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Biomedical subjects

F Kristensen

Publications and source records attributed to F Kristensen.

At least 55 records · Page 3Linked to original sources
PubMed1982

Human lymphocyte proliferation. I. Correlation between activated and proliferating T-lymphocytes.

The response of human peripheral blood lymphocytes to Con A and PHA has been analyzed by [3H]thymidine incorporation and cytofluorometry. Using the latter method, it is possible to quantitate the number of cells in the G0 phase (normal RNA and DNA content) and in the G1 phase (elevated RNA, but normal DNA content). A very high correlation is found between numbers of Con A or PHA-induced G1 cells and [3H]thymidine incorporation in healthy donors. This high correlation is found when culture medium is enriched with 10% autologous plasma or 10% AB-serum. The use of a recently developed defined serum-free medium (RPMI 1640 with albumin, alanine, transferrin, sodium selenite and zinc chloride), however, suggest that donors can be divided into two groups according to different medium requirements for PHA-stimulated lymphocytes. Because several immunoregulatory mechanisms at the level of T-lymphocytes take place in the G1 phase, it can therefore be expected that cytofluorometric analyses of lymphocytes in the various cell cycle phases may improve the interpretation of altered lymphocyte response to lectins and antigens.

Cell Cycle↗
PubMed1982

Evaluation of murine thymocyte stimulation using a defined culture medium.

The ability of RPMI 1640 enriched with FCS or AATSZ (L-alanine, BSA, human transferrin, zinc chloride, and sodium selenite) to support mitogen-induced activation (G0-G1 shift) and proliferation (G1-S shift) of thymocytes has been investigated. The two culture media were found to be equally supportive. In terms of viability, differences were detected in the number of recovered viable cells, but this could be related to alterations in adherent properties, rather than viability of the cells. For the examination of a PHA-induced proliferation, IL-1-containing suppernatants, deriving from normal or induced peritoneal macrophages, were prepared. The supportive capacity of these preparations showed no significant difference between AATSZ and FCS. Despite the excellent supportive capacity for the mitogen-stimulated thymocyte cultures, the AATSZ medium was not able to support all established cell lines tested. A T cell (MOLT 4F) and a macrophage cell line (SK 1) grew equally well in AATSZ- and FCS-enriched medium, but a B cell (U 266) and a null-cell line (Reh) did not proliferate at all. When cells from the latter two lines were cultured in AATSZ medium, they did not complete the RNA-synthesis required for DNA-synthesis, as judged by cytofluorography. From the experiments presented it is concluded that the AATSZ medium offers several advantages, such as easy standardization of culture conditions, and no essential disadvantages for studying mitogen-stimulated thymocytes in vitro. On the other hand, some lymphoid cell lines do require culture conditions that the AATSZ medium cannot provide.

Animals↗
PubMed1982

Development of a serum-free defined culture medium for lymphoblast transformation tests of mouse spleen and thymus cells.

By analysis of thymidine uptake during the first 4 h of incubation and by examining the responsiveness of unfractionated mouse spleen cells upon mitogenic or allogeneic stimulation, some serum factors of major importance for in vitro cultivation of lymphocytes have been examined. Albumin and l-alanine are essential for the maximal preservation of the in vivo-initiated lymphocyte activity during the first hours of incubation in vitro. Transferrin plays a major role in the lymphocyte proliferation, induced by mitogens in vitro, and, finally, zinc and selenium exert a clear enhancing effect on the response to an allogeneic stimulation. The AATSZ medium (RPMI 1640 enriched with l-alanine, albumin, transferrin, zinc chloride, and sodium selenite) enables a proliferation of the same magnitude as or higher than FCS medium. The kinetics are the same, and the cell viability is comparable, but standardization is much simpler with AATSZ. This is primarily because FCS binds some mitogens and contains inhibitors. Consequently, the standardization of such a culture system is dependent on variations from serum batch to serum batch. On the other hand, the current composition of the AATSZ medium promotes the sticking capacity of T lymphocytes and does not support growth of all lymphoid cell lines. Consequently, this defined medium, although not yet suitable as optimal medium for all lymphocyte functions, can advantageously be used for short-term studies of most murine lymphocyte functional and cooperation studies in vitro.

