Effects of 1,25-dihydroxyvitamin D3 on proliferation and differentiation of Caco-2 cells

The effect of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], or calcitriol, on the proliferation and differentiation of Caco-2 cells was studied. Vitamin D receptor mRNA was detected in both pre- and postconfluent cells, and its abundance was unchanged with time and in response to calcitriol. 1,25-(OH)2D3-binding activity increased during differentiation, but there was no difference in binding between 1,25-(OH)2D3-treated and control cells. 1,25-(OH)2D3 caused a dose-dependent reduction in proliferation, as assessed by [3H]thymidine incorporation and DNA content. 1,25-(OH)2D3 significantly enhanced the normal rise in alkaline phosphatase activity during differentiation and increased alkaline phosphatase mRNA abundance. In contrast, 1,25-(OH)2D3 inhibited the normal rise in sucrase-isomaltase activity and the corresponding mRNA level, although the inhibition occurred after the initial period of cell differentiation (> 10 days postplating). Morphological analysis demonstrated that by day 12 postplating, 1,25-(OH)2D3 increased the mean dome diameter and microvillus length and density. Although 1,25-(OH)2D3 decreases the proliferation of Caco-2 cells and enhances certain parameters of differentiation, not all brush-border hydrolases respond in a similar fashion, making it necessary to interpret with caution their individual use as markers of differentiation.

Properties of rat and mouse beta-glucuronidase mRNA and cDNA, including evidence for sequence polymorphism and genetic regulation of mRNA levels

cDNA clones containing partial sequences for beta-glucuronidase (beta G) were constructed from rat preputial gland RNA and identified by their ability to selectively hybridize beta G mRNA. One such rat clone was used to isolate several cross-hybridizing clones from a mouse-cDNA library prepared from kidney RNA from androgen-treated animals. Together, the set of mouse clones spans about 2.0 kb of the 2.6-kb beta G mRNA. Using these cDNA clones as probes, a genomic polymorphism for DNA restriction fragment size was found that proved to be genetically linked to the beta G gene complex. A fragment of beta G cDNA was subcloned into a vector carrying an SP6 polymerase promoter to provide a template for the in vitro synthesis of single-stranded RNA complementary to beta G mRNA. This provided an extremely sensitive probe for the assay of beta G mRNA sequences. Using either nick-translated cDNA or transcribed RNA as a hybridization probe, we found that mouse beta G RNA levels are strongly induced by testosterone, and that induction by testosterone is pituitary-dependent. During the lag period preceding induction, during the induction period itself, and during deinduction following removal of testosterone, beta G mRNA levels paralleled rates of beta G synthesis previously measured by in vivo pulse-labelling experiments. Genetic variation in the extent of induction affected either the level of beta G mRNA or its efficiency of translation depending on the strain of mice tested.

Impact of vacuum aspiration abortion on future childbearing: a review

Ever since induced abortion was legalized in the United States, there has been a running controversy over whether induced abortion affects subsequent childbearing; for example, it has been claimed that women who terminate a pregnancy are at a greater risk of miscarrying a subsequent pregnancy or of having a low-birth-weight baby. Ten studies of the later impact of first-trimester induced abortion by vacuum aspiration (the dominant method in the United States) are examined here; they find that compared with women who carry their first pregnancy to term, women whose first pregnancy ends in induced abortion have no greater risk of bearing low-birth-weight babies, delivering prematurely or suffering spontaneous abortions in subsequent pregnancies. However, these studies also show that induced abortion of a woman's first pregnancy does not have the protective effect on her first live birth that carrying a first birth to term has on later deliveries. In addition, some evidence from other studies links dilatation and curettage (D&C) procedures with later infertility, but most studies have found no such association. No definite conclusions can be reached about the impact of multiple induced abortions, since the results of 13 different epidemiologic studies are almost evenly divided between those that show no effect and those reporting related reproductive problems.

Repeat abortion in the United States: new insights

The increasing numbers and proportions of repeat abortions in the United States, including higher order repeat abortions, can be adequately explained by the increasing numbers of women at risk and the heterogeneity of the population in regard to the need for and utilization of abortion services. The same factors, rather than a deterioration of contraceptive practice following abortion, explain the higher levels of repeat abortion rates compared with first abortion rates.

Race-specific patterns of abortion use by American teenagers

Between 1972 and 1978, as legal abortion became more widely available nationally, abortion rates (abortions per 1,000 women) and ratios (abortions per 1,000 live births) increased for all American teenagers; from 1972 to 1975, the rates and ratios for teenagers for Black and other races increased faster than those for White teenagers. For all seven years, abortion rates were higher for teenagers of Black and other races than for white teenagers. This reflected both higher proportions of sexually active teenagers of Black and other races and a greater risk of pregnancy in these teenagers compared with White teenagers. Race-specific differences in legal abortion ratios narrowed during the seven-year interval, as did differences in alternative outcomes of teenage premarital pregnancies (term births, illegal abortions).

