The accident at Chernobyl and trisomy 21 in Finland.

Our objective was to explore whether the radiation fallout in Finland after the accident at the Chernobyl nuclear power plant in April 1986 led to an increased incidence of trisomy 21. In this geographic and temporal cohort study, the country was divided into three zones according to the amounts of radioactive fallout and internal radiation caused by two cesium isotopes. The 518 cytologically verified cases of trisomy 21 were divided into a control group (conceived before the accident), and a study group of children whose expected dates of birth were in the post-accident years 1987-1988, i.e., pregnancies commenced after May 1986. The cases were also divided into three subgroups according to the zones of radiation. There were no significant differences in prevalence of trisomy 21 between the control and study groups nor between the three zones in spite of the significant differences in the levels of radiation and in the body burden that prevailed throughout the study period. Power estimates showed that in the two zones of lower radiation, an increase of 0.5% in the prevalence would have been detected with a power of 0.85, and in the somewhat smaller zone of the highest radiation, with a power of 0.70. The study lends no further support to the view that the low radiation fallout in western Europe would have been causally associated with trisomy 21.     

Lipoprotein(a) binds to fibronectin and has serine proteinase activity capable of cleaving it.

The plasma concentration of human lipoprotein(a) [Lp(a)] is correlated with the risk of heart disease. A distinct feature of the Lp(a) particle is the apolipoprotein (a) [apo(a)], which is associated with apoB-100, the main protein component of low-density lipoprotein. We now report that apo(a), which has extensive homology to plasminogen, binds to immobilized fibronectin. The binding of Lp(a) was localized to the C-terminal heparin-binding domain of fibronectin. Incubation of Lp(a) with fibronectin resulted in fragmentation of fibronectin. The cleavage pattern, as visualized by gel electrophoresis and immunoblotting, was reproducibly obtained with Lp(a) purified from five different individuals and was distinct from that obtained upon proteolysis of fibronectin by plasmin or kallikrein. The use of synthetic peptide substrates demonstrated that the amino acid specificity for Lp(a) was arginine rather than lysine. The proteolytic activity of Lp(a) was localized to apo(a) and experiments with inhibitors indicated that the proteolytic activity was of serine proteinase-type.     

Respiration of plankton in two small,polyhumic lakes

The respiration of plankton of two polyhumic lakes was measured as production of carbon dioxide in dark bottles. The method proved to be enough sensitive for use in oligotrophic lakes with low alkalinity. The respiration of plankton followed broadly changes in temperature. However, the primary production of phytoplankton was probably the main factor governing the seasonal pattern of respiration. During summer the respiration of plankton was more than three times higher than the primary production of phytoplankton. This suggests that allochthonous humic substances are an important source of carbon and energy for organisms of polyhumic lakes.     

Weed species diversity and community composition in cropping practices at two intensity levels – a six-year experiment

Alternative cropping practices can be expected to increase the diversity and change the species composition of weed communities. In a six-year field experiment we compared species diversity and species composition in the weed community of cereal fields cultivated by conventional and by low-input cropping methods. In the conventional cropping both mineral fertilizers and herbicides were applied but in the low-input cropping the fertlizer was manure and herbicides were avoided altogether. The level of nitrogen fertilization was higher in conventional cropping. A five-year crop rotation comprising rye, oat-pea, barley and two-year grasslands was used in both cropping methods. We found that the species pool was larger (42 vs 35 species) and the average number of species higher (20.2 vs 13.1 species) in low-input than in conventional cropping. This was the case both in the data pooled across crops and in each crop separately. Herbicides affected species diversity and species composition more than did nitrogen fertilization. Species susceptible to the herbicides applied declined in abundance, which resulted in more skewed dominance patterns in the communities of conventional fields than in those of low-input fields. The crop affected the species composition of weed communities more than did the cropping method. Our results suggest that weed species diversity could be promoted by using low-intensity cropping practices.     

Effects of Experimental Acidification on Phyto-, Bacterio-and Zooplankton in Enclosures of a Highly Humic Lake

In situ enclosure experiments were performed in a highly humic lake to examine the effects of acidification on phyto-, bacterio- and zooplankton. The acidity of three enclosures was adjusted with H₂SO₄ to pH 3.5, 4 and 5 and one enclosure and the lake served as controls. The diversity of plankton as well as the mean concentration of chlorophyll α, primary production and respiration of plankton decreased with increasing acidity. Bacterial density was slightly lower in the pH 3.5 enclosure than in the other enclosures and in the lake, but there were no differences in the morphological type or mean volume of the cells between different treatments. In the acidified enclosures Cryptomonas ovata and Chlamydomonas spp. were the dominant phytoplankters, while Dinobryon and Mallomonas species seemed to be most sensitive to acidity. Keratella cochlearis, Kellicottia longispina and Bosmina longispina were the most tolerant zooplankton to acidity.     