Alanine↗
PubMed1982

Age-related changes in g0-g1 transition and proliferative capacity of mitogen-stimulated murine spleen cells.

The early kinetics of mitogen-stimulated of mitogen-stimulated spleen cells from young adult and aged NMRI mice were investigated. Using RNA synthesis as measured by cytofluorometry by cytofluorometry and 3H-leucine and 3H-thymidine incorporation as parameters, it was apparent that age-related changes occur at different levels during mitogen stimulation. First, in aged mice fewer cells per 10(6) spleen cells are being activated by mitogen, and, second, fewer of the activated lymphocytes will proliferate. However, the cells which initiate synthesis of RNA, protein, and DNA apparently behave in identical manners, chronologically, as cells from young adult mice.

Aging↗
PubMed1982

Aging and immunity: decrease in interleukin-2 production and interleukin-2-dependent RNA-synthesis in lectin-stimulated and murine spleen cells.

The RNA-content of G1 cells in lectin-stimulated spleen cell cultures of young and aged NMRI mice was determined by flow cytometry. In spleen cells of aged mice a preferential decrease of G1 cells with a high RNA-content, so-called G1b cells, was found. Since, as shown in a previous report, only cells with a high RNA-content are able to proliferate and the passage of low (G1a) to high (G1b) RNA-content is interleukin-2(IL-2)-dependent, the ability of young and old spleen cells to produce IL-2 was tested. In old spleen cells a diminished production of IL-2 was found. Addition of external IL-2, however, did not increase the proliferative capacity of old spleen cells, nor did it induce more G1b cells. Thus spleens of aged mice contain cells, which can be activated by lectin, but then fail to respond to IL-2. Both decrease in IL-2 production and receptivity for IL-2 may contribute to the diminishing immune response in aging individuals.

Aging↗
PubMed1982

Effect of macrophages on the go-gl and gl-S transition of thymocytes.

Thymocytes freed of adherent cells and stimulated by mitogens yield only a poor proliferative response ([3H]-thymidine uptake). However, the activation process assessed fluorocytometrically (RNA-synthesis) is not reduced to the same extent. Addition of adherent cells caused full restoration of both activation and proliferation, whereas 2-mercaptoethanol (2-ME) restores activation completely, but proliferation only partially. Cell viability is not influenced by the absence or presence of adherent cells or of 2-ME during the first 24 hr of incubation, which is the time period used to assess cell activation. Macrophages on the other hand, can be replaced completely by the addition of 2-ME and Interleukin (IL-1), or IL-2 containing supernatants. The addition of these substances even appears to be superior, suggesting that macrophages can as well suppress as enhance the thymocyte response to mitogens. The results presented further support the current concept of the multifunctional role of macrophages: depending on the selected mitogen, it appears that only the IL-1 production is an absolute, but indirect requirement for mitogen-stimulated thymocytes, in order to proceed through the cell cycle.

Animals↗
PubMed1982

Production of prostaglandin E and an interleukin-1 like factor by cultured astrocytes and C6 glioma cells.

When treated with lipopolysaccharide (LPS), cultured murine astrocytes released significant amounts of prostaglandin E, which caused an inhibition of the in vitro proliferative response of C3H/HeJ thymocytes to mitogen. In addition, an interleukin 1 (IL 1)-like factor secreted by LPS-treated glia cell cultures and by C6 glioma cells was detected. The characterization of the factor as an IL 1-like mediator is based on the findings that the factor 1) enhances the mitogen-induced thymocyte proliferation, 2) exhibits no interleukin 2 (IL 2) activity, but 3) augments IL 2 production by mitogen-stimulated thymocytes, and 4) has a m.w. between 13,500 and 18,000 when generated in serum-free conditions. These observations suggest that astrocytes may interact with the immune system by elaborating nonspecific factors that modulate lymphocyte proliferation. This property of astrocytes may be important in the generation of specific immune responses in the brain, which is considered to be an immunologically privileged organ as it is anatomically sequestered from the immune system.

