Cell-depleted Rats Research Articles

Mast cell activation ameliorates pentylenetetrazole-induced seizures in rats: The potential role for serotonin.

Neuroinflammation plays a key role in the pathogenesis of epilepsy, but the underlying mechanisms are not well understood. Mast cells are multifunctional immune cells that are also activated by stress. The effects of activated mast cells on epileptogenesis are not yet known. This study investigated the effects and mechanisms of compound 48/80-stimulated mast cell activation on pentylenetetrazole-induced epileptic seizures in rats. Male Wistar rats were separated into seven groups (n=12). Group-1(NS+PTZ) received intraperitoneal saline solution, while groups 2(C-48/80+PTZ-1), 3(C-48/80+PTZ-2), and 4(C-48/80+PTZ-3) received compound-48/80 at doses of 0.5, 1, and 2mg/kg, respectively, 30min before 45mg/kg pentylenetetrazole administration. Similarly, Group-5(Cr+C-48/80+PTZ) received 10mg/kg cromolyn plus 2mg/kg compound-48/80 before pentylenetetrazole, and Group-6(MC Dep+C-48/80+PTZ) was exposed to a mast cell-depletion process, and then received 2mg/kg compound-48/80. Group-7(5-HT+PTZ) received 10mg/kg serotonin. Seizure stages were evaluated using Racine's scale. Compound-48/80 at 2mg/kg induced anticonvulsive effects against pentylenetetrazole-induced seizures by extending onset-times of both myoclonic-jerk and generalized tonic-clonic seizures (p=0.0001), and by shortening the duration of generalized tonic-clonic seizure (p=0.008). These effects were reversed by cromolyn (p=0.0001). These effects were not observed in mast cell-depleted rats. Similarly to compound 48/80, serotonin also exhibited anticonvulsive effects against seizures (p<0.05). Compound 48/80 acts as an anticonvulsant by activating mast cells in a dose-dependent manner. The anticonvulsive effects of mast cell activation may be mediated by serotonin. Mast cell activation may therefore provide protective activity against seizures under appropriate circumstances.

Cultured thymus tissue implantation promotes donor-specific tolerance to allogeneic heart transplants.

Eighty-six infants born without a thymus have been treated with allogeneic cultured thymus tissue implantation (CTTI). These infants, who lack T cells and are profoundly immunodeficient at birth, after CTTI from an unmatched donor develop T cells similar to those of recipient that are tolerant to both their own major histocompatibility antigens and those of the donor. We tested use of CTTI with the goal of inducing tolerance to unmatched heart transplants in immunocompetent rats. We thymectomized and T cell-depleted Lewis rats. The rats were then given cultured thymus tissue from F1 (Lewis × Dark Agouti ) under the kidney capsule and vascularized Dark Agouti (DA) heart transplants in the abdomen. Cyclosporine was administered for 4 months. The control group did not receive CTTI. Recipients with CTTI showed repopulation of naive and recent thymic emigrant CD4 T cells; controls had none. Recipients of CTTI did not reject DA cardiac allografts. Control animals did not reject DA grafts, due to lack of functional T cells. To confirm donor-specific unresponsiveness, MHC-mismatched Brown Norway (BN) hearts were transplanted 6 months after the initial DA heart transplant. LW rats with LWxDA CTTI rejected the third-party BN hearts (mean survival time 10 days); controls did not. CTTI recipients produced antibody against third-party BN donor but not against the DA thymus donor, demonstrating humoral donor-specific tolerance. Taken together, F1(LWxDA) CTTI given to Lewis rats resulted in specific tolerance to the allogeneic DA MHC expressed in the donor thymus, with resulting long-term survival of DA heart transplants after withdrawal of all immunosuppression.

