Acellular and glutaraldehyde-preserved tendon allografts for reconstruction of superficial digital flexor tendon in bovines: Part I--Clinical, radiological and angiographical observations

Sixteen tenorrhaphies were performed at the mid-metatarsal region in eight buffalo calves under lignocaine epidural analgesia. A 2 cm long gap was created in the superficial digital flexor (SDF) tendon and immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II. In group III, the defect was repaired with autografts. This group served as control. The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Diclofenac sodium and Enrofloxacin was given post-operatively for 5 days. Clinical examination revealed significant increase (P < 0.05) in rectal temperature, heart and respiratory rate for 3-4 postoperative days in all the animals. Mild pain and exudation as well as early restoration of tendon gliding movements and weight-bearing were observed earlier in group I in comparison with group II. Air-tendograms revealed early organization, minimal adhesion formation and lesser thickening of tendon at the reconstructive site in the acellular group whereas in the glutaraldehyde group dense homogenous swelling with adhesions was seen along the flexors. Angiography on day 30 showed that the area of proximal and distal host tendon graft junction appeared hypervascularized, whereas the area occupied by the graft appeared relatively less vascularized. Normal vascularization was observed on day 90 in all the three groups.     

Acellular and glutaraldehyde-preserved tendon allografts for reconstruction of superficial digital flexor tendon in bovines: Part II--Gross, microscopic and scanning electron microscopic observations

Sixteen tenorrhaphies were performed at mid-metatarsal region in eight buffalo calves. A 2-cm long gap was created in the superficial digital flexor (SDF) tendon in all animals. The gap was immediately repaired with acellular grafts in animals of group I, 1% glutaraldehyde-preserved tendon allografts in group II, and in group III the defect was repaired with autografts (control group). The contralateral limb in each animal was operated after an interval of 60 days and the animals underwent the same procedure according to the designed groups. Gross observation revealed filling of host tendon-graft junction with fibrous connective tissue. Increased vascularity was seen in group I when compared with group II and III. Graft was resorbed in animals of group I and III, whereas partial absorption of graft was seen in group II. Histological observations on day 30 revealed restoration of cellularity in acellular graft and fragmentation and resorption of glutaraldehyde-preserved graft. Graft was replaced by newly formed fibrous connective tissue. Tissue reaction around polygalactin suture consisted of plasma cells, lymphocytes and macrophages. On day 90, most of the acellular graft was replaced by newly formed fibrous connective tissue. In group II the majority of graft portion remained at the site and was in a state of resorption. In the control group it was difficult to distinguish between the host tendon and the graft. Scanning electron microscopical observation showed densely packed neoformed tissue at host tendon-graft junction. Hydrolysis and invasion of connective tissue between polygalactin suture filaments, resorption of graft with cavity formation and dissolution of ground substance were observed.     

Carbon fibres and plasma-preserved tendon allografts for gap repair of flexor tendon in bovines: gross,microscopic and scanning electron microscopic observations

The efficacy of carbon fibres and plasma-preserved tendon allografts for gap repair in the superficial digital flexor tendon in the mid-metatarsal region was evaluated in 12 crossbred calves. Experimental tenectomies were performed, followed by implantation of carbon fibres in group I (12 legs) and plasma-preserved tendon allografts in group II (12 legs). Gross observations in group I showed filling of the defect with granulation tissue with more vascularity on day 7, which was less prominent at day 14. On day 30, the neotendon formed was slightly thicker and comparable to normal tendon in appearance and texture. On day 90, it exhibited all the characteristics of a fully developed tendon. Whereas, in group II increased vascularity at the site and encapsulation of the graft with connective tissue in early periods was observed. The gap between graft and host was filled with fibrous connective tissue. Peritendinous adhesions were maximum on day 7 which were gradually reduced in both groups. Microscopically, an acute inflammatory reaction in the periphery of carbon fibres was observed on day 7. Immature fibroblasts were arranged in a haphazard pattern at this stage. By day 14, numerous newly formed capillaries and comparatively more mature fibroblasts were present in between and around the carbon fibres which were aligning parallel to the longitudinal axis of the tendon. By day 30 the healing tissue exhibited longitudinal orientation of collagen fibres and was at a more advance stage of maturation. By day 90, the neotendon formed simulated the picture of normal tendon. In the grafted tendon group, there was normal healing tissue at the functional sites between host and grafted tendon. The fibroblastic activity appeared to be both extrinsic and intrinsic in origin. The connective tissue had invaded the graft to a variable distance and there was resorption of graft which was replaced by newly formed connective tissue on day 90. Scanning electron microscopic observation revealed formation of neotendon between carbon fibre strands, resulting in thickening of the implant. In later stages parallel collagen fibres resembling normal tendon were observed in both groups.     

