Growth Plate Width Research Articles

Effect of Subcutaneous Infusion of Pituitary-Derived Chicken Growth Hormone on Growth Performance of Broiler Pullets

The effect of subcutaneous infusion of pituitary-derived chicken growth hormone (p-cGH) on plasma hormone/metabolite status and growth performance of young broiler pullets was investigated. Two-week-old pullets were surgically prepared and maintained via a fluid swivel/spring tether/harness system. Birds were subcutaneously infused 24 h a day for 21 days with 1.0 mL/day of either a p-cGH or vehicle (control) solution (20 μg/kg BW/day).Subcutaneous infusion of p-cGH had no significant effect on growth performance parameters in comparison with controls. Differences between levels of overall feed intake, net BW gain, feed efficiency, and carcass composition were not significant for treatments. However, dressing percentage was lower in p-cGH treated birds than in vehicle infused birds (P<.04). Growth hormone treatment resulted in a modest degree of enlargement of the liver (P<.06). However treatment had no effect upon wet weights of other measured organs or upon parameters of longitudinal bone growth, including length and mass of the tibiotarsus and width of the epiphyseal growth plate. Differences between treatment groups in preinfusion plasma concentration of GH, insulin, and glucose were not significant. Postinfusion plasma concentrations of GH were elevated over three-fold by p-cGH treatment (P<.0001), with no treatment differences in plasma insulin or glucose concentrations. This study indicated that a sustained, 24-h elevation in plasma GH concentration in response to a physiological dosage of exogenous p-cGH is ineffective in altering growth performance of young, rapidly growing meat type chickens.

Insulin stimulates skeletal growth in vivo and in vitro--comparison with growth hormone in rats.

The effect of insulin on skeletal growth was examined by (1) systemic injection, (2) local administration into the tibia growth plate and (3) in vitro by use of chondrocytes in culture. (1) Male rats, body weight 60-75 g, were hypophysectomised. One week after the operation, the animals were divided into three groups. Group A received intraperitoneally saline, group B insulin (5-30 U.kg-1.day-1) and group C human growth hormone (250 micrograms/kg/day) for the following 10 days. In addition, on day 10 the rats were injected with 10 mu-Ci 35-S-sulfate intraperitoneally. Twenty-four h later in the non-fasting state plasma glucose, insulin, somatomedin activity (porcine assay), body weight, nose-rump length, width of the tibia growth plate, and the 35-S-sulfate incorporation into rib cartilage were determined. Compared to saline, growth hormone and insulin treatment significantly enhanced body weights, nose-rump lengths, the widths of the proximal tibia growth plates and the incorporation of sulfate into rib cartilage. For the three skeletal growth parameters, growth hormone was more effective than insulin, while body weights did not differ after insulin or growth hormone treatment. Somatomedin activity (U/ml) was low in group A (0.39 +/- 0.04, n = 9, Mean +/- SEM) and group B (0.34 +/- 0.08, n = 8) and high in the growth hormone treated group C (0.90 +/- 0.09, n = 7; p less than 0.002). (2) To test the possibility that insulin might directly augment skeletal growth, insulin (80 mU) was injected into the proximal tibia growth plate of one leg and saline into the cartilage zone of the other leg.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of bovine growth hormone and thyroxine on growth rate and carcass measurements in lambs.

The effects of bovine growth hormone (GH) and thyroxine (T4) on growth and carcass characteristics were assessed in Dorset ram lambs. Lambs in four groups (n = 10/group) were treated for 30 d as follows: controls, 3.33 mg (6 IU) GH/d (s.c.); 5-mg T4 implant (s.c.) on d 1 and a 10-mg T4 implant 21 d later; GH + T4. Blood samples were collected at 3-d intervals for analysis of GH, T4, triiodothyronine, somatomedin-C and testosterone concentrations. Six lambs/group were slaughtered for carcass measurements and composition. Daily GH injections increased (P less than .005) baseline plasma GH levels 10-fold, whereas plasma T4 concentrations were increased 10% (P less than .10) by the implants. Somatomedin-C increased with time in all groups, but the increments from d 0 to d 30 were higher (P less than .05) with GH treatment. Average daily gain (mean = 352 g/d), feed consumption and feed to gain ratio were not affected (P greater than .1) by GH or T4 treatment in ram lambs. Hot carcass weight and dressing percentage were increased (P less than .05) by T4. Growth hormone increased carcass protein content (P less than .005) and muscle weights while reducing carcass fat (P less than .05). Carcass composition was not altered by T4 alone, and the T4 x GH interaction was not significant; however, the combination of T4 and GH resulted in greater muscle and protein weight than did either hormone alone or no hormone administration. There were no differences in bone length or in the metacarpal growth plate width among groups. The beneficial effects of GH on carcass composition were not further enhanced by administration of thyroxine.

