Fetal Hemodynamic Parameters in Low Risk Pregnancies: Doppler Velocimetry of Uterine, Umbilical, and Middle Cerebral Artery.

Objective. To elaborate curves of longitudinal reference intervals of pulsatility index (PI) and systolic velocity (SV) for uterine (UtA), umbilical (UA), and middle cerebral arteries (MCA), in low risk pregnancies. Methods. Doppler velocimetric measurements of PI and SV from 63 low risk pregnant women between 16 and 41 weeks of gestational age. Means (±SD) for intervals of gestational age and percentiles 5, 50, and 95 were calculated for each parameter. The Intraclass Correlation Coefficients (ICC) were also estimated for assessing intra- and intervariability of measurements. Results. Mean PI of UtA showed decreasing values during pregnancy, but no regular pattern was identified for mean SV. For UA, PI decreased and SV increased along gestation. MCA presented PI increasing values until 32-35 weeks. SV showed higher levels with increasing gestation. High ICC values indicated good reproducibility. Conclusions. Reference intervals for the assessment of SV and PI of UtA, UA, and MCA were established. These reference intervals showed how a normal pregnancy is expected to progress regarding these Doppler velocimetric parameters and are useful to follow high risk pregnancies. The comparison between results using different curves may provide insights about the best patterns to be used.

Dynamics of remyelination in the brain of adult rats after exposure to ethidium bromide.

Diseases of the central nervous system with limited prognosis, as multiple sclerosis, have led to the development of experimental models to study the pathophysiology of such diseases. The present investigation deals with the ethidium bromide (EB) model of demyelination with the objective to study the pathogenesis of encephalic demyelinating lesions. A single 10 microliters injection of 0.1% EB in 0.15 M saline was inoculated in the ventral surface of the pons of adult Wistar rats and after times ranging from 24 h to 30 days, the animals were anaesthetized and perfused with Karnovsky fixative for light and electron microscopy studies. From 3 to 7 days after the EB injection the tissue had developed a spongiotic aspect with intra- and extracellular swelling, demyelinating fibers and a number of necrotic glial cells. By 11 days the reactive phase had begun, and a large number of macrophages had migrated to the foci of the lesion, initiating the absorption of the necrotic tissue. In addition, there were oligodendrocyte-remyelinating nerve fibers and astrocytic gliosis. At 15 days Schwann cells-remyelinating fibers were first seen at the periphery of the lesion while the central area acquired a cystic pattern. The results obtained with the EB-demyelinating model in brain of adult rats showed that 1) remyelination by oligodendrocytes surpassed that by Schwann cells and 2) astrocytic processes were present at the areas remyelinated by the former and absent from those remyelinated by the latter.

Biology of the repair of central nervous system demyelinated lesions: an appraisal.

The integrity of myelin sheaths is maintained by oligodendrocytes and Schwann cells respectively in the central nervous system (CNS) and in the peripheral nervous system. The process of demyelination consisting of the withdrawal of myelin sheaths from their axons is a characteristic feature of multiple sclerosis, the most common human demyelinating disease. Many experimental models have been designed to study the biology of demyelination and remyelination (repair of the lost myelin) in the CNS, due to the difficulties in studying human material. In the ethidium bromide (an intercalating gliotoxic drug) model of demyelination, CNS remyelination may be carried out by surviving oligodendrocytes and/or by cells differentiated from the primitive cell lines or either by Schwann cells that invade the CNS. However, some factors such as the age of the experimental animals, intensity and time of exposure to the intercalating chemical and the topography of the lesions have marked influence on the repair of the tissue.

Biology of the repair of central nervous system demyelinated lesions

The integrity of myelin sheaths is maintained by oligodendrocytes and Schwann cells respectively in the central nervous system (CNS) and in the peripheral nervous system. The process of demyelination consistin of the withdrawal of myelin sheaths from their axons is a characteristic feature of multiple sclerosis, the most common human demyelinating disease. Many experimental models have been designed to study the biology of demyelination and remyelination (repair of the lost myelin) in the CNS, due to the difficulties in studying human material. In the ethidium bromide (an intercalating gliotoxic drug) model of demyelination, CNS remyelination may be carried out by surviving oligodendrocytes and/or by cells differentiated from the primitive cell lines or either by Schwann cells that invade the CNS. However, some factor such as the age of the experimental anmnals, intensity and time of exposure to the intercalating clinical and the topography of the lesions have marked influente on the repair of the tissue.