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Biomedical subjects

R K Brown

Publications and source records attributed to R K Brown.

At least 37 records · Page 2Linked to original sources
PubMed1986

Magnetic resonance imaging artifacts: mechanism and clinical significance.

Many types of artifacts may occur in magnetic resonance imaging. These artifacts may be related to extrinsic factors such as patient motion or metallic artifacts; they may be due specifically to the MR system such as power gradient drop off and chemical shift artifacts; they may occur as a consequence of general image processing techniques, as in the case of truncation artifacts and aliasing. Change in patient position, pulse sequence, or other imaging variables may improve some artifacts. Although reduction of some artifacts may require a service engineer, the radiologist has the responsibility to recognize MR imaging problems. The radiologist's knowledge of MR imaging artifacts is important to the continued maintenance of high image quality and is essential if one is to avoid confusing artifactual appearances with pathology.

Diagnostic Errors↗
PubMed1986

Accurate demonstration of hepatic infarction in liver transplant recipients.

Serial HIDA scanning has proven to be a valuable tool in the postoperative management of liver transplant patients. Previous reports have documented its efficacy in detecting biliary leakage, abscess, and rejection. We have also found HIDA scanning to be a sensitive method for detecting early hepatic infarction before ultrasonographic changes occur. Two cases are presented to demonstrate the characteristic findings seen with hepatic infarctions.

Child↗
PubMed1984

The interaction of platelet proteins with three fibroblast-derived collagenases.

Three collagenases were purified from the culture medium of human skin fibroblasts using ammonium sulfate fractionation, ion-exchange chromatography and gel filtration. The cationic collagenase had a molecular weight of 42,000; two anionic collagenases had molecular weights of 63,000 and 115,000. Preincubation of the individual collagenases with purified human and bovine platelet heparin binding proteins resulted in the inhibition of the two anionic activities, but only by bovine low heparin affinity platelet protein (beta-TG). Such inhibition was dose-dependent at the microgram level, was not antagonized by heparin, and persisted even when the collagenases had been transformed into their 53,000 and 105,000 forms through treatment with p-aminophenylmercuric acetate. Neither human nor bovine high heparin affinity platelet factors (PF-4) nor human low heparin affinity platelet protein (beta-TG) were inhibitory to any of the three collagenases studied. This suggests that the ability of platelet proteins to inhibit collagenase is specifically influenced by the ionic nature of the enzyme and this inhibition is specifically dependent upon the species and type of platelet protein.

Animals↗
PubMed1983

Asbestosis and the serratus anterior muscle.

Twenty-seven patients with a history of asbestos exposure were reviewed at the UCLA Medical Center in December 1981. All patients were referred by the United States Department of Labor. The patients were told they had asbestosis on the basis of their history of exposure and chest radiographs taken at a local asbestos screening program and initially interpreted by a "B" reader. None of the 27 patients reviewed were found to have evidence of asbestosis either clinically or radiographically. The false-positive radiographic interpretations were due to the extrathoracic musculature (serratus anterior) mimicking intrathoracic disease. Since the study described here was done, an additional 330 patients have had their radiographs reviewed.

Adult↗
PubMed1982

The use of hybridoma antibodies to probe the antigenic determinants of thyroglobulin.

Using monoclonal antibodies we have begun to define the epitopes of the murine thyroglobulin molecule that elicit autoimmune responses. Based on the principle of complementation, 18 monoclonal antibodies were classified into 8 groups, defined by their reactions with the same or neighboring determinants. Further distinctions between the monoclonals were drawn from comparisons of their cross-reactions with thyroglobulins of other species and their patterns in isoelectric focusing. One low molecular weight fragment of bovine thyroglobulin, which cross-reacts extensively with thyroglobulins of other species, has been isolated and partially characterized.

Animals↗
PubMed1982

Pap smear screening and invasive cervical cancer.

Possible failures of Pap smear screening were assessed among 63 cases of invasive cervical cancer that occurred in a group practice population between 1965 and 1975. Review of medical records revealed 33 (53 percent) cases with no history of Pap smears within two years prior to diagnosis. Among the 30 patients with recent Pap screening, 11 (17 percent) had negative smears; these could only be explained as false negatives or unusually rapid progression of disease. The remaining 19 (30 percent) had abnormal smear results, a number of whom received suboptimal follow-up care. Similar experiences have been reported from several other health care settings. Implications for preventive practices are discussed.

