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Biomedical subjects

R J Olson

Publications and source records attributed to R J Olson.

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

Discrimination of eukaryotic phytoplankton cell types from light scatter and autofluorescence properties measured by flow cytometry.

Flow cytometric methods for recognizing several groups of eukaryotic marine phytoplankton were tested using 26 laboratory cultures. Each culture was divided into three aliquots, and these samples were analyzed for 1) Coulter volume; 2) light scatter (magnitude and polarization properties of forward scattered light and magnitude of right-angle scattered light) and autofluorescence emission (phycoerythrin and chlorophyll); and 3) autofluorescence excitation (by 488 nm and 515 nm light). Three kinds of cells could be easily distinguished from others in the culture collection: 1) The two cryptophytes and the rhodophyte had high phycoerythrin/chlorophyll ratios; 2) the two coccolithophores depolarized forward scattered light; and 3) the two pennate diatoms scattered only a relatively small amount of light in the forward direction compared with that at right angles. Mean chlorophyll fluorescence excited by blue light relative to that excited by green light was highest in the four chlorophytes, but there was overlap between some of these and some other kinds of cells. Unresolved cell types included centric diatoms, dinoflagellates, and naked coccolithophores. Forward light scatter and Coulter volume were closely related (except for the pennate diatoms) over a range of about 0.01 to 30 pL (equivalent spherical diameter about 3 to 40 microns), according to a logarithmic function.

Cells↗
PubMed1989

Effect of light on the cell cycle of a marine synechococcus strain.

Light-dependent regulation of cell cycle progression in the marine cyanobacterium Synechococcus strain WH-8101 was demonstrated through the use of flow cytometry. Our results show that, similar to eucaryotic cells, marine Synechococcus spp. display two gaps in DNA synthesis, at the beginning and at the end of the cell cycle. Progression through each of these gaps requires light, and their durations lengthen under light limitation.

Journal Article↗
PubMed1988

Long-term course of surgically induced astigmatism.

We performed an analysis of surgically induced astigmatism in 229 cases of extracapsular cataract extraction and posterior chamber lens implantation. The average length of follow-up for patients in this study was 34.4 months (2.87 years). We found that surgically induced astigmatism continued to change for at least three years after surgery. The preoperative astigmatism was found to have only minimal effect on the postoperative astigmatism if the corneal curvature was controlled with keratometry at the time of surgery. The optimal amount of with-the-rule astigmatism at three to five weeks postoperatively was found to be 0.75 diopter to 1.25 diopters for one surgeon and surgical technique.

Adult↗
PubMed1988

Corneal transplantation.

Corneal transplantation has become increasingly successful as a result of improved methods of tissue procurement and preservation, refined surgical techniques, better medical care, heightened public awareness and an expanded network of eye banks. Vision improves within a day of surgery and continues to improve for six months to one year. Careful screening of donors and donor corneal tissue is essential. Causes of transplantation failure include rejection, glaucoma and recurrent infections.

Corneal Transplantation↗
PubMed1987

Anterior chamber lenses. Part II: A laboratory study.

An analysis of 606 surgically removed anterior chamber intraocular lens (IOL) specimens revealed that 351 or 58% of these were small-diameter, round loop, closed-loop styles. Because of the extremely high percentage of IOLs with this design received in our laboratory and the correlation of clinical histories with our histopathologic findings, we have concluded that such IOLs do not provide the safety and efficacy achieved by other anterior chamber lens designs. The finely polished, one-piece, all-PMMA styles fared well in our study. Although these one-piece styles comprise well over 50% of the American market share of anterior chamber IOLs, they comprise only 14% of all anterior chamber IOLs accessioned in our laboratory, compared to 58% for closed-loop designs. We believe that implantation of anterior chamber lenses with small-diameter, round, closed loops is no longer warranted. Patients in whom these IOLs have already been implanted should be carefully followed. It is our opinion that the FDA should recall or closely monitor all IOLs of this design and that implantation of closed-loop lenses should be discontinued in the United States. Furthermore, we believe that an IOL deemed to be not medically sound or worthy of implantation in the United States should not be marketed or donated outside of this country.

Anterior Chamber↗
PubMed1986

Peters' anomaly as a consequence of genetic and nongenetic syndromes.

