Developmental expression of the cell adhesion molecule-like protein tyrosine phosphatases LAR, RPTPdelta and RPTPsigma in the mouse.

Using RNA in situ hybridization we compared the expression patterns of the cell adhesion molecule-like receptor-type protein tyrosine phosphatases LAR, RPTP sigma and RPTP sigma during mouse development. We found that LAR is expressed in basal lamina-associated epithelial tissues of (neuro)ectodermal, neural crest/ectomesenchyme and endodermal origin. RPTP sigma is found in (neuro)ectodermal, neural crest-derived systems and in mesoderm-derived tissues. The expression pattern of RPTP sigma largely parallels that of RPTP sigma, in concordance with their proposed evolutionary history

Constitutive and inducible expression of SKALP/elafin provides anti-elastase defense in human epithelia.

Skin-derived antileukoproteinase (SKALP), also known as elafin, is a serine proteinase inhibitor first discovered in keratinocytes from hyperproliferative human epidermis. In addition to the proteinase inhibiting domain which is directed against polymorphonuclear leukocyte (PMN) derived enzymes such as elastase and proteinase 3, SKALP contains multiple transglutaminase (TGase) substrate domains which enable crosslinking to extracellular and cell envelope proteins. Here we show that SKALP is constitutively expressed in several epithelia that are continuously subjected to inflammatory stimuli, such as the oral cavity and the vagina where it co-localizes with type 1 TGase. All epithelia from sterile body cavities are negative for SKALP. In general, stratified squamous epithelia are positive, whereas pseudostratified epithelia, simple/glandular epithelia and normal epidermis are negative. SKALP was found in fetal tissues of the oral cavity from 17 wk gestation onwards where it continued to be expressed up to adult life. Remarkably, in fetal epidermis SKALP was found from week 28 onwards, but was downregulated to undetectable levels in neonatal skin within three months, suggesting a role during pregnancy in feto-maternal interactions or in the early maturation phase of the epidermis. Immunoelectron microscopy revealed the presence of SKALP in secretory vesicles including the lamellar granules. In culture models for epidermal keratinocytes we found that expression of the endogenous SKALP gene provided protection against cell detachment caused by purified elastase or activated PMNs. Addition of exogenous recombinant SKALP fully protected the keratinocytes against PMN-dependent detachment whereas superoxide dismutase and catalase were only marginally effective. These findings strongly suggest that the constitutive expression of SKALP in squamous epithelia, and the inducible expression in epidermis participate in the control of epithelial integrity, by inhibiting PMN derived proteinases.

Abnormal myotonic dystrophy protein kinase levels produce only mild myopathy in mice.

Myotonic dystrophy (DM) is commonly associated with CTG repeat expansions within the gene for DM-protein kinase (DMPK). The effect of altered expression levels of DMPK, which is ubiquitously expressed in all muscle cell lineages during development, was examined by disrupting the endogenous Dmpk gene and overexpressing a normal human DMPK transgene in mice. Nullizygous (-/-) mice showed only inconsistent and minor size changes in head and neck muscle fibres at older age, animals with the highest DMPK transgene expression showed hypertrophic cardiomyopathy and enhanced neonatal mortality. However, both models lack other frequent DM symptoms including the fibre-type dependent atrophy, myotonia, cataract and male-infertility. These results strengthen the contention that simple loss- or gain-of-expression of DMPK is not the only crucial requirement for development of the disease.

Co-localization and functional coupling of creatine kinase B and gastric H+/K(+)-ATPase on the apical membrane and the tubulovesicular system of parietal cells.

Immunogold labelling of creatine kinase B (BB-CK) and gastric H+/K(+)-ATPase in the parietal cells of the stomach revealed colocalization of these two enzymes on the apical membrane and the membranes of the tubulovesicular system. Upon fractionation of hog parietal cells, a specific fraction of the BB-CK proteins remained associated with the purified vesicles, in which gastric H+/K(+)-ATPase is highly enriched. The BB-CK present in this highly purified preparation was able to support pronounced H+/K(+)-ATPase activity in K(+)-loaded vesicles in the presence of phosphocreatine and ADP, although only low levels of ATP were measured. In contrast, when pyruvate kinase, phosphoenolpyruvate and ADP were used as an ATP-generating system to sustain similar levels of H+/K(+)-ATPase activity, ATP levels were more than 10-fold higher. Changing the experimental conditions such that ATP levels were the same for both systems resulted in significantly elevated H+/K(+)-ATPase activities in the BB-CK/phosphocreatine system in comparison with the pyruvate kinase/phosphoenolpyruvate system. These results indicate that gastric H+/K(+)-ATPase has preferential access to ATP generated by creatine kinase co-localized on the membranes of the vesicles.

