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At least 217 records · Page 12Linked to original sources
PubMed1992

Effect of light intensity level during prelay light restriction on subsequent reproductive performance of turkey breeder hens.

Two trials were conducted to determine whether light intensity levels during the prelay (light restriction) and the lay (egg production) periods influenced subsequent photoinduced reproductive performance of turkey breeder hens. The light intensity levels were 22 and 270 lx and each was provided during the prelay and lay periods in a factorial arrangement. Each of the period light intensity levels were applied to half of the hens from each prelay treatment group. Data were collected for BW, rate of reproductive development, egg production, fertility, hatchability, egg weight, and poult weight. There were no interactions between the prelay and lay period treatments, nor a consistent prelay light intensity effect on rate of initiation of lay or duration of time to achieve 50% production. In addition, prelay and lay light intensity levels had no consistent effects on rate of lay, percentage of fertility and hatchability, egg weight, and poult weight. It was concluded that there was no advantage to the use of high-intensity light during short-day light restriction of the prelay period on subsequent reproductive performance.

Animals↗
PubMed1992

[Obtaining natural light photostability of drugs from lamp light exposure experiments].

The photostability of vitamin B2, vitamin K3, zinc sulfadiazine and vesnarinone, and the equivalent influences of different light sources on the photostability of the above drugs were studied under natural light and lamp lights. From this study, the photostability of drugs under different light sources can be converted to each other, and the natural light photostability of drugs can be conveniently obtained from lamp light exposure experiments. The relationship between the surface reflectance of the above drugs and the cumulative illumination of different light sources can be formulated as R = A + B(Et) + C/(Et + D) accurately, and the cumulative illumination of different light sources irradiated on the above drugs can be converted to each other equivalently.

Drug Stability↗
PubMed1991

The "ladder light chain" or "pseudo-oligoclonal" pattern in urinary immunofixation electrophoresis (IFE) studies: a distinctive IFE pattern and an explanatory hypothesis relating it to free polyclonal light chains.

I previously reported the occurrence of a pattern of multiple, equally spaced, low-concentration light chain bands in urine in immunofixation electrophoresis (IFE) studies (Clin Chem 1990;36:1526-7). Although the pattern varies somewhat among patients with regard to the number of bands, light chain type, and concentration, it is relatively invariant with regard to the location and spacing of three prominent kappa bands. The regular spacing of these urinary light chain bands imparts a "ladder rung" or "pseudo-oligoclonal" appearance. High-resolution, two-dimensional electrophoresis of these urine specimens reveals a regularly spaced, isomassic, restricted zonal distribution in the light chain region. These findings may be explained as the results of expression of superfamilies of related, polyclonal, free light chains, which co-migrate because of the limited variety of amino acid substitutions allowed by recombination constraints on light chain genes. This urinary IFE phenomenon is called the ladder light chain (LLC) pattern or pseudo-oligoclonal free light chain pattern to avoid implications of origin from specific clonal proliferation.

Bence Jones Protein↗
PubMed1990

Acidic residues comprise part of the myosin light chain-binding site on skeletal muscle myosin light chain kinase.

Myosin light chain kinase is a Ca2+/calmodulin-dependent protein kinase which exhibits a very high degree of protein substrate specificity. The regulatory light chain of myosin is the only known physiological substrate of the enzyme. Based upon epitope mapping of monoclonal antibodies which inhibit kinase activity competitively with respect to the light chain substrate, residues 235-319 of the rabbit skeletal muscle kinase have been proposed to contain a light chain-binding site (Herring, B. P., Stull, J. T., and Gallagher, P. J. (1990) J. Biol. Chem. 265, 1724-1730). With the expression of a truncated kinase, we have further localized this putative binding site to residues 235-294. Mutation of acidic residues at positions 269 and 270 of the kinase resulted in a 10-fold increase in the Km value for the myosin light chain, with no significant change in the Vmax value. In contrast, altering a cluster of acidic amino acids at positions 261-263 had little effect on the Km value for the myosin light chain. These results suggest that residues 269 and 270 may be involved in protein-substrate binding. Interestingly, these residues, located amino-terminal of the homologous catalytic core (positions 302-539), are in a region which is highly conserved among myosin light chain kinases, but not other protein kinases. It is probable that the homologous catalytic core contains structural elements required for phosphotransferase activity. The catalytic domain of myosin light chain kinase would therefore include these conserved elements together with additional specific substrate-binding residues.

