Collagen fibers carry out the scaffold the resists tensile forces, if the proteoglycan aggregates provide a hydrated, viscous gelatin that absorbs compressive forces.

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From: Encyclopedia of Immunology (Second Edition), 1998

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Collagen fibers are the many abundant type of yarn in one extracellular procession of connective tissue; this is also the situation for connective organization within a ar of the peripheral nerve. Nowadays we know practically 30 types of collagen molecules, however 4 basic types are many represented. Collagen form I is the many common, and also can be discovered in the dense connective tissue of the epineurium, along with collagen form II. Type III collagen, coated with a great of polysaccharides, is responsible for developing reticular fibers, very abundant in the connective tissue of the peripheral nerve, mostly in the endoneurium and also the perineurium. Usually (but mostly collagen form I), collagens room eosinophilic structures, therefore they are stained in pink as soon as using hematoxylin and eosin stain. However, eosin does not help us in differentiating collagen from cell cytoplasm or nerve fibers. So, many particular and selective staining approaches for visualizing collagen in ~ tissues have actually been developed. Instances of these room staining through aniline blue (collagen fibers space light blue), however typically trichrome staining techniques are used; techniques benefiting from a mixture of assorted dyes. From these dyes, one is always simple (for staining cell nuclei), another one is acidic (for cytoplasm), and also the third is certain for collagen fibrils. The an initial account the a triple stain was by Gibbs in 1880. Us can identify four straightforward trichromes:

Yellow trichrome (hematoxylin + eosin + saffron or tartrazine): collagen fibers space yellow, and also cell nuclei space blue.

Red trichrome (hematoxylin + eosin + acid fuchsin, xylidine ponceau, chromotrope 2R, biebrich scarlet, ponceau 6R, or phloxine): collagen fibers room red.

Blue trichrome (iron hematoxylin, either Weigert’s or Heidenhain’s hematoxylin + acid fuchsin + anilin blue, methyl blue, or water blue): collagen fibers are blue, and also cell nuclei space brownish black.


Green trichrome (iron hematoxylin + light green + orange G): most regularly used method, collagen fibers room in shades that green, and also the cabinet nuclei space brownish black color (Figure 6.9).



Ten percent neutral buffered formalin will certainly not yield optimal trichrome staining results. The much longer tissues remain in formalin fixatives, the less optimal the staining results. Trichromes are regularly named according to the discoverer. For example, Masson’s trichrome (Table 6.4), van Gieson's, Gömöri's, and Lendrum’s. However, trichrome staining is utilized mostly in pathology as the stain of selection for separating histological changes in tumors, connective organization diseases, muscle and fibroblast tumors, renal diseases, and dermatology cases. In neuropathology, in case of nerve biopsies, reactive fibrosis (scarring) in in between the small nerve processes and in between groups the them have the right to be assessed with the trichrome staining method.


Table 6.4. The Procedure for Staining Paraffin Sections through Masson’s Trichrome


1.

Staining1.Weigert’s stole hematoxylin (2 min)

2.

Distilled water—rinse

3.

Running water (3-10 min)

4.

1% acetic acid

5.

Distilled water—rinse

6.

Diluted ponceau fuchsin (4-20 s)a.Solution A:i.fuchsin S—1 g

ii.

1% acetic acid—200 mL

b.

Solution B:i.ponceau geigi—1 g

ii.

1% acetic acid—200 mL

7.

Distilled water—rinse (3 ×)

8.

1% phosphomolybdic acid (10 min, 2 ×)

9.

Light eco-friendly (2-5 min)a.dye—2.5 g

b.

distilled water—160 mL

c.

1% acetic acid—2.5 mL

10.

Distilled water—rinse (2 ×)

11.

1% acetic acid

2.

Dehydration1.96% alcohol (2 min)

2.

96% alcohol (2 min)

3.

Dry thoroughly

3.

Clearing1.Xylene i (2 min)

2.

Xylene II (2 min)

4.•

Various acrylic resins


Anne M. Robertson, Paul N. Watton, in carry in organic Media, 2013

8.6.7.5.1 The Collagen Fiber attachment Stretch λfa

Collagen fibers room in a regular state of deposition and also degradation in the present configuration κ. Vascular cells (fibroblasts in the adventitia and vascular smooth muscle cell in the media) job-related on the collagen fibers to affix them to the matrix in a state of stretch in this configuration. Consequently, the recruitment construction κR is inferred from the stretch in ~ which fibers room configured and also attached to the extracellular matrix in the present configuration κ. Top top this note, that is important to identify that the matrix is pulsating and also thus it is desirable for the an interpretation of the attachments stretch to explicitly take this right into account. Watton et al.<315> hypothesized that the fibers are configured come the matrix to accomplish a best stretch during the cardiac cycle and introduced the hatchet attachment stretch wherein λfa≥1.


