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Biomedical subjects

P MacLeod

Publications and source records attributed to P MacLeod.

At least 37 records · Page 2Linked to original sources

Diagnosis and management of infantile marfan syndrome.

Marfan syndrome is infrequently diagnosed early in infancy. The experience of the authors with 22 severely affected infants diagnosed as having Marfan syndrome in the first 3 months of life is described and the literature on 32 additional infants with Marfan syndrome is reviewed. It was found that serious cardiac pathology (82% of the patients described in the article, 94% of those described in the literature) may be present at birth, and that congenital contractures (64% of our cases, 47% of literature cases) are often an associated finding. Other useful clinical findings included arachnodactyly, dolichocephaly, a characteristic facies, a high-arched palate, micrognathia, hyperextensible joints, pes planus, anterior chest deformity, iridodenesis, megalocornea, and dislocated lenses. Echocardiography was useful as a noninvasive method for defining the extent of cardiovascular involvement and following its course. Characteristic cardiac findings in early life included mitral valve prolapse, valvular regurgitation, and aortic root dilation. Cardiac function ranged from normal to poor, with a tendency to worsen. Of the 22 cases 3 infants died during the first year of life. Morbidity and mortality may be high when Marfan syndrome is diagnosed during infancy, and prompt recognition of this phenotype can facilitate management and counseling. Most such severe cases appear to be due to a sporadic mutation in a single germ cell of one parent. Many familial cases may have milder manifestations, be more difficult to detect during infancy, and have a better prognosis.

Heart Defects, Congenital↗

[Presentation of the prototype of a fully implanted cochlear prosthesis].

Description of the prototype of a fully implanted cochlear implant demonstrating the feasibility of a prosthesis with no external component within the next few years. The battery is reloaded by means of electromagnetic induction, and the sound message is received by a subcutaneous microphone, which already has a satisfactory bandwitch and signal-to-noise ratio. This system can be generally applied to most types of permanent intracorporeal stimulation.

Cochlear Implants↗

DNA marker studies show that Machado Joseph disease is not an allele of the Huntington disease locus.

Machado Joseph Disease (MJD) is a progressive spinocerebellar atrophy (SCA) with an autosomal dominant mode of inheritance. On the basis of some similarities in the clinical features and in the abnormal profiles of brain proteins, it has been suggested that MJD might be an allele of the Huntington Disease (HD) locus. Using the DNA probe (pK082), we analyzed the linkage between the DNA marker locus D4S10 and the MJD locus in two large kindreds. The data exclude linkage between these two loci at a distance of 10 cm (Z = - 2.02). Since the D4S10 locus is linked to the HD locus at a distance of approximately 4 cm, we conclude that MJD is not an allele of the HD locus.

Alleles↗

Intracellular recordings from salamander olfactory supporting cells.

Stable intracellular potentials were recorded just below the surface of the salamander olfactory epithelium. The site of recording corresponded to the zone of highest density of supporting cell perikarya. The electrophysiological properties of cells recorded in this zone included: neither spontaneous nor evoked spike activity, high resting potential (-96 +/- 10 mV, n = 113) and low input resistance (15 +/- 12 M omega, n = 64). The cells were depolarized to -9 +/- 8 mV when the extracellular potassium concentration was increased from 2 to 100 mM. The membrane potential also changed during activation of the olfactory receptor neurons. Antidromic stimulation of olfactory axons elicited both rapid and slow depolarizations. Odorant stimulation induced graded depolarizations which always lagged behind the electro-olfactogram by more than 1 s. In contrast to the responses of the olfactory receptor neurons, these responses were nearly identical from one cell to another. Compared with the concomitant electro-olfactogram, they had almost the same amplitude, with a reversed polarity. These findings are discussed in the context of the possible auxiliary functions of supporting cells in olfactory processes.

Animals↗

Intracellular recordings from salamander olfactory receptor cells.

