This document studied the water permeability properties of several epithelial barriers (toad urinary bladder, rat caecum, distal human colon, human amnion) under different conditions. It measured three parameters: 1) hydraulic permeability (Phydr) in the presence of hydrostatic pressure, 2) osmotic permeability (Posm) in the presence of an osmotic gradient, and 3) transepithelial potential difference (dV). The results showed that Phydr correlated with dV but not with Posm or between Posm and Phydr. Phydr ranged from 0.079 to 0.32 cm/s and was highest in the human amnion. dV was also highest in the human amn
The document defines and describes several key networking and web technologies:
- An intranet refers to a private computer network within an organization, while an extranet allows controlled external access for business or education. Both enable easy information sharing within workgroups.
- A public network can be accessed by anyone, while a private network is locked down for the owner only. A leased line provides a dedicated symmetric telecommunications connection between two locations for a monthly fee.
- HTML defines web page formatting with tags, allowing hyperlinks between documents on the web. XML similarly defines data elements but allows custom tags, enabling it to function like a database.
This document is Ilaria Federici's alter-portfolio, showcasing artwork created for passion projects, friends, and competitions rather than chronologically. It includes designs for bands like 30 Seconds to Mars and Kings of Leon, such as pins, bookmarks, hoodies, and posters inspired by songs. It also shows paintings and illustrations in various styles, including replicas of famous works and life drawings. The portfolio serves to share a part of the artist and their thoughts through how they visualize music.
This chapter provides background on the author's experience in Haiti where he witnessed a mob attack on a woman. The author was sitting in a medical truck as the attack happened outside but did not intervene. The chapter then contrasts this with two previous occasions where the author was in fights to protect others - once in 1996 helping a woman being choked in an alley in Pittsburgh. It also describes the author's work with a priest in Haiti, loading medical supplies to bring into the dangerous Cite Soleil slum, though he was not prepared for the violence he would witness that day.
SpeakLike provides translation services through an online platform that uses crowdsourcing and machine translation. It can process translations quickly, with some texts translated in under an hour. The platform supports over 37 languages and has tools for companies to integrate translations into their websites, emails, chat, and other digital content. It aims to make expanding into new international markets faster and easier for businesses.
Web 1.0 focused on commerce while Web 2.0 emphasizes user participation and contribution. The concept of Web 2.0 emerged from a 2004 brainstorming session between O'Reilly and MediaLive International. Key principles of Web 2.0 include customization for individual users, harnessing collective intelligence by allowing users to contribute and edit content, and specialized databases to store user data. Web 2.0 applications are also characterized by a perpetual beta approach with frequent updates and a focus on services rather than single-device software.
The document defines and describes several key networking and web technologies:
- An intranet refers to a private computer network within an organization, while an extranet allows controlled external access for business or education. Both enable easy information sharing within workgroups.
- A public network can be accessed by anyone, while a private network is locked down for the owner only. A leased line provides a dedicated symmetric telecommunications connection between two locations for a monthly fee.
- HTML defines web page formatting with tags, allowing hyperlinks between documents on the web. XML similarly defines data elements but allows custom tags, enabling it to function like a database.
This document is Ilaria Federici's alter-portfolio, showcasing artwork created for passion projects, friends, and competitions rather than chronologically. It includes designs for bands like 30 Seconds to Mars and Kings of Leon, such as pins, bookmarks, hoodies, and posters inspired by songs. It also shows paintings and illustrations in various styles, including replicas of famous works and life drawings. The portfolio serves to share a part of the artist and their thoughts through how they visualize music.
This chapter provides background on the author's experience in Haiti where he witnessed a mob attack on a woman. The author was sitting in a medical truck as the attack happened outside but did not intervene. The chapter then contrasts this with two previous occasions where the author was in fights to protect others - once in 1996 helping a woman being choked in an alley in Pittsburgh. It also describes the author's work with a priest in Haiti, loading medical supplies to bring into the dangerous Cite Soleil slum, though he was not prepared for the violence he would witness that day.
SpeakLike provides translation services through an online platform that uses crowdsourcing and machine translation. It can process translations quickly, with some texts translated in under an hour. The platform supports over 37 languages and has tools for companies to integrate translations into their websites, emails, chat, and other digital content. It aims to make expanding into new international markets faster and easier for businesses.
