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Biomedical subjects

N Osborne

Publications and source records attributed to N Osborne.

12 recordsLinked to original sources
PubMed2000

A sphingosine-1-phosphate receptor regulates cell migration during vertebrate heart development.

Coordinated cell migration is essential in many fundamental biological processes including embryonic development, organogenesis, wound healing and the immune response. During organogenesis, groups of cells are directed to specific locations within the embryo. Here we show that the zebrafish miles apart (mil) mutation specifically affects the migration of the heart precursors to the midline. We found that mutant cells transplanted into a wild-type embryo migrate normally and that wild-type cells in a mutant embryo fail to migrate, suggesting that mil may be involved in generating an environment permissive for migration. We isolated mil by positional cloning and show that it encodes a member of the lysosphingolipid G-protein-coupled receptor family. We also show that sphingosine-1-phosphate is a ligand for Mil, and that it activates several downstream signalling events that are not activated by the mutant alleles. These data reveal a new role for lysosphingolipids in regulating cell migration during vertebrate development and provide the first molecular clues into the fusion of the bilateral heart primordia during organogenesis of the heart.

Alleles↗
PubMed2000

The Dictyostelium LIM domain-containing protein LIM2 is essential for proper chemotaxis and morphogenesis.

We have identified limB, a gene encoding a novel LIM domain-containing protein, LIM2, in a screen for genes required for morphogenesis. limB null cells aggregate, although poorly, but they are unable to undergo morphogenesis, and the aggregates arrest at the mound stage. limB null cells exhibit an aberrant actin cytoskeleton and have numerous F-actin-enriched microspikes. The cells exhibit poor adhesion to a substratum and do not form tight cell-cell agglomerates in suspension. Furthermore, limB null cells are unable to properly polarize in chemoattractant gradients and move very poorly. Expression of limB from a prestalk-specific but not a prespore-specific promoter complements the morphogenetic defects of the limB null strain, suggesting that the limB null cell developmental defect results from an inability to properly sort prestalk cells. LIM2 protein is enriched in the cortex of wild-type cells, although it does not colocalize with the actin cytoskeleton. Our analysis indicates that LIM2 is a new regulatory protein that functions to control rearrangements of the actin cytoskeleton and is required for cell motility and chemotaxis. Our findings may be generally applicable to understanding pathways that control cell movement and morphogenesis in all multicellular organisms. Structure function studies on the LIM domains are presented.

Actins↗
PubMed1999

Incidence of ponticulus posterior of the atlas in migraine and cervicogenic headache.

BACKGROUND: The clinical significance of the ponticulus posticus is far from clear. It has been associated with headaches, Barré-Lieou syndrome, photophobia, and migraine. However, little epidemiologic evidence for this exists. OBJECTIVE: This study investigated the relationship of ponticulus posticus on x-ray studies and headache symptoms in a series of chiropractic patients. METHODS: Eight hundred ninety-five patients who visited a chiropractic clinic for the first time and whose conditions required cervical spine x-ray examinations were studied. Complaints were categorized as migraine with aura, migraine without aura, cervicogenic headache, neck pain only, and other conditions. The presence or absence of the ponticulus posticus (whether partial or complete) was determined by means of a lateral cervical film and noted as a positive or negative finding. The data were analyzed by frequency analysis and Pearson's chi 2 test. RESULTS: Forty-six percent of the sample were men and the predominant complaint was neck pain (33%). Most patients were in the fourth decade of life. The frequencies of the other complaints were migraine with aura (7%), migraine without aura (4%), cervicogenic headache (22%), other conditions (33%). An 18% prevalence of ponticulus posticus was found. This finding was significantly associated with migraine without aura (chi 2 = 4.97; P = .03) and not with any other conditions. CONCLUSION: In a chiropractic patient population that required cervical x-ray examinations, a significant association was found between ponticulus posticus and migraine without aura, with an odds ratio of 2.19:1 in favor of this complaint being present with the osseous anomaly. The mechanism for this remains obscure but may be related to ischemic compression of the vertebral artery or by dural tension at the craniocervical junction.

