Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58,515 women with invasive breast cancer and 95,067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for >/=45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver.

Spatiotemporal dynamics of inositol 1,4,5-trisphosphate that underlies complex Ca2+ mobilization patterns

Inositol 1,4,5-trisphosphate (IP3) is a second messenger that elicits complex spatiotemporal patterns of calcium ion (Ca2+) mobilization and has essential roles in the regulation of many cellular functions. In Madin-Darby canine kidney epithelial cells, green fluorescent protein-tagged pleckstrin homology domain translocated from the plasma membrane to the cytoplasm in response to increased concentration of IP3. The detection of translocation enabled monitoring of IP3 concentration changes within single cells and revealed spatiotemporal dynamics in the concentration of IP3 synchronous with Ca2+ oscillations and intracellular and intercellular IP3 waves that accompanied Ca2+ waves. Such changes in IP3 concentration may be fundamental to Ca2+ signaling.

Encoding of Ca2+ signals by differential expression of IP3 receptor subtypes

Inositol 1,4,5-trisphosphate (IP3) plays a key role in Ca2+ signalling, which exhibits a variety of spatio-temporal patterns that control important cell functions. Multiple subtypes of IP3 receptors (IP3R-1, -2 and -3) are expressed in a tissue- and development-specific manner and form heterotetrameric channels through which stored Ca2+ is released, but the physiological significance of the differential expression of IP3R subtypes is not known. We have studied the Ca2+-signalling mechanism in genetically engineered B cells that express either a single or a combination of IP3R subtypes, and show that Ca2+-signalling patterns depend on the IP3R subtypes, which differ significantly in their response to agonists, i.e. IP3, Ca2+ and ATP. IP3R-2 is the most sensitive to IP3 and is required for the long lasting, regular Ca2+ oscillations that occur upon activation of B-cell receptors. IP3R-1 is highly sensitive to ATP and mediates less regular Ca2+ oscillations. IP3R-3 is the least sensitive to IP3 and Ca2+, and tends to generate monophasic Ca2+ transients. Furthermore, we show for the first time functional interactions between coexpressed subtypes. Our results demonstrate that differential expression of IP3R subtypes helps to encode IP3-mediated Ca2+ signalling.

Increased interleukin-17 production in patients with systemic sclerosis

OBJECTIVE

To determine the role of a novel T cell-derived cytokine, interleukin-17 (IL-17), which activates fibroblasts and endothelial cells, in the pathogenesis of systemic sclerosis (SSc).

METHODS

We examined IL-17 production by lymphocytes from the peripheral blood (PBL) and from fibrotic lesions of the skin and lungs of SSc patients by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. We also studied the effect of IL-17 on the proliferation of fibroblasts and on the production of cytokines and the expression of adhesion molecules on endothelial cells in vitro.

RESULTS

IL-17 messenger RNA was expressed in unstimulated PBL and lymphocytes from the skin and lungs of SSc patients, but not in similar samples from patients with systemic lupus erythematosus (SLE) or polymyositis/dermatomyositis or from healthy donors. IL-17 levels were also increased in the serum of SSc patients, but not in that of SLE patients or healthy donors. IL-17 overproduction was significantly related to the early stage of SSc, but not to other clinical features of SSc. Moreover, IL-17 enhanced the proliferation of fibroblasts and induced the expression of adhesion molecules and IL-1 production in endothelial cells in vitro.

CONCLUSION

IL-17 is overproduced by T cells from the peripheral blood and fibrotic lesions of the skin and lungs in SSc patients. These results suggest that IL-17 overproduction plays an important role in the pathogenesis of SSc, especially in the early stages of the disease, by inducing the proliferation of fibroblasts and the production of IL-1 and the expression of adhesion molecules on endothelial cells.

