Natural genetic variation in Arabidopsis for responsiveness to plant growth-promoting rhizobacteria.

The plant growth-promoting rhizobacterium (PGPR) Pseudomonas simiae WCS417r stimulates lateral root formation and increases shoot growth in Arabidopsis thaliana (Arabidopsis). These plant growth-stimulating effects are partly caused by volatile organic compounds (VOCs) produced by the bacterium. Here, we performed a genome-wide association (GWA) study on natural genetic variation in Arabidopsis for the ability to profit from rhizobacteria-mediated plant growth-promotion. To this end, 302 Arabidopsis accessions were tested for root architecture characteristics and shoot fresh weight in response to exposure to WCS417r. Although virtually all Arabidopsis accessions tested responded positively to WCS417r, there was a large variation between accessions in the increase in shoot fresh weight, the extra number of lateral roots formed, and the effect on primary root length. Correlation analyses revealed that the bacterially-mediated increase in shoot fresh weight is related to alterations in root architecture. GWA mapping for WCS417r-stimulated changes in root and shoot growth characteristics revealed 10 genetic loci highly associated with the responsiveness of Arabidopsis to the plant growth-promoting activity of WCS417r. Several of the underlying candidate genes have been implicated in important plant growth-related processes. These results demonstrate that plants possess natural genetic variation for the capacity to profit from the plant growth-promoting function of a beneficial rhizobacterium in their rhizosphere. This knowledge is a promising starting point for sustainable breeding strategies for future crops that are better able to maximize profitable functions from their root microbiome.

Functional analysis of Hyaloperonospora arabidopsidis RXLR effectors.

The biotrophic plant pathogen Hyaloperonospora arabidopsidis produces a set of putative effector proteins that contain the conserved RXLR motif. For most of these RXLR proteins the role during infection is unknown. Thirteen RXLR proteins from H. arabidopsidis strain Waco9 were analyzed for sequence similarities and tested for a role in virulence. The thirteen RXLR proteins displayed conserved N-termini and this N-terminal conservation was also found in the 134 predicted RXLR genes from the genome of H. arabidopsidis strain Emoy2. To investigate the effects of single RXLR effector proteins on plant defense responses, thirteen H. arabidopsidis Waco9 RXLR genes were expressed in Arabidopsis thaliana. Subsequently, these plants were screened for altered susceptibility to the oomycetes H. arabidopsidis and Phytophthora capsici, and the bacterial pathogen Pseudomonas syringae. Additionally, the effect of the RXLR proteins on flg22-triggered basal immune responses was assessed. Multifactorial analysis of results collated from all experiments revealed that, except for RXLR20, all RXLR effector proteins tested affected plant immunity. For RXLR9 this was confirmed using a P. syringae ΔCEL-mediated effector delivery system. Together, the results show that many H. arabidopsidis RXLR effectors have small effects on the plant immune response, suggesting that suppression of host immunity by this biotrophic pathogen is likely to be caused by the combined actions of effectors.

The rhizosphere revisited: root microbiomics.

The rhizosphere was defined over 100 years ago as the zone around the root where microorganisms and processes important for plant growth and health are located. Recent studies show that the diversity of microorganisms associated with the root system is enormous. This rhizosphere microbiome extends the functional repertoire of the plant beyond imagination. The rhizosphere microbiome of Arabidopsis thaliana is currently being studied for the obvious reason that it allows the use of the extensive toolbox that comes with this model plant. Deciphering plant traits that drive selection and activities of the microbiome is now a major challenge in which Arabidopsis will undoubtedly be a major research object. Here we review recent microbiome studies and discuss future research directions and applicability of the generated knowledge.

Pseudomonas cervical osteomyelitis with retropharyngeal abscess: an unusual complication of otitis media.

We present the unusual case of a 54-year-old diabetic man with chronic suppurative otitis media, presenting with cervical osteomyelitis and retropharyngeal abscess. This was treated with decompression, debridement and fusion from C2 to C4 with external halo-frame stabilization. Pseudomonas aeruginosa was cultured from the ear and the osteomyelitis specimen. Exploration of the left ear showed evidence of mucosal disease, with granulations in the middle ear and oedematous mucosa in the mastoid antrum, but no evidence of dural-plate dehiscence. Haematogenous spread probably led to cervical osteomyelitis and retropharyngeal abscess formation. Cervical osteomyelitis may develop as a rare complication and present as a cause of severe neck pain in patients with otitis media.

Adenovirus expressing an NPC1-GFP fusion gene corrects neuronal and nonneuronal defects associated with Niemann pick type C disease.

