[Differentiation between hyperintense hepatocellular carcinoma and focal nodular hyperplasia in hepatobiliary phase with multimodal parameters of magnetic resonance imaging].

Objective: To differentiate hyperintense hepatocellular carcinoma (HCC) with focal nodular hyperplasia (FNH) in the hepatobiliary phase by MRI multimodal parameters. Methods: A retrospective cross-sectional study method was adopted. Clinical data on 15 cases with hyperintense HCC and 15 cases with FNH in the hepatobiliary phase admitted to the First Affiliated Hospital of the Army Medical University from January 2012 to December 2019 were collected. All patients with solitary lesions who underwent Gd-EOB-DTPA-enhanced MRI examinations were included. Surgically resected specimens were verified by pathological and immunohistochemical examination. HCC and FNH imaging features were analyzed by two radiologists. Results: (1) HCC and FNH apparent diffusion coefficient (ADC) values were 1 205.07±239.65×10-3 mm2/s and 1 434.73±217.6×10-3 mm2/s, respectively, and the SIADC difference was statistically significant (P<0.05) between the two groups. (2) In the dynamic contrast-enhanced MRI sequence, 15 cases of HCC were significantly enhanced in the arterial phase, of which 13 cases were characterized by continuous enhancement, and 2 cases were characterized by wash-in and wash-out enhancement. There was no statistically significant difference (P>0.05) between the two groups. SIenhancement rate between HCC and FNH (1.39±0.60 vs. 1.33±0.50, P>0.05) had no significant difference. (3) HCC and FNH morphological features in the hepatobiliary phase included: annular hypointensity: HCC (8 cases) vs. FNH (0 cases); contrast filling defects: HCC (8 cases) vs. FNH (0 cases); linear hyposignal separation: HCC (10 cases) vs. FNH (0 cases); and stellate scars: HCC (0) vs. FNH (5 cases), and there were statistically significant differences (P<0.05) between the two groups . Conclusion: Multimodal MRI have significant value for differentiating hyperintense HCC and FNH in the hepatobiliary phase.

Modulation of rumen fermentation and microbial community through increasing dietary cation-anion difference in Chinese Holstein dairy cows under heat stress conditions.

AIMS: The effect of increasing dietary cation-anion difference (DCAD) on rumen fermentation and ruminal microbial community in dairy cows under heat stress (HS) conditions were evaluated. METHODS AND RESULTS: This study was performed as a two-period cross-over design during the summer season, with eight lactating dairy cows randomly distributed to either a control DCAD diet (CON: 33·5 mEq/100 g DM) or high DCAD diet (HDCAD: 50·8 mEq/100 g DM). Throughout the present study, the temperature and humidity index (THI; 80·2 ± 4·29) was generally elevated above the threshold (THI = 72) that is reported to cause HS in lactating dairy cows. Rumen liquid samples were collected on 15 and 21 d during each 21 d-period. The absolute concentration of ruminal total volatile fatty acid (TVFA) in HDCAD treatment was significantly (P < 0·05) higher than those in the control, whilst the ruminal pH, NH3 -N, and VFA molar percentages were unaffected through increasing DCAD. Furthermore, the copy numbers of the cellulolytic bacteria Ruminococcus albus and Ruminococcus flavefaciens in rumen fluid significantly (P < 0·05) rose along with the increment of DCAD. Although the Alpha diversity indexes and the bacterial microbiota structure were unaffected, increasing DCAD significantly (P < 0·05) enriched the phylum Fibrobacteres and genus Fibrobacter in the microflora of rumen fluid, whilst the genera Flexilinea and Dubosiella were the most differentially abundant taxa in the control. CONCLUSIONS: Increasing DCAD under HS conditions resulted in a greater concentration of total VFA without affecting rumen bacteria diversity or structure, although the enrichment of some cellulolytic/hemicellulolytic bacteria was observed. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study provides information on the modulation of rumen fermentation and microbial community through the increment of DCAD in Holstein dairy cows under HS conditions.

[Pathogenesis of piriformis syndrome: a magnetic resonance imaging-based comparison study].

