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Biomedical subjects

C B Frank

Publications and source records attributed to C B Frank.

At least 91 records · Page 5Linked to original sources
PubMed1990

Cytochemical evidence for a proteoglycan-associated filamentous network in ligament extracellular matrix.

The purpose of this investigation was to examine the extracellular matrix of rabbit ligament before and after digestion with glycosaminoglycan degrading enzymes. In order to preserve and enhance the visibility of negatively charged tissue components, particularly the glycosaminoglycan-containing proteoglycans, the cationic stains ruthenium red (RR) and ruthenium hexamine trichloride (RHT) were used. Cross-sections of the midsubstance of 10-month-old (mature) rabbit medial collateral ligaments fixed using conventional procedures revealed a sparse population of stellate-shaped cells that did not appear to be interconnected. Similar tissue fixed in either RR or RHT showed an extensive network of thin, electron-dense "seams" that interconnected cells and appeared to irregularly subdivide the extracellular matrix (ECM). These seams mainly consisted of a meshwork of microfilaments throughout which small granules were dispersed. Numerous 14-nm microfibrils, as well as mature elastic fibers were also present within the seams. The size and shape of the microfilaments, together with their threadlike, beaded appearance suggested that they could be Type VI collagen. The seam granules were easily removed with chondroitinase ABC, chondroitinase AC II, and mild (0.18 M) salt treatment. Only chondroitinase ABC succeeded in removing additional granules, tentatively identified as proteodermatan sulphate molecules, that were periodically located at d band sites along the Type I collagen fibrils. These results suggest that the seam granules are not dermatan sulphate containing proteoglycans, and further, that these proteoglycans may be sequestered into specific zones within the ECM through loose association with the seam microfilaments. While the functional significance of the seams remains unknown and their specific composition clearly requires further study, it is likely that they represent important functional (e.g., viscoelastic) or biological (e.g., nutritional) subdivisions of ligament substance.

Animals↗
PubMed1990

The developmental morphology of a "periosteal" ligament insertion: growth and maturation of the tibial insertion of the rabbit medial collateral ligament.

The structural properties of ligament insertions change dramatically during growth and maturation, but little is known about their developmental anatomy. This study describes and quantifies changes in the gross and microscopic anatomy of the tibial insertion of the rabbit medial collateral ligament (MCL) during development and at skeletal maturity. Eighty animals were used for growth and descriptive studies. From this group, 27 animals, ranging in age from 1 to 24 months, were injected with fluorescent bone markers and their tibial insertions were processed undecalcified for histology. Sections were examined by polarized light and fluorescence microscopy to identify matrix and cells and to quantify mineral formation. Results showed that animals achieved histological skeletal maturity between 9 and 12 months of age. Body weights were a poor index of skeletal maturity. The tibial insertion was composed of five tissue layers, which changed proportions during growth and maturation. In immature animals, MCL fibers entered the periosteum; in older animals, MCL fibers were cemented to the tibia by advancing mineral. The tibial attachment of the MCL was thus transferred from the periosteum to the cortex during growth, suggesting that the term "periosteal insertion" is imprecise in adults. The hypothesis is put forward that these structural changes account for the reported increase in tensile failure of this insertion near skeletal maturity.

Aging↗
PubMed1990

Establishment and comparison of fibroblast cell lines from the medial collateral and anterior cruciate ligaments of the rabbit.

We have developed a procedure to explant fibroblasts from the anterior cruciate ligament (ACL) and the medical collateral ligament (MCL) of the rabbit knee, and have optimized conditions for maintaining them in culture. Maximal growth for both ACL and MCL cells was obtained with Dulbecco's modified Eagle's medium supplemented with 15% fetal bovine serum and 250 microM ascorbate. ACL and MCL fibroblasts displayed intrinsic differences in their responses to changes in culture parameters. Specifically, they displayed different growth responses when plated at different densities and responded to RPMI 1640 medium in very different ways. There were also biochemical differences between the cell types. Both cell types produced similar amounts of collagen in culture, but the ratio of type I to type III, the major collagen subtypes produced by these cells, were different. ACL fibroblasts produced 86.7% type I and 13.3% type III, and MCL fibroblasts produced 71.1% type I and 28.9% type III. In addition, total protein produced by ACL fibroblasts was higher than that produced by MCL cells. This confirms the suggestions of previous researchers that such differences might exist.

