A framework for interpreting the leucine-rich repeats of the Listeria internalins

The surface protein InlB of the bacterial pathogen Listeria monocytogenes is required for inducing phagocytosis in various nonphagocytic mammalian cell types in vitro. InlB causes tyrosine phosphorylation of host cell adaptor proteins, activation of phosphoinositide 3-kinase, and rearrangements of the actin cytoskeleton. These events lead to phagocytic uptake of the bacterium by the host cell. InlB belongs to the internalin family of Listeria proteins, which also includes InlA, another surface protein involved in host cell invasion. The internalins are the largest class of bacterial proteins containing leucine-rich repeats (LRR), a motif associated with protein-protein interactions. The LRR motif is found in a functionally diverse array of proteins, including those involved in the plant immune system and in the mammalian innate immune response. Structural and functional interpretations of the sequences of internalin family members are presented in light of the recently determined x-ray crystal structure of the InlB LRR domain.

Differential expression of proteoglycan epitopes by ovine intervertebral disc cells

The alginate bead culture system has been utilised by several groups to examine the in vitro proteoglycan (PG) metabolism of chondrocytes and intervertebral disc cells, but the nature of the PGs produced has not been examined in detail. This is largely due to the difficulty of separating the anionically charged sodium alginate support matrix from PGs which are similarly charged. In the present study ovine annulus fibrosus, transitional zone and nucleus pulposus cells were dissociated enzymatically from their respective matrices by sequential digestion with pronase/clostridial collagenase and DNAase and then cultured in alginate beads for 10 d. The beads were solubilised and subjected to DEAE Sepharose CL6B anion exchange chromatography to separate the sodium alginate bead support matrix material quantitatively from the disc cell PGs. The alginate free bead PGs were then subjected to composite agarose polyacrylamide gel electrophoresis to resolve PG populations and the PGs were transferred to nitrocellulose membranes by semidry electroblotting. The PGs were identified by probing the blots with a panel of antibodies to defined PG core protein and glycosaminoglycan side chain epitopes. Alginate beads of disc cells were also embedded in paraffin wax and 4 microm sections cut to immunolocalise decorin, biglycan, versican, and the 7-D-4 PG epitope within the beads. Decorin and biglycan had similar distributions in the beads, being localised on the cell surface whereas versican and the 7-D-4 PG epitope were immunolocalised interterritoriarly. This study is the first to demonstrate that ovine disc cells synthesise versican in alginate bead culture. Furthermore the immunoblotting studies also showed that a proportion of the 7-D-4 PG epitope was colocalised with versican.

Role of hla class-I antigens in delusional disorder

The investigation was conducted to find out whether there is any association between delusional disorder and HLA antigens. The sample comprised 50 patients with delusional disorder and 282 control samples collected from normal controls. Statistical analysis revealed that the frequency of A3 antigen of the locus A are significantly higher. In case of HLA - B locus significantly higher frequency of B5 and B21 antigens have also been observed. The present study shows that there may be some association of HLA class-1 antigens with delusional disorder.

Effects of chronic alcohol treatment on the synthesis, sialylation, and disposition of nascent apolipoprotein E by peritoneal macrophages of rats

BACKGROUND

Plasma apolipoprotein (apo) E, a sialoprotein, plays an important role in reverse cholesterol transport. Previously, we showed that chronic alcohol consumption impairs glycosylation of apo E in rat liver. Peritoneal macrophages are another significant apo E synthesis site.

OBJECTIVE

The main purpose of this study was to determine the effects of chronic alcohol feeding of rats on the synthesis, sialylation, and sialic acid content of macrophage apo E and its ability to bind to the HDL(3) molecule in vitro.

DESIGN

Rats were fed an alcoholic diet or an isoenergetic control diet for 8 wk, after which peritoneal macrophages isolated from them were cultured and analyzed for apo E metabolism.

