A study of magnesium metabolism, depletion and repletion in young calves

The objectives of this experiment were: (1) to produce hypomagnesemia in young male calves; (2) to study the effects of magnesium (Mg) deficiency and excess dietary potassium (K) on mineral metabolism in hypomagnesemic and normal calves; and (3) to study the effects of MgCl2*6H2O enemas on plasma, cerebrospinal fluid (CSF) and red blood cell (RBC) mineral levels. In this study, calves were used as models for adult, lactating cows. Preliminary studies were initiated to establish procedures and determine the effectiveness of a semi-purified, low Mg, dry diet. Calves did poorly on the initial diet used in 2 preliminary trials in-volving 2 calves each. The composition of the diet was altered and a calf was maintained on this diet alone for 7 weeks. After the calf became severely hypomagnesemic, plasma and CSF Mg level were repleted using an enema of MgCl2*6H2O solution. Procedures for administering the enema and taking samples of blood and CSF were refined and finalized with this calf. Two trials were run involving 8 calves each which were fed 4 different diets. The diets were: Mg deficient basal diet, basal diet plus K, basal diet plus Mg and basal diet plus Mg and K. For the balance study, only samples collected from 9 calves were used for statistical analysis because of problems with diarrhea and anorexia. Samples of feces were collected using canvas collection bags and aliquots of urine were collected daily for a 5 day balance trial. All 16 calves were used in the repletion study which was initiated immediately after the balance study for both trials. Each calf was given an enema of MgCl2*6H2O solution while under general anesthesia. The enema was held in for 5 minutes and samples of blood and CSF were taken at 5, 15, 30, 60, 120 and 180 minutes after administration of the enema. For calves fed the Mg supplemented diets, the intake, fecal excretion and balance of Mg were greater (P\u3c .05) than calves fed deficient diets. Calf urinary excretion of Mg was not different among treatments. Supplemental K appeared to have no effect on Mg excretion or balance. Dietary K appeared to have no effect on plasma Mg level. The MgCl2*6H2O enemas caused a rapid increase in plasma Mg level. A significant increase in CSF Mg level was also observed in calves on the Mg deficient diets which had subnormal levels of CSF Mg. The MgCl2*6H2O enema appeared to have no effect on plasma calcium (Ca), and K, RBC minerals and packed cell volume (PCV). One calf in trial 1 had 4 episodes of tetany and was treated successfully 3 times with a MgCl2*6H2O enema. CSF samples taken during tetany had subnormal levels of Mg. Young dairy calves appeared to be good models for Mg studies in adult cows

Potassium, magnesium, insulin, glucagon and glucose interrelationships in ruminant hypomagnesemia

Effects of hyperkalemia and hypomagnesemia on insulin, glucagon, potassium (K), magnesium (Mg) and calcium (Ca) were investigated in calves. Glucose clearance studies without and with KCl infusion were conducted in normomagnesemic and hypomagnesemic calves fed adequate or excess K. Following glucose injection, insulin release and glucose clearance constants were greater (P\u3c.001) in hypomagnesemic than in normomagnesemic calves. When KCl was infused, insulin response was greater (P\u3c.001) and glucagon levels increased (P\u3c.001) during the third and fourth hour following glucose injections. Without KCl infusion, K levels dropped (P\u3c.05) during insulin elevations, while drops (P\u3c.05) in Mg occurred in normomagnesemic calves fed excess K. Experiments were also conducted in normomagnesemic and hypo magnesemic calves to determine effects of KCl infusions on glucose, insulin, glucagon, K, Mg and Ca fluxes across the portal-drained visceral, hepatic and hindlimb tissues. Increased (P\u3c.001) arterial K was accompanied by increased arterial insulin and glucagon and decreased arterial glucose. Elevated (P\u3c.001) insulin was associated with increased portal-drained visceral production (P\u3c.01). In hypo magnesemic calves, peripheral insulin was higher (P\u3c.001); however, increased portal-drained visceral production in hypomagnesemic calves was not significant. Increased (P\u3c.001) arterial glucagon was apparently due to decreased (P\u3c.10) hepatic extraction ratio in both groups of calves and concomitant nonsignificant increases in portal-drained visceral production. Peripheral glucagon was lower (P\u3c.001) in hypomagnesemic calves and portal-drained visceral production was lower (P\u3c.10). Drops (P\u3c.001) in peripheral glucose occurred in both groups of calves; however, changes in glucose flux were not significant. Portal-drained visceral K release decreased (P\u3c.05) while hindlimb K removal and extraction ratio increased (P\u3c.001) Tissue fluxes of Ca and Mg were unaffected

