The control of adrenocortical cytodifferentiation by extracellular matrix

The 'sweet' and 'bitter' involvement of glycosaminoglycans in lung diseases: pharmacotherapeutic relevance

The extracellular matrix (ECM) plays a significant role in the structure and function of the lung. The ECM is a three-dimensional fibre mesh, comprised of various interconnected and intercalated macromolecules, among which are the glycosaminoglycans (GAG). GAG are long, linear and highly charged, heterogeneous polysaccharides that are composed of a variable number of repeating disaccharide units (macromolecular sugars) and most of them, as their name implies, have a sweet taste. In the lung, GAG support the structure of the interstitium, the subepithelial tissue and the bronchial walls, and are secreted in the airway secretions. Besides maintaining lung tissue structure, GAG also play an important role in lung function as they regulate hydration and water homeostasis, modulate the inflammatory response and influence lung tissue repair and remodelling. However, depending on their size and/or degree of sulphation, and their immobilization or solubilization in the ECM, specific GAG in the lung either live up to their sweet taste/name, supporting normal lung physiology, or they are associated to 'bitter' effects, related to lung pathology. The present review discusses the biological role of GAG in the lung as well as the involvement of these molecules in various respiratory diseases. Given the great structural diversity of GAG, understanding the changes in GAG expression that occur in lung diseases may lead to novel targets for pharmacological intervention in order to prevent and/or to treat a range of lung diseases.

Development of functional zonation in the rat adrenal cortex

In an attempt to elucidate the mechanism(s) through which the functional adrenal cortex is established, we analyzed immunohistochemically the expression of various markers for the adrenocortical zones, i.e. the zona glomerulosa (zG), the zona fasciculata (zF), and the zona reticularis (zR), as well as markers for the medulla, and further examined the distribution and behavior of DNA-synthesizing cells in rat adrenal glands during development. The results showed that 1) separation of the cortex and medulla, and the development of functional zonation in the cortex began at around the time of birth, 2) at fetal stages when cortical zonation was not established, DNA-synthesizing cells were found scattered throughout the gland, where they proliferated without significant migration, and 3) after birth in the adrenal cortex with established cortical zonation, DNA-synthesizing cells were localized near the undifferentiated zone between zG and zF, and then they migrated centripetally. Cell death appeared to occur in the innermost portion of the cortex, where many resident macrophages are present. These findings illustrate basic processes underlying adrenal development and suggest that the undifferentiated region is apparently the stem cell zone of the adrenal cortex that maintains the cortical zonation.

Long-term culture of fully differentiated adult insect neurons

An identified group of cells, dorsal unpaired median (DUM) neurons, isolated from the central nervous system of adult cockroaches can be grown in vitro for extended periods. These cells often develop morphological characteristics that differ from their in situ appearance but physiological experiments demonstrate that they retain their distinctive in vivo membrane properties. A method for culturing insect CNS neurons, which includes the use of a haemolymph-derived growth-enhancing factor is described, and this technique is compared with other attempts to develop an efficient system for producing in vitro preparations of well-defined, identifiable neurons that would provide a model system for aspects of neuron developmental growth, repair and function.

Steroidogenic adrenocortical cells synthesize alpha 2-macroglobulin in vitro, not in vivo

We previously identified alpha 2-macroglobulin as the major protein secreted by primary cultures of adrenocortical cells. We report here that in the adrenal gland, the distribution of alpha 2-macroglobulin in the adrenocortical tissue is restricted to the endothelium of blood vessels and that no immunoreactivity is found in steroidogenic cells. A time course study revealed that freshly dissociated bovine adrenocortical cells were void of alpha 2-macroglobulin immunoreactivity whereas the proportion of alpha 2-macroglobulin-positive cells reached more than two-thirds of the population between day 4 and day 7 of culture. Double immunoenzymatic labeling of 6-day-old cultures revealed a co-localization of alpha 2-macroglobulin and the steroidogenic enzyme P-450SCC. Treatment of 5-day-old cultures (expressing alpha 2-macroglobulin) for 24 h by either ACTH (10(-9)-10(-6) M) or alpha 2-macroglobulin (2.5 mg/ml) resulted in a marked decrease of the expression of alpha 2-macroglobulin. These data indicate that ACTH and plasmatic alpha 2-macroglobulin could physiologically repress alpha 2-macroglobulin expression in the adrenal cortex in vivo.

