A Review of the 'Candidatus Liberibacter africanus' Citrus Pathosystem in Africa.

It has been nearly 100 years since citrus growers in two distinct regions in the northern provinces of South Africa noticed unusual symptoms in their citrus trees, causing significant crop losses. They had no idea that these symptoms would later become part of an almost global pandemic of a disease called greening or huanglongbing (HLB). The rapid spread of the disease indicated that it might be caused by a transmissible pathogen, but it took >50 years to identify the causative agent as 'Candidatus Liberibacter africanus'. Recently, the disease appeared in more African countries, spreading by both infected planting material and Trioza erytreae. To date, five 'Ca. L. africanus' subspecies have been identified in various rutaceous species, with 'Ca. L. africanus subsp. clausenae' the only subspecies for which a biovar was detected in citrus. Efforts to detect and differentiate HLB-causing Liberibacter species are ongoing, and recent developments are discussed here. This review focuses on aspects of the African form of HLB, including its specific bacterial species and subspecies, its main insect vector, its geographic distribution, and current management strategies.

Evolutionary Robotics Controllers with Proprioception Facilitated by Neural-Network-Based Simulators.

Taking inspiration from the navigation ability of humans, this study investigated a method of providing robotic controllers with a basic sense of position. It incorporated robotic simulators into robotic controllers to provide them with a mechanism to approximate the effects their actions had on the robot. Controllers with and without internal simulators were tested and compared. The proposed controller architecture was shown to outperform the regular controller architecture. However, the longer an internal simulator was executed, the more inaccurate it became. Thus, the performance of controllers with internal simulators reduced over time unless their internal simulator was periodically corrected.

Pavlovian conditioning-induced hallucinations result from overweighting of perceptual priors.

Some people hear voices that others do not, but only some of those people seek treatment. Using a Pavlovian learning task, we induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, we identified processes that differentiated voice-hearers from non-voice-hearers and treatment-seekers from non-treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations. These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without.

Timing of Mean Transit Time Maximization is Associated with Neurological Outcome After Subarachnoid Hemorrhage.

PURPOSE: Computed tomography perfusion (CTP) has gained significant relevance for the radiological screening of patients at risk of developing delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). Particularly, the impact of MTTPEAK, i.e., the maximal mean transit time value in a series of CTP measurements, for the prediction of long-term outcome has recently been demonstrated by our group. Complementing this recent work, the present study investigated how the timing of MTTPEAK affected the long-term outcome after aneurysmal subarachnoid hemorrhage. METHODS: CTP examinations from 103 patients with clinical deterioration attributed to DCI after aSAH were retrospectively analyzed for time interval between SAH ictus and onset of MTTPEAK in association with modified Rankin Scale (mRS) 23.1 months after SAH. RESULTS: Patients with unfavorable outcome (mRS > = 2) suffered significant earlier MTTPEAK onsets than patients with favorable outcome (mRS = 0 and 1). MTTPEAK within the first week was associated with significantly higher mRS scores compared to later MTTPEAK. Timing of MTTPEAK together with the value of MTTPEAK and initial World Federation of Neurosurgical Societies (WFNS) grade was a significant predictor for an unfavorable outcome (mRS > = 2). CONCLUSIONS: The current findings suggest a presumably higher vulnerability of the brain to early microcirculatory impairments after aSAH and highlight that timing of MTT elevations could be considered for the identification of patients at increased risk for poor neurological outcome due to DCI.

Two clonal lineages of Phytophthora citrophthora from citrus in South Africa represent a single phylogenetic species.

Phytophthora citrophthora from citrus in eastern Corsica and Spain consists of distinct clonal lineages. In South Africa the extent of genetic variation among citrus-associated P. citrophthora isolates is unknown. This was investigated with isolates from South Africa (n =60), Spain (n =10) and six isolates representing three P. citrophthora groups CTR1, CTR2 and CTR3 previously identified with isozyme polymorphisms (Mchau and Coffey 1994). South African and Spanish isolates belonged to two lineages (G1, G2) based on an internal transcribed spacer (ITS) phylogeny, random amplified microsatellites (RAMS) and random amplified polymorphic DNA (RAPD) profiling. Although combined RAMS and RAPD data identified 14 genotypes, unweighted pair group method with arithmetic mean (UPGMA) analyses grouped the isolates into two clusters corresponding to lineages G1 and G2. Lineage G1 predominated among isolates from South Africa (92%) and Spain (100%). Phylogenetic analyses of the ß-tubulin, cytochrome c oxidase subunit I (COX1) and ITS regions did not support the hypothesis that the two lineages represent distinct phylogenetic species but suggested that isozyme group CTR2 and possibly CTR3 are species distinct from P. citrophthora sensu stricto. Mating-type analyses, using tester strains from groups CTR2 and CTR3 revealed that most G1 lineage isolates (n =57) were sterile but that some were of the A1 mating type (n =8) whereas all G2 lineage isolates were A2 (n =5). The mating-type designation was confirmed with P. capsici tester strains. However, when A1 (G1 lineage) and A2 (G2 lineage including CTR1 reference isolates) mating-type isolates were paired in all possible combinations, no oogonia or antheridia were produced. This suggests that only tester strains P. capsici, CTR2 and CTR3 were able to produce sexual structures and that lineages G1 and G2 are sterile and reproductively isolated, which is supported by molecular data.

