Late onset pulmonary embolism in young male otherwise healthy COVID-19 patients.

SARS-CoV-2 infection is associated with increased risk of thrombosis in severely ill patients but little is known about the risk in outpatients with mild to moderate disease. Our case series consists of four male otherwise healthy patients between 32 and 50 years of age. Initial symptoms completely resolved but they developed new onset of dyspnea and thoracic pain at days 14 to 26. CT scan revealed pulmonary embolism in all patients which led to hospitalization. Standard anticoagulation practice needs to be re-evaluated and may  be considered for certain outpatients with COVID-19.

Body temperature and respiratory dynamics in un-shaded beef cattle.

In this study body temperature (BT, °C) and panting score (PS, 0-4.5; where 0 = no panting/no stress and 4.5 = catastrophic stress) data were obtained from 30 Angus steers housed outside over 120 days Steers were implanted with a BT transmitter on day -31, BT was recorded at 30-min intervals to a data logger and downloaded each day to a database. The cattle were housed in ten outdoor un-shaded pens with an earthen floor, eight of which had a pen floor area of 144 m2 (three transmitter steers plus five non-transmitter steers; 18 m2/steer) and two had an area of 168 m2 (three transmitter steers and six non-transmitter steers; 18.7 m2/steer). Only data from the transmitter steers were used in this study. The PS of the steers was obtained daily (± 15 min) at 0600 hours (AM), 1200 hours (MD) and 1600 hours (PM). At the same times climate variables (ambient temperature, black globe temperature, solar radiation, relative humidity, wind speed and rainfall) were obtained from an on-site weather station. PS observations were made from outside the pens so as not to influence cattle responses. The two closest BT values to the time when PS was obtained were downloaded retrospectively from a logger and averaged. A total of 8,352 observations were used to generate second order polynomial response curves: (AM) y = 39.08 + 0.009 x + 0.137x2 (R2 = 0.94; P < 0.001) (MD) y = 39.09 + 0.914x − 0.080x2 (R2 = 0.89; P < 0.001) and (PM) y = 39.52 + 0.790x − 0.068x2 (R2 = 0.83; P < 0.001) where y = BT (°C) and x PS. These data suggest that PS is a good indicator of body temperature. The BT at MD corresponded to slightly lower PS compared with PM, e.g., for PS 1; BT at MD = 39.1 ± 0.05 °C whereas BT at PM = 39.5 ± 0.05 °C. However during AM, BT was lower (P < 0.05) at PS 1, 2 and 2.5 compared with MD and PM. For example, when PS was 2.5 the BT at AM was 40.2 ± 0.04 °C, at MD it was 40.9 ± 0.04 °C and at PM BT was 41.1 ± 0.04 °C. When PS was 0 the BT at AM and MD were similar. The AM response curve suggests animals attempt to increase heat dissipation during the cooler AM period relative to MD and PM. Morning observation of cattle (before feeding) are crucial for effective heat load management especially on days when high heat load is expected. The MD and PM observations provide a good indication of the impact of high environmental heat load on cattle. Differences in PS between AM and PM observations suggest that more research is needed to determine the effect of night time conditions on BT, PS and overall respiratory dynamics of cattle during periods of hot weather.

Establishment of an optimized ex vivo system for artificial root canal infection evaluated by use of sodium hypochlorite and the photodynamic therapy.

