PubMed Health⌕ Search

Biomedical subjects

W L Smith

Publications and source records attributed to W L Smith.

At least 109 records · Page 6Linked to original sources
PubMed1996

Inflammatory bowel disease in children.

Pediatric inflammatory bowel disease is a complex area of pediatric gastrointestinal imaging. Multiple causative factors are discussed with emphasis upon disorders without known or presumed infectious etiology. Conditions discussed include Henoch-Schönlein purpura, Kawasaki disease, Behçet's disease, Crohn's disease, and ulcerative colitis with their respective clinical and radiological findings, differential diagnosis features, plus pertinent extraintestinal manifestations of inflammatory bowel disease.

Child↗
PubMed1995

Calcium-mediated translocation of cytosolic phospholipase A2 to the nuclear envelope and endoplasmic reticulum.

Cytosolic phospholipase A2 (cPLA2) is activated by a wide variety of stimuli to release arachidonic acid, the precursor of the potent inflammatory mediators prostaglandin and leukotriene. Specifically, cPLA2 releases arachidonic acid in response to agents that increase intracellular Ca2+. In vitro data have suggested that these agents induce a translocation of cPLA2 from the cytosol to the cell membrane, where its substrate is localized. Here, we use immunofluorescence to visualize the translocation of cPLA2 to distinct cellular membranes. In Chinese hamster ovary cells that stably overexpress cPLA2, this enzyme translocates to the nuclear envelope upon stimulation with the calcium ionophore A23187. The pattern of staining observed in the cytoplasm suggests that cPLA2 also translocates to the endoplasmic reticulum. We find no evidence for cPLA2 localization to the plasma membrane. Translocation of cPLA2 is dependent on the calcium-dependent phospholipid binding domain, as a calcium-dependent phospholipid binding deletion mutant of cPLA2 (delta CII) fails to translocate in response to Ca2+. In contrast, cPLA2 mutated at Ser-505, the site of mitogen-activated protein kinase phosphorylation, translocates normally. This observation, combined with the observed phosphorylation of delta CII, establishes that translocation and phosphorylation function independently to regulate cPLA2. The effect of these mutations on cPLA2 translocation was confirmed by subcellular fractionation. Each of these mutations abolished the ability of cPLA2 to release arachidonic acid, establishing that cPLA2-mediated arachidonic acid release is strongly dependent on both phosphorylation and translocation. These data help to clarify the mechanisms by which cPLA2 is regulated in intact cells and establish the nuclear envelope and endoplasmic reticulum as primary sites for the liberation of arachidonic acid in the cell.

Animals↗
PubMed1995

Fatty acid substrate specificities of human prostaglandin-endoperoxide H synthase-1 and -2. Formation of 12-hydroxy-(9Z, 13E/Z, 15Z)- octadecatrienoic acids from alpha-linolenic acid.

Human prostaglandin-endoperoxide H synthase-1 and -2 (hPGHS-1 and hPGHS-2) were expressed by transient transfection of COS-1 cells. Microsomes prepared from the transfected cells were used to measure the rates of oxygenation of several 18- and 20-carbon polyunsaturated fatty acid substrates including eicosapentaenoic, arachidonic, dihomo-gamma-linolenic > alpha-linolenic (delta 9, 12, 15), gamma-linolenic, and linoleic acids. Comparisons of kcat/Km values indicate that the order of efficiency of oxygenation is arachidonate > dihomo-gamma-linolenate > linoleate > alpha-linolenate for both isozymes; while the order of efficiency was the same for hPGHS-1 and hPGHS-2, alpha-linolenate was a particularly poor substrate for hPGHS-1. Gamma-Linolenate and eicosapentaenoate were poor substrates for both isozymes, but in each case, these two fatty acids were better substrates for hPGHS-2 than hPGHS-1. These studies of substrate specificities are consistent with previous studies of the interactions of PGHS isozymes with nonsteroidal anti-inflammatory drugs that have indicated that the cyclooxygenase active site of PGHS-2 is somewhat larger and more accommodating than that of PGHS-1. The major products formed from linoleate and alpha-linolenate were characterized. 13-Hydroxy-(9Z,11E)-octadecadienoic acid was found to be the main product formed from alpha-linoleate by both isozymes. The major products of oxygenation of alpha-linolenate were determined by mass spectrometry to be 12-hydroxy-(9Z,13E/Z,15Z)-octadecatrienoic acids. This result suggests that alpha-linolenate is positioned in the cyclooxygenase active site with a kink in the carbon chain such that hydrogen abstraction occurs from the omega 5-position in contrast to abstraction of the omega 8-hydrogen from other substrates.

Animals↗
PubMed1995

The virtual hospital. Providing multimedia decision support tools via the Internet.

