A financial analysis of twenty-one small business groups in Greater Boston from 1949 through 1952

Thesis (M.B.A.)--Boston Universit

Non-Destructive Lichen Biomass Estimation in Northwestern Alaska: A Comparison of Methods

Terrestrial lichen biomass is an important indicator of forage availability for caribou in northern regions, and can indicate vegetation shifts due to climate change, air pollution or changes in vascular plant community structure. Techniques for estimating lichen biomass have traditionally required destructive harvesting that is painstaking and impractical, so we developed models to estimate biomass from relatively simple cover and height measurements. We measured cover and height of forage lichens (including single-taxon and multi-taxa ‘‘community’’ samples, n = 144) at 73 sites on the Seward Peninsula of northwestern Alaska, and harvested lichen biomass from the same plots. We assessed biomass-to-volume relationships using zero-intercept regressions, and compared differences among two non-destructive cover estimation methods (ocular vs. point count), among four landcover types in two ecoregions, and among single-taxon vs. multi-taxa samples. Additionally, we explored the feasibility of using lichen height (instead of volume) as a predictor of stand-level biomass. Although lichen taxa exhibited unique biomass and bulk density responses that varied significantly by growth form, we found that single-taxon sampling consistently under-estimated true biomass and was constrained by the need for taxonomic experts. We also found that the point count method provided little to no improvement over ocular methods, despite increased effort. Estimated biomass of lichen-dominated communities (mean lichen cover: 84.9 ± 1.4%) using multi-taxa, ocular methods differed only nominally among landcover types within ecoregions (range: 822 to 1418 g m⁻²). Height alone was a poor predictor of lichen biomass and should always be weighted by cover abundance. We conclude that the multi-taxa (whole-community) approach, when paired with ocular estimates, is the most reasonable and practical method for estimating lichen biomass at landscape scales in northwest Alaska.Keywords: Macrolichen communities, Bryophyte

Environmental optimality, not heterogeneity, drives regional and local species richness in lichen epiphytes

Aim: We evaluate the scale dependence of species richness–environment relationships with a continent-wide analysis of lichen epiphyte communities. Specifically, our goals are to assess: (1) the dependence of local richness on regional processes, (2) whether species richness is primarily influenced by heterogeneity in environmental conditions or the central tendency of those conditions, and (3) whether the relative influence of these different aspects of the environment differs between local communities and regional species pools. Location: Forests of the contiguous United States. Methods: We used variation partitioning and model averaging of linear models to relate macrolichen richness at 1923 forest inventory plots (c. 4000 m2) to measures of environmental heterogeneity and mean conditions at local and regional scales. Data included 17 local environmental variables and 11 regional-scale variables which were obtained from a national forest inventory, herbarium records and several climate data sources. Results: Regional-scale variables explained more unique variation in local species richness and generally had stronger effects than variables measured locally. However, most variation in local richness was explained jointly by local and regional variables. At both local and regional scales, variables measuring environmental heterogeneity explained little variation in species richness and had weaker effects than variables characterizing mean environmental conditions. Main conclusions: Species richness of epiphytic macrolichens is not regulated by environmental heterogeneity locally or regionally and instead tracks large-scale climate gradients of water availability and temperature. Richness in local communities is influenced by processes operating at both regional and local scales, highlighting the importance of determining large-scale drivers of lichen richness across the North American continent. This research demonstrates a general method for comparing the influence of different aspects of the environment on species richness across scales and should be applicable to many different taxonomic groups

Three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective analysis of feasibility and adverse reaction to contrast material.

BACKGROUND: Computed Tomography Cholangiography (CTC) is a fast and widely available alternative technique to visualise hepatobiliary disease in patients with an inconclusive ultrasound when MRI cannot be performed. The method has previously been relatively unknown and sparsely used, due to concerns about adverse reactions and about image quality in patients with impaired hepatic function and thus reduced contrast excretion. In this retrospective study, the feasibility and the frequency of adverse reactions of CTC when using a drip infusion scheme based on bilirubin levels were evaluated. METHODS: The medical records of patients who had undergone upper abdominal spiral CT with subsequent three-dimensional rendering of the biliary tract by means of CTC during seven years were retrospectively reviewed regarding serum bilirubin concentration, adverse reaction and presence of visible contrast media in the bile ducts at CT examination. In total, 153 consecutive examinations in 142 patients were reviewed. RESULTS: Contrast media was observed in the bile ducts at 144 examinations. In 110 examinations, the infusion time had been recorded in the medical records. Among these, 42 examinations had an elevated bilirubin value (>19 umol/L). There were nine patients without contrast excretion; 3 of which had a normal bilirubin value and 6 had an elevated value (25–133 umol/L). Two of the 153 examinations were inconclusive. One subject (0.7%) experienced a minor adverse reaction – a pricking sensation in the face. No other adverse effects were noted. CONCLUSION: We conclude that drip infusion CTC with an infusion rate of the biliary contrast agent iotroxate governed by the serum bilirubin value is a feasible and safe alternative to MRC in patients with and without impaired biliary excretion. In this retrospective study the feasibility and the frequency of adverse reactions when using a drip infusion scheme based on bilirubin levels has been evaluated

Immunological comparison of the usual and atypical human serum cholinesterase phenotypes

Antiserum prepared against highly purified usual human serum cholinesterase (the most common phenotype) cross-reacted identically with the atypical serum cholinesterase. The level of circulating atypical enzyme protein, determined immunologically, was about 30% lower when the enzyme came from an atypical rather than a usual phenotype, and the level of enzyme activity measured enzymatically at V max with either o -nitrophenylbutyrate or benzoylcholine as substrate showed approximately the same degree of reduction. The average specific activity (activity at V max per microgram of enzyme protein) in sera from 28 usual and 20 atypical individuals did not differ significantly. These findings suggest that the atypical enzyme not only has altered catalytic properties ( K ) m but also might be synthesized more slowly, or cleared in vivo more rapidly, than the usual enzyme.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44145/1/10528_2004_Article_BF00498901.pd

Genetic variants of human serum cholinesterase influence metabolism of the muscle relaxant succinylcholine

People with genetic variants of cholinestrase respond abnormally to succinylcholine, experiencing substantial prolongation of muscle paralysis with apnea rather than the usual 2-6 min. The structure of usual cholinesterase has been determined including the complete amino acid and nucleotide sequence. This has allowed identification of altered amino acids and nucleotides. The variant most frequently found in patients who respond abnormally to succinylcholine is atypical cholonesterase, which occurs in homozygous from in 1 out of 3500 Caucasians. Atypical cholinesterase has a single substitution at nucleotide 209 which changes aspartic acid 70 to glycine. This suggests that Asp 70 is part of the anionic site, and that the absence of this negatively charged amino acid explains the reduced affinity of atypical cholinesterase for positively charged substrates and inhibitors. The clinical consequence of reduced affinity for succinylcholine is that one of the succinylcholine is hydrolyzed in blood and a large overdose reaches the nerve-muscle junction where junction where it causes prolonged muscle paralysis. Silent cholinesterase has a frame mutation at glycine 117 which prenaturely terminates protein synthesis and yields no enzyme. The K variant, named in honor of W. Kalow, has threonine in place of alanine 539. The K variant is associated with 33% lower activity. All variants arise from a single locus as there is only one gene for human cholinestrase (EC 3.1.1.8). Comparison of amino acid sequences of esterases and proteases shows that cholinesterase belongs to a new family of serine esterases which is different from the serine proteases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28774/1/0000606.pd