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Biomedical subjects

R L Sah

Publications and source records attributed to R L Sah.

At least 19 recordsLinked to original sources
PubMed2006

Continuous passive motion applied to whole joints stimulates chondrocyte biosynthesis of PRG4.

UNLABELLED: Continuous passive motion (CPM) is currently a part of patient rehabilitation regimens after a variety of orthopedic surgical procedures. While CPM can enhance the joint healing process, the direct effects of CPM on cartilage metabolism remain unknown. Recent in vivo and in vitro observations suggest that mechanical stimuli can regulate articular cartilage metabolism of proteoglycan 4 (PRG4), a putative lubricating and chondroprotective molecule found in synovial fluid and at the articular cartilage surface. OBJECTIVES: (1) Determine the topographical variation in intrinsic cartilage PRG4 secretion. (2) Apply a CPM device to whole joints in bioreactors and assess effects of CPM on PRG4 biosynthesis. METHODS: A bioreactor was developed to apply CPM to bovine stifle joints in vitro. Effects of 24h of CPM on PRG4 biosynthesis were determined. RESULTS: PRG4 secretion rate varied markedly over the joint surface. Rehabilitative joint motion applied in the form of CPM regulated PRG4 biosynthesis, in a manner dependent on the duty cycle of cartilage sliding against opposing tissues. Specifically, in certain regions of the femoral condyle that were continuously or intermittently sliding against meniscus and tibial cartilage during CPM, chondrocyte PRG4 synthesis was higher with CPM than without. CONCLUSIONS: Rehabilitative joint motion, applied in the form of CPM, stimulates chondrocyte PRG4 metabolism. The stimulation of PRG4 synthesis is one mechanism by which CPM may benefit cartilage and joint health in post-operative rehabilitation.

Animals↗
PubMed2006

Indentation probing of human articular cartilage: Effect on chondrocyte viability.

BACKGROUND: Clinical arthroscopic probes based on indentation testing are being developed. However, the biological effects of certain design parameters (i.e., tip geometry and size) and loading protocols (i.e., indentation depth, rate, and repetition) on human articular cartilage are unclear. OBJECTIVE: Determine if indenter design and indentation protocol modulate mechanical injury of probed cartilage samples. METHODS: The objectives of this study were to determine the effects of indentation testing using clinically applicable tips (0.4mm radius, plane- or sphere-ended) and protocols (indentation depths of 100, 200, or 300 microm, applied at a rate of 50 or 500 microm/s) on the extent and the pattern of chondrocyte death, should it occur. Grossly normal osteochondral blocks were harvested from human talar dome, indented, stained with live/dead dyes, and imaged en face on a fluorescence microscope. RESULTS: The occurrence and the extent of cell death generally increased with indentation depth, being undetected at an indentation depth of 100 microm but marked at 300 microm. In addition, tip geometry affected the pattern of cell death: ring- and solid circle-shaped areas of cell deaths were apparent when compressed to 300 microm using plane- and sphere-ended indenters. CONCLUSION: Indenter design and indentation protocol modulated the extent and the pattern of chondrocyte death. These results have implications for designing indentation probes and protocols, as well as clinicians performing arthroscopic probing.

Arthroscopy↗
PubMed2006

Effect of synovial fluid on boundary lubrication of articular cartilage.

