Bilateral familial inferotemporal retinal dialyses.
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Child↗
Biomedical subjects
P J Allen
Publications and source records attributed to P J Allen.
Automated blood pressure measurement at rest and during exercise: evaluation of the motion tolerant CardioDyne NBP 2000.
PURPOSE: The purpose of this study was to validate the use of a motion tolerant blood pressure monitor (CardioDyne NBP 2000, Luxtec, Worcester, MA) ) against standard manual auscultation at rest and during exercise. METHODS: Nineteen subjects (men, N = 9; women, N = 10) participated in the study (mean: age 21+/-1.2 yr; height 172.5+/-8 cm; mass 69.4+/-14.5 kg). Standard Bruce protocol treadmill exercise tests with 12-lead ECG and metabolic measures were administered to the subjects, with blood pressure measures taken at rest before, during, and after the exercise tests. Blood pressure by manual auscultatory sphygmomanometry and the CardioDyne NBP 2000 was recorded simultaneously in the same arm. Manual auscultatory blood pressure measures obtained by one experimenter were used as the criterion measure, and the data of two NBP 2000 audio reviewers were averaged for each data point recorded. RESULTS: Systolic blood pressure (SBP) and diastolic blood pressure (DBP) via manual auscultation and the NBP 2000 "automatic" values were not significantly different and were highly correlated at rest and during exercise. Resting intraclass correlation SBP values were high (range 0.95 to 0.98), as were DBP intraclass correlation values (range 0.83 to 0.95). Exercise intraclass correlation SBP values ranged from 0.94 to 0.99, and DBP intraclass correlation values from 0.88 to 0.93. CONCLUSION: We conclude that the NBP 2000 is simple to use at rest and during exercise stress testing and provides accurate and verifiable information.
Adult↗
Recording of EEG during fMRI experiments: patient safety.
The acquisition of electroencephalograms (EEG) during functional magnetic resonance imaging (fMRI) experiments raises important practical issues of patient safety. The presence of electrical wires connected to the patient in rapidly changing magnetic fields results in currents flowing through the patient due to induced electromotive forces (EMF), by three possible mechanisms: fixed loop in rapidly changing gradient fields; fixed loop in a RF electromagnetic field; moving loop in the static magnetic field. RF-induced EMFs were identified as the most important potential hazard. We calculated the minimum value of current-limiting resistance to be fitted in each EEG electrode lead for a representative worst case loop, and measured RF magnetic field intensity and heating in a specific type of current-limiting resistors. The results show that electrode resistance should be > or = 13 k(omega) for our setup. The methodology presented is general and can be useful for other centers.
Electroencephalography↗
Saphenous vein versus polytetrafluoroethylene carotid patch angioplasty.
BACKGROUND: The optimal material for carotid patch angioplasty after endarterectomy remains uncertain. This study compares the early outcome and recurrent stenosis rates between saphenous vein (SV) and expanded polytetrafluoroethylene (ePTFE) carotid patch angioplasty. METHODS: The results of 421 consecutive carotid endarterectomies performed over a 72-month period were reviewed. Postoperative complications and restenosis rates, defined as > OR = 60% narrowing measured by color flow duplex, were compared. RESULTS: Patch angioplasty was performed with SV in 287 and with ePTFE in 110 cases. Patients who had undergone primary closure (n = 20) or whose form of closure was unknown (n = 4) were excluded. The mean age of patients and length of follow-up was similar between groups. Women were more likely to be patched with ePTFE than were men (36% versus 23%, P = 0.02). One death occurred in each group (0.3% SV, 0.9% ePTFE, P = 0.47), and four strokes occurred in each group (1.4% SV, 3.6% ePTFE, P = 0.22). Cervical hematomas requiring operative evacuation occurred in five SV closures and in three ePTFE closures (1.7% versus 2.7%, P = 0.69). Vein harvest site complications occurred in 6 patients (2%) who had undergone SV patch angioplasty. Recurrent stenosis occurred in 3 patients with SV closure and in 3 patients with ePTFE closure (1.0% versus 2.7%, P = 0.35). The 60-month restenosis rates by life table analysis were 2.6% +/- 2.1% for SV and 10.7% +/- 7.9% for ePTFE (P = 0.17). CONCLUSIONS: The incidence of postoperative complications is similar with SV or ePTFE patch angioplasty; however, vein harvest site complications are avoided with the use of ePTFE. Recurrent stenosis at 5 years occurs infrequently with either SV or ePTFE.
