Circadian rhythm of calciotropic hormones, serum calcium, phosphorus and magnesium during the shortest and longest days of the year in horses in New Zealand.

A study was conducted to determine the circadian rhythms and trends of vitamin D metabolites including 25-hydroxyvitamin D3 , 25-hydroxyvitamin D2 , 1,25-dihydroxyvitamin D and parathyroid hormone, in addition to serum calcium, phosphorus and magnesium concentrations in horses over 48 h on the shortest and longest days of the year in 2013. Five healthy adult horses (Equus caballus) were on a constant pasture feeding regimen, and blood samples were collected from each horse every 3 h over a 48-h period, starting at 07:00 PM on day one and finishing at 07:00 PM on day three, for the measurement of calciotropic hormones and electrolytes. There was a significant difference between the serum concentration of calciotropic hormones, iCa, tCa, P and tMg between the shortest (winter) and longest (summer) days of the year in horses. Serum concentration of 25OHD3 was very low and mostly undetectable. Serum iCa, 1,25(OH)2 D and PTH concentrations clearly showed a circadian rhythm on the longest days of the year and serum tCa, P and tMg concentrations showed a diurnal pattern on the longest days (summer) of the year. None of the analytes showed any circadian rhythm on the shortest days (winter) of the year. The result of this study could have significant relevance to equine athletes travelling to international equestrian competitions and facing a huge time and seasonal differences that might affect their ability to adjust their circadian rhythms to new time zones.

Risk factors for horse falls in New Zealand Thoroughbred jumps racing.

This study aimed to determine the incidence of, and risk factors for race-day horse falls in Thoroughbred jumps (hurdle and steeplechase) racing in New Zealand. Incidence rates for race-day horse falls in jumps races from 2005/6 - 2018/19 racing seasons (n = 13,648 race day starts) were calculated per 1000 starts. Univariable and multivariable analyses of race-, horse- and jockey-level risk factors for horse falls were conducted using Poisson regression in a generalised linear mixed model. The incidence rate of horse falls in jumps races was 42 (95 % confidence intervals [CI], 39 - 45) per 1000 starts. Horse falls in steeplechase races were 1.6 (95 % CI, 1.4 - 1.9) times more likely than hurdle races. The incidence rate ratio (IRR) for horses falling at the last three jumps in comparison with the first three jumps was 3.1 (95 % CI, 2.8 - 3.5) for hurdle and 4.4 (95 % CI, 3.9 - 5.0) for steeplechase races. Greater jockey (age, P = 0.02) and horse experience (P = 0.001) were associated with a lower IRR of falls (P = 0.05). Longer races (P = 0.02) and those held in autumn compared to winter (IRR 1.4; 95 % CI, 1.0 - 1.8; P = 0.05) were associated with a higher rate of falling in steeplechase races. A regulatory change enhancing discretionary ability of jockeys to pull up 'in-race' was associated with reduced horse falls (IRR 0.65; 95 % CI, 0.51 - 0.82; P = 0.001). Pragmatic rule changes within the industry can have a positive effect on reducing risk and improving equine welfare.

1,25-Dihydroxyvitamin D3 production by human keratinocytes. Kinetics and regulation.

Human foreskin keratinocytes in vitro metabolize 25-hydroxyvitamin D3 to a number of metabolites, including 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). This metabolite remains mostly within the cell and does not accumulate in the medium under the conditions of these experiments. With time, 1,25(OH)2D3 is catabolized, and more polar metabolites appear in both the cells and the medium. The production of 1,25(OH)2D3 has an apparent Michaelis constant (Km) for 25-hydroxyvitamin D3 of 5.4 X 10(-8) M. The levels of 1,25(OH)2D3 within the cell are increased both by increased production and decreased catabolism when parathyroid hormone(1-34) and isobutylmethylxanthine are added. Exogenously added 1,25(OH)2D3 at concentrations as low as 10(-12) M reduces endogenous 1,25(OH)2D3 production, increases 1,25(OH)2D3 catabolism, and increases 24,25-dihydroxyvitamin D3 production by an actinomycin D-sensitive process. These data indicate that the regulation of 1,25(OH)2D3 production by keratinocytes is similar to, but not identical to the regulation of 1,25(OH)2D3 by the kidney.

