Effect of energy density in the diet and milking frequency on plasma metabolites and hormones in early lactation dairy cows

The effects of energy density in the diet [low = 0.86 SFU/kg dry matter (DM) or high = 1.06 SFU/kg DM] and daily milking frequency (two or three times) in early lactation on plasma concentrations of metabolites and hormones were evaluated in 40 Holstein dairy cows arranged in a 2 x 2 factorial block design. The four treatment combinations were L2, L3, H2 and H3, and the experimental period comprised the first 8 weeks of lactation. Plasma glucose, insulin and insulin-like growth factor (IGF)-I concentrations were on average 8 (3.43 versus 3.19 mmol/l), 114 (41.6 versus 19.4 pmol/l) and 60% (91.9 versus 57.4 ng/ml) higher, whereas beta-hydroxybutyrate (BOHB), plasma urea nitrogen (PUN) and growth hormone (GH) concentrations were on average 18 (0.73 versus 0.89 mmol/l), 14 (7.18 versus 8.35 mmol/l), and 63% (1.0 versus 2.6 ng/ml) lower for cows fed diet H than for cows fed diet L. Cows milked three times daily had a 6% (3.20 versus 3.42 mmol/l) lower plasma glucose concentration and a 19% (0.88 versus 0.74 mmol/l) higher plasma concentration of BOHB compared with cows milked two times daily. Plasma non-esterified fatty acid (NEFA) concentration was not affected by either treatment. Overall, it is concluded that increasing the daily milking frequency creates a higher metabolic imbalance in early lactation. Cows in early lactation will benefit from receiving a high energy density diet and thereby avoid a too high metabolic imbalance when mobilizing body tissue in support of milk production.

Characterisation of the quadriceps stretch reflex during the transition from swing to stance phase of human walking

The main objective of this study was to characterize the stretch reflex response of the human thigh muscles to an unexpected knee flexion at the transition from stance to swing during walking. Eleven healthy subjects walked on a treadmill at their preferred speed. Reliable and constant knee flexions (6-12 degrees amplitude, 230-350 degrees /s velocity, 220 ms duration) were applied during the late swing and early stance phase of human walking by rotating the knee joint with a specifically designed portable stretch apparatus affixed to the left knee. Responses from rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), medial hamstrings (MH) and medial gastrocnemius (GM) were recorded via bipolar surface electromyograms (EMG). The onset of the response in the RF, VL and VM, remained stable and independent of the time in the step cycle when the stretch was applied. Across all subjects the response onset (mean +/- SD) occurred at 23+/-1, 24+/-1 and 23+/-1 ms for RF, VL and VM, respectively. The duration of the initial response was 90-110 ms, at which time the EMG signal returned towards baseline levels. Three reflex response windows, labelled the short latency reflex (SLR), the medium latency reflex (MLR) and the late latency reflex response (LLR), were analysed. The medium and late reflex responses of all knee extensors increased significantly ( p=0.008) as the gait cycle progressed from swing to stance. This was not related to the background EMG activity. In contrast, during standing at extensor EMG levels similar to those attained during walking the reflex responses were dependent on background EMG. During walking, LLR amplitudes expressed as a function of the background activity were on average two to three times greater than SLR and MLR reflex amplitudes. Distinct differences in SLR and LLR amplitude were observed for RF, VL and VM but not in the MLR amplitude. This may be related to the different pathways mediating the SLR, MLR and LLR components of the stretch response. As for the knee extensor antagonists, they exhibited a response to the stretch of the quadriceps at latencies short enough to be monosynaptic. This is in agreement with the suggestion by Eccles and Lundberg (1958) that there may be functional excitatory connections between the knee extensors and flexors in mammals.

