Prominently decreased hippocampal neurogenesis in a spontaneous model of type 1 diabetes, the nonobese diabetic mouse.

In human diabetes, degenerative and functional disorders of the central nervous system, including depression, are common findings. Defective dentate gyrus (DG) neurogenesis is associated with affective-related disorders and depression. We previously demonstrated reduced DG neurogenesis in a pharmacological type 1 diabetes model, the streptozotocin (STZ)-treated mouse. Here, we explored DG neurogenesis in a spontaneous T1D model, the nonobese diabetic (NOD) mouse, at prediabetic and diabetic stages. Cell proliferation was assessed in the DG of 5, 8 and 12-week-old control C57BL/6 and BALB/c strains and NOD mice, killed 2 h after bromodeoxyuridine (BrdU) administration. Survival of the newly generated cells was studied in 15-week-old animals that were killed 21 days after BrdU injection. The number of proliferative BrdU-positive cells in the DG was, regardless of age, constantly and significantly lower in NOD than in control strains, showing the presence of hippocampal alterations far before clinical diabetes onset in NOD mice. Diabetes also strongly decreased cell survival in NOD DG. However, cell phenotype proportion, as assessed by co-localization with neuronal or glial markers and confocal microscopy, was not modified. Hippocampal neurogenesis is strongly diminished in the spontaneous NOD model, like in the STZ model. Notably, NOD hippocampal DG cell proliferation defect takes place during the prediabetic stage. Whether this early alteration might result, in this autoimmune strain, from hypothalamo-pituitary adrenal axis alterations and/or ongoing brain inflammatory process sharing many characteristics of aging is discussed and deserves further investigation.

Gene therapy for long-term restoration of circulating thymulin in thymectomized mice and rats.

Thymulin is a thymic peptide possessing hypophysiotropic activity and antiinflammatory effects in the brain. We constructed a synthetic DNA sequence encoding met-FTS, a biologically active analog of thymulin, and subsequently cloned it into different expression vectors. A sequence optimized for expression of met-FTS in rodents, 5'-ATGCAGGCCAAGTCGCAGGGGGGGTCGAACTAGTAG-3', was cloned in the mammalian expression vectors pCDNA3.1(+) and phMGFP (which expresses the Monster Green Fluorescent Protein), thus obtaining pcDNA3.1-metFTS and p-metFTS-hMGFP, which express met-FTS and the fluorescent fusion protein metFTS-hMGFP, respectively. The synthetic sequence was also used to construct the adenoviral vector RAd-metFTS, which expresses met-FTS. Transfection of HEK293 and BHK cells with pcDNA3.1-metFTS (experimental groups) or pcDNA3.1 (control), led to high levels of thymulin bioactivity (>600 versus <0.1 pg/ml in experimental and control supernatants, respectively). Transfection of HEK293 and BHK cells with pmetFTS-hMGFP revealed a cytoplasmic and nuclear distribution of the fluorescent fusion protein. A single intramuscular (i.m.) injection (10(7) plaque forming units (PFU)/mouse or 10(8) PFU/rat) of RAd-metFTS in thymectomized animals (nondetectable serum thymulin) restored serum thymulin levels for at least 110 and 130 days post-injection in mice and rats, respectively. We conclude that RAd-metFTS constitutes a suitable biotechnological tool for the implementation of thymulin gene therapy in animal models of chronic brain inflammation.

Fibronectin receptor defects in NOD mouse leucocytes: possible consequences for type 1 diabetes.

Integrins of the very late antigen (VLA) family mediate leucocyte traffic to lymphoid organs under physiological conditions and in chronic inflammatory situations such as autoimmunity. Accordingly, the current thinking is of a positive correlation between VLA expression and capability of the generation of autoimmunity. Herein we discuss recent findings on the defective expression of integrin-type fibronectin receptors alpha4beta1 (VLA-4) and alpha5beta1 (VLA-5) in the non-obese diabetic (NOD) mouse, a murine model of autoimmune insulin-dependent diabetes mellitus. As compared with normal animals, NOD thymocytes (including the CD4+CD25+ regulatory T cells) exhibit a decrease in the membrane expression of alpha5beta1, resulting in a functional impairment of fibronectin-mediated interactions, including cell migration. Interestingly, thymocytes that are trapped within the giant perivascular spaces seen in NOD thymus are consistently alpha5beta1 negative, suggesting that the progressive arrest of mature cells can be related to the alpha5beta1 defect. Peripheral T cells also exhibit decreased alpha5beta1 membrane expression and impaired fibronectin-driven migration. Additionally, we observed a defect in alpha4beta1 fibronectin receptor expression in NOD macrophages. Peritoneal, bone marrow-derived-precursor, as well as thymic macrophages of NOD mice showed an impaired upregulation of alpha4-integrin chain expression, dependent on the level of macrophage maturation. Overall these data lead to the notion that NOD leucocytes bear distinct fibronectin receptor-mediated cell migration defects, which may be involved in the pathogenesis and/or pathophysiology of the autoimmune events seen in NOD mice. Further studies will be helpful to define whether or not this concept can be applied for other autoimmune diseases.

