Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epikeratophakia is a rapidly evolving surgical procedure for the refractive correction of aphakia. Even when Snellen acuity after epikeratophakia is normal, patients often report a subjective degradation of the visual image through the surgically corrected eye. To further define visual performance in the patient with optically successful epikeratophakia, we examined contrast sensitivity in two patients surgically corrected for monocular aphakia. Contrast thresholds were measured over a range of spatial frequencies using both computer-generated sinusoidal gratings and a commercially available wall chart system. The eye with epikeratophakia in each case was compared with the opposite normal eye with comparable acuity. One patient was also tested prospectively in the same eye both before and after surgery. Data demonstrate a depression of the contrast sensitivity function in the middle and high spatial frequencies induced by the placement of an epikeratophakia lenticule when compared with the normal eye or contact lens-corrected, preoperative aphakic eye with comparable good acuity. These findings may explain the subjective experience of epikeratophakia patients.
Cornea 1988
PMID:Contrast sensitivity after epikeratophakia. 321 62

1. Crayfish exhibit steady-state compensatory eyestalk rotations in response to rotations of the organism or the visual surround. For stimuli in the vertical planes (pitch or roll) the visual reflexes are mediated by identified visual interneurons [sustaining fibers (SFs)], which synapse on identified oculomotor neurons (Mns) (18). 2. The optimal visual stimulus is broad-field intense illumination (simulated skylight) distributed over the dorsal half of the cornea. These stimuli are also optimal for eliciting a regular pacing discharge in SFs with dorsal receptive fields (17). Since a unique discharge pattern is associated with the reflex stimulus, we proposed that the pacing discharge interval encodes the stimulus condition and is optimal for driving the motoneuron discharge. 3. The cross-correlation of SF and Mn impulse trains exhibit large peaks (or troughs) at short latencies associated with strong excitatory (or inhibitory) interactions and "secondary effects" at longer delays associated with the periodicity of the Mn impulse train. The secondary peaks and troughs indicate delayed periods of elevated or depressed Mn excitability synchronized to the reference train (SF) events. From the structure of the cross-correlograms and the motoneuron autocorrelograms we predicted that the spike-to-spike synaptic throughput should be differentially sensitive to the various classes of SF interspike intervals. 4. The hypotheses were tested with logical-correlation functions that directly measure the relative synaptic efficacy of several classes of SF intervals during a continuous train at constant mean rate. The results indicate that the SF-to-Mn excitatory synapse is maximally driven by SF impulses separated by approximately 85 ms. These events are about 2.5 times as effective as the impulses associated with short intervals (less than 20 ms) and 1.4 times as effective as the spikes of long intervals (250 ms). The optimal interval in the various preparations is highly to correlated to the period of the Mn discharge and the SF modal interspike interval. Inhibitory synapses are also differentially sensitive to the SF interspike intervals, but they exhibit summation rather than depression in response to short interspike intervals. 5. These results are generally consistent with previously formulated relationships (39), which govern the synaptic modulation of pacemakers and may apply to any synaptic interaction in which the postsynaptic neuron exhibits a regular discharge. 6. Combinations of long and short intervals with the same mean rate as the optimal interval are not as effective in driving the SF-to-Mn synapse.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Interval coding and band-pass filtering at oculomotor synapses in crayfish. 334 5

It has recently been shown that wavelengths in the near-UV range (UV-A, 320-400 nm) are capable of influencing pineal melatonin content in the hamster. The purpose of this study was to compare the capacities of monochromatic visible and UV radiation for suppressing nocturnal pineal melatonin. Groups of male Syrian hamsters adapted to a 14-h light, 10-h dark cycle (lights on, 1700-0700 h) were exposed to irradiances of 500 or 360 nm light for 5 min during their dark phase. Both wavelengths suppressed pineal melatonin in a dose-related manner. The resultant fluence-response curves were similar in shape, although their corresponding threshold irradiances were markedly different. The calculated ED50 values for 500 and 360 nm light were 0.022 microW/cm2 (1.66 X 10(13) photons/cm2) and 0.306 microW/cm2 (1.66 X 10(14) photons/cm2), respectively. These data show that the induction of a 50% depression of pineal melatonin requires 10 times the number of 360-nm photons compared to 500-nm photons at the level of the cornea. Despite this difference in sensitivity to wavelength, environmental irradiances of UV-A are well above the threshold for melatonin suppression in the hamster. These results thus demonstrate the importance of considering UV-A, in addition to the visible wavelengths, in the regulation of hamster pineal physiology.
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PMID:The suppression of nocturnal pineal melatonin in the Syrian hamster: dose-response curves at 500 and 360 nm. 359 19

