Biosynthesis of extracellular polysaccharides in Klebsiella aerogenes

The cultural characteristics of the capaulate strains K« aerogenes Al and A4 were disoussed, and their mutation to strains which had lost the ability to synthesize exopolysaccharide• The presence of a capsule was shown to protect the micro-organism against dessication, against attaok by organic cations and enzymes degrading the cell wall, and against phage. A mutant of Al was found, A1S1, which produced exopolysaccharide in the form of slime. The exopoly- 14 saccharides were purified and analysed. Incubation of the cells with C - glucose-6-phosphate led to labelling of all the components of the polysaccharides. Total polysaccharide production was estimated during growth, and a comparison was made using washed cell suspensions between the rate of exopolysaccharide synthesis by A1S1 cells grown for various times in different media. The levels of nine enzymes involved in synthesis of the sugar nucleotide precursors of the exopolysaocharides were assayed in strains Al, A131 and A4. Their specific activities were also established in cultures of various ages, or grown at different incubation temperatures, or grown in different media which resulted in a variation in exopolysaccharide synthesis. There was generally little change in the level of any enzyme assayed. Non-mucoid (o) mutants of strains Al, A1S1 and A4 occurred spontaneously at low frequency and this rate was increased by use of mutagens such as 2-aminopurine and acriflavine. Attempts to obtain reversion of these mutants were unsuccessful. There was, however, some evidence that the ability to synthesize the exopoly¬ saccharide was regained in a few Al(o) strains by transduction. Using Al(o), AlSl(o) and A4(o) mutants, the levels of several enzymes synthesizing the nucleotide sugar precursors of the exopolysaccharides were assayed and compared to the parent strains. No enzyme was deficient and generally their specific activities were the same as the parent. A variant of A1 was found which was very unstable, giving rise to mucoid and non-muooid cells with equal frequency, and a mutent of M- produced far more exopolyaaccharide when grown on galactose as carbon source than on glucose. It appeared to be deficient in the enzyme UDPG pyrophosphorylase. A new class of mutants was discovered, the CR mutants, in which the presence of the exopolysaccharide was temperature dependent. It was only synthesized o at incubation temperatures above 30 . There was a second effect on lipopolysaccharide synthesis which led to altered phage sensitivity patterns, to the characteristic crenated appearance of oolonies, and to autoagglutinability in liquid culture at low incubation temperatures. Double mutants, which retained the CR appearance at all incubation temperatures but which had lost the ability to synthesize the exopolysaccharide, were also isolated. The properties of these mutants and the nature of the mutation were discussed. Finally a system was developed in which cell-free synthesis of the AA exopolysaocharide from the labelled nucleotide sugar precursors occurred. Good incorporation of glucose from UDPG into polysaccharide material was obtained. After pre-incubation of the system with UDPG, galactose from UDPGal was incor¬ porated to one-half this extent, and glucuronic acid from UBPG1UA to one-tenth this extent. Chloramphenicol stopped the incorporation of glucose into poly¬ saccharide material. The possibility of lipid-linked intermediates being involved was considered, and the effect of ADPG on the system found

A Short Circular History of Vitamin D from its Discovery to its Effects

The discovery of vitamin D.It was as early as the mid-1600s that Whistler (1) and Glisson (2)independently published scientific descriptions (in Latin!) of rickets, caused, we now know, by a vitamin D deficiency. However neither treatise recognised the crucial role of diet or exposure to sunlight on the prevention of this disease. Around 200 years later, in 1840, a Polish physician called Sniadecki realised that cases of rickets occurred in children living in the industrial centre of Warsaw but did not occur in children living in the country outside Warsaw. He surmised that lack of exposure to sunlight in the narrow, crowded streets of the city where there was considerable pollution due to the burning of coal and wood, caused the disease. Such a view was poorly received at the time as it seemed inconceivable that the sun could have any useful benefit on the skeleton. The prevalence of rickets increased as industrial processes and labour expanded and, by the end of the nineteenth century, this bone disorder was estimated to affect more than 90% of children living in such urban polluted environments in Europe. Similarly, as Boston and New York City grew in the late 1800s, so did the number of cases until, in 1900, more than 80% of children in Boston were reported to suffer from rickets

Climate change, public health and COP21 – a South African perspective

Current and future climate impacts on public health are a pressing global challenge. Southern Africa is predicted to experience significant changes in climate and by the end of the 21st century, annual average temperatures in the region may warm by up to 4 degrees Celsius. South Africa (SA) is considered to be among one of the most vulnerable countries in the world given the current high incidence of several life-threatening diseases, poverty and inequality. With the 21st session of the Conference of the Parties (COP21) to the United Nations Framework Convention on Climate Change taking place this year, we consider the challenges of and opportunities for SA to accelerate progress towards tackling the adverse impacts of climate change on human health.

More Than Effects in Skin: Ultraviolet Radiation-Induced Changes in Immune Cells in Human Blood

Cells of the skin and circulation are in constant two-way communication. Following exposure of humans to sunlight or to phototherapy, there are alterations in the number, phenotype and function of circulating blood cells. In this review, only data obtained from human studies are considered, with changes induced by UV radiation (UVR) exposure described for phagocytic leukocytes and peripheral blood mononuclear cells plus their component T and B cells, natural killer cells and dendritic cells. These immune modulations illustrate the potential of UVR to have therapeutic effects beyond the skin, and that sunlight exposure is an important environmental influence on human health

The epidemiology of skin cancer and public health strategies for its prevention in Southern Africa

