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Biomedical subjects

A Herman

Publications and source records attributed to A Herman.

At least 73 records · Page 4Linked to original sources
PubMed1999

Ruminant placental lactogens act as antagonists to homologous growth hormone receptors and as agonists to human or rabbit growth hormone receptors.

Growth hormone receptor (GHR)-mediated activity of ruminant placental lactogens (PLs) and ovine (o) GH was compared, using cells transfected with full size human (h), rabbit (rb), and oGHRs. All three PLs acted as agonists in heterologous bioassays, whereas in homologous bioassays in cells transfected with oGHRs they antagonized the oGH activity. Despite these differences, oGH and PLs bound with similar affinity to the oGHR extracellular domain (oGHR-ECD), indicating that the binding occurs through hormone site I. Gel filtration of complexes between oPL and oGHR-ECD showed a 1:1 stoichiometry, confirming this conclusion. The oPL T185D and bPL T188D, which exhibited weak biological activity mediated through GHRs, behaved as site I antagonists, whereas oPL G130R and bPL G133R formed a 1:1 complex with GHR-ECDs and bound to h/rb/oGHR-ECDs with affinity similar to that of wild-type oPL. They had no agonistic activity in all models transfected with h/rb and oGHRs, but were antagonistic to all of them. In conclusion, ruminant PLs antagonize the activity of oGH in homologous systems, because they cannot homodimerize oGHRs, whereas in heterologous systems they act as agonists. The structural analysis hints that minor differences in the sequence of the GHR-ECDs may account for this difference. Since the initial step in the activity transduced through cytokine/hemapoietic receptors family is receptor homodimerization or heterodimerization, we suggest that the question of homologous versus heterologous interactions should be reexamined.

Amino Acid Sequence↗
PubMed1999

Comparison of nuchal translucency measurement and second-trimester triple serum screening in twin versus singleton pregnancies.

Maternal serum screening for Down syndrome (DS) in twin pregnancies poses difficulties due to a lack of precise biochemical information about each co-twin. The current study attempts, for the first time, to compare two screening methods: nuchal translucency (NT) measurement and serum screening for DS, in twin pregnancies. 60 women with twin pregnancies (study group) underwent both first-trimester NT scanning and mid-trimester triple-marker serum screening, and were followed throughout their gestation. Nuchal translucency measurements were compared with a matched control of 120 singleton pregnancies with a similar (+/-2 years) maternal age and fetal crown-rump length (CRL) (+/-3 mm). In both analyses, a risk of 1:380, or higher, of having a DS newborn was considered screen positive. Both mean maternal age (31+/-3 years) and CRL (62+/-11 mm) were similar in the study and control groups. The median NT measurement expressed as multiples of the median (MOM) for CRL was similar in the study and control groups (0.85 and 0.88, respectively). Based on NT measurements, 5 per cent of the pregnancies in the study group and 2.5 per cent in the control group were defined as screen positive (p =N. S). Mid-gestation serum screening was associated with 15 per cent and 6 per cent screen-positive rate in study and control groups, respectively (p<0. 05). There was a ratio of 1:3 screen-positive rate between first and second-trimester screening tests within the study group. This high false-positive rate results led to 18.3 per cent amniocentesis rate in the study group compared with 7.5 per cent of the control group (p<0.03). Only one co-twin which was picked up by the NT screen was further diagnosed as trisomy 21, and one co-twin with cardiac and neural tube defect was missed by the two screening tests and was later picked up in an anomaly scan. Although the current series is too small to provoke any changes in screening practice, when twin pregnancies are diagnosed, it seems very reasonable to offer them NT measurement. A larger group may be needed to clarify which approach is the most beneficial screening policy for this highly selected group of pregnant women.

Adult↗
PubMed1999

Sociodemographic correlates of virginity in seventh-grade black and Latino students.

