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At least 901 records · Page 50Linked to original sources
PubMed2003

Fibroblast growth factor-2 protects endothelial cells from damage after corneal storage at 4 degrees C.

BACKGROUND: Since the introduction of cold corneoscleral segment storage prior to keratoplasty there have been continuous efforts to ameliorate the preservation media in order to better maintain the quality of the corneal epi- and endothelium. Recent studies have shown that basic fibroblast growth factor (FGF-2) preserves the viability of, for example, retinal ganglion cells and pigment epithelium cells. Therefore, we investigated the effect of different concentrations of FGF-2 added to a modified Optisol storage medium on endothelial damage after corneal storage at 4 degrees C. METHODS: . Bovine corneas were stored at 4 degrees C for 14 days and for another 24 h at 34 degrees C. Various FGF-2 concentrations (4, 20 and 40 ng/ml) were added to the medium either at day (D) 1, D14, or both D1 and D14. Quantitative evaluation of corneal damage after 14+1 days of storage was conducted by means of the Janus green photometry assay. Histological and ultrastructural investigations of the preserved endothelium were also performed. Bovine cell culture experiments using the TUNEL assay aimed to elucidate the role of FGF-2 on prevention of endothelial apoptosis. RESULTS: The mean endothelial damage in control corneas increased from 4.9 +/- 1.8% (fresh corneas) to 13.4 +/- 2.4% after 14+1 days of storage. FGF-2 at 20 ng/ml or 40 ng/ml added at any of the indicated time points significantly reduced the overall endothelial damage by 5.1-7.3%, corresponding to 38-54% less endothelial damage than in control corneas (P<0.001). Light- and electron microscopic investigations confirmed this protective effect of FGF-2 on corneal endothelial cells. The TUNEL assay revealed a true anti-apoptotic effect of FGF-2 on endothelial cells in culture. CONCLUSION: Our study clearly demonstrates the effectiveness of FGF-2 to enhance cell survival of the corneal endothelium after storage at 4 degrees C. A clinical interest could be seen in the potential future application of FGF-2 as an adjuvant to corneal preservation media in order to better maintain endothelial viability during corneal storage.

Animals↗
PubMed1998

Post-operative inflammation following deep sclerectomy with collagen implant versus standard trabeculectomy.

BACKGROUND: An investigation was carried out to compare post-operative inflammation following deep sclerectomy with collagen implant (DSCI) versus standard trabeculectomy. METHODS: In this prospective randomized study, 46 eyes of 46 Caucasian patients with medically uncontrolled chronic open-angle glaucoma and without previous glaucoma surgery underwent filtering surgery. Twenty-four eyes underwent DSCI. Twenty-two eyes underwent standard trabeculectomy. Pre- and post-operative flare, measured using laser flare photometry, were compared between the two groups. RESULTS: In both groups, the mean anterior chamber flare increased on the first post-operative day, then decreased progressively. DSCI was associated with lower flare measurements post-operatively. The difference was statistically significant up to 1 month post-operatively: 16.3 +/- 7.8 vs 72.5 +/- 38.9 (P < 0.001) at 1 day, 7.8 +/- 4.6 vs 44.7 +/- 29.2 (P < 0.001) at 1 week, 5.9 +/- 1.6 vs 7.0 +/- 2.8 (P = 0.012) at 1 month, 6.4 +/- 1.8 vs 6.5 +/- 1.9 (P = 0.77) at 2 months, 5.9 +/- 1.8 vs 6.1 +/- 1.6 (P = 0.65) at 3 months. CONCLUSION: Surgically induced inflammation can be reduced with DSCI. This may be due to the lack of iridectomy, irrigation, and penetration of the anterior chamber. Eyes at increased risk of post-operative inflammation, such as those with uveitic or traumatic glaucoma, may benefit from this procedure. Further studies are needed to evaluate the long-term functional and anatomical outcomes of DSCI.

