The effect of growth/differentiation factor-5 deficiency on femoral composition and mechanical behavior in mice.

A subclass of the bone morphogenetic proteins (BMPs), known as growth/differentiation factors (GDFs) 5, 6, and 7, have been shown to affect several skeletal processes, including endochondral ossification, synovial joint formation, and tendon and ligament repair. Mice deficient in GDF-5 have also been shown to exhibit biomechanical abnormalities in tendon that may be associated with altered type I collagen. The purpose of this study was to investigate the effect of GDF-5 deficiency on another type I collagen-rich tissue: cortical bone. Analyses were performed on femora from 8-week-old GDF-5-deficient male brachypodism mice. We hypothesized that GDF-5-deficient bones would exhibit altered geometric, structural, and material properties compared with control littermates. Mutant animals were significantly smaller in body mass than controls (-21%). Geometrically, mutant long bones were significantly shorter (-25%), had a lower polar moment of inertia (-34%), and a lower geometric strength indicator (analogous to the section modulus of a circular section) (-30%). When normalized by body mass, however, geometric differences were no longer significant. Structurally, GDF-5-deficient femora were weaker (-31%) and more compliant (-57%) than controls when tested to failure in torsion. Lower bone structural stiffness in the mutants was not completely explained by the smaller bone geometry, because mutant bones exhibited a significantly lower effective shear modulus (-36%). Although body mass did not fully explain the reduced structural strength in mutant bones, strength differences were adequately explained by bone cross-sectional geometry; maximum effective shear stress was not significantly different between mutants and controls, despite a statistically significant 6% lower ash fraction in mutant femora. No significant difference was detected in collagen content, as indicated by hydroxyproline per dry mass.

Altered hypertrophic chondrocyte kinetics in GDF-5 deficient murine tibial growth plates.

The growth/differentiation factors (GDFs) are a subgroup of the bone morphogenetic proteins best known for their role in joint formation and chondrogenesis. Mice deficient in one of these signaling proteins, GDF-5, exhibit numerous skeletal abnormalities, including shortened limb bones. The primary aim of this study was determine whether GDF-5 deficiency would alter the growth rate in growth plates from the long bones in mice and, if so, how this is achieved. Stereologic and cell kinetic parameters in proximal tibial growth plates from 5-week-old female GDF-5 -/- mice and control littermates were examined. GDF-5 deficiency resulted in a statistically significant reduction in growth rate (-14%, p=0.03). The effect of genotype on growth rate was associated with an altered hypertrophic phase duration, with hypertrophic cells from GDF-5 deficient mice exhibiting a significantly longer phase duration compared to control littermates (+25%, p=0.006). These data suggest that one way in which GDF-5 might modulate the rate of endochondral bone growth could be by affecting the duration of the hypertrophic phase in growth plate chondrocytes.

GDF-5 deficiency in mice delays Achilles tendon healing.

The aim of this study was to examine the role of one of the growth/differentiation factors, GDF-5, in the process of tendon healing. Specifically, we tested the hypothesis that GDF-5 deficiency in mice would result in delayed Achilles tendon repair. Using histologic, biochemical, and ultrastructural analyses, we demonstrate that Achilles tendons from 8-week-old male GDF-5 -/- mice exhibit a short-term delay of 1-2 weeks in the healing process compared to phenotypically normal control littermates. Mutant animals took longer to achieve peak cell density, glycosaminoglycan content, and collagen content in the repair tissue, and the time course of changes in collagen fibril size was also delayed. Revascularization was delayed in the mutant mice by 1 week. GDF-5 deficient Achilles tendons also contained significantly more fat within the repair tissue at all time points examined, and was significantly weaker than control tissue at 5 weeks after surgery, but strength differences were no longer detectable by 12-weeks. Together, these data support the hypothesis that GDF-5 may play an important role in modulating tendon repair, and are consistent with previously posited roles for GDF-5 in cell recruitment, migration/adhesion, differentiation, proliferation, and angiogenesis.

GDF-5 deficiency in mice alters the ultrastructure, mechanical properties and composition of the Achilles tendon.

