Fluctuations of grass pollen content in the atmosphere of East Perugia and meteorological correlations (year 1989)

Summary Gramineae pollination from a pollen monitoring station located in the eastern suburb of Perugia and meteorological correlations are reported. The data refers to the year 1989. Grass pollen peak pollination was from May to July; in this period the influence of relative humidity and of temperature on pollen concentration was very high. Phenological observations, to identify the time of maximum stamen extension in the most common genera in the area, are also reported. During the period of investigation the counts of pollen grains over four-hour periods showed a regular diurnal rhythm with peaks of concentration in the four-hour period 16.00–20.00. Aerosporological data and meteorological data related to four-hour periods were correlated following different criteria.     

Circular dichroism spectroscopy of the intermediates that precede the rate-limiting step of the refolding pathway of bovine pancreatic trypsin inhibitor. Relationship of conformation and the refolding pathway

Circular dichroism spectra of the partially folded trapped intermediates were measured in order to aid in the elucidation of the conformational forces which determine a nonrandom, nonsequential pathway of disulfide bond formation upon refolding of bovine pancreatic trypsin inhibitor. Whatever conformation was responsible for the kinetic rates of the intermediates should be stabilized by the presence of their trapped disulfide bonds. The near-ultraviolet spectra provide considerable information about the environments of the aromatic and disulfide side chains. The predominant single-disulfide intermediate has significant nonrandom conformation not present in the fully reduced protein, with aromatic rings and the disulfide bond in stabilized asymmetric environments. Forming either of the two nonnative, but kinetically important, second disulfides in this intermediate does not produce unequivocably different conformations. Forming a second native, but kinetically unproductive, disulfide produces a substantial decrease in randomness, which may hinder formation of the third disulfide. The largest conformational changes occur upon disulfide rearrangement to the stable, correctly refolded, two- and three-disulfide species. Interpretation of the far-ultraviolet spectra in terms of the secondary structure of the intermediates is uncertain, due to the atypical spectra of the folded forms of the protein. Consequently, we are unable to determine unambiguously the secondary structure of the intermediates. However, all the spectra show that nonrandom conformations of the polypeptide chain gradually appear as disulfide bond formation progresses, as expected from the nonrandom pathway of the latter.     

Seasonal variation of nitrification along a salinity gradient in an urban estuary

A review on salinity adaptation of marine molluscsbased on mainly Russian scientific literature ispresented. The existence of two relativelyindependent systems of adaptation to extreme(resistance level) and moderate (tolerance level)changes of environmental salinity was shown. Theresistance of molluscs is based mainly on an impededwater-salt exchange with the external medium due tomantle cavity hermetization. The tolerance ofmolluscs is determined by cellular mechanisms ofadaptation. Reversible changes of protein and RNAsynthesis, alteration of the pattern of multiplemolecular forms of different enzymes, and theregulation of ionic content and cell volume wereshown to be of importance for the above mentionedmechanisms. The efficiency of resistance andtolerance adaptations to salinity changes may varyin different species and in different colourphenotypes of the same species (intrapopulationalpolymorphism). Parasites (trematodes) may suppressthe resistance of the mollusc-host to extremesalinity changes without effecting the host'scapacity for adaptive changes in salinitytolerance.     

Limiting rates of ligand association to alcohol dehydrogenase.

