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Description is made of the various stages in the development of the problem. The earliest theories on atherosclerosis are discussed (Lobstein and others). Insofar development of the functional trend is concerned, the science of atherosclerosis is considered in the light of the classic works in the Russian medical literature of the second half of the XIXth century, mainly those of Botkin, Polotebnev etc. The author pays tribute also to the representatives of the French classical school (Euchart etc.). The problem of atherosclerosis is also dealt with in the light of recent advances of biochemistry, as well as in the light of the statements of A. L. Miasnikov on the issue about the relationship between atherosclerosis and hypertonia and his classification of atherosclerosis.

The discovery of the pathophysiological aspects of atherosclerosis--a review

Considering the morphological findings in egyptian mummies at the beginning of the 20th century, atherosclerotic lesions were also apparent in pharaoh mummies more than 3500 years ago. Hippokrates (469-377 b.c.) described the sudden (cardiac) death, whereas Erasistratos had documented the typical claudication intermittens symptoms of peripheral arterial disease approximately 300 b.c. Later on in 1575, Fallopius observed severe pathological findings in arteries which he has characterized as a 'degeneration to bones', suggesting the presence of calcified atherosclerotic lesions. The relation between coronary lesions and the symptoms of angina pectoris was postulated in 1799 by Parry, however, only more than 80 years later angina pectoris was interpreted as a result of myocardial ischemia by Potain. During that time, the term 'arteriosclerosis' was firstly created by Lobstein in his 'Lehrbuch der pathologischen Anatomie', published in 1835. With the beginning of the last century, the pathophysiological aspects of plaque development were investigated in more detail by a number of researchers. In this context, people such as Saltykow, Chalatow and Anitschkow are important to notice. In 1914, Anitschkow firstly described the role of cholesterol accumulation in the vessel wall for the development of atherosclerosis. He used a cholesterol-fed rabbit model, which is the most important model of experimental atherosclerosis up to now. He also firstly described the 'Cholesterinesterphagozyten', which today commonly are known as foam cells, derived from macrophages. Using the cholesterol-fed rabbit model as well, already in 1942, Ludden et al. could demonstrate the atheroprotective effect of estrogen experimentally, a finding, which got later confirmed in the primate model and epidemiological studies. In the last three decades our knowledge has expanded by a large number of findings, based on morphological, immunohistological and molecular methods. In this context, one major contribution was the discovery of the LDL-receptor and its importance for the development of atherosclerosis by Brown and Goldstein, and the setting up of the 'response to injury hypothesis' by Ross and Glomset. At the present, we understand atherosclerosis as a complex (and at least in part as a physiological) phenomenon, beginning in the early childhood. The pathological aspect, making it to a disease, is depending on individual growth dynamics and plaque localization. The following key processes during the development of atherosclerosis are identified: 1) Endothelial injury, 2) intimal cholesterol accumulation and monocyte invasion with subsequent foam cell formation, 3) migration and proliferation of smooth muscle cells with expression of extracellular matrix 4) local thrombus formation with secondary organization 5) calcification and/or plaque rupture 6) final occlusion due to plaque rupture/thrombus formation. The classical concept of cardiovascular risk factors does only partially explain the origin of atherosclerosis. For the future, further mechanism(s) need to be identified and studied (genomic pathways, hormonal aspects, infective components, etc.) probably opening an effective therapeutical strategy to prevent and treat atherosclerotic diseases.

Cholesterol in the year 2000

Cholesterol research was one of the key areas of scientific investigation in the 20th century. Little was known about the structure of cholesterol until the pioneering research of A. Windaus and H. Wieland in the first part of the century. The structure of cholesterol was completely elucidated in 1932. With the development of isotopic tracers in the 1930s studies on cholesterol biosynthesis were initiated. In 1942 K. Bloch and D. Rittenberg showed that deuterium-labeled acetate was incorporated into the ring structure and side chain of cholesterol. Another important discovery from Bloch's laboratory was that squalene was a precursor of cholesterol. In 1956, the main elements of the biosynthetic pathway became known when isopentenyl pyrophosphate was discovered as a precursor. In 1966, J. Cornforth and G. Popjak predicted that there were 16234 possible stereochemical pathways by which mevalonate could be converted into squalene. They subsequently showed which of these pathways was correct. In the 1970s and 1980s K. Bloch was able to provide intriguing evidence for an evolutionary advantage of cholesterol over lanosterol or some of the intermediates in the conversion of lanosterol to cholesterol. The last quarter of the 20th century was when M. Brown and J. Goldstein showed that the low density lipoprotein receptor was a key regulator of cholesterol homeostasis. They have also demonstrated that cholesterol balance in the cell is transcriptionally regulated via the sterol regulatory element binding protein. In the later part of the 20th century drugs were developed that effectively lower plasma cholesterol and lessen the risk of atherosclerosis and cardiovascular disease.

