Prevalence of tuberculosis symptoms and latent tuberculous infection among prisoners in northeastern Malaysia.

SETTING: There are currently no routine screening procedures for active tuberculosis (TB) or latent tuberculous infection (LTBI) in Malaysian prisons. OBJECTIVE: To determine the prevalence and correlates of LTBI and active TB symptoms among Malaysian prisoners with and without human immunodeficiency virus (HIV) infection using the tuberculin skin test (TST) and the World Health Organization TB symptom-based screening instrument. DESIGN: A cross-sectional survey of 266 prisoners was performed in Kelantan, Malaysia. Consenting participants underwent two-step TST and were screened for active TB symptoms. Standardized cut-offs of respectively ≥5 and ≥10 mm were used to define reactive TST among prisoners with and without HIV. Clinical and behavioral data were assessed and HIV-infected prisoners were stratified by CD4 status. RESULTS: Overall LTBI prevalence was 87.6%, with significantly lower TST reactivity among HIV-infected than non-HIV-infected prisoners (83.6% vs. 91.5%, P < 0.05); however, TB symptoms were similar (16.9% vs. 10.1%, P = 0.105). On multivariate analysis, previous incarceration (aOR 4.61, 95%CI 1.76-12.1) was the only significant correlate of LTBI. Increasing age (aOR 1.07, 95%CI 1.01-1.13), lower body mass index (aOR 0.82, 95%CI 0.70-0.96) and TST-reactive status (aOR 3.46, 95%CI 1.20-9.97) were correlated with TB symptoms. CONCLUSION: LTBI is highly prevalent, associated with previous incarceration, and suggests the need for routine TB screening on entry to Malaysian prisons.

Crystal structure of the kinase domain of human vascular endothelial growth factor receptor 2: a key enzyme in angiogenesis.

BACKGROUND: Angiogenesis is involved in tumor growth, macular degeneration, retinopathy and other diseases. Vascular endothelial growth factor (VEGF) stimulates angiogenesis by binding to specific receptors (VEGFRs) on the surface of vascular endothelial cells. VEGFRs are receptor tyrosine kinases that, like the platelet-derived growth factor receptors (PDGFRs), contain a large insert within the kinase domain. RESULTS: We report here the generation, kinetic characterization, and 2.4 A crystal structure of the catalytic kinase domain of VEGF receptor 2 (VEGFR2). This protein construct, which lacks 50 central residues of the 68-residue kinase insert domain (KID), has comparable kinase activity to constructs containing the entire KID. The crystal structure, determined in an unliganded phosphorylated state, reveals an overall fold and catalytic residue positions similar to those observed in other tyrosine-kinase structures. The kinase activation loop, autophosphorylated on Y1059 prior to crystallization, is mostly disordered; however, a portion of it occupies a position inhibitory to substrate binding. The ends of the KID form a beta-like structure, not observed in other known tyrosine kinase structures, that packs near to the kinase C terminus. CONCLUSIONS: The majority of the VEGFR2 KID residues are not necessary for kinase activity. The unique structure observed for the ends of the KID may also occur in other PDGFR family members and may serve to properly orient the KID for signal transduction. This VEGFR2 kinase structure provides a target for design of selective anti-angiogenic therapeutic agents.

Chondroid hamartoma presenting as a neonatal nasal mass.

We present a case of a 3-month-old female with a right nasal mass. Upon evaluation with computed tomography, magnetic resonance imaging and angiography, a large right intranasal mass extending through the cribiform plate, displacing the dura, was noted. The patient underwent a combined midfacial degloving and bifrontal craniotomy for complete resection of the tumor mass. Pathologic evaluation demonstrated a mesenchymal tumor with spindle and stellate cells from which islands of immature cartilage emerged. The spectrum of histologic features closely resembled a mesenchymal chondroid hamartoma typically located in the chest wall. It is the first reported case of a chondroid hamartoma of the head and neck in the literature to date. We examine the characteristics and treatment of this unusual tumor.

The conformation of hepatitis C virus NS3 proteinase with and without NS4A: a structural basis for the activation of the enzyme by its cofactor.