AIM: To establish a refined model of artificially infected root canals and confirm its suitability as a sensitive ex vivo method to assess the efficacy of disinfecting agents. Disinfection was evaluated using sodium hypochlorite (NaOCl), either blocked or unblocked by sodium thiosulphate, and a recently promoted method of disinfection, the antibacterial photodynamic therapy (PDT). METHODOLOGY: The roots of bovine incisors were sectioned into three parts, the canals of coronal and middle regions were filled with a suspension of Enterococcus faecalis and the apical region with culture medium. After 7 days, coronal sections were disinfected using NaOCl (0.5%, 1.0% and 3.0% for 30, 60 and 600 s) or a system for photoactivated chemotherapy (PACT; Cumdente, Tübingen, Germany) for antibacterial PDT. Apical sections served as sterile controls and middle sections as bacterial growth controls. In half of the NaOCl-treated specimens, disinfection was arrested. Dentine chips from biopsies at different depths from the central canal towards the periphery were plated and assessed for colony-forming units (CFU). Disinfection was considered biologically relevant if the reduction of CFU was at least three log10 orders of magnitude. RESULTS: Colony-forming units of 10³ - 104 in growth controls indicated effective artificial infection. A biologically relevant reduction of CFU was accomplished with unblocked NaOCl, but not after blocking with NaOCl nor with PDT. CONCLUSIONS: The system reliably detected disinfection of the root canal and dentinal tubules and proved suitable for ex vivo testing of root canal disinfection. The effect of NaOCl depended on the duration of impact. Under the present experimental conditions, the antibacterial PDT system did not achieve sufficient disinfection.

Evaluation of different point-of-care tests to characterize the vaginal discharge of sows after parturition and parameters' correlation with subsequent reproductive performance.

The lochia is the physiological uterine discharge post-partum, whereas abnormal fluids are often indicators of puerperal disorders in sows, which negatively influence the further reproductive performance. The aim of the study was to characterize the vaginal discharge in sows employing simple and feasible tests and to correlate the evaluated parameters with the subsequent reproductive performance of these sows. The birth process of 48 clinically healthy free farrowing sows was monitored and several parameters characterizing the vaginal discharge such as total amount, colour, amount of cells (somatic cell count) and cell characteristics (cytology) were collected daily from first to fifth day after parturition. Finally, the reproductive performance of the following gestation was evaluated and compared to the characteristics of the lochia. The amount of vaginal discharge was significantly increased on the second (p < 0.01), third (p = 0.019) and fourth (p = 0.011) day post-partum compared to day one. Furthermore, a decrease in the percentage of neutrophilic granulocytes from day one to three (p = 0.038), four (p = 0.038) and five (p = 0.048) post-partum was observed. The percentage of neutrophilic granulocytes in the yellowish vaginal discharge was increased compared to whitish (p = 0.02) or clear (p = 0.027) vaginal discharge. In addition, obstetrics (p = 0.003) and an increased farrowing duration (p = 0.017) significantly increased the amount of vaginal discharge. Sows with a high amount of vaginal discharge had a significant higher body temperature than sows with no (p = 0.014) or low amount (p < 0.01) of vaginal discharge. No correlation was detected between the evaluated parameters of the lochia and the subsequent reproductive performance. It is hypothesised that the amount of vaginal discharge alone is not a predictor for the performance of sows during their next gestation. However, it might serve as indicator for acute endometritis. In summary, the different parameters of the vaginal discharge determined by means of point-of-care tests might be useful to strengthen a presumptive diagnose of endometritis in sows during the first five days after parturition.

Atomic layer deposition (ALD) as a coating tool for reinforcing fibers.

Layers of alumina were deposited on to bundled carbon fibers in an atomic layer deposition (ALD) process via sequential exposure to vapors of aluminium chloride and water, respectively. Scanning electron microscopic (SEM) images of the coated fibers revealed that each individual fiber within a bundle was coated evenly and separately, fibers are not bridged by the coating. SEM and transmission electron microscopic (TEM) images indicate that the coating was uniform and conformal with good adhesion to the fiber surface. Average deposition rate, measured from SEM images, was 0.06 nm per cycle at 500 °C. SEM also revealed that at deposition temperatures of 500 °C few of the fibers were damaged. At temperatures of 300 °C, no damaged fibers were observed, the average deposition rate decreased down to 0.033 nm per cycle. Oxidation resistance of the alumina-coated fibers was characterized by thermogravimetric analysis (TGA). The alumina coating improved oxidation resistance of the carbon fiber significantly. Oxidation onset temperature was 600 °C for fibers coated with a 45 nm thick alumina. Uncoated fibers, on the other hand, started to oxidize at temperatures as low as 250 °C.

Tympanic temperature in confined beef cattle exposed to excessive heat load.

