Detrimental effect of fast neutrons on cultured immature rat hippocampal cells: relative biological effectiveness of in vitro cell death indices

This in vitro study compared the detrimental effect and relative biological effectiveness (RBE) of high-linear energy transfer (LET) fast neutrons on rat immature hippocampal cultured cells with those of low-LET γ rays. Immature hippocampal cells were exposed to fast neutrons or γ rays. Cytotoxicity and cell viability were analyzed using a lactate dehydrogenase (LDH)-release assay and a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, respectively. The cytotoxicity and cell viability with fast neutrons or γ rays varied in a dose-dependent pattern. In the LDH release and MTT assay indices, the RBEs of fast neutrons were approximately 2.35 and 2.42, respectively. Fast neutrons markedly induced apoptotic changes in immature hippocampal cells with increased expression of active caspase-3 and cleaved poly(ADP-ribose) polymerase. Increased cytotoxicity and decreased cell viability in immature hippocampal cells were seen in a dose-dependent pattern after fast-neutron and γ irradiation. Fast neutrons have a higher RBE for cell death indices than γ rays.

A mouse model of heterogeneous, c-MYC-initiated prostate cancer with loss of Pten and p53

Human tumors are heterogeneous and evolve through a dynamic process of genetic mutation and selection. During this process, the effects of a specific mutation on the incipient cancer cell may dictate the nature of subsequent mutations that can be tolerated or selected for, affecting the rate at which subsequent mutations occur. Here we have used a new mouse model of prostate cancer that recapitulates several salient features of the human disease to examine the relative rates in which the remaining wild type alleles of Pten and p53 tumor suppressor genes are lost. In this model, focal overexpression of c-MYC in a few prostate luminal epithelial cells provokes a mild proliferative response. In the context of compound Pten/p53 heterozygosity, c-MYC-initiated cells progress to prostatic intraepithelial neoplasia (mPIN) and adenocarcinoma lesions with marked heterogeneity within the same prostate glands. Using Laser Capture Microdissection and gene copy number analyses, we found that the frequency of Pten loss was significantly higher than that of p53 loss in mPIN but not invasive carcinoma lesions. c-MYC overexpression, unlike Pten loss, did not activate the p53 pathway in transgenic mouse prostate cells, explaining the lack of selective pressure to lose p53 in the c-MYC-overexpressing cells. This model of heterogeneous prostate cancer based on alterations in genes relevant to the human disease may be useful for understanding pathogenesis of the disease and testing new therapeutic agents.

Insulin resistance impairs nigrostriatal dopamine function

Clinical studies have indicated a link between Parkinson's disease (PD) and Type 2 Diabetes. Although preclinical studies have examined the effect of high-fat feeding on dopamine function in brain reward pathways, the effect of diet on neurotransmission in the nigrostriatal pathway, which is affected in PD and parkinsonism, is less clear. We hypothesized that a high-fat diet, which models early-stage Type 2 Diabetes, would disrupt nigrostriatal dopamine function in young adult Fischer 344 rats. Rats were fed a high fat diet (60% calories from fat) or a normal chow diet for 12 weeks. High fat-fed animals were insulin resistant compared to chow-fed controls. Potassium-evoked dopamine release and dopamine clearance were measured in the striatum using in vivo electrochemistry. Dopamine release was attenuated and dopamine clearance was diminished in the high-fat diet group compared to chow-fed rats. Magnetic resonance imaging indicated increased iron deposition in the substantia nigra of the high fat group. This finding was supported by alterations in the expression of several proteins involved in iron metabolism in the substantia nigra in this group compared to chow-fed animals. The diet-induced systemic and basal ganglia-specific changes may play a role in the observed impairment of nigrostriatal dopamine function.

Dry pleural dissemination in non-small cell lung cancer: prognostic and diagnostic implications

PURPOSE

To compare prognostic differences between dry pleural dissemination (DPD) and wet pleural dissemination (WPD) in patients with non-small cell lung cancer (NSCLC) andto review the applicability of computed tomographic (CT) findings of DPD for rendering the diagnosis of this disease.

MATERIALS AND METHODS

The institutional review board approved this retrospective study, and informed patient consent was waived. Of 98 patients (male-to-female ratio, 55:43; mean age, 60 years ± 12) with NSCLC, 20 patients had pathologically proved DPD, and the remaining 78 patients had pathologically proved WPD. Twelve patients, who had been lost to follow-up, were excluded from survival analysis. Observers looked for CT findings of multiple pleural or fissural nodules (more than six in number) and uneven thickening or bandlike thickness. Survival after initial presentation was analyzed and compared between patients with DPD (n = 19) and patients with WPD (n = 67) by using the Kaplan-Meier method and the log-rank test. The sensitivity of CT for depicting DPD was also calculated.

RESULTS

Median survival after initial presentation was significantly longer in patients with DPD than in patients with WPD; it was 38 months (95% confidence interval [CI]: 29.9 months, 46.0 months) in patients with DPD and 13 months (95% CI: 9.8 months, 16.2 months) in patients with WPD (P <.001). CT helped identify DPD in 90% (18 of 20) of patients with pathologically proved DPD. Multiple pleural or fissural nodules were noted on CT images in 16 (80%) of 20 patients. Uneven or bandlike pleural thickening was recognized in 15 (75%) patients.

CONCLUSION

Patients with DPD show better survival than patients with WPD. CT helps suggest strongly the presence of DPD preoperatively.