Cardiac rhabdomyoma presenting as left ventricular outflow tract obstruction in a neonate.

A case of congenital cardiac rhabdomyoma presenting as left ventricular outflow tract obstruction is reported. Congenital cardiac tumours are rare. Rhabdomyomas are the most common. Fifty-one to 86% of them are associated with tuberous sclerosis. They have a tendency for spontaneous regression. The indications for surgery include haemodynamic compromise and intractable arrhythmias.

Design and biological activity of (S)-4-(5-([1-(3-chlorobenzyl)-2-oxopyrrolidin-3-ylamino]methyl)imidazol-1-ylmethyl)benzonitrile, a 3-aminopyrrolidinone farnesyltransferase inhibitor with excellent cell potency.

The synthesis, structure-activity relationships, and biological properties of a novel series of imidazole-containing inhibitors of farnesyltransferase are described. Starting from a 3-aminopyrrolidinone core, a systematic series of modifications provided 5h, a non-thiol, non-peptide farnesyltransferase inhibitor with excellent bioavailability in dogs. Compound 5h was found to have an unusually favorable ratio of cell potency to intrinsic potency, compared with other known FTIs. It exhibited excellent potency against a range of tumor cell lines in vitro and showed full efficacy in the K-rasB transgenic mouse model.

End-of-life care in the intensive care unit: a challenge for nurses.

Results from several research studies combined with increasing public tensions surrounding physician-assisted suicide have fueled a growing awareness of the inadequacies of end-of-life care. Investigators also suggest that intensive care unit nurses have a limited role in end-of-life decision making and care planning. This article explores cultural issues influencing end-of-life care in intensive care units, explores factors surrounding the limited involvement of critical care nurses in end-of-life decision making and care planning, and offers recommendations for changing nursing practice. Because improving end-of-life care will require cultural changes, an understanding of the cultural issues involved is needed. Recommendations for changing nursing practice include a model of end-of-life care that incorporates the goals of both cure and comfort care, as well as a shared decision-making process. Nurses are essential to improving end-of-life care in today's intensive care units.

Early results of right ventricular-pulmonary artery conduits in patients under 1 year of age.

OBJECTIVES: Management strategies for the repair of many complex heart defects require the implantation of a valved conduit between the right ventricle (RV) and the pulmonary artery (PA), often using aortic or pulmonary homograft valves. Their limited availability, however, has led to the development and use of new conduits. We retrospectively compared our experience with small homografts in patients of less than 1 year of age with the TissueMed bioprosthetic valved conduit. METHODS: From March 1994 to November 1997 29 patients in their first year of life underwent conduit implantation for complex heart defects. These were retrospectively reviewed in order to determine the incidence of death or conduit stenosis. Seventeen patients received homografts and 12 TissueMed conduits. RESULTS: Diagnoses and operative details including conduit size were similar in the two groups and in all cases complete repair of the underlying defect was carried out. Early post-operative mortality was 4/17 (23.5%) in the homograft group and 3/12 (25%) in the TissueMed group. Echo Doppler evaluation within 1 month of operation showed no right ventricular outflow tract (RVOT) obstruction in any of the survivors. In the TissueMed group 8/9 (77%) survivors have gone on to develop significant RVOT obstruction within 12 months of operation. There have been three late deaths in this group all related to severe RVOT obstruction. Two patients died during an attempt at balloon dilatation and one patient died of progressive right heart failure. Five patients had successful replacement of the TissueMed conduit. One child remains well with no evidence of RVOT obstruction. At operation to replace conduit, or at autopsy, the stenoses were related to the deposition of fibrous tissue at the anastomotic suture lines. In the homograft group none of the survivors developed RVOT obstruction during the first 12 months post-operatively. There was one late death (non-cardiac in origin) and one child is awaiting conduit replacement 40 months after initial implantation for obstruction. CONCLUSIONS: The homograft is a satisfactory conduit for re-establishment of RV-PA continuity in infancy. Further work needs to be undertaken in order to elucidate the mechanisms of early graft failure in bioprosthetic conduits if these are to be a suitable alternative for RV outflow reconstruction in infants.

Imaging of abdominal hernias.

