Tetanus prophylaxis in horses: guidelines for New Zealand and Australia based on a critical appraisal of the evidence.

Horses are exquisitely sensitive to tetanus neurotoxin and are exposed to the risk of infection with Clostridium tetani throughout life. The vaccine against tetanus is highly effective at preventing disease, whereas tetanus in unvaccinated populations is associated with high mortality rates. Current guidelines in New Zealand and Australia for the available vaccine contain contradictions and limitations surrounding the optimal tetanus immunisation protocols for both adult horses and foals. This review critically evaluates the scientific literature on tetanus prophylaxis in horses within the context of equine practice and available products in New Zealand and Australia. The review was conducted by a panel of industry and specialist veterinarians to obtain agreement on nine equine tetanus prophylaxis guidelines for practising veterinarians. The primary protocol for tetanus toxoid (TT) immunisation consists of a three-dose series IM for all horses ≥ 6 months of age, and a four-dose series IM is proposed if commencing vaccination in foals between 3 and 6 months of age. Tetanus prophylaxis in foals < 3 months of age relies on passive immunity strategies. Following the completion of the primary protocol, a TT booster dose IM should be administered within 5 years, and every 5 years thereafter. When followed, these protocols should provide adequate protection against tetanus in horses. Additional tetanus prophylaxis guidelines are provided for veterinarians attending a horse experiencing a known "risk event" (e.g. wound, hoof abscess, surgery, umbilical infection). When a correctly vaccinated horse experiences a risk event, pre-existing immunity provides protection against tetanus. When an unvaccinated horse or one with unknown vaccination status, or a foal born to an unvaccinated dam, experiences a risk event, TT IM and tetanus antitoxin (TAT) 1,500 IU SC should be administered simultaneously at separate sites, and the TT primary immunisation protocol should subsequently be completed for the horse's respective age. In previously immunised pregnant broodmares, a TT booster dose administered 4-8 weeks prior to parturition optimises the transfer of passive immunity against tetanus to the newborn foal via colostrum; provided that post-natal IgG concentration in serum is > 800 mg/dL (8 g/L), such foals should be passively protected against tetanus up to 6 months of age. Survivors of clinical tetanus must still receive the primary protocol for vaccination against tetanus. In summary, all horses in New Zealand and Australia should be vaccinated against tetanus with protection maintained throughout life via TT booster doses, facilitated by accurate medical record keeping and client education.

Evaluation of the effects of medium-term (57-day) omeprazole administration and of omeprazole discontinuation on serum gastrin and serum chromogranin A concentrations in the horse.

BACKGROUND: Rebound gastric hyperacidity (RGH) secondary to hypergastrinemia has been suggested to contribute to the rapid recurrence of equine squamous gastric disease (ESGD) in horses after discontinuation of omeprazole. HYPOTHESIS/OBJECTIVES: To evaluate changes in serum gastrin and chromogranin A (CgA) concentrations in response to medium-term (57-day) omeprazole treatment and after omeprazole discontinuation. ANIMALS: Fourteen mature Thoroughbred racehorses in simulated race training. METHODS: Horses received 2.28 g of oral omeprazole PO q24h for 57 days within a 61-day period, excluding a withholding period applied mid-protocol during which treatment was stopped as part of a concurrent study. Serum samples were collected on day 0 before omeprazole treatment, on day 1 of each week of the treatment period, and for an additional 5 weeks after discontinuation of treatment. Serum gastrin and CgA concentrations were analyzed using radioimmunoassay (RIA) and ELISA, respectively. RESULTS: Median serum gastrin concentrations increased 2.5-fold from baseline to day 7 (P < .001) but did not increase further during the omeprazole treatment period. Median serum gastrin concentrations returned to baseline within 2 to 4 days after administration of the last dose of omeprazole. No effect of treatment or discontinuation was seen in serum CgA concentrations. CONCLUSIONS AND CLINICAL IMPORTANCE: Serum gastrin concentrations increased in response to omeprazole treatment but returned to baseline within 2 to 4 days after the last dose of omeprazole. No effect of treatment or discontinuation was seen in serum CgA concentrations. Our results do not support the use of tapering protocols in horses.

