Zinc Isotopes
Isotopes
Isotope Labeling
Nitrogen Isotopes
Oxygen Isotopes
Zinc Fingers
Comparison of estimates of zinc absorption in humans by using 4 stable isotopic tracer methods and compartmental analysis. (1/75)
BACKGROUND: Adjustment of gastrointestinal absorption is the primary means of maintaining zinc homeostasis; however, a precise, accurate method for measuring zinc absorption in humans has not been identified. OBJECTIVE: The purpose of this study was to compare the estimates of the fraction of dietary zinc absorbed (FZA) by using 4 stable isotopic tracer methods: mass balance (MB) corrected for endogenous secretion, fecal monitoring (FM), deconvolution analysis (DA), and the double isotopic tracer ratio (DITR) method. DESIGN: All 4 methods were applied to a single data set for each of 6 women. FZA was also determined for each subject by using a detailed compartmental model of zinc metabolism, and that value was used as the reference with which the simpler methods were compared. RESULTS: The estimates of FZA (&xmacr; +/- SD) determined by DA (0.27 +/- 0. 08) and the DITR technique in plasma (0.30 +/- 0.10), 24-h urine samples (0.29 +/- 0.09), and spot urine samples (0.291 +/- 0.089) all compared well with the FZA reference value from the compartmental model (0.30 +/- 0.10). The MB and FM methods tended to overestimate FZA compared with the reference value. CONCLUSIONS: The determination of FZA by MB or FM is laborious, is sensitive to subject compliance, and may result in an overestimate. DA, although relatively accurate, has the disadvantage of requiring multiple blood drawings over several days. In contrast, the DITR technique applied to a spot urine specimen obtained >/=3 d after tracer administration provides an accurate measure of FZA and is easy to implement; therefore, it is the recommended method for determination of FZA. (+info)Body weight-specific zinc compartmental masses in girls significantly exceed those reported in adults: a stable isotope study using a kinetic model. (2/75)
Maintaining optimal zinc status is important for normal growth and development in children, but minimal data are available regarding zinc metabolism in this age group. Our objectives were to utilize stable isotope-based compartmental modeling techniques to investigate zinc metabolism in healthy children; to expand a current stable isotope-based model to include red blood cell data; and to compare kinetic parameters in children with those previously reported in adults. Seven healthy girls, age 9.94 +/- 0.79 y, received 1.1 mg of a (67)zinc-enriched tracer orally and 0.5 mg of a (70)zinc-enriched tracer intravenously. Blood, urine and fecal samples were collected for 6 d. Stable isotope enrichments were measured by thermal ionization magnetic sector mass spectrometry. A six-compartment model based on a model previously reported in adults was used; the model excluded red blood cell data. Body weight-corrected masses of the body zinc compartments derived using this model were significantly greater in children than those reported in adults. Modification of the model to include a red blood cell compartment increased the total identifiable zinc mass of the nongastrointestinal compartments by approximately 2.5%. We conclude that compartmental modeling can be used to describe zinc kinetics in children, and that the body weight-corrected zinc pool masses are significantly greater in children than in adults. (+info)Radiation effects on testes. II. incorporation of 65Zn after partial body gamma-irradiation of rats. (3/75)
The decrease in the uptake of 65-Zn by irradiated testes (720 R) was followed by recovery after 30 days. After a dose of 2000 R, uptake of 65-Zn was systemtically reduced over a period of 74 days. Studies following the administration of testosterone and FSH germinal cells of the testes is under the control of pituitary gonadotrophins. (+info)Accuracy of simple techniques for estimating fractional zinc absorption in humans. (4/75)
