Reprint of "On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography" [J. Struct. Biol. 159 (2007) 507-522]

Labeling with heavy atom clusters attached to antibody fragments is an attractive technique for determining the 3D distribution of specific proteins in cells using electron tomography. However, the small size of the labels makes them very difficult to detect by conventional bright-field electron tomography. Here, we evaluate quantitative scanning transmission electron microscopy (STEM) at a beam voltage of 300kV for detecting 11-gold atom clusters (Undecagold) and 1.4nm-diameter nanoparticles (Nanogold) for a variety of specimens and imaging conditions. STEM images as well as tomographic tilt series are simulated by means of the NIST Elastic-Scattering Cross-Section Database for gold clusters embedded in carbon. The simulations indicate that the visibility in 2D of Undecagold clusters in a homogeneous matrix is maximized for low inner collection semi-angles of the STEM annular dark-field detector (15-20mrad). Furthermore, our calculations show that the visibility of Undecagold in 3D reconstructions is significantly higher than in 2D images for an inhomogeneous matrix corresponding to fluctuations in local density. The measurements demonstrate that it is possible to detect Nanogold particles in plastic sections of tissue freeze-substituted in the presence of osmium. STEM tomography has the potential to localize specific proteins in permeabilized cells using antibody fragments tagged with small heavy atom clusters. Our quantitative analysis provides a framework for determining the detection limits and optimal experimental conditions for localizing these small clusters.

Neonatal vaccination with Bacillus Calmette-Guérin elicits long-term protection in mouse-allergic responses

BACKGROUND

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccination has been shown to inhibit allergic airway inflammation in animal models, associated with the regulation of allergen-specific T-cell immunity. However, little is known about whether neonatal BCG treatment could inhibit allergic inflammation by regulating allergen-specific T-cell response in aged mice. This study was aimed to investigate the impact of neonatal BCG treatment on allergic asthma and possible mechanism(s) underlying the action of BCG in different ages of mice.

METHODS

C57BL/6 neonates were vaccinated with BCG on days 1, 7 and 14, sensitized with ovalbumin (OVA) at 5 and 7 weeks of age, and then challenged with allergen at 9 or 45 weeks of age for early- or late-challenged asthma. Their airway inflammation and allergen-specific T-cell responses were characterized.

RESULTS

Following early-challenge, BCG vaccination inhibited airway hyper-responsiveness (AHR), infiltration of eosinophils and mucous overproduction (P < 0.05), and shifted OVA-specific predominant Th2- to Th1-type cytokine responses in both the bronchoalveolar lavage fluid and the splenocyte supernatants (P < 0.05). In late-challenged mice, neonatal BCG treatment attenuated AHR and eosinophilia (P < 0.05), but failed to modulate allergen-specific cytokine responses.

CONCLUSIONS

Our data suggest that neonatal BCG vaccination has a long-term effect on inhibiting AHR and eosinophilia, which is associated with the modulation of Th1/Th2 cytokine production in early-, but not in late-challenged mice. Thus, different mechanisms may mediate the long-term protective effect of BCG neonatal vaccination differently in younger adult and aged mice.

Determination of quantitative distributions of heavy-metal stain in biological specimens by annular dark-field STEM

It is shown that dark-field images collected in the scanning transmission electron microscope (STEM) at two different camera lengths yield quantitative distributions of both the heavy and light atoms in a stained biological specimen. Quantitative analysis of the paired STEM images requires knowledge of the elastic scattering cross sections, which are calculated from the NIST elastic scattering cross section database. The results reveal quantitative information about the distribution of fixative and stain within the biological matrix, and provide a basis for assessing detection limits for heavy-metal clusters used to label intracellular proteins. In sectioned cells that have been stained only with osmium tetroxide, we find an average of 1.2+/-0.1 Os atom per nm(3), corresponding to an atomic ratio of Os:C atoms of approximately 0.02, which indicates that small heavy atom clusters of Undecagold and Nanogold can be detected in lightly stained specimens.

Reprint of "Three-dimensional elemental mapping of phosphorus by quantitative electron spectroscopic tomography (QuEST)" [J. Struct. Biol. 160 (2007) 35-48]

We describe the development of quantitative electron spectroscopic tomography (QuEST), which provides 3-D distributions of elements on a nanometer scale. Specifically, it is shown that QuEST can be applied to map the distribution of phosphorus in unstained sections of embedded cells. A series of 2-D elemental maps is derived from images recorded in the energy filtering transmission electron microscope for a range of specimen tilt angles. A quantitative 3-D elemental distribution is then reconstructed from the elemental tilt series. To obtain accurate quantitative elemental distributions it is necessary to correct for plural inelastic scattering at the phosphorus L(2,3) edge, which is achieved by acquiring unfiltered and zero-loss images at each tilt angle. The data are acquired automatically using a cross correlation technique to correct for specimen drift and focus change between successive tilt angles. An algorithm based on the simultaneous iterative reconstruction technique (SIRT) is implemented to obtain quantitative information about the number of phosphorus atoms associated with each voxel in the reconstructed volume. We assess the accuracy of QuEST by determining the phosphorus content of ribosomes in a eukaryotic cell, and then apply it to estimate the density of nucleic acid in chromatin of the cell's nucleus. From our experimental data, we estimate that the sensitivity for detecting phosphorus is 20 atoms in a 2.7 nm-sized voxel.

