Contraceptive methods and utilization in Rhode Island.
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Adult↗
Biomedical subjects
J Hesser
Publications and source records attributed to J Hesser.
Real-time direct volume rendering in functional magnetic resonance imaging.
Direct volume rendering is a visualization method that allows display of all information hidden in three-dimensional data sets of, for example, computed tomography or magnetic resonance imaging (MRI). In contrast to commonly used surface rendering methods, these algorithms need no preprocessing but suffer from a high computational complexity. A real-time rendering system, VIRIM (Vitec: Visualization Technology GmbH, Mannheim, Germany), cuts down rendering times of minutes on normal workstations to an interactive rate of 1 second or less. The immediate visual feedback allows interactive steering of the visualization process to achieve insight into the internal three-dimensional structure of objects. Additional information is obtained by using an interactive gray-value segmentation tool that both allows segmentation of the data set according to bone, tissue, and liquor and display of multifunctional data sets (e.g., functional MRI [fMRI] data sets). Thus, real-time direct volume rendering allows segmentation and volume data processing of functional and anatomical MR data sets simultaneously. As this method can be integrated in the clinical routine, it is of great importance for real-time motion artifact detection and the interpretation of fMRI data acquired during cognitive experiments with normal subjects and psychiatric patients. Because of the free programmability of VIRIM, more complex matching procedures are currently being investigated for future implementation.
Brain↗
Interactive operation planning and control with VIRIM.
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Algorithms↗
Cardiovascular responses to norepinephrine and arginine vasopressin infusion in chronically catheterized fetal lambs.
Fetal cardiovascular responses to infused norepinephrine (NE) and arginine vasopressin (AVP) were compared in bilaterally vagotomized and chronically catheterized (control) fetal lambs. In the control fetuses, NE infusion was characterized during the first five minutes by a decreased fetal heart rate (FHR) and increased mean arterial blood pressure (MABP) and by a preejection period (PEP) followed by a gradual return to the original values. NE infusion in vagotomized fetuses was followed by tachycardia, decreased PEP without the initial prolongation and an MABP response similar to that in the controls. AVP in control fetuses caused a persistent decrease in the FHR and increase in MABP and PEP. Vagotomy affected only the FHR response: the decrease was persistent but smaller. AVP produced persistent fetal cardiovascular responses regardless of vagotomy; however, the biphasic response FHR pattern, suggestive of NE tachyphylaxis, was eliminated by vagotomy.
Animals↗
A randomized trial of routine prenatal ultrasound.
Nine hundred fifteen of 2171 pregnant patients had no indication for ultrasound at their first prenatal visit and were randomly assigned to receive either a single routine screening ultrasound or usual prenatal care. The estimated date of confinement was altered in 24.9% of routine-ultrasound patients and in 11.6% of usual-care patients through ultrasound examinations obtained for a subsequent clinical indication. Of these, 8.3% of routine-ultrasound and 5.2% of usual-care patients had gestational age errors of 2 weeks or more. There were no differences between the groups in inductions for post-dates pregnancy (7.0 versus 7.5%; P = .87), total inductions (22.6 versus 24.9%; P = .61), or adverse perinatal outcomes (6.7 versus 8.3%; P = .63). Both sets of twins were detected in the screened group. In the usual-care group, five of seven pairs of twins (71%) were diagnosed by 24 weeks' gestation. There was no benefit found from routine ultrasound as performed in this study.
Adult↗
Effects of norepinephrine on lung fluid flow rate in the chronically catheterized fetal lamb.
The influence of norepinephrine on lung fluid flow rate was studied in seven chronically catheterized fetal lambs. Lung fluid was collected through a catheter inserted into the fetal trachea. In six experiments, continuous saline solution infusion for 1 hour followed by equivolumnar norepinephrine (3.0 micrograms/min) for 1 hour via the fetal jugular vein was carried out. In three additional experiments (two fetuses), a 3.0 mg intravenous bolus of propranolol was administered before norepinephrine infusion. Saline solution infusion did not influence the lung fluid flow rate or fetal biophysical and biochemical parameters. Norepinephrine increased fetal blood pressure by 22% and decreased lung fluid flow by 45% from control values. Lung fluid flow rate recovered within 2 hours after the end of the norepinephrine infusion. Pretreatment with propranolol did not alter the results. In addition to previous reports that demonstrated beta-sympathomimetic agonist-enhanced reabsorption of lung fluid from fetal alveolar epithelial cells, our present results suggest that a reduction in fetal lung fluid secretion may be implemented as well through stimulation of alpha-sympathomimetic receptor sites in the pulmonary vasculature.
Animals↗
Experimentally produced sinusoidal fetal heart rate pattern in the chronically instrumented fetal lamb.
A sinusoidal fetal heart rate and elevated fetal arginine vasopressin levels were found in two bled fetal lambs. Arginine vasopressin was continuously infused intravenously in chronically instrumented fetal lambs at rates ranging between 1.0 and 90 mlU/kg/min. No sinusoidal heart rate occurred in 21 experiments on six control animals with intact vagal nerves. Atropine at doses less than 0.4 mg had no effect (six experiments on three animals). Higher doses of atropine (greater than 1.2 mg) resulted in sinusoidal heart rate (24 experiments on six animals). Twenty-three infusions were performed in five bilaterally vagotomized fetuses, and the sinusoidal heart rate was successfully induced in 17 experiments. The arginine vasopressin infusion rate was less than 1.5 mlU/kg/min on the six occasions in which the sinusoidal heart rate did not appear. All sinusoidal heart rate patterns were associated with fluctuation of fetal arterial pressure at the same frequency. There was a linear correlation between the amplitude of sinusoidal heart rate and magnitude of arterial blood pressure fluctuation. The amplitude of sinusoidal heart rate increased with the concentration of arginine vasopressin infused. Modification of sinusoidal heart rate pattern was attempted with use of sympathetic agonists and antagonists. The possible etiology and mechanisms of sinusoidal heart rate pattern are discussed.
Animals↗
Some epidemiologic studies of HBSAg in Greece.
In an epidemiologic study in 17 villages from different areas of Greece, 2898 persons were examined in order to find possible relations between HBSAg prevalence, altitude and endemic goitre morbidity. A lower prevalence with a significant difference was found in areas with a high altitude as compared with those with a low one, in endemic goitre than non-endemic areas, and in low altitude endemic than in low altitude non-endemic areas. Goitrous subjects had a lower HBSAg prevalence than non-goitrous subjects, but the difference was of borderline significance. The results can probably be explained by the presence of an environmental factor associated with altitude acting together with a host factor predisposing to endemic goitre and favouring the immunity to HBV infection.
Altitude↗