85 THE IMPORTANCE OF GRWOTH HORMONE (GH) IN THE EPIPHYSEAL CARTILAGE AND BONE CHANGES OF HYOTHYROIDISM (HT)

To evaluate the role of GH in the growth retardation of HT, 7-weeks-old female rats were rendered HT by methimazol for 7 weeks (Grl). This resulted in serum T4<1μg/dl (ctr 2.4±0.4 μg/dl), growth arrest and 96% depletion of pituitary contents of GH (from 78±3 to 3±3 μg/pit). Supplementation with L-thyroxine (T4) for the last 2 weeks (Gr2) restored pituitary GH to 23±4 μg/pit and accelerated rats' growth from -3 g/wk to +9 g/wks. Treatment of HT rats with hGH for the last 2 weeks (wks 12-14 of life) (Gr3) resulted in intermediate growth of +3 g/wks. Combined treatment with T4 and hGH (Gr4) increased growth further to 12g, wk. The proximal tibiae were dissected and the epiphysis, metaphysis and growth plate were evaluated qualitatively and measured morphometrically. In the control group (ctr) the metaphyseal trabecular bone was 54±2% of the total bone. In Grs 1-4 it was 18±2, 36±3, 24±2 and 34±2% respectively. The epiphyseal trabecular bone in ctr and Grs 1-4 was 43±3, 30±2, 46±2, 41±2 and 36±2% resp. The width of the compact tibial midshaft was 597±21, 373±14, 432±19, 330±16 and 453±4 microns resp. The width of the epiphyseal growth plate was 189±6, 140±3, 262±14, 126±5 and 300±9 microns resp. While the HT plate was noted for more resting cells, less and smaller proliferating cell and arrest of cartilage remodelling into metaphyseal bone hGH replacement resulted in only minor improvement and T4 replacement enhanced proliferation and remodelling. Combined treatment resulted in further increase of proliferation. It is concluded that GH-deficiency is responsible for only a small part of the epiphyseal cartilage and bone changes of HT, and that GH requires thyroid hormones for its full expression.

Dietary Calcium and Metacarpal Growth in Ewes

The effects of excess dietary calcium on bone growth were quantified in 44 ewes fed ad libitum diets that contained one of four levels of dietary calcium (0.37, 0.56, 1.13 and 1.80%) and 0.42% phosphorus. Animals were slaughtered at one of six ages, circulating concentrations of hormones and minerals were measured and bone morphometry was evaluated. None of the diets impaired normal bone growth of the metacarpal as evaluated by overall length, cortical index and growth plate width. Circulating plasma concentrations of calcium and gastrin increased as dietary calcium levels increased, but all values were within the normal range for sheep. Plasma phosphorus was unaffected by the level of dietary calcium. Diet had no affect on T3, T4 or estradiol-17 beta. Age significantly (P less than 0.05) affected the metacarpal length, growth plate width and circulating calcium and phosphorus. The metacarpal in these ewes was 95% of mature length by 172 d of age. Attainment of mature length preceded growth plate closure by slightly over 300 d. These results demonstrate that elevated dietary calcium levels do not adversely influence bone growth and that the presence of an intact growth plate does not infer that further bone growth will occur.

