Developing a workable infection control policy for the dental laboratory

An enforced infection control policy in a laboratory will reduce occupational exposure to blood-borne pathogens and other infectious diseases and protect the dental laboratory personnel from exposure to infective disease. An outline of a workable laboratory infection control policy based on "Occupational Exposure to Bloodborne Pathogens" requirements is presented.     

Expression of high- and low-affinity receptors for C3a on the human mast cell line,HMC-1

The proteolytic cleavage product of complement component 3, (C3a), like C4a and C5a, is a potent anaphylatoxin and induces the production of inflammatory mediators in phagocytes. Notably, mast cells respond to C3a with the release of vasoactive substances, including histamine. We have examined the function and receptor binding of C3a in a human leukemic mast cell line, HMC-1. Similar to chemoattractant agonists in leukocytes, C3a induced rapid cytosolic free calcium concentration increases in HMC-1 cells. EGTA did not diminish this response, indicating that mobilizable Ca²⁺ was from intracellular stores. Receptors for C3a in HMC-1 cells couple in part to Bordetella pertussis toxin-sensitive G-proteins and, therefore, appear to belong to the family of serpentine receptors that require G-proteins for signal transduction. HMC-1 cells express two types of C3a receptors, C3aR1 and C3aR2, that were shown to bind ¹²⁵I-C3a with high-(K_d1 = 2.1–4.8 nM) or low-affinity (K_d2 = 30–150 nM), and both receptors are expressed at high level: 3 × 10⁵–6 × 10⁵ C3aR1/cell and 5 × 10⁵–2.3 × 10⁶ C3aR2/cell. Results from cross-linking experiments with ¹²⁵I-C3a fully agree with the presence of two different classes of C3a receptors in HMC-1 cells. Two membrane proteins with apparent molecular masses of 54–61 kDa (p57) and 86–107 kDa (p97) could be covalently modified with ¹²⁵I-C3a, and this cross-linking was inhibited with an excess of unlabeled C3a. Many of the known agonists for leukocytes including 13 chemokines (IL-8, NAP-2, GROα, ENA-78, IP10, PF4, MCP-1, 2 and 3, RANTES, MIP-1α, MIP-1β and 1309), three neuropeptides (neuropeptide Y, somatostatin and calcitonin), as well as C5a, did not activate HMC-1 cells, indicating that C3a is one of a few protein ligands for which this cell line expresses specific receptors. The apparent selectivity for C3a and the abundant expression of C3a receptors make the HMC-1 cell line an excellent choice for the cloning of the receptor genes.     

Recombinant soluble tumor necrosis factor receptor proteins protect mice from lipopolysaccharide-induced lethality.

The in vivo efficacy of human recombinant soluble tumor necrosis factor (TNF) receptor protein to prevent and to treat lipopolysaccharide (LPS)-induced lethal toxicity in D-galactosamine-treated mice was investigated. Chimeric proteins of the receptor extracellular domains fused to the hinge region of human IgG3 were expressed in myeloma cells (rsTNFR-h gamma 3). The fusion proteins had a disulfide-bonded dimeric structure. Upon intravenous injection, their serum concentration decreased relatively slowly after an initial phase of rapid elimination. D-galactosamine-sensitized mice were fully protected from the toxic effects of LPS, if the animal were pretreated with rsTNFR-h gamma 3 at 20 micrograms/animal. Partial protection was seen at significantly lower doses and when rsTNFR-h gamma 3 was given up to 3 h after LPS.     

Different strategies of mixed chimerism induction may determine stem/progenitor cell populations in recipient mice

Mixed chimerism has been suggested to induce tolerance to transplanted alloantigens. As the precise influence of mixed chimerism induction on the host organism has still not been fully elucidated, the aim of the present study was to explore this phenomenon in relation to the stem cell compartment.The experiment was performed on B6.SJL-Ptprc^aPep3^b mice. Mixed chimerism induction protocols involved 3 Gy TBI (Day − 1 of the experiment), injection of 20-30 × 10⁶ Balb C bone marrow cells (Day 0), and administration of blocking antibodies against CD40L (Day 0 and Day 4), anti-CD8 (Day − 2) with/without anti-NK1.1 (Day − 3). Selected groups of mice were also treated with cyclophosphamid (175 mg/kg) on Day 2. The presence of mixed chimerism was assessed in peripheral blood, bone marrow, and spleen, as well as in various subpopulations of leukocytes (CD4⁺, CD8⁺, CD45/B220⁺, Gr-1⁺, lin⁻/Sca-1⁺/c-kit⁻, lin⁻/Sca-1⁺/c-kit⁺, lin⁻/Sca-1⁻/c-kit⁺). Furthermore, the percentage of stem/progenitor cells (lin⁻/Sca-1⁺/c-kit⁻, lin⁻/Sca-1⁺/c-kit⁺, lin⁻/Sca-1⁻/c-kit⁺, VSEL, HSC) was analysed for the first time in bone marrow and peripheral blood of chimeric mice.The range of mixed chimerism differed significantly among various cell populations: it was lowest in CD8-positive cells and lin⁻/Sca-1⁺/c-kit⁻ cells, and highest in granulocytes. The induction of mixed chimerism revealed a significant impact on the stem/progenitor cell frequency in recipient mice, providing potential therapeutic insights into the long-term immunologic tolerance observed in chimeric mice. Collectively, these findings contribute to further optimization of mixed chimerism induction protocols and might help in the introduction of this phenomenon into clinical practice.     

