Xenon CT cerebral blood flow in patients with head injury: influence of pulmonary trauma on the input function.

The noninvasive xenon-enhanced CT (Xe CT) cerebral blood flow (CBF) method has been used in patients with severe traumatic brain injury (TBI) to identify the blood-flow thresholds for the development of irreversible ischaemia or infarction following severe TBI. Quantitative regional CBF (rCBF) estimates are based on the assumption of identity between the end-tidal xenon concentration curve, used as the input function, and the arterial xenon concentration curve, being the true input function to the brain. Accordingly, rCBF data addressing the issue of ischaemia should be viewed in relation to possible deviations between the end-tidal and arterial xenon concentration curves. To evaluate this possible source of error, we studied five patients with severe TBI (Glasgow coma score < or =7) who also had pulmonary trauma. CBF was studied with the Xe CT CBF method and flow rates were determined by fitting the Kety equation to each CT voxel using either the end-tidal or the arterial xenon curve as input function. In all patients rCBF estimates were lower using the end-tidal xenon curve than with the arterial xenon curve; the mean underestimation was 20.3% in gray metter and 17.3 % in white matter. The deviation between the end-tidal and arterial xenon concentration curves should be considered as a source of error when defining critical flow values according to the flow thresholds of tissue viability.

The 65-kDa carrot microtubule-associated protein forms regularly arranged filamentous cross-bridges between microtubules.

In plants, cortical microtubules (MTs) occur in characteristically parallel groups maintained up to one microtubule diameter apart by fine filamentous cross-bridges. However, none of the plant microtubule-associated proteins (MAPs) so far purified accounts for the observed separation between MTs in cells. We previously isolated from carrot cytoskeletons a MAP fraction including 120- and 65-kDa MAPs and have now separated the 65-kDa carrot MAP by sucrose density centrifugation. MAP65 does not induce tubulin polymerization but induces the formation of bundles of parallel MTs in a nucleotide-insensitive manner. The bundling effect is inhibited by porcine MAP2, but, unlike MAP2, MAP65 is heat-labile. In the electron microscope, MAP65 appears as filamentous cross-bridges, maintaining an intermicrotubule spacing of 25-30 nm. Microdensitometer-computer correlation analysis reveals that the cross-bridges are regularly spaced, showing a regular axial spacing that is compatible with a symmetrical helical superlattice for 13 protofilament MTs. Because MAP65 maintains in vitro the inter-MT spacing observed in plants and is shown to decorate cortical MTs, it is proposed that this MAP is important for the organization of the cortical array in vivo.

Adolescents' perceptions of caring in family, media, school, peer, and religious environments.

Adolescents were asked to select from two-word pairs the one that was emphasized more in their experiences with the environments of school, church, family, friends, or media. One of the word pairs was an indicator of caring, the other of justice. Analysis of responses of 87 adolescents indicated school was perceived as very low in caring compared to family, church, and friends.

Long crocidolite asbestos fibers cause polyploidy by sterically blocking cytokinesis.

Asbestos has been described as a physical carcinogen in that its carcinogenic effects appear to be related primarily to fiber dimensions. It has been hypothesized that long asbestos fibers may interfere with chromosome distribution during cell division, causing genomic changes that lead to cell transformation and neoplastic progression. Using high-resolution time-lapse light microscopy and serial-section electron microscopy, we have followed individual crocidolite asbestos fibers through the later stages of cell division in LLC-MK2 epithelial cells, and have detailed for the first time their effect on cytokinesis. We found that long fibers (15-55 microgram), trapped by the cleavage furrow, sterically blocked cytokinesis, sometimes resulting in the formation of a binucleated cell. The ends of blocking fibers were usually found within invaginations of the newly formed nuclei. Nuclear envelope-fiber attachment was evident when a chromatin strand ran with the fiber into the intercellular bridge. Such strands may break, causing chromosome structural rearrangements. Our data are the first to show that individual crocidolite fibers can cause genomic changes by sterically blocking cytokinesis and that fiber length and affinity for the nuclear envelope are important factors. Such genomic changes may be among the initial events leading to asbestos-induced cancers.