PACAP-38 infusion causes sustained vasodilation of the middle meningeal artery in the rat: Possible involvement of mast cells

In healthy human volunteers and in migraineurs, pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) infusion caused sustained vasodilation of the middle meningeal artery (MMA) and an immediate as well as a delayed headache. All the study subjects experienced facial flushing. Mast cells (MCs) might have a role in the long-lasting effect of PACAP-38 infusion. We hypothesized that in mast cell-depleted (MCD) rats the vascular responses to PACAP-38 would be lesser than in control rats because of a lack of vasodilatory products released during MC degranulation. MCs were depleted by chronic treatment with compound 48/80. The effect of 20 minutes' intravenous (i.v.) infusion of calcitonin gene-related peptide (CGRP), PACAP-38, PACAP(6-38) (PAC-1 receptor antagonist) and PACAP-27 on the diameter of the MMA and on mean arterial blood pressure (MABP) in control and MCD rats was recorded by using the genuine closed-cranial window (CCW) model. Vasoactive intestinal polypeptide (VIP) infusion was given only in control rats. A combination of the histamine H1 receptor antagonist mepyramine (4 mg kg(-1) i.v.) and the H2 receptor antagonist famotidine (1 mg kg(-1) i.v.) was given 10 minutes prior to PACAP-38 infusion. Increasing doses of PACAP-38, PACAP-27 and VIP were infused through the intracarotid artery (i.c.) in control and MCD rats to see the direct effects of these peptides on MMA diameter change. There was no significant change in CGRP-induced MMA diameter increase in control and MCD rats, and the dilated MMA immediately returned back to baseline after stopping the infusion. The delayed MMA dilation induced by PACAP-38 was abolished in MCD and antihistamine (AH)-pretreated rats. Compared to PACAP-38, the PACAP-27 i.v. infusion gave smaller peak dilation of MMA in control rats. In MCD rats, PACAP-27 did not induce any significant dilation. VIP i.v. infusion reduced MABP but did not dilate MMA significantly. PACAP(6-38), which is a potent MC degranulator, also gave a significant delayed dilation of MMA. PACAP-38 i.c. responses (direct receptor mediated response) were not affected by MC depletion. Only the maximum response (% E max) value of PACAP-27 (i.c.) was significantly lower in MCD rats compared to control rats. The delayed MMA dilatory responses to PACAP-38 infusion were attenuated in MCD and AH-pretreated rats, indicating a role of the MC mediator-histamine in PACAP-38-induced delayed dilation of MA.

Depletion of CD8α + lymphocytes attenuates CCL28 expression in villus epithelia in rats

To examine the involvement of CD8α + intraepithelial lymphocytes (IELs) in chemokine expression by villus epithelial cells, villus and crypt fractions were collected by mechanical isolation using a chelating buffer and specific antibodies in CD8α + cell-depleted rats. A larger population of CD8α + cells was observed by histochemical evaluation in villus epithelia than in crypt epithelia in rat small intestine, and CCL9 and CCL28 expression was higher in the crypt fraction than in the villus fraction. The mRNA expression of CCL28 in villus fractions isolated from rat small intestinal mucosa was significantly reduced compared to that of CCL9, and was accompanied by CD8α depletion. Using a combined histochemical and flow cytometric approach, CD8αα + cells were detected in the intraepithelial region of the villus epithelium. Thus, CCL28 expression in villus epithelial cells is partially supported by CD8αα + cells, and CD8α + IELs are involved in CCL28 expression.

CelTOS, a novel malarial protein that mediates transmission to mosquito and vertebrate hosts

The malarial parasite has two hosts in its life cycle, a vertebrate and a mosquito. We report here that malarial invasion into these hosts is mediated by a protein, designated cell-traversal protein for ookinetes and sporozoites (CelTOS), which is localized to micronemes that are organelles for parasite invasive motility. Targeted disruption of the CelTOS gene in Plasmodium berghei reduced parasite infectivity in the mosquito host approximately 200-fold. The disruption also reduced the sporozoite infectivity in the liver and almost abolished its cell-passage ability. Liver infectivity was restored in Kupffer cell-depleted rats, indicating that CelTOS is necessary for sporozoite passage from the circulatory system to hepatocytes through the liver sinusoidal cell layer. Electron microscopic analysis revealed that celtos-disrupted ookinetes invade the midgut epithelial cell by rupturing the cell membrane, but then fail to cross the cell, indicating that CelTOS is necessary for migration through the cytoplasm. These results suggest that conserved cell-passage mechanisms are used by both sporozoites and ookinetes to breach host cellular barriers. Elucidation of these mechanisms might lead to novel antimalarial strategies to block parasite's transmission.