Angus crossbred yearling steers (n = 168) were used to evaluate effects on performance and tympanic temperature (TT) of feeding additional potassium and sodium to steers exposed to excessive heat load (maximum daily ambient temperature exceeded 32°C for three consecutive days) during seasonal summer conditions. Steers were assigned one of four treatments: (1) control; (2) potassium supplemented (diet containing 2.10% KHCO3); (3) sodium supplemented (diet containing 1.10% NaCl); or (4) potassium and sodium supplemented (diet containing 2.10% KHCO3 and 1.10% NaCl). Overall, additional KHCO3 at the 2% level or NaCl at the 1% level did not improve performance or heat stress tolerance with these diet formulations. However, the addition of KHCO3 did enhance water intake. Independent of treatment effects, TT of cattle displaying high, moderate, or low levels of stress suggest that cattle that do not adequately cool down at night are prone to achieving greater body temperatures during a subsequent hot day. Cattle that are prone to get hot but can cool at night can keep average tympanic temperatures at or near those of cattle that tend to consistently maintain lower peak and mean body temperatures. In addition, during cooler and moderately hot periods, cattle change TT in a stair-step or incremental pattern, while under hot conditions, average TT of group-fed cattle moves in conjunction with ambient conditions, indicating that thermoregulatory mechanisms are at or near maximum physiological capacity.

Assessing the heat tolerance of 17 beef cattle genotypes.

Cattle production plays a significant role in terms of world food production. Nearly 82% of the world's 1.2 billion cattle can be found in developing countries. An increasing demand for meat in developing countries has seen an increase in intensification of animal industries, and a move to cross-bred animals. Heat tolerance is considered to be one of the most important adaptive aspects for cattle, and the lack of thermally-tolerant breeds is a major constraint on cattle production in many countries. There is a need to not only identify heat tolerant breeds, but also heat tolerant animals within a non-tolerant breed. Identification of heat tolerant animals is not easy under field conditions. In this study, panting score (0 to 4.5 scale where 0 = no stress and 4.5 = extreme stress) and the heat load index (HLI) [HLI(BG<25°C) = 10.66 + 0.28 × rh + 1.30 × BG - WS; and, HLI (BG> 25°C) = 8.62 + 0.38 × rh + 1.55 × BG - 0.5 × WS + e((2.4 - WS)), where BG = black globe temperature ((o)C), rh = relative humidity (decimal form), WS = wind speed (m/s) and e is the base of the natural logarithm] were used to assess the heat tolerance of 17 genotypes (12,757 steers) within 13 Australian feedlots over three summers. The cattle were assessed under natural climatic conditions in which HLI ranged from thermonuetral (HLI < 70) to extreme (HLI > 96; black globe temperature = 40.2°C, relative humidity = 64%, wind speed = 1.58 m/s). When HLI > 96 a greater number (P < 0.001) of pure bred Bos taurus and crosses of Bos taurus cattle had a panting score ≥ 2 compared to Brahman cattle, and Brahman-cross cattle. The heat tolerance of the assessed breeds was verified using panting scores and the HLI. Heat tolerance of cattle can be assessed under field conditions by using panting score and HLI.

Performance and carcass characteristics of steers fed with two levels of metabolizable energy intake during summer and winter season.