OBJECTIVES: The lubrication of articulating cartilage surfaces in joints occurs through several distinct modes. In the boundary mode of lubrication, load is supported by surface-to-surface contact, a feature that makes this mode particularly important for maintenance of the normally pristine articular surface. A boundary mode of lubrication is indicated by a kinetic friction coefficient being invariant with factors that influence formation of a fluid film, including sliding velocity and axial load. The objectives of this study were to (1) implement and extend an in vitro articular cartilage-on-cartilage lubrication test to elucidate the dependence of the friction properties on sliding velocity, axial load, and time, and establish conditions where a boundary mode of lubrication is dominant, and (2) determine the effects of synovial fluid (SF) on boundary lubrication using this test. METHODS: Fresh bovine osteochondral samples were analyzed in an annulus-on-disk rotational configuration, maintaining apposed articular surfaces in contact, to determine static (mu(static) and mu(static),(N(eq)) and kinetic ([mu(kinetic)] and [mu(kinetic),(N(eq))]) friction coefficients, each normalized to the instantaneous and equilibrium (N(eq)) normal loads, respectively. RESULTS: With increasing pre-sliding durations, mu(static) and mu(static),(N(eq)) were similar, and increased up to 0.43 +/- 0.03 in phosphate buffered saline (PBS) and 0.19 +/- 0.01 in SF, whereas [mu(kinetic)] and [mu(kinetic),(N(eq))] were steady. Over a range of sliding velocities of 0.1-1 mm/s and compression levels of 18% and 24%, [mu(kinetic)] was 0.072 +/- 0.010 in PBS and 0.014 +/- 0.003 in SF, and [mu(kinetic),(N(eq))] was 0.093 +/- 0.005 in PBS and 0.018 +/- 0.002 in SF. CONCLUSIONS: A boundary mode of lubrication was achieved in a cartilage-on-cartilage test configuration. SF functioned as an effective friction-lowering boundary lubricant for native articular cartilage surfaces.

Animals↗
PubMed2006

Platelet-rich plasma stimulates porcine articular chondrocyte proliferation and matrix biosynthesis.

OBJECTIVE: Platelet-rich plasma (PRP) is a fraction of plasma that contains high levels of multiple growth factors. The purpose of this study was to examine the effects of PRP on cell proliferation and matrix synthesis by porcine chondrocytes cultured in alginate beads, conditions that promote the retention of the chondrocytic phenotype, in order to determine the plausibility of using this plasma-derived material for engineering cartilage. DESIGN: PRP and platelet-poor plasma (PPP) were prepared from adult porcine blood. Adult porcine chondrocytes were cultured in the presence of 10% PRP, 10% PPP or 10% fetal bovine serum (FBS) for 3 days. Cell proliferation, proteoglycan (PG) and collagen synthesis were quantified, and the structure of newly synthesized PG and collagen was characterized. RESULTS: Treatment with 10% PRP resulted in a small but significant increase in DNA content (+11%, vs FBS; P<0.01; vs PPP; P<0.001). PG and collagen syntheses by the PRP-treated chondrocytes were markedly higher than those by chondrocytes treated by FBS or PPP (PG; PRP: +115% vs FBS; +151% vs PPP, both P<0.0001, collagen; PRP: +163% vs FBS; +163% vs PPP, both P<0.0001). Biochemical analyses revealed that treatment with PRP growth factors did not markedly affect the types of PGs and collagens produced by porcine chondrocytes, suggesting that the cells remained phenotypically stable in the presence of PRP. CONCLUSION: PRP isolated from autologous blood may be useful as a source of anabolic growth factors for stimulating chondrocytes to engineer cartilage tissue.

Alginates↗
PubMed2006

Modulation of depth-dependent properties in tissue-engineered cartilage with a semi-permeable membrane and perfusion: a continuum model of matrix metabolism and transport.

