Peak Identification in Visual Evoked Potentials

Waveform patterns evoked by 4 intensities of flash in normal subjects were studied in relation to intersubject variability. Time-frequency distribution curves of all peaks occurring between 11 and 280 msec after flash onset and meeting minimal criteria were obtained from 46 males. These distributions closely corresponded to similar data reported by others for single intensity stimulation. An algorithm was developed which identified in 67 to 100% of instances a single “peak event’ within the time ranges of each of 6 peak distributions. Many peak events appeared and disappeared within the 4 intensity sets of individuals. Latencies were obtained for these peak events. Application of the algorithm to a replicate sample of 29 Ss, which included 8 females, indicated generalizability. Test-retest data on 15 Ss showed its reliability. The data suggest that methodology significantly contributes to the variability of peak identification among subjects. This may be reduced by employing multiple intensities of stimulation.     

Polymérisation de thiirannes différemment substitués à l'aide du système chiral ZnEt2/(S)-dihydroxy-2,2′ binaphtyl-1,1′, 1. Stéréoélectivité de la polymérisation

Differently substituted thiiranes were polymerized using an atropoisomeric chiral initiator: ZnEt₂/(S)-2,2′-dihydroxy-1,1′-binaphthyl (DHBN) (mole ratio 1/1). It was observed that high stereoelectivities are obtained with monomers bearing small alkyl substituents and that the resolution efficiency of the initiator decreases as the bulkiness of the substituent increases. From the comparison of the results obtained with another initiator system, ZnEt₂/(R)-3,3-dimethyl-1,2-butanediol (DMBD) (mole ratio 1/1), the use of ZnEt₂/(S)-DHBN could be shown to be more suitable for the polymerization of thiiranes with linear alkyl substituents. Contrary to the case of polymerization initiated by the system ZnEt₂/(R)-DMBD, the polymerization reaction of thiiranes with ZnEt₂/(S)-DHBN was usually accompanied by the production of the corresponding olefins in various amounts.     

Production of a monoclonal antibody with specificity for deoxynivalenol, 3‐acetyldeoxynivalenol and 15‐acetyldeoxynivalenol

Monoclonal antibodies reactive with deoxynivalenol were generated following the immunization of mice with a deoxynivalenol‐mouse serum albumin conjugate. One of the anti‐deoxynivalenol monoclonal antibodies, designated C6–1, exhibited cross‐reactivity with 3‐acetyldeoxynivalenol and 15‐acetyldeoxynivalenol but not with nivalenol, T‐2 tetraol or scirpentriol. An indirect competitive ELISA based on this monoclonal antibody gave 50% inhibition values of 0–6 μg ml^‐1 for deoxynivalenol, 0–2 μg ml^‐1 for 15‐acetyldeoxynivalenol and 10 μg ml^‐1 for 3‐acetyldeoxynivalenol.     

Clinical and electrophysiological aspects of median intra-His bundle block with normal electrocardiogram at rest

The clinical and electrophysiological features and the natural history of median intra-His block with a normal resting electrocardiogram were studied: 11 patients had a fixed split H1-H2 potential with a spontaneous or induced block between H1 and H2. The patients (5 men and 6 women) were aged 17 to 70 years (average 53 years). Associated pathology included 2 cases of aortic stenosis (1 severe), 1 case of ischaemic heart disease (effort angina), 1 case of mitral valve prolapse and 2 cases of hypertension. The presenting symptoms were syncope (4 cases), dizziness (2 cases), effort angina (1 case) and tiredness (3 cases); 1 patient was asymptomatic. Holter monitoring (24 hours) was performed in 8 patients and s-owed paroxysmal conduction defects in 6 cases; 4 Mobitz II 2nd degree AV block, 1 3rd degree AV block with narrow QRS complexes and 1 case of blocked atrial extrasystoles at coupling intervals longer than 480 ms and sinus cycle lengths of over 800 ms. Exercise testing by bicycle ergometry (4 patients) was normal in 1 case and revealed Mobitz II 2nd degree AV block in 3 cases. Baseline electrophysiological studies showed an A-H1 interval ranging from 60 to 100 ms (average 78 ms), a H1-H2 interval of 20 to 40 ms (average 31 ms) and a H2-V interval of 30 to 50 ms (average 32 ms). Block between H1 and H2 was observed: "spontaneously" during electrophysiological investigation in 6 cases, after IV atropine in 1 case, during overdrive atrial pacing at rates slower than 150/min in 7 cases, after atrial extrastimulus with a functional intra-His refractory period of over 420 ms in 7 cases, after ajmaline in 3 of the 4 cases in which this test was performed. A cardiac pacemaker was implanted in 10 patients in whom the initial symptoms have all regressed; the remaining patient considered to be "epileptic" had another syncopal attack under therapy and was finally paced. This series demonstrates that the diagnosis of median intra-His block depends on precise electrophysiological criteria and should be looked for even when the presenting symptoms are atypical; some of our patients complained only of tiredness. The value of Holter monitoring and careful endocavitary investigation is emphasised. Median intra-His block should be distinguished from longitudinal and functional His bundle dissociation.     

