Subarachnoid haemorrhage: long-term follow-up results of late surgical versus conservative treatment

During 1964-9, 178 patients with subarachnoid haemorrhage from a single intracranial arterial aneurysm were allocated at random to receive operative or conservative treatment at an average of seven weeks after bleeding. During the follow-up fatal rebleeding episodes occurred in six of the 86 patients treated surgically and 16 of the 92 treated conservatively. This difference was significant. Fatal rebleeding occurred on average 40 months after the first episode. Deaths from all causes occurred in 17 of the 86 patients treated surgically and 22 of the 92 treated conservatively. Life-table analysis of the chances of surviving 1, 5, and 11 years gave probabilities of 95 and 91%, 87 and 86%, and 76 and 75% in the two treatment groups respectively. Of the 139 patients alive after a mean follow-up of nine years, 130 (94%) were fully independent in their daily lives, and only 43 (31%) were unable to work. The method of treatment did not affect the quality of survival.The results show that fatal rebleeding may occur even many years after the first episode. Nevertheless, if the patient is in good condition seven weeks after a haemorrhage from a single intracranial arterial aneurysm the outcome is good irrespective of whether operation is performed at this late stage.     

Thresholds in genotoxicity responses

It has been commonly accepted that risk assessments of genotoxic chemicals are based on linear extrapolation methods. However, there is substantial evidence that some chemicals may be genotoxic only at high doses by mechanisms that do not occur at low doses, or only under specific conditions in genotoxicity assays, but are inactive at concentrations within the range of human exposure levels. There are a variety of possible mechanisms of thresholded genotoxicity, including disruption of cell division and chromosome segregation, inhibition of DNA synthesis, overloading of oxidative defence mechanisms, metabolism or plasma binding capacity, disturbances of metal homeostasis, cytotoxicity and physiological perturbations in in vivo assays. The degrees of evidence supporting the proposed mechanisms are variable and not all are sufficiently robust to be universally accepted as yet by the scientific community. However, a survey of industrial companies indicated that data have been accepted by some regulatory authorities indicating thresholds contributing to genotoxicity responses.     

Potentiation of dimethylnitrosamine genotoxicity in rat hepatocytes isolated following ethanol treatment in vivo

Unscheduled DNA synthesis (UDS), following exposure to dimethylnitrosamine (DMN), was potentiated in cultured hepatocytes isolated following treatment of rats for 14 or 28 days with 20% ethanol/5% sucrose solution. Ethanol treatment was associated with increased UDS, a concomitant increase in hepatic microsomal protein concentration and DMN N-demethylase activity. Increased aniline hydroxylase activity of hepatic microsomes from ethanol-treated rats preceded the measured increase in microsomal protein content or DMN metabolism. The increase in metabolism of DMN in vitro and potentiation of DMN-induced UDS associated with ethanol treatment may contribute to a synergistic effect of ethanol on DMN hepatotoxicity and carcinogenicity. In contrast, ethanol pretreatment did not increase the cytotoxicity of DMN as characterized by enzyme release.     

Predator protection versus rapid growth in a montane leaf beetle

Summary Adults and larvae of Chrysomela aenicollis (Coleoptera: Chrysomelidae) feed on foliage of Salix species (Salicaceae) between 2,400–3,400 m above sea level in the eastcentral Sierra Nevada mountains of California. We predicted that (1) cold climatic conditions would be a more frequent source of mortality at higher elevations, (2) mildweather agents of mortality such as predation should be more severe at lower elevations, and (3) populations of C. aenicollis would be adapted to the local selective regime at each elevation. We tested these predictions in 1984 and 1985 by transferring over 6,000 eggs and larvae within and between two sites at 2,810 and 3,240 m elevation above sea level. During mild summer weather at both sites, survivorship on Salix branches isolated by a barrier of sticky resin was similar to that on control branches, and we concluded that aerial predators were the primary cause of mortality. At least one major predator, a solitary wasp (Symmorphus sp., Hymenoptera: Eumenidae), was specifically associated with C. aenicollis at the lower site, where beetle mortality was highest. At both sites in 1984 and 1985, larvae originating from the lower site remained in aggregations and survived more frequently than larvae from the upper site, suggesting that they are better defended against predators. During a storm with cold weather late in the 1984 season, larvae and pupae died more frequently at the upper site, and there was a marginally significant trend (P<0.1) for the lower site individuals to die more frequently than upper site larvae during the cold storm. Upper site larvae grew approximately 10% faster than lower site larvae at the lower site and under controlled conditions in the laboratory. These findings indicate that upper and lower site populations were adapted to the local selective regime, which suggest how populations of montane phytopagous insects may adapt to changing elevations.     

