Immune response to orally consumed antigens and probiotic bacteria

The gut mucosal system must fulfil conflicting roles in suppressing immune responses against orally fed antigens (tolerance) while still retaining the ability to respond to potential enteric pathogens. It must also, to a large degree, not mount an immune response against commensal enteric bacteria and the administration of large numbers of probiotic bacteria formulated as dietary supplements in food products. Contrary to this dogma, it has been found that feeding ovalbumin as a marker antigen, in association with selected probiotic bacteria, appears to prime for an intestinal immune response that is further augmented by skin vaccination. Skin immunization is known to stimulate a strong innate, humoral and cellular immune response. Such dominant immunogenic signals appear to override tolerogenic signals engendered by oral feeding of antigen. High-dose antigen feeding stimulated a strong Th2-dependent antibody response to skin vaccination but completely suppressed cytotoxic T cell responses. This was true even when ovalbumin was administered in conjunction with various selected probiotic bacteria. However, while yeast appeared to be better at priming for an enhanced humoral response, Lactobacillus fermentum and Staphylococcus carnosus were more effective in enhancing the postvaccinal lymphoproliferative response against ovalbumin.

Violence victimization after HIV infection in a US probability sample of adult patients in primary care

OBJECTIVES

This study estimated the proportion of HIV-infected adults who have been assaulted by a partner or someone important to them since their HIV diagnosis and the extent to which they reported HIV-seropositive status as a cause of the violence.

METHODS

Study participants were from a nationally representative probability sample of 2864 HIV-infected adults who were receiving medical care and were enrolled in the HIV Costs and Service Utilization Study. All interviews (91% in person, 9% by telephone) were conducted with computer-assisted personal interviewing instruments. Interviews began in January 1996 and ended 15 months later.

RESULTS

Overall, 20.5% of the women, 11.5% of the men who reported having sex with men, and 7.5% of the heterosexual men reported physical harm since diagnosis, of whom nearly half reported HIV-seropositive status as a cause of violent episodes.

CONCLUSIONS

HIV-related care is an appropriate setting for routine assessment of violence. Programs to cross-train staff in antiviolence agencies and HIV care facilities need to be developed for men and women with HIV infection.

Dissection plane of the human vocal fold lamina propria and elastin fibre concentration

To determine whether a natural plane of dissection occurs in the normal human vocal fold, semi-blunt instruments (Bouchayer laryngeal dissectors) were used to dissect the lamina propria. The depth of the plane of dissection was correlated with the elastin fibre concentration to determine whether the plane occurred at a predictable point in the elastin concentration as it increased between the superficial and middle layers. Eight human larynges were dissected using an operative microscope. The dissection plane consistently occurred between 23-50% depth into the lamina propria. No consistent correlation was found with the elastin fibre concentration. The depth of the plane of dissection has an interesting association with age: dissection planes occurred more superficially in older specimens.

Preparation of site-specific antibodies to acetylated histones

Synthetic peptides corresponding to regions within the amino-terminal domains of the core histones H2A, H2B, H3, and H4, in which epsilon-acetyllysine has been substituted for selected lysines, have been used to raise polyclonal antisera in rabbits. Such antisera can be specific not only for individual acetylated histones but also for histone isoforms acetylated at particular lysine residues. In this article, we describe procedures for the preparation, affinity purification, and initial characterization of site-specific antisera to acetylated histones.

MBD2 is a transcriptional repressor belonging to the MeCP1 histone deacetylase complex

Mammalian DNA is methylated at many CpG dinucleotides. The biological consequences of methylation are mediated by a family of methyl-CpG binding proteins. The best characterized family member is MeCP2, a transcriptional repressor that recruits histone deacetylases. Our report concerns MBD2, which can bind methylated DNA in vivo and in vitro and has been reported to actively demethylate DNA (ref. 8). As DNA methylation causes gene silencing, the MBD2 demethylase is a candidate transcriptional activator. Using specific antibodies, however, we find here that MBD2 in HeLa cells is associated with histone deacetylase (HDAC) in the MeCP1 repressor complex. An affinity-purified HDAC1 corepressor complex also contains MBD2, suggesting that MeCP1 corresponds to a fraction of this complex. Exogenous MBD2 represses transcription in a transient assay, and repression can be relieved by the deacetylase inhibitor trichostatin A (TSA; ref. 12). In our hands, MBD2 does not demethylate DNA. Our data suggest that HeLa cells, which lack the known methylation-dependent repressor MeCP2, use an alternative pathway involving MBD2 to silence methylated genes.

