Nanoscale resolution in infrared imaging of protein-containing lipid membranes.

The precise imaging of biomolecular entities contributes to an understanding of the relationship between their structure and function. However, the resolution of conventional infrared microscopic imaging is diffraction limited and does not exceed a few micrometres. Atomic force microscopy, on the other hand, can detect infrared absorption down to the sub-micrometer level. In the present report, we demonstrate that for multi-bilayer lipid samples containing the plant photosynthetic pigment-protein complex LHCII, the resolution of this latter technique can be better than 20 nm. Such a high resolution is attributable to two factors: (i) the relatively high infrared absorption by the complex that is integrated perpendicular to the plane of the multilayer film, and (ii) the distinctly different mechanical properties and thermal conductivity of the lipid and protein components of the sample.

Designing quantum dots for solotronics.

Solotronics, optoelectronics based on solitary dopants, is an emerging field of research and technology reaching the ultimate limit of miniaturization. It aims at exploiting quantum properties of individual ions or defects embedded in a semiconductor matrix. It has already been shown that optical control of a magnetic ion spin is feasible using the carriers confined in a quantum dot. However, a serious obstacle was the quenching of the exciton luminescence by magnetic impurities. Here we show, by photoluminescence studies on thus-far-unexplored individual CdTe dots with a single cobalt ion and CdSe dots with a single manganese ion, that even if energetically allowed, nonradiative exciton recombination through single-magnetic-ion intra-ionic transitions is negligible in such zero-dimensional structures. This opens solotronics for a wide range of as yet unconsidered systems. On the basis of results of our single-spin relaxation experiments and on the material trends, we identify optimal magnetic-ion quantum dot systems for implementation of a single-ion-based spin memory.

Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.

The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence.

TEM characterization of MBE grown CdTe/ZnTe axial nanowires.

CdTe/ZnTe axial nanowires were successfully fabricated by molecular beam epitaxy with the use of Au nano-catalysts and vapour-liquid-solid growth mechanism. Nanowires had zinc-blende structure with numerous stacking faults in the bottom ZnTe part and near perfect crystalline structure in the top CdTe part. Energy dispersive X-ray spectroscopy (EDXS) and lattice fringe spacing analysis revealed nonabrupt nature of hetero-interface, whose width was estimated to be 50-70 nm for the nanowires having a diameter in the range from 40 to 50 nm.

ZnTe-ZnO core-shell radial heterostructures grown by the combination of molecular beam epitaxy and atomic layer deposition.

ZnTe-ZnO core-shell radial heterostructures were grown using a new method of combining molecular beam epitaxy (MBE) and atomic layer deposition (ALD). Zinc telluride nanowires (core) were grown on a GaAs substrate using gold catalyzed vapor-liquid-solid mechanism. An atomic layer deposition technique using diethyl zinc and deionized water as precursors was applied for zinc oxide shell formation. The core-shell ZnTe-ZnO heterostructures thus obtained were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and photoluminescence measurements.

Zn(1-x)Mg(x)Te nanowires grown by solid source molecular beam epitaxy.

This paper reports on the epitaxial growth of single-crystalline ternary Zn(1-x)Mg(x)Te nanowires covering a broad compositional range of molar fraction 0≤x≤0.75. The nanowires were grown on (100), (110), and (111) GaAs substrates using a vapor-liquid-solid mechanism. Solid source molecular beam epitaxy and an Au-based nanocatalyst were used for these purposes. The composition of nanowires can be adjusted by changing the ratio of Mg to Zn molecular beam fluxes. Electron microscopy images show that the nanowires are smooth and slightly tapered. The diameters of the obtained nanowires are from 30 to 70 nm and their length is around 1 µm. X-ray diffraction analysis and transmission electron microscopy reveal that the nanowires have a zinc-blende structure throughout the whole range of obtained compositions, and have a [Formula: see text] growth axis. The Raman measurements reveal both the expected splitting and shift of phonon lines with increasing Mg content, thus proving the substitutional incorporation of Mg into metallic sites of the ZnTe lattice.

Transient hyperglycemia in ischemic stroke patients.

The aim of the study was to investigate glucose derangement and its short- and long-term prognostic significance in nondiabetic ischemic stroke patients. The study involved 262 consecutive patients, mean age: 70.1+/-12.4 years, with a supratentorial ischemic stroke. The following data were collected: patients characteristics, risk factors, comorbidities, and stroke severity assessed by the Scandinavian Stroke Scale (SSS). Serum glucose levels were measured on admission, on the next, 2nd, 3rd, 5th, 7th and 14th day after stroke onset. The outcome measures on day 30 were mortality and capacity to perform daily activities: the Barthel Index and Rankin Scale. The 1-year survival was estimated by the Kaplan-Meier method. Cox proportional hazards regression was used to assess predictors of 1-year mortality in nondiabetics. Diabetes mellitus was found in 24.8% of patients and transient hyperglycemia in 36.3% of patients. Patients with transient hyperglycemia scored lower on SSS in the subsequent days of assessment than patients with either diabetes mellitus or normoglycemia. They had larger ischemic lesions on computer tomography (CT) than diabetics and had higher 30-day mortality than normoglycemics (p<0.05). One-year mortality was similar in transient hyperglycemics and diabetics, and both were significantly higher than in normoglycemics (p<0.05). A proportional hazards model analysis showed that transient hyperglycemia is not an independent predictor of death within a year after stroke.

