Cortical microstructural involvement in cerebral small vessel disease

Background

In cerebral small vessel disease (CSVD), cortical atrophy occurs at a later stage compared to microstructural abnormalities and therefore cannot be used for monitoring short-term disease progression. We aimed to investigate whether cortical diffusion tensor imaging (DTI) and quantitative (q) magnetic resonance imaging (MRI) are able to detect early microstructural involvement of the cerebral cortex in CSVD.

Materials and Methods

33 CSVD patients without significant cortical or whole-brain atrophy and 16 healthy control subjects were included and underwent structural MRI, DTI and high-resolution qMRI with T2, T2* and T2' mapping at 3 T as well as comprehensive cognitive assessment. After tissue segmentation and reconstruction of the cortical boundaries with the Freesurfer software, DTI and qMRI parameters were saved as surface datasets and averaged across all vertices.

Results

Cortical diffusivity and quantitative T2 values were significantly increased in patients compared to controls (p < 0.05). T2 values correlated significantly positively with white matter hyperintensity (WMH) volume (p < 0.01). Both cortical diffusivity and T2 showed significant negative associations with axonal damage to the white matter fiber tracts (p < 0.05).

Conclusions

Cortical diffusivity and quantitative T2 mapping are suitable to detect microstructural involvement of the cerebral cortex in CSVD and represent promising imaging biomarkers for monitoring disease progression and effects of therapeutical interventions in clinical studies.

Better Social-emotional Behavior in Young Nepali Children is Associated with Household Wealth, Child Age, and Family Participation in a Community Development Intervention

Background Mental health and behavior problems are under-recognized in low- and middleincome countries, especially in young children. Early identification of these problems could encourage governments to address the shortages of child mental health professionals and promote early intervention programs to help children achieve their full developmental potential. Objective Describe the social-emotional development of young rural Nepali children; explore risk factors for poor development. Method The study was embedded in a longitudinal intervention trial comparing control households with those who received training in family nutrition+livestock management (Partial Package) or family nutrition+livestock management+community mobilization (Full Package). At midline, enumerators completed a 145-item household questionnaire, child anthropometry, and Administered the Ages and Stages Questionnaire-Social-Emotional (ASQ-SE) to all enrolled children age 33-47 months (n=310). Bivariate and regression analyses examined the relationship of child and household risk factors to administered the Ages and Stages QuestionnaireSocial-Emotional scores. Result Administered the Ages and Stages Questionnaire-Social-Emotional scores were below age cutoffs in 24% of children, suggesting worse social-emotional development. In bivariate analyses and the adjusted linear regression model, older child age, greater household wealth, and Full Package Intervention status were all associated with better social-emotional development scores. Partial Package Intervention status was associated with worse scores. Conclusion The Administered the Ages and Stages Questionnaire-Social-Emotional is a potential tool to assess child social-emotional development in the context of household and community level interventions. Further work is necessary to validate the administered the Ages and Stages Questionnaire-Social-Emotional and similar tools in Nepal, and to better understand the prevalence of challenges to optimal socialemotional development in young children in order to use this information to design and monitor needed interventions.

B1 mapping using an EPI-based double angle approach: A practical guide for correcting slice profile and B0 distortion effects

PURPOSE

Aim of this study was to develop a reliable B₁ mapping method for brain imaging based on vendor MR sequences available on clinical scanners. Correction procedures for B₀ distortions and slice profile imperfections are proposed, together with a phantom experiment for deriving the approximate time-bandwidth-product (TBP) of the excitation pulse, which is usually not known for vendor sequences.

METHODS

The double angle method was used, acquiring two gradient echo echo-planar imaging data sets with different excitation angles. A correction factor C (B₁ , TBP, B₀ ) was derived from simulations for converting double angle method signal quotients into bias-free B₁ maps. In vitro and in vivo tests compare results with reference B₁ maps based on an established in-house sequence.

RESULTS

The simulation shows that C has a negligible B₁ dependence, allowing for a polynomial approximation of C (TBP, B₀ ). Signal quotients measured in a phantom experiment with known TBP reconfirm the simulation results. In vitro and in vivo B₁ maps based on the proposed method, assuming TBP = 5.8 as derived from a phantom experiment, match closely the reference B₁ maps. Analysis without B₀ correction shows marked deviations in areas of distorted B₀ , highlighting the importance of this correction.

CONCLUSION

Double angle method-based B₁ mapping was set up for vendor gradient echo-echo-planar imaging sequences, using a correction procedure for slice profile imperfections and B₀ distortions. This will help to set up quantitative MRI studies on clinical scanners with release sequences, as the method does not require knowledge of the exact RF-pulse profiles or the use of in-house sequences.