Preventing coronary artery disease by lowering cholesterol levels: fifty years from bench to bedside

In the more than 50 years since the founding of the National Heart, Lung, and Blood Institute and the American Heart Association, medical science has moved from an era in which hypercholesterolemia, as it is now defined, was not believed to be abnormal to one in which controlling hypercholesterolemia is known to reduce not only coronary artery disease morbidity and mortality but also total mortality. While the efforts and successes of many researchers involved in this evolution are impressive, atherosclerosis is still a major cause of death and disability in many developed nations, mostly in the form of myocardial infarction and stroke, and is an increasing cause of morbidity and mortality in developing nations. Many questions about the detailed pathogenesis of the disease remain. Elucidating the roles of high-density lipoprotein, other lipoproteins, and homocysteine, as well as the roles of cytokines and growth factors, will permit better understanding and treatment of atherosclerosis. With continuing support for research and encouragement of physicians and patients to follow recommended preventive regimens, further progress can be made against this major cause of death.

Value of animal models for Chlamydia pneumoniae-related atherosclerosis

Chlamydia pneumoniae is strongly implicated in the pathogenesis of atherosclerosis in human beings. Animal models are important to help establish causality, to understand the mechanism of infection induced atherogenesis, to examine interaction of other factors or variables, to explore treatment regimens and their efficacy, and to help develop a vaccine for prevention. To date, the rabbit model is the only animal model shown to develop de novo atherosclerotic changes with C pneumoniae infection. However, the mouse model may be useful to show enhancement with other factors such as hypercholesterolemia and to explore pathogenic mechanisms. In our studies, we have shown that C pneumoniae respiratory infection in the rabbit results in early atherosclerotic changes in 26% with single inoculation and in 35% after triple inoculation, but sham infection or infection with Mycoplasma pneumoniae does not result in similar changes. Early treatment (5 days after inoculation) with 30 mg/kg per day azithromycin once every 6 days was 87% effective in preventing atherosclerotic changes, but delayed treatment (6 weeks after inoculation) was ineffective. Further studies are needed with longer or more aggressive regimens or possible combination of agents to determine whether it is possible to reverse preformed lesions. An effective vaccine for prevention of C pneumoniae -induced pneumonia and possibly atherosclerotic lesions in human beings would have tremendous application and would circumvent the shortcomings of antibiotic therapy.

History of recommendations to the public about dietary fat

Recommendations to Americans concerning dietary fat and heart disease began to appear in the late 1950s. This followed the publications of Gofman et al. (1950) and Keys (1953) relating to techniques for separating plasma lipoprotein fractions and the epidemiologic correlations between dietary fat, serum cholesterol and heart disease, respectively. Advice to the public after 40 years is similar to that given originally, namely, to reduce total fat, saturated fat and cholesterol intake, although cholesterol intake per se is not correlated strongly with cholesterolemia. Newer players on the heart disease stage are homocysteinemia, chlamydia infection and cytomegalovirus. These findings, when amplified, may alter the thrust of medical and dietary advice. In the meantime, since 1950, deaths from all causes in the U.S. (per 100,000, age-adjusted) have fallen by 40% and deaths from heart disease and stroke have fallen by 53 and 70%, respectively.

Nikolaj Nikolajewitsch Anitschkow (1885-1964) established the cholesterol-fed rabbit as a model for atherosclerosis research

The cholesterol-fed rabbit is a widely used model for experimental atherosclerosis research. In regard to this, one name is periodically mentioned: Nikolaj Nikolajewitsch Anitschkow. Those infrequent reminders of an important name in modern medical history do not pay an adequate tribute to basic findings concerning the pathology and pathogenesis of atherosclerosis. In contrast to research groups at that time conducting experiments with protein enriched diets, Anitschkow demonstrated, in 1913 in St. Petersburg, that it was cholesterol only that caused these atherosclerotic changes in the rabbit arterial intima, which was very similar to human atherosclerosis. By analysing the plaque's development and histology, Anitschkow was able to identify the cell types, on which modern atherosclerosis research is now focussing with a new set of immunohistochemical methods: smooth muscle cells, macrophages and lymphocytes. He noted early (fatty streaks) and advanced (atheromatous plaques) lesions and, by standardizing cholesterol feeding, he discovered that the amount of cholesterol uptake was directly proportional to the degree of atherosclerosis formation. His explanation for this observation was what modern terminology calls 'response-to-injury'. With modern immunohistochemical and molecular-biological methods, the cholesterol-fed rabbit can be used to investigate the pathophysiological aspects which also contribute to human atherosclerosis, such as lipoproteins, diabetes, mitogens, growth-factors, adhesion molecules, endothelial-function, receptor-pathways or platelets. This model can be combined with a number of other methods causing endothelial dysfunction and injury, such as balloon denudation, electric stimulation, cuff implantation, artificial hypertension, diabetes or infection. Bred strains of hereditary hypercholesterolemic rabbits or those resistant to a cholesterol-diet provide further possibilities to expand experimental designs.