Second-harmonic generation from organic molecules incorporated in sol-gel matrices

Orientation of optically nonlinear organic molecules inside sol-gel matrices upon application of an external D.C. electrical field is demonstrated for the first time. The quadratic nonlinear response of silicon oxide or transition metal oxide based gels containing organic molecules has been determined from Electric Field Induced Second Harmonic (EFISH) measurements. Large concentrations of Optically Nonlinear Organic Molecules (ONOM) have been either incorporated inside the macromolecular network or chemically bonded to the oxide backbone of the gels. These results demonstrate the feasibility of permanently poled doped sol-gel matrices. Moreover, EFISH measurements performed on organic molecules appear to be a useful tool for monitoring the changes occurring during sol-gel transformations.     

Quelques données ultrastructurales sur un myoépithélium: le pharynx d'un Bryozoaire

Résumé L'épithélium pharyngien d'Alcyonidium polyoum possède des cellules pourvues d'une très grande vacuole. L'incompressibilité du liquide vacuolaire permet un élargissement brusque de l'organe lors de la contraction du manchon musculaire strié qui enserre cette vacuole. Les fibres musculaires sont insérées sur le plasmalemme apical par des filaments unitifs. Le point d'attache est relié à la lame amorphe du cell-coat qui entoure les microvillosités par des fibrilles, réalisant probablement une liaison mécamique plus efficace. Le reticulum sarcoplasmique porte des ribosomes. Le cytoplasme apical renferme des vésicules de diverses catégories.

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Some ultrastructural data about a myoepithelium: The pharynx of a bryozoan

Summary Pharyngeal cells of Alcyonidium polyoum (Bryozoa) are provided with very large vacuoles. Each vacuole is enveloped by a thin layer of striated muscle, whose contraction enlarges the organ. Filaments join the muscular elements to the apical plasmalemma. This point of muscular insertion is connected by fibrils with the amorphic lamina of cell-coat which surrounds the microvilli. Ribosomes are often found on dyads. Various vesicles are located in the apical cytoplasm.

     

Basement membrane protein and matrix metalloproteinase deregulation in engineered human oral mucosa following infection with Candida albicans.

A variety of morphological changes in the basement membrane (BM) are known to occur in inflammatory diseases. Modifications of the BM can be associated with significant changes in protein content. Candida albicans (C. albicans) is normally a commensal organism and is a member of the natural flora of a large number of healthy individuals. However, under certain conditions, C. albicans can invade host tissues, causing inflammation and tissue damage. The aim of this study was to investigate the effect of C. albicans on the expression and production of structural (laminin-5 and type IV collagen) and inflammatory [matrix metalloproteinases (MMPs) and their inhibitors] proteins by human oral epithelial cells. Using engineered normal human oral mucosa infected with 10(5) C. albicans/cm2 for different periods of time, we were able to demonstrate that this yeast promotes significant laminin-5 and type IV collagen gene activation and protein secretion. These effects were accompanied by MMP-2 and MMP-9 gene activation. Interestingly, only the levels of active MMP-9 rose. The increase in MMP levels was paralleled by a decrease in the secretion of type 2 matrix metalloproteinase tissue inhibitors (TIMP-2). Our results demonstrated that C. albicans has a significant effect on tissue structure through BM protein and MMP modulation. This might help C. albicans overcome the mechanical and biological defenses of the tissue and allow it to disseminate, causing severe infections. If C. albicans uses MMPs (mainly MMP-9) to disseminate, inhibition of this protease could be of interest in treating a variety of inflammatory disorders, including oral candidiasis.     

Potent and specific blockade by AH 22216 of histamine-H2-receptor-mediated acid secretion in isolated rabbit gastric cells

AH 22216 is a new histamine-H₂-receptor antagonist which possesses a triazole ring. When compared to cimetidine, AH 22216 is about 100 times more potent (Ki = 0.21×10^–8 M) in inhibiting histamine-stimulated acid secretion in isolated rabbit gastric cells. These two antihistamines have no effect on carbachol-stimulated acid secretion in the system. The data indicate that AH 22216 interacts directly and specifically on the gastric H₂-receptor of the parietal cell and are consistent with the reported pharmacological potencies of AH 22216 and cimetidine on histamine-induced gastric-acid secretion in vivo. AH 22216 could thus be a useful therapeutic agent in patients with peptic ulcers.     

The Rab11-family interacting proteins reveal selective interaction of mammalian recycling endosomes with the Toxoplasma parasitophorous vacuole in a Rab11- and Arf6-dependent manner

After mammalian cell invasion, the parasite Toxoplasma multiplies in a self-made membrane-bound compartment, the parasitophorous vacuole (PV). We previously showed that Toxoplasma interacts with many host cell organelles, especially from recycling pathways, and sequestrates Rab11A and Rab11B vesicles into the PV. Here, we examine the specificity of host Rab11 vesicle interaction with the PV by focusing on the recruitment of subpopulations of Rab11 vesicles characterized by different effectors, for example, Rab11-family interacting roteins (FIPs) or Arf6. Our quantitative microscopic analysis illustrates the presence of intra-PV vesicles with FIPs from class I (FIP1C, FIP2, FIP5) and class II (FIP3, FIP4) but to various degrees. The intra-PV delivery of vesicles with class I, but not class II, FIPs is dependent on Rab11 binding. Cell depletion of Rab11A results in a significant decrease in intra-PV FIP5, but not FIP3 vesicles. Class II FIPs also bind to Arf6, and we observe vesicles associated with FIP3-Rab11A or FIP3-Arf6 complexes concomitantly within the PV. Abolishing FIP3 binding to both Rab11 and Arf6 reduces the number of intra-PV FIP3 vesicles. These data point to a selective process of mammalian Rab11 vesicle recognition and scavenging mediated by Toxoplasma, suggesting that specific parasite PV proteins may be involved in these processes.     

