Search PubMed⌕ Search

Biomedical subjects

T R Raju

Publications and source records attributed to T R Raju.

At least 73 records · Page 4Linked to original sources
PubMed1994

Endosulfan induces small but significant changes in the levels of noradrenaline, dopamine and serotonin in the developing rat brain and deficits in the operant learning performance.

The organochlorine insecticide, endosulfan was administered (6 mg/kg body weight) to Wistar rat pups of both sexes by gastric intubation daily from post-natal days 2-25. Its effect on levels of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) was assayed in olfactory bulb (OB), hippocampus (HI), visual cortex (VC), brainstem (BS) and cerebellum (CB) on days 10 and 25 using high-performance liquid chromatography (HPLC). The activity of acetylcholinesterase (AChE) was also estimated in the same regions of the brain. Performance in operant conditioning for solid food reward was assessed in 25-day-old rats. NA levels were increased in OB (12%, P < 0.01) and BS (10%, P < 0.05) at 10 days of age and in HI (20%, P < 0.01) and CB (12%, P < 0.05) at 25 days of age. DA level was decreased in HI at both 10 (42%, P < 0.001) and 25 (45%, P < 0.001) days. Serotonin levels were increased in OB (12%, P < 0.05), HI (41%, P < 0.001), VC (30%, P < 0.01) and BS (15%, P < 0.01) at 10 days of age but at 25 days, levels were decreased in BS (20%, P < 0.05) and CB (31%, P < 0.01). The activity of AChE was not different from the control groups in any of the regions studied. These data suggest that monoaminergic systems in the developing rat brain respond to endosulfan by undergoing something like a 'reorganization'. However, such changes do not ameliorate certain functional losses following the exposure to endosulfan as operant conditioning revealed deficits in acquisition as well as retention of memory.

Acetylcholinesterase↗
PubMed1994

Neurofilament phosphorylation is enhanced in cultured chick spinal cord neurons exposed to cerebrospinal fluid from amyotrophic lateral sclerosis patients.

Amyotrophic lateral sclerosis (ALS), a neurodegenerative disease, is characterized by degeneration of lower and upper motor neurons. Serum and cerebrospinal fluid (CSF) of ALS patients have been found to exert toxic effects on neurons in culture. We report here increased phosphorylation of neurofilaments (NF) in the soma of chick spinal cord neurons in culture when exposed to CSF of ALS patients. Spinal cord neurons were cultured from 10-day embryonic chick and exposed to culture medium supplemented with CSF or serum (10%) from ALS and non-ALS patients for 48 h. There was a significant increase in the number of neuronal soma staining with antibodies against phosphorylated NF, following exposure to CSF from ALS patients. Such an increase, however, was not observed in cultures exposed to serum from ALS patients and also serum and CSF from non-ALS patients. These results suggest that the CSF of ALS patients may contain factor(s) which induces aberrant phosphorylation of NF in the soma, a probable forerunner to the formation of neurofibrillary tangles and eventual degeneration of neurons.

Amyotrophic Lateral Sclerosis↗
PubMed1994

Facilitation of self-stimulation of ventral tegmentum by microinjection of opioid receptor subtype agonists.

Intracranial self-stimulation (ICSS) evoked from the ventral tegmental area-substantia nigra (VTA-SN) and lateral hypothalamus-medial forebrain bundle (LH-MFB) was assessed following microinjections of mu (Tyr-D-Ala2-N-Me-Phe4-Gly5ol: DAGO), delta-(D-Ala2, D-Met5)-enkephalin: DADME) or kappa (Dynorphin-B or Rimorphin) opioid receptor subtype agonists or saline into either VTA-SN or LH-MFB. The current intensity was fixed at an optimum level to obtain 60-70% of the maximum asymptotic response rate. DAGO (5 micrograms/0.5 microliters), DADME (2 micrograms/0.5 microliters) or Dynorphin B (0.5 microgram/0.5 microliters) injected into VTA-SN facilitated the self-stimulation rates of VTA-SN by 27%, 32%, and 59%, respectively. These microinjections did not alter the self-stimulation of LH-MFB when effects of these injections were still persisting in VTA-SN. Similar doses of these opioid receptor agonists injected into LH-MFB had no significant effect on the self-stimulation rates of either LH-MFB or VTA-SN. The facilitatory effects of DADME were completely abolished by naloxone (30 mg/kg IP). Taken together, these results suggest that all three opioid receptor subtypes of ventral tegmentum and not of lateral hypothalamus are involved in the electrically evoked self-stimulation of VTA-SN.

Analgesics↗
PubMed1994

Plasticity of hippocampal and motor cortical pyramidal neurons induced by self-stimulation experience.

