Biomedical subjects
Publications and source records attributed to R J Stewart.
Wandering spleen is a rare condition that commonly presents with splenic infarction secondary to torsion. Splenectomy was previously advocated as the treatment of choice, though recent reports suggest that the organ may be distorted, and splenopexy performed. This paper documents how the latter procedure may be done using adherent omentum.
Dynamic changes in microtubule (MT) length have long been thought to contribute to intracellular motility. Both the polymerization and depolymerization of tubulin have been shown to do work in vitro, but the biochemical complexity of objects moved, such as chromosomes, has complicated the identification of proteins that couple MT dynamics with motility. Work with MTs grown from and tethered to pellicles of lysed Tetrahymena has shown that disassembly-dependent movement of chromosomes in vitro can be inhibited with antibodies against the motor domain of kinesin. To study proteins that can function in disassembly-dependent motion, we have refined this motility assay, replacing chromosomes with protein-coated latex microspheres. We report here the ability of several enzymes, including kinesin, to support in vitro motility of latex microspheres on disassembling MTs (Fig. 1a). The polarity of kinesin's motor activity can be reversed by MT disassembly and interactions between a motor and a MT end can either slow or speed the rate of tubulin depolymerization.
It is clear that activation of the proinflammatory cytokine cascade is both the cause and the consequence of renal injury. Recently, it has been appreciated that a rich network of signaling pathways contributes to modulation of tumor necrosis factor-alpha (TNF) and interleukin-1 (IL-1) bioactivity, both in vitro and in vivo. Insight into the checks and balances that intervene or temper endogenous cytokine effector mechanisms has arisen from an explosion of new information on the cell biology of proinflammatory cytokines. Novel mechanisms of cytokine regulation are currently being described and hold promise for therapeutic potential: soluble cytokine receptors, endogenous receptor antagonists, and anti-inflammatory cytokines such as IL-4, IL-10, and IL-13.
The objective of the study was the evaluation of a screening service for fetal abnormality using early ultrasound scanning to date and establish viability of the pregnancy combined with maternal serum alpha-fetoprotein estimation at 16 weeks and thereafter selective detailed scanning at 18-20 weeks based on clinical indication. The study was designed to be retrospective, emphasizing the possibility of diagnosis. Early scans were performed by radiographers and radiologists, detailed ones by radiologists and obstetricians with subspecialty training in prenatal diagnosis. The study was carried out in the ultrasound department of a large University Hospital. The subjects studied were all cases of abnormality identified pre- or postnatally in women delivering in the hospital over 4 years and to whom the screening service applied. Information was obtained from ultrasound and maternity records, birth notifications, pathology and autopsy reports and a special needs register. Cases were classified as not detectable, potentially detectable and usually detectable. Major fetal anomalies numbered 255 (total deliveries 19,497), a prevalence of 1.3%; 130 (51%) were diagnosed by ultrasound with 64% before 24 weeks and 36% later. Eleven chromosomal anomalies (4%) were diagnosed by genetic methods and 114 (45%) anomalies were not diagnosed antenatally. The sensitivity of the program was 37% before 24 weeks. Chromosomal anomalies, lesions of the central nervous system and cardiac defects were most common, followed by lesions of the gastrointestinal and urinary tracts. A large proportion of the detected and detectable anomalies were lethal.(ABSTRACT TRUNCATED AT 250 WORDS)
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The expression of endothelin-1 (ET-1) and endothelial constitutive nitric oxide synthase (ecNOS) was assessed in two independent in vitro models: asynchronously differentially proliferating cultures and wounded endothelial cell monolayers. Northern blot analysis of RNA isolated from preconfluent, confluent, and postconfluent cells revealed a fourfold rise in ET-1 mRNA transcripts, whereas levels of ecNOS mRNA transcripts were reduced twofold in proliferating cells. Nuclear run-off analysis demonstrated that increased steady-state ET-1 mRNA content in proliferating cells was mediated, in part, by increased gene transcription. In contrast, ecNOS transcription rates in proliferating cells were not decreased compared with quiescent nonproliferating cells, indicating that mRNA destabilization mediated the decreased ecNOS mRNA levels in proliferating endothelium. Concordant changes in protein expression were documented for both ET-1 and ecNOS. In injured endothelial cell monolayers, in situ cRNA hybridization demonstrated increased mRNA transcript levels for ET-1 in growth fronts of injured endothelial monolayers. These data are taken to indicate that expression of ET-1 and ecNOS is reciprocally regulated in two different models of endothelial cell proliferation.
