Arthrodesis of the Equine Proximal Interphalangeal Joint: A Biomechanical Comparison of Two 7-Hole 3.5-mm Broad and Two 5-hole 4.5-mm Narrow Dynamic Compression Plates

OBJECTIVE: To compare the biomechanical characteristics and mode of failure of two different dynamic compression plate (DCP) techniques for proximal interphalangeal joint (PIPJ) arthrodesis in horses. STUDY DESIGN: Randomized block-design blocking on horse (1-5), method of fixation (two 7-hole, 3.5-mm broad DCP vs two 5-hole, 4.5-mm narrow DCP), side (left, right), and end (front, hind). Constructs were loaded to failure in 3-point bending in a dorsal-to-palmar (plantar) direction. SAMPLE POPULATION: Ten paired limbs from 5 equine cadavers. METHODS: Two 7-hole, 3.5-mm broad dynamic compression plates (bDCP) were used in 1 limb of a pair, and two 5-hole 4.5-mm narrow dynamic compression plates (nDCP) were used on the contralateral limb. Plates were positioned abaxially across the dorsomedial and dorsolateral aspect of the PIPJ. Arthrodesis constructs were loaded (19 mm/s) in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials-testing machine. Composite stiffness, yield point, and maximal bending moment at failure were obtained from bending moment-angular deformation curves. Data were analyzed using ANOVA, X(2) analysis, and Fisher's exact tests; the power of the test was calculated when differences were not significant. RESULTS: There were no significant differences in composite stiffness (P >.05; power = 0.8 @ delta = 21.9%), yield point (P >.05; power = 0.8 @ delta = 34.4%), or maximal bending moment (P >.05; power = 0.8 @ delta = 17.8%) between the two fixation techniques. For bDCP constructs, 11% (15 of 140) of the 3.5-mm screws were damaged; 7 of the screw heads pulled through plates where the plates bent, 1 screw head broke off, and 7 screws were bent or pulled out of the phalanx. For nDCP constructs, 8% (8 of 100) of the 4.5-mm screws were damaged; 1 screw head pulled through a plate, 1 screw head broke off, and 6 screws were bent or pulled out of the phalanx. CONCLUSIONS: There were no biomechanical or failure differences between bDCP and nDCP fixation of the PIPJ in horses when evaluated in single-cycle 3-point bending to failure. CLINICAL RELEVANCE: There is no biomechanical advantage to the use of two 7-hole, 3.5-mm bDCP in equine proximal interphalangeal arthrodesis compared with two 5-hole, 4.5-mm nDCP. Two 5-hole, 4.5-mm nDCP may be easier to place, whereas two 7-hole, 3.5-mm bDCP may provide more versatility in fracture repair.     

Long-term changes in fish populations of acid streams and lochs in galloway South West Scotland

During 1978–79, and again in 1984, fish populations were surveyed in 22 lochs and 27 streams in Galloway, southwest Scotland. Chemical analyses of these waters and of bulk precipitation were made over the same period. The study area includes moorland catchments and catchments with young or semi-mature coniferous forest. Trout were not caught in nets set in 5 lochs which were known to contain fish in the past. Angling records also indicated a decline in catches and increased average weight of trout in two other lochs. Evidence for the decline in fish populations suggests that this process has occurred over a period of at least 50 yr. In fishless lochs and streams the levels of acidity and Al were in the range known to be toxic to fish. Stream acidity and sulphate concentrations were significantly higher in catchments with semi-mature coniferous forests. The available evidence for long-term acidification of Galloway lochs and streams is discussed and it is concluded that acid depositions are likely to be the major cause of changes in the status of fisheries in this region.     

The FLAME Project: General Discussion and Conclusions

Detailed discussion of the FLAME data at individual country level is included in other papers in this volume but some aspects of the analyses and data interpretation are best discussed on a broader level and that is the aim of this paper. The spatial distribution of fly-ash particles in the participating countries shows good agreement with expected sources and this implies that the majority of particulates travel less than 100 km from their source although lower concentrations of particles were detected at all sample sites. Areas of elevated concentration mostly coincide with population centres and imply possible impacts on human health by fine particulates (e.g. PM₁₀) from fossil-fuel sources in these areas. Problems with the particle characterisation, developed within the FLAME project, include difficulties in allocation due to the overlap between coal-series fuels and the presence of a 'mineral coal' background at lake sites thought to be due to persistent sediment minerals surviving the chemical pre-treatment and becoming allocated to coal. This leads to implications for the inclusion of further fuels into the classification and the application of the technique to the same fuels beyond Europe. The combination of lake sediment SCP data and sediment and moss metals data can also provide an indication of the impact from anthropogenic contamination at a site and probable source types. Comparison with previous moss analyses from 1990 show that metal concentrations in central Europe may have decreased but levels in the UK have shown little change. Finally, comparisons of FLAME data with the EMEP model for pollutant budgets across Europe generally show good agreement for pathways, although further work is needed in receptor countries for additional confirmation.     

