Elemental Composition (C, N, P) and Cell Volume of Exponentially Growing and Nutrient-Limited Bacterioplankton

Marine bacterioplankton were isolated and grown in batch cultures until their growth became limited by organic carbon (C), nitrogen (N), or phosphorus (P). Samples were taken from the cultures at both the exponential and stationary phases. The elemental composition of individual bacterial cells was analyzed by X-ray microanalysis with an electron microscope. The cell size was also measured. The elemental content was highest in exponentially growing cells (149 ± 8 fg of C cell⁻¹, 35 ± 2 fg of N cell⁻¹, and 12 ± 1 fg of P cell⁻¹; average of all isolates ± standard error). The lowest C content was found in C-limited cells (39 ± 3 fg of C cell⁻¹), the lowest N content in C- and P-limited cells (12 ± 1 and 12 ± 2 fg of N cell⁻¹, respectively), and the lowest P content in P-limited cells (2.3 ± 0.6 fg of P cell⁻¹). The atomic C:N ratios varied among treatments between 3.8 ± 0.1 and 9.5 ± 1.0 (average ± standard error), the C:P ratios between 35 ± 2 and 178 ± 28, and the N:P ratios between 6.7 ± 0.3 and 18 ± 3. The carbon-volume ratios showed large variation among isolates due to different types of nutrient limitation (from 51± 4 to 241 ± 38 fg of C μm⁻¹; average of individual isolates and treatments ± standard error). The results show that different growth conditions and differences in the bacterial community may explain some of the variability of previously reported elemental and carbon-volume ratios.     

Genome size and ploidy of Paracoccidioides brasiliensis reveals a haploid DNA content: flow cytometry and GP43 sequence analysis

The aim of this study was to evaluate genome size and ploidy of the dimorphic pathogenic fungus Paracoccidioides brasiliensis. The cell cycle analysis of 10 P. brasiliensis isolates by flow cytometry (FCM) revealed a genome size ranging from 26.3+/-0.1Mb (26.9+/-0.1fg) to 35.5+/-0.2Mb (36.3+/-0.2fg) per uninucleated yeast cell. The DNA content of conidia from P. brasiliensis ATCC 60855-30.2+/-0.8Mb (30.9+/-0.8fg) -showed no significant differences with the yeast form, possibly excluding the occurrence of ploidy shift during morphogenesis. The ploidy of several P. brasiliensis isolates was assessed by comparing genome sizing by FCM with the previously described average haploid size obtained from electrophoretic karyotyping. The analysis of intra-individual variability of a highly polymorphic P. brasiliensis gene, GP43, indicated that only one allele seems to be present. Overall, the results showed that all analysed isolates presented a haploid, or at least aneuploid, DNA content and no association was detected between genome size/ploidy and the clinical-epidemiological features of the studied isolates. This work provides new knowledge on P. brasiliensis genetics/genomics, important for future research in basic cellular/molecular mechanisms and for the development/design of molecular techniques in this fungus.     

Taxonomic and Environmental Variability in the Elemental Composition and Stoichiometry of Individual Dinoflagellate and Diatom Cells from the NW Mediterranean Sea

Here we present, for the first time, the elemental concentration, including C, N and O, of single phytoplankton cells collected from the sea. Plankton elemental concentration and stoichiometry are key variables in phytoplankton ecophysiology and ocean biogeochemistry, and are used to link cells and ecosystems. However, most field studies rely on bulk techniques that overestimate carbon and nitrogen because the samples include organic matter other than plankton organisms. Here we used X-ray microanalysis (XRMA), a technique that, unlike bulk analyses, gives simultaneous quotas of C, N, O, Mg, Si, P, and S, in single-cell organisms that can be collected directly from the sea. We analysed the elemental composition of dinoflagellates and diatoms (largely Chaetoceros spp.) collected from different sites of the Catalan coast (NW Mediterranean Sea). As expected, a lower C content is found in our cells compared to historical values of cultured cells. Our results indicate that, except for Si and O in diatoms, the mass of all elements is not a constant fraction of cell volume but rather decreases with increasing cell volume. Also, diatoms are significantly less dense in all the measured elements, except Si, compared to dinoflagellates. The N:P ratio of both groups is higher than the Redfield ratio, as it is the N:P nutrient ratio in deep NW Mediterranean Sea waters (N:P = 20–23). The results suggest that the P requirement is highest for bacterioplankton, followed by dinoflagellates, and lowest for diatoms, giving them a clear ecological advantage in P-limited environments like the Mediterranean Sea. Finally, the P concentration of cells of the same genera but growing under different nutrient conditions was the same, suggesting that the P quota of these cells is at a critical level. Our results indicate that XRMA is an accurate technique to determine single cell elemental quotas and derived conversion factors used to understand and model ocean biogeochemical cycles.     

