[Mushroom poisoning by amatoxin--current diagnosis and treatment].
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Diuresis↗
Biomedical subjects
K Green
Publications and source records attributed to K Green.
Development of a gas chromatographic-mass spectrometric method using a stable isotope internal standard for quantitation of thromboxane B2.
Tetradeuterated 19, 19',20,20'-2H4-thromboxane B2 was synthesized and used as a stable isotope internal standard for the development of a gas chromatographic/mass spectrometric (GC/MS) method to quantitate thromboxane B2. Quantitation was based on the detection of fragment ions at m/z 301 for thromboxane B2 and m/z 305 for the corresponding tetradeuterated internal standard. At m/z 301/305 a response equivalent to a protium/deuterium ratio of 0.2% thromboxane B2 could be measured with a standard deviation of 15% when 100 nanograms of the tetradeuterated internal standard was analyzed. For measurement of cellular biosynthesis of thromboxane B2 in whole blood or platelet rich plasma, the internal standard and naturally occurring thromboxane B2 were i) isolated by solvent extraction, or sequestration to XAD-2 columns; ii) purified by reversed phase high performance liquid chromatography; and iii) converted to methoxime methyl ester trimethylsilyl ethers prior to analysis. A limited comparison was made using both radioimmunological and mass spectrometric quantitation of thromboxane B2.
Animals↗
Eye drops of RU 486-6, a peripheral steroid blocker, lower intraocular pressure in rabbits.
A peripheral corticosteroid blocker RU 486-6, instilled as a 1% suspension at random into one eye of 12 rabbits, produced a consistent fall in intraocular pressure as measured by a hand-held applanation tonometer, when compared with the fellow control eye. This or a similar drug may be applicable for treatment of human open-angle glaucoma, or ocular hypertension, by eliminating that part of ocular tension attributable to the effect on aqueous outflow of the normal and fluctuating level of tissue corticosteroids.
Animals↗
Effect of HEPES buffer on corneal storage in MK medium.
Rabbit corneas were stored for 7 days in either MK medium containing gentamicin or modified MK medium containing HEPES buffer, gentamicin and phenol red. Corneas stored for 7 days in modified MK medium were thicker than corneas stored in MK medium. Corneal endothelial permeability to inulin and dextran was similar following 7 days of storage in either solution. Transmission electron microscopy of corneal endothelial cells stored in either solution showed intact cell membranes and organelles. In vitro perfusion of rabbit corneas in the specular microscope with Krebs Ringer bicarbonate containing HEPES buffer swelled at 17 +/- 1 micron/h, whereas those perfused with Krebs Ringer bicarbonate alone swelled at 7 +/- micron/h. Perfusion with Krebs Ringer bicarbonate containing phenol red did not result in an increased corneal swelling rate. The work indicates that HEPES buffer has an adverse effect on corneal endothelial pumping function, and this results in corneal swelling during storage as well as during perfusion in the specular microscope. The adverse effect appears to be, at least in part, transient: however, the ultimate, long term effect of HEPES buffer on corneas stored prior to penetrating keratoplasty is not known and deserves continued investigation.
Animals↗
Aqueous humour turnover and intraocular pressure during menstruation.
Both intraocular pressure and aqueous humour turnover rate were determined at intervals over three months in three females in order to investigate whether a correlation existed between these variables and the menstrual cycle. Not only was there a lack of correlation between intraocular pressure or aqueous humour flow rate and menses but intraocular pressure and aqueous humour flow rate were also not related to each other. If pharmacologically administered doses of progesterone or oestrogen influence intraocular pressure, the present data indicate that the effect is probably mediated through effects on the aqueous outflow pathways.
Adult↗
Mental health, absences from work, stress and satisfaction in a sample of New Zealand primary school teachers.
A study of 296 primary school teachers in New Zealand revealed a very low correlation between mental health, measured by the General Health Questionnaire, and absence from work. The correlations between mental health and feelings of stress at work and between mental health and job satisfaction were higher. The most highly rated sources of stress were ranked, as were the most highly rated sources of satisfaction. It is suggested that teachers' experiences of stress are associated with lack of satisfaction with intrinsic aspects of their job rather than with dissatisfaction at their conditions of employment.