Aged↗
PubMed1998

Cicatrization of cytomegalovirus retinitis following introduction of highly active anti-retroviral therapy: uveitis as a possible indicator of good ocular prognosis.

PURPOSE: To quantify the inflammatory reaction that can be seen in HIV-infected patients with cytomegalovirus (CMV) retinitis after the introduction of an HIV protease inhibitor and correlate it with ocular findings and systemic HIV parameters. METHODS: Report of a patient with CMV retinitis systematically followed by slit-lamp examination, funduscopy, fundus photographs and laser flare photometry before and after introduction of an HIV protease inhibitor. RESULTS: Manifest granulomatous panuveitis developed 2 months after the introduction of the protease inhibitor indinavir (CD4 rise from 2 to 64 CD4/mm3) and coincided with cicatrization of the CMV retinitis in the absence of efficient anti-CMV therapy. CONCLUSION: Occurrence of uveitis in patients with CMV retinitis following the introduction of HIV protease inhibitors may be a factor indicating a good ocular prognosis, possibly pointing to the presence of the anti-CMV repertoire in the reconstituting CD4 cell population.

Adult↗
PubMed2003

Effects of extracellular sodium on mu-opioid receptors coupled to potassium channels coexpressed in Xenopus oocytes.

Wild-type or mutant H297N or H297Q of the mu-opioid receptor were co-expressed with the inwardly rectifying potassium channel GIRK1 in oocytes from Xenopus laevis. Under voltage clamp, pairs of concentration response curves were generated using the agonist normorphine in a bathing medium containing 38.5 mM sodium or an identical medium in which the sodium was replaced by an equimolar concentration of choline. The maximum currents were greater in the presence of sodium by about 30% at wild-type receptors and by about 100% at the mutant receptors. The EC(50) values tended to increase somewhat as well, though these differences reached statistical significance only for the mutant H297Q. Flame photometry detected no change in the intracellular sodium or potassium concentrations of oocytes, suggesting that the effect of sodium was solely extracellular. Thus sodium, long known for its effects on in vitro ligand binding at mu-opioid receptors, also affects overall transduction as revealed in the Xenopus oocyte model of a complete, living cell system.

Animals↗
PubMed1999

A transient and a persistent calcium release are induced by chlorocresol in cultivated mouse myotubes.

The effect of 4-chloro-m-cresol (4-CmC), a stabilizing agent used in commercial preparations of the muscle relaxant succinylcholine, on intracellular free calcium levels in cultivated mouse myotubes was studied. Calcium signals were monitored with an inverted microscope equipped for fluorescence photometry using fura-2 as the calcium indicator. Upon bath application of 500 microM 4-CmC for 90 s, two separate calcium signals, a transient and a sustained one, could be regularly discriminated. First, with a delay of 2 s, the intracellular calcium concentration increased from 41+/-13 to 541+/-319 nM, peaked after 2-5 s and declined within 10 s to nearly resting values (n=36). Then, after a delay of up to 20 s, intracellular calcium rose quickly again to almost the same value and stayed elevated as long as the drug was applied. Upon drug removal, intracellular calcium rapidly decreased to a new level that was always slightly higher than the original base line. At 250 microM 4-CmC, the response was small, whereas at 500 microM it was at its maximum. Thus, the concentration-response curve was very steep. Replacement of extracellular calcium by EGTA and application of calcium channel blockers revealed that, for both the transient and the sustained response, calcium was released from intracellular stores. Pre-treatment with thapsigargin (0.1 microM) or ryanodine (10 microM) abolished both signal components. Repeated short-term applications of 4-CmC suggest that the two components may arise from different systems.

Animals↗
PubMed2002

Histochemical analysis of phenylphenalenone-related compounds in Xiphidium caeruleum (Haemodoraceae).

