Formation of sphalerite (ZnS) deposits in natural biofilms of sulfate-reducing bacteria.

Abundant, micrometer-scale, spherical aggregates of 2- to 5-nanometer-diameter sphalerite (ZnS) particles formed within natural biofilms dominated by relatively aerotolerant sulfate-reducing bacteria of the family Desulfobacteriaceae. The biofilm zinc concentration is about 10(6) times that of associated groundwater (0.09 to 1.1 parts per million zinc). Sphalerite also concentrates arsenic (0.01 weight %) and selenium (0.004 weight %). The almost monomineralic product results from buffering of sulfide concentrations at low values by sphalerite precipitation. These results show how microbes control metal concentrations in groundwater- and wetland-based remediation systems and suggest biological routes for formation of some low-temperature ZnS deposits.

Gadolinium in human glioblastoma cells for gadolinium neutron capture therapy.

157Gd is a potential agent for neutron capture cancer therapy (GdNCT). We directly observed the microdistribution of Gd in cultured human glioblastoma cells exposed to Gd-diethylenetriaminepentaacetic acid (Gd-DTPA). We demonstrated, with three independent techniques, that Gd-DTPA penetrates the plasma membrane, and we observed no deleterious effect on cell survival. A systematic microchemical analysis revealed a higher Gd accumulation in cell nuclei compared with cytoplasm. This is significant for prospective GdNCT because the proximity of Gd to DNA increases the cell-killing potential of the short-range, high-energy electrons emitted during the neutron capture reaction. We also exposed Gd-containing cells to thermal neutrons and demonstrated the GdNC reaction effectiveness in inducing cell death. These results in vitro stimulated in vivo Gd-DTPA uptake studies, currently underway, in human glioblastoma patients.

Time-resolved fluorescence of S-100a protein in the absence and presence of calcium and phospholipids.

We have used phase-modulation fluorescence lifetime measurements to study the single Trp residue of the Ca(2+)-binding protein S-100a. Trp fluorescence decay was not exponential for the protein irrespective of the absence or presence of Ca2+. Fluorescence decay was best described by Lorentzian lifetime distributions centered around two components (approx. 3 and 0.7 ns) for protein in absence of Ca2+ and one component (approx. 2.9 ns) for the protein in presence of 2 mM Ca2+. Similar studies were performed with S-100a interacting with cardiolipin, phosphatidylserine or egg phosphatidylcholine, both in absence and in presence of 2 mM Ca2+. Our data suggest that the conformation of the protein and its Ca(2+)-binding properties vary depending on the characteristics of charge and structure of phospholipids.

A new human hemoglobin variant: Hb BARI (alpha 2 45 (CD3) His leads to Gln beta 2).

An alpha-chain variant hemoglobin was found in the hemolysate of a 21-year-old healthy male living in Bari (Puglia, Italy). Structural studies demonstrated a previously unreported amino acid substitution, alpha 2 45 (CD3) His leads to Gln beta 2, involving a distal heme contact. The new variant has been named Hb Bari. Its electrophoretic behavior was the same as for Hb A; it was stable to both isopropanol and heat denaturation and exhibited normal functional properties, with respect to whole blood and stripped hemolysate studies. The level of Hb Bari was about 20% in the observed carrier. No relative was available for further investigations.

Fibrinogen plasma levels as a marker of thrombin activation in diabetes.

This study attempted to verify the existence of a correlation between fibrinogen, a major cardiovascular risk factor in diabetes, and indexes of thrombin generation and action, prothrombin fragment 1 + 2 (F1 + 2), and D-dimer (D-D), in a group of diabetic subjects compared with a matched control group. Forty insulin-dependent diabetes mellitus patients and 30 matched healthy control subjects participated in this study. The subjects were tested for the following parameters: fibrinogen, prothrombin F1 + 2, D-D, fasting glycemia, and HbA1c. In addition, 5 diabetic subjects who maintained stable fibrinogen plasma levels > 300 mg/dl for at least 6 months before the study were treated with 12,500 U/day subcutaneous heparin for 7 days. Diabetic subjects showed increased levels of fibrinogen, prothrombin F1 + 2, and D-D plasma levels. Simple linear regression analysis detected a positive correlation between fibrinogen and prothrombin F1 + 2, D-D, and glycosylated HbA1c. In the five diabetic subjects treated with heparin fibrinogen, prothrombin F1 + 2 and D-D levels decreased at the end of the treatment. All these parameters returned to baseline after 7 days of washout. These data indicate that fibrinogen plasma levels are correlated to parameters of thrombin activation in plasma in diabetic patients and suggest that high fibrinogen plasma levels might be a risk marker for cardiovascular disease in diabetes because it is an expression of an existing thrombophilia.

