Trends and geographic variations in hospital admissions for asthma in Victoria. Opportunities for targeted interventions.

OBJECTIVE: To describe variations in rates of hospital admissions for asthma in Victoria as health indicators of quality of primary care services and access. DESIGN: Routine analyses of age and sex standardised admission rates of asthma in rural and metropolitan Victoria from 1993-1994 to 1999-2000. RESULTS: There were 10,079 admissions for asthma, with an average of 2.71 bed days in 1999-2000. The admission rate for asthma decreased from 3.1/1000 (95% CI: 3.1-3.2) in 1993-1994 to 2.2/1000 (2.1-2.2) in 1999-2000, with a 37% reduction in rural regions and 26% in metropolitan regions. Sixteen primary care partnerships (small areas), 13 of them rural, had significantly higher admission rates than the Victorian average. CONCLUSION: Although asthma hospital admission rates are falling faster in rural than metropolitan areas, rural areas still have higher admission rates with significant variation between small areas.

Regioselective hydroxylation of debrisoquine by cytochrome P4502D6: implications for active site modelling.

1. Debrisoquine, a prototypic probe substrate for human cytochrome P4502D6 (CYP2D6), is hydroxylated at the alicyclic C4-position by this enzyme. Phenolic metabolites of debrisoquine (5-, 6-, 7- and 8-hydroxydebrisoquine) have also been reported as in vivo metabolites, but the role of CYP2D6 in their formation is unclear. 2. As part of studies to develop a predictive model of the active site of CYP2D6 using pharmacophore and homology modelling techniques, it became important to determine the precise regioselective hydroxylation of debrisoquine by CYP2D6. 3. Data from studies with human liver microsomes and yeast microsomes containing cDNA-derived CYP2D6 demonstrated unequivocally that debrisoquine was hydroxylated by CYP2D6 at each aromatic site in the molecule, as well as at the alicyclic 4-position. The four phenolic metabolites amounted to > 60% of the total identified products and the pattern of regioselective hydroxylation (4-HD > 7-HD > 6-HD > 8-HD > 5-HD) was similar in both in vitro systems. 4. A pharmacophore model for CYP2D6 indicated that while the hydroxylation of debrisoquine at alternative positions could arise from the substrate adopting multiple binding orientations, the energy constraints for the aromatic hydroxylations were unfavourable. An alternative proposal involving essentially a single binding orientation and a mechanism of hydroxylation based on benzylic radical spin delocalization could satisfactorily rationalize all the hydroxylations of debrisoquine. 5. This latter proposal demonstrates the need to consider the mechanism of oxidation as well as the spatial orientation of the substrate in the development of a predictive model of the active site of CYP2D6.

In-hospital mortality after transurethral resection of the prostate in Victorian public hospitals.

BACKGROUND: The purpose of the present paper was (i) to identify trends in in-hospital mortality after transurethral resection of the prostate (TURP) in Victorian public hospitals; and (ii) to explore associations between in-hospital mortality after TURP and age, adverse events, type of admission (emergency/planned), location of the hospital (metropolitan/rural), teaching status of the hospital and length of stay. METHODS: Trends in in-hospital mortality after TURP and the associations between in-hospital mortality and the aforementioned variables were studied using International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) coded Victorian hospital morbidity data from public hospitals between 1987-88 and 1994-95. Crude and adjusted odds ratios (OR) and 95% confidence intervals (CI) were based on univariate and multivariate logistic regression, respectively. RESULTS: After adjustment for age, comorbidity, and other confounding variables, the trend in mortality reduction over time was highly significant (P for trend < 0.0001, 95% CI for trend: 0.84-0.95). Highly significant associations with mortality were observed for emergency admissions (OR = 1.99, P < 0.0001), presence of adverse events (OR = 2.69, P < 0.0001), length of hospital stay (P for trend < 0.0001, 95% for trend: 1.88-2.15) and age (P for trend < 0.0001; 95% CI for trend: 1.26-1.48). CONCLUSIONS: Routinely collected data from hospitals can provide tentative evidence of improved effectiveness of a surgical treatment, provided analysis takes careful account of potential sources of bias, especially those related to possible changes in case selection over time. These kinds of data should stimulate a joint effort between clinicians, quality assurance experts and epidemiologists to confirm this attribution, and to locate the causative factors.