The reeler gene encodes a protein with an EGF-like motif expressed by pioneer neurons

We have identified a strong candidate cDNA for the mouse reeler gene. This 5 kb transcript encodes a 99.4 kD protein consisting of 881 amino acids and possessing two EGF-like motifs. We assayed two independent mutant alleles--'Jackson reeler', which has a deletion of the entire gene, and 'Orleans reeler' which exhibits a 220 bp deletion in the open reading frame, including the second EGF-like motif and resulting in a frame shift. In situ hybridization reveals that the transcript is detected exclusively in the pioneer neurons which guide neuronal cell migration along the radial array. Our findings offer an explanation for how the reeler mutant phenotype causes a disturbance of the complex architecture of the neuronal network.

Overexpression of mitochondrial manganese superoxide dismutase promotes the survival of tumor cells exposed to interleukin-1, tumor necrosis factor, selected anticancer drugs, and ionizing radiation

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) selectively induce mitochondrial manganese superoxide dismutase (MnSOD) production in various cell types. We have evaluated the capacity of tumor cells that overexpress MnSOD to recover from the cytostatic and cytotoxic effects of cytokines (IL-1 and TNF), chemotherapeutic agents, and ionizing irradiation. Clones of human melanoma cell line, A375, which overexpressed MnSOD after sense MnSOD cDNA transfection, showed increased recovery from treatment with cytostatic and cytotoxic doses of IL-1 alpha and TNF alpha, whereas clones of A375 cells that were transfected with anti-sense MnSOD cDNA recovered less well than normal cells from IL-1 alpha and TNF alpha. In addition, Chinese hamster ovary (CHO) cells transfected with sense MnSOD cDNA showed increased survival after treatment with doxorubicin, mitomycin C, and gamma (gamma) radiation in vitro. It is hypothesized that mitochondrial MnSOD, by scavenging oxygen radicals induced by cytokines, some cytotoxic drugs, and ionizing radiation, is protective and promotes the survival of cells from the lethal effects of these treatments.

The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle

MgSiO3 perovskite has been assumed to be the dominant component of the Earth's lower mantle, although this phase alone cannot explain the discontinuity in seismic velocities observed 200-300 km above the core-mantle boundary (the D" discontinuity) or the polarization anisotropy observed in the lowermost mantle. Experimental and theoretical studies that have attempted to attribute these phenomena to a phase transition in the perovskite phase have tended to simply confirm the stability of the perovskite phase. However, recent in situ X-ray diffraction measurements have revealed a transition to a 'post-perovskite' phase above 125 GPa and 2,500 K--conditions close to those at the D" discontinuity. Here we show the results of first-principles calculations of the structure, stability and elasticity of both phases at zero temperature. We find that the post-perovskite phase becomes the stable phase above 98 GPa, and may be responsible for the observed seismic discontinuity and anisotropy in the lowermost mantle. Although our ground-state calculations of the unit cell do not include the effects of temperature and minor elements, they do provide a consistent explanation for a number of properties of the D" layer.

Nerve growth factor-induced neuronal differentiation requires generation of Rac1-regulated reactive oxygen species

Nerve growth factor (NGF) stimulation of pheochromocytoma PC12 cells transiently increased the intracellular concentration of reactive oxygen species (ROS). This increase was blocked by the chemical antioxidant N-acetylcysteine and a flavoprotein inhibitor, diphenylene iodonium. NGF responses of PC12 cells, including neurite outgrowth, tyrosine phosphorylation, and AP-1 activation, was inhibited when ROS production was prevented by N-acetylcysteine and diphenylene iodonium. The expression of dominant negative Rac1N17 blocked induction of both ROS generation and morphological differentiation by NGF. The ROS produced appears to be H(2)O(2), because the introduction of catalase into the cells abolished NGF-induced neurite outgrowth, ROS production, and tyrosine phosphorylation. These results suggest that the ROS, perhaps H(2)O(2), acts as an intracellular signal mediator for NGF-induced neuronal differentiation and that NGF-stimulated ROS production is regulated by Rac1 and a flavoprotein-binding protein similar to the phagocytic NADPH oxidase.

cDNA cloning and tissue-specific expression of a novel basic helix-loop-helix/PAS factor (Arnt2) with close sequence similarity to the aryl hydrocarbon receptor nuclear translocator (Arnt)