Preliminary investigations into a novel, long-acting, injectable, intramuscular formulation of omeprazole in the horse.

BACKGROUND: Pilot investigations have suggested that a novel, long-acting, injectable i.m. formulation of omeprazole (LA-OMEP) can induce acid suppression for up to 7 days following a single injection. OBJECTIVES: To investigate the pharmacodynamics and assess the clinical efficacy of the LA-OMEP formulation. STUDY DESIGN: Part A comprised a pharmacodynamic study. Part B consisted of a pilot clinical trial. METHODS: Part A enrolled six adult Thoroughbred horses with percutaneous gastrotomy tubes. Intragastric pH was measured for continuous 23-h periods (08.00-07.00 h) for eight consecutive days (days 0-7). A single 2.0-g dose of a 100 mg/mL LA-OMEP formulation was administered at 08.00 h on day 1. In Part B, 26 horses with squamous or glandular gastric disease were enrolled based on routine gastroscopic evaluation. Once enrolled, horses received 2.0 g of the 100 mg/mL LA-OMEP formulation by i.m. injection on days 0 and 7. Repeat gastroscopy was performed on days 14 (23 horses) or 16 (one horse). RESULTS: In Part A, the percentage of time during which pH was above 4 exceeded 66% for days 1-4 in all horses and days 1-7 in four of the six horses studied. In Part B, healing was observed in all 22 (100%, 95% confidence interval [CI] 89-100%) horses with squamous disease and in nine of 12 (75%, 95% CI 47-92%) horses with glandular disease. Improvement, by at least one grade, was observed in all 22 (100%, 95% CI 89-100%) horses with squamous disease and in all 12 (100%, 95% CI 81-100%) horses with glandular disease. No worsening of lesions was observed. Lesion grade decreased over time in both the squamous (P<0.0001) and glandular (P = 0.0024) mucosa. MAIN LIMITATIONS: Small sample sizes. CONCLUSIONS: The results of the present study compare favourably with previous reports on the pharmacodynamics of omeprazole and the clinical outcomes of trials reporting response to oral omeprazole therapy.

The effects of dose and diet on the pharmacodynamics of esomeprazole in the horse.

BACKGROUND: Esomeprazole warrants further investigation as a treatment for equine gastric ulcer syndrome. OBJECTIVES: To investigate the duration of intraday acid suppression achieved with two doses of esomeprazole under two dietary conditions. STUDY DESIGN: A four way crossover design. METHODS: Six adult Thoroughbreds instrumented with percutaneous gastrotomy tubes were used. Intragastric pH was measured for continuous 23 h periods (08.00-07.00 h) for 6 consecutive days (Days 0-5). Baseline data was recorded on Day 0 and esomeprazole was administered on Days 1-5. Two doses (0.5 and 2.0 mg/kg bwt/day per os once daily) and two diets (a high grain/low fibre (HG/LF) and ad libitum hay (HAY) diet) were studied. Data for the percentage of time pH was above 4 (%tpH>4) and median intraday pH was reported for two measurement points and analysed using generalised estimating equations. RESULTS: An inconsistent effect of both diet and dose was evident with mean %tpH>4 and mean of the median intraday pHs typically higher at the 2.0 mg/kg bwt dose and in HG/LF diet. A cumulative effect of dosing was present with the magnitude of acid suppression observed on Day 5 consistently higher than that observed on Day 1. The magnitude of acid suppression, at measurement point 1, compared favourably with previous reports on omeprazole and exceeded human therapeutic breakpoints for the 0.5 mg/kg bwt dose in the HG/LF diet and 2.0 mg/kg bwt dose in the HAY diet. MAIN LIMITATIONS: Instrumentation may have modified gastric function and horses were not fasted or exercised. CONCLUSIONS: The findings of the present study suggested that both dose and diet affect the response to esomeprazole in the horse and that a cumulative effect is present over the first 5 days of treatment. Further investigation into the clinical efficacy of esomeprazole and trials directly comparing esomeprazole and omeprazole appear to be warranted.