Tamoxifen treatment induces protection in murine cysticercosis

Administration of tamoxifen (an antiestrogen) produced an 80% parasite load reduction in female mice, and a weaker effect of 50% in male mice. This protective effect was associated in both sexes, with an increase in the mRNA levels of interleukin (IL)-2 (a cytokine associated with protection against cysticerci) and IL-4 (no effect on infection). tamoxifen treatment modified 17-beta estradiol production in females, whereas serum testosterone was not affected. However, the expression of the 2 types of estrogen receptor (ER), i.e., ER-alpha and ER-beta, in the spleen of infected mice of both sexes, was decreased by tamoxifen treatment. In vitro, treatment of Taenia crassiceps with tamoxifen reduced reproduction and loss of motility. These results indicate that tamoxifen treatment is a new therapeutic possibility to treat cysticercosis, because it can act at both ends of the host-parasite relationship, i.e., by increasing the cellular immune response protective against the parasite and by directly affecting the parasite's reproduction and survival.     

Current aspects in metal genotoxicity

While carcinogenic metal ions are mostly non-mutagenic in bacteria, different types of cellular damage have been observed in mammalian cells, which may account for their carcinogenic potential. Two modes of action seem to be predominant: the induction of oxidative DNA damage, best established for chromium compounds, and the interaction with DNA repair processes, leading to an enhancement of genotoxicity in combination with a variety of DNA damaging agents. In the case of Cd(II), Ni(II), Co(II), Pb(II) and As(III), DNA repair processes are disturbed at low, non-cytotoxic concentrations of the respective metal compounds. Even though different steps in DNA repair are affected by the diverse metals, one common mechanism might be the competition with essential metal ions.     

Yeast DEL assay detects protection against radiation-induced cytotoxicity and genotoxicity: adaptation of a microtiter plate version

The DEL assay in yeast detects DNA deletions that are inducible by many carcinogens. Here we use the colorimetric agent MTS to adapt the yeast DEL assay for microwell plate measurement of ionizing radiation-induced cell killing and DNA deletions. Using the microwell-based DEL assay, cell killing and genotoxic DNA deletions both increased with radiation dose between 0 and 2000 Gy. We used the microwell-based DEL assay to assess the effectiveness of varying concentrations of five different radioprotectors, N-acetyl-l-cysteine, l-ascorbic acid, DMSO, Tempol and Amifostine, and one radiosensitizer, 5-bromo-2-deoxyuridine. The microwell format of the DEL assay was able to successfully detect protection against and sensitization to both radiation-induced cytotoxicity and genotoxicity. Such radioprotection and sensitization detected by the microwell-based DEL assay was validated and compared with similar measurements made using the traditional agar-based assay format. The yeast DEL assay in microwell format is an effective tool for rapidly detecting chemical protectors and sensitizers to ionizing radiation and is automatable for chemical high-throughput screening purposes.     

