Somatic mitochondrial DNA mutations in cortex and substantia nigra in aging and Parkinson's disease

Oxidative damage to mitochondrial DNA (mtDNA) increases with age in the brain and can induce G:C to T:A and T:A to G:C point mutations. Though rare at any particular site, multiple somatic mtDNA mutations induced by oxidative damage or by other mechanisms may accumulate with age in the brain and thus could play a role in aging and neurodegenerative diseases. However, no prior study has quantified the total burden of mtDNA point mutation subtypes in the brain. Using a highly sensitive cloning and sequencing strategy, we find that the aggregate levels of G:C to T:A and T:A to G:C transversions and of all point mutations increase with age in the frontal cortex (FCtx). In the substantia nigra (SN), the aggregate levels of point mutations in young controls are similar to the levels in the SN or FCtx of elderly subjects. Extrapolation from our data suggests an average of 2.7 (FCtx) to 3.2 (SN) somatic point mutations per mitochondrial genome in elderly subjects. There were no significant differences between Parkinson's disease (PD) patients and age-matched controls in somatic mutation levels. These results indicate that individually rare mtDNA point mutations reach a high aggregate burden in FCtx and SN of elderly subjects.     

Molecular epidemiology of Pseudomonas aeruginosa colonization in a burn unit: persistence of a multidrug-resistant clone and a silver sulfadiazine-resistant clone

To study the epidemiology of Pseudomonas aeruginosa colonization in a 32-bed burn wound center (BWC), 321 clinical and 45 environmental P. aeruginosa isolates were collected by prospective surveillance culture over a 1-year period and analyzed by serotyping, drug susceptibility testing, and amplified fragment length polymorphism (AFLP) analysis. Among 441 patients treated at the center, 70 (16%) were colonized with P. aeruginosa, including 12 (17%) patients who were colonized on admission and 58 (83%) patients who acquired the organism during their stay. Of the 48 distinct AFLP genotypes found, 21 were found exclusively in the environment, 15 were isolated from individual patients only, and 12 were responsible for the colonization of 57 patients, of which 2 were also isolated from the environment, but secondary to patient carriage. Polyclonal P. aeruginosa colonization with strains of two to four genotypes, often with different antibiotic susceptibility patterns, was observed in 19 patients (27%). Two predominant genotypes were responsible for recurrent outbreaks and the colonization of 42 patients (60% of all colonized patients). The strain with one of those genotypes appeared to be endemic to the BWC and developed multidrug resistance (MDR) at the end of the study period, whereas the strain with the other genotype was antibiotic susceptible but resistant to silver sulfadiazine (SSD(r)). The MDR strain was found at a higher frequency in sputum samples than the SSD(r) strain, which showed a higher prevalence in burn wound samples, suggesting that anatomic habitat selection was associated with adaptive resistance to antimicrobial drugs. Repeated and thorough surveys of the hospital environment failed to detect a primary reservoir for any of those genotypes. Cross-acquisition, resulting from insufficient compliance with infection control measures, was the major route of colonization in our BWC. In addition to the AFLP pattern and serotype, analysis of the nucleotide sequences of three (lipo)protein genes (oprI, oprL, and oprD) and the pyoverdine type revealed that all predominant strains except the SSD(r) strain belonged to recently identified clonal complexes. These successful clones are widespread in nature and therefore predominate in the patient population, in whom variants accumulate drug resistance mechanisms that allow their transmission and persistence in the BWC.     

Differential activation of human and guinea pig complement by pentameric and hexameric IgM

Human and mouse IgM can be polymerized as a hexamer in addition to a pentamer. Our previous work with mouse IgM measured activation of guinea pig complement by highly enriched preparations of hexamer and pentamer and showed that hexamer is >100-fold more active than pentamer. In this report pentamer and hexamer were compared for their capacity to activate complement in a homogeneic system, i.e. chimeric mouse V/human Cmu IgM pentamer and hexamer were assayed separately for their capacity to activate human (and guinea pig) complement. In both the homogeneic and the xenogeneic systems hexamer was more active than pentamer, but the magnitude of the difference between hexamer and pentamer depended on the complement source. Whereas chimeric hexamer activated guinea pig complement >100-fold more efficiently than did chimeric pentamer, this hexamer was only 4-13-fold more active than pentamer when assayed with human complement. Similarly, mouse hexamer, which was >100-fold more active than mouse pentamer with guinea pig complement, was only approximately 2-fold more active than mouse pentamer with human complement. Mouse hexameric and pentameric IgM were each approximately 20-fold more active with human complement than were the corresponding chimeric isoforms of IgM.     

The relative contribution of direct and indirect antigen recognition pathways to the alloresponse and graft rejection depends upon the nature of the transplant

In this study, we measured direct and indirect T-cell alloresponses mediated by CD4(+) and CD8(+) T cells in three mouse transplantation models: skin, cornea, and retina. We show that the contribution of direct and indirect antigen recognition pathways to the alloresponse to fully allogeneic grafts varies depending upon the nature of the tissue/organ transplanted. The implications of this finding for understanding the cellular mechanisms by which rejection is mediated in different transplant models are discussed.     

