Trends in adolescent males' abortion attitudes, 1988-1995: differences by race and ethnicity.

CONTEXT: Studying how adolescent males view abortion and how their attitudes toward abortion have changed over time can improve our understanding of the sexual, contraceptive and abortion behavior of these males and their partners. METHODS: Data from the 1988 and 1995 National Survey of Adolescent Males are used to describe changes in young males' attitudes toward abortion over time, as well as differences in abortion attitudes by race and ethnicity. Multivariate models are used to examine the relationship between religiosity and abortion attitudes. RESULTS: Between 1988 and 1995, young males' approval of abortion decreased significantly. In 1995, 24% of U.S. males aged 15-19 agreed that it was all right for a woman to have an abortion "for any reason," down from 37% in 1988. This decrease was driven almost entirely by non-Hispanic white males; there was little change in the abortion attitudes of non-Hispanic blacks and Hispanics. The decrease in white males' approval of abortion coincides with a significant increase in the self-reported importance of religion and in the proportion of whites who identified themselves as born-again Christians. The proportion of non-Hispanic white males indicating that religion was very important increased from 28% in 1988 to 34% in 1995, while the proportion identifying themselves as born-again increased from 18% to 24%. Multivariate analyses indicate that religiosity was more strongly related to the abortion attitudes of non-Hispanic whites than to those of Hispanics or non-Hispanic blacks. CONCLUSIONS: The large decrease in approval of abortion among white teenage males has closed the racial and ethnic gap in attitudes toward abortion that was evident in 1988, when such youth held significantly more liberal attitudes toward abortion than did either Hispanics or blacks. This trend toward more conservative abortion-related attitudes among whites coincides with increasingly conservative attitudes regarding premarital sex and greater religiosity among white male adolescents.

Understanding changes in sexual activity among young metropolitan men: 1979-1995.

CONTEXT: Changes in the sexual behavior of teenagers can have a significant impact on levels of adolescent pregnancy and transmission of sexually transmitted diseases (STDs). Understanding the role played by attitudes and educational efforts will provide critical prevention information. METHODS: Data on the sexual behavior, sexual attitudes, educational experiences and demographics of 2,087 never-married metropolitan males aged 17-19 from the 1979 National Survey of Young Men and the 1988 and 1995 waves of the National Survey of Adolescent Males were analyzed through multivariate methods to examine factors that predict sexual behavior as well as those that predict sexual attitudes. RESULTS: The percentage of males aged 17-19 who had ever had sex increased from 66% in 1979 to 76% in 1988 and then decreased to 68% in 1995. The frequency of sexual intercourse in the year prior to the survey increased significantly over time, although the lifetime number of sexual partners did not. Acceptance of premarital sex increased significantly from 1979 to 1988, then decreased significantly from 1988 to 1995. Over time, young men were increasingly likely to prefer having and supporting a baby to marriage, abortion or adoption as the resolution to a nonmarital pregnancy. Trends in attitudes were strongly associated with sexual behaviors, with more conservative attitudes predicting less sexual activity. AIDS education, which was nearly universal in 1995, was associated with decreased sexual activity, although not among black youths. CONCLUSIONS: More conservative sexual attitudes and increased exposure to AIDS education are key predictors of decreased sexual activity among adolescent males. However, broader societal factors, such as fear of AIDS and increased awareness of problems associated with teenage pregnancy and STDs, may underlie both attitudinal and behavioral changes.

PIP: This study examined how attitudes about sex behavior and exposure to AIDS education have affected premarital sexual behavior among urban teenage (Black and non-Black) males aged 17-19 years in 1979, 1988, and 1995 in the US. Data were obtained from a 1979 National Survey of Young Men and the 1988 and 1995 National Surveys of Adolescent Males. The weighted pooled data set included 2087 never-married males aged 17-19 years. The percentage of those who had experienced sexual intercourse (SI) rose from 66% to 76% and then declined to 68% in 1995. For Black male youths, SI rates remained stable after 1988. The percentage with recent SI in the 4 weeks before the survey rose from 40% to 45% in 1979 and 1988, and then declined to 39% in 1995. The average number of female sexual partners (FSPs) was 4. The average number of FSPs declined among non-Blacks--from 3.8 in 1979 to 2.9 in 1995--and increased among Blacks--from 5.1 in 1979 to 6.9 in 1995. SI frequency during the prior year rose significantly from 14 encounters/year in 1979 to 21 in 1995. Among Black adolescents, SI frequency rose from 13 encounters/year in 1988 to 24 in 1995. Approval of nonmarital sex without an intention to marry followed similar increases and declines as for SI. Attitudes about premarital sex were strongly correlated with recent sexual activity. Teenagers who had received education about STDs or AIDS were significantly less likely to report having had recent SI. Birth control education and race were unrelated to sex behavior. Blacks were more supportive of marriage for nonmarital pregnancy in 1979. Black attitudes toward premarital sex grew more conservative. Less sexual activity is attributed, in part, to prevalence of AIDS education (except for Blacks) and more conservative attitudes, with unknown other factors.