RESULTS

Macrophages from alcohol-fed rats accumulated 33.3% more (P < 0.05) cholesterol than did those from control rats when incubated with acetylated LDL. These macrophages showed a 51-57% lower relative sialylation rate of apo E (P < 0.001) but no significant difference in relative protein synthetic rate. The sialic acid content of the intracellular and secreted forms of apo E was reduced by 41.8% (P < 0.001) and 50.3% (P < 0.001), respectively, with chronic alcohol treatment. Secretion of newly synthesized apo E was impaired by 53.7% (P < 0.001) and 26. 1% (P < 0.001) in the absence and presence of HDL in the medium, respectively. Macrophages of alcohol-treated rats secreted apo E with 47.6-67.2% lower (P < 0.001) HDL(3) binding ability; binding ability was restored completely by resialylation of the desialylated apo E.

CONCLUSION

In rats, an alcohol-mediated decrease in sialylation rate resulting in loss of sialic acid residues in apo E impairs the ability of apo E to bind to HDL and consequently in defective reverse cholesterol transport.

Bis[(benzo-15-crown-5)-15-yl methyl] pimelate forms ion channels in planar lipid bilayer: a novel model ion channel

Some crown ethers translocate cations across the liposomal membrane either by a carrier mechanism or by forming ion channels. We report formation of ion channels in lipid bilayer membranes by bis[(benzo-15-crown-5)-15-yl methyl] pimelate, a crown ether known to form ion inclusion complexes with alkali metal cations. The channels have characteristic long openings lasting several seconds and a low conductance (4 pS in 500 mM KCl and 2.5 pS in 500 mM NaCl). A model of the crown ether channel formed by stacking of four monomers is proposed. A large database of structural information on crown ethers and their ion inclusion complexes as well as large family of crown ethers with a variety of substitutions in the ring are commercially available. Thus the crown ether channel is an attractive model system to study the role of various chemical moieties in ion conduction which may provide deeper insight into understanding the mechanism(s) of selectivity, ion transport, etc. in biological ion channels.

The structure and stability of an HLA-A*0201/octameric tax peptide complex with an empty conserved peptide-N-terminal binding site

The crystal structure of the human class I MHC molecule HLA-A2 complexed with of an octameric peptide, Tax8 (LFGYPVYV), from human T cell lymphotrophic virus-1 (HTLV-1) has been determined. This structure is compared with a newly refined, higher resolution (1.8 A) structure of HLA-A2 complexed with the nonameric Tax9 peptide (LLFGYPVYV) with one more N-terminal residue. Despite the absence of a peptide residue (P1) bound in the conserved N-terminal peptide-binding pocket of the Tax8/HLA-A2 complex, the structures of the two complexes are essentially identical. Water molecules in the Tax8 complex replace the terminal amino group of the Tax9 peptide and mediate a network of hydrogen bonds among the secondary structural elements at that end of the peptide-binding groove. Thermal denaturation measurements indicate that the Tax8 complex is much less stable, DeltaTm = 16 degrees C, than the Tax9 complex, but both can sensitize target cells for lysis by some Tax-specific CTL from HTLV-1 infected individuals. The absence of a P1 peptide residue is thus not enough to prevent formation of a "closed conformation" of the peptide-binding site. TCR affinity measurements and cytotoxic T cell assays indicate that the Tax8/HLA-A2 complex does not functionally cross-react with the A6-TCR-bearing T cell clone specific for Tax9/HLA-A2 complexes.

Production of tissue inhibitor of metalloproteinases 3 is selectively enhanced by calcium pentosan polysulfate in human rheumatoid synovial fibroblasts

OBJECTIVE

To determine the effects of calcium pentosan polysulfate (CaPPS) on the production of matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMP), in cultures of rheumatoid synovial fibroblasts.

