Hippocampal histamine receptors and conflictive exploration in the rat: studies using the elevated asymmetric plus-maze

The possible role of histamine receptors in the hippocampal formation on the exploratory motivation and emotionality of the rat was studied. An elevated asymmetric plus-maze composed of 4 different arms (no walls, single high wall, high and low walls and two high walls) arranged at 90o angles was used. The exploration score, considered to be an index of exploratory motivation, and the permanency score, considered to be an index of emotionality (anxiety), were determined. Histamine was administered locally into the ventral hippocampus at three different doses (9, 45 and 90 nmol). Another group of rats was also microinjected with 45 nmol of pyrilamine (a histamine H1 receptor antagonist) or ranitidine (a histamine H2 receptor antagonist) in addition to 9 nmol of histamine in order to identify the possible type of histamine receptor involved. Histamine administration significantly inhibited the exploration score and increased the permanency score at the doses of 9 and 45 nmol in two of four arms. These effects were completely blocked by the administration of either histamine receptor antagonist. The present results suggest that in the hippocampal formation histamine inhibits exploratory motivation and decreases emotionality by activating both types of histamine receptors. Also, the elevated asymmetric plus-maze appears to be a suitable technique to quantify exploration and possibly" anxiety"

Aversive stimulation during the stress-hyporesponsive period does not affect the number of corticotroph cells in neonatal male rats

Immunohistochemistry was used to evaluate the effects of neonatal handling and aversive stimulation during the first 10 days of life on the number of corticotrophs in the anterior lobe of the pituitary of 11-day-old male Wistar rats. Since adult rats handled during infancy respond with reduced corticosterone secretion in response to stressors and with less behavior inhibition in novel environments, we assumed that neonatal stimulation could affect pituitary morphology during this critical period of cell differentiation. Three groups of animals were studied: intact (no manipulation, N = 5), handled (N = 5) and stimulated (submitted to 3 different aversive stimuli, N = 5). The percentage of ACTH-immunoreactive cells in the anterior lobe of the pituitary (number of ACTH-stained cells divided by total number of cells) was determined by examining three slices per pituitary in which a minimum of 200 cells were counted by two independent researchers. Although animals during the neonatal period are less reactive to stress-like stimulation in terms of ACTH and corticosterone secretion, results showed that the relative number of ACTH-stained cells of neonatal handled (0.25 ± 0.01) and aversive stimulated (0.29 ± 0.03) rats was not significantly different from intact (0.30 ± 0.03) animals. Neonatal stimulation may have a differential effect on the various subpopulations of corticotroph cells in the anterior pituitary

Veratridine increases the survival of retinal ganglion cells in vitro

Neuronal cell death is an important phenomenon involving many biochemical pathways. This degenerative event has been studied to understand how the cells activate the mechanisms that lead to self-destruction. Target cells and afferent cells play a relevant role in the regulation of natural cell death. We studied the effect of veratridine (1.5, 3.0, 4.5 and 6.0 µM) on the survival of neonatal rat retinal ganglion cells in vitro. Veratridine (3.0 µM), a well-known depolarizing agent that opens the Na+ channel, promoted a two-fold increase in the survival of retinal ganglion cells kept in culture for 48 h. This effect was dose-dependent and was blocked by 1.0 µM tetrodotoxin (a classical voltage-dependent Na+ channel blocker) and 30.0 µM flunarizine (a Na+ and Ca2+ channel blocker). These results indicate that electrical activity is also important for the maintenance of retinal ganglion cell survival in vitro