The distribution of NADPH-d activity in the spinal cord and dorsal root ganglia of the cat was studied to evaluate the role of nitric oxide in lumbosacral afferent and spinal autonomic pathways. At all levels of the spinal cord NADPH-d staining was present in neurons and fibers in the superficial dorsal horn and in neurons around the central canal and in the dorsal commissure. In addition, the sympathetic autonomic nucleus in the rostral lumbar segments exhibited prominent NADPH-d cellular staining whereas the parasympathetic nucleus in the sacral segments was not well stained. The most prominent NADPH-d activity in the sacral segments occurred in fibers extending from Lissauer's tract through laminae I along the lateral edge of the dorsal horn to lamina V and the region of the sacral parasympathetic nucleus. These fibers were very similar to VIP-containing and pelvic nerve afferent projections in the same region. They were prominent in the S1-S3 segments but not in adjacent segments (L6-L7 and Cx1) or in thoracolumbar and cervical segments. NADPH-d activity and VIP immunoreactivity in Lissauer's tract and the lateral dorsal horn were eliminated or greatly reduced after dorsal-ventral rhizotomy (S1-S3), indicating the fibers represent primary afferent projections. A population of small diameter afferent neurons in the L7-S2 dorsal root ganglia were intensely stained for NADPH-d. The functional significance of the NADPH-d histochemical stain remains to be determined; however, if NADPH-d is nitric oxide synthase then this would suggest that nitric oxide may function as a transmitter in thoracolumbar sympathetic preganglionic efferent pathways and in sacral parasympathetic afferent pathways in the cat.
OBJECTIVE: To determine whether treatment with the combination of hyperbaric oxygen and free-radical scavengers or inhibitors would result in increased skin-flap survival. DESIGN: An animal model with male Sprague-Dawley rats was used. The flap was a cranial-based dorsal 3 x 12-cm random-pattern skin flap that included the panniculus carnosus. Rats were randomly assigned to one of 10 treatment groups. INTERVENTIONS: The radical scavengers superoxide dismutase, catalase, and alpha-tocopherol acetate and the inhibitor allopurinol were used to combat or scavenge radicals. Oxygen (100%) treatments were for 90 minutes at 2.5 atm absolute daily. MAIN OUTCOME MEASURES: At 7 days, the flaps were examined for survival by fluorescein injection. Lipid peroxidation as a measure of tissue damage was measured by thiobarbituric acid-malondialdehyde analysis. RESULTS: The combination of treatments resulted in significantly increased flap survival compared with untreated controls (P < .05) except in the group treated with allopurinol and hyperbaric oxygen. Lipid peroxidation was inhibited by the superoxide dismutase plus catalase and the alpha-tocopherol treatments but not by treatment with allopurinol. CONCLUSION: Moderate doses of radical scavengers or antioxidants coupled with a conservative hyperoxic exposure regimen can result in the increased survival of random-pattern skin flaps.
