A distributed model of peritoneal-plasma transport: tissue concentration gradients

1985 ◽  
Vol 248 (3) ◽  
pp. F425-F435 ◽  
Author(s):  
M. F. Flessner ◽  
J. D. Fenstermacher ◽  
R. L. Dedrick ◽  
R. G. Blasberg

Peritoneal dialysis transport studies were carried out in anesthetized rats. Injections of [14C]EDTA were made by intravenous bolus or intraperitoneal dialysis solution, and blood and peritoneal fluid samples were collected for 1 h. After death and rapid freezing of the animal, transverse sections through the abdominal cavity were cut for quantitative macroautoradiography. The plasma-to-peritoneal transport experiments with a clinical dialysis solution resulted in essentially horizontal concentration profiles versus distance in all tissues except large intestine. Estimates of the extracellular tissue fraction were: small intestine, 0.34; large intestine, 0.28; stomach, 0.30; uterus, 0.66; liver 0.35; diaphragm, 0.16; and anterior abdominal wall, 0.15. Similar experiments with an isotonic salt solution resulted in larger (13-300%) extracellular fractions in all tissues. In contrast, peritoneal-to-plasma transport studies demonstrated decreasing concentration profiles in all visceral tissues, with the first 90% of the gradient contained in the initial 400 micron of tissue from the peritoneum. Parietal tissue gradients were less steep and had higher concentration levels deep within the tissue than visceral tissues. Computer simulations using a distributed model approach compared favorably with the experimental measurements and established the validity of this approach.

1927 ◽  
Vol 23 (2) ◽  
pp. 246-246
Author(s):  
I. Tsimkhes

For almost 20 years, in colorectal cancer, where the affected loop and adjacent healthy sections of the large intestine cannot be sufficiently mobilized, even after separation and ligation of the mesentery, the author has been cutting off the parietal peritoneum with fascia of the abdominal wound area and plunging them as deeply into the abdominal cavity as possible.


2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Matthias Zeiler ◽  
Antonio Federico ◽  
PAOLO LENTINI ◽  
Roberto Dell'Aquila ◽  
Antonio Granata ◽  
...  

Abstract Background and Aims The clinical approach to peritoneal catheter malfunction consists usually in laxative prescription, abdominal radiography, brushing of the catheter lumen, guide-wire manipulation or catheter fluoroscopy. Only specialized centers apply videolaparoscopy for catheter rescue interventions. Up to now, limited experience is present regarding the evaluation of the intraperitoneal tract of the peritoneal catheter in adult patients. The aim of the study was to evaluate the diagnostic capability of B-mode ultrasound (US) followed by colour Doppler US (Doppler US) in persistent peritoneal catheter malfunction. Method US followed by Doppler US of the intraperitoneal part of the catheter was performed prior to videolaparoscopy intervention in 40 adult patients presenting persistent peritoneal catheter malfunction despite non-invasive therapy such as laxative prescription and brushing of the catheter lumen. US and Doppler US diagnosis were compared to the corresponding at videolaparoscopy intervention, and the causes of mismatch analyzed. In all patients US was performed after filling of the abdominal cavity with peritoneal dialysis solution of at least one liter. Doppler US along the intraperitoneal segment of the catheter was performed by flushing with dialysis fluid. Results In US, causes of persistent malfunction were catheter dislocation combined with omental wrapping in 21 cases, omental wrapping without dislocation in 11 cases, dislocation only in 4 cases, adherences to non-omental structures in 3 cases and entrapment in the lateral inguinal fossa in one case. The correspondence of US and videolaparoscopy diagnosis was 90%, respectively in 36 of 40 cases. The discrepancies were due to improper visualization of the catheter caused by constipation and embedding of the catheter between intestinal loops, resulting in an erroneous US diagnosis of omental wrapping, whereas videolaparoscopy showed encasement of the catheter between intestinal loops in three cases and presence of adherences to tubal structures in one case. Doppler US clarified the functional aspects of the catheter, thus increasing the correspondence to videolaparoscopy up to 39 out of 40 cases (97.5%) Conclusion US combined with Doppler US is helpful in making a correct pre-operative diagnosis of persistent peritoneal catheter malfunction and in planning of the videolaparoscopy rescue intervention.