Animals↗
PubMed1990

The effects of temperature on the viscoelastic properties of the rabbit medial collateral ligament.

There are disparate views on the effects of temperature on the mechanical properties of ligaments and tendons. We attempted to resolve the inconsistencies by testing the medial collateral ligaments of twelve, three-month old New Zealand white rabbits in both elastic-dominated and viscous-dominated tests between 25 degrees C and 55 degrees C. We found that in elastic-dominated monotonic loading, the loading portions of the load-extension curves were mathematically similar. Differences could be accounted for through a base-line shift of the origin caused by additional relaxation and thermal contraction/expansion of the apparatus and specimen. In tests where the viscous component of behavior was manifest, we found results similar to those of other investigators. Thus we conclude that in assessing the effects of temperature on the mechanical properties of tissues it is important to account for both temperature and initial positions of the apparatus and specimen, and to consider the effects of both relaxation and thermal contraction/expansion.

Animals↗
PubMed1990

Elongation and forces of ankle ligaments in a physiological range of motion.

The purposes of this study were: (1) to measure the distances between the insertion sites of selected ankle ligament fibers, (2) to measure the force-elongation characteristics of isolated bone-ligament-bone preparations, and (3) to relate the force measurements to angular positions of the ankle. The findings can be used to discuss clinically the correlation between possible ligament injuries and associated foot movement. Three fresh cadaveric ankles were dissected to expose the anterior talofibular ligament, the calcaneofibular ligament, and the superficial deltoid ligament. The ankles were first mounted on a fixture, and insertion to insertion distances of the ligament fibers were measured for selected positions of the ankle/subtalar joint. Bone-ligament-bone preparations were then removed, returned to their anatomical length and uniaxial force-extension testing was performed. The forces in each ligament were recorded for distances corresponding to those measured in situ for various ankle positions. These results allowed: (1) estimation of the forces in these three ligaments in various ankle positions, (2) identification of positions where ligaments were carrying no force, and (3) identification of positions where they carry large forces. The clinical analysis reveals that the anterior talofibular ligament is sensitive to excessive plantarflexion or dorsiflexion, the calcaneofibular ligament is sensitive to excessive inversion or eversion as well as dorsiflexion or plantarflexion, and that the deltoid ligament appears to be sensitive to plantarflexion, external rotation, and eversion. The fact that all three ligaments tested demonstrated different ranges of tension supports the view that there are optimal positions for testing ankle ligament integrity.

Adult↗
PubMed1990

Fine vascular anatomy of adult rabbit knee ligaments.

The microvascular anatomy of discrete knee ligaments in adult rabbits is described. Epiligamentous plexuses give rise to a limited number of vessels which penetrate deeply into ligament substance. Intraligamentous vessels are usually longitudinally orientated, widely separated linear anastomoses but occasionally complex glomus-like configurations are present. The significance of these findings is discussed in relation to other articular connective tissues and to the possible roles of the intraligamentous microvasculature.

Animals↗
PubMed1989

The effect of cryopreservation on the biomechanical behavior of bovine articular cartilage.

The short-term effect of cryopreservation on specific mechanical behaviors of bovine articular cartilage has been investigated. A flat-ended nonporous indentor was used in a nondestructive, repetitive, axisymmetric unconstrained testing system. Cyclical indentation from a fixed position to a fixed load was applied until a steady-state load-deformation relationship (limit cycle) was achieved. Indentation behaviors measured from the limit cycles of each articular cartilage specimen before and after treatment were compared. Testing was done in vitro using fresh, mature bovine radiocarpal joints. Twenty pairs of cartilage-subchondral bone cores from anatomically similar sites on contralateral joints were separated into three groups; thickness controls, dimethylsulfoxide (DMSO) controls, and cryopreserved experimental samples. Thickness controls and DMSO controls were used to examine the isolated effects of the thickness measurement and DMSO incubation techniques on articular cartilage indentation characteristics. Experimental samples were cryopreserved using DMSO, their thicknesses similarly measured and indentation behaviors examined. Following testing, histological and histochemical assessment of the specimens confirmed the nondestructive nature of the tests. Intra- and intergroup comparisons of controls and experimentals revealed no statistical differences in the mechanical behaviors measured from the limit cycle or in cartilage thickness. These results indicate that the cryopreservation protocol used did not have an effect that we could measure on these specific mechanical behaviors of articular cartilage.

Animals↗
PubMed1989

A biomechanical study of suture pullout in linea alba.

