Biphasic response

Anderson et al., 1998 OVX, lactating rats low calcium diet genistein-rich protein source 3 doses isoflavones (0.5, 1.6, 5.0 mg/d) for 2 weeks A biphasic response to genistein was observed for bone weight (femur ash) low dose more protective than high dose... 

Transfer of the aquatic animals, after absorption of the cyclodiene, to insecticide-free water showed variations in elimination pattern related with the chemical as well as its concentration in the body. It follows a somewhat biphasic response, there is initial rapid elimination of high concentration followed by a slow elimination at lower body concentrations (Fig. 3)(21,22, 23). Xenopus, even at low body levels of cis-chlordane, eliminate it at slightly faster rate than fish. Photo-cis-chlordane seems to be eliminated at a faster rate than cis-chlordane by both goldfish and bluegill (Table 2). The elimination of photo-cis-chlordane by goldfish and bluegill and of photodieldrin by blue-gill shows a biphasic response (Fig. 3). 

Maitotoxin effects were investigated also by in )iXA,0 experiments. Miyahara oX dt (31) reported a biphasic response in the guinea-pig atria, an initial positive response followed by a progressive decrease of both the rate and the force of contractions. 

Cornel JH, Bax JJ, Elhendy A, Maat AP, Kimman GJ, Geleijnse ML et al. Biphasic response to dobutamine predicts improvement of global left ventricular function after surgical revascularization in patients with stable coronary artery disease imphcations of time course of recovery on diagnostic accuracy. J Am Coll Cardiol 1998 31 1002-1010... 

Some flavonoids (baicalein, myricetin, quercetagenin and scutellarein) under certain conditions may exert vasoconstrictor rather than vasodilator effects [122]. As described above, myricetin has been shown to exhibit a biphasic response in pre-contracted rat thoracic aorta. At low... 

Shen ES, Guengerich FP, Olson JR. 1989. Biphasic response for hepatic microsomal enzyme induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin in C57BL/6J and DBA/2J mice. Biochem Pharmacol... 

Hematological Effects. Both human and animal studies have shown that benzene exerts toxic effects on various parts of the hematological system. All the major types of blood cells are susceptible (erythrocytes, leukocytes, and platelets). In the less severe cases of toxicity, specific deficiencies occur in individual types of blood elements. A more severe effect occurs when there is hypoplasia of the bone marrow, or hypercellular marrow exhibiting ineffective hematopoiesis so that all types of blood cells are found in reduced numbers. This is known as pancytopenia. A biphasic response (i.e., a hyperplastic effect in addition to destruction of the bone marrow cells) has been observed (Aksoy et al. 1972, 1974 Doskin... 

Durrani and co-workers [122] reported on the influence of a carbopol coating on the corneal retention of pilocarpine-loaded liposomes, and demonstrated a biphasic response with an initial low intensity followed by a sustained reaction. 

In addition, SchistoFLRFamide had an effect upon the locust extensor-tibiae muscle preparation (somatic muscle). Low concentrations (.01 nM-10 nM) produced a potentiation of the amplitude of slow motor neuron induced twitch tension while higher concentrations (100 nM-1000 nM) produced a variable biphasic response with an amplitude of contraction decrease followed by an increase (25). 

Figure 4.4. Changes in membrane permeability induced by maitotoxin in bovine aortic endothelial cells. Ethidium (EB) uptake shows a biphasic response where the second phase corresponds with LDH release, indicative of cell lysis. Reproduced with permission from Estacion and Schilling 2001, BioMed Central.

Cat platelets readily aggregate in response to ADP, collagen, thrombin, serotonin, and arachadonic acid, and frequently exhibit a biphasic response (Meyers 1986). A biphasic response to ADP is consistently seen. Cat platelets generate relatively large amounts of thromboxane Bj when exposed to arachidonic acid and consistently aggregate irreversibly (Meyers et al. 1981). Arachidonic acid-induced aggregation appears to be independent of dense granule secretion. 

While it might he sjttculated that a similar biphasic ctlcct on metabolism could occur whenever a lipophilic xenobiotic capable of forming a stable inhibitory complex is administered, lew cases have been well documented. Even in the case of MDP interactions, the isoform spec if icily of cither inhibition or induction has not been well defined. Since both detoxification and activation of chemicals are. to a greater or lesser extent, isoform-sped lie, more recent studies have focused on clarifying which iso forms of P450 arc involved and the importance of these isoforms in the biphasic response (Lewandow ski ei a .. 

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