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Biomedical subjects

D R Anderson

Publications and source records attributed to D R Anderson.

At least 271 records · Page 15Linked to original sources
PubMed1980

Distribution of albumin in the normal monkey eye as revealed by Evans blue fluorescence microscopy.

Since intravenously injected Evans blue binds irreversibly to serum albumin, its distribution reflects albumin exchange between the intravascular and extravascular tissue compartments. In histologic specimens examined by fluorescence, microscopy, extravasated Evans blue--albumin complex was identified within the ciliary body and trabecular meshwork of normal monkey eyes. In eyes fixed by intra-arterial perfusion of fixative, no dye was identified in the choroid, retina, or optic nerve. With immersion fixation, however, some extravasation was seen in the choroid and adjacent optic nerve. In some specimens, the optic nerve was stained not only with material apparently leaking from the choroid but also from a breakdown of the blood-brain barrier in the major disc vasculature during the interval before fixative penetrates into the tissue. Perfusion fixation must be used to avoid this artifact, and freezing techniques would be even better.

Animals↗
PubMed1979

Blockade of rapid axonal transport. Effect of intraocular pressure elevation in primate optic nerve.

After acute intraocular pressure (IOP) elevation, an induced disturbance of rapid axonal transport at the optic nerve head began within three hours at the IOP levels tested. The accumulation of radioactive label at the scleral lamina cribrosa increased with time of IOP elevation. There was a 60% decrease in the amount of transported material in the optic nerve, tract, and lateral geniculate body (LGN). Detailed analysis suggests that this decrease is not due to a simple slowdown of transport, but results from a total block of rapid transport in some axons, with no impairment in other axons. This total blockade of rapid transport by elevated IOP in involved axons differs from the apparent slowdown of transport in experimental papilledema, and the difference may explain the response of ganglion cells to the two conditions.

Animals↗
PubMed1979

The mechanism of disc pallor in experimental optic atrophy. A fluorescein angiographic study.

Ascending optic atrophy was produced in 13 eyes of owl monkeys (Aotestrivirgatus) by retinal photocoagulation. Color fundus photography and fluorescein angiography were used to study and document the evolution of nerve head abnormalities. The optic nerve heads were also studied histopathologically. Except in certain instances of early transient (relative) filling defects, normal disc fluorescent patterns were preserved, despite clinically apparent optic nerve head pallor. Sectorial defects did not persist into the later phases of the angiogram. These findings may suggest a reduced blood flow, but neither angiographic nor histopathologic studies detected a reduced vascularity in the atrophic optic nerve. Pallor of the optic nerve head seems to result from alterations in the tissue reflectance and translucency following axonal loss and glial reorganization rather than from a decreased microvascular bed.

Animals↗
PubMed1979

The histology of retinal nerve fiber layer bundles and bundle defects.

The fiber bundle striations recognized clinically in normal monkey eyes appear to be bundles of axons compartmentalized within glial tunnels formed by Müller's-cell processes, when viewed histologically. The dark boundaries that separate individual bundles are the broadened foot endings of these cells near the inner surface of the retina. Within one week after focal retinal photocoagulation, characteristic fundus changes could be seen in experimental eyes. In histologic sections of the involved retina, there was marked cystic degeneration of the retinal nerve fiber layer. Within one month, atrophy of distal axon segments was complete. With the drop-out of damaged axons and thinning of individual fiber bundles, retinal striations became less prominent. The resulting fundus picture in these experimental eyes is similar to fiber bundle defects that can be seen clinically in various neuro-ophthalmic disorders.

Animals↗
PubMed1979

The course of axons through the retina and optic nerve head.

By identifying degenerating axons in tissue specimens from 22 primate eyes, it was possible to demonstrate the normal course of axon fibers. Nerve fiber bundles from a group of retinal ganglion cells travel together with little tendency to disperse laterally. In addition, axons are stratified such that processes from more central ganglion cells are successfully added to the inner strata of the retinal nerve fiber layer. Within and behind the lamina cribrosa, areas of degeneration following retinal photocoagulation were well circumscribed and confined to a group of adjacent axon bundles. This degree of retinotopic organization of axons within the nerve head and retinal fiber layer is believed to be consistent with the premise that isolated lesions within the lamina cribrosa could cause well-organized paracentral scotomas such as those characteristic of early glaucoma.

Animals↗
PubMed1979

The relationship of visual attention to children's comprehension of television.

The study experimentally tested the relationship between visual attention and comprehension of a TV program. 72 5-year-old children watched a 40-min version of the TV program "Sesame Street." Half the children viewed the program in the presence of a variety of toys and half viewed without toys. The children were then tested for their comprehension of the program. Although visual attention to the TV in the no-toys group was nearly twice that in the toys group, there was no difference between the groups in comprehension. There were, nevertheless, significant within-group correlations between visual attention and comprehension even for questions concerning only auditorily presented material. The results were interpreted as indicating that in a normal TV viewing setting, variations in the comprehensibility of the TV program may determine variations in children's attention to the TV.

Attention↗
PubMed1978

Clinical evaluation of the 6600 Autorefractor.

