Nonlinear dynamics of a double bilipid membrane

The nonlinear dynamics of a biological double membrane that consists of two coupled lipid bilayers, typical of some intracellular organelles such as mitochondria or nuclei, is studied. A phenomenological free-energy functional is formulated in which the curvatures of the two parts of the double membrane and the distance between them are coupled to the lipid chemical composition. The derived nonlinear evolution equations for the double-membrane dynamics are studied analytically and numerically. A linear stability analysis is performed, and the domains of parameters are found in which the double membrane is stable. For the parameter values corresponding to an unstable membrane, numerical simulations are performed that reveal various types of complex dynamics, including the formation of stationary, spatially periodic patterns.

Formation of porous metal oxides in the anodization process

A theory of the formation of nanoscale porous structures in oxides of metals grown by anodization is developed. It is shown that a growing oxide layer can become unstable which yields the formation of a spatially irregular array of pores. The instability is shown to result from a nonlinear dependence of electrochemical kinetics at the metal-oxide and oxide-electrolyte interfaces on the overpotential which is governed by the Butler-Volmer relation. The conditions for the instability of the oxide layer are found. The dependence of the oxide conductivity on the electric field is taken into account and is shown to have a destabilizing effect. A weakly nonlinear analysis is performed and it shows that the system evolution near the instability threshold is described by the Kuramoto-Sivashinsky equation. Farther from threshold, in the long-wave approximation, a system of strongly nonlinear equations is derived and solved numerically; this system describes the formation of deep irregular pores. In a particular case, a self-similar solution describing the propagation of a pore with a paraboloidal shape is found.

Long-term outcomes of laparoscopic heller cardiomyotomy without an anti-reflux procedure

Certain technical features of laparoscopic Heller cardiomyotomy (LHM) remain controversial, including the extent of the myotomy and the indication for an antireflux procedure. We completed a retrospective chart review of all patients who underwent LHM for achalasia at 1 tertiary care institution to review our institutional experience with LHM without an antireflux procedure. Forty patients underwent a LHM performed by 2 surgeons, 65% of whom had previous medical management (Botox: 12 patients, LES dilatation: 14). The operating time was significantly increased in patients with Botox injections (98.3 vs. 71.1 minutes, P = 0.005). There were 3 intraoperative complications (mucosal injury in 3 patients, 2 had Botox injections). Postoperative evaluation demonstrated a mean dysphagia score of 0.2, a mean heartburn score of 3.2, and a mean LES pressure of 6.32 mm Hg. Thirty-two patients are maintained on acid-suppressing medications with good control of reflux symptoms. LHM without an antireflux procedure achieves excellent clinical outcomes in most patients with achalasia regardless of previous medical management. Previous medical management may present a greater technical challenge and may place patients at increased risk of mucosal injury.

An Epstein-Barr virus deletion mutant associated with fatal lymphoproliferative disease unresponsive to therapy with virus-specific CTLs

There is a growing interest in using antigen-specific T cells for the treatment of human malignancy. For example, adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) has been effective prophylaxis and treatment of EBV-associated lymphoproliferative disease in immunocompromised patients. For all immunotherapies, however, there has been a hypothetical concern that mutations in tumor-specific antigens may lead to tumor escape. We now demonstrate that such events may indeed occur, with lethal outcome. A patient who developed lymphoma after marrow transplantation received donor-derived, EBV-specific CTLs but died with progressive disease. The tumor cells proved substantially less sensitive to cytolysis than the EBV-transformed B-cell line used for CTL generation. The major cytolytic activity of the donor CTL was directed against 2 HLA-A11-restricted epitopes in the viral EBNA-3B antigen. Sequence analysis of this gene in the tumor virus revealed a 245-base pair deletion, which removed these 2 CTL epitopes. Hence, the viral antigen in the tumor had mutated in a way that allowed escape from CTLs. Analysis of EBV polymorphisms demonstrated that before CTL infusion, more than one virus was present, including a virus with wild-type EBNA-3B. After CTL infusion, only the virus with the EBNA-3B deletion could be detected, suggesting that the infused CTLs had selected a resistant strain in vivo. Such an occurrence, even when polyclonal CTL lines are used against genetically stable virus antigens, suggests that escape mutants may be a serious problem when CTL therapy is directed against more unstable tumor cell-derived targets.

