Beijerinck's work on tobacco mosaic virus: historical context and legacy.
(9/2006)
Beijerinck's entirely new concept, launched in 1898, of a filterable contagium vivum fluidum which multiplied in close association with the host's metabolism and was distributed in phloem vessels together with plant nutrients, did not match the then prevailing bacteriological germ theory. At the time, tools and concepts to handle such a new kind of agent (the viruses) were non-existent. Beijerinck's novel idea, therefore, did not revolutionize biological science or immediately alter human understanding of contagious diseases. That is how bacteriological dogma persisted, as voiced by Loeffler and Frosch when showing the filterability of an animal virus (1898), and especially by Ivanovsky who had already in 1892 detected filterability of the agent of tobacco mosaic but kept looking for a microbe and finally (1903) claimed its multiplication in an artificial medium. The dogma was also strongly advocated by Roux in 1903 when writing the first review on viruses, which he named 'so-called "invisible" microbes', unwittingly including the agent of bovine pleuropneumonia, only much later proved to be caused by a mycoplasma. In 1904, Baur was the first to advocate strongly the chemical view of viruses. But uncertainty about the true nature of viruses, with their similarities to enzymes and genes, continued until the 1930s when at long last tobacco mosaic virus particles were isolated as an enzyme-like protein (1935), soon to be better characterized as a nucleoprotein (1937). Physicochemical virus studies were a key element in triggering molecular biology which was to provide further means to reveal the true nature of viruses 'at the threshold of life'. Beijerinck's 1898 vision was not appreciated or verified during his lifetime. But Beijerinck already had a clear notion of the mechanism behind the phenomena he observed. Developments in virology and molecular biology since 1935 indicate how close Beijerinck (and even Mayer, Beijerinck's predecessor in research on tobacco mosaic) had been to the mark. The history of research on tobacco mosaic and the commitments of Mayer, Beijerinck and others demonstrate that progress in science is not only a matter of mere technology but of philosophy as well. Raemaekers' Mayer cartoon, inspired by Beijerinck, artistically represents the crucial question about the reliability of our images of reality, and about the scope of our technological interference with nature. (+info)
Myocardial protection: the rebirth of potassium-based cardioplegia.
(10/2006)
The introduction of open-heart surgery more than 4 decades ago signaled a new era in medicine. For the 1st time, previously untreatable cardiac anomalies became amenable to surgical therapy. The use of the heart-lung machine seemed to grant the surgeon unlimited time in which to operate inside the heart. Still frustrated by poor operating conditions and the threat of air embolism, Denis Melrose introduced elective cardiac arrest in 1955. His use of a potassium citrate solution seemed to offer a safe method to effect a quiet, bloodless field. However, a few years after its inception, numerous reports began to question the safety of this approach, and the Melrose technique was abandoned in the early 1960s. Nearly 15 years elapsed before potassium-based cardioplegia regained popularity. During this period, topical hypothermia, coronary perfusion with intermittent aortic occlusion, and normothermic ischemia were evaluated and discarded. A few European investigators like Hoelscher, Bretschneider, and Kirsch had maintained their interest in chemical cardioplegia, and it was through their efforts that future researchers like Hearse and Gay spearheaded the return to potassium-based cardioplegia, which today forms the core of the cardiac surgeon's myocardial protective armamentarium and has contributed towards lowering operative mortality rates. (+info)
Can we learn from eugenics?
(11/2006)
Eugenics casts a long shadow over contemporary genetics. Any measure, whether in clinical genetics or biotechnology, which is suspected of eugenic intent is likely to be opposed on that ground. Yet there is little consensus on what this word signifies, and often only a remote connection to the very complex set of social movements which took that name. After a brief historical summary of eugenics, this essay attempts to locate any wrongs inherent in eugenic doctrines. Four candidates are examined and rejected. The moral challenge posed by eugenics for genetics in our own time, I argue, is to achieve social justice. (+info)
History of medicine and concepts of health.
(12/2006)
It was not until the exemplary social reform of the 19th century and the introduction of modern health insurance schemes that people started to consider health as some kind of basic right which could be ensured by insurance and doctors, rather than by individual responsibility. The recent explosion of health system costs in countries like Germany has given rise to an unprecedented situation whereby the limited capacities of insurance systems and state organizations are becoming more and more evident. Health economists are now questioning the feasibility of optimal medical treatment for everybody. One consequence of this situation is that people are being forced to recall the old virtue of individual responsibility for one's own physical and mental well-being. This article examines the nature of health from a historical point of view. The point is made that health is not the same thing as a life free from complaints, although this erroneous belief is wide-spread today. Galen himself identified a neutral physical state between health and illness (neutralitas), that could be observed in many people who could not be described as being either healthy or ill. It is necessary to accept this state as part of the natural fate of humankind and to understand that individual responsibility and the demands on society and insurance companies for well-being or absolute freedom from ailments are not one and the same thing. (+info)
Prisoners of the proximate: loosening the constraints on epidemiology in an age of change.