The effects of dose and diet on the pharmacodynamics of omeprazole in the horse.

BACKGROUND: Conflicting data are presented in the current literature regarding the efficacy of omeprazole for suppressing gastric acidity in the horse. OBJECTIVES: The objective of this study was to investigate the duration of intraday acid suppression achieved with two doses of omeprazole under two different dietary conditions. STUDY DESIGN: A four-way crossover design. METHODS: Six adult Thoroughbred horses instrumented with percutaneous gastrotomy tubes were used. Intragastric pH was measured for continuous 23 h periods (08.00-07.00 h) for six consecutive days (Days 0-5). Baseline data was recorded on Day 0 and omeprazole administered on Days 1-5. Two doses (1 mg/kg and 4 mg/kg bwt per os once a day) and two diets (a high grain/low fibre [HG/LF] and ad libitum hay [HAY)] diet) were studied. Data for the percent (%) time pH was above 4 (%tpH>4) and median intraday pH was reported for two measurement locations and analysed using generalised estimating equations. RESULTS: An effect of both diet and dose was evident with mean %tpH>4 and the mean of the median intraday pHs typically higher at the higher (4 mg/kg bwt) dose and in HG/LF diet. The overall efficacy of omeprazole in raising intragastric pH was good under the HG/LF conditions but relatively poor in the HAY diet. A cumulative effect of dosing, not previously reported in the horse, was observed. CONCLUSIONS: The overall efficacy of omeprazole in raising ventral gastric pH was less than previously reported. Both dose and diet may play a role in the efficacy of omeprazole in the horse. Therefore, the use of singular dosing recommendations that encompass all horse types and management conditions may not be appropriate and dosing recommendations that take into account the diet of the horse may be advantageous.

The effects of dose and diet on the pharmacokinetics of omeprazole in the horse.

This study aimed to investigate the effect of diet and dose on the pharmacokinetics of omeprazole in the horse. Six horses received two doses (1 and 4 mg/kg) of omeprazole orally once daily for 5 days. Each dose was evaluated during feeding either a high-grain/low-fibre (HG/LF) diet or an ad libitum hay (HAY) diet in a four-way crossover design. Plasma samples were collected for pharmacokinetic analysis on days 1 and 5. Plasma omeprazole concentrations were determined by ultra-high pressure liquid chromatography-mass spectrometry. In horses being fed the HG/LF diet, on day 1, the area under the curve (AUC) and maximal plasma concentration (Cmax ) were higher on the 4 mg/kg dose than on the 1 mg/kg dose. The AUC was higher on day 5 compared to day 1 with the 4 mg/kg dose on the HG/LF diet. On days 1 and 5, the AUC and Cmax were higher in horses being fed the HG/LF diet and receiving the 4 mg/kg dose than in horses being fed the HAY diet and receiving the 1 mg/kg dose. These findings suggest that both dose and diet may affect pharmacokinetic variables of omeprazole in the horse.

Pharmacokinetics and bioequivalence testing of five commercial formulations of omeprazole in the horse.

Omeprazole is widely used in the treatment of equine gastric ulcer syndrome. To date, little is known about the relative pharmacokinetics of the different formulations making comparisons between products difficult. The objectives of the study were to investigate the relative pharmacokinetics of five commercially available formulations of omeprazole in the horse and to test for bioequivalence of four of the formulations using one of the formulations as a reference standard. Twelve mature Thoroughbred horses were fasted for 16 h then administered 2 g of each formulation in a cross-over design. Serial blood samples were collected and plasma omeprazole concentration was determined by ultra high-performance liquid chromatography-mass spectrometry (UHPLC-MS). No significant differences were present between three of the formulations and the reference formulation, while the fourth formulation had a lower Cmax and longer Tmax than the reference formulation. Bioequivalence against the reference formulation could not be demonstrated for any of the formulations tested. The findings of the study suggested that the method of protection utilised by different formulations of omeprazole (enteric-coated granules vs. buffering) does not significantly alter the pharmacokinetics of the drug. Further work to establish bioequivalence is needed before direct comparisons can be drawn between different formulations.