In cell Biology (Third Edition), 2017

Dense Connective Tissue

Collagen fibers, with or there is no elastic fibers, comprise the bulk of dense connective tissue (Fig. 32.1B). Sparse fibroblasts are present to manufacture extracellular matrix. Other connective tissue cells are even rarer, together these tissues room not normally exposed to microorganisms. Collagen fibers can be i ordered it precisely, as in tendons or cornea (see Fig. 29.3), or less so, as in the wall of the intestine or the skin. Tendons consist almost exclusively of form I collagen fibers, all aligned along the size of the tendon to provide the tensile stamin that is required to transmit pressures from muscle come bone. The cornea that creates the transparent front surface of the eye is additionally well organized into orthogonal class of collagen fibrils.

Dense connective organization can likewise be elastic. For example, the wall surfaces of arteries (see Fig. 29.8) and also the dermal class of skin consists both collagen and also elastic fibers. Power from every heartbeat follow me the elastic yarn in the wall surfaces of arteries. Recoil of these elastic yarn propels blood between heartbeats and affects the blood pressure.

Approximately one in 5000 humans inherits a mutation in a gene because that fibrillar collagens kind I, kind III, or kind V, which causes a variety of connective tissue defects called Ehlers-Danlos syndrome. Most impacted individuals have thin skin and also lax joints. Serious mutations result in rupture of arteries, bowel, or uterus, often with deadly consequences. Ehlers-Danlos syndrome illustrates the prominence of this collagens through regard come the integrity of the affected tissues. Inheritance is dominant, together these collagens consist of trimers the three identical subunits. Given one mutant gene, just one in eight (½ × ½ × ½) procollagen molecule is normal.


Charles E. DeCamp DVM, MS, ... Susan L. Schaefer MS, DVM, in Brinker, Piermattei and also Flo's Handbook of small Animal Orthopedics and also Fracture fix (Fifth Edition), 2016

Fibers

Collagen yarn are installed in matrix. This fibers are not generally visible by light microscopy because the refractive table of contents is the very same as that of the floor substance.20 They might be viewed by phase-contrast microscopy or electron microscopy. The fibers form “hoops” or “wickets,” likewise known together Benninghoff’s arcade (Figure 6-4), an arrangement that results in the fibers gift parallel to the joint surface and also perpendicular come the subchondral bone.18,21 The surface arrangement of the cartilage fibrils provides a contempt irregular surface that stays clear of adhesions of opposing articular surfaces when lubricated by synovial fluid.20 This superficial class of tightly pack fibers resists shear forces during joint movement.22 once pressure is used at the surface, the fibrils broaden laterally if the thickness decreases. When the press is released, the fibrils rebound together a an outcome of their elasticity. This elasticity decreases with continuous compression or v age. The resiliency that cartilage likewise depends ~ above the fibrils being supported by procession proteoglycans.22 The intermediary layer has actually the greatest shock-absorbing capacity due to the fact that of the high contents of tied water.9

If the superficial layers of fibers are lost through erosion (trauma), the procession comes into closer call with degradative enzymes, leading to further loss of collagen fibers and also proteoglycans. Because of this the superficial layer deserve to be considered similar to the integument; that is a very first line that defense for all that it covers—in this situation the deeper great of the cartilage.


*

In turn, collagen fibers room bundles the densely-packed fibrils wherein collagen triple-helical molecule (of cross-sectional area Am and also length ℓm) are mutually interconnected into a head-to-tail setup through intermolecular covalent cross-links, described by their typical occurrence every molecule Λc. Therefore, fibril mechanics can be defined as pertained to molecular sliding (counteracted through cross-links with stiffness kc) in series with molecular elongation (Maceri et al., 2012; Marino, 2016).

At the nanoscale, the elongation the collagen molecules is administer by in-series entropic and also energetic mechanisms (Buehler and also Wong, 2007; Fratzl, 2008; Maceri et al., 2012; Marino, 2016). The previous are associated with thermal fluctuations (depending ~ above temperature T, molecule persistence ℓp and also contour ℓc lengths, and on molecular length ℓm,o in the recommendation configuration), and the last with the uncoiling and also the stretching of collagen triple helices (depending ~ above low-strain Eˆo and also high-strain Eˆ tangent moduli, molecular uncoiling stress, overload εoh, and uncoiling resistance η).


