PubMed Health⌕ Search

Biomedical subjects

J Sellers

Publications and source records attributed to J Sellers.

At least 19 recordsLinked to original sources
PubMed1999

Human platelet antigens: typing by PCR using sequence-specific primers and their distribution in blood donors resident in Wales.

We developed and validated HPA-1 to HPA-6 typing by PCR-SSP using a combination of established, modified and newly designed sequence-specific primers. We confirmed that the PCR primer mixtures functioned under the same PCR conditions as our standard HLA-A, -B, -C, -DR, -DQ PCR-SSP typing system. This allows concurrent testing for both HPA and HLA specificities and is therefore the system of choice for both clinical and large-scale blood donor panel HPA and HLA typing by PCR-SSP. Test validation included typing a population of blood donors living in Wales. These HPA frequencies were consistent with those of other European Caucasoid populations. HPA-4b and -6b were absent and HPA-5b, which shows some frequency variation, had a phenotype frequency of 18.9% (allele frequency 0. 0973), being close to that of the Dutch (19.7%) and Austrian (20.4%) populations and almost twice that found in Finns (10.0%). HPA genotype frequencies showed a good fit to Hardy-Weinberg equilibrium, further supporting the validity of our typing method.

Antigens, Human Platelet↗
PubMed1999

Regulation of AUF1 expression via conserved alternatively spliced elements in the 3' untranslated region.

The A+U-rich RNA-binding factor AUF1 exhibits characteristics of a trans-acting factor contributing to the rapid turnover of many cellular mRNAs. Structural mapping of the AUF1 gene and its transcribed mRNA has revealed alternative splicing events within the 3' untranslated region (3'-UTR). In K562 erythroleukemia cells, we have identified four alternatively spliced AUF1 3'-UTR variants, including a population of AUF1 mRNA containing a highly conserved 107-nucleotide (nt) 3'-UTR exon (exon 9) and the adjacent downstream intron (intron 9). Functional analyses using luciferase-AUF1 3'-UTR chimeric transcripts demonstrated that the presence of either a spliceable or an unspliceable intron 9 in the 3'-UTR repressed luciferase expression in cis, indicating that intron 9 sequences may down-regulate gene expression by two distinct mechanisms. In the case of the unspliceable intron, repression of luciferase expression likely involved two AUF1-binding sequences, since luciferase expression was increased by deletion of these sites. However, inclusion of the spliceable intron in the luciferase 3'-UTR down-regulated expression independent of the AUF1-binding sequences. This is likely due to nonsense-mediated mRNA decay (NMD) owing to the generation of exon-exon junctions more than 50 nt downstream of the luciferase termination codon. AUF1 mRNA splice variants generated by selective excision of intron 9 are thus also likely to be subject to NMD since intron 9 is always positioned >137 nt downstream of the stop codon. The distribution of alternatively spliced AUF1 transcripts in K562 cells is consistent with this model of regulated AUF1 expression.

Alternative Splicing↗
PubMed1998

Comparison of the Maxair Autohaler to wet nebulizer in patients with acute asthma.

STUDY OBJECTIVE: Patients with acute asthma often have difficulty using a conventional metered-dose inhaler. The Maxair Autohaler (3M Pharmaceuticals; St. Paul, MN) is a hand-held breath-actuated device developed to help patients coordinate drug administration. The study objective is to compare the efficacy of the Autohaler with inhaled beta-agonist administered by wet nebulizer in treating acute asthma exacerbations. DESIGN: Parallel, randomized, placebo-controlled clinical trial. SETTING: Emergency department (ED) of a university-affiliated hospital. PARTICIPANTS: Patients aged 18 to 55 years presenting to the ED with acute asthma and an FEV1 40 to 70% on hospital arrival. INTERVENTIONS AND MEASUREMENTS: Patients were given either six puffs of the Maxair Autohaler (1,200 microg pirbuterol) plus saline solution by nebulizer (active Autohaler group) or six puffs placebo by Autohaler plus 2,500 microg albuterol via nebulizer (active nebulizer group). Treatment was repeated at 30 and 60 min, with clinical evaluation performed before each treatment and again at 120 min. At 120 min, the protocol was completed. RESULTS: Twenty-four patients were enrolled, with 5 excluded because of protocol violations. Baseline FEV1 percent predicted values for the active Autohaler group were 53% vs 51% for the active nebulizer group (p=not significant [NS]). At time 120 min, values were 66% for Autohaler and 64% for nebulizer (p=NS). The average time to administer Autohaler was 2.9 min, vs 9.1 min for nebulizer. No patient was excluded because of the inability to use the Autohaler device adequately. CONCLUSION: In patients with moderate asthma exacerbations, similar improvements in pulmonary function are obtained when beta-agonists are given by either the Maxair Autohaler or a wet nebulizer device.

