The formation of nanocrystalline SrFeO(3-delta) using mechano-synthesis and subsequent sintering: structural and Mössbauer studies.

The influence of mechanical milling and subsequent sintering of a 2:1 molar mixture of SrCO3 and alpha-Fe2O3 on the formation of SrFeO(3-delta) pervoskite-related nanocrystalline particles is investigated. The structural evolution during the formation process is systematically investigated using X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Pre-milling the mixture in air for 120 h leads to the incorporation of Sr2+ in the alpha-Fe2O3 crystal structure thus facilitating the formation of a 2:1 nanocrystalline mixture of SrFeO3 and SrFeO2.875 by sintering the pre-milled mixture in air at 800 degrees C (12 h). This temperature is approximately 300 degrees C lower than those at which SrFeO(3-delta) phases are synthesized by the conventional ceramic techniques. Pre-milling the precursors was found to result in a smaller oxygen deficiency (delta) relative to conventional ceramic synthesis of SrFeO(3-delta). Rietveld refinement of the X-ray diffraction shows the interatomic distances in the resulting SrFeO2.875 nanocrystalline phase to be slightly different from those of the conventionally prepared bulk leading, in turn, to a crystal structure with tilted polyhedral cationic sites. This structural distortion is related to both small-size and surface effects in the nanoparticles that have no counterparts in the corresponding bulk material. The surface structure of the attained SrFeO(3-delta) nanocrystalline particles shows a significant partial reduction of Fe4+ to Fe3+ due to ambient conditions and the presence of an appreciable amount of SrCO3 as well.

Integrin expression, enterocyte maturation, and bacterial internalization.

BACKGROUND: Little is known about the molecular mechanisms involved in the translocation of enteric bacteria. Adhesion molecules mediate interactions between some enteric pathogens and mammalian cells, but no such interactions have been identified for enterocytes and normal enteric bacteria. Using enteric pathogens, adhesion molecule expression has been linked to bacterial internalization and to enterocyte differentiation. Therefore, experiments were designed to study enterocyte integrin expression and differentiation, as well as enterocyte internalization of Salmonella typhimurium, Proteus mirabilis, and Escherichia coli. MATERIALS AND METHODS: Relative expression of the alpha2, alpha3, and beta1 integrin subunits on Caco-2 and HT-29 enterocytes (mature and immature) was measured by ELISA. Bacteria-enterocyte surface interactions were observed by light and scanning electron microscopy. Bacterial internalization by enterocytes was quantified using the gentamicin protection assay. RESULTS: Expression of the alpha2, alpha3, and beta1 integrin subunits was consistently increased in immature compared to mature Caco-2 enterocytes; however, compared to mature enterocytes, immature HT-29 enterocytes had similar expression of alpha3 and beta1 but decreased alpha2. Compared to untreated mature enterocytes, bacterial internalization was increased in immature enterocytes as well as mature enterocytes with lateral membranes artifactually exposed. However, there was no difference in bacterial internalization between immature enterocytes and mature enterocytes treated to expose the lateral membrane. CONCLUSIONS: Bacterial internalization by enterocytes appeared to be due to factors other than integrin expression or enterocyte differentiation. Exposure of the lateral enterocyte membrane may play an important role in facilitating bacterial internalization by enterocytes.

Robust processing of intracranial CT angiograms for 3D volume rendering.

The goal of this study was to develop a robust and simple technique for processing of cranial CT angiograms (CTA) in the clinical setting. The method described in this paper involves segmentation of the bone, then dilation of the skull by adding three or four layers of voxels. This dilated skull is subtracted from the vessels object on a voxel-by-voxel basis, allowing segmentation and subsequent display of the vessels only. For evaluation of the technique, three groups of operators processed one CTA, and the quality of the 3D views obtained and the times taken were compared. One group was given training by an expert and a "recipe" for guidance, the second was given only the "recipe," and the third group consisted of expert operators. All operators were able to produce good or acceptable shaded-surface displays when compared with digital subtraction angiography, within 10 min for experienced users, an average of 17 min for trained operators and 26 min for those using only the recipe sheet. Using a simple scoring system for the appearance of feeding vessels and draining veins, no significant differences were found between the three levels of training and experience. This technique simplifies the processing of CTAs and is quick enough to make such examinations part of a routine clinical service.

