Search PubMed⌕ Search

Biomedical subjects

P Ebbesen

Publications and source records attributed to P Ebbesen.

At least 127 records · Page 7Linked to original sources
PubMed1984

Cancer and normal ageing.

Cancer has a monoclonal origin in a pre-mitotic cell and usually a multistep pathogenesis. The initiation of tumor development and most stages in tumor progression involve point mutations, chromosomal rearrangements, and often changes in gene dosage. Simultaneously, there is continuing selection of the cell clones most resistant to growth-regulating substances and/or lacking specific immunologic markers. Normal ageing is partly pre-programmed as demonstrated by the constancy of the maximum survival time for a species under various external conditions resulting in different mean survival times. Emerging evidence of characteristic DNA changes in post-mitotic cells of old individuals may turn out to be part of the programmed changes. However, random accumulation of mutational defects in both pre- and post-mitotic cells is an unavoidable consequence of physics and therefore contributes to normal ageing and the accompanying increase in cell diversity. Cancer incidence increases with age. Firstly, because extended exposure increases the risk of inflicting the DNA changes prerequisite to oncogenesis; secondly, because the progression from one malignant cell to detectable tumor is a matter of 10-30 per cent of a species maximum life span; and thirdly, because some alterations characteristic of normal ageing increase the susceptibility to carcinogens. There probably is an overlap of etiologic/accelerating factors for cancer and ageing. Such aspects of normal ageing such as decline in DNA repair capacity and decline in cellular immune reactivity should facilitate induction and early growth of neoplasia. Age changes that counteract cancer development include (hormonal) loss of proliferative stimulation and depletion of the pool of immature cells at greatest risk.

Aged↗
PubMed1984

Infectious mononucleosis in Greenland: a disease of the non-indigenous population.

Greenland Eskimos have one of the highest incidences of nasopharyngeal carcinoma (NPC) in the world. Asian and African areas endemic for NPC show early infection with Epstein-Barr virus (EBV), and few cases of infectious mononucleosis (IM). Among 40 000 Eskimos and 10 000 Caucasians in Greenland there were 82 reported cases of IM from 1963 to 1980. Incidence rates from 1975 to 1980, age adjusted to the "world" population distribution, were 12.0 and 5.2/100 000/yr for males and females, respectively. Comparable Danish data revealed incidence rates of 97.4 and 105.1. From 1970 to 1981 Greenland hospital records verified 16 cases, of which only 2 were in Eskimos. The IM incidence in Eskimos is extremely low, and Danes living in Greenland have a comparatively much higher incidence.

Adolescent↗
PubMed1984

Susceptibility to carcinogenic effect of irradiation. Relationship to age at time of exposure.

Age at time of exposure is an important host factor influencing the subsequent cancer risk. Before completion of organogenesis, the fetus may be rather resistant, but thereafter the growing tissues of children are more susceptible than those of young adults. At greater age of adults at the time of exposure there is an increase in the subsequent absolute number of 'excess' cancer cases, but the relative risk (excess in relation to expectation) is rather constant for a given kind of radiation exposure as judged from the presently rather small number of investigations.

Adult↗
PubMed1984

Virus-associated cancers in Greenland: frequent hepatitis B virus infection but low primary hepatocellular carcinoma incidence.

The incidence of primary hepatocellular carcinoma (PHC) in Greenland between 1960 and 1981 was determined and compared with the rate of this disease in Denmark. The annual age and sex rate (per 100,000) was not significantly different (overall, 1.9 vs. 2.2) despite a large difference in the prevalence of hepatitis B surface antigen (HBsAg) and anti-HBs markers of hepatitis. On the basis of a recent report of a very strong risk of PHC among male HBsAg carriers, 4.0 cases of PHC per year were expected in male Eskimos, but only 0.2 cases per year were observed. The incidence rates of other cancers suggested to be virally associated, including nasopharyngeal carcinoma, salivary gland cancer, and carcinoma of the cervix, were all high in Greenland compared to rates for the Danish population, and these high incidence rates are in accord with the markedly higher prevalences in Greenland Eskimos of viruses with which these other cancers have been associated. Thus Greenland Eskimos do not have a high incidence of PHC despite a high prevalence of HBsAg carriers, which suggests that other carcinogenic factors in this environment may be absent or that protective factors are present.

Carcinoma, Hepatocellular↗
PubMed1984

Efficiencies of experimental designs for an illness-death model.

Disease development is described by the progressive Markov illness-death model with one disease. The efficiencies of four experimental designs are discussed: the simple survival experiment, serial sacrifice, periodic diagnosis and complete observation. The discussion is based on the 'semiparametric' assumption of piecewise-constant intensities. Simple survival experiments are shown to have very low efficiency, serial sacrifice experiments to be moderately efficient, and periodic diagnosis to be almost as efficient as complete observation. An application to the analysis of the development of leukaemia in laboratory mice is given.

