HTII-280, a Biomarker Specific to the Apical Plasma Membrane of Human Lung Alveolar Type II Cells

The pulmonary alveolar epithelium is composed of two morphologically distinct cell types, type I (TI) and type II (TII) cells. Alveolar TII cells synthesize, secrete, and recycle surfactant components; contain ion transporters; and secrete immune effector molecules. In response to alveolar injury, TII cells have the capacity to act as progenitor cells, proliferating and transdifferentiating into TI cells. Although various proteins are associated with TII cells, a plasma membrane marker specific to human TII cells that would be useful for identification in tissue and for isolating this cell type has not been described previously. We devised a strategy to produce a monoclonal antibody (MAb) specific to the apical surface of human TII cells and developed an MAb that appears to be specific for human TII cells. The antibody recognizes a 280- to 300-kDa protein, HTII-280, which has the biochemical characteristics of an integral membrane protein. HTII-280 is detected by week 11 of gestation and is developmentally regulated. HTII-280 is useful for isolating human TII cells with purities and viabilities >95%. HTII-280 is likely to be a useful morphological and biochemical marker of human TII cells that may help to advance our understanding of various lung pathological conditions, including the origin and development of various lung tumors. (J Histochem Cytochem 58:891–901, 2010)     

Spatial variance of nutrient limitation of periphyton in montane, headwater streams (McLeod River, Alberta, Canada)

There have been few studies that have examined the spatial variance of nutrient limitation over the scale of an entire set of headwater streams. We used nutrient diffusing substrata experiments (control, nitrogen addition, phosphorus addition, and nitrogen+phosphorus addition) to examine how nutrient limitation varied throughout the five creeks that comprise the McLeod River headwaters (Alberta, Canada). We assessed the variance of chlorophyll a accrual at spatial scales within reach, within creek, among creeks and across linear distance within the entire watershed to assess the consistency and scale of nutrient limitation. We analyzed the importance of the spatial scale using several methods. We assessed the coefficient of variation at different scales, the spatial covariance of nitrogen and phosphorus deficiency indices using a spline correlogram, and the variance through traditional analyses of variance methods. Chlorophyll a accrual responded significantly to nutrients in all creeks, though the response varied in magnitude and in the limiting nutrient among reaches and among creeks. Variance in chlorophyll a accrual was due primarily to the factor of creek (R ²=0.40) and secondarily to reach (R ²=0.07). The CV was 31.4% among creeks, 18.4% among reaches, and 17.9% within reaches. The N deficiency index showed a positive correlation at sites located <4 km apart and a negative correlation at sites greater than 6.5 km apart. The P deficiency index showed no discernible spatial correlation. Our results suggest that nutrient limitation varies on small scales and is often driven by local processes.     

Alteration of the menstrual cycle in baboons placed on tethering devices and moved to individual housing--a stress model for a follicular phase defect

BACKGROUND: During an attempt to identify endocrine characteristics in the baboon that would more precisely predict ovulatory status for assisted reproductive techniques, we observed severe alterations in the menstrual cycle length upon introducing an environmental stress. This environmental stress involved moving animals from their baseline gang cage environment to individual indoor caging and placing them on a tethering apparatus. METHODS: Five adult female baboons were followed for changes in sex skin indicative of menstrual cycle timing and move from outdoor gang gages to individual indoor cages during the early follicular phase of their cycle. A tether device including a surgically implanted cannula was then installed to facilitate daily blood draws without sedation. Radioimmuonoassays were performed to monitor serum estradiol levels and lapraroscopic surveillance was used to confirm time of ovulation. RESULTS: Complete data sets were collected from four of the female baboons. In each case, a prolongation of the menstrual cycle was noted either during the cycle during which the females were moved to indoor caging or during the cycle immediately following the move. This prolongation was isolated to the follicular phase of the affected cycle. CONCLUSIONS: We conclude that otherwise normal handling procedures, including movement to new caging, and/or installation of a tether device, can impart a stress effect on reproductively cycling adult female baboons, such that folliculogenesis is delayed.     

