The beta-subunit of human chorionic gonadotrophin exists as a homodimer

The free beta-subunit of human chorionic gonadotrophin (hCGbeta) is well recognised as a product of many epithelial tumours. Recently, it has been shown that this ectopic production may have a functional relationship to tumour growth. The growth-promoting activity of hCGbeta may be explained by its structural similarity to a family of growth factors which all contain the same distinct topological fold known as the cystine-knot motif. Since the other members of this family all exhibit their activities as homo- and heterodimers, it is possible that the same may be true for hCGbeta. Using size-exclusion chromatography, low stringency SDS-PAGE and matrix assisted laser desorption/ionisation (MALDI) time-of-flight (TOF) mass spectrometry (MS) we have shown that pure preparations of hCGbeta contain hCGbetabeta homodimers. Size-exclusion chromatography revealed asymmetric elution profiles with a forward peak corresponding to the size-exclusion characteristic of a globular protein with an approximate mass of 44-54 kDa and a late shoulder centered around an elution position expected for a globular protein of approximately 29 kDa. Two immunoreactive hCGbeta species, of approximately 32 and 64 kDa, were clearly resolved by SDS-PAGE and Western blotting. When analysed by MALDI-TOF MS a |mf23 kDa monomer and a |mf46 kDa dimer were identified. Formation of hCGbetabeta homodimers is consistent with the behaviour of other cystine-knot growth factors and strengthens the inclusion of the glycoprotein hormones within this superfamily. It has yet to be determined whether it is this dimeric molecular species that is responsible for growth-promoting activity of hCGbeta preparations in tumours.

The effect of dihydrotestosterone on transcription of prostatic acid phosphatase mRNA in human hyperplastic gland

The effect of 5alpha-dihydrotestosterone (DHT) on the level of human prostatic acid phosphatase (hPAP) mRNA was studied using tissue slices from various benign prostatic hyperplastic glands. The absence of DHT in the incubation medium led to a gradual, significant decrease of the hPAP mRNA level. Addition of the hormone induced hPAP mRNA in a time- and dose-dependent manner. The maximal 2-4-fold induction by 10(-9) M DHT was observed after 3-5 h of incubation, and then the hPAP mRNA level was 6-20-fold higher than that in a parallel sample incubated without DHT. The results suggest that DHT is necessary to sustain the expression of hPAP in hyperplastic prostates.

Discrimination of mammalian growth hormones by peptide-mass mapping

Recognition by the legal authorities that growth hormones (GHs) may be abused to improve sporting performance and/or physique has led to the implementation of controls that make it an offence to produce, supply, possess or import and export GHs, with intent to supply, without the authority to do so. A method is described for the discriminatory analysis of human, equine, porcine and bovine GHs for forensic purposes. Peptide-mass mapping by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry following tryptic digestion gave sequence coverages of 97.4%, 93.7%, 94.2% and 90.6% for human, equine, porcine and bovine GHs respectively. The tryptic-mass maps generated were sufficient to discriminate between the four hormones analysed and thus provide unambiguous identification of each individual GH. Identification of the N-terminal peptides of recombinant equine and porcine GHs, which possess additional methionine residues, within the tryptic-mass maps may provide the basis of a test to indicate exogeneous administration rather than endogenous secretion of GH in performance dogs and horses.

The effect of dihydrotestosterone on transcription of prostatic acid phosphatase mRNA in human hyperplastic gland

The effect of 5alpha-dihydrotestosterone (DHT) on the level of human prostatic acid phosphatase (hPAP) mRNA was studied using tissue slices from various benign prostatic hyperplastic glands. The absence of DHT in the incubation medium led to a gradual, significant decrease of the hPAP mRNA level. Addition of the hormone induced hPAP mRNA in a time- and dose-dependent manner. The maximal 2-4-fold induction by 10(-9) M DHT was observed after 3-5 h of incubation, and then the hPAP mRNA level was 6-20-fold higher than that in a parallel sample incubated without DHT. The results suggest that DHT is necessary to sustain the expression of hPAP in hyperplastic prostates.

Tumor cell N-glycans in metastasis

Metastasis accounts for most of deaths caused by cancer. The increasing body of evidence suggests that changes in N-glycosylation of tumor cell proteins such as increased branching, increased sialylation, polysialylation, decreased fucosylation, enhanced formation of Lewis X and sialyl Lewis X antigens are among important factors determining metastatic potential of tumor cell. Most of the adhesion proteins, e.g., integrins, members of immunoglobulin superfamily, and cadherins are heavily N-glycosylated. The other proteins involved in adhesion, like galectins and type-C selectins, recognize N-glycans as a part of their specific ligands. In this review we focus on recent reports concerning the contribution of N-glycosylation of tumor cell adhesion molecules and some selected membrane proteins in the tumor invasion and metastasis.

