ALBERT

Notes: 1 The aim of this study was to characterize the histamine receptor type mediating relaxation of the vascular bed of the nasal mucosa from the guinea-pig, and to determine the role of cyclo-oxygenase products and nitric oxide in this relaxant response to histamine. These studies were performed in isolated nasal mucosae examined in vitro to obtain potencies of histamine receptor-type selective agonists in causing vasorelaxation and to determine affinities of histamine receptor antagonists for inhibiting histamine-induced relaxation. 2 After contraction of nasal mucosae with noradrenaline, histamine caused a maximal relaxation response that was 75 ± 6% of the contraction caused by noradrenaline with a mean EC50 value of 4.3 ± 0.5 μm. Neither dimaprit (H2-receptor selective) nor R-α-methylhistamine (H3-receptor selective) caused significant relaxation of nasal mucosae. In contrast, betahistine (H1-receptor selective) caused an 81 ± 7% relaxation of noradrenaline-induced tone with an EC50 value of 15 ± 1 μm. 3 pA2 experiments were performed to obtain KB values of chlorpheniramine (H1-receptor selective) and diphenhydramine (H1-receptor selective) for blocking histamine-stimulated relaxation of nasal mucosae. KB values for chlorpheniramine (0.87 nm) and diphenhydramine (7.4 nm) were consistent with their interaction at the H1-receptor type. Additionally, neither 10 μm cimetidine (H2-receptor selective) nor 1 μm thioperamide (H3-receptor selective) had any effect on the relaxation curve for histamine. 4 In the presence of 10 μm indomethacin (cyclo-oxygenase inhibitor), histamine caused a maximal relaxation response of 73 ± 5% of the noradrenaline-induced tone with an EC50 value of 2.9 ± 0.2 μm, which was not different from control values (EC50 = 5.0 ± 0.4 μm; maximal relaxation = 71 ± 6%). In contrast, 200 μm NG-nitro-l-arginine (nitric oxide synthase inhibitor) completely inhibited histamine-induced relaxation of nasal mucosae. 5 In conclusion, data from the present study suggest only the H1-receptor type mediates relaxation of nasal mucosal blood vessels to histamine, and histamine-induced relaxation of nasal mucosae is entirely dependent on nitric oxide production.

Notes: 1 This study was aimed at evaluating the effect of rutin and harmaline (1-methyl-7-methoxy-3,4-dihydro-β-carboline) on the development of the surgically induced reflux oesophagitis, on gastric secretion, lipid peroxidation, polymorphonucleocytes (PMNs) accumulation, superoxide and hydroxyl radical production in PMNs, cytokine [interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α)] production in blood and [Ca2+]i mobilization in PMNs. 2 Rutin and harmaline significantly prevented the development of reflux oesophagitis and gastric secretion. Treatments of oesophagitis rats with rutin and harmaline inhibited lipid peroxidation, and myeloperoxidase (MPO) in the oesophagus in comparison with untreated rats. 3 Superoxide anion and hydrogen peroxide production in 1 μm formylmethionylleucylphenylalanine (fMLP)- or 0.1 μg ml−1N-phorbol 12-myristate 13-acetate (PMA)-activated PMNs was inhibited by rutin and harmaline in a dose-dependent fashion. Rutin and harmaline effectively scavenged the hydroxyl radical and hydrogen peroxide. Treatments of oesophagitis rats with rutin and harmaline inhibited IL-1β production in the oesophagus in comparison with untreated rats, but TNF-α production was not affected by rutin and harmaline. The fMLP-induced elevation of [Ca2+]i was inhibited by rutin. 4 The results of this study suggest that rutin and harmaline may have beneficial protective effects against reflux oesophagitis by the inhibition of gastric acid secretion, oxidative stress, inflammatory cytokine production (i.e. IL-1β), and intracellular calcium mobilization in PMNs in rats.

Notes: 1 Although monumental efforts have been made to define the action sites of cough, the importance of neurotransmitter systems in the cough reflex has received limited attention. We studied the roles for four major neurotransmitters [acetylcholine, histamine, serotonin (5-hydroxytryptamine, 5-HT) and dopamine] in the modulation of the cough reflex. 2 Atropine (muscarinic cholinergic blocking agent), pyrilamine maleate (PM, histamine H1 blocker), cimetidine (histamine H2 blocker), 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT, specific 5-HT1A receptor agonist) and SCH-23390 (selective dopamine D1 receptor antagonist) were examined on the cough response to inhaled capsaicin in conscious guinea-pigs. 3 All the drugs significantly decreased the number of capsaicin-induced coughs in a dose-dependent manner. To compare the sensitivity of these drugs on cough response, we calculated the effective doses for 50% inhibition of cough (ED50) when the animals were exposed to 3 × 10−4 m capsaicin. The ED50 values were 0.03 μm kg−1 for atropine, 0.2 μm kg−1 for 8-OH-DPAT, 6.2 μm kg−1 for SCH-23390, 8.5 μm kg−1 for PM and 13.9 μm kg−1 for cimetidine. 4 These findings indicated that all these four neurotransmitters may be involved in the regulation of the cough reflex. Multiple changes of these neurotransmitters in disorders of the central nervous system might synergically affect the cough reflex.

Notes: 1 There is good evidence that β-blockers improve ventricular function, disease progression and survival in patients with left ventricular systolic dysfunction. The aim of this study was to determine the effects of atenolol therapy on the sympathetic nervous system at rest and after ergometric exercise, on left ventricular function and on baseline plasma atrial natriuretic factor (ANF) in ambulatory patients with chronic heart failure (CHF). 2 Twenty-two patients [left ventricular ejection fraction (LVEF) 〈36%; New York Heart Association II–III] were studied before atenolol treatment. Because of cardiac events (new Hospital admission or death) only 13 patients completed 1 year of treatment. Baseline noradrenaline (NE) concentrations were similar in patients and controls while ANF was higher in patients than in controls (328 ± 35 pg ml−1vs. 37 ± 3 pg ml−1; P 〈 0.01). 3 Patients with events showed higher NE (540 ± 87 pg ml−1vs. 303 ± 44 pg ml−1; P 〈 0.01) and ANF (460 ± 70 pg ml−1vs. 291 ± 44 pg ml−1; P 〈 0.03) at rest; and greater NE response to exercise (2.003 ± 525 pg ml−1vs. 694 ± 121 pg ml−1; P 〈 0.005). Atenolol treatment improved LVEF (19.5 ± 1.9%vs. 33 ± 3.9%; P 〈 0.001), increased exercise tolerance (9 ± 3.2 min vs. 17 ± 4.8 min; P 〈 0.001) and decreased plasma ANF (292 ± 42 pg ml−1vs. 133 ± 35 pg ml−1; P 〈 0.01). 4 Reduced basal dihydroxyphenylglycol (DHPG)/NE ratio (3.4 ± 0.46 vs. 4.3 ± 0.35; P 〈 0.01) was observed in patients compared with healthy volunteers. Atenolol increased DHPG plasma levels (1.398 ± 129 pg ml−1vs. 913 ± 86 pg ml−1; P 〈 0.005) but the DHPG/NE ratio during exercise was not modified after treatment, suggesting that re-uptake of released NE is not changed by β-blocker treatment. 5 In conclusion, the fact that atenolol treatment improves ventricular dysfunction and clinical status without changing plasma NE levels in CHF patients, suggests that plasma NE is a poor surrogate measurement for cardiac sympathetic activity in this pathology. In addition, decrease in plasma ANF produced by atenolol treatment may reflect the improvement of ventricular function.