METHODS

The production of MMP-1, -2, -3, -7, -8, -9, and -13 and of TIMP-1, -2, -3, and -4 in cultured rheumatoid synovial fibroblasts treated with 0.1, 1, and 10 microg/ml CaPPS in the presence and absence of 100 units/ml interleukin-1alpha (IL-1alpha) was examined by a sandwich enzyme immunoassay system and/or immunoblotting. The messenger RNA (mRNA) expression of TIMP-3 and membrane type 1 MMP was determined by Northern blotting, and the cells expressing TIMP-3 gene in rheumatoid synovium were identified by in situ hybridization. The synthesis and secretion of TIMP-3 protein were monitored by pulse-chase experiments. TIMP-3 was immunolocalized in untreated or CaPPS-treated rheumatoid synovial fibroblasts and synovium using an avidin-biotin-peroxidase complex method.

RESULTS

Treatment of cultured rheumatoid synovial fibroblasts with CaPPS resulted in a dose-dependent increase in the production of TIMP-3 in both cell lysates and media from the treated cells. However, CaPPS did not affect the levels of the other MMPs or TIMPs examined. The production of TIMP-3 was further enhanced in the cells treated with both IL-1alpha and CaPPS. Immunohistochemistry confirmed the enhanced production of TIMP-3 by cells exposed to CaPPS. The mRNA level of TIMP-3 increased 3.4-fold by treating rheumatoid synovial fibroblasts with IL-1alpha, but CaPPS itself did not alter the expression levels in the IL-1alpha-treated or -untreated cells. Pulse-chase studies demonstrated that translation for TIMP-3 protein was enhanced by CaPPS treatment. In situ hybridization and immunohistochemistry indicated that TIMP-3 was expressed mainly in the hyperplastic lining cells of rheumatoid synovium, and that the production of this protein by these immunoreactive lining cells was significantly increased by treatment with CaPPS.

CONCLUSION

The present study is the first to demonstrate that the new antiarthritic drug, CaPPS, selectively enhanced TIMP-3 production at the posttranscription level in cultured rheumatoid synovial fibroblasts and in the lining cells of rheumatoid synovium. By this mechanism, CaPPS may be able to modulate joint tissue destruction in rheumatoid arthritis.

Apoptosis-inducing vanadocene compounds against human testicular cancer

We systematically assessed the cytotoxic effects of five metallocene dichlorides containing vanadium (vanadocene dichloride), titanium (titanocene dichloride), zirconium (zircodocene dichloride), molybdenum (molybdocene dichloride), and hafnium (hafnocene dichloride) as the central metal atom and 19 other vanadocene complexes. These compounds were tested against the human testicular cancer cell lines Tera-2 and Ntera-2 using both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays and apoptosis assays. Notably, only the vanadium(IV)-containing metallocenes exhibited significant cytotoxicity against Tera-2 and Ntera-2 cells and induced apoptosis within 24 h. Vanadocenes with dithiocyanate [VCp2(SCN)2 x 0.5 H2O] and diselenocyanate [VCp2(NCSe)2] as ancillary ligands were identified as the most potent cytotoxic compounds. Vanadocenes, especially the lead compound VCp2(NCSe)2, may be useful in the treatment of testicular cancer.