Aged↗
Interspecific microsatellite markers for the study of pinniped populations.
Microsatellites have rapidly become the marker of choice for a wide variety of population genetic studies. Here we describe 20 pinniped microsatellite markers which have been tested across 18 pinniped species. The majority of these markers have broad utility in all pinnipeds and provide a strong base for detailed population genetic studies in the Pinnipedia.
Animals↗
Peripheral transscleral retinal diode laser for rubeosis iridis.
PURPOSE: To evaluate the results of peripheral transscleral retinal diode photocoagulation with or without transscleral cyclodiode therapy in patients with rubeosis iridis with or without elevated intraocular pressure and no fundal view. METHODS: Peripheral transscleral retinal diode photocoagulation was performed in 15 eyes of 13 patients in an attempt to promote regression of rubeosis. The fundus could not be seen in any of the 15 eyes, so conventional panretinal photocoagulation was not possible. Nine eyes had associated elevated intraocular pressure and were treated with concurrent transscleral diode cyclophotocoagulation. RESULTS: All eyes showed regression of rubeosis. Of the nine eyes treated with combination therapy, six had stabilized intraocular pressure, and three developed hypotony. None of the eyes developed a peripheral retinal detachment, and one eye lost the ability to perceive light. CONCLUSIONS: This method is effective in treating patients with rubeosis iridis when the view of the fundus is inadequate for conventional panretinal photocoagulation and more extensive intraocular surgery is precluded. It may be combined with transscleral cyclophotocoagulation therapy to manage concurrent high intraocular pressure in rubeotic glaucoma, but this involves a risk of postoperative hypotony.
Adult↗
Autoantibodies to the collagenous region of C1q occur in three strains of lupus-prone mice.
We have developed an ELISA to measure murine autoantibodies to the collagenous region (CLR) of C1q, using the whole human C1q molecule as the solid-phase ligand, in the presence of 1 M NaCl. The assay was validated by testing positive sera from 20 mice using purified mouse C1q, and from 10 mice using purified human C1q-CLR, as the solid-phase ligands. There were highly significant correlations between results obtained with human C1q (whole molecule) and: (i) mouse C1q (rsp = 0.73, P less than 0.001), and (ii) human Clq-CLR alone (rsp = 0.86, P = 0.001). Antibodies to Clq were measured in 53 MRL/lpr, 17 BXSB and 25 NZB/W lupus-prone mice. Median (range) anti-C1q (CLR) antibody levels in MRL/lpr, BXSB, and NZB/W autoimmune mice aged 3 months were 22 (16-66), 21 (17-39) and 19 (15-27) EU, respectively. The median anti-Clq antibody level in MRL/lpr mice aged 5 months was 76 (35-142) EU, significantly higher than that at 3 months (U = 558, P less than 0.0005). Median anti-C1q antibody level in NZB/W mice at 8 months was 37 (13-74) EU and in BXSB mice at 11 months was 62 (31-231) EU, significantly higher than corresponding values at 3 months (U = 326, and U = 4, P less than 0.001, respectively). This is the first demonstration of anti-C1q (CLR) antibodies in NZB/W and BXSB mice. The pathologic significance and the potential utility of these antibodies for monitoring disease in lupus-prone mice are under evaluation.
Aging↗
First seizures associated with playing electronic screen games: a community-based study in Great Britain.
Active surveillance by virtually all electroencephalographic departments throughout Great Britain identified 118 patients who had a first seizure while playing an electronic screen game during two 3-month periods. Patients were divided into Group A (46 patients)--those for whom there was thought to be a definite causal relationship (type 4 photoparoxysmal response); Group B (25 patients)--those for whom there was a probable causal relationship (types 1-3 photoparoxysmal response, clinical evidence of photosensitivity, subsequent recurrent seizures on repeat exposure to electronic screen games, and/or occipital spikes in the resting electroencephalogram); and Group C (47 patients)--those for whom there was no apparent causal relationship. The number of patients in Group C did not exceed that expected by the chance occurrence of two common events (playing electronic screen games and incidence of epilepsy). Most (103/118) of the patients were in the age range of 7 to 19 years. Within this age group the annual incidence of first seizures triggered by playing electronic screen games (Groups A and B combined) was estimated to be 1.5/100,000.
