The use of hair as an indicator of occupational 14C contamination

This paper presents a study in which the specific activity of ¹⁴C in hair has been investigated as an easily determined bio-indicator of the integrated ¹⁴C exposure (over several months). The study includes 28 Swedish workers handling ¹⁴C-labelled compounds, or working in a ¹⁴C-enriched environment. Hair samples from personnel at a Swedish nuclear power plant showed very low levels of ¹⁴C contamination, if any. In contrast, personnel at the investigated research departments showed ¹⁴C levels in hair of up to 60% above the natural specific activity of ¹⁴C. Much higher levels, up to 80 times the natural specific activity of ¹⁴C, were found in hair from individuals working at a pharmaceutical research laboratory. This contamination was, however, not solely an internal contamination. There were indications that most of the ¹⁴C in the hair originated from airborne ¹⁴C-compounds, which were adsorbed onto the hair. The difficulties in removing this external ¹⁴C contamination prior to analysis are discussed, as are the possibilities of using accelerator mass spectrometry to analyse various types of samples for retrospective dose assessment.     

Autoneuralization in the amphibian ectoderm--a species-specific and stage-specific phenomenon

Ectoderm from Ambystoma is especially prone to undergo 'autoneuralization'. This assertion has led to the maxim that ectoderm from this species is unsuitable for studying cell differentiation. Here we report that the degree of neuralization in cultured explants is stage-dependent. Control explants from blastulae (stage 8-9) show no neuralization, while explants treated with LiCl (10 mM) give rise to neuralization in about 70% of the cases. This difference between control and experiment decreases during gastrulation, in late gastrulae (stage 12) it is more or less negligible. Ectoderm from Cynops pyrrhogaster reacts like that of Ambystoma when exposed to LiCl, but like Triturus ectoderm it is insensitive to cyclic nucleotides.     

Employment of hydrolytic enzymes in the study of the level of DNA methylation

A new method for the determination of the level of DNA methylation was established. The method involves enzymatic hydrolysis of DNA by nuclease P1 and bacterial alkaline phosphatase, and separation of the resulting deoxyribonucleosides by HPLC. By this method, DNA was hydrolysed completely to the five deoxyribonucleosides and the complete base composition was determined. Pairing bases were shown to occur in similar amounts, and analysis could be performed on as little as 1 microgram of DNA with a high degree of reproducibility. Among other enzymes hitherto used in order to hydrolyze DNA, micrococcal nuclease, phosphodiesterase II and nuclease P1 have been shown to cause deamination of deoxyadenosine, while deoxyribonuclease I, phosphodiesterase I and bacterial alkaline phosphatase have been shown to be sensitive to contamination by RNA, and to release 5-methyldeoxycytidine at a slower rate than the other four deoxyribonucleosides. Neither of these effects was seen with the new method.     

Omeprazole and ranitidine, antisecretagogues with different modes of action, are equally effective in causing hyperplasia of enterochromaffin-like cells in rat stomach

Female rats were treated for 28 days with high doses of the gastric acid secretion inhibitors omeprazole and ranitidine. Omeprazole, which is long-acting, was given orally once daily. Ranitidine, which is short-acting, was given by continuous infusion (via osmotic minipumps, implanted subcutaneously). The aim was to produce a similar degree of acid inhibition with the two drugs. The inhibition of acid secretion over the day and night was more pronounced in the omeprazole-treated rats (maximal inhibition 100%, minimum 85%) than in those receiving ranitidine (mean 70%). In both groups, there was a great increase in plasma gastrin, somewhat greater after omeprazole than after ranitidine. The gastrin concentration in the antrum was almost doubled by both treatments and there was a moderate increase in the number of antral gastrin cells in the omeprazole-treated rats. The number of enterochromaffin-like (ECL) cells (per visual field) increased in the oxyntic mucosa to the same extent (greater than 100%) in the ranitidine- and omeprazole-treated rats. Apart from the gastrin cells in the antrum and the ECL cells in the corpus no other gastric endocrine cell type seemed to respond to treatments with antisecretagogues. We conclude that, regardless of the type of antisecretagogue used, effective and long-term suppression of gastric acid secretion results in sustained hypergastrinemia and increased number of ECL cells. Conceivably therefore, the ECL cell hyperplasia reflects the trophic effect of gastrin.     