A thymulin analogue peptide with powerful inhibitory effects on pain of neurogenic origin.

The effects of a synthetic peptide analog of thymulin (PAT) were tested on nociceptive behavior in two animal models for peripheral mononeuropathy and in another two models for capsaicin-induced hyperalgesia. Treatment with PAT (0.25-25 microg/rat, i.p.) produced significant reduction of the mechanical allodynia and heat hyperalgesia in rats subjected to either chronic constriction injury (CCI) or spared nerve injury (SNI) models for mononeuropathy. Cold allodynia was moderately reduced in the CCI model. The inhibition of neuropathic manifestations peaked at 1-2 h post-treatment and disappeared in 3-4 h. Daily treatment with PAT, however, produced progressive attenuation of all neuropathic manifestations in the SNI model. On the other hand, pretreatment with similar doses of PAT produced dose-dependent reduction of the hyperalgesia induced by intraplantar injection of capsaicin (10 microg in 50 microl). The highest dose of PAT (50 microg) produced significant reduction of abdominal aversive behavior induced by i.p injection of capsaicin (20 microg in 100 microl). Compared with the effects of treatment with morphine or meloxicam (injected at single doses known to produce analgesia), PAT exerted equal or stronger inhibitory effects on neuropathic manifestations. The reported results suggest a possible direct action of PAT on afferent nerve fibers but its mechanisms remain to be determined.

Zinc and immune function.

It is well recognized that zinc is an essential trace element, influencing growth and affecting the development and integrity of the immune system. Research has begun to clarify the molecular mechanisms underlying the action of zinc on the immune function. It is clear that this trace element has a broad impact on key immunity mediators, such as enzymes, thymic peptides and cytokines, explaining the paramount importance of zinc's status on the regulation of lymphoid cell activation, proliferation and apoptosis. Ongoing and future studies regarding the immunological status of zinc deficiency 'at risk' groups could lead to public health interventions with nutritional doses of zinc supplements to prevent alteration of the immune system and improve resistance to infections.

The thymus gland: a target organ for growth hormone.

Increasing evidence has placed hormones and neuropeptides among potent immunomodulators, in both health and disease. Herein, we focus on the effects of growth hormone (GH) upon the thymus. Exogenous GH enhances thymic microenvironmental cell-derived secretory products such as cytokines and thymic hormones. Moreover, GH increases thymic epithelial cell (TEC) proliferation in vitro, and exhibits a synergistic effect with anti-CD3 in stimulating thymocyte proliferation, which is in keeping with the data showing that transgenic mice overexpressing GH or GH-releasing hormone exhibit overgrowth of the thymus. GH also influences thymocyte traffic: it increases human T-cell progenitor engraftment into the thymus; augments TEC/thymocyte adhesion and the traffic of thymocytes in the lymphoepithelial complexes, the thymic nurse cells; modulates in vivo the homing of recent thymic emigrants, enhancing the numbers of fluroscein isothiocyanate (FITC)+ cells in the lymph nodes and diminishing them in the spleen. In keeping with the effects of GH upon thymic cells is the detection of GH receptors in both TEC and thymocytes. Additionally, data indicate that insulin-like growth factor (IGF)-1 is involved in several effects of GH in the thymus, including the modulation of thymulin secretion, TEC proliferation as well as thymocyte/TEC adhesion. This is in keeping with the demonstration of IGF-1 production and expression of IGF-1 by TEC and thymocytes. Also, it should be envisioned as an intrathymic circuitry, involving not only IGF-1, but also GH itself, as intrathymic GH expression is seen both in TEC and in thymocytes, and that thymocyte-derived GH could enhance thymocyte proliferation. Finally, the possibility that GH improve thymic functions, including thymocyte proliferation and migration, places this molecule as a potential therapeutic adjuvant in immunodeficiency conditions associated with thymocyte decrease and loss of peripheral T cells.