Web 1.0 focused on commerce while Web 2.0 emphasizes user participation and contribution. The concept of Web 2.0 emerged from a 2004 brainstorming session between O'Reilly and MediaLive International. Key principles of Web 2.0 include customization for individual users, harnessing collective intelligence by allowing users to contribute and edit content, and specialized databases to store user data. Web 2.0 applications are also characterized by a perpetual beta approach with frequent updates and a focus on services rather than single-device software.
The document summarizes a study that measured water permeability in different epithelial barriers (toad urinary bladder, rat caecum, distal human colon, and human amnion) under various conditions. The study simultaneously determined three parameters: 1) water permeability with a hydrostatic pressure gradient (Phydr), 2) water permeability with an osmotic gradient (Posm), and 3) transepithelial potential difference (dV). The results showed a good correlation between Phydr and dV but not between dV and Posm or between Posm and Phydr. Phydr was similar between toad bladders at rest and after vasopressin exposure but significantly higher with an osmotic gradient after vasopress
This document is Ilaria Federici's portfolio, which includes sections on her curriculum vitae, packaging design projects, logo design work, corporate design, poster design, and web design. The curriculum vitae section provides biographical information about Federici, including her education and qualifications, languages, IT skills, professional experiences, interests, and contact information.
O documento discute o gerenciamento da configuração de acordo com o Guia PMBOK. Ele define gerenciamento da configuração como um subsistema do gerenciamento de projetos que identifica, documenta, controla alterações e verifica a conformidade das características físicas e funcionais de um produto ou serviço. Além disso, o documento destaca que o gerenciamento da configuração se aplica ao ciclo de vida do produto e do projeto, identificando itens de configuração e controlando formalmente as mudanças.
Escopo custo e tempo gerando a qualidade do projetoSilas Serpa
Os primeiros conceitos que você precisa conhecer
Os 7 Passos da Gestão de Projetos
Triplice Restrição
Escopo
Custo
Tempo
Qualidade
Fatores Críticos do Sucesso
Palestra declaração do escopo é função do gerente de projetosSilas Serpa
Não se Gerencia o que não se Mede, não se Mede o que não se Define, não se Define o que não se Entende e não há Sucesso no que não se Gerencia.(William Edwards Deming)
Adidas is a sportswear company with a website at www.adidas-group.com. The document provides the company name and website but no other details. It was prepared by Robert Paul G. Magno, a student pursuing a BSIT degree.
데코레이터 함수는 다른 함수의 동작을 수정하거나 확장할 수 있는 함수입니다.
데코레이터 함수는 주로 다음과 같은 용도로 사용됩니다:
- 로깅, 메트릭 수집 등 추가 동작 수행
- 예외 처리
- 권한 확인
- 테스트 목적
OpenStack에서 데코레이터 함수는 주로 다음과 같이 사용됩니다:
1
The Leo Club meeting document announced upcoming events for club members to volunteer at, including glass crafting, catering, and the Midnight Vigil event. It also provided details on purchasing Leo t-shirts and sign-ups for the Christmas luncheon to welcome newcomers. A list of volunteers was included for the various events.
This document discusses the history and physiology of peritoneal dialysis. It describes how peritoneal dialysis evolved from early experiments in the 19th century to the development of continuous ambulatory peritoneal dialysis in the late 20th century. It also summarizes the anatomy of the peritoneum and various models that have been used to describe solute and fluid transport across the peritoneal membrane during dialysis.
1) Reverse osmosis membrane technology has advanced significantly since the 1950s. Early membranes allowed separation of salt from water but had low water fluxes, making the process impractical.
2) In the 1960s, Loeb and Sourirajan developed asymmetric cellulose acetate membranes with higher water fluxes and separations, making reverse osmosis separation possible on a practical scale.
3) Since then, new thin-film composite membranes have been developed that can withstand a wider range of conditions and have improved water flux and solute separation, enabling many reverse osmosis applications including desalination, wastewater treatment, and food processing.
The document discusses various methods and concepts related to measuring permeability across epithelial tissues, including the following key points:
- Short-circuit current (Isc) measures the sum of all active ion transport processes when the transepithelial potential is clamped to 0 mV. It provides information about epithelial function but is an unphysiological measurement.
- Electrical resistance (Rt) and open-circuit voltage (Vt) measurements can also be used to determine ion movement and epithelial function without short-circuiting the paracellular pathway.
