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Biomedical subjects

S MacRae

Publications and source records attributed to S MacRae.

48 records · Page 3Linked to original sources
PubMed1977

Differentiation of functionally active mouse T-lymphocytes from functionally inactive bone marrow precursors.

An investigation has been made of the development of various T cell functions in lethally irradiated mice reconstituted with anti-0 treated spleen or bone marrow cells. Evidence is presented to show that both organs contain a post-thymic precursor pool able to regenerate by 15 days limited T cell responses in thymectomized recipients. A prethymic pool also exists in each organ able to regenerate, at a later date, first a suppressor T cell population and probably later, mature functional T cells involved in helper functions and cell mediated lympholysis. The spleen is apparently a better source of precursors of the suppressor cells than bone marrow, while a poorer source of precursors of the other T cell functions. All T cell functions investigated apparently first appear in large cells which undergo a reversion to small cells without necessarily maturing to their full potential reactivity. By following the kinetics of appearance of T cell functions, and the physical parameters of the cells with which these functions are associated, it is shown that PHA responding and Con A responding cells, cytotoxic T cell progenitors, helper T cells for antibody production and helper T cells for cytotoxicity induction can all at some stage of differentiation be separated from one another.

Animals↗
PubMed1977

Differentiation of functionally active mouse T lymphocytes from functionally inactive bone marrow precursors II. Limited recovery of T-cell responses from mouse bone marrow in tissue culture.

The limited differentiation of mature T cell function from mouse bone marrow in tissue culture is described and compared with similar differentiation occuring in vivo in irradiated bone marrow protected mice. Data are presented to show that a pool of precursors, similar in size to that able to produce early (transient?) regeneration in thymectomized recipients, is responsible for the development of mitogen responsive T cells active in MLC (proliferation) and CML (development of cytotoxic cells) assays. In contrast, a helper cell population which augments antibody formation from T-depleted normal spleen cells derives from a pool of similar precursors yet does not seem to be theta positive. Similarly, larger cells (perhaps typical of those giving rise to suppressor T cells in vivo) give rise to a suppressor cell pool after 4 days of culture, though again only a fraction of this suppressor activity could be attributed to theta positive cells. It is suggested that much of the data for regenration of T lymphocytes in vitro from T-depleted sources needs to be re-interpreted in terms of this evidence for a pool of post-thymic precursors of T cells in such T-deficient cell populations.

Animals↗
PubMedDate not supplied

Photorefractive keratectomy to correct myopic or hyperopic astigmatism with a cross-cylinder ablation.

PURPOSE: To assess the efficacy and safety of a combined ablation of the steep and flat meridian to correct astigmatism with the excimer laser. METHODS: Twenty-two eyes with myopic, mixed, or hyperopic astigmatism (mean preoperative spherical equivalent refraction -4.30 +/- 4.70 D [range, -12.50 to +1.50 D] and mean preoperative cylinder magnitude -3.40 +/- 1.40 D [range, -1.50 to -6.00 D]) underwent PRK with the Nidek EC-5000 excimer laser. The surgical strategy involved ablating half the amount of the cylinder (in diopters) along steepest meridian, the other half in a subsequent step along the flattest meridian; thereafter, the spherical equivalent was corrected. RESULTS: Six months postoperatively, mean spherical equivalent refraction was -0.07 +/- 0.87 D and mean cylinder was -0.44 +/- 0.36 D. Mean spectacle-corrected visual acuity was 0.86 +/- 0.13 compared to 0.75 +/- 0.22 preoperatively. Mean corneal haze was 0.67 +/- 0.31. No patient lost 2 or more lines of spectacle-corrected visual acuity and there were no complaints about night halos or glare. CONCLUSIONS: Unlike other ablation strategies, the cross-cylinder method creates a smooth transition (low dioptric gradient) between the treated and untreated cornea. This is achieved by first treating the cylinder and making the corneal surface spherical and then ablating the spherical component of the refractive error.

Adult↗
PubMedDate not supplied

Customized and low spherical aberration corneal ablation design.

