Function Of Animal Age Research Articles

Age and dose dependent changes to the bone and bone marrow microenvironment after cytotoxic conditioning with busulfan.

Preparative regimens before Hematopoietic Cell Transplantation (HCT) damage the bone marrow (BM) microenvironment, potentially leading to secondary morbidity and even mortality. The precise effects of cytotoxic preconditioning on bone and BM remodeling, regeneration, and subsequent hematopoietic recovery over time remain unclear. Moreover, the influence of recipient age and cytotoxic dose have not been fully described. In this study, we longitudinally investigated bone and BM remodeling after busulfan treatment with low intensity (LI) and high intensity (HI) regimens as a function of animal age. As expected, higher donor chimerism was observed in young mice in both LI and HI regimens compared to adult mice. Noticeably in adult mice, significant engraftment was only observed in the HI group. The integrity of the blood-bone marrow barrier in calvarial BM blood vessels was lost after busulfan treatment in the young mice and remained altered even 6weeks after HCT. In adult mice, the severity of vascular leakage appeared to be dose-dependent, being more pronounced in HI compared to LI recipients. Interestingly, no noticeable change in blood flow velocity was observed following busulfan treatment. Ex vivo imaging of the long bones revealed a reduction in the frequency and an increase in the diameter and density of the blood vessels shortly after treatment, a phenomenon that largely recovered in young mice but persisted in older mice after 6weeks. Furthermore, analysis of bone remodeling indicated a significant alteration in bone turnover at 6weeks compared to earlier timepoints in both young and adult mice. Overall, our results reveal new aspects of bone and BM remodeling, as well as hematopoietic recovery, which is dependent on the cytotoxic dose and recipient age.

Meta-analysis of the parasitic phase traits of Haemonchus contortus infection in sheep

BackgroundThe parasitic nematode Haemonchus contortus shows highly variable life history traits. This highlights the need to have an average estimate and a quantification of the variation around it to calibrate epidemiological models.MethodsThis paper aimed to quantify the main life history traits of H. contortus and to identify explanatory factors affecting these traits using a powerful method based on a systematic review and meta-analysis of current literature. The life history traits considered are: (i) the establishment rate of ingested larvae; (ii) the adult mortality rate; (iii) the fertility (i.e. the number of eggs laid/female/day); and (iv) fecundity of female worms (i.e. the number of eggs per gram of faeces).ResultsA total of 37 papers that report single experimental infection with H. contortus in sheep and published from 1960 to 2015, were reviewed and collated in this meta-analysis. This encompassed 115 experiments on 982 animals. Each trait was analysed using a linear model weighted by its inverse variance. The average (± SE) larval establishment rate was 0.24 ± 0.02, which decreased as a function of the infection dose and host age. An average adult mortality rate of 0.021 ± 0.002) was estimated from the literature. This trait varied as a function of animal age, breed and protective response due to prior exposure to the parasite. Average female fertility was 1295.9 ± 280.4 eggs/female/day and decreased in resistant breeds and previously infected hosts. Average faecal egg count at necropsy was 908.5 ± 487.1 eggs per gram of faeces and varied as a function of infection duration and host resistance. The average sex ratio of H. contortus was 0.51 ± 0.006.ConclusionThis work is the first systematic review to summarise the available information on the parasitic phase of H. contortus in sheep. The results of the meta-analysis provide robust estimates of life history traits for parametrization of epidemiological models, their expected variation according to experimental factors, and provides correlations between these.

Foxn1 and Mmp-9 expression in intact skin and during excisional wound repair in young, adult, and old C57Bl/6 mice.

