Comparison of roles of three mitogen‐activated protein kinases induced by chromium(VI) and cadmium in non‐small‐cell lung carcinoma cells

Chromium(VI) Cr(VI) and cadmium (Cd) compounds are ubiquitous environmental carcinogens that have been associated with lung tumors and can induce apoptosis in various cell types. Three major mitogenactivation protein kinases (MAPKs), extracellular signalregulated kinase (ERK), cJUN Nterminal kinase (JNK) and p38, have been shown to regulate apoptosis. In this study we explore the abilities of Cr(VI) and Cd to activate JNK, p38 and ERK, including their roles in metalmediated growth inhibition and apoptosis in a human nonsmallcell lung carcinoma cell line, CL3. Exposure to K₂Cr₂O₇ markedly activated JNK and p38 and moderately activated ERK in a dose and timedependent manner. The activated p38 decreased markedly and rapidly and the activated JNK decreased gradually when Cr(VI) was removed from media. At low cytotoxic doses, CdCl₂ decreased ERK activity with concurrently transient activation of JNK, whereas at high cytotoxic doses it persistently activated all three MAPKs. The strength and duration of JNK and p38 activated by Cd were higher and longer than Cr(VI) did when compared at similar cytotoxic doses. In comparable experiment conditions Cd is a much stronger apoptotic inducer than Cr(VI) in CL3 cells. Crosstalk of MAPKs was observed in cells exposed to Cr(VI) but not Cd. Both metals could increase JNK activity through MKK7 but not MKK4. The Cdactivated JNK is involved in apoptosis, but the Cractivated JNK is not. PD98059, an inhibitor of the ERK upstream activators MKK1/2, greatly enhanced the cytotoxicity and apoptosis of cells treated with low Cd doses. SB202190, an inhibitor of p38, decreased the cytotoxicity and apoptosis induced by high Cd doses. Conversely, neither SB202190 nor PD98059 altered Cr(VI)induced cytotoxicity. The results suggest that JNK and p38 signals cooperatively participate in apoptosis induced by Cd and that the decreased ERK signal by low Cd doses contributes to growth inhibition or apoptosis. Oppositely, activation of ERK, JNK and p38 by Cr(VI) does not affect cytotoxicity.     

Immunohistochemical localization of β-glucosidases in lignin and isoflavone metabolism in Cicer arietinum L. seedlings

Coniferin specific- and isoflavone 7-glucoside specific -glucosidases have been localized in stem and root sections of chick pea (Cicer arietinum L.) seedlings by the indirect immunofluorometrical method. The coniferin specific -glucosidase has been found in the cell walls of the tracheary elements and of the endo-, epi-, and exodermis. All these tissues are known to contain either lignin or polymers, like suberin and cutin, which consist partially of phenylpropanoid elements. The localization of this -glucosidase is therefore in agreement with its postulated relationship to the phenylpropanoid metabolism. The isoflavone 7-glucoside specific -glucosidase, on the other hand, is predominantly located in the parenchymatic cortex cells, and obviously in the cytoplasm. These cells are known to contain the isoflavone formononetin, which has been shown to undergo turnover in chick pea seedlings. We therefore have good reason to assume that this -glucosidase is involved in the metabolism of the 7-glucoside of this isoflavone.Abbreviations SDS sodium dodecylsulfate - PBS physiological phosphate saline The results are part of the thesis of Gerd Burmeister, 1980, University of Münster     

Binding of [3H]muscimol to calf cerebrocortical synaptic membranes and the effects of sulphur-containing convulsant and non-convulsant compounds

Endogenous and xenobiotic sulphur-containing convulsant and non-convulsant compounds containing structural moieties of, or bearing a structural resemblance to, GABA and homocysteine were tested in binding studies for their potency in displacing the GABA-mimetic [³H]muscimol from specific, high-affinity sites (K _d=3.6 nM;B _max=3.94 pmol/mg protein) on freeze-thawed, Triton-treated calf-brain synaptic membranes. The xenobiotic convulsants, 4-mercaptobutyric acid (MBA), 3-mercaptopropionic acid (3-MPA) and 2-mercaptopropionic acid (2-MPA) were found to be two-site competitive inhibitors exhibiting apparent inhibition affinity constants (K _i ^app ) of 5000 M, 3750 M, and 4800 M, respectively; while homocysteic acid (K _i ^app =4800 M) was shown to be a one-site partial competitive inhibitor. Intermediary metabolites of methionine: S-adenosyl-l-homocysteine,l-cysteine, the convulsantl-homocysteine, and its non-convulsant disulphide oxidation product, homocystine, were found to be one-site partial competitive inhibitors exhibitingK _i ^app values of 5750 M, 8350 M, 5000 M, and 510 M, respectively. The endogenous anticonvulsant neuroeffector, taurine, and the tripeptide, reduced glutathione (GSH) were shown to be, respectively, one-site (K _i=20 M) and two-site (K _i ^app =4300 M) competitive inhibitors of [³H]muscimol binding. These findings are discussed with regard to a previously proposed mechanism for the convulsant action of homocysteine.     

