Atomic force microscopy of cholera toxin B-oligomers bound to bilayers of biologically relevant lipids

Cholera toxin B-oligomer was imaged by atomic force microscopy (AFM) on biologically relevant model membranes, such as 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine and egg yolk phosphatidylcholine at room temperature in solution at a resolution in the range of 1 to 2 nm. In addition, two-dimensional arrays were grown directly on these model membranes without any special treatment, and were also imaged by AFM. These results demonstrate the ability of AFM for imaging membrane proteins at high resolution without the need of chemical cross-linking, either within the membrane or to the substratum.

Alcohol induces interdigitated domains in unilamellar phosphatidylcholine bilayers

Using the atomic force microscope (AFM) in situ, we have demonstrated that acyl chain interdigitation can be induced reversibly by alcohol in supported unilamellar phospholipid bilayers. At alcohol concentrations considerably lower than the critical values determined by other experimental techniques, it was found that interdigitated domains can be induced and these domains were stable over a long period of time. The mechanism of such domain formation remains to be elucidated. This work also serves as an example to illustrate the uniqueness of the AFM as a powerful tool in the study of membrane structure and conformation under physiological conditions at high spatial resolution.

High-resolution atomic-force microscopy of DNA: the pitch of the double helix

Using a cationic lipid bilayer, we show that DNA can be reliably adsorbed to the bilayer surface for atomic force microscopy (AFM) in aqueous buffers at high resolution. The measured width of the dsDNA is close to 2 nm, and a periodic modulation on dsDNA is reproducibly detected by the AFM. The measured period is 3.4 +/- 0.4 nm, in excellent agreement with the known pitch of the double helix. The right-handedness of the double helix is directly discernible in high resolution AFM images. Thus, this approach can be readily applied to the study of DNA-protein interactions, as well as sequence mapping at high resolution.

Hepatitis E virus infection among domestic animals in eastern China

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Antibodies to HEV and HEV RNA have been detected in some Chinese population and swine groups but few other domestic animals. In this study, to investigate the HEV prevalence, we tested sera from 788 pigs, 100 cows, 50 goats, 49 horses, 101 pet dogs, 105 chickens, 47 duck and 45 pigeons in eastern China for anti-HEV immunoglobulin G (IgG). We also tested 50% of the swine sera, all of sera from the other domestic animals and 13 Shanghai human sera which were positive for anti-HEV immunoglobulin M (IgM) for HEV RNA using reverse transcriptase-polymerase chain reaction. Our results indicated that 82.5% (222/269) of the sows, 53.9% (104/193) of the 4- to 6-month-old swine, 63.4% (168/265) of the 1- to 3-month-old swine, 55.7% (34/61) of the slaughterhouse swine, 24% (12/50) of the goats, 16.3% (8/49) of the horses, 17.8% (21/101) of the pet dogs, 6% (6/100) of the cows, 12.8% (6/47) of the ducks, 4.4% (2/45) of the pigeons and 1.9% (2/105) of the chickens exhibited positive for anti-HEV IgG. Inhibition assay confirmed the infection with HEV or HEV-like viruses in these domestic animals except pigeons and chickens. From the sera, we isolated 18 swine HEV strains, one horse HEV strain and two human HEV strains. Sequence analysis showed that the horse HEV isolate and one swine isolate belonged to genotype 3. The other isolates belonged to genotype 4. The two human isolates were phylogenetically closely related to eight of the swine isolates. In short, the presence of anti-HEV antibody had been confirmed in several species of domestic animals in eastern China and HEV RNA has been identified in swine, human and horse. This suggested that the authorities should pay more attention to the prevalence of HEV in eastern China.

Tris(hydroxymethyl)aminomethane (C4H11NO3) induced a ripple phase in supported unilamellar phospholipid bilayers

A commonly used buffer compound, tris(hydroxymethyl)aminomethane (C4H11NO3), was found to induce a ripple phase in supported unilamellar phospholipid bilayers at room temperature. The ripple structure showed various types of domains that could extend to several micrometers in length with many well-defined bendings of either 120 degrees or 60 degrees. Two different periodic ripples were found to coexist in 1,2-dipentadecanoyl-sn-glycero-3-phosphatidylcholine bilayers. Some intermediate states during the transition to the ripple phase were also observed.

