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Biomedical subjects

D Smart

Publications and source records attributed to D Smart.

At least 73 records · Page 4Linked to original sources
PubMed1996

Effects of propofol and thiopentone on potassium- and carbachol-evoked [3H]noradrenaline release and increased [Ca2+]i from SH-SY5Y human neuroblastoma cells.

We have examined the effects of two intravenous anaesthetic induction agents, propofol and thiopentone, on K+ and carbachol evoked [3H]noradrenaline release from a human neuroblastoma cell line, SH-SY5Y. In this model, we have previously demonstrated that K+ evoked [3H]noradrenaline release was dependent on Ca2+ entry and carbachol evoked release was extracellular Ca(2+)- independent. Propofol inhibited K+ (100 mM)-evoked (IC50 of 42 +/- 11 microM), but not carbachol (1 mM)-evoked, [3H]noradrenaline release. Thiopentone inhibited both K+- and carbachol-evoked release with IC50 values of 116 +/- 15 microM and 169 +/- 39 microM, respectively. These inhibitory effects were not due to changes in the release dynamics, as assessed using perfused cells. Furthermore, thiopentone inhibition of carbachol-evoked release was not due to muscarinic receptor antagonism. Both propofol and thiopentone caused noncompetitive inhibition of K+-stimulated Ca2+ influx, with IC50 values of 127 +/- 7 microM and 121 +/- 10 microM, respectively. These effects were not due to interaction with GABAA receptors, but suggest that both compounds block voltage-sensitive Ca2+ channels. Thiopentone, but not propofol, inhibited carbachol-stimulated increased intracellular Ca2+ concentrations in the presence and absence of extracellular Ca2+. However, thiopentone had no effect on carbachol-stimulated inositol (1,4,5)-triphosphate formation, suggesting that thiopentone may directly inhibit Ca2+ release from intracellular stores.

Calcium↗
PubMed1996

Tyr-D-Arg2-Phe-sarcosine4 activates phospholipase C-coupled mu2-opioid receptors in SH-SY5Y cells.

The dermorphin analogue Tyr-D-Arg2-Phe-sarcosine4 acts as a mu1-opioid receptor agonist, but as a mu2-opioid receptor antagonist, in vivo, yet the biochemical effects of Tyr-D-Arg2-Phe-sarcosine4 are unknown. Therefore, we characterized the effects of Tyr-D-Arg2-Phe-sarcosine4 on the mu-opioid receptor-mediated stimulation of inositol(1,4,5)trisphosphate, and inhibition of cAMP, in SH-SY5Y cells. We report here for the first time that Tyr-D-Arg2-Phe-sarcosine4 has no effect on basal cAMP or inositol(1,4,5)trisphosphate formation, but reversed the effects of fentanyl on these second messengers, consistent with Tyr-D-Arg2-Phe-sarcosine4 acting as a mu2-opioid receptor antagonist, and confirming that the mu-opioid receptors in SH-SY5Y cells are of the mu2 subtype.

Analgesics↗
PubMed1996

Connections between reading disability and behavior problems: testing temporal and causal hypotheses.

In this study of children's reading and behavior problem status from Grade 2 to Grade 4 of elementary school, we tested hypotheses concerned with the temporal and causal connections between these two closely associated disorders. Children with both, either, or neither kinds of problems were followed up over 2 years. While reading disability remained stable over time, there was greater variability in behavior problem status. Our data did not support the claim that reading problems lead to the development of behavior problems. Children who were comorbid had the worst outcome at follow-up, suggesting that behavior problems may exacerbate reading delay. Reading-disabled children were lower (albeit in the normal range) on intelligence, but when IQ was controlled, large group differences on reading and spelling were still evident. Attention deficit hyperactivity disorder (ADHD) type behavior problems significantly differentiated children with comorbid problems from children with behavior problems alone. Sex differences were noted in the association, with two-thirds of reading-disabled boys also having behavior problems and two-thirds of reading-disabled girls having no behavior problems, suggesting that pathways to reading disability may be gender specific.

Aggression↗
PubMed1996

The stimulatory effects of opioids and their possible role in the development of tolerance.

Opioids have stimulatory as well as the traditional inhibitory effects on neurotransmission, but the underlying mechanisms are poorly understood. Here, Darren Smart and David Lambert review the stimulatory effects of opioids on second messengers, including inositol (1,4,5)-trisphosphate (IP3), protein kinase C (PKC), Ca2+, and cAMP, and propose that these coordinated changes at the cellular level underlie the facilitatory effects of opioids on neurotransmission. The evidence for a possible role for these stimulatory effects, particularly the activation of PKC by opioids, in the development of tolerance is also discussed.

