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Biomedical subjects

K M Miller

Publications and source records attributed to K M Miller.

At least 91 records · Page 5Linked to original sources
PubMed1989

Characterization of biomedical polymer-adherent macrophages: interleukin 1 generation and scanning electron microscopy studies.

Macrophage activation following attachment to biomedical polymers was studied using two systems of analysis. Supernatants generated by human peripheral blood monocytes cultured on the surface of several different biomedical polymers were evaluated for the presence of the secreted regulatory protein interleukin 1 (IL1). In addition, each cell-polymer culture surface was subjected to scanning electron microscopy for gross morphological evaluation. Results indicate that, although all materials were efficient in the attachment and activation of cells, the panel of polymers showed a differential capacity in attachment and activation of monocytes. Dacron and polyethylene surfaces had a greater density of cells showing morphology indicative of activation, corresponding to elevated levels of IL1 in these cultures. Biomer and polydimethylsiloxane surfaces showed fewer activated cells and had lower IL1 levels in culture. Expanded polytetrafluorethylene resulted in intermediate levels of IL1 and attached cells showing activated morphology.

Biocompatible Materials↗
PubMed1989

Aphakic reading adds. An error in traditional teaching.

It is traditionally taught in ophthalmic optics that the "effective" bifocal add is greater than the prescribed add in aphakic spectacles. Because the reading segment is fabricated on the front surface of the lens, the added back vertex power is significantly greater than the prescribed add. It is taught that the effective power should be measured at the back surface. The authors explain informally why the effective add is, in truth, exactly equal to the prescribed add and not equal to the difference in back vertex power between the top and bottom segments. Practitioners who prescribe spectacles by the traditional teaching may leave their aphakic patients with suboptimal reading vision.

Aphakia↗
PubMed1988

Human monocyte/macrophage activation and interleukin 1 generation by biomedical polymers.

In vitro cell culture techniques were used to evaluate the effect of several clinically significant biomedical polymers on monocyte activation and Interleukin 1 (IL1) production. Isolated human peripheral blood monocytes were cultured in the presence of a panel of five biomedical polymers routinely used in a variety of clinical applications: Polyethylene (PE), silica-free poly-dimethylsiloxane (PDMS), woven Dacron fabric, expanded polytetrafluoroethylene (ePTFE) and the segmented polyurethane, Biomer. Monocytes generated IL1 in the presence of all five materials. Maximal levels of IL1 were generated at 24 h in monocyte-polymer cultures supplemented with serum and additionally stimulated with lipopolysaccharide (LPS). No difference was observed due to serum source. Results from cultures supplemented with fetal bovine serum were not significantly different from those obtained with human serum supplemented cultures. The thymocyte proliferative activity generated by monocytes in the presence of these biomedical polymers was neutralized by a specific polyclonal anti-IL1 antiserum. Statistically significant differences in IL1 production were observed between polymers, allowing their classification according to reactivity into high (Dacron, PE), intermediate (ePTFE) and low (Biomer, PDMS) reactive groups.

Biocompatible Materials↗
PubMed1988

In vitro and in vivo interactions of cells with biomaterials.

The biocompatibility of materials at an implant site involves a complex interaction of cells and tissues with the biomaterial. This cell-cell and cell-polymer interaction evokes the release of mediators such as chemotactic and growth factors that elicit and sustain inflammatory responses at the implant site. In this review, we summarize the interaction of cells with biomaterials in vitro and in vivo.

Animals↗
PubMed1988

The Wilmer Information System. A classification and retrieval system for information on diagnosis and therapy in ophthalmology.

The Wilmer Information System is a computerized medical information system used for the storage and retrieval of data pertaining to patient demographics, diagnosis, and therapy. The heart of the system is an expandable, hierarchical code based on International Classification of Diseases, 9th Revision (ICD-9) diagnosis codes and Physicians' Current Procedural Terminology procedure codes. Customized coding sheets containing highly specific diagnosis and procedure codes have been designed for each subspecialty area in ophthalmology. Interactive database management software facilitates data entry and retrieval. The system can be used to search for patients who meet very specific criteria, or to produce cumulative visit reports and summary statistics.

