WordNet

set so close together as to be invulnerable to penetration; "in tight formation"; "a tight blockade"
affected by scarcity and expensive to borrow; "tight money"; "a tight market"
closely constrained or constricted or constricting; "tight skirts"; "he hated tight starched collars"; "fingers closed in a tight fist"; "a tight feeling in his chest"
of such close construction as to be impermeable; "a tight roof"; "warm in our tight little house"
packed closely together; "they stood in a tight little group"; "hair in tight curls"; "the pub was packed tight"
securely or solidly fixed in place; rigid; "the bolts are tight"
the state of being joined together (同)conjunction, conjugation, colligation
an act of joining or adjoining things (同)adjunction
something that joins or connects (同)conjunction
the place where two or more things come together
skintight knit hose covering the body from the waist to the feet worn by acrobats and dancers and as stockings by women and girls (同)leotards

PrepTutorEJDIC

『きっちり締まった(結ばれた)』 / 『すきまのない』,(水・空気などの)漏らない / 『ぴんと張った』 / (衣服などが)『きつい』 / (時間的・空間的に)余裕のない,ぎっしり詰まった / (立場などが)困難な,扱いにくい / 厳しい / 《話》けちな(stingy) / 《話》(試合などが)互角の / 《俗》酔った / (品物・仕事・取り引きなどが)試底した,詰まった,(金融が)ひっ迫した
〈U〉〈C〉連結すること(された状態),『結合』,連合,合体 / 〈C〉『結合点』,連結(接合,合流)点 / 〈C〉(鉄道の)『連絡駅』,接続駅
(軽業師・舞踊家・婦人・少女などが履く)タイツ

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/22 23:40:34」(JST)

wiki en

Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens), are the closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier to fluid. It is a type of junctional complex present only in vertebrates. The corresponding junctions that occur in invertebrates are septate junctions.

Structure

Tight junctions are composed of a branching network of sealing strands, each strand acting independently from the others. Therefore, the efficiency of the junction in preventing ion passage increases exponentially with the number of strands. Each strand is formed from a row of transmembrane proteins embedded in both plasma membranes, with extracellular domains joining one another directly. Although more proteins are present, the major types are the claudins and the occludins. These associate with different peripheral membrane proteins such as ZO-1 located on the intracellular side of plasma membrane, which anchor the strands to the actin component of the cytoskeleton. Thus, tight junctions join together the cytoskeletons of adjacent cells.

Functions

They perform vital functions:^[1]

They hold cells together.
Barrier function, which can be further subdivided into protective barriers and functional barriers serving purposes such as material transport and maintenance of osmotic balance:
- Tight Junctions help to maintain the polarity of cells by preventing the lateral diffusion of integral membrane proteins between the apical and lateral/basal surfaces, allowing the specialized functions of each surface (for example receptor-mediated endocytosis at the apical surface and exocytosis at the basolateral surface) to be preserved. This aims to preserve the transcellular transport.
- Tight Junctions prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells, so materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue. Investigation using freeze-fracture methods in electron microscopy is ideal for revealing the lateral extent of tight junctions in cell membranes and has been useful in showing how tight junctions are formed.^[2] The constrained intracellular pathway exacted by the tight junction barrier system allows precise control over which substances can pass through a particular tissue. (Tight junctions play this role in maintaining the blood–brain barrier.) At the present time, it is still unclear whether the control is active or passive and how these pathways are formed. In one study for paracellular transport across the tight junction in kidney proximal tubule, a dual pathway model is proposed: large slit breaks formed by infrequent discontinuities in the TJ complex and numerous small circular pores.^[3]

In human physiology there are two main types of epithelia using distinct types of barrier mechanism. Dermal structures such as skin form a barrier from many layers of keratinised squamous cells. Internal epithelia on the other hand more often rely on tight junctions for their barrier function. This kind of barrier is mostly formed by only one or two layers of cells. It was long unclear whether tight cell junctions also play any role in the barrier function of the skin and similar external epithelia but recent research suggests that this is indeed the case.^[4]

Classification

Epithelia are classed as "tight" or "leaky", depending on the ability of the tight junctions to prevent water and solute movement:^[5]

Tight epithelia have tight junctions that prevent most movement between cells. Examples of tight epithelia include the distal convoluted tubule, the collecting duct of the nephron in the kidney, and the bile ducts ramifying through liver tissue.
Leaky epithelia do not have these tight junctions, or have less complex tight junctions. For instance, the tight junction in the kidney proximal tubule, a very leaky epithelium, has only two to three junctional strands, and these strands exhibit infrequent large slit breaks.

