Plant mitochondria – past, present and future Møller, Ian Max; Rasmusson, Allan G.; Van Aken, Olivier
The Plant journal : for cell and molecular biology,
November 2021, Letnik:
108, Številka:
4
Journal Article
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SUMMARY
The study of plant mitochondria started in earnest around 1950 with the first isolations of mitochondria from animal and plant tissues. The first 35 years were spent establishing the basic ...properties of plant mitochondria and plant respiration using biochemical and physiological approaches. A number of unique properties (compared to mammalian mitochondria) were observed: (i) the ability to oxidize malate, glycine and cytosolic NAD(P)H at high rates; (ii) the partial insensitivity to rotenone, which turned out to be due to the presence of a second NADH dehydrogenase on the inner surface of the inner mitochondrial membrane in addition to the classical Complex I NADH dehydrogenase; and (iii) the partial insensitivity to cyanide, which turned out to be due to an alternative oxidase, which is also located on the inner surface of the inner mitochondrial membrane, in addition to the classical Complex IV, cytochrome oxidase. With the appearance of molecular biology methods around 1985, followed by genomics, further unique properties were discovered: (iv) plant mitochondrial DNA (mtDNA) is 10–600 times larger than the mammalian mtDNA, yet it only contains approximately 50% more genes; (v) plant mtDNA has kept the standard genetic code, and it has a low divergence rate with respect to point mutations, but a high recombinatorial activity; (vi) mitochondrial mRNA maturation includes a uniquely complex set of activities for processing, splicing and editing (at hundreds of sites); (vii) recombination in mtDNA creates novel reading frames that can produce male sterility; and (viii) plant mitochondria have a large proteome with 2000–3000 different proteins containing many unique proteins such as 200–300 pentatricopeptide repeat proteins. We describe the present and fairly detailed picture of the structure and function of plant mitochondria and how the unique properties make their metabolism more flexible allowing them to be involved in many diverse processes in the plant cell, such as photosynthesis, photorespiration, CAM and C4 metabolism, heat production, temperature control, stress resistance mechanisms, programmed cell death and genomic evolution. However, it is still a challenge to understand how the regulation of metabolism and mtDNA expression works at the cellular level and how retrograde signaling from the mitochondria coordinates all those processes.
Significance Statement
The history of plant mitochondria is briefly outlined. The present view of their unique properties and functions in cellular metabolism is described in detail both under standard conditions and in response to environmental stimuli.
Probiotics may be helpful in preventing upper respiratory tract infections, but the interventions and evidence are inconsistent. A systematic review of 14 RCTs included 10 trials (n = 3451) that ...provided sufficient data for pooling.34 Pediatric and adult populations from a wide variety of countries were included. Probiotic prophylaxis reduced the number of participants who had one or more upper respiratory tract infections (odds ratio OR 0.58, 95% confidence interval CI 0.36 to 0.92) and the number of upper respiratory tract infections per person-year (rate ratio 0.88, 95% CI 0.81 to 0.96). Both outcomes had inconsistent results in the individual studies, reflected in estimates of heterogeneity (I2 = 69% and 44%, respectively). However, use of probiotics reduced antibiotic use (risk ratio 0.67, 95% CI 0.45 to 0.98). In all but two studies, the probiotics varied in types of organisms, combinations of organisms, formulations (e.g., pills, liquids) and quantity (colonyforming units). These inconsistencies limit the clinical application of the study findings. Inhaled ipratropium bromide appears to improve cold symptoms, particularly rhinorrhea, with a moderate increase in adverse events such as epistaxis and dryness of the nose and mouth. A systematic review and meta-analysis of intranasal ipratropium bromide spray did not pool data because of variability in scales, measurements and other parameters.58 Four RCTs identified in the systematic review reported statistically significant improvement in rhinorrhea symptoms compared with placebo. However, four other RCTs found no improvement in nasal congestion compared with placebo. Two RCTs found a statistically significant improvement in the global assessment of symptoms, with 10%-15% more patients in the ipratropium group reporting themselves as "good or better" or "much better or better" on day 1 or 2 (e.g., in one study, 74% of patients using ipratropium and 61% of those using placebo rated themselves "much better or better" p = 0.02). Pooled