bluuebunny/crossref_metadata_2025 huggingface dataset:
MLR-induced inhibition of barosensory cells in the NTS
Authors: Degtyarenko Alexandr M. , Kaufman Marc P.
Published: July 2005

A central motor command arising from the mesencephalic locomotor region (MLR) is widely believed to be one of the neural mechanisms that reset the baroreceptor reflex upward during exercise. The nucleus tractus solitarius (NTS), a dorsal medullary site that receives input from baroreceptors, may be the site where central command inhibits baroreceptor input during exercise. We, therefore, examined the effect of electrical stimulation of the MLR on the impulse activity of cells in the NTS in decerebrate paralyzed cats. Of 129 NTS cells tested for baroreceptor input by injection of phenylephrine (7–25 μg/kg iv) or inflation of a balloon in the carotid sinus, 58 were stimulated and 19 were inhibited. MLR stimulation (80–150 μA) inhibited the discharge of 48 of the 58 cells stimulated by baroreceptor input. MLR stimulation had no effect on the discharge of the remaining 10 cells, each of which displayed no spontaneous activity. In contrast to the 77 NTS cells responsive to baroreceptor input, there was no change in activity of 52 cells when arterial pressure was increased by phenylephrine injection or balloon inflation. MLR stimulation activated each of the 52 NTS cells. For 23 of the cells, the onset latency to MLR stimulation was clearly discernable, averaging 6.4 ± 0.4 ms. Our findings provide electrophysiological evidence for the hypothesis that the MLR inhibits the baroreceptor reflex by activating NTS interneurons unresponsive to baroreceptor input. In turn, these interneurons may release an inhibitory neurotransmitter onto NTS cells receiving baroreceptor input.
Advances in biochemical and functional roles of angiotensin-converting enzyme 2 and angiotensin-(1–7) in regulation of cardiovascular function
Authors: Ferrario Carlos M. , Trask Aaron J. , Jessup Jewell A.
Published: July 2005

Angiotensin-converting enzyme 2 (ACE2) is the first human homologue of ACE to be described. ACE2 is a type I integral membrane protein that functions as a carboxypeptidase, cleaving a single hydrophobic/basic residue from the COOH-terminus of its substrates. Because ACE2 efficiently hydrolyzes the potent vasoconstrictor angiotensin II to angiotensin (1–7), this has changed our overall perspective about the classical view of the renin angiotensin system in the regulation of hypertension and heart and renal function, because it represents the first example of a feedforward mechanism directed toward mitigation of the actions of angiotensin II. This paper reviews the new data regarding the biochemistry of angiotensin-(1–7)-forming enzymes and discusses key findings such as the elucidation of the regulatory mechanisms participating in the expression of ACE2 and angiotensin-(1–7) in the control of the circulation.
Dynamic and static baroreflex control of muscle sympathetic nerve activity (SNA) parallels that of renal and cardiac SNA during physiological change in pressure
Authors: Kamiya Atsunori , Kawada Toru , Yamamoto Kenta , Michikami Daisaku , Ariumi Hideto , Miyamoto Tadayoshi , Shimizu Shuji , Uemura Kazunori , Aiba Takeshi , Sunagawa Kenji , Sugimachi Masaru
Published: July 2005

Despite accumulated knowledge on human baroreflex control of muscle sympathetic nerve activity (SNA), whether baroreflex control of muscle SNA parallels that of other SNAs, in particular renal and cardiac SNAs, remains unclear. Using urethane and α-chloralose-anesthetized, vagotomized and aortic-denervated rabbits ( n = 10), we recorded muscle SNA from tibial nerve by microneurography, simultaneously with renal and cardiac SNAs by wire electrode. To produce a baroreflex open-loop condition, we isolated the carotid sinuses from systemic circulation and altered the intracarotid sinus pressure (CSP) according to a binary white noise sequence of operating pressure ± 20 mmHg (for investigating dynamic characteristics of baroreflex) or in stepwise 20-mmHg increments from 40 to 160 mmHg (for investigating static characteristics of baroreflex). Dynamic high-pass characteristics of baroreflex control of muscle SNA, assessed by the increasing slope of transfer gain, showed that more rapid change of arterial pressure resulted in greater response of muscle SNA to pressure change and that these characteristics were similar to cardiac SNA but greater than renal SNA. However, numerical simulation based on the transfer function shows that the differences in dynamic baroreflex control at various organs result in detectable differences among SNAs only when CSP changes at unphysiologically high rates (i.e., 5 mmHg/s). On the other hand, static reverse-sigmoid characteristics of baroreflex control of muscle SNA agreed well with those of renal or cardiac SNAs. In conclusion, dynamic-linear and static-nonlinear baroreflex control of muscle SNA is similar to that of renal and cardiac SNAs under physiological pressure change.
Hypoxia suppresses elastin repair by rat lung fibroblasts
Authors: Berk John L. , Hatch Christine A. , Morris Shirley M. , Stone Phillip J. , Goldstein Ronald H.
Published: July 2005