Sm60, a mannose-binding protein from Schistosomamansoni with inflammatory property

We demonstrate here that a mannose-binding protein from Schistosoma mansoni, termed Sm60, was recovered in the mannose-eluted fraction (Man +) upon affinity chromatography on immobilised mannose of the soluble antigen fraction from adult worm tegument and cercariae. Sm60 was detected in the Man + fraction as a prominent doublet with an apparent molecular mass of 60–66 kDa by SDS–PAGE and appeared as a single band with a p I of ∼6.9 by isoelectrofocusing. Sm60 was also detected in preparations of schistosomula extract and soluble egg antigens using a mouse polyclonal anti-Sm60 serum on immunoblotting assay. This antiserum demonstrated that Sm60 was localised on the tegument of S. mansoni adult worm. In order to determine the role of Sm60 in host–parasite interactions, we showed that Sm60 induced in vitro migration of human neutrophil in a dose-dependent manner and in vitro mast cell degranulation. Sm60 triggered these activities through its carbohydrate-binding site, since these activities were selectively inhibited by 0.2 M d-mannose, but not by 0.2 M d-galactose. Furthermore, Sm60 induced in vivo neutrophil migration. In contrast, mast cell-depleted rats presented a significant reduction of the neutrophil migration induced by Sm60 as compared with non-depleted controls. These data suggest that in vivo neutrophil migration induced by Sm60 is modulated by mast cell-dependent mechanisms. Sm60 might play a key role in the host–parasite interaction, and its characterization opens perspective to examine the role of this molecule in the biology of S. mansoni.

Immune Mechanisms in Pain Control

Immune Mechanisms in Pain Control

Specific expression of spinal Fos after PAR-2 stimulation in mast cell-depleted rats.

Protease-activated receptor-2 (PAR-2) in the sensory neurons may be involved in nociceptive processing. We attempted to detect and characterize specific expression of spinal Fos, a marker of nociception, in mast cell-depleted rats. Intraplantar (i.pl.) administration of not only the PAR-2 agonist SLIGRL-NH2, but also the control peptide LSIGRL-NH2, induced Fos expression in naive rats, whereas only the former specifically produced Fos expression in mast cell-depleted rats. This Fos expression was blocked by intrathecal DAMGO, a mu-opioid agonist, and, in part, by i.pl. calphostin C, a protein kinase C (PKC) inhibitor. Thus, specific expression of spinal Fos following peripheral PAR-2 activation is detectable in mast cell-depleted rats, suggesting activation of spinal nociceptive neurons, which is partially mediated by activation of PKC.

Kupffer cell-mediated recruitment of dendritic cells to the liver crucial for a host defense.

Tissue recruitment of dendritic cells (DCs) is essential for antigen presentation. When latex particulates were injected intravenously into rats, DC precursors were recruited to the liver. Propionibacterium acnes also induced the recruitment of definite mouse DC precursors. These DCs initially showed a selective binding to Kupffer cells. In the Kupffer cell-depleted rats, DCs could neither be recruited to the liver nor adhere to sinusoidal walls. Pretreatment with varied monosaccharides in vitro showed that sugar residues consisting of N-acetylgalactosamine were necessary for this binding. Mouse DC precursors had CC-chemokine receptor 1 and 5, while granulama tissues and rat Kupffer cells expressed the corresponding chemokine, macrophage inflammatory protein-1α. Recruited DC precursors phagocytosed latex or bacteria and some of them soon translocated to hepatic nodes and induced the immune response there. We conclude that after invasion of pathogens, Kupffer cells not only scavenge them but also recruit DCs/DC precursors via chemokine- and N-acetylgalactosamine-mediated interactions. The accelerated DC traffic and the presence of blood-lymph translocation would induce rapid and efficient immune responses and thus contribute to the local defense to antigens within liver tissues as well as systemic defense to blood-borne antigens.

The protective role of Kupffer cells in the ischemia-reperfused rat liver.