Studies on the genotoxicity of endosulfan in bacterial systems

Endosulfan, an organochlorine pesticide, was subjected to the differential sensitivity assay in repair-deficient and repair-proficient strains of Escherichia coli K12, prophage lambda induction assay in WP2s (lambda) and mutation induction in E. coli K12. The induction of umu gene expression with endosulfan was studied also in Salmonella typhimurium TA1535/pSK1002 cells. The differential sensitivity assay revealed that the recA 13 strain was the most sensitive. Endosulfan induced prophage lambda in E. coli and umu gene expression in S. typhimurium cells; however, the extent of the effects were low. Endosulfan also induced a dose-dependent increase in forward mutations in E. coli K12 cells from ampicillin sensitivity to ampicillin resistance. Our studies indicate the genotoxic potential of endosulfan and the role of the recA gene in the repair of endosulfan-induced DNA damage.     

Ciprofloxacin: in vivo genotoxicity studies

The fluoroquinolone ciprofloxacin is widely used in antimicrobial therapy. It inhibits the bacterial gyrase and in high concentrations in vitro also the functionally related eukaryotic topoisomerase-II, which resulted in genotoxic effects in several in vitro tests. In order to evaluate the relevance of these findings, ciprofloxacin was tested in vivo for genotoxic activity using the following test systems: micronucleus test in bone marrow of mice, cytogenetic chromosome analysis in Chinese hamster, dominant lethal assay in male mice and UDS tests in primary rat and mouse hepatocytes in vivo. These results are compared with already published in vitro and in vivo studies with ciprofloxacin. All in vivo genotoxicity revealed no genotoxic effect for ciprofloxacin. In addition, ciprofloxacin was found to be non-carcinogenic in two rodent long-term bioassays. Therefore, ciprofloxacin is considered to be safe for therapeutic use.     

Liver-specific alpha 2 interferon gene expression results in protection from induced hepatitis

The current therapy for hepatitis B and C is based on systemic administration of recombinant human alpha interferon (r-hIFN-alpha). However, systemic delivery of r-hIFN-alpha is associated with severe side effects, but more importantly, it is effective in only a small percentage of patients. In an effort to maximize IFN-alpha antiviral efficacy, we have explored the therapeutic potential of murine IFN-alpha2 (mIFNalpha2) selectively expressed in the liver. To this end, we have developed a helper-dependent adenovirus vector (HD) containing the mIFN-alpha2 gene under the control of the liver-specific transthyretin promoter (HD-IFN). Comparison with a first-generation adenovirus carrying the same mIFN-alpha2 expression cassette indicates that at certain HD-IFN doses, induction of antiviral genes can be achieved in the absence of detectable circulating mIFN-alpha2. Challenge of injected mice with mouse hepatitis virus type 3 showed that HD-IFN provides high liver protection. Moreover, liver protection was also observed in acute nonviral liver inflammation hepatitis induced by concanavalin A at 1 month postinfection. These results hold promise for the development of a gene therapy treatment for chronic viral hepatitis based on liver-restricted expression of IFN-alpha2.     

Anti-pathogen protection versus survival costs mediated by an ectosymbiont in an ant host

The fitness effects of symbionts on their hosts can be context-dependent, with usually benign symbionts causing detrimental effects when their hosts are stressed, or typically parasitic symbionts providing protection towards their hosts (e.g. against pathogen infection). Here, we studied the novel association between the invasive garden ant Lasius neglectus and its fungal ectosymbiont Laboulbenia formicarum for potential costs and benefits. We tested ants with different Laboulbenia levels for their survival and immunity under resource limitation and exposure to the obligate killing entomopathogen Metarhizium brunneum. While survival of L. neglectus workers under starvation was significantly decreased with increasing Laboulbenia levels, host survival under Metarhizium exposure increased with higher levels of the ectosymbiont, suggesting a symbiont-mediated anti-pathogen protection, which seems to be driven mechanistically by both improved sanitary behaviours and an upregulated immune system. Ants with high Laboulbenia levels showed significantly longer self-grooming and elevated expression of immune genes relevant for wound repair and antifungal responses (β-1,3-glucan binding protein, Prophenoloxidase), compared with ants carrying low Laboulbenia levels. This suggests that the ectosymbiont Laboulbenia formicarum weakens its ant host by either direct resource exploitation or the costs of an upregulated behavioural and immunological response, which, however, provides a prophylactic protection upon later exposure to pathogens.