Jens D. Christensen

A comparative study of Mono Mac 6 cells, isolated mononuclear cells and Limulus amoebocyte lysate assay in pyrogen testing

Pyrogen induced secretion of interleukin 6 (IL-6) in Mono Mac 6 (MM6) cells was measured. The ability of the MM6 cell culture to detect pyrogens was compared to the Limulus amoebocyte lysate (LAL) test and isolated mononuclear cells (MNC). The detection limit of MM6 for lipopolysaccharide (LPS) and Staphylococcus aureus was comparable to that of MNC. Aspergillus niger and Candida albicans induced IL-6 in isolated MNC, but not in MM6. The detection limit for Salmonella typhimurium in the MM6 assay was comparable to that of the LAL assay. As expected, S. aureus and C. albicans did not show any LAL activity. A. niger and Influenza virus showed some activity in the LAL test, but could not be detected by MM6 cells. In conclusion, the MM6 assay is a good supplement to the current pyrogen assays for detection of LPS, S. aureus and S. typhimurium, but the MM6 assay could not detect A. niger, C. albicans and Influenza virus.

Interleukin-1β stimulates the release of vasopressin from rat neurohypophysis

Abstract he release of vasopressin from the isolated superfused rat neurohypophysis was measured. The electrically eveoked release of vasopressin after phasic submaximal stimulation was increased on exposure to the cytokine, interleukin-1β (44 pM). The release returned to its control level when the peptide was withdrawn. The results indicates a permissive role of interleukin-1β in the release of vasopressin.

Adrenaline influences the release of interleukin-6 from murine pituicytes: role of β2-adrenoceptors

In this study, we examined the effect of adrenaline and interleukin-1beta on interleukin-6 secretion from cultured murine neurohypophyseal cells. Cells were cultured from neurohypophyses of 3- to 5-week-old mice and experiments were performed after 13 days in culture. Interleukin-6 was measured in 24-h samples using a sandwich fluoroimmunoassay. Unstimulated cells released 19+/-3 fmol interleukin-6/neurohypophysis/24 h (mean +/- S.E.M., n = 42). Adrenaline and interleukin-1beta increased the release of interleukin-6 from the cells in a concentration-dependent manner. Incubation with adrenaline (10(-6) M) or interleukin-1beta (11 pM) induced maximal secretion of interleukin-6, resulting in a 2.2-fold and 19.8-fold increase, respectively (P<0.01). The action of adrenaline (10(-6) M) and interleukin-1beta (1.1 pM) was examined separately and together. The sum of the effect of the two compounds given alone was significantly less (P<0.05) than the effect when adrenaline and interleukin-1beta were given together. We examined the effect of the beta-adrenoceptor antagonist propranolol (3.4x10(-6) M), the beta2-adrenoceptor antagonist (+/-)-1-[2,3-(Dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methyl-eth yl)amino]-2-butanol (ICI 118551) (10(-7) M) and the beta1-adrenoceptor antagonist atenolol (10(-7) M and 10(-6) M) on the adrenaline-stimulated release of interleukin-6. Propranolol and ICI 118551 completely blocked the action of adrenaline, whereas atenolol was inactive. It is concluded that the stimulatory effect of adrenaline is mediated via beta2-adrenoceptors.

GABA receptor stimulation increases the release of vasopressin and oxytocin in vitro

The release of oxytocin and vasopressin from rat neurointermediate lobes was determined in vitro. The electrically evoked release of posterior pituitary hormones was markedly potentiated by the GABA receptor agonist, isogauvacin, an effect which was abolished by the GABAA receptor antagonist bicuculline. Spontaneous hormone outflow was not affected by the substances tested. The results suggest the existence of a GABA receptor on the terminal fibres in the pituitary, facilitating the release of oxytocin and vasopressin.

Endospores of B. subtilis are pyrogenic and activate Mono Mac 6 cells: importance of the CD14 receptor

The monocytic cell line Mono Mac 6 is sensitive to pyrogens and interleukin-6 secretion is induced after exposure to pyrogens. The aim of this study is to examine the pyrogenic activity and the interleukin-6-inducing capacity of the Gram-positive B. subtilis bacteria, endospores and isolated cell wall components. Furthermore the involvement of CD14 in activation of interleukin-6 release is investigated. All test substances are pyrogenic in the rabbit pyrogen test. The test substance is incubated with monocytic cells (Mono Mac 6) for 24 h and the secreted interleukin-6 is determined in a sandwich immunoassay. B. subtilis bacteria and endospores induce interleukin-6 in a dose-dependent manner. Endospores are less potent than bacteria. Lipoteichoic acid (LTA) isolated from B. subtilis induces interleukin-6 in a dose-dependent manner, whereas muramyl dipeptide (MDP) is unable to induce interleukin-6. Lipopolysaccharides (LPS) dose-dependently induce interleukin-6 release, but the curve differs from that of LTA both in shape and offset. The interleukin-6 secretion induced by LPS, LTA and B. subtilis bacteria can be blocked by 73-85% by an antibody directed against CD14, whereas the antibody only blocks 25% of B. subtilis endospores-induced interleukin-6 release. The results might indicate that B. subtilis endospores use an additional pathway to CD14 to activate mononuclear cells.

