Number Of Collagen Fibrils Research Articles

Biomechanical profile of refractive procedures; is there a biomechanical privilege?

AbstractThe cornea shows regional in‐plane variation in strain and deformation. Paracentral and peripheral cornea is stiffer than the central cornea due to differing orientation and number of collagen fibrils. Corneal elastic strength is a function of depth, with decreasing strength from the anterior to the posterior stroma.During central myopic ablation, an immediate circumferential severing of corneal lamellae is produced. resulting in a forward herniation. Additionally central ablation also relaxes lamellar tension in residual peripheral lamellar segments, which decreases local resistance to swelling leading to peripheral stromal thickening. Expansion of the peripheral stroma may generate centripetal stress in underlying lamellae through dense interlamellar connections at the margin of the ablation zone, resulting central flattening.Empirically, the hyperopic response is dominant when ablation is limited to the anterior stroma, and progressively deeper circumferential insults result in a shift towards corneal steepening. Central flattening response augments the effects of a myopic procedure but impedes efforts to correct hyperopia.

Особенности ультраструктурных изменений роговичного коллагена экспериментальных животных после уф кросслинкинга роговицы

Purpose. Electron microscopy analysis of collagen fibrils in the corneal stroma of rats after UV cross-linking. Material and methods. Experiments were carried out on rats in 2 groups: 1st – control (intact), 2nd – experiment (UV corneal cross-linking with riboflavin). The observation period is 3, 90 days. The UV irradiation power of the cornea is 3 mW / cm², the duration is 10 minutes. For electron microscopic examination, corneal pieces were fixed in a solution of 2 % glutaraldehyde. Dehydration and pouring were carried out according to the generally accepted method. Ultrathin sections were obtained using the ultramicrotome "Leica EM UC7" (Leica Microsystems) and viewed in the electron microscope JEM-1011 (Jeol). To determine the density of fibrillar packing of corneal collagen fibers, microphotographs were analyzed at magnification ×15,000. The number of collagen fibrils on an area of 250,000 nm² was calculated. The same microphotographs were used to measure the diameter of collagen fibrils. All numerical data were processed by the method of variational statistics. Histograms of the normal diameter distribution of collagen fibrils were analyzed. Results. The ultrastructure of corneal collagen on the 3rd day after UV corneal crosslinking was characterized by an increase in the interfibrillary space. This indicator was partially restored to its original values on the 90th day. At the same time, the fibrils retained the correct shape and sequence. The results of the analysis of the normal distribution of the diameter of collagen fibrils indicated an increase of an average of 10 %. Conclusion. An increase in the interfibrillary space after UV corneal crosslinking is probably associated with the development of postoperative stroma edema, which can be observed up to several months at the ultrastructural level. The revealed increase in the diameter of collagen fibrils is one of the factors increasing the strength and mechanical properties of the cornea. Keywords: UV cross-linking of rat cornea, electron microscopy, diameter of collagen fibrils, interfibrillary space.

Time-varying regularity of changes in biomechanical properties of the corneas after removal of anterior corneal tissue

BackgroundThe corneal biomechanical properties with the prolongation of time after corneal refractive surgery are important for providing a mechanical basis for the occurrence of clinical phenomena such as iatrogenic keratectasia and refractive regression. The aim of this study was to explore the changes of corneal elastic modulus, and stress relaxation properties from the 6-month follow-up observations of rabbits after a removal of anterior corneal tissue in simulation to corneal refractive surgery.MethodsThe anterior corneal tissue, 6 mm in diameter and 30–50% of the original corneal thickness, the left eye of the rabbit was removed, and the right eye was kept as the control. The rabbits were normally raised and nursed for 6 months, during which corneal morphology data, and both of corneal hysteresis (CH) and corneal resistance factor (CRF) were gathered. Uniaxial tensile tests of corneal strips were performed at months 1, 3, and 6 from 7 animals, and corneal collagen fibrils were observed at months 1, 3, and 6 from 1 rabbit, respectively.ResultsCompared with the control group, there were statistical differences in the curvature radius at week 2 and month 3, and both CH and CRF at months 1, 2, and 6 in experiment group; there were statistical differences in elastic modulus at 1, 3, and month 6, and stress relaxation degree at month 3 in experiment group. The differences in corneal elastic modulus, stress relaxation degree and the total number of collagen fibrils between experiment and control groups varied gradually with time, and showed significant changes at the 3rd month after the treatment.ConclusionsCorneas after a removal of anterior corneal tissue undergo dynamic changes in corneal morphology and biomechanical properties. The first 3 months after treatment could be a critical period. The variation of corneal biomechanical properties is worth considering in predicting corneal deformation after a removal of anterior corneal tissue.

