Pharmacology Course Redesign Using High-Impact Practices

BACKGROUND

Although pharmacology serves as a foundation for health care professions, a gap exists between education and the clinical application. Experiential learning has demonstrated benefit when integrated into pharmacology courses; however, professors struggle with the challenge of incorporating active learning modalities into traditional lecture courses.

METHOD

Active learning and high-impact educational practices, based on cognitive theory, were incorporated into a pharmacology course sequence. After course completion and entry into the clinical setting, qualitative data were collected from students and clinical preceptors.

RESULTS

Students and clinical preceptors reported an improvement in students' ability to recall and apply concepts clinically. Students identified the creation of cognitive aids as the most advantageous measure.

CONCLUSION

Integrating active learning and high-impact educational practices into pharmacology courses could potentially aid in the ability to recall and apply concepts clinically, reduce medication errors and expenditures, and increase student confidence when entering clinical education. [J Nurs Educ. 2021;60(9):529-533.].

Perioperative Goal-Directed Fluid Therapy: A Prime Component of Enhanced Recovery After Surgery

Perioperative goal-directed fluid therapy (GDFT) is a prime component of the Enhanced Recovery After Surgery (ERAS) protocol. Multiple studies have demonstrated a relationship between GDFT and positive patient outcomes, including shorter hospital stays, decreased ileus formation, reduced gastrointestinal-related issues, decreased nausea, and hemodynamic stability. Electrolyte disturbances following a positive fluid balance may occur, and GDFT is aimed at euvolemia to avoid a hypervolemic state. Carbohydrate loading, early discontinuation of postoperative intravenous fluids, and use of isoosmotic solutions all are components of GDFT. Lactated Ringer's solution is the fluid recommended for nonrenal patients and patients with hepatic compromise. The negative consequences associated with hypervolemia deem it pertinent to devise an individualized GDFT plan in the ERAS protocol.

Quantum circuits with many photons on a programmable nanophotonic chip

Growing interest in quantum computing for practical applications has led to a surge in the availability of programmable machines for executing quantum algorithms1,2. Present-day photonic quantum computers3-7 have been limited either to non-deterministic operation, low photon numbers and rates, or fixed random gate sequences. Here we introduce a full-stack hardware-software system for executing many-photon quantum circuit operations using integrated nanophotonics: a programmable chip, operating at room temperature and interfaced with a fully automated control system. The system enables remote users to execute quantum algorithms that require up to eight modes of strongly squeezed vacuum initialized as two-mode squeezed states in single temporal modes, a fully general and programmable four-mode interferometer, and photon number-resolving readout on all outputs. Detection of multi-photon events with photon numbers and rates exceeding any previous programmable quantum optical demonstration is made possible by strong squeezing and high sampling rates. We verify the non-classicality of the device output, and use the platform to carry out proof-of-principle demonstrations of three quantum algorithms: Gaussian boson sampling, molecular vibronic spectra and graph similarity8. These demonstrations validate the platform as a launchpad for scaling photonic technologies for quantum information processing.

Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

We report demonstrations of both quadrature-squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition-edge sensors. We measure 1.0(1) decibels of broadband quadrature squeezing (~4 decibels inferred on-chip) and 1.5(3) decibels of photon number difference squeezing (~7 decibels inferred on-chip). Nearly single temporal mode operation is achieved, with measured raw unheralded second-order correlations g ⁽²⁾ as high as 1.95(1). Multiphoton events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology.

Perioperative Pain Management Strategies in the Age of an Opioid Epidemic

According to the US Department of Health and Human Services 2016 and 2017 data, an estimated 130 people per day died from opioid-related drug overdoses; 42,249 people died from overdosing on opioids; and 2.1 million people had opioid-use disorder. Health care organizations such as the American Association of Nurse Anesthetists, the Association of periOperative Registered Nurses, the American Society of PeriAnesthesia Nurses, the American Society of Anesthesiologists, the American College of Surgeons, and the American Medical Association have information related to pain management and/or the opioid epidemic on their Web sites. It is imperative for health care providers to be cognizant of, and use low-dose opioid/opioid-free pain management therapies. This article reviews the pain process and outlines low-dose opioid/opioid-free pain management modalities.

The effects of auditory satellite navigation instructions and visual blur on road hazard perception

The distracting effects of mobile telephone use while driving are well known, however the effects of other sources of distraction, such as auditory navigation devices, are less well understood. Whether the effects of auditory distraction might interact with other sensory impairments, such as vision impairment, is of interest given that visual impairment is relatively common within the population, particularly as a result of uncorrected refractive error. In this experiment, 20 current drivers (mean age of 29.4 ± 3.2 years), binocularly viewed video recordings of traffic scenes presented as part of the Hazard Perception Test and responded to potential hazards within the traffic scenes. Half of the presented scenes included auditory navigation instructions as an auditory distractor. Additionally, some of the scenes were viewed through optical lenses to induce different levels of refractive blur (+0.50 DS, +1.00 DS and +2.00 DS). Hazard perception response times increased significantly (p < 0.05) with increasing blur. Participants were significantly slower in reacting to hazards for the +1.00 DS and +2.00 DS blur conditions compared to the control condition (with no blur). There was also a significant increase in response times to hazards in the presence of the auditory navigation instructions. The combined effect of blur and auditory instructions was additive, with the worst performance being in the presence of both blur and auditory instructions. These results suggest that the delivery of auditory navigation guidance for those with visual impairments, such as blur, which are relatively common in the population, should be further investigated.