Computers↗
PubMed1988

The clinical appearance of the lamina cribrosa as a function of the extent of glaucomatous optic nerve damage.

The authors evaluated the shapes of the largest clinically visible pores on the surface of the lamina cribrosa in 87 eyes of 52 glaucoma patients and found an apparent progression in pore shape as a function of the extent of glaucomatous optic nerve head damage. Small, round pores predominated in eyes with mild field loss, oval pores were more common in eyes with moderate field loss, and striate or slit-shaped pores were most frequent in eyes with advanced field loss. If the pores of the lamina cribrosa elongate as a function of increasing glaucomatous optic atrophy, and if large pore size is associated with an increased risk for pressure-related axonal damage, then the threshold for ganglion cell atrophy may drop as the damage to the optic nerve progresses.

Adult↗
PubMed1988

Calibration factors for Ge detectors used for field spectrometry.

Calibration factors to convert a measured full-absorption peak count rate to activity in the soil and dose rate in air are given for Ge detectors that are used for field measurements of radionuclides. The appropriate factors for a given detector are derived using three primary parameters: the manufacturer's quoted efficiency at 1332 keV relative to a 7.6 cm (3 in.) long by 7.6 cm (3 in.) diameter NaI(Tl) detector, the detector's orientation in the field (up or down) and the Ge crystal length/diameter ratio. The accuracy of the results obtained by using this simplified calibration technique is estimated to be 10-15%.

Calibration↗
PubMed1987

Studies on the mechanism of T cell inhibition by the Pseudomonas aeruginosa phenazine pigment pyocyanine.

Pseudomonas aeruginosa and its products have been shown to inhibit mitogen-induced human lymphocyte blastogenesis as measured by [3H]TdR uptake. The phenazine pigment pyocyanine has been identified as one of the inhibitors present in cellfree culture supernatants. To determine the mechanism of the inhibitory action of pyocyanine, we studied its effect on the early stages of T cell activation. Pyocyanine inhibited lymphocyte stimulation induced by specific antigens, the lectin concanavalin A and the calcium ionophore, ionomycin, suggesting that its inhibitory effect is not dependent on interference with the T cell antigen receptor complex itself. Using quin-2, we showed that pyocyanine did not interfere with the mitogen-induced increase in cytosolic-free Ca2+. We also showed that pyocyanine did not interfere with the function of calmodulin stimulated Ca2+-Mg2+ ATPase activity, indicating that the mechanism of action of pyocyanine differs from that of the structurally related phenothiazine compounds. Analysis of IL 2 production and IL 2 receptor expression clearly showed that pyocyanine inhibits the production of this essential lymphokine as well as the expression of IL 2 receptors on the T cell membrane. This inhibition is dose dependent and not due to cellular toxicity. There was parallel inhibition of growth in cell volume as well as [3H]TdR uptake. Thus, our results demonstrate that pyocyanine inhibits T cell proliferation by decreasing the production of the critical lymphokine IL 2 and by decreasing the expression of the IL 2 receptor. Local suppression of lymphocyte stimulation by phenazine pigments such as pyocyanine may interfere with cellular immune responses that may be necessary for eradication of chronic infection with P. aeruginosa.

Adult↗
PubMed1987

Intraocular lens style and refraction in eyes treated with silicone oil.

The comparatively high refractive index of silicone oil significantly alters the refractive power of the human eye when it is placed into the vitreous cavity during retinal reattachment surgery. If cataract extraction and intraocular lens (IOL) implantation are subsequently performed, significant refractive errors result with most IOL styles if standard formulas are used to determine lens power. Thick-lens optical analysis of four IOL styles showed that the meniscus style yields the smallest difference between predicted (Binkhorst, Sanders-Retzlaff-Kraff formulas) and actual postoperative refraction. This IOL style also minimizes the change in refractive error that accompanies subsequent alterations in the contents of the vitreous cavity, including removal of silicone oil and replacement with balanced salt solution.

