Increasing signal-to-noise ratio in over-determined Mueller matrices

This work investigates how the signal-to-noise ratio (SNR) of an over-determined Mueller matrix can be improved by changing the method of calculation. Specifically, our investigation focused on comparing SNRs achieved using the vector methodology from the field of partial Mueller polarimetry, and the matrix methodology. We use experimentally derived measurements from an investigation into the time-varying signal produced by the Mueller matrix of an electro-optic Bismuth Silicon Oxide (BSO) crystal undergoing cyclical impact of a Helium plasma ionisation wave. Our findings show that the vector methodology is superior to the matrix methodology, with a maximum SNR of 7.54 versus 4.97. We put forth that the superiority of the vector methodology is due to its greater flexibility, which results in the Mueller matrix being calculated with better condition matrices, and higher levels of SNR in the intensity measurements used for calculation.

Optimizing Mueller polarimetry in noisy systems through over-determination

Mueller polarimetry measurements are increasingly being used to image highly dynamic and short-lived phenomena such as plasma discharges. For phenomena such as these, exposure times below 1 µs must be used. Unfortunately, these low exposure times significantly reduce the signal-to-noise ratio, making accurate and consistent measurements difficult. To overcome this limitation, we investigated increasing the number of Stokes vectors produced from a polarization state analyzer and polarization state generator, a process known as over-determination. To conduct our analysis, we used results from physical experiments using Stokes vectors generated by liquid crystal variable retarders. These results were then verified using data from simulations. First, we conclude that increasing the degree of over-determination is a simple and effective way of dealing with this noise; however, we also convey that choosing the best scheme is not an entirely trivial process. Second, we demonstrate that over-determination gives rise to hitherto inaccessible information that allows for the quantification of statistical noise and, crucially, the pinpointing of the origin of systematic error, a highly beneficial process that has been lacking until now.

Sphenopalatine Ganglion Stimulation to Augment Cerebral Blood Flow

Background and Purpose—

Many patients with acute ischemic stroke are not eligible for thrombolysis or mechanical reperfusion therapies due to contraindications, inaccessible vascular occlusions, late presentation, or large infarct core. Sphenopalatine ganglion (SPG) stimulation to enhance collateral flow and stabilize the blood-brain barrier offers an alternative, potentially more widely deliverable, therapy.

Methods—

In a randomized, sham-controlled, double-masked trial at 41 centers in 7 countries, patients with anterior circulation ischemic stroke not treated with reperfusion therapies within 24 hours of onset were randomly allocated to active SPG stimulation or sham control. The primary efficacy outcome was improvement beyond expectations on the modified Rankin Scale of global disability at 90 days (sliding dichotomy), assessed in the modified intention-to-treat population. The initial planned sample size was 660 patients, but the trial was stopped early when technical improvements in device placement occurred, so that analysis of accumulated experience could be conducted to inform a successor trial.

Results—

Among 303 enrolled patients, 253 received at least one active SPG or sham stimulation, constituting the modified intention-to-treat population (153 SPG stimulation and 100 sham control). Age was median 73 years (interquartile range, 64–79), 52.6% were female, deficit severity on the National Institutes of Health Stroke Scale was median 11 (interquartile range, 9–15), and time from last known well median 18.6 hours (interquartile range, 14.5–22.5). For the primary outcome, improved 3-month disability beyond expectations, rates in the SPG versus sham treatment groups were 49.7% versus 40.0%; odds ratio, 1.48 (95% CI, 0.89–2.47); P =0.13. A significant treatment interaction with stroke location (cortical versus noncortical) was noted, P =0.04. In the 87 patients with confirmed cortical involvement, rates of improvement beyond expectations were 50.0% versus 27.0%; odds ratio, 2.70 (95% CI, 1.08–6.73); P =0.03. Similar response patterns were observed for all prespecified secondary efficacy outcomes. No differences in mortality or serious adverse event safety end points were observed.

Conclusions—

SPG stimulation within 24 hours of onset is safe in acute ischemic stroke. SPG stimulation was not shown to statistically significantly improve 3-month disability above expectations, though favorable outcomes were nominally higher with SPG stimulation. Beneficial effects may distinctively be conferred in patients with confirmed cortical involvement. The results of this study need to be confirmed in a larger pivotal study.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03767192.

Effect of blend moisture and extrusion temperature on physical properties of everlasting pea-wheat extrudates

The effect of everlasting pea in combination with wheat on physical properties and microstructure of extrudates were studied. The share of everlasting pea (Lathyrus sativus) was variable, at 35, 50 and 65 %, respectively. The everlasting pea-wheat mixtures were moistened to the required level (18, 21, and 24 %), homogenized, conditioned and extruded in twin-screw extruder with counter-rotating conical screws. All of the obtained extrudates were characterised by a slow degree of radial expansion and high specific density. The Pearson correlation analysis indicated a statistically significant linear Pearson correlation (p < 0.05) between chemical compositions of the blends and physical properties of the extrudates. The expansion ratio increased as the concentration of the fibers and proteins increased, while specific density and hardness decreased. Inverse relationship was observed for crude fat. The microstructure of the extrudates was determined by both the moisture of the blend and the process temperature. The differences observed in the size, number of air cells and in the cell wall shapes and thickness indicate possibilities of the modification of physical properties of everlasting pea-wheat extrudates. The extrudates produced from everlasting pea-wheat blends (50:50) at higher barrel temperature (110/140/180/170/130 °C) were characterised by more numerous air cells of smaller diameters. Increasing moisture content of extruded blends results in extrudates with a higher porosity. No significant effect was shown in the chemical compositions on the level of metal contamination in the extrudates. The application of a counter-rotating twin-screw extrusion-cooker in the study permitted the production of compact, hard everlasting pea-wheat extrudates for use in vegetarian lunch dishes.

