Cloning and expression of type III collagen in normal and injured tendons of horses

OBJECTIVE: To clone the 5' end of type III collagen and describe its pattern of mRNA and protein expression in normal and healing tendons in horses. ANIMALS: 14 healthy adult horses. PROCEDURE: The tensile region of collagenase-injured superficial digital flexor tendons was harvested at intervals from 1 to 24 weeks after injury. Total RNA was reverse-transcribed into cDNA for cloning and sequencing of type III collagen. Equine-specific nucleic acid probes were developed and used for northern blot analysis and in situ hybridization. Type III collagen protein and cyanogen bromide-cleaved collagen peptides were assessedby gel electrophresis. RESULTS: Type III collagen mRNA expression and protein content increased immediately after injury and remained increased. Type III collagen was localized to the endotenon in normal tendon and in injured tendon at 1 week. At 8 and 24 weeks, expression became more widely distributed throughout the tendon parenchyma. Injured tendon contained 6 times more type I than type III collagen mRNA. Quantities of type III collagen protein were maximal in the first 4 weeks after injury (approx 33%) and then began to decrease. CONCLUSIONS AND CLINICAL RELEVANCE: Type III collagen expression is increased initially in endotenon and subsequently in parenchyma of healing tendon; however, type III remains the minor collagen throughout the healing process. The role of type III collagen in tendon healing is not fully elucidated.     

Histology and immunohistochemistry study of ovine tendon grafted with cBMSCs and BMMNCs after collagenase-induced tendinitis

OBJECTIVES: The aim of this study was to compare the regeneration abilities of cultured bone marrow mesenchymal cells (cBMSC) and bone marrow mononuclear cells (BMMNC) with fibrin glue, saline solution and sham control in collagenase-induced tendinitis of the Achilles tendon in sheep. METHODS: Six sheep were recruited randomly to each group: cBMSC, BMMNC, fibrin, saline and sham control. Each group received the relative treatment two weeks after inducing lesions (T(0)). After eight weeks (T(8)) of treatment, the tendons were harvested and evaluated for histomorphology, Collagen type I, III, Cartilage Oligomeric Matrix Protein (COMP) and CD34 positive cells expression. RESULTS: Histology and immunohistochemistry showed similar capabilities of cBMSC and BMMNC to restore the architecture of fibres and Extra Cellular Matrix (ECM), with a high expression of collagen type I and COMP and a very low expression of collagen type III in treated tendons. The complete architectural disruption of fibres, dramatic reduction of collagen Type I and COMP expression and increase collagen type III expression were commonly observed in tendons treated with fibrin or saline only. The presence of CD34 positive cells was appreciable in the BMMNC group while few cBMSC showed this cluster of differentiation, not expressed in tendons treated with fibrin or saline. CLINICAL SIGNIFICANCE: The data in this study show the efficacy of cBMSC and BMMNC in regenerating tendon tissue after collagenase-induced tendinitis.     

Effect of adipose-derived nucleated cell fractions on tendon repair in horses with collagenase-induced tendinitis

OBJECTIVE: To assess the potential of adipose-derived nucleated cell (ADNC) fractions to improve tendon repair in horses with collagenase-induced tendinitis. ANIMALS: 8 horses. PROCEDURES: Collagenase was used to induce tendinitis in the superficial digital flexor tendon of 1 forelimb in each horse. Four horses were treated by injection of autogenous ADNC fractions, and 4 control horses were injected with PBS solution. Healing was compared by weekly ultrasonographic evaluation. Horses were euthanatized at 6 weeks. Gross and histologic evaluation of tendon structure, fiber alignment, and collagen typing were used to define tendon architecture. Biochemical and molecular analyses of collagen, DNA, and proteoglycan and gene expression of collagen type I and type III, decorin, cartilage oligomeric matrix protein (COMP), and insulin-like growth factor-I were performed. RESULTS: Ultrasonography revealed no difference in rate or quality of repair between groups. Histologic evaluation revealed a significant improvement in tendon fiber architecture; reductions in vascularity, inflammatory cell infiltrate, and collagen type III formation; and improvements in tendon fiber density and alignment in ADNC-treated tendons. Repair sites did not differ in DNA, proteoglycan, or total collagen content. Gene expression of collagen type I and type III in treated and control tendons were similar. Gene expression of COMP was significantly increased in ADNC-injected tendons. CONCLUSIONS AND CLINICAL RELEVANCE: ADNC injection improved tendon organization in treated tendons. Although biochemical and molecular differences were less profound, tendons appeared architecturally improved after ADNC injection, which was corroborated by improved tendon COMP expression. Use of ADNC in horses with tendinitis appears warranted.     

