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Kihara, H. (1981). Comparison of the redox reactions of various types of cytochrome c with iron hexacyanides. Biochimica et Biophysica Acta (BBA) – Bioenergetics, 634, 93–104.
Abstract: The dynamic behavior of various types of cytochromes c in the redox reaction with iron hexacyanides was studied using a temperature-jump method in order to elucidate the molecular mechanism of the redox reaction of cytochromes with their oxidoreductants. Transmittance after the temperature jump changed through a single exponential decay for all cytochromes investigated. Under a constant concentration of anion, the redox reaction of various types of cytochrome c with iron hexacyanides was analyzed according to the scheme: Ki=kt/k-i (i=1,2,3) where C(III) and C(II) are ferric and ferrous cytochromes, respectively, Fe(III) and Fe(II) are ferri- and ferrocyanides, respectively, C(III) [middle dot] Fe(II) is the ferricytochrome-ferrocyanide complex and C(II) [middle dot] Fe(III) is the ferrocytochrome-ferricyanide complex. When step B is slower than the other two steps A and C, τ-1 can be represented approximately as where the bar over the variables denotes the equilibrium value. In a large excess of ferrocyanide against cytochrome, we can estimate k2, k-2, K1 and K3 independently. In the case of horse cytochrome c at 18[degree sign]C in 0.1 M phosphate buffer at pH 7 with 0.3 M KNO3, the estimated parameters are k2 = 100 +/- 50 s-1, k-2 = (3.5 +/- 1.0) [middle dot] 103 s-1, K1 = 15 +/- 7 M-1 and K3 = (8.5 +/- 1.5) [middle dot] 10-4 M. From the same experiments for seven cytochromes (cytochrome c from horse, tuna, Candida krusei, Saccharomyces oviformis, Rhodospirillum rubrum cytochrome c2, Spirulina platensis cytochrome c-554 and Thermus thermophilus cytochrome c-552), the following results can be deduced. (1) Each parameter defined in the scheme above (k2, k-2, K1, K3) diverged beyond the error range. Above all, k2 values of cytochromes c-554 and c-552 are as large as 1 [middle dot] 104 s-1 and much larger than those for the other cytochromes (to 50 approx. 700 S-1). (2) The variance of k2K1 and k-2/K3 are relatively less than the variances of individual parameters (k2, k-2, K1 and K3), which suggests that the values of k2K1 and k-2/K3 have been conserved during the course of evolution.
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Kordal, R. J., & Parsons, S. M. (1979). Liver alcohol dehydrogenase subunit equivalence studied by rapid sampling of alcohol product formed from sequentially bound [4α-3H]NADH. Archives of Biochemistry and Biophysics, 194(2), 439–448.
Abstract: Horse liver alcohol dehydrogenase has been claimed to exhibit presteady-state “half-of-the-sites” reactivity with aromatic substrates under some circumstances. To clarify the role of half-of-the-sites reactivity in liver alcohol dehydrogenase the direct sampling of the alcohol product formed immediately after initiation of the reaction was studied using a rapid sampling device and [4α-3H]NADH. Liver alcohol dehydrogenase which contained a very low mole-ratio of [4α-3H]NADH bound to one subunit of the dimer was rapidly mixed with excess 4-(2'-imidazolylazo)benzaldehyde substrate and nonradioactive NADH to initiate the reaction, which was allowed to proceed for a short time before it was quenched. If strong HClO4 quench was used isolation of total free and bound azoalcohol product was possible. If NaOH quench was used isolation only of the azoalcohol product released by the enzyme was possible since most enzyme-bound azoalcohol was reversed back to azoaldehyde by the base. The pH-jump reversal reaction also was characterized spectroscopically by stopped flow technique. Nearly fullsites reactivity was observed for reaction in either direction. Furthermore (4α-3H]NADH bound firstly to one subunit in the dimer reacted essentially identically to NADH bound secondly to the other subunit. Thus, half-of-the-sites reactivity was not observed in these experiments nor did they give any indication of liver alcohol dehydrogenase active site nonequivalence induced by coenzyme binding or reaction.
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Wood, F. E., & Cusanovich, M. A. (1975). The reaction of Euglena gracilis cytochrome c-552 with nonphysiological oxidants and reductants. Archives of Biochemistry and Biophysics, 168(2), 333–342.
