An integrated model for simulating nitrogen trading in an agricultural catchment with complex hydrogeology.

Nitrogen loads to several New Zealand lakes are dominated by nonpoint runoff from pastoral farmland which adversely affects lake water quality. A 'cap and trade' scheme is being considered to help meet targets set for nitrogen loads to Lake Rotorua, and a numerical model, NTRADER, has been developed to simulate and compare alternative schemes. NTRADER models both the geophysics of nitrogen generation and transport, including groundwater lag times, and the economics of 'cap and trade' schemes. It integrates the output from several existing models, including a farm-scale nitrogen leaching and abatement model, a farm-scale management economic model, and a catchment-scale nitrogen transport model. This paper details modeling methods and compares possible trading program design features for the Lake Rotorua catchment. Model simulations demonstrate how a cap and trade program could be used to effectively achieve challenging environmental goals in the targeted catchment. However, results also show that, due to complex hydrogeology, satisfactory environmental outcomes may be not achieved unless groundwater lag times are incorporated into the regulatory scheme. One way to do this, as demonstrated here, would be to explicitly include lag times in the cap and trade program. The utility of the model is further demonstrated by quantifying relative differences in abatement costs across potential regulatory schemes.

Livestock-generated nitrogen exports from a pastoral wetland.

When wetlands are disturbed by cattle, pulses of contaminants may be released. We studied nitrogen exports from a small pastoral wetland (1725 m) in the Lake Taupo Catchment, New Zealand, to which cattle and sheep had periodic access. Flow, turbidity, and water quality samples were collected at the wetland outlet over 2 yr. Turbidity was used to trigger sampling during livestock grazing and as a surrogate for organic N (OrgN) and total N (TN) in flux estimation. The wetland flowed throughout the study (median 0.285 L s) and was baseflow dominated (73%) but responded to rainfall (peak storm flow 166 L s). Organic N was the dominant N form exported (median OrgN:TN ratio 0.86). During cattle grazing periods, concentrations and fluxes of all forms of nitrogen at the outlet were elevated compared with storm and baseflow conditions during nongrazed periods. The TN fluxes were nine times greater when cattle grazed the wetland (306 g d) than under nongrazed baseflow conditions (32 g d). Cattle grazing occurred 9% of the time but accounted for 34% of TN export over 11 mo. Excluding cattle from small wetlands is likely to have immediate water quality benefits.

Karyotypic abnormalities in benign adrenocortical tumors producing aldosterone.

Because familial hyperaldosteronism type II (FH-II) includes tumor formation, we examined the karyotypes of benign adrenocortical aldosterone-producing adenomas (APAs), including those from patients with FH-II. Cell culture was successful in 12 of 14 tumors removed, two of which were from patients with FH-II. Five of the 12 tumors cultured (one from a patient with FH-II) had abnormal karyotypes. All were from male patients, and loss of the Y chromosome was observed in each. One showed loss of chromosome 19, and another showed an unbalanced t(6;7) producing partial trisomy 7q. Oncogenes are present at these breakpoints, and loss of the Y chromosome and monosomy 19 have previously been reported in neoplasia. This is the first report of cytogenetic abnormalities in benign adrenocortical tumors.

Nitrate removal in riparian wetlands: interactions between surface flow and soils.

Riparian wetlands containing springs are thought to be ineffective at removing nitrate because contact times between the upwelled ground water and the underlying microbially active soils are short. Tracer experiments using lithium bromide (LiBr) and nitrate (NO3-N) injected at the surface were used to quantify residence times and NO3-N removal in a riparian swale characteristic of New Zealand hill-country pasture. An experimental enclosure was used with collecting trays at the downstream end to measure flow and concentration, shallow wells to measure subsurface concentrations, and an array of logging conductivity probes to monitor tracer continuously. The majority of added tracer reached the outlet more slowly than could be explained by surface flow, but more quickly than could be explained by Darcy seepage flow. There was evidence from the wells of tracer diffusing vertically to a depth of at least 5 cm into the surface soil layer, which was permanently saturated and highly porous. During dry weather 24 +/- 9% of added NO3-N was removed over a distance of 1.5 m largely by denitrification. The net uptake length coefficient for this wetland (K = 0.08 +/- 0.03 m(-1)) is slightly higher than the range (K = 0.01-0.07 m(-1)) measured in a small stream channel infested with macrophytes. Nitrate removal is expected to decrease with increasing flow. Seepage flow is estimated to have removed only 7 +/- 4% of the added NO3-N and we hypothesize that vertical diffusion substantially increases NO3-N removal in this type of wetland. Riparian wetlands with springs and surface flows should not be dismissed as having low NO3-N removal potential without checking whether there is significant vertical mixing.

