Topical application of calcitriol alters expression of filaggrin but not keratin K1 in mouse epidermis

Calcitriol (1 alpha,25-dihydroxyvitamin D3) and its analogues are antiproliferative agents which promote epidermal differentiation in vitro, possibly reflecting their modes of action in the treatment of psoriasis. We examined the effect of calcitriol on early and late terminal differentiation in mouse epidermis in vivo using an immunofluorescence assay to detect keratin K1 and filaggrin expression. Pulse labelling with the tymidine analogue 5-bromo-2-deoxyuridine (BrdUrd) was performed by intraperitoneal injection of mice immediately or 16 h after a single topical application of 0.72 nmol calcitriol. The BrdUrd labelling index (LI) and keratin K1 or filaggrin expression of postmitotic cell cohorts were scored by paired immunofluorescence staining for up to 72 h after BrdUrd labelling. Calcitriol induced cell proliferation as shown by a 100% increase in the BrdUrd LI 17 h after application. The onset of keratin K1 expression in the postmitotic period was, however, unchanged in both series after calcitriol treatment. Filaggrin expression appeared earlier after calcitriol treatment than in control epidermis, probably reflecting altered cell kinetics with increased epidermal turnover. The results suggest that calcitriol only influences the later stages of the keratinocyte differentiation programme, possibly secondarily to its hyperproliferative effect.

Topical application of 12-O-tetradecanoylphorbol-13-acetate induces dyssynchronous expression of keratins K1 and K10 in mouse epidermis

12-O-tetradecanoylphorbol-13-acetate (TPA) is a potent tumor promoter that causes severe alterations in the biosynthesis of epidermal keratins. This study shows that TPA induces a dyssynchronous effect on keratin expression in stratified squamous epithelium. The effect of TPA on the separate expression of the maturation-associated keratins K1 and K10 was studied by immunohistochemistry in an unperturbed replicative keratinocyte population of hairless mice epidermis in relation to changes in the cell cycle time during regeneration. Keratinocytes in DNA synthesis were pulse-labeled by intraperitoneal injection of the thymidine analogue 5-bromodeoxyuridine (BrdUrd) 1 h before a single topical application of TPA. The BrdUrd-labeled cell cohort, representing an originally unperturbed replicative keratinocyte population exposed to TPA mainly in the postreplicative period, was followed for up to 97 h. The results suggested unaltered timing of the onset of K1 and K10 expression compared with normal epidermis (18 and 24 h, respectively, following DNA synthesis). This indicates that the synthesis of both keratins was programmed before the keratinocytes entered their last DNA synthesis. A reduction in K10 expression from about 30 h compared with that of K1 expression was observed. Mathematical modeling suggested a delay in K10 expression related to the second and third rounds of cell divisions after pulse-labeling. How TPA induces such dyssynchrony in K1 and K10 regulation remains unknown.

Immunohistochemical and microfluorometric determination of hepatic DNA adduct removal in rats fed 2-acetylaminofluorene

Biphasic removal of DNA adducts has previously been demonstrated by radioimmunoassay in whole liver DNA from rats chronically fed 2-acetylaminofluorene for 28 days. In the present study, removal of N-(deoxyguanosin-8-yl)-2-aminofluorene was observed in situ by microfluorometry. Frozen liver sections from animals fed 0.02% 2-acetylaminofluorene for 28 days, followed by a control diet for 3, 7, 14, 21 and 28 days, were examined immunohistochemically for localization of N-(deoxyguanosin-8-yl)-2-aminofluorene with fluorescein-conjugated secondary antiserum. In addition, bile ducts and oval cells were stained with antibodies to keratins using Texas red-labeled indirect immunofluorescence. Hoechst dye was used to identify DNA in nuclei. During the 28 days on the control diet, after 28 days of feeding 2-acetylaminofluorene, the DNA adduct concentrations of parenchymal liver cells were reduced by 85%, as compared to animals fed only the carcinogen for 28 days. Periportal hepatocytes exhibited biphasic (fast and slow) adduct removal. Only fast adduct removal was demonstrated in midzonal and centrilobular hepatocytes, since the adduct levels were below the detectable range in these regions after 7 days on the control diet. After 28 days on the control diet, N-(deoxyguanosin-8-yl)-2-aminofluorene was detected in approximately 50% of periportal hepatocytes. These results are compatible with the previously observed biphasic removal profile determined by radioimmunoassay of whole liver DNA adducts and indicate that periportal hepatocytes remove adducts from two distinct genomic compartments.