A new syndrome includes Peters' anomaly and short-limbed dwarfism. A balanced chromosomal translocation in the brother (patient 1) appears to be coincidental to the physical abnormalities, because his sister (patient 2) has identical findings but normal fibroblast and lymphocyte karyotypes. Peters' anomaly, which includes corneal clouding, iris and/or lens adhesions to the cornea, and the absence of endothelium and Descemet's membrane, is often associated with systemic abnormalities. Since there are different genetic and nongenetic systemic conditions that include Peters' anomaly, and there are several ocular syndromes with features overlapping this disorder, we believe that Peters' anomaly is a morphologic finding rather than a distinct entity.

Abnormalities, Multiple↗
PubMed1986

Dominantly inherited keratitis.

A new, autosomal dominant keratitis is presented. The onset occurs in early childhood with episodes of red, irritated eyes but not recurrent erosions. There are no associated systemic abnormalities. The primary histopathologic features are vascularization and inflammation of the anterior corneal stroma, and replacement of Bowman's layer by fibrovascular tissue. Thus, this disease demonstrates characteristics of both a dystrophy with familial occurrence and early onset, and a degeneration with primary inflammation and vascularization.

Adult↗
PubMed1986

Light and dark control of the cell cycle in two marine phytoplankton species.

The effect of light and dark on growth, DNA replication and cell division of two marine phytoplankters Thalassiosira weissflogii (a diatom) and Hymenomonas carterae (a coccolithophorid) was investigated using flow cytometry. The two species displayed very differing behavior. When transferred from light to prolonged darkness, all coccolithophorid cells were arrested at the beginning of the G1 stage of the cell cycle. When shifted back into light, they resumed cycling at a rate slightly slower than prior to arrest. In contrast, diatom cells were arrested either in the G1 or G2 stage of the cell cycle in the dark. Upon re-exposure to light, cells which had been dark-arrested in G1 resumed cycling at the same rate as prior to arrest, while cells arrested in G2 cycled much more slowly. These results suggest that in both species, light control of cell cycle progression is effective only over a restricted part of the cell cycle, as has been hypothesized by Spudich & Sager (J cell biol 83 (1980) 136) [38] for Chlamydomonas. In the coccolithophorid there is a single light-dependent segment located at the beginning of G1, whereas the diatom appears to have two such segments, one in G1 and the other in G2, corresponding to two different light requiring processes.

Cell Cycle↗
PubMed1986

Sterile hypopyon secondary to ultrasonic cleaning solution.

During a 20-week period, 21 cases of sterile hypopyon occurred 24 hours after uncomplicated extracapsular cataract extraction and in-the-bag posterior chamber intraocular lens implantation at the Valley Eye Institute. While all cases responded to steroid treatment and exhibited no residual ocular effects, the cause of the hypopyon remained a mystery despite an on-going reevaluation of the surgical procedure and sterilization techniques. Several suspected causes were investigated and eliminated. It was clinically determined that surgical instruments placed in older ultrasonic cleaning solution caused the hypopyons. Further analysis at the Center for Intraocular Research at the University of Utah revealed that the instruments were contaminated by a heat-stable endotoxin that remained on the instruments through the autoclaving process. Surgeons currently using ultrasonic instrument cleaners should be aware that, with some models, following the manufacturer's recommended fluid changing procedures could result in endotoxic contamination of surgical instruments which could, in turn, cause severe inflammatory reactions in the immediate postoperative period.

Animals↗
PubMed1986

Effects of environmental stresses on the cell cycle of two marine phytoplankton species.

Cell cycle phase durations of cultures of Hymenomonas carterae Braarud and Fagerl, a coccolithophore, and Thalassiosira weissflogii Grun., a centric diatom, in temperature-, light- or nitrogen-limited balanced growth were determined using flow cytometry. Suboptimal temperature caused increases in the duration of all phases of the cell cycle (though not equally) in both species, and the increased generation time of nitrogen-limited cells of both species was due almost wholly to expansion of G(1) phase. In H. carterae light limitation caused only G(1) phase to expand, but in T. weissflogii both G(2) + M and G(1) were affected. These results are discussed in relation to cell division phasing patterns of these two species and to models of phytoplankton growth. Simultaneous measurements of protein and DNA on individual cells indicated that under all conditions, the protein content of cells in G(1) was a constant proportion of that of G(2) + M cells. Simultaneous measurements of RNA and protein on each cell indicated that the amounts of these two cell constituents were always tightly correlated. Under conditions of nitrogen limitation both protein and RNA per cell decreased to less than one-third of the levels found in nonlimited cells. This indicates, at least for nitrogen-replete cells, that neither protein nor RNA levels are likely to act as the trigger for cell cycle progression. Strict control by cell size is also unlikely since mean cell volume decreased as growth rates were limited by light and nitrogen supply, but increased with decreasing temperature.

