Involvement of a large inverted repeated sequence

Summary Southern hybridization of the total DNA of Agrocybe aegerita with cloned mitochondrial (mt) probes revealed a sequence homology between two distant mitochondrial restriction fragments. From the mtDNA restriction map and the distribution of restriction sites on the cross-hybridizing mitochondrial fragments, two copies of a large inverted repeated sequence (IR) of 3 kbp were located on the mitochondrial genome. These IR sequences divided the 80 kbp mtDNA into two singlecopy regions of 24 kbp (SSC) and 50 kbp (LSC). For the first time in higher fungi, this IR sequence has been shown to be involved in an intramolecular homologous recombinational event. Such a rearrangement led to an inversion of the orientation of the two unique-copy regions, without any change in mtDNA complexity. The location of the recombinational event was compared with previously reported plant and fungal mitochondrial rearrangements and the potential role of the IR sequence was discussed.     

The heat stable antigen (CD24) is not required for the generation of CD4+ effector and memory T cells by dendritic cells in vivo

Previous work has established that CD24 is a costimulatory molecule for T-cell clonal expansion. Studies using CD24 -/- mice demonstrated that CD24 plays a critical role in the CD28-independent immune response against virus and soluble antigens. The role of CD24 on dendritic cells (DCs) has not been reported. Here, we compare the CD24(+/+) and CD24(-/-) DCs in the induction of initial clonal expansion and elicitation of memory CD4(+) T cells in vivo. Our results demonstrate that the CD24 expressed on DCs is essential neither for the induction of initial T-cell clonal expansion nor for elicitation of memory activity of primed T cells in vivo.     

Design, testing, and clinical studies of a handheld polarized light camera

Polarized light imaging has been used to detect the borders of skin cancer and facilitate assessment of cancer boundaries. A design for an inexpensive handheld polarized camera is presented and clinical images acquired with this prototype are shown. The camera is built with two universal serial bus (USB) color video cameras, a polarizing beamsplitter cube, and a 4x objective lens. Illumination is provided by three white LEDs and a sheet polarizer. Horizontal and vertical linearly polarized reflected images are processed at 7 frames/s and a resulting polarized image is displayed on screen. We compare the performances of cheap USB camera and a 16-bit electronically cooled camera. Dark noise and image repeatability are compared. In both cases, the 16-bit camera outperforms the USB cameras. Despite these limitations, the results obtained with this USB prototype are very satisfactory. Examples of polarized images of lesions taken prior to surgery are presented.     

Behavioral and neurochemical effects induced by subchronic combined exposure to toluene at 40 ppm and noise at 80 dB-A in rats

We investigated whether exposure to noise, in addition to its well-known potentiating effect on toluene-induced ototoxicity, may also exacerbate behavioral disturbances and brain neurochemical alterations produced by subchronic exposure to low toluene concentration. To test this hypothesis, we evaluated whether subchronic combined exposure (16 weeks, 104 h per week) to noise at 80 dB-A and toluene at 40 ppm potentiates the recently reported neurotoxic effects of subchronic exposure to 40 ppm toluene. Locomotor and rearing activities, sensitization to narcosis induced by acute toluene at high concentration, and tyrosine and tryptophan hydroxylase activities in the caudate-putamen and hippocampus were investigated in both male and female rats. Our results confirm that subchronic exposure to 40 ppm toluene significantly decreases rearing activity and leads to a sensitization to toluene-induced narcosis, as evaluated by loss of righting reflex, but fails to demonstrate any adverse effect of noise, alone or in combination with toluene. Given that toluene has addictive properties, the lack of potentiating behavioral and neurochemical effect of noise is discussed with regards to a recent study that has shown that methamphetamine neurotoxicity is potentiated by exposure to loud noise.     