Accordingly, the collection SF that histological, biochemical and biophysical features, explicate collagen fiber mechanical behavior, results in


(4.4a)SF=Sf,HF,o,LF,o,rF,
(4.4b)Sf=Sm,kc,Λc,
(4.4c)Sm=ℓm,o,ℓp,ℓc,Am,T,Eˆo,Eˆ,εoh,

where the multiscale nature is emphasize by the inclusions Sm⊂Sf⊂SF.


It is worth discussing that, because of multiscale mechanisms, Ef, ℓF, and also HF are functions of the fiber along-the-chord large λF=LF/LF,o. In particular, it outcomes in ℓF=ℓF(λF)=λFLF,o/4, while features Ef=Ef(λF) and also HF=HF(λF) are identified from inter-scale compatibility relationships, to express by the system of differential equations (A.6) in postposition A.

Moreover, it is worth noticing the fibril modulus Ef in Eqs. (A.1) is fully defined in regards to structural parameters Sf. In order to to mark the explicit dependency of fiber mechanical solution by the collection of structural parameters SF in Eqs. (4.4), the functional kind CF=CF(λF,SF) is conveniently employed in what follows.


Leila Risteli, ... Juha Risteli, in developments in Clinical Chemistry, 2014

1 Introduction

Collagen fibers kind the extracellular structure of all tissues and also are important for tensile strength. The collagen molecules in this fibers are synthesized as bigger precursor proteins, well-known as procollagens, native which large propeptide domain names are enzymatically cleaved en bloc. As such, the synthesis rate of fibrillar collagens have the right to be established by measuring procollagen propeptides in blood. Assays are easily accessible for the 2 most common human fibrillar collagens, kind I and also III <1,2>.

Because collagens room normal organization constituents that undergo consistent renewal, procollagen propeptides room not tumor markers per se. In contrast, malignant tumor growth needs to invade surrounding organization via deterioration and new synthesis the the extracellular matrix. In soft tissues, this process can it is in a constant fibroproliferative reaction. Although the same, similar thing wound healing, this phenomenon is no self-limiting in cancer <3,4>. Procollagen propeptides released from a fibroproliferative reaction that malignancy have the right to potentially be used as markers of tumor behavior.

Bone, a special instance of connective tissue, nearly determines the concentration of circulating form I procollagen propeptides due to its relatively high turnover rate. In cancer, however, these concentrations can be affected by therapy also as development of skeleton metastases <5,6>.

This review summarizes the biochemistry and also physiology that procollagens and their propeptides. The fibroproliferative procedure in response to cancer and also bone turnover is presented. Communication of cancer cells with the extracellular matrix and also the process of bone metastases are likewise addressed.


Christopher M. Norris doctor MSc MCSP, in controlling Sports Injuries (Fourth Edition), 2011

Remodelling

The remodelling phase overlaps repair, and also may critical from 3 weeks to 12 month (Kellett, 1986). Throughout this stage, collagen is amendment to increase its sensible capacity. Remodelling is identified by a reduction in the wound size, boost in scar strength, and an change in the direction of the collagen fibres (Van der Meulen, 1982).

Contraction of granulation tissue will take place for as long as the elasticity the the fibres will enable (Van der Meulen, 1982). Fibroblast cells transform into myofibroblasts i m sorry then kind intercellular bonds. This contain contractile proteins (actomyosin) and behave much like smooth muscle fibres.

Three weeks ~ injury, the quantity of collagen has stabilized (Van der Meulen, 1982) yet the strength of the fibres continues to increase. Strength rises are a an outcome of an expansion in the variety of cross-bonds between the cells, and also the instead of collagen cell themselves. There is a consistent turnover the collagen, a process influenced through a number of factors, including the age of the patient, the type of tissue injured, the quantity of scar tissue present, the site and also direction of the scar and external forces (Van der Meulen, 1982; open minded et al., 1983).


Final collagen fibre alignment should enhance the tissue duty (Fig. 1.12). Fibres within a ligament will certainly respond to a variety of activity exercises i m sorry tense the ligament rhythmically. This may cause mild discomfort (VAS 2−3) but not pain (VAS 7−8). Pain is an indication of tissue damages indicating the the healing process has reverted ago from the remodelling stage to the inflammation stage. Fibres within muscle respond similarly, yet to pressure transmission encountered by energetic and light stood up to exercise during rehabilitation.


Keypoint

•Tissue have to be based on mild stress throughout rehabilitation however NOT pain.

Mild discomfort indicates that tissue is created to remodel, encouraging exactly collagen fibre alignment.

Pain is a sign of tissue damage and disruption forcing the healing procedure to revert back to its inflammatory stage.