Impaired oxygen extraction and adaptation of intracellular energy metabolism in cerebral small vessel disease

BACKGROUND

We aimed to investigate whether combined phosphorous (³¹P) magnetic resonance spectroscopic imaging (MRSI) and quantitative T 2 ' mapping are able to detect alterations of the cerebral oxygen extraction fraction (OEF) and intracellular pH (pH_i) as markers the of cellular energy metabolism in cerebral small vessel disease (SVD).

MATERIALS AND METHODS

32 patients with SVD and 17 age-matched healthy control subjects were examined with 3-dimensional ³¹P MRSI and oxygenation-sensitive quantitative T 2 ' mapping (1/ T 2 '  = 1/T₂* - 1/T₂) at 3 Tesla (T). PH_i was measured within the white matter hyperintensities (WMH) in SVD patients. Quantitative T 2 ' values were averaged across the entire white matter (WM). Furthermore, T 2 ' values were extracted from normal-appearing WM (NAWM) and the WMH and compared between patients and controls.

RESULTS

Quantitative T 2 ' values were significantly increased across the entire WM and in the NAWM in patients compared to control subjects (149.51 ± 16.94 vs. 138.19 ± 12.66 ms and 147.45 ± 18.14 vs. 137.99 ± 12.19 ms, p < 0.05). WM T 2 ' values correlated significantly with the WMH load (ρ=0.441, p = 0.006). Increased T 2 ' was significantly associated with more alkaline pH_i (ρ=0.299, p < 0.05). Both T 2 ' and pH_i were significantly positively correlated with vascular pulsatility in the distal carotid arteries (ρ=0.596, p = 0.001 and ρ=0.452, p = 0.016).

CONCLUSIONS

This exploratory study found evidence of impaired cerebral OEF in SVD, which is associated with intracellular alkalosis as an adaptive mechanism. The employed techniques provide new insights into the pathophysiology of SVD with regard to disease-related consequences on the cellular metabolic state.

Associations between biomass fuel use and child health: a community-based study in Bhaktapur, Nepal

Background

Biomass fuel use for cooking is widespread in low- and middle-income countries. Previous studies have mainly focused on adverse health outcomes in adults or specific diseases. In a cohort among young children living in Bhaktapur, Nepal, we aimed to describe the association between the use of biomass cooking fuels in families with child health using measures of linear growth, cognition and chronic illness.

Methods

Caregivers of 600 marginally stunted children aged 6-11 months were interviewed about their primary source of cooking fuel at enrolment into a randomized controlled trial. Children's body length (n = 572) was measured at age 18-23 months. At the same time, blood samples (n = 497) were taken, and we measured leukocyte telomere length (LTL) as a marker of chronic disease risk. We chose LTL expressed as z-scores as a measure of chronic disease. Cognitive abilities were measured by the Wechsler Preschool and Primary Scale of Intelligence, 4th edition (WPPSI-IV) and NEPSY-II subtests when the children were 4 years old (n = 531). Associations were estimated in multiple regression models.

Results

About 18% of all families used biomass as primary cooking fuel. Children from families using biomass fuel were on average slightly shorter (mean difference 0.14 Z-scores, 95% CI: 0.28, 0.00), had lower IQ scores (mean difference 2.2 (95% CI: 0.5, 3.9), and shorter LTL (mean difference: 0.09 (95% CI: 0.05 to 0.13) compared to those not using biomass fuel. The observed associations were unaltered after adjusting for relevant confounders.

Conclusions

In children from households in poor, urban neighborhoods in Nepal, biomass fuel use for cooking was associated with health indicators for child growth and cognition as well as longevity and chronic illnesses reflected in shortening of telomeres. As this was an observational study, residual confounding cannot be excluded. Our findings support the ongoing effort to reduce exposure to biomass fuel in low-resource settings.

Key messages

Qualitative and quantitative detectability of hypertrophic olivary degeneration in T2, FLAIR, PD, and DTI: A prospective MRI study

Purpose:

Hypertrophic olivary degeneration (HOD) is a pathology of the inferior olivary nucleus (ION) that occurs after injuries to the Guillain-Mollaret triangle (GMT). Lacking a diagnostic gold standard, diagnosis is usually based on T2 or FLAIR imaging and expert rating. To facilitate precise HOD diagnosis in future studies, we assessed the reliability of this rater-based approach and explored alternative, quantitative analysis.

Methods

Patients who had suffered strokes in the GMT and a matched control group prospectively underwent an MRI examination including T2, FLAIR, and proton density (PD). Diffusion tensor imaging (DTI) was additionally performed in the patient group. The presence of HOD was assessed on FLAIR, T2, and PD separately by 3 blinded reviewers. Employing an easily reproducible segmentation approach, relative differences in intensity, fractional anisotropy (FA), and mean diffusivity (MD) between both IONs were calculated.