This paper describes the molecular and biochemical properties of KLP68D, a new kinesin-like motor protein in Drosophila melanogaster. Sequence analysis of a full-length cDNA encoding KLP68D demonstrates that this protein has a domain that shares significant sequence identity with the entire 340-amin acid kinesin heavy chain motor domain. Sequences extending beyond the motor domain predict a region of alpha-helical coiled-coil followed by a globular "tail" region; there is significant sequence similarity between the alpha-helical coiled-coil region of the KLP68D protein and similar regions of the KIF3 protein of mouse and the KRP85 protein of sea urchin. This finding suggests that all three proteins may be members of the same family, and that they all perform related functions. KLP68D protein produced in Escherichia coli is, like kinesin itself, a plus-end directed microtubule motor. In situ hybridization analysis of KLP68D RNA in Drosophila embryos indicates that the KLP68D gene is expressed primarily in the central nervous system and in a subset of the peripheral nervous system during embryogenesis. Thus, KLP68D may be used for anterograde axonal transport and could conceivably move cargoes in fly neurons different than those moved by kinesin heavy chain or other plus-end directed motors.
Activated vascular endothelium evidences a diverse array of responses to biochemical and physical stimuli with modulating effects on leukocyte trafficking, vascular permeability and vasomotor tone controlling microvascular blood flow. Clearly, glomerular endothelial cells share in common with large-vessel endothelium some components of the cytokine-activated phenotype. These findings provide insight into mechanisms of glomerular injury. Speculation about potentially unique aspects of microvascular regulation which might be important in glomerular injury suggests that novel aspects of cytokine-activation may be evident in microvascular endothelial cells. Molecular mechanisms underlying signal transduction of stimulus-induced alterations in endothelial phenotype implicate cis-regulatory processes that are unique in diversity and expression. Further elucidation of these mechanisms may suggest interventions directed towards inhibiting the pathophysiologic sequelae of endothelial cell activation.
Respiratory complications, especially pulmonary edema, account for over 50% of mortalities in inhalation injuries. This study was conducted to determine the effect of free radical scavengers and hyperbaric oxygen (HBO) in vivo on reducing pulmonary edema. Adult New Zealand rabbits were allowed to breath cooled, cotton smoke until a significant inhalation lung injury was produced. Five percent of body weight lactated Ringer's solution was then administered i.v. over 2 h. The following free radical scavengers were given as bolus infusions at the beginning of fluids resuscitation: superoxide dismutase, catalase, butylated hydroxytoluene/piperonyl butoxide, and mannitol. At the completion of fluid administration, half of the subjects were given HBO treatment. Pulmonary edema was then measured as extravascular lung water and wet/dry lung weight. Results indicate that free radical scavengers or HBO reduce pulmonary edema. Free radical scavengers in conjunction with HBO showed no significant improvement over HBO or free radical scavengers alone.
Galactosylceramide (GalCer) and cerebroside sulfate (CBS) are the major glycolipids found in myelin. They occur in greater concentrations in this membrane than any other. Recently, it was reported that these two glycolipids can participate in a heterotypic carbohydrate-carbohydrate interaction [Hakomori et al. (1991) Glycoconjugate J. 8, 178]. In the present study, the effect of changes in the ceramide composition of both GalCer and CBS on this interaction has been examined. The interaction was monitored by measuring the aggregation of small unilamellar phosphatidylcholine/cholesterol liposomes containing GalCer with similar liposomes containing CBS, through the increase in optical density at 450 nm. Aggregation depends on the addition of a divalent cation and varies inversely with the ionic radius of the cation. Aggregation occurred at millimolar concentrations of divalent cation and was inhibited and reversed by the addition of EDTA. A lesser degree of homotypic self-aggregation of GalCer and of CBS liposomes also occurred in the presence of divalent cations, but the sum of this self-aggregation was significantly less than the heterotypic interaction between the two types of liposomes. Changes in the ceramide composition of GalCer and CBS significantly affected the extent of their interaction with each other. Increasing the fatty acid chain length of either GalCer or CBS resulted in increased aggregation. Hydroxylation of the fatty acid also increased the degree of aggregation of GalCer and CBS liposomes. These findings indicate that a divalent cation-mediated GalCer-CBS interaction could play a role in cell recognition and membrane adhesion phenomena such as the formation of compact multilamellar myelin.(ABSTRACT TRUNCATED AT 250 WORDS)
