The effect of urocortin on ingestive behaviours and brain Fos immunoreactivity in mice

The influence of urocortin (UCN) on ingestive behaviours and brain neural activity, as measured immunohistochemically by the presence of Fos protein, was determined in mice. Rat UCN was administered by continuous intracerebroventricular (ICV) or subcutaneous (SC) infusion. ICV infusion of UCN (100 ng/h, 14 days) transiently reduced daily food and water intakes (days 1-4) but body weight was reduced from day 2 into the post-infusion period. Sodium intake was reduced from day 3 to the end of infusion. SC infusion of UCN caused similar but smaller reductions in food and water intakes and body weight, without change in sodium intake. In separate experiments, Fos immunoreactivity was increased in several brain nuclei known to be involved in the control of body fluid and energy homeostasis, e.g. central nucleus of the amygdala, median preoptic nucleus, bed nucleus of the stria terminalis and arcuate nucleus. Increased Fos expression was similar for ICV and SC infusions when measured on days 2-3 or 6-7 of infusion. In conclusion, increases of brain activity by UCN may be associated with stimulation of adrenocorticotrophic hormone release and sympathetic nervous activity, but increases may also indicate suppression of ingestive behaviours by stimulating central inhibitory mechanisms located in areas known to control body fluid and energy homeostasis.

Cognitive deficit induced by acute tryptophan depletion in patients with Alzheimer's disease

OBJECTIVE

The study assessed the effects on global cognitive function and mood of a reduction of brain serotonin by means of acute tryptophan depletion in 16 patients with dementia of the Alzheimer type and in 16 cognitively intact comparison subjects.

METHOD

In a double-blind, crossover design, subjects received a tryptophan-free amino acid drink to induce acute tryptophan depletion and, on a separate occasion, a placebo drink containing a balanced mixture of amino acids. On each occasion, ratings of depressed mood were made at baseline and 4 and 7 hours later, and the Modified Mini-Mental State was administered at baseline and 4 hours later.

RESULTS

Patients with dementia of the Alzheimer type had a significantly lower mean score on the Modified Mini-Mental State after acute tryptophan depletion than after receiving placebo. The comparison group showed no difference in mean score on the Modified Mini-Mental State after acute tryptophan depletion and after receiving placebo. No significant changes in mood were found in either group.

CONCLUSIONS

Acute tryptophan depletion significantly impaired cognitive function in patients with dementia of the Alzheimer type. Compromised serotonergic function, in combination with cholinergic deficit, may make an important contribution to cognitive decline in dementia of the Alzheimer type.

Dependence of mast cell IgE-mediated cytokine production on nuclear factor-kappaB activity

BACKGROUND

The transcription factor nuclear factor-kappaB (NF-kappaB) has been implicated in the regulation of a number of inflammatory cytokines and has been the proposed target for anti-inflammatory therapeutics.

OBJECTIVE

Our purpose was to explore the role of NF-kappaB in the regulation of allergic inflammation.

METHODS

To determine whether NF-kappaB is activated during IgE-mediated reactions and what types of mediators it regulates, a mutant form of IkappaB was used to block the ability of NF-kappaB to translocate to the nucleus and promote the transcription of selected genes.

RESULTS

Mouse bone marrow-derived mast cells stimulated by IgE receptor cross-linking exhibited an activation of NF-kappaB as assessed by electrophoretic mobility shift assays. Transfected mast cells expressing the mutant IkappaB showed very little NF-kappaB activation. Both control and transfected cells released beta-hexosaminidase after specific antigen challenge, and this release could be potentiated by exogenous adenosine. Transfected mast cells that failed to develop NF-kappaB activation did not produce IL-6 messenger RNA or protein after IgE-mediated stimulation, but these cells retained the ability to produce transcripts for IL-4 and IL-5 in spite of the suppression of NF-kappaB activity.

CONCLUSIONS

It appears that NF-kappaB is activated during IgE-mediated allergic inflammation and that this activity is necessary for the production of IL-6, but not IL-4 or IL-5. When considering the use of agents that target NF-kappaB to reduce inflammatory processes, it is important to know precisely which cytokines are under its control.

The effects of angiotensin II on blood perfusion in the rat renal papilla

1. Systemic infusion of angiotensin II (AII) increased papillary blood perfusion (PBP) measured by laser-Doppler flowmetry in rats, aged about 5 weeks. 2. The mechanisms involved in this response were determined by infusion of AII in the presence of systemic doses of losartan (a type 1 AII receptor antagonist), HOE-140 (a bradykinin B2 receptor antagonist), and an inhibitor of NO production - Nomega-nitro-L-arginine (NOLA). 3. Mean arterial blood pressure (MAP) and PBP increased in a dose-dependent manner in response to intravenous infusions of AII. Infusion of losartan abolished these responses to AII but HOE-140 was without effect. Infusion of NOLA abolished the increase in PBP but did not affect the pressor response to AII. Systemic infusion of sodium nitroprusside restored the response to AII in experiments with NOLA infusion. 4. The results indicate that the increase in PBP caused by AII is mediated via angiotensin AT1 receptors and does not involve bradykinin B2 receptors. The AII-induced increase in PBP is dependent upon the presence of NO, thus providing a mechanism for maintenance of papillary perfusion in the face of generalized renal vasoconstriction due to AII.

