Automatically Determining the Confocal Parameters From OCT B-Scans for Quantification of the Attenuation Coefficients

The attenuation coefficient is a relevant biomarker for many diagnostic medical applications. Recently, the Depth-Resolved Confocal (DRC) technique was developed to automatically estimate the attenuation coefficients from Optical Coherence Tomography (OCT) data with pixel-level resolution. However, DRC requires that the confocal function parameters (i.e., focal plane location and apparent Rayleigh range) be known a priori. In this paper, we present the autoConfocal algorithm: a simple, automatic method for estimating those parameters directly from OCT imagery when the focal plane is within the sample. We present autoConfocal+DRC results on phantom data, ex-vivo biological tissue data, and in-vivo clinical data.

Low-power, low-cost urinalysis system with integrated dipstick evaluation and microscopic analysis

We introduce a coupled dipstick and microscopy device for analyzing urine samples. The device is capable of accurately assessing urine dipstick results while simultaneously imaging the microscopic contents within the sample. We introduce a long working distance, cellphone-based microscope in combination with an oblique illumination scheme to accurately visualize and quantify particles within the urine sample. To facilitate accurate quantification, we couple the imaging set-up with a power-free filtration system. The proposed device is reusable, low-cost, and requires very little power. We show that results obtained with the proposed device and custom-built app are consistent with those obtained with the standard clinical protocol, suggesting the potential clinical utility of the device.

Robust dipstick urinalysis using a low-cost, micro-volume slipping manifold and mobile phone platform

We introduce a novel manifold and companion software for dipstick urinalysis that eliminate many of the aspects that are traditionally plagued by user error: precise sample delivery, accurate readout timing, and controlled lighting conditions. The proposed all-acrylic slipping manifold is reusable, reliable, and low in cost. A simple timing mechanism ensures results are read out at the appropriate time. Results are obtained by capturing videos using a mobile phone and by analyzing them using custom-designed software. We show that the results obtained with the proposed device are as accurate and consistent as a properly executed dip-and-wipe method, the industry gold-standard, suggesting the potential for this strategy to enable confident urinalysis testing in home environments.

Multimodal 3D cancer-mimicking optical phantom

Three-dimensional (3D) organ-mimicking phantoms provide realistic imaging environments for testing various aspects of optical systems, including for evaluating new probe designs, characterizing the diagnostic potential of new technologies, and assessing novel image processing algorithms prior to validation in real tissue. We introduce and characterize the use of a new material, Dragon Skin (Smooth-On Inc.), and fabrication technique, air-brushing, for fabrication of a 3D phantom that mimics the appearance of a real organ under multiple imaging modalities. We demonstrate the utility of the material and technique by fabricating the first 3D, hollow bladder phantom with realistic normal and multi-stage pathology features suitable for endoscopic detection using the gold standard imaging technique, white light cystoscopy (WLC), as well as the complementary imaging modalities of optical coherence tomography and blue light cystoscopy, which are aimed at improving the sensitivity and specificity of WLC to bladder cancer detection. The flexibility of the material and technique used for phantom construction allowed for the representation of a wide range of diseased tissue states, ranging from inflammation (benign) to high-grade cancerous lesions. Such phantoms can serve as important tools for trainee education and evaluation of new endoscopic instrumentation.

Automated, Depth-Resolved Estimation of the Attenuation Coefficient From Optical Coherence Tomography Data

We present a method for automated, depth-resolved extraction of the attenuation coefficient from Optical Coherence Tomography (OCT) data. In contrast to previous automated, depth-resolved methods, the Depth-Resolved Confocal (DRC) technique derives an invertible mapping between the measured OCT intensity data and the attenuation coefficient while considering the confocal function and sensitivity fall-off, which are critical to ensure accurate measurements of the attenuation coefficient in practical settings (e.g., clinical endoscopy). We also show that further improvement of the estimated attenuation coefficient is possible by formulating image denoising as a convex optimization problem that we term Intensity Weighted Horizontal Total Variation (iwhTV). The performance and accuracy of DRC alone and DRC+iwhTV are validated with simulated data, optical phantoms, and ex-vivo porcine tissue. Our results suggest that implementation of DRC+iwhTV represents a novel way to improve OCT contrast for better tissue characterization through quantitative imaging.

Fabrication of healthy and disease-mimicking retinal phantoms with tapered foveal pits for optical coherence tomography

Optical coherence tomography (OCT) has become a standard tool in ophthalmology clinics for diagnosing many retinal diseases. Nonetheless, the technical and clinical communities still lack a standardized phantom that could aid in evaluating and normalizing the many protocols and systems used for diagnosis. Existing retinal phantoms are able to mimic the thickness and scattering properties of the retinal layers but are unable to model the morphology of the foveal pit, particularly the tapering of the retinal layers. This work demonstrates a new fabrication procedure that is capable of reliably and consistently replicating the shape and tapered appearance of the retinal layers near the foveal pit using a combination of spin-coating and replica molding. We characterize the effects of using different mold sizes which enable us to achieve a range of pit dimensions. We also present a modified procedure to replicate two diseased states of the retinal tissue, such as retinal detachment and dry aged-related macular degeneration. The ability to create an anatomically correct foveal pit for healthy and disease-mimicking phantoms will allow for a new standard better suited for intra- and inter-system evaluation and for improved comparison of retinal segmentation algorithms

Single-shot speckle noise reduction by interleaved optical coherence tomography

Speckle noise is one of the dominant factors that degrade image quality in optical coherence tomography (OCT). Here, we propose a new strategy, interleaved OCT (iOCT), for spatial compounding and angular compounding. We demonstrate the efficiency of compounding with iOCT to restrain speckle noise without compromising imaging speed in phantoms and tissue samples.

Quantitative measurements of strain and birefringence with common-path polarization-sensitive optical coherence tomography

We demonstrate the first system for optical coherence tomography (OCT) that enables simultaneous measurement of quantitative birefringence and strain in biological samples using a common-path configuration. Owing to its superior phase stability, common-path polarization sensitive optical coherence tomography (CoPPSe-OCT) achieves a sub-nanometer displacement sensitivity of 0.52 nm at an SNR of 48 dB. We utilize CoPPSe-OCT to measure reflectance, birefringence, and strain for distinguishing burnt regions in a birefringent biological sample (chicken breast muscle).

