Arterial tissues composition

Table B6.7 Variation of Normal Human Arterial Tissue Composition with Age ...

Dayton, S., Hashimoto, S., and Pearce, M. L. (1965). Influence of a diet high in unsaturated fat upon composition of arterial tissue and atheromata in man. Circulation 32, 911-924. 

The composition of normal human arterial tissues is altered with age in many aspects. Table B6.7 lists the observed changes in human aorta, pulmonary and femoral arteries [20]. There is a tendency that both the dry matter and nitrogen content of arterial tissues decreases with age. However, the relative quantity of collagen [22] and elastin [23, 24] in the arterial wall remains almost unchanged with age. Below the age of 39, the wall of human thoracic aorta has 32.1 5.5% elastin, between the age 40-69, the wall contains 34.4 9.3%, and from 70-89, the elastin content is 36.5 10.1 [24]. 

The initial work in this field consisted of in vitro work carried out on human vessels. Early work centred on fluorescence spectroscopy. Bartorelli and coworkers (1991) and Richards-Kortum and colleagues (1989) studied the use of spectra in the ultraviolet (UV) light region on diseased arterial tissue." " They independently demonstrated the ability of this technique to distinguish between atheromatous and normal tissue. However, recent work has centred on the use of Raman as this has an ability to distinguish different chemical compositions." Raman spectra are unique to compounds (which produce fingerprints as stated above) whereas fluorescence spectra are limited in their differences. 

Raman spectroscopy, particularly near-infrared FT-Raman has been applied to in vitro studies of human breast, gynecological and arterial tissues. The advantage of Raman spectroscopy is that it provides detailed information (with sharp vibrational transitions) relating to molecular structure and composition and, thus, can be used as a detailed signature associated with abnormality. The use of inlxared excitation for Raman is advantageous as it reduces the probability of interference (background) from autofluorescence and provides deeper penetration in a tissue. 

Cox, R.H., (1978) Passive mechanics and connective tissue composition of canine arteries. American Journal of Physiology 234 (5) H533-H541... 

The first elastomeric protein is elastin, this structural protein is one of the main components of the extracellular matrix, which provides stmctural integrity to the tissues and organs of the body. This highly crosslinked and therefore insoluble protein is the essential element of elastic fibers, which induce elasticity to tissue of lung, skin, and arteries. In these fibers, elastin forms the internal core, which is interspersed with microfibrils [1,2]. Not only this biopolymer but also its precursor material, tropoelastin, have inspired materials scientists for many years. The most interesting characteristic of the precursor is its ability to self-assemble under physiological conditions, thereby demonstrating a lower critical solution temperature (LCST) behavior. This specific property has led to the development of a new class of synthetic polypeptides that mimic elastin in its composition and are therefore also known as elastin-like polypeptides (ELPs). 

In the preceding two examples, Raman spectra were obtained from tissues and cell samples ex vivo. Recently, Buschman et al. (46) were able to measure Raman spectra of sheep arterial walls in vivo using a miniature fiberoptic probe. They have demonstrated that the in vivo intravascular Raman signal obtained directly from a blood vessel is a simple summation of signals from the blood vessel wall and blood itself. This technique may be useful in predicting the risk of arterial plaque rapture and determining plaque composition in human arteries. 

DESI, in contrast, and despite being a relatively new technique, has already delivered encouraging results in oncological research of lipids in the past few years. In a couple of sample-rich studies, lipid profiles were found to distinguish between diseased and healthy tissues from a variety of different cancers such as human prostate, colorectal, renal cell, bladder, and testis tumors (72-76). Moreover, Eberlin and coworkers reported the use of DESI lipid profiles for the determination of type, grade, and cell concentration in human brain tumors (77,78). DESI has not only been used in an oncological context. It was also used to image the lipid composition of arterial plaques (79). 

The formulation of parenteral products involves careful consideration of the proposed route of administration and the volume of the injection. Injections are administered to the body by many routes into various layers of the skin, the subcutaneous and muscle tissue, into arteries or veins, into or around the spinal cord, or directly into various organs (e.g., the heart or the eye). The volume to be injected can range from microliters, typically diagnostic agents administered intradermally or insulin administered subcutaneously, to several liters administered intravenously as infusions. The route of administration and the volume to be injected affect the composition of the formulation. 

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