Management of oral Kaposi's sarcoma and a proposal for clinical staging

Kaposi's sarcoma (KS) is the most common neoplastic disease in patients with disease due to human immunodeficiency virus (HIV), and oral KS (OKS) is the commonest oral neoplasia. OKS has been managed by local excision, intralesional chemotherapy regional radiotherapy, and systemic chemotherapy. Comparison between studies is difficult as the severity of oral involvement is not well defined in most studies. This paper reviews the approach to the management of OKS and also presents a proposal for the clinical staging of OKS. Clinical staging of OKS will facilitate comparisons of outcomes of treatment of OKS and improve our understanding of the natural history of the neoplasia, which has varied presentation and rates of progression.     

Effect of shunt surgery on spleen size, portal pressure and oesophageal varices in patients with non-cirrhotic portal hypertension

Shunt surgery is considered to be the treatment of choice in patients with non-cirrhotic portal hypertension. There is little data on the effect of side-to-side lieno-renal (SSLR) shunt on oesophageal variceal size, splenic size and splenic pulp pressure (SPP) in patients with non-cirrhotic portal hypertension. We evaluated pre- and postoperatively endoscopic grading of varices, splenic size and SPP for predicting shunt patency in 86 patients with non-cirrhotic portal hypertension: 56 with extrahepatic portal venous obstruction (EHPVO) and 30 with non-cirrhotic portal fibrosis (NCPF). The EHPVO patients with patent shunts (n= 47) showed significant reduction in SPP (pre-operative 43.56±7.9 vs postoperative 29.96±7.7 cm of saline), splenic size (6.5±2.8 vs 4.00±2.6 cm below costal margin) and varices grades (2.96±0.5 vs 0.92±0.8). Patients with blocked shunt (n= 9) did not show significant reduction in SPP and varices grades. However, there was reduction in spleen size (8.6±3.0 vs 6.3±4.3). In the NCPF group, 28 had patent shunts and showed significant reduction in SPP (46.3±13.5 vs 33.8±7.6 cm of saline), splenic size (9.1±3.3 vs 6.8±4.6 cm below costal margin) and varices grades (2.8±0.7 vs 1.05±0.96). As only two patients with NCPF had blocked shunts, no statistical comparison between patients with patent and patients with blocked shunts could be done. In conclusion, following SSLR, there is a significant reduction in SPP and varices grades in patients with patent shunts. Endoscopic grading of varices can be used to predict shunt patency. However, spleen size is not a good criteria for predicting shunt patency.     

小叶买麻藤中买麻藤甲素的结构研究

从小叶买麻藤[Gnetum parvifolium(Warb.)C.Y.Cheng]茎的乙酸乙酯部分得到五个成分,经理化常数测定、光谱(UV,IR,MS,~1HNMR,~(13)CNMR和2D-NMR)分析和衍生物制备,确定买麻藤甲素为一个新的2-苯基苯并呋喃类化合物,结构为2-(3′,5′-二羟基-4′-甲氧基苯基)_-3-甲氧基5-羟基苯并呋喃。另外三个鉴定为异丹叶大黄素、白黎芦醇和β-谷甾醇.还有一个化合物正在鉴定中。     

Chagas' disease diagnosis: evaluation of several tests in blood bank screening

Blood transfusion is one of the principal routes of transmission of Chagas' disease, a major endemic disease in Latin America. Methods for blood screening are not accurate and may yield false results that lead to high social and economic costs. This study compares two methods of diagnosing Chagas' disease (indirect immunofluorescence and hemagglutination) and several enzyme-linked immunosorbent assays (ELISAs) with regard to specificity and sensitivity, by using human sera with known serologic and parasitologic characteristics, as well as samples with discrepant results on conventional serologic tests. An ELISA using recombinant antigens showed no cross-reactivity with sera that were positive for other diseases. All evaluated ELISAs performed well, and their use may lead to a reduction of more than 50 percent in the number of discordant sera. Further improvements are needed in view of the complexity of the serologic diagnosis of Chagas' disease.     