Macrophage and neutrophil proteinases damage lung elastin, disrupting alveolar epithelium and filling alveoli with inflammatory exudate. Alveolar collapse and regional hypoxia occur. Whether low oxygen tension alters fibroblast-mediated lung repair is unknown. To determine the effect of chronic hypoxia on repair of enzyme-induced elastin disruption, primary rat lung fibroblasts produced elastin matrix for 5 wk before treatment with porcine pancreatic elastase (PPE). After exposure to PPE or saline, cultures recovered for 2 wk in normoxia (21% O2) or hypoxia (3% O2). Hypoxia suppressed regeneration of hot alkali-resistant elastin, achieving only 49% of the repair achieved in normoxic cultures. Vascular smooth muscle cells and lung fibroblasts repair elastin by two pathways: de novo synthesis and salvage repair. Although both pathways were affected, hypoxia predominantly inhibited de novo synthesis, decreasing formation of new elastin matrix by 63% while inhibiting salvage repair by only 36%. Prolonged hypoxia alone downregulated steady-state levels of elastin mRNA by 45%, whereas PPE had no significant effect on elastin gene expression. Electron microscopy documented preservation of intracellular organelles and intact nuclei. Together, these data suggest that regional hypoxia limits lung elastin repair following protease injury at least in part by inhibiting elastin gene expression.
Modulation of PGF2α- and hypoxia-induced contraction of rat intrapulmonary artery by p38 MAPK inhibition: a nitric oxide-dependent mechanism
Authors: Knock Greg A. , De Silva Anushika S. , Snetkov Vladimir A. , Siow Richard , Thomas Gavin D. , Shiraishi Mitsuya , Walsh Michael P. , Ward Jeremy P. T. , Aaronson Philip I.
Published: July 2005

The mechanisms through which p38 mitogen-activated protein kinase (p38 MAPK) is involved in smooth muscle contraction remain largely unresolved. We examined the role of p38 MAPK in prostaglandin F2α(PGF2α)-induced vasoconstriction and in hypoxic pulmonary vasoconstriction (HPV) of rat small intrapulmonary arteries (IPA). The p38 MAPK inhibitors SB-203580 and SB-202190 strongly inhibited PGF2α-induced vasoconstriction, with IC50s of 1.6 and 1.2 μM, whereas the inactive analog SB-202474 was ∼30-fold less potent. Both transient and sustained phases of HPV were suppressed by SB-203580, but not by SB-202474 (both 2 μM). Western blot analysis revealed that PGF2α(20 μM) increased phosphorylation of p38 MAPK and of heat shock protein 27 (HSP27), and this was abolished by SB-203580 but not by SB-202474 (both 2 μM). Endothelial denudation or blockade of endothelial nitric oxide (NO) synthase with Nω-nitro-l-arginine methyl ester (l-NAME) significantly suppressed the relaxation of PGF2α-constricted IPA by SB-203580, but not by SB-202474. Similarly, the inhibition of HPV by SB-203580 was prevented by prior treatment with l-NAME. SB-203580 (2 μM), but not SB-202474, enhanced relaxation-induced by the NO donor S-nitroso- N-acetylpenicillamine (SNAP) in endothelium-denuded IPA constricted with PGF2α. In α-toxin-permeabilized IPA, SB-203580-induced relaxation occurred in the presence but not the absence of the NO donor sodium nitroprusside (SNP); SB-202474 was without effect even in the presence of SNP. In intact IPA, neither PGF2α- nor SNAP-mediated changes in cytosolic free Ca2+were affected by SB-203580. We conclude that p38 MAPK contributes to PGF2α- and hypoxia-induced constriction of rat IPA primarily by antagonizing the underlying Ca2+-desensitizing actions of NO.
Constrictor-induced translocation of NFAT3 in human and rat pulmonary artery smooth muscle
Authors: Yaghi Asma , Sims Stephen M.
Published: July 2005

The transcription factor nuclear factor of activated T cells (NFAT) resides in the cytoplasm in resting cells and upon stimulation is dephosphorylated, translocates to the nucleus, and becomes transcriptionally active. NFAT is commonly activated by stimulation of receptors coupled to Ca2+mobilization; however, little is known about the regulation of NFAT in pulmonary vascular smooth muscle. The aim of this study was to investigate regulation of NFAT in human and rat intralobar pulmonary artery by two constrictors: phenylephrine (PE) and 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P-450 metabolite formed endogenously in lungs. Immunostaining of smooth muscle cells revealed cytoplasmic localization of NFAT in untreated cells, and PE or 20-HETE induced translocation to the nucleus, with maximal effect at 30 min. Cyclosporin A and FK-506 (both 1 μM) inhibited NFAT translocation, indicating involvement of calcineurin. Moreover, the Rho-kinase blocker Y-27632 prevented translocation. Translocation of NFAT was confirmed by Western blots, with NFAT3 the prominent isoform in pulmonary artery. Constrictors caused calcineurin-sensitive translocation of NFAT to nuclei in intact arteries, demonstrating regulation in native tissue. To investigate a role for Ca2+, cells were loaded with fura-2. Whereas PE caused an acute transient rise of [Ca2+]i, 20-HETE caused a prolonged low amplitude rise of [Ca2+]i. The involvement of Rho-kinase in PE- and 20-HETE-induced NFAT3 translocation in pulmonary artery suggests a level of control not previously recognized in smooth muscle. Constrictors of the pulmonary vasculature not only cause acute responses but also activate NFAT, which may alter gene expression in pulmonary health and disease.
Pulmonary abnormalities due to ABCA1 deficiency in mice
Authors: Bates Sandra R. , Tao Jian-Qin , Collins Heidi L. , Francone Omar L. , Rothblat George H.
Published: July 2005