Primary colorectal non-Hodgkin's lymphoma

Background: The gastrointestinal tract is the most common site of extranodal involvement in non-Hodgkin's lymphoma (NHL). Primary colorectal NHL comprises 13–18% of all gastrointestinal NHL but is not commonly reported as a separate entity. Methods: This was a retrospective review of the medical records of 19 patients over a 16-year period to evaluate the clinical features and behavior of colorectal NHL. Results: A pediatric group of seven male patients presented at an early stage with acute symptomatology. The primary tumor was located in the ileocecum in all cases and intussusception was common. An adult group of 12 patients presented at a later stage with chronic symptomatology. Staging study results were positive by bone marrow biopsy in four of 16 patients (25%), by lymphangiography in six of 11 patients (54.5%), and by gallium scan in eight of 10 patients (80%). Seven patients relapsed a median of 8 months after treatment. Three other patients died during treatment, one died of other causes, and one died without receiving treatment. The remaining seven patients are alive from 41 to 231 months without evidence of disease. Five of these patients are in the pediatric group, where the median survival was >72 months. The overall median survival was 45 months. Conclusion: Colorectal NHL is a disease that affects both the pediatric and adult population. Although pediatric patients have an excellent prognosis with anticipated long-term survival after treatment, long-term survival can be expected in 50% of adult patients. In both groups of patients, multimodality therapy with surgery, chemotherapy, and radiation is the treatment of choice.Presented at the 46th Annual Cancer Symposium of The Society of Surgical Oncology, Los Angeles, California, March 18–21, 1993.     

Construction,quality assurance and calibration of spherical isotropic fibre optic light diffusers

Spherical isotropic fibre optic light diffusers are used in photodynamic therapy either as a light source or as a light detector. The construction of light diffusers using different materials is described, viz. an optical method involving local polymerization of a dental fissure sealant, which is referred to as the Henderson method, and a second method using plastic or ceramic pre-fabricated spheres. Quality tests necessary for reliable clinical use are presented for the mechanical strength, output power and isotropy. The maximum pull-off force and blow-off output power for the different kinds of diffusers were determined. The calibration procedures are given for measurement of the output power and wavelength of the light emitted by a diffuser and for measurement of the fluence rate by a light-detecting diffuser, using a compact integrating sphere device. With all types of diffusers described, an isotropy can be obtained of better than ± 20% measured over a 320° angle for spheres as small as 1 mm. Larger ceramic diffusers are particularly suitable for delivering high output powers. A 3-mm-diameter ceramic diffuser mounted on a 600-m-core fibre can emit up to 5 W of continuous wave (CW) visible light in air. Diffusers used for light detection can measure the light fluence rate in tissue with 15% accuracy or better if calibration factors are determined for each individual probe.     

The influence of dairy products on plasma uric acid in women

Elevated levels of plasma uric acid have been linked to increased risk of cardiovascular diseases and their complications. As dairy proteins have been found to decrease plasma uric acid without increasing glomerular filtration rate, a sample of postmenopausal women living in Montreal was studied to investigate the nature of this relationship. Participants (158 Roman Catholic nuns) were randomly assigned to one of two test diets for a period of four weeks: the dairy foods group (n=81) consumed approximately 30 grams of dairy protein daily and the dairy-free diet group (n=77) ate no dairy foods at all. Subjects completed two one-day food records, a core questionnaire and a dairy foods diet history; blood specimens were obtained, and blood pressure, height and weight were measured. Average nutrient intakes differed as a consequence of the test diets, with significantly greater intakes of protein, fat, saturated fat, monounsaturated fat, potassium and calcium (p<0.01) in the dairy group after the study period, and lower dietary levels of protein, cholesterol, calcium and retinol (p<0.01) in the dairy-free group. Plasma uric acid was unchanged after the dietary intervention in the dairy group, but increased by 7.8 µmol/1 (p=0.03) in subjects on the dairy-free diet; however, diastolic blood pressure decreased in response to calcium (=–22.9, SE=10.0,p=0.02) among those whose diet included dairy foods. The study results suggest that proteins of dairy origin may play a role in stabilising or lowering plasma uric acid, and that calcium or other components found in milk products may also reduce diastolic blood pressure. While these findings have implications for dietary prevention to decrease cardiovascular risk in postmenopausal women, further investigations should examine these mechanisms in men over the age of 50 to ascertain whether a similar response would occur.