Ultraintense x-ray induced ionization, dissociation, and frustrated absorption in molecular nitrogen

Sequential multiple photoionization of the prototypical molecule N2 is studied with femtosecond time resolution using the Linac Coherent Light Source (LCLS). A detailed picture of intense x-ray induced ionization and dissociation dynamics is revealed, including a molecular mechanism of frustrated absorption that suppresses the formation of high charge states at short pulse durations. The inverse scaling of the average target charge state with x-ray peak brightness has possible implications for single-pulse imaging applications.

Tissue tropism and promoter sequence variation in caprine arthritis encephalitis virus infected goats

Caprine arthritis encephalitis virus is a lentivirus that infects goats and is closely related to maedi-visna virus of sheep. Infection with CAEV results in multiple discrete disease manifestations in goats which can include chronic arthritis, mastitis, pneumonia or encephalomyelitis. Presently, no satisfactory mechanistic rationale for viral tropism has been put forward. We propose that specific sequences in the lentiviral promoter (U3 region of the viral long terminal repeat) are associated with viral tissue tropism and subsequent disease expression. A total of 41 distinct CAE viral promoter regions were amplified, sequenced and phylogenetically compared from the tissues of 24 CAEV-infected goats demonstrating a variety of disease manifestations. Phylogenetically, we identified no tendency for clustering of these promoter sequences into tissue-specific groups. These results therefore do not provide evidence for the study hypothesis. However, multiple motifs within the U3 promoter region were highly conserved both within the entire collection of sequences and within tissue-specific groups.

Nucleic acid testing (NAT) of organ donors: is the 'best' test the right test? A consensus conference report

Nucleic acid testing (NAT) for HIV, HBV and HCV shortens the time between infection and detection by available testing. A group of experts was selected to develop recommendations for the use of NAT in the HIV/HBV/HCV screening of potential organ donors. The rapid turnaround times needed for donor testing and the risk of death while awaiting transplantation make organ donor screening different from screening blood-or tissue donors. In donors with no identified risk factors, there is insufficient evidence to recommend routine NAT, as the benefits of NAT may not outweigh the disadvantages of NAT especially when false-positive results can lead to loss of donor organs. For donors with identified behavioral risk factors, NAT should be considered to reduce the risk of transmission and increase organ utilization. Informed consent balancing the risks of donor-derived infection against the risk of remaining on the waiting list should be obtained at the time of candidate listing and again at the time of organ offer. In conclusion, there is insufficient evidence to recommend universal prospective screening of organ donors for HIV, HCV and HBV using current NAT platforms. Further study of viral screening modalities may reduce disease transmission risk without excessive donor loss.

Neuroendocrine and subjective responses to pharmacological challenge with citalopram: a controlled study in male and female ecstasy/MDMA users

Despite evidence that +/-3,4-methylenedioxymethamphetamine (MDMA; 'ecstasy') causes persistent alterations to the serotonergic system of animals, evidence for long-term neurological effects of ecstasy/MDMA in humans remains equivocal. The current study assessed serotonin functioning of nine male and 11 female recreational ecstasy polydrug users by measuring neuroendocrine (prolactin, cortisol) responses to pharmacological challenge with the selective serotonin reuptake inhibitor citalopram, compared with nine male and five female cannabis polydrug users and 11 male and 11 female non-drug using controls. A single-blind, randomised, placebo-controlled design was used. Subjective responses, other substance use, mood, personality traits and demographic variables were measured to control for potentially confounding variables. There were no significant differences between ecstasy polydrug users, cannabis polydrug users and non-drug using controls in neuroendocrine or subjective responses to serotonergic challenge, and there were no sex by drug group interactions. There was no relationship between extent of ecstasy use and neuroendocrine functioning, alone or in combination with potential confounding variables. Subjective responses to the pharmacological challenge (nausea, tremor, dry mouth), novelty seeking and lifetime dose of alcohol were the only variables that contributed to one or more of the neuroendocrine outcome variables. These data do not support the premise that recreational ecstasy/MDMA use results in measurable impairment of serotonergic control of endocrine activity.

