Biomedical subjects

G Lust

Publications and source records attributed to G Lust.

At least 73 records · Page 4Linked to original sources

PubMed1993

Keratan sulfate as a marker of articular cartilage catabolism and joint treatment in ponies.

Keratan sulfate (KS) is a glycosaminoglycan, distribution of which is confined mostly to hyaline cartilage. As such, it is a putative marker of hyaline cartilage catabolism. In experiment 1, a focal osteochondral defect was made arthroscopically in 1 radial carpal bone of 2 ponies, and in 2 other ponies, chymopapain was injected into the radiocarpal joint to induce cartilage catabolism. Sequential and concurrent plasma and synovial fluid concentrations of KS were measured, up to 13 months after induction of cartilage injury, to determine whether changes in KS concentrations reflected cartilage catabolism. In experiment 2, a large, bilateral osteochondral defect was made in the radial carpal bones of 18 ponies, which were subsequently given postoperative exercise and/or injected intra-articularly with 250 mg of polysulfated glycosaminoglycan (PSGAG). Medication was given at surgery, then weekly for 4 weeks. Blood samples were collected and synovial fluid was aspirated before surgery, when medication was given, and at postmortem examination (postoperative week 17). The KS concentration was measured in these fluids to determine whether changes in KS concentration indicated an effect of joint treatment. In experiment 1, the concentration of KS in synovial fluid was highest 1 day after joint injury, and the concentration in plasma peaked 2 days after joint injury. For ponies receiving chymopapain intra-articularly (generalized cartilage catabolism), a fivefold increase over baseline was observed in the concentration of KS in plasma (peak mean, 1.2 micrograms/ml), and a tenfold increase over baseline in synovial fluid (peak mean, 2.0 mg/ml) was observed. On average, these maxima were threefold higher than values in fluids of ponies with osteochondral defects (focal cartilage disease). In experiment 2, nonexercised ponies had lower KS concentration (as a percentage of the preoperative concentration) in synovial fluid than did exercised ponies at all postoperative times, and at postoperative week 17, this effect was significant (P < 0.05). This may be related to decreased turnover of KS in articular cartilage attributable to stall confinement and late increase in turnover related to exercise. Seventeen weeks after surgery, synovial fluid from exercised, medicated ponies had significantly (P < 0.05) higher KS content than did fluid from exercised, nomedicated ponies. This indicated that exercise, when combined with medication, may increase KS release from articular cartilage. Synovial fluid from medicated joints of nonexercised ponies had significantly (P < 0.05) lower KS concentration than did synovial fluid from nonmedicated joints of nonexercised ponies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Use of scintimetry to assess effects of exercise and polysulfated glycosaminoglycan on equine carpal joints with osteochondral defects.

Combined blood pool and delayed images produced by use of 99mTc-methylene diphosphonate (99mTcMDP) were evaluated as an objective measurement of the response of equine joints with osteochondral defects to postoperative exercise and intra-articularly administered polysulfated glycosaminoglycan (PSGAG). Osteochondral defects (approx 2.4 x 0.9 cm) were induced arthroscopically in the dorsodistal radial carpal bones of 18 ponies. These ponies were randomized (while balancing for age [range 2 to 15; median, 5.0; mean, 5.1 years]) to 2 treatment groups. Nine ponies were assigned to be exercised, and 9 were stall-rested. Six ponies in each group were administered PSGAG (250 mg) in 1 joint (medicated) and lactated Ringer's solution (LRS) in the contralateral joint. The 3 remaining ponies in each group were administered LRS in both joints (nonmedicated). Medication was given at surgery, then weekly for 4 weeks. The exercise protocol (begun at postoperative day 6 and conducted twice daily) started with 30 minutes walking (approx 0.7 m/s), and, by postoperative month 3, the ponies were being walked for 15 minutes and trotted (approx 1.6 m/s) for 25 minutes. Simultaneous dorsal images of both carpi were made 2 to 3 minutes after IV administration of 99mTcMDP (blood pool image) and 90 to 120 minutes later (delayed image). Scintimetry, in counts per minute per pixel per millicurie, was done before, and at 1, 2, 4, 8, 10, 13, and 17 weeks after surgery, prior to euthanasia. Radionuclide uptake on blood pool images decreased faster than that on delayed images, in which uptake remained high for 17 weeks. This indicated that bone was metabolically active for at least 17 weeks after surgery. Exercise significantly (P < 0.05) decreased uptake on the blood pool images of medicated joints up to 1 month after surgery. Thus, exercise (in the presence of PSGAG) probably had a transient, beneficial effect on soft tissues of the joint. Exercise, without PSGAG, promoted increased bone remodeling, because the highest uptake on delayed images was observed in exercised, nonmedicated ponies up to 3 months after surgery. This was consistent with development of osteoarthritis in these ponies. Medication alone stimulated bone remodeling, and data indicated that an identical effect may take place in contralateral LRS-injected joints, because of systemic circulation of the drug. However, the combination of exercise and medication appeared to moderate the independent effects of each. The combination of exercise and medication in individual joints resulted in notably (P < 0.05) decreased bone remodeling.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Temporal matrix synthesis and histologic features of a chondrocyte-laden porous collagen cartilage analogue.