Gene activation studied by immunological methods

Gene activation can be studied at several levels: transcription (mRNA), translation (proteins), or phenotypical alterations (functional activity or morphology). These levels can be studied in situ or biochemically by the use of specific probes for normal or altered DNA, mRNA, or proteins. Immunological probes are potent tools for studies of alterations induced by xenobiotics in target organs. When the effects of xenobiotics are studied in whole tissue, the cellular heterogeneity of the organ must be taken into account. For this reason, combined in situ and biochemical techniques are necessary. Antibodies to normal or altered cellular constituents are used for identification, quantitation, and cellular localization of proteins and modified DNA. Many xenobiotics alter gene activation by interactions with DNA. After activation, 2-acetylaminofluorene (AAF) forms DNA adducts, which can be identified immunologically. Combined with bromodeoxyuridine (BrdU) pulse labeling, techniques have been developed to demonstrate reduced adduct concentrations in proliferating cells and preneoplastic foci in the livers of AAF-fed rats. Carcinogen-induced DNA modifications are implicated as a major mechanism of altered gene activation in neoplasia, leading to phenotypical alterations. Also, cellular differentiation may be affected by xenobiotics. Differentiation-associated markers can be used for studies of gene activation. In mouse skin, the keratins K1 and K10 are only expressed in suprabasal, differentiating cells. BrdU pulse chase experiments combined with double immunofluorescence have revealed that K1 and K10 are sequentially turned on 18 to 24 hr after DNA synthesis and are followed by suprabasal migration. After a single application of the tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA), cell migration starts directly after mitosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of topical retinoic acid application on keratin K1 and filaggrin expression in mouse epidermis

Retinoic acid (RA) modulates epidermal homeostasis and affects differentiation-associated proteins such as keratin K1 and filaggrin. Because results from in vitro and in vivo studies have been conflicting with respect to RA effects on keratinization, we examined the terminal differentiation of epidermal cell cohorts after RA stimulation in vivo. Pulse-labelling with 5-bromo-2-deoxyuridine (BrdU) was performed by intraperitoneal injection of mice immediately or at 16 h after a single topical application of 100 nmol RA. The cell cohort labelled at the time of RA application consisted of previously unperturbed cells exposed to RA after initiation of S-phase, whereas the cohort labelled 16 h after RA application consisted of cells stimulated into the S-phase by RA. These two cohorts of partially synchronized cells were followed for up to 72 h after BrdU labelling. Such labelling combined with keratin K1 or filaggrin expression was scored by paired immunofluorescence staining of skin sections. The onset of keratin K1 expression was unchanged in both series after RA treatment, while filaggrin appeared earlier than in controls. The differential effect of RA on the maturation markers was related to the proliferative activity, the increased cell turnover, and the shortened epidermal transit time. The onset of keratin expression appeared to be regulated before the postmitotic period, whereas filaggrin expression appeared to be regulated during the late phase of the maturation process, thus being influenced by the actual epidermal kinetics and structural alterations. These results suggested that the effect of RA on epidermal differentiation is secondary to its effect on proliferation, as determined by the altered cellular age distribution following regenerative proliferation.

Application of cantharidin or 12-O-tetradecanoylphorbol-13-acetate on mouse epidermis induces a cell population shift that causes altered keratin distribution

The tumour promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) causes changes in epidermal protein expression, especially in the major differentiation products keratins K1 and K10. These keratins and filaggrin were studied in a pulse-labelled cell cohort in hairless mouse epidermis stimulated to proliferate by TPA or the hyperplasiogen cantharidin. Cells in DNA synthesis were pulse-labelled by 5-bromo-2-deoxyuridine (BrdU) 16 h after topical application of cantharidin or TPA. The BrdU-labelled cell cohort, the two keratins, and filaggrin were spatially mapped by paired immunofluorescence staining. Both cantharidin- and TPA-treated epidermis displayed altered distributions of K1 and K10 with expression only in the outermost cell layers, but the start of their postreplicative expression paralleled that in normal epidermis (18 h for K1 and 24 h for K10 after the last round of DNA synthesis). Cantharidin- and TPA-induced epidermal hyperplasia showed increased basal cell proliferation, accelerated suprabasal migration, and shortened transit time. Thus, the newly formed hyperplastic epidermis was composed of keratinocytes with a lower mean cellular age than that seen in unperturbed epidermis, which caused altered distribution of K1 and K10. Both hyperplastic and normal epidermis showed filaggrin expression in stratum granulosum; this started earlier in treated (30-36 h) than in untreated (96 h) skin. We concluded that the postmitotic onset of K1 and K10 expression was unaltered in regenerative epidermis, whereas filaggrin expression was considerably accelerated and thus influenced by the cell kinetic changes.

