Properties of an SV40-transformed hamster cell line resistant to actinomycin D (author's transl)

The changes in chromosome constitution that occur during induction of reversion in transformed cells have been studied. The culture of transformed cells at low cell density without a feeder layer, which induces reversion, also induced a change in chromosome number from diploid to aneuploid. The percentage of revertants formed under these conditions was related to the percentage of aneuploid cells. Most of the aneuploid cells had a subtetraploid chromosome number. The results indicate that the formation of aneuploids is due to the formation from binucleate cells of polyploid cells which later lose chromosomes, and suggest that conditions that stabilize the reverted state produce the right type of stable aneuploid cells required for reversion.     

Oxygen consumption in the kidney: effects of nitric oxide synthase isoforms and angiotensin II

BACKGROUND: Oxygen mitochondrial effects consumption by the kidney (Qo(2)), is linearly related to sodium reabsorption (T(na)), but recent studies suggest this relationship is variable and that metabolic efficiency (Qo(2)/T(na)) in kidney is regulated by hormonal factors. In the dog, nonselective inhibitors of nitric oxide synthase (NOS) increase Qo(2) and Qo(2)/T(na). Glomerular hemodynamic and reabsorptive consequences of NOS inhibition require angiotensin II (Ang II), implying an antagonistic relationship between nitric oxide and Ang II. Effects of NOS inhibition in the rat, the role of Ang II and the responsible NOS isoform have not been elucidated. METHODS: Kidney blood flow [renal blood flow (RBF)], glomerular filtration rate (GFR), and Qo(2)/T(na) were measured before and during intravenous administration of N(G)-monomethyl-l-arginine (L-NMMA), a nonselective NOS inhibitor, in control and losartan (Ang II receptor blocker)-treated rats and rats administered S-methyl-L-thiocitrulline (SMTC), a NOS-1 inhibitor. Effects of SMTC on oxygen consumption were also examined in freshly harvested proximal tubules. RESULTS: L-NMMA and high-dose SMTC decreased RBF, but L-NMMA + losartan and low-dose SMTC did not. Qo(2)/T(na) increased in both L-NMMA groups. Both low- and high-dose SMTC also increased Qo(2)/T(na). SMTC increased Qo(2) in proximal tubules in vitro at presumed lower levels of vectorial NaCl transport. Results suggest this effect was not mediated by influences on sodium transport alone. CONCLUSION: Nonselective NOS inhibition increases the oxygen costs of kidney function independent of Ang II. Kidney NOS-1 is responsible for these in vivo and in vitro effects. In vitro observations suggest that NOS-1 acts in part via effects on basal metabolism and mitochondrial function.     

Ineffective phagocytosis of amyloid-beta by macrophages of Alzheimer's disease patients

The defective clearance of amyloid-beta (Abeta) in the brain of Alzheimer's disease (AD) patients is unexplained. The immunohistochemical studies of the frontal lobe and hippocampus show perivascular and intraplaque infiltration by blood-borne macrophages containing intracellular Abeta but only inefficient clearance of beta deposits. Neurons and neuronal nuclei, respectively, express interleukin-1beta and the chemokine RANTES, which could induce the inflammatory cell infiltration. To clarify the pathophysiology ofbeta clearance, we examined Abeta phagocytosis by monocytes and macrophages isolated from the blood of age-matched patients and controls. Control monocytes display excellent differentiation into macrophages and intracellular phagocytosis of Abeta followed by beta degradation or export. AD monocytes show poor differentiation and only surface uptake of Abeta and suffer apoptosis. HLA DR and cyclooxygenase-2 are abnormally expressed on neutrophils and monocytes of AD patients. AD patients have higher levels of intracellular cytokines compared to controls. Thus Abeta clearance is not restricted to brain microglia and involves systemic innate immune responses. In AD, however, macrophage phagocytosis is defective, which may elicit compensatory response by the adaptive immune system.     

Maternal exposure to arsenic, cadmium, lead, and mercury and neural tube defects in offspring

Arsenic, cadmium, lead, and mercury are neurotoxins, and some studies suggest that these elements might also be teratogens. Using a case-control study design, we investigated the relation between exposure to these heavy metals and neural tube defects (NTDs) in offspring of Mexican-American women living in 1 of the 14 Texas counties bordering Mexico. A total of 184 case-women with NTD-affected pregnancies and 225 control-women with normal live births were interviewed about their environmental and occupational exposures during the periconceptional period. Biologic samples for blood lead and urinary arsenic, cadmium, and mercury were also obtained for a subset of these women. Overall, the median levels of these biomarkers for heavy metal exposure did not differ significantly (P > 0.05) between case- and control-women. However, among women in the highest income group, case-women were nine times more likely (95% confidence interval (CI) 1.4-57) than control-women to have a urinary mercury 5.62 microg/L. Case-women were 4.2 times more likely (95% CI 1.1-16) to report burning treated wood during the periconceptional period than control-women. Elevated odds ratios (ORs) were observed for maternal and paternal occupational exposures to arsenic and mercury, but the 95% CIs were consistent with unity. The 95% CIs of the ORs were also consistent with unity for higher levels of arsenic, cadmium, lead, and mercury in drinking water and among women who lived within 2 miles at the time of conception to industrial facilities with reported emissions of any of these heavy metals. Our findings suggest that maternal exposures to arsenic, cadmium, or lead are probably not significant risk factors for NTDs in offspring. However, the elevated urinary mercury levels found in this population and exposures to the combustion of treated wood may warrant further investigation.     

