Control of dynamic and static nuclear bag fibres and nuclear chain fibres by gamma and beta axons in isolated cat muscle spindels

1. The behaviour of nuclear bag and nuclear chain intrafusal fibres in isolated cat muscle spindles with a blood supply, during stimulation of dynamic gamma axons, dynamic beta axons, or static gamma axons in ventral root filaments was observed and recorded on still and moving film. 2. Most spindles were controlled by one dynamic gamma axon (sometimes a beta axon) and three static gamma axons, one of which was often non-selective in distribution. A large majority of fusimotor axons controlled one pole of the spindle only. 3. Dynamic gamma and beta axons produced focal contraction in only one of the two nuclear bag fibres in any spindle and this fibre was never activated by static gamma axons. Maximal tetanic contraction was attained slowly and the primary sensory spiral on this fibre was stretched by a small amount only. This fibre has been named the 'dynamic nuclear bag fibre'. 4. Static gamma axons produced either: (a) focal contraction in the second of the two nuclear bag fibres only; (b) local contraction in the bundle of nuclear chain fibres only; or (c) contraction in one nuclear bag fibre and the nuclear chain fibres together. Maximum tetanic contraction of this nuclear bag fibre stretched its primary sensory spiral considerably and the time to plateau was relatively short. This fibre has been named the 'static nuclear bag fibre'. 5. 'Driving' of the Ia afferent discharge could always be produced by non-selective static gamma axons, frequently by static gamma axons controlling nuclear chain fibres alone, and was probably due to mechanical oscillation in nuclear chain fibres. It was never produced by dynamic gamma axons and on one occasion only by a static gamma axon controlling a nuclear bag fibre alone. 6. The conduction velocities of dynamic gamma and static gamma axons overlapped extensively, though dynamic gamma axons were absent from the lower end, and static gamma axons innervating nuclear chain fibres only were absent from the upper end, of the range of velocities. 7. The observations are correlated with spindle structure and histochemistry. Dynamic and static nuclear bag fibres are shown to correspond with 'bag1 fibres' and 'bag2 fibres', respectively (Ovalle & Smith, 1972). 8. The possible origin of the dynamic and static actions of fusimotor axons and the role of the dynamic and static intrafusal systems in motor control are discussed.

Variation of reinforcement in performance of a motor skill

A simple experimental procedure administered by parents was used to study the effects of variation of reinforcement on performance of a motor skill by a 7-yr.-old retarded male. Owing to hemiplegia this subject has a very restricted range of movement in his left hand. The task required him to use his left hand to place wooden cubes within squares drawn on a paper sheet. Factors varied were type of reinforcer (3 consumables), schedule (continuous, fixed ratio and variable ratio), and frequency of reinforcement. Administration of variable ratio delivery was proceived as an enjoyable game by the subject who produced his best performances under this condition. Functional analyses (mini-experiments) should include type of reinforcer and form of delivery.

Response of osteoarthritis to ibuprofen or flurbiprofen

Flurbiprofen and ibuprofen, two propionic acid derivatives with anti-inflammatory and analgesic activity, were compared in a double-blind multiclinic study in 195 patients with osteoarthritis of the peripheral joints. The patients were given 80 mg/day flurbiprofen or 1600 mg/day ibuprofen for six weeks. Pain, subjective evaluation and functional tests improved significantly in both groups. There were no statistically significant differences between the two treatments in any of the responses. Gastro-intestinal side-effects, generally mild, developed in 5-6% of the patients.

Unusual, rod-shaped cytoplasmic inclusions (Hirano bodies) in a cerebellar hemangioblastoma

The present study reports unusual, long, tubular, rod-shaped cytoplasmic inclusions found in the stromal cells of a cerebellar hemangioblastoma, associated with von Hippel-Lindau syndrome. These inclusions have two layers of circular, laminated filaments, and longitudinally arranged filaments; and appear similar to the so-called "Hirano bodies", which have been previously found in normal and various pathologic conditions of the brain tissue, skeletal muscle cells in myopathy, and interstitial cells of the testis. A review of previous ultrastructural studies of cerebellar hemangioblastoma shows several different types of cytoplasmic inclusions, but none are found to be identical to the present report.

Motor control of nuclear bag and nuclear chain intrafusal fibres in isolated living muscle spindles from the cat

1. The behaviour of nuclear bag and nuclear chain intrafusal fibres in isolated cat muscle spindles was studied by direct observation during repetitive stimulation of the muscle nerve at different stimulus strengths. Contraction of intrafusal fibres and stretch of sensory endings was recorded on film. 2. Tenuissimus spindles are usually operated by a total of four or five fusimotor axons, and the individual action of all of them was studied in many cases. 3. The great majority of fusimotor axons produce activity at one spindle pole only. 4. In about 60% of spindles nuclear bag and nuclear chain intrafusal fibres are selectively controlled by different fusimotor axons, while in one third of these spindles the individual nuclear bag fibres are themselves controlled independently. The remaining 40% of spindles, in addition to some selective innervation, receive one non-selective axon which operates both nuclear chain and nuclear bag fibres though usually only one of the nuclear bag fibres is involved. Selective control is demonstrated in photographs. 5. The thresholds of fusimotor axons selectively innervating nuclear bag and nuclear chain fibres, and of non-selective fusimotor axons are not significantly different. 6. It is suggested that in spindles in which the nuclear bag fibres are controlled by the same axon, it is a 'dynamic' gamma, or occasionally beta, axon. Where one nuclear bag fibre is operated along with the nuclear chain fibres it is controlled by 'static' gamma axon(s), and the other nuclear bag fibre is selectively controlled by 'dynamic' gamma, and perhaps beta, axon(s). Where two nuclear bag fibres are separately operated one may be controlled by 'dynamic' axon(s) and the other by 'static' gamma axon(s). Nuclear chain fibres are always controlled by 'static' gamma axons.

Studies on a thermophilic bacillus: its isolation, properties, and temperature coefficient of growth

A thermophilic bacillus with minimal, optimal, and maximal growth temperatures of 40, 64.5, and 72 C, respectively, was isolated from soil. Biochemical and morphological studies place the isolate in group 1 of the classification of Walker and Wolf. After adaption to nitrate broth, the temperature coefficient for growth was found to be 20,400 cal/mol. When the temperature coefficient for growth of the isolate, psychrophilic bacteria, mesophilic bacteria, and a strain of Bacillus stearothermophilus are compared, there is no correlation with optimal temperature. The form of the Arrhenius equation, as used by some workers, is commented on.

The response of isolated cat muscle spindles to passive stretch

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