The transcription factor Foxn1 is essential for skin development. Our previous studies performed on young C57BL/6J mice model showed that Foxn1 acts as regulator of the skin wound healing process. The present study extended our initial research regarding the expression and potential role of Foxn1 in the intact and wounded skin as a function of animal age and stage of the wound healing process. We analyzed Foxn1 and Mmp-9 expression in the intact and postinjured skin of young, adult, and old C57BL/6J and transgenic Foxn1::Egfp mice. The similar levels of epidermal Foxn1 mRNA expression were detected in young and adult C57BL/6J mice and higher levels in old animals. Postinjured skin tissues displayed a gradual decrease of Foxn1 mRNA expression at Days 1, 5, and 7 after injury. Foxn1-eGFP positive cells were abundant at wound margin and in re-epithelialized epidermis at postwounded Days 1, 5, and 7 and colocalized with E-cadherin and Mmp-9. Postwounded skin at Days 14-36 displayed Foxn1-eGFP cells in the epidermis and in the dermal part of the skin (papillary dermis). Asubset of Foxn1-eGFP positive cells in the papillary dermis expressed the myofibroblast marker αSMA. Flow cytometric analysis of cells isolated from postwounded (Day 7) skin tissues showed a significant increase in the percentage of Foxn1-eGFP positive cells with phenotype of double positivity for E-cadherin/N-cadherin (epithelial/mesenchymal markers). Collectively, these data identify the transcription factor Foxn1 as a potential key epidermal regulator modifying both epidermal and dermal healing processes after cutaneous wounding.

Aging-associated dysregulation of homeostatic immune response termination (and not initiation).

SummaryImmunosenescence is a state of unbalanced immune responsiveness, characterized by a diverse repertoire of seemingly discreet and paradoxical alterations in all aspects of immunity arising in an aging‐associated manner. We asked whether aging‐associated alterations in the ability of apoptotic cells to elicit immunomodulatory responses (innate apoptotic immunity; IAI) or in IAI responses themselves might underlie the confounding aging‐associated anomalies of immunosenescence. We explored this question by examining, as a function of animal age, responsiveness of murine macrophages on the single cell level. We monitored the expression of pro‐ and anti‐inflammatory cytokines cytofluorimetrically in response to pro‐inflammatory Toll‐like receptor (TLR) stimulation and anti‐inflammatory treatment with apoptotic cells. While we found no alterations with age in the potency of apoptotic cells or in the initiation and magnitude of IAI responses, we did identify a cell‐intrinsic deficiency in anti‐inflammatory IAI response termination linked with age and preceding manifestations of immunosenescence. Further, we found that an aging‐associated deficiency in response termination also is evident following TLR stimulation. These surprising observations reveal that a loss of homeostatic immune control with animal age results from the dysregulation of response termination (as distinct from response initiation) and is exerted on the level of transcription. We suggest that, with advancing age, cells become locked into relatively longer‐lived response states. Aging‐associated immune dysfunctions may reflect a diminution in the cellular nimbleness of immune responsiveness.

Quantitative histological image analyses of reticulin fibers in a myelofibrotic mouse.

Bone marrow (BM) reticulin fibrosis (RF), revealed by silver staining of tissue sections, is associated with myeloproliferative neoplasms, while tools for quantitative assessment of reticulin deposition throughout a femur BM are still in need. Here, we present such a method, allowing via analysis of hundreds of composite images to identify a patchy nature of RF throughout the BM during disease progression in a mouse model of myelofibrosis. To this end, initial conversion of silver stained BM color images into binary images identified two limitations: variable color, owing to polychromatic staining of reticulin fibers, and variable background in different sections of the same batch, limiting application of the color deconvolution method, and use of constant threshold, respectively. By blind coding image identities, to allow for threshold input (still within a narrow range), and using shape filtering to further eliminate background we were able to quantitate RF in myelofibrotic Gata-1low (experimental) and wild type (control) mice as a function of animal age. Color images spanning the whole femur BM were batch-analyzed using ImageJ software, aided by our two newly added macros. The results show heterogeneous RF density in different areas of the marrow of Gata-1low mice, with degrees of heterogeneity reduced upon aging. This method can be applied uniformly across laboratories in studies assessing RF remodeling induced by aging or other conditions in animal models.