Abdominal hernias are a common clinical problem. The main types of abdominal hernias are external or abdominal wall hernias, which involve protrusion of abdominal contents through a defect in the abdominal wall; internal hernias, which involve protrusion of viscera through the peritoneum or mesentery and into a compartment in the abdominal cavity; and diaphragmatic hernias, which involve protrusion of abdominal contents into the chest. Clinical diagnosis of abdominal hernias can be difficult. However, plain radiography, radiography performed after administration of barium, and computed tomography allow evaluation of suspected abdominal hernias and detection of those that are clinically occult. The anatomic location of the hernia, the contents, and complications such as incarceration, bowel obstruction, volvulus, and strangulation can be demonstrated with radiologic examination. Occasionally, complications such as neoplasms or inflammatory conditions can be identified in the hernial contents. With abdominal imaging modalities, a variety of abdominal hernias can be confidently diagnosed.

Biostereometric measurement of oral tumour growth. Description of the technique and case report.

Following radiotherapy, it may be difficult to determine clinically whether tumour regression, stabilization or growth has occurred. Traditional diagnostic imaging may not be possible due to the small size of the tumour and the proximity of metallic restorations. A case of squamous cell carcinoma of the mandibular alveolar process in which these problems arose is presented. A computer-assisted biostereometric technique was used to identify volumetric change of the tumour. Polyvinylsiloxane impressions were obtained to record the anatomy of the tumour site. From these, stone models were made at four and eight weeks following radiotherapy. Using optical mapping techniques, tumour growth was demonstrated which was not evident on follow-up examinations. The methodolgy of biostereometry is presented and its advantages and potential applications are discussed.

Intraoral pyogenic granuloma after allogeneic bone marrow transplant. Report of three cases.

Allogeneic bone marrow transplant patients commonly have oral complications related to their disease or its treatment. Those reported include: xerostomia, mucositis, caries, infection, gingival hyperplasia, periodontitis, and graft-versus-host disease. These complications may be responsible for significant morbidity. This article reviews commonly reported oral complications of bone marrow transplantation and presents three cases in which intraoral pyogenic granuloma occurred. The cause of these lesions in post-bone marrow transplant patients is discussed.

The utilization of a multi-layer prosthesis to treat recurrent antral carcinoma: a case report and review of the literature.

This paper reviews the use of an intracavitary mold in the radiotherapeutic management of recurrent sub-orbital carcinoma of the maxillary sinus. An overview of the clinical features of antral carcinomas and the concept of brachytherapy in the management of these lesions is presented. Brachytherapy is usually reserved for relatively accessible lesions. Post-surgical and radiation-induced trismus can be a complicating factor, as in the case presented, where the inter-incisal distance was less than three millimeters. To circumvent the problem, a multi-layer antral plug was utilized as a carrier for the radioactive sources, and its construction is described.

Differential modulation of gene induction by glucocorticoids and antiglucocorticoids in rat hepatoma tissue culture cells.

Studies of glucocorticoid and antiglucocorticoid induction of tyrosine aminotransferase (TAT) in two rat hepatoma cell lines (Fu5-5 and HTC) are described. These studies revealed several phenomena that are not consistent with the current models of steroid hormone action: (a) TAT induction occurred at glucocorticoid levels below those required for comparable receptor occupancy in Fu5-5, but not in HTC, cells; (b) the ability of antiglucocorticoids to induce TAT is higher in Fu5-5 than in HTC cells; (c) the values of the amount of TAT agonist activity with the antiglucocorticoid dexamethasone 21-mesylate and of log10 of the dexamethasone concentration required for half-maximal induction of TAT were not constant over time but varied in a linear, reciprocal manner. This modulation was seen for several glucocorticoids and antiglucocorticoids at the level of both TAT enzyme and mRNA but not for two other glucocorticoid inducible genes in the same cells. These results, plus the fact that a similar difference in the concentration required for half-maximal TAT induction in Fu5-5 cells was seen for both glucocorticoids and cyclic AMP, argue that the modulation occurs at some point distal to receptor-steroid complex binding to the biologically active nuclear sites but proximal to translation of TAT mRNA. In order to explain these results, it is pointed out that models involving second messengers are entirely appropriate for steroid hormone action. The participation of a modulated trans-acting factor in such a model may explain the above results.

Inverse correlation between dexamethasone 21-mesylate agonist activity and sensitivity to dexamethasone for induction of tyrosine aminotransferase in rat hepatoma cells.