A Histological Evaluation of Rabbit Tendons Sutured Using the Bunnell Pattern

Development of ischemia in healing tendons was assessed in 18 rabbits. One superficial digital flexor tendon in each rabbit was incised and anastomosed using a Bunnell pattern. The repair site was enclosed in a porous, woven Dacron tube before skin closure. The limb was immobilized with a cast. Rabbits were euthanized 1, 4, and 8 weeks after surgery, and tendons were harvested and examined microscopically. Regions of the tendon included in the suture pattern were ischemic and acellular at 1 week, while adjacent areas still containing patent vessels remained viable. Within 4 weeks, a well vascularized neotendon with collagen bundles organized parallel to the long axis of the tendon developed along the periphery and between the opposed tendon ends. After 8 weeks, the ischemic regions of the tendon had not revascularized or become integrated with the neotendon. Adjacent collagen bundles not originally included in the Bunnell pattern were integrated with neotendon collagen fibers.     

Age-related changes to the molecular and cellular components of equine flexor tendons.

Specific tendons show a high incidence of partial central core rupture which is preceded by degeneration. In the performance horse, the superficial digital flexor tendon (SDFT) is most often affected. We have described previously the molecular changes that are associated with degeneration in the central core region of the equine SDFT. The pathophysiological mechanism leading to change in synthetic activity of central zone cells in degenerated tendons is not known. In this study, we test the hypothesis that ageing results in matrix composition changes within the central zone of the SDFT. Extracellular matrix composition and cellularity were analysed in equine SDFTs collected from Thoroughbred horses and compared with a flexor tendon which rarely shows degenerative change and subsequent injury (deep digital flexor tendon, DDFT). Data were examined for age-related changes to central and peripheral zone tissue of the SDFT and DDFT. Ageing in both tendons (SDFT and DDFT) resulted in a significant increase in collagen-linked fluorescence and a decrease in cellularity in the DDFT but not the SDFT. The central zone tissue from the SDFT had a significantly higher proportion of type III collagen than the peripheral zone of the tendon. The highest level of type III collagen was found in the central zone tissue of the SDFT from the older group of horses and this may represent the early stages of a degenerative change. Collagen content did not differ between the 2 flexor tendons; however, there were differences in collagen type and organisation. The SDFT had a higher type III collagen content, higher levels of the mature trifunctional collagen crosslink hydroxylysylpyridinoline, lower total chondroitin sulphate equivalent glycosaminoglycan content, smaller diameter collagen fibrils and a higher cellularity than the DDFT. In conclusion, differences in macromolecular composition exist between the flexor tendons and ageing contributes to a tendon specific change in composition.     

Molecular analysis of defect healing in rat diaphyseal bone.

Spatial expression of messenger ribonucleic acid (mRNA) for osteoblastic marker in drill hole defect healing of adult male rats was analyzed by in situ hybridization. The defect was filled with hematoma 3 days after surgery, expressing Type I collagen mRNA. Hematoma was replaced with fibrous tissue on day 7, and then with new trabecular bone on day 10, originated from the intra-medullary space, respectively. mRNA for Type I collagen, parathyroid hormone 1 receptor (PTHIR), and alkaline phosphatase (ALP) were expressed in the same cell population of fibrous tissue adjacent to newly-formed trabecular bone, and in osteoblasts lining the newly-formed trabecular bone. Hematopoietic marrow with osteoclasts subsequently invaded the region, also from the intra-medullary space, replacing all the new trabecular bone by day 21, except for a thin sub-periosteal layer. mRNA for Type I collagen, PTH1R and ALP was expressed on the periosteal surface of thin layer. Although cartilage formation was not histologically visible, mRNA for Type II collagen was weakly detected in the majority of osteoblasts lining the newly-formed trabecular bone.     

