Analysis of long-term water quality for effective river health monitoring in peri-urban landscapes--a case study of the Hawkesbury-Nepean river system in NSW, Australia.

The Hawkesbury-Nepean River (HNR) system in South-Eastern Australia is the main source of water supply for the Sydney Metropolitan area and is one of the more complex river systems due to the influence of urbanisation and other activities in the peri-urban landscape through which it flows. The long-term monitoring of river water quality is likely to suffer from data gaps due to funding cuts, changes in priority and related reasons. Nevertheless, we need to assess river health based on the available information. In this study, we demonstrated how the Factor Analysis (FA), Hierarchical Agglomerative Cluster Analysis (HACA) and Trend Analysis (TA) can be applied to evaluate long-term historic data sets. Six water quality parameters, viz., temperature, chlorophyll-a, dissolved oxygen, oxides of nitrogen, suspended solids and reactive silicates, measured at weekly intervals between 1985 and 2008 at 12 monitoring stations located along the 300 km length of the HNR system were evaluated to understand the human and natural influences on the river system in a peri-urban landscape. The application of FA extracted three latent factors which explained more than 70 % of the total variance of the data and related to the 'bio-geographical', 'natural' and 'nutrient pollutant' dimensions of the HNR system. The bio-geographical and nutrient pollution factors more likely related to the direct influence of changes and activities of peri-urban natures and accounted for approximately 50 % of variability in water quality. The application of HACA indicated two major clusters representing clean and polluted zones of the river. On the spatial scale, one cluster was represented by the upper and lower sections of the river (clean zone) and accounted for approximately 158 km of the river. The other cluster was represented by the middle section (polluted zone) with a length of approximately 98 km. Trend Analysis indicated how the point sources influence river water quality on spatio-temporal scales, taking into account the various effects of nutrient and other pollutant loads from sewerage effluents, agriculture and other point and non-point sources along the river and major tributaries of the HNR. Over the past 26 years, water temperature has significantly increased while suspended solids have significantly decreased (p < 0.05). The analysis of water quality data through FA, HACA and TA helped to characterise the key sections and cluster the key water quality variables of the HNR system. The insights gained from this study have the potential to improve the effectiveness of river health-monitoring programs in terms of cost, time and effort, particularly in a peri-urban context.

Use of cystatin C-based estimations of glomerular filtration rate in patients with type 2 diabetes.

AIMS/HYPOTHESIS: The Modification of Diet in Renal Disease (MDRD) equation has recognised limitations when using estimated GFR in persons at risk of chronic kidney disease. Equations based on cystatin C provide an alternative method. We compared performance of the MDRD equation with a selection of cystatin C-based formulae for estimation of GFR in normoalbuminuric patients with type 2 diabetes. METHODS: Estimated GFR was calculated using the MDRD equation and the cystatin C formulae proposed by several investigator teams. Isotopic GFR was measured using plasma clearance of (51)Cr-EDTA. RESULTS: We studied 106 participants, of whom 83 (78%) were men with the following characteristics, mean (SD): age 61 (9) years, HbA(1c) 7.10 (1.27)%, creatinine 89.0 (12.7) micromol/l, cystatin C 0.859 (0.234) mg/l and isotopic GFR 104.5 (20.1) ml min(-1) 1.73 m(-2). MDRD estimated GFR was 77.4 (13.6) ml min(-1) 1.73 m(-2) (p < 0.05 for difference from isotopic GFR). Cystatin C-based calculations of estimated GFR were: Perkins 124.5 (31.8), Rule 90.0 (30.0), Stevens (age) 96.0 (30.4) and Stevens (creatinine) 85.6 (19.0) ml min(-1) 1.73 m(-2) (p < 0.05 for difference with isotopic GFR). For Arnal's, MacIsaac's and Tan's formulae cystatin-C estimated GFR were 101.7 (34.8), 102.1 (27.0) and 101.6 (27.8) ml min(-1) 1.73 m(-2), respectively (p = NS for difference with isotopic GFR). Cystatin C-based formulae were less biased and, with the exception of Perkins' formula, more accurate to within 10% of isotopic GFR than MDRD. CONCLUSIONS/INTERPRETATION: Performance of cystatin C equations was superior to MDRD in normoalbuminuric patients with type 2 diabetes. These results support further evaluation of cystatin C for estimation of GFR in persons at risk of chronic kidney disease.

Performance of the revised '175' Modification of Diet in Renal Disease equation in patients with type 2 diabetes.