The effect of feeding on the pharmacokinetic variables of two commercially available formulations of omeprazole.

The objectives of this study were to investigate the impact of formulation (enteric coated and buffered) and feeding on pharmacokinetic variables associated with the oral administration of omeprazole in the horse. Six thoroughbred racehorses were studied in a crossover design. Each received 2 g of an enteric coated or buffered formulation in both the fed and fasted state. Plasma omeprazole concentrations were determined by UHPLC-MS. The effects of feeding or formulation on AUC0-inf_obs, half-life, Tmax or Cmax were not statistically significant. However, a wider-than-expected degree of variation was present and examination of the raw data suggests that an effect of feeding, wherein the bioavailability of omeprazole may be reduced in the fed animal, may be present. Further investigation in a larger population of animals to assess the factors that contribute to the wide degree of absorption observed is warranted.

The effect of haemolysis on the metabolomic profile of umbilical cord blood.

OBJECTIVES: Metabolomics is defined as the comprehensive study of all low molecular weight biochemicals, (metabolites) present in an organism. Using a systems biology approach, metabolomics in umbilical cord blood (UCB) may offer insight into many perinatal disease processes by uniquely detecting rapid biochemical pathway alterations. In vitro haemolysis is a common technical problem affecting UCB sampling in the delivery room, and can hamper metabolomic analysis. The extent of metabolomic alteration which occurs in haemolysed samples is unknown. DESIGN AND METHODS: Visual haemolysis was designated by the laboratory technician using a standardised haemolysis index colour chart. The metabolomic profile of haemolysed and non-haemolysed UCB serum samples from 69 healthy term infants was compared using both (1)H-NMR and targeted DI and LC-MS/MS approach. RESULTS: We identified 43 metabolites that are significantly altered in visually haemolysed UCB samples, acylcarnitines (n=2), glycerophospholipids (n=23), sphingolipids (n=7), sugars (n=3), amino acids (n=4) and Krebs cycle intermediates (n=4). CONCLUSION: This information will be useful for researchers in the field of neonatal metabolomics to avoid false findings in the presence of haemolysis, to ensure reproducible and credible results.

Pharmacokinetics of intravenous, plain oral and enteric-coated oral omeprazole in the horse.

The objectives were to document the pharmacokinetics of intravenous, enteric-coated oral and plain oral omeprazole in fasted horses and to investigate the impact of feeding on the bioavailability of an enteric-coated omeprazole. Twelve horses received four treatments: intravenous omeprazole (0.5 mg/kg) in the fasted state (IV-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fasted state (ECO-Fasted), enteric-coated omeprazole (4 mg/kg) orally in the fed state (ECO-Fed) and plain omeprazole (4 mg/kg) orally in the fasted state (PL-Fasted). Plasma omeprazole concentrations were determined by UHPLC-MS. Bioavailability was higher (P = 0.038) in the ECO-Fasted group (21.5 [9.0-27.7]%) than the PL-Fasted group (10.1 [7.7-13.3]%). Similarly, AUC0-∞ was higher in the ECO-Fasted group than the PL-Fasted group (P = 0.027). No significant differences were present between the ECO-Fasted and ECO-Fed groups with regards to bioavailability, Cmax , Tmax or AUC0-∞ . When the half-life data from the oral formulations was pooled, it was longer than that observed in the IV-Fasted group (100 [73-118] min) and 35 [34-39] min, respectively; P < 0.0001). Bioavailability of enteric-coated omeprazole was higher than previously reported and feeding had minimal impact. Bioavailability of plain omeprazole was approximately half that of enteric-coated omeprazole. The longer half-life observed following oral administration was consistent with the flip-flop effect and has not previously been described for omeprazole in the horse.