Mixed parenchymal-stromal populations of rat adrenocortical cells support the proliferation and differentiation of steroidogenic cells

The mechanisms which regulate adrenocortical steroidogenesis in differentiated parenchymal cells have been studied in great detail. However, the stem cells that are responsible for regeneration of the adult cortex have never been identified or isolated, and their characteristics are unknown. We have developed a tissue culture system that supports the simultaneous proliferation and differentiation of steroidogenic adrenocortical cells. Utilizing density gradient separation, a cell population composed of a mixture of stromal, endothelial and parenchymal cells (MIX) was isolated from the adult rat adrenal cortex. In primary culture, MIX populations formed high saturation density multilayers from which rounded cells emerged. These cells proliferated, contained lipid, and expressed the steroidogenic enzymes delta 5,3 beta-hydroxysteroid dehydrogenase and cholesterol side-chain cleavage cytochrome P-450scc. After selective passaging, rounded MIX-derived cells retained their steroidogenic potential, even in the absence of trophic hormone treatment. In contrast, parenchymal cells obtained from the zonae fasciculata (FASC) and glomerulosa (GLOM) respectively, formed homogeneous monolayers in primary culture, gradually de-differentiated, and no longer responded to trophic hormone treatment after passaging. Thus, primary MIX cultures provided a microenvironment that resulted in the production of adrenocortical cells with stem cell-like qualities. These cultures provide for the first time, a system for the identification of specific inducers that are responsible for both adrenocortical cytogenesis and its associated proliferation and steroidogenic differentiation.

Transforming growth factor beta 1 and adrenocorticotropin differentially regulate the synthesis of adrenocortical cell heparan sulfate proteoglycans and their binding of basic fibroblast growth factor

Adrenocortical differentiated functions are under the control of both endocrine hormones such as ACTH and local factors such as transforming growth factor beta (TGF beta) or basic fibroblast growth factor (bFGF). Besides their regulatory actions on the synthesis of corticosteroids, these two classes of factors also exert some important effects on the cellular environment. We have examined here the regulation by ACTH and TGF beta of adrenocortical cell proteoglycan synthesis and secretion. Under basal conditions, adrenocortical cells synthesized and secreted several species of sulfated proteoglycans, 80% of them being recovered in solution in the culture medium. When analyzed by ion exchange chromatography, the cell extracts and the media from cells metabolically labeled with 35S-sulfate were found to contain two and three species of radioactive sulfated proteoglycans, respectively. All species were proteoheparan-sulfates. Treatment of adrenocortical cells with TGF beta 1 or ACTH resulted in a significant increase of the incorporation of 35S into both secreted and cell-associated proteoglycans. ACTH stimulated more than three times the amount of secreted proteoglycans eluting from DEAE-Trisacryl as peak B, whereas TGF beta preferentially increased the amount of peak C. No important modification of the size of the synthesized proteoglycans was observed. The subpopulation of heparan sulfate proteoglycans capable to bind bFGF was also largely increased after ACTH or TGF beta treatment and paralleled the variation in overall proteoheparan sulfate synthesis. Thus those effects of TGF beta and ACTH on proteoglycan synthesis may participate in an increased ability of adrenocortical cells to bind and respond to bFGF.