Elemental ratios and the uptake and release of nutrients by phytoplankton and bacteria in three lakes of the Canadian shield

The dynamics of carbon (C), nitrogen (N), and phosphorus (P), elemental ratios, and dark uptake/release of N and P in bacterial and phytoplankton size fractions were studied during summer 1992 in three lakes of contrasting food web structure and trophic status (L240, L110, L227). We wished to determine if phytoplankton and bacteria differed in their elemental characteristics and to evaluate whether the functional role of bacteria in nutrient cycling (i.e., as sink or source) depended on bacterial elemental characteristics. Bacterial contributions to total suspended particulate material and to fluxes of nutrients in the dark were substantial and varied for different elements. This indicated that some techniques for assaying phytoplankton physiological condition are compromised by bacterial contributions. C/N ratios were generally less variable than C/P and N/P ratios. Both elemental ratios and biomass-normalized N and P flux indicated that phytoplankton growth in each lake was predominantly P-limited, although in L227 these data reflect the dominance of N-fixing cyanobacteria, and N was likely limiting early in the sampling season. In L227, phytoplankton N/P ratio and biomass-normalized N flux were negatively correlated, indicating that flux data were likely a reasonable measure of the N status of the phytoplankton. However, for L227 phytoplankton, P-flux per unit biomass was a hyperbolic function of N/P, suggesting that the dominant L227 cyanobacteria have a limited uptake and storage capacity and that P-flux per unit biomass may not be a good gauge of the P-limitation status of phytoplankton in this situation. Examination of N-flux data in the bacterial size fraction relative to the N/P ratio of the bacteria revealed a threshold N/P ratio (22:1 N/P, by atoms), below which, bacteria took up and sequestered added N, and above which, N was released. Thus, the functional role of bacteria in N cycling in these ecosystems depended on their N/P stoichiometry.     

氮磷营养限制影响三角褐指藻光合无机碳利用和碳酸酐酶活性

以海洋硅藻三角褐指藻为实验材料, 研究了不同氮磷比培养对其光合无机碳利用和碳酸酐酶活性的影响, 结果显示三角褐指藻生长速率在N:P=16:1时最大, 高于或低于16:1时明显下降, 表明其最适生长受到氮磷的限制。氮限制(N:P=4:1或1:1)导致叶绿素a含量分别下降30.1% 和47.6%, 磷限制(N:P=64:1或256:1)下降39.1%和52.4%, 但氮或磷限制对叶绿素c含量并没有明显影响。不同营养水平培养对光饱和光合速率具有明显的影响, 与营养充足培养相比, 在严重氮磷限制(N:P=1:1或256:1)培养下光饱和光合速率分别下降39.7%和48.0%, 光合效率与暗呼吸速率也明显下降。在氮磷限制培养下藻细胞pH补偿点明显下降; K0.5CO2值在磷限制下降低30%, 表明磷限制有助于提高细胞对CO2的亲和力, 但氮限制并没有明显影响。在氮磷限制培养的细胞反应液中Fe (CN)63-浓度下降速率较慢, 表明在氮磷限制环境中生长的细胞质膜氧化还原能力明显低于营养充足条件下生长的细胞。氮磷限制也导致胞内、外碳酸酐酶活性明显下降, 其中在氮限制下胞外碳酸酐酶活性分别下降50%和37.5%, 在磷限制下下降22.3%和42.1%。严重的氮(N:P=1:1)或磷(N:P=256:1)限制导致胞内碳酸酐酶活性下降36.5%和42.9%。研究结果表明, 三角褐指藻细胞在氮磷营养限制的环境中, 可以通过调节叶绿素含量、无机碳的利用方式和碳酸酐酶的活性以维持适度的生长。       