Gross and histomorphological observations following homologous deep frozen tendon grafting in equines

Experimental tenectomies were performed in the mid metacarpal region of the superficial digital flexor (SDF) tendon while the deep digital flexor (DDF) tendon was traumatized in 10 donkeys. In group I (n=8) the deep frozen tendons were used for grafting where as in group II (n=2) no grafting was done. Amniotic membrane casing was performed around grafted SDF and traumatized DDF tendons in group I only. Gross and histomorphological observations were recorded on the last day of the experiment, i.e., on the 15th (n=1), 30th (n=2), 60th (n=2), 90th (n=2) and 120th (n=1), post-operative days (POD) in group I and on the 60th (n=1) and 120th (n=1) POD in group II. Gross intraoperative observations suggested the presence of only thin filamentous adhesions in all but three animals at 30 (two animals) and 60 (one animal) days which were present only in the limited area of grafted tendon as compared to tenectomized SDF tendon that showed thick fibrous adhesion and thickening at both the cut ends. However, DDF tendon showed no adhesions in all except one animal of group I as compared to group II where adhesions were noticed in both the animals. Histological examination suggested an increase in fibroblastic activity at 2 weeks after grafting. Extrinsic and intrinsic healing response was observed in grafted tendons. Inflammatory reaction was reabsorbed by one month. The bundle formation was observed from two to three months. The histological structure appeared near normal by 4 months. Observation suggested that homologous tendon grafts remain viable by all histological criteria and healing was at a comparatively more advanced stage than tenectomized tendon. However, the traumatized DDF tendon healed completely by two months. It is concluded that the tendon healing was more rapid in animals where deep frozen grafts had been used.     

A preliminary study on the effect of ultrasound therapy on the healing of surgically severed achilles tendons in five dogs

This study was conducted on the left Achilles tendon in five clinically normal dogs. The Achilles tendon was surgically exposed and severed 3-4 cm proximal to the point of its insertion. Tenorrhaphy was undertaken by the application of three sutures on the various tendon units of the Achilles tendon using single locking-loop sutures with polyamide no. 1-0. The superficial digital flexor tendon was sutured with catgut using two horizontal mattress sutures. No ultrasound therapy was used in the animals of group I (control). Ultrasound therapy was given to the animals of group II (treated) starting from the third day post-operatively at 0.5 W/cm2 for 10 min daily for 10 days. A cortical screw was used for immobilization of the tibiotarsal joint which was removed 4 weeks after tenorrhaphy. Post-operatively, healing of the Achilles tendon was monitored using clinical observations, ultrasonography, gross and histomorphological observations at various intervals up to 120 days in both groups. Clinically, the dogs showed significant lameness for the first 4-5 days, which disappeared earlier in the ultrasound-treated (group II) animals than the controls (group I). Extension and flexion of the hock joint were found to be near normal at 6 weeks after the repair of the Achilles tendon. Ultrasonography showed anechoic to hypo-echoic echo-texture on days 3 and 7 after repair. By day 40, the echo-texture started to improve to hypo-echoic in group II, but in group I anechoic areas were still observed. However, the tendon showed near normal mottled hypo- to hyper-echoic texture in both groups by day 120. Gross observations suggested that the Achilles tendon in group II showed comparatively fewer adhesions than in group I animals. Histologically, in group II (treated), on day 40, the union was comparatively better without any inflammatory reaction. Bundle formation had begun in the ultrasound-treated animals which was not observed in the control animals. By day 90, more compact parallel bundle formation had taken place with minimum cellularity. Bundle formation was in its advanced stage in the treated animals. By day 120, the tendon tissue was comparatively acellular and looking like a normal tendon. The use of the cortical screw provided good immobilization and ultrasound therapy at 0.5 W/cm2 enhanced the Achilles tendon healing in dogs.     