Kupffer cells constitute a major source of the heme-degrading enzyme, heme oxygenase (HO). This study examined the roles of Kupffer cells in the modulation of accelerated heme catabolism in ischemia-reperfused rat livers. Livers from rats treated with or without liposome-encapsulated dichloromethylene diphosphonate, a Kupffer cell-depleting reagent, underwent a 20-min ligation of the portal vein followed by reperfusion, The time course of the biliary output of bilirubin, the terminal heme-degrading product, and the expression of HO-1 mRNA and protein were monitored. HO-1 mRNA levels were elevated 3 to 12 h after ischemia/reperfusion in both control and Kupffer cell-depleted rats. Immunohistochemical analyses of control livers revealed that Kupffer cells expressed high levels of HO-1 while its expression in hepatocytes was low. In Kupffer cell-depleted livers, however, periportal hepatocytes displayed marked HO-1 expression. Under these conditions the two groups exhibited distinct profiles of biliary bilirubin excretion. In the controls, total bilirubin excretion increased 8-fold and peaked at 10 h after ischemia/reperfusion. In contrast, the Kupffer cell-depleting treatment resulted in a significant acceleration of the initial rise in bilirubin production, which peaked at 4 h. However, the total amount of bilirubin excreted within the initial 10 h after reperfusion was reduced by 50% as compared with that of the controls. In Kupffer cell-depleted rats, the levels of GOT and GPT as well as serum endotoxin concentrations were elevated after ischemia/reperfusion. These results suggest that Kupffer cells serve as an ischemia/reperfusion sensor that upregulates heme degradation and bilirubin excretion, and that Kupffer cells protect hepatocytes from gut-derived stressers--including endotoxin--following ischemia/reperfusion.

Kupffer cell-mediated recruitment of rat dendritic cells to the liver: Roles of N-Acetylgalactosamine-Specific sugar receptors

Tissue recruitment of dendritic cells (DCs) is essential for antigen presentation. This study aimed to examine cellular and molecular mechanisms for DC recruitment to the liver. Purified rat DCs were injected into circulation and their traffics were analyzed in normal and Kupffer cell-depleted rats by intravital confocal microscopy and immunohistology. Affinities of DCs to sinusoidal cells were examined by a cell-binding assay. DC precursor recruitment was induced by particulate injection. Both DC precursors and DCs at the antigen-transporting stage could be recruited to the liver, and their majority initially showed a selective binding to Kupffer cells. In the Kupffer cell-depleted rats, DCs could neither be recruited to the liver nor adhere to sinusoidal walls. Pretreatment with varied monosaccharides showed that sugar residues consisting of N-acetylgalactosamine were necessary for this binding. The binding was calcium-dependent, implying the C-type lectin involvement. Furthermore, DCs could endocytose N-acetylgalactosamine polymers in a receptor-specific manner. The DC-Kupffer cell binding through N-acetylgalactosamine-specific C-type lectin-like receptors is crucial for DC recruitment to the liver. Rat DCs at least partly possess receptors for endocytosis of galactosylated antigens. These DC receptors as well as Kupffer cell lectins are presumably responsible for this binding.

Role of heme oxygenase-1 and Kupffer cells in the production of bilirubin in the rat liver.

Heme oxygenase (HO)-1, the heme-degrading enzyme in macrophages, plays a key role in bilirubin metabolism. HO-1 is expressed in various tissue macrophages, especially Kupffer cells. This study aimed to examine the roles of macrophages and HO-1 in the modulation of heme catabolism in rat livers. Rats treated with or without liposome-encapsulated dichloromethylene diphosphonate, a macrophage-depleting reagent, were administered with heat-denatured red blood cells (h-RBC), and the time course of the biliary output of bilirubin and the expressions of HO-1 mRNA and protein were monitored. Immunohistochemistry in the control rat liver revealed that Kupffer cells constitute a major cellular component expressing HO-1, while hepatocytes exhibited little expression. The levels of HO-1 expression in Kupffer cells were elevated immediately after injection of h-RBC. In Kupffer cell-depleted livers, however, HO-1-expressing cells were not detected even after h-RBC administration. HO-1 mRNA levels were elevated at 2 h after administration of h-RBC in control rat livers, while they were very low in Kupffer cell-depleted rat livers. The control and Kupffer cell-depleted groups exhibited distinct time courses of biliary bilirubin excretion. In the untreated control rats, total bilirubin excretion increased about two-fold at 5 h after h-RBC administration. In contrast, the Kupffer cell-depleting treatment decreased the level of bilirubin production; administration of h-RBC to Kupffer cell-depleted rats did not accelerate the generation of bilirubin. These results suggest that Kupffer cells serve both as a sensor for scenesent RBC clearance and an effector that upregulates heme-degrading capacity and bilirubin production.

