Fiber optic probe for polarized reflectance spectroscopy in vivo: design and performance

We present the design and construction of a fiber optic probe for elastic light scattering spectroscopy in vivo with polarized excitation and polarization sensitive detection. The performance of the fiber probe is evaluated using a suspension of polystyrene spheres placed atop a diffusely scattering substrate, and it demonstrates that the size-dependent characteristics of the scatterers can be extracted in the presence of a highly diffusely scattering background using a linear combination of forward and backward Mie scattering components of the scatterers. Subsequently, Mie theory calculations are performed over a broad range of diagnostically relevant parameters of nuclei-mean diameter, size distribution, and relative refractive index-to understand how the polarized reflectance measurements with the fiber probe can be used to extract morphological information about epithelial tissue. Finally, the feasibility of in vivo measurements with the fiber optic based polarization sensitive light scattering spectroscopy is demonstrated.     

Discrimination of human pathogenic subspecies of Francisella tularensis by using restriction fragment length polymorphism

We describe the use of two insertion sequence elements (ISFtu1 and ISFtu2) in Francisella tularensis to type strains by restriction fragment length polymorphism (RFLP). The RFLP profiles of 17 epidemiologically unrelated isolates were determined and compared. Our results showed that RFLP profiles can be used to assign F. tularensis strains into five main groups corresponding to strains of F. tularensis subsp. tularensis, F. tularensis strain ATCC 6223, strains of F. tularensis subsp. holarctica, strains of F. tularensis subsp. holarctica from Japan, and F. tularensis subsp. mediaasiatica. The results confirm the genetic identities of these subspecies and also support the suggestion that strains of F. tularensis subsp. holarctica from Japan should be considered members of a separate biovar. These findings should support future studies to determine the genetic differences between strains of F. tularensis at the whole-genome level.     

Cloning and expression of the major secreted cathepsin B-like protein from juvenile Fasciola hepatica and analysis of immunogenicity following liver fluke infection

The functions of the cathepsin B-like proteases in liver flukes are unknown and analysis has been hindered by a lack of protein for study, since the protein is produced in small amounts by juvenile flukes. To circumvent this, we isolated and characterized a cDNA encoding the major secreted cathepsin B from Fasciola hepatica. The predicted preproprotein is 339 amino acids in length, with the mature protease predicted to be 254 amino acids long, and shows significant similarity to parasite and mammalian cathepsin B. Only one of the two conserved histidine residues required for cathepsin B exopeptidase activity is predicted to be present. Recombinant preproprotein was produced in yeast, and it was shown that the recombinant proprotein can undergo a degree of self-processing in vitro to the mature form, which is active against gelatin and synthetic peptide substrates. The recombinant protein is antigenic in vaccinated rats, and antibodies to the protein are detected early after infection of rats and sheep with F. hepatica. The kinetics of the response to cathepsin B and cathepsin L after infection of sheep and rats confirm the temporal expression of these proteins during the life cycle of the parasite.     

Development of neural processes mediating rhyme judgments: Phonological and orthographic interactions

Development of neural processes underlying integration of phonological and orthographic information were assessed by measuring event-related brain potentials (ERPs), judgment accuracies and reaction times (RTs) in 20 children (9-10 years) and 20 adults performing visual rhyme judgments. Half the trials were phonologically and orthographically congruent across the prime-target pairs (e.g., thrown-own, cake-own), and half were incongruent (e.g., gown-own, cone-own). For both children and adults, behavioral performance was most affected when different phonological representations had to be encoded from similar orthographic representations (e.g., gown-own), and the amplitudes of the N350 reflected effects of both rhyme and phonological/orthographic congruency. Latencies of the N350 were shorter over the left hemisphere only in adults, and phonological/orthographic incongruence produced greater delays in children's processing. Therefore, it appears that neural systems mediating rhyming judgments develop early; however, adults exhibit increased efficiency for left-hemisphere processing and are less affected by interference from incongruent phonological and orthographic codes.     