Contrast-enhanced MR angiography of intracranial giant aneurysms.

BACKGROUND AND PURPOSE: Intravoxel phase dispersion and flow saturation often prevent adequate depiction of intracranial giant aneurysms on 3D time-of-flight (3D-TOF) MR angiography (MRA). Additional diagnostic difficulties may arise from T1 contamination artifact of an associated blood clot. Our aim was to assess whether contrast-enhanced MRA could improve the evaluation of giant aneurysms and to compare two different types of contrast-enhanced MRA. METHODS: We studied 11 aneurysms in 10 patients (age range, 31-77 years) with giant aneurysms of the anterior (n = 9) and posterior (n = 2) cerebral circulation by comparing 3D-TOF, first-pass dynamic contrast-enhanced MRA, and steady-state contrast-enhanced 3D-TOF sequences. Additional comparison with digital subtraction angiography (DSA) was performed in eight aneurysms. RESULTS: In nine of 11 aneurysms, 3D-TOF did not adequately show the lumen and exiting vessels. Contrast-enhanced 3D-TOF and dynamic contrast-enhanced MRA showed the aneurysm sac and exiting vessels in all of these cases. Dynamic contrast-enhanced MRA showed a better intravascular contrast than did contrast-enhanced 3D-TOF, which led to better delineation of the aneurysms. T1 contamination artifact from intra- or extraluminal blood clot was evident on the 3D-TOF images in four cases. The artifact was less marked on the contrast-enhanced 3D-TOF image and was completely eliminated on the dynamic contrast-enhanced MRA image by subtraction of precontrast images. The diagnostic information provided by dynamic contrast-enhanced MRA was comparable to that provided by DSA. CONCLUSION: Precontrast 3D-TOF is inadequate for the assessment of giant cerebral aneurysms. Both contrast-enhanced 3D-TOF and dynamic contrast-enhanced MRA reliably show the aneurysm sac and connected vessels. Dynamic MRA provides a superior contrast between flow and background and eliminates T1 contamination artifact. It should therefore be considered as the MRA sequence of choice.

Inducible expression of Enterococcus faecalis aggregation substance surface protein facilitates bacterial internalization by cultured enterocytes.

Aggregation substance (AS) is an Enterococcus faecalis surface protein that may contribute to virulence. Using a recently described system for controlled expression of AS in E. faecalis and the heterologous host Lactococcus lactis, experiments were designed to assess the effect of AS on bacterial internalization by HT-29 and Caco-2 enterocytes. AS expression was associated with increased internalization of E. faecalis by HT-29 enterocytes and of L. lactis by HT-29 and Caco-2 enterocytes. Compared to enterocytes cultivated under standard conditions, either cultivation in hypoxia or 1-h pretreatment of enterocytes with calcium-free medium resulted in increased internalization of both E. faecalis and L. lactis (with and without AS expression). Also, AS expression augmented these increases when E. faecalis was incubated with pretreated HT-29 enterocytes and when L. lactis was incubated with pretreated Caco-2 and HT-29 enterocytes. These data indicated that AS might facilitate E. faecalis internalization by cultured enterocytes.

Contrast-enhanced MR angiography in patients with carotid artery stenosis: comparison of two different techniques with an unenhanced 2D time-of-flight sequence.