Imaging of renal medullary interstitial cells in situ by confocal fluorescence microscopy

Renal medullary interstitial cells are a prevalent and characteristic feature of the inner medulla of the kidney, but the physiological significance of this is unclear. We have developed a method for imaging renal medullary interstitial cells in situ by loading the cells with fluorescent dyes and monitoring their distribution using confocal microscopy. The pH-sensitive probe 2'7'-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester was used as a marker of cytoplasmic volume and therefore of cell morphology. Nile Red was used to demonstrate the presence of renal medullary interstitial cell lipid droplets. Papillae were excised from 100 g Sprague-Dawley rats and loaded with the appropriate dye. The papillae were then examined using a Leica TCS 4D confocal microscope and oil immersion lenses. Fluorescence was excited (488 nm) using an argon laser and emission wavelengths above 515 nm collected using a long pass filter. Images of papillae loaded with 2'7'-bis-(carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester clearly demonstrate a ladder-like arrangement of renal medullary interstitial cells. More detailed examination revealed the presence of cytoplasmic extensions that appear to make close contact with adjacent loops of Henle. Three-dimensional reconstructions of serial sections revealed spiral arrangements in some ladders of renal medullary interstitial cells. Nile Red-labelled lipid droplets of 0.5-1.0 microm diameter were located throughout the cytoplasm of renal medullary interstitial cells and especially within the cytoplasmic extensions. These experiments highlight the ability of confocal microscopy to allow investigation of renal medullary interstitial cells in situ.

Seroprevalence of antibodies to Sarcocystis neurona in horses residing in Oregon

OBJECTIVE

To determine seroprevalence of antibodies to Sarcocystis neurona in neurologically normal horses residing in 4 regions of Oregon and to describe the effects of age, gender, breed, and housing on seroprevalence within each region.

DESIGN

Prevalence survey.

SAMPLE POPULATION

Serum samples from 334 horses systematically selected by practicing veterinarians.

PROCEDURE

Antibodies to S neurona were measured in sera, using a western blot. Information including age, gender, breed, housing, geographic location, and duration of residence was obtained for each horse. Data were analyzed, using descriptive statistics.

RESULTS

45% (149/334) of horses evaluated were seropositive for antibodies to S neurona with significant differences in the percentage of seropositive horses from different regions of the state. Seroprevalances of antibodies to S neurona in horses in regions I and II, west of the Cascade Range, were 65 and 60%, respectively; whereas seroprevalances in central and eastern Oregon, regions III and IV, were 43 and 22%, respectively. Seroprevalence consistently increased with age of horse for each region. Gender, breed, and housing were not associated with significant differences in seroprevalence of antibodies to S neurona in the overall sample population, or in comparisons of samples obtained from horses within a particular region, or among samples obtained from horses residing in different regions.

CLINICAL IMPLICATIONS

The high seroprevalence of antibodies to S neurona in neurologically normal horses indicates that analysis of serum alone would not be useful for definitive diagnosis of equine protozoal myeloencephalitis in horses in Oregon.

Mast cell adenosine induced calcium mobilization via Gi3 and Gq proteins

Adenosine is an important mediator of mast cell secretory responses. Adenosine appears to act through one or more adenosine receptor subtypes to activate several signal transduction pathways; however, the specific mechanisms involved are not clearly defined. We studied the pathways involved in adenosine receptor-mediated calcium fluxes in RBL-2H3 cells, a mucosal mast cell-like line. The role of endogenous heterotrimeric G proteins in adenosine mediated calcium mobilization was investigated by microinjection of inhibitory antibodies that block specific G protein subtype function. The calcium transients associated with adenosine and antigen stimulation were compared in noninjected cells and cells that were microinjected with affinity purified neutralizing antibodies to the alpha subunits of Gi3, Gq, or Gs. The percentage of cells responding to adenosine was decreased in the presence of antibodies to Gi3 and Gq, but not Gs. Pertussis toxin decreased the percentage of cells responding to adenosine, but not antigen. These studies demonstrated a functional requirement for the pertussis toxin sensitive Gi3 protein and the pertussis toxin insensitive Gq protein in adenosine mediated calcium mobilization in mast cells.

The phosphatidylinositol 3-kinase inhibitor wortmannin blocks mast cell exocytosis but not IL-6 production

Phosphatidylinositol 3-kinase (PI3-kinase) activity has been shown to be important in cellular signaling via receptors associated with tyrosine kinases and receptors coupled to small or heterotrimeric G proteins. The importance of this activity in mast cell degranulation, leukotriene C4 generation, and IL-6 production was examined in mouse bone marrow-derived mast cells stimulated by high affinity IgE receptor cross-linking, direct influx of calcium, and/or adenosine receptor agonist exposure. Wortmannin, a fungal metabolite that at nanomolar concentrations inhibits PI3-kinase relatively specifically, blocked the release of granule-associated mast cell mediators independent of the secretory stimulus used. This inhibition was most prominent after a 2- to 5-min preincubation with wortmannin and was equally effective in cells additionally treated with exogenous N-ethylcarboxamidoadenosine to potentiate preformed mediator release. Mast cell production of leukotriene C4 20 min after activation or IL-6 16 h after activation was unaffected by up to 100 nM of wortmannin exposure. Mast cells preincubated with wortmannin failed to develop the classic electronmicroscopic evidence of granule swelling and fusion, increased membrane ruffling, or exocytosis upon Ag challenge. Activation of PI3-kinase appears to be critical for mast cell degranulation but is not required for arachidonic acid metabolism or cytokine production to occur. Furthermore, the inhibition of mast cell secretion by wortmannin is not stimulus specific but is evident for both IgE receptor cross-linking and direct calcium influx.

The phosphatidylinositol 3-kinase inhibitor wortmannin blocks mast cell exocytosis but not IL-6 production

Phosphatidylinositol 3-kinase (PI3-kinase) activity has been shown to be important in cellular signaling via receptors associated with tyrosine kinases and receptors coupled to small or heterotrimeric G proteins. The importance of this activity in mast cell degranulation, leukotriene C4 generation, and IL-6 production was examined in mouse bone marrow-derived mast cells stimulated by high affinity IgE receptor cross-linking, direct influx of calcium, and/or adenosine receptor agonist exposure. Wortmannin, a fungal metabolite that at nanomolar concentrations inhibits PI3-kinase relatively specifically, blocked the release of granule-associated mast cell mediators independent of the secretory stimulus used. This inhibition was most prominent after a 2- to 5-min preincubation with wortmannin and was equally effective in cells additionally treated with exogenous N-ethylcarboxamidoadenosine to potentiate preformed mediator release. Mast cell production of leukotriene C4 20 min after activation or IL-6 16 h after activation was unaffected by up to 100 nM of wortmannin exposure. Mast cells preincubated with wortmannin failed to develop the classic electronmicroscopic evidence of granule swelling and fusion, increased membrane ruffling, or exocytosis upon Ag challenge. Activation of PI3-kinase appears to be critical for mast cell degranulation but is not required for arachidonic acid metabolism or cytokine production to occur. Furthermore, the inhibition of mast cell secretion by wortmannin is not stimulus specific but is evident for both IgE receptor cross-linking and direct calcium influx.

