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Biomedical subjects

J Rantanen

Publications and source records attributed to J Rantanen.

At least 19 recordsLinked to original sources
PubMed1995

Finnish Institute of Occupational Health Asbestos Program 1987-1992.

In 1987-1992, the Finnish Institute of Occupational Health (FIOH) implemented a nationwide asbestos program aimed at preventing asbestos-related risks in good cooperation with governmental authorities, industry, trade unions, the health care and insurance systems, and mass media. The goals were to minimize all exposure to asbestos, identify people exposed at work, and improve the diagnostics of asbestos diseases, especially cancers. The program entailed several concrete actions and extensive dissemination of information, training, services, and scientific research. As proposed by the State Asbestos Committee, new use of asbestos products was banned and strict regulations were applied to renovation and inspection of old buildings. The screening study of asbestos-induced diseases included 18,943 current and retired workers from house building, shipyard, and asbestos industries. Pleural and parenchymal changes were found in 4,133 persons (22%), who were referred to further clinical examinations as suspected cases of an occupational disease. It was estimated that past exposure of asbestos among the Finnish population of 5 million causes > 150 mesotheliomas and lung cancers annually, totalling > 2,000 asbestos-induced cancer deaths by the year 2010. Although several major control actions were made or started during the program, the bulk of the preventive work still lies ahead.

Asbestosis↗
PubMed1995

Denervated segments of injured skeletal muscle fibers are reinnervated by newly formed neuromuscular junctions.

A muscle fiber normally receives its innervation at a single neuromuscular junction (NMJ). Transection of myofiber usually leaves one (abjunctional) stump denervated, while the other (adjunctional) remains innervated. To determine the mechanism of reinnervation of the abjunctional stumps, we transected the rat extensor digitorum muscle (EDL) below the site of the distalmost NMJ. Myofiber regeneration was followed for up to 56 days. Reinnervation began with the appearance of irregular acetylcholinesterase and alpha-bungarotoxin-positive deposits on abjunctional stumps after 10 to 15 days. These deposits later developed into more regular NMJ. The newly formed NMJ were innervated by sprouting axons which penetrated through the connective tissue scar separating the stumps. While denervated, the myofibers of the abjunctional segments underwent marked atrophy, which was reversed when reinnervation had ensued. In conclusion, we demonstrate for the first time that mature myofiber segments devoid of previous NMJ can induce both sprouting from intact axon terminals and formation of new "ectopic" NMJ on their own surface. This type of reinnervation is likely to occur only when myofibers are asymmetrically transected by a trauma. The signaling molecules possibly involved in this phenomenon are discussed.

Animals↗
PubMed1995

Satellite cell proliferation and the expression of myogenin and desmin in regenerating skeletal muscle: evidence for two different populations of satellite cells.

BACKGROUND: Regeneration of mature skeletal muscle recapitulates closely fetal myogenesis. It is initiated by activation of the reserve myogenic precursor cells, the satellite cells, which proliferate, differentiate into myoblasts expressing muscle-specific proteins, fuse into myotubes, and finally mature into myofibers. The MyoD family of transcription factors participates in the regulation of the complex phenomenon of myogenic differentiation during development and in vitro. The function of these transcription factors in the regeneration of injured mature skeletal muscle in vivo is, however, still unclear. EXPERIMENTAL DESIGN: To clarify the primary events in myogenic precursor cell activation, the expression of myogenin was examined in rats 1 to 48 hours after either a contusion injury to the gastrocnemius or after toxic injury to the soleus muscle. Myogenin mRNA expression was studied by Northern blot hybridizations, and the results were correlated with the onsets of the mitotic activity (i.e., incorporation of bromodeoxyuridine) of the satellite cells and of the production of the myogenin and MyoD1 proteins, as well as muscle-specific intermediate filament protein, desmin. RESULTS: Both forms of muscle injury produced myofiber necrosis, followed by the activation of the satellite cells. The first sign of myogenic differentiation, an increase in myogenin mRNA expression, occurred between 4 and 8 hours after injury. The first desmin-, MyoD1- and myogenin-positive myoblasts were seen after 12 hours, but satellite cell proliferation was not seen until 24 hours after the injury. CONCLUSIONS: The schedule of the events in our study contradicts the general concept that differentiation should follow proliferation. To explain this discrepancy, we propose that there are two populations of precursor cells: committed satellite cells, which are ready for immediate differentiation without preceding cell division, and stem satellite cells, which undergo mitosis before providing one daughter cell for differentiation and another for future proliferation.

Animals↗
PubMed1994

Lumbar muscle fiber size and type distribution in normal subjects.