Serum IGF-I and IGF binding proteins 2 and 3 as potential markers of doping with human GH

OBJECTIVE

IGF-I and IGF binding protein (IGFBP)-3 levels in man are positively regulated by GH status; in contrast, evidence suggests an inverse relationship between GH status and IGFBP-2. We investigated the effects of somatropin administration on the serum concentrations of these analytes, together with serum and urinary concentrations of GH, to evaluate their potential as markers in the development of a test for detecting doping with GH in sports competitors.

DESIGN

Somatropin was administered subcutaneously at a dose of 0.15 U/kg bodyweight/day at 1000 h for 3 days to eight healthy men (20-32 years old).

MEASUREMENTS

Serum concentrations of GH, IGF-I, IGFBP-2 and -3 were determined in blood samples collected at 1600 h on the days prior to (day -1), during (days 0, 1 and 2), and following administration (days 3 and 7). Urine was collected continuously from days -2 to 3 and then on day 7.

RESULTS

Serum and urinary concentrations of GH were only raised on the days of administration whereas, following cessation of somatropin, the increases in the serum concentrations of IGF-I and IGFBP-3 were sustained for at least 1 day (30 h). Serum IGFBP-2 decreased during the period of administration and was still suppressed on day 3. The concentration ratios of IGFBP-3 to IGFBP-2 and IGF-I to IGFBP-2 increased markedly with administration and both ratios were still significantly augmented compared with basal values 30 h after the last administration.

CONCLUSION

With acute administration of somatropin to healthy men the serum concentration of IGFBP-2 decreases and the ratios of serum IGF-I/ IGFBP-2 and IGFBP-3/IGFBP-2 increase. These ratios should be considered in the development of a test for detecting somatropin administration in sport.

Tumor cell N-glycans in metastasis

Metastasis accounts for most of deaths caused by cancer. The increasing body of evidence suggests that changes in N-glycosylation of tumor cell proteins such as increased branching, increased sialylation, polysialylation, decreased fucosylation, enhanced formation of Lewis X and sialyl Lewis X antigens are among important factors determining metastatic potential of tumor cell. Most of the adhesion proteins, e.g., integrins, members of immunoglobulin superfamily, and cadherins are heavily N-glycosylated. The other proteins involved in adhesion, like galectins and type-C selectins, recognize N-glycans as a part of their specific ligands. In this review we focus on recent reports concerning the contribution of N-glycosylation of tumor cell adhesion molecules and some selected membrane proteins in the tumor invasion and metastasis.

Arylsulfatase A from human placenta possesses only high mannose-type glycans

It has been shown that the concentration of arylsulfatase A increases in the body fluids of patients with some forms of cancer and the carbohydrate component of arylsulfatase A synthesized in tumor tissues and transformed cells undergoes increased sialylation, phosphorylation and sulfation. The specificity of changes in the glycosylation of glycoproteins in cancer is still unknown. To understand the significance of any changes in glycosylation of arylsulfatase A in cancer, it is important to know the structure of its carbohydrate component in normal tissue. Here, carbohydrate moieties of human placental arylsulfatase A were studied by sequential lectin affinity chromatography after enzymatic cleavage and labelling with tritiated sodium borohydride. Labelled oligosaccharides were subjected to ion exchange chromatography. The uncharged fraction and the neuraminidase treated charged fraction were further analysed using the lectins: Concanavalin A (Con A), Ricinus communis (RCA I), Triticum vulgaris (L-PHA) and Aleuria aurantia (AAL). The results indicated that 97% of the arylsulfatase A oligosaccharides were low molecular weight high mannose type glycans possessing up to 5 mannose residues. This was supported by the approximately 2.4 kDa decrease in the molecular weight of arylsulfatase. A subunits upon complete peptide N-glycosidase F deglycosylation, as shown using SDS-PAGE. The remaining 3% of the arylsulfatase A oligosaccharides were of the high mannose type, possessing more than 5 mannose residues. Most (97.5%) of the glycans were uncharged, while 2.5% were charged. Neuraminidase treatment of the latter did not remove the charge, suggesting the presence of phosphate or sulfate residues. This study, of arylsulfatase A oligosaccharides separated from the protein part, shows that all glycans of the enzyme from human placenta are of the high mannose type.

