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Biomedical subjects

Judd M Aiken

Publications and source records attributed to Judd M Aiken.

17 recordsLinked to original sources
PubMed2006

Mitochondrial DNA-deletion mutations accumulate intracellularly to detrimental levels in aged human skeletal muscle fibers.

Skeletal muscle-mass loss with age has severe health consequences, yet the molecular basis of the loss remains obscure. Although mitochondrial DNA (mtDNA)-deletion mutations have been shown to accumulate with age, for these aberrant genomes to be physiologically relevant, they must accumulate to high levels intracellularly and be present in a significant number of cells. We examined mtDNA-deletion mutations in vastus lateralis (VL) muscle of human subjects aged 49-93 years, using both histologic and polymerase-chain-reaction (PCR) analyses, to determine the physiological and genomic integrity of mitochondria in aging human muscle. The number of VL muscle fibers exhibiting mitochondrial electron-transport-system (ETS) abnormalities increased from an estimated 6% at age 49 years to 31% at age 92 years. We analyzed the mitochondrial genotype of 48 single ETS-abnormal, cytochrome c oxidase-negative/succinate dehydrogenase-hyperreactive (COX-/SDH++) fibers from normal aging human subjects and identified mtDNA-deletion mutations in all abnormal fibers. Deletion mutations were clonal within a fiber and concomitant to the COX-/SDH++ region. Quantitative PCR analysis of wild-type and deletion-containing mtDNA genomes within ETS-abnormal regions of single fibers demonstrated that these deletion mutations accumulate to detrimental levels (>90% of the total mtDNA).

Aged↗
PubMed2006

Prions adhere to soil minerals and remain infectious.

An unidentified environmental reservoir of infectivity contributes to the natural transmission of prion diseases (transmissible spongiform encephalopathies [TSEs]) in sheep, deer, and elk. Prion infectivity may enter soil environments via shedding from diseased animals and decomposition of infected carcasses. Burial of TSE-infected cattle, sheep, and deer as a means of disposal has resulted in unintentional introduction of prions into subsurface environments. We examined the potential for soil to serve as a TSE reservoir by studying the interaction of the disease-associated prion protein (PrP(Sc)) with common soil minerals. In this study, we demonstrated substantial PrP(Sc) adsorption to two clay minerals, quartz, and four whole soil samples. We quantified the PrP(Sc)-binding capacities of each mineral. Furthermore, we observed that PrP(Sc) desorbed from montmorillonite clay was cleaved at an N-terminal site and the interaction between PrP(Sc) and Mte was strong, making desorption of the protein difficult. Despite cleavage and avid binding, PrP(Sc) bound to Mte remained infectious. Results from our study suggest that PrP(Sc) released into soil environments may be preserved in a bioavailable form, perpetuating prion disease epizootics and exposing other species to the infectious agent.

Aluminum Silicates↗
PubMed2006

Prion protein polymorphisms in white-tailed deer influence susceptibility to chronic wasting disease.

The primary sequence of the prion protein affects susceptibility to transmissible spongiform encephalopathies, or prion diseases, in mice, sheep and humans. The Prnp gene sequence of free-ranging, Wisconsin white-tailed deer was determined and the Prnp genotypes of chronic wasting disease (CWD)-positive and CWD-negative deer were compared. Six amino acid changes were identified, two of which were located in pseudogenes. Two alleles, a Q-->K polymorphism at codon 226 and a single octapeptide repeat insertion into the pseudogene, have not been reported previously. The predominant alleles--wild-type (Q95, G96 and Q226) and a G96S polymorphism--comprised almost 98% of the Prnp alleles in the Wisconsin white-tailed deer population. Comparison of the allelic frequencies in the CWD-positive and CWD-negative deer suggested that G96S and a Q95H polymorphism were linked to a reduced susceptibility to CWD. The G96S allele did not, however, provide complete resistance, as a CWD-positive G96S/G96S deer was identified. The G96S allele was also linked to slower progression of the disease in CWD-positive deer based on the deposition of PrP(CWD) in the obex region of the medulla oblongata. Although the reduced susceptibility of deer with at least one copy of the Q95H or G96S allele is insufficient to serve as a genetic barrier, the presence of these alleles may modulate the impact of CWD on white-tailed deer populations.

