The Impact of Positron Range on PET Resolution, Evaluated with Phantoms and PHITS Monte Carlo Simulations for Conventional and Non-conventional Radionuclides.

PURPOSE: The increasing interest and availability of non-standard positron-emitting radionuclides has heightened the relevance of radionuclide choice in the development and optimization of new positron emission tomography (PET) imaging procedures, both in preclinical research and clinical practice. Differences in achievable resolution arising from positron range can largely influence application suitability of each radionuclide, especially in small-ring preclinical PET where system blurring factors due to annihilation photon acollinearity and detector geometry are less significant. Some resolution degradation can be mitigated with appropriate range corrections implemented during image reconstruction, the quality of which is contingent on an accurate characterization of positron range. PROCEDURES: To address this need, we have characterized the positron range of several standard and non-standard PET radionuclides (As-72, F-18, Ga-68, Mn-52, Y-86, and Zr-89) through imaging of small-animal quality control phantoms on a benchmark preclinical PET scanner. Further, the Particle and Heavy Ion Transport code System (PHITS v3.02) code was utilized for Monte Carlo modeling of positron range-dependent blurring effects. RESULTS: Positron range kernels for each radionuclide were derived from simulation of point sources in ICRP reference tissues. PET resolution and quantitative accuracy afforded by various radionuclides in practicable imaging scenarios were characterized using a convolution-based method based on positron annihilation distributions obtained from PHITS. Our imaging and simulation results demonstrate the degradation of small animal PET resolution, and quantitative accuracy correlates with increasing positron energy; however, for a specific "benchmark" preclinical PET scanner and reconstruction workflow, these differences were observed to be minimal given radionuclides with average positron energies below ~ 400 keV. CONCLUSION: Our measurements and simulations of the influence of positron range on PET resolution compare well with previous efforts documented in the literature and provide new data for several radionuclides in increasing clinical and preclinical use. The results will support current and future improvements in methods for positron range corrections in PET imaging.

Comparing the effectiveness of nasal dilator strips: does race play a role?

BACKGROUND: Nasal dilator strips are thought to widen and stiffen the anterior nasal cavity, and thus improve symptoms of nasal obstruction. It is postulated that anthropomorphic differences in external nasal proportions between races may influence the effectiveness of such dilator strips. METHODS: Caucasian and Asian subjects were compared. Nasal peak inspiratory flow, nasal airway resistance, minimum cross-sectional area and visual analogue scale measurements of nasal obstruction were recorded at baseline and following the application of two different dilator strips. RESULTS: Nine Caucasian and six Asian subjects were recruited (n = 15). There was a significant difference between races in terms of nasal peak inspiratory flow improvements following nasal strip application (mean of 29.4 litres per minute in Caucasians vs 14.6 litres per minute in Asians; p = 0.04). Only Caucasians experienced a significant decrease in nasal airway resistance (median of 0.12 Pa/cm3/s; p < 0.01). CONCLUSION: Nasal peak inspiratory flow, minimum cross-sectional area and visual analogue scale values improved from baseline with strip application in both populations. Only Caucasians experienced significant nasal airway resistance improvement with strip application. Both cohorts experienced nasal peak inspiratory flow improvement, with Caucasians experiencing a significantly larger improvement.

Nasal peak inspiratory flow (NPIF) as a diagnostic tool for differentiating decongestable from structural nasal obstruction.

BACKGROUND: Identifying the cause of nasal obstruction is critical before surgical intervention. Structural nasal obstruction, due to nasal valve stenosis, is unlikely to benefit from simple septoplasty and turbinate reduction. This study assesses changes in nasal peak inspiratory flow (NPIF) as a tool for discriminating decongestable versus structural obstruction. METHODOLOGY: Cross-sectional study of patients undergoing nasal airflow assessment was performed. Rhinomanometry, nasal obstruction visual analogue scores (VAS) and NPIF were performed pre- and post-decongestion. Population groups were defined with decongestable or structural obstruction by relative post-decongestion changes in airways resistance and symptoms. RESULTS: Fifty two patients were assessed, 24 with decongestable, 28 with structural obstruction. Pre- and post-decongestion NPIF were similar between groups. Absolute and percentage NPIF change were larger with decongestable versus structural obstruction. Sensitivity and specificity for predicting decongestable obstruction were 75.0% and 60.7% for NPIF increase >20 L/min; 75.0% and 64.3% for NPIF increase >20%. The respective positive predictive values were 62.1% and 64.3%. CONCLUSION: NPIF increase after decongestion is larger with decongestable than structural nasal obstruction. NPIF alone cannot discriminate the two conditions and does not replace more formal assessment.