data on adverse events (from up to six RCTs) showed significantly increased epistaxis (OR 3.21, 95% CI 1.68 to 6.13), nasal dryness (OR 2.55, 95% CI 1.50 to 4.33) and dry mouth (OR 3.59, 95% CI 1.38 to 9.38). Inconsistent evidence from a meta-analysis suggests that orally administered zinc reduces the duration and severity of the common cold in adults.74 A 23-mg zinc gluconate lozenge every two hours was the most commonly studied regimen, although there was considerable variability across studies in dose (4.5 to 23.7 mg), frequency (twice daily to 10 times daily) and formulations (gluconate, sulfate or acetate).74 Zinc shortened the course of colds significantly (mean difference -1.65 d, 95% CI -2.5 to -0.8, compared with placebo),74 a finding similar to but somewhat better than the Cochrane review31 (standardized mean difference -0.97 d, 95% CI -1.56 to -0.38). However, zinc was found to have no significant effect on the duration of colds in children (mean difference -0.26, 95% CI -0.78 to 0.25), but the effect was significant in adults (mean difference -2.63, 95% CI -3.69 to -1.58).74 Higher doses appeared to be more effective than lower doses. Zinc did not significantly affect symptom severity in children (standard mean difference -0.05, 95% CI -0.27 to 0.17) but did reduce severity in adults (standard mean difference -0.64, 95% CI -1.05 to -0.24).74 Although the data were positive for adults, heterogeneity was consistently high in all results (I2 = 55% to 95%), which reflected a high level of inconsistency, even in subgroup testing.74 Use of oral zinc supplements was associated with an increased risk of adverse events such as bad taste and nausea (risk ratio 1.24, 95% CI 1.05 to 1.46).74 It is unclear why oral zinc treatment seems to benefit adults more than children.
Pharmaceutical costs are the fastest-growing health-care expense in most developed countries. Higher drug costs have been shown to negatively impact patient outcomes. Studies suggest that doctors ...have a poor understanding of pharmaceutical costs, but the data are variable and there is no consistent pattern in awareness. We designed this systematic review to investigate doctors' knowledge of the relative and absolute costs of medications and to determine the factors that influence awareness.
Our search strategy included The Cochrane Library, EconoLit, EMBASE, and MEDLINE as well as reference lists and contact with authors who had published two or more articles on the topic or who had published within 10 y of the commencement of our review. Studies were included if: either doctors, trainees (interns or residents), or medical students were surveyed; there were more than ten survey respondents; cost of pharmaceuticals was estimated; results were expressed quantitatively; there was a clear description of how authors defined "accurate estimates"; and there was a description of how the true cost was determined. Two authors reviewed each article for eligibility and extracted data independently. Cost accuracy outcomes were summarized, but data were not combined in meta-analysis because of extensive heterogeneity. Qualitative data related to physicians and drug costs were also extracted. The final analysis included 24 articles. Cost accuracy was low; 31% of estimates were within 20% or 25% of the true cost, and fewer than 50% were accurate by any definition of cost accuracy. Methodological weaknesses were common, and studies of low methodological quality showed better cost awareness. The most important factor influencing the pattern and accuracy of estimation was the true cost of therapy. High-cost drugs were estimated more accurately than inexpensive ones (74% versus 31%, Chi-square p < 0.001). Doctors consistently overestimated the cost of inexpensive products and underestimated the cost of expensive ones (binomial test, 89/101, p < 0.001). When asked, doctors indicated that they want cost information and feel it would improve their prescribing but that it is not accessible.
Doctors' ignorance of costs, combined with their tendency to underestimate the price of expensive drugs and overestimate the price of inexpensive ones, demonstrate a lack of appreciation of the large difference in cost between inexpensive and expensive drugs. This discrepancy in turn could have profound implications for overall drug expenditures. Much more focus is required in the education of physicians about costs and the access to cost information. Future research should focus on the accessibility and reliability of medical cost information and whether the provision of this information is used by doctors and makes a difference to physician prescribing. Additionally, future work should strive for higher methodological standards to avoid the biases we found in the current literature, including attention to the method of assessing accuracy that allows larger absolute estimation ranges for expensive drugs.