Paging through history: parchment as a reservoir of ancient DNA for next generation sequencing

Parchment represents an invaluable cultural reservoir. Retrieving an additional layer of information from these abundant, dated livestock-skins via the use of ancient DNA (aDNA) sequencing has been mooted by a number of researchers. However, prior PCR-based work has indicated that this may be challenged by cross-individual and cross-species contamination, perhaps from the bulk parchment preparation process. Here we apply next generation sequencing to two parchments of seventeenth and eighteenth century northern English provenance. Following alignment to the published sheep, goat, cow and human genomes, it is clear that the only genome displaying substantial unique homology is sheep and this species identification is confirmed by collagen peptide mass spectrometry. Only 4% of sequence reads align preferentially to a different species indicating low contamination across species. Moreover, mitochondrial DNA sequences suggest an upper bound of contamination at 5%. Over 45% of reads aligned to the sheep genome, and even this limited sequencing exercise yield 9 and 7% of each sampled sheep genome post filtering, allowing the mapping of genetic affinity to modern British sheep breeds. We conclude that parchment represents an excellent substrate for genomic analyses of historical livestock.

Direct evidence of milk consumption from ancient human dental calculus

Milk is a major food of global economic importance, and its consumption is regarded as a classic example of gene-culture evolution. Humans have exploited animal milk as a food resource for at least 8500 years, but the origins, spread, and scale of dairying remain poorly understood. Indirect lines of evidence, such as lipid isotopic ratios of pottery residues, faunal mortality profiles, and lactase persistence allele frequencies, provide a partial picture of this process; however, in order to understand how, where, and when humans consumed milk products, it is necessary to link evidence of consumption directly to individuals and their dairy livestock. Here we report the first direct evidence of milk consumption, the whey protein β-lactoglobulin (BLG), preserved in human dental calculus from the Bronze Age (ca. 3000 BCE) to the present day. Using protein tandem mass spectrometry, we demonstrate that BLG is a species-specific biomarker of dairy consumption, and we identify individuals consuming cattle, sheep, and goat milk products in the archaeological record. We then apply this method to human dental calculus from Greenland's medieval Norse colonies, and report a decline of this biomarker leading up to the abandonment of the Norse Greenland colonies in the 15^th century CE.

Wet degradation of keratin proteins: linking amino acid, elemental and isotopic composition

RATIONALE

Archaeological keratin samples are increasingly the subject of palaeodietary, provenancing and dating studies. Keratin samples from wet archaeological contexts are microbiologically and chemically degraded, causing differential diagenesis of protein structures in hair fibres. The effects of these processes on the analytical parameters of interest are currently unknown.

METHODS

This study examined the impact of degradation of wool fibres on isotopic (δ(13)C, δ(15)N, un-exchangeable δ(2)H and δ(18)O values) composition. It compared two models of archaeological protein degradation in wet burial environments: (1) short term (up to 8 years) experimental burial in three contrasting soil environments; and (2) laboratory wet conditions, in which elevated temperature (80 °C, 110 °C, and 140 °C) and pressure simulated longer exposure. Elemental and amino acid (AA) composition were also measured.

RESULTS

In experimentally soil-buried samples, AA, elemental and isotopic composition changes were small, despite extensive macroscopic alteration. Isothermally heated samples showed preferential loss of hydrophilic AAs (Asx, Glx, Ser, Gly) from wool residues, with depletion in (2)H and (18)O at higher temperatures (up to -73‰ change in δ(2)H and -2.6‰ in δ(18)O values). The δ(13)C and δ(15)N values showed little change except in densely pigmented samples at low temperatures only. Samples dyed with madder/alum were better preserved than undyed samples.

CONCLUSIONS

Diagenesis in experimentally soil-buried wool textiles was consistent with microbiological, non-protein-selective activity, in contrast to highly AA-selective hydrolytic behaviour under laboratory wet conditions. Changes in δ(2)H and δ(18)O values were correlated with degree of AA change, but the δ(13)C and δ(15)N values were not. The results contribute to a baseline for interpreting analytical data from archaeological hair samples preserved by burial in wet environments.

Comparison of isotopic variability in proteinaceous tissues of a domesticated herbivore: a baseline for zooarchaeological investigation

RATIONALE

A variety of metabolic, dietary and climatic influences on isotopic variation have been established in mammalian hair. The relevance of these factors to collagen isotopic composition is unknown, but would be of great interest to zooarchaeological analyses of faunal skeletal tissue.

METHODS

The relationships between carbon (δ(13)C), nitrogen (δ(15)N), non-exchangeable hydrogen (δ(2)H) and oxygen (δ(18)O) values of defatted, demineralised and gelatinised bone collagen and defatted wool keratin from two sheep flocks (n = 20, 5) in the UK were investigated, including testing for the effects of nutritional plane, sex, pregnancy and season of sample collection. The sulfur composition (δ(34)S values) was also investigated for tissues from the smaller flock.

RESULTS

Bulk collagen was enriched in (13)C over bulk keratin by 2.0 - 2.7‰ and in (2)H by 29 - 40‰ but depleted in (18)O relative to keratin by 1.8‰. Differences in δ(15)N values were within experimental error. The collagen samples were generally more enriched in (34)S than keratin, but this was very variable. Pregnancy, sex and season, but not nutritional plane, significantly affected isotope values but did not change overall keratin-collagen relationships.

CONCLUSIONS

This dataset provides a baseline measure of variability and comparability for isotopic investigations into origin and husbandry conditions in archaeological sheep tissues, both collagen and keratin.