Free 25-hydroxyvitamin D levels are normal in subjects with liver disease and reduced total 25-hydroxyvitamin D levels.

We determined the free fraction of 25-dihydroxyvitamin D (25OHD) in the serum of subjects with clinical evidence of liver disease and correlated these measurements to the levels of vitamin D binding protein and albumin. These subjects when compared to normal individuals had lower total 25OHD levels, higher percent free 25OHD levels, but equivalent free 25OHD levels. These subjects also had reduced vitamin D binding protein and albumin concentrations. The total concentration of 25OHD correlated positively with both vitamin D binding protein and albumin, whereas the percent free 25OHD correlated negatively with vitamin D binding protein and albumin. The free 25OHD levels did not correlate with either vitamin D binding protein or albumin. We conclude that total vitamin D metabolite measurements may be misleading in the evaluation of the vitamin D status of patients with liver disease, and recommend that free 25OHD levels also be determined before making a diagnosis of vitamin D deficiency.

Free 1,25-dihydroxyvitamin D levels in serum from normal subjects, pregnant subjects, and subjects with liver disease.

We measured the free concentration of 1,25-dihydroxyvitamin D (1,25[OH]2D) using centrifugal ultrafiltration, and the level of vitamin D-binding protein (DBP) in 24 normal subjects, 17 pregnant subjects, and 25 alcoholic subjects with liver disease. Our objective was to determine whether the increase in total 1,25(OH)2D levels in pregnant women and the reduction in total 1,25(OH)2D levels in subjects with liver disease reflected a true difference in free 1,25(OH)2D levels or whether such differences were due solely to the variations in DBP levels (and thus, the amount of 1,25[OH]2D bound) in these groups. In subjects with liver disease the mean total 1,25(OH)2D concentration (22.6 +/- 12.5 pg/ml) and the mean DBP concentration (188 +/- 105 micrograms/dl) were nearly half the normal values (41.5 +/- 11.5 pg/ml and 404 +/- 124 micrograms/dl, respectively, P less than 0.001), whereas the mean free 1,25(OH)2D level was similar to normal values (209 +/- 91 fg/ml and 174 +/- 46 fg/ml, respectively). In contrast, in pregnant subjects the mean total 1,25(OH)2D level (82 +/- 21 pg/ml) and mean DBP level (576 +/- 128 micrograms/dl) were significantly higher than normal (P less than 0.001). Although the mean percent free 1,25(OH)2D level in pregnant subjects was below normal (0.359 +/- 0.07% vs. 0.424 +/- 0.07%, P less than 0.001), the mean free 1,25(OH)2D level was 69% higher than normal (294 +/- 98 fg/ml vs. 174 +/- 46 fg/ml, P less than 0.001). When data from all three groups were combined, there was a linear correlation between total 1,25(OH)2D and DBP levels but not between DBP and percent free 1,25(OH)2D levels; the increased DBP levels in the pregnant subjects were associated with less of an effect on percent free 1,25(OH)2D than were the reduced DBP levels in the subjects with liver disease. Our data suggest that (a) free 1,25(OH)2D levels appear to be well maintained even in subjects with liver disease and reduced DBP levels, (b) free 1,25(OH)2D levels are increased during pregnancy despite the increase in DBP levels, and (c) free 1,25(OH)2D levels cannot be inferred accurately from measurements of total 1,25(OH)2D and DBP levels alone in subjects with various physiologic and pathophysiologic conditions.

Osteochondrosis and copper: histology of articular cartilage from foals out of copper supplemented and non-supplemented dams.

