Mechanism of action of a tyrphostin, 3,4-dihydroxy-α-cyanothiocinnamamide, in breast cancer cell growth inhibition involves the suppression of cyclin B1 and the functional activity of cyclin B1/p34cdc2 complex

Tyrphostins are a group of compounds specifically targeted for the inhibition of tyrosine phosphorylation in signal transduction pathways. We studied the effects of a tyrphostin, 3,4-dihydroxy--cyanothiocinnamamide (tyrphostin-47), on hormone-responsive MCF-7 and hormone-unresponsive MCF-7-5C cell growth by DNA analysis for a period of 10 days. The growth of both cell lines was inhibited by this drug at 50 and 100 µM concentrations. Flow cytometric analysis showed that tyrphostin treatment caused a significant delay in the progression of MCF-7 cells through Gl and S phases of the cell cycle. The level of cyclin B1, a component of the mitosis promoting factor (MPF), was reduced by 90% in the presence of 100 µM tyrphostin. The other component of MPF, p34cdc2 kinase, was not affected; however, its functional activity was dramatically reduced, as determined by histone H1 phosphorylation assay. In contrast, G1 cyclins (D1 and E) and tyrosine kinase activity were not markedly affected by tyrphostin-47, as determined by Western immunoblot detection with specific antibodies. Our results suggest that a possible mechanism of tyrphostin action in breast cancer cells might involve the suppression of cyclin B1 and inhibition of the functional activity of cyclin B1/p34cdc2 complex. Our data indicate that the cell cycle machinery might be a target for developing novel drugs for breast cancer.     

Insertion, efficacy, and removal of a nonendoscopically removable percutaneous endoscopic gastrostomy (PEG) tube

BACKGROUND: Externally removable PEG tubes require an internal bumper that can collapse to a size that is small enough to allow for its removal through the abdominal wall by external traction. Adequate force must be maintained to avoid accidental dislodgement of the tube prior to its desired removal. METHODS: A nonendoscopically removable PEG (Inverta-PEG, Ross Products Division, Abbott Laboratories, Columbus, OH, USA) was evaluated in a nonmasked, prospective clinical study involving 131 patients enrolled by 25 physicians. The over-the-wire (Sacks-Vine) technique was used for all placements. After insertion, patients were followed weekly for 8 weeks. During week 9, the PEGs were removed percutaneously (nonendoscopically). Insertion, efficacy, and removal performance were evaluated. RESULTS: Complication rate during insertion was 1.5% and removal was 1.2%. Qualitatively, investigators rated ease of insertion and removal as very easy, easy, average, difficult, or very difficult. Investigators rated 98.5% of insertions as very easy, easy, or average; 95.4% of removals were rated as very easy, easy, or average. Some patients exited the study prematurely due to leakage around the stoma (2.3%) and inadvertent tube removal (5.3%). These complication rates were consistent with earlier reports of other PEG studies. CONCLUSIONS: These results demonstrate that Inverta-PEG is a safe and effective tube that can be removed nonendoscopically with ease in 95% of the cases.     

Monoclonal antibodies reactive with epitopes restricted to glial fibrillary acidic proteins of several species

The highly reproducible histochemical localization of glial fibrillary acidic protein (GFAP)? qualifies it as an important marker of astrocytes in both research and clinical applications. The primary objective of this study was to produce monoclonal antibodies having the advantage of invariant specificity, affinity, and titer to GFAP-specific epitopes of wide species distribution. We report here the characterization of four monoclonal antibodies that recognize the same or spatially close epitopes specific to GFAP. The epitope(s) detected has been phylogenetically conserved; human, bovine, ovine, canine, porcine, rabbit, guinea pig, rat, murine, and chicken brain homogenates all specifically absorb monoclonal antibody activity. Of importance to the routine application of these new anti-GFAP monoclonal antibodies is the demonstration here of the stability of the antigen-antibody interaction in normal, reactive, and neoplastic astrocytes of both rat and human origing following various methods of fixation.     

Modelling the dynamic ventilatory response to hypoxia in humans

A two-component dynamic model was used to describe the ventilatory response to sustained hypoxia in humans. One component (X_s) represents the stimulating effects of hypoxia and the other component (X_d), the hypoxic ventilatory decline. The total ventilatory response to hypoxia is represented by the sum of the two components. A nonlinearity is included to account for the nonlinear steady-state ventilatory response to hypoxia. A sensitivity analysis of the model indicates that, with a step change in as the input, all the parameters can be estimated from the data except for the nonlinearity. The relative sensitivity of the parameters from the model analysis was confirmed in an experimental study. However, comparing steps into hypoxia versus steps out of hypoxia we found a decrease in the gains of both components. The most likely explanation for the decrease in the gains is that the combination of X_s and X_d is not entirely additive. Other models may be required to completely describe the ventilatory response to inputs more complex than steps.     

Child drownings: a changing pattern

Paediatric drownings in New South Wales during the years 1987-1990 are reviewed to document the current pattern. Over these three years we have registered 250 paediatric deaths by physical injury. Sixty-one (24%) of these deaths were by drowning. Twenty-nine of the 61 drownings (47%) occurred in domestic pools; 25 of these were in unfenced or inadequately fenced pools. Of the remaining four cases, one was associated with a chair being used to gain access and the other three remain unexplained. Thirty-three of the 61 drownings occurred in country areas; of these 10 were in pools, eight in rivers or creeks, six in boating accidents, four in the surf and three in dams. A changing trend identified by this study is the increasing percentage of drownings (44%) occurring in nominally "fenced" pools in which the fencing was not functioning because the gate was open or the fencing was in disrepair. Legislation must be supported by public education and council inspection if the full benefit of isolation fencing is to be realised. With respect to all drownings there is a continuing need for education about the dangers that bodies of water, even in the bath or a bucket, pose to young children, and the need for parents to strive for optimal supervision.     

The ultrastructure of the extracellular phase of bone as observed in frozen thin sections

Summary The fine structure of the extracellular phase of avian medullary bone and embryonic chick femur was examined in thin sections prepared by ultracryotomy and ultramicroincineration. Since contact with solutions was completely avoided, little or no loss or dislocation of mineral constituents could occur. Amorphous bone mineral (ABM) was present in two forms: as 15–30 nm spheres and as a structure-free haze. Removal of all organic material by low temperature ashing left the ABM intact. Crystals were usually associated with the ABM. In newly ossifying regions clusters or nodules of randomly oriented crystals and ABM appeared to coalesce when they reached approximately 1 m in diameter. In highly calcified regions crystals appeared to be oriented along collagen fibers. ABM did not appear to be associated with collagen. Unmineralized collagen was visible in osteoid after staining with dry OsO₄ vapor and it appeared to be diverted around nodules. Structures which resembled matrix vesicles were present. Selected area electron diffraction patterns indicated the presence of hydroxyapatite.