metabolites of tamoxifen: study by LC-MS/MS

On-line high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI MS) and tandem mass spectrometry (MS/MS) have been applied to the study of tamoxifen metabolism in liver microsomes and to the identification of potentially genotoxic metabolites. The results showed that the hydroxylated derivatives, including 4-hydroxytamoxifen and alpha-hydroxytamoxifen are detoxication metabolites, while arene oxides, their free radical precursors or metabolic intermediates, are the most probable species involved in DNA-adduct formation.

Resolution of gas exchange abnormalities and intrapulmonary shunting following liver transplantation

This prospective study evaluated pulmonary gas exchange in patients with severe liver disease, its relationship to intrapulmonary shunting, and its response to liver transplantation. Detailed clinical examinations, chest radiographs, and arterial blood gas estimations were performed on 74 consecutive patients before and after liver transplantation. Fifty percent of the 74 patients had a widened alveolar-arterial (A-a) oxygen gradient (> 15 mm Hg) and 45% a reduced PaCO2 (< 35 mm Hg). Twenty-two percent were hypoxemic (PaO2 < 80 mm Hg). Following transplantation mean PaO2 increased (pre-89 +/- 14 vs. post-94 +/- 8 mm Hg; P = .014) and A-a oxygen gradient decreased (pre-16 +/- 14 vs. post-8 +/- 9 mm Hg; P < .001), despite an increase in PaCO2 (pre-36 +/- 5 vs. post-39 +/- 4; P < .001). To examine this improvement in oxygen exchange further, a subgroup of 26 consecutive patients, with no obvious cardiorespiratory cause for abnormal gas exchange underwent, pre- and post-operative spirometry, measurement of carbon monoxide diffusion capacity (DLCO), intrapulmonary shunt estimations (100% oxygen technique), and echocardiography. In this subgroup, 23% were hypoxemic, 54% had a widened A-a oxygen gradient, and 85% had increased intrapulmonary shunting (> 5%) before transplantation. There was a significant correlation between the degree of pre-transplantation intrapulmonary shunting and A-a oxygen gradient (P < .01). Nineteen of the 22 patients with increased shunting improved following transplantation and improved A-a oxygen gradient correlated well with the reduction in shunting (P < .005). DLCO was reduced in 69% of these patients with a mean value of 73% of predicted. However, the post-transplantation mean DLCO did not increase despite the improvement in oxygen exchange. In conclusion, gas exchange abnormalities are common in patients with severe liver disease but these usually resolve post-transplantation. Intrapulmonary shunting is a major determinant of abnormal oxygen uptake in transplant candidates without evidence of cardiorespiratory disease. Finally, the mechanism for the reduced DLCO is unclear but appears different to that responsible for intrapulmonary shunting and abnormal oxygen exchange.

Assignment of the human gene encoding eukaryotic initiation factor 4E (EIF4E) to the region q21-25 on chromosome 4

We recently cloned genomic sequences containing the promoter region for the messenger RNA cap binding protein (eIF4E). As the rate-limiting step in translation, eukaryotic initiation factor 4E is important in cellular growth control. Using oligonucleotide primers specific for the promoter region in polymerase chain reactions (PCR), we amplified the human gene in a chromosome 4-specific human/rodent somatic cell panel. This panel mapped single copy genomic sequences for eIF4E in the region 4q21 to 4q25.

Heterogeneous proteolytic specificity and activity of the house dust mite proteinase allergen Der p I

BACKGROUND

Exposure of the skin or respiratory tract to proteinases is frequently associated with allergic sensitization. This is of particular significance in the domestic indoor environment where the proteolytic activity of Der p I, the group I allergen of the house dust mite Dermatophagoides pteronyssinus, may influence the allergenicity of mites. Using class-specific proteinase inhibitors and active-site affinity chromatography, we have previously shown that Der p I exhibits a mixed cysteine-serine proteinase activity. Measurement of the amount of cleavage, however, did not determine whether the inhibitors used were targeting exactly the same proteolytic mechanism.

OBJECTIVE

To resolve this issue, we have examined whether the cleavage specificity of the cysteine and serine proteinase activities of Der p I was the same.

METHODS

HPLC and mass spectrometry were used to analyse and identify the products of a Der p I-digested peptide substrate and thus identify the peptide bonds cleaved.

RESULTS

Der p I cleaves different peptide bonds, depending upon the class of proteolytic mechanism used. In the model peptide substrate insulin B chain, the cysteine and serine proteinase activities of Der p I showed preference for glutamic acid and arginine respectively in the P1 position.

CONCLUSION

These data suggest the existence of more than one mechanistic form of the allergen immunologically identified as Der p I. If proteolytic activity is indeed a function of allergenicity, this information may have important implications for the pathogenicity of Der p I and the ability of innate antiproteinase defences in the respiratory tract to prevent immune sensitization.