Copper (Cu) supplementation of dams in late gestation may be protective against articular cartilage abnormalities in foals. Articular cartilage was harvested from 22 Thoroughbred foals at 160 days of age, at sites predisposed to osteochondrosis (OC), and examined for evidence of early cartilage abnormalities and established dyschondroplastic (DCP) lesions to determine if there were any significant differences due to mare Cu supplementation by injection during late gestation, or foal liver Cu concentration. Cu supplemented mares received calcium Cu edetate injections in late gestation (250 mg at around 220, 248, 276 and 304 days gestation, then every two weeks until foaling). Foals were euthanased at 160 days of age and articular cartilage was harvested from four defined sites. Samples were examined for histological appearance of chondrocytes after staining with haematoxylin and eosin, and were also stained with toluidine blue to indicate proteoglycan content. Alkaline phosphatase (ALP) activity was detected by histochemistry, and histocytochemical techniques were used to determine the expression of cathepsin B. Cu supplementation of the dam, or liver Cu concentration of the foal at birth or 160 days of age had no statistically significant effect on the frequency of cartilage irregularities observed grossly, or abnormalities detected histologically at four defined sites. ALP expression was similar in all samples. Cathepsin B expression varied between sites, and was seen in chondrocyte clusters. The intensity of toludine blue staining varied between sites. Minor histological cartilage abnormalities were observed in cartilage from clinically normal animals. These abnormalities might be 'early' dyschondroplastic lesions, which could resolve or progress. The role of Cu in the development, resolution or progression of dyschondroplastic lesions is poorly understood.

Differential sensitivities of five rat hepatoma cell lines to anticancer drugs.

Five permanent tumor cell lines derived originally from either a solid or an ascites biopsy of rat hepatoma exhibited differential sensitivities to bleomycin, Adriamycin, 1-beta-D-arabinofuranosylcytosine, hydroxyurea, 1-trans-(2)-chloroethyl)-3-(4-methoylcyclohexyl)-1-nitrosourea, and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. The cells were least sensitive to hydroxyurea and 1-beta-D-arabinofurano-sylcytosine, with some cell lines being almost totally resistant to these drugs. However, from 25- to 700-fold differences in survival were obtained between cell lines treated with either bleomycin or Adriamycin.

Influence of blanketing and season on vitamin D and parathyroid hormone, calcium, phosphorus, and magnesium concentrations in horses in New Zealand.

The aims of the study were to determine the effect of season and blanketing on vitamin D synthesis in horses and examine the interaction between vitamin D and other analytes involved in calcium homeostasis. Twenty-one healthy horses at pasture were included; 5 were covered with standard horse blankets including neck rugs. Blood samples were collected for 13 mo and analyzed for 25-hydroxyvitamin D2 (25OHD2) and 25-hydroxyvitamin D3 (25OHD3), 1,25-dihydroxyvitamin D (1,25[OH]2D), ionized calcium (iCa), total calcium (tCa), phosphorus (P), total magnesium (tMg), and parathyroid hormone (PTH). Grass and hay samples were collected and analyzed for vitamin D, calcium, phosphorus, and magnesium. Climate data were also collected. The serum concentration of 25OHD3 in horses was either undetectable or below the detection limit of the assay, and the main form of 25OHD was 25OHD2. No differences in serum 25OHD2, 1,25(OH)2D, iCa, tCa, P, tMg, and PTH (P ≥ 0.05) concentrations were seen between the 2 groups. Associations were seen between iCa and PTH (P < 0.05), iCa and tMg (P < 0.05), and dietary vitamin D and 25OHD2 (P < 0.05). A strong seasonal trend was seen in serum 25OHD2 (P < 0.0001), which was higher during spring and summer when the amount of sunshine and UV radiation was higher. Parathyroid hormone and 1,25(OH)2D showed opposing trends with PTH higher in winter whereas 1,25(OH)2D was higher in summer. The results suggest that dietary vitamin D may be necessary for horses to fulfill their vitamin D requirements; however, further research is required to determine the contribution of vitamin D3 synthesis in the skin to the vitamin D status of the horse.

Increased sensitivity to kindling in mice lacking TSP1.

