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Physics of Radiation Biology
Published in Kedar N. Prasad, Handbook of RADIOBIOLOGY, 2020
The effective half-life includes both the physical half-life and the biological half-life (time to reduce the radioactivity in the body or in the organ to one half)
Tin and the Lymphatic System
Published in Nate F. Cardarelli, Tin as a Vital Nutrient:, 2019
It should be emphasized that the above experiments used oral dosing, which is an exceptional route. Almost all the published reports describe experiments using other modes of administration, mainly, i.v., i.m., or i.p. injection. Injected tin has an affinity for tumors25 and retards their growth.38 Biological half-life is somewhat longer,39 and accumulation is noted in the liver, at least with inorganic tin.40 Many organs show little or no tin content when administration is s.c.41 Very high blood tin levels are noted 24 hr after i.v. administration.42
Overview of the Basic Concepts of Radiation Protection
Published in Gaetano Licitra, Giovanni d'Amore, Mauro Magnoni, Physical Agents in the Environment and Workplace, 2018
If the physical half-life is much smaller than the biological half-life (for example, a short-lived radiopharmaceutical), the physical half-life predominates and the radioactive material will disappear into its daughter product (radioactive or not) faster than being excreted from the body; similarly, if the biological half-life is much smaller and predominates over the radioactive decay (for example, a long-lived alpha emitter), the total half-life will be very close to the biological clearance half-life, and the material will be cleared from the body faster than its radioactive decay.
Vitamin D: sources, physiological role, biokinetics, deficiency, therapeutic use, toxicity, and overview of analytical methods for detection of vitamin D and its metabolites
Published in Critical Reviews in Clinical Laboratory Sciences, 2022
Jiří Janoušek, Veronika Pilařová, Kateřina Macáková, Anderson Nomura, Jéssica Veiga-Matos, Diana Dias da Silva, Fernando Remião, Luciano Saso, Kateřina Malá-Ládová, Josef Malý, Lucie Nováková, Přemysl Mladěnka
Interestingly, most of the vitamin D, either taken orally or synthesized in the skin, fails to become 25(OH)D. Animal data showed that three-quarters of the vitamin D dose taken orally is not used for 25(OH)D synthesis [96]. A small fraction of unmetabolized vitamin D is stored in adipose tissue and muscles. Less than 5% of vitamin D synthesized in the skin was subsequently found in fat tissue in shaven mice, and the biggest portion of vitamin D entering circulation appeared to be excreted into the bile [97]. The half-life of unmetabolized vitamin D in circulation is 2 days [28]. However, in healthy individuals, the biological half-life is much longer. Even with no supply, vitamin D3 can be continuously released from storage tissues for a period of 2–3 months [98]. A plasma half-life of 25(OH)D is about 2 weeks [99]. But again, the biological half-life is much longer due to synthesis from vitamin D3 stored in the body. The biological half-life of the active form, calcitriol, is 12 h [28].
Toxicokinetics and Biliary Excretion of N-Nitrosodiethylamine in Rat Supplemented with Low and High Dietary Proteins
Published in Journal of Dietary Supplements, 2019
S. E. Kuyooro, J. K. Akintunde, F. C. Okekearu, E. N. Maduagwu
The elimination rate constant (K) and half-life (t1/2) of NDEA and nitrite in rat bile after a single (i.p.) dose of 43 µg NDEA/kg body weight are presented in Table 2. The corresponding values for the biological half-lives were 8.19 and 5.3 minutes, and the elimination rate constants were 1.41 x 10−3 sec−1 and 2.16 x 10−3 sec−1 for low-protein diet and high-protein diet, respectively. However, the group of animals supplemented with high dietary protein showed a higher elimination rate of nitrite and NDEA in a short period when compared with the low diatary protein groups. Similarly, the elimination profile (Table 3) showed biphasic kinetics of NDEA in rat bile after a combined single (i.p.) dose of 43 µg NDEA and AFB1. The corresponding values for the biological half-lives were 9.17 and 3.6 minutes, and the elimination rate constants were 1.26 x 10−3 sec−1 and 3.15 x 10−3 sec−1 for low-protein diet and high-protein diet, respectively. It was indicated that in presence of AFB1, the rats fed with low-protein diets excreted a higher amount of unchanged NDEA in the bile than the high-protein diet groups (Table 3); the experimental rats fed with high-protein diet showed high elimination rate constant of NDEA within a shorter time than the low diatary protein group (Table 3).
Surgical Management of Haemophilic Pseudotumors: Experience in a Developing Country
Published in Journal of Investigative Surgery, 2019
Yu He, Xi Zhou, Haomin Cui, Guixing Qiu, Xisheng Weng, Baozhong Zhang, Yong Liu
Without inhibitor, a pharmacokinetic evaluation was performed to determine the suitable requirements for perioperative factor replacement, and to achieve therapeutic effect partly. Before evaluation, factors were not administered for at least 48 hr. We suggested that an initial factor infusion bolus of 40-50 IU/kg was used. The factor activity (F:C) and activated partial thromboplastin time (APTT) were examined immediately, and at 1 hr, 3 hr, 6 hr, 8 hr, 12 hr, and 24 hr after infusion. The biological half-life (T1/2) of factor that determined the frequency of administration was estimated by concentration–time curve. To calculate the bolus dose and anticipate the patient's response to factors, the clinician must know the degree to which the plasma factor level will increase in terms of units per kilogram of body weight after intravenous infusion. Combining these results with the APTT allows for formulation of a perioperative scheme. Generally, the bolus dose calculated was intended to raise the circulating factor level to 80% at surgery and postoperative first day, 60% at postoperative 2–3 days, 50% at postoperative 4–7 days, and 30% at postoperative 8–14 days. The APTT should be reduced to 50 s or less during surgery. If surgery lasted longer than 6 hr or uncontrolled intraoperative bleeding occurred, an additional bolus of coagulation factor was given.