Notes: 1 The aim of the study was to investigate the role of the α1D-adrenoceptor in α1-adrenoceptor-induced contraction of human prostate by means of protection experiments. 2 Responses of human prostate strips to noradrenaline were recorded, along with responses of rat aorta and vas deferens, tissues possessing predominantly α1D- and α1A-adrenoceptors respectively, for comparison. α1-adrenoceptors were then inactivated by incubation with the irreversible antagonist phenoxybenzamine. In some tissues α1A- or α1D-adrenoceptors were ‘protected’ from inactivation by incubation in the presence of the selective α1A- or 1D-adrenoceptor antagonists 5-methylurapidil and BMY 7378 before recording further responses to noradrenaline. 3 Phenoxybenzamine reduced the maximum noradrenaline-induced response and the potency of noradrenaline in all tissues. In rat vas deferens and human prostate, 5-methylurapidil protected α1A-adrenoceptors in a concentration–dependent manner. In rat aorta, 10 nm BMY 7378 almost fully protected α1D-adrenoceptors. However, concentrations of BMY 7378 up to 30-fold higher failed to protect receptors in the human prostate. 4 These results suggest that in human prostate functional α1D-adrenoceptors do not contribute to noradrenaline-induced contractile responses.

Notes: 1 A triple organ bath method allowing the synchronous recording of the motor activity of the circular muscle layer belonging to the oral and anal segments of guinea-pig small intestine adjacent to an electrically stimulated middle segment was developed to study the ascending and descending reflex motor responses. 2 Electrical field stimulation (0.8 ms, 40 V, 5 Hz, 10 s) applied to the middle part of the segments elicited tetrodotoxin (1 μm)-sensitive ascending and descending contractile responses of the nonstimulated parts, oral and anal, respectively. The ascending contraction was more pronounced as compared with the descending contraction. 3 In the presence of phentolamine (5 μm), propranolol (5 μm) and atropine (3 μm) a significant decrease in the amplitude of the ascending contraction was seen and a descending relaxation, instead of a contraction was observed. 4 Met-enkephalin applied at a single concentration (0.1 μm) or cumulatively (0.001–1 μm) inhibited both non-adrenergic non-cholinergic (NANC) descending relaxation and ascending contraction with similar efficacy but different potency, IC50 being 5.9 ± 0.3 and 39.0 ± 4 nm, respectively. Naloxone (0.5 μm) prevented the effects of Met-enkephalin. 5 L-NNA (0.5 mm), an inhibitor of nitric oxide synthesis, increased the ascending contraction and strongly reduced but not abolished the descending relaxation. l-Arginine (0.5 mm) restored the motor responses to the initial level in l-NNA-pretreated preparations, d-Arginine (0.5 nm) had no effects. 6 Met-enkephalin (0.1 μm) depressed the l-NNA-dependent increase of the ascending contraction and failed to change the l-NNA-resistant part of the descending relaxation. 7 Met-enkephalin did not alter spontaneous NANC mechanical activity. SNP (1 or 10 μm), an exogenous donor of nitric oxide, caused a concentration-dependent relaxation. The effects of SNP persisted in Met-enkephalin (0.1 μm)-pretreated preparations. 8 NANC reflex ascending contraction and descending relaxation were synchronously induced by a local nerve stimulation indicating a functional coactivation of NANC orally projected excitatory and anally directed inhibitory pathways. Acting prejunctionally, Met-enkephalin provided a negative controlling mechanism inhibiting both ascending and descending, mainly nitric oxide mediated, reflex responses. A higher sensitivity of the descending relaxation to Met-enkephalin was observed suggesting an essential role of opioid(s) in reducing the efficacy of descending motor activity.

Notes: 1 The present study was designed to investigate the secretion of catecholamines (CA) evoked by stimulation of cholinergic receptors and membrane depolarization from the isolated perfused adrenal gland of spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto rats (WKYR) at adult age. 2 The wet weight of adrenal gland in SHR was greater than that in WKYR. The CA releasing responses evoked by acetylcholine (5.32 × 10−3 m), and high potassium (5.6 × 10−2 m), a membrane depolarizer, were significantly lower in WKYR than in SHR. 3 The secretory responses of CA evoked by DMPP (10−4 m for 2 min), a selective agonist of neuronal nicotinic receptors, and McN-A-343 (10−4 m for 2 min), a selective agonist of neuronal muscarinic receptors, were also significantly lower in WKYR than in SHR. 4 The CA release evoked by Bay-K-8644 (10−5 m), a dihydropyridine-sensitive Ca2+ channel activator, and cyclopiazonic acid (10−5 m), a selective inhibitor of Ca2+-ATPase in the endoplasmic reticulum, were also significantly greater in SHR than WKYR. 5 Taken together, these experimental results demonstrate that the CA secretion evoked by stimulation of cholinergic (nicotinic and muscarinic) receptors as well as membrane depolarization is enhanced more greatly in the perfused adrenal glands of SHR than in those of WKYR. It is suggested that the augmented CA release in SHR compared with WKYR was involved in essential hypertensive pathogenesis.

Notes: 1 The contractile capacity of smooth muscle cells depends on the cytoskeletal framework of the cell. The aim of this study was to determine the functional importance of both the actin and the tubulin components of the cytoskeleton in contractile responses of the bovine isolated iris sphincter muscle. 2 In each preparation, two contractions to the muscarinic agonist carbachol were obtained. The maximum responses of the first contractions were taken as 100%. The second contractions to carbachol were elicited in the presence of either cytochalasin B (50 and 5 μm), an inhibitor of the actin cytoskeleton, or colchicine (100 μm), an inhibitor of the tubulin cytoskeleton (30 min incubation). 3 Cytochalasin B, at a concentration of 50 μm, significantly decreased the contractions induced by carbachol, with the maximum response reduced to 21.8 ± 6.6% (n = 12) of the initial maximum. The maximal contractions to carbachol in the presence of colchicine reached 96.2 ± 7.9% (n = 9) of the initial contraction, which was not significantly different from control second responses to carbachol with neither drug present, which reached 113.3 ± 7.6% (n = 7). 4 The effect of cytochalasin B was dose-dependent, since at a lower concentration of 5 μm, the drug decreased the maximum contraction to carbachol to 60.3 ± 8.8% (n = 6). The effect of cytochalasin B was at least partially reversible, since after the use of the higher concentration of 50 μm, contractions to carbachol increased to 62.3 ± 15.5% (n = 4) of the maximal response, after 1 h repeated washing of the preparations. 5 Cytochalasin D, at a concentration of 50 μm, completely abolished the contractions induced by carbachol (n = 4). 6 These findings suggest that in bovine iris sphincter muscle, contractions to carbachol are highly dependent, from a functional point of view, on actin polymerization, and not, to any important degree, on the polymerization of tubulin.

Notes: 1 The parasympathetic nervous system is responsible for maintaining normal bladder function, contracting the bladder smooth muscle (detrusor) and relaxing the bladder outlet during micturition. 2 Contraction of the bladder involves direct contraction via M3 receptors and an indirect ‘re-contraction’ via M2-receptors whereby a reduction in adenylate cyclase activity reverses the relaxation induced by β-adrenoceptor stimulation. 3 Muscarinic receptors are also located on the epithelial lining of the bladder (urothelium) where they induce the release of a diffusible factor responsible for inhibiting contraction of the underlying detrusor smooth muscle. The factor remains unidentified but is not nitric oxide, a cyclooxygenase product or adenosine triphosphate. 4 Finally, muscarinic receptors are also located prejunctionally in the bladder on cholinergic and adrenergic nerve terminals, where M1-receptors facilitate transmitter release and M2 or M4-receptors inhibit transmitter release. 5 In pathological states, changes may occur in these receptor systems resulting in bladder dysfunction. Muscarinic receptor antagonists are the main therapeutic agents available for treatment of the overactive bladder, but whether their therapeutic effect involves actions at all three locations (detrusor, prejunctional, urothelial) has yet to be established.