Cartilage resurfacing by chondrocyte transplantation, using porous collagen matrices as a vehicle to secure the cells in cartilage defects, has been used experimentally in animals. This in vitro study evaluated the temporal morphologic features and proteoglycan synthesis of chondrocyte-laden collagen matrices. Forty-two porous collagen disks were implanted with a minimum of 6 x 10(6) viable chondrocytes, covered by a polymerized collagen gel layer, and 6 disks were harvested after 0, 3, 7, 10, 14, 18, or 22 days of incubation in supplemented Ham's F12 medium at 37 C and 5% CO2. Histologic and histochemical evaluation of formalin-fixed segments of the cultured disks indicated that the chondrocytes proliferated in the implant, producing small groups and linear segments of cells by day 14. The collagen framework remained intact over the course of the study with thick areas attributable to depositions of matrix material after day 10. Alcian blue-stained matrix was evident in the pericellular region of chondrocytes in sections of disks harvested on days 14, 18, and 22. Glycosaminoglycan (GAG) assay by dimethylmethylene blue dye binding after papain digestion of the disk segments revealed negligible amounts of GAG at day 0. Significant (P < or = 0.0001) increase in total GAG content was observed by day 3 (0.329 micrograms/mg of disk) and further increases were observed until a plateau in GAG quantity was seen on day 14. Mean peak GAG content was 0.553 +/- 0.062 micrograms/mg. Secondary treatment of the papain-digested implants with keratanase and chondroitinase ABC yielded similar trends in chondroitin sulfate (CS) and keratan sulfate (KS) concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effects of dietary electrolyte balance on subluxation of the femoral head in growing dogs.

Effects of increased dietary chloride and reduced sodium and potassium ion concentrations on coxofemoral joint conformation, as assessed by radiography, were examined in growing dogs. Dietary electrolyte balance was quantified by dietary anion gap (DAG), defined as Na+ + K+ - Cl- in milli-equivalents per 100 g of food. Diets had anion gap ranging from 8 to 41 mEq/100 g of food. One hundred sixty-seven pups from 27 litters representing 5 breeds were studied during the period of rapid growth. The extent of subluxation of the femoral head was measured on radiographs, using the method of Norberg. On average, less subluxation of the femoral head (P < 0.05) was observed when diets with lower DAG were fed. Differences in DAG balance did not result in different rates of weight gain; therefore, the reduction in coxofemoral joint subluxation attributable to low DAG was unrelated to weight gain. Norberg angles measured at 30 weeks of age were highly correlated with coxofemoral joint status at 2 years of age, as measured by the Swedish diagnostic system and the scoring system of the Orthopedic Foundation for Animals (lrl > or = 0.70, P < 0.0002, n = 24). This diet-related improvement in coxofemoral joint subluxation would be expected, on average, to delay or mitigate the characteristic clinical and radiographic signs of hip dysplasia in growing dogs.