Calcium↗
PubMed1996

delta-Opioids stimulate inositol 1,4,5-trisphosphate formation, and so mobilize Ca2+ from intracellular stores, in undifferentiated NG108-15 cells.

delta-Opioids mobilize Ca2+ from intracellular stores in undifferentiated NG108-15 cells, but the mechanism involved remains unclear. Therefore, we examined the effect of [D-Pen 2,5] enkephalin on inositol 1,4,5-trisphosphate formation in these cells. [D-Pen 2,5] enkephalin caused a dose-dependent (EC50= 3.1 nM) increase in inositol 1,4,5-trisphosphate formation (measured using a specific radioreceptor mass assay), which peaked (25.7+/-1.2 pmol/mg of protein with 1 microM, n=9) at 30 s and returned to basal levels (10.6+/-0.9 pmol/mg of protein, n=9) within 4-5 min. This response was fully naloxone (1 microM) reversible and pertussis toxin (100ng/ml for 24 h) sensitive. Preincubation with Ni2+ (2.5 mM) or nifedipine (1 microM) had no effect on the [D-Pen 2,5] enkephalin (1 microM)-induced inositol 1,4,5-triphosphate response, and K+ (80mM) was unable to stimulate inositol 1,4,5-trisphosphate formation, indicating Ca2+ influx-induced activation of phospholipase C is not involved. Preincubation with the protein kinase C inhibitor Ro 31-8220 (1 microM) enhanced, whereas acute expo sure to phorbol 12,13-dibutyrate (1 microM) abolished, the [D-Pen 2,5] enkephalin (0.1 microM)-induced inositol 1,4,5-triphosphate response, suggesting protein kinase C exerts an autoinhibitory feedback action. [D-Pen 2,5] Enkephalin also dose-dependently (EC50 =2.8 nM) increased the intracellular [Ca2+], which was maximal (24 nM increase with 1 microM, n=5) at 30 s. This close temporal and dose-response relationship strongly suggests that delta-opioid receptor-mediated increases in intracellular [Ca2+] results from inositol 1,4,5-trisphosphate-induced Ca2+ release from intracellular stores, in undifferentiated NG108-15 cells.

Analgesics↗
PubMed1996

Fentanyl increases intracellular Ca2+ concentrations in SH-SY5Y cells.

Classically, opioids inhibit Ca2+ influx, but recent reports suggest opioids may also stimulate Ca2+ entry. Therefore, we have measured the effect of opioids on intracellular Ca2+ ([Ca2+]i), fluorimetrically, in Fura-2-loaded SH-SY5Y cells. Fentanyl 0.3 mumol litre-1 caused a mean increase in [Ca2+]i of 18.8 (SEM 2.1) nmol litre-1 in some (30.3%) batches of SH-SY5Y cells. In responding cells, the fentanyl-induced increase in [Ca2+]i was dose-dependent, with an EC50 of 0.73 mumol litre-1. This response was naloxone-reversible, and the delta opioid agonist [D-Pen2,5]enkephalin had no effect on [Ca2+]i, suggesting the fentanyl-induced Ca2+ response was entirely mediated by the mu opioid receptor. Fentanyl 0.3 mumol litre-1 increased [Ca2+]i without preactivation of phospholipase C by another agonist, and this was markedly reduced by Ni2+ 2.5 mmol litre-1. These data suggest that mu opioids directly increase [Ca2+]i by stimulating Ca2+ influx in SH-SY5Y cells.

Analgesics, Opioid↗
PubMed1996

Laparoscopic cholecystectomy and previous abdominal surgery: a safe technique.

Previous abdominal surgery has been cited as a contraindication to the performance of laparoscopic cholecystectomy. The present paper describes a technique whereby a Hasson cannula was introduced into the right iliac fossa by the open technique, using a method similar to an appendicectomy. The laparoscope was then introduced through this port and the safe introduction of other ports was achieved. Any adhesions were divided at this stage. The laparoscope was then moved to the umbilical port and a conventional laparoscopic cholecystectomy performed. In the series of six patients with upper or upper and lower abdominal scars, no patient suffered a complication or required a conversion to laparotomy. However, the operating time was increased from 75 to 105 min. This method involves open introduction of the primary trocar in an area devoid of adhesions. It was shown to be safe and with this method previous abdominal surgery should not be regarded as a contraindication.

