Correlation of Radiation Dose Estimates by DIC with the METREPOL Hematological Classes of Disease Severity.

The degree of severity of hematologic acute radiation syndrome (HARS) may vary across the range of radiation doses, such that dose alone may be a less reliable predictor of clinical course. We sought to elucidate the relationship between absorbed dose and risk of clinically relevant HARS in humans. We used the database SEARCH (System for Evaluation and Archiving of Radiation Accidents based on Case Histories), which contains the histories of radiation accident victims. From 153 cases we extracted data on dose estimates using the dicentric assay to measure individual biological dosimetry. The data were analyzed according to the corresponding hematological response categories of clinical significance (H1-4). These categories are derived from the medical treatment protocols for radiation accident victims (METREPOL) and represent the clinical outcome of HARS based on severity categories ranging from 1-4. In addition, the category H0 represents a post-exposure hematological response that is within the normal range for nonexposed individuals. Age at exposure, gender and ethnicity were considered as potential confounders in unconditional cumulative logistic regression analysis. In most cases, victims were Caucasian (82.4%) and male (92.8%), who originated from either the Chernobyl (69.3%) or Goiânia (10.5%) accident, and nearly 60% were aged 20-40 years at time of exposure. All individuals were whole-body exposed (mean 3.8 Gy, stdev ±3.1), and single exposures were predominantly reported (79%). Seventy percent of victims in category H0 were exposed to ≤1 Gy, with rapidly decreasing proportions of H0 seen at doses up to 5 Gy. There were few HARS H4 cases reported at exposed dose of 1-2 Gy, while 82% of H4 cases received doses of >5 Gy. HARS H1-3 cases varied among dose ranges from 1-5 Gy. In summary, single whole-body radiation doses <1 Gy and >5 Gy corresponded in general with H0 and H3-4, respectively, and this was consistent with medical expectations. This underlines the usefulness of dose estimates for HARS prediction. However, whole-body doses between 1-5 Gy poorly corresponded to HARS H1-3. The dose range of 1-5 Gy was of limited value for medical decision-making regarding, e.g., hospitalization for H2-3, but not H1 and treatment decisions that differ between H1-3. Also, there were some H0 cases at high doses and H2-4 cases at low doses, thereby challenging an individual recommendation based solely on dose.

Correlated hybridization in transition-metal complexes.

We apply local orbital basis density functional theory (using SIESTA) coupled with a mapping to the Anderson impurity model to estimate the Coulomb assisted or correlated hybridization between transition-metal orbitals and ligand orbitals for a number of molecular complexes. We find remarkably high values which can have several physical implications including (i) renormalization of effective single-band or multiband Hubbard model parameters for the cuprates and, potentially, elemental iron, and (ii) spin polarizing molecular transistors.

A minimal model for stabilization of biomolecules by hydrocarbon cross-linking.

Programmed cell death regulating protein motifs play an essential role in the development of an organism, its immune response, and disease-related cellular mechanisms. Among those motifs the BH3 domain of the BCL-2 family is found to be of crucial importance. Recent experiments showed how the isolated, otherwise unstructured BH3 peptide can be modified by a hydrocarbon linkage to regain function. We parametrized a reduced, dynamic model for the stability effects of such covalent cross-linking and confirmed that the model reproduces the reinforcement of the structural stability of the BH3 motif by cross-linking. We show that an analytically solvable model for thermostability around the native state is not capable of reproducing the stabilization effect. This points to the crucial importance of the peptide dynamics and the fluctuations neglected in the analytic model for the cross-linking system to function properly. This conclusion is supported by a thorough analysis of a simulated Go model. The resulting model is suitable for rational design of generic cross-linking systems in silicio.

Optical conductivity of wet DNA.

Motivated by recent experiments, we study the optical conductivity of DNA in its natural environment containing water molecules and counterions. Our density functional theory calculations (using Siesta) for four base pair B-DNA with order 250 surrounding water molecules suggest a thermally activated doping of the DNA by water states which generically leads to an electronic contribution to low-frequency absorption. The main contributions to the doping result from water near DNA ends, breaks, or nicks and are thus potentially associated with temporal or structural defects in the DNA.

Effects of reconstituted high-density lipoprotein in persistent gram-negative bacteremia.