Label-free and non-contact optical biosensing of glucose with quantum dots

We present a label-free, optical sensor for biomedical applications based on changes in the visible photoluminescence (PL) of quantum dots in a thin polymer film. Using glucose as the target molecule, the screening of UV excitation due to pre-absorption by the product of an enzymatic assay leads to quenching of the PL of quantum dots (QDs) in a non-contact scheme. The irradiance changes in QD PL indicate quantitatively the level of glucose present. The non-contact nature of the assay prevents surface degradation of the QDs, which yields an efficient, waste-free, cost-effective, portable, and sustainable biosensor with attractive market features. The limit of detection of the demonstrated biosensor is ~3.5 µm, which is competitive with existing contact-based bioassays. In addition, the biosensor operates over the entire clinically relevant range of glucose concentrations of biological fluids including urine and whole blood. The comparable results achieved across a range of cost-affordable detectors, including a spectrophotometer, portable spectrometer, and iPhone camera, suggest that label-free and visible quantification of glucose with QD films can be applied to low-cost, point-of-care biomedical sensing as well as scientific applications in the laboratory for characterizing glucose or other analytes.

Three-dimensional, distendable bladder phantom for optical coherence tomography and white light cystoscopy

We describe a combination of fabrication techniques and a general process to construct a three-dimensional (3-D) phantom that mimics the size, macroscale structure, microscale surface topology, subsurface microstructure, optical properties, and functional characteristics of a cancerous bladder. The phantom also includes features that are recognizable in white light (i.e., the visual appearance of blood vessels), making it suitable to emulate the bladder for emerging white light+optical coherence tomography (OCT) cystoscopies and other endoscopic procedures of large, irregularly shaped organs. The fabrication process has broad applicability and can be generalized to OCT phantoms for other tissue types or phantoms for other imaging modalities. To this end, we also enumerate the nuances of applying known fabrication techniques (e.g., spin coating) to contexts (e.g., nonplanar, 3-D shapes) that are essential to establish their generalizability and limitations. We anticipate that this phantom will be immediately useful to evaluate innovative OCT systems and software being developed for longitudinal bladder surveillance and early cancer detection.

Transition across polymorphic phenotypes observed in a male Sternarchogiton nattereri (Gymnotiformes: Apteronotidae)

A transition between polymorphic phenotypes was observed within a single male Sternarchogiton nattereri. This individual was initially toothless, but developed into a toothed phenotype characterized by a swollen distal upper jaw and distinctive external dentition. Changes in morphological features were accompanied by shifts in electrocommunication (chirping) behaviour.

Experimental charge-density study on the nickel(II) coordination complex [Ni(H3 L)][NO3][PF6] [H3 L = N,N′,N′′-tris(2-hydroxy-3-methylbutyl)-1,4,7-triazacyclononane]: a reappraisal

The experimental charge density in the title complex has been re-examined. The original work, reported some 8 years ago [Smith et al. (1997). J. Am. Chem. Soc. 119, 5028–5034], was undertaken using a very early version of the XD software, which contained serious programming errors. A re-refinement, using the original data and a recent version of the XD software, shows that many of the unusual aspects of this earlier study are artefacts due to these programming errors. The topological properties of the newly obtained experimental density compare well with those calculated from a theoretical DFT (density-functional theory) UHF-SCF (unrestricted Hartree Fock–self-consistent field) density. This report corrects several erroneous conclusions regarding the charge density in the title complex – in particular, the highly unusual diffuse Laplacian distribution about the Ni atom, and the trifurcated bond path from the Ni atom to the alcohol oxygen donor atoms are no longer observed. An examination of a range of topological properties of the metal–ligand bonds leads to the conclusion that the Ni—N and Ni—O bonds have an intermediate character, with a significant shared interaction, but with a substantial ionic component. This new study also reveals a previously unrecognized intramolecular H...H interaction in the macrocyclic ligand.

Simulation of emission tomography using grid middleware for distributed computing

SimSET is Monte Carlo simulation software for emission tomography. This paper describes a simple but effective scheme for parallel execution of SimSET using NetSolve, a client-server system for distributed computation. NetSolve (version 1.4.1) is "grid middleware" which enables a user (the client) to run specific computations remotely and simultaneously on a grid of networked computers (the servers). Since the servers do not have to be identical machines, computation may take place in a heterogeneous environment. To take advantage of diversity in machines and their workloads, a client-side scheduler was implemented for the Monte Carlo simulation. The scheduler partitions the total decay events by taking into account the inherent compute-speeds and recent average workloads, i.e., the scheduler assigns more decay events to processors expected to give faster service and fewer decay events to those expected to give slower service. When compute-speeds and sustained workloads are taken into account, the speed-up is essentially linear in the number of equivalent "maximum-service" processors. One modification in the SimSET code (version 2.6.2.3) was made to ensure that the total number of decay events specified by the user is maintained in the distributed simulation. No other modifications in the standard SimSET code were made. Each processor runs complete SimSET code for its assignment of decay events, independently of others running simultaneously. Empirical results are reported for simulation of a clinical-quality lung perfusion study.

Integrating disinhibition and learning risk for alcohol use

In this study the authors tested the acquired preparedness model of problem drinking, which holds that trait disinhibition, defined as neurotic extraversion by C. M. Patterson and J. P. Newman (1993), leads to the biased formation of positive over negative alcohol expectancies. Positive expectancies thus mediate disinhibition's influence on drinking. The authors also hypothesized that disinhibition moderates the expectancy-drinking relationship such that disinhibited individuals are more likely to act on their positive expectancies. In Study 1, positive expectancies both mediated and moderated the disinhibition-drinking relationship. In Study 2, learning task results indicated that disinhibited individuals sought reward, even when passive avoidance of punishment was indicated. Study 2 also replicated Study I hypotheses for men but generally not for women.