Ultrasonication of pyrogenic microorganisms improves the detection of pyrogens in the Mono Mac 6 assay

The monocytic cell line Mono Mac 6 is sensitive to pyrogens. When exposed to pyrogens secretion of interleukin-6 is induced. However, some eukaryotic pyrogenic microorganisms are not detectable. The aim of this study is to introduce a pretreatment of samples to expand the detection range of the assay. The interleukin-6 inducing capacity of a broad spectrum of UV-killed and ultrasonicated microorganisms is examined in Mono Mac 6 cells. The interleukin-6 secretion is determined in a sandwich immunoassay (DELFIA). The Mono Mac 6 assay is able to detect UV-killed Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium, but neither Candida albicans nor Aspergillus niger. After ultrasonication of the microorganisms it is possible to detect C. albicans and A. niger. The interleukin-6 inducing ability of the examined microorganisms is in no case reduced after ultrasonic treatment. However, ultrasonication of S. aureus results in a 100-fold increase in the interleukin-6 response. Even after ultrasonication Streptococcus faecalis can not be detected. Ultrasonication is an easy and simple method for expanding the detection range in the Mono Mac 6 assay.

Biphasic effect of a κ-opioid receptor agonist on plasma oxytocin levels in rats

Abstract The effect of the κ-opioid receptor agonist, bremazocine, on plasma oxytocin leves in rats was measured by a sensitive radioimmunoassay. Initially, a decrease in plasma oxytocin levels was seen 30 min after injection. This was in accordance with the bremazocine inhibition of oxytocin release after submaximal electrical stimulation seen in isolated neurointermediate lobes. The initial decrease in plasma oxytocin reverse, and 4 h after injection of bremazocine a 20-fold increase in the oxytocin level was seen. The rise in plasma oxytocin was paralleled by a rise in plasma sodium. The biphasic time course of the plasma oxytocin response can be explained by a combination of an inhibition of oxytocin release from the neurohypophysis and an increased water excretion leading to an elevation in plasma sodium, which may be responsible for the late rise in plasma oxytocin. Down-regulation of the opioid receptors may also contribute to the delayed rise in plasma oxytocin.

Disulfiram treatment of three patients with nickel dermatitis

Diethyldithiocarbamate chelates nickel and accelerates its excretion in the urine. Disulfiram (Antabuse®) splits into two molecules of sodium diethyldithiocarbamate after absorption. Oral administration of disulfiram tablets starting with 50 mg a day with a gradual increase in dosage to 100 mg not more than twice a day readily cleared the eczema in three patients with severe and long‐standing nickel contact dermatitis.

Endotoxin-Stimulated Release of Cytokines by Cultured Cells from the Murine Neurohypophysis: Role of Dexamethasone and Indomethacin

It is well established that many cell types produce inflammatory cytokines and we were interested to see whether cells in the neurohypophysis had this ability. This study examines the effect of lipopolysaccharide (LPS) on cytokine production in cultured murine neural lobe (NL) cells. Cells were cultured from the neurohypophysis of mice not older than 5 days and the experiments were performed after 12 days in culture. The majority of cells in culture were immunoreactive for glial fibrillary acidic protein, indicating that the cells were pituicytes. Cytokines were measured in 24-hour samples using commercial ELISA kits. Cells growing in a medium free of endotoxin released 94.3 ± 6.6 pg IL-6/NL/24 h (mean ± SEM, n = 21). The release of interleukin-6 (IL-6) was reversible and increased concentration dependently with LPS in the concentration range of 0.1–1 ng/ml. The addition of 1 ng/ml LPS increased the IL-6 release 12-fold to a maximum value of 1,134 ± 85.5 pg IL-6/NL/24 h (mean ± SEM, n = 6). No trace of interleukin-1β (IL-1β) (<3 pg/NL/24 h) or tumor necrosis factor-α (<10 pg/NL/24 h) was detected after LPS stimulation. We examined the effect of dexamethasone (10–6 M) and indomethacin (10–4 M) on the release of IL-6 in submaximally stimulated cells. Dexamethasone inhibited the unstimulated and the LPS-stimulated release of IL-6 by 70 and 81%, respectively. Indomethacin had no influence on the release, and it is concluded that cyclooxygenase is not involved in the response. A close association exists between the membrane of the neurosecretory endings and the pituicytes in the neurohypophysis. This naturally raises the question as to whether IL-6 might reflect a physiological connection between the two cell types.

Dihydropyridine ligands influence the evoked release of oxytocin and vasopressin dependent on stimulation conditions

The effects of dihydropyridine ligands on the electrically evoked release of neurohypophysial hormones from isolated, rat neurointermediate lobes were investigated as a function of all combinations of two pulse widths (0.2 and 2 ms) and three stimulation frequencies (6.5, 13 and 30 Hz). The dihydropyridine agonist (S)-(+)-202-791 potentiated concentration dependently the release of both oxytocin and vasopressin at a pulse width of 2 ms and a frequency of 6.5 Hz. This effect of (S)-(+)-202-791 was abolished by the antagonist (-)-nitrendipine and stereospecifically by (R)-(-)-202-791 (only vasopressin). The antagonist (R)-(-)-202-791 alone inhibited the release of oxytocin at 13 Hz and 2 ms. The results presented show that the effects of the dihydropyridine ligands are dependent on the stimulation conditions, and thus demonstrate that the entry of Ca2+ through the dihydropyridine sensitive L-type Ca2+ channel is associated with electrically evoked release of neurohypophysial hormones under certain conditions.