Objective: To assess the morphological parameters of the piriformis muscle through magnetic resonance imaging(MRI) so as to further elucidate the pathogenesis of piriformis syndrome (PS). Methods: From September 2015 to October 2016, 30 suspected PS patients and 30 normal controls were enrolled in this study from the Nanfang Hospital, Southern Medical University. The possible causative factors of the PS in the patients were obtained, and the PS patients were divided into subgroups according to the anatomic site of the tender regions. The parameters of the maximum thickness (cm), area (cm(2)) and the volume (cm(3)) of the piriformis muscle of both groups were measured by MRI and were statistically compared between the groups with the independent-sample t test so as to investigate the pathogenesis of injured sciatic nerve. Results: Twenty-six patients were verified with PS, unhealthy sitting postures presented in 16 patients (61.5%) and no trauma history was recorded in these patients. Fifteen cases (57.7%) with tenderness located at the suprapiriformis foramen region (SPF group, n=15), 11 patients (42.3%) with tenderness at the piriformis muscle (PM group, n=11). The thickness, area and volume of the pathological side piriformis muscle in the PM group were all significantly higher than the corresponding indexes in the control group[(2.24±0.46) vs (1.66±0.30) cm, (14.4±2.2) vs (8.8±2.1) cm(2,) (23.9±3.8) vs (15.2±2.6) cm(3,) respectively, t=4.699, 7.437, 8.291, all P<0.05]and were all higher remarkably than those in the SPF group[(1.62±0.20) cm, (8.7±1.6) cm(2,) (14.1±4.8) cm(3,) respectively, t=4.640, 7.631, 5.589, all P<0.05]. No significant difference was observed in the up-mentioned indexes between the SPF and the control group (t=-0.439, -0.102, -1.083, all P>0.05). Conclusions: Tender region at the buttock indicates the lesion site in the PS patients. The PS patients with tenderness at the suprapiriformis region might originate from another pathogenesis independent of piriformis muscle compression, the injury of the sciatic nerve or its branch maybe due to the indirect crush by the soft tissue of the suprapiriformis region under an unhealthy sitting posture.

Effects of autologous SCF- and G-CSF-mobilized bone marrow stem cells on hypoxia-inducible factor-1 in rats with ischemia-reperfusion renal injury.

To explore the mechanism whereby stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF) jointly mobilize bone marrow stem cells (BMSCs) and promote kidney repair, male Sprague-Dawley rats were randomly assigned into 4 groups. In the treatment control group, rats were administered SCF (200 µg·kg(-1)·day(-1)) and G-CSF (50 µg·kg-1·day-1) for 5 days. In the treatment group, RIRI models were established, and 6 h later, SCF (200 µg·kg(-1)·day(-1)) and G-CSF (50 µg·kg(-1)·day(-1)) were administered for 5 days. In the model and treatment groups, tubular epithelial cell degeneration and necrosis were noticed, but the extent of repair in the treatment group was significantly better than in the model group. Five days after the operation, renal tissue CD34+ cells significantly increased in the model and treatment groups compared with the control and treatment control groups. HIF-1α, VEGF, and EPO expression in treatment groups increased significantly compared with the other groups. HIF- 1α, VEGF, EPO expression in the treatment control group increased significantly compared with the control group. Joint use of SCF and G-CSF increased the number of BMSCs in damaged kidney tissue and reduced the degree of renal tissue damage. BMSCs promote increased HIF-1α expression in renal tissue. Increased kidney tissue HIF- 1α and its target gene products VEGF and EPO expression possibly induce SCF and G-CSF to promote acute tubular necrosis repair.

Interfractional variability in intensity-modulated radiotherapy of prostate cancer with or without thermoplastic pelvic immobilization.