Adult↗
PubMed1999

A vital stain for studying membrane dynamics in bacteria: a novel mechanism controlling septation during Bacillus subtilis sporulation.

At the onset of sporulation in Bacillus subtilis, two potential division sites are assembled at each pole, one of which will be used to synthesize the asymmetrically positioned sporulation septum. Using the vital stain FM 4-64 to label the plasma membrane of living cells, we examined the fate of these potential division sites in wild-type cells and found that, immediately after the formation of the sporulation septum, a partial septum was frequently synthesized within the mother cell at the second potential division site. Using time-lapse deconvolution microscopy, we were able to watch these partial septa first appear and then disappear during sporulation. Septal dissolution was dependent on sigma E activity and was partially inhibited in mutants lacking the sigma E-controlled proteins SpoIID, SpoIIM and SpoIIP, which may play a role in mediating the degradation of septal peptidoglycan. Our results support a model in which sigma E inhibits division at the second potential division site by two distinct mechanisms: inhibition of septal biogenesis and the degradation of partial septa formed before sigma E activation.

Bacillus subtilis↗
PubMed1999

Serotonin-2A receptor mRNA expression in rat retinal pigment epithelial cells.

Previous studies have shown that rat retinal pigment epithelial (RPE) cells in culture express 5-HT2-type serotonin receptors coupled to phospholipase C activity. The presented data confirm this observation where it is shown that serotonin induced increases in radioactive inositol phosphates accumulation in RPE cells pretreated with tritiated inositol. This increase was significantly (p < 0.01) attenuated by 1 microM spiperone, ketanserin, mesulergine and metergoline while the same concentration of spiroxatrine or yohimbine had no effect, suggesting the involvement of 5-HT2A receptors. Using reverse transcriptase-polymerase chain reaction the presence of 5-HT2A receptor mRNA was demonstrated in total RNA isolated from rat RPE cell cultures. Amplification of a 5-HT2A receptor mRNA-derived product was additionally confirmed by Southern blot analysis. The combined data demonstrates the existence of functional 5-HT2A receptors in rat RPE cells.

Animals↗
PubMed1996

Color flow Doppler: a useful instrument in the diagnosis of funic presentation.

Color Doppler sonography offers the opportunity to evaluate the umbilical cord and to study blood velocity wave forms within the cord. Funic (cord) presentation can be diagnosed unequivocally with color Doppler sonography. Because funic presentation is likely to be the harbinger of cord prolapse, the morbidity and mortality associated with cord prolapse can be prevented if funic presentation is diagnosed before membrane rupture. This article describes the first case in the obstetric literature of funic presentation diagnosed with color Doppler sonography. The potential complications associated with cord prolapse were avoided with a cesarean section.

Adult↗
PubMed1995

Laparoscopy-assisted vaginal hysterectomy compared with abdominal hysterectomy.

The first 150 consecutive laparoscopic vaginal hysterectomy (LVH) cases done by Creighton University faculty members at Mercy Hospital, Council Bluffs, Iowa and at St Joseph Hospital, Omaha, Nebraska were compared with 194 abdominal hysterectomies (AHs) for benign or noninvasive disease. The results indicate that LVH can be accomplished with low morbidity, low length of stay, and with less patient discomfort than experienced by patients who undergo AH.

Adult↗
PubMed1994

Bilateral pneumothorax, an unusual complication of laparoscopic surgery.

Even though there are few complications with endoscopic surgery, some are life threatening. Pneumothorax is among these complications. Timely recognition and rapid diagnosis is essential. This is a case of a routine laparoscopy that was complicated by bilateral pneumothorax, and its diagnosis and treatment.

Adult↗
PubMed1985

Iterative deblurring algorithm for a multiplane tomographic scanner.

An iterative algorithm has been developed to reduce blur artefacts in images obtained from the Pho/Con multiplane tomographic scanner. In this technique estimates of the activity distribution are convolved with the detector response function and compared with the original blurred image planes. Successive estimates of the activity distribution are modified so as to minimise the square of the difference in pixel count between the two sets of blurred images. The technique has been tested with images containing non-correlated noise provided by computer simulation and images with correlated noise acquired in experimental phantom studies.

Humans↗