Nutrient content of the seagrass Thalassia testudinum reveals regional patterns of relative availability of nitrogen and phosphorus in the Florida Keys USA

Between 1992 and 2000, we sampled 504 randomly chosen locations in theFlorida Keys, Florida, USA, for the elemental content of green leaves of theseagrass Thalassia testudinum. Carbon content ranged from29.4–43.3% (dry weight), nitrogen content from 0.88–3.96%, andphosphorus content from 0.048–0.243%. N and P content of the samples werenot correlated, suggesting that the relative availability of N and P variedacross the sampling region. Spatial pattern in C:N indicated a decrease in Navailability from inshore waters to the reef tract 10 km offshore;in contrast, the pattern in C:P indicated an increase in P availability frominshore waters to the reef tract. The spatial pattern in N:P was used to definea P-limited region of seagrass beds in Florida Bay and near shore, and anN-limited region of seagrass beds offshore. The close juxtaposition ofN–and P-limited regions allows the possibility that N loading from thesuburban Florida Keys could influence the offshore, N-limited seagrass bedswithout impacting the more nearshore, P-limited seagrass beds.     

Ecoenzymatic stoichiometry of stream sediments with comparison to terrestrial soils

The kinetics and elemental composition of cellular units that mediate production and respiration are the basis for the metabolic and stoichiometric theories of ecological organization. This theoretical framework extends to the activities of microbial enzymes released into the environment (ecoenzymes) that mediate the release of assimilable substrate from detrital organic matter. In this paper, we analyze the stoichiometry of ecoenzymatic activities in the surface sediments of lotic ecosystems and compare those results to the stoichiometry observed in terrestrial soils. We relate these ecoenzymatic ratios to energy and nutrient availability in the environment as well as microbial elemental content and growth efficiency. The data, collected by US Environmental Protection Agency, include the potential activities of 11 enzymes for 2,200 samples collected across the US, along with analyses of sediment C, N and P content. On average, ecoenzymatic activities in stream sediments are 2–5 times greater per gC than those of terrestrial soils. Ecoenzymatic ratios of C, N and P acquisition activities support elemental analyses showing that microbial metabolism is more likely to be C-limited than N or P-limited compared to terrestrial soils. Ratios of hydrolytic to oxidative activities indicate that sediment organic matter is more labile than soil organic matter and N acquisition is less dependent on humic oxidation. The mean activity ratios of glycosidases and aminopeptidases reflect the environmental abundance of their respective substrates. For both freshwater sediments and terrestrial soils, the mean C:nutrient ratio of microbial biomass normalized to growth efficiency approximates the mean ecoenzymatic C:nutrient activity ratios normalized to environmental C:nutrient abundance. This relationship defines a condition for biogeochemical equilibrium consistent with stoichiometric and metabolic theory.     

Linking major nutrients (C,H, N,and P) to trace metals (Fe,Mn, and Cu) in lake seston in southern Brazil