A comparison of three doses of omeprazole in the treatment of equine gastric ulcer syndrome: A blinded, randomised, dose-response clinical trial.

REASONS FOR PERFORMING THE STUDY: A previous study demonstrated that a dose effect between 1.6 and 4.0 mg/kg bwt of omeprazole per os s.i.d. is present in the treatment of equine gastric ulceration. In the same study, healing of glandular ulceration appeared inferior to healing of squamous ulceration. However, several limitations were recognised in that study and further investigation is warranted. OBJECTIVES: To further investigate the presence of a dose relationship in the treatment of gastric ulceration under conditions that may favour omeprazole efficacy such as administration prior to exercise and after a brief fast, and potential differences between the response of squamous and glandular ulceration to omeprazole therapy. STUDY DESIGN: A blinded, randomised, dose-response clinical trial. METHODS: Sixty Thoroughbred racehorses with grade ≥2/4 squamous and/or glandular ulceration were identified by gastroscopy. Horses were randomly assigned to receive either 1.0, 2.0 or 4.0 mg/kg bwt of enteric coated omeprazole per os s.i.d. 1-4 h prior to exercise. Gastroscopy was repeated at approximately 28 days. RESULTS: The lower doses studied (1.0 and 2.0 mg/kg bwt) were noninferior to the reference dose (4.0 mg/kg bwt) in the treatment of squamous ulceration. Healing was greater in squamous ulceration than glandular ulceration (86% vs. 14%; P<0.0001). Improvement in ulcer grade was more likely in squamous lesions than glandular lesions (96% vs. 34%; P<0.0001). Worsening of the glandular ulcer grade was observed in 36% of horses. CONCLUSIONS: The results of this study suggest that, under the conditions studied, where omeprazole is administered before exercise and following a brief fast, doses of omeprazole as low as 1 mg/kg bwt per os s.i.d. may be as effective as higher doses. The proportion of glandular ulceration that heals with 28 days of omeprazole therapy is less than that of squamous ulceration.

Metabolomic profiling in multiple sclerosis: insights into biomarkers and pathogenesis.

Metabolomics enables the provision of sensitive bio-markers of disease. We performed 800 MHz (1)H-nuclear magnetic resonance (NMR) spectroscopic analyses of cerebrospinal fluid (CSF) specimens to identify biomarkers of multiple sclerosis (MS), yielding reproducible detection of 15 metabolites from MS (n=15) and non-MS (n=17) patients. Mean levels of choline, myo-inositol and threonate were increased, whereas 3-hydroxybutyrate, citrate, phenylalanine, 2-hydroxyisovalerate and mannose were decreased in MS-derived CSF (p<0.05), suggesting alterations to energy and phospholipid metabolism. Multivariate hierarchal cluster analysis indicated a high correlation within the metabolite profiles, significantly clustering samples into the two clinical groups, which was corroborated using principal components analysis. CSF metabolomics have the capacity to yield quantitative biomarkers and insights into the pathogenesis of MS.

A comparison of two doses of omeprazole in the treatment of equine gastric ulcer syndrome: a blinded, randomised, clinical trial.

REASONS FOR PERFORMING THE STUDY: Studies on omeprazole have reported that doses as low as 0.7 mg/kg bwt per os are potent suppressors of acid production. Yet, to date, no studies have compared treatment efficacy of different doses in clinical cases of equine gastric ulceration. Furthermore, no studies have been performed to compare the healing response of the squamous and glandular mucosa to acid suppression therapy. OBJECTIVES: To compare: 1) the efficacy of 2 doses of omeprazole in the treatment of primary squamous and glandular gastric ulceration; and 2) the healing response of primary squamous and glandular gastric ulceration to acid suppression therapy. STUDY DESIGN: A blinded, randomised, dose-response clinical trial. METHODS: Twenty Thoroughbred racehorses with grade ≥2/4 glandular ulceration were identified on gastroscopy. Seventeen horses also had grade ≥2/4 squamous ulceration. Horses were randomly assigned to one of 2 groups. Horses received either 2.0 g (high dose: 4.0 mg/kg bwt) or 0.8 g (low dose: 1.6 mg/kg bwt) of oral omeprazole per os once daily. Gastroscopy was repeated at 28-35 days. RESULTS: Time and dose significantly affected grades of squamous (P<0.0001, P = 0.02) and glandular (P = 0.006 and 0.005) ulceration. Data analysis did not support our hypothesis that the lower dose would have similar effects (i.e. be noninferior) to the higher dose when considering ulcer healing and ulcer improvement. Improvement was more likely with the high dose for the squamous (P = 0.05) but not glandular (P = 0.4) mucosa. The percentage of glandular ulcers that improved was less than squamous ulcers (P = 0.02). CONCLUSIONS: The results suggest that a dose-response exists for the treatment of both squamous and glandular ulcers. Improvement of glandular ulcers was not as complete as observed with squamous ulcers and current equine gastric ulcer syndrome treatment recommendations may not be appropriate for glandular disease.