Animals↗

PubMed1992

Effects of limited food consumption on the incidence of hip dysplasia in growing dogs.

Forty-eight 8-week-old Labrador Retrievers were allotted to 2 groups of 24 dogs each; 1 group was fed ad libitum and the other group was given 25% less of the same feed until the dogs were 2 years old. Radiography of the hip joints was done when the dogs were 30, 42, 54, 78, and 104 weeks old. Subluxation was measured by the Norberg angle on radiographs made with the dog in the standard (extended limb) position. Independent of age at which the radiography was done, there was less subluxation of the femoral heads in the limit-fed dogs. Using the Swedish method of hip joint evaluation on the same radiographs, it was found that fewer dogs on limited food intake had signs of hip dysplasia. Radiographs done when dogs were 2 years old, for all the methods used (Norberg angle in standard and frog-limb position, the Orthopedic Foundation for Animals [OFA] score, and the Swedish score), revealed less hip dysplasia (less joint subluxation and less degenerative joint disease) in the limit-fed dogs. Using the OFA method, 7 of the 24 limit-fed dogs and 16 of the 24 ad libitum-fed dogs were diagnosed as having hip dysplasia. Similarly, using the Swedish method, 5 of the 24 limit-fed dogs and 18 of the 24 ad libitum-fed dogs were diagnosed as having hip dysplasia. The food-intake-related differences were significant both for the OFA score and for the Swedish score.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1992

Fibronectin and keratan sulfate synthesis by canine articular chondrocytes in culture is modulated by dibutyryl cyclic adenosine monophosphate.

The ability of cyclic adenosine monophosphate (cAMP) to maintain differentiated properties of canine articular chondrocytes in culture is reported. Treatment with 0.5 mM dibutyryl cAMP (DBcAMP) caused the cells to adopt a more rounded morphology. This change in morphology seems to have no effect on the overall biosynthetic rates of the cells. After a pulse with 35S-methionine, there was no difference in the concentration of labeled proteins between cultures treated with DBcAMP and control cultures. After 6 days, the amount of fibronectin (FN) in the media of DBcAMP-treated cultures detected by an enzyme-linked immunosorbent assay was specifically reduced by 30%. The amount of 35S-FN purified by gelatin-affinity chromatography decreased 33%. Moreover, the percentage of FN containing the extra domain A sequence was reduced from 19.4 +/- 8.7% in control cultures to 9.6 +/- 4.2%. Concomitant with the decrease in FN, there was an increase in the concentration of keratan sulfate in the media of DBcAMP-treated cultures. After 6 days, treated cultures had 47% more keratan sulfate than controls did. These changes appear not to be the result of a change in the deposition of FN or keratan sulfate, because the amount of these molecules that could be extracted from the cell layer was typically below the limit of detection of the assays. Instead, it seems there is a phenotypic change in the chondrocytes pertaining to the production of FN and keratan sulfate.

Animals↗

PubMed1992

Effects of intramuscular administration of glycosaminoglycan polysulfates on signs of incipient hip dysplasia in growing pups.

