Response of preimplantation murine embryos to heat shock as modified by developmental stage and glutathione status

Objectives were to characterize developmental changes in response to heat shock in the preimplantation mouse embryo and to evaluate whether ability to synthesize glutathione is important for thermal resistance in mouse embryos. Heat shock (41 degrees C for 1 or 2 h) was most effective at disrupting development to the blastocyst stage when applied to embryos at the 2-cell stage that were delayed in development. Effects of heat shock on ability of embryos to undergo hatching were similar for 2-cell, 4-cell, and morula stage embryos. The phenomenon of induced thermotolerance, for which exposure to a mild heat shock increases resistance to a more severe heat shock, depended upon stage of development and whether embryos developed in vitro or in vivo. In particular, induced thermotolerance was observed for morulae derived from development in vivo but not for 2-cell embryos or morulae that developed in culture. Administration of buthionine sulfoximine to inhibit glutathione synthesis did not increase thermal sensitivity of 2-cell embryos or morulae but did reduce subsequent development of 2-cell embryos at both 37 degrees and 41 degrees C. In summary, changes in the ability of 2-cell through morula stages to continue to develop following a single heat shock were generally minimal. However, 2-cell embryos delayed in development had reduced thermal resistance, and therefore, maternal heat stress may be more likely to cause mortality of embryos that are already compromised in development. There were also developmental changes in the capacity of embryos to undergo induced thermotolerance. Glutathione synthesis was important for development of embryos but inhibition of glutathione synthesis did not make embryos more susceptible to heat shock.     

A BCR-ABL(p190) fusion gene made by homologous recombination causes B-cell acute lymphoblastic leukemias in chimeric mice with independence of the endogenous bcr product

BCR-ABL(p190) oncogene is the result of a reciprocal translocation between chromosomes 9 and 22 and is associated with B-cell acute lymphoblastic leukemia (B-ALL) in humans. Current models expressing the BCR-ABL(p190) chimeric gene fail to consistently reproduce the phenotype with which the fusion gene is associated in human pathology, mainly due to the difficulty of being expressed in the appropriate cell type in vivo. We have used here homologous recombination in ES cells to create an in-frame fusion of BCR-ABL(p190) that mimics the consequences of the human chromosomal translocation by fusion of BCR-ABL coding sequences into the bcr endogenous gene. The chimeric mice generated with the mutant embryonic stem cells systematically develop B-ALL. Using these chimeric mice, we further show that BCR-ABL oncogene does not require the endogenous bcr product in leukemogenesis. Our results show that BCR-ABL(p190) chimeric mice are a new model to study the biology of the BCR-ABL oncogene and indicate the efficacy of this strategy for studying the role of specific chromosome abnormalities in tumor development.     

The influence of copper precipitation and plastic deformation hardening on the impact-transition temperature of rolled structural steels

Commercial electric arc melted low-carbon steels, provided as I beams, were characterized both microstructurally and mechanically in the as-rolled, copper precipitation, and plastically pre-deformed conditions. Inclusion size distribution, ferrite grain size, pearlite volume fraction, precipitated volume fraction of copper, and size distribution of these precipitates were deter-mined by conventional quantitative optical and electron metallographic techniques. From the tensile tests conducted at a strain rate of 10^-3 s^-1 and impact Charpy V-notched tests carried out, stress/strain curves, yield stress, and impact-transition temperature were obtained. The spe-cific fractographic features of the fracture surfaces also were quantitatively characterized. The increases in yield stress and transition temperature experienced upon either aging or work hard-ening were related through empirical relationships. These dependences were analyzed semi-quantitatively by combining microscopic and macroscopic fracture criteria based on measured fundamental properties (fracture stress and yield stress) and observed fractographic parameters (crack nucleation distance and nuclei size). The rationale developed from these fracture criteria allows the semiquantitative prediction of the temperature transition shifts produced upon aging and work hardening. The values obtained are of the right order of magnitude.     

Photopolymerization of carbazolyloxiranes

Photopolymerizations of 1-allyloxy-3-(carbazol-9-yl)-2-propanol glycidyl ether and 1-(carbazol-9-yl)-4-oxa-2-pentanol glycidyl ether with diaryliodonium salts in solution and in bulk are reported. These reactions give oligomers of degree of polymerization 4–6. The influence of the functional groups of the monomers on the rate of polymerization, conversion limit and molecular weight is discussed. The effects of photoinitiator and reaction media on these factors have also been studied.     