Morphological and functional comparison of subcapsular small cells, subcapsular large cells and inner layer cells of bovine adrenal cortex

Subcapsular small cortical cells (SC cells) and subcapsular large cortical cells (LC cells) of bovine adrenal cortex were cultured separately after purification by unit gravity sedimentation, and then compared with inner-half layer cells (IL cells) prepared by the same method. Both SC and LC cells were polygonal in shape and their mitochondria were elongated with lamellar cristae. SC cells became as large as LC cells on day 6 of culture with increased cytoplasmic lipid droplets, whereas IL cells showed no change in size. IL cells were spindle-shaped and had mitochondria with tubulovesicular cristae. Both SC and LC cells produced 11 beta-deoxycorticosterone, corticosterone, aldosterone and small amounts of 17 alpha-hydroxyprogesterone (17 alpha-OH-Prog) and cortisol (F). IL cells produced much more 17 alpha-OH-Prog and F than SC or LC cells. When stimulated with ACTH, cortical cells in each group showed cellular retraction and their mitochondria became spherical. The amounts of 17 alpha-OH-Prog and F increased in all groups, especially in IL cells. These results show that LC cells have similar characteristics to SC cells in both morphology and function, and that they differ from IL cells, which correspond to classical fasciculata-reticularis cells.

V-K-ras transformation induces reversion to an earlier developmental form in adult rat adrenal cells

The basis for specific changes in differentiation that accompany ras-oncogene-mediated transformation are not understood. When short-term cultures of fibroblast-like cells from adult rat adrenal glands were transformed with Kirsten murine sarcoma virus (KiMSV), the original stromal characteristics of the target cells (metachromatic extracellular matrix, high collagen production, collagen incorporation into pericellular matrix and a fibroblastic morphology and growth pattern) diminished. In contrast, parenchymal differentiation markers (neutral lipid, delta 5, 3 beta-hydroxysteroid dehydrogenase, 21-hydroxylase and epithelial morphology) were enhanced. These changes in differentiation were initiated concurrently with the over-expression of the transforming protein v-p21, but were unrelated to the levels of v-p21 expression. They were independent of the immortalizing component of transformation mediated by v-K-ras, because they did not take place in spontaneously immortalized lines derived from the same target cells, unless the lines were also transformed with KiMSV. In normal embryonic development, stromal and parenchymal adrenocortical cells arise by divergent differentiation pathways from a common, multipotential mesenchymal precursor. The transformation-induced modulation from a predominantly stromal to a more-parenchymal phenotype is thus reminiscent of reversion to a more primitive, bipotential developmental stage.

Metabolism and toxicity of xenobiotics in the adrenal cortex, with particular reference to 7,12-dimethylbenz(a)anthracene

The adrenal cortex contains high amounts of detoxifying enzymes, as well as generators and protectors of reactive oxygen species. The high content of cytochrome P-450 enzymes in the adrenal cortex together with its remarkable tendency to accumulate hydrophobic substances probably contributes to the extraordinary vulnerability of the gland to a number of xenobiotics. The best studied adrenocorticolytic compounds are the potent carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) and its liver metabolite 7-hydroxymethyl-12-methylbenz(a)anthracene (7-OHM-12-MBA). Adrenocorticolysis generated by these agents in vivo as well as in vitro demonstrates high regioselective requirements and is strongly influenced by the presence of ACTH, steroids, cytochrome P-450 inhibitors and antioxidants. Furthermore, 7-OHM-12-MBA has been demonstrated to uniquely generate selective and massive oxidation of mitochondrial glutathione in cultured rat adrenal cells. The DMBA-induced adrenocorticolysis is thoroughly discussed in this review with particular emphasis on the metabolism of DMBA and the influence of various effectors. A working hypothesis involving a possible peroxidative mechanism is also presented.

