On the role of aging in carcinogenesis

We have studied cancer age-incidence patterns for the most common cancers in Connecticut from 1935 to 1994 and in locations throughout the world in the 1975 and 1990 eras. We defined "Age 1/2" as the age at which half the incidence occurs in any given year or era. In every population, we found the cancers could be ranked in the same order according to "Age 1/2", i.e., testis < ovary, corpus uterus, breast < stomach, colon, rectum, prostate. This order of cancers according to "Age 1/2" does not correlate with the order according to age-standardized rates, and "Age 1/2" values exhibit less than 10% the variability of age-standardized rates over time and place. We conclude that the determinant of "Age 1/2" is independent of the determinant of age-standardized rates and suggest that "Age 1/2" is determined by host genes that may vary among tissues of tumor origin but are common to all people.

Central venous catheter related thrombosis in children: analysis of the Canadian Registry of Venous Thromboembolic Complications

BACKGROUND

Central venous lines (CVLs) are frequently associated with deep venous thrombosis (DVT) in children; however, little is known about the epidemiologic characteristics or outcome of CVL-related DVT.

METHODS

The Canadian Childhood Thrombophilia Registry monitored 244 consecutive patients with objectively diagnosed CVL-related DVT for a median duration of 24 months (range 3 months to 7 years).

RESULTS

The incidence of CVL-related DVT was 3.5 per 10,000 hospital admissions. CVL-related DVTs were more frequent in the upper venous system. Ultrasonography or echocardiography were the most commonly used diagnostic tests (n = 183 patients). Venograms were performed on 82 (34%) patients. A variety of therapies were used. Thirty-nine children had pulmonary emboli, but most were not investigated for pulmonary emboli. Nine (3.7%) children died as a consequence of their thromboembolic disease. Recurrent DVT occurred in 16 (6.5%) children, and postphlebitic syndrome occurred in 23 (9.5%) children.

CONCLUSION

Currently no uniform guidelines exist for the prevention and management of CVL-related DVT in children. The frequency and clinical consequences of CVL-related DVTs justify controlled trials of primary prophylaxis in children requiring central venous access.

Characterization of the FET4 protein of yeast. Evidence for a direct role in the transport of iron

The low affinity Fe2+ uptake system of Saccharomyces cerevisiae requires the FET4 gene. In this report, we present evidence that FET4 encodes the Fe2+ transporter protein of this system. Antibodies prepared against FET4 detected two distinct proteins with molecular masses of 63 and 68 kDa. In vitro synthesis of FET4 suggested that the 68-kDa form is the primary translation product, and the 63-kDa form may be generated by proteolytic cleavage of the full-length protein. Consistent with its role as an Fe2+ transporter, FET4 is an integral membrane protein present in the plasma membrane. The level of FET4 closely correlated with uptake activity over a broad range of expression levels and is itself regulated by iron. Furthermore, mutations in FET4 can alter the kinetic properties of the low affinity uptake system, suggesting a direct interaction between FET4 and its Fe2+ substrate. Mutations affecting potential Fe2+ ligands located in the predicted transmembrane domains of FET4 significantly altered the apparent Km and/or Vmax of the low affinity system. These mutations may identify residues involved in Fe2+ binding during transport.

Intranigral or intrastriatal injections of GDNF: effects on monoamine levels and behavior in rats

The present studies were designed to determine whether administration of recombinant human glial cell line-derived neurotrophic factor (rhGDNF) into either the substantia nigra or striatum is capable of augmenting dopamine function of the nigrostriatal pathway in normal rats. Single bolus intracranial injections of rhGDNF at either site increased locomotor activity and decreased food and water consumption and body weight in a dose-dependent manner when compared to vehicle-treated animals. These behavioral responses returned to pre-control levels within 3 weeks post rhGDNF administration. Administration of rhGDNF intranigrally increased dopamine, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels of the ipsilateral substantia nigra at 2 and 6 weeks post injection but had no augmenting effects on dopamine or its metabolites in the striatum. Administration of rhGDNF intrastriatally increased DOPAC and HVA levels of the ipsilateral striatum, although striatal dopamine levels were unchanged. Ipsilateral nigral dopamine levels were increased after intrastriatal injection of rhGDNF. The effects of intracranial rhGDNF were not specific to the nigrostriatal dopamine system, since nigrostriatal serotonin, 5-hydroxyindoleacetic acid (5-HIAA), epinephrine and norepinephrine transmitter levels were altered depending on administration route for rhGDNF and dose. Taken together, these data demonstrate long-lasting neurochemical and behavioral changes which suggest that rhGDNF can augment function in adult rat dopamine neurons. Therefore, rhGDNF may have therapeutic potential for Parkinson's disease.