Bidirectional multiplexing of heralded single photons from a silicon chip

We demonstrate integrated spatial multiplexing of heralded single photons generated from a single 96 μm long silicon photonic crystal waveguide in a bidirectional pump configuration. By using a low-loss fiber-coupled opto-ceramic switch, the multiplexing technique enhances the brightness of the single photon source by 51.2±4.0% while maintaining the coincidence-to-accidental ratio. Compared with the demonstration of multiplexing two individual sources, the bidirectional pump scheme represents a twofold reduction in the footprint of nonlinear devices for future large-scale integration of on-chip single photon sources. The 51.2±4.0% gain will make any quantum operation requiring n photons 1.5(n) times faster.

Protein and mineral characterisation of rendered meat and bone meal

We report the characterisation of meat and bone meal (MBM) standards (Set B-EFPRA) derived from cattle, sheep, pig and chicken, each rendered at four different temperatures (133, 137, 141 and 145 °C). The standards, prepared for an EU programme STRATFEED (to develop new methodologies for the detection and quantification of illegal addition of mammalian tissues in feeding stuffs), have been widely circulated and used to assess a range of methods for identification of the species composition of MBM. The overall state of mineral alteration and protein preservation as a function of temperature was monitored using small angle X-ray diffraction (SAXS), amino acid composition and racemization analyses. Progressive increases in protein damage and mineral alteration in chicken and cattle standards was observed. In the case of sheep and pig, there was greater damage to the proteins and alteration of the minerals at the lowest treatment temperature (133 °C), suggesting that the thermal treatments must have been compromised in some way. This problem has probably impacted upon the numerous studies which tested methods against these heat treatments. We use protein mass spectrometric methods to explore if thermostable proteins could be used to identify rendered MBM. In more thermally altered samples, so-called 'thermostable' proteins such as osteocalcin which has been proposed as a ideal target to speciate MBM were no longer detectable, but the structural protein type I collagen could be used to differentiate all four species, even in the most thermally altered samples.

Acute mechanical effects of elastase on the infrarenal mouse aorta: implications for models of aneurysms

Intraluminal exposure of the infrarenal aorta to porcine pancreatic elastase represents one of the most commonly used experimental models of the development and progression of abdominal aortic aneurysms. Morphological and histological effects of elastase on the aortic wall have been well documented in multiple rodent models, but there has been little attention to the associated effects on mechanical properties. In this paper, we present the first biaxial mechanical data on, and associated nonlinear constitutive descriptors of, the effects of elastase on the infrarenal aorta in mice. Quantification of the dramatic, acute effects of elastase on wall behavior in vitro is an essential first step toward understanding the growth and remodeling of aneurysms in vivo, which depends on both the initial changes in the mechanics and the subsequent inflammation-mediated turnover of cells and extracellular matrix that contributes to the evolving mechanics.

Mechanical properties of suprarenal and infrarenal abdominal aorta: implications for mouse models of aneurysms

Multiple mouse models have been developed to increase our understanding of the natural history of abdominal aortic aneurysms. An advantage of such models is that one can quantify the time course of changes in geometry, histology, cell biology, and mechanics as a lesion develops. One of the most commonly used mouse models yields lesions in the suprarenal abdominal aorta whereas most other models target the infrarenal abdominal aorta, consistent with the clinical observation that nearly all abdominal aneurysms in humans occur in the infrarenal aorta. Understanding reasons for similarities and differences between diverse mouse models and human lesions may provide increased insight that would not be possible studying a single situation alone. Toward this end, however, we must first compare directly the native structure and properties of these two portions of the abdominal aorta in the mouse. In this paper, we present the first biaxial mechanical data and nonlinear constitutive descriptors for the suprarenal and infrarenal aorta in mice, which reveals only subtle mechanical differences despite marked morphological and histological differences. Such data promise to increase our ability to understand and model the natural history of these deadly lesions.

The short-term influence of exercise on axial length and intraocular pressure

PURPOSE

The aim of this study is to investigate the short-term influence of a period of dynamic exercise on axial length (AXL) and intraocular pressure (IOP) in young adult subjects.

PATIENTS AND METHODS

In all, 20 young adult subjects (10 myopes and 10 emmetropes) participated. Baseline measures of ocular biometrics, IOP and ocular pulse amplitude (OPA) were taken following a 20-min rest period. Subjects then performed 10 min of moderate intensity, low impact dynamic exercise (bicycle ergometry). Measures of ocular biometrics, IOP and OPA were repeated immediately after, and then 5 and 10 min after this exercise task. Systemic blood pressure and pulse rate were also monitored. A repeated measures analysis of variance was used to investigate the changes in the measured parameters.

RESULTS

Exercise resulted in significant changes in a range of ocular parameters. A small but significant decrease in AXL was observed following exercise (P<0.0001). The largest change in AXL was noted immediately following exercise (mean decrease -17±10 μm). IOP and OPA also decreased significantly following exercise (P<0.0001). A moderate but significant positive association was found between the changes in AXL and the changes in IOP (r(2)=0.36, P<0.0001). There were no significant differences found between the myopic and emmetropic subjects in the magnitude of changes observed in ocular parameters following exercise.

CONCLUSION

The physiological effects of dynamic exercise lead to changes in a range of ocular parameters, including significant reductions in IOP, OPA and decreases in AXL.

