PubMed Health⌕ Search

Biomedical subjects

A Bruinink

Publications and source records attributed to A Bruinink.

31 records · Page 2Linked to original sources
PubMed1993

Regulation of dopamine receptors by bupropion: comparison with antidepressants and CNS stimulants.

Acute treatment of rats with the antidepressant bupropion increased [3H]spiperone binding to D2 receptors in vivo. This dose- and time-dependent effect was greatest in striatum and minimal in cerebellum and pituitary. A parallel behavioral stimulation occurred in the same rats. Among 21 antidepressants and CNS stimulants tested, only those that activate dopamine (DA) transmission had similar effects: nomifensine, amineptine, methylphenidate, D-amphetamine, amfonelic acid, cocaine, benztropine and GBR 12909. Decreasing DA transmission with reserpine plus alpha-methyl-p-tyrosine prevented the action of bupropion. Finally, bupropion was inactive in vitro and ex-vivo. Therefore, we propose that bupropion and other DA-enhancing agents modify the characteristics of [3H]spiperone binding through the intervention of a dynamic regulation of the D2 receptors by the neurotransmitter itself.

Animals↗
PubMed1991

Neurotoxic effects of chloroquine in vitro.

In order to investigate chloroquine retinopathy, the effect of chloroquine on the viability and differentiation of primary cell cultures of embryonic chick neuronal retina, retinal pigment epithelium (RPE), brain and meninges were investigated. The sensitivity of the cells, measured as reduction of viability, showed the following order: RPE greater than brain greater than meninges greater than neuronal retina. The human serum chloroquine concentration range which leads to ocular damage in vivo was identical to the concentration range in the culture medium which affected RPE viability. In addition, the differentiation of nerve cells in brain cell cultures was affected at much lower chloroquine concentrations than astroglia cells or nerve cells in neuronal retina cell cultures. Some possible mechanisms for chloroquine retinopathy were assessed.

Animals↗
PubMed1991

Ontogeny of MAP2 and GFAP antigens in primary cultures of embryonic chick brain. Effect of substratum, oxygen tension, serum and Ara-C.

Brain cells from embryonic chick (stage 28-29) were cultivated for 16 days under serum-free conditions. Nerve cells were found to mature during the first 7 days in culture, as indicated by the presence and developmental pattern of the relative amount of dendritic-specific microtubule-associated protein type 2 (MAP2). Maximal amounts of MAP2 antigen were found to be directly correlated with the number of cells plated out. Astroglia cell proliferation and differentiation, as measured by the amounts of glial fibrillary acidic protein (GFAP), were found to stabilize after a certain astrocyte cell density was reached. Variation in culture plate coating procedure, oxygen tension and addition of serum or of the cytostatic drug Ara-C were found to differently affect viability and maturation processes of astroglia and of nerve cells. Moreover, optimal culture conditions for long-term brain cell cultures are described.

Animals↗
PubMed1987

Beta-adrenergic binding sites in fetal rat central nervous system and pineal gland: their relation to other receptor sites.

Regional development of beta-adrenergic binding sites in the rat fetal central nervous system and pineal gland were studied in relation to the ontogeny of different drug and neurotransmitter binding sites. 3H-dihydroalprenolol labels the olfactory bulb very early in fetal life. A comparatively early development of binding sites is also seen for benzodiazepines during late gestation. 3H-serotonin, 3H-muscimol, 3H-GABA and 3H-(N)-methylscopolamine additionally label the olfactory bulb, revealing quite different patterns. Around gestational day 16, beta-adrenergic sites were found in the neocortex, then in choroid plexus and in the pineal gland. Besides beta-adrenergic, only 3H-flunitrazepam binding sites are detectable in the fetal eye, the latter with a more restricted regional distribution. In the fetal pineal, beta-adrenergic, muscarinic cholinergic and serotonergic binding sites appear at different times in gestation. In the neocortex a variety of binding site patterns develop. Two more general types can be distinguished: appearance along with caudorostral maturation of the brain and appearance within distinct brain regions, possibly related to local differentiation processes. The simultaneous onset of various binding sites in distinct areas of the fetal brain might result in higher sensitivity of individual brain areas to drugs.

Animals↗
PubMed1986

Detection of dopamine receptors in homogenates of rat hippocampus and other brain areas.

