Synapses on axon collaterals of pyramidal cells are spaced at random intervals: a Golgi study in the mouse cerebral cortex

In this study we investigated the arrangement of synapses on local axon collaterals of Golgi-stained pyramidal neurons in the mouse cerebral cortex. As synaptic markers we considered axonal swellings visible at high magnification under the light microscope. Such axonal swellings coincide with synaptic boutons, as has been demonstrated in a number of combined light and electron microscopic studies. These studies also indicated that, in most cases, one bouton corresponds precisely to one synapse. Golgi-impregnated axonal trees of 20 neocortical pyramidal neurons were drawn with a camera lucida. Axonal swellings were marked on the drawings. Most swellings were ‘en passant’; occasionally, they were situated at the tip of short, spine-like processes. On axon collaterals, the average interval between swellings was 4.5 μm. On the axonal main stem, the swellings were always less densely packed than on the collaterals. Statistical analysis of the spatial distribution of the swellings did not reveal any special patterns. Instead, the arrangement of swellings on individual collaterals follows a Poisson distribution. Moreover, the same holds to a large extent for the entire collection of pyramidal cell collaterals. This suggests that a single Poisson process, characterized by only one rate parameter (number of synapses per unit length), describes most of the spatial distribution of synapses along pyramidal cell collaterals. These findings do not speak in favour of a pronounced target specificity of pyramidal neurons at the synaptic level. Instead, our results support a probabilistic model of cortical connectivity. Received: 6 June 1993/Accepted in revised form: 22 December 1993     

Complete and precise characterization of marker chromosomes by application of microdissection in prenatal diagnosis

A straightforward and extremely efficient reverse chromosome painting technique is described which allows the rapid and unequivocal identification of any cytogenetically unclassifiable chromosome rearrangement. This procedure is used to determine the origin of unknown marker chromosomes found at prenatal diagnosis. After microdissection of the marker chromosome and amplification of the dissected fragment by a degenerate oligonucleotide-primed polymerase chain reaction (DOP-PCR), fluorescence in situ hybridization (FISH) to aberrant and normal metaphase chromosomes with the marker-derived probe pool is performed. With this strategy, marker chromosomes present in amniotic fluid samples were successfully identified in three cases. The origin of the supernumerary markers was ascertained as deriving from 3p(p12-cen), 18p(pter-cen) and 9p(p12-cen), respectively. Since a specific FISH signal on chromosomes can be obtained within 2 working days using a probe generated without any pretreatment from one chromosomal fragment only and without additional image processing devices, this technique is considered to be highly suitable for routine application in pre- and postnatal cytogenetic analysis.     

Chemical bonding in carborane/aromatic co-polymers: a first-principles analysis of experimental photoemission spectra

First-principles density functional theory calculations have been used to study the relative stability and analyse the chemical bonding of novel cross-linked carborane polymers. Atomic charges with several population analysis methods based on fully relaxed structures were calculated to interpret the chemical binding energy shifts of XPS spectra of these boron carbide polymers. The results indicate that a base structure with one aromatic linking unit with carborane is energetically favoured. The linear relationship between experimental core-level photoemission binding energies and computational partial atomic charges from four population analysis methods (Mulliken, Hirshfeld, atoms-in-molecules (AIM) and natural bond order (NBO)) were analysed and the results indicate that cross-linking occurs at icosahedral B sites non-adjacent to icosahedral carbon sites, in agreement with recently reported experimental results. The role of basis set size in determining partial atomic charges was found to vary with population analysis method. Best linear correlations were identified with the more robust population analysis methods (Hirshfeld, AIM and NBO) with the AIM methods noted as being particularly sensitive to basis set size.     

Immunochip analysis identifies association of the RAD50/IL13 region with human longevity

Human longevity is characterized by a remarkable lack of confirmed genetic associations. Here, we report on the identification of a novel locus for longevity in the RAD50/IL13 region on chromosome 5q31.1 using a combined European sample of 3208 long‐lived individuals (LLI) and 8919 younger controls. First, we performed a large‐scale association study on 1458 German LLI (mean age 99.0 years) and 6368 controls (mean age 57.2 years) by targeting known immune‐associated loci covered by the Immunochip. The analysis of 142 136 autosomal single nucleotide polymorphisms (SNPs) revealed an Immunochip‐wide significant signal (P_Immunochip = 7.01 × 10^–9) for the SNP rs2075650 in the TOMM40/APOE region, which has been previously described in the context of human longevity. To identify novel susceptibility loci, we selected 15 markers with P_Immunochip < 5 × 10^–4 for replication in two samples from France (1257 LLI, mean age 102.4 years; 1811 controls, mean age 49.1 years) and Denmark (493 LLI, mean age 96.2 years; 740 controls, mean age 63.1 years). The association at SNP rs2706372 replicated in the French study collection and showed a similar trend in the Danish participants and was also significant in a meta‐analysis of the combined French and Danish data after adjusting for multiple testing. In a meta‐analysis of all three samples, rs2706372 reached a P‐value of P_{Immunochip+Repl} = 5.42 × 10^?7 (OR = 1.20; 95% CI = 1.12–1.28). SNP rs2706372 is located in the extended RAD50/IL13 region. RAD50 seems a plausible longevity candidate due to its involvement in DNA repair and inflammation. Further studies are needed to identify the functional variant(s) that predispose(s) to a long and healthy life.     