The macroanatomy of the clinically important lumbar muscles has recently been investigated in detail, whereas the information about their microscopic structure in healthy persons is still scanty. In this study we have analysed lumbar multifidus and erector spinae muscles from 21 previously healthy persons who died suddenly and were of working age (range 23-65 years, mean 44.7 years). The microscopic structure of myofibers within the lumbar muscles was found to be regionally uniform, which renders in vivo biopsies representative of the whole muscle bulk. Somewhat surprisingly, age did not significantly influence fiber type composition, fiber size, or proportion of nonmuscular tissue. There was a slight predominance of type 1 fibers. The size of type 1 fibers (mean lesser diameter 54.0 microns) corresponded to that in other skeletal muscles, with no significant sex difference (55.1/51.6 microns male/female). Selective type 2 fiber atrophy was a common finding in both sexes, but significantly less so in men (mean diameter 38.8/28.4 microns male/female). We suggest that the values of fiber type proportions and fiber size in the deep multifidus presented in this study can be used as reference values for healthy adults in the present society with limited physical activity.

Adult↗
PubMed1992

From research to practice. Role of a research institution in the development of the work environment.

To conclude, all the signals from the future working life and the society at large speak for the growing importance of research in the areas of environmental health and occupational health. This research, in order to have the best impact, should be guided by solid strategy based on the soundest health values presenting clear priorities, and directed to the preventive impact-oriented actions, and using the competence of highly motivated researchers. The researchers should be well supported by their research institutes with good operational capacity and facilities and be provided with close contacts with the consumers of the research. This would facilitate the application of research results in the practical work environment. If all these criteria are met we can also expect an impact. We are all called upon to take part in this exciting effort, and I am happy to state that the response of UOEH during its over 13 years of activity has been a most beautiful example for all of us. Let me transmit the warmest congratulations to UOEH for the past and wishes of success in the future.

International Cooperation↗
PubMed1992

Priority setting and evaluation as tools for planning research strategy.

The growing role of research as a factor for socioeconomic development has also stimulated efforts for setting priorities and for evaluating research strategies. Priorities can be set for problems which are known for their consequences or their existing characteristics. The only way to ensure research on new problems is to allow more space for basic research aimed at revealing new data and at describing new phenomena. Evaluation methods for applied research are available, and they have been successfully used for making research units more effective and for improving the quality of the research in question.

Evaluation Studies as Topic↗
PubMed1989

Lumbar muscles: structure and function.

We review new data derived from careful dissection studies on the macroscopic anatomy, innervation and function of the lumbar muscles, as well as information on the fibres in these muscles. The new findings correct previous misconceptions of the functional anatomy of the lumbar muscles. The innervation and function of the erector spinae and multifidus muscles are so different that they cannot be classified as a single unit. The new interpretation of the innervation of multifidus muscle is of importance, for example, for the neurophysiological examination of the lumbar muscles. The relative number of the slow and fast type of muscle fibres in lumbar muscles varies considerably, and selective atrophy of the fast fibres seems to ensue from inactivity, not only in patients with back pain but also in sedentary controls. The atrophy may be corrected by adequate exercise. Both the fibre type composition and degree of atrophy may well influence a person's susceptibility to low back pain arising from the muscles.

Adult↗
PubMed1985

Recent PCB accidents in Finland.

Twenty-eight polychlorinated biphenyl (PCB) accidents were recorded during a 1-year period in Finland. They comprised leaks, fires or explosions of capacitors. Some of the explosions and fires gave rise to high concentrations of PCBs in air and of PCBs and tetrachlorodibenzofurans (TCDFs), including 2,3,7,8-TCDF, on surfaces. One large explosion is described in detail, and biomedical data and findings of this case are compared with those of smaller accidents in Finland.

Accidents, Occupational↗
PubMed1984

Chemical exposures at work and cardiovascular morbidity. Atherosclerosis, ischemic heart disease, hypertension, cardiomyopathy and arrhythmias.

Relatively little systematic research has been directed towards the potential effects, either etiologic or aggravating, of industrial chemicals on cardiovascular diseases. While some evidence indicates that exposure to certain pesticides might affect lipoprotein metabolism in man, there is no consistent documentation to support the view that atherosclerosis is caused in man by chemical exposures in industry. In this respect results from some animal studies are highly interesting, eg, exposure to some carcinogens, but the hypotheses presented have not yet been vigorously tested in man. Exposure to carbon monoxide is detrimental to the myocardium, especially in patients with ischemic heart disease, but there are no reliable data on elevated cardiac mortality due to carbon monoxide exposure in industrial populations. A few studies have reported arrhythmias or sudden deaths among workers exposed to solvents and organic nitrates. The effects of lead and cadmium upon human blood pressure have remained controversial, although the bulk of controlled epidemiologic studies suggests that they, if at all existent, are not strong.