Modified Lund Mackay Postoperative Endoscopy Score for defining inflammatory burden in chronic rhinosinusitis.

OBJECTIVE: The Lund Mackay Postoperative Endoscopy Score (LMES) for chronic rhinosinusitis (CRS) is a poor measure of the patient experience. A proposed Modified Lund Mackay Postoperative Endoscopy Score (MLMES) aims to better describe the inflammatory burden in CRS. METHODS: A prospective study on CRS patients having endoscopic sinus surgery (ESS) was conducted. Endoscopy was recorded at the 6th and the 12th week post-op. The MLMES recorded changes in mucosa, mucus and purulence for each of the maxillary, ethmoid, sphenoid, frontal sinuses and olfactory fossa in post-ESS cavities. The correlation between MLMES and visual analogue scale of total rhinosinusitis symptoms, global anchor score of nasal function, Sino-Nasal Outcome Test 22 (SNOT-22) and nasal symptom score was analyzed. The inter-observer reliability, intra-observer reliability and correlation between the change in MLMES and in subjective measures were also investigated. RESULTS: Thirty patients were assessed. The MLMES significantly correlated with visual analogue scale, SNOT-22, global anchor and nasal symptom score. The change in MLMES correlated with the change in SNOT-22 and nasal symptom score. The inter-observer and intra-observer reliability were excellent. CONCLUSION: Objectives measurements for post-ESS patients can be reconsidered to represent the cumulative inflammatory burden of all sinuses. The proposed MLMES represents total sinus inflammatory burden and correlates well with patient reported outcome measures.

Patient self-assessment in discriminating the more obstructed side in nasal breathing.

BACKGROUND: Correlating patient perception of nasal obstruction sidedness to causative anatomy is important in surgical planning. The accuracy of patient-perceived asymmetry of nasal obstruction, as regards objective measures, is described. METHODS: Cross-sectional study of patients undergoing nasal airflow assessment. Unilateral obstruction was assessed using visual analogue scale scores and anterior rhinomanometry, without decongestion. Subjective obstruction asymmetry was defined using either the absolute score difference (right vs left) or the minimal clinically important difference, derived statistically. Correlation between subjective and objective obstruction measures was assessed. RESULTS: In 145 patients (mean age ± standard deviation, 42.8 ± 16.6 years; 54.5 per cent female), objective obstruction was right-sided in 32.4 per cent, left-sided in 36.6 per cent and symmetrical in 31.0 per cent. Subjective perception of obstruction sidedness had a sensitivity and specificity of 86.9 and 41.1 per cent, respectively, using the minimal clinically important difference. Positive predictive value was 59.4 per cent using absolute score difference and 53.7 per cent using minimal clinically important difference. Receiver operator characteristic curve analysis indicated correlation between subjective and objective measures (p < 0.001). CONCLUSION: Subjective perception of nasal obstruction asymmetry has limited accuracy. Corroboration with objective airway assessment may be helpful in patients whose symptoms are incongruous with clinical findings.

Comparative proteomics of chloroplasts envelopes from bundle sheath and mesophyll chloroplasts reveals novel membrane proteins with a possible role in c4-related metabolite fluxes and development.

As the world population grows, our need for food increases drastically. Limited amounts of arable land lead to a competition between food and fuel crops, while changes in the global climate may impact future crop yields. Thus, a second "green revolution" will need a better understanding of the processes essential for plant growth and development. One approach toward the solution of this problem is to better understand regulatory and transport processes in C4 plants. C4 plants display an up to 10-fold higher apparent CO2 assimilation and higher yields while maintaining high water use efficiency. This requires differential regulation of mesophyll (M) and bundle sheath (BS) chloroplast development as well as higher metabolic fluxes of photosynthetic intermediates between cells and particularly across chloroplast envelopes. While previous analyses of overall chloroplast membranes have yielded significant insight, our comparative proteomics approach using enriched BS and M chloroplast envelopes of Zea mays allowed us to identify 37 proteins of unknown function that have not been seen in these earlier studies. We identified 280 proteins, 84% of which are known/predicted to be present in chloroplasts. Seventy-four percent have a known or predicted membrane association. Twenty-one membrane proteins were 2-15 times more abundant in BS cells, while 36 of the proteins were more abundant in M chloroplast envelopes. These proteins could represent additional candidates of proteins essential for development or metabolite transport processes in C4 plants. RT-PCR confirmed differential expression of 13 candidate genes. Chloroplast association for seven proteins was confirmed using YFP/GFP labeling. Gene expression of four putative transporters was examined throughout the leaf and during the greening of leaves. Genes for a PIC-like protein and an ER-AP-like protein show an early transient increase in gene expression during the transition to light. In addition, PIC gene expression is increased in the immature part of the leaf and was lower in the fully developed parts of the leaf, suggesting a need for/incorporation of the protein during chloroplast development.