Dielectric properties of dog brain tissue measured in vitro across the 0.3–3 GHz band

Dielectric properties of dead Greyhound female dogs' brain tissues at different ages were measured at room temperature across the frequency range of 0.3-3 GHz. Measurements were made on excised tissues, in vitro in the laboratory, to carry out dielectric tests on sample tissues. Each dataset for a brain tissue was parametrized using the Cole-Cole expression, and the relevant Cole-Cole parameters for four tissue types are provided. A comparison was made with the database available in literature for other animals and human brain tissue. Results of two types of tissues (white matter and skull) showed systematic variation in dielectric properties as a function of animal age, whereas no significant change related to age was noticed for other tissues. Results provide critical information regarding dielectric properties of animal tissues for a realistic animal head model that can be used to verify the validity and reliability of a microwave head scanner for animals prior to testing on live animals. Bioelectromagnetics. 37:549-556, 2016. © 2016 Wiley Periodicals, Inc.

Radiation exposure prior to traumatic brain injury induces responses that differ as a function of animal age

Purpose: Uncontrolled radiation exposure due to radiological terrorism, industrial accidents or military circumstances is a continuing threat for the civilian population. Age plays a major role in the susceptibility to radiation; younger children are at higher risk of developing cognitive deterioration when compared to adults. Our objective was to determine if an exposure to radiation affected the vulnerability of the juvenile hippocampus to a subsequent moderate traumatic injury.Materials and methods: Three-week-old (juvenile) and eight-week-old young adult C57BL/J6 male mice received whole body cesium-137 (137Cs) irradiation with 4 gray (Gy). One month later, unilateral traumatic brain injury was induced using a controlled cortical impact system. Two months post-irradiation, animals were tested for hippocampus-dependent cognitive performance in the Morris water-maze. After cognitive testing, animals were euthanized and their brains frozen for immunohistochemical assessment of activated microglia and neurogenesis in the hippocampal dentate gyrus.Results: All animals were able to learn the water maze task; however, treatment effects were seen when spatial memory retention was assessed. Animals that received irradiation as juveniles followed by a moderate traumatic brain injury one month later did not show spatial memory retention, i.e., were cognitively impaired. In contrast, all groups of animals that were treated as adults showed spatial memory retention in the probe trials.Conclusion: Although the mechanisms involved are not clear, our results suggest that irradiation enhanced a young animal's vulnerability to develop cognitive injury following a subsequent traumatic injury.

Selective vulnerability of hippocampal sub-fields to oxygen–glucose deprivation is a function of animal age

For more than a century, the hippocampal sub-fields have been recognized as being differentially vulnerable to injury. While the cause remains unknown, the explanations generally considered have involved either vascular differences, or innate variability among cells. To examine the latter possibility, we prepared acute hippocampal slices from Sprague-Dawley rats, applied a brief period of oxygen–glucose deprivation (OGD; an in vitro model of ischemia), and assessed the viability of dissected sub-fields (CA1, CA3, dentate gyrus) by measuring mitochondrial 2,3,5-triphenyltetrazolium chloride (TTC) metabolism. In slices from young animals (15 weeks of age), post-OGD TTC metabolism was significantly reduced in the CA sub-fields relative to the dentate gyrus. Since previous studies found increasing age may worsen ischemic injury, we completed the same experiment using tissue from animals at 52 weeks of age, and found no differences in TTC metabolism across sub-fields. Given the established role of glutamate receptors in ischemic cell death, we examined two key subunit proteins (GluN1, found in all NMDA receptors, and GluA2, found in most AMPA receptors) across sub-fields and age to determine whether their expression complemented our viability data. We found that, relative to the CA1, the DG displayed greater GluN1 expression and lower GluA2 expression in both young and old animals. Our results confirm that regional vulnerability can be shown in a slice model, that the property is not intransigent, and that these features are likely not attributable to the expression pattern of key glutamate receptor subunits, but another molecular variable that changes over the lifespan.

Chronic administration of methylmalonate on young rats alters neuroinflammatory markers and spatial memory