Notes: 1 In this study, we have investigated the vasodilator response to acetylcholine under diabetes conditions in isolated renal arteries of rabbits. We have also examined the contribution of endothelium-derived nitric oxide (EDNO) and endothelium-derived hyperpolarizing factor (EDHF) to the endothelium-dependent relaxation caused by acetylcholine in the renal arteries of alloxan-induced diabetic rabbits. 2 Acetylcholine (10−10−10−4 m) produced cumulative concentration–response curve in the renal arteries of both control and diabetic rabbits. The EC50 values and maximal responses to acetylcholine were not significantly different relative to diabetic conditions. In order to isolate the EDHF component of acetylcholine-induced vasodilator response, l-nitro-methyl arginine ester (l-NAME, 10−4 m) and indomethacin (10−6 m) were added to the Krebs' solution throughout the experiment. Under these conditions, acetylcholine induced vasodilatation in the isolated renal arteries from both control and diabetic rabbits. The vasodilator response to acetylcholine was not affected under diabetic conditions. 3 Sodium nitroprusside (SNP)-induced relaxation was increased in the diabetic rabbits compared with the control animals. 4 Tetrabutyl ammonium (TBA, 0.5 mm) produced a significant reduction in acetylcholine-induced vasodilatation in both preparations from control and diabetic animals, consistent with involvement of K+ channels in mediating this response. Glibenclamide (1 μm) attenuated acetylcholine-induced vasodilatation in preparations from control animals only, while iberiotoxin (0.05 μm) significantly reduced the vasodilator response to acetylcholine in preparations from both control and diabetic animals. 5 The role of EDNO in mediating acetylcholine-induced vasodilatation was examined. The vascular preparations were incubated with 20 mm K+-Krebs' solution to inhibit the EDHF contribution to acetylcholine-induced vasodilatation. Under this condition, acetylcholine induced a vasodilator response in both preparations from control and diabetic rats. Pretreatment with l-NAME (10−4 m) attenuated acetylcholine-induced vasodilatation in both preparations, indicating an nitric oxide-mediated vasodilator response. 6 Our results indicated that acetylcholine-induced vasodilatation in the isolated renal arteries of alloxan-induced diabetic rabbits was not affected under diabetic conditions. Acetylcholine-induced vasodilatation is mediated by two vasodilator components; namely, EDHF and EDNO. The contribution of EDHF and EDNO to acetylcholine-induced vasodilatation was not affected under diabetic conditions and there was no indication of endothelial dysfunction associated with diabetes. EDHF component was found to act mainly through high conductance Ca2+-activated K+ channels under normal and diabetic conditions, while the adenosine triphosphate-dependent K+ channels were involved in mediating acetylcholine vasodilator response in the control preparations only.

Notes: Summary 1 It was shown recently that stimulation of cardiac muscarinic M2-receptors revealed an enhanced negative inotropic response in isolated rat left atria after exposure to hypochlorite-induced oxidative stress. This phenomenon was not observed after stimulation of the cardiac A1-receptor, which like the M2-receptor is coupled to Gi-proteins. Since even the contractile response to M3-receptor stimulation was not amplified in the rat portal vein, we hypothesized a M2-receptor specificity of this hypochlorite-induced enhancement. 2 The present study was performed in order to investigate whether the sympathoinhibitory response to presynaptically located M2-receptor stimulation would also be modified after exposure to hypochlorite in the rat tail artery. We applied electrical field stimulation (EFS) in order to mimic sympathetic neurotransmission. 3 EFS increased the vascular tone frequency-dependently (0.3–4 Hz). EFS-induced vasoconstriction could be attenuated by acetylcholine (30 nm−1 μm) in a concentration-dependent manner. Hypochlorite (10 and 100 μm) did not affect the sympathoinhibitory effect of acetylcholine (100 nm). 4 In conclusion, in contrast to cardiac M2-receptors, hypochlorite did not amplify the sympathoinhibitory effects of presynaptic M2-receptors. The different responsiveness between neuronal and cardiac M2-receptors to hypochlorite may be explained by the different G-protein subunits involved in the activation of the underlying signalling cascade.

Notes: 1 The effects of intraperitoneal (i.p.) lipopolysaccharide on vascular reactivity to noradrenaline in rat aorta under different conditions of passive tension, as well as on mortality in normotensive and hypertensive rats, were studied. 2 Concentration–response curves to noradrenaline were obtained in aorta rings, at two levels of passive tension: 3 and 0.5 g, from control and lipopolysaccharide-treated Wistar rats. Contractile responses were expressed as percentage of the maximal response to noradrenaline obtained in the beginning of the experiment at a resting tension of 2 g. The maxima were significantly larger (P 〈 0.05) at 3 g than at 0.5 g in both groups of rats: 117.8 vs. 62.3%, respectively, for control animals; 85.8 vs. 32.5%, respectively, for lipopolysaccharide-treated rats. 3 The 24-h mortality after the i.p. administration of lipopolysaccharide was lower in spontaneously hypertensive rats (1/12; 8%), when compared with control Wistar–Kyoto rats (5/11; 45%). However, mortality was higher in Wistar–Kyoto made hypertensive by 8-day administration of corticosterone (6/6; 100%). 4 We conclude that a differential sensitivity to noradrenaline of aortic smooth muscle at two different levels of passive tension is still present in lipopolysaccharide-treated animals. Chronic hypertension in SHR rats is associated with resistance to the lethal effects of lipopolysaccharide, whereas abrupt-onset hypertension induced by corticosterone leads to an increased mortality. 5 These results are compatible with the myofibrillary hypothesis, which explains vascular hyper-reactivity in chronic arterial hypertension, by postulating that a more favourable relative position (and/or proportion) for actin and myosin occurs, whereas in states of vascular hypo-reactivity, such as vasodilatory shock, the opposite phenomenon may exist.

Notes: 1 The present study aimed to evaluate the role of κ-opioid receptors at two peripheral sites, the vas deferens and the proximal colon, in κ-opioid receptor knockout mice. We investigated the role of the κ-opioid receptor in the vas deferens twitch response and in the colonic ‘off-contraction’, a rebound contractile response which follows the inhibitory response to low frequencies stimulation (10, 20, 30 Hz) and which has been suggested to ‘locally’ reproduce the contractile component of the peristaltic reflex. 2 Transmural stimulation of the vas deferens at lower frequencies (10 Hz, 10 V, 1 ms pulse trains lasting 0.5 s) evoked a contractile response that was significantly higher in the preparations from knockout mice because of lack of κ-opioid receptors than in wild type mice. A selective κ-opioid receptor agonist, U-50,488H, induced a dose-dependent inhibition of the electrically stimulated contraction in vas deferens. The percentages of reduction of the twitch response were significantly lower in knockout mice than in wild type mice after treatment with U-50,488H. The reduction of twitch response caused by U-50,488H was not reversed by administration of nor-binaltorphimine (nor-BNI) (5 × 10−6 m), a selective κ-opioid receptor antagonist, in preparations from both knockout mice and wild type mice. U-50,488H has no effect on postsynaptic adrenergic receptors, as its administration did not affect the direct contractile response to noradrenaline. 3 Transmural stimulation (5 Hz, 20 V, 2 ms pulse trains lasting 30 s) induced inhibition of spontaneous activity of colonic strips during the period of stimulation, followed by an ‘off-contraction’ after the cessation of stimulation. The statistical evaluation of the ‘off-contraction’ responses between the two strains showed no significant difference. The off-contraction, measured in specimens from knockout mice, was inhibited concentration-dependently by U-50,488H (P 〈 0.01) and significantly less than from wild type mice. 4 The effect of U-50,488H was not reversed by administration of nor-BNI (5 × 10−6 m), either in preparations from knockout mice or from wild type mice. 5 Our data may suggest that κ-opioid receptors are involved in some peripheral responses to the nerve stimulation, as indicated by the effect of U-50,488H, a selective κ-opioid receptor agonist. However, the involvement of κ-opioid receptor was also present, although less apparent, in κ -opioid receptor knockout mice, suggesting either that this drug acts not only on κ-opioid receptors but also on other receptor sites, such as κ-like receptors. An alternative interpretation can be related to a sodium channel blocking action of U-50,488H, which could explain the inhibitory effects of twitch response still present but less evident in knockout strain and the lack of effect of the antagonist nor-BNI.