Local and global structural drivers for the photoactivation of the orange carotenoid protein

Photoprotective mechanisms are of fundamental importance for the survival of photosynthetic organisms. In cyanobacteria, the orange carotenoid protein (OCP), when activated by intense blue light, binds to the light-harvesting antenna and triggers the dissipation of excess captured light energy. Using a combination of small angle X-ray scattering (SAXS), X-ray hydroxyl radical footprinting, circular dichroism, and H/D exchange mass spectrometry, we identified both the local and global structural changes in the OCP upon photoactivation. SAXS and H/D exchange data showed that global tertiary structural changes, including complete domain dissociation, occur upon photoactivation, but with alteration of secondary structure confined to only the N terminus of the OCP. Microsecond radiolytic labeling identified rearrangement of the H-bonding network associated with conserved residues and structural water molecules. Collectively, these data provide experimental evidence for an ensemble of local and global structural changes, upon activation of the OCP, that are essential for photoprotection.Photosynthetic organisms have evolved a protective mechanism known as nonphotochemical quenching (NPQ) to dissipate excess energy, thereby preventing oxidative damage under high light conditions (1). In plants and algae, NPQ involves pH-induced conformation changes in membrane-embedded protein complexes and enzymatic interconversion of carotenoids (2, 3). Cyanobacteria, in contrast, use a relatively simple NPQ mechanism governed by the water soluble orange carotenoid protein (OCP). The OCP is composed of an all α-helical N-terminal domain (NTD) consisting of two discontinuous four-helix bundles and a mixed α/β C-terminal domain (CTD), which is a member of the widely distributed nuclear transport factor 2-like superfamily (Fig. S1A) (4, 5). There are two regions of interaction between the NTD and CTD (4, 5): the major interface, which buries 1,722 Å of surface area, and the interaction between the N-terminal alpha-helix (αA) and the CTD (minor interface) (Fig. S1A). A single noncovalently bound keto-carotenoid [e.g., echinenone (ECN)] spans both domains in the structure of the resting (inactive) form of the protein (OCP^O).Open in a separate windowFig. S1.Structure of the OCP. (A) Crystal structure of Synechocystis OCP (PDB ID code 3MG1) consisting of two domains, NTD and CTD as described in the main text introduction, which form major and minor interfaces. (B) Amino acid residues within 3.9 Å of the carotenoid are shown by sticks. (C) Surface-bound water molecules at the major interface are shown in slate-colored spheres in Synechocystis OCP (PDB ID code 3MG1). This layer of water molecules fully or partially eclipses other water molecules, which are either conserved or found to be at the same location (within 0.5 Å) in the crystal structures of A. maxima and Synechocystis OCP (Fig. 4 A and B. Removal of the slate-colored spheres, exposing partially buried water, is shown in orange in D. The fully buried waters (red spheres) are invisible in the surface diagram of OCP. (E) Cross-sectional view to show the position of fully and partially buried structural waters in OCP^O. (F) Details of water–protein H-bonding network in water cluster 1 at the major interface. The absolutely conserved R155 is closely surrounded (<3.2 Å, capable of forming H-bond) by a number of buried (HOH1151,1200, and 1671) water molecules, which are involved in dense residue-water interactions as discussed in the main text. Similar H-bonding networks are also observed in the water clusters 2 and 3 (6). Exposure to blue light converts OCP^O to the active (red) form, OCP^R (7). OCP^R is involved in protein–protein interactions with the phycobilisome (PB) (5) and the fluorescence recovery protein (FRP), which converts OCP^R back to OCP^O (8). The OCP^R form is therefore central to the photoprotective mechanism, and determining the exact structural changes that accompany its formation are critical for a complete mechanistic understanding of the reversible quenching process in cyanobacteria. Although crystal structures exist of both the (inactive) OCP^O (4, 5) and the active NTD (effector domain) form of the protein (9), crystallization of the activated, full-length OCP^R has not been achieved. To identify the protein structural changes that occur after absorption of light by the OCP’s ECN chromophore, we undertook a hybrid approach to structurally characterize OCP^R in solution.In Synechocystis OCP^O, the 4-keto group on the “β1” ring of ECN is H-bonded to two conserved residues, Y201 and W288, in a hydrophobic pocket in the core of the CTD (Fig. S1B) (5). The other end of the carotenoid is positioned between the two four-helix bundles of the NTD. Several conserved residues within 3.9 Å of the carotenoid are known to interact with its extensive conjugation and result in fine tuning of the spectral characteristics of the OCP (Fig. S1B) (4, 5); these residues have been implicated in photochemical function via mutagenesis studies (5). A recent study of the OCP bound to the carotenoid canthaxanthin (OCP-CAN) showed that photoactivation of the OCP results in a substantial translocation (12 Å) of the carotenoid deeper into the NTD (9). Mutational analyses of the full-length OCP and biochemical studies on the constitutively active NTD [commonly known as the red carotenoid protein (RCP)] suggested that the NTD and CTD at least partially separate, resulting in the breakage of an interdomain salt-bridge (R155–E244) upon photoactivation (9–12). Together, the previous studies suggest that large-scale protein structural changes in the OCP accompany carotenoid translocation upon light activation; however, such changes in the context of the full-length protein have yet to be experimentally demonstrated. Here, we report use of X-ray radiolytic labeling with mass spectrometry (XF-MS) and hydrogen/deuterium exchange with mass spectrometry (HDX-MS), which detect residue-specific changes (13–15), to investigate the structural changes that occur during OCP photoactivation. In conjunction with small angle X-ray scattering (SAXS), which enables characterization of global conformational changes in the solution state (16), we show that dissociation of the NTD and CTD is complete in photoactivated OCP. This separation is accompanied by an unfolding of the N-terminal α-helix that is associated with the CTD in the resting state. We also pinpoint changes in specific amino acids and structurally conserved water molecules, providing insight into the signal propagation pathway from carotenoid to protein surface upon photoactivation. Collectively, these data provide a comprehensive view of both global and local intraprotein structural changes in the OCP upon photoactivation that are essential to a mechanistic understanding of cyanobacterial NPQ.     

