Clinical significance of elevated serum chromogranin A levels

BACKGROUND

Chromogranin A (CgA) has been shown to be a useful marker in the diagnosis of neuroendocrine (NE) tumours. The clinical significance of CgA has been studied mostly in patients with known NE tumours. The diagnosis was evaluated in 153 consecutive patients in whom CgA was measured in a given time interval.

METHODS

CgA in serum was measured by radioimmunoassay. Immunohistochemistry with an antibody against CgA was performed in tumours from patients with adenocarcinoma and elevated CgA levels using a conventional method and the more sensitive tyramide signal amplification (TSA) technique.

RESULTS

Elevated serum CgA levels were found in 44 patients; 19 had NE tumours and 6 had tumours classified as adenocarcinomas. With the TSA technique, a high proportion of CgA-positive cells were disclosed in five of the adenocarcinoma patients. Patients with atrophic gastritis (no. 2) and patients treated with inhibitors of gastric acid secretion (no. 6) also had elevated levels of CgA. A modest increase in CgA levels was observed in 2 patients with renal impairment, and in 9 patients without any obvious cause.

CONCLUSION

The current study confirms that serum CgA is a sensitive marker for the detection of NE neoplasia. Elevated levels found in patients with adenocarcinoma may indicate NE differentiation in the tumour. CgA is a useful tool in the monitoring of enterochromaffin-like (ECL) hyperplasia secondary to treatment with acid secretion inhibitors or atrophic gastritis.

Liquid chromatography with electrospray ion-trap mass spectrometry for the determination of yessotoxins in shellfish

Yessotoxins are a group of large polyether toxins, produced by marine dinoflagellates, which cause widespread contamination of filter-feeding shellfish. A new, sensitive liquid chromatography-mass spectrometry (LC-MS) method has been developed for the determination of yessotoxin (YTX) and 45-hydroxy-yessotoxin (45-OHYTX), a major metabolite in shellfish. The LC system was coupled, via an electrospray ionisation (ESI) source, to an ion-trap MS in negative mode. The molecular related ion species at m/z 1141 [M-2Na+H]- was used as the parent ion for multiple MS experiments. MS-MS and MS3 gave major fragment ions at m/z 1061 [1141-SO3H]- and m/z 945 [1061-C9H12O]-. Predominant ions, that are due to the fragmentation of the backbone structure of YTXs, were observed at the MS4 stage. Reversed-phase LC using a C16 amide column was preferable to C18 phases for the separation of YTX and 45-OHYTX. Optimum calibration and reproducibility data were obtained for YTX using LC-MS-MS; r 2=0.9960, RSD < or = 6.3% at 0.25 microg YTX/g (n=5). The detection limit (S/N=3) was 30 pg YTX on-column which corresponded to 3 ng/g shellfish tissue.

Comparison of oral and intraperitoneal toxicity of yessotoxin towards mice

Currently, yessotoxin is regulated among the toxins in the diarrhetic shellfish poisoning (DSP) complex. Yessotoxin is equally acutely toxic towards mice upon intraperitoneal injections as those algal toxins giving diarrhea, but is not diarrheagenic. Its presence in mussels may therefore lead to overestimation of risk of DSP in consumers when the standard mouse bioassay is used. Arguments are presented for the use of analytical methods instead of the mouse bioassay for the diarrheagenic DSP toxins and yessotoxin. Yessotoxin was found to be more than ten times less toxic to mice via the oral route, compared with intraperitoneal injections. Even at 10mg/kg body weight, the highest dose ever tested orally, yessotoxin did not kill the mice. By means of light microscopy of several organs, moderate changes were only observed in the heart. Ultrastructural studies revealed swelling of heart muscle cells leading to separation of the organelles. Effects were most pronounced close to the capillaries. The pathological changes were clearly dose dependent, and the lowest oral dose where any effects were seen was 2.5mg yessotoxin per kg.

The validity of two HPLC methods and a colorimetric PP2A assay related to the mouse bioassay in quantification of diarrhetic toxins in blue mussels (Mytilus edulis)

Validity of two HPLC methods and a PP2A assay in relation to the mouse bioassay for diarrhetic shellfish poisoning (DSP) toxins was evaluated. The mouse bioassay for DSP toxins was performed on a total of 177 mussel samples from the Sognefjord, Norway, using diethyl ether in the final step of extraction. For fluorimetric HPLC analyses, either 4-bromomethyl-7-methoxycoumarin (BrMMC) or 9-anthryl diazomethane (ADAM) were used for analysis of 48 and 118 of the samples, respectively. The colorimetric PP2A inhibition assay was performed on all 177 samples that were analysed with the mouse bioassay. When comparing the HPLC-BrMMC, the HPLC-ADAM and the PP2A assays with the mouse bioassay, cut off values of < or =4, 5 and 6 microg okadaic acid (OA) equivalents (eq.)/5 g digestive gland (DG) was used. With reference to the results from the mouse bioassay, the total number of failure and correct classification by HPLC-ADAM and the PP2A method was compared for the three cut off values. No significant differences between the methods were detected. However, all differences were found in favour of HPLC-ADAM. All three methods could replace the mouse bioassay in detecting levels of diarrhetic toxins approved internationally for safe consumption of mussels. However, HPLC-ADAM seems to be the method of choice.