Total effective radiation dose from spiral CT and conventional radiography of the pelvis with regard to fracture classification.

PURPOSE: In most departments CT has replaced special radiographic projections with regard to classification of pelvic fractures. This change of procedure calls for analysis in terms of dosimetry. METHODS: The total effective radiation doses given with spiral CT and conventional 5 projection radiography were determined according to ICRP 60 by measuring organ doses with an anthropomorphic Rando Alderson phantom packed with thermoluminescence dosimeters. For comparison, easily obtainable calculated effective doses were also determined, based on the CT dose index (CTDI), measured free-in-air and as entrance surface dose using organ conversion factors according to NRPB-R250 and NRPB-R262. RESULTS: The total effective radiation dose was lower in spiral CT than in conventional 5 projection radiography, 4.4 and 5.0 mSv, respectively. In spiral CT the calculated effective dose was 11% lower and in conventional radiography 68% higher than the dose obtained by actual measurement using the Alderson phantom. CONCLUSION: As CT gives important diagnostic information with regard to classification of pelvic fractures, and without a greater radiation risk than impacted by 5 projection conventional radiography, we recommend the performance of spiral CT instead of special projections.

Radiation dose by spiral CT and conventional tomography of the sternoclavicular joints and the manubrium sterni.

UNLABELLED: OBJECTIVE DESIGN AND PATIENTS: Conventional frontal tomography of the sternum has to some extent been replaced by spiral computed tomography (CT). The objective of this study was to analyse this change of procedure in terms of dosimetry by measurement of the radiation dose to individual organs using an anthropomorphic Rando Alderson phantom. RESULTS: The total effective radiation dose in examination of the sternoclavicular joints and the manubrium sterni was found to be lower using spiral CT than conventional tomography, the values being 0.6 and 0.8 mSv, respectively. CONCLUSION: As spiral CT is diagnostically comparable and in some respects superior to tomography, its use is recommended for studies of the sternum.

Behavior of crocidolite asbestos during mitosis in living vertebrate lung epithelial cells.

Asbestos has been described as a physical carcinogen in that long thin fibers are generally more carcinogenic than shorter thicker ones. It has been hypothesized that long thin fibers disrupt chromosome behavior during mitosis, causing chromosome abnormalities which lead to cell transformation and neoplastic progression. Using high-resolution time lapse video-enhanced light microscopy and the uniquely suited lung epithelial cells of the newt Taricha granulosa, we have characterized for the first time the behavior of crocidolite asbestos fibers, and their interactions with chromosomes, during mitosis in living cells. We found that the keratin cage surrounding the mitotic spindle inhibited fiber migration, resulting in spindles with few fibers. As in interphase, fibers displayed microtubule-mediated saltatory movements. Fiber position was only slightly affected by the ejection forces of the spindle asters. Physical interactions between crocidolite fibers and chromosomes occurred randomly within the spindle and along its edge. Crocidolite fibers showed no affinity toward chromatin and most encounters ended with the fiber passively yielding to the chromosome. In a few encounters along the spindle edge the chromosome yielded to the fiber, which remained stationary as if anchored to the keratin cage. We suggest that fibers thin enough to be caught in the keratin cage and long enough to protrude into the spindle are those fibers with the ability to snag or block moving chromosomes.

Sexual behavior of nonurban students in grades 7 and 8: implications for public policy and sex education.

In a study of 1,844 suburban and rural students in Grades 7 and 8 in public schools in Washington, Oregon, California, and Idaho, sexual activity was much lower than that reported by the popular media and in some scholarly journals. The difference was in part related to using measures other than asking the adolescents whether they had ever had sexual intercourse. The estimates based on those who have had sex more than just once decreased to 16% the number of adolescents who would be classified as sexually active. If the definition of sexually active is further limited to only those who have had sex recently (within the past 4 weeks), only 9% are sexually active. Further restrictions to those who have had sex 5 or more or 10 or more times reduce the percentage of sexually active adolescents to 6% and 2%, respectively. Over-all, the percentage of "sexually active" adolescents depends on the empirical definition of "sexually active," and there are many indications why "ever had sex" is not an adequate measure.

