Atomic-force microscopic study of dimensional changes in human dentine during drying

Six 1-mm thick sections of human dentine, three parallel to the occlusal surface and three perpendicular to the buccal surface, were prepared from non-carious third molars. The enamel was ground off, and the sections were polished with alumina powder to remove the smear layer. Each section was imaged by atomic-force microscopy with 20 nm horizontal and 0.1 nm vertical resolutions, initially while the samples were immersed in deionized water and then periodically during drying at room temperature. No dimensional changes over microscopic fields of view (scanned areas smaller than 50 x 50 microns) could be detected within the precision of the measurements (< 0.5%). Across the entire sample, however, vertical displacements of 10-20 microns were measured. Elasticity (Bernoulli beam) theory was used to calculate the engineering strain required to produce these displacements. The magnitude of the strain was 0.04% (SD = 0.01) in the buccal sections in the direction of the tubule axis and 0.09% (SD = 0.02) in the direction normal to the tubule axis. Also, the strain alternated between tension and compression across the samples. It was concluded that, as determined by using microscopic techniques, drying-induced strain is too small to require corrections for tubule size and tubule density.     

Comparison of uptake, oxidation and lipid distribution of 17-iodoheptadecanoic acid, 15-(p-iodophenyl)pentadecanoic acid and 15-(p-iodophenyl)-3,3-dimethylpentadecanoic acid in normal canine myocardium

The kinetics of 17-[123I]iodoheptadecanoic acid (IHDA), 15-(p-[125I]iodophenyl)pentadecanoic acid (pIPPA) and 15-(p-[131I]iodophenyl)-3,3-dimethylpentadecanoic acid (DMIPPA) were investigated in normal canine myocardium. After simultaneous intravenous injection, myocardial biopsy specimens and samples of arterial blood were taken over 80 min. IHDA showed the highest myocardial uptake (995 +/- 248 dpm/mg.mCi versus pIPPA: 785 +/- 197 dpm/mg.mCi, ns) and the largest size of oxidation (74% +/- 4% versus pIPPA: 65% +/- 5%, p < 0.05). Myocardial activity of IHDA decreased with a half-time value of 11.2 min (pIPPA: 13.2 min). Phospholipids were the main lipid fraction into which IHDA was incorporated, whereas pIPPA was predominantly incorporated into triacylglycerols. DMIPPA myocardial activity remained constant during the assay period and instead of being oxidized, DMIPPA was mainly incorporated into triacylglycerols (55% +/- 12%). The myocardium-to-blood ratios of DMIPPA were greater than 10:1. The ratios at peak for IHDA and pIPPA were 4.1:1 and 3.9:1, respectively (both p < 0.0001 versus DMIPPA). In conclusion, differences have been found in the myocardial uptake, oxidation and lipid distribution of IHDA, pIPPA and DMIPPA. DMIPPA is a promising tracer for fatty acid uptake studies with single-photon emission computerized tomography because of its prolonged retention and high myocardium-to-blood ratios.     

Pyomyositis and staphylococcal scalded skin syndrome

Pyomyositis is a rare musculoskeletal infection in non-tropical countries. We report a child who had pyomyositis complicated by staphylococcal scalded skin syndrome. This complication has not previously been described in patients with pyomyositis. Early diagnosis of pyomyositis was made by ultrasound examination, and percutaneous needle drainage under ultrasound guidance was performed. Pus aspirated and blood cultures grew Staphylococcus aureus. No open surgical drainage was required and resolution of the abscess was documented by serial ultrasound examinations.     

Endogenous dynorphins inhibit excitatory neurotransmission and block LTP induction in the hippocampus

Although anatomical and neurochemical studies suggest that endogenous opioids act as neurotransmitters, their roles in normal and pathophysiological regulation of synaptic transmission are not defined. Here we examine the actions of prodynorphin-derived opioid peptides in the guinea-pig hippocampus and show that physiological stimulation of the dynorphin-containing dentate granule cells can release endogenous dynorphins, which then activate kappa 1 opioid receptors present in the molecular layer of the dentate gyrus. Activation of kappa 1 receptors by either pharmacologically applied agonist or endogenously released peptide reduces excitatory transmission in the dentate gyrus, as shown by a reduction in the excitatory postsynaptic currents evoked by stimulation of the perforant path, a principal excitatory afferent. In addition, released dynorphin peptides were found to block the induction of long-term potentiation (LTP) at the granule cell-perforant path synapse. The results indicate that endogenous dynorphins function in this hippocampal circuit as retrograde, inhibitory neurotransmitters.     

Unique regulation of carbohydrate chemotaxis in Bacillus subtilis by the phosphoenolpyruvate-dependent phosphotransferase system and the methyl-accepting chemotaxis protein McpC

The phosphoenolpyruvate-dependent phosphotransferase system (PTS) plays a major role in the ability of Escherichia coli to migrate toward PTS carbohydrates. The present study establishes that chemotaxis toward PTS substrates in Bacillus subtilis is mediated by the PTS as well as by a methyl-accepting chemotaxis protein (MCP). As for E. coli, a B. subtilis ptsH null mutant is severely deficient in chemotaxis toward most PTS carbohydrates. Tethering analysis revealed that this mutant does respond normally to the stepwise addition of a PTS substrate (positive stimulus) but fails to respond normally to the stepwise removal of such a substrate (negative stimulus). An mcpC null mutant showed no response to the stepwise addition or removal of D-glucose or D-mannitol, both of which are PTS substrates. Therefore, in contrast to E. coli PTS carbohydrate chemotaxis, B. subtilis PTS carbohydrate chemotaxis is mediated by both MCPs and the PTS; the response to positive stimulus is primarily McpC mediated, while the duration or magnitude of the response to negative PTS carbohydrate stimulus is greatly influenced by components of the PTS and McpC. In the case of the PTS substrate D-glucose, the response to negative stimulus is also partially mediated by McpA. Finally, we show that B. subtilis EnzymeI-P has the ability to inhibit B. subtilis CheA autophosphorylation in vitro. We hypothesize that chemotaxis in the spatial gradient of the capillary assay may result from a combination of a transient increase in the intracellular concentration of EnzymeI-P and a decrease in the concentration of carbohydrate-associated McpC as the cell moves down the carbohydrate concentration gradient. Both events appear to contribute to inhibition of CheA activity that increases the tendency of the bacteria to tumble. In the case of D-glucose, a decrease in D-glucose-associated McpA may also contribute to the inhibition of CheA. This bias on the otherwise random walk allows net migration, or chemotaxis, to occur.