BACKGROUND: Hepatitis C virus (HCV) NS3 proteinase activity is required for the release of HCV nonstructural proteins and is thus a potential antiviral target. The enzyme requires a protein cofactor NS4A, located downstream of NS3 on the polyprotein, for activation and efficient processing. OBJECTIVES: Comparison of the proteinase three-dimensional structure before and after NS4A binding should help to elucidate the mechanism of NS4A-dependent enzyme activation. STUDY DESIGN: We determined the crystal structure of NS3 proteinase of HCV BK isolate (genotype 1b; residues 1-189) and also the crystal structure of this proteinase complexed with HCV BK-NS4A (residues 21-34). RESULTS: The core region (residues 30-178) of the enzyme without cofactor (NS3P) or with bound cofactor (NS3P/4A) is folded into a trypsin-like conformation and the substrate P1 specificity pocket is essentially unchanged. However, the D1-E1 beta-loop shifts away from the cofactor binding site in NS3P/4A relative to NS3P, thereby accommodating NS4A. One result is that catalytic residues His-57 and Asp-81 move closer to Ser-139 and their sidechains adopt more 'traditional' (trypsin-like) orientation. The N-terminus (residues 1-30), while extended in NS3P, is folded into an alpha-helix and beta-strand that cover the bound cofactor of NS3P/4A. A new substrate-binding surface is formed from both the refolded N-terminus and NS4A, potentially affecting substrate residues immediately downstream of the cleavage site. CONCLUSIONS: Direct comparison of the crystal structures of NS3P and NS3P/4A shows that the binding of NS4A improves the anchoring and orientation of the enzyme's catalytic triad. This is consistent with the enhancement of NS3P's weak residual activity upon NS4A binding. There is also significant refolding of the enzyme's N-terminus which provides new interactions with P'-side substrate residues. The binding surface for P'-side substrate residues, including the P1 specificity pocket, changes little after NS4A binding. In summary, we observe a structural basis for improved substrate turnover and affinity that follows complexation of NS3P with its NS4A cofactor.

Crystal structure of the coat protein from the GA bacteriophage: model of the unassembled dimer.

There are four groups of RNA bacteriophages with distinct antigenic and physicochemical properties due to differences in surface residues of the viral coat proteins. Coat proteins also play a role as translational repressor during the viral life cycle, binding an RNA hairpin within the genome. In this study, the first crystal structure of the coat protein from a Group II phage GA is reported and compared to the Group I MS2 coat protein. The structure of the GA dimer was determined at 2.8 A resolution (R-factor = 0.20). The overall folding pattern of the coat protein is similar to the Group I MS2 coat protein in the intact virus (Golmohammadi R, Valegård K, Fridborg K, Liljas L. 1993, J Mol Biol 234:620-639) or as an unassembled dimer (Ni Cz, Syed R, Kodandapani R. Wickersham J, Peabody DS, Ely KR, 1995, Structure 3:255-263). The structures differ in the FG loops and in the first turn of the alpha A helix. GA and MS2 coat proteins differ in sequence at 49 of 129 amino acid residues. Sequence differences that contribute to distinct immunological and physical properties of the proteins are found at the surface of the intact virus in the AB and FG loops. There are six differences in potential RNA contact residues within the RNA-binding site located in an antiparallel beta-sheet across the dimer interface. Three differences involve residues in the center of this concave site: Lys/Arg 83, Ser/Asn 87, and Asp/Glu 89. Residue 87 was shown by molecular genetics to define RNA-binding specificity by GA or MS2 coat protein (Lim F. Spingola M, Peabody DS, 1994, J Biol Chem 269:9006-9010). This sequence difference reflects recognition of the nucleotide at position -5 in the unpaired loop of the translational operators bound by these coat proteins. In GA, the nucleotide at this position is a purine whereas in MS2, it is a pyrimidine.

The crystal structure of hepatitis C virus NS3 proteinase reveals a trypsin-like fold and a structural zinc binding site.

During replication of hepatitis C virus (HCV), the final steps of polyprotein processing are performed by a viral proteinase located in the N-terminal one-third of nonstructural protein 3. The structure of NS3 proteinase from HCV BK strain was determined by X-ray crystallography at 2.4 angstrom resolution. NS3P folds as a trypsin-like proteinase with two beta barrels and a catalytic triad of His-57, Asp-81, Ser-139. The structure has a substrate-binding site consistent with the cleavage specificity of the enzyme. Novel features include a structural zinc-binding site and a long N-terminus that interacts with neighboring molecules by binding to a hydrophobic surface patch.