Are there differences between rural and urban populations in long-term outcome after systemic cerebral thrombolysis in a hospital located in an agricultural region?

INTRODUCTION

It is generally considered that rural hospitals have a much lower capacity to adequately care for patients with acute ischemic stroke (AIS). Analysis of the demographic and logistic factors affecting the outcome of intravenous (IV) thrombolysis in patients with AIS in a rural hospital are presented.

METHODS

The observational study included 300 patients with AIS who were consecutively treated with IV thrombolysis. Long-term outcome and hemorrhagic complication rate in patients from rural and urban populations were compared.

RESULTS

A total of 60.7% of patients were transported from rural areas. In the rural patients thrombolytic therapy at night was performed less frequently compared to that for urban patients (p=0.01). There were no differences in frequency of treatment between rural and urban patients treated with IV thrombolysis on weekends and on working days (p=0.47). In rural patients mortality was higher (p=0.04). The presence of hemorrhagic transformation (HT) (p=0.87) and of symptomatic intra-cerebral hemorrhage (SICH) (p=0.61) were similar in both groups. A multivariate analysis showed no impact of place of onset on favorable outcome after 3 months (p=0.9), on the presence of (SICH) (p=0.43) or on mortality rate (p=0.69).

CONCLUSIONS

Patients from rural areas are less likely to be treated with IV thrombolysis during the night. Rural and urban patients treated in the hospital located in the agricultural region had a similar efficacy and safety profile of thrombolytic treatment.

Note: Measuring breakdown characteristics during the hot re-ignition of high intensity discharge lamps using high frequency alternating current voltage

To investigate the cold and hot re-ignition properties of High Intensity Discharge (HID) lamps in more detail an automated setup was designed in such a way that HID lamps of various sizes and under different background pressures can be tested. The HID lamps are ignited with a ramped sinusoidal voltage signal with frequencies between 60 and 220 kHz and with amplitude up to 7.5 kV. Some initial results of voltage and current measurements on a commercially available HID lamp during hot and cold re-ignition are presented.

[Intravenous thrombolysis patients with acute ischemic stroke: the analysis of the 100 cases. Part I. Characteristic of the patients and effectiveness of treatment]

BACKGROUND

Intravenous thrombolytic therapy with recombinant tissue activator (rt-PA) in treating acute ischemic stroke is effective and safe in the time window 4.5 hours after symptom onset.

MATERIAL AND METHODS

In the study group of patients demographic and logistic data and vascular risk factors were analysed. We also analysed status of the patients at the moment of admission, after 24 hours, one month and 3 months after symptom onset according to National Institutes of Health Stroke Scale (NIHSS) and results of treatment after 3 months according to modified Rankin Score (mRS). We compared the selective variables with data from the register SITS.

RESULTS

Between September 2006 and April 2009 in the stroke unit in Sandomierz 807 patients with ischemic stroke were treated, including 100 patients (aged 42-88, mean 69.74 +/- 9.85; 55% of men) treated with rt-PA (12.39%). In 22% of patients treated rt-PA large and medium vessel disease, in 47%--cardiogenic embolism, in 4%--small vessel disease, in 3%-- other unusual causes and in 24%--infarct multiple etiology were diagnosed. The average time from the onset of the disease to the beginning of the treatment was 148.25 +/- 38.77 min. (in SITS centers--145 min.). At the moment of admission the average neurological conditions in NIHSS 12.03 +/- 4.94 (SITS--12); after 24 hours--8.51 +/- 6.09; after 7 days--6.51 +/- 6.38; after one month--4.27 +/- 5.15 and after 3 months--2.95 +/- 3.36 were evaluated. The results according to mRS were respectively: after 7 days--2.80 +/- 1.77; after 1 month--2.37 +/- 2.00 and after 3 months 2.16 +/- 2.16(SITS--2.5). After 3 months 53% of patients were functionally independent (SITS--53%), 29%--had moderate or severe disability (-32%) and 18%--died (-15%).

CONCLUSIONS

In analysed time in stroke unit in Sandomierz the percentage of patients with acute ischemic stroke treated with rt-PA was high. The presentation of results of intravenous thrombolysis in patients with acute ischemic stroke performed in different centers makes the important aspect of evaluation of the effectiveness and safety of this therapy.

[Intravenous thrombolysis patients with acute ischemic stroke--the analysis of the 100 cases. Part II. Neuroimaging, the analysis of hemorrhagic complications and deaths]

INTRODUCTION

Computed tomography (CT) remains the basic diagnostic examination in patients with ischaemic stroke. The main purpose of CT examination is distinguishing between hemorrhagic and ischemic stroke, exclusion of other diseases and revealing early ischemic radiological changes.

MATERIAL AND METHODS

The results of baseline CT scans and CT performed on 2nd and 7th days after symptom onset, in terms of patients' long-term outcome, presence of serious adverse events and deaths within 3 months were analyzed.

RESULTS

The analysis included 100 patients treated with rt-PA in stroke unit from September 2006 to April 2009. More than one third of patients had normal baseline CT, in one third--old ischemic changes and in one third--early ischemic changes were revealed. After 3 months the patients who had early changes in baseline CT, and those who had extensive ischemic changes in the area of MCA (middle cerebral artery) or ICA (internal carotid artery) had the worst clinical status. In this group deaths appeared most often (in a subgroup with ischemic signs in the whole territory of MCA, p < 0.01 and in a group of patients with stroke in the ICA territory, p < 0.001), similarly to a group of patients with old changes in baseline CT (34.3% died; p < 0.001) and a group with cerebral edema in control CT (32.4%; p < 0.01). Hemorrhagic transformation appeared in 18% of patients. In this group of patients we found higher risk of death within 3 months after stroke onset(p < 0.001).

