Abeta deposits in older non-demented individuals with cognitive decline are indicative of preclinical Alzheimer's disease.

Approximately 30% of healthy persons aged over 75 years show Abeta deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between Abeta burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and cognitive tests were performed on 34 elderly participants (age 73+/-6) from the longitudinal Melbourne Healthy Aging Study (MHAS). Subjects were classified as being cognitively 'stable' or 'declining' by an independent behavioural neurologist based on clinical assessment and serial word-list recall scores from the preceding 6-10 years. Decline was calculated from the slope of the word-list recall scores. Abeta burden was quantified using Standardized Uptake Value normalized to cerebellar cortex. Ten subjects were clinically classified as declining. At the time of the PET scans, three of the declining subjects had mild cognitive impairment, one had AD, and six were declining but remained within the normal range for age on cognitive tests. Declining subjects were much more likely to show cortical PiB binding than stable subjects (70% vs. 17%, respectively). Neocortical Abeta burden correlated with word-list recall slopes (r=-0.78) and memory function (r=-0.85) in the declining group. No correlations were observed in the stable group. Abeta burden correlated with incident memory impairment and the rate of memory decline in the non-demented ageing population. These observations suggest that neither memory decline nor Abeta deposition are part of normal ageing and likely represent preclinical AD. Further longitudinal observations are required to confirm this hypothesis.

CD4+ T cells from mice with intestinal immediate-type hypersensitivity induce airway hyperreactivity.

BACKGROUND: A subset of food-allergic patients does not only respond clinically with symptoms in the gastro-intestinal tract but also with asthmatic reactions. OBJECTIVE: The aim of this study was to analyse whether CD4+ T cells from mice with intestinal immediate-hypersensitivity reactions to food allergen are involved in the development of experimental asthma. METHODS: BALB/c mice were intraperitoneally sensitized to ovalbumin (OVA), followed by repeated intra-gastric (i.g.) OVA challenges. Control animals were either sham-sensitized or sham-challenged with phosphate-buffered saline (PBS). Duodenum, jejunum, ileum and colon were histologically examined. CD4+ T cells from mesenteric lymph nodes were transferred from various donor groups into recipient mice that received either OVA or PBS aerosol challenges. Recipients were analysed by measurements of lung function using head-out body-plethysmography and examination of broncho-alveolar lavage and lung histology. RESULTS: The highest levels of OVA-specific IgE antibody levels were detected in OVA-sensitized and OVA-challenged mice. Throughout the lower intestinal tract, a marked infiltration with eosinophils was observed, and goblet cell numbers as well as goblet cell area were significantly increased. The villus/crypt ratio was decreased compared with controls. The transfer of CD4+ T cells from mesenteric lymph nodes of OVA-sensitized and OVA-challenged mice triggered airway hyperreactivity and eosinophilic airway inflammation in recipients aerosol challenged with OVA, but not with PBS. CONCLUSION: We conclude that CD4+ T cells from mesenteric lymph nodes of mice with allergen-induced immediate-type hypersensitivity reactions in the gut are able to transfer the phenotype of experimental asthma.

Imaging beta-amyloid burden in aging and dementia.

OBJECTIVE: To compare brain beta-amyloid (Abeta) burden measured with [(11)C]Pittsburgh Compound B (PIB) PET in normal aging, Alzheimer disease (AD), and other dementias. METHODS: Thirty-three subjects with dementia (17 AD, 10 dementia with Lewy bodies [DLB], 6 frontotemporal dementia [FTD]), 9 subjects with mild cognitive impairment (MCI), and 27 age-matched healthy control subjects (HCs) were studied. Abeta burden was quantified using PIB distribution volume ratio. RESULTS: Cortical PIB binding was markedly elevated in every AD subject regardless of disease severity, generally lower and more variable in DLB, and absent in FTD, whereas subjects with MCI presented either an "AD-like" (60%) or normal pattern. Binding was greatest in the precuneus/posterior cingulate, frontal cortex, and caudate nuclei, followed by lateral temporal and parietal cortex. Six HCs (22%) showed cortical uptake despite normal neuropsychological scores. PIB binding did not correlate with dementia severity in AD or DLB but was higher in subjects with an APOE-epsilon4 allele. In DLB, binding correlated inversely with the interval from onset of cognitive impairment to diagnosis. CONCLUSIONS: Pittsburgh Compound B PET findings match histopathologic reports of beta-amyloid (Abeta) distribution in aging and dementia. Noninvasive longitudinal studies to better understand the role of amyloid deposition in the course of neurodegeneration and to determine if Abeta deposition in nondemented subjects is preclinical AD are now feasible. Our findings also suggest that Abeta may influence the development of dementia with Lewy bodies, and therefore strategies to reduce Abeta may benefit this condition.

