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L Valentin

Publications and source records attributed to L Valentin.

At least 55 records · Page 3Linked to original sources
PubMed2000

Mobility and activation energy of single-stranded DNA in denaturing cross-linked polyacrylamide slab gels.

An original apparatus based on laser-induced fluorescence detection is presented. One lane migration combined to four equidistant detection points allows the study of the dynamics of DNA bands during electrophoresis. We focus this article on the study of the mobility of DNA sequencing fragments as a function of temperature; mobility is determined in 4% T, 5% C and 4.3% T, 5% C cross-linked polyacrylamide gels at an electric field of 45 V/cm [T=(g acrylamide+g N,N'-methylenebisacrylamide)/100 ml solution; C=g N,N'-methylenebisacrylamide/% T]. Activation energy has been investigated under these experimental conditions with a temperature varying from 25 to 50 degrees C. The activation energy for migration through the cross-linked polyacrylamide gel decreases with fragment length under our experimental conditions and it varies along the migration.

DNA, Single-Stranded↗
PubMed2000

Comparison of Lerner score, Doppler ultrasound examination, and their combination for discrimination between benign and malignant adnexal masses.

OBJECTIVE: To determine whether the combined use of Lerner's morphologic score and color Doppler ultrasound examination results in better discrimination of benign and malignant adnexal masses than the use of Lerner's score alone or Doppler variables alone. DESIGN: One hundred and seventy-three consecutive women with a pelvic mass judged clinically to be of adnexal origin underwent preoperative ultrasound examination including color and spectral Doppler techniques. One hundred and forty-nine tumors were benign and 24 malignant. The sensitivity and false-positive rate with regard to malignancy were calculated for Lerner's score, six Doppler variables and combinations of Lerner's score and Doppler variables. Previously defined gray scale and Doppler criteria of malignancy were used and tested prospectively. The best method was defined as that detecting most malignancies with the lowest false-positive rate. RESULTS: Lerner's score had a sensitivity of 92% and a false-positive rate of 36%. The best Doppler variable--time-averaged maximum velocity--had similar diagnostic properties with a sensitivity of 100% and a false-positive rate of 41%. Combining Lerner's score with Doppler measurement of time-averaged maximum velocity--i.e. requiring both Lerner's score and time-averaged maximum velocity to indicate malignancy for a malignant diagnosis to be made--had a sensitivity of 92% and a false-positive rate of 19%. CONCLUSIONS: The combined use of Lerner's score and measurement of time-averaged maximum velocity is a better method for discrimination of benign and malignant adnexal masses than the use of Lerner's score alone or Doppler ultrasound examination alone. The clinical value of the combined method needs to be cross-validated prospectively in a new series of tumors.

Adnexal Diseases↗
PubMed2000

Effects of a vasopressin antagonist in women with dysmenorrhea.

We compared menstrual pain, uterine contractility and blood circulation, and plasma concentrations of vasopressin and prostaglandin F(2alpha) metabolite in women with versus without primary dysmenorrhea, and determined the effects of a vasopressin antagonist, 1-deamino-2-D-Tyr(OEt)-4-Thr-8-Orn-oxytocin (Atosiban), on these parameters. Our results do not support the contention that vasopressin is involved in the etiology of dysmenorrhea, plasma concentrations of vasopressin being similar in dysmenorrheic women and controls, and the vasopressin antagonist Atosiban having no effect on menstrual pain, intrauterine pressure or uterine artery pulsatility index in dysmenorrheic women.

Adult↗
PubMed1999

Prospective cross-validation of Doppler ultrasound examination and gray-scale ultrasound imaging for discrimination of benign and malignant pelvic masses.