The development of a hyperexcitable neuronal network is thought to be a critical event in epilepsy. Thrombospondins (TSPs) regulate synaptogenesis by binding the neuronal α2δ subunit of the voltage-gated calcium channel. TSPs regulate synapse formation during development and in the mature brain following injury. It is unclear if TSPs are involved in hyperexcitability that contributes to the development of epilepsy. Here we explore the development of epilepsy using a pentylenetetrazole (PTZ) kindling model in mice lacking TSP1 and TSP2. Unexpectedly, we found increased sensitivity to PTZ kindling in mice lacking TSP1, while mice lacking TSP2 kindled similar to wild-type. We found that the increased seizure susceptibility in the TSP1 knockout (KO) mice was not due to a compensatory increase in TSP2 mRNA as TSP1/2 KO mice were sensitive to PTZ, similar to the TSP1 KO mice. Furthermore, there were similar levels of TGF-B signal activation during kindling in the TSP1 KO mice compared to wild-type. We observed decreased expression of voltage-dependent calcium channel subunit CACNA2D1 mRNA in TSP1, TSP2, and TSP1/2 KO mice. Decreased CACNA2D2 mRNA was only detected in mice that lacked TSP1 and α2δ-1/2 protein levels in the cortex were lower in the TSP 1/2 KO mice. CACNA2D2 knockout mice have spontaneous seizures and increased PTZ seizure susceptibility. Here we report similar findings, TSP1, and TSP1/2 KO mice have low levels of CACNA2D2 mRNA expression and α2δ-1/2 receptor level in the cortex, and are more susceptible to seizures. CACNA2D2 mutations in mice and humans can cause epilepsy. Our data suggest TSP1 in particular may control CACNA2D2 levels and could be a modifier of seizure susceptibility.

Regulation of keratinocyte growth, differentiation, and vitamin D metabolism by analogs of 1,25-dihydroxyvitamin D.

1,25(OH)2D has numerous actions on many tissues. Analogs of 1,25(OH)2D are being sought that are selective, to further an understanding of the mechanisms of action of 1,25(OH)2D and to improve its therapeutic efficacy. Toward these ends we examined eight analogs of 1,25(OH)2D for their ability to regulate 25OHD metabolism by keratinocytes. Choosing the three most potent, we then examined their ability to inhibit keratinocyte proliferation, stimulate cornified envelope formation (a marker of differentiation), and bind to the 1,25(OH)2D receptor (VDR). 1,25(OH)2-24F2-D, 1,25(OH)2-delta 16-D, and 1,25(OH)2-delta 16,23yne-D proved the most potent in inhibiting 1,25(OH)2D production and stimulating 24,25(OH)2D production, being approximately 10-100 times more potent than 1,25(OH)2D itself. 1,25(OH)2-delta 16-D had the highest affinity for the VDR (fourfold higher than that for 1,25(OH)2D itself) and had the greatest ability both to inhibit proliferation and to stimulate differentiation. 1,25(OH)2-delta 16,23yne-D also had a higher affinity for the VDR but was of less or equal potency in stimulating cornified envelope formation and inhibiting proliferation. 1,25(OH)2-24F2-D, which was the most potent regulator of 25OHD metabolism, had a lower affinity for the VDR and was less potent than 1,25(OH)2D in inhibiting proliferation. Our results indicate that even in the same cell different analogs have different rank orders of potency for the various actions of 1,25(OH)2D.

Squamous carcinoma cell lines produce 1,25 dihydroxyvitamin D, but fail to respond to its prodifferentiating effect.

The active metabolite of vitamin D3, 1,25 dihydroxyvitamin D3 [1,25(OH)2D], is produced by normal human keratinocytes (NKC) and regulates their differentiation. Squamous carcinoma cell (SCC) lines lack the ability to differentiate in vitro, which might involve defective 1,25(OH)2D synthesis or response. To address this possibility we obtained four SCC lines (12F2, 12B2, 25, and A431) and first determined whether they could produce 1,25(OH)2D from its substrate 25 hydroxyvitamin D3 (250HD). All could (12F2 greater than NKC greater than 25 greater than 12B2 greater than A431). Furthermore, exogenously added 1,25(OH)2D inhibited 1,25(OH)2D production and stimulated 24,25 dihydroxyvitamin D3 [24,25(OH)2D] production in all cell lines but with different potency (25 = A431 greater than NKC greater than 12B2 greater than 12F2). Cellular binding studies suggested that the high-affinity binding site for 1,25(OH)2D in NKC is not found in 12F2 and 12B2. When the effect of 1,25(OH)2D on differentiation was determined, only NKC responded with an increase in cornified envelope formation, although some of the cell lines responded to the proliferative [at low 1,25(OH)2D concentration] or antiproliferative [at high 1,25(OH)2D concentration] effect of 1,25(OH)2D. Thus, although SCC lines synthesize 1,25(OH)2D and respond to exogenous 1,25(OH)2D with respect to appropriate regulation of endogenous 250HD metabolism, these cell lines fail to respond to the differentiating influence of this vitamin D metabolite.