Inhibition of protein kinase A fails to alter mast cell adenosine responsiveness

Adenosine activates adenylate cyclase and phospholipase C in mast cells and potentiates stimulated mediator release. To determine whether activation of adenylate cyclase is necessary for the effects of adenosine on the mast cell secretory process, a specific inhibitor of cAMP-dependent protein kinase, KT5720, was used. Antigen and adenosine each induced a rapid increase in mast cell cAMP-dependent protein kinase activity within 30 s. Preincubation with KT5720 (100 nM-10 microM) suppressed cAMP-dependent protein kinase activity and inhibited antigen-stimulated beta-hexosaminidase and leukotriene C4 releases. Adenosine retained its ability to potentiate beta-hexosaminidase release in antigen- and A23187-stimulated cells even in the presence of complete cAMP-dependent protein kinase inhibition. Mast cells rendered unresponsive to adenosine-related signals by preincubation with adenosine analogs maintained this hyporesponsiveness after incubation with KT5720. It appears that the abilities of adenosine to augment mast cell degranulation and induce receptor hyporesponsiveness are independent of changes in cAMP.

Cloning of two adenosine receptor subtypes from mouse bone marrow-derived mast cells

Adenosine potentiates the stimulated release of mast cell mediators. Pharmacologic studies suggest the presence of two adenosine receptors, one positively coupled to adenylate cyclase and the other coupled to phospholipase C activation. To identify mast cell adenosine receptor subtypes, cDNAs for the A1 and A2a adenosine receptors were obtained by screening a mouse brain cDNA library with the use of PCR-derived probes. Mouse bone marrow-derived mast cell cDNA libraries were constructed and screened with the use of A1 and A2a cDNA probes, which revealed the presence of A2a, but not A1, receptor clones. A putative A2b receptor was identified by using low stringency mast cell library screening. Northern blotting of mast cell poly(A)+ RNA with the use of receptor subtype probes labeled single mRNA bands of 2.4 kb and 1.8 kb for the A2a and A2b receptors, respectively. In situ cells. An A2a receptor-specific agonist failed to enhance mast cell mediator release, which suggests that the secretory process is modulated through the A2b and/or another receptor subtype. By using RNase protection assays, we found that mast cells that had been cultured in the presence of N-ethylcarboxamidoadenosine for 24 h exhibited a decrease in both A2a and A2b receptor RNA levels. Cells that had been cultured for 1 to 2 days in the presence of dexamethasone demonstrated increased amounts of A2a receptor mRNA, but no identifiable change in A2b receptor mRNA. Mast cells possess at least two adenosine receptor subtypes that may be differentially regulated.

Cloning of two adenosine receptor subtypes from mouse bone marrow-derived mast cells

Adenosine potentiates the stimulated release of mast cell mediators. Pharmacologic studies suggest the presence of two adenosine receptors, one positively coupled to adenylate cyclase and the other coupled to phospholipase C activation. To identify mast cell adenosine receptor subtypes, cDNAs for the A1 and A2a adenosine receptors were obtained by screening a mouse brain cDNA library with the use of PCR-derived probes. Mouse bone marrow-derived mast cell cDNA libraries were constructed and screened with the use of A1 and A2a cDNA probes, which revealed the presence of A2a, but not A1, receptor clones. A putative A2b receptor was identified by using low stringency mast cell library screening. Northern blotting of mast cell poly(A)+ RNA with the use of receptor subtype probes labeled single mRNA bands of 2.4 kb and 1.8 kb for the A2a and A2b receptors, respectively. In situ cells. An A2a receptor-specific agonist failed to enhance mast cell mediator release, which suggests that the secretory process is modulated through the A2b and/or another receptor subtype. By using RNase protection assays, we found that mast cells that had been cultured in the presence of N-ethylcarboxamidoadenosine for 24 h exhibited a decrease in both A2a and A2b receptor RNA levels. Cells that had been cultured for 1 to 2 days in the presence of dexamethasone demonstrated increased amounts of A2a receptor mRNA, but no identifiable change in A2b receptor mRNA. Mast cells possess at least two adenosine receptor subtypes that may be differentially regulated.

Activity of phenazine analogs against Mycobacterium leprae infections in mice

Twenty-five compounds structurally related to clofazimine were tested for their ability to inhibit the growth of Mycobacterium leprae using the kinetic method of drug evaluation in the mouse foot pad model of leprosy. Seven of the phenazine derivatives displayed anti-M. leprae activity comparable to that of clofazimine when administered at a concentration of 0.01% (w/w) in the diet. Three of the compounds, B746, B4087, and B4101, were active when administered at 0.001% in the diet. At a dietary concentration of 0.0001%, B4087 and B4101 were slightly more active than clofazimine, while B746 was less active. In the kinetic method of drug evaluation, greater anti-M. leprae activity of phenazine derivatives was generally associated with greater pigmentation of abdominal fat. Of the compounds which did not cause pigmentation when fed at a concentration of 0.01% in the diet B4090 was the most active. This compound also inhibits the growth of a clofazimine-resistant M. smegmatis strain.