Expression of keratins K6 and K16 in regenerating mouse epidermis is less restricted by cell replication than the expression of K1 and K10

Biosynthesis of the hyperproliferation-associated keratins K6 and K16 was studied in mouse epidermis following a single topical application of the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). An epidermal cell cohort was followed by pulse-labelling with the thymidine analogue 5-bromodeoxyuridine (BrdUrd). Mice were injected intraperitoneally with BrdUrd 1 h before a single topical application of TPA. TPA induced regenerative epidermal hyperplasia with hyperproliferation and shortened suprabasal transit time. The BrdUrd-labelled cell cohort was followed for 96 h after TPA-treatment by two-colour immunofluorescence staining with antibodies to BrdUrd, keratin K6 and K16. In control animals, K6 and K16 were found only in the hair follicles. K6 expression was immediately induced in all epidermal cell layers of TPA-treated epidermis, including actively replicating cells and it was expressed during the whole observation period. K16 was only present in post-mitotic cells and was transiently expressed 8-72 h after TPA treatment. Our results suggest that the expression of K6 and K16 is less restricted by cellular replication than the normally occurring K1 and K10 keratins.

In situ measurement of colorectal polyps to compare video and fiberoptic endoscopes

The present study was performed to test the reliability of in situ measurements of colorectal polyps when comparing videoendoscopes with fiberoptic endoscopes. In 25 small rectosigmoid polyps 3-12 mm) removed endoscopically, in situ diameters were measured before polypectomy using both video- and fiberoptic endoscopes. Polaroid and videoprint pictures were taken for computerised analysis of the area of the polyps on the pictures. The results showed a good correlation between the polyp diameter measured with the videoendoscope and fiberoptic endoscope (r = 0.97), with no significant difference by parametric testing. The diameter and weight of the removed polyp also correlated well with the diameter measured in situ using videoendoscopes (r = 0.92 and 0.77, respectively) or fiberoptic endoscopes (r = 0.90 and 0.81, respectively). Furthermore, the weight of the removed polyp correlated reasonably well to the computerised area measurement, the correlation coefficient being r = 0.90 for fiberoptic endoscopes and r = 0.75 for videoendoscopes. We conclude that in situ polyp diameter measurements using videoendscopes and fiberoptic endoscopes are similarly reliable and sensitive, and both instruments can be used interchangeably in follow-up studies of polyp growth.

Location of cAMP-dependent protein kinase type I with the TCR-CD3 complex

Selective activation of cyclic adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase type I (cAKI), but not type II, is sufficient to mediate inhibition of T cell replication induced through the antigen-specific T cell receptor-CD3 (TCR-CD3) complex. Immunocytochemistry and immunoprecipitation studies of the molecular mechanism by which cAKI inhibits TCR-CD3-dependent T cell replication demonstrated that regulatory subunit I alpha, along with its associated kinase activity, translocated to and interacted with the TCR-CD3 complex during T cell activation and capping. Regulatory subunit II alpha did not. When stimulated by cAMP, the cAKI localized to the TCR-CD3 complex may release kinase activity that, through phosphorylation, might uncouple the TCR-CD3 complex from intracellular signaling systems.

Binucleation and polyploidization patterns in developmental and regenerative rat liver growth

The hepatocellular binucleation rate, measured as the percentage of binuclear cells amongst newly formed bromodeoxyuridine-labelled and immunostained collagenase-isolated rat hepatocytes, decreased from 12% to 4% between days 30 and 40 after birth, rose to 20% between days 50 and 60, and then declined again to the adult rate of about 10% at day 80. During regenerative growth following a two-thirds partial hepatectomy, the rate of binucleation declined to about 3%, causing the fraction of binuclear cells to fall from 27% (before hepactectomy) to 5% (at 45 h after hepactectomy) as pre-existing binuclear cells replicated and formed mononuclear daughter cells. Essentially all (97%) hepatocytes replicated at least once, starting their DNA synthesis at around 13 h and reaching a peak at 30 h, irrespective of ploidy and nuclearity. At later time points, the diploid hepatocytes had a higher labelling index than the polyploid cells, suggesting a greater tendency to go through several cell cycles.