Pancreatic hormone and glutamic acid decarboxylase expression in the mouse thymus: a real-time PCR study.

We devised a real-time RT-PCR method for the quantification of preproinsulin 1 and 2, proglucagon, prosomatostatin, and GAD 65 and 67 mRNAs in the thymus, using specific primers and internal probes. Corresponding standard cRNA synthesis and normalization to 18S ribosomal RNA allowed direct quantification. Then, during the first month of life, the expression of each substance of interest was measured in the thymus of NOD mice (a spontaneous model of type 1 diabetes), C57BL/6, BALB/c and lymphocyte-deficient mice (NODscid, NODrag, BALB/cscid and C57BL/6rag). In all mouse thymuses, preproinsulin 1 and GAD 65 were undetectable, preproinsulin 2 and proglucagon showed low expression, whereas that of GAD 67 and somatostatin were high. In 7-day-old mice, GAD 67 and prosomatostatin thymic expressions were lower in NOD than in C57BL/6, and at the same age, the scid mutation but not the rag mutation induced higher expression of all investigated genes compared to control mice. In conclusion, our data allowed the quantification of the expression of pancreatic factors in the mouse thymus. Investigations are underway to quantify, at the cellular level, i.e., in thymic dendritic/macrophage cells, the RNA expression of potential autoantigens, such as preproinsulin 2 and GAD 67.

Altered functional responses with preserved morphology of gonadotrophic cells in congenitally athymic mice.

Neonatal thymectomy or congenital absence of the thymus induces severe reproductive deficiencies in female mice, which are associated with reduced levels of circulating and pituitary gonadotropins. In contrast, the reproductive function is well preserved in nude males. It was therefore of interest to assess gonadotrophic cell morphology and function in congenitally athymic male mice. Circulating gonadotropins were measured under basal and stressful conditions, taking as a reference their haired counterparts. Adult normal (+/+), heterozygous nude (nu/+), and homozygous (nu/nu) CD-1 mice were subjected to 1-h immobilization stress. Serum levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were assessed by RIA at 0, 30, and 60 min poststress. Athymic animals showed significantly lower basal levels of serum LH and FSH than their heterozygous littermates. Immunohistochemical assessment of LH and FSH cell populations revealed a normal morphology and cell number in the athymic animals compared to their normal littermates. Immobilization stress induced a significant reduction in gonadotrophin levels, particularly LH, in normal mice but had only a weak effect in athymic animals. It is concluded that congenital athymia in the adult male mouse is associated with decreased basal levels of serum LH and FSH, in the presence of a normal gonadotroph number and morphology. The anomalous responses of athymic mice to stress do not appear to be due to primary hypopituitarism but, rather, to an altered modulation of pituitary hormone secretion. .

Neuroendocrine control of thymus physiology.

The thymus gland is a central lymphoid organ in which bone marrow-derived T cell precursors undergo differentiation, eventually leading to migration of positively selected thymocytes to the peripheral lymphoid organs. This differentiation occurs along with cell migration in the context of the thymic microenvironment, formed of epithelial cells, macrophages, dendritic cells, fibroblasts, and extracellular matrix components. Various interactions occurring between microenvironmental cells and differentiating thymocytes are under neuroendocrine control. In this review, we summarize data showing that thymus physiology is pleiotropically influenced by hormones and neuropeptides. These molecules modulate the expression of major histocompatibility complex gene products by microenvironmental cells and the extracellular matrix-mediated interactions, leading to enhanced thymocyte adhesion to thymic epithelial cells. Cytokine production and thymic endocrine function (herein exemplified by thymulin production) are also hormonally controlled, and, interestingly in this latter case, a bidirectional circuitry seems to exist since thymic-derived peptides also modulate hormonal production. In addition to their role in thymic cell proliferation and apoptosis, hormones and neuropeptides also modulate intrathymic T cell differentiation, influencing the generation of the T cell repertoire. Finally, neuroendocrine control of the thymus appears extremely complex, with possible influence of biological circuitry involving the intrathymic production of a variety of hormones and neuropeptides and the expression of their respective receptors by thymic cells.