Combined ACTH and glucocorticoid treatment improves survival and organ maturation in premature newborn calves

Glucocorticoids play an important role in prenatal organ maturation in many species. In humans, maternal treatment with synthetic glucocorticoids improves neonatal adaptation of prematurely born infants. In cows, pre-term calf survival is improved following a single maternal glucocorticoid administration. We hypothesized that stimulation of endogenous cortisol secretion by adrenocorticotropin (ACTH) treatment combined with maternal dexamethasone treatment, would be even more efficient in stimulating organ maturation in the prematurely delivered calf. Three groups of premature calves were delivered by caesarian section at 90% of gestation length from dams which were either untreated or injected with dexamethasone before delivery, combined with either prenatal or postnatal ACTH treatment to the calf. During the first 24h after birth, thermoregulation, blood chemistry, liver values and organ weights were recorded. In the untreated calves, survival was significantly correlated with blood oxygenation, sodium and calcium levels at the moment of birth. There were marked maturational effects of the treatments on body temperature regulation, blood acid-base status, oxygenation, glucose, insulin, IGF-1 levels, weight of the heart, liver, gastrointestinal tract and thymus weight. For many of the measured metabolic, endocrine and organ weight parameters, the intrauterine ACTH treatment was associated with improved values relative to the postnatal ACTH treatment, which appeared to have no immediate effect on calf viability. In conclusion, the premature calf delivered by caesarian section at 90% of gestation length showed blood chemistry, metabolic, endocrine and organ growth characteristics that indicated severe prematurity. However, the maturation of organ function in newborn premature calves following maternal glucocorticoid injections was further enhanced if is was preceded by intra-fetal injections of ACTH.

Synthetic furanones inhibit quorum-sensing and enhance bacterial clearance in Pseudomonas aeruginosa lung infection in mice

INTRODUCTION

Antibiotics are used to treat bacterial infections by killing the bacteria or inhibiting their growth, but resistance to antibiotics can develop readily. The discovery that bacterial quorum-sensing regulates bacterial virulence as well as the formation of biofilms opens up new ways to control certain bacterial infections. Furanone compounds capable of inhibiting bacterial quorum-sensing systems have been isolated from the marine macro alga Delisea pulchra.

OBJECTIVES

Two synthetic furanones were tested for their ability to attenuate bacterial virulence in the mouse models of chronic lung infection by targeting bacterial quorum-sensing without directly killing bacteria or inhibiting their growth.

METHODS

Study I. Mice with Escherichia coli MT102 [luxR-PluxI-gfp(ASV)] lung infection were injected intravenously with N-acyl homoserine lactones with or without furanones to test the interference of furanones with quorum-sensing. Study II. Mice with lung infection by Pseudomonas aeruginosa PAO1 [dsred, lasR-PlasB-gfp(ASV)] were injected intravenously with furanones to evaluate their inhibiting effects on quorum-sensing. Study III. Mice with P. aeruginosa PAO1 lung infection were treated with different doses of furanones to evaluate the therapeutic effects of furanones on the lung infection.

RESULTS

Furanones successfully interfered with N-acyl homoserine lactone and suppressed bacterial quorum-sensing in lungs, which resulted in decreases in expression of green fluorescent protein. Furanones accelerated lung bacterial clearance, and reduced the severity of lung pathology. In a lethal P. aeruginosa lung infection, treatment with furanone significantly prolonged the survival time of the mice.

CONCLUSION

Synthetic furanone compounds inhibited bacterial quorum-sensing in P. aeruginosa and exhibited favourable therapeutic effects on P. aeruginosa lung infection.

Antibiotic and biosurfactant properties of cyclic lipopeptides produced by fluorescent Pseudomonas spp. from the sugar beet rhizosphere

Cyclic lipopeptides (CLPs) with antibiotic and biosurfactant properties are produced by a number of soil bacteria, including fluorescent Pseudomonas spp. To provide new and efficient strains for the biological control of root-pathogenic fungi in agricultural crops, we isolated approximately 600 fluorescent Pseudomonas spp. from two different agricultural soils by using three different growth media. CLP production was observed in a large proportion of the strains (approximately 60%) inhabiting the sandy soil, compared to a low proportion (approximately 6%) in the loamy soil. Chemical structure analysis revealed that all CLPs could be clustered into two major groups, each consisting of four subgroups. The two major groups varied primarily in the number of amino acids in the cyclic peptide moiety, while each of the subgroups could be differentiated by substitutions of specific amino acids in the peptide moiety. Production of specific CLPs could be affiliated with Pseudomonas fluorescens strain groups belonging to biotype I, V, or VI. In vitro analysis using both purified CLPs and whole-cell P. fluorescens preparations demonstrated that all CLPs exhibited strong biosurfactant properties and that some also had antibiotic properties towards root-pathogenic microfungi. The CLP-producing P. fluorescens strains provide a useful resource for selection of biological control agents, whether a single strain or a consortium of strains was used to maximize the synergistic effect of multiple antagonistic traits in the inoculum.