We isolated mouse cDNA clones (Arnt2) that are highly similar to but distinct from the aryl hydrocarbon receptor (AhR) nuclear translocator (Arnt). The composite cDNA covered a 2,443-bp sequence consisting of a putative 2,136-bp open reading frame encoding a polypeptide of 712 amino acids. The predicted Arnt2 polypeptide carries a characteristic basic helix-loop-helix (bHLH)/PAS motif in its N-terminal region with close similarity (81% identity) to that of mouse Arnt and has an overall sequence identity of 57% with Arnt. Biochemical properties and interaction of Arnt2 with other bHLH/PAS proteins were investigated by coimmunoprecipitation assays, gel mobility shift assays, and the yeast two-hybrid system. Arnt2 interacted with AhR and mouse Sim as efficiently as Arnt, and the Arnt2-AhR complex recognized and bound specifically the xenobiotic responsive element (XRE) sequence. Expression of Arnt2 successfully rescued XRE-driven reporter gene activity in the Arnt-defective c4 mutant of Hepa-1 cells. RNA blot analysis revealed that expression of Arnt2 mRNA was restricted to the brains and kidneys of adult mice, while Arnt mRNA was expressed ubiquitously. In addition, whole-mount in situ hybridization of 9.5-day mouse embryos showed that Arnt2 mRNA was expressed in the dorsal neural tube and branchial arch 1, while Arnt transcripts were detected broadly in various tissues of mesodermal and endodermal origins. These results suggest that Arnt2 may play different roles from Arnt both in adult mice and in developing embryos. Finally, sequence comparison of the currently known bHLH/PAS proteins indicates a division into two phylogenetic groups: the Arnt group, containing Arnt, Arnt2, and Per, and the AhR group, consisting of AhR, Sim, and Hif-1alpha.

Development of glomerular lesions in experimental long-term diabetes in the rat

Exact parameters for relevant glomerular structures in the course of streptozotocin diabetes in rats with 1 to 18 months' duration were obtained with stereological methods. Renal cortical tissue from diabetic (D) and control animals (C) was processed for light- and electron microscopy and measurements were performed on systematically sampled glomeruli. The thickness of the basement membrane (BM) increased with age in both groups, but the rate of increase was 50% higher in D: 19 +/- 1.2 nm/month (mean +/- SD) vs. 13 +/- 0.9 nm/month, P = 0.0003. The time course of other structural quantities was characterized by the acute changes constituting the glomerular hypertrophy, earlier shown to develop within the first few days of diabetes. All these changes were confirmed in the present study: In the earliest phase the diabetic rats showed an increased total volume of glomeruli, mesangium, and mesangial BM material, as well as an increased surface of the capillary walls. However, none of these differences between the groups showed progression with increasing duration. Mesangial changes corresponding to those of the glomerulopathy in long-term diabetes were not demonstrable within the experimental period. The streptozotocin diabetic rat, therefore, is not useful as a model of advanced diabetic glomerulopathy. But the BM thickness follows the same predictable time course as in human diabetes insofar as moderately advanced cases are concerned. BM thickness is the parameter of choice when a potential effect of different variables on the development of diabetic glomerulopathy is under study.

Embryonic lethality and abnormal cardiac myocytes in mice lacking ryanodine receptor type 2