Experimental study on allografts of amniotic epithelial cells in calcaneal tendon lesions of sheep

An experimental protocol was designed to study the survival and behaviour of an allograft of amniotic epithelial cells (AECs) in an ovine model. The study was conducted on three healthy adult sheep. A core lesion was created in both calcaneal tendons under ultrasound (US) guidance by injecting 400 UI of Type 1A collagenase diluted in 0.6 ml saline. The AECs were obtained from a 60–80-day-old fetus and cultured under standard conditions. After 15 days of collagenase treatment, 2 × 10⁶ AECs stained with a vital membrane fluorescent probe (PHK26) were injected under US guidance in 500 μl saline solution into the lesion of one limb. The contralateral untreated limb was used as a control. Animals were euthanatized 7 (1) and 30 (2) days later. Histological analyses performed on explanted tendons clearly demonstrate that AECs survived for at least 1 month inside the lesion without any adverse reactions. The damaged tissue of the treated tendons showed a high number of reparative cells in active proliferation that were accumulating collagen within the extracellular matrix. In addition, after 1 month, the neo-collagen began to be organized into parallel arrays of fibers oriented along the longitudinal axis of the tendon.

     

Comparison of carbon fibre and nylon suture for repair of transected flexor tendons in the horse

Carbon fibre-polylactic acid composites and monofilament non-absorbable suture material were compared for the repair of surgically transected superficial digital flexor tendons in 10 horses. All surgical wounds healed by first intention. The repaired tendons were enlarged, the carbon implanted tendons being larger than those sutured. The horses were killed at six, eight, 12,20 or 24 weeks. Greater fibrous thickening occurred in tendons repaired with carbon fibre, especially at 12 weeks postoperatively. Carbon fibre incited a greater histological response with macrophages, lymphocytes, plasma cells, eosinophils and fibroblasts. The fibrous tissue in the repair sites appeared to mature and the collagen to align at a similar rate irrespective of the method of repair. Only that tissue within and immediately surrounding the carbon bundles was immature at six months. There was minimal tendency for carbon filaments to separate and those that did were often surrounded by epithelioid macrophages forming a granuloma. Massive eosinophil concentrations were present between each granuloma. With each sequential test period the sutured tendons became increasingly stronger than the carbon implanted tendons. This may have been because of the immature core of tissue associated with the carbon bundles. No carbon particles were detected in draining lymph nodes.     

Healing of surgically created defects in the equine superficial digital flexor tendon: collagen-type transformation and tissue morphologic reorganization

Full-thickness defects were surgically created in the superficial digital flexor tendons of the front limbs of 20 horses. Tissues formed within the defect were evaluated histologically, and the collagen composition of the tissue was determined by immunofluorescence. Transformation occurred from loose fibrillar areas of types I and III collagen and pericellular types IV and V collagen to dense bundles of type I collagen fibers. Loose fibrillar areas of types I and III collagen were present after 24 weeks. Histologically, in horses killed after 2 weeks, the tissue within the defect was a randomly oriented mass of fibrovascular tissue. In horses killed after 24 weeks the tissue within the defect resembled normal tendon tissue.     

A connective tissue defect in two rabbits similar to the Ehlers-Danlos syndrome

A connective tissue disease resembling the human Ehlers-Danlos syndrome is reported in two sibling rabbits about four months old. The clinical signs included skin hyperextensibility and fragility and poor wound healing. There were ultrastructural abnormalities in the structure of the collagen fibrils and in their arrangement in bundles of fibres. Affected rabbits may be a useful laboratory animal model for collagen disorders in human beings.     