Mice gene targeted for ATP-binding cassette transporter A1 (ABCA1; Abca1−/−) have been shown to have low-serum high-density lipoprotein and abnormal lung morphology. We examined alterations in the structure and function of lungs from −/− mice (DBA1/J). Electron microscopy of the diseased mouse lung revealed areas of focal disease confirming previous results ( 47 ). Lipid analysis of the lung tissue of −/− mice showed a 1.2- and 1.4-fold elevation in total phospholipid (PL) and saturated phosphatidylcholine, respectively, and a marked 50% enrichment in total cholesterol content predominately due to a 17.5-fold increase in cholesteryl ester compared with wild type (WT). Lung surfactant in the −/− mice was characterized by alveolar proteinosis (161%), a slight increase in total PL (124%), and a marked increase in free cholesterol (155%) compared with WT. Alveolar macrophages were enriched in cholesterol (4.8-fold) due to elevations in free cholesterol (2.4-fold) and in cholesteryl ester (14.8-fold) compared with WT macrophages. More PL mass was cleared from the alveolar space of −/− mice lungs, measured using intratracheal installation of3H-PL liposomes. Compared with WT mice, the Abca1−/−mice demonstrated respiratory distress with rapid, shallow breathing. Thus the lungs of mice lacking ABCA1 protein demonstrated abnormal morphology and physiology, with alveolar proteinosis and cholesterol enrichment of tissue, surfactant, and macrophages. The results indicate that the activity of ABCA1 is important for the maintenance of normal lung lipid composition, structure, and function.
Effects of RSV infection on pulmonary surfactant protein SP-A in cultured human type II cells: contrasting consequences on SP-A mRNA and protein
Authors: Alcorn Joseph L. , Stark James M. , Chiappetta Constance L. , Jenkins Gaye , Colasurdo Giuseppe N.
Published: July 2005

Respiratory syncytial virus (RSV) is the most important cause of serious lower respiratory illness in infants and children. Surfactant proteins A (SP-A) and D (SP-D) play critical roles in lung defense against RSV infections. Alterations in surfactant protein homeostasis in the lung may result from changes in production, metabolism, or uptake of the protein within the lung. We hypothesized that RSV infection of the type II cell, the primary source of surfactant protein, may alter surfactant protein gene expression. Human type II cells grown in primary culture possess lamellar bodies (a type II cell-specific organelle) and the ability to express surfactant protein mRNA. These cells were infected with RSV (by morphology and antibody binding). Surfactant protein mRNA levels determined by quantitative RT-PCR indicated a marked increase in SP-A mRNA levels (3-fold) 24 h after RSV exposure, whereas SP-D mRNA levels were unaffected. In contrast to mRNA levels, total SP-A protein levels (determined by Western blot analysis) were decreased 40% after RSV infection. The percentage of secreted SP-A was 43% of the total SP-A in the RSV-infected cells, whereas the percentage of secreted SP-A was 61% of the total SP-A in the uninfected cells. These changes in SP-A transcript levels and protein secretion in cultured human cells were recapitulated in RSV-infected mouse lung. Our findings suggest that type II cells are potentially important targets of RSV lower respiratory infection and that alterations in surfactant protein gene expression and SP-A protein homeostasis in the lung may arise via direct effects of RSV.
Gradient-Based Adaptation of General Gaussian Kernels
Authors: Glasmachers Tobias , Igel Christian
Published: July 2005

Gradient-based optimizing of gaussian kernel functions is considered. The gradient for the adaptation of scaling and rotation of the input space is computed to achieve invariance against linear transformations. This is done by using the exponential map as a parameterization of the kernel parameter manifold. By restricting the optimization to a constant trace subspace, the kernel size can be controlled. This is, for example, useful to prevent overfitting when minimizing radius-margin generalization performance measures. The concepts are demonstrated by training hard margin support vector machines on toy data.
Optimal Signal Estimation in Neuronal Models
Authors: Lánský Petr , Greenwood Priscilla E.
Published: July 2005

We study optimal estimation of a signal in parametric neuronal models on the basis of interspike interval data. Fisher information is the inverse asymptotic variance of the best estimator. Its dependence on the parameter value indicates accuracy of estimation. Our models assume that the input signal is estimated from neuronal output interspike interval data where the frequency transfer function is sigmoidal. If the coefficient of variation of the interspike interval is constant with respect to the signal, the Fisher information is unimodal, and its maximum for the most estimable signal can be found. We obtain a general result and compare the signal producing maximal Fisher information with the inflection point of the sigmoidal transfer function in several basic neuronal models.
Fast Access to Concepts in Concept Lattices via Bidirectional Associative Memories
Authors: Rajapakse Rohana , Denham Michael
Published: July 2005

Bidirectional associative memories (BAMs) are shown to be capable of precisely learning concept lattice structures by Radim Bělohlávek. The focus of this letter is to show that the BAM, when set up with a concept lattice by setting up connection weights according to the rule proposed by Bělohlávek, always returns the most specific or most generic concept containing the given set of objects or attributes when a set of objects or attributes is presented as input to the object or attribute layer. A proof of this property is given here, together with an example, and a brief application of the property is provided.
Coding of Temporally Varying Signals in Networks of Spiking Neurons with Global Delayed Feedback
Authors: Masuda Naoki , Doiron Brent , Longtin André , Aihara Kazuyuki
Published: July 2005

