NORDLING (1953) examined the age specific mortality for cancer of all sites from the published statistics of the United States, the United Kingdom, France and Norway and noted that the tumour death rate rose with the sixth power of the age. He suggested the carcinogenesis might depend on a series of mutations in the affected cells and that the clinical manifestation was dependent on the cumulative effect of this series of mutations. Stocks (1963) examined the mortality rates for gastric cancer in males for a series of cohorts and reached the conclusion that the pattern observed could be explained on the basis that there was a series of 5 mutations and a preclinical development period of about 17 years.Armitage and Doll (1954) made a detailed analysis of the death rates for a number of tumours and showed how the hypothesis of a small number of random discrete changes in cell structure and function could account for the observable steady rise in cancer mortality with age. Three years later (Armitage and Doll, 1957) they published an alternative analysis which suggested that the observed death rates could be explained on the basis of a " two hit " theory; that only two changes in cell function, the first involving enhancement ofthe rate of multiplication of cells and the second release from control, were necessary.The relevant mathematical expressions which Armitage and Doll derived were: where I incidence N number of cells at risk p probability of change in any cell in any year r number of changes k= a constant This paper is an attempt, partly statistical and partly pathological, to decide between these two analyses.The difference between the two possible expressions was studied in the case of deaths from gastric cancer in females. The mean annual age specific incidence of death from gastric cancer in women in England and Wales was calculated from the 36,236 deaths reported from this cause in the six years 1958 to 1963 inclusive by the Registrar General
The production and release of dissolved organic carbon (DOC) from peat soils is thought to be sensitive to changes in climate, specifically changes in temperature and rainfall. However, little is known about the actual rates of net DOC production in response to temperature and water table draw-down, particularly in comparison to carbon dioxide (CO 2 ) fluxes. To explore these relationships, we carried out a laboratory experiment on intact peat soil cores under controlled temperature and water table conditions to determine the impact and interaction of each of these climatic factors on net DOC production. We found a significant interaction (Po0.001) between temperature, water table draw-down and net DOC production across the whole soil core (0 to À55 cm depth). This corresponded to an increase in the Q 10 (i.e. rise in the rate of net DOC production over a 10 1C range) from 1.84 under high water tables and anaerobic conditions to 3.53 under water table draw-down and aerobic conditions between À10 and À40 cm depth. However, increases in net DOC production were only seen after water tables recovered to the surface as secondary changes in soil water chemistry driven by sulphur redox reactions decreased DOC solubility, and therefore DOC concentrations, during periods of water table draw-down. Furthermore, net microbial consumption of DOC was also apparent at À1 cm depth and was an additional cause of declining DOC concentrations during dry periods. Therefore, although increased temperature and decreased rainfall could have a significant effect on net DOC release from peatlands, these climatic effects could be masked by other factors controlling the biological consumption of DOC in addition to soil water chemistry and DOC solubility. These findings highlight both the sensitivity of DOC release from ombrotrophic peat to episodic changes in water table draw-down, and the need to disentangle complex and interacting controls on DOC dynamics to fully understand the impact of environmental change on this system.
Tropical forests are experiencing unprecedented high‐temperature conditions due to climate change that could limit their photosynthetic functions. We studied the high‐temperature sensitivity of photosynthesis in a rainforest site in southern Amazonia, where some of the highest temperatures and most rapid warming in the Tropics have been recorded. The quantum yield (Fv/Fm) of photosystem II was measured in seven dominant tree species using leaf discs exposed to varying levels of heat stress. T50 was calculated as the temperature at which Fv/Fm was half the maximum value. T5 is defined as the breakpoint temperature, at which Fv/Fm decline was initiated. Leaf thermotolerance in the rapidly warming southern Amazonia was the highest recorded for forest tree species globally. T50 and T5 varied between species, with one mid‐storey species, Amaioua guianensis, exhibiting particularly high T50 and T5 values. While the T50 values of the species sampled were several degrees above the maximum air temperatures experienced in southern Amazonia, the T5 values of several species are now exceeded under present‐day maximum air temperatures.