We tested the hypothesis that treatment of growing, susceptible (to hip dysplasia) pups by IM administration of glycosaminoglycan polysulfates would mitigate the signs of incipient hip dysplasia. In 1 experiment, 7 pups, selected at random from 2 litters, were administered glycosaminoglycan polysulfates (2.5 mg/kg of body weight, IM) twice weekly, and 7 control pups from the same litters were given sterile buffered 0.9% saline solution from the age of 6 weeks to 8 months. Hip joints were examined by radiography, with pups in the standard, limbs-extended position. At 8 months of age, all pups in this experiment did not manifest femoral head subluxation radiographically. The Norberg angle, a measure of coxofemoral congruity, improved from a mean +/- SEM value of 102 degrees +/- 1 degrees in controls to 106 degrees +/- 1 degrees in treated pups (P = 0.008). Pups were not subjected to necropsy. In the second experiment, 8 pups were selected at random from 2 litters and were administered 5 mg of glycosaminoglycan polysulfates/kg, IM, twice weekly from 6 weeks to 8 months of age. Similarly, 8 control pups were administered saline solution. At 8 months of age, hip joints were examined by radiography with pups in the standard position; at necropsy, intra-articular tissues were evaluated macroscopically and biochemically. Of 8 treated pups, none had subluxation radiographically, whereas 4 of 8 control dogs had femoral head subluxation. Mean Norberg angle on the radiographs was 109.7 degrees +/- 1.6 degrees for the treated group and was 101.5 degrees +/- 1.6 degrees for controls, representing a mean improvement in coxofemoral congruity of 8.2 degrees in the treated pups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Effects of three antiarthritic drugs on fibronectin and keratan sulfate synthesis by cultured canine articular cartilage chondrocytes.

Because articular chondrocytes are a target for drugs that can influence the integrity of cartilage, we investigated the effects of 3 antiarthritic drugs, glycosaminoglycan polysulfate, diclofenac-Na, and S-adenosylmethionine sulfate p-toluenesulfonate on total protein, fibronectin, and DNA synthesis, as well as on extradomain-A fibronectin and keratan sulfate content. Glycosaminoglycan polysulfate stimulated dose-dependent incorporation of [35S]methionine into protein and fibronectin, whereas incorporation of [3H]thymidine into DNA was unaffected. Total fibronectin, extradomain-A fibronectin, and keratan sulfate content were high in chondrocyte cultures treated with glycosaminoglycan polysulfate. In contrast, fibronectin and DNA synthesis, as well as extradomain-A fibronectin and keratan sulfate content were unaffected by diclofenac-Na. S-Adenosyl-methionine decreased dose-dependently the synthesis of fibronectin, as well as the content of fibronectin and keratan sulfate. At the highest concentration of S-adenosyl-methionine tested, findings suggest that cell viability was impaired as assessed by the release of lactate dehydrogenase into the media.

Animals↗

PubMed1992

Isolation, propagation, and cryopreservation of equine articular chondrocytes.

Equine articular chondrocytes were isolated from explant cartilage cultures by digestion in a 0.075% collagenase solution for 15 to 19 hours. Cartilage from late-term fetal and neonatal foals resulted in mean chondrocyte yield of 51.99 x 10(6) cells/g of cartilage (wet weight), compared with a yield of 17.83 x 10(6) cells/g for foals 3 to 12 months old. Propagation of chondrocytes in monolayer and 3-dimensional culture was accomplished, using Ham's F-12 as the basal medium, with supplements of fetal bovine serum (10%), ascorbic acid, alpha-ketoglutarate, and L-glutamine. The medium was buffered with HEPES, and penicillin and streptomycin were added for microorganism control. In primary monolayer cultures of freshly isolated chondrocytes, the population doubling time was approximately 6 days. Dedifferentiation of chondrocytes toward a more fibroblastic-appearing cell was observed after the fifth passage (subculture), but was hastened by lower cell-plating density. Chondrocytes were frozen for periods of up to 9 months, using 10% dimethyl sulfoxide as the cryoprotectant. Cell viability of late-term fetal and neonatal foal chondrocytes after storage at -196 C decreased from 86% at 3 weeks to 31% at 12 weeks. Viability of cells derived from older foals and young adult horses was considerably better than that of cells from neonatal foals. Frozen chondrocytes can be stored for extended periods and thawed for immediate implantation or can be sustained in vitro in monolayer or 3-dimensional culture. Such cultures would be suitable for cartilage resurfacing experiments or in vitro assessment of various pharmaceuticals.

Animals↗

PubMed1991

Modulation of fibronectin and proteoglycan synthesis by chondrocytes.