Abscission and thinning of young fruit and thier regulation by plant hormones and bioregulators

Natural abscission of young fruit and its regulation by plant hormones isconsidered and compared to the generally accepted model of senescencetriggered abscission of, for example, leaves or mature fruit. It isconcluded that abscission of young fruit cannot be explained by this model.Alternatively, it is suggested that the senescence triggered initial step inthe classical abscission model should be replaced by a correlativelytriggered step. Polar basipetal IAA transport with its autostimulation andautoinhibition components is the main regulating signal in this correlativeacting system and replaces ethylene as the initial driving force from thesenescence triggered model.Results supporting this model are presented and tested against existingresults from the literature. Finally, this hypothesis is tested as a possibleexplanation of the mode of action of some thinning chemicals orbioregulators. It is speculated how a thinning chemical should be designedto function in a more reliable way, at least as far as its interference with the endogenous hormone system is concerned.     

Sensory deficits induced by cadmium in banded kokopu, Galaxias fasciatus, juveniles

The potential for cadmium to produce sensory deficits in the mechanosensory lateral line and olfactory systems was examined in migratory Galaxias fasciatus juveniles or whitebait. Using a two-choice chamber apparatus, three groups of whitebait were tested for a known attraction to adult pheromones and then exposed to either 0.1, 0.5 or 1g Cd⁺² l^-1 for 48h and retested. The attraction to adult pheromones had been eliminated after exposure to concentrations of 0.5 and 1g Cd⁺² l^-1, indicating these levels of cadmium exposure had impaired olfactory function. Rheotaxis trials were conducted to determine the level of cadmium exposure which would inhibit lateral line function. The lateral line system was not blocked until a concentration of 2g Cd⁺² l^-1. The blocking of the lateral line and olfactory sensory systems was reversible. After 14 days recovery in clean freshwater both rheotaxis and the attraction to adult pheromones had returned. Whitebait were also tested for a preference/avoidance response at 2g Cd⁺² l^-1. Fish showed neither a preference for, or an avoidance of, a concentration which would disable both the lateral line and olfactory sensory systems. The disabling of these sensory systems may render migratory cues undetectable, affecting habitat selection by whitebait, which may ultimately affect the distribution of banded kokopu populations.     

Heterogeneity of epithelial cells in the human thymus

Summary To evaluate interrelationships among epithelial cells, and between morphology and function in the microenvironment, we studied the ultrastructural morphology of epithelial cells in sections of human thymus from donors aged 2 months to 31 years. Six types of epithelial cells were observed: subcapsular-perivascular (type 1); pale (type 2); intermediate (type 3); dark (type 4); undifferentiated (type 5); and large-medullary (type 6). Cells of types 2, 3 and 4 were found throughout the organ. The type-2 to -4 epithelial cells may represent various stages in a differentiation process. In this, type-2 cells are very active and type-4 cells are possibly degenerating elements. Type-4 cells can also contribute to Hassall's corpuscles. Type-5 cells were located mainly in the cortico-medullary region and showed the morphological characteristics of undifferentiated elements. Type-6 cells were located exclusively in the medulla and displayed characteristics of cellular activity. Small Hassall's corpuscles consisted of type-6 epithelial cells; in larger corpuscles many nuclei of type-6 cells were found. Cells of types 2 and 6 contained tubular structures (diameter approximately 20 nm).Concerning the function of thymus epithelial cells, the features associated with protein synthesis observed in cellular types 2 and 6 make them likely candidates for humoral factor-producing and/or secreting elements. In addition, type-2 and -3 cells in the cortex appear to contribute to a special pattern of epithelium-lymphocyte interaction (thymic nurse cells), as demonstrated by the intracytoplasmic location of lymphocytes in the epithelial cells. The various steps in intrathymic T-cell maturation occur at locations in a microenvironment composed of morphologically distinct epithelial cells.     

