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At least 829 records · Page 46Linked to original sources
PubMed1990

Interaction between Light Quality and Light Quantity in the Photoregulation of Anthocyanin Production.

The interaction between phytochrome photoequilibrium (phi) and photon flux in the photoregulation of anthocyanin production under prolonged irradiation was studied in seedlings of Brassica oleracea L. and Lycopersicon esculentum Mill. In cabbage, anthocyanin production increases with decreasing phi, reaching a maximum at the lowest value (phi = 0.13) used in this study; in tomato, the extent of the response is higher at intermediate values, reaching a maximum at phi = 0.46. In cabbage, the response increases with increasing photon flux at all phi values; however, the response to changes in photon flux is minimal at phi = 0.85, and, at phi = 0.13, minimal at photon fluxes higher than 5 micromolar per square meter per second. In tomato, the response increases with increasing photon flux at phi = 0.46, 0.65, and 0.85, the response to changes in photon fluxes being minimal at phi = 0.85; at phi = 0.13 and 0.29 the response first increases (significantly at phi = 0.29 and minimally at phi = 0.13) and then decreases with increasing photon fluxes, the transition occurring at about 1 micromolar per square meter per second at phi = 0.13, and at 5 micromolar per square meter per second at phi = 0.29. The patterns of light quality-quantity interaction in the photoregulation of anthocyanin production are significantly different in cabbage and tomato and are also significantly different than those observed for other photomorphogenic responses to prolonged irradiations.

Journal Article↗
PubMed1975

Sequence variability of rabbit antibody light chains. Familial occurrence of n-terminal sequence differences between b4 and b9 light chains.

Amino acid sequence analyses of the IgG light (L) chains from selected members of a rabbit family with allotypes b4 and b9 showed N-terminal substitutions that segregated with the b4 allotype. The L chains of allotype b4 had tyrosine at step 2, whereas this residue was absent from that step in the b9 L chains. Steps 12 and 13 of b4 L chains yielded a high percentage of glutamic acid, whereas a low percentage was observed for the b9 L chains. These tyrosine and glutamic acid substitutions were observed with the same frequency in L chains from homogeneous antibodies as in the L chains of the IgG samples. The data suggest that, in the family studied, separate and distinct V-region gene complexes are linked to the b4 and b9 allotypic genes.

Amino Acid Sequence↗
PubMed1993

The major intrinsic light-harvesting protein of Amphidinium: characterization and relation to other light-harvesting proteins.

A major light-harvesting complex (LHC) has been obtained from thylakoids of Amphidinium carterae solubilized with digitonin or decylmaltoside and separated by sucrose-gradient centrifugation. The digitonin-LHC forms a dark brown band at approximately 17% sucrose and the decylmaltoside LHC one at approximately 7% sucrose. Excellent energy transfer is retained from chlorophyll c and carotenoid to chlorophyll a. Absorbance and fluorescence excitation spectra show the existence of two major forms of chlorophyll c, one absorbing at 634 nm and the other at 649 nm. Linear dichroism spectra show the Qy transition of both forms of chlorophyll c to be aligned at < 35 degrees to the membrane plane. On sodium dodecylsulfate polyacrylamide gels the complex resolves as a single band of 19 kDa. A partial amino acid sequence shows the N-terminus to be unblocked but modified; there is a persistent ambiguity of Ser/Asn at residue 4 and evidence for multiple but very similar polypeptides within the 19 kDa band. The peptide has strong identity with the N-terminal regions of LHC from Phaeodactylum and Pavlova and LHC 1 of higher plants. Antibodies to the 19 kDa peptide react weakly with LHC of brown algae, diatoms and Prymnesiophytes but not with those of higher plants or Cryptophytes.

Amino Acid Sequence↗
PubMed1990

Regulation of the chicken embryonic myosin light-chain (L23) gene: existence of a common regulatory element shared by myosin alkali light-chain genes.

