Cutaneous tumour of northern pike Esox lucius L.: evidence for a monocytic neoplasm

An epidemic of cutaneous tumours occurs in northern pike from the Åland Islands of Finland. Lymphocytes of pike could be triggered to synthesize DNA in vitro by mitogens. Tumour cells had a high basic metabolic rate and mitogens did not enhance their incorporation of ³H-thymidine. High percentages of peripheral blood, spleen, and head kidney mononuclear cells were surface (SIg) and cytoplasmic (CIg) immunoglobulin-positive by indirect immunofluorescence, using rabbit anti-pike IgM antibodies. Lower but still substantially high percentages of SIg and CIg immunofluorescence were observed with mouse anti-carp IgM antibodies. Tumour cells, however, were SIg- and Clg-negative, suggesting that the neoplasm is not a B cell lymphoma or plasmacytoma. A majority of tumour cells exhibited an intense diffuse staining pattern for alpha-naphthyl acetate esterase which was inhibited by sodium fluoride and was reminiscent of that in human monocytes. By electron microscopy (EM), the tumour cells were seen to be closely apposed with a lack of cell-cell junctions, and characteristically contained groups of lysosomes and large numbers of cytoplasmic lipid droplets, which are features of histiomonocytic cells. Although the marker studies do not completely rule out a T-lymphocytic origin, we suggest that the EM findings lend support for the view that the Åland pike neoplasm may be derived from the monocytic lineage.     

Identification of a deletion in the LDL receptor gene A Finnish type of mutation

A cDNA probe for the low density lipoprotein (LDL) receptor gene was used to screen DNA samples from 52 unrelated Finnish patients with the heterozygous form of familial hypercholesterolemia (FH) and 51 healthy controls. Southern blot analysis using the restriction enzyme PvuII revealed an abnormal 11 kb (kilo base-pair) restriction fragment in 16 (31%) of the patients but none of the controls. A more detailed restriction enzyme analysis of the DNA from patients revealed a mutation which apparently is due to an 8 kb deletion extending from intron 15 to exon 18 of the LDL receptor gene. Co-segregation of FH with the mutated gene was demonstrated in three families. These data are consistent with a ‘founder gene effect’ and support the assumption that recombinant DNA methods may have great impact on the diagnostics of FH in genetically homogeneous populations.     

Polymorphisms of the apolipoprotein and angiotensin converting enzyme genes in young North Karelian patients with coronary heart disease

The genes encoding apolipoproteins (apos) A-I, B, C-III and E as well as that encoding the angiotensin converting enyzme (ACE) have been proposed as candidate genes for coronary heart disease (CHD). We determined the common polymorphisms of the apo genes, previously found to influence serum lipid levels at the population level, and the insertion/deletion polymorphism of the ACE gene, recently reported to reflect the risk of myocardial infarction, in 82 very young (mean, 41 years) North Karelian Finns with symptomatic CHD and 50 controls of similar age. Patients with familial hypercholesterolemia had been excluded from this material. None of the polymorphisms examined, including the apo A-I promoter MspI, apo C-III SstI and apo B XbaI restriction fragment polymorphisms, a common variation of apo E (2, 3 and 4 alleles) and an ACE insertion/deletion (I/D) polymorphism, was significantly associated with the risk of premature CHD. Patients with CHD had a higher mean serum LDL cholesterol/HDL cholesterol ratio than controls (3.15±1.30 vs 2.72±0.98, P < 0.05), but no significant associations between the common apo gene polymorphisms and serum lipid levels were disclosed in either group. It is possible that other genetic loci than those proposed to be associated with accelerated atherosclerosis may be more important as risk factors of symptomatic CHD at the age of 40 years.     

