The oxygen evolution methodology affects photosynthetic rate measurements of microalgae in well‐defined light regimes

Designing photobioreactors correctly is a must for the success of microalgal mass production. Optimal photobioreactor design requires a precise knowledge of photosynthesis dynamics in fluctuating light conditions and hence a method for the measurement of photosynthetic rates in specific light regimes. However, it is not uncommon in literature that experimental protocols used to obtain oxygen generation rates are described ambiguously and the reported rates of photosynthesis vary widely depending on the methodology. Additionally, quite a number of methods overlook certain aspects that can affect the estimated rates significantly, and can therefore affect photobioreactor design. We have developed a method based on oxygen evolution measurements that accurately determines photosynthetic rates under well‐defined light regimes. Our experimental protocol takes into account most of the issues that can affect the rates of oxygen generation, such as depletion of nutrients during the measurements and precision of the measurements. We have focused on the basic applications in photobioreactor design and used a dynamic model of photosynthesis to analyze our results and compare them with available published data. The results suggest that our oxygen evolution method is consistent. Biotechnol. Bioeng. 2010;106: 228–237. © 2010 Wiley Periodicals, Inc.     

The lampbrush chromosomes of Xenopus laevis: preparation,identification, and distribution of 5S DNA sequences

Details are given of a technique for making permanent preparations of the lampbrush chromosomes of Xenopus laevis. Stained preparations allow all 18 bivalent chromosomes to be identified, and a working map showing the major features has been constructed. Fifteen of the Xenopus chromosomes have one telomere conspicuously larger than the other; the two smallest chromosomes, and one other, lack large telomeres. Similar preparations, extracted with RNase and denatured, have been hybridized in situ with a ³H-labelled 5S cRNA probe. Chromosomes can be identified in the resulting autoradiographs. 5S DNA sequences are present at all the larger telomeres and at three of the smaller ones, but are absent from the telomeres at both ends of the two smallest chromosomes. There are also five interstitial sites of hybridization. At one of these, label is on the chromosome axis; at the other four, label extends well away from the axis.     

Novel mouse mammary cell lines for in vivo bioluminescence imaging (BLI) of bone metastasis

ABSTRACT: BACKGROUND: Tumor cell lines that can be tracked in vivo during tumorigenesis and metastasis provide vital tools for studying the specific cellular mechanisms that mediate these processes as well as investigating therapeutic targets to inhibit them. The goal of this study was to engineer imageable mouse mammary tumor cell lines with discrete propensities to metastasize to bone in vivo. Two novel luciferase expressing cell lines were developed and characterized for use in the study of breast cancer metastasis to bone in a syngeneic mouse model. RESULTS: The 4T1.2 luc3 and 66c14 luc2 cell lines were shown to have high levels of bioluminescence intensity in vitro and in vivo after orthotopic injection into mouse mammary fat pads. The 4T1.2 luc3 cell line was found to closely model the sites of metastases seen in human patients including lung, liver, and bone. Specifically, 4T1.2 luc3 cells demonstrated a high incidence of metastasis to spine, with an ex-vivo BLI intensity three orders of magnitude above the commercially available 4T1 luc2 cells. 66c14 luc2 cells also demonstrated metastasis to spine, which was lower than that of 4T1.2 luc3 cells but higher than 4T1 luc2 cells, in addition to previously unreported metastases in the liver. High osteolytic activity of the 4T1.2 luc3 cells in vivo in the bone microenvironment was also detected. CONCLUSIONS: The engineered 4T1.2 luc3 and 66c14 luc2 cell lines described in this study are valuable tools for studying the cellular events moderating the metastasis of breast tumor cells to bone.     

The sources of variation for individual prey-to-predator size ratios

The relative body size at which predators are willing to attack prey, a key trait for predator-prey interactions, is usually considered invariant. However, this ratio can vary widely among individuals or populations. Identifying the range and origin of such variation is key to understanding the strength and constraints on selection in both predators and prey. Still, these sources of variation remain largely unknown. We filled this gap by measuring the genetic, maternal and environmental variation of the maximum prey-to-predator size ratio (PPSR_max) in juveniles of the wolf spider Lycosa fasciiventris using a paternal half-sib split-brood design, in which each male was paired with two females and the offspring reared in two food environments: poor and rich. Each juvenile spider was then sequentially offered crickets of decreasing size and the maximum prey size killed was determined. We also measured body size and body condition of spiders upon emergence and just before the trial. We found low, but significant heritability (h² = 0.069) and dominance and common environmental variance (d² + 4c² = 0.056). PPSR_max was also partially explained by body condition (during trial) but there was no effect of the rearing food environment. Finally, a maternal correlation between body size early in life and PPSR_max indicated that offspring born larger were less predisposed to feed on larger prey later in life. Therefore, PPSR_max, a central trait in ecosystems, can vary widely and this variation is due to different sources, with important consequences for changes in this trait in the short and long terms.Subject terms: Evolutionary biology, Behavioural ecology, Heritable quantitative trait, Evolutionary ecology     