AIMS/HYPOTHESIS: Estimation of GFR (eGFR) is recommended for the assessment of kidney function in all patients with diabetes. We studied performance of the traditional '186' Modification of Diet in Renal Disease (MDRD) equation, and the 2005 revised '175' MDRD equation in patients with type 2 diabetes. METHODS: Two hundred and ninety-three mainly normoalbuminuric (267/293) patients were recruited. Patients were classified as having mild renal impairment (group 1, GFR <90 ml min(-1) 1.73 m(-2)) or normal renal function (group 2, GFR >or=90 ml min(-1) 1.73 m(-2)). eGFR was calculated by the traditional 186 MDRD equation using traditional creatinine values and the revised 175 MDRD equation using isotope dilution mass spectrometry-standardised creatinine values. Isotopic GFR was measured by the four-sample plasma clearance of (51)Cr-EDTA. RESULTS: For patients in group 1, mean +/- SD isotopic (51)Cr-EDTA GFR (iGFR) was 83.8 +/- 4.3 ml min(-1) 1.73 m(-2), and eGFR was 73.2 +/- 11.9 and 75.8 +/- 13.7 ml min(-1) 1.73 m(-2) using the 186 and 175 MDRD equations, respectively. Method bias was -10.6 with the 186 MDRD and -7.9 ml min(-1) 1.73 m(-2) (p < 0.05) with the 175 MDRD equation. In group 2, iGFR was 119.4 +/- 20.2 ml min(-1) 1.73 m(-2), and eGFR was 92.3 +/- 18.6 and 97.5 +/- 21.6 ml min(-1) 1.73 m(-2) using the 186 and 175 MDRD equations, respectively. Method bias was -27.1 with the 186 MDRD equation and -21.9 ml min(-1) 1.73 m(-2) (p < 0.05) with the 175 MDRD equation. CONCLUSIONS/INTERPRETATION: In patients newly diagnosed with type 2 diabetes, the revised 175 MDRD equation was less biased than the traditional 186 MDRD equation. Despite a continued tendency to underestimate isotopically measured GFR, use of standardised creatinine values is a positive step towards improved estimation of GFR.

Type 2 diabetes mellitus--genes or intrauterine environment? An embryo transfer paradigm in rats.

AIMS/HYPOTHESIS: The familial predisposition to Type 2 diabetes mellitus is mediated by both genetic and intrauterine environmental factors. In the normal course of events, maternal genes always develop in the same uterus, thus restricting studies aimed at investigating the relative contribution of these factors. We have developed an embryo transfer paradigm in rats to overcome this difficulty. METHODS: Euglycaemic female Wistar rats were superovulated and mated with male Wistar rats. The following day, fertilised eggs were transferred into pseudo-pregnant female Wistar rats or hyperglycaemic Goto Kakizaki (GK) rats. Pregnancies were allowed to go to term. Offspring were weighed at 6 weeks, 3 months and 6 months of age and an intravenous glucose tolerance test was carried out at 6 months of age. RESULTS: Offspring from Wistar into Wistar embryo transfers (n=20) were not significantly hyperglycaemic compared to the non-manipulated Wistar stock colony (n=26). However, offspring from Wistar gametes reared in hyperglycaemic GK mothers (n=51) were significantly lighter at 6 weeks of age (156+/-4.1 g vs 180+/-6.1 g [mean +/- SEM], p<0.01) and significantly more hyperglycaemic at 6 months of age (fasting glucose 6.6+/-0.18 mmol/l vs 4.8+/-0.21 mmol/l, mean blood glucose during glucose tolerance test 14.3+/-0.31 mmol/l vs 11.1+/-0.28 mmol/l, p<0.01) than Wistar gametes transferred back into euglycaemic Wistar mothers. When GK rats were superovulated and mated together, transfer of 1-day-old embryos into pseudo-pregnant Wistar dams did not alleviate hyperglycaemia in adult offspring. CONCLUSIONS/INTERPRETATION: In GK rats, a euglycaemic intrauterine environment cannot overcome the strong genetic predisposition to diabetes. However, in Wistar rats with a low genetic risk of diabetes, exposure to hyperglycaemia in utero significantly increases the risk of diabetes in adult life.

Is human Type 2 diabetes maternally inherited? Insights from an animal model.

