Acid-base and electrolyte effects of shortening steeplechase in a three-day-event

This study was designed to characterise the acid-base and electrolyte effects of shortening the distance required during steeplechase (Phase B) in the face of hot and humid weather conditions during a treadmill-simulated Speed and Endurance test. Eight conditioned Thoroughbred horses underwent 3 randomised permutations of a standardised exercise test on a high speed treadmill. Each test consisted of trotting at 3.7 m/s for 10 min (Phase A); galloping at 11 m/s (Phase B) for 4 (cool laboratory conditions), 3 (hot and humid), or 2 (hot and humid) min; trotting at 3.7 m/s for 30 min (Phase C); and walking at 1.8 m/s for 10 min (Phase X). The treadmill slope was 4% for trotting and galloping and 0% for walking. Cool versus hot and humid conditions were 20 degrees C and 50-60% relative humidity vs. 26-28 degrees C and 80-85% relative humidity, respectively. Pulmonary artery blood samples were obtained at rest prior to exercise (Rest); at the end of Phases A (A10) and B (B2-4); at 10 (C10), 20 (C20) and 30 (C30) min through Phase C; and at 5 min into Phase X (X5). Additional samples for lactate (LA) and glucose (GLC) analysis were obtained 5 min into Phase C (C5) and at the end of Phase X (X10). Samples were analysed for packed cell volume (PCV), haemoglobin (HB), total plasma protein (TP), sodium (Na), potassium (K), chloride (Cl), anion gap (AG), plasma glucose (GLC) and lactate (LA), pH, PCO2, bicarbonate (HCO3) and base excess (BE). Shortening steeplechase distance by 50% under hot and humid conditions (2 min B) resulted in a consistent return to control measurements (4 min B) only for plasma LA. Changes in PCV, HB, TP, K and Cl were related more to the longer galloping distance in the 4 min B trials than to hot vs. cold laboratory conditions. Alternatively, changes in LA, GLC, pH, PCO2 and AG were more related to hot and humid laboratory conditions than they were to galloping distance. These latter variables, when combined with physical measures such as core temperature, bodyweight loss, point of fatigue on Phase C and recovery heart rates may serve as the best monitors of positive responses in future studies of proposed modifications to Phase C, rather than those variables which were more distance than weather-related.     

Physiological, metabolic and biochemical responses of horses competing in the speed and endurance phase of a CCI*****3-day-event

The present study was undertaken to investigate physiological, metabolic, haematological and biochemical changes in horses competing in the Speed and Endurance test of a Concours Complet International (CCI)*****3-day-event held under FEI rules. A total of 28 horses competing in the Burghley Horse Trials Speed and Endurance test were selected to be monitored: 11 horses in 1993 and 17 horses in 1994. Of the 28 horses selected, 17 completed the Speed and Endurance test and went on to complete the showjumping test. Mean +/- s.d. shade temperature and relative humidity, black globe temperature and wind speed were 13 +/- 1 and 20 +/- 2 degrees C, 54 +/- 3 and 55 +/- 10%, 17 +/- 2 and 29 +/- 4 degrees C and 2.7 +/- 0.7 and 1.2 +/- 0.3 m/s, for 1993 and 1994, respectively. Mean heart rate during Phases A, B and D was not significantly different between years, but mean heart rate during Phase C and X was significantly higher in 1994. Mean (+/- s.d.) heart rate on Phase B and D for all horses in both 1993 and 1994 was 198 +/- 8 and 188 +/- 11 beats/min, respectively. Mean heart rate during Phase D showed a poor correlation with mean speed (r = 0.412). Total mean (+/- s.d.) weight loss from the start of Phase A to the end of Phase D was 15.5 +/- 6.1 kg in 1993 and 16.5 +/- 5 kg in 1994 and did not differ significantly between years. Following 14-18 h completion of Phase D, mean bodyweight was not significantly different from that at the start of Phase A in either year. Mean rectal temperature at the end of Phase D was 41 +/- 0.6 degrees C and 41.1 +/- 0.6 degrees C in 1993 and 1994, respectively (P > 0.05). Both the lowest (39.7 degrees C) and highest (41.8 degrees C) rectal temperatures were recorded at the end of Phase D in 1994. Plasma lactate concentrations at the end of Phase D were 8.5-38.5 mmol/l. The highest lactate concentration also coincided with the highest plasma glucose concentration (11.4 mmol/l) as well as the joint fastest time in either year, although overall lactate showed only weak correlations with mean speed on Phase D (r = 0.12, 1993; r = 0.58, 1994). While the Speed and Endurance test at CCI*****level run in a temperate climate presents a considerable challenge to the fitness and ability of the horses competing, the metabolic and physiological changes are not extreme. The majority of horses that finish the test appear to undergo a rapid and considerable degree of recovery and are able to present sound at the final inspection, take part in the showjumping test and complete the competition.     

Poly(A) tail shortening by a mammalian poly(A)-specific 3'-exoribonuclease

3'-Exonucleolytic removal of the poly(A) tail is the first and often rate-limiting step in the decay of many eucaryotic mRNAs. In a cytoplasmic extract from HeLa cells, the poly(A) tail of mRNA was degraded from the 3'-end. In agreement with earlier in vivo observations, prominent decay intermediates differed in length by about 30 nucleotides. The Mg2+-dependent, poly(A)-specific 3'-exoribonuclease responsible for this poly(A) shortening activity was purified from calf thymus. A polypeptide of 74 kDa copurified with the activity. The deadenylating nuclease (DAN) required a free 3'-OH group, released solely 5'-AMP, degraded RNA in a distributive fashion, and preferred poly(A) as a substrate. At low salt concentration, the activity of purified DAN was strongly dependent on spermidine or other, yet unidentified factors. Under these reaction conditions, DAN was also stimulated by the cytoplasmic poly(A)-binding protein I (PAB I). At physiological salt concentration, the stimulatory effect of spermidine was weak and PAB I was inhibitory. At either salt concentration DAN and PAB I reconstituted poly(A) shortening with the same pattern of intermediates seen in cytoplasmic extract. The properties of DAN suggest that the enzyme might be involved in the deadenylation of mRNA in vivo.     

