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PubMed1991

On the significance of remodeling space and activation rate changes in bone remodeling.

This paper quantifies the relative contributions of the remodeling space and the accumulation of Haversian canals to bone porosity at various ages. It also examines the importance of variations in the rate of bone remodeling that occur during growth and aging, and as a result of trauma and disease. The dependence of the remodeling space (cavities due to resorbing, reversing, and refilling BMUs) and the Haversian canal components of porosity on the Basic Multicellular Unit (BMU) activation frequency are mathematically formulated. A graph is developed using data for the cortex of the human rib which shows the extent to which porosity is primarily due to the remodeling space in children, and to accumulated Haversian canals in adults. It is shown that the diminution of activation frequency between birth and age 35 contributes to the concurrent increase in bone volume fraction, and the increase in activation frequency after age 35 contributes to the subsequent decline of bone volume fraction. An equation is derived for determining the time rate of change of activation frequency using two fluorochrome labels.

Aging↗
PubMed1992

Combined effects of body size, parity, and menstrual events on breast cancer incidence in seven countries.

A biologically motivated breast cancer incidence rate function was fit to data from a published case-control study conducted in countries whose incidence is high (Wales and the United States), moderate (Brazil, Greece, and Yugoslavia), and low (Japan and Taiwan). The data include personal characteristics of 3,925 breast cancer cases and 11,327 controls interviewed in selected hospitals in 1964-1968. Parameters in the function specify the dependence of age-specific breast cancer incidence rates on age at menarche, age at menopause, occurrence and timing of full-term pregnancies, and body mass. Parameters were estimated separately for high-, moderate-, and low-risk countries. Examination of residuals provided little evidence of inadequacy of the fitted function in describing combined effects of the characteristics studied. The following patterns were seen in all three risk groups: 1) Incidence rates jump to a higher level after first childbirth, but then increase with age more slowly thereafter. 2) Rates increase with age more slowly after menopause than before. 3) Rates change quadratically with body mass index among all women, although the main trend varies: Rates decrease with body mass among premenopausal women in high-risk countries, but increase with body mass in all other groups of women. Similarities of parameter estimates across countries suggest that reproductive events and body fat exert similar effects on all women, regardless of breast cancer rates in their country of residence.

Adult↗
PubMed1991

Fertility rates in 238 HIV-1-seropositive women in Zaire followed for 3 years post-partum.

Birth-control use and fertility rates were prospectively determined in 238 HIV-1-seropositive and 315 HIV-1-seronegative women in Kinshasa, Zaire, during the 36-month period following the delivery of their last live-born child. No women delivered children during the first follow-up year. Birth-control utilization rates (percentage use during total observation time) and fertility rates (annual number of live births per 1000 women of child-bearing age) in the second year of follow-up were 19% (107.4 per 1000) for HIV-1-seropositive women and 16% (144.7 per 1000) for HIV-1-seronegative women. In the third year of follow-up these rates were 26 (271.0 per 1000) and 16% (38.6 per 1000) for HIV-1-seropositive and HIV-1-seronegative women, respectively (P less than 0.05 for the difference in birth-control utilization and fertility rates between seropositive and seronegative women in the third year of follow-up). Seven (2.9%) of the 238 HIV-1-seropositive women initially included in the study brought their sex partners in for HIV-1 testing; three (43%) of these men were found to be HIV-1-seropositive. New HIV-1 infection did not have a dramatic effect on the fertility of seropositive women. The nearly uniform unwillingness of HIV-1-seropositive women to inform husbands or sexual partners of their HIV-1 serostatus accounted in large part for the disappointingly high fertility rates in seropositive women who had been provided with a comprehensive program of HIV counseling and birth control. Counseling services for seropositive women of child-bearing age which do not also include these women's sexual partners are unlikely to have an important impact on their high fertility rates.

AIDS-Related Complex↗
PubMed1988

Pseudo-exponential growth in length of the fission yeast, Schizosaccharomyces pombe.

The growth patterns of individual cells of the fission yeast (Schizosaccharomyces pombe wild-type cells, strain 972 h-; cells exposed to hydroxyurea; and cdc mutants, 11-123, 2-33) were investigated by time-lapse photomicrography. Wild-type cells showed one, two, or three linear-growth segments followed by a constant-length stage. Cells with two segments were most frequent. Hydroxyurea cells that divided as oversized cells (about three times the birth length) had three linear-growth segments in a cycle. Mutant cdc11-123 cells did not divide but had a constant-length stage separating the cycles; both the first and second cycles consisted of two linear-growth segments, and cells were oversized at the second constant-length stage (about 3.5 times the birth length). Elongating cdc2-33 cells that did not divide and were oversized (about five times the birth length) while under observation, showed four linear-growth segments. Cells of all strains showed 30 to 40% increase in growth rate at the rate-change point and maintained approximate exponential (pseudo-exponential) growth. We conclude that the normal growth pattern of individual fission-yeast cells is the pseudo-exponential pattern.