Adult↗
PubMed1996

Reading disabilities with and without behaviour problems at 7-8 years: prediction from longitudinal data from infancy to 6 years.

Seven-year-old children with reading disabilities (RD-only), behaviour problems (BP-only), both conditions (RD-BP) and neither condition (Comparison) were compared on indices including temperament and behaviour, gathered in five periods between infancy and 6 years of age. The RD-BP group differed clearly from the RD-only group from infancy onwards. This comorbid group was similar to the BP-only group, while the RD-only group was similar to the Comparison group, until school age. The gender composition of the two RD groups differed, and the RD-BP boys showed the most problematic characteristics. The findings indicate different developmental pathways for "pure' RD children and those with comorbid BPs.

Attention Deficit Disorder with Hyperactivity↗
PubMed1996

Nociceptin induced inhibition of K+ evoked glutamate release from rat cerebrocortical slices.

Nociceptin, an endogenous ligand for the orphan receptor ORL1, has recently been described. In this study we have shown that nociception inhibits 46 mM K(+)-stimulated glutamate release from rat perfused cerebrocortical slices with an IC50 of 51 nM. At 100 nM the inhibition amounted to 68 +/- 14% and was naloxone (10 microM)-insensitive excluding an activation of mu, delta and kappa opioid receptors. These data demonstrate the functional coupling of ORL1 in glutamatergic neurones and implicates a role for nociceptin in glutamatergic neurotransmission.

Amino Acid Sequence↗
PubMed1996

Mass transfer in the biological fast lane: high CO2 and a shallow root zone.

Elevated atmospheric CO2, which is common in regenerative systems, increases photosynthesis, plant growth, and root respiration, which increases the O2 demand in the root zone. Closed systems must make efficient use of volume and thus have shallow root zones. The root density and O2 demand in these artificial systems is 10 to 100 times higher than in field environments. Rapid hydroponic flow rates supply O2 to the root zone, but anaerobic microsites occur because of nonuniform flow rates. Our measurements suggest that, probably because of low O2 in such microsites, up to 30% of the nitrogen can volatilize from denitrification. We improved nitrogen recovery to about 85% by increasing the solution flow rate and reducing the nitrate concentration in solution to 100 micromoles.

Ammonia↗
PubMed1995

Mu-opioids activate phospholipase C in SH-SY5Y human neuroblastoma cells via calcium-channel opening.

We have recently reported that, in SH-SY5Y cells, mu-opioid receptor occupancy activates phospholipase C via a pertussis toxin-sensitive G-protein. In the present study we have further characterized the mechanisms involved in this process. Fentanyl (0.1 microM) caused a monophasic increase in inositol 1,4,5-trisphosphate mass formation, with a peak (20.5 +/- 3.6 pmol/mg of protein) at 15 s. Incubation in Ca(2+)-free buffer abolished this response, while Ca2+ replacement 1 min later restored the stimulation of inositol 1,4,5-trisphosphate formation (20.1 +/- 0.6 pmol/mg of protein). In addition, nifedipine (1 nM-0.1 mM), an L-type Ca(2+)-channel antagonist, caused a dose-dependent inhibition of inositol 1,4,5-trisphosphate formation, with an IC50 of 60.3 +/- 1.1 nM. Elevation of endogenous beta/gamma subunits by selective activation of delta-opioid and alpha 2 adrenoceptors failed to stimulate phospholipase C. Fentanyl also caused a dose-dependent (EC50 of 16.2 +/- 1.0 nM), additive enhancement of carbachol-induced inositol 1,4,5-trisphosphate formation. In summary, we have demonstrated that in SH-SY5Y cells activation of the mu-opioid receptor allows Ca2+ influx to activate phospholipase C. However, the possible role of this mechanism in the process of analgesia remains to be elucidated.

Calcium↗
PubMed1995

Transport-induced stress responses in fed and fasted donkeys.