PURPOSE: The purpose of this study was to use the Arizona Eye Model to help guide customization of corneal excimer ablation and reduce spherical aberration. METHODS: Myopic eyes were treated with the Nidek EC-5000 excimer laser with a 5.5-mm diameter optic ablation zone and a 7.0-mm diameter transition ablation zone. We analyzed preoperative and postoperative corneal topographies using height mapping. From this data, refractive error profiles and maps were constructed using the Arizona Eye Model. The first group of patients had refractions between -2.00 and -5.00 D. Data was obtained by subtracting postoperative topography from preoperative topography. We then plotted the ideal ablation pattern if no additional spherical aberration was introduced when compared to preoperative topographies. RESULTS: We found that in the central 4 mm, the ablation pattern was highly acceptable, with negligible spherical aberration. As the ablation moved out toward 6 mm, there was increasing spherical aberration. Newer ablation designs require more flattening in the midperiphery of the cornea. These flatter peripheral designs require more blending in the periphery and larger transition zones. CONCLUSION: The use of computerized corneal topography in eye modeling is helpful in designing new ablation patterns to reduce optical and spherical aberration. Ablation zone design is critical to maximizing optical and biologic tolerance.

Astigmatism↗
PubMedDate not supplied

Sterile interface keratitis after laser in situ keratomileusis: three episodes in one patient with concomitant contact dermatitis of the eyelids.

PURPOSE: To illustrate a case in which sterile interface keratitis after laser in situ keratomileusis (LASIK) occurred concomitantly with an allergic contact dermatitis of the eyelids. METHODS: Retrospective case review. RESULTS: Resolution of the interface keratitis and dermatitis occurred following an intense course of topical corticosteroids and brief course of oral corticosteroids. Despite an attempt to eliminate potential causes, the same patient developed interface keratitis in the fellow eye following both the initial LASIK and an enhancement, in which no microkeratome was used. Intense treatment with both topical and oral corticosteroids led to a final uncorrected visual acuity of 20/20 in the right eye and 20/25+2 in the left eye. CONCLUSION: The etiology and mechanism of sterile interface keratitis after LASIK are unknown, but are probably multifactorial. The concomitant contact dermatitis reaction may indicate a common immune mechanism.

Adult↗
PubMedDate not supplied

Slit skiascopic-guided ablation using the Nidek laser.

PURPOSE: To present the approach of using a scanning slit refractometer (the ARK 10000) in conjunction with a corneal topography system to guide customized corneal ablation. This diagnostic system is coupled with the Nidek EC-5000 system which combines scanning slit and a scanning small area ablation (1.0 mm) to perform a customized ablation. METHODS: The ARK 10000 diagnostic system which contains a scanning slit refractometer is described. Information generated from the ARK 10000 wavefront sensor and corneal topography system can be coupled to the new Nidek EC-5000 excimer laser system, which combines the larger area of scanning slit ablation with the small area (1.0 mm) ablation. RESULTS: The Nidek ARK 10000 diagnostic system captures wavefront information using a retinoscopic system which is converted into a refractive power map. This is different from other autorefraction systems in that it has four sensors at different diameters of the cornea and captures 1440 points in 0.4 seconds. This map is used in conjunction with corneal topography-captured simultaneously. This information is then combined to perform a customized ablation using the new Nidek EC-5000 system. CONCLUSIONS: The ARK 10000 diagnostic system represents a different approach to customized ablation in that it combines a corneal topography system with a wavefront system and a larger treatment area of the traditional scanning slit ablation with a new small area ablation treatment for greater efficiency.

Accommodation, Ocular↗
PubMedDate not supplied

Intraocular drugs used in cataract surgery and their effect on the corneal endothelium.

Cataract surgery has evolved dramatically over the last 20 years largely because of developments in intraocular drugs and solutions, as well as intraocular mechanical devices used for removing cataracts. These include viscoelastic materials, intraocular miotics, intraocular irrigating solutions, and intraoperative mydriatics. It also involves attention to subtle details which may cause idiopathic postoperative corneal edema such as the avoidance of using surfactant cleaners or soaps on instruments that are used in the eye. The following discussion briefly outlines some of the intraocular drug issues of which cataract surgeons need to be aware.

