Use of aerosols to estimate mean air-space size in chronic obstructive pulmonary disease

Using in vivo measures of aerosol recovery (RC) as a function of breath-hold time (t) (Gebhart et al. J. Appl. Physiol. 51: 465-476, 1981), we estimated the mean diameter (D) of the pulmonary air spaces in subjects diagnosed with chronic obstructive pulmonary disease (COPD) (n = 8) and in subjects with normal pulmonary function (n = 10). For each subject, RC (aerosol expired/aerosol inspired) decreased exponentially with t. Based on a model of the lung as a system of randomly oriented cylindrical tubes, the half time (t1/2) (i.e., the breath-hold time to reach 50% of RC with no breath hold) is proportional to a mean diameter (D) of air spaces filled with aerosol. Subjects with normal pulmonary function had a mean t1/2 = 6.5 +/- 0.8 s, corresponding to a mean D = 0.36 +/- 0.05 mm. On the other hand, subjects with COPD had a mean t1/2 = 12.7 +/- 3.2 s, corresponding to a mean D = 0.70 +/- 0.18 mm [i.e., twice as large (P less than 0.01) as normal subjects]. Furthermore, D correlated significantly with diffusing capacity in the patients with COPD (r = -0.95, P less than 0.001 for D vs. percent predicted diffusing capacity of CO) but not with any other measure of pulmonary function. In contrast, D varied only slightly in normals and did not correlate with any measure of pulmonary function. We conclude that in vivo measures of RC vs. t, in conjunction with other pulmonary function tests, may be a useful tool for identifying actual changes in pulmonary air-space sizes associated with pulmonary disease.     

Perfusion dehydration fixes elastin and preserves lung air-space dimensions

We sought a technique to preserve lung tissue for micrography with air-space dimensions unchanged from the fresh state. In our hands, conventional techniques were problematical. Aware of the possibility that distortion might be caused by inadequate mechanical fixation of elastin, we dehydrated the still-inflated lung by intravascular perfusion with graded ethanols. Canine and rabbit lungs so prepared had straighter alveolar septa, greater air-space dimensions, and an improved correlation with light-scattering measurements. Bovine ligamentum nuchae (mostly elastin) was only partially fixed by glutaraldehyde or osmium tetroxide but was effectively stiffened by dehydration. We conclude that perfusion dehydration aids in the faithful preservation of parenchymal configuration, probably by mechanical fixation of elastin.     

Use of aerosols to measure in vivo volume-dependent changes in lung air space dimensions

Using measurements of aerosol recovery following a 5-s breath hold [NRC(5)] as indices of lung air space dimensions, we evaluated the in vivo changes in these dimensions associated with changes in lung volume (VL). In anesthetized dogs, single breaths of a 1.2-micron monodisperse aerosol were introduced into the respirator's cycle at a number of isovolume points on the inflation and deflation limb of the pressure-volume curve for the dog's lungs. At isovolume, NRC(5) measured off the inflation limb was slightly larger than NRC(5) measured off the deflation limb, implying a larger mean air space dimension for the air space configuration on the inflation vs. the deflation limb. Since a constant aerosol tidal volume (VT) was used for all VL in all dogs, the proportion of the lung filled with aerosol, VT/VL = Pn (where Pn is defined as an index of aerosol penetration into the lung periphery), varied along with VL. In all dogs, we found that, for NRC(5) measurements with Pn less than 0.33, NRC(5) steadily increased with increasing VL, which implies an increasing mean air space dimension as VL increases. However, when we account for the effect that changes in Pn with increasing VL have on NRC(5), we conclude that the observed increase in NRC(5) with VL is primarily due to decreases in Pn and not increases in the mean air space dimension as VL increases.(ABSTRACT TRUNCATED AT 250 WORDS)     

Simple stereological procedure to estimate the number and dimensions of root hairs

We demonstrate a simple procedure for systematic, uniformly random sampling of a root system of known length to obtain practically unbiased estimates of the total number and dimensions of root hairs. Irrespective of the length of the root system, only 100 root hairs need to be counted to estimate the total number with sufficient precision. Numbers and dimensions of root hairs were estimated for five crested wheatgrass (Agropyron cristatum L.) root systems that had been grown for one month in a gel. Less than one hour was required to obtain estimates of root hair parameters for a single plant. There was low variability of spatial density of root hairs within a given branching order (CV < 15%); however, because of large variation in the total length of laterals, the total number of root hairs varied greatly (CV ∼70%). On average, root hairs provided half of the total surface area of a root system and a total length 20 times that of the roots. This revised version was published online in June 2006 with corrections to the Cover Date.     

