An endo-acting proline-specific oligopeptidase from Treponema denticola ATCC 35405: evidence of hydrolysis of human bioactive peptides

An endo-acting proline-specific oligopeptidase (prolyl oligopeptidase [POPase], EC 3.4.21.26) was purified to homogeneity from the Triton X-100 extracts of cells of Treponema denticola ATCC 35405 (a human oral spirochete) by a procedure that comprised five successive fast protein liquid chromatography steps. The POPase is a cell-associated 75- to 77-kDa protein with an isoelectric point of ca. 6.5. The enzyme hydrolyzed (optimum pH 6.5) the Pro-pNA bond in carbobenzoxy-Gly-Pro-p-nitroanilide (Z-Gly-Pro-pNA) and bonds at the carboxyl side of proline in several human bioactive peptides, such as bradykinin, substance P, neurotensin, angiotensins, oxytocin, vasopressin, and human endothelin fragment 22-38. The minimum hydrolyzable peptide size was tetrapeptide P3P2P1P'1, while the maximum substrate size was ca. 3 kDa. An imino acid residue in position P1 was absolutely necessary. The hydrolysis of Z-Gly-Pro-pNA was potently inhibited by the following, with the Ki(app) (in micromolar) in parentheses: insulin B-chain (0.7), human endothelin-1 (0.5), neuropeptide Y (1.7), substance P (32.0), T-kinin (4.0), neurotensin (5.0), and bradykinin (16.0). Chemical modification and inhibition studies suggest that the POPase is a serine endopeptidase whose activity depends on the catalytic triad of COOH ... Ser ... His but not on a metal. The amino acid sequence around the putative active-site serine is Gly-Gly-Ser-Asn-Pro-Gly. The enzyme is suggested to contain a reactive cysteinyl residue near the active site. Amino acid residues 4 to 24 of the first 24 N-terminal residues showed a homology of 71% with the POPase precursor from Flavobacterium meningosepticum and considerable homology with the Aeromonas hydrophila POPase. The ready hydrolysis of human bioactive peptides at bonds involving an imino acid residue suggests that enzymes like POPase may contribute to the chronicity of periodontal infections by participating in the peptidolytic processing of those peptides.     

Increased expression of CD80, CD86 and CD70 on T cells from HIV-infected individuals upon activation in vitro: regulation by CD4+ T cells

T cells express CD28 and CD27 which transduce co-stimulatory signals after interaction with their ligands on antigen-presenting cells (APC). These ligands, CD80, CD86 and CD70, are also expressed to some extent on activated T cells. Here, we show that in human immunodeficiency virus (HIV)-infected individuals, CD28 and CD27 expression is decreased on CD8+ T cells. On the other hand, T cell stimulation in vitro induced high CD80, CD86 and CD70 expression on T cells from HIV-infected individuals. It appeared that an inverted CD4:CD8 T cell ratio could explain this enhanced expression of co-stimulatory ligands. Indeed, high expression levels of CD80, CD86 and CD70 were found on activated CD8+ T cells from HIV- individuals cultured in the absence of CD4+ T cells. Addition of CD4+ T cells prevented this up-regulation. However, in HIV-infected individuals, addition of excess autologous or healthy control CD4+ T cells did not completely counteract up-regulation of co-stimulatory ligand expression on CD8+ T cells. Thus, to some extent, CD8+ T cells in HIV-infected individuals appeared to be refractory to CD4+ T cell-mediated regulation of ligand expression in vitro. Activated T cells from HIV-infected individuals and activated CD8+ T cells from healthy controls were able to act as accessory cells in CD3-induced T cell proliferation, which was dependent on cell-cell contact. Thus, we showed that T cells from HIV-infected individuals express enhanced levels of co-stimulatory ligands upon activation, which provides them with accessory cell properties. Enhanced stimulatory potential of these nonprofessional APC may contribute to persistently high levels of immune activation in HIV infection related to disease progression.     

Brain HMPAO-SPECT and ocular microangiopathic syndrome in HIV-1-infected patients

