Increase In Pigment Content Research Articles

Feeding of micro- and macrozooplankton at the subsurface chlorophyll maximum in the subtropical North Pacific

Diel variations of grazing rate of micro- and macrozooplankton were examined at a subsurface chlorophyll maximum in the subtropical North Pacific (28°N, 136°E) using gut fluorescence measurements. Hydrocasts and vertical net hauls were carried out at 4–5-h intervals during a 72-h sampling period near a drifter to which a drogue was attached at the depth of the subsurface chlorophyll maximum. Nocturnal feeding was observed in microzooplankton, and in small macrozooplankton (95–350 μm) collected from the subsurface chlorophyll maximum and from depths below it. In contrast small macrozooplankton collected from depths above the chlorophyll maximum and the large macrozooplankton (> 350 μm) showed no nocturnal increase in pigment contents. Grazing rate of microzooplankton was estimated to be 56–100% of daily chlorophyll production. On the other hand, that of the small and large macrozooplankton was quite small, 4 and 2%, respectively. These results clearly showed that microzooplankton were the major consumer of phytoplankton in the chlorophyll maximum in this subtropical area and their grazing was balanced to phytoplankton production within the time scale of several days.

The nature and properties of squirrel lens yellow pigment

The low molecular weight yellow pigment in the gray squirrel lens is confirmed to be n-acetyl-3-OH-kynurenine (NAK). This conclusion is based upon the results of studies of the compoud's optical, chromatographic, and mass spectroscopic properties. The original tentative identification of this compound was reported by Van Heyningen (1971, 1973). The pigment is distributed equivalently throughout the lens. Its absorbance increases with age, but the increase is related to the growth of the lens and not to an increase in pigment concentration. The function of NAK in the squirrel lens is to enhance vision by eliminating short-wavelength light that causes scattering and chromatic aberration. The pigmented lens also protects the retina from near-UV radiation-associated damage to the photoreceptors Collier and Zigman 1987.

Photosynthetic characteristics and pigment content and composition in Littorella uniflora (L.) Aschers. in a depth gradient

The isoetid Littorella uniflora (L.) Aschers. showed distinct light-shade adaptation within its depth limits (0–2.3 m) in Lake Kalgaard, Denmark. Plants collected at 2.3-m depth had significantly higher concentrations of total chlorophyll (9.9 μg mg −1 leaf dry weight (LDW)) than plants from 0.2 m (6.0 μg mg −1 LDW). Furthermore, the deep-water plants had a significant enrichment with chlorophyll b. The chlorophyll a: b ratios were 2.6 and 3.2 in plants from deep and shallow water, respectively. Photosynthetic characteristics, such as low light compensation points, a steep initial slope of photosynthesis vs. irradiance and low irradiance at 1 2 maximum photosynthetic rate confirmed the adaptation to low light levels by the deep water plants. The only deviation of the deep-water vs. shallow-water plants from the general features of terrestrial shade plants was the substantially higher photosynthetic rates at light saturation. Plants from both depths showed increased pigment concentrations and a lowering of the light compensation points in the early winter.

Ignitability and explosibility of polyester/epoxy resins for electrostatic powder coating

The use of electrostatic powder coating is expanding. In view of the dust explosion hazard related to this process, a comprehensive investigation of ignitability and explosibility properties of 11 polyester/epoxy resin powders used in electrostatic powder coating has been carried out. The powders differed with respect to the ratio of polyester to epoxy, pigment type, pigment content, density and particle size distribution. The powders were tested in the closed Hartmann bomb for establishing the maximum explosion pressure and the maximum rate of pressure rise, in the open Hartmann tube fitted with the CMI electric spark generator for measurement of the minimum ignition energy, and in the ‘Nordtest Fire 011’ apparatus for determination of the minimum explosible dust concentration. Attempts were also made at conducting some explosibility tests in the Swiss closed 20-litre spherical vessel, but severe blocking problems in the dust dispersion system were encountered. Particle size distributions of the powders were determined using a laser diffraction method, and the specific surface areas were measured by nitrogen adsorption. All the powders gave approximately the same maximum explosion pressures in the Hartmann bomb, whereas the maximum rate of pressure rise decreased with increasing pigment content and particle size. Clouds in air of all the resins had quite low minimum ignition energies, from below 3 mJ to approximately 20 mJ. Except for one or two powders the minimum ignition energy increased fairly systematically with particle size. There was no systematic influence of the pigment content, although the powders with the highest pigment contents also had the highest minimum ignition energies. The minimum explosible dust concentration increased systematically with increasing pigment content, in such a way that the concentration of combustible material at the minimum explosible dust concentration was nearly the same for all the dusts, and close to the minimum explosible concentration of gaseous hydrocarbons like methane and propane.

