Electrostatic force spectroscopy on insulating surfaces: the effect of capacitive interaction.

Scanning surface probes delivered from atomic force microscopy (AFM) are expected to investigate local electrostatic properties on insulating surfaces by forces. Electrostatic force spectroscopy is especially suitable to clarify the capacitive interaction. In order to perform it at a well-defined tip-surface separation, we developed a dynamic mode, in which the tip-surface separation is regulated by maintaining the cantilever oscillation amplitude with an active feedback, while the electrostatic force gradient is simultaneously detected with a variable resonant frequency shift. Using the method, it turns out that the quadratic dependence of the electrostatic force gradient on an applied bias observed on an insulating Al(2)O(3)(0001) is comparable to those on a metallic Au(111). It results from the potential difference between the tip and the insulator surface being only one order smaller than that between the tip and the metal surface despite the spacing between electrodes for the insulator being 10(6) times larger than for the metal, because the capacitive interaction is modified primarily between the sharp AFM tip and the surface.

Electrostatic force microscopy: imaging DNA and protein polarizations one by one.

We present electrostatic force microscopy images of double-stranded DNA and transcription complex on an insulating mica substrate obtained with molecular resolution using a frequency-mode noncontact atomic force microscope. The electrostatic potential images show that both DNA and transcription complexes are polarized with an upward dipole moment. Potential differences of these molecules from the mica substrate enabled us to estimate dipole moments of isolated DNA and transcription complex in zero external field to be 0.027 D/base and 0.16 D/molecule, respectively. Scanning capacitance microscopy demonstrates characteristic contrast inversion between DNA and transcription complex images, indicating the difference in electric polarizability of these molecules. These findings indicate that the electrostatic properties of individual biological molecules can be imaged on an insulator substrate while retaining complex formation.

High-density DNA alignment on an Au(111) surface starting from folded DNA.

High-density uniform DNA alignment on a metal substrate is essential for creating sensitive DNA devices. We develop a self-sensing DNA alignment process starting from folded DNA to achieve high-density, uniform DNA alignment on an Au(111) surface. We demonstrate that folded DNA plays a critical role in avoiding DNA aggregation and distributing the DNA uniformly on an Au(111) surface at the greatest density and quality ever attained. We also verify that the distributed, folded DNA can be stimulated to align only when the appropriate buffer flow is applied. This selective self-sensing DNA alignment on an Au surface will be a key technology for creating dynamic DNA sensors and switches.

Ischemic preconditioning enhances regenerative capacity of hepatocytes in long-term ischemically damaged rat livers.

BACKGROUND AND AIMS: Ischemic preconditioning (IPC) protects tissues against ischemia and reperfusion (I/R) injury. The aim of this study was to examine the impact of IPC on protection and regeneration of hepatocytes after prolonged I/R injury. METHODS: A rat model of segmental (70%) hepatic ischemia was used to determine the effect of 10-min IPC preceding 40, 60, 90, or 120 min of liver ischemia. The effect was assessed by comparing cytolysis markers and necrotic areas of the liver, as well as the regenerative capacity of hepatocytes using the proliferating cell nuclear antigen labeling index (PCNA-LI) and weight of the ischemic liver lobe. Protein kinase B/Akt (Akt) and caspase-9 were investigated immunohistochemically to determine the effect of IPC on activation of survival and anti-apoptotic signals. RESULTS: In the model of 40 min I/R, which resulted in focal necrosis of the liver, IPC significantly protected against I/R injury by reducing the area of focal necrosis, level of PCNA-LI and immunoreactivities to Akt and caspase-9. In contrast, IPC did not prevent ischemic damage in the 90- and 120-min ischemic model with massive liver necrosis. However, IPC enhanced the regenerative capacity of the remaining hepatocytes with higher levels of PCNA-LI, number of Akt-positive cells and mean weight of the liver lobe postoperatively than in the controls. CONCLUSIONS: In a model of focal necrosis of the liver, IPC protected hepatocytes against I/R injury. In addition, in a model of massive necrosis, IPC maintained the regenerative capacity of the remaining hepatocytes by enhancing the survival signals.

Prognostic impact of p53 protein overexpression in patients with node-negative lung adenocarcinoma.

Prognostic value of p53 protein expression in node-negative lung adenocarcinoma is still controversy. The expression of p53 protein was examined immunohistochemically in lung adenocarcinoma using monoclonal antibody BP53-12. A total 131 cases of primary lung adenocarcinoma were examined. Relationship between expression of p53 protein and clinicopathologic factors were studied. Overexpression of p53 protein was found in 19 patients (14.5%). Univariate and multivariate analysis showed that overexpression of p53 protein was an independent prognostic factor in node-negative lung adenocarcinoma. p53 alteration could be a valuable predictor for prognosis in node-negative lung adenocarcinoma.

[Tissue array analysis of the aberrant expression of HLA class I molecules in human non small cell lung cancer].

A clinical significance of the aberrant expression of HLA class I molecules including HLA class I and HLA-G was analyzed using tissue array analysis. Our institute has established a two millimeter spot sized tissue array set of 105 clinical cases of resected human non small cell lung cancer tissues. A loss of HLA class I was observed in the 58.3% of cancer tissues. The aberrant expression of HLA G was also observed in the 55.2% of cancer tissues. Statistically significant correlations were observed among HLA class I expression and tumor size, nodal involvement and pathological stage. Survival analyses were shown that the HLA class I loss was correlated to a recurrence free survival time. The HLA-G expression did not correlate with any clinico-pathological parameters. A loss of HLA class I was probably involved due to a cancer progression in human non-small cell lung cancer through the mechanism of immune escape from the host immune system.