Influence of carbon supply on the stimulation of light-saturated photosynthesis by blue light in Laminaria saccharina: implications for the mechanism of carbon acquisition in higher brown algae

In saturating irradiances of red light, photosynthesis of Laminaria saccharina (L.) Lamouroux was stimulated by low irradiances of continuous blue light only when the supply of dissolved inorganic carbon (DIC) was limiting. The degree of this stimulation was inversely proportional to the logarithm of the concentration of free CO₂, whether this was adjusted by varying the total DIC or the pH at a given DIC concentration. The final pH reached in a closed system was higher in blue light than in red light. Both acetazolamide and ethoxyzolamide suppressed the responses to blue light almost completely, but reduced photosynthesis in red light by only 30%. Buffering the pH of the seawater also suppressed the stimulation of photosynthesis by blue light without affecting the photosynthetic rate in red light. The transient stimulation of O₂ evolution by a blue light pulse was not accompanied by a corresponding increase in CO₂ consumption. These observations could be explained if, in analogy to the mechanism proposed for Ectocarpus (Schmid, Mills & Dring 1996, Plant Cell and Environment 19,373–382, this issue, accompanying paper), photosynthesis was supported by a blue-light-activated release of CO₂ from an internal store. We suggest that the store is located in the vacuoles of the cortical tissue of the blades. The main photosynthetic tissue, however, is in the overlying meristoderm, and blue-light-activated mobilization of the store could stimulate O₂ evolution only if periplasmic carbonic anhydrase was available to facilitate CO₂ uptake from the cortex.     

Mitogenic activity of pituitary hormones on cell cultures of normal and carcinogen-induced tumor epithelium from rat mammary glands

Cell suspension containing normal or tumor epithelium were readily obtained by enzymatically digesting rat mammary glands from perphenazine-treated (prolactin-hypersecreting) cycling, female virgin animals or hormone- responsive mammary tumors from animal treated with dimethylbenzanthracene. Cell suspensions were fractioned into predominantly epithelial and predominantly stromal cells by their differential rates of attachment to culture dishes. Both normal mammary and tumor epithelial cells were characterized by the presence of specific cell-junctional complexes, desmosome-like structures, surface microvilli, and their ability to synthesize casein. Serum-dependent protease activity was greater in cultures derived from tumors, and cells from such cultures grew in agarose whereas those from the non-neoplastic gland did not. The addition of prolactin to the culture medium stimulated DNA synthesis in primary or secondary epithelial cultures from tumors, whereas additional insulin and hydrocortisone with prolactin were required for similar levels of DNA synthesis in cultures from non-neoplastic glands. The fraction of cells synthesizing DNA was, however, smaller than that with 10 percent serum measured in the same time period. Both growth hormone and epidermal growth factor stimulated DNA synthesis but to a lesser extent than did prolactin. Prolactin with hydrocortisone and insulin were relatively inactive in promoting DNA synthesis of the nonepithelial cells whereas pituitary fibroblast growth factor was more active. These mitogenic effects were obtained when the hormones were added to the medium at near physiological concentrations, and paralleled the known activities of the hormones in control of mammary gland growth and development in the rat.     

One "different kind of gentleman": Alfred Merle Norman (1831–1918), invertebrate zoologist

Alfred Merle Norman (1831–1918), an active clergyman in rural Co. Durham, England, came from an ancient Somerset family. He began to study marine biology during the early 1850s and during the 1860s was an important participant in John Gwyn Jeffreys' expeditions to the Shetland Islands. Norman's field collecting all over the British Isles was extensive and he made important trips to Norwegian fjords for dredging. His best known discoveries were Rhabdopleura and Synagoga , but he published major work on Protozoa, Porifera, Coelenterata, Mollusca, Crustacea, Echinodermata and other invertebrates. The publication Museum Normanianum summarized Norman's collection of 11,086 species, which was acquired by the British Museum (Natural History). His library, which incorporated John Gwyn Jeffreys' library on molluscs, is now in the Department of Zoology, Cambridge University. Norman was primarily a taxonomist secondarily interested in zoogeography who avoided Darwinian controversies.
A bibliography of Norman's 218 publications is included.     

Fertilization effects with P on accumulated leaf area duration,biomass and yield of three cultivars of maize in Toluca,Mexico

The effect of six phosphorus levels (0, 40, 80, 120, 160 and 200 kg/ha) on the duration of cumulative leaf area, biomass and agronomic yield was determined in the maize cultivars: Amarillo Almoloya, Cacahuacintle and Condor in 2010 and 2011. Such cultivars were sown in the Cerrillo Piedras Blancas Mexico. A completely randomized complete block design with factorial arrangement was utilized. High phosphorus levels (120, 160 and 200 kg/ha) positively affected the duration of cumulative leaf area; greatest values were obtained in Cacahuacintle. A greater duration of accumulated leaf area contributes to determine high values of biomass accumulation and grain yield in this cultivar. Leaf area duration appeared to be a useful tool for evaluating different genotypes in a given environment.     

