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Biomedical subjects

K Berg

Publications and source records attributed to K Berg.

At least 343 records · Page 19Linked to original sources
PubMed1986

Lp(a) lipoprotein as a risk factor for myocardial infarction.

The Lp(a) lipoprotein is structurally related to low-density lipoprotein but is found in lower plasma concentration. It has been associated with coronary disease in several white populations. To test the generalizability of this association, we measured serum Lp(a) by quantitative immunoelectrophoresis in 303 Hawaiian men of Japanese ancestry with a prior myocardial infarction (MI) and in 408 population-based controls. Mean values were 17.1 and 13.7 mg/dL (0.171 and 0.137 g/L), respectively. Increased risk for MI was shown mainly for men in the upper quartile of the Lp(a) lipoprotein distribution (greater than or equal to 20.1 mg/dL [greater than or equal to 0.201 g/L]). Odds ratios at younger than 60, 60 to 69, and 70 years of age or older were 2.5, 1.6, and 1.2 times those for men in the lower three quartiles, respectively. In a multiple logistic model the association with MI remained significant and was not explained by differences in total cholesterol levels, high-density lipoprotein or low-density lipoprotein cholesterol levels, subscapular skin fold, systolic blood pressure, history of smoking, alcohol consumption, or age. We conclude that Lp(a) is an important attribute that should often be considered when coronary heart disease risk is assessed.

Aged↗
PubMed1986

Genetic linkage between the antigenic group (Ag) variation and the apolipoprotein B gene: assignment of the Ag locus.

The antigenic group (Ag) system of homospecific human serum antigens of low density lipoprotein is detected by antiserum from multiply transfused patients. A complex series of common Ag alleles has been described, but the biochemical nature of this polymorphism is uncertain. Here we report that DNA polymorphisms at the human apolipoprotein B (apoB) locus are very closely linked to alleles of the Ag system. We also show a strong association between Ag(x) and a polymorphism detected with the restriction endonuclease Xba I. We conclude that the immunologically determined Ag system represents protein polymorphism of apoB rather than primary genetic differences in posttranslational processing or lipid binding. These studies therefore demonstrate that the Ag locus is located on the short arm of human chromosome 2 in the region p23-p24 to which the apoB gene has been assigned. Since the Ag(x) antigen is associated with altered plasma lipid levels, this determinant may indicate a functionally important domain of apoB.

Apolipoproteins B↗
PubMed1986

Use of freshly prepared rat hepatocytes to study toxicity of blooms of the blue-green algae Microcystis aeruginosa and Oscillatoria agardhii.

Extracts from blue-green algal blooms (Microcystis aeruginosa and Oscillatoria agardhii) from different lakes in southeastern Norway were tested for toxicity toward freshly prepared rat hepatocytes. The toxicity effects were scored by means of morphological studies of the cells and by measuring leakage of the enzyme lactate dehydrogenase (LDH) from the cells. The results with the hepatocytes correspond well with results from the traditional mouse bioassay, concerning both ability to distinguish between toxic and nontoxic samples and estimation of relative toxicity. Morphological changes due to toxic effects on the plasma membrane appeared earlier than leakage of enzyme from damaged cells. The results indicate that the hepatocyte-toxicity assay system might be well suited for screening purposes concerning water contamination by blue-green algae.

Animals↗
PubMed1986

Synergistic effects of HuIFN-gamma on 2',5'-oligoadenylate synthetase induction by HuIFN-alpha.

Human skin fibroblast cells were treated with three types of human interferon (HuIFN), alpha, beta, and gamma separately, and in series of combinations at different concentrations. The IFN-induced enzyme, 2',5'-oligoadenylate (2-5A) synthetase, which is thought to be mediating the major part of the antiviral activity, was measured subsequent to 24 h treatment. The HuIFN-gamma potentiated the induction of 2-5A synthetase elicited by either HuIFN-alpha or HuIFN-beta, but the effect was seen only at low levels, i.e., 1-10 units. At higher levels, an antagonistic effect was seen. The individual subspecies of the HuIFN-alpha from native HuIFN-alpha were purified, separated, and analyzed for their ability to induce antiviral activity in human and bovine cells together with their capacity to induce 2-5A synthetase. Of the 12 species with molecular weights between 16,950 and 22,900 daltons, one species (MW 21,800) exerted peculiar properties in that it protected human cells better than bovine--at the same IFN level--and, it induced more 2-5A synthetase in human cells than in bovine cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1986

Epitope localization of a monoclonal antibody, LO-22, with broad specificity for interferon-alpha subtypes.