Journal Article↗
PubMed1986

The effects of nonfixated lower lens haptics of Binkhorst lenses on corneal endothelial cell density.

At specified intervals up to 56 months postoperatively, we took central corneal endothelial cell measurements of 52 patients who had undergone extracapsular cataract extraction (ECCE) with placement of a Heyer-Schulte IC-10 iridocapsular intraocular lens. We then compared the endothelial cell density of patients in whom the lower lens haptic was fixated within the capsule with those in whom it was nonfixated. We found that nonfixation of the lower lens haptic, which in essence converts the irido-capsular lens to an iris-supported lens, does not cause continuing endothelial cell loss.

Aged↗
PubMed1986

The effects of prolonged phacoemulsification time on the corneal endothelium.

The question of whether or not phacoemulsification causes significant corneal endothelial damage has been studied in many ways. In this study, we used videotaped specular microscopy and nitroblue tetrazolium (NBT) staining to assess cell damage under conditions in which the two most commonly blamed sources of damage--probe tip trauma and lens fragments--cannot be implicated. After 15 minutes of irrigation, aspiration, and ultrasound in a modified corneal viewing and storage (CVS) chamber, the four test corneas showed less than 5% cell damage as assessed by NBT staining, which was no more than in the control. In one case, an unexpected air bubble on the endothelium caused a loss of endothelial cells. Because small air bubbles are common during phacoemulsification, and because such air bubbles may represent a cause of endothelial cell loss, the endothelial damage caused by air bubbles during phacoemulsification merits further study.

Adult↗
PubMed1986

Differences between men and women as related to intraocular lens implantation.

We examined 291 cases of IOL implantation in order to evaluate differences between males and females for several factors. We found that women have shorter axial lengths, older age at time of surgery, greater preoperative corneal curvature, higher power of IOL implanted, more surgically induced astigmatism, and a higher rate of complications. Insignificant differences between the two groups included pre- and postoperative refraction, preoperative astigmatism, visual acuity, type of IOL implanted, corneal thickness, endothelial cell count, and percent of patients requiring discissions.

Aged↗
PubMed1985

Factors associated with poor predictability by intraocular lens calculation formulas.

In this study, we evaluated and compared two groups of posterior chamber intraocular lens (IOL) implantation cases. One group consisted of patients whose postoperative refraction was accurately predicted by IOL calculation formulas, while the other group included patients whose postoperative refraction was poorly predicted by the same formulas. We found that although postoperative astigmatism was greater in the poorly predicted group, preoperative to postoperative changes in astigmatism did not differ between the two groups. The poorly predicted group also had a shorter average axial length, a greater proportion of females, and an increased variability in most of the measurements we performed. The two groups did not differ significantly in terms of measured postoperative anterior chamber depth, age at the time of the surgery, IOL power and style implanted, complication rate, or preoperative corneal integrity.

Age Factors↗
PubMed1985

Clinical evaluation of six intraocular lens calculation formulas.

We examined the results of posterior chamber intraocular lens (IOL) implantation and evaluated six commonly used IOL power calculation formulas (original Binkhorst, modified Binkhorst, Colenbrander, Shammas, Hoffer, and SRK regression) to determine which ones produce the most accurate and predictable results. We found that the accuracy of the various formulas depends upon several factors, including the surgeon's technique, the type and style of posterior chamber IOL implanted, and the axial length of the eye being operated on. Furthermore, we found that the results using the different formulas vary in a consistent pattern. Surgeons must therefore evaluate their cases periodically to determine which formulas and IOL styles will provide their patients with the most accurate and satisfying results.

Biometry↗