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A Väisänen

Publications and source records attributed to A Väisänen.

7 recordsLinked to original sources
PubMed2000

The determination of certain major and minor elements in geological samples by inductively coupled plasma atomic emission spectrometry. Some interference problems with the analysis of geological standard reference materials and nutrition supplements.

Direct ICP-AES measurements of the digested geological standard reference material samples yielded the wrong information about their composition. The differences between certified and measured concentrations of the samples were due to the complicated sample matrix. The measured concentrations can be successfully corrected by using a multiple linear regression technique. The correction is based on the multiple regression line calculated from the analytical results at synthetic mixtures of matrix elements, where concentrations varied on five levels. There were no significant (P = 0.05) differences between certified and measured concentrations in standard reference materials after the correction. The same method was used in the analysis of nutrition supplements.

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PubMed1999

Matrix metalloproteinase-2 (MMP-2) immunoreactive protein--a new prognostic marker in uveal melanoma?

Uveal melanoma is the most common primary intraocular tumour. Once haematogenous metastasis has occurred, there is no cure for the disease and there is an obvious need for new biological prognostic markers to estimate the risk of metastasis. In this study, the expression of matrix metalloproteinase-2 (MMP-2) was characterized immunohistochemically in 29 human uveal melanomas. Enzyme-linked immunoassays and gelatin zymographies were assessed in order to quantify the expression of gelatinases A and B, as well as the tissue inhibitor of metalloproteinases (TIMPs), in the vitreous body. A total of 49 per cent of the uveal melanomas displayed a positive immunoreaction for MMP-2 in melanoma cells, the epithelioid cells showing the most frequent staining. There was no correlation between the positivity of MMP-2 staining and the size of the primary tumour, gender or age. The expression of MMP-2 was associated with a dismal prognosis: the 5-year overall survival rate for MMP-2-positive cases was significantly inferior to that of the MMP-2 negative cases, 49 per cent vs. 86 per cent, respectively (p=0.02). A patient group at high risk of metastatic disease was identified; only 38 per cent of patients with a MMP-2-positive non-spindle cell uveal melanoma survived for 5 years. The analyses of MMPs or TIMPs in the vitreous body had no prognostic value. Positive immunostaining for MMP-2 was observed in the retinal pigment epithelium, corneal epithelium, and fibroblasts in the ciliary body and choroid. It is concluded that immunohistochemical analysis of MMP-2 may help to predict a risk of metastasis in uveal melanoma.

Adult↗
PubMed1998

Roles of acid/base nature and molecular weight in drug release from matrices of gelfoam and monoisopropyl ester of poly(vinyl methyl ether-maleic anhydride).

Ophthalmic drug inserts are usually placed in the conjunctival sac. Being in contact with the conjunctiva, they may provide means to deliver large and hydrophilic molecules, such as peptides and oligonucleotides into the eye. We evaluated Gelfoam and monoisopropyl ester of poly(vinyl methyl ether/maleic anhydride) (PVM/MA) as potential polymers for ocular inserts. Matrices were solvent cast with model drugs that had different pKa, molecular weight and hydrophilicity. Drug release from the matrices as well as charge and swelling of Gelfoam(R)-matrix were studied. The release of drugs from PVM/MA-matrices was by erosion of the polymer matrix. The molecular weight and other variants of the releasing compound did not affect their release. In Gelfoam(R)-matrices the release was diffusion controlled and it was affected by the pH of the external solution as well as the charge and molecular weight of the studied compound.

Buffers↗
PubMed1998

Prognostic value of MMP-2 immunoreactive protein (72 kD type IV collagenase) in primary skin melanoma.