Acute Disease↗
PubMed1995

Effect of cAMP on GnRH stimulated LH secretion from individual pituitary gonadotropes.

Enhanced responsiveness of the pituitary gland to GnRH is a fundamental step required for secretion of the proestrous LH surge, and is achieved primarily by the actions of ovarian steroid hormones on the gonadotropes. The mechanisms involved are still unclear but the cAMP second messenger pathway can mediate some of these activities. The present study was undertaken to determine the effects of in vitro cholera toxin (CTX; increases cAMP) pretreatment of pituitary cells from proestrous and diestrous 1 rats relative to their LH secretory response to GnRH using a reverse hemolytic plaque assay. The number of gonadotropes that secrete LH in the group treated with CTX increased at low doses of GnRH and also in the absence of the peptide, but decreased at high doses, showing a dual effect: stimulation of some gonadotropes and inhibition of others. The inhibition was achieved within 3 h of pretreatment in proestrous cells but it was not seen until 20 h in diestrous 1 cells. This suggests the existence of at least two subpopulations of gonadotropes, one of which is stimulated by cAMP and another which is inhibited.

Animals↗
PubMed1993

Factors affecting filament velocity in in vitro motility assays and their relation to unloaded shortening velocity in muscle fibers.

The measurement of fluorescently labeled actin filament movement driven by mechanoenzymes (e.g. myosin) is an important methodology for the study of molecular motors. It is assumed that the filament velocity, Vf, is analogous to the unloaded shortening velocity, Vu, seen in muscle fibers. To evaluate this assumption we compared Vf to literature values for Vu with regard to the effects of [ATP], [ADP], [Pi], pH, ionic strength (10-150 mM) and temperature (15-30 degrees C). Vf and Vu are quantitatively similar with respect to the effects of substrate and product concentrations and temperatures > 20 degrees C. However, Vf is more sensitive to decreases in pH and temperatures < 20 degrees C than is Vu. At ionic strengths of 50-150 mM, Vf and Vu exhibit similar ionic strength dependencies (decreasing with ionic strength). At ionic strengths < 50 mM, Vf is markedly reduced. Thus while Vf is a good analogue for Vu under certain conditions (elevated ionic strength and temperatures > 20 degrees C), under others it is not. The results of motility assays must be cautiously interpreted.

Actin Cytoskeleton↗
PubMed1992

Regulation of the actin-activated ATPase and in vitro motility activities of monomeric and filamentous Acanthamoeba myosin II.

The actin-activated Mg(2+)-ATPase activity of filamentous Acanthamoeba myosin II is inhibited by phosphorylation of 3 serine residues at the tip of the tail of each heavy chain. From previous studies, it had been concluded that the activity of each molecule in the filament was regulated by the global state of phosphorylation of the filament and was independent of its own phosphorylation state. The actin-activated Mg(2+)-ATPase activity of monomeric phosphorylated myosin II was not known because it polymerizes under the ionic conditions necessary for the expression of this activity. We have now found conditions to maintain myosin II monomeric and active during the enzyme assay. The actin-activated Mg(2+)-ATPase activities of monomeric dephosphorylated and phosphorylated myosin II were found to be the same as the activity of filamentous dephosphorylated myosin II. These results support the conclusion that phosphorylation regulates filamentous myosin II by affecting filament conformation. Consistent with their equivalent enzymatic activities, monomeric and filamentous dephosphorylated myosin II were equally active in an in vitro motility assay in which myosin adsorbed to a surface drives the movement of F-actin. In contrast to their very different enzymatic activities, however, filamentous and monomeric phosphorylated myosin II had similar activities in the in vitro motility assay; both were much less active than monomeric and filamentous dephosphorylated myosin II. One interpretation of these results is that the rate-limiting steps in the two assays are different and that, while the rate-limiting step for actin-activated Mg(2+)-ATPase activity is regulated only at the level of the filament, the rate-limiting step for motility can also be regulated at the level of the monomer.

Acanthamoeba↗
PubMed1991

Identification of the 1H-NMR spectra of complex oligosaccharides with artificial neural networks.