Microtubule-associated distribution of specific granules and secretion of atrial natriuretic factor in primary cultures of rat cardiomyocytes

A close spatial relationship between specific granules containing atrial natriuretic factor (ANF) and microtubules was demonstrated in primary cultures of neonatal rat cardiac myocytes. For the detection of specific granules and microtubules, the myocytes were double immunolabeled with antibodies against alpha-ANF and beta-tubulin and examined by conventional fluorescence or laser scanning confocal microscopy. In addition, the ultrastructural distribution of specific granules was demonstrated by electron microscopy. In the atrial myocytes, ANF was stored in numerous specific granules that were mainly localized in the perinuclear sarcoplasm. In the ventricular myocytes, however, a minority of the cells (10%) exhibited limited ANF immunoreactivity after 4 days in culture. Microtubules were present throughout the sarcoplasm of the myocytes. They were most densely packed in the perinuclear regions. Depolymerization of the microtubules with nocodazole was followed by dispersal of ANF immunostaining both in the atrial myocytes and in the ventricular myocytes exhibiting ANF immunoreactivity. When the microtubules were allowed to recover, the perinuclear distribution of specific granules, as seen in non-treated myocytes, reappeared. Measurements of secreted immunoreactive ANF by radioimmunoassay revealed that the secretion of ANF from atrial myocytes into the medium was significantly reduced following nocodazole treatment, whereas a similar decrease in secretion from ventricular myocytes was not observed. These findings indicate that ANF-containing specific granules are closely associated with microtubules within the myocytes. It is suggested that secretion of ANF from the atrial myocytes, in contrast to the ventricular myocytes, is microtubule-dependent.

Ultrastructural morphometric analysis of human blood platelets exposed to minimal handling procedures

A detailed morphometric study of normal human blood platelets is described. The purpose has been to evaluate the morphological characteristics of platelets exposed to minimal handling procedures in order to obtain an optimal basis for the appraisal of platelets in disease. Blood from 10 healthy volunteers was collected directly into buffered glutaraldehyde and processed for electron microscopy. This platelet fixation procedure resulted in excellent preservation of resting platelet ultrastructure with one exception: the dense bodies. Compared to platelets fixed following washing procedures, our directly fixed platelets comprised fewer pseudopods and contained more glycogen. An unexpected feature of the open canalicular system was the apparent release of blisters interpreted as microvesicles. Employing a computerized image analyzer, 300 of the platelets were examined morphologically. The morphometric data thus obtained were analyzed statistically, resulting in a set of standard values for morphological characteristics of human platelets which we have found useful in subsequent evaluations of platelet morphology in disease. Significant inter-individual variance was, however, detected in two instances, in the section area of the alpha granules, as well as the area fraction of platelet sections occupied by channels of the open canalicular system (OCS). This should be taken into consideration when appraising platelet ultrastructure in health and disease.

Epithelial expression of HLA, secretory component (poly-Ig receptor), and adhesion molecules in the human alimentary tract

Epithelial HLA class II is differentially expressed (DR >> DP) only after birth in salivary glands and small intestinal mucosa, in contrast to class I determinants and secretory component (SC) which appear early in gestation. However, there is a brisk postnatal increase in SC expression along with the class II induction, suggesting stimulation by cytokines from activated immune cells. T lymphocytes remain quite scanty in postnatal salivary glands, and the striking SC and class II expression might reflect a synergistic effect of IFN-gamma and TFN-alpha on immature epithelial cells. Enhanced epithelial expression of both SC and class II in salivary glands from sudden infant death victims could be the effect of immunostimulation caused by an infectious agent. Strikingly upregulated SC and epithelial class II expression (DR > DP > DQ) is seen in various inflammatory lesions such as obstructive sialadenitis, Sjögren's syndrome, chronic gastritis, and celiac disease. IFN-gamma and TNF-alpha are most likely involved as the expression patterns can be reproduced with these cytokines in vitro on colonic epithelial cell lines. However, these molecules of the Ig supergene family do not show a selective response in epithelia of inflammatory lesions because increased expression is also seen for lysozyme, lactoferrin and some other proteins. ICAM-1 can be upregulated on epithelial cells by various cytokines in vitro although the situation remains uncertain in mucosal inflammation. The expression pattern in IBD is complicated by dysplastic epithelial changes leading to reduced SC levels which may thus, in turn, jeopardize the poly-Ig transport mechanism. Epithelial class II molecules appear to have antigen-presenting properties, but the immunopathologic role of their increased expression in inflammatory disease in terms of induction of autoimmunity and/or abrogation of oral tolerance is a matter of continuing dispute.