PURPOSE: To examine rates of virginity in seventh-grade black and Latino students and assess the extent to which various sociodemographic factors are correlated with virginity. METHODS: A total of 523 seventh-grade students from five junior high schools and one middle school in the District of Columbia completed an anonymous self-administered questionnaire. Students responded to questions about age at first intercourse, demographics, grades, educational expectations, and risk behaviors. Multivariate analysis was used to determine the independent strength of the association of these variables with virginity. RESULTS: Eighty-one percent of girls and 44% of boys reported never having had sexual intercourse, i.e., being virgins. Black and Latino students were equally as likely to report being virgins. Younger age and absence of other risk behaviors, including smoking and alcohol use, were associated with virginity for males and females. For boys, reporting high academic achievement and living with both parents was significantly correlated with virginity and appeared to be protective. CONCLUSIONS: Although prevalent particularly in seventh-grade black and Latino boys, sexual activity was clearly associated with other risk behaviors in both boys and girls. Sociodemographic correlates of virginity were gender-specific. School-based efforts to delay the onset of initiation of sexual activity in high-risk populations should be targeted at boys 12 years and younger with interventions which are gender-specific. This study underscores a need to examine correlates of virginity to generate practical approaches to prevention of early sexual activity.

Adolescent↗
PubMed1999

Implementation of nuchal translucency image-scoring method during ongoing audit.

OBJECTIVE: The aim of this study was to evaluate the contribution of an ongoing audit, using the image-scoring method, to the quality of nuchal translucency images and to set the basic standards required from the examiners. DESIGN: Evaluation of nuchal translucency images, before, during and after the implementation of an ongoing audit, without knowledge of the time period or the examiner. SUBJECTS: A total of 315 nuchal translucency scans were performed by three examiners. METHODS: Each of the retrospective, intermediate and prospective time periods included blind scoring of 105 images. The effect of the ongoing audit was examined by comparing the distribution of the quality groups and the mean final score between the time periods, for all cases and for each examiner separately. Improvement of the criteria was assessed by comparing the rate of scans meeting the demands between the time periods. RESULTS: The quality of the images improved significantly as the mean final score changed from 4.62 +/- 0.21 to 6.19 +/- 0.19 and to 6.91 +/- 0.16 (p < 0.0001) and the rate of obtaining acceptable scans rose from 72% to 88% and to 92% (p < 0.001), respective to the three time periods. Whereas the three major criteria improved significantly before and after implementation of the audit (mid-sagittal section from 48% to 94%, caliper placement from 60% to 75% and skin line from 19% to 77%), the minor criteria remained unchanged (image size 90%, amnion demonstration 25% and head position 77%). The average scores of two examiners, for whom improvement was more pronounced, were used to determine the basic standards required from examiners subjected to the audit as follows: unacceptable, none; intermediate, 5%; reasonable, 65%; excellent, 30%; with a mean final score of 7.25. CONCLUSIONS: Implementation of an ongoing audit, using the image-scoring method, proved to be an efficient method for surveillance and improving the quality of nuchal translucency images. We recommended centers or individuals practicing first-trimester ultrasound screening to consider its routine utilization, in an unbiased and strict manner.

Analysis of Variance↗
PubMed1999

Can nuchal cord cause transient increased nuchal translucency thickness?

When detected in a first trimester scan, an increased thickness of nuchal translucency (NT) may be associated with chromosomal, cardiac or genetic disorders. However, less attention has been devoted to the outcome of those fetuses who have confirmed normal anatomies and karyotyping, but have abnormal first trimester scans. Thus, a challenging new issue is how to counsel such cases of transient increased NT in which the translucency rapidly vanishes with no evidence of other underlying abnormalities. Two cases of transient increased thickness of NT are reported. In both, a nuchal cord was ultrasonographically demonstrated and a thorough work-up revealed chromosomally and anatomically normal fetuses. The pathophysiological theories behind these observations and their significance are discussed. Based on these observations, we suggest that transvaginal sonography combined with Doppler flow studies should be utilized for the presize detection of cord patterns to accomplish the work-up in cases of increased NT.

Adult↗
PubMed1999

The feasibility of nuchal translucency measurement in higher order multiple gestations achieved by assisted reproduction.