- Tight junctions can vary in permeability between epithelia (tight vs leaky) and selectivity based on claudin composition, acting as aqueous pores or sie
1) The study demonstrated three-level trophic transfer of quantum dots (QDs) in an aquatic food chain, from protozoa (Astasia longa) to zooplankton (Moina macrocopa) to fish (Danio rerio).
2) Using bioimaging techniques like fluorescence microscopy and multiphoton laser scanning microscopy, the researchers were able to visually observe the transfer of QDs from A. longa exposed to QDs to M. macrocopa which consumed the protozoa, and then from M. macrocopa to D. rerio which consumed the zooplankton.
3) Measurement of cadmium concentration in the organisms using I
Simulation of Pollution Transport in Coastal Aquifers under Tidal MovementsAmro Elfeki
). Simulation of Pollution Transport in Coastal Aquifers under Tidal Movements. Presented at the Workshop on Environmental Pollution at Coastal Areas, Organized by Water Recourses Center at King Abdulaziz University, Jeddah, Saudi Arabia.
This study compared the movement of wild-caught guppies from Trinidadian rivers to laboratory-reared guppies in a circular flow tank. The tank was divided into zones of different water flow speeds and each fish's movement was video recorded for 5 minutes. While the total distance traveled did not differ between groups, the laboratory-reared guppies had a higher mean velocity in the faster flow zones, suggesting differences in rheotactic behavior when facing currents. This preliminary data will inform a larger study on how predation level and habitat affect guppy rheotaxis.
The study explored the effects of low salinity water on ion transporter expression and distribution in the gill of the longhorn sculpin (Myoxocephalus octodecimspinosus). Sculpins were exposed to 10% or 20% seawater for 24 or 72 hours. Exposure to 10% seawater resulted in 20-25% lower plasma ion levels but did not affect transporter localization or expression. Sculpins maintained ion levels in 20% seawater and showed no physiological effects. The results suggest sculpins can tolerate brackish water for days but not long term due to an inability to regulate transporters at low salinities.
Longhorn sculpin are traditionally considered marine fish but can be found in estuaries during high tide. This study explored the effects of low salinity exposure on ion transporter expression and distribution in the longhorn sculpin gill over 24 and 72 hours. Sculpin exposed to 20% seawater for 24-72 hours were able to regulate ion levels normally, but exposure to 10% seawater resulted in a 20-25% loss of ions with no change in transporter expression or localization. This suggests sculpin can tolerate brackish water for days but not long periods at lower salinities due to an inability to regulate transporters.
The document discusses various biological processes related to digestion, transport, and excretion. It includes topics like the levels of biological organization, different modes of nutrient acquisition like suspension feeding and substrate feeding, and membrane transport mechanisms like diffusion, osmosis, and aquaporins. It also covers organ system functions, comparing the digestive and excretory systems of carnivores and herbivores, as well as osmoregulation in fish and mammals.
The steady-state Starling principle throws a whole new light on fluid physiology. We now know that most capillaries filter fluid to the interstitium but cannot reabsorb filtered fluid because of a one-way mechanism called the Michel-Weinbaum model.
As a consequence filtered fluid circulates back to the cardiovascular system as lymph, and the lymphatics are a vital circulatory system.
The balance between intravascular volume (plasma) and extrascular volume (tissue fluid/ edema) can be manipulated if we apply our appreciation of the new physiology to rational treatment strategies.
The document summarizes a study of the near-contact-line dynamics of evaporating sessile drops containing bacteria. As the drop evaporates, an internal flow develops that transports bacteria outward and concentrates them near the contact line, where experiments show they form periodic jets. The study develops a theoretical model and numerical simulation of the averaged flow properties and bacteria behavior. Initial 1D simulations show bacteria transitioning from isotropic to aligned with flow near the edge, and bacteria density peaking near the edge matching experiments. Future 2D simulations aim to reproduce the periodic jet pattern observed.
Modeling dispersion under unsteady groundwater flow conditionsAmro Elfeki
This presentation is for and MSc Student working on some of the projects at TU Delft. The thesis title is: Modeling dispersion under unsteady groundwater flow conditions.