The functional properties of cartilaginous tissues are determined predominantly by the content, distribution, and organization of proteoglycan and collagen in the extracellular matrix. Extracellular matrix accumulates in tissue-engineered cartilage constructs by metabolism and transport of matrix molecules, processes that are modulated by physical and chemical factors. Constructs incubated under free-swelling conditions with freely permeable or highly permeable membranes exhibit symmetric surface regions of soft tissue. The variation in tissue properties with depth from the surfaces suggests the hypothesis that the transport processes mediated by the boundary conditions govern the distribution of proteoglycan in such constructs. A continuum model (DiMicco and Sah in Transport Porus Med 50:57-73, 2003) was extended to test the effects of membrane permeability and perfusion on proteoglycan accumulation in tissue- engineered cartilage. The concentrations of soluble, bound, and degraded proteoglycan were analyzed as functions of time, space, and non-dimensional parameters for several experimental configurations. The results of the model suggest that the boundary condition at the membrane surface and the rate of perfusion, described by non-dimensional parameters, are important determinants of the pattern of proteoglycan accumulation. With perfusion, the proteoglycan profile is skewed, and decreases or increases in magnitude depending on the level of flow-based stimulation. Utilization of a semi-permeable membrane with or without unidirectional flow may lead to tissues with depth-increasing proteoglycan content, resembling native articular cartilage.

Biological Transport↗
PubMed2005

Osteogenic protein-1 promotes the formation of tissue-engineered cartilage using the alginate-recovered-chondrocyte method.

OBJECTIVE: This study examined the effects of a growth factor, recombinant human osteogenic protein-1 (rhOP-1), on the formation of tissue-engineered cartilaginous tissue by adult bovine articular chondrocytes using the alginate-recovered-chondrocyte (ARC) method. DESIGN: To ascertain if rhOP-1 enhances the formation of the cell-associated matrix (CM) and the characteristics of CM formation, bovine articular chondrocytes were first cultured for up to 14 days in alginate beads in medium supplemented with serum, with or without rhOP-1. Then, the recovered chondrocytes and their associated CM were resuspended in medium, with or without OP-1, seeded onto culture inserts, and incubated for an additional 14 days. The fabricated ARC tissues were subjected to biochemical and histological analyses. RESULTS: The addition of rhOP-1 to the medium in the alginate bead culture step resulted in an increased accumulation of both proteoglycan (PG) and collagen, with a ratio of PG to collagen that was higher than that found in native adult cartilage. The addition of rhOP-1 in the second step had a similar stimulatory effect during 14 days of culture. Histological examination of the tissue formed under all conditions revealed a cartilage-like matrix, stained strongly by toluidine blue. The thickness of the tissues obtained from culture conditions that included the addition of rhOP-1 was four times greater than that of the tissues cultured without rhOP-1. CONCLUSIONS: Using the ARC method, rhOP-1 enhanced the formation of matrix and generated a voluminous tissue-engineered cartilaginous construct. These characteristics may be beneficial in generating constructs that can cover large defects.

Alginates↗
PubMed2005

Kinetics of collagen crosslinking in adult bovine articular cartilage.

OBJECTIVE: Determine the kinetics of collagen crosslinking in adult bovine articular cartilage explants using radiolabel pulse-chase studies. METHODS: Explant cultures of adult bovine articular cartilage were radiolabeled with [14C]lysine in medium including fetal bovine serum and ascorbate, and then maintained for chase periods up to 28 days. In some samples, beta-aminopropionitrile (BAPN) was included during chase to inhibit lysyl oxidase-mediated collagen crosslinking. Tissue was hydrolyzed and analyzed for [14C]metabolites in the forms of lysine, hydroxylysine, dehydrodihydroxylysinonorleucine (DeltaDHLNL), and hydroxylysyl pyridinoline (HP). RESULTS: Explant cultures of adult bovine articular cartilage metabolized lysine into hydroxylysine and the collagen crosslinks, DeltaDHLNL and HP. During chase, [14C]hydroxylysine maintained steady-state levels, [14C]DHLNL rose to a plateau, and [14C]HP increased gradually. Addition of BAPN inhibited formation of [14C]DHLNL. Analysis of raw data and that normalized to [14C]hydroxylysine gave characteristic time constants for formation of DeltaDHLNL and HP crosslinks of 1-2 and 7-30 days, respectively. The distribution of [14C]lysine metabolites in collagen crosslinks was described by peak values in [14C]DHLNL/[14C]hydroxylysine of 0.047-0.064 and in [14C]HP/[14C]hydroxylysine of 0.03. CONCLUSION: Collagen crosslinks form in cartilage explants in vitro according to the classical lysyl oxidase-mediated pathway.

