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PubMed1989

Foveal cone thresholds.

The method of constant stimuli was used to estimate the psychometric functions for detection of one or two flashes when two light pulses were presented. The test stimulus consisted of two simultaneous 0.5 msec, 1' pulses separated by 17'. Observers reported seeing 0, 1 or 2 flashes. A computer-controlled direct-view apparatus allowed sampling of slightly different foveal locations on each trial. The data were analyzed assuming a binomial probability for sampling of L and M cones and Poisson distributed quantal fluctuation. Under these assumptions, the measurements imply that detection requires a minimum of 5-7 quanta absorbed per cone, and that the effective number of cones illuminated by the 1', 0.5 msec pulse is two. The estimated L/M cone ratio was 1.6 for one observer and 4.0 for the other; each observer's ratio was in general agreement with the value estimated independently by heterochromatic flicker photometry.

Adult↗
PubMed1993

Genetic basis of polymorphism in the color vision of platyrrhine monkeys.

It was earlier proposed that the polymorphism of color vision observed in some neotropical monkeys could be accounted for by assuming that these animals have only a single photopigment gene locus on the X-chromosome. Three kinds of evidence have been added to existing data sets in an effort to evaluate the adequacy of the single locus model: (1) photopigment complements of squirrel monkeys (Saimiri sciureus) have been determined using electroretinogram flicker photometry; (2) photopigment pedigrees have been established for several families of squirrel monkey; (3) X-chromosome pigment genes obtained from six dichromatic monkeys (three squirrel monkeys; three tamarins--Saguinus fuscicollis) have been examined to search for sequence polymorphisms at those gene loci believed crucial for spectral tuning. All of these results are in accord with the idea that some species of platyrrhine primate have only a single type of photopigment gene on the X-chromosome.

Animals↗
PubMed1993

Link-specific adaptation in the luminance and chromatic channels.

We present evidence that adaptation occurs in the separate links that connect the receptors to the luminance and the chromatic channels. The relative effectiveness of the L and M cone inputs to the luminance and red/green chromatic channels was determined by using, respectively, heterochromatic flicker photometry and a cancellation technique which maintained a pure yellow. The findings provide evidence for a link-specific adaptation model, wherein one receptor system provides two separate links to the luminance and chromatic channels and the outputs of an individual cone to these two postreceptoral channels can be separately attenuated or weighted at each of these links by colored adapting lights. One line of evidence for link-specific adaptation is that colored adapting fields selectively suppress L and M cone inputs to the red/green chromatic channel by a smaller factor than the luminance channel. A second line of evidence is that there is not only a magnitude difference but also a dynamic difference between adaptive processes operating in the luminance and chromatic channels: the luminance channel has a faster gain change and recovery from adaptation than does the chromatic channel. The results, together with other evidence, make it plausible that an important component of light adaptation in cone vision occurs at the cone-bipolar synapse.

Adaptation, Ocular↗
PubMed1995

The prediction of hue and saturation for non-spectral lights.

The Jameson and Hurvich opponent-colors model of hue and saturation was tested for spectral and non-spectral lights. Four observers described the color of lights by scaling hue and saturation. The lights ranged from 440 to 640 nm and consisted of five purities: 1.0, 0.80, 0.60, 0.40 and 0.20. Admixtures of monochromatic and a xenon-white light yielded the different colorimetric purities. For each subject, chromatic response functions were measured by the method of hue cancellation at each purity, and an achromatic response function was measured by the method of heterochromatic flicker photometry for spectral lights. Chromatic response functions measured for a particular purity and the achromatic response function were used to predict hue and saturation for that purity. The model successfully predicted hue at each level of purity, but failed to predict precisely the Abney effect. The model made relatively poor predictions of saturation, tending to overestimate short-wave lights and underestimate long-wave lights. An additional experiment found that stimulus parameters that favor rod contribution weaken the model's predictions of saturation, while stimulus parameters that do not favor rod contribution improve the model's predictions of saturation.

Adult↗
PubMed1996

ERG measurements of the spectral sensitivity of common chimpanzee (Pan troglodytes).

The spectral sensitivity of the common chimpanzee (Pan troglodytes) was measured with electroretinogram (ERG) flicker photometry. Chromatic adaptation conditions were used to establish the presence of S-, M- and L-cone pigments. Each of 26 chimpanzees showed substantial and approximately equivalent adaptational changes over the middle and long wavelengths implying an absence of any significant polymorphic variations in the M- and L-cone pigments. As inferred from ERG measurements, the S-cone pigment of the chimpanzee has a spectral peak of about 430 nm. Chimpanzee spectral sensitivity measurements were compared to those obtained from equivalently tested normal human trichromats. The spectral sensitivity of the two species is very similar, chimpanzees being slightly more sensitive to short wavelength lights and slightly less sensitive to long wavelength lights than human subjects. Curve-fitting analyses suggest that spectral filtering may be lower in the chimpanzee lens than it is in the human lens, and that the L/M cone ratio is lower in the chimpanzee.