Forecasting rehabilitation outcomes for degraded New Zealand pastoral streams.

To understand the timescales and magnitude of responses that can be expected following catchment and riparian rehabilitation, we forecast changes to selected stream ecosystem attributes following tree planting in a pastoral catchment. All planting scenarios were predicted to lead to decreases in daily maximum water temperature after 15-20 years to levels that would be suitable for sensitive invertebrate species. Cooling and reheating were rapid so that most benefits to water temperature along the mainstem were forecast to accrue from shading all of the stream channel network. All planting scenarios were predicted to increase sediment yields over the status quo over the 25-year timeframe examined, with maximal sediment yield occurring about 15 years after planting due to expected erosion of the streambanks under the developing forest shade. Sediment yield was greatest for full catchment planting over 25 years, although sediment yield would be lowest with this scenario over longer timescales. A macroinvertebrate biotic index was predicted to increase by 25% over 15 years if whole catchment afforestation were implemented, compared to 9% if only the 4th order mainstem were planted with riparian trees. The use of ecological forecasting to predict likely outcomes for a range of scenarios should prove useful for prioritising rehabilitation actions.

Quantifying temporal and spatial variations in sediment, nitrogen and phosphorus transport in stream inflows to a large eutrophic lake.

High-frequency sampling of two major stream inflows to a large eutrophic lake (Lake Rotorua, New Zealand) was conducted to measure inputs of total suspended sediment (TSS), and fractions of nitrogen and phosphorus (P). A total of 17 rain events were sampled, including three during which both streams were simultaneously monitored to quantify how concentration-discharge (Q) relationships varied between catchments during similar hydrological conditions. Dissolved inorganic nitrogen (DIN) concentrations declined slightly during events, reflecting dilution of groundwater inputs by rainfall, whereas dissolved inorganic P (PO4-P) concentrations were variable and unrelated to Q, suggesting dynamic sorptive behaviour. Event loads of total nitrogen (TN) were predominantly DIN, which is available for immediate uptake by primary producers, whereas total phosphorus (TP) loads predominantly comprised particulate P (less labile). Positive correlations between Q and concentrations of TP (and to a lesser extent TN) reflected increased particulate nutrient concentrations at high flows. Consequently, load estimates based on hourly Q during storm events and concentrations of routine monthly samples (mostly base flow) under-estimated TN and TP loads by an average of 19% and 40% respectively. Hysteresis with Q was commonly observed and inclusion of hydrological variables that reflect Q history in regression models improved predictions of TN and TP concentrations. Lorenz curves describing the proportions of cumulative load versus cumulative time quantified temporal inequality in loading. In the two study streams, 50% of estimated two-year loads of TN, TP and TSS were transported in 202-207, 76-126 and 1-8 days respectively. This study quantifies how hydrological and landscape factors can interact to influence pollutant flux at the catchment scale and highlights the importance of including storm transfers in lake loading estimates.

Abnormal "activated" rosette formation in patients with gastrointestinal cancer.

The mean percentage of peripheral blood lymphocytes forming fast spontaneous rosettes with sheep red blood cells was estimated in 40 patients presenting with gastrointestinal symptoms suggestive of cancer. Patients who were eventually diagnosed as having cancer had significantly lower numbers (P less than 0.01 Mann Whitney Test) of rosette forming cells than patients who had gastrointestinal tumours successfully removed, or patients with other gastrointestinal diseases. The use of this test as an aid to the diagnosis of gastrointestinal malignancy and its possible application to the detection of recurrences of cancer after surgery are discussed.