Abnormal expression of intermediate filament proteins in X-linked myotubular myopathy is not reproduced in vitro.

Expression patterns of the intermediate filament proteins (IFPs) desmin and vimentin, in biopsy material taken from a 1 day old boy with fatal neonatal X-linked myotubular myopathy (XLMTM) were compared with the expression of these proteins in cultured myotubes, from the same patient. Immunohistochemical studies revealed the persistence of high levels of desmin in virtually all, and vimentin in most, of the myofibres within the patient's biopsy. Analysis of intermediate filament expression in differentiating, cultured muscle cells did not reveal overt differences between XLMTM cultures and cultures of control muscle. Titin distribution patterns indicated a normal process of myofibrillogenesis in XLMTM myotubes. We conclude that the failure to properly regulate IFP-expression is not intrinsic to XLMTM muscle fibres. The possibility that this failure is due to a defective external, possibly neural factor, is discussed.

Increased expression of a 68-kDa protein in the corpus cavernosum of some men with erectile dysfunction.

Erectile dysfunction (ED) may be caused by abnormalities of intracavernous penile structures. In order to investigate whether specific proteins could be identified that might be related to ED, the composition of structural proteins in cavernous tissues of patients with ED was compared to that of normal cavernous tissues by gel electrophoresis. Increased expression of a 68-kDa nonionic detergent extraction-resistant protein was demonstrated in tissues of more than half of the patients with vasculogenic ED, whereas only one out of nine normal cavernous tissues showed the same phenomenon. Increased expression was not related to a specific type of vascular insufficiency, aging, or diabetic constituency. Histochemical and immunochemical studies revealed that the increased amount of the 68-kDa protein is not merely the result of a surplus of nervous, smooth muscle, or elastic tissues. Furthermore, antibodies specific for 68-kDa neurofilament and 62- to 67.5-kDa tropoelastin did not recognize the 68-kDa protein on Western blots. The possibility that the 68-kDa protein may help us understand the etiology of certain cases of erectile dysfunction is discussed.

Distribution and features of melanocytes during inner ear development in pigmented and albino rats.

In this developmental study, the distribution and features of melanocytes in the inner ear of pigmented and albino rats was investigated with the use of an antibody, which specifically reacts with a melanocyte differentiation antigen present in the membranes of (pre)melanosomes. Melanocyte precursors could be traced from 13 days post conception onwards and the course was followed to their targets in the inner ear. Melanocytes which settle in the modiolus appeared to reach their target along another pathway than strial and vestibular melanocytes. No difference was observed in the melanocyte distribution between pigmented and albino rats. The integration of melanocytes into the stria vascularis was associated with an increased rate of melanosome production in both strains, but in the albinos far fewer melanosomes were produced. After the stria had reached maturity, melanosome production was arrested and melanosomes were subject to lysosomal digestion. In the stria of the pigmented rats, cells with aggregations of disintegrating melanosomes appeared and persisted into adulthood. In the adult, the majority of the intermediate cells contained only a few scattered melanosomes, while melanosomes could only rarely be detected in the albinos. These observations indicate that there is a close relationship between melanosome production and the process of interdigitation of melanocytes with the marginal cells. It seems unlikely that melanosomes or melanin make any important contribution to the function of the adult stria vascularis. Outside the stria, the features of melanocytes in both strains were similar to skin melanocytes.

Tissue- and cell-specific distribution of creatine kinase B: a new and highly specific monoclonal antibody for use in immunohistochemistry.

A synthetic 17-mer peptide corresponding to an unique sequence in the amino-terminal region of human creatine kinase B was used to raise a new and highly B-subunit-specific monoclonal antibody, CK-BYK/21E10. We show here that the monoclonal antibody is suitable for immunohistochemistry of unfixed frozen sections as well as formaldehyde- or Bouin-fixed, paraffin-embedded sections of human, rabbit, and mouse tissues. Moreover, in the study of cell- and tissue-specific distribution patterns, parallel Western blot analysis and immunoelectron microscopy is possible using this antibody. Our analyses demonstrate that creatine kinase B expression is restricted to a specific subset of cell types in various tissues. In brain, the B-subunit was found only in neurocytes, but not in glia cells. High expression was also observed in inner segments of photoreceptor cells and the outer plexiform layer of the retina, in the parietal cells of the stomach and in gut enterocytes, gallbladder and epithelial cells of the urogenital system. The possible roles of the creatine kinase/phosphocreatine-ATP system in these tissues are discussed.

