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D Mort

Publications and source records attributed to D Mort.

11 recordsLinked to original sources
PubMed2002

Orbitofrontal cortex mediates inhibition of return.

Recent accounts have proposed that orbitofrontal cerebral cortex mediates the control of behavior based on emotional feedback and its somatic correlates. Here, we describe the performance of a patient with circumscribed damage to orbitofrontal cortex during a task that requires switching between sensory-motor mappings, contingent on the occurrence of positive and negative reward feedbacks. In this test, normal subjects and other patients with prefrontal damage show an increase in latencies for eye movements towards locations at which a negative feedback was presented on the preceding trial. In contrast, our patient does not show this reward-dependent inhibition of return effect on saccades. She was also found to make an increased rate of ocular refixations during visual search and used a disorganized search strategy in a token foraging task. These findings suggest that orbital regions of the prefrontal cortex mediate an inhibitory effect on actions directed towards locations that have been subject to negative reinforcement. Further, this mechanism seems to play a role in controlling natural search and foraging behavior.

Adult↗
PubMed2001

Ocular flutter associated with a localized lesion in the paramedian pontine reticular formation.

Ocular flutter is a rare horizontal eye movement disorder characterized by rapid saccadic oscillations. It has been hypothesized that it is caused by loss of "pause" neuronal inhibition of "burst" neuron function in the paramedian pontine reticular formation (PPRF); however, there have been no imaging studies confirming such anatomical localization. We report the case of a woman with an acute attack of multiple sclerosis associated both with ocular flutter and a circumscribed pontine lesion, mainly involving the PPRF on magnetic resonance imaging. As she recovered from the attack, both the midline pontine lesion and the ocular flutter dramatically improved. This case is the first clear evidence that at least some cases of ocular flutter are due to lesions involving the PPRF.

Adult↗
PubMed2001

Effect of acute exposure to ammonia on glutamate transport in glial cells isolated from the salamander retina.

A rise of brain ammonia level, as occurs in liver failure, initially increases glutamate accumulation in neurons and glial cells. We investigated the effect of acute exposure to ammonia on glutamate transporter currents in whole cell clamped glial cells from the salamander retina. Ammonia potentiated the current evoked by a saturating concentration of L-glutamate, and decreased the apparent affinity of the transporter for glutamate. The potentiation had a Michaelis-Menten dependence on ammonia concentration, with a K(m) of 1.4 mM and a maximum potentiation of 31%. Ammonia also potentiated the transporter current produced by D-aspartate. Potentiation of the glutamate transport current was seen even with glutamine synthetase inhibited, so ammonia does not act by speeding glutamine synthesis, contrary to a suggestion in the literature. The potentiation was unchanged in the absence of Cl(-) ions, showing that it is not an effect on the anion current gated by the glutamate transporter. Ammonium ions were unable to substitute for Na+ in driving glutamate transport. Although they can partially substitute for K+ at the cation counter-transport site of the transporter, their occupancy of these sites would produce a potentiation of < 1%. Ammonium, and the weak bases methylamine and trimethylamine, increased the intracellular pH by similar amounts, and intracellular alkalinization is known to increase glutamate uptake. Methylamine and trimethylamine potentiated the uptake current by the amount expected from the known pH dependence of uptake, but ammonia gave a potentiation that was larger than could be explained by the pH change, and some potentiation of uptake by ammonia was still seen when the internal pH was 8.8, at which pH further alkalinization does not increase uptake. These data suggest that ammonia speeds glutamate uptake both by increasing cytoplasmic pH and by a separate effect on the glutamate transporter. Approximately two-thirds of the speeding is due to the pH change.

ATP-Binding Cassette Transporters↗
PubMed2000

Bilirubin does not modulate ionotropic glutamate receptors or glutamate transporters.

Bilirubin, a product of haemoglobin metabolism, has been suggested to damage neurons by increasing activation of N-methyl-D-aspartate (NMDA) receptors when it reaches high levels in the blood [15,19], as occurs in neonatal jaundice [7]. Bilirubin is also generated in the brain following synthesis of the messenger carbon monoxide (CO) by haem oxygenase, and haem oxygenase is upregulated in Alzheimer's disease [23]. We examined the effect of bilirubin on currents generated by NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors in hippocampal pyramidal cells, and on glutamate transporter currents in retinal glial cells. Bilirubin did not modulate either receptor-gated currents or transporter currents. These data show the negative, but important result that bilirubin does not induce neuronal death by acting directly on NMDA or AMPA receptors, nor indirectly by blocking glutamate uptake and raising the extracellular concentration of glutamate.

ATP-Binding Cassette Transporters↗
PubMed1999

Stereo-specific cytotoxic effects of gossypol enantiomers and gossypolone in tumour cell lines.