Bone lesions in clinically normal and in lame pigs

A pathological study was made of the femur, rib and sternum of 76 clinically normal Yorkshire × Landrace pigs weighing 2·8 to 100·0 kg (10 days to 6 months of age) and on 26 lame Yorkshire × Landrace weighing 134·9 to 149·1 kg (9 months). Locomotor dysfunction of the hind legs occurred in all animals 6 months old or more and progressed with increase in age. In clinically normal pigs, unevenness of the width of the femoral growth plate was seen in pigs weighing 20 kg or more. Furthermore, the top of the great trochanter was lower than that of the femoral head, and the angle between the long axis of the femoral head and that of the great trochanter became gradually larger with increasing body weight. Histological changes in the femoral growth plate were characterized by necrosis of the cartilage in the area adjacent to the metaphysis or epiphysis, eosinophilic streaks, loosening of the cartilage matrix, and oblique arrangement of chondrocytic columns. These changes were seen in the pigs weighing 2·8 kg or more. In the rib, changes in the growth plate were essentially similar to those in the femur. No appreciable changes were seen in the sternum. In the lame pigs, noteworthy gross changes were an abnormal high position of the top of the great trochanter in relation to the level of the femoral head and a markedly open angle between the long axis of the femoral head and that of the great trochanter. Although the nature of the histological changes in the femur is essentially the same as those of clinically normal pigs, the changes such as oblique arrangement of chondrocytic columns and loosening of the cartilage matrix were more marked than those of the clinically normal pigs. Loosening of the cartilage matrix and oblique arrangement of chondrocytic columns were found in the growth plate of the rib. Cracks, eosinophilic streaks and loosening of the cartilage matrix were also observed in the growth plate of the sternum.

Effect of diet on longitudinal bone growth and osteochondrosis in swine.

Weanling gilts were fed either a 12% or 16% protein diet for 10 weeks. Animals fed the 12% protein diet had reduced body weights and reduced longitudinal bone growth as measured in the distal radial growth plate. There was no difference in the growth plate widths between the two animal groups, but there was a significant reduction in the daily rate of cell production in the proliferative zone of animals fed the 12% protein diet. No effect of diet on the rate of expansion of the epiphysis at the articular-epiphyseal junction of the distal femur or humerus could be detected. All animals in both groups had morphologic cartilage lesions consistent with early changes associated with osteochondrosis (OCD), and there was no difference in the lesion morphology between the dietary groups. Areas of disorderly endochondral ossification in the radial growth plate were associated with perpendicular growth cartilage infractions. Growth plate lesions were characterized by increased widths of the maturing cartilage zone without increased width of the proliferative zone or an increase in the daily rate of cell production. Focal growth plate lesions developed because of a transitory inhibition of cartilage mineralization and resorption. Disorderly foci of endochondral ossification beneath articular cartilage were characterized by an area of chondrocyte necrosis which prevented normal cartilage matrix mineralization. Lamellae of cartilage necrosis were also present within the reserve zone of the articular cartilage. These were associated with abnormalities of the cartilage canal vessels, and chondrocyte necrosis was considered to precede degenerative changes in articular cartilage matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Tibial epiphyseal development: a cross-sectional histologic and histomorphometric study in the New Zealand white rabbit.

Sequential histomorphometric studies on the developing rabbit tibia from birth to skeletal maturity demonstrate that growth plate height lessens as longitudinal growth diminishes. Differing rates of development proximally and distally are documented. Distally, growth plate height, width, and area and total epiphyseal area peak or reach near maximum values by 3 weeks, whereas proximally, they do so by 8 weeks (except for height, which also peaks at 3 weeks). The distal growth plate is being obliterated by 16 weeks, at which time the proximal growth plate remains well structured and open. The distal tibia and fibula develop as one tissue mass. The articular cartilage and epiphyseal cartilage are continuous from birth, whereas a single ossification center and a single growth plate are present by 8 weeks. The data point to the presence of intrinsic growth plate, as well as systemic, control mechanisms affecting skeletal growth. Knowledge of temporal and quantitative features of epiphyseal and growth plate development will greatly aid in the elucidation of the underlying controls.

Calcitriol corrects bone loss induced by oophorectomy in rats.