Crystallization of the MS2 translational repressor alone and complexed to bromouridine.

The coat protein from the MS2 bacteriophage plays a dual role by encapsidating viral RNA and also by binding RNA as a translational repressor. In order to study the isolated dimer in a conformation not influenced by capsid interactions, a mutant molecule was crystallized that is defective in capsid assembly but is an active repressor. The unassembled dimer crystallized in the space group P21212 with a = 76.2, b = 55.7, and c = 28.4 A. In these crystals, monomers were related by twofold symmetry. When this dimer was co-crystallized with 5-bromouridine, crystals formed in space group R3 with a = b = 155.9 A, c = 29.9 A, gamma = 120 degrees; the dimer was the asymmetric unit.

Crystal structure of the MS2 coat protein dimer: implications for RNA binding and virus assembly.

BACKGROUND: The coat protein in RNA bacteriophages binds and encapsidates viral RNA, and also acts as translational repressor of viral replicase by binding to an RNA hairpin in the RNA genome. Because of its dual function, the MS2 coat protein is an interesting candidate for structural studies of protein-RNA interactions and protein-protein interactions. In this study, unassembled MS2 coat protein dimers were selected to analyze repressor activity and virus assembly. RESULTS: The crystal structure of a mutant MS2 coat protein that is defective in viral assembly yet retains repressor activity has been determined at 2.0 A resolution. The unassembled dimer is stabilized by interdigitation of alpha-helices, and the formation of a 10-stranded antiparallel beta-sheet across the interface between monomers. The substitution of arginine for tryptophan at residue 82 results in the formation of two new inter-subunit hydrogen bonds that further stabilize the dimer. Residues that influence RNA recognition, identified by molecular genetics, were located across the beta-sheet. Two of these residues (Tyr85 and Asn87) are displaced in the unliganded dimer and are located in the same beta-strand as the Trp-->Arg mutation. CONCLUSIONS: When compared with the structure of the coat protein in the assembled virus, differences in orientation of residues 85 and 87 suggest conformational adjustment on binding RNA in the first step of viral assembly. The substitution at residue 82 may affect virus assembly by imposing conformational restriction on the loop that makes critical inter-subunit contacts in the capsid.

The effect of halothane, isoflurane, or sufentanil on the hypertensive response to cerebellar retraction during posterior fossa surgery.

The blood pressure (BP) response to cerebellar retraction during microvascular decompression of the fifth cranial nerve was investigated in 26 ASA physical status 2 or 3 patients with trigeminal neuralgia. One surgeon performed all operations. To determine the effect of three anesthetic techniques on the BP response, patients were randomly assigned to receive halothane, isoflurane, or sufentanil in sufficient doses with 60% nitrous oxide to achieve a precerebellar retraction systolic BP that was 10-20% below the average ward systolic BP (as per standard clinical practice). The resultant doses were halothane 1.65 +/- 0.27 (mean +/- SD) MAC, isoflurane 1.56 +/- 0.17 MAC (P greater than 0.05), and sufentanil 2.7 micrograms/kg (MAC values include 0.6 MAC contribution from 60% nitrous oxide). In all patients BP increased during the cerebellar retractor placement period compared with the preretractor placement period (P less than 0.05). The peak increase in systolic BP in response to cerebellar retraction was 17 +/- 6 mmHg for halothane, 38 +/- 20 mmHg for isoflurane, and 26 +/- 19 mmHg for sufentanil. The difference between halothane and isoflurane was significant (P less than 0.05). Mean and diastolic BP showed similar significant differences. The authors conclude that halothane attenuates the hypertensive response to cerebellar retraction more than isoflurane when administered in approximately 1.6 MAC concentrations (MAC value includes contribution from nitrous oxide).

Skull metastases from follicular thyroid carcinoma.

Distant metastatic disease from thyroid carcinoma is becoming a rare problem. Physicians and the public are increasingly aware of minimally invasive methods of early diagnosis of thyroid malignancy, such as fine-needle aspiration with cytologic examination. Total thyroidectomy itself has become less associated with morbidity than it once was. We describe three patients with follicular thyroid carcinoma metastatic to the skull who were seen recently. Two of these patients had masses neglected for 20 and 50 years, respectively. The management of this disease entity is discussed.