The Role of Thymus-Dependent T Cells in Hexachlorobenzene-Induced Inflammatory Skin and Lung Lesions

The involvement of thymus-dependent T cells in the inflammatory skin and lung lesions and spleen effects induced by hexachlorobenzene (HCB) was investigated by using genetically athymic and euthymic WAG/Rij rats and Brown Norway (BN) rats with or without depletion of T cells by adult thymectomy, lethal irradiation, and bone marrow reconstitution. Rats were exposed to diets with no supplementation or diets supplemented with 150 or 450 mg HCB per kg diet for 4 (BN) or 6 (WAG/Rij) weeks. Skin lesion development and body weight gains were assessed during exposure and spleen and liver weights as well as histopathologic changes in skin, lung, and spleen were assessed after exposure. Oral HCB exposure of athymic and euthymic rats of both rat strains resulted in a dose-dependent increase of relative liver weight at doses of 150 and 450 mg/kg HCB and increased relative spleen weights at a dose of 450 mg/kg. HCB exposure of both strains further resulted in inflammatory changes in skin, lungs, and splenic red pulp independent of the T cell status except for skin lesions in the BN strain. HCB-exposed T cell-competent BN rats showed faster skin lesion development than the T cell-depleted rats, although qualitatively and quantitatively similar skin pathology was observed at the end of the 4-week exposure in both groups. In the WAG/Rij strain skin lesions could not be comparatively assessed due to preexistent inflammatory skin pathology in the nude rats. This study showed that thymus-derived T cells are not required for the induction of skin and lung pathology and splenic changes by HCB and therefore it is suggested that HCB acts differently from many allergenic and autoimmunogenic low molecular weight compounds that trigger pathology via thymus-dependent mechanisms. A role for mononuclear phagocytes and, in BN rats, eosinophilic granulocytes, in the HCB-induced pathology is suggested since these cells were prominently present in the HCB-induced lesions.

Superoxide anion release into the hepatic sinusoid after an acute ethanol challenge and its attenuation by Kupffer cell depletion.

Superoxide anion release into the hepatic sinusoids and subsequent damage to the endothelial cells of the hepatic sinusoids after ethanol challenge was examined. A 250 mg/kg body weight/hr dose of ethanol was given to rats for 3 hr, and superoxide anion release into the hepatic sinusoids was examined in a liver perfusion model using the cytochrome c method. Ethanol treatment resulted in superoxide anion release into the hepatic sinusoids (0.20 +/- 0.01 vs. 0.12 +/- 0.02 o.d., p < 0.05) and an increase in the purine nucleoside phosphorylase/alanine aminotransferase ratio in the liver perfusate, a marker of damage to the endothelial cells of the hepatic sinusoids (0.003 +/- 0.002 vs. 0.008 +/- 0.002; p < 0.05). Tumor necrosis factor-alpha was not detectable in either group, and there were no significant differences in the population of hepatic macrophages, leukocytes, or Kupffer cells between the two groups. To clarify the role of Kupffer cells in the mechanism, 10 mg/kg of body weight of gadolinium chloride was given to rats twice, 24 hr apart, resulting in depletion of ED2-positive cells from the hepatic lobules. The superoxide anion release after the ethanol challenge was significantly attenuated in the Kupffer cell-depleted rats, compared with the controls (0.14 +/- 0.02; p < 0.05, compared with ethanol alone). The change was associated with a significant decrease in the purine nucleoside phosphorylase/alanine aminotransferase ratio in the liver perfusate (0.004 +/- 0.002; p < 0.05, compared with ethanol alone). Ethanol causes superoxide anion release into the hepatic sinusoid and subsequent damage to the sinusoidal endothelial cells. These changes were reduced by Kupffer cell depletion. This supports the view that Kupffer cell depletion has a protective effect on ethanol-induced liver injury.

Partial restoration of hair growth in the DEBR model for Alopecia areata after in vivo depletion of CD4+ T cells.