Repeatability and validity of a fluorimetric HPLC method in the quantification of yessotoxin in blue mussels (Mytilus edulis) related to the mouse bioassay

Repeatability and validity of a fluorimetric HPLC method in quantification of yessotoxin (YTX) in mussels related to the mouse bioassay was studied. Blue mussels (Mytilus edulis) from the Sognefjord, Norway were sampled from March to November, 1997, and October to December, 1998. A total of 75 samples were analysed for YTX by HPLC using 4-[2-(6,7-dimethoxy-4-methyl-3-oxo-3, 4-dihydroquinoxalinyl) ethyl]-1,2,4-triazoline-3, 5-dione (DMEQ-TAD) as a fluorimetric derivatization agent. Among these, 28 of the samples were analysed by HPLC in duplicate. All samples were analysed by the mouse bioassay using both chloroform and ether in the final step of extraction. The duplicate measurements using HPLC was found equal and the method repeatable (p<0.05). The absolute difference between the two measurements was found to increase with increasing level of measurements. This significant positive correlation (p<0.05) was mainly due to concentrations of YTX higher than 200 microg/100g mussel meat. However the precision of the results obtained was not found to be less in the upper level than in the lower level. Based on the internal correlation analysis including the mouse bioassay and the HPLC method a cut-off value of < or =10 microg YTX/5 g digestive gland was found preferable. The mouse bioassay of ether extracts often failed to detect high levels of YTX, and as demonstrated by the low kappa-values, the agreement between the mouse bioassay of ether extracts and the HPLC method was very weak. The HPLC method was found to give repeatable results and thereby found to be reliable. Consequently, the HPLC method seems to the method of choice for detection and quantification of YTX in mussels when compared with the mouse bioassay.

Monthly variations in diarrhetic toxins and yessotoxin in shellfish from coast to the inner part of the Sognefjord, Norway

Monthly concentrations of diarrhetic shellfish poisoning (DSP) toxins and yessotoxin (YTX) in mussels from the coast to the inner part of the Sognefjord were determined. Mussels from nine locations were sampled from March to November 1997. The DSP toxins and YTX were analysed by a colorimetric protein phosphatase 2A (PP2A) inhibition assay or fluorometric HPLC, respectively. The mouse bioassay for DSP toxins was performed including either chloroform or diethyl ether in the final step of extraction. Using ether in the final step normally facilitated extraction of the DSP toxins, okadaic acid (OA) and dinophysis toxin-1 (DTX-1), while chloroform extraction included a wider spectrum of toxins, including YTX and a fast acting toxin(s) with neurotoxic effects. The concentrations of DSP toxins and YTX in mussels increased with distance from the coast. The highest concentrations of YTX (574 microg YTX/100 g mussel meat) and diarrhetic toxins (349 microg OA equivalents/100 g mussel meat) were measured in May and August, respectively, at locations in the inner part of the fjord. Since concentrations of DSP toxins and YTX in mussels increased with distance from the coast, the locations for mussel farming in the Sognefjord close to the coast, seem to be preferable.

The repeatability of two HPLC methods and the PP2A assay in the quantification of diarrhetic toxins in blue mussels (Mytilus edulis)

Repeatability in the quantification of diarrhetic shellfish toxins was investigated for two fluorometric HPLC methods and a colorimetric PP2A assay, using agreement analysis. Blue mussels (Mytilus edulis) from the Sognefjord on the southwest coast of Norway were sampled during the periods of July to October, 1996, March to November, 1997, and October to December, 1998. The results from the first and the duplicate measurement were found to be very similar for both HPLC methods using two fluorogenic reagents, 4-bromomethyl,7-methoxycoumarin and 9-anthryl diazomethane, and the colorimetric PP2A inhibition assay in detection of diarrhetic shellfish toxins. The levels of agreement between the measurements were satisfactory for all three methods. Significant correlations were found between the level of observation and the absolute difference between the two measurements and were mainly due to concentrations of OA/DTX-1 higher than 100 microg/100 g mussel meat. However, the precision of quantifying DSP toxins in the upper level was not found to be less than in the lower level. Both the HPLC methods and the PP2A assay were found to give repeatable results and thereby found to be reliable.

Structure and fluorometric HPLC determination of 1-desulfoyessotoxin, a new yessotoxin analog isolated from mussels from Norway

A new analog of yessotoxin, 1-desulfoyessotoxin, was isolated from the digestive glands of mussels growing in the Sognefjord, Norway. Its structure was determined by NMR and negative ion CID MS/MS experiments. 1-Desulfoyessotoxin can be detected by the fluorometric HPLC method analogous with other yessotoxins.

Strain- and sex-specific differences in the glutathione S-transferase class pi in the mouse examined by gradient elution of the glutathione-affinity matrix and reverse-phase high performance liquid chromatography

A gradient elution with glutathione (GSH) from a GSH-Sepharose 6B affinity column separated the hepatic mouse glutathione S-transferases (GST) to the alpha-, mu- and pi-classes. The GST-dependent conjugation of atrazine and glutathione was catalyzed by a pi-class GST. The pi- and mu-classes were both identified by their respective specific substrates, and after reverse-phase HPLC, by N-terminal analysis of 19-35 of the amino acids. The alpha-class GST was associated with a high selenium-independent GSH peroxidase activity and the purified protein had a N-blocked terminal. Strain related differences in the pi-class GST of the CD-1, C57BL/6, DBA/2 and Swiss-Webster males were observed by PhastGel electrophoresis of the GSH affinity chromatograph separated fractions, reverse phase HPLC and by N-terminal amino acid sequence analysis.