Climate change is producing an increase on extreme weather events around the world such as flooding, drought and extreme ambient temperatures impacting animal production and animal welfare. At present, there is a lack of studies addressing the effects of climatic conditions associated with energy intake in finishing cattle in South American feed yards. Therefore, two experiments were conducted to assess the effects of environmental variables and level of metabolizable energy intake above maintenance requirements (MEI) on performance and carcass quality of steers. In each experiment (winter and summer), steers were fed with 1.85 or 2.72 times of their requirements of metabolizable energy of maintenance. A total of 24 crossbred steers per experiment were used and located in four pens (26.25 m2/head) equipped with a Calan Broadbent Feeding System. Animals were fed with the same diet within each season, varying the amount offered to adjust the MEI treatments. Mud depth, mud scores, tympanic temperature (TT), environmental variables, average daily gain, respiration rates and carcass characteristics plus three thermal comfort indices were collected. Data analysis considered a factorial arrangement (Season and MEI). In addition, a repeated measures analysis was performed for TT and respiration rate. Mean values of ambient temperature, solar radiation and comfort thermal indices were greater in the summer experiment as expected (P<0.005). The mean values of TT were higher in steers fed with higher MEI and also in the summer season. The average daily gain was greater during summer v. winter (1.10±0.11 v. 0.36±0.06) kg/day, also when steers were fed 2.72 v. 1.85 MEI level (0.89±0.12 v. 0.57±0.10) kg/day. In summer, respiration rate increased in 41.2% in the afternoon. In winter, muddy conditions increased with time of feeding, whereas wind speed and rainfall had significant effects on TT and average daily gain. We conclude that MEI and environmental variables have direct effects on the physiology and performance of steers, including TT and average daily gain, particularly during the winter. In addition, carcass characteristics were affected by season but not by the level of MEI. Finally, due to the high variability of data as well as the small number of animals assessed in these experiments, more studies on carcass characteristics under similar conditions are required.

A 10-Gbit/s EML link using detuned narrowband optical filtering.

In this paper, the effects of asymmetric narrowband optical filtering are investigated in a 10-Gbit/s optical communication link using integrated electro-absorption modulated lasers (EML). We investigate the effect of EML chirp on link performance as well as the optimal filter bandwidth and wavelength detuning. We show that both the phase response and the spectral narrowing of the filter will enable a longer distance transmission by interacting with the EML transient chirp and compensating for the fiber chromatic dispersion. Experimentally, an 8.75-GHz filter is shown to improve the link distance by 40 km from 65 to 105 km, when transmitting over standard single mode fiber.

Generation of repetitive Ca2+ transients by bombesin requires intracellular release and influx of Ca2+ through voltage-dependent and voltage independent channels in single HIT cells.

In the present study, the bombesin-induced changes in cytosolic free Ca2+ ([Ca2+]i) were investigated in single Fura-2 loaded SV-40 transformed hamster beta-cells (HIT). Bombesin (50-500 pM) caused frequency-modulated repetitive Ca2+ transients. The average frequency of the Ca2+ transients induced by bombesin (200 pM) was 0.58 +/- 0.02 min-1 (n = 121 cells). High concentrations of bombesin (> or = 2 nM) triggered a large initial Ca2+ transient followed by a sustained plateau or by a decrease to basal levels. In Ca(2+)- free medium, bombesin caused only one or two Ca2+ transients and withdrawal of extracellular Ca2+ abolished the Ca2+ transients. The voltage-dependent Ca2+ channel (VDCC) blockers, verapamil (50 microM) and nifedipine (10 microM), reduced amplitude and frequency of the Ca2+ transients and stopped the Ca2+ transients in some cells. Thapsigargin caused a sustained rise in [Ca2+]i in the presence of extracellular Ca2+ while in its absence the rise in [Ca2+]i was transient. Verapamil (50 microM) inhibited the thapsigargin-induced increase in [Ca2+]i by about 50%. Depletion of intracellular Ca2+ stores by repetitive stimulation with increasing concentrations of bombesin or thapsigargin in Ca(2+)-free medium caused an agonist-independent increase in [Ca2+]i when extracellular Ca2+ was restored, which was larger than in control cells that had been incubated in Ca(2+)-free medium for the same period of time. This rise in [Ca2+]i and the thapsigargin-induced increase in [Ca2+]i were only partly inhibited by VDCC-blockers. Thus, depletion of the agonist-sensitive Ca2+ pool enhances Ca2+ influx through VDCC and voltage-independent Ca2+ channels (VICC). In conclusion, the bombesin-induced Ca2+ response in single HIT cells is periodic in nature with frequency-modulated repetitive Ca2+ transients. Intracellular Ca2+ is mobilized during each Ca2+ transient, but Ca2+ influx through VDCC and VICC is required for maintaining the sustained nature of the Ca2+ response. Ca2+ influx in whole or part is activated by a capacitative Ca2+ entry mechanism.