References

^ Department, Biology. Davidson College http://www.bio.davidson.edu/people/kabernd/berndcv/lab/epithelialinfoweb/Tight%20Junctions.html. Retrieved 2013-09-20. Missing or empty |title= (help)
^ Chalcroft, J. P.; Bullivant, S (1970). "An interpretation of liver cell membrane and junction structure based on observation of freeze-fracture replicas of both sides of the fracture". The Journal of Cell Biology 47 (1): 49–60. doi:10.1083/jcb.47.1.49. PMC 2108397. PMID 4935338.
^ Guo, P; Weinstein, AM; Weinbaum, S (Aug 2003). "A dual-pathway ultrastructural model for the tight junction of rat proximal tubule epithelium.". American journal of physiology. Renal physiology 285 (2): F241–57. doi:10.1152/ajprenal.00331.2002. PMID 12670832.
^ Kirschner, Nina; Brandner, JM (June 2012). "Barriers and more: functions of tight junction proteins in the skin.". Annals of the New York Academy of Sciences 1257: 158–166. doi:10.1111/j.1749-6632.2012.06554.x.
^ Department, Biology. "Tight Junctions and other cellular connections". Davidson College. Retrieved 2013-09-20.

External links

An Overview of the Tight Junction at Zonapse.Net
Occludin in Focus at Zonapse.Net
Tight Junctions at the US National Library of Medicine Medical Subject Headings (MeSH)
Histology image: 20502loa – Histology Learning System at Boston University

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. Chapter 1A：腎機能の概要 chapter 1a introduction to renal function
2. Chapter 3A：近位尿細管輸送の細胞モデル chapter 3a cell model for proximal transport
3. Chapter 5A：遠位尿細管と接合部分 chapter 5a distal tubule and connecting segment
4. マグネシウムバランスの調節 regulation of magnesium balance
5. 乳汁分泌の生理学 physiology of lactation

English Journal

EGF Regulates Claudin-2 and -4 Expression Through Src and STAT3 in MDCK Cells.

García-Hernández V1, Flores-Maldonado C, Rincon-Heredia R, Verdejo-Torres O, Bonilla-Delgado J, Meneses-Morales I, Gariglio P, Contreras RG.
Journal of cellular physiology.J Cell Physiol.2015 Jan;230(1):105-15. doi: 10.1002/jcp.24687.
Epidermal Growth Factor (EGF) is a key regulator of epithelial paracellular permeability, a property that depends on tight junctions (TJ) and can be evaluated through the measurement of the transepithelial electrical resistance (TER). EGF increases the TER of MDCK monolayers by inducing ERK1/2-depen
PMID 24909426

Biocompatibility and inflammatory response in vitro and in vivo to gelatin-based biomaterials with tailorable elastic properties.

Ullm S1, Krüger A2, Tondera C1, Gebauer TP3, Neffe AT3, Lendlein A3, Jung F3, Pietzsch J4.
Biomaterials.Biomaterials.2014 Dec;35(37):9755-66. doi: 10.1016/j.biomaterials.2014.08.023. Epub 2014 Sep 5.
Hydrogels prepared from gelatin and lysine diisocyanate ethyl ester provide tailorable elastic properties and degradation behavior. Their interaction with human aortic endothelial cells (HAEC) as well as human macrophages (Mɸ) and granulocytes (Gɸ) were explored. The experiments revealed a good bi
PMID 25199786

TLR4/PKC-mediated tight junction modulation: A clinical marker of chemotherapy-induced gut toxicity?

Wardill HR1, Gibson RJ, Logan RM, Bowen JM.
International journal of cancer. Journal international du cancer.Int J Cancer.2014 Dec 1;135(11):2483-92. doi: 10.1002/ijc.28656. Epub 2014 Jan 10.
Chemotherapy-induced gut toxicity is a major clinical and economic burden to oncology practice. The mechanisms responsible for its development are ill defined, hampering the development of therapeutic interventions. In light of newly published research foci and clinical practice guidelines in suppor
PMID 24310924

Japanese Journal

Claudin-1 Is Associated with Invasive Growth of Human Pancreatic Cancer Cells

Kondo Jun,Sato Fuyuki,Wu Yunyan,Seino Hiroko,Morohashi Satoko,Kijima Hiroshi
弘前医学 63(2-4), 127-135, 2012-11-30
… Claudin is one of tight junction proteins which connect with the actin cytoskeleton and participate in the intracellular signaling. …
NAID 120004994680