Biomedical subjects
Publications and source records attributed to J Duncan.
It has been a widely accepted view that epilepsy is usually a chronic condition in which the prognosis is generally poor and any remissions that do occur are usually temporary. In this article recent studies challenging this view will be considered, other aspects of the long-term prognosis for seizure control in epilepsy reviewed, and the mortality rates and causes of premature death in epilepsy outlined.
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A 15-year-old girl presented with recurrent encephalopathic episodes, epilepsy, myopathy and chronic lactic acidosis. A muscle biopsy revealed the presence of ragged red fibres and mitochondria with paracrystalline inclusions. Biochemical studies on freshly isolated skeletal muscle mitochondria demonstrated a deficiency of NADH-CoQ reductase activity. Investigation of her gastrocnemius muscle at rest by phosphorus nuclear magnetic resonance displayed a reduced phosphocreatine concentration with elevated levels of inorganic phosphate and ADP. Abnormalities were also apparent in her brain spectrum. It is therefore possible that the mitochondrial defect present in skeletal muscle is also being expressed in the brain.
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We measured several biochemical effects of 10 days of intragastric administration of phosphatidylcholine (10 mmoles/kg) to rats because of the expanding clinical use of chronic phosphatidylcholine treatment for disorders involving impaired cholinergic neurotransmission. The plasma and erythrocyte choline concentrations were increased 3.5-fold, which was the same percent increase as found after an acute treatment with phosphatidylcholine. The lipid and fatty acid compositions of the plasma were also altered; free and total cholesterol levels increased, triglycerides increased, the monoene fatty acids generally decreased, and the diene and tetraene fatty acids generally increased. We found no effect of this treatment on the hepatic microsomal cytochrome P-450 activity or on the N-demethylation of benzphetamine or methamphetamine. Ten days of phosphatidylcholine treatment increased the concentration of choline in the brain but had no effect on the concentration of acetylcholine, the activity of choline acetyltransferase, cholinesterase activity, the apparent KD or Bmax of muscarinic receptors, or the fatty acid composition of rat brain lipids. These findings indicate that the largest effect caused by this treatment was an increase in the choline levels. No indication of altered cholinergic metabolism was observed. Further studies of the effects of chronic phosphatidylcholine treatment are required to clarify its therapeutic mechanism of action.
Theories of visual attention deal with the limit on our ability to see (and later report) several things at once. These theories fall into three broad classes. Object-based theories propose a limit on the number of separate objects that can be perceived simultaneously. Discrimination-based theories propose a limit on the number of separate discriminations that can be made. Space-based theories propose a limit on the spatial area from which information can be taken up. To distinguish these views, the present experiments used small (less than 1 degree), brief, foveal displays, each consisting of two overlapping objects (a box with a line struck through it). It was found that two judgments that concern the same object can be made simultaneously without loss of accuracy, whereas two judgments that concern different objects cannot. Neither the similarity nor the difficulty of required discriminations, nor the spatial distribution of information, could account for the results. The experiments support a view in which parallel, preattentive processes serve to segment the field into separate objects, followed by a process of focal attention that deals with only one object at a time. This view is also able to account for results taken to support both discrimination-based and space-based theories.
A field trial in Egypt of the plant molluscicide, Ambrosia maritima is described. Applications of 140, 70 and 35 mg/l-1 dry, whole plant were made to irrigation canals and drains in June. The treatment effect took between 1 and 5 weeks to become fully established. The reduction in the numbers of alive Biomphalaria alexandrina snails was generally more than 90% and was virtually the same at all treatment levels and in both types of watercourse. The snail population remained at a low level for at least 3 months until September-October. The possible use of a single, annual application in April or May in controlling snails throughout the main schistosomiasis transmission season in Lower Egypt is suggested.
Thirty-five patients were implanted with the Sequicor DDD pacemaker between September 1, 1981 and March 1, 1982. The mean age was 61.7 years (range, 17-88). According to their ECGs, the patients fell into two distinct groups--those with A-V block and those with sick sinus syndrome. Our initial experience has indicated an excellent electronic component function (except for 1 discrepant reed switch); high battery drain of the Sequicor; complications similar to those seen with DVI or VVI pacing; and an increase in the hemodynamic benefits resulting from DDD as compared to DVI or VVI pacing in 70% of patients.