Societal and parental influences on adolescent sexual behavior.

A study of 1551 high school students in four midwestern states showed that more girls than boys reported "some" or "a lot" of encouragement to abstain from having sex. More boys than girls reported societal pressure to become sexually active. The sources of encouragement for abstinence were mother, father, and teacher. The largest difference reported between boys and girls was for friends; more than twice as many girls as boys reported that friends encouraged abstinence. Virgin vs nonvirgin comparisons showed similar results, with mother and father chosen most frequently, but nonvirgins chose guest speaker instead of teacher for third place. Regarding important decision-making factors, both boys and girls selected own feelings, health, future, boy- or girlfriend, and parents' feelings. Girls considered parents' feelings more while boys rated boy- or girlfriends' feelings higher. It was concluded that society exerts a strong influence through the media, but parents have the strongest influence on adolescents' sexuality.

Religiosity, denomination, and mental health among young men and women.

The relations among religiosity, denomination, and mental health were studied. Comparisons of groups high, medium, and low in religiosity were made possible by extracting data from a large data set for three denominational groups and gender in a three-way analysis of variance design. There were significant main effects, with higher scores on three mental health measures for high religious groups, Mormons, and men. There were interactions resulting from highly religious Mormon women, but not highly religious Mormon men scoring higher. The three scores were self-esteem, emotional maturity, and nondepression.

Frequency of curettage in middle-aged women treated with sequential preparations versus untreated women.

Over a 2-month period a register was kept of all dilatation and curettage procedures performed in Frederiksborg County, Denmark, involving women aged 40-59 years. The total recorded was 284. In the same period, questionnaires were sent out to 1200 women in the county who fell within the same, randomly selected age group, to establish the number of women treated with sequential oestrogen/progestogen and those who had been hysterectomized. Based on the results and the total female population in the county, it was calculated that the frequency of the procedure in sequentially-treated women as compared with untreated women was 3.1 times higher in the 55-59 age group. In the 40-54 age group no difference in the incidence of curettage in the sequentially-treated women could be demonstrated.

Differences in school behavior and achievement between children from intact, reconstituted, and single-parent families.

Differences in school behavior and achievement between students from intact, reconstituted, and single-parent families were analyzed. Students from intact two-parent families had fewer absences and tardies, higher grade point averages, and fewer negative and more positive teacher behavioral ratings than did those from reconstituted and single-parent families.

Adolescent sexuality and public policy.

In recent decades, various attempts have been made to determine the level of sexual activity among adolescents. This information has been used in the planning and evaluation of sex-related programs. However, there is a flaw in using only the initial estimates of the behavior--that a sexually active person is defined as one who has had sexual intercourse. This narrow definition distorts the perception of adolescent sexual behavior. Sexual activity can more accurately be designated by focusing on the actual frequency with which teenagers have sex. In this research report, adolescents were considered sexually active if they had had sex within the last four weeks. Using this definition, adolescents were found to be substantially less sexually active than has been previously reported. This finding was then used to look at various policy decisions in the areas of sex education, family planning, and sexually transmitted disease prevention.

PIP: This analysis of national surveys of teenage sexual behavior in the US provides a more useful and precise estimate of teenage sexual activity for policy and program decisions. Data were taken from the 1979 National Survey of Men (NSYM), and Women (NSYW), and the 1982 National Survey of Family Growth (NSFG). Analysis was based on 1) the % of unmarried respondents who were sexually experienced and the % who were sexually active, and 2) the % sexually experienced who were sexually active. The distinction between sexual activity vs. experience shows considerable differences; i.e., for women 15-19 in 1979, 46% were sexually experienced but only 26% were sexually active at the time of the survey. Further delineation is made for never, seldom, monthly, and currently active by race. Black women 15-19 in 1982 were shown to be no more sexually active than white women. However, from the NSYM black males followed the traditional pattern of higher sexual activity, with 68.2% for blacks vs. 60.1% for whites. The data dispute the typical image of rampant sexual portrayed by the popular press. The public policy response to this epidemic was to adopt a family planning (FP) approach to teenage pregnancy prevention. Reduced adolescent pregnancy rates as a measure of program effectiveness have not been shown, and program effectiveness must be based on other measures. Sex education also has had limited success in reducing adolescent pregnancy. The suggestion is that access to accurate information, student liking, parental support, and knowledge acquisition are more reasonable criteria for demonstrating success of sex education programs. Abstinence programs help reduce the risks of teenage pregnancy by emphasizing skills in decision making and resisting pressures to be sexually involved. The example is given of an Atlanta-based program, Postponing Sexual Involvement, which reported that 84% resisted becoming sexually involved after completion of the program. Other abstinence programs show promise and are an inexpensive alternative to FP, albeit evaluations are needed. Contraceptive approaches are appropriate for the already sexually active population.