With the use of a micropolarographic system, the effects of a series of isopropyl alcohol concentrations on oxygen uptake by the corneal epithelium of the rabbit were measured in vivo. Based on an exposure period of 10 sec, followed by a saline rinse, concentrations of greater than 31% were found to cause an abrupt and severe decline in oxygen uptake, with oxygen flux responses associated with 44% and greater being indistinguishable 60 min later from those of an epithelially denuded cornea. Initial flux variations, e.g. a mild depression at 24% and a mild elevation at just under 31%, were still evident 1 h following exposure. A slope model for estimating that concentration, the aerobic reduction dosage, which would reduce the oxygen flux activity of the epithelium to half, called here the ARD50, was found for this exposure time to be 37%. That estimate is in very close agreement with measured responses. A susceptibility ratio (SR), for comparing the relative toxicities of different agents based on the quotient of their ARD50 values, was calculated here for sodium hydroxide and isopropyl alcohol, and found to be 50:1.
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PMID:Aerobic responses of the cornea to isopropyl alcohol, measured in vivo. 361 54

The corneal and blink reflexes were evaluated in 20 normal subjects and in 30 patients with motor deficits secondary to unilateral hemispheral lesions of vascular origin. In the normal population there were no differences between subjects below and subjects above 50 years of age. In the patients the reflex evoked by electrical stimulation of the cornea of the clinically affected side was depressed in 24 out of 30 cases. The depression mainly affected the afferent branch of the circuit, which triggers both homolateral and contralateral orbicularis oculi discharge (afferent abnormality). In three cases the depression was exerted concomitantly on the efferent branch (afferent and efferent abnormality) and only in one case was it limited to the efferent branch (efferent abnormality). The late R2 component of the blink reflex was depressed in 15 out of 30 patients. The early R1 component was slightly facilitated on the affected side. The changes of the corneal reflex and of the R2 component of blink reflex were similar, but the blink reflex had a greater safety factor. The patients with an abnormal corneal reflex had more extensive damage than had the patients with normal corneal response, as shown by computer tomography, but the site of the lesion was comparable in the two groups. Conduction through the brain stem circuits mediating the orbicularis oculi response is normally under pyramidal facilitatory influences while facial motoneurons are subjected to pyramidal inhibition. After pyramidal damage the transmission of impulses in the brain stem was slowed down, ultimately to a degree that abolished the reflex. Removal of pyramidal inhibition on facial motoneurons is probably the basis of the slight facilitation of the R1 component of the blink reflex.
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PMID:The orbicularis oculi response after hemispheral damage. 631 88

To clarify the mechanisms by which incisions and sutures produce corneal astigmatism, we made incisions and wedge resections closed by sutures in the corneoscleral limbus of human eye bank eyes, studying the changes in corneal curvature by shadowgraph photography of the corneal contour, by central keratometry, and by measurement of corneal diameter. The compression of tissue within the sutures or the closure of an excision of a wedge of tissue by sutures induced astigmatism in the meridian of surgery regardless of changes in the sagittal depth of the anterior chamber. Sutures and wedge resections closed by sutures in the anterior part of the cornea compressed or removed more tissue from the anterior part than the posterior part, producing a depression of the limbal cornea toward the anterior chamber and steepening the central cornea in the meridian of surgery. The corneal diameter decreased in that meridian. In the opposite meridian, the cornea flattened, the corneal diameter increased, and the sagittal depth decreased.
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PMID:Changes in corneal curvature induced by sutures and incisions. 639 Nov 81

Local anesthetics may have a cytotoxic effect which causes a depression in the apparent epithelial oxygen uptake rate (AEOR) of the cornea. We measured the AEOR of human corneas in vivo before and after applying 1% tetracaine (amethocaine) HCl and 0.4% benoxinate HCl. These drugs had no effect on AEOR. In human corneas that had been subjected to a period of hypoxia, AEOR was slightly higher after administration of benoxinate, a result in the opposite direction to that expected on the grounds of toxicity. The increase was not statistically significant. We conclude that clinical doses of tetracaine HCl and benoxinate HCl normally have a minimal cytotoxic effect, and that this is similarly true when benoxinate is applied to the cornea after contact lens wear.
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PMID:Apparent respiration rate of the human corneal epithelium with tetracaine HCl and benoxinate HCl. 666 Feb 79