Growth of legionella and other heterotrophic bacteria in a circulating cooling water system exposed to ultraviolet irradiation

The effect of ultraviolet irradiation on the growth and occurrence of legionella and other heterotrophic bacteria in a circulating cooling water system was studied. Water of the reservoir was circulated once in 28 h through a side-stream open channel u.v. radiator consisting of two lamps. Viable counts of legionellas and heterotrophic bacteria in water immediately after the u.v. treatment were 0—12 and 0·7—1·2% of those in the reservoir, respectively. U.v. irradiation increased the concentration of easily assimilable organic carbon. In the u.v. irradiated water samples incubated in the laboratory the viable counts of heterotrophic bacteria reached the counts in reservoir water within 5 d. The increase in viable counts was mainly due to reactivation of bacterialcells damaged by u.v. light, not because of bacterial multiplication. Despite u.v. irradiation the bacterial numbers in the reservoir water, including legionellas, did not decrease during the experimental period of 33 d. The main growth of bacteria in the reservoir occurred in biofilm and sediment, which were never exposed to u.v. irradiation.     

Fc receptor endocytosis is controlled by a cytoplasmic domain determinant that actively prevents coated pit localization

Macrophages and B-lymphocytes express two major isoforms of Fc receptor (FcRII-B2 and FcRII-B1) that exhibit distinct capacities for endocytosis. This difference in function reflects the presence of an in-frame insertion of 47 amino acids in the cytoplasmic domain of the lymphocyte isoform (FcRII-B1) due to alternative mRNA splicing. By expressing wild type and mutant FcRII cDNAs in fibroblasts, we have now examined the mechanism by which the insertion acts to prevent coated pit localization and endocytosis. We first identified the region of the FcRII-B2 cytoplasmic domain that is required for rapid internalization. Using a biochemical assay for endocytosis and an immuno-EM assay to determine coated pit localization directly, we found that the distal half of the cytoplasmic domain, particularly a region including residues 18-31, as needed for coated pit-mediated endocytosis. Elimination of the tyrosine residues at position 26 and 43, separately or together, had little effect on coated pit localization and a partial effect on endocytosis of ligand. Since the FcRII-B1 insertion occurs in the membrane-proximal region of the cytoplasmic domain (residue 6) not required for internalization, it is unlikely to act by physically disrupting the coated pit localization determinant. In fact, the insertion was found to prevent endocytosis irrespective of its position in the cytoplasmic tail and appeared to selectively exclude the receptor from coated regions. Moreover, receptors bearing the insertion exhibited a temperature- and ligand-dependent association with a detergent-insoluble fraction and with actin filaments, perhaps in part explaining the inability of FcRII-B1 to enter coated pits.     

Long-term needle litterfall of a Scots pine Pinus sylvestris stand: relation to temperature factors

Summary Needle litterfall of a Scots pine was caught over 24 years (1962–1986) with litter-traps in a Scots pine stand in southeastern Finland. The age of the trees averaged 111 years in 1962. The stand was naturally recruited and only minor silvicultural treatments occurred during its history. Litterfall showed great year-to-year variation, the minimum being 18 g/m² (in 1968) and maximum 213 g/m² (in 1973). There was no overall trend in the amount of litterfall, and the age of the stand was thus not important in determining the needle fall. We used time domain time series analysis (ARIMA) and standard climatic data (temperature, precipitation) to investigate the relationship of litterfall to climatic factors. Mean July temperature was clearly correlated with needle litterfall. High temperature in July coincided with enhanced litterfall in the same and the next year. Litterfall enhanced litterfall in the same and the next year. Litterfall increased also after high temperatures during March–April, but only in the same year. In addition to these the litterfall had a 4-year self-dependency. This is approximately the same as the mean longevity of needles in the study area. Altogether the time series model we propose covers about 90% of the variance of the original time series.     

Demonstration of laminin,a basement membrane glycoprotein,in routinely processed formalin-fixed human tissues

Summary Laminin was demonstrated by immunoperoxidase and immunofluorescence staining in sections of normal human tissues fixed in formalin and routinely processed in paraffin. Exposure of the sections to a solution of pepsin (Burns et al. (1980) Histochemistry 6773–78) revealed the antigenicity of this basement membrane glycoprotein. Sections from paraffin blocks stored for years at room temperature could be stained with this procedure. Normal human tissues, developing fetal tissues and tumors could be stained with this method. The staining patterns were similar to those seen in unfixed frozen sections. It thus appears that basement membrane components can be detected by immunohistological means from routinely processed histological samples, once the sections are pretreated with proteases. Staining for laminin could be used in embryonic studies and in histopathology to study the relation of cells to basement membranes and for the visualization of normal and abnormal vascularization.To whom offprint requests should be sent