Plasma endocrine and metabolic responses to transport for 30 minutes and four hours were investigated in six fed donkeys. In the unstressed animals there was a pulsatile secretion of cortisol at two-hour intervals, from minima of 51.4 +/- 17.6 nmol litre-1 to maxima of 160.0 +/- 11.0 nmol litre-1, but during transport this pulsatility was lost and the animals' stress response was characterised by steady high concentrations of 110 to 220 nmol litre-1. The cortisol concentration decreased after the journey and remained at a minimum until the restoration of pulsatile secretion 8.5 to 10.5 hours later. The transport-induced adrenocortical response did not produce any significant changes in the plasma concentrations of triglycerides, cholesterol, glucose, total protein, albumin, globulin or urea. The donkeys' responses to transport for four hours were also investigated after they had been deprived of food for one or three days. Food deprivation alone increased plasma cortisol and triglyceride concentrations, and decreased glucose and insulin concentrations, and transport consistently, and feeding after the journey sometimes, accentuated their adrenocortical function; the changes in cortisol concentrations as a result of the journey tended to be lower than in the fed animals. Transport had no effect upon the triglyceride response to either period of fasting. Hyperglycaemia was induced by transport in four of the six donkeys fasted for one day and in all of them after three days of fasting.

Analysis of Variance↗
PubMed1995

Localization of Diploptera punctata allatostatin-like immunoreactivity in helminths: an immunocytochemical study.

The nervous systems of helminths are predominantly peptidergic in nature, although it is likely that the full range of regulatory peptides used by these organisms has yet to be elucidated. Attempts to identify novel helminth neuropeptides are being made using immunocytochemistry with antisera raised against peptides isolated originally from insects. One of these antisera was raised against allatostatin III, a peptide isolated originally from the cockroach, Diploptera punctata, and a member of a family of related peptides found in insects. Allatostatin immunoreactivity was found throughout the nervous systems of Mesocestoides corti tetrathyridia, and adult Moniezia expansa, Diclidophora merlangi, Fasciola hepatica, Schistosoma mansoni, Ascaris suum and Panagrellus redivivus. Immunostaining was observed in the nerve cords and anterior ganglia of all the helminths. It was also apparent in the subtegumental nerves and around the reproductive apparatus of the flatworms, in neurones in the pharynx of D. merlangi, F. hepatica, A. suum and P. redivivus, and in fibres innervating the anterior sense organs in the nematodes. Immunostaining in all species was both reproducible and specific in that it could be abolished by pre-absorption of the antiserum with allatostatins I-IV. These results suggest that molecules related to the D. punctata allatostatins are important components in the nervous systems of a number of helminth parasites, and a free-living nematode. Their distribution within the nervous system suggests they function as neurotransmitters/neuromodulators with roles in locomotion, feeding, reproduction and sensory perception.

Animals↗
PubMed1995

Activation of phospholipase C in SH-SY5Y neuroblastoma cells by potassium-induced calcium entry.

1. We used SH-SY5Y human neuroblastoma cells to investigate whether depolarization with high K+ could stimulate inositol (1,4,5)trisphosphate (Ins(1,4,5)P3) formation and, if so, the mechanism involved. 2. Ins(1,4,5)P3 was measured by a specific radioreceptor mass assay, whilst [Ca2+]i was measured fluorimetrically with the Ca2+ indicator dye, Fura-2. 3. Depolarization with K+ caused a time- and dose-dependent increase in [Ca2+]i (peak at 27 s, EC50 of 50.0 +/- 9.0 mM) and Ins(1,4,5)P3 formation (peak at 30 s, EC50 of 47.4 +/- 1.1 mM). 4. Both the K(+)-induced Ins(1,4,5)P3 formation and increase in [Ca2+]i were inhibited dose-dependently by the L-type voltage-sensitive Ca2+ channel closer, (R+)-BayK8644, with IC50 values of 53.4 nM and 87.9 nM respectively. 5. These data show a close temporal and dose-response relationship between Ca2+ entry via L-type voltage-sensitive Ca2+ channels and Ins(1,4,5)P3 formation following depolarization with K+, indicating that Ca2+ influx can activate phospholipase C in SH-SY5Y cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Desensitization of the mu-opioid activation of phospholipase C in SH-SY5Y cells: the role of protein kinases C and A and Ca(2+)-activated K+ currents.