The naturally occurring compound, gossypol, has been previously used as a male oral contraceptive, for the treatment of benign gynaecological conditions and cancer patients. Long-term daily dosing with gossypol is associated with minimal side effects and no myelosuppression. Since gossypol exhibits atropisomerism due to the restricted rotation about the 2,2' carbon bond, we have isolated the l- and d-isomers by Schiff's base formation using a chiral amine and regenerated the enantiomers by acid hydrolysis. The enantiomers and the proposed oxidative metabolite, gossypolone, were characterized by HPLC, 1H-NMR and optical rotation. The cytotoxicity was assessed in cell cultures derived from melanoma, lung, breast, cervix, and leukaemia using the MTT viability assay. The cytotoxicity of gossypolone was similar to racemic gossypol in five out of the six cell lines studied. The l-enantiomer of gossypol induced a dose-dependent cell kill in all cell lines with a mean IC50 of 20 microM and was significantly more potent than racemic gossypol, the d-enantiomer of gossypol and gossypolone. In addition, when the leukaemia line was exposed to l-gossypol (0.5-10 microM) over a 4-day period, a schedule-dependent decrease in cell viability was observed. l-Gossypol was also compared with respective drugs used to treat patients with melanoma, lung cancer and leukaemia. The data indicate that l-gossypol was significantly more active than cisplatin, melphalan and dacarbazine in the two melanoma lines, cisplatin and daunorubicin in the lung line and hydroxyurea and busulphan in the leukaemia line. Preliminary studies using one melanoma line showed that the l-isomer induced cell shrinkage, membrane blebbing and DNA fragmentation, characteristics suggestive of apoptotic cell death.

Antineoplastic Agents↗
PubMed1996

Epirubicin, cisplatin and continuous infusion 5-fluorouracil (ECF) as neoadjuvant chemotherapy in gastro-oesophageal cancer.

High response rates have been reported in the treatment of advanced gastric cancer with epirubicin, cisplatin and continuous infusion 5-fluorouracil (ECF), including instances of unresectable disease being rendered operable by chemotherapy. We report our experience with ECF as neoadjuvant treatment in gastric and lower oesophageal carcinoma. Twenty-seven patients were treated, of whom ten (37%) had carcinoma of the stomach and 17 (63%) tumours of the lower oesophagus. Histology in the majority of cases, 21 (78%), was adenocarcinoma. Before chemotherapy ten patients (37%) had evidence of initially unresectable locally advanced disease, 16 (59%) had localised disease only and one patient (4%) had a localised primary with a single liver metastasis. Epirubicin (50 mg m(-2) i.v.) and cisplatin (60 mg m(-2) i.v.) were administered every 3 weeks for four cycles together with a continuous 12 week infusion of 5-fluorouracil (200 mg m(-2) day(-1)). Fifteen of 24 assessable patients (62%) had symptomatic improvement on chemotherapy. On combined surgical and/or radiological assessment, 15 of the 27 patients (56%) had objective evidence of tumour response. In all patients assessment for radical surgery was made following chemotherapy. Eighteen patients (67%) proceeded to operation: of these, 11 had complete resection of their disease, one had a histologically incomplete resection and six were found to have unresectable disease. No pathological complete responses were observed. Only one of the ten patients with locally advanced disease achieved complete surgical resection after chemotherapy. At a median follow-up of 36 months from date of diagnosis (range 30-47 months), 19 of the 27 patients (70%) have died. Of 11 patients who had a complete surgical resection, one died post-operatively, three have subsequently relapsed (of whom two have died) and seven remain disease free. Toxicity from treatment was mild and included emesis, myelosuppression, stomatitis and exfoliation. Myelosuppression caused modification of treatment in 14 of 108 chemotherapy cycles (13%). There was one surgical death but no chemotherapy-related deaths. These early results show encouraging symptomatic and objective responses of gastro-oesophageal carcinoma to ECF, but provide no instances of ECF achieving complete pathological response. Only randomised trials can establish the role of neoadjuvant ECF chemotherapy in both initially resectable and unresectable carcinoma of the stomach and lower oesophagus.

Adult↗
PubMed1994

5-fluorouracil and folinic acid-induced mucositis: no effect of oral glutamine supplementation.

In some clinical situations the endogenous production of glutamine may be insufficient to maintain optimal tissue structure and function such that glutamine becomes a conditionally essential amino acid. Studies in laboratory animals have demonstrated that glutamine supplementation can reduce the incidence and severity of cytotoxic-induced mucositis. This study examined the role of oral glutamine supplementation in the management of mucositis caused by 5-fluorouracil (5-FU) and folinic acid. Twenty-eight patients with gastrointestinal cancers were randomised to receive 16 g of glutamine per day for 8 days, or placebo, in a randomised double-blind trial before crossing over to the alternative supplement during the second treatment cycle. The supplement was well tolerated with no apparent adverse effects, but failed to have any significant effect on oral mucositis assessed by the patients or investigator. The possible reasons for this apparent lack of benefit are discussed.

Administration, Oral↗
PubMed1986

Length of follow-up in teratomas--results of a modification of Einhorn's regime in testicular teratomas.

A modification of Einhorn's original chemotherapy schedule was used to treat 40 patients with metastatic testicular teratomas. Each cycle of chemotherapy consisted of cisplatin (100 mg/m2), bleomycin (30 mg X 3) and vinblastine (5 mg/m2 X 2). Four patients failed to achieve a complete response and died with advanced disease. There was one treatment death. Only two of 14 patients who had residual masses resected still had active tumour. The 2-year actuarial disease free survival for patients in first remission was 85%, but this fell to 77% at 5 years as 3 patients relapsed (34, 36, 37 months). The results are comparable with other series but are associated with less toxicity. The need for continued follow-up is demonstrated in view of relapses occurring after 2 years.

Aged↗