PURPOSE: To determine the variability of patient positioning errors associated with intensity-modulated radiotherapy (IMRT) for prostate cancer and to assess the impact of thermoplastic pelvic immobilization on these errors using kilovoltage (kV) cone-beam computed tomography (CBCT). MATERIALS AND METHODS: From February 2012 to June 2012, the records of 314 IMRT sessions in 19 patients with prostate cancer, performed with or without immobilization at two different facilities in the Korea University Hospital were analyzed. The kV CBCT images were matched to simulation computed tomography (CT) images to determine the simulation-to-treatment variability. The shifts along the x (lateral)-, y (longitudinal)- and z (vertical)-axes were measured, as was the shift in the three dimensional (3D) vector. RESULTS: The measured systematic errors in the immobilized group during treatment were 0.46 ± 1.75 mm along the x-axis, - 0.35 ± 3.83 mm along the y-axis, 0.20 ± 2.75 mm along the z-axis and 4.05 ± 3.02 mm in the 3D vector. Those of nonimmobilized group were - 1.45 ± 7.50 mm along the x-axis, 1.89 ± 5.07 mm along the y-axis, 0.28 ± 3.81 mm along the z-axis and 8.90 ± 4.79 mm in the 3D vector. The group immobilized with pelvic thermoplastics showed reduced interfractional variability along the x- and y-axes and in the 3D vector compared to the nonimmobilized group (p < 0.05). CONCLUSION: IMRT with thermoplastic pelvic immobilization in patients with prostate cancer appears to be useful in stabilizing interfractional variability during the planned treatment course.

Association of aldehyde dehydrogenase 1 expression and biologically aggressive features in breast cancer.

UNLABELLED: Aldehyde dehydrogenase 1 (ALDH1) has been regarded as a breast cancer stem cell marker. Several studies have reported that ALDH1 expression is associated with poor prognosis in breast cancer. We aimed, therefore, to determine the prognostic value of ALDH1 expression and its association with several biomarkers in breast cancer tissue using immunohistochemistry. Furthermore, we investigated the characteristics of and differences between cellular and stromal expression of ALDH1. We performed tissue microarray (TMA) analysis of 425 breast cancer tissue samples collected during surgery. Immunohistochemical staining was then performed to measure the expression of ALDH1 and other breast cancer biomarkers. Statistical analysis of the relationship between ALDH1 expression and clinicopathologic characteristics was performed for 390 TMA samples. We found that ALDH1 was expressed in 71 cases (18.2%) in the tumor cells and/or stroma. Of these cases, 38 (9.7%) showed ALDH1 expression in tumor cells and 38 (9.7%) showed ALDH1 expression in the stroma. ALDH1 expression was significantly associated with markers of a poor prognosis, such as young age, estrogen receptor negativity, progesterone receptor negativity, a high histological grade, and a high Ki-67 index. However, ALDH1 expression was not associated with p53, transforming growth factor-beta, Gli-1, YKL-40, or sonic hedgehog expression status. With regard to the expression site, the clinical characteristics did not differ between cases of cellular expression and those of stromal expression. However, ALDH1 expression in tumor cells was correlated with hormone receptor status, histological grade, molecular subtype, epidermal growth factor receptor expression status, and cytokeratin 5/6 expression status while stromal expression of ALDH1 was only correlated with hormone receptor status. Overall, these findings suggest that ALDH1 expression in tumor tissue is associated with a biologically aggressive phenotype. KEYWORDS: ALDH1, biologically aggressive, breast cancer.

Set-up uncertainty during breast radiotherapy. Image-guided radiotherapy for patients with initial extensive variation.

