Enhancement of acetylcholine release by homoanatoxin-a from Oscillatoria formosa

The strain NIVA-CYA 92 of Oscillatoria formosa Bory ex Gormont produces phycotoxins with neurotoxic properties. Chemical analysis by gas chromatography/mass spectrometry of a water extract of lyophilized material of the organism showed the presence of only homoanatoxin-a. The mechanism of action of homoanatoxin-a on peripheral cholinergic nerves is so far not known. The neurotoxicity of O. formosa containing homoanatoxin-a was investigated in rat bronchi, rat brain synaptosomes and in GH(4)C(1) cells. The water extract of lyophilized material of the organism produced a concentration-dependent reversible increase in the release of [(3)H]acetylcholine from both K(+) (51 mM) depolarised and non-depolarised cholinergic nerves of the rat bronchial smooth muscle. The K(+)-evoked release of [(3)H]acetylcholine was enhanced by about 75% by a water extract from 15-20 mg/ml of lyophilized algal material. The enhanced release of [(3)H]acetylcholine was substantially reduced by the L-type Ca(2+)-channel blocker verapamil (100 μM) and not by the N-type Ca(2+)-channel blocker ω-conotoxin GVIA (1.0 μM) or the P-type Ca(2+)-channel blocker ω-agatoxin IV-A (0.2 μM). Chelation of intra-cellular Ca(2+) by 1,2-bis-(aminofenoxi)etan-N,N,N',N'-tetraacidic acid/acetoxymethyl (BAPTA/AM) (30 μM) had no effect on the phycotoxin-induced release of [(3)H]acetylcholine, indicating that an extracellular pool of Ca(2+) was important for the action of the phycotoxin on the release of [(3)H]acetylcholine from peripheral cholinergic nerves. In rat brain synaptosomes the algal extract enhanced the influx of (45)Ca(2+) in a tetrodotoxin (1.0 μM) and ω-conotoxin MVIIC (blocker of N-, P- and Q-type Ca(2+) channels) (1.0 μM) insensitive manner. Patch-clamp studies showed that the phycotoxin opened endogenous voltage dependent L-type Ca(2+) channels in neuronal GH(4)C(1) cells. These Ca(2+) channels and the effect of the toxin on the channels were blocked by the L-type Ca(2+)-channel antagonist gallopamil (200 μM). The present results suggest, therefore, that the investigated strain of O. formosa contains homoanatoxin-a, which enhances the release of acetylcholine from peripheral cholinergic nerves through opening of endogenous voltage dependent neuronal L-type Ca(2-) channels.     

Assessment of aldehyde dehydrogenase in viable cells

Cytosolic aldehyde dehydrogenase (ALDH), an enzyme responsible for oxidizing intracellular aldehydes, has an important role in ethanol, vitamin A, and cyclophosphamide metabolism. High expression of this enzyme in primitive stem cells from multiple tissues, including bone marrow and intestine, appears to be an important mechanism by which these cells are resistant to cyclophosphamide. However, although hematopoietic stem cells (HSC) express high levels of cytosolic ALDH, isolating viable HSC by their ALDH expression has not been possible because ALDH is an intracellular protein. We found that a fluorescent aldehyde, dansyl aminoacetaldehyde (DAAA), could be used in flow cytometry experiments to isolate viable mouse and human cells based on their ALDH content. The level of dansyl fluorescence exhibited by cells after incubation with DAAA paralleled cytosolic ALDH levels determined by Western blotting and the sensitivity of the cells to cyclophosphamide. Moreover, DAAA appeared to be a more sensitive means of assessing cytosolic ALDH levels than Western blotting. Bone marrow progenitors treated with DAAA proliferated normally. Furthermore, marrow cells expressing high levels of dansyl fluorescence after incubation with DAAA were enriched for hematopoietic progenitors. The ability to isolate viable cells that express high levels of cytosolic ALDH could be an important component of methodology for identifying and purifying HSC and for studying cyclophosphamide-resistant tumor cell populations.     

Synergistic effect of aqueous extract of Telfaria occidentalis on the biological activities of artesunate in Plasmodium berghei infected mice

Background

Resistance to most antimalarial drugs has encouraged the use of herbal preparations along with prescribed orthodox drugs.

Objective

To investigate effect of co-administration of aqueous extract of T. occidentalis leaves; commonly used as antimalarial and haematinic agent in Nigeria and artesunate using P. berghei animal model.