The effects of calcitriol on histomorphometric parameters of bone structure, formation, and resorption were evaluated in 21 normal or oophorectomized rats. Twelve rats were oophorectomized; six of these received daily subcutaneous injections of 135 pmol of calcitriol for 14 wk starting 38 wk after oophorectomy. Nine rats were sham operated; five of these received the same treatment with calcitriol. There were no differences in serum calcium and phosphorus between sham-operated and oophorectomized animals and rats with or without calcitriol. Calcitriol treatment of sham-operated rats produced an increase in cancellous and cortical bone mass. Oophorectomy resulted in decreased cancellous and cortical bone mass and in a decreased ratio between mineralized and nonmineralized bone. There was no difference in bone-osteoclast interface and osteoid seam width among all groups of rats. Calcitriol corrected, at least in part, the bone loss in oophorectomized animals, normalized the ratio between mineralized and nonmineralized bone, and restored mean growth plate width to normal.

Bone calcification and calcium homeostasis in rats with non-insulin-dependent diabetes induced by streptozocin.

The effect of mild, non-insulin-dependent diabetes (NIDDM) on bone calcification and calcium (Ca) homeostasis was studied in growing rats (males and females). The diabetic state was characterized by mild insulin deficiency, plasma levels being 73% of controls, and mild hyperglycemia, with nonfasting plasma glucose levels of 1.5 times normal. There was no difference in plasma levels of Ca, phosphate (Pi), magnesium (Mg), alkaline phosphatase, immunoreactive parathyroid hormone (iPTH), calcitonin, 25-(OH)vitamin D (25[OH]D), 1,25-dihydroxyvitamin D (1,25[OH]2D), and 24,25-dihydroxyvitamin D (24,25[OH]2D) between the NIDDM rats and their controls of either sex. Metabolic Ca and Pi balance studies revealed that the experimental animals of both sexes were in positive Ca and Pi balance similar to that of their controls. Histologic studies of the kidney and intestinal slices from the experimental group were normal. Ca and Pi bone content calculated per gram bone ash of the femur, mandible, and second and fourth caudal vertebrae, and the organic content in the bones of the NIDDM animals showed no difference from their controls. Femur bone density and tibial epiphyseal growth plate width and morphology were similar histologically in the experimental and control rats. No decreased osteoid content in the tibial bone was found in the diabetic rats compared with controls. Physiologic sex differences, consisting of lower plasma Pi, higher plasma calcitonin levels, increased ratio of femur dry bone weight to total body weight, and increased percentage of mineralized and total bone volume at the tibial metaphysis seen in female compared with male control rats were also seen in the diabetic animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a fluorinated bisphosphonate on bone remodeling in vivo

A new fluorinated bisphosphonate, difluoromethylene bisphosphonate (F 2MBP), was studied for its effects on physiologic bone remodeling in the actively growing rat tibia. Young male Sprague-Dawley rats were given daily subcutaneous injections of either saline (control) or 30 mg/kg per day of F 2MBP, dichloromethylene bisphosphonate (Cl 2MBP), or 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) for 30 days. Microradiographs of the epiphysealmetaphyseal region of tibiae from animals treated with either F 2MBP or Cl 2MBP demonstrated increased radiodensity but, unlike those treated with HEBP, without an increase in the width of the epiphyseal growth plate. Quantitative analyses of these microradiographs showed that there was an increase of calcified tissue in the metaphyseal region in all diphosphonate groups when compared with controls. However, the HEBP-treated animals exhibited significantly less increase than either F 2MBP-treated or Cl 2MBP-treated rats. In addition, the total area of calcified tissue in the diaphyseal transverse sections was greater in the F 2MBP-treated animals than in controls. Elemental calcium, phosphorus, and fluorine, as detected by the electron probe, also increased in the metaphyseal region of the F 2MBP-treated animals, but no significant differences in the calcium: phosphorus ratio were found among the control, F 2MBP, and Cl 2MBP treatment groups, indicating no alterations in the chemical composition of bone. The greater amount of fluorine in the tibiae of F 2MBP-treated animals reflected the presence of the F 2MBP molecule. Thus, this study has demonstrated that this new fluorinated bisphosphonate, like Cl 2MBP, inhibits physiologic bone remodeling without disturbing mineralization. Furthermore, the presence of fluorine in F 2MBP allows the precise localization of the incorporation of the bisphosphonate within the bone.

The effect of glibenclamide on plasma insulin, plasma somatomedin bioactivity and skeletal growth in hypophysectomized rats.