Factors associated with failure to list HIV-positive kidney transplant candidates

With improved survival in the antiretroviral era, data from ongoing studies suggest that HIV patients can be safely transplanted. The disproportionate burden of HIV-related end-stage renal disease in minority populations may impose additional obstacles to successful completion of the transplant evaluation. We retrospectively reviewed 309 potentially eligible HIV patients evaluated for kidney transplant at our institution since 2000. Only 20% of HIV patients have been listed, compared to 73% of HIV-negative patients evaluated over the same period (p < 0.00001). Failure to provide documentation of CD4 and viral load (36% of candidates) was the most common reason for failure to progress beyond initial evaluation. Other factors independently associated with failure to complete the evaluation included CD4 < 200 at initial evaluation (OR 15.17; 95% CI 1.94-118.83), black race (OR 2.33; 95% CI 1.07-5.06), and history of drug use (OR 2.56; 95% CI 1.22-5.37). More efficient medical record sharing and an awareness of factors associated with failure to list HIV-positive transplant candidates may enable transplant centers to more effectively advocate for these patients.

The use of vitamin E for prevention of chemotherapy-induced peripheral neuropathy: A phase III double-blind, placebo controlled study—N05C31

9532

Background: Chemotherapy induced peripheral neuropathy (CIPN) continues to be a substantial problem for many cancer patients (pts). Pursuant to promising appearing pilot data, the current study evaluated the use of vitamin E for the prevention of CIPN. Methods: A phase III, randomized, double-blind, placebo controlled study was conducted in pts undergoing therapy with neurotoxic chemotherapy, utilizing twice daily dosing of vitamin E (400mg)/placebo. The primary endpoint was the incidence of grade 2+ sensory neuropathy (SN) toxicity (CTCAE v 3.0) in each treatment arm, analyzed by Chi-square testing. Major eligibility criteria included: planned curative intent adjuvant chemotherapy with neurotoxic chemotherapy, ≥ 18 years of age, ECOG PS of ≤2, no existing peripheral neuropathy or coronary artery disease, no prior treatment with neurotoxic chemotherapy, and no concurrent treatment with neuropathic or opioid pain medication. Planned sample size was 100 patients per arm, to provide 80% power to detect a difference in incidence of grade 2+ SN toxicity from 25% in the placebo group to 10% in the vitamin E group. Results: Two-hundred seven pts were enrolled between 12/01/2006 and 12/14/2007. Cytotoxic agents included taxanes (109), cisplatin (8), carboplatin (2), oxaliplatin (50) or combination (20). Eleven pts canceled prior to starting treatment and there were 7 ineligible pts on study. Thus there were 189 evaluable pts included in the current analysis. In this analysis, there was no difference in the incidence of grade 2+ SN between the 2 arms (vitamin E- 34% [95% CI- 25.0–44.8%] placebo- 29% [20.1–39.4%]; P=0.43). There, likewise, were no significant differences between treatment arms for time to onset of neuropathy (P= 0.72), for chemotherapy dose reductions due to neuropathy (P= 0.21) or patient questionnaire reported neuropathy symptoms. The treatment was well tolerated overall. Conclusions: Vitamin E did not appear to reduce the incidence of sensory neuropathy in the studied group of patients receiving neurotoxic chemotherapy but it appeared to be well tolerated.

No significant financial relationships to disclose.

Factors associated with failure to list HIV-positive kidney transplant candidates

With improved survival in the antiretroviral era, data from ongoing studies suggest that HIV patients can be safely transplanted. The disproportionate burden of HIV-related end-stage renal disease in minority populations may impose additional obstacles to successful completion of the transplant evaluation. We retrospectively reviewed 309 potentially eligible HIV patients evaluated for kidney transplant at our institution since 2000. Only 20% of HIV patients have been listed, compared to 73% of HIV-negative patients evaluated over the same period (p < 0.00001). Failure to provide documentation of CD4 and viral load (36% of candidates) was the most common reason for failure to progress beyond initial evaluation. Other factors independently associated with failure to complete the evaluation included CD4 < 200 at initial evaluation (OR 15.17; 95% CI 1.94-118.83), black race (OR 2.33; 95% CI 1.07-5.06), and history of drug use (OR 2.56; 95% CI 1.22-5.37). More efficient medical record sharing and an awareness of factors associated with failure to list HIV-positive transplant candidates may enable transplant centers to more effectively advocate for these patients.

