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Biomedical subjects

J Andrews

Publications and source records attributed to J Andrews.

At least 343 records · Page 19Linked to original sources
PubMed1969

Vitamin C supplementation in the elderly: a 17-month trial in an old persons' home.

Seventeen months' supplementation of the diet with vitamin C in elderly residents in an old persons' home failed to show any changes in sublingual lesions, which on histological examination proved to be aneurysmal dilatations of the venules. Nine months' supplementation of 40 to 80 mg. daily of vitamin C was necessary before the white-cell vitamin levels reached that found in younger people. There was a marked individual variation in response.

Aged↗
PubMedDate not supplied

MR-guided aspiration cytology in the head and neck at high field strength.

Published reports of magnetic resonance (MR)-guided needle biopsy have involved low- and mid-field-strength systems because of the concern of needle artifact and risk of increased needle torque at higher field strengths. To the authors' knowledge, this is the first report of a high-field-strength (1.5-T) system used to guide aspiration cytology in the head and neck in a patient. The procedure was successfully accomplished without additional needle torque or substantial increase in image artifact relative to lower-field-strength imaging.

Biopsy, Needle↗
PubMedDate not supplied

Vestibulo-ocular reflexes in peripheral labyrinthine lesions: III. Bilateral dysfunction.

Measurements were made of the lesion-induced changes in vestibulo-ocular reflexes (VOR) to rotatory stimuli in a group of patients with bilateral peripheral labyrinthine lesions. All the patients had caloric responses that were below the confidence levels used for normal responses in our laboratory. Responses to rotatory stimuli were greatly decreased or absent at low frequencies of stimulation, but present to a much greater degree at the higher frequencies. Phase measurements showed an increase in relationship to the velocity of the stimulus; there was a corresponding shortening of the time constant as obtained from impulse response measurements. A parametric study indicated that the changes in the responses can be described by a decrease in the sensitivity coefficient and in the basic time constant of a simplified pendulum model equation of vestibular function. A theoretical analysis of the data using a new model for the organization of the vestibular pathways indicated that the preservation of the high-frequency responses was the result of adaptive changes brought about in the central vestibular pathways and/or changes in the receptor-neuron transduction characteristics. Thus, despite the almost complete absence of any caloric response, the vestibular system reflexes remained adequate to maintain gaze during normal head movements.

Adult↗
PubMedDate not supplied

A modified two primer approach to oligonucleotide-directed in vitro mutagenesis.

Using oligonucleotide-directed mutagenesis, we are trying to define the features of the protein structure that are important for the DNA and c-AMP binding by CAP from E. coli, the enzymic activity and putative DNA binding of dihydrofolate reductase of L. casei, and the functionally important regions of the self-splicing RNA of the r-RNA intron of Tetrahymena thermophila. We have used a modification of the method described by Norris et al. [1]. A mutagenic primer and an M13 universal sequencing primer are annealed simultaneously to a template from an M13 clone containing the DNA to be mutagenised and, after DNA strand extension, the fragment is cut out and recloned into either M13 or plasmid vectors. We have analysed the effect on the frequency of mutation of: the temperature used for strand extension; the class of base change attempted; the host mismatch repair system. A recently developed system for phenotypic detection of mutations in the Tetrahymena intron aided in determining mutation frequencies.

Animals↗
PubMedDate not supplied

Facilitatory effect of thinking about movement on motor-evoked potentials to transcranial magnetic stimulation of the brain.

Two experiments using transcranial magnetic stimulation (TMS) were undertaken to investigate facilitatory effects of thinking about a specific movement without voluntary discharges on motor-evoked potentials (MEP). First, surface electromyographic (EMG) responses from the abductor pollicis brevis were recorded with maximal stimulator output in the three conditions: the muscle being at rest, contracting with 10% of maximal muscle activity, and with the subject "only thinking" about thumb abduction (nine subjects). Median value of MEP amplitudes during "only thinking" was twice that at rest (P = 0.008) and one-half that during voluntary contraction (P = 0.008). Second, needle EMG responses from the first dorsal interosseus were compared at rest, during thinking about index finger abduction, and during TMS at threshold intensity. Four normal subjects were tested with stimulation of each cerebral hemisphere for a total of eight tests. The number of detectable MEP responses of 20 stimuli to one hemisphere was counted for each condition of rest or thinking. The mean MEP response rate during thinking (58%) was higher than that at rest (12%) (P < 0.005). These results demonstrate that thinking about a specific movement has facilitatory effects on MEP and that the degree of facilitation in thinking is smaller than in voluntary contraction.

Adult↗