Physicians in the clinical setting remain isolated from important sources of medical information. The authors have created a multimedia database known as The Virtual Hospital that improves access to current medical data, which is used to improve patient care decisions. The Virtual Hospital is a digital health sciences library stored on a server (computer) at The University of Iowa and delivered via the Internet to inexpensive personal computers in the workplace. The emerging standard of the World Wide Web is used to provide cross-platform distribution.

Computer Communication Networks↗
PubMed1995

Expression-activity profiles of cells transfected with prostaglandin endoperoxide H synthase measured by quantitative fluorescence microscopy.

Transfection of cos-1 cells with either prostaglandin endoperoxide H synthase-1 (PGHS-1) or -2 (PGHS-2) results in a mixed population of cells containing a diverse range of expressed enzyme. The use of fluorescent substrates and antibodies, in conjunction with fluorescence microscopy, provides the means to quantitate expression and activity of the enzyme within individual cells. Data obtained from individual cells can be utilized to construct enzyme activity curves for a population of transfected cells. This method has been employed to prepare expression-activity profiles within a population of cos-1 cells expressing PGHS-1 or -2. A direct correlation was observed between enzyme expression and activity as measured in single cells. The data demonstrate that activity-expression analyses can now be performed within single adherent cells growing in tissue culture.

Amino Acid Sequence↗
PubMed1995

Different intracellular locations for prostaglandin endoperoxide H synthase-1 and -2.

The subcellular locations of prostaglandin endoperoxide synthase-1 and -2 (PGHS-1 and -2) were determined by quantitative confocal fluorescence imaging microscopy in murine 3T3 cells and human and bovine endothelial cells using immunocytofluorescence with isozyme-specific antibodies. In all of the cell types examined, PGHS-1 immunoreactivity was found equally distributed in the endoplasmic reticulum (ER) and nuclear envelope (NE). PGHS-2 immunoreactivity was also present in the ER and NE. However, PGHS-2 staining was twice as concentrated in the NE as in the ER. A histofluorescence staining method was developed to localize cyclooxygenase/peroxidase activity. In quiescent 3T3 cells, which express only PGHS-1, histofluorescent staining was most concentrated in the perinuclear cytoplasmic region. In contrast, histochemical staining for PGHS-2 activity was about equally intense in the nucleus and in the cytoplasm, a pattern of activity staining distinct from that observed with PGHS-1. Our results indicate that there are significant differences in the subcellular locations of PGHS-1 and PGHS-2. It appears that PGHS-1 functions predominantly in the ER whereas PGHS-2 may function in the ER and the NE. We speculate that PGHS-1 and PGHS-2 acting in the ER and PGHS-2 functioning in the NE represent independent prostanoid biosynthetic systems.

3T3 Cells↗
PubMed1995

Localization of prostaglandin endoperoxide synthase-1 to the endoplasmic reticulum and nuclear envelope is independent of its C-terminal tetrapeptide-PTEL.

Prostaglandin endoperoxide H (PGH) synthases 1 and 2 are both membrane-associated proteins localized to the endoplasmic reticulum (ER) and nuclear envelope. The carboxyl terminal tetrapeptides of PGH synthases 1 and 2 are of the form -P/STEL. These sequences are similar to the -KDEL retention signal sequence characteristic of many proteins localized to the ER. To determine if the -PTEL sequence (residues 597-600) functions as an ER retention signal for ovine PGH synthase-1, we prepared and analyzed five mutants (L600N, L600R, L600V, E599Q, and delta 597), all having modifications that would be expected to alter the subcellular location of PGH synthase-1 if the -PTEL sequence were involved in ER targeting. Native ovine PGH synthase-1 and each of the five mutants were subcloned into the pSVT7 expression vector and were expressed transiently in cos-1 cells. The L600N, L600R, E599Q, and delta 597 mutants retained both cyclooxygenase and peroxidase activities. Moreover, when subjected to immunocytofluorescent staining, cos-1 cells expressing native and mutant enzymes showed similar patterns of fluorescence corresponding to ER and nuclear envelope localization. Finally, culture media bathing cos-1 cells transfected with native or mutant PGH synthases were tested for secreted PGH synthase-1 protein by Western blotting, but no PGH synthase-1 was detected in any of the culture media. Our results demonstrate that mutations in the C-terminal sequence-PTEL do not change the subcellular location of ovine PGH synthase-1. Thus, targeting of PGH synthase-1 to the ER can occur independent of its -PTEL sequence.

Amino Acid Sequence↗
PubMed1995

Selective inhibition of prostaglandin endoperoxide synthase-1 (cyclooxygenase-1) by valerylsalicylic acid.