Niemann Pick type C (NPC) disease is an autosomal recessive disorder characterized by abnormal cholesterol metabolism and accumulation in lysosomal and endosomal compartments. Although peripheral organs are affected, the progressive neurodegeneration in the brain is typically most deleterious, leading to dystonia, ataxia, seizures, and premature death. Although the two genes underlying this disorder in humans and mouse models of the disease have been identified (NPC1 in 95% and NPC2/HE1 in 5% of human cases), their cellular roles have not Been fully defined, and there is currently no effective treatment for this disorder. To help address these issues, we constructed a recombinant adenovirus, Ad(NPC1-GFP), which contains a cDNA encoding a mouse NPC1 protein with a green fluorescent protein (GFP) fused to its C-terminus. Fluorescence microscopy and cholesterol trafficking assays demonstrate that the GFP-tagged NPC1 protein is functional and detectable in cells from different species (hamster, mouse, human) and of different types (ovary-derived cells, fibroblasts, astrocytes, neurons from peripheral and central nervous systems) in vitro. Combined with results from time-lapse microscopy and in vivo brain injections, our findings suggest that this adenovirus offers advantages for expressing NPC1 and analyzing its cellular localization, movement, functional properties, and beneficial effects in vitro and in vivo.

Reliability of the WAIS-III subtests, indexes, and IQs in individuals with substance abuse disorders.

Reliability of the WAIS-III for 100 male patients with substance abuse disorders was determined. Means for age and education were 46.06 were (SD = 8.81 years) and 12.70 years (SD = 1.51 years). There were 63 Caucasians and 37 African Americans. Split-half coefficients for the 11 subtests (Digit Symbol-Coding, Symbol Search, and Object Assembly were omitted) ranged from .92 for Vocabulary and Digit Span to .77 for Picture Arrangement. The median subtest reliability coefficient was .86. Composite reliabilities were excellent for the Indexes (.94 to .95) and IQs (.94 to .97), with all coefficients > or = .94. Using the Fisher z test to compare correlation coefficients from independent samples, none of the reliability estimates differed significantly from those reported for the WAIS-III standardization sample. Similar findings emerged when reliabilities were determined separately for Caucasian and African American participants.

Adrenalectomy for isolated adrenal metastases from non-adrenal cancer.

Adrenalectomy for metastatic cancer is rarely performed. The survival benefit for patients undergoing resection of isolated adrenal metastases is not clear. The goal of this study was to compile a series of such cases from national and international sources and examine patient survival. The patient series was derived from published series and case reports, plus eight new cases from an international registry of patients. We found 77 patients. We examined the effect of primary tumor site, metastasis size, and disease-free interval on postoperative survival duration, including only cases where complete resection with negative margins was achieved. We compared these patients with a large series from Memorial Sloan-Kettering Cancer Center (N=37). The median survival time after adrenalectomy was 23 months, with an operative mortality rate of 3.9%. There was a significant difference in survival duration depending on primary tumor site. A longer disease-free interval from time of primary cancer therapy to adrenal metastasis was associated with a longer postoperative survival after adrenalectomy. Metastasis size did not affect survival. Survival times for USA and non-USA patients were similar. Survival duration of the 77 analytical patients was similar to that of the 37 non-analytical patients from Memorial Sloan-Kettering Cancer Center. Selected patients, particularly those with long disease-free intervals and favorable tumor biology, should be offered resection for isolated adrenal metastases.

Embryonic striatal neurons from niemann-pick type C mice exhibit defects in cholesterol metabolism and neurotrophin responsiveness.

Niemann-Pick type C (NP-C) disease is a progressive and fatal neuropathological disorder previously characterized by abnormal cholesterol metabolism in peripheral tissues. Although a defective gene has been identified in both humans and the npc(nih) mouse model of NP-C disease, how this leads to abnormal neuronal function is unclear. Here we show that whereas embryonic striatal neurons from npc(nih) mice can take up low density lipoprotein-derived cholesterol, its subsequent hydrolysis and esterification are significantly reduced. Given the importance of cholesterol to a variety of signal transduction mechanisms, we assessed the effect of this abnormality on the ability of these neurons to respond to brain-derived neurotrophic factor (BDNF). In contrast to its effects on wild type neurons, BDNF failed to induce autophosphorylation of the TrkB receptor and to increase neurite outgrowth in npc(nih) neurons, despite expression of TrkB on the cell surface. The results suggest that abnormal cholesterol metabolism occurs in neurons in the brain during NP-C disease, even at embryonic stages of development prior to the onset of phenotypic symptoms. Moreover, this defect is associated with a lack of TrkB function and BDNF responsiveness, which may contribute to the loss of neuronal function observed in NP-C disease.