The effect of geographic location, breed, and pituitary dysfunction on seasonal adrenocorticotropin and α-melanocyte-stimulating hormone plasma concentrations in horses.

BACKGROUND: Plasma α-melanocyte-stimulating hormone (α-MSH) and adrenocorticotropin (ACTH) concentrations in horses vary with season, confounding diagnostic testing for pituitary pars intermedia dysfunction (PPID). HYPOTHESIS: The goals of this study were to determine whether seasonal variation in plasma α-MSH and ACTH concentrations in horses is influenced by geographic location, breed, or PPID. ANIMALS: Healthy light breed horses residing in Florida, Massachusetts, and Finland (n = 12 per group); healthy Morgan horses (n = 13); healthy ponies (n = 9) and horses with PPID (n = 8). METHODS: Monthly plasma α-MSH and ACTH concentrations were measured by radioimmunoassay. Nonlinear regression analysis was used to estimate the time of peak hormone concentrations. Mean hormone concentrations in fall and nonfall months were compared. RESULTS: The fall peak plasma α-MSH concentration occurred earlier in horses residing at more northern locations. Mean seasonal α-MSH concentrations were similar in all healthy groups at all locations, but in the fall, plasma ACTH concentrations were higher in horses living in more southern locations. Plasma ACTH but not α-MSH concentrations were higher in Morgan horses compared with light breed horses from the same location. Hormone concentrations of ponies did not differ from those of horses during either season. Concentrations of both hormones were high in the fall compared with the spring in horses with PPID. CONCLUSIONS AND CLINICAL IMPORTANCE: These findings suggest geographic location of residence and breed may affect the onset, amplitude, or both of the seasonal peak of pars intermedia (PI) hormones and should be considered when performing diagnostic testing for PPID. Horses with PPID maintain seasonal regulation of PI hormone output.

Caenorhabditis elegans diet significantly affects metabolic profile, mitochondrial DNA levels, lifespan and brood size.

Diet can have profound effects on an organism's health. Metabolic studies offer an effective way to measure and understand the physiological effects of diet or disease. The metabolome is very sensitive to dietary, lifestyle and genetic changes. Caenorhabditis elegans, a soil nematode, is an attractive model organism for metabolic studies because of the ease with which genetic and environmental factors can be controlled. In this work, we report significant effects of diet, mutation and RNA interference on the C.elegans metabolome. Two strains of Escherichia coli, OP50 and HT115 are commonly employed as food sources for maintaining and culturing the nematode. We studied the metabolic and phenotypic effects of culturing wild-type and mutant worms on these two strains of E. coli. We report significant effects of diet on metabolic profile, on mitochondrial DNA copy number and on phenotype. The dietary effects we report are similar in magnitude to the effects of mutations or RNA interference-mediated gene suppression. This is the first critical evaluation of the physiological and metabolic effects on C.elegans of two commonly used culture conditions.

Equine endotoxaemia--a state-of-the-art review of therapy.

