Kinetics of transepithelial movement of heavy metals in rat jejunum

1987 ◽  
Vol 253 (2) ◽  
pp. G134-G138
Author(s):  
E. C. Foulkes ◽  
D. M. McMullen
Keyword(s):  
Heavy Metals ◽  
Venous Blood ◽  
Compartment Model ◽  
Intestinal Lumen ◽  
Rat Jejunum ◽  
Temperature Dependent ◽  
Appearance Time ◽  
Portal Venous Blood ◽  
Kinetics Of

The kinetics of the transepithelial movement of heavy metals were studied in the perfused rat jejunum in situ. The peak appearance time (TET) of Zn, Ni, and Cd in portal venous blood was determined after their transient (10 s) introduction into the intestinal lumen. Observed TET values for these metals were positively correlated with their affinities for metallothionein and agreed with those predicted on the basis of a linear three-compartment model that does not allow for paracellular pathways. Further evidence was provided to support the hypothesis that Cd absorption consists first of Cd binding to negative membrane charges followed by a temperature-dependent internalization step.

Absorption of beta-casomorphins from autoperfused lamb and piglet small intestine

1990 ◽  
Vol 259 (3) ◽  
pp. G443-G452 ◽  
Author(s):  
L. C. Read ◽  
A. P. Lord ◽  
V. Brantl ◽  
G. Koch
Keyword(s):  
Small Intestine ◽  
Intestinal Lumen ◽  
Physiological Conditions ◽  
Naturally Occurring ◽  
Gut Epithelium ◽  
Measured Absorption ◽  
Beta Casein ◽  
Kinetics Of

beta-Casomorphins (beta-CMs) derived from milk beta-casein may exert various opiate activities in milk-fed infants. To assess the physiological significance of beta-CMs as a source of circulating opioids in infants, we measured absorption rates of several beta-CMs under near-physiological conditions using in situ autoperfused lamb intestine. The naturally occurring beta-CMs, beta-CM-7 and beta-CM-4-amide, were absorbed readily into blood with no transfer into lymph. Uptake peaked within several minutes of the luminal infusion of peptide but then declined sharply and stopped within a further 10-15 min. The recovery in blood, intestinal contents, and tissue at the end of the 30-min experiment was less than 1% of the infused dose. The low recovery was due to rapid proteolysis based on in vitro studies that demonstrated half-lives of less than 5 min in lamb blood, luminal contents, and lymph. The synthetic dipeptidyl peptidase IV-resistant analogue beta-[D-Ala2]CM- 4-amide was stable during incubation in blood, lymph, or luminal contents and was absorbed into blood at rates that were maximal within several minutes and remained steady for the 30-min period. We conclude that although natural beta-CMs are transferred across the lamb small intestine, rapid degradation within the intestinal lumen, gut epithelium, and blood would prevent entry into the circulation under normal conditions. Val-beta-CM-7, a putative stable precursor, had similar stability and kinetics of absorption to beta-CM-7, results that exclude Val-beta-CM-7 as a stable precursor for delivery of beta-CMs to the circulation. Essentially identical results to those in lambs were obtained in 7-day-old piglets.

scholarly journals Intestinal Permeability Assays: a Review

2021 ◽  
Vol 31 (1) ◽  
pp. 20-30
Author(s):  
A. A. Iakupova ◽  
S. R. Abdulkhakov ◽  
R. K. Zalyalov ◽  
A. G. Safin ◽  
R. A. Abdulkhakov
Keyword(s):  
Intestinal Permeability ◽  
Ex Vivo ◽  
Venous Blood ◽  
Intestinal Barrier ◽  
Intestinal Lumen ◽  
Alcoholic Fatty Liver ◽  
Key Points ◽  
Assessment Techniques ◽  
Portal Venous Blood

Aim. A literature review of intestinal permeability assessment techniques.Key points. The intestinal barrier is a functional entity separating the intestinal lumen and internal body, and intestinal permeability is a measure of the barrier functionality. The intestinal barrier integrity and permeability assays differ by the application setting (in vivo or ex vivo), subject (human or animal), marker molecules used to assess permeability (ions, various size carbohydrates, macromolecules, antigens, bacterial products and bacteria), biomaterial for the marker concentration assays (peripheral blood, portal venous blood, urine, stool). Despite a great variety of methods for assessing intestinal permeability, their clinical application requires further studies due to a lack of standardisation, the complexity of selected techniques and occasional limited reliability of results.Conclusion. Further investigation and improvement of intestinal permeability assays is required. The assay and result standardisation will facilitate practice in functional and organic intestinal diseases, as well as allergies, diabetes mellitus, non-alcoholic fatty liver disease and some other illnesses.