Adaptation, Ocular↗
PubMed1987

Cell surface oligosaccharide modulation during differentiation. II. Membrane mobility of oligosaccharide lectin conjugates.

The quantitative, population doubling level (PDL) dependent changes in cell surface oligosaccharides on IMR-90 cells, were investigated from the perspective of membrane mobility of the lectin-oligosaccharide conjugates. Concanavalin-A (CON-A), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA-120), and Dolichos biflorus agglutinin (DBA) were all observed to cluster, cap, and endocytose in cultured human diploid fibroblasts (IMR-90). Quantitative photometry at 37 degrees C over defined periods of time indicated that as the IMR-90s approached cellular senescence a specific lectin-dependent inability to either endocytose or process the capped complex occurred. The development of a biotin/avidin/enzyme amplification assay permitted the assignment of the accumulating signal to the internal compartment. Kinetic data indicate that there are at least three separate (and separable) mechanisms for the PDL related changes in lectin binding. Data for the CON-A complex indicates that at least two classes of functional complexes are present. Regression analysis of the kinetic data for the RCA-120 complex indicates a similar membrane clearance for the IMR-90s at all population doubling levels (PDL), suggesting that the quantitative differences observed earlier were due to simple quantitative reductions in the RCA complexing molecules. Data for WGA mobility on the membrane indicates that they are both changes in the number and mobility status of the complexes. These results indicate that the quantitative changes in lectin binding observed previously as IMR-90 cells approach senescence are correlated with alterations in membrane mobility patterns of the lectin oligosaccharide conjugates.

Cell Compartmentation↗
PubMed1992

A method for quantitative determination of flow induced human platelet adhesion and aggregation.

Adhesivity and aggregability of blood platelets may reflect normal and diseased states. A quantitative assessment of such reactivity should thus provide further insight into disease mechanism. The well defined conditions of stagnation point flow using platelet-rich-plasma (PRP) as fluid permit quantitative treatment of the formation of platelet microthrombi on the stagnation plate. By measuring the growth kinetics (photometry) and corresponding morphology (light- and electron microscopy) of the microthrombus, platelet adhesion as well as aggregation could be analyzed separately by means of a quantitative procedure. Parameters are evaluated for PRP samples obtained from patients exhibiting deep venous thrombosis, arterial angiopathy or myocardial infarction, respectively. The results obtained demonstrate the usefulness of the proposed method for quantifying platelet reactivity as reflected by type and degree of flow induced platelet deposition. This, in turn, provides a basis for correlating the in vitro findings with the disease state.

Humans↗
PubMed1996

Optimisation of platelet aggregometry utilising micotitreplate technology and integrated software.

The possible applications of the measurement of platelet aggregation by conventional photometry are limited by the short lifetime of platelet suspensions. Recently a microplate-based technique was introduced, which promised to revolutionize experimental design by enabling simultaneous assessment of 96 platelet samples. However, adoption of this technique has been slow since the available equipment was not able to satisfy all the conditions required for conventional aggregometry, especially adequate agitation of samples whilst maintaining total control of incubation temperature. This report describes how these problems may be overcome, together with the introduction of on-line analysis of data using commercially available software, obviating the complexities of data management previously encountered.

Blood Coagulation Tests↗
PubMed1994

Effects of visible light and other environmental factors on the production of oxygen radicals by hamster embryos.