Patent foramen ovale: association between the degree of shunt by contrast transesophageal echocardiography and the risk of future ischemic neurologic events

This study investigated whether there is an association between the degree of interatrial shunting across a patent foramen ovale, as determined by saline contrast transesophageal echocardiography, and the risk of subsequent systemic embolic events, including stroke. Thirty-four patients found to have foramen ovale during transesophageal echocardiography were divided into two groups on the basis of the maximum number of microbubbles in the left heart in any single frame after intravenous saline contrast injection: group 1 (n = 16) with a "large" degree of shunt ( > or = 20 microbubbles) and group 2 (n = 18) with a "small" degree of shunt ( > or = 3 microbubbles). Patients were followed up over a mean period of 21 months for subsequent systemic embolic events, including transient ischemic attack and stroke. Five (31%) of the patients with large shunts had subsequent ischemic neurologic events, whereas none of the patients with small shunts had embolic events (p = 0.03). These events occurred in spite of antiplatelet or anticoagulant therapy. We conclude that patients with a large degree of shunt across a patient foramen ovale, as determined by contrast transesophageal echocardiography, are at a significantly higher risk of subsequent adverse neurologic events compared with patients with a small degree of shunt.

Ulcerated atherosclerotic plaques in the thoracic aorta are associated with cryptogenic stroke: a multiplane transesophageal echocardiographic study

Atherosclerotic plaque ulcers > or = 2 mm in depth and width in the thoracic aorta have been implicated by autopsy study as a cause of unexplained or cryptogenic ischemic strokes. Transesophageal echocardiography (TEE) allows visualization of complex atherosclerotic lesions of the thoracic aorta. We compared the prevalence of thoracic aorta ulcerated plaques (ulcers > or = 2 mm in both depth and width) in three age-matched groups undergoing multiplane TEE: group 1, 23 patients with cryptogenic ischemic stroke; group 2, 26 patients with known-cause strokes; and group 3, 57 control patients without strokes. TEEs were interpreted in a blinded fashion. Ulcerated plaques were found in 9 (39%) group 1 patients but in only 2 (8%) group 2 patients and in only 4 (7%) group 3 patients (p < 0.001). There was an association between advancing age and the presence of ulcerated plaques (p < 0.02). We conclude that ulcerated atherosclerotic plaques in the thoracic aorta are associated with cryptogenic ischemic stroke and should be considered a potential source of cerebral emboli.

Epstein-Barr virus nuclear antigen 3C is a transcriptional regulator

Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) is one of five viral nuclear proteins that are essential for EBV-induced immortalization of primary human B lymphocytes in vitro. Previous studies have implied that EBNA-3C acts as a transcription factor. Using transient transfection assays, we demonstrate that EBNA-3C has two effects on reporter genes that are linked to the latent membrane protein 1 promoter, (i) low-level activation by EBNA-3C alone, as well as potentiation of EBNA-2-mediated transactivation, and (ii) inhibition of the normally strong activation mediated by EBNA-2. These two disparate effects seem to be mediated at different stages following cell feeding. The inhibitory effect of EBNA-3C was localized to a known EBNA-2 response element that had previously been shown to be recognized by the DNA-binding protein RBP-J kappa. In addition, direct interaction between RBP-J kappa and EBNA-3C was observed by coimmunoprecipitation. Activation by EBNA-3C, however, seems to be achieved via sequences that are distinct from RBP-J kappa sites, since activation remained even after these sites had been mutated. Consistent with its ability to activate transcription, a region of EBNA-3C which has homology to the glutamine-rich activation domain of Sp1 can function as a transcription activation domain when it is fused to the heterologous DNA-binding domain of Gal4 and can partially restore the activity of a mutant EBNA-2 protein with a deletion in the transactivation domain. Collectively, these data strongly support the role of EBNA-3C as a transcriptional regulator.

Antigenic and sequence variation in the C-terminal unique domain of the Epstein-Barr virus nuclear antigen EBNA-1

The Epstein-Barr virus (EBV) nuclear antigen EBNA-1 is essential for viral genome maintenance in vitro and may be the only EBV protein expressed by the majority of latently infected cells in vivo. EBNA-1 may therefore be critical to the evasion of host immunity which allows persistent infection. EBNA-1 includes a polymorphic internal repeat domain of unknown significance and unique regions which mediate all known functional activities and which have hitherto been assumed to be conserved between strains. Monoclonal antibodies were generated using a construct based on EBNA-1 of the prototype B95-8 strain, deleted for the repeat domain. These antibodies showed a limited profile of recognition of EBNA-1 in common laboratory EBV+ cell lines by immunoprecipitation and immunostaining. The observed antigenic heterogeneity also extended to spontaneously transformed B lymphoblastoid cell lines (LCLs) representing viral isolates circulating within US and UK populations. DNA fragments spanning the C-terminal unique domain of EBNA-1 from eleven spontaneous LCLs were amplified by polymerase chain reaction for sequencing, which directly demonstrated extensive and unexpected variability between diverse type 1 EBV isolates. The resulting polymorphism affects most of the putative MHC Class I binding epitopes which could be identified within this region using published sequence motifs, and influences MHC binding by variants of at least one such peptide in the processing mutant cell line T2. These findings could be related to the apparent lack of recognition of EBNA-1 by cytotoxic T lymphocytes.