A classification of the New World species of Aster (Asteraceae)

In order effectively to list and comment on the results of cytological investigations inAster in a companion paper, a scheme of infrageneric classification is presented which utilizes the basic chromosome number as a pivotal diagnostic character. Reasons are stated as to why, with the exception ofUnamia Greene which is transferred toSolidago, and the commonly recognized generaLeucelene Greene,Machaeranthera Nees andXylorhiza Nutt., none of the segregate genera previously proposed or recorded in the literature is upheld. Instead, these taxa are being given subgeneric or sectional rank. Two additional subgenera are established to accommodate the species groups traditionally placed in “Aster proper,” which are characterized by having basic chromosome numbers ofx = 5 andx = 8, respectively. Altogether ten subgenera of the genusAster, five of them subdivided further into a total of 24 sections, are recognized as having representative species in the New World. All basionyms and type species are listed, and a number of new combinations and status changes are validated in accordance with the International Rules of Botanical Nomenclature. Where known (from literature and personal research), chromosome numbers are recorded for the species.     

ENVIRONMENTAL EFFECTS ON THE PERCENTAGE OF STAINABLE AND PRESUMED NORMAL POLLEN IN ASTER (COMPOSITAE)

Pollen stainability is often equated with pollen viability or fertility and is used by botanists to evaluate degree of hybridity among individuals of a plant population. Under certain conditions, however, the effects of meiotic irregularities resulting from hybridization may be masked by those of the environment. In the genus Aster high percentages of pollen stainability were obtained in most samples from plants flowering in the greenhouse, including hybrids of distantly related species. When grown outdoors, plants of the same clones frequently suffered significant reduction in the amounts of normal pollen produced. During the period of flower development, two climatic parameters were assessed, relative humidity and maximum/minimum temperatures. Fluctuations in relative humidity were considerable but of nearly equal amplitude both in the greenhouse and in the open field. Diurnal temperature fluctuations, however, were much less drastic in the greenhouse than outdoors. The differential percentages of stainable pollen observed are probably attributable to the sum of environmental factors, including hard rains and strong winds, rather than any single parameter. In the genus Aster high amounts of aborted pollen grains appear to be largely a reflection of sensitivity to unfavorable microclimatic conditions during the post-meiotic period of flower development, and data on pollen stainability cannot be employed as a measure of fertility or degree of hybridity.     

OBSERVATIONS ON THE SHAPE AND EXPOSURE OF STYLE BRANCHES IN THE ASTEREAE (COMPOSITAE)

A survey of over 30 species of Aster and 61 species in other genera of Astereae indicates that the somewhat flattened style branches of perfect disk florets characteristically unfold and spread in a pronate, rather than a supinate manner. While not exhibited in all genera (Baccharis and Conyza are among the exceptions), this phenomenon appears to be restricted to and, therefore, diagnostic for the tribe. The slender style branches of pistillate ray florets display the supinate expansion which is regularly observed in other tribes of Compositae.     

ICOS Mediates the Generation and Function of CD4+CD25+Foxp3+ Regulatory T Cells Conveying Respiratory Tolerance

Costimulatory molecules like ICOS are crucial in mediating T cell differentiation and function after allergen contact and thereby strongly affect the immunologic decision between tolerance or allergy development. In this study, we show in two independent approaches that interruption of the ICOS signaling pathway by application of a blocking anti-ICOSL mAb in wild-type (WT) mice and in ICOS(-/-) mice inhibited respiratory tolerance development leading to eosinophilic airway inflammation, mucus hypersecretion, and Th2 cytokine production in response to OVA sensitization. Respiratory Ag application almost doubled the number of CD4(+)Foxp3(+) regulatory T cells (Tregs) in the lung of WT mice with 77% of lung-derived Tregs expressing ICOS. In contrast, in ICOS(-/-) mice the number of CD4(+)CD25(+)Foxp3(+) Tregs did not increase after respiratory Ag application, and ICOS(-/-) Tregs produced significantly lower amounts of IL-10 than those of WT Tregs. Most importantly, in contrast to WT Tregs, ICOS(-/-) Tregs did not convey protection when transferred to "asthmatic" recipients demonstrating a strongly impaired Treg function in the absence of ICOS signaling. Our findings demonstrate a crucial role of ICOS for the generation and suppressive function of Tregs conveying respiratory tolerance and support the importance of ICOS as a target for primary prevention strategies.     

Cripto binds transforming growth factor beta (TGF-beta) and inhibits TGF-beta signaling

Cripto is a developmental oncoprotein and a member of the epidermal growth factor-Cripto, FRL-1, Cryptic family of extracellular signaling molecules. In addition to having essential functions during embryogenesis, Cripto is highly expressed in tumors and promotes tumorigenesis. During development, Cripto acts as an obligate coreceptor for transforming growth factor beta (TGF-beta) ligands, including nodals, growth and differentiation factor 1 (GDF1), and GDF3. As an oncogene, Cripto is thought to promote tumor growth via mechanisms including activation of mitogenic signaling pathways and antagonism of activin signaling. Here, we provide evidence supporting a novel mechanism in which Cripto inhibits the tumor suppressor function of TGF-beta. Cripto bound TGF-beta and reduced the association of TGF-beta with its type I receptor, TbetaRI. Consistent with its ability to block receptor assembly, Cripto suppressed TGF-beta signaling in multiple cell types and diminished the cytostatic effects of TGF-beta in mammary epithelial cells. Furthermore, targeted disruption of Cripto expression by use of small inhibitory RNA enhanced TGF-beta signaling, indicating that endogenous Cripto plays a role in restraining TGF-beta responses.