OBJECTIVE: To cross-validate, prospectively, the diagnostic performance of established ultrasound methods for discrimination of benign and malignant pelvic masses. METHODS: A total of 173 consecutive women with a pelvic mass judged clinically to be of adnexal origin underwent preoperative ultrasound examination including color and spectral Doppler techniques. A total of 149 tumors were benign, and 24 were malignant. The sensitivity and false-positive rate with regard to malignancy were calculated for the following methods, using cut-off values recommended in previous publications: Lerner score; ultrasound morphology, i.e. tumors without solid components being classified as benign and tumors with solid components as malignant; tumor color score; pulsatility index; resistance index; time-averaged maximum velocity; peak systolic velocity; the combined use of ultrasound morphology and tumor color score and the combined use of ultrasound morphology and peak systolic velocity. Sensitivity and false-positive rate were also calculated for subjective evaluation of the gray-scale ultrasound image and for subjective evaluation of the gray-scale ultrasound image supplemented with subjective evaluation of color Doppler ultrasound examination. The confidence with which the diagnosis was made, based on subjective evaluation, was rated on a visual analog scale. RESULTS: Subjective evaluation of the gray-scale ultrasound image was by far the best method for distinguishing benign from malignant tumors (sensitivity 88%, false-positive rate 4%), followed in descending order by subjective evaluation of the gray-scale ultrasound image supplemented with color Doppler examination, the Lerner score and the time-averaged maximum velocity. Adding Doppler examination to subjective evaluation of the gray-scale image did not increase the number of correct diagnoses, but it increased the confidence with which a correct diagnosis was made in 14% of tumors. In 11 tumors (6% of the series as a whole), the addition of Doppler examination changed the diagnosis based on subjective evaluation of the gray-scale ultrasound image from an incorrect (n = 1) or uncertain (n = 10) diagnosis to a correct and confident diagnosis. CONCLUSION: In experienced hands, subjective evaluation of the gray-scale ultrasound image is the best ultrasound method for discriminating between benign and malignant adnexal masses. The main advantage of adding Doppler examination to subjective evaluation of the gray-scale image is an increase in the confidence with which a correct diagnosis is made.

Adnexal Diseases↗
PubMed1999

Pattern recognition of pelvic masses by gray-scale ultrasound imaging: the contribution of Doppler ultrasound.

OBJECTIVE: To determine the extent to which Doppler ultrasound examination contributes to a correct specific diagnosis of a pelvic mass when the preliminary diagnosis is based on subjective evaluation of the gray-scale ultrasound image (pattern recognition). METHODS: In 173 consecutive cases, women scheduled for surgery because of a pelvic mass judged clinically to be of adnexal origin underwent preoperative gray-scale and color Doppler ultrasound examination. On the basis of subjective evaluation of the gray-scale ultrasound image, the ultrasound examiner classified each tumor as probably benign or malignant. If possible, a specific diagnosis was made, e.g. 'endometriosis' or 'dermoid cyst'. The confidence with which the diagnosis was made was rated subjectively on a visual analog scale. The diagnosis based on gray-scale imaging was re-evaluated after color Doppler examination, the diagnostic confidence after Doppler examination also being rated on a visual analog scale. 'Malignancy' was not considered a specific diagnosis. RESULTS: Pattern recognition of the gray-scale ultrasound image resulted in no unequivocal specific diagnosis in 51% (88/173) of cases, a correct specific diagnosis in 42% (72/173) and an incorrect specific diagnosis in 7% (13/173). Doppler examination added to a correct specific diagnosis in only 5% (8/173) of cases, either by changing an incorrect specific diagnosis to a (more) correct one (five tumors), or by increasing the confidence with which a correct specific diagnosis was made (three tumors). Doppler examination was misleading in one tumor. CONCLUSION: By using pattern recognition of the gray-scale ultrasound image, a correct specific diagnosis can be made in almost half of adnexal tumors scheduled for surgery. Subjective assessment of the color content of the tumor scan contributed little to the specific diagnosis of pelvic tumors.

Adolescent↗
PubMed1999

Ultrasound measurements of subcutaneous adipose tissue in infants are reproducible.

BACKGROUND: The purpose of this study was to evaluate the ultrasound technique for measuring subcutaneous adipose tissue in infants. METHODS: Twenty infants were investigated at 3, 6, and 12 months of age. All measurements were made by the same investigator in triplicate on the left side of the body at the triceps and subscapular anatomic landmarks and at the abdomen and thigh. An ultrasound system equipped with a linear 7.0-MHz transducer was used. RESULTS: The intraclass correlation coefficients were 0.88 to 0.99. Random errors ranged from 0.01 to 0.19 mm. For log-transformed values, the random error ranged from 2.4% to 5.7%. CONCLUSIONS: Measurements of subcutaneous fat in infants using ultrasound are reproducible when performed by the same observer.

