Biomedical subjects
D McLeod
Publications and source records attributed to D McLeod.
Extraction and characterisation of the intact form of bovine vitreous type IX collagen.
We provide the first biochemical characterisation of intact type IX collagen extracted from bovine vitreous. It possesses a shortened alpha 1(IX) chain (M(r) 64K) compared to its cartilage counterpart (M(r) 84K). All the vitreous type IX collagen is in a proteoglycan form, its glycosaminoglycan constituent being a chondroitin/dermatan sulphate component of M(r) 15-60K attached to the alpha 2(IX) chain. This contrasts with previous findings in chick vitreous where a very long glycosaminoglycan chain of M(r) approximately 350K was demonstrated.
Modulators and milieu in preretinal neovascularisation.
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Prolongation of rat corneal graft survival by treatment with anti-CD4 monoclonal antibody.
A rat model of orthotopic corneal graft rejection was used to investigate the effect of depletion of subpopulations of immune cells by treatment with monoclonal antibodies. Though CD4+ cells were not eliminated completely by anti-CD4 monoclonal antibodies there was a profound delay in the rejection times of orthotopic corneal allografts. Furthermore a third of the CD4+ depleted animals failed to reject corneal allografts by 100 days post grafting. Despite an almost complete depletion of circulating CD8+ cells, the anti-CD8 antibody treated animals rejected corneal allografts in a similar time course to allografted controls treated with a non-reactive control antibody OX21. These results demonstrate that CD8+ T-cells are not required for rejection of corneal allografts whereas CD4+ T-cells play a critical role in the rejection response. Treatment with anti-CD4 antibodies may have a useful clinical application.
The effect of blood transfusions on rat corneal graft survival.
To determine whether a preoperative blood transfusion could influence corneal graft rejection, full-thickness 3 mm orthotopic corneal grafts were performed in Dark Agouti (DA) rats from syngeneic (DA) or allogeneic (Brown Norway and Lewis) inbred donors and in Lewis rats from syngeneic (Lewis) or allogeneic (DA) donors. Rats with syngeneic grafts showed no signs of rejection. The corneal buttons remained clear indefinitely, although vessels grew up to the wound. All allogeneic grafts in nontransfused rats rejected between 6 and 25 d (the interval depended on the strain combination). The median survival of BN to DA grafts was 9 d, and the median survival of Lewis to DA grafts was 7 d. Therefore, both can be described as high responder strain combinations. The DA to Lewis grafts survived longer, with a median survival of 15 d. This was described as a low responder strain combination. A single preoperative transfusion of blood from the same strain as the corneal graft donor prolonged the survival of corneal allografts in the two high responder combinations, an effect called active enhancement. However, a blood transfusion did not enhance the survival of allografts in the Lewis rat. Corneal grafts from animals of a third party strain were not enhanced but were rejected, following the same time course as nontransfused controls. Thus, preoperative donor-specific blood transfusion specifically delayed the immune response to corneal allografts in some strain combinations but not in others. This may limit the clinical application of this technique.
Injected corticosteroids in refractory asthma.
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Effect of varying oxygen concentrations on the proliferation of retinal microvascular cells in vitro.
Microvascular fragments and pure cultures of either retinal microvascular endothelial cells, retinal pericytes or Tenon's capsule fibroblasts were grown on a gas permeable substrate while exposed to varying oxygen concentrations (5, 10, 20, 40 and 95% oxygen). For all three cell types cell proliferation was greatest under the lowest oxygen concentration and decreased as the oxygen concentration increased. The decrease in the proliferative ability of cells exposed to the higher oxygen concentrations could be reversed if the cells were returned to a normoxic environment. Endothelial cells were the most sensitive to changes in oxygen tensions showing a proliferative response after 24 hr exposure as opposed to 48 hr for pericytes and fibroblasts. These results suggest a direct mechanism by which the intra-vitreal and intra-retinal oxygen tension may influence both the development of preretinal new vessels (in response to retinal ischaemia) and also the regression of neovascularization following scatter photocoagulation or vitrectomy.
Microsurgical management of neovascularisation secondary to posterior segment ischaemia.
Structural, metabolic and functional rehabilitation of eyes affected by the haemorrhagic and tractional sequelae of neovascularisation secondary to posterior segment ischaemia is discussed. Microsurgical management must pay due attention not only to the mechanical but also to the underlying cell-biological implications of the surgical pathology. The appropriateness of case selection for surgery rests upon the likelihood of successful technical and functional outcomes and also upon the overall visual status of the patient, issues of particular relevance to diabetes.
Extraction of the intact form of type IX collagen from mammalian vitreous.
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Inhibition of microvascular endothelial cell proliferation by vitreous following retinal scatter photocoagulation.
Laser photocoagulation of pig retina induced breakdown of the blood-retinal barrier, with the appearance of serum proteins in the vitreous as determined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting techniques. Vitreous from lasered eyes inhibited the proliferation of cultured retinal microvascular endothelial cells in comparison with vitreous from non-lasered control eyes, and the inhibitory effect in the lasered eyes persisted for at least seven days. Inhibition was specific for endothelial cells, since no effect was observed when retinal pericytes or Tenon's fibroblasts were the target cells. These results suggest that indirect scatter photocoagulation may induce regression of neovascularisation by causing breakdown of the blood-retinal barrier and thus releasing into the vitreous serum components which result in inhibition of retinal microvascular endothelial cell growth.
Ultrasonic examination in severe diabetic eye disease.
B-scan ultrasound of the posterior segment is reported in 154 patients with severe diabetic eye disease. Epiretinal fibrosis, vitreous haemorrhage, vitreous detachment, and retinal detachment were frequently diagnosed. The ultrasonic findings are discussed in relation to the pathological changes in the vitreous in proliferative diabetic retinopathy.
B-scan ultrasound in massive preretinal retraction.
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Complications of explants used in retinal detachment surgery.
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Vitreo-retinal traction associated with intraocular foreign bodies.
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