Cytokeratins as epithelial differentiation markers in premalignant and malignant oral lesions

The keratin expression pattern in oral stratified epithelium is related to the cellular differentiation level. The normal pattern shows the keratin pair K5 and K14 in the stratum basale whereas K1 and K10, or K4 and K13, are the two pairs associated with differentiating suprabasal cells. Monoclonal and polyclonal antibodies to individual keratins (K10, K13 and K14) were used in a two-color immunofluorescence staining method to study their coexpression in single cells. Altered keratin expression in premalignant and malignant lesions indicated abnormal differentiation. Monospecific keratin antibodies were suggested to be useful for evaluation of epithelial differentiation changes in oral dysplasias and oral squamous cell carcinomas.

Analytical methods for the study of liver cell proliferation

Various cytometric methods for analysis of regenerating rat liver growth (DNA ploidy distributions, binucleation, and DNA synthesis by in vivo BrdUrd incorporation) were evaluated. The overall hepatocellular growth rate (labeling index), the binucleation rate, and separate indices for mononuclear and binuclear cells could be measured simply by microscope counting of collagenase-isolated hepatocytes immunostained for BrdUrd. Flow cytometry of cells stained for BrdUrd and DNA provided labeling indices for the various hepatocellular DNA ploidy classes as well as for nonparenchymal cells (identified by their size-dependent light scatter), but could not distinguish between mononuclear and binuclear hepatocytes. Image cytometry, using fluorescence or Feulgen staining, was inferior to flow cytometry in terms of speed and DNA resolution, but allowed a complete analysis of all hepatocellular DNA ploidy and nuclearity classes. It may therefore be the method of choice, particularly for analysis of liver cell cultures from which single cells are not easily obtained. Fluorescence staining would seem to be preferable to Feulgen staining, since the latter could not be used simultaneously with BrdUrd staining and therefore required a two-step analysis. A non-immunological method, based on the ability of incorporated BrdUrd to quench DNA staining by a Hoechst dye, could only be applied to isolated nuclei, thus giving no information about binucleation. The latter method may be useful for analysis of tumors which are difficult to dissociate to intact whole cells.

Altered regulation of growth and expression of differentiation-associated keratins in benign mouse skin tumors

Alterations in the pattern of epidermal cell differentiation and proliferation in mouse skin and benign skin tumors were studied by two-color immunofluorescence using monospecific antibodies. Replicating cells were identified by 5-bromo-deoxyuridine (BrdU) pulse-labeling and differentiating cells by keratins K1 and K10. In normal mouse skin, pulse-chase experiments for 120 h revealed that replication was restricted to a single layer of basal cells. Replicating cells did not express K1 or K10, but these keratins were sequentially expressed in post-mitotic basal cells 18 and 24 h following DNA synthesis respectively, and cells expressing these keratins migrated into the suprabasal layers. In phorbol-ester- or cantharidin-stimulated hyperplastic skin, replicating cells were also confined to the basal cell compartment and suprabasal cells expressed keratins 1 and 10. In papillomas induced by initiation with 7,12-dimethylbenz[a]anthracene and promotion with 12-O-tetradecanoylphorbol-13-acetate, replication occurred predominantly in cells in an expanded basal cell compartment (two to four layers above the basement membrane). Cells in these basal layers did not express K1 or K10, but more superficial cells did. After a 1 h pulse of BrdU, replication was also identified in suprabasal cells expressing the differentiation-associated keratins. These and other results suggest that benign tumor cells escape the obligatory growth arrest associated with differentiation. Replication of K1- and K10-expressing suprabasal cells may represent an early alteration during mouse skin carcinogenesis.