Animals↗
PubMed1981

Immunoglobulins in demyelinating lesions in canine distemper encephalitis. An immunohistological study.

The brains of 14 dogs with canine distemper encephalitis were examined with immunohistologic techniques to search for immunoglobulin in demyelinating lesions. Four types of lesions presumably representing a temporal sequence of lesion development were distinguished. Immunohistologic findings included immunoglobulin bearing lymphoid cells, amorphous Ig containing material, immunoglobulin bound to the tissue and immunoglobulin containing macrophages and astrocytes. The humoral immune response was absent or very minimal in acute lesions and very intense in chronic lesions. It was concluded that early demyelination in canine distemper encephalitis occurs in the absence of a local humoral immune response but that this response may aggravate and accelerate myelin destruction in the later stages of the disease.

Acute Disease↗
PubMed1981

Age-related changes of mitogen responsiveness in different lymphoid organs from outbred NMRI mice.

Lymphocytes from spleen, thymus and lymph nodes from individual young adult (3--4 months) and aged (26--30 months) NMRI mice were stimulated with the mitogens Con A, PHA and LPS. 24 hours later, the number of cell with increased RNA-content (G1 cells) was determined by cytofluorometry. In parallel the 3H-thymidine incorporation after 48 hours was measured for the same cell samples. Aged animals in average produced less G1 cells and incorporated less 3H-thymidine as compared to young adults. By calculating the 3H-thymidine incorporation per G1 cell, the proliferative capacity of mitogen-induced G1 cells can be estimated. These ratios are lower in aged mice as compared to young adult, suggesting that in these animals not only less cells can be activated as measured by cytofluorometry, but also from these activated cells again fewer continue the cell cycle by initiating DNA-synthesis. In response to Con A and PHA, aged mice in average produce less G1 cells in all of the three lymphoid organs tested. In response to LPS, however, the young adult produced only few G1 cells in lymph nodes and practically none in thymus, whereas in aged animals a considerable number of G1 cells was found in both organs. Corresponding results were found for the 3H-thymidine incorporation. These results indicate that in addition to the reduction of the mitogen-response an age-related change in the distribution of mitogen-responsive cells in the different lymphoid organs takes place.

Aging↗
PubMed1981

The influence of serum on lymphocyte cultures. II. Cell cycle specificity of serum action in spleen cells.

Serum exerts several effects in lymphocyte cultures, one of them being manifested very early. The presence of fetal calf serum (FCS) results in a markedly higher thymidine uptake within a few minutes, as compared with serum-free cultures. On the other hand, the uptake of uridine and other purine bases seem to be little influences by serum. Experiments comparing the uptake of thymidine into the cytoplasm or into trichloroacetic acid-precipitable material suggested that the intracellular thymidine pool increases in size when FCS is added. Using a Lineweaver--Burk plot for thymidine and uridine uptake over a 4-h period, no changes in uridine uptake were observed in the presence of FCS; on the contrary, serum induced an increased Vmax for thymidine, whereas Km remained constant. Cytofluorographic quantitation of G0 and G1 cells indicated that cells disappear more rapidly from the G1 phase in the presence of FCS. The addition of hydroxyurea to the cultures prevented this disappearance. The results taken together strongly suggest that serum contains a factor promoting the shift of G1 cells into the S phase. When a 4-h culture period was used, all sera from different species tested at low concentrations appeared to contain this activity.

Aging↗
PubMed1981

Ageing and immunity in outbred NMRI mice: lack of correlation between age-related decline of the response to T cell mitogens, the antibody response to a T-dependent antigen and lifespan in outbred NMRI mice.

