Effect of imipramine treatment on the prolactin response to fenfluramine and placebo challenge in depressed patients

As an index of central serotonergic function, plasma prolactin response to fenfluramine (60 mg orally) and placebo challenge was examined in 10 depressed patients before and after treatment with imipramine 200 mg/day for 3 weeks. Although baseline prolactin levels were not altered by imipramine, the prolactin response to fenfluramine was significantly (P = 0.01) increased compared to the response in the untreated state. The response to placebo was also enhanced but this effect was of lesser magnitude and not statistically significant. These findings complement previous reports and suggest that tricyclic antidepressant treatment enhances serotonergically mediated neuroendocrine responses.

[Ergospirometry and blood lactate data in the assessment of conditioning of soldiers in relation to physical activity within the scope of military service in the Austrian army]

21 soldiers completing their military service in the Austrian army were assessed before and at the finalizing of their basic military training, also to disarmament by spiroergometric and lactate tests according to their physical condition. Soldiers employed in fighting duties improved slightly in physical fitness at commencement of the basic training. By the time they reached disarmament there was significant improvement. The monitoring of administration personal significantly increased their physical fitness after the basic training, nevertheless the physical condition achieved before disarmament relapsed to the same standard as prior to military service. As a conclusion we suggest that the physical inactive group should be kept as small as possible and get an efficient training program in future.

Monolayer culture of adult rat pancreatic islets on extracellular matrix: long term maintenance of differentiated B-cell function

Fragmented islets, obtained by mild overdigestion of the adult rat pancreas with collagenase, readily formed monolayer cultures on dishes coated with extracellular matrix derived from bovine corneal endothelial cells. Contaminating fibroblasts were removed by treatment with sodium ethylmercurithiosalicylate. The cultured islets remained functional for over 6 weeks in primary culture and up to 9 weeks in secondary culture, as indicated by their substantial insulin response to an acute glucose stimulus. Insulin secretion from islet monolayers showed biphasic kinetics. The functional competence of the monolayers was further evaluated by studying glucose-stimulated insulin release in the presence of various modulators of B-cell function. The response to physiological agents such as somatostatin, epinephrine, glucagon, and arginine was retained for at least 4 weeks in culture. The sensitivity to inhibition by somatostatin and epinephrine (ID50 = 10 ng/ml) and that to stimulation by glucagon (ED50 = 3 ng/ml) were similar to or better than those for freshly isolated islets. We have thus obtained a fibroblast-free monolayer culture of pancreatic islets from adult rats containing B-cells that retain normal function for long periods. This experimental system appears ideally suited for studying chronic modulations of islet cell function under controlled in vitro conditions, which can allow the stimulation of normal and diabetic environments.

Polymyxin B is an inhibitor of insulin-induced hypoglycemia in the whole animal model. Studies on the mode of inhibitory action

The cyclic decapeptide, polymyxin B (PMXB), was found to inhibit hypoglycemia in mice receiving exogenous insulin (Amir, S., and Shechter, Y. (1985) Eur. J. Pharmacol. 110, 283-285). In this study, we have extended this observation to rats. Insulin-dependent hypoglycemia in rats is efficiently blocked at a 12:1 molar ratio of PMXB to insulin. This effect is highly specific, as it could not be mimicked by a variety of antibiotics or positively charged substances. Chemical modifications of PMXB have revealed that the ring structure, rather than the tail structure, is important for anti-insulin-like activity. Colistin A, which differs from PMXB by one conservative amino acid substitution in the ring structure, is devoid of this activity. Polymyxin B does not interact with insulin, nor does it alter the rate of insulin absorption and/or degradation, or the ability of insulin to bind to target tissues. This peptide inhibits hypoglycemia by blocking insulin-dependent activation of the hexose transport mechanism, as deduced by in vitro studies. The effect of insulin in stimulating hexose uptake (and subsequent glucose metabolism) in both isolated muscle tissue and adipocytes is blocked with little or no effect on the basal activities of these processes. Colistin A has no significant inhibiting effect. Other insulin-dependent activities, such as inhibition of lipolysis in adipocytes or synthesis of DNA in muscle cells, are not inhibited. It is concluded that PMXB inhibits, in a highly specific manner, the action of insulin in stimulating hexose transport and subsequent glucose metabolism, both in vitro and in the whole animal model.