Cataract Extraction↗
PubMedDate not supplied

Survival of streptococcus in optisol-GS medium.

BACKGROUND: Donor cornea contamination as a cause of endophthalmitis is one of the most serious complications of penetrating keratoplasty. Optisol-GS corneal storage medium with the combination of gentamicin and streptomycin was designed to provide wider antibiotic coverage, most notably against streptococcal species. However, many enterococci are resistant to streptomycin and genta micin. METHODS/RESULTS: We report a case in which Enterococcus faecium was isolated from cultures of the donor limbus prior to corneal excision and again from preoperative cultures of the donor corneal rim despite 5 days of preservation in Optisol-GS. The isolate was found to be resistant to both gentamicin and streptomycin. CONCLUSIONS: This case illustrates the need to raise awareness that streptococcus can remain a viable contaminant of donor corneas despite storage in Optisol-GS medium.

Chondroitin Sulfates↗
PubMedDate not supplied

The treatment of persistent wound leak after radial keratotomy.

BACKGROUND: Macroperforation of the cornea during refractive keratotomy can result in persistent wound leak and may need treatment by suturing. METHODS: We describe two eyes that developed a macroperforation during radial keratotomy with persistent leakage of aqueous. The wounds were sutured with 10-0 and 11-0 nylon sutures. RESULTS: The sutures induced irregular astigmatism as shown by corneal topography. Removal of sutures improved the topography and led to an acceptable outcome. CONCLUSION: Macroperforations with persistent aqueous leaks should be sutured. Suture removal within a few weeks after surgery can avoid persistent irregular astigmatism and lead to a good refractive result.

Adult↗
PubMedDate not supplied

Effects of organizational change in the medical intensive care unit of a teaching hospital: a comparison of 'open' and 'closed' formats.

OBJECTIVE: To compare the effects of change from an open to a closed intensive care unit (ICU) format on clinical outcomes, resource utilization, teaching, and perceptions regarding quality of care. DESIGN: Prospective cohort study; prospective economic evaluation. SETTING: Medical ICU at a university-based tertiary care center. For the open ICU, primary admitting physicians direct care of patients with input from critical care specialists via consultation. For the closed ICU, critical care specialists direct patient care. PATIENTS: Consecutive samples of 124 patients admitted under an open ICU format and 121 patients admitted after changing to a closed ICU format. Readmissions were excluded. MAIN OUTCOME MEASURES: Comparison of hospital mortality with mortality predicted by the Acute Physiology and Chronic Health Evaluation II (APACHE II) system; duration of mechanical ventilation; length of stay; patient charges for radiology, laboratory, and pharmacy departments; vascular catheter use; number of interruptions of formal teaching rounds; and perceptions of patients, families, physicians, and nurses regarding quality of care and ICU function. RESULTS: Mean +/- SD APACHE II scores were 15.4 +/- 8.3 in the open ICU and 20.6 +/- 8.6 in the closed ICU (P=.001). In the closed ICU, the ratio of actual mortality (31.4 percent) to predicted mortality (40.1 percent) was 0.78. In the open ICU, the ratio of actual mortality (22.6 percent) to predicted mortality (25.2 percent) was 0.90. Mean length of stay for survivors in the open ICU was 3.9 days, and mean length of stay for survivors in the closed ICU was 3.7 days (P=.79). There were no significant differences between periods in patient charges for radiology, laboratory, or pharmacy resources. Nurses were more likely to say that they were very confident in the clinical judgment of the physician primarily responsible for patient care in the closed ICU compared with the open ICU (41 percent vs 7 percent; P<.Ol), and nurses were the group most supportive of changing to a closed ICU format before and after the study. CONCLUSIONS: Based on comparison of actual to predicted mortality, changing from an open to a closed ICU format improved clinical outcome. Although patients in the closed ICU had greater severity of illness, resource utilization did not increase.

APACHE↗