Traumatic vertebral arterial dissection and vertebrobasilar arterial thrombosis successfully treated with endovascular thrombolysis and stenting.

A case of traumatic extracranial vertebral arterial dissection leading to vertebrobasilar thrombosis and respiratory compromise requiring mechanical ventilation was managed with intraarterial thrombolysis and stenting of the vertebral intimal dissection. In contrast to similar, previously reported cases, this critically ill patient made a full recovery, returning to his job as a secondary school teacher.

Appendicectomy and ulcerative colitis.

The aetiology of ulcerative colitis (UC) is unknown. However, much interest has been devoted recently to the relationship between appendicectomy and ulcerative colitis. A case-control study was conducted, comparing appendicectomy rates between 110 patients with UC (group 1) and 136 patients attending an orthopaedic clinic free from UC (group 2). The appendicectomy rates were 0.9% (group 1) and 10.3% (group 2), respectively (P < 0.002). The present study shows that patients with ulcerative colitis had rarely undergone appendicectomy before the first manifestation of colitis. Further research on this relationship is called for.

Some inhibitory neurons in the spinal cord develop c-fos-immunoreactivity after noxious stimulation.

In order to determine which types of spinal neuron produce c-fos in response to noxious stimulation, we have combined pre-embedding detection of c-fos-like immunoreactivity with post-embedding immunocytochemistry using antibodies against GABA and glycine, 2 h after subcutaneous injection of formalin into a hindpaw of anaesthetized rats. Throughout the spinal cord, the majority of c-fos-immunoreactive neurons (72-81%) did not possess GABA- or glycine-like immunoreactivity, while the remaining cells contained one or both types of immunoreactivity. In the superficial dorsal horn (laminae I and II) and dorsal white matter, between 14 and 20% of c-fos-immunoreactive neurons were GABA-immunoreactive, and some of these were also glycine-immunoreactive. A single neuron in lamina I in one animal was glycine- but not GABA-immunoreactive. In the remainder of the spinal cord, between 21 and 35% of the c-fos-immunoreactive cells were GABA- or glycine-immunoreactive, and the majority of these neurons contained both types of immunoreactivity. These results suggest that some inhibitory neurons in both the superficial and deep parts of the dorsal horn are activated by noxious stimuli. It is known that some of the cells which produce c-fos in response to noxious stimulation are projection neurons, with axons ascending to the brainstem or thalamus, however, because of the large number of c-fos-immunoreactive cells in the dorsal horn, it is likely that many are interneurons, and some of these are probably excitatory cells which use glutamate as a transmitter. It therefore appears that after noxious stimulation c-fos is produced in several types of spinal neuron, including projection cells and both excitatory and inhibitory interneurons.

Immunocytochemical evidence that neurotensin is present in glutamatergic neurons in the superficial dorsal horn of the rat.

In order to determine whether glutamate is enriched in neurotensin-containing axons in the superficial dorsal horn of the rat spinal cord, we have carried out preembedding immunocytochemistry with an antiserum to neurotensin and then used a postembedding immunogold method with antiserum to glutamate. The immunogold label (corresponding to glutamate-like immunoreactivity) over 40 neurotensin-immunoreactive boutons in laminae I and II of the lumbar dorsal horn was compared with that over nearby axons that formed asymmetrical or symmetrical synapses. In addition, for 20 of these boutons, the labeling was compared with that over mossy and parallel fiber terminals (both of which are thought to use glutamate as a transmitter) from sections of cerebellum that had been processed together with those of spinal cord. Glutamate-like immunoreactivity was consistently high over neurotensin-immunoreactive boutons relative to most surrounding profiles. Immunostaining over these boutons was slightly (11%) lower than that over matched terminals that formed asymmetrical synapses, but considerably higher than that over the terminals that formed symmetrical synapses. The level of glutamate immunoreactivity in neurotensin-immunoreactive boutons in dorsal horn was similar to that in cerebellar parallel fiber terminals, but significantly lower than that in mossy fiber terminals. These results suggest that glutamate is a transmitter used by neurotensin-immunoreactive axons in the dorsal horn, and since these axons are thought to be largely or entirely derived from neurotensin-containing neurons in laminae I-III, they provide immunocytochemical evidence for a population of excitatory glutamatergic neurons in this region.

Physiological properties of tandem muscle spindles in neck and hind-limb muscles.

