Blood vessel injury was found to release intracellular pools of protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT) into the extracellular milieu, where it became trapped. Trapped PIMT was able to utilize radiolabeled S-adenosyl-L-methionine (AdoMet) introduced into the circulation to methylate blood vessel proteins containing altered aspartyl residues specifically at the site of injury. In vitro studies more fully characterized this endogenous PIMT activity in thoracic aorta and inferior vena cava. At least 50% of the PIMT activity released during injury, was resistant to non-ionic detergent extraction, suggesting that the enzyme activity can become trapped within or behind the extracellular matrix (ECM). Analysis of inferior vena cava, found that 90% of the altered aspartyl residues in blood vessels are inaccessible to methylation by intracellular PIMT under physiological conditions. Subfractionation of inferior vena cava on the basis of solubility found that at least 40% of the altered aspartyl containing proteins in blood vessels are insoluble in non-ionic detergent containing buffers and are highly resistant to extraction by protein denaturants. Analysis of peptides revealed that the majority of the altered aspartyl groups in blood vessels are located extracellularly. Digestion of these extracellular matrix proteins with cyanogen bromide (CNBr), followed by methylation with (PIMT), found that about 60% of the altered aspartyl residues in the ECM are solubilized by this treatment. The presence of hydroxyproline in amino acid hydrosolates of this fraction and acidic pH gel electrophoresis of methylated peptides, allowed the identification of collagen as the major PIMT substrate in the CNBr-soluble material. CNBr peptides derived from both type I and type III collagen were found to methylated. It is estimated that one centimeter of blood vessel contains on the order of 5 x 10����� altered aspartyl residues involving 1% to 5% of the total extracellular protein. / Graduation date: 1997

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 73-90). Also available in print.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Gabor Forgacs. Vita. Includes bibliographical references.

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Pharmacology and Pharmacy / Doctoral / Doctor of Philosophy

published_or_final_version / Surgery / Master / Master of Surgery

published_or_final_version / abstract / toc / Pharmacology / Master / Master of Philosophy

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

The arterioles of the cat sartorius muscle dilate when arterial pressure is reduced. It has been suggested that this dilation is due to a decrease in blood flow which in turn decreases oxygen delivery and increases tissue production of vasodilator substances. The latter diffuse into the vicinity of the arterioles and cause vascular relaxation. This vascular dilation acts to maintain blood flow through the tissue near the control level at a time when perfusion pressure is reduced. This phenomenon, called autoregulation of blood flow, has been observed in most organs of the body. In the following experiments, we attempted to test the hypothesis that a fall in the oxygen level of the tissue is responsible for blood flow autoregulation. We did this by studying the response of cat sartorius arterioles to arterial pressure reduction under conditions where the muscle was supplied with oxygen from the environment in addition to that normally supplied by the blood. Tissue PO₂ was altered by placing the isolated, auto-perfused cat sartorius muscle in contact with silicone fluid equilibrated with a 0% to 20% oxygen gas mixture. As oxygen tension in the bathing fluid was increased, the preponderant response was a decrease in arteriolar diameter, blood velocity and arteriolar volume flow. To illustrate, 8% of the arterioles constricted by an average of 10% and 18% when the muscle was exposed to oxygen tensions of 66 and 132 mmHg, respectively. When blood flow autoregulation was investigated, it was found that elevated oxygen tension in the bathing fluid abolished any significant arteriolar dilation or flow autoregulation in the majority of arterioles studied. In addition, the elevated oxygen environment caused complete cessation of blood flow in many of the smaller arterioles (< 15μ in diameter). The results of this study strongly suggest that the O₂ level of the tissue is an important determinant in local blood flow regulation.

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