Hydroxyurea↗
PubMed1975

Family planning services in the United States.

In recent years the United States has made considerable progress in providing family planning services for those in need. This does not mean, however, that the problems posed by unwanted pregnancies and unwanted births have been completely overcome. Estimates of the number of low-income women needing and receiving family planning services indicate that roughly 3.6 million women at risk of an unwanted pregnancy were receiving family planning services in 1973. This represented almost two-thirds of those in need at the time. Many programs are also seeking to meet the teenage need demonstrated by very high rates of out-of-wedlock births, premarital conceptions, obstetric problems, and legal abortion demands of women 15 to 19 years of age. As of 1973, it appeared that between 1.3 and 2.2 million never-married teenagers were in need of organized family planning services, and that of these, services were being received by between 25 and 42 per cent.

Abortion, Legal↗
PubMed1975

The containment of world population growth.

The world has reached the present position of unprecedentedly rapid population growth not by achieving uniquely high fertility but by bringing about extraordinarily low mortality. The high growth rate and the built-in momentum of the age structure are obstacles to achievement of an acceptable standard of living for most of the world's population. Although government population programs have the potential to curb this growth rate, this potential has not been realized, and such programs are too often perceived both by their administrators and the population concerned as an end in themselves rather than a means toward a better standard of living. It is in this latter perspective, and in the context of the total development process, that population programs should be implemented.

Adult↗
PubMedDate not supplied

Population and family planning: an international perspective.

Since the 1960s, the U.S. government has supported population and family planning programs in Third World countries, on the grounds that rapid population growth impairs the ability of those countries to develop economically; family planning programs contribute to fertility decline; and such programs help improve the health of mothers and children. Although the United States remains the largest single donor of funding for international population programs, its support has weakened during the eight years of the Reagan administration and patterns of funding for those programs have changed substantially. Since the 1960s, however, contraceptive use has increased in the Third World and fertility has fallen substantially. The decline has been uneven, though--considerable in some countries, moderate in others but very small in many. The performance of family planning programs around the world has varied widely, and questions remain as to what, if anything, can be done to increase success. For the future, three aspects of population and fertility control in developing countries merit special attention: the supply of contraceptive commodities going to family planning programs; the maintenance and strengthening of the family planning infrastructure; and the need to examine the policy implications of differing patterns of fertility and population growth for national development and individual well-being.

Developing Countries↗
PubMedDate not supplied

Contraceptive paths toward the reduction of unintended pregnancy and abortion.

Based on data from the 1982 National Survey of Family Growth, exposure to the risk of unintended pregnancy is classified by use of specific contraceptive methods and by nonuse, and average rates of unintended pregnancy are estimated for each type of exposure. Three hypothetical models of improved contraceptive practice are then applied to the data for all women and for age, race and marital-status subgroups. The first two models assume increases in the use of some existing contraceptive methods, but only the second model additionally assumes the introduction of new methods. The third model assumes the complete elimination of nonuse of contraception. These models yield different estimates of the reduction in unintended pregnancy rates which are illustrated for various age-groups, for whites and blacks and for married and unmarried women. Among all women aged 15-44, the changes assumed by Model I imply a 32 percent reduction in unintended pregnancy; Model II implies a 56 percent reduction; and Model III implies a 57 percent reduction. The implied reductions in abortion are in a similar range.

Abortion, Induced↗
PubMedDate not supplied

Characteristics of U.S. women having abortions, 1982-1983.

