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Biomedical subjects

E L Howes

Publications and source records attributed to E L Howes.

At least 73 records · Page 4Linked to original sources
PubMed1978

Histopathology of delayed hypersensitivity reacitons in the guinea pig uveal tract.

Two distinct patterns of delayed-onset, cell-mediated hypersensitivity have been induced in the guinea pig eye with the same soluble protein antigen and two different methods of immunization. The predominant histologic feature of these reactions was the large number of eosinophils which infiltrated the uveal tract and the limbus. Skin test reactions in the same animals contained very few eosinophils and were typical of cutaneous basophil hypersensitivity or classic delayed hypersensitivity of the tuberculin type. It is suggested that local factors play a role in determining the character of immune expression in different tissues.

Animals↗
PubMed1977

Diverse effects of triamicinolone on the ocular response to circulating endotoxin.

The ocular response to circulating bacterial endotoxin (E coli 055:B5, 100 microgram/kg) can be either significantly reduced or made more servere by pretreatment with the synthetic glucocorticoid triamcinolone. A single injection (25 mg/kg) 3 hr prior to endotoxin sharply curtails the response. Daily injections for 3 days preceding endotoxin produces an enhanced response. With this regimen, an enhanced alteration in ocular vascular permeability is produced 4 hr following endotoxin if 5 mg of triamcinolone is injected daily; if larger quantities of steroid are employed (25 mg), there is a slight reduction in ocular vascular permeability, but an enhanced intravascular fibrin accumulation in ocular blood vessels as well as in capillaries of renal glomeruli (generalised Shwartzman reaction). Once the enhancement of the ocular response to endotoxin has been established by prior treatment with steroids, additional triamcinolone given 2--3 hr before endotoxin is no longer effective in protecting against ocular or renal changes. These divergent effects of steroid could be produced by either subcutaneous or intra-orbital injection, and the response was equal in both eyes following intra-orbital injection, suggesting that steroids probably do not exert their effects locally in this situation. Although different mechanisms of action of corticosteroids may be responsible for these diverse effects, it is suggested that a loss of responsiveness to steroids may be important in their ability to enhance the effects of endotoxinemia.

Animals↗
PubMed1977

Effect of hypovolemic shock on the generalized Shwartzman reaction.

The generalized Shwartzman reaction was produced in rabbits by two intravenous injections of endotoxin given 20-22 h apart. Prior to the second injection of endotoxin, the animals were made hypovolemic by removal of 40% blood volume or reduction of the systolic pressure to 70% of normal whichever came first. This blood removal produced a persistent hypotensive episode. 8/9 rabbits made hypotensive in this manner had evidence of glomerular capillary thrombi compared to 8/8 in a group that did not have blood removed. It is concluded that hypovolemic shock of this magnitude does not prevent the generalized Shwartzman reaction.

Animals↗
PubMed1976

Correlation between degree of malignancy and the radioactive phosphorus uptake test in ocular melanomas.

Twenty-nine patients who had undergone enucleation for ocular malignant melanoma were studied. The results of the radioactive phosphorus uptake (32P) tests were correlated with histopathologic observations. There was a positive correlation between the 32P test results and the histologic degree of malignancy. Mixed cell melanomas were more frequent in the patients ranked with higher 32P test results. Spindle cell melanomas occurred more frequently in patients with lower 32P test results. Mitoses per field and degree of malignancy correlated positively with 32P test results when ranked in a masked manner by two ocular pathologists. Tumor volume and clinical factors did not correlate with the 32P test results. While patients with mixed cell melanomas had higher mean 32P test results than those with spindle cell melanomas, a large variance was noted. Because of this the 32P test is unreliable in predicting the histopathology of a tumor in individual cases.

Aged↗
PubMed1976

The effects of aspirin and indomethacin on the ocular response to circulating bacterial endotoxin in the rabbit.

A transient iridocyclitis is produced in rabbits by the intravenous injection of bacterial endotoxin. A major feature of this response is an altered vascular permeability which can be measured by the ocular accumulation of circulating 125I-labeled albumin. The present study was made to determine the effects of inhibitors of prostaglandin synthesis of the ocular response to an E. coli 055:B5 endotoxin. Aspirin pretreatment prevented the ocular response following the intravenous injection of 10 mug per kilogram of endotoxin, but had no effect following 100 mug per kilogram. Indomethacin pretreatment prevented an alteration in ocular vascular permeability 1 1/2 hours after the injection of 100 mug per kilogram of endotoxin and significantly reduced the alteration 4 hours after endotoxin. Thus inhibitors of prostaglandin synthesis can prevent the ocular response to circulating endotoxin depending on their relative potency and the amount of injected endotoxin. These results suggest that prostaglandins are important in the ocular response to circulating endotoxin in the rabbit.

Animals↗
PubMed1975

Circulating immune complexes. Effects on ocular vascular permeability in the rabbit.