The effects of three abstinence sex education programs on student attitudes toward sexual activity.

The effects of three abstinence sex education programs on student attitudes toward sexual activity were studied. The programs were administered to 7th- and 10th-grade students in three school districts in the State of Utah. All students were administered a pre- and posttest survey to determine attitude change. The independent variables were program, grade level, gender, and pre/posttest. The dependent variable was the combined and averaged response to 12 questions taken from the survey. There was a four-way interaction between the independent variables. The Sex Respect program produced the most positive attitude change.

PIP: Abstinence programs in 14 Utah junior and high schools were evaluated during the 1988-89 school year. The 3 programs under review were the Sex Respect Program and the Teen Aid Program in suburban districts and the Values and Choices Program in a rural area. The population represented the sociodemographic and economic structure of Utah. It was predicted that there would be a positive change between pre- and posttest scores and an increase in abstinence values, and that older students would be more resistant to change. A 105-item instrument was developed by the Institute for Research and Evaluation. The questions used pertaining to attitudes toward premarital sex are provided. A single-scale score was derived from the 13 items for the dependent variable. Independent variables were program, grade level, gender, and test. A factor analysis was performed on the measure of attitudes toward premarital sex and only 1 item had a reliability correlation lower than .66; it was discarded. The remaining items were reanalyzed and yielded a Cronbach's alpha coefficient of .938 for raw variables. In the 4-way analysis of variance with the 12-item averaged scale score, test, program, and grade level, all effects were significant and interactive. The pattern of change from pre- to posttest varied with gender, grade level, and program. The amount of attitude change between males and females was similar, but females scored higher in all 3 programs on the pre- and posttest and were more positive about abstinence. Younger students were similar to older students except for the Teen Aid Program which showed an increase from pre- to post test. More change occurred in the Sex Respect Program and the least in the Values and Choices Program. Junior high students did not increase the pre- and posttest scores in the Teen Aid Program. The Sex Respect Program may have contributed to more change because it used the student's vernacular and had better visual aids. The 1st hypothesis was substantiated; the 2nd, on older student's resistance to change, was not supported. In fact the Teen Aid Program was more effective for high school students. In fact the Teen Aid Program was more effective for high school students. Attitude toward sexual behavior was correlated with actual sexual behavior as indicated with the Pearson coefficient of -.548. This association needs to be explored further to ascertain if the changed attitudes will indeed change behavior.

The effects of family structure on the sexual behavior of adolescents.

The effects of two family structures, single- and two-parent homes, on adolescent sexual behavior were studied. The variables of race, age, and gender were controlled. The analysis compared the age at first intercourse, frequency of intercourse in the last four weeks, and virgin/nonvirgin status of adolescents from black single-parent families, white single-parent families, black two-parent families, and white two-parent families. For males, the two-parent family was related to less sexual activity and older age at first intercourse. For females, the two-parent family was not as important as race in influencing sexual behavior. The white females from two-parent families were more likely to be virgins, but once having had sexual intercourse, tended to have a higher level of sexual activity than did black females from two-parent homes.