On the lack of X-ray iron line reverberation in MCG-6-30-15: Implications for the black hole mass and accretion disk structure

We use the method of Press, Rybicki & Hewitt (1992) to search for time lags and time leads between different energy bands of the RXTE data for MCG-6-30-15. We tailor our search in order to probe any reverberation signatures of the fluorescent iron Kalpha line that is thought to arise from the inner regions of the black hole accretion disk. In essence, an optimal reconstruction algorithm is applied to the continuum band (2-4keV) light curve which smoothes out noise and interpolates across the data gaps. The reconstructed continuum band light curve can then be folded through trial transfer functions in an attempt to find lags or leads between the continuum band and the iron line band (5-7keV). We find reduced fractional variability in the line band. The spectral analysis of Lee et al. (1999) reveals this to be due to a combination of an apparently constant iron line flux (at least on timescales of few x 10^4s), and flux correlated changes in the photon index. We also find no evidence for iron line reverberation and exclude reverberation delays in the range 0.5-50ksec. This extends the conclusions of Lee et al. and suggests that the iron line flux remains constant on timescales as short as 0.5ksec. The large black hole mass (>10^8Msun) naively suggested by the constancy of the iron line flux is rejected on other grounds. We suggest that the black hole in MCG-6-30-15 has a mass of M_BH~10^6-10^7Msun and that changes in the ionization state of the disk may produce the puzzling spectral variability. Finally, it is found that the 8-15keV band lags the 2-4keV band by 50-100s. This result is used to place constraints on the size and geometry of the Comptonizing medium responsible for the hard X-ray power-law in this AGN.Comment: 11 pages, 13 postscript figures. Accepted for publication in Ap

Intravenous glucagon like peptide-1 infusion does not affect dry matter intake or hypothalamic mRNA expression of neuropeptide Y, agouti related peptide and proopiomelanocortin in wethers

The objectives of the present study were to determine the effects of jugular vein infusions of glucagon like peptide-1 (GLP-1) and dietary fat inclusion on dry matter intake, nutrient digestibility and hypothalamic mRNA concentration of neuropeptide Y, agouti related peptide, and proopiomelanocortin in growing sheep. Thirty-six wethers were used (40.793.3 kg BW). Treatments were a control diet (n=11), dietary addition (6% of dry matter) of Ca salts of palm oil fatty acids (n=12), or 6-d jugular vein infusions of 0.155 μg/kg body weight/day of GLP-1 21 (n = 11). Hormone concentrations were measured in jugular vein plasma from samples taken on days 1, 4 and 6. On day 7, the wethers were slaughtered for ypothalamus collection to measure mRNA concentration. The dietary addition of 6% of Ca salts of palm oil increased plasma GLP-1 concentration (PB0.01) and decreased dry matter intake on day 1, but not on day 6 (time x treatment interaction, PB0.05). The infusion of GLP-1 did not change dry matter intake (P>0.20), but increasedneutral detergent fibre digestibility (PB0.01). In conclusion, glucagon like peptide-1 infusion or feeding fat did not decrease dry matter intake or affect hypothalamic neuropeptide mRNA concentrations of sheep

XMM-Newton Archival Study of the ULX Population in Nearby Galaxies

We present the results of an archival XMM-Newton study of the bright X-ray point sources (L_X > 10^38 erg/s) in 32 nearby galaxies. From our list of approximately 100 point sources, we attempt to determine if there is a low-state counterpart to the Ultraluminous X-ray (ULX) population, searching for a soft-hard state dichotomy similar to that known for Galactic X-ray binaries and testing the specific predictions of the IMBH hypothesis. To this end, we searched for "low-state" objects, which we defined as objects within our sample which had a spectrum well fit by a simple absorbed power law, and "high-state" objects, which we defined as objects better fit by a combined blackbody and a power law. Assuming that ``low-state'' objects accrete at approximately 10% of the Eddington luminosity (Done & Gierlinski 2003) and that "high-state" objects accrete near the Eddington luminosity we further divided our sample of sources into low and high state ULX sources. We classify 16 sources as low-state ULXs and 26 objects as high-state ULXs. As in Galactic black hole systems, the spectral indices, Gamma, of the low-state objects, as well as the luminosities, tend to be lower than those of the high-state objects. The observed range of blackbody temperatures for the high state is 0.1-1 keV, with the most luminous systems tending toward the lowest temperatures. We therefore divide our high-state ULXs into candidate IMBHs (with blackbody temperatures of approximately 0.1 keV) and candidate stellar mass BHs (with blackbody temperatures of approximately 1.0 keV). A subset of the candidate stellar mass BHs have spectra that are well-fit by a Comptonization model, a property similar of Galactic BHs radiating in the "very-high" state near the Eddington limit.Comment: 54 pages, submitted to ApJ (March 2005), accepted (May 2006); changes to organization of pape