Testing the aminostratigraphy of fluvial archives: the evidence from intra-crystalline proteins within freshwater shells

Until recently few studies of amino acid racemization of fossil bivalves and gastropods collected from river terrace deposits in Europe were based on the analysis of the intra-crystalline fraction. Instead they were based on the epimerization (racemization) of a single amino acid, isoleucine, and its inter-conversion to alloisoleucine. This paper presents data from the analysis of the intra-crystalline fraction of the shells, using a preparation technique of sample bleaching to remove the leachable matrix, thus leaving a component that exhibits closed-system behaviour. Reverse-phase HPLC separation with fluorescence detection allows the interpretation of four amino acids in detail: aspartic acid, glutamic acid, alanine and valine. The intra-crystalline fraction offers greater potential for improved resolution, especially when combined with the analysis of multiple amino acid d/l values, which racemize at different rates. This is explored using three species of freshwater gastropods (Bithynia tentaculata and troschelii, Valvata piscinalis) and the bivalve Corbicula. Sites of different ages within the Lower Thames river terrace sequence are used as a stratigraphical framework, with samples from other southern UK sites providing supplementary evidence. The results indicate better resolution using the intra-crystalline fraction over that obtained using unbleached shells, with differentiation possible at sites of up to MIS 7 age. However, for older sites, although values are always higher, the separation is less successful. A species effect has been identified between the gastropod shells. Despite the analysis of intra-crystalline protein, amino acid data from Corbicula remain problematical. Preliminary data on the opercula from Bithynia indicate that better resolution is possible, particularly at older sites.

Implications of a congenitally abnormal valve: a study of 1025 consecutively excised aortic valves

Background:

An increasing proportion of patients with congenitally abnormal aortic valves (AV) present for AV replacement.

Aims:

To review morphological changes in a large contemporary patient population undergoing AV replacement.

Methods:

A detailed review was conducted for all 1025 patients who underwent AV replacement from 2002 to 2005, including the clinical indication for surgery, the type of native AV disease, the pathological changes observed in each valve and the need for related surgery.

Results:

Tricuspid (TAV), bicuspid (BAV) and unicuspid (UAV) aortic valves were observed in 64.5%, 31.9% and 3.0% of all patients respectively. A decreased number of cusps was associated with increasing predilection for male gender (83.9%, 73.4%, 59.2% for UAV, BAV, TAV respectively), a younger patient age at surgery (41.6 (14.3), 61.3 (12.8), 67.5 (12.9) years), and an increased occurrence of pathological changes in the cusps, including calcification of both the cusp and the base, ossification and ulceration. UAV and BAV were also associated with increasing replacement of the ascending aorta due to dilatation and aneurysm formation (54.8, 38.8%, 16.6%). The incidence of infective endocarditis and rheumatic heart disease was 3.8% and 11.2% of all excised valves respectively.

Conclusion:

UAV and BAV were increasingly likely to affect men, fail at an earlier age, and show an increasing incidence of pathological changes in the cusps and ascending aorta than TAV. These results suggest that TAV, BAV and UAV may represent a phenotypic continuum of a similar disease process.

Variation in the histopathological features of patients with ascending aortic aneurysms: a study of 111 surgically excised cases

Background:

Ascending aortic aneurysms (AA) are a common, though poorly understood medical condition.

Aims:

To document the histological changes in a large series of human ascending AA, and to correlate these changes with clinical variables.

Methods:

111 ascending AA were excised at surgery over a 3 year period. Each aneurysm was received as a continuous ring of tissue. Sections were taken from the anterior, posterior, greater and lesser curvature of the aorta and graded in a semi-quantitative fashion for the degree of elastin fragmentation, elastin loss, smooth muscle cell (SMC) loss, intimal changes and inflammation.

Results:

Mean patient age at surgery was 58.7 (15.6) years; there were 70 men and 41 women. 12 patients had Marfan syndrome, 34 (30.6%) had a bicuspid aortic valve (BAV), while 71 (64.0%) had a tricuspid aortic valve (TAV). Inflammatory cells were present in 28 cases (25.2%) and were confined to the adventitia. No particular region of the aortic circumference was more severely affected, however a BAV was associated with significantly less intimal change, and less fragmentation and loss of elastic tissue compared with patients with a TAV. Advanced age (>65 years), female gender and Marfan syndrome were all associated with more severe elastin degeneration and smooth muscle cell loss (p<0.05 for all).

Conclusion:

Results indicate a wide variation in the histological appearance in ascending AA, depending on patient characteristics. They suggest that the underlying aneurysm pathogenesis may also be highly variable; this warrants further investigation.

The application of amino acid racemization in the acid soluble fraction of enamel to the estimation of the age of human teeth

Estimation of age-at-death for skeletonised forensic remains is one of the most significant problems in forensic anthropology. The majority of existing morphological and histological techniques are highly inaccurate, and show a bias towards underestimating the age of older individuals. One technique which has been successful in forensic age estimation is amino acid racemization in dentine. However, this method cannot be used on remains where the post-mortem interval is greater than 20 years. An alternative approach is to measure amino acid racemization in dental enamel, which is believed to be more resistant to change post-mortem. The extent of amino acid racemization in the acid soluble fraction of the enamel proteins was determined for modern known age teeth. A strong correlation was observed between the age of the tooth and the extent of racemization. No systematic bias in the direction of age estimation errors was detected. For the majority of teeth analyzed, the presence of dental caries did not affect the results obtained. In a minority of cases, carious teeth showed a higher level of racemization than would be expected given the age of the individual. These results indicate that amino acid racemization in enamel has the potential to be used in age estimation of skeletal remains.

The Effect of the Lipid Layer on Tear Film Behaviour

This paper investigates the effect of surfactants during tear film deposition and subsequent thinning. The surfactants occur naturally on the surface of the tear film in the form of a lipid layer. A lubrication model is developed that describes lipid spreading and film height evolution. It is shown that lipids may play an important role in drawing the tear film up the cornea during the opening phase of the blink. Further, nonuniform distributions of lipids may lead to a rapid thinning of the tear film behind the advancing lipid front (shock). Experiments using a fluorescein dye technique and using a tearscope were undertaken in order to visualise the motion of the lipid layer and any associated shocks immediately after a blink. It is found that the lipid layer continues to spread upwards on the cornea after the opening phase of the blink, in agreement with the model. Using the experimental data, lipid particles were tracked in order to determine the surface velocity and these results are compared to the model predictions.