1. In SH-SY5Y cells, mu-opioids cause a rapidly desensitizing activation of phospholipase C (PLC), that appears secondary to Ca2+ influx via L-type voltage-sensitive Ca2+ channels (VSCCs). The aim of the present study was to characterize the mechanisms of desensitization of the mu-opioid-induced inositol (1,4,5) triphosphate (Ins(1,4,5)P3) response, by use of a stereospecific radioreceptor mass assay. 2. (R+)-Bay K 8644 (1 nM-10 microM) dose-dependently inhibited fentanyl-induced Ins(1,4,5)P3 formation, with an IC50 of 28.5 nM, confirming our earlier observations that mu-opioids open L-type VSCCs, thus allowing Ca2+ influx to activate PLC. 3. Ro 31-8220 (0.1 nM-10 microM), a protein kinase C inhibitor, dose-dependently enhanced fentanyl-induced Ins(1,4,5)P3 formation (EC50 = 20.0 nM), whilst acute phorbol 12,13-dibutrate (1 microM) abolished the response. 4. H-89 (1 nM-10 microM), a protein kinase A inhibitor, also dose-dependently enhanced fentanyl-induced Ins(1,4,5)P3 formation (EC50 = 93 nM), whilst dibutryl cyclic AMP (0.5 mM) abolished the response. 5. Blockade of Ca(2+)-activated K+ currents with 4-aminopyridine (2 mM) or iberiotoxin (10 nM) had no effect on fentanyl-induced Ins(1,4,5)P3 formation but further increased the Ro 31-8220-enhanced response. 6. All three mechanisms had additive, or even supra-additive, effects, but only at later (120-300 s) time points. In addition, fentanyl-induced Ins(1,4,5)P3 formation, even if enhanced by H-89, Ro 31-8220 and/or 4-aminopyridine, was inhibited by nifedipine (1 nM-10 microM). 7. In conclusion, desensitization of the mu-opioid-induced activation of PLC is multifactorial, involving protein kinases C and A and Ca(2+)-activated K+ efflux, but the L-type VSCC is of critical importance and may be a possible common site of action.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

Peptides related to the Diploptera punctata allatostatins in nonarthropod invertebrates: an immunocytochemical survey.

The allatostatins are a family of peptides isolated originally from the cockroach, Diploptera punctata. Related peptides have been identified in Periplaneta americana and the blowfly, Calliphora vomitoria. These peptides have been shown to be potent inhibitors of juvenile hormone synthesis in these species. A peptide inhibitor of juvenile hormone biosynthesis has also been isolated from the moth, Manduca sexta; however, this peptide has no structural homology with the D. punctata-type allatostatins. Investigations of the phylogeny of the D. punctata allatostatin peptide family have been started by examining a number of nonarthropod invertebrates for the presence of allatostatin-like molecules using immunocytochemistry with antisera directed against the conserved C-terminal region of this family. Allatostatin-like immunoreactivity (ALIR) was demonstrated in the nervous systems of Hydra oligactis (Hydrozoa), Moniezia expansa (Cestoda), Schistosoma mansoni (Trematoda), Artioposthia triangulata (Turbellaria), Ascaris suum (Nematoda), Lumbricus terrestris (Oligochaeta), Limax pseudoflavus (Gastropoda), and Eledone cirrhosa (Cephalopoda). ALIR could not be demonstrated in Ciona intestinalis (Ascidiacea). These results suggest that molecules related to the allatostatins may play an important role in nervous system function in many invertebrates as well as in insects and that they also have an ancient evolutionary lineage.

Amino Acid Sequence↗
PubMed1994

Characterisation of mu-opioid receptors on SH-SY5Y cells using naloxonazine and beta-funaltrexamine.

The irreversible opioid receptor antagonists naloxonazine and beta-funaltrexamine have been used to determine whether multiple mu-opioid receptors exist on undifferentiated SH-SY5Y human neuroblastoma cells. Naloxonazine binds irreversibly to the mu 1-opioid receptor subtype and reversibly to the mu 2-opioid receptor subtype. On SH-SY5Y cells naloxonazine afforded a Ki of 3.4 +/- 0.7 nM, and was fully reversible, indicating the mu-opioid receptor population on SH-SY5Y cells was solely of the mu 2-opioid receptor subtype. The alkylating agent beta-funaltrexamine was maximally able to alkylate only 60% of the mu-opioid receptor sites on SH-SY5Y cells, labelled with [3H]diprenorphine or [3H][D-Ala2,MePhe4,Gly(ol)5]enkephalin (DAMGO). The reversible binding of naloxonazine and the insensitivity of a percentage of the mu-opioid receptor sites to alkylation by beta-funaltrexamine suggests that differences do exist in the mu 2-opioid receptor population on undifferentiated SH-SY5Y cells. This may indicate further heterogeneity or the inability of beta-funaltrexamine to alkylate all relevant nucleophilic groups in a single population of receptors.

Amino Acid Sequence↗