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311.
A study was carried out into the hematological abnormalities of peripheral blood bone marrow in patients chronically exposed to benzene. The metabolic biotransformation and the mechanisms involved in toxicity are described. Hematological data are described and discussed. Macrocytosis and lymphopenia are the earliest hematological signs of benzene toxicity. Bone marrow abnormalities are demonstrated by the complementary methods of cytology and histology. Global hypocellularity was mainly due to the granulocytic series. Mastocytosis, eosinophilia and magakariocytic abnormalities are also presented. Inflammatory abnormalities and signs of dismyelopoiese could also be observed. The importance of peripheral blood abnormalities and the need for a critical approach to this important public health problem are emphasized. 相似文献
312.
A study of the functional state of the heart conduction system by means of electrophysiologic testing of 46 patients with the Wolff-Parkinson-White syndrome has shown that the peculiarities of atrioventricular conduction and the development of an electrocardiographic picture in this disease are determined by the functions of anomalous accessory atrioventricular pathways--more frequently of the Kent's bundle and more infrequently of the Macheim's bundle. In addition, the degree of manifestations of the ventricular pre-excitation on the ECG depends on the correlation between impulse conduction times along the anomalous and normal pathways. The slow conduction along the Kent bundle form the basis of the latent WPW syndrome not recorded by the ECG. 相似文献
313.
The first total synthesis and stereochemical assignment of cytoblastin were reported. Key steps included the palladium-mediated coupling of N-SEM-7-bromoindolactam V ((-)-11) with allylstannane c-13, and osmium tetroxide-mediated dihydroxylation of 14, both of which were stereoselective. The stereochemistry of cytoblastin was determined as 1A via spectroscopic analysis of the pentacyclic derivative 21 of cytoblastin. A connection was then made between the stereochemistry so elucidated and the Kishi/Rando hypothesis for the structural correlation between (S)-1,2-diacylglycerol and tumor promoters for the process of protein kinase C activation. 相似文献
314.
In genetic systems there is a non-trivial interface between the sequence of symbols which constitutes the chromosome, or 'genotype', and the products which this sequence encodes--the 'phenotype'. This interface can be thought of as a 'computer'. In this case the chromosome is viewed as an algorithm and the phenotype as the result of the computation. In general, only a small fraction of all possible sequences of symbols makes any sense for a given computer. The difficulty of finding meaningful algorithms by random mutation is known as the brittleness problem. In this paper we show that mutation and crossover favor the emergence of an algorithmic language which facilitates the production of meaningful sequences following random mutations of the genotype. We base our conclusions on an analysis of the population dynamics of a variant of Kitano's neurogenetic model wherein the chromosome encodes the rules for cellular division and the phenotype is a 16-cell organism interpreted as a connectivity matrix for a feed-forward neural network. We show that an algorithmic language emerges, describe this language in extenso, and show how it helps to solve the brittleness problem. 相似文献
315.
316.
DD Ivy SR Neish OA Knudson MR Nihill MS Schaffer RW Tyson SH Abman EM Shaffer L Valdes-Cruz 《Canadian Metallurgical Quarterly》1998,81(6):740-748
We sought to describe the morphologic characteristics of pulmonary arteries by intravascular ultrasound (IVUS) in children with and without pulmonary hypertension to compare these anatomic findings with those of pulmonary wedge angiography, and to determine the relation between these structural findings and functional reactivity to pulmonary vasodilators. Direct evaluation of pulmonary vascular structure in children with pulmonary hypertension with current imaging techniques has been limited and little is known about the relation between structural and functional characteristics of the pulmonary vasculature. In 23 children undergoing cardiac catheterization (15 with pulmonary hypertension and 8 controls) we performed IVUS and pulmonary wedge angiography of the distal pulmonary arteries in the same lobe. IVUS was performed in 44 pulmonary arteries measuring 2.5 to 5.0 mm internal diameter with a 3.5Fr 30-MHz IVUS catheter. We assessed vasoreactivity to inhaled nitric oxide (NO) and oxygen in 13 of 15 children with pulmonary hypertension. Baseline pulmonary vascular resistance (PVR) was greater in the 15 children with pulmonary hypertension than in the 8 controls (9.5+/-1.9 vs 1.5+/-0.3 U x m2, p <0.05). NO lowered PVR in patients with pulmonary hypertension (p <0.05). IVUS studies in patients with pulmonary hypertension showed a thicker middle layer, wall thickness ratio, and diminished pulsatility than did those in controls (p <0.05). The inner layer was not visualized by IVUS in any control patient, but was seen in 9 of 15 patients with pulmonary hypertension. Pulmonary artery wedge angiography correlated with baseline mean pulmonary artery pressure and PVR as well as with IVUS findings of wall thickness ratio and inner layer thickness. The inner layer was not visualized by IVUS in any patient with grade 1 wedge angiograms or in 86% of patients with grade 2 wedge angiograms. All patients with grade 4 and 80% of patients with grade 3 wedge angiograms had a visible inner layer. Vasoreactivity to NO and oxygen did not correlate with structural assessment of the pulmonary vasculature by IVUS. Structural changes in the pulmonary arteries in children with pulmonary hypertension can be directly visualized by IVUS, but are not predictive of NO-induced pulmonary vasodilation. IVUS examination of pulmonary arteries may complement current techniques utilized in the evaluation of children with pulmonary hypertension. 相似文献
317.
318.
OA Kost TA Orth II Nikolskaya SN Nametkin AV Levashov 《Canadian Metallurgical Quarterly》1998,44(3):535-542
Regulation of the catalytic activity and supramolecular structure of angiotensin-converting enzyme was studied in reverse micelles of Aerosol OT in octane as biomembrane model. The kinetic experiments and the sedimentation analysis demonstrated that the enzyme can function both in monomeric and dimeric form. The degree of dimerization was strongly dependent on the concentration and structure of mono- and disaccharides added to the media, indicating the specific role of carbohydrates in forming the supramolecular structure of angiotensin-converting enzyme. The existence of carbohydrate-binding center on the enzyme molecule is proposed. 相似文献
319.
The concentrations of allergen-specific IgE were measured in 146 children with respiratory, skin, and mixed forms of allergic diseases. The spectrum of the allergens was determined and specific features for each of the studied patient populations defined. 相似文献
320.
In a study of 188 patients and 109 controls, the detection of antibody by counterimmunoelectrophoresis was used as a diagnostic aid in human infections with Bacteroides fragilis. It was found that positive results indicated current infection and negative results were not conclusive. The method used was simple, rapid, and easily performed in a routine laboratory, but further work is needed to enhance antigen potency. 相似文献