Notes: 1 The effects of neuropeptide Y (NPY) upon the isolated vasculature are reviewed. 2 The vasconstrictor responses to periarterial nerve stimulation (PNS) and neurotransmission by noradrenaline (NA) and ATP are discussed and illustrated using canine isolated perfused splenic artery. 3 Modulation of the vascular responses to PNS by NPY via pre- and post-junctional NPY Y2 and Y1 receptors is discussed. 4 Evidence is presented for different α1-adrenoceptor subtypes mediating vasoconstriction to exogenous and endogenously released NA and their different locations in the neurovascular junction and extrajunctional regions. 5 Activation of NPY Y1-receptors potentiates sympathetic nerve activated α1-adrenoceptor vasoconstriction. The proposal that the postjunctional α1B adrenoceptor may be linked to the NPY Y1-receptor and is responsible for co-operation between sympathetic and NPYergic interactions in the vasculature is discussed.

Notes: Summary 1 GABAB1 receptor subunit knockout mice were generated and the effects of the GABAB receptor agonist, baclofen, were evaluated within the peripheral nervous system (PNS) of wildtype (+/+), heterozygote (+/–) and knockout (–/–) animals. For this purpose, neuronally-mediated responses were evoked in both the isolated ileum and urinary bladder, using selective electrical field stimulation (EFS). 2 In ileum resected from 4–8-week-old-mice, low frequencies of EFS (0.5 Hz) evoked irregular muscle contractions which were prevented by atropine 1 μM and reduced by baclofen (33.4 ± 5.6%, 100 μm). The latter effect was antagonized by the GABAB receptor antagonist CGP54626 0.2 μm. Baclofen 100 μm did not affect contractions of similar amplitude induced by carbachol, indicating that the ability of baclofen to inhibit cholinergic function in mouse ileum may be due to an action at prejunctional GABAB receptors. 3 To avoid the development of grand mal seizure by GABAB1 (–/–) mice, a behaviour observed when the mice were greater than 3 weeks old, it was necessary to study the effects of this knockout in 1–3-week-old-animals. However, at this age, EFS at 0.5 Hz did not evoke robust muscle contractions. Consequently we used EFS at 5 Hz, which did evoke cholinergically mediated contractions, found to be of similar amplitude in (+/+) and (+/–) mice, of both 1–3 weeks and 4–8 weeks of age. At this frequency of EFS, baclofen reduced the amplitude of the evoked contractions [n=6 (+/+) and n=5 (+/–), IC50 19.2 ± 4.8 μm) and this effect was greatly reduced in the presence of CGP54626 0.2 μm. 4 In urinary bladder from 1–3-week-old-mice, using higher frequencies of EFS to evoke clear, nerve-mediated contractions (10 Hz), baclofen 10–300 μm concentration-dependently inhibited contractions in (+/+) mice (IC50 9.6 ± 3.8 μm). This effect was inhibited by CGP54626 (0.2 μm, 46.2 ± 13.6% inhibition, 300 μm baclofen n=7) a concentration which, by itself, had no effect on the EFS-evoked contractions. 5 The effects of baclofen in both ileum and urinary bladder were absent in the GABAB1 receptor subunit (–/–) mice; however, responses to EFS were unaffected in (–/–) when compared to the (+/+) mice. 6 Our data suggest that, as in the central nervous system (CNS), the GABAB1 receptor subunit is an essential requirement for GABAB receptor function in the enteric and PNS. As such, these data do not provide a structural explanation for the existence of putative subtypes of GABAB receptor, suggested by studies such as those in which different rank-orders of GABAB agonist affinity have been reported in different tissues.

Notes: 1 Type 2 diabetes is associated with diverse oral pathologies in which salivary flow reduction is one of the causes of these oral abnormalities. Scarce literature exists regarding noradrenergic transmission and adrenergic-induced salivary flow in submaxillary and parotid glands of type 2 diabetic rats. 2 We studied noradrenergic transmission as well as the secretory response to α1- and β-adrenoceptor stimulation in the parotid and submaxillary glands of type 2 diabetic rats. 3 Diabetic rats exhibited diminished neuronal uptake, release and endogenous content of noradrenaline (NE) in both salivary glands. Further, NE synthesis was also diminished accompanied by decreased tyrosine hydroxylase activity. Salivary flow responses to α1-(methoxamine) and β-(isoprenaline) adrenoceptor stimulation were reduced in the submaxillary as well as the parotid glands of diabetic rats. 4 Our results suggest that the reduction of noradrenergic transmission in the salivary glands of type 2 diabetic rats is in part responsible for the diminished salivary flow evoked by α1- and β-adrenergic stimulation. Reduced noradrenergic activity may contribute to the pathophysiology of oral abnormalities in diabetic patients.

Notes: 1 We investigated the effects of exogenously applied steroids and endogenously released cortisol on catecholamine (CA) secretion induced by cholinergic agonists in perfused guinea-pig adrenal glands. 2 Acetylcholine (ACh) and electrical stimulation induced CA secretion, which was reversibly inhibited by cortisol. Adrenocorticotropic hormone (ACTH) increased the concentration of cortisol in the perfusion effluent and partly inhibited the secretory response to ACh. 3 Cortisol or aldosterone dose-dependently inhibited secretory responses to nicotine and muscarine. These inhibitory effects were not antagonized by mifepristone and spironolactone, respective cortisol and aldosterone receptor blockers. 4 Dexamethasone, cortisone, corticosterone, 11-deoxycortisol, 11-deoxycorticosterone, prednisolone and cholesterol inhibited nicotine-evoked CA secretion. The secretory response to muscarine was inhibited by these compounds except for dexamethasone and prednisolone. 5 Dexamethasone, cortisol and aldosterone had no effect on CA secretion induced by high KCl. 6 These results suggest that steroids affect nicotinic and muscarinic ACh receptor-mediated responses through distinct mechanisms, and that cortisol released from the adrenal cortex inhibits CA secretion from the adrenal medulla.

Notes: 1 The aim of this study was to characterize the adenosine receptor mediating vasodilation in the microvasculature of the hamster cheek pouch in vivo. A range of adenosine agonists was used including N6-cyclopentyladenosine (CPA) (A1 agonist), 5′-N-ethylcarboxamidoadenosine (NECA) (non-selective), 2-chloroadenosine (2CADO) (non-selective), 2-p-(2-carboxyethyl)-phenethylamino-5′-N-ethylcarboxamidoadenosine (CGS 21680) (A2A agonist), N6-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IBMECA) (A3 agonist) and adenosine, as well as the adenosine antagonists 8-sulphophenyltheophylline (8-SPT) (A1/A2 antagonist), 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (A1 antagonist) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]-triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) (A2A antagonist). 2 All the adenosine analogues used induced vasodilation at concentrations between 10 nm and 1 μm, and the potency order was NECA 〉 CGS 21680 〉 2CADO 〉 CPA=IBMECA 〉〉 adenosine, indicating an action at A2A receptors. 8-SPT (50 μm) antagonized vasodilator responses to NECA with an apparent pKB of 5.4, consistent with an action at A1 or A2 receptors and confirming that A3 receptors are not involved in this response. 3 DPCPX (10 nm) had no effect on vasodilation evoked by NECA, suggesting that this response was not mediated via A1 receptors, while ZM 241385 (10 nm) antagonized dilator responses to NECA with an apparent pKB of 8.9 consistent with an action via A2A receptors. 4 Overall these results suggest that adenosine A2A receptors mediate vasodilation in the hamster cheek pouch in vivo.