The methylmalonic acidemia is an inborn error of metabolism (IEM) characterized by methylmalonic acid (MMA) accumulation in body fluids and tissues, causing neurological dysfunction, mitochondrial failure and oxidative stress. Although neurological evidence demonstrate that infection and/or inflammation mediators facilitate metabolic crises in patients, the involvement of neuroinflammatory processes in the neuropathology of this organic acidemia is not yet established. In this experimental study, we used newborn Wistar rats to induce a model of chronic acidemia via subcutaneous injections of methylmalonate (MMA, from 5th to 28th day of life, twice a day, ranged from 0.72 to 1.67μmol/g as a function of animal age). In the following days (29th–31st) animal behavior was assessed in the object exploration test and elevated plus maze. It was performed differential cell and the number of neutrophils counting and interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) levels in the blood, as well as levels of IL-1β, TNF-α, inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine (3-NT) in the cerebral cortex were measured. Behavioral tests showed that animals injected chronically with MMA have a reduction in the recognition index (R.I.) when the objects were arranged in a new configuration space, but do not exhibit anxiety-like behaviors. The blood of MMA-treated animals showed a decrease in the number of polymorphonuclear and neutrophils, and an increase in mononuclear and other cell types, as well as an increase of IL-1β and TNF-α levels. Concomitantly, MMA increased levels of IL-1β, TNF-α, and expression of iNOS and 3-NT in the cerebral cortex of rats. The overall results indicate that chronic administration of MMA increased pro-inflammatory markers in the cerebral cortex, reduced immune system defenses in blood, and coincide with the behavioral changes found in young rats. This leads to speculate that, through mechanisms not yet elucidated, the neuroinflammatory processes during critical periods of development may contribute to the progression of cognitive impairment in patients with methylmalonic acidemia.

Moving an incisor across the midline: A treatment alternative in an adolescent patient

A 13-year-old sought treatment for a severely compromised maxillary left central incisor and an impacted fully developed left canine. Extraction of both teeth became necessary. As the key component of the revised comprehensive treatment plan, the right maxillary central incisor was moved into the position of the left central incisor. All other maxillary teeth were moved mesially to close any gaps. Active orthodontic treatment was completed after 34 months. Frenectomy, minor periodontal surgeries, and bonded lingual retainers were used to improve aesthetics and stabilize the tooth positions. The patient was pleased with the treatment outcome. Cone-beam computed tomography provided evidence that the tooth movement was accompanied by a deviation of the most anterior portion of the median palatine suture. This observation may make relapse more likely if long-term retention cannot be ensured. Root resorption was not observed as a consequence of the major tooth movement.

Cortical bone composition and orientation as a function of animal and tissue age in mice by Raman spectroscopy

Important aspects of bone tissue quality include the physicochemical properties of its main constituents, the organic matrix and the mineral crystals. One of the most commonly reported measurements of Raman analysis of bone is the mineral to matrix ratio, obtained from the ratio of the integrated areas of any of the phosphate and amide peaks which depend on both tissue organization and composition. Cube-like samples of normal mouse cortical bone taken from the diaphysis and metaphysis of the femur were investigated within different age groups (2, 4, 8 and 12 weeks) by Raman microspectroscopy. Anatomically identical bone in both longitudinal and transverse directions was analyzed, enabling the discrimination between orientation and composition changes both as a function of animal age, and tissue age within the same animal. The results of the present study indicate that there is a parallel evolution of both orientation and chemical composition as a function of animal age, as well as tissue age within the same specimen. Our tissue age modified ratio of the carbonate to phosphate Raman peaks suggests that the bone mineral crystallite maturity remains relatively constant with animal age. Comparisons of polarized and depolarized experiments in the transversal plane of the diaphysis show a lack of orientation effects as a function of tissue age within the same animal, but exhibit differences as a function of animal age. In the metaphysis, the orientation effect is evident too, albeit less pronounced. This is most likely due to either the age difference between the two tissues within the same specimen in the long bone axis, as metaphyseal bone is generally younger than diaphyseal, or the more random orientation of the tissue collagen itself.