Synthesis of fibronectin and proteoglycan by chondrocytes in both cell and organ culture was affected by the culture conditions. Less than 2% of the fibronectin extracted from cartilage contained the ED-III-A sequence, however, chondrocytes placed in primary culture began to synthesize increased amounts of ED-III-A fibronectin (up to 36% of the total fibronectin). Expression of ED-III-A fibronectin was selectively reduced when the chondrocytes were cultured in the presence of 0.5 mM dibutyryl cyclic AMP. The amount of fibronectin in the media of DBcAMP treated cultures was reduced by 30% but there was no effect on the overall protein biosynthetic rates of the cells. Concomitant with the decrease in fibronectin was an increase in the concentration of keratan sulfate in the media of treated cultures. Treatment with 0.5 mM dibutyryl cAMP caused the cells to adopt a more rounded morphology. Proteoglycan synthesis in cartilage explants was maintained at levels comparable to those at Day 0 for up to twelve days in a medium supplemented with insulin. Fibronectin and collagen synthesis, however, declined relative to Day 0 levels in this medium. The addition of TGF-beta at 2 and 10 ng/ml to the medium not only prevented the decline in fibronectin synthesis but progressively increased its rate of synthesis until the Day 0 levels were exceeded 4-fold. Experiments were initiated to study also the effects of mechanical factors on cartilage explant metabolism.

Animals↗

PubMed1990

Fibronectin and proteoglycan synthesis in long term cultures of cartilage explants in Ham's F12 supplemented with insulin and calcium: effects of the addition of TGF-beta.

Canine cartilage explants were maintained in a basal medium supplemented with a commercially available supplement (ITSCR+) which includes insulin for up to 12 days in culture. During this time it was found that proteoglycan synthesis, as measured by 35SO4 incorporation into high molecular weight proteoglycans, was maintained at levels comparable to those at Day O. This is in substantial agreement with the results of McQuillan et al. (1) for bovine cartilage explants. Since the basal medium which we used, Ham's F12, is low in calcium, we found that supplementation with additional calcium also was needed for maintenance of proteoglycan synthesis. This defined medium was not adequate to prevent a decrease in fibronectin, total protein, and collagen synthesis relative to Day O levels. The addition of transforming growth factor-beta (TGF-beta) at 2 and 10 ng/ml to the defined medium not only prevented the decline in fibronectin synthesis but progressively increased the rate of fibronectin synthesis until the Day O levels were exceeded by an average of fourfold. This TGF-beta-induced increase in fibronectin synthesis was contrasted with the increase in fibronectin synthesis previously reported for degenerated cartilage of osteoarthritic joints (2,3), and possible implications for understanding the disease were discussed.

Animals↗

PubMed1990

Diurnal variation of serum progesterone, but not relaxin, prolactin, or estradiol-17 beta in the pregnant bitch.

The concentrations of progesterone (P), relaxin (Rlx), estradiol (E2) and PRL were measured by specific RIAs in serum samples collected twice daily at 8:00 am and 3:00 pm at weekly intervals after mating and until whelping in five Labrador Retriever bitches. From weeks 3 to 6 of pregnancy, P exhibited a conspicuous and statistically significant diurnal pattern (P less than 0.05), its serum concentration being approximately twice as high at 8:00 am as at 3:00 pm. A similar but nonsignificant trend was observed weeks 2, 7, and 8, and the overall ratio of the am/pm P concentrations was 2.4 +/- 0.28 (P less than 0.001). Rlx, E2, and PRL did not show a diurnal pattern at any time during pregnancy. The glandular sources and regulation of secretion of Rlx were further investigated. Rlx bioactivity was detected in canine placentas and ovaries, providing supportive evidence that these organs may be a dual source of the hormone in canine pregnancy. Injection of ovine PRL in three pseudopregnant bitches significantly increased serum P concentration as compared with seven untreated pseudopregnant controls, but Rlx was not detectable in serum before, during or after PRL treatment. The data support the view that Rlx and P are independently regulated in the bitch; PRL may be a regulator of P, but not of Rlx secretion. However, as PRL showed no diurnal changes in concentration, it does not appear to be directly responsible for the diurnal pattern exhibited by P.

