Functional and antigenic characterization of human, rhesus macaque, pigtailed macaque, and murine DC-SIGN

DC-SIGN, a type II membrane protein with a C-type lectin binding domain that is highly expressed on mucosal dendritic cells (DCs) and certain macrophages in vivo, binds to ICAM-3, ICAM-2, and human and simian immunodeficiency viruses (HIV and SIV). Virus captured by DC-SIGN can be presented to T cells, resulting in efficient virus infection, perhaps representing a mechanism by which virus can be ferried via normal DC trafficking from mucosal tissues to lymphoid organs in vivo. To develop reagents needed to characterize the expression and in vivo functions of DC-SIGN, we cloned, expressed, and analyzed rhesus macaque, pigtailed macaque, and murine DC-SIGN and made a panel of monoclonal antibodies (MAbs) to human DC-SIGN. Rhesus and pigtailed macaque DC-SIGN proteins were highly similar to human DC-SIGN and bound and transmitted HIV type 1 (HIV-1), HIV-2, and SIV to receptor-positive cells. In contrast, while competent to bind virus, murine DC-SIGN did not transmit virus to receptor-positive cells under the conditions tested. Thus, mere binding of virus to a C-type lectin does not necessarily mean that transmission will occur. The murine and macaque DC-SIGN molecules all bound ICAM-3. We mapped the determinants recognized by a panel of 16 MAbs to the repeat region, the lectin binding domain, and the extreme C terminus of DC-SIGN. One MAb was specific for DC-SIGN, failing to cross-react with DC-SIGNR. Most MAbs cross-reacted with rhesus and pigtailed macaque DC-SIGN, although none recognized murine DC-SIGN. Fifteen of the MAbs recognized DC-SIGN on DCs, with MAbs to the repeat region generally reacting most strongly. We conclude that rhesus and pigtailed macaque DC-SIGN proteins are structurally and functionally similar to human DC-SIGN and that the reagents that we have developed will make it possible to study the expression and function of this molecule in vivo.     

Isolation of an actin polymerization stimulator from bovine thyroid plasma membranes

An actin polymerization stimulator was purified from bovine thyroid plasma membranes by DNase I affinity column chromatography. Although the molecular weight of the protein was about 42,000 (42K) by sodium dodecyl sulfate polyacrylamide gel electrophoresis, it did not comigrate with actin. In the presence of 30 mM KCl, the 42K protein facilitated formation of actin filaments when analyzed by a centrifugation method, accelerated the initial phase of actin polymerization as measured in an Ostwald viscometer and increased the length of filaments as shown by electron microscopy. The 42K protein also accelerated the initial phase of actin polymerization in the presence of 100 mM KCl and 2 mM MgCl₂ but did not affect the final viscosity. The effect of the 42K protein was diminished by 5 uM cytochalasin B or 1 uM cytochalasin D. This 42K protein may anchor actin filaments onto the thyroid plasma membrane.     

Molecular size of nerve growth factor in dilute solution.

Nerve growth factor (NGF) is a protein composed of two identical chains of mass 13,259. An analysis of the sedimentation equilibrium, sedimentation velocity, and gel filtration behavior of dilute solutions of NGF indicates the existence of a rapidly reversible monomer in equilibrium dimer equilibrium and that the association constant K for the reaction at neutral pH is 9.4 X 10(6)M-1. Reaction mixtures consist of equal concentrations of monomer and dimer at a total protein concentration as high as 1.4 mug/ml, and at 1 ng/ml, monomer accounts for greater than 99% of the total. The latter concentration is 20 to 30 times that required for the biological activity of NGF. Several lines of evidence suggest that the dimerization reaction is highly stereospecific, although its biological significance is not known.     

The influence and biomechanical role of cartilage split line pattern on tibiofemoral cartilage stress distribution during the stance phase of gait

This study presents an evaluation of the role that cartilage fibre ‘split line’ orientation plays in informing femoral cartilage stress patterns. A two-stage model is presented consisting of a whole knee joint coupled to a tissue-level cartilage model for computational efficiency. The whole joint model may be easily customised to any MRI or CT geometry using free-form deformation. Three ‘split line’ patterns (medial–lateral, anterior–posterior and random) were implemented in a finite element model with constitutive properties referring to this ‘split line’ orientation as a finite element fibre field. The medial–lateral orientation was similar to anatomy and was derived from imaging studies. Model predictions showed that ‘split lines’ are formed along the line of maximum principal strains and may have a biomechanical role of protecting the cartilage by limiting the cartilage deformation to the area of higher cartilage thickness.     