Phenylphenalenones represent a typical group of secondary metabolites of the Haemodoraceae. Some of these phenolic compounds show organ-specific distribution within the plant. However, detailed information on cellular localisation is still lacking. To this end, confocal laser-scanning microscopy, microspectral photometry and high-performance liquid chromatography were used to study the tissue localisation of phenylphenalenone-type compounds in Xiphidium caeruleum Aubl. From the autofluorescence potential of these compounds, specific distribution of allophanylglucosides and non-glucosidic compounds of the phenylphenalenone-type in distinct cells of the roots (apical meristem, cortex, cap, epidermis) and the shoot system was revealed. Fluorescence enhancement using "Naturstoff reagent A" (NA) indicated the occurrence of NA-positive natural products in the vacuoles of leaf epidermal cells. The present results provide new insights into the possible functions of phenylphenalenone-related compounds in the context of their localisation. Additionally, the advantages and limitations of the techniques are discussed.

Caffeic Acids↗
PubMed1996

Mitotic activity of the hemocytes in the tick Ixodes ricinus (Acari; Ixodidae).

The blood cells, or hemocytes, of Ixodes ricinus have been shown to recognize, attack, and phagocytose microorganisms invading the body cavity, or hemocoel, of this tick. Regulated proliferation and differentiation of hemocytes, also referred to as immunocytes, is basic to an effective immune response to invading microorganisms. Therefore, this study dealt with hemopoiesis in I. ricinus, the vector tick of the Lyme disease spirochete Borrelia burgdorferi. Histological evidence for the presence of hemopoietic tissue, a preferential proliferation site of hemocytes, is presented. Mainly the mitotic activity of free-floating hemocytes was examined. By means of microscopical photometry and flow cytometry, all three types of hemocytes in engorging female I. ricinus were found in different stages of the cell cycle. In the engorging tick, up to 40% of the hemocytes counted were in the S phase or the G2/M phase. From this study we conclude that the differentiated hemocyte types do not differentiate from stem cells in the adult tick. Moreover, microorganisms entering the hemocoel of engorging ticks are confronted with high numbers of hemocytes and, therefore, with an effective cellular immune response.

Animals↗
PubMed2000

CO2 environment influences the growth of cultured human cancer cells dependent on insufflation pressure.

BACKGROUND: Experimental and clinical studies, have suggested that the CO2 pneumoperitoneum influences the development of intraabdominal tumor dissemination and port site metastases. Previous experiments performed both in vitro and in vivo have proved that CO2 insufflation stimulates malignant cell growth. Therefore, we designed a study to investigate the influence of CO2 insufflation administered at different pressures on the growth of cultured human tumor cells. METHODS: Two human tumor cell lines (CX-2 colon adenocarcinoma, DAN-G pancreas adenocarcinoma) were exposed to a CO2 environment maintained at different pressures (0 mmHg, 6 mmHg, 12 mmHg). Tumor growth was determined at different times after exposure to CO2 using fluorescence photometry. Cytotoxity of the CO2 environment different pressures was investigated using flow cytometry. RESULTS: At 1-4 days after exposure to CO2 insufflation, CX-2 and DAN-G tumor cell growth was decreased significantly (p < 0.01). Proliferation of pancreatic adenocarcinoma DAN-G increased significantly from day 5 to day 15 independent of the insufflation pressure (p < 0.01). Proliferation of colon adenocarcinoma CX-2 increased significantly from day 5 to day 15 but was found to be dependent on the insufflation pressure. CX-2 growth increased significantly with higher pressures (p < 0.05). CONCLUSION: CO2 insufflation influences the growth of cultured human tumor cells. After a short period of suppression, the CO2 environment stimulates malignant cell growth. The insufflation pressure may also have additional effects in promoting tumor growth.

Adenocarcinoma↗
PubMed2006

Effect and mechanism of betaxolol and timolol on vascular relaxation in isolated rabbit ciliary artery.

