Biomedical subjects
R M Thompson
Publications and source records attributed to R M Thompson.
Prevalence of morbillivirus antibodies in Scottish harbour seals.
Explore the source record for details and available documents.
Systematic generation of all nonequivalent closest-packed stacking sequences of length N using group theory.
An algorithm has been developed that generates all of the nonequivalent closest-packed stacking sequences of length N. There are 2(N) + 2(-1)(N) different labels for closest-packed stacking sequences of length N using the standard A, B, C notation. These labels are generated using an ordered binary tree. As different labels can describe identical structures, we have derived a generalized symmetry group, Q approximately equal to D(N) x S(3), to sort these into crystallographic equivalence classes. This problem is shown to be a constrained version of the classic three-colored necklace problem.
A unique approach to multidisciplinary cancer education.
BACKGROUND: Almost every health care worker, regardless of specialty, interacts with individuals who have histories of cancer. Some health care workers are relatively unfamiliar with the cancer experience and those who are familiar with it are interested in additional information. METHOD: The Mayo Clinic Cancer Center Education Subcommittee designed a monthly educational program titled Cancer Connections: A Multidisciplinary Update. The goals of this program were to provide: 1) up-to-date information about cancer issues, 2) a better understanding of various team members' roles in caring for people with cancer, 3) insight into patients' responses to the diagnosis and treatment of their cancers, and 4) greater awareness of the resources available to cancer patients and their families. Each session consists of a "panel" of presenters: three healthcare professionals and a patient. RESULTS AND DISCUSSION: The success of this program is reflected in the regular high attendance and consistently positive evaluations of the participants.
Quantifying distortion from ideal closest-packing in a crystal structure with analysis and application.
A parameter, U(cp), that quantifies the distortion of the anion skeleton in a crystal from ideal closest-packing has been developed. It is a measure of the average isotropic displacement of the observed anions from their ideal equivalents. An ideal closest-packed structure can be fit to an observed structure by varying the radius of the ideal spheres, orientation and translation, such that U(cp) is minimized. Ideal structures were fit to the M1M2TO(4) polymorphs, pyroxenes and kyanite. The distortions of these crystals were analyzed in terms of the two parameters, U(cp) and the ideal radius. Changes in structures due to temperature, pressure and compositional effects were characterized in terms of these parameters.
The polyglutamine expansion in spinocerebellar ataxia type 6 causes a beta subunit-specific enhanced activation of P/Q-type calcium channels in Xenopus oocytes.
Spinocerebellar ataxia type 6 (SCA6) is a dominantly inherited degenerative disorder of the cerebellum characterized by nearly selective and progressive death of Purkinje cells. The underlying mutation in SCA6 consists of an expansion of a trinucleotide CAG repeat in the 3' region of the gene, CACNA1A, encoding the alpha(1A) subunit of the neuronal P/Q-type voltage-gated calcium channel. Although it is known that this mutation results in an expanded tract of glutamine residues in some alpha(1A) splice forms, the distribution of these splice forms and the role of this mutation in the highly selective Purkinje cell degeneration seen in SCA6 have yet to be elucidated. Using specific antisera we demonstrate that the pathological expansion in SCA6 can potentially be expressed in multiple isoforms of the alpha(1A) subunit, and that these isoforms are abundantly expressed in the cerebellum, particularly in the Purkinje cell bodies and dendrites. Using alpha(1A) subunit chimeras expressing SCA6 mutations, we show that the SCA6 polyglutamine expansion shifts the voltage dependence of channel activation and rate of inactivation only when expressed with beta(4) subunits and impairs normal G-protein regulation of P/Q channels. These findings suggest the possibility that SCA6 is a channelopathy, and that the underlying mutation in SCA6 causes Purkinje cell degeneration through excessive entry of calcium ions.
Spinocerebellar ataxia type 6: gaze-evoked and vertical nystagmus, Purkinje cell degeneration, and variable age of onset.
Spinocerebellar ataxia type 6 (SCA6) was recently identified as a form of autosomal dominant cerebellar ataxia associated with small expansions of the trinucleotide repeat (CAG)n in the gene CACNL1A4 on chromosome 19p13, which encodes the alpha1 subunit of a P/Q-type voltage-gated calcium channel. We describe clinical, genetic, neuroimaging, neuropathological, and quantitative oculomotor studies in four kindreds with SCA6. We found strong genetic linkage of the disease to the CACNL1A4 locus and strong association with the expanded (CAG)n alleles in two large ataxia kindreds. The expanded alleles were all of a single size (repeat number) within the two large kindreds, numbering 22 and 23 repeat units. It is noteworthy that the age of onset of ataxia ranged from 24 to 63 years among all affected individuals, despite the uniform repeat number. Radiographically and pathologically, there was selective atrophy of the cerebellum and extensive loss of Purkinje cells in the cerebellar cortex. In addition, clinical and quantitative measurement of extraocular movements demonstrated a characteristic pattern of ocular motor and vestibular abnormalities, including horizontal and vertical nystagmus and an abnormal vestibulo-ocular reflex. These studies identify a distinct phenotype associated with this newly recognized form of dominant SCA.
