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Biomedical subjects

D R Anderson

Publications and source records attributed to D R Anderson.

At least 289 records · Page 16Linked to original sources
PubMed1977

Failure of increased intracranial pressure to affect rapid axonal transport at the optic nerve head.

In owl monkeys, elevation of intracranial pressure to 500 mm. saline for 4 to 7 hours failed to cause an accumulation at the optic nerve head of protein carried by rapid axonal transport. This suggests that the block of rapid transport observed by others during papilledema may be the result of axon swelling, not its cause. Alternatively, more than 8 hours may be required for intracranial pressure to show an effect, only the slow transport may be affected initially, or other factors than simple hydrostatic pressure may be operative in papilledema. In addition, the elevated intracranial pressure did not prevent the block of axonal transport at the lamina cribrosa produced by elevated intraocular pressure, even though the elevated intracranial pressure reduced the pressure gradient to which the axon is subjected as it crosses the lamina cribrosa. Perhaps the block produced by intraocular pressure is not due to a simple mechanical or hydrostatic mechanism.

Animals↗
PubMed1977

Distribution of axonal transport blockade by acute intraocular pressure elevation in the primate optic nerve head.

We studied the degree of axonal transport blockade in various areas of the optic nerve head with acute intraocular pressure (IOP) elevation in 19 squirrel monkey eyes. When IOP was raised to 20 to 50 mm. Hg for 7 hr., mild axonal transport blockade occurred in each area of the disk, most prominently in nerve fiber bundles of the superior pole. With 7 hr. IOP elevations between 50 and 90 mm. Hg, a somewhat greater degree of transport blockade occurred throughout the nerve head, although again the superior and inferior poles were somewhat more affected. The distribution of short-term transport blockade over the entire nerve head corresponds to the diffuse damage of acute glaucoma, but the pattern hints at the preference for damage near the poles of the disk seen in chronic glaucoma. However, before these results can be fully evaluated, further information is needed on axonal pathways through the optic nerve head and on the relationship between transport obstruction and ganglion cell death.

Animals↗
PubMed1976

Effect of the intraocular lens on intraocular pressure.

In the Miami Intraocular Lens Collaborative Study, 17 patients with glaucoma had a Copeland lens implanted at the time of cataract extraction. Seven additional glaucoma patients received a Binkhorst lens. Lens implantation did not adversely affect intraocular pressure or control of glaucoma, except in one patient who developed central retinal artery occlusion with rubeosis 1 1/2 years postoperatively and in one patient who had the lens removed because of iritis with uncontrolled glaucoma. Of 606 eyes that did not have glaucoma before cataract extraction and Copeland lens implant, many had transient postoperative pressure rise. Twenty-six (4.3%) developed prolonged pressure elevation. Nineteen patients were maintained on long-term medical therapy. The other seven were patients with iritis and glaucoma who had the implanted lens removed, including one who later had glaucoma surgery and one whose eye was later enucleated.

Arterial Occlusive Diseases↗
PubMed1976

Surgical decisions in chronic angle-closure glaucoma.

A retrospective study of 57 eyes with chronic angle-closure showed that eyes with visual field loss are less likely to be improved by iridectomy than those without visual field loss in the presence of visual field loss, trabeculectomy achieved more satisfactory control of glaucoma than did iridectomy, and there was no noticeable difference in surgical complications between iridectomy and trabeculectomy in this small series. It is suggested that iridectomy is indicated for most cases of chronic angle closure without visual field loss, especially if the pressure is medically controllable. In the presence of visual field loss, iridectomy is usually a wise choice if medical control is easily achieved preoperatively. However, trabeculectomy might be the best choice in most patients with visual field loss and medically uncontrolled pressure, regardless of the gonioscopic findings.

Glaucoma↗
PubMed1976

Reevaluation of the optic disk vasculature.

The optic disk vessels of owl monkeys and humans were studied in whole mounts injected with silicone rubber and by serial sections of paraffin-embedded tissue. The capillary bed of the optic nerve head in continuous on one side with the retinal vessels and on the other side with the optic nerve behind the globe. The choriocapillaris is a separate capillary bed, even though it and the disk capillaries are both supplied by branches of the posterior ciliary artery. At the junction between choroid and optic disk is a cuff of vessels that seems equivalent to an anterior extension of the pial vessels. This cuff includes capillaries of the central nervous system, was well as arterial branches of the posterior ciliary artery that pass retrograde from the peripapillary choroid and sclera into the pial plexus. While not contradicting previous descriptions of the vascular anatomy in this region, we emphasized that the microvascular bed of the disk is anatomically an integral part of the retina-optic nerve vascular system and deemphasized its relationship to the choroidal vasculature.

Animals↗
PubMed1976

The dynamics and location of axonal transport blockade by acute intraocular pressure elevation in primate optic nerve.