Differential binding patterns of monoclonal antibody 2C4 to the ErbB3-p185her2/neu and the EGFR-p185her2/neu complexes

2C4 (Pertuzumab, Omnitarg) is a monoclonal antibody targeting p185(her2/neu), which is overexpressed in 30% of invasive breast cancer. 2C4 is currently in phase II clinical trials for several types of cancers. This antibody has been reported to disrupt the association between p185(her2/neu) and ErbB3. In our studies of epidermal growth factor receptor (EGFR)-p185(her2/neu) heterodimerization, we noted that 2C4 formed associations with the EGFR-p185(her2/neu) receptor complex. Our data argue against 2C4 as a universal heterodimerization blocker for p185(her2/neu), but indicate that cocktails of monoclonal antibodies binding distinct interaction surfaces of p185(her2/neu) will emerge as the most potent targeted therapy.

Theoretical study of simultaneous water and VOCs adsorption and desorption in a silica gel rotor

One-dimensional partial differential equations were used to model the simultaneous water and VOC (Volatile Organic Compound) adsorption and desorption in a silica gel rotor which was recommended for indoor air cleaning. The interaction among VOCs and moisture in the adsorption and desorption process was neglected in the model as the concentrations of VOC pollutants in typical indoor environment were much lower than that of moisture and the adsorbed VOCs occupied only a minor portion of adsorption capacity of the rotor. Consequently VOC transfer was coupled with heat and moisture transfer only by the temperatures of the rotor and the air stream. The VOC transfer equations were solved by discretizing them into explicit up-wind finite differential equations. The model was validated with experimental data. The calculated results suggested that the regeneration time designed for dehumidification may be prolonged to allow complete removal of the VOC pollutants from the rotor. The regeneration temperature designed for dehumidification provides considerable efficiency for indoor air cleaning. The application of the model in estimating the cleaning capacity of the rotor for VOC pollutants was demonstrated.

PRACTICAL IMPLICATIONS

Silica gel rotors, usually used to dehumidify air, were found to be effective to remove VOCs by experiments recently. But the removal characteristics of VOCs are different from that of moisture. Therefore, the rotor structure and operating parameters for dehumidification needs to be optimized for the use of removing moisture and VOCs. This paper gives a way for the optimization.

Rifampicin exacerbates isoniazid-induced toxicity in human but not in rat hepatocytes in tissue-like cultures

BACKGROUND AND PURPOSE

Rifampicin has been extensively reported to exacerbate the hepatotoxicity of isoniazid in patients with tuberculosis. However, this was controversially claimed by previous reports using rat models. This study evaluated the effect of rifampicin on isoniazid-induced hepatocyte toxicity by using human and rat hepatocytes in tissue-like culture.

EXPERIMENTAL APPROACH

Hepatocytes in tissue-like gel entrapment were used to examine isoniazid toxicity, as shown by cell viability, intracellular glutathione content and albumin secretion. For demonstration of the differential effects of rifampicin on human and rat hepatocytes, induction by rifampicin of cytochrome P450 (CYP) 2E1, a major enzyme associated with isoniazid hepatotoxicity, was detected by 4-nitrocatechol formation and RT-PCR analysis.

KEY RESULTS

Rifampicin (12 microM) enhanced isoniazid-induced toxicity in human hepatocytes but not in rat hepatocytes. Enhanced CYP 2E1 enzymic activity and mRNA expression were similarly detected in human hepatocytes but not in rat hepatocytes. Both rat and human hepatocytes in gel entrapment were more sensitive to isoniazid treatment compared with the corresponding hepatocytes in a monolayer culture.

CONCLUSIONS AND IMPLICATIONS

The difference in induction of CYP 2E1 by rifampicin between rat and human hepatocytes accounted for the difference in exacerbation of isoniazid hepatocyte toxicity by rifampicin, with more significant toxicity in gel entrapment than in monolayer cultures. Thus, human hepatocytes in tissue-like cultures (gel entrapment) could be an effective model for hepatotoxicity research in vitro, closer to the in vivo situation.

