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Biomedical subjects

M F Walker

Publications and source records attributed to M F Walker.

30 records · Page 2Linked to original sources
PubMed1990

The accuracy of predictions about progress of patients on a stroke unit.

The aim of the study was to check the accuracy of predictions about the factors which affect the progress, in physical abilities and activities of daily living, of patients admitted to a stroke unit. A series of 60 patients admitted consecutively to a stroke unit were assessed on tests of motor, functional and cognitive abilities at admission. On the basis of these assessments predictions were made about the abilities of the patients at discharge. Patients were assessed for level of motor abilities and activities of daily living at discharge and the accuracy of the predictions checked. Predictions were found to be significantly correlated with outcome but the relationships were not so close as to be useful for the clinical management of individual patients.

Activities of Daily Living↗
PubMed1989

Three-dimensional phase contrast angiography.

Bipolar flow-encoding gradients can be used in a three-dimensional magnetic resonance imaging procedure to provide a noninvasive measure of in vivo blood flow. The resulting volume angiogram is a three-dimensional data matrix which can be retrospectively analyzed and displayed in a variety of ways. This angiographic technique provides good suppression of signals arising from stationary tissue, thereby permitting the visualization of small vessels having relatively slow flow. This suppression is obtained by modulating the amplitude of the flow-encoding gradient pulse to either cancel the stationary tissue signal or displace it relative to the flow signal in the volume image.

Angiography↗
PubMed1989

Three-dimensional time-of-flight magnetic resonance angiography using spin saturation.

A three-dimensional Fourier transform magnetic resonance imaging technique is presented. This procedure can be used to selectively detect flowing material such as blood in arteries and veins. Since flow is detected in a manner in which velocity-induced phase shifts are compensated, signal loss arising from complex flow and turbulence is minimized. The flow image is sensitive to all velocity components of flow. Applications of this technique are limited, however, to relatively straight vessels having appreciable flow. Examples of application of this technique to healthy and diseased carotid arteries are shown.

Angiography↗
PubMed1988

Time-resolved magnetic resonance angiography.

A time-resolved phase contrast magnetic resonance angiography technique is described. This technique provides a series of angiograms obtained at different phases of the cardiac cycle. Such a series of angiograms can be used to evaluate blood flow dynamics. For example, turbulent flow in the regions of vessel bifurcations is easily demonstrated and followed during systole and diastole. Retrograde flow can also be observed. Dynamic angiography can be particularly useful in distinguishing transient image features, such as signal voids due to turbulent flow, from static features arising from vessel morphology.

Angiography↗
PubMed1970

Interpretation of the [ClIII] Lines in Gaseous Nebulae.

The intensity ratio of the green lambdalambda5517 and 5537 lines of [ClIII] serves as an indicatrix of the electron density in many gaseous nebulae whose spectra can be observed with an image converter. Quantitative interpretation of the line ratio requires accurate values of the collisional strengths and transition probabilities. With improved values of these parameters we have revised electron densities for a number of nebulae; the results seem to be in good accord with those derived from other criteria.

Journal Article↗
PubMedDate not supplied

Animal model of isolated gonadotropin deficiency. I. Hormonal responses to LHRH immunoneutralization.