Alleles↗
PubMed2005

Age-related changes in cardiac structure and function in Fischer 344 x Brown Norway hybrid rats.

The effects of aging on cardiovascular function and cardiac structure were determined in a rat model recommended for gerontological studies. A cross-sectional analysis assessed cardiac changes in male Fischer 344 x Brown Norway F1 hybrid rats (FBN) from adulthood to the very aged (n = 6 per 12-, 18-, 21-, 24-, 27-, 30-, 33-, 36-, and 39-mo-old group). Rats underwent echocardiographic and hemodynamic analyses to determine standard values for left ventricular (LV) mass, LV wall thickness, LV chamber diameter, heart rate, LV fractional shortening, mitral inflow velocity, LV relaxation time, and aortic/LV pressures. Histological analyses were used to assess LV fibrotic infiltration and cardiomyocyte volume density over time. Aged rats had an increased LV mass-to-body weight ratio and deteriorated systolic function. LV systolic pressure declined with age. Histological analysis demonstrated a gradual increase in fibrosis and a decrease in cardiomyocyte volume density with age. We conclude that, although significant physiological and morphological changes occurred in heart function and structure between 12 and 39 mo of age, these changes did not likely contribute to mortality. We report reference values for cardiac function and structure in adult FBN male rats through very old age at 3-mo intervals.

Aging↗
PubMed2005

MtDNA point mutations are associated with deletion mutations in aged rat.

The age-dependent accumulation of point mutations in the control region of human mtDNA has been suggested to contribute to aging processes. We investigated whether mtDNA point mutations accumulate to detectable levels in this region of mtDNA from aged Fischer 344 X Brown Norway F(1) hybrid rats. The control region and a portion of the major arc region (nucleotides 4386-7707) of the mtDNA were PCR-amplified and directly sequenced from microdissected single cardiomyocytes and single skeletal muscle fibers of 36-month old rats. Point mutations were not observed in these regions of the full-length mtDNA. Point mutations were, however, associated with deletion mutations, especially in cardiac cells. Approximately 40% of the deletion mutations identified in heart contained a point mutation, whereas only 1.9% of deletion mutations in skeletal muscle contained a point mutation. Point mutations were located adjacent to the deletion breakpoints and each point mutation was unique. In aged rats, point mutations are clonally expanded only when associated with deletion events suggesting that there are important differences between rats and humans in the mechanisms that cause mtDNA abnormalities.

Aging↗
PubMed2005

Muscle mass loss in Rhesus monkeys: age of onset.

Sarcopenia, the decline in skeletal muscle mass and function with age, contributes to increased frailty and decreased functional performance in the aging human population. The negative health consequences of muscle mass loss emphasize the need for development of a nonhuman primate model for the prevention or attenuation of sarcopenia. The age of onset for muscle mass loss in Rhesus macaques was determined using three datasets; (i) dual-energy X-ray absorptiometry (DXA) data from a cross-sectional study of 90 adult Rhesus monkeys; (ii) lean tissue mass and estimated skeletal muscle mass (ESM) from 727 DXA scans taken in 38 monkeys in a long-term, longitudinal aging study; and, (iii) quadriceps weights taken at necropsy from 13 male and 28 female Rhesus monkeys. These data indicate that both male and female Rhesus monkeys develop sarcopenia with age. The onset of sarcopenia is 14.1 +/- 2.8 years in females and 15.8 +/- 2.5 years in males. Muscle loss reaches 20% in males by 23.2 years of age and in females by 24.5 years of age. Furthermore, our data indicate percentage declines in ESM similar to those seen in humans with advancing age. These data support the suitability of the Rhesus monkey as a primate sarcopenia model.

Absorptiometry, Photon↗
PubMed2004

Labeling of the scrapie-associated prion protein in vitro and in vivo.