Contribution of spinal cord biopsy to diagnosis of aquaporin-4 antibody positive neuromyelitis optica spectrum disorder.

Longitudinally extensive transverse myelitis is characteristic but not pathognomonic for neuromyelitis optica spectrum disorders (NMOSDs) and may mimic local tumors. In this retrospective study based on a cohort of 175 NMOSD patients we identified seven patients who initially presented with a longitudinally extensive spinal cord lesion and underwent spinal cord biopsy due to magnetic resonance imaging (MRI)-suspected malignancies. Remarkably, routine neuropathology was inconclusive and did not guide the diagnostic process to anti-aquaporin-4 (AQP4)-seropositive NMOSD. Serious postoperative complications occurred in 5/7 patients and persisted during follow-up in 2/7 patients (29%). Considering these sequelae, AQP4-antibody testing should be mandatory in patients with inconclusive longitudinally extensive spinal cord lesions prior to biopsy.

T2' Imaging of Native Kidneys and Renal Allografts - a Feasibility Study.

PURPOSE: To evaluate the feasibility of T2' mapping in native kidneys and renal allografts. MATERIALS AND METHODS: Following approval of the local ethics committee, 24 renal allograft recipients and 10 control subjects (healthy volunteers) were included in this study. Multi-echo T2 and T2* imaging was performed on a 1.5 Tesla scanner. Allograft recipients were assigned to two groups: group a), 8 patients with good (glomerular filtration rate of more than 40 ml/min) allograft function and no evidence of transplant rejection, transplant renal artery stenosis or ureteral obstruction; group b), 16 patients with deterioration of renal graft function (glomerular filtration rate (GFR) of 40 ml/min or less). Two different imaging protocols were tested. RESULTS: The mean T2' relaxation parameters were 108.33 msec ± 13.34, 100.00 msec ± 18.89 and 124.57 msec ± 6.51 for groups a), b) and for control subjects, respectively. The reduction of T2' values in patient group b) was not statistically significant. However, significant correlations could be demonstrated between T2' values and the glomerular filtration rate (GFR) of renal allograft function. The reproducibility was tested and the coefficients of variation of T2' values in the cortex of transplanted kidneys were 11.1% within subjects and 11.3% between subjects. CONCLUSION: Our results indicate that T2' imaging is a promising non-enhanced technique, which seems to reveal information on transplant function. Further studies are required to determine the clinical value of T2' mapping for monitoring renal allograft recipients.

[Evaluation of ADC mapping as an early predictor for tumor response to chemotherapy in recurrent glioma treated with bevacizumab/irinotecan: proof of principle]. / Evaluation des ADC-Mappings als Prädiktor für ein Ansprechen von Glioblastomrezidiven auf eine Therapie mit Avastin.

PURPOSE: The assessment of the radiological response of recurrent glioma is based on the Macdonald or RECIST criteria 8 to 10 weeks from the start of treatment. Magnetic resonance imaging using an apparent diffusion coefficient map may provide an earlier measure for predicting the response to therapy of recurrent glioma. MATERIALS AND METHODS: Twelve patients with recurrent high-grade glioma were enrolled in a feasibility study of pretreatment MRI on day 1, intra-treatment MRI in week 3, and post-treatment MRI in week 12. Prognostically relevant ADC values (ADCprog) of each recurrent glioma at 3 weeks were calculated as a function of their pre- and intra-therapy ADC values (ADCpre - ADCintra = ADCprog). Because we hypothesized that smaller ADC values correlate with less Brownian motion of water molecules in the extracellular space and that a higher cell density may restrain this water diffusion, we set smaller ADC values at a second time point as "progressive disease" (PD) and higher ADC values as "partial response" (PR). A change in ADCprog of less than 10 × 10⁻6mm² /sec was set as "stable disease" (SD). The ADCprog values were always calculated before the final scan after 3 months was performed. The readers were blinded to the future development of the tumor. RESULTS: In 10 of the 12 patients we could correctly predict the tumor response to chemotherapy. One patient died before the three-month control, and one recurrent glioma did not develop as predicted. ADC mapping is found to predict patient response at 3 weeks from the start of treatment, revealing that early changes in tumor diffusion values could be used as a prognostic indicator also for chemotherapeutically treated recurrences of high-grade glioma.