Peroxidase activation of 4-hydroxytamoxifen to free radicals detected by EPR spectroscopy

4-Hydroxytamoxifen is a major metabolite of the antiestrogenic drug tamoxifen used in the treatment of women with breast cancer. 4-Hydroxytamoxifen is broken down by a horseradish peroxidase/H2O2 system very much more rapidly than tamoxifen and causes much greater DNA damage determined by 32P-postlabelling. EPR spin trapping of 4-hydroxytamoxifen reaction products in the presence of the free radical trap 5,5-dimethyl-1-pyrroline N-oxide, together with glutathione as a hydrogen donor, resulted in the generation of a species with the characteristics of the glutathione thiyl radical (aN approximately 15.3 G, aH approximately 16.2 G). Support for the creation of thiyl radicals comes from the close to stoichiometric time dependent formation of glutathione disulfide concomitant with the loss of glutathione. Similar results were obtained using 4-hydroxytoremifene but no radical formation or glutathione loss could be detected using 3-hydroxytamoxifen (droloxifene). On-line LC-ESI MS analysis of the incubation products from 4-hydroxytamoxifen has identified three products with a protonated molecular mass of 773, consistent with the formation of dimers of 4-hydroxytamoxifen. The role that radical mechanisms have in the carcinogenic effects of tamoxifen in the endometrium or other target organs of women taking this drug remains to be established.

Activity of doramectin against nematode and arthropod parasites of swine

The efficacy of doramectin, a novel avermectin, was assessed against both naturally-acquired and experimentally-induced infections of gastrointestinal roundworms, lungworms, kidneyworms, lice and mites in studies conducted across North America and Europe. Twenty-two studies evaluated efficacy against fourth larval and adult stages of the following nematode species: Hyostrongylus rubidus, Ascaris suum, Strongyloides ransomi, Oesophagostomum dentatum, Oesophagostomum quadrispinulatum, Trichuris suis, Metastrongylus spp. and Stephanurus dentatus. Efficacy was evaluated against the louse Haematopinus suis in six studies and against the mite Sarcoptes scabiei in four studies. A common study design was employed for each study type. In all studies, animals were allotted at random to a doramectin-treated or a saline-treated group. The doramectin-treated group received the drug at 300 micrograms kg-1 by intramuscular injection while the saline-treated group received saline by the same route. In the nematode studies, worm burdens were determined for each animal at slaughter 14-16 days after treatment. Efficacy against each nematode species/stage was assessed on the basis of percentage reduction in geometric mean worm burden in doramectin-treated animals compared with saline-treated controls. In louse and mite studies, counts were made immediately before treatment and then at weekly intervals for four weeks. Efficacy was based on a comparison of the level of infestation on the day of treatment with that on the last day of test. Data from individual studies were combined to derive a single estimate of efficacy against each of the parasite species represented in the study program. Efficacy of doramectin was 98% or greater against all nematode species except T. suis for which the efficacy was 87% and 79% against adult and fourth larval stage, respectively. Efficacy was 100% against both Haematopinus suis and Sarcoptes scabiei.

Field evaluation of doramectin for treatment of gastrointestinal nematode infections and louse infestations of cattle

OBJECTIVE

To evaluate the safety and efficacy of doramectin given by injection at a dosage of 200 micrograms/kg of body weight for treatment of gastrointestinal nematodiasis or louse infestations of cattle.

ANIMALS

1,031 mixed-breed cattle were treated in the nematode study and 418 were treated in the louse study.

PROCEDURE

Naturally parasitized cattle were given 200 micrograms of doramectin/kg or an equivalent volume of saline solution, SC. In nematode experiments, fecal samples were collected from each animal 1 week before treatment, at time of treatment, and at weekly intervals there after for 3 weeks. In louse experiments, louse counts were carried out for each animal on the day of treatment and 14 and 28 days later. All cattle were weighted at the time of treatment and at the end of the experiment.

RESULTS

By 21 days after doramectin treatment, fecal egg counts had decreased to zero in 9 of 10 experiments and to 1 egg/g in the remaining experiment. Differences between treatment groups were significant (P < 0.0001) in all instances. Pretreatment coproculture identified Haemonchus, Ostertagia, Cooperia, Trichostrongylus, and Nematrodirus as the represented genera. Doramectin was 100% effective in eliminating infestation with Linogna thus vituli, Haematopinus eurysternus, and Solenopotes capillatus. Infestation with the chewing louse Damalinia bovis was reduced overall by 86%. For all species, post treatment louse counts were significantly (P < 0.02) less for doramectin-treated cattle than for controls. Adverse reactions to doramectin were not apparent in either study.

CONCLUSION AND CLINICAL RELEVANCE

Injectable doramectin at a dosage of 200 micrograms/kg is safe and effective for treatment of gastrointestinal nematodiasis and louse infestations of cattle under field conditions.