Immunophenotyping of congenital myopathies: disorganization of sarcomeric, cytoskeletal and extracellular matrix proteins.

We have studied the expression and distribution patterns of the intermediate filament proteins desmin and vimentin, the sarcomere components titin, nebulin and myosin, the basement membrane constituents collagen type IV and laminin, and the reticular layer component collagen type VI in skeletal muscle of patients with "classic" congenital myopathies (CM), using indirect immunofluorescence assays. In all biopsy specimens obtained from patients with central core disease (CCD), nemaline myopathy (NM), X-linked myotubular myopathy (XLMTM) and centronuclear myopathy (CNM), disease-specific desmin disturbances were observed. Vimentin was present in immature fibres in severe neonatal NM, and as sarcoplasmic aggregates in one case of CNM, while the amounts of vimentin and embryonic myosin, observed in XLMTM, decreased with age of the patients. Abnormal expression of myosin isoforms was found in several CM biopsies, although the organization of myosin and other sarcomere components was rarely disturbed. Basement membrane and reticular layer proteins were often prominently increased in severe cases of CM. We conclude that (i) desmin is a marker for individual types of CM and might be used for diagnostic purposes; (ii) the expression patterns of the differentiation markers desmin, vimentin and embryonic myosin in XLMTM, point either to a postnatal muscle fibre maturation or to a variable time-point of maturational arrest in individual patients; (iii) the correlation between the distribution patterns of extracellular matrix proteins and clinical presentation points to a role of these proteins in pathophysiology of CM.

Design of immunoliposomes directed against human ovarian carcinoma.

Factors (protein/lipid ratio, pH of incubation medium, incubation time, anchor molecule density in the bilayer) affecting the covalent binding of anti-ovarian carcinoma Fab' to liposomes containing the anchor molecule MPB-PE (N-(4-(p-maleimidophenyl)butyryl)phosphatidylethanolamine) were explored. Standard experimental conditions were chosen and information on the relevant physicochemical parameters of the liposome dispersions was collected (mean particle diameter, size distribution, charge). The reproducibility of standard immunoliposomes prepared in subsequent batches in terms of Fab' binding, particle size and charge was established. In addition, preservation of immunoreactivity, no marker loss, and no aggregation/fusion was found for the standard immunoliposomes over a period of at least 3 weeks at 4 degrees C. In vitro up to 35,000 immunoliposomes were estimated to bind per human ovarian carcinoma cell. Internalization of the immunoliposomes could not be demonstrated. Electron micrographs showed binding of specific immunoliposomes to human ovarian carcinoma cells growing intraperitoneally in athymic nude mice.

Mitochondrial creatine kinase: a major constituent of pathological inclusions seen in mitochondrial myopathies.

Overaccumulation of abnormally organized mitochondria in so-called "ragged-red" skeletal muscle fibers is a morphological hallmark of mitochondrial myopathies, in particular of mitochondrial encephalomyopathies. Characteristic for the abnormal mitochondria is the occurrence of highly ordered crystalline inclusions. Immuno-electron microscopy revealed that these inclusions react heavily with specific antibodies against mitochondrial creatine kinase (Mi-CK). Image processing of selected crystalline inclusions, sectioned along the crystallographic b, c planes, resulted in an averaged picture displaying an arrangement of regular, square-shaped particles with a central cavity. The overall appearance, dimensions, and symmetry of these building blocks are very reminiscent of single isolated Mi-CK octamers. Taking these findings together, it is concluded that Mi-CK octamers indeed represent the major, if not the only, component of these mitochondrial inclusions.

Myotonic dystrophy kinase is a component of neuromuscular junctions.

