Studies on the Effects of Bromodeoxyuridine (BUdR) on Differentiation

The effects of BUdR on morphogenesis in Acetabularia mediterranea and on embryonic development (sea urchin, tunicate and amphibian embryos) have been studied.
In the presence of BUdR, cap development is affected in both the anucleate and nucleate fragment of the unicellular alga Acetabularia mediterranea . In the nucleate fragment, the initiation of cap formation can be inhibited. BUdR exerts various inhibitory effects on embryonic development. Modifications of sensitivity to BUdR during development are also observed: in Paracentrotus , a change in sensitivity towards the drug occurs at the 16 cell stage, while in amphibian eggs, a modification can be shown after the gastrula stage.
The significance of these observations is discussed.     

The Pattern of Protein Synthesis in Acetabularia mediterranea

In cells of Acerabularia mediterranea Lamouroux the zone ofgrowth and differentiation is restricted to the approximately2 mm-long outermost apical region of the cylindrical stalk.Protein synthesis along the cell forms a pattern with two statesof intensity corresponding to the growing and the non-growingzone. An identical two-step pattern is obtained when cytoplasmicprotein synthesis is inhibited with D-MDMP, which suggests thatorganellar synthesis on 70S ribosomes contributes to the unevenintensity. The gradient is eliminated by amputation of the apicalall part, and it is re-established concomitant with the emergenceof a new growth zone. Protein synthesis on 80S ribosomes isa pre-requisite for the re-establishment. A two-step patternexists also in anucleate cells persisting for at least 2 weekspost-enucleation. Acetabularia, gradient, morphogenesis, polarity, protein synthesis     

Effectiveness of a red-visor cap for preventing light-induced melatonin suppression during simulated night work

Bright light at night improves the alertness of night workers. Melatonin suppression induced by light at night is, however, reported to be a possible risk factor for breast cancer. Short-wavelength light has a strong impact on melatonin suppression. A red-visor cap can cut the short-wavelength light from the upper visual field selectively with no adverse effects on visibility. The purpose of this study was to investigate the effects of a red-visor cap on light-induced melatonin suppression, performance, and sleepiness at night. Eleven healthy young male adults (mean age: 21.2±0.9 yr) volunteered to participate in this study. On the first day, the subjects spent time in dim light (<15 lx) from 20:00 to 03:00 to measure baseline data of nocturnal salivary melatonin concentration. On the second day, the subjects were exposed to light for four hours from 23:00 to 03:00 with a nonvisor cap (500 lx), red-visor cap (approx. 160 lx) and blue-visor cap (approx. 160 lx). Subjective sleepiness and performance of a psychomotor vigilance task (PVT) were also measured on the second day. Compared to salivary melatonin concentration under dim light, the decrease in melatonin concentration was significant in a nonvisor cap condition but was not significant in a red-visor cap condition. The percentages of melatonin suppression in the nonvisor cap and red-visor cap conditions at 4 hours after exposure to light were 52.6±22.4% and 7.7±3.3%, respectively. The red-visor cap had no adverse effect on performance of the PVT, brightness and visual comfort, though it tended to increase subjective sleepiness. These results suggest that a red-visor cap is effective in preventing melatonin suppression with no adverse effects on vigilance performance, brightness and visibility.     

Photopreferendum of migratory and nonmigratory larvae of European river lamprey <Emphasis Type="Italic">Lampetra fluviatilis</Emphasis>

In the light gradient installation, the larvae of European river lamprey Lampetra fluviatilis of 0+ age, migrating downstream (downstream migrants), are distributed predominantly over the zone of dusk illumination (150–1 lx) and less so over the daylight zone (2500–150 lx) and night illumination zone (<1 lx). In 0+ larvae that passed over to the sedentary lifestyle, the photopreferendum changes: they avoid the dusk and daytime illumination and prefer nighttime illumination. Such photopreferendum is retained in later larvae of lamprey (1+ and older).     