Effect of energy density in the diet and milking frequency on hepatic long chain fatty acid oxidation in early lactating dairy cows

The objective of this study was to examine the effects of diet energy density (high versus low) and increased milk yield, induced by increased milking frequency (two versus three times daily), on the hepatic status of triacylglycerol (TAG) and glycogen content and hepatic long chain fatty acid (LCFA) oxidation capacity in early lactation in a 2 x 2 factorial design. Forty multiparous Danish-Holstein dairy cows were used from 8 weeks before to 8 weeks after calving. Liver biopsies and blood samples were taken in weeks -2, 2, and 7 from calving. The cows fed the high energy density diet, compared with the cows fed the low energy density diet, had an 18 and 28% higher milk production and net energy intake, respectively. Milk yield was increased by 10% when the cows were milked three times compared with twice daily. Complete (CO2 production) and incomplete (ketone body production) LCFA oxidation capacity in the liver were 35 and 32% higher, respectively, and liver TAG content was 48% lower for the cows fed the high energy density diet compared with the low energy density diet. Overall there was no effect of milking frequency on liver parameters. However, a significant interaction between diet and milking frequency showed that the cows milked three times daily and fed the low energy density diet had the lowest liver LCFA oxidation (CO2 and ketone body) capacity. Furthermore, these cows had the numerically highest liver TAG content. The results for liver LCFA metabolism are discussed in relation to the plasma concentration of metabolites and insulin. In conclusion, cows in early lactation given a high energy density diet will, in general, have a lower risk of high TAG infiltration in the liver.

Effects of hyperinsulinaemia under euglycaemic condition on liver fat metabolism in dairy cows in early and mid-lactation

The objective was to examine the effects of insulin under euglycaemic conditions on liver long chain fatty acids (LCFA) metabolism with special focus on the aetiology of hepatic lipidosis in early lactation. A 4-day hyperinsulinaemic-euglycaemic clamp (clamp) was conducted on four dairy cows starting in weeks 4 and 17 postpartum. Insulin was infused continuously (1 microg/kg BW per h) and a 50% glucose solution was infused to maintain euglycaemia. Liver biopsies were taken 6 days before, the last day of, and 5 days after the clamp, and blood samples were taken in the same period. In the liver tissue, the relative triglyceride content decreased (P < 0.01) and the glycogen content increased (P < 0.0001) in response to the clamp. Hepatic in vitro palmitate oxidation capacity was lowest during the clamp period and could be explained by a significant decrease in incomplete oxidation (ketogenesis) (P < 0.04) and a tendency to a decreased complete oxidation of palmitate (P < 0.10). Plasma non-esterified fatty acids concentration was decreased during the clamp in early lactation (P < 0.05) but there was no effect on the mid-lactation clamp. The present study shows that increased insulin under euglycaemic conditions seems to depress hepatic LCFA oxidation capacity. However, in terms of preventing hepatic lipidosis, the anti-lipolytic effect of insulin on adipose tissue, which results in decreased mobilization of and hence hepatic load with LCFA, appears more important.