On the role of aging in carcinogenesis

Correlation coefficients for age-standardized incidence rates between cancers of the stomach, colon, rectum and lung over place (worldwide) and time (in Connecticut) vary from positive to negative values, indicating that these cancers are not caused by common environmental agents. Correlation coefficients for age-incidence patterns (the variation in age-specific rates with age) between these cancers, on the other hand, are all highly positive for both sexes. We conclude that the carcinogenic determinants that vary with age are common to the cancers studied and to both sexes, and distinct from the carcinogenic determinants that vary with place and time. For the cancers studied, incidence rates are negligible until age 30, at which time they increase dramatically and continue to increase at least until age 75. The rate of increase, however, diminishes continuously with advancing age after 30. We suggest that the role of aging in cancer incidence is determined by two components, one responsible for the dramatic rate increase beginning near age 30 and one responsible for the gradual diminution in that rate increase. The former may correspond to the activation of quiescent cells with damaged DNA or to the deactivation of DNA surveillance or repair or to impaired apoptosis, while the latter may correspond to the loss of cell division potential.

Science as cancer prevention for American inner city residents

Eighty parents and guardians of high-risk elementary school children from Hartford, America's fourth poorest city, participated in a 12-week Saturday programme of science and cancer risk reduction while their children participated in a science programme designed to be interesting and fun. The children learned to enjoy biology as innovative recreation. Their parents and guardians learned to appreciate the health risks associated with passive thinking. Cigarette advertisements and misleading food claims were exposed to scientific scrutiny with the result that parents and guardians came to view scientific thinking as a means to protect their children and themselves from cancer. They also learned to reduce cancer risk through proper nutrition. Attendance was excellent and the majority of parents and guardians completing the programme believed they had learned to identify and avoid cancer risks.

The role of aging in cancer incidence: an epidemiological study

Age-specific and age-standardized incidence rates for cancers of the bronchus, stomach, colon, rectum, pancreas, skin, male bladder, and female breast, uterus, and ovary in 1975 were studied in populations throughout the world, and, for bronchus and stomach cancers, over time from 1960 to 1975. The variation in age-specific rates with age was similar for all cancers, as demonstrated by large positive correlation coefficients between age-incidence patterns averaged over all populations. In addition, the age-incidence patterns for bronchus and stomach cancer were similar and essentially invariant over time. The variation in age-standardized rates among the populations was not similar for all cancers, as demonstrated by correlation coefficients that were small in some cases and negative in others. Between bronchus and stomach cancer, age-standardized rates varied in opposite directions from 1960 to 1975. It is obvious, therefore, that the cause for the variation in age-specific rates with age is not related to the cause for the variation in age-standardized rates among populations or over time. The shape of age-incidence patterns for the cancers studied must be determined by a factor that is common to the tissues of tumor origin, and invariant among populations and over time. The intrinsic aging process is the most reasonable candidate for this role.

On the role of aging in cancer incidence: analysis of the skin cancer data

Worldwide age-incidence patterns for melanoma, non-melanoma skin cancer, and the group of all cancers except non-melanoma skin cancer from 1971 to 1976 were normalized for differences in frequency of occurrence and compared. The percentage of total cancer incidence that occurred in young subjects was greater for melanoma and less for non-melanoma skin cancer than for the group of all cancers. The risk for melanoma was apparent by age 15, much earlier than for non-melanoma skin cancer and the group of all cancers. While the risk for non-melanoma skin cancer and the group of all cancers increased continuously with advancing age, the risk for melanoma was constant beyond age 35. We conclude that risk for melanoma is unusually concentrated among the young, and, therefore, that protection from sun exposure is particularly important for this group.

Estimating reference ranges in clinical pathology: an objective approach

Conventional reference ranges evolve from subjective criteria for health and disease. We offer an objective method for distinguishing typical from atypical values by purely statistical criteria. We define typical values as those exhibiting a linear relationship with percentiles on a value versus percentile plot. Identification of percentiles at which deviation from linearity occurs results from calculation of correlation coefficients between values and percentiles over centrally expanding ranges of percentiles. One selects arbitrarily some minimum value for these correlation coefficients, for example, 0.990, as the criterion for deviation from linearity. Values encompassed by these percentiles of deviation constitute an objective reference range. Identification of any correlations between atypical values and symptoms of disease requires clinical follow-up studies.

On the role of aging in cancer incidence: cohort analyses of the lung cancer data

Lung cancer age-specific mortality rates for male and female cohorts born in the United States between 1903 and 1928 increase from age 32 to 52 according to an equation of the form log (mortality rate) = m(age) + b, where m and b are constants. Variation exists among the cohorts in the magnitudes of m and b, but correlation coefficients between age-mortality patterns among all cohorts are highly positive (r greater than 0.98, p less than 0.01), indicating that the form of the equation is similarly appropriate for each cohort. Because cigarette smoking behavior has varied among cohorts and between sexes, we conclude that the form of the equation, i.e., the exponential nature of the lung cancer age-mortality pattern, is independent of environmental carcinogenicity and is best attributed to some aspect of the intrinsic aging process.