Ultrastructural charachteristic of benign and anaplastic meningiomas

Taking into account high prevalence of meningiomas (35 %) among other intracranial tumors and variety of their histological structure, electron microscopy (EM) can provide important diagnostic information and be substantially complementary to light microscopy data and immunohistochemical studies.Objective: to study ultrastructural changes in benign and anaplastic meningiomas and to establish the main differential diagnostic ultrastructural features of meningiomas of different grades.Material and Methods: light microscopy and EM studies were conducted using 35 cases of meningioma.Results: Our EM data allow highlighting the characteristic ultrastructural changes in different subtypes of benign meningiomas. In particular, meningothelial subtype comprised of cells with homogeneous structure with light oval nuclei, with evenly arranged finely granular chromatin, well differentiated cell-cell contacts such as desmosomes. Cytoplasmic membranes of adjacent cells adhered to one another, forming small intussusceptions sometimes, which penetrated into the neighboring cells, which significantly increased the contact area of adjacent cells. Fibroblastic meningiomas were rich in modified fibroblasts, which contained bizarre nuclei of irregular shape with compact chromatin arrangement near the nuclear membrane. Also there were plenty bundles of collagen fibrils with the orderly assembled collagen fibers as well as with a chaotic arrangement. Transitional meningiomas were characterized by the combination of meningothelial like areas and areas of typical fibroblastic differentiation. EM changes were similar to meningothelial and fibrous meningiomas.Anaplastic meningiomas were characterized by increased in size or pyknotic nuclei, presence of nuclei with deep intussusceptions, a significant dilution of chromatin structure, focal disturbances of karyolemma integrity, vacuolization of intracellular membrane structures and extracellular edema, a significant reduction of cell-cell contacts.Conclusions: The ultrastructural features of benign meningiomas are reflected in the presence of desmosomes in meningothelial subtypes, a significant number of collagen fibrils in the fibroblastic subtypes, which confirms the double epithelial-mesenchymal histogenesis of these tumors. The cells of anaplastic meningiomas were characterized by marked signs of nuclear polymorphism, processes of alteration such as karyopyknosis and apoptosis, as well as a significant reduction of cell-cell contacts, which can promote recurrence and possible metastasizing.

Anisotropic Collagen Fibrillogenesis Within Microfabricated Scaffolds: Implications For Biomimetic Tissue Engineering

Anisotropic collagen fibrillogenesis is demonstrated within the pores of an accordion-like honeycomb poly(glycerol sebacate) tissue engineering scaffold. Confocal reflectance microscopy and image analysis demonstrate increased fibril distribution order, fibril density, and alignment in accordion-like honeycomb pores compared with collagen gelled unconstrained. Finite element modeling predicts how collagen gel and scaffold mechanics couple in matching native heart muscle stiffness and anisotropy.

EGR1 and EGR2 Involvement in Vertebrate Tendon Differentiation

The molecules involved in vertebrate tendon formation during development remain largely unknown. To date, only two DNA-binding proteins have been identified as being involved in vertebrate tendon formation, the basic helix-loop-helix transcription factor Scleraxis and, recently, the Mohawk homeobox gene. We investigated the involvement of the early growth response transcription factors Egr1 and Egr2 in vertebrate tendon formation. We established that Egr1 and Egr2 expression in tendon cells was correlated with the increase of collagen expression during tendon cell differentiation in embryonic limbs. Vertebrate tendon differentiation relies on a muscle-derived FGF (fibroblast growth factor) signal. FGF4 was able to activate the expression of Egr genes and that of the tendon-associated collagens in chick limbs. Egr gene misexpression experiments using the chick model allowed us to establish that either Egr gene has the ability to induce de novo expression of the reference tendon marker scleraxis, the main tendon collagen Col1a1, and other tendon-associated collagens Col3a1, Col5a1, Col12a1, and Col14a1. Mouse mutants for Egr1 or Egr2 displayed reduced amounts of Col1a1 transcripts and a decrease in the number of collagen fibrils in embryonic tendons. Moreover, EGR1 and EGR2 trans-activated the mouse Col1a1 proximal promoter and were recruited to the tendon regulatory regions of this promoter. These results identify EGRs as novel DNA-binding proteins involved in vertebrate tendon differentiation by regulating type I collagen production.