Effects of a four-day hyperinsulinemic-euglycemic clamp in early and mid-lactation dairy cows on plasma concentrations of metabolites, hormones, and binding proteins

The effects of insulin, using a 4 d hyperinsulinemic-euglycemic clamp, on plasma concentrations of hormone, metabolites, and binding proteins were evaluated in four Holstein dairy cows during wk 4 and 17 of lactation. Insulin was infused at 1 microg/kg/hr for 96 hr during the clamp period. Compared with the pre-clamp period, plasma insulin concentrations increased 7-fold and 4-fold during the clamp periods in early and mid-lactation, respectively. The total amount of glucose infused was higher (P < 0.05) during the clamp in early lactation. The clamp decreased plasma concentrations of non-esterified fatty acids (P < 0.001) during early lactation while differences in mid-lactation were minor. The clamp also decreased plasma concentration of beta-hydroxybutyrate (P < 0.001), plasma urea nitrogen (P < 0.001), and true protein (P < 0.01) although the patterns of decline differed between early and mid-lactation. Growth hormone (GH) concentrations decreased (P < 0.001) and insulin-like growth factor-1 (IGF-1) increased (P < 0.01) during the clamp period suggesting a direct effect of insulin on the un-coupling of the GH/IGF-1 axis. Levels of IGF binding protein-2 (IGFBP-2) decreased (P < 0.01) during the clamp period. The relative proportion of IGFBP-2 decreased (P < 0.001) and that of IGFBP-3 increased (P < 0.001) during the clamp period. There were no interactions between the clamp period and stage of lactation on GH, IGF-1, or IGFBPs. Overall, most plasma variables measured were affected in the same way during the two clamps, but the pattern of change often varied with stage of lactation.

Group II muscle afferents probably contribute to the medium latency soleus stretch reflex during walking in humans

1. The objective of this study was to determine which afferents contribute to the medium latency response of the soleus stretch reflex resulting from an unexpected perturbation during human walking. 2. Fourteen healthy subjects walked on a treadmill at approximately 3.5 km h(-1) with the left ankle attached to a portable stretching device. The soleus stretch reflex was elicited by applying small amplitude (approximately 8 deg) dorsiflexion perturbations 200 ms after heel contact. 3. Short and medium latency responses were observed with latencies of 55 +/- 5 and 78 +/- 6 ms, respectively. The short latency response was velocity sensitive (P < 0.001), while the medium latency response was not (P = 0.725). 4. Nerve cooling increased the delay of the medium latency component to a greater extent than that of the short latency component (P < 0.005). 5. Ischaemia strongly decreased the short latency component (P = 0.004), whereas the medium latency component was unchanged (P = 0.437). 6. Two hours after the ingestion of tizanidine, an alpha(2)-adrenergic receptor agonist known to selectively depress the transmission in the group II afferent pathway, the medium latency reflex was strongly depressed (P = 0.007), whereas the short latency component was unchanged (P = 0.653). 7. An ankle block with lidocaine hydrochloride was performed to suppress the cutaneous afferents of the foot and ankle. Neither the short (P = 0.453) nor medium (P = 0.310) latency reflexes were changed. 8. Our results support the hypothesis that, during walking the medium latency component of the stretch reflex resulting from an unexpected perturbation is contributed to by group II muscle afferents.

Effects of temperature and oxygen availability on circulating catecholamines in the toad Bufo marinus

The release of catecholamines during hypoxia has received limited attention in amphibians and the adrenergic regulation of cardio-pulmonary functions is, therefore, not well understood at the organismic level. To describe the changes in plasma catecholamine concentrations, we exposed toads (Bufo marinus) to different levels of hypoxia at two temperatures (15 and 25 degrees C). In addition, blood oxygen binding properties were determined in vitro at 15 and 25 degrees C at two different pH values. Hypoxia elicited a significant increase in plasma catecholamines (adrenaline and noradrenaline) at both temperatures, in spite of a respiratory alkalosis. At 15 degrees C, the increase was from 2.6+/-1.0 in normoxia to 4.8+/-1.4 ng ml(-1) at an inspired oxygen fraction of 0.05. At 25 degrees C, the hypoxic release of catecholamines was significantly higher (maximum levels of 44.8+/-11.6 ng ml(-1)). Plasma noradrenaline concentration was elevated at the most severe hypoxic levels, suggestive of an adrenal release. The arterial oxygen threshold for catecholamine release were approximately 1.0 mmol O(2) l(-1) blood or a PaO(2) of 30 mmHg. The P(50) values at 15 degrees C were 23.5+/-0.7 and 28.9+/-1.0 mmHg at pH 7.98+/-0.01 and 7.62+/-0.02, respectively, and increased to 36.5+/-0.6 and 43.0+/-1.1 mmHg at pH 8.04+/-0.04 and 7.67+/-0.05, respectively, at 25 degrees C. The oxygen equilibrium curves were linear when transformed to Hill-plots and Hills n (the haemoglobin subunit co-operativity) ranged between 2.24 and 2.75. The in vitro blood O(2) binding properties corresponded well with in vivo data.

