Autoantibodies against the serotoninergic 5-HT4 receptor and congenital heart block: a reassessment

The specificity of autoantibodies against the serotoninergic 5-HT4 receptor in congenital heart block has led to conflicting observations. In order to clarify the situation, a collaborative effort was undertaken to discover the reasons for these discrepancies and to reassess the importance of such autoantibodies by making use of the Research Registry for Neonatal Lupus. Sera from 128 patients (101 anti-SSA/Ro52 positive mothers among which 74 have children with congenital heart block (CHB), 9 anti-SSA/Ro52 negative patients of which 1 had a child with heart block and 18 healthy donors) were assessed in a single blind test using an ELISA coated with a 5-HT4 receptor-derived peptide. Discrepancies between previous observations in our two groups could be ascribed to small differences in the set up of the assay. Of the 75 sera from mothers of children with CHB, 12 were reactive with the 5-HT4 peptide. Four sera among which three were from 35 Ro52 negative mothers without affected children as well as 2 in the 18 controls were positive. Interestingly, in 1 mother with an isolated child with CHB but who had no detectable anti-SSA/Ro52 antibodies and 1 mother with a child with a structural heart block and no detectable antibodies to any component of SSA/Ro, reactivity with the 5-HT4 receptor was noted. While 5-HT4 receptor autoantibodies do not have the predictive value of anti-Ro52 autoantibodies, the presence of these antibodies in a minor subset of mothers whose children have CHB suggests an additional risk factor which may contribute to the pathogenesis of disease.     

Adrenaline and the plateau phase of the cardiac action potential

Summary Conduction block in heart cells by K⁺ rich, or Na⁺ depleted solutions can be overcome by adrenaline. In order to explain this phenomenon, the effect of adrenaline on the membrane resting and action potentials of cow Purkinje fibers was measured at various extracellular concentrations of Na⁺, K⁺ and Ca⁺⁺, in the presence of tetrodotoxin, Mn⁺⁺ and beta-receptor antagonists.It was found that adrenaline specifically increases the amplitude and duration of the plateau phase of the cardiac action potential. Plateu-like action potentials, without preceding Na⁺-spike, can be generated and conducted in an all-or-nothing way. In K⁺ rich solutions and under the influence of adrenaline, the depolarization proceeds in two steps. The first step corresponds to the Na⁺-spike. The second step or secondary depolarization corresponds to the plateau; it was not modified by changes of the membrane potential between –85 and –55 mV, or by reduction of extracellular Na⁺ ions, but was specifically blocked by Mn⁺⁺ ions and beta-receptor antagonists. Its amplitude increased by 17 mV for a tenfold change in extracellular Ca⁺⁺. Tetrodotoxin preferentially blocked the Na⁺-spike, but also slowed the rate of potential change during the secondary depolarization.The simplest explanation for the observed phenomena can be found in an increase of Ca⁺⁺ inward current under the influence of adrenaline. The existence of an inward Na⁺⁺ current, different in characteristics from the Na⁺ conductance during the fast upstroke, cannot be ruled out. Some data are in accord with a decrease in K⁺ conductance.     

Immunological Markers of the R4 Protein of Streptococcus agalactiae

This study focuses on immunological markers of R4, an important Streptococcus group B (GBS) protein. The results obtained by using rabbit antisera and purified proteins for antigens in enzyme-linked immunosorbent assay-based experiments provided evidence that R4 possesses two antigenic determinants. One of the determinants is shared with the alpha-like protein 3 (Alp3) of GBS, was named R4/Alp3 common, and was expressed by GBS, which possessed the Alp3-encoding gene alp3 or the R4-encoding gene rib. The other antigenic determinant was detected only in rib-positive GBS organisms and was named R4 specific. This determinant probably is an immunological marker unique to the R4 protein. Neither of the antigenic R4 determinants showed serological cross-reactivity with the GBS proteins Cα, Cβ, and R3 or with alpha-like protein 2. Of 60 clinical serotype III GBS strains, 56 (93%) isolates possessed the rib gene and 50 (89%) of the rib-positive isolates expressed levels of R4 detectable by antibody-based tests, consistent with R4 expression failure or low-level expression in ~10% of rib-positive GBS. alp3 was not detected in type III GBS but was possessed by six of eight type V strains and six of six type VIII strains. All alp3-positive strains were recognized by the R4/Alp3 common antibodies, but none of them were recognized by the R4-specific antibodies. NCTC 9828, a reference strain for R3 and R4, expressed the determinant R4/Alp3 common but not R4 specific. A monoclonal R4 antibody, previously considered to be R4 specific and used in GBS serotyping, targeted R4/Alp3 common and is thus not R4 specific. The results show that failure to discriminate between R4 specific and R4/Alp3 common by antisera designed for GBS serotyping can result in the false identification of Alp3 as R4 or vice versa, whereas anti-R4 antibodies targeting only the determinant R4 specific will detect only R4. Both R4 and Alp3 need further evaluation with respect to the immunobiological function of each distinct antigenic determinant, for instance, with regard to their potential as GBS vaccine components.     