[Diagnostic difficulties with differentiating noninfectious diseases with coexisting cerebrospinal fluid changes--personal observations from the Department of Infectious Diseases, Jagiellonian University in Cracow]. / Trudnosci diagnostyczne w rozpoznawaniu schorzen niezakaznych przebiegajacych ze zmianami w plynie mózgowo-rdzeniowym--obserwacje wlasne z Kliniki Chorób Zakaznych Collegium Medicum Uniwersytetu Jagiellonskiego w Krakowie.

We present two cases of women admitted to our department with suspicion of meningitis. They were transferred from Neurology Unit. CSF changes found in both cases were not of infectious origin. Authors pay attention to diagnostic difficulties in such cases.

Immunohistochemical localization of gap junction protein channels in hamster sinoatrial node in correlation with electrophysiologic mapping of the pacemaker region.

INTRODUCTION: Gap junction proteins are thought to form the low resistance pathways that connect neighboring cells within the sinoatrial node, and to mediate pacemaker synchronization. METHODS AND RESULTS: We have carried out microelectrode mapping experiments of the hamster sinoatrial region to localize the primary pacemaker area for subsequent light, electron, and immunofluorescence microscopic studies aimed at testing the hypothesis that the major cardiac gap junction protein (connexin43) is present in such an area. The site of earliest activation is unifocal and the pattern of activation, obtained by multiple sequential microelectrode recordings of the sinoatrial region, is qualitatively similar to that previously described for other species. However, quantitatively, the impulse transmission time from the primary pacemaker area to the crista (sulcus) terminalis in the hamster sinoatrial node is about 50% briefer than that of the guinea pig and five times faster than that of the rabbit. Immunolocalization studies in the hamster sinoatrial node using anti-connexin43 antisera demonstrated specific staining at the areas of cell-to-cell apposition and suggested that the apparently high degree of electrical coupling in this tissue is the result of abundant connexin43 expression. The immunofluorescence data were supported by light microscopic studies, which demonstrated the typical morphologic characteristics of sinus nodal cells in the pacemaker area. In addition, an electron microscopic study of the sinoatrial region revealed the presence of gap junctions in the junctional complex at areas of cell-to-cell contact. CONCLUSION: Our results demonstrate that cells in the sinoatrial region of the hamster heart are electrically well coupled and strongly suggest that such coupling is mediated by gap junctional channels formed by connexin43.

Gap junctional channels in adult mammalian sinus nodal cells. Immunolocalization and electrophysiology.

The subcellular mechanism of cell-to-cell communication in the natural pacemaker region of the mammalian heart was studied using electrophysiological and immunofluorescence techniques in isolated pairs of rabbit sinus nodal cells. By measuring whole-cell currents using a double patch-clamp approach, it was demonstrated that communication in the sinus node is mediated through gap junctional channels similar to those in other types of adult cardiac cell pairs. Macroscopic sinus nodal junctional resistance had a mean value of 387.9 +/- 97.1 M omega (mean +/- SEM, n = 10) and was greatly increased by superfusion with alkanols. Single-channel junctional conductance could be resolved in three cell pairs. Given their high membrane resistance (1.16 +/- 0.32 G omega, n = 12), the electrical coupling provided by as few as three gap junctional channels between nodal cells will allow for pacemaker synchronization. Further evidence for the presence of the channels was obtained from immunofluorescent double-labeling of desmin and the gap junction protein (connexin43) in sinus nodal tissue as well as in cultured sinus nodal cells. Using antisera against residues 243-257 of the connexin43 protein, a specific staining at the site of cell-to-cell apposition was demonstrated. These data provide direct evidence in favor of electronic coupling as the means for achieving pacemaker synchronization in the rabbit sinus node.

Immunolocalization and expression of functional and nonfunctional cell-to-cell channels from wild-type and mutant rat heart connexin43 cDNA.