Synthesis and evaluation of a thymidine analog for positron emission tomography study of tumor DNA proliferation in vivo.

This study describes the synthesis, radiolabelling and biological evaluation of 5-(2,4-difluoro-5-[18F]fluoromethyl-phenyl)-2-hydroxymethyl-tetrahydrofuran-3-ol, 13. Radiolabelling was achieved by reaction of the tosylate 3 with K[18F] in the presence of Kryptofix 222. Good stability in saline and serum solutions at physiological temperatures in vitro was observed. A cell incorporation study of 13 using SW1222 tumor cells showed a linear uptake, unfortunately, in vivo studies indicated that 13 was undergoing defluorination. Rapid defluorination of the radiotracer was confirmed by an in vitro stability study in blood plasma. Finally, a comparison between the DNA uptake of 13 and tritiated thymidine was performed in vitro to asses the potential utility of more stable analogs. These studies showed that 13 and its analogs are unsuitable as potential tracers to image DNA proliferation and highlighted the difficulty in predicting the in vivo stability of novel radiotracers.

Reduced baroreceptor sensitivity during hypotension in ANP-knockout mice.

We studied baroreflex gain in inactin-anesthetized mice that had been genetically modified to be depleted of atrial natriuretic peptide (ANP -/-). Wild-type mice (ANP +/+) served as controls. ANP -/- mice had a significantly higher basal arterial blood pressure (ABP) than ANP +/+ mice [112+/-7 vs. 80+/-5 mmHg (mean +/- SEM)]. Their basal heart rates were not different (491+/-13 vs. 446+/-19 bpm). A third group, composed of ANP +/+ mice only, was rendered acutely hypertensive by an intravenous infusion of arginine vasopressin acetate (0.3 pg bolus followed by 0.3 pg/h) so as to serve as a control for the elevated ABP in the ANP -/- mice. Transient changes in ABP were caused by bolus injections of oxymetazoline hydrochloride (1.5-3 ng) or sodium nitroprusside (20-100 ng). Baroreflex gain was calculated as the ratio of the peak heart rate change that followed the peak change in mean ABP resulting from injection of oxymetazoline or nitroprusside. There were no significant differences among the groups in their responses to transient hypertension. On the other hand, the ANP -/- mice showed a significantly depressed tachycardic response to transient hypotension when compared with the other two groups. We conclude that the ANP -/- mice are unable to increase efferent sympathetic nervous activity adequately above the high basal activity that is a feature of this animal model.

Sleep as a teaching tool for integrating respiratory physiology and motor control.

Sleep exerts major effects on most fundamental homeostatic mechanisms. Current data suggest, however, that students of physiology and medicine typically receive little or no formal teaching in sleep. Because sleep takes up a significant component of our life span, it is proposed that current teaching in systems and integrative physiology is not representative if it is confined to functions describing wakefulness only. We propose that sleep can be readily integrated into various components of physiology and medical curricula simply by emphasizing how commonly taught physiological processes are importantly affected by sleep mechanisms. In our experience, this approach can be used to reinforce basic physiological principles while simultaneously introducing sleep physiology into the students' training. We find that students have a general and inherent interest in sleep and related clinical disorders, and this proves useful as an effective means to teach the material. In this paper, examples of how sleep influences motor control and the respiratory system will illustrate these points. These considerations also highlight some important gaps in traditional teaching of respiratory physiology.