Azo anion radical complexes of osmium and related nonradical species

The reaction of [Os(H)(Br)(CO)(PPh3)3], 5, with 2-(phenylazo)pyridine (pap) in boiling dry heptane has afforded the azo anion radical complex [Os(pap.-)(Br)(CO)(PPh3)2], 6a, as the major product and [Os(pap)(H)(CO)(PPh3)2]Br, 7, as a minor byproduct. Upon replacing pap by the better pi-acceptor azo-2,2'-bipyridine (abp) in the above synthesis, the radical complex [Os(abp.-)(Br)(CO)(PPh3)2], 6b, becomes the sole product. It is proposed that 6 is formed via homolytic cleavage of the Os-H bond in 5; in the formation of 7, the Os-Br bond of 5 is heterolytically cleaved. The X-ray structures of 6b and 7.CH2Cl2 have been determined. In 6b, the N-N length is 1.35(2) A, consistent with the anion radical description; in 7.CH2Cl2 the length is 1.27(1) A. The spin-bearing extended Huckel HOMO in a model of 6 is found to be approximately 70% azo-pi* in character associated with a small metal contribution. An electronic band observed in the range 600-700 nm in solutions of 6 is assigned to the HOMO --> LUMO transition, the LUMO being 95% pyridine-pi* in character. One-electron paramagnetic 6 displays well-defined anisotropic EPR features near g = 2.00. The anisotropy arises from the metal character of HOMO and is magnified by the large spin-orbit coupling in osmium. In a moisture-free environment 6 is indefinitely stable in the solid state, but in CH2Cl2-MeCN solution 6a is rapidly oxidized by air, affording [Os(pap)(Br)(CO)(PPh3)2]+, 6a+, which has been isolated as the diamagnetic PF6- salt; 6b+PF6- has been similarly prepared. The voltammetric reduction potentials of the 6+/6 couple follow the order 6a+/6a < 6b+/6b, and the carbon monoxide stretching frequencies follow the order 6a < 6b and 6a+ < 6b+. These trends are consistent with the pi-acidity order pap < abp. Crystal data are as follows: (6b, C47H38BrN4OOsP2) monoclinic, space group P21/c (no. 14), a = 10.215(4) A, b = 17.634(7) A, c = 22.473(8) A, beta = 97.67(3) degrees , Z = 4; (7.CH2Cl2, C49H42BrCl2N3OOsP2) monoclinic, space group P2(1/n) (no. 14), a = 15.323(7) A, b = 15.201(6) A, c = 19.542(7) A, beta = 92.51(3) degrees, Z = 4.

Structure of the lnlB leucine-rich repeats, a domain that triggers host cell invasion by the bacterial pathogen L. monocytogenes

The L. monocytogenes protein lnlB activates phosphoinositide 3-kinase and induces phagocytosis in several mammalian cell types. The 1.86 A resolution X-ray crystal structure of the leucine-rich repeat domain of lnlB that is both necessary and sufficient to induce phagocytosis is presented here. The structure supports a crucial role for calcium in host cell invasion by L. monocytogenes and supplies a rationale for its function. Calciums are bound to the protein in an unusually exposed manner that suggests that the metals may act as a bridge between lnlB and mammalian cell surface receptors. The structure also identifies surfaces on the curved and elongated molecule that may constitute additional interaction sites in forming a bacterial-mammalian signaling complex.

Cardiac operations in patients with low-grade small lymphocytic malignancies

BACKGROUND

Low-grade small lymphocytic (B cell) malignancies (encompassing chronic lymphocytic leukemia and some types of non-Hodgkin lymphoma) are diseases of the elderly. Open cardiac procedures are known to have increased risk of postoperative infection and other morbidities in these immunodeficient patients. Outcome of open cardiac procedures in these patients was reviewed retrospectively.

PATIENTS

Thirteen patients (aged 58-82 years, 11 men, 2 women) with these lymphocytopathologic diseases (8 with chronic lymphocytic leukemia and 5 with non-Hodgkin lymphoma) underwent cardiac operations between January 1977 and June 1998. Mean age was 72 +/- 2.1 years. Isolated coronary artery bypass grafting was performed in 11 and combined procedures and double valve replacement were performed in 1 each. Preoperatively, 9 patients were in a low-risk clinical stage. Mean preoperative duration of lymphocytopathologic disease was 6.1 +/- 1.6 years. Mean preoperative New York Heart Association functional class was 2.8.

RESULTS

There was no operative death. Average stay in the intensive care unit was 41.4 +/- 8.6 hours. Postoperative leg and superficial sternal wound infections were encountered in 3 patients. Average postoperative hospital stay was 10.0 +/- 1.7 days. During the follow-up up to 72 months, 1 patient underwent a second cardiac operation. There was 1 late death 4 years later. Coronary stenting was done in 1 patient and a cardioverter-defibrillator was implanted in another patient for recurrent angina. Three patients underwent chemotherapy. Cardiac and lymphocytopathologic status remained stable in others.

