Diurnal Illumination Research Articles

Interdependent effects of the ionophore A23187 and serum on the serotonin N-acetyltransferase activity of cultured chick pineal glands.

Marked effects of the ionophore A23187 on the cycle of N-acetyltransferase (NAT) activity in cultured chick pineal glands were observed under three conditions of illumination. However, the effects were qualitatively and quantitatively dependent on the batch of fetal calf serum used in the medium and time of explanation into culture. Ionophore increased the level of NAT activity remaining in glands exposed prematurely to light regardless of the serum used. The ionophore suppressed the "spike" in cyclic GMP content of glands cultured in the dark, and extended the period of maximum cyclic GMP content of glands under diurnal illumination.

Fast and slow artificial diurnal rhythms (light-darkness-light) and the rate of progression of retinal degeneration in dystrophic RCS rats. An electroretinographic study.

The RCS rat strain is characterized by a hereditary progressive degeneration of retina and pigment epithelium. The possible influence of varying artificial diurnal rhythms on the rate of progression of the degeneration was investigated with electroretinography (ERG). Light intensity of the 'day'-periods and the total light exposure were constant in two groups of RCS rats subjected to 2 h light/2 h darkness and to 24 h light/24 h darkness periods respectively. No difference in the rate of degeneration as mirrored by the ERG was seen between the two groups. The ERGs were unrecordable after 7-8 weeks, and the experiments started at birth. No changes in the ERG of controls, genetically identical with the RCS strain except for the retinal dystrophy gene, were seen when they were subjected to the two diurnal rhythms. The results lessen the probability that careful long-term patching of an eye in patients with retinitis pigmentosa or other related hereditary degenerative diseases (in order to diminish the influence of diurnal illumination changes leading to shedding of receptor outer segments) will halt or modify the progression of the disease in man.

Phase-shifting of cycles in level of serotonin N-acetyltransferase activity and cyclic GMP content of cultured chick pineal glands by methotrexate.

Methotrexate at 1 microM stimulated increase of serotonin N-acetyltransferase (NAT) activity in chick pineal glands cultured under each of three conditions of illumination. The peak of the circadian rhythm in NAT activity and the "spike" in content of cyclic GMP were both advanced in pineal glands cultured in the dark from midphotoperiod. In contrast, the time of peak NAT activity in glands cultured in the dark from late photoperiod was unaffected. In addition, methotrexate did not affect times of reaching maximum NAT activities in glands cultured from midphotoperiod in the light or under diurnal illumination. Doubling the concentration of methotrexate also eliminated the lag phase in increase of NAT activity in glands cultured in the dark. However, at a concentration of 5 microM methotrexate the curve depicting increase of NAT activity was biphasic, and neither time nor level of peak NAT activity differed from those of control glands. Results of attempts to demonstrate persistent effects of exposure to methotrexate were inconclusive.

Neopterin retards loss of serotonin N-acetyltransferase activity from cultured chick pineal glands.

D-Neopterin at 10 microM delayed start of the decline of serotonin N-acetyltransferase (NAT) activity from the peak level in the cycle exhibited by chick pineal glands cultured under standard conditions in the dark. A less marked retardation of decline of NAT activity was found with glands cultured under diurnal illumination or those exposed prematurely to light. There were no significant effects of neopterin on the increases of NAT activity or peak levels of activity developed. The pteridine also retarded loss of NAT activity from the peak level developed in the dark when the time of explanting into culture was later in the (solar) day, but not when it was earlier. Neopterin had no effect on the cycle in cyclic GMP content of cultured chick pineal glands.

Relationship between cycles in level of serotonin N-acetyltransferase activity and cyclic GMP content of cultured chick pineal glands.