PIP: The hypotheses in this study of adolescent sexual behavior are that the effects of single-parent homes will be greater for white males, that males in single-parent families would differ more from males in intact families than the corresponding females, and that traditional 2-parent families may be related to less adolescent sexual behavior. Data were available from the 1979 National Survey of Young Men and the 1979 National Survey of Young Women on never-married persons 17-19 years (609 males and 892 females). There were 150 black males and 184 black females living with 1 parent, 80 white males and 184 females living with 1 parent, 107 black males and 184 females living with 2 parents, and 272 white males and 418 females living with 2 parents. Family types were grouped based on what woman raised you and what man raised you and for how long between birth and 12 years for males and 10 years for females. Dependent variables were sexual experience and frequency of sexual intercourse within the month. The results were that the race/family variable was significantly related to sexual experience for males and females. When gender and race are controlled for, persons from 1-parent families were more likely to have had sexual intercourse than from 2- parent families, i.e., for black males (84.7% vs. 72.0%), white males (73.8% vs. 64.7%), black females (84.8% vs. 76.1%), and white females (65.1% vs. 50.0%). Blacks were more likely than whites to have had sexual intercourse when gender and family structure are controlled for. The data do not support the hypothesis that males are more influenced by family structure, or that white males are more influenced than black males. The analysis of variance showed a significant race/family effect (F=3.81, df=3/974, p.01) and a significant family/race by gender interaction (F=2.63, df=6/974, p.05). Blacks had a lower frequency of sexual activity than whites, as well as persons from 2-parent families that from 1-parent families. Race was the most important influence females, and family structure among males, especially white males. Sexually experienced black females had less sexual intercourse than white females, regardless of family structure. Regardless of race, 1- parent females had the same frequency of intercourse as 2-parent females. Black males and whit males had similar patterns of intercourse, but any males from 2-parent families had sex less frequently than from 1-parent families. Sexual involvement was influenced by family structure. Frequency of intercourse and initiation of intercourse clearly distinguish adolescent sexual behavior by race. It is important how sexual activity is measured.

Microdensitometer-computer correlation analysis of two distinct, spatially segregated classes of microtubule bridges in Allogromia pseudopodia.

Previous video-light microscopic studies have shown that the microtubule bundles in the pseudopodia of foraminiferan protists display several types of movements in vivo, including active bending, zipping/splaying, and axial translocations. To gain insight into the types and arrangement of microtubule-associated proteins (e.g., mechanoenzymes, crosslinkers) in such a highly dynamic system, we employed microdensitometric-computer correlation methods to analyze, quantitatively, intermicrotubule bridges in thin-section electron micrographs of Allogromia laticollaris and Allogromia sp. (strain NF). Two distinct bridges occupying mutually exclusive zones between adjacent microtubules were identified. Type I bridges displayed a single axial repeat (34 nm for A. laticollaris and 28 nm for Allogromia sp.) and Type II bridges showed a typical 12-dimer helical superlattice pattern. In A. laticollaris, the two types of bridges were morphologically distinct: Type I bridges were aligned perpendicular to the microtubule wall and were 23-nm wide with an electron-lucent core; Type II bridges were irregular filaments projecting from the microtubules at various angles. When compared with the known distribution of microtubule-associated proteins in other systems, our findings indicate that, in vivo, Allogromia pseudopodial microtubules are decorated with MAP2-like bridges interrupted by discrete clusters of a dynein-like component.

The relationship between early development and psychosexual behaviors in adolescent females.

The relationship between early sexual maturation and the psychosexual behaviors of dating and sexual intercourse was investigated using a national sample of adolescent females aged 15 to 19. Among both black and nonblack subjects, early-maturing girls were more likely to have experienced earlier dating and coital onset than were their later-maturing peers. Blacks experienced menarche and first intercourse at earlier ages, yet dating onset at later ages. Early menarche was also associated with marriage at an early age for nonblacks, but not for blacks. These racial differences were explained in terms of diverse socialization patterns or cultural expectations. For both blacks and nonblacks, those with earlier coital experience were found to have had menarche and dating onset at earlier ages.