Previous studies have demonstrated that developing hamster embryos are very sensitive to visible light. In order to elucidate why visible light exerts a toxic effect on hamster embryos, we examined the effect of visible light on the production of hydrogen peroxide (H(2)O(2)) within individual embryos, using a fluorimetric method. In addition, we examined the H(2)O(2) generating capacity of other factors which are known to be related to the in vitro developmental capacity of hamster embryos. One-cell hamster embryos were cultured with 2',7'-dichlorodihydrofluorescin diacetate, and the fluorescence emissions of the H(2)O(2)-dependent oxidative product in the embryos were measured using an Olympus microscopic photometry system. When embryos were exposed to visible light (14,000 lux) for a specified period (0, 0.5, 1, 2 or 3 min) prior to measurement, the fluorescence emissions from embryos increased with the time of exposure to visible light. An exposure of even 0.5 min resulted in a significant increase in hydrogen peroxide. This increase was more rapid in embryos cultured under 20% O(2) than in those cultured under 5% O(2), and the response was quicker than that observed in mouse embryos. The fluorescence emissions from embryos cultured under 5% O(2) were significantly (P<0.001) lower than those from embryos cultured under 20% O(2) in TLP medium. However, the effects of different oxygen tensions on fluorescence emissions were medium-dependent, and were not significant in embryos cultured in HECM-1 medium. The addition of L-cysteine to or elimination of phenol red from the media decreased the fluorescence emissions from embryos (P<0.001), but glucose and phosphate did not affect them. These results suggest that the toxic effect of visible light on the in vitro development of hamster embryos might be due to increased generation of reactive oxygen species, induced by the visible light. This could be one of the explanations for the strict conditions required for overcoming the in vitro developmental block. It is also suggested that the promotive effects of low oxygen culture and L-cysteine on embryo development seem to be derived from their ability to reduce reactive oxygen species.

Journal Article↗
PubMed1980

a new fiber-optic liquid crystal catheter for oxygen saturation and blood flow measurements in the coronary sinus.

A new catheter for oxygen saturation and thermodilution measurements in the coronary sinus is described. The distinctive feature of this catheter is a new cholesteric liquid crystal (CLC) temperature sensor. Described in brief are the constructive and performance characteristics of the sensor, which permits temperature measurement by means of luminous pulses transmitted through optical fibres. The advantages of this solution are pointed out in terms of patient safety and instrumental integration of the thermodilution and oxygen saturation measurements both achieved through reflection photometry via optical fibres. Two possible configurations of the new catheter, with a double or a single optical connector, are illustrated and the instruments designed to be used with each catheter, are also described. Preliminary animal experiments on the application of the new catheter for the study of the coronary circulation are finally reported.

Animals↗
PubMed1994

Conformation of (2-->1)-beta-D-fructan in aqueous solution.

The conformation and dilute solution properties of (2-->1)-beta-D-fructan in aqueous solution were studied by gel permeation chromatography, low-angle laser light-scattering photometry, viscometry, small-angle X-ray scattering and electron microscopy. Fractions covering a broad range of weight-average molecular weights (Mw) from 1.49 x 10(4) to 5.29 x 10(6) were obtained from a native sample by ultrasonic degradation and fractional precipitation. For Mw < 4 x 10(4), the intrinsic viscosity [eta] varies with Mw0.71, indicating that the fructan chain behaves as a random coil expanded by an excluded-volume effect in this molecular weight region. For Mw > 10(5), [eta] exhibits an unusually weak dependence on Mw and finally becomes almost independent of molecular weight. This behaviour is interpreted in terms of a globular conformation of the high-molecular-weight fructan molecules. Small-angle X-ray-scattering measurements and electron microscopic observations support this interpretation of the values of [eta] observed.

Aspergillus↗
PubMed1995

IgG-induced Ca2+ oscillations in differentiated U937 cells; a study using laser scanning confocal microscopy and co-loaded fluo-3 and fura-red fluorescent probes.

We have investigated, at the single cell level, intracellular Ca2+ ([Ca2+]i) modulations triggered by the high affinity receptor for IgG, Fc gamma RI, in the monocytic cell line, U937. Cells were co-loaded with the Ca(2+)-sensitive dyes, Fluo-3 and Fura-Red, by incubation with their acetoxymethyl (AM) esters and confocal ratio imaging was used to monitor the [Ca2+]i changes induced by antibody cross-linking of IgG-loaded Fc gamma RI. A single Ca2+ spike was observed in 81% of untreated cells whereas dibutyryl cAMP-induced differentiation into a more macrophage cell type resulted in a sub-population of cells (44%) responding to receptor cross-linking with calcium oscillations. This change in calcium signalling may explain the difference in functional responses triggered by Fc gamma RI in monocytes and macrophages. Analysis of the Fluo-3 and Fura-Red fluorescence, after AM-ester loading, showed that both dyes have similar photobleach rates and intracellular localization allowing compensation for shifts in focal plane, dye photobleaching and non-uniformity of dye loading. In addition, because the binding kinetics of both dyes are equivalent, accurate temporal information can be gained about [Ca2+] changes. There are, however, two major problems with this dual indicator technique. Firstly, loading from AM esters results in considerable variation between cells in the intracellular concentration ratio of the two dyes, making calibration difficult. Secondly, the fluorescence ratio, Fluo-3/Fura-Red, behaves non-linearly at Ca2+ concentrations less than approximately 500 nM and comparison with Fura-2-loaded single cell photometry studies suggests there is considerable amplitude distortion of the signal when the ratios are displayed on a linear scale. These problems may considerably limit the application of Fluo-3/Fura-Red ratiometric measurements.