AIMS: Patients with Type 2 diabetes mellitus more often report a history of an affected mother than father. However, in the few studies where both parents and offspring have been directly tested, this apparent maternal excess has not been confirmed. Rodent models of diabetes have the advantage that all parents and offspring can undergo glucose tolerance testing at a specific age in adult life. The aim of this study was to gain insights into the inheritance of human Type 2 diabetes by using a rat model. METHODS: Goto Kakizaki (GK) rats (a model of Type 2 diabetes) were mated with non-diabetic Wistar rats. Offspring were produced from 20 GK female vs. Wistar male and 20 Wistar female vs. GK male crosses. Fasting blood glucose was measured at 6 weeks and 3 months of age and an intravenous glucose tolerance test (0.8 g/kg) performed at 6 months of age. RESULTS: Wistar mothers produced litters with almost twice as many viable offspring as GK mothers (14.1 vs. 7.4, P < 0.001). Despite the larger litter size, offspring in the two groups were of comparable weight at 6 weeks and 6 months of age. At 3 months of age, male offspring of Wistar mothers were heavier than offspring of GK mothers (415.7 g vs. 379.5 g, P = 0.016) but this difference was not sustained at 6 months of age. Fasting blood glucose at all ages and average blood glucose during the glucose tolerance test were similar in both groups. CONCLUSIONS: We therefore conclude that there is no evidence for maternal transmission of diabetes in the GK rat. Mothers were able to adjust their supply of milk so that offspring attained similar weights independent of litter size. The weight of the offspring remained independent of litter size into adult life.

Effect of software manipulation (Photoshop) of digitised retinal images on the grading of diabetic retinopathy.

AIMS: To determine whether software processing of digitised retinal images using a "sharpen" filter improves the ability to grade diabetic retinopathy. METHODS: 150 macula centred retinal images were taken as 35 mm colour transparencies representing a spectrum of diabetic retinopathy, digitised, and graded in random order before and after the application of a sharpen filter (Adobe Photoshop). Digital enhancement of contrast and brightness was performed and a X2 digital zoom was utilised. The grades from the unenhanced and enhanced digitised images were compared with the same retinal fields viewed as slides. RESULTS: Overall agreement in retinopathy grade from the digitised images improved from 83.3% (125/150) to 94.0% (141/150) with sight threatening diabetic retinopathy (STDR) correctly identified in 95.5% (84/88) and 98.9% (87/88) of cases when using unenhanced and enhanced images respectively. In total, five images were overgraded and four undergraded from the enhanced images compared with 17 and eight images respectively when using unenhanced images. CONCLUSION: This study demonstrates that the already good agreement in grading performance can be further improved by software manipulation or processing of digitised retinal images.

Day-to-day variability of fasting plasma glucose in newly diagnosed type 2 diabetic subjects.

OBJECTIVE: To determine the day-to-day intraindividual variability of fasting plasma glucose (FPG) in newly diagnosed Caucasian type 2 diabetic subjects. RESEARCH DESIGN AND METHODS: A total of 193 newly diagnosed, previously untreated, Caucasian type 2 diabetic subjects (135 men, 58 women) had FPG measured on two consecutive days (FPG1, FPG2). Ethical approval and subjects' full informed consent were obtained. Subjects fasted for 12 h before each study day and rested for at least 30 min before blood was taken. Plasma glucose was analyzed by a glucose oxidase method with intra- and interassay coefficients of variation (CVs) < 2%. Variability of FPG was assessed by comparison of percentage differences (PDs): PD = 100 (FPG2 - FPG1)/FPG1, with averaged FPG (FPGaver = [FPG1 + FPG2]/2). Biological and analytical variability were determined by use of SD2total = SD2biological + SD2analytical, where SD2analytical approximately equal to 2 x (CVglucose measurement)2. Given normally distributed data with zero mean, 95% of daily percentage differences will be expected to fall within a range of +/- 2 SDtotal. RESULTS: Subjects were age 54 +/- 10 years (mean +/- SD) and had BMI of 29.3 +/- 5.3 kg/m2. FPG values for both days were 12.2 +/- 3.4 mmol/l (FPG1) and 12.1 +/- 3.3 mmol/l (FPG2), with a mean paired difference (95% CI) of 0.1 (0.0 to 0.3) mmol/l. The variance of these differences increased with increasing FPGaver. The PDs did not exhibit this effect and were normally distributed (mean -0.6% [-1.7 to 0.4]; SD 7.4% [6.8 to 8.3]), giving a 95% variability (2 SD) of 14.8%. Biological variability (2 SDbiological) was 13.7%. No significant difference in PD was found between men and women (mean difference 1.3% [-1.0 to 3.6]; SDmale 7.4%, SDfemale 7.3%; P = 0.62). CONCLUSIONS: A total of 95% of the FPG values for this group of newly diagnosed type 2 diabetic subjects varied within approximately +/- 15% on a daily basis, with approximately 14% caused by biological variability. As these results are expressed in percentage terms, subjects in the group with higher FPG values are likely to experience larger changes in FPG values measured from day to day. This variability should be considered when using FPG for the diagnosis and/or monitoring of response to treatment in patients with type 2 diabetes.