NADPH-diaphorase activity and nitric oxide synthase-like immunoreactivity colocalize in the electromotor system of four species of gymnotiform fish

The electric organ discharge (EOD) of gymnotiform electric fish is controlled by a well-characterized neural circuit in the brainstem and spinal cord. NADPH-diaphorase (NADPH-d) activity was previously found in phase-locking and/or rapidly firing neurons in the electromotor and electrosensory systems of Apteronotus leptorhynchus [Turner and Moroz, 1995]. These findings suggested that nitric oxide synthase (NOS) is expressed in these neurons and may regulate their precise, high frequency firing. We extended these results by examining the distribution of both NADPH-d activity and NOS-like immunoreactivity (NOS-lir) in the electromotor systems of four gymnotiform species that differ in the frequency and modulation of their EODs. NOS-lir colocalized with NADPH-d staining throughout the electromotor system, indicating that NADPH-d is a faithful indicator of NOS in this system. The distribution of NOS-lir and NADPH-d was similar in the electromotor systems of all four species in this study, with one exception: NOS and NADPH-d staining was consistently less intense in pacemaker and relay cells in Sternopygus macrurus, which produces low frequency EODs, than in the three other species that produce higher frequency EODs. This species difference in NOS expression in the pacemaker nucleus may be related to species differences either in EOD frequency or in modulations of the EOD (e.g., the jamming avoidance response). In Apteronotus species, NOS-lir and NADPH-d were concentrated in bands along the axons of their nerve-derived electric organs. These bands corresponded to regions surrounded by little or no staining with a Schwann cell-specific antibody, suggesting that the NOS-positive regions lie near nodes of Ranvier. In Sternopygus and Eigenmannia, the innervated, posterior membranes of muscle-derived electrocytes were more intensely labeled for NADPH-d and NOS than inexcitable portions of the membrane. Thus, in both muscle- and nerve-derived electric organs, NOS is concentrated near excitable membranes. These results indicate that NOS is well-positioned within the electromotor system to regulate the frequency, precision, amplitude, and waveform of EODs.

Integrating disinhibition and learning risk for alcohol use

In this study the authors tested the acquired preparedness model of problem drinking, which holds that trait disinhibition, defined as neurotic extraversion by C. M. Patterson and J. P. Newman (1993), leads to the biased formation of positive over negative alcohol expectancies. Positive expectancies thus mediate disinhibition's influence on drinking. The authors also hypothesized that disinhibition moderates the expectancy-drinking relationship such that disinhibited individuals are more likely to act on their positive expectancies. In Study 1, positive expectancies both mediated and moderated the disinhibition-drinking relationship. In Study 2, learning task results indicated that disinhibited individuals sought reward, even when passive avoidance of punishment was indicated. Study 2 also replicated Study I hypotheses for men but generally not for women.

The role of family of origin food-related experiences in bulimic symptomatology

OBJECTIVE

With the goal of developing a model relating family of origin experiences to maladaptive cognitions to bulimic symptom formation, the authors developed a measure of family of origin food-related experiences called the Family History Inventory.

METHOD

A number (N = 662) of sixth to eighth-grade adolescents completed the inventory, eating and dieting expectancy measures, and the Bulimia Test-Revised (BULIT-R).

RESULTS

Fourteen scales were identified in the inventory. They emphasized family teasing about weight, negative maternal modeling regarding food, and family rules concerning eating. Eleven of the 14 scales correlated with the BULIT-R. Two superordinate factors called Family Teasing and Negative Maternal Modeling summarized 8 of the 14 subscales. Statistical tests were consistent with the hypothesis that eating and dieting expectancies mediate the influence of Family Teasing and Negative Maternal Modeling on bulimic symptomatology.

DISCUSSION

There was good evidence for the validity of the Family History Inventory. The theoretical implications of the mediation tests are discussed.

Hippocampal volume does not change seasonally in a non food-storing songbird

Seasonal differences in hippocampal morphology have been reported in food-storing birds. Non food-storing species have not been investigated however. It is therefore unclear whether seasonal changes in the hippocampus are specifically related to food-storing or reflect a more general seasonal mechanism that occurs in both food-storing and non food-storing birds alike. We determined the volumes of the hippocampal formation and remaining telencephalon in the non-storing male song sparrow (Melospiza melodies morphna) in two experiments comparing birds collected in the spring and fall of 1992-94 (Experiment 1) and 1997 (Experiment 2). Although pronounced seasonal changes in song control nuclei such as the HVC and RA were previously reported for the same brains used in Experiment 1, we found that hippocampal volume did not change with season in either Experiment 1 or 2 for these song sparrow brains. These results suggest that seasonal changes in the hippocampus do not occur in this non food-storing species and may be specific to food-storing birds.

Hamster and rat fetal cells have low spontaneous mutation frequencies and rates

Somatic cells of whole Syrian hamster fetuses (gestation day 13) were isolated and tested by an in vivo/in vitro mutation assay for spontaneous mutation frequencies using independent 6-thioguanine (6-TG), diphtheria toxin (DT), and ouabain mutation selection systems. Optimum conditions were ascertained. For 6-TG mutants, a total of 21 mutants were found in cells from 24 litters on 1993 plates, for an overall mutant frequency of 1.8 x 10(-7) per viable cell with 12 positive litters. In all, 26 litters were tested using DT; 77 mutants were found in 840 plates, yielding an overall mutant frequency of 2.6 x 10(-7), with 20 positive litters. No correlations or familial effects were found among 23 litters tested for both DT and 6-TG. Of 14 litters which were tested for ouabain mutants, 4 were positive, with a total of 5 mutants found on 988 plates, for an overall mutant frequency of 7.6 x 10(-8). For 14 F344 rat fetuses, the overall 6-TG spontaneous mutation frequency was determined to be 1.6 x 10(-7). From the data, estimates of mutation rates were calculated. For mutation to 6-TG resistance the rate was 8.3 x 10(-8), for mutation to DT resistance the rate was 8.1 x 10(-8) and for ouabain, the spontaneous mutation rate was 5.7 x 10(-8). For F344 rat, the spontaneous mutation rate was 1.1 x 10(-7). Induced mutant frequencies after in utero exposure to 1 mmol/kg N-ethyl-N-nitrosourea (ENU) were 311, 135 and 200 times the spontaneous value for 6-TG, DT and ouabain, respectively, for Syrian hamster fetal cells and 125 times the spontaneous 6-TG value for fetal F344 rat cells. Both spontaneous mutation frequencies and underlying spontaneous mutation rates are low, consistent with the view that fetal cells exercise extremely tight control over DNA fidelity.