A novel approach to predicting P450 mediated drug metabolism. CYP2D6 catalyzed N-dealkylation reactions and qualitative metabolite predictions using a combined protein and pharmacophore model for CYP2D6.

A combined protein and pharmacophore model for cytochrome P450 2D6 (CYP2D6) has been extended with a second pharmacophore in order to explain CYP2D6 catalyzed N-dealkylation reactions. A group of 14 experimentally verified N-dealkylation reactions form the basis of this second pharmacophore. The combined model can now accommodate both the usual hydroxylation and O-demethylation reactions catalyzed by CYP2D6, as well as the less common N-dealkylation reactions. The combined model now contains 72 metabolic pathways catalyzed by CYP2D6 in 51 substrates. The model was then used to predict the involvement of CYP2D6 in the metabolism of a "test set" of seven compounds. Molecular orbital calculations were used to suggest energetically favorable sites of metabolism, which were then examined using modeling techniques. The combined model correctly predicted 6 of the 8 observed metabolites. For the well-established CYP2D6 metabolic routes, the predictive value of the current combined protein and pharmacophore model is good. Except for the highly unusual metabolism of procainamide and ritonavir, the known metabolites not included in the development of the model were all predicted by the current model. Two possible metabolites have been predicted by the current model, which have not been detected experimentally. In these cases, the model may be able to guide experiments. P450 models, like the one presented here, have wide applications in the drug design process which will contribute to the prediction and elimination of polymorphic metabolism and drug-drug interactions.

Inter-hospital comparison of mortality rates.

OBJECTIVE: To compare crude and adjusted in-hospital mortality rates after prostatectomy between hospitals using routinely collected hospital discharge data and to illustrate the value and limitations of using comparative mortality rates as a surrogate measure of quality of care. METHODS: Mortality rates for non-teaching hospitals (n = 21) were compared to a single notional group of teaching hospitals. Patients age, disease (comorbidity), length of stay, emergency admission, and hospital location were identified using ICD-9-CM coded Victorian hospital morbidity data from public hospitals collected between 1987/88 and 1994/95. Comparisons between hospitals were based on crude and adjusted odds ratios (OR) and 95% confidence intervals (CI) derived using univariate and multivariate logistic regression. Model fit was evaluated using receiver operating characteristic curve i.e. statistic, Somer's D, Tau-a, and R2. RESULTS: The overall crude mortality rates between hospitals achieved borderline significance (alpha2=31.31; d.f.=21; P=0.06); these differences were no longer significant after adjustment (chi2=25.68; P=0.21). On crude analysis of mortality rates, four hospitals were initially identified as 'low' outlier hospitals; after adjustment, none of these remained outside the 95% CI, whereas a new hospital emerged as a 'high' outlier (OR=4.56; P= 0.05). The adjusted ORs between hospitals compared to the reference varied from 0.21 to 5.54, ratio = 26.38. The model provided a good fit to the data (c=0.89; Somer's D= (0.78; Tau-a = 0.013; R2= 0.24). CONCLUSIONS: Regression adjustment of routinely collected data on prostatectomy from the Victorian Inpatient Minimum Database reduced variance associated with age and correlates of illness severity. Reduction of confounding in this way is a move in the direction of exploring differences in quality of care between hospitals. Collection of such information over time, together with refinement of data collection would provide indicators of change in quality of care that could be explored in more detail as appropriate in the clinical setting.

Novel approach to predicting P450-mediated drug metabolism: development of a combined protein and pharmacophore model for CYP2D6.

A combined protein and pharmacophore model for cytochrome P450 2D6 (CYP2D6) has been derived using various computational chemistry techniques. A combination of pharmacophore modeling (using 40 substrates), protein modeling, and molecular orbital calculations was necessary to derive a model which incorporated steric, electronic, and chemical stability properties. The initial pharmacophore and protein models used to construct the combined model were derived independently and showed a high level of complementarity. The combined model is in agreement with experimental results concerning the substrates used to derive the model, with site-directed mutagenesis data available for the CYP2D6 protein, and takes into account the site-directed mutagenesis results for a variety of other 2-family P450s.

Pharmacokinetics and metabolism of sildenafil in mouse, rat, rabbit, dog and man.

