Search PubMed⌕ Search

Biomedical subjects

R A Clark

Publications and source records attributed to R A Clark.

At least 469 records · Page 26Linked to original sources
PubMed1971

Defective granulocyte chemotaxis in the Chediak-Higashi syndrome.

In vivo and in vitro studies of granulocyte chemotaxis were performed in three patients with the Chediak-Higashi syndrome. Rebuck skin windows showed a decreased accumulation of leukocytes at an inflammatory site. Studies in Boyden chambers documented a cellular defect in granulocyte chemotaxis. The chemotactic response of Chediak-Higashi cells by this technique averaged approximately 40% of normal and was consistently reduced using several different chemotactic stimuli. This deficit was magnified by shortening the chamber incubation time or by decreasing the pore size of the micropore filter and was independent of granulocytopenia. No abnormalities of passive motility, adhesiveness, viability, or pH optimum for migration were found in these cells. Chediak-Higashi serum contained no inhibitors of chemotaxis and was capable of generating normal amounts of chemotactic factors with the exception of one patient with the accelerated phase of the disease. Heterozygotes for the Chediak-Higashi trait had normal chemotactic function. This cellular defect in chemotaxis may contribute to the marked susceptibility to pyogenic infections which is so characteristic of patients with the Chediak-Higashi syndrome.

Adolescent↗
PubMedDate not supplied

Ct of congenital anomalies of the inferior vena cava.

The authors report six congenital abnormalities of the inferior vena cava detected on computed tomography (CT). The CT findings of one of these, the left inferior vena cava, have not been previously reported. The embryology of the inferior vena cava and the possible congenital abnormalities that can occur are discussed. Congenital abnormalities of the inferior vena cava are rare but potentially important to the radiologist, the surgeon, and the patient. They are easily identified on CT and should be considered when interpreting any CT of the abdomen or chest.

Humans↗
PubMedDate not supplied

CT of mediastinal pancreatic fluid collections.

Mediastinal extension of an extrapancreatic fluid collection is a rare event. Only 30 cases have been previously reported in the literature. An additional case is presented. In the appropriate clinical setting, plain film and contrast examination of the esophagus and stomach may suggest the diagnosis. While ultrasound may identify supradiaphragmatic extension of fluid, computed tomography is better able to demonstrate the nature and extent of a mediastinal extrapancreatic fluid collection. Preoperatively it is important to recognize that a mediastinal mass represents an extrapancreatic fluid collection because the preferred surgical approach is abdominal.

Adult↗
PubMedDate not supplied

Image segmentation in digital mammography: comparison of local thresholding and region growing algorithms.

Local thresholding and region-growing algorithms are developed and applied to digitized mammograms to quantify the parenchymal densities. The algorithms are first evaluated and optimized on phantom images reflecting varying image contrast, X-ray exposure conditions, and time-related changes. The difference between the segmentation results of the two techniques is less than 6% on the phantom images and 11% on the mammograms. The agreement between the computerized procedures and a manual one is in the range of 74-98%, depending on the breast parenchymal pattern and segmentation algorithm. The results show that computerized parenchymal classification of digitized mammograms is possible and independent of exposure.

Algorithms↗