Ontogeny of Skeletal Maturation in the Juvenile Rat

Systemic regulation of the cellular processes that produce endochondral elongation and endochondral mineralization during postnatal skeletal maturation are not completely understood. In particular, a mechanism coupling the decline of cellular activity in the bone microenvironment to the onset of sexual maturity remains elusive. The purpose of this study was to empirically integrate the dynamic progression of bone mineral accrual and endochondral elongation as a function of animal age in growing male and female Sprague-Dawley rats. We used serial dual-energy X-ray absorptiometry (DXA) and radiography to study the temporal progression of bone growth and mineral accrual from weaning to adulthood. We observed that skeletal maturation proceeds in a pattern adequately described by the Gompertz function. During this period of growth, we found that serum markers of osteoblastic bone formation declined with age, while osteoclastic bone resorption activity remained unchanged. We also report a slight lag in the age at inflection in the rate of bone mineral accrual relative to the rate of tibial elongation and that both endochondral processes eventually come to asymptotic equilibrium by approximately 20 weeks of age. In addition, we studied tibial growth plate histomorphometry at select time points through 1 year of age. We report that, despite the histologic persistence of physeal cartilage, very little proliferative or elongative activity was measured in this tissue beyond 20 weeks of age. Taken together, these data provide insight to the temporal coordination of postnatal endochondral growth processes.

Dielectric properties of porcine cerebrospinal tissues at microwave frequencies: in vivo, in vitro and systematic variation with age

The dielectric properties of pig cerebrospinal tissues were measured in vivo and in vitro, in the frequency range of 50 MHz–20 GHz. The total combined measurement uncertainty was calculated at each frequency point and is reported over representative frequency regions. Comparisons were made for each tissue between the two sets of data and with the literature of the past decade. The in vitro study was extended to include tissue from pigs weighing approximately 10, 50 and 250 kg to re-visit the question of the variation of dielectric properties with age. White matter and spinal chord showed significant variation as function of animal age, no age-related variations were recorded for grey matter.

Long-term periarticular bone adaptation in a feline knee injury model for post-traumatic experimental osteoarthritis

This study investigates the long-term changes of the periarticular bone, including cancellous bone and the subchondral plate, in an anterior cruciate ligament (ACL)-transected cat for post-traumatic osteoarthritis (OA). These periarticular bone changes are related to the health of all knee tissues including articular cartilage degeneration and may be a key component of osteoarthritic development. Thirteen cats (mean mass 4.9+/-1.9 kg) were divided into three experimental groups: (1) normal controls, (2) 16 week, and (3) 5 year post unilateral ACL-transection (ACLT). Micro-computed tomography was used to scan the three-dimensional (3D) bone architecture of the proximal tibia, and analysis was performed on the subchondral plate and cancellous bone in the epiphyseal and metaphyseal regions of each bone. A decrease in cancellous bone mass (BV/TV) and subchondral plate thickness (Ct.Th) was observed 16 week post-ACLT, and the trend was statistically significant for the long-term animals (>5 year post-ACLT: BV/TV decreased 16.8%, P<0.003; Ct.Th decreased 36.8%, P<0.03). A decrease in bone mass was also observed as a function of animal age by comparing the young and aged normal control animals, however ACLT intensified those changes, particularly Ct.Th (P<0.009) and anisotropy (P<0.045). It was speculated that decreased internal joint loading despite normal kinematics may play an important role in the long-term reduction of cancellous bone volume and subchondral plate thinning. The periarticular bone changes measured in this study were concurrent with articular cartilage degeneration, and suggest that bone may be a contributing factor in the aetiology of post-traumatic OA development.

Alterations in mineral composition observed in osteoarthritic joints of cynomolgus monkeys

Osteoarthritis (OA) is a prevalent joint disease that affects more than 40 million Americans and is characterized by degeneration of the articular cartilage and thickening of the underlying subchondral bone. Although subchondral bone thickening has been implicated in articular cartilage degeneration, very little is known about the composition of subchondral bone in OA. In the present study, infrared microspectroscopy (IRMS) was used to determine the chemical composition of the calcified cartilage–subchondral bone plate in a monkey model of OA. Specifically, the levels of mineralization (mineral/protein ratio), carbonate accumulation (carbonate/protein ratio), crystallinity, and collagen structure were determined as a function of animal age and OA severity. OA severity was assessed using a grading scheme that included scores or measurements for several histomorphometric parameters including articular cartilage fibrillation or clefting, subchondral bone thickness, and numbers of tidemarks and chondrocyte clones. Individual scores and measurements were summarized using principal components (factor) analysis. Results demonstrated that the level of mineralization and carbonate content increased as a function of animal age. In addition, bone mineralization level increased as subchondral bone thickness increased. Dramatic increases in the mineralization level and carbonate accumulation were also observed as a function of the number of tidemarks. The presence of multiple tidemarks indicates the occurrence of one or more additional phases of cartilage calcification, suggesting that the observed compositional changes are due to cartilage mineralization. Our results support a reactivation of endochondral ossification that occurs with age, which is more pronounced in OA. No relationships were observed between mineral crystallinity and collagen cross-linking as a function of age or OA severity. In summary, compositional analysis of the mineralized plate beneath the articular cartilage in OA is characterized by thickened, overmineralized calcified cartilage or subchondral bone, which likely puts added mechanical stress on the joint, contributing to the progression of OA.

