Complex Coacervation of Lysozyme and Heparin: Complex Characterization and Protein Stability

No HeadingPurpose. To characterize complex coacervates/flocculates of lysozyme and heparin in terms of binding stoichiometry and to determine the effect of complexation on protein structure and stability.Methods. Insoluble lysozyme-heparin complexes were formed at pH 7.2 and the binding stoichiometry determined using a solution depletion method. Protein structure was determined by infrared spectroscopy and intrinsic fluorescence. Protein stability was evaluated using differential scanning calorimetry and followed in a 12-weeks storage stability study at 37C.Results. Binding stoichiometry between heparin and lysozyme was found to be dependent on ionic strength of the solution. At low ionic strength (I 0.01) about 11 lysozyme molecules could bind to a 17 kDa heparin chain, 3 to a 6 kDa chain, and less than 2 to a 3 kDa chain. At higher ionic strength (I 0.1), only 7 lysozyme molecules could bind to a 18 kDa heparin chain.. Above ionic strengths of approximately 0.32 M, no insoluble complexes were observed. Infrared spectroscopy and intrinsic fluorescence did not show any major changes in protein structure upon complexation to heparin. In contrast, differential scanning calorimetry showed a large decrease in the melting temperature of the protein, from 77C to 61C. Moreover, after 12-weeks storage at 37C, only 60% protein recovery was observed for the complexes, with no loss of protein for the uncomplexed protein.Conclusions. Heparin has multiple binding sites for lysozyme, amounting to at most one lysozyme molecule per 3 disaccharide units of heparin. Complexation decreased lysozyme stability, suggesting that heparin has a higher affinity for the unfolded state than the native state. Similar destabilization may occur for other proteins upon interaction with highly charged polymeric compounds or surfaces.     

Laxative treatment elevates plasma homocysteine: a study on a population-based Swedish sample of old people

Objectives Elevated plasma homocysteine might indicate an increased risk of cancer, and cardiovascular and neurological diseases. The homocysteine level depends on the supply of folate and cobalamine, and constipation and/or laxative treatment might compromise this supply. The present study examined the impact of constipation and laxative treatment on the blood levels of homocysteine, folate and cobalamine in a population-based sample of aged people, including consideration of frailty and impaired renal function, both of which may also influence the homocysteine level.Methods The study was based on biochemical tests in 341 females and 183 males aged 82 years or older. The concentrations of homocysteine (plasma), folate, cobalamine and urea (serum) were measured in subjects with and without ongoing treatment with laxative drugs. Values were adjusted for age, gender and frailty, as well as for clinical diagnoses and drug therapies known to affect homocysteine levels.Results Homocysteine levels were increased and those of folate reduced in aged subjects on laxatives. Homocysteine remained elevated after adjusting for frailty and various neurological disorders. There was no significant effect on homocysteine and folate in constipated subjects without laxatives.     

Phenotypic yeast growth analysis for chronic toxicity testing

In Saccharomyces cerevisiae the pH-dependent growth inhibition of the heavy metals Cu(2+), Cr(6+), Zn(2+), Co(2+), and Cd(2+) was examined in comparison to that of organic solvents and pure compounds DMSO, MNNG, 4-NQO, MTBE, ethanol, and 2-AA. The assay was based on both S. cerevisiae wild-type and genetically modified cells deleted in the transporters Pdr5, Snq2, and Yor1 that facilitate pleiotropic drug resistance to explore the potential for short-term chronic aquatic toxicity tests. The strain deleted in the proteins that mediate the efflux of structurally diverse hydrophobic compounds exhibited high sensitive growth inhibition at low (0.04 mg/L 4-NQO) to moderate (5.5 mg/L DMSO) organic compound exposure. At pH 6.4 the EC(50)'s, for all tested heavy metals were significantly low, in contrast to acidic pH conditions, in which both strains were able to grow in the presence of high concentrations of the transition metals Cu(2+), Zn(2+), and Co(2+), with the pdr5 yor1 snq2 mutant being more tolerant. Cd(2+) exerted the highest toxicity, with an EC(50) of 0.49 mg/L. Obtained results were compared with data determined from growth-inhibition tests involving other unicellular species. The comparison provided evidence that yeast is a sensitive and practical model system for toxicological risk assessment.     

The H4IIE cell bioassay as an indicator of dioxin-like chemicals in wildlife and the environment

The H4IIE cell bioassay has proven utility as a screening tool for planar halogenated hydrocarbons (PHHs) and structurally similar chemicals accumulated in organisms from the wild. This bioassay has additional applications in hazard assessment of PHH exposed populations. In this review, the toxicological principles, current protocols, performance criteria, and field applications for the assay are described. The H4IIE cell bioassay has several advantages over the analytical measurement of PHHs in environmental samples, but conclusions from studies can be strengthened when both bioassay and analytical chemistry data are presented together. Often, the bioassay results concur with biological effects in organisms and support direct measures of PHHs. For biomonitoring purposes and prioritization of PHH-contaminated environments, the H4IIE bioassay may be faster and less expensive than analytical measurements. The H4IIE cell bioassay can be used in combination with other biomarkers such as in vivo measurements of CYP1A1 induction to help pinpoint the sources and identities of dioxin-like chemicals. The number of studies that measure H4IIE-derived TCDD-EQs continues to increase, resulting in subtle improvements over time. Further experiments are required to determine if TCDD-EQs derived from mammalian cells are adequate predictors of toxicity to non-mammalian species. The H4IIE cell bioassay has been used in over 300 published studies, and its combination of speed, simplicity, and ability to integrate the effects of complex contaminant mixtures makes it a valuable addition to hazard assessment and biomonitoring studies.     

