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Biomedical subjects

A D Collins

Publications and source records attributed to A D Collins.

At least 19 recordsLinked to original sources
PubMed1999

Effects of Duane's retraction syndrome on sensory visual development.

PURPOSE: To study the effects of Duane's retraction syndrome on sensory visual development. METHODS: Monocular and binocular visual function and ocular motility have been studied and pattern reversal visual evoked potentials recorded from 22 patients with Duane's syndrome aged from 4 to 55 years. RESULTS: Sixteen of the patients maintained binocular single vision using an abnormal head posture. All had normal visual acuities in both eyes. The 12 adults in this group had a mean stereoacuity of 78 seconds of arc with the Titmus stereotest and 101 seconds of arc with the TNO test. Both these values were significantly worse than for normal adults with a similar age range. The binocular VEPs from these patients showed enhancement of the binocular P100 VEP amplitude compared to the mean monocular P100 amplitude when they used their head posture but, unlike in normal subjects, this binocular enhancement was not reduced significantly after the age of 5. Six patients had lost binocular function and had a manifest convergent squint. Of these, 4 were anisometropic. VEPs in this group showed mildly delayed P100 latencies in the affected eye with asymmetric amplitudes even though their amblyopia had been successfully treated by patching and only one patient had a substantially reduced acuity. In neither group was there any relationship between the degree of restriction of ocular motility and the sensory changes. CONCLUSION: Patients with Duane's syndrome who retain binocular single vision show abnormal binocular visual maturation after the age of 5 years. This results in reduced stereoacuity in the absence of amblyopia.

Adolescent↗
PubMed1998

The role of anti-endothelial antibodies in the immunopathogenesis of transplant associated coronary artery disease (Review).

Transplant coronary artery disease (TxCAD) is manifest as a diffuse, concentric intimal proliferation which results in occlusion of the allograft vessel lumen, and is responsible for limiting the long-term success of cardiac transplantation. The recent discovery of high circulating levels of anti-endothelial antibodies (AEAs) in patients with TxCAD has resulted in increased clinical and experimental research interests in understanding their patho-physiological roles in TxCAD. Increasing evidence suggests that AEAs are cross-reactive towards an endothelial protein doublet of 56-58 kDa which has now been characterised and identified as the cytoskeletal protein vimentin. Despite this recent progress the immunopathogenesis of TxCAD remains unclear. In this review recent developments and mechanisms of the involvement of AEAs in the immunopathogenesis of TxCAD are discussed.

Animals↗
PubMed1996

Localisation of a gene for central areolar choroidal dystrophy to chromosome 17p.

Central areolar choroidal dystrophy (CACD) is a rare inherited retinal disease which causes progressive profound loss of vision in patients during their 4th decade. We have identified a Northern Irish family with 19 affected individuals in three living generations. We have performed a total genome search and established linkage of CACD in this family to chromosome 17p (multipoint Zmax = 5.65 at D17S938). The genes for phosphatidylinositol transfer protein (PITPN), retinal guanylate cyclase (GUC2D), beta-arrestin 2 (ARRB2), pigment epithelium-derived factor (PEDF) and recoverin (RCV1) map to this region and are candidate genes for retinal disease. Analysis of the coding region of the PITPN gene failed to reveal any mutation in this family.

Arrestins↗
PubMed1995

Delayed visual evoked potentials in adults after monocular visual deprivation by a dense cataract.

PURPOSE: To study the effect of monocular visual deprivation caused by dense unilateral cataracts in adults. METHODS: Visual evoked potentials have been recorded in 11 patients after removal of a dense unilateral cataract acquired in adulthood. These were compared with those from 8 control patients after removal of a mild lens opacity. RESULTS: Visual evoked potentials recorded on the first day after removal of a longstanding, dense, unilateral cataract showed a marked delay to stimulation of the operated eye compared to the unoperated eye. No delay was found in the operated or unoperated eye of control patients. Delays in the visual evoked potential returned to normal within approximately 3 months after surgery, with the exception of the two patients with the most longstanding cataracts in whom the delays persisted much longer. CONCLUSIONS: The adult central visual system is sensitive to visual deprivation caused by a longstanding, dense, unilateral cataract. The changes found may be important in understanding the causes of intractable diplopia, which sometimes occurs after the removal of such cataracts.

Adult↗
PubMed1994

Binocular enhancement of the visual evoked potential in patients with Duane's syndrome.

Monocular and binocular visual evoked potentials were recorded in eight patients with Duane's syndrome who used an abnormal head posture to maintain binocular single vision. With their abnormal head posture, all patients had stereoscopic vision, although with mildly reduced stereoacuity, and the visual evoked potential showed binocular enhancement (mean binocular to monocular ratio, 1.44). Without their head posture, the patients experienced diplopia or suppressed vision in one eye. Binocular visual evoked potentials recorded under these conditions were of lower amplitude (mean binocular to monocular ratio, 1.05). However, without the abnormal head posture, a manifest strabismus was present and the deviating eye was not fixating the stimulus screen. Monocular visual evoked potentials recorded with the eye fixating just to one side of the screen gave little or no response, and this lack of fixation may account for the loss of binocular enhancement of the visual evoked potential in strabismus.

Adult↗
PubMed1993

Pseudorandom binary sequence stimulation applied to the visual evoked response. Normative data and a comparative study with pattern and flash stimulation.