Oscillatory and synchronized neural activities are commonly found in the brain, and evidence suggests that many of them are caused by global feedback. Their mechanisms and roles in information processing have been discussed often using purely feedforward networks or recurrent networks with constant inputs. On the other hand, real recurrent neural networks are abundant and continually receive information-rich inputs from the outside environment or other parts of the brain. We examine how feedforward networks of spiking neurons with delayed global feedback process information about temporally changing inputs. We show that the network behavior is more synchronous as well as more correlated with and phase-locked to the stimulus when the stimulus frequency is resonant with the inherent frequency of the neuron or that of the network oscillation generated by the feedback architecture. The two eigenmodes have distinct dynamical characteristics, which are supported by numerical simulations and by analytical arguments based on frequency response and bifurcation theory. This distinction is similar to the class I versus class II classification of single neurons according to the bifurcation from quiescence to periodic firing, and the two modes depend differently on system parameters. These two mechanisms may be associated with different types of information processing.
Attention-Gated Reinforcement Learning of Internal Representations for Classification
Authors: Roelfsema Pieter R. , Ooyen Arjen van
Published: July 2005

Animal learning is associated with changes in the efficacy of connections between neurons. The rules that govern this plasticity can be tested in neural networks. Rules that train neural networks to map stimuli onto outputs are given by supervised learning and reinforcement learning theories. Supervised learning is efficient but biologically implausible. In contrast, reinforcement learning is biologically plausible but comparatively inefficient. It lacks a mechanism that can identify units at early processing levels that play a decisive role in the stimulus-response mapping. Here we show that this so-called credit assignment problem can be solved by a new role for attention in learning. There are two factors in our new learning scheme that determine synaptic plasticity: (1) a reinforcement signal that is homogeneous across the network and depends on the amount of reward obtained after a trial, and (2) an attentional feedback signal from the output layer that limits plasticity to those units at earlier processing levels that are crucial for the stimulus-response mapping. The new scheme is called attention-gated reinforcement learning (AGREL). We show that it is as efficient as supervised learning in classification tasks. AGREL is biologically realistic and integrates the role of feedback connections, attention effects, synaptic plasticity, and reinforcement learning signals into a coherent framework.
Introduction: Viewing Animals
Authors: Fudge Erica
Published: July 2005

The introduction to this special issue of Worldviews goes back to the first European encounters with the New World as a way of opening up a discussion about the nature of viewing animals. I argue that, just as the Europeans transformed this New World into a recognisable one in the sixteenth century, so too do we constantly transform the natural world that we view. The process of comprehension is offered as classification followed by observation, then representation, and all of these elements of our engagements with animals take place, I argue, in particular contexts: historical, geographical, cultural, intellectual. The critic "reading" animals, and reading human observations of animals must take these factors into consideration when thinking about the act of engagement.
Contested Exhibitions: The Debate over Proper Animal Sights in Post-Revolutionary America
Authors: Mizelle Brett
Published: July 2005

Animal exhibitions served as a crucial site in which Americans struggled to come to terms with their post-revolutionary society. This essay analyzes those debates over proper ways of seeing animals in the early republic that reveal an emerging distinction between legitimate and problematic displays of animals, between exhibitions of exotic creatures that provided "instructive amusement" and those animal acts that did not. While this distinction was, in actuality, seldom clear, this effort to define what types of animal exhibitions were acceptable both reflected and helped to produce the modern divide between humans as subjects and animals as objects. It also reveals other significant transformations in American culture, including the segmentation of American audiences, the division of culture into high and low, and the place of ideas about animals in defining the citizen and the nation.
"Viewing" the Body: Toward a Discourse of Rabbit Death
Authors: Smith Julie Ann
Published: July 2005

Traditional academic discourse on animal death denies non-human animals an understanding of death based on an inability to have a "concept" of death. A different view has emerged within a rabbit rescue organization to which I belong called the House Rabbit Society. HRS members live closely with rabbits inside their homes and as a matter of practice place the body of a deceased rabbit with his or her surviving partner or group for "viewing." Observing rabbits in this context, HRS members grant to them the capacity to understand that a partner has undergone a permanent and catastrophic change. This conclusion is best understood within a larger discourse of rabbits shaped by three modes of viewing rabbits while they are alive: a rationalist approach, an emotionally engaged view, and an active suspension of interpretation.
Public Knowledge and Common Secrets. Secrecy and its Limits in the Early-Modern Netherlands
Authors: Davids Karel
Published: July 2005

Openness of knowledge was in the Dutch Republic no more a natural state of affairs than in other parts of Europe at the time, but it became dominant there at an earlier date than elsewhere. This puzzling phenomenon is the subject of this essay. The article shows that tendencies to secrecy in crafts and trades in the Netherlands were by no means absent and that public authorities were not principled supporters of openness. Openness of knowledge did not prevail because arguments in favour of a free exchange of knowledge won the day against a rhetoric in defense of secrecy or because a rapid change in methods of production and marketing rendered the maintenance of craft secrecy practically impossible. The weakness of secrecy in the early-modern Netherlands, this essay argues, can be explained by the relative tardiness of the growth of the corporate system and the typical features of the institutional structure of the Dutch Republic. Craft secrecy in the Dutch Republic, as far as it existed before the middle of the eighteenth century, was normally based on a contractual relationship between individual actors rather than on any form of enforcement by public agencies.
Trunk muscle activity during bridging exercises on and off a Swissball
Authors: Lehman Gregory J , Hoda Wajid , Oliver Steven
Published: July 2005

Background

A Swiss ball is often incorporated into trunk strengthening programs for injury rehabilitation and performance conditioning. It is often assumed that the use of a Swiss ball increases trunk muscle activity. The aim of this study was to determine whether the addition of a Swiss ball to trunk bridging exercises influences trunk muscle activity.