Induction of in vitro resistance to 4'-epidoxorubicin and cis-dichlorodiammineplatinum in hepatoma cells

We have developed in vitro resistance to 4'-epidoxorubicin (Epi-A) and cis-dichlorodiammineplatinum (cis-DDP) in one rat (MH1C1) and one human hepatoma cell line (HepG2). When compared to their parental cells, the Epi-A resistant rat cells were 17 times and the resistant human cells 27 times more resistant to Epi-A in terms of GI50 in the cell growth inhibition assay. The cis-DDP resistant rat cells were 20 times and the resistant human cells 12 times more resistant to cis-DDP. Cross-resistance to cis-DDP was observed in the Epi-A resistant rat cells but not in the human cells. The multidrug resistant gene product, GP 170, was markedly expressed in both Epi-A resistant substrains compared with their parent lines, suggesting a role of this protein in the development of resistance to Epi-A. Cadmium-binding proteins of metallothionein (MT) size bound 52% of cytosolic 109cadmium in the cis-DDP resistant human cells compared with 8% in the parental cells. This may indicate that these proteins contribute to the observed cis-DDP resistance.

Carcinogen-induced alterations in rat liver DNA adduct formation determined by computerized fluorescent image analysis

These studies employed continuous feeding of a carcinogenic level of N-2-acetylaminofluorene to male rats for 28 days. Under these conditions normal hepatocytes are known to be inhibited from proliferation, whereas xenobiotic-resistant putative preneoplastic hepatocytes with altered liver enzyme phenotypic expression appear to have a growth advantage. A novel technique using computerized fluorescent image analysis of triple-stained frozen liver sections was developed and used to visualize three different molecular markers in individual hepatic cells. Proliferating liver cells were identified by anti-5-bromodeoxyuridine immunostaining in livers of rats injected with 5-bromodeoxyuridine 1 hour before sacrifice. Anti-cytokeratin immunostaining was used to identify bile ducts and putative oval cells. Characterization of DNA adduct formation was achieved with an antiserum specific for N-(deoxyguanosine-8-yl)-2-aminofluorene, the major DNA adduct of 2-acetylaminofluorene. The image analysis demonstrated low but distinct DNA adduct concentrations in putative oval cells identified by anti-cytokeratin staining and in scattered, replicating liver cells recognized by anti-5-bromodeoxyuridine. Adducts were not detected in replicating foci consisting of 3 to 11 nuclei. It is possible that proliferating liver cells that have low N-2-acetylaminofluorene-DNA adduct levels may clonally expand to become foci protected from further adduct accumulation and preneoplastic liver lesions. Thus, the computerized fluorescent image analysis demonstrated here may provide a novel procedure for identification of carcinogen-induced liver cell alterations.

Quantitation and immunohistochemical localization of DNA adducts in rat embryos and associated yolk sac membranes exposed in vitro to N-acetoxy-2-acetylaminofluorene (N-Ac-AAF)

Specific antibodies and radioimmunoassay (RIA) were used to measure the levels of acetylated and deacetylated C-8 substituted deoxyguanosine adducts in day 11 rat embryos and their associated yolk sacs after exposure of whole rat conceptuses in vitro to the teratogen N-acetoxy-2-acetylaminofluorene (N-Ac-AAF). The deacetylated adduct predominates in both the embryo and the associated yolk sac, and a dose response for adduct formation was observed when adducts were quantitated by RIA. Immunohistochemical localization of the deacetylated adducts revealed that adducts were confined to the nuclei in all tissues examined and that the abundance of adducts varied within and between tissues. Our initial findings indicate that specific DNA adduct antibodies may be useful in the study of teratogenesis induced by a wide variety of agents that modify DNA.

The spermatogenic cycle in the blue fox (Alopex lagopus): relative frequency and absolute duration of the different stages

The spermatogenic cycle of the blue fox was divided into eight distinct stages, based on an analysis of different cell associations of the seminiferous epithelium. The criteria used for classification of the stages were the type of spermatogonia, the occurrence of meiotic figures, and the shape and location of spermatids. The relative frequencies of the stages I to VIII were 25.7, 9.8, 8.7, 5.9, 13.8, 9.9, 10.6 and 15.5%, respectively. The duration of one cycle of the seminiferous epithelium was 12.0 +/- 0.2 days as determined from the progression of 5-bromo-2-deoxyuridine (BrdU)-labelled cells at various time intervals. The absolute duration of stages I to VIII was calculated to be 3.1, 1.2, 1.0, 0.6, 1.7, 1.2, 1.3 and 1.9 days, respectively. The estimated life span of primary spermatocytes was 19.2 days, of secondary spermatocytes less than 0.6 days, of spermatids with round nuclei 9.2 days and of spermatids with elongated nuclei 8.9 days.