Disinhibition and expectancy in risk for alcohol use: comparing black and white college samples

OBJECTIVE

This study tested several predictions of the "acquired preparedness" model in both black and white samples of college students. The acquired preparedness model holds that trait disinhibition affects alcohol-related learning and, ultimately, alcohol use. This model maintains that the reward focus typical of disinhibited individuals increases the likelihood of forming overly positive expectancies about the effects of alcohol. Alcohol expectancy, then, acts as a mediator of the relationship of disinhibition and drinking behavior.

METHOD

Participants (N = 479, 341 women) were 279 white and 200 black college students. Self-reported alcohol expectancy, disinhibition and drinking behavior were assessed. Covariance structure analysis was used to test hypotheses separately for each sample, controlling for socioeconomic status.

RESULTS

Black participants scored significantly lower on disinhibition, expectancy and drinking. However, invariance testing indicated that the relationships between these variables were not different across groups. Results were consistent with the stated hypotheses in both samples--alcohol expectancy functioned as a mediator of the disinhibition-drinking relationship. Results did not differ across expectancy content.

CONCLUSIONS

These results provide support for the validity of the acquired preparedness model. Despite mean differences in risk and drinking levels between black and white samples, psychosocial learning appears to mediate the influence of disinhibition on drinking for both groups.

Evaluation of heart time-activity curves as a predictor of hepatic extraction of 99mTc-mebrofenin in dogs

In this study, heart time-activity curve, created following intravenous injection of 99mTc-mebrofenin were used to quantify hepatic function in normal dogs and dogs with induced hepatic parenchymal cell damage. The results were compared to a direct measurement of hepatic extraction following mesenteric venous injection of 99mTc-mebrofenin. The heart time-activity curves were normalized and the area under the curve from 0-30 minutes and 0-60 minutes were determined. In addition, the half-time clearance rate of the heart time-activity curve was analyzed using a two-compartment model. Linear regression analysis was used to describe the relationship between the area under the normalized heart time-activity curve and hepatic extraction. There was good correlation between the area under the normalized heart time-activity curve and hepatic extraction. The best correlation was obtained from the 0-30 minute data (r2 = 0.92). A formula for calculating hepatic extraction was derived using linear regression analysis: Hepatic extraction = 1.092 - (0.0000308 x AUC0-30 minutes). There was good correlation between the half-time clearance rates from the heart time-activity curve and hepatic extraction. The best correlation was between the fast phase half-time clearance and hepatic extraction (r2 = 0.88). The area under a normalized heart time-activity curve can be used as a simple alternative to deconvolutional analysis for the determination of hepatic extraction as a measure of hepatic parenchymal cell function in the dog.

K-ras p21 expression and activity in lung and lung tumors

Although K-ras is mutated in many human and mouse lung adenocarcinomas, the function of K-ras p21 in lung is not known. We sought evidence for the prevalent hypothesis that K-ras p21 activates raf, which in turn passes the signal through the extracellular signal regulated kinases (Erks) to stimulate cell division, and that this pathway is upregulated when K-ras is mutated. Results from both mouse lung tumors and immortalized cultured E10 and C10 lung type II cells failed to substantiate this hypothesis. Lung tumors did not have more total K-ras p21 or K-ras p21 GTP than normal lung tissue, nor were high levels of these proteins found in tumors with mutant K-ras. Activated K-ras p21-GTP levels did not correlate with proliferating cell nuclear antigen. Special features of tumors with mutant K-ras included small size of carcinomas compared with carcinomas lacking this mutation, and correlation of proliferating cell nuclear antigen with raf-1. In nontransformed type II cells in culture, both total and activated K-ras p21 increased markedly at confluence but not after serum stimulation, whereas both Erk1/2 and the protein kinase Akt were rapidly activated by the serum treatment. Reverse transcriptase-polymerase chain reaction (RT-PCR) assays of K-ras mRNA indicated an increase in confluent and especially in postconfluent cells. Together the findings indicate that normal K-ras p21 activity is associated with growth arrest of lung type II cells, and that the exact contribution of mutated K-ras p21 to tumor development remains to be discovered.

The diagnostic utility of the lognormal behavior of PET standardized uptake values in tumors

A meta-analysis of data primarily from PET oncologic investigations using FDG PET was performed. Its purpose was to establish statistical features of the distributions of standardized uptake values (SUVs) as possible aids in the diagnostic process.

METHODS

We obtained 1536 values of oncologic markers from patient studies of 40 investigations in the literature. Statistical parameters were tabulated for analysis.

RESULTS

A significant observation is that, unlike skewed SUV histograms, log10SUV has Gaussian behavior, which is not uncommon for biologic quantities. This was found for SUVs of FDG and 2 amino acids as well as a few other cancer markers. A possible model for explaining this is proposed. For FDG, the SD sigma of the log10SUVs for an average cancer category was 0.23. Examining data within the framework of the model points to physiologic factors as dominating SUV variability rather than PET protocols. When data for a single cancer category were available from multiple institutions, averages, mean(SUV)s, disagree beyond chance expectations. Diagnostic utility suggestions include a universal linear relationship between sensitivity and severity, defined as SUV/mean(SUV), on semilogarithmic probability paper; a generic receiver-operating-characteristic curve for all cancers; using [log10(mean(SUVmal)/mean(SUVnorm))] divided by (sigma(mal)2 + sigma(norm)2)(1/2) as a simple diagnostic effectiveness measure; and using Gaussian log10SUVs to avoid erroneous P values.

CONCLUSION

Using the logarithms of markers, such as SUVs, several advantages stemming from their Gaussian nature can be achieved with benefits ensuing to the diagnostic process.

