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Biomedical subjects

K Berg

Publications and source records attributed to K Berg.

At least 325 records · Page 18Linked to original sources
PubMed1987

Heterogeneity of Müller cell endfeet in the rabbit retina as revealed by freeze-fracturing.

The Müller cell membranes of the rabbit retina were investigated by means of freeze-fracturing. Orthogonal arrays of particles (OAP) were found almost exclusively where the Müller cell endfoot had direct contact with the vitreous body. In the center of the retina where the Müller cells are long and thin, the density of OAP was about 170/microns2. In the periphery where the Müller cells are shorter and thicker, the density of OAP was about 20/microns2. In this area, only half of the Müller cell endfeet were equipped with OAP. The results are discussed with respect to electrophysiological studies on the role of various K+ channels in glial cells. It is proposed that OAP might possibly represent specialized 'maxi'-K+ channels which are involved in K+ spatial buffering of the extracellular space.

Animals↗
PubMed1987

Genetics of coronary heart disease and its risk factors.

Lipoprotein parameters related to coronary heart disease (CHD) exhibit impressive heritability, and several traditional genetic marker systems are associated with lipid levels or CHD. Recent studies indicate a population-attributable risk of 28% for myocardial infarction for men below age 60 in the top quartile of Lp(a) lipoprotein levels. Thus, a high level of Lp(a) lipoprotein emerges as a major genetic risk factor for premature CHD. Studies of DNA polymorphisms at apolipoprotein loci have uncovered associations with lipid levels and genetic linkage between DNA polymorphisms at the apolipoprotein B (apoB) locus and the Ag(x) antigenic polymorphism of low density lipoprotein. This finding proves that the Ag(x) antigenic variation resides in apoB and co-assigns its locus to chromosome 2. Lipid associations of the Ag(x) polymorphism and of DNA polymorphisms at the apoB locus are internally consistent and consistent with association between Ag(x) and DNA variants. A new approach to the study of gene-environment interactions, using monozygotic twin pairs makes it possible to uncover genes that contribute to the frame within which lifestyle factors can cause changes in a clinically relevant quantitative parameter such as serum cholesterol concentration. A new concept of interaction between 'level genes' and 'variability genes' in the aetiology of atherosclerosis emerges from these studies.

Apolipoproteins↗
PubMed1987

Twin studies of coronary heart disease and its risk factors.

Traditional twin studies have resulted in higher concordance rates for premature coronary heart disease (CHD) in MZ than in DZ twin pairs. This is in agreement with strong evidence from several other studies, that genetic factors are of importance in the etiology of early onset CHD. Also, in a study of 291 Norwegian twin pairs the concordance rate for hypertension wa 0.36 in MZ and 0.08 in DZ pairs. Relationship between diseases and traditional gene markers have been extensively studied and several associations have been uncovered for CHD. Our group has developed a method to examine a possible permissive or restrictive effect of single genes on the degree of variation that environmental and/or life style factors can cause in a given parameter. This method for studying gene-environment interaction is based on the fact that MZ twins are identical with respect to genes, so that any difference between the two members of an MZ pair must necessarily be caused by environmental or life style factors. The possibility that a given gene influences the degree of variability in a parameter such as cholesterol is examined by comparing the within-pair difference in cholesterol level between MZ pairs possessing, and MZ pairs lacking the gene in question, and results of such studies will be presented. New possibilities to study restriction fragment length polymorphisms (RFLPs) at apolipoprotein loci have added a new dimension to research on genetics of CHD and hyperlipidemias. Association between apolipoprotein B, cholesterol and fasting triglyceride levels on one hand and DNA variation at the apolipoprotein B locus on the other has been found.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoproteins A↗
PubMed1987

Freshly prepared rat hepatocytes used in screening the toxicity of blue-green algal blooms.

The acute toxicity of extracts of blue-green algae was tested in freshly prepared rat hepatocytes in suspension. The results were compared with the traditional in vivo mouse bioassay. Sixty samples of natural algal blooms from freshwater lakes in Norway, Sweden, and Finland and 14 samples cultured in the laboratory were tested. The mouse bioassay revealed hepatotoxins in a large number of the algae, while neurotoxins were not found. Acute hepatotoxicity in vitro was scored by measurement of leakage of the enzyme lactate dehydrogenase (LDH) from damaged cells and of morphological changes of the cells. The correlation coefficients between mouse toxicity and LDH, mouse toxicity and morphological cell damage, and between LDH and morphological cell damage were 0.812, 0.735, and 0.882, respectively. Consequently, the rat hepatocyte toxicity test seems to be well suited for screening blooms of blue-green algae for the presence of hepatotoxins.