CYCLIC adenosine 3',5'-monophosphate potentiates Ca2+ signaling and insulin secretion by phospholipase C-linked hormones in HIT cells.

Neurotransmitters and hormones, by binding to receptors linked to adenylate cyclase or phospholipase C (PLC), increase cytosolic free Ca2+ and potentiate glucose-induced insulin release from beta-cells. Interactions between both signaling pathways may occur and be of relevance to the regulation of insulin secretion. We demonstrate here that in single insulin-secreting HIT cells, forskolin and 8-bromo-cAMP, which stimulate Ca2+ influx through voltage-dependent Ca2+ channels (VDCC), cause a marked increase in the frequency, amplitude, and duration of Ca2+ transients evoked by hormones linked to PLC, such as arginine vasopressin (AVP) or bombesin. Forskolin also potentiates AVP- or bombesin-induced insulin secretion from populations of HIT cells in the presence of elevated glucose (10 mM). BAY K 8644, an activator of VDCC, mimicked the effects of elevated cAMP on both AVP- and bombesin-induced Ca2+ transients and insulin release, which suggests that enhanced Ca2+ influx through VDCC activated by cAMP-dependent mechanisms underlies the positive interactions of both signaling pathways on Ca2+ signaling and insulin secretion. Physiologically, synergistic cross-signaling between the cAMP- and Ca2+ -phosphoinositide signaling pathway could be important for the regulation of insulin release under conditions where extracellular glucose is high and beta-cells are exposed to multiple stimuli activating adenylate cyclase or PLC at the same time.

Ca2+/calmodulin inhibition and phospholipase C-linked Ca2+ Signaling in clonal beta-cells.

Neurotransmitters and hormones, such as arginine vasopressin (AVP) and bombesin, evoke frequency-modulated repetitive Ca2+ transients in insulin-secreting HIT-T15 cells by binding to receptors linked to phospholipase C (PLC). The role of calmodulin (CaM)-dependent mechanisms in the generation of PLC-linked Ca2+ transients was investigated by use of the naphthalenesulfonamide CaM antagonists W-7 and W-13 and their dechlorinated control analogs W-5 and W-12. W-7 (10-30 microM) and W-13 (30-100 microM), but not W-5 (100 microM) and W-12 (300 microM), reversibly inhibited the AVP- and bombesin-induced Ca2+ transients. As the generation of PLC-linked Ca2+ transients requires mobilization of internal Ca2+ and Ca2+ influx through voltage-sensitive (VSCC) and -insensitive (VICC) Ca2+ channels, the effects of the W compounds on these processes were further investigated. First, W-7 dose dependently diminished K+ (45 mM)-induced Ca2+ signals (IC50, approximately 25 microM), and W-13 (100 microM) reduced the K+ (45 mM)-induced [Ca2+]i rise by about 40-60%, whereas W-5 (100 microM) and W-12 (300 microM) had no effect. In addition, W-7 (100 microM) inhibited whole cell Ca2+ currents in mouse beta-cells by about 60%. Second, pretreatment of cells (5 min) with W-7 (30 microM), but not W-5 (30 microM), inhibited agonist-induced internal Ca2+ mobilization by about 75% in Ca2+-free medium. Neither W-7 (30 microM) nor W-5 (30 microM) affected AVP (100 nM)-stimulated formation of IP3. Third, capacitative Ca2+ influx through VICC activated by thapsigargin (2 microM) in the presence of verapamil (50 microM) was inhibited by W-7 (30 microM) but not by W-5 (30 microM). As all of the W compound effects corresponded well to their reported anticalmodulin activity, a specific anticalmodulin action can be assumed. Thus, Ca2+ via activation of CaM-dependent processes could provide positive feedback on the generation of PLC-linked Ca2+ transients in HIT-T15 cells. This appears to involve CaM-dependent regulation of both mobilization of internal Ca2+ and Ca2+ influx through VSCC and VICC.

Metabolism of 5-fluoro-dopa and 6-fluoro-dopa enantiomers in aggregating cell cultures of fetal rat brain.