The influence of muscle load on tibiofemoral knee kinematics

A comparative kinematics study was conducted on six cadaver limbs, comparing tibiofemoral kinematics in five conditions: unloaded, under a constant 130 N ankle load with a variable quadriceps load, with and without a simultaneous constant 50 N medial and lateral hamstrings load. Kinematics were described as translation of the projected centers of the medial (MFT) and lateral femoral condyles (LFT) in the horizontal plane of the tibia, and tibial axial rotation (TR) as a function of flexion angle. In passive conditions, the tibia rotated internally with increasing flexion to an average of −16° (range: −12/−20°, SD = 3.0°). Between 0 and 40° flexion, the medial condyle translated forwards 4 mm (range: 0.8/5.5 mm, SD = 2.5 mm), followed by a gradual posterior translation, totaling −9 mm (range: −5.8/−18.5 mm, SD = 4.9 mm) between 40–140° flexion. The lateral femoral condyle translated posteriorly with increasing flexion completing −25 mm (range: −22.6 to −28.2 mm, SD = 2.5 mm). Dynamic, loaded measurements simulating a deep knee bend were carried out in a knee rig. Under a fixed ankle load of 130 N and variable quadriceps loading, tibial rotation was inverted, mean TR = 4.7° (range: −3.3°/11.8° SD = 5.4°), MFT = −0.5 mm (range: = −4.3/2.4 mm, SD = 2.4 mm), LFT = 3.3 mm (range: = −3.6/10.6 mm, SD = 5.1 mm). Compared to the passive condition, all these excursions were significantly different (p ≤ 0.015). Adding medial and lateral hamstrings force of 50 N each reduced TR, MFT, and LFT significantly compared to the passive condition. In general, loading the knee with hamstrings and quadriceps reduces rotation and translation compared to the passive condition. Lateral hamstring action is more influential on knee kinematics than medial hamstrings action. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:419–428, 2010     

Risk factors for pre-eclampsia in Mulago Hospital, Kampala, Uganda

Objective Pre‐eclampsia contributes significantly to maternal, foetal and neonatal morbidity and mortality. The risk factors for pre‐eclampsia have not been well documented in Uganda. In this paper, we describe the risk factors for pre‐eclampsia in women attending antenatal clinics at Mulago Hospital, Kampala. Methods This casecontrol study was conducted from 1st May 2008 to 1st May 2009. 207 women with pre‐eclampsia were the cases, and 352 women with normal pregnancy were the controls. The women were 15–39 years old, and their gestational ages were 20 weeks or more. They were interviewed about their socio‐demographic characteristics, past medical history and, their past and present obstetric performances. Results The risk factors were low plasma vitamin C (OR 3.19, 95% CI: 1.54–6.61), low education level (OR 1.67, 95% CI: 1.12–2.48), chronic hypertension (OR 2.29, 95% CI 1.12–4.66), family history of hypertension (OR 2.25, 95% CI: 1.53–3.31) and primiparity (OR 2.76, 95% CI: 1.84–4.15) and para≥5 (3.71, 95% CI:1.84–7.45). Conclusion The risk factors identified are similar to what has been found elsewhere. Health workers need to identify women at risk of pre‐eclampsia and manage them appropriately so as to prevent the maternal and neonatal morbidity and mortality associated with this condition.     

Human defensin alpha-1 causes Trypanosoma cruzi membrane pore formation and induces DNA fragmentation, which leads to trypanosome destruction

Human defensins play a fundamental role in the initiation of innate immune responses to some microbial pathogens. Here we show that human defensin alpha-1 displays a trypanocidal role against Trypanosoma cruzi, the causative agent of Chagas' disease. The toxicity of human defensin alpha-1 against T. cruzi is mediated by membrane pore formation and the induction of nuclear and mitochondrial DNA fragmentation, leading to trypanosome destruction. Exposure of trypomastigote and amastigote forms of T. cruzi to defensin alpha-1 significantly reduced parasite viability in a peptide concentration-dependent and saturable manner. The toxicity of defensin alpha-1 against T. cruzi is blocked by anti-defensin alpha-1 immunoglobulin G. Electron microscopic analysis of trypomastigotes exposed to defensin alpha-1 revealed pore formation in the cellular and flagellar membranes, membrane disorganization, and blebbing as well as cytoplasmic vacuolization. Furthermore, human defensin alpha-1 enters the trypanosome when membrane pores are present and is associated with later intracellular damage. Trypanosome membrane depolarization abolished the toxicity of defensin alpha-1 against the parasite. Preincubation of trypomastigotes with defensin alpha-1 followed by exposure to human epithelial cells significantly reduced T. cruzi infection in these cells. Thus, human defensin alpha-1 is an innate immune molecule that causes severe toxicity to T. cruzi and plays an important role in reducing cellular infection. This is the first report showing that human defensin alpha-1 causes membrane pore formation in a human parasite, leading to trypanosome destruction.     

A self-administered rheumatoid arthritis disease activity index (RADAI) for epidemiologic research

Objective. To examine the psychometric properties and construct validity of a self-administered Rheumatoid Arthritis Disease Activity Index (RADAI). Methods. Five items of the Rapid Assessment of Disease Activity in Rheumatology (RADAR) questionnaire were aggregated into the RADAI and assessed for their factor loading, internal consistency, and construct validity. Results. In 55 patients with RA, the RADAI had a high internal consistency (Cronbach's alpha = 0.91) and correlated with physician's assessment of disease activity (r = 0.54, P < 0.01), the swollen joint count (r = 0.54, P < 0.01), and the C-reactive protein value (r = 0.43, P < 0.01). Conclusion. The RADAI is a highly reliable and valid self-administered measure of disease activity for clinical, health services, and epidemiologic research. Its sensitivity to change in longitudinal studies needs further study.