Hydro-climatic changes promote shifts in zooplankton composition and diversity in wetlands of the Lower Paraná River Delta

Hydrobiologia - The Paraná River Delta is one of the most biodiverse and largest mosaic of wetland ecosystems in South America. Yet its natural hydrological patterns are being strongly...     

Naturally arising recombinants that are missing portions of the simian virus 40 regulatory region.

When simian virus 40 (SV40) is serially passaged at high multiplicity, a heterogeneous collection of naturally arising variants is generated. Those which are the most abundant presumably have a selective replicative advantage over other defective and wild-type helper SV40s. Two such naturally arising host-substituted variants of SV40 have been characterized in terms of complete nucleotide sequence determination. Evolutionary variant ev-1101 (previously isolated by Lee et al., Virology 66:53-69, 1975) is from undiluted serial passage 13, whereas ev-2101 is newly isolated from undiluted serial passage 6 of an independently-derived evolutionary series. Both variants contain a five-times tandemly repeated segment of DNA consisting of viral Hin C and Hin A sequences that have recombined with a segment of host DNA that is not highly reiterated in the monkey genome. The monkey segment differs in the two variants as does the size of the viral segment retained. In two additional host-substituted variants, ev-1102 (previously isolated from serial passage 20 by Brockman et al., Virology 54:384-397, 1973) and ev-1108 (newly isolated from serial passage 40), the SV40 sequences derived from the replication origin are present as inverted repetitions. The inverted repeat regions of these two variants have been analyzed at the nucleotide sequence level and are compared with SV40 variant ev-1104 from passage 45 (previously characterized by Gutai and Nathans, J. Mol. Biol. 126:259-274, 1978). The viral segment containing the regulatory signals for replication and viral gene expression is considerably shortened in later serial passages as demonstrated by these five variants. It is of interest that the variants presumably arose due to their enhanced replication efficiency, yet are missing some of the sequence elements implicated in the regulation of replication. Furthermore, a comparison of the structure of the replication origin regions indicates that additional changes occur in the SV40 regulatory region with continued undiluted serial passage.     

Using suitable projects in adding value to nonwood forest products in The Philippines: The Copal (Agathis Philippinensis) trade in Palawan

Using Suitable Projects in Adding Value to Nonwood Forest Products in the Philippines: The Copal (Agathis philippinensis)Trade in Palawan. Economic Botany 58(3):476-485, 2004. The Philippines is a country that has little low-forest cover left, but it still has many useful forest species. Despite the decline of forest area and the degradation of forests, many of the poorest households, both indigenous and migrant, are pushed into the remaining forest area and depend on forest goods for their subsistence and monetary income. These goods are inevitably nonwood forest products (NWFPs) because timber extraction is now illegal in many parts of the country. The extraction of nonwood forest products, such as resin and rattan, is the only source of a cash income for many households. However, despite the long tradition of NWFP extraction in forest-edge villages, the income that collectors get from these products is still minimal. The impediments to a more equitable and efficient trade in NWFPs are examined, and possible ways of adding value locally to NWFPs are presented, using almaciga (Agathis philippinensis) resin extraction as a case study.     

Proportion of soft tissue in selected bone cuts fed primarily as enrichments to large carnivores

Zoos often offer large bones or cuts of meat containing bone (bone cuts) to carnivores to provide oral stimulation and behavioral enrichment. Because of its abrasive action, the act of chewing on a bone can increase the oral health of large felids as well as provide an enriching activity. Unfortunately, because the quantity of edible tissue on the bones is usually unknown, when feeding these cuts one can easily miscalculate an animal's caloric and nutrient intake. To fully comprehend the contribution of bones as a dietary item as opposed to an enrichment item, we removed the soft tissue from a total of 70 samples, representing 14 types of bone cuts commonly used in managed carnivore feeding programs. Across types of cuts, soft tissue averaged 50% of wet weight, with pork knuckles averaging the lowest (23%) and horse shanks the greatest (74%) percent soft tissue. Zoo Biol 27:154–158, 2008. © 2008 Wiley‐Liss, Inc.