Results

In total, 15 patients were included in this study. The interrater reliability was best for FLAIR, followed by T2 and PD (Fleiss κ = 0.87 / 0.77 / 0.65). The 3 raters diagnosed HOD in 38–46% (FLAIR), 40–47% (T2), and 53–67% (PD) of patients. False-positive findings in the control group were less frequent in T2 than in PD and FLAIR (2.2% / 8.9% / 6.7%). In 53% of patients, the intensity difference between both IONs on PD was significantly increased in comparison with the control group. These patients also showed significantly decreased FA and increased MD.

Conclusion

While the rater-based approach yielded the best performance on T2 imaging, a quantitative, more sensitive HOD diagnosis based on ION intensities in PD and DTI imaging seems possible.

Machine Learning Approach to Predict Positive Screening of Methicillin-Resistant Staphylococcus aureus During Mechanical Ventilation Using Synthetic Dataset From MIMIC-IV Database

Background: Mechanically ventilated patients are susceptible to nosocomial infections such as ventilator-associated pneumonia. To treat ventilated patients with suspected infection, clinicians select appropriate antibiotics. However, decision-making regarding the use of antibiotics for methicillin-resistant Staphylococcus aureus (MRSA) is challenging, because of the lack of evidence-supported criteria. This study aims to derive a machine learning model to predict MRSA as a possible pathogen responsible for infection in mechanically ventilated patients. Methods: Data were collected from the Medical Information Mart for Intensive Care (MIMIC)-IV database (an openly available database of patients treated at the Beth Israel Deaconess Medical Center in the period 2008-2019). Of 26,409 mechanically ventilated patients, 809 were screened for MRSA during the mechanical ventilation period and included in the study. The outcome was positivity to MRSA on screening, which was highly imbalanced in the dataset, with 93.9% positive outcomes. Therefore, after dividing the dataset into a training set (n = 566) and a test set (n = 243) for validation by stratified random sampling with a 7:3 allocation ratio, synthetic datasets with 50% positive outcomes were created by synthetic minority over-sampling for both sets individually (synthetic training set: n = 1,064; synthetic test set: n = 456). Using these synthetic datasets, we trained and validated an XGBoost machine learning model using 28 predictor variables for outcome prediction. Model performance was evaluated by area under the receiver operating characteristic (AUROC), sensitivity, specificity, and other statistical measurements. Feature importance was computed by the Gini method. Results: In validation, the XGBoost model demonstrated reliable outcome prediction with an AUROC value of 0.89 [95% confidence interval (CI): 0.83-0.95]. The model showed a high sensitivity of 0.98 [CI: 0.95-0.99], but a low specificity of 0.47 [CI: 0.41-0.54] and a positive predictive value of 0.65 [CI: 0.62-0.68]. Important predictor variables included admission from the emergency department, insertion of arterial lines, prior quinolone use, hemodialysis, and admission to a surgical intensive care unit. Conclusions: We were able to develop an effective machine learning model to predict positive MRSA screening during mechanical ventilation using synthetic datasets, thus encouraging further research to develop a clinically relevant machine learning model for antibiotics stewardship.

Flower colour and size signals differ depending on geographical location and altitude region

Bees are major pollinators of angiosperms and have phylogenetically conserved colour vision but differ in how various key species use achromatic information that is vital for both flower detection and size processing. We modelled green contrast and colour contrast signals from flowers of different countries where there are well established differences in availability of model bee species along altitudinal gradients. We tested for consistency in visual signals as expected from generalization in pollination principles using phylogenetically informed linear models. Patterns of chromatic contrast, achromatic green contrast and flower size differed among the three floras we examined. In Nepal there is a significant positive correlation between flower size and colour contrast in the subalpine region, but a negative correlation at the lower altitudes. At high elevations in Norway, where pollinators other than bees are common, flower size was positively correlated with colour contrast. At low and medium altitudes in Norway and in Australia, we did not observe a significant relationship between size and colour contrast. We thus find that the relationship between size, green and colour contrast cannot be generalized across communities, thus suggesting that flower visual signal adaptations to local pollinators are not limited to chromatic contrast.

Multicenter Prospective Analysis of Hypertrophic Olivary Degeneration Following Infratentorial Stroke (HOD-IS): Evaluation of Disease Epidemiology, Clinical Presentation, and MR-Imaging Aspects

Introduction: Ischemic and hemorrhagic strokes in the brainstem and cerebellum with injury to the functional loop of the Guillain-Mollaret triangle (GMT) can trigger a series of events that result in secondary trans-synaptic neurodegeneration of the inferior olivary nucleus. In an unknown percentage of patients, this leads to a condition called hypertrophic olivary degeneration (HOD). Characteristic clinical symptoms of HOD progress slowly over months and consist of a rhythmic palatal tremor, vertical pendular nystagmus, and Holmes tremor of the upper limbs. Diffusion Tensor Imaging (DTI) with tractography is a promising method to identify functional pathway lesions along the cerebello-thalamo-cortical connectivity and to generate a deeper understanding of the HOD pathophysiology. The incidence of HOD development following stroke and the timeline of clinical symptoms have not yet been determined in prospective studies—a prerequisite for the surveillance of patients at risk.