Dynamics of ocular surface topography

PURPOSE

To investigate fluctuations in the ocular surface, we used high-speed videokeratoscopy (50 Hz) to measure the dynamics of the ocular surface topography.

METHODS

Ocular surface height difference maps were computed to illustrate the changes in the tear film in the inter-blink interval. Topography data were used to derive the ocular surface wavefront aberrations up to the fourth radial order of the Zernike polynomial expansion. We examined the ocular surface dynamics and temporal changes in the ocular surface wavefront aberrations in the inter-blink interval.

RESULTS

During the first 0.5 s following a blink, the ocular surface height at the upper edge of the topography map increased by about 2 mum. Temporal changes occurred for some ocular surface wavefront aberrations and appeared to be related to changes in the distribution of tear film.

CONCLUSION

In the clinical measurement of ocular surface topography using videokeratoscopy or optics of the eye using wavefront sensors, care should be taken to avoid the initial tear film build-up phase following a blink to achieve more consistent results.

Coronary artery stents: identification and evaluation

First introduced in the 1980s, the coronary stent has been used to reduce the rate of arterial restenosis. Coronary stent implantation is currently a common procedure performed by interventional cardiologists, and the market for development and design is constantly expanding and evolving. This article was designed to assist pathologists in the accurate identification of coronary stents that are currently available, in addition to some that are no longer being implanted. The stents reviewed here were chosen based on frequency of use and/or occurrence in the literature. Some of the newer models have yet to undergo extensive clinical testing. The summaries accompanying each stent include concise physical descriptions and documented complications, intended to serve as a guide for the investigating pathologist.

Dynamics of tear film deposition and draining

This paper investigates the deposition of the tear film on the cornea of the human eye. The tear film is laid down by the motion of the upper eyelid and then subsequently flows and thins. Of particular interest is the stability of the tear layer and the development of dry patches on the cornea. While there has been significant research on the behaviour of tear films between blinks, this paper focuses on understanding the mechanisms which control the shape and thickness of the deposited film and how this affects the subsequent film behaviour. Numerical and analytical methods are applied to a lubrication model which includes the effects of surface tension, viscosity, gravity and evaporation. The model reveals the importance of the eyelid velocity, motion of the surface lipid layer and the storage of tear film between blinks.

Analysis of prosthetic cardiac devices: a guide for the practising pathologist

Pathologists all over the world increasingly encounter prosthetic cardiac devices. A good evaluation of these devices is a valuable source of information, which can contribute to patient care and the appreciation and understanding of the pathobiology involved in the changes occurring between the host and the implanted prosthetic device. This article summarises the considerations underlying the analysis of prosthetic devices (particularly prosthetic heart valves), including the identification of the devices, the major morphological features of the devices, their modes of failure, and some technical details about evaluation and pitfalls.

Aspartic acid racemization: evidence for marked longevity of elastin in human skin

BACKGROUND

In extracellular proteins, aspartic acid racemization (AAR) has the potential to identify long-lived or permanent proteins.

OBJECTIVES

We present data to show an age-dependent increase in AAR in chronologically aged skin elastin.

METHODS

Elastin was purified in a multistep procedure designed to remove contaminating proteins and to avoid induced racemization. As a control experiment, elastin was also purified from the richest elastin bearing tissue, the yellow ligaments of the spine.

RESULTS

In total skin, specimens displayed a slight age-dependent increase in d-aspartyl residues, but in purified elastin the rate of increase was rapid and highly correlated with age (r = 0.98). Similar rates were observed in the control data from the yellow ligaments. The AAR rates were found to be higher in elastin from skin (and yellow ligaments) than previous studies of lung parenchyma and from aorta had shown. These differences appear to be related to the purity of the extracted elastin product, and to a significant in vivo degradation of elastin in skin.

CONCLUSIONS

The age-dependent accumulation of modified aspartic acid residues appears to be a common feature in ageing elastin, independent of the tissue source. This indicates a lack of turnover and an accumulation of elastin damage in diverse ageing tissues, possibly as part of programmed ageing.

The stability of corneal topography in the post-blink interval

PURPOSE

Videokeratoscopes provide a wealth of information about the topography of the ocular surface. Although there have been numerous studies of the accuracy and precision of videokeratoscopes with inanimate test objects, little information exists on their precision (repeatability) for real eyes.

METHODS

To investigate the stability of the ocular surface in the inter-blink period, 10 patients were recruited for videokeratoscopy. Tear break-up time was measured and videokeratographs were acquired immediately post-blink and again at 4, 8, and 12 seconds post-blink. To permit statistical inferences to be drawn from the data, we acquired 24 videokeratographs for each of the four post-blink intervals. The videokeratograph data were interpolated (bilinear) to a common grid, and average and standard deviation (SD) maps were derived for each post-blink condition. t Tests were used to test the significance of changes observed in the topography.

RESULTS

The instantaneous power SD maps showed increasing variation toward the periphery, with most maps showing less than +/-0.5 diopters (D) of SD in the central 4 to 5 mm and variation in the periphery often reaching more than +/-1 D SD at the edge of an 8-mm diameter. When the 4-, 8-, and 12-second average maps were subtracted from the average map acquired immediately after blinking, regions of statistically significant ( p < 0.001) change were apparent in the upper and lower regions of the maps. The upper and lower bands of change were found to correlate with the natural position of the patients' lid margins.