Amino Acid Sequence↗
PubMed1989

Light chain deposition disease derived from the kappa I light chain subgroup. Biochemical characterization.

The authors biochemically analyzed the nonamyloidotic light chain deposits, the first studied in this way, from a patient with systemic kappa light chain deposition disease (LCDD). The light chain deposits from myocardium were extracted in 6 M guanidine-HCl under reducing conditions, partially purified by column chromatography, and analyzed by immunoblotting and amino-terminal sequencing. The extracted material contained four main bands reactive with anti-kappa antibody: intact kappa light chain (MW, 28 kd), under reducing conditions, and 3 fragments (MW, 20, 16, and 15 kd). As revealed by the aminoterminal sequencing performed on three of the four bands, the intact light chain molecule and two fragments belong to the kappa I subgroup. Thus, similar to light chain amyloid (AL), the deposits in LCDD are derived from both intact light chain and fragments. Unlike in AL, amyloid P component was not detected in the deposits of this patient or those examined previously. The differences demonstrated thus far between AL and LCDD are the lack of fibrils and amyloid P component in LCDD, suggesting that local tissue factors may be responsible for different processing of the light chain deposits in LCDD.

Adult↗
PubMed1994

Coaction of blue light and light absorbed by phytochrome in control of glutamine synthetase gene expression in Scots pine (Pinus sylvestris L.) seedlings.

The level of plastidic glutamine synthetase (GS; EC 6.3.1.2) in the cotyledonary whorl of the Scots pine (Pinus sylvestris L.) seedling was previously reported to be regulated by light. In the present paper we report on the control by light of the GS transcript level. A full-length GS cDNA clone of Scots pine was isolated (pGS1), sequenced and employed to measure GS transcript levels. Using dichromatic light treatments it was found that the transcript level is regulated by phytochrome. The strong specific effect of blue light is to be attributed to an increase of the responsiveness to phytochrome. Since no direct correlation between the transcript level and the rate of GS protein synthesis was observed, it was concluded that GS gene expression is only coarsely regulated at the level of transcript accumulation. Synthesis of GS protein is by itself light-dependent (light-mediated fine tuning of gene expression). This control at the translational level is also exerted via phytochrome with blue light determining the responsiveness of the process toward phytochrome. If the level of the far-red absorbing form of phytochrome (Pfr) is kept very low, blue light is not capable of bringing about synthesis of GS protein.

Amino Acid Sequence↗
PubMed1994

Low temperature increases the abundance of early light-inducible transcript under light stress conditions.

Green pea plants respond to light stress by expression of a nuclear ELIP (early light-inducible protein) gene. Here we report that the accumulation of ELIP transcript in pea plants during light stress is enhanced by low temperature treatment. The enhanced level of ELIP transcript during combined light and cold stress was found to be due to an increased stability of ELIP messenger RNA under these conditions. This transcript is translatable in vitro. In vivo, however, the amount of accumulated protein in the thylakoids declines with the decrease in the temperature because the translational activity is strongly reduced already at 10 degrees C. Plants exposed to light stress at temperatures that do not allow accumulation of ELIP transcript respond by induction of ELIP mRNA and protein during recovery at low light intensity and ambient temperature. The amount of protein that accumulates as a result of this "memory effect" is, however, much lower than that which accumulates as a result of direct light stress. The memory of a perceived light stress persists in plants stored at low temperature for at least 3 h, and the stress response can be released after an increase in temperature. Prolonged cold treatment, however, has a negative effect on the translatability of the ELIP transcript that accumulates during recovery.