Osteitic bone: a surrogate marker of eosinophilia in chronic rhinosinusitis.

BACKGROUND: Causes of osteitis in chronic rhinosinusitis (CRS) other than previous surgery are poorly defined. Patients with eosinophilic CRS (ECRS) have more severe disease and poorer outcomes despite repeated surgery. Associations between osteitis and markers of ECRS are not well described. METHODS: A cross-sectional study of CRS patients undergoing sinus surgery was conducted. Osteitis was scored radiologically using previously published measures. Associations between osteitis and histopathology, symptoms, endoscopy, CT mucosal score and seromarkers were analyzed. RESULTS: Eighty-eight patients were assessed of whom forty-five had osteitis. Patients undergoing revision surgery recorded higher osteitis scores. Patients with mucosal eosinophilia had higher osteitis score than those without. Patients with osteitis had higher serum eosinophil. Similar relationships were also found in primary surgery. Osteitis was associated with endoscopic and radiologic, but not symptomatic disease severity. CONCLUSIONS: Osteitis is associated with tissue and serum eosinophilia in both patients with and without prior surgery. Patients with these features may benefit from post-operative corticosteroid therapy to prevent osteitis.

Interplay of rotational, relaxational, and shear dynamics in solid 4He.

Using a high-sensitivity torsional oscillator (TO) technique, we mapped the rotational and relaxational dynamics of solid helium-4 ((4)He) throughout the parameter range of the proposed supersolidity. We found evidence that the same microscopic excitations controlling the torsional oscillator motions are generated independently by thermal and mechanical stimulation. Moreover, a measure for the relaxation times of these excitations diverges smoothly without any indication for a critical temperature or critical velocity of a supersolid transition. Finally, we demonstrated that the combined temperature-velocity dependence of the TO response is indistinguishable from the combined temperature-strain dependence of the solid's shear modulus. This implies that the rotational responses of solid (4)He attributed to supersolidity are associated with generation of the same microscopic excitations as those produced by direct shear strain.

Evidence for a superglass state in solid 4He.

Although solid helium-4 (4He) may be a supersolid, it also exhibits many phenomena unexpected in that context. We studied relaxation dynamics in the resonance frequency f(T) and dissipation D(T) of a torsional oscillator containing solid 4He. With the appearance of the "supersolid" state, the relaxation times within f(T) and D(T) began to increase rapidly together. More importantly, the relaxation processes in both D(T) and a component of f(T) exhibited a complex synchronized ultraslow evolution toward equilibrium. Analysis using a generalized rotational susceptibility revealed that, while exhibiting these apparently glassy dynamics, the phenomena were quantitatively inconsistent with a simple excitation freeze-out transition because the variation in f was far too large. One possibility is that amorphous solid 4He represents a new form of supersolid in which dynamical excitations within the solid control the superfluid phase stiffness.

Reducing gaseous nitrogen loss from stored laying hen manure by the addition of carbohydrates.

Three separate experiments were conducted to determine if the addition of carbohydrate sources directly to freshly-produced laying hen manure reduced the loss of gaseous nitrogen containing compounds during 7 d of storage. The addition of sucrose (8 g/kg) to the manure resulted in a greater increase in bacterial numbers, a greater loss of carbon and a trend for a reduced loss of nitrogen. Although glucose addition to the manure increased bacterial numbers and tended to increase carbon loss, nitrogen loss increased relative to the control. Addition of straw to the manure did not affect the change in bacterial numbers or rate of nitrogen loss compared to the control treatment. Experiment 2 indicated that, when either sucrose or maltose were mixed (8 g/kg) with laying hen manure, microbial numbers were increased and gaseous nitrogen losses were reduced. A combination of starch plus alpha-amylase did not affect the characteristics of the manure. Experiment 3 showed that increasing sucrose addition gave a non-linear reduction in nitrogen loss. Minimum nitrogen loss was obtained with 35 g/kg sucrose, though the maximum increase in bacterial numbers occurred at 20 g/kg of added sucrose.

Effect of moisture content and ambient temperature on the gaseous nitrogen loss from stored laying hen manure.