Use of fractal dimensions to quantify coral shape

A morphometrical method to quantify and characterize coral corallites using Richardson Plots and Kaye’s notion of fractal dimensions is presented. A Jurassic coral species (Aplosmilia spinosa) and five Recent coral species were compared using the Box-Counting Method. This method enables the characterization of their morphologies at calicular and septal levels by their fractal dimensions (structural and textural). Moreover, it is possible to determine differences between species of Montastraea and to tackle the high phenotypic plasticity of Montastraea annularis. The use of fractal dimensions versus conventional methods (e.g., measurements of linear dimensions with a calliper, landmarks, Fourier analyses) to explore a rugged boundary object is discussed. It appears that fractal methods have the potential to considerably simplify the morphometrical and statistical approaches, and be a valuable addition to methods based on Euclidian geometry.     

Using multivariate adaptive regression splines to estimate subadult age from diaphyseal dimensions

Subadult age estimation is considered the most accurate parameter estimated in a subadult biological profile, even though the methods are deficient and the samples from which they are based are inappropriate. The current study addresses the problems that plague subadult age estimation and creates age estimation models from diaphyseal dimensions of modern children. The sample included 1,310 males and females between the ages of birth and 12 years. Eighteen diaphyseal length and breadth measurements were obtained from Lodox Statscan radiographic images generated at two institutions in Cape Town, South Africa, between 2007 and 2012. Univariate and multivariate age estimation models were created using multivariate adaptive regression splines. k‐fold cross‐validated 95% prediction intervals (PIs) were created for each model, and the precision of each model was assessed. The diaphyseal length models generated the narrowest PIs (2 months to 6 years) for all univariate models. The majority of multivariate models had PIs that ranged from 3 months to 5 and 6 years. Mean bias approximated 0 for each model, but most models lost precision after 10 years of age. Univariate diaphyseal length models are recommended for younger children, whereas multivariate models are recommended for older children where the inclusion of more variables minimized the size of the PIs. If diaphyseal lengths are not available, multivariate breadth models are recommended. The present study provides applicable age estimation formulae and explores the advantages and disadvantages of different subadult age estimation models using diaphyseal dimensions. Am J Phys Anthropol 154:376–386, 2014. © 2014 Wiley Periodicals, Inc.     

Use of surface electromyography to estimate neck muscle activity

This paper reviews the literature concerning the use of surface electromyography (sEMG) for the study of the neck musculature in response to work and workplace design during light work and semi-static tasks. The paper also draws upon basic research and biomechanical modeling in order to provide methodological recommendations for the use of surface electromyography in this region of the body and to identify areas which require further investigation. The paper includes review and discussion of electrode site location, methods of normalization, data reliability, and factors that can affect sEMG signals from this region, including noise, physiologic artifact, stress, visual deficiencies, and pain. General guidance for maximum exertions with the neck musculature, for sEMG normalization or other purposes, is also included.     

Use of distraction loading to estimate subject-specific knee ligament slack lengths

Knee ligaments guide and restrain joint motion, and their properties influence joint mechanics. Inverse modeling schemes have been used to estimate specimen-specific ligament properties, where external joint forces are assumed to balance with internal ligament and contact forces. This study simplifies this assumption by adjusting experimental loads to remove internal contact forces. The purpose of this study was to use novel experimental loading in an inverse modeling scheme to estimate ligament slack lengths, perform validation using additional loading scenarios, and evaluate sensitivity to the applied loading. Joint kinematics and kinetics were experimentally measured for a set of load cases. An optimization scheme used a specimen-specific forward kinematics model to estimate ligament slack lengths by minimizing the residual between model and experimentally measured kinetics. The calibrated model was used for a form of validation by evaluating non-optimized load cases. Additionally, uncertainty analysis related kinetic errors to previously reported kinematic errors. The six DOF tibial reactions realized RMS errors less than 23 N and 0.75 Nm for optimized load cases, and 33 N and 2.25 Nm for the non-optimized load cases. The uncertainty analysis, which was performed using the optimized load cases, showed average kinetic RMS errors less than 26 N and 0.45 Nm. The model’s recruitment patterns were similar to those found in clinical and cadaveric studies. This study demonstrated that experimental distraction loading can be used in an inverse modeling scheme to estimate ligament slack lengths with a forward kinematics model.     