We investigated the relationships between major nutrients (C, H, N, and P) and trace metals (Cu, Fe, and Mn) in seston samples from ten lake/lagoon systems in southern Brazil. The systems were characterized by a diverse set of limnological features, including surface areas from 10⁻¹ to 10² km², water color, a _CDOM(440), from 1.4 to 12.9 m⁻¹, and electrical conductivity from 50 to 100 000 μS cm⁻¹. Seston concentrations also varied a great deal, 32-fold. The elemental (C: N, C: P, and N: P) and C: Chl-a ratios in the seston samples indicated, however, common features; i.e., most of the lakes were N-and/or P-limited, and the seston organic fraction was composed of nonvascular plants (e.g., phytoplankton). Our intersystem comparison revealed that the relative content of organic matter in seston and seston concentrations in lake water tended to correlate positively and negatively, respectively, with trace metal concentrations across the seston samples. Possible influences of elemental and C: Chl-a ratios on the association of metals with seston matrices, although theoretically important, were only partially evidenced here; positive correlations were found between C: N and also Org-H: N ratios with trace metal concentrations. We speculate that such results could be circumstantial, as the nature of the seston matrices appeared to be very similar among them. This hypothesis should thus be the theme of further research. In short, our findings suggest that C: N and Org-H: N ratios as well as the relative content of major nutrients in seston and seston concentrations can be importantly related to trace metal concentrations in seston samples. In discussing the results, however, we consider that metal-seston relationships depend on a variety of physical, chemical, and biological factors and/or variables other than those measured in this study, which could also contribute for defining and explaining variations in metal-seston concentrations in lake ecosystems.     

天童常绿阔叶林演替系列植物群落的N∶P化学计量特征

 土壤氮磷养分对植物生长的限制性可通过植被的N∶P化学计量特征来反映。该研究以常绿阔叶林演替系列为对象,将N∶P作为诊断指标,揭示 常绿阔叶林次生演替过程中植物群落的N∶P化学计量特征和养分限制作用。结果显示：1)物种水平的N∶P大小不一,但演替系列总体的变化特 征表现出了较高的一致性。2）在群落水平上,次生演替初期的灌草丛N∶P极小(7.38),远远低于14,当演替进入灌丛阶段,N∶P 显著增高到 19.96,在进入演替中期的针叶林(14.29)和针阔混交林(14.21)时,N∶P显著下降到 14～16之间,演替中后期的木荷(Schima superba)群落 (18.77)和栲树(Castanopsis fargesii)群落(20.13)的N∶P发生了显著的升高过程 。根据以往对N∶P临界值的确定,可以认为,常绿阔叶林次 生演替初期的植物群落生产力主要受到氮素的限制作用;演替中期的针叶林和针阔混交林主要受氮磷的共同限制,但以氮素的限制作用更为强 烈;演替中后期植物群落主要受到土壤磷素的限制作用。     

PHOSPHATE UPTAKE UNDER NITRATE LIMITATION BY SCENEDESMUS SP. AND ITS ECOLOGICAL IMPLICATIONS1

Under nitrogen limitation the phosphate content of Scenedesmus sp. shows little variation regardless of growth rate and the N/P atomic ratio of the medium. P uptake therefore can be calculated as the product of P content and N-dependent growth rate. The maximum rate of P uptake in N limitation is lower by a factor of about 8 than the rate in P limitation. As reported earlier, P uptake by this alga under P limitation is described by the kinetics resembling non-competitive enzyme inhibition, with one or several intracellular P fractions as inhibitors. These fractions include surplus P (water extractable) and inorganic polyphosphate fractions A (acid soluble) and B, C, and D (acid insoluble). In N limitation, the ratios of fractions A, B, C, and D are quite different from the ratios of P limitation at comparable growth rates. The concentrations of polyphosphate fraction A in N-limited cells are much, higher than the levels in P-limited cells, and this fraction becomes more predominant at low growth rates in N limitation. This fraction, if introduced as the inhibitor into the noncompetitive scheme, explains the uptake kinetics in both N- and P-limited cells and the low maximum uptake rate in N limitation. This finding may have two significant ecological implications: (1) A nutrient imbalance which brings about changes in the internal, level or the metabolism, of fraction A would affect P uptake. (2) Nitrogen sufficiency would cause a competitive advantage in P uptake. This advantage would be shared by N₂ fixers and algae with low optimum N/P ratios. In Scenedesmus sp. P limitation switches to N limitation and vice versa when the cell N/P atomic ratio is about 30.     