Analysis of influenza A H3N2 strains isolated in England during 1995-1996 using polymerase chain reaction restriction

A polymerase chain reaction-restriction (PCR-restriction) endonuclease assay was developed to allow rapid analysis of influenza A H3N2 viruses circulating in England during 1995-1996. Restriction endonuclease digestion with two enzymes of amplicons derived from PCR of the HA1 portion of the influenza haemagglutinin (HA) gene was able to differentiate antigenically similar influenza strains into two groups. Group I variants were similar genetically to the 1995/96 vaccine strain, A/Johannesburg/33/94, whereas the HA sequences of Group II variants were similar genetically to the reference virus A/Thessaloniki/1/95. Of the 700 England A H3N2 strains isolated between February 1995 and the end of April 1996, 384 were analysed by this method. PCR-restriction analysis of sequential influenza isolates revealed a temporal alteration in prevalence of two variants. Groups I and II variants cocirculated with equal frequency during a period of sporadic influenza activity, but following the onset of epidemic influenza activity in 1995, only Group II variants were detected. PCR- restriction analysis was found to be a rapid method for studying genetic variation which could be applied to a large number of samples and provide information about the direction of genetic drift in the HA gene of influenza virus.

Preliminary characterization of the oligosaccharide component of arylsulfatase B from human placenta

Isoelectric focusing of homogenous arylsulfatase B from human placenta pointed to the presence of enzymatically active and inactive forms of high pI (pH 9-8) and of lower pI (pH 6.5-5.5). Glycan chain analysis performed with the use of a Glycan Differentiation Kit showed that basic forms of arylsulfatase B from human placenta contained mostly high mannose/hybrid type glycans, with 6-O-L-fucose bound to the innermost N-acetylglucosamine residue, whereas acidic forms of the enzyme contained complex type glycans containing fucose and sialic acid. However, the latter forms constitute a small percentage of the total carbohydrate component. Lectin affinity chromatography of the native enzyme confirmed the presence of a core fucose and a sialic acid.

Neurotropic malignant melanoma presenting as a trigeminal sensory neuropathy

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Tryptic mapping of human chorionic gonadotropin by matrix-assisted laser desorption/ionization mass spectrometry

The potential of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for use in the identification of human chorionic gonadotropin (hCG) seized by law enforcement agencies is investigated. Analysis of untreated hCG revealed signals corresponding to the molecular ions of the intact hCG heterodimer and both its non-covalently linked subunits. Unfortunately, due to carbohydrate heterogeneity, the peaks are broad which makes accurate mass assignment, and consequently identification, difficult. Peptide mapping by MALDI-TOF following tryptic digestion gave sequence coverage of 59% and 52% for the alpha- and beta-subunits respectively. Nevertheless, the tryptic map was considered to provide unambiguous identification of hCG. This was confirmed by searching peptide-mass databases with the experimentally determined masses. Our data suggest that peptide mapping by proteolytic digestion followed by MALDI-TOF mass spectrometry is a suitable analytical technique for the identification of hCG seized by the legal authorities.

Characterization of human arylsulfatase A glycans

Despite numerous studies on arylsulfatase A, the structure of the glycans present in each of its two subunits has not been determined. This is important because the carbohydrate component of human arylsulfatase A synthesized in tumor tissues and transformed cells has been shown to undergo apparent changes. This study elucidates some of their major features. Glycan chain analysis of native and deglycosylated arylsulfatase A as well as its subunits was performed with the use of a Glycan Differentiation Kit and lectin affinity chromatography. Each of the two subunits of arylsulfatase A from placenta, separated electrophoretically on polyacrylamide gel in reducing conditions, reacted with digoxigenin-labelled Galantus nivalis agglutinin and Aleuria aurantia agglutinin, while those from liver enzyme reacted with the former only. The subunits of both enzymes did not react with Sambucus nigra, Maakia amuriensis, Datura stramonium or Peanut agglutinin. Deglycosylation of arylsulfatase A with peptide N-glycosidase F and endo-beta-N-acetylglucosaminidase F resulted in complete cleavage of its carbohydrate component from each subunit. Their molecular weights decreased by 3 kDa. Neuraminidase treatment of the enzyme from liver and placenta followed by isoelectrofocusing separation showed the presence of sialylated forms which constituted a small percentage of total enzyme activity. Placental arylsulfatase A became bound to Lens culinaris agglutinin agarose, while no interaction with Ricinus communis or Griffonia simplicifolia agglutinin agarose was observed. The study shows that both subunits of arylsulfatase A from human placenta possess two high mannose/hybrid type glycans as major structures, with at least one 6-O-L-fucose bound to the innermost N-acetylglucosamine on each.(ABSTRACT TRUNCATED AT 250 WORDS)

New decision limits and quality-control material for detecting human chorionic gonadotropin misuse in sports

Male athletes may administer human chorionic gonadotropin (hCG) to enhance performance. Despite imposing a ban on hCG doping, the International Olympic Committee has no recommended procedure to confirm the presence of hCG. Our aim was to establish a limit for hCG in urine above which a sample may be considered positive. We measured hCG concentrations in urine samples from 1400 men with the Serono MAIAclone IRMA. Statistical evaluation of the results gave a "far outside" value [75th percentile + (3 x interquartile range)] of 5.0 IU/L; greater values are extremely unusual. Immunoreactive material in urine samples from a reference group of 120 noncompeting individuals was concentrated about sevenfold by centrifugal ultrafiltration; all these concentrated samples gave assay values < 5.0 IU/L. To ensure with the greatest possible degree of certainty that no false-positive result is reported, we propose a decision limit of 10 IU/L in nonconcentrated ultrafiltered samples. We also prepared quality-control material to contain hCG at 10 IU/L. This material provides a decision limit above which, after confirmatory procedures, a sample should be considered positive. This should help establish comparability of results among laboratories testing for sports drugs.

