KINETICS OF GROWTH AND DEATH IN ANABAENA FLOS-AQUAE (CYANOBACTERIA) UNDER LIGHT LIMITATION AND SUPERSATURATION

The kinetics of population growth and death were investigated in Anabaena flos-aquae (Lyngb.) Bréb grown at light intensities ranging from limitation to photoinhibition (5 W·m⁻² to 160 W·m⁻²) in a nutrient-replete turbidostat. Steady-state growth rate (μ, or dilution rate, D) increased with light intensity from 0.44·day⁻¹ at a light intensity of 5 W·m⁻² to 0.99·day⁻¹ at 20 W·m⁻² and started to decrease above about 22 W·m⁻², reaching 0.56·day⁻¹ at 160 W·m⁻². The Haldane function of enzyme inhibition fit the growth data poorly, largely because of the unusually narrow range of saturation intensity. However, it produced a good fit (P < 0.001) for growth under photoinhibition. Anabaena flos-aquae died at different specific death rates (γ) below and above the saturation intensity. When calculated as the slope of a v_x⁻¹ and D⁻¹ plot, where v_x and D are cell viability (or live cell fraction) and dilution rate, respectively; γ was 0.047·day⁻¹ in the range of light limitation and 0.103·day⁻¹ under photoinhibition. Live vegetative cells and heterocysts, either in numbers or as a percentage of the total cells, showed a peak at the saturation intensity and decreased at lower and higher intensities. The ratio of live heterocysts to live vegetative cells increased with intensity when light was limiting but decreased when light was supersaturating. In cells growing at the same growth rate, the ratio was significantly lower under light inhibition than under subsaturation and the cell N:C ratio was also lower under inhibition. The steady-state rate of dissolved organic carbon (DOC) production increased with light intensity. However, its production as a percentage of the total C fixation was lowest at the optimum intensity and increased as the irradiance decreased or increased. The rate and percentage was significantly higher under photoinhibition than limitation in cells growing at the same growth rate. About 22% of the total fixed carbon was released as DOC at the highest light intensity. No correlation was found between the number of dead cells and DOC.     

CIRCADIAN GROWTH RHYTHM IN JUVENILE SPOROPHYTES OF LAMINARIALES (PHAEOPHYTA)1

A circadian rhythm in growth was detected by computer-aided image analysis in 3–4-cm-long, juvenile sporophytes of the kelp species Pterygophora California Rupr. and in seven Laminaria spp. In P. californica, the free-running rhythm occurred in continuous white fluorescent light, had a period of 26 h at 10°or 15°C, and persisted for at least 2 weeks in white or blue light. The rhythm became insignificant in continuous green or red light after 3 cycles. Synchronization by white light-dark regimes, e.g. by 16 h light per day, resulted in an entrained period of 24 h and in a shift of the circadian growth minimum into the middle of the light phase. A morning growth peak represented the decreasing portion of the circadian growth curve, and an evening peak the increasing portion. The circadian growth peak was not visible during the dark phase, because growth rate decreased immediately after the onset of darkness. At night, some growth still occurred at 16 or 12 h light per day, whereas growth stopped completely at 8 h light per day, as in continuous darkness. During 11 days of darkness, the thallus area became reduced by 3.5%, but growth rate recovered in subsequent light–dark cycles, and the circadian growth rhythm reappeared in subsequent continuous light.     