Einige neue oder bemerkenswerte Flechten mit gyalectoiden Apothecien von Nord-Indien und Nepal

This paper presents the results of taxonomic investigation of 8 species of lichens with gyalectoid apothecia collected in North-India and Nepal. Four species are recognized as new:Dimerella isidiata (sp. nova),D. nepalensis (sp. nova),Gyalideopsis lithophila (sp. nova) andRamonia nepalensis (sp. nova). Four species are reported for the first time from Nepal:Coenogonium moniliforme, Gyalectidium caucasicum, Gyalidea lecideopsis andG. scutellaris.     

Characterization of the cell adhesion molecules L1, N-CAM and J1 in the mouse intestine.

To gain insight into the cellular and molecular mechanisms underlying epithelial cell surface interactions in the adult mouse intestine, we have characterized the cell adhesion molecules L1, N-CAM and J1 by immunocytological, biochemical and cell biological methods. Whereas N-CAM and J1 expression was found to be confined to the mesenchymal and neuroectodermally-derived parts of the intestine, L1 was localized in the proliferating epithelial progenitor cells of crypts, but not in the more differentiated epithelial cells of villi. L1 was detected in crypt cells by Western blot analysis in the molecular forms characteristic of peripheral neural cells, with apparent mol. wts of 230, 180 and 150 kd. Aggregation of single, enriched crypt, but not villus cells, was strongly inhibited in the presence of Fab fragments of polyclonal L1 antibodies. These observations show that L1 is not confined to the nervous system and that it may play a functional role in the histogenesis of the intestine in the adult animal.     

Light Harvesting and State Transitions in Cyanobacteria

Cyanobacteria are oxygenic phototrophic prokaryotes and are considered to be the ancestors of chloroplasts. Their photosynthetic machinery is functionally equivalent in terms of primary photochemistry and photosynthetic electron transport. Fluorescence measurements and other techniques indicate that cyanobacteria, like plants, are capable of redirecting pathways of excitation energy transfer from light harvesting antennae to both photosystems. Cyanobacterial cells can reach two energetically different states, which are defined as “State 1” (obtained after preferential excitation of photosystem I) and “State 2” (preferential excitation of photosystem II). These states can be distinguished by static and time resolved fluorescence techniques. One of the most important conclusions reached so far is that the presence of both photosystems, as well as certain antenna components, are necessary for state transitions to occur. Spectroscopic evidence suggests that changes in the coupling state of the light harvesting antenna complexes (the phycobilisomes) to both photosystems occur during state transitions. The finding that the phycobilisome complexes are highly mobile on the surface of the thylakoid membrane (the mode of interaction with the thylakoid membrane is essentially unknown), has led to the proposal that they are in dynamic equilibrium with both photosystems and regulation of energy transfer is mediated by changes in affinity for either photosystem.     

The homeodomain LIM protein Isl-1 is expressed in subsets of neurons and endocrine cells in the adult rat.

We have used immunocytochemical methods to localize the homeodomain LIM protein Isl-1 in the adult rat. Isl-1 immunoreactivity is expressed in polypeptide hormone-producing cells of the endocrine system, in neurons of the peripheral nervous system, and in a subset of brain nuclei. Isl-1 is also expressed in a subset of motoneurons in the spinal cord and brain stem, but not in regions of the central nervous system involved in sensory function or in neocortical areas. The pattern of expression of Isl-1 suggests that this gene may be involved in the specification and maintenance of differentiated phenotypical properties of these cells.     

Segment-specific generation of Drosophila Capability neuropeptide neurons by multi-faceted Hox cues

In the Drosophila ventral nerve cord, the three pairs of Capability neuropeptide-expressing Va neurons are exclusively found in the second, third and fourth abdominal segments (A2–A4). To address the underlying mechanisms behind such segment-specific cell specification, we followed the developmental specification of these neurons. We find that Va neurons are initially generated in all ventral nerve cord segments and progress along a common differentiation path. However, their terminal differentiation only manifests itself in A2–A4, due to two distinct mechanisms: segment-specific programmed cell death (PCD) in posterior segments, and differentiation to an alternative identity in segments anterior to A2. Genetic analyses reveal that the Hox homeotic genes are involved in the segment-specific appearance of Va neurons. In posterior segments, the Hox gene Abdominal-B exerts a pro-apoptotic role on Va neurons, which involves the function of several RHG genes. Strikingly, this role of Abd-B is completely opposite to its role in the segment-specific apoptosis of other classes of neuropeptide neurons, the dMP2 and MP1 neurons, where Abd-B acts in an anti-apoptotic manner. In segments A2–A4 we find that abdominal A is important for the terminal differentiation of Va cell fate. In the A1 segment, Ultrabithorax acts to specify an alternate Va neuron fate. In contrast, in thoracic segments, Antennapedia suppresses the Va cell fate. Thus, Hox genes act in a multi-faceted manner to control the segment-specific appearance of the Va neuropeptide neurons in the ventral nerve cord.