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Remodelling of the extracellular matrix requires tight control not only of matrix synthesis, but also of matrix degradation. Control of matrix degradation is achieved mainly through the matrix metalloproteinase (MMP) enzymes. In the glomerulus, MMP-2 and MMP-9 are believed to be particularly important, as they have activity against type IV collagen. This study has demonstrated by immuno-electron microscopy that most of the immunoreactivity for MMP-2 in the normal glomerulus is located within the glomerular basement membranes and mesangial matrix. mRNA for MMP-2 is also detectable in normal glomeruli, but the other main gelatinase, MMP-9, could not be localized by immuno-electron microscopy. In the normal glomerulus, it seemed likely that MMP-2 is present in an inactive form. To confirm this, in situ zymography was carried out using frozen sections of normal kidney. Baseline activity of normal kidney was relatively weak, but this was dramatically increased by chemical activation of metalloproteinases. The results imply that MMP-2, in an inactive form, is a normal constituent of the extracellular matrix and glomerular basement membranes. Activation would presumably render the matrix 'self-degrading'; membrane-bound MMPs (MT-MMPs) seem particularly likely to be involved in leukocyte penetration of basement membranes in inflammation.

The uterus and the placenta synthesize insulin-like growth factors (IGFs) and insulin-like binding proteins (IGFBPs). These growth factors are implicated in processes of proliferation and differentiation that occur in the uterus. To determine the patterns of expression of IGFs during rat pregnancy we used in situ hybridization with digoxigenin labeled probes on uterus from day 7 to day 16 of pregnancy. In early gestation days (7-8) both IGF mRNAs showed similar tissue distribution with relative abundance in the stroma and circular muscle layer. On days 11 and 12 expression for IGF-I mRNA was found in the mesometrial decidua and metrial gland and in the ectoplacental cone while clear expression of IGF-II mRNA could only be found in the latter. On days 13 and 14, expression for IGF-I mRNA could be detected in the mesometrial decidua and metrial gland but no expression was observed for IGF-II mRNA. A gradient of IGF-I mRNA expression could be observed in the placenta on day 16, with the trophoblastic cells of the basal zone expressing the signal with stronger intensity than in the labyrinthine zone. For IGF-II mRNA the highest expression was associated with the labyrinthine zone. Endovascular trophoblast was positive for both mRNAs. The spatial and temporal patterns of expression suggests a role for IGFs in the process of decidualization as well as in the establishment, growth and differentiation of the various trophoblast cells of the placenta.

It is not clear whether the rare combination of Hodgkin's diseases with non-Hodgkin lymphomas are true composite lymphomas or differentiation stages of one tumour cell clone. We used in situ hybridization and immunohistochemistry for the demonstration of immunoglobulin light chains in order to investigate the relationship between the two lymphoma components. In three cases of nodular lymphocyte predominance Hodgkin's disease combined with diffuse large B-cell lymphoma the Hodgkin cells, as well as the tumour cells in the diffuse large B-cell lymphoma, showed the same messenger RNA for one light chain. Thus, using in situ hybridization in nodular lymphocyte predominance Hodgkin's disease combined with diffuse large B-cell lymphoma in a small number of cases a possible genetic relationship between the two components could be shown. In nodular sclerosis combined with diffuse large B-cell lymphoma, in situ hybridization did not support a common clonal origin of both tumour parts. However, a unique clonal derivation cannot be excluded by the techniques applied.

Previous studies using immunohistochemistry have shown variable hormone production by carcinoid tumours of the appendix. In order to confirm the existence of a specific subset of these tumours, in situ hybridization using synthetic oligonucleotide probes to detect pre-proglucagon and pre-proinsulin mRNA was performed in formalin-fixed, paraffin-embedded material from eight tubular carcinoids, 12 insulin carcinoids, and two mucinous carcinoids. The results were correlated with standard silver and mucin stains. All tubular carcinoids but none of the insular or mucinous carcinoids contained proglucagon mRNA. Proinsulin mRNA was not detected in any of the tumours. Tubular carcinoids of the appendix constitute a definable subset of appendiceal carcinoids which have a similar distribution and prognosis to typical insular carcinoids and can be diagnosed on haematoxylin and eosin-stained sections confirmed by routine special stains. The main need for recognition is to avoid confusion with mucinous carcinoids, which have a worse prognosis and may require more aggressive treatment.

Model experiments were designed to assess whether DNA could be recovered from formol-saline fixed peripheral blood lymphocytes and tonsil tissue for use in Southern blot gene analysis. Lymphocytes were fixed for 30 min and tonsil for 6 and 24 h, then paraffin embedded. High molecular weight DNA was extracted by prolonged digestion (2-7 days) with proteinase K or protease XXIV in the presence of 1 per cent sodium dodecyl sulphate. Restriction, transfer and hydridization were possible without modification of standard procedures. Multiple copy sequences were demonstrated using Mspl and Bst Nl restriction and hybridization for the Y chromosome (pHY 2.1 probe), single copy genes using EcoRI and BamHl restriction for the T-cell receptor beta chain (T beta probe), and Bgl II and Hind III for the immunoglobulin heavy chain (JH probe). Identical banding to unfixed tissue was achieved except when 24 h fixed extracts were used. With these, demonstration of the 24 KB Bam Hl/T beta and 9.2 KB Hind III/JH bands was not obtained. These findings suggest that as the fixation time is extended, alterations to DNA will limit the available range of restriction enzyme/probe combinations. However, with careful choice of these the extraction of DNA from formalin fixed and paraffin embedded pathological tissue for Southern blotting should be profitable.

A laser videodisc, holding 54 000 still frames per side, can be used to provide visual material of excellent quality for pathology teaching. In a collaborative project between ten pathology departments, the first pathology videodisc has recently been completed and the production of the disc is described. When used as illustrative material for computer-assisted learning programs, the videodisc offers accurate random access of still frames and allows the overlay of computer-generated graphics onto the video picture. This can be used to pre-identify every individual feature of a particular frame, and an example tutorial program is described to show how this may be used to improve the students' understanding of what they see. Details and costs are given for a workstation suitable for this application and potential future developments for this teaching method are discussed. Although objective assessment of the cost-effectiveness of interactive video in teaching pathology has yet to be undertaken, one suitably designed program can give individual tuition to many students, making this a most efficient use of teaching time.