An essential E box in the promoter of the gene encoding the mRNA cap-binding protein (eukaryotic initiation factor 4E) is a target for activation by c-myc

The mRNA cap-binding protein (eukaryotic initiation factor 4E [eIF4E]) binds the m7 GpppN cap on mRNA, thereby initiating translation. eIF4E is essential and rate limiting for protein synthesis. Overexpression of eIF4E transforms cells, and mutations in eIF4E arrest cells in G, in cdc33 mutants. In this work, we identified the promoter region of the gene encoding eIF4E, because we previously identified eIF4E as a potential myc-regulated gene. In support of our previous data, a minimal, functional, 403-nucleotide promoter region of eIF4E was found to contain CACGTG E box repeats, and this core eIF4E promoter was myc responsive in cotransfections with c-myc. A direct role for myc in activating the eIF4E promoter was demonstrated by cotransfections with two dominant negative mutants of c-myc (MycdeltaTAD and MycdeltaBR) which equally suppressed promoter function. Furthermore, electrophoretic mobility shift assays demonstrated quantitative binding to the E box motifs that correlated with myc levels in the electrophoretic mobility shift assay extracts; supershift assays demonstrated max and USF binding to the same motif. cis mutations in the core or flank of the eIF4E E box simultaneously altered myc-max and USF binding and inactivated the promoter. Indeed, mutations of this E box inactivated the promoter in all cells tested, suggesting it is essential for expression of eIF4E. Furthermore, the GGCCACGTG(A/T)C(C/G) sequence is shared with other in vivo targets for c-myc, but unlike other targets, it is located in the immediate promoter region. Its critical function in the eIF4E promoter coupled with the known functional significance of eIF4E in growth regulation makes it a particularly interesting target for c-myc regulation.

High frequency of p16 (CDKN2/MTS-1/INK4A) inactivation in head and neck squamous cell carcinoma

The tumor suppressor gene p16 (CDKN2/MTS-1/INK4A) can be inactivated by multiple genetic mechanisms. We analyzed 29 invasive primary head and neck squamous cell carcinomas (HNSCC) for p16 inactivation with immunohistochemistry utilizing a new monoclonal antibody (mAb), DCS-50. p16 staining of the primary lesions was correlated with genetic analysis including: (a) detailed microsatellite analysis of markers at the p16 locus to detect homozygous deletion; (b) sequence analysis of p16; and (c) Southern blot analysis to determine the methylation status of the 5' CpG island of p16. Twenty-four of 29 (83%) head and neck squamous cell carcinoma tumors displayed an absence of p16 nuclear staining using immunohistochemistry. Of these 24 tumors, we found that 16 (67%) harbored homozygous deletions, 5 (21%) were methylated, 1 displayed a rearrangement at the p16 locus, and 1 displayed a frameshift mutation in exon 1. These data suggest that: (a) inactivation of the p16 tumor suppressor gene is a frequent event in squamous cell carcinomas of the head and neck; (b) p16 is inactivated by several distinct and exclusive events including homozygous deletion, point mutation, and promoter methylation; and (c) immunohistochemical analysis for expression of the p16 gene product is an accurate and relatively simple method for evaluating p16 gene inactivation.

Sevoflurane degradation by soda lime in a circle breathing system

Sevoflurane is degraded by soda lime to a vinyl ether commonly referred to as compound A. We measured the concentration of compound A in the circle breathing system of 31 patients receiving sevoflurane anaesthesia. Inspiratory and expiratory gas samples were analysed using gas chromatography and flame ionisation detection. The end-tidal sevoflurane concentration and soda lime temperature were recorded. The peak compound A concentration ranged between 10 to 32 ppm in the inspiratory limb and 7 to 26 ppm in the expiratory limb. There was a positive correlation between the peak compound A concentration and the end-tidal sevoflurane concentration (r2 = 0.545, p < 0.0001) and the soda lime temperature (r2 = 0.301, p = 0.0014). We conclude that the end-tidal concentration of sevoflurane and the temperature of the soda lime are important variables in determining concentration of compound A in a circle system.

Biliary complications after liver transplant: the Victorian experience

BACKGROUND

Biliary complications remain a continuing problem in liver transplantation. The goals of this study were to document the frequency of biliary complications following orthotopic liver transplantation in the Victorian programme, and to examine associations with suspected risk factors with reference to biliary stenosis.

METHODS

Data were collected from 129 consecutive transplants in 123 patients (106 adults, 17 children) at the Austin Hospital, Melbourne during the period 1988-94. The 2 year actuarial survival was 88%. Biliary reconstruction was by end-to-end anastomosis in 89 patients and Roux-en-Y in 40. Complications were suspected on clinical, biochemical or microbiological evidence. Biliary stenoses were considered to be radiological evidence of duct narrowing.

RESULTS

Biliary complications occurred in 19% and biliary stenosis in 8.5%. Of the stenoses, 1/35 occurred in the first 20 month period, 9/47 in the second and 1/47 in the third. There was a significant difference between the middle period and other periods (P<0.05, Chi-square test). This change may be related to incomplete flushing of bile from the donor liver. Recurrence of the original disease was suspected for one stenosis. The length of the donor bile duct from hilum to anastomosis, cold ischaemia time and total hepatic artery flow at transplant did not relate to stenosis. Cholangitis was not diagnosed in patients without strictures. Strictures were managed by dilatation (5/11) and by operative repair (6).

CONCLUSIONS

Stenoses were not related to the length of the donor bile duct, cold ischaemia time or total hepatic artery flow. Meticulous adherence to the protocol for flushing out bile at the donor operation was associated with a significant reduction in frequency of biliary stenoses.