The clinical manifestation of myotonic dystrophy (DM) is correlated to the extent of expansion of an unstable [CTG]n DNA motif. Recent studies have demonstrated that this trinucleotide motif forms part of the last, 3' untranslated exon of a gene which potentially encodes multiple protein isoforms of a serine/threonine protein kinase (myotonic dystrophy protein kinase, DM-PK). We report here on the development of antisera against synthetic DM-PK peptide antigens and their use in biochemical and histochemical studies. Immunoreactive DM-kinase protein of 53 kD is present at low levels in skeletal and cardiac muscle extracts of DM patients and normal controls. Immunohistochemical staining revealed that DM-PK is localised prominently at sites of neuromuscular and myotendinous junctions (NMJs and MTJs) of human and rodent skeletal muscles. Furthermore, very low levels of immunoreactive DM-PK protein are present in the sarcoplasm of predominantly type I fibres in various muscles. Strikingly, presence of the protein can also be demonstrated for NMJs of muscular tissues of adult and congenital cases of DM, with no gross changes in structural organisation. Our findings provide a basis for further characterisation of the role of the kinase in protein assembly processes or signal mediation at synaptic sites and ultimately for the understanding of the complex pathophysiology of DM.

Titin aggregates associated with intermediate filaments align along stress fiber-like structures during human skeletal muscle cell differentiation.

Differentiating human skeletal muscle cell cultures were used to study the association of titin with other sarcomeric and cytoskeletal proteins during myofibrillogenesis. Several developmental stages of these cultures were double stained with antibodies to titin in combination with antibodies to alpha-actin, alpha-actinin, myosin heavy chain (MHC), nebulin, desmin, and beta-tubulin. The first indications of titin expression were found in postmitotic mononuclear myoblasts where it is located in a random, punctate fashion. At the light microscope level no evidence was found for an association of these titin spots with any of the other proteins studied, with the exception of MHC, which colocalized with titin in a small minority of the titin expressing cells. Subsequently the titin spots were found to be linked to longitudinally oriented stress fiber-like structures (SFLS), containing alpha-actinin and sarcomeric alpha-actin, but not MHC, nebulin or desmin. Upon further maturation titin antibodies seemed to stain SFLS in a rather homogeneous fashion together with MHC, alpha-actin and alpha-actinin. Thereafter a more periodic localization of titin, MHC, alpha-actin and alpha-actinin on SFLS became obvious. From these structures myofibrils developed as a result of further differentiation. Initially only short stretches with a striated titin, MHC, F-actin and alpha-actinin organization were found. Nebulin was integrated in these young myofibrils at a later developmental stage. Desmin was not found to be incorporated in these myofibrils until complete alignment of the sarcomeres in mature myotubes had occurred. At the ultrastructural level titin antibodies recognized aggregates that were associated with intermediate filaments (IF) in postmitotic mononuclear myoblasts. At a later maturational stage, prior to the development of cross-striated myofibrils, the IF-associated titin aggregates were found in close association with subsarcolemmally located SFLS. We conclude that IF and SFLS play an important role in the very early stages of in vitro human myofibrillogenesis. On the basis of our results we assume that titin aggregates are targeted to SFLS through IF. The association of titin with SFLS might be crucial for the unwinding of titin necessary for the assembly of sarcomeres and the first association of titin with other sarcomeric proteins.

Biological effects of high energy shock waves in mouse skeletal muscle: correlation between 31P magnetic resonance spectroscopic and microscopic alterations.

To investigate the in vivo effects of electromagnetically generated high energy shock waves (HESW) on skeletal muscle, we used in vivo 31P nuclear magnetic resonance (NMR) spectroscopy (MRS) measurements and correlated the results with microscopical studies. Mouse skeletal muscle (calf muscle) was exposed to 200 or 800 HESW (Pmax: 37.5 MPa, Pmin: 5.2 MPa, tr: 30-120 ns, tw: 340 ns, frequency: 1.25 Hz). In the 31P MRS spectra, transient alterations were observed. A prominent increase of inorganic phosphate (Pi) peaks was found, as well as the appearance of Pi with different chemical shifts, reflecting the presence of different pH values (5.4-7.1) in cellular or tissue compartments. Within 20-96 h after exposure, pH values and Pi levels returned to normal. The changes were more pronounced in the animals treated with 800 HESW as compared to 200 HESW. Light and electron microscopy demonstrated focal degenerations of muscle fibers. This process consisted of disorganization of myofilaments and structural changes in sarcoplasmic organelles and was progressive in time. The (ultra)structural changes were not present in all myofibers (i.e., between affected degenerating fibers unaffected intact fibers were seen). Several ultrastructural abnormalities were also found in capillaries even up to severe dilatation and disruption, as well as in the peripheral nerves. The degeneration of the preexisting myofibers was predominantly confined to type 1 fibers and was followed by a regeneration of the muscle tissue by proliferation of myoblasts. A notable amount of myotubes still showed vacuolization. We conclude that in vivo HESW exposure of skeletal muscle tissue results in a degeneration of myofibers. The cellular effects are present in foci and associated with changes in the 31P NMR spectra. The NMR spectroscopy technique provides us with a noninvasive method to evaluate in a longitudinal way the biological effects of HESW.

