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Biomedical subjects

M R Newton

Publications and source records attributed to M R Newton.

32 records · Page 2Linked to original sources
PubMed1993

Comparative IgE responses to extracts of five species of house dust mite, using western blotting.

IgE responses towards extracts of Dermatophagoides pteronyssinus, D. farinae, D. microceras, Euroglyphus maynei and Gymnoglyphus longior have been evaluated with sera from a mite sensitive population and the international reference pool of sera, NIBSC 82/528, using Western blotting. Using mite body and faecal extracts 21 of 29 mite protein bands responded to by sera were common to all five species of mite. All sera were unique with respect to proteins bound and species recognized. Mite proteins bound by more than 40% of sera included the Group II and III main allergens and protein bands 14 (MW 40.4 kD) and 21 (MW 27.8 kD), all of which were found in every mite species studied. The Group I allergen, found in all species, was bound by 29.4% of sera. Similar response profiles between mite species suggest that human specific IgE may bind predominantly to crossreactive determinants on mite allergens.

Adolescent↗
PubMed1993

Ictal SPECT using technetium-99m-HMPAO: methods for rapid preparation and optimal deployment of tracer during spontaneous seizures.

Ictal SPECT provides unique information for the clinician treating patients with refractory epilepsy and reveals insights into the pathophysiology of seizures. We describe our methods for the routine attainment of ictal images using 99mTc-HMPAO. We have devised and implemented techniques for rapid reconstitution of 99mTc-HMPAO adjacent to the video-EEG monitoring suite such that the tracer can be rapidly injected into patients when spontaneous seizures occur. Our quality assurance data show that this can be done safely outside a nuclear medicine department. The clinical results in patients with temporal lobe epilepsy show that ictal injections (97% correct lateralization of focus, 0% incorrect) are more sensitive and accurate compared to interictal studies (48% correct, 10% incorrect), demonstrating that the implementation of these techniques is worthwhile.

Brain↗
PubMed1992

Postictal switch in blood flow distribution and temporal lobe seizures.

The ictal increase of regional cerebral blood flow has yet to be fully utilised in the investigation of focal seizures. Although single photon emission tomography (SPECT) is being increasingly used in the localisation of epileptic foci, the evolution and time courses of the peri-ictal perfusion changes have yet to be clarified. We performed serial SPECT studies in the interictal, ictal and immediate postictal states in 12 patients with refractory temporal lobe epilepsy to define the patterns and duration of peri-ictal cerebral blood flow changes. Visual analysis showed a constant pattern of unilateral global increases in temporal lobe perfusion during seizures which suddenly switched to a pattern of relative mesial temporal (hippocampal) hyperperfusion and lateral temporal hypoperfusion in the immediate postictal period. Quantitative analysis confirmed the visual assessment. Lateral temporal cortex ictal/normal side to side ratios were increased by mean 35.1% (95% confidence interval 21.8% to 48.4%) more in the ictal studies than in the interictal studies and mesial temporal cortex ratios increased by mean 30.8% (22.4% to 39.2%). In the postictal state, however, lateral temporal ratios were reduced by mean 7.7% (-15.8% to 0.4%) compared with interictal values, whereas mesial temporal perfusion was maintained compared with the interictal studies. These observations provide critical information for interpreting scans which can be used in the localisation of epileptic foci. This postictal switch in blood flow patterns may reflect the underlying metabolic processes of neuronal activation and recovery and have implications for understanding the neurobiology of human epileptic seizures.

Basal Ganglia↗
PubMed1992

A study comparing SPECT with CT and MRI after closed head injury.

After closed head injury nineteen patients had single photon emission tomography (SPECT) using the lipophilic tracer 99m-Technetium hexamethyl-propylene-amineoxime (HMPAO) to compare the defects shown by CT and MRI. SPECT showed more focal cerebral lesions than either CT or MRI alone or in combination. Most lesions shown by SPECT were not shown by CT or MRI in the corresponding anatomical regions. The most severely disabled patients showed the highest number of SPECT lesions (average four per patient) and the lowest (mean, SE) cerebral blood flow (718, 69 ml/min) compared with the less disabled patients (two per patient and 1058, 51 ml/min, p less than 0.05). There was a correlation between the Glasgow Outcome Scale grade and the global cerebral blood flow (r 0.74, p less than 0.05). The perfusion defects may correlate with clinical signs that were not explained by CT or MRI findings. SPECT may complement the clinical evaluation in the assessment of outcome after head injury.

Brain Injuries↗
PubMed1992

Frequent involvement of the optic radiation in patients with acute isolated optic neuritis.