Primary aldosteronism: are we diagnosing and operating on too few patients?

Many cases of potentially curable primary aldosteronism are currently likely to be diagnosed as essential hypertension unless screening tests based on suppression of renin are carried out in all hypertensive patients. More than half of the patients with primary aldosteronism detected in this way have normal circulating potassium levels, so measurement of potassium is not enough to exclude primary aldosteronism. When primary aldosteronism is diagnosed, fewer than one-third of patients are suitable for surgery as initial treatment, but this still represents a significant percentage of hypertensive patients. After excluding glucocorticoid-suppressible primary aldosteronism, adrenal venous sampling is essential to detect unilateral production of aldosterone and diagnose angiotensin-responsive aldosterone-producing adenoma. One cannot rely on the computed tomography scan. If all hypertensive patients are screened for primary aldosteronism and the workup is continued methodically in those with a positive screening test, patients with unilateral overproduction of aldosterone who potentially can be cured surgically are not denied the possibility of cure.

Cobalt-dependent transcriptional switching by a dual-effector MerR-like protein regulates a cobalt-exporting variant CPx-type ATPase.

CoaR associates with and confers cobalt-dependent activation of the coaT operator-promoter. A CoaR mutant (Ser-Asn-Ser) in a carboxyl-terminal Cys-His-Cys motif bound the coaT operator-promoter but did not activate expression in response to cobalt, implicating thiolate and/or imidazole ligands at these residues in an allosteric cobalt binding site. Deletion of 1 or 2 nucleotides from between near consensus, but with aberrant (20 base pairs) spacing, -10 and -35 elements enhanced expression from the coaT operator-promoter but abolished activation by cobalt-CoaR. It is inferred that cobalt effects a transition in CoaR that underwinds the coaT operator-promoter to realign promoter elements. In the absence of cobalt, CoaR represses expression (approximately 50%). CoaR is a fusion of ancestral MerR (mercury-responsive transcriptional activator)- and precorrin isomerase (enzyme of vitamin B(12) biosynthesis)-related sequences. Expression from the coaT operator-promoter was enhanced in a partial mutant of cbiE (encoding an enzyme preceding precorrin isomerase in B(12) biosynthesis), revealing that this pathway "inhibits" coaT expression. Disruption of coaT reduced cobalt tolerance and increased cytoplasmic (57)Co accumulation. coaT-mediated restoration of cobalt tolerance has been used as a selectable marker.

High incidence of primary aldosteronism in 199 patients referred with hypertension.

1. This study sought to assess the incidence of primary aldosteronism in 199 hypertensives who were normokalaemic and in whom the question of primary aldosteronism had never been raised. 2. The screening test applied was the aldosterone to renin ratio in plasma, which was raised in 40 and normal in 159 patients. A second ratio was normal in 14 of these 40. 3. Twenty-two patients with two further raised ratios required fludrocortisone suppression testing. This has been completed in 17, and failure to suppress led to a diagnosis of primary aldosteronism in all. 4. A dexamethasone suppression test (DST) excluded ACTH-dependent hyperaldosteronism and laterality of aldosterone production was determined by adrenal vein sampling. 5. Unilaterality in five patients led to adrenalectomy in four and spironolactone in one. Bilaterality in six patients led to spironolactone. 6. This study so far provides a proven (minimum) incidence for primary aldosteronism of 8.5%, a probable incidence of 12.0% (including two raised ratios) and a possible (maximum) incidence of 13.0% (leaving out those with second ratio normal). Exclusion of hypokalaemic hypertensives will lead to an underestimation of the true incidence of primary aldosteronism. 7. Based on this and other evidence, it is estimated that the incidence of primary aldosteronism in the 'essential hypertensive' population is between 5 and 15%, and is probably around 10%.

A second iron-regulatory system in yeast independent of Aft1p.

