Morphological and biochemical integrity of human liver slices in long-term culture: effects of oxygen tension

We tested the effects of low (20% O2) and high (70% O2) oxygen tension on the morphological and biochemical integrity of human liver slices incubated for up to 72 h in supplemented Williams' E medium in a dynamic rotating culture system. High oxygen tension was more effective than low oxygen tension for preserving morphological integrity in long-term culture (48-72 h). After 72 h of culture with 70% O2, the lobular pattern was well preserved, and the survival of hepatocytes (approximately 80%) and other cell types was good. Immunohistochemical studies showed good preservation of the region-specific expression of CYP2EI and CYP3A4 isoenzymes for up to 72 h of incubation in 70% O2. As compared to 20% O2, the oxidized glutathione content and reactive oxygen species production were slightly increased in 70% O2, suggesting that minimal oxidative stress occurred with the high oxygen tension. In conclusion, despite slight oxidative stress associated with high oxygen tension, 70% O2 appeared more appropriate than 20% O2 for preserving the morphological and biochemical integrity of human liver slices cultured in a dynamic organ culture system for up to 72 h.

Cryopreserved rat liver slices: a critical evaluation of cell viability, histological integrity, and drug-metabolizing enzymes

The effects of a cryopreservation procedure on the biochemical, morphological and functional integrity of rat liver slices just after thawing and after 24 h culture were evaluated. Freshly prepared slices were incubated in modified University of Wisconsin solution containing 50% fetal calf serum and 10% dimethyl sulfoxide for 20 min on ice prior to a rapid cooling in liquid nitrogen. After 10-40 days, slices were thawed rapidly at 42 degrees C. Total protein content and (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) (MTT) reduction were well preserved at thawing, whereas ATP content was markedly decreased relative to freshly prepared slices (-83%). The major microscopic findings in sections of just-thawed liver slices consisted of hepatocellular dissociation and minimal apoptosis. The qualitative profile of antipyrine (AP) metabolism was well preserved in cryopreserved slices, but the amounts of phase I and phase II AP metabolites produced over a 3-h incubation period were markedly reduced relative to fresh slices (-58 to -71%). When cryopreserved slices were cultured for 24 h after thawing, the viability was markedly reduced, as reflected by the almost complete absence of MTT reduction and the loss of ATP content. Histological examinations showed extensive cellular necrosis. The amount of AP metabolites produced by cryopreserved slices was similar after a 3- or a 24-h culture period, indicating that AP metabolism capacities were lost at 24 h culture. In conclusion, our results suggest that cryopreserved rat liver slices may be a useful model for short-term in vitro determination of drug metabolism pathways. Further work is required to extend their use for toxicological studies.

Magnetic resonance imaging in a patient with a dual-chamber pacemaker

The presence of an implanted cardiac pacemaker has been considered an absolute contraindication for magnetic resonance imaging due to the interactions between the pulse generators and the magnetic and radiofrequency fields generated by the magnetic resonance unit. We describe the case of a patient with a dual-chamber pacemaker who underwent two magnetic resonance imaging examinations of the head without any sequelae. Both procedures were performed with a 1 Tesla unit, with the pacemaker programmed to the AOO mode. The only interference observed was activation of the reed switch -probably due to the static magnetic field- resulting in asynchronous atrial pacing at the magnet rate. Although the general policy of never exposing a patient with a pacemaker to magnetic resonance imaging should not be revised, we think that if the testing is considered essential, it could be safely used in certain carefully selected patients.