Magnetic resonance imaging revealed asymptomatic lesions in white matter regions corresponding with the optic radiations in 20 of 28 patients (71%) with clinically isolated optic neuritis. In contrast to the findings with symptomatic lesions, there was no relationship between the latency of the visual evoked potential and the presence of these asymptomatic posterior visual pathway lesions.

Acute Disease↗
PubMed1992

Dystonia, clinical lateralization, and regional blood flow changes in temporal lobe seizures.

We analyzed the lateralizing value of ictal dystonia and head-turning in temporal lobe epilepsy, and sought the biologic basis of these clinical signs by studying the regional changes in perfusion with ictal single-photon emission computed tomography (SPECT). We identified unilateral temporal lobe epilepsy in 40 of 42 patients undergoing evaluation for temporal lobe surgery, and with ictal SPECT all 40 showed striking hyperperfusion of the epileptogenic temporal lobe. Twenty-five of the 40 patients showed unilateral or predominantly unilateral upper limb dystonia, which was opposite the epileptic temporal lobe in all cases. Analysis of regional count ratios in cases with ictal dystonia, compared with those without, showed significant changes only in the basal ganglia. Specifically, we found that ictal dystonia was associated with a relative increase in perfusion of the basal ganglia opposite the dystonic limb. Although we found 26 cases with head-turning, the sign was of no lateralizing value, even when only those with major or "tonic" versions (n = 11) were analyzed. Slight increases in cortical blood flow on the side opposite the direction of version were associated with head-turning, irrespective of the side of seizure focus. In clinical practice, ictal SPECT is a highly accurate aid in the lateralization of temporal lobe foci, in addition to providing a new method to investigate the pathophysiology of clinical signs in focal seizures.

Adolescent↗
PubMed1991

Preliminary experience with 99mTc-HMPAO SPECT in cerebral ischaemia.

To assess the sequential changes seen in cerebral blood flow using Single Photon Emission Computed Tomography with 99mtechnetium-hexamethylpropylene amine oxime (99mTc-HMPAO SPECT) in acute ischaemic stroke, 35 patients were prospectively studied from June 1990- to March 1991. Scans were performed during the acute phase (1-7 days), sub-acute phase (8-21 days) and chronic phase of stroke (greater than 1 month). Nine patients underwent scans in all 3 phases, 15 patients had 2 scans, and 11 patients had one scan. The majority of infarcts were in the middle cerebral territory (15 patients), while 4 infarcts were in the posterior cerebral territory and two in the anterior cerebral territory. There was a total of 4 lacunar infarcts. Image analysis was by visual inspection and by semiquantitation using homologous regions of interest in opposite hemispheres. SPECT in the acute phase identified the final vascular territory affected in 19 of 27 patients. There were 8 patients in whom early SPECT predicted the vascular territory as seen on late CT scan when the early CT scan was normal. Hyperaemia or reperfusion in the involved vascular territory was identified in 10 patients on scans performed during the sub-acute phase. Late SPECT scans showed perfusion defects greater than the infarct size seen on CT scan in the majority of patients. In all cases, the perfusion defect on the late SPECT scan was equal to or larger than the defect seen on the acute or sub-acute scan. Crossed cerebellar diaschisis was identified in 8 patients, and cortical/subcortical diaschisis in one patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Cognitive event-related potentials in multiple sclerosis.

Twenty-three patients with multiple sclerosis (MS) and 1 patient with isolated optic neuritis (mean age 37.5 yrs, average duration of disease 10 yrs) were tested with auditory and visual cognitive event-related potentials (ERPs) using an oddball paradigm. The results were compared with data from 19 age-matched healthy controls. All patients had magnetic resonance imaging (MRI) head scans and 19 had comprehensive neuropsychological testing. The stimulus-related components of the ERPs were normal for nearly all patients, but 10 showed abnormalities of the later cognitive-related components and another 3 had waveforms in which the cognitive components could not be identified. These abnormalities were found mainly for the auditory test. Of these 13 patients, 11 had significantly prolonged reaction times (RT) or reduced target recognition performance. Five of 8 MS patients with normal IQ and memory function tests had abnormal ERPs with the reverse being true for 4 of 10 patients. Patients with abnormal ERPs showed a higher MRI cerebral lesion score and had a longer duration of illness and greater physical disability than patients with normal ERPs. It is concluded that the generation of ERPs is in part dependent on the integrity of cerebral white matter and that ERPs may indicate subtle degrees of cognitive dysfunction not always detected by standard tests of intellect.