Characterization of seven human melanoma cell lines: melanogenesis and secretion of plasminogen activators.

Permanent cell lines (UCT-Mel 1 through 7) were established from biopsies of metastatic tissue taken from seven patients with malignant melanoma. Cells from these lines were all aneuploid and all grew as non-contact-inhibited, adherent monolayers. All of the lines, with the remarkable exception of UCT-Mel 6, formed tumours in nude mice, expressed the melanoma M-18 antigen and synthesized plasminogen activators exclusively of the tissue-type. UCT-Mel 6 cells were non tumourigenic, they lacked the M-18 antigen and they synthesized plasminogen activators exclusively of the urokinase type. UCT-Mel 1 and UCT-Mel 2 formed pigment in vitro and both of these lines showed an increase in pigment content and tyrosinase synthesis with increasing cell density. The rate of plasminogen activator released by UCT-Mel 1 and UCT-Mel 3 declined strikingly as the cells became confluent. Assuming that proteolytic activity is required for cell migration in vivo; that tyrosinase synthesis reflects expression of the differentiated phenotype and that melanoma cells retain some of the characteristics of neural crest cells, we suggest that the effects of confluence and close cell-cell contact provide a useful experimental counterpart for the study of normal neural crest all behaviour that is characterized by an inverse relationship between migration and a protease secretion on the one hand and pigmentation on the other.

Influence of very low doses of ionizing radiation on Synechococcus lividus metabolism during the initial growth phase.

Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomitant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.

Pigment bleaching by soybean lipoxygenase type-2 and the effect of specific chemical modifications

In contrast to lipoxygenase-1 of the soybean, the lipoxygenase-2 isomer had very little anaerobic activity as determined by diene formation, carbonyl production and pigment bleaching. Chlorophyll and carotene inhibited the aerobic activity of this isomer. The inhibition at low concentrations appeared to be noncompetitive and at higher concentrations, competitive. Increasing pigment concentrations over 20 μg/ml for carotene and 3.75 μg/ml for chlorophyll decreased the rate of bleaching. When chlorophyll was added after the lipoxygenase had begun to react, diene formation was inhibited but pigment bleaching was even greater than when the chlorophyll was added together with the lipoxygenase linoleic acid mixture. This increased bleaching is most probably due to the presence of free radicals. Antioxidants reduced diene and carbonyl formation as well as chlorophyll and carotene bleaching through their action as free radical scavengers. Bromosuccinimide and iodoacetic acid caused a pronounced decrease in activity. The former indicates the involvement of tryptophan in the active center as shown as well by the change in spectrum caused by this reagent. The latter indicates that methionine is most probably involved in the lipoxygenase action. Methyl mercuric iodide and tetranitromethane had very little effect on the lipoxygenase activity, indicating for the former that no sulphydryl groups are involved and for the latter that tyrosine is not in the active center. This is in contrast to the effects of these reagents on lipoxygenase-1. A scheme is proposed to show the pathways of lipoxygenase-2 activities.

The effect of oxygen on the amplitude of photodriven electron transfer across the lipid bilayer-water interface

The surprisingly small effect of oxygen on photoelectron transfer in pigmented lipid bilayers is traced to a short lifetime of the excited states. Decreasing the oxygen concentration by greater than 100-fold decreases the half saturating concentration of acceptor by only threefold and has no effect on the maximum photovoltage observed at acceptor saturation. This holds true for both magnesium octaethylporphyrin and chlorophyll with both ferricyanide and methyl viologen as acceptors. Since oxygen quenches excited states at near the encounter limit, the lifetime of reactive state must be short, less than 100 ns. About 100-fold higher concentrations of acceptor are required to quench the fluorescence (in liposomes) than to saturate the photoeffect. Thus the reactive state is most likely the triplet. The short life of the excited state is caused by concentration quenching, i.e., their reaction with ground state molecules. The increase of photovoltage with increasing pigment concentration shows that this quenching in a condensed form of the pigment produces ions that lead to the observed photovoltage by interfacial reaction of the anion with acceptor.