CONCLUSIONS

The imaging examinations are very important in process of qualification of patients for thrombolytic treatment. Safety of intravenous thrombolysis in patients with ischemic stroke depends on the detailed analyses of the CT scans.

Self-evaluation in dialysis patients

Objective

The aim of this study is to present the results of a self-reported evaluation of the psychoemotional status by dialysis patients. The level of self-esteem influences the emotions felt, both positive and negative, which in turn may determine the adherence to treatment instructions, and which certainly is reflected in the somatic condition.

Material and methods

The study was a randomized controlled trial using a sample of 102 fully informed and consenting patients with end-stage renal disease and 102 people from the general population. The survey instrument used was a Self-Esteem inventory.

Results

The results show that there were differences between the dialysis patients and the general population concerning Physical Self-Esteem and Acting/Task Self-Esteem. The patients scored significantly lower than the healthy subjects lower on both subscales. No differences were noted between the two groups of subjects regarding of Social Self-Esteem and emotional Self-Esteem. The results also show that the level of self-esteem in dialyzed patients under the age 50 years was higher than in those above 50 regarding the sociability, sense of humor, memory, and the sense of being accepted by others.

Conclusion

We conclude that there are differences in the self-reported level of self-esteem between dialyzed patients and the general population. The patients' age also factors in the self-reported assessment.

Quality of life in thalassemia: a comparison of SF-36 results from the thalassemia longitudinal cohort to reported literature and the US norms

Thalassemia is a chronic, inherited blood disorder, which, in its most severe form, causes life-threatening anemia. Advances in treatment have led to increased life expectancy however the need for chronic blood transfusions and chelation therapy remains a significant burden for patients. Our study compared health related quality of life (HRQOL) from the Thalassemia Clinical Research Network's (TCRNs) Thalassemia Longitudinal Cohort (TLC) study to US norms and assessed association with clinical variables. There were 264 patients over age 14 who completed the Medical Outcomes Study 36-Item Short Form Health Survey version 2 (SF36v2) baseline assessment. When compared to US norms, TLC patients had statistically significant (P < 0.05) worse HRQOL on five of the eight subscales (physical functioning, role-physical, general health, social functioning, and role-emotional) and on both summary scales (physical component summary and mental component summary). Women, older patients, and those with more disease complications and side effects from chelation reported lower HRQOL. In general, adolescents and adults with thalassemia report worse HRQOL than the US population, despite contemporary therapy. The SF-36 should become a standard instrument for assessing HRQOL in thalassemia to determine predictors of low HRQOL which may be better addressed by a multidisciplinary team.

Sequential translocation of tyrosine kinases Lyn and Syk to the activated Fcgamma receptors during phagocytosis

Tyrosine phosphorylation of numerous proteins is one of the earliest events detectable during Fcgamma receptor-mediated phagocytosis. We demonstrate that IgG-coated particles associated with the surface of macrophages are enriched with numerous tyrosine-phosphorylated proteins. During particle internalization the proteins are still associated with particles but their phosphorylation is reduced. Lyn kinase is phosphorylated both at particle binding and internalization steps. The phosphorylated Syk kinase is the major kinase associated with engulfed particles. Imnunofluorescent studies confirm spatial and temporal distribution of Lyn and Syk kinases at different stages of phagocytosis. Our data indicate that ligation of Fcgamma receptors activates Lyn followed by Syk kinase and in the result multimolecular complex of the kinases and several accompanying tyrosine phosphorylated proteins with Fcgamma receptors is organized leading to local reorganization of actin-based skeleton and particle uptake.

The clustered Fcgamma receptor II is recruited to Lyn-containing membrane domains and undergoes phosphorylation in a cholesterol-dependent manner

Phosphorylation of clustered Fcgamma receptor II (FcgammaRII) by Src family tyrosine kinases is the earliest event in the receptor signaling cascade. However, the molecular mechanisms for the interaction between FcgammaRII and these kinases are not elucidated. To asses this problem we isolated high molecular weight complexes of cross-linked FcgammaRII from non-ionic detergent lysates of U937 monocytic cells. CD55, a glycosylphosphatidylinositol-anchored protein, a ganglioside GM1 and Lyn, a Src family tyrosine kinase, were also located in these complexes. Gradient centrifugation demonstrated that the complexes containing cross-linked FcgammaRII displayed a low buoyant density. The FcgammaRII present in the complexes underwent tyrosine phosphorylation. Cross-linked FcgammaRII and Lyn occupied common 100-200 nm detergent-resistant membrane fragments, as demonstrated by immunoprecipitation and microscopy studies. Pretreatment of the cells with beta-cyclodextrin, a cholesterol acceptor, depleted membrane cholesterol and released CD55, GM1 and Lyn from the detergent-resistant complexes. In parallel, the association of Lyn with cross-linked FcgammaRII was disrupted and phosphorylation of the receptor inhibited. Reincorporation of cholesterol evoked the relocation of Lyn into the detergent-resistant membrane fraction and restored both Lyn association with cross-linked FcgammaRII and tyrosine phosphorylation of the receptor. Our data demonstrate that cholesterol-enriched membrane rafts can facilitate tyrosine phosphorylation of clustered FcgammaRII by Lyn kinase.