MRS Advances ◽  
2017 ◽  
Vol 2 (26) ◽  
pp. 1393-1398 ◽  
Author(s):  
Saeid Lotfian ◽  
Gesa Rolink ◽  
Andreas Weisheit ◽  
Martin Palm

ABSTRACTBy laser metal deposition (LMD) samples from Fe–28Al (at.%) have been built on iron and various steels. Chemically graded iron aluminium and Fe–28Al/steel samples were fabricated with intended concentration gradients by controlling the feed rates of the powders. All samples were subsequently heat treated at 700 °C for 1000 h to study possible reactions between Fe–28Al and the steels and the long-term stability of the composition gradients. Microstructures were characterized by scanning electron microscopy (SEM) and concentration profiles along the building direction were analysed by energy- and wavelength-dispersive spectrometry (EDS, WDS).


1991 ◽  
Author(s):  
C.S. Pitcher ◽  
P.C. Stangeby

2006 ◽  
Vol 291 (6) ◽  
pp. H2950-H2964 ◽  
Author(s):  
Xiaobing Zhang ◽  
Roger H. Adamson ◽  
Fitz-Roy E. Curry ◽  
Sheldon Weinbaum

The recent experiments in Hu et al. ( Am J Physiol Heart Circ Physiol 279: H1724–H1736, 2000) and Adamson et al. ( J Physiol 557: 889–907, 2004) in frog and rat mesentery microvessels have provided strong evidence supporting the Michel-Weinbaum hypothesis for a revised asymmetric Starling principle in which the Starling force balance is applied locally across the endothelial glycocalyx layer rather than between lumen and tissue. These experiments were interpreted by a three-dimensional (3-D) mathematical model (Hu et al.; Microvasc Res 58: 281–304, 1999) to describe the coupled water and albumin fluxes in the glycocalyx layer, the cleft with its tight junction strand, and the surrounding tissue. This numerical 3-D model converges if the tissue is at uniform concentration or has significant tissue gradients due to tissue loading. However, for most physiological conditions, tissue gradients are two to three orders of magnitude smaller than the albumin gradients in the cleft, and the numerical model does not converge. A simpler multilayer one-dimensional (1-D) analytical model has been developed to describe these conditions. This model is used to extend Michel and Phillips’s original 1-D analysis of the matrix layer ( J Physiol 388: 421–435, 1987) to include a cleft with a tight junction strand, to explain the observation of Levick ( Exp Physiol 76: 825–857, 1991) that most tissues have an equilibrium tissue concentration that is close to 0.4 lumen concentration, and to explore the role of vesicular transport in achieving this equilibrium. The model predicts the surprising finding that one can have steady-state reabsorption at low pressures, in contrast to the experiments in Michel and Phillips, if a backward-standing gradient is established in the cleft that prevents the concentration from rising behind the glycocalyx.


1990 ◽  
Vol 72 (5) ◽  
pp. 865-873 ◽  
Author(s):  
Sven Björkman ◽  
Donald R. Stanski ◽  
Davide Verotta ◽  
Hideyoshi Harashima

1992 ◽  
Vol 58 (3) ◽  
pp. 931-940 ◽  
Author(s):  
Kevin H. Dykstra ◽  
John K. Hsiao ◽  
Paul F. Morrison ◽  
Peter M. Bungay ◽  
Ivan N. MefFord ◽  
...  

Author(s):  
Jacky S. H. Lee ◽  
Yandong Hu ◽  
Dongqing Li

Creation of concentration gradients is important in the study of biological and chemical processes that are sensitive to concentration variations. This paper presents a simple method to generate a linear concentration gradient in electroosmotic flow in microchannels with converging and diverging geometries. The method is based on the enhanced diffusive mixing inside the microchannel. By varying the converging-diverging geometries, the degree of diffusive mixing can be controlled. Different concentration gradients can be obtained by varying the applied potential and the geometry. Concentration profiles with minimal axial variations can be achieved with a deviation of 7% and 3% over a channel length of 3mm and 1mm, respectively, for a 400μm wide microchannel. Although the underlying physics and mechanisms for creating concentration profiles in a converging-diverging microchannel are the same as a T-shaped micromixer, the converging-diverging microchannel can produce desired concentration profiles in a much shorter distance (shorter by a factor of 2∼3.5 compared to a T-shape mixer). A serially connected concentration gradient generator is also realized with the ability to generate two concentration gradient ranges in the same microchannel. Numerical simulations and experiments were carried out to investigate the factors contributed to the generation of the concentration gradients.


