Architectural alterations in rat cerebral microvessels after hypobaric hypoxia

We performed 3-dimensional studies of vascular casts of the microvasculature of the cerebral cortex of rats that were exposed to three weeks of hypobaric hypoxia and of control rats. Scanning electron microscopy of the casts gave the qualitative impression of increased vascularity of the cerebral cortex, particularly the deeper layers, in hypoxic rats. Quantitative analysis of capillary segment lengths revealed a significant shift in the frequency distribution to longer lengths (from 77 ± 8 to 90 ± 14 μm) in the deep, but not in the superficial, layers of the cerebral cortex of hypoxic rats. These findings agree with previous results reporting increased capillary density in the brain after exposure to prolonged hypobaric hypoxia and suggest that capillary segment elongation plays a role in the increased capillary density in the deeper layers of the cerebral cortex.     

Clinical Results of Dynamic Cardiomyoplasty

Thirty-five cardiomyoplasty procedures were performed in five patients with dilated and 30 patients with ischemic cardiomyopathies. Russian-made cardiomyostimulators (CMS) were implanted in these patients. Twenty-one patients underwent a one-step procedure using a left thoracotomy for cardiomyoplasty, while in 14 patients, a two-step procedure that included a mid-line sternotomy was carried out. During the average follow-up period of 9 ± 2.1 months, studies were carried out that showed in survivors improved clinical functional status and decreased heart failure symptoms. Evidence of revascularization of the ischemic myocardium from the latissimus dorsi muscle (LDM) wrap was obtained by angiography and radioactive scintigraphy. In five patients, the CMS had to be removed due to complications, and in all these patients, their clinical functional status deteriorated following the cessation of cardiomyostimulation.     

A Neuroanatomical Construct for the Amnesic Effects of Propofol

Background: This study was designed to identify neuroanatomical locations of propofol's effects on episodic memory by producing minimal and maximal memory impairment during conscious sedation. Drug-related changes in regional cerebral blood flow (rCBF) were located in comparison with rCBF increases during a simple word memory task.

Methods: Regional cerebral blood flow changes were assessed in 11 healthy volunteers using H215O positron emission tomography (PET) and statistical parametric mapping (SPM99) at 600 and 1,000 ng/ml propofol target concentrations. Study groups were based on final recognition scores of auditory words memorized during PET scanning. rCBF changes during propofol administration were compared with those during the word memory task at baseline.

Results: Nonoverlapping memory effects were evident: low (n = 4; propofol concentration 523 +/- 138 ng/ml; 44 +/- 13% decrement from baseline memory) and high (n = 7; 829 +/- 246 ng/ml; 87 +/- 6% decrement from baseline) groups differed in rCBF reductions primarily in right-sided prefrontal and parietal regions, close to areas activated in the baseline memory task, particularly R dorsolateral prefrontal cortex (Brodmann area 46; x, y, z = 51, 38, 22). The medial temporal lobe region exhibited relative rCBF increases.     

Study of the molecular structure of ethylene-propylene copolymers obtained with catalysts of different composition

The monomer composition and sequence distribution in ethylene-propylene copolymers (EPCs) obtained with supported titanium/magnesium (TMC) and vanadium/magnesium (VMC) catalysts as well as with titanium trichloride was studied by means of ¹³C NMR spectroscopy. Based on these data ethylene-propylene reactivity ratios were determined. The EPCs obtained on these catalysts are inhomogeneous in composition; the soluble fractions contain larger amounts of propylene. The microstructures of copolymers obtained on TMCs and TiCl₃ are similar. For EPCs obtained on VMCs, propylene “head-to-head” or “tail-to-tail” inversions and a more homogeneous distribution of propylene are observed.     

Quantification of tissue plasma volume in the rat by contrast-enhanced magnetic resonance imaging

Magnetic resonance imaging enhanced with a macromolecular contrast medium (MMCM), albumin-Gd-DTPA, was used to estimate the plasma volume in vivo in the myocardium, lung, liver, and skeletal muscle of 10 normal rats. The plasma volumes of the same tissues in a parallel group of six rats were estimated in vitro by a conventional radioisotopic technique (¹¹¹In-transferrin). Plasma volumes of myocardium, lung, liver, and skeletal muscle estimated by the MR technique (μl plas. ia cc-¹ of tissue) were 101,109,163, and 11.0, respectively, while plasma volumes measured by the In-transferrin radioisotope technique (mg plasma g-¹ of tissue) were 78.6, 215,143, and 11-2, respectively. Assuming a ratio of densities of aerated lung to blood of 0.45 and of other tissues to blood of 1.0, correlation between the methods was excellent (R² = 0.99) indicating that MR imaging enhanced with MMCM permits reliable in vivo estimation of tissue plasma volume in the rat.     