The antiproliferative effect of interferon and the mitogenic activity of growth factors are independent cell cycle events. Studies with vascular smooth muscle cells and endothelial cells

We studied the antagonistic effects of interferon (IFN) and growth factors in G0/G1-arrested normal bovine aortic smooth muscle cells (SMC) which were stimulated by serum, or purified platelet derived growth factor (PDGF), supplemented with plasma-derived serum (PDS). The growth response, measured as [3H]thymidine incorporation into DNA, was dependent on the concentration of the mitogen. Human IFN alpha, recombinant human IFN alpha 2, or a crude bovine-IFN preparation prepared from virus-infected bovine aortic endothelial cells, inhibited SMC growth induced by either serum or PDGF with PDS. The extent of IFN inhibition was inversely related to the concentration of the mitogenic stimulus. We also investigated whether IFN inhibited the early events in G1 phase, stimulated by the competence factor PDGF, or the progression of the cell into the S phase induced by PDS. The results indicated that IFN inhibited these two stages of the G1 phase independently. In addition, we investigated the antiproliferative effect of IFN on bovine aortic endothelial cells (BAEC), which do not respond to PDGF but to the mitogenic activity of fibroblast growth factor (FGF). IFN inhibited the mitogenic activity of FGF in a dose-dependent manner. The results indicate that the anti-proliferative activity of IFN and the mitogenic effects of different growth factors are independent.

Binding, degradation, and biological activity of insulin in vascular smooth muscle cells

The interaction of insulin with the vascular smooth muscle was studied using cultures derived from the bovine aortic arch. The cultured cells exhibited specific binding of 125I-insulin that was reversible and dependent on pH. Both insulin and insulinlike growth factor (IGF) I competed for 125I-insulin binding; IGF I, however, was less effective than insulin by at least an order of magnitude. Insulin binding was accompanied by internalization and degradation of the hormone in a temperature- and time-dependent manner. Chloroquine and other lysosomotropic agents elevated the internalized insulin and reduced its degradation. Pre-exposure of cell cultures to insulin resulted in downregulation of cell surface receptors. Insulin stimulated alpha-aminoisobutyric acid transport in confluent smooth muscle cells. The maximal response was observed at 100 ng/ml insulin with a half-maximal effect at 10 ng/ml. Sparse, serum-starved smooth muscle cells responded to insulin with a dose-dependent increase in [3H]-thymidine incorporation into DNA. Although the effect was already apparent at 1 ng/ml insulin, it reached near maximal level only at 10,000 ng/ml. IGF I also stimulated DNA synthesis in smooth muscle cells; however, at low concentrations insulin was more efficient in this respect. Human growth hormone was inactive. The data indicate the presence of specific receptors for insulin in bovine aortic smooth muscle cells. These receptors appear to mediate the metabolic activity as well as part of the mitogenic effect of insulin in these cells.

The effect of estradiol on human myelomonocytic cells. 1. Enhancement of colony formation

Cyclic changes were observed in the content of blood monocytes during the menstrual cycle of normal women. Elevated blood monocytes were found during the ovulation period as well as in other conditions which are associated with increased blood estradiol (E2). To understand the possible association between E2 and monocytosis, we analysed the in vitro effect of E2 on the development of myelomonocytic colonies in culture. E2 in physiological concentrations was found to increase the number of colonies developed from peripheral blood mononuclear cells (PBM) of both females and males. The optimal concentration for the augmenting effect on males' PBM was lower than that for females. Mononuclear cells derived from cord blood, which yielded much higher numbers of colonies than adult PBM, also responded to the stimulatory effect of E2. Estrone and estriol were less effective than E2 in adult PBM. In contrast, progesterone, diethylstilbestrol and testosterone did not affect the number of colonies at the range of physiological concentrations tested. The anti-estrogen Tamoxifen did not inhibit the stimulatory effect of E2. The augmenting effect of E2 on monomyelocytic colony formation may explain at least in part the increase in blood monocyte content of women with high E2 as well as other phenomena of macrophage and granulocyte changes associated with the menstrual cycle.