The collagen fibres are flexible with a high tensile strength. Generally, every collagen fibre is comprised of thread-like subunits dubbed collagen fibrils. Each fibril in turn is comprised of collagen molecules that room aligned head come tail in overlapping rows. The fibril's stamin is because of covalent bonds between collagen molecules of adjacent rows. The collagen molecule (called tropocollagen) is composed of three linked polypeptide chain (each of i m sorry is called an alpha chain) that kind a right-handed triple helix. Except for the end of the chain, every 3rd aminoacid is a glycine. Sugar teams are connected with the triple helix, for this reason collagen is properly dubbed a glycoprotein. The alpha chains that form the helix are not all alike and, based on differences in ~ the chains, many varieties of collagen have actually been identified. They room classified by roman numerals on the basis of chronology of discovery and also the many important varieties are:

Type i is the many prevalent type of collagen and constitutes about 90% of body collagen. That is the collagen discovered in the dermis that the skin, bone, tendon, fasciae, organ capsules and also many other areas. This fibrils accumulation to kind thick bundles of 2–10 µ in diameter and give the CT high tensile strength (500–1000 kg/cm2).

Type II is the main constituent the cartilage and also these fibres room finer.

Type III or reticular fibres have actually a narrow diameter and also typically execute not kind bundles to come to be thick fibres. They space arranged in a mesh-like pattern and carry out a supporting structure for the cellular ingredient of various tissues and organs, e.g. The liver. This fibres are additionally found in ~ the boundary of the epithelium, in loose CT, and also around adipocytes, small blood vessels, nerves, tendons and intramuscular CTs (Fig. 1.3). They space the very first to it is in secreted during the advancement of all the CTs and also in the formation of brand-new CT, as in a scar.

Type IV forms a internet rather 보다 fibrils and is a fundamental component of the basal lamina of epithelia.


The synthetic of collagen fibrils is carry out by the fibroblasts. Form III fibres which assistance the stroma of the haemopoietic and lymphatic tissues space made by reticular cells, and also the endoneurium the peripheral nerves is produced by Schwann cells. The smooth muscle cell (present in the tunica media that blood vessels and the muscularis externa of the alimentary canal) are able come secrete all of the CT fibre types.

Single collagen fibres normally align follow me the key lines of a mechanical load. Under pathological circumstances, early to changes in the density of soil substance, the collagen fibres obtain closer to each other and may kind pathological cross-links. This might prevent the capacity of a regular collagen network come develop.


Collagen fibre turnover is normally about 300–500 days. Carano and Siciliani (1996) prove that extending fibroblasts can increase sales by boosting the cheap of collagenase, an enzyme that plays an important role in the destruction of collagen fibres. These authors demonstrated that cyclical stretching is more effective 보다 a constant stretch. Extending or compressing it is intended an immediate and proportional deformation the the fibroblasts, however after 10–15 min the cabinet morphology readapts to the brand-new mechanical environment, resulting in a ns of the organic activation. This suggests that a brand-new mechanical stimulus is necessary to induce a new biological reaction.


Clinical Pearl 1.1 Ehlers–Danlos Syndrome

Etiology: a defect in the synthesis of form I or III collagen fibres that reasons progressive destruction of collagens. Various sites that the body might be affected, such as joints, heart valves, body organ walls and also arterial walls, and also give various Ehlers–Danlos syndrome types. Symptom such together joint hypermobility, pain and reduced muscle strength are common. Clayton et al (2013), through demonstrating that these patients have proprioceptive impairment, support our theory that CT handicap is a an essential element in proprioception (see chapter 3).


The collagen fibers and fiber majority of the myofascial mechanism are to a high degree connected in parallel arrays that provide them their good tensile strength and flexibility, while in ~ the very same time offering them a high degree of crystallinity. This is a residential or commercial property of soft tissues the is not constantly taken right into account. The crystals in the living matrix have little resemblance to familiar mineral crystals such as quartz or diamond. The hardness of mineral crystals arises since the systems (atoms and also molecules) of i beg your pardon they are composed are about spherical and also are pack tightly together in very strong polygonal arrays. In contrast, the essential crystals making up the myofascial mechanism are created of long, thin, flexible filaments such together actin, myosin, collagen, and also elastin. The result is flexible fairly than strictly crystals. In fact, lock are best described together liquid crystals.

Liquid crystallinity offers organisms your characteristic flexibility, exquisite sensitivity and responsiveness, and optimizes the rapid noiseless intercommunication that permits the biology to duty as a meaningful coordinated whole.