Combining Therapeutic Laser and Herbal Remedy for Treating Ligament Injury: An Ultrastructural Morphological Study

We examined the ultrastructural morphology (number of collagen fibrils, mean and mass-averaged diameter) of isolated and combined treatments of a therapeutic laser and herbs for medial collateral ligament (MCL) injury in rats. Twenty-eight rats, divided into seven groups: laser (L), herb (H), laser + herb (LH), laser control (LC), herb control (HC), laser sham (LS) and herb sham (HS), were studied. Right MCL of groups L, H, LH, LC and HC were transected, while that of LS and HS remained intact. Group L received 9 treatment sessions of GaAlAs laser with a dosage of 3.5 Jcm(-2); group H received herbal plaster treatment; groups LH had combined treatments of laser and herb; group LC had placebo laser; group LS had no treatment; groups HC and HS received only bandage without herb. All MCLs were analyzed using transmission electron microscopy at 3 weeks. Differences (p < 0.05) existed in mean fibril diameters among groups. Core mass-averaged diameters of groups L and H were larger than the control groups (LC and HC). Fibril diameter of group LH (combined treatment) was even larger and approaching that of the intact MCL. Combined therapeutic laser and herbal treatment hastened collagen fibril maturation in MCL repair.

Formation of stromal collagen fibrils and proteoglycans in the developing zebrafish cornea

Collagen fibrils and proteoglycans are the main components of the corneal extracellular matrix and corneal transparency depends crucially on their proper arrangement. In the present study, we investigated the formation of collagen fibrils and proteoglycans in the developing cornea of the zebrafish, a model organism used to study vertebrate embryonic development and genetic disease. We employed thin-section electron microscopy to investigate the ultrastructure of the zebrafish cornea at different developmental stages. The layering of the zebrafish cornea into an epithelium, a Bowman's layer, stroma and endothelium was observed starting at 72 hr post-fertilization. At this stage, the stroma contained orthogonally arranged collagen fibrils and small proteoglycans. The density of proteoglycans increased gradually throughout subsequent development of the cornea. In the stroma of 2-week-old larvae, the collagen fibrils were organized into thin lamellae and were separated by very large, randomly distributed proteoglycans. At 4 weeks, a regular arrangement of proteoglycans in relation to the collagen fibrils was observed for the first time and the lamellae were also thickened. The present study, for the first time, provides ultrastructural details of collagen fibril and proteoglycan development in the zebrafish cornea. Furthermore, it directly correlates the collagen fibril and proteoglycan composition of the zebrafish cornea with that of the human cornea. The similarities between the two species suggest that the zebrafish could serve as a model for investigating the genetics of human corneal development and diseases.

Aging of myocardial collagen.

The objective of this article was to present a review of the collagen tissue of the heart muscle as a function of age. The myocardial collagen matrix consists of a network of fibrillar collagen which is intimately connected to the myocyte. Most collagen fibers reside in parallel with myocytes. These fibers may have a wavy, taut or coiled appearance. Fibrillar collagen types I and III are the major components of the myocardial collagen matrix. Collagen type I has been found to represent nearly 80% of the total collagen protein, while type III collagen is present in lower proportions (approximately 11%). Cardiac fibroblasts are the cellular source of fibrillar collagen, cardiac myocytes expressing only mRNA for type IV collagen. Collagens types I and III exhibit a high tensile strength which plays an important role in the behavior of the ventricle during the cardiac cycle. The collagen concentration and the intermolecular cross-linking of collagen increase with age. Measurements of collagen content in myocardial tissue suggest that it is the type I collagen fibers that increase in number and thickness in the aged. At the same time, electron microscopic observations have shown an increase in the number of collagen fibrils with a large diameter in the aging heart. The mechanism responsible for the myocardial fibrosis in the senescent myocardium is unclear. The collagen deposition in the myocardium could be due to the regulation of collagen biosynthesis at pre-translational levels. It is possible that the regulatory elements involved in this process are growth factors such as TGF-beta 1 and hormones and neurotransmitters. Details of regulatory mechanism that may come into play during aging may be elucidated by further investigations. The accumulation of collagen within the myocardium increases muscle stiffness. Myocardial function is affected by this process; this is usually reflected by incomplete relaxation during early diastolic filling, and presumably account for the decrease in early left ventricular diastolic compliance.

