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Biomedical subjects

G Papadopoulos

Publications and source records attributed to G Papadopoulos.

At least 73 records · Page 4Linked to original sources
PubMed1988

Mechanism of action of prothymosin alpha in the human autologous mixed lymphocyte response.

Prothymosin alpha(Prot alpha), an immunologically active polypeptide derived initially from rat thymus, and now pig thymus, was tested for its effect on autoantigen-induced human T cell proliferation in vitro. Pig ProT alpha was found to enhance the autologous mixed lymphocyte response (auto-MLR). Optimum enhancement was achieved at doses which varied among different donors. Treatment of the stimulatory monocytes with ProT alpha resulted in considerably higher auto-MLR responses as compared to those with non treated monocytes. ProT alpha was without effect on T lymphocytes. In contrast, T lymphocytes exhibited enhanced proliferative activity when treated with ProT alpha in the environment of autologous monocytes. Moreover, supernatants from cultures of monocytes incubated with ProT alpha (ProT alpha-sup) were also shown to enhance the human auto-MLR either after addition in cultures or after preincubation with responder T lymphocytes. In addition, ProT alpha-sup did not demonstrate any detectable interleukin 1 (IL 1) or interleukin 2 (IL 2) - like activity. Furthermore, ProT alpha-sup induced an increase in IL 2 production in auto-MLR cultures. The enhancement of T-cell proliferation and IL 2 production by ProT alpha-sup was maximal when this material was added at the beginning of the auto-MLR, and no effect of ProT alpha-sup was seen if the latter was added 3 days after initiation of the culture. Finally, Prot alpha-sup was also shown to increase the expression of IL 2 receptors on T lymphocytes activated in the auto-MLR. These studies suggest that ProT alpha enhances the human auto-MLR through ProT alpha-sup which is released after interaction of monocytes with ProT alpha ProT alpha-sup then increases directly T lymphocyte proliferation by elevating IL 2 production and expression of IL 2 specific receptors on autoactivated T lymphocytes.

Animals↗
PubMed1987

Retinal projections in the hedgehog (Erinaceus europaeus). An autoradiographic and horseradish peroxidase study.

The retinal projections of the hedgehog were studied using tritiated leucine and horseradish peroxidase as orthograde tracers. In both series of experiments labeling was seen bilaterally in the suprachiasmatic nucleus, the dorsal and the ventral lateral geniculate nucleus, the superior colliculus, and the pretectal area and contralaterally in the terminal nuclei (dorsal, lateral and medial) of the accessory optic system. A retino-intergeniculate leaflet projection is described for the first time in this species, and its significance is discussed.

Animals↗
PubMed1986

Thalamic projections to the posterior sylvian and posterior ectosylvian gyri of the sheep brain, revealed with the retrograde transport of horseradish peroxidase.

The auditory area of the sheep cerebral cortex was studied on the basis of its afferents from the medial geniculate nucleus, traced with the horseradish peroxidase retrograde transport method. The results show that the medial geniculate nucleus projects only to the anterior parts of the posterior ectosylvian gyrus and the posterior sylvian gyrus. A small area of the posterior ectosylvian gyrus receives afferents exclusively from the ventral part of the medial geniculate nucleus, while the anterior part of the posterior sylvian gyrus receives also afferents from the posterior nucleus of the thalamus and the pulvinar. In addition, it was found that the medial part of the medial geniculate nucleus projects in a sparse way to the auditory cortex. The middle part of the posterior ectosylvian gyrus receives afferents from the posterior nucleus of the thalamus, the suprageniculate nucleus and the pulvinar, while the posterior part of the posterior ectosylvian gyrus together with the posteriormost part of the posterior sylvian gyrus receive afferents from the pulvinar. Finally, the area located between the anterior and the posteriormost part of the posterior sylvian gyrus receives afferents from both the posterior nucleus of the thalamus and the pulvinar.

Animals↗
PubMed1986

Monoclonal antibodies against pancreatic islet-cell-surface antigens selected by flow cytofluorometry.