The role of cell interactions in the differentiation of teratocarcinoma-derived parietal and visceral endoderm

Cell interactions have been implicated in the differentiation of visceral and parietal endoderm in the developing mouse embryo. Embryoid bodies formed from F9 embryonal carcinoma cells have been useful in characterizing the events which lead to endoderm formation. As part of our effort to specify the interactions which may be involved in this process we have isolated visceral endoderm-like cells (VE) from F9 embryoid bodies and cultured them under various conditions. Using a combination of immunoprecipitation and enzyme-linked immunosorbent assay, we demonstrate that monolayer culture of these cells on a number of different substrates leads to a dramatic decrease in the level of alphafetoprotein (AFP), a VE-specific marker. Northern blot analysis of AFP mRNA indicates very low levels of this message are present after 48 hr in monolayer culture. Coincident with the drop in AFP levels is an increase in the levels of the cytokeratin Endo C and tissue plasminogen activator, both markers for parietal endoderm (PE). Morphological evidence at the ultrastructural level supports a transition from VE to PE. In contrast, the VE phenotype can be maintained in vitro by interaction with aggregates, but not monolayers, of stem cells. In addition, culturing the cells on the curved surface of gelatin-coated dextran beads, but not on a flat gelatin surface facilitates AFP expression and the cells are morphologically intermediate between VE and PE cells. The potential role of junctional complexes and cell shape are discussed.

The responsiveness to (1-24) ACTH of Mongolian gerbil adrenals superfused in vitro as a function of basal secretion

Wide variations have been found in the responsiveness to (1-24)ACTH of Mongolian gerbil adrenal glands superfused in vitro. These variations were not correlated to corticosteroid plasma levels or to adrenal weights. In contrast, (1-24)ACTH-stimulated secretion greatly depended on basal in vitro secretion (quarters: r = 0.97, p less than 0.01; slices: r = 0.90, p less than 0.001) indicating that the fine adjustment of basal corticosteroidogenesis forms an important part of the regulatory mechanisms modulating (1-24)ACTH-stimulated corticosteroid secretion in vitro.

Corticosteroidogenesis in the isolated Mongolian gerbil adrenal gland during continuous and discontinuous superfusion

Corticosteroid (C) release by adrenals of male Mongolian gerbils (Meriones unguiculatus) has been studied during continuous and discontinuous (flow stop) superfusion. Flow stops of superfusion for 1, 5, 10 or 20 min resulted in a significant accumulation of C within adrenal tissue and superfusion flask. Amounts of C in the first 2-min samples after re-start of superfusion were positively correlated with the amounts secreted during continuous superfusion (5 min: r = 0.97, 10 min: r = 0.97, 15 min: r = 0.74, 20 min: r = 0.84, all p less than 0.001) and with the length of flow stops (1-20 min: r = 0.92, p less than 0.001). However, C concentrations in superfusates were significantly lower than values calculated from secretion during continuous superfusion and the length of flow stops (0 min = 100%, 1 min: 92%, 5 min: 65%, 10 min: 49%, 15 min: 39%, 20 min: 35%). As is evident from the very similar C amounts secreted by adrenals incubated for 15 min without or with 95%O2/5%CO2 (234 vs 256% of basal secretion), flow stop-induced inhibition of corticosteroidogenesis was not due to a lack of oxygen during flow stops. The results demonstrate that superfusion of sliced adrenal tissue gives insights into regulatory mechanisms, including the rapid changes of corticosteroidogenesis during short-lasting flow stops, which cannot be studied in static incubation of either tissue slices or isolated cells. The possibility that the observed decline in steroidogenesis during flow stops may be due to a local feedback inhibition resulting from C accumulating in the microenvironment of adrenal cells is discussed.

Effects of protease inhibitors on adenylate cyclase activation and aldosterone production in rat adrenal zona glomerulosa cells