Gramicidin A aggregation in supported gel state phosphatidylcholine bilayers

Using an atomic force microscope, supported bilayers of saturated phosphatidylcholine (in the gel state) containing various amounts of gramicidin A (gA) were imaged in aqueous solutions and at room temperature. gA clusters were directly observed for the first time under these conditions. It was found that, at a lower gA concentration, gA aggregated into domains, composed of small clusters along with a considerable amount of lipids. This basic aggregation unit, most likely a hexamer, remained the same for acyl chain lengths from 14 to 18 carbons. These small clusters were observed to form elongated aggregates (line type) but never into extended pure gA domains. When gA concentrations were increased, for bilayers with 16 carbons or less, gA aggregated into larger domains but the basic unit remained separated by lipid molecules. At about 5 mol % gA, a percolation-like transition occurred at which the line type aggregates were connected to each other. However, for bilayers with more than 16 carbons, multiple lamellar structures were formed at higher gA fractions and the top layer had a ripple-like surface morphology. The molecular mechanism for the formation of these peculiar structures remains to be elucidated.

Cryo atomic force microscopy: a new approach for biological imaging at high resolution

A low-temperature atomic force microscope (cryo-AFM), operated in liquid nitrogen vapor, has been constructed for biological applications. The system provides an adjustable imaging temperature from 77 to 220 K with atomic resolution achieved on crystalline specimens. Imaging with NaCl microcrystals demonstrates that the system is free from surface contamination. Below 100 K, several biological specimens, including immunoglobulins and DNA as well as red blood cell ghosts, were imaged at high spatial resolution. Measurements on individual macromolecules showed that the mechanical strength is significantly greater at cryogenic temperatures with an estimated Young's modulus 1000-10,000 times that of a hydrated protein at room temperature, providing a solid basis for future improvements and applications of cryo-AFM in structural biology.

High resolution surface structure of E. coli GroES oligomer by atomic force microscopy

Using atomic force microscopy (AFM) in aqueous solution, we show that the surface structure of the oligomeric GroES can be obtained up to 10 angstroms resolution. The seven subunits of the heptamer were well resolved without image averaging. The overall dimension of the GroES heptamer was 8.4 +/- 0.4 nm in diameter and 3.0 +/- 0.3 nm high. However, the AFM images further suggest that there is a central protrusion of 0.8 +/- 0.2 nm high and 4.5 +/- 0.4 nm in diameter on one side of GroES which displays a profound seven-fold symmetry. It was found that GroEL could not bind to the adsorbed GroES in the presence of AMP-PNP and Mg2+, suggesting that the side of GroES with the central protrusion faces away from the GroEL lumen, because only one side of GroES was observed under these conditions. Based on the results from both electron and atomic force microscopy, a surface model for the GroES is proposed.

Structure and stability of pertussis toxin studied by in situ atomic force microscopy

Pertussis toxin, both complete and the B-oligomer, were imaged by atomic force microscopy (AFM), using specimens prepared by simple surface adsorption on mica without further manipulation. The spatial arrangement of the subunits of the B-oligomer was clearly resolved, representing the first protein quaternary structure obtained by AFM in situ. The results suggest that the B-oligomer is a flat pentamer with the two large subunits located next to each other, and the catalytic A-subunit situated at the center above. We found that the B-pentamer was structurally stable for temperatures up to 60 degrees C and within the pH range of 4.5-9.5. It is also demonstrated that the AFM was capable of resolving features down to 0.5 nm on the B-oligomers, indicating its great potential for structural determination.

Molecular resolution atomic force microscopy of soluble proteins in solution

We introduce a simple specimen preparatory method for atomic force microscopy of soluble proteins in aqueous solutions. It is demonstrated that the mica surface is suitable for direct adsorption of macromolecules that are sufficiently stable to withstand the disturbance of the probe for reproducible imaging at high resolution. It is also shown that the main problem impeding successful imaging is the excessive adsorption of macromolecules, as loosely bound macromolecules readily stick to the tip and produce various imaging artifacts.

Chaperonins GroEL and GroES: views from atomic force microscopy

The Escherichia coli chaperonins, GroEL and GroES, as well as their complexes in the presence of a nonhydrolyzable nucleotide AMP-PNP, have been imaged with the atomic force microscope (AFM). We demonstrate that both GroEL and GroES that have been adsorbed to a mica surface can be resolved directly by the AFM in aqueous solution at room temperature. However, with glutaraldehyde fixation of already adsorbed molecules, the resolution of both GroEL and GroES was further improved, as all seven subunits were well resolved without any image processing. We also found that chemical fixation was necessary for the contact mode AFM to image GroEL/ES complexes, and in the AFM images. GroEL with GroES bound can be clearly distinguished from those without. The GroEL/ES complex was about 5 nm higher than GroEL alone, indicating a 2 nm upward movement of the apical domains of GroEL. Using a slightly larger probe force, unfixed GroEL could be dissected: the upper heptamer was removed to expose the contact surface of the two heptamers. These results clearly demonstrate the usefulness of cross-linking agents for the determination of molecular structures with the AFM. They also pave the way for using the AFM to study the structural basis for the function of GroE system and other molecular chaperones.