CONCLUSIONS

For normal eyes, the central regions of videokeratographs show high stability in the inter-blink period. However, the upper and lower edges of 8-mm diameter maps show statistically significant variability, which appears to be related to the effects of eyelid pressure.

Ambient air quality at the site of a former manufactured gas plant

Prior to the 1950's, manufactured gas was commercially produced from the pyrolysis of coal, coke, and oil at facilities that are termed manufactured gas plants (MGPs). The constituents of residual coal tar present on many MGP sites are an environmental health concern because of their toxicity and the possibility for their off-site migration via water and air. Atmospheric concentrations of five volatile organic compounds (VOCs, e.g., benzene), sixteen polycyclic aromatic hydrocarbons (PAHs, e.g., naphthalene) and particulate matter less than 10 microns in aerodynamic diameter (PM10) were measured at the site of a former MGP. Air samples were obtained before, during, and after excavation of subterranean coal tar at the site. The results of this investigation indicate that subterranean coal tar was not a primary source of VOCs and PAHs in the local atmosphere before or after remediation of the site. However, excavation, treatment, blending, and transfer of the coal tar during remediation generated concentrations of selected aromatic and semi-volatile organic compounds that were substantially greater than typical ambient levels. In addition, these data suggest that blending and mixing of coal tars could lead to exceedance of the U.S. National Ambient Air Quality Standard for PM10, although additional research is required to fully evaluate this possibility. Nuisance odors associated with the site remediation were likely the result of naphthalene and possibly isomers of xylene. Air pollutant concentrations measured adjacent to the excavation area and at the site perimeter during remediation activities were less than the relevant occupational and environmental exposure limits.

Quality assurance in age estimation based on aspartic acid racemisation

Estimates of the age of living and dead individuals, obtained in order to answer legal or social questions, require minimum quality standards in order to guarantee data quality. We present an outline strategy (with recommendations) for the attainment of quality assurance in age estimation based on aspartic acid racemisation. The strategy is based on a definition of minimum standards for laboratories, including documentation of procedures, methodology and levels of expertise, and the formulation of guidelines for intralaboratory and interlaboratory quality control.

Optimal modeling of corneal surfaces with Zernike polynomials

Zernike polynomials are often used as an expansion of corneal height data and for analysis of optical wavefronts. Accurate modeling of corneal surfaces with Zernike polynomials involves selecting the order of the polynomial expansion based on the measured data. We have compared the efficacy of various classical model order selection techniques that can be utilized for this purpose, and propose an approach based on the bootstrap. First, it is shown in simulations that the bootstrap method outperforms the classical model order selection techniques. Then, it is proved that the bootstrap technique is the most appropriate method in the context of fitting Zernike polynomials to corneal elevation data, allowing objective selection of the optimal number of Zernike terms. The process of optimal fitting of Zernike polynomials to corneal elevation data is discussed and examples are given for normal corneas and for abnormal corneas with significant distortion. The optimal model order varies as a function of the diameter of the cornea.

Flexure of thin rigid contact lenses

The flexure of spherical rigid contact lenses was measured on the eyes of 10 young subjects using a videokeratoscope. Five subjects had little or no with-the-rule astigmatism (<0.75 D) andfive had moderate levels of with-the-rule astigmatism (1.00-2.00 D). Two lens materials (polymethylmethacrylate [PMMA] and Boston XO) in three centre thicknesses (0.05, 0.10 and 0.15 mm) were used in the study. No significant difference in the amount of flexure was found between the two materials tested. The degree of regular astigmatism on the lens front surface was found to increase as the centre thickness of the contact lens decreased. For the astigmatic group, the lenses with centre thicknesses of 0.05 mm had levels of front surface astigmatism similar to those of the underlying cornea. On spherical corneas the level of regular astigmatism can exceed that of the cornea for thinner lenses. When sphero-cylinder variations are accounted for, residual higher order aberration (root mean square) levels were found to approach those of the cornea when the lens thickness was reduced to 0.05 mm.

Effects of laser in situ keratomileusis (LASIK) on the corneal endothelium 3 years postoperatively

PURPOSE

To investigate the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium 3 years postoperatively.

METHODS

Patients who were subjects of a previous prospective study (Am J Ophthalmol 125:465-471, (April) 1998) were contacted for a follow-up analysis of the central corneal endothelium. Noncontact specular microscopy was performed 35 to 37 months after LASIK on 52 eyes of 27 patients of the original cohort of 98 eyes of 65 patients and six eyes of three patients who were previously lost to follow-up after their initial post-LASIK evaluation. Patient age ranged from 29 to 66 years at the time of the original LASIK procedure. Attempted corrections ranged from 2.25 to 14.5 diopters of myopia, giving theoretical ablation depths of 182 to 332 microm below the corneal surface. Forty-eight eyes (83%) had a history of preoperative contact lens use (3 to 33 years). Central endothelial cell density, coefficient of variation of cell size, and percent of hexagonal cells were analyzed using 72 to 152 cells from each image. Multivariate analysis was used to search for factors that might predict changes in cell density, coefficient of variation, and percent of hexagonal cells.

RESULTS

The mean +/- SD preoperative cell density was 2,498 +/- 354 cells per mm(2), the mean coefficient of variation was 0.36 +/- 0.07, and the percent of hexagonal cells was 58 +/- 6. Three years after surgery there was no statistically significant change in the mean endothelial cell density (2,489 +/- 335 cells per mm(2); P = 0.88, paired t test) or the percent of hexagonal cells (60 +/- 7; P = 0.14, paired t test). The mean coefficient of variation was significantly lower postoperatively (0.32 +/- 0.04; P = 0.0006, paired t test); a repeated measures analysis showed that this significant improvement could not be explained by cessation of contact lens wear after LASIK (P = 0.34). Multivariate analysis did not identify any factors that were predictive of change in cell density, coefficient of variation, and percent of hexagonal cells.