PURPOSE: In order to clarify the vasodilatory mechanism of betaxolol and timolol, we studied the effects of these drugs in isolated rabbit ciliary arteries. METHODS: Rabbit ciliary artery specimens were mounted in a double myograph system, and betaxolol, timolol, or another agent was introduced into the organ chamber. The mechanical response of the arteries was studied using an isometric tension recording method. The intracellular free calcium concentration [Ca2+]i was also measured using fluorescence photometry. RESULTS: Betaxolol and timolol induced dose-dependent relaxation in the rabbit ciliary arteries precontracted by high-K+ Krebs solution. The minimum concentrations required to cause relaxation were 10 microM of betaxolol, and 30 microM of timolol. At the maximum concentration of 1 mM, betaxolol induced almost complete relaxation of the ciliary arteries, whereas timolol induced approximately 70% relaxation. These actions were not inhibited by pretreatment with 100 microM NG-nitro-l-arginine methylester (L-NAME), a nitric oxide synthase inhibitor, or by denudation of the vascular endothelium. However, 300 microM of betaxolol or timolol decreased the [Ca2+]i of the vascular smooth muscle, an action similar to that of diltiazem, a typical L-type voltage calcium-channel blocker. CONCLUSIONS: Betaxolol, a selective beta1-adrenoceptor antagonist, and timolol, a nonselective beta-adrenoceptor antagonist, both frequently used in the medical management of glaucoma, decrease [Ca2+]i by acting as Ca2+ channel blockers, thus causing relaxation of isolated rabbit ciliary artery.

Adrenergic beta-Antagonists↗
PubMed2005

Physicochemical characterization of the reassembled dimer of an integral membrane protein OmpF porin.

The in vitro reassembled species of OmpF porin, which was renatured from its denatured monomer using n-octyl-beta-D-glucopyranoside, was characterized by low-angle laser light scattering photometry, circular dichroism spectroscopy and synchrotron radiation small-angle X-ray scattering measurements. The light scattering measurement reconfirmed that the reassembled species was the dimer of the protein. Circular dichroism spectra of the reassembled dimer showed a native-like beta-structure. A small-angle X-ray scattering measurement indicated that the size of the reassembled dimer was nearly equal to that of the native trimer under the present experimental conditions. In a thermal denaturation experiment followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the reassembled dimer was less stable than the native trimer.

Dimerization↗
PubMed2004

RNA synthetic activity of glutamate dehydrogenase: determination of enzyme purity, RNA characteristics, and deamination/amination ratio.

The activity of glutamate dehydrogenase (GDH), an important enzyme in carbon and nitrogen metabolism, is routinely assayed by photometry. The RNA synthetic activity of the enzyme provides new technologies for assaying its activity. The enzyme was made to synthesize RNAs in the absence of DNA and total RNA but with different mixes of the four nucleoside triphosphates (NTPs) in order to investigate the RNA characteristics. RNase VI (hydrolyzes base-paired residues) digested the poly (U,A) RNA completely because the U and A residues were evenly distributed to produce many base-paired regions. Therefore, the synthesis of RNA by GDH was by random addition of NTPs. The RNA synthetic activity of the enzyme was at least 50-fold more active in the deamination than in the amination direction, thus providing a robust technology for assay of the enzyme's activity. cDNAs prepared from the RNAs were subjected to restriction fragment differential display polymerase chain reaction analyses. Sequencing of the cDNA fragments showed that some of the RNA synthesized by GDH shared sequence homology with total RNA. Database searches showed that the RNA fragments shared sequence homologies with the G proteins, adenosine triphosphatase, calmodulin, phosphoenol pyruvate (PEP) carboxylase, and PEP carboxykinase, thus explaining the molecular mode of their functions in signal transduction.

Amination↗
PubMed2002

Retinal photoreceptors of Syrian hamsters undergo oxidative stress during streptozotocin-induced diabetes.