Plasminogen activator and protease inhibitor activities in isolated rat thymocytes

Plasminogen Activator (PA) and its response to glucocorticoids and androgens was studied in viable rat thymocytes in suspension. PA was measured by its ability to convert plasminogen to plasmin, and the formed plasmin determined by cleavage of 14C-labeled globin. Using this functional assay, PA was found to be associated with the outer surface of thymic cells, and only negligible activity recovered from the incubation medium. Rat thymocytes also contain cytoplasmic and nuclear inhibitor(s) of the serine proteases plasmin, trypsin, chymotrypsin and thymic PA. Release of these inhibitors prevented determination of thymic PA activity in presence of lysed cells. The specific activity of PA in thymocytes isolated from adrenalectomized-castrated rats did not differ significantly from the specific activity associated with cells from intact animals. Furthermore, treatment of adrenalectomized-castrated rats with 0.1 mg of dexamethasone/kg for 2 days induced thymic involution without affecting thymic PA activity. These observations suggest that PA activity of thymocytes is not involved in glucocorticoid-mediated thymic involution.

Development of macrophage and granulocyte colonies from human peripheral blood

The presence of macrophage and granulocyte progenitor cells in the human peripheral blood enabled the establishment of colonies from this accessible tissue and obviated the need for bone marrow to achieve this task. We have developed a method of obtaining reproducible growth of macrophage/granulocyte colonies from human peripheral blood. Colonies of macrophages and granulocytes were obtained by plating peripheral blood mononuclear cells (PBM) in methylcellulose containing medium in the presence of medium conditioned by nonstimulated PBM (CM). At early stages of colony growth both macrophage and granulocyte colonies were detected while following 20-25 days in culture all colonies tested revealed monocyte-macrophage morphology. To obtain higher numbers of colonies, we tested different cell sources, different CM preparations and the effect of steroid hormones on colony development. We found that the mononuclear cells obtained from cord blood (CB) or from some patients with inflammatory bowel disease yielded much higher numbers of colonies than PBM from normal individuals. Colony development from these two sources did not depend on an external source of colony stimulating factor (CSF) but was augmented as a result of CSF supplementation. CM obtained from CB mononuclear cells as well as supernatants from some human monoblastic cell lines were similar in their CSF activity to CM from normal PBM and made possible the development of macrophage/granulocyte colonies. Higher numbers of colonies were induced by including physiological concentrations of estradiol in the culture medium, in the absence of external sources of CSF. The system described above enabled the analysis of cloned macrophages and their circulating progenitor cells as well as the assay of different preparations of CSF.

Effect of lysine vasopressin in depressed patients on mood and 24-hour rhythm of growth hormone, cortisol, melatonin and prolactin

Lysine-8-vasopressin (LVP) for 10 days and in doses up to 13.5 LVP units did not significantly alter the Hamilton Depression Rating Scale scores of 12 severely depressed, treatment-resistant patients who were evaluated in a double-blind crossover study. The 24-h rhythms of melatonin, cortisol, growth hormone and prolactin appeared remarkably stable over the course of repeated measurement. LVP administration did not affect these 24-h rhythms.

Insulin binding and degradation in vascular endothelial cells: modulation by cell growth and culture organization

The interaction of insulin with the vascular endothelium and its modulation by cell growth and culture organization was studied using bovine aortic endothelial cells in monolayer cultures. Three types of cultures were investigated: 1) confluent nondividing cultures, organized and differentiated as the in vivo tissue; 2) subconfluent, not yet organized cell cultures, representing proliferating endothelium; and 3) endothelial cell cultures modified to lose their property of contact inhibition, growing in multiple layers. All three types of cultures exhibited specific binding of 125I-insulin to high and low affinity cell surface receptor sites, and were capable of degrading 125I-insulin. Preexposure of the cultures to insulin resulted in a time dependent reduction in the availability of cell surface receptors (down-regulation). Insulin binding per cell was 2.4-fold and 10-fold higher in the subconfluent and modified cultures, respectively, as compared to the contact-inhibited confluent cultures. Similarly, the rate of insulin degradation was higher in the subconfluent and modified cultures (2.3-fold and 20-fold, respectively). Subconfluent cultures were more sensitive than confluent cultures to the down-regulatory effect of insulin. They exhibited a 60% decrease in insulin binding as compared to a 40% decrease in confluent cultures after preexposure to 50 ng/ml insulin. The increase in insulin binding and degradation in growing endothelial cells suggests a role for the hormone in the regulation of endothelial cell growth, e.g. in response to injury. This was further supported by the observation of a dose-dependent stimulation of [3H]thymidine incorporation into sparse, serum-starved endothelial cells by physiological concentrations of the hormone.