Arabidopsis Proteins↗
PubMed1994

Ca(2+)-dependent phosphorylation of myosin light chain kinase decreases the Ca2+ sensitivity of light chain phosphorylation within smooth muscle cells.

Myosin light chain kinase (MLCK) is phosphorylated in contracting smooth muscle. The rate of phosphorylation of MLCK is slower than the rates of increase in cytosolic Ca2+ concentrations and phosphorylation of the regulatory light chain of myosin in intact tracheal smooth muscle cells in culture. In permeable cells, increasing the Ca2+ concentration increased the extent of myosin light chain and MLCK phosphorylation. The Ca2+ concentration required for half-maximal phosphorylation was 500 nM for MLCK and 250 nM for myosin light chain. Addition of KN-62 or a synthetic peptide CK II, inhibitors of multifunctional Ca2+/calmodulin-dependent protein kinase II activity, abolished MLCK phosphorylation. Under these conditions, the Ca2+ concentration required for half-maximal light chain phosphorylation decreased to 170 nM. Thus, the Ca2+ concentrations required for MLCK phosphorylation are greater than those required for light chain phosphorylation in smooth muscle cells. Furthermore, phosphorylation of MLCK decreases the Ca2+ sensitivity of light chain phosphorylation. These results can be explained by a regulatory scheme in which calmodulin available for myosin light chain kinase activation is limiting. This is supported by the retention of calmodulin when tracheal smooth muscle cells and tissues are permeabilized in relaxing solution and by the low mobility of rhodamine-calmodulin in intact tracheal smooth muscle cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Secretion from rat basophilic RBL-2H3 cells is associated with diphosphorylation of myosin light chains by myosin light chain kinase as well as phosphorylation by protein kinase C.

The phosphorylation of myosin light chains and heavy chains by protein kinase C is known to be temporally correlated with Ca(2+)-dependent secretion of granules from RBL-2H3 cells (Ludowyke, R. I., Peleg, I., Beaven, M. A., and Adelstein, R. S. (1989) J. Biol. Chem. 264, 12492-12501). We now report that whereas myosin light chains are predominantly monophosphorylated by the Ca2+/calmodulin-dependent myosin light chain kinase at serine 19 in unstimulated cells, stimulation of RBL-2H3 cells with antigen or other stimulants causes additional phosphorylation of myosin light chains by myosin light chain kinase at threonine 18, as well as by protein kinase C at serine 1 or serine 2. This diphosphorylation at serine 19 and threonine 18 by myosin light chain kinase and the monophosphorylation by protein kinase C is correlated with the rate and extent of degranulation. Secretion occurs whenever phosphorylation by both enzymes is stimulated by antigen or by the combination of low concentrations of A23187 (50 nM) and phorbol 12-myristate 13-acetate (20 nM). These phosphorylations appear to be closely associated with exocytosis in RBL-2H3 cells. Thus, phosphorylation, as well as secretion, can be blocked by the kinase inhibitors KT5926 and ML-7. More specifically, phorbol ester alone induces phosphorylation of myosin light chains by protein kinase C exclusively, but fails to induce secretion until accompanied by low concentrations of A23187, which activates myosin light chain kinase. Conversely, selective suppression of phosphorylation by protein kinase C (with Ro31-7549 in antigen-stimulated cells) suppresses degranulation, thereby indicating a requirement for protein kinase C.

Alkaloids↗
PubMed1995

Light curtails sleep in anesthetized hornets: extraretinal light perception.