1. Pharmacokinetics were studied in mouse, rat, rabbit, dog and man after single intravenous and/or oral doses of sildenafil or [14C]-sildenafil (Viagra). 2. In man, absorption from the gastrointestinal tract was essentially complete. With the exception of male rat, Tmax occurred at approximately 1 h or less. Bioavailability was attenuated by pre-systemic hepatic metabolism in all species. 3. The volume of distribution was similar in rodents and humans (1-2 l/kg) but was greater in dog (5.2 l/kg), due to lower plasma protein binding (84 versus 94-96% respectively). 4. High clearance was the principal determinant of short elimination half-lives in rodents (0.4-1.3 h), whereas moderate clearance in dog and man resulted in longer half-lives (6.1 and 3.7 h respectively). Clearances were in agreement with in vitro metabolism rates by liver microsomes from the various species. 5. After single oral or intravenous doses of [14C]-sildenafil, the majority of radioactivity was excreted in the faeces of all species. No unchanged drug was detected in the excreta of man. 6. Five principal pathways of metabolism in all species were piperazine N-demethylation, pyrazole N-demethylation, loss of a two-carbon fragment from the piperazine ring (N,N'-deethylation), oxidation of the piperazine ring and aliphatic hydroxylation. Additional metabolites arose through combinations of these pathways. 7. Sildenafil was the major component detected in human plasma. Following oral doses, AUC(infinity) for the piperazine N-desmethyl and piperazine N,N'-desethyl metabolites were 55 and 27% that of parent compound respectively.

Metabolism of delavirdine, a human immunodeficiency virus type-1 reverse transcriptase inhibitor, by microsomal cytochrome P450 in humans, rats, and other species: probable involvement of CYP2D6 and CYP3A.

The metabolism of delavirdine was examined using liver microsomes from several species with the aim of comparing metabolite formation among species and characterizing the enzymes responsible for delavirdine metabolism. Incubation of 10 microM [14C]delavirdine with either an S9 fraction from human jejunum or liver microsomes from rat, human, dog, or monkey followed by high pressure liquid chromatography analysis showed qualitatively similar metabolite profiles among species with the formation of three significant metabolites. The major metabolite was desalkyl delavirdine; however, the identity of MET-7 and MET-7a (defined by high pressure liquid chromatography elution) could not be unambiguously established, but they seem to be related pyridine hydroxy metabolites, most likely derived from 6'-hydroxylation of the pyridine ring. The apparent KM for delavirdine desalkylation activity ranged from 4.4 to 12.6 microM for human, rat, monkey, and dog microsomes, whereas Vmax ranged from 0.07 to 0.60 nmol/min/mg protein, resulting in a wide range of intrinsic clearance (6-135 microL/min/mg protein). Delavirdine desalkylation by microsomes pooled from several human livers was characterized by a KM of 6.8 +/- 0.8 microM and Vmax of 0. 44 +/- 0.01 nmol/min/mg. Delavirdine desalkylation among 23 human liver microsomal samples showed a meaningful correlation (r = 0.96) only with testosterone 6beta-hydroxylation, an indicator of CYP3A activity. Among ten human microsomal samples selected for uniform distribution of CYP3A activity, formation of MET-7 was strongly correlated with CYP3A activity (r = 0.95) and with delavirdine desalkylation (r = 0.98). Delavirdine desalkylation was catalyzed by cDNA-expressed CYP2D6 (KM 10.9 +/- 0.8 microM) and CYP3A4 (KM 5.4 +/- 1.4 microM); however, only CYP3A4 catalyzed formation of MET-7 and MET-7a. Quinidine inhibited human liver microsomal delavirdine desalkylation by about 20%, indicating a minor role of CYP2D6. These findings suggest the potential for clinical interaction with coadministered drugs that are metabolized by or influence the activity of CYP3A or CYP2D6.

Adverse events after prostatectomy in Victorian public hospitals.