Prothymocytes in postirradiation regenerating rat thymuses: a model for studying early stages in T cell differentiation

Prothymocytes were obtained from regenerating thymuses of intrathymic-irradiated, bone marrow-shielded rats. In contrast to cortical thymocytes, which are small nondividing cells containing nuclear TdT, prothymocytes are characterized by their large size, high mitotic activity, lack of natural attachment, absence of PNA-binding capacity, nonexpression of membranal thymic specific antigens, and absence of nuclear TdT. In addition, these cells are capable of responding to the mitogens Con-A and PHA, and are sensitive to in vitro lysis by physiologic concentrations of corticosterone and cortisol. Prothymocytes incubated for 3 days on thymic monolayers differentiated into small lymphocytes expressing cortical thymocyte characteristics. Light and electron microscopy studies demonstrated the infiltration of prothymocytes from the circulation via the thymic blood vessel wall into the perivascular sinuses. Prothymocytes isolated from the thymuses, however, did not exhibit specific "homing" to the thymus when transfused back into the animals. In view of the observed accelerated thymic repopulation in adrenalectomized rats, and the high in vitro glucocorticoid sensitivity of the prothymocytes, it is suggested that thymic homeostasis is regulated by specific effect of adrenocortical hormones on the prothymocyte subset.

Prothymocytes in postirradiation regenerating rat thymuses: a model for studying early stages in T cell differentiation

Prothymocytes were obtained from regenerating thymuses of intrathymic-irradiated, bone marrow-shielded rats. In contrast to cortical thymocytes, which are small nondividing cells containing nuclear TdT, prothymocytes are characterized by their large size, high mitotic activity, lack of natural attachment, absence of PNA-binding capacity, nonexpression of membranal thymic specific antigens, and absence of nuclear TdT. In addition, these cells are capable of responding to the mitogens Con-A and PHA, and are sensitive to in vitro lysis by physiologic concentrations of corticosterone and cortisol. Prothymocytes incubated for 3 days on thymic monolayers differentiated into small lymphocytes expressing cortical thymocyte characteristics. Light and electron microscopy studies demonstrated the infiltration of prothymocytes from the circulation via the thymic blood vessel wall into the perivascular sinuses. Prothymocytes isolated from the thymuses, however, did not exhibit specific "homing" to the thymus when transfused back into the animals. In view of the observed accelerated thymic repopulation in adrenalectomized rats, and the high in vitro glucocorticoid sensitivity of the prothymocytes, it is suggested that thymic homeostasis is regulated by specific effect of adrenocortical hormones on the prothymocyte subset.

Binding, internalization, and degradation of insulin in vascular endothelial cells

The interaction of insulin with the vascular endothelium was studied using bovine aortic endothelial cells in monolayer cultures. Confluent cell cultures exhibited specific binding of 125I-insulin to high- and low-affinity cell surface receptor sites. Binding was reversible, saturable, and accompanied by internalization and degradation of the bound hormone in a temperature- and time-dependent manner. Pre-exposure of the cultures to insulin resulted in a time-dependent reduction in the availability of cell surface receptors (downregulation). It is concluded that the occurrence of reversible insulin binding and of insulin degradation in endothelial cells supports the concept that the vascular endothelium compartment may regulate the level of insulin in the circulation.