Abstract: The reaction of Euglena gracilis cytochrome c-552 (cytochrome f) with the nonphysiological reactants potassium ferrocyanide, potassium ferricyanide, sodium ascorbate, sodium dithionite, and Chromatium vinosum high potential nonheme iron protein was studied by stopped-flow and temperature-jump kinetic methods. The reaction of the purified, water-soluble protein with the reactants was investigated as a function of ionic strength, pH, and temperature. The results demonstrated that reduction and oxidation takes place at a negatively charged site on the cytochrome c-552 surface. Participation of specific amino acid residues in electron transfer is implicated from the pH results. The results obtained for the nonphysiological reactions of cytochrome c-552 are compared with available data for horse heart cytochrome c and Rhodospirillum rubrum cytochrome c2. The results strongly suggest that Euglena gracilis cytochrome c-552 undergoes nonphysiological oxidation and reduction by a mechanism different from that found for cytochrome c or cytochrome c2.
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Mizuguchi, M., Arai, M., Ke, Y., Nitta, K., & Kuwajima, K. (1998). Equilibrium and kinetics of the folding of equine lysozyme studied by circular dichroism spectroscopy. Journal of Molecular Biology, 283(1), 265–277.
Abstract: The equilibrium unfolding and the kinetics of unfolding and refolding of equine lysozyme, a Ca2+-binding protein, were studied by means of circular dichroism spectra in the far and near-ultraviolet regions. The transition curves of the guanidine hydrochloride-induced unfolding measured at 230 nm and 292.5 nm, and for the apo and holo forms of the protein have shown that the unfolding is well represented by a three-state mechanism in which the molten globule state is populated as a stable intermediate. The molten globule state of this protein is more stable and more native-like than that of α-lactalbumin, a homologous protein of equine lysozyme. The kinetic unfolding and refolding of the protein were induced by concentration jumps of the denaturant and measured by stopped-flow circular dichroism. The observed unfolding and refolding curves both agreed well with a single-exponential function. However, in the kinetic refolding reactions below 3 M guanidine hydrochloride, a burst-phase change in the circular dichroism was present, and the burst-phase intermediate in the kinetic refolding is shown to be identical with the molten globule state observed in the equilibrium unfolding. Under a strongly native condition, virtually all the molecules of equine lysozyme transform the structure from the unfolded state into the molten globule, and the subsequent refolding takes place from the molten globule state. The transition state of folding, which may exist between the molten globule and the native states, was characterized by investigating the guanidine hydrochloride concentration-dependence of the rate constants of refolding and unfolding. More than 80% of the hydrophobic surface of the protein is buried in the transition state, so that it is much closer to the native state than to the molten globule in which only 36% of the surface is buried in the interior of the molecule. It is concluded that all the present results are best explained by a sequential model of protein folding, in which the molten globule state is an obligatory folding intermediate on the pathway of folding.
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Buechner-Maxwell, V. A., Elvinger, F., Thatcher, C. D., Murray, M. J., White, N. A., & Rooney, D. K. (2003). Physiological Response of Normal Adult Horses to a Low-Residue Liquid Diet. Journal of Equine Veterinary Science, 23(7), 310–317.
Abstract: Abstract The anorexic or dysphagic adult horse often requires nutritional support. Providing nutrients by the enteral route is the safest and most economic choice, but the dietary options available for use in horses are somewhat limited. The objective of this study was to compare the physiologic response of normal horses with a low-residue liquid or normal diet over a 10-day feeding period. Two groups of 6 normal adult horses were maintained on 1 of 2 diets for a 10-day period. Diets were formulated to meet the caloric needs of a horse maintained in a stall. The control group was fed 70% timothy hay and 30% textured concentrate for the test period, and the experimental group received the low-residue liquid diet, similar to liquid nutritional formulas designed for human use. Clinical parameters, body weight, packed cell volume, total plasma solids, blood glucose, and serum electrolytes were recorded daily for each horse during the dietary trial period. On days 1, 5, and 10 of the study, a complete blood count, serum biochemical profile, and urinalysis were performed. Horses' serum total bilirubin concentration and pattern of weight loss differed between groups. All other physical parameters, blood chemistry, complete blood count, and urinalysis results remained within the normal reference interval for the horses regardless of diet, although some statistical differences were observed. Horses returned to pasture and free-choice grass diet without complications at the end of the dietary trial period. These results demonstrate that few differences of biologic significance were observed between horses being fed low-residue diet and horses receiving a normal diet of hay and grain over a 10-day period. (Equine Vet J 2003;23:310-317)
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Casey, R. (2002). Clinical Problems Associated with the Intensive Management of Performance Horses. In The Welfare of Horses (pp. 19–44).
Abstract: The physical as well as the behavioural requirements of the horse changed little through the process of domestication. This means that horses kept within an intensively housed environment and used for performance, physically and behaviourally are susceptible to specific clinical conditions, injuries and diseases. In this chapter, physiological and clinical problems such as those causing pain related behaviours and head shaking are discussed. The most commonly associated problems with horses kept in intensive housing conditions or used in specific competitive disciplines are highlighted. Despite the increasing amount of information about injury and disease in the horse, there is little research relating such problems to the situations performance horses have to cope with. This is particularly the case with pain, whose recognition of pain amongst professionals is still variable and often subjective and not widely recognised as a cause of behavioural change.