The document summarizes a study that measured water permeability in different epithelial barriers (toad urinary bladder, rat caecum, distal human colon, and human amnion) under various conditions. The study simultaneously determined three parameters: 1) water permeability with a hydrostatic pressure gradient (Phydr), 2) water permeability with an osmotic gradient (Posm), and 3) transepithelial potential difference (dV). The results showed a good correlation between Phydr and dV but not between dV and Posm or between Posm and Phydr. Phydr was similar between toad bladders at rest and after vasopressin exposure but significantly higher with an osmotic gradient after vasopress
This document is Ilaria Federici's portfolio, which includes sections on her curriculum vitae, packaging design projects, logo design work, corporate design, poster design, and web design. The curriculum vitae section provides biographical information about Federici, including her education and qualifications, languages, IT skills, professional experiences, interests, and contact information.
O documento discute o gerenciamento da configuração de acordo com o Guia PMBOK. Ele define gerenciamento da configuração como um subsistema do gerenciamento de projetos que identifica, documenta, controla alterações e verifica a conformidade das características físicas e funcionais de um produto ou serviço. Além disso, o documento destaca que o gerenciamento da configuração se aplica ao ciclo de vida do produto e do projeto, identificando itens de configuração e controlando formalmente as mudanças.
Escopo custo e tempo gerando a qualidade do projetoSilas Serpa
Os primeiros conceitos que você precisa conhecer
Os 7 Passos da Gestão de Projetos
Triplice Restrição
Escopo
Custo
Tempo
Qualidade
Fatores Críticos do Sucesso
Palestra declaração do escopo é função do gerente de projetosSilas Serpa
Não se Gerencia o que não se Mede, não se Mede o que não se Define, não se Define o que não se Entende e não há Sucesso no que não se Gerencia.(William Edwards Deming)
Adidas is a sportswear company with a website at www.adidas-group.com. The document provides the company name and website but no other details. It was prepared by Robert Paul G. Magno, a student pursuing a BSIT degree.
데코레이터 함수는 다른 함수의 동작을 수정하거나 확장할 수 있는 함수입니다.
데코레이터 함수는 주로 다음과 같은 용도로 사용됩니다:
- 로깅, 메트릭 수집 등 추가 동작 수행
- 예외 처리
- 권한 확인
- 테스트 목적
OpenStack에서 데코레이터 함수는 주로 다음과 같이 사용됩니다:
1
The Leo Club meeting document announced upcoming events for club members to volunteer at, including glass crafting, catering, and the Midnight Vigil event. It also provided details on purchasing Leo t-shirts and sign-ups for the Christmas luncheon to welcome newcomers. A list of volunteers was included for the various events.
This document discusses the history and physiology of peritoneal dialysis. It describes how peritoneal dialysis evolved from early experiments in the 19th century to the development of continuous ambulatory peritoneal dialysis in the late 20th century. It also summarizes the anatomy of the peritoneum and various models that have been used to describe solute and fluid transport across the peritoneal membrane during dialysis.
1) Reverse osmosis membrane technology has advanced significantly since the 1950s. Early membranes allowed separation of salt from water but had low water fluxes, making the process impractical.
2) In the 1960s, Loeb and Sourirajan developed asymmetric cellulose acetate membranes with higher water fluxes and separations, making reverse osmosis separation possible on a practical scale.
3) Since then, new thin-film composite membranes have been developed that can withstand a wider range of conditions and have improved water flux and solute separation, enabling many reverse osmosis applications including desalination, wastewater treatment, and food processing.
The document discusses various methods and concepts related to measuring permeability across epithelial tissues, including the following key points:
- Short-circuit current (Isc) measures the sum of all active ion transport processes when the transepithelial potential is clamped to 0 mV. It provides information about epithelial function but is an unphysiological measurement.
- Electrical resistance (Rt) and open-circuit voltage (Vt) measurements can also be used to determine ion movement and epithelial function without short-circuiting the paracellular pathway.
- Tight junctions can vary in permeability between epithelia (tight vs leaky) and selectivity based on claudin composition, acting as aqueous pores or sie
1) The study demonstrated three-level trophic transfer of quantum dots (QDs) in an aquatic food chain, from protozoa (Astasia longa) to zooplankton (Moina macrocopa) to fish (Danio rerio).
2) Using bioimaging techniques like fluorescence microscopy and multiphoton laser scanning microscopy, the researchers were able to visually observe the transfer of QDs from A. longa exposed to QDs to M. macrocopa which consumed the protozoa, and then from M. macrocopa to D. rerio which consumed the zooplankton.
