Tissue, human, properties

Phosphofructokinase (PFK) is a key regulatory enzyme of glycolysis that catalyzes the conversion of fructose-6-phosphate to fructose-1,6-diphosphate. The active PFK enzyme is a homo- or heterotetrameric enzyme with a molecular weight of 340,000. Three types of subunits, muscle type (M), liver type (L), and fibroblast (F) or platelet (P) type, exist in human tissues. Human muscle and liver PFKs consist of homotetramers (M4 and L4), whereas red blood cell PFK consists of five tetramers (M4, M3L, M2L2, ML3, and L4). Each isoform is unique with respect to affinity for the substrate fructose-6-phosphate and ATP and modulation by effectors such as citrate, ATP, cAMP, and fructose-2,6-diphosphate. M-type PFK has greater affinity for fructose-6-phosphate than the other isozymes. AMP and fructose-2,6-diphosphate facilitate fructose-6-phosphate binding mainly of L-type PFK, whereas P-type PFK has intermediate properties. 

Doornbos RMP, Lang R, Aalders MC, Cross FW, Sterenborg HJCM. The determination of in vivo human tissue optical properties and absolute chromophore concentrations using spatially resolved steady-state diffuse reflectance spectroscopy. Physics in Medicine and Biology 1999, 44, 967-981. 

Some properties of electromagnetic waves depend on frequency. For example, some wavelengths are visible. Some can penetrate and heat materials, including human tissue. Some properties apply across the spectmm. For example, energy from a radiation source diminishes with the square of the distance from the source. Compared to one unit from a source, the energy level at two units away will be one fourth. 

Vibration motion may apply to the entire human body or to individual parts. The human body is a complex system of organs and tissue masses restrained by other tissue. Each type of tissue has properties that limit or dampen motion from vibration. Some tissues are elastic and have properties similar to springs. Trauma to tissues results when external vibrating forces accelerate the body or a body part and achieve amplitudes that exceed the capabilities of tissues. If the exciting frequency is a natural frequency of a body part, the resulting motion may produce severe damage. Amplitudes less than necessary for trauma can impede performance or be uncomfortable. 

Hydroxyapatite (Hench, 1993), /3-tricalcium phosphate (Wilson, 1993), Bioglass (Hench, 1991) and Glass Ceramics A-W (Yamamuro, 1993 Kokubo, 1991) are typical inorganic materials that can directly bond to bone tissues when embedded in human bodies. They have already been used as bone-substitutes in clinics. Such tissue-bonding property is denoted as bioactivity and is exceptional because it is only found for a limited kind of materials (Ohtsuki, 1991, 1992) and the rest of all materials, i.e., metals, ceramics, and polymers are not bioactive. However, those ceramic materials are far from ideal tissue substitutes since their fracture toughness is lower than that ofhuman cortical bone, and too hard to be applied to soft tissue replacement. Hence, they find a limited range of use. 

Nonlinear ionic channels conductance, 28-8 Nonmineralized human tissues, mechanical properties,... 

Substrate hydrophilicity is required for the adhesion of certain biomaterials, such as living tissues. This property has an important role for human body implants, such as orthopedic prostheses. A typical case in which substrate hydrophobicity is required relates to an ophthalmologic scenario, when the surfaces of an intraocular polymer lens should preferably not adhere to proteins in order to avoid the formation of inflammatory cells. 

Biomine is a dense, dark red, mobile liquid tkat vaporizes readily at room temperature to give a ted vapor that is highly corrosive to many materials and human tissues. Bromine hquid and vapor, up to about 600°C, ate diatomic (Bt2). Table 1 summarizes the physical properties of bromine. 

Fluoroplastic FPs have superior heat and chemical resistance, excellent electrical properties, but only moderate strength. Variations include PTFE, FEP, PFA, CTFE, ECTFE, ETFE, and PVDF. Used for bearings, valves, pumps handling concentrated corrosive chemicals, skillet linings, and as a film over textile webs for inflatables such as pneumatic sheds. Excellent human-tissue compatibility allows its use for medical implants. 

CYP2J2 is abundant in cardiovascular tissue and active in the metabolism of arachidonic acid to eicosanoids that possess potent anti-inflammatory, vaso-dilatory, and fibrinolytic properties. Polymorphic alleles with reduced function are known. Some other CYP2 subfamilies and isozymes listed in Table 1 are still not well characterized, in part because most of them were discovered in the course of the human genome project. 

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