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M R Phillips

Publications and source records attributed to M R Phillips.

59 records · Page 4Linked to original sources
PubMedDate not supplied

The role of induced contrast in images obtained using the environmental scanning electron microscope.

Generation of contrast in images obtained using the environmental scanning electron microscope (ESEM) is explained by interpretation of images acquired using the gaseous secondary electron detector (GSED), ion current, and the Everhart-Thornley detector. We present a previously unreported contrast component in GSED and ion current images attributed to signal induction by changes in the concentration of positive ions in the ESEM chamber during image acquisition. Changes in positive ion concentration are caused by changes in electron emission from the sample during image acquisition and by a discrepancy between the drift velocities of negative and positive charge carriers in the imaging gas. The proposed signal generation mechanism is used to explain contrast reversal in images produced using the GSED and ion current signals and accounts for discrepancies in contrast observed, under some conditions, in these types of images. Combined with existing models of signal generation in the ESEM, the proposed model provides a basis for correct interpretation of ESEM images.

Aluminum Oxide↗
PubMedDate not supplied

The results of conservative management of juvenile osteochondritis dissecans using joint scintigraphy. A prospective study.

A prospective clinical study used joint scintigraphy to investigate conservative treatment of juvenile osteochondritis dissecans (JOCD) of the femoral condyle. The predictive value of scintigraphic evaluation and various parameters (age at onset, sex, location and size of lesion) were analyzed. Over a 10 year period, the senior author followed 92 knees in 76 patients, 60 of whom were male and 16 female (11 and 5 bilaterals, respectively). All patients were participants in athletics or exercise programs. All patients had orthopaedic assessment, roentgenographic studies (AP, lateral, and tunnel views), 99m-Technetium phosphate compound joint scintigraphy, and instruction in a symptom-free existence (with all athletic activity proscribed). Patients were reevaluated and scanned every 8 weeks. No casts or braces were used, although crutches were sometimes necessary to maintain symptom-free levels. Based on specific indications for failure of conservative treatment, 50% of these patients failed and underwent surgery. Of the 92 knees, 52 were successfully treated conservatively, while 40 failed. Average followup was 4.2 years. Average age at onset was 12.5 years; the success group averaged 12.1 years and the failure group 13.0 years. The average lesion size was 363.2 mm2, with 309.5 mm2 in the success group and 436.0 mm2 in the failure group. Parameters of location, sex, and scan classification were not statistically significant as predictive factors. This study found no predictors for the success or failure of treatment beyond a moderate correlation of larger lesion size with failed conservative treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Acutely sodded expanded polytetrafluoroethylene grafts produce only prostacyclin: a qualitative difference from saphenous veins.

Select subsets of patients require prosthetic graft material for revascularization. Although arterial prosthetic grafts of large caliber perform acceptably, grafts of <6 mm exhibit a high attrition rate. Microvessel endothelial sodding, a method resulting in the lining of prosthetic grafts with autologous endothelium, improves graft patency; however, aggressive antiplatelet therapy is still required, because terminating an antiplatelet regimen accelerates graft attrition. The present investigation was designed to address the acute production of vasoactive substances in microvessel endothelial cell sodded expanded polytetrafluoroethylene (ePTFE) grafts in an attempt to delineate a possible mechanism behind the continued requirement for antiplatelet therapy. Equal lengths of acutely sodded ePTFE grafts (canine falciform ligament source) and saphenous veins (SV) (canine source) were evaluated by superfusion bioassay. Basal secretion from ePTFE grafts relaxed the biodetector ring 1 +/- 3%, whereas SV relaxed the ring 10 +/- 3% (p < 0.05, ePTFE vs. SV). Relaxation with acetylcholine stimulation was 49 +/- 7% in grafts and 50 +/- 10% in veins (p = NS). Calcium ionophore stimulation produced relaxation of 37 +/- 9% from ePTFE grafts and 100 +/- 23% from SV (p < 0.05). Indomethacin added to perfusate reduced relaxations from sodded ePTFE grafts to 20.2 +/- 9.2% with acetylcholine stimulation and 12.5 +/- 4.3% with calcium ionophore (p < 0.05 vs. control); addition of N(G)-monomethyl-L-arginine (L-NMMA) had no effect on the release of vasoactive substances from ePTFE grafts. In contrast, relaxations of effluent from SV stimulated by acetylcholine and calcium ionophore were significantly attenuated with indomethacin and L-NMMA (p < 0.05 vs. control). Scanning electron microscopy demonstrated confluent endothelium in SV and a nonconfluent endothelial cell layer in grafts. Acutely sodded ePTFE grafts produce vasoactive substances that quantitatively and qualitatively differ from those produced by canine SV. The ePTFE grafts produce mainly prostanoids, whereas SV produce both nitric oxide and prostanoids. The endothelial cell isolation procedure and absence of immediate graft luminal confluence may contribute to the observed differences.

Acetylcholine↗
PubMedDate not supplied

Comparison of chlorpropamide and glibenclamide treatment of maturity-onset diabetes: control assessed by fasting plasma glucose concentrations.

Twelve maturity-onset diabetic subjects were treated with chlorpropamide once daily, glibenclamide once daily, or glibenclamide twice daily in a crossover design study. Doses were increased until the fasting blood glucose concentrations became less than 6 mmol/L (108 mg/dl), at which time the patients were admitted for a 24-h study period. There was little difference between the plasma glucose and insulin responses to chlorpropamide or glibenclamide given twice daily (mean doses 489 and 11 mg/day, respectively). When glibenclamide was given once daily (mean dose 9 mg/day), similar plasma glucose concentrations during the day were obtained with slightly higher plasma glucose concentrations during the night. Four patients had chlorpropamide-induced flushing with alcohol, and six patients had postprandial hypoglycemia on glibenclamide. Chlorpropamide once daily or glibenclamide twice daily are suitable for control based on fasting blood glucose measurements.

Adult↗