The ryanodine receptor type 2 (RyR-2) functions as a Ca2+-induced Ca2+ release (CICR) channel on intracellular Ca2+ stores and is distributed in most excitable cells with the exception of skeletal muscle cells. RyR-2 is abundantly expressed in cardiac muscle cells and is thought to mediate Ca2+ release triggered by Ca2+ influx through the voltage-gated Ca2+ channel to constitute the cardiac type of excitation-contraction (E-C) coupling. Here we report on mutant mice lacking RyR-2. The mutant mice died at approximately embryonic day (E) 10 with morphological abnormalities in the heart tube. Prior to embryonic death, large vacuolate sarcoplasmic reticulum (SR) and structurally abnormal mitochondria began to develop in the mutant cardiac myocytes, and the vacuolate SR appeared to contain high concentrations of Ca2+. Fluorometric Ca2+ measurements showed that a Ca2+ transient evoked by caffeine, an activator of RyRs, was abolished in the mutant cardiac myocytes. However, both mutant and control hearts showed spontaneous rhythmic contractions at E9.5. Moreover, treatment with ryanodine, which locks RyR channels in their open state, did not exert a major effect on spontaneous Ca2+ transients in control cardiac myocytes at E9.5-11.5. These results suggest no essential contribution of the RyR-2 to E-C coupling in cardiac myocytes during early embryonic stages. Our results from the mutant mice indicate that the major role of RyR-2 is not in E-C coupling as the CICR channel in embryonic cardiac myocytes but it is absolutely required for cellular Ca2+ homeostasis most probably as a major Ca2+ leak channel to maintain the developing SR.

Identification of an imprinted U2af binding protein related sequence on mouse chromosome 11 using the RLGS method

A new imprinted gene has been discovered in mice using the technique of restriction landmark genomic scanning (RLGS) with methylation sensitive enzymes. Eight out of 3,100 strain-specific NotI and BssHII spots were identified as imprinted in reciprocal F1 hybrids. Subsequently, we isolated a genomic clone for one locus on proximal chromosome 11 near the Glns locus, an imprinted region in uniparental disomic mice, and its corresponding cDNA clone. Expression of this transcript from the paternal allele was established using RT-PCR of reciprocal F1-hybrid mice. The amino-acid sequence deduced from the cDNA showed significant homology to the U2 small nuclear ribonucleoprotein auxiliary factor 35 kDa subunit.

Inhibition of NADPH oxidase 4 activates apoptosis via the AKT/apoptosis signal-regulating kinase 1 pathway in pancreatic cancer PANC-1 cells

Pancreatic adenocarcinoma is an aggressive human malignancy and is characterized by resistance to apoptosis. Recently, NADPH oxidase (Nox) 4-mediated generation of intracellular reactive oxygen species (ROS) was proposed to confer antiapoptotic activity and thus a growth advantage to pancreatic cancer cells. The signaling mechanism by which Nox4 transmits cell survival signals remains unclear. Here, we show that both a flavoprotein inhibitor, diphenylene iodonium (DPI), and small interfering RNAs designed to target Nox4 mRNA (siNox4RNAs) inhibited superoxide production in PANC-1 pancreatic cancer cells, and depletion of ROS by DPI or siNox4RNAs induced apoptosis. Parallely, DPI treatment and siNox4RNA transfection blocked activation of the cell survival kinase AKT by attenuating phosphorylation of AKT. Furthermore, AKT phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) on Ser-83 was reduced by DPI and siNox4RNAs. When ASK1Ser83Ala (an AKT phosphorylation-defective ASK1 mutant) was introduced into PANC-1 cells, this mutant alone induced apoptosis. But, addition of DPI or co-transfection of siNox4RNA had no additive effect, indicating that the mutant can substitute for these reagents in apoptosis induction. Taken together, these findings suggest that ROS generated by Nox4, at least in part, transmit cell survival signals through the AKT-ASK1 pathway in pancreatic cancer cells and their depletion leads to apoptosis.

A large-scale, hospital-based case-control study of risk factors of breast cancer according to menopausal status