3) Measurement of cadmium concentration in the organisms using I
Simulation of Pollution Transport in Coastal Aquifers under Tidal MovementsAmro Elfeki
). Simulation of Pollution Transport in Coastal Aquifers under Tidal Movements. Presented at the Workshop on Environmental Pollution at Coastal Areas, Organized by Water Recourses Center at King Abdulaziz University, Jeddah, Saudi Arabia.
This study compared the movement of wild-caught guppies from Trinidadian rivers to laboratory-reared guppies in a circular flow tank. The tank was divided into zones of different water flow speeds and each fish's movement was video recorded for 5 minutes. While the total distance traveled did not differ between groups, the laboratory-reared guppies had a higher mean velocity in the faster flow zones, suggesting differences in rheotactic behavior when facing currents. This preliminary data will inform a larger study on how predation level and habitat affect guppy rheotaxis.
The study explored the effects of low salinity water on ion transporter expression and distribution in the gill of the longhorn sculpin (Myoxocephalus octodecimspinosus). Sculpins were exposed to 10% or 20% seawater for 24 or 72 hours. Exposure to 10% seawater resulted in 20-25% lower plasma ion levels but did not affect transporter localization or expression. Sculpins maintained ion levels in 20% seawater and showed no physiological effects. The results suggest sculpins can tolerate brackish water for days but not long term due to an inability to regulate transporters at low salinities.
Longhorn sculpin are traditionally considered marine fish but can be found in estuaries during high tide. This study explored the effects of low salinity exposure on ion transporter expression and distribution in the longhorn sculpin gill over 24 and 72 hours. Sculpin exposed to 20% seawater for 24-72 hours were able to regulate ion levels normally, but exposure to 10% seawater resulted in a 20-25% loss of ions with no change in transporter expression or localization. This suggests sculpin can tolerate brackish water for days but not long periods at lower salinities due to an inability to regulate transporters.
The document discusses various biological processes related to digestion, transport, and excretion. It includes topics like the levels of biological organization, different modes of nutrient acquisition like suspension feeding and substrate feeding, and membrane transport mechanisms like diffusion, osmosis, and aquaporins. It also covers organ system functions, comparing the digestive and excretory systems of carnivores and herbivores, as well as osmoregulation in fish and mammals.
The steady-state Starling principle throws a whole new light on fluid physiology. We now know that most capillaries filter fluid to the interstitium but cannot reabsorb filtered fluid because of a one-way mechanism called the Michel-Weinbaum model.
As a consequence filtered fluid circulates back to the cardiovascular system as lymph, and the lymphatics are a vital circulatory system.
The balance between intravascular volume (plasma) and extrascular volume (tissue fluid/ edema) can be manipulated if we apply our appreciation of the new physiology to rational treatment strategies.
The document summarizes a study of the near-contact-line dynamics of evaporating sessile drops containing bacteria. As the drop evaporates, an internal flow develops that transports bacteria outward and concentrates them near the contact line, where experiments show they form periodic jets. The study develops a theoretical model and numerical simulation of the averaged flow properties and bacteria behavior. Initial 1D simulations show bacteria transitioning from isotropic to aligned with flow near the edge, and bacteria density peaking near the edge matching experiments. Future 2D simulations aim to reproduce the periodic jet pattern observed.
Modeling dispersion under unsteady groundwater flow conditionsAmro Elfeki
This presentation is for and MSc Student working on some of the projects at TU Delft. The thesis title is: Modeling dispersion under unsteady groundwater flow conditions.
This document discusses fluid management during surgery. It begins by reviewing human physiology related to fluid distribution and movement. About 70% of body weight is water distributed between intracellular and extracellular spaces. Fluid movement is regulated by osmolarity, oncotic pressure, the renin-angiotensin-aldosterone system, and other hormonal systems. The document then focuses on fluid movement at the capillary level in peripheral tissues versus the blood-brain barrier in the central nervous system. It explains how fluid movement is governed by the Starling forces and describes differences between capillaries and the unique properties of the blood-brain barrier.
Pptx of slides for jones ray effect finalpatrons99
This document proposes a new unified theory of disease based on the Jones-Ray effect, which describes how certain salts affect the surface tension of water. It suggests that the Jones-Ray effect influences interfacial tensions in the body, which are important for processes like cell engulfment and signaling. Electron micrographs show how cholesterol sulfate can stabilize red blood cell membranes by reducing water stress at interfaces. The theory posits that membrane-bound water exhibits quantum properties and waves that resonate between exclusion zones and cell membranes. Maintaining optimal interfacial tensions may be clinically significant for conditions like membrane stability and neuroreceptor function.