Intracellular protease activity in glucocorticoid-mediated thymolysis

The effect of dexamethasone on rat thymus protease activity was tested by following hydrolysis of 14C-labeled globin. Most of the proteolytic activity was located in the cytoplasmic fraction obtained from either whole thymus homogenates or isolated thymic lymphocytes. The protease showed an acid pH optimum and was inhibited by pepstatin and leupeptin. The particulate fractions exhibited only a negligible proteolytic activity throughout the pH range tested. The administration of dexamethasone (9 alpha-fluoro-11 beta, 17,21-trihydroxy-16 alpha-methylpregna-1,4-diene-3,20-dione; 1 mg/kg, ip) to adrenalectomized castrated rats caused a marked increase in the acid protease activity assayed in the cytosol of whole thymus or thymic lymphocytes, with no change in the particular enzyme activity. The sensitivity of the cytosolic enzyme to several protease inhibitors was unchanged after glucocorticoid treatment. Minimal effective dexamethasone doses for thymic involution and increases in protease activity were 0.01 and 0.1 mg/kg BW, respectively. The half-maximal thymolytic effect was obtained at 0.05 mg/kg dexamethasone, while the half-maximal effect on the protease was observed only at 0.30 mg/kg dexamethasone. In contrast, in vitro exposure of isolated thymic lymphocytes to 8.3 X 10(-6) M dexamethasone failed to affect the acid protease activity in the cytosol, but produced a marked time-dependent cytolytic response. These observations suggest that glucocorticoid-induced cytolysis in rat thymic lymphocytes is not mediated by a direct effect of the hormone on endogenous proteases.

Regulation of phosphodiesterase and ornithine decarboxylase by cAMP is cell cycle independent

Cyclic AMP (cAMP) causes growth arrest in G1 and induction of cAMP phosphodiesterase and decrease of ornithine decarboxylase in S49 mouse lymphoma cells. Dibutyryl cAMP treatment of partially synchronized cells causes similar changes in activities of both enzymes, regardless of position in the cell cycle. This suggests that cAMP regulation of these enzymes is not mediated by growth perturbation.

Calcium dependence of ionophore A23187-induced lymphocyte cytotoxicity

Concentrations of the divalent cation ionophore, A23187, optimal for the transformation of human and pig lymphocytes, were cytotoxic to lymphocytes from rats and mice. The biochemical effects associated with A23187-induced cytolysis in rat thymocytes included inhibition of [3H]uridine uptake and incorporation into macromolecules and stimulation of [14C]-alpha-aminoisobutyric acid uptake. The biochemical effects, as well as the reduction in the number of viable cells, were dose dependent and were blocked by the omission of ionic calcium from the incubation medium. At a given ionophore concentration, the magnitude of lysis of thymocytes was proportional to the concentration of Ca2+ in the extracellular medium. Sr2+ was less effective than was Ca2+ in supporting A23187-induced thymocyte lysis. A comparison of the lytic response of lymphocytes of various origins showed that extracellular Ca2+ plays a role in ionophore-induced cytolysis in thymocytes and lymph node lymphocytes but not in mouse lymphosarcoma P1798 cells.

Further studies on the role of calcium in glucocorticoid-induced lymphocytolysis

In a previous study comparing the effects of triamcinolone acetonide (TA) and a divalent cation ionophore (A23187) on rat thymocytes, we proposed an important contributory role for Ca2+ in glucocorticoid-induced cytolysis. The plausibility of this hypothesis was tested further in thymic lymphocytes (thymocytes) and lymph node lymphocytes (LN-lymphocytes). Thymocytes incubated in a Ca2+-containing medium responded to TA or A23187 with a concentration-dependent decrease in the number of viable cells. TA-induced cytolysis was reduced in Ca-free medium and was equally supported by Ca2+ and Sr2+, but not by Ba2+. A23187-induced cytolysis was supported by Ca2+ greater than Sr2+, but not by Ba2+. Thymocytes were also lysed by increasing concentrations of Ca2+ even in the absence of TA and A23187. LN-Lymphocytes, however, were less sensitive to the cytotoxic effects of Ca2+ under the same conditions. In the presence of Ca2+, thymocytes were lysed to a greater extent than LN-lymphocytes by TA, whereas the sensitivities to A23187-induced cytolysis were the same in both populations. Omission of Ca2+ from the incubation medium inhibited the cytolytic response to TA only in thymocytes. In contrast, A23187-induced cytolysis was impaired in Ca-free medium in both thymocytes and LN-lymphocytes. These observations confirm the previous findings on Ca2+ dependence of glucocorticoid-induced cytolysis in thymocytes. This pathway, however, may not be involved in glucocorticoid-induced cytolysis of LN-lymphocytes. Thus, a more basic and as yet undefined mechanism probably mediates the lymphocytolytic process.

