Improved anchorage in osteoporotic vertebrae with new implant designs.

The goal of our study was to evaluate two newly developed implant designs and their behavior in terms of subsidence in lumbar vertebral bodies under cyclic loading. The new implants were evaluated in two different configurations (two small prototypes vs. one large prototype with similar load-bearing area) in comparison to a conventional screw-based implant (MACS TL). A pool of 13 spines with a total of 65 vertebrae was used to establish five testing groups of similar bone mineral density (BMD) distribution with eight lumbar vertebrae each. In additional to BMD assessment via dual-energy X-ray absorptiometry, cancellous BMD and structural parameters were determined using a new generation in vivo 3D-pQCT. The specimens were loaded sinusoidally in force control at 1 Hz for 1000 cycles at three load levels (100, 200, and 400 N). A survival analysis using the number of cycles until failure (Cox regression with covariates) was applied to reveal differences between implant groups. All new prototype configurations except the large cylinder survived significantly longer than the control group. The number of cycles until failure was significantly correlated with the structural parameter Tb.Sp. and similarly with the cancellous BMD for three of five implants. In both large prototypes the cycle number until failure significantly correlated with the preoperative distance to the upper endplates. Although the direct relationship between bone structure or density and mechanical breakage behavior cannot be conclusively proven, all the prototypes adapted for poor bone structure performed better than the comparable conventional implant.     

Incidence and Clinical Significance of Ventricular Late Potentials in Idiopathic Dilated Cardiomyopathy Compared to Coronary Artery Disease

Objective: This prospective study was designed to compare incidence and clinical significance of ventricular late potentials between patients with idiopathic dilated cardiomyopathy (IDC) and postinfarct patients (CAD) using exactly the same method of signal-averaged electrocardiography (SAECG) in both patient groups. Methods: Time-domain analysis of SAECG was performed in 120 consecutive patients with IDC, 120 patients with CAD, and 60 healthy controls. Ventricular late potentials were detected in 27 of 120 patients with IDC (23%) compared to 41 of 120 patients with CAD (34%; P < 0.05). Results: Ventricular late potentials were found in 2 of 60 controls (3%). During 15 ± 7 months follow-up, serious arrhythmic events occurred in 17 of 120 patients with IDC (14%) and in 13 of 120 patients with CAD (11%). The sensitivity of ventricular late potentials for future arrhythmic events was 35% for IDC compared to 77% for CAD (P < 0.05). The positive predictive value of late potentials detected by time-domain analysis was 22% for IDC versus 24% for CAD (P = ns). Conclusion: In this selected patient population with IDC and CAD, time-domain analysis of SAECG revealed a lower incidence of ventricular ate potentials in patients with IDC as compared to postinfarct patients. Whereas ventricular late potentials had a high sensitivity but a low positive predictive value for identification of postinfarct patients with serious arrhythmic events during follow-up, both sensitivity and positive predictive value of ventricular late potentials for future serious arrhythmic events were low in the setting of IDC.     

Levels of high energy phosphates in human lung cancer cell lines by 31P nuclear magnetic resonance spectroscopy

Human lung cancers are divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) based on established criteria. SCLC differs from NSCLC by the expression of biomarkers, including creatine kinase-BB isoenzyme (EC 2.7.3.2). Subtypes of SCLC are referred to as classic and variant, both of which have elevated levels of creatine kinase-BB isoenzyme. We, therefore, applied 31P nuclear magnetic resonance spectroscopy to cell lines of classic SCLC, variant SCLC, and NSCLC human tumors, using continuous perfusion to identify any differences in the detectable levels of intracellular high-energy phosphate compounds. The spectra indicate that only the variant SCLC cells maintain high levels of phosphocreatine. Additionally, the classic SCLC cells express elevated levels of a diphosphodiester. Neither phosphocreatine nor diphosphodiesters are found in the NSCLC cell spectra.     