Particle size distribution of forages and mixed rations, and their relationship with ration variability and performance of UK dairy herds

The particle size of the ration has been proposed as a key factor, along with its fibre and non-forage carbohydrate concentration, to ensure healthy rumen function and optimal performance of dairy cows. The current particle size distribution recommendations for forages and rations are primarily based on lucerne-haylage and maize silage (MS) and may not be suitable for the wetter grass silage (GS) based rations typically fed in Northern Europe. In order to characterize the particle size distribution of forages and rations in the UK, fifty commercial dairy herds feeding a range of GS and MS based rations were sampled during the winter of 2015/2016. The particle size distribution of the fresh forages and mixed rations (MR; total and partial mixed rations) were analysed using a modified Penn State Particle Separator with six screens of hole size 60, 44, 26.9, 19, 8, and 4 mm. The fresh MR was collected at 5-equally-spaced locations along the length of the feed-face for each herd within 5-min of feeding to determine the consistency of ration mixing, and again from the same locations 4h post-feeding. Grass silage was the main forage fed on 50 herds, with 80.3% of the dry matter (DM) being retained above the 19 mm sieve, which is considerably higher than the North-American recommendations for lucerne-haylage. The particle size distribution of MS followed the general recommendations for North American forages, however, the 8-19 mm fraction was higher and the 60 mm fraction of the MR had the lowest (0.1% DM) DM retention, and the 8-19 mm fraction the highest (34.9% DM). The MR had a higher proportion of particles retained on the 26.9 mm sieve when GS was the sole forage. Fifty eight % of herds were considered to have either moderately or poorly mixed rations, whilst 66% had evidence of diet selection (either preferential consumption or selective refusals). Particle size of the MR accounted for 33% of the variance in the milk fat content and 12% of milk yield. In conclusion, the particle size distribution of the GS and MR fed on UK dairy herds is different from the current recommendations, suggesting that the particle size of UK dairy rations is too long or new guidelines using additional sieves with larger pore sizes are required. There is also a high proportion of herds with poor mixing and/or evidence of diet selection

Liquid atmospheric pressure matrix-assisted laser desorption/ionization mass spectrometry adds enhanced functionalities to MALDI MS profiling for disease diagnostics

A liquid matrix-assisted laser desorption/ionization (liquid MALDI) method has been developed for high-throughput atmospheric pressure (AP) mass spectrometry (MS) analysis of the molecular content of crude bioliquids for disease diagnostics. The presented method is rapid and highly robust, enabling its application in environments where speed and low-cost high-throughput analyses are required. Importantly, because of the creation of multiply charged analyte ions, it provides additional functionalities that conventional solid MALDI MS profiling is lacking, including the use of high-performance mass analyzers with limited m/z range. The concomitant superior MS/MS performance that is achieved similar to ESI MS/MS adds greater analytical power and specificity to MALDI MS profiling while retaining the advantages of a fast laser-based analysis system and off-line large-scale sample preparation. The potential of this MALDI MS profiling method is demonstrated on the detection of dairy cow mastitis, which is a substantial economic burden on the dairy industry with losses of hundreds of dollars per diseased cow per year, equating to a total annual loss of billions of dollars, as well as leading to the use of large quantities of antibiotics, adding to the proliferation of antimicrobial resistance. Only small amounts of aliquots obtained from the daily farm milking process were prepared for liquid MALDI MS profiling using a simple one-pot/two-step analyte extraction. Automated analysis was performed using a custom-built AP-MALDI ion source, enabling the simultaneous detection of lipids, peptides, and proteins. Diagnostic, multiply charged, proteinaceous ions were easily sequenced and identified by MS/MS experiments. Samples were classified according to mastitis status using multivariate analysis, achieving 98.5% accuracy (100% specificity) determined by “leave 20% out” cross-validation. The methodology is generally applicable to AP-MALDI MS profiling on most commercial high-resolution mass spectrometers, with the potential for expansion into hospitals for rapid assessment of human and other biofluids