Prion diseases are a group of infectious neurodegenerative diseases that affect both animals and humans. A characteristic of prion diseases is the aggregation and accumulation of a disease-associated isoform of the prion protein in the brains of infected individuals. The amyloid imaging probe (trans,trans)-1-bromo-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (BSB) has shown potential in the diagnosis of other amyloid disorders and we hypothesized that this compound would be effective in labeling prion protein plaques in vitro and in vivo. To test this, we compared BSB fluorescence to prion protein immunostaining on infected and uninfected brain tissue sections from scrapie-infected hamsters. We found that both methods labeled the same plaques in infected tissues while not substantially staining uninfected tissues. To test the potential of BSB as an in vivo label for prion aggregates, we perfused scrapie-infected animals with BSB and observed BSB labeled plaques co-stained with an anti-prion protein antibody. These results suggest that BSB may have use as a diagnostic tool for prion diseases. We were unable to detect BSB staining in preclinical scrapie-infected hamsters suggesting that the diagnostic potential of BSB could be limited in cases of prion disease that do not have plaques either due to a preclinical lack of pathology or disease agents like sporadic Creutzfeldt-Jakob disease (CJD), which generally lack prion plaques. However, BSB may be a useful for prion diseases where plaques are present, such as clinical variant CJD.

Animals↗
PubMed2004

Calorie restriction limits the generation but not the progression of mitochondrial abnormalities in aging skeletal muscle.

The effect of early-onset calorie restriction and aging on the accumulation of electron transport system (ETS) abnormalities was studied in rat skeletal muscle. Rectus femoris and vastus lateralis muscle fibers were analyzed for cytochrome c oxidase (COX) and succinate dehydrogenase (SDH) enzyme activities. Fibers displaying COX negative and SDH hyper reactive (COX-/SDH++) phenotype were followed through 1000-2000 micrometers to determine the frequency and length of these abnormalities as well as the physiological impact on fiber structure. Calorie restricted rats had fewer ETS abnormal muscle fibers. The mean length of ETS abnormal regions in ad libitum rat muscle fibers was similar to calorie restricted rat muscles. ETS abnormal fibers from both diet groups exhibited intra-fiber atrophy. A negative correlation between ETS abnormality length and fiber cross-sectional area (CSA) ratio was observed in both ad libitum and calorie- restricted rats. Although calorie restriction reduced the number of ETS abnormalities, it did not affect the length or associated fiber atrophy of ETS abnormal regions once the abnormality was established. Thus, calorie restriction affects the onset but not the progression of electron transport system abnormalities, thereby, limiting a process that ultimately results in fiber breakage and fiber loss.

Aging↗
PubMed2004

Delay in onset of prion disease for the HY strain of transmissible mink encephalopathy as a result of prior peripheral inoculation with the replication-deficient DY strain.

We report that the replication-deficient DY strain of transmissible mink encephalopathy (TME) can delay disease caused by the pathogenic HY TME strain. In this study, competition between the HY and DY TME agents was investigated following superinfection of the sciatic nerve and peritoneal cavity. Initially, DY TME infection was examined in the absence of superinfection and it was found that inoculation into the brain and sciatic nerve resulted in prion disease and PrP(Sc) deposition in brain but not lymphoreticular tissues. Conversely, intraperitoneal inoculation of the DY TME agent did not result in clinical symptoms, DY TME agent replication or PrP(Sc) deposition 400-600 days after infection. These findings indicate that the DY TME agent does not replicate in secondary lymphoid organs and is non-pathogenic when neuroinvasion is dependent on prior infection of the lymphoreticular system. However, intraperitoneal inoculation of the DY TME agent at 60 days, but not at 30 days, prior to intraperitoneal inoculation of the HY TME agent resulted in an extension of the HY TME incubation period. Inoculation of the DY TME agent into the sciatic nerve at 60 days prior to intrasciatic nerve inoculation of the HY TME agent did not delay the incubation period of HY TME. The ability of the DY TME agent to delay HY TME infection following extraneural inoculation, but not neural infection, suggests that HY and DY TME agent competition can occur in a common replication site whose cellular location precedes infection of both the lymphoreticular and peripheral nervous systems.

Animals↗
PubMed2004

Molecular analyses of mtDNA deletion mutations in microdissected skeletal muscle fibers from aged rhesus monkeys.