Functional significance of the morphology and micromechanics of collagen fibres in relation to partial rupture of the superficial digital flexor tendon in racehorses

The high incidence of partial rupture of the superficial digital flexor tendor in the equine athlete represents a major cause for concern in the racing industry. Frequently, the lesion is localised to the central core of the tendon. This study tested the hypothesis that the site specific structural failure results from differences in the collagen fibre morphology and associated micromechanics between central and peripheral regions of the tendon. Bundles of collagen fibres were dissected from central and peripheral sites in the mid-metacarpal region of the tendon. Crimp morphology was quantified by polarised light microscopy and mechanical characteristics determined using a fibre tensometer. In older horses, centrally located fibres showed significantly lower values for crimp angle, crimp length and toe limit strain than seen peripherally. There were no significant differences in these features between corresponding sites in the younger horses. No significant difference between sites was found in elastic modulus in either group. These data indicate a non-uniform functional stress distribution which may result from ageing or be related to the exercise history as a feature of accumulated damage. These observations may explain the location of central core lesions seen on clinical examination.     

The management of tendon injuries in dogs

An account is provided of the management of 68 dogs with tendon injury. Of the 33 with Achilles rupture, 23 sustained tendon severance, seven had disrupted the gastrocnemius muscle/tendon junction, and in three an attachment of the gastrocnemius was avulsed. The standard operative procedure comprised fixing the hock in extension with a screw, and exploring the damaged structures with a view to repair and the introduction of carbon fibre implants. The majority regained normal limb use and the main complications concerned loosening or fracture of the screw. The 32 with digital flexor tendon severance had cuts, on a fore foot in nine and a hind foot in 23. Exploration and reconstruction were routinely practised and carbon fibre implants were frequently used. The standard of recovery was good in those dealt with fresh but was less satisfactory in chronic cases. The two dogs with digital extensor tendon and the one with flexor carpi ulnaris tendon severance responded well to repair.     

The effects of polyester (terylene) fibre implants on normal equine superficial digital flexor tendon

AIM: To determine the effect of polyester (terylene) fibre implants on normal equine superficial digital flexor (SDF) tendon structure. METHODS: Normal forelimb SDF tendons (n=24) of 12 horses were divided into unoperated, sham-operated, and implanted (terylene fibre implant) groups. Horses were assessed for lameness and ultrasonographic changes to SDF tendons at intervals up to 48 weeks post-operatively. After euthanasia, SDF tendons were collected for histological and ultrastructural examination. Histological sections were examined for alcian blue staining intensity, cellularity, fibril bundle alignment, fascicle separation and crimp morphology. Mass-average diameters (MADs) of collagen fibrils were calculated from electron micrographs and compared between treatment groups. RESULTS: Insertion of terylene fibre implants resulted in short-term (8 weeks) lameness in implanted limbs. Ultrasonographically, the implants could be detected in 50% of implanted tendons, but were associated with tendon swelling and the presence of hypoechoic core lesions in 7/8 implanted limbs. There were significant alterations in alcian blue staining, cellularity and crimp morphology in the central fascicles of sham-operated and implanted tendons, and alteration in fibril alignment in the central fascicles of implanted tendons. Unoperated tendons remained histologically normal. MADs of collagen fibrils did not differ between sham-operated, implanted and unoperated limbs. CONCLUSIONS: Both the sham procedure and the insertion of terylene fibre implants led to alterations in tendon structure that persisted for up to 48 weeks. Persistence of disorganised connective tissue at the proximal and distal ends of the terylene fibre implants may predispose implanted tendons to continued risk of injury. CLINICAL RELEVANCE: It is unlikely that terylene fibre implants offer any advantage over standard non-surgical treatments for mild to moderate cases of SDF tendonitis in the horse.     

Pathological and immunological study of goose embryos and goslings inoculated with an attenuated strain of Derzsy's disease virus.