CONCLUSIONS

Laser in situ keratomileusis for the correction of 2.25 to 14.5 diopters of myopia had no significant effect on central corneal endothelial cell density or the percent of hexagonal cells 3 years after surgery. The coefficient of variation of cell size improved significantly 3 years after surgery.

Age estimation: the state of the art in relation to the specific demands of forensic practise

Age estimation in cadavers, human remains and living individuals may clarify issues with significant legal and social ramifications for individuals as well as for the community. In such cases methods for estimating age should fulfil the following specific demands: (1) they must have been presented to the scientific community, as a rule by publication in peer-reviewed journals, (2) clear information concerning accuracy of age estimation by the method should be available, (3) the methods need to be sufficiently accurate and (4) in cases of age estimation in living individuals principles of medical ethics and legal regulations have to be considered. We have identified and summarized the methods that essentially fulfil these specific demands. In childhood and adolescence morphological methods based on the radiological examination of dental and skeletal development are to be recommended. In adulthood, the accuracy of most morphological methods is much reduced. Here a biochemical method based on aspartic acid racemization in dentine provides the most accurate estimates of age, followed by special morphological dental and skeletal methods. The choice of method has to take account of the individual circumstances of each case. Most methods require either the consultation of specialised and trained scientists or an adequate calibration by the "user". Very few attempts have been made to find common standardisation, calibration and evaluation procedures or to develop means of quality assurance for methods of age estimation. Efforts in these directions are necessary to guarantee quality standards and adequate answers to the important legal and social issue of age estimation in forensic medicine.

The accuracy and precision performance of four videokeratoscopes in measuring test surfaces

In this study we evaluated the accuracy and precision of three placido-disk videokeratoscopes (the Keratron, Medmont and TMS) and one videokeratoscope that uses the raster-stereogrammetry technique (PAR-CTS) in elevation topography with six test surfaces. The test surfaces were a sphere, an asphere, a multicurve, and three bicurve surfaces. Each instrument performed well on certain test surfaces, but none of the instruments excelled on all of the surfaces. The results showed high accuracy of the Keratron and Medmont instruments in measuring the sphere, asphere, and multicurve surfaces, but not the bicurve surfaces. The precision of the Keratron and Medmont instruments were high. The TMS and PAR-CTS instruments showed poorer accuracy than the Keratron and Medmont instruments for the multicurve test surface but showed better performance for the bicurve surfaces. The PAR-CTS had the poorest performance in precision of the four instruments. The use of the Noryl spherical test surface instead of polymethyl methacrylate (PMMA) resulted in small differences in the accuracy performance of the placido-disk videokeratoscopes only.

An improved method for the immunological detection of mineral bound protein using hydrofluoric acid and direct capture

Immunological detection of proteins adsorbed to mineral and ceramic surfaces has proved not only difficult but controversial. Unlike the immunological detection of proteins associated with carbonate or phosphate minerals (e.g. shells and bones) proteins adsorbed to siliceous minerals cannot readily be removed by dissolution of the mineral phase. We have previously examined alternative extraction methodologies which claim to bring the protein into solution, but found none of these to be effective. Here we report a novel strategy for immuno-detection of proteins adsorbed to siliceous minerals, the Digestion and Capture Immunoassay (DACIA). The method involves the use of cold, concentrated (4M) hydrofluoric acid (HF) with the simultaneous capture of liberated protein onto a solid phase. The combination of low temperatures and surface stabilisation enables us to detect epitopes from even partially degraded proteins. The method may have a wide application in forensic, archaeological, soil and earth sciences.

A review of the methodological aspects of aspartic acid racemization analysis for use in forensic science

Accurate age determination of adult cadavers and human remains is a key requirement in forensic practice. The current morphological methods lack accuracy and precision, require specialist training and are costly. The use of aspartic acid racemization (AAR) in human dentine provides a simple, cost-effective solution and the method can achieve accuracies of +/- 3 years at best. Currently, there are differences in AAR methodology between laboratories which produce different results on the rate of racemization in teeth. These inconsistencies must be resolved if the technique is to be successfully applied to age determinations in forensic cases. This paper reviews the differences in protocol which have been used, discusses how each method will affect the results obtained from AAR analysis and gives recommendations for optimization of the methological protocol as a first step towards international standardization.

Hydroxyproline interference during the gas chromatographic analysis of D/L aspartic acid in human dentine

The proportion of D- to L-enantiomers of aspartic acid in metabolically isolated proteins has been used by forensic scientists to estimate age at death. We have demonstrated the interference of a derivative of hydroxyproline (N-TFA isopropyl Hyp ester) with the N-TFA isopropyl L-Aspartic (Asp) acid ester during gas chromatography of amino acids. This has serious implications for the accurate quantification of the D- to L-Asp ratio extracted from collagenous proteins. Having demonstrated the potential for this co-elution in amino acid standards, acid-soluble dentine proteins and non-mineralised collagen, we argue that this problem can be overcome either by high resolution separation or by analysis of the (Hyp-poor) non-collagenous protein fraction.

Metastatic esophageal carcinoma to the orbit

PURPOSE

To report a case of esophageal adenocarcinoma and areas of gastric differentiation in the esophagus (Barrett esophagus) metastatic to the orbit.

METHODS

A 47-year-old man with a history of esophageal carcinoma developed turgescence around his left eye. He underwent a biopsy and histologic examination of a left orbital mass.

RESULTS

Histopathology of the orbital tumor was consistent with metastatic adenocarcinoma from the esophagus.