Maternal histone deacetylase is accumulated in the nuclei of Xenopus oocytes as protein complexes with potential enzyme activity

Reversible acetylation of core histones plays an important regulatory role in transcription and replication of chromatin. The acetylation status of chromatin is determined by the equilibrium between activities of histone acetyltransferases (HATs) and histone deacetylases (HDACs). The Xenopus protein HDACm shows sequence homology to other putative histone deacetylases, but its mRNA is expressed only during early development. Both HDACm protein and acetylated non-chromosomal histones are accumulated in developing oocytes, indicating that the key components for histone deposition into new chromatin during blastula formation are in place by the end of oogenesis. Here we show that the 57 kDa HDACm protein undergoes steady accumulation in the nucleus, where it is organized in a multiprotein complex of approx. 300 kDa. A second, major component of the nuclear complex is the retinoblastoma-associated protein p48 (RbAp48/46), which may be used as an adaptor to contact acetylated histones in newly assembled chromatin. The nuclear complex has HDAC activity that is sensitive to trichostatin A, zinc ions and phosphatase treatment. The 57 kDa protein serves as a marker for total HDAC activity throughout oogenesis and early embryogenesis. The active HDACm complex and its acetylated histone substrates appear to be kept apart until after chromatin assembly has taken place. However, recombinant HDACm, injected into the cytoplasm of oocytes, not only is translocated to the nucleus, but also is free to interact with the endogenous chromatin.

Chromatin structure analysis of the mouse Xist locus

The Xist gene is expressed exclusively from the inactive X chromosome and plays a central role in regulating X chromosome inactivation. Here we describe experiments aimed at defining the extent of the active chromatin domain of the expressed Xist allele. By using an allele-specific general DNaseI sensitivity assay we show that there is preferential digestion of the expressed allele at sites within the transcribed locus but not in flanking sites located up to 70 kb 5'. A putative proximal boundary for the Xist domain is located within 10 kb upstream of promoter P1. Chromatin in the expressed domain was found to be acetylated at H4 in XX somatic cells but also in XY cells, where Xist is never expressed. A single clear exception to this was the Xist promoter, which is acetylated only in XX cells. These observations concur with the view that H4 acetylation may not be a general marker of active chromatin domains and further support data implicating local promoter acetylation as being of primary functional significance in vivo.

A developmental switch in H4 acetylation upstream of Xist plays a role in X chromosome inactivation

We have investigated the role of histone acetylation in X chromosome inactivation, focusing on its possible involvement in the regulation of Xist, an essential gene expressed only from the inactive X (Xi). We have identified a region of H4 hyperacetylation extending up to 120 kb upstream from the Xist somatic promoter P1. This domain includes the promoter P0, which gives rise to the unstable Xist transcript in undifferentiated cells. The hyperacetylated domain was not seen in male cells or in female XT67E1 cells, a mutant cell line heterozygous for a partially deleted Xist allele and in which an increased number of cells fail to undergo X inactivation. The hyperacetylation upstream of Xist was lost by day 7 of differentiation, when X inactivation was essentially complete. Wild-type cells differentiated in the presence of the histone deacetylase inhibitor Trichostatin A were prevented from forming a normally inactivated X, as judged by the frequency of underacetylated X chromosomes detected by immunofluorescence microscopy. Mutant XT67E1 cells, lacking hyperacetylation upstream of Xist, were less affected. We propose that (i) hyperacetylation of chromatin upstream of Xist facilitates the promoter switch that leads to stabilization of the Xist transcript and (ii) that the subsequent deacetylation of this region is essential for the further progression of X inactivation.

Experimental validation of forensic evidence: a study of the decomposition of buried pigs in a heavy clay soil

In a murder investigation, where the victim had been strangled and buried in a shallow grave, there were discrepancies between the post mortem interval (PMI) as estimated from entomological studies and estimations determined from other evidence. This inconsistency provided the impetus for examining the decay process using pig carcasses as analogues for the human cadaver. The pigs were buried in the immediate vicinity of the original burial site in December 1996, which was the month when the victim was purported to have been interred in the previous year. The buried pigs were then monitored for 5 months which, based on the evidence other than the entomological, was the period over which the corpse was thought to have lain in the ground. The pig corpses were disturbed by scavengers in mid April: this was the same time that the human corpse was discovered in the previous year by scavengers. Insects played no role in the decomposition process until the pig carcasses had been exposed by animals. Blowflies, notably Calliphora vomitoria, were attracted to the exposed tissues and laid eggs from which larvae developed. Calliphora vomitoria is a species often used to estimate PMI. This investigation has shown that soil conditions and low seasonal temperatures had preserved the pig carcasses for longer than might be expected. Using the blowfly larvae to estimate PMI would have produced erroneous results had not the burial environment and exhumation history been investigated.