The relationship of suture bite size, suture diameter, and fascial thickness to strength of wound closure was studied in cadaveric linea alba. All soft tissue was removed from the fascia of 12 abdominal walls that were cut into 346 test sections. A single suture loop was placed in each section, simulating laparotomy closure with interrupted technique. Suture bite size (0.3, 0.6, 0.9, 1.2, 1.5, and 1.8 cm) and gauge (00, 0, 1, and 2) were randomly assigned. The force and energy required to pull out suture loops were measured. Mean linea alba thickness was greater above the linea semicircularis than below (1.19 vs 0.77 mm; p less than 0.001). Similarly, mean pullout force was greater above the linea semicircularis (58.2 vs 31.6 N; p less than 0.001). Regression analysis found that fascial thickness and bite size accounted for 68% of observed variability in pullout force. Suture diameter was unrelated to pullout force. Optimum security was obtained with bites of at least 1.2 to 1.5 cm.

Abdominal Muscles↗
PubMed1988

A new method of measuring the cross-sectional area of connective tissue structures.

There appears to be no generally accepted method of measuring in-situ the cross-sectional area of connective tissues, particularly small ones, before mechanical testing. An instrument has therefore been devised to measure the cross-sectional area of one such tissue, the rabbit medial collateral ligament, directly and nondestructively. However, the methodology is general and could be applied to other tissues with appropriate changes in detail. The concept employed in the instrument is to measure the thickness of the tissue as a function of position along the width of the tissue. The plot obtained of thickness versus width position is integrated to provide the cross-sectional area. This area is accurate to within 5 percent, depending mainly on alignment of the instrument and pre-load of the ligament. Results on the mid-substance of the rabbit medial collateral ligaments are repeatable and reproducible. Values of maximum width and thickness are less variable than those obtained with a vernier caliper. The measured area is considerably less than that estimated assuming rectangular cross-section and slightly less than that estimated on the assumption of elliptical cross-section.

Animals↗
PubMed1987

Collagen alteration in medial collateral ligament healing in a rabbit model.

The purpose of this study was to evaluate changes over time in surgically ruptured medial collateral ligament (MCL) with respect to collagen synthesis, collagen degradation and collagen type. Our method involved prelabeling collagen in growing rabbits using 3H-proline followed by surgical injury to the MCL. Animals were sacrificed at intervals up to 40 weeks post-injury. At each time point total hydroxyproline, changes in collagen mass, and collagen synthesis and degradation were determined and related to the unruptured control MCL. A separate semiquantitative determination of collagen type was also performed on the midsubstance of each healing and control ligament. Results showed an increase in total collagen mass and a decrease in collagen concentration in all healing ligaments. Concommitantly, an increase in the collagen turnover rate was observed. Relative turnover was greatest at 3 to 6 weeks after injury and returned toward the normal rate by 40 weeks. Type I collagen was partially replaced by type III, probably as a result of increased synthesis during scar formation. The mechanism for collagen remodeling (replacement of mass and concentration in an organized fashion) in untreated rabbit MCL scar appears functional by virtue of its chronicity but, due to a shift in collagen type, it may also be qualitatively inadequate.

Animals↗
PubMed1986

Tensile properties of the medial collateral ligament as a function of age.

The biomechanical properties of the rabbit medial collateral ligament (MCL) as a function of maturation and age were investigated. Femur-MCL-tibia (F-M-T) preparations were obtained from rabbits of different age groups (open or closed epiphysis). Parallel increases in the animal body weight and ligament cross-sectional area were recorded with age. Cyclic and tensile failure tests were performed to obtain the structural properties of the F-M-T complex and the mechanical properties of the MCL substance. There were significant increases in the load at failure, energy-absorbing capability of the bone-ligament junction, and in the tensile strength of the ligament substance as a result of maturation and subsequent aging. Increases in the area of hysteresis obtained during cyclic loading-unloading were also documented. At the closing of the epiphysis, the mode of failure of the F-M-T structure progressed from tibial avulsion to failure in the midsubstance of the ligament. An asynchronous rate of maturation was observed between the structural properties of the bone-ligament complex and the mechanical properties of the ligament substance.

Aging↗
PubMedDate not supplied

Electrothermal shrinkage reduces laxity but alters creep behavior in a lapine ligament model.