The self-stimulation (SS) induced neuronal plasticity was observed in CA3 hippocampal and layer V motor cortical pyramidal neurons. SS experience was allowed daily for a total of 1 hour for 10 days through four bipolar electrodes implanted bilaterally in lateral hypothalamus (LH) and substantia nigra-ventral tegmental area (SN-VTA) in adult male Wistar rats. Examination of pyramidal neurons stained by rapid Golgi technique was made in a total of 1,600 neurons out of 80 rats consisting of 4 groups. The dendritic intersections were quantified upto 200 and 120 microns radial distances in apical and basal dendrites respectively. The CA3 hippocampal and layer V motor cortical pyramidal neurons of SS group revealed significant increase (P < 0.001, two-way ANOVA) in dendritic intersections in both apical and basal dendrites, compared to normal control (NC), sham control (SH) and experimenter-administered (EA) group of animals. These results demonstrate that SS experience promotes increase in dendritic length in hippocampal and motor cortical pyramidal neurons.

Animals↗
PubMed1993

Neuronal plasticity induced by self-stimulation rewarding experience in rats--a study on alteration in dendritic branching in pyramidal neurons of hippocampus and motor cortex.

Self-stimulation rewarding experience promoted structural changes in pyramidal neurons of the CA3 region of the hippocampus and the Vth layer of the motor cortex in adult male Wistar rats. Self-stimulation experience was allowed for 1 h daily for a duration of 10 days through bipolar electrodes placed bilaterally in lateral hypothalamus and substantia nigra--ventral tegmental area. At the end of 10 days, rats were sacrificed, and rapid Golgi examination of the CA3 hippocampal and layer V pyramidal neurons of the motor cortex was made for a grand total of 1600 neurons from 80 rats divided into 4 groups. The neurons of the self-stimulation experienced (SS) group revealed a significant (ANOVA, F-test) increase in dendritic branching in the perisomatic domains. Such changes were not observed in neurons of sham control (SH), experimenter administered stimulation (EA) and normal control (NC) groups. SS animals also showed a significant increase in the thickness of lacunosum and radiatum laminae of CA3 neurons of the hippocampus. Our results reveal that both limbic and neocortical neurons undergo changes in dendritic branching patterns due to self-stimulation rewarding experience. It is tempting to hypothesize that neuronal plasticity is the result of motivation and learning experienced by rats which underwent self-stimulation.

Animals↗
PubMed1993

Mercuric chloride-induced alterations of levels of noradrenaline, dopamine, serotonin and acetylcholine esterase activity in different regions of rat brain during postnatal development.

Wistar rats were fed mercuric chloride, 4 mg/kg body weight per day chronically from postnatal day 2 to 60 by gastric intubation. Mercury consumption was then discontinued until 170 days to allow time for recovery. Since mercury caused reduction in body weight, an underweight group was also included besides the normal saline group. Levels of noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5-HT) and the activity of acetylcholine esterase (AChE) were assayed in various brain regions in different age groups. By 60 days of age, the mercury group showed elevations of NA levels in olfactory bulb (OB), visual cortex (VC) and brain stem (BS) but not in striatum-accumbens (SA) and hippocampus (HI). DA levels were also increased in OB, HI, VC and BS but not in SA. AChE activity was decreased in the mercury group only in HI and VC at 20 days of age. The Mercury group showed no behavioural abnormality outwardly; however, operant conditioning revealed a deficiency in performance. Nevertheless, all these changes disappeared after discontinuation of mercury intake. Thus the changes occurring in the brain at this level of oral mercuric chloride intake seem to reflect adaptive neural mechanisms rather than pathological damage.

Acetylcholinesterase↗
PubMed1987

Retinal ganglion cell survival and neurite regeneration requirements: the change from Müller cell dependence to superior colliculi dependence during development.

A study has been made of the effects of Müller conditioned media or neonatal superior collicular extracts on the survival in dissociate culture of retinal ganglion cells (RGC) from differently aged rats. Embryonic and neonatal RGC were identified either by retrograde horseradish peroxidase (HRP) or Thy-1 antibody labelling techniques. Müller conditioned media supported the survival, over 24 h in culture, of 85% of the RGC plated from 17-day embryos (E17); in contrast, superior collicular extract only maintained 45% of these RGC. With further development there was a decline in the survival enhancing effects of the Müller conditioned media and an increase in the survival due to superior collicular extracts: by postnatal day 12 (P12), the survival of RGC had declined to 20% in the Müller media, but had increased to over 90% in the colliculus extract. This transition in the dependence of RGC from Müller cells to superior colliculi was examined with homogeneous cultures of RGC, obtained using cell sorting techniques. RGC in these cultures showed the same transition in dependence from Müller cells to superior colliculi, indicating that the survival-enhancing effects were not mediated by the other intrinsic cells of the retina. The results suggest that the survival of RGC is at first dependent on the intrinsic glia of the retina and only later, as development proceeds, on the targets of the RGC in the superior colliculus. The normal RGC death period in the rat extends from near birth to about 6 days postnatal. The question then arises as to the timing of trophic support from Müller glia and from neurones in the tectum in relation to the duration of the normal RGC death period. This has been examined in the present work.

Animals↗
PubMed1986

Retinal ganglion cell survival requirements: a major but transient dependence on Müller glia during development.

