Evidence for involvement of a tumor suppressor gene on 1p in malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNST) are rare soft-tissue malignancies. The genetic basis of these tumors is still poorly understood. Cytogenetic analyses predominantly revealed complex karyotypes, precluding the identification of recurrent chromosomal changes. We report loss of 1p material in a near-diploid karyotype with few or no additional structural chromosome changes in two sporadic cases of MPNST, indicating an important role of 1p loss in MPNST development. In one of these two tumors, a distal 1p deletion (1p31.2 approximately pter) was detected suggesting involvement of a tumor suppressor gene located within this distal region of 1p. Further evidence for recurrent 1p loss in MPNST was obtained by interphase fluorescence in situ hybridization, which showed loss of 1p material in 3 out of 13 tumors. These findings together with data from the literature suggest that loss of a tumor suppressor gene located within distal 1p is implicated in the pathogenesis of MPNST.     

Sulfolipid deficiency does not affect the virulence of Mycobacterium tuberculosis H37Rv in mice and guinea pigs

Lipids that are found only in the cell envelope of pathogenic mycobacteria, such as those containing multiple methyl-branched fatty acids, have long been thought to play a role in pathogenesis. Among these complex lipids, sulfolipids have been the most extensively studied over the last 50 years. The numerous biological effects exhibited by purified sulfolipids on phagocytic cells led to the idea that these molecules are probably important virulence factors facilitating the intracellular survival of Mycobacterium tuberculosis. However, definitive evidence to support this concept has been lacking. The recent construction of an isogenic sulfolipid-deficient mutant of M. tuberculosis H37Rv (Sirakova et al., J. Biol. Chem. 276:16833-16839, 2001) has for the first time provided the opportunity to directly assess the contribution of these complex lipids to pathogenesis. In the present study, we show that against all expectations, sulfolipid deficiency does not significantly affect the replication, persistence, and pathogenicity of M. tuberculosis H37Rv in mice and guinea pigs or in cultured macrophages.     

Dendritic cells transfected with cytopathic self-replicating RNA induce crosspriming of CD8+ T cells and antiviral immunity

A potential shortcoming of nonlive vaccines is their relative inefficiency in generating T cell responses, thus limiting their application in infections requiring cellular immunity. Here, we present a system to induce cellular immunity and to study the immunological implications of time-delayed dendritic cell (DC) apoptosis and antigen reprocessing in vivo. We generated a self-replicating cytopathic pestivirus RNA to enhance production and presentation of hepatitis C virus (HCV) antigens and to induce apoptosis in DC 24-48 hr after transfection. Replicon-transfected H-2(b) DCs used to immunize HLA-A2 transgenic mice induced protection upon challenge with a vaccinia virus expressing HCV antigens. Induction of cell death enhanced the immunogenicity of DC-associated antigen. Transfer of cellular material from vaccine DCs to endogenous antigen presenting cells was visualized in lymph nodes and spleen, and crossprimed CD8(+) T cells were characterized. The findings are relevant for the rational design of vaccines against noncytopathic pathogens like HCV.     

Inhibition of CDK activity and PCNA-dependent DNA replication by p21 is blocked by interaction with the HPV-16 E7 oncoprotein

p21 inhibits cyclin-dependent kinase (CDK) activity and proliferating cell nuclear antigen (PCNA)-dependent DNA replication by binding to CDK/cyclin complexes and to PCNA through distinct domains. The human papillomavirus (HPV)-16 E7 oncoprotein (16E7) abrogated a DNA damage-induced cell cycle arrest in vivo, despite high levels of p21. Using cell lysates and purified proteins we show that 16E7 prevented p21 both from inhibiting CDK2/cyclin E activity and PCNA-dependent DNA replication, whereas the nononcogenic HPV-6 E7 had reduced effects. Inactivation of both inhibitory functions of p21 was attained through binding between 16E7 and sequences in the carboxy-terminal end of p21 that overlap with the PCNA-binding site and the second p21 cyclin-binding motif. These data imply that the carboxyl terminus of p21 simultaneously modulates both CDK activity and PCNA-dependent DNA replication and that a single protein, 16E7, can override this modulation to disrupt normal cell cycle control.     

Hfq-dependent regulation of OmpA synthesis is mediated by an antisense RNA

This paper shows that the small RNA MicA (previously SraD) is an antisense regulator of ompA in Escherichia coli. MicA accumulates upon entry into stationary phase and down-regulates the level of ompA mRNA. Regulation of ompA (outer membrane protein A), previously attributed to Hfq/mRNA binding, is lost upon deletion of the micA gene, whereas overexpression of MicA inhibits the synthesis of OmpA. In vitro, MicA binds to the ompA mRNA leader. Enzymatic and chemical probing was used to map the structures of MicA, the ompA mRNA leader, and the complex formed upon binding. MicA binding generates a footprint across the ompA Shine-Dalgarno sequence, consistent with a 12 + 4 base-pair interaction, which is additionally supported by the effect of mutations in vivo and by bioinformatics analysis of enterobacterial micA/ompA homolog sequences. MicA is conserved in many enterobacteria, as is its ompA target site. In vitro toeprinting confirmed that binding of MicA specifically interferes with ribosome binding. We propose that MicA, when present at high levels, blocks ribosome binding at the ompA translation start site, which-in line with previous work-secondarily facilitates RNase E cleavage and subsequent mRNA decay. MicA requires the presence of the Hfq protein, although the mechanistic basis for this remains unclear.     

