The microenvironment dictates glycocalyx construction and immune surveillance

Efforts to identify anti-cancer therapeutics and understand tumor-immune interactions are built with in vitro models that do not match the microenvironmental characteristics of human tissues. Using in vitro models which mimic the physical properties of healthy or cancerous tissues and a physiologically relevant culture medium, we demonstrate that the chemical and physical properties of the microenvironment regulate the composition and topology of the glycocalyx. Remarkably, we find that cancer and age-related changes in the physical properties of the microenvironment are sufficient to adjust immune surveillance via the topology of the glycocalyx, a previously unknown phenomenon observable only with a physiologically relevant culture medium.

Microelectromechanical system assembled ion optics: An advance to miniaturization and assembly of electron and ion optics

Deep-reactive ion etching of n-doped silicon-on-insulator is utilized to make ion optical components to aid in the miniaturization of mass analyzers. The microelectromechanical system components are bound to aluminum nitride substrates and employed three-dimensional assembly. The assembly methods are tested for breakdown (V(b)), durability, and alignment. Demonstration of ion manipulation is shown with a 1 mm Bradbury-Nielsen gate, 500 mum Einzel lens, 500 mum coaxial ring ion trap, and reflectron optics. Data are presented showing the resolution, attenuation, and performance of each of these devices. We demonstrate advantages and disadvantages of this technology and its applications to mass analysis.

Liver histology of Asian patients with chronic hepatitis B on prolonged lamivudine therapy

BACKGROUND

Long-term effect of YMDD mutations on liver histology in Chinese hepatitis B patients is unknown.

AIM

To examine the effect of prolonged lamivudine treatment on liver histology in Chinese patients with and without YMDD mutations.

METHODS

Liver histology was assessed in 85 patients on long-term lamivudine at baseline and year 1, and at year 3 for 25 patients.

RESULTS

Comparing patients with and without YMDD mutations at year 1, the former had higher baseline median necroinflammatory (11 vs. six respectively, P = 0.014) and fibrosis scores (three vs. one respectively, P = 0.001). The proportion of patients with improvement in necroinflammation and worsening of fibrosis was comparable for patients with and without YMDD mutations at year 1 (57.1%, 14.3% vs. 55%, 15% respectively) and year 3 (57.9%, 26.3% vs. 50%, 16.7% respectively). Comparing the histology at year 1 and 3, more patients with YMDD mutations developing after year 1 had worsening of necroinflammation than patients with persistent YMDD wild type (53.8% vs. 25% respectively).

CONCLUSIONS

Patients who developed YMDD mutations had higher baseline histological scores. With YMDD mutations, the liver histology became less favourable after 3 years than at the first year, although there was still improvement when compared with that at baseline.

Progression into the first meiotic division is sensitive to histone H2A-H2B dimer concentration in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae contains two genes for histone H2A and two for histone H2B located in two divergently transcribed gene pairs: HTA1-HTB1 and HTA2-HTB2. Diploid strains lacking HTA1-HTB1 (hta1-htb1 delta/hta1-htb1 delta, HTA2-HTB2/HTA2-HTB2) grow vegetatively, but will not sporulate. This sporulation phenotype results from a partial depletion of H2A-H2B dimers. Since the expression patterns of HTA1-HTB1 and HTA2-HTB2 are similar in mitosis and meiosis, the sporulation pathway is therefore more sensitive than the mitotic cycle to depletion of H2A-H2B dimers. After completing premeiotic DNA replication, commitment to meiotic recombination, and chiasma resolution, the hta1-htb1 delta/hta1-htb1 delta, HTA2-HTB2/HTA2-HTB2 mutant arrests before the first meiotic division. The arrest is not due to any obvious disruptions in spindle pole bodies or microtubules. The meiotic block is not bypassed in backgrounds homozygous for spo13, rad50 delta, or rad9 delta mutations, but is bypassed in the presence of hydroxyurea, a drug known to inhibit DNA chain elongation. We hypothesize that the deposition of H2A-H2B dimers in the mutant is unable to keep pace with the replication fork, thereby leading to a disruption in chromosome structure that interferes with the meiotic divisions.

Accommodation of time delay variations in automatic infusion of sodium nitroprusside

A new self-tuning regulator for control of mean arterial blood pressure using sodium nitroprusside is presented. In addition to adapting to various patient response gains and time constants, the controller can accommodate variations in pure time delays, a problem that has not been addressed fully in previously proposed controllers. The control algorithm derivation is based on incorporating a self-tuning controller with an adaptive discrete time delay compensator. The derivation, however, is general and can potentially be applied to other pharmacological agents in addition to sodium nitroprusside. The a priori information required for implementation of the controller is the estimate of the order of the patient response transfer function and the range of the pure time delay. An attractive feature of the controller is its capability to optimize the level of the infused drug during the transient phase of the control without creating an output offset. This feature tends to reduce the overall level of the infused drug. Hence, it may be useful when the cost of a drug or its long-term administration side effects is of concern, such as in the case of sodium nitroprusside.

Two- and three-dimensional image reconstructions from stained and autoradiographed histological sections

A complete system has been developed to utilize histological serial sections for two- and three-dimensional image reconstructions. Eighty to 120 sections are digitized using a personal computing system augmented with a imaging board and CCD camera. The image files are transmitted to a VAX computer for processing and image reconstruction, and the processed images are transmitted back to the personal computer for display and recording using a film recorder or PostScript printer. The software developed for the system allows serial sections to be placed into proper registration in a 256(3) array, 256 grey levels. Autoradiographs of the sections are obtained in the presence of appropriate standards which are used to recalibrate grey levels to represent linearly the radioactivity of each pixel in the sections and scale the values to allow maximum use of the grey scale. Starting from coronally sectioned material the system has been used to analyse and reconstruct rat nasal turbinates. In two dimensions horizontal and sagittal sections have been obtained while in three dimensions back-to-front and surface-rendered images have been constructed. Useful rendering of differential metabolic activity within an organ of complex geometry has been obtained, and there appears to be no reason why the system cannot be used for any material for which serial sectioning is appropriate.

Venous admixture effect during one-lung anaesthesia

The venous admixture was measured before, during, and after deflation of one lung during anaesthesia for thoracotomy in 10 subjects ventilated with 50% oxygen. The mean oxygen saturation fell from 99% before deflation of the lung to 89% after 30 minutes’ atelectasis. The pH and carbon dioxide tension did not change significantly. The shunt was 38% of cardiac output five minutes after and 41% 30 minutes after deflation. The reciprocal of the arterial venous oxygen content difference correlated positively with the shunt, suggesting that increased venous admixture is accompanied by increased cardiac output.