Neonatal rat retinal ganglion cells (RGC), identified by a retrograde horseradish peroxidase labelling technique, survived over a 16-h culture period when cultured on monolayers of rat Müller glia or in conditioned media derived from these cells. Maximal survival of neonatal RGC was obtained at 1:4 dilution of conditioned media. However, extensive neurite outgrowth from RGC was seen only when they were cultured on glial monolayers. Homogeneous cultures of RGC, obtained using cell sorting techniques, also survived in Müller-conditioned media. This indicates that other intrinsic cells of the retina do not mediate the effect of Müller-conditioned media on RGC. Conditioned media from Müller glia do not significantly enhance the survival of RGC from 6 day retinae. However, these older RGC are supported in culture by extracts derived from their target tissue. These results suggest that as development proceeds RGC survival is dependent on factors produced by target rather than those produced by Müller glia.

Animals↗
PubMed1985

Retinal ganglion cell survival is mediated by cell contact with immature rat astroglia.

The survival of identified retinal ganglion cells (RGGs) in vitro increased when they were plated over subcultured monolayers of astrocytes. Immunofluorescence labelling of these monolayers showed that over 85% of the cells were glial fibrillary acidic protein (GFAP) positive and consisted of large, flat immature astrocytes. Less than 7% of the total cell population in the monolayers were fibroblasts, leptomeningeal or endothelial cells. Coculturing of RGCs with subcultured astrocytes revealed that the trophic interaction between astrocytes and RGCs is mediated through cell contact.

Animals↗
PubMed1985

Motoneurone survival is induced by immature astrocytes from developing avian spinal cord.

Dissociated spinal cords of 6-day chick embryos were grown on monolayers consisting primarily of either flat (relatively immature) or process-bearing (relatively mature) astrocytes. Cultures rich in flat astrocytes maintained about 80% of the motoneurones originally plated for 48 h in vitro. However, process-bearing astrocytes were unable to support motoneurone survival. Medium conditioned by contact with the monolayers of flat astrocytes also promoted motoneurone survival for 48 h. Maximal activity occurred over the concentration range 55-110 micrograms/ml protein. After 48 h, the number of motoneurones dropped to control levels both in the conditioned medium and on the monolayers. This effect could not be reversed by the introduction of fresh conditioned media at 48 h. This indicated a decrease in the requirements of more mature motoneurones for this media as muscle-conditioned medium could support 80% of the motoneurones initially plated for 96 h. Thus, relatively immature astrocytes were capable of supporting the survival of 6-day montoneurones in vitro for up to 48 h and this effect is mediated through the release of a soluble substance.

Animals↗
PubMed1984

Effects of cultured astroglia on the survival of neonatal rat retinal ganglion cells in vitro.

Retinal ganglion cells (RGC), as identified by retrograde horseradish peroxidase (HRP) labeling technique, were cultured in a minimal medium; only 20% of them survived after 16 hr in vitro. However, superior colliculus-conditioned medium was capable of supporting 100% of RGC over this assay time; enhanced neurite expression also was evident. It was decided to investigate whether glial cells within the superior colliculus may provide a soluble factor capable of supporting RGC. Glial-conditioned medium prepared over monolayers of either predominantly flat astrocytes (relatively immature) or predominantly process-bearing (mature) astrocytes failed to maintain RGC. The possibility that astrocytes may provide support for RGC via membrane contact was then investigated. Dissociated retinae were grown on monolayers consisting primarily of either flat or process-bearing astrocytes. Cultures rich in flat astrocytes maintained over 70% of RGC originally present, and many of them exhibited extensive neurite outgrowth and elongation. Process-bearing astrocytes were unable to support RGC survival. Immature astroglial cells may therefore support RGC via glial-neuronal interaction.

Animals↗
PubMed1981

Claims that intermediate filaments contain F-actin are unwarranted.

Examination of sectioned, embedded material showed that almost all intermediate filaments normally present in cultured chick embryo fibroblasts, IMR-33 cells, and BHK-21 cells were eliminated by trypsinization. At the same time atypical filaments of intermediate size were formed by close apposition of thin filaments. Previous observations (Buckley et al., 1978, J. Cell Biol. 78:644-652) on negatively stained and on critical-point-dried whole-cell mounts confused these different filament types and, on the basis of heavy meromyosin binding to the atypical intermediate-sized filaments, we suggested that many normal intermediate filaments contain f-actin. The present results show that this suggestion was unwarranted and we therefore retract it.

Actins↗
PubMed1978

Heavy meromyosin labeling of intermediate filaments in cultured connective tissue cells.

Mild treatment with trypsin causes a radical change in the heavy meromyosin (HMM) binding properties of intermediate filaments in glycerinated, myosin-extracted cultured chick embryo connective tissue cells. In non-trypsin-treated cells, HMM labeling of filaments was often indistinct and variable in its distribution. By contrast, in cells treated with trypsin (under conditions which allowed most intermediate filaments to survive), virtually all filaments, including those of intermediate size, decorated with HMM to give distinct arrowhead patterns. We suggest that most intermediate filaments in such cells contain a core of F-actin masked by trypsin-labile accessory proteins.

Actins↗