The theoretical basis of the accuracy of a number of simple techniques for estimating fractional zinc absorption (FZA) in humans using stable isotopic tracers has not been evaluated. These techniques include fecal monitoring (FM), deconvolution analysis (DA), double isotopic tracer ratio (DITR) and indicator dilution methods. Using a compartmental model, we investigated the accuracy and logic of each of these techniques. Time-dependent estimates of FZA based on the simple techniques were simulated using the compartmental model and compared with the known FZA derived from the model. The analysis elucidated logical errors in some of the FM techniques, and even when these problems were corrected, the FM technique was still prone to errors due to incomplete fecal tracer recovery and variable gastrointestinal (GI) transit time. Although logically correct, the indicator dilution techniques were also highly sensitive to incomplete fecal tracer recovery and variable GI transit time. The DA and DITR techniques were the most robust in that they were logically correct and were insensitive to incomplete fecal tracer recovery and variable GI transit time. Although all of the DA and DITR methods provided similarly good estimates of FZA relative to the compartmental model, the DITR technique performed on a spot urine specimen obtained several days after tracer administration was the preferred choice because of its simplicity and minimal requirements for patient compliance. (+info)Effect of acute zinc depletion on zinc homeostasis and plasma zinc kinetics in men. (5/75)
BACKGROUND: Zinc homeostasis and normal plasma zinc concentrations are maintained over a wide range of intakes. OBJECTIVE: The objective was to identify the homeostatic response to severe zinc depletion by using compartmental analysis. DESIGN: Stable zinc isotope tracers were administered intravenously to 5 men at baseline (12.2 mg dietary Zn/d) and after 5 wk of acute zinc depletion (0.23 mg/d). Compartmental modeling of zinc metabolism was performed by using tracer and mass data in plasma, urine, and feces collected over 6-14 d. RESULTS: The plasma zinc concentration fell 65% on average after 5 wk of zinc depletion. The model predicted that fractional zinc absorption increased from 26% to essentially 100%. The rate constants for zinc excretion in the urine and gastrointestinal tract decreased 96% and 74%, respectively. The rate constants describing the distribution kinetics of plasma zinc did not change significantly. When zinc depletion was simulated by using an average mass model of zinc metabolism at baseline, the only change that accounted for the observed fall in plasma zinc concentration was a 60% reduction in the rate constant for zinc release from the most slowly turning over zinc pool. The large changes in zinc intake, excretion, and absorption-even when considered together-only explained modest reductions in plasma zinc mass. CONCLUSION: The kinetic analysis with a compartmental model suggests that the profound decrease in plasma zinc concentrations after 5 wk of severe zinc depletion was mainly due to a decrease in the rate of zinc release from the most slowly turning over body zinc pool. (+info)Folic acid enrichment of bread does not appear to affect zinc absorption in young women. (6/75)
BACKGROUND: In several countries cereals are now enriched with folic acid to reduce the risk of neural tube defects. Human studies suggest that folic acid interferes with zinc absorption. This raises concerns about the zinc status of high-risk groups such as infants, pregnant women, and older persons. OBJECTIVE: We sought to determine the effect of added folic acid on zinc absorption from white bread with high and low zinc contents. DESIGN: Zinc absorption was measured in 15 healthy women (22-33 y), each of whom consumed 4 single meals spaced 2 wk apart in a randomized crossover design. The servings of bread (100 g) differed in zinc and folic acid contents as follows: A, 1.2 mg Zn and 17 microg folic acid; B, 1.2 mg Zn and 144 microg folic acid; C, 3.0 mg Zn and 17 microg folic acid; and D, 2.9 mg Zn and 144 microg folic acid. Meals were extrinsically labeled with 65Zn and absorption was estimated from whole-body retention measurements. Folate status was assessed by measuring plasma and erythrocyte folate and plasma homocysteine concentrations. RESULTS: Mean (+/-SD) zinc absorption did not differ significantly in relation to the folate content of the breads at either the low zinc content (38.8 +/- 13.5% and 40.6 +/- 16.5% for A and B, respectively; P = 0.74) or the high zinc content (26.7 +/- 9.3% and 22.7 +/- 6.6% for C and D, respectively; P = 0.16). There was no significant correlation between folate status and zinc absorption (r < 0.3, P > 0.1). CONCLUSION: Fortification of white bread with a commonly used amount of folic acid did not appear to influence zinc absorption at either a high or a low zinc content. (+info)Fractional zinc absorption using a single isotope tracer. (7/75)