Nuchal translucency (NT) measurement for screening chromosomal abnormalities and detecting fetal anomalies is an effective ultrasonographic marker, originally developed for singleton pregnancies. This study sought to evaluate the feasibility of NT measurements in higher order multiple gestations. Pregnant patients who conceived following assisted reproduction and were carrying three or more fetuses were enrolled in the study. Each fetus was ultrasonographically assessed, a NT measurement was obtained, and the findings were used for counselling prior to any invasive procedure. In all, 24 pregnant patients, initially carrying 79 fetuses aged 10-14 weeks of gestation, were compared with 79 consecutively matched, singleton controls, naturally conceived, having similar crown-rump lengths (+/- 3 mm). NT measurements were feasible for both study and control fetuses, which exhibited similar NT measurements for 5th, 50th and 95th centiles. Also, mean NT thicknesses [measurements in mm or multiple of the medians (MOM)] were similar for both groups (1.41 +/- 0.41 and 1.35 +/- 0.39 mm respectively and 0.87 +/- 0.23 and 0.83 +/- 0.25 MOM respectively). Prenatally no chromosomal abnormalities were detected in either group, and, of those infants who had no karyotyping, no traits were observed that warranted chromosomal analysis. NT measurements are feasible in higher order multiple gestations. Since there is no other effective screening modality for these pregnancies, it seems reasonable to recommend NT measurement for antenatal screening services for higher order multiple gestations.

Chromosome Aberrations↗
PubMed1999

Oxidized low-density lipoprotein enhances intimal thickening and alters vascular reactivity.

Oxidized low density lipoprotein (oxLDL) is present in atherosclerotic lesions and has been implicated in the etiopathogenesis of atherosclerosis mainly based on in vitro studies. In view of the lack of data on the activity of oxLDL in vivo, we decided to study its effects in the rabbit by local application at the level of the vascular wall. Intimal thickening was evoked by the placement of a silicone collar around the carotid arteries during 2 weeks. The collar was connected to an osmotic minipump containing human oxLDL (7 micrograms h-1), LDL (7 micrograms h-1) or phosphate-buffered saline. Collar placement resulted in a thickening of the intima thereby increasing the thickness from 5 +/- 1 to 26 +/- 5 microns with the appearance of alpha-actine positive smooth muscle cells. Perivascular infusion of LDL or oxLDL significantly enhanced the intima, containing large amounts of T-lymphocytes, collagen and smooth muscle cells. The placement of the collar and the infusion of oxLDL during 14 days resulted in an increased sensitivity to serotonin and a decreased sensitivity to acetylcholine. The maximal relaxation to acetylcholine was reduced by 50% whereas the endothelium-independent relaxation to nitroglycerin were not affected. These results show for the first time that the local application of oxLDL in vivo promotes intimal thickening and impairs the endothelium-dependent relaxations thereby supporting the suggestion that oxLDL plays an important role in the morphological and functional changes present in atherosclerotic blood vessels.

Animals↗
PubMed1999

Comparison of nuchal translucency measurement and mid-gestation serum screening in assisted reproduction versus naturally conceived singleton pregnancies.

It has been reported that second-trimester serum markers may be affected by assisted reproduction leading to a higher false-positive rate. The current study compares 10-14 week nuchal translucency (NT) measurement and early mid-trimester serum screening in pregnancies resulting from assisted reproduction versus naturally conceived pregnancies. 75 pregnant women with a singleton pregnancy achieved by assisted reproduction underwent both 10-14 weeks NT measurement and second-trimester triple test and were followed throughout gestation. They were compared with matched controls for gestation and maternal ages. A risk of 1:380 or higher or having a fetus with Down syndrome was considered as screen-positive in both tests. The mean maternal age (30+/-3 years) and crown-rump length (61+/-9 mm) were similar, and there was no difference in NT thickness distribution between the groups. Based on NT measurement, 4 (5 per cent) women in the study and 2 (3 per cent) in the control groups, were defined as screen positive (p=NS). However, 11 (15 per cent) women in the study group and 4 (5 per cent) in the control group were found screen-positive by the triple test (p<0.05). A significantly higher amniocentesis rate of 20 per cent was noted in the study group compared with 8 per cent in the controls (p<0.05). All karyotypes were normal and no miscarriages or structural malformation were diagnosed in either group. We confirm the observation that assisted reproduction may adversely affect second-trimester screening results, which did not affect the NT screening test. Since these series are relatively small, larger series may be needed to clarify the most beneficial screening policy for this highly selected group of pregnant women.

Adult↗
PubMed1998

Effects of fetal sex and race on risk of very preterm birth in twins.