Methods and Analysis: Patients with ischemic and hemorrhagic strokes in the brainstem and cerebellum with a topo-anatomical relation to the GMT are recruited within certified stroke units of the Interdisciplinary Neurovascular Network of the Rhine-Main. Matching lesions are identified using a predefined MRI template. Eligible patients are prospectively followed up and present at 4 and 8 months after the index event. During study visits, a clinical neurological examination and brain MRI, including high-resolution T2-, proton-density-weighted imaging, and DTI tractography, are performed. Fiberoptic endoscopic evaluation of swallowing is optional if palatal tremor is encountered.

Study Outcomes: The primary endpoint of this prospective clinical multicenter study is to determine the frequency of radiological HOD development in patients with a posterior fossa stroke affecting the GMT at 8 months after the index event. Secondary endpoints are identification of (1) the timeline and relevance of clinical symptoms, (2) lesion localizations more prone to HOD occurrence, and (3) the best MR-imaging regimen for HOD identification. Additionally, (4) DTI tractography data are used to analyze individual pathway lesions. The aim is to contribute to the epidemiological and pathophysiological understanding of HOD and hereby facilitate future research on therapeutic and prophylactic measures.

Clinical Trial Registration: HOD-IS is a registered trial at https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00020549.

A fast and novel method for amide proton transfer-chemical exchange saturation transfer multislice imaging

Amide proton transfer-chemical exchange saturation transfer (APT-CEST) imaging provides important information for the diagnosis and monitoring of tumors. For such analysis, complete coverage of the brain is advantageous, especially when registration is performed with other magnetic resonance (MR) modalities, such as MR spectroscopy (MRS). However, the acquisition of Z-spectra across several slices via multislice imaging may be time-consuming. Therefore, in this paper, we present a new approach for fast multislice imaging, allowing us to acquire 16 slices per frequency offset within 8 s. The proposed fast CEST-EPI sequence employs a presaturation module, which drives the magnetization into the steady-state equilibrium for the first frequency offset. A second module, consisting of a single CEST pulse (for maintaining the steady-state) followed by an EPI acquisition, passes through a loop to acquire multiple slices and adjacent frequency offsets. Thus, the whole Z-spectrum can be recorded much faster than the conventional saturation scheme, which employs a presaturation for each single frequency offset. The validation of the CEST sequence parameters was performed by using the conventional saturation scheme. Subsequently, the proposed and a modified version of the conventional CEST sequence were compared in vitro on a phantom with different T1 times and in vivo on a brain tumor patient. No significant differences between both sequences could be found in vitro. The in vivo data yielded almost identical MTR_asym contrasts for the white and gray matter as well as for tumor tissue. Our results show that the proposed fast CEST-EPI sequence allows for rapid data acquisition and provides similar CEST contrasts as the modified conventional scheme while reducing the scanning time by approximately 50%.

Prevalence and Pattern of Cardiovascular Diseases among ESRD Patients Undergoing Short Term and Long Term Hemodialysis

Background: Cardiovascular diseases (CVD) are the major causes of mortality and morbidity among End Stage Renal Disease (ESRD) patient undergoing hemodialysis (HD). The cardiovascular diseases in dialysis patient is related to chronic volume overload, anemia, inflammation, oxidant stress, homocysteine and other aspects of the uremic milieu. The duration of ESRD undergoing dialysis is related to the severity of cardiovascular diseases. The objective is to study the pattern of cardiovascular disease among the ESRD patient undergoing dialysis. Methods: This comparative study was done at Collage of Medical Sciences Bharatpur, Nepal from 1st June 2020 to 30th July 2020. This study included total number of 300 dialysis patients divided into two groups; 150 patients undergoing dialysis for less than one year and rest undergoing dialysis for more than one year. Patients with primary heart disease were excluded from study. Patients were evaluated with demographic data, clinical history, and physical examination with focus on cardiovascular system, lab investigations, electrocardiography (ECG) and echocardiogram variables. The pattern of cardiovascular diseases was compared among patients undergoing short term and long term hemodialysis. Results: The echocardiographic evaluation of the cases under study revealed a diversity of pattern. In this study concentric or eccentric LVH was found in 60 %( n=90) of patients with short-term hemodialysis and 75 %( n=112) of patients with long-term hemodialysis. 30 %( n=45) of patients with short-term hemodialysis had degenerative/atherosclerotic valvular heart disease while the number was 35%(n=52) in patients undergoing long-term hemodialysis. Pericardial effusion was present in 9 %( n=13) of short-term hemodialysis patient and in 5%(n=7) of long-term hemodialysis patient. 18%(n=27) of short-term hemodialysis patient had systolic dysfunction while such change was present in 27%(n=40) of long-term hemodialysis patient. Diastolic dysfunction was present in 35%(n=52) of short-term hemodialysis patient and 49%(n=73) of long-term hemodialysis patient. Pulmonary Artery Hypertension(PAH) was present in 20%(n=30) of short term hemodialysis patient and 32%(n=48) of long term hemodialysis patient. Atrial fibrillation was present in 7 %(n=10) of short-term hemodialysis patient and 5%(n=7) of long term hemodialysis patients.       Conclusions: Variety of cardiovascular diseases are common in ESRD patient undergoing hemodialysis. CVD is more prevalent in patient undergoing hemodialysis for long term.