1. The objectives of this study were to compare the effect of 4 storage temperatures (15.3, 18.5, 21.9 and 25.4 degrees C) and three moisture contents of laying hen manure (722, 752 and 796 g/kg) on the rate of nitrogen loss and manure decomposition characteristics over a 10-d storage. 2. The rate of loss of dry matter, nitrogen and water increased linearly with increased ambient storage temperature. The initial moisture content had a non-linear effect on the rate of loss nitrogen and moisture. The greatest rate of loss of nitrogen and lowest loss of water occurred in the intermediate manure moisture treatment. 3. There was a temperature x manure moisture interaction with a large increase in the rate of nitrogen loss of the intermediate manure moisture samples when they were stored at the highest temperature. 4. This experiment quantified the marked effect that relatively small changes in manure moisture and storage temperature can have on gaseous nitrogen losses.

Development of synchronized activity of cranial motor neurons in the segmented embryonic mouse hindbrain.

Spontaneous electrical activity synchronized among groups of related neurons is a widespread and important feature of central nervous system development. Among the many places from which spontaneous rhythmic activity has been recorded early in development are the cranial motor nerve roots that exit the hindbrain, the motor neuron pool that, at birth, will control the rhythmic motor patterns of swallow, feeding and the oral components of respiratory behaviour. Understanding the mechanism and significance of this hindbrain activity, however, has been hampered by the difficulty of identifying and recording from individual hindbrain motor neurons in living tissue. We have used retrograde labelling to identify living cranial branchiomeric motor neurons in the hindbrain, and [Ca2+]i imaging of such labelled cells to measure spontaneous activity simultaneously in groups of motor neuron somata. We find that branchiomeric motor neurons of the trigeminal and facial nerves generate spontaneous [Ca2+]i transients throughout the developmental period E9.5 to E11.5. During this two-day period the activity changes from low-frequency, long-duration events that are tetrodotoxin insensitive and poorly coordinated among cells, to high-frequency short-duration events that are tetrodotoxin sensitive and tightly coordinated throughout the motor neuron population. This early synchronization may be crucial for correct neuron-target development.

Effect of ambient temperature on losses of volatile nitrogen compounds from stored laying hen manure.

Eight one tonne lots of laying hen manure were stored in individual, environmentally controlled chambers for 18-weeks at one of four constant temperatures: 12, 15, 20 and 25 degrees C. The losses of volatile nitrogen compounds, ammonia, and changes in dry matter and pH were measured during the storage period. There was a linear (P < 0.001) loss of nitrogen from the manure over the 18-week storage period. This loss represented approximately 60% of the initial nitrogen present in the manure. The rate of nitrogen loss increased non-linearly (P < 0.05) with increasing storage temperature. Poultry housing systems that provide low temperature storage of manure are recommended to reduce the volatile nitrogen losses from egg-laying enterprises.

Alcohol consumption alters insulin secretion and cardiac autonomic activity.

BACKGROUND: Alcohol may have a cardioprotective effect. One possible mechanism is by modifying insulin resistance/secretion. The aims of this study were: (i) to examine the effect of short-term alcohol consumption on the metabolic control of glucose tolerance; (ii) to study the influence of short-term alcohol consumption on cardiac autonomic activity using spectral analysis of heart rate variability. METHODS: Twenty-one healthy subjects, in a randomized crossover design, either received three units of ethanol daily for 1 week or abstained from ethanol. The control of glucose tolerance was assessed using the intravenous glucose tolerance test with minimal modelling. RESULTS: There was no difference in fasting glucose, fasting insulin or insulin sensitivity between the two groups. Alcohol showed a lower insulin first phase insulin response (no alcohol 659.0 +/- 394.1 SD, alcohol 535.2 +/- 309.1) pmol L-1 min-1, P = 0.027). There was no difference in heart rate or blood pressure but a significant difference in the ratio of high to low frequency spectral power of heart rate variability; (no alcohol 4.55 +/- 3.78, alcohol 8.16 +/- 6.77, P = 0.033). This suggests decreased sympathetic and/or increased vagal modulation of heart rate in the alcohol group. CONCLUSION: The finding of no difference in insulin sensitivity between the two groups contrasts with, but does not entirely contradict, the results of previous epidemiological studies--perhaps suggesting that longer term changes such as liver enzyme induction may be important. The difference in insulin secretion questions the validity of previous studies of the influence of alcohol on insulin sensitivity, where insulin levels were used as a surrogate for insulin resistance.

Perfectionism in women with binge eating disorder.