Acromesomelic dysplasia of the Hunter-Thompson and Grebe types are rare human disorders based on growth/differentiation factor (GDF)-5/CDMP-1 genetic mutations. Numerous skeletal abnormalities are present in these individuals, including shortened limb bones and severe dislocations of the knee. In the GDF-5 deficient brachypodism mouse, similar, although less severe, phenotypes are observed. It is unknown whether the joint dislocations observed in these disorders are due to a defect in the original formation of joints such as the knee, or to abnormalities in the tendons and ligaments themselves. We hypothesized that tendons from GDF-5 deficient mice would exhibit altered composition, mechanical properties, and ultrastructure when compared with heterozygous control littermates. GDF-5 deficient Achilles tendons were structurally weaker than controls, and structural strength differences appeared to be caused by compromised material properties: after normalizing by collagen per unit length, mutant tendons were still 50% weaker (P < 0.0001) and 50% more compliant (P < 0.001) than controls. Despite comparable levels of skeletal maturity in the two cohorts, the majority of mutant tendon failures occurred in the mid-substance of the tendon (64% of all failures), whereas the majority of control failures occurred via avulsion (92% of all failures). Mutant Achilles tendons contained 40% less collagen per microgram of DNA when compared to controls (P = 0.004). No significant difference in glycosaminoglycan (GAG)/DNA was detected. Ultrastructural analyses indicated a slight trend toward increased frequency of small diameter (30-100 nm) collagen fibrils in the mutant Achilles. Our findings suggest that increased tendon and ligament laxity may be the cause of the joint dislocations seen in patients with Hunter-Thompson and Grebe type dysplasia, rather than developmental abnormalities in the joints themselves.

Supplementation to meet metabolizable protein requirements of primiparous beef heifers: II. Pregnancy and economics.

Metabolizable protein (MP) requirements of spring calving heifers increase over the winter due to advancing gestation. The MP content of grazed winter forage is low, which may result in an MP deficiency. The objective was to compare the response of supplementing pregnant yearling heifers to meet MP requirements versus conventional CP supplementation. In 1997-98 and in 1998-99, pregnant, March-calving heifers (2,120 animals; 358 kg) at two locations of a commercial ranch in the Nebraska Sandhills, were used following breeding through calving as 2-yr-olds (cows). Heifers were randomly allotted to one of two supplementation treatments (about 265 heifers/treatment) each year at each of two locations (Ashby and Whitman, NE). Treatments were 1) supplementation to meet MP requirements (MPR) or 2) supplementation to meet CP requirements (CPR). Heifers grazed upland range and meadow and were offered supplements three times weekly from mid-September to mid- or late-February. Increasing amounts of meadow hay were fed from mid-December through calving. After supplementation ended in February, heifers were managed in one group at each location until the following October. Body weights and body condition scores were taken in September, February, and October. Two-yr-old pregnancy rates were determined via rectal palpation in October. Capital budgeting techniques were used to determine the economic return of supplementation strategies. There were no differences in BW (P = 0.41) or body condition score (P = 0.99) change during the winter among treatment groups across years and locations, but MPR cows were heavier (425 kg) than CPR cows (421 kg) at the time of 2-yr-old pregnancy testing (P = 0.07). Pregnancy rate was higher (P = 0.001) in the MPR (91%) compared to the CPR treatment (86%). Regression analysis showed that the response of the MPR treatment on pregancy rates tended to be negatively correlated with precalving body condition score (P = 0.11), body condition score loss over the winter (P = 0.07), and body condition score at weaning of the first calf (P = 0.08). The improvement in 2-yr-old pregnancy by supplementing to meet MP requirements improved the value of each bred heifer by 13.64 dollars. We conclude that balancing MP requirements during gestation may result in a subsequent increase in 2-yr-old pregnancy and increase the value of young females.

Age of calf at weaning of spring-calving beef cows and the effect on cow and calf performance and production economics.