A novel sequence to improve auditory functional MRI with variable silent delays

PURPOSE

Auditory functional MRI (fMRI) often uses silent inter-volume delays for stimulus presentation. However, maintaining the steady-state of the magnetization usually requires constant delays. Here, a novel acquisition scheme dubbed "pre-Saturated EPI using Multiple delays in Steady-state" (SEPIMS) is proposed, using spin saturation at a fixed delay before each volume to maintain steady-state conditions, independent of previous spin history. This concept allows for variable inter-volume delays and thus for flexible stimulus design in auditory fMRI. The purpose was to compare the signal stability of SEPIMS and conventional sparse EPI (CS-EPI).

METHODS

The saturation module comprises two non-selective adiabatic saturation pulses. The efficiency of the saturation and its effect on the SEPIMS signal stability is tested in vitro and in vivo.

RESULTS

Data show that SEPIMS yields the same signal stability as CS-EPI, even for extreme variations between inter-volume delay durations. However, dual saturation pulses are required to achieve sufficiently high saturation efficiency in compartments with long T₁ values. Importantly, spoiler gradient pulses after the EPI readout have to be optimized to avoid eddy-current-induced image distortions.

CONCLUSION

The proposed SEPIMS sequence maintains high signal stability in the presence of variable inter-volume durations, thus allowing for flexible stimulus design.

Rewardlessness in orchids: how frequent and how rewardless?

About one-third of orchid species are thought to offer no floral reward and therefore attract pollinators through deception. Statements of this idea are common in the botanical literature, but the empirical basis of the estimate is rarely mentioned. We traced citation pathways for the one-third estimate in a sample of the literature and found that the paths lead to empirical foundations that are surprisingly narrow. Moreover, recent measurements have detected minute quantities of sugar available to insect visitors in some orchids thought to be rewardless, raising the possibility of a pollination strategy that is largely deceitful but different to absolute rewardlessness. The orchids are a well-studied group and there is no doubt that rewardlessness is common in the family. However, greater empirical effort is needed to verify rewardlessness in orchids and to explore geographic and environmental variation in the proportion of rewardless species.

Distribution of Cortical Diffusion Tensor Imaging Changes in Multiple Sclerosis

Purpose

Diffuse cortical damage in relapsing–remitting multiple sclerosis (RRMS) is clinically relevant but cannot be directly assessed with conventional MRI. In this study, it was aimed to use diffusion tensor imaging (DTI) techniques with optimized intrinsic eddy current compensation to quantify and characterize cortical mean diffusivity (MD) and fractional anisotropy (FA) changes in RRMS and to analyze the distribution of these changes across the cortex.

Materials and Methods

Three-Tesla MRI acquisition, mapping of the MD providing information about the integrity of microstructural barriers and of the FA reflecting axonal density and surface-based analysis with Freesurfer were performed for 24 RRMS patients and 25 control subjects.

Results

Across the whole cortex, MD was increased in patients (p < 0.001), while surface-based analysis revealed focal cortical FA decreases. MD and FA changes were distributed inhomogeneously across the cortex, the MD increase being more widespread than the FA decrease. Cortical MD correlated with the Expanded Disability Status Scale (EDSS, r = 0.38, p = 0.03).

Conclusion

Damage of microstructural barriers occurs inhomogeneously across the cortex in RRMS and might be spatially more widespread than axonal degeneration. The results and, in particular, the correlation with the clinical status indicate that DTI might be a promising technique for the monitoring of cortical damage under treatment in larger clinical studies.