CONCLUSIONS

Acceptable outcome may be anticipated after cardiac operations in patients with low-grade chronic lymphocytic leukemia and non-Hodgkin lymphoma in early stages. However, the possibility of infection and progression of cardiac and lymphocytopathologic status in these patients should call for caution.

Amino acid substitution in alpha-helix 7 of Cry1Ac delta-endotoxin of Bacillus thuringiensis leads to enhanced toxicity to Helicoverpa armigera Hubner

Insecticidal proteins or delta-endotoxins of Bacillus thuringiensis are highly toxic to a wide range of agronomically important pests. The toxins are formed of three structural domains. The N-terminal domain is a bundle of eight alpha-helices and is implicated in pore formation in insect midgut epithelial membranes. All the delta-endotoxins share a common hydrophobic motif of eight amino acids in alpha-helix 7. A similar motif is also present in fragment B of diphtheria toxin (DT). Site-directed mutagenesis of Cry1Ac delta-endotoxin of B. thuringiensis was carried out to substitute its hydrophobic motif with that of DT fragment B. The mutant toxin was shown to be more toxic to the larvae of Helicoverpa armigera (cotton bollworm) than the wild-type toxin. Voltage clamp analysis with planar lipid bilayers revealed that the mutant toxin opens larger ion channels and induces higher levels of conductance than the wild-type toxin.

On the inhibitory activities of a new boron compound and ultrasound against the mouse ascites tumour

The inhibitory effects of a new boron compound, dihydroxy (oxybiguanido) boron (III) hydrochloride monohydrate (HB), and ultrasound (US) of a frequency 25 kHz on the growth of ascites tumour in female Swiss mice were studied by monitoring the survival, weight of tumour-associated material, tumour cell count, serum alkaline phosphatase activity and the haematological parameters of the treated animals. 5-Fluorouracil (5-FU), a well-known anticancer agent, was used as positive control. While HB exhibited a very significant antitumour action, US alone produced a small but significant inhibitory effect. The combination of US with HB or 5-FU produced an extra antitumour action as compared to the actions of these chemicals used singly. The mechanisms of action of the new boron compound (HB) and US are discussed.

Structural and functional characterization of seven spermicidal vanadium(IV) complexes: potentiation of activity by methyl substitution on the cyclopentadienyl rings

In a systematic effort to identify and develop effective vanadocene(IV) complexes as a new class of contraceptive agents, the effect of methyl substitution in the cyclopentadienyl rings of Cpx2VCl2 on their spermicidal activity has been examined. The spermicidal activities of compounds Cpx2VCl2 [Cpx = Me5Cp (Cp*) (1), Cp (3), MeCp (Cp') (5)], as well as two of their corresponding vanadium(V) oxidation products Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), were examined by computer-assisted sperm analysis (CASA). These analyses have established that penta-substitution of the Cp ring by electron-donating methyl groups augments the spermicidal activity 10-fold. The corresponding V(V) oxo compounds, Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), tested under identical conditions did not show as effective spermicidal activity even though these complexes have a pseudo-tetrahedral geometry similar to the active vanadocene(IV) dichlorides. Two pseudo-octahedral V(IV) complexes with tris-pyrazolyl borate as ligand, (HBpz3)V(O)Cl.DMF (6) and (HB(3,5-Me2pz)3)V(O)Cl.DMF (7), were also found to exhibit potent spermicidal activity. Although some vanadium(IV) complexes may immobilize sperm due to the generation of .OH radicals, the lack of spermicidal activity of VOSO4 which generates .OH radicals, and the potent spermicidal activity of [Cp2V(acac)][O3SCF3] (8), and [Cp2V(DeDtc)][O3SCF3] (9) which do not generate .OH radicals, indicate that .OH radical mediated reactions may not be essential for the spermicidal activity of vanadium(IV) complexes.