Hypoxia promotes murine bone-marrow-derived stromal cell migration and tube formation

Recent evidence indicates that bone-marrow-derived stromal cells (MSCs) have a histology coherent with endothelial cells that may enable them to contribute to tumor angiogenesis through yet undefined mechanisms. In this work, we investigated the angiogenic properties of murine MSCs involved in extracellular matrix degradation and in neovascularization that could take place in a hypoxic environment such as that encountered in tumor masses. MSCs were cultured in normoxia (95% air and 5% CO(2)) or in hypoxia (1% oxygen, 5% CO(2), and 94% nitrogen). We found that hypoxic culture conditions rapidly induced MSC migration and three-dimensional capillary-like structure formation on Matrigel. In vitro, MSC migration was induced by growth-factor- and cytokine-enriched conditioned media isolated from U-87 glioma cells as well as from MSCs cultured in hypoxic conditions, suggesting both paracrine and autocrine regulatory mechanisms. Although greater vascular endothelial growth factor levels were secreted by MSCs in hypoxic conditions, this growth factor alone could not explain their greater migration. Interestingly, matrix metalloproteinase (MMP)-2 mRNA expression and protein secretion were downregulated, while those of membrane-type (MT)1-MMP were strongly induced by hypoxia. Functional inhibition of MT1-MMP by a blocking antibody strongly suppressed MSC ability to migrate and generate capillary-like structures. Collectively, these data suggest that MSCs may have the capacity to participate in tumor angiogenesis through regulation of their angiogenic properties under an atmosphere of low oxygen that closely approximates the tumor microenvironment.     

Role of lipopolysaccharides in adherence of Actinobacillus pleuropneumoniae to porcine tracheal rings.

The ability of 17 Actinobacillus pleuropneumoniae isolates, representing serotypes 1, 2, 5, and 7, to adhere to tracheal rings maintained in culture was examined. Porcine tracheal rings were infected, and 8 h after inoculation, adherent bacterial cells were evaluated. A. pleuropneumoniae adhered to tracheal rings, and marked variations were observed between and even within serotypes, suggesting that adherence of this microorganism is not primarily related to the serotype of the isolate. No relationship was found between adherence to porcine tracheal rings and plasmid profiles, virulence in mice, hemagglutination, capsular material thickness, or whole-cell protein profiles. On the other hand, we observed that all isolates of serotypes 1 and 5 had a semirough-type lipopolysaccharide (LPS), whereas isolates of serotypes 2 and 7 had a smooth-type LPS (75%) or a semirough-type LPS (25%). Results showed that 83% of isolates with a smooth-type LPS adhered in large numbers to tracheal rings, whereas 80% of isolates with a semirough-type LPS adhered poorly (P less than 0.007). Our data indicated that the degree of adherence of A. pleuropneumoniae to porcine tracheal rings appeared to be related, at least in part, to LPS profiles. Furthermore, LPS seemed to be the adhesin of A. pleuropneumoniae, since purified LPS blocked adherence of this microorganism to porcine tracheal rings.     

Follow-up of soluble interleukin-2 receptor levels after thymectomy in patients with myasthenia gravis.

Soluble interleukin-2 receptor (sIL-2R) levels were followed up after thymectomy by a quantitative immunoradiometric assay in 59 patients with myasthenia gravis (MG). Increased levels of sIL-2R were found in 30.5% of the patients before thymectomy. Serum levels were significantly higher in severely affected patients. Sequential sampling after thymectomy indicated a significant and progressive decline of sIL-2R levels within 2 years after surgery, which was well associated with clinical improvement or remission. The sIL-2R purified from sera of patients with MG had a molecular mass of 45 kDa as the normal sIL-2R. The decline after thymectomy of sIL-2R titers suggests a possible role of the thymus in the occurrence of sIL-2R in the periphery. Soluble IL-2R levels may represent a marker of disease severity in MG, which might be useful in the follow-up of individual patients.     

T-cell tolerance and autoimmunity in transgenic models of central and peripheral tolerance

Experiments with transgenic mice expressing genes encoding both antigens in defined tissues and T-cell receptor genes of known specificities have enhanced our understanding of the mechanisms involved in the pathogenesis of autoimmune states. They have also shed light on the means by which potentially autoreactive cells may be prevented from exerting their autoaggressive potential. The value of the transgenic approach is that it can overcome the low frequency of peptide-specific T cells occurring in normal animals, and also provide a tissue-specific, cognate antigen that is absent in controls. These factors allow reactive T cells to be isolated or quantified by flow cytometry and their responses to antigen in vitro and in vivo be defined.