We examined effects of supplements on cycles in cyclic GMP content and serotonin N-acetyltransferase (NAT) activity in cultured chick pineal glands. Increases in cyclic GMP content and NAT activity were stimulated by 1-ethyl-4(isopropylidene-hydrazino)-1H-pyrazolo[3,4-b]pyridene-5-c arboxylic acid, ethyl ester, hydrochloride and isobutylmethyl xanthine under diurnal illumination and in constant darkness, but subsequent decreases were not inhibited. Hypoxanthine had little effect on NAT activity under all lighting conditions, or on the content of cyclic GMP in glands cultured in the dark. However, it markedly stimulated accumulation of cyclic GMP in illuminated cultures. EGTA or additional Ca2+ had no effect on pineal NAT activity. However, EGTA markedly stimulated accumulation of cyclic GMP both in the light and in the dark. Supplementary Ca2+ slightly retarded accumulation of cyclic GMP in the dark but stimulated slightly in the light.

Effect of Temperature on Nitrogenase Functioning in Cowpea Nodules

Nitrogenase (EC 1.7.99.2) activity of a cowpea (Vigna unguiculata (L.) Walp cv Caloona) symbiosis formed with a Rhizobium strain (176A27) lacking uptake hydrogenase and maintained under conditions of a 12-hour day at an air temperature of 30 degrees C (800-1000 microeinsteins per square meter per second) and a 12-hour night at an air temperature of 20 degrees C showed a marked diurnal variation in ratio of nitrogen fixed to hydrogen evolved. As little as 0.3 micromole nitrogen was fixed per micromole hydrogen evolved in the photoperiod versus up to 0.6 in the dark period. In plants maintained under the same diurnal illumination regime but at constant (day and night) air temperature (30 degrees C), this difference was abolished and a relatively constant ratio of nitrogen fixed to hydrogen evolved (around 0.3 micromole per micromole) was observed day and night. Exposure of nodulated roots to a range of temperatures maintained for 2 hours in a single photoperiod indicated that, whereas hydrogen evolution increased with increasing temperature from 15 degrees C to a maximum around 35 degrees C, nitrogen fixation was largely unaffected over this temperature range. Both functions of the enzyme declined sharply at temperatures above 38 degrees C. A similar general response of nitrogen fixation to root temperature was observed in glasshouse-grown, sand-cultured plants maintained under a range of temperatures (from 15 to 35 degrees C) for a 14-day period in mid vegetative growth. The effect of temperature on the proportion of electrons allocated to proton reduction compared with nitrogen reduction showed a linearly increasing relationship (correlation coefficient = 0.96) between 15 degrees C and 47 degrees C.

Computer control of an algal bioreactor with simulated diurnal illumination

AbstractDesign details are presented for the construction of a microcomputer based system to measure and control the growth of an algal population in a continuous‐flow bioreactor. Diurnal variation in the light intensity was simulated by computer control of a Venetian blind placed in front of the solar lamps. An indirect method of biomass estimation was based on balancing the amount of nitrogen (NH3) in and out of the system. The computer‐control system held the algal biomass at a constant concentration while fluctuations in CO2 partial pressure, turbulence and light intensity occurred. Under diurnal illumination, CO2 assimilation began without lag when illumination started, although there was a lag before ammonia utilisation began.

Change in the receptive fields of the visual cortex of the cat in relation to the level of wakefulness.

1. Clear and reliable changes in the dimensions, area and form of the RFs in 94% of the neurons investigated were detected within 10–30 minutes after a puff of air. 2. With respect to neurons possessing RFs with an excitatory center (79%), in two-thirds of the cases a contraction of this zone was observed and in 25–30% an expansion. The inhibitory periphery of such RFs in three-quarters of the neurons expanded after a puff of air and more rarely (19%) contracted. The inhibitory centers of the RFs in off-central neurons changed in the same way (21%) 3. The change in the inhibitory zone of the RF after a puff of air is expressed more sharply with regard to its magnitude and duration as well as the probability of its manifestation. 4. The reorganizations of the RFs appears clearly at different levels of adaptation of the visual system, although their expression is diminished to an insignificant extent with diurnal background illumination. 5. The contraction of the excitatory centers of the RFs with transition from calm alertness to a state of strained attention, owing to an expansion of their inhibitory peripheral zone, may apparently provide the animal with a more precise identification of the form of objects 6. The data obtained reinforce our hypothesis concerning the leading role of cortical inhibition in the formation of the RFs of the neurons of the visual cortex and their modification in relation to a change in the state of the organism.

