Multiparametric MRI of Epiphyseal Cartilage Necrosis (Osteochondrosis) with Histological Validation in a Goat Model

Purpose

To evaluate multiple MRI parameters in a surgical model of osteochondrosis (OC) in goats.

Methods

Focal ischemic lesions of two different sizes were induced in the epiphyseal cartilage of the medial femoral condyles of goats at 4 days of age by surgical transection of cartilage canal blood vessels. Goats were euthanized and specimens harvested 3, 4, 5, 6, 9 and 10 weeks post-op. Ex vivo MRI scans were conducted at 9.4 Tesla for mapping the T₁, T₂, T_1ρ, adiabatic T_1ρ and T_RAFF relaxation times of articular cartilage, unaffected epiphyseal cartilage, and epiphyseal cartilage within the area of the induced lesion. After MRI scans, safranin O staining was conducted to validate areas of ischemic necrosis induced in the medial femoral condyles of six goats, and to allow comparison of MRI findings with the semi-quantitative proteoglycan assessment in corresponding safranin O-stained histological sections.

Results

All relaxation time constants differentiated normal epiphyseal cartilage from lesions of ischemic cartilage necrosis, and the histological staining results confirmed the proteoglycan (PG) loss in the areas of ischemia. In the scanned specimens, all of the measured relaxation time constants were higher in the articular than in the normal epiphyseal cartilage, consistently allowing differentiation between these two tissues.

Conclusions

Multiparametric MRI provided a sensitive approach to discriminate between necrotic and viable epiphyseal cartilage and between articular and epiphyseal cartilage, which may be useful for diagnosing and monitoring OC lesions and, potentially, for assessing effectiveness of treatment interventions.     

A new species of Pliopithecus Gervais, 1849 (Primates: Pliopithecidae) from the Middle Miocene (MN8) of Abocador de Can Mata (els Hostalets de Pierola,Catalonia, Spain)

Pliopithecus (Pliopithecus) canmatensis sp. nov. is described from several Late Aragonian localities from Abocador de Can Mata (ACM) in els Hostalets de Pierola (Vallès‐Penedès Basin, Catalonia, Spain), spanning from ～11.7 to 11.6 Ma (C5r.3r subchron), and being correlated to the MN8 (reference locality La Grive L3). The ACM remains display a pliopithecine dental morphology with well‐developed pliopithecine triangles on M/2 and M/3. This, together with other occlusal details, negates an attribution to the subgenus Epipliopithecus. Although slightly smaller, the ACM remains are most similar in size to comparable elements of P. piveteaui and P. antiquus. Several occlusal details (such as the greater development of the buccal cingulid in lower molars) and dental proportions (M/3 much longer than M/2), however, indicate greater similarities with P. antiquus from Sansan and La Grive. The ACM remains, however, differ from P. antiquus in dental proportions as well as occlusal morphology of the lower molars (including the less peripheral position of the protoconid and more medial position of the hypoconulid, the more mesial position of the buccal cuspids as compared to the lingual ones, the narrower but distinct mesial fovea, the higher trigonid, and the more extensive buccal cingulid, among others). These differences justify a taxonomic distinction at the species level of the ACM pliopithecid remains with respect to P. antiquus. Previous pliopithecid findings from the Vallès‐Penedès Basin, previously attributed to P. antiquus, are neither attributable to the latter species nor to the newly erected one. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Genetic and environmental influence on maize kernel proteome

Comparative targeted compositional analysis is currently an important element in the safety assessment of genetically modified plants. Profiling methods have been suggested as nontargeted tools to improve the detection of possible unintended effects. In this study, the capability of 2-dimensional electrophoresis to detect significant differences among seven conventional maize (Zea mays) cultivars grown in six different locations in Germany during two consecutive seasons was evaluated. Besides maize genotype, both geographic location and season had a significant effect on protein profiles. Differences as high as 55- and 53-fold in the quantity of specific proteins were recorded, the median observed difference being around 6- and 5-fold between the genotypes and growing locations, respectively. Understanding the variation in the quantity of individual proteins should help to put the variation of endogenous proteins and the novel proteins in the genetically modified plants in perspective. This together with the targeted analyses the profiling methods, including proteomics, could also help to get a deeper insight into the unintended alterations that might have occurred during the genetic modification process.     

Random processes and geographic species richness patterns: why so few species in the north?

In response to the suggestion that the latitudinal gradient in species richness is the result of stochastic processes of species distributions, we created a computer simulation program that enabled us to study random species distributions over irregularly shaped areas. Our model could not explain latitudinal variation in species richness of New World mammals and created species richness patterns that differed dramatically from previous stochastic models. The interplay of speciation and species migration in our simulation generated the highest species richness in the middle of a landmass, not in the middle of its latitudinal stretch as was found in previous one-dimensional models. The discrepancy between the results of this study and previous empirical studies suggests that the effect of randomness in species-richness distribution is on a continental scale restricted by other, dominant determinants that limit the effect of chance.     