Increased condom use among teenage males, 1988-1995: the role of attitudes.

CONTEXT: Understanding whether and to what degree changes in young men's attitudes explain increases in condom use over time can be useful in developing more effective disease prevention strategies. METHODS: Data from the 1988 and the 1995 National Survey of Adolescent Males are used to determine changes in attitudes toward condoms, pregnancy prevention and HIV and AIDS. Two-limit tobit models are employed to investigate the association between these attitudes and condom-use behavior and to examine how this relationship may have changed over time. RESULTS: Between 1988 and 1995, young men's attitudes toward partner appreciation of condom use, condom-use embarrassment and pleasure reduction from condom use all changed in a direction suggestive of more consistent condom use. However, attitudes related to pregnancy prevention and AIDS avoidance changed in a direction suggestive of less-consistent condom use. Changes over time in the strength of the relationship between three attitude measures (masculinity, pleasure reduction and partner appreciation) and condom use also were predictive of lower levels of condom-use consistency. Only the strength of the relationship between condom-use embarrassment and consistent condom use changed in a direction corresponding to observed increases in rates of condom use among young men. CONCLUSIONS: Many of the significant changes in young males' attitudes toward condoms do not explain the increase in consistent condom use among adolescent males that occurred between 1988 and 1995. However increasing male contraceptive responsibility and emphasizing the risks and consequences of contracting HIV appear to be viable routes for policymakers to explore. Efforts particularly need to be targeted toward Hispanics.

PIP: This study examined the role of attitudes and beliefs in explaining increased adolescent condom use during 1988-95 in the US. Data were obtained from the 1988 and 1995 waves of the National Survey of Adolescent Males among a nationally representative, multistage probability sample of never-married 15-19 year old men (1262 in 1988; 1032 in 1995). Findings indicate that condom use became more consistent and increased by 24% between 1988 and 1995. Changes occurred in men's attitudes about masculinity, pleasure reduction, condom use embarrassment, and partner appreciation. Attitudes that advanced greater condom use were related to less condom use embarrassment and less attention to pleasure reduction. Changes in attitudes on pregnancy prevention and AIDS avoidance suggest less consistent condom use. Less consistent condom use was also predicted by changes in masculinity, pleasure reduction, and partner appreciation. Use increased in the prior 12 months from 56% to 69%. Increases varied by race and ethnicity. Condom use consistency rose among Blacks from 63% to 73%; it increased the least among Hispanics. Beliefs in the potential for a future pregnancy with condom use declined from 71% to 64%. Males were less likely to agree that men should ask their partner about contraception use and to report that a lot of men would associate pregnancy with manhood. AIDS worry and perceived risk declined. Lower regular condom use was associated with two pregnancy prevention and two AIDS avoidance attitudes. It may be that female partners expect greater condom use.

Family structure, economic status, and educational attainment.

"This study examines the effect of family structure on high school graduation by race and gender using data from the first twenty-one waves of the [U.S.] Panel Study of Income Dynamics and recently available retrospective marital histories.... The analysis tests the hypothesis that the negative effect on educational attainment often associated with living in a mother-only or stepfather family stems primarily from the reduced level of economic resources available to these households. Empirical findings indicate that living with a widowed, divorced, or separated mother has little or no effect on educational attainment once we control for economic status. However, living in a stepfather family appears to have a persistent negative effect on high school graduation rates."

Oxidation of proline by plant mitochondria.

Mitochondria isolated from etiolated shoots of corn (Zea mays), wheat (Triticum aestivum), barley (Hordeum vulgare), soybean (Glycine max L. Merr.), and mung bean (Phaseolus aureus) exhibited a proline-dependent O(2) uptake subject to respiratory control. ADP/O ratios with proline as substrate were intermediate between ratios obtained with exogenous NADH and malate + pyruvate as substrates. Isotope studies showed proline metabolism to be dependent on O(2), but not NAD. The major ninhydrin-positive product formed via Delta(1)-pyrroline-5-carboxylic acid was glutamate. Mitochondria were capable of further metabolism of glutamate, as radioactive CO(2), organic acids, and aspartate were recovered after [(14)C]proline feeding experiments. These results demonstrate the mitochondrial association and O(2) dependence of plant proline metabolism.

Metabolism of [5-h]proline by barley leaves and its use in measuring the effects of water stress on proline oxidation.

