Rheological properties of two-dimensional model networks

We measured the tensio-active properties of octamethylene dimethacrylate ( 1 ), octamethylene diisobutyrate ( 2 ) and octamethylene isobutyrate methacrylate ( 3 ) at the oil-water interface. The results indicate that these molecules are strongly adsorbed at the boundary between oil and water. The amphiphatic compounds in the monolayer can be polymerized and cross-linked by UV irradiation. The kinetics of surface gelation was studied by measuring the two-dimensional shear modulus as a function of the time of irradiation. A two-dimensional sol-gel transition was observed which is in fairly good agreement with percolation theories. The kinetics of the two-dimensional polymerization can be completely interpreted in terms of a simple reaction scheme. The elasticity of the two-dimensional films depends strongly on the surface concentration of the cross-linking agent. The rheological properties of the polymerized films exhibit typical features of rubber-elastic systems and there exists an interesting analogy to corresponding structures of three-dimensional networks.     

ELEVATED EPIDERMAL GROWTH FACTOR RECEPTOR LEVELS IN HYPERTENSIVE LYON RAT KIDNEY AND AORTA

1. The adult spontaneously hypertensive Lyon rats (LH strain) exhibited increased maximal epidermal growth factor (EGF) binding in freshly prepared kidney and aortic tissue membranes compared with age-matched normotensive (LN) or hypotensive (LL) strains. However, the binding affinity of the receptors to EGF was the same in all the three strains studied. These findings indicate an increased number of EGF receptors (EGFR) in the hypertensive LH strain. 2. Protein tyrosine kinase activity associated with the EGFR was also elevated in the LH strain compared with LN or LL strains, indicating that these receptors are functionally active. 3. There was a correlation between maximal EGF binding by aortic membranes and blood pressure in individual animals (r = 0.55; P < 0.001). 4. Taken together with previously reported similar findings in other models of genetic hypertension, the present results suggest a possible role for increased levels of EGFR in the development and maintenance of genetic hypertension.     

Comparison of panoramic and intraoral radiography and pocket probing for the measurement of the marginal bone level

Panoramic, bitewing and periapical radiography and probing for measurement of the marginal bone level were compared. Altogether 237 sites of 23 patients were examined. Radiographs were taken with a splint containing steel balls to allow calculation of the enlargement of the radiographs. Probing was done before and during flap surgery using the same splint. The open bone measurement represented the true value. All radiographs were assessed by 5 observers. The mean enlargement of panoramic radiography was 27% in the upper and 26% in the lower arch. For bitewing and periapical radiography, it was 8% in the upper and 4-5% in the lower arch. All methods underestimated the bone loss. Probing bone level before surgery was most accurate, deviating at most 5% from the true value. Periapical radiography was more accurate than panoramic and bitewing radiography (p less than 0.001). Panoramic radiography presented a slightly lower mean accuracy than bitewing radiography (p less than 0.05). The underestimation of the bone loss ranged from 13 to 32% in orthopantomograms, 11-23% in bitewing and 9-20% in periapical radiographs. The interobserver variation of the radiographic methods was substantial.     

Heart myosin adenosine triphosphatase and light subunits in experimental chronic aortic insufficiency in the rabbit

Cardiac myofibrillar and myosin ATPases were studied in experimentally induced aortic insufficiency in the rabbit, in order to elucidate the pathogenesis of the defect in myofibrillar ATPase shown in chronically hypertrophied and/or failing hearts. The rabbits were killed 345 ± 32 days after the operation; 24% of them had clinical or anatomical signs of failure. They all had hypertrophic hearts (mean degree of hypertrophy, 64%) with dilatation.Heart myofibrillar Ca²⁺ ATPase was found to be lowered in aortic insufficiency. Three different preparations of myosin were also studied. The purity of these preparations was assessed by urea or SDS polyacrylamide gel electrophoresis or by measuring Mg²⁺-ATPase in a medium of low ionic strength. The first preparation (homogenized muscle) was highly contaminated by thin-filament proteins; the second (minced muscle) was rather pure but still contaminated by a nucleoprotein; the latter was separated by chromatography in the third preparation. Myosin Ca²⁺-ATPase measured in a medium of low or high ionic strength at pH 7.0 was decreased in aortic insufficiency when all three preparations were tested.On electrophoresis myosin light subunits were normal in aortic insufficiency. The search for an inhibitor was unsuccessful: the two myosin ATPase activities were additive and ribonuclease treatment did not normalize hypertrophied heart myosin. The “nucleoprotein” peak separated from myosin during chromatography had an inhibitory effect on myosin ATPase but was present in controls as well as in aortic insufficiency.This work suggests that myosin itself is abnormal in chronic aortic insufficiency, but an abnormality residing in a very closely associated factor could not definitely be excluded. Because myosin subunits were only studied by electrophoresis, their structures and relative amounts would need more detailed study before final conclusions could be reached.     

Educational strategies in oral and maxillofacial radiology

In this paper, we interpret a trend in higher education in terms of its relation to oral and maxillofacial radiology education. Specifically, we describe an evidence-based dental education – borrowing from the concept of evidence-based health care. Three key findings from cognitive science are presented; these simple tenets form the basis of problem-based learning and can be implemented to enhance student learning. As an example of what we mean by evidence-based dental education, the different levels of the so-called MalmÖ model are outlined, along with a discussion of the pertinent strategies of programs based on this model.     

Chronic idiopathic orofacial pain. A long-term follow-up study

Patients suffering facial pain that does not fit with the traditional diagnostic criteria and which does not respond to dental treatment constitute a clinical problem. These patients lack a proper diagnosis and are frequently exposed to excessive and inadequate invasive treatment. The aim of this investigation was to study the long-term development of pain and the result of treatment in a cohort of patients suffering chronic idiopathic facial pain. The 74 patients referred to the Facial Pain Diagnostic Group at the Karolinska Institute School of Dentistry between 1981 and 1992 were invited to take part in a follow-up study. As 16 subjects were unwilling or unable to take part in the study and 13 had died, the remaining 45 were interviewed either in accordance with a standard protocol or by filling out a questionnaire mailed to them. The interview revealed that 10 were free of orofacial pain, but only 2 were totally free of pain. Over the 9-19 years' follow-up period the relationship between facial pain and pain in the rest of the body had changed substantially. Of 14 patients and more than 100 extractions, permanent pain relief was felt by only 3 patients. It is concluded that a diagnosis was given in only 2 cases. The distribution of the pain has changed dramatically. The low success rate of invasive treatments suggests that such therapeutic methods are to be considered contraindicated in patients suffering from idiopathic orofacial pain.