Reconstituted high-density lipoproteins (rHDL) have been shown bind bacterial LPS and reduce its toxic effects. Since the effect of rHDL on LPS in vitro cannot be directly extrapolated to the in-vivo picture of Gram-negative septic shock, we have investigated the effects of rHDL in a rabbit model of Gram-negative bacteremia. Rabbits were anesthetized, ventilated, and invasively monitored for 6 hours. Escherichia coli (4 x 10(9) CFU/kg) were infused over 2 hours in rabbits given rHDL (75 mg/kg) before the bacterial challenge. Antibiotics were not used in this model. The bacterial infusion resulted in a bacteremia that persisted until the end of the study. The sepsis-induced TNF peak was significantly lowered by rHDL treatment (10 +/- 3 ng/mL in rHDL treated versus 33 +/- 5 in controls, P = 0.001). Blood pressure, although not statistically significant, tended to be higher in the rHDL group. Acidosis was significantly attenuated up to 3 hours after the beginning of the bacterial challenge (7.39 +/- 0.05 versus 7.27 +/- 0.05 in controls, P = 0.041). rHDL treatment produced some transient beneficial effects in this model of persistent Gram-negative bacteremia. Additional studies, investigating the effects of rHDL in combination with antibiotics, are warranted.

Phosphatidic acid activation of protein kinase C in LA-N-1 neuroblastoma cells.

Phosphatidic acid (PA), a hydrolytic product of phospholipase D activity, stimulated cytosolic protein kinase C (PKC) activity when LA-N-1 neuroblastoma cells in culture were treated with PA, without translocating the enzyme to the membrane. Treatment of cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) translocated and activated PKC in a dogmatic manner. Partially purified PKC activity derived from LA-N-1 neuroblastoma cells was stimulated by PA alone or in the presence of phosphatidylserine or TPA, without affecting [3H]phorbol dibutyrate binding, indicating that the site of action of PA was different from the phorbol ester or diacylglycerol binding site. These results suggest an unorthodox pattern of PKC stimulation mediated by PA which appears to be yet another mode of PA signal transduction.

Protective effects of reconstituted high-density lipoprotein in rabbit gram-negative bacteremia models.

Reconstituted high-density lipoproteins (rHDLs) have the ability to bind bacterial lipopolysaccharide and to reduce its endotoxin activity in vitro and in vivo. The aim of the present studies was to investigate the therapeutic potential of rHDL in bacteremia models. Gram-negative sepsis was induced in anesthetized rabbits by intravenous infusion of Escherichia coli organisms (4 x 10(9) CFU/kg infused over 2 hours) and treated with appropriate antibiotics. rHDL or placebo was infused either before (prophylaxis) or 1 hour after (therapy) the beginning of the bacterial challenge. In the control groups, the bacterial challenge resulted in transient bacteremia, high plasma levels of lipopolysaccharide, secretion of TNF, and symptoms of sepsis, including hypotension and acidosis. rHDL had no influence on blood bacterial counts; however, plasma lipopolysaccharide levels were significantly reduced. Peak plasma TNF concentrations were reduced after prophylactic but not after therapeutic rHDL administration. Both prophylactic and therapeutic rHDL improved clinical outcome: acidosis was significantly attenuated and blood pressure tended to be higher in the rHDL groups. No effects of rHDL were seen in a similar model of gram-positive sepsis induced by the infusion of Staphylococcus aureus.

Reconstituted high-density lipoprotein reduces LPS-stimulated TNF alpha.

Reconstituted high-density lipoprotein (rHDL), an artificial lipoprotein consisting of apolipoprotein A-I and phosphatidylcholine (1:150, molar ratios) dose-dependently reduces lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF) production in in vitro, ex-vivo, and in-vivo model systems. In an in-vitro whole blood assay, rHDL (1 mg/ml) added concomitantly with LPS increased cellular resistence to LPS stimulation approximately 1000-fold. Even with extremely high levels of LPS (10 micrograms/ml), rHDL > or = 0.5 mg/ml caused > 50% decrease in TNF production. Preincubation of rHDL with LPS was not required for activity. rHDL (> or = 1 mg/ml) reduced TNF production by 50% even when added to cultures 2 hr after their stimulation with LPS (10 micrograms/ml). In an ex-vivo study, rabbits were infused with rHDL at doses of 25, 50, and 75 mg/kg. Blood was drawn and stimulated with LPS ex vivo and bioactive TNF was assessed using the L929 cytotoxicity assay. Fifteen minutes after rHDL infusion, there was a significant difference in ex-vivo-induced TNF activity between groups (750 +/- 160, 170 +/- 40, 80 +/- 30, 60 +/- 30 pg TNF/ml, for the control, 25, 50, and 75 mg/kg rHDL dose groups, respectively; P < 0.0001). The duration of ex-vivo TNF inhibition was dependent on the dose of rHDL. Even at 2 hr, rHDL showed a pronounced TNF inhibition (control: 950 +/- 120 pg TNF/ml; 75 mg/kg: 140 +/- 60 pg TNF/ml). Further studies showed that a prophylactic infusion of rHDL diminished LPS-induced TNF production in a rabbit endotoxemia model.(ABSTRACT TRUNCATED AT 250 WORDS)

A reconstituted, apolipoprotein A-I containing lipoprotein reduces tumor necrosis factor release and attenuates shock in endotoxemic rabbits.