The objective of these experiments was to determine the fate of tritium from the 5 position of proline and to assess the validity of its loss to H(2)O as a measure of proline oxidation. When [5-(3)H]proline was fed to barley (Hordeum vulgare) leaves, tritium was recovered in H(2)O and metabolites such as glutamate, glutamine, organic acids, aspartate, asparagine, and gamma-aminobutyrate. Collectively these metabolites, which are oxidation products of proline, accounted for 8% of the (3)H recovered after 5 hours. In spite of the amount recovered in metabolites, the rates of proline oxidation estimated by measuring (3)H(2)O recovery from [5-(3)H]proline were only slightly lower than rates estimated by incorporation of (14)C into oxidized products and loss of (14)C from total proline. Therefore, (3)H(2)O recovery from [5-(3)H]proline is useful in assessing the effects of stress on proline metabolism.Water stress inhibited proline oxidation, as reported previously. In addition, a reconversion of proline oxidation products to proline occurred in stressed leaves. This observation probably indicates a breakdown in cellular compartmentation of proline synthesis and proline oxidation.

Contribution of Arginine to Proline Accumulation in Water-stressed Barley Leaves.

Barley (Hordeum vulgare cv Prior) leaves converted l-U-(14)C-arginine to labeled proline. Accumulation of radioactivity in proline was greater in wilted leaves, but only after 9 hours of incubation. As the increase in free proline was detectable after only 3 to 6 hours, it is likely that the observed stimulation of proline labeling represents a result rather than a cause of proline accumulation. Furthermore, the loss of total arginine during water stress was only 10 to 15% of the increase in proline. We conclude that arginine probably contributes less than 1% of the carbon in the expanding proline pool of wilted barley leaves.

Effect of water stress on proline synthesis from radioactive precursors.

Barley (Hordeum vulgare L. var. Prior) leaves converted more (14)C-glutamic acid to free proline when water-stressed than when turgid; neither decreased protein synthesis nor isotope trapping by the enlarged free proline pools found in wilted tissue seemed to account for the result. This apparent stimulation of proline biosynthesis in wilted leaves was not observed when radioactive ornithine or P5C (Delta(1)-pyrroline-5-carboxylate, an intermediate following glutamate in proline synthesis) were used as proline precursors unless proline levels were high as a result of previous water stress. We interpret this to mean that any stimulation of proline synthesis by water stress must act on P5C formation rather than its reduction to proline. Experiments showing greater apparent conversion of (14)C-glutamate to proline do not unequivocally prove that proline synthesis is stimulated by water stress, as P5C feeding studies show that proline oxidation is inhibited under comparable conditions. This inhibition could account, at least in part, for increased proline labeling, and must be considered an alternate possibility.

Partial Purification and Properties of Ornithine Transcarbamoylase from Nostoc muscorum Kützing.

Ornithine transcarbamoylase (carbamoyl phosphate:l-ornithine carbamoyltransferase, EC 2.1.3.3) has been partially purified from the blue-green alga Nostoc muscorum Kützing, an organism in which the enzyme seems to be involved in a bicarbonate-fixing pathway leading to citrulline. Pertinent to possible regulation of this pathway, the enzyme shows hyperbolic substrate kinetics, has a molecular weight estimated at 75,000 daltons, and its catalytic capability is little influenced by a selection of metabolites that might conceivably act as regulators in vivo. Thus it seems unlikely that this enzyme is the control point for bicarbonate fixation. In terms of energy of activation (12.3 kcal/mole), size and Km for carbamoylphosphate, the Nostoc enzyme resembled preparations from liver and higher plants more than preparations from Streptococcus and Mycoplasma. The enzymes from Streptococcus and Mycoplasma are probably specialized for citrulline breakdown rather than citrulline synthesis. The Km for ornithine was 2.5 mm at a saturating concentration of carbamoylphosphate and the Km for carbamoylphosphate was 0.7 mm at an ornithine concentration of 2 mm. Ornithine was inhibitory at concentrations greater than 2 mm. Phosphate was a competitive inhibitor with respect to carbamoylphosphate. The pH optimum for citrulline synthesis was 9.5.

Delta-Pyrroline-5-carboxylic Acid Dehydrogenase in Barley, a Proline-accumulating Species.

The characteristics of the enzyme Delta(1)-pyrroline-5-carboxylic acid dehydrogenase from etiolated barley (Hordeum distichum) shoots have been examined. The bulk of the enzyme activity was found in the 10,000g pellet fraction, this activity being displayed only after detergent treatment of the suspended pellet. The enzyme was most active at pH 8, and activity was NAD-dependent. Enzyme activity was unaffected by either mannitol or sucrose in the reaction mixture up to a concentration of 0.45 m but was strongly inhibited by Cl(-) and, to a lesser extent, SO(4) (2-). The inhibition attributable to KCl was reversed by increasing the concentration of Delta(1)-pyrroline-5-carboxylic acid in the reaction mixture.