New decision limits and quality-control material for detecting human chorionic gonadotropin misuse in sports

Male athletes may administer human chorionic gonadotropin (hCG) to enhance performance. Despite imposing a ban on hCG doping, the International Olympic Committee has no recommended procedure to confirm the presence of hCG. Our aim was to establish a limit for hCG in urine above which a sample may be considered positive. We measured hCG concentrations in urine samples from 1400 men with the Serono MAIAclone IRMA. Statistical evaluation of the results gave a "far outside" value [75th percentile + (3 x interquartile range)] of 5.0 IU/L; greater values are extremely unusual. Immunoreactive material in urine samples from a reference group of 120 noncompeting individuals was concentrated about sevenfold by centrifugal ultrafiltration; all these concentrated samples gave assay values < 5.0 IU/L. To ensure with the greatest possible degree of certainty that no false-positive result is reported, we propose a decision limit of 10 IU/L in nonconcentrated ultrafiltered samples. We also prepared quality-control material to contain hCG at 10 IU/L. This material provides a decision limit above which, after confirmatory procedures, a sample should be considered positive. This should help establish comparability of results among laboratories testing for sports drugs.

Adrenal spindle-cell sarcoma with features of malignant peripheral nerve sheath tumor

An unusual malignant spindle-cell tumor of the adrenal medulla originally diagnosed as leiomyosarcoma is illustrated. On the evidence of histological and immunohistochemical findings, the neoplasm was rediagnosed as a spindle-cell sarcoma with features of malignant peripheral nerve sheath tumor. Unlike ordinary pheochromocytoma, which may also show a spindling cell pattern, such lesions are malignant and its recognition may have implications for prognosis and management of patients.

Suprabasal acantholysis--an unusual feature of necrolytic migratory erythema

A 67-year-old man with diabetes, weight loss and anaemia initially presented with a widespread scaling erythematous rash; a skin biopsy demonstrated marked suprabasal acantholysis. A subsequent biopsy showed localized upper epidermal necrolysis and the diagnosis of glucagonoma syndrome was later confirmed. Glucagonoma syndrome should be considered in patients with diabetes, weight loss and anaemia who present with a scaling rash, the histology of which shows suprabasal acantholysis. The extent of any upper epidermal necrolysis may be be very limited.

Arylsulfatase A in serum from patients with cancer of various organs

Arylsulfatase A was radioimmunoassayed in serum specimens of 96 healthy volunteers and 368 patients with histopathologically confirmed cancer of gastrointestinal tract, breast, lung, central nervous system, kidney and woman genital tract. Sensitivity, specificity and predictive value of the test were 43%, 82% and 90%, respectively, which means that a positive test is significant for diagnosis of cancer regardless of its localization. More detailed statistical analysis of the results indicates that determination of the serum concentration of arylsulfatase A might be helpful in the diagnosis of lung (59% sensitivity, 82% specificity) and central nervous system cancer (60% sensitivity, 82% specificity). Further studies should also be continued in respect to renal and women genital tract cancers for which the results of the test, although promising, are at present not conclusive due to the small numbers of examined cases. Particularly, determination of serum arylsulfatase A in case of endometrial cancer seems to be of diagnostic value. Arylsulfatase A concentration in serum with a lower than 40% sensitivity of the test cannot be considered as a valuable tumor indicator in the case of cancer of breast and gastrointestinal tract, although 80% predictive value of the test for the latter group of tumors is quite high and perhaps merits additional consideration.

Sequential processing of lysosomal acid phosphatase by a cytoplasmic thiol proteinase and a lysosomal aspartyl proteinase

BHK cells expressing human lysosomal acid phosphatase (LAP) transport LAP to lysosomes as an integral membrane protein. In lysosomes LAP is released from the membrane by proteolytic processing, which involves at least two cleavages at the C terminus of LAP. The first cleavage is catalysed by a thiol proteinase at the outside of the lysosomal membrane and removes the bulk of the cytoplasmic tail of LAP. The second cleavage is catalysed by an aspartyl proteinase inside the lysosomes and releases the luminal part of LAP from the membrane-spanning domain. The first cleavage at the cytoplasmic side of the lysosomal membrane depends on acidification of lysosomes and the second cleavage inside the lysosomes depends on prior processing of the cytoplasmic tail. These results suggest that the cytoplasmic tail controls the conformation of the luminal portion of LAP and vice versa.