There is little absolute data in the form of prospective studies in patients with specific illnesses who are on oral contraceptives (OCs). Consequently, the clinician must depend on well-founded empiric decisions in prescribing the pill for these patients. The basis for the decision should be a firm understanding of the pathophysiology and laboratory effects of OCs. This needs to be juxtaposed with an understanding of the efficacy and effects of the estrogen and progestational components of the birth control pill and their interactions with maintenance medications. Available evidence is reviewed for the following medical disorders: central nervous system disorders (depression, Wilson's disease, headaches, epilepsy, multiple sclerosis, and the eye); immunologic and connective tissue diseases; diseases of the endocrine system, the gastrointestinal system, the genitourinary system, the memopoietic system; and skin disorders. 7% of women on OCs have increased or newly reported depression. Whether these are primarily psychogenic or metabolically derived is yet to be definitively determined. Wilson's disease can be exacerbated by OCs because of increased plasma ceruloplasmin and increased absorption of copper from the gastrointestinal tract. Headaches can be either a vague or a specific symptom, such as migraines, but 1/3 of these patients will become worse on OCs. There is good evidence that the headaches are caused by falling estrogen levels. There is no good evidence that epilepsy, in general, becomes worse on OCs. OCs have relatively no effect on the longterm prognosis in multiple sclerosis. Increased corneal sensitivity has been observed with OC use, and this has usually presented an intolerance to the use of contact lenses. This is primarily the result of increased edema of the cornea and changing of its contour. By inference, OCs cause some basic universal changes in the immunologic system. OCs have been reported as a cause of a rare form of rheumatoid arthritis, but the Royal College reports a decrease in incidence of cell-mediated immunologic disease, specifically rheumatoid arthritis in its more familiar form. There is no evidence that OCs markedly influence thyroid disease, but they do markedly alter thyroid function testing. OCs do not produce a chronic addisonian state nor do they inhibit the ability of the adrenal-pituitary axis to respond to stress. OCs can be used in thyroid disease but with some caution in hypothyroid states. They should not be used in patients with Cushing's syndrome and are not recommended in patients with adenomas. In general, estrogen works as an irritant to the gastric mucosa, but there is no increase in peptic ulcer diseases associated with OC use, and the incidence of duodenal ulcer disease is decreased. The most striking liver disease seen with OCs is cholelithiasis. The incidence is increased 2-fold. OCs should not be prescribed for patients with chronic renal disease because of the vascular effects as well as the reported increased risk of urinary tract infection. The Royal College report has shown a decreased incidence of iron deficiency anemia in patients on OCs. Various skin changes have been reported in women using OCs. The most common of these is chloasma. In all the diseases studied thus far, the use of OCs has not precipitated a catastrophic change.
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PMID:The use of birth control pills in women with medical disorders. 702 14

1. The afferent responses evoked by mechanical and thermal stimulation of the cat cornea were recorded extracellularly from strands of long and mixed ciliary nerves under deep anaesthesia. 94% of the units studied (n = 53) responded consistently to both stimuli. 2. Conduction velocities, measured by electrical stimulation of the receptive field, corresponded to the lower range of the A-delta fibre group (average = 5.4 m/sec). Receptive fields covered approximately a quadrant of the corneal surface and showed continuous sensitivity and overlapping. Units were silent in the absence of stimulation but an ongoing activity was commonly present after repeated mechanical and thermal stimulation. 3. Mechanical responses were evoked at low thresholds and consisted of a dynamic and static response that paralleled the amplitude of the stimulus. The pattern of the discharge was irregular and fatigue was easily developed by repeated stimulation. 4. Thresholds to heating were above 38 degrees C and the response increased monotonically with the temperature over the range from threshold to 50 degrees C. The heat response could be sensitized by repeated long suprathreshold stimulation while variable changes in the response were induced by briefer stimuli. Also depression was observed in some circumstances. A weak response to cooling was present in 50% of the units tested. 5. Damaging mechanical stimulation or the application of a strong acid solution evoked a vigorous response followed by an earlier discharge that persisted for hours. 6. The relation of these receptors to other polymodal nociceptors and corneal sensation is considered.
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PMID:Responses of cat corneal sensory receptors to mechanical and thermal stimulation. 733 16

It was established previously that depression of the mitotic activity in the rat cornea induced by pyrogenal administration and exposure to cooling was not attended by changes in the level of labeled nuclei (LLN) and pathological mitoses (PM). This paper shows that adrenalectomized rats developed an increase in PM from 3.9--4.6% (control animals) to 13..9--16.8% (animals exposed to cooling or given pyrogenal). This increase was associated with the reduced LLM and label intensity. Cytophotometric analysis of the DNA content in the nuclei revealed an increase in the number of tetraploid nuclei from 3.2% (in the cornea of intact rats) to 10.9% in rats with adrenals, 6 hours after pyrogenal administration. This phenomenon was accounted for by prolongation of G2M phase. The action of the stressor on adrenalectomized animals produced no changes in tetraploid nuclei. The evidence obtained indicates that the stressor-induced increase in the level of PM in the cornea of rats with reduced adaptability is not a single event in the cell cycle.
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PMID:[Effect of stressors on the mitotic regime and certain cell cycle events in the corneal epithelium of adrenalectomized rats]. 740 56


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