Methods

Surface electrodes recorded the myoelectric activity of trunk muscles during bridging exercises. Bridging exercises were performed on the floor as well as on a labile surface (Swiss ball).

Results and Discussion

During the prone bridge the addition of an exercise ball resulted in increased myoelectric activity in the rectus abdominis and external oblique. The internal oblique and erector spinae were not influenced. The addition of a swiss ball during supine bridging did not influence trunk muscle activity for any muscles studied.

Conclusion

The addition of a Swiss ball is capable of influencing trunk muscle activity in the rectus abdominis and external oblique musculature during prone bridge exercises. Modifying common bridging exercises can influence the amount of trunk muscle activity, suggesting that exercise routines can be designed to maximize or minimize trunk muscle exertion depending on the needs of the exercise population.
Surface-Enhanced Raman Spectroscopy of Bacteria and Pollen
Authors: Sengupta Atanu , Laucks Mary L. , Davis E. James
Published: July 2005

A technique for distinguishing biological material based on surface-enhanced Raman scattering (SERS) is reported in this work. Of particular interest is biological material that can be airborne. Silver colloidal particles with diameters in the range 10 to 20 nm and with a characteristic ultraviolet–visible (UV-VIS) absorption band at 400 nm were used to obtain SERS spectra of Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium bacteria and a number of tree and grass pollens ( Cupressus arizonica (cypress), Sequoia sempervirens (redwood), Populus deltoides (cottonwood), Poa pratensis (Kentucky bluegrass), and Anthoxanthum odoratum (sweet vernal grass)). While differences in the SERS spectra among the bacteria were small, we found that the pollen spectra we analyzed could readily be distinguished from the bacteria spectra, and there were significant differences between pollen from different families. In order to obtain reproducible results, we studied the parameters controlling the interaction between the analyte and the nanoscale metallic surface. Our results show that the volume ratio of analyte to colloidal particles must be within a narrow range of values to optimize the signal-to-noise ratio of the SERS spectra and minimize the fluorescence from the analyte. Also, we found that the time-dependent behavior of colloidal/bacterial suspensions (or adsorption rate of the silver colloid particles on the bacteria) is strongly dependent on pH, density of bacteria in solution, and even, to some extent, the type of bacteria.
Determination of Glucose in Human Aqueous Humor Using Raman Spectroscopy and Designed-Solution Calibration
Authors: Pelletier Christine C. , Lambert James L. , Borchert Mark
Published: July 2005

Glucose concentrations of in vitro human aqueous humor (HAH) samples from cataract patients were determined using 785 nm Raman spectra and partial least squares (PLS) calibration. PLS models were created from spectra of prepared calibration solutions rather than aqueous humor samples. Spectra were obtained with an excitation energy (100 mW for 150 s), which was higher than can be applied in vivo, to decrease the models' contribution to prediction uncertainty. The solutions contained experimentally designed levels of glucose, bicarbonate, lactate, urea, and ascorbate. Multiplicative signal correction of spectra helped compensate for the ±20% drift in laser power observed at the sample over six noncontiguous days of data collection. Seventeen HAH samples containing 38–775 mg/dL of glucose exhibited a root-mean-square error (RMSEP) of 22 mg/dL, coefficient of determination ( r2) of 0.989, and bias of 6 mg/dL when predicted from lower energy (30 s) spectra collected contemporaneously with fifty calibration spectra. Similar results were obtained even when spectral data were gathered separately for human aqueous humor samples and calibration samples: 10 HAH samples, calibrated on 25 solutions measured 3.6 weeks earlier, exhibited an RMSEP of 23 mg/dL, r2 of 0.992, and bias of 9 mg/dL. The results demonstrate progress toward the determination of glucose levels in patient-derived aqueous humor using laboratory-derived “artificial aqueous humor” calibration solutions.
Discrimination of Nylon Polymers Using Attenuated Total Reflection Mid-Infrared Spectra and Multivariate Statistical Techniques
Authors: Enlow Elizabeth M. , Kennedy Jennifer L. , Nieuwland Alexander A. , Hendrix James E. , Morgan Stephen L.
Published: July 2005