Neuronal responses in the tectum opticum ofSalamandra to visual prey stimuli

Summary In the tectum opticum ofSalamandra salamandra neurons were recorded that showed different selectivity to visual prey stimulus parameters. 21 of 80 neurons responded stronger to rectangles oriented horizontally (wormlike configuration) than to the same patterns oriented vertically. With increasing stimulus velocity, however, these neurons showed non-uniform response characteristics. Although there are partial similarities between behavior and neuronal activity, no response curve of tectal neurons corresponds strictly to response curves of salamander preycapture behavior. So none of the neuron types can be called a prey detector.Supported by the Deutsche Forschungsgemeinschaft     

Localisation par immunofluorescence des hormones corticotropes et mélanotropes dans l'hypophyse du rongeur Ellobius lutescens (Th)

Résumé Les réactions d'immunofluorescence induites par l'Ac. anti -(1–24) corticotropine nous ont permis d'identifier les cellules ACTH dans le lobe antérieur de l'hypophyse d'Ellobius lutescens; il s'agit de petites cellules de forme irrégulière, à fins prolongements cytoplasmiques aboutissant à des capillaires et entourant souvent d'autres cellules préhypophysaires; ces mêmes cellules réagissent également, mais d'une façon atténuée, avec l'Ac. anti -MSH. Ce dernier induit une réaction très forte au niveau de toutes les cellules de la pars intermedia, alors que seulement certaines d'entre elles réagissent intensément avec l'Ac. anti -(1–24) corticotropine. L'improbabilité de réactions croisées entre l'Ag. -MSH et l'Ac. -(1–24) corticotropine et vice-versa est discutée. Par ailleurs, seules les cellules de la pars intermedia réagissent avec l'Ac. anti -MSH.

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Immunofluorescent localisation of corticotrophic and melanotrophic hormones in the pituitary gland of the rodent Ellobius lutescens (Th)

Summary Immunofluorescence induced by the antibody to -(1–24) corticotrophin has been used to identify the ACTH cells in the anterior lobe of the pituitary gland in Ellobius lutescens. The cells are small, irregular, with fine cytoplasmic extensions ending near capillaries and often encircling other anterior lobe cell types. They also react, although less strongly, with the antibody to -MSH. The latter antibody induced a marked reaction in all cells of the pars intermedia while only some of them reacted strongly with the antibody to -(1–24) corticotrophin. The unlikeliness of cross-reactions between the antigen -MSH and antibody to -(1–24) corticotrophin is discussed. Furthermore only the cells of the pars intermedia reacted with the antibody to -MSH.

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Abréviations ACTH hormone corticotrope - Ac. anticorps - Ag. antigène - Cell. cellules - C.M.C. fraction inactive de la purification d'ACTH porcine au stade 140 U/mg - C.R.F. fraction inactive de la purification d'ACTH porcine au stade 73 U/mg - Irrég. irrégulières - P.A.S. Periodic Acid-Schiff - P.A. Pars Anterior - P.I. Pars Intermedia     

Benzyladenine induction of buds and somatic embryogenesis in Picea omorika (Pančić) Purk.

Somatic embryogenesis and adventitious bud formation, initiated from shoot explants of Picea omorika is described. Benzyladenine (BA) as the only growth regulator, added to modified Von Arnold and Eriksson medium, induced formation of both adventitious buds and embryogenic tissue. Optimal BA concentration for bud induction was 4.5 M and further bud development and plantlet formation was achieved on growth regulator-free medium. The embryogenic tissue formation was induced when the explants were first grown on the medium with high BA content (22.5 M) and then transferred to medium without growth regulators. Subsequent proliferation of embryogenic tissue was accomplished by subculturing on medium containing 9 M 2,4-dichlorophenoxyacetic acid and 4.5 M BA, and further embryo development was achieved on medium with 12 M abscisic acid. Embryos cultured on growth regulator-free medium formed roots and rooted plantlets were successfully established in soil in the greenhouse.     