Visceral anomalies in the Meckel syndrome

The visceral abnormalities of 32 autopsied Meckel's syndrome cases were analysed macroscopically and histologically in order to observe the distribution and spectrum of internal abnormalities in this hereditary malformation syndrome. All cases showed the classical triad of central nervous system anomaly, postaxial polydactyly, and cystic kidneys. Five cases were midterm fetuses and 27 cases were perinatal deaths. The kidneys were grossly enlarged in almost all of the cases (29) and showed a uniform histological pattern of fibrocystic proliferation, which is considered characteristic of MS. Fibrosis and proliferation of the bile ducts in the hepatic portal tracts were found in each case. Severe hypoplasia of the male genitalia associated with cryptorchidism was the third consistent anomaly. Derivatives of the müllerian ducts were present in four males, and the initial sex determination of the male infants was sometimes difficult. Epididymal cysts (39%) and ductal dilatation as well as fibrosis of the pancreas (31%) were further common anomalies. This series showed that a number of gross and microscopic abnormalities are consistently present in MS and that histological investigation is invaluable in defining the syndrome in doubtful cases.     

Plant colonization of a bare peat surface: population changes and spatial patterns

Abstract. Changes in size and spatial arrangement of plant populations established on an initially bare peat surface were described over a period of 5 yr by following plant individuals on a 1-cm grid in an area of 10 m x 25 m. The spatial pattern of populations and association between species was analyzed statistically. The study site was very slowly colonized by 14 perennial plant species. The early successional stage was dominated by Carex rostrata, with a clumped spatial distribution, and the homogeneously distributed Eriophorum vaginatum and Pinus sylvestris. Both the growth in size of populations and changes in their spatial distribution were interpreted as a result of species dispersal ability, tolerance to severity of the substrate and pattern of reproduction.     

Effects of artificial plant cover on plant colonization of a bare peat surface

Abstract. This paper describes the effect of artificial plant cover on plant colonization of a bare peat surface, resulting from peat harvesting. Plant species colonization was compared on plots supplied with plastic models simulating Vaccinium vitis-idaea plants and plots without this artificial cover. After two growing seasons, species composition and total biomass of the established plant cover were similar in the two plot types. However, the number of established seedlings in the plots with artificial cover was significantly higher than that in the plots without cover. Out of 13 species observed four differed significantly in their performance on the two plot types. Betula spec. had both higher seedling numbers and higher biomass on the test plots; Deschampsia cespitosa had a higher biomass, whereas the seedlings were too numerous to be counted; Salix phylicifolia had higher seedling numbers. On the contrary, the number of seedlings of Epilobium angustifoliwn was lower on plots with artificial cover. It is suggested that colonization by Betula, D. cespitosa and S. phylicifolia was facilitated mainly by the improved microclimatic and soil moisture conditions under the artificial plant cover. On the other hand, germination of E. angustifolium may be negatively influenced by the increased shade on the test plots.     

Socioeconomic conditions in childhood and ischaemic heart disease during middle age.

OBJECTIVE--To examine the association between socioeconomic conditions in childhood and ischaemic heart disease in middle aged men, including the role of physiological and behavioural risk factors. DESIGN--Prevalence study with extensive examination and testing and with recall of childhood conditions. SETTING--Population based study in Kuopio, Finland. SUBJECTS--Representative sample of 2679 men aged 42, 48, 54, and 60. MAIN OUTCOME MEASURES--Ischaemic findings on progressive maximal exercise test. RESULTS--Low socioeconomic style in childhood was associated with significantly higher prevalence of findings indicating ischaemias. Compared with those in the highest tertile of childhood socioeconomic conditions, the age adjusted odds ratio for subjects in the lowest tertile was 1.44 and for those in the middle tertile 1.35. Adjustment for years of cigarette smoking times the average number of cigarettes smoked, ratio of high density lipoprotein to low density lipoprotein cholesterol, fibrinogen and serum selenium concentrations, and adult height did not appreciably weaken the association. Adjustment for adult socioeconomic state resulted in a 16% decline in the association. The association was reduced to non-significance by adjustment for measures of prevalent cardiovascular illness. CONCLUSIONS--Socioeconomic state in childhood was significantly associated with ischaemic heart disease in middle aged men. Levels of risk factors measured at middle age did not account for this association, nor did adult height. Because childhood socioeconomic conditions precede the development of ischaemic heart disease the substantial impact of prevalent illness on the observed association suggests that ischaemic heart disease develops earlier in those with lower socioeconomic state during childhood.