一剂复方中药对家兔骨骼愈合的影响

复方中药对骨折愈合的作用机制目前尚不明确,本试验通过观察复方中药对家兔桡骨骨折后血清钙、磷、碱性磷酸酶和X线影像学等指标的影响,分析该中药促骨愈合的效能及其可能作用机理。试验选用48只成年家兔,制成骨缺损标准模型,随机分为试验组和空白对照组,试验组每日在饲料中添加复方中药2.5 g/kg饲喂,对照组给予普通饲料。分别于术后2、4、6、8周进行生化指标和X线影像学检测。试验结果表明,试验组血清钙、血清磷、血清碱性磷酸酶及X线片评分骨折后明显高于对照组。该复方中药能缩短骨折愈合过程所需时间,提高骨折愈合质量,有利于骨折愈合。     

Application of Exogenous Esterified Hyaluronan to Equine Distal Limb Wounds

The objective of this study was to evaluate the efficacy of topical application of a hyaluronan (HA) derivative in wound healing with respect to the rate of epithelialization, fibroplasia, angiogenesis and contraction, magnitude of the local inflammatory response, local expression of transforming growth factor-β 1 and 3 (TGF-β 1 and 3), tumor necrosis factor-α (TNF-α), and collagen type III deposition. In six healthy adult horses, six full-thickness skin wounds were created on the dorsal aspect of both metacarpi using a sterile template. Sites were sampled at 0, 1, 2, 5, 14, 21, and 35 days following wounding. Wounds on one limb were dressed with commercially available esterified HA fleece under a nonadherent dressing. The opposite limb was covered with the nonadherent dressing alone (control). Images of the most proximal wounds were used to determine the area of total healing and the relative contributions of epithelialization and contraction to healing. At each sample time, a control and treatment biopsy were taken for histological evaluation and special stains. All samples were evaluated for degree of inflammation, fibroplasia and angiogenesis; in situ hybridization for type III collagen, TGFβ1 and 3, and immunohistochemistry for TNF-α. Mean percentages of total wound healing, epithelialization, and wound contraction were not significantly different between control and treatment groups. In treated horses, initial wound expansion was significantly decreased during the first 2 weeks. Mononuclear cell numbers, counted in the granulation tissue, increased in both control and treated limbs over the entire course of the study. However at day 35 the macrophage numbers counted in the treated horses were significantly increased compared with the control limbs (P < .05). Although not statistically significant, relative staining for type III collagen in the treated wounds was less than that of control wounds. Results of the present study do not support a benefit of an exogenous HA-derivative in the healing of distal limb wounds in horses. The shortcomings of the study design are discussed.     

The effects of moxifloxacin ophthalmic solution 0.5% or gatifloxacin ophthalmic solution 0.3% treatment on corneal wound healing in pigmented rabbits following anterior keratectomy

Purpose These studies examined corneal healing rates, Type‐IV collagen and zonula occludens membrane‐associated protein (ZO‐1) expression, as well as aqueous PGE₂ and IL‐1β concentrations in pigmented rabbits treated with either moxifloxacin 0.5%, gatifloxacin 0.3% or BSS^® following anterior keratectomy. Methods Anterior keratectomy surgery was followed by topical administration with commercial ophthalmic formulations of either moxifloxacin or gatifloxacin or BSS^® (TID for 96 h). Images of the fluorescein‐stained healing corneas were analyzed for wound area. At 48 or 96 h following surgery, aqueous humor samples were collected and analyzed for the inflammatory mediators PGE₂ and IL‐1β using an ELISA. The corneas were subsequently evaluated using both scanning and transmission electron microscopy. In a second parallel study, corneas were evaluated at both 48 and 96 h for Type‐IV collagen and ZO‐1 expression using immunohistochemistry. Results Fluorescein‐stained corneal images at 96 h postsurgery demonstrated that 90% ± 8% re‐epithelialization for moxifloxacin, 81% ± 14% for gatifloxacin, and 88 ± 6% for BSS^® (P > 0.05). PGE₂ levels in the aqueous humor of fluoroquinolone treated eyes were reduced at 48 h compared to BSS^® treated eyes. IL‐1β was undetectable in all samples. No differences in Type‐IV collagen or ZO‐1 expression were observed between any treatment groups. There were no differences between groups in histological appearance or in ultrastructural healing processes. Conclusions These studies demonstrated that the commercial ophthalmic formulations of moxifloxacin and gatifloxacin were similar to each other in their effects on the levels of aqueous humor PGE₂ and rates of corneal wound re‐epithelialization.     