This document discusses the history and physiology of peritoneal dialysis. It outlines the key contributors to the development of PD from the 1800s onward. It then describes the anatomy of the peritoneal membrane and its blood supply. The three pore model of peritoneal transport is explained, including diffusion, convection, ultrafiltration and their roles in solute and fluid removal. Long term changes to the peritoneal membrane are also summarized.
This document discusses fluid, electrolyte and acid-base balance. It defines normal ranges for electrolytes like sodium, potassium, calcium and chloride. It describes the differences between intracellular and extracellular fluid compartments and how fluid moves between compartments via osmosis and active transport. Key concepts covered include fluid balance, calculating fluid deficits, and the roles of antidiuretic hormone and aldosterone in maintaining fluid homeostasis.
(I) The document discusses different types of transport across cell membranes, including diffusion, facilitated diffusion, active transport, and vesicular transport.
(II) It also discusses concepts like the Donnan effect, which describes how a nondiffusible ion on one side of a membrane affects the distribution of diffusible ions.
(III) The Gibbs-Donnan equilibrium establishes that at equilibrium, the concentration ratios of diffusible ions will be equal across a membrane permeable to some ions but not others.
1. biology the Cell, (1989) 145-148
of 66 145
@ Elsevier, Paris
Water permeability in different epithelial barriers
C. CAPURRO, E. ESCOBAR, C. IBARRA, M. PORTA and M. PARIS1
Section de Biomembranas, Departamento de Fisiologia, Facultad de Medicina, Universidad de Buenos Aires, Argentina
Thewater permeability properties of a series of epithelial barriers(the toad urinary bladder [TUB], the rat caecum CRC],
the distal human colon [DHC], and the human amnion [DA] were studied in different experimental conditions. Three
parameterswere simultaneously determined: t?le water permeability coefficient in the presence of a transepithelial
hydrostaticgradient (P,,); the water permeability coefficient in the presence of an osmotic gradient (PO,,); and the
transepithelialpotential difference (dV). AR experiments were performed with the same experimental device, allowing
comparison of the permeability properties of the barriers tested. The results obtained were : (1) TUB (N= 8) :
= 0.079 f 0.008 cm/s ; P,,, = 0.0004 f 0.0002 cm/s; dV = 31 f 5 mV ; (2) TUB after ADH (N= 8) :
FlE= 0.093 f 0.012 cm/s; P =0.0065~0.0011 cm/s; dV=52&8; (3) RC (N=lO): P,,,=O.18&0.02 cm/s;
= 0.0019 f 0.0004 cm/s; iv= 3.9 f 0.1 mV ; (4) RC adapted to a high K diet (N = 10) : Pbydr 0.21 f 0.02 cm/s;
=
:= = 0.0018 f 0.0006 cm/s ; dV = 4.5 f 0.5 mV ; (5) DHC (N = 6) : P,, dr= 0.22 f 0.03 cm/s ; Posm 0.002 f 0.05 cm/s ;
=
dv%5f3 mV; (6) HA (N=lO): P,,,=O.32&0.05 cm/s; Posm=0.0154 f 0.9015 ; dV = 0. The results show a good cor-
relation between Pnvac and dV, but not between dV and P,,, or between Posmand P,,,.
toad bladder - rat caecum - distal human colon - human amnion
INTRODUCTION MATERIALS AND METHODS
Fromter Diamondin a worknow considered
and classical The tested epithelial barriers were placed as a diaphragm bet-
161,
classifiedepithelialbarriers “tight” and “leaky”.
as ween 2 lucite chambers, and the transepithelialnet water flux
The criterion employed to state, for example, that the pro- (Jw) was measuredat 1-minintervals by a techniquepreviously
ximal convoluted tubule of the kidney is a leaky barrier, described[I]. In most experiments2 fragmentsof the same tissue
whereas the collector tube is a tight one, was transepi- were tested simultan!zously. The transepithelial potential dif-
thelial conductance. This situation is reflected in the ference (dV) was measured through conventional agar bridges
and calomel electrodes.