PURPOSE: The aim of this work was to establish a customized strategy for image-guided radiotherapy during whole breast irradiation. Risk factors associated with extensive errors were assessed. METHODS AND MATERIALS: A series of 176 consecutive breasts in 174 patients were retrospectively assessed. Electronic portal images from 914 medial and 807 lateral directions were reviewed. On the basis of the chest wall, the deviations between the simulation and each treatment were measured. The systematic (Σ) and random error (σ) of population, and the planning target volume (PTV) margin (2 Σ + 0.7σ) were calculated for each direction. Extensive set-up errors were defined as the fraction over the PTV margins in any direction. For extensive set-up errors, χ(2) tests and logistic regression analyses were conducted. RESULTS: The medial and lateral PTV margins for the right-left, superior-inferior, and anterior-posterior axes and the rotation of collimator were 2.6 and 2.4 mm, 4.6 and 4.6 mm, and 3.1 and 3.3 mm and 2.8 and 2.9 ° and cut-off values for extensive errors were 3, 5, and 4 mm and 3 °, respectively. In χ(2) tests, tumor in upper outer quadrant (p = 0.012) and chest wall thickness ≥ 2.0 cm (p = 0.003) for medial portals and age group (p = 0.036) for lateral portals were associated with extensive errors. In multivariate tests, the extensive error on the initial fraction had a high probability of extensive set-up errors in both medial (OR = 4.26, p < 0.001) and lateral portals (OR = 3.07, p < 0.001). CONCLUSION: In terms of the set-up uncertainty during breast irradiation, patients with extensive error in the initial treatment should be closely observed with serial image-guided radiotherapy.

Host Transcriptome Analysis of Ferret Tissues Following Henipavirus Infection.

Ferrets are commonly used as experimental models of infection for a variety of viruses due to their susceptibility to human respiratory viruses and the close resemblance of pathological outcomes found in human infections. Even though ferret-specific reagents are limited, the use of ferrets as a preclinical experimental model of infection has gained considerable interest since the publication of the ferret transcriptome and draft ferret genome. These advances have made it feasible to easily perform whole-genome gene expression analysis in the ferret infection model. Here, we describe methods for genome-wide gene expression analysis using RNA sequence (RNAseq) data obtained from the lung and brain tissues obtained from experimental infections of Hendra (HeV) and Nipah (NiV) viruses in ferrets. We provide detailed methods for RNAseq and representative data for host gene expression profiles of the lung tissues that show early activation of interferon pathways and later activation of inflammation-related pathways.

Towards hard-magnetic behavior of CoFe2O4 nanoparticles: a detailed study of crystalline and electronic structures, and magnetic properties.

We have used the coprecipitation and mechanical-milling methods to fabricate CoFe2O4 nanoparticles with an average crystallite size (d) varying from 81 to ∼12 nm when changing the milling time (t m) up to 180 min. X-ray diffraction and Raman-scattering studies have proved the samples crystalizing in the spinel structure. Both the lattice constant and residual strain tend to increase when t m(d) increases (decreases). The analysis of magnetization data has revealed a change in the coercivity (H c) towards the hard-magnetic properties. Specifically, the maximum H c is about 2.2 kOe when t m = 10 min corresponding to d ≈ 29 nm; beyond this t m(d) value, H c gradually decreases. Meanwhile, the increase of t m always reduces the saturation magnetization (M s) from ∼69 emu g-1 for t m = 0 to 35 emu g-1 for t m = 180 min. The results collected as analyzing X-ray absorption data have indicated a mixed valence state of Fe2+,3+ and Co2+ ions. We think that the migration and redistribution of these cations between the tetrahedral and octahedral sites together with lattice distortions and defects induced by the milling process have impacted the magnetic properties of the CoFe2O4 nanoparticles.

Risk factors related to interfractional variation in whole pelvic irradiation for locally advanced pelvic malignancies.

