A history of M.S. and Ph.D. programs offered by schools and colleges of optometry in North America

This paper gives an overview of the history of M.S. and Ph.D. graduate programs offered by schools and colleges of optometry. It also highlights some of the contributions of Henry Hofstetter to graduate education.     

Maximum cardiac output during incremental exercise by first-pass radionuclide ventriculography

A flow injection hydride atomic absorption spectrometric (FI-HAAS) method was developed for determining selenium in human milk and whole blood after microwave digestion of the sample. The sample (2 mL human milk or 0.25 mL blood) was introduced into the microwave vessel with 1.5 mL HNO3 and 0.25 mL H2O2 and 300 W (4 min) and 600 W (4 min) were applied. The digestion was completed by heating to 140 degrees C (2-3 h). Se (VI) was reduced to Se (IV) with hydrochloric acid. The instrumental conditions for FI-HAAS (concentrations of reducing agent and carrier acid, flow rate of argon carrier gas, and sample volume injected) were optimized. The detection limit of the proposed method was 0.23 ng/mL (assay) or 115 pg Se (absolute) in biological samples (1.15 ng/mL milk, 10.4 ng/mL blood). The precision values were 5.0% for milk and 4.0% for blood. The accuracy was evaluated with 2 reference materials, National Institute of Standards and Technology Non-Fat Milk Powder (found: 104.3 +/- 7.2 ng/g, certified: 110 +/- 10 ng/g) and Whole Blood Seronorm (found: 81 +/- 7.3 ng/mL, reference: 83 +/- 4 ng/mL). The results show the suitability of the method for selenium determination in human milk and whole blood. The method was applied to whole blood samples obtained from pregnant women and to human milk.     

Estimating eye care workforce supply and requirements

PURPOSE: To estimate the workforce supply and requirements for eye care in the United States. METHODS: Three models were constructed for analysis: supply of providers, public health need for eye care, and demand (utilization) for eye care. Ophthalmologists, other physicians, and optometrists were included in the models. Public health need was determined by applying condition-specific prevalence and incidence rates from population-based and other epidemiologic studies. Demand was determined by use of national databases, such as the National Ambulatory Care Survey, National Hospital Discharge Survey, and Medicare Part B. Time requirements for care were obtained through a stratified sample survey of the membership of the American Academy of Ophthalmology. RESULTS: Under modeling assumptions that use a work-time ratio of one between optometrists and ophthalmologists and between specialist and generalist ophthalmologists, a significant excess of eye care providers exists relative to both public health need and demand. Changes in the work-time ratio, work-hours per year per provider, care patterns for the same condition, or other factors could significantly reduce or eliminate the surplus relative to need. CONCLUSION: If optometrists are the preferred primary eye care provider, ophthalmologists would be in excess under all demand scenarios and all need scenarios where the optometrist to ophthalmologist work-time ratio is greater than 0.6. No excess of ophthalmologists would exist if ophthalmologists are the preferred primary eye care provider. Data on the appropriate work time ratio will help refine estimates of the imbalance between supply and requirements.     

Intraocular pressure fluctuations during scleral buckling surgery

PURPOSE: The purposes of this study are to measure real-time intraocular pressure (IOP) during scleral buckling and to determine the effects of elevated IOPs on ocular perfusion. PATIENTS AND METHODS: A standard 4-mm, 20-gauge infusion cannula was inserted through the pars plana, connected to a standard hemodynamic monitoring unit with an electronic pressure transducer, and calibrated. The authors measured real-time IOP in 20 eyes undergoing scleral buckling surgery for primary rhegmatogenous retinal detachments and determined the IOP required to close the central retinal artery. Pressure measurements were read from the monitor videoscreen intraoperatively and from a continuous paper tracing postoperatively. RESULTS: The patients ranged in age from 24 to 88 years (mean, 59.7 years). The highest IOP elevations occurred during scleral depression and cryopexy, ranging up to 210 mmHg (mean, 116 mmHg). Pressures at which the central retinal artery closed ranged from 48 to 110 mmHg (mean, 79.2 mmHg). Manipulations of the globes caused IOPs greater than the central retinal artery perfusion pressures in 13 of the 20 patients. The duration of pressures in excess of the central retinal artery perfusion pressure ranged from 6 to 402 seconds (mean, 118.8 seconds). There were no intraoperative or postoperative complications from the infusion cannula. CONCLUSIONS: Conventional scleral buckling surgery causes wide fluctuations in IOP and may impair ocular perfusion. Additional studies are needed to determine the long-term consequences of these pressure elevations.     