Flexible iris hooks for phacoemulsification in patients with iridoschisis

Flexible iris hooks, or retractors, can be used to facilitate cataract removal by phacoemulsification in patients with primary iridoschisis. This rare condition is associated with fibrillary degeneration of the iris, narrow drainage angles, and cataract. In addition to their conventional use as iris retractors, iris hooks can control the degenerate fibrillary iris stroma to improve the view and access to the lens, preventing further damage during phacoemulsification and cortical cleanup. Iris hooks are widely available, easily handled, and can transform a difficult case into one that is almost routine.

Parvocells: a novel interneuron type in the pacemaker nucleus of a weakly electric fish

Gymnotiform weakly electric fish produce electric organ discharges (EODs) that function in electrolocation and communication. The command signal for the EOD is produced by the medullary pacemaker nucleus, which contains two well-characterized neuron types: pacemaker cells and relay cells. In this study, we characterized a third neuron type in the pacemaker nucleus. These neurons, which we have named parvocells, were smaller (7-15 microm in diameter) than relay and pacemaker cells. The parvocells were labeled with an antibody against the neuronal calcium-binding protein, parvalbumin, and were not labeled with several glial-specific antibodies. Parvocells had one to three fine processes that often terminated at the periphery of relay and pacemaker cell bodies. The parvalbumin-positive terminals of the parvocells colocalized with immunoreactivity for SV-2, suggesting that the parvocells form chemical synapses on the relay and pacemaker cells. Parvalbumin-positive neurons are frequently gamma-aminobutyric acid (GABA)ergic or glycinergic, and the cytoplasm of the parvocell somata was immunoreactive with a glycine antibody. Antibodies against glycine receptors and gephyrin, however, did not label any cells in the pacemaker nucleus, suggesting that the pacemaker nucleus does not contain glycine or GABA((A)) receptors. Electron microscopy revealed gap junctions between the membranes of parvocells and adjacent terminal-like structures. Furthermore, neurobiotin injected into individual pacemaker or relay cells labeled parvocells as well as other pacemaker and relay cells, demonstrating that the parvocells are dye-coupled to the other neuron types in the pacemaker nucleus. These findings indicate that the parvocells are histochemically distinct from relay and pacemaker cells and that they receive electrotonic inputs from and make chemical synapses back onto pacemaker and relay cells. Further study is needed to investigate the function of these neurons in regulating the EOD.

Analysis of genetic and phenotypic heterogeneity in juvenile polyposis

BACKGROUND

Juvenile polyposis syndrome (JPS) is characterised by gastrointestinal (GI) hamartomatous polyposis and an increased risk of GI malignancy. Juvenile polyps also occur in the Cowden (CS), Bannayan-Ruvalcaba-Riley (BRRS) and Gorlin (GS) syndromes. Diagnosing JPS can be problematic because it relies on exclusion of CS, BRRS, and GS. Germline mutations in the PTCH, PTEN and DPC4 (SMAD4) genes can cause GS, CS/BRRS, and JPS, respectively.

AIMS

To examine the contribution of mutations in PTCH, PTEN, and DPC4 (SMAD4) to JPS.

METHODS

Forty seven individuals from 15 families and nine apparently sporadic cases with JPS were screened for germline mutations in DPC4, PTEN, and PTCH.

RESULTS

No patient had a mutation in PTEN or PTCH. Five different germline mutations were detected in DPC4; three of these were deletions, one a single base substitution creating a stop codon, and one a missense change. None of these patients had distinguishing clinical features.

CONCLUSIONS

Mutations in PTEN and PTCH are unlikely to cause juvenile polyposis in the absence of clinical features indicative of CS, BRRS, or GS. A proportion of JPS patients harbour DPC4 mutations (21% in this study) but there remains uncharacterized genetic heterogeneity in JPS.

On the sins of short-form development

The empirical short-form literature has been characterized by overly optimistic views of the transfer of validity from parent form to short form and by the weak application of psychometric principles in validating short forms. Reviewers have thus opposed constructing short forms altogether, implying researchers are succumbing to an inappropriate temptation by trying to abbreviate measures. The authors disagree. The authors do not oppose the development of short forms, but they do assert that the validity standards for short forms should be quite high. The authors identify 2 general and 9 specific methodological sins characterizing short-form construction and offer methodological suggestions for the sound development of short forms. They recommend a set of 6 a priori steps researchers should consider and 9 methodological procedures researchers can use to develop valid abbreviated forms of clinical-assessment procedures.

On the sins of short-form development

The empirical short-form literature has been characterized by overly optimistic views of the transfer of validity from parent form to short form and by the weak application of psychometric principles in validating short forms. Reviewers have thus opposed constructing short forms altogether, implying researchers are succumbing to an inappropriate temptation by trying to abbreviate measures. The authors disagree. The authors do not oppose the development of short forms, but they do assert that the validity standards for short forms should be quite high. The authors identify 2 general and 9 specific methodological sins characterizing short-form construction and offer methodological suggestions for the sound development of short forms. They recommend a set of 6 a priori steps researchers should consider and 9 methodological procedures researchers can use to develop valid abbreviated forms of clinical-assessment procedures.

Temperature dependence of electrocommunication signals and their underlying neural rhythms in the weakly electric fish, Apteronotus leptorhynchus

Weakly electric fish emit an electric communication signal that is controlled by a highly specialized neural circuit. In Apteronotus, the continuous electric organ discharge (EOD) is generated by electrotonically coupled neurons in the hindbrain pacemaker nucleus, and transient EOD modulations involve chemical synapses from descending midbrain and thalamic prepacemaker nuclei. We characterized the effects of temperature change (18-32 degrees C) on both the continuous EOD and EOD modulations, chirps, in A. leptorhynchus. EOD frequency was linearly related to temperature (Q(10)=1.62). By contrast, the temperature dependence of EOD amplitude changed with temperature. Amplitude increased steeply with temperature below 25 degrees C (Q(10)=2.0), but increased only gradually above 25 degrees C (Q(10)=1.15). EOD waveform, and consequently harmonic content, was also affected by temperature. The amplitude of the second harmonic was relatively high at both low and high temperature and relatively low at intermediate temperatures. The amplitude of the third harmonic increased monotonically with temperature. Thus, temperature has qualitative as well as quantitative effects on the production of the EOD. Chirp rate (Q(1)0=3.2) had a higher temperature dependence than that of the continuous EOD, which likely reflects its reliance on chemical rather than electrotonic synapses. In vitro pacemaker firing frequency had a similar, but slightly higher Q(10) (1.82) than that of the EOD frequency.

