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Biomedical subjects

K T Smith

Publications and source records attributed to K T Smith.

At least 73 records · Page 4Linked to original sources
PubMed1978

Mathematical aspects of divergent beam radiography.

At the present time, largely because of a breakthrough in radiology called computed tomography, the attenuation of x-ray beams is measured in extremely sensitive quantitative ways, and the information from many x-ray sources is assembled and analyzed on a computer. In this situation mathematics can make significant contributions concerning the nature of the information conveyed by x-rays from many sources, the extent to which this information determines the object x-rayed, suitable configurations of sources, methods for using the data to build a detailed reconstruction of the object, etc. This article announces results on these topics for the divergent x-ray beam. The three-dimensionally divergent beam, or cone beam, presents new problems that do not appear in the two-dimensional, or fan beam, case.

Journal Article↗
PubMed1978

Zinc absorption and metabolism by isolated, vascularly perfused rat intestine.

An isolated vascularly perfused rat intestine system was utilized to examine various aspects of zinc absorption in an attempt to more clearly examine the mechanisms involved. The lumen was perfused with a modified tissue culture medium containing 65Zn. The vascular system was perfused from the superior mesenteric artery to the portal vein, with Krebs-Ringer bicarbonate buffer containing 5% rat serum. The criterion for absorption was the amount of radioactivity transferred to the vascular perfusate. When the intestines were obtained from rats that had consumed a zinc-deficient diet the amount of zinc absorbed increased markedly. Conversely, elevation of zinc status decreased the amount of 65Zn that could be transferred to the vascular perfusate. These data strongly suggest that the isolated, perfused rat intestine retains the ability to exercise homeostatic control over 65Zn absorption. Transfer of infused 65Zn to the vascular perfusate was significantly decreased by aspirin, phytate, and prostaglandin E2. Uptake of 65Zn from the lumen into the intestinal cells was significantly increased by histidine and significantly decreased by phytate and prostaglandin E2. Thus, the isolated, vascularly perfused rat intestine appears to be capable of differentiating between the cellular uptake and cell to plasma transfer phases of zinc absorption.

Animals↗
PubMed1977

Coordinate and non-coordinate accululation of aspartate transcarbamylase and dihydroorotase in synchronous Chlorella cells growing on different nitrogen sources.

Regulation of the levels of aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) and dihydroorotase (L-5,6-dihydro-orotate amidohydrolase, EC 3.5.2.3) was studied in synchronous cultures of the eucaryotic microorganism Chlorella. Analytical polyacrylamide gel electrophoresis and sucrose density-gradient centrifugation studies revealed that these cells contain a single aspartate transcarbamylase and a dihydroorotase with apparent molecular weights of 160 000 and 80 000, respectively. In synchronous cells cultured in nitrate medium, these two enzymes accumulated in single step-patterns over different periods of the cell cycle. In contrast, these enzymes accumulated in a coordinate manner throughout the cell cycle in ammonium medium. Experiments with inhibitors of protein and RNA synthesis indicated that dihydroorotase is stable in vivo and suggested that cell cycle changes in the turnover rate of aspartate transcarbamylase might determine whether or not these enzymes accumulate in a coordinate manner. Although uracil and uridine could be absorbed and metabolized by the cells, synthesis of these two enzymes could not be repressed by culturing synchronous cells in medium, containing high concentrations (29-40 mM) of uracil or uridine, for an entire cell cycle.

Amidohydrolases↗
PubMed1977

The diagnosis of breast cancer in mammograms by the evaluation of density patterns.

Standard mammograms from 33 patients with surgically proved adenocarcinoma or fibrocystic disease were analyzed with a scanning microdensitometer and computer. A quickly computable number called the linear mass ratio is introduced. This simple ratio discriminated correctly between the 16 adenocarcinomas and 17 fibrocystic lesions of the study, all cases in which diagnosis had required biopsy.

Adenocarcinoma↗
PubMed1974

Reconstruction of objects from radiographs and the location of brain tumors.

The objective of this research is two-fold: (i) the development of a method for locating hemorrhages, blood clots, and tumors in the brain by means of ordinary hospital radiographs and without the introduction of contrast material; and (ii) the uncovering of new mathematical results through this point of view. The present note deals mainly with the first objective, but the mathematical setting and convergence and indeterminacy theorems are also described.

Absorptiometry, Photon↗
PubMedDate not supplied

Injury prevention.

Explore the source record for details and available documents.

Accident Prevention↗
PubMedDate not supplied

The biology of papillomaviruses and their role in oncogenesis.

A large number of different papillomavirus types have been identified. Several viruses often infect the same species and each virus is associated with a defined tissue. Recent evidence has shown that certain benign lesions can undergo malignant transformation in both animals and humans in response to genetic or environmental factors. Fine mapping of the structure and function of the viral genome may enhance our understanding of the interaction between the virus and the cofactors involved in malignant transformation.

Animals↗