Ascorbic acid prevents water maze behavioral deficits caused by early postnatal methylmalonic acid administration in the rat

Methylmalonic acidemia consists of a group of inherited neurometabolic disorders biochemically characterized by accumulation of methylmalonic acid (MA) and clinically by progressive neurological deterioration whose pathophysiology is not yet fully established. In the present study we investigated the effect of chronic administration (from the 5th to the 28th day of life) of methylmalonic acid (MA) on the performance of adult rats in the Morris water maze task. MA doses ranged from 0.72 to 1.67 μmol/g of body weight as a function of animal age; control rats were treated with the same volume of saline. Chronic postnatal MA treatment had no effect on body weight and in the acquisition of adult rats in the water maze task. However, administration of MA provoked long lasting reversal learning impairment in this task. Motor activity, evaluated by the swim speed in the maze, was not altered by MA administration, indicating no deficit of locomotor activity in rats injected with the metabolite. We also determined the effect of ascorbic acid administered alone or combined with MA on the same behavioral parameters in order to test whether free radicals might be responsible for the behavioral changes observed in MA-treated animals. Ascorbic acid was able to prevent the behavioral alterations provoked by MA. Moreover, the in vitro exposure of hippocampal and striatal preparations to MA revealed that the acid significantly reduced total radical-trapping antioxidant potential (TRAP) and total antioxidant reactivity (TAR) in the striatum, but not in the hippocampus. Furthermore, MA increased the thiobarbituric acid–reactive substances (TBA–RS) measurement in both structures. These data indicate that oxidative stress might be involved in the neuropathology of methylmalonic acidemia and that early MA administration induces long-lasting behavioral deficits, which are possibly caused by oxygen reactive species generation.

A protein free diet uncovers the potential age-difference in the hepatic detoxifying system, glutathione S-transferase, in female mice

Female C57BL mice of six different ages (from 6 to 26 months) were given a protein free-diet (PFD) for 1 week and then given a normal diet (ND). Mice were examined for enzyme activities of glutathione S-transferase (GST) in the hepatic cytosol fraction using l-chloro-2, 4-dinitrobenzene (CDNB) as substrate. Enzyme activities were very close among the six different age groups when examined for basal levels as well as after 1 week of PFD. However, a remarkable age difference became manifest when animals were examined 2 days after the start of ND refeeding following 1 week of PFD. In young animals (6, 8 months), activities became much higher than their respective basal levels while in old animals (24, 26 months) enzyme levels remained significantly lower than their basal levels on day 2 of ND refeeding. A significant negative linear correlation between enzyme activities ( Y axis) and animal age ( X axis) was demonstrated only on day 2 or 3 of ND refeeding, while in control animals or animals given 1 week of PFD diet, no significant correlation could be found between enzyme activities and animal age. We conclude that liver cytosolic GST activity is a function of animal age only after a dietary manipulation such as a PFD and ND refeeding, while basal GST activities remain stable throughout the observation period of animal age.