Biochemical characterization of Epstein-Barr virus nuclear antigen 3A and 3C proteins

Among the viral proteins expressed in Epstein-Barr virus (EBV)-infected B cells are a family of nuclear proteins known as the Epstein-Barr virus nuclear antigen 3 (EBNA-3) proteins. Two of these, EBNA-3A and EBNA-3C, have an essential but uncharacterized role in the transformation of primary B cells by EBV. EBNA-3C increases expression of two genes likely to be important for B cell growth transformation by EBV, the B cell activation antigen CD21 and the EBV latent membrane protein-1. Since EBNA-3 proteins exhibit DNA-binding capability in crude protein extracts from EBV-transformed cell lines and EBNA-3C contains sequences homologous to a basic leucine zipper motif found in one class of mammalian transcription factors, it is likely that EBNA-3C functions as a transcriptional transactivator. In this paper, we have overexpressed EBNA-3A and -3C in the baculovirus-expression system. To determine whether the ability to bind to DNA is an intrinsic property of the EBNA-3 proteins, we have examined the ability of the recombinant protein to bind to DNA-cellulose. Unlike EBNA-3 proteins in lysates from EBV-transformed cells, neither recombinant protein exhibits significant DNA-binding capability as evidenced by the inability to bind to double-stranded DNA-cellulose. Since this difference in DNA binding could be a result of post-translational modifications, we have examined the phosphorylation status of the EBNA-3 proteins both in EBV-transformed cells and in infected insect cells. EBNA-3A and EBNA-3C were phosphorylated in both cell types. Therefore, if indeed these proteins function as transcriptional transactivators, they may bind to DNA via an indirect mechanism. The recombinant proteins will be invaluable in the further clarification of the role of EBNA-3A and EBNA-3C in EBV-induced immortalization of B cells.

The Epstein-Barr virus nuclear protein 1 promoter active in type I latency is autoregulated

The only member of the Epstein-Barr virus family of nuclear proteins (EBNAs) expressed during type I and type II latent infections is EBNA-1. This is in contrast to type III latency, during which all six nuclear proteins are expressed from a common transcription unit. The exclusive expression of EBNA-1 during type I and II latency is mediated through a recently identified promoter, Fp. The objective of this study was to characterize Fp in the Burkitt lymphoma cell background, where it is known to be differentially utilized. Using a short-term transfection assay and reporter gene plasmids containing Fp linked to the human growth hormone, we examined Fp activity in type I and type III latently infected and virus-negative Burkitt lymphoma cells. The data suggested that Fp is predominantly regulated through two distinct elements located between +24 and +270 relative to the transcription start site. One element positively mediates Fp activity, probably at the level of transcription, and acts in a virus-independent manner. The second element contains the EBNA-1 DNA binding domain III and negatively regulates Fp-directed gene expression in trans with EBNA-1 in type III as well as type I latency. Thus, we have identified a third function of EBNA-1, i.e., that of a repressor of gene expression, in addition to its known role in viral DNA replication and its ability to trans-activate gene expression. The overall activity of Fp in type I latently infected Burkitt cells was approximately sixfold lower than in virus-negative Burkitt cells, in which there is no autoregulation, suggesting that there is a fine balance between these two opposing regulatory elements during type I latency.

Restricted Epstein-Barr virus protein expression in Burkitt lymphoma is due to a different Epstein-Barr nuclear antigen 1 transcriptional initiation site

Epstein-Barr virus (EBV) expresses six nuclear antigens (EBNAs) and three integral latent membrane proteins (LMPs) in latently infected growth-transformed B lymphoblastoid cell lines (LCLs). In contrast, EBV protein expression in Burkitt lymphoma tissue or in newly established Burkitt lymphoma cell lines is frequently restricted to the EBV genome maintenance protein, EBNA-1. EBNA-1 expression in the absence of other EBNAs and LMP-1 has been an enigma since, in LCLs, all EBNA mRNAs are processed from a single transcript. We now show that the basis for restricted EBV expression in Burkitt lymphoma cells is selective EBNA-1 mRNA transcription from a hitherto unrecognized promoter that is 50 kb closer to the EBNA-1-encoding exon than previously described EBNA-1 promoters. Infected cells with EBNA-1-restricted expression could preferentially persist in vivo in the face of EBV-immune T-cell responses, which are frequently directed against other EBNAs and are also dependent on LMP-1 expression.