2009 ◽  
Vol 296 (6) ◽  
pp. H1960-H1968 ◽  
Author(s):  
Jacek Waniewski ◽  
Joanna Stachowska-Pietka ◽  
Michael F. Flessner

Based on a distributed model of peritoneal transport, in the present report, a mathematical theory is presented to explain how the osmotic agent in the peritoneal dialysis solution that penetrates tissue induces osmotically driven flux out of the tissue. The relationships between phenomenological transport parameters (hydraulic permeability and reflection coefficient) and the respective specific transport parameters for the tissue and the capillary wall are separately described. Closed formulas for steady-state flux across the peritoneal surface and for hydrostatic pressure at the opposite surface are obtained using an approximate description of the concentration profile of the osmotic agent within the tissue by exponential function. A case of experimental study with mannitol as the osmotic agent in the rat abdominal wall is shown to be well described by our theory and computer simulations and to validate the applied approximations. Furthermore, clinical dialysis with glucose as the osmotic agent is analyzed, and the effective transport rates and parameters are derived from the description of the tissue and capillary wall.


2021 ◽  
Vol 49 ◽  
Author(s):  
Eric Arantes da Silva ◽  
Igor Borges Oliveira ◽  
Thâmara Rossi Martins Da Silva ◽  
Andreia Vitor Couto do Amaral ◽  
Raphaella Barbosa Meirelles-Bartoli ◽  
...  

Background: Trichuris vulpis, a species that belongs to Trichuris and shows a cosmopolitan distribution, parasitizes the gastrointestinal system of dogs causing trichuriasis. The infection occurs owing to ingestion of larval eggs and subsequent fixation of their adult form in the large intestine of the host. The objective of this paper is to report the case of a Border Collie dog that arrived at the Veterinary Pathology Laboratory (LPV) of the Federal University of Jataí (UFJ) after exhibiting signs of intense dehydration and sudden death caused by severe T. vulpis infection, and to elucidate the macroscopic and microscopic histopathological correlations observed during necropsy.Case: A 7-year-old male Border Collie dog was referred for routine necroscopic examination on suspicion of death from intoxication. In the history, there were reports of bone ingestion, restlessness, and polydipsia for three days, followed by sudden death. Although the animal presented an adequate body state during the necroscopic procedure, enophthalmia and pale oral and ocular mucosa were observed, which are characteristic signs of severe dehydration and anemia. On opening the abdominal cavity, the visceral serosa were found to be stained and severely dry. Greenish mucous content was observed throughout the intestine, and in the large intestine, a moderate amount of mucus associated with high parasitic infestation by elongated parasites attached to the mucosa was identified. The parasites were harvested, stored in airtight vials containing 70% alcohol, processed, and subsequently identified as T. vulpis.Discussion: The necroscopic findings associated with the histopathology were compatible with T. vulpis infestation at high parasite intensity, with severe destruction of the intestinal mucosa and inability of water absorption, resulting in severe dehydration. In cases of parasitism, villous atrophy with crypt hypertrophy occurs, a fact observed in the present case. Possibly crypt hypertrophy occurs prior to villous atrophy, and occurs independently of previous lesions of the absorptive compartment. This results in poor absorption. Advanced loss of gastrointestinal tract fluids can usually be extensive and lead to progressive dehydration with loss of isotonic and hypertonic fluids, which can also be observed in the observation of blood components, severely accelerating changes such as hypovolemia and posterior hemoconcentration. Hypovolemia from severe dehydration also decreases renal perfusion and reduces the rate of glomerular filtration. Hypovolemia also leads to decreased blood pumping capacity, which may lead to heart failure and pulmonary circulatory disorders with notable effects on gas exchange, which may cause hypoxemia and possibly lethal metabolic acidosis. The necropsy performed on the animal found a severe dehydration that could be sustained mainly owing to signs of hypovolemia, associated with a series of pathophysiological events with the massive presence of parasites identified as T. vulpis. The damage caused to the intestinal mucosa by the oral stylet, the movement, and toxins of the parasites led to a severe condition of villosities destruction and tissue necrosis, leading to a large loss of the absorption function of nutrients in the intestines and especially of water, resulting in a condition of severe dehydration. This imbalance of system functioning also alters cardiac function because of increased blood viscosity generating possible lardaceous clots, which in turn are indicative of anemia. This cycle of deleterious changes can result in hypovolemic shock and consequent sudden death.


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