Free, and not total, 1,25-dihydroxyvitamin D regulates 25-hydroxyvitamin D metabolism by keratinocytes.

Greater than 99% of the total circulating 1,25-dihydroxyvitamin D [1,25-(OH)2D] is bound to proteins such as the vitamin D-binding protein (DBP) and albumin; in the normal human only 0.4% of the circulating 1,25-(OH)2D is free. Although it is often assumed that only the free concentration of 1,25-(OH)2D is available to cells, this has not been demonstrated. In particular, it is not clear whether the DBPs facilitate 1,25-(OH)2D entry into target cells or serve only to transport these metabolites within the circulation. To address this question, we evaluated one of the best characterized target tissue responses to 1,25-(OH)2D, namely its ability to inhibit its own production and induce that of 24,25-(OH)2D, using one of the most sensitive cells, the human foreskin keratinocyte. We incubated keratinocytes in the presence of 1,25-(OH)2D (from 10(-11)-10(-8) M) in medium containing albumin (from 0.1-10%) or serum (from 0.1-10%) for 4 h [to inhibit the 25-hydroxyvitamin D (250HD) 1 alpha-hydroxylase] or 16 h (to induce the 250HD 24-hydroxylase) before evaluating [3H]250HD metabolism by these cells during a 1-h incubation in serum- and albumin-free medium. The free fraction of 1,25-(OH)2D was determined in each medium by centrifugal ultrafiltration and varied from 36% to 0.57% in direct proportion to the albumin or serum in the medium. Increasing the serum or albumin concentration in the medium increased the concentration of total 1,25-(OH)2D needed to inhibit its own production or stimulate that of 24,25-(OH)2D. In contrast, the concentration of free 1,25-(OH)2D needed to half-maximally inhibit its own production or induce 24,25-(OH)2D production remained constant at approximately 10(-11) M. We conclude that the free, not the total, 1,25-(OH)2D concentration regulates 250HD metabolism by keratinocytes, that DBPs do not facilitate 1,25-(OH)2D entry into the cell, and that these cells sense only free 1,25-(OH)2D.

Tumor necrosis factor-alpha regulation of 1,25-dihydroxyvitamin D production by human keratinocytes.

The keratinocyte has receptors for, responds to, and produces both tumor necrosis factor-alpha (TNF) and 1,25-dihydroxyvitamin D [1,25-(OH)2D]. Both TNF and 1,25-(OH)2D facilitate the differentiation of keratinocytes. To explore the possibility that TNF stimulates keratinocyte differentiation at least in part by regulating 1,25-(OH)2D production we examined the effect of TNF on both 1,25-(OH)2D production and differentiation (transglutaminase activity, cornified envelope formation) at different stages of differentiation. 1,25-(OH)2D production, transglutaminase activity, and cornified envelope formation are sequentially increased during differentiation such that 1,25-(OH)2D production occurs first, followed by transglutaminase activity and, finally, cornified envelope formation. In preconfluent cells, TNF stimulated 1,25-(OH)2D production. Interferon-gamma also stimulated 1,25-(OH)2D production at low concentrations, but this was not additive to that by TNF. The stimulatory effect of TNF was maximal after 1-2 days of incubation and decreased with prolonged incubation. TNF had little effect on cornified envelope formation and transglutaminase activity in the preconfluent cells. Once keratinocytes achieved confluence, TNF stimulated transglutaminase activity and cornified envelope formation, but inhibited 1,25-(OH)2D production. Our results suggest that TNF regulates 1,25-(OH)2D production as part of its ability to accelerate keratinocyte differentiation; whether TNF stimulates or inhibits 1,25-(OH)2D production depends on whether TNF is added before or after the cell has reached its maximal capacity to make 1,25-(OH)2D.