Determining true glomerular filtration status in newly presenting type 2 diabetic subjects using age and sex adjustment.

OBJECTIVE: To determine age- and sex-adjusted reference ranges (ASARRs) for glomerular filtration status using data from nondiabetic subjects and to apply these to newly presenting type 2 diabetic subjects. RESEARCH DESIGN AND METHODS: Glomerular filtration rate corrected for body surface area (cGFR) was determined using a radionuclide (51Cr-EDTA) method in 75 non-diabetic subjects (37 men, 38 women) and 219 type 2 diabetic subjects (157 men, 62 women). The 95% constant reference ranges (CRRs) were calculated as mean nondiabetic cGFR+/-1.96 SD. The 95% ASARRs were calculated by Altman's method from the nondiabetic cGFR versus age regression residuals for both male and female subjects. RESULTS: Using Altman's method, the intercepts, but not the gradients, of the cGFR versus age regressions were significantly different between male and female subjects (intercept difference [95% CI] 8.2 [1.3-15.1], gradient difference -0.4 [-1.1 to 0.3]). Fitting a common gradient, 95% ASARRs for normofiltration were found to be from 123.9 - (0.89 X age) to 181.7 - (0.89 x age) for male subjects, and from 116.0 - (0.89 X age) to 173.2 - (0.89 X age) for female subjects. The 95% CRR for normofiltration was 70.2-138.1 ml x min(-1) x (1.73 m)(-2). When applied to the diabetic cGFRs, the CRRs and ASARRs gave, respectively, 17% (37/219) versus 21% (46/219) hyperfiltrators and 83% (181/219) versus 79% (172/219) normofiltrators. Using the ASARRs, 14 normofiltrators (6 men, 8 women) were reclassified as hyperfiltrators (change [n/total n] [95% CI] 8% [14/181] [4-12]), and 5 hyperfiltrators (5 men, 0 women) were reclassified as normofiltrators (change 14% [5/37] [5-30]). CONCLUSIONS: We conclude that age and sex adjustment are essential to assess glomerular filtration status.

Intranasal insulin: the effects of three dose regimens on postprandial glycaemic profiles in type II diabetic subjects.

In both fasting normal and diabetic subjects, nasally administered insulin achieves significant falls in plasma glucose concentrations. Repeated administration before and during a meal has been necessary to lower postprandial glycaemic excursion in subjects with NIDDM. We have studied the use of Novolin Nasal which employs a non-irritant, lecithin-based enhancer as a vehicle for human insulin, on postprandial glucose profiles in NIDDM subjects to determine efficacy, optimal dose frequency, and tolerability. Seventeen NIDDM subjects (15 men, 2 women) participated in a randomized, partially blinded, placebo-controlled, crossover trial of three active treatment regimens (nasal insulin, 120 U at 0 min, 60 U at 0 and +20 min or 120 U at +20 min) in relation to a standardized mixed meal given at 0 min. All active treatments significantly reduced postprandial glucose concentrations compared to placebo. Intranasal insulin given at 0 min at a dose of 60 U or 120 U resulted in a 50% reduction in postprandial incremental glucose compared to placebo over the first 2 h, whereas treatment with 60 U both at 0 and 20 min lead to a 70% reduction over the 240 min postprandial period. Post-prandial intravenous insulin was the least effective. There were no episodes of symptomatic hypoglycaemia. Local tolerability was excellent with only four reports of transient nasal irritation out of a total of 68 doses. The delivery device was accurate with intra-device CV of delivered dose of 4.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

A glimpse of the 'natural history' of established type 2 (non-insulin dependent) diabetes mellitus from the spectrum of metabolic and hormonal responses to a mixed meal at the time of diagnosis.

