Modulation of multisegmentalmonosynaptic responses in a variety of leg muscles during walking and running in humans

Motor responses evoked by stimulating the spinal cord percutaneously between the T11 and T12 spinous processes were studied in eight human subjects during walking and running. Stimulation elicited responses bilaterally in the biceps femoris, vastus lateralis, rectus femoris, medial gastrocnemius, soleus, tibialis anterior, extensor digitorum brevis and flexor digitorum brevis. The evoked responses were consistent with activation of Ia afferent fibres through monosynaptic neural circuits since they were inhibited when a prior stimulus was given and during tendon vibration. Furthermore, the soleus motor responses were inhibited during the swing phase of walking as observed for the soleus H-reflex elicited by tibial nerve stimulation. Due to the anatomical site and the fibre composition of the peripheral nerves it is difficult to elicit H-reflex in leg muscles other than the soleus, especially during movement. In turn, the multisegmental monosynaptic responses (MMR) technique provides the opportunity to study modulation of monosynaptic reflexes for multiple muscles simultaneously. Phase-dependent modulation of the MMR amplitude throughout the duration of the gait cycle period was observed in all muscles studied. The MMR amplitude was large when the muscle was activated whereas it was generally reduced, or even suppressed, when the muscle was quiescent. However, during running, there was a systematic anticipatory increase in the amplitude of the MMR at the end of swing in all proximal and distal extensor muscles. The present findings therefore suggest that there is a general control scheme by which the transmission in the monosynaptic neural circuits is modulated in all leg muscles during stepping so as to meet the requirement of the motor task

The acute effect of bull presence on plasma profiles of luteinizing hormone in postpartum, anoestrous dairy cows

The objective of this study was to investigate whether bull exposure affects LH profiles in postpartum, anoestrous dairy cows. Eight cows between 10 and 17 days after parturition were used. On Day 1, blood samples were taken at 10 min intervals for 8 h. On Day 2, blood sampling continued at 10 min intervals and after 2 h a bull was introduced behind a fence, and blood sampling continued for another 8 h. Time of resumption of luteal activity was between 25 and more than 80 days after parturition for these animals and was not related (P > 0.1) with frequency of LH pulses, amplitude of pulses and basal LH concentration on either Day 1 or Day 2. In 6 of the 8 cows, average and basal LH concentration were greater (P <0.001) during the 8 h of bull presence (0.56 ± 0.33 and 0.39 ± 0.26 ng/ml, respectively) compared to the 8 h without a bull (0.50 ± 0.30 and 0.35 ± 0.24 ng/ml, respectively). Pulse amplitude did not differ (P = 0.85) between Day 2 (0.45 ± 0.24 ng/ml) or Day 1 (0.45 ± 0.14 ng/ml). LH pulse frequency was greater (P <0.1) on Day 2 (5.3 pulses/8 h) compared to the Day 1 (4.6 pulses/8 h). In conclusion, fenceline bull exposure early postpartum seems to have an acute effect on LH-release in anoestrous dairy cows. Whether sustained bull exposure can hasten first ovulation after calving through an effect on LH release in dairy cows is an interesting area of research

Strain-induced structural changes in thin YBa2Cu3O7-x films on SrTiO3 substrates

High-energy synchrotron radiation is used to obtain reciprocal space maps of thin YBa2Cu3O7−x films grown by pulsed laser deposition on (001) SrTiO3 substrates. The films show a transition from a tetragonal to an orthorhombic structure with increasing film thickness. The critical thickness is found to be 11.5±0.6 nm, whereas the thickness characterizing the tetragonal-to-orthorhombic transition is estimated to be 23±1 nm. Furthermore, it is shown that for miscut angles of the vicinal substrates up to approximately 1.2°, the films grow parallel to the optical surface-normal, rather than to the crystallographic c-axis of the substrates. The feasibility of using high energy X-rays allows for the use of complicated sample chambers, needed for in-situ studies of the growth and behaviour of thin films under controlled atmosphere and at elevated temperatures