ANP in regulation of arterial pressure and fluid-electrolyte balance: lessons from genetic mouse models.

The recent development of genetic mouse models presenting life-long alterations in expression of the genes for atrial natriuretic peptide (ANP) or its receptors (NPR-A, NPR-C) has uncovered a physiological role of this hormone in chronic blood pressure homeostasis. Transgenic mice overexpressing a transthyretin-ANP fusion gene are hypotensive relative to the nontransgenic littermates, whereas mice harboring functional disruptions of the ANP or NPR-A genes are hypertensive compared with their respective wild-type counterparts. The chronic hypotensive action of ANP is determined by vasodilation of the resistance vasculature, which is probably mediated by attenuation of vascular sympathetic tone at one or several prejunctional sites. Under conditions of normal dietary salt consumption, the hypotensive action of ANP is dissociated from the natriuretic activity of the hormone. However, during elevated dietary salt intake, ANP-mediated antagonism of the renin-angiotensin system is essential for maintenance of blood pressure constancy, inasmuch as the ANP gene "knockout" mice (ANP -/-) develop a salt-sensitive component of hypertension in association with failure to adequately downregulate plasma renin activity. These findings imply that genetic deficiencies in ANP or natriuretic receptor activity may be underlying causative factors in the etiology of salt-sensitive variants of hypertensive disease and other sodium-retaining disorders, such as congestive heart failure and cirrhosis.

Increased central AT(1)-receptor activation, not systemic vasopressin, sustains hypertension in ANP knockout mice.

We tested the hypothesis that hypertension in atrial natriuretic peptide (ANP) knockout mice is caused in part by disinhibition of angiotensin II-mediated vasopressin release. Inactin-anesthetized F(2) homozygous ANP gene-disrupted mice (-/-) and wild-type (+/+) littermates were surgically prepared for carotid arterial blood pressure measurement (ABP) and background intravenous injection of physiological saline or vasopressin V(1)-receptor antagonist (Manning compound, 10 ng/g body wt) and subsequent intracerebroventricular (left lateral ventricle) injection of saline (5 microl) or ANP (0.5 microg) or angiotensin II AT(1)-receptor antagonist losartan (10 microg). Only (-/-) showed significant decrease in ABP after intracerebroventricular ANP or losartan. Both showed significant hypotension after intravenous V(1) antagonist, but there was no difference between their responses. We conclude that 1) vasopressin contributes equally to ABP maintenance in ANP-disrupted mice and wild-type controls; 2) permanently elevated ABP in ANP knockouts is associated with increased central nervous angiotensin II AT(1)-receptor activation; 3) disinhibition of central nervous angiotensin II AT(1) receptors in ANP-deficient animals does not lead to a significant increase in the importance of vasopressin as a mechanism for blood pressure maintenance.

Granulocyte-macrophage colony-stimulating factor modulates lipopolysaccharide (LPS)-binding and LPS-response of human macrophages: inverse regulation of tumour necrosis factor-alpha and interleukin-10.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a well-known stimulus for the activation, differentiation and survival of monocytes (MO). Up to now most investigations focused on the short-term effects of GM-CSF. In this study we investigated the effects of GM-CSF on the long-term differentiation of human MO in the presence of serum. We found that MO-derived macrophages (Mphi) cultured with serum plus GM-CSF (GM-Mphi) were different from control Mphi (SER-Mphi) in terms of lipopolysaccharide (LPS)-stimulated cytokine release: GM-Mphi showed an increased tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) production, especially at lower LPS concentrations, but the secretion of IL-10 was diminished. In addition, GM-Mphi secreted TNF-alpha but not IL-6 and IL-10, spontaneously. The spontaneous TNF-alpha production was not due to LPS contamination as it could not be blocked by anti-CD14 antibody. Flow cytometry revealed, however, that the receptor for LPS, CD14, was up-regulated on GM-Mphi and those Mphi released twice as much soluble CD14 into the supernatant as compared with SER-Mphi. The higher CD14 expression also resulted in an enhanced LPS-binding capacity of GM-Mphi. Furthermore, the LPS-response of GM-Mphi could only be blocked by about fourfold higher concentration of anti-CD14 antibody compared with SER-Mphi. In summary, GM-CSF promotes the generation of a pro-inflammatory type of Mphi in two different ways: first, the down-regulation of autocrine IL-10 production increases the release of cytokines such as IL-6 and TNF-alpha and second, the up-regulation of membrane and soluble CD14 expression leads to a higher sensitivity towards LPS-stimulation.