transepithelial potential difference (dV) that, in general,
increases with barrier tightness. The net water movements
observed in epithelia were also divided, according to their Tissuesemployid
origins, into 2 main groups : (1) the so called “isotonic
transfer”, which is associated with an ionic transport in Human amniotic membranes were obtained immediatelyafter
the absence of any transepithelial gradient [3, 1l] ; and uncomplicatedterm vaginaldelivery. They were separatedfrom
(2)the osmoticallydriven net water flux, of which the the other placental tissuesand mounted, as previouslydescrib-
classical
example is the flux controlledby antidiuretic ed, for permeabilitymeasurements.Fragmentsof human distal
hormone (ADH) in some tight epithelia. There is general colons (sigmoidor rectum) were obtained from surgicallyextir-
agreement that in ADH-sensitive tissues water moves pated organsin patientswithcanceror other diseases.Immediate-
mainly transcellularly, with the regulatory barrier located ly after ablation, apparently nonaffected regionswere dissected
in the apical border of the target cell [7,8]. Much less clear free, and the mucosaland submucosal layerswereseparatedfrom
is the case of isotonic transfer, where the relative the underlying tissues and mounted for permeability
significance of transcellular and paracellular routes for measurements. Human materialswereobtainedfrom the Univer-
sity Hospital (Hospital de Clinicas)at Buenos Aires, according
water movement is still under discussion [S, 141. to the formal rules of this institution.
We have now studied a series of epithelial barriers (toad The rat caecum was removed immediately after decapitation
urinary bladder, rat caecum, distal human colon, and of the animal, washed, opened sagitally, and placed in the ex-
human amnion) in different experimental conditions. perimental chamber, Two groups of rats (Wistar) were studied :
Three parameters were simultaneously determined : water the first group was fed normally, whilst the other received a high
permeability in the presence of a transepithelial hydrostatic potassium diet (HKD) for 10 d before the experiments.
gradient (P,, &; water permeability in the presence of Toad urinary bladders were obtained from pithed animals
a transepitheiial osmotic gradient (PO,,); and dV. All ex- (Bufo arenarum) originating from the Buenos Aires area and
periments were performed by means of the same ex- mounted for.permeability measurements as previously describ-
ed. Mammalian tissues were incubated at 37°C during the ex-
perimental device, thus allowing a valid comparison of the periments and toad bladders at 20°C. Both sides of the
permeability properties of the different epithelial barriers. preparations were bathed with the same saline solution. The
The results obtained show a good correlation between 2 basic compositions were the following : Mammaliah tissues
l&, and dV, but not between dV and Posm or between (mM): 114 NaCl, 5 KCI, 1.2 CaCl,, 25 NaHCOJ, 5 glucose,
‘OS~and phydr* 2.4 K,HPO,, 1.O KH,PO, ; Toad urinary bladder MM) :
3. Water permeability in epithelia 147
/
1. 0.26.G00 ( n . 6 ) 9"HUMAN AMNION tal device with different tissues and it can be accepted that
2- O. 18-~G03 ( n . 7) / in all cases, the leaky path was similar. Two observations
- 3. O. 17.G02 ( n . 7 ) /
/ AO
indicate that it does not bring a major contribution to the
4. O. 1 6 * G 0 4 ( . . 6 ) / .,
5BO.O3t(X02 (n.lO) ~ / observed Jw: (1) The lowest Phydr values were observed
/ 4p~TOAD BLADDER in the toad urinary bladder, the tissue that shows the
highest mechanical fragility; (2) The observed dV values
So~ in different tissues were similar to those previously
¢
reported in acceptable experimental conditions [2, 10]. It
can also be mentioned here that in the human amnion the
observed Ph..dr was sensitive to changes in the pH of the
medium [9]. This result indicates that in this tissue, which
AN COLON shows the highest Phydr values, the parameter represents
the paracellular path.
