Phantoms for specifications and quality assurance of MR imaging scanners

The accompanying paper examines the subject of NMR phantoms. The paper reports on initial experience with existing phantoms and reviews proposals from various standards groups and professional organizations. Many image tests are illustrated by existing vendor phantoms. The paper concludes that many phantoms already meet or exceed most of the suggestions for tests of classical imaging parameters, which can be pursued by first order adaptations of CT phantoms. The paper does, however, point out the limitations of existing phantoms and raise the possibility of developing phantoms that more accurately reflect human shapes and cavities, and which present more realistic resistive losses, and T1 and T2 values.     

Heteromeric connexons in lens gap junction channels.

Gap junction channels are formed by paired oligomeric membrane hemichannels called connexons, which are composed of proteins of the connexin family. Experiments with transfected cell lines and paired Xenopus oocytes have demonstrated that heterotypic intercellular channels which are formed by two connexons, each composed of a different connexin, can selectively occur. Studies by Stauffer [Stauffer, K. A. (1995) J. Biol. Chem. 270, 6768-6772] have shown that recombinant Cx26 and Cx32 coinfected into insect cells may form heteromeric connexons. By solubilizing and subfractionating individual connexons from ovine lenses, we show by immunoprecipitation that connexons can contain two different connexins forming heteromeric assemblies in vivo.     

Hidden financial costs in treatment for childhood cancer: an Australian study of lifestyle implications for families absorbing out-of-pocket expenses

PURPOSE: The impact of out-of-pocket expenses on five domains of family lifestyle were explored: social, assets, credit, utilities, and charity. METHODS: Using a cross-sectional survey, 100 parents of pediatric cancer patients reported on the types of out-of-pocket expenses incurred and the perceived lifestyle impact of meeting those expenses. RESULTS: Eighty percent of the sample reported a minimum of five different out-of-pocket expenses (total mean value = 19,064 Australian dollars; approximately 9,723 US dollars). The majority reflected travel, accommodation, and communication costs, use of work-related entitlements, and changes in paid employment. In lifestyle terms, the area of greatest impact was found for the social domain, such as cancelling vacations and giving up recreational pleasures and social expenditure. Those families living furthest from the major cancer treatment center reported the greatest range of out-of-pocket expenses and subsequent lifestyle impact. While there were few differences as a function of cancer type, results suggested that families most vulnerable to financial distress tended to be those whose child had spent relatively longer on treatment. CONCLUSIONS: In meeting out-of-pocket expenses, parents primarily seek ways to "trim the fat" off existing family expenditure. While all families may incur extra expenses, parents of patients located a significant distance from the cancer treatment center remain especially vulnerable (despite increased government allowances). Creative solutions for addressing some expenses may include applications of telemedicine to augment outreach services.     

Chloroplast DNA methylation and inheritance in Chlamydomonas

When Chlamydomonas reinhardtii cells mate, a zygotic maturation program is activated, part of which leads to destruction of chloroplast DNA (cpDNA) from the mating type minus (mt-) parent, and, therefore, to uniparental inheritance of mating type plus (mt+) cpDNA. A long-standing model that explains the selective destruction of mt(-) cpDNA in zygotes invokes a methylation-restriction system. We tested this model by using the potent methylation inhibitor 5-aza-2'-deoxycytidine (5adc) to hypomethylate parental cpDNA and found that the pattern of cpDNA inheritance is altered by 5adc in a manner that is consistent with the model. Surprisingly, however, hypomethylated mt+ cpDNA is not destroyed in zygotes as the methylation-restriction model predicts it should be. Destruction of mt- cpDNA is also unaffected when the parental mt+ cpDNA is hypomethylated. Instead, loss of methylation affects the relative rates of replication of residual mt- cpDNA and mt+ cpDNA in germinating zygotes. The mode of action for 5adc on cpDNA replication in germinating zygotes may be via hypomethylation of mt+ cpDNA, but is also consistent with its action as a DNA-damaging agent. Interestingly, 5adc causes reduced cpDNA replication only in germinating zygotes, not in vegetatively grown cells, indicating that cpDNA replication is qualitatively different in these two stages of the life cycle. Our results demonstrate that methylation is not necessary for protection of the mt+ cpDNA in early zygotes and uncover a novel stage of the Chlamydomonas life cycle when replication of cpDNA is highly susceptible to perturbation. Our data support a model in which differential cpDNA replication in germinating zygotes is used as a mechanism to selectively amplify intact and properly methylated cpDNA molecules.     

Respiratory control in infants at increased risk for sudden infant death syndrome.

There is much debate relating to possible abnormalities in respiratory control mechanisms in infants considered at increased risk for sudden infant death syndrome (SIDS). The P0.1 occlusion technique was used to assess the central respiratory response to hyperoxic hypercapnia during quiet sleep in 21 normal infants, 13 siblings of SIDS victims, and 17 infants with apparent life threatening events. The slope of P0.1 plotted against carbon dioxide concentration increased exponentially with age, independent of body weight in each group. Birth weight has a significant effect on slope with a lower weight predisposing to a lower slope. Siblings as a group had a significantly lower slope at any given age than normal infants, whereas the infants who had had apparent life threatening events were not significantly different from the controls. As intragroup variation in both siblings and control groups greatly exceeded the significant intergroup differences observed, the technique cannot identify individual infants as belonging to one or other group.     

Individual differences in moral judgment competence influence neural correlates of socio-normative judgments

To investigate how individual differences in moral judgmentcompetence are reflected in the human brain, we used event-relatedfunctional magnetic resonance imaging, while 23 participantsmade either socio-normative or grammatical judgments. Participantswith lower moral judgment competence recruited the left ventromedialprefrontal cortex and the left posterior superior temporal sulcusmore than participants with greater competence in this domainwhen identifying social norm violations. Moreover, moral judgmentcompetence scores were inversely correlated with activity inthe right dorsolateral prefrontal cortex (DLPFC) during socio-normativerelative to grammatical judgments. Greater activity in rightDLPFC in participants with lower moral judgment competence indicatesincreased recruitment of rule-based knowledge and its controlledapplication during socio-normative judgments. These data supportcurrent models of the neurocognition of morality according towhich both emotional and cognitive components play an importantrole.     

Factors Associated with Time to Appropriate Treatment in Pertussis Cases in Georgia, 2009 to 2013

Pertussis is endemic in the United States, with periodic epidemics that continue to highlight its importance as a public health issue. The clinical presentation of pertussis can vary by age and vaccination status. However, little is known about the factors that affect time to antibiotic treatment of pertussis cases. We analyzed 5 years of data from the Georgia Department of Public Health to understand how factors such as age, symptoms, and vaccination status can alter the clinical picture of pertussis and affect time to treatment. We used multivariable linear regression to assess the impact of each variable on time to antibiotic treatment. There was little consistency across age groups for symptom and demographic predictors of time to antibiotic treatment. Overall, the multivariate linear regression showed that among patients ≤18 years old, none of the variables had an impact on time to antibiotic treatment greater than −0.25 to 1.47 days. Among patients >18 years old, most variables had little impact on time to treatment, though two (paroxysmal cough in >18- to 40-year-olds and hospitalization in individuals over 40) were associated with an additional 5 days in time to treatment from cough onset. This study highlights how the difficulties in pertussis diagnosis, particularly among adults, can affect time to antibiotic treatment; adults may not begin antibiotic treatment until there is an accumulation of symptoms. Health care providers need to recognize the variety of symptoms that pertussis can present with and consider confirmatory testing early.