Artificial networks can be used to identify hydrogen nuclear magnetic resonance (1H-NMR) spectra of complex oligosaccharides. Feed-forward neural networks with back-propagation of errors can distinguish between spectra of oligosaccharides that differ by only one glycosyl residue in twenty. The artificial neural networks use features of the strongly overlapping region of the spectra (hump region) as well as features of the resolved regions of the spectra (structural reporter groups) to recognize spectra and efficiently recognized 1H-NMR spectra even when the spectra were perturbed by minor variations in their chemical shifts. Identification of spectra by neural network-based pattern recognition techniques required less than 0.1 second. It is anticipated that artificial neural networks can be used to identify the structures of any complex carbohydrate that has been previously characterized and for which a 1H-NMR spectrum is available.

Artificial Intelligence↗
PubMed1991

Myosin I: a new insight into the mechanism and cellular significance of actin-based motility.

From our work on brush border myosin I structure, activity, regulation, and function, we can begin to understand the significance of the diversification of myosin proteins. While myosin I and II proteins retain conserved elements of structure that may dictate their similar mechanisms of motility and actin-activated MgATPase activity, their unique structures may provide the basis for the distinct localization and regulation of the two myosin types. How does the tropomyosin-inhibited actin-binding site of myosin I differ from that of the tropomyosin-activated myosin II actin-binding site? What elements of the sites of interaction of the 110K-protein and calmodulin contribute to the conserved, light-chain dependent coupling of MgATPase activity to translocation and which confer the novel calcium regulation of dissociation in vitro? It seems that the evolutionary demand for diversification of cellular motility functions has been met, at least in the actin-based system, by the evolution of isoforms tailored in structure, activity, regulation, and localization to serve complementary needs.

Actins↗
PubMed1983

Cardiovascular anomalies with imperforate anus.

In 68 patients with anorectal malformations cardiovascular anomalies (CVA) were seen in 15 and genitourinary (GU) anomalies in 30. CVA were more frequent (33%) whenever there was a GU anomaly. Ventricular septal defect was the most frequent lesion. All but 1 CVA occurred with type III anorectal malformation. The complexity of the cardiac lesion did not parallel that of the GU anomaly.

Abnormalities, Multiple↗
PubMed1982

Frequency and transmissibility of trimethoprim resistance in enterobacteria from urinary infections.

In a survey of 8,986 enterobacterial strains from urinary tract infections collected between September 1980 and June 1981, the overall frequency of resistance to trimethoprim was 3.5%. Strains collected from long-stay patients showed the highest frequency (7.7%); those from general practice the lowest frequency (2.3%), while those from hospital in-patients and out-patients were intermediate with 4.7 and 3.2 respectively. All these differences were statistically significant. In a further study of 117 resistant strains, Escherichia coli accounted for 47% of strains and Proteus sp. for 27%. Transfer of trimethoprim resistance occurred in 44% of E. coli strains and 22% of Klebsiella. A significant increase in the frequency of resistant strains was noted between the first 5 months of the study and the second 5.

Drug Resistance, Microbial↗
PubMed1982

Clinical experience with azlocillin in the treatment of urinary tract infections with Pseudomonas aeruginosa.

27 patients, aged 19-23 yr, with symptomatic urinary tract infection or epididymitis due to Pseudomonas aeruginosa were treated with azlocillin. All pseudomonas strains were sensitive to azlocillin. The microorganism was eradicated in 25/26 evaluable patients. 25/27 patients were clinically cured. Bacteriological relapse occurred in 11 patients. No serious drug reactions were noted.

Adult↗
PubMed1980

Neurotrophic influence on lobster skeletal muscle.

The correlation between histochemical properties of muscle fibers and the pattern of innervation by the two motor neurons was studied in the asymmetric claw closer muscles of the lobster. The closer muscle of the cutter claw is composed of 65 percent fast muscle fibers and 35 percent slow muscle fibers, whereas that in the crusher claw has all slow muscle fibers. In both claws, myofibrillar adenosinetriphosphatase activity was independent of the pattern of innervation. Oxidative capacity, as measured by reduced nicotinamide adenine dinucleotide activity, was correlated with motor axon presence: Muscle fibers innervated solely by the "fast" motor axon had low oxidative capacity, muscle fibers receiving only the slow motor axon had very high oxidative capacity, and fibers innervated by both axons had intermediate properties. The data suggest that the motor neurons may exert trophic influences that control certain muscle fiber properties but not others.

Adenosine Triphosphatases↗