Impacts of gold mine waste disposal on a tropical pelagic ecosystem.

We used a comparative approach to investigate the impact of the disposal of gold mine tailings into the ocean near the Lihir mine (Niolam Island, Papua New Guinea). We found abundance and diversity of zooplankton, micronekton and pelagic fish to be similar or higher in the mine region compared to the reference site. We also found relatively high trace metal concentrations in lower trophic level groups, especially zooplankton, near the mine discharge, but few differences in tissue concentrations of micronekton, baitfish and pelagic fish between the two regions. Biomagnification of some trace metals by micronekton, and of mercury by fish was evident in both regions. We conclude that ocean mine waste disposal at Niolam Island has a local impact on the smaller and less mobile pelagic communities in terms of trace metal concentrations, but has little effect on the abundance and biodiversity of the local food web.

Impacts of gold mine waste disposal on deepwater fish in a pristine tropical marine system.

Little is known about the impacts of mine waste disposal, including deep-sea tailings, on tropical marine environments and this study presents the first account of this impact on deepwater fish communities. The Lihir gold mine in Papua New Guinea has deposited both excavated overburden and processed tailings slurry into the coastal environment since 1997. The abundances of fish species and trace metal concentrations in their tissues were compared between sites adjacent to and away from the mine. In this study (1999-2002), 975 fish of 98 species were caught. Significantly fewer fish were caught close to the mine than in neighbouring regions; the highest numbers were in regions distant from the mine. The catch rates of nine of the 17 most abundant species were lowest, and in three species were highest, close to the mine. There appears to be limited contamination in fish tissues caused by trace metals disposed as mine waste. Although arsenic (several species) and mercury (one species) were found in concentrations above Australian food standards. However, as in the baseline (pre-mine) sampling, it appears they are accumulating these metals mostly from naturally-occurring sources rather than the mine waste.

Minimal residual disease in childhood acute lymphoblastic leukaemia quantified by aspirate and trephine: is the disease multifocal?

The level of minimal residual disease (MRD) in marrow early in treatment strongly predicts outcome in childhood acute lymphoblastic leukaemia (ALL). Using PCR we studied 30 pairs of aspirates and trephines taken during induction treatment. Consensus PCR primers showed a monoclonal gene rearrangement in eight pairs, polyclonal rearrangement in 18 pairs and a monoclonal rearrangement only in the trephine in four pairs. MRD was quantified by leukaemia-specific primers in 22 pairs. There was a linear relationship between the logarithms of MRD levels of aspirate and trephine, with a residual variance which increased as the level of MRD fell. The mean level of MRD in the trephines was 4.1-fold greater than that in the aspirates, probably due to greater dilution of the aspirates with peripheral blood. The high variance at low levels of MRD could not be explained by measurement variation, which had an MRD-independent value of 0.42 log10 units, and was attributed to sampling variation due to patchiness of disease at low MRD levels. The magnitude of the variation was such that predictions of outcome could well be confounded for many patients. We suggest that MRD sampling variability could be minimized either by taking multiple marrow samples or by measuring MRD in peripheral blood.

Differential passage time of mistletoe fruits through the gut of honeyeaters and flowerpeckers: effects on seedling establishment.

McKey's (1975) hypothesis that avian dispersers with a specialized gut provide higher quality seed dispersal than unspecialized frugivores was tested using grey mistletoe (Amyema quandang) fruits, and captive mistletoebirds (Dicaeum hirundinaceum) and spinycheeked honeyeaters (Acanthagenys refogularis) in arid South Australia. Mistletoebirds have a specialized gut, unlike spiny-cheeked honeyeaters. The gut passage time of A. quandang fruits through mistletoebirds was 820±29 s (mean±SE, n=188), compared to 2434±36 s (n=436) for honeyeaters. The seeds defecated by both bird species were deployed on twigs of host trees. Despite the longer retention time of fruit in the gut of honeyeaters, the germination percentage of seeds defecated by mistletoebirds (85% of 485 seeds) and honeyeaters (81% of 485 seeds) did not differ significantly 1 week after deployment. However, after 5 months, a significantly greater proportion of seedlings had established from seeds passed by mistletoebirds (42.7%) than from seeds defecated by honeyeaters (31.1%). The data support the notion that the more gentle treatment of seeds in the gut of specialized dispersers translates into higher seedling establishment.

Factors influencing the probability of residual cholesteatoma.

Data from the records of 251 consecutive patients with aural cholesteatoma treated surgically by one surgeon (R.E.G.) between 1962 and 1980, using mainly wide access approaches of atticotomy and attico-antrostomy, and assiduously followed up, formed the basis of an analysis to determine what variables influence the chance of residual cholesteatoma. There were 42 cases of residual cholesteatoma; 20 in the mesotympanum (including two annular), 17 in the epitympanum, and five in the mastoid. The most important variables for the prognosis of residual disease included age, the state of the stapes, the state of the middle ear mucosa, and the number of sites in the middle ear cleft affected by cholesteatoma. A logistic model was constructed to describe the dependence of the probability of residual cholesteatoma on the two determining variables age and state of the stapes. The implications of these findings for the surgical management of cholesteatoma are discussed.

Otosclerosis in South Australia.