The rate of force generation by the myocardium is not influenced by afterload

The influence of afterload on the rate of force generation by the myocardium was investigated using two types of preparations: the in situ dog heart (dP/dt) and isolated papillary muscle of rats (dT/dt). Thirteen anesthetized, mechanically ventilated and thoracotomized dogs were submitted to pharmacological autonomic blockade (3.0 mg/kg oxprenolol plus 0.5 mg/kg atropine). A reservoir connected to the left atrium permitted the control of left ventricular end-diastolic pressure (LVEDP). A mechanical constriction of the descending thoracic aorta allowed to increase the systolic pressure in two steps of 20 mmHg (conditions H1 and H2) above control values (condition C). After arterial pressure elevations (systolic pressure C: 119 ± 8.1; H1: 142 ± 7.9; H2 166 ± 7.7 mmHg; P<0.01), there were no significant differences in heart rate (C: 125 ± 13.9; H1: 125 ± 13.5; H2: 123 ± 14.1 bpm; P>0.05) or LVEDP (C: 6.2 ± 2.48; H1: 6.3 ± 2.43; H2: 6.1 ± 2.51 mmHg; P>0.05). The values of dP/dt did not change after each elevation of arterial pressure (C: 3,068 ± 1,057; H1: 3,112 ± 996; H2: 3,086 ± 980 mmHg/s; P>0.05). In isolated rat papillary muscle, an afterload corresponding to 50% and 75% of the maximal developed tension did not alter the values of the maximum rate of tension development (100%: 78 ± 13; 75%: 80 ± 13; 50%: 79 ± 11 g mm-2 s-1, P>0.05). The results show that the rise in afterload per se does not cause changes in dP/dt or dT/dt

Effects of estradiol benzoate on 5'-iodothyronine deiodinase activities in female rat anterior pituitary gland, liver and thyroid gland

There is little information on the possible effects of estrogen on the activity of 5'-deiodinase (5'-ID), an enzyme responsible for the generation of T3, the biologically active thyroid hormone. In the present study, anterior pituitary sonicates or hepatic and thyroid microsomes from ovariectomized (OVX) rats treated or not with estradiol benzoate (EB, 0.7 or 14 µg/100 g body weight, sc, for 10 days) were assayed for type I 5'-ID (5'-ID-I) and type II 5'-ID (5'-ID-II, only in pituitary) activities. The 5'-ID activity was evaluated by the release of 125I from deiodinated 125I rT3, using specific assay conditions for type I or type II. Serum TSH and free T3 and free T4 were measured by radioimmunoassay. OVX alone induced a reduction in pituitary 5'-ID-I (control = 723.7 ± 67.9 vs OVX = 413.9 ± 26.9; P<0.05), while the EB-treated OVX group showed activity similar to that of the normal group. Thyroid 5'-ID-I showed the same pattern of changes, but these changes were not statistically significant. Pituitary and hepatic 5'-ID-II did not show major alterations. The treatment with the higher EB dose (14 µg), contrary to the results obtained with the lower dose, had no effect on the reduced pituitary 5'-ID-I of OVX rats. However, it induced an important increment of 5'-ID-I in the thyroid gland (0.8 times higher than that of the normal group: control = 131.9 ± 23.7 vs ovx + EB 14 µg = 248.0 ± 31.2; P<0.05), which is associated with increased serum TSH (0.6-fold vs OVX, P<0.05) but normal serum free T3 and free T4. The data suggest that estrogen is a physiological stimulator of anterior pituitary 5'-ID-I and a potent stimulator of the thyroid enzyme when employed at high doses

Plasma testosterone and 11-ketotestosterone levels of male pacu Piaractus mesopotamicus (Cypriniformes, Characidae)

The levels of testosterone (T) and 11-ketotestosterone (11-KT) of the South American pacu Piaractus mesopotamicus were determined by radioimmunoassay during two stages of the reproductive cycle, i.e., resting and maturation, and the gonadosomatic index (GSI) was calculated. The highest levels of T and 11-KT were reached during the maturation stage (T = 2400 ± 56 pg/ml; 11-KT = 2300 ± 60 pg/ml) and lower levels were maintained during the resting period. The rise in androgen levels occurred with the appearance of spermatozoa in the maturation stage, when GSI was highest

Horizontal projections of area 17 in Cebus monkeys: metric features, and modular and laminar distribution

Metric features and modular and laminar distributions of intrinsic projections of area 17 were studied in Cebus apella. Anterogradely and retrogradely labeled cell appendages were obtained using both saturated pellets and iontophoretic injections of biocytin into the operculum. Laminar and modular distributions of the labeled processes were analyzed using Nissl counterstaining, and/or cytochrome oxidase and/or NADPH-diaphorase histochemistry. We distinguished three labeled cell types: pyramidal, star pyramidal and stellate cells located in supragranular cortical layers (principally in layers IIIa, IIIb a, IIIb ß and IIIc). Three distinct axon terminal morphologies were found, i.e., Ia, Ib and II located in granular and supragranular layers. Both complete and partial segregation of group I axon terminals relative to the limits of the blobs of V1 were found. The results are compatible with recent evidence of incomplete segregation of visual information flow in V1 of Old and New World primates