Regulation of 1,25-dihydroxyvitamin D production in human keratinocytes by interferon-gamma.

Interferon-gamma (IFN gamma) and 1,25-dihydroxyvitamin D [1,25-(OH)2D] each have potent antiproliferative and prodifferentiating effects on keratinocytes. Since keratinocytes produce 1,25-(OH)2D, we explored the possibility that IFN gamma acted on keratinocytes in part by regulating 1,25-(OH)2D production. We cultured human neonatal foreskin keratinocytes for various periods of time in the presence of various concentrations of IFN gamma before assessing their ability to produce 1,25-(OH)2D. The production of 1,25-(OH)2D by preconfluent keratinocytes grown in the presence of serum (which retards differentiation) was stimulated by 1.8 nM IFN gamma. Postconfluent keratinocytes did not respond to 1.8 nM IFN gamma. The production of 1,25-(OH)2D by keratinocytes grown in serum-free medium was maximally stimulated by 0.006 nM IFN gamma and inhibited at concentrations greater than 0.06 nM. Keratinocytes grown in 0.1 mM calcium serum-free medium (which prevents differentiation) were more sensitive to both the stimulatory and inhibitory effects of IFN gamma than keratinocytes grown in 1.2 mM calcium serum-free medium (which permits differentiation). The stimulatory effect of IFN gamma on 1,25-(OH)2D production was maximal after 2 days of incubation. Incubations longer than 2 days showed increasingly less stimulation at the low IFN gamma concentrations and increasingly greater inhibition at the higher IFN gamma concentrations. The inhibitory effects of IFN gamma on 1,25-(OH)2D production paralleled the inhibitory effects of IFN gamma on cell growth. Thus, IFN gamma does regulate 1,25-(OH)2D production by keratinocytes. However, this regulation is modulated by the state of keratinocyte proliferation and differentiation and is influenced by calcium and undefined factors in serum. The data are consistent with the possibility that IFN gamma alters keratinocyte differentiation in part by regulating 1,25-(OH)2D production.

Assessment of the free fraction of 25-hydroxyvitamin D in serum and its regulation by albumin and the vitamin D-binding protein.

We measured the free fraction of 25-hydroxyvitamin D (25OHD) in human serum and determined that 25OHD bound to a component with an affinity constant of 7 X 10(8) M-1 and a concentration of 4.5 X 10(-6) M. This concentration was equal to that of the vitamin D-binding protein (DBP) in the same serum sample. We removed DBP from the serum using actin affinity columns and found that the affinity for 25OHD of the remaining serum components was equivalent to that of human serum albumin (6 X 10(5) M-1). We then measured the free fractions of 25OHD, DBP, and albumin in normal and cirrhotic subjects. We calculated that 88 +/- 3% (+/- SD) and 83 +/- 8% of the 25OHD were bound to DBP in the serum of normal and cirrhotic subjects, respectively. We compared previously reported data for the free fraction and the free concentration of 1,25-dihydroxyvitamin D in these subjects with the current data for the free fraction and free concentration of 25OHD. The total concentrations and free fractions of both metabolites correlated to each other and to the DBP and albumin concentrations in these subjects, but the free concentrations of these metabolites did not. We conclude that 25OHD, like 1,25-dihydroxyvitamin D, is transported in blood bound primarily to DBP and albumin. Changes in the concentrations of DBP and albumin affected the total and free fractions of 25OHD in serum, but the actual free concentration of 25OHD was independent of such changes.

Consequences of ornithine decarboxylase inactivation by alpha-difluoromethylornithine and 5-fluorouracil on the growth of rabbit fibroblasts.

The role of ornithine decarboxylase and polyamines in proliferative vitreoretinopathy (PVR) is ill-defined. An increase in the activity of this enzyme concurrent with an increase in polyamine levels may be essential in the process of intraocular cellular proliferation. Therefore, in this study, cultured rabbit fibroblasts were exposed to DL-alpha-difluoromethylornithine (alpha-DFMO), a mechanism-based irreversible inactivator of ornithine decarboxylase, alone and in combination with 5-fluorouracil (5-FU). Concentrations of 0.1mM alpha-DFMO and 0.125mM 5-FU decreased rabbit fibroblast cell number by 60% and 65%, respectively, after three days, while with either 5.0mM alpha-DFMO or 0.25mM 5-FU, cell number is decreased by 95%. The effectiveness of inhibitory concentrations of 5-FU and alpha-DFMO together in reducing cell number is additive.