The cerebral metabolism of enantiomers of 5-fluoro-DOPA (5F-DOPA) and 6-fluoro-DOPA (6F-DOPA) was characterized in organotypic cell cultures of fetal rat brain. This system permits the investigation of metabolic processes in brain tissue exclusively, without the effects of peripheral metabolism and transport. Metabolic profiles for each substrate were determined in comparison with those of L-DOPA and D-DOPA. The uptake of DOPA and fluoro-DOPA in aggregating brain cell cultures is strongly preferential for L-enantiomers. Decarboxylation by aromatic L-amino acid decarboxylase is an active step: the major products are dopamine (DA) or 6F-DA and their corresponding products of oxidative deamination, i.e. dihydroxyphenylacetic acid (DOPAC) or 6F-DOPAC, respectively. Decarboxylation products of D-enantiomers occur in lower amounts, and 5F-D-DOPA is not decarboxylated. However, 5F-DOPA is O-methylated to a great extent, and levels of 3-O-methyl-5F-DOPA are higher after incubation with 5F-D-DOPA than with 5F-L-DOPA. These data may serve as a support for more detailed modeling of [18F]F-DOPA metabolism than can be applied to the evaluation of the cerebral biochemistry of the DA system with positron emission tomography in vivo.

Impairment of ATP-induced Ca2+ -signalling in human thyroid cancer cells.

Extracellular nucleotides like ATP that activate the Ca2+ -phosphatidylinositol (PI) signalling pathway have been suggested to participate in the regulation of normal human thyroid function. We examined, whether P2y-purinergic receptors are expressed on human thyroid cancer cells and whether post-receptor Ca2+ signalling is altered by malignant transformation. Extracellular ATP caused a biphasic increase in cytosolic free Ca2+ ([Ca2+]i) in normal human thyrocytes and in human follicular (FTC) and papillary (PTC) thyroid carcinoma cells. In FTC and PTC cell lines the dose-response curves for ATP-induced changes in [Ca2+]i were shifted to the right when compared with normal thyrocytes, whereas in undifferentiated thyroid carcinoma (UTC) cells even high concentrations of ATP (500 microM) failed to stimulate a rise in [Ca2+]i. By contrast, ATP stimulated inositol 1,4,5-trisphosphate (IP3) formation and capacitative Ca2+ entry was operational as judged by thapsigargin in normal thyrocytes and all thyroid cancer cells. Thus, P2y-purinergic receptors are expressed on thyroid tumor cells independent of degree of differentiation. In UTC cells, however, impairment in the Ca2+ -phosphatidylinositol (PI) signalling cascade occurs distal to the formation of IP3 and proximal to the activation of capacitative Ca2+ entry. Disturbed ATP-induced Ca2+ -signalling and alterations in the Ca2+ -PI signalling cascade may contribute to decreased expression or loss of specific thyroid functions in thyroid cancer cells.

Calcific band keratopathy associated with the use of topical steroid-phosphate preparations.

OBJECTIVE: To report a possible adverse effect of topical steroid-phosphate preparations and to identify factors that may contribute to the development of this effect. DESIGN: The medical records of five patients who developed calcium deposition in the cornea were reviewed and analyzed for possible contributing factors. PATIENTS: Five cases of calcium deposition in the cornea associated with the use of topical steroid-phosphate preparations are described. Scrapings from the cornea and/or specimens obtained at keratoplasty were available in all cases. These cases had the following characteristics in common: use of steroid-phosphate preparations (n = 5); multiple topical drops (n = 5); penetrating keratoplasty (n = 3); presence of epithelial defects (n = 4); history of herpetic stromal keratitis (n = 3) [corrected]; and history of iritis (n = 3). A hypothesis explaining calcium deposition in association with steroid-phosphate preparations is presented. CONCLUSIONS: We recommend withdrawal of steroid-phosphate preparations in patients who develop band keratopathy.

Cerebral blood velocity and other cardiovascular responses to 2 days of head-down tilt.