PURPOSE: The goal of the present study was to demonstrate risk factors affecting the interfractional variation in whole pelvic irradiation. PATIENTS AND METHODS: Daily image acquisitions of 101 patients with locally advanced pelvic malignancy were undertaken using a kilo-voltage orthogonal on-board imager. The baseline deviation (the shift between the initial treatment and each fraction; Value(Base)) and day-to-day variation (the shift between the previous treatment and each fraction; Value(DD)) were measured. The standard deviations (SD) along the x- (right-left), y- (cranial-caudal), and z- (anterior-posterior) axes (SD[x], SD[y], and SD[z], respectively), the 3D vector of the SD (SD[3D]), and the mean of 3D shift (mean[3D]) were calculated in each patient. Various clinical factors, lumbar pelvic balance and rotation, and the shift of 5 consecutive fractions from the initial treatment (Value(5Fx)) were investigated as risk factors. RESULTS: The prone set-up showed a larger mean(Base)[3D] than in the supine position (p =0 .063). A body mass index (BMI) ≥ 30 kg/m(2) resulted in the largest mean(DD)[3D] (p = 0.078) and SD(DD)[3D] (p = 0.058). All the SD(5Fx) along the x-, y-, and z-axes had moderate linear relationships with SD(Base) and SD(DD) (p < 0.001). The SD(5Fx)[3D] also had a moderate linear relationship with the mean(Base)[3D], mean(DD)[3D], SD(Base)[3D], and SD(DD)[3D] (p < 0.001). In multivariate analysis, the SD(5Fx) had the same significant relationship with SD(Base) and SD(DD) (p < 0.001). A BMI ≥ 30 kg/m(2) was associated with the largest SD(DD)[x] (p = 0.003). CONCLUSION: Close surveillance through high-quality and frequent image guidance is recommended for patients with extensive variations of the initial five consecutive fractions or obesity.

Strong correlation between flux pinning and epitaxial strain in the GdBa2Cu3O7-x /La0.7Sr0.3MnO3 nanocrystalline heterostructure.

The effect of magnetic flux pinning is investigated in GdBa2Cu3O7 (GdBCO) thin films with two different types of ferromagnetic La0.7Sr0.3MnO3 (LSMO) buffers (nanoparticles and a layer) deposited on an STO substrate. Magnetization analyses reveal the presence of multiple flux pinning mechanisms responsible for the improvement in the critical current density of GdBCO films. While core pinning becomes a dominant pinning mechanism in GdBCO films with LSMO nanoparticles, a hybrid effect of magnetic-volume and core-point pinning is observed in GdBCO films with LSMO layers. Examinations of local structures for both LSMO and GdBCO using extended X-ray absorption fine structure spectroscopy (EXAFS) exhibit a close relation between the parameters in the pinning force scaling and the length ratio of the Mn-O bond to the Cu-O bond. This result implies that the origin of core pinning is probably attributed to epitaxial strain induced by lattice mismatch between LSMO and GdBCO. Therefore, an appropriate strain state of LSMO is required for an effective operation of magnetic pinning.

TGFalpha and EGFR in ovine preimplantation embryos and effects on development.

The present study aimed to assess location and relative amounts of transforming growth factor alpha (TGFalpha) and its receptor (EGFR) in ovine oocytes and preimplantation embryos by using immunohistochemical technique that was graded on a relative scale of 0-3, with 0 representing absence of staining, and 3 exhibiting prominent staining, and to evaluate the effects of TGFalpha/EGF on in vitro development of preimplantation embryos by adding different concentrations of EGF and TGFalpha to culture medium. The results showed that EGFR was abundant in cell plasma membranes in immature and mature oocytes, cumulus cells of immature cumulus-oocyte complexes (COC), fertilized oocytes and at different stages of embryo development. However, the relative amounts in inner cell mass (ICM) (1+) was less than that in trophectoderm (TE) cells (2+) at the blastocysts stage. The staining pattern for TGFalpha was a similar to EGFR. However, the staining for TGFalpha slightly increased in the fertilized oocytes (1-2+) as compared to immature and mature oocytes (1+). TGFalpha was mainly detected in the cytoplasm close to the membrane in both ICM and trophectoderm (TE) cells. The developmental rate of 8-cell stage embryos cultured with 5 ng/ml TGFalpha was increased as compared to other treatments (P<0.05). There was no significant difference in the rate of development of blastocysts cultured with 5 ng/ml TGFalpha, 20 ng/ml EGF, 20 ng/ml EGF+5 ng/ml TGFalpha or the control treatment (P>0.05). In addition, there was no significant difference in the number of cells in blastocyst stage as compared with different treatments (P>0.05). However, TGFalpha alone enhanced cell survival rated (P<0.01) and reduced apoptosis. We concluded that TGFalpha can improve development of ovine preimplantation embryos at the 8-cell and blastocyst stages in vitro.

MicroRNA-214 functions as an oncogene in human osteosarcoma by targeting TRAF3.