Visualization of intracellular ice formation using high-speed video cryomicroscopy

A high-speed video cryomicroscopy system was developed, and used to observe the process of intracellular ice formation (IIF) during rapid freezing (130 °C/min) of bovine pulmonary artery endothelial cells adherent to glass substrates, or in suspension. Adherent cells were micropatterned, constraining cell attachment to reproducible circular or rectangular domains. Employing frame rates of 8000 frames/s and 16,000 frames/s to record IIF in micropatterned and suspended cells, respectively, intracellular crystal growth manifested as a single advancing front that initiated from a point source within the cell, and traveled at velocities of 0.0006-0.023 m/s. Whereas this primary crystallization process resulted in minimal change in cell opacity, the well-known flashing phenomenon (i.e., cell darkening) was shown to be a secondary event that does not occur until after the ice front has traversed the cell. In cells that were attached and spread on a substrate, IIF initiation sites were preferentially localized to the peripheral zone of the adherent cells. This non-uniformity in the spatial distribution of crystal centers contradicts predictions based on common theories of IIF, and provides evidence for a novel mechanism of IIF in adherent cells. A second IIF mechanism was evident in ∼20% of attached cells. In these cases, IIF was preceded by paracellular ice penetration; the initiation site of the subsequent IIF event was correlated with the location of the paracellular ice dendrite, indicating an association (and possibly a causal relationship) between the two. Together, the peripheral-zone and dendrite-associated initiation mechanisms accounted for 97% of IIF events in micropatterned cells.     

Lack of in vivo transcription of Acetabularia mediterranea 1175 bp ctDNA fragment homologous to the Drosophila per locus.

The period (per) locus of Drosophila melanogaster has a fundamental role in the expression of biological rhythms. A DNA sequence homologous to a short region of the Drosophila per locus was detected in the chloroplast of Acetabularia mediterranea. A 1175 bp DNA fragment containing the sequence was used as a probe in 'Northern' hybridization experiments. It was found that this DNA was not transcribed or only marginally transcribed in A. mediterranea, at least at the developmental stage just prior to cap formation. It seems that the 1175 bp ctDNA fragment is not involved in the Acetabularia biological rhythm mechanism.     

Spatial separation of light perception and growth response in maize root phototropism

Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.     

稀有鮈鲫对不同生境的选择性偏好

对不同生境的识别和选择性偏好是保障鱼类生存和繁衍的重要能力之一。以稀有鮈鲫（Gobiocypris rarus）为研究对象,使用沙、水草和石块在观测水缸中进行多种排列组合以构建不同的生境类型,基于在各区域的停留时长和中线跨越次数两项参数,测试稀有鮈鲫对不同生境类型的偏好以及营养状态、生境组成物数量、环境照度对该行为影响。结果表明,稀有鮈鲫对不同的生境类型具有明显的选择性偏好,对仅水草生境偏好程度最高,对仅石块生境的偏好程度最低。该偏好行为在24 h的禁食后变化不显著（P > 0.05）,但生境组成物数量和环境照度对该行为具有显著影响（P < 0.05）,其偏好程度随水草数量和照度的增加而增加,在包含8棵水草及1 000 lx的照度下最高。     

Electrochemical Regulation of Budding Yeast Polarity

Cells are naturally surrounded by organized electrical signals in the form of local ion fluxes, membrane potential, and electric fields (EFs) at their surface. Although the contribution of electrochemical elements to cell polarity and migration is beginning to be appreciated, underlying mechanisms are not known. Here we show that an exogenous EF can orient cell polarization in budding yeast (Saccharomyces cerevisiae) cells, directing the growth of mating projections towards sites of hyperpolarized membrane potential, while directing bud emergence in the opposite direction, towards sites of depolarized potential. Using an optogenetic approach, we demonstrate that a local change in membrane potential triggered by light is sufficient to direct cell polarization. Screens for mutants with altered EF responses identify genes involved in transducing electrochemical signals to the polarity machinery. Membrane potential, which is regulated by the potassium transporter Trk1p, is required for polarity orientation during mating and EF response. Membrane potential may regulate membrane charges through negatively charged phosphatidylserines (PSs), which act to position the Cdc42p-based polarity machinery. These studies thus define an electrochemical pathway that directs the orientation of cell polarization.     