Although tandem muscle spindle complexes are found in small but significant numbers in most muscles, experimental investigation of their properties has been problematic because of the difficulty of distinguishing their afferents from those of "normal" single spindles. Of particular interest are the afferents from b2c capsules of tandem spindles, which unlike normal spindles contain only a static b2 nuclear bag fibre and some nuclear chain fibres. The absence of a dynamic b1 nuclear bag fibre from b2c spindles has engendered much speculation as to their response properties and their possible role in motor control. We have recently developed a method for the identification of afferents from b2c spindles in electrophysiological experiments, using infusion or topical application of succinylcholine (SCh). SCh causes the contraction of the dynamic b1 and static b2 nuclear bag intrafusal fibres, and paralyses the nuclear chain fibres. Afferents from b2c spindles are characterized by a strong "biasing" of their discharge rate to about 100 impulses per second (i.p.s.) when activated by SCh (reflecting the contraction of the static b2 fibre), while primary afferents from normal b1b2c spindles show a large increase in dynamic sensitivity as well as "biasing" (reflecting the contraction of both dynamic b1 and static b2 bag fibres). Histological examination of tenuissimus spindles activated by SCh has confirmed this relationship between the pattern of activation by SCh and the number of intrafusal nuclear bag fibres in the spindle. In this paper we review the value of SCh as a means of testing spindle afferents for functional inputs from sensory terminals on the nuclear bag fibres, and discuss the properties of b2c afferents from tandem spindles in the context of their possible function.

The effect of high-frequency ventilation on pattern of breathing of anaesthetized rabbits.

The lungs of anaesthetized rabbits were ventilated with a frequency of 30 Hz and a displacement of 5 ml. High-frequency ventilation (HFV) was superimposed on static inflation or deflation pressures of 2.5 and 5 cmH2O and was maintained for 10 s. Changes in pattern of breathing in response to this procedure were recorded before and during block of pulmonary stretch receptors by SO2. With lung stretch receptors intact apnoea or extended duration of expiration demonstrated the predominant role of pulmonary stretch receptors in the response to HFV. Block of stretch receptors exposed effects of other pulmonary afferents, presumably rapidly adapting receptors, during HFV, and demonstrated the influence of their sustained stimulation on pattern of breathing as augmented breaths and the reduction of duration of expiration. High-frequency ventilation may represent a useful experimental method of stimulating rapidly adapting receptors.

Interaction between the vestibulo-collic reflex and the cervico-collic stretch reflex in the decerebrate cat.

1. Interactions between the sagittal vestibulo-collic reflex (v.c.r.) and the cervico-collic stretch reflex (c.c.r.) have been studied in the neck extensor muscles biventer cervicis (b.c.) in the decerebrate cat. The v.c.r. was evoked by a 'standard' vestibular stimulus consisting of a sinusoidal nose-up, nose-down head movement of 6-8 deg amplitude at 1 Hz. The c.c.r. was evoked by sinusoidal stretching of the b.c. muscles at 1 Hz. The amplitude of muscle stretching, and its phase in relation to head movement, were systematically varied. 2. When muscle stretching was applied in phase with head movement (so that the muscles were stretched as the head moved in the nose-down direction), the gain of the combined (v.c.r. + c.c.r.) reflex in the b.c. muscles increased above that of the v.c.r. If the muscle stretching was applied out of phase with head movement (so that the muscles shortened as the head moved downward), the gain of the combined reflex was reduced to a value below that of the v.c.r. 3. The effects on the gain of the combined reflex varied in proportion to the amplitude of muscle stretching. The gain and phase of the combined reflex is modelled reasonably well by a linear vectorial addition between the v.c.r. and the c.c.r. over a wide range of amplitudes of muscle stretching. The linear summation model contains a proportionality constant K, which may represent a factor by which the two reflexes are 'calibrated' against each other. 4. If one of the b.c. muscles was held at a fixed length and the other stretched sinusoidally, the c.c.r. was evoked only in the stimulated muscle. Vestibular stimulation then summed with the c.c.r in the stimulated muscle, while on the contralateral side the reflex response was the same as that of the v.c.r. alone. It would appear therefore that the motoneurone pools of the b.c. muscles are organized as independent entities without mutually excitatory or inhibitory reflex linkages. This arrangement presumably allows flexibility in the supraspinal control of the b.c. muscles, which are often used either as synergists during sagittal head movement or as antagonists during horizontal or roll movements of the head. 5. The interaction between the v.c.r. and the c.c.r. results in an apparent 'servo-assistance' role for the muscle afferent feed-back from the b.c. muscles, amplifying or attenuating the reflex response of the muscles to a given head movement.(ABSTRACT TRUNCATED AT 400 WORDS)

Properties of cat neck muscle spindles and their excitation by succinylcholine.

The sensitivity to sinusoidal stretching and small-amplitude vibration, and the variability of the resting discharge rate of de-efferented muscle spindles in the neck extensor muscle biventer cervicis (b.c.) of the cat have been studied. The effects of intra-arterial infusion of succinylcholine (SCh) on the response of the receptors to ramp stretches of the muscle were also determined. When activated by SCh, one group of afferents showed only a slow facilitation of their discharge rate, similar to that of spindle secondary sensory endings in hind-limb muscles. A second group of afferents developed a large dynamic response and a marked increase in their static discharge rate and were presumed to originate in "normal" b1b2 c spindles in the b.c. muscle. A third group of afferents developed only a marked increase in static discharge, without potentiation of the dynamic response, suggesting an origin in the b2c units of tandem spindles which are relatively common in the neck muscles. On the basis of their passive characteristics alone, afferents from b1b2c units could not be readily distinguished from those from b2c units. The characteristics of these receptors, and their differences from the well-studied hind-limb spindle afferents, are discussed.