Transcranial magnetic stimulation and stretch reflexes in the tibialis anterior muscle during human walking

Stretch of the ankle dorsiflexors was applied at different times of the walking cycle in 17 human subjects. When the stretch was applied in the swing phase, only small and variable reflex responses were observed in the active tibialis anterior (TA) muscle. Two of the reflex responses that could be distinguished had latencies which were comparable with the early (M1) and late (M3)components of the three reflex responses (M1, M2 and M3) observed during tonic dorsiflexion in sitting subjects. In the stance phase a single very large response was consistently observed in the inactive TA muscle. The peak of this response had the same latency as the peak of M3, but in the majority of subjects the onset latency was shorter than that of M3. The TA reflex response in the stance phase was abolished by ischaemia of the lower leg at the same time as the soleus H-reflex, suggesting that large muscle afferents were involved in the generation of the response. Motor-evoked potentials (MEPs) elicited in the TA by transcranial magnetic stimulation (TMS) were strongly facilitated corresponding to the peak of the stretch response in the stance phase and the late reflex response in the swing phase. A similar facilitation was not observed corresponding to the earlier responses in the swing phase and the initial part of the response in stance. Prior stretch did not facilitate MEPs evoked by transcranial electrical stimulation in the swing phase of walking. However, in the stance phase MEPs elicited by strong electrical stimulation were facilitated by prior stretch to the same extent as the MEPs evoked by TMS. The large responses to stretch seen in the stance phase are consistent with the idea that stretch reflexes are mainly involved in securing the stability of the supporting leg during walking. It is suggested that a transcortical reflex pathway may be partly involved in the generation of the TA stretch responses during walking.

gfp-based N-acyl homoserine-lactone sensor systems for detection of bacterial communication

In order to perform single-cell analysis and online studies of N-acyl homoserine lactone (AHL)-mediated communication among bacteria, components of the Vibrio fischeri quorum sensor encoded by luxR-P(luxI) have been fused to modified versions of gfpmut3* genes encoding unstable green fluorescent proteins. Bacterial strains harboring this green fluorescent sensor detected a broad spectrum of AHL molecules and were capable of sensing the presence of 5 nM N-3-oxohexanoyl-L-homoserine lactone in the surroundings. In combination with epifluorescent microscopy, the sensitivity of the sensor enabled AHL detection at the single-cell level and allowed for real-time measurements of fluctuations in AHL concentrations. This green fluorescent AHL sensor provides a state-of-the-art tool for studies of communication between the individuals present in mixed bacterial communities.

Development and dynamics of Pseudomonas sp. biofilms

Pseudomonas sp. strain B13 and Pseudomonas putida OUS82 were genetically tagged with the green fluorescent protein and the Discosoma sp. red fluorescent protein, and the development and dynamics occurring in flow chamber-grown two-colored monospecies or mixed-species biofilms were investigated by the use of confocal scanning laser microscopy. Separate red or green fluorescent microcolonies were formed initially, suggesting that the initial small microcolonies were formed simply by growth of substratum attached cells and not by cell aggregation. Red fluorescent microcolonies containing a few green fluorescent cells and green fluorescent microcolonies containing a few red fluorescent cells were frequently observed in both monospecies and two-species biofilms, suggesting that the bacteria moved between the microcolonies. Rapid movement of P. putida OUS82 bacteria inside microcolonies was observed before a transition from compact microcolonies to loose irregularly shaped protruding structures occurred. Experiments involving a nonflagellated P. putida OUS82 mutant suggested that the movements between and inside microcolonies were flagellum driven. The results are discussed in relation to the prevailing hypothesis that biofilm bacteria are in a physiological state different from planktonic bacteria.