Effects of pulsing electromagnetic fields on the ligament healing in rabbits.

Effects of pulsing electromagnetic fields (PEMFs) on ligament healing were investigated using 80 rabbits. All animals received square resection (4 mm x 4 mm) of both patellar ligaments in full thickness at their center. They were divided into 4 groups of 20 rabbits each and stimulated with different electromagnetic intensity of 0 (control), 2, 10, and 50 gauss (G) for 6 hr daily. Pulse frequency and pulse width were 10 Hz and 25 microseconds, respectively. After PEMFs stimulations for 1, 2, 3 and 4 weeks, 5 animals of each group were euthanized and the regenerated tissue at the defective portion was investigated histologically and biomechanically. Histologically, the tissue stimulated by PEMFs showed an earlier increase in capillaries and fibroblasts and more matured, prominent longitudinal orientation of collagen fibers than those of control groups. Among the rabbits stimulated electromagnetically, those stimulated at 50 G revealed the earliest ligament healing. Tensile strength of regenerated ligament tissues of any PEMFs groups increased significantly at 1 and 2 weeks after operation, however, at 3 and 4 weeks after operation, there were no significant differences between groups. Among these values, those of 50 G group were the highest consistently during most of the experimental period. From the above results, PEMFs enhanced the earlier stage of ligament healings and 50 G gauss seemed to be the most effective among the 3 field intensities used. This promoting effect may potentiate the earlier recovery of the function after the ligament injury.     

Effect of sodium hyaluronate in collagenase-induced superficial digital flexor tendinitis in horses.

Superficial digital flexor tendinitis was induced in each forelimb of 8 horses by injecting 4,000 U of collagenase into the midmetacarpal region of the tendon. In each horse, each tendon was treated 24 and 96 hours after the collagenase injection with SC injections of sodium hyaluronate (treated limbs) or an equal volume of 0.9% NaCl solution (control limbs). Exercise was restricted for the first 3 weeks of the study, and a controlled exercise program was instituted for the remainder of the study. Horses were evaluated clinically for lameness, tendon swelling, and midmetacarpal limb circumference. Ultrasonographic examinations were performed regularly (11 examinations/horse) throughout the study, and all horses were euthanatized 12 weeks after collagenase injections. Tendons from 4 horses were harvested for biomechanical testing, and samples were obtained from tendons from the remaining 4 horses for biochemical analysis of collagen. Samples were obtained from all tendons for microscopic evaluation. Significant differences between treated and control tendons were not noticed in any of the variables examined in live horses, although trends toward less lameness in treated limbs and toward better healing on ultrasonographic examination in control limbs were recorded. Significant differences were not noticed in biomechanical or biochemical evaluations, and the only significant (P < 0.05) microscopic finding was more severe inflammation in tendons from treated limbs. This study did not reveal significant benefits of treatment with sodium hyaluronate outside a synovial sheath on tendon repair in collagenase-induced tendinitis.     

Gunshot Fractures of Extremities: Classification, Management, and Complications

Fifteen clinical cases of gunshot fractures were studied. A radiographic classification of the fractures was developed to aid in fracture evaluation. Type I fractures involved a simple transverse or oblique fracture with minimal soft tissue damage. Type II fractures were severely comminuted with no cortical bone defect and minimal soft tissue damage. Type III fractures were "shatter" fractures, characterized by severe comminution, cortical bone defects, and extensive soft tissue damage. Type I and Type II fractures (combined 26.7%) healed in 8 weeks or less. Eleven of the 15 cases evaluated (73.3%) were found to be Type III fractures, requiring more than 14 weeks for complete cortical healing. Osteomyelitis was associated with 3 cases of Type III tibial fractures, 2 of which developed after a second surgical intervention. Management, complications, and prognosis of gunshot fractures are discussed.     