Changes in stoichiometric constraints on epilithon and benthic macroinvertebrates in response to slight nutrient enrichment of mountain rivers

1. To assess changes in stoichiometric constraints on stream benthos, we measured elemental composition of epilithon and benthic macroinvertebrates in intrinsically P‐limited mountain rivers, upstream and downstream of low‐level anthropogenic nutrient enrichment by effluents of municipal wastewater treatment plants. 2. While there was a broad range in the elemental composition of epilithon (C : P ratios of 200–16 500, C : N ratios of 8–280, N : P ratios of 8–535) and heptageniid mayfly scrapers (C : P ratios of 125–300, C : N ratios of 5.1–7.2, N : P ratios of 20–60), the average C : P ratio of epilithon was 10‐fold lower and the average C : N ratio twofold lower at more nutrient‐rich downstream sites. Nutrient ratios in benthic macroinvertebrates were lower than in epilithon and varied little between relatively nutrient‐poor and nutrient‐rich sites. 3. We modified the existing definition of producer‐consumer elemental imbalance to allow for variation in consumer nutrient content. We defined this ‘non‐homeostatic’ imbalance as the perpendicular distance between the producer and consumer C : P, C : N, or N : P ratios, and the 1 : 1 line. 4. At P‐limited sites, the estimated mayfly N : P recycling ratio was higher than the N : P ratio in epilithon, suggesting nutrient recycling by consumers could accentuate P‐limitation of epilithon. 5. Measuring the degree of producer–consumer nutrient imbalance may be important in predicting the magnitude of effects from nutrient enrichment and can help elucidate the causes and consequences of ecological patterns and processes in rivers.     

Effects of medium carbon-to-nitrogen ratio on biofilm formation and plasmid stability

Biofilm formation and plasmid segregational instability in biofilm cultures of Escherichia coli DH5alpha (pMJR1750) were investigated under different medium-carbon-to-nitrogen (C/N) ratios. At C/N ratios of 0.07 and 1, net accumulation of both biofilm plasmid-bearing and plasmid-free cells continued through the entire experiment without attaining any apparent steady state. At C/N ratios of 5 and 10, net biofilm cell accumulation for the two populations reached apparent steady states after 84 and 72 h, respectively. At C/N ratios of 0.07 and 1, polysaccharide production increased slowly and reached about 2g alginate equivalent/cm(2) by the end of both experiments. At a C/N ratio of 5, polysaccharide increase significantly after 84 h, reaching about 7mug alginate equivalent/cm(2) prior to termination. At a C/N ratio of 10, polysaccharide increased significantly after 72 h and reached 21 mug alginate equivalent/cm(2) at 108 h. At C/N ratios of 0.07 and 1, protein production reached 6.5 and 4 mug/cm(2), respectively. At C/N ratios of 5 and 10, protein production increased slightly for the first 84 h and reached a maximum at 108 h, at 3 and 2 mug/cm(2), respectively, then decreased over the last 12 h of the experiment. Ratios of polysaccharide to protein increased with increasing C/N ratios. At C/N ratios of 0.07 and 1, the ratios between extracellular polysaccharide (EP) and protein were no more than 205 mug polysaccharide/mug protein, whereas those at C/N ratios of 5 and 10 increased to about 7 and 12 mug polysaccharide/mug protein, respectively.Probabilities of plasmid loss in the biofilm cultures increased with increasing C/N ratios. At C/N ratios of 0.07, 1, and 5, the probabilities of plasmid loss were 0.0013 +/- 0.011, 0.020 +/- 0.006 and 0.122 +/- 0.021, respectively. At a C/N ratio of 10, the probability of plasmid loss was significantly higher, reaching 0.38 +/- 0.125. The increase of probability of plasmid loss at higher C/N ratios results from competition between cell replication and extracellular polysaccharide production. (c) 1994 John Wiley & Sons, Inc.     

