A laser-based method for measuring thermal nociception of cattle

We describe a method for measuring nociception in cattle using a CO(2) laser aimed at the caudal aspect of the metatarsi. In Experiment 1, infrared thermography showed that calves responded by lifting their legs when skin temperatures reached 45-55 degrees C. In Experiment 2a, the validity of the method was tested by comparing the response latencies of 14 calves to two power settings (2.25 W vs. 4.5 W) with each setting being applied six times. We found that both leg-lift latencies and tail-flick latencies were lower at the higher power setting, and the calves were more likely to respond by kicking than by simply moving the leg. The standard deviations between and within calves were smaller at the higher power setting, and the large within-calf variation means that at least three tests were required to obtain reliable measures that could differentiate between calves. In Experiment 2b, application of the laser at a range of power settings (2.0, 3.0, 4.0, 4.5, 5.0 and 5.5 W) on 16 calves showed that response latencies decreased as power increased up to 4.5 W, after which no further change occurred. In Experiment 3, the repeatability of the method was evaluated on nine measures with the high power setting (4.5 W). The coefficient of variation associated with repetition of the measures was 36%. In general, we found little change in response latencies with repeated use of the laser, except that responses on the second test tended to be shorter. Experiment 4 showed that ambient temperatures between 16 degrees C and 27 degrees C did not affect response latencies, but these were longer at temperatures of 7 degrees C. We suggest that the method is a useful way of measuring cattle's sensitivity to nociception as the animals need not be restrained and the distance to the animal need not be closely controlled. However, to obtain accurate, valid and reliable measures it is necessary to use a high power setting (4.5 W) and take at least three consecutive measures of the response latency.     

Clustering Timber Harvests and the Effect of Dynamic Forest Management Policy on Forest Fragmentation

To integrate multiple uses (mature forest and commodity production) better on forested lands, timber management strategies that cluster harvests have been proposed. One such approach clusters harvest activity in space and time, and rotates timber production zones across the landscape with a long temporal period (dynamic zoning). Dynamic zoning has been shown to increase timber production and reduce forest fragmentation by segregating uses in time without reducing the spatial extent of timber production. It is reasonable to wonder what the effect of periodic interruptions in the implementation of such as strategy might be, as would be expected in a dynamic political environment. To answer these questions, I used a timber harvest simulation model (HARVEST) to simulate a dynamic zoning harvest strategy that was periodically interrupted by changes in the spatial dispersion of harvests, by changes in timber production levels, or both. The temporal scale (period) of these interruptions had impacts related to the rate at which the forest achieved canopy closure after harvest. Spatial dynamics in harvest policies had a greater effect on the amount of forest interior and edge than did dynamics in harvest intensity. The periodically clustered scenarios always produced greater amounts of forest interior and less forest edge than did their never clustered counterparts. The results suggest that clustering of harvests produces less forest fragmentation than dispersed cutting alternatives, even in the face of a dynamic policy future. Although periodic episodes of dispersed cutting increased fragmentation, average and maximum fragmentation measures were less than if clustered harvest strategies were never implemented. Clustering may also be useful to mitigate the fragmentation effects of socially mandated increases in timber harvest levels. Implementation of spatial clustering during periods of high timber harvest rates reduced the variation in forest interior and edge through time, providing a more stable supply of forest interior habitat across the landscape. Received 19 September 1997; accepted 6 August 1998.     

Spectrometric studies on stability of tenuazonic acid (TeA) solution in organic solvents

The stability of tenuazonic acid solution at different temperatures and storage times was studied using methanol, methanol-water (8:2 v/v), benzene and benzene-acetonitrile (98:2 v/v) as solvents. Solutions were analysed by a spectrometric method TeA U.V.-spectrum was recorded. Results indicated that the optimum temperature for long-time storage period of tenuazonic acid solution in any solvent assayed is -20°C. Benzene and benzene-acetonitrile (98:2 v/v) could be advised to make tenuazonic acid solution which will be stored less than 2 months at 4°C. Methanol and methanolwater (8:2 v/v) are not recommended because a low stability of TeA solution in this solvents.     