Syk kinase, tyrosine-phosphorylated proteins and actin filaments accumulate at forming phagosomes during Fcgamma receptor-mediated phagocytosis

Phagocytosis mediated by Fcgamma receptors (FcgammaRs) is thought to be regulated by a cascade of tyrosine phosphorylation events that finally leads to the rearrangement of submembranous actin-based cytoskeleton and internalization of particles. Suggestions concerning the functional relationship between protein tyrosine kinases, their substrates, and actin filament reorganization prompted us to determine cellular distribution of these elements during uptake of IgG-coated particles in murine thio-macrophages. We found that the onset of uptake of the particles was accompanied by tyrosine phosphorylation of several proteins, among which 90, 50, 40, 30, and 25 kDa polypeptides were distinguished. In most of the proteins the tyrosine hyperphosphorylation persisted up to 3 min of the uptake; however, kinetics of the phosphorylation of individual proteins varied. Immunofluorescence data showed that the phosphotyrosine-bearing proteins were localized in regions of the particle uptake, being concentrated at phagocytic cups and nascent phagosomes. The local enrichment in tyrosine phosphorylated proteins was correlated with accumulation of actin filaments at these early stages of phagosome formation. During phagosome maturation, both tyrosine phosphorylated proteins and microfilaments disappeared from the periphagosomal regions. Syk, one of the tyrosine kinases, was translocated to the regions where FcgammaR-mediated phagocytosis had started. On the contrary, no enrichment in phosphatidylinositol 3-kinase was detected in these places.

Local accumulation of alpha-spectrin-related protein under plasma membrane during capping and phagocytosis in Acanthamoeba

During capping and phagocytosis the interaction between cluster cell surface receptors and the submembraneous actin-based skeleton may be mediated by spectrin-like proteins. To test this possibility we examined the localization of an alpha-spectrin immunoanalogue, that had been previously identified in whole extracts of Acanthamoeba, during capping of Con A receptors and during phagocytosis of Con A-coated yeast. During capping alpha-spectrin and filamentous actin co-migrated with the Con A receptors and accumulated in the region of cap formation, as demonstrated by double immunofluorescence studies. Immunoelectron microscopy revealed submembraneous location of alpha-spectrin in cells exposed to Con A, both at the time of initial cross-linking and during accumulation of alpha-spectrin in the region of the cap. Phagocytosis studies showed that alpha-spectrin and actin filaments were concentrated around phagocytic cups that enclosed ConA-coated yeast upon internalization. The proteins also surrounded nascent phagosomes present in the vicinity of the plasma membrane but were absent at the later time point of phagosome maturation. These data demonstrate a correlation between clustering of cell surface receptors and submembraneous localization of alpha-spectrin, suggesting an involvement of spectrin-like proteins in mediating the interaction of receptor clusters with the actin cytoskeleton.

Tyrosine phosphorylation/dephosphorylation controls capping of Fcgamma receptor II in U937 cells

In the capping of cell-surface receptors two stages can be distinguished: 1) clustering of the receptors (patching) induced by cross-linking with specific antibodies and 2) subsequent assembly of patches into a cap which is driven by the actin-based cytoskeleton. We found that patching of Fcgamma receptor II in U937 cells was correlated with tyrosine phosphorylation of certain proteins, most prominently those of 130, 110, 75 and 28 kDa. The phosphotyrosine-bearing proteins were accumulated at the receptor patches. Formation of the receptor caps was coincident with dephosphorylation of these proteins. Inhibition of protein tyrosine kinases with herbimycin A and genistein attenuated the protein tyrosine hyperphosphorylation and blocked capping in a dose-dependent manner. Phenylarsine oxide and pervanadate, inhibitors of protein tyrosine phosphatases, also suppressed capping of Fcgamma receptor II in a concentration-dependent fashion. Simultaneously, tyrosine hyperphosphorylation of proteins occurred. In the presence of the tyrosine kinase and phosphatase inhibitors the receptors were arrested at the patching stage. In contrast, okadaic acid, a serine/threonine phosphatase blocker, did not affect assembly of the receptor caps. The inhibitory effect of phenylarsine oxide was rapidly reversed by dithiols, 2,3-dimercapto-1-propanoldithiol and dithiotreitol, and was coincident with dephosphorylation of protein tyrosine residues. Extensive washing of pervanadate-exposed cells also resulted in progressive restoration of the cap assembly. Using streptolysin O-permeabilized cells we confirmed regulatory function played by dephosphorylation of tyrosine residues in capping of Fcgamma receptor II. Exogenous phosphatases, applied to permeabilized cells in which activity of endogenous tyrosine phosphatases was blocked, evoked dephosphorylation of protein tyrosine residues that was accompanied by recovery of capping ability in the cells.

The role of cholesterol and sphigomyelin in tyrosine phosphorylation of proteins and capping of Fcgamma receptor II

Cross-linking of cell surface receptors by multivalent ligands, e.g. by antibodies, evokes their clustering -- patching. Subsequently, these clusters can be translocated by the acto-myosin machinery toward one pole of the cell and assembly cap. Patching of FcgammaRII in U937 cells correlates with tyrosine phosphorylation of several proteins while cap assembly correlates with their dephosphorylation. To study the mechanism of activation of tyrosine kinases during FcgammaRII activation we disturbed the organization of the putative plasma membrane microdomains by depletion of membrane cholesterol and sphingomyelin. Cholesterol was removed with the use of beta-cyclodextrin while sphingomyelin was decomposed by exogenous sphingomyelinase. Cyclodextrin at 5-10 mM removed about 70% of cholesterol from the cells and abolished the assembly of FcgammaRII caps thereby arresting the receptors at the patching stage. Similarly, 70 mU/ml sphingomyelinase inhibited cap formation by 60%. Cholesterol and sphingomyelin depletion also suppressed the tyrosine phosphorylation of proteins which accompanied cross-linking of FcgammaRII. The observations indicate that cholesterol and sphingomyelin can control the interactions of tyrosine kinases with clustered FcgammaRII.