OV-TL 12/30 (keratin 7 antibody) is a marker of glandular differentiation in lung cancer.

The immunoreactivity of OV-TL 12/30, a monoclonal antibody to keratin 7 was investigated on paraffin-embedded human lung cancer tissues of 61 patients. A modified AEC-immunoperoxidase method with pepsin pre-digestion was used. In normal lung tissue keratin 7 was found in bronchial and bronchiolar epithelium, pneumocytes and compound glands. Squamous metaplasia of the bronchial tree was negative. All 24 squamous cell carcinomas were negative irrespective of grade of differentiation. All differentiation grades of 20 adenocarcinomas including bronchioalveolar carcinomas were positive. Since six large cell anaplastic carcinomas did not react with keratin 7 antibody these tumours are considered to be of squamous cell rather than adenocarcinomatous origin. Small cell anaplastic carcinomas were negative in 10 of 11 cases. Our study demonstrates that this keratin 7 antibody is useful in differentiating between squamous cell carcinoma and adenocarcinoma of the lung and it may be particularly useful in making the correct diagnosis in small lung biopsy specimens.

The rat bladder tumor model system RBT resembles phenotypically and cytogenetically human superficial transitional cell carcinoma.

A cohort of 300 ACI rats was kept under standard laboratory conditions. After 30 months or upon natural death, complete autopsy was performed. In the genitourinary tract four kidney and five bladder tumors were found. Two of these bladder tumors, RBT323 and RBT157, are serially transplantable. In the fifth transplant generation the RBT323 tumor becomes metastatic to the lungs in more than 90% of animals. The metastatic ability of the RBT157 tumor changes from low to intermediate (50% of the rats have lung metastases) in the fourth passage. Histologically, the initial passages of the RBT323 and 157 tumors are grade II transitional cell carcinoma (TCC). The histological pattern of the RBT157 tumor remains essentially unchanged, whereas the RBT323 tumor progresses to a grade III tumor in the third passage. Electron microscopical studies reveal oblong elliptical and round vesicles lined by an asymmetrical unit membrane in the tumor cells, which stresses the urothelial origin of the tumors. Immunohistochemically both tumors show expression of cytokeratin 5, 7, 8 and 18. The progression of the tumors to a metastatic phenotype, however, is not associated with a specific change in the morphological characteristics. Cytogenetic analysis shows that both tumors are peridiploid with few marker chromosomes. Interestingly, both of these independently arising tumors exhibit a loss of chromosome 5. Rat chromosome 5 is syntenic to the major portion of human chromosome 9 (p23-qter). Loss of chromosome 9 is a cytogenetic trait of human superficial TCC, hence the RBT model is also in cytogenetic respect similar to human TCC.(ABSTRACT TRUNCATED AT 250 WORDS)

Differentiation of human skeletal muscle cells in culture: maturation as indicated by titin and desmin striation.

This report describes a phenotyping study of differentiating human skeletal muscle cells in tissue culture. Satellite cells (adult myoblasts), isolated from biopsy material, showed a proliferative behaviour in high-nutrition medium, but fused to form myotubes when grown in low-nutrition medium. The expression and structural organization of the intermediate filament proteins desmin and vimentin as well as the sarcomeric constituents alpha-actin, alpha-actinin, nebulin, myosin and especially titin during myofibrillogenesis in vitro, were studied by means of indirect immunofluorescence assays. The proliferating myoblasts contained both desmin and vimentin, alpha-actinin and the filamentous form of actin. Shortly after the change of medium, expression of titin, sarcomeric myosin and skeletal muscle alpha-actin was found in mononuclear cells in a diffuse, filamentous (titin, myosin, alpha-actin) or punctate (titin, myosin) pattern. Four to 10 days after the medium change, mature myotubes showed desmin, titin, alpha-actinin, nebulin, sarcomeric myosin and actin cross-striations, while vimentin was no longer detected. We conclude that human skeletal muscle cell cultures are an appropriate model system to study the molecular basis of myofibrillogenesis. Especially the presence of desmin in a striated fashion points to a high degree of maturation of the muscle cell cultures.