A novel principle for quantitation of fast intracellular calcium changes using Fura-2 and a modified image processing system--applications in studies of neutrophil motility and phagocytosis.

A new principle is described for imaging intracellular free calcium [Ca2+]i changes in single, living cells utilizing the fluorescent probe Fura-2. It is based upon video color mixing in real time and allows high-speed visualization, at maximum image resolution, of [Ca2+]i changes without digital image ratioing. The epifluorescence images produced by 340 and 380 nm excitations are stored in two memory buffers of a personal computer-based image processing system. Two video signals are generated independently from each buffer and connected to the red and green inputs of a video display. An image is this way created, in which [Ca2+]i shows up as a specific hue, whereas changes in dye concentration, light intensity, cell thickness show up as variations in brightness of the imaged cells. The method has advantages over conventional ratio imaging, notably simplicity and speed, since no calculations are made. Yet it can be combined with traditional digital image processing. The imaging technique allows monitoring of [Ca2+]i changes in rapidly moving cells, like neutrophils. It is demonstrated that during random locomotion on serum-coated glass surfaces, [Ca2+]i levels appeared to oscillate and that the frequency of the oscillations are related to locomotive activity. Furthermore, in Ca2+ free medium, the cells continue to move and phagocytose in the presence of Ca2+ ionophore (ionomycin) and 2 mM EGTA. In the presence of 1 mM extracellular Ca2+, ionomycin-treated cells were not able to move or phagocytose.     

Effect of exogenous circulating anti-bPL antibodies on bovine placental lactogen measurements in foetal samples

Background  

The involvement of placental lactogen (PL) in the regulation of foetal growth has been investigated in different species by in vivo immunomodulation techniques. However, when circulating antibodies are present together with the hormone, the procedure for hormonal measurement becomes considerably complex. The aim of this study was the immunoneutralization of bovine placental lactogen (bPL) concentrations in bovine foetal circulation by direct infusion of rabbit anti-bPL purified immunoglobulins (IgG) via a foetal catheter (in vivo study). The ability of a RIA based on guinea pig anti-bPL antiserum, for the measurement of bPL concentrations in samples containing exogenous rabbit anti-bPL immunoglobulins, was also analyzed in in vitro and in vivo conditions.     

Slow modulation of synaptic transmission by brain-derived neurotrophic factor leads to the central sensitization associated with neuropathic pain

Chronic constriction injury (CCI) of the rat sciatic nerve increases the dorsal horn excitability. This “central sensitization” leads to behavioral manifestations analogous to those related to human neuropathic pain. We found, using whole-cell recording from acutely isolated spinal cord slices, that 7-to 10-day-long CCI increases excitatory synaptic drive to putative excitatory “delay”-firing neurons in the substantia gelatinosa but attenuates that to putative inhibitory “tonic”-firing neurons. A defined-medium organotypic culture (DMOTC) system was used to investigate the long-term actions of brain-derived neurotrophic factor (BDNF) as a possible instigator of these changes. When all five neuronal types found in the substantia gelatinosa were considered, BDNF and CCI produced similar patterns, or “footprints,” of changes across the whole population. This pattern was not seen with another putative “pain mediator,” interleukin 1β. Thus, BDNF decreased synaptic drive to “tonic” neurons and increased synaptic drive to “delay” neurons. Actions of BDNF on “delay” neurons were presynaptic and involved increased mEPSC frequency and amplitude without changes in the function of postsynaptic AMPA receptors. By contrast, BDNF exerted both pre-and post-synaptic actions on “ tonic” cells to reduce the mEPSC frequency and amplitude. These differential actions of BDNF on excitatory and inhibitory neurons contributed to a global increase in the dorsal horn network excitability as assessed by the amplitude of depolarization-induced increases in the intracellular [Ca²⁺]. Experiments with the BDNF-binding protein TrkB-d5 provided additional evidence for BDNF as a harbinger of neuropathic pain. Thus, the cellular processes altered by BDNF likely contribute to “central sensitization” and hence to the onset of neuropathic pain. Neirofiziologiya/Neurophysiology, Vol. 39, Nos. 4/5, pp. 315–326, July–October, 2007.     