AIMS/HYPOTHESIS: The aim of this study was to verify whether retinal photoreceptors, like other tissues, are subject to oxidative stress during diabetes. METHODS: Oxidative stress was monitored by the oxidation of preloaded dehydrorhodamine 123 into fluorescent rhodamine 123, during a period of intense illumination of isolated rod retinal receptor cells. These were obtained from 22 Syrian hamsters injected with streptozotocin (50 mg/kg body weight., intraperitoneal route) 90 days before the study began. Eleven hamsters were treated daily with melatonin (0.4 mg/kg body wt., per os), an antioxidant synthesized within photoreceptors. Isolated photoreceptors were bathed on the stage of a Leitz Orthoplan microscope, where the fluorescent lamp also served as the light stimulus (485 nm). Fluorescence irradiance was measured by photometry and stored in a personal computer for further analysis. RESULTS: The light-induced oxidant production greatly decreased and was also delayed in the streptozotocin-injected hamsters compared with the control hamsters matched for age. Similar effects were obtained in control photoreceptors after 40 min incubation with 2-2'-azobis (2-amidinopropane) dihydrochloride, a potent lipoperoxidation inducer. The effect of melatonin was to partially restore the light-induced fluorescence response. CONCLUSION/INTERPRETATION: The depression of the light-induced oxidative response in diabetic photoreceptors could be ascribed to a hyperglycaemia-induced background of oxidative stress whereby the light-oxidizable substrate is actually lowered. Melatonin induces a larger fluorescence response during illumination, probably as a consequence of its antioxidant effect during diabetes, which would provide more oxidizable lipids.

Amidines↗
PubMed1983

Automated methods for detection of bacteriuria.

Urine specimens represent a large portion of cultures received by the clinical microbiology laboratory. Much time and effort are spent screening these specimens and approximately 80 percent show no growth. The methods employed for detection of bacteriuria include microscopic, chemical, culture, and automated. The most widely used procedure has been an agar plate culture method. However, this method requires overnight incubation and therefore results are delayed. Within the last decade many automated methods have been introduced for detecting bacteriuria, and results are available more rapidly than with the agar plate culture method. In addition to decreased detection time, these systems are accurate and cost-effective. The purpose of this report is to review these automated bacteriuria screening systems, which include bioluminescence, colorimetry, electrochemical screening, electrical impedance, microcalorimetry, photometry, and radiometry. Accuracy, detection time, and cost are also discussed in this review.

Adenosine Triphosphate↗
PubMed1984

Photometric and fluorometric continuous kinetic assay of acid phosphatases with new substrates possessing longwave absorption and emission maxima.

A direct and continuous kinetic method for the photometric and fluorometric determination of various acid phosphatases is described. It is based on new coumarin-derived phosphates, which after enzymatic hydrolysis undergo dissociation to form intensely colored and strongly fluorescent phenolate anions. The latter have absorption maxima ranging from 385 to 505 nm, and fluorescence maxima between 470 and 595 nm. The new substrates were compared with respect to their rate of enzymatic hydrolysis, optimum pH, and detection limits of acid phosphatase from potato and wheat germ. Detection limits of 0.001 unit/ml were found by photometry, and as low as 0.00006 unit/ml by fluorometry. The principal advantages of the new substrates over existing ones are longwave absorptions and emissions, large Stokes shifts, and the low pKa values of the corresponding phenols, thus allowing a direct and continuous assay of acid phosphatase even in weakly acidic solutions.

Acid Phosphatase↗
PubMed1976

Kinetic studies of phototransients in bacteriorhodopsin.