Alopecia areata (AA) is widely believed to be an autoimmune disease. Hair loss is associated with a peri- and intrafollicular inflammatory infiltrate of anagen hair follicles primarily composed of CD4 + and CD8 + cells. A previous investigation involved in vivo depletion of CD8 + cells in the DEBR rat model to examine the cells' potential pathogenic activity in AA. The rat model is used here in a comparable study of CD4 + cell pathogenic activity. Eight AA affected DEBR rats were given intraperitoneal injections of a CD4 + cell depleting OX-35/OX-38 monoclonal antibody (MoAb) cocktail over a 15-day therapy course. A further eight AA-affected rats comprised a control group and were injected with equivalent volumes of an irrelevant MoAb, OX-21. Changes in both CD4 + and CD8 + peripheral blood cell populations were analysed by flow cytometry, and macrophotography was used to record any changes in hair growth. Of the eight CD4 + cell-depleted rats six responded with hair growth. The rats revealed significant hair growth within 23 days of treatment initiation. With rapid replacement of the CD4 + cell population the newly generated pelage hair was eventually lost. Two control rats also showed limited hair growth within the 112-day study period. In vivo depletion of CD4 + cells partially restores hair growth in AA affected rats. The response suggests that CD4 + cells may be actively involved in the pathogenesis of AA. Further research may elucidate whether CD4 + cells have a direct effect on hair follicles or exert their influence through their classic T helper cell supporting role for CD8 + cells.

Permanent CD8(+) T cell depletion prevents proteinuria in active Heymann nephritis.

Active Heymann nephritis (HN) is a rat model of human idiopathic membranous nephropathy in which injury is thought to be mediated by membrane attack complex of complement (MAC) activated by antibody (Ab) to glomerular epithelial cells. Recent work has shown that HN develops in C6-deficient rats which cannot assemble MAC, and that infiltration of activated cytotoxic CD8(+) T cells and macrophages into glomeruli coincides with proteinuria. This study examined the role of CD8(+) T cells in mediating glomerular injury in HN by permanent CD8(+) cytotoxic T cell depletion via adult thymectomy (ATx) and anti-CD8 mAb. Groups of rats were depleted of CD8(+) T cells either before immunization for HN or 6 wk after immunization when Ab responses and glomerular IgG deposition were well established. These were compared with groups of HN, ATx/HN, and complete Freund's adjuvant (CFA) controls. Neither group of CD8(+) T cell-depleted rats developed proteinuria, although there was normal development and deposition of Ab. CD8(+) T cell-depleted rats developed neither T cell or macrophage infiltrates nor their effector cytokines, which are present in glomeruli of rats with HN. Examination of lymph node (LN) draining sites of immunization showed these findings were not explained by altered immune events within these LNs. It was concluded that CD8(+) cytotoxic T cells are essential to the mediation of glomerular injury in HN and may be relevant to the pathogenesis and treatment of membranous nephropathy.

Bile ducts and portal and central veins are major producers of tumor necrosis factor alpha in regenerating rat liver

BACKGROUND & AIMS: Tumor necrosis factor (TNF) alpha mediates both liver injury and regeneration. Kupffer cells are thought to produce TNF because gadolinium chloride (GdCl), a drug that depletes Kupffer cells, prevents TNF-mediated injury. However, GdCl increases liver TNF and regeneration after partial hepatectomy (PH), suggesting that other cells produce TNF during regeneration. The aim of this study was to identify the source(s) of TNF after PH in normal and Kupffer cell- depleted rats. METHODS: Livers were harvested at 0, 1, or 48 hours after PH from saline- or GdCl-treated rats. TNF expression was evaluated by in situ reverse-transcription polymerase chain reaction and immunohistochemistry. RESULTS: In saline-treated rats, neither TNF transcripts nor protein was detected before PH, but both increased after PH. One hour after PH, 64% +/- 8% portal areas had TNF-positive bile ducts or veins and 61% +/- 1% central veins were TNF positive; by 48 hours, 57% +/- 1% portal areas, 40% +/- 1% central veins, and a few sinsusoidal cells expressed TNF. In GdCl-treated rats, TNF was expressed in 22% +/- 6% portal areas before PH; in 76% +/- 3% portal areas and 75% central veins at 1 hour; and in 88% +/- 2% portal areas and 80% +/- 9% central veins at 48 hours after PH. CONCLUSIONS: In the regenerating livers of both normal and Kupffer cell-depleted rats, bile ducts and veins are the predominant sources of TNF-alpha. (Gastroenterology 1997 Jun;112(6):2089-98)

Intraplantar injection of nerve growth factor into the rat hind paw: local edema and effects on thermal nociceptive threshold

