Do regular ovulatory cycles increase breast cancer risk?

The "estrogen window hypothesis" of the etiology of breast cancer proposes that unopposed estrogen stimulation is the most favorable state for tumor induction and that normal postovulation progesterone secretion reduces susceptibility. The authors believe that epidemiologic and experimental studies suggest rather that the opposite is true, i.e.

23Na and 39K nuclear magnetic resonance studies of perfused rat hearts. Discrimination of intra- and extracellular ions using a shift reagent.

High-resolution 23Na and 39K nuclear magnetic resonance (NMR) spectra of perfused, beating rat hearts have been obtained in the absence and presence of the downfield shift reagent Dy(TTHA)3- in the perfusing medium. Evidence indicates that Dy(TTHA)3- enters essentially all extracellular spaces but does not enter intracellular spaces. It can thus be used to discriminate the resonances of the ions in these spaces.

Statistical errors invalidate conclusions in "Caffeine and unsaturated fat diet significantly promotes DMBA-induced breast cancer in rats".

The conclusion drawn in a recent paper by Minton and associates (Cancer 1983; 51:1249-1253), that caffeine and an unsaturated fat diet significantly promoted dimethylbenz(a)anthracene (DMBA)-induced breast cancer in rats, is based on fallacious statistical reasoning. Minton and associates based their conclusion on the mean latency to first tumor appearance for rats diagnosed with tumors. However, evaluation of percentages of tumor-bearing rats yields contrary results.

Smoking and other risk factors for lung cancer in women.

A case-control study among white women in Los Angeles County was conducted to investigate the role of smoking and other factors in the etiology of lung cancer in women. A total of 149 patients with adenocarcinoma (ADC) and 71 patients with squamous cell carcinoma (SCC) of the lung and their age- and sex-matched controls were interviewed. Personal cigarette smoking accounted for almost all of SCC and about half of ADC in this study population.

Estrogen and sex hormone-binding globulin levels in nulliparous and parous women.

The hormone profiles of nulliparous and parous women on day 11 of their menstrual cycle have been studied in an attempt to seek evidence for the hormonal basis of the protective effect of first birth on breast cancer risk. A previous publication reported that there were significantly lower (26%) early morning prolactin levels in parous women as compared to those levels in nulliparous women but that there were no differences in plasma and urinary estrogen levels. The present study shows, however, that parous women had significantly shorter cycle lengths than nulliparous women of the same age, and the data were reevaluated with this difference being taken into account.

Some tautologous aspects of the comparison of carcinogenic potency in rats and mice.

In risk estimation, the results of rodent carcinogenesis experiments are often used to quantitatively predict effects in man. The justification for this approach has in large part been dependent upon the good correlation of carcinogenic potency found between mice and rats over large numbers of test chemicals. Using the data base of chemicals tested by the NCI Bioassay Program, we observe that there is a very high correlation of the maximum doses tested (max-d) for rats and mice on a milligram per kilogram body weight per day basis.

The TD50: a proposed general convention for the numerical description of the carcinogenic potency of chemicals in chronic-exposure animal experiments.

A generally accepted format for the numerical description of the carcinogenic potency of a particular chemical in a particular strain of animals is desirable so that statements from different sources about potency and attempts by different authors to correlate potency with particular laboratory measurements will be comparable. The choice of an appropriate standard format is to a certain extent arbitrary. In this paper we recommend that the TD50 (tumorigenic dose rate 50) be used.

Apparent doubling of frequency of undescended testis in England and Wales in 1962-81.

Examination of Hospital Inpatient Enquiry data for England and Wales for the years 1962-81 shows that the annual number of discharges with a diagnosis of undescended testicle has risen by a factor of 2.3. Cohort analysis suggests that the cumulative rate to age 15 of discharge for undescended testis has risen from 1.

Effects of reserpine on prolactin levels and incidence of breast cancer in postmenopausal women.

Epidemiological studies of reserpine use and breast cancer have generally found only small increases in breast cancer risk, even after long-term use. Prolactin levels in short-term reserpine users have been reported to be in the range of those of lactating women, levels which rodent experiments suggest should greatly increase breast cancer incidence. We measured prolactin levels in 15 women who had been taking reserpine-containing drugs for at least 5 years and compared them to levels in 15 women taking non-reserpine-containing antihypertensives and 15 women taking no antihypertensive medicines.

High-resolution 23Na-NMR studies of human erythrocytes: use of aqueous shift reagents.

Aqueous shift reagents were used to clearly distinguish intra-and extracellular 23Na-nuclear magnetic resonance (NMR) signals in samples consisting of whole blood or suspensions of washed human erythrocytes (both fresh and outdated). The lanthanide chelates Dy(PPP)2(7-) and Tm( TTHA )3- were used to shift the extracellular signals upfield, and Dy( TTHA )3- and Tm(PPP)2(7-) were similarly used to shift extracellular resonances downfield. The absolute intensities of the signals were used along with the measured hematocrit to simultaneously determine the intra- and extracellular Na+ concentrations.

Calculation of carcinogenic potency from long-term animal carcinogenesis experiments.

An index of carcinogenic potency for chemicals tested in chronic animal experiments is described. By analogy with the well-known 'lethal dose 50' (LD50) of quantal bioassay, a 'tumorigenic dose 50' (TD50) may be defined (in the absence both of tumors in the control group and of intercurrent deaths) as that (daily) dose of chemical which gives 50% of the test animals tumors by some fixed age. Tumors in the control (zero-dose) group are handled exactly as for the LD50, and intercurrent deaths are handled by life-table methods.

A chemoattractant receptor on macrophages exists in two affinity states regulated by guanine nucleotides.

The binding characteristics of the oligopeptide chemoattractant receptor on guinea pig macrophages and macrophage membrane preparations were characterized using detailed binding studies and computer analysis. Viable macrophages bound the radiolabeled chemoattractant N-formyl-methionyl-leucyl-[3H]phenylalanine with single dissociation constant (KD) of 18.4 +/- 4.

Intrathoracic extramediastinal cystic hygroma.

A case of intrathoracic, extramediastinal cystic hygroma presenting with pneumonia in a 6 year old boy is described.

Age at natural menopause and breast cancer risk: the effect of errors in recall.

Many case-control studies of breast cancer have reported estimates of relative risk of approximately 1.9 for menopause after 54 years of age when compared with menopause before 45 years of age. These estimates may be biased towards unity because of errors in recall of a woman's age at menopause.

Chemoattractant receptors on phagocytic cells.

Chemoattractant receptors on leukocytes can trigger a number of cellular responses, including the cytoskeletal reorganization, changes in cell shape, directed motility, lysosomal enzyme secretion, and activation of the respiratory burst. The dose of chemoattractants required to induce motility-related functions is generally at least ten-fold smaller than the dose required to initiate secretory and respiratory burst activities. This finding and other pharmacological evidence clearly indicate that the two types of functions (i.

Transductional mechanisms of chemoattractant receptors on leukocytes.

Phagocytic leukocytes contain receptors for chemoattractants on their cell surface. Binding of chemotactic factors to these receptors initiates a number of coordinated cellular responses in a strict dose-dependent manner. Motility-related functions such as shape change, cytoskeletal rearrangement, and chemotaxis are stimulated by relatively low doses of chemoattractants, while microbiocidal or cytotoxic functions (i.