金线莲组织培养中若干因素的研究

研究了影响金钱莲组培芽的增殖和营养器官分化的几个因素。结果表明:植物细胞分裂素及生长素的种类、浓度和配比对瓶苗茎发育有很大影响,在增殖期使用浓度为1.0mg/L BA、0.5mg/L IBA,器官分化生长期使用浓度为增殖期激素量的三分之一;瓶移植量10～15株;光照量显著影响植株生长期叶片生长,500lx较合适;活性炭明显提高诱导根的生长质量,添加浓度0.5％效果最好。     

Innate immunity,oxidative stress and body indices of Eurasian perch Perca fluviatilis after two weeks of exposure to artificial light at night

Artificial light at night (ALAN) can disrupt biological rhythms of fish and other vertebrates by changing the light information of the nocturnal environment. Disrupted biorhythms can impair the immune system of vertebrates as it has been shown for conditions with continuous illumination or long-day photoperiod in many vertebrates, including fish. Nonetheless, this has not been shown so far for typical ALAN scenarios with high light intensities during day and low light intensities at night. Therefore, in this study, proxies for the innate immune system and oxidative stress as well as body indices of Eurasian perch Perca fluviatilis were measured under a wide range of intensities of nocturnal illumination. The authors found no changes in parameters of the innate immune system and no significant changes in proxies for oxidative stress after 2-week exposures to nocturnal illuminance ranging from 0.01 lx to 1 lx in one experiment or from 1 lx to 100 lx in a second experiment. A decrease in the hepato-somatic index at the highest tested light intensity of 100 lx compared to the dark control was the only significant difference in all parameters among treatments. After 2 weeks of exposure, ALAN does not seem to seriously challenge the innate immune system and seems to cause less oxidative stress than expected. The results of this study contradict the findings from other studies applying continuous illumination or long-day photoperiod and highlight the importance of further research in this field. Because ALAN represents a sustained modulation of the environment that may have cumulative effects over time, long-term studies are required for a better understanding of how ALAN modulates the health of fish.     

Polar distribution of RNA in the cytoplasm of Acetabularia mediterranea]

The distribution of total RNA and its individual fractions in two regions of Acetabularia mediterranea stem during regeneration was investigated. During regeneration of both the nuclear and enucleated cells, RNA concentration increases in the cytoplasm of growth zone whereas it changes insignificantly in the central stem region. A study of the qualitative RNA composition in the same stem regions has shown that during regeneration high molecular weight RNA fractions (main peaks - 0,56-10(6) and 1.04-10(6) Dalton) are found in the growth zone and are practically absent from the central cell region. Low molecular weight RNA (supposedly, tRNA and products of RNA destruction) are present in both the cell regions under study.     

Effect of illumination intensity and inhibition of carotenoid biosynthesis on assembly of peripheral light-harvesting complexes in purple sulfur bacteria <Emphasis Type="Italic">Allochromatium vinosum</Emphasis> ATCC 17899