The pH sensitivity of APT-CEST using phosphorus spectroscopy as a reference method

The pH value is a potential physiological marker for clinical diagnosis as it is altered in pathologies such as tumors. While intracellular pH can be measured noninvasively via phosphorus spectroscopy (³¹ P MRSI), Amide Proton Transfer-Chemical Exchange Saturation Transfer (APT-CEST) MRI has been suggested as an alternative method for pH quantification. To assess the suitability of APT-CEST contrast for pH quantification, two approaches (magnetization transfer ratio asymmetry [MTR_asym ] and Lorentzian difference analysis [LDA]) for analyzing the Z-spectrum have been correlated with pH values obtained by ³¹ P MRSI. Fourteen patients with glioblastoma and 12 healthy controls were included. In contrast to MTR_asym , the LDA is modeling the direct water saturation and the semi-solid magnetization transfer, allowing a separate evaluation of the aliphatic nuclear Overhauser effect and the APT-CEST. The results of our study show that the pH values obtained by ³¹ P MRSI correspond well with both methods describing the APT-CEST contrast. Two-sample t-test showed significant differences in MTR_asym , LDA and pH obtained by ³¹ P MRSI for regions of interest in glioblastoma, contralateral control areas and normal appearing white matter (P < 0.001). A slightly improved correlation between the amide signal and pH was found after performing LDA (r = 0.78) compared with MTR_asym (r = 0.70). While both methods can be used to monitor pH changes, the LDA approach appears to be better suited.

Colour evolution within orchids depends on whether the pollinator is a bee or a fly

Orchids are a classic angiosperm model for understanding biotic pollination. We studied orchid species within two species-rich herbaceous communities that are known to have either hymenopteran or dipteran insects as the dominant pollinators, in order to understand how flower colour relates to pollinator visual systems. We analysed features of the floral reflectance spectra that are significant to pollinator visual systems and used models of dipteran and hymenopteran colour vision to characterise the chromatic signals used by fly-pollinated and bee-pollinated orchid species. In contrast to bee-pollinated flowers, fly-pollinated flowers had distinctive points of rapid reflectance change at long wavelengths and a complete absence of such spectral features at short wavelengths. Fly-pollinated flowers also had significantly more restricted loci than bee-pollinated flowers in colour space models of fly and bee vision alike. Globally, bee-pollinated flowers are known to have distinctive, consistent colour signals. Our findings of different signals for fly pollination is consistent with pollinator-mediated selection on orchid species that results from the distinctive features of fly visual systems.

Spectrum of Infections in Living Donor Kidney Transplant Recipients: An Experience From a Tertiary Center in Nepal

BACKGROUND

Kidney transplant recipients are always at risk of infections because they are on lifelong immunosuppressive medications. The spectrum of infections in this special population is not the same as in the general population. Post-transplant infections are extensively studied in the developed world. Publications about post-transplant infections from Nepal are scarce. This study was carried out to study the spectrum of infections, the trends in treatment, and the incidence of tuberculosis in kidney transplant recipients.

METHODS

This is a retrospective analysis of the patient data in Tribhuvan University Teaching Hospital, Kathmandu, Nepal. Follow-up data from the first 100 kidney transplant recipients was recorded in a Microsoft Excel worksheet and descriptive analysis was done.

RESULTS

In the first 100 transplants done until 21 September 2011, 92 patients' data were recorded and 8 patients' data were missing. The mean follow-up period was 61.03 months. The population was 76.09% male (n = 70) and 23.91% female (n = 22). A total of 641 episodes of infections were recorded. Urinary tract infections were the most common type of infection. Escherichia coli was the most common organism isolated (36% of all cultures). There were 17 (2.65%) episodes of viral and 42 (6.6%) episodes of fungal infections. Tuberculosis was diagnosed in 6 (6.5%) patients.

CONCLUSION

Urinary tract infection is the most common type of infection in post-kidney transplant patients. Quinolones were the most common agents used to treat urinary tract infections. The incidence of tuberculosis in kidney transplant recipients is 6.5% in 5 years' follow-up.

Abnormalities in Protocol Graft Kidney Biopsy 6 Months Posttransplantation in a Tertiary Care Center Hospital of Nepal

BACKGROUND

Increasing graft survival is the prime focus of every transplantation program. Detection of subclinical abnormalities with the help of protocol renal graft biopsies performed at predetermined intervals after transplantation has been one of the approaches. The objective was to study the abnormalities in protocol renal graft biopsy specimens at 6 months posttransplantation.

METHODS

This was a hospital-based observational descriptive study. It included the recipients who underwent kidney transplantation between October 2014 and September 2015. The recipients were followed up postoperatively on an outpatient basis, as per the institution protocol. At 6 months posttransplantation, protocol graft biopsy was performed in all patients with normal functioning allograft without proteinuria after obtaining informed written consent.