Axonal transport in primate optic nerve axons was studied by autoradiography, scintillation counting, and electron microscopy under conditions of short-term intraocular pressure elevation. With elevation of intraocular pressure to 30 mm. Hg below mean arterial blood pressure, blockage of transport was detected within 2 hours by autoradiography and within 1 hour by electron microscopy. The earliest buildup of radioactively labeled protein and ultrastructurally visible cellular organelles was within the scleral lamina cribrosa. The degree of blockage, judged by amount of label buildup, increased with time. Some transported material traversed the lamina cribrosa despite pressure elevation at the level tested. Reversal of transport blockade occurred rapidly after normalization of intraocular pressure.

Acute Disease↗
PubMed1976

Mathematical models for nonparametric inferences from line transect data.

A general mathematical theory of line transects is develoepd which supplies a framework for nonparametric density estimation based on either right angle or sighting distances. The probability of observing a point given its right angle distance (y) from the line is generalized to an arbitrary function g(y). Given only that g(O) = 1, it is shown there are nonparametric approaches to density estimation using the observed right angle distances. The model is then generalized to include sighting distances (r). Let f(y/r) be the conditional distribution of right angle distance given sighting distance. It is shown that nonparametric estimation based only on sighting distances requires we know the transformation of r given by f(O/r).

Animals↗
PubMed1975

Calcium-promoted aggregation of erythrocyte membrane proteins.

Introduction of Ca2+ (greater than 1 mM) into erythrocytes during hemolysis causes formation of an aggregate which is highly resistant to disruption by sodium dodecyl-sulfate and other denaturing agents. The process is temperature dependent, but it does not require incubation in isotonic medium. Aggregation can be prevented but not reversed with chelating agents such as ATP or EDTA. The aggregate can be isolated by chromatography in dodecylsulfate on Sepharose 4B. Its amino acid composition indicates that it contains spectrin as the primary, but not exclusive, polypeptide component. Aggregate formation does not require increased Ca2+ binding to the membranes, and no 45Ca2+ could be detected in the aggregate which had been separated by acrylamide electrophoresis on sodium dodecylsulfate. This indicates that the Ca2+ is important in the formation of the aggregate, but not in its stabilization or maintenance once it has been formed.

Amino Acids↗
PubMed1975

Sensitivities of ocular tissues to acute pressure-induced ischemia.

Intraocular pressure was artificially elevated for eight hours in eight owl monkeys. The first permanent effect (produced at a perfusion pressure of plus 15 mm Hg) was partial necrosis of iris stroma and ciliary processes, associated with microscopic lesions in the photoreceptors and retina pigment epithelium around the disc and in the retinal periphery. At a slightly higher pressure, visual nerve fibers in the retina and optic nerve and their ganglion cells were affected. Simultaneously, the outer retinal layers showed damage to the pigment epithelium, photoreceptors, and other nuclear layers. At even higher pressures, nearly all the other intraocular tissues were affected except for Müller cells, astroglia in the optic nerve head, epithelium of the pars plana, and the pigment cells of the choroid. The possibility is raised of a nonischemic pressure-induced mechanism for destruction of disc astrocytes in human chronic glaucoma.

Acute Disease↗
PubMed1975

Laser iridotomy for aphakic pupillary block.

In six patients with aphakic pupillary block, argon laser produced full-thickness iridotomies that succeeded in restoring anterior chamber and intraocular pressure to normal. In one case, it was shown that location of iridotomy is important in determining whether or not iridotomy will succeed in relieving aphakic pupillary block. In two cases, pupillary block had resulted in shallowing of the anterior chamber without pressure elevation. Cases reported here show that continuous laser energy, such as from an argon laser, can produce a full-thickness opening, in contrast to the short duration pulse of the ruby, which will destroy only pigmented structures without producing a full-thickness iris opening. This need to produce some degree of spread of damage to unpigmented tissue elements in order to achieve and iris opening is a problem in phakic patients where injury to the lens must be avoided.

Aged↗
PubMed1975

Malignant glaucoma" in an eye with no antecedent operation or miotics.

The diagnosis of malignant glaucoma was entertained preoperatively in a patient with no previous history of glaucoma surgery or use of miotics. The marked asymmetry in the anterior chamber depth and angle configuration between the two eyes was the significant clue. The findings at operation confirmed the diagnosis. The closure of the angle appeared to be due to retrovitreal fluid displacing the vitreous and the iris-lens diaphram forward.

Aged↗
PubMed1975

Comparison of 125I-labelled fibrinogen uptake and venography in the detection of recent deep-vein thrombosis in the legs.

Both techniques were used to examine 72 legs, and agreed about the presence or absence of thrombus in 54 cases (72 per cent). In 41 legs both tests were positive and in 13 legs both tests were negative. In 16 legs the 125I fibrinogen test only was positive, and if the seven legs with clinical conditions known to increase fibrinogen uptake are excluded, there were nine legs (13 per cent) with an increased fibrinogen uptake in the calf and a normal venogram. In two legs the venogram only was positive, and in both cases there was evidence of clot retraction which suggested that the thrombus was more than a week old. The use of radio-opaque markers attached to the skin made it possible to compare the site of thrombosis detected by the two techniques and the results of this comparison indicate that the fibrinogen test underestimated the extent of femoral vein thrombosis in a significant proportion of cases. (p less than 0-001).

Adolescent↗