BACKGROUND: Fractional absorption of zinc (Zn) has been measured using dual isotopes of Zn given simultaneously. An oral test dose and an intravenous (i.v.) reference dose are administered, followed by the measurement of the double isotopic enrichment (E) in urine 48 h after administration. We postulated that an estimate of the %E in urine for a given i.v. dose of Zn may be used to eliminate the need for venipuncture and the second Zn isotope. OBJECTIVES: To determine a constant (k) for the Zn enrichment of urine after i.v. administration of a dose of labeled Zn in Zn-replete subjects. To use 'k' to calculate fractional absorption of Zn, and to compare these values to values obtained using the standard dual isotope method. DESIGN: Single-arm cohort. SETTING: The Hospital for Sick Children, Toronto, Canada. SUBJECTS: Twenty-three healthy adults were recruited from the Metropolitan Toronto area. Seventeen subjects completed the study. INTERVENTIONS: A 2.29 mg i.v. dose of (67)Zn followed immediately by a 2.50 mg oral dose of (70)Zn. RESULTS: Population mean percentage enrichment (%E) of (67)Zn in urine was 1.43 (95% CI 1.26, 1.60). The ratio of the i.v. dose to mean %E in urine (k) was estimated to be 1.60 mg (95% CI 1.43, 1.82). There was no difference in the mean fractional absorption of Zn calculated using the single compared to the dual isotope method: 12.58% (95% CI 2.22, 22.94) vs 12.68% (95% CI 4.52, 20.85), respectively (P=0.89). The correlation coefficient between the two methods was 0.81 (P<0.0001). CONCLUSIONS: The dual isotope method may be replaced by using a constant (k) and a single oral dose of isotopic-enriched Zn to estimate fractional absorption of Zn within a population. SPONSORSHIP: Gerber Products Company, Fremont, MI. (+info)Double isotope tracer method for measuring fractional zinc absorption: theoretical analysis. (8/75)
Several approaches for estimation of fractional zinc absorption (FZA) by calculating the ratio of oral to intravenous stable isotopic tracer concentrations (at an appropriate time) in urine or plasma after their simultaneous administration have been proposed in the last decade. These simple-to-implement approaches, often referred to as the double isotopic tracer ratio (DITR) method, are more attractive than the classical "deconvolution" method and the more commonly used single-tracer methods based on fecal monitoring and indicator dilution, after oral or intravenous tracer administration, respectively. However, the domain of validity of DITR for measuring FZA has recently been questioned. In this paper, we provide a theoretical justification of the validity of four different "approximate" formulations of the DITR technique by demonstrating mathematically that their accuracy is a consequence of the particular properties of zinc kinetics. (+info)Zinc isotopes refer to variants of the chemical element zinc, each with a different number of neutrons in their atomic nucleus. Zinc has five stable isotopes: zinc-64, zinc-66, zinc-67, zinc-68, and zinc-70. These isotopes have naturally occurring abundances that vary, with zinc-64 being the most abundant at approximately 48.6%.
Additionally, there are also several radioactive isotopes of zinc, including zinc-65, zinc-71, and zinc-72, among others. These isotopes have unstable nuclei that decay over time, emitting radiation in the process. They are not found naturally on Earth and must be produced artificially through nuclear reactions.
Medical Definition: Zinc isotopes refer to variants of the chemical element zinc with different numbers of neutrons in their atomic nucleus, including stable isotopes such as zinc-64, zinc-66, zinc-67, zinc-68, and zinc-70, and radioactive isotopes such as zinc-65, zinc-71, and zinc-72.
Isotopes are variants of a chemical element that have the same number of protons in their atomic nucleus, but a different number of neutrons. This means they have different atomic masses, but share similar chemical properties. Some isotopes are stable and do not decay naturally, while others are unstable and radioactive, undergoing radioactive decay and emitting radiation in the process. These radioisotopes are often used in medical imaging and treatment procedures.
Isotope labeling is a scientific technique used in the field of medicine, particularly in molecular biology, chemistry, and pharmacology. It involves replacing one or more atoms in a molecule with a radioactive or stable isotope of the same element. This modified molecule can then be traced and analyzed to study its structure, function, metabolism, or interaction with other molecules within biological systems.
