Solution Radioactivated by Hadron Radiation Can Increase Sister Chromatid Exchanges

When energetic particles irradiate matter, it becomes activated by nuclear reactions. Radioactivation induced cellular effects are not clearly understood, but it could be a part of bystander effects. This investigation is aimed at understanding the biological effects from radioactivation in solution induced by hadron radiation. Water or phosphate buffered saline was activated by being exposed to hadron radiation including protons, carbon- and iron-ions. 1 mL of radioactivated solution was transferred to flasks with Chinese hamster ovary (CHO) cells cultured in 5 mL of complete media. The induction of sister chromatid exchanges (SCE) was used to observe any increase in DNA damage responses. The energy spectrum and the half-lives of the radioactivation were analyzed by NaI scintillation detector in order to identify generated radionuclides. In the radioactivated solution, 511 keV gamma-rays were observed, and their half-lives were approximately 2 min, 10 min, and 20 min. They respectively correspond to the beta+ decay of ¹⁵O, ¹³N, and ¹¹C. The SCE frequencies in CHO cells increased depending on the amount of radioactivation in the solution. These were suppressed with a 2-hour delayed solution transfer or pretreatment with dimethyl sulfoxide (DMSO). Our results suggest that the SCE induction by radioactivated solution was mediated by free radicals produced by the annihilated gamma-rays. Since the SCE induction and DMSO modulation are also reported in radiation-induced bystander effects, our results imply that radioactivation of the solution may have some contribution to the bystander effects from hadron radiation. Further investigations are required to assess if radioactivation effects would attribute an additional level of cancer risk of the hadron radiation therapy itself.     

Production of vitamin B12 in an upflow anaerobic filter continuous reactor using Acetobacterium sp.

The accumulation of biofilm by Acetobacterium sp. during continuous culture in an upflow anaerobic filter (UAF) growing on methanol-formate was the result of space velocity and inlet concentrations of substrate and Co⁺². To achieve good development of biofilm, a space velocity of 0.38 h^–1, inlet substrate concentrations of 125 mM of both methanol and formate, and Co⁺² at 0.16 mM were required. Cell productivities in the effluent of the UAF-reactor were about 6-fold higher than in chemostat cultures (0.20 g l^–1 h^–1 for UAF and 0.035 g l^–1 h^–1 for chemostat) (previous studies), and the maximum vitamin B₁₂ specific concentration was 5.1 mg g cell^–1.     

Winter energetics of Virginia opossums Didelphis virginiana and implications for the species' northern distributional limit

While climatic limitations are widely recognized as primary factors determining the distributions of many species, the physiological link between climate and species' persistence is poorly understood. The Virginia opossum Didelphis virginiana is a species for which winter energetics have been evaluated and a northern geographical limit has been hypothesized. Expansion of opossum populations beyond this limit, however, suggests that a previous winter energetics model requires modification. I update this energetics model by incorporating random foraging success to estimate the probability of opossum survival under varying winter temperature regimes. Estimation of opossum "success" for winters in Amherst, Massachusetts, since 1926 showed that juvenile females, the key breeding component of the population, would survive at a rate high enough to maintain a stable population in only 4 of the 77 yr. The model correctly predicted the fate of 13 of 14 opossums monitored in the Amherst area during the winters of 2000–2003. The current energetics model does not correctly predict autumn weight gain, but it does accurately estimate opossum winter survival. However, the model predicts that opossums should be winter-limited in areas such as Amherst, Massachusetts, where in fact they are well established. This discrepancy may be explained in three ways: weather station data do not adequately reflect available microclimates, opossums show high levels of flexibility in cold-weather foraging behavior, and most likely, humans provide food and shelter that mitigate the effect of winter.     

Neuronal pathways from low-threshold muscle and cutaneous afferents innervating tail to trunk muscle motoneurons in the cat

We studied neuronal pathways from low-threshold muscle (group I, II) and cutaneous afferents (group A(alpha)beta) innervating the tail to motoneurons innervating trunk muscles (m. iliocostalis lumborum and m. obliquus externus abdominus) in 18 spinalized cats. Stimulation of group I muscle afferents produced excitatory postsynaptic potentials or excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials in all motoneurons innervating the m. iliocostalis lumborum which showed effects (32%), and predominantly inhibitory postsynaptic potentials in motoneurons innervating the m. obliquus externus abdominus (47%). Stimulation of group I+II afferents produced significant increases of the incidence of motoneurons showing postsynaptic potentials (the notoneurons innervating the m. iliocostalis lumborum, 87%; the motoneurons innervating the m. obliquus externus abdominus, 82%). The effects of low threshold cutaneous afferents were bilateral, predominantly producing inhibitory postsynaptic potentials in motoneurons innervating both muscles. These results suggest that neuronal pathways from muscle afferents to back muscle motoneurons mainly increase the stiffness of the trunk to maintain its stability, while those to abdominal muscles help to extend the dorsal column by decreasing their activities. The results also indicate that neuronal pathways from cutaneous afferents to trunk motoneurons functionallY disconnect the tail from the trunk.     

Intervention of somatic mutational events in vivo by a germline defect at the adenine phosphoribosyltransferase locus

Both germline and somatic mutations are known to affect phenotypes of human cells in vivo. In previous studies, we cloned mutant peripheral blood T cells from germline heterozygous humans for adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) deficiency and found that approximately 1.3 × 10^–4 peripheral T cells had undergone in vivo somatic mutations. Loss of heterozygosity (LOH) was the major cause of the mutations at the APRT locus since approximately 80% of the mutant T cell clones exhibited loss of normal alleles. In the present study, we identified three heterozygous individuals for APRT deficiency (representing two separate families), in whom none of the somatic mutant cells exhibited LOH at the APRT locus. The germline mutant APRT alleles of these heterozygotes from two unrelated families had the same gross DNA abnormalities detectable by Southern blotting. None of the germline mutant APRT alleles so far reported had such gross DNA abnormalities. The data suggest that the germline mutation unique to these heterozygous individuals is associated with the abrogation of LOH in somatic cells. The absence of LOH at a different locus has already been reported in vitro in an established cell line but the present study describes the first such event in vivo in human individuals. Received: 10 May 1996     

Abortive Infection of L Cells by Influenza B Virus: Defect in Bud Formation

Host-dependent restriction of influenza B virus replication in L cells was analysed in comparison with productive infection in MDCK or 1–5C-4 cells. The synthesis and intracellular distribution of virus-specific proteins and the production of cytoplasmic ribonucleoproteins in nonpermissive L cells were similar to those in permissive MDCK cells. However, an electron microscopic study of infected L cells showed neither extracellular virions nor budding virus particles on the cell surface, in contrast to MDCK cells which produced numerous virus particles. PAGE analysis of the plasma membrane isolated from the cells demonstrated no significant difference in the composition of viral polypeptides between permissive 1-5C-4 and nonpermissive L cells. It was noted that the abortiveness of influenza B virus infection in L cells may be due to a defect in host cell function involved in the initiation of virus budding.