Evaluation of transmission methodology and attenuation correction for the microPET Focus 220 animal scanner

An accurate, low noise estimate of photon attenuation in the subject is required for quantitative microPET studies of molecular tracer distributions in vivo. In this work, several transmission-based measurement techniques were compared, including coincidence mode with and without rod windowing, singles mode with two different energy sources ((68)Ge and (57)Co), and postinjection transmission scanning. In addition, the effectiveness of transmission segmentation and the propagation of transmission bias and noise into the emission images were examined. The (57)Co singles measurements provided the most accurate attenuation coefficients and superior signal-to-noise ratio, while (68)Ge singles measurements were degraded due to scattering from the object. Scatter correction of (68)Ge transmission data improved the accuracy for a 10 cm phantom but over-corrected for a mouse phantom. (57)Co scanning also resulted in low bias and noise in postinjection transmission scans for emission activities up to 20 MBq. Segmentation worked most reliably for transmission data acquired with (57)Co but the minor improvement in accuracy of attenuation coefficients and signal-to-noise may not justify its use, particularly for small subjects. We conclude that (57)Co singles transmission scanning is the most suitable method for measured attenuation correction on the microPET Focus 220 animal scanner.     

Sympathectomy-mediated vasodilatation: a randomized concentration ranging study of epidural bupivacaine

Purpose

We tested the hypothesis that the development of sympathectomy-mediated vasodilatation is dependent on the concentration rather than the dose of epidural local anesthetic administered.

Methods

Sixty subjects receiving lumbar epidural bupivacaine were randomised to one of three groups: A: 10 ml 0.5% (50 mg); B: 10 ml 0.25% (25 mg); and C: 40 ml 0.0625% (25 mg). Groups A and B had equal volume but a twofold difference in drug dose, while groups B and C had equal drug dose, but a fourfold difference in drug volume. At baseline and 5, 10, and 20 min following epidural bupivacaine administration, we assessed the following indices of sympathectomy: pulse oximeter perfusion index in the toe and finger, skin temperature in the toe and finger, and mean arterial pressure. We also assessed sensory level (pinprick, cold, and light touch) and motor block.

Results

There was an increase in the pulse oximeter perfusion index by 20 min of 280%, 303%, and 59% in groups A, B, and, C, respectively. There was a significant sympathectomy-mediated vasodilatation in the toe for both groups A (P = 0.002) and B (P < 0.001) but not C (P = 0.22). Vasoconstriction in the finger was observed in group A only (P = 0.015) but not in group B (P = 0.09) or group C (P = 0.20). There were similar blood pressure changes and similar sensory changes in all groups. The intensity of motor block increased with increasing drug concentration.

Conclusions

Our observations suggest that drug concentration is more important than drug dose in determining the degree of sympathectomy following lumbar epidural local anesthesia.     

Antimicrobial activity of pyrimidinophanes with thiocytosine and uracil moieties

Reactions of pyrimidinophanes with two 6-methylthiocytosine and one 5(6)-alkyluracil moieties bridged with each other by polymethylene spacers with methyl or nonyl p-toluenesulfonate, p-toluenesulfonic acid, methanesulfonate and trifluorosulfonate afforded amphiphilic macrocyclic bis-p-toluene-, methane- and trifluorosulfonates. Despite the presence of several reaction centers in the initial pyrimidinophane molecules, protonation and methylation occurred only at the N(1) atom (with quaternization) of the 6-methylthiocytosine moieties. The bacteriostatic and fungistatic activity of the products was estimated. Macrocyclic tosylates exhibit a remarkable selectivity towards Staphylococcus aureus, with MIC values comparable with a reference drug. Bacteriostatic activity of the amphiphilic pyrimidinophanes depends on the size of the macrocycles, and the highest activity corresponds to definite lengths of polymethylene bridges. Besides, the antimicrobial activity of the screened pyrimidine derivatives depends on their topology. While macrocyclic tosylates are more active against bacteria than against fungi, acyclic tosylate with the same structural fragments shows a dramatical decrease of MIC towards mold and yeast with respect to the corresponding macrocycle. It is found that macrocyclic and acyclic tosylates in high dilutions decrease the extracellular lipase activity.     