KINETICS OF CELL DEATH IN THE CYANOBACTERIUM ANABAENA FLOS-AQUAE AND THE PRODUCTION OF DISSOLVED ORGANIC CARBON1

Kinetics of cell death and the production of dissolved organic carbon (DOC) were investigated in Anabaena flos-aquae (Lyngb.) Bréb grown on three different N sources (N₂nitrate, and ammonium) in a phosphorus (P)-limited chemostat. The fraction of live cells in the total population increased as growth rate increased with decreasing P limitation. Cell death was less in nitrate and ammonium media than in N₂. The specific death rate (γ), when calculated as the slope ofv^?1_x vs. D^?1, where v_xand D are live cell fraction (or cell viability) and dilution rate, respectively, was 0. 0082 day^?1 in N₂and 0.0042 day^?1 in nitrate. The slope of the plot in ammonium culture was not significant; however, the value of the live cell fraction was within the range for the NO^?₃culture. The fraction of live vegetative cells in N₂ culture was constant at all growth rates and the increase in the overall live cell fraction with growth rate was due entirely to an increase in live heterocysts. Live heterocysts comprised 3.5% of the total cells at a growth rate of 0.25 day^?1 and increased to 6.3% at 0.75 day^?1 with the ratio of live heterocysts to live vegetative cells linearly increasing with growth rate. The fraction of live vegetative cells was invariant in nitrate cultures us in N₂cultures. The live heterocysts fraction also increased with growth rate in nitrate cultures, along with the live heterocysts : live vegetative cells ratio, but the level was lower than in N₂cultures. DOC released from dead cells increased inversely with growth rate in N₂from 36.4% of the total DOC at a growth rate of 0.75 day^?1 to 54.15% at 0.25 day^?1. The contribution of cell death to the total DOC production in nitrate and ammonium media was significantly less than that under N₂DOC from dead cells consisted mainly of high-molecular-weight compounds, whereas DOC excreted from live cells was largely of low molecular weight.     

EFFECT OF SODIUM AND NITRATE ON GROWTH OF ANABAENA FLOS-AQUAE (CYANOPHYTA)1

The growth response of a nitrogen fixing cyanobacterium, Anabaena flos-aquae (Lyng) Bréb., to sodium and nitrate was examined in batch culture under controlled laboratory conditions. Sodium (range 0-12 mg Na⁺· L^-1) enhanced growth of the cyanobacterium under nitrate-sufficient (5.7 mg NO³-N · L^-1) but not nitrate-limited (0.49 mg NO³- N · L^-1) conditions. The magnitude of the growth response was related to the nutritional history of the culture. No significant effect of sodium on nitrate utilization was observed. The increase in ambient sodium levels in many lakes may provide a competitive advantage to cyanobacteria.     

哺乳动物似昼夜节律研究概要

本文参阅了50年代以来有关昼夜节律研究的重要著作,并根据近年来国内外发表的节律研究论文综合整理写成。     

GROWTH AND NITROGEN FIXATION OF THE DIAZOTROPHIC FILAMENTOUS NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS 101 IN DEFINED MEDIA: EVIDENCE FOR A CIRCADIAN RHYTHM1

Trichodesmium sp. IMS 101, originally isolated from coastal western Atlantic waters by Prufert-Bebout and colleagues and maintained in seawater-based media, was successfully cultivated in two artificial media. Its characteristics of growth, nitrogen fixation, and regulation of nitrogen fixation were compared to those of natural populations and Trichodesmium sp. NIBB 1067. Results indicate that the culture grown in artificial media had nitrogen fixation characteristics similar to those when the culture is grown in seawater-based medium and to those of Trichodesmium sp. in the natural habitat. The study provides practical artificial media to facilitate the physiological studies of these important diazotrophic cyanobacteria, as well as the cultivation of other Trichodesmium species in future studies. Manipulations of the light/dark cycle were performed to determine whether or not the daily cycle of nitrogen fixation is a circadian rhythm. Cultures grown under continuous light maintained the cycle for up to 6 days. We demonstrated that the daily cycle of nitrogen fixation in Trichodesmium sp. IMS 101 was at least partially under the control of a circardian rhythm.     