Combination therapy in Alzheimer's disease: a review of current evidence

Treating dementia has become a major challenge in clinical practice. Presently, acetylcholinesterase inhibitors are the first-line drugs in the treatment of Alzheimer's disease (AD). These options are now complemented by memantine, which is approved for the treatment of moderate-to-severe AD. Altogether, a minimum of six agent classes already exist, all of which are approved for clinical use and are either already being tested or ready for phase III clinical trials for the treatment of AD. These include cholinesterase inhibitors, blockers of the NMDA receptor, antioxidants or blockers of oxidative deamination (including Gingko biloba), anti-inflammatory agents, neurotrophic factors (including hormone replacement therapy and drugs acting on insulin signal transduction) and antiamyloid agents (including cholesterol-lowering therapy). These approaches hold promise for disease modification and have a potential to be used as combination therapy for cognitive enhancement. Presently, only nine clinical studies have been published that have investigated the effects of a combination regimen on cognitive performance or AD. Among those, one study was conducted in elderly cognitively intact persons; the others involved patients with AD. Only five of the treatment studies followed a randomised, controlled design. Not all studies favoured the superior efficacy of combination therapy over monotherapy. Some studies, however, showed some evidence for synergistic combination effects of symptomatic therapy, including delay or prevention of disease progression in AD patients. In addition, six studies investigated the effects of AChE inhibitor in combination with antipsychotic or antidepressant therapy on behavioural aspects of AD symptomatology. In four of those studies there were indications that combination therapy had greater efficacy over monotherapy. The treatment of AD patients requires optimised options for all stages of illness based on the available drugs. There is a great need for further well designed studies on combination therapy in AD.     

Lymphadenitis colli due to non-tuberculous mycobacteria (NTM): a case-series and review of the literature

OBJECTIVE: Lymphadenitis colli due to NTM should always be considered in children with cervical Lymphadenitis. For Germany there is a lack of data concerning the incidence, the epidemiology, the diversity and frequency of the different bacteria, the diagnosis, the clinical manifestation and the medical treatment. METHODS: By means of a questionnaire, which was retrospective for 1985 to 1994 and was sent to 277 children's hospitals in Germany, we collected data on Lymphadenitis colli in Germany. In our study we also incorporated cases from the "National Laboratory for Mycobacteria" in Borstel as well as six cases from our hospital in Mainz. Therefore our data includes both clinical (28) and laboratory (30) cases. Additionally we screened the literature on "Lymphadenitis colli in children due to NTM". RESULTS: A total of 51 cases of Lymphadenitis due to NTM could be identified. The illness occurs typically in young children up to six years of age. The most frequent cause were species of the Mycobacterium avium-intracellulare-scrofulaceum complex. Except for the local diagnosis of a cervical Lymphadenitis other clinical symptoms are missing, just as specific laboratory parameters with a subacute or chronic course. The tuberculin skin test can be false positive. The diagnosis is confirmed by biopsy and histology as well as through microbiological tests. CONCLUSIONS: The best treatment is complete surgical excision, whereas the importance of additional or exclusive treatment with Clarithromycin, Rifabutin and other antibiotics could not be clarified completely. But in patients with AIDS Rifabutin and other drugs could perhaps be useful, even for prophylaxis. Also if complete excision is impossible, treatment with certain drugs (Clarithromycin or Azithromycin in combination with Rifampicin) will be recommended. It still remains in question if NTM infections in children are really increasing.     

Association of right ventricular dysfunction and Cheyne-Stokes respiration in patients with chronic heart failure

Cheyne-Stokes respiration (CSR) is present in up to 40% of patients with congestive heart failure (CHF) and is an independent risk factor for increased overall mortality. We examined whether CSR is associated with right ventricular (RV) dysfunction in CHF patients. Parameters of RV function were assessed by two-dimensional echocardiography and tissue velocity imaging in 42 patients (aged 23-75 years) with a left ventricular (LV) ejection fraction below 40%. Respiratory polygraphy revealed CSR with an central apnea-hypopnea index (CAHI) >10 h-1 in 13 of the 42 patients (31%). Demographic characteristics did not differ among the patient groups. The velocity of the tricuspid annular systolic motion (TASM), a parameter reflecting systolic RV function, was significantly reduced in CHF patients with CSR (10.5 +/- 2.3 cm s-1) compared with those without CSR (15.0 +/- 5.1 cm s-1, P = 0.004), and was inversely associated with the CAHI (y = 15.2-0.2x; r = 0.46, P = 0.003). The RV dimensions were significantly increased and the fractional RV area changes significantly reduced in CHF patients with CSR (33 +/- 17 versus 48 +/- 20%; P = 0.04). Doppler parameters of pulmonary artery flow indicate higher pulmonary artery pressures in CSR patients compared with patients without CSR, which is also reflected by an increased RV free-wall thickness in CSR patients (6.5 +/- 1.1 vs. 5.3 +/- 1.3 mm; P = 0.05). Parameters of systolic LV function, forced expiratory volume in 1 s (FEV1), and PaO2 and PaCO2 were not different among patients with or without CSR. In conclusion, CSR is associated with depressed systolic RV function and increased RV dimensions in CHF patients. Future studies will show whether optimized treatment of CSR will improve RV function.