A murine monoclonal antibody, LO-22, with broad cross-reactivity to human interferon-alpha (HuIFN-alpha) subtypes and some animal IFN-alpha species was found to bind less efficiently to IFN-alpha A (IFN-alpha 2a). In contrast, LO-22 bound strongly to IFN-alpha 2 (IFN-alpha 2b) and IFN-alpha 2C (IFN-alpha 2c) which differ by one or two amino acids, respectively, from IFN-alpha A; the latter has lysine at position 23 whereas the other closely related IFNs have arginine. LO-22 also bound efficiently to IFN-alpha D which is only 83% related to IFN-alpha A, but which also has arginine at position 23. These results strongly suggest that LO-22 recognizes a conserved epitope among IFN-alpha subtypes in which arginine at position 23 is involved. The specificity of a second monoclonal antibody, MT4/E4, is also reported and compared to that of LO-22.

Animals↗
PubMed1986

Effects of arm ergometry training in an adolescent with myelodysplasia. A case report.

The purpose of this article is to report the effects of arm ergometry training on upper extremity strength, body composition, and oxygen uptake in a 13-year-old adolescent with myelodysplasia. The subject trained three times a week for eight weeks at 75% of maximum heart rate. The following measurements were determined before and after the training period: maximal and submaximal heart rate and oxygen uptake, percent body fat, and peak torque of the elbow and shoulder flexor and extensor muscles. The results indicated that maximal oxygen uptake and percent body fat did not change, but maximal physical work capacity increased from 274 kg . m/min to 569 kg X m/min. Heart rate and oxygen uptake decreased at each submaximal work load, and peak torque increased an average of 22.3% for the movements tested. We concluded that arm ergometry training in an adolescent with myelodysplasia can reduce the energy cost of performing submaximal arm ergometry work.

Adipose Tissue↗
PubMed1986

DNA polymorphisms around the apo AI gene in normal and hyperlipidaemic individuals selected for a twin study.

We have investigated the allele frequencies, in a Norwegian population, of two restriction fragment length polymorphisms (RFLPs) in the apolipoprotein (apo) AI-CIII-AIV gene region. The study group consisted of clinically well twins and their unrelated spouses. In the normotriglyceridaemic individuals tested, the frequency of the rare allele (S2) of the RFLP detected using the restriction enzyme Sst I was 0.17; for the RFLP detected with the enzyme Xmn I, the rare allele (X2) frequency was 0.06. The frequency of the S2 allele was lower in individuals with serum triglyceride levels above 1.7 mmol l-1, but this was not statistically significant. Conversely, the frequency of the X2 allele was higher in individuals with raised serum triglyceride levels, but similarly, did not reach statistical significance. Taken together with the data from our previous study on UK individuals, these results support the suggestion that inherited variations in this apolipoprotein gene cluster are involved in the determination of serum triglyceride levels.

Alleles↗
PubMed1986

Increased levels of apo-transcobalamins I and II in amniotic fluid from pregnant women with previous neural tube defect offspring.

In an attempt to identify biochemical components of the genetic predisposition to neural tube defects (NTDs), levels of folate, cobalamin, apo-transcobalamins I and II and alpha-fetoprotein were studied in midtrimester amniotic fluid from 24 pregnant women who had previously had a child with NTD. The control group consisted of 76 mothers, subjected to amniocentesis for reasons other than risk of NTD in offspring. Only pregnancies with normal outcome were included. No differences were found between groups for levels of folate, cobalamin or alpha-fetoprotein. Folate intake or metabolism did not appear to differ between groups. In contrast, the level of apo-transcobalamin I was doubled and the level of apo-transcobalamin II tripled in amniotic fluid from women who had had a child with NTD compared with the control group. Since the variation in apo-transcobalamin II in adults is to a high degree genetically determined, the present results may suggest that the genetic predisposition to NTD is associated with variation in this protein. Further studies are needed to substantiate or reject this possibility.

