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Biomedical subjects

A M Kerr

Publications and source records attributed to A M Kerr.

At least 37 records · Page 2Linked to original sources
PubMed1992

A review of the respiratory disorder in the Rett syndrome.

The characteristics and physiological accompaniments of the respiratory disorder in the Rett syndrome are reviewed and placed in the context of other clinical studies. Events are indicated which may play a part in the occurrence of vacant spells. A scheme is proposed to explain the various manifestations of the Rett syndrome disorder throughout life. The Rett syndrome is viewed as a developmental disorder in which the evolving clinical signs are due to the effects of maturation and aging on an abnormal brain rather than to primary degenerative disease. Thus development elicits preexisting defects which subsequently become clinically manifest. The clinical evidence is suggestive of a genetically determined early defect in central receptive processing which leads to failure of central motor planning with release of extrapyramidal rhythms.

Child↗
PubMed1991

Rett syndrome.

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Carbon Dioxide↗
PubMed1990

Neurophysiological observations on corticospinal projections to the upper limb in subjects with Rett syndrome.

The aim of the present study was to investigate the excitability of corticospinal neurons and the integrity of their projections to the alpha motor neurons through the corticospinal tract in subjects of different ages with Rett syndrome. Electromagnetic stimulation of the motor cortex and cervical motor roots was used to evoke motor action potentials in the biceps brachii and hypothenar muscles. The phasic stretch reflex in the biceps brachii was also recorded to study the excitability of spinal alpha motor neurons. Motor cortex stimulation evoked motor action potentials at low threshold and with abnormally short latencies and prolonged durations. In contrast cervical motor root stimulation resulted in responses of normal latency and duration. The phasic stretch reflex had a low threshold, short latency and prolonged duration. It is concluded that in Rett syndrome the corticospinal pathway is intact. The results suggest disordered synaptic control of the Betz cell of the motor cortex and/or the spinal alpha motor neuron, although the involvement of the latter might be a consequence of dysfunction in supraspinal descending motor pathways.

Adolescent↗
PubMed1990

Rett's syndrome.

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Adolescent↗
PubMed1988

A low-cost method for simultaneous video-recording of ambulant subject and electroencephalograph: the Quarrier's system.

A system is described by means of which the ambulant subject may be video-filmed over several hours with the electroencephalograph superimposed on the same tape, allowing correlations to be observed in the active state. Our first subjects have been girls with Rett syndrome. Requirements are: one portable video camera/recorder, a conventional e.e.g. machine, the 'Medilog 9000' system for prolonged ambulatory recording (Oxford Medical), a specialized video mixer (videogram ForA FVG600, commercially available) a video timer, a conventional video cassette recorder and a television monitor. The cost is small for a department already equipped to carry out ordinary ambulatory e.e.g. monitoring. The method is safe, well tolerated, simple to use and adaptable. To the best of the authors' knowledge, they are the first to use this system and they believe that it should find wider application when it is desirable to correlate the behaviour of a subject with physiological parameters, on a restricted budget.

Ambulatory Care↗
PubMed1988

Hyperventilation in the awake state: potentially treatable component of Rett syndrome.

Hyperventilation, which occurs in some patients with severe mental handicap, is a prominent feature in the histories of most girls with Rett syndrome but its mechanism and effects have not been established. Respiratory function was therefore studied in 18 patients with Rett syndrome and 23 healthy controls. Ten of the patients (56%), but none of the controls, hyperventilated only when awake, and began doing so after a period of normal breathing without hypoxaemia. After hyperventilation was established it was interspersed with prolonged periods of apnoea (over 19 seconds) accompanied by Valsalva manoeuvres. Hypoxaemia (less than 90%) occurred in 47% of these periods of apnoea and five (50%) of the patients had oxygen saturation values of under 50%. During hyperventilation severe hypocapnia developed in every patient, and recorded arterial pH measurements ranged from 7.47 to 7.60. A further four patients (22%) did not hyperventilate, but had clear histories of hyperventilation when younger. All had frequent apnoeic pauses accompanied by Valsalva manoeuvres. The remaining four girls (22%) neither hyperventilated nor gave a clear history of doing so. Three had occasional apnoeic pauses associated with the Valsalva manoeuvres. All but one of the 18 patients had increased quantities of periodic apnoea compared with the control subjects. The hypocapnic alkalaemia and hypoxaemia resulting from hyperventilation may contribute to the cerebral impairment in Rett syndrome. Since the hyperventilation is 'primary', and not secondary to preceding apnoea, it is potentially treatable. Further studies will determine if treatment is practical and of benefit.