Adult↗
PubMed1979

Metal cluster chemistry: Structure and stereochemistry in the polynuclear rhodium hydrides H(n)Rh(n)[P(OR)(3)](2n).

Crystallographic analyses of x-ray and neutron diffraction data have provided a definitive structural representation of {HRh[P(O-i-C(3)H(7))(3)](2)}(2) and {HRh[P(OCH(3))(3)](2)}(3). These polynuclear hydrides are generated from square planar H(2)Rh[P(OR)(3)](2) units by edge (hydrogen atom) sharing and by vertex (hydrogen atom) sharing to form the dimeric and trimeric structures, respectively. The square-planar units are held together through four-center and three-center two-electron Rh-H-Rh bonds in the dimer and trimer, respectively. The dimer and trimer molecules each add one molecule of hydrogen to form H[(i-C(3)H(7)O)(3)P](2)RhH(3)Rh [P(O-i-C(3)H(7))(3)](2) and H(5)Rh(3)[P(OCH(3))(3)](6), respectively. NMR spectral information has served to define the stereochemical features of these polyhydrides. The significance of this chemistry in the metal cluster-metal surface analogy is described.

Journal Article↗
PubMed1979

The broken wire suture.

The body is a hostile environment for wire sutures. Although the problems of electrochemical corrosion, direct chemical attack on the suture, and inflammation produced in reaction to the suture have been largley eliminated by the use of austenitic stainless steel wires, failure of the wires may still occur due to mechano-chemical cracking -- the combined effect of insignificant stresses, usually from cold working, and insignificant chemical potentials produced by body fluids. Although stainless steel wire remains a satisfactory material for sternotomy closure or for reattaching costal cartilages, the two spectacular complications of a broken wire point out the need for care in using wire sutures. Bending, twisting, kinking and knotting must be avoided as much as possible.

Adult↗
PubMed1977

Pharmacokinetics of the absorption, distribution, and elimination of melphalan in the dog.

[14C]melphalan ([14C]L-PAM) was rapidly absorbed from the gut of dogs after oral dosing and reached a maximum concentration in the serum by 30 minutes. The disappearance of L-PAM (intact drug) from the serum was biphasic after iv administration, with half-lives of 14 and 66 minutes for the alpha and beta phases, respectively. The urinary excretion accounted for 44% of the total radioactivity and 25% appeared in the feces. Approximately 8% of the dose was excreted unchanged in the urine. Biliary excretion was rapid, with 11% of the dose being accounted for in the bile after 30 minutes; approximately 80% of these drug equivalents (materials containing radioactivity) was parent compound. Since large amounts of L-PAM appeared in the bile, the agent may prove to be active against cancers of the gall bladder, bile ducts, and duodenum.

Animals↗
PubMed1975

Multiple antigenic sites on an eicosapeptide. I. Precipitin studies in the goat.

Purified peptide 105-124, an antigenic determinant from the carboxy terminus ribonuclease, was found to form an immune precipitate with antibody to that region prepared by affinity chromatography from goat hyperimmune antiserum to reduced carboxymethylated ribonuclease (CM-RNase). Cm-rnase also gave an immune precipitate with the antibody. Purified antibody to another region of similar size (40-61) did not form a precipitate with CM-RNase but did co-precipitate in the presence of antibody to peptide 105-124 and CM-RNase. The precipitin reaction between antibody to peptide 105-124 and CM-RNase was inhibited by two synthetic derivatives, peptides 118-124 and ala114-RNase 114-124. Stoichiometry of the precipitin reactions of antibody to 105-124 with CM-RNase or peptide 105-124 suggested an antigen valency of three or more. Consistent with this both peptides 105-124 and ala114-RNase 114-124 elicited immediate cutaneous reactions but 118-124 did not. These findings suggest that the eicosapeptide 105-124 is multivalent since at least three antibodies can react simultaneously with it.

Animals↗