UNCOUPLING OF SILICON COMPARED WITH CARBON AND NITROGEN METABOLISMS AND THE ROLE OF THE CELL CYCLE IN CONTINUOUS CULTURES OF THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE) UNDER LIGHT,NITROGEN, AND PHOSPHORUS CONTROL1

The elemental composition and the cell cycle stages of the marine diatom Thalassiosira pseudonana Hasle and Heimdal were studied in continuous cultures over a range of different light‐ (E), nitrogen‐ (N), and phosphorus‐ (P) limited growth rates. In all growth conditions investigated, the decrease in the growth rate was linked with a higher relative contribution of the G2+M phase. The other phases of the cell cycle, G1 and S, showed different patterns, depending on the type of limitation. All experiments showed a highly significant increase in the amount of biogenic silica per cell and per cell surface with decreasing growth rates. At low growth rates, the G2+M elongation allowed an increase of the silicification of the cells. This pattern could be explained by the major uptake of silicon during the G2+M phase and by the independence of this process on the requirements of the other elements. This was illustrated by the elemental ratios Si/C and Si/N that increased from 2‐ to 6‐fold, depending of the type of limitation, whereas the C/N ratio decreased by 10% (E limitation) or increased by 50% (P limitation). The variations of the ratios clearly demonstrate the uncoupling of the Si metabolism compared with the C and N metabolisms. This uncoupling enabled us to explain that in any of the growth condition investigated, the silicification of the cells increased at low growth rates, whereas carbon and nitrogen cellular content are differently regulated, depending of the growth conditions.     

Microcystin production by Microcystis aeruginosa in a phosphorus-limited chemostat

The production of microcystins (MC) from Microcystis aeruginosa UTEX 2388 was investigated in a P-limited continuous culture. MC (MC-LR, MC-RR, and MC-YR) from lyophilized M. aeruginosa were extracted with 5% acetic acid, purified by a Sep-Pak C(18) cartridge, and then analyzed by high-performance liquid chromatography with a UV detector and Nucleosil C(18) reverse-phase column. The specific growth rate (mu) of M. aeruginosa was within the range of 0.1 to 0.8/day and was a function of the cellular P content under a P limitation. The N/P atomic ratio of steady-state cells in a P-limited medium varied from 24 to 15 with an increasing mu. The MC-LR and MC-RR contents on a dry weight basis were highest at mu of 0.1/day at 339 and 774 microg g(-1), respectively, while MC-YR was not detected. The MC content of M. aeruginosa was higher at a lower mu, whereas the MC-producing rate was linearly proportional to mu. The C fixation rate at an ambient irradiance (160 microeinsteins m(-2) s(-1)) increased with mu. The ratios of the MC-producing rate to the C fixation rate were higher at a lower mu. Accordingly, the growth of M. aeruginosa was reduced under a P limitation due to a low C fixation rate, whereas the MC content was higher. Consequently, increases in the MC content per dry weight along with the production of the more toxic form, MC-LR, were observed under more P-limited conditions.     

喀斯特峰丛洼地不同森林类型植物和土壤C、N、P化学计量特征

研究西南喀斯特峰丛洼地人工林、次生林、原生林3个不同森林类型的6个代表性植物群落C、N、P化学计量特征及其与土壤的关系.结果表明: 不同森林类型植物和土壤C、N、P含量均存在显著差异.土壤C和N含量均为次生林最高,人工林最低,土壤P含量为人工林最高,原生林最低;植物C和P含量变化趋势为人工林>原生林>次生林,植物N含量为次生林最高,原生林最低.土壤C∶P、N∶P以及植物C∶P均为原生林显著高于次生林和人工林,土壤C∶N在不同森林类型间差异不显著;植物N∶P为次生林最高,人工林最低,植物C∶N为原生林>人工林>次生林.在不同森林类型中,乔木叶片N含量与P含量、C∶N与C∶P以及C∶P与N∶P之间均呈显著线性正相关,除了植物叶片C∶N与N∶P以及土壤C∶N与N∶P之间呈显著线性负相关外,植物和土壤的C、N、P、C∶P均无显著相关性,说明土壤C、N、P供应量对乔木叶片C、N、P含量影响不大.     