[Toxicology and clinical significance of base-catalized degradation of sevoflurane to Compound A]

Sevoflurane breaks down in basic environments to form a vinyl ether known as Compound A. This compound is toxic in the rat, with an LC50 of about 400 ppm after 3 h exposure and with renal damage evident between 50 and 100 ppm. There is no valid current evidence that Compound A is toxic in man, and the rat may not be an appropriate model for determination of this breakdown product's toxic potential in humans. The main factors influencing the degree of patient exposure to Compound A include fresh gas flow, sevoflurane concentrations, absorber temperature and composition, and the patient's carbon dioxide production.

On-line high-performance liquid chromatographic-electrospray ionization mass spectrometric method for the study of tamoxifen metabolism

An on-line high-performance liquid chromatographic (HPLC)-electrospray ionization mass spectrometric (ESI-MS) method has been developed and optimized for the study of tamoxifen metabolism. Metabolism in mouse liver microsomes was chosen to demonstrate the applicability and superiority of the method, since mice metabolize tamoxifen faster and produce more metabolites than rats or humans. Mouse liver microsomal preparations were incubated with tamoxifen in the presence of NADPH and MgCl2. The metabolites formed were separated and analyzed by the optimized HPLC-ESI-MS system. The separation was performed on a Res Elute-BD column (5 microns particle size, 250 x 4.6 mm I.D.) with 70% (v/v) methanol in 0.5 M ammonium acetate as the mobile phase. A total of eleven metabolites have been detected, some of which have not been previously reported. The metabolites identified are: tamoxifen N-oxide, N-desmethyltamoxifen, 4-hydroxytamoxifen, 4'-hydroxytamoxifen, 4-hydroxytamoxifen N-oxide, 4'-hydroxytamoxifen N-oxide, 4-hydroxy-N-desmethylamoxifen, 4'-hydroxy-N-desmethyltamoxifen, 3,4-dihydroxytamoxifen, 3,4-epoxytamoxifen and 3,4-epoxytamoxifen N-oxide.

Subcellular location of the tetrapyrrole synthesis enzyme porphobilinogen deaminase in higher plants: an immunological investigation

A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase (EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidopsis thaliana (L.) Heynh. has been constructed, and used to transform Escherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-fold) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation of enzyme activity and immuno-gold electron microscopy. The results indicate that the enzyme is confined to plastids in both leaves and roots. The implications of this finding for plant tetrapyrrole synthesis are discussed.

Comparison of ondansetron and droperidol in reducing postoperative nausea and vomiting associated with patient-controlled analgesia

In a randomised, placebo-controlled trial we have compared the efficacy of ondansetron and droperidol in reducing postoperative nausea and vomiting associated with patient-controlled analgesia after orthopaedic surgery. One hundred and forty five patients, ASA 1 and 2, undergoing major orthopaedic surgery were anaesthetised using a standardised technique. They were randomly allocated to receive patient-controlled analgesia as morphine 1 mg.ml-1 alone; morphine as before plus a single dose of 1.25 mg droperidol together with 0.083 mg.ml-1 in the infusion syringe; or morphine as before plus 4 mg ondansetron and 0.13 mg.ml-1 in the syringe. The patient-controlled analgesia bolus dose was set at 1 ml with a 5 min lockout and a 4 h maximum dose of 30 mg morphine. There was no background infusion. The occurrence of nausea, vomiting and sedation was assessed every 4 h. The incidence of vomiting decreased from 59% in the morphine-only group to 35% and 14% in the droperidol (p < 0.05) and ondansetron groups (p < 0.001) respectively. The number of patients suffering from nausea alone was not significantly different between the three groups, although those in the ondansetron group experienced less severe nausea (p < 0.05) when using a two point scale. The droperidol group had significantly higher sedation scores than the other two groups (p < 0.005). We conclude that ondansetron is superior to droperidol when used with patient-controlled analgesia and causes less sedation.

Is there a need for a new inhalational anaesthetic agent?

New anaesthetic agents are continually being developed in an effort to prepare the ideal agent. Isoflurane is the first choice of many anaesthetists, although it clearly falls short of the ideal on a number of counts. The need and place for any new agent depends on comparing the properties of a theoretically ideal agent with those of isoflurane and the new agent. Desflurane is a step towards a more ideal inhaled agent; however, there is still the need to synthesise and evaluate new chemical entities in order that the ideal can more nearly be approached.