Previous results demonstrated that both the level of induction of the liver specific enzyme tyrosine aminotransferase (TAT) by the irreversible antiglucocorticoid dexamethasone 21-mesylate (Dex-Mes) and the concentration of the reversible glucocorticoid dexamethasone (Dex) required for 50% of maximal TAT induction (i.e. EC50) were different in HTC and Fu5-5 rat hepatoma culture cells. In the present study, a retrospective analysis of these two parameters over an 8 yr period indicates that the absolute values of both parameters varied within each cell line over time in a reversible manner. The variation of both parameters appears to be causally related since a linear, reciprocal relationship exists between the amount of Dex-Mes agonist activity and log10 (Dex EC50) in both cell lines (correlation coefficient is -0.896 for n = 46). This relationship was independent of changes in basal TAT level, culture medium, and serum lot. Results with cloned HTC cells indicate that these temporal variations are not due to fluctuations in the relative abundance of two cell populations displaying either high or low amounts of agonist activity with Dex-Mes. While these analyses relied on the detection of enzyme levels, the amount of TAT mRNA is shown to parallel the enzyme levels. Thus the variation in parameters of TAT induction by Dex and by Dex-Mes appears to be modulated at a pre-translational step. Such variations have not previously been observed for the control of specific gene transcripts by other steroid hormones and may be related to the known differences in agonist activity seen for most antisteroids in various systems.

Comparison of glucocorticoid receptors in two rat hepatoma cell lines with different sensitivities to glucocorticoids and antiglucocorticoids.

Two independently derived rat hepatoma cell lines, HTC and Fu5-5, differ in their sensitivities to both glucocorticoids and antiglucocorticoids, despite virtually identical number and affinity of glucocorticoid receptors. The present study further examined both receptors for differences that could account for the nonidentical responses of the two cell lines. HTC and Fu5-5 cell receptors that were covalently labeled with [3H] dexamethasone 21-mesylate ([3H]DM) had the same mol wt of about 97,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the same isoelectric point of about 6.4 by nonequilibrium pH gradient electrophoresis. Limited proteolysis of receptor-[3H]DM complexes with three different proteases generated identical protease-specific digestion patterns regardless of the cellular origin of the receptors. Receptor-[3H]dexamethasone complexes prepared from either Fu5-5 or HTC cells bound calf thymus DNA with the same affinity in vitro. In intact cells, the intracellular distribution of receptor-dexamethasone or receptor-DM complexes at equilibrium was almost identical in the two cell lines. Thus, we detected no differences in the size, sequence, or net charge of Fu5-5 or HTC cell receptors; additionally, there were no significant differences in steroid uptake, receptor binding, or activation, translocation, and nuclear binding of receptor-steroid complexes. However, the DM labeling efficiency, calculated as the percentage of total receptors covalently labeled by DM, was higher in HTC cells (65.9 +/- 12.9%; n = 5) than in Fu5-5 cells (39.3 +/- 7.7%; n = 5). The labeling efficiency of DM correlated inversely with its ability to induce tyrosine aminotransferase activity, suggesting that DM forms noncovalent, as well as covalent, complexes in vivo which mediate the glucocorticoid and antiglucocorticoid activities of DM, respectively. Further research is required to identify the factor(s) that influences DM labeling efficiency, thereby affecting the amount of DM agonist activity and, possibly, the sensitivity of the cells to glucocorticoids.

Antiglucocorticoid steroids have increased agonist activity in those hepatoma cell lines that are more sensitive to glucocorticoids.

FU5-5 rat hepatoma (Reuber H35) cells are hypersensitive in that the same percentages of full induction of tyrosine aminotransferase (TAT) occur at much lower concentrations of glucocorticoids than in the related HTC rat hepatoma (Morris) cells. Unexpectedly, these hypersensitive FU5-5 cells also exhibited more agonist activity with the affinity labeling antiglucocorticoids cortisol 21-mesylate and dexamethasone 21-mesylate than did HTC cells (Mercier et al., Endocrinology 112, 601-609 [1983]). In the present study, several other antiglucocorticoids (11-desoxycortisone, progesterone, dexamethasone oxetanone, and RU 486 in addition to dexamethasone 21-mesylate) and the antiandrogen cyproterone acetate were examined to see if chemically unreactive, reversible antisteroids also would exhibit an altered activity (i.e. increased agonist activity) in FU5-5 cells. Each antiglucocorticoid examined did display a 2-fold increased amount of agonist activity in FU5-5 cells, as compared to HTC cells; only RU 486 was predominantly an antagonist in FU5-5 cells but the potency of RU 486 was about 9-fold less than in HTC cells. Dexamethasone, and especially progesterone, was metabolized in FU5-5 and HTC cells. However, differential metabolism in FU5-5 vs HTC cells cannot account for the increased induction of TAT in FU5-5 cells since the amount of agonist activity seen for dexamethasone mesylate (or its metabolites) depended not on the cell type used but rather on the glucocorticoid inducible enzyme monitored, i.e. TAT or glutamine synthetase. The combined data suggest that the hypersensitivity of FU5-5 cells towards glucocorticoid induction of TAT may be linked with the ability of both reversible and irreversible antiglucocorticoids to display increased TAT agonist activity in FU5-5 cells. This behavior was somewhat steroid specific since the antiandrogen cyproterone acetate did not display increased TAT agonist activity in FU5-5 cells compared to HTC cells and was only 2-fold less effective as an antiglucocorticoid in FU5-5.