An attenuated Derzsy's disease virus strain, designated BAV, was studied in goose embryos. A total of 248 embryonated goose eggs, coming from a susceptible laying flock with no yolk-derived immunity (group I) and from a vaccinated laying flock (group II) were used. The eggs were inoculated into the allantoic cavity with 10(1.9), 10(2.9) or 10(3.9) EID 50/0.2 ml virus on day 12 or day 20 of incubation. Embryos were killed at 5-day intervals. The dead embryos and the hatched goslings (up to 2 weeks of age) were examined by gross and histopathological methods. Reisolation of the virus from the organs was attempted, serum samples were tested for the presence of antibodies, and lymphocytes separated from the circulating blood were used in the lymphocyte stimulation and immunorosette formation tests. Embryos of both groups I and II, inoculated at either time of incubation, showed a body mass gain inferior to that of the controls. Sixteen (group I) and 12 (group II) of the embryos inoculated on day 12 of incubation died. Some (group I: 15, group II: 6) of the embryos inoculated on day 20 of incubation failed to hatch. The pathomorphological changes seen in the embryos killed between days 17 and 22 of incubation were of degenerative character. In embryos killed later (between days 23 and 58 of incubation) the degenerative changes were accompanied by infiltration by inflammatory cells. Reisolation of the virus strain was mostly successful between postinoculation (PI) days 5 and 10. Specific virus-neutralizing antibodies and cellular immune response were demonstrable already at hatching.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tendonitis of the branches of insertion of the superficial digital flexor tendon in horses

Objective To describe clinical findings, ultrasonographic features and outcome of injury to the branches of insertion of the superficial digital flexor (SDF) tendon in horses.
Design Retrospective study of 14 cases.
Procedure Fourteen Thoroughbred horses with tendonitis affecting the branches of insertion of the SDF tendon were examined for lameness, location and amount of swelling, and the presence of other musculoskeletal abnormalities. The flexor tendons were assessed by ultrasonographic examination, and recommendations were made for management of the cases. Outcome was assessed by re-examination of some horses, direct communication with the owner or trainer, and examination of race records.
Results The lateral SDF branch was affected in 10 horses; the medial branch in three, and both branches in one horse. Two horses had concurrent injuries to the SDF tendon in the metacarpal region of the contralateral limb. Ultrasonographic findings included swelling of the affected SDF branch, peritendinous fluid accumulation, disruption of normal fibre alignment on sagittal scan, and variable loss of echogenicity. As healing occurred, there was return of normal echogenicity, but normal fibre alignment did not return completely and apparent adhesions formed between the affected SDF branch and adjacent structures. Seven of 10 horses which returned to their previous use were able to compete without further tendon injury. Recurrence of injury occurred in one case, and another two horses developed tendonitis in the metacarpal region. One horse was retired from racing but was able to compete at dressage without recurrence of injury. Two horses were retired for breeding without returning to training, and one horse was sold and lost to follow up but did not race.
Conclusion The prognosis is fair for return to previous use following injury to the branches of insertion of the SDF tendon in athletic horses.     

Effects of sodium hyaluronate on tendon healing and adhesion formation in horses

Sodium hyaluronate reduces adhesions after tendon repair in rodents and dogs, and has been used in limited clinical trials in people. To evaluate its effect on tendon healing and adhesion formation in horses and to compare these effects with those of a compound of similar visco-elastic properties, a study was performed in horses, using a model of collagenase injection in the flexor tendons within the digital sheath. Eight clinically normal horses were randomly allotted to 2 groups. Adhesion formation between the deep digital flexor tendon and the tendon sheath at the pastern region was induced in the forelimbs of all horses. Using tenoscopic control, a 20-gauge needle was inserted into the deep digital flexor tendon of horses under general anesthesia and 0.2 ml of collagenase (2.5 mg/ml) was injected. The procedure was repeated proximally at 2 other sites, spaced 1.5 cm apart. A biopsy forceps was introduced, and a 5-mm tendon defect was created at each injection site. Group-A horses had 120 mg of sodium hyaluronate (NaHA) gel injected into the tendon sheath of one limb. Group-B horses had methylcellulose gel injected at the same sites. The contralateral limbs of horses in both groups served as surgical, but noninjected, controls. Horses were euthanatized after 8 weeks of stall rest. Ultrasonographic evaluation revealed improved tendon healing after NaHa injection, but no difference in peritendinous adhesion formation. Tendon sheath fluid volume and hyaluronic acid (HA) content were greater in NaHA-treated limbs. Gross pathologic examination revealed considerably fewer and smaller adhesions when limbs were treated with NaHA. However, significant difference in pull-out strengths was not evident between NaHA-treated and control limbs. Histologically, the deep digital flexor tendon from the NaHA-treated limbs had reduced inflammatory cell infiltration, improved tendon structure, and less intratendinous hemorrhage. Treatment with methylcullulose had no significant effect on tendon healing, adhesion size, quantity, or strength or on the volume and composition of the tendon sheath fluid. Sodium hyaluronate, administered intrathecally, appears to have a pharmaceutically beneficial action in this collagenase-induced tendinitis and adhesion model in horses.     