The carboxyl terminal cytoplasmic domain of distinct gap junction proteins may play an important role in assembly of functional channels as well as differential responsiveness to pH, voltage, and intracellular second messengers. Oligonucleotide-directed site-specific mutagenesis in a paired Xenopus laevis oocyte expression system was used to examine the expression of mRNAs encoding wild-type and carboxyl terminal mutant connexin43 (Cx43) proteins. Oocytes were stripped, injected with mRNA or distilled water (dH2O), preincubated for 16-20 hours, and then paired for 5-10 hours; this process was followed by electrophysiological recording using the dual voltage-clamp technique. Initial experiments compared the relative junctional conductances (Gjs) in oocyte pairs expressing Cx43 (382 amino acid residues) and two truncated mutants lacking most or a portion of the cytoplasmic carboxyl terminal. The shortest mutant (M241) contained 240 amino acid residues and was devoid of all phosphorylatable serine residues in the cytoplasmic tail; its length approximated the length of liver connexin26. The longest mutant (M257) tested contained 256 amino acid residues, including two serine residues. Oocyte pairs expressing M241 yielded a Gj similar to that of oocytes injected with dH2O, whereas M257 yielded a Gj similar to that of oocytes injected with Cx43. Immunoprecipitation studies showed that Cx43, M257, and M241 proteins were readily detectable in oocytes injected with their respective mRNAs, indicating that the lack of Gj observed with the M241 mRNA was not due to reduced translation. Immunocytochemical studies revealed that wild-type and both truncated mutants were localized to the area of cell-to-cell contact between the paired oocytes, indicating that protein targeting to the membrane was not inhibited in oocytes injected with M241 mRNA. Oocyte pairs expressing mutants in which serine residues were replaced with nonphosphorylatable amino acids (serine codon No. 255 AGC was converted to GCC, alanine, designated as M255S----A, and serine codon No. 244 AGC was converted to GGC, glycine, designated as M244S----G) showed Gjs similar to M257, indicating that these serine residues and, by inference, their phosphorylation state are not critical for expression of functional channels. The importance of the length of the carboxyl terminus was assessed by comparing the Gjs in a series of mutants that were intermediate in length between M257 and M241. Gradual shortening of the carboxyl terminus produced a gradual reduction of Gj relative to M257. However, simple deletion of amino acid residues 241-257 from the wild-type Cx43 did not affect Gj relative to M257.(ABSTRACT TRUNCATED AT 400 WORDS)

[Cytoprotective action of guanylate cyclase stimulators on human leukocytes]. / Cytoprotekcyjne dzialanie stymulatorów cyklazy guanylowej na ludzkie leukocyty.

An original experimental model has been presented for studying of cytoprotection of non-stimulated leukocytes. The model consists in determining of a degree of inhibition of the release of lactic acid dehydrogenase (LDH) by isolated human neutrophils (PMNs) in the course of their "ageing" at the room temperature (22 degrees C). Using this model for the first time, cytoprotective action was pointed-out of following compounds: NO (EDRF) in aqueous solution; natrium nitroprusside; active metabolite of molsidomine--SIN-1; N-acetyl-S-nitroso-penicillamine (SNAP) which are believed to owe their anti-platelet and vasodilatory activity to stimulation of cyclic-GMP--and iloprost (a stable prostacyclin analogue) and prostaglandin E2 (PGE2) which activate cyclic AMP. Effectiveness of cytoprotective action of these compounds increased as follows: NO (IC50 = 58.4) less than PGE2 (IC50 = 38) less than SIN-1 (IC50 = 9.2) less than SNAP (IC50 = 3.2) less than natrium nitroprusside (IC50 = 1.2) less than iloprost (IC50 = 0.2)(nmoles/5 x 10(6) PMNs; moreover, iloprost and SIN-1 showed a synergic action. Among ++nitroso-vasodilators, nitroglycerin had no cytoprotective action; it may indicate that to achieve cytoprotection in leukocytes a nitro- vasodilator should contain in its chemical structure -NO group and not -NO3 group, as it is in nitroglycerin. In neutrophils stimulated with calcium ionophore, arachidonic acid or FMLP, nitro-vasodilators are of no influence on production of superoxide anions O2-, hydroxyeicosatetraenoic acids (5-HETE and 12-HETE) and leukotriene B4. A hypothesis has been put forward on the relationship of function of c-GMP and c-AMP in the mechanism of cytoprotection of human leukocytes.

Interaction between NO donors and iloprost in human vascular smooth muscle, platelets, and leukocytes.

Endothelium-derived relaxing factor (EDRF) and donors of nitric oxide (NO) (glyceryl trinitrate, SIN-1--a metabolite of molsidomine--S-nitroso-N-acetyl-penicillamine, and sodium nitroprusside) but not prostacyclin and its analog, iloprost, relax strips of rabbit aorta. Strips of human coronary artery also relax when exposed to NO donors and prostacyclin; in this artery, SIN-1 and iloprost exert additive but not synergistic relaxant action. In mildly activated human platelets and leukocytes, SIN-1 and iloprost have a synergistic suppressive action. A similar synergistic thrombolytic effect between NO and prostacyclin was observed in whole rabbit blood in interactions with rabbit aortic endothelium. These findings suggest that because of this cell-selective synergism between NO donors and prostacyclin analogs, the concomitant use of molsidomine and iloprost for the treatment of ischemic heart and peripheral vascular disease should be attempted.