Outer membrane vesicles of Tannerella forsythia: biogenesis, composition, and virulence

Tannerella forsythia is the only ‘red‐complex’ bacterium covered by an S‐layer, which has been shown to affect virulence. Here, outer membrane vesicles (OMVs) enriched with putative glycoproteins are described as a new addition to the virulence repertoire of T. forsythia. Investigations of this bacterium are hampered by its fastidious growth requirements and the recently discovered mismatch of the available genome sequence (92A2 = ATCC BAA‐2717) and the widely used T. forsythia strain (ATCC 43037). T. forsythia was grown anaerobically in serum‐free medium and biogenesis of OMVs was analyzed by electron and atomic force microscopy. This revealed OMVs with a mean diameter of ~100 nm budding off from the outer membrane while retaining the S‐layer. An LC‐ESI‐TOF/TOF proteomic analysis of OMVs from three independent biological replicates identified 175 proteins. Of these, 14 exhibited a C‐terminal outer membrane translocation signal that directs them to the cell/vesicle surface, 61 and 53 were localized to the outer membrane and periplasm, respectively, 22 were predicted to be extracellular, and 39 to originate from the cytoplasm. Eighty proteins contained the Bacteroidales O‐glycosylation motif, 18 of which were confirmed as glycoproteins. Release of pro‐inflammatory mediators from the human monocytic cell line U937 and periodontal ligament fibroblasts upon stimulation with OMVs followed a concentration‐dependent increase that was more pronounced in the presence of soluble CD14 in conditioned media. The inflammatory response was significantly higher than that caused by whole T. forsythia cells. Our study represents the first characterization of T. forsythia OMVs, their proteomic composition and immunogenic potential.

Predicting how individuals approach enrichment: regulatory focus in cotton-top tamarins (Sanguinus oedipus)

Evidence is mounting that personality is associated with health and well-being in humans and other animals. In a step towards increasing our understanding of this link, we applied regulatory focus theory, a motivational perspective from social psychology, to the behavior of zoo-housed cotton top tamarins. We tested whether regulatory focus "personality," that is stable differences in whether an individual is motivated by gains versus safety, would 1) produce individual differences in behavior and 2) predict how individuals interact with enrichment. First, we characterized individuals with respect to several key behaviors: eating in the open, hiding, and time spent near the front of the exhibit. The monkeys were consistent in their behavioral tendencies across the 6-month study, allowing regulatory focus classification. One monkey showed evidence of being a promotion-individual, that is, more motivated by gains than safety. One monkey showed evidence of being a prevention-individual, that is, more motivated by safety than gains. The other monkeys were stable in their behavior and showed evidence of being intermediate-individuals, that is, they favored neither gains nor safety. Using these characterizations, we predicted distinct patterns of individual-object interactions with enrichment. For example, we predicted that a promotion-individual (favoring gains over safety) would approach potential gains faster than a prevention-individual (favoring safety over gains). Counter-intuitively, however, we also predicted that a promotion-individual would approach non-gains slower than a prevention-individual concerned with safety. We found support for our predictions, which suggests that regulatory focus theory could be a useful tool for understanding how and why individuals interact with environmental enrichment.

Escape of intraluminal platelets into brain parenchyma after subarachnoid hemorrhage

Platelet aggregates are present in parenchymal vessels as early as 10 min after experimental subarachnoid hemorrhage (SAH). Structural injury to parenchymal vessel walls and depletion of collagen-IV (the major protein of basal lamina) occur in a similar time frame. Since platelets upon activation release enzymes which can digest collagen-IV, we investigated the topographic relationship between platelet aggregates, endothelium, and basal lamina after SAH produced by endovascular perforation, using triple immunofluorescence and confocal microscopy with deconvolution. The location of platelet aggregates in relation to zymography-detected active collagenase was also examined. As reported previously, most cerebral vessels profiles contained platelets aggregates at 10 min after SAH. High-resolution three-dimensional image analysis placed many platelets at the ab-luminal (basal) side of endothelium at 10 min, and others either within the vascular basal lamina or in nearby parenchyma. By 24 h post hemorrhage, large numbers of platelets had entered the brain parenchyma. The vascular sites of platelet movement were devoid of endothelium and collagen-IV. Collagenase activity colocalized with vascular platelet aggregates. Our data demonstrate that parenchymal entry of platelets into brain parenchyma begins within minutes after hemorrhage. Three-dimensional analysis suggests that platelet aggregates initiate or stimulate local disruption of endothelium and destruction of adjacent basal lamina after SAH.