Evidence for transcortical reflex pathways in the lower limb of man

The existence of transcortical reflex pathways in the control of distal arm and hand muscles in man is now widely accepted. Much more controversy exists regarding a possible contribution of such reflexes to the control of leg muscles. It is often assumed that transcortical reflex pathways play no, or only a minor, role in the control of leg muscles. Transcortical reflex pathways according to this view are reserved for the control of the distal upper limb and are seen in close relation to the evolution of the primate hand. Here we review data, which provide evidence that transcortical reflexes do exist for lower limb muscles and may play a significant role in the control of at least some of these muscles. This evidence is based on animal research, recent experiments combining transcranial magnetic stimulation with peripheral electrical and mechanical stimulation in healthy subjects and neurological patients. We propose that afferent activity from muscle and skin may play a role in the regulation of bipedal gait through transcortical pathways.

Integration of metabolism and intake regulation: a review focusing on periparturient animals

There has been great interest in dry matter intake regulation in lactating dairy cattle to enhance performance and improve animal health and welfare. Predicting voluntary dry matter intake (VDMI) is complex and influenced by numerous factors relating to the diet, management, housing, environment and the animal. The objective of this review is to identify and discuss important metabolic factors involved in the regulation of VDMI and their integration with metabolism. We have described the adaptations of intake and metabolism and discussed mechanisms of intake regulation. Furthermore we have reviewed selected metabolic signals involved in intake regulation. A substantial dip in VDMI is initiated in late pregnancy and continues into early lactation. This dip has traditionally been interpreted as caused by physical constraints, but this role is most likely overemphasized. The dip in intake coincides with changes in reproductive status, fat mass, and metabolic changes in support of lactation, and we have described metabolic signals that may play an equally important role in intake regulation. These signals include nutrients, metabolites, reproductive hormones, stress hormones, leptin, insulin, gut peptides, cytokines, and neuropeptides such as neuropeptide Y, galanin, and corticotrophin-releasing factor. The involvement of these signals in the periparturient dip in intake is discussed, and evidence supporting the integration of the regulation of intake and metabolism is presented. Still, much research is needed to clarify the complex regulation of VDMI in lactating dairy cows, particularly in the periparturient animal.

[Treatment of severe acute disseminated encephalomyelitis with intravenous immunoglobulin]

A three year-old boy with severe acute disseminated encephalomyelitis (ADEM) responding dramatically to treatment with intravenous immunoglobulin (IVIG) 1 g/kg/day is described. Initial treatment with intravenous methylprednisolone 2 mg/kg/day had failed. This and two earlier case reports indicate that IVIG might be efficient in the treatment of ADEM, and we believe that its use should be considered, at least in cases of severe ADEM with insufficient treatment effect of steroids. A synergistic effect of treatment with steroids and IVIG in ADEM is possible.

[Acute disseminated encephalomyelitis in children]

Acute disseminated encephalomyelitis (ADEM) is a demyelinating autoimmune inflammatory disease of the central nervous system. It is most often seen in children a few days to several weeks after certain infections or vaccinations. Clinically, ADEM can hardly be distinguished from primary viral encephalitis. The diagnosis is most frequently established on the basis of characteristic findings on MRI of the brain. Mostly the disease seems to be self-limiting, but in untreated patients the mortality rate may be as high as 20% and the risk of permanent neurological deficits 10-33%. Treatment with glucocorticoids seems to be effective in the majority of patients and should at least be started in all patients with an affected level of consciousness. Treatment with intravenous immunoglobulin has recently been given in a few patients with apparent success.