Chronic regulation of arterial blood pressure in ANP transgenic and knockout mice: role of cardiovascular sympathetic tone.

OBJECTIVE: Atrial natriuretic peptide (ANP) lowers arterial blood pressure (ABP) chronically, in association with vasodilation of the resistance vasculature. The mechanism mediating the chronic relaxant effect of ANP is likely indirectly mediated by interactions with tonic vasoeffector mechanisms, inasmuch as the resistance vasculature is relatively insensitive to direct cGMP-mediated relaxation by ANP. On the basis of evidence that ANP has widespread sympatholytic activity, the current study investigated whether the chronic hypotensive effect of ANP is mediated by attenuation of tonic cardiovascular sympathetic tone. METHODS: Total plasma catecholamine concentration and changes in basal ABP and heart rate (HR) following autonomic ganglionic blockade were measured as indices of underlying sympathetic nerve activity in hypotensive ANP-overexpressing transgenic mice (TTR-ANP), hypertensive ANP knockout mice (-/-) and the genetically-matched wild type (NT and +/+, respectively) control mice. Pressor and chronotropic responses to norepinephrine infusion were measured in ganglion-blocked mice of all genotypes, and norepinephrine receptor binding was assessed in representative tissues of -/- and +/+ mice, in order to determine whether peripheral adrenergic receptor responsiveness is altered by ANP-genotype. RESULTS: Basal ABP was significantly lower in TTR-ANP and higher in -/- compared to their wild-type controls. Basal HR did not differ significantly between mutant and control mice. Autonomic ganglionic blockade reduced ABP and HR in all genotypes, however, the relative decrease in ABP was significantly smaller in TTR-ANP and greater in -/- mice than in their respective controls. Total plasma catecholamine was significantly higher in -/- than in +/+ mice but did not differ significantly between TTR-ANP and NT mice. Norepinephrine infusion during ganglionic blockade elicited quantitatively similar pressor and chronotropic responses in mutant and control mice. Tissue norepinephrine binding did not differ significantly between -/- and +/+ mice. CONCLUSIONS: The present study shows that differences in endogenous ANP activity in mice, resulting in chronic alterations in ABP are accompanied by directional changes in underlying cardiovascular sympathetic tone, and suggests that the chronic vasodilator effect of ANP is, at least partially, dependent on attenuation of vascular sympathetic tone, possibly at a prejunctional site(s).

Are prostaglandins involved in atrial natriuretic peptide mechanisms of cardiovascular control?

Atrial natriuretic peptide (ANP) can excite cardiac nerve endings and invoke a decrease in arterial blood pressure and a reduction in renal sympathetic nerve activity. Our laboratory has previously demonstrated that this renal depressor reflex was invoked by systemic injection of ANP and not by the direct application of ANP to the epicardium, a major locus for vagal afferents. We now examine whether inhibition of prostaglandin synthesis impairs reflex responses that are normally associated with ANP injections. Renal sympathetic nerve activity, arterial blood pressure, and heart rate were recorded in anesthetized rats. Indomethacin was used to inhibit prostaglandin synthesis through the cyclooxygenase pathway. The ANP-mediated decrease in arterial blood pressure and renal sympathetic nerve activity, observed when prostaglandin synthesis was inhibited, did not differ significantly from the decreases observed in these parameters when prostaglandin synthesis was not inhibited. Heart rate remained unchanged. Our results suggest that the sympatho-inhibitory effects of ANP do not require prostaglandins as intermediary compounds.