CD11c+ eosinophils in the murine thymus: developmental regulation and recruitment upon MHC class I-restricted thymocyte deletion.

Eosinophils are bone marrow-derived cells released into the circulation during hypersensitivity reactions and parasitic infections. Under normal conditions most eosinophils are tissue bound, where their physiologic role is unclear. During in situ analysis of the thymic microenvironment for CD11c+ dendritic cell subpopulations (APC critical in the process of thymic negative selection) a discrete population of CD11b/CD11c double-positive cells concentrated in the cortico-medullary region of young mice was detected. Thymic CD11c+ cells were isolated, and the CD11b+ subpopulation (CD44high, class IIlow, CD11cint) was identified as mature eosinophils based on: scatter characteristics, major basic protein mRNA expression, and eosinophilic granules. They are hypodense, release high levels of superoxide anion, and express CD25, CD69, and mRNA for IL-4 and IL-13, but not GM-CSF or IL-5, suggesting a distinct state of activation. Thymic eosinophils are preferentially recruited during the neonatal period; absolute numbers increased 10-fold between 7-14 days to reach parity with dendritic cells before diminishing. In a model of acute negative selection, eosinophil numbers were increased 2-fold 6 h after cognate peptide injection into MHC class I-restricted female H-Y TCR transgenic mice. In both peptide-treated female and negatively selecting male H-Y TCR mice, clusters of apoptotic bodies were associated with eosinophils throughout the thymus. Our data demonstrate a temporal and spatial association between eosinophil recruitment and class I-restricted selection in the thymus, suggesting an immunomodulatory role for eosinophils under nonpathological conditions.

Pentostatin (Nipent) in T-cell malignancies. Leukemia Cooperative Group and the European Organization for Research and Treatment of Cancer.

Within this phase II trial of the European Organization for Research and Treatment of Cancer, we have investigated the safety and efficacy of pentostatin (Nipent; SuperGen, San Ramon, CA) in refractory lymphoid malignancies. Pentostatin was administered at a dosage of 4 mg/m2 every week for the first 3 weeks, then every 14 days, followed by maintenance therapy of 4 mg/m2 monthly for a maximum of 6 months. We have previously reported the results in T- and B-cell prolymphocytic leukemia, B-cell chronic lymphocytic leukemia, and hairy cell leukemia This report focuses on the outcome in T-cell malignancies: T-cell chronic lymphocytic leukemia, Sézary syndrome, mycosis fungoides, and T-zone lymphoma. Of 92 patients with these diagnoses enrolled, 76 were evaluable for response and toxicity, ie, 25 of 28 with T-cell chronic lymphocytic leukemia, 21 of 26 with Sézary syndrome, 22 of 26 with mycosis fungoides, and eight of 12 with T-zone lymphoma. All patients had progressive and advanced disease. Sixteen patients (21%) died during the first 9 weeks of treatment: 12 of progressive disease, two of infectious complications thought to be unrelated to treatment, one of myocardial infarction, and one of renal failure related to administration of intravenous contrast. Major toxicity (grades 3 and 4) included infection in 10.5% of patients, nausea/vomiting in 5%, and hepatotoxicity in 3%. One patient (1.3%) achieved a complete remission and 15 (19.7%) a partial remission. Better results were achieved in patients with Sézary syndrome or mycosis fungoides (complete remission + partial remission = 33.4% and 22.7%, respectively) than in patients with T-cell chronic lymphocytic leukemia (8%) or T-zone lymphoma (25%). We conclude that pentostatin is active in low-grade T-cell malignancies. Toxicities are mild to moderate at the dose schedule administered. Severe hematologic toxicity has not been observed. The efficacy at the present dose level is moderate. A higher dose might be necessary for some T-cell malignancies.

The role of cytokines and prostaglandin-E(2) in thymulin induced hyperalgesia.