Animals↗

PubMed1989

Expression of the ED B fibronectin isoform in adult human articular cartilage.

The most recently described region of alternate splicing of fibronectin mRNA results in expression of an isoform which includes the type III repeat termed ED B (EIII B). To date this isoform has been detected in transformed cells in culture, in the synovial membrane and ovary but in no other adult tissue, and in embryonic chick cartilage to a much greater extent than in other cells of mesenchymal origin. Monoclonal antibody BC-1, which recognizes an epitope within the ED B segment, was used in two different assays and provided evidence that adult human articular cartilage contains ED B fibronectin. The extent of expression of this isoform, however, was variable and less than that found in fibronectin produced by the transformed fibroblast cell line WI-38VA13.

Adult↗

PubMed1989

Molecular and immunologic differences in canine fibronectins from articular cartilage and plasma.

Two new monoclonal antibodies (Mabs) which reacted with canine fibronectin were produced and characterized. Data supported the conclusion that the epitope recognized by Mab 1H9A4 is within the first three Type III homology repeats of the Hep 2 domain and that the epitope for Mab 13G3B7 is within the last Type III homology repeat of fibronectin. These antibodies, along with three others, Mabs IST-2, IST-7, and IST-9, produced and characterized in the laboratories of L. Zardi of Genoa, Italy, were used to characterize canine cartilage and plasma fibronectin. In addition, cartilage explants were labeled with [35S]methionine in order to characterize newly synthesized cartilage fibronectin. The following observations were made. (i) Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (NaDodSO4-PAGE) of reduced canine plasma fibronectin revealed a characteristic doublet; reduced cartilage fibronectin revealed two major bands and one minor band. The lower molecular weight band was 10 kDa less than the beta subunit of plasma fibronectin. In Western blots, this band stained with Mab 1H9A4 but failed to react with Mab 13G3B7. (ii) Western blots of thermolysin and trypsin digests of cartilage fibronectin revealed cleavage patterns which differed from those obtained from digestions of plasma fibronectin. (iii) The ED-A sequence, detected by Mab IST-9, was present in less than 2% of the cartilage fibronectins. (iv) NaDodSO4-PAGE of purified and reduced 35S-labeled fibronectin revealed two major radioactive bands and one minor radioactive band which comigrated with the fibronectin from the cartilage but not with plasma fibronectin. We concluded that like "cellular" fibronectin, the ratio of alpha-type subunits to beta subunits was greater than 4 to 1 in cartilage fibronectin compared to 1.25 to 1 for plasma fibronectin; however, cartilage fibronectin was not a cellular fibronectin by the criterion of the presence of the ED-A sequence. Another difference between plasma and cartilage fibronectin was the presence in cartilage fibronectin of a subpopulation of subunits on which the last Type III homology repeat could not be detected. Biosynthetic data were consistent with the concept that cartilage fibronectin originates from local synthesis by the chondrocyte.

Animals↗

PubMed1989

Canine serum keratan sulfate and hyaluronate concentrations. Relationship to age and osteoarthritis.

Elevated serum levels of keratan sulfate (KS) and hyaluronate (HA) in patients with osteoarthritis (OA) have been reported. We measured KS and HA in dogs to determine if there was an elevation of these serum glycosaminoglycans in a canine model of OA. A single intraarticular injection of 1 mg of chymopapain into a shoulder joint increased serum KS by tenfold, and HA by less than twofold, in 24 hours. Serum KS and HA levels were 3-5-fold higher in dogs younger than 2 months of age than in older dogs. Serum KS and HA concentrations and synovial fluid KS concentrations were unrelated to spontaneous cartilage degeneration in 1-year-old dogs. Higher KS levels in synovial fluid correlated with higher KS levels in serum (r = 0.54, P less than 0.025). The mean KS concentration in sera of older dogs (greater than 3 years old) with OA was 37% higher than that in disease-free controls, but the difference between the groups was not statistically significant. Thus, elevated levels of serum KS and HA do not appear to have clinical significance in this model of OA.