It has been shown that serine proteases are involved in aldosterone and 18-hydroxycorticosterone production by the rat adrenal zona glomerulosa in response to a variety of stimulants. From evidence presented for various tissues, including the rat adrenal cortex, the observation that adenylate cyclase can be activated by proteolytic enzymes and inhibited by protease inhibitors has led to the suggestion that serine proteases may also be involved in the hormonal stimulation of adenylate cyclase. In studies designed to test this hypothesis using protease inhibitors, only high concentrations (greater than 10(-4) M) of TAME (p-tosyl-L-arginine methyl ester) inhibited ACTH stimulated steroid and cAMP production in rat adrenal glomerulosa cells. TPCK (tosyl-L-phenylalanine chloromethylketone) and TLCK (tosyl-L-lysine chloromethylketone) were found to have a similar effect at very high concentrations (10(-2) M) but had no effect at the serine protease inhibitory concentration of 5 X 10(-6) M. Other protease inhibitors tested had no effect on ACTH-stimulated cAMP but the inhibitory effect of high concentrations of protease inhibitors on ACTH-stimulated adenylate cyclase was duplicated by the polyanion dextran sulphate. The results suggest that the inhibitors act through non-specific membrane effects and that proteases are not involved in the activation of zona glomerulosa adenylate cyclase by ACTH. In view of these findings it is concluded that a more rigorous approach should be applied to the use of protease inhibitors in whole cell systems, and that the concept of hormonal activation of adenylate cyclase via proteolytic events, which is based on studies with such inhibitors, should be reconsidered.

Distribution of 3 beta-hydroxysteroid dehydrogenase during development of the rat adrenal cortex and capsule

Fibroblasts of the adult adrenal cortex are considered to be nonsteroidogenic connective-tissue cells. However, it has been reported that in response to regenerative stimuli, adrenocorticotropic hormone (ACTH), and transformation to malignancy, these cells acquire characteristics of parenchymal cells, which includes delta 5, 3 beta-hydroxysteroid-dehydrogenase (delta 5, 3 beta-HSD) activity. To determine whether such delta 5, 3 beta-HSD activity in adult adrenocortical fibroblasts was due to the activation or augmentation of gene expression normally occurring during embryogenesis, a histochemical study of adrenocortical development, with particular attention to the connective-tissue capsule, was undertaken. Cryostat sections of rat embryos, from 14-days postconception (PC) to birth, and of adrenal glands 1-8, 44 and 90 days after birth were tested histochemically for delta 5, 3 beta-HSD. The same or adjacent sections were stained for PAS-positive material and reticulin, and with hematoxylin and eosin. delta 5, 3 beta-HSD activity overlapped with fibroblast-like cells and with extracellular connective-tissue components in the periphery of the glands from day-17 PC onward. delta 5, 3 beta-HSD activity over the capsule diminished shortly after birth and was absent in the adult. Appropriate controls showed that the staining within the capsule was specific and not an artifact. 3 beta-HSD activity in the capsule was more intensive when dehydroepiandrosterone (DHEA) was replaced by etiocholan-3 beta-ol-17-one (ETIO) as the steroid substrate. Furthermore, the spatial distribution of 3 beta-HSD activity in the cortex differed depending on the substrate used, and the distribution patterns changed with developmental age. (ABSTRACT TRUNCATED AT 250 WORDS)

Type, location and role of glycosaminoglycans in cloned differentiated chick retinal pigmented epithelium

In clonal culture, colonies of 3-4 week old chick retinal pigmented epithelial cells exhibit Alcian Blue positive extracellular matrix (ECM) material on the surface of the cells. Alcian blue positive ECM is located between undifferentiated cells at the edges of the disc-shaped colonies and beneath the differentiated cells in the colony center. The latter material is associated with the basement membrane. The staining properties suggest that glycosaminoglycans (GAG) are present in these regions. Extraction of GAG from homogenates of colonies, followed by electrophoresis on cellulose acetate strips, results in three bands with mobilities similar to those of hyaluronic acid, heparan sulfate, and chondroitin sulfate, respectively. All three bands label with [3H]glucosamine, and the last two also label with [35S]sulfate. The composition appeared to differ when colonies were grown in different media. Digestion of the GAG preparations with various enzymes suggests that bands II and III represent heparan sulfate and chondroitin sulfate, respectively, in colonies grown in Ham's F10g medium. The composition of band I is as yet undetermined. In minimal Eagle's medium (MEM), bands I and III consisted of hyaluronic acid and chondroitin sulfate, respectively, while band II had properties suggestive of a copolymer of heparan sulfate and an unidentified GAG. Cells release only one [3H]glucosamine-labelled GAG into the medium. This material has a mobility similar to hyaluronic acid and is digested by Streptomyces hyaluronidase, suggesting that it is hyaluronic acid. Staining with Alcian Blue at different pH suggests that it may represent the material associated with the upper surface of the cells. Some of the ECM located between the undifferentiated cells and associated with the basement membrane in the differentiated regions of the colonies stains with Alcian Blue at pH 1.0 and 0.2 suggesting that it may contain GAGs found in bands I and II. Colonies treated with medium containing 6-diazo-5-oxo-L-norleucine (DON), an inhibitor of GAG synthesis, for 48 hr showed a reduced Alcian Blue staining of the ECM in the undifferentiated regions. After 72 hr of treatment with DON, the undifferentiated cells had detached from the plate, whereas the differentiated cells remained intact. The results suggest that the GAG may be involved in cellular adhesion, particularly of the undifferentiated cells.