Effects of corticosterone on reproduction in male Sprague-Dawley rats

Corticosterone, the predominant circulating adrenal corticosteroid in rodents, was investigated for its effects on reproduction in male Sprague-Dawley rats. Male rats (in groups of 50, 25, and 50) were administered corticosterone at doses of 0, 10, and 25 mg/kg/d, respectively, by subcutaneous injection once daily for 6 weeks; the highest dose was decreased to 20 mg/kg/d after 15 d. During the last 2 weeks of the 6-week treatment period, 25 males per group were paired with untreated females. The remaining 25 males from the 0 and 25/20 mg/kg/d groups were allowed a 6-week recovery period and, during the last 2 weeks of this period, these males were also paired with untreated females. At the end of the treatment period, the males had markedly elevated plasma corticosterone concentrations and decreased weight gain. They also produced fewer copulatory plugs than controls, which may have been secondary to observed adverse effects on the accessory sex organs (decreased weights and microscopic changes in prostate and seminal vesicles). However, no adverse effects on sperm motility, sperm count, or microscopic features of the testes were observed. Serum testosterone concentration of the high-dose males was elevated, but luteinizing hormone was unaffected. The numbers of embryonic implantation sites and live fetuses in females mated to these males were reduced. All of these effects except decreased prostate weights were reversible upon cessation of corticosterone administration. Thus, exogenous administration of corticosterone to male rats produced reversible effects on implant count and litter size of female rats mated to these males. These effects on male rat reproduction may have been secondary to reduced accessory sex organ function, which resulted in diminished secretions and fewer copulatory plugs.

[Isotopic ventriculography in healthy young volunteers. Their response to different types of stress]

BACKGROUND

Due to the increasing use of pharmacologic stress tests and the lack of comparative studies on ventricular function, this study was designed to establish the average limits in ventricular function with different kinds of stress, and to compare the response among them.

METHODS

A randomized, open, controlled phase II clinical trial in 4 parallel groups was designed. Forty healthy male volunteers between 18 and 25 years were randomized into 4 groups of 10 individuals each: physical exercise (group 1), dobutamine (group 2), adenosine triphosphate (ATP) (group 3) and dipyridamole (group 4). Each volunteer underwent equilibrium radionuclide angiography, at rest and during stress.

RESULTS

The global and regional ejection fraction increased significantly with the 4 kinds of stress. The maximal increase was reached with dobutamine and the minimal with dipyridamole. Physical exercise induced an increase in global ejection of 13 +/- 5%; dobutamine 16 +/- 6%; ATP 9 +/- 3% and dipyridamole 4 +/- 3%.

CONCLUSIONS

The global and regional ejection fraction increases significantly more with dobutamine than with the other stress tests. Dipyridamole elicits the minimal increase.

Antiestrogens prevent the stimulatory effects of L-triiodothyronine on cell proliferation

This paper studies the modulatory effects of two antiestrogens, the steroid ICI 164 384 and the nonsteroidal compound 4-hydroxytamoxifen (4-OH-tam), on the proliferation of L-T3-stimulated cell lines. Three cell lines known to be stimulated by thyroid hormones and to contain estrogen receptors but to have a different estradiol sensitivity to estradiol were used; F4Z2 and MCF-7 cells were stimulated, whereas GH3 cells were insensitive. Cells were counted 6-7 days after hormones and antihormones were added to the culture medium, separately or in association (a fixed hormone concentration and increasing antihormone concentrations and vice versa). In F4Z2 and MCF-7 cells, antiestrogens prevented noncompetitively the stimulatory effect of L-T3 and, as expected, competitively the stimulatory effect of estradiol. In GH3 cells, antiestrogens had proper inhibitory effects, but they did not prevent significantly the proliferative effect of L-T3. To investigate the mechanisms of the modulatory effects in F4Z2 cells we examined the consequences of antiestrogens on thyroid hormone receptors (nuclear binding of L-T3 and mRNAs of thyroid hormone receptors, i.e. c-erbA alpha and -beta) and insulin-like growth factor-I (IGF-I; secretion and mRNAs). Antiestrogens neither competed with L-[125I]T3 nor reproducibly decreased the number and affinity of thyroid hormone-binding sites. While 4-OH-tam frequently decreased the amount of c-erbA beta transcripts, ICI 164 384 did not alter the distribution of alpha and beta cDNA transcripts. Further, neither antiestrogen prevented the increases in IGF-I accumulation in conditioned medium and IGF-I mRNA concentrations induced by L-T3 (0.1 nM). In conclusion, 1) antiestrogens are potent noncompetitive inhibitors of the action of L-T3 on the proliferation of cells whose growth is responsive to estradiol (F4Z2 and MCF-7), but not of the action on a cell line whose growth is insensitive to estradiol (GH3). 2) The loss of L-T3 sensitivity is not due to a loss of thyroid receptors or a decrease in IGF-I production. 3) In addition to estrogen receptors, factors involved in the estradiol control of cell proliferation appear to be required for the antiestrogen inhibition of L-T3 action.