DURING the 11 years 1955 to 1965 just under 6,000,000 people died in England and Wales, 1,084,751 of them, 18-4 per cent, of malignant disease (Registrar General, 1967). The total number of deaths from tumour in men was 579,527, 19 1 per cent of the total male deaths; while in women the total of tumour deaths was 505,224, 17-6 per cent of the total deaths. This close approximation however gives a false impression as tumour deaths occur predominantly among the older members of the population and there are many more older women than men.A better idea of the relative frequency of neoplasms in men and women may be obtained from a study of the different rates of tumour mortality throughout life. In the six year period 1958 to 1963 the deaths of 234,508 women were attributed to malignant disease, had the age-specific death rates for malignant tumours experienced by men applied to women 379,175 deaths would have been expected.It must be remembered, moreover, that the sex organs differ in the two sexes both in anatomical form and physiological function and also in their liabilityto neoplasia. Tumours of the ovary are far commoner than those of the testis, uterine cancer is commoner, especially in younger women than is prostatic cancer which tends to occur most often in much older men. The breast is a large active organ in the female but a rudimentary vestige in the male. Lung cancer on the other hand is very much commoner in males than in females and this difference can reasonably be attributed in large part to the greater frequency of cigarette smoking in men than in women (Kreyberg, 1962). For these reasons I thought it useful to calculate the relative frequencies of tumours in the two sexes after excluding neoplasms of the lung, the breast and the genital organs. In the same six year period, 1958 to 1963, the number of deaths in this category in women totalled 160,120 while, had the rates seen in men applied to women, the total would have been expected to be 285,352, a female to male ratio of 0-56. A similar calculation was made on the data on the incidence of cancer in four regions of England and Wales for the three vears 1962-64 given in " Cancer Incidence in Five Continents " (Doll, Payne and Waterhouse, 1966). The total cases in women were 42,933; had the male rates applied the total would have been 70,378, a female to male ratio of 0-61.An equivalent calculation is that which compares the age-adjusted incidence and mortality rates. Dorn and Cutler (1955) gave such rates for the white and non-white elements of the population in 10 Metropolitan areas of the United States. The resident cancer incidence rate per 100,000 was 338-3 for white males and 333-4 for white females, a female to male ratio of 0 99. It was 252-6 for nonwhite males and 293-0 for non-white females, female to male ratio 1-16. After deduction of the rates for cancer of the lung, breast and genital system the rates
Gold mining has rapidly increased across the Amazon Basin in recent years, especially in the Guiana shield, where it is responsible for >90% of total deforestation. However, the ability of forests to recover from gold mining activities remains largely unquantified. Forest inventory plots were installed on recently abandoned mines in two major mining regions in Guyana, and re‐censused 18 months later, to provide the first ground‐based quantification of gold mining impacts on Amazon forest biomass recovery. We found that woody biomass recovery rates on abandoned mining pits and tailing ponds are among the lowest ever recorded for tropical forests, with close to no woody biomass recovery after 3–4 years. On the overburden sites (i.e. areas not mined but where excavated soil is deposited), however, above‐ground biomass recovery rates (0.4–5.4 Mg ha−1 year−1) were within the range of those recorded in other secondary forests across the Neotropics following abandonment of pastures and agricultural lands. Our results suggest that forest recovery is more strongly limited by severe mining‐induced depletion of soil nutrients, especially nitrogen, than by mercury contamination, due to slowing of growth in nutrient‐stripped soils. We estimate that the slow recovery rates in mining pits and ponds currently reduce carbon sequestration across Amazonian secondary forests by ~21,000 t C/year, compared to the carbon that would have accumulated following more traditional land uses such as agriculture or pasture. Synthesis and applications. To achieve large‐scale restoration targets, Guyana and other Amazonian countries will be challenged to remediate previously mined lands. The recovery process is highly dependent on nitrogen availability rather than mercury contamination, affecting woody biomass regrowth. The significant recovery in overburden zones indicates that one potential active remediation strategy to promote biomass recovery may be to backfill mining pits and ponds with excavated soil.
EDITORIAL COMMENT During a study of the epidemiology of appendicitis it was found that acute appendicitis is equally common in men and in women. Appendicectomy for non-acute appendicitis is commoner in women, and it is suggested that these patients are suffering from pain originating in the genital organs. Acute appendicitis in Wales is equally common amongst the Welsh and non-Welsh population. Appendicectomy for non-acute appendicitis is commoner in people of Welsh origin. Acute appendicitis is commoner in the spring but there is no seasonal variation in the case of appendicectomy for non-acute conditions.Appendicitis is one of the commonest conditions responsible for the admission of patients to hospital for surgical treatment. Admissions to hospital for appendicitis are exceeded only by the total of admissions for all malignant disease, admission for abdominal hernia in the male, for old age and injury in both sexes, and for chronic inflammatory disease of the nose and throat. It is the third commonest operation in the male, being exceeded only by the removal of tonsils and by the repair of hernia, and the second commonest operation in the female, exceeded only by the removal of tonsillar tissue (Ministry of Health and General Register Office, 1964). Approximately one person in seven in the population of England and Wales may expect to undergo appendicectomy at some time in his life. Appendicitis is generally regarded as an inflammatory condition, reflected by the suffix to its name, but it is apparently not influenced by the antibiotics which have come into use during the last twenty years; antibiotics are not used in the definitive treatment of the condition and there has been no apparent fall in the incidence of the disease.This investigation is based on three approaches to the problem of the aetiology of the disease. First, the age and sex specific incidence of appendicitis was studied in a series of 848 patients who had undergone appendicectomy. Secondly, a genetic study was made of the relative incidence of the disease in the Welsh and non-Welsh moieties of the population of the Swansea area. Finally, an examination of the seasonal incidence of appendicitis was made on a series of 1,325 consecutive appendicectomies during the calendar years 1960 to 1965.The material on which the investigation was based consisted of specimens of the vermiform appendix removed at operation from patients in this hospital. This is a large acute general hospital into which are admitted a high proportion of the abdominal emergencies occurring in the town of Swansea and in the neighbouring rural and semi-urban districts.There is no conscious bias in selection of cases for admission to this institution. In 60% of the cases histological examination of the excised appendix showed an acute inflammation. This was recognized by the presence of infiltration with polymorphonuclear leucocytes, always of the submucosa and the mucosa, often of the muscularis and the serosa, and often with exudation of pus in the lumen of the viscus. In...
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