Variance in practice emergency medical admission rates: can it be explained?

BACKGROUND: Emergency admission rates have been rising steadily in recent years, with the majority of the increase owing to emergency medical admissions. Possible causative factors include changing demography, incidence of disease, admission thresholds, multiple admissions, and appropriateness of admission. AIM: To investigate the impact of patient and practice factors on variance in general practices' emergency medical admissions rates. DESIGN OF STUDY: Multiple regression analysis relating emergency medical admission rates of general practices to patient and practice characteristics. SETTING: The study was conducted between 1996 and 1997 in the acute hospital trust serving the study area, Dundee, Scotland. METHOD: Scottish Morbidity Record 1 (SMR1) data, which contains details of all hospital consultant episodes, was used to calculate individual practices emergency medical admission rates. These rates were then standardised to an expected value of 100. Forward selection was used to find a suitable multiple regression model to predict each practice's emergency medical admission rate from practice and patient variables. RESULTS: Crude emergency medical admission rates for general practices showed a 1.8-fold variation between the top and bottom deciles. The deprivation status and age of patients explained 42% of the variance in admission rates (64% with the exclusion of one practice that had a poor fit to the model). After correcting for age and deprivation there was a 1.2-fold variation in general practices' emergency medical admission rates. CONCLUSION: The most important factors in explaining variance in general practices' emergency medical admission rates are socio-demographic, with age and deprivation explaining a large proportion of the variation. We found no evidence to support the contention that general practice factors were linked with admission rates.     

Factors associated with BMI, weight perceptions and trying to lose weight in African-American smokers

This study examined sociodemographic, behavioral and psychosocial factors associated with BMI, weight perceptions and trying to lose weight among African-American smokers (N=600, M=44.2 years, 70% female). Sixty-eight percent of the sample were overweight or obese (sample BMI M=28.0, SD=6.7). Three separate, simultaneous multivariable regression models were used to determine which factors were associated with BMI, weight perceptions and trying to lose weight. Poorer health, female gender and high-school education or higher were significantly associated with higher BMIs (p<0.05). Being female (OR=5.8, 95% CI=3.6-9.3) and having a higher BMI (OR=0.6, 95% CI=0.5-0.6) was associated with perception of overweight and smoking more cigarettes per day (OR=1.0, 95% CI=1.0-1.1), and perceiving oneself as overweight (OR=14.1, 95% CI=8.2-24.2) was associated with trying to lose weight. Participants somewhat underestimated their BMI in their weight perceptions. Those who perceived themselves as overweight were more likely to be trying to lose weight; therefore, increasing participant awareness of actual BMI status may lead to improved weight-control efforts in African-American smokers. Several expected associations with outcomes were not found, suggesting that BMI and weight constructs are not well-understood in this population.     

Intact perceptual and conceptual priming in temporal lobe epilepsy: neuroanatomical and methodological implications

Explicit memory appears to be supported by medical temporal lobe structures, whereas separate neocortical regions may mediate perceptual and conceptual implicit memory. Children and adults with temporal lobe epilepsy (TLE) and matched controls were administered experimental verbal memory tests. Performance on implicit tests--word identification and word generation--was contrasted with explicit recognition and recall. Encoding conditions emphasized either conceptual or perceptual aspects of study words and were crossed with presentation modality. The priming performance of participants with TLE did not differ from controls, but participants with TLE did show deficits on recognition and recall measures. Thus, intact left temporal cortex does not appear to be necessary for normal implicit memory performance, even when conceptual processing is emphasized at study or test.     