Freshly isolated mouse 4F7+ splenic dendritic cells process and present exogenous antigens to T cells

The antibody 4F7 was reported to recognize an epitope expressed on dendritic cells (DC) from various tissues. To study the ability of splenic 4F7⁺ dendritic cells to process antigen for presentation to CD4⁺ T cells, DC were enriched using a separation procedure avoiding overnight culture which could lead to an altered phenotype. These DC were used as antigen-presenting cells (APC) in stimulation cultures of major histocompatibility complex class II-restricted T cells. It was found that they induce antigen-dependent lymphokine production by T cells and therefore could present exogenous antigens. These processing takes place intracellularly, because fixation abrogates presentation to T cells. Moreover, antigen presentation needs intracellular processing within endo- or lysosomes as chloroquine-treatment prevents T cell activation. Titration of APC numbers revealed that contaminating APC most likely did not account for antigen-specific T cell activation by DC. No evidence was found for release of antigenic peptides or for partial antigen processing possibly done by cell surface located enzymes on DC. In conclusion, these results indicate that freshly enriched DC are able to process antigens similarly to other APC.     

The effect of lysozyme on the complement-dependent bactericidal action of different antibody classes.

Preparations of rabbit, dog and sheep IgA, IgA and IgM were examined for their antibacterial effects using a complement-dependent bactericidal assay. IgM and IgG were effecient bactericidal antibodies in the presence of complement; IgA, however, contained negligible activity. Except for sheep IgG no enhancement of bactericidal activity was observed in the presence of added lysozyme.     

Influence of various macrophage populations on Con-A induced T-cell proliferation.

The effect of different macrophage populations and supernatants derived from these macrophages on Con-A induced lymphocyte activation in macrophage depleted lymph node cells has been investigated. All macrophage populations tested were able to restore the lymphocytic response to Con A. Macrophages of different origin and differently elicited were heterogeneous with respect to the lymphocyte-activating and inhibitory activity. Bone marrow macrophages, cultured from 6 to 14 days or obtained from animals stimulated in vivo by BCG were quite inefficient in restoring the lymphocyte proliferation and showed no inhibitory activity up to the percentage per culture tested. Normal or BCG or proteose-peptone induced peritoneal macrophages were quite efficient stimulators, thioglycollate-broth elicited peritoneal macrophages were less efficient in this respect, but very efficient inhibitors. This is reflected to some degree in the supernatants derived from these macrophages which contain T-lymphocyte activating factor (TAF) and inhibitory factors, most likely low molecular weight inhibitory factors. Bone-marrow derived macrophages do not produce either factors in amounts measurable in this assay. These results demonstrate that macrophages, depending on their origin and possibly influenced by external activation signals, are heterogeneous with respect to their function in T-cell proliferation.     

Immunohistochemical demonstration of migration inhibitory factor (MIF) in experimental allergic contact dermatitis.

The kinetics of appearance of MIF+ cells was investigated in experimental contact dermatitis using a monoclonal antibody (7D10) against murine MIF which was reacted with cryostat sections of tissues and detected by the indirect immunoperoxidase test. Four groups of BALB/c mice were investigated: (1) sensitized with 2,4-dinitrofluorobenzene (DNFB); (2) unsensitized controls; (3) tolerized; (4) unsensitized. A challenge dose of DNFB was applied to the ear of animals of groups 1-3 and of croton oil to those of group 4. Three phases could be distinguished in group 1: (a) an initial vascular and exudative reaction; (b) an early cellular phase; and (c) a late cellular phase. At zero time rarely any T lymphocytes (Lyt 1+; Lyt 2+) were seen in all four groups. Within less than 30 min venous endothelial cells became strongly MIF+. This was followed by an influx of monocytes/macrophages reaching a maximum of 72 h in group 1 and a slight peak at 12 h in groups 2 and 3. At 16-24 h in all groups the endothelial reaction weakened while many 7D10+ macrophages appeared in group 1. By double-labelling it was shown that lymphocytes were 7D10-. The influx of lymphocytes, part of which carried the T cell receptor, began at 12 h, reaching a maximum at 72 h in group 1. In groups 2 and 3 only a weak lymphocytic infiltrate developed which declined at 24 h. Group 4 developed an inflammatory reaction after the initial phase with similar kinetics as in group 1. The data suggest that an immune inflammatory reaction is preceded by a nonspecific reaction of the vascular endothelium and the mononuclear phagocytic system and that MIF is playing a central role in these events.