Amino Acids↗
PubMed2003

Tissue engineering of stratified articular cartilage from chondrocyte subpopulations.

OBJECTIVE: To test if subpopulations of chondrocytes from different cartilage zones could be used to engineer cartilage constructs with features of normal stratification. ESIGN: Chondrocytes from the superficial and middle zones of immature bovine cartilage were cultured in alginate, released, and seeded either separately or sequentially to form cartilage constructs. Constructs were cultured for 1 or 2 weeks and were assessed for growth, compressive properties, and deposition, and localization of matrix molecules and superficial zone protein (SZP). RESULTS: The cartilaginous constructs formed from superficial zone chondrocytes exhibited less matrix growth and lower compressive properties than constructs from middle zone chondrocytes, with the stratified superficial-middle constructs exhibiting intermediate properties. Expression of SZP was highest at the construct surfaces, with the localization of SZP in superficial-middle constructs being concentrated at the superficial surface. CONCLUSIONS: Manipulation of subpopulations of chondrocytes can be useful in engineering cartilage tissue with a biomimetic approach, and in fabricating constructs that exhibit stratified features of normal articular cartilage.

Animals↗
PubMed2003

Immunosuppression in broiler chicks fed aflatoxin and inoculated with fowl adenovirus serotype-4 (FAV-4) associated with hydropericardium syndrome.

A total of 240 unvaccinated day-old broiler chicks, which had been found to be negative for antibodies against FAV-4, were divided into four groups of 60 chicks each. Group A was fed aflatoxin at 1 ppm from 7 days to 7 weeks of age. Group V was infected intra-abdominally at 14 days of age with 0.2 ml of FAV-4, having a titre of 10(5.5) TCID50 per 0.2 ml. The combined group AV was given the aflatoxin and infected with FAV-4. The fourth group C served as the control. More pronounced clinical signs, a higher mortality rate (56.7%), and reductions in body weight gain and in the organ to body weight ratios of the bursa and spleen were recorded in group AV. A significant (p < 0.01) reduction in the HI antibody titre following vaccination against Newcastle disease, and of skin thickness in the delayed hypersensitivity test following sensitization with DNCB, indicated an additive immunosuppressive effect from aflatoxin and FAV-4 on the humoral and cell-mediated immune responses in group AV compared to groups A and V. Microscopically, marked depletion and degeneration of lymphocytes in the thymus, bursa, spleen and caecal tonsils were observed in group AV up to 5 weeks PI.

Adenoviridae Infections↗
PubMed2002

Integrative articular cartilage repair: dependence on developmental stage and collagen metabolism.

OBJECTIVES: The objectives of this research were to determine whether the integrative repair of bovine cartilage explants was dependent on developmental stage, and whether observed differences in integration with developmental stage were related to deposition of newly synthesized collagen and lysyl oxidase-mediated collagen cross-linking. METHODS: Pairs of fetal, newborn calf, and adult bovine cartilage blocks were cultured in partial apposition for 2 weeks in medium supplemented with serum, ascorbate, and [3H]proline. Following culture, mechanical integration between apposed cartilage blocks was assessed by measuring adhesive strength in a single-lap shear configuration. Formation and stabilization of newly synthesized protein and collagen was investigated by determination of [3H]proline and [3H]hydroxyproline in tissue digests and guanidine extracts. RESULTS: Calf cartilage exhibited a relatively high integrative repair phenotype, achieving an adhesive strength that was three--four-fold that of adult or fetal specimens. The low and high integrative repair phenotypes appeared related in part to different levels of collagen biosynthesis, which was approximately four--five-fold higher in calf cartilage samples than in the adult. However, fetal cartilage also exhibited a high level of biosynthesis. The different integrative repair phenotypes were not associated with marked differences in the kinetics of chemical stabilization of newly synthesized collagen, as the proportion of incorporated [3H]proline and newly-formed [3H]hydroxyproline that was resistant to extraction by 4M guanidine-HCl following culture was similar for cartilage from all developmental stages. Integration of calf cartilage appeared to depend on lysyl oxidase-mediated collagen cross-link formation, since inclusion of beta-aminopropionitrile (BAPN) in the culture medium completely eliminated development of adhesive strength. BAPN treatment also increased the percentage of newly synthesized protein in the guanidine extracts from 10% to 36% of the total, and that of newly synthesized collagen from 2% to 20%, while having only slight inhibitory effects on overall protein and collagen biosynthesis. CONCLUSION: The finding that cartilage exhibits enhanced integrative repair at a certain developmental stage suggests that it may ultimately be possible to enhance repair when needed in clinical situations.