Rapid changes in hepatic glucose output after a pulse of growth hormone in dogs

1984 ◽  
Vol 246 (1) ◽  
pp. E14-E20
Author(s):  
P. Vaitkus ◽  
A. Sirek ◽  
K. H. Norwich ◽  
O. V. Sirek ◽  
R. H. Unger ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Venous Blood ◽  
Compartment Model ◽  
Glucose Turnover ◽  
Base Line ◽  
Indwelling Catheter ◽  
Two Compartment Model ◽  
Portal Venous Blood ◽  
Glucose Output

In response to a single intravenous injection of bovine growth hormone (GH, 100 micrograms/kg) the non-steady-state turnover of glucose, as well as portal levels of insulin (IRI), glucagon (IRG), somatostatin (SRIF), and glucose were determined in normal conscious dogs. Using the two-compartment model validated to calculate rapid turnover changes and tracer infusion methods, the rate of hepatic output of glucose [Ra(t)] was found to be increased, reaching a maximum of 224 mg/min, 7.4 times the basal rate, 4 min after injection of GH. Ra(t) returned to its basal level 35 min later in a damped oscillatory manner. Hormone determinations were carried out in portal venous blood drawn every 2 min for 2 h from an indwelling catheter. IRG peaked 2 min after GH injection and levels of IRI, SRIF, and glucose peaked between 4 and 8 min. Hormone concentrations returned to normal, i.e., were oscillating around base-line levels, about 30 min after GH. These experiments demonstrate for the first time in vivo that a pulse of GH causes transient changes of glucose turnover and measurable alterations of the hormonal homeostasis in the splanchnic area.

Kinetics of zinc absorption by the rat jejunum: effects of adrenalectomy and dexamethasone

1983 ◽  
Vol 244 (3) ◽  
pp. G314-G320 ◽  
Author(s):  
R. F. Bonewitz ◽  
E. C. Foulkes ◽  
E. J. O'Flaherty ◽  
V. S. Hertzberg
Keyword(s):  
Compartment Model ◽  
The Body ◽  
Adult Rat ◽  
Two Compartment Model ◽  
65Zn Uptake ◽  
Mathematical Simulations ◽  
Adrenocortical Hormone ◽  
Perfusion Period ◽  
Kinetics Of

Effects of dexamethasone and adrenalectomy on the kinetics of jejunal 65Zn uptake and absorption were studied in the anesthetized adult rat. The jejunal lumen was perfused in situ with 5 mM glucose in 150 mM saline containing 65Zn and [14C]polyethylene glycol as volume marker. Over the 30-min perfusion period, the rate of net 65Zn removal from the perfusate was biexponential due to the establishment of a return flux to the lumen. An open two-compartment model satisfactorily describes these observations: (formula; see text) Dexamethasone (2 mg/kg ip 7 h before perfusion) increased k12 by 75% (P less than 0.0002) and decreased k20 by 45% (P less than 0.04). Both effects were independent of adrenalectomy. Mathematical simulations using the compartmental model and experimentally determined kinetic constants predicted that transfer of 65Zn into the body should be enhanced by adrenalectomy and retarded by dexamethasone administered to adrenalectomized rats. Dexamethasone and adrenalectomy thus differentially affect Zn uptake and absorption in this system, suggesting a possible adrenocortical hormone involvement in the regulation of Zn absorption. These changes are apparently not mediated via metallothionein.

In situ observations of the amorphous-to-gamma transformation in ion-implanted Al2O3

1989 ◽  
Vol 47 ◽  
pp. 654-655
Author(s):  
P. S. Sklad
Keyword(s):  
Amorphous Material ◽  
Temperature Dependent ◽  
Surface Layers ◽  
Thermally Activated ◽  
Transmission Electron ◽  
In Situ Experiments ◽  
Amorphous Surface ◽  
Transformation Front ◽  
Kinetics Of

Transmission electron microscopy (TEM) was used in an investigation of the recrystallization behavior of amorphous surface layers on single crystal [0001] α-Al2O3. Conventional imaging and diffraction techniques were used to characterize the microstructures produced by annealing bulk specimens in the temperature range from 800°C to 1200°C. It was found that the amorphous Al2O3 first transforms to γ-Al2O3, a cubic transitional form, which in turn transforms to α-Al2O3. The γ to α transformation begins at the original crystalline-amorphous interface and proceeds toward the specimen surface. By measuring the position of the γ-α interface as a function of annealing temperature and time it was possible to determine the temperature-dependent velocity of the γ-α transformation front. Assuming a thermally activated process, the data are consistent with an activation energy of 3.6 eV for the transformation. However, no amorphous material remained, after even the shortest anneals (15 min) at the lowest temperature (800°C). These results indicate that the kinetics of the amorphous to γ transformation are faster than those of the γ to α transformation. Therefore a series of in-situ experiments was carried out to investigate the transformation of amorphous Al2O3 to γ-Al2O3. Amorphous Al2O3 surface layers, free of implanted impurities, were produced by implantation at −185°C with 2 × 1016 Al/cm2 at 90 keV and 3 × 1016 O/cm2 at 55 keV. Cross-sectioned specimens were prepared following established techniques.2 The specimens were annealed in-situ in a Philips CM12 operating at 120 kV with a Gatan Model 628 single tilt heating holder. Progress of the transformations was monitored with a Gatan model 622 video system.