Adenosine Triphosphate↗
PubMedDate not supplied

Development, physicochemical characterization and preclinical efficacy evaluation of a water soluble glucan sulfate derived from Saccharomyces cerevisiae.

This report describes the development, characterization and preclinical efficacy evaluation of water soluble glucan sulfate. Glucan sulfate was derived from insoluble beta-1,3-D-glucan isolated from Saccharomyces cerevisiae. The proposed repeating unit empirical formula of glucan sulfate is [(C6H10O5)5.3H2SO4]n. Two polymer peaks were resolved by aqueous high-performance size exclusion chromatography (HPSEC) with on-line multi-angle laser light scattering (MALLS) photometry and differential viscometry. Peak 1 (MW = 1219697 Da) represents approximately 1% of the total polymers, while peak 2 (MW = 8884 Da) accounts for approximately 99% of polymers. 13C-NMR spectroscopy suggests that glucan sulfate polymer strands may be partially cross-linked. Glucan sulfate (250 mg/kg, i.v.) increased (P less than 0.01) macrophage vascular clearance of 131I-reticuloendothelial emulsion by 42% (P less than 0.01) and in vitro bone marrow proliferation by 46% (P less than 0.05). Glucan sulfate (250 mg/kg, i.v.) increased (P less than 0.05) median survival time of C57B1/6J mice with syngeneic melanoma B16 or sarcoma M5076. In addition, glucan sulfate immunoprophylaxis increased resistance of mice to challenge with Escherichia coli, Candida albicans or Mouse Hepatitis Virus strain A-59. We concluded that: (1) insoluble beta-1,3-D-glucan can be converted to a water soluble sulfated form; (2) glucan sulfate activates macrophages and stimulates bone marrow; (3) glucan sulfate exerts antitumor therapeutic activity, and (4) glucan sulfate immunoprophylaxis will modify the course of experimental infectious disease.

Animals↗
PubMed1996

Effects of interleukin-1 beta on scanning electron microscopic appearance and thyroid peroxidase content of human thyrocytes in monolayer culture.

Interleukin (IL-1), an inflammatory cytokine that is detected in the thyroid tissues of patients with autoimmune thyroiditis, is believed to be involved in the disease process. To clarify the role of IL-1 in the development of autoimmune thyroiditis, we investigated the effects of interleukin-1 beta (IL-1 beta) on the morphology of human thyrocytes in monolayer culture as well as the effect on thyroid peroxidase (TPO) content of these cells. Human normal thyrocytes were cultured with IL-1 beta for 4 days in the presence and absence of TSH. In morphologic studies, cultured cells were fixed for examination by scanning electron microscopy and for immunofluorescent staining of acting filaments. IL-1 produced striking morphologic changes in the cultured thyrocytes, including the cytoplasmic retraction and dissociation and/or depolymerization of actin filaments. These changes were unrelated to TSH stimulation. For detection of TPO, cultured cells were stained by an immunofluorescent technique and analyzed by fluorescence photometry. IL-1 reduced the TPO content and inhibited the TSH-induced increase in TPO in a concentration-dependent manner. These morphological changes and the reduction in TPO content of cultured thyrocytes suggest that IL-1 modulates the pathophysiology of autoimmune thyroiditis.

Adult↗
PubMed1989

Effects of superior mesenteric and coeliac ganglionectomy on the small intestinal mucosa in the Hanford mini pig. I. Histological and enzyme-histochemical study.

The effects of total superior mesenteric and coeliac ganglionectomy on the thickness of the mucosa, the cell composition of the epithelium and the enzyme activity of the absorptive cells was studied in 10 Hanford mini pigs 3 weeks and 6 months after ganglionectomy. The mucosal thickness increased after ganglionectomy by 10-33% (P less than 0.02) mainly due to increase in the villus height. Differential cell counts showed a postganglionectomy decrease in percentage of goblet cells of 20-40%. Absorptive cell counts increased significantly (P less than 0.05). Enterochromaffin cells (stained with the Masson-Fontana method) and 5-hydroxytryptamine (5-HT)-immunoreactive cells did not change significantly in the small intestine. The activity of L-leucine-amino-peptidase, non-specific alkaline phosphatase, adenosintriphosphatase, non-specific acid phosphatase, non-specific esterase and succinate dehydrogenase, as assessed by absorption photometry, increased by 2-18% (P less than 0.01) after ganglionectomy. Total ganglionectomy thus results in a rise in villus height and in an increase in the number of absorptive cells which, by their enzymatic activity, appear to be fully mature.