Abdomen↗
PubMed1999

Do pre-, early, and mid-pregnancy life events influence gestational length?

The aim of this study was to determine whether the frequency and quality of reported life events during the 6 months before pregnancy to mid-pregnancy influence gestational age at birth. Seventy nulliparous women were studied at 12 and 25 gestational weeks with a 64-item self-rated life event questionnaire developed for obstetric groups. Life events were categorised into eight psychosocial areas according to the diagnostic and statistic manual (DSM-III-R). The women rated each experienced event as strainful or not strainful. Gestational age was determined by ultrasound biometry before 20 gestational weeks. The number of life events during the following periods was recorded from 6 months before pregnancy to 12 gestational weeks, from 12 gestational weeks to 25 gestational weeks, from 6 months before pregnancy to 25 gestational weeks. No significant relationships were found between the number of reported life events and pregnancy duration. Life events in different psychosocial areas also did not influence gestational age at birth. A non-significant relationship (p = 0.06) was found between pregnancy duration and the number of strainful events reported from 6 months before pregnancy to 25 gestational weeks, shorter pregnancy duration being found in women reporting many strainful events. Our findings suggest that life events in general do not influence pregnancy duration. However, if they are perceived as strainful, pregnancy length tends to decrease.

Adult↗
PubMed1999

MULTISCAN--a Scandinavian multicenter second trimester obstetric ultrasound and serum screening study.

AIM: To study the detection rates of second trimester ultrasound screening for neural tube defects (NTD), abdominal wall defects (AWD) and Down's syndrome (DS) in low risk populations at tertiary centers, and to compare the ultrasound screening detection rates with those that were obtainable by biochemical serum screening (double test: alpha-fetoprotein/human chorion gonadotrophin/age test). STUDY DESIGN: Prospective multicenter study with a three year inclusion period: 1/1/1989-31/12/1991. SUBJECTS: 27,844 low-risk women at 18-34 years of age who had a second trimester ultrasound screening examination. Of these, 10,264 also had a serum test. METHODS: An ultrasound malformation scan and a serum test were carried out at 17-19 weeks of gestation. Risk calculations regarding DS were based on alpha-fetoprotein, human chorion gonadotrophin and maternal age; performed retrospectively for the first two years. RESULTS: In total 73 cases were identified in the study population: NTD (n=34), AWD (n=7) and DS (n=32). The detection rates, (%, with 95% confidence interval) for ultrasound screening were: NTD: 79.4 (62.1-91.3); AWD: 85.7 (42.1-99.6); DS: 6.3 (0.8-20.8). In the subgroup of women who had both tests, the detection rates for ultrasound screening vs double test were: NTD: 62.5 (24.5-91.5) vs 75.0 (34.9-96.8); AWD: 66.7 (9.4-99.2) vs 100 (29.2-100.0); DS: 7.7 (0.2-36.0) vs 46.2 (19.2-74.9). The false positive rates (%) for ultrasound screening vs double test were: NTD: 0.01/3.3; AWD: 0.01/3.3; DS: 0.1/4.0. CONCLUSION: Second trimester ultrasound screening in a low risk population gave a low detection rate for fetal DS (6.3%) and an acceptable detection rate for NTD (79.4%) and AWD (85.7%). In the subgroup of women who had both tests, serum screening performed better than ultrasound as applied in the present study, especially regarding DS.

Abdominal Muscles↗
PubMed1998

A new high resolution radioimager for the quantitative analysis of radiolabelled molecules in tissue section.

We present a high-speed, high-resolution imager of beta particles. It is devoted to be used in autoradiography experiments such as receptor binding or in situ hybridization experiments, either instead of, or in complement with autoradiographic film and emulsions. It allows the user to locate and perform quantitative analyses of (3H, 14C, 35S, 33P, 32P, 125I) labelled molecules with a 15 microm spatial resolution on a 0.9 x 1.3 cm2 sensitive area. Combining recent techniques (specific scintillator thin sheets and intensified charge-coupled device (CCD)) this imager offers a wide dynamic range and real-time acquisition.