RESULTS

A total of 57 patients with chronic kidney disease underwent renal transplantation during the study period. Protocol biopsy was performed in 47 recipients. Subclinical rejection was found in 4 (8.5%) recipients. Two recipients had significant tubulitis and interstitial inflammation. One of them showed features of Banff Type IA cellular rejection (t2, i2) and another showed Banff Type IB cellular rejection (t3, i2). Biopsy specimen of 1 recipient showed significant glomerulitis and peritubular capillaritis (g3, ptc1). Another recipient showed significant peritubular capillaritis (ptc2) with C4d positivity. IgA nephropathy was present in 6 (12.8%) recipients. BK virus nephropathy was found in 2 (4.3%) recipients.

CONCLUSION

This study demonstrates that abnormal histologic findings occur in protocol graft biopsy specimens at 6 months post renal transplantation in patients without any clinical or laboratory abnormalities.

Preoperative serum uric acid predicts incident acute kidney injury following cardiac surgery

Background

Acute kidney injury (AKI) following cardiac surgery is a frequent complication and several risk factors increasing its incidence have already been characterized. This study evaluates the influence of preoperative increased serum uric acid (SUA) levels in comparison with other known risk factors on the incidence of AKI following cardiac surgery.

Methods

During a period of 5 month, 247 patients underwent elective coronary artery bypass grafting, valve replacement/ repair or combined bypass and valve surgery. Datas were prospectively analyzed. Primary endpoint was the incidence of AKI as defined by the AKI criteria comparing patients with preoperative serum uric acid (SUA) levels below versus above the median. Multivariate logistic regression analysis was used to identify independent predictors of postoperative AKI.

Results

Thirty (12.1%) of the 247 patients developed postoperative AKI, 24 of 30 (80%) had preoperative SUA- levels above the median (≥373 μmol/l) (OR: 4.680, CI 95% 1.840; 11.904, p = 0.001). In the multivariate analysis SUA levels above the median (OR: 5.497, CI 95% 1.772; 17.054, p = 0.003), cardiopulmonary bypass (CPB) time > 90 min (OR: 4.595, CI 95% 1.587; 13.305, p = 0.005), cardiopulmonary bypass (CPB) > 30 kg/m² (OR: 3.208, CI 95% 1.202; 8.562; p = 0.02), and preoperative elevated serum-creatinine levels (OR: 1.015, CI 95% 1.001; 1.029, p = 0.04) were independently associated with postoperative AKI.

Conclusions

Serum uric acid is an independent risk marker for AKI after cardiac surgery. From all evaluated factors it showed the highest odds ratio.

Quantitative in vivo T2 mapping using fast spin echo techniques - A linear correction procedure

A method is presented for correcting the effects of stimulated and indirect echoes on quantitative T2 mapping data acquired with multiple spin echo techniques, such as turbo spin echo. In contrast to similar correction techniques proposed in the literature, the method does not require a priori knowledge of the radio frequency (RF) pulse profiles. In a first step, for the T2 mapping protocol under investigation, signal decay curves S(TE) are simulated for a range of different RF pulse profiles. The actual signal decay S(TE) is then measured on a phantom with known T2, so the approximate RF pulse profiles can be derived via comparison with the simulated decay curves. In a second step, with the RF pulses obtained from step one, signal decay curves S(TE) are simulated for different T2 values and fitted mono-exponentially, thus allowing to deduce the relationship between true T2 and the apparent T2 (T2app) values. Results show that this relationship is approximately linear, allowing for a direct correction of T2app maps. If the amplitude of the transmitted RF field (B1) does not exceed the nominal value by more than 10%, it is shown that a B1-independent correction of T2app maps yields sufficiently accurate results for T2. A B1-dependent version is also presented. The method is tested in vitro on a phantom with different T2 values and in vivo on healthy subjects.

Protease-activated receptor-1 inhibits proliferation but enhances leukemia stem cell activity in acute myeloid leukemia