The transcriptional regulation of the chicken myosin alkali light-chain (MLC) L23 gene was analyzed. Two different types of cis-regulatory regions were identified: one was a silencerlike region located between 3.7 and 2.7 kilobases upstream of the mRNA initiation site, and the other was essential for the expression of L23 in skeletal muscle cells and was located between 106 and 91 base pairs upstream of the cap site. This 16-base-pair cis-acting element was designated as the MLC box since it is well conserved in various muscle-specific MLC promoter regions. The activity of the MLC box showed tissue specificity. To analyze the relationship between the nucleotide sequence and the activity of the MLC box precisely, mutation analysis was performed. The 16-base-pair sequence was indispensable for the active transcription of L23 gene, and the MLC box could function in either orientation. The inverted sequence of the MLC box was similar to the sequence of the alpha-actin CArG box. By using a gel mobility retardation assay, the nuclear protein(s) that binds to both MLC box and CArG box was detected with nuclear extract prepared from chicken embryonic breast muscle. These observations imply that a common factor regulates the coordinate expression of these contractile proteins in muscle differentiation.

Animals↗
PubMed2005

Autofluorescence bronchoscopy with white light bronchoscopy compared with white light bronchoscopy alone for the detection of precancerous lesions: a European randomised controlled multicentre trial.

BACKGROUND: The potential of autofluorescence bronchoscopy (AFB) to detect precancerous lesions in the central airways and its role in lung cancer screening is uncertain. A study was undertaken to evaluate the prevalence of moderate/severe dysplasia (dysplasia II-III) and carcinoma in situ (CIS) using a newly developed AFB system in comparison with conventional white light bronchoscopy (WLB) alone. METHODS: In a prospective randomised multicentre trial, smokers > or = 40 years of age (> or = 20 pack-years) were stratified into four different risk groups and investigated with either WLB+AFB (arm A) or WLB alone (arm B). RESULTS: 1173 patients (916 men) of mean age 58.7 years were included. Overall (arms A and B), preinvasive lesions (dysplasia II-III and CIS) were detected in 3.9% of the patients. The prevalence of patients with preinvasive lesions in the WLB arm was 2.7% compared with 5.1% in the WLB+AFB arm (p = 0.037). For patients with dysplasia II-III, WLB+AFB increased the detection rate by a factor of 2.1 (p = 0.03), while for CIS the factor was only 1.24 (p = 0.75). The biopsy based sensitivity of WLB alone and WLB+AFB for detecting dysplasia II-III and CIS was 57.9% compared with 82.3% (1.42-fold increase). The corresponding specificity was 62.1% compared with 58.4% (0.94-fold decrease). CONCLUSIONS: This first randomised study of AFB showed that the combination of WLB+AFB was significantly superior to WLB alone in detecting preneoplastic lesions. Our findings do not support the general use of AFB as a screening tool for lung cancer, but suggest that it may be of use in certain groups. The precise indications await further study.

Adult↗
PubMed1980

Comparative light and electron microscopic study of the human, dog and rat prostate. An approach to an experimental model for human benign prostatic hyperplasia (light and electron microscopic analysis)--a review.

Stereology was shown in several studies to be a relevant method to study the quantitative amount of tissue and cell compartments of normal and pathological altered prostatic tissue. A morphological comparison of the rat (ventral lobe), dog and human prostate was performed by quantitative morphology. In comparing the light microscopic analysis of the rat ventral prostatic lobe with that of the dog prostate, the volumetric amount of the glandular cells in the dog prostate is two times greater than in the rat (ventral prostatic lobe). In the normal human prostate the volumetric amount of the glandular part was calculated to be 55% of the outer part, respectively 45% in the inner part of the prostate. Regarding the stromal tissue, there is no difference between the dog and the normal human prostate, but a striking difference compared to the rat ventral prostatic lobe, where stromal development seems to be sparse (25%). The quantitative measurements of spontaneous dog and human prostate hyperplasia show that the dog hyperplasia is primarily a glandular disease whereas human benign prostatic hyperplasia reflects more stromal activation. As shown by the electron microscopic measurements in the normal human and dog prostate, there is a similar great volumetric amount of secretory granules. In comparing the data of the rough endoplasmic reticulum, in the rat there is a higher amount than in the normal human and dog prostate. Conversely, the amount of secretory granules is higher in the dog and human prostate than in the rat (ventral prostatic lobe).

Animals↗
PubMed2002

Error sources and algorithms for white-light fringe estimation at low light levels.

We address the problem of highly accurate phase estimation at low light levels, as required by the Space Interferometry Mission (SIM). The most stringent SIM requirement in this regard is that the average phase error over a 30-s integration time correspond to a path-length error of approximately 30 pm. Most conventional phase-estimation algorithms exhibit significant enough bias at the signal levels at which the SIM will be operating so that some correction is necessary. Several algorithms are analyzed, and methods of compensating for their bias are developed. Another source of error in phase estimation occurs because the phase is not constant over the integration period. Errors that are due to spacecraft motion, the motion of compensating optical elements, and modulation errors are analyzed and simulated. A Kalman smoothing approach for compensating for these errors is introduced.