Pharmacokinetics and bioequivalence of parenterally administered doramectin in cattle

Plasma concentrations of doramectin in 40 cattle dosed by subcutaneous (sc) or intramuscular (i.m.) injection (200 micrograms/kg) were compared to assess the bioequivalence of the two routes of administration. Peak concentration (Cmax), and areas under the concentration curve (AUC0-infinity) were determined from plasma concentrations. Animals treated by the sc route showed a mean AUC0-infinity of 457 +/- 66 ng.day/mL (+/- SD) and a mean Cmax of 27.8 +/- 7.9 ng/mL. Results from the i.m. treatment group showed a mean AUC0-infinity of 475 +/- 82 ng.day/mL and a mean Cmax of 33.1 +/- 9.0 ng/mL. Absorption constants (ka) determined by modelling were 0.542 +/- 0.336 day-1 after sc administration and 0.710 +/- 0.357 day-1 after i.m. administration. The 90% confidence limits on the difference between mean AUC0-infinity values for the sc and i.m. groups fell within 20% of the mean value for the subcutaneous group. Cmax was somewhat greater for the i.m. route. The 90% confidence limits on the difference in mean In(Tmax +1) also fell within 20% of the mean sc value. Based on this analysis, bioequivalence of the sc and i.m. formulation has been established.

Serum fluoride concentration and urine osmolality after enflurane and sevoflurane anesthesia in male volunteers

The purpose of this study was to measure the serum fluoride concentration after enflurane or sevoflurane anesthesia and to compare the effects of prolonged anesthesia with these drugs on renal concentrating function in male volunteers. The study was subdivided into three stages; an ascending dose study of 3.0 and 6.0 minimum alveolar anesthetic concentration (MAC) hours of sevoflurane alone, a 6.0-MAC-hour comparison of enflurane and sevoflurane, and a 9.0-MAC-hour comparison of enflurane and sevoflurane. Renal concentrating function was assessed by an 18-h period of fluid deprivation and the serum fluoride concentration was measured at intervals until 60 h postanesthesia. The maximum serum fluoride concentration was greater in the volunteers exposed to sevoflurane and reached a peak in the 9-MAC-hour sevoflurane group of 36.6 microM (SD 4.3) compared with 27.5 microM (SD 2.6) in the 9-MAC-hour enflurane group. However, the rapid decrease in the serum fluoride concentration after sevoflurane was such that there was no difference between the areas under the fluoride concentration-time curves. There were no significant differences between the median maximum urine osmolalities after enflurane or sevoflurane anesthesia. Prolonged anesthesia with enflurane or sevoflurane is not associated with impaired renal concentrating function despite an increase in the serum fluoride concentration.

Mivacurium in special patient groups

In special patient groups, drug response may be different from that in the healthy adult patient. Mivacurium dose requirements vary with age, and children require larger doses to obtain any given degree of block, but the elderly often require smaller doses. However, the dose requirements of the neonate do not necessarily differ greatly from those of the adult. There is a relationship between the duration of action of a bolus dose as well as infusion requirements to maintain block and the plasma cholinesterase activity. Patients with renal disease may have a decreased cholinesterase activity and may require smaller doses of mivacurium. Patients with severe liver disease may have a marked decrease in cholinesterase activity, and in these patients a substantially smaller dose of the drug may be needed to obtain and maintain any given degree of block. If the variation in dose requirements is kept in mind and the degree of block appropriately monitored, mivacurium may be used with safety in special patient groups, such as children, the elderly, or those with renal or hepatic impairment.

The role of continuous positive airway pressure during weaning from mechanical ventilation in cardiac surgical patients

We investigated the effects of providing patients with continuous positive airway pressure during a short weaning period from mechanical ventilation to extubation. Following elective primary aortocoronary bypass surgery employing cardiopulmonary bypass, 80 patients received intermittent positive pressure ventilation for 5 h. At the end of this time patients were randomly allocated to one of the following three groups for a 2 h period of spontaneous respiration prior to extubation: group CPAP0 = T-piece circuit (n = 27); group CPAP5 = 5 cmH2O of continuous positive airway pressure (n = 27); group CPAP10 = 10 cmH2O of continuous positive airway pressure (n = 26). Following extubation, pulmonary gas exchange was assessed after 1, 2, 4, and 24 h. All patients had good pre-operative lung function. There was a significant increase in the median alveolar-arterial oxygen partial pressure difference and a decrease in the oxygenation index in all three groups during the period of added inspired oxygen which persisted until 24 h post-extubation, but there were no differences between the groups. In patients with good pre-operative lung function requiring primary aortocoronary bypass surgery, the use of continuous positive airway pressure confers no advantage over a simple T-piece attachment during the short period of weaning from mechanical ventilation to extubation.

Prazosin reduces myocardial ischemia/reperfusion-induced Ca2+ overloading in rat heart by inhibiting phosphoinositide signaling

The aim of this study was to establish whether or not alpha 1-adrenergic receptors are implicated in triggering phosphoinositide hydrolysis and intracellular Ca2+ accumulation during myocardial ischemia and reperfusion. In isolated perfused rat hearts, the selective alpha 1-receptor antagonist prazosin abolished the increase in radioactivity incorporation into cellular inositol phosphates induced by 30 min ischemia followed by 30 min reperfusion, and selectively blocked the degradation of phosphoinositides; only minor changes in the ischemia/reperfusion-induced loss of other classes of phospholipids were seen. In addition, a prazosin-induced decrease of ischemia/reperfusion Ca2+ overloading was documented in real-time recordings of epicardial cytosolic free Ca2+ in fura 2-loaded hearts. An inhibition of early ischemic Ca2+ rise was observed, as well as a lower peak of cytosolic free Ca2+ and a more rapid reversal to normal values during reperfusion. Moreover, alpha 1-adrenergic blockade resulted in a significant improvement in the recovery of myocardial function during reperfusion: an increased left ventricular developed pressure and maximum rate of rise of systolic pressure paralleled the decrease in time-averaged cytosolic Ca2+ and the increase in amplitude of Ca2+ transients, respectively. It is concluded that myocardial Ca2+ overloading during ischemia and reperfusion may be triggered by alpha 1-adrenergic receptor-induced polyphosphoinositide hydrolysis.