OBJECTIVE: Osteosarcoma is a malignant bone tumor with high incidence. The prognosis of osteosarcoma is very poor when it is diagnosed with metastasis. Numerous studies have demonstrated that aberrant expressions of microRNAs are involved in cancer initiation and development. However, the potential role of miR-214 in osteosarcoma remains largely unrevealed. The current study investigated the relationship between the miR-214 and TNF receptor-associated factor 3 (TRAF3) in osteosarcoma tissues and cell lines. We also aimed to evaluate the potential roles of miR-214 on the occurrence and metastasis in osteosarcoma and verify its effect on the regulation of TRAF3. PATIENTS AND METHODS: The miR-214 expression and TRAF3 expression in osteosarcoma tissue samples and cell line were measured using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR). Followed by transfection assays, transwell assay was conducted to detect the migration and invasion abilities of osteosarcoma cells. Subsequently, Western blotting and luciferase reporter assay were performed in osteosarcoma cells to confirm the target of miR-214. RESULTS: The results showed that miR-214 expression levels were significantly increased not only in osteosarcoma tissues but also in osteosarcoma cell lines as compared with adjacent normal tissues and matched cell lines, respectively. On the contrary, the TRAF3 expression levels in osteosarcoma tissues and cell lines were frequently decreased compared to the control group. Moreover, TRAF3 was identified as a direct target of miR-214 and the inverse relationship between them was also observed in osteosarcoma tissues. Additionally, we found that miR-214 restoration could significantly promote osteosarcoma cell invasion and migration via targeting TRAF3. CONCLUSIONS: MicroRNA-214 functioned as an oncogene in osteosarcoma via targeting TRAF3, which may provide new insights into osteosarcoma prevention and treatment.

Presenilin structure, function and role in Alzheimer disease.

Numerous missense mutations in the presenilins are associated with the autosomal dominant form of familial Alzheimer disease. Presenilin genes encode polytopic transmembrane proteins, which are processed by proteolytic cleavage and form high-molecular-weight complexes under physiological conditions. The presenilins have been suggested to be functionally involved in developmental morphogenesis, unfolded protein responses and processing of selected proteins including the beta-amyloid precursor protein. Although the underlying mechanism by which presenilin mutations lead to development of Alzheimer disease remains elusive, one consistent mutational effect is an overproduction of long-tailed amyloid beta-peptides. Furthermore, presenilins interact with beta-catenin to form presenilin complexes, and the physiological and mutational effects are also observed in the catenin signal transduction pathway.

Single crystals of a winter flounder antifreeze polypeptide.

Component 6 of the winter flounder's antifreeze polypeptides has been crystallized. The space group is P21, with cell parameters of a = 38.14 A, b = 37.19 A, c = 21.82 A, beta = 101.5 degrees. There are two molecules of 3300 Mr per asymmetric unit.

Crystallization of Bacillus subtilis tryptophanyl-tRNA synthetase.

Tryptophanyl-tRNA synthetase from Bacillus subtilis was overexpressed in Escherichia coli and was purified using column chromatography on DEAE-Sephacel and hydroxyapatite columns. Single crystals of the synthetase were grown by vapor diffusion at 4 degrees C from pH 5.5 solutions of polyethylene glycol 8000 containing magnesium ATP and L-tryptophan. The crystals diffracted to about 4.0 A resolution at -150 degrees C and appeared to belong to the orthorhombic space group P2(1)2(1)2 with unit cell dimensions: a = 143.6 A, b = 111.6 A, c = 50.6 A with one dimer in the asymmetric unit.

Single crystals of a type III antifreeze polypeptide from ocean pout.

Antifreeze protein (HPLC-2) from ocean pout was purified from serum using column chromatography on Sephadex G75 and reverse-phase HPLC columns. Single crystals were grown by batch methods at 4 degrees C from a 1.5 M solution of ammonium sulphate (pH 7.1). The crystals diffracted to about 2.5 A resolution at 4 degrees C and belong to the monoclinic space group P2(1), with cell parameters: a = 39.77 A, b = 58.51 A, c = 30.27 A, beta = 102.28 degrees, with two molecules of 6000 M(r) per asymmetric unit.

