Loss of heterozygosity on chromosome 10 in human glioblastoma multiforme

Recessive mutations, revealed by loss of the wild-type allele, have been associated with the development of a variety of cancers in children and adults. Polymorphic chromosome 10 markers were used to screen paired tumor and lymphocyte DNA samples in 13 patients with glioblastoma multiforme. Ten patients showed loss of constitutional heterozygosity in the tumor samples. This finding suggests that a recessive gene involved in the development of glioblastoma multiforme is present on chromosome 10.     

Characterization of an aminoacylase from the hyperthermophilic archaeon Pyrococcus furiosus.

Aminoacylase was identified in cell extracts of the hyperthermophilic archaeon Pyrococcus furiosus by its ability to hydrolyze N-acetyl-L-methionine and was purified by multistep chromatography. The enzyme is a homotetramer (42.06 kDa per subunit) and, as purified, contains 1.0 +/- 0.48 g-atoms of zinc per subunit. Treatment of the purified enzyme with EDTA resulted in complete loss of activity. This was restored to 86% of the original value (200 U/mg) by treatment with ZnCl(2) (and to 74% by the addition of CoCl(2)). After reconstitution with ZnCl(2), the enzyme contained 2.85 +/- 0.48 g-atoms of zinc per subunit. Aminoacylase showed broad substrate specificity and hydrolyzed nonpolar N-acylated L amino acids (Met, Ala, Val, and Leu), as well as N-formyl-L-methionine. The high K(m) values for these compounds indicate that the enzyme plays a role in the metabolism of protein growth substrates rather than in the degradation of cellular proteins. Maximal aminoacylase activity with N-acetyl-L-methionine as the substrate occurred at pH 6.5 and a temperature of 100 degrees C. The N-terminal amino acid sequence of the purified aminoacylase was used to identify, in the P. furiosus genome database, a gene that encodes 383 amino acids. The gene was cloned and expressed in Escherichia coli by using two approaches. One involved the T7 lac promoter system, in which the recombinant protein was expressed as inclusion bodies. The second approach used the Trx fusion system, and this produced soluble but inactive recombinant protein. Renaturation and reconstitution experiments with Zn(2+) ions failed to produce catalytically active protein. A survey of databases showed that, in general, organisms that contain a homolog of the P. furiosus aminoacylase (> or = 50% sequence identity) utilize peptide growth substrates, whereas those that do not contain the enzyme are not known to be proteolytic, suggesting a role for the enzyme in primary catabolism.     

Lamin B is a prompt heat shock protein

The cellular response to hyperthermia involves the increased synthesis of heat shock proteins (HSPs) within several hours after treatment. In addition, a subset of proteins has been shown to be increased immediately after heating. These “prompt” HSPs are predominantly found in the nuclear matrix–intermediate filament fraction and are not present or detectable in unheated cells. Since the nuclear matrix has been suggested to be a target for heat-induced cell killing, prompt HSPs may play a prominent role in the heat shock response. Using Western blotting and flow cytometry, we found that an increase in the synthesis of lamin B, one of the major proteins of the nuclear lamina, is induced during heating at 45.5°C but not during heating at 42°C. Since it is an abundant protein which is constitutively expressed in mammalian cells, lamin B appears to be a unique member of the prompt HSP family. The kinetics of induction of lamin B during 45.5°C heating did not correlate with the dose-dependent reduction in cell survival. While increased levels of lamin B during 45.5°C heating do not appear to confer a survival advantage directly, a possible role for lamin B in cellular recovery after heat shock cannot be discounted. J Cell Physiol 178:28–34, 1999. © 1999 Wiley-Liss, Inc.     

A new parallelism acceptance criterion for validating large plate bioassay results

Large plate bioassays are normally assessed by analysis of variance. The British Pharmacopoeial approach requires a validation of the assay through a test for parallelism. This approach is shown to be impractical as it does not allow for improvements in technique which tend to reduce the error mean square value for the bioassay and hence increase the F ratio for parallelism. A new parallelism acceptance criterion is proposed in which a critical value for parallelism mean square is determined by multiplying the appropriate critical F value for parallelism by the value for error mean square which provides a limiting value for the fiducial limits. This approach allows for improved bioassay technique but does not lead to the acceptance of doubtful assay results. The results of 15 months of bioassays covering over 500 assays using the proposed parallelism acceptance criterion are discussed.     

Dread and the Disvalue of Future Pain

Standard theories of decision-making involving delayed outcomes predict that people should defer a punishment, whilst advancing a reward. In some cases, such as pain, people seem to prefer to expedite punishment, implying that its anticipation carries a cost, often conceptualized as ‘dread’. Despite empirical support for the existence of dread, whether and how it depends on prospective delay is unknown. Furthermore, it is unclear whether dread represents a stable component of value, or is modulated by biases such as framing effects. Here, we examine choices made between different numbers of painful shocks to be delivered faithfully at different time points up to 15 minutes in the future, as well as choices between hypothetical painful dental appointments at time points of up to approximately eight months in the future, to test alternative models for how future pain is disvalued. We show that future pain initially becomes increasingly aversive with increasing delay, but does so at a decreasing rate. This is consistent with a value model in which moment-by-moment dread increases up to the time of expected pain, such that dread becomes equivalent to the discounted expectation of pain. For a minority of individuals pain has maximum negative value at intermediate delay, suggesting that the dread function may itself be prospectively discounted in time. Framing an outcome as relief reduces the overall preference to expedite pain, which can be parameterized by reducing the rate of the dread-discounting function. Our data support an account of disvaluation for primary punishments such as pain, which differs fundamentally from existing models applied to financial punishments, in which dread exerts a powerful but time-dependent influence over choice.