Engagement of spectrin and actin in capping of FcgammaRII revealed by studies on permeabilized U937 cells

Plasma membrane receptors can undergo translocation in the plane of plasma membrane after binding of polyvalent ligands. Ligand/receptor clusters, named patches, can collect into a polar cap, presumably due to their association with the submembrane actin-based cytoskeleton. We found that the assembly of Fcgamma receptor II caps in human monocytic U937 cells was accompanied by the accumulation of spectrin and actin in the cap region. Permeabilization of cells with streptolysin O rendered capping sensitive to inhibition by phalloidin, an actin filament stabilizing agent. A rabbit antibody directed against the chicken erythrocyte alpha-subunit of spectrin, an actin- and membrane-binding protein, also blocked the capping in a dose dependent manner. The inhibition reached approximately 50% after 20 minutes of cell treatment with the antibody. Anti-alpha-spectrin targeted specifically its submembrane antigen, in contrast to unspecific antibodies which remained dispersed in the cell interior and had no influence on the cap assembly. Our results indicate an active engagement of spectrin and actin filaments in the capping of Fcgamma receptor II.

Signaling pathways in phagocytosis

Phagocytosis is an uptake of large particles governed by the actin-based cytoskeleton. Binding of particles to specific cell surface receptors is the first step of phagocytosis. In higher Eucaryota, the receptors able to mediate phagocytosis are expressed almost exclusively in macrophages, neutrophils, and monocytes, conferring immunodefence properties to these cells. Receptor clustering is thought to occur upon particle binding, that in turn generates a phagocytic signal. Several pathways of phagocytic signal transduction have been identified, including the activation of tyrosine kinases and (or) serine/threonine kinase C in pivotal roles. Kinase activation leads to phosphorylation of the receptors and other proteins, recruited at the sites of phagocytosis. Monomeric GTPases of the Rho and ARF families are likely to be engaged downstream of activated receptors. The GTPases, in cooperation with phosphatidylinositol 4-phosphate 5-kinase and phosphatidylinositol 3-kinase lipid modifying enzymes, can modulate locally the assembly of the submembranous actin filament system leading to particle internalization.

The role of cholesterol and sphigomyelin in tyrosine phosphorylation of proteins and capping of Fcgamma receptor II

Cross-linking of cell surface receptors by multivalent ligands, e.g. by antibodies, evokes their clustering -- patching. Subsequently, these clusters can be translocated by the acto-myosin machinery toward one pole of the cell and assembly cap. Patching of FcgammaRII in U937 cells correlates with tyrosine phosphorylation of several proteins while cap assembly correlates with their dephosphorylation. To study the mechanism of activation of tyrosine kinases during FcgammaRII activation we disturbed the organization of the putative plasma membrane microdomains by depletion of membrane cholesterol and sphingomyelin. Cholesterol was removed with the use of beta-cyclodextrin while sphingomyelin was decomposed by exogenous sphingomyelinase. Cyclodextrin at 5-10 mM removed about 70% of cholesterol from the cells and abolished the assembly of FcgammaRII caps thereby arresting the receptors at the patching stage. Similarly, 70 mU/ml sphingomyelinase inhibited cap formation by 60%. Cholesterol and sphingomyelin depletion also suppressed the tyrosine phosphorylation of proteins which accompanied cross-linking of FcgammaRII. The observations indicate that cholesterol and sphingomyelin can control the interactions of tyrosine kinases with clustered FcgammaRII.

Tyrosine phosphorylation and Fcgamma receptor-mediated phagocytosis

Phagocytosis of IgG-opsonized particulate material in hematopoietic cells is mediated by Fcgamma receptors (FcgammaRs). Interaction of the receptors with Fc domains of IgG triggers transduction of phagocytic signal in which a key role is played by phosphorylation of tyrosine residues of the receptors. These residues are arranged into a specific motif (immunoreceptor tyrosine-based activation motif; ITAM) which is located either in the cytoplasmic part of FcgammaRIIA or in gamma chains associated with FcgammaRI and FcgammaRIIIA. The conserved tyrosine residues are phosphorylated by, and associate with, tyrosine kinases of Src and Syk families. Coordinated action of these components initiates numerous intracellular events leading finally to local rearrangement of the actin-based cytoskeleton and internalization of the particles.

Interaction of annexins IV and VI with phosphatidylserine in the presence of Ca2+: monolayer and proteolytic study

Annexins, Ca2+- and phospholipid-binding proteins are known to bind to artificial and biological membranes in a calcium-dependent manner. However, the precise mechanism of the annexin-membrane interactions still remains to be studied in detail. In this paper we describe the results of studies on the interactions of the annexin/Ca complexes with phospholipids, obtained by the Wilhelmy balance method of assessing the surface pressure of a phospholipid monolayer. We show that the annexin IV/Ca as well as annexin VI/Ca complexes significantly reduce the surface pressure of a phosphatidylserine monolayer, when its initial value is close to collapse pressure. The effect is highly specific for monolayers composed of phosphatidylserine and strongly sensitive to pH and ionic strength. The most pronounced changes have been observed at pH 7.0-7.5, at a protein/Ca molar ratio of 1:2 for annexin IV and 1:4 for annexin VI. In the presence of sodium chloride at concentrations exceeding 400mM this effect was almost completely abolished. The obtained results point to the mainly electrostatic character of the annexin/phosphatidylserine interactions. In addition, using large multilamellar lipid vesicles and serine proteases, we demonstrate that annexins, when bound in a ternary complex with phospholipids and calcium ions, are partially protected against proteolysis. Our observation that annexin molecules, complexed with calcium ions, are protected against proteolytic attack in the presence of PS liposomes does not have to be necessarily explained in terms of partial penetration of protein within the membrane bilayer.