~P'~/~ ~"~'- - TOAD BLADDER
- CONTROL Figure 2 and Table I indicate that Phydr ranged from
7.9:i:0.8×10 -2 cm/s in the toad urinary bladder to
0 I/ I I J_ . - 3 2 + 5 × 10 -2 cm/s in the human amnion. These values
:f 2o 40 co - can be compared with the 15 × 10 -2 cm/s previously
PEG (mOsm)
reported in the rabbit gallbladder epithelium [13]. When
FIOURE3. -- The observed Jw as a function of the applied a correlation plot was made between P hydr and dV a
osmotic gradient in different epithelial barriers. Regression lines negative and statistically significant potential correlation
calculated as in Fig. 2. 1, 2, 3, 4, and $ represent the calculated was observed (r = 0.9 + 0.1, P < 0.05; Fig. 4). This would
ordinate intercept• indicate that in general, leaky barriers have higher
hydraulic permeabilities and conversely, tight epithelia
Spontaneouspotential difference
Table I shows the spontaneously observed potential dif-
ferences, 10 rain after mounting, in different epithelial bar- I MAN AMNION
riers. The Phydr and Po,m values are also represented. It
can be observed that K-adaptation induced an important
U
increase in dV with no change in Phydr or Posm" On the 0
W
other hand, ADH action increased dV and Posm in the ,~A.-,-.u,-(1) Control
toad urinary bladder, with no change in Phydr" 6 20 ...... "~(a) HKD
ul
,g HUMAN COLON
w TOAD BLADDER
lo " ~,,,~.Control' "ADH
DISCUSSION
z
It is generally accepted that hydrostatic pressure, in the
range employed in this study (24.4 cm H20 = lmOsM), I I I _
0 25 50 -
does not move water transcellularly. The observed Jw can Transepitheilal potential (mV)
thus take place only in a paracellular or a leaky pathway
(the last resulting from damage to cells or from any other FIOURE 4. - Correlation plot between the observed Phydr and
artifactual path generated during membrane manipulation transepithelial potential values in different epithelial barriers. The
and mounting). We employed here the same experimen- curve represents the regression potential function (r = 0.9 ± 0.1).
TABLEI. - Water permeability coefficients and potential differences in epithelial barriers.
N Phydr* (cm'sec-l'102) Posm**(cm'sec-t'102) V (mV)
Toad bladder control 8 7.94-0.8 O.04+0.O2 31.0±5.0
Toad bladder + ADH 8 9.3 4-1.2 0.65+0.11 52.0 + 8.0
Human colon 6 22.0 4-3.0 0.2O+0.O5 15.0+3.0
Rat caecum 10 18.0±2.0 0.19±0.04 3.9+0.1
Rat caecum + HKD 6 21.0±2.0 0.18±0.06 8.5+0.5
Human amnion 10 32.04-5.0 1.544-0.15 0
*Phydr: water permeability coefficient (Pf) under hydrosmotic pressure•
** Posm: water permeability coefficient (Pf) under osmotic gradient.
4. 148 C. Capurro et al.
show low Ph-dr values. It must be remarked however, that
. • 3' . • • • • •
m 2 cases m which dV was increased m a specific barrier ~ HUMANAMNION
(ADH action in toad urinary bladder or K-adaptation in
the rat caecum), there were no changes in the correspond-
ing Phydr- .
The observeo values for Posm ranged from O.08x 2
10 -2 cm/s for the toad bladder at rest to 1.5 x 10 -2 cm/s ~" 1.O
|
in the human umnion (compared to 0.93 x 10 -2 cm/s in
the rabbit gall bladder epithelium [13]• These results would
indicate that the hydrostatic pressure was between 30 and g
100 times more effective than the osmotic gradient in driv- 8 o.~ I ADH
ing a net water flux in the amnion. It must be considered,
however, that our Posm values (measured in steady-state i-.. ; ; COLON
HUMAN
, TOAD t
B'AODE.
conditions) are probably underestimated because of the I --~_ co.Jro0
"sweeping away" and "solute polarization" phenomena ,AT=ECU. . . . . ,
associated with the presence of unstirred layers [3]. Never- O 25 50 "
theless, and because all experiments were made in the same Transepithelial potential (mV)
expe"nmental conditions, we can accept, as a first approach
to the problem, that the values obtained in different tissues FIGURE6. -- Correlation plot between osmotic permeability and
(all representing a single cell layer and having similar total transepithelial potential in different epithelial barriers.
thickness) can be compared.
Figures 5 and 6 show that no clear correlation was
observed between Ph-dr and Posm or between Posm
• . .v
and Vd. This ts probably due to the fact, in addition to
the unstirred layer problem previously described, that
water may be moved osmotically either between the cells
or through the cells [4, 14]. Interestingly enough, some REFERENCES
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w;'
0
0
1-15
m
11 Sackim H. & Boulpaep E.L. (1975) Model for coupling of
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UMAN COLON Necturus kidney. J. Oen. Physiol. 66, 671-734
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