Light and time correlated migration of invasive hemocytes in the crayfish compound eye

AbstractThe number and radial distribution of hemocytes discovered periodically invading the retinas of crayfish compound eyes (Figs. 1–3) were measured under a variety of light and dark adaptation programs (Fig. 4, Table 1). Overall the density of these cells in the eye was significantly less in light than in darkness (Figs. 5–8, Table 2). The corresponding hemocyte ebb and flow occurred in intercellular spaces between retinulas, not in blood vessels which are absent from decapod crustacean eyes everywhere distal to the basement membrane.Hemocytes under all conditions were most dense just below the basement membrane. Within the retina their occurrence ranged from maximum at the basement membrane to minimum or zero near the distal tip of the rhabdom, beyond which they rarely occurred (Figs. 5, 6, Table 3). The effectiveness of light in reducing hemocyte concentrations was maximal distally and minimal proximally and hence had a gradient inverse that for cell density (Fig. 8).Bilateral experiments with one eye covered and the other exposed showed that light could independently and unilaterally induce hemocyte emigration from the retina (Fig. 5). But in time‐of‐day experiments hemocyte movements occurring before the programmed cyclic diurnal illumination changes proved that endogenous control mechanisms must also participate (Fig. 7). Such experiments also showed the fewest retinal hemocytes (≈︁0) at 18:00 hours, when the rate of rhabdom synthesis should be near maximum.So far no direct phagocytic uptake of identifiable photoreceptor membrane has been found in crayfish retinal hemocytes. Nevertheless these cells were seen to make junctionlike contacts with retinular cells and appeared to be actively ingesting interstitial detritus in the retina at levels coincident with the radial extent of the rhabdoms (Figs. 1–3). Previously phagocytic wandering cells were known to participate in photoreceptor membrane turnover in teleost eyes and in reptile pineal organs although fixed retinal pigment epithelial cells are normally involved in this function in birds and mammals.

Distribution of the hordatines in barley

Concentrations of agmatine, coumarylagmatine and the antifungal hordatines in the shoots of barley seedlings have been determined at various stages of growth. Coumarylagmatine declined with age on a fresh weight basis, both in diurnal illumination and in continuous darkness. Hordatines A and B (estimated together) declined in the light to the 30th day after germination but their concentrations were stable in the dark to the 12th day. Hordatine M declined in the light to the 30th day and in the dark to the 12th day from germination. Agmatine declined in both light and dark to the 12th day. On the 30th day from germination potassium deficiency caused an increase in hordatines A + B ( × 6), hordatine M ( × 2) and agmatine ( × 13). Infection of the 11-day-old seedlings with mildew ( Erysiphe graminis) caused an increase in the content of hordatine A + B ( × 6), hordatine M ( × 2) and agmatine ( × 2) 13 days later. Hordatines occurred in seedlings of H. bulbosum, H. distichon, H. murinum and H. spontaneum, though not in seedlings of H. jubatum, maize, millet, oats, rice, rye or wheat. Arginine decarboxylase activity declined with age in barley seedlings grown in the light or dark from the 3rd to the 12th day.

Polyamines in barley seedlings

Abstract Polyamine levels in barley seedlings grown in the dark or in diurnal illumination have been determined, by direct dansylation, 3, 6 and 12 days after g

THE INFLUENCE OF ENVIRONMENTAL LIGHTING ON THE GROWTH AND PROMETAMORPHIC DEVELOPMENT OF LARVAL RANA PIPIENS.

This study was designed to investigate whether the larval development of an anuran amphibian could be modified by raising the animals in continuous light or darkness instead of under conditions of diurnal illumination, and to quantify the effects of these treatments at various intervals during this period of development. Larvae of the frog, Rana pipiens, were raised through metamorphosis under conditions of constant light, constant darkness, or diurnal lighting. As measured by stages of development, body weight, tail length and body length at 20-day intervals, no significant differences in growth rate or metamorphic change were observed until near the middle of the prometamorphic period, which began at approximately the 50th day of development. After midmetamorphosis, a significant acceleration in the measured parameters was seen for the animals raised in conditions of constant light in comparison with those in constant darkness. Those with diurnal lighting were intermediate. These results suggested that light, or its absence, can respectively stimulate or retard amphibian metamorphosis in late larval stages after the hypothalamo-hypophyseal-thyroid axis has matured. Neither continuous light nor continuous darkness during larval development prevented the transformation from tadpole to frog.