Euchromatic domains in plant chromosomes as revealed by H4 histone acetylation and early DNA replication

Using specific polyclonal antisera raised against acetylated isoforms of histone H4, we have analyzed their distribution in the dioecious plant Silene latifolia (syn. Melandrium album) possessing heteromorphic sex chromosomes. Our previous studies on this species have shown that one of the two X chromosomes in homogametic female cells is heavily methylated and late replicating, as a possible consequence of dosage compensation. Here we report that there are no detectable differences in intensity and distribution of H4 acetylation between these two X chromosomes. In S. latifolia only distal-subtelomeric chromosome regions, on both the sex chromosomes and autosomes, display strong signals of H4 acetylation at N-terminal lysines 5, 8, and 12. These acetylated domains correspond to the very early replicating distal chromosome regions as revealed by 5-bromodeoxyuridine pulses followed by the indirect immunofluorescence microscopy. The distribution of H4 acetylated at lysine 16 was uniform along the chromosomes. The unique distal-subtelomeric H4 acetylation signals were also observed in three other Silene species (S. vulgaris, S. pendula, and S. chalcedonica), but not in two non-related plant species tested (Allium cepa and Nicotiana tobacum). The presented data as well as our recent studies on the structure of S. latifolia chromosome ends indicate that Silene species possess the specific distal-subtelomeric location of euchromatin, gene-rich regions on chromosomes.

Histone deacetylases: complex transducers of nuclear signals

Histone acetylation influences both gene transcription and chromatin assembly after DNA replication and the enzymes that regulate this property of chromatin are likely to play a key role in regulating these crucial genomic functions. The steady-state level of histone acetylation is established and maintained by multiple histone acetyltransferases (HATs) and deacetylases (HDACs). Both groups of enzymes contain numerous family members, most of which have been highly conserved through evolution. The HDACs have been implicated in repression of gene expression by facilitating chromatin condensation and, like the HATs, operate as part of multi-protein complexes. The non-catalytic components of these complexes can either target the catalytic subunit to specific sites on the genome or regulate its enzymatic specificity. Kinase and phosphatase activities of intracellular signal transduction pathways may modify components of these complexes and thereby regulate their assembly, targeting or enzymatic function.

Expanded lysine acetylation specificity of Gcn5 in native complexes

The coactivator/adaptor protein Gcn5 is a conserved histone acetyltransferase, which functions as the catalytic subunit in multiple yeast transcriptional regulatory complexes. The ability of Gcn5 to acetylate nucleosomal histones is significantly reduced relative to its activity on free histones, where it predominantly modifies histone H3 at lysine 14. However, the association of Gcn5 in multisubunit complexes potentiates its nucleosomal histone acetyltransferase activity. Here, we show that the association of Gcn5 with other proteins in two native yeast complexes, Ada and SAGA (Spt-Ada-Gcn5-acetyltransferase), directly confers upon Gcn5 the ability to acetylate an expanded set of lysines on H3. Furthermore Ada and SAGA have overlapping, yet distinct, patterns of acetylation, suggesting that the association of specific subunits determines site specificity.

Xist RNA exhibits a banded localization on the inactive X chromosome and is excluded from autosomal material in cis

The propagation of X chromosome inactivation is thought to be mediated by the cis- limited spreading of the non-protein coding Xist transcript. In this report we have investigated the localization of Xist RNA on rodent metaphase chromosomes. We show that Xist RNA exhibits a banded pattern on the inactive X and is excluded from regions of constitutive heterochromatin. The banding pattern suggests a preferential association with gene-rich, G-light regions. Analysis of X:autosome rearrangements revealed that restricted propagation of X inactivation into cis -linked autosomal material is reflected by a corresponding limited spread of Xist RNA. We discuss these results in the context of models for the function of Xist RNA in the propagation of X inactivation.

H4 acetylation, XIST RNA and replication timing are coincident and define x;autosome boundaries in two abnormal X chromosomes

The inactive X (Xi) differs from its active homologue (Xa) in a number of ways, including increased methylation of CpG islands, replication late in S phase, underacetylation of histone H4 and association with XIST RNA. Global changes in DNA methylation occur relatively late in development, but the other properties all change during or shortly after the establishment of Xi and may play a role in the mechanism by which an inactive chromatin conformation spreads across most of the chromosome. In the present report, we use two human X;autosome translocation chromosomes to study the spreading of inactive X chromatin across X;autosome boundaries. In one of these chromosomes, t(X;6), Xp distal to p11.2 is replaced by 6p21.1-6pter and, in the other, ins(X;16), a small fragment derived from 16p13 is inserted into the distal third of Xq. In lymphoid cells from patients carrying these translocations in an unbalanced form, Xi was shown by HUMARA assay to be derived exclusively [t(X:6)] or predominantly [ins (X;16)] from the derived X chromosome. We used a combination of immunolabelling and RNA/DNA fluorescence in situ hybridization to define the distribution of XIST RNA, deacetylated H4 and late-replicating DNA across the two derived X chromosomes in inactive form. Within the limits of the cytogenetic techniques employed, the results show complete coincidence of these three parameters, with all three being excluded from the autosomal component of the derived X chromosome.