Over a 5-yr period, spring-calving cows were used in a carry-over design experiment to evaluate effects of calf age at weaning on cow and calf performance and production economics. Weaning management groups were early (n = 60, calf age 150 d, EW), traditional (n = 60, calf age 210 d, NW), and late (n = 60, calf age 270 d, LW). Cow body condition score (BCS) and weights at the last weaning date were different (P < .05) for EW (5.8, 583 kg), NW (5.5, 560 kg), and LW (5.2, 541 kg) management groups. Pregnancy rates among groups were similar. Days on feed for groups differed (P = .001) and was 247 for EW, 204 for NW, and 164 d for LW steers. Average daily gain in the feedlot differed (P = .01) among groups and averaged 1.5 kg for LW, 1.4 kg for NW, and 1.3 kg for EW steers. Dry matter intake while steers were in the feedlot was greater (P = .001) for LW than for NW and EW calves. Hot carcass weight was greater (P = .01) for EW (328 kg) and NW (332 kg) calves than for LW (321 kg) steers, and fat depth was greater (P = .05) for EW and NW steers than for LW steers. When carcass data for the NW and LW steers were adjusted to the fat depth of EW steers, carcass characteristics among groups were similar. Net income per steer at slaughter for the feedlot phase was greater (P < .001) for the EW ($75.36) and NW ($62.16) steers than for the LW ($10.09) steers. Again, when carcass data for the NW and LW steers were adjusted to the same fat depth of the EW steers, net income differences among groups were reduced. Replacement heifers were developed in a drylot and costs were higher (P < .001) for the EW than for NW and LW heifers. Annual cow costs were greater (P < .10) for the LW ($443.45) than for the EW ($410.09) and NW ($421.35) groups. Break-even for each system on a steer financial basis was not different between the NW and LW groups, and both the NW and LW groups had lower (P = .08) break-evens than the EW group. Age of the calf at weaning affects cow weight and BCS. Net income in each system is influenced by cow costs, month of the year that steer calves are purchased into the feedlot and finished steers are sold, month of the year cull cows are marketed, and replacement heifer development costs.

A clinico-pathologic study of cases with Schistosoma japonicum infection in Indonesia.

Combined clinico-pathological and laboratory examinations were carried out on 52 S. japonicum infected patients from an endemic area in Central Sulawesi, Indonesia. All of these patients exhibited signs and symptoms of chronic hepato-splenic schistosomiasis. None of the patients showed evidence of liver cirrhosis on histopathological examination. However, varying degrees of portal fibrosis were exhibited. The correlation between the degree of fibrosis and the clinical and laboratory findings were presented and discussed. Based on the results, liver biopsy proved to be a vaulable method of diagnosis in this particular type of infection. This study provides new information on S. japonicum infection in the area and may support a more solid basis for treatment.

Drug trial of Schistosoma japonicum enfection in Indonesia.

A limited drug trial was carried out on 42 cases with schistosomiasis japonica from an endemic area of Central Sulawesi. The drugs used were niridazole and stibophen. The effects of treatment were reported and discussed. The results of this study offer promise for treating S. japonicum infection in Central Sulawesi on a larger scale.

Effect of prebreeding body weight or progestin exposure before breeding on beef heifer performance through the second breeding season.

Two experiments evaluated prebreeding target BW or progestin exposure for heifers developed lighter than traditional recommendations. Experiment 1 evaluated the effects of the system on heifer performance through subsequent calving and rebreeding over 3 yr. Heifers (229 kg) were assigned randomly to be developed to 55% of mature BW (299 kg) before a 45-d breeding season (intensive, INT; n = 119) or 50% of mature BW (272 kg) before a 60-d breeding season (relaxed, RLX; n = 142). Prebreeding and pregnancy diagnosis BW were greater (P 0.15) between systems. Cost per pregnant 2-yr-old cow was less for the RLX than the INT heifer development system. Of heifers that failed to become pregnant, a greater proportion (P = 0.07) of heifers in the RLX than in the INT system were prepubertal when the breeding season began. Therefore, a second 2-yr experiment evaluated melengestrol acetate (MGA, 0.5 mg/d) as a means of hastening puberty in heifers developed to 50% of mature BW. Heifers were assigned randomly to the control (n = 103) or MGA (n = 81) treatment for 14 d and were placed with bulls 13 d later for 45 d. Prebreeding and pregnancy diagnosis BW were similar (280 and 380 kg, respectively; P > 0.10) for heifers in the control and MGA treatments. The proportion of heifers pubertal before breeding (74%), pregnancy rate (90%), calving date, calf weaning weight, and second breeding season pregnancy rate (92%) were similar (P > 0.10) between treatments. Developing heifers to 50 or 55% of mature BW resulted in similar overall pregnancy rates, and supplementing the diets of heifers developed to 50% of mature BW with MGA before breeding did not improve reproductive performance.

An evaluation of production and economic efficiency of two beef systems from calving to slaughter.