Role of gut microbiota in early infant development

Early colonization of the infant gastrointestinal tract is crucial for the overall health of the infant, and establishment and maintenance of non-pathogenic intestinal microbiota may reduce several neonatal inflammatory conditions. Much effort has therefore been devoted to manipulation of the composition of the microbiota through 1) the role of early infant nutrition, particularly breast milk, and supplementation of infant formula with prebiotics that positively influence the enteric microbiota by selectively promoting growth of beneficial bacteria and 2) oral administration of probiotic bacteria which when administered in adequate amounts confer a health benefit on the host. While the complex microbiota of the adult is difficult to change in the long-term, there is greater impact of the diet on infant microbiota as this is not as stable as in adults. Decreasing excessive use of antibiotics and increasing the use of pre- and probiotics have shown to be beneficial in the prevention of several important infant diseases such as necrotizing enterocolitis and atopic eczema as well as improvement of short and long-term health. This review addresses how the composition of the gut microbiota becomes established in early life, its relevance to infant health, and dietary means by which it can be manipulated.

A biomechanical study comparing the compressive forces generated by a conventional 4.5 AO/ASIF cortical lag screw with a differentially pitched cortical compression screw

The aim of this study was to compare the interfragmentary compression generated across a simulated femoral fracture model by a conventional 4.5 mm AO/ASIF cortical lag screw with a differentially pitched cortical compression screw. A 45-degree osteotomy was made in a whole bone composite femoral shaft, this was internally fixed with either a conventional 4.5 mm AO/ASIF cortical lag screw or the differentially pitched cortical screw and the compressive force generated at the fracture site measured on an Instron 8874 Axial/Torsion Servohydraulic Testing System. The mean interfragmentary compression generated by the differentially pitched screw was 81.4% of that generated by the 4.5 mm AO/ASIF cortical lag screw. The 4.5 mm AO/ASIF cortical screw produces a steep rise in compression per turn of the screw. The screw based on the differential pitch design creates a more gradual increase to peak compression. The resistance to torque was greater for the AO screw than for the differential pitch screw. Maximal interfragmentary compression is achieved within 4 180 degrees turns after the head engages the near cortex for the 4.5 mm AO/ASIF screw but required 5 180 degrees turns for the differentially pitched screw. Interfragmentary compression is achievable in cortical bone using differential pitch technology. A differentially pitched screw offers obvious advantages over a conventional screw allowing independent placement of lag screw and neutralisation plate, without needing additional exposure of the fracture site, limiting the insult to local fracture biology. It is proposed as an adjunct to osteosynthesis in long bone fractures.

CT perfusion quantification of small-vessel ischemic severity

BACKGROUND AND PURPOSE

Cerebral blood flow (CBF) abnormalities are previously demonstrated in white matter disease. A gradation of change may exist between patients with mild and more severe white matter disease. An association between blood brain barrier dysfunction, increasing age and white matter disease is also suggested. The purpose of this study was to quantify and correlate white matter disease severity and CT perfusion (CTP)-derived CBF and to determine whether permeability surface abnormality increases with white matter disease severity.

MATERIALS AND METHODS

One hundred twenty patients with strokelike symptoms underwent CTP and MR imaging. Of these, 35 patients (15 women, 20 men; age, 66 +/- 15.7 years) with rapidly resolving symptoms and normal imaging characteristics consistent with transient ischemic attack were retrospectively reviewed and constituted the study cohort. Two blinded neurologists rated white matter severity, assigning age-related white matter change (ARWMC) scores. Patients were dichotomized a priori into mild and moderate-to-severe. CBF, cerebral blood volume (CBV), mean transit time (MTT), and permeability surface product maps were calculated for periventricular and subcortical white matter regions and average white and gray matter. Associations with white matter severity were tested by uni- and multivariate logistic regression analyses. Receiver operating characteristic analysis was performed.

RESULTS

White matter disease was mild in 26 patients and moderate-to-severe in 9. Age was associated with increased likelihood of having moderate-to-severe white matter disease (P = .02). ARWMC correlated with subcortical (r = -0.50, P < .001) and average CBF (r = -0.55, P < .001). White matter severity was associated with subcortical (P = .03) and average (P = .03) white matter CBF, with a trend toward periventricular white matter CBF (P = .05). Uni- and multivariate analysis controlling for the confounding effect of age demonstrated significant association between white matter severity and subcortical (P = .032) white matter CBF. Area under the curve was 0.82. No permeability surface abnormality was found.

