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Biomedical subjects

I M Donaldson

Publications and source records attributed to I M Donaldson.

At least 55 records · Page 3Linked to original sources
PubMed1988

Afferent signals from cat extraocular muscles in the medial vestibular nucleus, the nucleus praepositus hypoglossi and adjacent brainstem structures.

The responses of single units in the vestibular nuclei, nucleus praepositus hypoglossi and in the brainstem, deep and posterior to the abducens nucleus, were studied in anaesthetized, paralysed cats. Natural vestibular stimulation was provided by horizontal, sinusoidal oscillation of the animal and extraocular muscle afferents of the ipsilateral eye were activated either by passive eye-movement or by electrical stimulation of the inferior oblique branch of the oculomotor nerve in the orbit. Unit responses to vestibular and/or orbital stimuli were examined in sets of peristimulus time histograms interleaved in time. Of 127 units exposed to both types of stimulus, 40 (32%) responded only to vestibular input; 46 (32%) were affected only by the orbital afferent signal and 19 (15%) received both signals; the remaining 22 units (17%) were discarded because they had polymodal (usually somaesthetic) input. Of the 93 units whose recording sites were determined histologically, 24 were in the medial vestibular nucleus, 16 in the n. praepositus hypoglossi and 45 in the magnocellular nucleus of the reticular formation posterior and deep to the abducens nucleus. In these three nuclei 19 units in total were found which carried the orbital proprioceptive afferent signal and also responded to horizontal vestibular stimulation. The input from the eye muscles proved able to modify the vestibular response by adding excitation or inhibition or both. Effects of the orbital signal were generally phasic. About half of the units which responded to passive eye-movement showed statistically significant differences between their responses to horizontal and to vertical eye-movement. We have shown previously that signals from extraocular muscle proprioceptors reach the vestibulo-oculomotor system in an amphibian and a bony fish; the present experiments show that this is the case in a mammal also. The fact that the visual and visuomotor behaviour of these three species is very different suggests that the proprioceptive signal may play some rather fundamental role in the vestibulo-ocular system. The principal interest of the present results is that they demonstrate that units in the central vestibular system of the cat, in structures which are known to be concerned in oculomotor control, and particularly in the organization of horizontal eye-movement, receive an afferent signal from the eye muscles during passive eye-movement. These brainstem nuclei are known to receive various combinations of input from the vestibular and visual systems and of signals which represent neck movement and eye position and velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Neck muscle vibration modifies the representation of visual motion and direction in man.

The retinal coordinates of an image are normally insufficient to define the direction of an object in body-centred visual space. Gaze direction, specified by information on the position of eye-in-head and on the position of head-on-torso, is also required. While the source of the eye-in-head signal is controversial, it is clear that proprioceptive signals from neck muscles are sufficient to provide head-on-torso information. Observations by Goodwin et al., beginning in 1972, that vibration of limb muscles modifies proprioception from them, and induces illusory motion and false perception of limb position, suggested this study of the effects of neck muscle vibration on the representation of visual space. Verbal reports, supported by objective measures, revealed that vibration of muscles on one side of the neck induces a visual illusion: contralateral displacement of a small visual target viewed in the dark. Pointing movements towards the target are similarly affected, confirming that the representation of directions in visual space is modified by neck muscle vibration. A second vibration-induced illusion was uncovered when apparent displacement ceased. This is an illusion of pure target motion in the same direction as the previously observed displacement. The magnitudes of both the displacement and pure motion illusions were dependent on vibration amplitude and were unrelated to real or apparent movements of eyes or head. Taken together these observations indicate that vibration of neck muscles can modify independently (1) the central representation of the instantaneous direction of gaze and (2) the signal of the velocity with which this direction is changing.

Adult↗
PubMed1988

Intravenous enoxacin for the treatment of acute pyelonephritis: pharmacokinetic and clinical study.

1. Eight women with acute pyelonephritis were treated with i.v. enoxacin for 5 days. All were clinically cured and five had a bacteriological cure. Five women reported side effects. 2. During treatment there was no significant accumulation of enoxacin and the total clearance of the drug did not alter with repeated dosing. Drug elimination half-life (mean 4.3 h, s.d. 2.1) was similar to that reported in healthy volunteers. 3. Enoxacin should be compared with the aminoglycosides and beta-lactam antibiotics for the treatment of severe or complicated urinary tract infections.

Acute Disease↗
PubMed1987

Diabetic focal myelopathy.

