Protein diffusion in crowded electrolyte solutions

We report on a combined cold neutron backscattering and spin-echo study of the short-range and long-range nanosecond diffusion of the model globular protein bovine serum albumin (BSA) in aqueous solution as a function of protein concentration and NaCl salt concentration. Complementary small angle X-ray scattering data are used to obtain information on the correlations of the proteins in solution. Particular emphasis is put on the effect of crowding, i.e. conditions under which the proteins cannot be considered as objects independent of each other. We thus address the question at which concentration this crowding starts to influence the static and in particular also the dynamical behaviour. We also briefly discuss qualitatively which charge effects, i.e. effects due to the interplay of charged molecules in an electrolyte solution, may be anticipated. Both the issue of crowding as well as that of charge effects are particularly relevant for proteins and their function under physiological conditions, where the protein volume fraction can be up to approximately 40% and salt ions are ubiquitous. The interpretation of the data is put in the context of existing studies on related systems and of existing theoretical models.     

Die submikroskopische Struktur der Assimilatleitbahnen von Polytrichum commune

Summary In the young part of the stem of Polytrichum commune the protoplasts of the two types of conducting cells, the leptoids and parenchyma cells, are nearly identically equipped with cell organelles and cytoplasmic structures. Both types contain a nucleus, chloroplasts, mitochondria, and dictyosomes. The endoplasmic reticulum builds characteristic cisterns in form of hollow cylinders extending from one end wall to the other. The cisterns are connected with many plasmodesmata, which occur only in the end walls. Leptoids have oblique end walls with 16 to 20 plasmodesmata per m², and parenchyma cells show cross walls perpendicular to the axis with 9 to 12 plasmodesmata per m².Since the leptoids are supposed to be the pathways for the longitudinal transport of assimilates (Eschrich and Steiner, 1967, 1968), it is of interest that early in their development these elements undergo a change in their protoplasmatic structure. Two to 3 cm below the apical cell the protoplasts degenerate and show lysosome-like structures. The endoplasmic reticulum and other structures are deformed or dissolved; the plasmodesmata are constricted by callose deposits. At the same level the parenchyma cells still retain the original structure of their protoplasts.Thus, assimilates moving upward in one row of leptoids may penetrate the whole lumen of the leptoids at lower levels, but they are restricted to the cisterns of the endoplasmic reticulum at higher levels of the stem.     

Gating in iodate-modified single cardiac Na+ channels

Summary Elementary Na⁺ currents were recorded at 19°C during 220-msec lasting step depolarizations in cell-attached and inside-out patches from cultured neonatal rat cardiocytes in order to study the modifying influence of iodate, bromate and glutaraldehyde on single cardiac Na⁺ channels.Iodate (10 mmol/liter) removed Na⁺ inactivation and caused repetitive, burst-like channel activity after treating the cytoplasmic channel surface. In contrast to normal Na⁺ channels under control conditions, iodate-modified Na⁺ channels attain two conducting states, a short-lasting one with a voltage-independent lifetime close to 1 msec and, likewise tested between –50 and +10 mV, a long-lasting one being apparently exponentially dependent on voltage. Channel modification by bromate (10 mmol/liter) and glutaraldehyde (0.5 mmol/liter) also included the occurrence of two open states. Also, burst duration depended apparently exponentially on voltage and increased when shifting the membrane in the positive direction, but there was no evidence for two bursting states. Chemically modified Na⁺ channels retain an apparently normal unitary conductance (12.8±0.5 pS). Of the two substates observed, one of them is remarkable in that it is mostly attained from full-state openings and is very short living in nature; the voltage-independent lifetime was close to 2 msec. Despite removal of inactivation, open probability progressively declined during membrane depolarization. The underlying deactivation process is strongly voltage sensitive but, in contrast to slow Na⁺ inactivation, responds to a voltage shift in the positive direction with a retardation in kinetics. Chemically modified Na⁺ channels exhibit a characteristic bursting state much shorter than in DPI-modified Na⁺ channels, a difference not consistent with the hypothesis of common kinetic properties in noninactivating Na⁺ channels.     

Distal deletion of the long arm of chromosome number 1 (q43-->qter) associated with severe mental retardation and a nonspecific dysmorphic syndrome.

A 6 8/12-year-old girl with severe mental retardation, multiple congenital malformations and a de novo distal deletion of the long arm of chromosome 1 [del 1 (q43-->qter)] is here described. A review of the reported patients does not allow to distinguish different phenotypes related to distal deletion 1q42 and/or 1q43.     