岩藻多糖对肉兔生长性能、血清生化指标及养分表观消化率的影响

本试验旨在研究日粮中添加不同水平岩藻多糖对肉兔生长性能、屠宰性能、内脏器官指数、血清生化指标和养分表观消化率的影响，为岩藻多糖作为抗生素替代物在肉兔日粮中的应用提供理论依据。从200只35日龄健康断奶福建黄兔中选取36只体重相近的试验兔，采用单因素试验设计，随机分为4组，每组3个重复，每个重复3只。对照组饲喂基础日粮，试验Ⅰ、Ⅱ、Ⅲ组分别饲喂添加100、200和300 mg·kg^-1岩藻多糖的日粮，预试期5 d，正试期22 d。结果表明：1）试验Ⅲ组末重、平均日采食量（ADFI）、平均日增重（ADG）显著高于对照组（P<0.05），料重比（F/G）显著低于对照组（P<0.05）。2）试验Ⅲ组宰前活重显著高于对照组（P<0.05）。其他各项指标均无显著差异（P>0.05）。3）各试验组胸腺指数均显著高于对照组（P<0.05）。各组间脾脏指数和圆小囊指数均无显著差异（P>0.05）。试验Ⅱ和Ⅲ组蚓突指数显著高于对照组（P<0.05）。其他各项指标均无显著差异（P>0.05）。4）试验Ⅲ组丙氨酸氨基转移酶（ALT）含量显著低于其他组（P<0.05）。试验Ⅰ和Ⅱ组低密度脂蛋白胆固醇（LDL）、胆固醇（CHO）含量显著低于对照组（P<0.05）。试验Ⅲ组超氧化物歧化酶（SOD）活性显著高于对照组（P<0.05）。各试验组丙二醛（MDA）含量均显著低于对照组（P<0.05），谷胱甘肽过氧化物酶（GSH-Px）活性均显著高于对照组（P<0.05），其中试验Ⅲ组显著高于Ⅰ组（P<0.05）。其他各项指标均无显著差异（P>0.05）。5）各试验组干物质（DM）、中性洗涤纤维（NDF）、粗灰分（Ash）表观消化率均显著高于对照组（P<0.05）。试验Ⅲ组酸性洗涤纤维（ADF）表观消化率显著高于对照组（P<0.05）。各组粗蛋白（CP）表观消化率均无显著差异（P>0.05）。综上所述，日粮中添加岩藻多糖可显著提高肉兔ADFI和ADG，显著降低F/G，提高内脏器官指数和抗氧化能力，同时显著提高日粮中DM、ADF、NDF和Ash表观消化率，在本试验条件下，添加水平为300 mg·kg^-1时，效果最佳。     

Effects of beta-aminopropionitrile on equine tendon metabolism in vitro and on effects of insulin-like growth factor-I on matrix production by equine tenocytes

