Age-related activity of catalase in different genotypes of drosophila melanogaster

The enzyme catalase protects aerobic organisms from oxygen free radical damage by converting hydrogen peroxide to molecular oxygen and water before it can decompose to form the highly reactive hydroxyl radical. This damage has been implicated in the increased risk of disease and death associated with aging. In order to study the age-specific activity of catalase in male D. melanogaster three different genotypes (Oregon w.t., ebony mutant, and the F₁ hybrids of the two), whose mean life spans are about 55, 40, and 63 days, respectively, were used in the experiments. As the mean life span of the mutant is the shortest the enzyme activity was measured until the 43rd day, whereas in Oregon w.t., it continued until the 72nd day and in hybrids until the 79th day (longest-lived group). Although the enzyme activity in mutant flies increased sharply till the 9th day (and attained the highest level), later it declined sharply. In the other genotypes, the enzyme activity increased gradually until the 20–25th days, and then declined steadily in comparison to that of the ebony mutant. We found that higher catalase activity is associated with reduced life span for ebony mutant. It is obvious that some relationship exists between life span and antioxidant enzymes; however, a review of the literature does not at the moment allow as to understand the underlying mechanism involved in aging.     

Reduced DNA repair in progeria cells and effects of γ-ray irradiation on UV-induced unscheduled DNA synthesis in normal and progeria cells

A reduction in the amount of UV-induced unscheduled DNA synthesis (UDS), and reduced cell survival and host-cell reactivation against UV exposure in Hutchinson-Gilford progeria syndrome cell strains were shown. UV-induced UDS in 4 progeria cell strains was 33–50% of the normal level. A similar reduction in the UV-induced UDS in normal cells was caused by γ-ray irradiation to the cells before UV irradiation. The dose of γ-rays required to cause a reduction in UDS of normal cells to the level of progeria cells was 40 Gy and the reduction was reversible after 2 days. In progeria cells, γ-ray irradiation further reduced UDS with a lower γ-ray dose required than in normal cells, and the reduction was also reversible but with less relative recovery than in normal cells. The presence of a ‘built-in’ defect in progeria cells responsible for the reduced DNA-repair capacity was suggested, and such defect may share a common mechanism with the reduction of UV-induced UDS in normal cells caused by γ-ray irradiation.     

Tumor mutation burden determined by a 645-cancer gene panel and compared with microsatellite instability and mismatch repair genes in colorectal cancer

BackgroundTumor mutation burden (TMB) assessed by tumor-related gene panels (CRGP), microsatellite instability (MSI), and mismatch repair (MMR) has been proven to be associated with prognosis, and these factors are prognostic indicators in predicting the benefits of immune checkpoint blockade (ICB) in solid tumors. However, whether the TMB calculated by CRGPs, MSI, and MMR is associated with overall survival (OS) in patients with colorectal cancer (CRC) remains to be explored.MethodsThe prognostic threshold of the panel-TMB was explored by a panel of 645 genes (GP645) from 41 CRC patients in Jiangsu Cancer Hospital (JCH dataset). The results were further validated using 531 CRC patients from The Cancer Genome Atlas (TCGA) database.ResultsMutations of the GP645 genes were distributed on 21 chromosomes. Spearman correlation analysis showed that the panel-TMB was positively correlated with TMB measured by whole-exome sequencing (WES) (wTMB) in the TCGA dataset (R=0.75, P<0.001). Kaplan-Meier survival analysis demonstrated that higher panel-TMB in CRC patients was significantly associated with a poor OS (P=0.0062). MSI and MMR status were determined using the GP645 by next-generation sequencing (NGS). The proportions of MSI-H and dMMR accounted for less than 10% in CRC, the vast majority of MSI-H/dMMR samples also had high TMB [positive predictive value (PPV) =66.6%], and only 13.3% of samples with high TMB were classified as MSI-high/dMMR. In addition, patients with low-TMB were associated with MSS/pMMR (96.2%), and these results are consistent with earlier studies.ConclusionsGP645 was constructed to evaluate OS in Chinese CRC patients. Panel-TMB and MSI/MMR might be potential prognostic predictors of CRC patients using the GP645.     

Effects of combretastatin on murine tumours monitored by 31P MRS, 1H MRS and 1H MRI

Purpose: Combretastatins have tubulin-binding activity and are being investigated for their toxicity against tumour vasculature. We report the use of ³¹P and ¹H magnetic resonance (MR) spectroscopy and ¹H MR imaging for monitoring the effects of combretastatin A-4 prodrug (100mg/kg, i.p.) on energy metabolism and necrosis, respectively, in the C3H murine mammary tumour.Materials and Methods: The tumours (volume ca. 200mm³) were grown in the hind foot of mice. MR examinations were performed without anaesthesia within a 7.1 Tesla magnet. ³¹P MRS (TR = 6 s) was performed before treatment and at 1-, 2-, 3-, and 24-h after injection of drug or saline via an i.p. line. ¹H MRS (PRESS; 24μl voxel; TR = 2 s; TE = 135 ms) and both T₁-weighted (TR = 0.2 s; TE = 0.02 s) and T₂-weighted (TR = 2 s; TE = 0.20 s) ¹H MRI were performed before treatment and 2.5 and 24 h afterwards.Results: The ratio β-nucleotide triphosphate/inorganic phosphate fell by 33% within 1 h of treatment and remained constant for a further 2 h. A small but significant fall in pH (by 0.11 units) was observed at 1 h. Although an increase in the ¹H MR spectroscopy signal at about 1.32 ppm (predominantly from lactate) was observed in some tumours following combretastatin treatment, this effect was not seen consistently. No changes in the intensity of T₂-weighted ¹H MR images or in tumour necrosis (measured histologically) were detected within 3 h of treatment.Conclusions: The reduction in tumour energetics and pH was consistent with a reduction in tumour blood flow but this occurred before any significant incidence of haemorrhagic necrosis was detected. The combretastatin dose used to achieve these effects was less than one tenth of the maximum tolerated dose in mice.     