In the present study effects of light on the sleep duration of anesthetized hornets (Vespa orientalis) were investigated. Following initial anesthesia by diethyl ether the sleeping time of workers and drones at 22 degrees C in the dark was 59 +/- 15 min. After repeated anesthesia the sleeping time was 30 +/- 15 min in the dark. When exposed to polychromatic light from a halogen lamp of 230 mW/cm2, focused on a spot of the cuticle of the hornet, the sleeping time was markedly shortened so that following initial as well as repeated anesthesia the hornets woke up after 4.5 +/- 2.9 min. Any decrease in light intensity resulted in an increase in the sleeping time but irradiances of less than 14 mW/cm2 had no measurable influence on the wake-up time. After illumination with polychromatic light from a mercury lamp the sleeping times were much shorter than after illumination with a halogen lamp at the same conditions and intensity. This difference is attributed to the relatively higher portion of U.V. light in the total emission of the Hg lamp. Effects of the spectral composition of the incident light beam on the wake-up of the sleeping hornets were also investigated. Near U.V. light in the 300-400 nm region was found to be most efficient. Shorter wavelengths as well as wavelengths between 400-470 nm had less influence and wavelengths above 470 nm had very little effect on the wake up. The sleeping times of hibernating queens were relatively longer than those of workers and drones under the same conditions. These effects are ascribed to the extraretinal light perception. The possible reasons underlying this phenomenon are discussed.

Anesthesia↗
PubMed1988

Isolation of the chick myosin alkali light chain gene expressed in embryonic gizzard muscle and transitional expression of the light chain gene family in vivo.

A chick embryonic myosin alkali light chain L23 gene that is expressed transiently at embryonic stages in chick skeletal, cardiac and smooth muscles and in brain continuously from embryo to adult stages, was isolated and characterized. Sequence analysis showed that the exonic sequence of this gene was identical with that of embryonic myosin light chain mRNA except for one base replacement. This gene is a single gene of 5200 bases, which is divided into seven exons by six introns, and the positions of inserts of all the introns are well-conserved as in the skeletal and cardiac muscle myosin alkali light chain genes. Therefore, this embryonic myosin light chain gene can be classified as a member of the myosin alkali light chain gene family, and these three genes may have originated from a common ancestral gene. Transcription of the embryonic light chain gene starts from the same initiation site 33 bases upstream from ATG in embryonic muscle tissues and brain. Comparison of the nucleotide sequence around the promotor region of the embryonic myosin light chain gene with the corresponding regions of the skeletal and cardiac myosin light chain genes showed that the 11-base consensus sequence (TCCTATTTATAG) is present about 100 bases upstream from the transcription initiation site in each gene.

Animals↗
PubMed1999

Light perception and the role of the xanthophyll cycle in blue-light-dependent chloroplast movements in lemna trisulca L

In most higher plants, chloroplasts move towards the periclinal cell walls in weak blue light (WBL) to increase light harvesting for photosynthesis, and towards the anticlinal walls as an escape reaction, thus avoiding photo-damage in strong blue light (SBL). The photo- receptor(s) triggering these responses have not yet been identified. In this study, the role of zeaxanthin as a blue-light photoreceptor in chloroplast movements was investigated. Time-lapse 3D confocal imaging in Lemna trisulca showed that individual chloroplasts responded to local illumination when one half of the cell was treated with light of different intensity or spectral quality to that received by the other half, or was maintained in darkness. Thus the complete signal perception, transduction and effector system has a high degree of spatial resolution and is consistent with localization of part of the transduction chain in the chloroplasts. Turnover of xanthophylls was determined using HPLC, and a parallel increase was observed between zeaxanthin and chloroplast movements in SBL. Ascorbate stimulated both a transient increase in zeaxanthin levels and chloroplast movement to profile in physiological darkness. Conversely, dithiothreitol blocked zeaxanthin production and responses to SBL and, to a lesser extent, WBL. Norflurazon preferentially inhibited SBL-dependent chloroplast movements. Increases in zeaxanthin were also observed in strong red light (SRL) when no directional chloroplast movements occurred. Thus it appears that a combination of zeaxanthin and blue light is required to trigger responses. Blue light can cause cis-trans isomerization of xanthophylls, thus photo-isomerization may be a critical link in the signal transduction pathway.

Journal Article↗
PubMed1992

Fast Fluorescence Quenching from Isolated Guard Cell Chloroplasts of Vicia faba Is Induced by Blue Light and Not by Red Light.