克里雅绿洲旱生芦苇根茎叶C、N、P化学计量特征的季节变化

旱生芦苇在水分限制、元素匮乏的环境条件下,经长期进化适应形成了自身独特的生理生态特征,研究其C、N、P化学计量特征随生长季节的变化规律有助于深入了解该植物生存和适应策略。系统分析了克里雅绿洲旱生芦苇根、茎、叶的C、N、P化学计量特征及其季节动态,深入探讨了不同生长季、不同器官以及两因素的交互作用对以上特征的影响。结果表明:旱生芦苇C、N、P含量均值分别为393.36、12.43、1.25 mg/g,C∶N、N∶P、C∶P均值分别为54.55、9.96、441.27。整个生长季内芦苇各器官间C、N、P平均含量的变化规律一致,为叶茎根,C、N、P化学计量比的变化规律不一致;芦苇C含量随生长季节的变化不断增加,N、P随季节的变化逐渐减少,C、N、P化学计量比随季节的变化规律也不尽相同。对芦苇C、N、P含量及其化学计量比整体变异来源分析显示,生长季节的变化对芦苇C、P、C∶N、C∶P变化的贡献大于器官间差异,器官间差异对芦苇N、N∶P变化的贡献大于生长季节的变化;说明芦苇生长发育过程中各生长季各器官对元素的吸收利用具有特异性。结合N、P元素含量及N∶P值的大小可知,研究区芦苇生长受到N、P共同限制,且更易受N元素的限制。     

Human uterine mast cells. Isolation, purification, characterization, ultrastructure, and pharmacology.

As part of an ongoing investigation of human mast cell heterogeneity, we have isolated, partially purified, and characterized the uterine mast cell and compared it with mast cells isolated from other organs. The average histamine content of myometrium and leiomyofibroma obtained from hysterectomies was 2.1 +/- 0.3 (mean +/- SEM) microgram/g of tissue (n = 10), and the histamine content of the two tissues did not differ significantly. A mild collagenase, hyaluronidase, and DNase digestion was used to disperse the uterine mast cells, with an average yield of 9.5% (range, 0 to 21%). The average histamine/uterine mast cell was 2.1 +/- 0.2 pg (n = 3), and 61 +/- 7% (n= 3) of the uterine mast cells survived overnight culture. Early purification efforts with Percoll gradients have yielded up to 80% pure uterine mast cells, with an average of 27 +/- 10% (n = 5). Uterine mast cells released histamine in response to the secretogogues anti-IgE and A23187 but did not respond to substance P or to the basophil secretogogues FMLP, C5a, and 12-O-tetradecanoylphorbol-13-acetate. After 1 microgram/ml anti-IgE stimulation, the uterine mast cell appeared to make significant quantities of PGD2 (89 +/- 26 ng/10(6) cells, n = 6) (p less than 0.05), as assayed by RIA. Simultaneously, leukotriene C4 release was 45 +/- 15 ng/10(6) cells, (n = 6) (p less than 0.05), as assayed by RIA. Combined gas-chromatography mass spectroscopy analysis of anti-IgE-stimulated cell supernatants confirmed the production of PGD2. In pharmacologic studies, isobutyl-methylxanthine and isoproterenol blocked anti-IgE-induced histamine release. The uterine mast cell is similar to the lung mast cell in terms of response to secretogogues and release of arachidonic acid metabolites. Ultrastructurally, the uterine mast cell contains scroll granules, crystal granules, combined granules, homogeneously dense granules, and large lipid bodies, many with focal lucencies within them. Particle granules, most frequently present in gut mast cells of mucosal origin, were absent from uterine mast cells. Although certain features are analogous to the ultrastructure of skin or lung mast cells, the combination of structures is distinctive for uterine mast cells.     