CIRCADIAN GROWTH IN PORPHYRA UMBILICALIS (RHODOPHYTA): SPECTRAL SENSITIVITY OF THE CIRCADIAN SYSTEM

The circadian rhythm in growth of the red macroalga Porphyra umbilicalis (Linnaeus) J. Agardh was investigated under different spectral light conditions in laboratory-grown thalli. A free-running rhythm was observed in constant green or red light at irradiances of 2.5 to 20 μmol photons·m⁻²·s⁻¹, whereas arhythmicity occurred in constant blue light at 6–20 μmol photons·m⁻²·s⁻¹. The circadian oscillator controlling growth rhythmicity in Porphyra uses most of the visible sunlight spectrum and possibly multiple photoreceptors with a high sensitivity for blue light and a lower sensitivity for red light. This was inferred from three experimental results: (1) The free-running period, τ, of the growth rhythm decreased with increasing irradiance, from approximately 25 h at 2.5 μmol photons·m⁻²·s⁻¹ to 22 h at 20 μmol photons·m⁻²·s⁻¹ in red or green light, (2) Dark pulses of 3 h duration, interrupting otherwise continuous green or red light, caused advances during the subjective day and delays during the subjective night; the circadian oscillator in Porphyra can discriminate darkness from green or red light, and (3) Low-irradiance blue light pulses (2.5 μmol photons·m⁻²·s⁻¹) shifted the growth rhythm in red light of higher irradiance (e.g. 10 μmol photons·m⁻²·s⁻¹), and a strong, high amplitude, type 0 phase response curve was obtained that is usually observed with light pulses shifting a circadian rhythm in otherwise continuous darkness.     

GROWTH RESPONSE OF A NITROGEN FIXER (ANABAENA FLOS-AQUAE,CYANOPHYCEAE) TO LOW NITRATE1

Anabaena flos-aquae (Lyngb.) Bréb. was grown in varying concentrations of nitrate. Specific growth rates, as estimated in batch culture, were constant and approached the maximum rate at all concentrations of NO₃^?-N tested bewteen 0 and 400 μ/L. Steady-state biomass, as determined in semicontinuous culture, did not vary with NO₃^? at slower dilution rates. However at a faster dilution rate, significantly less biomass occurred in intermediate concentrations of NO₃^? than in either higher or lower concentrations. The results indicate that both growth rate and standing crop are maximized by either N₂ fixation or NO₃^? assimilation, but extracellular NO₃^? reduces the rate of N₂ fixation. Consequently, at very low NO₃^? concentrations, growth is virtually maximized by N₂ fixation alone, and at high concentrations of NO₃^?, N₂ fixation is inhibited but growth is maximized by assimilation of NO₃^?. At intermediate concentrations of NO₃^?, growth becomes a function of NO^3? assimilation augmented by N₂ fixation. In this case, full growth potential is realized only if hydraulic residence time is sufficiently long to compensate for the reduced rate of N₂ fixation. Growth rate and standing crop are not diminished in response to the large amount of energy allocated to N₂ fixation. Instead, other cellular processes are probably affected negatively during N₂ fixation.     

CIRCADIAN RHYTHM OF PHOTOSYNTHETIC OXYGEN EVOLUTION IN KAPPAPHYCUS ALVAREZII (RHODOPHYTA): DEPENDENCE ON LIGHT QUANTITY AND QUALITY

The rate of oxygen evolution of the tropical red alga Kappaphycus alvarezii (Doty) Doty was measured for 6 days in the laboratory using a computer-aided method for long-term recording. In cool white light, Kappaphycus exhibited a robust circadian rhythm of O₂ evolution in the irradiance range of 100 to 1000 μmol photons·m ^{− 2}·s ^{− 1}. With increasing irradiance, the period of the free-running rhythm, τ, decreased in blue and increased in red light but did not change significantly in green light. The accelerating or slowing action of blue or red light, respectively, points to two photoreceptors used in the light transduction pathway of the circadian oscillator controlling oxygen evolution or the light reactions of photosynthesis in Kappaphycus. No significant changes of τ were observed with increasing irradiance in cool white light, possibly due to the additive opposing responses caused by blue and red light.     