A scanning electron microscopic study of the sporogonic development of Plasmodium falciparum in Anopheles stephensi.

The full development of Plasmodium falciparum in Anopheles stephensi mosquitoes was studied by scanning electron microscopy. Ookinetic development was described from in vitro cultures. Growing oocysts beneath the basal lamina of the midgut wall mechanically stretch this lamina until it is torn and displaced by day 7. In young oocysts the wall appears smooth. In older oocysts wrinkles in the wall are visible after routine fixation. Osmium tetroxide postfixation greatly reduced the occurrence of these wrinkles. Intracapsular development of sporozoites was visualized after mechanical manipulation of the oocysts during sample preparation. In contrast to P. berghei, no ectopic development was seen in P. falciparum in the mosquito midgut. The mechanism of sporozoite escape from the oocyst appears to be similar to that described for rodent malaria. Fracturing of salivary glands provided the first view by scanning electron microscopy of sporozoites located in proximal and distal gland cells and in the draining duct.

Immunocytochemical markerprofile of endometriotic epithelial, endometrial epithelial, and mesothelial cells: a comparative study.

A comparative immunocytochemical study was performed on endometriotic epithelial versus endometrial epithelial and normal mesothelial cells in order to obtain further evidence for either the endometrial implantation or mesothelial metaplasia theory. The three cell types could not be distinguished by keratin subtyping, using monoclonal antibodies (MAbs) to keratins 5, 7, 8, 14, 18, and 19. The epithelial markers HMFG-2 and BW 495/36, and a newly developed MAb NEND-3 (against endometrial cells) discriminated between generally negatively reacting mesothelial cells and positively reacting endometrial and endometriotic epithelial cells. The MAb NEND-3 appeared to be specific for endometrial (and endometriotic) epithelial cells since no reactivity with other epithelial cell types was found. Typing with MAbs against ovarian carcinoma related antigens (OV-TL 3, OV-TL 10 and OC 125) did not permit sufficient distinction. The marker profile of cultured endometrial, endometriotic and mesothelial cells confirmed the immunocytochemical findings on frozen sections. Although the data are consistent with the endometrial implantation theory, mesothelial metaplasia can not be excluded with regard to the histogenesis of endometriosis since metaplastic mesothelium may express different antigen markers.

Immunohistochemical demonstration of keratin 7 in routinely fixed paraffin-embedded human tissues.

The immunoreactivity of OV-TL 12/30, a monoclonal anti-keratin 7 antibody (Mab), was investigated on frozen as well as paraffin-embedded human tissues. Its reactivity patterns were compared with another well-characterized monoclonal antibody to keratin 7 (RCK 105), and with broadly cross-reacting monoclonal (OV-TL 12/5) as well as polyclonal (pKer) keratin antisera. In frozen sections of normal and malignant human tissues both keratin 7 Mabs gave similar staining patterns. The immunoreactivity for OV-TL 12/30 and the polyclonal antibody (pKer) in tissue sections fixed in 4 per cent formalin or Bouin solution, was completely restored when pretreated with 0.1 per cent pronase, 0.1 per cent trypsin in phosphate-buffered saline (PBS) or with 0.5 per cent pepsin in 0.01 N HCl. Except for loss of immunoreactivity on human normal stomach surface epithelium and glandular mucous cells, Mab OV-TL 12/30 reacted strongly positive with essentially all those formalin- or Bouin-fixed paraffin-embedded tissues that had been shown to stain in non-fixed, frozen sections. In addition to the good correlation in human tissues, a complete correlation between the reactivity on frozen and paraffin-embedded human carcinomas (n = 86) was found as well. While both RCK 105 (anti-keratin 7) and OV-TL 12/5 (anti-keratin 5, 7, 14, 19) did not stain on paraffin-embedded sections, the polyclonal control antiserum (pKer) lost immunoreactivity in some cell types (e.g. mucous cells in compound glands, hepatocytes, pancreatic acinar cells, and proximal and distal convoluted tubules of the kidney). Our study shows that the keratin 7 Mab OV-TL 12/30 is an excellent marker for tumour histopathology since it is reactive in paraffin-embedded formalin-fixed human tissues.