Methods

In vivo curative antiplasmodial effect of T. occidentalis (200mg/kg) alone and combination with artesunate (2mg/kg) were evaluated using albino mice infected with 10⁶ parasitized erythrocytes of P. berghei intraperitoneally. The haematological parameters: haemoglobin level, red blood cells and white blood cells and packed cell volume were monitored using standard methods.

Results

Aqueous extract of T. occidentalis, artesunate and the combination gave 72.17±4.07%, 70.43± 4.27% and 85.43±3.65% reduction in parasitaemia after 48hours respectively. A significant enhancement of the PCV was obtained with the coadministration of artesunate and aqueous extract (p< 0.01). Similar trends were also observed with heamatological parameters at 72hours of administration.

Conclusion

This study revealed a synergistic effect of the co-administration on parasite clearance rate of P. berghei infection in mice, with a significant enhancement of haematological parameters within 48 hours of administration. This indicates a rapid rate of recovery from plasmodial infections with the co-administration.     

Osteosarcoma: use of MR imaging and MR spectroscopy in clinical decision making

Magnetic resonance (MR) imaging was performed on 14 patients with histologically proved osteosarcoma (mean age, 14.4 years). There was excellent correlation of intramedullary tumor extent as determined with MR imaging and pathologic examination (r = 99%). This was facilitated by the presence of a chemical shift artifact at the tumor-marrow interface on the T1-weighted images. The correlation between CT and pathologic findings was not as good (r = 84%). In a single patient, however, a 10-cm length of sclerotic bone was incorrectly interpreted as being tumor. If this case is excluded, the correlation between CT and pathologic findings improves significantly (r = 96%). T2-weighted images were optimal in demonstrating soft-tissue bulk and breach of the epiphysis or cortex. Vascular involvement was also readily defined. The T2 value of the tumor soft-tissue component decreased in patients who were deemed to have responded well to therapy. Two patients with very high T2 values after chemotherapy developed wide-spread metastatic disease and died. Phosphorus-31 MR spectroscopy of five patients with osteosarcoma showed elevated levels of phosphomonoesters (PMEs), inorganic phosphate (Pi), and phosphodiesters (PDEs). PME and PDE peak areas decreased in three patients after chemotherapy, while Pi peak areas increased.     

Ankle: surface coil MR imaging at 1.5 T

High-field surface coil magnetic resonance (MR) images were obtained of 12 ankles: two from healthy volunteers, seven from patients, and three from fresh cadavers. The cadaver ankles were sectioned in the coronal, sagittal, and axial planes for direct comparison with the MR images. Plain film confirmation of pathologic conditions was obtained in all patients, and five underwent arthroscopy or surgery, or both. MR imaging provided excellent delineation of ligaments and cartilaginous structures in all cases.     

Occupational voice demands and their impact on the call-centre industry

Background  

Within the last decade there has been a growth in the call-centre industry in the UK, with a growing awareness of the voice as an important tool for successful communication. Occupational voice problems such as occupational dysphonia, in a business which relies on healthy, effective voice as the primary professional communication tool, may threaten working ability and occupational health and safety of workers. While previous studies of telephone call-agents have reported a range of voice symptoms and functional vocal health problems, there have been no studies investigating the use and impact of vocal performance in the communication industry within the UK. This study aims to address a significant gap in the evidence-base of occupational health and safety research. The objectives of the study are: 1. to investigate the work context and vocal communication demands for call-agents; 2. to evaluate call-agents' vocal health, awareness and performance; and 3. to identify key risks and training needs for employees and employers within call-centres.     

Synthesis of cystine peptides 21–25/70–73 and 35–39/56–59 of the β-subunit of human choriogonadotropin

Syntheses of two asymmetrical cystine peptides with the amino acid residues 21–25/70–73 and 35–39/56–59, based on the linear amino acid sequence and the disulfide bond assignment in the β-subunit of human choriogonadotropin (hCG-β), are described. S-trityl and S-acetamidomethyl peptide fragments of each cystine peptide were prepared in solution phase and were subjected to oxidation with I₂/MeOH to form the disulfide bridge. The cystine peptides were characterized by their amino acid analyses and fast atom bombardment mass spectrometry. Immunological characterization by several homologous radioimmunoas-say systems showed that peptide 21–25/70–73 had significant hCG, hCG-β, and hLH activities while peptide 35–39/56–59 failed to reveal any immunoreactivity.