Herd immunity to filarial infection is a function of vector biting rate

Despite the existence of an impressive body of work on human immune responses against filarial infections, the occurrence of a protective response to infection remains unclear. Here, we use a combined modelling and comparative data analysis framework to address this issue for human infections with the filarial parasite, Wuchereria bancrofti. By analogy with previous work, the analysis involves the comparison of observed field patterns of infection with epidemiological patterns predicted by a mathematical model of parasite immunity. Unlike most other human helminths, which are transmitted by ingestion or dermal penetration, exposure to infection with lymphatic filariasis can be measured explicitly in terms of vector mosquito biting rates, thereby also allowing, probably for the first time, examination of the suggested role of exposure in generating herd immunity to macroparasites. Observed field patterns in this study were derived from 19 different published studies, which gave parallel estimates of community exposure rates and the corresponding age--prevalence patterns of infection, while predictions of the epidemiological impact of herd immunity were obtained using a catalytic model framework. The results provide the first conclusive evidence to date that variations in the observed age--prevalence patterns of infection in filariasis can be effectively explained by the occurrence of an exposure-driven acquisition of herd immunity. We discuss this result in terms of implications for the new World Health Organization-led initiative for the global control of this parasitic disease.     

Lead differentially modifies cytokine production in vitro and in vivo

An imbalance between helper T cell type 1 (Th1) and helper T cell type 2 (Th2) activation can result in immunodysregulations leading to impaired cell-mediated immunity with an increased incidence of infectious disease or cancer and/or aberrant humoral immunity that may culminate with an autoimmune disease. Mercury, a heavy-metal toxicant, is known to induce renal autoimmunity characterized by a predominant Th2 response. Lead, another metal toxicant, causes enhanced B cell activities and impairs host resistance to several bacterial and viral infections. In addition, Pb was reported to enhance Th2 proliferation and inhibit Th1 proliferation. The differential effects of Pb on Th subset activation have been further investigated. In vitro IL-4 production by a Th2 clone was significantly increased by the addition of PbCl2, whereas IFN gamma production by a Th1 clone was decreased by the addition of PbCl2. When BALB/c mice were subcutaneously exposed to PbCl2, ex vivo Il-4 production by anti-CD3-stimulated splenic T cells was enhanced, but IFN gamma production was inhibited. Additionally, the plasma IL-4 and IgE levels of Pb-exposed mice were increased, and the plasma IFN gamma levels were significantly lowered in the absence of any additional exogenous antigen. In vitro, ex vivo, and in vivo treatment with HgCl2 produced similar findings. This study is the first report of the preferential activation of a Th2 response by Pb in vivo and suggests that PB, like Hg, may induce autoimmune responses by upsetting the balance between Th1- and Th2-like cells, which could enhance production of antibodies to self antigens.     

A base-pairing interaction between U2 and U6 small nuclear RNAs occurs in > 150S complexes in HeLa cell extracts: implications for the spliceosome assembly pathway

In mammalian cells, base pairing between the U2 and U6 small nuclear RNAs is required during pre-RNA splicing. We show by psoralen crosslinking of HeLa nuclear extract that U2.U6 base pairing occurs within abundant ribonucleoprotein complexes that sediment at > 150 S in glycerol gradients. All of the spliceosomal RNAs (U1, U2, U4, U5, and U6) cosediment with these large complexes, suggesting that they may be related to small nuclear RNA-containing structures called speckles/coiled bodies or snurposomes, which have been visualized in mammalian or amphibian nuclei, respectively. In contrast to nuclear extract, S100 extract, which is splicing-defective and lacks the > 150S complexes, does not contain base-paired U2.U6. However, U2.U6 base pairs form in S100 extract that has been made splicing-competent by supplementation with Ser/Arg-rich (SR) proteins, ATP, and an adenovirus splicing substrate. During splicing in supplemented S100 extract, U2.U6 base pairing precedes the appearance of splicing intermediates and occurs initially in an approximately 60S spliceosome complex but also in progressively larger (100-300 S) complexes. Possible functional relationships between the 60S spliceosome and the > 150S complexes are discussed.