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Biomedical subjects

B M Bush

Publications and source records attributed to B M Bush.

At least 37 records · Page 2Linked to original sources
PubMed1978

The incidence of significant bacteriuria in the dog.

Counts of the number of bacteria in canine urine samples have a bimodal distribution similar to that found in man. Therefore it is reasonable to accept the same criterion of significant bacteriuria in the dog as in man, namely a count of 10(5) or more organisms/ml. of urine. The incidence of significant bacteriuria in the total canine population was 1.4%. It was higher in bitches compared with male dogs, and higher in older animals. The larger proportion of Boxers affected was attributed to their greater age compared with the mean of the sample population. The most frequently observed clinical signs in case of significant bacteriuria were haematuria, incontinence and frequent urination, and only 4.1% of such cases were asymptomatic.

Age Factors↗
PubMed1978

The auditory midbrain of a marsupial: the brush-tailed possum (Trichosurus vulpecula).

A microelectrode survey was made of the midbrain auditory nuclei of the brushtailed possum (Trichosurus vulpecula), a common Australian marsupial. Information was sought on the tuning characteristics of individual neurones, tonotopic organization and mechanisms of sound localization. It was felt that such information would be of use in future studies of the development and evolution of mammalian hearing. Twelve possums were anaesthetized with ketamine and chloralose-urethane, and recordings were made of extracellular unit discharges in the inferior colliculus during monaural and binaural tonal stimulation. The inferior colliculus of the possum consists of a central nucleus - a darkly stained, densely packed group of cells - flanked laterally by an external nucleus with a lower density of paler cells. Tonotopic organization was demonstrated by discretelytuned elements in the central nucleus, but was not observed in the external nucleus. In the latter region broad and irregular tuning was commonly seen. Most units in both divisions were influenced by binaural stimuli, with patterns of binaural interaction similar to those observed in the cat inferior colliculus. Cells influenced by changes in the interaural time and intensity difference were commonly observed, but only a subclass of these were suited in sensitivity for sound localization. In general, the midbrain auditory system of the possum was similar in unit discharge characteristics and organization to those of the eutherian mammals commonly studied.

Acoustic Stimulation↗
PubMed1978

Deficient influence of peripheral stimuli on precentral neurones in monkeys with dorsal column lesions.

1. Four male monkeys (M. fascicularis) were trained in a movement performance task which involved pulling a horizontal lever into a target zone and then collecting, from one of a variety of positions, a small food reward. The same animals were also trained to sit quietly and accept passive manipulation and natural stimulation of the arm and hand while remaining relaxed. 2. After complete bilateral section of the cuneate fasciculi or division of a major part of these dorsal column afferents at C1-C2 or at C5 level, the animals were still able to perform movement tasks normally. Disturbance of discrimination ability was revealed after vision was occluded it the animal was required to detect differences in texture with only a small cutaneous area in contact with the object (e.g. using only the tip of the index finger). Contactual-placing reactions could be performed in the absence of vision and the movements the animal made in these reactions were well controlled and appropriately directed. Minimal disturbance of contact placing was noticed if the surface touched was on the hand or fingers or if the reaction involved crossed placing. 3. An examination of the natural discharges of 342 percentral neurones revealed that the patterns of activity exhibited in relation to complex movements were indistinguishable from patterns recorded in normal monkeys carrying out similar tasks. 4. Discharges of ninety-one of 321 precentral neurones could be produced by appropriate natural stimuli delivered within the cell's afferent input zone at the periphery. The zone from which a given cell could be influenced was usually limited and its location could be on any part of the contralateral forelimb. However, all but nine of these responses were found in animals in which a small proportion of the cuneate fibres remained intact. In an animal with histologically proven complete section of the cuneate faciculi very few (nine of 171) precentral neurones were influenced by natural activation of peripheral receptors in the forelimb. The zones from which these few afferent inputs were found could all have been proximal to the level of the cuneate lesion. 5. The very small number of responding pre-central neurones found in an animal with complete section of the cuneate fasciculi made it likely that the dorsal columns provide the major pathway for effects from circumscribed peripheral receptors in the forelimb to influence precentral neurones. However, even in an animal with complete interruption of cuneate fibres, a proportion of post-central neurones could still be influenced by natural activation of peripheral receptors within restricted regions of the forelimb. Hence the 'sensory' cortex was still in receipt of afferent projections which could be revealted readily by the tests used. 6...