Adolescent↗
Incidence of photosensitive epilepsy: a prospective national study.
We undertook a prospective nationwide study to determine the incidence of photosensitive epilepsy (PE). Virtually all EEG departments in Great Britain (providing approximately 90% coverage of all EEGs performed on people with newly diagnosed seizures) screened cases referred to them over a 3 month period and identified all new cases of epilepsy (defined as one or more recognised seizures) whose first EEG showed a photoparoxysmal response (PPR) on intermittent photic stimulation (IPS). 191 cases were identified, 143 of whom had type 4 PPRs (generalised spike and wave on IPS) on their first EEG. The annual incidence of cases of epilepsy with type 4 PPRs on their first EEG was conservatively estimated to be 1.1 per 100,000, representing approximately 2% of all new cases of epilepsy. When restricted to the age range 7-19 years, the annual incidence rose to 5.7 per 100,000-approximately 10% of all new cases of epilepsy presenting in this age range. To ascertain if there was a significant seasonal variation in PE, 5 EEG departments (which together contributed 15% of cases in the first study period) were visited during a second 3 month study period to identify all new cases of epilepsy with type 4 PPRs on their first EEG. No significant seasonal variation in incidence between summer and winter was found.
Adolescent↗
Lower extremity lymphedema caused by acquired immune deficiency syndrome-related Kaposi's sarcoma: case report and review of the literature.
A case of severe lymphedema of the lower extremity caused by obstruction by human immunodeficiency virus-associated Kaposi's sarcoma is presented. A review of the signs and symptoms of obstructive lymphedema and Kaposi's sarcoma is provided. Early recognition of this clinical entity may allow use of simple preventative measures and help to avoid this life- and limb-threatening situation.
Acquired Immunodeficiency Syndrome↗
Microsatellite variation in grey seals (Halichoerus grypus) shows evidence of genetic differentiation between two British breeding colonies.
Eight highly variable microsatellite loci were used to examine the genetic variability and differentiation of grey seals (Halichoerus grypus) at two widely spaced British breeding colonies. Samples were collected from adults and pups on the island of North Rona, off the north-west coast of Scotland, and on the Isle of May, situated at the mouth of the Firth of Forth on the east coast. Highly significant differences in allele frequencies between these two sites were found for all eight loci, indicating considerable genetic differentiation. Thus, although grey seals are known to range over very large areas outside the breeding season, site fidelity of adults and philopatry of pups for these breeding colonies must be sufficiently common to have effects, through genetic drift, at the sub-population level. Migration rate was estimated using Wright's fixation index (FST), Slatkin's private alleles model and the new statistic, RST, which is analogous to FST but which takes into account the process of microsatellite mutation. An almost 8-fold discrepancy between the values we obtained provides cautionary evidence that microsatellite loci may contravene one or more of the assumptions on which these methods are based.
Alleles↗
Partial purification and reconstitution of the sarcolemmal L-lactate carrier from rat skeletal muscle.
Purified sarcolemmal membranes from mixed rat hindlimb muscle were solubilized with octylglucoside and the extract subjected to hydroxylapatite (HA) chromatography. Following protein elution with a sodium phosphate gradient and detergent removal by dialysis, the HA eluate was reconstituted into asolectin liposomes using a freeze-thaw procedure. Specific L-[14C]lactate transport activity eluting from the 0.2 M sodium phosphate fraction was 30-fold higher compared with native sarcolemmal vesicles (31.64 versus 1.06 nmol/min per mg). The reconstituted carrier exhibited Michaelis-Menten saturation kinetics with Km and Vmax. values of 46.2 +/- 6.6 mM and 498.7 +/- 17.2 nmol/15 s per mg respectively. L-Lactate transport activity was inhibited 57% by preincubation of proteoliposomes with 10 mM alpha-cyano-4-hydroxycinnamate, a known inhibitor of lactate transport. Analysis of the HA eluates by SDS/PAGE showed the presence of a 34 kDa band corresponding to lactate transport activity. Reconstitution of lactate transport activity eluting from the HA column, together with SDS/PAGE analysis suggests the presence of a 34 kDa polypeptide mediating sarcolemmal lactate exchange in rat skeletal muscle.
