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N Obel

Publications and source records attributed to N Obel.

At least 73 records · Page 4Linked to original sources
PubMed1992

Staphylococcus albus-induced protein kinase C translocation in human neutrophils: the effect of opsonization, cytochalasin B, pertussis toxin, intra- and extracellular calcium, and R59022.

Membrane-associated protein kinase C has been proposed to be essential in transmembrane signalling systems activating neutrophils. A main function of the neutrophil is phagocytosis and killing of microorganisms. Nevertheless, previously published reports mainly have described the effect of artificial or soluble stimulators upon neutrophil protein kinase C activity. Therefore, membrane-associated protein kinase C was studied in neutrophils stimulated by Staphylococcus albus. The bacteria were found to induce a striking increase in membrane-associated protein kinase C, an effect which depended upon a previous opsonization of the bacteria. Cytochalasin B, which inhibits phagocytosis, was shown to abrogate S. albus-induced protein kinase C translocation. Chelation of intracellular calcium totally abolished S. albus-induced protein kinase C translocation, a phenomenon that could not exclusively be ascribed to chelation of extracellular calcium. The diacylglycerol kinase inhibitor R59022, which has been reported to increase endogenous diacylglycerol accumulation, nearly doubled the effect of S. albus upon membrane-associated protein kinase C. Pertussis toxin in concentrations which completely inhibited fLMP-induced superoxide generation did not affect S. albus-induced protein kinase C translocation. It is concluded that phagocytosis of S. albus is accompanied by a translocation of protein kinase C to the cell membrane, a phenomenon that relies upon enhanced diacylglycerol production and calcium transients and occurs independently of pertussis toxin-inhibitable G-proteins.

Biological Transport↗
PubMed1991

Possible importance for laminitis research of recent studies on substances influencing the differentiation of cultured keratinocytes.

After a survey of the state of laminitis research the authors conclude that none of the present concepts of the pathogenesis of laminitis unequivocally explains the basic clinical and morphological observations in this disease. There is therefore reason to consider the advances that have been made during the last decades in respect to the influence of various substances on the differentiation of cultured skin keratinocytes. The technique is available for studying hoof keratinocytes in a comparable way. Relevant literature on cultured skin keratinocytes is surveyed. Some of the results from experimental studies on skin keratinocytes have an obvious connection with observations in laminitis, a fact which has led the authors to hypothesize that laminitis may be a "multifactorial" disease and that it may be provoked by agents stimulating multiplication of hoof keratinocytes with consequent reduction of differentiation.

Animals↗
PubMed1990

Distribution of labelled cysteine and methionine in the matrix of the stratum medium of the wall and in the laminar layer of the equine hoof.

The distribution of 35-S-labelled cysteine and methionine in the epidermis of the equine hoof following 2 hours of intra-arterial injection was studied by microautoradiography. Material for autoradiography was obtained by biopsy about 1 hour after termination of the intra-arterial injection and also 10 and 40 days later. In the specimens obtained one hour after the injection of labelled cysteine and methionine, the amount of radioactivity in the matrix and in the most proximal part of the laminar layer was very high. There was a clear difference between the distribution of the two labelled amino acids in the keratinizing epidermis of the hoof. Cystine was located mainly in keratinocytes of the keratogenous zone in the matrix and in the nucleated keratinocytes that formed the incompletely keratinized basal part of the primary epidermal laminae and covered the lateral surface of the outer, fully keratinized part of those laminae. Methionine was located mainly in the stratum basale and in the stratum spinosum of the matrix and in the secondary epidermal laminae of the laminar layer. In the specimens obtained 10 days after injection of labelled cysteine a considerable number of keratinocytes, both in the matrix and in the laminar layer, had attained terminal differentiation with residual labelling. Neither in the cysteine specimens obtained after 40 days or in the methionine specimen obtained after 10 days was radioactivity significantly above the basal level observed in the hoof epidermis. The possible importance of the results for research on the pathogenesis of laminitis and on the growth of the hoof is discussed.

Animals↗
PubMed1990

Cultivation of tissue from the matrix of the stratum medium of the equine and bovine hoof walls.