CONCLUSIONS

CTP-derived subcortical white matter CBF is independently associated with white matter disease severity.

Evidence for the aqueous absorption of gas from the eye following vitreoretinal surgery

A standard part of vitrectomy surgery is to inject a bubble of gas into the eye, and an important question for the surgeon and patient alike is to know the volume of the bubble and how long it is likely to last. A related question of considerable importance is the mechanism by which it is absorbed. In this paper, we show how to use patients' measurements of the daily variation of their far points to calculate the changing volume of the bubble and hence the rate of gas absorption throughout the post-operative period. The results show that the rate of absorption contains a term in time squared, indicative of absorption through the exposed surface area of the aqueous fluid rather than via the exposed retina.

HIV-infected liver and kidney transplant recipients: 1- and 3-year outcomes

Improvements in human immunodeficiency virus (HIV)-associated mortality make it difficult to deny transplantation based upon futility. Outcomes in the current management era are unknown. This is a prospective series of liver or kidney transplant recipients with stable HIV disease. Eleven liver and 18 kidney transplant recipients were followed for a median of 3.4 years (IQR [interquartile range] 2.9-4.9). One- and 3-year liver recipients' survival was 91% and 64%, respectively; kidney recipients' survival was 94%. One- and 3-year liver graft survival was 82% and 64%, respectively; kidney graft survival was 83%. Kidney patient and graft survival were similar to the general transplant population, while liver survival was similar to the older population, based on 1999-2004 transplants in the national database. CD4+ T-cell counts and HIV RNA levels were stable; and there were two opportunistic infections (OI). The 1- and 3-year cumulative incidence (95% confidence intervals [CI]) of rejection episodes for kidney recipients was 52% (28-75%) and 70% (48-92%), respectively. Two-thirds of hepatitis C virus (HCV)-infected patients, but no patient with hepatitis B virus (HBV) infection, recurred. Good transplant and HIV-related outcomes among kidney transplant recipients, and reasonable outcomes among liver recipients suggest that transplantation is an option for selected HIV-infected patients cared for at centers with adequate expertise.

Rural internships for final year students: clinical experience, education and workforce

INTRODUCTION

The James Cook University School of Medicine is the only complete medical school in northern Australia, and it has a mission to prepare graduates to meet the unique needs of the region with a particular emphasis on rural, remote, Indigenous and tropical health. Eight-week 'rural internships' have been undertaken by all sixth-year medical students at James Cook University since 2005. Each student had previously completed at least 12 weeks of structured rural placements in years 2 and 4, as well as other core teaching in rural health including the year 2 subject, 'Rural, Remote, Indigenous and Tropical Health'. Students worked in rural hospitals across northern Australia developing and practising clinical skills under the supervision of senior staff. Students undertook full-time inpatient and outpatient responsibilities under supervision, being rostered for after-hours work with appropriate support. Assessment involved a learning portfolio, including multi-source feedback from peers, supervisors and patients, and a population health project and a telephone referral exercise.

METHODS

This article describes the development, implementation and assessment of the first years of the program, from 2005 to 2007. Evaluation included student questionnaires, site visits and interviews, and follow-up teleconferences with preceptors.

RESULTS

The rural internship provides senior medical students with valuable experience by active participation in the healthcare team. Students reported a rich and varied clinical experience. Students accept limited supervised responsibility and further their ability and confidence to undertake the role of the intern. Importantly, they proved not to be a burden to the system. This rotation therefore appears to meet educational needs without compromising the local workforce (and indeed may add to it). Students felt welcomed by their communities and enjoyed the social and cultural aspects of their attachment, as well as the clinical aspects and the opportunity to further their understanding of rural communities, rural health care and the healthcare team. Preparation of the students, the preceptors and the communities emerged as a key element of success.

CONCLUSION

This model extends and enhances the traditional apprenticeship model by its rural focus and distributed nature, and involvement of the entire student cohort. In addition, the contribution to patient care by senior students and junior doctors enables a consultant-registrar-resident model, in which experienced rural doctors function as consultants providing advice, support and tuition rather than predominantly face-to-face patient care. This approach also provides a means to address an emerging paradox: rural preceptors and communities want to teach students, appreciating the long-term workforce implications, but are increasingly constrained by resources, particularly time. Similar innovative approaches should be explored in other settings.