Trichuris sp. and Strongyloides sp. infections in a free-ranging baboon colony

We conducted cross-sectional surveys of parasites infecting a large free-living colony of baboons at the Southwest National Primate Research Center in San Antonio in October 2003 and April 2004, immediately before, and 6 mo after, treatment with ivermectin. Trichuris sp. was the predominant species present, infecting 79 and 69% of individual animals in the 2 surveys, with fecal egg counts (FEC) of up to 60,200 eggs per g (epg) (mean = 1,235 in October 2003 and 1,256 in April 2004). Prevalence remained fairly stable across age groups, and intensity was highest in animals <1 or >15 yr old, in contrast to patterns observed in humans, where school-age children show the heaviest infections. Strongyloides sp. was also identified, but the species identity remains uncertain. Small subunit ribosomal DNA sequences differed from published sequences of Strongyloides fuelleborni at multiple sites, but resided in a monophyletic group with other Strongyloides species with 92% bootstrap support. This may reflect a recent acquisition from a local host, or that the published sequence of S. fuelleborni is incorrect. Widespread infections with 2 nematode genera in a free-ranging baboon colony that are an important source of morbidity in human populations provide a useful model system for work on the epidemiology, control, pathology, and genetics of these parasites in a host species that is physiologically, immunologically, and genetically similar to humans.     

Berger C. Mayne (1920–2011): a friend and his contributions to photosynthesis research

We provide here insights on the life and work of Berger C. Mayne (1920-2011). We remember and honor Berger, whose study of photosynthesis began with the most basic processes of intersystem electron transport and oxygen evolution, continued with application of fluorescence techniques to the study of photophosphorylation and the unique features of photosystems in specialized cells, and concluded with collaborative study of photosynthesis in certain nitrogen fixing symbioses. Berger loved the outdoors and was dedicated to preserving the environment and to social justice, and was a wonderful friend.     

The species–area relationship in centipedes (Myriapoda: Chilopoda): a comparison between Mediterranean island groups

The present study article examines the shapes of centipede species–area relationships (SARs) in the Mediterranean islands, compares the results of the linear form of the power model between archipelagos, discusses biological significance of the power model parameters with other taxa on the Aegean archipelago, and tests for a significant small‐island effect (SIE). We used 11 models to test the SARs and we compared the quality‐of‐fit of all candidate models. The power function ranked first and Z‐values was in the range 0.106–0.334. We assessed the presence of SIEs by fitting both a continuous and discontinuous breakpoint regression model. The continuous breakpoint regression functions never performed much better than the closest discontinuous model as a predictor of centipede species richness. We suggest that the relatively low Z‐values in our data partly reflect better dispersal abilities in centipedes than in other soil invertebrate taxa. Longer periods of isolation and more recent island formation may explain the somewhat lower constant c in the western Mediterranean islands compared to the Aegean islands. Higher breakpoint values in the western Mediterranean may also be a result of larger distance to the mainland and longer separation times. Despite the differences in the geological history and the idiosyncratic features of the main island groups considered, the overall results are quite similar and this could be assigned to the ability of centipedes to disperse across isolation barriers. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 146–159.     

The foldon substructure of staphylococcal nuclease

To search for submolecular foldon units, the spontaneous reversible unfolding and refolding of staphylococcal nuclease under native conditions was studied by a kinetic native-state hydrogen exchange (HX) method. As for other proteins, it appears that staphylococcal nuclease is designed as an assembly of well-integrated foldon units that may define steps in its folding pathway and may regulate some other functional properties. The HX results identify 34 amide hydrogens that exchange with solvent hydrogens under native conditions by way of large transient unfolding reactions. The HX data for each hydrogen measure the equilibrium stability (ΔG_HX) and the kinetic unfolding and refolding rates (k_op and k_cl) of the unfolding reaction that exposes it to exchange. These parameters separate the 34 identified residues into three distinct HX groupings. Two correspond to clearly defined structural units in the native protein, termed the blue and red foldons. The remaining HX grouping contains residues, not well separated by their HX parameters alone, that represent two other distinct structural units in the native protein, termed the green and yellow foldons. Among these four sets, a last unfolding foldon (blue) unfolds with a rate constant of 6 × 10^− 6 s^− 1 and free energy equal to the protein's global stability (10.0 kcal/mol). It represents part of the β-barrel, including mutually H-bonding residues in the β4 and β5 strands, a part of the β3 strand that H-bonds to β5, and residues at the N-terminus of the α2 helix that is capped by β5. A second foldon (green), which unfolds and refolds more rapidly and at slightly lower free energy, includes residues that define the rest of the native α2 helix and its C-terminal cap. A third foldon (yellow) defines the mutually H-bonded β1-β2-β3 meander, completing the native β-barrel, plus an adjacent part of the α1 helix. A final foldon (red) includes residues on remaining segments that are distant in sequence but nearly adjacent in the native protein. Although the structure of the partially unfolded forms closely mimics the native organization, four residues indicate the presence of some nonnative misfolding interactions. Because the unfolding parameters of many other residues are not determined, it seems likely that the concerted foldon units are more extensive than is shown by the 34 residues actually observed.