Eradication of leukemia stem cells (LSCs) is the ultimate goal of treating acute myeloid leukemia (AML). We recently showed that the combined loss of Runx1/Cbfb inhibited the development of MLL-AF9-induced AML. However, c-Kit⁺/Gr-1^- cells remained viable in Runx1/Cbfb-deleted cells, indicating that suppressing RUNX activity may not eradicate the most immature LSCs. In this study, we found upregulation of several hemostasis-related genes, including the thrombin-activatable receptor PAR-1 (protease-activated receptor-1), in Runx1/Cbfb-deleted MLL-AF9 cells. Similar to the effect of Runx1/Cbfb deletion, PAR-1 overexpression induced CDKN1A/p21 expression and attenuated proliferation in MLL-AF9 cells. To our surprise, PAR-1 deficiency also prevented leukemia development induced by a small number of MLL-AF9 leukemia stem cells (LSCs) in vivo. PAR-1 deficiency also reduced leukemogenicity of AML1-ETO-induced leukemia. Re-expression of PAR-1 in PAR-1-deficient cells combined with a limiting-dilution transplantation assay demonstrated the cell-dose-dependent role of PAR-1 in MLL-AF9 leukemia: PAR-1 inhibited rapid leukemic proliferation when there were a large number of LSCs, while a small number of LSCs required PAR-1 for their efficient growth. Mechanistically, PAR-1 increased the adherence properties of MLL-AF9 cells and promoted their engraftment to bone marrow. Taken together, these data revealed a multifaceted role for PAR-1 in leukemogenesis, and highlight this receptor as a potential target to eradicate primitive LSCs in AML.

Floral colours in a world without birds and bees: the plants of Macquarie Island

We studied biotically pollinated angiosperms on Macquarie Island, a remote site in the Southern Ocean with a predominately or exclusively dipteran pollinator fauna, in an effort to understand how flower colour affects community assembly. We compared a distinctive group of cream-green Macquarie Island flowers to the flora of likely source pools of immigrants and to a continental flora from a high latitude in the northern hemisphere. We used both dipteran and hymenopteran colour models and phylogenetically informed analyses to explore the chromatic component of community assembly. The species with cream-green flowers are very restricted in colour space models of both fly vision and bee vision and represent a distinct group that plays a very minor role in other communities. It is unlikely that such a community could form through random immigration from continental source pools. Our findings suggest that fly pollination has imposed a strong ecological filter on Macquarie Island, favouring floral colours that are rare in continental floras. This is one of the strongest demonstrations that plant-pollinator interactions play an important role in plant community assembly. Future work exploring colour choices by dipteran flower visitors would be valuable.

Three-dimensional echo-planar cine imaging of cerebral blood supply using arterial spin labeling

OBJECTIVE

Echo-planar imaging (EPI) with CYlindrical Center-out spatiaL Encoding (EPICYCLE) is introduced as a novel hybrid three-dimensional (3D) EPI technique. Its suitability for the tracking of a short bolus created by pseudo-continuous arterial spin labeling (pCASL) through the cerebral vasculature is demonstrated.

MATERIALS AND METHODS

EPICYCLE acquires two-dimensional planes of k-space along center-out trajectories. These "spokes" are rotated from shot to shot about a common axis to encode a k-space cylinder. To track a bolus of labeled blood, the same subset of evenly distributed spokes is acquired in a cine fashion after a short period of pCASL. This process is repeated for all subsets to fill the whole 3D k-space of each time frame.

RESULTS

The passage of short pCASL boluses through the vasculature of a 3D imaging slab was successfully imaged using EPICYCLE. By choosing suitable sequence parameters, the impact of slab excitation on the bolus shape could be minimized. Parametric maps of signal amplitude, transit time, and bolus width reflected typical features of blood transport in large vessels.

CONCLUSION

The EPICYCLE technique was successfully applied to track a short bolus of labeled arterial blood during its passage through the cerebral vasculature.

UBASH3B/Sts-1-CBL axis regulates myeloid proliferation in human preleukemia induced by AML1-ETO

The t(8;21) rearrangement, which creates the AML1-ETO fusion protein, represents the most common chromosomal translocation in acute myeloid leukemia (AML). Clinical data suggest that CBL mutations are a frequent event in t(8;21) AML, but the role of CBL in AML1-ETO-induced leukemia has not been investigated. In this study, we demonstrate that CBL mutations collaborate with AML1-ETO to expand human CD34+ cells both in vitro and in a xenograft model. CBL depletion by shRNA also promotes the growth of AML1-ETO cells, demonstrating the inhibitory function of endogenous CBL in t(8;21) AML. Mechanistically, loss of CBL function confers hyper-responsiveness to thrombopoietin and enhances STAT5/AKT/ERK/Src signaling in AML1-ETO cells. Interestingly, we found the protein tyrosine phosphatase UBASH3B/Sts-1, which is known to inhibit CBL function, is upregulated by AML1-ETO through transcriptional and miR-9-mediated regulation. UBASH3B/Sts-1 depletion induces an aberrant pattern of CBL phosphorylation and impairs proliferation in AML1-ETO cells. The growth inhibition caused by UBASH3B/Sts-1 depletion can be rescued by ectopic expression of CBL mutants, suggesting that UBASH3B/Sts-1 supports the growth of AML1-ETO cells partly through modulation of CBL function. Our study reveals a role of CBL in restricting myeloid proliferation of human AML1-ETO-induced leukemia, and identifies UBASH3B/Sts-1 as a potential target for pharmaceutical intervention.