Study of the use of vitamin K in neonates in France

Our objective was to assess flow velocity waveforms of the portal venous system of the anemic fetus prior to and immediately following intravascular transfusion. Color-guided pulsed Doppler was used to obtain flow velocity waveforms from the fetal portal vein in 14 anemic fetuses that were transfused in utero for rhesus alloimmunization The portal vein velocity pattern was defined as continuous when no change in velocity during the cardiac cycle was noted. It was defined as pulsatile when a deflection of the wave was present. The flow velocity waveforms were quantified by using the ratio between the peak (highest, H) and the nadir (lowest, L) velocities (H/L ratio). Fourteen intravascular transfusions were performed. Gestational age ranged from 19.5 to 35 weeks (mean +/- SD, 26.7 +/- 5.3 weeks). The hematocrit ranged from 5.9 to 31.2% (mean +/- SD, 20.3 +/- 9%) prior to transfusion; after transfusion it was between 24.8 and 56.7% (mean +/- SD, 42 +/- 10.4%). In six cases (43%) the waveforms were pulsatile prior to transfusion; in the other eight (57%) they were continuous. The pulsatile pattern was present following transfusion in 13 cases (93%, p < 0.05). The mean of the H/L ratio was 1.3 +/- 0.38 prior to transfusion and 2.0 +/- 0.86 after transfusion (p < 0.05). Because the portal vein has continuous non-pulsatile flow in the normal fetus, the presence of pulsatility in the waves of six anemic fetuses (43%) may suggest portal hypertension. Compared to normal fetuses, there was an increased number of cases with pulsation, and even more so after transfusion. The pattern corresponds to findings in children with portal hypertension.     

Backscattered electron imaging of the undersurface of resin-embedded cells by field-emission scanning electron microscopy

In this study backscattered electron (BSE) imaging was used to display cellular structures stained with heavy metals within an unstained resin by atomic number contrast in successively deeper layers. Balb/c 3T3 fibroblasts were cultured on either 13-mm discs of plastic Thermanox, commercially pure titanium or steel. The cells were fixed, stained and embedded in resin and the disc removed. The resin block containing the cells was sputter coated and examined in a field-emission scanning electron microscope. The technique allowed for the direct visualization of the cell undersurface and immediately overlying areas of cytoplasm through the surrounding embedding resin, with good resolution and contrast to a significant depth of about 2 μm, without the requirement for cutting sections. The fixation protocol was optimized in order to increase heavy metal staining for maximal backscattered electron production. The operation of the microscope was optimized to maximize the number of backscattered electrons produced and to minimize the spot size. BSE images were collected over a wide range of accelerating voltages (keV), from low values to high values to give ‘sections' of information from increasing depths within the sample. At 3–4 keV only structures a very short distance into the material were observed, essentially the areas of cell attachment to the removed substrate. At higher accelerating voltages information on cell morphology, including in particular stress fibres and cell nuclei, where heavy metals were intensely bound became more evident. The technique allowed stepwise ‘sectional’ information to be acquired. The technique should be useful for studies on cell morphology, cycle and adhesion with greater resolution than can be obtained with any light-microscope-based system.     

Intracellular location of inapparently infecting Chlamydia in synovial tissue from patients with Reiter's syndrome

Culture of Chlamydia trachomatis from synovial tissues/fluids from Reiter's syndrome (RS) patients frequently yields negative results. However, we have identified chlamydial RNA at that site in such patients, suggesting that viable organisms may be present. Here we define the cellular location of chlamydia within the synovium via in situ hybridization. Using a chlamydial ribosomal RNA-directed probe, we show that synovial tissue from culture-negative RS patients gives strong hybridization which is often localized to a subsynovial cell layer, rather than to the synovial lining; in some cases, hybridizing cells are dispersed through the synovium. All hybridization signal is located within host cells, indicating that infectious extracellular elementary bodies are rare or absent. These data confirm the extensive intracellular presence of inapparent chlamydia in the synovia of RS patients and provide some insight into the usual culture negativity of synovial tissues for the organism.     

Circadian variations in the occurrence of cardiac arrests: initial and repeat episodes

The purpose of this study was to predict diameters of lesions induced by laser-induced thermotherapy (LITT) of benign prostatic hyperplasia (BPH) from MRI signal/tissue temperature correlations during on-line monitoring with a temperature-sensitive fast low-angle shot (FLASH) sequence. Twenty LITT procedures with Nd:YAG (1,064 nm) and diode (830 nm) lasers were monitored on line with a T1-weighted FLASH sequence at 1.5 Tesla. Interstitial prostate temperature (T) was measured on line in 10 LITT procedures and laser energy deposition in 12. Slopes of linear regression curves for signal intensity (SI) over T were applied to determine SI at 60 degrees C to estimate diameters of intraprostatic LITT lesions. Diameters of unperfused LITT lesion cores in contrast-enhanced T1-weighted images served as gold standards. Linear regression curves with an average slope of -.54% SI/degrees C were obtained in 17 LITT procedures. Correlation coefficients were r = .92-.95 for SI/T and SI/energy deposition. Baseline variation of SI at body temperature was +/-3.9%, corresponding to +/-7 degrees C. Prediction of size (13 lesions) from on-line FLASH imaging was correct in 10 of 13, whereas 3 lesions were overestimated. Prediction of LITT lesion diameters from on-line MRI monitoring is possible with a temperature-sensitive FLASH sequence in the prostate. Accuracy may suffice to assign target regions of interest to tissue locations to be protected from coagulation.