Use of impedance measurements to estimate numbers of antibiotic resistant Salmonella strains

Impedance detection times were compared with traditional plating methods for enumerating antibiotic-resistant strains of Salmonella stanley, Salm. thompson and Salm. infantis grown in laboratory medium and pork slurry. The correleation of log₁₀ counts of salmonellas with detection times was highly significant ( r = -0·96 for broth and r = -0·94 for slurries. The confidence limits (± og₁₀ 1·0 for broth and ± log₁₀ 1·65 for slurry) indicated that detection times could reliably be used as a rapid means of enumerating salmonellas when large numbers of counts of known strains are required for growth studies. Use of antibiotic-resistant strains also permitted their selective detection by impedance from the natural spoilage flora of pork slurry when the same antibiotics were incorporated in the detection medium.     

Use of chitin measurement to estimate fungal biomass in solid state fermentation

Twenty-two strains of twelve species of Deuteromycotina: Hyphomycetes were studied. Most of them had a variable glucosamine amount (standard deviation higher than 5%). However, if we consider that the amount of glucosamine is constant, the accuracy of the method remains satisfactory (10% instead of 5%, which is the accuracy of the chitin hydrolysis and colorimetric glucosamine measurement). So, by means of this measurement, the fungal growth kinetics could be followed on different solid media (vegetable material such as sugar beet pulp and sponge or mineral like clay granules) used. It is important to note that this method should not be used to compare different media without calibration.     

Use of short-term breath measures to estimate daily methane production by cattle

Methods to measure enteric methane (CH₄) emissions from individual ruminants in their production environment are required to validate emission inventories and verify mitigation claims. Estimates of daily methane production (DMP) based on consolidated short-term emission measurements are developing, but method verification is required. Two cattle experiments were undertaken to test the hypothesis that DMP estimated by averaging multiple short-term breath measures of methane emission rate did not differ from DMP measured in respiration chambers (RC). Short-term emission rates were obtained from a GreenFeed Emissions Monitoring (GEM) unit, which measured emission rate while cattle consumed a dispensed supplement. In experiment 1 (Expt. 1), four non-lactating cattle (LW=518 kg) were adapted for 18 days then measured for six consecutive periods. Each period consisted of 2 days of ad libitum intake and GEM emission measurement followed by 1 day in the RC. A prototype GEM unit releasing water as an attractant (GEM water) was also evaluated in Expt. 1. Experiment 2 (Expt. 2) was a larger study based on similar design with 10 cattle (LW=365 kg), adapted for 21 days and GEM measurement was extended to 3 days in each of the six periods. In Expt. 1, there was no difference in DMP estimated by the GEM unit relative to the RC (209.7 v. 215.1 g CH₄/day) and no difference between these methods in methane yield (MY, 22.7 v. 23.7 g CH₄/kg of dry matter intake, DMI). In Expt. 2, the correlation between GEM and RC measures of DMP and MY were assessed using 95% confidence intervals, with no difference in DMP or MY between methods and high correlations between GEM and RC measures for DMP (r=0.85; 215 v. 198 g CH₄/day SEM=3.0) and for MY (r=0.60; 23.8 v. 22.1 g CH₄/kg DMI SEM=0.42). When data from both experiments was combined neither DMP nor MY differed between GEM- and RC-based measures (P>0.05). GEM water-based estimates of DMP and MY were lower than RC and GEM (P<0.05). Cattle accessed the GEM water unit with similar frequency to the GEM unit (2.8 v. 3.5 times/day, respectively) but eructation frequency was reduced from 1.31 times/min (GEM) to once every 2.6 min (GEM water). These studies confirm the hypothesis that DMP estimated by averaging multiple short-term breath measures of methane emission rate using GEM does not differ from measures of DMP obtained from RCs. Further, combining many short-term measures of methane production rate during supplement consumption provides an estimate of DMP, which can be usefully applied in estimating MY.     