Adolescent↗
PubMed1987

The hands, and the mind, pre- and post-regression, in Rett syndrome.

Forty girls with Rett syndrome were included in a study of behaviour, with particular regard to the hands, before, during and after regression. Data was taken from examination of each girl, and in some cases from detailed developmental histories given by parents, and films taken before, during and after regression. The important findings are shown in two tables and described. Pre-regression abnormalities included hypotonia, jerky incoordination, an excess of patting or waving activity and involuntary movements which included alternate opening and closing of the fingers and twisting of wrists or arms. Hand use did not progress beyond the ten- to twelve-month stage. Language did not develop beyond the stage of one word utterances. When well-developed, the stereotyped hand movements were simple and clumsy, consisting of tapping, rubbing and clasping, with the hand moved as a unit. Before regression hands were usually separate, during regression usually together and thereafter with increasing age inclined to separate again. Voluntary hand use was observed when girls were relaxed and strongly motivated, particularly during musical interactions. The characteristic abnormalities of behaviour in pre-regression Rett syndrome, and hand behaviour in later childhood should allow earlier and more accurate diagnosis.

Adolescent↗
PubMed1987

In vitro chemosensitivity testing using the multicellular tumor spheroid model.

Using growth delay and clonogenic cell survival as end points, we have shown that the 3-dimensional structure of human lung tumour spheroids confers a degree of resistance to the anthracyclines doxorubicin and 4'-deoxydoxorubicin, relative to cells grown as monolayer. 4'-deoxydoxorubicin induces a longer growth delay and greater clonogenic cell kill than doxorubicin in spheroids, although it is no more cytotoxic in monolayer. Using fluorescent microscopy we have demonstrated, qualitatively, that lipophilic anthracycline analogues partition into the spheroid more rapidly and to a greater degree than doxorubicin. It is apparent that penetration is an important aspect of anthracycline drug resistance in spheroids, and the spheroid model may represent a better in vitro system for testing lipophilic analogues of cytotoxic drugs.

Antibiotics, Antineoplastic↗
PubMed1986

Comparative intracellular uptake of adriamycin and 4'-deoxydoxorubicin by non-small cell lung tumor cells in culture and its relationship to cell survival.

4'-Deoxydoxorubicin (4'-deoxy) is a new adriamycin analogue with a similar spectrum of antitumour activity but is significantly more lipophilic than the parent compound. We report the kinetics and uptake of the two drugs by human non-small cell lung tumour cells in monolayer culture and the relationship between intracellular drug levels and cytotoxicity. The rate and degree of cell uptake of 4'-deoxy (Vmax = 30 ng/10(5) cells/min) was greater than that of adriamycin (Vmax = 0.15 ng/10(5) cells/min). Although for a given intracellular drug concentration adriamycin was more lethal, on the basis of extracellular drug concentration, cell kill was virtually identical. The log cell survival vs intracellular drug concentration plot was linear for adriamycin but biphasic for 4'-deoxy. Intracellular distribution of the two drugs was followed by fluorescent microscopy and it was apparent that adriamycin was localized mainly within the nucleus whereas 4'-deoxy accumulated within the cytoplasm. Our results suggest that the relationship between intracellular distribution of the two drugs could reflect different modes of action for the drugs with respect to binding sites or could be a non-specific phenomenon, unrelated to lethal effects.