A fragment of Staphylococcus aureus DNA encoding the alpha-hemolysin determinant was cloned from strain Wood 46 by inserting Sau3A-generated genomic DNA fragments between the BamHI sites of the lambda replacement vector L47.1. Phages expressing alpha-hemolysin were detected by overlaying plaques formed from several thousand independent recombinant phage with erythrocytes and looking for zones of hemolysis. One phage expressing alpha-hemolysin was purified and named lambda w alpha 3. This was subsequently shown to contain a 10.2-kilobase pair insert of S. aureus DNA. A 7.6-kilobase pair HindIII fragment encoding the alpha-hemolysin was subcloned from lambda w alpha 3 into the plasmid vector pACYC184 to form the hybrid plasmid pDU1148. Escherichia coli K-12 cells harboring pDU1148 synthesized a low level of alpha-hemolysin which remained associated with the cells and was not secreted into culture supernatants. When the same strain was stabbed onto blood agar plates, no zones of hemolysis were detected after overnight growth at 37 degrees C but hemolysis developed if the plates were left at room temperature for 48 h. By introducing specific deletions or Tn5 insertions into plasmid pDU1148, the alpha-hemolysin gene was mapped to a region within a 3.3-kilobase pair EcoRI-HindIII fragment which was subcloned onto the vector plasmid pBR322. A specific enzyme-linked immunosorbent assay with peroxidase-labeled rabbit anti-alpha-hemolysin antibodies was used to measure the levels of alpha-hemolysin antigen expressed in E. coli K-12 cells harboring pDU1148 or a variety of pDU1148::Tn5 and pDU1148 deletion mutants.
The number of pituitary GnRH receptors (GnRH-BC) is stable throughout the day in ovariectomized-estradiol treated rats, but undergo an acute transient reduction prior to the afternoon gonadotropin surge. To investigate the mechanisms controlling GnRH-BC we studied the effects of opioid-active compounds in this model. Morphine, given at 1400h, abolished both the LH surge and the preceding fall in GnRH-BC. Morphine given at 0900h increased GnRH-BC 30 min later, and this effect was abolished by simultaneous administration of naloxone. Naloxone alone produced an acute transient fall in GnRH-BC of similar magnitude to that seen before the spontaneous LH surge. These data suggest that alterations in endogenous opioid activity can modulate GnRH receptors and may form part of the mechanisms which initiate the afternoon gonadotropin surge.
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Control of Schistosoma mansoni transmission in a town in northern Ethiopia was attempted using the natural product, endod (Phytolacca dodecandra), and its use compared with niclosamide. Within a five year period prevalence was reduced from 61.5 to 36.4% in the area where endod was used. Most of this decline was accounted for by the reduction in prevalence among 1-6 year old subjects. The practical use of endod as a molluscicide was demonstrated to have a performance which compared favourably with the commercial product, and although more expensive than niclosamide still at minimal annual cost (US + 0.06 per capita).
Some effects of chronic, low-dosage treatment of Biomphalaria glabrata eggs and adults with nicotinanilide, are reported. The susceptibility of eggs decreased with age. The development and hatching of 0-1 day old eggs could be prevented by continuous exposure to 0.0005-0.001 mg/l-1 whereas prehatch stages had a susceptibility similar to that of adult snails (0.1-0.2 mg/l-1). The possible use of slow-release formulations of nicotinanilide in the control of field populations of snails and schistosomiasis transmission is discussed.
The composite plant, Ambrosia maritima is toxic to the snail intermediate hosts of schistosomiasis. A field trial was required to confirm this activity. A preliminary survey of irrigation canals and drains was conducted using two snail sampling methods. The results have been used to indicate the minimum number of watercourses which would have to be treated and the number of sampling stations per watercourse required to establish statistical significance in a kill of snails obtained from a molluscicide treatment.