BALB/c mice were immunized with human islets of Langerhans, and spleen cells from two mice, found to develop cell-surface antibodies against insulin-producing rat islet tumour RIN-5F cells, were fused with mouse myeloma cells. Antibody-producing hybrids were cloned on the basis of their production of surface antibodies reactive with paraformaldehyde-fixed RIN-5F cells by indirect immunofluorescence analysis in the fluorescence-activated cell sorter. Among 236 primary clones, eight stable cell lines producing islet-cell-surface antibodies were eventually cloned. Antibody 2G3 (IgM) reacted with viable normal rat islet cells and high insulin-producing rat islet tumour RIN5-A2 cells, while 3G3 (IgM) only reacted with RIN5-A2 cells. Antibody beta B1 (IgG1) reacted with all islet cells tested and detected an Mr21k component in immunoblotting experiments with RIN-5AH cell plasma membrane proteins electrophoretically transferred to nitrocellulose filters. Antibody 7F6 (IgM) reacted with all islet and non-islet cells tested and detected bands of Mr 66k and 27k by immunoblotting. Antibodies gamma B3, gamma B6, gamma C2, and 6B1 (all IgM) showed varying degrees of binding to different islet cells, but reacted only weakly with non-islet human cells. It is concluded that monoclonal antibodies against pancreatic islet cells may define specific endocrine islet-cell-surface determinants.

Animals↗
PubMed1985

Thalamic projections to motor, prefrontal, and somatosensory cortex in the sheep studied by means of the horseradish peroxidase retrograde transport method.

In this study the motor, prefrontal, and somatosensory areas of the sheep cerebral cortex were defined on the basis of their thalamic afferents traced with the horseradish peroxidase method. The motor area (areas 4 and 6) occupies the cruciate gyrus. It receives a substantial projection from the thalamic nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and centralis lateralis and a smaller one from the nuclei ventralis medialis, centralis medialis, paracentralis, lateralis dorsalis, lateralis posterior, centromedianus, parafascicularis, suprageniculatus, ventralis posterolateralis, and the midline nuclei. Area 4 receives afferents mainly from the nuclei ventralis anterior, ventralis lateralis, medialis dorsalis, and lateralis posterior, whereas area 6 receives afferents mainly from the nuclei ventralis anterior, medialis dorsalis, and lateralis posterior and fewer afferents from the nucleus ventralis medialis. The prefrontal area occupies the gyrus proreus and receives numerous afferents from the nucleus medialis dorsalis and fewer from the nuclei lateralis posterior and ventralis medialis. The area extending between the lateral fissure, the coronal sulcus, the presylvian sulcus, and the rostral branch of the lateral fissure is connected mainly with sensory thalamic nuclei. Thalamic afferents were found to emanate from the nuclei ventralis posteromedialis (its parvicellular part included), ventralis posterolateralis, ventralis medialis, paracentralis, lateralis posterior, medialis dorsalis, centromedianus, suprageniculatus, paraventricularis, the substantia nigra, and the ventral part of the lateral geniculate nucleus. The first somatosensory area (Johnson et al., '74, J. Comp. Neurol. 158:81-108) was found to extend between the coronal, the diagonal, and the anterior suprasylvian sulci and to receive afferents almost exclusively from the nucleus ventralis posteromedialis.

Animals↗
PubMed1984

Acquisition and extinction of L-maze and conditioned avoidance behaviours following kainic acid-induced lesions of the ventromedial thalamic nuclei in rats.

Rats with kainic acid-induced lesions of the ventromedial thalamic (VMt) nucleus were compared with sham-operated controls on two behavioural tasks. The kainic acid injection resulted in loss of local neurons in the VMt nuclei with no appreciable damage to other thalamic nuclei or to other distant brain areas. VMt nuclei lesion animals learned to run in an L-maze for food reinforcement and to avoid electric foot-shock in the two way active avoidance shuttle-box procedure. Extinction of the food reinforced response was not altered by the lesion. One week retention of the acquired two-way active avoidance response was almost abolished on the animals with the lesion. Open field locomotion or escape latencies were not influenced by the lesion. It is concluded that VMt nuclei of rats are involved in the retention of aversively reinforced behaviours.

Animals↗
PubMed1984

Spontaneous in vitro immunoglobulin secretion at the diagnosis of insulin-dependent diabetes.