Acid Toxicity Levels in Nova Scotian Rivers Have Not Declined in Synchrony with the Decline in Sulfate Levels

The Atlantic salmon (Salmo salar) resource of eastern Canada is impacted by acid rain in the Southern Upland (Atlantic Coast) area of Nova Scotia. Salmon runs in this area have become extinct in 14 rivers, are severely impacted in 20 rivers, and lightly impacted in 15 rivers. Water chemistry and fish communities in nine Southern Upland salmon rivers were studied from 1982 to 1996 as part of the effort to monitor the effects of the emission controlprograms in Canada and the United States. There hasbeen no statistically significant change in total ioncontent of Southern Upland river water, but there wasa significant decline in sulfate levels that was balanced by an increase in organic anions, and declines in calcium and magnesium that were balanced by increases in sodium and potassium. A geochemical scenario is proposed to account for these chemical changes. River water pH levels showed no overall linear trend, but at borderline toxicity sites the year-to-year variations in pH were correlated withchanges in juvenile salmon population densities. Tenfish species were collected, but none showed anysignificant overall time trend in population density.Fish species diversity was positively correlated with pH.     

Breast-feeding initiation and exclusive duration at 6 months by social class--results from the Millennium Cohort Study

OBJECTIVES: To assess breast-feeding initiation and rates of exclusive breast-feeding for the first 6 months after birth, and to examine social class differences in breast-feeding rates. DESIGN: First sweep of a longitudinal population-based survey, the Millennium Cohort Study. SETTING: Four countries of the UK. SUBJECTS: Subjects were 18 125 singletons born over a 12-month period spanning 2000-01. Data were collected by parental interview on the initiation of breast-feeding and exclusivity at 1, 4 and 6 months after birth. RESULTS: Overall breast-feeding was initiated for 71% of babies, and by 1, 4 and 6 months of age the proportions being exclusively breast-fed were 34%, 3% and 0.3%, respectively. There were clear social class differences and mothers with routine jobs with the least favourable working conditions were more than four times less likely (odds ratio (OR) 0.22, 95% confidence interval (CI) 0.18-0.29) to initiate breast-feeding compared with women in higher managerial and professional occupations. Women in routine jobs were less likely to exclusively breast-feed their infants at 1 month (OR 0.42, 95% CI 0.36-0.50) and 4 months (OR 0.5, 95% CI 0.31-0.77) compared with women in higher managerial and professional occupations. CONCLUSIONS: Clear social class differences in breast-feeding initiation and exclusivity for the first 4 months were apparent in this large UK sample. By 6 months, less than 1% of babies were being exclusively breast-fed. A co-ordinated multi-faceted strategy is required to promote breast-feeding, particularly among lower-income women.     

Participation of c-myc protein in DNA synthesis of human cells

The protein product of oncogene c-myc is believed to be important in regulation of the cell cycle. However, its direct role in DNA synthesis has not been explored. Experiments presented here show that the addition of affinity-purified antibodies against the human c-myc protein to nuclei isolated from several types of human cells reversibly inhibited DNA synthesis and DNA polymerase activity of these nuclei. This suggests that c-myc encodes a protein that is functionally involved in DNA synthesis.     

Treatment of anovulatory anoestrous postpartum dairy cows with a gonadotropin-releasing hormone (GnRH), prostaglandin F2𝛂, GnRH regimen or with progesterone and oestradiol benzoate

AIM: To compare 2 treatments for anovulatory anoestrus (AA) in postpartum dairy cows. The treatments were combinations of gonadotropin-releasing hormone (GnRH) and prostaglandin F_2𝛂 (PG) or progesterone (P4) and oestradiol benzoate (ODB).

METHODS: Forty AA cows from each of 5 herds were blocked by age (2 or >2 years old) and randomly assigned to 1 of 2 treatments. The first group (GPG) were treated with 250 𝛍g of a GnRH analogue, gonadorelin, followed 7 days later by 15 mg of the PG analogue, luprostiol. Two days later the cows were injected with 250 𝛍g of gonadorelin. Cows were artificially inseminated 16–24 h after the second GnRH injection. The second group (P4+ODB) were treated with an intravaginal P4 releasing device for 6 days, followed 24 h after device removal by injection of 1 mg of ODB. Cows were pregnancy tested 35–40 days after the initial insemination and twice again at 6–8 week intervals thereafter.

RESULTS: There was no significant difference between P4+ODB and GPG groups in the percentage of cows submitted for insemination in the first 7 days (94.0% vs 100% for P4+ODB vs GPG, respectively; p>0.3), in conception rate to first insemination within the first 7 days (43.6% vs 35.0% for P4+ODB vs GPG, respectively; p>0.2), in the percentage of cows conceiving in the first 28 days of the breeding period (68.0% vs 58.3%, P4+ODB vs GPG, respectively; p>0.1), or in median interval from the end of treatment to conception (20 vs 21days;p>0.1).

CONCLUSIONS: No differences in the reproductive performance of AA cows treated with either P4+ODB or GPG were detected. However, given the small number of animals enrolled, further data are required before the GPG protocol can be recommended for treatment of AA cows.     

Fitness correlates of heritable variation in antibody responsiveness in a wild mammal

A functional immune system is important for survival in natural environments, where individuals are frequently exposed to parasites. Yet strong immune responses may have fitness costs if they deplete limited energetic resources or cause autoimmune disease. We have found associations between fitness and heritable self-reactive antibody responsiveness in a wild population of Soay sheep. The occurrence of self-reactive antibodies correlated with overall antibody responsiveness and was associated with reduced reproduction in adults of both sexes. However, in females, the presence of self-reactive antibodies was positively associated with adult survival during harsh winters. Our results highlight the complex effects of natural selection on immune responsiveness and suggest that fitness trade-offs may maintain immunoheterogeneity, including genetic variation in autoimmune susceptibility.