Interleukin-15 as a potential regulator of the innate immune response

Interleukin-15 (IL-15) is a newly-discovered cytokine that is produced by activated monocytes early in the course of the innate immune response. IL-15 is able to bind to components of the interleukin-2 receptor (IL-2R) despite the fact that it has no sequence homology with IL-2. IL-15 stimulates human natural killer cell proliferation, cytotoxicity, and cytokine production and can substitute for IL-2 under most conditions. In vitro studies indicate that monocyte-derived IL-15 may be an important determinant of IFN-gamma production by NK cells. In addition, IL-15 is able to promote the survival of natural killer cells under serum-free conditions. The IL-15 receptor is a heterotrimeric complex which is composed of the IL-2Rß and g chains in combination with a unique alpha chain (IL-15a). The IL-15Ra chain has strong sequence homology to the IL-2Ra chain and confers high affinity binding to the IL-15R. In contrast to IL-2, transcript for IL-15 and IL-15a is expressed in a number of tissues and indicates that IL-15 may be an important ligand for cells that express components of the IL-2R

Chemokines, lymphocytes, and HIV

Chemokines are members of a family of more than 30 human cytokines whose best-described activities are as chemotactic factors for leukocytes and that are presumed to be important in leukocyte recruitment and trafficking. While many chemokines can act on lymphocytes, the roles of chemokines and their receptors in lymphocyte biology are poorly understood. The recent discoveries that chemokines can suppress infection by HIV-1 and that chemokine receptors serve, along with CD4, as obligate co-receptors for HIV-1 entry have lent urgency to studies on the relationships between chemokines and lymphocytes. My laboratory has characterized Mig and Crg-2/IP-10, chemokines that are induced by IFN-g and that specifically target lymphocytes, particularly activated T cells. We have demonstrated that the genes for these chemokines are widely expressed during experimental infections in mice with protozoan and viral pathogens, but that the patterns of mig and crg-2 expression differed, suggesting non-redundant roles in vivo. Our related studies to identify new chemokine receptors from activated lymphocytes resulted in the cloning of STRL22 and STRL33. We and others have shown that STRL22 is a receptor for the CC chemokine MIP-3a, and STRL22 has been re-named CCR6. Although STRL33 remains an orphan receptor, we have shown that it can function as a co-receptor for HIV-1 envelope glycoproteins, and that it is active with a broader range of HIV-1 envelope glycoproteins than the major co-receptors described to date. The ability of STRL33 to function with a wide variety of envelope glycoproteins may become particularly important if therapies are instituted to block other specific co-receptors. We presume that investigations into the roles of chemokines and their receptors in lymphocyte biology will provide information important for understanding the pathogenesis of AIDS and for manipulating immune and inflammatory responses for clinical benefit

Eosinophil-active chemokines: assessment of in vivo activity

The selective recruitment of eosinophils in tissue is a striking feature of allergic diseases. Recently, a family of chemoattractant molecules, namely chemokines, has been described which potently activates eosinophil function in vitro. We have developed a murine model of eosinophil recruitment to compare the relative potency and efficacy of chemokines in vivo. Of the chemokines tested, only eotaxin and MIP-1a induced significant accumulation of eosinophils in vivo, but eotaxin was more effective than MIP-1a. Chemokines, especially eotaxin acting via the CCR-3 receptor, may have a fundamental role in determining selective eosinophil recruitment in vivo

Extracellular ATP in the lymphohematopoietic system: P2Z purinoceptors and membrane permeabilization

The effects of extracellular nucleosides and nucleotides on many organs and systems have been recognized for almost 50 years. The effects of extracellular ATP (ATPo), UTPo, ADPo, and other agonists are mediated by P2 purinoceptors. One of the most dramatic effects of ATPo is the permeabilization of plasma membranes to low molecular mass solutes of up to 900 Da. This effect is evident in several cells of the lymphohematopoietic system and is supposed to be mediated by P2Z, an ATP4--activated purinoceptor. Here, we review some basic information concerning P2 purinoceptors and focus our attention on P2Z-associated phenomena displayed by macrophages. Using fluorescent dye uptake, measurement of free intracellular Ca2+ concentration and electrophysiological recordings, we elucidate some of the events that follow the application of ATP to the extracellular surface of macrophages. We propose a regulatory mechanism for the P2Z-associated permeabilization pore. The presence of P2 purinoceptors in cells of the lymphohematopoietic system makes them potential candidates to mediate immunoregulatory events