Abstract. Male rats, body weight 60–75 g, were hypophysectomized. Three days after operation the animals were divided into two groups. Group B received solvent solution and group C 1 mg/kg body weight per day of glibenclamide ip for the following 9 days. Group A consisted on non-operated normal rats. Twenty-four hours after the last injections and after a 12 h overnight fast the body weights of groups B and C were not different, the increase during the 10 days being 10% in both groups. Serum insulin (IRI) was significantly higher in group C than in group B (C: 8.0 ± 0.3 μU/ml, n = 14 vs B: 4.9 ± 1.0 μU/ml, n = 14; P &lt; 0.01, mean ± sem) as was serum somatomedin bioactivity (SM)-porcine cartilage assay — (C: 1.06 ± 0.1 U/ml, n = 14 vs B:0.41 ± 0.01 U/ml, n = 14; P &lt; 0.001). Skeletal growth was determined with the tibia test and by a radiograph of each rat. The width of the proximal epiphyseal growth plate of the tibia was significantly increased in group C compared to group B (C: 204 ± 4.8 μm, n = 12 vs 181 ± 6.5 μm, n = 13; P &lt; 0.005). On the radiograph the area of the right femur was not different between the two groups of animals, while the height and the area of the first lumbar spine were significantly augmented in group C. The results show that glibenclamide stimulates IRI, SM and skeletal growth in hypophysectomized rats. Compared to the glibenclamide treated hypophysectomized animals the normal rats of group A had doubled their body weights. IRI (59 ± 5 μU/ml, n = 4) and skeletal growth (tibia test: 454 ± 5.8 μm) were greatly increased. SM did not differ between group A (1.21 ± 0.35 U/ml and group C. T4 was much lower in group B (0.64 ± 0.09 μg/100 ml, n = 5) than in group A (4.1 ± 0.3 μg/100 ml, n = 6; P &lt; 0.001). It is concluded that a normal SM concentration is not necessarily associated with appropriate growth.

Circulating growth factor studies in growth plate versus resting cartilage in vitro: tissue responsiveness.

We attempted to develop a system in which cartilage growth-plate responses could be examined in vitro. In vivo, rat osteochondral growth-plate width was decreased by hypophysectomy and restored toward normal by GH. Subsequently, segments of resting costal cartilage and osteochondral growth plate from hypophysectomized rats were incubated in vitro with [35S]sulfate and [3H]thymidine. Within ribs, growth plate generally had basal uptake greater than resting cartilage and a greater increase in activity on addition of normal rat serum. Across ribs 3-9, there was little change in growth plate or resting cartilage sulfate uptake, and only a modest increase in thymidine uptake caudally. Increasing concentrations of normal rat serum provided parallel stimulation for both growth plate and resting cartilage, with significant responses to as little as 1 microliter (sulfate uptake) or 5 microliters (thymidine uptake). Stimulation for both growth plate and resting cartilage by hypophysectomized rat serum was significantly less than by normal rat serum; activity was restored by GH in vivo, establishing growth plate responsiveness to GH- and pituitary-dependent factors. Growth plate and resting cartilage were generally unaffected by exposure in vitro to supraphysiological concentrations of GH, cortisol, testosterone, estradiol, or T3. Use of osteochondral junction tissue appears to yield an assay system that is sensitive and sufficiently reproducible to allow study of growth factor action at the growth plate in vitro.

Studies on the role of 24-hydroxylation of vitamin D in the mineralization of cartilage and bone of vitamin D-deficient rats.

To test the importance of 24-hydroxylation of vitamin D3 on bone mineralization, rat pups born to vitamin D-deficient females were given either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3 for 16 days beginning at the time of weaning. Following such treatment analysis of blood samples revealed no detectable 24R,25-(OH)2D3 and 1,25-(OH)2D3 in the rats given the difluoro compound while revealing the expected 24,24-difluoro-25-hydroxyvitamin D3 and 24,24-difluoro-1,25-dihydroxyvitamin D3. The rats given 25-hydroxyvitamin D3 had the expected levels of 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D3, and 1,25-dihydroxyvitamin D3. Following sacrifice at day 17, postweaning bone mineralization and modeling were studied in long bones using histological methods. Bones taken from vitamin D-deficient rats at the beginning and end of the experimental period had lesions typical of rickets. These included wide growth plates, excessive amounts of osteoid, and metaphyseal fibrosis. Following treatment with either 25-hydroxyvitamin D3 or 24,24-difluoro-25-hydroxyvitamin D3, bone mineralization returned to normal. Growth plate widths and the amount of osteoid on bone surfaces were both substantially reduced and to a similar degree in both treatment groups. Normal cartilage core formation and trabecularization of the metaphyseal primary spongiosa were also restored to a similar degree in both groups. In effect, no difference was observed in any bone parameter studied between the 25-hydroxyvitamin D3- and the 24,24-difluoro-25-hydroxyvitamin D3-treated animals. These results provide strong evidence that 24-hydroxylation of the vitamin D molecule plays little or no role in the modeling and mineralization of bone.