OBJECTIVE: To investigate effects of beta-aminopropionitrile and a combination of insulin-like growth factor (IGF)-I and beta-aminopropionitrile on metabolism of equine tendon fibroblasts. SAMPLE POPULATION: Flexor tendon explants from 3 horses. PROCEDURE: Explants received 1 of 4 treatments (control, IGF-I, beta-aminopropionitrile, and IGF-I/beta-aminopropionitrile) for 10 days, and message expression for collagen types I and III was assessed by use of in situ hybridization. Histologic findings, new protein production, and quantitative determinations of glycosaminoglycan, DNA, and de novo collagen synthesis were made. RESULTS: Insulin-like growth factor-I stimulated an anabolic response in tendon. Collagen synthesis and glycosaminoglycan and DNA content of explants were all increased. Beta-aminopropionitrile significantly suppressed collagen synthesis, which was not ameliorated by concurrent IGF-I treatment. Beta-aminopropionitrile caused alterations in cell morphology characterized by large round cells with eccentric nuclei and decreased density of collagen fibers. Protein production and collagen type-III mRNA expression were reduced in these cells. CONCLUSIONS AND CLINICAL RELEVANCE: Treatment with beta-aminopropionitrile resulted in decreased production of protein and collagen synthesis, which could be expected to suppress tendon healing. The negative effects of beta-aminopropionitrile could not be abrogated by addition of IGF-I to the medium. Treatment resulted in alterations in cell morphology and matrix consistency, which could further delay tendon healing. Beta-aminopropionitrile may impair tendon healing at a cellular level by decreasing collagen production or increasing rate of degradation of existing matrix. Because of reduced crosslinking during beta-aminopropionitrile treatment, in combination with transiently decreased tensile strength, alterations in collagen content and structure may weaken the healing tendon.     

Histology and ultrastructure of the developing superficial digital flexor tendon in rabbits

This study was designed to investigate the developmental changes in the superficial digital flexor tendon (SDFT) of the white New Zealand rabbit, from 5 to 7 days pre-natal to 112 days post-natal (PN), at histological and ultrastructural levels. The tendons changed from being highly cellular with 13079 ± 2538 cell/mm² and little directional organization to a longitudinally oriented, predominantly connective tissue structure with relatively few, mature tenocytes (2384 ± 365 cell/mm²). Fibrillogenesis was seen in isolated vacuoles of fibroblast cytoplasm during fetal life as well as after birth, but less frequently with increasing age. At the ultrastructural level, there was a progressive increase in the mean diameter of collagen fibrils with age throughout the population , until PN day 28. A bimodal distribution of collagen fibril size was first observed on PN day 56 while at day 112, the fibrils were fully differentiated and showed a multimodal size distribution. The development of elastic fibres preceded that of collagen fibres and accompanied progressively more marked sinusoidal crimping in collagen fibres on PN days 7 and 14. The tendons of older animals became less tightly crimped. The cells of the epi- and endotenon were less mature and relatively undifferentiated compared with the cells in the body of the tendon of the same age, which might explain their ability to initiate healing of tendon injuries in older animals. In conclusion, extensive changes were observed in tendons during growth and maturation, with diameters of collagen fibrils, tissue orientation and cellularity being the parameters affected, probably due largely to increased physical activity.     

Morphologic and biochemical characterization of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in llamas

OBJECTIVE: To determine the morphologic and biochemical characteristics of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in llamas. ANIMALS: 12 adult llamas (6 with bilateral hyperextension of the metacarpophalangeal or metatarsophalangeal joints and 6 age- and sex-matched control llamas). PROCEDURES: Llamas were evaluated by use of lameness examination, ultrasonography, and radiography. A CBC, serum biochemical analysis, and determination of concentrations of trace minerals in serum and liver samples were performed. Llamas were euthanized, and samples of the superficial digital flexor tendon, deep digital flexor tendon, and suspensory ligament were obtained from 4 areas and snap-frozen in liquid nitrogen or suspended in neutral-buffered 10% formalin. Immunohistochemical evaluation of collagen types I and III and assays for measurement of lysyl oxidase activity were performed. RESULTS: 2 affected llamas had a visible gait deficit associated with metacarpophalangeal joint hyperextension. Radiographic evidence of osteoarthritis was detected in 1 severely affected llama, and ultrasonographic changes of soft tissue mineralization and suspensory desmitis were observed in 2 llamas. Liver concentrations of copper were lower and serum concentrations of zinc higher in affected llamas, compared with values in control llamas. Lysyl oxidase activity and collagen distribution did not differ significantly between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Hyperextension of the metacarpophalangeal or metatarsophalangeal joints in llamas does not appear to be the result of injury or degeneration of the suspensory ligament or flexor tendons. Lower copper concentrations coupled with higher zinc concentrations in affected llamas may be indicative of secondary copper deficiency.