The binding of [3H]spiperone (24-26 pM) specifically to the dopaminergic (DAergic) D2 site has been investigated in homogenates of rat hippocampus, pineal gland and cerebellum. It was found that specific binding in hippocampal homogenates was heat-labile and for a part pH-sensitive. Like striatal tissue, binding to the dopaminergic D2 site in hippocampal and cerebellar homogenates was greatly reduced by (pre)incubation with the iron chelator o-phenanthroline. The binding characteristics in hippocampus and cerebellum have been compared to those in the striatum. In all tissues tested, low (74-138 times fewer than in striatum) but significant numbers of DAergic D2 sites were found. The DAergic D2 site in the hippocampus, as far as measured in cerebellum and pineal gland exhibited similar binding characteristics to that in the striatum.

Animals↗
PubMed1986

Catecholaminergic binding sites in cat retina, pigment epithelium and choroid.

The distribution of catecholaminergic binding sites was studied in the cat eye by measuring binding of [3H]spiperone and [3H]dihydroalprenolol in central and peripheral parts of the neural retina, in retinal pigment epithelium, and in choroid homogenates. Significant binding to beta-adrenergic sites was present in central and peripheral neural retina and choroid homogenates, whereas significant binding to dopaminergic D2 sites was found in homogenates of neural retina and retinal pigment epithelium.

Animals↗
PubMed1984

Beta-adrenergic binding sites in fetal rat brain.

The ontogeny of beta-adrenergic binding sites was studied in forebrain homogenates from male and female rats. Specific [3H]dihydroalprenolol binding was defined by the difference between binding in the presence and in the absence of 330 nM (+)oxprenolol. Significant binding was detected at prenatal stages. The dissociation constants (KD) of [3H]dihydroalprenolol binding were similar at gestational day (GD) 19 3/4 and postnatal day (PN) 31. Binding was first detected in forebrain at GD 15 3/4. The amount of binding sites increased until PN 31, when adult values were reached. No sex differences could be detected at any of the stages tested (GD 19 3/4-PN 31).

Aging↗
PubMed1984

Early postnatal development of pituitary intermediate lobe control in the rat by dopamine neurons.

In fetal and postnatal rats, serum melanophore-stimulating hormone (MSH) levels, pituitary 3H-spiperone binding, pituitary catecholamine content, and other parameters were measured to characterize the development of pars intermedia pituitary control by the tubero-hypophyseal dopamine system. Bioassay of serum for MSH revealed low but significant levels 6 days before birth (gestational day 17), rising to a peak 4 days after birth (postnatal day 5). Levels declined after PN 6, reached a low 2 weeks after birth, and then rose gradually throughout the next several weeks until adult values were attained. From excised pituitaries, significant catecholamine fluorescence in the neurointermediate lobe was first demonstrated on the 2nd postnatal day, with the highest density of fibers being attained at 2 weeks after birth. Thereafter, the density of terminals decreased in the pars intermedia until the adult pattern of innervation was observed at day 60. Total dopamine content of the neurointermediate lobe roughly paralleled the morphological observations through the first 2 weeks after birth. Later, content was seen to stabilize, while concentration decreased in line with the reduction in terminal density. Dopamine levels exceeded norepinephrine concentration by a factor of 10. 3H-spiperone binding sites were present in the pituitary before birth. Their density increased rapidly in the neurointermediate lobe during the 2 postnatal weeks, then diminished until adult densities were reached at day 30. Binding in the anterior pituitary slowly rose throughout the first 30 days after birth, although values were only about one-quarter of that found in the neurointermediate lobe. In vitro incubation of neurointermediate lobes with dopamine showed a dose-dependent inhibition of spontaneous MSH secretion as early as 2 days after birth. Blockade of dopaminergic binding sites by i.p. administration of cis-flupenthixol (1 mg/kg) to rat pups had no effect until days 8, 15, and 22 where there was a significant rise in serum MSH levels as compared with controls. These data indicate that the intermediate lobe is responsive to dopamine at around birth, while the inhibitory dopaminergic control develops only during the 1st postnatal week, in conjunction with marked changes in circulating MSH levels.

Animals↗
PubMed1984

Effects of pH and ascorbic acid on 3H-spiperone and 3H-dihydroalprenolol binding in rat forebrain homogenates.