Proteoglycans and cell adhesion. Their putative role during tumorigenesis

In this review, evidence that proteoglycans are involved in cell adhesion and related behavior is considered, together with their putative role(s) during tumorigenesis. Proteoglycans are large, carboxylated and/or sulfated structures that interact with specific binding sites on cell surfaces. Their distribution and synthesis in tissues alter with the onset of tumorigenesis so that hyaluronic acid is generally increased and heparan sulfate decreased in the developing tumor and surrounding tissue. However, the precise role of proteoglycans during the tumorigenic process is far from clarified. Data suggest any putative roles will be related to the adhesive properties that these molecules confer to cells. Hyaluronic acid and chondroitin sulfate appear to be weakly adhesive molecules that may promote 'transformed' characteristics when they occur on cells in large amounts. These characteristics include reduced cell spreading, increased cell motility, as well as reduced contact inhibition. Consistent with such properties, neither hyaluronic acid nor chondroitin sulfate are localized in specialized adhesion sites such as focal or close contacts. In contrast, heparan sulfate is associated with increased cell-substratum adhesion and is involved in the spreading of cells onto fibronectin and other substrata. Its presence is generally associated with reduced motility and with a well-spread morphology. Unlike hyaluronate and chondroitin sulfate, heparan sulfate is found in specialized contacts. These adhesive properties of proteoglycans predict an instructive role in tumor development, and recent experiments have defined an involvement of these molecules in metastatic arrest. Additional studies utilizing invasive and metastatic tumor variants including tumor cells that employ different mechanisms to invade are required to clarify the role of proteoglycans in tumor progression.

Correlation of the cell phenotype of cultured cell lines with their adhesion to components of the extracellular matrix

The differential adhesion of cultured mammalian clonal cell lines to components of the extracellular matrix was examined by kinetic adhesion and long-term growth assays. Uniform artificial matrices were prepared by air drying collagen Type I solution (C) onto a microtiter well and then air drying a solution containing a single glycosaminoglycan (GAG): hyaluronic acid (HA), chondroitin sulfate-4 (CHS-4), or chondroitin sulfate-6 (CHS-6). The adhesion of [3H]thymidine-prelabeled cells suspended in fibronectin (FN) depleted medium was measured at 2 and 6 hr. Neuroblastoma (N18, Lan 1) and melanoma (B16, G361, S91) cell lines exhibited a significantly greater percentage of cells adhering to one or more C-GAG matrices compared with C matrices. Maximal adhesion at 2 hr was to C-HA. In contrast at 2 hr, two glial, two epithelial, and one fibroblastic cell line showed unchanged or significantly decreased binding to C-GAG compared with C matrices. Further experiments using a neuroblastoma (N18) and a glioma (C6) cell line indicated that the adhesion patterns were not altered either by the method of dissociation from the tissue culture dish, preincubation with exogenous GAG, or the addition of exogenous fibronectin. Assays of N18 and C6 adhesion to matrices made from a non-GAG polyanionic compound, polygalacturonic acid (PGA), did not yield the same adhesion patterns as C-HA matrices. Long-term growth studies of a neuroblastoma (N18) melanoma (S91), and glioma (C6) cell line on nonuniform matrices deliberately prepared with GAG-rich and GAG-poor regions complemented the observations from the kinetic adhesion assays. N18 and S91 cells did not grow on areas which did not contain GAG by toluidine blue staining. However, the C6 cells did not grow on areas which did strongly stain for GAG. A quantitative analysis of the long term growth of N18 and C6 cells substantiated these observations. All these data indicate that the cellular phenotype may be correlated with matrix adhesion. Neuroblastomas and melanomas have a greater affinity for GAG-containing matrices while glial, epithelial, and fibroblastic cells appear to have a greater or equal affinity for collagen matrices.