A 3-yr experiment was conducted with cows and their calves to evaluate resource inputs, animal performance, and carcass characteristics of two production systems. In the control system, cows (CON; n = 99/yr) grazed pasture and were fed hay during the winter, and CON steer calves were finished in the feedlot for 211 d after weaning. In the treatment system (TRT; n = 100/yr), cows grazed pasture and crop residue during the winter and were fed hay. Treatment steer calves grazed crop residue after weaning, grazed pasture in the spring and summer, and were finished in the feedlot for 90 d. Body condition scores after TRT cows returned from crop residue grazing were greater (P < 0.01) for CON than for TRT cows. Calving rates were similar for both groups (CON = 91%; TRT = 93%). In the feedlot, CON steers had lower (P < 0.05) ADG and DMI, but were more efficient (P < 0.01) than TRT steers. Treatment steers had greater (P < 0.05) final weight, hot carcass weight and longissimus muscle area, and decreased marbling score. The cost per weaned calf and weaning breakeven were greater (P = 0.07) for the CON system than for the TRT system (CON = 455.12 dollars, 0.91 dollar/0.45 kg; TRT = 421.43 dollars, 0.84 dollar/0.45 kg). When steers were priced into the postweaning phase on an economic basis, slaughter breakeven was lower (P = 0.01), and profit potential tended (P = 0.14) to be greater for TRT steers when they were sold on a live basis. When steers were priced into the postweaning phase on a financial basis, slaughter breakeven was lower (P = 0.03) and profit potential from the sale of steers on a live basis was greater (P = 0.07) for TRT than for CON steers. Economic evaluation of the total system resulted in greater (P = 0.06) profit potential for the TRT system when steers were priced into the system on either an economic or a financial basis and when steers were sold on a live basis, but no differences were observed when steers were sold on a grid basis. Despite differences in cow weight and body condition, calving rates did not differ between systems. Although calves were herdmates, feedlot performance and carcass characteristics differed between systems. The TRT system had lower weaning and slaughter breakeven, lower cost per weaned calf, and greater profit potential when finished steers were sold on a live basis.

Neuropsychological deficits in tests of executive function in asymptomatic and symptomatic HIV-1 seropositive men.

There has been much debate about the exact nature and time of onset of the cognitive impairments associated with infection by the human immunodeficiency virus type 1 (HIV-1). Studies to date have not reached consistent conclusions. The present study comprised 22 asymptomatic and 18 symptomatic HIV-1 seropositive men, whose only risk factor for contraction of the virus was sexual intercourse, and 18 seronegative controls matched for age and IQ. Subjects were given computerized neuropsychological tests from the CANTAB battery, which assessed visuospatial memory, attention and executive function. Both the asymptomatic and the symptomatic HIV-1 seropositive subjects showed a selective pattern of deficits relative to the controls. In addition, the seropositive subjects were subtly but significantly impaired on tests of executive function but unimpaired on certain tests of visual memory. This finding supports an hypothesis that frontostriatal dysfunction occurs in HIV-1 infected individuals prior even to the expression of clinical symptoms.

GDF-5 deficiency in mice leads to disruption of tail tendon form and function.

Although the biological factors which regulate tendon homeostasis are poorly understood, recent evidence suggests that Growth and Differentiation Factor-5 (GDF-5) may play a role in this important process. The purpose of this study was to investigate the effect of GDF-5 deficiency on mouse tail tendon using the brachypodism mouse model. We hypothesized that GDF-5 deficient tail tendon would exhibit altered composition, ultrastructure, and biomechanical behavior when compared to heterozygous control littermates. Mutant tail tendons did not display any compositional differences in sulfated glycosaminoglycans (GAG/DNA), collagen (hydroxyproline/DNA), or levels of fibromodulin, decorin, or lumican. However, GDF-5 deficiency did result in a 17% increase in the proportion of medium diameter (100-225 nm) collagen fibrils in tail tendon (at the expense of larger fibrils) when compared to controls (p < 0.05). Also, mutants exhibited a trend toward an increase in irregularly-shaped polymorphic fibrils (33% more, p > 0.05). While GDF-5 deficient tendon fascicles did not demonstrate any significant differences in quasistatic biomechanical properties, mutant fascicles relaxed 11% more slowly than control tendons during time-dependent stress-relaxation tests (p < 0.05). We hypothesize that this subtle alteration in time-dependent mechanical behavior is most-likely due to the increased prevalence of irregularly shaped type I collagen fibrils in the mutant tail tendons. These findings provide additional evidence to support the conclusion that GDF-5 may play a role in tendon homeostasis in mice.