Animals↗
PubMed1987

The influence of secular effects and gravidity on the rate of ectopic pregnancy in a Norwegian population.

In order to assess the influence of secular effects and gravidity on the incidence rate of ectopic pregnancy, information from reproductive history questionnaires was obtained for 7804 gravid females identified through the Norwegian Twin Panel. The overall ectopic pregnancy incidence rate was 5.6 per 1000 estimated conceptions, with rates increasing for women born after 1950. Women experiencing their first pregnancy were at lowest risk for that pregnancy being ectopic. When women were stratified by whether they were born before or after 1950, gravidity still had an effect on the incidence rate of ectopic pregnancy. Conversely, year of birth was influential when stratifying by gravidity. The results obtained here suggest that the recent increase in the incidence of ectopic pregnancy is unrelated to the number of prior pregnancies.

Diseases in Twins↗
PubMed1987

The effect of perinatal screening in Norway on the magnitude of noninherited risk factors for congenital dislocation of the hip.

Several investigators have noted an increase in the rate of congenital dislocation of the hip shortly after the initiation of neonatal screening procedures. This increase has been attributed to the detection of temporarily unstable hips which require no corrective treatment. To test whether neonatal screening had low specificity, the authors obtained data on 17,145 offspring of 7,896 twins from the Norwegian Twin Panel. Information from maternal reproduction history questionnaires was available on the presence or absence of congenital dislocation of the hip, type of obstetric delivery, and parity. The reported prevalence of the disorder did indeed begin to rise sharply during the late 1950s, at which time neonatal screening started in Norway. Infants were then grouped by year of birth (born before or after 1960), and odds ratios were calculated for breech delivery and early (first or second) parity. For the pre-screening group, the odds ratio of congenital dislocation of the hip was 7.7 among children delivered by breech presentation and 2.6 among those of early parity. These values are similar to those found in other studies. In the post-screening group, the odds ratios for breech delivery and early parity were 1.5 and 1.2, respectively. Breech delivery and early parity have been consistent risk factors for congenital dislocation of the hip. Their diminished influence in the post-screening group, as well as sharply increased rates of the disorder, suggests that in Norway neonatal screening programs may have had low specificity in detecting cases that required treatment.

Cross-Sectional Studies↗
PubMed1987

Prenatal diagnosis of glycerol-kinase deficiency associated with a DNA deletion on the short arm of the X-chromosome.

Amniocentesis was performed in a woman who previously had given birth to a boy who died at 12 months of age with a diagnosis of glyceroluria and adrenal insufficiency. A high amount of glycerol (9.0 standard deviations above mean for controls) was found in the amniotic fluid. Enzyme activity of glycerol-kinase (ATP:glycerol-3-phosphotransferase, EC 2.7.1.30) in the cultured amniotic fluid cells was very low. The pregnancy was terminated and a male fetus was aborted. Examinations of DNA isolated from the fetus did demonstrate deletions of two out of 16 DNA probes mapping to the short arm of the X-chromosome. The probes failing to hybridize to DNA from the fetus were C7 (DXS28) and L1.4 (DXS68), both mapping to Xp21.3 and located terminal to the Duchenne locus.

Abortion, Induced↗
PubMed1987

Evidence for a sperm mutation resulting in Duchenne muscular dystrophy.

DNA analysis of Xp21 markers in a family with two brothers affected with Duchenne muscular dystrophy (DMD) revealed that the mutation most likely had occurred in a grandpaternal sperm. There is therefore a low risk that the maternal aunts and their daughters are carriers of the DMD gene.

DNA↗
PubMed1987

Effect of haptoglobin subtypes on serum lipid levels.

Haptoglobin (Hp) subtypes were analysed by two-dimensional high-resolution gel electrophoresis in 81 Norwegian individuals with moderate hypercholesterolemia and in 316 Norwegian control subjects. The frequencies of the genes Hp2SS and Hp2SF were higher in individuals with hypercholesterolemia than in controls but the differences did not reach statistical significance (p = 0.087). Within the control population, no effect of the different Hp subtypes was found on total serum cholesterol, triglycerides or high-density lipoprotein (HDL) cholesterol. However, in the controls a significantly higher frequency of Hp2-2 types was found among those with HDL cholesterol values in the upper quartile as compared to those with HDL cholesterol in the lower quartile. A similar phenomenon was not uncovered in analyses of total serum cholesterol or triglycerides. Our results are in agreement with others which indicate that genes belonging to the Hp polymorphism play a role in predicting an individual's total serum cholesterol level. However, our data indicate that the cholesterol effect is on the HDL rather than on the total cholesterol level.

Cholesterol↗
PubMed1987

Left-handedness in twin families: support of an environmental hypothesis.