Journal Article↗
PubMed2005

Fabrication of subwavelength structure for improvement in light-extraction efficiency of light-emitting devices using a self-assembled pattern of block copolymer.

A new fabrication method to improve the optical extraction efficiency of light-emitting devices is presented. The morphology of a self-assembled block copolymer was transferred to the surface of a compound semiconductor to achieve a subwavelength columnar structure. The optical extraction efficiency of the substrates with subwavelength columnar structures of 350 nm pillar height, 130 nm diameter, and 180 nm pitch, improved 2.2 times compared to unprocessed substrates. This method does not require expensive exposure lithography tools and is therefore suitable for conventional semiconductor processes.

Journal Article↗
PubMed2003

Spatially correlated light emission from a resonant-cavity light-emitting diode.

We present the angular-resolved intensity noise characteristics of a resonant-cavity light-emitting diode under quiet pumping conditions. Measurements by a sensitivity-enhanced lock-in amplifier detection scheme yielded a spatial anticorrelation between the intensity noise of the central and peripheral parts of the emitted far field. Proposals for possible explanations of this anticorrelation from a semiconductor emitter point of view and its consequences for applications in quantum optical imaging are discussed.

Journal Article↗
PubMed1984

The light-harvesting polypeptides of Rhodospirillum rubrum. II. Localisation of the amino-terminal regions of the light-harvesting polypeptides B 870-alpha and B 870-beta and the reaction-centre subunit L at the cytoplasmic side of the photosynthetic membrane of Rhodospirillum rubrum G-9+.

The unspecific proteinase K and the specific proteases alpha-chymotrypsin, trypsin and S. aureus V 8 protease were used in order to determine the orientation of the polypeptides B 870-alpha and B 870-beta from the major antenna complex B 870 of Rs. rubrum G-9+ within the chromatophore membrane (inside-out vesicle). Although B 870-alpha exhibits cleavable peptide bonds, treatment with specific proteases yielded splitting only in B 870-beta within the N-terminal region. In the case of proteinase K, which was most effective, mainly 6 (B 870-alpha) and 16 (B 870-beta) amino acid residues were removed from their N-terminal parts as proved by means of Edman degradation of cleavage products. The major peptide bonds cleaved were identified as Gln6-Leu7 in B 870-alpha and as Lys16-Glu17 in B 870-beta. The central hydrophobic stretch regions and the relatively hydrophilic C-terminal parts of both light-harvesting polypeptides were not affected by proteinase K. On the basis of these degradation experiments a transmembrane orientation of B 870-alpha and B 870-beta is postulated, with their N-terminal towards the cytoplasm and their C-termini towards periplasm with regard to the photosynthetic membrane. This hypothesis is supported by the transmembrane model proposed by Brunisholz et al. (Hoppe-Seyler's Z., Physiol. Chem., (1984) 365, 675-688) in which the hydrophobic stretch of B 870-alpha and of B 870-beta forming an alpha-helix would span the membrane once. Organic solvent extraction of chromatophores treated with proteinase K yielded a fairly pure polypeptide fragment with an apparent molecular mass of 14000 Da. Its N-terminal amino-acid sequence is identical with the sequence within the N-terminal region of the reaction centre subunit L of Rs. rubrum G-9+. Thus it is most likely that as in the case of B 870-beta, proteinase K removed 16 amino acid residues from the N-terminal part of subunit L. This subunit therefore also seems to be exposed at the surface of the cytoplasmic side of the chromatophore membrane.

Amino Acids↗
PubMed2001

[Scanning electron microscopy and light microscopy under polarized light of a submandibular salivary gland calculus].