Iron fluorescence from within the innermost stable orbit of black hole accretion disks

The fluorescent iron Ka line is a powerful observational probe of the inner regions of black holes accretion disks. Previous studies have assumed that only material outside the radius of marginal stability can contribute to the observed line emission. Here, we show that fluorescence by material inside the radius of marginal stability, which is in the process of spiralling towards the event horizon, can have a observable influence on the iron line profile and equivalent width. For concreteness, we consider the case of a geometrically thin accretion disk, around a Schwarzschild black hole, in which fluorescence is excited by an X-ray source placed at some height above the disk and on the axis of the disk. Fully relativistic line profiles are presented for various source heights and efficiencies. It is found that the extra line flux generally emerges in the extreme red wing of the iron line, due to the large gravitational redshift experienced by photons from the region within the radius of marginal stability. We apply our models to the variable iron line seen in the ASCA spectrum of the Seyfert nucleus MCG-6-30-15. It is found that the change in the line profile, equivalent width, and continuum normalization, can be well explained as being due to a change in the height of the source above the disk. We discuss the implications of these results for distinguishing rapidly-rotating black holes from slowly rotating holes using iron line diagnostics.Comment: 20 pages, LaTeX. Accepted for publication in Astrophysical Journal. Figures 3 to 7 replaced with corrected versions (previous figures affected by calculational error). Some changes in the best fitting parameter

Elemental Abundances of Nearby Galaxies through High Signal-to-Noise XMM-Newton Observations of ULXs

(abridged) In this paper, we examined XMM Newton EPIC spectra of 14 ultra-luminous X-ray sources (ULXs)in addition to the XMM RGS spectra of two sources (Holmberg II X-1 and Holmberg IX X-1). We determined oxygen and iron abundances of the host galaxy's interstellar medium (ISM) using K-shell (O) and L-shell (Fe) X-ray photo-ionization edges towards these ULXs. We found that the oxygen abundances closely matched recent solar abundances for all of our sources, implying that ULXs live in similar local environments despite the wide range of galaxy host properties. Also, we compare the X-ray hydrogen column densities (n_H) for 8 ULX sources with column densities obtained from radio H I observations. The X-ray model n_H values are in good agreement with the H I n_H values, implying that the hydrogen absorption towards the ULXs is not local to the source (with the exception of the source M81 XMM1). In order to obtain the column density and abundance values, we fit the X-ray spectra of the ULXs with a combined power law and one of several accretion disk models. We tested the abundances obtained from the XSPEC models bbody, diskbb, grad, and diskpn along with a power law, finding that the abundances were independent of the thermal model used. We comment on the physical implications of these different model fits. We also note that very deep observations allow a breaking of the degeneracy noted by Stobbart et al. (2006) favoring a high mass solution for the absorbed grad + power law model.Comment: 18 pages, accepted to Ap

ASCA Observation of an X-Ray-Luminous Active Nucleus in Markarian 231

We have obtained a moderately long (100 kilosecond) ASCA observation of the Seyfert 1 galaxy Markarian 231, the most luminous of the local ultraluminous infrared galaxy (ULIRG) population. In the best-fitting model we do not see the X-ray source directly; the spectrum consists of a scattered power-law component and a reflection component, both of which have been absorbed by a column N_H \approx 3 X 10^(22)/cm^2. About 3/4 of the observed hard X-rays arise from the scattered component, reducing the equivalent width of the iron K alpha line. The implied ratio of 1-10 keV X-ray luminosity to bolometric luminosity, L_x/L_bol \sim 2%, is typical of Sy 1 galaxies and radio-quiet QSOs of comparable bolometric luminosities, and indicates that the bolometric luminosity is dominated by the AGN. Our estimate of the X-ray luminosity also moves Mrk 231 in line with the correlations found for AGN with extremely strong Fe II emission. A second source separated by about 2 arcminutes is also clearly detected, and contributes about 25% of the total flux.Comment: 11 pages, 3 figures; to appear in ApJ Letter