Absenteeism↗
Effect of topical epinephrine and timolol on ocular and optic nerve blood flow in phakic and aphakic rabbit eyes.
The effects of 4% epinephrine bitartrate and 0.5% timolol on ocular and optic nerve blood flow were studied in phakic and aphakic rabbit eyes using a radioactive microsphere (85Sr) technique. Either epinephrine or timolol was given topically as eight drops in the hour immediately preceding blood flow measurements (one drop every 7.5 minutes). Epinephrine decreased anterior uveal blood flow in both phakic and aphakic eyes, whereas timolol exhibited no effect. Retinal and choroidal blood flow were not affected by either timolol or epinephrine in phakic eyes. In aphakic eyes, epinephrine increased choroidal blood flow without altering retinal blood flow, whereas timolol increased both retinal and choroidal blood flow. Optic nerve blood flow was increased in epinephrine treated phakic and aphakic eyes and also in timolol treated aphakic eyes.
Animals↗
Potassium superoxide induction of rabbit corneal endothelial cell damage.
Rabbit corneal endothelial cells were perfused with a Krebs Ringer bicarbonate solution to which potassium superoxide had been added. Concentrations of potassium superoxide of 0.5 mM and higher resulted in severe anatomic and physiologic alteration of endothelial cells that resulted in corneal swelling. Catalase offered protection whereas the toxic effect was unaltered by superoxide dismutase, ascorbic acid, DETAPAC, EDTA, EDTA-FeC1(20, or DMSO. The data suggests that hydrogen peroxide is the toxic species and that superoxide anion and hydroxyl free radical are either not toxic in this system or are at such low concentrations that cell damage does not occur. The role of singlet oxygen cannot be defined, but its participation appears unlikely. Endothelial intracellular glutathione levels and redox state were unaffected by perfusion with a solution to which 0.3 mM potassium superoxide had been added.
Animals↗
Intracellular potential and pH of rabbit corneal endothelial cells.
Rabbit corneal endothelial pH and electrical potential have both been determined using tracer distribution techniques. Intercellular pH was measured using the dimethyloxazolidine-dione method and intracellular potential was measured using tetraphenylphosphonium bromide. Intracellular pH was determined as 7.10 in an ambient solution of pH 7.5. The only solution variations which altered intracellular pH were variations in the external solution pH, bathing in sodium-free or bicarbonate-free solution, incubation for 3 hours with 10(-6) or 10(-4) M ouabain or for 1 hour with 10(-4) M ouabain or in a high (60 mM) bicarbonate solution. The data indicate a close correlation between sodium and bicarbonate needs for the endothelium which corresponds with known effects of these ions on transendothelial ion fluxes. Intracellular potentials were measured of -34 mV, which were stable in the face of all environmental perturbations except 1 mM acetazolamide and 10(-6) M ouabain exposure for 3 hours. These newer techniques may be employed to provide some clues into the mechanism of endothelial transport systems.
4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
Marihuana-derived material: distribution and effects after systemic administration.