Some properties of an isolate of tobacco rattle virus from Northern Ireland

A virus obtained from soil in which potato plants had shown severe spraing symptoms induced symptoms on indicator plants typical of tobacco rattle virus (TRY). Purified virus preparations of a local-lesion isolate contained particles of two modal lengths, 192 nm and 94 nm containing RNA molecules of mol. wt 2.4 × 10⁶ and 1.23 × 10⁶. Virus coat protein had a mol. wt of c. 21 500. The virus was serologically distantly related to TRY (SYM) and pea early browning virus (PEBV) SP5, but did not react with TRY (CAM) or TRY (PRN) antisera. However, cDNA hybridisation indicated that the virus was more closely related to TRY (PRN) than either TRY (SYM) or PEBV (SP5). The virus isolate has been designated TRY (NI).     

A Pseudomonas aeruginosa TIR effector mediates immune evasion by targeting UBAP1 and TLR adaptors

Bacterial pathogens often subvert the innate immune system to establish a successful infection. The direct inhibition of downstream components of innate immune pathways is particularly well documented but how bacteria interfere with receptor proximal events is far less well understood. Here, we describe a Toll/interleukin 1 receptor (TIR) domain‐containing protein (PumA) of the multi‐drug resistant Pseudomonas aeruginosa PA7 strain. We found that PumA is essential for virulence and inhibits NF‐κB, a property transferable to non‐PumA strain PA14, suggesting no additional factors are needed for PumA function. The TIR domain is able to interact with the Toll‐like receptor (TLR) adaptors TIRAP and MyD88, as well as the ubiquitin‐associated protein 1 (UBAP1), a component of the endosomal‐sorting complex required for transport I (ESCRT‐I). These interactions are not spatially exclusive as we show UBAP1 can associate with MyD88, enhancing its plasma membrane localization. Combined targeting of UBAP1 and TLR adaptors by PumA impedes both cytokine and TLR receptor signalling, highlighting a novel strategy for innate immune evasion.     

Inferences About Ungulate Population Dynamics Derived From Age Ratios

Abstract: Age ratios (e.g., calf:cow for elk and fawn:doe for deer) are used regularly to monitor ungulate populations. However, it remains unclear what inferences are appropriate from this index because multiple vital rate changes can influence the observed ratio. We used modeling based on elk (Cervus elaphus) life-history to evaluate both how age ratios are influenced by stage-specific fecundity and survival and how well age ratios track population dynamics. Although all vital rates have the potential to influence calf:adult female ratios (i.e., calf:cow ratios), calf survival explained the vast majority of variation in calf:adult female ratios due to its temporal variation compared to other vital rates. Calf:adult female ratios were positively correlated with population growth rate (Λ) and often successfully indicated population trajectories. However, calf:adult female ratios performed poorly at detecting imposed declines in calf survival, suggesting that only the most severe declines would be rapidly detected. Our analyses clarify that managers can use accurate, unbiased age ratios to monitor arguably the most important components contributing to sustainable ungulate populations, survival rate of young and Λ. However, age ratios are not useful for detecting gradual declines in survival of young or making inferences about fecundity or adult survival in ungulate populations. Therefore, age ratios coupled with independent estimates of population growth or population size are necessary to monitor ungulate population demography and dynamics closely through time.     

DNA Synthesis in Chloroplasts: III. THE DNA GYRASE INHIBITORS NALIDIXIC ACID AND NOVOBIOCIN INHIBIT BOTH THYMIDINE INCORPORATION INTO DNA AND PHOTOSYNTHETIC OXYGEN EVOLUTION BY ISOLATED CHLOROPLASTS

The influence of two DNA gyrase inhibitors, nalidixic acid andnovobiocin, on DNA synthesis in isolated pea chloroplasts wasexamined. Novobiocin at 1–5 mol m^–3 markedly lowered[³H]thymidine incorporation into DNA (30–95% inhibition);while less effective, nalidixic acid at similar concentrationsalso diminished incorporation (25–35% inhibition). Theinhibition of chloroplast DNA (ctDNA) biosynthesis by nalidixicacid and novobiocin was confirmed by autoradiography and densitometry.These data are consistent with the view that chloroplasts containa DNA gyrase-like enzyme which is necessary for DNA replication.Despite this, interpretation of the results is not straightforward,as both nalidixic acid and novobiocin also inhibited photosyntheticactivity. Each substance (at millimolar levels) reduced ferricyanide-dependentO₂ evolution in isolated chloroplasts. However, at lower concentrations(0.05–0.3 mol m^–3) they slightly enhanced photosyntheticelectron flow; thus, these compounds may act as uncouplers ofphotophosphorylation as well as inhibitors of electron transport.Nalidixic acid and novobiocin at relatively low (0.1 mol m^–3)concentrations also strongly reduced CO₂-dependent O₂ evolution(an index of CO₂ photo-assimilation) in isolated plastids. Thus,caution must be exercised in assessing results from studiesin which nalidixic acid and novobiocin are used with whole plants,cells, protoplasts or isolated chloroplasts. Key words: Chloroplast, DNA replication, novobiocin, nalidixic acid, DNA gyrase