Age related changes of the collagen network of the human heart

The objective of this work was to study the collagen tissue of the human heart muscle as a function of age. The types of collagen, their disposition, as well as the density of collagen tissue and diameter of collagen fibrils were examined. Pieces of the ventricular wall from 12 human hearts, six from young individuals and six from aged individuals were studied by the Picrosirius–polarization method and by transmission electron microscopy (TEM). The results obtained showed the presence of two types of collagen fibers in the ventricular walls — thin, weakly birefringent, greenish fibers (collagen type III) and thick, yellow or red, strongly, birefringent fibers (collagen type I), both in the endomysium and perimysium. In the hearts obtained from old subjects, there were no significant differences in the arrangement of the collagen fibers in relation to the hearts obtained from young subjects. Measurements of collagen content in myocardial tissue suggest that both perimysial and endomysial collagen type I fibers increase in number and thickness in the old. These histochemical results obtained coincided with the electron microscopic observations in showing increase in the number of collagen fibrils with large diameter in the old hearts. These ultrastructural and histochemical characteristics of collagen may provide insights important to assessing the pathogenesis of the cardiac lesions of several cardiopathies in the aged heart.

A novel technique of taking tendon biopsies in the horse

SummaryTo evaluate a novel tendon biopsy technique for use in the horse and to assess the effect of different exercise levels on the healing process of minimally damaged superficial digital flexor tendons (SDFT), 24 Dutch Warmblood foals were randomly divided into 3 equally sized groups one week after birth. One group was box rested, one group got box rest with additional enforced exercise, and one group got free pasture exercise. Biopsies from the peripheral region of the SDFT were taken at age 2 months using a new micro-biopsy technique. At age 5 months the foals were euthanized and samples from the biopsy site and a control site were harvested. Collagen fibrillar index (CFI, the total amount of collagen as a percentage of the measured area), mass-average diameter (MAvD, mean of the diameter versus area distribution) and collagen fibrillar diameter frequency (the distribution of collagen fibril sizes expressed as a percentage of the number of collagen fibrils) were calculated. The CFI, MAvD values were significantly lower in the wound samples. It is concluded that the biopsy technique may be a useful tool for research applications. The absence of exercise-induced effects on the collagen fibril population in the wound samples suggests that the first phase of the process of tendon healing in immature equine SDFT’s sustaining a minor surgically-induced wound, is not exercise-dependent. However, findings may be different in mature horses sustaining accidental trauma.A novel technique to take biopsies from immature equine flexor tendons was developed and used to evaluate the effect of various levels of exercise on the development of the collagen fibril diameter distribution in the resulting wounds. The technique appeared to be minimally invasive, but complication rate was deemed too high for clinical use. There was no effect of exercise on mass average diameter of collagen fibrils, suggesting that the repair process, at least in its initial stage, is exercise-independent.

Denervation of Pacinian Corpuscles: Electron Microscopic Observations in the Rat Following Nerve Transection

Nerve transection using rat sciatic nerves was employed to observe morphologic changes in the periodic denervation of Pacinian corpuscles. During periods of from 1 to 20 weeks after surgery, a total of 15 corpuscles were obtained under the operating microscope and processed for morphologic analysis using light and electron microscopes. Based on the morphologic findings, normal corpuscles were composed of an axon terminal and inner and outer core cells. Following nerve transection, the axon terminal immediately disappeared at 1 week, but the original inner and outer core cells were preserved, with macrophage migration occurring in the outer core. After 8 weeks, the circular regularity of the inner and outer core lamellae was occasionally broken. The lamellae had wavy courses and there were many empty spaces in the inner core. Even at 20 weeks after denervation, there was interruption in the continuity of the outer core cells; the membranous structure of the outer core and the lamellar structure of the inner core were well-preserved; the outer and inner core cells were still present. Simultaneously, a small number of collagen fibrils were observed between the inner and outer core cells from the earliest postoperative stage. These fibrils increased in number in later stages. The results suggest that, immediately after destruction of axon terminals, macrophages migrate into the interlamellar spaces where they engulf the debris of the degenerated axon terminals. The degeneration of the corpuscles seems to be similar to that of denervated nerve axons; therefore, the inner core cells, which are continuous with the Schwann cells, maintain their original condition for at least 20 weeks after corpuscle denervation. The outer core cells, which are continuous with the perineurial nerve cells, are assumed to be the main cells producing the collagen fibrils in the denervated Pacinian corpuscles.