Sudden transient, alteration in vascular permeability is producible in rabbit eyes by intravenous injection of large quantities of antigen, bovine gamma-globulin (BGG), into immunized animals or by intravenous injection of large amounts of antigen-antibody complexes (BGG-antiBGG) prepared in antigen excess (20 to 25times) in normal rabbits. Change is measured by ocular accumulation of iodinated I125 serum albumin, relative to that in heart blood, in intact eyes and separate anatomical compartments, in aqueous, in the anterior eye including (lens plus vitreous), and in the posterior segment. Primarily affected are vessels in the iridial portion of ciliary processess; edema is the primary finding. The same vessels are affected by intravenous injection of bacterial endotoxin, but compared with endotoxin, altered vascular permeability is short-lived and is not associated with formation of platelet plugs and intravenous fibrin strands.

Animals↗
PubMed1975

Ocular pathology of infantile Niemann-Pick disease. Study of fetus of 23 weeks' gestation.

A fetus of 23 weeks' gestation was aborted following the demonstration of sphingomyelinase deficiency (infantile form of Niemann-Pick disease) in cultured amniotic fluid cells that were obtained by amniocentesis. Histopathologic study of the eyes disclosed normal findings for the fetal age, except for fine lipid droplets in the inner plexiform layer of the retina. By electron microscopy, membranous cytoplasmic bodies (MCB) characteristic of lipid storage diseases were identified in many ocular tissues, including corneal epithelium and keratocytes, lens epithelial cells and fibroblasts of choroid and sclera, and in extraocular muscle. Selective accumulation of MCB in ganglion cells in the primitive macular region was not apparent. An extremely fine membranous component (30 to 40 Angstroms) was seen in some inclusions, suggesting a relatively pure phospholipid content.

Abortion, Therapeutic↗
PubMed1975

Effects of intravascular clotting on the activation of the complement system: The role of the platelet.

Total hemolytic complement activity and the third component of complement were found to be significantly depressed in vivo in rabbits following the induction of disseminated intravascular coagulation by both thrombin and thromboplastin. Production of severe thrombocytopenia by the administration of platelet antiserum prior to the infusion of thrombin or thromboplastin partially prevented complement activation. The data show that, when clotting is triggered, complement activation takes place and that platelets are required to some extent for this reaction.

Animals↗
PubMed1975

The effect of shock on the inflammatory response. A reevaluation of the role of platelets in the active arthus reaction.

The active Arthus reaction can be inhibited by hypovolemic shock or the infusion of catecholamines. A reevalution of previous work with platelet antiserum indicates that shock rather than thrombocytopenia was responsible for preventing the active Arthus reaction. Immunofluorescent studies of the inhibited Arthus sites reveal that immune precipitates are not present in the extravascular tissues. Since leukocyte aggregates can be seen within venules at the inhibited sites, and they phagocytize BSA-anti-BSA complexes, their failure to migrate out of the vessels is due to the absence of complexes in the extravascular spaces. (Am J Pathol 78:159-170, 1975)

Animals↗
PubMed1975

Comparison of the ocular effects of circulating endotoxin and immune complexes: role of vasoactive amines.

Both bacterial endotoxin and soluble immune complexes (BGG-anti BGG) injected i.v. in rabbits produce an alteration in ocular vascular permeability confined primarily to the vessels of the iridial portion of the ciliary processes. These effects have been measured by the ocular accumulation of 125I-albumin relative to cardiac plasma. Ten micrograms per kilogram of Escherichia coli bacterial endotoxin (055:B5) produce a consistent alteration in ocular vascular permeability over a 90-min period after injection. Fifty to 100 mmug/kg of endotoxin result in a prolonged effect that is maximum 4 hr after injection. Large quantities of immune complexes (BGG-antiBGG) prepared in 20 to 25 times antigen excess produce an anaphylaxis and approximately a 70% reduction in platelets and CH50. The alteration in ocular vascular permeability is half as great as that produced by 10 ug/kg of endotoxin over the 90-min period after their injection. A combined treatment with antihistamine, pyrilamine maleate, and antiserotonin, methysergide maleate, results in a significant reduction in ocular 125I-albumin in normal animals, virtually prevents the ocular effect of immune complexes, and reduces the average effect of endotoxin by 30%. Increasing the quantities of injected antihistamine and antiserotonin does not have a further effect on the response to 10 ug of endotoxin.

Animals↗
PubMed1973

The participation of the platelet in the vascular response to endotoxemia in the rabbit eye.

Platelet depletion by a specific goat antirabbit platelet antiserum profoundly affected the response of the ocular blood vessels to intravenous endotoxin. The altered permeability of the vessels of the iridial portion of the ciliary processes in the thrombocytopenic animals was reduced by 50% at 1(1/2) hours and by 30 to 58% at 4 hours after endotoxin administration. Intravascular fibrin at the 4-hour period could be eliminated by a properly timed platelet depletion. By preventing platelet aggregations and fibrin formation, the permeability alteration could be reduced by 66% and the usual stromal hemorrhages practically eliminated. Underlying these effects of the platelet was evidence of a vascular trauma unrelated to platelet activity and probably dependent to some extent on adrenergic stimulation. Platelet aggregation and/or fibrin formation had to be superimposed on the underlying vascular trauma to produce endothelial denudation.

Animals↗