Mast cell desensitization to IgE fails to induce a parallel adenosine receptor desensitization

Desensitization induced by challenge of mast cells with antigen is specific for IgE-dependent signals. During the secretory process mast cells release adenosine, which can induce a desensitization of adenosine receptors. To determine whether adenosine receptors may be desensitized from a previous antigen challenge, mast cells were sensitized with anti-DNP IgE antibody, challenged with DNP-BSA antigen, returned to culture overnight, resensitized, and rechallenged. Previously challenged cells exhibited increased spontaneous beta-hexosaminidase release, but adenosine retained its ability to augment beta-hexosaminidase release. Adenosine enhanced A23187-stimulated release of beta-hexosaminidase in control and previously challenged cells. Leukotriene C4 generation followed a similar pattern. Mastoparan, a direct G protein activator and mast cells secretagogue, produced a doubling of beta-hexosaminidase release in previously challenged cells. Results using other G protein activators were equivocal. Degranulation alone is insufficient to induce adenosine receptor hyposensitization. Whether the hyperresponsiveness to mastoparan is a consequence of uncoupling of IgE receptors from G proteins remains uncertain.

Altered blood pressure, renal tubular function and levels of circulating inhibitors of Na-K-ATPase in mature SHR exposed to low salt diet in the perinatal period

1. It has been shown previously that low salt diet, confined to the perinatal period only, reduces blood pressure (BP) and sodium retention in spontaneously hypertensive rat (SHR) offspring at maturity when compared with those given high salt diet. 2. In this study it is shown that such high salt diets are associated with an increased level of circulating Na-K-ATPase inhibitor (CINK) activity. 3. Animals given perinatal high salt diet have a significantly greater tubular reabsorptive capacity when compared with those given low salt diet. 4. The finding of a high level of circulating Na-K-ATPase inhibitory material in the face of increased renal tubular capacity and blood pressure suggests that while this inhibitory material may play a role in the elevated blood pressure of animals given high salt diet, it cannot cause the elevated rate of fluid reabsorption.

Clarithromycin is bactericidal against strains of Mycobacterium leprae resistant and susceptible to dapsone and rifampin

The anti-Mycobacterium leprae activity of clarithromycin when administered alone and in combination with rifampin and dapsone in the diet was determined using the kinetic method of drug evaluation in mice. Clarithromycin when administered at a concentration of 0.1% (w/w) in the diet completely prevented growth of 2 pan-susceptible, 3 dapsone-resistant, 2 rifampin-resistant, and 2 rifampin and dapsone double resistant strains of M. leprae. A 0.03% (w/w) concentration also completely prevented growth of M. leprae in all mice infected with 2 of 7 strains tested, but in only some of the mice infected with the remaining 5 strains. No antagonistic drug interactions were observed between clarithromycin and dapsone or rifampin. The addition of clarithromycin to the currently recommended multidrug regimen should improve the rate of killing of M. leprae and help to prevent the growth of dapsone-resistant and rifampin-resistant strains.

Lysophosphatidylcholine induces mast cell secretion and protein kinase C activation

Lysophosphatidylcholine (lyso-PC), a natural product of phospholipase A2 activity, induced the secretion of both granule-associated beta-hexosaminidase and newly generated leukotriene C4 from mouse bone marrow-derived mast cells. Micromolar concentrations of lyso-PC potentiated the release of beta-hexosaminidase induced by specific antigen but not the calcium ionophore, A23187. Exogenous adenosine was relatively ineffective in enhancing beta-hexosaminidase release from cells challenged with lyso PC. Lyso-PC caused a marked increase in intracellular free-calcium levels and induced the activation of protein kinase C (PKC). These effects could not be abrogated by a prolonged preincubation with pertussis toxin. Staurosporine, an inhibitor of PKC, partially inhibited the abilities of antigen and A23187 to induce beta-hexosaminidase release but was ineffective when lyso-PC was the secretagogue. Lyso-PC appears to activate mast cell PKC, but its ability to stimulate mast cell mediator release appears to be related to its ability to elevate intracellular free calcium concentrations.

Evaluation of the oral vitamin E absorption test in horses

An oral vitamin E absorption test used in human beings was modified for use in horses. The most appropriate techniques with which to measure gastrointestinal tract absorption of vitamin E (alpha-tocopherol) in horses were developed. Vitamin E was administered orally, and serum values of alpha-tocopherol were measured by use of high-performance liquid chromatography at 0, 3, 6, 9, 12, and 24 hours after vitamin E administration. Variables included comparison of 2 dosages (45 and 90 IU/kg of body weight), routes of administration, and absorption dynamics of 3 preparations of dl-alpha-tocopherol. Absorption of the 2 doses of dl-alpha-tocopherol acetate indicated a dose response; the area under the curve at 24 hours (AUC24) was 4.3 micrograms.h/ml for the 45-IU/kg dose and 32.2 micrograms.h/ml (P less than 0.01) for the 90-IU/kg dose. Maximal absorption was apparent when vitamin E was naturally consumed in grain, compared with administration of identical preparations by stomach tube or paste. In the same horses, dl-alpha-tocopherol and dl-alpha-tocopherol acetate plus polyethylene glycol had statistically similar absorption curves and both had significantly greater AUC24, compared with dl-alpha-tocopherol acetate; values for the 3 compounds were 23.6, 25.8, and 12.6 micrograms.h/ml, respectively. The AUC24 varied between individual horses, but time of peak value was consistently observed between 6 and 9 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Filtration failure induced by p-aminophenol in rats is due to raised intratubular pressure and not changes in glomerular function

1. The p-aminophenol (pAP) model of tubular necrosis displays elevated tubular pressures equivalent to 'stop-flow', with low glomerular filtration rate (GFR) but maintained blood flow and urine output. Renal function, micropuncture, and morphological studies were performed in anaesthetized rats to examine the causes of filtration failure. 2. At the height of pAP-induced renal failure proximal tubular fluid reabsorption (Jv(a] was markedly reduced while proximal and distal free-flow rates measured by tubular fluid collections during venting of the nephron were not significantly different from saline-injected controls. Renal blood flow was maintained over the 4 h observation period despite extensive and selective proximal tubular necrosis. There was no temporal relationship between increased tubular pressure and cast formation. 3. Maintained blood and tubular fluid flow rates indicate that activation of tubuloglomerular feedback plays little or no part in pAP-induced renal failure, which is apparently due to high fluid flow resistance in the region of the connecting tubule, late distal convolution or collecting ducts. Morphological appearances were consistent with compression of these segments.