The penetration of the subepithelial basement membrane is the first critical step in the dissemination of melanoma. In vitro studies have suggested that the 72 kD type IV collagenase (MMP-2) may be important in melanoma invasion. It has recently been demonstrated that the expression of MMP-2 immunoreactive protein increased with increasing atypia in melanocytic tumours and was associated with later haematogenous metastases in melanoma. This paper investigates the value of MMP-2 as a possible prognostic marker in melanoma. The expression of MMP-2 immunoreactive protein was studied with immunoperoxidase staining in paraffin-embedded sections of 50 cases of primary skin melanoma by using specific, affinity purified antibodies. Positive immunostaining was quantified by counting the percentage of positive cancer cells and was compared with clinical patient characteristics and survival. Sixty-four per cent of the primary melanoma cases displayed positive cytoplasmic immunostaining for MMP-2 in tumour cells. Marked overexpression of MMP-2 protein (> or = 34 per cent of melanoma cells positive) correlated with the 5-year survival of the patients when compared with patients with lower MMP-2 positivity, 55 per cent vs. 85 per cent, respectively (P < 0.05). Male patients displayed positive staining more often than females (75 per cent vs. 54 per cent, respectively). There was no correlation between MMP-2 positivity and Clark level or Breslow classification. A distinct group with unfavourable prognosis was identified. The 10-year survival for MMP-2-positive male melanoma patients was 39 per cent as opposed to 79 per cent with the other melanoma patients (P < 0.05). In the hierarchic Cox regression model for survival, MMP-2 immunoreactive protein was found to be independent of Clark level and Breslow classification. Overexpression of MMP-2 protein indicated a 4.5-fold relative risk of dying from melanoma. It is concluded that MMP-2 immunoreactive protein in melanoma cells is an independent prognostic factor for survival. High MMP-2 expression in male melanoma patients indicates an unfavourable prognosis.

Adult↗
PubMed1996

Matrix metalloproteinase-2 (72 kD type IV collagenase) expression occurs in the early stage of human melanocytic tumour progression and may have prognostic value.

Matrix metalloproteinase-2 (MMP-2), a member of the matrix metalloproteinase family, participates in degradation of the pericellular and extracellular matrix during neoplastic growth and metastasis. Experimental data have substantiated its role in melanoma invasion, but there is no information at present concerning its expression in histological specimens from human melanocytic tumors. This study describes the occurrence and immunolocalization of MMP-2 in human melanocytic lesions, defining distinct steps in melanoma progression. Paraffin-embedded sections from 118 melanocytic lesions were immunostained using a specific antibody to 72 kD type IV collagenase. The material included 34 common naevocellular naevi, 14 dysplastic naevi, 21 in situ melanomas, 20 primary malignant melanomas, and 29 melanoma metastases. Intracytoplasmic MMP-2 immunoreactive protein was found in the 'naevocytic nests' of common naevi, in junctional naevus cells, and in melanoma cells. The surrounding normal skin stained negatively, except for occasional macrophages, sweat glands, and hair follicles. The number of MMP-2-positive cells increased with decreasing architectural organization and increasing atypia in the melanocytic lesions. The MMP-2 positivity in the primary and subcutaneous melanoma lesions correlated with later haematogenous metastasis. The data suggest that MMP-2 expression is an early event in melanocytic tumour progression, but is nevertheless prognostic for haematogenous metastasis in melanoma.

Adult↗
PubMed1994

Modulation of M(r) 72,000 and M(r) 92,000 type-IV collagenase (gelatinase A and B) gene expression by interferons alpha and gamma in human melanoma.

The purpose of this study was to determine how interferons alpha and gamma influence the expression of M(r) 72,000 type-IV collagenase (gelatinase A) and M(r) 92,000 type-VI collagenase (gelatinase B) genes and whether there are differences in their gene expression. Special emphasis was focused on the treatment time. Total cellular RNA from A2058 human melanoma cells treated for various time periods with IFN-alpha or gamma was analyzed by Northern- and slot-blot hybridization. Both M(r) 72,000 and M(r) 92,000 type-IV collagenase mRNAs were detectable in A2058 cells and mRNA levels for both gelatinases were significantly up-regulated in the cells treated for a short time period with either IFN-alpha or gamma. In contrast, a long-term treatment (7 days) with these drugs markedly down-regulated the genes for both gelatinase A and B. Zymographic analysis showed that human melanoma primarily secretes the gelatinase-A activity, which showed changes similar to those seen in the corresponding mRNA after the treatments with interferons. The expression of gelatinase-B activity was, however, detectable only transiently during the stimulating phase with IFN-alpha. Western immunoblot analysis showed that alterations in the levels of immunoreactive protein of gelatinase A in the cells correlated with the mRNA levels after the treatments. These findings suggest that IFN-alpha and IFN-gamma are potent regulators of both M(r) 72,000 and M(r) 92,000 type-IV collagenase/gelatinase A and B genes in human melanoma showing biphasic and parallel effects on mRNA levels of both enzymes, depending on the treatment time, and that the M(r) 72,000 metalloproteinase/gelatinase A is the predominant basement-membrane-degrading type-IV collagenase in human melanoma.

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