On the role of aging in cancer incidence: analysis of the lung cancer data

Age-specific lung cancer mortality rates for U.S. males and females from 1935 to 1978 were normalized to describe the percentage of total mortality in a given era which occurred at a given age interval. Correlation coefficients between age-mortality patterns for various eras were calculated and found to be highly positive. We conclude that the shape of the lung cancer age-mortality pattern has remained remarkably constant despite dramatic changes in the carcinogenicity of the lung environment, and suggest that shape is determined by an invariant influence which is best attributed to some aspect of the aging process.

On the role of aging in cancer incidence: an interpretation of the prostate cancer anomaly with implications for routine screening

Cross-sectional age-incidence patterns for the common male and female cancers in Connecticut were normalized to describe the percentage of total incidence that occurred at each age. The pattern for prostate cancer was atypical--less than the 99% confidence limit from the mean at ages less than 60 and greater than the 99% confidence limit from the mean at ages greater than 75. The available international data on latent carcinoma of the prostate, when normalized as above, resembled the mean male and female cancer patterns in Connecticut and suggested that the atypical behavior of clinical prostate cancer was the result of a lag between the incidence of latent carcinoma and promotion to clinical disease. Confirmation of this suggestion, with the potential to distinguish epidemiologically those latent carcinomas that remain asymptomatic from those that progress to malignancy, awaits routine screening for the latent carcinoma.

The incidence of female cancers: correlations with etiologic implications

Correlation coefficients were calculated between incidence rates for the most frequent female cancers in populations throughout the world. Positive correlations were generally weak, and we conclude that most female cancers do not share a dominant etiologic factor which is inherent in cancer incidence rates. However, most cancers do exhibit similar age-incidence patterns. We also conclude that the determinant of shape in cancer age-incidence patterns is common to most female cancers, internationally invariant, and independent of the determinants of cancer incidence rates. Breast cancer exhibits an unusual age-incidence pattern with a peculiar dependence on the frequency of breast cancer occurrence.

The oral glucose tolerance test: an objective method of interpretation

Oral glucose tolerance test results from a positively-skewed, unimodal distribution were analyzed in such a way as to uncover a natural division within the set of results for each time point. The division in results was obtained from a break in the curve formed when plasma glucose concentration was plotted vs the percentile of the population described by those concentrations. The percentile at which the break occurs separated normal from abnormal glucose concentrations objectively. Previously natural divisions between normal and abnormal glucose concentrations had been found only in bimodal distributions from atypical populations such as the Pima Indians and Nauruans of Micronesia. The glucose concentrations at which separations in our unimodal distribution occur compare well with the available data from the atypical populations. According to one measure of reliability, the 3-h time point was more effective than the more commonly utilized 2-h point in distinguishing normal from abnormal plasma glucose concentration.

On estimating biological variation in diagnostic tests: application to the oral glucose tolerance test

Biological variation (BV) in diagnostic tests can be conveniently estimated by the equation, BV = magnitude of reference limit - reference median magnitude of - 2(SD)A, where "reference limit" refers to either the 2.5th or 97.5th percentile in the reference population, magnitude of indicates absolute value, and (SD)A is the standard deviation of random analytical variation at the reference median. The value of (SD)A is calculated from the equation, (SD)A = (CV)A (reference median)/100, where (CV)A, the coefficient of variation of random analytical variation, is obtained from routine stable quality control material. The BV was calculated for plasma glucose concentration at the time points in the oral glucose tolerance test in an asymptomatic reference population and found to vary in the order: fasting less than 3 hour less than 1/2 hour less than 1 hour less than 2 hour. We present correlation coefficients between subject age and plasma glucose concentration that suggest that BV at the fasting, 1/2, 1, and 2 hour points might be reduced by subdividing reference populations according to subject age.

The incidence of female breast and genital cancer: analysis of the age-dependence

Worldwide age-incidence patterns for female breast and genital cancers were normalized for differences in frequency of tumor occurrence and compared. The percentage of total cancer incidence which occurred in elderly subjects differed between populations but was similar for cancer of the breast, ovary, and corpus uteri within a given population. In addition, cancers of the breast, ovary, and corpus uteri exhibited similar ranges of distribution about the worldwide median incidence at all age intervals and strong positive correlations between crude incidence rates in the populations studied. Despite these and other similarities, breast cancer exhibited a correlation between crude incidence rate and percentage of total incidence which occurred in elderly subjects which was not apparent in the genital cancers. We cannot exclude the possibility that this correlation is coincidental. However the possibility of identifying factors predisposing to or protecting against breast cancer is attractive. The results of this study suggest that such factors would apply to breast but not to genital tissue.

Evaluation of extracranial cerebrovascular disease in the hypertensive patient with ocular pneumoplethysmography at 500 mm Hg

OPG-300 is a reliable noninvasive method of detecting hemodynamically significant stenoses of the internal carotid circulation. An important limitation of the method is that patients with systemic blood pressure greater than 160 mm Hg cannot be studied; in our laboratory this represented 55 percent of the patients referred for testing. The addition of the 500 mm Hg vacuum modification now allows us to reliably test 95 percent of patients referred to our laboratory for evaluation of the extracranial cerebrovascular circulation.