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At least 703 records · Page 39Linked to original sources
PubMedDate not supplied

Influence of isoluminant monochromatic and polychromatic background on single neuron activity in cat visual cortex after stimulation with moving light bars and light bars flashed on/off.

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds, either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum PSTH peaks of some 40% of the neurons tested was influenced by both moving and stationary bars. About two thirds of maximum peak-sensitive cells also showed altered direction selectivity. Latencies, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.

Animals↗
PubMed1975

[Transforming activity of phage T4r+ DNA, treated with ultraviolet light, nitrous acid, hydroxylamine and visible light in the presence of methylene blue].

The efficiency of phages T4rIIB-638v+ and T4rIIB-638v- transformation by native and denatured DNA treated with UV, nitrous acid, hydroxylamine and visible light in the presence of methylene blue is studied. A greater transformation efficiency of UV-irradiated T4r+ phage native and denatured DNA was observed in the v+ recipient as compared with v- recipients. Denatured donor DNA treated with nitrous acid has higher transformation activity in spheroplasts infected with T4v+ phage than in those infected with T4v- phage. Native donor DNA, treated with methylene blue and visible light-irradiated, developed a decrease of the transformation activity in T4v- phage-infected spheroplasts as compared with T4v+ phage-infected spheroplasts. Hydroxylamine treatment of native and denatured donor DNA did not reveal any differences in the transforming activity for v+ and v- recipients. Denatured donor DNA was more resistant to the effect of hydroxylamine than native DNA.

Coliphages↗
PubMed2004

[Effects of sustained chilling and low light on gas exchange, chlorophyll fluorescence quenching and absorbed light allocation in cucumber leaves].

Exposure of cucumber plants to low light (25 degrees C/18 degrees C, 100 micromol m(-2) s(-1)) and low temperature (12 degrees C/12 degrees C, 100 micromol m(-2) s(-1); 7 degrees C/7 degrees C, 100 micromol m(-2) s(-1)) resulted in a retardation or complete inhibition of plant growth, decreases in chlorophyll content, net photosynthetic rate, stomatal conductance and photosynthetic electron transport rate, but an increase in intracellular CO(2) concentration. Significant reversible reduction in Fv/Fm was found in plants after chilling at 7, but not in those after chilling at 12 degrees C. Chilling and low light treatment resulted in a decrease in chlorophyll content, followed by a decreased allocation of photons absorbed by PSII antenna to the photosynthetic electron transport and an increased allocation of thermal dissipation and excessive energy. Plant chilled at 12 degrees C showed higher recovery capacity than those chilled at 7 degrees C upon returning to normal conditions.

Chlorophyll↗
PubMed1991

Effect of phosphorylation of myosin light chain by myosin light chain kinase and protein kinase C on conformational change and ATPase activities of human platelet myosin.

Human platelet myosin forms 10S and 6S conformations, and its Ca(2+)- and Mg(2+)-ATPase activities are parallel with the transition between 10S and 6S conformation, as judged by the gel filtration, intrinsic fluorescence, and viscosity methods. The 20,000-dalton myosin light chain (LC20) is phosphorylated by both myosin light chain kinase (MLC kinase) and Ca2+, phospholipid-dependent protein kinase (protein kinase C [PKC]). The phosphorylation (1 mol of phosphate/mol of LC20) by MLC kinase shifts the equilibrium toward the 6S conformation, but that by PKC does not. The prephosphorylation of myosin by PKC prevents the effect of phosphorylation by MLC kinase on actin-activated Mg(2+)-ATPase activity, but not the effect on conformational change. Inhibition of actin-activated ATPase activity by PKC is due to a decreased affinity of myosin for actin, and no change in Vmax is observed. These results suggest that sequential phosphorylation of myosin by both kinases plays an important role in the ATPase activities of human platelet myosin.

Actins↗
PubMedDate not supplied

[Light-optical device for fiber light guides].

The paper gives a calculation method for a lighting optical device consisting of light flux concentrator lamps rigidly installed in an ellipsoid reflector with heat-permeable coating, and the parameters of two big concentrator lamps for fibre endoscopes.

Endoscopes↗
PubMed1978

Kinetics of interaction of heavy and light chains in immunoglobulins. Use of a sulfhydryl-specific light chain fluorescent probe.