In situ study of electron beam-induced chemical vapor deposition of Au in an environmental TEM

1995 ◽  
Vol 53 ◽  
pp. 256-257
Author(s):  
J. Drucker ◽  
R. Sharma ◽  
J. Kouvetakis ◽  
K.H.J. Weiss
Keyword(s):  
Electron Beam ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Quantum Effect ◽  
Line Drawing ◽  
Chemical Vapor ◽  
Environmental Cell ◽  
Engineering Changes ◽  
Kinetics Of

Patterning of metals is a key element in the fabrication of integrated microelectronics. For circuit repair and engineering changes constructive lithography, writing techniques, based on electron, ion or photon beam-induced decomposition of precursor molecule and its deposition on top of a structure have gained wide acceptance Recently, scanning probe techniques have been used for line drawing and wire growth of W on a silicon substrate for quantum effect devices. The kinetics of electron beam induced W deposition from WF6 gas has been studied by adsorbing the gas on SiO2 surface and measuring the growth in a TEM for various exposure times. Our environmental cell allows us to control not only electron exposure time but also the gas pressure flow and the temperature. We have studied the growth kinetics of Au Chemical vapor deposition (CVD), in situ, at different temperatures with/without the electron beam on highly clean Si surfaces in an environmental cell fitted inside a TEM column.

Ultrastructure of rat alveolar macrophages activated in situ by poly:IC

1987 ◽  
Vol 45 ◽  
pp. 768-769
Author(s):  
A. M. Klinkner ◽  
R. A. Weiss ◽  
A. Kelley ◽  
P. J. Bugelski
Keyword(s):  
Venous Blood ◽  
Intratracheal Instillation ◽  
Buffy Coat ◽  
Fischer 344 Rats ◽  
Blood Monocytes ◽  
Fischer 344 ◽  
Polyinosinic:Polycytidylic Acid ◽  
Macrophage Activator ◽  
Endogenous Peroxidase

Polyinosinic:polycytidylic acid is an inducer of interferon and a macrophage activator. We have found that intratracheal instillation of polyI:C (IT-pI:C) activates rat bronchoalveolar lavage cells (BAL) for a variety of functions. Examination of Giemsa stained, cytocentrifuge preparations showed that IT-pI:C induced a population of BAL not seen in resident BAL. The morphology of these cells suggested that they might be derived from blood monocytes. To test this hypothesis we have examined several populations of macrophages that had been stained for endogenous peroxidase activity as a marker of cells derived from the monocyte-macrophage lineage.Macrophages were obtained from Fischer 344 rats. Peritoneal exudate cells (PEC) were collected by lavage 4 days after i.p. injection of 20 ml 3% thioglycolate. Buffy coat monocytes were separated from venous blood from naive rats.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

Growth kinetics of Al2Cu in an Al-1.5Cu thin film by in Situ TEM

1993 ◽  
Vol 51 ◽  
pp. 1172-1173
Author(s):  
M. Park ◽  
S.J. Krause ◽  
S.R. Wilson
Keyword(s):  
Thin Film ◽  
In Situ Tem ◽  
Collector Plate ◽  
Transmission Electron ◽  
Device Processing ◽  
Corrosion Susceptibility ◽  
Precipitation Phenomena ◽  
Semiconductor Chips ◽  
Kinetics Of

Cu alloying in Al interconnection lines on semiconductor chips improves their resistance to electromigration and hillock growth. Excess Cu in Al can result in the formation of Cu-rich Al2Cu (θ) precipitates. These precipitates can significantly increase corrosion susceptibility due to the galvanic action between the θ-phase and the adjacent Cu-depleted matrix. The size and distribution of the θ-phase are also closely related to the film susceptibility to electromigration voiding. Thus, an important issue is the precipitation phenomena which occur during thermal device processing steps. In bulk alloys, it was found that the θ precipitates can grow via the grain boundary “collector plate mechanism” at rates far greater than allowed by volume diffusion. In a thin film, however, one might expect that the growth rate of a θ precipitate might be altered by interfacial diffusion. In this work, we report on the growth (lengthening) kinetics of the θ-phase in Al-Cu thin films as examined by in-situ isothermal aging in transmission electron microscopy (TEM).

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

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