Aging↗

PubMed1989

Changes in articular cartilage after intra-articular injections of methylprednisolone acetate in horses.

Eight mature horses with no prior signs of joint disease or history of intra-articular therapy were treated with 8 weekly intra-articular injections of methylprednisolone acetate. Treatments were given at a dose of 120 mg/joint into the right radiocarpal and intercarpal joints, with the left joints as untreated controls. Articular cartilage samples were obtained at necropsy 1, 4, and 8 weeks after the last injection. Compared with controls, cartilage from injected joints had a loss of hematoxylin basophilia and decreased intensity of staining in safranin O fast green dye. Chondrocyte necrosis and hypocellularity were observed in all samples of cartilage from treated joints. Proteoglycan content and its rate of synthesis were reduced. There was a progressive loss of proteoglycan content, whereas proteoglycan synthesis increased somewhat 4 and 8 weeks after treatment. Collagen content was unchanged, but its rate of synthesis was markedly inhibited. Collagen synthesis did not recover, but remained decreased at 5 to 15% of the values from untreated cartilage. Water percentage was increased, but fibronectin content was not significantly different. A single injection of methylprednisolone acetate was also given into the right metacarpophalangeal joints of 3 of the 8 horses in this group, with the left joints serving as untreated controls. Sixteen weeks after the treatment, cartilage of the treated joints had a loss of histochemical staining and proteoglycan content was reduced to 50% of control values. The mean rate of proteoglycan synthesis and mean fibronectin content were increased, but the differences were not statistically significant (P greater than 0.05). Other variables were essentially unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Serum relaxin and progesterone concentrations in pregnant, pseudopregnant, and ovariectomized, progestin-treated pregnant bitches: detection of relaxin as a marker of pregnancy.

Serum concentrations of relaxin and progesterone were measured by specific radioimmunoassays in pregnant, pseudopregnant, or ovariectomized (between gestation weeks 4 and 5) pregnant Labrador Retriever bitches. Daily administration of 17 alpha-ethyl-19-nortestosterone was performed to maintain gestation in the ovariectomized pregnant bitches. This synthetic gestagen was selected because it did not interfere with the assay for endogenously secreted progesterone concentration in serum. Serum progesterone concentration was high in ovarian-intact pregnant or pseudopregnant bitches, but the mean progesterone concentration in pseudopregnant bitches (evaluated at 4 weeks after mating) was only 56% of the concentration in pregnant bitches. After ovariectomy, serum progesterone concentration decreased to undetectable values. Unlike progesterone, serum relaxin concentration increased during the latter half of pregnancy in the ovarian-intact and in the ovariectomized pregnant bitches, but relaxin was not detectable at any time in the pseudopregnant bitches. The amount of relaxin measured in the ovariectomized pregnant bitches was less (P less than 0.05) than that in ovarian-intact bitches, suggesting that the ovaries may have contributed to the total circulating relaxin concentration in the latter. Placental production of relaxin might have accounted for the serum relaxin concentration after ovariectomy; thus, the ovary and placenta each may secrete relaxin during gestation in bitches. Regardless of its source, measurement of serum relaxin concentration may offer a useful way of distinction between pregnancy and pseudopregnancy in dogs.

Animals↗

PubMed1988

Dibutyryl cyclic AMP decreases expression of ED-A fibronectin by canine chondrocytes.

The presence of Extra Domain A (ED-A) in fibronectins from cartilage and from the culture medium of chondrocytes cultured under various conditions was determined with monoclonal antibody IST-9. Less than 2% of the fibronectin extracted from cartilage was fibronectin which contained the ED-A sequence (ED-A fibronectin). Chondrocytes placed in primary culture began to synthesize increased amounts of ED-A fibronectin (6% to 36% of the total fibronectin). Expression of ED-A fibronectin was selectively reduced when the chondrocytes were cultured in the presence of 0.5 mM dibutyryl cyclic AMP.

Animals↗