Attachment of osteocyte cell processes to the bone matrix

In order for osteocytes to perceive mechanical information and regulate bone remodeling accordingly they must be anchored to their extracellular matrix (ECM). To date the nature of this attachment is not understood. Osteocytes are embedded in mineralized bone matrix, but maintain a pericellular space (50-80 nm) to facilitate fluid flow and transport of metabolites. This provides a spatial limit for their attachment to bone matrix. Integrins are cell adhesion proteins that may play a role in osteocyte attachment. However, integrin attachments require proximity between the ECM, cell membrane, and cytoskeleton, which conflicts with the osteocytes requirement for a pericellular fluid space. In this study, we hypothesize that the challenge for osteocytes to attach to surrounding bone matrix, while also maintaining fluid-filled pericellular space, requires different "engineering" solutions than in other tissues that are not similarly constrained. Using novel rapid fixation techniques, to improve cell membrane and matrix protein preservation, and transmission electron microscopy, the attachment of osteocyte processes to their canalicular boundaries are quantified. We report that the canalicular wall is wave-like with periodic conical protrusions extending into the pericellular space. By immunohistochemistry we identify that the integrin alphavbeta3 may play a role in attachment at these complexes; a punctate pattern of staining of beta3 along the canalicular wall was consistent with observations of periodic protrusions extending into the pericellular space. We propose that during osteocyte attachment the pericellular space is periodically interrupted by underlying collagen fibrils that attach directly to the cell process membrane via integrin-attachments.

[Letters from Clara Happel, in New York, to her son: 1936-1945]

Many psychoanalysts of the second generation, among them Clara Happel (1889-1945) were forced to emigrate at the time of the National Socialist domination. The experience of a total upheaval in the history of the world during the emigration period shattered this second generation's feeling of being pioneers. On the intra-psychic plane this was the equivalent of a serious identity crisis. The psychic state among the emigrés is described, using the fate of Clara Happel as an example. She had to master and work through "doubts and losses of all kinds". She did not succeed in escaping the reality of the annihilation which threatened her. The experience of the Nazi domination, the ravages of the Second World War, the reality of a policy of the extermination of men by men and the rise of the danger of nuclear destruction sharpened the process of mourning for things lost. She plunged into a conflict of profound ambivalence. The materialization of the nuclear danger with the dropping of atomic bombs on Hiroshima and Nagasaki brought her face to face with her own frenzy for revenge. The shadow of objective reality fell across her ego in the form of melancholia. She lost the struggle with a reality which had become psychotic. The outside world replaced her inner life. She committed suicide on September 15, 1945. Her fate as a refugee shows that there are some situations where it is impossible to work through the conflict of ambivalence.

Developmental expression of mouse Krüppel-like transcription factor KLF7 suggests a potential role in neurogenesis

To identify potential functions for the Krüppel-like transcription factor KLF7, we have determined the spatiotemporal pattern of gene expression during embryogenesis and in the adult organism. We show that the profile of Klf7 expression predominantly involves the central and peripheral nervous systems and is broadly identified by three separate phases. The first phase occurs early in embryogenesis with increasingly strong expression in the spinal cord, notably in motor neurons of the ventral horn, in dorsal root ganglia, and in sympathetic ganglia. The second robust phase of Klf7 expression is confined to the early postnatal cerebral cortex and is downregulated thereafter. The third phase is characterized by high and sustained expression in the adult cerebellum and dorsal root ganglia. Functionally, these three phases coincide with establishment of neuronal phenotype in embryonic spinal cord, with synaptogenesis and development of mature synaptic circuitry in the postnatal cerebral cortex, and with survival and/or maintenance of function of adult sensory neurons and cerebellar granule cells. Consistent with Klf7 expression in newly formed neuroblasts, overexpression of the gene in cultured fibroblasts and neuroblastoma cells repressed cyclin D1, activated p21, and led to G1 growth arrest. Based on these data, we argue for multiple potential functions for KLF7 in the developing and adult nervous system; they include participating in differentiation and maturation of several neuronal subtypes and in phenotypic maintenance of mature cerebellar granule cells and dorsal root ganglia.

Oligodendrocyte precursor differentiation is perturbed in the absence of the cyclin-dependent kinase inhibitor p27Kip1

During development of the central nervous system, oligodendrocyte progenitor cells (O-2A) undergo an orderly pattern of cell proliferation and differentiation, culminating in the ability of oligodendrocytes to myelinate axons. Here we report that p27(Kip1), a cyclin-dependent kinase inhibitor, is an important component of the decision of O-2A cells to withdraw from the cell cycle. In vitro, accumulation of p27 correlates with differentiation of oligodendrocytes. Furthermore, only a fraction of O-2A cells derived from p27-knockout mice differentiate successfully compared to controls. Inability to differentiate correlates with continued proliferation, suggesting that p27 is an important component of the machinery required for the G1/G0 transition in O-2A cells. In vivo, expansion of O-2A precursors before withdrawal, in part, leads to a greater number of oligodendrocytes. Together these data indicate a role for p27 during the decision to withdraw from the cell cycle in the oligodendrocyte lineage.