Ultrastructure of the rat epiphyseal growth plate following chronic ethanol ingestion.

We have previously demonstrated that ethanol has a direct toxic effect on the rat skeleton characterized by decreased trabecular bone volume. In the present study, we examined the ultrastructure of the distal radial epiphyseal growth plates in these same animals. Eight weeks of ethanol administration to 12 male rats results in serum alcohol levels of 140 mg/dl but did not alter the width or light microscopic appearance of the radial growth plate. Quantitative electron microscopy failed to demonstrate morphologic evidence of toxicity in the skeletal cells. We conclude that although ethanol appears to have a direct effect on rat bone characterized by enhanced resorption, toxicity is not attended by ultrastructural changes in the skeletal cells.

Observations of growth plate development in achondroplastic (cn/cn) mice.

The autosomal recessive gene for achondroplasia (cn) in the homozygous condition inhibits the growth of the cartilaginous skeleton in mice. Changes in the width of the proximal growth plate of the tibia and the caudal vertebrae and in the number of proliferative and hypertrophic cells were recorded in normal and achondroplastic (cn/cn) mice during the first 30 neonatal days. In normal mice as in achondroplastics, the width of the cartilaginous growth plate decreased progressively with increasing age. The proliferative zone of cn/cn mice was similar in structure to that of normal mice and showed no significant difference. Hypertrophied cartilage was less wide and there were fewer hypertrophic cells at the epiphyseal plates than found in normal mice. The data of the present study show that retarded longitudinal bone growth in cn/cn mice is due to reduced hypertrophy of the chondrocytes.

BIOASSAY OF GROWTH HORMONE

ABSTRACT The longitudinal bone growth of proximal tibia determined by tetracycline in hypophysectomized rats was used for the bioassay of growth hormone. Female Sprague-Dawley rats were hypophysectomized at 60 days of age and after a post-operative control period of 15 days growth hormone (NIH-GH-B16) was given daily for 5 or 10 days followed by a 10 day period after its withdrawal. A linear log dose-response relation was found for the two administration models with high precision. In the present investigation the longitudinal bone growth was more favourable as a growth parameter for the bioassay of growth hormone than the body weight and the width of the proximal tibial growth plate.

Cell kinetics and morphology of the growth plate in the normal and hypophysectomized rat

The width of the proximal growth plate of the tibia, its undifferentiated and columnar zone and the size of the degenerative cell close to the metaphysis, were determined in normal and hypophysectomized Sprague-Dawley rats. The cell production in the growth plate was calculated from the longitudinal bone growth determined with oxytetracycline and the degenerative cell size. It was found that the decrease in longitudinal bone growth with increasing age and after hypophysectomy, is due partly to a decrease in cell production, and partly to a decrease in degenerative cell size in the growth plate. The influence of cell production and thus the mitotic activity predominates.

Studies of the influence of estradiol and growth hormone on the hypophysectomized immature rat epiphyseal cartilage growth plate

These studies were designed to ascertain the differential effect of estrogen (E2) on epiphyseal maturation and growth of the long bones. The influence of treatment with estrogen alone, growth hormone alone, or both in combination on the tibial cartilage growth plate (CGP) width and tritiated thymidine uptake within the CGP was studied in hypophysectomized immature male rats. The effect on femur length was also evaluated. GH caused resumption of growth and widening of the CGP as well as increased thymidine uptake. E2 depressed these effects in a dose-related manner. It is concluded that E2 administration to immature rats accelerates epiphyseal maturation without simultaneously accelerating linear growth.