BACKGROUND: A retrospective analysis of data from the Victorian Inpatient Minimum Database (VIMD) was conducted to analyse trends in prostatectomy rates in Victorian public acute-care hospitals from 1989/90 to 1994/95. The study also sought to identify predictors of adverse events (AE) after prostatectomy, and to compare in-hospital complications between open prostatectomy and transurethral resection of prostate (TURP). METHODS: All patients who had undergone any prostatectomy were identified according to the relevant ICD-9-CM procedure codes (60.2-60.4) documented in the VIMD. The main outcome measures, AE, were identified using the ICD-9-CM supplementary classification of external cause of injury (E850-858, E870-876, E878-879, E930-949). The variables used as predictors were year of prostatectomy, type of admission (planned, emergency), location of the hospital (rural, metropolitan), type of procedure (TURP, open), and teaching status of the hospital. Crude and adjusted odds ratios (OR) were based on univariate and multivariate logistic regression. RESULTS: The rates of prostatectomies have significantly increased over the 6-year study period (P for trend < 0.0001). The percentage of AE after prostatectomy increased simultaneously from 6.1 to 12.9% (P < 0.0001). During the same period, the in-hospital mortality rate after prostatectomy decreased from 1.2 to 0.5%, and length of stay decreased from 10.3 to 6.1 days (Kruskal-Wallis P < 0.0001). The significant predictors of outcome were year of prostatectomy (P for trend < 0.0001), emergency admissions (OR = 1.57; P < 0.0001), metropolitan hospitals (OR = 0.81; P = 0.0003), non-teaching hospitals (OR = 0.78; P < 0.0001), and open prostatectomy (OR = 1.52; P = 0.04). More in-hospital complications were associated with open prostatectomy than with TURP. CONCLUSIONS: The rise in AE rate after prostatectomy is unlikely to reflect poor quality of care, because in the same period there was a significant decrease in in-hospital mortality after prostatectomy. A more likely explanation is heightened awareness of AE with a lower threshold for reporting such events. Important factors other than variations in quality of care can result in an increase in AE. Hence the reported increase should be interpreted with caution before attempting to conclude that changes in clinical practice could have a direct impact on these rates.

Predictors of length of stay for transurethral prostatectomy in Victoria.

BACKGROUND: Transurethral resection of prostate (TURP) is among the top 10 surgical conditions that account for hospital admission in Victoria. Bed utilization for TURP is an increasing concern in current times. This paper describes trends in length of stay (LOS) and identifies predictors of LOS for TURP in Victoria. METHODS: Trends in TURP were studied using ICD-9-CM coded Victorian hospital morbidity data from public hospitals from 1987/88 to 1994/95. Detailed morbidity data from the same source for the financial year 1995/96 were used to study predictors of LOS by logistic regression. RESULTS: Length of stay decreased significantly between 1987 and 1995 from 10.6 to 6.1 days. The strongest predictor of increased LOS was admission through the emergency room (odds ratio (OR) 14.7; 95% confidence interval (CI) 11.8-18.3). Other significant predictors were older age, lower socio-economic status, presence of comorbid conditions, occurrence of procedural morbidity, and hospital type and location. CONCLUSIONS: The trend in decreasing LOS may be explained by increasingly efficient bed management in hospitals who are faced with an increasing need for cost control. Advances in surgical techniques and peri-operative care have also contributed to the decrease in LOS. Other factors that influence LOS can be divided into three categories: intrinsic patient factors, such as co-morbid conditions; procedure-specific factors such as peri-operative morbidity; and intrinsic hospital factors relating to capacity and resources. Such determinants of LOS may be of value to policy makers when considering the effective application of newer methods for treatment of benign prostatic hyperplasia.

Accuracy of ICD-9-CM codes in hospital morbidity data, Victoria: implications for public health research.

Hospital morbidity data in the form of International classification of diseases, 9th revision, clinical modification codes are often used for epidemiological studies and disease surveillance. We aimed to evaluate the reliability of the Victorian In-patient Minimum Database for use in epidemiological studies and disease surveillance. Data from 1993-94 were collected, as part of a coding audit of public hospitals in Victoria, from 7052 randomly selected records. The frequency of discrepancy in any coding field was 53 per cent, and of discrepancy in the principal diagnosis, 22 per cent. New Australian national diagnosis-related group (ANDRG) codes were assigned as a result of discrepancy in 13.6 per cent of cases. Discrepancy rates increased with increasing rarity of ANDRG, from 50 per cent to 56 per cent. Predictors of change in ANDRG assignment were discrepancy in the principal diagnosis, ANDRG frequency of over 0.6 per cent, more than three diagnoses, medical ANDRGs, length of stay over five days and rural hospitals. Rates of any discrepancy increased from 36 per cent in patients with one diagnosis to 94 per cent in patients with 12 diagnoses. The discrepancy rates were consistent with those of other studies. Coding discrepancy is likely to be caused by universal difficulties associated with the coding of hospital records, rather than any unique local problems. The predictors of discrepancy suggest that more complex cases are more prone to coding discrepancy. In areas where the database is less reliable, use of a supplementary data source, such as link-age studies, would improve reliability.