Skin cancer is a non-communicable disease that has been underexplored in Africa, including Southern Africa. Exposure to solar ultraviolet radiation (UVR) is an important, potentially modifiable risk factor for skin cancer. The countries which comprise Southern Africa are Botswana, Lesotho, Namibia, South Africa, and Swaziland. They di er in population size and composition and experience di erent levels of solar UVR. Here, the epidemiology and prevalence of skin cancer in Southern African countries are outlined. Information is provided on skin cancer prevention campaigns in these countries, and evidence sought to support recommendations for skin cancer prevention, especially for people with fair skin, or oculocutaneous albinism or HIV-AIDS who are at the greatest risk. Consideration is given to the possible impacts of climate change on skin cancer in Southern Africa and the need for adaptation and human behavioural change is emphasized.Table S1: Absence (x) or presence (X) of evidence of online skin cancer prevention campaigns (any focus—could be in relation to albinism) in English by country in Africa. Websites valid as at the 17 December 2019.The South African Medical Research Council and the National Research Foundation (South Africa).http://www.mdpi.com/journal/ijerpham2020Geography, Geoinformatics and Meteorolog

Solar ultraviolet radiation in Africa : a systematic review and critical evaluation of the health risks and use of photoprotection

Most information on the harmful health effects of solar ultraviolet radiation (UVR) has been obtained in populations in which the majority has fair skin. Here a systematic review of evidence on diseases related to solar UVR in Africa was undertaken, and the appropriateness of effective photoprotection for these people considered. There are few population-based studies on UV-induced skin cancers (melanoma, squamous and basal cell carcinomas) in Africa, although limited reports indicated that they occur, even in people with deeply pigmented skin. The incidence of melanoma is particularly high in the white population living in the Western Cape of South Africa and has increased significantly in recent years. Cataract is extremely common in people of all skin colours and is a frequent cause of blindness, particularly in the elderly. For both skin cancer and cataract, the proportion of the disease risk that is attributable to exposure to solar UVR in African populations, and therefore the health burden caused by UV irradiation is unclear. There was little published information on the use of sun protection in Africa. The potential disease burden attributable to solar UVR exposure of Africans is high, although accurate data to quantify this are sparse. Information is required on the incidence, prevalence and mortality for the range of UVrelated diseases in different populations living throughout Africa. Photoprotection is clearly required, at least for those subpopulations at particularly high risk, but may be limited by cost and cultural acceptability.www.rsc.org/ppsam2016Geography, Geoinformatics and Meteorolog

Risk factors in Central Poland for the development of superficial and nodular basal cell carcinomas

INTRODUCTION: In the last decades the number of skin carcinomas has dramatically increased, which is mainly connected with changes in lifestyle, especially with common use of artificial light sources such as sunbeds. Basal cell carcinoma (BCC) is the most common form of skin cancer in white populations. Basal cell carcinomas are divided into subtypes, depending on their clinical picture and histology. The main groups are nodular (nBCC) and superficial (sBCC) ones. The major recognized risk factors for basal cell carcinoma (BCC) are exposure to chronic and intermittent burning doses of sunlight. Other risk factors leading to the development of the nBCC and sBCC subtypes of BCC are not well established. MATERIAL AND METHODS: An analysis of 123 patients with either nBCC or sBCC, living in Lodz, Poland, regarding various intrinsic and environmental parameters was undertaken following the histological diagnosis of BCC. RESULTS: No statistical differences were observed between the BCC subtype and sex, age, hair colour, eye colour, smoking, family history of skin cancer, occupation, or past episodes of sunburn. While sBCCs tended to occur on unexposed body sites in phototype I/II subjects who mainly avoided direct sunlight, nBCCs tended to occur on sun-exposed body sites in phototype III subjects who were frequently in direct sunlight. CONCLUSIONS: Thus the development of particular BCC subtypes is partially dependent on phototype and personal sun behaviour

Human health impacts in a changing South African climate

Climate change is projected to lead to warmer temperatures, especially in southern Africa, where the warming is predicted to be 2°C higher than the global increase. Given the high burden of disease already associated with environmental factors in this region, this temperature increase may lead to grave challenges for human health and quality of life. HIV/AIDS, poverty, food and water insecurity together with inequality and unemployment will further complicate the manner in which we will need to address the challenges of a changing climate. The health impacts are direct, such as increased temperatures leading to heat exhaustion, and indirect, such as likely increases in infectious diseases from contaminated water and changes in the distribution and/or magnitude of vector-borne diseases. The most effective measures for adapting to climate change to ensure healthy populations are to implement basic public health systems and services. These range from a continuous supply of clean water to adequate primary healthcare services. Support for required interventions is required not only from government, but also from healthcare professionals and communities. The need for disease surveillance, data capturing and more focused research is paramount.http://www.samj.org.zaam201

The impact of solar ultraviolet radiation on human health in sub-Saharan Africa

Photoprotection messages and ‘SunSmart’ programmes exist mainly to prevent skin cancers and, more recently, to encourage adequate personal sun exposure to elicit a vitamin D response for healthy bone and immune systems. Several developed countries maintain intensive research networks and monitor solar UV radiation to support awareness campaigns and intervention development. The situation is different in sub-Saharan Africa. Adequate empirical evidence of the impact of solar UV radiation on human health, even for melanomas and cataracts, is lacking, and is overshadowed by other factors such as communicable diseases, especially HIV, AIDS and tuberculosis. In addition, the established photoprotection messages used in developed countries have been adopted and implemented in a limited number of sub-Saharan countries but with minimal understanding of local conditions and behaviours. In this review, we consider the current evidence for sun-related effects on human health in sub-Saharan Africa, summarise published research and identify key issues. Data on the prevalence of human diseases affected by solar UV radiation in all subpopulations are not generally available, financial support is insufficient and the infrastructure to address these and other related topics is inadequate. Despite these limitations, considerable progress may be made regarding the management of solar UV radiation related health outcomes in sub-Saharan Africa, provided researchers collaborate and resources are allocated appropriately