Modulation of mast cell responses to adenosine by agents that alter protein kinase C activity

The acute incubation of mouse bone marrow-derived mast cells with low concentrations of agents known to activate protein kinase C [phorbol myristate acetate (PMA), 1,2-dioctanoyl-sn-glycerol (diC8), and 1-oleoyl-2-acetyl-glycerol (OAG)] caused an enhancement of beta-hexosaminidase release stimulated by the calcium ionophore A23187. Higher concentrations of protein kinase C activators tended to inhibit A23187- or antigen-induced preformed mediator release. All concentrations studied induced a striking mast cell hyporesponsiveness to the mediator release augmenting effect of adenosine. Agents that have been reported to block protein kinase C activity [1-(5-isoquinolinesulfonyl)-2-methyl-piperazine dihydrochloride (H-7) and sphingosine] demonstrated diverse responses in this system. Up to 100 microM H-7 failed to affect mast cell beta-hexosaminidase release in the presence or absence of PMA and secretagogue. Sphingosine (10 microM) was a potent inhibitor of antigen- or A23187-induced mediator release as well as adenosine responsiveness. Sphingosine also blocked the effects of PMA noted above in a dose-dependent fashion. The generation of leukotriene C4 (LTC4) by stimulated mast cells surprisingly was not affected by concentrations of diC8 that significantly inhibited granule-associated mediator release. Translocation of protein kinase C activity from the cytosol to the mast cell membrane was evident in cells briefly pretreated with A23187, adenosine alone, and diC8 in the presence of Tyrode's buffer, A23187, or adenosine. These findings lend further support to the contention that signal transduction from mast cell adenosine receptors to processes that regulate degranulation may involve protein kinase C.

Myelitis in a cat infected with Toxoplasma gondii and feline immunodeficiency virus

Severe necrotizing myelitis secondary to localization and reactivation of Toxoplasma gondii within the spinal cord of a domestic shorthair cat was diagnosed by use of light and electron microscopy and immunohistochemistry. The cat also was infected with feline immunodeficiency virus. This case may have useful comparative features to T gondii infections in human patients with acquired immunodeficiency syndrome.

Pretreatment with phorbol esters abrogates mast cell adenosine responsiveness

Adenosine potentiates preformed mediator release from mouse bone marrow-derived mast cells stimulated with specific Ag or the calcium ionophore A23187. When these mast cells were cultured for 30 to 120 min with the phorbol ester PMA (10(-8) or 10(-7) M), protein kinase C activity was increased and Ag-stimulated beta-hexosaminidase release was modestly inhibited, whereas A23187-stimulated release was synergistically enhanced. However, in both cases, exogenous adenosine failed to augment beta-hexosaminidase release. Overnight PMA exposure produced a decrease in protein kinase C activity and a decrease in both Ag- and A23187-stimulated preformed mediator release, as well as a lack of responsiveness to adenosine. This hyporesponsiveness could be reversed by 24 h after washing the cells free of PMA. The generation of the arachidonic acid metabolite leukotriene C4 was not altered by mast cell PMA exposure. The ability of adenosine to increase intracellular cAMP concentrations was modestly blunted by high doses of PMA, and PMA abrogated the increase in intracellular free calcium levels usually observed in cells stimulated with Ag in the presence of 10(-5) M adenosine. PMA exposure induces a hyporesponsiveness to adenosine in mast cells, either by a direct effect on protein kinase C activity and/or by an effect on adenosine receptor expression or recycling.

Pretreatment with phorbol esters abrogates mast cell adenosine responsiveness

Adenosine potentiates preformed mediator release from mouse bone marrow-derived mast cells stimulated with specific Ag or the calcium ionophore A23187. When these mast cells were cultured for 30 to 120 min with the phorbol ester PMA (10(-8) or 10(-7) M), protein kinase C activity was increased and Ag-stimulated beta-hexosaminidase release was modestly inhibited, whereas A23187-stimulated release was synergistically enhanced. However, in both cases, exogenous adenosine failed to augment beta-hexosaminidase release. Overnight PMA exposure produced a decrease in protein kinase C activity and a decrease in both Ag- and A23187-stimulated preformed mediator release, as well as a lack of responsiveness to adenosine. This hyporesponsiveness could be reversed by 24 h after washing the cells free of PMA. The generation of the arachidonic acid metabolite leukotriene C4 was not altered by mast cell PMA exposure. The ability of adenosine to increase intracellular cAMP concentrations was modestly blunted by high doses of PMA, and PMA abrogated the increase in intracellular free calcium levels usually observed in cells stimulated with Ag in the presence of 10(-5) M adenosine. PMA exposure induces a hyporesponsiveness to adenosine in mast cells, either by a direct effect on protein kinase C activity and/or by an effect on adenosine receptor expression or recycling.