Genetic and phenotypic targeting of β-adrenergic signaling in heart failure

Heart failure is a leading cause of hospitalization worldwide. No major significant improvements in prognosis have been achieved for heart failure over the last several decades despite advances in disease management. Heart failure itself represents a final common endpoint for several disease entities, including hypertension and coronary artery disease. On a molecular level, certain biochemical features remain common to failing myocardium. Among these are alterations in the -adrenergic receptor (-AR) signaling cascade. Recent advances in transgenic and gene therapy techniques have presented novel therapeutic strategies for management of heart failure via genetic manipulation of -AR signaling including the targeted inhibition of the -AR kinase (ARK1 or GRK2). In this review, we will discuss the -AR signaling changes that accompany heart failure as well as corresponding therapeutic strategies. We will then review the evidence from transgenic mouse work supporting the use of -AR manipulation in the failing heart and more recent in vivo applications of gene therapy directed at reversing or preventing heart failure. (Mol Cell Biochem 263: 5–9, 2004)     

Uptake of a monoclonal antibody against CEA (Tumak 431/31) in a human colon tumor (Co-112) xenografted in the nude mouse

Summary A monoclonal antibody (Tumak) against carcinoembryonic antigen (CEA) was injected into nude mice bearing a human colon carcinoma (Co-112). The tumor uptake was found to be dependent on the size of the tumors: relative uptake (percentage of the injected dose/gram tumor (% i. d./g) decreased for tumors with weights up to 1 g, although the absolute uptake (% i. d./tumor) still increased over the same weight range. In the constant region (1 g) mean relative tumor uptake was 4% i. d./g.The same tumor size dependence was found for the relative Tumak uptake in the other mouse organs studied (e.g., blood, liver, spleen and muscle). Consequently tumor/organ ratios were found to be independent of tumor size.Tumor uptake was also studied for various doses of Tumak (0.07–120 g) in tumors of 1 g. Evidence was found for a threshold dose of 0.1 g under which no serious tumor uptake appeared. From 1 to 120 g no further dependence of Tumak distribution on applied dose was found: the relative uptake of all organs remained the same but the absolute uptake increased with dose.     

Signal transduction pathways of muscarinic receptors in circular smooth muscle from the rabbit caecum

The effects of muscarinic acetylcholine receptor stimulation on phosphoinositides breakdown and adenylate cyclase activity were examined in the circular smooth muscle of the rabbit caecum. InMyo-[³H]inositol-labeled circular smooth muscle cells, carbachol caused a concentration-dependent increase in [³H]inositol phosphates ([³H]IPs) accumulation (EC₅₀ of 3±1 M). The M₁-selective antagonist pirenzepine (PRZ), the M₂-selective AF-DX 116 (11-2[[2-[(diethyl-amino)methyl]-1-piperidinyl]acetyl]-5, 11-dihydro-6Hpyrido[2,3-b][1,4]benzodiazepin-6-one) and the M₃-selective para-fluoro-hexahydrosiladifenidol (p-F-HHSiD) inhibited the carbachol-induced [³]inositol phosphates accumulation with the following order of potency: p-F-HHSiD>PRZ>AF-DX 116. In saponin-permeabilized circular smooth muscle cells, carbachol and GTP[S] elicited a concentration-dependent increase in [³H]inositol phosphates accumulation. The concentration-response curve for GTP[S] was shifted to the left when cells were incubated with 1 M carbachol. The [³H]inositol phosphates accumulation elicited by simultaneous addition of 0.1 M GTP[S] and 1 M carbachol to permeabilized cells was significantly decreased (78.28±18.23% inhibition) when cells were preincubated for 5 min with 0.1 mM GDP[S]. In nonpermeabilized cells, pertussis toxin did not alter the carbachol-induced increase in [³H]inositol phosphates accumulation. On the other hand, the 0.1 mM carbachol-induced inhibition of forskolin-stimulated adenylate cyclase activity in circular smooth muscle homogenates was significantly reversed by atropine and AF-DX 116, whereas PRZ and p-F-HHSiD were ineffective (muscarinic antagonists were used at 1 M final concentration). Moreover, the carbachol-induced inhibition of the cyclic AMP accumulation elicited by 10 M isoproterenol was abolished by pertussis toxin pretreatment of isolated circular smooth muscle cells. In conclusion, our data suggest that in circular smooth muscle of rabbit caecum, the muscarinic receptor stimulation of [³H]inositol phsophates accumulation is mediated by M₃ subtype receptors coupled to a pertussis toxin-insensitive G protein, whereas inhibition of adenylate cyclase activity is mediated by M₂ subtype receptors coupled to a pertussis toxin-sensitive GTP-binding protein G_i.     

Toxic effects of 70-hydroxycholesterol on rat liver primary cultures,epithelial lines and co-cultures.