Peroxidase activation of tamoxifen and toremifene resulting in DNA damage and covalently bound protein adducts

When [14C]tamoxifen was incubated with horseradish peroxidase and H2O2, two major metabolites, separated and identified by HPLC, were N-desmethyltamoxifen and tamoxifen N-oxide. Toremifene incubated in a similar system yielded N-desmethyltoremifene and toremifene N-oxide. No 4-hydroxylated metabolites were detected with either drug. When calf thymus DNA was included in peroxidase incubation mixtures, DNA damage, as assessed by 32P-postlabelling, could also be detected. The extent of damage caused by tamoxifen and toremifene was similar. The major adducts formed following incubation of DNA with tamoxifen had similar Rf values to two of the 32P-postlabelled adducts seen following dosing of rats with tamoxifen. Peroxidase was able to activate both drugs to derivatives which covalently bound to bovine serum albumin. The pH optimum for covalent binding and N-demethylation was near to pH 6.0. Results from liquid chromatography-electrospray secondary ion mass spectrometry suggest that tamoxifen and toremifene are metabolized by peroxidase to putative reactive epoxide intermediates responsible for the genotoxic effects. It is proposed that peroxidase oxidizes tamoxifen to a carbon-centred free radical which reacts with oxygen to form peroxy radicals capable of inserting an oxygen atom into tamoxifen. Lactoperoxidase and prostaglandin synthase are also able to catalyse tamoxifen N-demethylation and binding to protein. These data show that peroxidase can activate both tamoxifen and toremifene to an intermediate(s) that can damage DNA and covalently react with protein. Since it is known that women treated with tamoxifen can develop endometrial tumours, it may be relevant to determine whether activation of tamoxifen by peroxidases may contribute to its carcinogenic action at extrahepatic sites.

Some advantages of long-term grazing trials, with particular reference to changes in botanical composition

Comments are made about some advantages of long-term grazing trials, with special reference to the fact that important botanical changes may occur only after many years, sometimes with subsequent changes in animal production. Rainfall variability is a major reason for these delayed changes, but other factors such as changing soil fertility, longevity of individual plants, and the cumulative effect of stocking rates are involved. The need for trials to document the long-term effect of treatments on botanical change is in conflict with the current (1995) trends for research funding to be directed towards shorter term projects; and yet, botanical change is an important component of sustainability, which is currently accorded high priority. Various ways of addressing the problem of predicting long-term botanical change are discussed, including the use of modelling. Suggestions are made about ways in which long-term grazing trials can be made more effective. Extensive 'on-farm' surveys, provided the pastures concerned are in widespread commercial use, may be a partial alternative to grazing trials.

Hepatitis B virus precore mutant infection is associated with severe recurrent disease after liver transplantation

The factors that predispose patients undergoing liver transplantation for hepatitis B virus (HBV) disease to severe recurrence of infection are unclear. In this study we examined the effect of pretransplantation infection with HBV and precore variant strains of HBV on posttransplantation outcome and allograft histology in 24 patients who survived more than 3 months after liver transplantation. Based on pretransplantation serum HBV DNA status as detected by the polymerase chain reaction (PCR) and direct sequencing, the 24 patients could be assigned to three groups. In group 1 there were 4 patients HBV DNA-negative before transplantation and none of these patients suffered recurrence of infection posttransplantation. In group 2, of 10 patients with pretransplantation infection with wild-type virus, 7 became reinfected, and 1 of these developed HBV-related graft failure. In group 3, 9 of 10 patients infected with precore mutant HBV strains became reinfected. However, in contrast to the patients in group 2, 7 patients in group 3 developed HBV-related graft loss, and 5 of these patients had fibrosing cholestatic hepatitis (FCH). These results indicate that infection with precore mutant strains of HBV predisposes a patient to early graft loss following transplantation.

Urinary porphyrin profiles by laser desorption/ionization time-of-flight mass spectrometry without the use of classical matrices

A method is described for the rapid analysis of mixtures of porphyrin methyl esters using laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF MS). Ions corresponding to [M+H]+ for each component have been observed without the need for added matrix. LDI-TOF MS has been applied to the analysis and characterization of porphyrin methyl esters derived from urine samples of patients suffering from various porphyrias. This technique has been shown to provide "fingerprint" profiles of the porphyrins present in each urine sample, characteristic of the porphyria, which compare favourably with those obtained with the established method of high-performance liquid chromatography. LDI-TOF MS is a rapid and reliable method for the screening of urine from patients suffering from porphyria.