Animals↗
PubMed2002

Biochemical quantification of DNA in human articular and septal cartilage using PicoGreen and Hoechst 33258.

OBJECTIVE: To compare two fluorometric assays, utilizing (1) the bisbenzimidazole Hoechst 33258 and (2) PicoGreen, for determining DNA content in human cartilage. METHODS: Human articular and nasal septal cartilage explants were digested using proteinase K. Portions of sample digest were analysed for intrinsic and dye-enhanced fluorescence with either Hoechst 33258 or PicoGreen. RESULTS: Intrinsic tissue fluorescence in both articular and septal cartilage increased with age and was prominent at wavelengths used for Hoechst 33258 but relatively low at wavelengths used for PicoGreen. The relative contribution of intrinsic fluorescence to total dye-enhanced fluorescence of human cartilage was markedly greater for Hoechst 33258 (19-57%) than for PicoGreen (2-7%). Thus, in many situations, DNA in human cartilage can be assayed using PicoGreen without the need to correct for intrinsic cartilage fluorescence. The enhancement of fluorescence by each dye was found to be specific for DNA, as shown by fluorescence spectra, >90% sensitivity to DNase, and resistance to RNase. In addition, little or no interference was caused by non-DNA tissue components, since DNA caused an equal enhancement in the absence or presence of proteinase K digested human cartilage, once intrinsic cartilage fluorescence was subtracted. PicoGreen was more sensitive for assaying DNA (0.9ng DNA/ml) than Hoechst 33258 (6ng DNA/ml) and can also be used in a microplate reader. CONCLUSION: PicoGreen can be used in a rapid and sensitive assay to quantify DNA in small samples of human cartilage.

Adult↗
PubMed2001

Depth- and strain-dependent mechanical and electromechanical properties of full-thickness bovine articular cartilage in confined compression.

Compression tests have often been performed to assess the biomechanical properties of full-thickness articular cartilage. We tested whether the apparent homogeneous strain-dependent properties, deduced from such tests, reflect both strain- and depth-dependent material properties. Full-thickness bovine articular cartilage was tested by oscillatory confined compression superimposed on a static offset up to 45%. and the data fit to estimate modulus, permeability, and electrokinetic coefficient assuming homogeneity. Additional tests on partial-thickness cartilage were then performed to assess depth- and strain-dependent properties in an inhomogeneous model, assuming three discrete layers (i = 1 starting from the articular surface, to i = 3 up to the subchondral bone). Estimates of the zero-strain equilibrium confined compression modulus (H(A0)), the zero-strain permeability (kp0) and deformation dependence constant (M), and the deformation-dependent electrokinetic coefficient (ke) differed among individual layers of cartilage and full-thickness cartilage. HiA0 increased from layer 1 to 3 (0.27 to 0.71 MPa), and bracketed the apparent homogeneous value (0.47 MPa). ki(p0) decreased from layer 1 to 3 (4.6 x 10(-15) to 0.50 x 10(-15) m2/Pa s) and was less than the homogeneous value (7.3 x 10(-15) m2/Pa s), while Mi increased from layer 1 to 3 (5.5 to 7.4) and became similar to the homogeneous value (8.4). The amplitude of ki(e) increased markedly with compressive strain, as did the homogeneous value: at low strain, it was lowest near the articular surface and increased to a peak in the middle-deep region. These results help to interpret the biomechanical assessment of full-thickness articular cartilage.