Intracellular recordings were obtained from salamander olfactory receptor cells. The occurrence of an intracellular spike in response to the antidromic stimulation of the olfactory fibers was considered as a physiological criterion of a neuronal impalement. The mean resting potential was -56 +/- 9 mV (mean +/- S.D.; n = 70). Fifty-two cells presented a spontaneous spike activity lower than 2 impulses/s. Appropriate olfactory stimulation generally evoked a slow and graded decrease (up to 28 mV) of the intracellular potential. The input resistance of the cell decreased markedly during the response. The slow potential change induced a repetitive firing. Increasing the intensity of the olfactory stimulation increased the instantaneous frequency of firing (up to 25 s-1) and reduced the spike amplitude. The spikes presented an inflexion in the rising phase indicating a two-stage depolarization. With the strongest intensities of stimulation the impulse activity was stopped during the repolarizing phase of the cell response when the membrane potential was still appreciably depolarized.

Animals↗

Cytoplasmic body myopathy. Report on a family and review of the literature.

A 15-year-old girl who was seen for scoliosis presented with cardiorespiratory failure associated with a respiratory infection. She was found to have weakness predominant in the face, sternomastoid, proximal limb, respiratory, spinal and cardiac muscles. The serum creatine kinase level was slightly elevated and the electrocardiogram was abnormal. The electromyograph was consistent with a myopathy. The course was malignant. Her 14-year-old brother had similar findings and succumbed at the age of 14 and one-half years from cardiorespiratory failure. The mother had minimal weakness of proximal limb muscles since early life. The tendon reflexes were normal as was the serum creatine kinase level. The course was benign. On light microscopy the muscle biopsy in the girl showed fibre diameter variation, centrally placed nuclei, necrosis, fibrosis and cytoplasmic bodies. The muscle biopsy in the brother and mother had similar findings except that the inclusion bodies were not seen in the mother. On electron microscopy, the girl showed typical cytoplasmic bodies, involving predominantly type 1 fibres. The mother also had these structures. The literature is reviewed and the origin, pathogenesis and aetiology of the cytoplasmic body are discussed.

Adolescent↗

Implantation of multiple intracochlear electrodes for rehabilitation of total deafness: preliminary report.

Many instances of total deafness are due to destruction of the organ of Corti but with partial or complete preservation of the function of the cochlear nerve. In such cases, it is possible to restore some hearing by electrically stimulating the fibers of the cochlear nerve with the help of implanted electrodes. Preoperative testing with electric shocks applied to the round window have aroused sensations of noise in 45 cases of total bilateral deafness with a great variety of etiologies. The only negative results were in two cases of operated acoustic neuromas. Our operation places up to eight intracochlear electrodes, each with a separate fenestration opening into an electrically isolated compartment of the scala tympani. Stimulation of each electrode yields a different sound sensation of a pitch that depends on its location along the cochlea. Electric filters direct different frequency bands to the appropriate electrodes, with the necessary compression of dynamic range. In three experimental cases of unilateral deafness, pitch matches to the normal ear were made. In seven therapeutic operations on adult cases of acquired total bilateral deafness, speech recognition was usually relearned within a month or two. Improvement of voice quality was also dramatic. The intracochlear electrodes have been well tolerated for months, but the method of connection to the external equipment still presents difficulties.

Adult↗

Partial ornithine carbamyl transferase deficiency: an inborn error of the urea cycle presenting as orotic aciduria in a male infant.

Recurrent vomiting without apparent cause should alert the physician to the possibility of a disorder of ammonia metabolism. Crystalluria in a three-month-old male infant with a history of intermittent vomiting since birth and incipient coma led to the discovery of orotic aciduria. A diagnosis of ornithine carbamyl transferase (OCT) deficiency was derived from study of the liver after the infant had died; residual activity was about 5% of normal. Ammonia intoxication was the presumed cause of death. Overproduction of orotic acid and other pyrimidines reflects the deficiency of OCT. The possibility of genetic heterogeneity for the hereditary trait under observation must be considered because it may influence prognosis and counselling.

Ammonia↗

Olfactory discrimination in the rabbit olfactory glomerulus.

Slow potentials evoked by odor stimulation were recorded from individual glomeruli in the olfactory bulb. Systematic analysis of responses to nine different, arbitrarily selected stimuli strongly suggests a certain amount of discrimination. This fact seems to reflect in the first synapse of the olfactory tract the type of discrimination that was recently demonstrated within olfactory neuroepithelium.

1-Propanol↗