We conducted a large-scale, hospital-based case-control study to evaluate differences and similarities in the risk factors of female breast cancer according to menopausal status. This study is based on a questionnaire survey on life style routinely obtained from outpatients who first visited the Aichi Cancer Center Hospital between January 1, 1988 and December 31, 1992. Among 36,944 outpatients, 1,186 women with breast cancer detected by histological examination were taken as the case group (607 premenopausal women and 445 postmenopausal women) and 23,163 women confirmed to be free of cancer were selected as the control group. New findings and reconfirmed factors of breast cancer were as follows. 1) The risk of at least one breast cancer history among subjects' first-degree relatives was relatively high among pre- as well as post-menopausal women. 2) A protective effect of physical activity against breast cancer was observed among both pre- and post-menopausal women. 3) Dietary control decreased the risk of premenopausal breast cancer. 4) Current smoking and drinking elevated the risk of breast cancer in premenopausal women. 5) Decreasing trends of breast cancer risk were associated with intake of bean curd, green-yellow vegetables, potato or sweet potato, chicken and ham or sausage in premenopausal women, while in postmenopausal women a risk reduction was associated with a more frequent intake of boiled, broiled and/or raw fish (sashimi). Further study will be needed to clarify the age group- and/or birth cohort-specific risk factors for breast cancer among the young generation in Japan.

Tea and coffee consumption and the risk of digestive tract cancers: data from a comparative case-referent study in Japan

OBJECTIVES

The purpose of this study was to examine the hypothesis that tea and coffee consumption have a protective effect against development of digestive tract cancers.

METHODS

A comparative case-referent study was conducted using Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC) data from 1990 to 1995 in Nagoya, Japan. This study comprised 1,706 histologically diagnosed cases of digestive tract cancers (185 esophagus, 893 stomach, 362 colon, 266 rectum) and a total of 21,128 non-cancer outpatients aged 40 years and over. Logistic regression was used to analyze the data, adjusting for gender; age; year and season at hospital-visit; habitual smoking and alcohol drinking; regular physical exercise; fruit, rice, and beef intake; and beverage intake.

RESULTS

The odds ratio (OR) of stomach cancer decreased to 0.69 (95 percent confidence interval [CI] = 0.48-1.00) with high intake of green tea (seven cups or more per day). A decreased risk was also observed for rectal cancer with three cups or more daily intake of coffee (OR = 0.46, CI = 0.26-0.81).

CONCLUSIONS

The results suggest the potential for protective effect against site-specific digestive tract cancer by consumption of green tea and coffee, although most associations are limited only to the upper category of intake and have no clear explanation for site-specificity.

Timing of the administration of tranexamic acid for maximum reduction in blood loss in arthroplasty of the knee

We studied 99 patients who were undergoing total knee arthroplasty (TKA) to determine the optimum protocol for the administration of tranexamic acid (TNA) in order to reduce blood loss. It decreased by more than 40% after the administration of TNA. The haemostatic effect was greatest when TNA was given preoperatively and on deflation of the tourniquet. There was no increase in the incidence of adverse affects in the patients receiving TNA, compared with a control group. We conclude that two injections of TNA, one given preoperatively and one on deflation of the tourniquet, significantly reduce blood loss without increasing the risk of thromboembolic complications.

MgcRacGAP is involved in cytokinesis through associating with mitotic spindle and midbody

We have recently cloned a cDNA for a full-length form of MgcRacGAP. Here we show using anti-MgcRacGAP antibodies that, unlike other known GAPs for Rho family, MgcRacGAP localized to the nucleus in interphase, accumulated to the mitotic spindle in metaphase, and was condensed in the midbody during cytokinesis. Overexpression of an N-terminal deletion mutant resulted in the production of multinucleated cells in HeLa cells. This mutant lost the ability to localize in the mitotic spindle and midbody. MgcRacGAP was also found to bind alpha-, beta-, and gamma-tubulins through its N-terminal myosin-like domain. These results indicate that MgcRacGAP dynamically moves during cell cycle progression probably through binding to tubulins and plays critical roles in cytokinesis. Furthermore, using a GAP-inactive mutant, we have shown that the GAP activity of MgcRacGAP is required for cytokinesis, suggesting that inactivation of the Rho family of GTPases may be required for normal progression of cytokinesis.