Mitochondrial DNA (mtDNA) deletion mutations co-localize with electron transport system (ETS) abnormalities in rhesus monkey skeletal muscle fibers. Using laser capture microdissection in conjunction with PCR and DNA sequence analysis, mitochondrial genomes from single sections of ETS abnormal fibers were characterized. All ETS abnormal fibers contained mtDNA deletion mutations. Deletions were large, removing 20-78% of the genome, with some to nearly all of the functional genes lost. In one-third of the deleted genomes, the light strand origin was deleted, whereas the heavy strand origin of replication was conserved in all fibers. A majority (27/39) of the deletion mutations had direct repeat sequences at their breakpoints and most (36/39) had one breakpoint within or in close proximity to the cytochrome b gene. Several pieces of evidence support the clonality of the mtDNA deletion mutation within an ETS abnormal region of a fiber: (a) only single, smaller than wild-type, PCR products were obtained from each ETS abnormal region; (b) the amplification of mtDNA from two regions of the same ETS abnormal fiber identified identical deletion mutations, and (c) a polymorphism was observed at nucleotide position 16103 (A and G) in the wild-type mtDNA of one animal (sequence analysis of an ETS abnormal region revealed that mtDNA deletion mutations contained only A or G at this position). Species-specific differences in the regions of the genomes lost as well as the presence of direct repeat sequences at the breakpoints suggest mechanistic differences in deletion mutation formation between rodents and primates.

Aged↗
PubMed2004

Low levels of mtDNA deletion mutations in ETS normal fibers from aged rats.

The objectives were (1) to determine whether deletion mutations occur in phenotypically normal type I and type II fibers, (2) to quantify the levels of both deletion mutant and wild-type (wt) mtDNA (nondeletion) within single normal fibers containing mutant mtDNA, and (3) to quantify the amount of wt mtDNA in genotypically and phenotypically normal type I and type II fibers. Deletion mutations in normal fibers are not restricted to specific fiber types, although clonal accumulation of mtDNA deletion mutations and subsequent ETS abnormalities occur exclusively in type II fibers.

Aging↗
PubMed2003

Identification of a putative calcium-binding protein as a dioxin-responsive gene in zebrafish and rainbow trout.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a widespread environmental contaminant that causes multiple effects in vertebrates. TCDD elicits its toxicity through aryl hydrocarbon receptor (AhR)-mediated modulation of gene regulation, increasing intracellular free calcium, and inducing calcium-mediated apoptosis in cell culture. Two TCDD-responsive cDNAs, which encode putative calcium-binding proteins, have been isolated from zebrafish and rainbow trout. The zebrafish and rainbow trout sequences are 88% similar to each other at the amino acid level and are orthologs of the human S100A4 calcium-binding protein. In zebrafish liver cell culture, treatment with TCDD increases S100A4a mRNA abundance. In juvenile rainbow trout, S100A4 mRNA was constitutively expressed in the heart, kidney, intestine, and spleen, but not in the liver. Exposure to TCDD significantly increased rainbow trout S100A4 mRNA abundance in the rainbow trout kidney. Taken together, these findings demonstrate in zebrafish and rainbow trout that dioxin increases expression of this EF-hand calcium-binding protein gene in a tissue-dependent fashion. However, demonstration that the encoded S100A4 proteins actually bind calcium and play a role in dioxin toxicity will require further study.

Amino Acid Sequence↗
PubMed2003

Mitochondrial DNA mutations as a fundamental mechanism in physiological declines associated with aging.

The hypothesis that mitochondrial DNA damage accumulates and contributes to aging was proposed decades ago. Only recently have technological advancements, which facilitate microanalysis of single cells or portions of cells, revealed that mtDNA deletion mutations and, perhaps, single nucleotide mutations accumulate to physiologically relevant levels in the tissues of various species with age. Although a link between single nucleotide mutations and physiological consequences in aging tissue has not been established, the accumulation of deletion mutations in skeletal muscle fibres has been associated with sarcopenia. Different, and apparently random, deletion mutations are specific to individual fibres. However, the mtDNA deletion mutation within a phenotypically abnormal region of a fibre is the same, suggesting a selection, amplification and clonal expansion of the initial deletion mutation. mtDNA deletion mutations within a muscle fibre are associated with specific electron transport system abnormalities, muscle fibre atrophy and fibre breakage. These data point to a causal relationship between mitochondrial DNA mutations and the age-related loss of muscle mass.

Aging↗
PubMed2002

Age-associated changes in function, structure and mitochondrial genetic and enzymatic abnormalities in the Fischer 344 x Brown Norway F(1) hybrid rat heart.