STORAGE OF PHOSPHORUS IN NITROGEN-FIXING ANABAENA FLOS-AQUAE (CYANOPHYCEAE)1

P accumulation and metabolic pathway in N₂-fixing Anabaena flos-aquae (Lyngb.) Bréb were investigated in P-sufficient (20 μMP) and P-limited (2 μMP) turbidostats in combined N-free medium. The cyanobacterium grew at its maximum rate (μ_max, 1.13 d^?1) at the high P concentration and at 65% of μ_max under P limitation, with total cell P concentrations (Q_P) at steady states of 12.0 and 5.2 fmol·cell^?1, respectively. At steady state, polyphosphates (PP_i) accounted for only 3% of Q_P (0.4 fmol·cell^?1) in P-rich cells. Its concentration in P-limited cells was 5.8% (0.3 fmol·cell^?1). On the other hand, sugar P was very high at 22% of Q_P in P-rich cells and was undetectable in P-limited cells. Pulse chase experiments with ³²P showed that P-rich cells initially incorporated the labeled P into the acid-soluble PP_i fraction within the first few minutes and to a lesser extent into nucleotide P. Radioactivity in the PP_i then declined rapidly with concomitant increases in sugar P and nucleotide P fractions. In contrast, in P-limited cells, no radiolabel was detected in acid-soluble PP_i, and ³²P was initially incorporated into nucleotide P, sugar P, and ortho P fractions. The latter two fractions then subsequently declined. Therefore, under N₂-fixing conditions the cyanobacteria appeared to store P as sugar P and also utilize P through different pathways under P-rich and -limited conditions. When nitrate was supplied as the N source under P-sufficient conditions, PP_i accounted for about 15% of steady-state Q_P, but no sugar P was detected. Therefore, the same organism stored P in different cell P fractions depending on its N sources.     

大鼠肝糖皮质激素受体的昼夜节律

雄性成年大鼠102只,分自然光组、人工光组和明暗颠倒组,于不同时间处死,测定肝胞坡和胞核的糖皮质激素受体(GCR_c和GCR_o)。发现GCR_c和GCR_o都以23:00和O2:00为最高,中午最低。明暗颠倒组的GCR_c以23:00为最高,02:00—11:00都在低水平。同时还测定了肝的酪氨酸转氨酶活性和血浆皮质酮,讨论了三者昼夜节律的相互关系。     

CIRCADIAN RHYTHM OF DOUBLE (RATE-PRESSURE) PRODUCT IN HEALTHY NORMOTENSIVE YOUNG SUBJECTS

The double product (DP), systolic blood pressure multiplied by heart rate, is a surrogate measure of myocardial oxygen demand and cardiac workload used increasingly today in medicine. The double product is more strongly correlated with left ventricular mass than the daily blood pressure mean. The purpose of this study was to describe the normative circadian pattern of the double product in healthy normotensive young adults. We studied 125 men and 75 women, 23.0 ± 3.3 (mean ± SD) years of age, without medical history of hypertension and 24h ambulatory systolic/diastolic blood pressure mean consistently below 135/85 mm Hg. Subjects underwent ambulatory blood pressure monitoring at 30-minute intervals for 48 consecutive hours once each season of the year, yielding 930 protocol-correct blood pressure and heart rate time series. Subjects maintained their usual routine of diurnal activity and nocturnal sleep and avoided use of over-the-counter and other medication. Circadian rhythmicity in the double product was established by population multiple-component analysis. The double product rose rapidly from the lowest value, attained 3h before awaking from sleep at night, to a markedly elevated level at the commencement of morning activity. The double product was highest in the afternoon, roughly 7h after the commencement of diurnal activity. In both men and women, the shape of the highamplitude circadian rhythm in the double product was best described by a complex model composed of three cosine curves having periods of 24h, 12h, and 6h. The 24h mean in the double product of 8092.51 ±42.76 (mean ±SD) in men was significantly lower than that of 8353.17 ±37.48 in women (P <.001). The circadian double amplitude of the rhythm was statistically significantly greater (P <.001) in men (50% of the 24h mean) than women (44% of the 24h mean). The double product did not differ between seasons in women, but it did in men (P =.017) due to reduced heart rate in summer. The circadian pattern of large amplitude in the double product and its gender differences must be taken into account when using this variable to assess cardiac workload, risk of left ventricular hypertrophy, and efficiency of antihypertensive therapy. (Chronobiology International, 18(3), 475–489, 2001)     