The existence of myelopathy as a complication of diabetes is debatable and, in the few reported cases, spinal involvement has been diffuse. We describe 2 cases of focal myelopathy. Two insulin-dependent, middle-aged men with adult-onset diabetes presented with gradually ascending lower limb pain and numbness without sphincteric symptoms. Examination showed mixed upper and lower motor signs in the lower limbs, with a severe impairment of cutaneous sensation below a sharply demarcated band at the T9-10 level with relative preservation of posterior column function. Myelography was normal. CSF showed mild elevation of protein and in one case showed 23 x 10(6) white cells/L. Nerve conduction studies showed a co-existing, mild sensorimotor neuropathy. There was no evidence of truncal radiculopathy on paraspinal EMG. Extensive investigation for other causes of myelopathy was negative.

Adult↗
PubMed1986

Volvular epilepsy. A distinctive and underreported seizure type.

In a volvular seizure, the patient walks repetitively in small circles. This may form the whole of the attack or may precede a generalized tonoclonic seizure. It may be due to primary epilepsy or secondary to focal intracranial pathology. The direction of rotation may be ipsiversive or contraversive to the side of the epileptic focus. Although associated with complex partial and adversive seizures, it forms a distinctive entity, which may be due to involvement of the striatum. It has probably been underreported in the past. Four cases are reported herein.

Adolescent↗
PubMed1986

[Vibration of neck muscles changes the apparent position of a visual target].

The discharge rate of muscle spindle afferents normally provides a precise signal of muscle length. Vibration of a muscle or its tendon induces an increase in afferent discharge which then no longer represents true muscle length; however, this increased proprioceptive input is interpreted in the central nervous system as a lengthening of the muscle. The incremented signal gives rise to illusions of displacement, or movement, of a fixed, vibrated limb. A visual target attached to such a vibrated limb also appears to move. We now report that vibration of the neck muscles influences visual localisation by inducing illusory movement of targets in visual space. Subjects were seated in a totally dark room and viewed a light-emitting diode (LED). The LED was placed at eye level approximately in the body midline at a distance of 70 cm. They held a physiotherapy vibrator in the left hand with its tip against the left side of the neck. When vibration was initiated the LED appeared to move rightward. The position of the tip of the vibrator was adjusted to produce the maximum apparent displacement to the right. In some subjects the illusion had a vertical component. Subjects maintained the vibrator in position and described the illusion when vibration began, during vibration and at its end. They reported that, initially, the target moved to the right but this displacement ceased after a second or two. The target then appeared to continue in motion without changing its position. When vibration ended the target returned to its initial position.(ABSTRACT TRUNCATED AT 250 WORDS)

Central Nervous System↗
PubMed1985

"Psychometric" assessment during transient global amnesia.

A patient "psychometrically" assessed during an attack of transient global amnesia showed total inability to form new long term memories but normal immediate recall. There was nearly perfect preservation of other psychological functions with good recall of distant events and no dysphasia, dyslexia, dysgraphia, dyspraxia, right-left disorientation, constructional apraxia or visual agnosia. Calculation was probably also normal. Some of the 5 previously reported patients, who have been similarly studied during attacks of transient global amnesia, showed evidence of damage to the brain beyond the hippocampal forniceal system. The present patient demonstrates the market selectivity of memory disturbance in "pure transient global amnesia".

Amnesia↗
PubMed1985

A case of partial deficiency of alpha 1-antichymotrypsin.

A 20-year-old woman, admitted to a neurological ward with a diagnosis of benign intracranial hypertension, was found on specific protein electroimmunoassay to have a consistently decreased concentration of alpha 1-antichymotrypsin in her plasma. Serum from her father showed the same result. Further investigation of her family demonstrated that this partial deficiency was transmitted in an autosomal dominant fashion and was not associated with any obvious specific clinical abnormalities.

Adult↗
PubMed1984

Deaths from strokes.

Explore the source record for details and available documents.

Cerebrovascular Disorders↗
PubMed1984

Cerebral mucormycosis.

The clinical and pathological features of two patients who died of rhinocerebral mucormycosis are described. The cases illustrate two of the major mechanisms by which the brain may be affected in this condition. Although the diagnosis is often made only at post mortem the clinical features are often distinctive enough to allow recognition of this disease during life.

Adult↗
PubMed1984

Input from proprioceptors in the extrinsic ocular muscles to the vestibular nuclei in the giant toad, bufo marinus.