PIP: The relationship between early sexual maturation and the psychosexual behaviors of dating and sexual intercourse was investigated using a national sample of US adolescent females aged 15-19. The purpose of the study was to clarify the relationship between sexual maturation, dating onset, and premarital intercourse. It was hypothesized that a positive correlation exist between the age of menarche, age of dating onset, and age of 1st intercourse for both black and nonblack subjects. Also, it was hypothesized that those who have 1st intercourse at an early age will, when compared with those who have 1st intercourse at a moderate or later age, have experienced menarche and dating onset at earlier ages. The sample was divided into 2 racial categories: 581 blacks, and 1253 nonblacks. The variables studied included age at menarche, age began dating, ever had intercourse, and age at 1st intercourse. Statistical analysis was conducted on the data. For both blacks and nonblacks, the most commonly reported ages at menarche were 12 and 13. Among both black and nonblack subjects, early-maturing girls were more likely to have experienced earlier dating and coital onset than were their later- maturing peers. Blacks experienced menarche and 1st intercourse at an earlier age (black' mode=15 and nonblacks' mode=16), yet dating onset at later ages (blacks' mode=16 and nonblacks' mode=15). Early menarche was also associated with marriage at an early age for nonblacks, but not for blacks. These racial differences were explained in terms of diverse socialization patterns or cultural expectations. These differences include the differing interpretation of the ritual of dating and the more liberal attitudes existing concerning births outside marriage in the black culture. For both blacks and nonblacks, those with earlier coital experience were found to have had menarche and dating onset at earlier ages. There was a tendency for the majority of adolescent females to have complied with societal norms and engaged in psychosexual behaviors by the end of their teen years. Also, the results of this study suggest that early-maturing girl are prone to earlier psychosexual behaviors. Therefore, it is suggested that menarche be a target age for stressing sex education.

Oscillatory movements of monooriented chromosomes and their position relative to the spindle pole result from the ejection properties of the aster and half-spindle.

During mitosis a monooriented chromosome oscillates toward and away from its associated spindle pole and may be positioned many micrometers from the pole at the time of anaphase. We tested the hypothesis of Pickett-Heaps et al. (Pickett-Heaps, J. D., D. H. Tippit, and K. R. Porter, 1982, Cell, 29:729-744) that this behavior is generated by the sister kinetochores of a chromosome interacting with, and moving in opposite direction along, the same set of polar microtubules. When the sister chromatids of a monooriented chromosome split at the onset of anaphase in newt lung cells, the proximal chromatid remains stationary or moves closer to the pole, with the kinetochore leading. During this time the distal chromatid moves a variable distance radially away from the pole, with one or both chromatid arms leading. Subsequent electron microscopy of these cells revealed that the kinetochore on the distal chromatid is free of microtubules. These results suggest that the distal kinetochore is not involved in the positioning of a monooriented chromosome relative to the spindle pole or in its oscillatory movements. To test this conclusion we used laser microsurgery to create monooriented chromosomes containing one kinetochore. Correlative light and electron microscopy revealed that chromosomes containing one kinetochore continue to undergo normal oscillations. Additional observations on normal and laser-irradiated monooriented chromosomes indicated that the chromosome does not change shape, and that the kinetochore region is not deformed, during movement away from the pole. Thus movement away from the pole during an oscillation does not appear to arise from a push generated by the single pole-facing kinetochore fiber, as postulated (Bajer, A. S., 1982, J. Cell Biol., 93:33-48). When the chromatid arms of a monooriented chromosome are cut free of the kinetochore, they are immediately ejected radially outward from the spindle pole at a constant velocity of 2 micron/min. This ejection velocity is similar to that of the outward movement of an oscillating chromosome. We conclude that the oscillations of a monooriented chromosome and its position relative to the spindle pole result from an imbalance between poleward pulling forces acting at the proximal kinetochore and an ejection force acting along the chromosome, which is generated within the aster and half-spindle.

The emission of atoms and molecules accompanying fracture of single-crystal MgO.

We have been investigating the emission of particles due to deformation and fracture of materials. We observe the emission of electrons (exoelectron emission), ions, neutral species, photons (triboluminescence), as well as long wavelength electromagnetic radiation; collectively we refer to these emissions as fractoemission. In this paper we describe measurements of the neutral emission accompanying the fracture of single-crystal MgO. Masses detected are tentatively assigned to the emission of H2, CH4, H2O, CO, O2, CO2, and atomic Mg. Other hydrocarbons are also observed. The time dependencies of some of these emissions relative to fracture are presented for two different loading conditions.