Mucosal bromodomain-containing protein 4 mediates aeroallergen-induced inflammation and remodeling

1. Download high-res image (248KB)
2. Download full-size image

     

Comparison of β-adrenoceptors mediating vasodilatation in canine subcutaneous adipose tissue and skeletal muscle

Blood flow changes in response to various drugs in simultaneously autoperfused canine subcutaneous adipose tissue and gracilis muscle were compared to study the vascular β-adrenoceptors. Compared to isoprenaline the β₂-selective agonist salbutamol was 4–6 times more potent as a vasodilator in the muscle than in adipose tissue. Furthermore two β₁-selective agonists (Tazolol and H80/62) caused vasodilatation in adipose tissue but not in the gracilis muscle. When given by close i.a. injection after β-adrenoceptor blockade, adrenaline was a more potent vasoconstrictor than noradrenaline in both tissues. Before β-blockade, however, noradrenaline was the more potent vasoconstrictor in the gracilis muscle whereas adrenaline was more potent in adipose tissue. Intravenous infusion of adrenaline in doses causing vasodilatation in the muscle caused vasoconstriction in adipose tissue whereas intravenous infusion of noradrenaline caused vasoconstriction in both tissues. The present findings suggest that the β-adrenoceptors mediating vasodilatation in skeletal muscle are mainly of the β₂-type, whereas β₁-adrenoceptors seem to predominate in subcutaneous adipose tissue. Since adrenaline is a much more potent β₂- than β₁-agonist, these differences point to different roles of intravascular adrenaline in the two sites. In skeletal muscle circulating adrenaline is mainly a vasodilator whereas in subcutaneous adipose tissue it mainly acts as a vasoconstrictor.     

Upper and lower body functional asymmetries in the newborn: Do they have the same lateral biases?

It is still an open question as to whether functional asymmetries in the human newborn derive from a single lateralized system or multiple subsystems based on different neural mechanisms. In the present study, asymmetries in head turning were compared to those in leg movements during stepping and placing, with the latter also being related to differences in leg mass. The effects of an active versus an inactive state or condition were examined for all three behaviors. No overall lateral biases were found for head turning or for the first foot to move in stepping and placing, and there were no concordances among them; however, there was an asymmetry in that the left foot had a shorter onset latency when compared to the right foot for both stepping and placing. Findings are discussed in terms of what they imply about underlying neural systems that have a bearing on expressions of newborn laterality, and also with regard to the impact of methodological differences in this area of study.     

Extrinsic risk factors for compromised blood flow in the vertebral artery: anatomical observations of the transverse foramina from C3 to C7

The vertebral artery (VA) is often involved in the occurrence of complications after spinal manipulative therapy. Due to osteophytes compressing the VA anteriorly from the uncinate process or posteriorly from the facet complex, the VAs are susceptible to trauma in the transverse foramina. Such altered anatomical configurations are of major clinical significance, as spinal manipulations may result in dissection of the VA with serious consequences for the blood supply to the vertebrobasilar region. The purpose of this study is to describe numerous structural features of the third to seventh cervical vertebrae in order to contribute to the understanding of pathological conditions related to the VA. The minimal and maximal diameter of 111 transverse foramina in dry cervical vertebrae were studied. The presence of osteophytes and their influence on the VA were evaluated at the vertebral body and at the superior and inferior articular facets. The diameter of the transverse foramina increased from C3 to C6, while the transverse foramina of C7 had the smallest diameter. At all levels the mean dimensions of the left foramina were greater than those of the right side. Osteophytes from the uncinate process of C5 and C6 vertebrae were found in over 60% of dry vertebrae. Osteophytes from the zygapophyseal joints were more frequent at C3 and C4 vertebrae. About half of the osteophytes of the uncinate and of the superior articular process partially covered the transverse foramina. This was less common with those of the inferior articular facets. Osteophytes covering the transverse foramen force the VAs to meander around these obstructions, causing narrowing through external compression and are potential sites of trauma to the VAs potentially even leading to dissection. We strongly advocate that screening protocols for vertebrobasilar insufficiency (VBI) be used prior to any manipulation of the cervical spine and should include not only extension and rotation but any starting position from which the planned manipulation will be performed.