Characterization of inducible nature of MRP3 in rat liver

We found previously that expression of multidrug resistance-associated protein (MRP) 3 is induced in a mutant rat strain (Eisai hyperbilirubinemic rats) whose canalicular multispecific organic anion transporter (cMOAT/MRP2) function is hereditarily defective and in normal Sprague-Dawley (SD) rats after ligation of the common bile duct. In the present study, the inducible nature of MRP3 was examined, using Northern and Western blot analyses, in comparison with that of other secondary active [Na(+)-taurocholic acid cotransporting polypeptide (Ntcp), organic anion transporting polypeptide 1 (oatp1), and organic cation transporter (OCT1)] and primary active [P-glycoprotein (P-gp), cMOAT/MRP2, and MRP6] transporters. alpha-Naphthylisothiocyanate treatment and common bile duct ligation induced expression of P-gp and MRP3, whereas expression of Ntcp, oatp1, and OCT1 was reduced by the same treatment. Although expression of MRP3 was also induced by administration of phenobarbital, that of cMOAT/MRP2, MRP1, and MRP6 was not affected by any of these treatments. Moreover, the mRNA level of MRP3, but not that of P-gp, was increased in SD rats after administration of bilirubin and in Gunn rats whose hepatic bilirubin concentration is elevated because of a defect in the expression of UDP-glucuronosyl transferase. However, the MRP3 protein level was not affected by bilirubin administration. Although the increased MRP3 mRNA level was associated with the increased concentration of bilirubin and/or its glucuronides in mutant rats and in SD rats that had undergone common bile duct ligation or alpha-naphthylisothiocyanate treatment, we must assume that factor(s) other than these physiological substances are also involved in the increased protein level of MRP3.

A fluorescent indicator for visualizing cAMP-induced phosphorylation in vivo

We have developed a method for visualizing phosphorylation of proteins in living cells using a novel fluorescent indicator composed of two green fluorescent protein (GFP) variants joined by the kinase-inducible domain (KID) of the transcription factor cyclic adenosine monophosphate (cAMP)-responsive element binding protein (CREB). Phosphorylation of KID by the cAMP-dependent protein kinase A (PKA) decreased the fluorescence resonance energy transfer (FRET) among the flanking GFPs. By transfecting COS-7 cells with an expression vector encoding this indicator protein (termed ART for cAMP-responsive tracer), we were able to visualize activation dynamics of PKA in living cells.

Reactive oxygen species in chick hair cells after gentamicin exposure in vitro

Reactive oxygen species have been invoked as a causative agent of cell death in many different developmental and pathological states. The presence of free radicals and their importance of hair cell death due to aminoglycosides is suggested by a number of studies that have demonstrated a protective effect of antioxidants. By using dichlorofluorescin (DCFH) a fluorescent compound that is a reporter of reactive oxygen species, we have shown that free radicals are rapidly produced by avian hair cells in vitro after exposure to gentamicin. In addition, free radical scavengers, catalase and glutathione, were tested with DCFH fluorescent imaging for their ability to quench the production of reactive oxygen species in hair cells after drug exposure. Both free radical scavengers were very effective in suppressing drug-induced production of free radicals. Next, we investigated the ability of these antioxidants to preserve the structural integrity of hair cells after exposure to gentamicin. We were not able to detect any attenuation of the hair cell loss using antioxidants in conjunction with gentamicin. This result must be qualified by the fact that the antioxidants used were not effective over long-term gentamicin exposure. Therefore, methodological constraints prevented adequately testing possible protective effects of the free radical scavengers in this model system.

Critical duration of intracellular Ca2+ response required for continuous translocation and activation of cytosolic phospholipase A2