Associations between postnatal weight gain, change in postnatal pulmonary function, formula feeding and early asthma

BACKGROUND

A study was undertaken to examine factors that might influence lung function during infancy and to test the hypothesis that change in weight during infancy is negatively associated with change in lung function.

METHODS

Weight, length and maximal flow at functional residual capacity (V'maxFRC) were measured at ages 1 and 12 months. V'maxFRC was adjusted for length. Asthma symptoms and age at introduction of formula feeds were identified from questionnaires. Groups were dichotomised by V'maxFRC at 1 month and change in V'maxFRC.

RESULTS

154 infants were assessed at ages 1 and 12 months. The change in V'maxFRC was inversely associated with change in weight (r = -0.18, r2 = 0.13, p<0.001). The group with lower V'maxFRC at 1 month and reduced change in V'maxFRC over infancy had the greatest weight gain (p = 0.003) and increased risk for asthma symptoms by 3 years (p = 0.017) but not afterwards. Exclusive breast feeding to 6 months was associated with a mean reduction in weight gain at age 12 months in comparison with earlier introduction of formula milk (mean difference 0.65 kg, p = 0.001), and was also associated with reduced asthma symptoms at 3 years (odds ratio 0.44, p = 0.043) but not at 6 or 11 years of age.

CONCLUSIONS

Weight gain in infancy is inversely associated with change in lung function during infancy. Postnatal weight gain may be indirectly associated with early transient asthma symptoms via an influence on lung growth during infancy, and this is potentially modifiable by breast feeding. These associations could be relevant to the clinically recognised syndrome of the "fat happy wheezer".

Protracted effects of chronic oral haloperidol and risperidone on nerve growth factor, cholinergic neurons, and spatial reference learning in rats

The primary therapeutic agents used for schizophrenia, antipsychotic drugs, ameliorate psychotic symptoms; however, their chronic effects on cognition (or the physiologic processes of the brain that support cognition) are largely unknown. The purpose of this rodent study was to extend our previous work on this subject by investigating persistent effects (i.e. during a 14 day drug-free washout period) of chronic treatment (i.e. ranging from 45 days to 6 months) with a representative first and second generation antipsychotic. Drug effects on learning and memory and important neurobiological substrates of memory, the neurotrophin, nerve growth factor (NGF) and its receptors, and certain components of the basal forebrain cholinergic system were investigated. Behavioral effects of oral haloperidol (2.0 mg/kg/day), or risperidone (2.5 mg/kg/day) were assessed in an open field, a water maze task, and a radial arm maze procedure and neurochemical effects in brain tissue were subsequently measured by enzyme-linked immunosorbent assays (ELISAs). The results indicated that both antipsychotics produced time-dependent and protracted deficits in the performance of a water maze procedure when compared with vehicle-treated controls, while neither drug was associated with significant alterations in radial arm maze performance. Interestingly, haloperidol, but not risperidone, was detectible in the rodent brain in appreciable levels for up to 2 weeks after drug discontinuation. Both antipsychotics were also associated with reduced levels of NGF protein in the basal forebrain and prefrontal cortex and significant (or nearly significant) decreases in phosphorylated tropomyosin-receptor kinase A (TrkA) protein and the vesicular acetylcholine transporter (depending on the brain region analyzed). Neither antipsychotic markedly affected TrkA or p75 neurotrophin receptor levels. These data in rats indicate that chronic treatment with either haloperidol or risperidone may be associated with protracted negative effects on cognitive function as well as important neurotrophin and neurotransmitter pathways that support cognition.

Behavioural symptoms of children with HIV infection living in the Dominican Republic

OBJECTIVE

The purpose of this report is to describe behavioural problems encountered in a group of Dominican children living with Human Immunodeficency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) in the Dominican Republic. They were not receiving antiretroviral treatment.

METHOD

The participants were 43 children with HIV infection (2 to 8 years of age) who were attending an immunology clinic in the largest paediatric hospital in the Dominican Republic. All of the participants were vertically infected with the HIV virus (mother-to-child transmission) and had a very low socio-economic status. The children's caregivers were administered the Child Behavioural Checklist (CBCL) by trained psychologists to determine the caregivers 'perception of the children's behavioural problems. Behavioural findings were examined according to the CBCL age format: younger children (under 5 years of age) and older children (over 6 years of age).

RESULTS

Descriptive statistics revealed a high proportion of the children, both younger (approximately 40%) and older (46%) scored in the borderline/clinical ranges for internalizing problems, including anxiety, withdrawn-depressed and somatic complaints. In addition, 46% of the older children were perceived as having externalizing problems (rule breaking and aggressive behaviour).