The fluorescent probe N-(iodoacetylaminoethyl)-8-naphthylamine-1-sulfonic acid (1,8-I-AEDANS) reacts stoichiometrically with the COOH-terminal cysteine residue of a human immunoglobulin light (L) chain. The absorption and fluorescence spectral properties of the L-AEDANS product and the environmental sensitivity of the fluorescence suggest the utility of L-AEDANS in the study of the subtle conformational changes accompanying interactions between light chain and other proteins or ligands. Its applicability to the problem of immunoglobulin assembly is illustrated by the association of L-AEDANS with heavy chain dimers, which results in an enhancement of fluorescence. The data indicate that L-AEDANS binds to kinetically equivalent, noninteracting sites with an apparent second order rate constant of 6 X 10(6) liters mol(-1) s(-1) at 20 degrees, pH 7.5.

Dansyl Compounds↗
PubMed1983

Effects of relaxin on rat uterine myosin light chain kinase activity and myosin light chain phosphorylation.

Isometrically suspended uteri from estrogen-primed rats were stimulated with prostaglandin F2 alpha and then exposed to relaxin. Relaxin-dependent decreases in the ratio of phosphorylated to total myosin light chains (MLC) and in MLC kinase activity, measured in the presence of 0.5 mg/ml of uterine myosin and the absence and presence of Ca2+-calmodulin (CaM), were observed. The time-course and concentration-response of these biochemical effects of relaxin paralleled the hormone-induced inhibition of uterine contractile activity. Relaxin treatment resulted in a change in the requirements of MLC kinase for Ca2+, CaM, and myosin. Titrations of MLC kinase activity showed a shift in K50 values for Ca2+ from 82 to 260 nM and for CaM from 2.2 to 25 nM in extracts from control and relaxin-treated tissues, respectively. The myosin Km values of MLC kinase from control and relaxin-treated tissues were 0.33 and 0.71 mg/ml, respectively. Under optimal assay conditions (100 microM Ca2+, 1 microM CaM, and 1.2 mg/ml of myosin) the activities of MLC kinase in both extracts were identical, regardless of hormone concentration or exposure time. These data suggest that relaxin-treatment results in a change in the affinity of MLC kinase for its substrate and modulator and that relaxin inhibits uterine contractile activity by a mechanism which involves a decrease in MLC kinase activity and, in turn, a decrease in phosphorylation of the 20,000-dalton light chains of myosin.

Animals↗
PubMed1980

Untranslated immunoglobulin kappa light chain mRNA in a lambda light chain-producing mouse myeloma, MOPC104E.

Fourteen clones were isolated in culture from a mouse myeloma, MOPC104E. All clones had kappa and lambda types of light chain mRNAs in approximately equimolar quantity as assayed by hybridization with specific complementary DNA (cDNA). However, the myeloma produces and secretes only lambda-type light chain protein. Both kappa- and lambda-type mRNAs in these clones were indistinguishable from kappa- and lambda-type mRNAs of other myelomas with respect to (a) adsorption to oligo-(dT) cellulose, (b) molecular size (12.6 S), and (c) thermal stability of the hybrids formed with corresponding cDNA. The kappa chain mRNA of MOPC104E cells, however, was translated very inefficiently both in vivo and in vitro, whereas the lambda chain mRNA was translated efficiently. These results indicate that each cell of MOPC104E myeloma synthesizes a crippled kappa chain mRNA in addition to a normal lambda chain mRNA.

Animals↗
PubMed1983

[Light transmittance and light-protective action of containers for phenylalkylamine solutions. 84: Contributions to problems concerning the use of plastic containers for liquid pharmaceutical preparations; 18: Stability of drugs and preparations].

Using glass as a comparison material, the authors determined spectrophotometrically the light transmittance of plastic containers of different composition and evaluated their ability to protect phenylalkylamine solutions against ultraviolet irradiation. The material best suitable for these solutions is low-density polyethylene coloured with 0.05% of pigment orange G. Brown glass, which meets all requirements as to the protection from light, favours the degradation of phenylalkylamines as it releases heavy metal ions.

Amines↗
PubMed1982

PAVE LOW III: interior lighting reconfiguration for night lighting and night vision goggle compatibility.