The pathophysiology of endotoxaemia, a leading cause of death in the horse, is beginning to be understood in greater detail. Endotoxin may be absorbed into the systemic circulation in a number of different ways: most commonly the body's normal defense mechanisms are disrupted or bypassed, or the normal clearance mechanisms overwhelmed. Following this wide-spread effects are observed, although the most significant are seen in the cardiovascular system. Fever, arterial hypoxaemia and signs of abdominal pain are also common. With increased understanding of the disease new therapeutic agents have become available, however, while the newer agents offer some advantages it is important to recognise that supportive care is the mainstay of treatment for endotoxaemia. Supportive care consists of aggressive fluid therapy (crystalloid, colloid and hypertonic), the administration of non-steroidal antiinflammatory drugs and, where appropriate, antimicrobials. The principles of supportive care are discussed in detail. Other therapies such as hyperimmune plasma, polymyxin B, pentoxifylline, dimethyl sulfoxide and heparin are commonly used in the treatment of equine endotoxaemia and their use is reviewed here. Furthermore, newer agents such as anti-tumour necrosis factor antibodies, detergent, activated protein C and insulin, which have yet to gain widespread acceptance but may have an important role in the treatment of endotoxaemia in the future, are examined.

Genetic evidence for a family-based Scandinavian settlement of Shetland and Orkney during the Viking periods.

The Viking age witnessed the expansion of Scandinavian invaders across much of northwestern Europe. While Scandinavian settlements had an enduring cultural impact on North Atlantic populations, the nature and extent of their genetic legacy in places such as Shetland and Orkney is not clear. In order to explore this question further, we have made an extensive survey of both Y-chromosomal and mitochondrial DNA (mtDNA) variation in the North Atlantic region. Our findings indicate an overall Scandinavian ancestry of approximately 44% for Shetland and approximately 30% for Orkney, with approximately equal contributions from Scandinavian male and female subjects in both cases. This contrasts with the situation for the Western Isles, where the overall Scandinavian ancestry is less ( approximately 15%) and where there is a disproportionately high contribution from Scandinavian males. In line with previous studies, we find that Iceland exhibits both the greatest overall amount of Scandinavian ancestry (55%) and the greatest discrepancy between Scandinavian male and female components. Our results suggest that while areas close to Scandinavia, such as Orkney and Shetland, may have been settled primarily by Scandinavian family groups, lone Scandinavian males, who later established families with female subjects from the British Isles, may have been prominent in areas more distant from their homeland.

Temperature dependence of dynamics and thermodynamics of the regulatory domain of human cardiac troponin C.

Binding of Ca(2+) to the regulatory domain of troponin C (TnC) in cardiac muscle initiates a series of protein conformational changes and modified protein-protein interactions that initiate contraction. Cardiac TnC contains two Ca(2+) binding sites, with one site being naturally defunct. Previously, binding of Ca(2+) to the functional site in the regulatory domain of TnC was shown to lead to a decrease in conformational entropy (TDeltaS) of 2 and 0.5 kcal mol(-1) for the functional and nonfunctional sites, respectively, using (15)N nuclear magnetic resonance (NMR) relaxation studies [Spyracopoulos, L., et al. (1998) Biochemistry 37, 18032-18044]. In this study, backbone dynamics of the Ca(2+)-free regulatory domain are investigated by backbone amide (15)N relaxation measurements at eight temperatures from 5 to 45 degrees C. Analysis of the relaxation measurements yields an order parameter (S(2)) indicating the degree of spatial restriction for a backbone amide H-N vector. The temperature dependence of S(2) allows estimation of the contribution to protein heat capacity from pico- to nanosecond time scale conformational fluctuations on a per residue basis. The average heat capacity contribution (C(p,j)) from backbone conformational fluctuations for regions of secondary structure for the regulatory domain of cardiac apo-TnC is 6 cal mol(-1) K(-1). The average heat capacity for Ca(2+) binding site 1 is larger than that for site 2 by 1.3 +/- 0.8 cal mol(-1) K(-1), and likely represents a mechanism where differences in affinity between Ca(2+) binding sites for EF hand proteins can be modulated.