Effectiveness and utility of acoustic recordings for surveying tropical birds

ABSTRACT Although acoustic recordings have recently gained popularity as an alternative to point counts for surveying birds, little is known about the relative performance of the two methods for detecting tropical bird species across multiple vegetation types. During June and July 2008, we collected species detection/nondetection data to compare the performance of a quadraphonic acoustic recording system and point counts for estimating species richness and composition and detection probabilities of 15 rare, moderately common, and common tropical bird species across six structurally distinct vegetation types (coastal dune scrub, mangrove, low‐stature deciduous thorn forest, early and late successional medium‐stature semievergreen forest, and grazed pastures) in the northern Yucatan Peninsula. We selected five rare species endemic to the Yucatan Peninsula and 10 moderately common and common species that also occur in other tropical regions. Species richness and composition did not differ between survey methods in any of the vegetation types. At the population level, however, we found support for an effect of method on detection probability for most species. For 13 species, regardless of their abundance, acoustic recordings yielded detection probabilities as high as or higher than those for point counts across all vegetation types. The remaining two species were better detected by point counts in pastures and coastal scrub, where greater visibility likely improved sightings of these species. However, these species were detected as well as or better by acoustic recordings in forests and mangroves where detections were primarily auditory. In tropical regions where experienced field observers may not be available and funding for field surveys may be limited, acoustic recordings offer a practical solution for determining species richness and composition and the occupancy patterns of most species. However, for some species, a combination of methods will provide the most reliable data. Regardless of the method selected, analyses that account for variation in detection probability among vegetation types will be necessary because most species in our study demonstrated vegetation‐dependent detection probabilities.     

The Hylemon-Björkhem pathway of bile acid 7-dehydroxylation: history,biochemistry, and microbiology

Bile acids are detergents derived from cholesterol that function to solubilize dietary lipids, remove cholesterol from the body, and act as nutrient signaling molecules in numerous tissues with functions in the liver and gut being the best understood. Studies in the early 20th century established the structures of bile acids, and by mid-century, the application of gnotobiology to bile acids allowed differentiation of host-derived “primary” bile acids from “secondary” bile acids generated by host-associated microbiota. In 1960, radiolabeling studies in rodent models led to determination of the stereochemistry of the bile acid 7-dehydration reaction. A two-step mechanism was proposed, which we have termed the Samuelsson-Bergström model, to explain the formation of deoxycholic acid. Subsequent studies with humans, rodents, and cell extracts of Clostridium scindens VPI 12708 led to the realization that bile acid 7-dehydroxylation is a result of a multi-step, bifurcating pathway that we have named the Hylemon-Björkhem pathway. Due to the importance of hydrophobic secondary bile acids and the increasing measurement of microbial bai genes encoding the enzymes that produce them in stool metagenome studies, it is important to understand their origin.     

Cell membrane permeability coefficients determined by single-step osmotic shift are not applicable for optimization of multi-step addition of cryoprotective agents: As revealed by HepG2 cells

HepG2 cells have a number of research applications and cryopreservation of these cells would improve supply and thus facilitate the study. Development of effective cryopreservation protocols relies on knowledges of the fundamental mass transport characteristics of HepG2 cell membrane. Currently, the permeability parameters estimated from single-step addition are routinely used to predict the osmotic responses of the cells in multistep protocols, as well as used for prediction of optimal cooling rates. However, the reasonability of this approach has not been rigorously studied. Here we measured the hydraulic conductivity (L_p) and the permeability coefficient (P_s) of HepG2 cells in the absence/presence of dimethyl sulfoxide (Me₂SO) at various temperatures with single and multistep addition of Me₂SO. We found that the permeability yielded via one-step addition of the Me₂SO cannot exactly predict the volume change of the cells when the CPA was added in multiple steps.     

Avian prey-dropping behavior. II. American crows and walnuts

Complex and energetically expensive foraging tasks should beshaped by natural selection to be efficient. Many species ofbirds open hard-shelled prey by dropping the prey repeatedlyonto the ground from considerable heights. Urban-dwelling Americancrows (Corvus brachyrhynchos) forage in this way on two speciesof walnuts in central California, USA. As predicted from a theoreticalmodel, crows dropped nuts with harder shells from greater heightsand dropped them from greater heights when over softer substrates.The height selected for dropping nuts decreased in the presenceof numerous nearby conspecifics, indicating that crows weresensitive to the risk of kleptoparasitism when selecting dropheights. Drop height decreased with repeated drops of the samewalnut, suggesting that crows adjusted for the increasing likelihoodthat a repeatedly-dropped nut would break on subsequent drops.Crows did not alter height of drop in accordance with differencesin the mass of the prey. When faced with multiple prey typesand dropping substrates, and high rates of attempted kleptoparasitism,crows adjusted the height from which they dropped nuts in waysthat decreased the likelihood of kleptoparasitism and increasedthe energy obtained from each nut.     