The mechanism of protein crystal growth from lipid layers.

Two-dimensional (2D) crystals of proteins on lipid monolayers can initiate the formation of large three-dimensional (3D) crystals suitable for X-ray diffraction studies. The role of the 2D crystals in this process has not been firmly established. While it is likely that the 2D crystals serve as nuclei for epitaxial crystal growth, other mechanisms, such as non-specific nucleation induced by the high local concentration of the protein at the surface of the lipid layer, cannot be excluded. Using streptavidin as a model system, we have now firmly established that 3D crystal growth from 2D crystals on lipid layers occurs by epitaxy. We show that 2D crystals of streptavidin (space group C222) on biotinated lipid layers nucleate the growth of a 3D crystal form (space group I4I22) that possesses a structural similarity with the 2D crystal, but have no effect on the growth of 3D crystal forms (I222 and P2(1)) that are unrelated to the 2D crystal. At lower pH, a new 3D crystal form (space group P1), unrelated to the previously described 2D crystals, grew from lipid layers. This discovery initially raised concern about the validity of the epitaxial mechanism, but these concerns were alleviated with the subsequent discovery of a structurally related 2D P1 crystal that grew in similar solution conditions. Some parameters affecting epitaxial growth of both the P1 and I4I22 crystals were investigated, revealing several noteworthy features of the epitaxial growth. (1) 2D crystals are very effective nucleating agents; for instance, the P1 2D crystals can direct the growth of P1 3D crystals even under conditions that favour the growth of other crystal forms. (2) The epitaxial 3D crystal grow very rapidly and at amazingly low protein concentrations; P1 3D crystals can be grown from solutions as low as 10 microM streptavidin. (3) There is no obligate requirement for the deposition of pre-formed 2D crystals; lipid layers alone are equally effective at promoting epitaxial crystal growth.

Structural studies of soluble oligomers of the Alzheimer beta-amyloid peptide.

Recent studies have suggested that non-fibrillar soluble forms of Abeta peptides possess neurotoxic properties and may therefore play a role in the molecular pathogenesis of Alzheimer's disease. We have identified solution conditions under which two types of soluble oligomers of Abeta40 could be trapped and stabilized for an extended period of time. The first type of oligomers comprises a mixture of dimers/tetramers which are stable at neutral pH and low micromolar concentration, for a period of at least four weeks. The second type of oligomer comprises a narrow distribution of particles that are spherical when examined by electron microscopy and atomic force microscopy. The number average molecular mass of this distribution of particles is 0.94 MDa, and they are are stable at pH 3 for at least four weeks. Circular dichroism studies indicate that the dimers/tetramers possess irregular secondary structure that is not alpha-helix or beta-structure, while the 0.94 MDa particles contain beta-structure. Fluorescence resonance energy transfer experiments indicate that Abeta40 moieties in amyloid fibrils or protofibrils are more similar in structure to those in the 0.94 MDa particles than those in the dimers/tetramers. These findings indicate that soluble oligomeric forms of Abeta peptides can be trapped for extended periods of time, enabling their study by high resolution techniques that would not otherwise be possible.

Binding of secretory component to protein 511, a pIgA mouse protein lacking 36 amino acid residues of the C alpha 3 domain.

Protein 511, a murine IgA protein described previously by Robinson and Appella [Proc. natn. Acad. Sci. U.S.A. 77, 4909-4913 (1980)] which lacks 36 amino acids in the C alpha 3 domain, was tested for its ability to bind to radiolabelled secretory component (125I-rat SC) and to be transported from blood to bile in the rat, a function described previously to be mediated by the poly Ig receptor (pIg R). When compared to other mouse pIgA proteins, the naturally occurring mutant protein 511 bound 125I-rat SC and was transported from blood to bile in a manner indistinguishable from wild-type pIgA protein. We conclude that the region of Fc alpha which is missing in protein 511, is not involved in mediating the binding of pIgA to the pIg R.