Animals↗
PubMed2001

Integrative cartilage repair: adhesive strength is correlated with collagen deposition.

Procedures to repair focal articular cartilage defects often result in poor integration between the host cartilage and the graft tissue, and this may be related to the lack of matrix deposition and the death of chondrocytes near a cut cartilage surface. The objective of this study was to determine if cartilage repair was related to deposition of newly synthesized collagen. The mechanical integration that occurred between two live adult bovine cartilage blocks cultured in partial apposition for two weeks was correlated with [3H]proline incorporation, a measure of protein synthesis, of which more than 66% was accounted for by collagen. A similar level of mechanical integration occurred in sample pairs consisting of a live and killed cartilage block, and this adhesive strength was also correlated with [3H]proline deposition into both the live and the killed blocks. In these samples, the [3H]proline deposited into the killed cartilage appeared to originate from chondrocytes in the live cartilage, since live cells were not detected in the killed cartilage block by either viability staining or [35S]sulfate incorporation. These results suggest a mechanism of integrative cartilage repair in which live chondrocytes within cartilage secrete matrix molecules that are components of a collagen network, and subsequent deposition of these molecules near the repair interface contributes to functional integration.

Adhesiveness↗
PubMed2001

Mechanisms of chondrocyte adhesion to cartilage: role of beta1-integrins, CD44, and annexin V.

The initial adhesion of transplanted chondrocytes to surrounding host cartilage may be important in the repair of articular defects. Adhesion may position cells to secrete molecules that fill the defect and integrate repair tissue with host tissue. While chondrocytes are known to become increasingly adherent to cartilage with time, the molecular basis for this is unknown. The objective of this study was to investigate the role of beta1-integrin, CD44, and annexin V receptors in chondrocyte adhesion to cartilage. Chondrocytes were cultured in high density monolayer, released with trypsin, and allowed to recover in suspension for 2 h at 37 degrees C. Under these conditions, flow cytometry analysis showed that chondrocytes expressed beta1-integrins, CD44, and annexin V. In a rapid screening assay to assess chondrocyte adhesion to cartilage, cell detachment decreased from 79% at 10 min following transplantation to 10% at 320 min. Treatment of cells with a monoclonal antibody to block beta1-integrins significantly increased chondrocyte detachment from cartilage compared to untreated controls. Similarly, results from a parallel-plate shear flow adhesion assay showed that blocking beta1-integrins significantly increased chondrocyte detachment from cartilage compared to untreated controls at each level of applied shear (0-70 Pa). In both assays, treatment of cells with reagents that block CD44 (hyaluronan oligosaccharides or monoclonal Ab IM7) or annexin V (polyclonal Ab #8958) had no detectable effect on adhesion. With cartilage treated with chondroitinase ABC, blocking beta1-integrins also increased chondrocyte detachment, while blocking CD44 and annexin V also had no detectable effect. Under the conditions studied here, beta1-integrins appear to mediate chondrocyte adhesion to a cut cartilage surface. Delineation of the mechanisms of adhesion may have clinical implications by allowing cell manipulations or matrix treatments to enhance chondrocyte adhesion and retention at a defect site.

Animals↗
PubMed2001

Compressive properties and function-composition relationships of developing bovine articular cartilage.