Calcium dependence of glucocorticoid-induced lymphocytolysis

A potent glucocorticoid, triamcinolone acetonide (9alpha-fluoro-11beta, 16alpha,17alpha, 21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide) and a divalent cation ionophore (A23187) had similar effects in vitro on [3H]uridine uptake and on lysis of thymocytes of adrenalectomized rats. Removal of Ca2+ from the medium blunted the cytolytic action of triamcinolone acetonide and virtually eliminated that of A23187. In Ca2+-free media, treatment of the thymocytes for 15 hr with triamcinolone acetonide or A23187 followed by re-introduction of Ca2+ resulted in a rapid decrease in cell survival. Based on the time courses of the responses, triamcinolone acetonide and A23187 evoked proportionate increases in 45Ca uptake and lysis of the thymocytes. These findings implicate enhanced Ca2+ uptake in glucocorticoid-dependent lymphocytolysis.

Interaction of glucocorticoid hormones with rat skeletal muscle: catabolic effects and hormone binding

The mechanism of action of glucocorticoid hormones on rat skeletal muscle was studied by following their effect on muscle weight, free amino acid content, activity of amino acid-metabolizing enzymes, and binding to cytoplasmic receptor proteins. A significant reduction of gastrocnemius muscle and body weight occurred following administration of cortisol, triamcinolone diacetate, and triamcinolone acetonide to adrenalectomized rats. Treatment with triamcinolone diacetate also reduced the level of several free amino acids and enhanced the activity of a myofibrillar protease in skeletal muscle. The hormone had, however, no effect on the activity of various enzymes involved in amino acid catabolism in muscle. In nephrosis, another condition of muscle wasting, the level of several muscle amino acids were also reduced to a lesser extent. Cortisol and triamcinolone acetonide, both of which induce muscle wasting, were found to bind to two distinct cytoplasmic proteins in muscle. Binding of the labeled hormones was followed at 0 C and could be observed in presence of a 1000-fold excess of the catabolically inactive steroid epicortisol. Binding of 3H-triamcinolone acetonide. In vitro competition experiments further suggest a correlation between steroid binding to the 3H-dexamethasone or 3H-triamcinolone acetonide site and their potency to induce muscle catabolism. It is concluded that skeletal muscle is a direct target organ for glucocorticoids, and that muscle responsiveness involves binding of the active hormones to cytoplasmic receptor sites.

Cortisol binding in rat skeletal muscle

Studies of the reversible binding of [3H]cortisol by rat gastrocnemius muscle cytoplasm in vitro reveal specific binding in the 27,000 times g supernatant fraction at 0 degrees. The [3H]cortisol-binding molecule had an apparant Kd value of 1.7 times 10-7 M and the number of binding sites was 0.99 pmol per mg of cytosol protein. Only a single class of [3H]cortisol-binding sites could be detected, whose protein nature was suggested by its susceptibility to nagarse. The [3H]cortisol-protein complex sedimented at similar to 4 S in a 5 to 20% sucrose gradient either in the presence or absence of 0.3 M KCl. Binding increased more than 2-fold in adrenalectomized rats and was markedly reduced in the muscle of rats pretreated with cortisol. In contrast to the binding of [3H]dexamethasone and [3H]triamcinolone acetonide to receptor proteins in muscle, no correlation was found between the ability of various steroids to complete wtth [3H]cortisol binding and their glucocorticoid potency: [3H]cortisol binding was inhibited by a 1000-fold higher concentration of unlabeled cortisol and progesterone but not by dexamethasone or triamcinolone acetonide. It is therefore suggested that the [3H]cortisol-binding reaction is not directly involved in the biological effects of all potent glucocorticoids in skeletal muscle. The [3H]cortisol-binding protein in muscle cytosol could not be unequivocally distinguished from rat plasma corticosteroid-binding globulin, because both had similar steroid specificity and temperature stability, were not markedly affected by--SH reagents, and displayed similar sedimentation properties.