Hypothalmic influences on the electrical activity of the olfactory pathway

The cycle of events which leads to an impairment of the immune response in the malnourished child includes poverty, food deprivation and frequent infections. It is of great significance, however, that the marked suppression of the immune response can be repaired reasonably promptly, if the disease commences after the child has attained 1 year of age. Prenatal infection not only generates growth retardation but also a higher maternal to foetal IgG ratio, higher IgM in the neonate and a sustained immune depression. Passive cutaneous anaphylaxis measurements in the baboon skin and specific IgE determinations reveal that the elevated IgE in PEM is due to parasitic infestation and common allergens and has little or no relationship with decreased T-cell function.     

A new mutation in the yeast aspartate kinase induces threonine accumulation in a temperature-regulated way

In Saccharomyces cerevisiae, aspartate kinase (the HOM3 product) regulates the metabolic flux through the threonine biosynthetic pathway through feedback inhibition by the end product. In order to obtain a strain able to produce threonine in a controlled way, we have isolated a mutant allele (HOM3-ts31d) that gives rise to a deregulated aspartate kinase. This allele has been isolated as an extragenic suppressor of ilv1, which confers an Ilv+ phenotype at 37 degrees C but not at 22 degrees C. We have stated that at high temperature the mutant aspartate kinase is slightly more deregulated and shows a higher specific activity, inducing threonine accumulation. The HOM3-ts31d allele carries a mutation that leads to a Ser399 --> Phe substitution in the postulated regulatory region of the enzyme. We have detected other changes in the nucleotide sequence but they are also present in the parental strain, reflecting the genetic differences between different wild-type strains. A sequence comparison among all the reported mutant aspartate kinases suggests that not all residues involved in regulation of the activity are clustered in the so-called regulatory domain, as is the case of that mutated in AK-R7, another deregulated aspartate kinase obtained with the same strategy of ilv1 suppression.     

Preliminary characterization of an experimental breast cancer cells brain metastasis mouse model by MRI/MRS

PURPOSE: Chemotherapy increases survival in breast cancer patients. Consequently, cerebral metastases have recently become a significant clinical problem, with an incidence of 30-40% among breast carcinoma patients. As this phenomenon cannot be studied longitudinally in humans, models which mimic brain metastasis are needed to investigate its pathogenesis. Such models may later be used in experimental therapeutic approaches. MATERIAL AND METHODS/RESULTS: We report a model in which 69% of the animals (9/13 BALB/c nude mice) developed MR-detectable abnormal masses in the brain parenchyma within a 20 to 62-day time window post intra-carotid injection of 435-Br1 human cells. The masses detected in vivo were either single (7 animals) or multiple (2 animals). Longitudinal MR (MRI/MRS) studies and post-mortem histological data were correlated, revealing a total incidence of experimental brain metastases of 85% in the cases studied (11/13 animals). ADC maps perfectly differentiated edema and/or CSF areas from metastasis. Preliminary MRS data also revealed additional features: decrease in N-acetyl aspartate (NAA) was the first MRS-based marker of metastasis growth in the brain (micrometastasis); choline-containing compounds (Cho) rose and creatine (Cr) levels decreased as these lesions evolved, with mobile lipids and lactate also becoming visible. Furthermore, MRS pattern recognition-based analysis suggested that this approach may help to discriminate different growth stages. CONCLUSIONS: This study paves the way for further in vivo studies oriented towards detection of different tumor progression states and for improving treatment efficiency.     

Familiar/unfamiliar face classification from EEG signals by utilizing pairwise distant channels and distinctive time interval

The aim of the study is to classify single trial electroencephalogram and to estimate active regions/locations on skull in unfamiliar/familiar face recognition task. For this purpose, electroencephalographic signals were acquired from ten subjects in different sessions. Sixty-one familiar and fifty-nine unfamiliar face stimuli were shown to the subjects in the experiments. Since channel responses are different for familiar and unfamiliar classes, the channels discriminating the classes were investigated. To do so, three distances and four similarity measures were employed to assess the most distant channel pairs between familiar and unfamiliar classes for a 1-s time duration; 0.6 s from the stimulus to 1.6 s in a channel selection process. It is experimentally observed that this time interval is maintaining the greatest distance between two categories. The electroencephalographic signals were classified using the determined channels and time interval to measure accuracy. The best classification accuracy was 81.30% and was obtained with the Pearson correlation as channel selection method. The most discriminative channel pairs were selected from prefrontal regions.