Effect of illumination intensity and inhibition of carotenoid biosynthesis on assemblage of different spectral types of LH2 complexes in a purple sulfur bacterium Allochromatium (Alc.) vinosum ATCC 17899 was studied. Under illumination of 1200 and 500 lx, the complexes B800-850 and B800-840 and B800-820 were assembled. While rhodopine was the major carotenoid in all spectral types of the LH2 complex, a certain increase in the content of carotenoids with higher numbers of conjugated double bonds (anhydrorhodovibrin and didehydrorhodopin) was observed in the B800-820 complex. At 1200 lx, the cells grew slowly at diphenylamine (DPA) concentrations not exceeding 53 μM, while at illumination intensity decreased to 500 lx they could grow at 71 μM DPA (DPA cells). Independent on illumination level, the inhibitor is supposed to impair the functioning of phytoene synthetase (resulting in a decrease in the total carotenoid content) and of phytoene desaturase, which results in formation of neurosporene hydroxy derivatives and ζ-carotene. In the cells grown at 500 lx, small amounts of spheroidene and OH-spheroidene were detected. These carotenoids were originally found under conditions of carotenoid synthesis inhibition in bacteria with spirilloxanthin as the major carotenoid. Carotenoid content in the LH2 complexes isolated from the DPA cells was ~15% of the control (without inhibition) for the B800-850 and ~20% of the control for the B800-820 and B800-840 DPA complexes. Compared to the DPA pigment-containing membranes, the DPA complexes were enriched with carotenoids due to disintegration of some carotenoidless complexes in the course of isolation. These results support the supposition that some of the B800-820, B800-840, and B800-850 complexes may be assembled in the cells of Alc. vinosum ATCC 17899 without carotenoids. Comparison of the characteristics obtained for Alc. vinosum ATCC 17899 and the literature data on strain D of the same bacteria shows that they belong to two different strains, rather than to one as was previously supposed.     

Complex physiological and molecular processes underlying root gravitropism

Gravitropism allows plant organs to guide their growth in relation to the gravity vector. For most roots, this response to gravity allows downward growth into soil where water and nutrients are available for plant growth and development. The primary site for gravity sensing in roots includes the root cap and appears to involve the sedimentation of amyloplasts within the columella cells. This process triggers a signal transduction pathway that promotes both an acidification of the wall around the columella cells, an alkalinization of the columella cytoplasm, and the development of a lateral polarity across the root cap that allows for the establishment of a lateral auxin gradient. This gradient is then transmitted to the elongation zones where it triggers a differential cellular elongation on opposite flanks of the central elongation zone, responsible for part of the gravitropic curvature. Recent findings also suggest the involvement of a secondary site/mechanism of gravity sensing for gravitropism in roots, and the possibility that the early phases of graviresponse, which involve differential elongation on opposite flanks of the distal elongation zone, might be independent of this auxin gradient. This review discusses our current understanding of the molecular and physiological mechanisms underlying these various phases of the gravitropic response in roots.     

Temporal characteristics of downstream migration of smolts of the European river lamprey <Emphasis Type="Italic">Lampetra fluviatilis</Emphasis> in the Chernaya River

Data on the seasonal and diurnal dynamics of downstream migration of smolts of the European river lamprey Lampetra fluviatilis are obtained. On the basis of published data and surveys in nature, it is shown that in the largest part of the area the downstream migration of smolts occurs mainly in spring, in the period of high water in rivers caused by snow melting. The smolts undertake downstream migration at night, under minimal illumination. It has been determined experimentally that the smolts are characterized by negative photopreferendum (>90% of smolts preferred illumination <0.4 lx).     

Chlorophyll production from Spirulina platensis: cultivation with urea addition by fed-batch process

The cyanobacterium Spirulina platensis is an attractive alternative source of the pigment chlorophyll, which is used as a natural color in food, cosmetic, and pharmaceutical products. In this work, the influence of the light intensity and urea supplementation as a nitrogen source using fed-batch cultivation for S. platensis growth and chlorophyll content was examined. Cultivations were carried out in 5 l open tanks, at 30+/-1 degrees C. Response surface methodology was utilized for analysis of the results, and models were obtained for biomass productivity, nitrogen-cell conversion factor and chlorophyll productivity. The best cellular growth was observed with 500 mg/l of urea at a light intensity of 5600 lx, whereas the highest concentration of chlorophyll in the biomass was observed with 500 mg/l of urea at a light intensity of 1400 lx. Overall, the best chlorophyll productivity was observed with 500 mg/l of urea at a light intensity of 3500 lx, providing the optimal balance between the cellular growth and the biomass chlorophyll content.     