Aqueous suspensions of bacteriorhodopsin in purple membrane fragments from Halobacterium halobium have bben subjected to microsecond flash photometry utilizing both unpolarized and polarized light. Depletion of the ground state chromophore centered at 570 nm is accompanied by the formation of transients absorbing maximally at 410 nm and 660 nm with rise times of about 0.4 and 6 ms, respectively. Decay of both transients and reformation of the ground state chromophore occurs with identical first-order kinetics with a half life of about 6 ms. All three chromophores are polarized with dichroic ratios which remain constant throughout the transient lifetimes, indicating that Brownian rotation of the chromophore within the membrane is considerably restricted. Whereas agents which induce permeability of membranes to protons (2,4-dinitrophenol, carbonylcyanide-m-chlorophenylhydrazone) and non-specific univalent cations (gramicidin) or inhibit ATPase (ouabain) had no influence, the K+-specific ionophore valinomycin in the presence of K+ inhibited and quenched the formation of the 660 nm transient with concomitant increase in lifetime of the 410 nm transient and delay in recovery of the 570 nm chromophore. High concentrations of Na+ produced an effect similar to that of valinomycin. The relationship of these data to the mechanism of the proton pump in the intact bacterium is discussed, with the conclusion that the 410 nm transient performs a key role.

Bacteriorhodopsins↗
PubMed1978

Influence of membrane lipids on the photochemistry of bacteriorhodopsin in the purple membrane of Halobacterium halobium.

Purple membrane fragments from Halobacterium halobium were reconstituted with the native lipids replaced by dipalmitoyl phosphatidylcholine and by egg lecithin. In parallel studies the temperature dependence of bacteriorhodopsin phototransient lifetime and absorption dichroism and of in situ lipid microviscosity were determined; the former two by, respectively, conventional and polarization flash photometry, and the latter by observation of emission depolarization of an embedded fluorescent dye, 1,6-diphenyl-1,3,5-hexatriene. Discontinuities in lipid microviscosity profiles in native and egg lecithin purple membrane were reflected in both the photochemical cycle frequency and bacteriorhodopsin chromophore rotational mobility. The influence exerted by membrane-lipid viscosity appears to be a secondary effect, and points to the bacteriorhodopsin chromophoric group being situated in the protein interior.

Bacteriorhodopsins↗
PubMed1981

Lipid-protein interaction in the photolysis of octopus rhodopsin.

Microvillar membranes of octopus photoreceptor cells were treated with phospholipase A2, phospholipase C, hexane, or their combinations. By these means, various membrane preparations containing qualitatively and quantitatively different lipids were obtained. The lipid composition and phospholipid content of the membrane preparations obtained by the above methods were determined. Photochemical processes in the digitonin extract of the native and treated membranes have been studied by flash photometry. The results suggest that several different variations in the lipids can affect the rates of the photochemical transformations; these are: the content of phospholipid, the amount of unsaturated hydrocarbon chains and free fatty acids.

Animals↗
PubMed1982

K+ transport in 'tight' epithelial monolayers of MDCK cells. Evidence for a calcium-activated K+ channel.

Measurements of 86Rb efflux across the apical and basal-lateral aspects of intact monolayers of 'high-resistance' MDCK cells mounted in Ussing chambers have been made. A transient increase in 86Rb efflux across both epithelial borders upon stimulation with adrenalineeeeeee or ionophore A23187 is observed. The increased 86Rb across the basal cell aspects is of greatest quantitative importance. Measurements of total cellular K+ contents by flame photometry of tissue extracts indicate a net loss of K+ following adrenalin addition. The effects of adrenalin and ionophore A23187 upon 86Rb efflux are abolished in 'Ca2+ -free' media. The properties of the Ca2+ -dependent increase in 86Rb efflux show similarities to Ca2+ -activated K+ conductances in other tissues, notably human red cells, including inhibition by quinine (1 mM), tetraethylammonium (25 mM) and insensitivity to bee venom toxin (apamin) (25 nM). Adrenalin is only effective when applied to the basal bathing solution suggesting that the receptors mediating adrenalin action are located upon the basal-lateral membranes. Half maximal stimulation of 86Rb efflux by adrenalin is observed at 9.1 X 10(-7) M. The action of various adrenergic receptor agonists and antagonists are consistent with adrenalin action being mediated by an alpha-adrenergic receptor.

Animals↗