Use of cytosolic metabolite patterns to estimate free magnesium in normoxic myocardium

Cytosolic free magnesium (Mg_f) is considered relatively constant. To test this concept, Mg_f was estimated during hyperkalemic ventricular akinesis, normal and maximum adrenergic stimulation, and sulfate loading of the normoxic perfused guinea-pig heart. The Mg_f estimates utilized a new sliding scale derived from the Mg²⁺-dependence of glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase (GAPDH/PGK). The pseudo constant K_GAPDH′·K_PGK′ was measured as ([creatine phosphate][3-phosphoglycerate][lactate]K_LDH/([creatine][P_i[glyceraldehyde 3-phosphate][pyruvate]K_CK), which varied with magnesium due to K_CK (CK, LDH = creatine kinase, lactate dehydrogenase). However, the correct magnesium dependencies of the true constants K_GAPDH·K_PGK and K_CK were taken from the literature. The [Mg²⁺] at which pseudo K_GAPDH′·K_PGK′ equalled true K_GAPDH·K_PGK was the best estimate of Mg_f. Mg_f fell to ≈0.13 mM in hyperkalemic arrest from a control of ≈0.6 mM, rising to ≈0.85 mM only during maximum adrenergic stress. Mg_f increased further to ≈1.3 mM during sulfate loading which induced ATP catabolism. Mg_f and ATP were reciprocally related. Thus; (1) myocardial free [Mg²⁺] judged from GAPDH/PGK mass-action relations changed appreciably only under extreme physiological states; (2) ATP was a major chelator of Mg²⁺ in perfused myocardium, i.e., acute ATP pool size reduction may be associated with increments in Mg_f.     

Liposomal dry powders as aerosols for pulmonary delivery of proteins

The purpose of this research was to develop liposomal dry powder aerosols for protein delivery. The delivery of stable protein formulations is essential for protein subunit vaccine delivery, which requires local delivery to macrophages in the lungs. β-Glucuronidase (GUS) was used as a model protein to evaluate dry powder liposomes as inhaled delivery vehicles. Dimyristoyl phosphatylcholine:cholesterol (7∶3) was selected as the liposome composition. The lyophilization of liposomes, micronization of the powders, aerosolization using a dry powder inhaler (DPI), and in vitro aerodynamic fine particle fraction upon collection in a twinstage liquid impinger were evaluated. After lyophilization and jet-milling, the total amount of GUS and its activity, representing encapsulation efficiency and stability, were evaluated. The GUS amount and activity were measured and compared with freshly-prepared liposomes in the presence of mannitol, 43% of initial GUS amount, 29% of GUS activity after lyophilization and 36% of GUS amount, 22% of activity after micronization were obtained. Emitted doses from dry powder inhaler were 53%, 58%, 66%, and 73% for liposome powder:mannitol carrier ratios of 1∶0, 1∶4, 1∶9, and 1∶19. Fifteen percent of the liposome particles were less than 6.4 μm in aerodynamic diameter. The results demonstrate that milled liposome powders containing protein molecules can be aerosolized effectively at a fixed flow rate. Influences of different cryoprotectants on lyophilization of protein liposome formulations are reported. The feasibility of using liposomal dry powder aerosols for protein delivery has been demonstrated but further optimization is required in the context of specific therapeutic proteins. Published: December 21, 2005     

Use of artificial seedlings to estimate damage of forest seedlings due to litterfall and animals

Abstract. The artificial seedling assay method has been used in several tropical and temperate forests to estimate seedling damage and subsequent mortality due to non‐trophic micro‐disturbances such as litterfall and trampling. However, there has been no evidence presented to support the assumption that artificial seedling damage correlates with natural seedling mortality. In this study we evaluated the use of artificial seedlings in five New Zealand forests by comparing damage rates of artificial seedlings with damage and mortality rates of an equal number of selected natural seedlings. A total of 1200 artificial, and 1200 natural seedlings were monitored monthly for two years. Litterfall damage rates of natural seedlings were correlated with those of artificial seedlings. However, there was no relationship found between artificial and natural seedling damage due to animals, or between artificial seedling damage and natural seedling mortality for either cause. Artificial seedlings should not therefore be used to estimate seedling mortality due to non‐trophic microdisturbance. Monitoring natural seedlings enabled non‐trophic animal damage to be readily detected and provided additional information on animal‐plant interactions. The value of using artificial seedlings is that they provide a measure of the litterfall disturbance potential that is independent of the patchy distribution of natural seedlings within safe sites, and independent of species specific resistance to damage. They therefore provide an indication of the selective pressure on seedlings due to litterfall and are useful for comparing the relative ‘safety’ of different forests and microsites. Monitoring natural seedlings provides a measure of the damage and mortality due to litterfall for a specific seedling size class. Concurrently monitoring artificial and natural seedlings for litterfall disturbance provides more information than the same effort expended on either method alone.