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Biomedical subjects

I C Smith

Publications and source records attributed to I C Smith.

At least 271 records · Page 15Linked to original sources
PubMed1968

Proton magnetic resonance of transfer RNA.

The temperature dependence of the areas under the proton magnetic resonance spectra of unfractionated yeast transfer RNA in 1.0 molar NaCl is a consequence of salt-induced aggregation and does not constitute a monitor of the melting of secondary molecular structure. Such melting can be observed by following the widths of the resonances in the various regions of the spectra. Peaks attributable to dihydrouracil and the methyl groups of the methylated bases are detected in the spectra of unfractionated transfer RNA and alanine transfer RNA.

Chemical Phenomena↗
PubMedDate not supplied

Classification of 1H MR spectra of human brain neoplasms: the influence of preprocessing and computerized consensus diagnosis on classification accuracy.

We study how classification accuracy can be improved when both different data preprocessing methods and computerized consensus diagnosis (CCD) are applied to 1H magnetic resonance (MR) spectra of astrocytomas, meningiomas, and epileptic brain tissue. The MR spectra (360 MHz, 37 degrees C) of tissue specimens (biopsies) from subjects with meningiomas (95; 26 cases), astrocytomas (74; 26 cases), and epilepsy (37; 8 cases) were preprocessed by several methods. Each data set was partitioned into training and validation sets. Robust classification was carried out via linear discriminant analysis (LDA), artificial neural nets (NN), and CCD, and the results were compared with histopathological diagnosis of the MR specimens. Normalization of the relevant spectral regions affects classification accuracy significantly. The spectra-based average three-class classification accuracies of LDA and NN increased from 81.7% (unnormalized data sets) to 89.9% (normalized). CCD increased the classification accuracy of the normalized sets to an average of 91.8%. CCD invariably decreases the fraction of unclassifiable spectra. The same trends prevail, with improved results, for case-based classification. Preprocessing the 1H MR spectra is essential for accurate and reliable classification of astrocytomas, meningiomas, and nontumorous epileptic brain tissue. CCD improves classification accuracy, with an attendant decrease in the fraction of unclassifiable spectra or cases.

Astrocytoma↗
PubMedDate not supplied

Identification of lactate, threonine and alanine in rat thymus and tumorigenic lymphoid cells using 1H 2-D COSY NMR spectroscopy.

One- and two-dimensional 1H NMR spectra were obtained for normal murine thymus and malignant lymphoma tissue, as well as for the supernatant fractions from high speed centrifugal separations. Crosspeaks in the two-dimensional spectra resembled those reported by others for adenocarcinoma and leukemic lymphoblast cells, assigned tentatively to the carbohydrate fucose. However, for the present systems, spectral analysis and the spectral response to addition of known compounds led to assignment of the crosspeaks as follows: 1.33-4.12 ppm, lactate anion; 1.33-4.26 ppm, threonine; 1.48-3.78 ppm, alanine. Differences between the NMR data for the normal and malignant specimens were only in the relative intensities of the peaks. No peaks characteristic of fucose were found in spectra of cytosol, tissue or membrane lipids. Thus, the NMR data for malignant lymphoma cells are significantly different from those for adenocarcinoma and leukemic lymphoblasts. The NMR characteristics of different types of cancer cell must be individually determined.

Alanine↗
PubMedDate not supplied

NM23 gene product expression does not predict lymph node metastases or survival in young patients with colorectal cancer.

NM23 gene product is a putative metastases suppressor gene which has structural homology to a nucleoside diphosphate kinase. Previous studies examining the relationship between NM23 gene product expression and survival in patients with colorectal cancer have revealed conflicting results. However, no study has focused on young patients with colorectal cancer. This study was carried out to determine if expression of the NM23 gene product was correlated with metastatic potential and survival in young patients (45 years and under) with colorectal cancer. Eighty- one patients with colorectal cancer were studied and the presence of the NM23 gene product (H1) was detected using standard immunohistochemical techniques. NM23 gene product expression did not correlate with tumour stage, lymph node involvement by tumour, presence of distant metastases, extramural vascular invasion or degree of tumour differentiation. Independent risk factors for overall survival were: Dukes' stage (p=0.00001) and extramural vascular invasion (p=0.003). NM23 expression was not an independent prognostic indicator (p=0.55). Therefore, NM23 expression does not correlate with existing indicators of tumour aggressiveness and behaviour nor is it an independent predictor of survival in young patients with colorectal cancer.

Adolescent↗
PubMedDate not supplied

1H magnetic resonance spectroscopy evidence that aberrant crypt foci are preneoplastic lesions in the colon.

BACKGROUND: Histopathological and genetic studies support the hypothesis that aberrant crypt foci (ACF) represent one of the earliest events in colon carcinogenesis. The purpose of this study is to make use of 1H MRS in conjunction with multivariate methods of analysis to ascertain the validity of the above mentioned hypothesis. MATERIALS AND METHODS: ACF, colonic mucosa and tumor samples taken from thirty-two carcinogen (azoxymethane)-treated Sprague Dawley rats, and of colon mucosa taken from ten healthy animals, were investigated ex vivo by 1H MRS and analyzed using multivariate methods of analysis. RESULTS: The 1H magnetic resonance peak intensities and areas of ACF lie between those from normal and carcinogen- treated mucosa samples and tumors. Multivariate analysis classification of the spectra suggests that the ACF exhibit biochemical characteristics intermediate between the control and AOM-mucosa samples and the tumor groups. CONCLUSION: The use of sophisticated methods of data classification has enabled us to support the hypothesis that ACF represent preneoplastic lesions of the colon.

Animals↗
PubMedDate not supplied

A pilot study with long term follow up of hyperbaric oxygen pretreatment in patients with locally advanced breast cancer undergoing neo-adjuvant chemotherapy.

Work in an animal cancer model suggests that pretreatment with hyperbaric oxygen can improve tumor vascularity rendering chemotherapy more effective. Accordingly 32 subjects with locally advanced breast carcinoma (>5cm diameter) entered into a randomized clinical trial where a course was administered of six intravenous pulses of cyclophosphamide 1000mg/m2 i.v., doxorubicin 50mg/m2 i.v. and vincristine 1.5mg/m2 i.v. In the case group this was preceded by ten, once daily, sessions of hyperbaric oxygen therapy (HBO2) administered either at 2.4 or 2.0 atmospheres absolute. Eleven out of 15 subjects tolerated a full course of HBO2 and chemotherapy. All 17 control subjects tolerated a full course of chemotherapy. Tumor extravascular extracellular or edema fluid was reduced after HBO2 but there was no reduction in tumor cell volume and no indication of increased vascularity on MRI. Clinical and pathological responses to chemotherapy were the same in both groups and there was no evidence of neovascularisation. Five year survival in those who tolerated the trial regime was 73% and did not differ between the groups. This mortality was cancer related.

Adult↗
PubMedDate not supplied

Mobile lipid accumulation in necrotic tissue of high grade astrocytomas.

Multiple samples from 42 astrocytomas were investigated ex vivo by 1H MR spectroscopy followed by histological assessment. MR visible lipids were detected in 27 of 32 grade 4 astrocytomas. These lipids were heterogeneously distributed within the tumours. Their amount correlated positively with the amount of histologically detected necrosis. Mobile lipids were also observed in grade 4 astrocytoma samples without necrosis, as well as in one of three grade 3, two of three grade 2 and two of four grade 1 astrocytomas. The clinical significance of MR visible lipids, their cellular location, and their possible biological bases are discussed.

Astrocytoma↗