We hypothesized that cardiac aging in the rat involves mitochondrial genetic damage and mitochondrial enzymatic dysfunction of individual cardiomyocytes as has been demonstrated previously only in primate myocardium. Myocardium from Fischer 344 x Brown Norway F(1)hybrid rats of ages 5, 18 and 36-38 months was examined for mitochondrial genetic and enzymatic abnormalities. In-vivo hemodynamic measurements revealed age-related changes of left ventricular function while histological evaluation demonstrated an increase in percent area fibrosis from 7%+/-5 in the 5-month-old hearts to 38%+/-2 in the subendocardium of the left ventricle of 38-month-old rats. Mitochondrial genomes lacking 8000 to 9000 bp of primary sequence were detected in tissue homogenates from right and left ventricular myocardium and the abundance of these deleted genomes increased with age. In-situ histochemical staining of serial cryomicrotome sections of myocardial tissue revealed individual cardiomyocytes displaying abnormal, primarily absent, activities of cytochrome c oxidase and succinate dehydrogenase. The area density of histochemically-abnormal cardiomyocytes increased from 0.05 per mm(2)to 0.3 per mm(2)between 5 and 36-38 months of age in the left ventricle, and they were localized primarily to the left ventricular subendocardium. The presence of age-related mitochondrial genetic and enzymatic abnormalities in the Fischer 344 x Brown Norway F(1)hybrid rat heart suggests the role of mitochondrial dysfunction, secondary to mtDNA mutations, in age-related cardiomyocyte loss and subsequent cardiac aging.

Age Factors↗
PubMed2002

Mitochondrial DNA deletion mutations: a causal role in sarcopenia.

Mitochondrial DNA (mtDNA) deletion mutations accumulate with age in tissues of a variety of species. Although the relatively low calculated abundance of these deletion mutations in whole tissue homogenates led some investigators to suggest that these mutations do not have any physiological impact, their focal and segmental accumulation suggests that they can, and do, accumulate to levels sufficient to affect the metabolism of a tissue. This phenomenon is most clearly demonstrated in skeletal muscle, where the accumulation of mtDNA deletion mutations remove critical subunits that encode for the electron transport system (ETS). In this review, we detail and provide evidence for a molecular basis of muscle fiber loss with age. Our data suggest that the mtDNA deletion mutations, which are generated in tissues with age, cause muscle fiber loss. Within a fiber, the process begins with a mtDNA replication error, an error that results in a loss of 25-80% of the mitochondrial genome. This smaller genome is replicated and, through a process not well understood, eventually comprises the majority of mtDNA within the small affected region of the muscle fiber. The preponderance of the smaller genomes results in a dysfunctional ETS in the affected area. As a consequence of both the decline in energy production and the increase in oxidative damage in the region, the fiber is no longer capable of self-maintenance, resulting in the observed intrafiber atrophy and fiber breakage. We are therefore proposing that a process contained within a very small region of a muscle fiber can result in breakage and loss of muscle fiber from the tissue.

Aging↗
PubMed2002

Mitochondrial abnormalities are more frequent in muscles undergoing sarcopenia.

The hypothesis that the accumulation of electron transport system (ETS) abnormalities and sarcopenia are linked was investigated. Vastus lateralis, soleus, and adductor longus muscles were studied in 5-, 18-, and 36-mo-old male Fischer 344 x Brown Norway F(1) hybrid rats. A significant decrease in soleus and vastus lateralis muscle mass was observed with age. Adductor longus was resistant to muscle mass loss. Multiple serial sections were analyzed for the activities of cytochrome-c oxidase (COX) and succinate dehydrogenase (SDH). The number of fibers exhibiting a COX(-)/SDH(++) phenotype increased with age in both vastus lateralis and soleus muscles. No ETS-abnormal fibers were identified in adductor longus at any age. Cross-sectional area of ETS-abnormal fibers decreased in the abnormal region (region displaying COX(-)/SDH(++) phenotype), whereas control fibers did not. The vastus lateralis muscle, which undergoes a high degree of sarcopenia, exhibited more ETS abnormalities and associated fiber loss than the soleus and adductor longus muscles, which are more resistant to sarcopenia, suggesting a direct association between ETS abnormalities and fiber loss.

Anatomy, Cross-Sectional↗