Randomized, double-blind clinical trial comparing basal insulin peglispro and insulin glargine, in combination with prandial insulin lispro, in patients with type 1 diabetes: IMAGINE 3

AIMS

To compare the efficacy and safety of basal insulin peglispro (BIL), which has a flat pharmacokinetic and pharmacodynamic profile and a long duration of action, with insulin glargine (GL) in patients with type 1 diabetes.

MATERIALS AND METHODS

In this phase III, 52-week, blinded study, we randomized 1114 adults with type 1 diabetes in a 3 : 2 distribution to receive either BIL (n = 664) or GL (n = 450) at bedtime, with preprandial insulin lispro, using intensive insulin management. The primary objective was to compare glycated haemoglobin (HbA1c) in the groups at 52 weeks, with a non-inferiority margin of 0.4%.

RESULTS

At 52 weeks, mean (standard error) HbA1c was 7.38 (0.03)% with BIL and 7.61 (0.04)% with GL {difference -0.22% [95% confidence interval (CI) -0.32, -0.12]; p < 0.001}. At 52 weeks more BIL-treated patients reached HbA1c <7% (35% vs 26%; p < 0.001), the nocturnal hypoglycaemia rate was 47% lower (p < 0.001) and the total hypoglycaemia rate was 11% higher (p = 0.002) than in GL-treated patients, and there was no difference in severe hypoglycaemia rate. Patients receiving BIL lost weight, while those receiving GL gained weight [difference -1.8 kg (95% CI -2.3, -1.3); p < 0.001]. Treatment with BIL compared with GL at 52 weeks was associated with greater increases from baseline in levels of serum triglyceride [difference 0.19 mmol/l (95% CI 0.11, 0.26); p < 0.001] and alanine aminotransferase (ALT) levels [difference 6.5 IU/l (95% CI 4.1, 8.9), p < 0.001], and more frequent injection site reactions.

CONCLUSIONS

In patients with type 1 diabetes, treatment with BIL compared with GL for 52 weeks resulted in a lower HbA1c, more patients with HbA1c levels <7%, and reduced nocturnal hypoglycaemia, but more total hypoglycaemia and injection site reactions and higher triglyceride and ALT levels.

Defining migration and its health impact in China

The scale and rapid expansion of urbanization resulting from socio-economic transformation in China at the beginning of the 21st century has accelerated rural-urban migration. Public health concerns from this increasing internal population mobility are now receiving attention from researchers. The health problems from internal migration pose particular demands on healthcare systems and relate to its demographic characteristics, with many younger and older people being left behind in the rural countryside. A review of literature, census, policy reports, government documents and media was undertaken to look at the classification system and health characteristics of China's internal migrants. It suggests that public health bears the consequences of political and economic decisions made elsewhere in society.

The effect of deformation on the lateral resolution of atomic force microscopy

A computer model based on the elastic properties of rubber is introduced for the evaluation of the lateral resolution in atomic force microscopy of deformable specimens. The computational results show that, if the full width at half-height can be defined as the lateral resolution, it is continuously improved at greater probe forces, at the expense of a reduced molecular height, In fact, even for a probe that is bigger than the molecule, the real size of the molecule can be 'recovered' at about 25% compression. This result demonstrates that for a better lateral resolution, a greater probe force can be beneficial, provided that the molecule is not moved or damaged and the response remains elastic. Measurements on isolated low-density lipoproteins (LDL) show that with 26% vertical compression, the lateral size measured in atomic force microscopy is only 72% of the value predicted by a simple convolution, and is only slightly larger (approximately 13%) than the known size of LDL. Therefore, the results on LDL provide a direct support for the conclusions of the computational model.

Public health services in Shenzhen: a case study

As one of the fastest growing cities in Pearl River Delta of southern China, Shenzhen accommodates a higher percentage and increasing number of internal migrants, mainly coming from the inland areas. The public health issues that challenge its local government include the special population structure, high incidence of infectious diseases, high prevalence of mental problems, rising chronic disease burdens, and maternal and children’s health issues, although progress has been made in the past years. The health authority of Shenzhen has realized that provision of high quality equitable public health services to its residents, including migrants is of high priority, and should be supported by innovations in the health insurance system and establishment of community-based primary care networks. Making changes within the national-level health reform framework and learning from international experiences are necessary and important.

