Translating chemometric analysis into physiological insights from in vivo confocal Raman spectroscopy of the human stratum corneum

The superficial layer of the skin, the stratum corneum (SC), consists of corneocytes surrounded by lipid regions and acts as a protective barrier for the body against water loss, toxic agents and microorganisms. As most substances permeate the stratum corneum through the lipid regions, lipid organization is considered crucial for the skin barrier function. Here, we investigate the potential of in vivo confocal Raman spectroscopy to describe the composition and organization of the SC. Confocal Raman spectroscopy is finding increasing use in the characterization of skin in biomedical, pharmaceutical and cosmetic applications. In this work, we analyze the spectra using chemometric methods and obtain principal components that correspond to the primary skin constituents: protein (keratin), natural moisturizing factor (NMF), water and lipid contributions in both ordered (orthorhombic) and disordered structural organization. By identifying these important components of the SC, these results highlight the utility of this in vivo, non-invasive, and depth resolved tool at the forefront of skin research.     

Small-angle neutron and X-ray scattering analysis of the supramolecular organization of rhodopsin in photoreceptor membrane

The supramolecular organization of the visual pigment rhodopsin in the photoreceptor membrane remains contentious. Specifically, whether this G protein-coupled receptor functions as a monomer or dimer remains unknown, as does the presence or absence of ordered packing of rhodopsin molecules in the photoreceptor membrane. Completely opposite opinions have been expressed on both issues. Herein, using small-angle neutron and X-ray scattering approaches, we performed a comparative analysis of the structural characteristics of the photoreceptor membrane samples in buffer, both in the outer segment of photoreceptor cells, and in the free photoreceptor disks. The average distance between the centers of two neighboring rhodopsin molecules was found to be ~5.8 nm in both cases. The results indicate an unusually high packing density of rhodopsin molecules in the photoreceptor membrane, but molecules appear to be randomly distributed in the membrane without any regular ordering.     

Demography,group composition,and dispersal in wild cotton-top tamarin (Saguinus oedipus) groups

Groups of individually marked cotton-top tamarins (Saguinus oedipus), located in La Reserva Forestal Protectora Serranía de Coraza-Montes de María in Colosó Colombia, were studied over a period of 5 years. Data on group composition, stability, birthing seasons, and dispersal patterns are used to examine the reproductive strategies and tactics used by males and females. Both monogamous groups and groups containing two pregnant females have been observed. All groups contained at least one adult female and male, with several groups containing several adult males and females. Both males and females dispersed to neighboring groups, and there were no sex differences in rates of emigration. Males were more likely to immigrate into a new group following the death/emigration of a resident male. Females appeared to tolerate immigrating females but would actively defend their breeding position during fertile periods. © 1996 Wiley-Liss, Inc.     

Structural conservation of the transposon Tam3 family in Antirrhinum majus and estimation of the number of copies able to transpose

We have investigated the organization of the transposon Tam3 family in Antirrhinum majus. Genomic hybridization experiments and characterization of 40 independent Tam3 clones isolated from an A. majus plant revealed that the Tam3 family is quite conserved and the copy sizes are uniform. We did not find any copy with a deleted internal sequence, unlike what is usually observed in other transposons. This exceptionally conserved structure of the Tam3 family was confirmed by PCR and sequencing analyses. Sequencing analysis identified eight copies with sequences completely identical to that of the Tam3 transposase gene. These results suggested that a considerable number of autonomous Tam3 copies are present in the genome of A. majus. Among 24 copies which are surrounded by single copy regions of the genome, 14 copies are present as specific insertions in the line which we used, but absent in other lines. These copies are therefore predicted to be movable. If this ratio is the same for all Tam3 copies in a genome, then a maximum of 60% of the copies are estimated to be movable in the genome. The relatively high frequency of gene tagged by Tam3 might reflect the large number of movable copies in the genome.     

Odontoblasts induced from mesenchymal cells of murine dental papillae in three-dimensional cell culture

In an organ culture system under a three-dimensional microenvironment that provides the conditions needed for odontoblast differentiation, a row of odontoblasts can be induced (Kikuchi et al. 1996, 2001). Therefore, in a newly designed three-dimensional cell culture system that fulfils the conditions necessary for odontoblast differentiation (Kikuchi et al. 2002), we examined whether dental papilla cells in rat mandibular incisors could differentiate into tubular dentine-forming cells. In our previously established organ culture system, CM-Dil-labeled cells that were microinjected into isolated dental papillae were replaced by a row of odontoblasts. In a three-dimensional cell culture system, which consists of two kinds of type I collagen in the upper layer over multi-layered cells seeded onto collagen containing Matrigel in the lower layer and which acts as a structural meshwork, dental papilla cells were incubated as multi-layered cells in an artificial extracellular matrix (ECM). The cells aggregated to form a cell mass and invaginated as a cell mass into the ECM. The cells also extended fine fibrillar processes into the ECM. With regard to invagination, the proteolytic activities of matrix metalloproteinase-2 (MMP-2)/membrane type 1-matrix metalloproteinase (MT 1-MMP) were observed on the outer multi-layers of cells within a cell mass adjacent to the ECM. The cell mass progressively shrank to about one-half to one-third of its original diameter and was organized as a tissue surrounded by a newly secreted ECM, like dental pulp-dentine. The cells adjacent to the secreted ECM were constructed as a row of polarized columnar cells. They extended slender processes into the new ECM, which is characteristic of tubular matrix. Dentine sialophosphoprotein (DSPP) and dentine matrix protein 1 (DMP 1) genes, which are specific for odontoblast differentiation, were expressed in an aggregated cell mass where tubular matrix-forming cells were induced. Furthermore, the tubular matrix became mineralized under prolonged culture. These results imply that the putative progenitor cells/stem cells residing in dental papillae can differentiate into odontoblasts under appropriate conditions in vitro.     

A CAF-1 dependent pool of HP1 during heterochromatin duplication

To investigate how the complex organization of heterochromatin is reproduced at each replication cycle, we examined the fate of HP1-rich pericentric domains in mouse cells. We find that replication occurs mainly at the surface of these domains where both PCNA and chromatin assembly factor 1 (CAF-1) are located. Pulse-chase experiments combined with high-resolution analysis and 3D modeling show that within 90 min newly replicated DNA become internalized inside the domain. Remarkably, during this time period, a specific subset of HP1 molecules (alpha and gamma) coinciding with CAF-1 and replicative sites is resistant to RNase treatment. Furthermore, these replication-associated HP1 molecules are detected in Suv39 knockout cells, which otherwise lack stable HP1 staining at pericentric heterochromatin. This replicative pool of HP1 molecules disappears completely following p150CAF-1 siRNA treatment. We conclude that during replication, the interaction of HP1 with p150CAF-1 is essential to promote delivery of HP1 molecules to heterochromatic sites, where they are subsequently retained by further interactions with methylated H3-K9 and RNA.