The composition of cartilage is known to change during fetal and postnatal development. The objectives of this study were to characterize the compressive biomechanical properties of the 1 mm thick articular layer of cartilage of the distal femur from third-trimester bovine fetuses, from 1 to 3 week old bovine calf and from young adult bovine knees, and to correlate these properties with tissue components. The confined compression modulus increased 180% from the fetus to the calf and adult. The hydraulic permeability at 45% offset compression (relative to the free-swelling thickness) decreased by 70% from fetus to adult. These development-associated changes in biomechanical properties were primarily associated with a marked (approximately 2-3-fold) increase during development in collagen content and no detectable change in glycosaminoglycan (GAG) content. A role for collagen in the compressive properties of cartilage and the gradual increase in collagen during development suggest that collagen metabolism is critical for cartilage tissue engineering and repair therapies.

Age Factors↗
PubMed2001

A morphologic, biochemical, and biomechanical assessment of short-term effects of osteochondral autograft plug transfer in an animal model.

PURPOSE: The objective of this study was to assess the short-term changes that occur after an osteochondral autograft plug transfer from the femoral trochlea to the medial femoral condyle in a goat model. TYPE OF STUDY: Articular cartilage repair animal study. METHODS: Six adult male goats were used in this study. Two 4.5-mm osteochondral plugs were transferred from the superolateral femoral trochlea to 2 recipient sites in the central portion of the medial femoral condyle for a survival period of 12 weeks. Postmortem, the global effects of the procedure were assessed by gross morphologic inspection and by analyzing the synovial DNA for inflammatory response. The recipient sites were also evaluated histologically and biomechanically. Metabolic activity was determined by (35)SO(4) uptake, and viability was assessed using a live/dead stain and by confocal laser microscopy. RESULTS: There was no evidence of significant gross morphologic or histologic changes in the operative knee as a result of the osteochondral donor or recipient sites. The patella, tibial plateau, and medial meniscus did not show any increased degenerative changes as a result of articulating against the donor or recipient sites of the osteochondral autografts. Analysis of synovial DNA revealed no inflammatory response. Biomechanically, 6- to 7-fold greater stiffness was noted in the cartilage of the transferred plugs compared with the control medial femoral condyle. Furthermore, on histologic examination, the healing subchondral bone interface at the recipient site had increased density. Glycosaminoglycan synthesis as determined by (35)SO(4) uptake was upregulated in the transplanted cartilage plug relative to the contralateral control, showing a repair response at the site of implantation. And finally, confocal microscopy showed 95% viability of the transferred plugs in the medial femoral condyle region. CONCLUSIONS: Our findings demonstrate the ability to successfully transfer an osteochondral autograft plug with maintenance of chondrocyte cellular viability. The transferred cartilage is stiffer than the control medial femoral condyle cartilage, and there is concern regarding the increased trabecular mass in the healing subchondral plate, but these do not result in increased degenerative changes of the opposing articular surfaces in the short term.

Animals↗
PubMed2001

Studies on the pathogenicity of Newcastle disease virus isolates in guinea fowl.

Newcastle disease viruses isolated from chickens and guinea fowl were characterized as viscerotropic, velogenic strains on the basis of their mean death time, intracerebral pathogenicity index, intravenous pathogenicity index and cloacal and conjunctival mean death time. The pathogenesis of the disease caused by both the strains was studied in 4-week-old guinea fowl. Both strains had an incubation period of 5 days and the birds showed dullness, depression, anorexia, diarrhoea and paralysis of the legs. They also exhibited nervous signs such as incoordination, muscle tremors and trembling of the neck at the advanced stage of the disease. Mortality reached 52% in the group infected with the chicken isolate but it was only 8% in the birds infected with the guinea fowl isolate. No specific changes were observed at post-mortem examination except haemorrhages at the tip of the glands of the proventriculus and in the caecal tonsil. Changes in the lymphoid organs and brain were always present in both the groups. Despite the low mortality, the guinea fowl isolated had multiplied in various organs in the birds. In both groups, the frequency of virus isolation increased from 5 to 10 days post infection.

Animals↗