OBJECTIVE: This study examined self-oriented (SOP), socially prescribed (SPP), and other-oriented (OOP) perfectionism in 127 obese women with binge eating disorder (BED). METHOD: Relationships between eating disorder and general psychopathology variables and SOP, SPP, and OOP were assessed. Levels of SOP, SPP, and OOP in the BED sample were compared with those of 32 normal weight women with bulimia nervosa (BN) and 60 obese non-eating-disordered individuals (NED). Structural equation modeling (SEM) was used to test models of the maintenance of BED. RESULTS: Only SPP was significantly associated with eating disorder variables related to BED. All three groups demonstrated similar levels of SPP and OOP. BN and BED groups scored significantly higher than the NED group on SOP only. SEM resulted in two models with good fits. DISCUSSION: Further research is needed on the roles of SPP and SOP in BED and on weight and shape overconcern in BED maintenance models.

The crystal structure of D-lactate dehydrogenase, a peripheral membrane respiratory enzyme.

d-Lactate dehydrogenase (d-LDH) of Escherichia coli is a peripheral membrane respiratory enzyme involved in electron transfer, located on the cytoplasmic side of the inner membrane. d-LDH catalyzes the oxidation of d-lactate to pyruvate, which is coupled to transmembrane transport of amino acids and sugars. Here we describe the crystal structure at 1.9 A resolution of the three domains of d-LDH: the flavin adenine dinucleotide (FAD)-binding domain, the cap domain, and the membrane-binding domain. The FAD-binding domain contains the site of d-lactate reduction by a noncovalently bound FAD cofactor and has an overall fold similar to other members of a recently discovered FAD-containing family of proteins. This structural similarity extends to the cap domain as well. The most prominent difference between d-LDH and the other members of the FAD-containing family is the membrane-binding domain, which is either absent in some of these proteins or differs significantly. The d-LDH membrane-binding domain presents an electropositive surface with six Arg and five Lys residues, which presumably interacts with the negatively charged phospholipid head groups of the membrane. Thus, d-LDH appears to bind the membrane through electrostatic rather than hydrophobic forces.

Antibiotic susceptibility profiles for group B streptococci isolated from neonates, 1995-1998.

Antibiotic susceptibility profiles were analyzed for 119 invasive and 227 colonizing strains of group B streptococci isolated from neonates at 6 US academic centers. All strains were susceptible to penicillin, vancomycin, chloramphenicol, and cefotaxime. The rate of resistance to erythromycin was 20.2% and to clindamycin was 6.9%. Resistance to erythromycin increased in 1997. Type V strains were more resistant to erythromycin than were type Ia (P=.003) and type Ib (P=.004) strains and were more resistant to clindamycin than were type Ia (P<.001), type Ib (P=.01), and type III (P=.001) strains. Resistance rates varied with geographic region: in California, there were high rates of resistance to erythromycin and clindamycin (32% and 12%, respectively), and low rates in Florida (8.5% and 2.1%, respectively). Penicillin continues to be the drug of choice for treatment of group B streptococcus infection. For women who are penicillin intolerant, however, the selection of an alternative antibiotic should be guided by contemporary resistance patterns observed in that region.

Tandem arrayed ligation of expressed sequence tags (TALEST): a new method for generating global gene expression profiles.

We have developed a new and simple method for quantitatively analyzing global gene expression profiles from cells or tissues. The process, called TALEST, or tandem arrayed ligation of expressed sequence tags, employs an oligonucleotide adapter containing a type IIs restriction enzyme site to facilitate the generation of short (16 bp) ESTs of fixed position in the mRNA. These ESTs are flanked by GC-clamped punctuation sequences which render them resistant to thermal denaturation, allowing their concatenation into long arrays and subsequent recognition and analysis by high-throughput DNA sequencing. A major advantage of the TALEST technique is the avoidance of PCR in all stages of the process and hence the attendant sequence-specific amplification biases that are inherent in other gene expression profiling methods such as SAGE, Differential Display, AFLP, etc. which rely on PCR.

Does the size of a binge matter?

OBJECTIVE: The aim of this study was to examine whether objective and subjective binges differ significantly from each other in relation to measures of psychopathology in a sample of women who meet DSM-IV diagnostic criteria for bulimia nervosa. METHOD: Baseline data from the Eating Disorder Examination (EDE) were analyzed and the average of the sum of and the difference between objective and subjective binge episodes were converted to z scores. Regressions were run with other baseline measures including the Structured Clinical Interview for Diagnosis of DSM-III-R (SCID) I and II disorders, EDE subscales, and psychological measures. RESULTS: We found no significant difference between the two types of binges on all but one measure, the "Can Do" subscale of the Self-Efficacy Questionnaire, in a regression with the z score of total binges. DISCUSSION: The lack of significant findings questions the diagnostic validity of the "large amount of food" criterion used to define binge eating in the DSM-IV.