Conventional time-of-flight (TOF) MR angiography (MRA) in carotid artery stenosis relies on flow-related enhancement to produce signal from vascular structures. Intravoxel phase dispersion, due to vortices, causes loss of signal and is the reason for the tendency to overestimate the degree of stenosis. In contrast-enhanced MRA, intravascular signal is mainly dependent on T1 shortening of the blood. We compared first-pass contrast-enhanced MRA (contrast-enhanced 3D gradient echo, ce3D GRE) and contrast-enhanced 2D TOF (ce2D TOF) sequences with an unenhanced 2D TOF in 13 patients with carotid artery stenosis, assessing delineation of the carotid bifurcation, enhancement of veins and grade of stenosis. The contrast-enhanced techniques produced more morphological detail, the ce3D GRE being superior to the ce2D TOF. Four carotid arteries were reclassified into lesser stenosis categories using the ce3D GRE technique. However, seven carotid arteries (27%) were rated as nondiagnostic on the ce3D GRE, mainly due to masking of the carotid bifurcation by veins. The latter can be avoided by decreasing the acquisition time; on our 1.5-T system we could achieve a minimum time of 23 s per 3D GRE. Further reduction of acquisition time would be necessary to incorporate this method into clinical routine, requiring higher-performance gradients, which are not available in many UK hospitals.

The free gingival graft combined with the frenectomy: a clinical review.

Abnormal labial frena are capable of retracting gingival margins, creating diastemas, and limiting lip movement. When these frena are present, the traditional frenectomy alone generally is successful. However, when the frenulum is extensive, the possibility of coronal reformation exists. Several procedures have combined the frenectomy with either a lateral pedicle flap, free papilla graft, or free gingival (mucosal) graft taken from the palate. Three case reports demonstrate the continued efficacy of the traditional palatal free gingival graft when the patient has an extensive frenulum or an area of minimal esthetic concern is involved.

Evaluation of the accuracy and precision of lung aerosol deposition measurements from planar radionuclide imaging using simulation.

Planar images of known, theoretical distributions of radioaerosol in the lung have been simulated using lung models derived from magnetic resonance studies on human subjects. Total lung activity was evaluated from the simulated images together with the absolute penetration index (PI) and a relative value expressed as a fraction of that in a simulated ventilation image. The accuracy and precision of these measurements were calculated by comparison with the true values used in the simulation. Total activity was assessed with systematic errors within 5% and precision within 6.5%. Measured PIs varied only slowly with true PI and inter-model variation masked changes between measurements on the different distributions. The relative PI reduced inter-model variation and provided significant differences between all the distributions. PI was significantly affected by misalignment of the lung region of interest. The conducting airways deposition fraction (CADF) used in the simulation correlated linearly with the fractional activity in a central lung region, allowing CADF to be estimated with a precision of 21%.

Selective alteration of personality and social behavior by serotonergic intervention.

OBJECTIVE: The authors sought to test the causal hypothesis that serotonergic function modulates aspects of the normal spectrum of individual differences in affective experience and social behavior in humans. METHOD: A selective serotonin reuptake inhibitor (SSRI), paroxetine, 20 mg/day (N = 26), or placebo (N = 25) was administered to normal volunteers in a double-blind manner for 4 weeks, and personality variables and social behavior were assessed at baseline and at weeks 1 and 4 of treatment. RESULTS: Relative to placebo, SSRI administration reduced focal indices of hostility through a more general decrease in negative affect, yet did not alter indices of positive affect. In addition, SSRI administration increased a behavioral index of social affiliation. Changes in both negative affect and affiliative behavior were significantly related to volunteers' plasma SSRI levels at the end of the experiment. CONCLUSIONS: Central serotonergic function may modulate a dimension of normal personality characterized by reduced negative affective experience and increased affiliative behavior. SSRI administration has significant and detectable effects on these measures even in the absence of baseline clinical depression or other psychopathology.

Magnetic resonance imaging manifestations of idiopathic haemochromatosis in the wrist.