Affinity-labeling steroids as biologically active probes of antiglucocorticoid hormone action.

The role of the glucocorticoid receptor in the expression of antiglucocorticoid action has been investigated with a chemically-reactive derivative of three glucocorticoid steroids with differing biological potencies, i.e. the C-21 mesylates of cortisol, dexamethasone and deacylcortivazol. Dexamethasone 21-mesylate (Dex-Mes) was the most useful derivative due to its favorable balance of high receptor affinity and predominantly irreversible antiglucocorticoid activity. A number of criteria have been used to conclude that [3H]Dex-Mes covalently labels glucocorticoid receptors in the steroid-binding cavity. The available data indicate that covalent Dex-Mes-labeled receptors (mol. wt approximately equal to 98,000) are responsible for the irreversible antiglucocorticoid activity while the partial agonist activity of Dex-Mes is due to non-covalent Dex-Mes-bound receptors. Further support for this hypothesis comes from the observations that deacylcortivazol 21-mesylate was a full glucocorticoid and did not affinity label receptors (and marginally labeled cytosol proteins) although it was capable of covalently-labeling bovine serum albumin. Several mechanisms for the expression of irreversible antiglucocorticoid activity by covalent Dex-Mes-labeled receptors were examined and can be eliminated. Covalent receptor-Dex-Mes complexes formed in whole HTC cells were found to have a decreased capacity for nuclear binding. This decreased nuclear-binding capacity could be responsible for the whole-cell irreversible antiglucocorticoid activity of Dex-Mes.

Covalent and noncovalent receptor-glucocorticoid complexes preferentially bind to the same regions of the long terminal repeat of murine mammary tumor virus proviral DNA.

Dexamethasone 21-mesylate, an irreversible antiglucocorticoid in HTC cells, forms a covalent receptor-steroid complex which can be activated in cell-free systems. The molecular basis of its antiglucocorticoid activity is unknown; it might result from altered DNA sequence preferences and/or affinities of the covalent receptor-steroid complex. To test this hypothesis, the affinities of both covalent receptor-antagonist and noncovalent receptor-agonist complexes for defined DNA sequences were measured in a DNA binding competition assay. This assay requires neither purified complexes nor large quantities of DNA, yet it provides quantitative comparisons of the affinities of different double-stranded DNAs for binding receptor-steroid complexes. In this assay, activated covalent receptor-dexamethasone 21-mesylate complexes in crude cytosol bound to calf thymus DNA and cloned subregions of the long terminal repeat (LTR) of murine mammary tumor virus (MMTV) proviral DNA with approximately the same relative affinities as did noncovalent receptor-dexamethasone complexes. Both types of complex exhibited similar orders of preferential binding to DNA sequences. LTR subregions, as well as the entire LTR, were 2-20 times more potent competitors than calf thymus DNA. Cloned sequences from the 3' terminus of the LTR were more effective competitors than either the entire LTR or comparably sized DNAs from the 5' terminus. The DNA sequences with the greatest affinities for both covalent and noncovalent complexes are located within the region of -221 to -67. These studies support the theory that recognition by regulatory elements of specific DNA sequences upstream of responsive genes is an integral step of hormone action.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of DNA binding properties of activated, covalent and noncovalent glucocorticoid receptor-steroid complexes from HTC cells.

