Biomedical subjects
Publications and source records attributed to J Ives.
The radiological techniques that can be used to selectively embolise small arteries have improved markedly in the past few years. This article discusses the use of transcatheter embolisation in the management of three patients with aneurysms involving the intrahepatic arterial tree.
The accuracy with which electrical sources in the brain can be localized by using electroencephalograms measured on the scalp is not well known. In this study, tests of localization accuracy were performed by using implanted dipolar sources in the human brain. These dipoles are created by passing a weak (subthreshold) current through intracerebral electrodes implanted in the brains of epileptic patients for seizure monitoring. The locations of these dipoles are accurately known from roentgenographs. First, 16 electroencephalograms produced by these dipoles were recorded, then inverse solutions were calculated for the apparent sources of these electroencephalograms. Finally, the locations of the apparent sources were compared with the known locations of the implanted dipoles to determine localization error. The average localization error for a total of 28 dipoles in 3 subjects was 1.1 cm. These results indicate that good localization accuracy for focal sources in the brain can be provided by scalp electroencephalograms.
It is believed that the magnetoencephalogram (MEG) localizes an electrical source in the brain to within several millimeters and is therefore more accurate than electroencephalogram (EEG) localization, reported as 20 mm. To test this belief, the localization accuracy of the MEG and EEG were directly compared. The signal source was a dipole at a known location in the brain; this was made by passing a weak current pulse simulating a neural signal through depth electrodes already implanted in patients for seizure monitoring. First, MEGs and EEGs from this dipole were measured at 16 places on the head. Then, computations were performed on the MEG and EEG data separately to determine the apparent MEG and EEG source locations. Finally, these were compared with the actual source location to determine the MEG and EEG localization errors. Measurements were made of four dipoles in each of three patients. After MEGs with weak signals were discounted, the MEG average error of localization was found to be 8 mm, which was worse than expected. The average EEG error was 10 mm, which was better than expected. These results suggest that the MEG offers no significant advantage over the EEG in localizing a focal source. However, this does not diminish other uses of the MEG.
The application of current health promoting behaviour models for understanding psycho-social determinants of condom use is discussed. It was concluded that their utility is reduced because they are individualistic models and do not take into account interaction between couples, and contextual factors. Systemic AIDS counselling and relapse prevention approaches to invervention may provide a better basis for developing an appropriate methodology for studying condom use because they incorporate contextual factors. Some future directions for research into the determinants of condom use and the implications for health education and counselling are proposed.
We compared the pulsatile secretion of luteinizing hormone (LH) between 13 men with clinically and electrographically documented temporal lobe seizures and 8 age-matched controls. Serum for LH measurement was drawn every 15 minutes during 8 hours of EEG telemetry in both groups. The 2 groups did not differ significantly in average mean baseline LH secretion, total LH secretion, or average pulse amplitude. The group with seizures, however, showed a significantly greater (p less than 0.05) variability of baseline LH secretion and pulse frequency. Among the men with unilateral paroxysmal EEG findings, pulse frequency was significantly greater (p = 0.05) with right epileptiform discharges or left slowing (6.4 +/- 0.4) than with left epileptiform discharges or right slowing (3.0 +/- 1.3). The relationship of pulse frequency to the nature and laterality of paroxysmal discharges makes it unlikely that endocrine abnormalities can be attributed to medication alone and strengthens the notion that temporal lobe epileptiform discharges may disrupt hypothalamic regulation of pituitary secretion.
Expression of the bacteriophage Mu mom gene is subject to a variety of regulatory controls. Both the host Dam DNA-adenine methylase and the phage Mu C protein are required for mom gene transcription. In addition, the Mu com gene product is required for production of the mom protein. Because the com and mom genes overlap on the same mRNA transcript (with com being located proximal to the 5' end), it is likely that Com function is exerted after transcription initiation. To study the role of Com, two segments of Mu were cloned in both orientations (+ and -) into the HindIII site of the galactokinase expression vector, pKG1800; the HindIII site is located between the galK structural gene and its promoter. In (+) plasmids, the Mu DNA inserts were transcribed from the gal promoter in the same orientation as in the phage genome; (-) plasmids had the Mu DNA inserted in the reverse orientation. Each Mu insert contained the same segment of the mom gene from the 3' terminus, but differed in the extent of com gene included at the 5' terminus; one contained a truncated com gene and the other a complete com gene, as well as upstream Mu regulatory sequences. The results are summarized as follows: (1) both (-) plasmids produced only about 10% as much galactokinase activity following fucose induction as the parental vector, pKG1800; (2) plasmid pGTVH(+), with an intact com gene produced about 30% as much galactokinase as pKG1800; (3) plasmid pMTVH(+), with a truncated com gene, produced only about 10% as much enzyme as pKG1800.(ABSTRACT TRUNCATED AT 250 WORDS)
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The reliability of a standardized brief-pulse stimulus in eliciting a satisfactory convulsive response was evaluated under normal clinical conditions. A total of 89 patients were given 961 initial treatments. Of these, 757 were at the standardized level with a success rate of 89%. A total of 204 trials were given at higher-than-standardized levels. Treating these as standardized level failures, the overall success rate was 70%. The probability that a standardized stimulus given to any patient at any point in the treatment series would be successful was about 7 chances in 10. Implications for the selection of ECT stimuli were discussed.
