Biomedical subjects

F Stonek

Publications and source records attributed to F Stonek.

5 recordsLinked to original sources

PubMed2006

Comparison between three-dimensional placental volume at 12 weeks and uterine artery impedance/notching at 22 weeks in screening for pregnancy-induced hypertension, pre-eclampsia and fetal growth restriction in a low-risk population.

OBJECTIVES: To compare the value of three-dimensional placental volume at 12 weeks and uterine artery Doppler at 22 weeks for predicting pregnancy-induced hypertension (PIH), pre-eclampsia and fetal growth restriction in a low-risk population. METHODS: Over a 20-month period we calculated the placental quotient (PQ = placental volume/crown-rump length) at 11-13 weeks' gestation in all women with singleton pregnancies who booked for delivery in our hospital. At 22 weeks, in the same population, we calculated the mean pulsatility index (PI) of both uterine arteries and the presence of an early diastolic notch was noted. Logistic regression models, the PQ and Doppler parameters were used to compare the two screening methods for subgroups of pregnancy outcome. RESULTS: Complete outcome data were obtained in 2489 consecutive singleton pregnancies. Logistic regression models for the detection of pre-eclampsia had a sensitivity of 38.5% (PQ) vs. 44.8% (Doppler); for the detection of small-for-gestational age (SGA) the sensitivity was 27.1% (PQ) vs. 28.1% (Doppler) at a specificity of 90%. Taking a PQ of or= 90th centile and a bilateral notch, the sensitivity for detection of SGA was 25.0%, 20.2% and 22.0%, respectively; for PIH it was 9.5%, 4.8% and 4.8%; for pre-eclampsia without SGA it was 20.0%, 28%, 12%; for PIH/pre-eclampsia with SGA it was 30.8%, 46.1% and 69.2%. In the group with the most severe complications, in which delivery took place before 34 weeks, the sensitivity was 50.0%, 50.0% and 38.9%, respectively. CONCLUSIONS: PQ at 12 weeks and uterine artery Doppler at 22 weeks have similar sensitivities for predicting pre-eclampsia and fetal growth restriction, although uterine artery Doppler is marginally more sensitive for the prediction of pre-eclampsia. While both methods are insufficient for screening in a low-risk population, the PQ method has the potential advantage of being performed in the first trimester.

Adolescent↗

PubMed2001

Calculated background elimination in quantifying nitric-oxide synthase enzyme activity.

Measuring nitric-oxide synthase (NOS) activity by monitoring the conversion of L-arginine to L-citrulline is currently the standard assay for NOS activity. We describe a simple method of quantifying low values of NOS activity by removing the background mathematically. When performing NOS activity studies in samples with low protein amount (< 25 microg/microl), we encountered the problem of sample values that can hardly be differentiated from blank values probably originating from radioactive-labeled arginine in the final eluate. Our method determines mathematically these background values and may be an improvement of the citrulline assay.

Arginine↗

PubMed2001

Estrogen increases endothelial carbon monoxide, heme oxygenase 2, and carbon monoxide-derived cGMP by a receptor-mediated system.

Carbon monoxide, a gaseous activator of soluble guanylyl cyclase formed by a subtype of the enzyme heme oxygenase designated heme oxygenase-2 in vascular endothelium, has been found to dilate blood vessels independently from nitric oxide. Because of the parallels between nitric oxide and carbon monoxide, we speculated that estrogen might affect carbon monoxide production in vascular endothelium. Endothelial cells of human origin (umbilical vein and uterine artery) were incubated for 4 or 24 h with 10(-12)-10(-6) M 17beta-estradiol. 17beta-Estradiol, at a concentration such as that attained during the ovulatory phase of the menstrual cycle (10(-10) M), administrated for 4 h led to a 2-fold increase in intracellular carbon monoxide production and heme oxygenase-2 protein levels (P < 0.05). A reporter assay, measuring the formation of cGMP as the direct product of carbon monoxide-induced activation of soluble guanylyl cyclase in endothelial cells, also revealed a 56% increase in cellular cGMP after treatment with 10(-10) M E2 17beta-estradiol (P < 0.05). By contrast, higher 17beta-estradiol concentrations had no significant respective effects due to nitric oxide synthase inhibition of carbon monoxide release. This 17beta-estradiol effect appeared to be ER dependent, as preincubation with tamoxifen (10(-6) M) blocked the stimulatory effect of 17beta-estradiol in each instance. Our preliminary data indicate a potential role for carbon monoxide as a biological messenger molecule in estrogen-mediated regulation of vascular tone.

Arteries↗

PubMed1999

Elevation of inducible nitric oxide synthase activity in human endometrium during menstruation.

Nitric oxide (NO) is a known agonist of programmed cell death (apoptosis). In order to discover its potential role during menstrual shedding, a process associated with extensive apoptosis, we evaluated activity and mRNA levels of the inducible and constitutive isoforms of NO synthase (NOS) in endometrial specimens of the proliferative (n = 11), late-secretory (n = 7), and menstrual (n = 17) phase of the cycle. These levels were compared with the proportion of apoptotic cells by detection of histochemically labeled DNA fragments. Inducible NOS (iNOS) activity during menstruation was six times that of the proliferative or late-secretory phase (p < 0.05), whereas constitutive NOS activity remained unchanged. Competitive reverse transcription-polymerase chain reaction revealed 146% and 77% increases of iNOS mRNA expression in the late-secretory and menstrual phases, respectively, compared to the proliferative phase (p < 0.05), whereas constitutive NOS mRNA expression remained constant. Inducible NOS immunostaining was restricted to epithelial cells, whereas constitutive NOS immunostainig was confined to vascular endothelia. In addition, the proportion of apoptotic cells within the glands of late-secretory or menstrual endometrium was twice that of the proliferative phase (p < 0.05). We conclude that local production of NO is involved in the signal transduction mechanisms leading to endometrial breakdown during menstruation.

Adult↗

PubMed1999

Human cervical ripening is associated with an increase in cervical inducible nitric oxide synthase expression.

The mechanisms that ultimately regulate cervical ripening during parturition remain largely unknown. A possible role for nitric oxide (NO) has recently emerged; however, the expression of NO synthase (NOS) within the human cervix in the ripening process has not been investigated. The purpose of this study was to identify cell types in the human cervix that contain NOS isoforms and to examine changes in their expression during the ripening process and the nonpregnant state. Inducible NOS (iNOS) immunoreactivity was observed in the epithelial cells and stromal spindle cells in 17 of 20 biopsies from cervices obtained within 10 min postpartum, but in only 4 of 12 nonpregnant controls (p = 0.03). Endothelial NOS (eNOS) immunoreactivity was restricted to vascular endothelia in all sections, whereas neuronal NOS was not detectable. Inducible NOS activity in the postpartum group was 3.2 times that of the control group (p = 0.0005), whereas constitutive NOS activity remained unchanged in both groups (p = 0.222). Competitive reverse transcription-polymerase chain reaction revealed no differences in the expression of iNOS (p = 0.443) or eNOS mRNA (p = 0.409). The existence of iNOS in the human postpartum cervix suggests that increased production of NO, probably induced by cytokines, may be relevant to the process of natural cervical ripening in humans.

Adult↗