Alteration of mast cell responsiveness to adenosine by pertussis toxin

Adenosine potentiates mouse bone marrow-derived mast cell mediator release by a mechanism that appears to involve cell surface adenosine receptors. In an attempt to explore possible interactions between G proteins and adenosine receptors, mast cells were incubated with activated pertussis toxin, an agent that ADP-ribosylates and inactivates some G protein subtypes, prior to challenge with specific antigen or the calcium ionophore A23187. Mast cells preincubated with 10 ng/ml pertussis toxin for at least 2 hr exhibited an inhibition of antigen-induced beta-hexosaminidase and leukotriene C4 release. The ability of adenosine to potentiate beta-hexosaminidase release was attenuated to an even greater degree by pertussis toxin. A23187-stimulated mediator release was not altered by pertussis toxin, although a modest inhibition of the ability of adenosine to enhance A23187-induced beta-hexosaminidase release was observed in pertussis toxin-treated mast cells. Although up to 24-hr exposure to 100 ng/ml pertussis toxin did not alter resting mast cell cyclic AMP levels, the ability of adenosine to elevate cell cyclic AMP concentrations was diminished markedly by doses of the toxin higher than those required to affect mediator release. Neither antigen-stimulated intracellular free calcium level augmentation alone nor the additional potentiation of these levels by adenosine was changed by pertussis toxin treatment. Inositol trisphosphate was generated by mast cells stimulated by IgE-mediated mechanisms, but a preincubation with pertussis toxin did not influence its generation. In summary, adenosine appeared to produce some of its alterations in mast cell biochemical events by a mechanism that was partially inhibited by pertussis toxin. The nature of the G protein linked to the mast cell adenosine receptor is yet to be determined.

Inhibition of mast cell adenosine responsiveness by chronic exposure to adenosine receptor agonists

Mast cell adenosine receptors are up-regulated functionally and numerically by chronic exposure to receptor antagonists, but their response to long-term treatment with receptor agonists has not been studied. To address this issue cultured mouse bone marrow-derived mast cells were exposed to N-ethylcarboxamide adenosine (NECA), an adenosine receptor agonist that augments stimulated mast cell mediator release. Cells grown for 3 days in 1 nM NECA responded normally to A23187 or antigen in releasing beta-hexosaminidase, but the ability of exogenous adenosine to potentiate this mediator release was attenuated markedly. This inhibition of adenosine responsiveness was partially present after 10 min of 1 microM NECA exposure and complete after 4 hr. The inhibitory effects could be reversed by washing NECA-exposed cells and returning them to culture for more than 4 hr. The adenosine present in the fetal calf serum coupled with deoxycoformycin attenuated mast cell adenosine responsiveness. The NECA-treated cells also exhibited a hyporesponsiveness to adenosine's augmentation of cell cyclic AMP content. This hyporesponsiveness was specific for adenosine receptors in that exogenous isoproterenol was able to increase cyclic AMP levels to a similar degree in both control and NECA-treated cells. Thus, chronic NECA exposure induces a homologous desensitization of mast cell adenosine receptors.

Activity of selected beta-lactam antibiotics against Mycobacterium leprae

Twelve beta-lactam antibiotics were tested for activity against Mycobacterium leprae growing in the foot pads of mice. Two cephalosporins (7-aminocephalosporanic acid and cefuroxime) and one cephamycin (cefoxitin) showed significant activity against M. leprae, and one penicillin (mezlocillin) exerted possible growth-promoting activity. These results suggest that particular molecular structures may be required for activity against M. leprae.

Ribavirin inhibits mast cell mediator release

Ribavirin (1-beta-D-ribofuranosyl-1,2-4-triazole-3-carboxamide) is a promising antiviral agent as well as a structural analog of guanosine. Although at different concentrations it has been reported to induce either immunosuppression or immune stimulation, its effects upon immediate hypersensitivity reactions are largely unknown. Because purine metabolism appears to be important in mast cell secretion, the effects of ribavirin on mouse bone marrow-derived mast cell functions were investigated. When ribavirin was added to mast cells at the time of stimulation with A23187 or specific antigen, no effect on the release of beta-hexosaminidase, a preformed mediator, was evident. However, mast cells cultured in 1 to 20 microM ribavirin for 1 to 7 days exhibited dose- and time-dependent inhibitions of stimulated beta-hexosaminidase and leukotriene C4 releases without altering mast cell mediator content. This inhibition occurred even when ribavirin had no effect on cell growth. A concomitant decrease in antigen-challenged mast cell intracellular Ca concentration was also observed after ribavirin treatment. Chronic ribavirin exposure in vitro inhibits mast cell secretory processes stimulated by both immunoglobulin E- and nonimmunoglobulin E-related signals. Its precise mechanism of action and any potential efficacy as an antiallergic agent remain to be elucidated.

Cromolyn inhibition of mediator release in mast cells derived from mouse bone marrow

Mast cells derived from mouse bone marrow fail to demonstrate a disodium-cromoglycate-induced inhibition of mediator release when the cromolyn is added simultaneously with a secretagogue. To investigate the long-term effects of cromolyn exposure, cells from BALB/C femoral bone marrow stimulated with IL-3 were cultured in the presence of 1 to 100 microM cromolyn and demonstrated a similar viability and ability to proliferate as cells cultured in medium alone. Those cultured in cromolyn exhibited a significantly decreased A23187- or antigen-induced release of beta-hexosaminidase (4.3 +/- 0.7% versus 9.2 +/- 1.0%, p less than 0.01) compared with control cells. The adenosine-induced potentiation of mediator release was diminished to a comparable degree after cromolyn exposure in culture. This inhibition was dose-dependent between 1 and 100 microM cromolyn, evident by 5 days, reversible in 6 more days, and applied to immunoreactive leukotriene C4 generation as well. Bone marrow mast cells respond to chronic cromolyn exposure with a global inhibition of mediator release, but the basis for this response is unknown.