Studies have been made in an attempt to elucidate the mode of action of water-soluble marihuana-derived material (MDM). MDM lowers intraocular pressure (IOP) at systemic dose levels greater than 5 micrograms/rabbit by reducing aqueous humor inflow. Blood pressure, body temperature, and PO2 remain constant despite the wide variation in IOP caused by high dose levels of MDM, viz. an initial hypertensive phase followed by a hypotensive phase. Blood PCO2 and pH, however, both decrease with 1 mg MDM/rabbit indicating an acidosis which may partially explain some of the fall in IOP caused by MDM at this high dose level. Low doses of MDM (50 micrograms/animal), however, induce no such changes in systemic chemistry, illustrating the absence of an MDM effect which can explain the greater than 50% fall in IOP. Repeated injections of MDM on a weekly basis indicate a sequentially reduced effect on IOP. MDM, when incubated in vitro for 6 hours with saline, aqueous or vitreous, always induced a fall in IOP; incubation in these media for 24 hours, however, reduced the capacity to induce an IOP decrease. When aqueous or vitreous was removed from animals which had received intravitreal injections of MDM 24 hours previously (thus, at a time when the IOP in these animals was low) and was reinjected intravitreally into fresh recipient rabbits, the IOP fell in the recipients with aqueous, but not vitreous. Only when high doses of MDM (greater than or equal to 2 mg) were given systemically to a donor rabbit was any evidence obtained of a fall in IOP in recipient rabbits at short times after the donor injection (less than 10 min); at greater times after the donor injections whole blood or serum from donor rabbits failed to elicit a fall in IOP in recipient animals. These data indicate that, in vivo, MDM is bound or metabolized rapidly in rabbits when MDM is given systemically.
Animals↗
A revised technique for extracapsular lens extraction in the rabbit.
The surgical procedure described here for extracapsular lens extraction utilizes a bent 25 gauge needle as an irrigating cystotome , a 100 degrees superior clear corneal incision, a single clean incision of the lens capsule, a muscle hook for expression of the nucleus, no cortical cleanup, and interrupted 9-0 nylon sutures to close the incision. We have found it a simple and effective technique which utilizes inexpensive instruments commonly available in an ophthalmology department or ophthalmic research laboratory.
Animals↗
Effect of ionic changes, amino acids, and metabolic inhibitors on hydraulic conductivity of the isolated rabbit iris-ciliary body.
The hydraulic conductivity (Lp) of the rabbit ciliary epithelium has been measured under various conditions. Of the ionic changes in the bathing medium imposed upon the tissue, replacement of sodium and either depletion of bicarbonate or deletion of potassium all caused an increase in Lp. Chloride replacement had no effect on Lp. The changes in Lp occur more slowly than the changes in electrical parameters caused by the same perturbations and indicate that ions and fluid move across this tissue by different routes. Of the 10 amino acids tested, only three increased Lp; 2 basic and 1 neutral amino acid. No correlation existed between posterior chamber: plasma ratios, or the nature of the amino acid (i.e., basic, neutral, or acidic) and the effect on Lp. Of the metabolic inhibitors, only iodoacetic acid induced an increase in Lp. The transport inhibitor, ouabain, at concentrations up to 10(-4) M for 4 hours was without effect. The effects of these agents on electrophysiological parameters, therefore, must be confined to net ionic pathways. Inulin and sucrose permeabilities were determined under either a zero or 10 mmHg hydrostatic pressure gradient using radioactive tracers. Application of a hydrostatic pressure gradient increased sucrose permeability by ten-fold but only increased inulin permeability by 20%. This data, together with control tissues run in parallel with many of the experimental tissues, indicates that the tissue is not highly leaky and does not change characteristics with time.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acids↗
A distinction between the effects of sentential speaking rate and semantic congruity on word identification.
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Humans↗
On the nature of rate-dependent processing during phonetic perception.
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Humans↗
Cornea endothelial rose bengal photosensitization. Effect on permeability, sodium flux, and ultrastructure.
Rabbit corneal endothelial cells demonstrated an increase of endothelial membrane permeability to inulin following perfusion with 5 X 10(-6) M rose bengal and exposure to 1050 muW/cm2 incandescent light for either 1 min or 5 min when compared to corneas similarly perfused with rose bengal but not exposed to light. Endothelial permeability to dextran was unaltered following the photosensitization reaction. Rose bengal perfusion in the absence of light caused an increase in the unidirectional sodium fluxes (J stroma endothelium and J endothelium stroma); however, a net sodium flux was still present and directed from the stroma to the endothelium. Exposure of rose bengal perfused endothelial cells to incandescent light resulted in a further increase in the unidirectional passive sodium flux in both directions and a reduction in the active component of the sodium flux from stroma to endothelium. This caused a reduction in the net active transport of sodium across the endothelium following the photosensitization reaction. Transmission electron microscopy showed no alteration of endothelial cell ultrastructural integrity following rose bengal perfusion in the absence of light. However, rose bengal perfusion accompanied by exposure to 1050 muW/cm2 incandescent light caused swelling of endoplasmic reticulum and mitochondria. The data indicate that rose bengal photosensitization has an adverse effect on endothelial cell energy production as well as transport and barrier function.