Nerve growth factor (NGF) is known to produce hyperalgesia as well as to stimulate synthesis of neuropeptides in dorsal root ganglia (DRG). In the present study, we wanted to determine the effects of local NGF administration and assess to which extent mast cell-dependent factors are mediating NGF responses. Rats received 1 daily unilateral intraplantar injection for 3 days. Local edema (days 1–3), changes in thermal nociceptive threshold (days 1–4), and the content of calcitonin gene-related peptide (CGRP) and substance P (SP) in the sciatic nerve (day 4), were determined. NGF injection caused edema which was absent in rats pretreated with compound 48 80 as well as in rats treated neonatally with capsaicin (‘capsaicin denervation’). NGF-induced edema was not reduced by the neurokinin-1 receptor antagonist SR140333, but attenuated by the CGRP receptor antagonist CGRP[8–37]. On each day, NGF injection caused a decrease in thermal nociceptive threshold which lasted for less than 3 h. Capsaicin denervation, but not treatment with indomethacin, abolished NGF-induced thermal hyperalgesia. Treatment with compound 48 80 attenuated hyperalgesia produced by the first, but not by subsequent, NGF injections. On day 4, 24 h after the last of 3 NGF injections, thermal nociceptive threshold was not different from control values, but at that time, CGRP and SP were elevated in the sciatic nerve. We suggest therefore that NGF-induced local edema was caused by mast cell-derived vasoactive compounds which act together with afferent neuron-derived CGRP to increase vascular permeability. NGF-induced thermal hyperalgesia most likely was caused by an increased sensitivity of peripheral endings of capsaicin sensitive afferents. This effect of NGF was not mediated by products of the cyclooxygenase pathway, and was also observed in mast cell-depleted rats.

CD8+ T-cells are required for adoptive transfer of the BB rat diabetic syndrome.

LGLs with NK activity account for the majority of BB rat PBLs expressing CD8, and it has been suggested that these LGL/NK cells are involved in the pathogenesis of the BB rat diabetic syndrome. By using a recently developed mouse MoAb, 3.2.3, specific for rat LGL, we demonstrate that BB and WF rat LGLs are phenotypically and functionally similar. To directly assess the role of LGLs in the development of diabetes in vivo, an adoptive transfer of T-cells to young LGL/NK cell-depleted diabetes-prone BB rats was performed. CD4+8- and CD4-8+ T-cells (> 98.5% pure), isolated from diabetic BB rats, were activated in vitro and injected into 30-day-old diabetes-prone BB rats. Recipients were either chronically injected with 3.2.3 (n = 15) or received an isotype-matched irrelevant MoAB (n = 14). Secondary lymphoid organs of 3.2.3-treated recipients contained < 0.1% 3.2.3+ lymphocytes, and this depletion was associated with a major decrease in the NK activity of their splenocytes. Despite this, the incidence of diabetes in 3.2.3-treated animals (40%) was not significantly different from that observed in control recipients (57%). Thus, the BB rat diabetic syndrome can be adoptively transferred in the absence of LGL/NK cells, suggesting that BB rat CD8+ T-cells are involved in the diabetogenic process. To assess the pathogenic role of CD8+ T-cells, we compared the incidence of diabetes in three groups of diabetes-prone BB recipients after injection of T-cells isolated from diabetic donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Testicular blood flow and vasomotion can be maintained by testosterone in Leydig cell-depleted rats.

The effect of testosterone supplementation on testicular blood flow, testicular vasomotion, the number of polymorphonuclear leucocytes (PMN's) in testicular blood vessels and prostatic blood flow were studied in rats in which the Leydig cell had been destroyed specifically by a single injection of ethane dimethylsulfonate (EDS). Other rats were supplemented with testosterone by subcutaneous injection of 25 mg testosterone propionate on days 1, 3 and 6. In some experiments, the effect of a single injection of 25 or 125 mg testosterone was studied. Testicular and prostatic blood flow and the number of PMN's in testicular blood vessels decreased, and vasomotion disappeared in Leydig cell-depleted rats, but testosterone supplementation restored all parameters to normal values. Moreover, a single injection of testosterone was able to restore testicular and prostatic blood flow to normal levels but had an inconsistent effect on vasomotion. These results suggest that testosterone may play a role in the physiological control of the testicular microcirculation.