Responses to different mitogens and the primary in vitro antibody response to a T-dependent antigen (SRBC) were tested in individual mice of various ages from an outbred strain (NMRI). Comparing mean values, an age-related decrease was found only for the responses to Con A and PHA but not for LPS nor for the primary in vitro antibody response to SRBC. The magnitude of the responses obtained in individual mice of the same age varied greatly. Some of the young as well as aged animals could respond very well to antigen, mitogen or both and there was a complete lack of correlation between the magnitude of individual responses to mitogen and the number of PFC produced in the in vitro antibody response to SRBC. Additionally, we investigated whether the magnitude of the immune responses measured in individual mice had any influence on their lifespan. The mitogen response and the in vitro PFC production of spleen cells from individual semi-splenectomized mice were therefore compared with their lifespan. The lifespan did not appear to be influenced by any of the immune responses measured.

Aging↗
PubMed1977

Cold hemagglutinin disease in a dog.

Cold hemagglutinin disease, a form of autoimmune hemolytic anemia caused by cold-acting erythrocyte autoantibodies, was diagnosed in a dog. Cold-acting antibodies differ from warm-acting antibodies in several ways, including temperature-dependent reactivity below 32 C. The autoantibody in this case (immunoglobulin M) was in the serum in higher than normal concentrations and was reactive at temperatures approaching freezing. The course of the disease was chronic and was characterized by cyanosis and necrosis of the body extremities. Immunosuppressive therapy with corticosteroids was successful in alleviating the clinical signs and reducing the autoantibody activity in the dog. The cause of this disorder was not determined.

Agglutinins↗
PubMed1977

A comparison of four commonly used local analgesics.

In a double-blind, cross-over, clinical study with nine probands, the efficiency parameters of four commonly used local analgesics were evaluated: 2% Carbocain with adrenaline 1:200,000, 3% Citanest with Octapressin 0.03 iu/mul, 3% Carbocain Dental, and 2% Xylocain with adrenaline 1:80,000. It was found that 3% Carbocain Dental (no vasoconstrictor content) demonstrated significantly shorter duration of analgesia than the other solutions in the soft tissues as well as in the dental pulp. 3% Citanest with Octapressin exhibited the longest soft tissue duration, but as far as duration of tooth analgesia was concerned there was no significant difference between 3% Carbocain Dental and 2% Carbocain with adrenaline. The longest duration of tooth analgesia was shown with 2% Xylocain with adrenaline; this solution also possessed the highest frequency of analgesia and extent of analgesia. All probands personally preferred injections with 3% Carbocain Dental as injection with this solution resulted in the least discomfort.

Adult↗
PubMed1977

Analysis of serum proteins in clinically normal pet and colony cats, using agarose electrophoresis.

The relative and absolute values of the electrophoretic fractions of serum proteins of 50 clinically normal cats were determined, using agarose as the supporting matrix. Six protein fractions were clearly and consistently resolved: albumin and alpha1-, alpha2-, beta1-, beta2-, and gamma-globulins. In many cats, the alpha1-, alpha2-, and beta2-fractions were each divided into 2 subfractions. Cats which lived in a research colony environment were found to have significantly increased levels of gamma-globulins as compared with the values in cats kept as house pets. The results of serum protein fractionation using this technique have been compared with the normal feline values reported in the literature.

Alpha-Globulins↗
PubMed1977

Analysis of serum proteins, using agarose electrophoresis in normal dogs and in dogs naturally infected with Dirofilaria immitis.

The electrophoretic pattern of 130 serum samples from clinically normal dogs was evaluated, using agarose as the supporting matrix. The relative mobility of each globulin fraction in relationship to the mobility of albumin was determined in 70 dogs, and nomenclature based on the mobilities (Rf values) was proposed. Biuret protein determinations were done, and relative and absolute values of each serum protein fraction were determined. Changes in the fractions of serum proteins were evaluated in regard to sex and age of the dogs and the presence of microfilariae of Dirofilaria immitis, as determined by modified Knott tests.

Alpha-Globulins↗