Eye↗
PubMed1987

Vascular graft-associated complement activation and leukocyte adhesion in an artificial circulation.

Complement-associated leukocyte adhesion appears to be a consistent in vitro and in vivo finding for many types of polymers; however, very little work has been done on the interaction of leukocytes with vascular graft materials. An in vitro perfusion system was used to study complement and leukocyte activation associated with the following vascular graft materials when tested with human blood: expanded polytetrafluoroethylene (ePTFE), crimped Dacron Bionit (DB) and preclotted Dacron Bionit. A decrease in the total leukocyte concentration with perfusion time was seen for all materials tested, and paralleled leukocyte adhesion to the graft surface as observed by scanning electron microscopy. The most dramatic decrease in leukocyte concentration was observed for the interaction of heparinized whole blood with Dacron. This was due to a selective decrease in neutrophils and monocytes, and was correlated with an increase in both leukocyte adhesiveness and complement activation, as measured by C5a elevation. Inhibiting complement activation by use of the anticoagulant, sodium citrate, curtailed Dacron-induced leukocyte adhesion. Little leukocyte or complement activation was observed for ePTFE or the silicone rubber control regardless of the anticoagulant used.

Adult↗
PubMed1987

Television retinoscopy with a slit-aperture retinoscope and a highly sensitive camera.

The low light level of the retinoscopic reflex and the small aperture required to obtain the customary shape of the reflex make it difficult to photograph the actual reflex for teaching or permanent recording. We describe the design and application of a television retinoscopy system that solves this problem. The system uses a standard streak retinoscope modified to gather more light, a highly sensitive television camera, and an image processor. The system can be used for live demonstration of retinoscopic techniques or for videotape recordings for teaching or research.

Equipment Design↗
PubMed1987

A teaching attachment for retinoscopy.

A teaching attachment for a conventional streak retinoscope allows a second observer to view the retinoscopic reflex during retinoscopy. The device weighs 200 grams and is attached to the retinoscope by a semi-flexible, rotatable linkage. A beam splitter, one-power telescope, and erecting mirror form a displaced aerial image of the retinoscope peephole for the observer. With identical retinoscopic reflexes observed through the actual peephole and its aerial image, the device can be used to teach basic retinoscopy techniques to new refractionists, or to demonstrate subtle reflexes to more experienced observers.

Equipment Design↗
PubMed1987

In vitro effect of synthetic pyocyanine on neutrophil superoxide production.

Pyocyanine, a low-molecular-weight phenazine pigment produced by Pseudomonas aeruginosa, has previously been shown to strongly inhibit human lymphocyte blastogenesis. We now report that synthetic pyocyanine can also affect the generation of superoxide by human peripheral blood polymorphonuclear leukocytes (PMNs) in a dose-dependent manner. Superoxide production by PMNs stimulated with phorbol myristate acetate (PMA) was measured in the presence and absence of pyocyanine, phenazine, and trifluoperazine, a phenothiazine of similar chemical structure to the phenazine pigments. Pyocyanine at 50 microM inhibited superoxide production to 28.9 +/- 2.8% of PMA control values, whereas at the lower concentration of 1 microM, the production of superoxide was significantly enhanced (203 +/- 31.7% of PMA control values). Phenazine, the tricyclic parent compound of pyocyanine, had only a minor effect. Trifluoperazine had a marked inhibitory effect on superoxide generation at concentrations above 1 microM. None of the compounds induced superoxide generation in the absence of PMA. Pyocyanine at all concentrations, unlike phenothiazines, had very little effect on the release of neutrophil granule enzymes. The effect of P. aeruginosa phenazine pigments on polymorphonuclear phagocytes is of significance, since inhibition of host PMN function at sites of infection could result in ineffective bacterial killing, whereas enhanced PMN function could lead to greater tissue damage. These two possibilities are not mutually exclusive and may coexist depending on local pyocyanine concentrations.