Adult↗
PubMed1986

DNA polymorphism at the apolipoprotein B locus is associated with lipoprotein level.

A strong association has been uncovered between DNA variation at the apolipoprotein B (apoB) locus (detectable with the restriction endonuclease XbaI) and apoB level. The findings are suggestive of associations also between this DNA polymorphism and total cholesterol as well as fasting triglyceride levels, confirming recent results reported by British workers. The data suggest that lipid/apolipoprotein associations with the XbaI polymorphism are primarily caused by an effect on apoB level. In the present and in a previously reported study we found a strong association between the XbaI polymorphism and the homospecific Ag antigenic variation in low density lipoprotein (LDL) which had previously exhibited associations with lipid levels. The present data indicate that the apoB/lipid associations of the Ag and XbaI polymorphisms may reflect the same phenomenon. The associations reported could reflect variation in an apoB domain close to Ag as well as to the XbaI restriction site that is of importance for lipid binding by apoB. Alternatively, the association of apoB level with the XbaI polymorphism (which reflects a silent third base mutation in a threonine codon) could reflect phenomena related to codon usage.

Adult↗
PubMed1986

A cytotoxic substance (CTS-51) produced by human buffy coat cultures stimulated by staphylococcal enterotoxin B: further characterizations and combined action with interferon.

A recently recognized unique cytotoxic substance, CTS-51, was tested for the hear or acid stability, trypsin digestion and dialysis. Moreover, influences of elevated incubation temperatures or serum concentrations of medium on the cytotoxic activity of CTS-51, and the combination effects of CTS-51 and human leucocyte interferon (HuIFN-alpha (Le)) were investigated. The cytotoxic activity of CTS-51, which is promoted by a small molecule easily passable the dialysis membrane, was found to be very stable to heat (even at 100 degrees C for 30 min) or acid (pH 2.0 for 24 hr at 4 degrees C) treatments. The treatment with 0.75% trypsin for 1 hr did not diminish the CTS-51 activity. The susceptibility of Daudi lymphoma cells to the antiproliferative action of HuIFN-alpha (Le) was further potentiated by treating the cells with CTS-51 for 16 hr. On the other hand, the CTS-51 activity which was revealed to be prescribed by its concentration in the medium, was not potentiated at 39 degrees C when compared to that at 37 degrees C in contrast to HuIFN-alpha (Le) action, and was reduced according to the increase of the fetal calf serum concentration in the medium.

Biological Products↗
PubMed1986

Low density lipoprotein receptor determination in peripheral blood mononuclear cells: influence of differences in cell concentration.

Low density lipoprotein (LDL) receptor determination in peripheral blood mononuclear cells (PBMCs) is influenced by differences in cell concentration. As the cell concentration increases, measured LDL receptor activity decreases. This inter-relationship is caused by a PBMC-induced modification of 125I-LDL. The PBMC-modified 125I-LDL results from shedding of polyanionic cell membrane constituents that subsequently bind to 125I-LDL, and has reduced capacity of binding to the LDL receptors, to the cell membrane independent of the receptors and even to plastic. The cell membrane constituents contain sulphate, have a MW = 200,000-300,000, are heat stable and are rapidly released at 37 degrees C as well as at 4 degrees C. They probably represent a heterogeneous group of proteoglycans, glycoproteins and glycolipids. The higher the cell concentration is, the more polyanionic cell membrane constituents are released, and at high concentrations they may even form aggregates of LDL. We conclude that differences in PBMC concentration interfere with LDL receptor analyses through shedding of different amounts of polyanionic cell membrane constituents into the medium. Thus, standardisation of the experimental procedures with respect to cell number is of great importance in LDL receptor determination in PBMCs.

Cell Count↗