Animals↗
PubMed1983

AIDS in Europe.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Seminal fluid excretion of cytomegalovirus related to immunosuppression in homosexual men.

Seminal fluid samples from 84 Danish homosexual men were successfully cultured to determine the prevalence of cytomegalovirus excretion. Ten (15%) out of 66 men positive for the antibody were found to be excreting the virus. Although the proportion excreting was inversely related to age (p less than 0.01), three men aged over 30 and with many years of homosexual experience excreted the virus. In addition, a 50 year old man with Kaposi's sarcoma excreted the virus. A further study of the ratio of T cell helpers to suppressors in the men aged over 30 and a series of age matched non-excreting homosexual control or heterosexual men showed that those excreting cytomegalovirus in their seminal fluid had statistically lower ratios (all less than 0.77) than the controls (p less than 0.05). Excretion of cytomegalovirus may be related to re-emergence of latent infection in immunosuppressed homosexual men.

Adolescent↗
PubMed1983

No male-female difference in vitro lifespan of skin fibroblasts from humans and mice.

To determine if the difference in mean survival time of males and females is related to the mechanism restricting the number of in vitro cell doublings, we established cultures of human skin fibroblasts and murine embryo cells. The maximum number of in vitro doublings was found to be very similar for the two sexes in both species. Furthermore, human cultures receiving repeated treatments with three alkylating carcinogens had the same in vivo survival as untreated controls.

Adolescent↗
PubMed1983

Decreasing leukemia risk in old AKR mice.

Leukemia incidence and survivorship were studied in 480 untreated adult female AKR mice using repeated blood testing on live animals and autopsy for diagnosis. The data were statistically analysed within the framework of a Markov illness-death model. The leukemia risk was close to zero below an age of four-five months, increased sharply to a maximum at eight-nine months, and then declined markedly. Old AKR mice therefore should be useful for studies of age dependent alterations that reduce the risk of leukemia development. The observed age-dependence of the leukemia risk is at variance with the simplest version of the multistep hypothesis. Allowing for individual tendencies for leukemia development, good correlation between expected and observed values can be obtained.

Age Factors↗
PubMed1983

Lifestyle and antiviral antibody studies among homosexual men in Denmark.

Two-hundred and fifty-nine male homosexuals (HS) of a large and a small Danish town were studied for antibodies to various virus and their statistical relationship to sex habits, drug use and other lifestyle factors. Prevalence rates against cytomegalovirus (CMV) were 86.7% of HS men from Copenhagen and 73.3% of HS men from the smaller community of Aarhus, against 30% of a control group. Antibody prevalence in homosexuals was significantly related to number of years of homosexual activity (p less than 0.0001), number of partners (p less than 0.01), nitrite inhalant use in the past year (p less than 0.01), and independently to venereal disease during the past year (p less than 0.01). Titer levels correlated with number of years of HS activity (p less than 0.001), number of partners (p less than 0.01), and independently with nitrite use in the past year (p less than 0.01). The association between lifestyle and antibodies was not detectable for VCA-IgG, VCA-IgA, VCA-IgM, and EA antibodies to Epstein-Barr virus (EBV) or for antibodies to herpes simplex virus type 1 and type 2, parvovirus and rotavirus. In a subset of 78 HS men, T-helper/T-suppressor ratio was determined. No correlation was found between level of ratio and either prevalence or titer of antibodies against CMV, EBV-components or herpes type 1 and 2.

Acquired Immunodeficiency Syndrome↗
PubMed1983

Danish children in Greenland have high Epstein-Barr virus titers.

Danish children brought to Greenland have somewhat higher mean titers of antibodies to Epstein-Barr virus than do Danish children in Denmark, although their titers are lower than those found in Eskimo children. This study presents the first evidence of increases in Epstein-Barr virus titers in migrant children.

Antibodies, Viral↗
PubMed1983

Hodgkin's disease: in vitro susceptibility of skin fibroblasts to infection with virus and to lysis by autologous lymphocytes.

Fibroblast cultures established from the skin of 16 untreated stage 1 and stage 2 Hodgkin's patients (HD) and 60 healthy controls were studied in their 3rd, 4th and 5th in vitro passage. HD cultures were similar to control cultures with respect to transformation with Simian sarcoma virus (SSV) and SV40 and with respect to interferon release. HD cultures, however, showed a depressed replication of both herpes simplex virus (HSV) type 1 and type 2. Preliminary evidence for enhanced immune interaction with fibroblasts in HD was a more frequent injury of HD than control fibroblast cultures when incubated 4 hours with autologous mononuclear leucocytes in the presence of autologous serum.

Adolescent↗