Humpback whale abundance in the North Pacific estimated by photographic capture‐recapture with bias correction from simulation studies

We estimated the abundance of humpback whales in the North Pacific by capture‐recapture methods using over 18,000 fluke identification photographs collected in 2004–2006. Our best estimate of abundance was 21,808 (CV = 0.04). We estimated the biases in this value using a simulation model. Births and deaths, which violate the assumption of a closed population, resulted in a bias of +5.2%, exclusion of calves in samples resulted in a bias of ?10.5%, failure to achieve random geographic sampling resulted in a bias of ?0.4%, and missed matches resulted in a bias of +9.3%. Known sex‐biased sampling favoring males in breeding areas did not add significant bias if both sexes are proportionately sampled in the feeding areas. Our best estimate of abundance was 21,063 after accounting for a net bias of +3.5%. This estimate is likely to be lower than the true abundance due to two additional sources of bias: individual heterogeneity in the probability of being sampled (unquantified) and the likely existence of an unknown and unsampled breeding area (?8.7%). Results confirm that the overall humpback whale population in the North Pacific has continued to increase and is now greater than some prior estimates of prewhaling abundance.     

Yeast Glucan in the Cyst Wall of Pneumocystis carinii

Ultrastructurally, the cyst wall of Pneumocystis carinii consists of an electron-dense outer layer, an electron-lucent middle layer, and an innermost plasmalemma. This is similar in appearance to the cell wall of some yeasts, e.g. Saccharomyces cerevisiae , which consists of an outer dense layer of mannan, a middle lucent layer of β−1,3-glucan (yeast glucan) and an innermost plasmalemma. The cyst wall P. carinii , as well as the cell wall of S. cerevisiae , can be labeled by a variety of methods which stain polysaccharides, such as Gomori's methenamine silver (GMS) and by Aniline blue, a dye which selectively stains β-1,3-glucan. The treatment of P. carinii cysts with Zymolyase, which the key enzyme is β,3-gIucan laminari-pentaohydrolase, results in lysis of the outer 2 layers of the cyst wall and the loss of positive staining by both GMS and Aniline blue. The lysis of elements of the cyst wall of P. carinii is achieved under the same conditions and concentration at which Zymolyase lyses the outer 2 layers of the cell wall of viable cells of S. cerevisiae . These observations indicate that a major component of the cyst wall of P. carinii is β-1,3-glucan.     

Mutualism fails when climate response differs between interacting species

Successful species interactions require that both partners share a similar cue. For many species, spring warming acts as a shared signal to synchronize mutualist behaviors. Spring flowering plants and the ants that disperse their seeds respond to warming temperatures so that ants forage when plants drop seeds. However, where warm‐adapted ants replace cold‐adapted ants, changes in this timing might leave early seeds stranded without a disperser. We investigate plant seed dispersal south and north of a distinct boundary between warm‐ and cold‐adapted ants to determine if changes in the ant species influence local plant dispersal. The warm‐adapted ants forage much later than the cold‐adapted ants, and so we first assess natural populations of early and late blooming plants. We then transplant these plants south and north of the ant boundary to test whether distinct ant climate requirements disrupt the ant–plant mutualism. Whereas the early blooming plant's inability to synchronize with the warm‐adapted ant leaves its populations clumped and patchy and its seedlings clustered around the parents in natural populations, when transplanted into the range of the cold‐adapted ant, effective seed dispersal recovers. In contrast, the mutualism persists for the later blooming plant regardless of location because it sets seed later in spring when both warm‐ and cold‐adapted ant species forage, resulting in effective seed dispersal. These results indicate that the climate response of species interactions, not just the species themselves, is integral in understanding ecological responses to a changing climate. Data linking phenological synchrony and dispersal are rare, and these results suggest a viable mechanism by which a species' range is limited more by biotic than abiotic interactions – despite the general assumption that biotic influences are buried within larger climate drivers. These results show that biotic partner can be as fundamental a niche requirement as abiotic resources.     

