Microfluidic tectonics: a comprehensive construction platform for microfluidic systems.

A microfluidic platform for the construction of microscale components and autonomous systems is presented. The platform combines liquid-phase photopolymerization, lithography, and laminar flow to allow the creation of complex and autonomous microfluidic systems. The fabrication of channels, actuators, valves, sensors, and systems is demonstrated. Construction times can be as short as 10 min, providing ultrarapid prototyping of microfluidic systems.

Microfabricated elastomeric stencils for micropatterning cell cultures.

Here we present an inexpensive method to fabricate microscopic cellular cultures, which does not require any surface modification of the substrate prior to cell seeding. The method utilizes a reusable elastomeric stencil (i.e., a membrane containing thru holes) which seals spontaneously against the surface. The stencil is applied to the cell-culture substrate before seeding. During seeding, the stencil prevents the substrate from being exposed to the cell suspension except on the hole areas. After cells are allowed to attach and the stencil is peeled off, cellular islands with a shape similar to the holes remain on the cell-culture substrate. This solvent-free method can be combined with a wide range of substrates (including biocompatible polymers, homogeneous or nonplanar surfaces, microelectronic chips, and gels), biomolecules, and virtually any adherent cell type.

Management issues in chordoma: a case series.

This study presents a combined case series of chordomas from two Canadian institutes. Twenty-seven patients were identified for the period 1954-1998. Management issues with regard to diagnostic pitfalls, selection of charged particle treatment and retreatment of recurrences are discussed. The diagnosis of early stage chordoma requires a high index of suspicion. One patient in the series presented with hoarseness and is described in detail. The diagnosis was made coincidentally by a computed tomographic scan of the head, performed after a motor vehicle accident. The planning of both surgery and radiotherapy was optimized by using magnetic resonance imaging. A review of the literature supports the use of a combined surgical and radiotherapeutic approach.

Apoptosis induced by retinoic acid in Hep 3B cells in vitro.

Human hepatoma Hep 3B cells underwent apoptosis in response to 100 microM all-trans retinoic acid (RA) in full serum (10% fetal calf serum) condition in vitro. Cell death began approximately 24 h following treatment, with more than 80% of the cells dead after 60 h. The dead cells, mainly detached cells, exhibited condensed chromatin and DNA fragmentation, which are indicative of endonuclease activation and are the hallmarks of apoptosis in epithelial cells. Concurrent exposure to 1 microM cycloheximide (CX) prevented approximately 50% of cell death and DNA fragmentation induced by RA. Thus, other toxic injury to the cells as well as apoptosis might be involved in cell death. Sixty hours exposure of RA decreased the percentage of cells in G1 phase (16.3 +/- 0.4% versus 52.4 +/- 2.1%; P < or = 0.01) and in G2/M phase (13.4 +/- 1.2% versus 21.2 +/- 0.7%; P < or = 0.01), but did not change percent of cells in S phase (20.8 +/- 0.2% versus 20.7 +/- 0.5%) of the cell cycle compared with control. RA may have caused accumulation of Hep 3B cells before G1 phase, and that G0/G1 transition is a main check point in the active process of apoptosis. Electron micrographs of the cells treated with RA revealed typical morphologic changes of apoptosis, besides toxic injury to the cells. These data strongly indicate that RA is able to induce apoptosis and the induction of apoptosis may contribute to the antitumor activity of RA against hepatoma cells.

Laser Raman spectroscopy of snake venom neurotoxins: conformation.

Laser Raman spectra of neurotoxins of Pelamis platurus (yellow-bellied sea snake) and Laticauda semifasciata (broad-banded blue sea snake) were investigated. The amide I band appeared at 1672 cm-1 for both toxins, which presents an indication of anti-parallel beta structure. Since this agrees well with the result from the CD-ORD studies of snake neurotoxin, it was concluded that snake neurotoxins mainly consist of beta structure. The amide III band appeared at 1245 cm-1 for P. platurus toxin and 1248 cm-1 for L. semifasciata toxin. The four disulfide bonds present in the toxin have a very similar geometry. After vigorous heat treatment, the backbone configuration of the toxin molecule basically remained the same although it was partially denatured. The major peak at 512 cm-1 was not altered by the heat treatment but a new shoulder appeared at 546 cm-1. This suggests that a new type of S-S stretching vibration (trans-gauche-trans) was produced as a result of heat treatment. However, the majority of the S-S vibrations remained in the gauche-gauche-gauche orientation. A substantial change in the interactions between a tyrosine aromatic ring and neighboring residues was apparently the alteration caused by the heat treatment.