The lifetime of hypoxic human tumor cells

Purpose: For hypoxic and anoxic cells in solid tumors to be a therapeutic problem, they must live long enough to be therapeutically relevant, or else be rapidly recruited into the proliferating compartment during therapy. We have, therefore, estimated lifetime and recruitment rate of hypoxic human tumor cells in multicell spheroids in vitro, or in xenografted tumors in SCID mice.Materials and Methods: Cell turnover was followed by flow cytometry techniques, using antibodies directed at incorporated halogenated pyrimidines. The disappearance of labeled cells was quantified, and verified to be cell loss rather than label dilution. Repopulation was studied in SiHa tumor xenografts during twice-daily 2.5-Gy radiation exposures.Results: The longevity of hypoxic human tumor cells in spheroids or xenografts exceeded that of rodent cell lines, and cell turnover was slower in xenografts than under static growth as spheroids. Human tumor cells remained viable in the hypoxic regions of xenografts for 4–10 days, compared to 3–5 days in spheroids, and 1–3 days for most rodent cells in spheroids. Repopulation was observed within the first few radiation treatments for the SiHa xenografts and, with accumulated doses of more than 10 Gy, virtually all recovered cells had progressed through at least one S-phase.Conclusion: Our results suggest an important difference in the ability of human vs. rodent tumor cells to withstand hypoxia, and raise questions concerning the increased longevity seen in vivo relative to the steady-state spheroid system.     

Cost analysis of transmural home care for terminal cancer patients

The economic implications of home care service programmes for oncology patients remain unclear. This quasi-experimental study investigated the costs of a transmural home care programme for terminal cancer patients and compared them to those of the standard care available. The programme intended to optimize communication, cooperation and coordination between the intra- and extra- mural health care organizations (transmural care). Complete sets of data could be retrieved for 57 of the 79 patients in the intervention group, and for 29 of the 37 patients in the control group. Comparison of the intervention and control group revealed significantly lower pharmaceutical and rehospitalization costs in the intervention group, whilst community nursing and home help costs were significantly higher. However, no significant difference could be found for total health care costs between the groups. In view of this, and that the programme has proved to have significantly positive effects on both the patient's and direct caregiver's quality of life, the installation of such programmes in every hospital with a multidisciplinary oncology unit is recommended.     

Experimental evaluation of bleeding complications,thrombogenicity and neointimal characteristics of prosthetic patch materials used for carotid angioplasty

Experiments were designed to compare perioperative blood loss, early thrombogenicity and morphologic and functional characteristics of the neointima of three types of prosthetic materials used for carotid artery patch angioplasty. Bilateral carotid patch angioplasties were performed in 20 dogs, using 20 gelatin-impregnated fluoropassivated Dacron (GIF), 10 untreated knitted Dacron and 10 expanded polytetrafluoroethylene (PTFE) patches (5 cm²). Intraoperative blood loss, platelet deposition at 24 h and neointimal morphology at 6 weeks after the operation were assessed. Bioassay of the neointima was performed at 6 weeks in 16 patches. Mean (s.e.m.) blood loss was significantly less in GIF patches (14.7 (2.7) ml) compared with either PTFE (75.6 (24) ml) or untreated Dacron (64. 3 (9.5)) (P < 0.005). Mean (s.e.m.) platelet deposition in GIF patches (1380 (328) platelets/cm²) was approximately 50% less at 24 h than in untreated Dacron (2562 (1035) platelets/cm²) or PTFE (2140 (998) platelets/cm²) patches (P < 0.05). Neo-intimal coverage was greater in PTFE (94 (1.3%)) compared with GIF (79 (2.7%)) or untreated Dacron (86 (2.4%)) patches (P < 0.05). The thickness of the neointimal layer of PTFE (0.5 (0.01) mm) patches was greater than other patch types; GIF (0.2 (0.01) mm) or untreated Dacron (0.3 (0.01) mm) (P < 0.05). Under bioassay conditions, acetylcholine caused release of vasoactive relaxing factor(s) from all patches. However, relaxations from baseline were less with GIF patches (−37.9 (11.7)% versus −54.5 (9.6) for untreated Dacron; −50.2 (15.2)% for PTFE) (P = n.s.). Endothelin-1 release occurred from all patches and was increased with the extent of neointimal coverage. These data demonstrate that GIF patches caused the least perioperative bleeding, were the least thrombogenic at 24 h and developed the thinnest neointima at 6 weeks. All patch materials developed a functioning neointima. Copyright © 1996 The International Society for Cardiovascular Surgery.