Kinetics, human

Rigid bones are needed for kinetic motion, support of internal organs, and muscle strength. The bones that compose the human thigh are pound for pound stronger than steel. Nature meets these needs by separating the skeleton into several bones and bone systems, creating joints where the bones intersect. 

Humans can not know the ultimate and detailed true reaction mechanism of any reaaJon, or the kinetics that can be derived from it.. Bodenstein (1906) studied the mechanism of the H2 + Br2 = 2 HBr reaction and after several decades of work and dozens of publications wrote the final paper on the subject. Within a few years one of his students published a correction to Bodenstein s explanations. 

Sissons, C. H., Cutress, T. W., and Pearce, E. I. F. (1985). Kinetics and product stoichiometry of ureolysis by human salivary bacteria and artificial mouth plaques. Arch. Oral Biol. 30, 781-790. 

Hyland, L., et al., 1991. Human immunodeficiency viru.s-1 protea.se 1 Initial velocity. studies and kinetic characterization of reacdon intermediates by Isotope exchange. Biochemistry 30 8441-8453. 

Historically humans have used three natural sources of kinetic energy wind, water, and tides. 

Although early humans often inadvertently tapped into the kinetic energy of moving air or water to do things such as separate grain from chaff or float downstream, the deliberate use of kinetic energy to power machinery came only in the historical era. 

The electrons of atoms in their ground state are in perpetual motion. Also, in a gas, each atom has an average kinetic energy (motion) depending on the temperature of the gas. These motions don t count ei th er because humans demand something on their own scale that they can see or take advantage of before they consider it as true perpetual motion. 

Now it is realized that there are developing constraints on the utilizable sources of fuel and energy that feed the entire kinetic complex of human society. The prospect of the primary rate constants becoming limiting, diminishing, or even vanishing, places the associated problems high on the... 

Might we assume then that the search for relevance is a search for ways to be reoriented toward the higher or highest evolutionary priorities Even discarding the (controversial) need for growth in humanity s kinetic machinery, there is a clear need for effort to just sustain the feeder reactions and to control the undesirable end products from the total system. The catalytic scientist surely feels that he must already be—and is—a key participant in that very play (or drama) of human survival or evolution. 

So the question should never be (nor has it ever been) one of choosing between all catalytic chemists studying ortho-para hydrogen conversion, molecular orbitals and the like, or all catalytic chemists studying fuel synthesis and exhaust catalysts a healthy society is a judiciously balanced society, and the concern for relevance is one for a shift toward greater dedication in the direction of the most vital needs for the survival and health of the kinetic system of human society. 

Why Do We Need to Know Ihis Material Chemical kinetics provides us with tools that we can use to study the rates of chemical reactions on both the macroscopic and the atomic levels. At the atomic level, chemical kinetics is a source of insight into the nature and mechanisms of chemical reactions. At the macroscopic level, information from chemical kinetics allows us to model complex systems, such as the processes taking place in the human body and the atmosphere. The development of catalysts, which are substances that speed up chemical reactions, is a branch of chemical kinetics crucial to the chemical industry, to the solution of major problems such as world hunger, and to the development of new fuels. 

Figure 2. Force generation and energy metabolism in human quadriceps femoris muscle stimulated intermittently at 20 Hz, with 1.6 sec tetani with 1.6 sec rest periods between tetani. The upper panel shows force, ATP turnover rate, and pH the middle panel, the concentrations of PCr, P and lactate and the lower panel, ATP, ADP, IMP, H, and calculated H2PO4. From Hultman et al. (1990), with permission from Human Kinetics Publishers.

Figure 5. The relationships between force generation and calculated concentration of H2PO4 (closed circles) and between force and lactate content (open circles) in the stimulated muscle presented in Figure 2. Corresponding relationships are also presented for the muscle during a 3 min recovery period (small closed and open circles). In the recovery period, the muscle was stimulated at 20 Hz for 1.6 sec at 30 sec and at one, two, and three min after the fatiguing contraction. From Hultman et al. (1990), with permission from Human Kinetics Publishers.

Faulkner, J.A., Claflin, D.R., McCully, K.K. (1986). Power output offast and slow fibers from human skeletal muscles. In Human Muscle Power (Jones, N. L., McCartney, N., McComas, A.J., eds.), pp. 81-94, Human Kinetics, Champaign, IL. 

While these calculations provide information about the ultimate equilibrium conditions, redox reactions are often slow on human time scales, and sometimes even on geological time scales. Furthermore, the reactions in natural systems are complex and may be catalyzed or inhibited by the solids or trace constituents present. There is a dearth of information on the kinetics of redox reactions in such systems, but it is clear that many chemical species commonly found in environmental samples would not be present if equilibrium were attained. Furthermore, the conditions at equilibrium depend on the concentration of other species in the system, many of which are difficult or impossible to determine analytically. Morgan and Stone (1985) reviewed the kinetics of many environmentally important reactions and pointed out that determination of whether an equilibrium model is appropriate in a given situation depends on the relative time constants of the chemical reactions of interest and the physical processes governing the movement of material through the system. This point is discussed in some detail in Section 15.3.8. In the absence of detailed information with which to evaluate these time constants, chemical analysis for metals in each of their oxidation states, rather than equilibrium calculations, must be conducted to evaluate the current state of a system and the biological or geochemical importance of the metals it contains. 

COMPARATIVE KINETICS AND METABOLISM IN LABORATORY ANIMALS AND HUMANS... 

There are no data on kinetics or metabolism in humans therefore, no conclusions can be drawn as to the relevance of animal data to human metabolism of these compormds. 

Absorption, Distribution, Metabolism, and Excretion. Evidence of absorption comes from the occurrence of toxic effects following exposure to methyl parathion by all three routes (Fazekas 1971 Miyamoto et al. 1963b Nemec et al. 1968 Skiimer and Kilgore 1982b). These data indicate that the compound is absorbed by both humans and animals. No information is available to assess the relative rates and extent of absorption following inhalation and dermal exposure in humans or inhalation in animals. A dermal study in rats indicates that methyl parathion is rapidly absorbed through the skin (Abu-Qare et al. 2000). Additional data further indicate that methyl parathion is absorbed extensively and rapidly in humans and animals via oral and dermal routes of exposure (Braeckman et al. 1983 Flollingworth et al. 1967 Ware et al. 1973). However, additional toxicokinetic studies are needed to elucidate or further examine the efficiency and kinetics of absorption by all three exposure routes. 

Margosiak SA, Vanderpool DL, Sisson W, Pinko C, Kan CC (1996) Dimerization of the human cytomegalovirus protease kinetic and biochemical characterization of the catalytic homodimer. Biochemistry 35 5300-5307... 

Platt EJ, Dumin IP, Rabat D (2005) Kinetic factors control efficiencies of cell entry, efficacies of entry inhibitors, and mechanisms of adaptation of human immunodeficiency virus, J Virol 79 4347 356... 

In summary, genotoxicity studies of endosulfan have provided evidence that this compound is mutagenic and clastogenic, and that it induces effects on cell cycle kinetics in two different mammalian species. However, some of these data may be suspect because some formulations of endosulfan have contained epichlorohydrin, a known genotoxic chemical, as a stabilizer (Hoechst 1990). It should be noted that humans may also be exposed to epichlorohydrin along with endosulfan. 

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