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Biomedical subjects

H van Dijk

Publications and source records attributed to H van Dijk.

97 records · Page 6Linked to original sources
PubMed1978

Evidence for the involvement of corticosterone in the ontogeny of the cellular immune apparatus of the mouse.

The effects of corticosterone deprivation in the cellular immune system of the mouse have been studied. Adrenalectomy was performed from three weeks after birth; at an earlier age oral administration of aminoglutethimide phosphate (AGP) had to be used. Three effects could be recognized: (1) Adrenalectomy or AGP treatment, at any age studied, resulted in an enhanced delayed hypersensitivity (DH) to sheep red blood cells (SRBC). This effect has previously been ascribed to monocytes. (2) An altered T lymphocyte distribution was observed as consequence of early adrenalectomy or continuous AGP administration. The lymph nodes were depleted whereas the thymus was increased in size and blood-leucocytes increased in number. This effect appeared reversible on restoration of adrenal function. (3) Irreversible damage to the cellular immune system following early AGP intake was observed in DH after recovery of the adrenal function. As corticosterone is the principal glucocorticoid produced by mice the effects described under (2) and (3) may be ascribed to this hormone. Our results suggest that thymic involution during life, is at least partially, under adrenal control.

Adrenal Glands↗
PubMed1975

Oxisuran and immune reactions: mediation of oxisuran action by the adrenal glands.

Oxisuran was tested in a TAR system and for the DH on SRBC. Besides immunosuppressive properties in the TAR and DH also mentioned by other authors, stimulation was found after prolonged administration. No effect of oxisuran on the humoral response was observed. The action of oxisuran was suggested to be indirect, effected by stimulation of the PAG system. Adrenalectomy of mice made animals non-liable for oxisuran action measured in the TAR assay. Oxisuran caused an increase of the corticosterone plasma level with a peak after four daily injections. This was paralleled by a peak in adrenal gland weight and a minimum in thymus size. The reduction in these effects after five injections (tachyphylaxis) suggest that a feedback mechanism is involved. Comparison of thymus weights after oxisuran and corticosterone administration indicates that a daily dose of 100 mg oxisuran/kg corresponds with 1.5 mg corticosterone/kg. The effects of oxisuran in the TAR and on the DH and the feedback phenomenon could be imitated with 1.5 mg corticosterone/kg. The mononuclear phagocyte has been proposed as the main target cell of oxisuran action, mediated by the PAG system.

Adrenal Glands↗
PubMedDate not supplied

Immunomodulatory activity of an aqueous extract of Azadirachta indica stem bark.

The interference of an aqueous extract of the stem bark of Azadirachta indica with different parts of the human immune system was investigated. The extract showed strong anticomplementary effects which were dose-and time-dependent and most pronounced in the classical complement pathway assay. Moreover, a dose-dependent decrease in the chemiluminescence of polymorphonuclear leukocytes was observed and a dose-dependent increase in the production of migration inhibition factor by lymphocytes.

Adjuvants, Immunologic↗
PubMedDate not supplied

Two functionally and chemically distinct immunomodulatory compounds in the gel of Aloe vera.

An aqueous extract of Aloe vera gel was analyzed guided by modulatory activity with regard to the in vitro activation of human complement and of human polymorphnuclear leucocytes (PMN). Upon ultrafiltration a high (h-Mr) and a low (l-Mr) molecular mass fraction were obtained. Pre-incubation of human pooled serum with the h-Mr fraction resulted in a depletion of classical and alternative pathway complement activity. In contrast, only the l-Mr fraction could inhibit the production of free oxygen radicals by activated PMNs. The latter activity cannot be attributed to non-specific effects like toxicity, interference with stimulant binding or scavenger activity.

Adjuvants, Immunologic↗
PubMedDate not supplied

In vitro immunosuppressive activities of recently developed anthracycline cytostatics.

The effects of a series of seven anthracycline cytostatics on various human leukocyte functions, namely the production of Migration Inhibition Factor (MIF) by lymphocytes and the production of chemiluminescence by activated polymorphonuclear leukocytes (PMNs), as well as on classical and alternative pathways of activation of human complement were investigated. In addition, lipophilic and electrochemical properties of the compounds were determined, by measuring their High Performance Liquid Chromatography (HPLC) capacity ratio (k') and half-wave reduction potential (E1/2). The antitumor agents under investigation suppressed, in most cases, lymphocyte and PMN functions, whereas complement activity remained unaffected. The extent of suppressive effects showed a good correlation with the lipophilicity of the compounds, while no correlation with reduction potentials was found.

Antibiotics, Antineoplastic↗