Several differences in the interaction with DNA of noncovalent vs. covalent glucocorticoid receptor-steroid complexes are described. HTC cell glucocorticoid receptors were incubated under cell-free conditions with the potent reversible glucocorticoid dexamethasone and with the irreversible antiglucocorticoid dexamethasone 21-mesylate to yield noncovalent and covalent complexes, respectively. Using DNA immobilized on cellulose, we found that the noncovalent dexamethasone complexes were activated (by dilution in pH 8.8 buffer at 0 degree C) to a DNA binding species 2-fold faster than were covalent dexamethasone 21-mesylate labeled complexes. The affinity of activated, noncovalent dexamethasone complexes for DNA in an equilibrium binding assay was 2-fold higher than that of the activated, covalent dexamethasone 21-mesylate complexes. This conclusion was supported by the observations in a DNA-cellulose pellet assay that covalent receptor-steroid complex binding to DNA was disrupted by lower NaCl concentrations than was noncovalent complex binding. The same studies of DNA binding at various NaCl concentrations failed to provide evidence that glucocorticoid receptor-steroid complex binding to DNA is a multistep process. These quantitative distinctions in the DNA binding properties of covalent and noncovalent receptor-steroid complexes represent the first physicochemical differences between the complexes of antiglucocorticoid and glucocorticoid steroids and may partially account for their divergent biological properties.

Glycolipid-dependent interaction between human migration-inhibitory factor and mononuclear phagocytes.

It has been previously established in the guinea pig that the response of peritoneal macrophages to migration inhibitory factor (MIF) is enhanced by a macrophage glycolipid and that gangliosides reversibly bind MIF. This suggests that glycolipids function as cell surface receptors for MIF. In this report, it is demonstrated that the response of human peripheral blood monocytes to human MIF is augmented by preincubation of these cells with glycolipid-enriched material extracted from the human macrophage-like cell line U937 or human peripheral blood monocytes and with a purified glycolipid from guinea pig peritoneal macrophages. In addition, a mixed ganglioside preparation from bovine brain shows the same effect. In contrast, the pure gangliosides, GM1 and GD1a, and glycolipids from the HL-60 cell line, which is a MIF-unresponsive cell line, were not able to enhance the response to human MIF. The specificity of enhancement by particular glycolipids could not be attributed to an increased uptake of only enhancing glycolipids since there was no significant difference between the association of monocytes with radioactive liposomes containing biologically active or inactive glycolipids. Pronase treatment did not affect the enhancing activity of the U937 glycolipid-enriched material. Incubation of cells with glycolipids results in enhancement only if done at 37 degrees C and not at 4 degrees C. Therefore, the association of lipid with the monocyte surface appears to be dependent on temperature. Further evidence for the receptor nature of these enhancing glycolipids is provided by experiments involving affinity purification experiments. Coupling of bovine brain mixed gangliosides to agarose resulted in a matrix capable of reversibly binding MIF. GD1a-agarose was inactive in this respect.

Dexamethasone induction of an inhibitor of plasminogen activator in HTC hepatoma cells.

Incubation of HTC rat hepatoma cells with dexamethasone causes a rapid decrease in cellular plasminogen activator (PA) activity. Mixing experiments show the presence of an inhibitor of PA in dexamethasone-treated cells. This study investigates whether the decrease in PA activity is secondary to the induction of an inhibitor by glucocorticoids, to a decrease in the amount of PA, or to a combination of both mechanisms. PA and its inhibitor are dissociated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under non-reducing conditions, and both activities are then recovered and quantitated. HTC cells have two major forms of PA with Mr values of 110,000 and 64,000. Although PA activity in the unfractionated extracts from dexamethasone-treated cells is inhibited by 90% relative to control, there is no decrease in the total activity of sodium dodecyl sulfate-dissociated PA activity, suggesting that dexamethasone causes no decrease in the amount of the enzyme. PA inhibitor activity migrates as a single band of Mr = 50,000. The total activity of inhibitor increases in a time-dependent fashion, reaching a maximum of greater than 10 times control after a 4-6-h incubation with 0.1 microM dexamethasone. The induction of inhibitor requires both RNA and protein synthesis and shows a dependence on dexamethasone concentration identical to that for responses known to be mediated by glucocorticoid receptors. We conclude that dexamethasone inhibits PA activity by inducing the synthesis of an inhibitor rather than by decreasing the amount of PA.

Paradoxical effects of glucocorticoids on regulation of plasminogen activator activity. Mediation by glucocorticoid receptors.