Effects of beta-aminopropionitrile fumarate and exercise on equine tendon healing: Gross and histological aspects

In the present study, the effects of intralesional injections of beta-aminopropionitrile fumarate (BAPN-F) was assessed in equine experimental tendinitis. BAPN-F is a lathyrogen which inhibits, crosslinking of collagen, permitting more time for parallel reorientation of the repair tissue. Sixteen two-year-old Arabian horses without health problems were used in this experiment. The animals were divided into two groups: group one was left in box rest, and group two was submitted to controlled exercise during the experiment. Tendinitis was induced with collagenase in the superficial flexor tendon of both forelimbs. Twenty days after the induction of tendinitis, intralesional treatment with BAPN-F was performed and the contralateral limbs received saline. A biopsy was obtained and gross and histopathological analysis was performed on the 150th day of the experiment. The collagen fibrillar alignment pattern in the healing area was better in the BAPN-F group submitted to controlled exercise than in the other group, as observed by sonographic and histopathologic examination. The present results indicate that BAPN-F in combination with controlled loading improved scar remodeling and tendon wound collagen maturation.     

The Effect of Misoprostol on Aspirin-Induced Gastroduodenal Lesions in Dogs

Misoprostol, a synthetic prostaglandin E₁, analog, is effective in treating and preventing nonsteroidal antiin-flammatory drug (NSAID)-induced gastrointestinal lesions in humans. The effectiveness of misoprostol in preventing aspirin-induced gastroduodenal injury was studied in 3 groups of 6 adult mixed breed dogs. Group I received 3 μg/kg misoprostol PO tid. Group II received 3 μg/kg misoprostol PO tid and 35 mg/kg aspirin PO tid. Group III received 35 mg/kg aspirin PO tid. Endoscopy was performed on days 0, 5, 14, and 30. Five regions of the upper gastrointestinal tract were qualitatively scored from 1 to 12 based on the presence of submucosal hemorrhage, erosion, or ulceration, with ulceration receiving a higher numerical score than submucosal hemorrhage. A total score was assigned based on the sum of the scores from all regions. Comparisons among groups on each day were performed using the Kruskal-Wallis test. Differences within a group among different time periods were determined using appropriate multiple comparisons. Significant difference in mean gastroduodenal lesion score was found among all groups at 5, 14, and 30 days. Mean total score on days 5, 14, and 30 were as follows: group 1,5.0,5.2, 9.0; group II, 12.0, 12.7, 16.2; and group III, 26.0, 23.8, 21.5, respectively. Significant differences within a group among different time periods were found from days 0 to 5 in groups I and II, and from days 14 to 30 in group I. It was concluded that misoprostol effectively decreased endoscopically detectable mucosal lesions in dogs given aspirin.     

Evaluation of a collagen patch as a method of enhancing ventriculotomy healing in Japanese quail (Coturnix coturnix japonica)

OBJECTIVE: To assess the ability of a porcine submucosal collagen patch to enhance ventriculotomy healing in quail. STUDY DESIGN: Histologic assessment of wound repair after ventriculotomy. Animal Population-Eighteen adult Japanese quail. METHODS: All quail had a ventriculotomy through the caudoventral thin muscle. The quail were randomly assigned to 1 of 2 groups: group I (n = 9) had routine closure and group II (n = 9) had routine closure and the application of a porcine submucosal collagen patch over the serosal surface of the ventricular suture line. Three quail from each group underwent necropsy at 7, 14, and 21 days after surgery and healing of the ventriculotomy site was evaluated by microscopy. RESULTS: Ventricular mucosal epithelium was completely healed at 21 days postoperatively. Time to restoration of the ventricular submucosal integrity was variable in both groups. There was evidence of a gross or microscopic perforation in 4 quail in group II, which was statistically significant (P =.041). Quail with perforations had significantly elevated numbers of ventricular serosal lymphoid aggregates compared with those without perforations (P =.029). There were no other significant temporal differences between group I and group II for mortality or histopathologic grading of wound healing. CONCLUSIONS: A porcine collagen patch did not enhance ventriculotomy wound healing. Subjectively, the collagen patch might have contributed to perforation by the generation of a lymphocytic xenograft rejection response. CLINICAL RELEVANCE: Ventriculotomy can be safely performed using routine closure methods in healthy birds.     