Frequent genetic and biochemical alterations of the PI 3-K/AKT/PTEN pathway in head and neck squamous cell carcinoma

We investigated the status of the PI 3-kinase/AKT/PTEN signaling pathway in a series of 117 head and neck squamous cell carcinomas (HNSCC) in a search for molecular alterations in genes/proteins with potential prognostic value. For this purpose, PIK3CA and AKT2 gene amplification was assessed by multiplex and Quantitative Real-Time PCR. Protein expression of AKT, p-AKT, p110alpha and PTEN was determined by Western blot. PTEN allelic loss was evaluated by microsatellite analysis. PTEN-exon 5 was screened for point mutations by PCR-SSCP. Homozygous deletions were determined by multiplex PCR. PIK3CA gene was amplified in 43/117 (37%) fresh tumor samples, a frequency that did not differ from that found in archival premalignant tissues: 15/38 (39%); 12/40 (30%) fresh tumors harbored AKT2 gene amplification. AKT was found activated in 6/36 (17%) fresh tumor samples, when compared to their normal tissue counterparts. Of these 6 cases, 1 showed p110alpha overexpression and 5 displayed PTEN protein downregulation. Neither allelic loss (found in 11/77 informative cases) nor point mutations or homozygous deletions accounted for the reduced PTEN protein expression observed in our tumor series. The histologically normal mucosa of 4 patients displayed some of the molecular alterations analyzed. Dysregulation of the PI 3-K/AKT/PTEN pathway might contribute to early HNSCC tumorigenesis and might constitute a potential clinical target. Overall, 17/36 (47%) cases showed at least 1 of the molecular alterations studied here, which makes the PI 3-kinase-initiated signaling pathway one of the most frequently altered in HNSCC.     

Polysomy of chromosome 17 in breast cancer tumors showing an overexpression of ERBB2: a study of 175 cases using fluorescence in situ hybridization and immunohistochemistry

IntroductionOne of the most common genetic aberrations associated with breast cancer is the amplification and overexpression of the ERBB2 proto-oncogene located at chromosome 17, bands q12-21. The amplification/overexpression occurs in 25 to 30% of all breast cancers. In breast cancer, aneusomy of chromosome 17, either monosomy or polysomy, is frequently observed by conventional cytogenetics and fluorescence in situ hybridization (FISH). The aim of this study was to discover whether or not numerical aberrations on chromosome 17 have a correlation to the amplification or overexpression of the ERBB2 gene and to analyze their clinical implications in subgroups showing 2+ or 3+ positive scores by immunohistochemistry (IHC).MethodsWe used FISH on a series of 175 formalin-fixed paraffin-embedded breast carcinomas to detect ERBB2 amplification, using a dual-probe system for the simultaneous enumeration of the ERBB2 gene and the centromeric region of chromosome 17, as well as using IHC to detect overexpression. We analyzed clinical and pathological variables in a subgroup of patients with 2+ and 3+ IHC scores (147 patients), to describe any differences in clinicopathological characteristics between polysomic and non-polysomic cases with the use of the χ² test.ResultsWe found 13% of cases presenting polysomy, and three cases presented monosomy 17 (2%). According to the status of the ERBB2 gene, instances of polysomy 17 were more frequently observed in non-amplified cases than in FISH-amplified cases, suggesting that the mechanism for ERBB2 amplification is independent of polysomy 17. Polysomy 17 was detected in patients with 2+ and 3+ IHC scores. We found that nodal involvement was more frequent in polysomic than in non-polysomic cases (P = 0.046).ConclusionsThe determination of the copy number of chromosome 17 should be incorporated into the assesment of ERBB2 status. It might also be helpful to differentiate a subgroup of breast cancer patients with polysomy of chromosome 17 and overexpression of ERBB2 protein that probably have genetic and clinical differences.     

Abrasive blasting agents: designing studies to evaluate relative risk

Workers exposed to respirable crystalline silica used in abrasive blasting are at increased risk of developing a debilitating and often fatal fibrotic lung disease called silicosis. The National Institute for Occupational Safety and Health (NIOSH) recommends that silica sand be prohibited as abrasive blasting material and that less hazardous materials be used in blasting operations. However, data are needed on the relative risks associated with exposure to abrasive blasting materials other than silica. NIOSH has completed acute studies in rats (Hubbs et al., 2001; Porter et al., 2002). To provide dose-response data applicable to making recommendation for occupational exposure limits, NIOSH has collaborated with the National Toxicology Program (NTP) to design longer term studies with silica substitutes. For risk assessment purposes, selected doses will include concentrations that are relevant to human exposures. Rat lung burdens achieved should be comparable to those estimated in humans with working lifetime exposures, even if this results in "overloading" doses in rats. To quantify both dose and response, retained particle burdens in the lungs and lung-associated lymph nodes will be measured, as well as biochemical and pathological indices of pulmonary response. This design will facilitate assessment of the pulmonary fibrogenic potential of inhaled abrasive blasting agents at occupationally relevant concentrations.