CONCLUSION

These findings suggest that a high incidence of behavioural and mood problems may be prevalent among Dominican children with HIV Thefindings are discussed in terms of future research to examine other risk factors that might contribute to the high rate of maladaptive behaviours observed in the present report, including the contribution of socio-economic status, caregiver illness, caregiver education and parental loss.

Three-dimensional elemental mapping of phosphorus by quantitative electron spectroscopic tomography (QuEST)

We describe the development of quantitative electron spectroscopic tomography (QuEST), which provides 3-D distributions of elements on a nanometer scale. Specifically, it is shown that QuEST can be applied to map the distribution of phosphorus in unstained sections of embedded cells. A series of 2-D elemental maps is derived from images recorded in the energy filtering transmission electron microscope for a range of specimen tilt angles. A quantitative 3-D elemental distribution is then reconstructed from the elemental tilt series. To obtain accurate quantitative elemental distributions it is necessary to correct for plural inelastic scattering at the phosphorus L(2,3) edge, which is achieved by acquiring unfiltered and zero-loss images at each tilt angle. The data are acquired automatically using a cross correlation technique to correct for specimen drift and focus change between successive tilt angles. An algorithm based on the simultaneous iterative reconstruction technique (SIRT) is implemented to obtain quantitative information about the number of phosphorus atoms associated with each voxel in the reconstructed volume. We assess the accuracy of QuEST by determining the phosphorus content of ribosomes in a eukaryotic cell, and then apply it to estimate the density of nucleic acid in chromatin of the cell's nucleus. From our experimental data, we estimate that the sensitivity for detecting phosphorus is 20 atoms in a 2.7 nm-sized voxel.

On the feasibility of visualizing ultrasmall gold labels in biological specimens by STEM tomography

Labeling with heavy atom clusters attached to antibody fragments is an attractive technique for determining the 3D distribution of specific proteins in cells using electron tomography. However, the small size of the labels makes them very difficult to detect by conventional bright-field electron tomography. Here, we evaluate quantitative scanning transmission electron microscopy (STEM) at a beam voltage of 300 kV for detecting 11-gold atom clusters (Undecagold) and 1.4 nm-diameter nanoparticles (Nanogold) for a variety of specimens and imaging conditions. STEM images as well as tomographic tilt series are simulated by means of the NIST Elastic-Scattering Cross-Section Database for gold clusters embedded in carbon. The simulations indicate that the visibility in 2D of Undecagold clusters in a homogeneous matrix is maximized for low inner collection semi-angles of the STEM annular dark-field detector (15-20 mrad). Furthermore, our calculations show that the visibility of Undecagold in 3D reconstructions is significantly higher than in 2D images for an inhomogeneous matrix corresponding to fluctuations in local density. The measurements demonstrate that it is possible to detect Nanogold particles in plastic sections of tissue freeze-substituted in the presence of osmium. STEM tomography has the potential to localize specific proteins in permeabilized cells using antibody fragments tagged with small heavy atom clusters. Our quantitative analysis provides a framework for determining the detection limits and optimal experimental conditions for localizing these small clusters.

VEGF-D expression in lung adenocarcinoma with or without acquired resistance to gefitinib and normal lung

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Background: VEGF-D is related with pathogenesis and metastasis of lung cancer, however, its relationship with resistance to gefitinib in NSCLC remains unknown. Methods: Lung adenocarcinoma, normal lung tissues adjacent to the carcinoma and adenocarcinoma with acquired resistance to gefitinib including some metastastic lymph nodes were obtained during operation. Relative quantitation of VEGF-D gene expression was performed by SYBR Green real-time PCR with beta actin gene as the endogenous control. VEGF-D expression of each group was analyzed by comparing them qualitatively and quantitatively. The expression ratios were compared by Fisher’s exact test and expression levels were compared by two-related-samples nonparametric test. Results: CVEGF-D expression ratio of lung adenocarcinoma with acquired resistance to gefitinib (16.7%, 1/6) was not different from lung adenocarcinoma (50%, 7/14, P=0.325) but was significantly lower than that of normal lung (93.8%, 15/16, P=0.001). The logarithmically transformed VEGF-D relative expression levels in six lung adenocarcinomas and the matched normal lung tissues, which were 2.214±0.376 and 3.388±0.209, were found to be significantly different from each other by the analysis of Wilcoxon signed ranks test (P=0.028). Conclusions: VEGF-D expression is in a high-level state in normal lung tissues while in low-level or absent in lung adenocarcinoma with or without acquired resistance to gefitinib, suggesting that the role VEGF-D plays in normal lung tissue could be different from in lung adenocarcinoma with or without acquired resistance to gefitinib.

No significant financial relationships to disclose.