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Biomedical subjects

W J Logan

Publications and source records attributed to W J Logan.

52 records · Page 3Linked to original sources
PubMed1972

Specific glycine--accumulating synaptosomes in the spinal cord of rats.

Subcellular fractionation of rat spinal cord on continuous sucrose density gradients provides evidence for the existence of a specific synaptosomal fraction (enriched in pinched-off nerve endings) that accumulates glycine selectively by way of a high-affinity transport system. The particles in this fraction sediment to a less-dense portion of sucrose gradients than do particles that accumulate neutral, basic, aromatic, and acidic amino acids. Particles accumulating gamma-aminobutyric acid are even less-dense than those storing exogenous glycine. The glycine-specific synaptosomal fraction also exists in the brain stem but not in the cerebral cortex. These findings provide neurochemical support for the suggestion that glycine has a specialized synaptic function, perhaps as neurotransmitter, in mammalian spinal cord.

Aminobutyrates↗
PubMed1970

Extraneural metastases in ependymoma of the cauda equina.

A case of ependymoma of the cauda equina, presumably originating from the filum terminale in a girl aged 17 at the onset of illness, eventually developed remote metastases in the lungs, pleura, and one para-aortic lymph node. This case is compared with three other previously reported examples. The unusual features in the present instance were (1) the total length of the clinical history, amounting to 29 years; (2) the development, six years after the removal of the original spinal tumour, of another ependymomatous mass in the fourth ventricle, interpreted as a rostral metastasis that seeded via the cerebrospinal fluid; and (3) the demonstration of anaplastic cytological changes at the primary site, interpreted as the result of irradiation. The salient aspects of this and the three other reported cases are briefly reviewed, and the pathway of distant dissemination, resulting from venous permeation at the primary site, is emphasized.

Adolescent↗
PubMedDate not supplied

Amino acid transport by a muscle cell line.

An established rat muscle cell culture, L-6, was employed for the evaluation of muscle amino acid transport. The initial influx of 16 radiolabeled amino acids into these cells was determined, and an overall uptake profile was constructed. L-6 cells accumulate amino acids progressively with time by saturable, temperature-dependent processes. As found in other preparations, several amino acids have sodium-dependent uptake systems. There is a wide range in the rate of transport of the different amino acids. The overall profile of uptake is fairly reproducible and may be characteristic of muscle tissue; it does not resemble that previously found in other cell types. The profile of amino acid uptake into these cells compares favorably with the pattern of amino acid transfer from the bloodstream to muscle found in intact rats. It is concluded that muscle cell transport is basically similar to that of other cell types. L-6 muscle cells have an amino acid uptake profile which resembles that of intact muscle; they should thus prove useful in the further delineation of muscle amino acid transport mechanisms.

Amino Acids↗
PubMedDate not supplied

Somatosensory evoked potentials: Part I. A review of neural generators and special considerations in pediatrics.

Despite the recognition of evoked potentials in the late nineteenth century and the recording of somatosensory evoked potentials (SEPs) in 1947, there still is much to be learned about the origin of the SEP and its applications, particularly in the field of pediatric neurology. We summarize relevant data from the literature concerning the neural sources and present the currently accepted generators of the various peripheral, subcortical, and cortical components. The importance of factors such as growth, maturation, and the effects of sedation and sleep are discussed. The clinical applications of SEPs in pediatric neurology will be presented in Part II.

Afferent Pathways↗
PubMedDate not supplied

Somatosensory evoked potentials: Part II. A review of the clinical applications in pediatric neurology.

Fundamental to the clinical application of somatosensory evoked potentials is an understanding of the neural generators, the changes in disease states, and the effects of growth and maturation; aspects relevant to pediatric somatosensory evoked potentials were discussed previously (Part I). The importance of establishing normative data across age- and size-matched controls in the pediatric population, however, cannot be overstated. The following review of the clinical applications of somatosensory evoked potentials in pediatric neurology is based on a review of the literature and on the experience gained from over 900 studies performed in our laboratory during the last 4 years.

Child↗
PubMedDate not supplied

Primary thalamic and caudate hemorrhage in term neonates presenting with seizures.

Two previously well term neonates who presented with seizures are described: one with thalamic hemorrhage and the other with thalamic and caudate hemorrhage. These 2 patients were the only neonates found with thalamic hemorrhage in a review of 54 term infants with intracranial hemorrhage at The Hospital for Sick Children over a 10 year period (1976-1986). Partial seizures occurred at 5 and 7 days after birth and were easily controlled. Prognosis was generally good in these 2 patients, as well as in 4 previously reported patients.

Caudate Nucleus↗
PubMedDate not supplied

Neonatal Guillain-Barré syndrome.

A term female infant had the clinical manifestations and accompanying electrophysiologic studies to fulfill the criteria of Guillain-Barré syndrome. At birth, she presented with generalized hypotonia, paucity of lower limb movements, and diminished muscle stretch reflexes. At 3 weeks of age, motor nerve conduction studies demonstrated evidence of demyelination and axonal involvement. Progressive clinical improvement was observed beginning at the age of 2 weeks with subsequent normalization of clinical examinations and nerve conduction studies. To our knowledge, this patient is the youngest reported with Guillain-Barré syndrome.

Female↗
PubMedDate not supplied

Spinal cord birth injury: value of computed tomographic myelography.

The value of myelography in the assessment of spinal cord injury in the early neonatal period has not been documented, although this study has been recommended frequently in the literature. Eight neonates are reviewed who presented with the clinical features of spinal cord injury and who had myelography performed. Clinical features included difficult delivery, absent respiration, flaccid paralysis, sensory level, and neurogenic bladder. Myelography revealed that 7 patients had the early changes of swollen cord and 1 patient had the late changes of cord atrophy. None of the neonates had surgical intervention. One neonate died at 3 days of age, while 2 others died after prolonged ventilation. Of the 5 infants who survived, 3 still require ventilation and have spastic quadriparesis, 1 has almost recovered completely and 1 had spontaneous respiration and limb movement but brisk deep tendon reflexes when last examined at 1 month of age. Myelography, which was performed in the early neonatal period in our infants, was abnormal in all patients. Myelography is useful in confirming the diagnosis, outlining the level and extent of the lesion, and excluding extramedullary compression. Myelography may assist in the assessment of prognosis but did not alter management in our patients.

Birth Injuries↗