Iron homeostasis in the yeast Saccharomyces cerevisiae is regulated at the transcriptional level by Aft1p, which activates the expression of its target genes in response to low-iron conditions. The yeast genome contains a paralog of AFT1, which has been designated AFT2. To establish whether AFT1 and AFT2 have overlapping functions, a mutant containing a double aft1Deltaaft2Delta deletion was generated. Growth assays established that the single aft2Delta strain exhibited no iron-dependent phenotype. However, the double-mutant aft1Deltaaft2Delta strain was more sensitive to low-iron growth conditions than the single-mutant aft1Delta strain. A mutant allele of AFT2 (AFT2-1(up)), or overexpression of the wild-type AFT2 gene, led to partial complementation of the respiratory-deficient phenotype of the aft1Delta strain. The AFT2-1(up) allele also increased the uptake of (59)Fe in an aft1Delta strain. DNA microarrays were used to identify genes regulated by AFT2. Some of the AFT2-regulated genes are known to be regulated by Aft1p; however, AFT2-1(up)-dependent activation was independent of Aft1p. The kinetics of induction of two genes activated by the AFT2-1(up) allele are consistent with Aft2p acting as a direct transcriptional factor. Truncated forms of Aft1p and Aft2p bound to a DNA duplex containing the Aft1p binding site in vitro. The wild-type allele of AFT2 activated transcription in response to growth under low-iron conditions. Together, these data suggest that yeast has a second regulatory pathway for the iron regulon, with AFT1 and AFT2 playing partially redundant roles.

Laparoscopic adrenalectomy for adrenal tumours causing hypertension and for 'incidentalomas' of the adrenal on computerized tomography scanning.

1. In a 19 month period from June 1993 to December 1994, 60 patients (mean age 54.8 +/- 1.5 years s.e.m.; 32 males, 28 females) underwent unilateral laparoscopic adrenalectomy by one of us (JCR) for the treatment of hypertension due to primary aldosteronism (n = 48), phaeochromocytoma (n = 3) and cortisol-producing adenoma (n = 1) or to remove adrenal massess incidentally discovered on abdominal computerized tomography scanning ('incidentaloma') performed for other reasons (seven adenomas without biochemical evidence of excessive steroid hormone or catecholamine secretion and one carcinoma autonomously producing cortisol). 2. Compared with conventional open procedures, laparoscopic adrenalectomy was associated with reduced recovery time and a low complication rate (one pulmonary embolus and one port site incisional hernia). 3. Operation time with experience approximates that of open procedures (60 min), but is significantly longer in obese than in non-obese patients, and in males than in females. 4. Patients with adrenal causes of hypertension were cured or significantly improved by laparoscopic unilateral adrenalectomy. 5. Because of our concern regarding malignant potential of incidentalomas and high patient acceptance of laparoscopic techniques, we have reduced our size criteria for removal of incidentalomas.

Laparoscopic adrenalectomy.

Using the transperitoneal, laparoscopic approach, we performed 67 successful adrenalectomies between June 1993 and July 1995 at Greenslopes Hospital, Brisbane. There were 30 women and 37 men. Syndromes of primary adrenal hormone overproduction--primary aldosteronism (n = 52), pheochromocytoma (n = 6), and hypercortisolism (n = 1)--were present in 59 patients and apparently nonfunctioning adrenal tumors (of which one was malignant) in 8 patients. There was a significant difference in the time of operation between patients weighing < 80 kg and those weighing > 80 kg. Operations on males were slower than those on females, possibly explained by males being significantly heavier. Left-sided tumors outnumbered right-sided tumors; removal of right-sided adrenals took, on average, longer, but this difference was not significant.

A modified leukocyte adherence inhibition test in the laboratory investigation of gastrointestinal cancer.

A modification of the leukocyte adherence inhibition (LAI) technique has been used to test 60 hospital patients with gastrointestinal symptoms, for specific immunoreactivity against extracts of tumours of colon, pancreas and stomach. The modified technique employed mononuclear cells and soluble tumour extracts in glass test tubes, the non-adherent cells being enumerated in an electronic counter. Laboratory tests were completed before the eventual diagnosis was known. Groups of patients with adenocarcinoma of colon or rectum (11), carcinoma of pancreas (3) and adenocarcinoma of stomach (6) were clearly distinguished from each other and from patients with non-malignant diseases or with neoplasms of different histological type.

Success of surgery for primary aldosteronism judged by residual autonomous aldosterone production.