Interleaved echo planar imaging on a standard MRI system.
This work describes an interleaved echo planar imaging (EPI) method for use on a standard whole body scanner. The data acquisition is divided into two to eight repetitions rather than one to two, as implemented by dedicated EPI systems. Interleaving allows the use of a lower sampling bandwidth with a significant increase in signal-to-noise. The method also has the advantages of relative ease of implementation, no need for postprocessing to remove image distortion, and no need for shimming on a case-by-case basis. The interleaved EPI method was applied to two applications ideally suited to EPI: breathhold T2-weighted abdominal imaging and functional imaging. In vivo liver-lesion contrast as measured in a 35-patient study showed increased contrast for the interleaved EPI by an average factor of 1.21 (+/- 0.34) over conventional spin-echo imaging. CNR measurements showed the EPI to be comparable with conventional spin echo with a relative factor of 1.00 (+/- 0.36). Functional imaging with an eight-shot interleaved EPI sequence provided 128 x 128 images of cerebral activation during bilateral finger tapping.
Sensory motor cortex: correlation of presurgical mapping with functional MR imaging and invasive cortical mapping.
PURPOSE: To describe a clinically useful application of functional magnetic resonance (MR) imaging--presurgical mapping of the sensory motor cortex--and to validate the results with established physiologic techniques. MATERIALS AND METHODS: Functional MR mapping of the sensory motor cortex was performed in two women, aged 24 and 38 years. Both had intractable, simple partial motor seizures due to tumors located in or near the sensory motor cortex. They subsequently underwent invasive cortical mapping--direct cortical stimulation and/or sensory-evoked-potential recording--to localize the affected sensory motor area prior to tumor resection. RESULTS: In both patients, the functional MR study demonstrated task activation of the sensory motor cortex. In both cases, results of cortical functional mapping with invasive techniques matched those obtained with functional MR imaging. CONCLUSION: Presurgical mapping of the sensory motor cortex is a potentially useful clinical application of functional MR imaging.
Imaging of cerebral activation at 1.5 T: optimizing a technique for conventional hardware.
PURPOSE: To empirically optimize a two-dimensional magnetic resonance (MR) imaging technique for detecting changes in signal intensity during cerebral activation with a standard clinical imager. MATERIALS AND METHODS: Visual activation experiments were performed while imaging parameters were manipulated in a serial fashion, to test their effect on the percentage change in signal intensity (PCSI). The parameters tested were section thickness, echo time (TE), field of view (FOV), flip angle, radio-frequency (RF) spoiling, number of readout points, and number of signals averaged. RESULTS: The PCSI for visual activation experiments was typically in the 1%-5% range. The best results were achieved with a small section thickness, long TE, and large FOV. Variations in other acquisition parameters had a negligible influence on the PCSI. CONCLUSION: Good results can be obtained at functional MR imaging with standard 1.5-T hardware. Markedly improved results can be obtained by optimizing several key variables, namely, section thickness, TE, and FOV.
Differential induction of indoleamine-2,3-dioxygenase (IDO) by interferon-gamma in human gynecologic cancer cells.
Induction of indoleamine-2,3-dioxygenase (IDO) by interferon-gamma (IFN-gamma) is thought to be one mechanism underlying IFN-gamma's antineoplastic properties. Since clinical trials with IFN-gamma have yielded variable efficacy in treating cancers of gynecological origin, we tested the effects of IFN-gamma on cell growth and IDO activity in cell lines from seven gynecologic and five breast cancers. At a dose of 250 IU/ml, IFN-gamma suppressed cell growth and induced IDO activity in one cervical (C41), one vulva (A431), one breast (HS578T) and two ovarian (OVCAR-3, CAOV-3) cancer cell lines. Differing inhibition of cell growth, but with no induction of IDO activity, was found with IFN-gamma treatment of the other cell lines.
Angiosarcoma after tylectomy and radiation therapy for carcinoma of the breast.
BACKGROUND: Angiosarcoma (AS) is an uncommon tumor that rarely develops after external beam radiation therapy (EBRT). Thirty-six cases have been reported in the literature. METHODS: The authors present two additional cases. Each of these patients received breast-conserving treatment for breast carcinoma that consisted of tylectomy and EBRT. In each case, AS developed in the field of prior irradiation. RESULTS: Currently, seven cases of AS after radiation therapy for breast-conserving treatment of breast carcinoma have been reported. The average time interval between the administration of radiation therapy and the development of AS is 8.6 years. CONCLUSIONS: This complication is rare and should not influence the decision to offer breast-conserving therapy to patients. However, patients should be informed that AS may develop as a result of radiation therapy.