Isolated Posterior Cruciate Ligament Insufficiency Induces Morphological Changes of Anterior Cruciate Ligament Collagen Fibrils

Summary: We studied the ultrastructural changes of the human anterior cruciate ligament (ACL) with transmission electron micrograph cross-sections following isolated posterior cruciate ligament (PCL) injury. Biopsy specimens were obtained from the proximal third and anteromedial aspect of the ACL. Fourteen patients with PCL-deficient knees at a mean of 22.1 months from injury to surgery and 5 normal knees amputated secondary to malignant tumors or traumatic injuries were used as controls. A significant difference was found in the number of collagen fibrils per l μm 2 between the PCL-deficient knee group and the control group. There was a significant difference found in the collagen fibril diameter between the PCL-deficient knee group and the control group. The collagen packing density (the percentage of sampled area occupied by collagen fibrils) was also significantly different between the PCL-deficient knee and the control group. The current study shows that an isolated PCL insufficiency can induce morphological changes in ACL collagen fibrils, suggesting that a PCL insufficiency can have adverse effects on other ligamentous structures in the knee joint. Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 15, No 3 (April), 1999: pp 292–296

The adverse effects of sectioning the posterior cruciate ligament in rabbits. Changes in the structural and morphological properties of the femur-anterior cruciate ligament-tibia complex.

This study examined the changes in the structural properties of the femur-anterior cruciate ligament-tibia complex (FATC) and the histologic changes of the anterior cruciate ligament (ACL) following sectioning of the posterior cruciate ligament (PCL) of 20 rabbits. The PCL in the right knee was sectioned through an arthrotomy. The left knee underwent arthrotomy only and was used as a control. The animals were killed 3 and 6 months postoperatively. The tensile properties of the FATCs were tested, and the ACLs were histologically examined using polarized light microscopy and transmission electron microscopy. There were significant decreases in the ultimate load following sectioning of the PCL, although there were no significant changes in the stiffness. There were no significant differences in either the crimp period or the crimp amplitude of the ACL following sectioning of the PCL. There were significant increases in the number of collagen fibrils per square micrometer, and significant decreases in the collagen fibril diameter and proportion of total collagen fibril area per square micrometer following sectioning of the PCL. These findings suggest that isolated PCL injury may cause pathological changes in the ACL and its insertion sites.

Ultrastructural effects of immobilization on rat muscle spindles

The ultrastructure of rat muscle spindles was examined after the anterior tibial muscles had been immobilized in a plaster cast. There was an increase in the number of collagen fibrils and external laminae around the outer capsules and in the intracapsular space 2 weeks after immobilization. The changes in the intrafusal muscle fibers within 4 weeks included disorientation of myofilaments. After 6 weeks, Z bands had become disarranged, and there was vacuolar degeneration of the sarcoplasmic reticulum in some fibers. Myelin sheaths of many of the myelinated nerve fibers (especially the thick ones, which were probably sensory nerve fibers) had degenerated within 2 weeks. These results indicate that immobilization of skeletal muscles affects not only extrafusal muscle fibers but also the structure of the muscle spindle.

Fibroblasts are required for Schwann cell basal lamina deposition and ensheathment of unmyelinated sympathetic neurites in culture.

The ability to purify and recombine populations of peripheral neurons, Schwann cells and fibroblasts in tissue culture has enabled us to examine the contribution of fibroblasts to Schwann cell basal lamina assembly and ensheathment of unmyelinated rat superior cervical ganglion neurites in vitro. Purified perinatal superior cervical ganglion neurons were grown in culture either with Schwann cells or with Schwann cells plus fibroblasts derived from either superior cervical ganglion capsule or cranial periosteum. The cultures were maintained for 2-8 weeks on a collagen substratum in a medium known to promote Schwann cell differentiation (myelin, basal lamina formation) in the presence of dorsal root ganglion neurons. The extent of Schwann cell differentiation (ensheathment, basal lamina formation) in the presence of superior cervical ganglion neurons was evaluated in this study using electron microscopy. In superior cervical ganglion neuron plus Schwann cell cultures (without fibroblasts), Schwann cells achieved only a moderate degree of ensheathment; also, Schwann cell basal lamina was discontinuous and extracellular collagen fibrils were sparse. Although only discontinuous basal lamina was demonstrable by electron microscopy in these cultures, surprisingly, Schwann cell/neurite fascicles were uniformly immunostained for laminin, type IV collagen, and heparan sulfate proteoglycan. The addition of fibroblasts to superior cervical ganglion neuron plus Schwann cell cultures increased the deposition of basal lamina around the Schwann cell/neurite units, the number of collagen fibrils, and the extent of neurite ensheathment. We propose that the presence of basal lamina increases the Schwann cell's ability to ensheathe superior cervical ganglion neurites, possibly through an augmentation of specific extracellular matrix components or by increasing in some way the capacity of these components to become organized into basal lamina. We conclude that, unlike dorsal root ganglion neurons, superior cervical ganglion neurons are unable to stimulate full Schwann cell extracellular matrix expression with the result that these Schwann cells require the extraneuronal influence of fibroblasts to deposit basal lamina and attain their mature phenotype in culture.