Salt-sensitive hypertension in ANP knockout mice is prevented by AT1 receptor antagonist losartan.

Mice harboring a functional deletion of the pro-atrial natriuretic peptide (ANP) gene (-/-) develop salt-sensitive hypertension relative to their wild-type (+/+) counterparts after prolonged (>1 wk) maintenance on high-salt (HS, 8% NaCl) diet. We reported recently that the sensitization of arterial blood pressure (ABP) to dietary salt in the -/- mice is associated with failure to downregulate plasma renin activity. To further characterize the role and mechanism of ANG II in the sensitization of ABP to salt in the ANP "knockout" mice, we measured ABP, heart rate (HR), and plasma catecholamine and aldosterone concentrations in -/- and +/+ mice maintained on HS for 4 wk and treated with daily injections of AT1 receptor antagonist DuP-753 (losartan) or distilled water (control). Daily food and water intake and fluid and electrolyte excretion were also measured during the first and last weeks of the dietary regimen. Cumulative urinary excretion of fluid and electrolytes did not differ significantly between genotypes and was not altered by chronic treatment with losartan. Basal ABP and HR were significantly elevated in control -/- mice compared with control +/+ mice. Losartan did not affect ABP or HR in +/+ mice, but reduced ABP and HR in the -/- mice to the levels in the +/+ mice. Total plasma catecholamine was elevated by approximately ten-fold in control -/- mice compared with control +/+ mice. Losartan reduced plasma catecholamine concentration significantly in -/- mice and abrogated the difference in plasma catecholamine between -/- and +/+ mice on HS diet. Plasma aldosterone did not differ significantly between genotypes and was not altered by losartan. We conclude that salt sensitivity of ABP in ANP knockout mice is mediated, at least in part, by a synergistic interaction between ANG II and sympathetic nerve activity.

Chronic hypertension in ANP knockout mice: contribution of peripheral resistance.

Atrial Natriuretic Peptide (ANP) exerts a chronic hypotensive effect which is mediated by a reduction in total peripheral resistance (TPR). Mice with a homozygous disruption of the pro-ANP gene (-/-) fail to synthesize ANP and develop chronic hypertension in comparison to their normotensive wild-type (+/+) siblings. In order to determine whether alterations in basal hemodynamics underlie the hypertension associated with lack of endogenous ANP activity, we used anesthetized mice to measure arterial blood pressure (ABP) and heart rate (HR), as well as cardiac output (CO) by thermodilution technique. -/- (n = 7) and +/+ (n = 10) mice of comparable weight and age were used. Stroke volume (SV) and TPR were derived from CO, HR, and ABP by a standard formula. ABP (mm Hg) was significantly higher in -/- (132+/-4) (P < 0.0001) than in +/+ mice (95+/-2). CO (ml min(-1)), HR(beats min(-1))and SV (microl beat(-1)) did not differ significantly between -/- and +/+ mice (CO -/- = 7.3+/-0.5, +/+ = 8.3+/-0.6; HR -/- = 407+/-22, +/+ = 462+/-21; SV -/- = 17.6+/-1.1, +/+ = 17.6+/-1.7). However, TPR (mm Hg ml(-1) min(-1)) was significantly elevated in -/- mice (18.4+/-0.7) compared to +/+ mice (12.3+/-1) (P = 0.0003). Autonomic ganglion blockade with a mixture of hexamethonium and pentolinium was followed by comparable percent reductions in CO (-/- = 28+/-4, +/+ = 29+/-3), HR (-/- = 9+/-4, +/+ = 16+/-4) and SV(-/- = 21+/-4, +/+ = 15+/-6) in both genotypes. However, the concomitant decrease in ABP (%) in -/- (41+/-2) was significantly greater than in +/+ (23+/-4) mice (P = 0.0009) and was accompanied by a significant reduction in TPR. We conclude that the hypertension associated with lack of endogenous ANP is due to elevated TPR, which is determined by an increase in cardiovascular autonomic tone.

Chronic regulation of arterial blood pressure by ANP: role of endogenous vasoactive endothelial factors.