Pharmacological characterization of ionic currents that regulate the pacemaker rhythm in a weakly electric fish

Electric organ discharge (EOD) frequency in the brown ghost knifefish (Apteronotus leptorhynchus) is sexually dimorphic, steroid-regulated, and determined by the discharge rates of neurons in the medullary pacemaker nucleus (Pn). We pharmacologically characterized ionic currents that regulate the firing frequency of Pn neurons to determine which currents contribute to spontaneous oscillations of these neurons and to identify putative targets of steroid action in regulating sexually dimorphic EOD frequency. Tetrodotoxin (TTX) initially reduced spike frequency, and then reduced spike amplitude and stopped pacemaker activity. The sodium channel blocker muO-conotoxin MrVIA also reduced spike frequency, but did not affect spike amplitude or production. Two potassium channel blockers, 4-aminopyridine (4AP) and kappaA-conotoxin SIVA, increased pacemaker firing rates by approximately 20% and then stopped pacemaker firing. Other potassium channel blockers (tetraethylammonium, cesium, alpha-dendrotoxin, and agitoxin-2) did not affect the pacemaker rhythm. The nonspecific calcium channel blockers nickel and cadmium reduced pacemaker firing rates by approximately 15-20%. Specific blockers of L-, N-, P-, and Q-type calcium currents, however, were ineffective. These results indicate that at least three ionic currents-a TTX- and muO-conotoxin MrVIA-sensitive sodium current; a 4AP- and kappaA-conotoxin SIVA-sensitive potassium current; and a T- or R-type calcium current-contribute to the pacemaker rhythm. The pharmacological profiles of these currents are similar to those of currents that are known to regulate firing rates in other spontaneously oscillating neural circuits.

Clinical Utility of FDG-PET in Detecting Head and Neck Tumors. A Comparison of Diagnostic Methods and Modalities

Positron emission tomography (PET) using F-18-fluoro-2-deoxy-d-glucose(F-18-FDG) is gaining acceptance as a useful imaging method for head and neck tumors. Results of 59 PET scans done on 45 patients with head and neck tumors were evaluated retrospectively. Thirty-six patients had prior treatment consisting of surgery, radiation therapy, chemotherapy, or a combination of these modalities. PET results were compared to computed tomography and magnetic resonance imaging results and validated by histologic findings or survival. PET identified 36 out of 37 tumors (sensitivity 97%) and 18 of 22 benign processes (specificity 82%). Tumor was ruled out in 18 out of 19 patients. For CT, the sensitivity was 80% (20/25) and specificity was 31% (4/13). FDG-PET facilitates differentiation of recurrent head and neck tumors from treatment related changes sometimes difficult to characterize by CT or MRI and may have a significant impact on the management of patients reducing morbidity and costs.

Vitrectomy for phacolytic glaucoma in a patient with homocystinuria

PURPOSE

To determine the successful treatment of unilateral phacolytic glaucoma by vitrectomy and trabeculectomy in a patient with homocystinuria whose lens had dislocated into the vitreous at least 15 years earlier.

METHODS

In a 32-year-old woman with homocystinuria, bilateral dislocation of the lens into the vitreous, and phacolytic glaucoma in her left eye a three-port pars plana vitrectomy was performed with the patient under general anesthesia. The lens was removed and a trabeculectomy fashioned. Special precautions for general anesthesia included preoperative aspirin and compression stockings for thromboembolic prophylaxis and intraoperative dextrose infusion, 5%, to maintain intravascular volume and prevent hypoglycemia.

RESULTS

The intraocular pressure and uveitis resolved postoperatively with improvement in the visual acuity and intraocular pressure, which returned to normal without further treatment.

CONCLUSIONS

Phacolytic glaucoma is best resolved by removal of the exciting lens material. Pars plana vitrectomy with the patient under general anesthesia can be carried out safely despite the risks traditionally associated with homocystinuria.

Children's perceptions of parental drinking: the eye of the beholder

OBJECTIVE

Children learn about alcohol and about how to drink through modeling experience, in part. Modeling is typically studied by asking parents to describe their drinking behavior. However, children's perception of parents' drinking may differ from the way parents describe it. This study examined the degree to which children's perceptions and parents' reports agreed.

METHOD

A sample of 177 grade-school children and their parents was drawn from a public school in Kentucky. Children completed questionnaires inquiring about their perceptions of the quantity, frequency and the positive and negative consequences of their parents' drinking. Their parents completed similar questionnaires describing their own drinking and its consequences.

RESULTS

As hypothesized, first and second grade children's perceptions of parents' drinking were unrelated to parents' self-reports: Most of these children perceived their parents as nondrinkers even though parents reported drinking. Also as hypothesized, children's perceptions and parents' reports were significantly correlated for third through sixth grade students. However, there was a great deal of reliable, but unshared variance between these older children's perceptions and parents' reports. Children's perceptions and parents' reports were consistently quite different, even when both child and parent described the parent as a drinker.

CONCLUSIONS

Studies of modeling influences on children regarding drinking should assess children's perceptions of their parents' behavior rather than parents' self-reports.