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.     

Association between bone mineral density (DXA), body structure,and body composition in middle‐aged men

The association between bone mass, body structure, and body composition was explored in 156 men, 40 years of AGE . Bone mineral density (total body, lumbar spine, left arm, and left leg) was obtained by dual‐energy X‐ray absorptiometry (DXA; Hologic QDR 4500A). Body structure was determined from a battery of anthropometric dimensions with a principal components analysis. Body composition was estimated with DXA. From the 24 anthropometric dimensions, three components were extracted and identified as muscle, fat, and skeletal length. Significant correlations between the muscle component and all BMD measurements (r = 0.28–0.44) were obtained. Except for BMD of the left arm, which correlated significantly, but negatively, with the fat component (r = ?0.16), no significant relations were found between the fat component and BMD. There were significant correlations between lean mass, fat mass, and BMD measurements. The correlations were higher between lean mass and BMD (r = 0.22–0.44) than between fat mass and BMD (r = 0.08–0.24). The multiple regression analysis revealed that except for BMD of the left arm only lean mass or the muscle component, and not fat mass or the fat component, were independent predictors of BMD. It is concluded that the principal anthropometric determinant of BMD in middle‐aged men is lean mass or muscle. Am. J. Hum. Biol. 14:735–742, 2002. © 2002 Wiley‐Liss, Inc.     

The effect of sodium lauryl sulphate and triclosan on hamster cheek pouch mucosa

It has recently been shown that triclosan protects the human skin from the inflammation that may be caused by exposure to sodium lauryl sulphate (SLS). The aim of the present study was to examine whether triclosan can protect the hamster cheek pouch mucosa from the irritation caused by exposure to SLS. After four daily applications of a paste containing SLS, the epithelium of the hamster cheek pouch showed consistently prominent structural changes, especially basal hyperplasia, acanthosis, hypergranulosis, and hyperkeratosis. Identical morphological changes were also observed after applications of a paste containing SLS together with triclosan. In contrast, after applications of a paste containing triclosan alone, the cheek pouch mucosa revealed a histological structure essentially similar to the non-treated control mucosa. From these results, we may conclude that SLS, but not triclosan, irritates the hamster cheek pouch epithelium. Moreover, triclosan does not protect the cheek pouch mucosa against structural changes induced by SLS. It must be taken into account that triclosan does not always offer protection against the side-effects of SLS.     

Near-haploid clones in a malignant fibrous histiocytoma

Near-haploid solid tumors are very rare. In a storiform-pleomorphic malignant fibrous histiocytoma (MFH) of bone, we found three cell populations: one with a near-haploid, a second with a near-diploid, and a third with a near-tetraploid chromosome number. The near-haploid cells had few structural rearrangements: i(12p) and t(13q21q) in one clone, and these two and an additional t(19;?)(p11;?) in another clone. One structurally normal copy of all chromosomes was also present, except that the only chromosome 13 was involved in the t(13q21q). There were also two near-diploid clones, one without the t(19;?) and one with a single copy of this derivative chromosome. This is the first MFH reported to have a near-haploid modal chromosome number, and also the first tumor with i(12p) among bone and soft tissue tumors.     

Trisomy 5 and loss of the Y chromosome as the sole cytogenetic anomalies in a cavernous hemangioma/angiosarcoma

Cytogenetic analysis of a cavernous hemangioma with transition to angiosarcoma revealed the mosaic karyotype 47, XY,+5/46, X,-Y,+5/45, X,-Y/46, XY. No cytogenetically analyzed hemangiomas or angiosarcomas have been reported before.