Five intact male mongrel dogs, characterized by an episodic secretory pattern of LH and normal serum testosterone concentrations, were actively immunized against LHRH by subcutaneous injections of 200 micrograms of a LHRH-human serum albumin conjugate at 0, 4, and 8 weeks. After 12 weeks, two dogs having the highest antibody titers to LHRH (25% and 51% binding of 125I-LHRH in serum diluted 1:1000 B/Bo) had low to nondetectable serum concentrations of LH and testosterone, whereas serum FSH concentrations were significantly reduced in only one of these dogs. Immunocytochemical techniques showed that the pituitaries of these same two dogs had smaller and fewer LH immunoreactive gonadotropes than did the pituitaries of another three immunized-nonaffected dogs or of the five nonimmunized control dogs. The two LHRH-immunized dogs characterized by hypogonadotropism also had reduced testis (4.0 and 4.0 g) and prostate (2.1 and 1.7 g) weights when compared to control dogs (testis: 12.1 +/- 1.0 g and prostate: 9.2 +/- 1.9 g). LHRH antibody titers in three immunized dogs were demonstrable (8.1, 9.8, and 14.2% B/Bo), but effects on LH, FSH, and testosterone concentrations, pituitary gonadotropes, and reproductive tissue weights were not apparent. The similarity in hormonal and tissue responses observed between dogs effectively immunized against LHRH and men with isolated gonadotropin deficiency suggests that the LHRH-immunized dog may provide a suitable experimental model for the study of patients with isolated gonadotropin deficiency.

Animals↗
PubMedDate not supplied

Animal model of isolated gonadotropin deficiency. II. Morphologic responses to LHRH immunoneutralization.

Morphologic changes in the male reproductive system of mongrel dogs immunized against LHRH were quantitated using linear measurements and morphometric techniques at the light-microscopic level. Two experimental groups (5 nonimmunized control animals and 5 actively immunized animals) were killed 12 weeks after the primary immunization. No significant differences were observed between three immunized dogs having low LHRH antibody titers (immunized-unaffected) and the five nonimmunized control dogs. The two immunized dogs (affected) with the highest antibody titers against LHRH were characterized by atrophy and dedifferentiation of the testes, prostate, and excurrent ducts. The morphologic changes in the testes of these two dogs were striking and included an apparent arrest or significant reduction in the spermatogenic process, concurrent epithelial degeneration, and apparent diminution of Leydig cell mass. Drastic reductions in the size of the prostatic acini and epithelial cells, as well as loss of secretory granules, reflected depression of function and androgen production. Similarly, in the excurrent ducts decreases in the measured parameters and loss of regional cytoplasmic specialization denoted functional decrescence. This study demonstrates the regressive effects of LHRH immunoneutralization on the morphology of the reproductive system in the male dog and further supports the feasibility of this system as an animal model for the study of isolated gonadotropin deficiency.

Animals↗
PubMedDate not supplied

Quantitative flow measurement in phase contrast MR angiography.

The quantitative nature of phase contrast magnetic resonance angiography is explored, and a technique of blood flow measurement that is independent of system and patient parameters is presented. Phantom and patient studies demonstrate that quantitative flow measurements by phase contrast angiography can be routinely obtained with good accuracy despite nonuniform sensitivity profiles, blood flow pulsatility, and patient-to-patient changes in system gain. The calibration method requires the acquisition of only two flow images and thus can be performed as part of an angiographic session. Flow calibration of any flow profile can be accomplished with this technique. The solutions for plug flow and parabolic flow are presented.

Adult↗
PubMedDate not supplied

Reacquisition of dressing skills after stroke.

A group of stroke patients were assessed over four occasions using the Nottingham stroke dressing assessment. A similar pattern of difficulty in dressing was found for both males and females. The consistency of ordering of problems was highly significantly correlated in each of the four assessments.

Activities of Daily Living↗
PubMedDate not supplied

The treatment of visual neglect using feedback of eye movements: a pilot study.

Feedback of eye movements was evaluated as a treatment for visual neglect in right hemisphere stroke patients. Patients with visual neglect identified on the Behavioural Inattention Test (BIT) were randomly allocated to two groups. One group (n = 9) was treated for 2 h 40 min a week for 4 weeks, by wearing glasses which provided a reminder bleep if patients failed to move their eyes to the left in a 15 s interval. The control group (n = 9) received no treatment for their visual inattention. Comparison of the groups after 4 weeks treatment and a further 4 weeks follow-up showed no significant difference either in eye movements or on the BIT. However, there was a trend towards a difference between eye movements in the two groups at 8 weeks, suggesting treatment may have influenced eye movements without changing neglect.

Aged↗