Molecular analysis of theArabidopsis pattern formation geneGNOM: gene structure and intragenic complementation

TheGNOM gene is required for pattern formation along the main body axis of the embryo in the flowering plantArabidopsis thaliana. Mutations in theGNOM gene alter the asymmetric division of the zygote and interfere with the formation of distinct apical-basal regions in the developing embryo. We have isolated theGNOM gene by positional cloning, characterised its structure and determined the molecular lesions in mutant alleles. Although the predicted 163 kDa GNOM protein has a conserved domain in common with the yeast secretory protein Sec7p, it is most closely related in size and overall similarity to the product of the yeastYEC2 gene, which is not essential for cell viability. Four fully complementinggnom alleles carry missense mutations in conserved regions, seven partially complementing alleles have premature stop codon mutations and two non-complementing alleles have splice-site lesions. Our results suggest that the GNOM protein acts as a complex of identical subunits and that partial complementation may involve low levels of full-length protein generated by inefficient translational read-through.Communicated by H. Saedler     

Enhancing the structural diversity between forest patches—A concept and real-world experiment to study biodiversity,multifunctionality and forest resilience across spatial scales

Intensification of land use by humans has led to a homogenization of landscapes and decreasing resilience of ecosystems globally due to a loss of biodiversity, including the majority of forests. Biodiversity–ecosystem functioning (BEF) research has provided compelling evidence for a positive effect of biodiversity on ecosystem functions and services at the local (α-diversity) scale, but we largely lack empirical evidence on how the loss of between-patch β-diversity affects biodiversity and multifunctionality at the landscape scale (γ-diversity). Here, we present a novel concept and experimental framework for elucidating BEF patterns at α-, β-, and γ-scales in real landscapes at a forest management-relevant scale. We examine this framework using 22 temperate broadleaf production forests, dominated by Fagus sylvatica. In 11 of these forests, we manipulated the structure between forest patches by increasing variation in canopy cover and deadwood. We hypothesized that an increase in landscape heterogeneity would enhance the β-diversity of different trophic levels, as well as the β-functionality of various ecosystem functions. We will develop a new statistical framework for BEF studies extending across scales and incorporating biodiversity measures from taxonomic to functional to phylogenetic diversity using Hill numbers. We will further expand the Hill number concept to multifunctionality allowing the decomposition of γ-multifunctionality into α- and β-components. Combining this analytic framework with our experimental data will allow us to test how an increase in between patch heterogeneity affects biodiversity and multifunctionality across spatial scales and trophic levels to help inform and improve forest resilience under climate change. Such an integrative concept for biodiversity and functionality, including spatial scales and multiple aspects of diversity and multifunctionality as well as physical and environmental structure in forests, will go far beyond the current widely applied approach in forestry to increase resilience of future forests through the manipulation of tree species composition.     

Evolution of 28S Ribosomal DNA in Chaetognaths: Duplicate Genes and Molecular Phylogeny

The chaetognaths are an extraordinarily homogeneous phylum of animals at the morphological level, with a bauplan that can be traced back to the Cambrian. Despite the attention of zoologists for over two centuries, there is little agreement on classification within the phylum. We have used a molecular biological approach to investigate the phylogeny of extant chaetognaths. A rapidly evolving expansion segment toward the 5′ end of 28S ribosomal DNA (rDNA) was amplified using the polymerase chain reaction (PCR), cloned, and sequenced from 26 chaetognath samples representing 18 species. An unusual finding was the presence of two distinct classes of 28S rDNA gene in chaetognaths; our analyses suggest these arose by a gene (or gene cluster) duplication in a common ancestor of extant chaetognaths. The two classes of chaetognath 28S rDNA have been subject to different rates of molecular evolution; we present evidence that both are expressed and functional. In phylogenetic reconstructions, the two classes of 28S rDNA yield trees that root each other; these clearly demonstrate that the Aphragmophora and Phragmophora are natural groups. Within the Aphragmophora, we find good support for the groupings denoted Solidosagitta, Parasagitta, and Pseudosagitta. The relationships between several well-supported groups within the Aphragmophora are uncertain; we suggest this reflects rapid, recent radiation during chaetognath evolution. Received: 19 March 1996 / Accepted: 5 August 1996     

Interstitial deletion (2)(p13p15)

Summary A dysmorphic 5-year-old girl with severe growth and mental deficiency was studied. She presented a de novo interstitial 2p deletion. Karyotype: 46,XX,del(2)(p13p15).     

Madelung deformity as a pathognomonic feature of the onycho-osteodysplasia syndrome.

On the occasion of the observation of the Onycho-osteo-dysplasia syndrome (HOOD syndrome--Nail-Patella syndrome) in a 4-generation family we were impressed by the presence of a Madelung deformity in the four examined family members. A critical review of the literature showed that a true Madelung deformity was present in a great number of previously reported patients but that no specific attention was given to this apparently important symptom.