Explants from the matrix of the stratum medium of the wall of the equine and bovine hoof each were cultured on a microporous membrane, using a standard culture medium. After incubation at 37 C, the outgrowth was a mixture of keratinocytes and fibroblasts, with predominance of the latter. After incubation at 34 C, the keratinocytes dominated, covering the lateral surfaces of the explant as well as the basal surface. Lateral outgrowth of keratinocytes was observed at the borderline of the original epidermis and at the borderline of the explant's contact with the membrane. Epithelial outgrowth from the former consisted of rounded aggregates protruding into the medium, whereas outgrowth from the latter formed a pluristratified carpet occupying a considerable part of the membrane. In the outer layers, keratinocytes covering the cut surfaces of the dermis of the explant had a differentiation pattern of the kind that characterizes the keratinocytes of the hoof; differentiation was not observed in the lateral outgrowth.

Animals↗
PubMed1989

Sampling of lymph from lymph vessels afferent to the supramammary lymph gland in the cow.

A technique for catheterization of a lymph vessel afferent to the supramammary lymph gland in the cow is described. The operation was made with the cow under general anaesthesia. The lymph vessel was catheterized with a 30 cm long heparinized polyethylene catheter with an external diameter of 2.5 to 3 mm. Generally at least 5 ml of lymph could be collected within a period of 3 to 5 minutes. In 11 out of 15 cows lymph could be collected for 7 days or longer.

Animals↗
PubMed1986

Concentrations of penicillin, streptomycin, and spiramycin in bovine udder tissue liquids.

Concentrations of benzylpenicillin and spiramycin adipate were determined in bovine plasma and milk and in lymph draining the udder tissue after IM or IV administration. Combined benzylpenicillin and dihydrostreptomycin sulfate concentrations were also determined in the same fluids after intramammary injection. A superficial parenchymal lymph vessel, afferent to the supramammary lymph gland of the left quarters, was cannulated with a polythene catheter from which the lymph was allowed to drain freely. After injections of 9.5 mg of benzylpenicillin/kg of body weight IM, a mean peak concentration (PC) in lymph (3.7 micrograms/ml), constituting 77% of the PC in plasma (4.8 micrograms/ml), was obtained 0.5 to 1 hour after PC in the plasma. The benzylpenicillin lymph concentration was close to that in plasma for about 7 hours after injection. Thereafter, the benzylpenicillin lymph concentration continued to exceed that in plasma, but not that in milk. After IV administration of spiramycin adipate, the lymph concentration was almost identical to that in plasma. After intramammary injection of procaine benzylpenicillin (400 mg), in combination with the same amount of dihydrostreptomycin sulfate, into 2 udder quarters each, mean PC in the lymph of 3.5 micrograms/ml and 8.4 micrograms/ml, respectively, were obtained 6 hours after injection. In plasma, the mean PC of benzylpenicillin (0.07 micrograms/ml) and of dihydrostreptomycin sulfate (0.85 micrograms/ml) were obtained after 4 and 6 hours, respectively. In milk from the nontreated quarters, a mean concentration of 5 ng of benzylpenicillin/ml was obtained, whereas dihydrostreptomycin sulfate (greater than or equal to 0.3 microgram/ml) was not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

A new surface marker on equine peripheral blood lymphocytes. I. Subpopulations of lymphocytes with receptors for Helix pomatia A hemagglutinin (HP).

Untreated and neuraminidase-treated equine peripheral blood lymphocytes were analysed for binding of the A hemagglutinin of the snail Helix pomatia (HP). For optimal staining by direct immunofluorescence, the concentration of neuraminidase had to be increased as compared to that needed for other species. Moreover, higher concentrations of HP were required for optimal staining of equine lymphocytes as compared to lymphocytes from other species. Even so, the maximal number of equine lymphocytes exhibiting positive staining was only about 20%. No, or very few, HP-positive lymphocytes were seen when neuraminidase treatment was omitted. However, when the more sensitive method of indirect immunofluorescence was used, approximately 60% of the lymphocytes were HP positive without prior treatment with this enzyme. Neuraminidase treatment significantly increased this figure to about 75%. In all instances, HP binding was specific since it was inhibited by the competitive sugar hapten N-acetyl-D-galactosamine (D-GalNAc) while addition of D-glucose (D-Glc) gave no inhibition. HP binding to neuraminidase-treated lymphocytes was also investigated quantitatively by means of 125I-labeled HP. The number of HP molecules bound per HP-positive cell was approximately 3 X 10(5) and the apparent association constant for the binding of HP to its cellular receptors was approximately 8 X 10(7) 1/mol. No binding of HP to untreated lymphocytes could be recorded in these experiments.