Detecting tumor response to treatment using hyperpolarized 13C magnetic resonance imaging and spectroscopy

Measurements of early tumor responses to therapy have been shown, in some cases, to predict treatment outcome. We show in lymphoma-bearing mice injected intravenously with hyperpolarized [1-(13)C]pyruvate that the lactate dehydrogenase-catalyzed flux of (13)C label between the carboxyl groups of pyruvate and lactate in the tumor can be measured using (13)C magnetic resonance spectroscopy and spectroscopic imaging, and that this flux is inhibited within 24 h of chemotherapy. The reduction in the measured flux after drug treatment and the induction of tumor cell death can be explained by loss of the coenzyme NAD(H) and decreases in concentrations of lactate and enzyme in the tumors. The technique could provide a new way to assess tumor responses to treatment in the clinic.     

Role of sterol type on lateral pressure profiles of lipid membranes affecting membrane protein functionality: Comparison between cholesterol, desmosterol, 7-dehydrocholesterol and ketosterol

Lateral pressure profiles have been suggested to play a significant role in many cellular membrane processes by affecting, for example, the activation of membrane proteins through changes in their conformational state. This may be the case if the lateral pressure profile is altered due to changes in molecular composition surrounding the protein. In this work, we elucidate the effect of varying sterol type on the lateral pressure profile, an issue of topical interest due to lipid rafts and their putative role for membrane protein functionality. We find that the lateral pressure profile is altered when cholesterol is replaced by either desmosterol, 7-dehydrocholesterol, or ketosterol. The observed changes in the lateral pressure profile are notable and important since desmosterol and 7-dehydrocholesterol are the immediate precursors of cholesterol along its biosynthetic pathway. The results show that the lateral pressure profile and the resulting elastic behavior of lipid membranes are sensitive to the sterol type, and support a mechanism where changes in protein conformational state are facilitated by changes in the lateral pressure profile. From a structural point of view, the results provide compelling evidence that despite seemingly minor differences, sterols are characterized by structural specificity.     

Profiling of membrane protein variants in a baculovirus system by coupling cell-surface detection with small-scale parallel expression

Production of structure-grade mammalian membrane proteins in substantial quantities has been hindered by a lack of methods for effectively profiling multiple constructs expression in higher eukaryotic systems such as insect or mammalian cells. To address this problem, a specialized small-scale eukaryotic expression platform by Thomson Instrument Company (Vertiga-IM) was developed and used in tandem with a Guava EasyCyte microcapillary 96-well cytometer to monitor cell density and health and evaluate membrane protein expression. Two proof of concept experiments were conducted using the human beta(2)-adrenergic receptor (beta(2)AR) and the gap junction protein connexin26 (Cx26) in a baculovirus expression system. First, cell surface expression was used to assess the expression levels of 14 beta(2)AR truncation variants expressed using the Vertiga-IM shaker. Three of these variants were then compared to wild-type beta(2)AR using three metrics: cell surface expression, saturation ligand binding and protein immunoblot analysis of dodecylmaltoside extracted material. Second, a series of systematic Cx26 truncation variants were evaluated for expression by protein immunoblot analysis. The cumulative results for these two systems show that the Vertiga-IM instrument can be used effectively in the parallel insect cell microexpression of membrane protein variants, and that the expression of cell surface molecules as monitored with the Guava EasyCyte instrument can be used to rapidly assess the production of properly folded proteins in the baculovirus expression system. This approach expedites the in vitro evaluation of a large number of mammalian membrane protein variants.     

Light acclimation involves dynamic re‐organization of the pigment–protein megacomplexes in non‐appressed thylakoid domains

Thylakoid energy metabolism is crucial for plant growth, development and acclimation. Non‐appressed thylakoids harbor several high molecular mass pigment–protein megacomplexes that have flexible compositions depending upon the environmental cues. This composition is important for dynamic energy balancing in photosystems (PS) I and II. We analysed the megacomplexes of Arabidopsis wild type (WT) plants and of several thylakoid regulatory mutants. The stn7 mutant, which is defective in phosphorylation of the light‐harvesting complex (LHC) II, possessed a megacomplex composition that was strikingly different from that of the WT. Of the nine megacomplexes in total for the non‐appressed thylakoids, the largest megacomplex in particular was less abundant in the stn7 mutant under standard growth conditions. This megacomplex contains both PSI and PSII and was recently shown to allow energy spillover between PSII and PSI (Nat. Commun., 6, 2015, 6675). The dynamics of the megacomplex composition was addressed by exposing plants to different light conditions prior to thylakoid isolation. The megacomplex pattern in the WT was highly dynamic. Under darkness or far red light it showed low levels of LHCII phosphorylation and resembled the stn7 pattern; under low light, which triggers LHCII phosphorylation, it resembled that of the tap38/pph1 phosphatase mutant. In contrast, solubilization of the entire thylakoid network with dodecyl maltoside, which efficiently solubilizes pigment–protein complexes from all thylakoid compartments, revealed that the pigment–protein composition remained stable despite the changing light conditions or mutations that affected LHCII (de)phosphorylation. We conclude that the composition of pigment–protein megacomplexes specifically in non‐appressed thylakoids undergoes redox‐dependent changes, thus facilitating maintenance of the excitation balance between the two photosystems upon changes in light conditions.