OBJECTIVE: Our purpose was to determine whether the risk of twin preterm birth correlates with the number of male fetuses. STUDY DESIGN: Among 8109 white and 1884 black twin pregnancies in the Missouri Successive Pregnancy Birth/Death Data Set, 1978 through 1990, risk for preterm birth at various gestational ages was determined with 0, 1, or 2 male infants. RESULTS: Studied as individuals, white preterm twins <35 weeks' gestation demonstrated a 9.2% excess of male fetuses (P < .001). Adjusted for monozygosity, risk for preterm birth <35 weeks' gestation was 15.7% in white female-female pairs, 17.9% in unlike-sex white fetuses, and 20.2% in white male-male pairs (r = .999, P = .01). The effect was absent in black pregnancies and was unrelated to birth order, cesarean delivery, parity, twins' weight differential, year, or season. CONCLUSIONS: In white twin gestations the observed linear relationship between the number of male fetuses and the likelihood of preterm birth <35 weeks' gestation suggests a fetal mechanism for preterm birth <35 weeks' gestation linked to fetal sex. Studies of mechanisms for preterm birth must stratify by fetal sex and race.

Black People↗
PubMed1998

Association of sociodemographic variables with risk for very preterm birth in twins.

OBJECTIVE: To assess the influence of maternal race, age, marital status, and education on risk for earlier and later preterm births in twin pregnancies. METHODS: We analyzed 8109 white and 1906 black liveborn twin pregnancies in the Missouri Linked Sibship files for the years 1978-1990, using contingency tables and multiple logistic regression. RESULTS: Black twin gestations had 1.61-fold (95% confidence interval [CI] 1.46, 1.76) greater risk than whites for preterm birth before 34 weeks' gestation. However, there was no race difference after 33 weeks. Among whites, teen age, unmarried status, and education fewer than 12 years were independently associated with risk for delivery before 34 weeks in multivariate analysis (odds ratios [OR] 1.28-1.51, each P < or=.001). These associations were diminished or absent for preterm births after 33 weeks' gestation. White unmarried teen mothers with fewer than 12 years of education had 1.83-fold (95% CI 1.39, 2.40) greater risk for preterm birth before 34 weeks' gestation compared with white married women more than 19 years of age with at least 12 years of education. In blacks, this difference was 1.47-fold (95% CI 1.13, 1.92). In both races, these differences were absent after 33 weeks' gestation. CONCLUSION: Traditional sociodemographic risk factors were present for twin preterm birth, but mainly before 34 weeks' gestation. This, together with previous data from Missouri Linked Sibship files, indicates that dominant pathogenic mechanisms of early preterm birth in twin gestations are likely to be different from those causing later preterm twin birth. Therefore, gestational age should be accounted for in future studies seeking to identify predictive factors or biomechanisms for twin preterm birth.

Adult↗
PubMed1998

In vitro volume measurement by three-dimensional ultrasound: comparison of two different systems.

The aim of this study was to compare volumetric capabilities in vitro between two different three-dimensional technical modalities with a transvaginal transducer. We intended to evaluate the effect of different sizes and shapes on the accuracy of the measurements, and to establish criteria for choosing the appropriate system for three-dimensional volume measurement. We did not find significant differences between the two systems, either in the results or in their operation. We confirmed the high accuracy of three-dimensional volume measurements in vitro.

Analysis of Variance↗
PubMed1998

Image magnification does not contribute to the repeatability of caliper placement in measuring nuchal translucency thickness.

The objective of this study was to assess whether nuchal translucency image magnification contributes to the repeatability of caliper placement. Twenty-seven women undergoing first-trimester ultrasound screening at 11-14 weeks were examined by two qualified examiners. Fetal nuchal translucency thickness was measured twice by each examiner on a regular-sized image and subsequently on the same still image magnified. Intraobserver repeatability coefficients of the regular-sized images were 0.28 mm and 0.34 mm for examiners A and B, respectively. Identical intraobserver repeatability coefficients of 0.28 mm were attained for both examiners on the magnified images. Interobserver repeatability of regular-sized image measurements showed a significant difference (p < 0.01) but the mean difference (+/- standard deviation) of 0.10 (0.18) mm was negligible. Similarly, interobserver repeatability of the magnified-image measurements yielded a significant difference (p < 0.02), but again with a small mean difference of 0.13 (0.26) mm. There were also significant differences when regular-sized images and magnified images were compared for both examiners: 0.08 (0.16) mm for examiner A (p < 0.02) and 0.10 (0.17) mm for examiner B (p < 0.01). Our results demonstrate that nuchal translucency image magnification does not contribute to the reproducibility of the measurement. Despite significantly smaller mean values obtained from the magnified images, compared to the regular-sized measurements, those differences do not justify modification of the criteria for caliper placement on magnified images. Blind repeated measurements on a regular-sized and/or magnified image are recommended as a tool for self-assessment, quality control and training.