The role of the PACAP signaling system in depression

Major Depressive Disorder (MDD) is a psychiatric condition that represents an important public health concern in modern society. Current pharmacological antidepressant treatments improve depressive symptoms through complex mechanisms that are incompletely understood. There is a consensus that in the clinic they act through the modulation of monoaminergic neurotransmission, primarily involving the serotonin and norepinephrine systems. Recent studies have suggested that action of antidepressants on synaptic plasticity is mediated by their regulatory influence not only upon small-molecule neurotransmitters, but also via neuropeptides which may act both as neurotransmitters and as neuromodulators. Prominent among these neuropeptides is PACAP, whose signaling system is intensively studied for its pleiotropic involvement in various physiological and pathological conditions. This review outlines the current knowledge concerning the PACAP signaling system's involvement in depressive disorders.     

Association between tobacco smoking and bipolar affective disorder: clinical, epidemiological, cross-sectional, retrospective study in outpatients

PurposeAlthough high rates of smoking have been reported among psychiatric patients, only a few studies examined the prevalence of smoking in bipolar disorder, and findings are inconsistent. We investigated smoking among bipolar patients.MethodsWe examined the prevalence of smoking in of 102 patients that met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for bipolar I disorder in Israel and evaluated the relationship between smoking and demographic and clinical data.ResultsFifty-five of the bipolar patients (53.9%) smoked, with a rate that is 2.36 times higher than among the general population in Israel (22.8%). Significant relationships were revealed between smoking and lifetime history of alcohol dependence/abuse (P = .02), between smoking and history of drug use (P ≤ .01), and between smoking and age of illness onset (P = .04).LimitationsThe cross-sectional nature of the study and the relatively small sample size preclude generalization of the findings. Nicotine levels were not measured; thus, the information regarding smoking was subjective.ConclusionsBipolar patients smoke more than the general population. Bipolar patients that are moderate or heavy smokers are more likely than nonsmokers to consume alcohol and abuse psychoactive substances. Contrary to findings of previous studies, no association was found between clinical variables of bipolar patients and smoking.     

Molecular signaling in necrotizing enterocolitis: regulation of intestinal COX-2 expression

Necrotizing enterocolitis (NEC) is the most common surgical emergency in premature infants. The underlying etiology of NEC remains unknown, although bacterial colonization of the gut, formula feeding, and perinatal stress have been implicated as putative risk factors. The disease is characterized by exuberant gut inflammation leading to ischemia and coagulation necrosis of the intestinal epithelium. The molecular and cellular mechanisms responsible for these pathologic changes are poorly understood. It has been shown that various exogenous and endogenous mediators such as lipopolysaccharide, inflammatory cytokines, platelet activating factor, and nitric oxide may play a role in the pathogenesis of NEC. Recent studies in our laboratory and others have established a link between NEC and activation of cyclooxygenase-2, the enzyme that catalyzes the rate-limiting step in the biosynthesis of prostanoids. The challenge is in defining the molecular signaling pathways leading to accumulation of these mediators early in the disease progression, before the onset of tissue necrosis and systemic sepsis. Identification and characterization of these pathways could lead to the development of novel treatment strategies to alleviate the morbidity and mortality associated with NEC.     

An isolation method for assessment of brain mitochondria function in neonatal mice with hypoxic-ischemic brain injury

This work was undertaken to develop a method for the isolation of mitochondria from a single cerebral hemisphere in neonatal mice. Mitochondria from the normal mouse brain hemisphere isolated by the proposed method exhibited a good respiratory control ratio of 6.39 +/- 0.53 during glutamate-malate-induced phosphorylating respiration. Electron microscopy showed intact mitochondria. The applicability of this method was tested on mitochondria isolated from na?ve mice and their littermates subjected to hypoxic-ischemic insult. Hypoxic-ischemic insult prior to reperfusion resulted in a significant (p < 0.01) inhibition of phosphorylating respiration compared to na?ve littermates. This was associated with a profound depletion of the ATP content in the ischemic hemisphere. The expression for Mn superoxide dismutase and cytochrome C (markers for the integrity of the mitochondrial matrix and outer membrane) was determined by Western blot to control for mitochondrial integrity and quantity in the compared samples. Thus, we have developed a method for the isolation of the cerebral mitochondria from a single hemisphere adapted to neonatal mice. This method may serve as a valuable tool to study mitochondrial function in a mouse model of immature brain injury. In addition, the suggested method enables us to examine the mitochondrial functional phenotype in immature mice with a targeted genetic alteration.     