Since February 1996 we have prospectively assessed residual adrenal autonomy by the fludrocortisone suppression test (FST) in 23 patients 3 months after unilateral adrenalectomy for Conn syndrome and in 45 patients after a longer interval. In regard to blood pressure, 36 (53%) patients were cured of hypertension and the remaining 32 (47%) patients had improved hypertension control at the time of their latest postoperative clinical assessment. In regard to the outcome of surgery, patients who achieved normal suppressibility of aldosterone were regarded as cured, and those who had greater suppressibility after surgery were considered improved. Time since surgery for the whole group averaged 26 months. By these biochemical criteria, 42 patients (62%) were cured by surgery, and the rest improved; 16 (76%) of 21 women were cured, and 26 (55%) of 47 men. The women (mean +/- SD age 47 +/- 11 years) were significantly (p < 0.05) younger than the men (52 +/- 9 years). Preoperative aldosterone levels before and after FST were similar in the cured and improved groups and fell significantly (p < 0.01) in both groups following surgery. After surgical reduction of autonomous aldosterone production, mean plasma renin activity levels increased sixfold in the cured group and threefold in the improved group. Surgical mortality in this group of 68 patients with Conn syndrome was zero.

Response to unilateral adrenalectomy for aldosterone-producing adenoma: effect of potassium levels and angiotensin responsiveness.

1. Normokalaemic primary aldosteronism (PA) masquerades as 'essential hypertension', and 50% of patients with aldosterone-producing adenoma (APA) are normokalaemic at presentation to this unit. 2. Angiotensin-responsive (AII-R) APA is as common as angiotensin-unresponsive (AII-U) APA, and requires adrenal venous sampling for differentiation from bilateral adrenal hyperplasia (BAH). 3. From 1981 to 1992, 55 patients with APA underwent unilateral adrenalectomy and were followed up for at least 12 months postoperatively. Hypertension was cured in 55% and improved in the remainder. 4. Cure rate was lower (P < 0.001) in males (11/32, 34%) vs females (19/23, 83%), lower (P < 0.005) in patients over 45 years of age (13/33, 39%) vs those 45 years or younger (17/22, 77%), lower (P < 0.05) in AII-R APA (11/28, 39%) vs AII-U APA (19/27, 70%) and tended to be lower (not significant) in normokalaemic APA (7/17, 41%) vs hypokalaemic APA (23/38, 61%). 5. A higher proportion (P <0.001) of AII-R APA patients were males (23/28, 82%) vs AII-U APA (9/27, 33%), and a higher proportion were from the older age group AII-U APA 13/27, 48%; P < 0.05). Females with AII-U APA who were hypokalaemic had a very high cure rate (16/17, 94%). 6. Since unilateral adrenalectomy cures or improves blood pressure in normokalaemic and AII-R as well as in hypokalaemic and AII-U patients, all hypertensives should be screened for PA, and AII-R APA differentiated from BAH in proven PA.

An association of primary aldosteronism and adrenaline-secreting phaeochromocytoma.

1. Two patients with adrenaline-only secreting phaeochromocytomas and primary aldosteronism were studied. 2. Urinary adrenaline levels were raised and plasma adrenaline was not suppressed normally following administration of clonidine. Plasma aldosterone to plasma renin activity ratios were repeatedly elevated. 3. Both had large intra-adrenal phaeochromocytomas visible on computerized tomography (CT) scanning. Surrounding adrenal cortical tissue contained an adenoma in one and nodular hyperplasia in the other. 4. Following removal of the adrenal gland containing the phaeochromocytoma, plasma and urinary adrenaline levels, and plasma aldosterone to plasma renin activity ratios returned to normal. 5. Adrenaline-only secreting phaeochromocytomas and primary aldosteronism have been rarely diagnosed even as separate entities, but reliable screening tests are now available. 6. Simultaneous presence of these two conditions of hormone excess is probably a chance occurrence. Alternatively, there may be a genetic predisposition to endocrine dysplasia, or an interaction between the contiguous medullary and cortical tissues, particularly after the normal architecture has been disturbed by an enlarging phaeochromocytoma.