Atrial natriuretic peptide (ANP) exerts a chronic hypotensive effect due to a decrease in total peripheral resistance (TPR). This study examines if chronic ANP-dependent vasodilation is attributable to differences in the cardiovascular regulatory activity of vascular endothelium (VE), based on evidence that ANP affects synthesis/release and target cardiovascular effects of endothelin-1 (ET-1), C-type natriuretic peptide (CNP), and nitric oxide (NO). To determine if the synthetic activity of resistance vasculature VE is chronically altered by plasma ANP activity, we measured ET-1, CNP, and endothelial constitutive NO synthase (ecNOS) concentration and total NOS enzyme activity in homogenates of kidney, heart, lung, hindquarter skeletal muscle, and brain from hypotensive transgenic mice with elevated plasma ANP, hypertensive knockout mice (-/-) characterized by the absence of ANP, and the corresponding normotensive wild-type (NT, +/+) mice. Tissue distribution and abundance patterns of ET-1, CNP, ecNOS, and NOS enzyme activity were comparable between the different genotypes and did not differ significantly between mutant and control mice. Antagonism of ETA/B receptors in -/- and +/+ mice in vivo with SB-209670 reduced arterial blood pressure (ABP) significantly and comparably in both genotypes (-27 +/- 4 and -25 +/- 2% change for -/- and +/+ mice, respectively) independent of any significant changes in heart rate (HR) (-6 +/- 8 and -4 +/- 4% change for -/- and +/+ mice, respectively). Immunoneutralization of CNP-specific guanylate cyclase-linked receptors (GC-B) with monoclonal antibodies (3G12) increased ABP slightly, but not significantly, by similar relative amounts in both -/- (10 +/- 6% change) and +/+ mice (8 +/- 3% change), without changing HR significantly (4 +/- 1% change for both +/+ and -/- mice). Inhibition of NOS activity (by NG-nitro-L-arginine methyl ester) significantly increased ABP, but the changes were comparable between -/- (53 +/- 5% change) and +/+ mice (50 +/- 6% change) and occurred in the absence of significant changes in HR (-1 +/- 5 and 7 +/- 5% change for -/- and +/+ mice, respectively). We conclude that the differences in ABP associated with chronic variations in endogenous ANP activity are not due to alterations in synthesis or responsiveness of the cardiovascular system to the effects of ET-1, CNP, or NO.

Hypertension development in Dahl S and R rats on high salt-low potassium diet: calcium, magnesium and sympathetic nervous system.

Dietary combination of high salt with low potassium (HSLK) exacerbates hypertension development in Dahl salt-sensitive (S) rats, and produces a mild degree of hypertension in otherwise salt-resistant (R) rats. Increased blood pressure in both strains is associated with increased urinary excretion of calcium and magnesium. The objective of this study was to determine the effect of blood pressure on body balance of these ions in Dahl rats on HSLK diet. Two groups of S and two groups of R weanlings were all placed on HSLK diet (NaCl=8%, K=0.2%) for eight weeks. One group of each strain was subjected to chemical sympathectomy with 6-hydroxydopamine (6-OHDA) to counteract hypertension development. Urinary norepinephrine was used to determine efficacy of 6-OHDA treatment. Systolic blood pressures of conscious animals were measured daily throughout the study. The last three days on the diet were used to determine total dietary intake and urinary as well as fecal excretion of sodium, calcium and magnesium. At the end of the study, extracellular fluid volume, serum aldosterone and parathyroid hormone were analyzed. Final systolic blood pressures in the 4 groups were as follows: S=235+/-9 mmHg (n=9); R=155+/-3 mmHg (n=8); 6-OHDA S=151+/-6 mm Hg (n=8); 6-OHDA R=117+/-6 mm Hg. Chemical sympathectomy decreased blood pressure in both S and R rats. There was no indication of sodium accumulation in S rats. Associated with reduced parathyroid hormone levels the S strain had significantly less positive balance for calcium than the R strain, primarily due to increased urinary excretion. A less positive balance for magnesium was also observed, due mainly to relatively reduced intestinal absorption of the ion. We conclude that the HSLK diet is associated with inappropriate activation of the sympathetic nervous system and increased arterial pressure in both strains. In addition, since divalent cations may influence blood pressure, we suggest that the observed abnormalities in calcium and magnesium metabolism might independently promote hypertension development in the S strain.