Changes in liver copper concentration of thoroughbred foals from birth to 160 days of age and the effect of prenatal copper supplementation of their dams.

OBJECTIVES: To monitor the change in liver copper concentration of Thoroughbred foals from birth to 160 days of age and to determine the effects of supplementation by two injections of copper edetate given to dams in late gestation on the liver copper concentration of their foals at birth. PROCEDURE: Ten mares pregnant to the same stallion were randomised into two groups on the basis of age, liver copper concentration and expected foaling date. The treatment group mares were given 100 mg and 250 mg copper edetate intramuscularly during the ninth and tenth months of gestation respectively. Foals had liver biopsies taken weekly in the first month of life, then monthly for four months. Foals were euthanased at 160 days of age; liver samples were taken and the copper concentrations were determined. RESULTS: Two distinct patterns of age dependent decline in liver copper concentration were evident. The mean (+/- SD) liver copper concentration of the foals was high at birth (374 +/- 130 mg/kg DM), and for seven it declined to adult values by 160 days of age (21 +/- 6 mg/kg DM). In three foals the decline was at a slower rate than in the other seven and at 160 days of age the mean concentration was 162 +/- 32 mg/kg DM. Repeated measures analysis showed significant differences between each biopsy (P < 0.01) and between 'normal' and 'accumulator' foals (P < 0.002). Copper injections given to mares in late pregnancy had no effect on the liver copper concentration of foals at birth. CONCLUSIONS: The significance of the two patterns of age dependant decline in liver copper concentration is unknown. Parenteral copper supplementation of the dam in late gestation had no effect on the liver copper concentration of the foal at birth.

Dealing direct. If you want to play in the big leagues of direct contracting, pay attention to these risks.

There's danger in direct contracting with employers, but big advantages if you know how to steer clear. In this excerpt from Dealing Direct, a recent book from American Hospital Publishing, the authors point out common obstacles--from retaliation by insurers to managing high-risk enrollees to shifts in the market.

Sub-optimal efficacy of ivermectin against Parascaris equorum in foals on three Thoroughbred stud farms in the Manawatu region of New Zealand.

AIM: To ascertain whether resistance was present in Parascaris equorum to the macrocyclic lactone anthelmintic ivermectin, using faecal egg count reduction tests. METHODS: Thirty-nine foals aged between 11 and 28 weeks on three Thoroughbred stud farms (Farms A; n=20, B; n=5 and C; n=14) were treated with ivermectin (Day 0) and faecal egg counts (FEC) were monitored before and for 21 (Farms A and B) or 14 (Farm C) days after treatment. On Farms A and B, the foals were treated with a macrocyclic lactone/benzimidazole/praziquantel combination on Day 21 and FEC assessed on Day 35. The three farms were all in the Manawatu region in the southern half of New Zealand's North Island. RESULTS: Of the 39 foals, 15 were not shedding P. equorum eggs on the day they were treated with ivermectin, but all 15 did so post-treatment. The FEC on Farms A and B showed no evidence of a reduction at any time between Day 7 and 21; egg output increased steadily over this period. Following combination treatment FEC were reduced by 94% on farm A and 100% on Farm B. On Farm C, there was a 69% reduction in P. equorum FEC on Day 14. Twelve of the 14 foals on Farm C were shedding strongylid eggs on Day 0 and on Day 14 FEC were reduced by 84%. CONCLUSIONS: Without comparison to untreated control animals, these results do not allow a reliable estimation of the exact level of efficacy of ivermectin against P. equorum, but they nevertheless show that, within the farms studied, ivermectin no longer achieved a complete kill of egg-laying adults and that foals treated with this drug may continue to shed considerable numbers of eggs after treatment. The results also indicate that ivermectin had sub-optimal efficacy against strongylid nematodes on one of the farms.