Accuracy of injury coding in Victorian hospital morbidity data.

In Victoria injury surveillance data are drawn from hospital morbidity data. The accuracy and reliability of these data are often questioned. We aimed to ascertain the reliability of injury data in the Victorian inpatient minimum database. A random sample of 546 public hospital separations with principal diagnosis ICD-9-CM codes 800-999 was selected from four metropolitan hospitals. Medical records were reviewed, and the hospital coding was compared with the record content. The frequency of error in any coding field was 73 per cent (349/480); of diagnosis error, 61 per cent (292/480); of procedure error, 45 per cent (168/370); of error in the principal diagnosis, 19 per cent (93/480); and of error in external-cause codes (E-codes), 16 per cent (75/480). Ninety-four per cent of errors (87/93) in the principal diagnosis involved recoding within the same group of codes. Only 6 per cent (6/93) were recoded to principal diagnoses other than injury. Sixty-two per cent (181/292) were errors of omission of codes for comorbid conditions. Nearly half the errors in the principal diagnosis were minor, involving the last two digits. E-codes were more complete than diagnosis codes. The best predictors of error in the principal diagnosis were greater length of stay, type of injury code (poisonings and toxic effects were associated with lower error rates) and death as the outcome. While selection of data from secondary diagnosis fields may not provide complete data, the use of the principal-diagnosis code and E-codes for injury surveillance is feasible and reliable. The database is a valuable source of injury surveillance data, bearing in mind the limitations of coded hospital morbidity data.

Postoperative complications of cholecystectomy in Victorian public hospitals.

Cholecystectomies in Victorian public hospitals were evaluated by analysis of hospital morbidity data. The Victorian Inpatient Minimum Dataset (VIMD) contains data on postoperative complications from all cholecystectomies in Victorian public hospitals. Hospital separations associated with cholecystectomy were identified according to Australian national diagnosis-related groups and the procedures were grouped as open, laparoscopic or conversion from laparoscopic to open cholecystectomy (conversion). Postoperative complications were identified by ICD9-CM external-cause codes (E-codes) in the VIMD. The 35593 cholecystectomies performed between 1987-88 and 1993-94 were analysed. A further detailed analysis of all cholecystectomies performed in 1993 was based on logistic regression. This identified the adjusted odds (AOR) of occurrence of complications and included covariates of age, sex, admission type, diagnosis-related group and hospital identification code. The annual frequency of cholecystectomy increased after introduction of laparoscopic cholecystectomy in 1990, and was associated with an increase in rates of separations having adverse events, but laparoscopic cholecystectomy had the lowest rate (66.7 per 1000 separations). Adverse-event rates for open procedures increased to 157.5 per 1000 in 1993-94, and for conversions to 290.0 per 1000. Of 5627 cholecystectomies in 1993, 74.4 per cent were laparoscopic, 21.5 per cent open and 4.1 per cent conversions. Postoperative complications were more likely in males (AOR 1.67, 95 per cent confidence interval (CI) 1.38 to 2.04), in patients admitted as an emergency (1.27, CI 1.01 to 1.60), and in those having open cholecystectomies (2.25, 1.78 to 2.85) or conversions (4.29, 3.05 to 6.03). Analysis of the VIMD has provided information for the evaluation of cholecystectomy. The VIMD is a useful tool for monitoring postoperative complications and the quality of care in Victorian hospitals.

Influence of amino acid residue 374 of cytochrome P-450 2D6 (CYP2D6) on the regio- and enantio-selective metabolism of metoprolol.