Animals↗
PubMed1998

Does the prenatal diagnosis of fetal urinary tract anomalies affect perinatal outcome?

A review of the literature is presented. Congenital renal and urinary tract anomalies are described, and the possible consequences of detecting them in utero are discussed. Prenatal detection of lethal anomalies affords the parents the option of terminating the pregnancy. If termination of pregnancy is not an acceptable option for the parents, the antenatal knowledge of lethal fetal anomaly helps the clinician to avoid unnecessary obstetric intervention, e.g., cesarean delivery for fetal distress. In certain cases of nonlethal renal and urinary tract anomalies, antenatal detection may influence both obstetric and postnatal management. It seems reasonable to anticipate that this might improve the prognosis of some children in terms of better preservation of kidney function. However, no scientific evidence is available to support such a statement. There are no randomized trials evaluating the outcome of congenital renal and urinary tract anomalies using different prenatal and postnatal diagnostic and therapeutic approaches. It is hoped that further research will lead to more rational antenatal and postnatal management protocols.

Female↗
PubMed1998

Factors affecting color Doppler energy ultrasound recordings in an in-vitro model.

Compared to conventional color Doppler ultrasound imaging, the new color Doppler modality "color Doppler energy" (CDE) has improved the possibility of visualizing blood vessels having low blood-flow velocities, but appears to be influenced by the settings of the ultrasound instrument and motion artefacts. The aim of this methodological study was to evaluate the effects of the different factors on the CDE signal. The CDE mode of a commercially available ultrasound system (Acuson 128 XP) was tested in an in vitro study. The effect of depth, angle of insonation, flow velocity, instrument power output, gain and other instrument settings were evaluated. The CDE signals obtained were stored on videotape and subsequently subjected to off-line computer analysis. The CDE signal intensity was found to be influenced mainly by fluid flow velocity, but was also affected by depth and instrument settings. Gain and power had, however, limited influence in this setting. Thus, the intensity of the CDE signal is influenced by several factors. Our results emphasize the need for optimum fixed preinstalled instrument settings when attempting to quantify organ perfusion by use of this new technique.

Artifacts↗
PubMed1997

Use of colour and spectral Doppler ultrasound examination in gynaecology.

Objective: To review and sum up the published literature on gynecological Doppler ultrasound examination. Methods: Publications on gynecological Doppler ultrasound examination already known by the author, publications found in the bibliographic database Medline, and publications found in the reference lists of available studies were read, and relevant information was extracted and summarized. Results: Reference data representative of normal findings at transvaginal color and spectral Doppler ultrasound examination of the uterine and ovarian arteries have been established in healthy pre- and post-menopausal women and in normal early pregnancies. Blood flow velocities in the uterine and ovarian arteries change during the normal menstrual cycle and are very different in pre- and post-menopausal women. Lower blood flow velocities and higher pulsatility index (PI) values have been recorded in the ovarian arteries after the menopause. Uterine artery blood flow velocities increase and uterine artery PI values and resistance index (RI) values decrease with gestational age in the first trimester. There is not yet an established role of the gynecological Doppler ultrasound examination in clinical practice. It remains unclear whether the gynecological Doppler ultrasound examination contributes substantially to the clinical management of early pregnancy complications or infertility problems, to the differential diagnosis of pelvic masses or uterine pathology. Conclusions: Large prospective studies-preferably randomized controled trials-are needed to determine the clinical value of the gynecological Doppler ultrasound examination. Copyright 1997 Elsevier Science Ireland Ltd.

Journal Article↗
PubMed1997

Gray scale sonography, subjective evaluation of the color Doppler image and measurement of blood flow velocity for distinguishing benign and malignant tumors of suspected adnexal origin.