Tissue factor is rapidly induced in arterial smooth muscle after balloon injury

Tissue factor (TF) is a major activator of the coagulation cascade and may play a role in initiating thrombosis after intravascular injury. To investigate whether medial vascular smooth muscle provides a source of TF following arterial injury, the induction of TF mRNA and protein was studied in balloon-injured rat aorta. After full length aortic injury, aortas were harvested at various times and the media and adventitia separated using collagenase digestion and microscopic dissection. In uninjured aortic media, TF mRNA was undetectable by RNA blot hybridization. 2 h after balloon injury TF mRNA levels increased markedly. Return to near baseline levels occurred at 24 h. In situ hybridization with a 35S-labeled antisense rat TF cRNA probe detected TF mRNA in the adventitia but not in the media or endothelium of uninjured aorta. 2 h after balloon dilatation, a marked induction of TF mRNA was observed in the adventitia and media. Using a functional clotting assay, TF procoagulant activity was detected at low levels in uninjured rat aortic media and rose by approximately 10-fold 2 h after balloon dilatation. Return to baseline occurred within 4 d. These data demonstrate that vascular injury rapidly induces active TF in arterial smooth muscle, providing a procoagulant that may result in thrombus initiation or propagation.

In situ hybridization analysis of myelin gene transcripts in developing mouse spinal cord

We analyzed the location and abundance of transcripts for the 4 CNS myelin protein genes, myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG), and 2',3'-cyclic nucleotide phosphohydrolase (CNP), in the mouse cervical spinal cord from the time of rapid myelination until adulthood (8-45 d). In the white matter, maximal levels of transcripts were found for each of the myelin genes at the peak of myelination (8 d). Total MBP and PLP mRNAs stayed high until 20 d and showed a minor decrease thereafter. In contrast, MAG and the MBP exon 2 containing transcripts (coding for the 21.5 and 17 kDa MBP isoforms) decreased sharply between 8 and 20 d, suggesting that high levels of these transcripts are needed primarily during the initiation of myelination. CNP transcripts were less abundant, maintained high expression until 20 d, and then decreased sharply. PLP, MAG, and CNP transcripts were clustered in the oligodendrocyte cell body, while MBP mRNAs were scattered throughout the cell body and processes. In contrast to the white matter, all these myelin specific transcripts in the gray matter showed a marked increase from 8 to 20 d, as did the number of oligodendrocytes identified by CNP immunostaining. MAG transcripts were found in white matter and in satellite and other oligodendrocytes of the gray matter but not in neurons identified by their expression of neurofilament transcripts. The results of our quantitative in situ hybridization study are in good agreement with those of previous molecular studies and provide new information on the cellular and topographic distribution of myelin-specific mRNAs during myelination.

Expression of a homeo domain protein in noncontact-inhibited cultured cells and postmitotic neurons

The murine Hox 1.3 gene is one of six homeo box genes clustered on chromosome 6. Our analysis of Hox 1.3 cDNA and genomic clones indicates that the gene is organized into two exons and encodes a 270-amino-acid homeo domain protein. The predicted protein is rich in serine, glycine, and proline residues, and its homeo domain is identical to the Hox 2.1 domain. During embryogenesis, the gene is maximally expressed at midgestation but is also expressed to a lesser extent in many adult tissues possessing different cell lineages. Hox 1.3 transcripts are also present in cultured fibroblasts. The Hox 1.3 protein accumulates in the nuclei of nonconfluent cultured fibroblasts but is greatly diminished in contact-inhibited nongrowing cells. Thus, the expression of the Hox 1.3 gene correlates with growth in embryos and cultured cells. Paradoxically, it is also expressed in certain subsets of postmitotic, fully differentiated neurons, most notably the Purkinje neurons of the cerebellum, the pyramidal and dentate neurons of the hippocampus, and the motor neurons of the spinal cord. This complex pattern of expression suggests that Hox 1.3 may provide a function required by many cell types in addition to any role it may have in morphogenesis.

Myelin-specific proteolipid protein is expressed in myelinating Schwann cells but is not incorporated into myelin sheaths

Contrary to widely held beliefs, the gene encoding proteolipid protein (PLP), the major structural protein of central nervous system myelin, is expressed in Schwann cells and their tumors. Proteolipid mRNA was identified in human acoustic neuromas and in rat and rabbit sciatic nerves using a human PLP cDNA as a probe. Proteolipid protein itself was shown to be present in human and rat sciatic nerve Schwann cells by immunofluorescence microscopy and by Western blot analysis using antisera raised to a synthetic PLP polypeptide. Although easily detected in the Schwann cell body, PLP was not detected in the peripheral myelin itself, suggesting that the PLP is preferentially excluded from this portion of the Schwann cell membrane.