The PAVE LOW III aircraft is a modified HH-53H helicopter that has a low altitude--below 30.48 m (100 ft)--night/day rescue mission. The desired night flying configuration is for the pilot to wear night vision goggles (NVGs) to fly the aircraft while the copilot, without NVGs, observes the video display and monitors the aircraft instruments. The problems of NVG incompatibility in the cockpit were successfully countered using several light control techniques. The light control modifications were evaluated on the ground in the PAVE LOW III helicopter at Kirtland AFB in April, 1980, by PAVE LOW instructor pilots. The evaluation results were extremely positive.

Aircraft↗
PubMed1993

Effects of argon laser light, alternate source light, and cyanoacrylate fuming on DNA typing of human bloodstains.

Restriction fragment length polymorphism (RFLP) profile results were obtained from deoxyribonucleic acid (DNA) isolated from human bloodstains that had been subjected to cyanoacrylate ester ("superglue") fuming, argon ion laser light and alternate light sources. All RFLP profile results obtained from treated samples were consistent with the DNA pattern from untreated bloodstains.

Argon↗
PubMed2001

The Light Shall Show the Way-Or: The Conformational Changes of the Retinal Chromophore in Rhodopsin upon Light Activation.

The visual pigment rhodopsin constitutes the interface between the physical event of light absorption and the biochemical process of visual transduction within the photoreceptor cells. The signal transduction is initiated by an 11-cis→all-trans photoisomerization of the retinal chromophore of rhodopsin which causes a series of thermally driven conformational changes of the chromophore and the protein moiety. A rhodopsin conformation is generated which allows interaction with a heterotrimeric G-protein. Two recent publications follow the chromophore motions after light absorption by cross-linking experiments and by solid-state NMR spectroscopy.

NMR spectroscopy↗
PubMed1994

Multiple labeling using two-color immunofluorescence with only one light source, two fluorescence photomultiplier tubes, and two light scatter detectors.

Multiple labeling is necessary for the detailed phenotyping of cells in many biological systems in human and animal species. In a previous report, we described an approach permitting the study of three labels simultaneously by using the two-color immunofluorescence and one light source (Mansour et al., Cytometry 11:636-641, 1990). This approach allowed enumeration of cell subpopulations positive for only one label and negative for many others (X+ A- B- ...). We here present an improvement of the previous approach to allow analysis of double positive phenotypes (X+ Y+ A- B- ...), using only two fluorescence photomultiplier tubes and light scatter detectors. It consists of a two-step analysis that does not require additional material than that used in the former technique. Briefly, all antibodies are conjugated to only two fluorochromes: either FITC or PE. For the analysis of the X+ Y+ A- B- ... phenotype, the Y, A and B labels are all coupled to the same dye (FITC, e.g.) and the X label to the other dye (i.e, PE). In a first step, cells are labeled with X, A, and B, and in a second step, the second positive (Y) label is added. Two examples are supplied: CD56+ CD2+ CD3- CD16- decidua infiltrating cells and CD3+ TCR delta+ CD4- CD8- peripheral blood lymphocytes. This technique is useful for qualitative as well as quantitative analysis, with cytometers that do not have the appropriate hardware to do true three-color immunofluorescence analysis.

Antigens, CD↗
PubMed1993

Phosphorylation of cardiac myosin light chain 2 by protein kinase C and myosin light chain kinase increases Ca(2+)-stimulated actomyosin MgATPase activity.

Myosin light chain 2 (MLC2) phosphorylation in rat cardiac whole myosin by cardiac myosin light chain kinase (MLCK) or by protein kinase C (PKC) resulted in increased actin-stimulated myosin MgATPase activity. The phosphorylation also increased Ca(2+)-stimulated myofibrillar MgATPase activity upon substitution of the phosphorylated myosin into myofibrils. In addition, phosphorylation of MLC2 in myofibrils by MLCK increased both the Ca(2+)-sensitivity and maximum activity of the myofibrillar Ca(2+)-stimulated MgATPase activity. The latter effect was inhibited by PKC-phosphorylation of troponin I, troponin T and C-protein. A role for both PKC and MLCK in regulating cardiac myofibrillar activity, via phosphorylation of various contractile proteins, is indicated.