Blood loss and transfusion requirements in liver transplantation: experience with the first 75 cases

The blood loss data and transfusion requirements including blood bank, salvaged washed red cells, fresh frozen plasma and cryoprecipitate were analysed for the first 75 cases of liver transplantation performed at the Austin Hospital between June 1988 and October 1992. The mean blood loss was 8.8 litres (standard deviation 14.1) with a median value of 4.0 litres. Blood product use expressed as mean number of units (SD) was bank red blood cells 7.1 (12.7), washed red blood cells 3.9 (5.9), fresh frozen plasma 7.1 (9.1), platelets 5.1 (7.4), and cryoprecipitate 1.7 (5.1). These results demonstrate that liver transplantation can be performed without imposing excessive demands on blood transfusion services. Management should include surgical techniques to minimize bleeding and use of autologous transfusion. Use of component therapy (FFP, platelets and cryoprecipitate) should not be empirical. It should be selective on the basis of clinical bleeding assessment and guided by results of the laboratory coagulation profile and changes in thrombelastographic (TEG) parameters.

Patterns of coagulopathy during liver transplantation: experience with the first 75 cases using thrombelastography

Using both conventional laboratory clotting profile and thrombelastography, coagulation status was monitored intraoperatively during liver transplantation in the first 75 cases performed at the Austin Hospital between June 1988 and October 1992. Superimposed on a baseline coagulopathy due to liver disease is a specific pattern of coagulation disturbance which occurs during a liver transplant. Fibrinolysis occurs in the anhepatic stage, worsens with early reperfusion and then spontaneously resolves. In addition reperfusion is associated with a transient clotting defect. If blood loss is excessive, coagulopathy due to massive transfusion may compound the situation. Thrombelastography is a measurement technique allowing rapid on-site assessment of functional clotting status. It is particularly useful in liver transplant surgery. In combination with clinical bleeding assessment it facilitates selective use of component therapy (fresh frozen plasma, platelets and cryoprecipitate) and specific drug treatment only when it is appropriate. It also acts as a liver function test, being especially useful in assessing the graft after reperfusion.

Lymphoproliferative disease of donor origin arising in patients after orthotopic liver transplantation

BACKGROUND

Lymphoproliferative disease is a well recognized complication of organ transplantation and in many cases is associated with Epstein-Barr virus (EBV) infection. It is widely though that posttransplantation lymphoproliferative disease (PTLPD) arises from recipient lymphoid cells. However, solid organ allografts are likely to include donor lymphoid tissue around or within the transplanted organ. Therefore, it is possible that transplanted donor lymphocytes may proliferate to form PTLPD:

METHODS

The genetic origin of tumor cells was determined by microsatellite DNA fingerprinting using the polymerase chain reaction (PCR). Their EBV association and clonality were established by PCR amplification of DNA extracted from formalin fixed, paraffin embedded tissue using primers to conserved regions of the EBV genome and the immunoglobulin heavy chain gene, respectively.

RESULTS

The authors have demonstrated two cases of lymphoproliferative disease that were derived from donor lymphocytes in orthotopic liver transplant recipients. In both cases, the proliferating cells were EBV DNA positive. Furthermore, the PTLPD was restricted to allograft tissue around the porta hepatis. However, the two cases differed in their clonal properties and response to treatment: one case was oligoclonal and regressed after antiviral therapy and a modest reduction of immunosuppression, whereas the other contained two clonal populations and was controlled only after treatment with antineoplastic chemotherapy.

CONCLUSION

This study has demonstrated two cases of PTLPD that were derived from donor lymphoid tissue. Although both cases were associated with EBV and remained localized to allograft tissue, their clonality and response to therapy differed.

In vitro potency and mode of action of ANQ9040: a novel fast acting muscle relaxant

1. The in vitro potency and mode of action of the novel, rapid-onset steroidal relaxant ANQ9040 were characterized in the rat isolated phrenic nerve hemidiaphragm. 2. At 32 degrees C, ANQ9040 antagonized neurally evoked contractures with EC50s of 21.5 microM for unitary twitches; 14.4 microM for 2 Hz 'trains of four'; and 7.5 microM for 50 Hz (2 s) tetanic stimulus trains. 3. (+)-Tubocurarine was 22-24 times more potent than ANQ9040 in comparative organ bath experiments. 4. Intracellular recording from endplates revealed that ANQ9040 (0.53-10.0 microM) dose-dependently and reversibly decreased the amplitude of miniature-endplate potentials (IC50 of circa 0.95 microM) without changing transmembrane potential. 5. Surmountable antagonism of subthreshold responses to exogenous (ionophoretic) acetylcholine provided evidence for a non-depolarizing and competitive blockade of post-junctional nicotinic receptors. 6. Sucrose gap recordings of phrenic nerve action potentials revealed that, at concentrations up to 32 microM, ANQ9040 produced no tonic or frequency-dependent antagonism of axonic Na+ channels. 7. We conclude that ANQ9040 is a relatively low-affinity, non-depolarizing, nicotinic antagonist. The in vitro results are discussed in relation to factors impinging on relaxant kinetics and current models for frequency-dependent fade.