Phagocytosis occurs in Acanthamoeba castellanii after electroporation

Acanthamoeba cells treated with an electric discharge were porated and their cytoplasm became accessible to exogenous molecules. Over a broad range of electric field densities low molecular weight markers (trypan blue, ruthenium red), normally unable to penetrate a plasma membrane, gained access to cytoplasm of 80-90% of the cells. Macromolecules (albumin-FITC and IgG-FITC) penetrated into 63-86% of the cells when electroporation was carried out over the range of 1500V/25 microF-400V/250 microF. Pulse labeling with fluorescent markers evidenced that even 3 hrs. after an electric pulse the plasma membrane was still permeable to exogenous fluorescent probes. Following this stage, the pores were gradually closed. The cells electroporated at 400 V/250 microF were able to ingest yeast particles. The uptake of the particles seems to be an active process since it was inhibited by azide and phalloidin. Therefore, the electroporation of Acanthamoeba makes possible the introduction of macromolecules into the cells and subsequent analysis of their effect on active motile processes such as phagocytosis. This should greatly facilitate characterization of the mechanisms by which such processes do occur.

The effect of annexin IV and VI on the fluidity of phosphatidylserine/phosphatidylcholine bilayers studied with the use of 5-deoxylstearate spin label

An effect of annexin IV and VI on the fluidity of phosphatidylserine/phosphatidylcholine (PS/PC) membranes was studied by spin labeling technique with the use of 5-doxylstearic acid. It was found that calcium ions at micromolar concentrations induced a marked decrease in the order parameter of PS/PC membranes. This effect was completely abolished by both annexins. The influence of annexins on the mobility of fatty acid chains in the studied region in PE/PC membranes was insignificant.

Annexins IV (p32) and VI (p68) interact with erythrocyte membrane in a calcium-dependent manner

Purification of annexin IV and VI from porcine liver was achieved by Mono Q ion exchange chromatography at pH 8.9 and pH 7.5, respectively. The isolated proteins interacted with erythrocyte membrane as function of calcium ion and the protein concentration. Half-maximal binding of annexin VI to erythrocyte membrane was found to occur at 8 microM Ca2+. The maximal binding was estimated as 2 micrograms of annexin VI per 1 microgram or erythrocyte membrane protein, in the presence of 100 microM Ca2+. The property of erythrocyte membrane to interact with annexins was utilized in preparation of a affinity-column with polyacrylamide-immobilized erythrocyte membrane.

Actin-binding proteins involved in the capping of epidermal growth factor receptors in A431 cells

A capping process of epidermal growth factor receptors (EGF-Rs) was used for the study of the relation between the receptors and the actin-binding proteins (spectrin, vinculin, annexin I) that may be involved in EGF-R-cytoskeleton interaction. In intact, adherent A431 cells, EGF-Rs were diffusively distributed on the cell surface. Spectrin, vinculin, and annexin I were located beneath the plasma membrane. An abundance of EGF-Rs as well as submembrane proteins was observed in regions of membrane ruffles and cell-cell contacts. Annexin I was localized also in cytoplasm being attached to filamentous structures surrounding the nucleus and extending to the cell periphery. Under polyvalent ligand treatment, EGF-Rs of adherent cells were aggregated on one side of the cell. Spectrin, vinculin, and annexin I dislocated together with EGF-Rs and were concentrated under plasma membrane at regions where cap formation took place. In suspended A431 cells only spectrin was located under the plasma membrane whereas annexin I and vinculin were diffusively distributed through the cells. During cap formation only spectrin was colocalized with EGF-Rs. The results confirmed the major role of spectrin as a receptor-microfilament linking protein.

Identification and purification of calpactins from cardiac muscle and their effect on Na+/Ca2+ exchange activity

Calpactins were purified from bovine cardiac muscle by a slightly modified Glenney et al. procedure (J. Cell. Biol. 104, 503-511, 1987). Two major proteins (apparent MW of 36 and 68 kDa) able to bind phospholipids in a Ca2(+)-dependent manner were identified. These proteins completely reversed the inhibition of Na+/Ca2+ exchange activity of cardiac sarcolemmal vesicles consequent to EGTA-treatment. A modulation of cardiac Na+/Ca2+ exchange activity by calpactins is suggested.

Alpha-spectrin immunoanalog in Acanthamoeba cells

A monospecific, affinity purified antibody was prepared against chicken erythrocyte alpha-spectrin. The antibody cross-reacted with only one high molecular weight polypeptide (235 kDa) from whole Acanthamoeba cells. The localization of alpha-spectrin-related antigen in Acanthamoeba cells was examined using immunofluorescence and postembedding cytochemical techniques. Three patterns of distribution of alpha-spectrin immunoanalog were distinguished: as submembranous layer, cytoplasmic aggregates and uniform dispersion through the cytoplasm. Immunoelectron microscopic studies showed that the colloidal gold label was located in the cytoplasm in the vicinity of the plasma membrane. The gold particles were also aggregated around unidentified cytoplasmic filamentous structures. The presence of spectrin-related protein in protozoan cells of Acanthamoeba is in accordance with previous assumptions of the widespread occurrence of spectrin-related proteins. The heterogenous distribution of the immunoanalog of alpha-spectrin protein in Acanthamoeba cells is discussed.