Mannose-specific endocytosis receptor of alveolar macrophages: demonstration of two functionally distinct intracellular pools of receptor and their roles in receptor recycling

Receptor-mediated endocytosis of rat preputial beta-glucuronidase and the glycoconjugate mannose-BSA by rat alveolar macrophages is inhibited by chloroquine and ammonium chloride. We have previously reported that these drugs cause a loss of cell surface binding activity and that they do not inhibit internalization of receptor ligand complexes when incubated with cells at 37 degrees C. In this report we more clearly delineate the intracellular site of weak base inhibition of receptor recycling and the mechanism of that inhibition. From our analysis of the kinetics of ligand transport we conclude that there are two functionally distinct intracellular pools of receptor. One of these, the cycling pool, is not sensitive to the presence of weak bases, and receptor-ligand complexes return from this pool to the cell surface intact. The second pool is responsible for the time-dependent intracellular delivery of ligand to acid vesicles, which is inhibited by weak bases. Chloroquine and ammonium chloride appear to inhibit the dissociation of receptor-ligand complexed in this second pool and thereby the production of free receptors for the continuation of receptor-mediated endocytosis. We examine the internalization and binding of ligand in normal and paraformaldehyde-treated cells and find that these are strongly affected by pH. In particular, the dissociation rate of receptor ligand complexes is enhanced greater than 7.5 fold by lowering the medium pH from 7 to 6. From these results we propose that weak bases raise the pH of acid intracellular compartments, slowing the rate of receptor-ligand dissociation and thereby reducing the cellular pool of free receptors available for further uptake of ligand. In addition, we demonstrate that receptor-ligand complexes cannot return to the cell surface from the amine-sensitive (acid) intracellular pool that led us to call this the nonreleasable pool. This final observation indicates that receptor movements through these two pools are functionally distinct processes.

Abortion in the United States, 1977-1978

There were 1.32 million legal abortions in the United States in 1977 and a projected 1.37 million in 1978, an increase of four percent between 1977 and 1978 compared with one of 12 percent between 1976 and 1977. In 1978, 29 percent of pregnant women chose to terminate their pregnancies by abortion. Almost three percent of U.S. women of reproductive age obtained an abortion in 1978. From 1967 through 1978, approximately six million women obtained almost eight million legal abortions; about one in eight U.S. women of reproductive age has had a legal abortion. The number of hospitals reporting that they provided abortion services dropped slightly from 1,695 in 1976 to 1,661 in 1977, but the number of nonhospital abortion clinics increased from 448 to 522, and the number of physicians who reported performing abortions in their offices grew from 424 to 533. Between 1976 and 1977, the average number of abortions per hospital facility decreased from 246 to 237, while the average number per nonhospital provider increased from 875 to 879. The percentage of abortions performed in hospitals declined from 35 in 1976 to 30 in 1977, while the percentage reported by free-standing clinics increased from 61 to 66; the percentage performed in physicians' offices remained at four. Ninety-five percent of abortions in 1977 occurred in metropolitan areas, where 75 percent of the women in need of abortion services live. In 1977, there were identified abortion providers in only 23 percent of U.S. counties. Nine percent (more than 118,000) of the women who obtained abortions in 1977 had to travel to another state for services, and many traveled to other, often distant, counties in their home states. One in three abortions in 1977 were obtained by teenagers, and three in four were obtained by unmarried women. Twenty-eight percent of the women estimated to be in need of abortion services in 1977, and 26 percent in 1978, were unable to obtain them. In FY 1977, before Hyde amendment restrictions on government financing of abortions for poor women, 133,000 of the estimated 427,000 Medicaid-eligible women in need of publicly funded abortion services were unable to obtain them.(ABSTRACT TRUNCATED AT 400 WORDS)

Unintended pregnancies in the United States, 1970--1972

There were about 2.0--2.3 million unintended pregnancies in the United States each year during the early 1970s. Within this framework, the rapid rise in the number of abortions since 1973, to 1.3 million in 1977, is quite predictable.

Survey of abortion providers in Seoul, Korea

A survey of abortion providers in Seoul in late 1977 reveals a threefold increase in the rate of abortion and a greater than threefold rise in the ratio of abortions to live births since 1970. The survey findings also show that the overwhelming proportion of these abortions are performed in private clinics, by obstetrician-gynecologists, during the first trimester. The Seoul figures, which are similar to those of Romania and are higher than those of Japan in the early 1960s, indicate that abortion has contributed substantially to Korea's reduced fertility.

The pill and mortality from cardiovascular disease: another look

Analysis of U.S. mortality statistics shows that since adoption of the pill, deaths among women of reproductive age from cardiovascular diseases have declined much more steeply than have death rates for comparable men. This suggests that the high level of risk of death from such diseases associated with pill use in other studies are exaggerated.

The mathematics of repeat abortion: explaining the increase

In any given population, an increase in the proportion of repeat abortions, and a repeat-abortion rate that is substantially higher than the first-abortion rate, can be anticipated to occur over a number of years after abortion has been legalized. These are the findings of an analysis of repeat abortion for a population of women aged 15--44, using simple mathematical models based on the assumptions that the risk of abortion is constant over time and independent of prior abortion experience. The data generated by the models explain both the rapidly increasing percentage and the high rate of repeat abortion following legalization and refute assertions that making abortion widely available discourages the practice of contraception.

Abortion in the United States, 1976--1977

In 1976, about 1.2 million, and in 1977 some 1.3 million, abortions were performed in the U.S. More than half a million women were without the abortion services that they wanted. Poor, rural, young and black women were disporportionately represented among those not yet served.