The source and lateral transport of growth inhibitors in geotropically stimulated roots of Zea mays and Pisum sativum

Summary The positive geotropic responses of the primary roots of Zea mays and Pisum sativum seedlings depend upon at least one growth inhibiting factor which arises in the root cap and which moves basipetally through the apex into the extending zone. The root apex (as distinct from the cap) and the regions more basal to the extending zone are not sources of growth regulators directly involved in the geotropic response. A difference in the concentration or effectiveness of the inhibitory factor(s) arising in the cap must be established between the upper and lower halves of a horizontal root. Positive geotropic curvature in a horizontal root is attributable, at least in part, to a downward lateral transport of inhibitor(s) from the upper to the lower half of the organ.     

Phototropism in Vaucheria geminata II. The mechanism of bending and branching

The mechanism of phototropic bending and branching in Vaucheriageminata was analyzed. Using the half-side-illumination methodit was shown that phototropic bending is initiated by the formationof a new growth center on the illuminated side of the apicaldome of the tube, not by the difference in growth rate betweenthe lighted and shaded sides of the tip. Branching was alsoinitiated when the part proximal to the apical dome was illuminated.Blue light was effective for branching as it was for phototropicbending. The refractive indices measured at the growing tipand an area other than the tip were 1.36 and 1.34 respectively.A hyaline patch resembling the hyaline cap, which appeared priorto the onset of tip-growth in the apical dome, was invariablyformed shortly before the initiation of a new branch at theilluminated locus. (Received December 20, 1974; )     

Light effects in yeast: inhibition by visible light of growth and transport in Saccharomyces cerevisiae grown at low temperatures.

Growth rate, sugar transport, and amino acid transport of yeast cells grown at 12 degrees C were inhibited by cool-white fluorescent light. At light intensities below 1,250 lx, growth and membrane transport were only slightly inhibited. Above 1,250 lx, there was increasing inhibition of both processes. Transport of histidine was completely inhibited after 3 to 5 days in cultures grown at 12 degrees C under 3,500-lx illumination. Cells grown at 20 degrees C were not inhibited by light intensities that caused complete loss of viability and membrane transport activity in cells grown at 12 degrees C.     

Nitrogenase and photosynthetic activities of chemostat cultures of Rhodobacter capsulatus 37b4 grown under different illuminations

Nitrogen fixation as well as structural and functional properties of the photosynthetic apparatus were studied with phototrophically grown chemostat cultures of Rhodobacter capsulatus strain 37b4. Illumination was varied between 3,000 and 30,000 lx at a constant dilution rate of D=0.075 h^-1. Steady state parameters of growth revealed two forms of limitation, i.e. energy limitation in the range of 3,000 to about 10,000 lx and nitrogen limitation at higher illuminations. Over the entire range of illumination, the specific bacteriochlorophyll content and the amount of total bacteriochlorophyll per photochemical reaction center remained essentially constant. Photophosphorylation activity remained constant up to 20,000 lx but was slightly increased at 30,000 lx. Hydrogen evolution and acetylene reduction activities of cellular nitrogenase were assayed under saturating light conditions with samples taken from cultures growing under steady state conditions. In spite of the apparent constancy of the composition and activity of the photosynthetic apparatus under energy limitation, maximal specific acetylene reduction and hydrogen evolution activities increased by factors of 3 and 8, respectively, when illumination of the culture was raised from 3,000 to about 15,000 lx. Above 15,000 lx, both activities of nitrogenase approached constancy.We, therefore, conclude that neither under energy limitation nor under nitrogen limitation the function of nitrogenase depended on the photosynthetic activities. Moreover, it is suggested that light did not influence nitrogenase activity under conditions of nitrogen limitation, while under conditions of energy limitation light seemed to influence nitrogenase activities indirectly via glutamate consumption of the cells.