Peptides of type II collagen can induce the cleavage of type II collagen and aggrecan in articular cartilage.

The objective of this study was to determine whether a fragment(s) of type II collagen can induce cartilage degradation. Fragments generated by cyanogen bromide (CB) cleavage of purified bovine type II collagen were separated by HPLC. These fragments together with selected overlapping synthetic peptides were first analysed for their capacity to induce cleavage of type II collagen by collagenases in chondrocyte and explant cultures of healthy adult bovine articular cartilage. Collagen cleavage was measured by immunoassay and degradation of proteoglycan (mainly aggrecan) was determined by analysis of cleavage products of core protein by Western blotting. Gene expression of matrix metalloproteinases MMP-13 and MMP-1 was measured using Real-time PCR. Induction of denaturation of type II collagen in situ in cartilage matrix with exposure of the CB domain was identified with a polyclonal and monoclonal antibodies that only react with this domain in denatured but not native type II collagen. As well as the mixture of CB fragments and peptide CB12, a single synthetic peptide CB12-II (residues 195-218), but not synthetic peptide CB12-IV (residues 231-254), potently and consistently induced in explant cultures at 10 microM and 25 microM, in a time, cell and dose dependent manner, collagenase-induced cleavage of type II collagen accompanied by upregulation of MMP-13 expression but not MMP-1. In isolated chondrocyte cultures CB12-II induced very limited upregulation of MMP-13 as well as MMP-1 expression. Although this was accompanied by concomitant induction of cleavage of type II collagen by collagenases, this was not associated by aggrecan cleavage. Peptide CB12-IV, which had no effect on collagen cleavage, clearly induced aggrecanase specific cleavage of the core protein of this proteoglycan. Thus these events involving matrix molecule cleavage can importantly occur independently of each other, contrary to popular belief. Denaturation of type II collagen with exposure of the CB12-II domain was also shown to be much increased in osteoarthritic human cartilage compared to non-arthritic cartilage. These observations reveal that peptides of type II collagen, to which there is increased exposure in osteoarthritic cartilage, can when present in sufficient concentration induce cleavage of type II collagen (CB12-II) and aggrecan (CB12-IV) accompanied by increased expression of collagenases. Such increased concentrations of denatured collagen are present in adult and osteoarthritic cartilages and the exposure of chondrocytes to the sequences they encode, either in soluble or more likely insoluble form, may therefore play a role in the excessive resorption of matrix molecules that is seen in arthritis and development.     

Calibration-in-time versus calibration-in-space (transfer function) to quantitatively infer July air temperature using biological indicators (chironomids) preserved in lake sediments

Calibration-in-space (i.e. modern taxonomic assemblages of biota from many lakes located along a wide temperature gradient calibrated against meteorological data) is generally used to derive species-specific optima and tolerances. This results in transfer functions which then are applied to subfossil assemblages to quantitatively reconstruct environmental variables such as air/water temperature. Developing such transfer functions is time- and money-consuming, thus many biota-inferred temperature records are either based on transfer functions from other regions which might not take into account local characteristics or are only used qualitatively. In varved Lake Silvaplana (Engadine, Switzerland), another way of obtaining quantitative climate reconstructions from taxonomical assemblages preserved in lake sediments was assessed for the past 1000 years. A calibration-in-time (i.e. taxonomic-assemblage-of-biota time series calibrated against meteorological data covering the same time period) was developed for chironomids (non-biting midges) using a weighted-average-partial-least-square (WAPLS) model and compared with a calibration-in-space model. The calibration-in-time had a weaker correlation coefficient (r² = 0.71) than the calibration-in-space (r² = 0.86), but the error of prediction (RMSEP = 0.58 °C) and the maximum bias (Max Bias = 0.73 °C) outperformed the statistics of the calibration-in-space (RMSEP = 1.5 °C; Max Bias = 1.72). This result is probably due to the smaller temperature gradient of the calibration-in-time (6.5 °C) than the calibration-in-space (11.5 °C). For the last 150 years, the Pearson correlation coefficient was significant between the two reconstructions (r_Pearson = 0.52; p < 0.01) suggesting that both models recorded a similar pattern of temperature changes. On the millennium time-scale, both models showed a warm “Medieval Climate Anomaly”, a cold “Little Ice Age” and a warming through the present with significant correlations (rPearson corrected for autocorrelation (corr) = 0.61, p < 0.01) until ca. 1780 AD and between ca. 1937 and 2000 AD (r_{Pearson corr} = 0.90, p < 0.01). The reconstructions using both models significantly diverged between ca. 1780 and 1937 AD (r_{Pearson corr} = ?0.47, p < 0.01). The results of both reconstruction methods were compared with four independent local and regional records of early instrumental and documentary data during the period of divergence. Both reconstructions showed similarities with the early instrumental/documentary records, thus it was inconclusive which of the reconstruction models provides the better estimates. However, these results suggest that a calibration-in-time can be used to reconstruct climate over the last 1000 years when no calibration-in-space is available.