The binding of the neuroleptic agent 3H-spiperone and the beta-blocker 3H-dihydroalprenolol (3H-DHA) was investigated in rat forebrain homogenates. The pH of the buffer medium was found to specifically affect binding to certain sites. Omission of ascorbic acid from the binding assay influenced binding in a pH-dependent way. Preincubation with a relatively low concentration of ascorbic acid markedly reduced the binding of both ligands except the nonspecific binding of 3H-spiperone. Lipid peroxidation as revealed by malonyldialdehyde formation, was increased by low and decreased by high ascorbic acid concentrations. The possible relationship between changes in number of binding sites and liposolubility is discussed.

Alprenolol↗
PubMed1983

Ontogeny of diurnal rhythms of central dopamine, serotonin and spirodecanone binding sites and of motor activity in the rat.

The binding of 3H-spiperone to its 3 high affinity sites (dopaminergic D2, serotonergic S2 and spirodecanone site) was determined in forebrain homogenates of 14,30 and 88-90 day old male rats at different times of the day. Diurnal variations were seen in the spirodecanone site from postnatal day 15, in the D2 and S2 sites at the age of 30 days. Each site showed a different diurnal rhythm, moreover, the rhythms of the D2 and S2 sites differed between immature and adult animals. Diurnal variations of motor activity were recorded at the age of 30 and 88-90 days. The two developmental stages differed with respect to the activity pattern of the dark phase. At both stages, the motor activity pattern was found to be a mirror image of the variation in D2 binding sites during the dark phase. Our data point to differences in the regulation of various neuroleptic binding sites in immature and adult animals. They further suggest a link between the dopaminergic D2 site and motor activity which is evident throughout ontogeny.

Aging↗
PubMed1983

Pre- and postnatal ontogeny and characterization of dopaminergic D2, serotonergic S2, and spirodecanone binding sites in rat forebrain.

The ontogeny of binding sites for [3H] spiperone was studied in time-pregnant rats. Binding of [3H]spiperone to fresh homogenates of pre- and postnatal rat forebrain was characterized by Scatchard analysis and competition experiments with a number of dopaminergic and serotonergic agonists and antagonists and additional substances. A convenient discrimination of three high-affinity sites, i.e., the dopaminergic D2, serotonergic S2, and spirodecanone (Sd) sites, was obtained with l-(-)sulpiride and cis-flupenthixol. The analgesic R5573 was found not to be specific for the Sd site but to interact with all three sites. The three binding sites became detectable in sequential order. S2 and D2 binding sites were first found at embryonic days 15.75 and 17.75, respectively. The Sd site did not appear before postnatal day 8. All three binding sites reached adult values at approximately postnatal day 30. During the prenatal period, the increase in the number of D2 binding sites paralleled the rise in forebrain dopamine concentrations. The kinetics of D2 and S2 sites were the same at embryonic day 19.75 and postnatal day 30. These observations provide evidence for the presence of the receptor substrate for actions of neuroleptics on dopaminergic and serotonergic systems during fetal life.

Aging↗
PubMed1979

Macrophage immunity to influenza virus: in vitro and in vivo studies.

Using M-TUR, a macrophage-adapted avian influenza A virus (Hav1, Nav3), antiviral resistance of peritoneal macrophages obtained from specifically or nonspecifically immunized mice towards in vitro infection was assessed. M-TUR grew to high titers in macrophages from nonimmune mice thereby causing a marked cytopathic effect. In contrast, peritoneal macrophages from mice specifically immunized with TUR virus were not affected by infection with M-TUR in vitro. This antiviral immunity was specific: mice immunized with antigenetically unrelated influenza strains such as influenza A/Hong Kong/1/68 (H3, N2) or influenza B/Lee yielded susceptible macrophages. Specific macrophage immunity could be abrogated by trypsin treatment in vitro. Susceptible macrophages from nonimmune hosts became resistant following in vitro exposure to homologous anti-TUR sera. Peritoneal exudate cells from BCG-infected animals were less susceptible to in vitro challenge with M-TUR than control macrophages. In vivo treatment of mice with the unspecific immunostimulants BCG or Corynebacterium parvum did not protect the animals against lethal infection with a hepatotropic variant of TUR.

Animals↗