Nylons are an important class of synthetic polymers, from an industrial, as well as forensic, perspective. A spectroscopic method, such as Fourier transform infrared (FT-IR) spectroscopy, is necessary to determine the nylon subclasses (e.g., nylon 6 or nylon 6,6). Library searching using absolute difference and absolute derivative difference algorithms gives inconsistent results for identifying nylon subclasses. The objective of this study was to evaluate the usefulness of peak ratio analysis and multivariate statistics for the identification of nylon subclasses using attenuated total reflection (ATR) spectral data. Many nylon subclasses could not be distinguished by the peak ratio of the N–H vibrational stretch to the sp3 C–H2 vibrational stretch intensities. Linear discriminant analysis, however, provided a graphical visualization of differences between nylon subclasses and was able to correctly classify a set of 270 spectra from eight different subclasses with 98.5% cross-validated accuracy.
Surface-Enhanced Micro-Raman Detection and Characterization of Calix[4]Arene—Polycyclic Aromatic Hydrocarbon Host—Guest Complexes
Authors: Leyton P. , Sanchez-Cortes S. , Campos-Vallette M. , Domingo C. , Garcia-Ramos J. V. , Saitz C.
Published: July 2005

Surface-enhanced micro-Raman spectroscopy (micro-SERS) was used to detect traces of the hazardous pollutant polycyclic aromatic hydrocarbons (PAHs) pyrene and benzo[c]phenanthrene deposited onto a calix[4]arene-functionalized Ag colloidal surface. High spectral reproducibility and very low molecular detection limits (10−8 M) were obtained by using 25,27-carboethoxy-26,28-hidroxy-p- tert-butylcalix[4]arene as host molecule. Films of immobilized aggregated Ag nanoparticles, obtained by chemical reduction with hydroxylamine, were prepared by direct adhesion on a glass surface. The influence of the aggregation degree of the initial Ag nanoparticles on the micro-SERS detection effectiveness was checked. Different relative concentrations of the host (calixarene receptor) and the guest (PAHs) were attempted in order to optimize detection of the pollutant. The obtained results indicated that the detection limit is much lower in the case of benzo[c]phenanthrene than in pyrene when exciting with the 785 nm line of a diode laser. A detailed interpretation of the Raman spectra was accomplished in order to obtain more information about the interaction mechanism of the host-guest complex, which could be useful in the future for the design of powerful detection systems.
Spectrofluorimetry and Chemometrics for Investigation of Norfloxacin Distribution in Multilamellar Liposomes
Authors: Zalloum N. L. , Biloti D. N. , Pessine F. B. T.
Published: July 2005

Norfloxacin (NFX), a fluoroquinolone, was encapsulated in multi-lamellar liposomes (MLV) of soy-bean phosphatidylcholine at pH 7.0. The observed affinity of this class of drugs for hydrophobic environments, such as phospholipid bilayers, could lead to a better understanding of the mechanism of uptake in bacteria. The fluorescent properties of NFX were examined both free in solution and in MLV, using anisotropy and fluorescence quenching measurements. The latter data was treated with a chemometric method to deconvolute the overlapped spectra of zwitterionic and neutral species of NFX in equilibrium at this pH. The results show that NFX incorporates into the lipidic bilayers with two different distributions of species: the zwitterionic form in the lipid/aqueous interface, and the neutral one, more towards the center of the bilayer.
Improved Dispersion of Bacterial Endospores for Quantitative Infrared Sampling on Gold Coated Porous Alumina Membranes
Authors: Schiza Maria V. , Perkins David L. , Priore Ryan J. , Setlow B. , Setlow P. , Bronk Burt V. , Wong Diane M. , Myrick M. L.
Published: July 2005

An improved method for qualitative and quantitative sampling of bacterial endospores using Fourier transform infrared (FT-IR) microscopy on gold-coated porous alumina membranes is presented. Bacillus subtilis endospores were filtered onto gold-coated alumina membranes serving as substrates. Studies in the mid-infrared (MIR) region revealed the characteristic bacterial absorption spectrum at low surface concentration, while scanning electron microscopy (SEM) images of the same samples provided precise calculation of the surface concentration of the bacterial endospores. Under the conditions of study, the average concentration of endospores was determined to be 1356 ± 35 spores in a 100 × 100 μm2 area, with a relative standard deviation of 0.0260. Examination of ten random spots on multiple substrates with FT-IR microscopy apertured to the same area gave an average relative standard deviation of 0.0482 in the signal strength of the amide A band at 3278 cm−1. An extinction cross-section in reflection of σext = (7.8 ± 0.6) × 10−9 cm2/endospore was calculated for the amide A band at the frequency of its peak absorbance, 3278 cm−1. The absorption cross-section of the amide A band in reflection is estimated to be σabs ≈ (2.10 ± 0.12) × 10−9 cm2/endospore.
Characterization of Infrared Chemical Sensors Modified with ZnO Nanowires for the Detection of Volatile Organic Compounds
Authors: Yang Jyisy , Shih Yu-Ru , Chen I-Cherng , Kuo Chung-I , Huang Yih-Shiaw
Published: July 2005

In this paper we describe the application and characterization of zinc oxide (ZnO) nanowires in an infrared (IR) chemical sensing system for the detection of volatile organic compounds (VOCs). Under suitable conditions, we grew ZnO nanowires on the surfaces of IR internal reflection elements (IREs) and obtained successful results for the detection of VOCs. ZnO nanowires offer a large surface area to effectively adsorb the examined species; the sensitivity of these IR sensing systems was increased by 3- to 15-fold after surface treatment with the ZnO nanowires. To explore the performance of this type of sensor, we correlated the morphologies of the ZnO nanowires grown on the surfaces of the IREs with the adsorption behavior observed during the sensing of the VOCs. To characterize the properties of the ZnO nanowires during the detection of VOCs having a range of functionalities, we classified the VOCs and examined their enrichment factors by comparing the IR signals detected in the presence and absence of the ZnO nanowires. Our results indicate that the ZnO nanowires exhibited better performance for the detection of aromatic-type VOCs than they did for non-aromatic compounds. For quantitative analyses, we examined several compounds for their responses toward varying quantities of injected VOCs. Our results indicate that the IREs treated with ZnO nanowires display acceptable linearity in their standard curves; the linear regression coefficients were higher than 0.995 for a range of volatile compounds.
Fungus Covered Insulator Materials Studied with Laser-Induced Fluorescence and Principal Component Analysis
Authors: Bengtsson M. , Wallström S. , Sjöholm M. , Grönlund R. , Anderson B. , Larsson A. , Karlsson S. , Kröll S. , Svanberg S.
Published: July 2005