Animals↗
PubMed1983

Determination of molecular weight of membrane proteins by the use of low-angle laser light scattering combined with high-performance gel chromatography in the presence of a non-ionic surfactant.

An assessment study was carried out to evaluate the performance of the low-angle laser light scattering technique combined with high-performance gel chromatography in the presence of a nonionic surfactant, octaethyleneglycol n-dodecyl ether, precision differential refractometry and ultraviolet photometry. It was found that the combined technique is highly promising as a method for the determination of the molecular weight of a membrane protein solubilized by the surfactant. For trial, molecular weights of the following membrane proteins of Escherichia coli, both solubilized in oligomeric forms, were measured; porin that forms the transmembrane diffusion pore in the outer membrane, and lambda-receptor protein that facilitates the diffusion of maltose-maltodextrins across the outer membrane. The result obtained indicates that both porin and lambda-receptor protein exist as trimers in the surfactant solution.

Bacterial Outer Membrane Proteins↗
PubMed1988

Interaction between cell-binding domain and extracellular matrix-binding domain of fibronectin determined by fluorescence depolarization.

Interaction of domains in fibronectin was observed by photometry of fluorescence polarization of three kinds of dye; [N-(1-anilinonaphthyl-4)]maleimide (ANM tau = 5 ns), [N-(3-fluoranthyl)]maleimide (FAM tau = 20 ns), and [N-(3-pyrene)]maleimide (PRM tau = 100 ns). Each dye was labeled at a free sulfhydryl group in the cell-binding domain. Neither fluorescence of ANM with short fluorescent lifetime, FAM with long lifetime, nor PRM with longer fluorescent lifetime on fibronectin depolarized as much as the free dye. It was found that each dye was firmly fixed in the cell-binding domain. When heparin or gelatin was added in the solution of PRM-fibronectin complex, the fluorescence polarization tended to increase principally by combining heparin or gelatin to fibronectin. It was found that the rotation of whole or partial fibronectin containing the cell-binding domain through fluorescent lifetime of 100 ns was suppressed by combining of heparin or gelatin to fibronectin. When heparin or gelatin was added in the solution of ANM- or FAM-fibronectin complex, on the contrary, the fluorescence polarization tended to decrease, that is, slightly depolarize through the fluorescent lifetime of 5 or 20 ns, respectively. It was found that the rotation of the cell-binding domain, or of part of the fibronectin molecule containing the domain, was slightly promoted by combining heparin or gelatin to its domain. These results indicate that an interaction of the heparin- or gelatin-binding domain with the cell-binding domain was induced by the combining of heparin or gelatin to the respective domains.

Animals↗
PubMed1996

Elevated erythrocyte sodium-lithium counter-transport in hypertensive patients with non-insulin-dependent diabetes mellitus.

Increased erythrocyte (RBC) sodium-lithium (Na-Li) counter transport (CT) has been reported to be a genetic marker for essential hypertension (EHT). In addition, increased RBC Na-Li CT has been demonstrated in insulin-dependent diabetic (IDDM) patients with nephropathy, indicating that a predisposition to hypertension may cause renal damage and impaired renal function. Therefore, the present study was designed to determine RBC Na-Li CT in subjects with essential hypertension (EHT) and non-insulin-dependent diabetics (NIDDM) with or without hypertension (NIDDMHT or NIDDMNT), using the method of Canessa et al. with a slight modification by flame photometry and expressed as nmol Li/5 x 10(6) RBC/h. Na-Li CT in patients with EHT (0.159 +/- 0.051 (S.D.), n = 26) or NIDDMHT (0.168 +/0 0.083, n = 42) was higher than that in NIDDMNT patients (0.127 +/- 0.059, n = 27, P < 0.05). Among the NIDDMHT patients, those with clinical nephropathy had the same levels of Na-Li CT as those without nephropathy. When the NIDDM patients were divided into two groups with or without insulin treatment, the Na-Li CT in hypertensives was higher than that in normotensives, irrespective of whether or not they were on insulin therapy. Addition of insulin to RBCs in vitro did not augment the Na-Li CT activity. These results suggest that an increase of Na-Li CT may not be due to the stimulatory effect of endogenous or exogenous insulin, and reflect a genetic predisposition for hypertension, and hence diabetic nephropathy, not only in IDDM but also NIDDM patients.

Antiporters↗