We have recently reported that intraperitoneal (i.p.) injection of thymulin at low doses (50 ng) resulted in thermal and mechanical hyperalgesia and upregulation of the level of interleukin-1beta in the liver. In this study, we demonstrate that such injections of thymulin result in a significant elevation in the levels of TNF-alpha (P<0.01), NGF (P<0.01) and PGE(2) (P<0.01) in the liver of the treated rats, in addition to the increase in the levels of IL-1beta. Pretreatment with specific antagonists to each of these factors (polyclonal anti-TNF-alpha, anti-NGF antiserum and IL-1 receptor antagonist) did not result in the abolition of the hyperalgesia as assessed by the paw pressure, hot plate, paw immersion and tail flick tests. However, pretreatment with a combination of the above antagonist and antisera almost completely prevented thymulin-induced hyperalgesia. The cyclooxygenase inhibitor, meloxicam, reversed in a dose dependent manner (0.2, 0.4 and 2 mg/kg) thymulin effects as assessed by the different pain tests. It also abolished the thymulin-induced increase in the level of cytokines and NGF in the liver. Our results indicate that PGE(2) could be the key mediator of the hyperalgesic action of thymulin and the observed upregulation of proinflammatory cytokines and NGF.

Studies on the gonadotropin-releasing activity of thymulin: changes with age.

We assessed the ability of thymulin, a zinc-dependent nonapeptide produced by the thymic epithelial cells, to influence the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from dispersed anterior pituitary (AP) cells from young, adult, and senescent female rats. Perifusion of young and senescent AP cells with thymulin doses of 10(-6) to 10(-5) M gave a significant stimulatory response for LH but not FSH. Gonadotropin release was always lower in the senescent cells. AP cells from both age groups incubated with 10(-8) to 10(-3) M thymulin showed a time- and dose-dependent response for both gonadotropins, with a maximal stimulation at 10(-7) M. Preincubation of thymulin with an antithymulin serum completely quenched the secretagogue activity of the hormone. Coincubation of thymulin with the secretagogue gonadotropin-releasing hormone (GnRH) revealed a synergistic effect on LH release and an additive effect on the release of FSH. The calcium chelator EGTA blocked the gonadotropin-releasing activity of thymulin in AP cells. The cAMP enhancers, caffeine, NaF, and forskolin significantly increased the thymulin-stimulated release of gonadotropins. The inositol phosphate enhancer LiCl potentiated the action of thymulin on gonadotropins. It is concluded that the gonadotropin-releasing activity documented here for thymulin is an age- and receptor-dependent effect mediated in part by calcium, cAMP, and inositol phosphates.

Is there a role for growth hormone upon intrathymic T-cell migration?

Intrathymic T-cell differentiation is essentially driven by the thymic microenvironment, a tridimensional network formed by thymic epithelial cells and to a lesser extent, dendritic cells, macrophages, fibroblasts, and extracellular matrix components. Thymocyte migration throughout the thymus is partially dependent on extracellular-matrix (ECM)-mediated interactions. Herein we investigated the putative role of growth hormone (GH) upon events related to intrathymic T-cell migration. We demonstrated that GH upregulates the expression of ECM ligands and receptors in distinct preparations of cultured thymic epithelial cells TECs). We also showed that adhesion of thymocytes to thymic epithelial cells was significantly increased by GH treatment, an effect that could be consistently abrogated when TECs were treated to antifibronectin, anti-VLA5, antilaminin, or anti-VLA6 antibodies before addition of thymocytes to the cultures. We also studied thymic nurse cells (TNCs), lymphoepithelial complexes that can be isolated ex vivo from the thymus. In this system, we had previously demonstrated that ECM ligands and receptors control both inward and outward thymocyte traffic. We then showed that GH enhances thymocyte release from TNCs, as well as the reconstitution of these lymphoepithelial complexes. Lastly, we evaluated the in vivo influence of GH on thymocyte exit. This was done by means of intrathymic injection of GH plus fluorescein isothiocyanate (FITC), and further analysis of recent thymic emigrants (FITC+ cells) in peripheral lymphoid organs, as defined by CD4/CD8-based cytofluorometric phenotyping. The proportions of FITC+ T cells appeared augmented in lymph nodes in GH-treated mice, as compared to controls. Taken together, these data indicate that GH stimulates intrathymic T-cell traffic, an effect that is at least partially mediated by extracellular matrix-mediated interactions.

Role of thymic peptides as transmitters between the neuroendocrine and immune systems.