Action Potentials↗
PubMed1978

Intersegmental reflex coordination by a single joint receptor organ (CB) in rock lobster walking legs.

In the decapod Crustacea, Palinurus vulgaris and Fasus lalandii, the reflex influences of one particular proprioceptor organ, the coxo-basal chordotonal organ (CB), on all the muscles operating the proximal and distal joints of the same leg, have been analysed. The distal end of CB was clamped in fine forceps mounted on a servo-controlled stretcher, and CB length changes of 2 mm were applied. Motor unit activity of the different muscles was recorded as electromyograms (EMGs). 1. Two types of proprioceptive reflex evoked by CB length changes have been investigated: (a) resistance reflexes of the two levator and two depressor muscles of the same leg segment, the coxopodite, i.e. 'intrasegmental reflexes', (b) 'intersegmental reflexes' induced in the muscles operating the proximal (T-C) joint of the same leg, and in all eight muscles of the limb segments distat to CB. 2. Both levator muscles respond reflexly to imposed CB stretch (which normally occurs with limb 'depression'), while both depressors respond during CB shortening (or passive "elevation" of the leg). 3. Intersegmentally CB stretch reflexly activates the M-C extensor muscle, and sometimes facilitates the T-C remotor and C-P bender muscles. Shortening of the single CB organ of a leg excites one or two tonic motor units of the T-C promotor and M-C flexor muscles, and also facilitates the remotor, I-M reductor, and the single stretcher-opener excitatory motoneurone. 4. Some of the muscles, particularly the M-C flexor and extensor muscles, are also influenced intersegmentally by the resting length of CB, usually but not invariably in the same direction as for the corresponding dynamic reflexes. The role of the CB chordotonal organ is discussed, with particular consideration of its intersegmental reflex influence on the posture of the entire leg, and on the more complex motor behaviour of locomotion, where it may be specially significant in coordination of the limb in lateral walking. A complex picture of both tonic and dynamic, inra- and intersegmental reflex regulation of the positions and movements of the limb segments, thus emerges.

Animals↗
PubMed1978

Intersegmental reflex actions from a joint sensory organ (CB) to a muscle receptor (MCO) in decapod crustacean limbs.

In the walking legs of decapod crustaceans, intersegmental reflex actions originate from various joint proprioceptors. The activity of the 'accessory flexor' (AF) muscle, which with the myochordotonal organ (MCO) constitutes a muscle proprioceptor for the mero-carpopodite (M-C) joint, is modulated by the sensory discharge of a joint receptor (CB chordotonal organ) for the more proximal, coxo-basal (C-B) joint. Selective mechanical stimulation of the CB organ also reflexly modifies the motor activities of the main M-C flexor and extensor muscles (recorded as EMGs). 1. Dynamic CB stretch (as would occur during a dorso-ventral C-B movement - i.e. 'depression' of the limb) stimulates motor discharge to the M-C extensor muscle, while dynamic release of CB (as during a ventrodorsal C-B movement - or leg 'elevation') excites the accessory flexor as well as the main flexor muscle. 2. Successive M-C muscle responses to repetitive sinusoidal changes of CB length differ quantitatively according to the direction (stretch or release) of the first CB movement, in some cases increasing but more commonly 'adapting' with repetition. 3. Reflex discharge frequencies of the extensor, flexor and accessory flexor motoneurones increase with velocity of CB movement. 4. Eye illumination, and spontaneous or other sources of increased central excitability, generally increase the CB reflex drive to the flexor and accessory flexor muscles and, in parallel, decrease the reflex action on the extensor muscle. The results are discussed in terms of the role of proprioceptive reflexes in intersegmental co-ordination of the leg joints. In particular the significance of the reflex regulation of the myochordotonal receptors, and thereby the gain of the M-C resistance reflexes, is considered in the light of the observed 'co-activation' of main flexor and receptor muscle motoneurones.

Action Potentials↗
PubMed1976

Exaggerated natural measles following attenuated virus immunization.

An adolescent girl, devoid of a detectable humoral immunity to measles virus despite two inoculations of live, attenuated vaccine, developed an exaggerated atypical rubeola illness following exposure to wild virus. This observation suggests that attenuated virus may be capable of immunologically sensitizing some individuals as has been described with killed virus vaccine.

Adolescent↗