Possible involvement of transforming growth factor-beta in the inhibition of rat pituitary tumor growth by estradiol

We have shown that growth of F4Z2 cells and F4Z2 tumors was stimulated by estradiol, that of MtTF4 and F4P tumors was inhibited and that of F4P cells remained insensitive. In the present work we explore the possible role of transforming growth factor-beta (TGF-beta) as a mediator of estradiol action in these pituitary tumors and cell lines. In vivo, estradiol treatment increased the concentration of TGF-beta 1 mRNAs in tumors whose growth was inhibited by estradiol (MtTF4 and F4P) but not in tumors whose growth was stimulated (F4Z2). F4Z2 and F4P cell lines also contained TGF-beta 1 transcripts. These cells and tumors differed by two points: the level of TGF-beta 1 transcript was higher in F4Z2 than in F4P cells while the opposite situation was observed in vivo and the concentration of TGF-beta 1 mRNA in cultured cells was insensitive to estradiol (1 or 100 x 10(-9) M). Moreover, the secretion of TGF-beta like activity assayed by two different methods was estradiol insensitive and the growth of both cell lines was dose-dependently inhibited by TGF-beta 1 (ED50:2 x 10(-11) M). Since estradiol increases TGF-beta 1 mRNA in the tumors MtTF4 and F4P whose growth is inhibited by estradiol and that TGF-beta 1 inhibits the proliferation of F4P cells it is proposed as a working hypothesis that TGF-beta 1 is one of the mediators of the inhibitory effect of estradiol in pituitary tumors. No data favor the hypothesis that estradiol stimulates pituitary tumor proliferation by decreasing TGF-beta production.

Multihormonal control of cell proliferation: opposite effects of two stimulators (17 beta-estradiol and L-triiodothyronine) and one inhibitor (dexamethasone) on F4Z2 pituitary tumor cells

From the MtTF4 tumor of rat pituitary origin we established the F4Z2 cell line whose growth is stimulated by 17 beta-estradiol (E2). Taking E2 actions as references we investigated actions of other effectors on the proliferation, protein, and insulin growth factor-I (IGF-I) secretions of F4F2 cells. Dexamethasone (Dex) and L-T3 were chosen because they have also intracellular receptors and they act in pituitary cells. Cells were cultured in 96-well plates in RPMI 1640 medium supplemented either with charcoal-treated fetal calf serum (CT-FCS) or with BSA and transferrin. Hormones were added at the time of seeding and cells were counted 2-10 days later without renewing the culture medium. The accumulation of immunoreactive IGF-I in conditioned medium was used as an index of IGF-I secretion. For studies on protein secretion, cells were incubated for 24 h with [35S]methionine and labeled proteins were separated by polyacrylamide gel electrophoresis. We found that: 1) L-T3, like E2, stimulated in a dose-dependent and specific manner the proliferation of F4Z2 cells cultured in the presence of 5% CT-FCS; EC50 was: 1 X 10(-11) M and 0.2 X 10(-11) M for L-T3 and E2, respectively. In contrast, L-T3 but not E2 remained active in serum-free medium; 2) Dex was a strong inhibitor of cell proliferation in serum-free medium and in medium supplemented with 5% CT-FCS (EC50: 5 X 10(-9) M). The antiglucocorticoid RU 38 486 prevented this inhibitory effect; 3) when a stimulator (E2 or L-T3) was simultaneously incubated with the inhibitor (Dex) the number of cells depended on the ratio of hormone concentrations. When there was no large excess of one effector this number was intermediary between those counted in the presence of each hormone separately and L-T3 was more potent than E2 in preventing Dex inhibition; 4) Dex, E2, and L-T3 modified the electrophoretic patterns of secreted proteins but there was no evidence for a correlation between these modifications and the inhibition or the stimulation of cell proliferation, and 5) the accumulation of immunoreactive IGF-I was insensitive to E2, increased by L-T3, and markedly decreased by Dex. L-T3 but not E2 prevented the effect of Dex.(ABSTRACT TRUNCATED AT 400 WORDS)