Retinoic acid inhibits monocyte to macrophage survival and differentiation.

Vitamin A metabolites are potent differentiation-inducing agents for myelomonocytic cell lines in vitro and are successfully used for the treatment of patients with acute promyelocytic leukemia. However, little is known about the effects of vitamin A on normal hematopoietic cells. Therefore, we investigated the effect of vitamin A on differentiation and activation of human blood monocytes (MO). Culturing MO for up to 4 days with 9-cis retinoic acid (RA) and all-trans RA but not retinol reduced MO survival, with the remaining cells being morphologically comparable to control cells. Because macrophage colony-stimulating factor (M-CSF) is a well-known survival factor for MO, we measured the M-CSF content of MO culture supernatants using enzyme-linked immunosorbent assay and found that RA suppressed the constitutive secretion of M-CSF. Northern analysis showed that the M-CSF mRNA expression was only slightly reduced by RA treatment, suggesting regulation on the posttranscriptional level. In contrast to MO, M-CSF secretion by MO-derived macrophages (MAC) was not altered by RA, suggesting a differentiation-dependent switch in the responsiveness of MO/MAC to RA. Because M-CSF is not only a survival-promoting but also a differentiation-promoting factor for myeloid cells, we analyzed the effect of RA on MO to MAC maturation. RA suppressed the expression of the maturation-associated antigen carboxypeptidase M (CPM)/MAX.1 at both the protein and mRNA levels and modulated the lipopolysaccharide-stimulated cytokine secretion of MO/MAC. The addition of exogenous M-CSF to RA-containing MO cultures fails to overcome the RA-induced inhibition of MO differentiation. However, the survival rate was improved by exogenous M-CSF. We conclude that RA acts via two different mechanisms on monocyte survival and differentiation: posttranscriptionally by controlling M-CSF secretion, which decreases MO survival, and transcriptionally regulating the expression of differentiation-associated genes. The regulation of M-CSF production may contribute to the antileukemic effect of RA in vivo by reducing autocrine M-CSF production by leukemic cells.

Nucleotide sequence and deduced amino acid sequence of a putative asparagine synthetase in the mosquito Aedes aegypti (L.).

A cDNA was cloned from a Aedes aegypti head cDNA library, containing the complete coding sequence for an asparagine synthetase homolog. The predicted polypeptide sequence exhibits high homology with different proteins of the 'purF' glutamine amidotransferase enzyme family. The aminoterminal region, containing Cys-1 which is crucial to perform the glutaminase reaction, was highly conserved among the asparagine synthetase family. Subsequent expression of the cDNA yielded a 54,000 Da protein corresponding to the molecular weight of other asparagine synthetases.

Atrial natriuretic peptide and mechanisms of cardiovascular control. Role of serotonergic receptors.

Atrial natriuretic peptide (ANP) inhibits renal sympathetic nerve activity (RSNA), provided the vagi are intact. Afferents from chemosensitive cardiopulmonary receptors are specifically required. Such receptors produce the Bezold-Jarisch reflex, are prominent on the ventricular epicardium, and are richly supplied with 5-hydroxytryptamine type 3 (5-HT3) receptors. We tested the hypothesis that epicardial 5-HT3-sensitive neurons mediate depressor effects of ANP. Through a special catheter, anesthetized, sinoaortically denervated rats received pericardial test injections of ANP (28-amino acid rat ANP; 100 and 1,000 ng) in the presence or absence of 5-HT3 antagonist (Ondansetron, 20 micrograms/kg; n = 9). In other groups we observed the effects of systemic ANP while blocking either epicardial or systemic 5-HT3 receptors. Arterial blood pressure (ABP), heart rate, and RSNA were recorded continuously. Intravenous ANP (100 or 200 ng) decreased ABP and RSNA significantly. In contrast, intrapericardial ANP (100 or 1,000 ng) caused no significant fall in ABP or RSNA. Both intravenous and pericardial Ondansetron reduced the effects of intravenous ANP significantly, but the intravenous antagonism was significantly greater. We conclude that epicardial chemosensitive afferents are not sensitive to ANP and that sympathoinhibitory effects of ANP arise from a 5-HT3 agonist that cannot be produced when ANP is confined to the pericardial space.