Quantitative structure-activity relationship studies of [(biphenyloxy)propyl]isoxazole derivatives. Inhibitors of human rhinovirus 2 replication

The 50% cytotoxic concentration (CC50) in HeLa cells, the 50% inhibitory concentration (IC50) against human rhinovirus 2 (HRV-2), and the selectivity index (SI = CC50/IC50) of [(biphenyloxy)propyl]isoxazole derivatives were used to develop quantitative structure-activity relationships (QSAR) based on simplex representation of molecular structure. Statistic characteristics for partial least-squares models are quite satisfactory (R2 = 0.838 - 0.918; Q2 = 0.695 - 0.87) for prediction of CC50, IC50, and SI values and permit the virtual screening and molecular design of new compounds with strong anti-HRV-2 activity. The quality of prognosis for designed compounds was additionally estimated by analysis of domain applicability for each QSAR model. A hypothesis to the effect that terminal benzene substituents must have negative electrostatic potential and definite length (approximately 5.5-5.6 A) to possess strong antiviral activity has been suggested. The quality of developed analysis, i.e., high level of antiviral action of three new designed compounds, has been confirmed experimentally.     

Cellular vitamin C increases chromate toxicity via a death program requiring mismatch repair but not p53

Ascorbate (Asc) plays a key role in reductive activation ofcarcinogenic chromium(VI) in vivo. In addition to much higherrates (t_1/2 = 1 min for 1 mM Asc), its reactions at physiologicalconditions differ from other reducers by low yields of Cr(V)intermediates. Human cells in culture are severely Asc deficient,which results in distorted metabolism and potentially abnormalresponses to Cr(VI). We found that restoration of physiologicalAsc levels in human lung cells (primary IMR90 fibroblasts andepithelial H460 cells) increased clonogenic lethality and apoptosisby Cr(VI). Enhanced cytotoxicity in mass cultures was more evidentafter normalization for lower Cr uptake caused by leakage ofAsc into media. Asc did not change uptake-adjusted yields ofCr–DNA adducts and had no effect on cytotoxicity whendelivered shortly after Cr(VI) exposure. Protein and Ser-15phosphorylation levels of p53 did not show any association withthe presence of Asc and there were no increases in p53-drivenreporter activity in Cr-treated cells. Stable silencing of p53expression by short hairpin RNA (shRNA) had no effect on toxicityof Cr(VI) in both –Asc and +Asc IMR90 and H460 cells.In contrast, shRNA-mediated depletion of essential componentsof MutS or MutL mismatch repair complexes greatly improved survivalof all Cr-treated cells and eliminated Asc-potentiated effectson cell death. Thus, mismatch repair-mediated enhancement ofCr(VI) cytotoxicity by Asc should promote the selection of MSI+/wt-p53phenotype found among chromate-induced human lung cancers. Ourfindings also indicate that Asc plays a dual role in Cr(VI)toxicity: protective outside and potentiating inside the cell. Abbreviations: Asc, ascorbate; DHA, dehydroascorbic acid; PBS, phosphate-buffered saline; SDS, sodium dodecyl sulfate; shRNA, short hairpin RNA Received December 12, 2006; revised January 25, 2007; accepted February 3, 2007.     

Four novel missense mutations in the CYP21A2 gene detected in Russian patients suffering from the classical form of congenital adrenal hyperplasia: identification, functional characterization, and structural analysis

CONTEXT: Congenital adrenal hyperplasia is a group of autosomal recessive inherited disorders of steroidogenesis. The most frequent cause is the deficiency of steroid 21-hydroxylase (CYP21) due to mutations in the CYP21A2 gene. OBJECTIVE: We analyzed the functional and structural consequences of the four CYP21A2 missense mutations (C169R, G178R, W302R, and R426C) to prove their clinical relevance and study their impact on CYP21 function. RESULTS: Analyzing the mutations in vitro revealed an almost absent or negligible CYP21 activity for the conversion of 17-hydroxyprogesterone to 11-deoxycortisol and progesterone to deoxycorticosterone. Protein translation and intracellular localization were not affected by the mutants, as could be demonstrated by Western blotting and immunofluorescence studies. Analysis of these mutants in a three-dimensional model structure of the CYP21 protein explained the observed in vitro effects because all the mutations severely interfere either directly or indirectly with important structures of the 21-hydroxylase protein. CONCLUSION: The in vitro expression analysis of residual enzyme function is a complementary method to genotyping and an important tool for improving the understanding of the clinical phenotype of 21-hydroxylase deficiency. This forms the foundation for accurate clinical and genetic counseling and for prenatal diagnosis and treatment. Moreover, this report demonstrates that the combination of in vitro enzyme analysis and molecular modeling can yield novel insights into CYP450 structure-functional relationships.