BACKGROUND: The salivary calculus is an ancient pathologic condition, called sublingual stone by Hyppocrates. It is well-defined from a anatomo-pathologic, diagnostic and topographic viewpoint, though some pathogenesis-related doubts still exist. This work aims at relating the micro-morpho-structural aspect of a salivary calculus of remarkable dimensions with the current calculogenetic hypotheses. METHODS: A 1.1 g salivary calculus removed from the initial section of Wrthon s duct in the right-hand submandibular gland of a 42 year old male has been studied. Following the fixation in 4% buffered formalin and the inclusion in resin, it was serially sectioned in 15-20 micron slices. Some sections were coloured with toluidine blue O and acid fuchsin. The exeresis of the calculus was carried out intraorally, with marsupialization under local anesthesia. The analysis was performed using a SEM with backscattered electrons and a polarised and transmitted light microscope. RESULTS: The investigations have outlined the presence of various organic cores and a concentric, stratiform architecture interrupted by radial elements. CONCLUSIONS: The formation of this calculus may be due to mixed secondary lithiasis resulting from the formation of colloids and crystalloids.

Adult↗
PubMed1975

[The behavior of the b-wave in the electroretinogram of light-adapted frogs during serial light exposure].

In light-adapted frogs (adaptation luminance 10(3) asb) repeated flashes of high intensity (10(5) asb) caused decrease of the b-wave in the electroretinogram as compared to the results obtained with dark-adapted animals. The amplitude changes were monotonous in all cases; they were dependent on the spacing and duration of the stimulus. With short intervals (2-10 sec) the amplitude adjusted to a new level no later than after 8 flashes. With longer intervals (30 and 60 sec), however, the amplitude decreased slowly and steadily over the whole period of experiment. Under these conditions, adjustment to a new level was prevented by disturbing factors, which additionally reduced the retinal sensitivity depending on the duration of the experiment.

Adaptation, Ocular↗
PubMed1980

Enhanced experimental metastasis of ultraviolet light-induced fibrosarcomas in ultraviolet light-irradiated syngeneic mice.

Some ultraviolet light (UV)-induced fibrosarcomas produce more experimental pulmonary tumor colonies in UV-irradiated hosts than in normal syngeneic recipients. The number of experimental metastases produced following i.v. injection of these tumors increases in proportion to the dose of UV radiation. This enhancement can be transferred with lymphoid cells to lethally X-irradiated recipients and with partially purified T-lymphocytes to untreated syngeneic mice. Some UV-induced fibrosarcomas do not form experimental metastases readily, even in UV-irradiated recipients, suggesting that both immunological and nonimmunological factors are important in limiting metastasis formation.

Animals↗
PubMed1984

Seasonal changes in the circadian activity rhythm of light-dark (LD) and completely dark (DD) regimen in the mouse submandibular gland in the presence of light-dark (LD) and completely dark (DD) regimen.

Influence of seasons on circadian activity changes and the influence of one and six weeks of DD upon these changes of acid phosphatase (AP) and beta-acetylglucosaminidase (AM) was studied in the submandibular gland of sexually mature male mice. Total enzyme activity was determined in tissue homogenates at four-hour intervals in March, June, October, and February under standard LD12/12 conditions and after one and six weeks of the DD regime. The rhythms were analysed according to cosinor method. Under constant lighting conditions the seasonal differences in the AM circadian activity rhythm were found. AP activity was considerably less influenced by seasonal changes. Both enzyme activity changes were independent of each other and each rhythm was differently influenced by DD. In the case of AM the most pronounced circadian activity changes had the highest amplitude and mesor occurred in summer. The strongest influence of DD upon this enzyme activity rhythm was observed in spring and summer especially after the first week, after six weeks the acrophase returned to the LD group value (spring). In autumn and winter the reaction to DD was different to that of summer and spring. For AP the circadian changes of activity were non-rhythmic in spring, whereas in all other seasons the acrophases occurred almost at the same time in the afternoon. In DD the activity rhythm significantly changed after six weeks. In all seasons, except spring the circadian rhythm of activity was not observed after six weeks of DD. An attempt was made to explain the observed results by the certain kind of genetic memory present in laboratory animals the neurohormonal system of which is influenced by seasonal changes.

Acetylglucosaminidase↗
PubMed1984

Conservation in rat liver of light and heavy subunit sequences of mammalian ferritin. Presence of unique octopeptide in the light subunit.