NOTE ESTABLISHMENT OF AXENIC CULTURES OF ANABAENA FLOS-AQUAE AND APHANOTHECE NIDULANS (CYANOBACTERIA) BY LYSOZYME TREATMENT

A new method using lysozyme for the production of axenic cultures of Anabaena flos-aquae De Brebisson and Aphanothece nidulans P. Richter was developed. Cyanobacterial growth was not inhibited at concentrations up to 1.2 g·L⁻¹ of lysozyme, whereas the growth of heterotrophic bacteria was suppressed. At concentrations up to 0.8 g·L⁻¹ of lysozyme, ampicillin caused a reduction of heterotrophic bacteria. The axenic cultures of these strains were acquired through a simple treatment using 1.0 g·L⁻¹ of lysozyme without ampicillin. These cyanobacteria resisted digestion by lysozyme at our experimental concentrations, whereas bacteria were digested selectively. This method of purification seems to be especially useful with cyanobacterial species that are sensitive to antibiotics or other germicidal agents.     

大袋蛾性信息素分泌的时辰节律和内分泌控制

本文报道用定量生测方法发现在成虫期短、无多次生殖循环、成虫不取食的鳞翅目昆虫中存在内分泌对性信息素的控制.大袋蛾Clania variegata雌虫的信息素腺体含量表现每日双峰的时辰节律.将雌虫饲养于两种光暗条件下,不同雌虫的峰期被错开,将恰在峰期前的雌虫中抽取的血淋巴注射于处于低含量期的雌虫中能诱导被注射的雌虫显著增加信息素的分泌.除头、摘除咽侧体或切断心侧体与咽侧体之间的神经均有效地消除信息素的分泌,但对摘除咽侧体的雌虫重植咽侧体却未能恢复其信息素的分泌.然而对低含量期的雌虫注射保幼激素类似物738,能诱导其显著增加信息索的分泌,而江射却未能恢复交配后雌虫的信息素分泌能力.根据本文结果讨论了Barth(1965)的假说.     

THE CIRCADIAN RHYTHM OF BIOLUMINESCENCE IN PYROCYSTIS IS NOT DUE TO DIFFERENCES IN THE AMOUNT OF LUCIFERASE: A COMPARATIVE STUDY OF THREE BIOLUMINESCENT MARINE DINOFLAGELLATES

The biochemistry and circadian regulation of luminescence in two Pyrocystis species, P. lunula Hulburt and P. noctiluca Murray et Haeckel, were compared with a well-studied species, Gonyaulax polyedra Stein. All exhibit circadian rhythms and all have similar luciferins and luciferases. However, the Pyrocystis species lack a second protein involved in the reaction in Gonyaulax , the luciferin (substrate) binding protein, which sequesters the luciferin at the cytoplasmic pH and releases it upon acidification, thus controlling the characteristic flashing, which is similar in the three species. More striking is the difference in the circadian regulation of luminescence, which in Gonyaulax involves the daily synthesis and destruction of the two proteins, along with the luminous organelles (scintillons) from which light is emitted, and which are present in all species. In the Pyrocystis species, the amount of luciferase is the same in extracts made during the day and night phases; its circadian regulation in vivo may be attributed to a change in its localization from day to night phase.     