Italian University System has to Match Educational Needs in Adherence to European Standards and Professional Scenario

The effect of a water-soluble fraction (WSF) of a non-pathogenic strain of Mycobacterium phlei was studied in bovine subclinical mastitis (SCM) by measuring the myeloperoxidase and acid phosphatase enzyme levels in the milk leukocytes. Forty-five cows were divided into three equal groups. Group I, consisting of 15 healthy cows, served as the control, whereas groups II and III each contained 15 cows with subclinical mastitis on the basis of a positive reaction in the California mastitis test (CMT). The cows in group II received 100 microg of WSF in 5 ml sterile phosphate-buffered saline, pH 7.4 (PBS) once only, while those in group III received 5 ml sterile PBS daily for 7 days, both treatments being given by the intramammary route. Observations were made up to 30 days after treatment (AT). The CMT of the healthy milk was negative (0), whereas it ranged between 1 and 2 points in SCM. The somatic cell count (SCC) increased significantly (p < 0.05) on day 3, then fell steeply from day 7 up to day 30 AT in the cows in group II. A steady decrease in the total bacterial count (TBC) was observed in the group treated with WSF but the bacterial counts remained high in the groups treated with PBS. The mean acid phosphatase level was enhanced by 119% on day 3 AT in group II but only by 18.7% in the cows in group III. The mean myeloperoxidase level was enhanced by 100% in the cows in group II but only by 18% in those in group III on day 3 AT. This significant reduction in the bacterial load in infected cows caused by intramammary infusion of WSF may be due to activation of the microbicidal activity of the neutrophils, but this requires confirmation.     

硝酸稀土对湘东黑山羊血液蛋白及非蛋白氮指标的影响

选27只断奶湘东黑山羊随机等分为对照组、试验I组、试验II组,I组按10 mg/kg体重、II组按15 mg/kg体重的剂量添加硝酸稀土添加剂,隔天饮水1次,试验期为30d。定期采血,进行总蛋白(TP)、非蛋白氮(NPN)、白蛋白(A)、血红蛋白(Hb)、球蛋白(G)的测定。结果表明,试验组测定的G值和试验II组的Hb值低于文献报道值,其他测定值在文献报道值内,且TP、A、G值组间差异显著(P<0.05),NPN、Hb值组间差异不显著(P>0.05)。     

Effect of dry, soft moist, and canned dog foods on postprandial blood glucose and insulin concentrations in healthy dogs

The effect of dry, soft moist, and canned dog foods on immediate postprandial plasma glucose and insulin concentrations was evaluated in clinically normal dogs. Dogs were fed either dry (10 dogs; group I), soft moist (10 dogs; group II), or canned (8 dogs; group III) dog food for 5 consecutive days. On the fifth day, plasma glucose and insulin concentrations were determined in each dog prior to, during, and at 5, 10, 15, 30, 45, 60, 90, 120, 180, and 240 minutes after ingestion of the food. The alterations in plasma glucose concentrations were not significantly different from prefeeding values until 240 and 180 minutes after feeding for groups I and III, respectively. In contrast, the increments in plasma glucose were significantly (P less than 0.01) increased from basal concentrations at 30 and 45 minutes after feeding in group-II dogs. The maximal mean postprandial plasma glucose concentration was significantly (P less than 0.0001) less for group III, compared with concentrations for groups I and II, but there was no significant difference between concentrations for groups I and II. Although a biphasic insulin secretory response was found in all 3 groups of dogs, the patterns of phase-2 insulin secretion and the total amount of insulin secreted during the study were significantly different. There was a rapid increase in the plasma insulin concentration immediately after phase 1 in group II, with maximal plasma insulin concentrations occurring 30 minutes after feeding, followed by a gradual decrease in concentrations throughout the remainder of the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.