Regulation of growth and photosynthesis byOscillatoria agardhiigrown with a light/dark cycle

The cyanobacterium Oscillatoria agardhii was grown in turbidostat cultures with the light energy supply in either the continuous mode or in the pulsed mode (8/16 h light/dark (L/D) cycle). The light irradiance value used was sufficient to allow the maximal growth rate to be attained, when supplied continuously. Adaptation of O. agardhii to the L/D cycle was characterized by an increase in pigment content and photosynthetic performance, accompanied by a decrease in growth rate. This mode of adaptation resembled the adaptation of O. agardhii to continuous low light intensities. It is suggested that in this case the L/D cycle provokes this adaptation in order to allow the cells to accumulate carbohydrate rapidly during the light period. This was attributed to the storage of polyglucose, which served as a carbon and energy source for growth in the dark. The utilization of polyglucose in the dark was able to sustain the synthesis of all other cell components at the same rate as when cells were growing in the light. The growth yield in the dark, whilst metabolizing internally stored polyglucose, was 0.52 g cell C/g polyglucose C, or 0.62 g cell dry weight/g polyglucose. Although in the pulsed mode there is a 66% loss in light irradiance per 24 h when compared with a continuous light regime, the growth rate of the cyanobacteria grown in the pulsed mode was only 35% lower than the growth rate of a culture grown in continuous light. This can be explained by a high growth yield in the dark and by increased CO2 fixation rates in the light of cells grown in the pulsed mode.

Comparison of M. longissimus dorsi pigment concentration from implanted and control Angus and Limousin bulls and steers

M. longissimus dorsi total pigment concentration, visual color score and 24-h pH values were evaluated in a 2 3 factorial design that included bulls versus steers, Zeranol implants versus control and Angus versus Limousin comparisons. Bulls had greater total pigment concentration than steers (3.25 versus 2·90 mg/g; P < 0·01) and darker colored lean ( P < 0·01). Twenty-four hour pH values did not differ between bulls and steers. Zeranol implanting and breed had no effect on total pigment concentration or visual color score; however, Limousin had higher ( P < 0·05) 24-h pH values than Angus. The initial slaughter group (N = 10; average age = 256 days) had 34% less total pigment than the final slaughter group (N = 48; average age = 458 days). The correlation between visual color score and total pigment concentration was −0·65. These results indicate that the darker colored lean from bulls is due in part to an increase in pigment concentration.

Development of pigment in the echiuran worm Bonellia viridis

An account is given of the development of green pigment in the early larval stages of the echiuran worm, Bonellia viridis. The green pigment first appears in scattered epidermal cells of the gastrula, before the development of the trochal rings. It is contained in spherical vacuoles (0.5‐1.0 μm in diameter). As the gastrula develops into the trochophore there is an increase in total pigment content, as well as an increase in number of pigment cells and size of pigment vacuoles. The increase in pigment cell number in the trochophore results from the proliferation of the pigment cells of the gastrula. The pigment content increases rapidly before the trochophores hatch but shows little relative increase after hatching whilst the trochophores remain undifferentiated. We suggest that the pigment may have a protective role in the free‐living trochophore for camouflage or chemical defence. In trochophores that undergo male differentiation the pigmentation is lost. Since the males do not lead a free‐living existence but live as commensals inside the uterus of the female camouflage or chemical defence would be unnecessary. In trochophores undergoing female differentiation there is an increase in pigment content of the preoral lobe which develops into the proboscis. Following the enlargement of the coelom, clusters of coelomic cells accumulate green pigment whilst still in the coelom and then migrate to the integument of the body wall.

Influence de l'intensité lumineuse sur la teneur en bactériochlorophylle et sur la croissance de sulfobactéries phototrophes marines

Eight strains of Chromatiaceae isolated from marine sediments are cultivated under light intensities of 50-5000 lx. A decreased in the light intensity brings about an increase in the specific bacteriochlorophyll content and also in the length of development. In certain strains, the increase in pigment contents partly compensates for the loss in light intensity, up to the maximum concentration of bacteriochlorophyll. This mechanism is only a physiological compatibility which ensures the survival of these organisms under feeble light intensities.

The intensification of absorbance changes in leaves by light-dispersion

In dispersive samples, like leaves, the absorbance of pigments is intensified. The intensification is due to a longer optical path through the dispersive sample. However, in chloroplast suspensions the optical path is not much longer than in clear solutions. The factor of intensification β (=the lengthening of the optical path) is calculated by comparing the absorbance of leaves and the absorbance of chloroplast suspensions with equal pigment-content. This method also includes the influence of possible sieve effects which could decrease absorbance. The measurements are carried out with high- and low-light leaves of different thickness and pigment content. The intensification of absorbance was 2-2.5 fold. In highlight leaves it was somewhat less than in low-light leaves. The factor β is better correlated to the pigment content than to the thickness of the leaves. The plot of absorbance versus the pigment content of the leaves shows that β decreases with increasing pigment content. In contrast, chloroplast suspensions show a linear dependence as expected from Lambert-Beer's law. Thus, in leaves with very low pigment content the absorbance is intensified up to 6 fold while the intensification decreases with increasing absorbance. These results are in good agreement with measurements of Tsel'niker (1975) and with the theoretical predictions of Butler's formula (1960). Absorbance changes due to photooxidation of P-700 and cytochrome f in intact leaves are measured, and β is used to calculate the amount of the oxidized components. Without correction for β the values would be much greater than the amount actually present. The corrected data show that between 70 and 90% of the present P-700 and cytochrome f can be photooxidized in the intact leaf.