Additional degrees of freedom in a fractional-order control strategy for power electronic converters are well received despite the lack of reliable tuning methods. Despite artificial/swarm ...intelligence techniques have been used to adjust controller parameters to improve more than one characteristic/property at the same time, smart tuning not always leads to realizable structures or reachable parameter values. Thus, adjustment boundaries to ensure controller viability are needed. In this manuscript the fractional-order approach is described in terms of El-Khazali biquadratic module, which produces the lowest order approximation, instead of using a definition. A two-modes controller structure is synthesize depending on uncontrolled plant needs and parameters are adjusted through particle swarm and genetic optimization algorithms for comparison. Two error-based minimization criteria are used to consider output performance into the process. Two restrictions complement the optimization scheme, one seeks to ensure desired robustness while the other prevents from synthesizing a high-gain controller. Optimization results showed similarity between minima obtained and significant difference between parameters of those controller optimized without the proposed constraints was determined. Numerical and experimental results are provide to validate proposed approach effectiveness. Effective regulation, good tracking characteristic and robustness in the presence of load variations are the main results.
Interest in structural brain connectivity has grown with the understanding that abnormal neural connections may play a role in neurologic and psychiatric diseases. Small animal connectivity mapping ...techniques are particularly important for identifying aberrant connectivity in disease models. Diffusion magnetic resonance imaging tractography can provide nondestructive, 3D, brain-wide connectivity maps, but has historically been limited by low spatial resolution, low signal-to-noise ratio, and the difficulty in estimating multiple fiber orientations within a single image voxel. Small animal diffusion tractography can be substantially improved through the combination of ex vivo MRI with exogenous contrast agents, advanced diffusion acquisition and reconstruction techniques, and probabilistic fiber tracking. Here, we present a comprehensive, probabilistic tractography connectome of the mouse brain at microscopic resolution, and a comparison of these data with a neuronal tracer-based connectivity data from the Allen Brain Atlas. This work serves as a reference database for future tractography studies in the mouse brain, and demonstrates the fundamental differences between tractography and neuronal tracer data.
Three-dimensional digital brain atlases represent an important new generation of neuroinformatics tools for understanding complex brain anatomy, assigning location to experimental data, and planning ...of experiments. We have acquired a microscopic resolution isotropic MRI and DTI atlasing template for the Sprague Dawley rat brain with 39μm isotropic voxels for the MRI volume and 78μm isotropic voxels for the DTI. Building on this template, we have delineated 76 major anatomical structures in the brain. Delineation criteria are provided for each structure. We have applied a spatial reference system based on internal brain landmarks according to the Waxholm Space standard, previously developed for the mouse brain, and furthermore connected this spatial reference system to the widely used stereotaxic coordinate system by identifying cranial sutures and related stereotaxic landmarks in the template using contrast given by the active staining technique applied to the tissue. With the release of the present atlasing template and anatomical delineations, we provide a new tool for spatial orientationanalysis of neuroanatomical location, and planning and guidance of experimental procedures in the rat brain. The use of Waxholm Space and related infrastructures will connect the atlas to interoperable resources and services for multi-level data integration and analysis across reference spaces.
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•High-resolution MRI and DTI template for the Sprague Dawley rat brain•Atlas of major anatomical structures with detailed delineation criteria•Internal landmarks for implementing ‘Waxholm Space’ spatial reference system•Cranial landmarks for translation to stereotaxic coordinate system•The template and atlas form a new tool for spatial orientation in the rat brain.
This study investigated the self-healing of metakaolin-based geopolymers by incorporation of crystalline admixture (CA), expansive agent (EA), and hydrated lime (HL). Cracks were made in the samples ...at 3 days of age and their sealing was checked during 112 days of water immersion. The phases formed during self-healing were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses. The results showed that self-healing did not occur in the mixtures without HL incorporation due to the insignificant calcium content in the material. However, partial self-healing occurred in the 10% HL mixtures. Therefore, the calcium from HL was predominant for the occurrence of self-healing in geopolymers. SEM/EDS analysis showed that calcite formation was the main phase of self-healing. However, C-A-S-H gel and vaterite were also identified as self-healing products. In summary, the results showed that EA is not suitable and CA has the potential to improve self-healing in geopolymers.