Ionic currents that contribute to a sexually dimorphic communication signal in weakly electric fish

Weakly electric fish produce a communication signal, the electric organ discharge, that is species specific, and in many species, sexually dimorphic. Because the neural circuit that controls the electric organ discharge is relatively simple, it is an excellent model in which to study both the biophysical mechanisms underlying a rhythmic behavior and the neuroendocrine control of a sexually dimorphic behavior. By studying the effects of ion channel blockers on neurons in the medullary pacemaker nucleus, I pharmacologically characterized three ionic currents that influence the pacemaker rhythm, and thus electric organ discharge frequency, in the gymnotiform fish, Apteronotus leptorhynchus. These currents included a tetrodotoxin-sensitive sodium current; a potassium current that was sensitive to 4-aminopyridine; and a calcium current that was sensitive to nickel and cadmium, but resistant to specific blockers of L-, N-, P-, and Q-type calcium currents. The pharmacological profiles of the ionic currents in the pacemaker nucleus are similar to those of ionic currents involved in pacemaking in other neuronal oscillators. Because these ionic currents dramatically influence pacemaker firing frequency, which is directly related to electric organ discharge frequency, these ionic currents are likely targets of steroid hormone action in producing sexual dimorphisms in electric organ discharge frequency. Additional studies are needed to determine how these ionic currents interact to generate the electric organ discharge rhythm and to investigate the possibility that sexual dimorphism in the electric organ discharge results from the actions of gonadal steroids on these ionic currents.

Cell sensitivity to transplacental mutagenesis by N-ethyl-N-nitrosourea is greatest during early gestation in the Syrian hamster

The extremely high rate of cell division that occurs during early embryogenesis is hypothesized to predispose to high rates of mutation after chemical exposure. We tested this supposition experimentally. To probe the variation in susceptibility to mutation induction as a function of gestation stage, somatic cells of the developing Syrian hamster were isolated after transplacental treatment with N-ethyl-N-nitrosourea (ENU). Mutants were quantified using either 6-thioguanine (6-TG) or diphtheria toxin (DT) as selective agents. Several different approaches were used. In one, three litters were exposed on each gestation day and fetuses were removed on day 13. Maximum fetal sensitivity to ENU's genotoxic action was noted when treatment was at days 8 and 9, fewer mutants being obtained with earlier and later exposures. To compensate for the low numbers of target cells early in gestation, this experiment was repeated using larger numbers of litters exposed at the earlier time points, and the highest mutation frequency was now found to occur after treatment on gestation days 6 and 7. In the second approach, mutations were quantified in cells harvested 24 h after transplacental ENU exposure. Here again, embryos exposed at earlier times of gestation were more susceptible than those treated at later periods. Based on the total cell numbers in embryos and fetuses at each gestation day, we conclude that mutation frequency is maximal on day 6, corresponding to the primitive streak stage with extremely high rates of cell division.

Plasticity of the electric organ discharge: implications for the regulation of ionic currents

Weakly electric fish emit electric organ discharges (EODs) to locate objects around themselves and for communication. The EOD is generated by a simple hierarchically organized, neurophysiologically accessible circuit, the electromotor system. A number of forms of plasticity of the EOD waveform are initiated by social or environmental factors and mediated by hormones or neurotransmitters. Because the behavior itself is in the form of electric discharges, behavioral observations easily lead to testable hypotheses about the biophysical bases of these plasticities. This allows us to study ionic channels in their native cellular environments, where the regulation of various parameters of these currents have obvious functional consequences. In this review, we discuss three types of plasticity: a rapidly occurring, long-lasting, N-methyl-d-aspartate (NMDA)-receptor-dependent increase in baseline firing frequency of neurons in the pacemaker nucleus that underlies a readjustment of the baseline EOD frequency after long bouts of the jamming avoidance response; a rapidly occurring diurnal change in amplitude and duration of the EOD pulse that depends in part on modulation of the magnitude of the electrocyte Na+ current by a protein kinase; and a slowly occurring, hormonally modulated tandem change in pacemaker firing frequency and in the duration of the EOD pulse in which changes in EOD pulse duration are mediated by coordinated shifts in the activation and inactivation kinetics of the electrocyte Na+ and K+ currents.

Telemedicine for dermatology care in rural patients

BACKGROUND

Rural patients who develop dermatologic disorders often do not seek specialty care because of multiple logistical and economic factors.

OBJECTIVE

To assess the effect of teledermatology consultations on the cost of care for a given episode of illness.

METHODS

Telemedicine records were reviewed for 119 visits by 87 patients referred for teledermatology consultation over a 17-month period.

RESULTS

Seven patients (8%) required follow-up in the dermatologist office for extended care, while 20 patients (23%) (52 visits) underwent follow-up teledermatology evaluation. The average duration of the dermatologic condition for each patient prior to the telemedical consultation was 17 months. The average of care for the diagnosed dermatologic condition, for all patients during an average period of 8 months prior to teledermatology was $294, compared with $141 for the 6 months after diagnosis by teledermatology.

CONCLUSIONS

Telemedicine can be effective for dermatology consultation in new patients referred from rural communities. Our data indicate teledermatology can decrease the cost of care for the diagnosed condition.

Validation of deconvolutional analysis for the measurement of hepatic function in dogs with toxic-induced liver disease

The extraction of the hepatobiliary radiopharmaceutical 99mTc-mebrofenin (Choletec) by the liver can be used to evaluate the severity of hepatocellular disease. The hepatic parenchymal cells extract mebrofenin from the blood by the same active transport mechanism as bilirubin. The ability of the liver to extract 99mTc-mebrofenin is a measure of hepatic parenchymal cell function. In this study, we induced hepatocellular disease by administration of a hepatotoxic drug and compared a direct method of determining the hepatic extraction of 99mTc-mebrofenin to hepatic extraction fraction derived from deconvolutional analysis. We also compared both methods of calculating the hepatic extraction of 99mTc-mebrofenin to liver histopathology. Hepatic extraction fraction derived from deconvolutional analysis correlated very well to the direct measurement technique (R=0.922, p < 0.001). Both methods of determining hepatic extraction correlated well to quantitative histopathology, having the same correlation coefficient and p values. (R=-0.833, p=0.003). As the hepatic extraction 99mTc-mebrofenin decreased, the severity of the histopathologic lesions of the liver increased in a linear fashion. There was a significant correlation of the hepatic excretion T1/2 to quantitative histopathology (R=0.949, p < 0.001). The hepatic excretion T1/2 increased as the severity of the histopathologic lesions of the liver increased. Hepatic extraction (HEF) and excretion of 99mTc-mebrofenin are good predictors of the severity of hepatocellular damage in toxic induced liver disease. This study helps validate the premise that HEF derived from deconvolutional analysis is a good predictor of the actual first pass hepatic extraction of 99mTc-mebrofenin.