Animals↗
Hydrogen peroxide-mediated corneal endothelial damage. Induction by oxygen free radical.
Polymorphonuclear leukocytes and other inflammatory cells release superoxide anion and additional oxidant species following stimulation. Corneal endothelial cells were exposed to a flux of chemically generated superoxide anion (oxygen-free radical) produced by the combination of 1 mM hypoxanthine and 0.06 U/ml xanthine oxidase. Exposure of endothelial cells to the combination of hypoxanthine and xanthine oxidase resulted in anatomic disruption of the cells with interference in the function of endothelial water movement and resultant swelling of the corneal stroma. Catalase reduced the corneal swelling caused by exposure of endothelium to the oxygen-free radical generating system, whereas superoxide dismutase, ascorbic acid, D-mannitol, and ethanol did not prevent damage. The data suggest that hydrogen peroxide produced during the dismutation reaction of the superoxide anion is one of the toxic species, whereas the superoxide anion itself and the hydroxyl-free radical probably do not participate. The data suggest that corneal endothelial cells are susceptible to physiologic and anatomic damage induced by the products of reactive oxygen species, which, from previous studies, are known to be generated by inflammatory cells. The development of therapeutic modalities directed at the prevention of damage produced by hydrogen peroxide and other oxidant species may be of benefit in reducing corneal endothelial cell damage secondary to ocular inflammatory disease processes.
Animals↗
Inner ring deiodination of thyroxine and 3,5,3'-triiodothyronine by human fetal membranes.
Indirect evidence, based on injection of thyroxine (T4) into the amniotic cavity of humans, and maternal thyroidectomy in the rat, suggests that fetal membranes might be capable of converting T4 to 3,3',5'-triiodothyronine (rT3) by virtue of inner ring iodothyronine deiodinase activity. The present study was undertaken to provide direct evidence that human fetal membranes contain inner ring iodothyronine deiodinase activity directed toward T4 and 3,5,3'-triiodothyronine (T3). Homogenates of human fetal membranes were incubated with 125I-labeled T4, rT3, and T3, and with stable T4. Conversion of 125[I]-T4 to 125[I]-rT3 was noted in chorion and amnion. 125I-T3 was converted to 125[I]-3,3'-diiodothyronine (T2) in chorion and amnion. 125[I]-rT3 was stable in fetal membranes under the incubation conditions employed. Time-, temperature-, pH-, and protein content-dependent conversion of stable T4 to rT3 was found in fetal membranes. Iodothyronine metabolism did not occur in the absence of dithiothreitol. These studies indicate that human fetal membranes contain an inner ring deiodinase enzyme. Because of its intimate contact with the amniotic cavity, this enzyme may generate a portion of the rT3 found in amniotic fluid.
Amnion↗
Topical epinephrine and regional ocular blood flow in aphakic eyes of rabbits.
The effects of 4% topical epinephrine bitartrate on regional ocular blood flow were studied in normal, "sham-operated," and aphakic eyes of rabbits. Anterior uveal blood flow decreased in all cases, but reductions in the ciliary processes were less pronounced in aphakic eyes than in sham-operated eyes. Doubling the dose (from 2 to 4 drops) abolished this difference in the ciliary processes, but the increased dose was accompanied by the emergence of a similar (although lesser) effect in the iris. The latter dose additionally decreased retinal blood flow in aphakic eyes compared with the sham-operated eyes. Lens extraction, thus, seems to remove a notable diffusion barrier to topical epinephrine, resulting in both attenuation of its anterior segment effects and in potentiation of a vasoconstrictive response in the posterior pole.
Animals↗