Subject plaque

Laser ablation systems hold considerable promise if restenosis (reblocking of the arteries) rates are reduced. The rate as of 1995 is 30%, typically within six months. Mechanical or atherectomy devices to cut, shave, or pulverize plaque have been tested extensively in coronary arteries. Some of these have also been approved for peripheral use. The future of angioplasty, beyond the tremendous success of conventional balloon catheters, depends on approaches that can reduce restenosis rates. For example, if appHcation of a dmg to the lesion site turns out to be the solution to restenosis, balloon catheters would be used for both dilating the vessel and deUvering the dmg. An understanding of what happens to the arterial walls, at the cellular level, when these walls are subjected to the various types of angioplasty may need to come first. 

The process by which porous sintered plaques are filled with active material is called impregnation. The plaques are submerged in an aqueous solution, which is sometimes a hot melt in a compound s own water of hydration, consisting of a suitable nickel or cadmium salt and subjected to a chemical, electrochemical, or thermal process to precipitate nickel hydroxide or cadmium hydroxide. The electrochemical (46) and general (47) methods of impregnating nickel plaques have been reviewed. 

In most cases, the impregnation process is followed by an electrochemical formation where the plaques are assembled into large temporary cells filled with 20—30% sodium hydroxide solution, subjected to 1—3 charge—discharge cycles, and subsequentiy washed and dried. This eliminates nitrates and poorly adherent particles. It also increases the effective surface area of the active materials. 

Furthermore, there is some evidence for pleiotrophic effects (e.g., effects on hemostasis, vascular function, anti-inflammatory effects, and stabilizing effects on atherosclerotic plaques) of statins. The clinical relevance of this (and the potential difference between the various statins) is at present uncertain but subject to intense investigation. 

The identification, using analytical microprobe and solid-state magic-angle nuclear magnetic resonance (NM techniques, of aluminosilicate deposits in the cores of the pathognomic senile plaques in the brains of Alzheimer subjects (Candy et al., 1986) has prompted widespread scientific and public concern, and controversy with regard to the possible aetiological role of environmental aluminium and aluminosilicates in senile dementia (Walton, 1991). 

An important validation of the mice that overexpress human mutant 3APP as a platform for testing therapeutics targeting 3-peptide deposition has been provided by the Elan company, using their PDAPP mouse [146]. Immunization of the mice, either at an early age or after plaques had formed, resulted in clearance of immunoreactive plaques and peptide from the subjects brains. Although the elucidation of the mechanism explaining... 

We test the impact resistance of polymer plaques using the configuration shown in Fig. 8.8. We subject circular injection molded plaques to the shock of a falling weight with a hemispherical impacter. This test is also known as the Dart Drop Test . Samples can fail in a brittle or a ductile manner. Brittle samples often shatter. Ductile samples can split or a small disk may be punched out of their center. This test provides results that are analogous to those obtained from un-notched impact beam testing. 

In addition, the thermoset polymer prepared from 1,1,1 -tris(4-trifluoroviny-loxyphenyl)ethane was cast into plaques according to the procedure outlined in the Section 3.2, and was subjected to thermal, mechanical, and dielectric tests. The results of these tests are listed in Table 3.3. 

Bacterial pigments. Some bacteria commonly found in caries lesions are known to produce pigments. For example, the black staining of plaque is related with Actinomyces (Slots, 1974), but its chemical nature remains unknown. Black pigmented Prevotella produces both iron sulphide and heme pigments (Shah et ah, 1979). In addition, Propionibacterium forms porphyrins (Lee et al., 1978). Bacterial iron-binding peptides, which can contribute to discoloration, increase in the saliva of subjects with a high caries frequency (Nordh, 1969). 

Although chlorhexidine affects virtually all bacteria, gram-positive bacteria are more susceptible than are gram-negative organisms. Furthermore, Streptococcus mutans and Antinomies viscosus seem to be particularly sensitive. S. mutans has been associated with the formation of carious lesions in fissures and on interproximal tooth surfaces and has been identified in large numbers in plaque and saliva samples of subjects with high caries activity. 

In addition, a recent study in which reconstituted HDL was infused into human subjects after acute coronary syndromes showed a significant reduction in plaque volume in the coronary arteries as assessed by intravascular ultrasound (32). 

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