COLOR EVALUATION OF SELECTED CAPSICUMS

ABSTRACTThe extractable color values of fifteen selected cultivars of red‐peppers and two methods of measuring color intensity were compared. Significant differences were found between cultivars for objective and subjective color values. Extractable red pigment values were much greater than yellow in all cases. As xanthophyll content increased, beta‐carotene content increased. All Gardner values decreased with increasing pigment content. The Gardner Color Difference Meter proved to be a better indicator of extractable pigments than the subjective evaluation.

Early formation of intracytoplasmic membranes in Rhodospirillum rubrum

Cytoplasmic and intracytoplasmic membranes were isolated from Rhodospirillum rubrum by equilibrium sucrose density gradient centrifugation. Immediately after the induction of photosynthetically active intracytoplasmic membranes, bacteriochlorophyll is incorporated predominantly into the cytoplasmic membrane. With increasing pigment concentrations the newly arising intracytoplasmic membranes become sites of preferential bacteriochlorophyll incorporation. During this process the infrared absorption band of the pigment shows a red shift. The shift is more pronounced with intracytoplasmic than with cytoplasmic membranes. Pulse-chase of cytoplasmic membrane proteins reveals that such proteins become constituents of intracytoplasmic membranes.

Oxygen equilibrium and subunit aggregation of a holothurian hemoglobin

The hemoglobin of the sea cucumber Cucumaria miniata Brandt has a mol. wt of about 36 000 in the oxy- form with a s 20,w equal to 2.9 and a subunit molecular weight of 18 000 by sodium dodecylsulfate gel electrophoresis. This pigment aggregates when deoxygenated to an oligomer with a s 20,w equal to 4.7, an aggregation which is reversible upon subsequent oxygenation. The hemoglobin shows a sigmoid binding equilibrium with “ n” equal to 1.8 and a decrease in oxygen affinity with an increase in pigment concentration. This hemoglobin is compared with other hemoglobins showing oxygenation-linked subunit aggregation.

Rheological characteristics of pigment dispersions: Flow behaviour under steady shear flow

The rheological characteristics under steady shear flow of dispersions of pigment in a mid-litho oil varnish have been examined. Using a Weissenberg rheogonio-meter the influence of pigment concentration and dispersion temperature on flow behaviour have been examined in some detail. Data have been examined in terms of the initial peak stresses and of the equilibrium stresses encountered. By taking the ratio of these two as a measure of thixotropy it would appear that thixotropy goes through a maximum with increasing pigment concentration. The results also indicate that particle/particle interaction controls flow up to the point at which a peak stress occurs. Thereafter the flocculation/deflocculation process predominates.

A Study of the Phenomenon of Rheological Dilatancy in an Aqueous Pigment Suspension

The objective of this study was to gain a better understanding of the mechanisms responsible for rheological dilatancy in an aqueous pigment suspension. Of particular interest was the relationship between the extent of dilatancy and colloidal stability. This relationship was studied using iron oxide suspensions which were dispersed by addition of sodium polymethacrylate having a molecular weight of 4000. The level of colloidal stability was varied by changing the degree of dissociation of the carboxyl groups on the polymer. Measurements of the extent of adsorption of the dispersant were made and the adsorbed charge was found to correlate very well with low-shear viscosity measurements. Additional experiments were made to determine the effect of pigment volume concentration on dilatancy over the range of 40–47%. A cup-and-bob viscometer was used to measure the shear stress over a shear rate range of 100–4000 sec−1. The extent of rheological dilatancy was found to increase with (a) decreasing colloidal stability, and (b) increasing pigment concentration. Based on these findings, it was postulated that rheological dilatancy results from a progressive increase in flocculation due to shear. The fact that a suspension can exhibit both pseudoplasticity and dilatancy was explained by considering floc formation and floc disruption as competitive rate processes.