Subnuclear localization and phosphorylation of Epstein-Barr virus latent infection nuclear proteins

Functions of the six Epstein-Barr virus latent infection nuclear proteins (EBNA-1, -2, -3A, -3B, -3C, or -LP) in maintaining latent infection or cell growth transformation are only partially understood. Using antibodies specific for each EBNA in immunofluorescence microscopy, EBNA-2, -3A, and -3C localized to subnuclear granules which fill much of the nucleus, excluding nucleoli. EBNA-LP localized to a small number of discrete subnuclear particles, also excluding nucleoli. Only EBNA-1 associated with metaphase chromosomes. Concordantly, in biochemical nuclear fractionation studies, EBNA-1 was the major chromatin-associated EBNA. EBNA-1 also differed from the other EBNAs in the extent of its association with the nucleoplasm and in its lack of nuclear matrix association. EBNA-LP, -2, -3A, and -3C were associated with the nuclear matrix, although they were also found in the nucleoplasm and to a lesser extent in the chromatin fractions. Metabolic 32Pi-labeling of cells followed by two-dimensional gel electrophoresis showed that EBNA-LP could be resolved into multiple phosphorylated isoforms. EBNA-2 was also phosphorylated and many isoforms were detected by isoelectric focusing.

Epstein-Barr virus latent membrane protein (LMP1) and nuclear proteins 2 and 3C are effectors of phenotypic changes in B lymphocytes: EBNA-2 and LMP1 cooperatively induce CD23

Latent Epstein-Barr virus (EBV) infection and growth transformation of B lymphocytes is characterized by EBV nuclear and membrane protein expression (EBV nuclear antigen [EBNA] and latent membrane protein [LMP], respectively). LMP1 is known to be an oncogene in rodent fibroblasts and to induce B-lymphocyte activation and cellular adhesion molecules in the EBV-negative Burkitt's lymphoma cell line Louckes. EBNA-2 is required for EBV-induced growth transformation; it lowers rodent fibroblast serum dependence and specifically induces the B-lymphocyte activation antigen CD23 in Louckes cells. These initial observations are now extended through an expanded study of EBNA- and LMP1-induced phenotypic effects in a different EBV-negative B-lymphoma cell line, BJAB. LMP1 effects were also evaluated in the EBV-negative B-lymphoma cell line BL41 and the EBV-positive Burkitt's lymphoma cell line, Daudi (Daudi is deleted for EBNA-2 and does not express LMP). Previously described EBNA-2- and LMP1-transfected Louckes cells were studied in parallel. EBNA-2, from EBV-1 strains but not EBV-2, induced CD23 and CD21 expression in transfected BJAB cells. In contrast, EBNA-3C induced CD21 but not CD23, while no changes were evident in vector control-, EBNA-1-, or EBNA-LP-transfected clones. EBNAs did not affect CD10, CD30, CD39, CD40, CD44, or cellular adhesion molecules. LMP1 expression in all cell lines induced growth in large clumps and expression of the cellular adhesion molecules ICAM-1, LFA-1, and LFA-3 in those cell lines which constitutively express low levels. LMP1 expression induced marked homotypic adhesion in the BJAB cell line, despite the fact that there was no significant increase in the high constitutive BJAB LFA-1 and ICAM-1 levels, suggesting that LMP1 also induces an associated functional change in these molecules. LMP1 induction of these cellular adhesion molecules was also associated with increased heterotypic adhesion to T lymphocytes. The Burkitt's lymphoma marker, CALLA (CD10), was uniformly down regulated by LMP1 in all cell lines. In contrast, LMP1 induced unique profiles of B-lymphocyte activation antigens in the various cell lines. LMP1 induced CD23 and CD39 in BJAB; CD23 in Louckes; CD39 and CD40 in BL41; and CD21, CD40, and CD44 in Daudi. In BJAB, CD23 surface and mRNA expression were markedly increased by EBNA-2 and LMP1 coexpression, compared with EBNA-2 or LMP1 alone. This cooperative effect was CD23 specific, since no such effect was observed on another marker, CD21.(ABSTRACT TRUNCATED AT 400 WORDS)

An islet amyloid peptide is derived from an 89-amino acid precursor by proteolytic processing

Amyloid deposits occurring in the islets of Langerhans in patients with noninsulin-dependent diabetes mellitus and some insulinomas contain a 37-amino acid peptide that is structurally related to calcitonin gene-related peptide. We have identified three cDNA clones encoding islet amyloid polypeptide (IAPP) or diabetes-associated peptide (DAP) by oligonucleotide screening of a lambda gt10 human insulinoma cDNA library. Two of the three cDNAs contained a domain encoding IAPP/DAP but had an intron-like sequence in their 5' region. The other cDNA contained an open reading frame encoding an 89-amino acid precursor having a typical signal peptide followed by a small prohormone-like sequence containing within it the IAPP/DAP peptide bracketed at its NH2 and COOH termini by Lys-Arg and Gly-Lys-Arg, respectively. These data indicate that this amyloid peptide is generated by proteolytic processing similar to that for proinsulin and other islet prohormones and also that the peptide may be carboxyamidated. The isolation of cDNA clones having 5'-unprocessed intron-like sequences suggests that inefficient or alternative splicing of this mRNA occurred in the insulinoma.