Chlorophyll a fluorescence transients from isolated Vicia faba guard cell chloroplasts were used to probe the response of these organelles to light quality. Guard cell chloroplasts were isolated from protoplasts by passing them through a 10-mum nylon net. Intact chloroplasts were purified on a Percoll gradient. Chlorophyll a fluorescence transients induced by actinic red or blue light were measured with a fluorometer equipped with a measuring beam. Actinic red light induced a monophasic quenching, and transients induced by blue light showed biphasic kinetics having a slow and a fast component. The difference between the red and blue light-induced transients could be observed over a range of fluence rates tested (200-800 mumol m(-2) s(-1)). The threshold fluence rate of blue light for the induction of the fast component of quenching was 200 mumol m(-2) s(-1), but in the presence of saturating red light, fluence rates as low as 25 mumol m(-2) s(-1) induced the fast quenching. These results indicate that guard cell chloroplasts have a specific response to blue light.

Journal Article↗
PubMed1974

Light-controlled Stem Elongation in Pea Seedlings Grown under Varied Light Conditions.

There appears to be an orderly transition from one photosensitive state to another in light-controlled stem elongation in the garden pea, Pisum sativum L. cv. Alaska. Stem elongation in dark-grown plants is known to be phytochrome-controlled. However, seedlings are insensitive to phytochrome after a red light pretreatment. An action spectrum for inhibition in these seedlings has peaks at 440 and 620 nm. Protochlorophyll is suggested as the photoreceptor. If these red pretreated seedlings are further exposed to white light, sensitivity to 440 to 620 nm light is lost. Promotion by blue-green light is the only photoresponse shown by these seedlings. Inhibition of completely white light-grown seedlings required simultaneous exposure to high intensity blue light and 600 nm light.

Journal Article↗
PubMed1981

White Light Effects on the mRNA for the Light-Harvesting Chlorophyll a/b-Protein in Lemna gibba L. G-3.

Translation products of poly(A) mRNA isolated from Lemna gibba L. G-3 include a major polypeptide of 32,000 daltons which is immunoprecipitated by antiserum to chlorophyll a/b-protein from Chlamydomonas. This 32,000 dalton polypeptide represents a precursor to the light-harvesting chlorophyll a/b-protein of molecular weight 28,000 found in the thylakoid membranes of Lemna gibba. The amount of this translatable mRNA decreases relative to other translatable mRNAs when green plants grown in continuous white light are placed in darkness. This decrease occurs rapidly. The most rapid decline occurs during the first day; after 4 days of darkness, only a low level of this mRNA can be detected by in vitro translation. When the plants are returned to white light there is an increase in the relative level of this mRNA which can be easily detected within two hours. The in vivo synthesis of this protein has been assayed under the different light conditions. The light effects on the in vivo synthesis of the chlorophyll a/b-protein reflect the light effects on the translatable mRNA for the polypeptide. The results indicate that light induced changes in the synthesis, processing, or degradation of chlorophyll a/b-protein mRNA could account for the light-induced changes observed in the effective synthesis rates for the chlorophyll a/b-protein in vivo.

Journal Article↗
PubMed1988

Light Regulation of Peridinin-Chlorophyll a-Protein (PCP) Complexes in the Dinoflagellate, Glenodinium sp. : Use of Anti-Pcp Antibodies to Detect Pcp Gene Products in Cells Grown in Different Light Conditions.