Hepatic artery anatomy in relation to reconstruction in liver transplantation: some unusual variations

The anatomy of the hepatic artery and its variations were studied in 70 donor livers harvested for liver transplantation in the Austin Hospital. Forty three (61.5%) had a 'normal' vascular anatomy and 27 (38.5% had anomalous anatomy. The anomalies were single in 13 instances and multiple in 14 and involved the origin of the right or left hepatic arteries or the coeliac axis. The hepatic artery was reconstructed most frequently by end-to-end anastomosis of the donor to the recipient common hepatic artery (79%). A Carrel patch, an interposition aortic graft and the donor superior mesenteric artery were other techniques used for reconstruction. Two patients (3%) had a postoperative hepatic artery thrombosis, with one of those patients having a further reconstruction. When one vascular anomaly is found, there is a high probability of others being present. The authors' experience confirms that safe hepatic arterial anastomosis can be performed even in the presence of abnormalities of the vascular arterial system.

Purification and properties of porphobilinogen deaminase from Arabidopsis thaliana

Porphobilinogen deaminase (EC 4.3.1.8) has been purified to homogeneity (16,000-fold) from the plant Arabidopsis thaliana in yields of 8%. The deaminase is a monomer of M(r) 35,000, as shown by SDS/PAGE, and 31,000, using gel-filtration chromatography. The pure enzyme has a Vmax. of 4.5 mumol/h per mg and a Km of 17 +/- 4 microM. Determination of the pI and pH optimum revealed values of 5.2 and 8.0 respectively. The sequence of the N-terminus was found to be NH2-XVAVEQKTRTAI. The deaminase is heat-stable up to 70 degrees C and is inhibited by NH3 and hydroxylamine. The enzyme is inactivated by arginine-, histidine- and lysine-specific reagents. Incubation with the substrate analogue and suicide inhibitor, 2-bromoporphobilinogen, results in chain termination and in inactivation.

Comparison of desflurane and fentanyl-based anaesthetic techniques for coronary artery bypass surgery

We have compared, in 51 ASA II and III patients undergoing coronary artery bypass surgery, an inhaled anaesthetic technique based on desflurane, supplemented with low-dose (10 micrograms kg-1) fentanyl, with an i.v. technique using high-dose (50 micrograms kg-1) fentanyl with midazolam for induction. Satisfactory records were available for analysis in 50 patients. There were no differences between groups in operating time, cardiopulmonary bypass time, aortic cross-clamp time or duration of stay in the intensive care unit after surgery. Desflurane maintained mean systemic arterial pressure at the awake level during incision and sternotomy (end-tidal concentrations 3.7% and 4.6%, respectively) but decreased it significantly at all other times. With fentanyl, mean systemic arterial pressure was unchanged from awake values during induction and laryngoscopy but increased significantly at incision and sternotomy by 8% and 12.8%, respectively, to exceed the desflurane group at sternotomy by 20 mm Hg (P < 0.001). With desflurane, heart rate remained at 60-67 beat min-1 at all times before cardiopulmonary bypass. This was always lower than the fentanyl group by 5-15 beat min-1 and the difference was significant at induction, during skin preparation and before aortic cannulation. In comparison with the desflurane group, cardiac index was significantly greater in the fentanyl group at induction, laryngoscopy and during skin preparation, but was significantly less before aortic cannulation. The need for vasodilator intervention was significantly more common in the fentanyl group before, during and after cardiopulmonary bypass and for beta adrenoceptor block before cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of laparoscopic versus open cholecystectomy

OBJECTIVE

To compare open cholecystectomy (OC) with laparoscopic cholecystectomy (LC) in terms of clinical aspects and a limited review of costs.

SETTING

The Austin Hospital, Melbourne, a university teaching hospital.

DESIGN

Prospective LC patients were compared with a retrospective group of OC patients whose surgery had been performed by the same surgeons.

METHODS

Consecutive patients undergoing LC were interviewed, their medical records were analysed and the cost of their hospitalisation was assessed. Similar data, collected previously from patients undergoing OC, were used for comparison.

RESULTS

There were 108 patients in each group, 93.5% treated electively. All had gallstones. No deaths or common bile duct injury occurred. The mean operating room time was 131 +/- 3.7 minutes for OC and 164 +/- 4.7 minutes for LC. Operative cholangiography was attempted in 80% in each group, being successful when attempted in all OCs and in 95% of LCs. The conversion rate of LCs to OCs was 4.5%. Minor complications were more frequent with OCs. The mean duration of hospital stay was 6.5 +/- 0.3 days for OCs and 2.0 +/- 0.2 days for LCs. The amount and period of analgesia were significantly less in the LC group. Patients recovered significantly faster after LC (P < 0.01) during the first eight weeks after surgery. There was no difference by 12 weeks. The overall cost for each LC was $838 less than OC for the entire hospital stay.

CONCLUSION

These results support the view that LC is a safe and justified replacement for OC in the elective situation, with benefits to the patient, hospital and general community. The hospital cost for LC was less than for OC.