Origins of the differences in function of rat adrenal zona glomerulosa cells incubated as intact tissue and as collagenase-prepared cell suspensions

While in vitro incubation of dispersed cell preparations of adrenal cell types has been widely used as an experimental model, few studies have addressed the possibility that the enzymic and mechanical treatments involved may affect tissue functions. Using rat adrenal whole capsule tissue, consisting of glomerulosa cells still attached to the connective tissue capsule together with some fasciculata cells, and dispersed glomerulosa cell preparations formed by a variety of enzymic and incubation treatments, striking differences have been demonstrated between the functions of the various preparations in vitro. Under ACTH stimulation, whole capsules produced (ng per pair +/- s.e.) 405 +/- 35 ng aldosterone, 650 +/- 60 ng 18-hydroxycorticosterone (18-OH-B) and 850 +/- 90 ng corticosterone. In cells dispersed by collagenase incubation followed by repeated pipetting and filtration, aldosterone and 18-OH-B yields under ACTH stimulation fell to values less than 10% of those produced by whole tissue, whereas corticosterone values were unchanged. Omitting the filtration step gave a less well marked decline in aldosterone and 18-OH-B to 50% of intact tissue values. When the tissue was not dispersed after collagenase incubation, aldosterone and 18-OH-B outputs were similar in the two preparations. The decline in aldosterone and 18-OH-B is not attributable to loss in cell-cell contact alone, since short term culture of collagenase dispersed cells on contracting collagen discs did not restore the capacity to produce these steroids, and a decline in their output also occurred in similar culture of intact capsule tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of glycosaminoglycan metabolism by ACTH in bovine adrenocortical cells in primary culture

Bovine adrenocortical cells in primary culture actively incorporated [35S]sodium sulphate and [3H]glucosamine into glycosaminoglycans (GAGs). Most of the synthesized GAGs were found associated with the pericellular material and secreted in the culture medium, while less than 15% remained associated with the cell pellet. In all these fractions the major product was identified by its molecular properties and selective degradation procedures as a heparan sulphate structure. Exposure of the cells to ACTH induces a shift of the synthesized GAGs from the cellular to the pericellular compartment, an increase in the heparan sulphate labelling and the occurrence of an additional product characterized as a hyaluronate. These data suggest that GAG metabolism of the adrenocortical cell may be under hormonal control and open the possibility of a modulation of cell activity through modifications of its GAG components, especially those involved in the cell matrix architecture.

Effects of diazo-oxo-norleucine on cell kinetics and odontoblast differentiation in cultured embryonic mouse molars

Diazo-oxo-norleucine (DON), an analogue of glutamine, prevented odontoblast differentiation in cultured tooth germs. Diazo-oxo-norleucine added after the onset of odontoblast differentiation, did not affect the secretion of predentine or the functional differentiation of ameloblasts. DON decreased explant volume and modified cell kinetics, decreasing mitotic index, labelling index and number of grains per nucleus; the 5 phase of the cell cycle was lengthened. These modifications of cell kinetics should be considered when interpreting the effects of DON on odontoblast differentiation.