A method combining laser-induced fluorescence and principal component analysis to detect and discriminate between algal and fungal growth on insulator materials has been studied. Eight fungal cultures and four insulator materials have been analyzed. Multivariate classifications were utilized to characterize the insulator material, and fungal growth could readily be distinguished from a clean surface. The results of the principal component analyses make it possible to distinguish between algae infected, fungi infected, and clean silicone rubber materials. The experiments were performed in the laboratory using a fiber-optic fluorosensor that consisted of a nitrogen laser and an optical multi-channel analyzer system.
Investigation of the Aqueous Dissolution of Semicrystalline Poly(Ethylene Oxide) Using Infrared Chemical Imaging: The Effects of Molecular Weight and Crystallinity
Authors: Coutts-Lendon Carrie , Koenig Jack L.
Published: July 2005

Fourier transform infrared (FT-IR) imaging was used to successfully explore several factors influencing the dissolution of poly(ethylene oxide). The effect of the degree of crystallinity on the rate of dissolution of mid-range molecular weight PEO was negligible over the temperature ranges studied. The influence of molecular weight on polymer dissolution was found to be much greater than the changes in morphology. An examination of the polymer and solvent images and absorbance profiles, compared with the results of the bulk polymer/solvent boundary movement, confirmed this relationship. An investigation of the bulk polymer/solvent boundary using a crystalline-sensitive polymer band showed the crystalline to amorphous phase change occurred over a short distance. Moreover, solvent diffusion ahead of the bulk polymer/solvent front was minimal, most likely a result of the required phase change, which in turn regulated the degree of solvent ingress. Modeling of the dissolution was performed using the Peppas (power law) model. Physical parameters of the dissolution process were obtained from fitting the release profiles to the power law (fraction released = k × tn, where k is the dissolution rate constant and n is the release exponent). Results indicated the model worked well to describe dissolution at all molecular weights. By varying the number of data points input to the model and then comparing the generated graphs, it becomes clear that not only does the dissolution slow down over the course of the experiment, but an increase in molecular weight enhances this effect. The effect of different types of drug on the rate of polymer dissolution was also studied. The dissolution of neat polymer was compared to the dissolution of polymer containing 10% (by weight) of theophylline, etophylline, or testosterone. The general trend of all the dissolution curves was the same, with the addition of etophylline and testosterone tracing almost the same route in terms of movement of the bulk polymer/solvent front.
External Reflection Fourier Transform Infrared Spectroscopy of Surfactants at the Air—Water Interface: Separation of Bulk and Adsorbed Surfactant Signals
Authors: Campbell Richard A. , Day James P. R. , Bain Colin D.
Published: July 2005

External reflection Fourier transform infrared spectroscopy (ERFTIRS) has been used to obtain spectra of monolayers of the hydrocarbon surfactant octaethylene glycol monodecyl ether (C10E8) and the fluorocarbon surfactant ammonium perfluorononanoate (APFN) at the expanding liquid surface of an overflowing cylinder. The use of target factor analysis (TFA) to separate out the contributions of water, adsorbed surfactant, and dissolved surfactant is demonstrated. For both surfactants, there is a linear relationship between the component weight of the adsorbed surfactant, obtained by TFA, and the surface excess determined independently by ellipsometry or neutron reflection. This linear relationship suggests that the monolayers behave like isotropic films with a constant density. A sensitivity of less than 10% of a monolayer is demonstrated. The benefits of using a multivariate curve fitting procedure to analyze sets of ER-FTIR spectra are discussed and some potential pitfalls are identified. This technique is also applicable to static interfaces.
Spatially Resolved Stress Analysis in Al2O3/3Y-TZP Multilayered Composite Using Confocal Fluorescence Spectroscopy
Authors: Zhu Wenliang , Pezzotti Giuseppe
Published: July 2005

Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al2O3/3Y-TZP (3 mol % Y2O3-stabilized ZrO2) composite using the chromophoric fluorescence spectra of Al2O3. The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.
Prediction of Potential Mushroom Yield by Visible and Near-Infrared Spectroscopy Using Fresh Phase II Compost
Authors: Sharma H. S. S. , Kilpatrick M. , Lyons G.
Published: July 2005