Notes: 1 The hypothesis that the non-adrenergic, non-cholinergic excitatory (NANC-e) innervation is involved in the induction of asthma and that antagonists of NANC-e neurotransmitter could reduce bronchoconstriction during asthma was tested. 2 The first objective was to identify the neurotransmitter(s) of NANC-e innervation from a group of selected putative neurotransmitters. The second objective was to use the antagonist of the identified neurotransmitter(s) to determine its effectiveness against bronchoconstriction to ovalbumin (OVA) in sensitized guinea-pigs. 3 Neurotransmitter identification was performed using the ‘tracheal pouch’, a surgical preparation established for demonstrating NANC innervation, in anaesthetized guinea-pig airways. A segment of trachea was cannulated and clamped at one end and the other end was connected to a pressure transducer. The stump of the trachea was connected to a ventilator to keep the blood gas values within the normal range. The vagus nerve and the sympathetic nerves were isolated bilaterally and cut. The left carotid artery was cannulated to monitor blood pressure and for sampling blood for blood gas analysis. The jugular vein was cannulated for administration of test agents. 4 Both NANC-e and NANC-i (inhibitory) control responses of airways were obtained by bilateral vagal stimulation after complete autonomic blockade with atropine, propranolol and prazosin. The relaxation of the tracheal pouch was indicative of the NANC-i response and the increase in insufflation pressure of the ventilated peripheral airways was due to NANC-e stimulation. 5 The involvement of the putative neurotransmitters such as neurokinin-A (NK-A), histamine, serotonin and endothelin (ET) was investigated by using the respective antagonists, MEN-10376, pyrilamine maleate, cyproheptadine hydrochloride, and two ET receptor antagonists (BQ-123 and IRL-1038), respectively. The antagonists were administered at the dose rate of 4 mg kg−1 i.v. which was determined from preliminary studies by testing against the respective agonists. 6 MEN-10376 (neurokinin-2 receptor antagonist) significantly inhibited the insufflation pressure (peripheral airway pressure) increase caused by NANC-e stimulation. MEN-10376 also inhibited the fall in blood pressure caused by bilateral vagal stimulation. The 5-HT antagonist, cyproheptadine, significantly enhanced the NANC-e response. 7 After identifying the NANC-e neurotransmitter as NK-A, the effectiveness of its antagonist, MEN-10376, was evaluated for its ability to attenuate the increase in insufflation pressure (bronchoconstriction) induced in guinea-pigs sensitized by OVA. Guinea-pigs were sensitized to OVA (200 mg i.p.) and 10 days later prepared for the determination of tracheal pouch and insufflation responses to 100 μg of OVA administered i.v. (challenge dose). This caused an increase in insufflation pressure in the presence of adrenergic and cholinergic blockade, which was significantly attenuated by MEN-10376. 8 These studies indicated that neurokinin-2 receptors were involved in the vagally mediated efferent neurotransmission of NANC-e and that NANC-e plays a role in allergen-induced bronchoconstriction.

Notes: 1 The effect of WAY100635 (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride), a 5-HT1A receptor antagonist, on cardiovascular function was studied. 2 The i.v. injection of WAY100635 dose-dependently decreased blood pressure in anaesthetized rats; while in pithed rats WAY100635 (1 mg  kg−1) displaced the phenylephrine pressor effect. 3 WAY100635 antagonized phenylephrine-induced contraction in rabbit and rat aorta (pA2 of 6.88 and 7.93 and Schild slopes of −0.83 and −1.21, respectively); while in rat caudal artery pKB was 7.45 and the Schild slope of −0.56, suggesting a complex interaction in this vessel. 4 The results show that WAY100635 induced hypotension in the anaesthetized rat and suggest that this effect could be partially explained by antagonism of vascular α1-adrenoceptors.

Notes: 1 Purinergic transmission from sympathetic nerves in the guinea-pig vas deferens was monitored using intracellular recording techniques. Stimulation of the hypogastric nerve with trains of 15 pulses at 1 Hz evoked excitatory junction potentials (EJPs) which increased in amplitude from the first pulse and reached a maximum after 6–8 pulses. 2 Caffeine (3 and 10 mm), depolarized cells by 5–10 mV and increased the amplitude of the first few EJPs in each train but reduced the maximum amplitude of EJPs late in the train. 3 The adenosine receptor antagonist 8-p-sulphophenyl-theophylline (8-SPT; 30 μm) had no effect on either the resting membrane potential or the EJP amplitude; however, at 100 μm it reduced the amplitude of all EJPs by 5–10%. 4 Adenosine (10 and 30 μm) reduced the amplitude of EJPs in a concentration-dependent manner. The inhibitory effect of adenosine on EJP amplitude was prevented by pretreatment with either caffeine (3 mm) or 8-SPT (30 μm). 5 Ryanodine (30 μm) did not alter EJP amplitude and did not inhibit the enhancement of the first EJP by caffeine (3 mm). Incubation of the tissue with the cell permeable calcium chelator 1-2-bis(o-aminophenoxy)ethane-N,N-N′,N′-tetraacetic acid (BAPT-AM) resulted in a depression of EJP amplitude and a longer time to reach maximum amplitude. In cells that had been exposed to BAPT-AM, caffeine 3 mm still increased amplitude of EJP early in the train. 6 The phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX; 500 μm), hyperpolarized cells and increased the amplitude of EJP throughout the train of stimulation. In the presence of IBMX, caffeine 3 mm still depolarized the cells and enhanced the EJP early in the train of stimulation. 7 The findings in this study confirm that caffeine and 8-SPT are effective inhibitors of the actions of adenosine. However, caffeine has an additional action to enhance EJP early during a train of stimulation, which cannot be attributed to blockade of adenosine receptors, but which may be related to inhibition of phosphodiesterase.

Notes: 1 The β3-adrenoceptor agonist ZD 7114, like the non-selective β-adrenoceptor agonist isoprenaline, but unlike the β1-adrenoceptor agonist dobutamine and the β2-adrenoceptor agonist salbutamol, produced an increment on mouse embryonic fibroblast proliferation. The half-maximal stimulation of cell growth occurred at substantially lower concentrations with the β3-adrenoceptor agonist (EC50: 5.5 × 10−8 m) than with isoprenaline (EC50: 1.25 × 10−6 m). 2 The selective β3-adrenoceptor antagonist SR 5923 OA prevented the β3-stimulated fibroblast proliferation. Conversely, practolol and butoxamine did not prevent fibroblast growth. 3 Additionally, a decrease of cAMP was obtained in fibroblasts cells upon stimulation with isoprenaline and ZD 7114. 4 The expression of β-adrenoreceptors on fibroblast cells was also studied by radioligand binding. The Ki values in the presence of β1- and β2-adrenoceptor antagonist was two-fold higher than the Ki values for β3 adrenoceptor antagonist indicating the presence of A3-receptor subtype. 5 Inhibitors of different intracellular coupling pathways including phospholipase C (U 73122), protein kinase C (staurosporine), calcium/calmodulin (trifluoroperazine) and calcium channel (verapamil), prevented the stimulatory actions of the selective β3-adrenoceptor agonist ZD 7114. 6 The presence of β3-adrenoceptors on embryonic mouse fibroblast cells may play a role in the modulation of cell growth and biologic activity. The mechanism by which ZD 7114 triggers cell proliferation and function, involves the activation of phospholipase C, PKC, calcium/calmodulin and the influx of calcium.

Notes: 1 Cytokines may parallel or regulate the beneficial effects of β-adrenoceptor antagonist treatment observed in chronic heart failure (CHF) patients. Therefore, this study was performed in order to investigate alterations of cytokine levels in β-blocker-treated patients suffering from CHF. 2 We investigated plasma cytokine levels in eight healthy controls and 12 CHF patients. The patients were treated with standard medication (CHFstd) or with standard medication and additional β1-blocker metoprolol (CHFmet). Interleukin-(IL)-1α, IL-1β, IL-1 receptor antagonist (IL-1ra), IL-2, IL-6, IL-8, IL-10, tumor necrosis factor-α (TNF), soluble TNF receptor type 1 (sTNF-R1), sTNF-R2, and sCD14 were measured by ELISA. 3 IL-1α and IL-1β were not detectable in any of the tested groups. IL-2, TNF, or sCD14 were not altered as compared with healthy control subjects. CHFstd patients expressed enhanced IL-1ra, IL-6, IL-8, IL-10, sTNF-R1 and sTNF-R2. In CHFmet patients IL-1ra, IL-6 and IL-8 remained at the same level. In contrast, sTNF-R1 levels were significantly reduced, although not to control, whereas the sTNF-R2 and IL-10 were reduced to control levels. 4 The cAMP levels of mononuclear cells – recalculated for the patients included in this study from previous work [Werner et al. (2001). Basic Res. Cardiol., 96, 290]– correlated inversely with the sTNF-R2 data (Pearson, r=−0.46; P=0.041; Spearman, r=−0.64, P=0.002). 5 The present data indicate an interaction of the neurohumoral and the cytokine system in CHF patients at the cAMP level. Thus, measurement and correlation of sTNF-R2 and cAMP may provide a tool useful during investigation of β-blocker therapy.