•Self-healing in metakaolin-based geopolymer with CA, EA, and HL was investigated.•The amount of calcium available in geopolymer was critical to self-healing.•Calcite, vaterite, and C-A-S-H gel were identified as products of self-healing.•Crystalline admixture promoted matrix densification during self-healing.
The multilayered myelin sheath wrapping around nerve axons is essential for proper functioning of the central nervous system. Abnormal myelination leads to a wide range of neurological diseases and ...developmental disorders. Non-invasive imaging of myelin content is of great clinical importance. The present work demonstrated that loss of myelin in the central nervous system of the shiverer mouse results in a dramatic reduction of magnetic susceptibility in white matter axons. The reduction resulted in a near extinction of susceptibility contrast between gray and white matter. Quantitative magnetic susceptibility imaging and diffusion tensor imaging were conducted on a group of control and shiverer mice at 9.4T. We measured the resonance frequency distribution of the whole brain for each mouse. Magnetic susceptibility maps were computed and compared between the two groups. It was shown that the susceptibility contrast between gray and white matter was reduced by 96% in the shiverer compared to the controls. Diffusion measurements further confirmed intact fiber pathways in the shiverer mice, ruling out the possibility of axonal injury and its potential contribution to the altered susceptibility. As an autosomal recessive mutation, shiverer is characterized by an almost total lack of central nervous system myelin. Our data provide new evidences indicating that myelin is the predominant source of susceptibility differences between deep gray and white matter observed in magnetic resonance imaging. More importantly, the present study suggests that quantitative magnetic susceptibility is a potential endogenous biomarker for myelination.
► Quantitative magnetic susceptibility mapping provides unique gray and white matter contrast. ► Susceptibility provides a more intrinsic tissue characterization then phase. ► Dysmyelination results in extinction of susceptibility contrast between gray and white matter. ► Myelin is the predominant source of susceptibility contrast in the deep brain white matter. ► Quantitative magnetic susceptibility is a potential sensitive marker for myelination.
Perry and Allan discuss the prevention of respiratory syncytial virus (RSV) in older adults. For roughly every 380 medically stable patients, RSV vaccination prevents 1 RSV-associated lower ...respiratory tract disease per season. Fatigue occurs in 34% of patients. Guidance suggests administering based on shared decision making, mainly in those at higher risk.
Advanced biophysical models like neurite orientation dispersion and density imaging (NODDI) have been developed to estimate the microstructural complexity of voxels enriched in dendrites and axons ...for both in vivo and ex vivo studies. NODDI metrics derived from high spatial and angular resolution diffusion MRI using the fixed mouse brain as a reference template have not yet been reported due in part to the extremely long scan time required. In this study, we modified the three-dimensional diffusion-weighted spin-echo pulse sequence for multi-shell and undersampling acquisition to reduce the scan time. This allowed us to acquire several exhaustive datasets that would otherwise not be attainable. NODDI metrics were derived from a complex 8-shell diffusion (1000–8000 s/mm
2
) dataset with 384 diffusion gradient-encoding directions at 50 µm isotropic resolution. These provided a foundation for exploration of tradeoffs among acquisition parameters. A three-shell acquisition strategy covering low, medium, and high
b
values with at least angular resolution of 64 is essential for ex vivo NODDI experiments. The good agreement between neurite density index (NDI) and the orientation dispersion index (ODI) with the subsequent histochemical analysis of myelin and neuronal density highlights that NODDI could provide new insight into the microstructure of the brain. Furthermore, we found that NDI is sensitive to microstructural variations in the corpus callosum using a well-established demyelination cuprizone model. The study lays the ground work for developing protocols for routine use of high-resolution NODDI method in characterizing brain microstructure in mouse models.
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