Ferritin, an iron-storage protein found in all life forms examined, is composed of varying proportions of two subunits of different molecular weight, heavy (H) and light (L). Using cDNA clones, we have determined the nucleotide sequence corresponding to the mRNA of the L-subunit of rat liver ferritin. The coding region of 546 nucleotides (182 amino acids) is flanked by 5'- and 3' -untranslated regions of approximately 130 and 150 nucleotides, respectively. The rat liver L-subunit amino acid sequence derived from the reading frame of the cDNA showed 88% and 82% homology, respectively, with the amino acid sequences of horse spleen ferritin (Heusterspreute, M., and Crichton, R. R. (1981) FEBS Lett. 129, 322-327), and human spleen ferritin (Wustefeld, C., and Crichton, R. R. (1982) FEBS Lett. 150, 43-48), thus demonstrating evolutionary conservation of the L-subunit sequence. However, a major difference between the rat and the horse and human sequences is the insertion of an octopeptide near the COOH-terminus of the rat protein resulting in a slightly longer peptide chain in this species. The reading frame and parts of the derived amino acid sequence including the octopeptide sequence were confirmed by direct amino acid sequencing of cyanogen bromide peptides from rat liver ferritin. Minor fragments of rat liver ferritin, presumably derived from the H-subunit, were also isolated after cyanogen bromide treatment. On sequencing, these H-peptides showed limited homology with regions of the L-sequence but extensive homology with published H-sequences from human liver and spleen. The H-subunit sequence did not contain the octopeptide found as part of the L-subunit sequence.

Amino Acid Sequence↗
PubMed1995

Role of light chain variable region in myeloma with light chain deposition disease: evidence from an experimental model.

Light chain deposition disease (LCDD) results from a propensity of some human monoclonal L chains to form tissue deposits. We designed an experimental model for in vivo expression of human kappa L chain sequences in mice and compared a somatically mutated LCDD chain with a closely related control kappa chain, both encoded by the unique V kappa IV gene. Mice secreting the LCDD chain but not those producing the control chain showed deposits with a distribution similar to that observed in patients. These data show that discrete changes in V region sequences can play a major role in tissue deposition of human L chains.

Amino Acid Sequence↗
PubMed1975

[Retinal reactions to intense light. I. Threshold lesions. Experimental, morphological and clinical studies of pathological and therapeutic effects of laser and white light].

The effects of intense light produced by an argon laser, a helium-neon laser and a xenon are photocoagulator in the retinas of gray chinchilla rabbits, cynomolgus monkeys, and rhesus monkeys were studied clinically and histopathologically including electron microscopy. An improved experimental set-up was used allowing a very good consistency of the inflicted lesions. Threshold lesions were produced in chinchilla rabbits and cynomolgus monkeys by an argon laser and a helium-neon laser. The lesions were evaluated ophthalmoscopically and histograms were drawn indicating ophthalmoscopic ED50 values. For the two lasers examined these values were 12 and 17 mW, respectively, for exposure durations in the range of the blink reflex (125-150 msec). Histopathologically, ophthalmoscopic threshold lesions of both laser types showed evidence of thermal damage of the outer retinal half. This damage was principally identical in both species involving the retinal pigment epithelium and the full extension of the photoreceptor cells up to their synapses within the outer plexiform layer. The ophthalmoscopic threshold value was associated, therefore, with an irreversible loss of visual function within the retinal area concerned. No evidence for primary sites of significant energy absorption within the neural retina was found. The width of ophthalmoscopic threshold lesions was determined by measuring within the histologic sections with a microscope and a calibrated graticule the extension of damage at the level of the retinal pigment epithelium and at the level of the outer nuclear layer. In the cynomolgus monkey for ophthalmoscopic argon laser threshold lesions the extension at the level of the RPE was 70-80 mum in diameter and at the level of the outer nuclear layer it was 40-50 mum in diameter. Laser lesions that had a diameter of 60 mum at the level of the RPE and of 30 mum at the level of the outer nuclear layer were ophthalmoscopically subvisible. It is concluded that probably also in man such laser lesions, as well as various other pathologic changes of this size or smaller, cannot be evaluated by clinical ophthalmoscopy. The ophthalmoscopic threshold was correlated with a histopathologic threshold as defined by minimal histopathologic damage. Very likely, such damage lies within the range of functional recovery, and the histopathologic threshold demarcates at the same time the decisive functional threshold. The conversion ratio between histopathologic-functional and ophthalmoscopic threshold for argon lesions in cynomolgus monkeys was somewhat greater than 3, e.i. the ophthalmoscopic threshold was more than 3 times higher than the histopathologic-functional threshold. Using this data together with additional biologic and optical considerations, a safety threshold for man for cw-lasers within the visible spectrum was estimated to be 1-2 mW.

Animals↗