Carcinoma, Squamous Cell↗
PubMed1986

A study of the natural history of Rett syndrome in 23 girls.

We have studied 23 patients with Rett syndrome with particular reference to the character and natural history of the clinical disorder. We found a prevalence of 0.8 per 10,000 girls 0-14 years in the region from which cases came. We consider that the disorder of tone, posture and movement is extrapyramidal in nature and suggest that the gradual emergence of its fully developed pattern leads to the familiar regression in skills on presentation. We have not found proof of dementia at this stage but rather of severe mental handicap.

Adolescent↗
PubMed1986

The effect of adriamycin and 4'-deoxydoxorubicin on cell survival of human lung tumour cells grown in monolayer and as spheroids.

Using growth delay and clonogenic cell survival as end points, we have shown that the 3-dimensional structure of human lung tumour spheroids confers a degree of resistance to the anthracyclines adriamycin and 4'-deoxydoxorubicin, relative to cells grown as monolayer. 4'-deoxydoxorubicin induces a longer growth delay and greater clonogenic cell kill than adriamycin in spheroids, although it is no more cytotoxic in monolayer (exponential and plateau phase). There is a log linear relationship between clonogenic cell survival and duration of adriamycin exposure in monolayers, and biphasic curve with a lesser degree of cell kill for disaggregated spheroid cells. Using fluorescent microscopy we have demonstrated, qualitatively, that the more lipophilic analogue partitions into the spheroid more rapidly and to a greater degree than adriamycin. It is possible that adriamycin penetration is a relatively important aspect of spheroid drug resistance, which may be related to intraspheroidal pH gradients, and that we have partially overcome this by using a lipophilic analogue.

Cell Survival↗
PubMed1985

Rett's syndrome in the west of Scotland.

Nineteen girls with characteristic features of Rett's syndrome, including normal initial development, regression at about 12 months of age, repetitive hand movements, and severe mental handicap were studied. This represents an estimated incidence of one in 30 000 live births (one in 15 000 girls) in the west of Scotland. Although the children were often initially considered to be autistic, they did not conform to this diagnosis as they made good personal contact within the limits of their mental development. The developmental regression was sometimes falsely attributed to vaccination. Each child showed striking involuntary movements and abnormality of tone, varying from hypotonia, which was found only in the youngest, to rigidity, which was common in older girls; this permitted classification into three clinical subtypes. The abnormalities were highly suggestive of an extrapyramidal disorder, and this has implications for further research and possible treatment.

Adolescent↗
PubMed1985

Pycnodysostosis in a Pakistani family: case presentation and review.

Pycnodysostosis is described for the first time in a Pakistani family. Two cases are presented and are contrasted with cases of osteopetrosis seen in this hospital over a twenty year period. The possibility of confusion with osteopetrosis is indicated and discussed.

Child, Preschool↗
PubMed1981

Acetazolamide in prevention of acute mountain sickness: a double-blind controlled cross-over study.

Twenty-four amateur climbers took part in a double-blind controlled cross-over trial of acetazolamide versus placebo for the prevention of acute mountain sickness. They climbed Kilimanjaro (5895 m) and Mt Kenya (5186 m) in three weeks with five rest days between ascents. The severity of acute mountain sickness was gauged by a score derived from symptoms recorded daily by each subject. On kilimanjaro those taking acetazolamide reached a higher altitude (11 v 4 reached the summit) and had a lower symptom score than those taking placebo (mean 4.8 v 14.3). Those who had taken acetazolamide on Kilimanjaro maintained their low symptom scores while taking placebo on Mt Kenya (mean score 1.9), whereas those who had taken placebo on Kilimanjaro experienced a pronounced improvement when they took acetazolamide on Mt Kenya (mean score 2.5). Acute mountain sickness prevented one subject for completing either ascent. Acetazolamide was acceptable to 23 of the 24 subjects. Acetazolamide is recommended as an acceptable and effective prophylactic for acute mountain sickness.

Acetazolamide↗