A randomized clinical trial comparing basal insulin peglispro and insulin glargine, in combination with prandial insulin lispro, in patients with type 1 diabetes: IMAGINE 1

AIMS

The primary objective was to demonstrate that basal insulin peglispro (BIL) was non-inferior compared with insulin glargine (GL) for haemoglobin A1c (HbA1c) at 26 weeks with a non-inferiority margin of 0.4%.

MATERIALS AND METHODS

IMAGINE 1 was a Phase 3, open-label, parallel-arm study conducted in nine countries. Adults with type 1 diabetes (n = 455) were randomized (2:1) to bedtime BIL or GL in combination with prandial insulin lispro for 78 weeks, with a primary endpoint of 26 weeks. An electronic diary facilitated data capture and insulin dosing calculations for intensive insulin management.

RESULTS

At 26 weeks, mean HbA1c was 7.06% ± 0.04% and 7.43% ± 0.06% for patients assigned to BIL (N = 295) and GL (N = 160), respectively (difference -0.37% [95% CI: -0.50 to -0.23], P < .001); more patients on BIL achieved HbA1c <7% (44.9% vs 27.5%, P < .001). Compared with GL, patients using BIL lost weight, with lower fasting serum glucose and between-day fasting blood glucose variability, and 36% less nocturnal hypoglycemia, 29% more total hypoglycemia and more severe hypoglycemia. Total and prandial insulin doses were lower with BIL; basal insulin doses were higher. Alanine aminotransferase increased with BIL, with more patients having elevations ≥3 × ULN. BIL treatment was associated with more frequent injection site reactions and an increase from baseline in serum triglycerides.

CONCLUSIONS

In patients with type 1 diabetes, treatment with BIL compared to GL for 26 weeks was associated with lower HbA1c, less nocturnal hypoglycemia, lower glucose variability and weight loss. Increases in total and severe hypoglycemia, triglycerides, aminotransferases and injection site reactions were also noted.

Paradoxical immune reconstitution inflammatory syndrome associated with cryptococcal meningitis in China: a 5-year retrospective cohort study

We performed a retrospective cohort study of hospitalised cryptococcal meningitis (CM) patients at a single centre to evaluate the clinical epidemiological features of paradoxical cryptococcal-related immune reconstitution inflammatory syndrome (CM-IRIS) in a setting in China. A total of 154 AIDS patients with CM were involved, and 17.5% experienced IRIS at a median of 27 days after initiation of antiretroviral therapy (ART). Overall, 3 deaths were directly attributed to IRIS. The occurrences of CM-IRIS were independently associated with the pre-ART CD4+count, pre-C-reactive protein level, and the timing of ART initiation.

Abnormalities of Cerebral White Matter Microstructure in Children With New-Onset, Untreated Idiopathic-Generalized Epilepsy

Despite evidence for microstructural brain alterations in epilepsy patients, little is known about how these develop with age and the progress of the disease. The aim of this study was to investigate microstructural abnormalities of the white matter (WM) in children with new-onset, untreated idiopathic-generalized epilepsy (IGE) using the MRI technique of diffusion tensor imaging (DTI). The study was approved by the institutional review board, and all individuals or their parents gave signed informed consent. In total, 45 patients with IGE (age 5-18 years, male: female 26:19) and 32 healthy controls (HCs; age 5-18 years, male: female 21:11) were included. Voxel-based analysis (VBA) was used to compare patients and controls, and Pearson correlation analysis was used to investigate relationships between altered DTI metrics and clinical parameters. Compared with controls, patients with IGE showed increased mean diffusivity (MD) in the left splenium of the corpus callosum, increased fractional anisotropy (FA) in the right WM of the superior and middle frontal gyri, increased axial diffusivity (AD) in the WM of right corona radiata and left occipital lobe, and decreased AD in the WM of the left thalamus and the right middle cerebellar peduncle. There was no correlation between the altered diffusion parameters and clinical measures. Our study demonstrated several distinct microstructural impairments in children with new-onset, untreated IGE, of which altered AD might be the most sensitive marker of dysmyelination. The increased FA in the IGE group might suggest an initiating or compensatory mechanism that is activated prior to cognitive decline in these children.