As a step toward developing the tools needed to study the molecular bases of light regulation of gene expression in dinoflagellates, light-harvesting peridinin-chlorophyll a-protein (PCP) complexes from Glenodinium sp. were purified and used to generate anti-PCP antibodies. Affinity purified anti-PCP antibodies were isolated from the crude anti-PCP antiserum resulting in improved specificity of immune reactions. The affinity purified anti-PCP antibodies were shown to react strongly and specifically with all major isoforms of PCP complexes in Glenodinium sp. cells, and were used to assess qualitative changes in the levels of PCP gene products in cells grown under different light conditions. Western blot analysis revealed a two- to three-fold increase in detectable PCP apoprotein in low light compared to high light grown cells. In vitro translation reactions supplied with total RNA from high and low light grown Glenodinium sp. cultures also showed an approximate twofold increase in translatable PCP mRNAs in low light grown cells as determined by immunoprecipitation of the primary translation products with affinity purified anti-PCP antibodies. In addition, PCP apoproteins appear to be encoded as larger pre-proteins, since the major immunoprecipitated products from in vitro translation are 23 and 22 kilodaltons, while mature PCP apoproteins are 15.5 kilodaltons. The parallel increases in PCP apoprotein and translatable PCP mRNAs indicate that light regulation of PCP complexes occurs at the level of PCP mRNA abundance.

Journal Article↗
PubMed1991

Separation of Light-Induced [C]ent-Kaurene Metabolism and Light-Induced Germination in Grand Rapids Lettuce Seeds.

The effect of light on the metabolism of [(14)C]kaurene in light-requiring lettuce seeds (Lactuca sativa L. cv Grand Rapids) was investigated. Seeds were soaked in a solution of [(14)C]ent-kaurene in methylene chloride with 0.01% Tween-20, dried, and incubated in 20% polyethylene glycol (PEG) to prevent seedling development. Labeled metabolites were extracted and analyzed by high performance liquid chromatography and gas chromatography-radio counting. [(14)C]ent-Kaurenol and [(14)C]ent-kaurenal were identified in seeds incubated in constant white light, while no ethyl acetate-soluble metabolites were found in seeds incubated in the dark. In time course experiments using acid scarified seeds, metabolism began after 18 hours of incubation and greatly increased after 24 hours of incubation in 20% PEG. By 48 hours, several unidentified, more polar metabolites were found. Germination was induced in seeds imbibed in 20% PEG by 4 hours of red or 4 hours of white light following 20 hours in the dark, and was fully reversed by 2 hours of far red light. However, in metabolism experiments, [(14)C]ent-kaurene oxidation was observed only with constant white light. These results indicate that although ent-kaurene oxidation is a light sensitive step in the biosynthesis of gibberellins in Grand Rapids lettuce seeds, ent-kaurene metabolism is not required for light-induced germination.

Journal Article↗
PubMed1997

Novel functions of clathrin light chains: clathrin heavy chain trimerization is defective in light chain-deficient yeast.

Clathrin is a major coat protein involved in sorting and retention of proteins at the late Golgi and in endocytosis from the cell surface. The clathrin triskelion contains three heavy chains, which provide the structural backbone of the clathrin lattice and three light chains, which are thought to regulate the formation or disassembly of clathrin coats. To better understand the function of the clathrin light chain, we characterized yeast strains carrying a disruption of the clathrin light chain gene (CLC1). Light chain-deficient cells showed phenotypes similar to those displayed by yeast that have a disruption in the clathrin heavy chain gene (CHC1). In clc1-delta cells, the steady state level of the clathrin heavy chain was reduced to 20%-25% of wild-type levels and most of the heavy chain was not trimerized. If CHC1 was overexpressed in clc1-delta cells, heavy chain trimers were detected and several clc1-delta phenotypes were partially rescued. These results indicate that the light chain is important for heavy chain trimerization and the heavy chain still has some function in the absence of the light chain. In yeast, deletion of CHC1 is lethal in strains carrying the scd1-i allele, while strains carrying the scd1-v allele can survive without the heavy chain. In previous studies we isolated several multicopy suppressors of inviability of chc1-delta scd1-i cells. Surprisingly, one of these suppressors, SCD4, is identical to CLC1. Overexpression of CLC1 in viable chc1-delta scd1-v strains rescued some but not all of the phenotypes displayed by these cells. In the absence of the heavy chain, the light chain was not found in a high molecular mass complex, but still associated with membranes. These results suggest that the light chain can function independently of the clathrin heavy chain in yeast.

Clathrin↗