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Biomedical subjects

A R Butler

Publications and source records attributed to A R Butler.

28 records · Page 2Linked to original sources
PubMed1979

Contrast enhanced CT scan and radionuclide brain scan in supratentorial gliomas.

The preoperative contrast enhanced CT and radionuclide brain scans of 60 patients with surgically verified supratentorial astrocytomas were evaluated and compared. Results indicated that the mechanisms of contrast enhancement and radionuclide uptake are identical in the detection of supratentorial gliomas. These diagnostic methods apparently mirror the integrity of the blood-brain barrier and therefore can be useful in assessing the degree of malignancy of supratentorial gliomas. However, lesions with an intact blood-brain barrier will be missed with radionuclide imaging. These parenchymal abnormalities and/or the associated mass effect will be detected with contrast enhanced computed tomography. These findings firmly establish contrast enhanced computed tomography. These findings firmly establish contrast enhanced CT as the primary investigate tool in the suspected brain tumor.

Adolescent↗
PubMed1978

The contrast-enhanced CT scan and the radionuclide brain scan: parallel mechanisms of action in the detection of supratentorial astrocytomas.

The preoperative contrast-enhanced CT scan and the radionuclide brain scan of 70 patients with surgically verified supratentorial astrocytomas were evaluated and compared. The results indicate parallel mechanisms of action of contrast enhancement and radionuclide uptake. These diagnostic modalities apparently mirror the integrity of the blood-brain barrier (BBB) and therefore are useful in assessing the degree of malignancy of supratentorial gliomas. However, lesions with an intact BBB will be missed with RN imaging. These lesions and/or the associated mass effect will be detected with contrast-enhanced computed tomography. Our findings firmly establish contrast-enhanced CT as the primary investigate tool in the suspected brain tumor.

Astrocytoma↗
PubMed1978

Non-contrast CT scanning: limited value in suspected brain tumor.

Most patients who have computed tomography because of a suspected brain tumor are subjected to a noncontrast scan followed by a contrast study. Analysis of the scans of all such patients over a two-year period indicates that in most cases a single contrast scan affords the same degree of diagnostic accuracy as a combined pre- and postcontrast study.

Brain Neoplasms↗
PubMed1978

Computed tomography in astrocytomas. A statistical analysis of the parameters of malignancy and the positive contrast-enhanced CT scan.

Four histopathological indices of malignancy--cellularity, pleomorphism, vascularity, and necrosis--were correlated with the positive-contrast CT scan in 84 patients with pathologically proved astrocytoma. Vascularity and necrosis correlated best with the scan in supratentorial tumors, while vascularity and cellularity correlated significantly with the scan in cerebellar astrocytomas. These findings indicate that the degree of malignancy of a supratentorial astrocytoma can be inferred from the contrast-enhanced scan, but that this is not generally possible with posterior fossa tumors.

Adolescent↗
PubMedDate not supplied

Intracellular expression of Kluyveromyces lactis toxin gamma subunit mimics treatment with exogenous toxin and distinguishes two classes of toxin-resistant mutant.

The Kluyveromyces lactis toxin is a heterotrimeric protein which irreversibly arrests proliferation of sensitive Saccharomyces cerevisiae cells in the G1 phase of the cell cycle. By expressing the gamma subunit of the toxin in sensitive yeast cells from a conditional promoter, it was previously demonstrated that it alone is required for inhibition (Tokunaga et al. (1989). Nucleic Acids Res. 17, 3435-3446). Here we show that, like native exogenous toxin, intracellular gamma subunit expression promotes a striking arrest of sensitive cells in G1. However, unlike the G1 arrest caused by native toxin, that induced by the gamma subunit alone does not result in reduced cellular viability and is fully and rapidly reversible, suggesting that the G1 arrest and the irreversibility of action may reflect different aspects of the toxin's interaction with sensitive cells. We have selected a large number of S. cerevisiae mutants which are highly resistant to the toxin in order to study its mode of action in more detail. Complementation analysis demonstrated that all but one of the mutants were recessive and these defined four separate genes. Members of two complementation groups concurrently acquired resistance to intracellular gamma subunit expression, suggesting that they contain a modified toxin target site. The other two genes appear to be required for entry of the gamma subunit into the sensitive cells since these mutants, while refractory to exogenous toxin, were fully sensitive to intracellular gamma subunit expression.

Culture Media↗