Virus-like particles in the brown algaStreblonema

Summary Ultrastructural examination ofStreblonema sp. revealed icosahedral virus-like particles (135–150 nm) throughout the cytoplasm of vegetative cells. The densely packed particles consist of an osmiophilic coat around a fibrillar core. Most cytoplasmic organelles are excluded from the regions where the particles are extremely abundant, but no degeneration of plastids, mitochondria or dictyosomes is evident. The virogenic stroma contains many ribosomes and fibers possibly representing DNA strands remaining from the lysed nucleus. No decrease in vigor seemed to be associated with the presence of the particles.     

DNA loops generate intracentromere tension in mitosis

The centromere is the DNA locus that dictates kinetochore formation and is visibly apparent as heterochromatin that bridges sister kinetochores in metaphase. Sister centromeres are compacted and held together by cohesin, condensin, and topoisomerase-mediated entanglements until all sister chromosomes bi-orient along the spindle apparatus. The establishment of tension between sister chromatids is essential for quenching a checkpoint kinase signal generated from kinetochores lacking microtubule attachment or tension. How the centromere chromatin spring is organized and functions as a tensiometer is largely unexplored. We have discovered that centromere chromatin loops generate an extensional/poleward force sufficient to release nucleosomes proximal to the spindle axis. This study describes how the physical consequences of DNA looping directly underlie the biological mechanism for sister centromere separation and the spring-like properties of the centromere in mitosis.     

Cannabinoid receptor 1 ligands revisited: Pharmacological assessment in the ACTOne system

In vitro cannabinoid pharmacology has evolved over time from simple receptor binding to include [³⁵S]GTPγ, β-arrestin, and cAMP assays. Each assay has benefits and drawbacks; however, no single functional system has been used for high-throughput evaluation of compounds from binding to pharmacological functionality and antagonist assessment in a well-characterized human cell line. In this study, we evaluated and validated one system—ACTOne human embryonic kidney cells transfected with a cyclic nucleotide gated channel and cannabinoid receptor 1 (CB1)—and compared human CB1 affinity, functional, and antagonistic effects on cAMP with previously published results. The study was conducted on a diverse group of CB1 ligands, including endocannabinoids and related compounds, 2-AG, AEA, MAEA, and ACEA, the phytocannabinoid Δ⁹ THC, and synthetic cannabinoids CP 55,940, WIN 55,212-2, SR 141716A, CP 945,598, and WIN 55,212-3. Our results were compared with literature values where human CB1 was used for affinity determination and cAMP was used as a functional readout. Here we report the first detailed evaluation of the ACTOne assay for the pharmacological evaluation of CB1 ligands. The results from the study reveal some interesting deviations from previously reported functional activities of the aforementioned ligands.     

Characterization of a glucuronyltransferase: neolactotetraosylceramide glucuronyltransferase from rat brain

The properties of a rat brain glucuronyltransferase, which is presumed to be associated with the biosynthesis of the HNK-1 epitope on sulfoglucuronyl glycolipids, are described. The enzyme required divalent cations for reaction, with maximal activity at 10mm Mn²⁺, and exhibited a dual optimum at pH 4–5 and pH 6 depending upon the buffer used, with the highest activity at pH 4.5 in MES buffer. This enzyme strictly recognized the Gal1-4GlcNAc terminal structure, and was highly specific for neolacto (type 2) glycolipids as acceptor. The enzyme was localized specifically in the brain, and was barely detected in other issues, including the thymus, spleen, liver, kidney, lung, and sciatic nerve fibres. Phosphatidylinositol and phosphatidylserine increased the enzymatic reaction 4.4- and 2.3-fold, respectively, whereas phosphatidylcholine slightly decreased the rate.Abbreviations GlcA glucuronic acid - Lc-PA₁₄ lactotetraose-phenyl-C₁₄H₂₉ - nLc-PA₁₄ neolactotetraose-phenyl-C₁₄H₂₉ - nLcOse₄-Cer neolactotetraosylceramide - NP-40 Nonidet P-40 - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - SGGL sulfoglucuronyl glycolipid