The reported glucose and immunoreactive insulin (IRI) responses to oral and intravenous glucose in subjects with Type 2 diabetes have not always been consistent. This may have resulted from variations in the method of glucose administration, the ethnic backgrounds of subjects, the diagnostic criteria applied, the duration of the disease or IRI assay methods. The use of a mixed meal rather than glucose has been shown to provide a more physiological stimulus to the pancreatic beta-cell due to both glucose and non-glucose secretagogues. We have analysed the metabolic and hormonal responses of 188 newly diagnosed Caucasian subjects with Type 2 diabetes and 38 non-diabetic subjects to a 500 kcal mixed meal. The diabetic subjects were stratified according to fasting plasma glucose (FPG) (< 9, 9-12, 12-15 and > or = 15 mmol/l) and body mass index (BMI) (< 26.5, 26.5-30 and > or = 30 kg/m2). Increasing FPG was associated with higher peak glucose concentrations and increasing failure to achieve basal glucose levels by 4 h. Median fasting IRI concentrations were similar to those of normal subjects, but all diabetic subjects had reduced early-phase insulin secretion. Diabetic subjects with FPG < 9 mmol/l showed augmented IRI area under the curve (AUC) at 2 and 4 h, whereas those with FPG > 9 mmol/l had progressive falls in IRI AUC to below that of the normal subjects (P < 0.0001 for the trend). Peak IRI concentrations declined progressively with increasing FPG. Despite equivalent glucose exposure simple trends of increasing AUC, IRI with increasing BMI were statistically significant (P < 0.001, P < 0.02, P < 0.001 and P < 0.01, respectively for each FPG group). Both fasting and AUC non-esterified fatty acid concentrations increased significantly with FPG regardless of BMI (P < 0.001 for the trends). These results using a more physiological mixed meal challenge in a large number of recently diagnosed Type 2 diabetic subjects demonstrate a marked and increasing loss of beta-cell secretory function with increasing fasting hyperglycaemia aggravated by insulin resistance with increasing obesity.

A mathematical model of insulin secretion.

Diabetes mellitus is a chronic state of excessive blood glucose levels (hyperglycaemia), which may result from many environmental and genetic factors, often acting jointly. The major regulator of glucose concentration in the blood is insulin. It is known that about 50% of the insulin is taken up by the liver on passing through it after secretion from the pancreas. The precise value of this fractional uptake is not known, so the prehepatic insulin secretion rates cannot be readily estimated from the plasma insulin concentration levels. By utilizing the equimolar secretion of insulin and connecting peptide (C-peptide) from the pancreas, a noninvasive method has been formulated. This was based on a compartmental model which involved the pancreas, liver, and plasma. The resulting differential equation yielded a gamma variate solution which could be readily linearized. The model was then tested on 56 normal (51 nonobese and 5 obese) subjects, and three groups of subjects with diabetes who could be labelled as mild, moderate, and severe (based on the fasting plasma glucose concentration) with 83, 88, and 64 subjects respectively. We have focused on the human patient environment of the clinician to produce a distinct model which gave a consistent pattern within all four groups with good fits between observed and theoretical values of the plasma insulin levels. The consequent rates for insulin secretion were consistent across the groups and were clinically meaningful.

Reduced sampling protocols in estimation of insulin sensitivity and glucose effectiveness using the minimal model in NIDDM.

Recent work in healthy subjects, the aged, and subjects with gestational diabetes or drug-induced insulin resistance using minimal model analysis of the tolbutamide-modified frequently sampled intravenous glucose tolerance test suggested that a reduced sampling regimen of 12 time points produced unbiased and generally acceptable estimates of insulin sensitivity (SI) and glucose effectiveness (SG) compared with a full sampling schedule of 30 time points. We have used data from 26 insulin-modified frequently sampled intravenous glucose tolerance tests in 21 subjects with NIDDM to derive and compare estimates of SI and SG from the full sampling schedule (SI(30), SG(30)) with those estimated from the suggested 12 time points (SI(12), SG(12)) and those estimated with the addition of a 25-min time point (SI(13), SG(13)). Percentage relative errors were calculated relative to the corresponding 30 time-point values. A statistically significant bias of 15% (97% confidence interval from 7.4 to 25.6%, interquartile range 25%) was introduced by the estimation of SI(12) but not SI(13) (1%, 97% confidence interval from -9.4 to 9.3%, interquartile range 21%). Results for SG(12) (-12%, 97% confidence interval from -46.7 to 1.2%, interquartile range 49%) and SG(13) (-5%, 97% confidence interval from -27.8 to 6.8%, interquartile range 37%) were statistically equivocal. The precision of estimation of SI(12), SG(12), and SG(13) measured by the interquartile range of the percentage relative errors was poor. The precision of determination measured by the median minimal model coefficient of variation was 18, 29, and 27% for SI(30), SI(12), and SI(13) and 9, 11, and 11% for SG(30), SG(12), and SG(13), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)