Program evaluation: a value-added approach to hospital cost reduction

As the pace of provider integration and aggregation begins to diminish, many systems are looking for ways to get more value from their new organizations. Brett Turner, a principal with Hamilton/HMC, explains both broad-based and targeted approaches to evaluating programs to determine whether they should be continued.

Oral health care issues in HIV disease: developing a core curriculum for primary care physicians

BACKGROUND

Given the high occurrence of oral manifestations in patients infected with human immunodeficiency virus (HIV), the relative ease in recognizing these manifestations on physical examination, and their potential impact on the health care and quality of life in these patients, it is critical to provide adequate training for primary care physicians in this area.

METHODS

Based on a review of the published literature and the consensus of a national panel of primary care physicians and dentists with clinical and research expertise in this area, a core curriculum was developed for primary care physicians regarding oral health care issues in HIV disease.

RESULTS AND CONCLUSIONS

We describe the process of developing the core curriculum of knowledge, skills, and attitudes regarding oral health care issues in HIV disease. The final curriculum is in a format that allows for easy accessibility and is organized in a manner that is clinically relevant for primary care physicians.

Molecular cloning of Drosophila melanogaster cDNAs that encode a novel histone deacetylase dHDAC3

The steady-state level of histone acetylation in eukaryotes is established and maintained by multiple histone acetyltransferases (HATs) and histone deacetylases (HDACs) and affects both the structure and the function of chromatin. Histone deacetylases play a key role in the regulation of transcription, and form a highly conserved protein family in many eukaryotic species. Here we describe the cloning, sequencing and genetic mapping of two histone deacetylase genes in Drosophila melanogaster: dHDAC1 is essentially identical to the previously cloned D. melanogaster d-Rpd3 gene and dHDAC3, a novel gene, is orthologous to the human and the chicken (Gallus gallus) HDAC3 genes. The predicted amino acid sequence (438 aa) of dHDAC3 shows 58.1% identity with dHDAC1/d-Rpd3, the only previously known member of the HDAC family in this organism. The map positions on polytene chromosomes for dHDAC1 and dHDAC3 were determined as 64C1-6 and 83A3-4 respectively. A search for other dHDAC3-like genes failed to find other potential paralogues in D. melanogaster, but identified significant homologies with bacterial and fungal genes encoding enzymes that metabolise acetyl groups, and with genes for other hydrolyases such as carboxypeptidase. In addition, histone deacetylase activity in D. melanogaster nuclear extracts can be inhibited by high concentrations of zinc and activated by low concentrations, which is identical to the properties of bovine carboxypeptidase A. On the basis of sequence and functional similarities, we suggest that histone deacetylases are metal-substituted enzymes.

Prognostic significance of colony-stimulating factor receptor expression in ipsilateral breast cancer recurrence

The macrophage colony-stimulating factor receptor (CSF-1R), the product of the c-fms proto-oncogene, regulates normal proliferation and differentiation of macrophages and trophoblasts. Recent research found abnormal expression of CSF-1R in human carcinomas of the breast, endometrium, and ovary. Furthermore, activation of CSF-1R by its ligand has been shown to regulate invasiveness and anchorage-independent growth in breast carcinoma cells. To study the significance of CSF-1R expression in breast cancer, we designed a case-controlled immunohistochemical study. We chose 80 patients from a database of 1200 early stage I or II breast cancer patients treated with conservative surgery and radiation therapy. Expression of CSF-1R in the tumors of 40 patients who experienced an ipsilateral breast tumor recurrence (IBTR) as a primary site of relapse were compared with 40 patients who had not experienced an IBTR. The index and control patients were matched by age, clinical stage, nodal status, and follow-up. Paraffin-embedded sections were immunostained with antibodies directed toward CSF-1R. For the CSF-1R antibody, a total of 28 index cases (70%) demonstrated strong staining, whereas only 16 control cases (40%) demonstrated high immunoreactivity (P = 0.007). The CSF-1R antibody showed a positive correlation for local relapse, but no correlation was found between CSF-1R expression and distant metastasis. In summary, our findings provide evidence for the poor prognostic role of CSF-1R in IBTR.