Reduced DNA adduct formation in replicating liver cells during continuous feeding of a chemical carcinogen

To investigate early cellular alterations in liver DNA during hepatocarcinogenesis, we have visualized replicating cells and analyzed their DNA adduct content in livers of rats continuously fed a carcinogenic level (0.02%) of 2-acetylaminofluorene for periods up to 4 weeks. One hour prior to sacrifice, cells undergoing DNA synthesis were pulse-labeled with the thymidine analogue 5-bromodeoxyuridine. Replicating cells were visualized immunohistochemically with anti-(5-bromodeoxyuridine), and identification of aminofluorene-DNA adducts in replicating nuclei was achieved by staining with an antiserum specific for N-(deoxyguanosin-8-yl)-2-aminofluorene; both stains were observed simultaneously by two-color immunofluorescence. Data were obtained for all cells, including large hepatocytes (nuclei greater than 6 microns) and small cells (nuclei less than 6 microns), such as hepatocytes sliced asymmetrically, oval cells, Kuppfer cells, and sinusoidal lining cells. Based on the size of their nuclei, the hepatocytes were the only cells that could be identified separately from the total. A distinct increase in the number of cells synthesizing DNA was observed after 25 days of 2-acetylaminofluorene feeding; replicating cells were either scattered randomly throughout the liver or clustered in discrete foci. At times up to 28 days, cells with both large and small nuclei that were synthesizing DNA showed reduced aminofluorene-DNA adduct immunofluorescence compared to nonreplicating cells. The results suggest that liver cells replicating during carcinogen exposure have altered metabolic capacities resulting in reduced aminofluorene-DNA adduct formation. It is possible that such cells constitute the progenitors of preneoplastic foci, which have a replicative advantage as compared to normal liver.

Relation between T cell number and epithelial HLA class II expression quantified by image analysis in normal and inflamed human gastric mucosa

Epithelial expression of HLA class II determinants and the number of lamina propria and intraepithelial T cells were quantified in gastric body mucosa by means of paired immunofluorescence staining which was subjected to computerised image analysis. In normal mucosa, epithelial HLA-DR expression was virtually absent. A significantly increased expression was seen in simple chronic gastritis, most extensively in the isthmus zone, where a positive reaction was seen in 34% of the epithelial area when the gastritis was of low degree and in 85% when it was of moderate severity. The most extensive HLA-DR expression was found in moderate 'stump gastritis' 28 to 32 years after Billroth II resections. In these patients the epithelial area in the foveolar and isthmus zones showed 83% and 92% positive responses, respectively. The HLA subregion products were expressed in a differential manner (DR greater than DP greater than DQ). The number of both intraepithelial and lamina propria T cells increased significantly with increasing severity of gastritis, and the fraction of putative memory T cells was also raised. Correlation analyses showed a positive relation between the epithelial expression of HLA-DR and the intraepithelial as well as the lamina propria density of T cell. These results suggest a biological link between T cells, aberrant HLA-DR expression, and gastritis, although the pathogenic importance of this relation is unknown. Enhanced epithelial presentation of autoantigens or luminal antigens, or both leading to increased activation of T cells is one possible explanation.

Two-colour immunofluorescence marker study of pleomorphic adenomas

Extensive use of two-colour immunofluorescence staining for various cell markers in pleomorphic adenoma, revealed three consistent phenotypic features: (1) keratin polypeptide No. 14, which was virtually restricted to myoepithelial cells (MEC) in normal salivary glands, appeared in a large fraction of the tumour cells, suggesting that the principal neoplastic element is derived from MEC or their immediate precursors; (2) a complex co-expression pattern of various cell markers was found, with extensive concurrence of keratin and vimentin in strands of MEC-like and myxoid tumour cells, probably reflecting different degrees of tumour cell differentiation; and (3) two phenotypically distinctive dendritic cell populations were identified, one consisting of keratin positive tumour cells and the other of HLA-DR positive but keratin negative stromal cells. The significance of these findings with regard to the histogenesis and complex morphology of pleomorphic adenoma is discussed.