Notes: 1 The effects of BIIE 0246, a novel and non-peptide neuropeptide Y (NPY) Y2 receptor antagonist on sympathetic vasoconstriction of the canine splenic artery were investigated. 2 The vasoconstrictor response to periarterial electrical nerve stimulation was described to be a double peaked vasoconstriction consisting of an initial transient, dominantly P2X purinoceptor-mediated constriction followed by a prolonged, mainly α1 adrenoceptor-induced response. 3 BIIE 0246 at a concentration of 0.1–1 μm dose-dependently potentiated double peaked constrictions at low frequencies (1 and 4 Hz), whereas at high frequency (10 Hz), it failed to affect these responses. BIIE 0246 (1 μm) also enhanced double peaked responses even in the presence of rauwolscine (0.1 μm). NPY (13–36) (1–100 nm), a selective Y2 receptor agonist reduced these two peaked responses in a dose-related manner. The vasoconstriction to noradrenaline (0.1–10 nmol) or adenosine triphosphate (0.01–1 μmol) was not significantly influenced by either 1 μm BIIE 0246 or 100 nm NPY (13–36). Exposure of tissues to 1 μm BIIE 0246 almost completely prevented the suppression of double peaked constrictions by NPY (13–36) (10 nm) or by NPY (10 nm). 4 We conclude that NPY inhibits sympathetic purinergic and adrenergic vasoconstrictions through an activation of prejunctional Y2 receptor subtype in the neurovascular junction of the canine splenic artery.

Notes: Summary 1 The agonistic and antagonistic effects of labetalol, the α1- and β-adrenoceptor antagonist, were studied on β3-adrenoceptors in the guinea-pig gastric fundus. 2 Labetalol caused a concentration-dependent relaxation with a pD2 value of 5.58 ± 0.09 and an intrinsic activity of 0.64 ± 0.06, which was not affected by pretreatment with both the selective β1-adrenoceptor antagonist, (±)-atenolol (100 μM), and the selective β2-adrenoceptor antagonist, (±)-butoxamine (100 μM). 3 However, the non-selective β1-, β2- and β3-adrenoceptor antagonist, (±)-bupranolol (3–30 μM), shifted the concentration–response curve of labetalol to the right (pA2 value=5.97 ± 0.08). 4 In the presence of (±)-atenolol (100 μM) and (±)-butoxamine (100 μM), relaxations to catecholamines [(−)-isoprenaline, (−)-noradrenaline and (−)-adrenaline], to the selective β3-adrenoceptor agonist, BRL37344, and to the non-conventional partial β3-adrenoceptor agonist, (±)-CGP12177A, were weakly antagonized by labetalol (10 μM). 5 These results indicate that labetalol, the arylethanolamine, acts as a partial agonist on β3-adrenoceptors in the guinea-pig gastric fundus.

Notes: 1 This study examined the potentiating effects of competitive antagonists of the adrenergic alpha2 receptors and of phenoxybenzamine (POB) an irreversible antagonist, on the stimulation-induced efflux of [3H]-noradrenaline in arterial tissue of rabbit. This was done to determine if the lack of concordance of efflux potentiation by antagonists with the expectations of presynaptic negative feedback theory can be attributed to increasingly successful competition from rising perineuronal transmitter concentrations, when stimulation parameters are increased, in the presence of a fixed concentration of competitive antagonist. 2 Tissues were stimulated with a fixed pulse number and frequency, to rule out confounding factors, and major alterations in the concentration of released transmitter were achieved through variations in the pulse duration. 3 Rauwolscine potentiated transmitter release less at the longest, rather than at the shortest pulse duration, and showed a potentiation of release that was indifferent to the quantities of released transmitter. This was also seen with POB although it binds covalently to the presynaptic receptor. 4 Noradrenaline inhibited stimulation-induced transmitter release confirming the presence of presynaptic alpha inhibitory sites. 5 Yohimbine potentiated transmitter release the same as did rauwolscine and POB, and protected the relevant sites against POB potentiation, confirming site identity. The combination of POB and rauwolscine had no greater effect than did either alone certifying that they acted similarly and that maximally effective concentrations of each were used. 6 Consequently, noradrenaline breakthrough of presynaptic receptor blockade does not explain the non-conforming observations made with competitive antagonists in tests of presynaptic theory.

Notes: 1 The present study attempted to pharmacologically characterize the subtypes of α-adrenoceptors mediating the vasoconstriction in the isolated and perfused canine vesical artery. 2 Noradrenaline (NA) and phenylephrine (PE, an α1-adrenoceptor agonist) induced a dose-dependent vasoconstriction, whereas xylazine (an α2-agonist) did not induce any clear vascular constrictor response. 3 Prazosin at 0.01 μm and rauwolscine at 0.1 μm failed to affect the NA-induced vasoconstriction. Prazosin at 0.1 μm antagonized the vasoconstrictor responses to NA, with pKB value of 7.8. 4 WB 4101 at 0.01–0.1 μm dose-dependently inhibited the responses to NA, with a pKB value of 8.9. The vasoconstrictor responses to NA were not significantly affected by chloroethylclonidine (10–30 μm) or BMY 7378 (0.1 μm). 5 The present results indicate that the canine vesical arteries dominantly contain α1-adrenoceptors but have no α2-adrenoceptors, and the functional subtype of α1-adrenoceptor is characterized as an α1A-adrenoceptor subtype.

Notes: 1 The aim of this study was to examine whether sodium nitroprusside (SNP)-induced relaxation of rat fundus longitudinal smooth muscle involves ryanodine-sensitive Ca2+ release. 2 SNP (300 nm–30 μm) elicited concentration-dependent relaxation of precontracted (1 μm carbachol) rat fundus, an effect almost abolished by the selective guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ, 10 μm). 3 SNP-mediated relaxations were almost abolished by 10 μm ryanodine. 4 SNP-mediated relaxations were also reduced by either 1 μm apamin (a selective small conductance Ca2+-sensitive K+ channel, SKCa, inhibitor) or the selective L-type Ca2+ channel inhibitor, nicardipine (3 μm). 5 SNP-induced relaxations were insensitive to 1 mm tetraethylammonium chloride (an inhibitor of large-conductance Ca2+-sensitive K+ channels) and 1 μm glibenclamide (an ATP-sensitive K+ channel inhibitor). 6 These data suggest that SNP-mediated fundus relaxation occurs via a cGMP-mediated and ryanodine-sensitive mechanism which requires, at least in part, SKCa and L-type Ca2+ channel activity.

Notes: 1 The aim of this work was to investigate the effect of acute and chronic exposure of rat pheochromocytoma (PC12) cells to elevated cAMP, using forskolin, dibutyryl-cAMP (db-cAMP) or isobutylmethylxanthine (IBMX), on endogenous dopamine content and release and on [3H]-1-methyl-4-phenylpyridinium ([3H]-MPP+) uptake and release, under basal conditions and under KCl-stimulation. 2 Cultured PC12 cells synthetized and accumulated large amounts of dopamine, but not noradrenaline or adrenaline. The release of dopamine by the cells was markedly increased in response to 50 mm KCl. 3 Acute and chronic treatment of the cells with forskolin (30 μm), but not IBMX (100 μm), slightly increased the spontaneous release of dopamine and significantly decreased the release induced by 50 mm KCl. 4 Chronic treatment of the cells with forskolin (30 μm), but not IBMX (100 μm), markedly decreased the cellular content of dopamine. 5 Cultured PC12 cells removed and accumulated [3H]-MPP+, which, similarly to dopamine, was released by KCl. 6 Acute treatment of the cells with forskolin (30 μm) or db-cAMP (2.5 mm), but not IBMX (100 μm), slightly increased the spontaneous release, but did not affect KCl-induced release of [3H]-MPP+. On the other hand, chronic treatment of the cells with forskolin produced, on [3H]-MPP+, similar effects to those obtained for dopamine. 7 Acute and chronic treatment of the cells with reserpine (50 nm) produced similar results to those obtained with forskolin on either dopamine or [3H]-MPP+ handling. 8 In conclusion, cAMP, similarly to reserpine, increases the spontaneous release and decreases the KCl-induced release of [3H]-MPP+ and dopamine. This suggests that cAMP impairs the vesicular monoamine transporter.

