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Biomedical subjects

G E Scott

Publications and source records attributed to G E Scott.

14 recordsLinked to original sources
PubMed1990

The fracture strength of ceramic brackets: a comparative study.

Recent demand for esthetic brackets has led to the development and use of ceramic brackets in orthodontics. The purpose of this study was to compare the fracture strength of different ceramic brackets under different surface conditions and ligation methods using a torsional wire bending force. Five different bracket types (two polycrystalline, two single-crystal, and one metal) were tested using elastic and wire ligation, with half being scratched and the other half remaining unscratched. Results showed a significant difference between bracket types and surface conditions. Non-scratched single-crystal brackets had higher fracture strengths and slightly higher fracture loads than polycrystalline brackets. However, single-crystal brackets were significantly adversely affected by surface damage (scratching), while polycrystalline brackets were not significantly affected by surface damage. The fracture behavior of ceramic brackets followed the Griffith model where fracture strength decreased following surface damage.

Analysis of Variance↗
PubMed1990

Changes in vascular extracellular matrix accumulation reflect phenotypic differences between the arterial wall of pigeons resistant and susceptible to the development of spontaneous atherosclerosis.

White Carneau pigeons have previously been shown to be genetically susceptible to the development of spontaneous atherogenesis. The severity of development of atheromatous lesions is considerably greater than a more resistant breed of Show Racer pigeons. Analysis of levels of total hydroxyproline and isodesmosine in the thoracic aorta and celiac bifurcation of prelesion, six-week-old White Carneau and Show Racer pigeons, revealed an increased accumulation of total collagen and cross-linked elastin in the White Carneau arterial tissue. Using dot blot hybridization, measurements of steady state levels of several mRNAs in total RNA extracted from pigeon aortic tissue were also determined. While the increased deposition of extracellular matrix proteins was paralleled by a significantly greater recovery of mRNAs coding for pro alpha 1(1) collagen and elastin, in RNA extracted from White Carneau aortal tissue, increased recovery of mRNAs coding for an intracellular protein, gamma-actin were also observed in White Carneau aortal tissue. No differences in steady state levels of mRNAs coding for pro alpha 1(1) collagen and elastin were observed in RNA extracted from pigeon liver, suggesting a tissue specific increase in the mRNAs coding for these connective tissue proteins in aorta. A markedly reduced cell population however, was responsible for this overall increase in biosynthetic activity in White Carneau pigeon aortic tissue. This was demonstrated by a reduced cell count and by the recovery of reduced levels of total DNA in the thoracic aorta and celiac bifurcation of the White Carneau pigeon. The cell population in White Carneau aortic tissue exhibits therefore a markedly different phenotype with respect to a capacity for the biosynthesis of extracellular and intracellular proteins.

Actins↗
PubMed1989

Detailed structural analysis of a genome rearrangement in bovine rotavirus.

A genome rearrangement involving RNA segment 11 of a bovine rotavirus has been analysed by molecular cloning and sequencing. This revealed that the rearranged genome segment was generated by a head to tail concatemerisation of two almost full length copies of segment 11. The upstream copy of the gene has lost its 3' end and the downstream copy its 5' end. The truncation of the upstream copy of the gene occurs within the termination codon for VP11 converting it from a UAG to a UGA, the rearranged gene is therefore still able to encode a normal VP11. The possible mechanisms by which this rearrangement may have been generated are discussed.

Amino Acid Sequence↗
PubMed1988

Increased elastin mRNA levels associated with surgically induced intimal injury.

Quantitative levels of mRNAs coding for elastin, types I and III procollagen and gamma-actin were measured in porcine vascular material following balloon catheterization. A balloon catheter was introduced into the thoracic aorta and jugular vein of 3-6 week old pigs; following distention and six days of postoperative recovery, tissue samples were obtained for histopathology, electron microscopy, RNA extraction and mRNA quantitation. Using a series of mammalian cDNA clones and the procedure of slot blot hybridization, we have shown that elastin and types I and III procollagen mRNA levels rose significantly during the postoperative period following vascular distention. The increase correlated with an increase in the cell mass present in both the venous and arterial intimal layers. Changes in gamma-actin mRNA levels were also associated with this rapid proliferative response but in arterial tissue only.

Actins↗
PubMed1988

Gastrointestinal complications after cardiac surgery.

Gastrointestinal (GI) complications after cardiac surgical procedures are infrequent but severe. Thirty-three GI complications were identified in 25 patients who underwent cardiac surgery during a 7-year period (2.0% incidence). The mortality rate for patients having these GI complications was 44%. Acute acalculous cholecystitis was the most lethal complication (86%). Acute pancreatitis was the most common complication (eight patients). Most patients responded well to conservative measures. Five patients had upper GI hemorrhage and three had lower GI bleeding that required more than 2 U of packed red blood cells. All patient conditions were diagnosed endoscopically and none necessitated operation. Of the remaining patients, one was operated on because of perforated duodenal ulcer, one because of perforated diverticulitis, and one because of pseudo-obstruction of the colon, and one patient underwent diagnostic laparotomy and showed negative results for presumed acalculous cholecystitis. Liver failure was fatal in all three patients in whom it occurred. GI complications correlated significantly with advanced age, prolonged bypass times, valve surgery, and the female sex. We conclude that septic GI complications--particularly acute acalculous cholecystitis and perforated viscus--after cardiac surgery are uncommon but lethal. Clinical features are often subtle, and a high index of suspicion is necessary for an early diagnosis and the institution of appropriate treatment.

Acute Disease↗
PubMed1987

Clinical experience with the Jahnke-Barron heart support.

The Jahnke-Barron heart support has proven to be a useful adjunct to coronary artery surgery by allowing an easy access to the coronary arteries while maintaining a quiet operating field. Further, the use of this device eliminates the need for a surgical assistant or a heart holder.

Coronary Artery Bypass↗
PubMed1981

A portable device for the rapid concentration of viruses from large volumes of natural freshwater.

A portable device for the rapid concentration of viruses from natural freshwaters described and its performance in field use is evaluated. The system handled up to 500 litres of water in less than 90 min at a cost of only 2 pounds per sample. Where the samples contained sufficient bacteriophages for detection by direct plating the apparent phage recoveries were greater than 75%. Plant and animal viruses were also concentrated from waters with this system.

Bacteriophages↗
PubMed1975

A rapid method for obtaining the half saturation tension of small blood samples using a standard Clark electrode system.

A method is described which allows the half saturation tension (T50 value) of blood to be obtained within 5 min on samples of 100 mul volume, using a standard Clark PO2 electrode A PO2-time trace is recorded on a blood/buffer suspension from which the oxygen is removed at a constant rate using yeast cells. The T50 value is then derived graphically. The values taken for 210 traces show the graphical solutions to lie within +/- 0.5 mmHg of the tensions calculated from complete dissociation curves. Values from a further 590 traces show the T50 estimates are also reproducible with a standard error of less than 0.3 mmHg.

Blood Gas Analysis↗