Information on handedness, assessed as writing-hand, was collected from 197 MZ twin pairs and 203 DZ twin pairs and from their parents, spouses, and children. Associations for pairs of relatives were studied by 2 X 2 tables, computing chi squared-values and tetrachoric correlations. Correlations of about .3 were obtained for mother-offspring and sibling pairs, while for cousins the correlation was .25 (in a small sample). No other significant associations were found, not even for twins. These results suggest only a small, if any, genetic effect, and only a small environmental between family effect, most of which seems to be a maternal effect. The lack of cotwin correlations and correlations for one of the twins with her/his ordinary brothers/sisters suggest the existence of an effect specific to twins, since the correlation for pairs of ordinary siblings is significant. Conclusions drawn from twin studies alone may be biased. The frequency of left-hand writers has increased from 1% to 10% in the different age groups born during the last century in Norway. This age effect is present mainly in hand writing and not so much in handedness generally, suggesting a decrease in cultural repression against left-hand writing.

Adult↗
PubMed1987

Absorption and elimination of mannitol solution when used as an isotonic irrigating agent in connection with transurethral resection of the prostate.

12 patients were studied in connection with transurethral resection of the prostate using the intermittent technique and isotonic 5% mannitol solution as an irrigating fluid. No diuretics were given postoperatively. The serum creatinine concentrations were normal in 10 patients and slightly elevated in 2. The plasma mannitol levels were followed for four hours postoperatively. The highest concentration observed in the series was 6,275 mg/l (34.9 mmol/l) immediately postoperatively. The maximum level was observed immediately postoperatively in all patients (mean 2,140 mg/l, 11.9 mmol/l). The mean half-life of mannitol in plasma was 163 min (10 patients). The patient with the highest serum creatinine concentration preoperatively (138 mumol/l) showed a marked prolongation of the half-life (692 min). The mean intravenous fluid absorption calculated from the immediate postoperative mannitol concentrations was 0.68 l (range 0.05-1.78 l). A decrease in the serum sodium concentration was observed immediately postoperatively (mean 5.4 mmol/l, range 0-19 mmol/l). There was a correlation between the decreases in the serum sodium concentration and the simultaneous plasma mannitol concentration. There was no significant change in plasma osmolality. Mannitol elimination in urine was followed for 24 hours postoperatively in 7 patients. The mean absorbed volume of irrigating fluid was calculated from the elimination data and was found to be 0.481, which should be compared with the figure obtained from the calculation based on the immediate postoperative plasma mannitol concentration, which gave 0.49 l (mean) in the same 7 patients. This shows that, in spite of the theoretical assumptions made in the calculation of absorbed fluid volume from the plasma mannitol concentration, this method of calculation is valid.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Strategies to control cancer through genetics.

Although genetic factors may be essential in only a fraction of common cancers, it is important to identify individuals who merit genetic evaluation. The occurrence of cancer in an individual under one of the following circumstances may indicate an increased susceptibility to malignancy as a result of predisposing factors: cancer in both of paired organs, thought not to be the result of metastasis; more than one focus of cancer in a single organ (multifocal tumors); histologically similar malignant neoplasms in different parts of the same organ system; two histologically distinct cancers (multiple primary malignancies); cancer at an atypical age; at an atypical site; in the usually less often affected sex; associated with birth defects; associated with precursor lesions; in a person with immunodeficiency; or in a patient with one of the 200 Mendelian disorders where cancer is part of the clinical picture or a frequent complication. At risk are first-degree relatives of people who meet any of the above criteria. Also, a person should be considered at risk if two first-degree relatives had any form of cancer. A strategy to control cancers utilizing genetic knowledge should include such measures as: genetic counseling of individuals at risk for specific cancers because of a congenital or genetic disease in themselves or their relatives, or because of the pattern of cancer occurrence in the family; prenatal diagnosis for families with genetic conditions that predispose to cancer and are amenable to prenatal testing; surveillance of high-risk individuals to detect early manifestations of new or recurrent disease; prophylactic removal of the target organ or tissue in appropriate cases; limiting exposure of high-risk individuals to known carcinogens or supplementing diets of high-risk individuals with anticarcinogens; and educational and administrative measures to promote practical application of genetic knowledge and to increase awareness of genetic factors in the etiology of cancer. Far from all individuals who are exposed to carcinogenic factors contract cancer, and in another common disease, atherosclerosis, it is well known that there is genetically determined variation in response to environmental or lifestyle factors that can cause disease. The emerging fields of human ecogenetics and predictive testing together with research progress in medical and molecular genetics are likely to improve greatly the possibilities for utilizing genetic knowledge to control cancer.

Environment↗