Ascorbic acid prevents cognitive deficits caused by chronic administration of propionic acid to rats in the water maze

Propionic acidemia is an inherited neurometabolic disorder characterized by progressive neurological deterioration with psychomotor delay/mental retardation, convulsions and coma, and whose pathophysiology is poorly unknown. In the present study, we investigated the effect of chronic administration (from the 5th to the 28th days of life) of propionic acid (PA), the major metabolite accumulating in tissues of patients affected by propionic acidemia, on the cognitive performance of adult rats in the Morris water maze task. PA doses ranged from 1.44 to 1.92 μmol/g body weight as a function of animal age. Control rats were treated with saline in the same volumes. Chronic postnatal days (5–28) PA treatment had no effect on body weight. However, it impaired spatial performance in the water maze. We also determined the effect of ascorbic acid (AA) administered, alone or combined with PA, on the same behavioral parameters in order to test whether free radicals could be responsible for the behavioral alterations observed in PA-treated animals. AA was able to prevent the behavioral alterations provoked by PA, implying that oxidative stress may be involved in these effects. Furthermore, we also investigated the total radical-trapping antioxidant potential (TRAP) in the hippocampus of the animals. We observed that TRAP was significantly reduced in the brain of propionic acidemic rats and that co-administration of AA prevented this effect. The results provide evidence that early PA treatment induces long-lasting behavioral deficits, which are possibly caused by oxygen reactive species generation, and suggest that oxidative stress may be involved in the neuropathology of propionic acidemia.

Age- and genotype-dependence of bone material properties in the osteogenesis imperfecta murine model (oim)

Cortical mineralization of long bones was studied in collagen α2(I)-deficient mice (oim) used as a model for human osteogenesis imperfecta. Aspects of the age development of the mice were characterized by combining nanometer- to micrometer-scale structural analysis with microhardness measurements. Bone structure was determined from homozygous (oim/oim) and heterozygous (oim/+) mice and their normal (+/+) littermates as a function of animal age by small-angle X-ray scattering (SAXS) and quantitative backscattered electron imaging (qBEI) measurements. SAXS studies found anomalies in the size and arrangement of bone mineral crystals in both homozygous and heterozygous mice aged 1–14 months. Generally, the crystals were smaller in thickness and less well aligned in these mice compared with control animals. An increase in the mean crystal thickness of the bone was found within all three genotypes up to an age of 3 months. Vicker’s hardness measurements were significantly enhanced for oim bone (homozygotes and heterozygotes) compared with controls. The microhardness values were correlated directly with increased mineral content of homozygous and heterozygous compared with control bone, as determined by qBEI analysis. There was also a significant increase of mineral content with age. Two possibilities for collagen-mineral association are discussed for explaining the increased hardness and mineral content of oim/oim bone, together with its decreased toughness and thinner mineral crystals. As a consequence of the present measurements, one model for oim bone could incorporate small and densely packed mineral crystals. A second model for possible collagen-mineral association in oim material would consist of two families of mineral crystals, one being smaller and the other being much larger than the crystals found in normal mouse long bones.

Chronic postnatal administration of methylmalonic acid provokes a decrease of myelin content and ganglioside N-acetylneuraminic acid concentration in cerebrum of young rats

Levels of methylmalonic acid (MMA) comparable to those of human methylmalonic acidemia were achieved in blood (2-2.5 mmol/l) and brain (1.35 umol/g) of rats by administering buffered MMA, pH 7.4, subcutaneously twice a day from the 5th to the 28th day of life. MMA doses ranged from 0.76 to 1.67 umol/g as a function of animal age. Control rats were treated with saline in the same volumes. The animals were sacrificed by decapitation on the 28th day of age. Blood was taken and the brain was rapidly removed. Medulla, pons, the olfactory lobes and cerebellum were discarded and the rest of the brain ("cerebrum") was isolated. Body and "cerebrum" weight were measured, as well as the cholesterol and triglyceride concentrations in blood and the content of myelin, total lipids, and the concentrations of the lipid fractions (cholesterol, glycerolipids, phospholipids and ganglioside N-acetylneuraminic acid (ganglioside-NANA)) in the "cerebrum". Chronic MMA administration had no effect on body or "cerebrum" weight, suggesting that the metabolites per se neither affect the appetite of the rats nor cause malnutrition. In contrast, MMA caused a significant reduction of plasma triglycerides, but not of plasma cholesterol levels. A significant diminution of myelin content and of ganglioside-NANA concentration was also observed in the "cerebrum". We propose that the reduction of myelin content and ganglioside-NANA caused by MMA may be related to the delayed myelination/cerebral atrophy and neurological dysfunction found in methylmalonic acidemic children.