UV-ozone ashing of cells and tissues for spatially resolved trace element analysis.

UV/ozone ashing of thin tissue sections and cell cultures is a simple technique to enhance relative elemental concentrations, while maintaining their spatial location at the sub-micron level. This approach may enhance the capability of spatially resolved analysis techniques to detect the distribution of trace elements in biological matrices. We present results from light microscopy and x-ray spectromicroscopy studies of tissues and cells demonstrating that the micro-structure is very well conserved. We show the signal enhancement resulting from the removal of carbon, which allows otherwise undetectable gadolinium to be mapped in cancer tissue for a novel neutron capture therapy.

Aluminium in rat cerebellar neural cultures.

A systematic microchemical analysis of unstained and uncoated neurone cultures was performed with synchrotron radiation photoemission spectromicroscopy after exposure to an aluminium solution. Clear evidence was found for localized aluminium uptake in a few cells. Their possible identification based on morphology is discussed.

Aluminium in rat cerebellar primary cultures: glial cells and GABAergic neurones.

Experimental evidence of the preferential uptake of aluminium by GABAergic neurones and glial cells was provided by synchrotron spectromicroscopy studies. We observed rat cerebellar cultures enriched for GABAergic neurones or glial cells exposed to aluminium ions, detecting the presence and identifying the chemical status of aluminium on cell structures.

Neurone decapping characterization by atomic force microscopy: a topological systematic analysis.

We tested a new approach to cell decapping on rat cerebellar neurones, and observed its effects on cell topography by atomic force microscopy (AFM). The results clearly demonstrate the effectiveness of our decapping approach, and also the ability of AFM to reveal fine details of the decapped cells. Specifically, varying the conditions and duration of the decapping process modifies the extent of the decapping. Such a method can be used to investigate the cytoplasm with surface sensitive techniques.

Metal uptake in neurone cultures: a systematic study.

We present the first comparative study of the uptake of metal ions by neurons, performed for Zn, Cr, Co, Mo, Al, Ni, Mn and Cd. The study reveals substantial differences in the uptake of different metals, under similar exposure procedures. In particular, we found very large uptakes for aluminium and molybdenum. We also found significant effects of excitatory substances, in particular kainate, as stimulants of uptake of some of the metals.

High sensitivity quantitative analysis of cobalt uptake in rat cerebellar granule cells with and without excitatory amino acids.

We quantified the effect of the excitatory amino acids kainate and glutamate on the uptake of cobalt in primary rat cerebellar granule neurons, by using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). We quantitatively demonstrated that Co2+ uptake, although enhanced by glutamate and kainate also takes place in the absence of excitatory amino acids. We also found that cobalt uptake is not significantly altered by the presence of glutamate receptor competitive or noncompetitive antagonists, indicating that cobalt uptake in granule neurons does not require glutamate receptor stimulation. Our results suggest, therefore, that Co2+ may enter the cell by passive diffusion through the plasma membrane.

Abscisic acid-induced microheterogeneity in phospholipid vesicles. A fluorescence study.

Changes in the thermal behavior of DMPC (dimyristoyl-L-phosphatidylcholine) and an equimolar mixture of DMPC and DMPE (dimyristoyl-L-phosphatidylethanolamine) induced by the plant hormone abscisic acid (ABA) have been investigated using fluorescent probes. The fluorescence decay of the hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in these vesicles has been measured using frequency-domain fluorometry, and has been analyzed using both models of discrete exponential components and continuous lifetime distributions. In the DMPC vesicles, using the distributional approach, higher center and width values were observed in the presence of abscisic acid (ABA), indicating a decrease in the dielectric constant of the lipid phase that we attribute to a decrease in the water concentration within the bilayer. Moreover, the presence of ABA in the liposomes increased the phospholipid phase transition temperature. The addition of ABA to the DMPC/DMPE mixture strongly increased the microheterogeneity of the system as reported by the FWHM (full-width at half-maximum) of the distributional approach.