Spaceflight induces a cephalad redistribution of fluid volume and blood flow within the human body, and space motion sickness, which is a problem during the first few days of spaceflight, could be related to these changes in fluid status and in blood flow of the cerebrum and vestibular system. To evaluate possible changes in cerebral blood flow during simulated weightlessness, we measured blood velocity in the middle cerebral artery (MCA) along with retinal vascular diameters, intraocular pressure, impedance cardiography, and sphygmomanometry on nine men (26.2 +/- 6.6 yr) morning and evening for 2 days during continuous 10 degrees head-down tilt (HDT). When subjects went from seated to head-down bed rest, their heart rate and retinal diameters decreased, and intraocular pressures increased. After 48 h of HDT, blood flow velocity in the MCA was decreased and thoracic impedance was increased, indicating less fluid in the thorax. Percent changes in blood flow velocities in the MCA after 48 h of HDT were inversely correlated with percent changes in retinal vascular diameters. Blood flow velocities in the MCA were inversely correlated (intersubject) with arterial pressures and retinal vascular diameters. Heart rate, stroke volume, cardiac output, systolic arterial pressure, and at times pulse pressure and blood flow velocities in the MCA were greater in the evening. Total peripheral resistance was higher in the morning. Although cerebral blood velocity is reduced after subjects are head down for 2 days, the inverse relationship with retinal vessel diameters, which have control analogous to that of cerebral vessels, indicates cerebral blood flow is not reduced.

Viral keratitis.

Viruses that affect the cornea produce changes that range from benign, self-limited conjunctivitis to sight-threatening scarring and vascularization of the cornea. In this article, the forms of viral keratitis most commonly encountered by the clinician are reviewed. The epidemiology, clinical presentation, and treatment of infection by Herpes simplex virus, varicella zoster virus, and the adenoviruses are discussed. Also included are other viral infections of the cornea.

Refractive changes at extreme altitude after radial keratotomy.

PURPOSE: We studied the effects of altitude on four corneas that had undergone radial keratotomy and four normal corneas exposed to increasing elevation during a high-altitude excursion. METHODS: We measured visual acuity, cycloplegic refraction, keratometry, and intraocular pressure at sea level and after 24-hour exposure to 12,000 and 17,000 ft. RESULTS: We observed a significant increase in spherical equivalence (hyperopic shift) in radial keratotomy eyes exposed to altitude as compared to controls (P < .0001). The average change in spherical equivalent cycloplegic refraction from sea level to 12,000 ft was 1.03 +/- 0.16 diopters and from sea level to 17,000 ft was 1.94 +/- 0.26 diopters. We also observed a significant decrease in keratometry values at altitude as compared with control corneas (P < .0001). The average change in keratometry from sea level to 12,000 ft was 0.59 +/- 0.19 diopter and from sea level to 17,000 ft was 1.75 +/- 0.27 diopters. CONCLUSIONS: Although the specific origin of these changes is open to question, we hypothesize that hypoxic corneal expansion in the area of the radial keratotomy incisions may lead to central corneal flattening and a hyperopic shift in refractive error. The cornea that has undergone radial keratotomy appears to adjust constantly to changing environmental oxygen concentration, producing a new refractive error over a period of 24 hours or more. Additional study is required to identify with certainty the specific origin of the hyperopic shift at high altitude.

Stability of vision during space flight in an astronaut with bilateral intraocular lenses.

PURPOSE: To report excellent and stable vision in an astronaut during space flight after bilateral cataract surgery with intraocular lenses. METHODS: A 60-year-old physician mission specialist astronaut developed cataracts and underwent phacoemulsification with insertion of one-piece polymethylmethacrylate intraocular lenses that had 6-mm optics bilaterally. Several months later, he flew on a space shuttle mission. Ocular examinations were performed before and after the mission, and the patient was questioned about visual changes during flight. RESULTS: Ocular examinations demonstrated stable bilateral posterior chamber intraocular lenses. Our subject reported excellent vision during liftoff, 18 days of microgravity, changes in cabin pressure, and reentry. CONCLUSION: Results suggest that intraocular lenses are safe, effective, and well tolerated during space flight.