Temporal and spatial variability in stable isotope compositions of a freshwater mussel: implications for biomonitoring and ecological studies

Stable isotopes can be used to elucidate ecological relationships in community and trophic studies. Findings are calibrated against baselines, e.g. from a producer or primary consumer, assumed to act as a reference to the isotopic context created by spatio-temporal attributes such as geography, climate, nutrient, and energy sources. The ability of an organism to accurately represent a community base depends on how, and over what time-scale, it assimilates ambient materials. Freshwater mussels have served as references for trophic studies of freshwater communities and as indicators of change in nutrient pollution load or source. Their suitability as reference animals has not yet been fully explored, however. We conducted a series of studies examining the suitability of freshwater mussels as isotopic baselines, using their ability to reflect variation in ambient nutrient loads as a case scenario. (1) We analyzed bivalve foot tissue δ¹⁵N and δ¹³C from 22 stream reaches in the Piedmont region of North Carolina, USA to show that compositions varied substantially among locations. Site mean bivalve δ¹³C values correlated with site ambient particulate organic matter (POM) δ¹³C values, and site mean bivalve δ¹⁵N values correlated with site ambient water dissolved δ¹⁵N-NO₃ values. (2) Similarity of results among sample types demonstrated that the minimally invasive hemolymph sample is a suitable substitute for foot tissue in δ¹⁵N analyses, and that small sample sizes generate means representative of a larger population. Both findings can help minimize the impact of sampling on imperiled freshwater mussel populations. (3) In a bivalve transplantation study we showed that hemolymph δ¹⁵N compositions responded to a shift in ambient dissolved δ¹⁵N-NO₃, although slowly. The tissue turnover time for bivalve hemolymph was 113 days. We conclude that bivalves serve best as biomonitors of chronic, rather than acute, fluctuations in stream nutrient loads, and provide initial evidence of their suitability as time-integrated isotopic baselines for community studies.     

Relationship of aerobic and anaerobic parameters with 400 m front crawl swimming performance

The aims of the present study were to investigate the relationship of aerobic and anaerobic parameters with 400 m performance, and establish which variable better explains long distance performance in swimming. Twenty-two swimmers (19.1±1.5 years, height 173.9±10.0 cm, body mass 71.2±10.2 kg; 76.6±5.3% of 400 m world record) underwent a lactate minimum test to determine lactate minimum speed (LMS) (i.e., aerobic capacity index). Moreover, the swimmers performed a 400 m maximal effort to determine mean speed (S400m), peak oxygen uptake (V.O2PEAK) and total anaerobic contribution (C_ANA). The C_ANA was assumed as the sum of alactic and lactic contributions. Physiological parameters of 400 m were determined using the backward extrapolation technique (V.O2PEAK and alactic contributions of C_ANA) and blood lactate concentration analysis (lactic anaerobic contributions of C_ANA). The Pearson correlation test and backward multiple regression analysis were used to verify the possible correlations between the physiological indices (predictor factors) and S400m (independent variable) (p < 0.05). Values are presented as mean ± standard deviation. Significant correlations were observed between S400m (1.4±0.1 m·s^-1) and LMS (1.3±0.1 m·s^-1; r = 0.80), V.O2PEAK (4.5±3.9 L·min^-1; r = 0.72) and C_ANA (4.7±1.5 L·O₂; r= 0.44). The best model constructed using multiple regression analysis demonstrated that LMS and V.O2PEAK explained 85% of the 400 m performance variance. When backward multiple regression analysis was performed, C_ANA lost significance. Thus, the results demonstrated that both aerobic parameters (capacity and power) can be used to predict 400 m swimming performance.