The magnetic resonance imaging features of the wrist of a patient suffering from the arthropathy of haemochromatosis are presented. It is apparent that the deposition of iron within the bone marrow is focal in origin and may be associated with cyst formation. In addition, changes in serum ferritin levels with treatment suggest that the deposition is irreversible. Studies of two other patients with haemochromatosis without cyst formation in the wrists did not yield similar artefacts, in spite of having high ferritin levels and arthritis.

Demonstration of a geode by magnetic resonance imaging: a new light on the cause of juxta-articular bone cysts in rheumatoid arthritis.

The magnetic resonance imaging (MRI) features of a rheumatoid arthritic geode are presented. Development of such a cyst from before x ray diagnosis to its coalescence with the wrist joint is described. The evidence suggests that these juxta-articular cysts are not merely an intrusion of the synovial cavity into the bone marrow but start as isolated structures beneath the subchondral bone.

Antagonism of ethanol effects on cerebellar Purkinje neurons by the benzodiazepine inverse agonists Ro 15-4513 and FG 7142: electrophysiological studies.

Ro 15-4513, a benzodiazepine inverse agonist, has been reported to antagonize the ataxic effects of ethanol. The present study investigates the Ro 15-4513 sensitivity of rat cerebellar Purkinje neurons to the depressant effects of locally applied ethanol. Local applications of ethanol by pressure ejection from multibarrel micropipettes caused reversible and dose-dependent depressions of the neuronal firing rates of single cerebellar Purkinje neurons. The ethanol-induced depressions could be antagonized by local applications of Ro 15-4513 applied from another barrel of the same micropipette. This antagonism was not competitive, suggesting that Ro 15-4513 does not interfere directly with the initial step of the ethanol mechanism of action. A beta-carboline inverse agonist, FG 7142, was more efficacious than Ro 15-4513 for antagonizing the ethanol-induced depressions, but appeared to be less potent. Recovery of ethanol-induced depressions of Purkinje neurons firing rates after Ro 15-4513 antagonism was not usually observed for 1 hr or more after the antagonist application. In contrast to ethanol effects, qualitatively similar gamma-aminobutyric acid-induced depressions of these same neurons were not antagonized by the doses of Ro 15-4513 used. We conclude that the electrophysiological depressant effects of ethanol on cerebellar neuronal activity can be antagonized by the benzodiazepine inverse agonists, Ro 15-4513 and FG 7142.

A murine model of squamous intraepithelial neoplasia.

Focal areas of intraepithelial neoplasia were induced in the skin of mice by 1 intraperitoneal injection of urethane followed by twice weekly topical applications of 12-0-tetra-decanoyl phorbol-13-acetate (TPA). Microscopic lesions with histologic characteristics of intraepithelial neoplasia were seen in all animals after 11 weeks of TPA application. Fluorescence microscopy verified the increased DNA content of these lesions. This easily produced animal model of premalignant disease might be valuable in the preclinical testing of topically applied antineoplastic agents.

Genetic variation in activity of the enzymes of glycolysis and gluconeogenesis between inbred strains of mice.

Variation in the activity of 21 liver and 15 erythrocyte enzymes between seven inbred strains of mice has been studied in a single area of metabolism, glycolysis and gluconeogenesis. Most of the variation between the strains is genetic. From the variation within and between inbred strains heritabilities (H2) were determined. Out of 35, 26 showed significant values above 0.4. A comparison with previously published work suggests that enzyme activities have mainly dominance and interaction components of variance, and this is discussed in relation to the variation in quantitative characters such as growth. In nine of the pairwise comparisons of the strains, the activity of the enzyme varied more than two-fold. In these cases the genetics and biochemistry of the enzyme was studied; F2 progeny were produced and assessed for segregation, and the heat stability of the enzyme was determined. No unequivocal segregation was observed, although in one case we found a considerable difference in heat stability. The variations found were not considered to be great enough to be useful as models of human inborn errors of metabolism or to study metabolic control. If such variants are to be found, sources of variation other than inbred strains must be used.