In 1982 and 1983, as in previous years, the majority of abortions in the United States were obtained by young women (62 percent), white women (70 percent) and unmarried women (81 percent). Half of all abortions were performed eight or fewer weeks after the last menstrual period, and 91 percent, at 12 weeks or earlier. The proportion of abortions that were repeat procedures continued to rise, to 37 percent in 1982 and 39 percent in 1983. The rate of abortion, 29 per 1,000, has remained essentially the same since 1981. Women aged 18-19 continue to have the highest abortion rate of any age-group (60 per 1,000). While most abortions are obtained by white women, the nonwhite abortion rate is more than twice that of whites. Thirty percent of all pregnancies were terminated by abortion in 1983, the same proportion as in 1982 and 1981. The highest abortion ratios are found among unmarried women (63 percent), women 40 and older (51 percent), teenagers (42 percent) and nonwhites (40 percent). Teenage nonwhites and whites have about the same abortion ratios. After rising during the 1970s, the adolescent pregnancy rate peaked around 1980-1981 and fell slightly in 1982-1983. The relative differentials between the pregnancy, birth and abortion rates of nonwhite and white teenagers narrowed somewhat between 1978 and 1981, but then widened slightly between 1981 and 1983.

Abortion, Induced↗
PubMed1987

[Studies on the interrelation of fetal heart rate change, placental findings and fetal outcome].

The relation between antepartum fetal heart rate (FHR) non stress test (NST), maternal serum estriol, intrapartum FHR change, birth weight, placental findings and Apgar score were studied in 168 normal gestations and 36 high-risk pregnancies including 25 EPH-gestosis cases. The frequency of placental infarcts was higher in severe gestosis than in other high-risk pregnancies and normal gestation. Abnormal NST was more frequent in high-risk pregnancy than normal. Light for date (LFD) infants were more numerous in high-risk pregnancy than normal, and also frequent in the cases of placental infarcts. Particularly in high-risk pregnancy patients with abnormal NST and placental infarcts, 3 out of 5 showed LFD infants. Intrapartum fetal distress was more common in the cases of abnormal NST than normal. The five minute Apgar score was lower in the patients with abnormal NST and in the cases of placental infarcts than normal. The placental infarct ratio was higher in high-risk pregnancies with abnormal NST than normal. The maternal serum estriol level was not changed in cases of high-risk pregnancy, abnormal NST or placental infarcts when compared to normal gestation. The cases of succeeding fetal death, however, showed a low serum estriol level. In conclusion, antepartum abnormal NST suggests severe placental dysfunction caused by its infarcts and the prognosis is poor in patients with high-risk pregnancies, particularly EPH-gestosis. Coping with abnormal antepartum NST is regarded as important in fetal management.

Apgar Score↗
PubMedDate not supplied

Contraceptive use and fertility in Honduras, 1981-84.

This paper presents data on contraceptive use and fertility in Honduras obtained from a household survey conducted in 1984, and compares these data with similar information obtained from surveys carried out in 1981 and 1983. About half of the increase that has taken place in contraceptive use in Honduras is accounted for by sterilization. In 1981, 27 percent of women in union aged 15-49 years were practicing contraception; in 1984, the percentage of those 15-44 was 35 percent. The increase in urban areas was smaller (from 47 percent to 51 percent) than in rural areas (from 16 percent to 24 percent). Also, fertility remained almost unchanged in urban areas while declining in rural areas. Information from questions on place of purchase, price, and brand of contraceptive (for orals) was used to determine source of supply. The use of multiple questions to determine source results in a higher percentage of contraceptive use attributed to the Honduran Family Planning Association as compared with answers to a single question. The duration of breastfeeding in Honduras has increased, with the greatest changes occurring among women in urban areas and women with the highest levels of education. Efforts have been made to promote breastfeeding in urban areas and these results suggest that the efforts have been successful.

Adolescent↗
PubMed1978

What will 1984 be like? Socioeconomic implications of recent twists in age structure.

Since 1940, under conditions of restricted immigration and high and sustained growth in aggregate demand, shifts in the relative number of younger versus older adults have had a pervasive impact on American life. Before 1960, younger males were in increasingly short supply and their relative economic position substantially improved; after 1960, the opposite was true. Since the early sixties, as the relative condition of young adults has deteriorated, marriage has been increasingly deferred and fertility reduced. The labor force participation of young women has risen at above average rates, and that of older women has risen at below average rates. Changes in the age structure of the working age population have also contributed to a combination of rising unemployment and accelerating inflation. Cohort divorce rates, suicide among young males, crime rates, and political alienation have worsened. The rise in college enrollment rates has been interrupted, and SAT scores have declined. In contrast, in the period 1940-1960, changes in these various magnitudes were typically of a more favorable sort. The United States is now at the start of a new period of growing scarcity of young adults as a result of the birth rate decline that set in after 1960. This implies that the 1980s will see a turnaround or amelioration in a wide variety of these social, political, and economic conditions, some of which have been taken as symptomatic of a hardening social malaise.

Adult↗