Major role for sensory feedback in soleus EMG activity in the stance phase of walking in man

1. Sensory feedback plays a major role in the regulation of the spinal neural locomotor circuitry in cats. The present study investigated whether sensory feedback also plays an important role during walking in 20 healthy human subjects, by arresting or unloading the ankle extensors 6 deg for 210 ms in the stance phase of gait. 2. During the stance phase of walking, unloading of the ankle extensors significantly (P < 0.05) reduced the soleus activity by 50 % in early and mid-stance at an average onset latency of 64 ms. 3. The onset and amplitude of the decrease in soleus activity produced by the unloading were unchanged when the common peroneal nerve, which innervates the ankle dorsiflexors, was reversibly blocked by local injection of lidocaine (n = 3). This demonstrated that the effect could not be caused by a peripherally mediated reciprocal inhibition from afferents in the antagonist nerves. 4. The onset and amplitude of the decrease in soleus activity produced by the unloading were also unchanged when ischaemia was induced in the leg by inflating a cuff placed around the thigh. At the same time, the group Ia-mediated short latency stretch reflex was completely abolished. This demonstrated that group Ia afferents were probably not responsible for the decrease of soleus activity produced by the unloading. 5. The findings demonstrate that afferent feedback from ankle extensors is of significant importance for the activation of these muscles in the stance phase of human walking. Group II and/or group Ib afferents are suggested to constitute an important part of this sensory feedback.

The influence of experimental muscle pain on the human soleus stretch reflex during sitting and walking

OBJECTIVES

The stretch reflex is functionally important during human locomotion. Muscle pain has been found to increase the stretch reflex amplitude during sitting, possibly due to an altered fusimotor drive. To further study the importance of altered fusimotor activity due to muscle pain we investigated the combined effect of muscle pain and motor task on the soleus stretch reflex.

METHODS

Stretch reflexes were elicited before, during and after experimentally induced muscle pain in soleus (i.m. infusion of 6% saline) in 3 experiments: (1) in the relaxed soleus muscle and before, during and after an isometric ramp contraction (500 ms, 0-10 Nm), (2) at 3 different time periods during walking, and (3) at matched pain intensity and soleus activity during sitting and walking.

RESULTS

Infusion of hypertonic saline into the soleus muscle caused a significant facilitated stretch reflex in the relaxed muscle (P<0.01), but not during walking or during sitting and walking at matched soleus EMG and matched pain levels. The infusion of isotonic saline (non-painful) did not cause any changes (P = 0.75).

CONCLUSIONS

The main findings of the present study were that experimental muscle pain facilitated the stretch reflex during pain in the relaxed muscle, but caused no changes in stretch reflex amplitude during sitting and walking at higher "functional" background EMG levels.

Metabolites of [(14)C]-5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2,3, 6-tetrahydropyridine in mice, rats, dogs, and humans

The M1 muscarine agonist, 5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2, 3,6-tetrahydropyridine (Lu 25-109), is extensively metabolized in mice, rats, dogs, and humans. The metabolite profile after an oral dose of [(14)C]Lu 25-109 was determined in plasma and in urine. Lu 25-109 was metabolized by N-demethylation (Lu 25-077), N-oxidation (Lu 32-181), and N-deethylation (Lu 31-126). In addition, combined N-demethylation and N-deethylation (Lu 31-190), and formation of a pyridine derivative took place (Lu 31-102). Lu 25-109 was also oxidized to pyridinium (Lu 29-297), 3-hydroxy-pyridinium (Lu 35-080), N-deethyl-2-pyridone (Lu 35-026), and a glucuronide of a 4, 6-dihydroxy-pyridinium ("m/z 398") compounds. A glucuronide of a dihydroxylated dihydro-pyridine compound ("m/z 400") was isolated from human urine, but not fully identified. In vitro studies were undertaken to elucidate the order of formation of the metabolites. In human plasma, the concentrations of Lu 25-109 and the pharmacologically active N-demethyl metabolite (Lu 25-077) were small compared with the N-oxide (Lu 32-181) and the N-deethyl-2-pyridone (Lu 35-026) at the first sample time (0.75 h). The N-deethyl metabolite (Lu 31-126) was the major component in human plasma between 3 and 10 h postdose. The major human metabolites in urine (Lu 32-181, Lu 35-026, and Lu 31-126) and the minor metabolites (Lu 25-077, Lu 35-080, Lu 31-190, and Lu 29-297) were all present in urine from rats, dogs, and mice, whereas m/z 398 was present in only mice and humans, and Lu 31-102 in only rats. The minor human metabolite m/z 400 was not detected in mice, rats, or dogs.