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GABA(B) receptors function as a heteromeric assembly of the subunits GABA(B)R1 and GABA(B)R2

The principal inhibitory neurotransmitter GABA (gamma-aminobutyric acid) exerts its effects through two ligand-gated channels, GABA(A) and GABA(C) receptors, and a third receptor, GABA(B) , which acts through G proteins to regulate potassium and calcium channels. Cells heterologously expressing the cloned DNA encoding the GABA(B)R1 protein exhibit high-affinity antagonist-binding sites, but they produce little of the functional activity expected from studies of endogenous GABA(B) receptors in the brain. Here we describe a new member of the GABA(B) polypeptide family, GABA(B)R2, that shows sequence homology to GABA(B)R1. Neither GABA(B)R1 nor GABA(B)R2, when expressed individually, activates GIRK-type potassium channels; however, the combination of GABA(B)R1 and GABA(B)R2 confers robust stimulation of channel activity. Both genes are co-expressed in individual neurons, and both proteins co-localize in transfected cells. Moreover, immunoprecipitation experiments indicate that the two polypeptides associate with each other, probably as heterodimers. Several G-protein-coupled receptors (GPCRs) exist as high-molecular-weight species, consistent with the formation of dimers by these receptors, but the relevance of these species for the functioning of GPCRs has not been established. We have now shown that co-expression of two GPCR structures, GABA(B)R1 and GABA(B)R2, belonging to the same subfamily is essential for signal transduction by GABA(B) receptors.     

The acute phase reaction syndrome: the acute phase reactants (a review)

The acute phase reaction of the organism, which determines the response that follows the injury of tissues and organs and helps the survival of the individual is reviewed. The main participants, the induction of the reaction and the regulatory mechanisms are shortly discussed, with special respect to the prominent role of interleukin-6. The relationship between the production and synthesis of the acute phase reactants under physiological and pathophysiological conditions is analyzed. The particular functions of orosomucoid and alpha 2HS-glycoprotein are summarized. Finally, the common biological actions of IL-6 and the acute phase reactants are mentioned.     

Recrystallization behavior of a heavily cold-rolled Ni3Al(B,Zr) alloy

The present article describes the microstructural changes during recrystallization annealing of a 73 pct cold-rolled Ni₃Al(B,Zr) alloy along with a study of the recrystallization kinetics. The deformed γ regions, mostly within and near the shear bands, appear to recrystallize first. The recrystallization front leaves behind a lamellar discontinuous precipitation within the newly formed strain-free γ grains, when annealing is done at lower temperatures. At higher annealing temperatures, the precipitates within γ assume a globular morphology. This precipitate is presumably made up of γ′ particles. When γ recrystallization is nearly complete, the γ′ regions start to recrystallize. The two-stage recrystallization process is also corroborated from the kinetics results, which show that the activation energy up to 50 pct recrystallization of the material is only 117 kJ/mole, whereas beyond 50 pct until the completion of recrystallization, an activation energy of ∼274 kJ/mole is obtained.     

Crystal structure and phase relations of Pr_2Fe_(14)B-La_2Fe_(14)B system

The crystal structure and phase relations of the Pr_2Fe_(14)B-La_2Fe_(14) B system were investigated by X-ray powder diffraction(XRD), differential scanning calorimetry(DSC) and scanning electron microscopy(SEM) equipped with energy dispersive X-ray spectroscopy(EDS). The crystal structure parameters were determined by full-profile Rietveld refinements. The results revealed that all alloys of(Pr_(1–x)La_x)_2Fe_(14)B crystallized the Nd_2Fe_(14)B-type structure with the space group P4_2/mnm and formed a continuous solid solutions between x=0.0 and 1.0. The lattice parameter a, c, unit-cell volume V and c/a ratio increased linearly with the La concentration. Determined by thermogravimetry analysis, the Curie temperature(T_C), phase transition temperature and melting temperature of(Pr_(1–x)La_x)_2Fe_(14)B decreased linearly upon the La content. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Pr_2Fe_(14)B-La_2Fe_(14) B system was built up.     

Simulated phase evolution rewinding (SPHERE): a technique for reducing B0 inhomogeneity effects in MR images

A novel method for reducing field inhomogeneity effects in magnetic resonance images is described in this paper. Observing that image degradation arises from B0 inhomogeneity-induced phase accrual during data acquisition, the present method numerically rewinds the accumulated phase in the k-space data based on an initial estimate of the image and a corresponding field map. The rewinding process generates a corrected k-space data set that is subsequently Fourier transformed to produce the final image. In this paper, a theoretical analysis of the method and applications of the technique to magnetic resonance imaging data are presented. The theoretical analysis of the method indicates that it is a general approach applicable to a variety of sequences. Results obtained by applying the method to experimental data acquired with single-shot echo-planar imaging, segmented echo-planar imaging with centric reordering, and spiral sequences demonstrate that it is robust in reducing image degradation induced by B0 inhomogeneity.