The toxic effects of 7,8-hydroxycholesterol (7-OHC) on cultures and co-cultures of rat hepatocytes, rat liver epithelial cell lines, and rat liver fibroblast lines were investigated. Hepatocytes in primary culture or co-cultured with proliferative epithelial cells, were not affected by the presence of 7,8-OHC at a concentration of 400µM over a period of 72 hours. In contrast, Proliferative cultures of liver epithelial cell lines and liver fibroblast lines were killed by 50 µM 7-OHC within the first 24 hours. Established liver epithelial cells (hyperploid) were more sensitive to 7,8-OHC than the same line at early passages (diploid). When hepatocytes and liver epithelial cells were co-cultured and treated with 100 µM 7-OHC only epithelial cells were lysed. A concentration of 50 µM 7-OHC was toxic to co-cultures of liver epithelial cell and fibroblasts together. In a serum free medium, the cytotoxic concentration of 7-OHC was lower than that in the serum-supplemented medium. Thus, liver epithelial cells cultured alone or co-cultured with hepatocytes were killed at 12.5 µM and 50 µM 7-OHC, respectively. Finally, cholesterol concentrations four fold that of 7-OHC antagonized the lethal effects of 7-OHC in the serum free medium.Abbreviations 7-OHC 7-hydroxycholesterol - SFM serum-free medium - SSM serum-supplemented medium 1. Author to whom all correspondence should be addressed.     

Synthesis and secretion of caseins by the mouse mammary gland: Production and characterization of new polyclonal antibodies

Polyclonal antibodies to mouse - and /-caseins were raised in rabbits. These antibodies display tissue- and species specificity as shown by immunoblotting. Immunohistochemical analyses demonstrate that both - and /-caseins were synthesized and secreted from virtually all lactating mammary epithelial cells, in a pattern very similar to that of the mouse -lactalbumin. Residual amounts of caseins were located also in the apical surface of epithelial cells surrounding the ducal lumen of virgin mammary gland sections. In contrast to the significant level of -casein in the milk, the amount of this protein compared to - or -caseins was extremely low in medium conditioned for 24 h by mammary explants of mid-pregnant mice immediately after explantation or after 4 days.     

Comparative studies on the localization of esteroproteases and kallikrein-like activity in primate organs

Summary Various organs of three species of monkey were screened histochemically for esteroproteases usingN-acethyl-l-methionine--naphthylester ( N-O-met) as the substrate and also for enzymes with kallikrein-like activity usingd-Val-Leu-Arg-4-methoxy-2-naphthylamide as the substrate. Characteristic differences were found in the localization of the reaction products obtained with both substrates. In the main salivary glands, esteroproteases ( N-O-met reactivity) were found in mucous cells (submandibular gland), intercalated duct cells (parotid gland), acinar cells (sublingual gland), striated and interlobular duct cells (all glands). They were also localized in superficial lining epithelial cells of the digestive system, in liver cells, and acinar cells of the pancreas.Enzymes with kallikrein-like activity were found only in the striated and interlobular duct cells of salivary glands, in acinar cells of the pancreas, and in proximal tubular cells of the kidney. Free cells (including mast cells) normally distributed in the connective tissue of various organs showed reactivity towards N-O-met. Some of these cells were also reactive against Val-Leu-Arg-4-MNA.     

Glycosylphosphatidylinositol (GPI) hydrolysis by Transforming Growth Factor-β1 (TGF-β1) as a potential early step in the inhibition of epithelial cell proliferation

Glycosylphosphatidylinositol (GPI) was previously identified in rabbit articular chondrocytes as being a precursor of inositolphosphate glycan (IPG), released upon (Transforming Growth Factor-) (TGF-) exposure, and capable of mimicking the proliferative effects of the growth factor. Here, using mink lung epithelial cells (CCL 64), which are known to be growth-inhibited by TGF-, we studied the potential role of GPI-derived molecules in the antiproliferative effect of TGF-1. We first identified an endogenous pool of GPI material and three different anionic forms of IPG in epithelial cells pre-labeled with [3H] glucosamine. Shortly (8 min) after TGF-1 addition, the cells responded by a rapid and transient hydrolysis of GPI, accompanied by the release of the most anionic form of IPG. This TGF--released IPG, after partial purification, was shown to decrease the proliferation of CCL 64 cells. Moreover, anti-IPG antibodies reduced the effects of TGF- and blocked the effects of partially purified IPG. These data strongly suggest that GPI hydrolysis may be an early step of the TGF- signalling pathway involved in growth inhibition of epithelial cells.     