Adenosine receptors on mouse bone marrow-derived mast cells: functional significance and regulation by aminophylline

Adenosine receptors on mouse bone marrow-derived mast cells were identified by functional criteria and radioligand binding. The stimulated release of beta-hexosaminidase from these cells was significantly augmented by the simultaneous addition of secretagogue and adenosine, NECA, or L-PIA. Similar enhancement of pre-formed mediator release occurred after a 10-min preincubation with adenosine. Resting mast cell cAMP levels increased within 15 sec after the addition of adenosine, and remained elevated for at least 60 sec. Although the antigen-or A23187-induced release of beta-hexosaminidase was markedly potentiated by exogenous adenosine, the stimulated release of [14C]-labeled arachidonic acid metabolites was minimally affected by adenosine, suggesting a differential effect of adenosine on granule-associated release as compared to generated mediator release. Bone marrow mast cells exhibited 5470 +/- 740 [3H]adenosine binding sites/cell, with a binding affinity of 24.4 +/- 3.8 nM. Cells cultured in the presence of 100 microM aminophylline for 6 days were hyperresponsive to exogenous adenosine, releasing a maximum of 162% of the amount of beta-hexosaminidase released from control cells in the presence of adenosine. The number of [3H]adenosine binding sites on the xanthine-treated cells increased to 156% of control values, suggesting an up-regulation of adenosine receptors induced by chronic exposure to an adenosine receptor antagonist. Mouse bone marrow mast cells possess functionally significant adenosine receptors that are regulated by aminophylline and that, when stimulated, produce many alterations in the mast cell secretory process.

Adenosine receptors on mouse bone marrow-derived mast cells: functional significance and regulation by aminophylline

Adenosine receptors on mouse bone marrow-derived mast cells were identified by functional criteria and radioligand binding. The stimulated release of beta-hexosaminidase from these cells was significantly augmented by the simultaneous addition of secretagogue and adenosine, NECA, or L-PIA. Similar enhancement of pre-formed mediator release occurred after a 10-min preincubation with adenosine. Resting mast cell cAMP levels increased within 15 sec after the addition of adenosine, and remained elevated for at least 60 sec. Although the antigen-or A23187-induced release of beta-hexosaminidase was markedly potentiated by exogenous adenosine, the stimulated release of [14C]-labeled arachidonic acid metabolites was minimally affected by adenosine, suggesting a differential effect of adenosine on granule-associated release as compared to generated mediator release. Bone marrow mast cells exhibited 5470 +/- 740 [3H]adenosine binding sites/cell, with a binding affinity of 24.4 +/- 3.8 nM. Cells cultured in the presence of 100 microM aminophylline for 6 days were hyperresponsive to exogenous adenosine, releasing a maximum of 162% of the amount of beta-hexosaminidase released from control cells in the presence of adenosine. The number of [3H]adenosine binding sites on the xanthine-treated cells increased to 156% of control values, suggesting an up-regulation of adenosine receptors induced by chronic exposure to an adenosine receptor antagonist. Mouse bone marrow mast cells possess functionally significant adenosine receptors that are regulated by aminophylline and that, when stimulated, produce many alterations in the mast cell secretory process.

Early functional and morphological changes in renal tubular necrosis due to p-aminophenol

Functional and morphological changes developed rapidly in rats after the intravenous administration of the organic nephrotoxin p-aminophenol. Proximal intratubular pressure remained close to its mean control value of 14.9 +/- 0.9 mm Hg up to 40 min after injection of the nephrotoxin then rose rapidly over the following 50 min to a maximum of 38.7 +/- 7.4 mm Hg. Distal tubular pressure also rose in the same manner. Renal blood flow remained constant, but GFR fell to 11% of control values while fractional excretion of sodium and water rose 12 and five times, respectively. Morphological changes developed in parallel with the functional changes. They were widespread, varied in intensity from cell to cell, were more severe in the distal third of the proximal convoluted tubule and consisted of cytoplasmic swelling, reduced organelle concentration, reduction or loss of basal infoldings, widening of lateral intercellular spaces, extrusion of bubbles of cell sap into the tubular lumen; brush borders were preserved. No casts were present up to 90 min. Similar results were seen when p-aminophenol was added to the perfusate of the isolated perfused kidney. It is proposed that metabolic and morphological damage leads rapidly to both impairment of proximal tubular sodium reabsorption and increased flow resistance in the cortical collecting system. Both effects contribute to a rise in tubular pressures which oppose glomerular filtration.

Comparison of the immunogenicity of vaccines prepared from viable Mycobacterium bovis BCG, heat-killed Mycobacterium leprae, and a mixture of the two for normal and M. leprae-tolerant mice

Intradermal vaccines consisting of viable Mycobacterium bovis BCG, heat-killed Mycobacterium leprae, or mixtures of the two were titrated in mice in doses of 10(5.2), 10(5.8), 10(6.4), 10(7.0), and 10(7.6) acid-fast bacilli. The immune response was measured by sensitization (48 to 72 h foot pad enlargement on challenge with 10(7.0) heat-killed M. leprae) and by protection against infection with a viable M. leprae challenge. There was increasing response with increasing dose of vaccine, and overall the responses to the three vaccines were similar. At the lowest dose, however, the combination of BCG and M. leprae gave superior protection. The local reaction to the vaccines in the lower dose range was less severe with the M. leprae vaccine. In another experiment, the three vaccines were compared in normal mice and in mice that had been rendered tolerant by intravenous injection of M. leprae. The tolerant mice developed no measurable sensitization on vaccination with M. leprae, but they developed partial but distinct sensitization on vaccination with BCG, alone or in combination with M. leprae. The tolerant mice developed little or no protection with any of the vaccines, however.

Sensitization or tolerance to Mycobacterium leprae antigen by route of injection

Aqueous suspensions of heat-killed Mycobacterium leprae in a dose of 10(7) organisms were highly immunogenic when injected intradermally (i.d.). The same dose of bacteria did not sensitize when given intraperitoneally (i.p.) or intravenously (i.v.), and did so only minimally at best when given subcutaneously. The i.d. route was the most immunogenic for sheep erythrocytes also. M. leprae injected i.p. or i.v. stimulated immune tolerance to M. leprae challenge i.d. In older mice (greater than or equal to 8 weeks), the i.v. injections gave more complete tolerance. Mice that had been rendered tolerant by i.v. injections maintained their tolerance for at least 168 days. Prior UV irradiation of intact mice prevented sensitization by the i.d. route. In normal mice, living M. bovis BCG given i.d. produced good sensitization to M. leprae. Mice that had been made tolerant by i.v. injection of M. leprae could be partially sensitized to M. leprae by i.d. immunization with BCG; mixtures of living BCG and heat-killed M. leprae were no more effective than BCG alone. These findings appear to have relevance to the pathogenesis of lepromatous leprosy and its immunoprophylaxis.