OBJECTIVE: To compare the capacity of transvaginal Doppler ultrasound examination with that of gray scale sonography as an aid in distinguishing benign and malignant pelvic tumors of suspected adnexal origin. STUDY DESIGN: One hundred and fifty-one women scheduled for laparotomy or laparoscopic surgery because of a pelvic mass of suspected adnexal origin underwent ultrasound examination including color and spectral Doppler techniques within 8 days preceding the operation. Based on the gray scale ultrasound image, each tumor was classified as being either a unilocular cyst, a multilocular cyst, a unilocular cyst with solid parts, a multilocular cyst with solid parts or a solid tumor. Tumor vascularization was visualized with the color Doppler technique, each tumor being characterized by the color content of the scan, as rated subjectively on a visual analogue scale ('tumor color score'). Blood flow velocity waveforms were obtained by placing the Doppler gate over the colored area with the tumor. The blood flow velocity waveform with the highest time averaged maximum velocity was used to characterize the tumor . The results of gray scale imaging and Doppler ultrasound examination were compared with the histology of the specimen. RESULTS: Ultrasound morphology correctly identified all the malignant tumors, with a false-positive rate of 61%; none of the 49 unilocular or multilocular cysts without solid parts was malignant, whereas 24% (24/102) of the tumors with solid components were. Among multilocular cysts with solid parts, both tumor color scores and time average maximum blood flow velocities were significantly higher in malignant than in benign tumors, but among solid tumors there was complete overlap in Doppler results between the malignant and benign subgroups. Using Doppler examination to discriminate between benign and malignant multilocular cysts with solid parts and ultrasound morphology for differentiation of the remaining tumors, all the malignancies in the study were detected with a false-positive rate of 32 or 38% depending on which Doppler variable was used. CONCLUSION: The present technique of Doppler ultrasound examination is helpful only in the differential diagnosis of multilocular cysts with solid parts. Therefore, the degree to which Doppler examination can contribute to the differential diagnosis of pelvic tumors will depend on the proportion of multilocular cysts with solid parts in the population studied: the greater this proportion, the greater the potential of the Doppler examination to improve diagnostic accuracy.

Adnexa Uteri↗
PubMed1997

Maternal anxiety in late pregnancy and fetal hemodynamics.

The aim of this study was to investigate if fetal circulation is affected by maternal anxiety. 37 nulliparous women were studied prospectively in the third trimester of pregnancy, with self-rate tests of anxiety (STAI). Doppler ultrasound examination of the umbilical artery and fetal middle cerebral artery was performed at 37-40 gestational weeks. The pulsatility index (PI) was calculated and corrected for heart rate. The women were divided into groups of increasing levels of anxiety. The fetuses of women with high trait anxiety scores had significantly higher PI values in the umbilical artery (p = 0.0056), significantly lower PI values in the fetal middle cerebral artery (p = 0.0029) and significantly lower cerebro-umbilical PI ratios (p = 0.0002), suggesting a change in blood distribution in favor of brain circulation in the fetuses. Maternal weight, weight-increase, height, age, marital status, smoking habits, drinking habits and socio-economic factors known to affect fetal well-being did not interfere with these findings. No significant differences in birth-weight, length and head circumference were found between infants born to mothers with higher trait anxiety levels compared to mothers with lower trait anxiety levels. Our results suggest that maternal stress, in terms of trait anxiety, influences fetal cerebral circulation.

Adolescent↗
PubMed1996

A numerical study of persistence length effects on DNA conformation in sequencing electrophoresis.

We have developed a program to evaluate the influence of DNA stiffness on molecular mobility and conformation during electrophoresis. This (currently) two-dimensional numerical study models DNA as a chain of uniformly charged beads connected to one another by elastic segments, of finite mean size, in the presence of fixed obstacles representing gel fibers. Contrary to the standard biased reptation model (BRM), our Langevin-type dynamics for the chain are microscopic and warrant studies of fine effects such as inner chain orientation. Using this model, we show that the introduction of a persistence length decreases the (saturated) mobility at high electric fields, providing strong evidence that the gel generates a friction force and not only a (dissipation-free) constraint force. We also show that the persistence length leads to an increase of the chain orientation in the field direction. This suggests that DNA stiffness causes the saturation plateau value to be reached for smaller chain sizes than those predicted by the BRM model.

DNA↗