Axenic culture of the bacteria associated with phony disease of peach and plum leaf scald

Bacteria associated with phony disease of peach (PDP) and plum leaf scald (PLS) were consistently isolated from diseased trees but not from healthy trees. Colonies of the bacteria grew slowly on PW agar, reaching 0.2 mm to 0.7 mm in diameter in 2 to 3 weeks. The bacteria did not grow on nutrient agar or other general-purpose media. Cells of the bacteria were 0.3 m to 0.4 m in width and 2.6 m to 20.0 m in length. The topography of the cell walls revealed numerous ridges and furrows. Cells extracted from diseased plants and those from culture gave a strong fluorescence when stained with immunoglobulin G to cells and purified membranes of the bacteria extracted from peach and plum in earlier studies. Immunoglobulin G to cells of the Pierce's disease bacterium from culture also reacted with the bacteria. No discernible differences were observed between strains associated with PDP and PLS in the United States and PLS in Brazil.     

A low molecular weight alkaline proteinase fromConidiobolus coronatus

Summary An extracellular, low molecular weight alkaline proteinase (alkaline proteinase B) has been purified to homogeneity from the culture filtrate ofConidiobolus coronatus (NCIM 1238). A 12-fold purification was achieved with a specific activity of 29,760 u/mg. The enzyme had an optimum pH and temperature of 9.7 and 45°C respectively. It was most active towards casein and had a molecular weight of 6,800, the lowest reported so far. It was stable between pH 6.5–7.5. Alkaline proteinase B is a serine proteinase. It showed an esterolytic activity on N-benzoyl-L-tyrosine ethyl ester (BTEE) and was successfully used to resolve the racemic mixture of D, L-phenylalanine and D,L-phenylglycine and can thus potentially replace subtilisin Carlsberg in resolving the racemic mixture of amino acids.     

Limbal Stem Cells in Health and Disease

Stem cells are present in all self-reviewing tissues and have unique properties. The ocular surface is made up of two distinct types of epithelial cells, constituting the conjunctival and the corneal epithelia. These epithelia are stratified, squamous and non-keratinized. Although anatomically continuous with each other at the corneoscleral limbus, the two cell phenotypes represent quite distinct subpopulations. The stem cells for the cornea are located at the limbus. The microenvironment of the limbus is considered to be important in maintaining stemness of the stem cells. They also act as a barrier to conjunctival epithelial cells and prevent them from migrating on to the corneal surface. In certain pathologic conditions, however, the limbal stem cells may be destroyed partially or completely resulting in varying degrees of stem cell deficiency with its characteristic clinical features. These include conjunctivalization of the cornea with vascularization, appearance of goblet cells, and an irregular and unstable epithelium. The stem cell deficiency can be managed with auto or allotransplantation of these cells. With the latter option, systemic immunosuppression is required. The stem cells can be expanded ex vivo on a processed human amniotic membrane and transplanted back to ocular surface with stem cell deficiency without the need of immunosuppression.     

Over‐expression of the murine polymeric immunoglobulin receptor gene in the mammary gland of transgenic mice

The polymeric immunoglobulin receptor (pIgR), a transmembrane protein, transports dimeric IgA (dIgA) across the epithelial cells of the mucosal surfaces into the external secretions, for example milk from the mammary glands. The pIgR is consumed during the transcytosis of dIgA and is cleaved at the apical side of the epithelial cells, regardless of the binding to its ligand (dIgA), to form secretory component (SC). We hypothesize that the expression level of the endogenous murine pIgR gene in the epithelial cells is ratelimiting for the transport of dIgA across the epithelial cells into the secretions. We address this key issue by generating transgenic mice overexpressing the pIgR gene in their mammary glands in order to examine the effect on dIgA levels in the milk. Here we report on the generation of transgenic mice and analysis of the expression level of pIgR in their mammary glands. We cloned and characterized the murine pIgR gene and constructed an expression cassette bearing the pIgR gene under the control of the regulatory sequences of the bovine _s1casein gene. Four transgenic lines were made, expressing the pIgR construct at RNA and protein level only in their mammary glands. The levels of the SC protein in the milk ranged from 0.1 to 2.7mg/ml during midlactation. These levels are 10–270 times higher than wildtype SC levels (0.01mg/ml).