Intrasubtest scatter on the WAIS-III information subtest and psychometrically defined retrieval deficits.

Milberg, et al. (1996) postulated that significant intrasubtest scatter on the Wechsler Information subtest reflects impaired retrieval. From a pool of 205 male referrals at a VA medical center with complete WAIS-III and WMS-III protocols, 28 participants with impaired retrieval (Group I) defined by a high Retrieval Composite score were identified. A sample (Group II) without similar evidence of impaired retrieval was matched to Group I on age, education, Full Scale IQ, race, and diagnosis. Intrasubtest scatter on the Information subtest was the same across groups (Group I M = 6.3, SD = 2.7; Group II M = 6.9, SD = 3.4). A second study identified impaired retrieval using the WMS-III Word Lists subtest. 21 participants (Group III) had impaired retrieval indicated by a Recognition scaled score being > or = 4 points higher than the Delayed Recall scaled score. A matched sample (Group IV) of VA patients without similar evidence of impaired retrieval was constituted. Intrasubtest scatter on the Information subtest did not differ across groups (Group III M = 6.6, SD = 2.4; Group IV M = 6.0, SD = 2.5). Evaluations of the retrieval deficit hypothesis should be based on responses of participants whose Information performance is characterized by abnormal amounts of intrasubtest scatter. It is possible that a specific amount of response variability must be present within the subtest before retrieval problems can be detected.

Modelling and analysis of time-lags in some basic patterns of cell proliferation.

In this paper, we present a systematic approach for obtaining qualitatively and quantitatively correct mathematical models of some biological phenomena with time-lags. Features of our approach are the development of a hierarchy of related models and the estimation of parameter values, along with their non-linear biases and standard deviations, for sets of experimental data. We demonstrate our method of solving parameter estimation problems for neutral delay differential equations by analyzing some models of cell growth that incorporate a time-lag in the cell division phase. We show that these models are more consistent with certain reported data than the classic exponential growth model. Although the exponential growth model provides estimates of some of the growth characteristics, such as the population-doubling time, the time-lag growth models can additionally provide estimates of: (i) the fraction of cells that are dividing, (ii) the rate of commitment of cells to cell division, (iii) the initial distribution of cells in the cell cycle, and (iv) the degree of synchronization of cells in the (initial) cell population.

Effects of carbon dioxide-induced anesthesia on cholinergic parameters in rat brain.

We report that acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities in rat brain were virtually identical whether the rat was anesthetized with carbon dioxide (CO2) before decapitation or decapitated without prior sedation. The AChE and ChAT activities were measured in three brain regions: the hippocampus, cerebral cortex, and cerebellum. Enzyme activities varied significantly by brain region, with the highest values in the hippocampus and the lowest values in the cerebellum. Enzyme activities, however, did not vary with the method of euthanasia, either CO2-induced anesthesia prior to decapitation or decapitation without anesthesia. These data suggest that CO2-induced anesthesia prior to decapitation does not alter activities of these cholinergic markers in rat hippocampus, cerebral cortex, and cerebellum. This method of euthanasia eliminates the need to capture a conscious animal, which reduces stress to the animal and the experimenter.

Spatial and behavioral correlates of hippocampal neuronal activity.

The firing rate of hippocampal neurons in rats was related both to spatial location and to multiple behavioral variables as rats performed 2 kinds of tasks that rely on hippocampal function: a spatial navigation task similar in performance demands to the radial-arm maze task and a simultaneous cue odor-discrimination task. In the place task, most cells had distinct single or multiple place fields, that is, neurons increased firing when the rat was in a particular location or locations. However, in most of these cells, firing rate also varied systematically in relation to behavioral variables, including the speed, direction, and turning angle of the rat as it moved through the place field. In addition, the activity of most cells was time-locked to task-relevant approach movements. In the odor task, most cells fired as the rat sampled discriminative cues or when it executed specific, task-relevant approach movements. Some cells fired selectively in relation to which odors were presented, the configuration of odor cues, the locus of the response, or a combination of these variables. Many cells with spatial correlates in the place task also had striking behavioral correlates when rats performed the odor task in the same environment, and the locus of the increased firing associated with behavior in the odor task was not the same as the place field in the place task. Thus, while the complex stimuli that compose spatial cues are reflected in hippocampal neuronal activity, hippocampal processing is not limited to the representation of spatial location. Rather, the domain of hippocampal representation includes both spatial and nonspatial relations among multiple cues and the actions directed in relation to these cues, across cue modalities, and across behavioral paradigms.