[Severe aseptic leucoencephalopathy. Manifested as immune reconstitution inflammatory syndrome in Caucasian and African patients]. / Schwere Leukenzephalopathie. Manifestationsform des aseptischen Immune-reconstitution-inflammatory-Syndroms bei Kaukasiern und Afrikanern.

BACKGROUND: We hypothesize that CNS immune reconstitution inflammatory syndrome (IRIS) after highly active antiretroviral therapy (HAART) in HIV-1-positive patients may become manifest without any opportunistic infection as an aseptic leucoencephalopathy. This opens a window of opportunity for successful treatment with corticosteroids. DESIGN: We describe a case series of immunocompromised HIV-1-positive patients who were started on HAART. All of them had clinical laboratory follow-up tests and cerebral MRI in order to investigate the course and the underlying pathophysiology of this aseptic form of IRIS. One African patient died and we performed a neuropathological examination. RESULTS: No infectious agent was detected before and during HAART. Three of four immunocompromised patients were successfully treated with corticosteroids while HAART was never interrupted and have survived up to now. One African patient died within 2 days despite intensive care due to cerebral oedema. CONCLUSIONS: Starting HAART, HIV-1-positive patients may develop an aseptic type of IRIS of the CNS without any detectable opportunistic infection, a finding that has not yet been published. This makes them susceptible for successful treatment with corticosteroids. Perhaps IRIS has a higher incidence in African patients and the patients have a poorer outcome than Caucasians.

[Functional MRI of transplanted kidneys using diffusion-weighted imaging]. / Funktionelle MRT der Transplantatnieren: klinische Wertigkeit der Diffusionsbildgebung.

PURPOSE: Contrast-enhanced MRI is considered problematic in renal allograft recipients due to the association of gadolinium administration and the development of NSF. Therefore, we assessed the clinical value of mono- and biexponential analysis of diffusion-weighted imaging (DWI). MATERIALS AND METHODS: A total of 32 patients were divided into four groups: (a) patients with stable function of renal allograft for at least 6 months, (b) patients with acute deterioration of allograft function, patients who recently underwent transplantation (< 14 days) with good (c) or decreased (d) renal function. T 2w ax. and T 1w cor. and a diffusion-weighted sequence with 16 b-values (b = 0 - 750 s/mm (2)) were performed on a 1.5 T scanner (Magnetom Avanto, Siemens Medical Solutions). ROI-based analysis of the renal cortex was analyzed using the software "Table Curve 2D". RESULTS: Monoexponential analysis showed an ADC (mono) of 1961 +/- 104 1801 +/- 150, 2053 +/- 169 and 1720 +/- 191 10 (-6)mm (2) /sec for patient group a, b, c and d respectively. The difference in ADC (mono) between group (a) and (b) (p < 0.006) and between group (c) and (d) (p < 0.04) was statistically significant. Biexponential analysis revealed a mean perfusion fraction of 0.21, 0.23, 0.32 and 0.24 for group (a), (b), (c) and (d), respectively. Biexponential ADC showed a higher numerical accuracy. There were no statistically significant inter-group differences in diffusion (ADC (D)) and perfusion (ADC (P)). CONCLUSION: Unenhanced evaluation of renal allografts with DWI is feasible. ADC (mono) of renal cortex correlates with renal function. The significance of the higher numerical accuracy of biexponential analysis in clinical settings requires further evaluation in larger-scale studies.

[Comèl's ichthyosis linearis circumflexa: treatment with Ro 10-9359. Electron microscopic study]. / Ichtyose linéaire circonflexe de Comèl: traitement par Ro 10-9359. Etude en microscopie électronique.

The authors show the noteworthy efficacy of the aromatic retinoid Ro 10-9359 in the treatment of ichthyosis linearis circumflexa. The initial dose was 1 mg/kg daily; later on, the maintenance dose was 0.3 mg/kg daily. Ultrastructurally, transitional cells were observed between the granular and the horny layer. After treatment, large perinuclear pseudovacuoles appeared, as well as numerous microvilli.