Extracellular unit records were made from the left brain stem of decerebrate, paralysed giant toads (Bufo marinus) during passive movement of the ipsilateral eye. Units in the vestibular nuclear complex (VN) were identified by their short-latency responses to electrical stimulation of the anterior branch of the ipsilateral VIII cranial nerve. Of 58 units in the region of VN, as judged from field potentials to VIII nerve stimulation, fourteen gave phasic excitatory responses to passive movement of the eye and were also identified as vestibular nuclear units. A further twelve units which responded to eye-movement could not be assigned to VN; the remaining 32 units were in VN but did not respond to passive eye-movement. Also, of 16 units whose recording sites were identified histologically in the VN complex, 11 gave responses to vestibular nerve stimulation and to passive eye-movement and 5 responded to eye-movement only. Control experiments eliminated auditory, visual and cutaneous sources for the signal produced by passive eye-movement; thus, the signal must have arisen from intraorbital proprioceptors. Units in VN were also found which were excited by electrical stimulation of the intraorbital part of the fourth (trochlear) nerve; this provides strong evidence that proprioceptors in the extrinsic ocular muscles (EOM) are included in the receptors which provide the signal to VN during passive eye-movement. The effects of vestibular stimulation and of passive eye-movement were found to interact upon units in VN. When passive eye-movement and vestibular stimulation were paired the response to the second stimulus was significantly reduced over a range of interstimulus intervals. The conclusions are that orbital proprioceptive signals, including those from the EOM, project to the vestibular nuclei in the toad and, there, are able to influence processing of vestibular afferent signals. We suggest, therefore, that orbital proprioceptive signals may play a part in oculomotor control. The significance of the results is discussed in relation to the strategic position of the VN in the oculomotor control system.

Acoustic Stimulation↗
PubMed1984

Directional selectivity in the responses of units in cat primary visual cortex to passive eye movement.

The responses of single units in the primary visual cortex (Area 17) of anaesthetized, paralysed cats, to passive movement of the ipsilateral eye were studied. Responses to passive eye movement were found in about one-third of the cortical units isolated. Appropriate control experiments excluded visual, auditory and cutaneous inputs as the source of the effective signal during passive eye movement. The magnitudes of the responses to a number (usually four) of radial directions of passive eye movement were estimated from sets of peristimulus time histograms "interleaved" in time. Units were defined as "radially selective" if the responses to movement along one radius (e.g. vertically upwards) exceeded that along at least one other orthogonal radius (e.g. horizontal-temporal). Of 60 units tested, 53 (88%) were "radially selective" according to this definition. Some of the "radially selective" units showed an additional type of specificity to passive eye movement: (a) Some units responded preferentially to movement along one of the arcs of passive eye movement which were tested (e.g. vertical movement above the equator of the orbit). These units we have called "arc selective". (b) Other units were sensitive to the direction of movement and preferred movement in a particular direction over more than one arc (e.g. horizontal movement towards the temporal side in both nasal and temporal halves of the orbit). These we have called "direction selective". Twenty-one "radially selective" units showed one of these additional properties, nine were arc selective and twelve were direction selective. The implications of these results for the understanding of the function of orbital proprioceptive signals in the cortex are discussed briefly. Responses to passive eye movement were found in all of layers II-VI in Area 17 and the implications of this for the understanding of the pathway by which orbital proprioceptive signals reach the primary visual cortex are discussed. The experiments have shown that many units in cat visual cortex respond to passive eye movement and that most of these units have some specificity for particular radial directions of movement while some have additional specific properties. We believe that these properties of radial, directional and arc sensitivity are likely to be important in understanding the function of the orbital proprioceptive signal which arises during eye movement and they are particularly interesting in relation to the findings of others that this proprioceptive signal appears to be concerned in the normal development of visual properties in the cortex and in the control of visually guided movement in adult cats.

Animals↗
PubMed1983

Persisting neurologic sequelae of lithium carbonate therapy.

Persisting neurologic damage rarely follows lithium salt therapy. We encountered two cases and found 15 others in the literature. There are usually signs of damage at multiple sites in the nervous system, but cerebellar features tend to be most prominent. The patient's sex and age, the lithium ion dosage, and the maximum blood levels of lithium ion do not correlate well with the persistence of damage. Individual susceptibility may be important. Severe lithium ion intoxication may occur in the first one or two months after the drug is introduced but can arise even after several years of satisfactory maintenance therapy at a constant dosage. Infection, dehydration, deteriorating renal function, or the addition of other drugs to the regimen may precipitate acute toxicity. Neurologic damage can occur despite low plasma levels of lithium ion. The patient's clinical state may be the best indication of intoxication.

Drug Synergism↗
PubMed1983

An evaluation of cerebrospinal fluid oligoclonal banding confirmed by immunofixation on agarose gel.

The cerebrospinal fluid (CSF) from 115 consecutive patients undergoing diagnostic lumbar puncture or myelography was examined to determine the usefulness of immunofixation, following agarose gel electrophoresis, in the detection of oligoclonal IgG. All electrophoretic patterns were evaluated with and without immunofixation, and the interpretation of 9% of specimens was altered by immunofixation. The demonstration of oligoclonal IgG was shown to be more reliable in the diagnosis of multiple sclerosis than other indices of intrathecal synthesis of IgG. It is concluded that immunofixation should be used routinely when examining CSF for oligoclonal banding.

Diagnosis, Differential↗