When cells are exposed to certain external stimuli, arachidonic acid (AA) is released from the membrane and serves as a precursor of various types of eicosanoids. A Ca2+-regulated cytosolic phospholipase A2 (cPLA2) plays a dominant role in the release of AA. To closely examine the relation between Ca2+ response and AA release by stimulation of G protein-coupled receptors, we established several lines of Chinese hamster ovary cells expressing platelet-activating factor receptor or leukotriene B4 receptor. Measurement of intracellular Ca2+ concentration ([Ca2+]i) demonstrated that cell lines capable of releasing AA elicited a sustained [Ca2+]i increase when stimulated by agonists. The prolonged [Ca2+]i elevation is the result of Ca2+ entry, because this elevation was blocked by EGTA treatment or in the presence of Ca2+ channel blockers (SKF 96365 and methoxyverapamil). cPLA2 fused with a green fluorescent protein (cPLA2-GFP) translocated from the cytosol to the perinuclear region in response to increases in [Ca2+]i. When EGTA was added shortly after [Ca2+]i increase, the cPLA2-GFP returned to the cytosol, without liberating AA. After a prolonged [Ca2+]i increase, even by EGTA treatment, the enzyme was not readily redistributed to the cytosol. Thus, we propose that a critical time length of [Ca2+]i elevation is required for continuous membrane localization and full activation of cPLA2.

Regular consumption of green tea and the risk of breast cancer recurrence: follow-up study from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan

Experimental studies suggest various features of anticancer activity of green tea including inhibitory effect of tumor invasion and metastasis. This study was conducted to examine the association between regular green tea consumption prior to diagnosis and subsequent risk of breast cancer recurrence. The Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC) was started in 1988, in which information on lifestyle has routinely been collected from all first-visit outpatients by questionnaire. A total of 1160 new surgical cases of female invasive breast cancers with HERPACC information diagnosed between June 1990 and August 1998 were followed up through December 1999, and the risk (hazard ratio: HR) of recurrence was assessed with reference to daily green tea consumption using a Cox proportional hazard model. During 5264 person-years of follow-up, 133 subjects (12%) were documented to suffer recurrence of breast cancer. A decreased HR for recurrence adjusted for stage was observed with consumption of three or more daily cups of green tea (HR=0.69, 95% confidence interval (95%CI)=0.47-1.00). Particularly in stage I, the HR was decreased statistically significantly (HR=0.43, 95%CI=0.22-0.84). A similar tendency was observed for stage II subjects, but was not present among more advanced stages. Although careful interpretation is needed, these results suggest the possibility that regular green tea consumption may be preventive against recurrence of breast cancer in early stage cases.

Relation of initial infarct size to extent of left ventricular remodeling in the year after acute myocardial infarction

OBJECTIVES

This study attempted to determine the relation between infarct size after acute myocardial infarction and subsequent left ventricular remodeling using precise clinical measurements.

BACKGROUND

Animal studies have demonstrated that the degree of left ventricular remodeling after myocardial infarction is linearly related to infarct size. Clinical studies have not clearly replicated these results because of imprecise measurements and failure to adjust for patency of the infarct-related artery.

METHODS

Infarct size was measured from technetium-99m (Tc-99m) sestamibi perfusion images in 14 patients (12 with an anterior, 2 with an inferior infarction) by a threshold method previously described and expressed as percent of the left ventricle (32 +/- 17% left ventricle [mean +/- SD], range 6% to 58%). Absolute end-systolic volume, end-diastolic volume and ejection fraction were determined by electron beam computed tomographic images performed at discharge and at 6 weeks, 6 months and 1 year after myocardial infarction. All patients had documented infarct-related artery patency after reperfusion therapy.

RESULTS

At hospital discharge, there was no correlation between infarct size and end-systolic and end-diastolic volumes or ejection fraction. There was significant left ventricular dilation in the study group over the next year. As remodeling progressed, there was closer correlation between infarct size and ejection fraction and end-systolic volume measures (infarct size vs. end-systolic volume, from r = 0.43 at discharge to r = 0.80 at 1 year; infarct size vs. ejection fraction, from r = -0.39 at discharge to r = -0.84 at 1 year). There was a strong inverse correlation between infarct size at discharge and subsequent changes over the next year in end-systolic volume (r = 0.63, p = 0.02) and ejection fraction (r = -0.66, p = 0.01).

CONCLUSION

Infarct size as measured by Tc-99m sestamibi at hospital discharge after an index infarction is predictive of subsequent change in left ventricular volume and function in the year after myocardial infarction. Patients with a large infarct demonstrated the greatest degree of dilation in the setting of patency of the infarct-related artery.