Detailed stopped-flow kinetic studies of the association of 2,2-bipyridine, 1,10-phenanthroline, and 5-chloro-1,10-phenanthroline to the zinc ion at the active site of alcohol dehydrogenase have demonstrated that a process with a limiting rate constant of about 200 s^?1 restricts the binding of the bidentate chelating agents to the free enzyme. The formation of the enzyme-ligand complexes has been followed by means of the characteristic absorption spectra of the resulting complexes or by the displacement of the fluorescent dye, auramine O. Monodentate ligands, upon binding to the free enzyme or enzyme-NAD⁺ and enzyme-NADH complexes, do not exhibit a comparable limiting rate. In analogy with simple inorganic systems, these observations have been interpreted in terms of the rate limiting dissociation of an inner sphere water molecule following the rapid formation by the bidentate ligand of an outer sphere complex. The displacement of a water molecule from the zinc ion by 1,10-phenanthroline has been observed in crystallographic studies which have also established that the zinc ion in the enzyme-1,10-phenanthroline complex is pentacoordinate. Monodentate ligands, which are substrate analogs, do not exhibit limiting rates because displacement of water is not required for their addition to a coordinate position which is apparently vacant in the free enzyme. If a water molecule remains bound to the zinc ion in the kinetically competent ternary complex, it could play an essential role in the proton transfer reaction accompanying catalysis.     

Emergence activity at hibernacula differs among four bat species affected by white‐nose syndrome

Prior to the introduction of white‐nose syndrome (WNS) to North America, temperate bats were thought to remain within hibernacula throughout most of the winter. However, recent research has shown that bats in the southeastern United States emerge regularly from hibernation and are active on the landscape, regardless of their WNS status. The relationship between winter activity and susceptibility to WNS has yet to be explored but warrants attention, as it may enable managers to implement targeted management for WNS‐affected species. We investigated this relationship by implanting 1346 passive integrated transponder (PIT) tags in four species that vary in their susceptibility to WNS. Based on PIT‐tag detections, three species entered hibernation from late October to early November. Bats were active at hibernacula entrances on days when midpoint temperatures ranged from −1.94 to 22.78°C (mean midpoint temperature = 8.70 ± 0.33°C). Eastern small‐footed bats (Myotis leibii), a species with low susceptibility to WNS, were active throughout winter, with a significant decrease in activity in mid‐hibernation (December 16 to February 15). Tricolored bats (Perimyotis subflavus), a species that is highly susceptible to WNS, exhibited an increase in activity beginning in mid‐hibernation and extending through late hibernation (February 16 to March 31). Indiana bats (M. sodalis), a species determined to have a medium–high susceptibility to WNS, remained on the landscape into early hibernation (November 1 to December 15), after which we did not record any again until the latter portion of mid‐hibernation. Finally, gray bats (M. grisescens), another species with low susceptibility to WNS, maintained low but regular levels of activity throughout winter. Given these results, we determined that emergence activity from hibernacula during winter is highly variable among bat species and our data will assist wildlife managers to make informed decisions regarding the timing of implementation of species‐specific conservation actions.     

Allometric Models for Predicting Aboveground Biomass in Two Widespread Woody Plants in Hawaii

Allometric models are important for quantifying biomass and carbon storage in terrestrial ecosystems. Generalized allometry exists for tropical trees, but species‐ and site‐specific models are more accurate. We developed species‐specific models to predict aboveground biomass in two of the most ubiquitous natives in Hawaiian forests and shrublands, Metrosideros polymorpha and Dodonaea viscosa. The utility of the M. polymorpha allometry for predicting biomass across a range of sites was explored by comparing size structure (diameter at breast height vs. tree height) of the trees used to develop the models against trees from four M. polymorpha‐dominated forests along a precipitation gradient (1630–2380 mm). We also compared individual tree biomass estimated with the M. polymorpha model against existing generalized equations, and the D. viscosa model with an existing species‐specific model. Our models were highly significant and displayed minimal bias. Metrosideros polymorpha size structures from the three highest precipitation sites fell well within the 95% confidence intervals for the harvested trees, indicating that the models are applicable at these sites. However, size structure in the area with the lowest precipitation differed from those in the higher rainfall sites, emphasizing that care should be taken in applying the models too widely. Existing generalized allometry differed from the M. polymorpha model by up to 88 percent, particularly at the extremes of the data range examined, underestimating biomass in small trees and overestimating in large trees. The existing D. viscosa model underestimated biomass across all sizes by a mean of 43 percent compared to our model. The species‐specific models presented here should enable more accurate estimates of biomass and carbon sequestration in Hawaiian forests and shrublands.