Blood mononuclear cells obtained from 17 newly diagnosed insulin-dependent diabetic (IDDM) patients treated with insulin for 5-7 days were assessed for the number of spontaneous and pokeweed mitogen (PWM)-stimulated immunoglobulin-secreting cells in a reverse haemolytic plaque assay. The spontaneous in vitro immunoglobulin secretion was evanescent and decreased in individual patients within 1-4 months of insulin treatment. Compared to matched controls, 53% (9/17) of the IDDM patients had an elevated spontaneous secretion of immunoglobulin, 41% (7/17) for IgG, 35% (6/17) for IgM, and 35% (6/17) for IgA. The quantities of PWM-stimulated IgG, IgM, or IgA secreting cells in IDDM were comparable to the controls. The IDDM patients with spontaneous immunoglobulin secreting cells had higher fasting C-peptide levels compared to the patients with immunoglobulin-producing cells within the normal range (P less than 0.05). The average titre of islet cell cytoplasmic antibodies was 1:26 in (9 out of 9 were positive) patients with, compared to 1:1 in patients (4 out of 8 were positive) without spontaneous secretion (P = 0.025). These results suggest that the clinical onset of IDDM is associated with a polyclonal B lymphocyte activation and that higher levels of fasting C-peptide islet cell antibodies are associated with this immunoregulatory abnormality.

Adolescent↗
PubMed1983

Turning behavior after unilateral lesion of the subthalamic nucleus in the rat.

Unilateral stereotaxic lesions of the subthalamic nucleus of rats with kainic acid induced a transient spontaneous ipsiversive turning which was present for several days, and which could be blocked by i.p. administration of haloperidol. After the 20th postoperative day, when no spontaneous turning activity was present, i.p. administration of apomorphine or amphetamine in the kainic acid lesioned rats induced ipsiversive turning, while i.p. haloperidol in the same rats induced contraversive turning. These findings suggest that the subthalamic nucleus is involved in the dopaminergic mechanisms mediating turning behavior of rats.

Amphetamine↗
PubMed1981

The influence of unilateral 6-OH-dopamine lesions of the substantia nigra in the absence of the telencephalon.

Rats were injected unilaterally into the rostral substantia nigra pars compacta with 8 micron of 6-OHDA. Those animals that conformed to be behavioral criteria for an effective nigrostriatal dopamine lesion by turning ipsilaterally to the injected side upon IP amphetamine, and contralaterally upon apomorphine injection were bilaterally detelencephalized (neocrotex, hippocampus, striatum, septum, amygdaloid complex were removed). Most detelencephalized animals exhibited spontaneous turning to the contralateral side, i.e. no longer behaved like 6-OHDA-lesioned rats, but instead, acted like animals with nigral kainic acid or electrolytic lesions. Amphetamine (2-3 mg/kg) increased general activity but no longer influenced turning. Apomorphine in doses of 2-3 mg/kg completely suppressed all motility. In small doses (0.1-0.2 mg/kg) it reversed the spontaneous contraversive turning. This effect could be blocked by haloperidol (0.1 mg/kg) pretreatment. High doses of haloperidol (5.0-7.5 mg/kg) reversed the direction of circling from contraversive to ipsiversive. Arecoline (10-12 mg/kg) induced tremor as in normal animals. Atropine (50-100 mg/kg) did not affect turning, but increased activity level in the thalamic rats.

Animals↗
PubMed1980

Removal of the telencephalon spares turning induced by injection of GABA agonists and antagonists into the substantia nigra.

Unilateral injections into the substantia nigra of GABA agonists or the GABA-related agents muscimol (5-50 ng), baclofen (10-50 ng) or B-aminobutyric acid (25-50 ug) induced intensive turning in the direction contralateral to the injected hemisphere. Intranigral injection of the GABA antagonist picrotoxin (100-500 ng) led to ipsiversive turning. Surgical removal of the whole telencephalon (including the neocortex, hippocampus, striatum, septal nuclei and amygdalae) influenced neither direction nor magnitude of the turning responses induced by these various drugs. A GABAergic system in the substantia nigra can, therefore, cause turning independent of telencephalic structures.

Aminobutyrates↗
PubMed1979

Contralateral turning after unilateral electrolytic lesion of substantia nigra in thalamic rats.

Unilateral electrolytic lesions of the substantia nigra of rats induced contralateral turning in intact as well as 'thalamic' rats (devoid of neocortex, hippocampus, striatum, amygdala, septal nuclei, including most of n. accumbens). Therefore, telencephalic structures, including nigrostriatal neurons, are not critically involved in the turning that follows electrolytic nigral lesions.

Animals↗