Alterations in erythrocyte membrane lipids induced by low doses of ionizing radiation as revealed by 1,6-diphenyl-1,3,5-hexatriene fluorescence lifetime.

Damage in membrane lipids induced by low doses of ionizing radiation in the presence of oxygen has been detected in rabbit erythrocyte ghosts labelled with 1,6-diphenyl-1,3,5-hexatriene (DPH). Multifrequency phase and modulation fluorometry was used to measure DPH fluorescence lifetime. This technique is particularly suited for the observation of heterogeneous fluorescence decays. DPH decay in erythrocyte membranes is described by a two-component continuous distribution of lifetimes. The value of the distribution width of the long-lived component is found to be affected by radiation-induced membrane lipid damage at doses as low as 0.5 Gy, well within the dose range used to measure cell survival. The width of the DPH lifetime distribution decreases when the ghosts are irradiated in the presence of oxygen. Such a decrease is a linear function of the logarithm of the dose. After a dose of 110 Gy and above, the fractional intensity of the short-lived component of the DPH decay increases linearly, indicating severe membrane damage. Experiments performed in the absence of oxygen do not show any change in the fluorescence parameters up to a dose of 550 Gy. The molecular identification of the produced damage has not been accomplished, but the necessity of oxygen to observe the damage suggests that hydroperoxides and lipids crosslinks are produced.

Charging phenomena in PEEM imaging and spectroscopy.

Spectromicroscopy with the imaging technique of X-ray photoelectron emission microscopy (X-PEEM) is a microchemical analytical tool installed in many synchrotron radiation laboratories, and which is finding application in diverse fields of research. The method of sample analysis, X-ray absorption spectroscopy, does not encounter the same problems as X-ray photoemission spectroscopy when sample charging occurs, hence even good insulators may often be analyzed without any apparent artifacts in images or spectra. We show, however, that charging effects cannot be neglected. We model the effect of surface charge formation on the secondary electron yield from uniform samples to demonstrate that surface charge primarily reduces the yield of electrons which may contribute to the detected signal. We illustrate that on non-uniform insulating samples, localized centers of charge may substantially affect microscope imaging and resolution as the electrostatic field close to the surface is distorted. Finally, in certain circumstances non-uniform surface charge may lead to unexpected lineshapes in X-ray absorption spectra causing, in some extreme cases, negative spectra. These negative spectra are explained, and several strategies are reviewed to minimize the impact of sample charging when analyzing poorly conducting samples of any nature.

[Transfusion risks and alternatives to transfusion]. / Rischi trasfusionali e alternative alla trasfusione.

The emergence of the acquired immunodeficiency syndrome (AIDS) has fueled concerns of both physicians and their patients about safety of blood transfusions. Although AIDS has generated the most fear, the risk today is extremely remote (1/60.000 units of blood). The risk of transmitting infectious disease by homologous transfusion is decreasing, as more donor screening and testing measures are implemented. The blood supply is safer that at any time, but small transfusion risks exist. The most common problems associated with transfusions are temporary: one in 100-300 recipients will experience fever or rash. The biggest problem is a mismatch of the well-known ABO blood groups and once in every 100-400.000 transfusions the hemolytic reaction is fatal. Viral hepatitis is another serious and important risk. At present hepatitis seems to strike between 1 and 3 percent of transfusion recipients. Most, if not all, of transfusion-associated hepatitis cases are caused by hepatitis C virus. Cytomegalovirus can cause primary infection, reactivation or reinfection by transfusion. Immunosuppressed patients are more likely to develop more severe disease. Epstein-Barr virus does not seem to cause significant post-transfusion disease. Bacterial or protozoal infections are an infrequently encountered adverse effect of transfusion. However, some clinical cases document the potential hazard of blood components as a vector for bacteria or protozoa. Homologous blood transfusion down-regulates some immune functions. Host defences against malignancy and infection may in some instances be severely compromised by transfusions of homologous blood.(ABSTRACT TRUNCATED AT 250 WORDS)