Changes in the distributions of epiphytic lichens in southern Sweden using a new statistical method

Past studies on changes in species distribution have mainly been based on analysis of range boundaries. In contrast, the method used here evaluates shifts in species' geographic centroids within a predefined area. We used presence/absence data on epiphytic lichens collected 1986 and 2003 from 64 sites in southern Sweden. A centroid was calculated each year, for each lichen species and substrate. The distance of centroid movement was evaluated in a permutation procedure. In total, 56 lichen species on 22 tree species were involved in the analyses, yielding 30 cases that had sufficient sample sizes both years to be evaluated. Out of these, three exhibited a significant movement of their centroid. The shift of lichen centroids of Hypogymnia physodes (L.) Nyl. and Vulpicida pinastri (Scop.) J.-E. Mattsson & M. J. Lai on the tree species Juniperus communis L. was 50 and 151 km with the direction 27° and 48°, respectively. For Hypogymnia physodes on Pinus sylvestris L., corresponding values were 41 km and 30°. The northnortheast shifts of these species in Sweden could be a response to a warming climate.     

Interaction of the hepatic receptor protein for 2,3,7,8-tetrachlorodibenzo-p-dioxin with DNA

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) binds to a specific, high-affinity, low-capacity protein in rat liver cytosol. The TCDD-receptor complex is a large molecule with a Stokes radius of 6.6 nm as determined by gel filtration on calibrated columns. The receptor complex sediments at 5.0 S on glycerol gradients. The calculated molecular weight from the physical parameters was 136 000 and the frictional ratio 1.79.The TCDD-receptor complex binds to DNA-cellulose without preceding heat activation or incubation at high ionic strength. The receptor must first bind TCDD before it can interact with DNA. The DNA-binding ability can be removed from the TCDD receptor by limited proteolysis with trypsin. This treatment does not affect the TCDD-binding site of the receptor. The proteolytic fragment of the TCDD-receptor complex containing the TCDD-binding site but not the ability to bind to DNA appears to be approximately the same size as the native receptor, as judged from chromatography of Sepharose CL-6B and glycerol gradient centrifugation.     

Household salt for retrospective dose assessments using OSL: signal integrity and its dependence on containment,sample collection,and signal readout

The aim of this work was to determine how a latent optically stimulated luminescence (OSL) signal in irradiated household salt is preserved under various ambient conditions, from the time of exposure to the time of signal readout. The following parameters were examined: optical fading in fluorescent light and under darkroom conditions (red light), thermal stability of the OSL signal during storage in a light-tight container, optical fading in representative container types, and sensitization effects of the OSL signal in exposed household salt. Furthermore, the influence of grain mixing within the saltshaker or salt container was studied by determining the dose gradient within typical salt packages. Finally, the signal integrity of salt irradiated under field conditions in a village in Belarus contaminated by Chernobyl fallout was investigated. The results show that the OSL signal in household salt is preserved in large cardboard box containers, but not in white plastic salt containers or in small portion bags used in, e.g., fast food restaurants. Furthermore, the continuous wave blue OSL signal in household salt does not fade significantly during storage up to 140 days. On the contrary, the signal appears to slowly increase during storage (“inverse fading”). Field tests of two different salt containers (with and without black tape to block light) located in Belarussian households confirmed that the signal is preserved in white plastic salt containers when they are covered with extra light-shielding material.     

Promoting islet cell function after transplantation

Engraftment (i.e., the adaptation of transplanted pancreatic islets to their new surroundings with regard to revascularization, reinnervation, and reorganization of other stromal compartments) is of crucial importance for the survival and function of the endocrine cells. Previous studies suggest that transplantation induces both vascular and stromal dysfunctions in the implanted islets when compared with endogenous islets. Thus the vascular density and the blood perfusion of islet grafts is decreased and accompanied with a capillary hypertension. This leads to hypoxic conditions, with an associated shift toward anaerobic metabolism in grafted islets. An improved engraftment will prevent or compensate for the vascular/stromal dysfunction seen in transplanted islets and thereby augment survival of the islet implant. By such means the number of islets needed to cure the recipient will be lessened. This will increase the number of patients that can be transplanted with the limited material available.     

Identification and functional characterization of new missense SNPs in the coding region of the TP53 gene

Infrequent and rare genetic variants in the human population vastly outnumber common ones. Although they may contribute significantly to the genetic basis of a disease, these seldom-encountered variants may also be miss-identified as pathogenic if no correct references are available. Somatic and germline TP53 variants are associated with multiple neoplastic diseases, and thus have come to serve as a paradigm for genetic analyses in this setting. We searched 14 independent, globally distributed datasets and recovered TP53 SNPs from 202,767 cancer-free individuals. In our analyses, 19 new missense TP53 SNPs, including five novel variants specific to the Asian population, were recurrently identified in multiple datasets. Using a combination of in silico, functional, structural, and genetic approaches, we showed that none of these variants displayed loss of function compared to the normal TP53 gene. In addition, classification using ACMG criteria suggested that they are all benign. Considered together, our data reveal that the TP53 coding region shows far more polymorphism than previously thought and present high ethnic diversity. They furthermore underline the importance of correctly assessing novel variants in all variant-calling pipelines associated with genetic diagnoses for cancer.Subject terms: Tumour-suppressor proteins, Genetics research