Undetectable tumor necrosis factor-alpha in spinal fluid from HIV-1-infected patients.
Explore the source record for details and available documents.
Increased neopterin levels in brains of patients with human immunodeficiency virus type 1 infection.
Postmortem levels of native neopterin (D-erythro-neopterin) were measured in cerebral cortical samples from 44 human immunodeficiency virus type 1-infected and eight uninfected, nonneurological control patients. Cerebral cortical gray and white matter neopterin levels for the controls ranged from 0.5 to 7.2 pmol/mg of protein in contrast to neopterin levels in brains of the virus-infected patients, which frequently were more than threefold and occasionally more than 30-fold higher than mean control levels. Cortical neopterin levels did not correlate with severity of the acquired immunodeficiency syndrome dementia complex, but subcortical levels correlated with the presence of active human immunodeficiency virus type 1 infection, as reflected by pathological evidence of multinucleated giant cell encephalitis. Evidence of opportunistic cytomegalovirus infections in approximately 25% of the human immunodeficiency virus type 1-infected patients was associated with enhanced levels of neopterin in frontal cortex.
A rostral-caudal concentration gradient in cerebrospinal fluid adrenocorticotropin.
In two separate experiments, cerebrospinal fluid (CSF) adrenocorticotropin immunoreactive (ACTH-IR) concentrations in the rhesus monkey followed a significant rostral-caudal gradient. In the first study, CSF was sampled from an indwelling catheter in awake animals. The mean ACTH-IR concentration in the cisternal region was 12.3 pg/ml, as compared to 8.56 pg/ml in the lumbar region. In the second study, CSF was sampled in a different group of monkeys by percutaneous puncture at the cisterna magna and at L5-L6. In this study, the mean ACTH-IR concentration in samples collected from the cistern was also greater than the concentration from L5-L6. In addition, a significant correlation within subjects was found between samples collected from the two sites (r = 0.86). These results demonstrate that the site of CSF sampling is a variable in determining CSF ACTH-IR concentrations and suggest that lumbar CSF ACTH-IR concentrations in humans may be interpreted as indexes of ACTH changes at higher levels in the central nervous system.
Propionyl coenzyme A carboxylase deficiency presenting as non-ketotic hyperglycinaemia.
A 4-month-old girl presented with myoclonic seizures and an electroencephalogram showing hypsarrhythmia. Hyperglycinuria and a cerebrospinal fluid to plasma glycine ratio of 0.2 suggested the diagnosis of non-ketotic hyperglycinaemia. Propionic acid and methyl citric acid were present in the urine, and propionyl coenzyme A carboxylase was deficient in leucocytes and fibroblasts. The ketotic and non-ketotic hyperglycinaemias cannot be differentiated by CSF: plasma glycine ratios.
Conjugation of fatty acids to DDT in the rat: possible mechanism for retention.
Palmitic, stearic, oleic, and linoleic fatty acid conjugates of DDT were retained in vivo in livers and spleens of male and female rats given chronic i.p. injections of DDT. These DDT fatty acid conjugates could also be produced in vitro in a rat liver coenzyme A fortified microsomal system using the DDT hydroxylated metabolite DDOH as the substrate. The phenomenon of fatty acid conjugation to DDT may be a mechanism by which it is retained in the body and ultimately exerts its toxic effect.
Mass spectrometry of some ultraviolet absorbing derivatives of sugars and related alditols: identification in biologic fluids after separation by high performance liquid chromatography.
The 70 eV electron impact mass spectra of the acyclic perbenzoyl 0-benzyloximes of several mono- and disaccharides of clinical interest and the perbenzoates of certain related alditols have been obtained and compared with those of other similar derivatives studied previously. In general, the spectra of the benzyloximes contain molecular ions and characteristic fragments due to [C6H5]+,[C7H7]+,[C6H5CO]+ and [C6H5CooH]+., losses of HCHO, C6H5COO. and C6H5COOH, and cleavages along the carbon chain. The most unique ions in these spectra arise from the combined loss of C7H7. and C6H5COO.from the molecular ion: m/z 191 (C3), m/z 339 (deoxy-C5), m/z 459 (C5), m/z 473 (deoxy-C6), and m/z 593 (C6). The alditol benzoates fragment similarly, but they do not yield molecular ions. These data are being used to help confirm the identities of carbohydrates in biologic fluids fractionation by high performance liquid chromatography, prior to the establishment of routine quantitative assays for several of these compounds.