The investigation of patients who are unable to fixate the pattern visual stimulus generally requires the use of diffuse flash stimulation to elicit the visual evoked response. However, by comparison with pattern, flash stimulation has proved relatively insensitive in identifying lesions of the visual pathway. We investigated a more complex method of flash stimulation. A pseudorandom binary sequence has been used to generate the diffuse visual evoked response stimulus. The pseudorandom binary sequence, rather than producing a single flash, switches in a pseudorandom fashion between two levels of illumination. The result is a diffuse visual stimulus approximating band-limited white noise. The series is periodic, enabling signal averaging to be performed. By applying the methods of random signal analysis, the impulse or transient response of the visual pathway can be determined. Our normal pseudo-random binary sequence visual evoked response impulse function, derived from 29 normal subjects, had the morphologic characteristics of the conventional flash visual evoked response and a major positive component (P100), whose latency mean and standard deviation closely matched that of our normative pattern visual evoked response. However, the P100 amplitude standard deviation was significantly greater than that produced by conventional pattern and flash stimulation. We investigated 140 patients by means of pattern, flash and pseudorandom binary sequence stimulation. The pseudorandom binary sequence visual evoked response proved to be almost 12 times more effective than flash visual evoked response in detecting lesions of the visual system.

Adolescent↗
PubMed1987

Electrical injury of the eye.

A 17-year-old male suffered superficial and deep facial burns after coming into contact with a high tension electrical cable with his head and right side of the face. The right eye sustained severe thermal coagulative injuries and subsequently was enucleated. Histopathological examination showed that the retinal neuropile was relatively intact although the retinal and choroidal circulations were severely compromised. The left eye was less affected but a dense cataract developed and required lensectomy. Visual acuity remained poor in the left eye due to retinal atrophy, retinal vascular attenuation and optic nerve degeneration. Electroretinographic tests and pseudo-random binary stimulus visually evoked responses were useful in predicting the visual outcome.

Adolescent↗
PubMed1987

An experimental study of quinine blindness.

An experimental model of quinine induced blindness is presented. Electrophysiological, angiographical and morphological examinations were made. The occurrence of blindness and any recovery from blindness was dependent upon the dose of quinine taken. As no evidence of acute retinal ischaemia was found it is concluded that quinine is retinotoxic.

Animals↗
PubMed1976

Isoproterenol, endotoxin shock, and the generalized shwartzman reaction.

Adult hybrid albino rabbits were divided into seven groups. Three groups were given two respective intravenous doses of 10 mug, 25 mug, or 100 mug of endotoxin at an interval of 24 hours. Three other groups were given endotoxin as above, and, in addition, were given 0.5 mg of isoproterenol hydrochloride (Isuprel) by subcutaneous injections at eight-hour intervals beginning at the time of the first injection of endotoxin. A single group was given isoproterenol only. The animals were observed for clinical signs of shock beginning at the time of the first injection of endotoxin. The mortality during the course of the experiment was noted. At the time of death, the animals were studied grossly, and sections were taken for light microscopy. Results showed no meaningful enhancement of endotoxin toxicity as manifested by shock, generalized Shwartzman reaction, or mortality.

Animals↗
PubMed1975

The site of metal ion binding in a nickel derivative of adenosine 5'-monophosphate: an x-ray study.

Single-crystal X-ray methods have been used to characterize a nickel derivative of adenosine 5'-monophosphate, of stoicheiometry [Ni(5'-AMP)(H2O)5]-H2O. The metal atom binds to the N(7) position on the adenine base, with the five remaining octahedral coordination sites about nickel occupied by water molecules. The phosphate group is connected via intramolecular hydrogen bonds to coordinated water molecules.

Adenosine Monophosphate↗
PubMedDate not supplied

Electrophysiology findings in a large family with central areolar choroidal dystrophy.

PURPOSE: To perform an electrophysiological study of central areolar choroidal dystrophy (CACD) in the affected members of a four generation family. METHODS: Eight affected family members from the last three generations of a family affected by CACD were assessed by full-field electroretinograms (rod response, maximal combined response, oscillatory potentials, single-flash cone response and 30 Hz flicker responses) and electro-oculograms. In addition three members of the youngest generation, who were visually asymptomatic, had pattern visual evoked potentials (PVEPs) and pattern electroretinograms (PERGs) performed. Affected status had been determined previously by genetic analysis. RESULTS: Three youngest generation family members, who were considered affected by genetic haplotype analysis, had no visible optic nerve or retinal abnormalities. All of these subjects had abnormal PVEPs and PERGs in both eyes. Abnormalities were also detected in two of these subject's Rod ERGs, Cone ERGs and one of these subject's Maximal ERGs and 30 Hz ERGs. Electrophysiological examination in the older generations demonstrated a similar, more advanced, cone and rod dysfunction. CONCLUSIONS: All affected, but clinically normal, youngest generation patients had bilaterally abnormal PVEPs and PERGs. In CACD the PVEP and PERG proved to be the most sensitive electrophysiological tests of preclincial macular dysfunction, 3/3 subjects abnormal. ERG recording to ISCEV guidelines were very useful in these cases; 7/8 subjects abnormal. The EOG was less useful; 4/8 subjects abnormal. CACD produces a widespread photoreceptor dysfunction in its later stages.

Adolescent↗