Aspirin causes a time-dependent inhibition of prostaglandin endoperoxide H synthases (PGHS)-1 and -2 by acetylating active site serines present in both isozymes. In the case of PGHS-1, aspirin acetylation blocks cyclooxygenase activity, apparently by preventing arachidonate binding to the cyclooxygenase active site. With PGHS-2, acetylation does not block substrate binding but rather alters the enzyme in such a way that the acetylated form of PGHS-2 produces 15R-hydroxyeicosatetraenoic acid (15R-HETE) instead of the usual prostaglandin endoperoxide product. Based on these differences between PGHS-1 and PGHS-2, we reasoned that a salicylate ester containing an acyl group somewhat larger than the acetyl group of aspirin might be a selective inhibitor of PGHS-2. Accordingly, we prepared and tested eight different acyl salicylates as inhibitors of human (h) PGHS-1 and -2 expressed transiently in cos-1 cells. Valeryl(pentanoyl)salicylate (VSA) was the only compound in this series which showed isozyme selectivity, and, surprisingly, VSA inhibited hPGHS-1 much more effectively than hPGHS-2. Inhibition of hPGHS-1 by VSA was time-dependent. VSA also inhibited ovine PGHS-1 but did not inhibit the S530A mutant of ovine PGHS-1. This latter mutant, which lacks the active site serine hydroxyl group, is also refractory to inhibition by acetylsalicylate. Thus, we conclude that VSA acylates the active site serine of PGHS-1. VSA inhibited prostanoid synthesis by serum-starved murine NIH 3T3 cells which express only PGHS-1; in contrast, VSA caused only partial inhibition of prostanoid synthesis by serum-stimulated 3T3 cells which express both PGHS isozymes. Our results establish that VSA can be used as a reasonably selective inhibitor of PGHS-1.

3T3 Cells↗
PubMed1995

An examination of the source of the tyrosyl radical in ovine prostaglandin endoperoxide synthase-1.

A tyrosyl radical, which may initiate the cyclooxygenase reaction, has been detected in prostaglandin H synthase by electron paramagnetic resonance spectroscopy. In the crystal structure of ovine prostaglandin H synthase-1, Tyr348 and Tyr385 are in close proximity to the heme. We mutated these residues to phenylalanine to test for their involvement in tyrosyl radical formation. Native enzyme formed a tyrosyl radical centered at g = 2.0036 with a width of 28 gauss. The Y348F mutant formed a singlet signal similar to that of native enzyme with a width of 28 gauss (g = 2.0039). In contrast, the radical signals seen with the Y385F and Y348F/Y385F mutants were 23 gauss (g = 2.004) and 22 gauss (g = 2.0037). In short, tyrosyl radicals are formed even in the absence of both Tyr348 and Tyr385. In Y345F containing mutants, a cluster of aromatic amino acids which surrounds the heme group may provide an alternate pathway for electron abstraction from a more distant tyrosine, yielding a narrow tyrosyl radical signal.

Amino Acid Sequence↗
PubMed1995

Congenital syphilis mimicking child abuse.

It has been reported that fractures complicating congenital syphilis can mimic child abuse. We present such a finding in an 8-week-old infant who presented with paralysis of the left arm.

Child Abuse↗
PubMed1995

Radiological features in a case of Münchausen syndrome by proxy.

Munchausen syndrome by proxy is a type of child abuse which is usually diagnosed on clinical grounds. In occasional instances, radiological diagnosis plays a role in the recognition of this disorder. We present the radiological findings in a child with an unusual osteomyelitis owing to Münchausen syndrome by proxy.

Child, Preschool↗
PubMed1995

Imaging evaluation of breast-feeding and bottle-feeding systems.

OBJECTIVE: To compare infant sucking and swallowing patterns during feeding with a new artificial nipple and during breast-feeding. METHODS: Fifteen healthy, term infants were fed successfully for 1 week with use of the new tricut nipple; then each infant's oral cavity was examined during feeding by using real-time ultrasonography. Measurements of nipple length and compression were made, together with observations concerning the integrity of the seal formed by the infant's mouth around the nipple. These data were compared with similar data from previous studies of 16 breast-fed infants. RESULTS: Although no artificial feeding system exactly simulates breast-feeding, the new tricut nipple was sucked in a manner similar to the way the human nipple is sucked and delivered milk posteriorly to the foramen cecum region of the tongue, just as the breast does. CONCLUSION: Although further studies are necessary, to evaluate other characteristics of the new tricut nipple, the measurements from this investigation are useful additions to the ultrasound data these investigators have accumulated on various artificial feeding systems. These data may also prove helpful in determining the most appropriate nipples for infants with various feeding disorders.

Bottle Feeding↗
PubMed1995

Balancing life.

Explore the source record for details and available documents.

Attitude of Health Personnel↗