A reconstituted lipoprotein, containing human apolipoprotein A-I and phosphatidylcholine (1:200, molar ratio), referred to as ApoLipo, was used prophylactically in an endotoxin shock model in anesthetized rabbits. ApoLipo was administered at a dose of 75 mg protein/kg body weight 15 min before the beginning of a slow, continuous lipopolysaccharide (LPS, endotoxin) infusion (4.17 micrograms LPS/kg/hr). During the 6 hr LPS infusion, the Control-LPS group manifested a marked increase in serum tumor necrosis factor (TNF, peak value 7.82 [2.7-11.2] ng/ml at 1 hr), and many of the pathophysiologic sequelae of endotoxin shock, including hypotension (MAP: 59 +/- 7 mmHg) and metabolic acidosis (BE: -9.9 +/- 2.7) at 3 hr, and a severe neutropenia developed rapidly (PMN count: 5 +/- 3% of baseline at 30 min). In the ApoLipo treated group, serum TNF levels did not rise during the course of LPS infusion (0.1 [0.06-0.64] ng/ml at 1 hr). Hypotension (77 +/- 2 mmHg) and acidosis (-2.7 +/- 0.4) were also significantly attenuated, and the appearance of leukopenia was delayed by 1 hr (110 +/- 12% at 30 min, but 9 +/- 2% at 2 hr). Endotoxemia in the ApoLipo treated group was reduced in comparison to controls, albeit nonsignificantly. The infusion of the same dose of phosphatidylcholine without apoA-I was significantly less efficacious.

Muscarinic binding sites in a catecholaminergic human neuroblastoma cell line.

Tyrosine hydroxylase (TH) a characteristic enzyme activity for the catecholaminergic clonal cell line LA-N-1 and choline acetyltransferase (ChAT) a characteristic enzyme activity for the cholinergic clonal cell line LA-N-2 were previously shown to be increased in these cells exposed to 10(-5) M retinoic acid (RA) as differentiating agent. An investigation of the receptor characteristics suggests a complementarity between the two cell lines. The binding of QNB, a muscarinic ligand, was undetectable with the LA-N-2 cells but was present in the LA-N-1 cells and possessed a kD of 1.8 nM and 2.2 nM and a Bmax of 0.56 and 0.68 for control and RA grown cells respectively. There was a gradual increase in QNB binding to LA-N-1 cells from 2 days in vitro (DIV) until 6 DIV in both control and RA grown cells. An IC50 of 2.5 x 10(-8) M and 0.9 x 10(-8) M for atropine inhibition was obtained for the control and RA grown cells respectively. The corresponding values for carbachol inhibition were 7 x 10(-2) M and 3 x 10(-2) M respectively. The inhibition by the agonist oxotremorine is comparable to that of carbachol and 1 mM pilocarpine inhibited the binding by 21%. QNB binding showed a low affinity for pirenzepine and for AF-DX-116 but was inhibited with a rather high affinity by 4-DAMP (IC50:110 microM) thus suggesting the presence of an M3 receptor. Acetylcholine (100 microM) plus eserine (50 microM) and BW284c55 (1 microM), an acetylcholinesterase inhibitor, reduced the binding of QNB by approximately 25%.(ABSTRACT TRUNCATED AT 250 WORDS)

Exogenous gangliosides may affect methylation mechanisms in neuronal cell cultures.

Primary neurons in culture from chick embryo cerebral hemispheres were treated with a mixture of gangliosides added to the growth medium (final concentration: 10(-5)M and 10(-8)M) from the 3rd to the 6th day in vitro. Under these conditions methylation processes measured with [3H] and [35S] methionine and [3H]ethanolamine as precursors showed an increased methylation of [3H]ethanolamine containing phospholipids, a correspondent increased conversion of these compounds to [3H]choline containing phospholipids, and a general increased methylation of trichloroacetic acid precipitable macromolecules containing labeled methionine. A small increase in protein synthesis was observed after incubation of neurons with [3H]- and [35S]methionine. This was confirmed after electrophoretic separation of a protein extract with increased 3H- and 35S-labeling in protein bands with moecular weights between 50 and 60 KDaltons. A protein band of about 55 KDaltons appeared to be preferentially labelled when [3H] methionine was the precursor. The treatment with gangliosides increased the incorporation of [methyl-3H] label after incubation of neurons with [3H] methionine, into total DNA and decreased that of total RNA. The treatment of neurons in culture with exogenous gangliosides hence affects differently methylation processes, a finding which may confirm the involvement of gangliosides on the intracellular mediation of neuronal information mechanisms.