Endothelial nitric oxide (NO) synthase is a unique NO synthase isoform that is expressed constitutively by vascular endothelium both in vivo and in vitro and is believed essential to local vascular homeostasis. This calcium/calmodulin-dependent isoform is distinct from neuronal NO synthase. Genomic clones encoding the human endothelial NO synthase were isolated and the structural organization of the gene was determined. The gene contains 26 exons spanning approximately 21 kilobases of genomic DNA, encodes a messenger RNA of 4052 nucleotides, and is present as a single copy in the haploid human genome. Characterization of 5'-flanking genomic regions indicates that the endothelial NO synthase promoter is "TATA-less" and exhibits proximal promoter elements consistent with a constitutively expressed gene that is found in endothelial cells, namely Sp1 and GATA motifs. The 5'-flanking region contains putative AP-1, AP-2, NF-1, heavy metal, acute-phase response shear stress, and sterol-regulatory cis-elements. The human endothelial NO synthase gene was assigned to the 7q35-->7q36 region of chromosome 7 by Southern blot hybridization of human-rodent somatic cell hybrid lines and fluorescence in situ hybridization, whereas human neuronal NO synthase localized to the 12q24.2 region of chromosome 12.
Factors which influence the accessibility, or exposure, of the carbohydrate head group of the glycolipid galactosylceramide (GalCer) at the membrane surface have been examined in lipid model membranes using the technique of galactose oxidase-tritiated sodium borohydride labeling. Both the ceramide composition of GalCer and the lipid composition of its membrane environment were varied. We have shown that GalCer is oxidized in a membrane environment, by purification of the labeled galactosyl moiety of the glycolipid by high-performance anion exchange chromatography. Using semisynthetic molecular species of GalCer with acyl chain lengths ranging from 16 to 26 carbons, incorporated into liposome membranes of egg phosphatidylcholine (PC), and reverse-phase HPLC separation of mixtures of the molecular species, we have shown that increasing the fatty acid chain length of GalCer increases its oxidation by galactose oxidase. In addition, the degree of oxidation is reduced when the fatty acid chain of GalCer is hydroxylated. GalCer incorporated into liposomes containing synthetic species of PC with different fatty acid chain lengths (together with cholesterol) was oxidized less as the PC acyl chain length, and hence the bilayer thickness, was increased. The oxidation of GalCer in liposomes composed of sphingomyelin/cholesterol was reduced compared to its oxidation in PC liposomes. Furthermore, changes in the fatty acid chain length of GalCer had no effect on its oxidation in sphingomyelin liposomes. These findings indicate that the ceramide composition and lipid membrane environment can influence the exposure of the lipid carbohydrate, and hence, they could modulate the receptor activity of glycolipids at the membrane surface.
The kinesin heavy chain and the ncd (non-claret disjunctional) gene product of Drosophila are microtubule-associated motor proteins related by sequence similarity within an approximately 340-aa domain. Despite the sequence similarity, the kinesin heavy chain and ncd protein move in opposite directions on microtubules. To investigate the molecular basis for direction of movement, we created a series of truncated kinesin heavy chain and ncd proteins. We found that the conserved domain of both proteins has microtubule motor activity, although the efficiency with which ATP hydrolysis is coupled to microtubule movement declines dramatically with increasing truncation. Further, the direction of movement is intrinsic to the conserved motor domains, rather than being a consequence of domain organization or adjacent sequences.
Oesophageal duplication cysts in infants (usually males) should be recognized as a cause of respiratory distress which worsens during the neonatal period, and which is associated with feeding difficulties. Their radiological appearance is that of a right-sided posterior mediastinal mass, which is shown to be cystic on ultrasound. Excision is curative.
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