Cytochrome P-450 2D6 (CYP2D6) is an important human drug-metabolizing enzyme responsible for the oxidation of more than 30 widely used therapeutic agents. The enzymes encoded by the published genomic [Kimura, Umeno, Skoda, Meyer and Gonzalez (1989) Am. J. Hum. Genet. 45, 889-904] and cDNA [Gonzalez, Skoda, Kimura, Umeno, Zanger, Nebert, Gelboin, Hardwick and Meyer (1988) Nature 331, 442-446] sequences of CYP2D6, and presumed to represent wild-type sequences, differ at residue 374 and encode valine (CYP2D6-Val) and methionine (CYP2D6-Met) respectively. The influence of this amino acid difference on cytochrome P-450 expression, ligand binding, catalysis and stereoselective oxidation of metoprolol was investigated by the heterologous expression of the corresponding cDNAs in the yeast Saccharomyces cerevisiae. The level of expression of apo- and holo-protein was similar with each form of CYP2D6 cDNA, and the binding affinities of a series of ligands to CYP2D6-Val and CYP2D6-Met were identical. The enantioselective O-demethylation and alpha-hydroxylation of metoprolol were also similar with each form of CYP2D6, O-demethylation being R-(+)- enantioselective (CYP2D6-Val: R/S, 1.6; CYP2D6-Met: R/S, 1.4), whereas alpha-hydroxylation showed a preference for S-(-)-metoprolol (CYP2D6-Val: R/S, 0.7; CYP2D6-Met: R/S, 0.8). However, although the favoured regiomer overall was O-demethylmetoprolol (ODM), the regioselectivity for O-demethylation of each metoprolol enantiomer was significantly greater for CYP2D6-Val [R-(+)-: ODM/alpha-hydroxymetoprolol (alpha OH), 5.9; S-(-)-: ODM/alpha OH, 2.5) than that observed for CYP2D6-Met [R-(+)-: ODM/alpha OH, 2.2; S-(-)-: ODM/alpha OH, 1.4]. The stereoselective properties of CYP2D6-Val were consistent with those observed for CYP2D6 in human liver microsomes. The difference in the stereoselective properties of CYP2D6-Val and CYP2D6-Met were rationalized with respect to a homology model of the active site of CYP2D6 based on an alignment with the crystal structure of the bacterial cytochrome P-450BM-3' CYP102.

Health status of Victorian special school children.

OBJECTIVE: This study sought to determine the health status and health needs of a sample of students attending special schools for the intellectually disabled in Victoria, Australia. METHODOLOGY: Two hundred and forty-nine students not previously seen by a Community Child Health Medical Officer (CCHMO) were assessed at school. Data on student, parent and staff needs were obtained through personal interviews and documented on a standard questionnaire. Health status was documented using data obtained from parents and teachers as well as the clinical assessment. RESULTS: Comparison of the number of problems reported by parents with the number confirmed at examination showed significant underreporting of vision, hearing and general medical problems. However, behaviour problems were nearly all reported. Many students had multiple problems with 63% having 2-4 problems and 11% having 5-8 problems. Ninety-nine (40%) of the 249 children seen had newly detected problems; vision (24), hearing (24) and obesity (9) were the most common. Two hundred and forty-four (98%) had known problems and 27% of these had insufficient information available from parents or staff to completely ascertain their health status. In 115 cases the primary problem was intellectual impairment of unknown cause. Down syndrome was the next most common underlying diagnosis (30) followed by autism (24), epilepsy (21) and cerebral palsy (15). The most common secondary diagnoses were asthma (16), congenital heart defects (12), seizures (8) and skin problems (8). Many students required referral for further management both for newly detected problems (64%) and known problems (18%). Parents required counselling and/or discussion on a number of issues for both newly detected problems (66%) and known problems (39%); when counselling had taken place parent and staff concerns had reduced significantly by the time of the follow-up assessment. CONCLUSIONS: This study demonstrated that in those students with known intellectual impairment there were many with other unrecognized health problems and unmet needs. These findings have implications for health services provided to children attending special schools.

Evidence that aspartic acid 301 is a critical substrate-contact residue in the active site of cytochrome P450 2D6.