Thermal denaturation of collagen in ligament tissue has the potential to enhance arthroscopic shoulder stabilization. Previous studies have shown that laser energy produces significant capsular shortening without alteration of viscoelastic properties, but little information is available on the effects of radio frequency electrothermal energy. We assessed the acute effects of radio frequency shrinkage with use of the lapine medial collateral ligament model, in which the tibial insertion was shifted proximally to produce abnormal laxity. Thermal treatment resulted in restoration of laxity from 3.33 +/- 0.25 mm to 0.66 +/- 0.31 mm, which was not significantly different from medial collateral ligaments replaced anatomically (0.50 +/- 0.34 mm). When tested at 4.1 megapascals, cyclic and static creep strains were increased twofold to threefold in thermally-treated ligaments (P <.01), and partial failure occurred in 2 of 8 cases. We conclude that radio frequency electrothermal shrinkage is effective at reducing laxity but significantly alters viscoelastic properties, posing a risk of recurrent stretching-out at "physiological" loads.

Analysis of Variance↗
PubMedDate not supplied

Influence of exogenous growth factors on the expression of plasminogen activators by explants of normal and healing rabbit ligaments.

In this investigation we have demonstrated that specific growth factors are able to modify plasminogen activator (PA) activity in explants from both normal and healing ligaments. Specifically, the addition of insulin-like growth factor 2 (IGF-2; 100 ng/mL) and transforming growth factor beta 1 (TGF-beta 1; 2.5 ng/mL) to explants of unoperated and healing ligaments resulted in a decrease in both PA and PA--PA-binding protein complex in conditioned medium from several tissues, and particularly in medial collateral ligament (MCL) scar tissue. This effect was observed in the explants from 3-, 6-, and 12-week healing scar tissue. In addition, IGF-2 and TGF-beta 1 influenced PA release from MCL tissue derived from the unoperated knee joint of 3-week healing animals. In contrast, basic fibroblast growth factor (b-FGF; 10 ng/mL) and IGF-1 (100 ng/mL) did not cause a detectable alteration of PA and PA--PA-binding protein complex activity in any of the healing or unoperated ligaments analyzed. These results indicate that specific growth factors are able to modify the activity of cells in explants of ligament and healing ligament in a distinct manner.

Animals↗
PubMedDate not supplied

Influence of exogenous growth factors on the synthesis and secretion of collagen types I and III by explants of normal and healing rabbit ligaments.

In this investigation it has been demonstrated that specific growth factors are able to modify collagen secretion in explants from healing rabbit medial collateral ligaments. The addition of 2.5 ng transforming growth factor beta 1 (TGF-beta 1)/mL to 3-week-old scar explants resulted in an increase in the total amount of collagen secreted. Analysis of collagen types I and III individually revealed that the increase mediated by TGF-beta 1 was due primarily to an increase in collagen type I secretion. This led to a ratio of type I:type III that is closer to that found in normal ligament tissue. The addition of 100 ng insulin-like growth factor 2 (IGF-2) to explant cultures of 3-week-old scar tissue also led to an increase in the quantity of collagen secreted, but the increase was in both type I and III collagens. These effects were observed to a lesser degree in 6-week-old scar tissue, and by 12 weeks postinjury, minimal effects of the growth factors on collagen synthesis was detected. Neither growth factor influenced collagen secretion by normal ligament or synovium. In contrast, IGF-1 (100 ng/mL) or basic fibroblast growth factor (bFGF) (10 ng/mL) did not exert a detectable effect on collagen secretion by any of the normal or healing tissues. These results indicate that TGF-beta 1 and IGF-2 can modify the metabolic activity of cells in explants of healing ligaments early after injury and may enhance the repair process leading to improved function.

Animals↗
PubMedDate not supplied

Linea alba closure: determination of ideal distance between sutures.

An experiment was conducted to determine the optimal distance between sutures in closure of abdominal midline incisions. Human cadaveric fascia was harvested soon after death and stored at -70 degrees C until testing. Suture pullout tests were performed to determine the maximal force applied to the fascia before pullout. Fascia from the opposite side of the same cadaver was used as a control. In a first series of testing, we observed that the pullout force of two sutures dropped linearly as they were brought closer than 12 mm apart. In a second series we observed no increase in pullout force using multiple sutures closer together compared to fewer sutures 15 mm apart. The experiments suggest that the mechanical requirements of closing a midline abdominal incision are met by placing sutures 10-15 mm apart.

Abdominal Muscles↗