Animals↗
PubMed1983

Carbon monoxide-induced brain injury: neurochemical studies after single and repeated exposures.

Biochemical effects of a single and once-repeated exposure to carbon monoxide (0.2% CO, 30 min) were studied in mouse brain. The effect of the severity of the first exposure on the brain reaction to the second exposure (0.2% CO, 30 min) was also studied after exposure to four different CO doses (0.2% CO for 0, 2 or 5 h, and 0.3% CO for 2 h). 1. The DNA content of brain decreased after single and once-repeated CO exposures. The effect of the second exposure was greater than that of the first. 2. The changes in the glycosphingolipid synthesis of brain were measured as the specific rate of precursor incorporation into the two isolated galactolipid fractions, i.e., cerebrosides and gangliosides following a 2-h pulse-labelling with 3H-galactose in vivo. The synthesis of cerebrosides was substantially inhibited for a short period after the first and the second exposures. A late compensatory over-recovery of synthesis was found only after the second exposure. The rate of galactose incorporation into gangliosides was not immediately depressed after CO exposure, but otherwise the changes were similar to those of cerebrosides. 3. The protein, phospholipid and cerebroside contents of brain were also affected in parallel fashion with the changes of DNA content. The content of gangliosides was increased after the first, but not after the second exposure. The enhanced reaction of brain to the second CO poisoning suggests the existence of sublethal brain cell injury which is produced by the first CO exposure and manifested by altered reactions to the second exposure.

Animals↗
PubMed1983

Community and occupational studies of lung cancer and polycyclic organic matter.

Finland is used as a model in attempts to study the possible association of the incidence of lung cancer and exposure of population to fossil fuel combustion products. Unfortunately because of great geographical variation of unknown origin in the incidence of lung cancer in Finland, detailed studies of the possible role of an individual exposure in the lung cancer risk are not possible. This background variation in the incidence is much greater than variation carried by any known etiological factor and does not clearly correlate with the degree of urbanization, industrialization, regional use of fossil fuels, number of motor vehicles or smoking habits. To get more precise information on the possible association of lung cancer incidence with exposure to fossil fuel combustion products, occupational studies serve as powerful tools. The definition of population is more reliable and the measurement of exposures can be done more precisely; moreover the management of confounding and modifying factors is more effective than in community studies. So far the studies carried out among the Finnish working population exposed to PAH compounds reveal an association between the lung cancer risk and exposure to PAHs.

Adult↗
PubMed1983

Occupational health and safety in Finland.

The tradition of Finnish legislation on occupational health and safety began 180 years ago. The renewal cycle of the principal acts has been about 20 to 30 years. At present the Finnish occupational health and safety legislation meets the Scandinavian standard well, though the structure of the Finnish legislation meets the Scandinavian standard well, though the structure of the Finnish legislation is more fragmented. The organization and manpower resources of occupational health and safety comprise more than 100,000 persons (5% of the labor force), and the number of full-time experts is about 3,600. The finances amount to 0.3% of the gross national product. Although intensive reforms for strengthening legislation, research, and practice were carried out during the 1970s, one-third of the labor force still works under daily health and safety risks. Several occupational and nonoccupational risk consequences cummulate into one and the same high risk population. Accident risk still remains the most prevalent and severe type of risk in the Finnish work environment. Three major national programs (National Occupational Health and Safety Program, National Occupational Health Service Program and National Program for Science Policy) were established so that the needs of occupational health and safety can be met. The programs are designed to respond not only to current problems, but also to those which can be expected in the future (caused, eg, by the large-scale implementation of new technology).

Accident Prevention↗
PubMed1982

Exposure limits and medical surveillance in occupational health.

The standards for pollutants in workplace air constitute a social consensus or agreement about acceptable levels of occupational hygiene. This agreement to exposures up to these limits inevitably includes a finite risk to the health of the workers. The numeric values of standards are needed to assess the requirements for ventilation and other occupational hygiene conditions. Planning and everyday practice in industry also need hygienic standards so that practical hygienic and safety measures can be maintained. These standards are not, however, levels below which there is no risk to health. While the hygienic standard itself carries acceptance of a certain risk, doctors cannot ethically accept any health risk to workers whatever the source of exposure. Thus personnel working in occupational health have to think about the risks of ill health even when the hygienic standards are met. The physician in occupational health has to be especially concerned to discover and estimate the risks to anyone particularly susceptible to exposures within the hygienically acceptable conditions. To do this, the occupational health physician uses medical examinations and specific investigations. In the follow-up of workers, health occupational health personnel use medical examinations in order to detect possible risks or to assess the general health status of individual workers. Health examinations are also used to detect specific injuries caused by the agents to which workers are known to be exposed in their work.

Carcinogens↗