Effect of Shipment, Storage, Anticoagulant, and Cell Separation on Lymphocyte Proliferation Assays for Human Immunodeficiency Virus-Infected Patients

Lymphocyte proliferation assays (LPA), which can provide important information regarding the immune reconstitution of human immunodeficiency virus (HIV)-infected patients on highly active antiretroviral therapy, frequently involve shipment of specimens to central laboratories. In this study, we examine the effect of stimulant, anticoagulant, cell separation, storage, and transportation on LPA results. LPA responses of whole blood and separated peripheral blood mononuclear cells (PBMC) to different stimulants (cytomegalovirus, varicella-zoster virus, candida and tetanus toxoid antigens, and phytohemagglutinin) were measured using fresh specimens shipped overnight and frozen specimens collected in heparin, acid citrate dextrose (ACD), and citrate cell preparation tubes (CPT) from 12 HIV-infected patients and uninfected controls. Odds ratios for positive LPA responses were significantly higher in separated PBMC than in whole blood from ACD- and heparin-anticoagulated samples obtained from HIV-infected patients and from ACD-anticoagulated samples from uninfected controls. On separated PBMC, positive responses were significantly more frequent in fresh samples compared with overnight transportation for all antigens and compared with cryopreservation for the candida and tetanus antigens. In addition, viral antigen LPA responses were better preserved in frozen PBMC compared with specimens shipped overnight. CPT tubes yielded significantly more positive LPA results for all antigens, irrespective of the HIV patient status compared with ACD, but only for the candida and tetanus antigens and only in HIV-negative controls compared with heparin. Although HIV-infected patients had a significantly lower number of positive antigen-driven LPA responses compared with uninfected controls, most of the specimen processing variables had similar effects on HIV-positive and -negative samples. We conclude that LPA should be performed on site, whenever feasible, by using separated PBMC from fresh blood samples collected in either heparin or ACD. However, if on-site testing is not available, optimal transportation conditions should be established for specific antigens.     

In vitro degradation of silk fibroin

A significant need exists for long-term degradable biomaterials which can slowly and predictably transfer a load-bearing burden to developing biological tissue. In this study Bombyx mori silk fibroin yarns were incubated in 1mg/ml Protease XIV at 37 degrees C to create an in vitro model system of proteolytic degradation. Samples were harvested at designated time points up to 12 weeks and (1) prepared for scanning electron microscopy (SEM), (2) lyophilized and weighed, (3) mechanical properties determined using a servohydraulic Instron 8511, (4) dissolved and run on a SDS-PAGE gel, and (5) characterized with Fourier transform infrared spectroscopy. Control samples were incubated in phosphate-buffered saline. Fibroin was shown to proteolytically degrade with predictable rates of change in fibroin diameter, failure strength, cycles to failure, and mass. SEM indicated increasing fragmentation of individual fibroin filaments from protease-digested samples with time of exposure to the enzyme; particulate debris was present within 7 days of incubation. Gel electrophoresis indicated a decreasing amount of the silk 25 kDa light chain and a shift in the molecular weight of the heavy chain with increasing incubation time in protease. Results support that silk is a mechanically robust biomaterial with predictable long-term degradation characteristics.     

Spontaneous alpha peak frequency predicts working memory performance across the age span.

Working memory capacity has been consistently shown to decline with increasing age. Mechanisms underlying this decline are poorly understood. One index that has been found to predict performance on memory tests is alpha peak frequency, the peak of spectral alpha power of the EEG. Activity in the alpha band has been also associated with higher cognitive functions including attention and anticipation and has been shown to slow with age. Few studies, however, have examined whether there might be a relationship between WM decline and alpha peak frequency. The present study specifically investigated this relationship. Digit span was used as the index of WM function. The study made use of 550 normal subjects aged between 11 and 70 years in the Brain Resource International Database. The data were acquired from six laboratories located in the USA (2), Europe (2) and Australia (2). Forward and reverse digit span were found to be lower in older relative to younger age groups. Spontaneous alpha peak frequency slowed with age and more so at anterior than posterior sites. Frontal alpha peak frequency was found to be a significant predictor of reverse digit span, with each 1 Hz increase in frequency associated with a 0.21 increase in reverse digit span score and this was independent of age, indicating a positive relationship between alpha peak frequency and working memory performance.