Thymic peptides, a heterogenous family of polypeptidic hormones synthesized within the thymus, not only exert important regulatory effects within both the immune and neuroendocrine systems but are also themselves subject to control by hormones derived from the hypothalamic-pituitary-adrenal axis (HPA) and other endocrine glands. Regarding thymic hormonal function, thymulin production is up-regulated by several hormones, including prolactin, growth hormone and thyroid hormones. Other aspects of the physiology of thymic epithelial cells can also be modulated by hormones and neuropeptides, particularly cytokeratin expression, cell growth and production of extracellular matrix proteins, thus characterizing the pleiotrophic action of these molecules on the thymic epithelium. Conversely, thymic-derived peptides also regulate hormone release from the HPA axis and may act directly on target endocrine glands of this axis, modulating gonadal tissues. In addition, it has recently been shown that thymulin can modulate some peripheral nervous sensory functions, including those related to sensitivity to pain. According to the dose given, thymulin induces or reduces hyperalgesia related to both mechanical and thermal nociceptors and thus represents an important interface between the immune, endocrine and nervous systems.

Growth hormone (GH) and prolactin receptors in human peripheral blood mononuclear cells: relation with age and GH-binding protein.

GH receptors (GHRs) and PRL receptors (PRLRs) were studied in human peripheral blood mononuclear cells (PBMC) using flow cytometry, biotinylated anti-GH receptor monoclonal antibody 10B8, and biotinylated human PRL. Variations of GHR and PRLR expression and the relationship of plasma GHBP and GH receptor in PBMC subsets were examined as a function of age and sex. By double immunofluorescence staining, we show that about 30% of total cells express GH receptors, with a low expression in T cells, whereas almost all B cells and monocytes are GH receptor positive. Four age groups were defined among the 64 normal volunteers, aged 12 to 85 yr, who were included in the study. The percentage of PBMC expressing GH receptors is significantly lower in group 2 (20-40 yr) than in group 1 (12-20 yr) and group 4 (>60 yr). In T cells, monocytes and B cells, no significant changes are detected in either the percentage of GH receptor positive cells or in the GH receptor level per cell. The level of PRLRs expressed in PBMC is significantly higher in age group 2 than in age group 4. A negative correlation is observed between plasma GHBP and the percentage of PBMC expressing GH receptors. These results suggest that regulation of GH receptors in lymphocytes and in other target cells could be different.

Thymic expression of the pancreatic endocrine hormones.

The thymus plays a central role in the selection of T lymphocytes that are tolerant to 'self' antigens and responsive to foreign pathogens. We and others have reported the expression of the pancreatic endocrine hormones, preproinsulin, proglucagon, prosomatostatin and propancreatic polypeptide in the human and mouse thymus. While mRNA expression is very low there is evidence for the presence of the translated product. In addition, we have investigated the cell types responsible for expression. In the thymus, hormone expression is enriched in the antigen-presenting cell population. Interestingly, while proglucagon, prosomatostatin and propancreatic polypeptide appear to be expressed in a macrophage population, preproinsulin expression was restricted to dendritic cells which are more potent antigen-presenting cells. The functional significance of the endogenous expression of insulin in the thymus has been indirectly investigated using transgenic models in which the transgene is introduced by the rat insulin promoter. The data suggest that thymic expression of the transgene is critical in the induction of T-cell tolerance to the transgene in the periphery. Taken together, the evidence suggests that the low-level pancreatic hormone expression in the thymus may be involved in central tolerance to proteins of restricted expression.

Immunoneuroendocrine connectivity: the paradigm of the thymus-hypothalamus/pituitary axis.

It is now largely established that the immune and neuroendocrine systems cross-talk by using similar ligands and receptors. In this context, the thymus-hypothalamus/pituitary axis can be regarded as a paradigm of connectivity in both normal and pathological conditions. For example, cytokines and thymic hormones modulate hypothalamic-pituitary functions: (a) interleukin (IL)-1 seems to upregulate the production of corticotropin-releasing factor and by adrenocorticotropin by hypothalamic neurons and pituitary cells, respectively; (b) thymulin enhances LH secretion. Conversely, a great deal of data strongly indicate that the hypothalamic-pituitary axis plays a role in the control of thymus physiology. Growth hormone (GH) for example, enhances thymulin secretion by thymic epithelial cells (TEC), both in vivo and in vitro, also increasing extracellular matrix-mediated TEC/thymocyte interactions. Additionally, gap junction-mediated cell coupling among TEC is upregulated by ACTH. In a second vein, it was shown that GH injections in aging mice increased total thymocyte numbers and the percentage of CD3-bearing cells, as well concanavalin-A mitogenic response and IL-6 production. In addition to mutual effects, thymus-pituitary similarities for cytokine and hormone production have been demonstrated. Cytokines such as IL-1, IL-2, IL-6, interferon-gamma, transforming growth factor-beta and others can be produced by hypothalamic and/or pituitary cells. Conversely, hormones including GH, PRL, LH, oxytocin, vasopressin and somatostatin can be produced intrathymically. Moreover, receptors for various cytokines and hormones are expressed in both the thymus and the hypothalamus/pituitary axis. Lastly, it is noteworthy that a thymus-pituitary connectivity can also be seen under pathological situations. In this regard, an altered HPA axis has been reported in AIDS, human falciparum malaria and murine rabies, that also show a severe thymic atrophy.