[The role of local health departments in reducing inequalities in health in Switzerland]. / Die Rolle der kommunalen Gesundheitsdienste im Umgang mit sozialer Ungleichheit und Gesundheit in der Schweiz.

Examples from Switzerland: In Switzerland, as in other countries, several studies have demonstrated social inequality in health. The aim of this study is to demonstrate practical approaches to reducing these differences, as they offer themselves on the local level, and to analyse the implications for the functioning of local departments of Public Health. Case studies, mainly from the health department of the city of Bern, are used to demonstrate measures taken 1. to identify and correct unmet needs of the socially disadvantaged disabled elderly; 2. to find children from marginal groups who failed to be immunised before entering school age, and to arrange for them to be immunised; and 3. to include psychosocial measures when routine school health examinations have led to observations of a biomedical nature. Recent difficulties are pointed out which developed in this connection as a consequence of the privatisation of traditional Public Health functions. The examples show that considerable effort is needed if local health departments attempting to correct social inequalities try to solve individual problem cases. The task is often multidisciplinary. It involves other administrative sectors such as education, social services and housing construction, and is greatly influenced by measures taken on the Federal or Cantonal (Federal Provincial) level. Whereas demonstrating social inequalities through periodic health reporting can be seen as belonging to the traditional activities of health departments, eliminating or reducing the inequalities not only requires a far-reaching re-orientation of local Public Health services, but also a re-definition of the job description and training of Public Health physicians; and as this process continues, it appears that health departments in Continental Europe will increasingly be led to adopt approaches developed previously by Public Health departments in Anglo-Saxon countries.

Insulin-mediated secretion of ecdysteroids from mosquito ovaries and molecular cloning of the insulin receptor homologue from ovaries of bloodfed Aedes aegypti.

The reproductive cycle of female mosquitoes is activated by ingestion of blood from vertebrate hosts. Shortly after feeding, neurohormones are released from the brain neurosecretory system and stimulate the ovaries to secrete ecdysteroids, which are necessary for vitellogenesis by the fat body. Because bombyxins, which are insulin-like peptides, stimulate ecdysteriodgenesis in silkworm larvae, we tested porcine insulin and found that it activates ecdysteroidogenesis and protein synthesis in ovaries isolated from unfed mosquitoes. To further characterize the regulation of ecdysteroidogenesis in female mosquitoes, we cloned the mosquito insulin receptor (MIR) homologue from ovarian mRNA. The sequence of the extracellular domain shows moderate homologies with vertebrate and Drosophila insulin receptor homologues, as well as with the insulin receptor-related receptor, the latter being an "orphan" receptor with an unknown function. In the intracellular domain, high homologies are observed, particularly in those subdomains that are responsible for ATP binding and kinase activity. Northern blot analysis of MIR demonstrated a highly specific expression in ovaries, and cloning experiments indicated its presence in the brain. Recombinant MIR extracts from a baculovirus expression system contained high constitutive kinase activity in the presence of manganese or magnesium. Activation was independent of a ligand. SDS-gel analysis suggested that the recombinant receptor was not post-translationally processed into an alpha- and beta-subunit as was expected from a putative cleavage signal. Enzymatic properties of the proreceptor are presented: the Km for ATP was between 15 and 50 microM in the presence of a synthetic substrate: maximal kinase activity to 100-fold over basic activity was reached in the presence of 1 mM manganese. Stimulation of key oogenic processes by porcine insulin and identification of a MIR indicate that insulin-like neurohormones may have an important regulatory role in mosquito oogenesis.