Dexamethasone, a synthetic glucocorticoid, decreases the plasminogen activator (PA) activity of HTC rat hepatoma cells in tissue culture. Paradoxically, dexamethasone enhances the cyclic nucleotide stimulation of PA activity in these cells 2-4-fold. In this report, we investigated whether this paradoxical glucocorticoids as the induction of tyrosine aminotransferase activity. We compared the concentration-dependences for several classes of steroids, previously classified as full agonists, partial agonists, antagonists or inactive steroids with respect to induction of the transaminase, for both enhancement of cyclic nucleotide stimulation of PA activity and induction of tyrosine aminotransferase activity in parallel cultures. The full agonists dexamethasone and cortisol, the partial agonists deoxycorticosterone and 11 beta-hydroxyprogesterone, the inactive steroid tetrahydrocortisol, and the antagonist 17 alpha-methyltestosterone exhibited similar potencies with respect to both phenomena. Furthermore, when cells were incubated with both dexamethasone and 17 alpha-methyltestosterone, the latter blocked enhancement by dexamethasone in a concentration-dependent fashion. We conclude that glucocorticoid enhancement of cyclic nucleotide stimulation of PA activity is mediated by the same glucocorticoid receptors which mediate direct regulatory effects.

Role of plasminogen activator in the morphological alterations induced by derivatives of adenosine cyclic 3':5'-monophosphate in hepatoma tissue culture cells.

We have reported previously that derivatives of adenosine cyclic 3':5'-monophosphate dramatically stimulate the activity of plasminogen activator (PA), an arginine-specific serine protease, in HTC rat hepatoma cells. We report here that these derivatives also cause striking alterations in hepatoma tissue culture cell morphology. Because PA has been shown to alter cell morphology in other cell lines, we investigated whether the morphological changes induced by cyclic nucleotides were mediated by the stimulation of PA activity. Alterations in PA activity, measured by the plasminogen-dependent solubilization of 125I-labeled fibrin, and in cell morphology, detected by evaluation of cell flattening and process extension with phase-contrast microscopy, were assessed in the same cultures under various experimental conditions. Several lines of evidence clearly dissociate these two adenosine cyclic 3':5'-monophosphate-mediated phenomena. (a) The morphological changes precede increases in either cell-associated or extracellular PA activity. (b) Upon removal of the effectors, the morphological effects are completely reversed at a time when PA activity is still considerably elevated. (c) when protein synthesis is inhibited by the addition of cycloheximide, the stimulation of PA activity by cyclic nucleotides is blocked completely, whereas the induction of morphological alterations still occurs. (d) An exogenous PA, urokinase, does not elicit the characteristic changes in cell shape. We conclude that the morphological alterations induced by adenosine cyclic 3':5'-monophosphate derivatives in HTC cells are not mediated by the stimulation of PA activity and that these two membrane-associated properties are regulated independently.

Hormonal regulation of plasminogen activator in rat hepatoma cells.

Plasminogen activators are membrane-associated, arginine-specific serine proteases which convert the inactive plasma zymogen plasminogen to plasmin, an active, broad-spectrum serine protease. Plasmin, the major fibrinolytic enzyme in blood, also participates in a number of physiologic functions involving protein processing and tissue remodelling, and may play an important role in tumor invasion and metastasis. In HTC rat hepatoma cells in tissue culture, glucocorticoids rapidly decrease plasminogen activator (PA) activity. We have shown that this decrease is mediated by induction of a soluble inhibitor of PA activity rather than modulation of the amount of PA. The hormonally-induced inhibitor is a cellular product which specifically inhibits PA but not plasmin. We have isolated variant lines of HTC cells which are selectively resistant to the glucocorticoid inhibition of PA but retain other glucocorticoid responses. These variants lack the hormonally-induced inhibitor; PA from these variants is fully sensitive to inhibition by inhibitor from steroid-treated wild-type cells. Cyclic nucleotides dramatically stimulate PA activity in HTC cells in a time- and concentration-dependent manner. Paradoxically, glucocorticoids further enhance this stimulation. Thus glucocorticoids exert two separate and opposite effects on PA activity. The availability of glucocorticoid-resistant variant cell lines, together with the unique regulatory interactions of steroids and cyclic nucleotides, make HTC cells a useful experimental system in which to study the multihormonal regulation of plasminogen activator.