Model building studies have intimated a role for aspartic acid 301 in the substrate binding of cytochrome P450 2D6 (CYP2D6). We have tested this hypothesis by generating a range of CYP2D6 mutants substituting a variety of amino acids at this site. The mutant proteins, which included substitution with a negatively charged glutamic acid residue or neutral asparagine, alanine, or glycine residues, were expressed in Saccharomyces cerevisiae. In addition, a mutant where aspartic acid 301 was deleted was also tested. All the mutants expressed approximately equivalent amounts of recombinant apoprotein and, apart from the alanine 301 and the aspartic acid 301 deletion mutants, gave carbon monoxide difference spectra of similar magnitude to the wild type. In the cases of the alanine and deletion mutants, the amount of holoprotein was significantly reduced or absent relative to the amount of apoprotein, indicating restricted heme incorporation. The glutamic acid mutant was shown to have similar catalytic properties to the wild type enzyme toward the substrates debrisoquine and metoprolol; however, some differences in regioselectivity and ligand binding were observed. The mutants containing neutral amino acids at position 301 exhibited marked reductions in catalytic activity. At low substrate concentrations little, if any, activity toward debrisoquine and metoprolol was measured. However, at a higher substrate concentration (2 mM) some activity was observed (about 10-20% of wild type levels). Consistent with the above findings, the debrisoquine-induced spin changes in the mutant proteins were markedly reduced. These data collectively demonstrate that aspartic acid 301 plays an important role in determining the substrate specificity and activity of CYP2D6 and provide experimental evidence supporting the role of this amino acid in forming an electrostatic interaction between the basic nitrogen atom in CYP2D6 substrates and the carboxylate group of aspartic acid 301.

Health status of Victorian special school children.

OBJECTIVE: This study sought to determine the health status and health needs of a sample of students attending special schools for the intellectually disabled in Victoria, Australia. METHODOLOGY: Two hundred and forty-nine students not previously seen by a Community Child Health Medical Officer (CCHMO) were assessed at school. Data on student, parent and staff needs were obtained through personal interviews and documented on a standard questionnaire. Health status was documented using data obtained from parents and teachers as well as the clinical assessment. RESULTS: Comparison of the number of problems reported by parents with the number confirmed at examination showed significant underreporting of vision, hearing and general medical problems. However, behaviour problems were nearly all reported. Many students had multiple problems with 63% having 2-4 problems and 11% having 5-8 problems. Ninety-nine (40%) of the 249 children seen had newly detected problems; vision (24), hearing (24) and obesity (9) were the most common. Two hundred and forty-four (98%) had known problems and 27% of these had insufficient information available from parents or staff to completely ascertain their health status. In 115 cases the primary problem was intellectual impairment of unknown cause. Down's syndrome was the next most common underlying diagnosis (30) followed by autism (24), epilepsy (21) and cerebral palsy (15). The most common secondary diagnoses were asthma (16), congenital heart defects (12), seizures (8) and skin problems (8). Many students required referral for further management both for newly detected problems (64%) and known problems (18%). Parents required counselling and/or discussion on a number of issues for both newly detected problems (66%) and known problems (39%); when counseling had taken place parent and staff concerns had reduced significantly by the time of the follow-up assessment. CONCLUSIONS: This study demonstrates that in those students with known intellectual impairment there were many with other unrecognized health problems and unmet needs. These findings have implications for health services provided to children attending special schools.

Correlation between site specificity and electrophilic frontier values in the metabolic hydroxylation of biphenyl, di-aromatic and CYP2D6 substrates: a molecular modelling study.

1. A series of biphenyl, di-aromatic and CYP2D6 substrates known to undergo metabolic aromatic hydroxylation was derived from the literature, several animal species were represented. 2. Molecular orbital calculations were performed on the substrates using the AM1 semi-empirical force field and the electrophilic frontier values (f(E)) plotted for each available aromatic site. 3. A qualitative correlation was observed between the sites of oxidation and high f(E) values, suggesting the role of frontier orbitals in the metabolic hydroxylation of these substrates. 4. The mechanistic implications for the involvement of frontier orbitals in aromatic hydroxylation are discussed. It is proposed that electron abstraction occurs in the region of high electron density to form a radical cation. Hydrogen abstraction by Fe++O- then occurs followed by oxygen rebound. 5. The method can be helpful in indicating regio-specificity in the metabolic hydroxylation of bi-phenyls, related di-aromatic compounds and possibly CYP2D6 aromatic substrates.