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Davidson, N., & Harris, P. (2002). Nutrition and Welfare. In The Welfare of Horses (pp. 45–76).
Abstract: The horse is a social species living in herds and spending the majority of its time roaming and foraging in a diverse and seasonally-varying environment. As a non-ruminant herbivore it is well suited to a high fibre, low starch diet. Domestication has resulted in a number of benefits to the horse, reflected in its continued prevalence and apparently increased life expectancy, but it has not been without its price. Especially in developed countries, horses kept for leisure purposes (which includes all competition and racing horses) are often confined, possibly away from conspecifics, within a stable for a large proportion of the day. Due to increased energy requirements many horses now receive one to two large meals a day, consisting of feedstuffs with a low water content and often a radically different nutritional profile from the diet that they would be able or would choose to select in the wild. These modern practices have benefits but also potential disadvantages to the horse both nutritionally and behaviourally which may have an impact on welfare. This chapter highlights areas where dietary imbalances or inappropriate feeding practices may potentially have an adverse effect on welfare and gives suggestions on how these may be ameliorated.
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Mills, D., & Clarke, A. (2002). Housing, Management and Welfare. In The Welfare of Horses (pp. 77–97).
Abstract: Horses tend to be housed in loose boxes, stalls, barns and shelters for ease of management, however these systems present several possible threats to equine health and welfare. These systems are reviewed together with the concerns they raise. A common system for the evaluation of the welfare of contained animals focuses on the provision of five freedoms. These are freedom from hunger, thirst and malnutrition, from discomfort, from pain, injury and disease, from fear and distress and to express most normal patterns of behaviour. This approach is used to assess the ways in which horse welfare may be compromised by certain housing practices and management regimes. Recommendations as to how these problems can be resolved and to promote good practice are provided.
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Cooper, J., & McGreevy, P. (2002). Stereotypic Behaviour in the Stabled Horse: Causes, Effects and Prevention without Compromising Horse Welfare. In The Welfare of Horses (pp. 99–124).
Abstract: Apparently functionless, repetitive behaviour in horses, such as weaving or crib-biting has been difficult to explain for behavioural scientists, horse owners and veterinarians alike. Traditionally activities such as these have been classed amongst the broad descriptor of undesirable stable vices and treatment has centred on prevention of the behaviours per se rather than addressing their underlying causes. In contrast, welfare scientists have described such activities as apparently abnormal stereotypics, claiming they are indicative of poor welfare, citing negative emotions such as boredom, frustration or aversion in the stable environment and even suggesting prevention of the activities alone can lead to increased distress. Our understanding of equine stereotypics has advanced significantly in recent years with epidemiological, developmental and experimental studies identifying those factors closely associated with the performance of stereotypics in stabled horses. These have allowed the development of new treatments based on removing the causal factors, improving the horses“ social and nutritional environment, re-training of horses and their owners and redirection of the activities to less harmful forms. Repetitive activities conventionally seen as undesirable responses to the stable environment, their causal basis and the effectiveness of different approaches to treatment are discussed, both in terms of reducing the behaviour and improving the horse”s quality of life.
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Waran, N., McGreevy, P., & Casey, R. (2002). Training Methods and Horse Welfare. In The Welfare of Horses (pp. 151–180).
Abstract: Many aspects of horse care and handling are based upon convenience and traditional practices. Many of these methods of management and practice do not take into account the natural behaviour of horses. This is despite the belief that although domestic horses are probably more docile, stronger, faster growing and faster moving than their ancestors, they are unlikely to have lost any natural behaviours. The performance or sport horse is expected to perform a wide variety of movements and tasks, some of which are unnatural or exaggerated and most of which must be learned. The term “training” is commonly used to describe the processes whereby the human handler introduces the horse to new situations and associations. Performance horses are often required to tolerate stimuli that are innately aversive or threatening, such as having a person on their backs. They are also trained to respond to a stimulus with often unnatural or over-emphasised behaviour, such as some of the dressage movements. Effective and humane training requires an understanding of the processes underlying behaviour. These include knowledge of behaviour under natural conditions, learning processes, the influence of early experience and motivational forces. Horses differ from the other main companion animal species, namely cats and dogs, in that they are a prey species. They most commonly flee from dangerous and painful situations. Horses readily learn to avoid potentially threatening situations and if their attempts to avoid associated stimuli are prevented, they will often exhibit problem behaviours. In this chapter the history of horse training, the application of learning theory and a knowledge of equine behaviour to training, and innovative training methods are all considered.
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