The role of torovirus in nosocomial viral gastroenteritis at a large tertiary pediatric centre

OBJECTIVE:

To describe the viral etiology and epidemiology of nosocomial viral gastroenteritis (NVG) at a tertiary care pediatric hospital and identify any changes over the past two decades.

METHODS:

Retrospective review of all patients with laboratory-confirmed NVG at The Hospital for Sick Children (Toronto, Ontario), from January 1, 2004, to December 31, 2005.

RESULTS:

One hundred forty-two episodes of NVG were found among 133 patients, occurring in 0.48 of 100 admissions. The median age was two years; 42% were <1 year of age and 41% were immunocompromised. The most commonly detected pathogen was torovirus (67% of episodes), followed by rotavirus (19%) and adenovirus (9%). Seventy-five cases (53%) were epidemiologically linked in 32 separate clusters (median cluster size two, range two to four). The NVG rate fell from 0.63 of 100 to 0.22 of 100 admissions after March 2005 (P<0.001) when enhanced infection control precautions were instituted in response to an outbreak of vancomycin-resistant Enterococcus.

CONCLUSIONS:

Torovirus remains the most commonly identified cause of NVG at The Hospital for Sick Children. Most NVG cases were epidemiologically linked, and a significant reduction in cases occurred after the institution of enhanced infection control practices following an outbreak of vancomycin-resistant Enterococcus. Improved education and surveillance for NVG should lead to further reduction in this problem.     

Beta thalassemia in Melanesia: association with malaria and characterization of a common variant (IVS-1 nt 5 G----C)

Data on the distribution of beta thalassemia among over 6,000 Melanesians reveals a major difference in the carrier rates between populations in the malarious coastal regions of New Guinea and those living in the historically malaria-free Highlands. The island of Maewo in Vanuatu has a particularly high incidence of beta + thalassemia associated with a single restriction enzyme haplotype. Direct cloning into a plasmid vector and sequence analysis demonstrate that the mutation is a G to C transversion at position 5 of intron 1 of the beta- globin gene. Oligonucleotide probe surveys indicate that this variant accounted for all cases of beta thalassemia studied from Maewo. It is also common in coastal Papua New Guinea where haplotype and oligonucleotide probe data suggest that the molecular basis of beta thalassmia is more heterogeneous.     

Partial plasma exchange using albumin replacement: removal and recovery of normal plasma constituents

Using albumin and crystalloid as the only replacement fluids, the effect of partial plasma exchange on the removal and recovery of normal plasma constituents was studied. The results of 30 procedures on 10 individuals were evaluated. Four patterns of removal are described: reduction in the concentration of fibrinogen and C3 were greater than would be expected based upon the extent of the exchange, while IgG, IgM, cholesterol, alkaline phosphatase and SGPT were removed as expected. Reduction of serum glutamicoxalacetic transaminase (SGOT), lactate dehydrogenase (LDH), amylase, and creatine phosphokinase (CPK) averaged 17% less, and uric acid, calcium and K+ averaged 53% less than expected. Concentrations of HCO-3 and glucose did not change. The mean recovery for all constituents except fibrinogen, C3, cholesterol. IgG and IgM was near 100% at 48-72 hr postpheresis. The 72-hr recovery of fibrinogen and complement was 66% and 60%, respectively. Cholesterol recovery was also slow, requiring a minimum of 1 wk to reach prepheresis levels. Measured at a time when quantitative IgM levels were still reduced, alloantibody agglutinating activity (anti-A and anti-B) in a postpheresis sample exceeded prepheresis agglutinating activity. These data demonstrated that, depending upon quantity and frequency of pheresis, partial plasma exchange using albumin replacement may cause progressive marked reduction in concentrations of immunoglobulin, complement, fibrinogen, and cholesterol. Furthermore, newly synthesized antibody may have increased biologic activity.