Ho (1997)


Highly ordered equipment of this kind have special properties that have been learned by physicists for a long time. The biological significance of these crystals was emphasized through Szent-Györgyi (1941):

If a great number of atom is arranged with regularity in close proximity, as for instance, in a decision lattice, the…electrons… stop to belong to one or 2 atoms only, and belong come the whole system…A an excellent number of molecules may sign up with to form energy continua, along which energy, viz., excited electrons, may travel a particular distance.


This statement introduced the essential discovery, now confirmed, the proteins space semiconductors, and also laid the foundation for the new field of digital biology or solid-state biochemistry. Very couple of scientists evaluate the significance of this development. The barrier seemed to be unwillingness among most biologists to investigate the biological significance of quantum physics. Happily this instance has changed dramatically, and also Szent-Györgyi's seminal job-related in molecule electronics and semiconduction in collagen is finally being well-known (Hush 2006).

Another necessary property of liquid crystals is piezoelectricity. As soon as put under compression or tension, this materials build electric fields. Deformations of bones, teeth, tendons, blood ship walls, muscles, and skin all offer rise come weak electrical fields, i beg your pardon is assumed to be a result of the piezoelectric effect. The piezoelectric continuous for a dried tendon, for example, is nearly the same as that for a quartz decision (Braden et al. 1966).

There is part disagreement regarding whether the electrical fields developed by deformations the connective tissues room entirely because of the piezoelectric effect. Another mechanism that could contribute to the electrical properties is the streaming potential (Bassett 1968).

There has been interest in the biological significance the these electric effects. It shows up that every activity made through the body generates electric fields because of the compression or stretching of bones, tendons, muscles, etc. In addition, electric fields take place as a repercussion of nerve conduction and the depolarization the the muscle cell membranes. It has been propose that every one of these electric fields spread out through the bordering tissues, offering signals that educate the cell of the nature the the movement, loads, or other tasks occurring elsewhere in the body. Cells such together fibroblasts and also osteoblasts are thus able to readjust their tasks in maintaining and also remodeling the tissues according come the loads they space carrying. This is believed to it is in the system of Wolff's Law, and the procedure by i m sorry movement and exercise maintain the skeleton, while long periods the bed rest or space travel in zero gravity conditions lead come loss of bone mass. Bodywork, energetic, and also movement therapists of all kinds are acquainted with the reality that tendons end up being thickened and hardened in an answer to chronic stress. Castle are additionally familiar through therapeutic approaches that to decrease the stress in the myofascial network, by relaxing chronically tightened muscles and softening thick regions, specifically at the locations where the tendons insert into the bones.

Athletes, musicians, dancers, and also other performers suffer the gradual adaptations the structure, function, motion, and also energy that occur when an activity is practiced again and again. Severe example is the body-builder, who with the economic stimulation of constant exertion, brings about a dramatic alteration in human body form. Not just do the muscles rise in size and also strength, but the other materials of the myofascial system increase as well. The breakable skill of the concert violin is an instance of the exact same phenomenon – the steady perfection of kind and movement as the human body adapts come the means it is used. The is thought that the orderly and concerted transforms in structure simply described, coordinated by the communications in between the various tissues and the cells, are, at least in component mediated by electric fields produced, through the piezoelectric effect, streaming potentials, and also other tasks related to engine control. A stimulus because that the research study was the exploration by Dr. Robert O. Becker and others the weak electrical currents have the right to facilitate the healing of bone fractures.

While a success through a therapeutic technique does no necessarily prove the theoretical mechanism that the strategy is based upon, there is no concern that clinical applications of weak electrical fields deserve to stimulate osteogenesis to the level that the an approach has become widely provided for treating nonunion and also delayed union of bone fractures, even in skeleton unhealed for as lengthy as 40 years (Bassett 1995).

Precisely exactly how do electrical fields generated during motor activity get from their resources to surrounding fibroblast or osteoblast cells, and also thence come the cell nucleus whereby protein synthetic is regulated? Bassett (1995) summarized a cascade of tasks that the cross the cabinet membrane, moves through the cytoskeleton to the nucleus and DNA. Physiologists consistently view charge carry as the activities of fee carriers such as sodium, potassium, and chloride ions, together in other physiological processes. It is likely that various other charge carriers and also other creates of power are connected as well. Light and also sound may also be involved.

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Interest in light emission from the fascial liquid crystals is supported by the discoveries of Fröhlich (1988), that demonstrated from both theoretical and also experimental perspective that once the power levels in these fluid crystals with a details point, the molecules begin to vibrate coherently, bring about the emission of meaningful light. This light emissions have actually now been documented.