INTIMAL LAMINATED ELASTOSIS IN THE INTRARENAL ARTERIES An Electron Microscopic Study

Using kidneys from diabetic patients, the morphogenesis of elastic hyperplasia ("laminated elastosis") in the intrarenal arteries was studied by electron microscopy. In the thickened intima, myointimal cells produced ground substance, collagen fibers and elastic tissue. The elastic tissue was stained black electron microscopically with orcein. Newly-formed elastic tissue in the intima was first found on either the basement membrane or basement membrane-like materials around the myointimal cells and endothelial cells. Subsequently, small areas of elastic tissue aggregated and fused to form larger areas of elastic tissue or concentric thick elastic laminae, the latter containing a large number of collagen fibrils. Upon treatment with elastase, newly-formed elastic tissue was digested, but the microfibrillar component remained unstained.

Abnormalities of intramuscular nerves in old mice: An ultrastructural study

Intramuscular branches of tibial nerves of 5- and 27-month-old mice were compared. Seventeen intramuscular nerve fascicles were studied in each group: 174 myelinated axons were evaluated in the young mice, and 136 in the aged mice. The old mice showed significant decreases in numbers of myelinated axons per nerve, and these had significant decreases in concentrations of mitochondria. Interaxonal collagen and numbers of collagen fibrils were increased, as was the concentration of unmyelinated axons. Myelinated axons of old mice demonstrated myelin disorganization, myelin nodules, degeneration of axoplasm and Schwann cells.

Ultrastructure of the cysts of Sarcocystis rangiferi from skeletal muscle of reindeer (Rangifer tarandus tarandus)

Cysts of Sarcocystis rangiferi from reindeer (Rangifer tarandus tarandus) were examined by transmission electron microscopy. The cysts were located within skeletal muscle cells which were encapsulated by a thick layer of connective tissue. The connective tissue capsule consisted of numerous fibroblasts and a matrix with a moderate number of collagen fibrils, and represents an analogue of the so-called secondary cyst wall of Sarcocystis gigantea and various Besnoitia species. The cysts were limited by a unit membrane, the cyst membrane, which in part was reinforced by a thin subjacent layer of electron-dense material. The cyst surface was covered by closely packed, villiform protrusions, measuring 12–14 μm in length and 8 μm in diameter. The cyst membrane formed vesiclelike invaginations at and between the bases of the protrusions. Cyst ground substance divided the interior of the cyst into numerous compartments containing metrocytes or cystozoites. The cystozoites multiplied by endodyogeny.

The effect of long-term denervation on the ultrastructure of Pacinian corpuscles in the cat.

The ultrastructure of Pacinian corpuscles of the cat located in the crural region and innervated by the interosseous nerve was studied 1 to 14 months after denervation. Both the Pacinian inner core and capsule remained well preserved one month after denervation. However, the denervated inner cores underwent progressive atrophy and wasting, which resulted in a gradual reduction of the amount of inner-core cells and lamellae, widening of interlamellar clefts, formation of empty spaces in the axial region and a considerable increase in the number of collagen fibrils. In spite of the wasting, the inner core still survived 14 months after denervation, but at least half of its volume became occupied by collagen fibrils which surrounded the remaining inner-core cells and lamellae. Collagen fibrils assembled in the denervated core were markedly thinner than those found in the capsule, as is also the case in normal Pacinian corpuscles. In the capsule, discrete focal degeneration, occasional pyknosis of the innermost capsular cells and macrophage infiltration were observed from the first month after nerve section onward, but the number of capsular layers remained within the normal range (30-40) up to 14 months after denervation.