Animals↗
PubMed1985

A new surface marker on equine peripheral blood lymphocytes. II. Characterization and separation of purified blood lymphocytes with receptors for Helix pomatia A hemagglutinin (HP).

In a preceding report we have shown that the lectin Helix pomatia A hemagglutinin (HP) binds to two subpopulations of neuraminidase-treated equine peripheral blood lymphocytes (PBL), constituting about 20% and 75% of PBL, respectively. The aim of the present study was to further characterize these HP+ cells in regard to other surface markers such as receptors for guinea pig erythrocytes (GPR+ cells), membrane-bound immunoglobulins (sIg+ cells), receptors for activated complement (C3R+ cells) and receptors for IgG (Fc alpha R+ cells). This was done by double marker analysis and by lymphocyte fractionation either on columns charged with HP coupled to Sepharose beads or by rosetting with guinea pig erythrocytes. The fractions were also analysed for their proliferative response in the mixed lymphocyte tumor cell interaction (MLTC) assay and to the mitogens leucoagglutinin (La) and concanavalin A (Con A). The results revealed that the majority of GPR+ cells also expressed high avidity receptors for HP, as defined by means of direct immunofluorescence. These cells constituted a subpopulation of GPR+/HP+ cells T cells comprising approximately 20% of PBL. In contrast, about 75% of the HP+ cells in indirect immunofluorescence were GPR-. The fractionation experiments showed that HP+ and GPR+ cells were probably not B cells since they were sIg-. The C3R+ and Fc alpha R+ lymphocytes were heterogeneous in regard to HP receptors but the majority of these cells was also found in the fractions depleted of HP+ and GPR+ lymphocytes. The fractions eluted from HP columns gave a strong proliferative response in MLTC, whereas fractions depleted of HP+ cells responded poorly. However, in contrast to the GPR+-depleted fractions, those enriched in GPR+ lymphocytes responded poorly to the T cell mitogens La and Con A. The mitogenic response of the HP-column fractions to La and to Con A was variable. The results are discussed in relation to HP being a surface marker for a heterogeneous population of equine T cells.

Animals↗
PubMed1985

Natural cytotoxicity of human lymphocytes against equine target cells in vitro.

Human lymphocytes displayed a frequent natural cytotoxicity (NK) in vitro against normal equine dermal fibroblasts (ED) and against equine tumour cells of a virus-containing cell line (Mc-1). Similarly, human normal sera contained antibodies that induced antibody-dependent cellular cytotoxicity (ADCC) by normal human lymphocytes against the same target cells. Both NK and ADCC varied for different donors. For individual donors, however, cytotoxicity against the two target cells was significantly correlated both in NK and ADCC. For ED there was also a significant correlation between ADCC and NK activity. Both NK and ADCC showed some selectivity as assessed by cold target cell inhibition. Inhibition studies with Fab fragments of anti-human IgG established the involvement of immunoglobulins in the NK reaction. In this context, a marked and mainly immunoglobulin-dependent increase in both NK and ADCC activity against Mc-1 was observed in a laboratory worker frequently exposed to the target cells. The results indicate that variations of natural cytotoxicity in individual donors may sometimes be an indication of an ongoing spontaneous sensitization.

Animals↗
PubMed1985

Incorporation of L-75Se-cystine in tissue fragments from the matrix of the hoof and the claw--a tool for studying the pathogenesis of laminitis?

An in vitro method has been designed and used to study the incorporation of 75Se-cystine into matrix fragments from hooves and claws of healthy horses and cattle. Tissue fragments from the zone of keratinisation were incubated with L-75Se-cystine in a tissue culture medium for 4 to 6 h, during which time there was continuous incorporation of the labelled selenocystine. The incorporation was greatly decreased by adding L-cystine to the incubation mixture. It is concluded that the incorporation of 75Se-cystine depends on the presence of a specific receptor for cystine in the tissue fragments studied. The possible application of the method to studies of the pathogenesis of laminitis is discussed.

Animals↗