Cardiac reoperations in octogenerians

OBJECTIVE

In recent years, satisfactory outcome of primary cardiac operation in octogenerians and increased ageing of cardiac surgical population in western hospitals have led to increased expectations and referrals for reoperation. Outcome of reoperation in this aged subset was analysed.

METHODS

Consecutive 18 octogenerians (mean age 81.2 years, 10 men, eight women) undergoing cardiac reoperations from November 1989 through August 1998 were retrospectively reviewed.

RESULTS

They represented 6.2% of all octogenerian cardiac surgical patients and 2.7% of all reoperations during the same period. Mean preoperative NYHA class was 3.4 and Parsonnet score was 29.4. The interval to reoperation was 114.5+/-11.96 (4-188) months. Priority was urgent in 11 and elective in seven patients. The procedures included four AVRs, five MVRs (including two associated TVAs), six CABGs and one each of MVR with CABG, AVR with CABG and AVR, MVR and CABG. Average graft/patient was 2.3. Mean ICU stay was 4.6+/-1.5 (1-28) days. There was one hospital death (5.5%) on 18 pod after MVR in an 83-year-old woman. Mean postoperative stay was 20.2+/-5.13 (8-93) days. There were three late deaths (17.6%)--at 32 months after MVR, at 44 and 63 months after CABG. Long-term survivors were 90% among men and 50% among women who were followed up for 42.7+/-6.9 (9-93) months. Mean Karnofsky score in survivors at 1 year of follow-up was 78.5+/-2.9. Despite continued medication in all survivors, mean current NYHA is 1.9 and most have improved lifestyle.

CONCLUSIONS

Satisfactory outcome may be expected after cardiac reoperations in highly selected octogenerians. However, increased procedural risks, complications, hospital stay and slower convalescence during early follow-up may be anticipated, and will indicate very careful screening. These results indicate a need to reconsider the treatment policy in primary operation with regard to choice of graft conduits and prosthetic valves in other elderly patients.

Biomechanical, histological and immunohistological studies of patellar cartilage in an ovine model of osteoarthritis induced by lateral meniscectomy

OBJECTIVE

To evaluate the biomechanical, histological and immunohistochemical changes induced in patellar articular cartilage (AC) in ovine stifle joints 3 months after bilateral lateral meniscectomy, a procedure known to induce experimental osteoarthritis (OA) in the femoro-tibial joint (FTJ).

METHODOLOGY

Fifteen mature adult Merino female sheep were used in this study. Ten were subjected to bilateral-lateral meniscectomy, while the remaining five were used as 'non-operated controls' (NOC). All animals were killed 3 months post-surgery. Topographical biomechanical indentation tests were performed on each patellae using a UMIS-2000 micro-indentation system. Initial load, relaxed and unload shear moduli were determined using an elastic analytical model, while the permeability was assessed by comparing the indentation response to a simulated indentation test conducted using a poroelastic finite element model. Immunohistochemical, normal and polarized histological studies were performed on each specimen after biomechanical testing.

RESULTS

Patellar AC from meniscectomized joints exhibited an overall decrease in initial (-34%), relaxed (-32%) and unload shear modulus (-22%), and an increase in the permeability (+72%) relative to NOC cartilage (P< 0.01). The most significant differences in mechanical properties occurred on the lateral and central aspects of the patellae. There were no significant histological difference in staining between sections from NOC and meniscectomized joint AC using Toluidine Blue, a dye which binds to proteoglycans. However immunohistochemical staining with monoclonal antibody MAb 3B3(-), a putative marker of early OA change in PGs, demonstrated increased binding in the lateral and central regions of patellar sections from meniscectomized joints relative to the same regions of NOC AC. Moreover polarized light microscopy of Picro Sirius red stained sections revealed a significant decrease in birefringence intensity in the superficial-middle zones of the lateral and central regions of the patellar cartilage derived from the meniscectomized joints.

CONCLUSION

This study has demonstrated that lateral meniscectomy is a procedure which was known to induce classical OA like changes in AC and subchondral bone of the FTJ also produced an early pathological response in the patellar AC.