In this paper we report on the prevalence of clinical otosclerosis in South Australia, and discuss some aspects of its distribution and character. Our data comes from an exhaustive search for stapedectomy patients in a relatively closed population within a fixed time span, and hence our figures represent a lower limit for the true prevalence and not an unbiased estimate. Nevertheless, even with no allowance for this downward bias it would seem that South Australia has a high prevalence of otosclerosis by world standards, particularly of obliterative cases. The highest prevalence is about 5 per 1 000 of population for men and 10 per 1 000 of population for women, which occurs in the 50-59 year old age group. In common with many other studies, our data shows a prevalence for females approximately twice that for males, over most age groups.

Pregnancy and otosclerosis.

A retrospective study has been made of a sample of 479 women with deafness from otosclerosis, classified according to the number of pregnancies they have had and whether there had been a subjective impression of deterioration of hearing during or immediately after at least 1 pregnancy. The study confirms previous reports that pregnancy does involve a risk of aggravating deafness in clinical otosclerosis. The chance of female patients with bilateral otosclerosis reporting a subjective deterioration of hearing in pregnancy can be accurately described by a simple mathematical model and varies from about 33% after 1 pregnancy to about 63% after 6 pregnancies. In women with unilateral otosclerosis pregnancy-related deterioration of hearing is much less commonly perceived. There is no strong evidence that pregnancies cause any alteration to the actual footplate pathology of female patients.

A note on progression of the otosclerotic focus.

One thousand and thirteen consecutive patients in South Australia with stapedial fixation from otosclerosis were classified by duration of deafness, age at onset and degree of footplate pathology to determine whether there is an orderly progression in severity of the oval window lesion with duration of symptoms. The conclusions drawn were as follows. (1) An early age of onset of clinical otosclerosis, during the period of skeletal growth, dramatically increases the chance of contracting a fulminating lesion with severe and diffuse involvement of the stapedial footplate or obliteration of the oval window niche. (2) A late age of onset of clinical otosclerosis tends to be associated with lesions of the stapes footplate that are limited to the anterior pole, and there is good evidence that the lesion tends to remain stable or to progress only very slowly. (3) The case for a regular and orderly pathological progression of the otosclerotic lesion through various patterns of severity from minor to major degrees of footplate pathology is not established by the data; nor is it convincingly refuted. It is clear that if a pathological progression of the lesion does take place it must be at vastly different rates for different individuals.

Growth rate and recurrence of residual epidermoid cholesteatoma after tympanoplasty.

One hundred and forty-one consecutive patients with chronic otitis media and cholesteatoma treated mainly by open surgical techniques between 1965 and 1972 were studied to investigate the phenomenon of residual cholesteatoma. The average rate of emergence of residual cholesteatoma was 0.25% of the cases per month during the first 5 years, after which the rate of discovery almost ceased. Observed cumulative frequencies of recurrence were 1.4% at 10 months, 14.9% at 5 years and 17.0% at 8.3 years postoperatively. The null hypothesis of no apparent predilection of cholesteatoma for recurrence at any one site was retained. Parameters of growth rates of epidermoid cysts arising from residual cholesteatoma were estimated. Epitympanic cysts grew fairly rapidly, doubling in diameter every 10 months. Mastoid cysts were slower, doubling in diameter every 25 months. Results for the mesotympanum were inconclusive. The practical implications of this information for the management of future cases is discussed.

Otosclerotic obliteration of oval window niche: an analysis of the results of surgery.

1. The massive otosclerotic focus, obliterating the oval window niche, has a relatively high case incidence of 11-2 per cent in South Australia. The three classes of obliterated footplate are defined. 2. Basic data of 109 consecutive surgical cases of obliterative otosclerosis are given. A brief description of operative techniques--vein graft and polyethylene tube in nine, and piston technique in 100--is given and the difficulties and complications arising at or after surgery are discussed. 3. Post-operative follow-up of patients with yearly audiometric assessment has been achieved in 105/109 (= 96-33%) at four years, and in 94/109 (= 86-26%) at five years. 4. The results of surgery are presented by many and varied methods including bar diagrams, post-operative hearing gains, post-operative bone-air gaps, speech discrimination studies and standard statistical analysis techniques. 5. The vein graft technique (nine cases) is very much inferior to the piston technique. Vein graft cases had a 33% incidence of profound sensori-neural loss due to bony reclosure of the window. 6. The piston technique (100 cases) gave hearing gains of 20 decibels or more in 91%, 30 decibels or more in 71%, and 40 decibels or more in 41% of cases at five years post-operatively. The bone-air gap at five years post-operatively was diminished to 20 decibels or less in 88%, to 15 decibels or less in 85%, to 10 decibels or less in 77%, and complete closure or over-closure occurred in 52% of the patients. 7. Data analysis has established there is no change with time of the post-operative mean bone-air gap 500--2,000 Hz. over a period of at least five years, and thus that the piston operation gives a persisting and stable hearing result. 8. In predicting the effect of the piston operation only a rough guide can be obtained from other variables. In particular bone hardness, mucosal characteristics, sex and piston diameter appear to be irrelevant. Patients with a large bone conduction reading or a large air-bone gap appear to do slightly worse than patients with smaller values for these variables. There are no grounds for excluding a patient from operation on account of age, or the finding of active otosclerosis (soft bone and thickened vascular muco-periosteum). 9. From the data of piston operations, the estimated mean bone-air gap for the five-year examination period was 4-14 db. with a standard deviation of 12-5 db. 10. The piston operation is highly recommended as a safe and suitable method of alleviating, in the long-term, the conductive hearing loss of patients with obliterative otosclerosis of the oval window.