Expression of the bacteriophage Mu mom gene is under tight regulatory control. One of the factors required for mom gene expression is the trans-acting function (designated Dad) provided by another Mu gene. To facilitate studies on the signals mediating mom regulation, we have constructed a mom-lacZ fusion plasmid which synthesizes beta-galactosidase only when the Mu Dad transactivating function is provided. lambda pMu phages carrying different segments of the Mu genome have been assayed for their ability to transactivate beta-galactosidase expression by the fusion plasmid. The results of these analyses indicated that the Dad transactivation function is encoded between the leftmost EcoRI site and the lys gene of Mu; this region includes the C gene, which is required for expression of all Mu late genes. Cloning of an approx. 800-bp fragment containing the C gene produced a plasmid which could complement MuC- phages for growth and could transactivate the mom-lacZ fusion plasmid to produce beta-galactosidase. These results suggest that the C gene product mediates the Dad transactivation function.
An ubiquitous digital clock 'time-scribe' with a unique pen-galvanometer writer section has been described which should greatly improve the correlation of a long term EEG with any other time related event or medium. The output of the clock generates on any pen-galvanometer based chart recorder numerical and some alpha characters which are easily and immediately readable. Because of its convenience, simplicity and basic practical application it should also stimulate discussion for the unification of time write-out standards and methods.
Forced lateralized head-turning, occurring as the first clinical sign in 106 epileptic seizures in 43 patients, was recorded on videotape simultaneously with the EEG. Forty-five ictal EEGs were obtained with stereotaxically implanted intracerebral electrodes. Forced head-turning was seen with seizures that had a frontal, temporal, unilateral diffuse, or a generalized onset in the EEG. Ipsilateral was as common as contralateral head-turning in all groups, including the seizures with frontal lobe onset. Initial head-turning in a seizure has no localizing or lateralizing significance.
A young woman had seizures suggestive of temporal lobe origin with some clinical features indicative of occipital onset. Electroencephalograms recorded through scalp and sphenoidal electrodes showed predominantly right posterior temporooccipital epileptogenic discharges. Stereotaxic depth electrode recordings from the right temporal and occipital lobes demonstrated that some seizures arose independently from either the temporal or occipital lobes. Most arose within the occipital lobe, but, to become clinically evident, the seizure discharge had to spread to the temporal lobe. Following temporal lobe resection, including excision of limbic structures, the patient has remained seizure free for four years except for a few generalized seizures before and after delivery of her child.
Three studies of parameters of short-pulse ECT are reported: (i) voltage threshold, (ii) interpulse interval, an (iii) pulse polarity. Using a defined standard stimulus, voltage thresholds were found to vary from 110-250 V with a mean of 185 V. Some patients also required an increased number of pulses. The interpulse interval study demonstrated that intervals from 30 to 50 msec were successful in over 90% of the group. An interpulse interval of 30 msec was adopted as a standard treatment. The third study demonstrated no difference in efficiency of convulsion production when all positive, all negative, or alternating positive and negative pulse stimuli were applied.
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Using a low-energy brief-pulse stimulus, the threshold number-of-pulses required to produce a bilaterally manifested tonic-clonic seizure with unilateral and bilateral electrode placement was investigated. Unilateral placement required significantly fewer pulses; bilateral placement resulted in greater post-ictal confusion with no apparent advantage in clinical efficacy. A possible explanation in terms of intracerebral current density is proposed.
The study concerns an epileptic patient whose absence attacks were contingent on the viewing of striped patterns. A series of experiments demonstrated first that seizures were not due to the intermittent stimulation of retinal cells produced as physiological nystagmus vibrated the image of the pattern, and secondly that seizures were triggered at the cortical level, probably by the firing of complex cells. Spectacles which occluded pattern vision in one eye were highly effective in reducing seizure incidence.
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