Identical abnormality of the short arm of chromosome 18 in two Philadelphia-positive chronic myelocytic leukemia patients with erythroblastic transformation,resulting in duplication of BCR-ABL1 fusion

Two patients with Ph-positive chronic myelocytic leukemia in erythroblastic transformation and rearrangement of the short arm of chromosome 18 are reported. Fluorescence in situ hybridization studies showed that the 18p rearrangement resulted from translocation of the main part of chromosome 22 long arm to 18p, including BCR-ABL1 fusion. The 18p abnormality resulted, thus, in loss of 18p and duplication of BCR-ABL1 in both patients. The possible relation to the erythroblastic type of blastic phase is briefly discussed. In addition an apparently intact germline ABL1 gene was duplicated and inserted into chromosome 6 at band p21 in one of these patients.     

Training to yoga respiration selectively increases respiratory sensation in healthy man

Because yoga practitioners think they are benefiting from their breath training we hypothesized that yoga respiration training (YRT) could modify the respiratory sensation. Yoga respiration (YR) ("ujjai") consisted of very slow, deep breaths (2-3 min(-1)) with sustained breath-hold after each inspiration and expiration. At inclusion in the study and after a 2-month YRT program, we determined in healthy subjects their eupneic ventilatory pattern and their capacity to discriminate external inspiratory resistive loads (respiratory sensation), digital tactile mechanical pressures (somesthetic sensation) and sound-pressure stimulations (auditory sensation). Data were compared to a gender-, age-, and weight-matched control group of healthy subjects who did not undergo the YRT program but were explored at the same epochs. After the 2-month YRT program, the respiratory sensation increased. Thus, both the exponent of the Steven's power law (Psi=kPhin) and the slope of the linear-linear plot between Psi and mouth pressure (Pm) were significantly higher, and the intercept with ordinate axis of the Psi versus Pm relationship was lower. After YRT, the peak Pm developed against inspiratory loads was significantly lower, reducing the load-induced activation of respiratory afferents. YRT induced long-lasting modifications of the ventilatory pattern with a significant lengthening of expiratory duration and a modest tidal volume increase. No significant changes in somesthetic and auditory sensations were noted. In the control group, the respiratory sensation was not modified during a 15-min period of yoga respiration, despite the peak Pm changes in response to added loads were then significantly reduced. These data suggest that training to yoga respiration selectively increases the respiratory sensation, perhaps through its persistent conditioning of the breathing pattern.     

Electron microscopic analysis of two-dimensional crystals of the Ca2+-transport ATPase — a freeze-fracture study

Summary Two distinct forms of Ca²⁺-ATPase crystals have been analysed in sarcoplasmic reticulum (SR) membranes. The E₁-type crystals, induced by Ca²⁺ or lanthanide ions, consist of single chains of ATPase monomers, and the E₂-type crystals, induced by vanadate ions, consist of dimer chains. Using improved freeze-fracture techniques we have obtained high-resolution images of complementary surface replicas of SR membranes containing these crystal forms. In E₁ crystals, the concave fracture (P) faces display obliquely oriented rows of intramembrane particles (IMPs) spaced at - 6–7 nm along both crystal axes, while the convex fracture (E) faces show corresponding rows of pits. In E₂ crystals, regular arrays of oblique parallel ridges with spacing of - 10.5–11 nm appear on the P-faces and complementary grooves or furrows on the E-faces. In many instances the ridges break up into elongated particles repeating every 5.5 nm. When the direction of the shadow is almost parallel to the axis of the ridges, these 9.5 nm particles can be resolved into two domains, which represent intramembranous contacts between the two monomers of the two adjacent dimer chains. Complementary grooves on the E-faces can also be resolved into rows of pits complementary to the particles of the ridges on the P-faces. In the control SR membranes, randomly dispersed IMPs and corresponding pits are observed on the P- and E-faces, respectively. The data suggest that transport of Ca²⁺ involves significant structural changes of the enzyme molecule, reflected in the ATPase-ATPase interactions both on the cytoplasmic surface and in the lipid bilayer.     

Recurring bone epithelioid hemangioma

Bone vascular tumors are very rare. Epithelioid types are described according to their architecture, their degree of vascular differentiation, and their cytonuclear atypia. The include epithelioid hemangioma, epithelioid hemangioendothelioma, and angiosarcoma. We report a case of L4 corpus vertebral bone epithelioid hemangioma. The patient was a 25-year-old man with a tumor that recurred twice. The lesion was characterized by a vascular lumen lined by cells with regular nuclei and inflammatory infiltrates. Capillaries were lined by prominent epithelioid endothelial cells, associated with CD31+ and cytokeratin-.