OBJECTIVE: The pathogenesis of neurologic and neuropsychologic dysfunction in HIV-1 infection is unclear. The purpose of the study was to determine an association between cerebral perfusion and HIV-1-related ocular microangiopathic syndrome. METHODS: We studied 28 HIV-1-infected patients, seven of whom presented with asymptomatic HIV infection, nine with lymphadenopathy syndrome or AIDS-related complex, and 12 with AIDS. Cerebral perfusion was semi-quantitatively measured by single photon emission computed tomography of the brain using technetium-99 hexamethyl-propylenamine oxime (HMPAO-SPECT). The conjunctival manifestation of HIV-1-related microangiopathic syndrome was measured by a rating scale determining blood-flow sludging and, retinal cotton-wool spots were counted. CD4 count, neopterin, beta 2-microglobulin (beta 2M), haemoglobin, and age were determined as putative confounding variables. RESULTS: Mean conjunctival sludge in patients with normal HMPAO-SPECT findings was 1.3 +/- 0.5 (mean +/- s.e.m.); no cotton-wool spots were present. In patients with slightly impaired HMPAO-SPECT, it was 2.1 +/- 0.6 and mean cotton-wool spot count was 1.1 +/- 0.4. In patients with severely impaired HMPAO-SPECT, mean conjunctival sludge was 4.5 +/- 0.3 and mean cotton-wool spot count was 4.9 +/- 1.1 HMPAO-SPECT findings were closely associated with conjunctival sludge (r = 0.72; P < 0.001) and number of cotton-wool spots (r = 0.78; P < 0.001), whereas only a slight association with staging of HIV disease was found (P = 0.052). Analysis of covariance controlling for CD4 count neopterin, beta 2M, age, and haemoglobin demonstrated a significant difference between the three HMPAO-SPECT groups for both the number of cotton-wool spots (P < 0.001) and the conjunctival sludge rating (P < 0.001). CONCLUSION: There was a close association between severity of HIV-1-related ocular microangiopathic syndrome and severity of cerebral hypoperfusion. Microvascular alterations might contribute to the pathogenesis of neurological and neuropsychological symptoms in patients with HIV-1 disease. Furthermore, the conjunctival sludge rating and the number of cotton-wool spots might be appropriate indicators for severity of microvascular changes of the central nervous system [corrected].     

Treatment of chronic cardiac insufficiency with coenzyme Q10, results of meta-analysis in controlled clinical trials

Meta-analysis applied to eight controlled clinical trials of coenzyme Q10 (CoQ10)-treatment of congestive heart failure revealed a significant improvement a several important cardiac parameters such as ejection fraction (EF), stroke volume (SV), cardiac output (CO), cardiac index (CI) and end diastolic volume index (EDVI). Concerning the improvement in SV and CO the average patient in the CoQ10 group had a higher score than respectively 76% and 73% of the patients in the placebo group. The improvement in CO and SV was also significant when considering of homogeneity. Additional controlled clinical trials seem justified which may strengthen the power of the meta-analyses. However, based on available results, it can not be excluded that CoQ10 may have a future role a adjunctive therapy in a dosage of 100-200 mg/day in the treatment of chronic congestive heart failure.     

Visual association encoding activates the medial temporal lobe: a functional magnetic resonance imaging study

The involvement of structures in the medial temporal lobe during the encoding of visual associations was studied with functional magnetic resonance imaging. In 11 out of 12 normal healthy volunteers this task resulted in activation in posterior portions of the parahippocampal region, close to the collateral sulcus. In seven subjects activation was encountered in the hippocampal formation. The visual association task as adapted for this study may provide a sensitive measure to study anterograde amnesia prevalent in Alzheimer's disease. Therefore, the present paradigm enables the study of individual changes in learning and memory capacities over time.     

Lymphoma in patients with rheumatoid arthritis: association with the disease state or methotrexate treatment

Although long-term clinical studies have shown no excessive risk of lymphoma in rheumatoid arthritis (RA) patients treated with methotrexate (MTX), an increasing number of reports of this association continue to appear. We describe two cases, review the cases in the world's literature, and summarize their important characteristics. Possible oncogenic mechanisms are discussed. Most lymphoproliferation cases presented here have features of immunosuppression-associated lymphoma. The immunosuppressed state is attributable to a combination of factors, such as RA itself and the actions of MTX. The risk factors for RA patients to develop lymphoma while on MTX include severe disease, intense immunosuppression, genetic predisposition, and an increased frequency of latent infection with prooncogenic viruses such as Epstein-Barr virus (EBV). The spontaneous remission of lymphomas in eight RA patients after MTX was stopped highlights the likely causative role of the drug in the development of these malignancies. If the clinical situation permits, a period of observation for spontaneous remission after MTX is stopped is advisable. The physicians caring for RA patients on MTX should maintain a high surveillance for signs and symptoms suggestive of lymphoma.     

快中子探测器的效率刻度

本文叙述了用n-p散射方法刻度快中子探测器效率的基本原理、实验方法和测量结果。400 keV氘束轰击T-Ti靶,由T(d,n)~He反应得到15.2 MeV的中子,散射体是一个圆柱塑料闪烁体(φ2.2×3cm),飞行距离2m,时间分辨率约1.5ns,效率测量的能区范围为1—14MeV,对多次散射和几何条件作了修正,总的误差约2%。