Size heterogeneity of affinity labeled estrogen receptors in the MtTF4 tumor whose growth is inhibited by estradiol, in pituitary gland and uterus

Estrogen receptors (ER) of the MtTF4 tumor whose growth is inhibited by estradiol (E2) were analyzed and compared to those of tissues whose growth is stimulated by E2 (uterus and pituitary gland). Cytosol prepared in buffer containing protease inhibitors was incubated with [3H]tamoxifen aziridine ([3H]TAZ) in the presence or absence of non-radioactive competitor. The labeled proteins were precipitated, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis in denaturing conditions and detected by fluorography. Two classes of ER were identified. The first class is of high molecular weight (Mr = 65,000-64,000). In normal tissues, it is indeed frequently made up of two subtypes as revealed by the presence of a doublet on autoradiograms. In the MtTF4 tumor these subtypes were only rarely suspected and never they were as marked and distinct as in normal tissues. The second class, of low molecular weight (Mr ! 54,000-52,000), is also frequently made up of two subtypes in the uterus and the proportion of this class is higher in the uterus of mature than of immature rats. The MtTF4 tumor contains this class of ER but, due to the presence of non-specifically labeled proteins in this region, its relative amount cannot be estimated and the doublet was exceptionally revealed. In the pituitary gland, this small receptor has not been found.

CONCLUSIONS

(i) On the basis of molecular weight analyses, estrogen receptors are heterogeneous, (ii) the ER pattern depends on the type of tissue and the sexual maturity of rats but all the tissues examined contained at least one type of the "classic" high molecular weight receptor, and (iii) no evident correlation was found between the ER pattern and the positive or negative response to estradiol.

Inhibition of the MtTF4 tumor growth by dexamethasone

It is known that estradiol, but not progesterone or dihydrotestosterone, slows down the growth of the MtTF4 tumor. In the present paper, it is shown that: (1) this tumor contains glucocorticoid receptors, (2) its growth is also inhibited by treatment with dexamethasone (Dex), and (3) the growth rate of a cell line and several clones established from the tumor is negatively controlled by Dex 10(-7) M in culture medium containing 10% gelding serum. Unlike estradiol, Dex does not induce cell hypertrophy. This work suggests that the inhibition of the MtTF4 tumor growth by Dex may be due in part to a direct action on tumor cells and, taking into consideration previous reports, it allows us to forward the hypothesis that both Dex and estradiol inhibit MtTF4 tumor growth in two different ways.

Properties of the estrogen receptors contained in the MtTF4 tumor whose growth is inhibited by estradiol: 17 beta-estradiol, 17 alpha-estradiol and DNA bindings

