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Biomedical subjects

D E Mitchell

Publications and source records attributed to D E Mitchell.

88 records · Page 5Linked to original sources
PubMed1972

A neural effect of partial visual deprivation in humans.

Certain human subjects have considerable sensitivity differences in the visual resolution of vertical gratings as compared to horizontal gratings. Although only subjects with pronounced ocular astigmatism exhibit this effect, the differences are of neural, rather than optical, origin. It is argued that the resolution anisotropies result from early abnormal visual input caused by astigmatism. This abnormal input permanently modifies the brain.

Astigmatism↗
PubMedDate not supplied

Bilateral amblyopia after a short period of reverse occlusion in kittens.

The majority of neurones in the visual cortex of both adult cats and kittens can be excited by visual stimulation of either eye. Nevertheless, if one eye is deprived of patterned vision early in life, most cortical cells can only be activated by visual stimuli presented to the nondeprived eye and behaviourally the deprived eye is apparently useless. Although the consequences of monocular deprivation can be severe, they can in many circumstances be rapidly reversed with the early implementation of reverse occlusion which forces the use of the initially deprived eye. However, by itself reverse occlusion does not restore a normal distribution of cortical ocular dominance and only promotes visual recovery in one eye. In an effort to find a procedure that might restore good binocular vision, we have examined the effects on acuity and cortical ocular dominance of a short, but physiologically optimal period of reverse occlusion, followed by a period of binocular vision beginning at 7.5 weeks of age. Surprisingly, despite the early introduction of binocular vision, both eyes attained acuities that were only approximately 1/3 of normal acuity levels. Despite the severe bilateral amblyopia, cortical ocular dominance appeared similar to that of normal cats. This is the first demonstration of severe bilateral amblyopia following consecutive periods of monocular occlusion.

Amblyopia↗
PubMedDate not supplied

An improved measurement of progesterone in saliva and clinical applications.

Measurement of progesterone in saliva offers several advantages when compared to assays of serum progesterone, especially when ovarian activity is being assessed. Most published methods for the determination of progesterone in saliva are based on assays developed in research centers, which employ "in-house" reagents that are critically dependent on supplies of highly selected antisera. In this report, the adaptation of a readily available commercial progesterone "kit", the Pantex Immunodirect Progesterone (125I) is described for the measurement of salivary progesterone. A single extraction step was added, however, to improve assay performance and to ensure that total salivary progesterone was measured.

Female↗