Scope and limitation in algal modelling – an example from the Thames Valley reservoirs

Major aspects of algal modelling are defined.Prediction and explanation are suggested as mainobjectives. Examples of the development and use ofshort-term prediction and more general explanatoryalgal models for reservoirs are given. It is concludedthat good prediction and explanation are not likely tobe simultaneously achievable. Possible means ofassessing the capabilities of ecosystem models andmodelling are considered. Some suggestions as to howthe present situation may be coped with, and improved,are proposed.     

PEDIATRIC ENDOCRINOLOGY—Notes on Some Recent Advances

Until recently, congenital adrenocortical hyperplasia has defied most medical and surgical therapeutic efforts. However, in properly selected patients, cortisone will suppress the abnormal cortical hormone production. This, in turn, will lead to previously inhibited maturation and developmental progress.Adrenocortical insufficiency calls for much diagnostic alertness, as early recognition and immediate treatment are of paramount importance. The available therapeutic means are beneficial, although their limitations and potential dangers should be heeded.Among newly developed diagnostic techniques, thyrograms promise to be helpful in the study of thyroid hyperplasia and neoplasia. Thyroid cancer, occurring infrequently in childhood, should at the earliest possible time be treated surgically and with postoperative radiation therapy.     

Notes on the Potentilleæ

Background: Various rare and endangered temperate ferns are being threatened by their recent population decline, but there is limited understanding of the causes behind it.

Aims: This study attempted to identify the possible drivers of regional population decline and extinction in the globally distributed woodland fern Polystichum braunii.

Methods: A comparison was undertaken of the climatic, edaphic and phytosociological characteristics of sites with increasing, decreasing or recently extinct populations in Germany.

Results: A significantly higher frequency of episodes of low relative air humidity (<60%) was found at sites with decreasing or extinct populations compared to habitats with population increases. Sites with decreasing or extinct populations were also characterised as having less summer precipitation (<500 mm year^?1) and a shorter duration of snow cover (<110 days year^?1) than sites with increasing populations. The latter had significantly higher moss cover (56% of the forest floor), but less cover by a tree litter layer (23%) compared to decreasing (36% and 38%) or recently extinct populations (22% and 52%). All increasing populations were located in intact Tilia – Acer ravine forests, while those suffering population decline were mostly located in Fagus-dominated forests.

Conclusions: It was concluded that the probable causes of the recent decline in German P. braunii populations are reduced air humidity levels, decreasing snow duration or a shift from moss-covered to tree litter-covered forest floors due to climate warming or altered forest management.     

Cancer Mortality Trends in Canada—1944-1963

A 20-year statistical review was undertaken to ascertain significant changes in cancer mortality in Canada by site and sex. Cancer in nine major sites and leukemia were studied. Trend lines were fitted to the death rates and the probability was computed that the slopes of these lines had changed significantly. Of the 17 analyses made, significant decreases in mortality were found in six and significant increases in six. In the remaining five analyses no significant change in mortality was found.     

Evaluation of the “Steal” Phenomenon on the Efficacy of Hypoxia Activated Prodrug TH-302 in Pancreatic Cancer

Pancreatic ductal adenocarcinomas are desmoplastic and hypoxic, both of which are associated with poor prognosis. Hypoxia-activated prodrugs (HAPs) are specifically activated in hypoxic environments to release cytotoxic or cytostatic effectors. TH-302 is a HAP that is currently being evaluated in a Phase III clinical trial in pancreatic cancer. Using animal models, we show that tumor hypoxia can be exacerbated using a vasodilator, hydralazine, improving TH-302 efficacy. Hydralazine reduces tumor blood flow through the “steal” phenomenon, in which atonal immature tumor vasculature fails to dilate in coordination with normal vasculature. We show that MIA PaCa-2 tumors exhibit a “steal” effect in response to hydralazine, resulting in decreased tumor blood flow and subsequent tumor pH reduction. The effect is not observed in SU.86.86 tumors with mature tumor vasculature, as measured by CD31 and smooth muscle actin (SMA) immunohistochemistry staining. Combination therapy of hydralazine and TH-302 resulted in a reduction in MIA PaCa-2 tumor volume growth after 18 days of treatment. These studies support a combination mechanism of action for TH-302 with a vasodilator that transiently increases tumor hypoxia.     

Notes on New Zealand mammals 4. Animal road‐kill “blackspots”

Abstract

Repeated counts of road‐killed animals have revealed sites where possums (Trichosurus vulpecula), rabbits (Oryctolagus cuniculus), hedgehogs (Erinaceus europaeus), gulls (Larus dominicanus, L. novaehollandiae) and shags (Phalacrocorax carbo) were killed in unusual numbers. These “blackspots” were not correlated with the volume of traffic, but were mapped at or near places where animals are presumed to crowd together or were most likely to venture onto the road. For example, in Hawkes Bay, 81% of possum corpses were counted on or within 200 m of road bridges, and a disproportionate number of hedgehogs were also killed on bridges or approaches to bridges. At least in this area, human and animal traffic blackspots did not coincide. I suggest that this information could be useful to agencies controlling the spread of tubercular possums, and the technique of systematic counting of road‐kills could be extended to National Parks and other areas of natural interest.