Treatment of End-Stage Renal Disease in Central and Eastern Europe: Overview of Current Status and Future Needs

The situation of end-stage renal disease (ESRD) patients in central and eastern Europe was very poor for many years during the so called socialistic era. Economical and political liberation resulted in the significant growth of renal replacement facilities in this region. The number of hemodialysis units increased significantly (56%) during the period 1990–1996, and the number of patients treated with this modality has risen by 75%. More dramatic progress was achieved in peritoneal dialysis. The number of units performing this method of renal replacement therapy (RTT) increased by 277% and the number of patients by more than 300%. Not only quantitative but also qualitative changes were observed. More modern hemodialysis machines installed in the vast majority of units allow for the performance of bicarbonate dialysis, controlled ultrafiltration, and sodium profile modeling. Also, a wider choice of biocompatible dialyzers has become available during the last few years. The number of centers performing renal transplantation has increased significantly, but the number of renal transplants has not followed this progress. Despite all the progress, further development of all RRT methods is necessary to achieve acceptance rates comparable to those observed in developed countries.     

Surface acidic sites on supported titanium-magnesium catalyst for propylene polymerization: ESR study via adsorption of stable nitroxyl radicals

ESR was used for studying the interaction between the stable nitroxyl radical TEMPO (2,2,6,6-tetramethylpyperidin-1-oxyl) and the titanium-magnesium catalysts TiCl₄/MgCl₂ and TiCl₄/MgCl₂ · nD (D is either diisobutyl phthalate or 2,2-diisobutyl-1,3-dimethoxypropane), as well as TiCl₄/MgCl₂ · nD treated with triethylaluminium. In all cases, only part of the surface titanium complexes (18–53 mol-%) exhibit Lewis acid properties and can interact with TEMPO. The portion of titanium complexes with acidic properties depends on the composition and preparation of the catalysts, and it decreases upon treatment with triethylaluminium.     

Integrated photothermal flow cytometry in vivo

The capability of integrated flow cytometry to detect, in real time, moving cells in their natural states in vivo is demonstrated in a study of circulating red and white blood cells in lymph and blood flow of rat mesentery. This system combines dual pump-probe photothermal (PT) techniques, such as PT imaging, the PT thermolens method, and PT velocimetry, with high-resolution (up to 0.3 microm), high-speed (up to 1000 fps) transmission digital microscopy (TDM) and fluorescence imaging. All PT techniques are based on irradiation of cells in rat mesenteric microvessels with a spectrally tunable laser pulse (420 to 570 nm, 8 ns, 0.1 to 300 microJ) and on detection of temperature-dependent variations of the refractive index with a second continuous probe laser beam (633 nm, 1.4 mW). We focus on intravital monitoring of the integral PT response from single, moving, unlabeled cells (from 100 to 500 cells in one measurement). Potential in vivo applications of this new optical tool, called PT flow cytometry (PTFC), are discussed, including identification of selected cells with differences in natural absorptive properties and sizes, determination of laser-induced cell damage, estimation of flow velocity, and monitoring of circulating cells labeled with PT probes.     

Osteogenic differentiation of human bone marrow stromal cells on partially demineralized bone scaffolds in vitro

Tissue engineering has been used to enhance the utility of biomaterials for clinical bone repair by the incorporation of an osteogenic cell source into a scaffold followed by the in vitro promotion of osteogenic differentiation before host implantation. In this study, three-dimensional, partially demineralized bone scaffolds were investigated for their ability to support osteogenic differentiation of human bone marrow stromal cells (BMSCs) in vitro. Dynamic cell seeding resulted in homogeneous cell attachment and infiltration within the matrix and produced significantly higher seeding efficiencies when compared with a conventional static seeding method. Dynamically seeded scaffolds were cultured for 7 and 14 days in the presence of dexamethasone and evaluated on biochemical, molecular, and morphological levels for osteogenic differentiation. Significant elevation in alkaline phosphatase activity was observed versus controls over the 14-day culture, with a transient peak indicative of early mineralization on day 7. On the basis of RT-PCR, dexamethasone-treated samples showed elevations in alkaline phosphatase and osteocalcin expression levels at 7 and 14 days over nontreated controls, while bone sialoprotein was produced only in the presence of dexamethasone at 14 days. Scanning electron microscopy evaluation of dexamethasone-treated samples at 14 days revealed primarily cuboidal cells indicative of mature osteoblasts, in contrast to nontreated controls displaying a majority of cells with a fibroblastic cell morphology. These results demonstrate that partially demineralized bone can be successfully used with human BMSCs to support osteogenic differentiation in vitro. This osseous biomaterial may offer new potential benefits as a tool for clinical bone replacement.