Animals↗
PubMed1995

Augmented expression of atrial myosin light chain 1 in ventricular aneurysms of human: enzyme immunoassay for atrial myosin light chain 1.

We established an enzyme immunoassay (EIA) for atrial myosin light chain 1 (ALC1) using monoclonal antibodies KA1 and KB1, which were specific for ALC1 and for both ALC1 and ventricular myosin light chain 1, respectively. The serum ALC1 levels of healthy subjects were 0.28 +/- 0.14 ng/ml (mean +/- SD). The tissue ALC1 levels of normal adult human atria were much higher than those of ventricles (p < 0.01, 2,120 +/- 1,200 in right atria, 2,180 +/- 1,450 in left atria vs. 36.0 +/- 20.2 in right ventricles, 37.7 +/- 15.3 in left ventricles, ng/mg of proteins). The tissue ALC1 levels of ventricular aneurysms were significantly higher than those of normal ventricles (p < 0.01, 206.7 +/- 101.8). These results indicate that ALC1 is augmented in aneurysms and that the EIA provides a useful tool to investigate the roles of ALC1.

Adult↗
PubMed2001

Light Scattering Study of Turbid Heat-Set Globular Protein Gels Using Cross-Correlation Dynamic Light Scattering.

The structure factor of aqueous solutions of the globular protein beta-lactoglobulin was determined as a function of heating time at 76 degrees C. We show how the effect of multiple scattering on the scattered light intensity can be effectively corrected using cross-correlation dynamic light scattering even if the transmission is only 1%. The structure factor of aggregated and gelled proteins can be described by the Ornstein-Zernike equation. The system is characterized by a correlation length that increases with heating time and stabilizes some time after the gel is formed. The correlation length of the protein gels decreases with decreasing concentration. Measurements after progressive dilution of a sample close to the gel point showed that the protein aggregates are initially interpenetrated and disinterpenetrate upon dilution. Copyright 2001 Academic Press.

Journal Article↗
PubMed1987

The binding of Mn2+ to bovine plasma protein C, des(1-41)-light chain protein C, and activated des(1-41)-light chain activated protein C.

The binding isotherms of Mn2+ to bovine plasma protein C (PC), des(1-41)-light chain protein C (GDPC), and activated GDPC (GDAPC) have been measured. PC contains 14-16 total Mn2+ binding sites, a value that is reduced to approximately 7-8 in the presence of NaCl. The average Kd of the latter sites is 230 +/- 30 microM. Upon removal of a 41-residue peptide from the amino terminus of the light chain of PC, and, concomitantly, all of the gamma-carboxyglutamic acid residues, the resulting protein, GDPC, possesses a single Mn2+ site of Kd = 120 +/- 20 microM. Activation of GDPC to GDAPC results in a slight lowering of the Kd for the single Mn2+ binding site to 53 +/- 8 microM, a value that is essentially unchanged in the presence of monovalent cations, a competitive inhibitor of the enzyme, or an active site directed affinity label. The Mn2+ on GDAPC is displaced by Ca2+, suggesting that the protein binding site for these two divalent cations is the same. These studies establish that Mn2+ is a suitable spectroscopic probe for the Ca2+ binding site of GDAPC, and that the divalent cation site is separate from the monovalent cation site(s) and the active site of the enzyme.

Animals↗
PubMed1987

Position of the amino terminus of myosin light chain 1 and light chain 2 determined by electron microscopy with monoclonal antibody.

The position of the N terminus of myosin light chain 1 (LC1) and myosin light chain 2 (LC2) of rabbit skeletal muscle was mapped on the myosin head with a monoclonal antibody (SI304), which recognized the amino acid sequence N-trimethylalanyl-prolyl-lysyl-lysyl at the N terminus of LC1 and LC2. The complex of the antibody and myosin was observed by electron microscopy. By selective cleavage of the N terminus of LC1 or LC2 with papain or chymotrypsin, the position of the N terminus of LC1 and LC2 was determined separately. The N terminus of LC2 is located at the head-rod junction. The N terminus of LC1 is 11 nm (+/- 3 nm, standard deviation) from the head-rod junction. This position is near the actin-binding site of the myosin head.

Amino Acid Sequence↗