A comparative study: perfusion of the micro- and macrocirculation as a function of the hematocrit value

The fluidity (the inverse of viscosity) of red blood cell (RBC) suspensions in vivo was estimated by means of microcirculatory measurements such as RBC flow velocity, micropressure in arterioles and venules, and vessel geometry, and by means of simultaneous macrocirculatory measurements such as volume flow and perfusion pressure in the whole organ. These in vivo data were compared to in vitro data obtained by viscometry. The experiments were performed on the isolated rat mesentery perfused with a nonaggregating and an aggregating suspension: Human RBC were either suspended in Ringer's or Ficoll 400 solution. The tissue was perfused at various perfusion pressures and hematocrit values. The microcirculatory perfusion was recorded by means of microscopy using a video TV system. Five major results have been identified: First, microfluidities calculated from velocity data in capillaries of the mesenteric membrane were almost identical to the fluidities calculated from macroflow data (volume flow rates and perfusion pressure in the whole organ). Second, in vivo fluidities of both suspensions decrease with increasing hematocrit value but seem to be independent of driving pressure between 4 and 10 kPa. Third, the fluidity of the Ficoll suspensions is lower than the fluidity of the Ringer's suspensions by the same ratio as the continuous phases. Fourth, the in vivo fluidities of the Ringer's suspensions and the Ficoll suspensions for hematocrit values from 20 to 70% and a range of wall shear stresses from 0.6 to 1 Pa were higher than those measured in vitro. Finally, it has been quantified that an increasing number of vessels became stagnant (that is packed by red blood cells) at high hematocrit values, low perfusion pressure, and increased aggregability of RBC.

Polyamine metabolism in Acanthamoeba: polyamine content and synthesis of ornithine, putrescine, and diaminopropane

Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff). These included in order of decreasing abundance: 1,3-diaminopropane, spermidine, spermine, norspermidine, and putrescine. Only diaminopropane and norspermidine had been found previously. Spermine was present in cultures grown in broth, but not in defined medium. Radioactive substrates were used to establish that putrescine was synthesized by decarboxylation of ornithine, ornithine was synthesized from arginine or citrulline, and diaminopropane was synthesized from spermidine. The presence of ornithine decarboxylase (EC 4.1.1.17), arginase (EC 3.5.3.1), and urease (EC 3.5.1.5) and the absence of arginine decarboxylase (EC 4.1.1.19) were established. A scheme for polyamine biosynthesis in A. castellanii is proposed.

Subplasmalemmal calcium-binding microregions in Acanthamoeba

Acanthamoeba cells, fixed with glutaraldehyde supplemented with calcium ions, show Ca-dependent, electron-dense deposits (CaDD) at the cytoplasmic surface of the plasma membrane. The formation of CaDD is stimulated by pre-incubation and fixation of the cells in the presence of ATP. Chemical analysis of the trichloroacetic acid extracts of CaDD-containing cells demonstrates that adenosine monophosphate, pyrophosphate and inorganic phosphate are probably the compounds involved in the formation of CaDD. Treatment of CaDD-containing cells with exogenous phosphatase evokes the disappearance of electron-dense material and a fine fibrillar network can be observed inside the ‘empty’ CaDD. The ability to restore CaDD in the presence of calcium ions with either pyrophosphate or orthophosphate confirms the suggestion that calcium/phosphate salts may be deposited in special subplasmalemmal calcium-binding microregions.

Displacement of cell-surface associated calcium inhibits phagocytosis and Ca-ATPase activity in amoeba

Displacement of calcium from the cell surface region was observed in cells treated with either chlorpromazine or reserpine with chlorotetracycline being used as a calcium-fluorescent probe. The drugs also significantly inhibit the intensity of phagocytosis and Ca-ATPase activity. The possible role of Ca associated with the cell surface region in regulation of both phagocytosis and Ca-ATPase was discussed.

Correlation between potassium and phosphorus content and their nonuniform distribution in Acanthamoeba castellanii

Biologically important elements: K, Na, Mg, Ca, Cl, P, and S were analyzed in Acanthamoeba castellanii. A higher potassium content, as compared with other cations, was detected. Total content of the cation-forming elements: K, Na, Mg, and Ca was ca. 360 mmoles/kg dry weight of the cells. Phosphorus content was estimated as 492 mmoles/kg dry weight. Content of chlorine, a basic cellular anion, was 173 mmoles/kg dry weight. The low level of chlorine appears not the be sufficient to balance all the cations in Acanthamoeba. Distribution of potassium in Acanthamoeba cells was nonuniform and similar to that of phosphorus as shown by X-ray microanalysis technique. Quantitative correlation between phosphorus and potassium as well as the similar distribution of these elements suggests that in Acanthamoeba phosphorus is an essential anion which, being nonuniformly distributed in the cell, determines also a nonuniform distribution of potassium.

Capillary resistance to flow of hardened (diamide treated)red blood cells (RBC)

Pressure-flow curves for control and hardened (diamide treated) human RBC's were obtained in capillaries of the isolated rat mesentery, in order to evaluate resistance to flow of hardened RBC's. Blood vessels were maximally dilated by an infusion of 10(-5) mol/l acetylcholine and isoprenaline and perfused with freshly collected human RBC's as well as with RBC's hardened by a treatment (hct 40%; pH 8.0; 37 degree C) with 0.5 mmol/l or 1.5 mmol/l diamide, respectively, suspended in Albumin (0.05%) - Ringer solution. The mesentery was perfused via a hydrostatic pressure reservoir. Arterio-venous pressure difference was varied from 4-10 kPa, and corresponding arteriolo-venular pressure gradients changed from about 200-500 Pa/mm. No significant difference in resistance to flow was observed between control and diamide treated cells over the whole pressure range. However, the flow through the microvascular bed was inhomogeneous upon perfusion with diamide treated cells, caused by a deceleration and stoppage of the cells at capillary narrowing (ratio of cell to vessel diameter greater than 2). The time of stagnation increased with decreasing pressure gradient.