Adult↗
PubMed1987

Comparison of optic disc features in low-tension and typical open-angle glaucoma.

This study was undertaken to identify features of optic nerve head architecture that might explain, in part, why ganglion cell loss occurs in patients with low-tension glaucoma. We compared retrospectively the disc photographs of 25 patients with low-tension glaucoma with those of 26 control patients with typical open-angle glaucoma. No differences were observed in any of the following features: pore length, shape, or size variation; cup/disc and disc/arteriole ratio; clock positions of total rim loss; central retinal vessel entry site; rim pallor; number of rim-crossing vessels; and presence or absence of peripapillary nerve fiber layer hemorrhages, optic pits, and central retinal vessel canals. An hour-glass appearance of connective tissue bundles within the scleral lamina cribrosa, however, was present statistically less often in patients with low-tension glaucoma (p = 0.007). We speculate that the microscopic arrangement of fiber bundles within the lamina cribrosa may play an etiologic role in the pathogenesis of low-tension glaucoma.

Adult↗
PubMed1985

Perinatal influences on in vitro B lymphocyte differentiation in human neonates.

In vitro differentiation of B lymphocytes present in cord blood mononuclear cell preparations into immunoglobulin secreting cells was studied in 126 neonates with gestational ages (GA) ranging from 20 to 44 wk. Eight infants had a GA less than 27.9 wk, 24 had GA 28-32.9 wk, 30 had GA 33-37.9 wk, 51 had GA 38-41.9 wk, and 13 had GA above 42 wk. B cell differentiation in response to pokeweed mitogen plus hydrocortisone was assessed using a plaque forming cell assay. All neonates had a measurable plaque-forming cell response in this assay. An increased plaque-forming cell response was observed in some neonates in all gestational age groups. The magnitude of in vitro neonatal B cell differentiation underwent a continuous and significant (p less than 0.002) reduction as gestational age increased. The influence of intrauterine growth retardation on in vitro B lymphocyte differentiation was studied and compared to gestational age-matched controls with a normal intrauterine growth. Intrauterine growth retardation was not associated with changes in B cell responsiveness. An analysis of perinatal factors revealed that cesarean section, and low 1-min Apgar scores were factors that predisposed cord blood cells to be triggered in vitro to produce increased numbers of plaque-forming cells.

Apgar Score↗
PubMed1985

Intestinal lymphangiectasia and thymic hypoplasia.

We have evaluated the immunological abnormalities present in a 6 year old patient with primary intestinal and generalized lymphangiectasia confirmed by intestinal, lung and lymph node biopsies. Lymphocyte loss through the gut was confirmed by the detection of lymphocytes in her stool. An increased enteric protein loss was suggested by hypoproteinaemia, peripheral oedema, and a very short half-life for i.v. immune serum globulin (3 days). Lymphocyte subpopulation analysis revealed a selective loss of T lymphocytes, with a proportionally increased loss of the OKT4 positive helper/inducer subpopulation. Functionally, there was a decrease in proliferative responses to some mitogens and to allogeneic cells, and a lack of T cell help for in vitro B lymphocyte differentiation into immunoglobulin secreting cells. Natural killer function was normal. In this patient, a concomitant thymic deficiency was documented by failure to identify thymic tissue on a thymus biopsy and by an absence or decrease of the serum thymic factor (thymulin) and thymosin alpha 1. No compensatory lymphopoiesis was detected in the bone marrow. In an attempt to increase T lymphocyte development, the patient was treated with thymosin fraction 5. Daily treatment with this preparation resulted in a transient clinical improvement which could not be sustained on a weekly thymosin treatment schedule. However, lymphocyte numbers did not increase during this treatment. The findings in this patient support the notion that T lymphocytes are needed to stimulate thymic epithelium. In situations of excessive loss of long lived T lymphocytes a secondary thymic atrophy may occur and further contribute to the development of a deficiency in cell-mediated immunity.

Child↗