Notes: 1 The aim of this study was to determine if stimulation of duodenal motility by duodenal fluid distension or by administration of carbachol, activates the sphincter of Oddi-duodenal reflex, in an in vitro preparation from the Australian possum. 2 Duodenal distension was achieved by infusion of Krebs solution (0–8 cm H2O). In separate experiments, the sphincter of Oddi (SO) was partitioned from the duodenum and carbachol (10−7−5 × 10−6 m) added to the duodenal compartment. 3 Fluid distension increased duodenal motility to 120–600% of control activity. These treatments induced increased SO motility (to 120–390% of control) in six preparations, reduced activity (to 60% of control) in one and no response in another. 4 Addition of carbachol to the duodenal compartment resulted in increased duodenal motility. SO motility was increased in seven preparations, reduced in another two and no response were evoked in two others. All SO responses were blocked by tetrodotoxin pretreatment. 5 These data suggest that the SO receives inputs from duodenal mechano and/or stretch receptors resulting in excitatory or inhibitory responses, with the excitatory response dominating. These findings support the role for the SO-duodenal reflex in preventing duodeno-biliary/pancreatic reflux during periods of elevated duodenal activity.

Notes: 1 It has been suggested that opioids may play an indirect role in the regulation of the peripheral circulation through the control of nitric oxide (NO) release in vascular tissue. The current study was undertaken to investigate the effect of nitric oxide synthase (NOS) blockade on responses to morphine in phenylephrine (PE)- or KCl-precontracted rat aortic rings. 2 Morphine (3 × 10−8−3 × 10−5 m) administration did not cause any significant effect on basal tonus of endothelium-intact or endothelium-denuded preparations. Morphine produced concentration-dependent relaxation responses in endothelium-intact as well as in endothelium-denuded rat aortic rings precontracted by PE or KCl. Removal of endothelium did not significantly alter the relaxation responses to morphine. 3 The relaxant responses to morphine were significantly and partially inhibited by pretreatment of tissues with naloxone (NAL, 3 × 10−5 m) for 5 min. The inhibitory effect of NAL on relaxant responses to morphine in PE- or KCl-precontracted rings did not differ significantly between endothelium-intact and endothelium-denuded preparations. 4 Incubation of endothelium-intact or endothelium-denuded rat aortic rings with NOS inhibitor, Nω-nitro-l-arginine methyl ester (l-NAME, 10−4 m) for 20 min did not cause a significant inhibition on relaxation responses to morphine. 5 These findings confirmed the presence of opiate receptors in rat thoracic aorta, but suggested that mechanisms other than NO release play a role in the relaxant effect of morphine on rat aortic rings.

Notes: Summary 1 Bradykinin (BK) is a nine amino acid peptide (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) formed from the plasma precursor kininogen during inflammation and tissue injury. The actions of BK are mediated by G protein-coupled cell surface receptors, designated B1 and B2. 2 BK has a plethora of effects in the airways including bronchoconstriction, bronchodilation, stimulation of cholinergic and sensory nerves, mucus secretion, cough and oedema resulting from promotion of microvascular leakage. These airway effects are mediated in the main by the B2 receptor subtype. 3 BK acts mainly indirectly, primarily through airway nerve activation, but also by the release of prostanoids, thromboxanes and nitric oxide (NO). 4 Airway responses to BK have been studied in detail in guinea-pigs, mice, sheep and rats. This review describes the effects of BK in these species and draws comparison with its effects in normal humans and patients with respiratory diseases. 5 Despite its many and varied effects in the airways of animals and man, the exact contribution of BK to airways disease remains unclear.

Notes: 1 The purpose of this study was to demonstrate that the adrenergic nervous system regulates the in vivo choline levels in the mouse major salivary glands. 2 Methoxamine (α1-adrenoceptor agonist, 2.5–20 mg kg−1, s.c.) elevated choline levels dose-dependently and the effect of methoxamine (10 mg kg−1) was completely inhibited by the α-adrenoceptor antagonist phentolamine (5 mg kg−1, i.p.) but not by the β-adrenoceptor antagonist propranolol (3 mg kg−1, i.p.). 3 In contrast, isoprenaline (β-adrenoceptor agonist 0.25–20 mg kg−1, s.c.) lowered choline levels and the effect of isoprenaline (2 mg kg−1) was inhibited by propranolol, but not by phentolamine. 4 Noradrenaline (1–4 mg kg−1, s.c.) manifested both the α- and β-adrenergic actions depending on its dose. Noradrenaline at 1–2 mg kg−1, lowered choline levels and the effect of noradrenaline (1 mg kg−1) was inhibited by propranolol, but not by phentolamine. On the other hand, noradrenaline (4 mg kg−1) elevated choline levels and the effect was blocked by phentolamine, but not by propranolol. 5 Tyramine (5–80 mg kg−1, s.c.) elicited the release of noradrenaline from sympathetic nerve terminals and induced essentially the same effects on the choline levels as noradrenaline. Tyramine (10 mg kg−1) lowered choline levels and the effect was inhibited by propranolol, but not by phentolamine. However, tyramine (80 mg kg−1) elevated choline levels and the effect was inhibited by phentolamine, but not by propranolol. 6 These results suggest that choline levels in the salivary glands may be under separate α- and β-adrenergic control and suggest a possibility that the neurotransmitter noradrenaline released for sympathetic nerve terminals can manage the dual control of choline levels in some autonomic organs in a characteristic dose-dependent manner.

Notes: 1 The purpose of this study was to investigate the protective effects of defibrotide, a single-stranded polydeoxyribonucleotide, on ischaemia–reperfusion injury to the liver using a rat model. 2 Ischaemia of the left and median lobes was created by total inflow occlusion for 30 min followed by 60 min of reperfusion. Hepatic injury was assessed by the release of liver enzymes (alanine transferase, ALT and lactic dehydrogenase, LDH). Hepatic oxidant stress was measured by superoxide production, lipid peroxidation and nitrite/nitrate formation. Leukocyte–endothelium interaction and Kupffer cell mobilization were quantified by measuring hepatic myeloperoxidase (MPO), polymorphonuclear leukocyte adherence to superior mesenteric artery (SMA) and immunostaining of Kupffer cell. 3 Defibrotide treatment resulted in a significant inhibition of postreperfusion superoxide generation, lipid peroxidation, serum ALT activity, serum LDH activity, MPO activity, serum nitrite/nitrate level, leukocyte adherence to SMA, and Kupffer cell mobilization, indicating a significant attenuation of hepatic dysfunction. 4 A significant correlation existed between liver ischaemia/reperfusion and hepatic injury, suggesting that liver ischaemia/reperfusion injury is mediated predominantly by generation of oxygen free radicals and mobilization of Kupffer cells. 5 We conclude that defibrotide significantly protects the liver against liver ischaemia/reperfusion injury by interfering with Kupffer cell mobilization and formation of oxygen free radicals. This study provides strong evidence that defibrotide has important beneficial effects on acute inflammatory tissue injury such as that occurring in the reperfusion of the ischaemic liver.

Notes: This paper examines the evolution of patent activities across U.S. states from 1963 to 1997. Several patterns are uncovered. First, there is invention catch-up by some lagging states. Second, the evidence is consistent with knowledge diffusion. Third, leading states unable to reinvent themselves lose their leads. Fourth, catch-up can be across a diverse field of activities or focused on select activities. State patent growth is positively correlated to industry R&D and a variable capturing labor skill and infrastructure quality. These provide rationale for state policy makers to increase support to programs that enhance labor skill (e.g., education) and infrastructure quality.