Adult↗
PubMed1988

Chronic unilateral optic neuropathy: a magnetic resonance study.

We studied the clinical, electrophysiological, and magnetic resonance imaging (MRI) features of 20 patients with chronic unilateral optic neuropathy (CUON): progressive unilateral visual failure lasting a minimum of 6 months. The patients, 10 male and 10 female, ranged in age from 12 to 77 years (mean 44) and had a mean duration of symptoms of 22 months. All had signs of optic nerve dysfunction. Each patient was studied with MRI using a short TI inversion recovery (STIR) sequence to delineate the optic nerve from surrounding orbital tissue. Three distinct groups of patients with CUON were identified using MRI. In the first group (8/20) the optic nerve was compressed by an extrinsic mass, whereas in the second group (5/20) CUON resulted from an intrinsic tumor of the optic nerve or sheath. In both groups STIR sequences compared favorably with computed tomography in identifying mass lesions. MRI was superior in delineating distortion of the optic nerve by mass or tumor extension beyond the orbit. In the third group (7/20) no mass was evident on MRI. However, STIR sequences revealed altered signal (long T1) in clinically symptomatic nerves. In 4 of the patients T2-weighted cerebral MRI disclosed periventricular lesions suggestive of disseminated white matter disease. We conclude that MRI complements clinical and electrophysiological testing in the assessment of CUON.

Adolescent↗
PubMed1988

Magnetic resonance imaging of the optic nerve in optic neuritis.

Magnetic resonance imaging (MRI) of the optic nerves using the STIR (short inversion time inversion recovery) sequence was performed in 37 adult patients with a recent or past attack of optic neuritis. MRI revealed high-signal regions in 84% of symptomatic and 20% of asymptomatic nerves. The mean longitudinal extent of lesions was 1 cm. Slow or poor visual recovery was associated with more extensive lesions, or lesions within the optic canal. Disk swelling was usually associated with anterior lesions but also occurred with lesions in the canal. Visual evoked potentials were even more sensitive than MRI in detecting lesions and are still the investigation of choice in suspected demyelinating disease involving the optic nerve.

Adult↗
PubMed1988

Cytoskeletal involvement in the sequential capping of rat thymocyte surface glycoproteins.

The independent capping of the three major rat thymocyte glycoproteins, the leucocyte-common (L-C) antigen, the leucocyte sialoglycoprotein (LSGP) and Thy-1, was investigated using specific monoclonal antibodies. The capping of each antigen did not require redistribution of the other major surface glycoproteins, and was accompanied by a partial co-capping of the cytoskeletal proteins fodrin and actin, but not of tubulin. A study of the ability of a cell that already possesses one glycoprotein cap to cap a second different glycoprotein showed that this was possible in all cases to varying degrees, the second cap always forming at the same position on the cell surface as the first. Colchicine failed to perturb this observed sequential capping polarity, indicating that microtubules did not direct this second capping event.

Actins↗
PubMed1986

A monoclonal alloantibody detecting a polymorphism of the rat leucocyte common (LC) antigen.

A monoclonal antibody, NDS 58, was produced by fusing the rat myeloma line Y3 Ag 1.2.3 with spleen cells from AS rats immunized with LEW thymocytes. The determinant recognized by this antibody is leucocyte-specific and present on all thymocytes, lymph node lymphocytes and some bone marrow cells. The strain distribution of NDS 58 was consistent with it being directed at the RT7a allele. Biochemical studies established that this antigen was carried on a cell surface glycoprotein with an apparent molecular weight on thymocytes of 190,000. This study confirms that the alloantigen originally designated Ly-1, and now termed RT7, is an allodeterminant of the LC molecule, and the controversy in this area, particularly with regard to the ART-1 alloantigen, is discussed.

Alleles↗
PubMed1983

Major histocompatibility complex antigens in the rat pancreas, isolated pancreatic islets, thyroid, and adrenal.

Monoclonal antibodies to rat class I and class II MHC antigens have been used with the peroxidase-antiperoxidase technique to localize these antigens in the DA rat pancreas, isolated pancreatic islets, adrenal, and thyroid tissue. The class I (RT1A) antigens were found to be expressed by pancreatic islet cells, adrenal cortical cells, thyroid follicular cells, and--in low concentration--on cells of the adrenal medulla. These same cells did not express class II (Ia or RT1B) antigens. However, interstitial dendritic cells, staining intensely for class II antigens were present in thyroid, adrenal and pancreatic tissue, and within isolated pancreatic islets. These cells probably represent the immunogenic passenger leukocyte.

Adrenal Glands↗