The steroid and the DNA bindings of the estrogen receptor of the MtTF4 tumor whose growth is inhibited by estradiol where characterized and compared to those of uterine estrogen receptors. In the tumor cytosol: E protects its binding sites against thermal denaturation, depending on the effects of sodium molybdate upon the dissociation rate of [3H]E at 20 degrees C and the ability of receptor to bind to DNA, the activation (or transformation) process, supposed to be necessary for the full action of estrogen ligand, occurs on estrogen receptor complexes and the calf thymus DNA interacts with estrogen receptor with an affinity similar to that of uterine estrogen receptor. Kinetic and equilibrium studies with 17 alpha-[3H]E both in uterus and tumor indicate that this ligand is fast-associating, fast-dissociating and that its affinity for ER is 2- to 4-fold lower than that of 17 beta-[3H]estradiol one. Competition experiments between 17 beta-[3H]estradiol and the unlabelled 17 alpha epimer reveal, in both uterus and tumor, a time-dependent decrease of the apparent potency of 17 alpha-E to inhibit the binding of [3H]E. It is concluded that the estrogen receptors are very similar in MtTF4 tumor and uterus and the diversity of the response of cell growth to E is due rather to differences at the post-receptor level.

Induction of progestin receptors in the rat MtTF4 tumor of pituitary origin whose growth is inhibited by estradiol

When the MtTF4 pituitary tumor was grown in male rats not treated by estradiol, the cytosol prepared from it contained very few binding sites for the synthetic [3H]ORG progestin. Following estradiol treatment there was a reversible increase of these binding sites. The ligand specificity and the sedimentation constant were shown to be similar to those of progestin receptors contained in other tissues. Daily treatment for 8 days with 10 micrograms 17 alpha-estradiol, 50 micrograms dihydrotestosterone or 50 micrograms dexamethasone did not induce progestin binding.

IN CONCLUSION

(1) the virtual absence of progestin receptors in a tumor does not allow an absence of response to endocrine manipulation to be predicted; (2) the progestin receptors are induced by estradiol in the MtTF4 tumor despite the fact that the growth of this tumor is inhibited by estradiol; and (3) this work, taken together with previous reports, suggests that the estrogen receptors known to be located in the MtTF4 tumor have some functional properties in common with those tissues or cells whose growth is either stimulated by or insensitive to estradiol.

Down-regulation by 17 beta-estradiol of D2 dopamine receptors in the MtTF4 pituitary tumor

We have recently reported that 17 beta-estradiol (E2) paradoxically inhibits the growth of the rat MtTF4 pituitary tumor which has been induced by estrogen administration. While looking for a molecular explanation for these divergent effects, we observed that E2 treatment resulted in a marked decrease of D2 dopamine receptors (RDA) in the tumor but not in normal pituitary glands. Herein, we characterize further the effect of E2 on RDA concentration in the tumor. Three weeks after a sc injection of a MtTF4 -cell suspension, adult male Fischer rats were treated, or not, either with E2 or with various other steroids. The number of dopamine-binding sites (Bmax) was determined on crude membranes by Scatchard analyses with the dopamine antagonist [3H]spiroperidol. Only one kind of binding site was observed, and the affinity constant for [3H]spiroperidol was not significantly modified by any of the various treatments used. The decrease of Bmax after 8 days of treatment was dose dependent and was maximal with 5-micrograms daily doses of E2. With 10 micrograms E, daily, Bmax decreased exponentially with the duration of the treatment; t 1/2 was approximately 5 days. Treatment for 8 days with progesterone (50 micrograms/day), dihydrotestosterone (50 micrograms/day) or 17 alpha-estradiol (10 micrograms/day), known to be inactive on tumor growth, did not alter Bmax, whereas diethylstilbestrol (10 micrograms/day) or dexamethasone (50 micrograms/day), which inhibit tumor growth, were as efficient as E2 in decreasing Bmax. In conclusion, the number of dopamine-binding sites in the membranes of MtTF4 tumor is decreased by E2 in a time- and dose-dependent fashion. Circumstantial evidence suggests that this decrease is due to a loss of RDA per cell rather than the loss of RDA-bearing cells. The relationship between the control of dopamine-binding sites and cell growth is not clear; however, this model may be useful for the elucidation of the mechanism by which E2 modulates cell membrane properties.