Positron emission tomography for the evaluation of pancreatic disease

Efficient techniques for native-labeling of amino acids have been combined successfully with emission tomography to yield significant improvements in pancreatic imaging. Carbon-11-labeled tryptophan appears to be the best agent available currently for imaging the pancreas. Optimum scanning times begin 30 min after tracer administration. Positron emission tomography with 11C-tryptophan is capable of defining both morphological and functional alterations in the pancreas. Tumors as small as 2 cm in diameter can be detected, but reliable differentiation of pancreatic cancer from pancreatis may not be possible even with this improved imaging technique. Longitudinal multiplane emission tomography in single-photon mode with the Pho/Con provides an efficient and satisfactory approach to pancreatic imaging with the positron-emitting radiopharmaceuticals.     

Effect of length of gestation on maternal cellular immunity to human trophoblast antigens

Maternal lymphocyte reactivity to human trophoblast antigens was studied in placentas of gestational ages 8 to 14 weeks and 32 to 34 weeks, respectively. Significant trophoblast lysis became apparent after 24 hours' incubation in the latter case compared with a time lag of 72 hours in the terminated gestations. Maternal cellular immunity, therefore, was not detected during the first 3 1/2 months of pregnancy, but was detectable by the time of parturition. The possible significance is discussed with respect to the antigenic stimulus and survival of the fetal allograft.     

Progressive systemic sclerosis: intrathecal pain management

PURPOSE: To determine if lucanthone crossed the blood-brain barrier in experimental animals; and to determine accelerated tumor regression of human brain metastases treated jointly with lucanthone and whole brain radiation. METHODS AND MATERIALS: The organ distribution of 3H lucanthone in mice and 125I lucanthone in rats was determined to learn if lucanthone crossed the blood-brain barrier. Size determinations were made of patients' brain metastases from magnetic resonance images or by computed tomography before and after treatment with 30 Gy whole brain radiation alone or with lucanthone. RESULTS: The time course of lucanthone's distribution in brain was identical to that in muscle and heart after intraperitoneal or intravenous administration in experimental animals. Lucanthone, therefore, readily crossed the blood-brain barrier in experimental animals. CONCLUSION: Compared with radiation alone, the tumor regression in patients with brain metastases treated with lucanthone and radiation was accelerated, approaching significance using a permutation test at p = 0.0536.     

Structural features of arabinoxylans from Sonalika variety of wheat: comparison between whole wheat flour and wheat bran

Arabinoxylans (AX) were extracted from Sonalika variety of wheat (whole wheat flour and wheat bran) with barium hydroxide and sodium hydroxide and purified by a combination of alcohol precipitation and glucoamylase digestion. Structural features of purified AX were elucidated by methylation analysis, ¹³C NMR, FT‐IR, periodate oxidation and optical rotation measurements. The AX showed a backbone of xylose residues with β(1–4) linkages and were branched mainly through O‐3 of xylose residues. Completely branched xylosyl residues were also present. Copyright © 2003 Society of Chemical Industry     

Direct numerical simulation of laminar flame–wall interaction for a novel H2-selective membrane/injector configuration

Direct numerical simulations are performed to investigate the transient processes of laminar flame–wall interaction and quenching near a porous, permeable wall and compared against a reference case of a non-porous impermeable wall. A boundary condition formulation that models species (hydrogen in this case) transport through a permeable wall, driven by the fuel species partial pressure difference between the feed and the permeate side of a selective membrane, has been implemented in a high-order finite difference direct numerical simulation code for reactive flows (S3D) by Chen et al. (2009) [1]. The present results are obtained for lean, stoichiometric and rich initial mixture conditions on the permeate side of the permeable wall and indicate that the characteristic parameters of the flame–wall interaction (wall heat flux, quenching distance) are affected to a large extent by the presence of the membrane hydrogen flux. Concurrently, the hydrogen flux through the membrane is also strongly affected by the presence of the flame during the transient flame–wall interaction process, finally resulting in a strong feedback mechanism between the membrane hydrogen flux and the flame that greatly increases boundary layer flashback speeds at fuel lean conditions.     

Modulation of stability properties of bovine trypsin after in vitro structural changes with a variety of chemical modifiers

Controlled chemical modification of enzymes, targeting groups not involved in the active site, can lead to modified catalysts that are intrinsically more efficient and resistant to heat and denaturing agents. Bovine pancreatic trypsin was covalently modified up to 75-85% with monomeric glutaraldehyde (MGA), polymeric glutaraldehyde (PGA), oxidized sucrose and oxidized sucrose polymers (OSP 70 and OSP 400). Virtually no loss in activity occurred upon modification. Temperature optima of trypsin shifts from 45-76 degrees C and T50 from 54-76 degrees C for the best modified sample made with OSP. The efficiency of the modifiers in stabilization was ranked in the order: OSP 400-T > OSP 70-T > PGA-T > MGA-T > Sucrose-T. Half-life of modified enzymes also followed the same trend. Both stabilization factor and t1/2 decreased with increasing temperatures. The free energy of activation for inactivation delta(deltaG*) varies from 12-20 kJ/mol and the activation enthalpy delta(deltaH*) of the modified trypsin by 80-120 kJ/mol indicating stabilization. Inactivation of modified trypsin by urea is less noticeable. The character of the two-step inactivation process of trypsin changes with the degree of stabilization in that the duration of phase I one increased noticeably as stabilization increases. Native trypsin fluoresces less intensely showing a red shift under the influence of denaturation. Such a fluorescence change is not so obvious for the modified enzymes indicating conformational stability acquired by modification.      

Reaction of melanocytes in vertebrate retina to the exposure to constant magnetic field

The influence of a constant magnetic field (strain 40 kA/m) on retina pigmentary cells of grass frog (Rana temporaria) and grey pigeon (Columba livia) eyes was investigated. Changes in the number and length of melanocytes appendixes were noticed accompanied by formation of thickenings in which melanosomes sized from 0.1 to 0.5 micron are moving. It is established that magnetic properties of eye retina pigmentary cells depend on the presence of Fe3+ in melanin. A theoretical model of paramagnetic receptor has been elaborated, according to which the induction of a magnetic field, formed by melanocyte, makes of the order 100 pT1. This value well compares with the size of magnetic field of a nervous impulse (120 pT1), extending throughout a nervous fibre of the frog sciatic nerve (Wikswo et al., 1980). This allows to suggest a possible unsynaptic way of transferring the information about the perceived magnetic field.