Hepatic extraction efficiency of technetium-99m-mebrofenin in the dog with toxic-induced acute liver disease

Extraction of the hepatobiliary radiopharmaceutical 99mTc-N-(3-bromo-2,4,6-trimethyacetanilide) iminodiacetic acid (mebrofenin; Choletec, Squibb Diagnostic, Princeton, NJ) by the liver may be used as an index of hepatocellular function. The hepatic parenchymal cells extract mebrofenin from the blood using the same active transport mechanism as bilirubin.

METHODS

In this study, we induced hepatocellular disease by administering a hepatotoxic drug and compared the hepatic extraction efficiency (HEE), measured directly from an afferent injection of 99mTc-mebrofenin, to quantitative histopathology and to serum biochemistry analysis.

RESULTS

The baseline HEE was 95.9% +/- 2.71% (mean +/- s.d.). Dogs that were affected by the hepatotoxic drug had reduced HEE. HEE correlated well to the severity of histologic lesions (r = -0.83, p = 0.003). HEE also correlated well to the increases in the activities of alanine aminotransferase (ALT; r = -0.85, p = 0.002) and aspartate aminotransferase (AST; r = -0.89, p = <0.001), the concentration of fasting bile acid (r = -0.97, p = <0.001), bilirubin (r = -0.92, p = <0.001) and, to a lesser degree, to the activities of alkaline phosphatase (Alk Phos; r = -0.73, p = 0.016). HEE had higher correlation coefficients to the serum biochemistry analysis than did the quantitative liver histopathology.

CONCLUSION

Hepatic extraction of 99mTc-mebrofenin is a good predictor of the severity of hepatocellular damage in toxic-induced liver disease.

Seasonal plasticity and sexual dimorphism in the avian song control system: stereological measurement of neuron density and number

Differences in neuron density and number are associated with seasonal plasticity and sexual dimorphism in the avian song control system. In previous studies, neuron density and number in this system have been quantified primarily through nonstereological approaches in thick tissue sections by using the nucleolus as the unit of count. The reported differences between seasons and sexes may be inaccurate due to biases introduced by neuron splitting during sectioning. We used the unbiased optical disector technique on tissue from three previous studies (two investigations of seasonal plasticity and one investigation of sexual dimorphism in avian song nuclei) to assess seasonal and sex differences in neuron density and number. In two song nuclei, HVc and the robust nucleus of the archistriatum (RA), the optical disector yielded intergroup differences in neuron density and number that coincided well with the three previous reports. We also estimated neuron number and density with a random, systematic, nonstereological counting protocol that used the neuronal nucleolus as the unit of count. We compared this method directly to the optical disector. In all cases, the two neuron-counting methods produced similar estimates of neuron number and density; the differences between treatment groups were equally discernible regardless of the counting method used. This study confirms previously reported seasonal and sex differences in the HVc and the RA by use of stereology and indicates that a random, systematic, nonstereological neuron-counting protocol is accurate and is well suited to the study of these phenomena in the avian song control system.

Evaluation of the direct genotoxic potential of cadmium in four different rodent cell lines

Cadmium is a toxic environmental contaminant that is carcinogenic in humans and laboratory animals. Although the mechanism underlying cadmium carcinogenesis has not yet been determined experimental evidence suggests that the stress-inducible, metal-binding proteins, metallothioneins, may mediate organ specificity. In the present study, four different rodent cell lines (Chinese hamster ovary cells, rat L6 myoblast cells, rat Clone 9 liver cells, and rat TRL 1215 liver cells) were exposed to 0, 1, 5, 10, 50, or 100 microM CdCl2 and monitored for evidence of direct DNA damage. A microfiltration assay was used to measure DNA strand breaks and a filter-binding assay was used to measure DNA-protein crosslinks, two lesions that have been associated with cadmium exposure and may mediate genotoxicity of the metal. Although variability in sensitivity to DNA damage was evident between the different cell lines, in all of the cell lines tested, increases in DNA damage were observed only at cadmium doses that completely arrested cell growth. In addition, in three of the four cell lines tested, induction of metallothionein had no substantial protective effect against cadmium-induced cytotoxicity or genotoxicty. While protection against cadmium-induced DNA strand breakage with metallothionein preinduction was observed in the TRL 1215 rat liver cells, metallothionein preinduction did not protect against cadmium-induced DNA-protein crosslinking in that cell line. Taken together, our results support the hypothesis that cadmium is not directly genotoxic.

Effect of cadmium exposure on background and anti-5 methylchrysene-1,2-dihydrodiol 3,4-epoxide-induced mutagenesis in the supF gene of pS189 in human Ad293 cells

Cadmium is a toxic environmental contaminant that is carcinogenic in humans and rodents. Although cadmium has proven to be mutagenic in a variety of assay systems, exactly how cadmium achieves gentoxicity is poorly understood. To define the mechanism(s) underlying the mutagenicity and comutagenicity of cadmium, human Ad293 cells were exposed to subtoxic doses of the metal and transfected with untreated or anti-5-methylchrysene-3,4-dihydrodiol 1,2-epoxide (5-MCDE)-treated pS189 shuttle vector. Alterations in the frequency, types, and distribution of mutations were subsequently assessed in the supF gene of pS189 that was replicated in Ad293 cells and screened in indicator bacteria. Doses of 0.5 and 1 microM CdCl2 increased the mutation frequency of untreated pS189 by approximately 4- and 8-fold, respectively, with no apparent effect on the types of mutations generated. In contrast, host-cell exposure to cadmium had little or no effect on the frequency, types, or distribution of mutations generated with 5-MCDE-treated pS189. These results indicate that cadmium increases mutagenesis of untreated pS189 by affecting a process that is not involved in mutagenesis of the 5-MCDE-treated vector. Although it is not clear exactly how host-cell exposure to cadmium increases background mutagenesis, presumably, the mutagenic effect does not involve cadmium interaction with the cellular machinery used to replicate past bulky DNA lesions.