Potential mushroom ( Agaricus bisporus) yield of phase II compost is determined by interactions of key quality parameters including dry matter, nitrogen dry matter, ammonia, pH, conductivity, thermophilic microorganisms, C: N ratio, fiber fractions, ash, and certain minerals. This study was aimed at generating robust visible and near-infrared (Vis-NIR) calibrations for predicting potential yield, using spectra from fresh phase II compost. Four compost comparative trials were carried out during the winter and summer months of 2001–2003, under controlled experimental conditions employing six commercially prepared composts, with eight replicate (8 bag) plots per treatment (48 × 8 = 384). The substrates were prepared by windrow or bunker phase I, followed by phase II production. The fresh samples were scanned for Vis-NIR (400–2498 nm) spectra, averaged, transformed, and regressed against the recorded yield by employing a modified partial least squares algorithm. The best calibration model generated from the database explained 84% of yield variation within the data set with a standard error of calibration of 13.75 kg/tonne of fresh compost. The model was successfully tested for robustness with yield results obtained from a validation trial, carried out under similar experimental conditions in early 2004, and the standard error of prediction was 18.21 kg/tonne, which was slightly higher than the mean experimental error (17.94 kg/tonne) of the trial. The accuracy of the model is acceptable for estimating potential yield by classifying phase II substrate as poor (180–220 kg), medium (220–260 kg), and high (260–300 kg) yielding compost. The yield prediction model is being transferred to a new instrument based at Loughgall for routine evaluation of commercial phase II samples.
New Approach to Avoid Erroneous Interpretation of Results Derived from Generalized Two-Dimensional Correlation Analysis for Applications in Catalysis
Authors: Haider Peter , Haller Gary L. , Pfefferle Lisa , Ciuparu Dragos
Published: July 2005

Surface characterization and catalysis can significantly benefit from the application of generalized two-dimensional (2D) correlation analysis. This two-dimensional approach allows a better resolution of overlapping peaks, can reveal new features not readily observable in the raw spectra, gives clear evidence for spectral intensities that change as an effect of a perturbation applied to the system, and allows the establishment of time sequences for the changes occurring in different spectral features of interest for determining reaction intermediates and/or mechanisms. The interpretation of the synchronous and asynchronous plots was observed to lead to erroneous time sequences when spectral features change in a nonmonotonic way, such as a biphasic or oscillatory behavior, under the influence of a perturbation. We propose a new approach to the 2D correlation analysis to avoid misinterpretation of the results calculated in the asynchronous plot. Progressive correlation analysis (ProCorA) calculates the synchronous plot from the first two spectra of the data matrix and one spectrum is added at every step of the analysis. The sequence of changes can be set up from the progressive evolution of peaks in both the synchronous and asynchronous plots.
Confocal Raman Microscopy of Liquid-Crystal-Filled Polymer Capsules Made by Photo-Enforced Stratification
Authors: Mank A. J. G. , Vorstenbosch I. , Penterman R. , Vogels J. P. A. , Klink S. I. , Broer D. J.
Published: July 2005

The applicability of confocal Raman microscopy for characterizing thin liquid-crystal (LC) filled polymer capsules obtained by photoenforced stratification is demonstrated. The investigated structure consists of an array of polymer capsules (typical size 500 × 500 × 20 μm) filled with LC material and is made by photopolymerization of a mixture of monomers and LC. Such an array can be used as the electro-optical component in liquid crystal displays. Confocal Raman microscopy does not require complex sample preparation, is non-invasive, and is shown to have adequate spatial and depth resolution. Although Raman spectroscopy is inherently insensitive, the use of data preprocessing and computational modeling makes it possible to quantify both the conversion of monomer to polymer and the compositions of both the polymer-rich and the LC-rich phase.
Hepascore: An Accurate Validated Predictor of Liver Fibrosis in Chronic Hepatitis C Infection
Authors: Adams Leon A , Bulsara Max , Rossi Enrico , DeBoer Bastiaan , Speers David , George Jacob , Kench James , Farrell Geoffrey , McCaughan Geoffrey W , Jeffrey Gary P
Published: July 2005

Background: Staging hepatic fibrosis by liver biopsy guides prognosis and treatment of hepatitis C, but is invasive and expensive. We sought to create an algorithm of serum markers that accurately and reliably predict liver fibrosis stage among hepatitis C patients.

Methods: Ten biochemical markers were measured at time of liver biopsy in 117 untreated hepatitis C patients (training set). Multivariate logistic regression and ROC curve analyses were used to create a predictive model for significant fibrosis (METAVIR F2, F3, and F4), advanced fibrosis (F3 and F4), and cirrhosis (F4). The model was validated in 104 patients from other institutions.

Results: A model (Hepascore) of bilirubin, γ-glutamyltransferase, hyaluronic acid, α2-macroglobulin, age, and sex produced areas under the ROC curves (AUCs) of 0.85, 0.96, and 0.94 for significant fibrosis, advanced fibrosis, and cirrhosis, respectively. In the training set, a score ≥0.5 (range, 0.0–1.0) was 92% specific and 67% sensitive for significant fibrosis, a score <0.5 was 81% specific and 95% sensitive for advanced fibrosis, and a score <0.84 was 84% specific and 71% sensitive for cirrhosis. Among the validation set, the AUC for significant fibrosis, advanced fibrosis, and cirrhosis were 0.82, 0.90, and 0.89, respectively. A score ≥0.5 provided a specificity and sensitivity of 89% and 63% for significant fibrosis, whereas scores <0.5 had 74% specificity and 88% sensitivity for advanced fibrosis.

Conclusions: A model of 4 serum markers plus age and sex provides clinically useful information regarding different fibrosis stages among hepatitis C patients.