Carotenoid Synthesis in Leaves of Wheat after Irradiation by Red Light

AbstractA short inipulse of red light induces a Carotenoid synthesis in dark‐grown wheat leaves. This effect is particularly evident if the leaves, having received a short light impulse, are kept in darkness for six hours prior to a period of continuous irradiation for six hours. During this second period of irradiation much more carotenoids are formed than during an irradiation period of the same length, but not preceded by a pre‐irradiation. The main increase in pigment contents can be brought back to β‐carotene. For this pigment the short light impulse nearly doubles the pigment synthesis during a subsequent dark and light period of six + six hours as compared to the amount formed during six hours of light without pre‐irradiation.

Studies on the muscles of meat animals III. Comparative composition of various muscles in pigs of three weight groups

1. The contents of moisture, total nitrogen and intramuscular fat (and its iodine number), and the ultimate pH, were determined on longissimus dorsi (lumbar and thoracic regions), psoas major, rectus femoris, triceps (lat. head), superficial and deep digital flexor, sartorius and extensor carpi radialis muscles from ten pigs, of accurately known history, in each of three weight groups—pork, bacon and manufacturing (150, 200 and 250 lb. live weight, respectively).2. In addition, the myoglobin content of longissimus dorsi (lumbar), psoas major, rectus femoris, triceps (lat. head) and extensor carpi radialis was also determined. In all five muscles there was an increase in pigment content with increase of body weight, but there was some suggestion that the myoglobin content of psoas major and triceps showed a proportionally greater increment between pork and bacon weights and rectus femoris and extensor carpi radialis between bacon and manufacturing weights.3. In pigs of all three weight groups there were highly significant differences in fat-free moisture content between muscles and between animals. The mean, fat-free moisture content of longissimus dorsi (lumbar) (76·33%) is significantly less than that of longissimus dorsi (thoracic) (76·94%) and the mean value in the latter is significantly less than that in all the muscles except psoas major (77·28%). The mean fat-free moisture content of deep digital flexor (80·00%) is significantly higher than that in all the other muscles studied. There is evidence for a direct, but not linear, relationship between the contents of fat-free moisture and connective tissue (as calculated from hydroxyproline concentration).4. Differences in ultimate pH between animals and between muscles were highly significant; but not those between the three weight groups, although there was a tendency for higher values in the muscles from bacon and manufacturing groups.5. Both for the data overall, and within a given muscle, there was a direct proportionality between ultimate pH and fat-free moisture content. Except in the case of deep digital flexor correlation coefficients between these two parameters were significant. These correlations varied in significance for different muscles between the three weight groups.6. Overall, the mean total nitrogen content (fat-free) of longissimus dorsi (lumbar) (3·77%) was significantly greater than that of longissimus dorsi (thoracic) (3·69%) and the latter greater than that of psoas major (3·58%). Such differences were also apparent within each weight group. The values were significantly greater than those for the six other muscles studied. The overall mean fat-free nitrogen content of deep digital flexor (3·17%) was very significantly less than that for all the other muscles. For the muscles of pork, bacon and manufacturing weights, overall nitrogen contents (fat-free) were 3·38, 3·44 and 3·55%, respectively. There was a significant inverse correlation between nitrogen (fat-free) and moisture (fat-free) (r = –0·88).7. The ranking of muscles with respect to their contents of intramuscular fat was significantly different between weight groups. In contrast to the bovine, there was no significant difference overall between the intramuscular fat contents of longissimus dorsi in lumbar and thoracic regions; and these were both significantly higher than levels in psoas major, although the converse is true in the bovine.8. Variation in the intramuscular fat content of the lumbar region of longissimus dorsi was strongly reflected by those in longissimus dorsi (thoracic), psoas major, rectus femoris, triceps and superficial digital flexor; but little with those in extensor carpi radialis and deep digital flexor; and not at all with that in sartorius.9. There was no significant difference overall in the iodine number of intramuscular fat between weight groups. Iodine numbers in both thoracic and lumbar regions of longissimus dorsi were significantly lower than those in all the other muscles studied. The overall correlations between intramuscular fat and its iodine numbers were r = –0·70, – 0·71 and – 0·66 in pigs of pork, bacon and manufacturing weights: each of these was significant.10. In discussing the results, it is suggested that those circumstances causing a high ultimate pH in muscle (e.g. fatigue) may concomitantly effect redistribution of body water and hence explain the observed proportionality between water content and ultimate pH. Significant differences in moisture content between muscles may be related to their relative proportion of connective tissue or to its nature. On the basis of much of the chemical data obtained, the muscles studied appear to fall into three groups—longissimus dorsi (lumbar and thoracic), deep digital flexor, and the rest, although such a conclusion does not accord with that suggested by anatomical dissection. Aspects of the relative maturity of the muscles are considered.