Effects of fatty acid and phosphorus content of food on the growth, survival and reproduction ofDaphnia

1. Mixtures of microencapsulated lipids and Scenedesmus quadricauda grown at different degrees of P limitation were used as food for Daphnia galeata in two growth experiments. Thereby, food quality in terms of ω3-fatty acid (ω3-FA) or phosphorus (P) content could be assessed without interference from other factors.
2. ω3-highly unsaturated fatty acids (ω3-HUFA), given to Daphnia as fish oil or eicosapentaenoic acid (EPA) together with non P-limited algae, decreased the time to first reproduction. When fed fish oil, somatic growth and survival were also enhanced. Linolenic acid also decreased the time to first reproduction but to a lesser extent than EPA.
3. Food quality depended to a large extent on the degree of P limitation of Scenedesmus , which is consistent with P limitation of Daphnia. The overall impact of P was always larger than the effect of ω3-FA. Growth, survival and reproduction were elevated when Daphnia were fed non P-limited Scenedesmus compared to treatments with P-limited algae.
4. The relative importance of ω3-HUFA and P content in the food changed over a C : P gradient, with stronger effects of ω3-HUFA at low C : P ratios.     

Effects of light and temperature on the cell size and some biochemical components in two freshwater cryptophytes

The effects of light and temperature on cell size and cellular composition (chlorophyll, protein, carbohydrate) of two freshwater cryptophytes were studied with batch cultures. Neither of the species had a constant cell size but the size varied with growth conditions. At each temperature the smallest cells were recorded at the lowest experimental photon flux density. The smallest cells of Cryptomonas 979/67 had an average volume of 232 μm³ and the largest ones 1 020 μm³. In Cryptomonas 979/62 the smallest and largest cells measured 4 306 μm³ and 12 450 μm³. Both species increased their cellular chlorophyll content when PFB dropped below 110–120 μmol m^-2 s^-1. The highest and lowest chlorophyll contents of 979/67 were 7.45 fg μm^-3 and 0.55 fg μm^-2 respectively. For 979/62 the corresponding values were 10.23 fg μm^-3 and 0.93 fg μm^-3. In both species the protein content remained stable at PFDs higher than 110–120 μmol m^-2 S^-1. The highest content of protein measured in 979/67 was 638 fg μm^-3 and the lowest 147 fg μm^-3. For 979/62 these values were 1 036 fg μm^-3 and 148 fg μm^-3 respectively. The carbohydrate results were less clear and no pattern either in response to photon flux density or temperature was obvious. The lowest and highest contents recorded for 979/67 were 62 fg μm^-3 and 409 fg μ^-3 and for 979162, 36 fg μm^-3 and 329 fg μm^-3     

Carbon and nitrogen content of Noctiluca scintillans in the Seto Inland Sea, Japan

The carbon and nitrogen content of Noctiluca scintillans cellsfrom the Seto Inland Sea, Japan was investigated in order toestimate its biomass in natural samples. The carbon contentof N.scintillans ranged from 123 to 627 ng C cell^–1 witha mean value of 353 ng C cell^–1, or 1.12 to 2.67 fg Cµm^–3 with a mean value of 1.98 fg C µm^–3.The nitrogen content ranged from 36.0 to 232 ng N cell^–1with a mean value of 131 ng N cell^–1, or 0.499 to 0.910fg N µm^–3 with a mean value of 0.694 fg N µm^–3.Total cell carbon and nitrogen increased but the carbon andnitrogen per cell volume decreased with increasing cell volume.The C/N ratio of the cells ranged from 2.3 to 4.4, which wasrelatively low compared with the Redfield ratio. The carbonand nitrogen content was extremely low (91.2 ng C cell^–1,41.8 ng N cell^–1) for starved cells, whereas it was extremelyhigh (528 ng C cell^–1, 205 ng N cell^–1) for cellswhich had ingested the large diatom, Coscinodiscus wailesii.Our results suggest that the carbon and nitrogen content ofN.scintillans varies depending on its physiological conditionand the type of food that it has recently consumed.