Animals↗
A specialised computer-based monitoring system for intraoperative electrocorticography.
We have developed a computer-based intraoperative ECoG monitoring system which offers the flexibility of digital recording and allows detailed review of recorded events without interrupting monitoring. In addition, a diagram showing the electrode positions on the brain can be generated on computer screen and subsequently displayed during monitoring--this allows automatic indication of the electrode positions corresponding to specific ECoG channels and can provide the surgeon with a clear visual impression of the area of spiking.
Cerebral Cortex↗
Hemicentral retinal vein occlusion associated with ocular hypertension and clotting abnormality.
Hemicentral retinal vein occlusion in a young adult man occurred after a high corticosteroid-induced increase in intraocular pressure (IOP), supporting the accepted association between raised IOP and retinal vein occlusion. However, detection of a plasminogen activator deficiency in this patient indicated a particular susceptibility to intravascular clotting episodes.
Adult↗
Very high-frequency rhythmic activity during SEEG suppression in frontal lobe epilepsy.
Intracerebral EEG (SEEG) recordings showing the development of fast rhythmic activity at seizure onset provide important evidence for the localisation of an epileptic focus. However, very high-frequency activity (greater than 50 Hz) of low amplitude relative to the background may not be apparent on the paper record due to the limited bandwidth and dynamic range of conventional SEEG recording and display methods. The use of a digital telemetry system with a fast sampling rate (400 Hz) and a wide dynamic range (1 microV resolution, 4 mV range) has allowed us to utilize expanded time scale SEEG plots and autoregressive spectral estimation to identify this activity in chronic SEEG studies. This may be particularly useful in frontal lobe epilepsy, where rapid propagation often prevents adequate localization using conventional methods of analysis.
Adult↗
Measurement of interhemispheric time differences in generalised spike-and-wave.
We have compared interhemispheric time differences (ITD) calculated by coherence/phase and linear and non-linear correlation analyses of generalised spike-wave episodes in 30 patients (15 with primary generalised epilepsy (PGE), 5 with secondary generalised epilepsy (SGE) and 10 with a lateralised epileptogenic area). Most cases were recorded during routine departmental EEGs. No significant difference was found between measures of interhemispheric synchrony (IS) (proportion of ITDs that are synchronous) calculated using the linear and the non-linear correlation techniques, although the latter gave slightly more (average 7%) valid ITD estimates. This suggests that the non-linear correlation technique does not provide significantly more time difference information than its linear counterpart. Similarly, no significant differences in IS values were identified between the coherence/phase and the correlation techniques. For all 3 techniques, IS values greater than 50% were derived for most patients with PGE and SGE; the proportion of patients with a lateralised epileptogenic area showing this was smaller. However, broad overlap in the distribution of IS values between the 3 groups suggests that individual patients cannot reliably be distinguished using these methods.
Action Potentials↗
The effect of sleep on the dyskinetic movements of Parkinson's disease, Gilles de la Tourette syndrome, Huntington's disease, and torsion dystonia.
The effect of sleep on the involuntary movements or dyskinesias in Parkinson's disease, Huntington's disease, primary and secondary torsion dystonia, and Gilles de la Tourette syndrome was studied in a total of 52 patients and 10 normal subjects using video electroencephalographic telemetry. Movements typical of the wake pattern were seen occasionally during unequivocal sleep in all but two completed studies, and in each condition reappeared under similar circumstances. The movements were most likely to occur after awakenings or lightenings of sleep, or in stage one sleep. The movements were very rare during the deeper phases of sleep. Those movements that occurred during sleep without awakenings were usually preceded by arousal phenomena and, rarely, by sleep spindles or slow waves. The control group showed normal "semipurposeful" movements under the same conditions during sleep. The rare appearance of the different dyskinesias and normal movements under similar circumstances during sleep could be a result of common effects on the generator systems or changes in the excitability of the final common motor pathway.
Brain↗