CONCLUSIONS

This metastatic adenocarcinoma to the orbit likely arose in Barrett esophagus.

Predicting protein decomposition: the case of aspartic-acid racemization kinetics

The increase in proportion of the non-biological (D-) isomer of aspartic acid (Asp) relative to the L-isomer has been widely used in archaeology and geochemistry as a tool for dating. the method has proved controversial, particularly when used for bones. The non-linear kinetics of Asp racemization have prompted a number of suggestions as to the underlying mechanism(s) and have led to the use of mathematical transformations which linearize the increase in D-Asp with respect to time. Using one example, a suggestion that the initial rapid phase of Asp racemization is due to a contribution from asparagine (Asn), we demonstrate how a simple model of the degradation and racemization of Asn can be used to predict the observed kinetics. A more complex model of peptide bound Asx (Asn + Asp) racemization, which occurs via the formation of a cyclic succinimide (Asu), can be used to correctly predict Asx racemization kinetics in proteins at high temperatures (95-140 degrees C). The model fails to predict racemization kinetics in dentine collagen at 37 degrees C. The reason for this is that Asu formation is highly conformation dependent and is predicted to occur extremely slowly in triple helical collagen. As conformation strongly influences the rate of Asu formation and hence Asx racemization, the use of extrapolation from high temperatures to estimate racemization kinetics of Asx in proteins below their denaturation temperature is called into question. In the case of archaeological bone, we argue that the D:L ratio of Asx reflects the proportion of non-helical to helical collagen, overlain by the effects of leaching of more soluble (and conformationally unconstrained) peptides. Thus, racemization kinetics in bone are potentially unpredictable, and the proposed use of Asx racemization to estimate the extent of DNA depurination in archaeological bones is challenged.

Does pulse oximetry reliably detect aspiration in dysphagic stroke patients?

BACKGROUND AND PURPOSE

The aim of the present study was to examine the value of pulse oximetry in the diagnosis of aspiration by comparing it with the gold standard, videofluoroscopy, by use of a prospective, controlled, single-blind study design.

METHODS

Pulse oximetry was performed simultaneously with videofluoroscopy in 54 consecutive dysphagic stroke patients. Oxygen saturation measurements were taken before the video-fluoroscopic examination (baseline), on swallowing and continuously for 2 minutes after swallowing, and 10 minutes later.

RESULTS

Pulse oximetry reliably predicted aspiration or lack of it in 81.5% of cases. The predictive value of the test was low in patients aged > or = 65 years and possibly those with chronic lung disease. One smoker also had a false-negative pulse oximetry result, ie, normal oxygen saturation despite radiological evidence of aspiration.

CONCLUSIONS

Pulse oximetry is a reliable method of diagnosis of aspiration in most dysphagic patients. However, careful interpretation of pulse oximetry data is necessary in older subjects, possibly those with chronic pulmonary disease, and smokers. The method is noninvasive, simple, and quick, and can be used routinely in the clinical assessment of dysphagic patients.

Measurement of ultraviolet radiation at the surface of the eye

PURPOSE

A new method for the measurement of ultraviolet radiation that reaches the surface of the eye is described.

METHODS

The technique uses contact lenses produced from the ultraviolet-sensitive plastic polysulfone. Two types of polysulfone contact lenses (9 mm and 12 mm in diameter) were manufactured from a polysulfone rod. The 9-mm polysulfone contact lens could be calibrated and used to determine the ocular-to-ambient exposure ratio in a fashion similar to polysulfone film badges. The 12-mm polysulfone contact lens was designed as a "piggy-back" lens and required a larger diameter polymethlylmethacrylate carrier lens to fit the eye adequately. A method of in vivo stabilization was developed to minimize lens rotation.

RESULTS

During four wearing trials, the ratio of ocular-to-ambient ultraviolet exposure ranged from 4% to 23%.

CONCLUSIONS

Contact lenses manufactured from polysulfone offer the potential to study the exposure of the eye to ultraviolet radiation. The smaller diameter lens can measure an average ocular exposure, whereas the larger, stabilized, piggy-back design may allow regional dose assessment across the entire lens surface.

Angles of entry of ultraviolet radiation into welding helmets

To investigate the angles of entry of ultraviolet (UV) radiation into welding helmets, a UV detector was placed in the eye socket of a head form that was then fitted with a range of welding helmets. The head form was exposed to a collimated beam of UV radiation from various orientations, and the amount of infiltration was measured. Radiation was found to be reflected from the filter plate and into the detector (eye) after entering through (1) an opening between the edge of the shield and the side of the face, and (2) an opening between the top edge of the shield and the top of the head. These results have significance for UV exposure when welding is performed in highly reflective and enclosed situations, and for the design of welding helmets.

Personal ultraviolet radiation exposure of workers in a welding environment

The personal ultraviolet radiation exposure levels of a group of welders and nearby workers were estimated using a photosensitive polymer film, polysulphone. The polysulphone film was attached to the inner and outer surfaces of eye protection, the workers' clothing, and also placed throughout the work area. The estimated average ocular exposures (inside the helmets) for welders and boiler-makers were between four and five times the maximum permissible exposure (MPE) limit, and the estimated exposures at the spectacles of nonwelders were around 9 times MPE. Body exposures (at the clothing surface) for welders were estimated to be around 3000 times MPE and for nonwelders around 13 times MPE. The ambient ultraviolet radiation levels in the factory were found to exceed the MPE by an average of 5.5 times, even in nonwelding areas. The results suggest that welders require additional ocular protection to supplement conventional welding helmets, and any exposed skin areas of workers in this environment should also be protected.