(13/2006)
"Modern epidemiology" has a primary orientation to the study of multiple risk factors for chronic noncommunicable diseases. If epidemiologists are to understand the determinants of population health in terms that extend beyond proximate, individual-level risk factors (and their biological mediators), they must learn to apply a social-ecologic systems perspective. The mind-set and methods of modern epidemiology entail the following four main constraints that limit engagement in issues of wider context: 1) a preoccupation with proximate risk factors; 2) a focus on individual-level versus population-level influences on health; 3) a typically modular (time-windowed) view of how individuals undergo changes in risk status (i.e., a life-stage vs. a life-course model of risk acquisition); and 4) the, as yet, unfamiliar challenge of scenario-based forecasting of health consequences of future, large-scale social and environmental changes. The evolution of the content and methods of epidemiology continues. Epidemiologists are gaining insights into the complex social and environmental systems that are the context for health and disease; thinking about population health in increasingly ecologic terms; developing dynamic, interactive, life-course models of disease risk acquisition; and extending their spatial-temporal frame of reference as they perceive the health risks posed by escalating human pressures on the wider environment. The constraints of "the proximate" upon epidemiology are thus loosening as the end of the century approaches. (+info)
Pesticides and inner-city children: exposures, risks, and prevention.
(14/2006)
Six million children live in poverty in America's inner cities. These children are at high risk of exposure to pesticides that are used extensively in urban schools, homes, and day-care centers for control of roaches, rats, and other vermin. The organophosphate insecticide chlorpyrifos and certain pyrethroids are the registered pesticides most heavily applied in cities. Illegal street pesticides are also in use, including tres pasitos (a carbamate), tiza china, and methyl parathion. In New York State in 1997, the heaviest use of pesticides in all counties statewide was in the urban boroughs of Manhattan and Brooklyn. Children are highly vulnerable to pesticides. Because of their play close to the ground, their hand-to-mouth behavior, and their unique dietary patterns, children absorb more pesticides from their environment than adults. The long persistence of semivolatile pesticides such as chlorpyrifos on rugs, furniture, stuffed toys, and other absorbent surfaces within closed apartments further enhances urban children's exposures. Compounding these risks of heavy exposures are children's decreased ability to detoxify and excrete pesticides and the rapid growth, development, and differentiation of their vital organ systems. These developmental immaturities create early windows of great vulnerability. Recent experimental data suggest, for example, that chlorpyrifos may be a developmental neurotoxicant and that exposure in utero may cause biochemical and functional aberrations in fetal neurons as well as deficits in the number of neurons. Certain pyrethroids exert hormonal activity that may alter early neurologic and reproductive development. Assays currently used for assessment of the toxicity of pesticides are insensitive and cannot accurately predict effects to children exposed in utero or in early postnatal life. Protection of American children, and particularly of inner-city children, against the developmental hazards of pesticides requires a comprehensive strategy that monitors patterns of pesticide use on a continuing basis, assesses children's actual exposures to pesticides, uses state-of-the-art developmental toxicity testing, and establishes societal targets for reduction of pesticide use. (+info)
A bit of history.
(15/2006)
Reviews of scientific literature began to appear in the 17th century. Journals dedicated to them soon followed, leading eventually to this one, which emerged in the 1930s as Bacteriological Reviews; it adapted to the many changes in our fluid discipline, evolving into the present, much broader Microbiology and Molecular Biology Reviews. (+info)
Child mortality in Stockholm during 1885-1910: the impact of household size and number of children in the family on the risk of death from measles.
(16/2006)
Previous studies have associated overcrowding at the household level with increased mortality, especially from airborne diseases. This association may be confounded by associations with adverse socioeconomic conditions or low age at infection. This study investigated the effect of crowding on the risk of measles death. Individual entries in a population-based register and on death certificates for children aged 0-15 years living in one parish in Stockholm in 1885, 1891, and 1910 (n = 36,718) were used to analyze cause-specific and overall death rates in relation to household size and the number of children in the household, using Cox regression analysis. Bivariate analysis identified significant relations between crowding and the cause-specific risk of death, which were subsequently tested while controlling for other known risk factors for childhood death. Significant negative associations between crowding and the risk of death from pneumonia and bronchitis disappeared when controlling for other risk factors. A negative association between the risk of overall death and large household size became significantly positive when controlling for other risk factors. The increased risk of death from measles associated with proxies for crowding remained after controlling for other risk factors. In conclusion, crowding may have a statistically independent effect on the risk of death from measles. (+info)