Radioisotope labeling uses unstable radioactive isotopes that emit radiation, allowing for detection and quantification of the labeled molecule using various imaging techniques, such as positron emission tomography (PET) or single-photon emission computed tomography (SPECT). This approach is particularly useful in tracking the distribution and metabolism of drugs, hormones, or other biomolecules in living organisms.
Stable isotope labeling, on the other hand, employs non-radioactive isotopes that do not emit radiation. These isotopes have different atomic masses compared to their natural counterparts and can be detected using mass spectrometry. Stable isotope labeling is often used in metabolic studies, protein turnover analysis, or for identifying the origin of specific molecules within complex biological samples.
In summary, isotope labeling is a versatile tool in medical research that enables researchers to investigate various aspects of molecular behavior and interactions within biological systems.
Nitrogen isotopes are different forms of the nitrogen element (N), which have varying numbers of neutrons in their atomic nuclei. The most common nitrogen isotope is N-14, which contains 7 protons and 7 neutrons in its nucleus. However, there are also heavier stable isotopes such as N-15, which contains one extra neutron.
In medical terms, nitrogen isotopes can be used in research and diagnostic procedures to study various biological processes. For example, N-15 can be used in a technique called "nitrogen-15 nuclear magnetic resonance (NMR) spectroscopy" to investigate the metabolism of nitrogen-containing compounds in the body. Additionally, stable isotope labeling with nitrogen-15 has been used in clinical trials and research studies to track the fate of drugs and nutrients in the body.
In some cases, radioactive nitrogen isotopes such as N-13 or N-16 may also be used in medical imaging techniques like positron emission tomography (PET) scans to visualize and diagnose various diseases and conditions. However, these applications are less common than the use of stable nitrogen isotopes.
Oxygen isotopes are different forms or varieties of the element oxygen that have the same number of protons in their atomic nuclei, which is 8, but a different number of neutrons. The most common oxygen isotopes are oxygen-16 (^{16}O), which contains 8 protons and 8 neutrons, and oxygen-18 (^{18}O), which contains 8 protons and 10 neutrons.
The ratio of these oxygen isotopes can vary in different substances, such as water molecules, and can provide valuable information about the origins and history of those substances. For example, scientists can use the ratio of oxygen-18 to oxygen-16 in ancient ice cores or fossilized bones to learn about past climate conditions or the diets of ancient organisms.
In medical contexts, oxygen isotopes may be used in diagnostic tests or treatments, such as positron emission tomography (PET) scans, where a radioactive isotope of oxygen (such as oxygen-15) is introduced into the body and emits positrons that can be detected by specialized equipment to create detailed images of internal structures.
Zinc fingers are a type of protein structural motif involved in specific DNA binding and, by extension, in the regulation of gene expression. They are so named because of their characteristic "finger-like" shape that is formed when a zinc ion binds to the amino acids within the protein. This structure allows the protein to interact with and recognize specific DNA sequences, thereby playing a crucial role in various biological processes such as transcription, repair, and recombination of genetic material.
Carbon isotopes are variants of the chemical element carbon that have different numbers of neutrons in their atomic nuclei. The most common and stable isotope of carbon is carbon-12 (^{12}C), which contains six protons and six neutrons. However, carbon can also come in other forms, known as isotopes, which contain different numbers of neutrons.
Carbon-13 (^{13}C) is a stable isotope of carbon that contains seven neutrons in its nucleus. It makes up about 1.1% of all carbon found on Earth and is used in various scientific applications, such as in tracing the metabolic pathways of organisms or in studying the age of fossilized materials.
Carbon-14 (^{14}C), also known as radiocarbon, is a radioactive isotope of carbon that contains eight neutrons in its nucleus. It is produced naturally in the atmosphere through the interaction of cosmic rays with nitrogen gas. Carbon-14 has a half-life of about 5,730 years, which makes it useful for dating organic materials, such as archaeological artifacts or fossils, up to around 60,000 years old.
Carbon isotopes are important in many scientific fields, including geology, biology, and medicine, and are used in a variety of applications, from studying the Earth's climate history to diagnosing medical conditions.