Essential and redundant functions of histone acetylation revealed by mutation of target lysines and loss of the Gcn5p acetyltransferase

The Gcn5p histone acetyltransferase exhibits a limited substrate specificity in vitro. However, neither the specificity of this enzyme in vivo nor the importance of particular acetylated residues to transcription or cell growth are well defined. To probe these questions, we mutated specific lysines in the N-termini of histones H3 and H4 and examined the effects of these mutations in yeast strains with and without functional GCN5. We found that in vivo, GCN5 is required either directly or indirectly for the acetylation of several sites in H3 and H4 in addition to those recognized by the recombinant enzyme in vitro. Moreover, in the absence of GCN5, cells accumulate in G2/M indicating that Gcn5p functions are important for normal cell-cycle progression. Mutation of K14 in H3, which serves as the major target of recombinant Gcn5p acetylation in vitro, confers a strong, synthetic growth defect in gcn5 cells. Synergistic growth defects were also observed in gcn5 cells carrying mutations in lysine pairs (K8/K16 or K5/K12) in histone H4. Strikingly, simultaneous mutation of K14 in H3 and K8 and K16 in H4 to arginine, or deletion of either the H3 or the H4 N-terminal tail, results in the death of gcn5 cells. Mutation of these same three sites to glutamine is not lethal. Indeed, this combination of mutations largely bypasses the need for GCN5 for transcriptional activation by Gal4-VP16, supporting an important role for histone acetylation in Gcn5p-mediated regulation of transcription. Our data indicate that acetylation of particular lysines in histones H3 and H4 serves both unique and overlapping functions important for normal cell growth, and that a critical overall level of histone acetylation is essential for cell viability.

Transcriptional repression by the methyl-CpG-binding protein MeCP2 involves a histone deacetylase complex

Cytosine residues in the sequence 5'CpG (cytosine-guanine) are often postsynthetically methylated in animal genomes. CpG methylation is involved in long-term silencing of certain genes during mammalian development and in repression of viral genomes. The methyl-CpG-binding proteins MeCP1 and MeCP2 interact specifically with methylated DNA and mediate transcriptional repression. Here we study the mechanism of repression by MeCP2, an abundant nuclear protein that is essential for mouse embryogenesis. MeCP2 binds tightly to chromosomes in a methylation-dependent manner. It contains a transcriptional-repression domain (TRD) that can function at a distance in vitro and in vivo. We show that a region of MeCP2 that localizes with the TRD associates with a corepressor complex containing the transcriptional repressor mSin3A and histone deacetylases. Transcriptional repression in vivo is relieved by the deacetylase inhibitor trichostatin A, indicating that deacetylation of histones (and/or of other proteins) is an essential component of this repression mechanism. The data suggest that two global mechanisms of gene regulation, DNA methylation and histone deacetylation, can be linked by MeCP2.

Effect of neuromuscular blockers and opiates on the cerebrovascular response to endotracheal suctioning in adults with severe head injuries

BACKGROUND

Intracranial hypertension occurs in response to routine procedures such as endotracheal suctioning in patients with severe head injuries. In some patients, the intracranial pressure does not immediately return to baseline levels.

OBJECTIVES

To examine the effect of drug administration on cerebrovascular response to endotracheal suctioning in adults with severe head injuries.

METHODS

Seventy-one subjects were divided into 3 groups: those who received no drugs, those treated with opiates only (morphine sulfate and fentanyl citrate), and those treated with a neuromuscular blocking agent (vecuronium bromide) plus opiates. A controlled protocol involving 2 sequences of endotracheal suctioning that included hyperoxygenation, hyperinflation, and suctioning was used for all subjects. Two-way repeated-measures analyses of variance were done with type of drug as the between-subject factor and phase of suctioning as the within-subject factor. Survival analysis was used to compare the return of intracranial pressure to baseline levels among the 3 groups.

RESULTS

Changes in intracranial pressure were significantly smaller in subjects who received a neuromuscular blocking agent plus opiates than in subjects who did not receive any drugs or received opiates only. The greatest increase in intracranial pressure from baseline was in the first and second phases of suctioning. The 3 groups showed no significant difference in the return of intracranial pressure to baseline level.

CONCLUSIONS

Neuromuscular blockers attenuate the increases in intracranial pressure that occur with endotracheal suctioning. It is not known whether control of procedurally induced elevations in intracranial pressure affects long-term outcomes in adults with severe head injuries.