Cryoprotectant-dependent control of intracellular ice recrystallization in hepatocytes using small molecule carbohydrate derivatives

To promote the recovery of cells that undergo intracellular ice formation (IIF), it is imperative that the recrystallization of intracellular ice is minimized. Hepatocytes are more prone to IIF than most mammalian cells, and thus we assessed the ability of novel small molecule carbohydrate-based ice recrystallization inhibitors (IRIs) to permeate and function within hepatocytes. HepG2 monolayers were treated with N-(4-chlorophenyl)-d-gluconamide (IRI 1), N-(2-fluorophenyl)-d-gluconamide (IRI 2), or para-methoxyphenyl-β-D-glycoside (IRI 3) and fluorescent cryomicroscopy was used for real time visualization of intracellular ice recrystallization. Both IRI 2 and IRI 3 reduced rates of intracellular recrystallization, whereas IRI 1 did not. IRI 2 and IRI 3, however, demonstrated a marked reduction in efficiency in the presence of the most frequently used permeating cryoprotectants (CPAs): glycerol, propylene glycol (PG), dimethyl sulfoxide (DMSO), and ethylene glycol (EG). Nevertheless, IRI 3 reduced rates of intracellular recrystallization relative to CPA-only controls in the presence of glycerol, PG, and DMSO. Interestingly, IRI preparation in trehalose, a commonly used non-permeating CPA, did not impact the activity of IRI 3. However, trehalose did increase the activity of IRI 1 while decreasing that of IRI 2. While this study suggests that each of these compounds could prove relevant in hepatocyte cryopreservation protocols where IIF would be prominent, CPA-mediated modulation of intracellular IRI activity is apparent and warrants further investigation.     

Nitrite as an Energy-Conserving Electron Sink for the Acetogenic Bacterium <Emphasis Type="Italic">Moorella thermoacetica</Emphasis>

Nitrite served as an energy-conserving electron acceptor for the acetogenic bacterium Moorella thermoacetica. Growth occurred in an undefined (0.1% yeast extract) medium containing 20 mM glyoxylate and 5 mM nitrite and was essentially equivalent to that observed in the absence of nitrite. In the presence of nitrite, acetate (the normal product of glyoxylate-derived acetogenesis) was not detected during growth. Instead, growth was coupled to nitrite dissimilation to ammonium, and acetogenesis was limited to the stationary phase. Furthermore, membranes from glyoxylate-grown cells under nitrite-dissimilating conditions were deficient in the b-type cytochrome that is typically found in the membranes of acetogenic cells. Unlike glyoxylate, other acetogenic substrates (fructose, oxalate, glycolate, vanillin, and hydrogen) were not growth supportive in the undefined medium containing nitrite, and glyoxylate-dependent growth did not occur in a nitrite-supplemented, basal (without yeast extract) medium. Glyoxylate-dependent growth by Moorella thermoautotrophica was not observed in the undefined medium containing nitrite. Received: 1 April 2002 / Accepted: 9 July 2002     

Head and neck squamous cell carcinomas among males of the three largest Asian diasporas in the US, 2004–2013

BackgroundHead and neck squamous cell carcinomas (HNSCC) have not been fully examined in the Asian diasporas in the US, despite certain Asian countries having the highest incidence of specific HNSCCs.MethodsNational Cancer Database was used to compare 1046 Chinese, 887 South Asian (Indian/Pakistani), and 499 Filipino males to 156,927 Non-Hispanic White (NHW) males diagnosed with HNSCC between 2004−2013. Multinomial logistic regression was used to assess the association of race/ethnicity with two outcomes – site group and late-stage diagnosis. Temporal trends were explored for site groups and subsites.ResultsSouth Asians had a greater proportion of oral cavity cancer [OCC] compared to NHWs (59 % vs. 25 %; OR_adj =7.3 (95 % CI: 5.9–9.0)). In contrast, Chinese (64 % vs. 9%; OR_adj =34.0 (95 % CI: 26.5–43.6)) and Filipinos (47 % vs. 9%; OR_adj =10.0 (95 % CI: 7.8–12.9)) had a greater proportion of non-oropharyngeal cancer compared to NHWs. All three Asian subgroups had a higher likelihood of being diagnosed by age 40 (14 % Chinese, 10 % South Asian and 8% Filipino compared to 3% in NHW; p < 0.001). Chinese males had lower odds of late-stage diagnosis, compared to NHWs. South Asian cases doubled from 2004 to 2013 largely due to an increase in OCC cases (34 cases in 2004 to 86 in 2013).ConclusionAsian diasporas are at a higher likelihood of specific HNSCCs. Risk factors, screening and survival need to be studied further, and policy changes are needed to promote screening and to discourage high-risk habits in these Asian subgroups.