THE INTERACTION OF KINETIN, AUXIN AND OTHER FACTORS IN THE DEVELOPMENT OF NORTH TEMPERATE ORCHIDS

SummaryConcentrations (w/v) of 1–10 ppm kinetin, with or without 1 ppm indoleacetic acid, may retard the germination of Dactylorhiza (Orchis) purpurella seed but increase the rate of growth of protocorms to the point where shoot initials form. Subsequently diurnal illumination enhances the development of the shoot initial. Chlorophyll production is independent of growth factors and occurs most rapidly at temperatures below 15°C. Green shoot‐initials undergo further development only after prolonged cold treatment and this stage appear to be independent of growth factors or symbiotic fungi. Similar results were obtained with Coeloglossum viride and Platanthera bifolia.Goodyera repens, an evergreen rhizomatous species, did not respond to mixtures of kinetin and indoleacetic acid, or coconut milk, but grew well on potato or yeast extracts, or after infection with symbiotic fungi.Symbiotic development of north temperate orchids occurs on defined media lacking growth factors and is always more rapid than that in any axenic system so far tested.

MATING IN CHLAMYDOMONAS CHLAMYDOGAMA AT VARIOUS TEMPERATURES UNDER CONTINUOUS ILLUMINATION

Trainor, Francis R. (U. Connecticut, Storrs). Mating in Chlamydomonas chlamydogama at various temperatures under continuous illumination. Amer. Jour. Bot. 47(6) : 482–484. Illus. 1960.—Mating experiments were conducted with C. chlamydogama under continuous illumination of 400 ft.‐c. at temperatures of 22, 26, 30, 34 and 38°C. In 4‐day experiments, low zygospore yields were obtained unless the mixed mating types were stored in darkness at 22°C. after temperature treatment. High zygospore yields, approximately 70%, were obtained at temperatures of 30 and 34°C, if followed by 24 hr. in darkness at 22°C. This yield is the same as that obtained in the controls under 12‐hr. diurnal illumination at room temperature. Temperature increase probably speeds up the mechanism stimulated by nitrogen deficiency and thus evokes gametogenesis.

Mating in Chlamydomonas chlamydogama at Various Temperatures Under Continuous Illumination

Trainor, Francis R. (U. Connecticut, Storrs). Mating in Chlamydomonas chlamydogama at various temperatures under continuous illumination. Amer. Jour. Bot. 47(6) : 482–484. Illus. 1960.—Mating experiments were conducted with C. chlamydogama under continuous illumination of 400 ft.-c. at temperatures of 22, 26, 30, 34 and 38°C. In 4-day experiments, low zygospore yields were obtained unless the mixed mating types were stored in darkness at 22°C. after temperature treatment. High zygospore yields, approximately 70%, were obtained at temperatures of 30 and 34°C, if followed by 24 hr. in darkness at 22°C. This yield is the same as that obtained in the controls under 12-hr. diurnal illumination at room temperature. Temperature increase probably speeds up the mechanism stimulated by nitrogen deficiency and thus evokes gametogenesis.

Zonation in Allomyces arbuscula

SUMMARY1. Zonation in Allomyces arbuscula, represents a periodic massing of hyphae and reproductive structures.2. Under the conditions ordinarily obtaining in the laboratory, there is a diurnal rhythm in zonation, a heavy ring being laid down between 6+ A.M. and 12+ P.M., a diffuse one between 12+ P.M. and 6+ A.M.3. Diurnal illumination shows no apparent causal relationship with ring growth.4. Growth rings are caused by diurnal fluctuations in temperature.5. A fluctuation between ½° and 1½° C. is enough to cause growth ring formation.6. The knowledge that fungus mycelia may be extremely sensitive to temperature changes suggests that temperature may exert a more profound influence on zonation than has been assumed.