The 6600 Autorefractor was evaluated on 200 patients undergoing refraction. The automatic refractor showed a high degree of accuracy in determining the needed refractive correction, but the errors are sufficient that the automatic refractor alone without subjective refinement cannot be substituted for conventional complete refracting methods with subjective refinement. However, for aphakic patients and for patients with clear media and cylindric corrections over 0.50 diopters, the automatic refractor can be used as a substitute for retinoscopy in determining the starting point for a subjective refraction.

Adolescent↗
PubMed1978

Is the Autorefractor reading closest to manifest refraction? A comparison of the patient's previous spectacles and the 6600 Autorefractor reading.

In a study of 56 patients, the old glasses of a previously refracted individual were as close to the final subjective refraction as the reading obtained with a 6600 Autorefractor. Therefore, the previous spectacle correction might logically be used for the starting point of a subjective refraction, with retinoscopy or automatic refractor results being used for this purpose in patients whose previous spectacle refraction is unknown or in the first refraction of an aphakic patients.

Computers↗
PubMed1978

Retinal ganglion cell degeneration in experimental optic atrophy.

By ophthalmoscopic and histopathologic examinations at various intervals after retinal injury, we studied progressive ganglion cell atrophy following retinal photocoagulation in 25 owl monkey eyes. A reduced ganglion cell population was apparent within three to four weeks after the photocoagulation and was maximal by six weeks.

Animals↗
PubMed1978

The effect of biogenic monomines on rapid axonal transport in the rabbit optic nerve.

Since L-dopa and serotonin have been reported to increase the rate of axonal transport in rat sciatic nerve, we decided to study the effect of these monoamines on rapid orthograde transport in the rattit optic nerve. To do this, tritiated leucine was injected into the vitreous of both eyes of 56 albino rabbits, and arrival of radioactive labeled proteins at the superior colliculus was measured at various intervals by liquid scintillation counting. Rabbits were studied 24 hr after intraperitoneal injections of (1) Sinemet + L-dopa, (2) Sinemet + 5-hydroxytryptophan, or (3) pargyline. There were 14 rabbits in each group compared to 14 controls that received no monoamies. In the monoamine-treated groups, transported labeled proteins arrived at the superior colliculus earlier, and an increased amount of radioactivity accumulated during the next several hours. The maximum amount of radioactive proteins accumulating in drug-treated animals did not differ significantly from the maximum amount in control animals. As judged by autoradiographic densitometry, retinal ganglion cell synthesis was similar in control and drug-treated animals. We suspect that the rate of rapid axonal transport is increased by monoamines, although an increased rate of ganglion cell protein synthesis is another possibility.

5-Hydroxytryptophan↗
PubMed1977

Short-term dose response characteristics of acetazolamide in man.

Nine patients with ocular hypertension each randomly received on separate days 0, 63, 125, 250, and 500 mg of acetazolamide (Diamox). In a double masked manner, acetazolamide plasma levels and intraocular pressure were monitored for seven hours following administration. Plasma levels increased linearly with dose, reaching 30 microgram/ml with the 500-mg dose. Maximum plasma levels occurred at one hour, and the minimum IOP was at two hours. The maximum IOP effect was a 30% to 35% fall. The IOP response was related to dose and plasma level, up to a 63-mg dose, which produced an average fall of 8.2 mm Hg. Little further average effect was documented at higher doses or plasma levels. The duration of response was slightly prolonged by 250 mg, but 500 mg showed no greater response. Thus, a 63-mg dose or a plasma level of 4 to 5 microgram/ml was as effective in lowering IOP as higher doses that produced plasma levels of 10 microgram/ml or more.

Acetazolamide↗
PubMed1977

The histologic basis of optic disk pallor in experimental optic atrophy.

We studied the clinical and microscopic appearances of the optic nerve head in squirrel monkeys with optic nerve degeneration produced by optic nerve transection at the orbital apex. The ophthalmoscopic development of optic disk pallor coincided with the loss of nerve fiber bundles and the rearrangement of the remaining disk astrocytes into dense parallel layers across the nerve head. No astrocytic mitoses were observed and the estimated volume of astrocytes increased only slightly from normal. Among the astrocytes in atrophic disks, many capillaries had patent lumens and ultrastructurally normal endothelial cells. Pallor of the optic disk seems to result from a decrease in the transmission of light into the cytoarchitecture of the atrophic nerve head, not from the absence of capillaries or from extensive astrocytic proliferation.

Animals↗
PubMed1977

Descending optic nerve degeneration in primates.

We cut the optic nerve at the orbital apex in squirrel monkeys to study the descending degeneration of optic nerve axons and their ganglion cell bodies. We could not detect progressive disintegration of the axon from the site of injury back to the cell body. Instead, the entire length of individual axons seemed to degenerate simultaneously as early as 3 weeks and as late as 6 weeks after injury, as judged both by ultrastructural integrity and by continued slow axonal transport, a reflection of local physiologic function. We could not relate the time of degeneration to the distance of the injury from the cell body. Evidently there is a signal of injury to the cell body after axotomy, though the nature of the signal and the mechanism by which it leads to cell death are unknown.

Animals↗