Aging and immunoglobulin isotype patterns in oral tolerance

In the present review we address oral tolerance as an important biological phenomenon and discuss how it is affected by aging. Other factors such as frequency of feeding and previous digestion of the antigen also seem to influence the establishment of oral tolerance. We also analyze immunoglobulin isotypes of specific antibodies formed by tolerant and immunized animals of different ages submitted to different conditions of oral antigen administration. Isotypic patterns were studied as a parameter for assessing the pathways of B and T cell interactions leading to antibody production

New strategies in hematopoietic stem cell transplantation: G-CSF-mobilized unprocessed whole blood

Transplantation of mobilized peripheral blood stem cells (PBSC) for rescue of bone marrow function after high-dose chemo-/radiotherapy is widely used in hematologic malignancies and solid tumors. Mobilization of stem cells to the peripheral blood can be achieved by cytokine treatment of the patients. The main advantage of autologous PBSC transplantation over bone marrow transplantation is the faster recovery of neutrophil and platelet counts. The threshold number of PBSC required for adequate rescue of bone marrow is thought to be about 2 x 106 CD34+ cells/kg, if the stem cells are collected by leukapheresis and subsequently cryopreserved. We show that this critical number could be further reduced to as few as 0.2 x 106 cells/kg. In 30 patients with multiple myeloma and 25 patients with bad risk lymphoma 1 liter of granulocyte colony-stimulating factor (G-CSF)-mobilized unprocessed whole blood (stored at 4oC for 1-3 days) was used for transplantation. Compared to a historical control group, a significant reduction in the duration of neutropenia, thrombocytopenia and the length of hospital stay was documented. Furthermore, the effect of stem cell support was reflected by a lower need for platelet and red cell transfusions and a reduced antibiotic use. Considering the data as a whole, a cost saving of about 50% was achieved. To date, this easy to perform method of transplantation is only feasible following high-dose therapies that are completed within 72 h, since longer storage of unprocessed blood is accompanied by a substantial loss of progenitor cell function. Ongoing investigations include attempts to prolong storage times for whole blood

Role of Th1 and Th2 cells in autoimmune demyelinating disease

Evidence is accumulating that Th1 cells play an important role in the development of multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE), whereas Th2 cells contribute to recovery from disease. A major determinant in the development of Th1 and Th2 cells is the type of antigen-presenting cell (APC) involved and its functional characteristics, e.g., the production of interleukin-12. Therefore, modulation of APC might interfere with the development of Th1 type responses and as such be beneficial for MS and EAE. The potential of cytokines, in particular interleukin-10, and glucocorticoids to exert a selective effect on APC, and as a consequence to affect the Th1-Th2 balance in EAE, is discussed

Relationship of cytokines and cytokine signaling to immunodeficiency disorders in the mouse

The contributions of cytokines to the development and progression of disease in a mouse model of retrovirus-induced immunodeficiency (MAIDS) are controversial. Some studies have indicated an etiologic role for type 2 cytokines, while others have emphasized the importance of type 1 cytokines. We have used mice deficient in expression of IL-4, IL-10, IL-4 and IL-10, IFN-g, or ICSBP - a transcriptional protein involved in IFN signaling - to examine their contributions to this disorder. Our results demonstrate that expression of type 2 cytokines is an epiphenomenon of infection and that IFN-g is a driving force in disease progression. In addition, exogenously administered IL-12 prevents many manifestations of disease while blocking retrovirus expression. Interruption of the IFN signaling pathways in ICSBP-/- mice blocks induction of MAIDS. Predictably, ICSBP-deficient mice exhibit impaired responses to challenge with several other viruses. This immunodeficiency is associated with impaired production of IFN-g and IL-12. Unexpectedly, however, the ICSBP-/- mice also develop a syndrome with many similarities to chronic myelogenous leukemia in humans. The chronic phase of this disease is followed by a fatal blast crisis characterized by clonal expansions of undifferentiated cells. ICSBP is thus an important determinant of hematopoietic growth and differentiation as well as a prominent signaling molecule for IFNs