Female↗
PubMed1998

Nuchal translucency audit: a novel image-scoring method.

OBJECTIVE: The aim of this study was to evaluate the feasibility and reproducibility of a novel image-scoring method of first-trimester nuchal translucency measurement as an objective tool of ongoing audit and training. DESIGN: This was an independent evaluation of nuchal translucency images by three separate reviewers unaware of the examiner. SUBJECTS: There were 105 consecutive singleton pregnancies undergoing first-trimester screening. METHODS: Each image was scored according to the following criteria: section (oblique, 0; mid-sagittal, 2), caliper placing (misplaced, 0; proper, 2), skin line (nuchal only, 0; nuchal and back, 2), image size (unsatisfactory, 0; satisfactory, 1), amnion (not visualized, 0; visualized, 1) and head position (flexion/hyperextension, 0; straight, 1). The final score was categorized into one of four quality groups: excellent (8-9), reasonable (4-7), intermediate (2-3), unacceptable (0-1). RESULTS: The distributions of the four quality groups were similar between the three reviewers: 11.4% were classified as excellent, 57.1% as reasonable, 25.7% as intermediate and 5.7% as unacceptable. Inter-reviewer agreement showed identical classification, by each pair of reviewers, from 65.7% to 74.3%, and partial agreement to neighboring quality groups from 25.7% to 34.3% of the cases. In none of the cases did the reviewers differ in categorizing cases to remarkably different quality groups. Application of the auditing method to the examiners showed similar distribution to the various quality groups and similar mean final score of 4.69 (0.39, SE), 4.54 (0.15, SE) and 4.65 (0.15, SE). CONCLUSIONS: The described image-scoring method represents a new approach towards the evaluation of ultrasound performance as a whole and nuchal translucency measurement in particular. It may be employed by every center in an independent manner with minimal resources and regardless of the method of risk assessment. More studies will be needed to determine the standards required from the examiners and to elucidate the contribution of the proposed auditing method to the examination's quality and the process of training.

Female↗
PubMed1998

[Trisomy 18 anomalies on sonography and calculated risk of chromosomal abnormalities during first trimester].

Trisomy 18 is a chromosomal disorder giving multiple anomalies. Its frequency depends on maternal age. We report a 28-year-old woman in her first pregnancy, who underwent first trimester scanning for screening. Due to increased nuchal translucency and exomphalos, chorionic villous sampling was performed. Cytogenetic diagnosis was trisomy 18 and termination of pregnancy was carried out immediately.

Abortion, Induced↗
PubMed1997

Differential effects of sulindac on renal hemodynamics and function in the rat.

Renal hemodynamics were studied using an electromagnetic perivascular flow sensor in anesthetized rats injected i.v. with vehicle, 5 or 10 mg/kg body weight (b.w.) sulindac. No hemodynamic changes occurred with vehicle (n = 6), but mean arterial pressure was significantly decreased (by 15 mmHg) with sulindac (n = 12). In the 5 mg/kg b.w. sulindac group (n = 7), renal blood flow progressively and significantly increased from 7.88 +/- 0.36 to 8.98 +/- 0.58 ml/min, except during concomitant intrarenal infusion of 3 mg/kg b.w. per h proadifen (n = 7). The pressure limits for efficient and no renal blood flow autoregulation remained unchanged (approx. 100 and 80 mmHg, respectively). In the 10 mg/kg b.w. sulindac group (n = 5), renal blood flow did not change but autoregulatory pressure limits were lowered by 10 mmHg 2 h after treatment (P < 0.025). Also, Na+ retention was marked. Prostanoid excretion in urine was significantly reduced with either dose but basal plasma renin activity was not (about 8 ng/ml per h; n = 15). When plasma renin activity was enhanced after a reduction in renal perfusion pressure (n = 21), it was decreased from 11.5 +/- 1.2 to 7.4 +/- 0.2 ng/ml per h only by 10 mg/kg b.w. sulindac (P < 0.05; n = 6). In conclusion, differential effects of sulindac on renal hemodynamics, Na+ excretion and plasma renin activity were demonstrated. Renal hemodynamic changes could be related in part to the cytochrome P-450 arachidonic acid pathway.

Animals↗