Foot pad enlargement as a measure of induced immunity to Mycobacterium leprae

Foot pad enlargement (FPE) has been used as a measure of induced immunity to M. leprae, FPE peaked at 2-3 days, but it sometimes persisted for 4 weeks or more. Both as the inducing and eliciting antigen, heat-killed M. leprae were effective, and the optimum dose was about 1 x 10(7) bacilli. Higher doses were associated with flattening of the dose-response curve. Disrupted bacilli were not effective in immunizing mice, but they elicited FPE responses in mice immunized with intact bacilli. Cord factor was not found to have adjuvant activity for M. leprae. In immunization, the intradermal route was confirmed to be more effective than the foot pad route; the subcutaneous route was effective in providing protection against infection. FPE tests were used to investigate the steps of standard purification procedures for M. leprae in armadillo livers. A trypsin-chymotrypsin digestion step was found to be harmful to immunogenicity in one of two experiments.

Searches among mycobacterial cultures for antileprosy vaccines

All mycobacteria species share some antigens, so there may be cultivable mycobacterial cultures that can provide vaccine protection against leprosy. Vaccine protection against Mycobacterium leprae infections in mice has been demonstrated for M. leprae itself, as living or heat-killed suspensions, and for Mycobacterium bovis (BCG), as living suspensions. Results are reported here with 17 other cultures. The mycobacterial suspensions were injected intradermally, and the mice were challenged in the footpad with infectious suspensions of M. leprae. In two experiments the mice were also challenged by footpad injections of 10(7) heat-killed M. leprae so the footpad enlargment could be measured. That some mycobacterial suspensions were immunogenic for some of their own antigens was suggested by reactions at the vaccine site and enlargement of the regional lymph nodes. Some mycobacterial suspensions also stimulated footpad enlargement on challenge by homologous suspensions or by challenge with M. leprae suspensions. Consistent protection against infectious challenge with M. leprae was observed only with BCG and M. leprae, however.

Cloned Cauliflower Mosaic Virus DNA Infects Turnips (Brassica rapa)

Cauliflower mosaic virus DNA cloned in the Sal I site of bacterial plasmid pBR322 infects turnip plants. The cloned viral DNA must be excised from the recombinant plasmid to infect, but need not be circularized and ligated in vitro. The cloned viral DNA lacks site-specific single-strand breaks found in DNA obtained directly from the virus. However, these breaks are reintroduced into the viral genome during multiplication of the virus in the plant host.

Heat stability of Mycobacterium leprae immunogenicity

The protection provided to mice by vaccines administered intradermally was measured after footpad challenge with Mycobacterium leprae. The protection offered by M. leprae suspensions was not decreased when the vaccines were killed by 60 degrees C heat or at the higher temperatures tested, which included 215 degrees C (autoclave). Even highly purified suspensions retained their immunogenicity. In contrast, the vaccine protection provided by intradermal M. bovis (strain BCG) was markedly reduced when heated to 60 degrees C. The enlargement of the lymph nodes regional to the intradermal vaccines was measured and found generally to parallel the vaccine protection provided by M. leprae and by BCG.

Immunity to Mycobacterium leprae infections induced in mice by BCG vaccination at different times before or after challenge

Viable suspensions of BCG, an attenuated strain of Mycobacterium bovis, have been previously shown to immunize mice against infections with M. leprae. Usually, the mice have been vaccinated about 1 month before challenge. Experiments have now been carried out with single intradermal injections of BCG given before or after the M. leprae challenge. Approximately equal immunizing effect was seen in one experiment when the BCG was given at -168, -119, -70, and -28 days relative to challenge. Approximately equal protection was observed in another experiment when the vaccine was given at -28, +28, and +56 days. In the latter experiment, however, vaccine given at +91 days appeared to be somewhat less effective. Enlargement of the lymph nodes regional to the intradermal vaccine site persisted for at least the duration of the experiment, approximately 400 days. Thus, antigenic stimulation appears to have continued throughout the period of observation.

Effect of levamisole on Mycobacterium leprae in mice

Levamisole, an antihelminthic drug that is capable of enhancing immune responses in mice and in humans, was tested in experimental Mycobacterium leprae infections in mice by a number of schedules. Intermittent schedules were used, and administration of the drug was started (i) around the time of inoculation with M. leprae, (ii) when the M. leprae population was approaching the plateau level, (iii) after the onset of the plateau phase, or (iv) after BCG vaccination 28 days following the inoculation with M. leprae. No effect of drug could be discerned with any of the schedules.

Identification and Properties of the Messenger RNA Activity in Chlamydomonas reinhardi Coding for the Large Subunit of d-ribulose-1,5-bisphosphate Carboxylase

Properties of the mRNA coding for the large subunit of ribulose-1,5-bisphosphate carboxylase from Chlamydomonas reinhardi were determined. Large subunit synthesis, directed by RNA from partially purified whole cell extracts, was detected by specific immunoprecipitation of polypeptide products synthesized in a heterologous translation system derived from Escherichia coli. Large subunit synthesis showed sharp RNA concentration dependence in an E. coli translation system, and at optimal RNA concentrations, immunoprecipitable large subunit synthesis accounted for 2% of the total incorporation. Large subunit messenger activity sedimented at 12 to 14S on nondenaturing sucrose gradients and did not bind to oligo(dT)-cellulose suggesting the mRNA is not polyadenylated. The immunoprecipitable products translated in vitro are not complete polypeptide chains, but are smaller peptides identifiable as large subunit fragments by tryptic fingerprint analysis. No immunoprecipitable product was obtained when similar RNA fractions were tested in a wheat germ translation system.