Growth phase dependent alterations in the surface coat of Acanthamoeba castellanii

Application of ruthenium red, cationized ferritin and concanavalin A to exponentially growing trophozoites reveals on their plasma membrane negatively charged surface coat bearing sugar residues. In the coat of trophozoites from advanced stationary growth phase no sugar residues can be visualized. In mature cysts the external layer of their wall is negatively charged, however, on their protoplast surface no terminals reacting with the 2 polycations, or with concanavalin A can be revealed, even though the penetration of the reagents has been ensured by enzymatic impairing of the cyst wall. The results are confronted with the known facts concerning alterations of physiological properties of plasma membrane occurring during the life cycle of Acanthamoeba.

A RNA helix-destabilizing protein is a major component of Artemia salina nuclear ribonucleoproteins

A major component of 30S heterogeneous nuclear ribonucleoprotein (hnRNP) particles from Artemia salina is HD40, a protein that has been characterized as a RNA helix-destabilizing protein [Marvil, D. K., Nowak, L. & Szer, W. (1980) J. Biol. Chem. 255, 6466-6472; Nowak, L., Marvil, D. K., Thomas, J. O., Boublik, M. & Szer, W. (1980) J. Biol. Chem. 255, 6473-6478]. HD40 binds to and disrupts the secondary structure of nuclear RNA fragments isolated from 30S hnRNP with a stoichiometry of one protein per 10-12 nucleotides. The addition of HD40 in excess of this ratio results in the formation of bead-like HD4-nuclear RNA complexes that are similar in properties and appearance to native 30S hnRNP particles. The heterogeneous nuclear RNA (hnRNA) in the HD40-hnRNA complexes is unstacked and unfolded to about the same extent as the RNA in the native 30S hnRNP particles. HD40 is strikingly similar in molecular weight (40,000) and amino acid composition (no cysteine, high glycine, presence of dimethylarginine, and blocked NH2 terminus) to eukaryotic hnRNP proteins isolated from many cell types. HD40 can be separated into three isoelectric species with basic pIs, which appears to be posttranslational modifications of a single polypeptide chain.

Heterogenous distribution of potassium and phosphorus in Acanthamoeba castellanii

Using x-ray microanalysis technique the distribution of potassium, phosphorus and sulphur was analysed in Acanthamoeba castellanii cells. Distribution of potassium was nonuniform; the high level of the element was observed in the cortex region of these cells. Distribution of phosphorus was shown to be similar to that of potassium, whereas sulphur was rather uniformly distributed.

Developmental changes in the localization of calcium binding sites in Acanthamoeba castellanii

Vegetative cells of Acanthamoeba castellanii have the ability to bind calcium on the plasma membrane in form of the electron-dense deposits. The appearance of the deposits depends on the age of Acanthamoeba culture. In 24-h-old culture the deposits are very small, with diameter of 26 nm. During aging of culture, at both logarithmic and stationary growth phases, the diameter of deposits is larger (70-80 nm), while the deposits are localized only on the plasma membrane. During differentiation of Acanthamoeba cells into cysts electron-dense deposits with a diameter of about 170 nm appear in the mitochondria, whereas no deposits are observed on the plasma membrane. However, at the first stage of differentiation electron-dense material together with extruded membraneous fragments are also observed outside of some newly-formed young cysts. These results suggest that in Acanthamoeba cells, depending on the stage of life cycle, either plasma membrane or mitochondria may be involved in storage of excess cellular calcium.

Visualization of calcium-binding sites at plasma membrane of shock-frozen Acanthamoeba cells

Electron-dense deposits appear at the protoplasmic side of plasma membrane in Acanthamoeba log-phase cells when fixed either with glutaraldehyde or formaldehyde supplemented with Ca2+. Similar deposits appear when the cells are preloaded with Ca2+ and thereafter shock-frozen and prepared for electron microscopic examination by freeze-substitution technique. This suggests that their formation reflects the presence of a physiologically active system involved in capturing excess of inflowing calcium.

Calcium content and distribution in egg vesicles of Galleria mellonella (Lepidoptera) as determined by X-ray microanalysis

In egg vesicles of Galleria mellonella (Lepidoptera) electron microprobe analysis reveals calcium in concentrations of 9 and 3 mmoles per 1,000 g tissue wet weight in oocyters and accompanying trophic cells, respectively. This high average level of calcium characterizes both pre- and postvitellogenic oocytes, but the distribution of calcium is not uniform. In postvitellogenic vesicles the central area of the ooplasm shows a higher content of Ca than peripheral one, what may be correlated with the distribution of mature yolk platelets within the ooplasm.

Effect of a membrane-stabilizing compound on calcium binding to the plasma membrane of Acanthamoeba castellanii

Binding of calcium ions at the plasma membrane was studied in Acanthamoeba cells pretreated with ZIMET 3164, a benzimidazole nitrogen mustard derivative, which is known to show a potent immunosuppressive action combined with a membrane-stabilizing effect in mice. For reference, 2 compounds were applied: ZIMET 3393 (Cytostasan¿), another benzimidazole mustard derivative, which exerts only a moderate membrane effect and acts as a strong cytostatic, and ZIMET 176/68, a barbituric acid derivative, which acts as an inhibitor of humoral immune responses but without membrane-stabilizing effect. Application of any of the 3 compounds does not reduce the appearance of calcium binding sites, visualized by means of ultracytochemical reaction, notwithstanding their different action in the mammalian organism. On the contrary, it was estimated by morphometric analysis that the number of Ca-dependent deposits was augmented after treatment with low doses of any of the 3 compounds, what seems to be connected with the induced metabolic disturbances in low molecular phosphates level. High doses and/or prolongation of treatment of the cells resulted in diminution of the number of deposits and induces profound disturbances in cell ultrastructure, probably due to the toxic action of the applied doses. In these cases, band-like structures crosslinking the two leaflets of the plasma membrane may be observed; it is suggested that they represent integral membrane proteins.