Growth hormone-releasing activity of thymulin on pituitary somatotropes is age dependent.

Thymulin is a Zn-bound nonapeptide produced by the thymic epithelial cells (TEC) whose secretion is modulated by growth hormone (GH), among others. We assessed the ability of thymulin to influence the release of GH from dispersed anterior pituitary (AP) cells from young, middle-aged and senescent Sprague-Dawley female rats. Perifused and incubated AP cells were used in different sets of experiments and GH release was measured by RIA. Perifusion of young and senescent AP cells with thymulin doses, ranging from 10(-8) to 10(-5) M, gave a logarithmic dose-response pattern of GH. Supernatants from TEC lines also showed GH secretagogue activity. The GH release was always lower in the senescent cells. AP cells incubated with 10(-8)-10(-3) M thymulin showed a time- and dose-dependent response, the latter being bell-shaped with a maximum at 10(-7) M thymulin. Preincubation of thymulin with an antithymulin serum completely quenched the secretagogue activity of the hormone. Coincubation of thymulin with GHRH revealed a semiadditive release of GH in young and middle-aged AP cells and an additive effect in senescent cells. In middle-aged AP cells, the synthetic GH secretagogue GHRP-6 showed a synergistic effect with thymulin on GH release. The calcium chelator EGTA, but not the calcium ionophore A23187, blocked the GH-releasing activity of thymulin in AP cells. The cAMP enhancers, caffeine, NaF and forskolin significantly increased the thymulin-stimulated release of GH while trifluoperazine, a protein kinase C inhibitor, had no effect. The inositol phosphate enhancer LiCl potentiated the action of thymulin on GH release. The data suggest that the GH-releasing activity of thymulin is receptor-mediated and involves calcium, cAMP and inositol phosphates. In addition, senescence appears to impair somatotrope responsiveness to thymulin.

Centre effect on treatment outcome for patients with untreated acute myelogenous leukaemia? An analysis of the AML 8A Study of the Leukemia Cooperative Group of the EORTC and GIMEMA. European Organization for Research and Treatment of Cancer (EORTC) Leukemia Cooperative Group and the Gruppo Italiano Malattie Ematologiche Maligne dell'Adulto (GIMEMA).

In the AML 8A study patients were treated with remission-induction therapy followed by one consolidation course. Patients in complete remission (CR) were randomised between autologous bone marrow transplantation (ABMT) and a second intensive consolidation course, except for those with a histocompatible sibling donor, who received allogeneic bone marrow transplantation (alloBMT). This analysis was performed to determine whether centres which only performed induction and consolidation therapy, achieved similar results as centres who also performed transplantation. 542/676 (80%) from transplantation centres and 150/194 (77%) from referring centres achieved CR, with an early death rate of 5% and 11%, respectively (P = 0.01). 66% of patients with a donor from transplantation centres received alloBMT in first CR compared with 57% from referring centres (P = 0.2). Transplantation centres randomised 64% of patients without a donor, referring centres 47% (P = 0.04). The full protocol treatment was completed by 275/542 (51%) and 61/150 (41%) patients, respectively (P = 0.04). The overall survival rate at 6 years from diagnosis was 34% and 36%, respectively (P = 0.9). In conclusion, the type of centre did not appear to have an influence on overall survival. The feasibility of the study was acceptable for both types of centres. The referring centres applied more selection for transplantation. Despite a more intensive second-line treatment at transplantation centres, the overall outcome remained similar to that of referring centres.