MEASUREMENT OF IN SITU SPECIFIC GROWTH RATES OF MICROCYSTIS (CYANOBACTERIA) FROM THE FREQUENCY OF DIVIDING CELLS1

Diel changes in the frequency of dividing cells (FDC) of three Microcystis species were investigated in a small eutrophic pond from July to October 2005. The representative species was M. aeruginosa (Kütz.) Kütz., constituting 57%–86% of the Microcystis population throughout the study period, and the remainder were M. viridis (A. Braun) Lemmerm. and M. wesenbergii (Komárek) Komárek. The FDC of M. aeruginosa and M. wesenbergii increased in the daytime and fell in the nighttime in July and August, but this regular variation was not observed in September or October. The in situ specific growth rates of Microcystis species were estimated based on the assumption that the specific growth rate can be given as an absolute value of the derivative of FDC with respect to time. The calculated values were similar among species—0.15–0.38 · d^?1 for M. aeruginosa, 0.14–0.63 · d^?1 for M. viridis, and 0.18–0.61 · d^?1 for M. wesenbergii. The specific growth rates in July and August slightly exceeded those in September and October. The analysis of the in situ specific growth rate of Microcystis indicated that recruitment of the benthic population or morphological change, rather than massive growth, was at least partly responsible for the dominance of M. aeruginosa in the study pond.     

RELATIONSHIP BETWEEN THE NUMBER OF DIVIDING AND NONDIVIDING CELLS OF CYANOBACTERIA IN NORTH ATLANTIC PICOPLANKTON1

In the North Atlantic over a wide geographic region that includes various oceanic regimes and a temperature range from 10 to 22° C, an increase in the number of nondividing Synechococcus cells (X) was generally accompanied by a greater-than-proportional increase in the number of dividing cells (Y). As a result, the fraction of dividing cells (FDC = Y · (Y + X)^?1) was positively related to population size (Y + X). Recognizing that FDC is generally greater in a rapidly growing population than in a slowly growing one, our empirical finding implies a positive correlation between specific growth rate and standing stock for Synechococcus. One notable exception occurred during winter (T < 5°C) in a eutrophic coastal embayment when a decrease in cell abundance was not matched by a decrease in FDC.     

树■排尿的昼夜节律及其在视交叉上核损毁后的变化

为探讨树视交叉上核是否参与泌尿昼夜节律的调控,对正常树及视交叉上核损毁后的树排尿的昼夜时间规律进行了观测分析。结果表明,正常树排尿呈现明显的昼夜节律———白天尿量为全天尿量的（８８５２±１５４０）％;视交叉上核损毁后,树排尿的昼夜节律明显改变———白天尿量仅为全天尿量的（６２８６±１８１８）％,同时树的尿量（特别是夜间的尿量）明显憎多。以上结果说明视交叉上核在树体内也参与了泌尿昼夜节律的调节。     

高原鼠兔松果腺褪黑激素含量昼夜节律的研究

自然光照条件下,高原鼠兔（Ｏｃｈｏｔｏｎａｃｕｒｚｏｎｉａｅ）松果腺褪黑激素（Ｍｅｌａｔｏｎｉｎ,ＭＬＴ）含量呈现明显的昼夜节律（Ｐ＜０．００１,夜间组含量均值与白天组含量均值差异显著性比较）。在２月份的实验中,对１８只鼠兔（体重１２２—１６４克）松果腺的采样时间分别为０２．００,０９．００,１２．００,１８．００,２２．００和２４．００时。白天ＭＬＴ含量波动为５６—６４微微克／松果腺,夜间波动为１１３—１７０微微克／松果腺。夜间ＭＬＴ含量高峰值出现在２４．００时。在１０月份的实验中,对６０只鼠兔（体重１０２—１５３克）松果腺的采样时间分别为０３．００,０６．００,０９．００,１２．００,１５．００,１８．００,２１．００和２４．００时。白天ＭＬＴ含量波动为７７—１１９微微克／松果腺,夜间波动为１３９—５０５微微克／松果腺。夜间ＭＬＴ含量高峰值出现在０３．００时。将２月份和１０月份高原鼠兔松果腺ＭＬＴ含量进行差异显著性比较,１０月组显著高于２月组（Ｐ＜０．０５）。结果表明,该动物的松果腺本身对光周期具有敏感性,它能够感知环境光周期的变化,成功地完成神经内分泌的转换。