Notes: Economic impact studies overestimate the direct impact of an airport on travelers' expenditures. This occurs for two reasons. First, impact studies assume that the number of visitors traveling to the local area via the airport would fall to zero in the absence of the airport. Second, impact studies implicitly assume that local residents would continue to travel outside the local area in the same numbers as when the local airport is available. In other words, it is assumed that the demand for travel into the local area by visitors is perfectly elastic with respect to the time and money costs of travel, while the demand for travel by local residents is perfectly inelastic with respect to these variables. This paper develops a methodology that avoids both of these sources of error by explicitly incorporating air travel demand into the analysis. The methodology is applied to Tampa International Airport for the year 1996. It is shown that using the standard methodology would have resulted in an estimate of direct impacts sixteen times the size of the estimate made by using the methodology of this paper.

Notes: Book reviewed:Sumila Gulyani, Innovating with Infrastructure: The Automobile industry in India

Notes: Despite the prevalence of multiple jobholding, there is relatively little research into its causes. Existing research has tested the predictions of standard labor models with micro data. Yet, there has been virtually no research into the relationship between moonlighting and structural differences in regional labor markets such as wages and employment growth. In this manner, this study examines the large differences in multiple jobholding rates across U.S. states. The findings indicate that multiple jobholding acts as a short-term shock absorber to cyclical changes. However, in the long-term, these effects dissipate, indicating that moonlighting plays a similar role as do changes in unemployment and labor-force participation to regional labor market shocks. Conversely, multiple jobholding rates are inversely related to average weekly earnings. Thus, job growth accompanied by real wage (and productivity) growth may result in a decline in multiple jobholding, further exacerbating potential labor shortages. Other key factors found to influence multiple jobholding include occupational structure and education.

Notes: Many researchers and practitioners agree that evaluation of economic development planning programs is important, although the perspectives on the approaches, methods, and use of results vary widely. Confounding the issue are cases in which development programs have a small number of participants and typical measures such as parametric statistics are not valid. The alternate evaluation technique presented here uses a non-parametric approach, incorporating a control group for comparison purposes. The paper begins with a review of evaluation issues for economic development planning programs, followed by an illustration of the approach suitable for programs with small numbers of participants. It utilizes a case study of a publicly-funded small business incubator program, the Advanced Technology Development Center, located in Atlanta, Georgia. By explaining how the analysis is constructed and the results interpreted, the paper illustrates a potentially useful methodological approach to evaluating community economic development programs.

Notes: The industrial rise of the Third Italy has been characterized by the growth of dynamic networks of flexible small and medium–sized enterprises (SMEs) that are spatially concentrated in specialized industrial districts. This network type of coordination has been associated with horizontal, trust–based relations rather than vertical relations of power and dependency between local organizations. This would lower transaction costs (essential for local systems with an extreme division of labor), facilitate the transmission and exchange of (tacit) knowledge (and thus, learning and innovation), encourage cooperation mechanisms (such as the establishment of research centers), and stimulate political–institutional performance (e.g. through regulation of potential social conflicts).From an evolutionary perspective, the focus is on the dynamics of industrial districts drawing from current experiences in Italy. In this respect, this paper concentrates on two main features of industrial districts that have largely contributed to their economic success in the past, that is, their network organization and the collective learning process. The evolution of industrial districts is described in terms of organizational adjustments to structural change. The way in which the size distribution of firms has changed is discussed (in particular the role of large companies), how the (power) relationships between local organizations have evolved, what are the current sources and mechanisms of learning, and to what extent institutional lock–in has set in. Finally, a number of trajectories districts may go through in the near future are presented.

Notes: State governments offer a variety of programs to assist technology intensive entrepreneurial firms yet there is a limited understanding of how firms use these programs. This paper provides a framework for categorizing state technology programs and uses detailed case studies to examine how these programs augment firms’ capabilities. It is concluded that firms made extensive use of state programs that provide access to university intellectual property and research facilities. In addition, firms participated in programs that provided incentives for faculty to conduct joint research with industry. Finally, state venture capital programs, though small relative to federal R&D grants or venture capital, appear to nurture firms’ development.

Notes: This paper proposes an evolutionary reading of rural development referred to cases of rapid industrial growth, where a strong concentration process has involved the main urban centers and the successful industrial districts. This territorial development pattern has gradually extinguished rural society and its institutional basis, creating a clear separation between new central and peripheral areas. The consequent effects on local economy and social dynamics reveal the long-term risks raised in terms of development sustainability. An empirical study of two Italian provinces is also carried out to show how this framework can be helpful in interpreting real historical patterns.

Notes: After a long period of industrialization based on import substitution (ISI), Mexico started to open up its economy by accessing the General Agreement on Tariffs and Trade (GATT) in 1986. The export-promotion strategy was transformed into one of regional integration with the signing of the North American Free Trade Agreement (NAFTA) in 1994. The paper explores the impact of the opening of the economy on regional disparities in Mexico using σ and β-convergence analyses. Four different samples have been employed to control for possible data bias linked to the inclusion of oil-producing and maquiladora-based states. The results show that whereas the final stages of the ISI period were dominated by convergence trends, trade liberalization (GATT) and economic integration (NAFTA) have led to divergence. In particular, the NAFTA period is related to divergence regardless of the type of analysis chosen and the sample used.

Notes: This paper examines return migrants and new migrants to Montana: Who are they? Why do they move? Do return migrants move for different reasons than new migrants? Data from the 1994–1997 Montana Poll, a representative survey of Montana households, are used. A comparison of socio-economic differences of return and new migrants shows that the two migrant types are very similar in terms of education, income, and age. This stands in contrast to the findings of others who maintain that return migrants are negatively selected with respect to education. Logistic regressions were employed to identify the effect of age and place ties on reasons for moving. Return migrants and new migrants move to Montana for very similar reasons, with family being the most important primary reason for moving. Moving for lifestyle reasons, such as environmental quality and urban amenities, were found to systematically change with age. This could explain why people return to a place they left earlier in life. While other research on return migration compared return migrants and other migrants who left the same place of origin, this paper offers a comparison of return migrants and other migrants who seek out the same destination. Results from the Montana Poll suggest that the same destination attracts return migrants and new migrants with similar socio-economic characteristics who move there for very similar reasons.

Notes: The U.S. machine tool (MT) sector has undergone substantial restructuring over the past three decades. Despite signs of a commercial rebound in recent years, however, a number of critical issues remain for this industry. Not all firms share these concerns, in that differences exist between producers located in the core manufacturing belt and those located elsewhere. This paper examines the characteristics, competitive problems, and markets of firms located in these two regions. Survey data from a sample of 104 machine tool companies reveal that significant core–periphery differences exist with regard to firm–specific difficulties and markets served. The data also show that firms in the periphery have been growing significantly faster than firms in the core. The paper concludes with a discussion of the likely reasons for regional variability in the characteristics of firms in this industry. Directions for future research are also suggested, notably with regard to the interplay between national regulatory conditions and the competitive performance of MT firms.

Notes: Despite an increase of 200,000 jobs in business and professional services in the Atlanta metropolitan area between 1982 and 1997, the central city saw employment as a percentage of these services drop by approximately 20 percent. Most growth occurred in the northern suburbs, resulting in a dispersed distribution of business and professional services in Atlanta. To understand the spatial distribution and suburbanization of business and professional services in Atlanta, regression analysis was carried out for 1982 and 1992. Flexible female workers, corporate headquarters, well –educated professionals, and highway access turned out to be important location determinants, with the latter two being increasingly responsible for the suburbanization of business and professional services.

Notes: This paper considers the case of Bangkok where, as in many Asian cities, the expansion of urban areas has outpaced the ability of public entities to manage and provide basic services. One potential way to improve the capacity of neighborhoods to assist in provision or improvement in environmental services is to enhance the positive contributions provided by local social networks and social capital. A conceptual framework is presented to explore the role of social networks in environmental management in polluted urban environments. This is followed by a brief description of the methodology and survey instrument used to collect information from a sample of community households in Bangkok and an analysis of the results from this survey regarding environmental practices, community action, and social networks. Some of the results suggest that increasing the number of social interactions that residents of a community experience is associated with increased community participation as, apparently, is increasing knowledge about what happens to waste or waste water after it leaves the community. Local public education efforts that focus on useful knowledge about environmental impacts may well be an effective way to encourage community participation.

Notes: Recent years have witnessed widespread expansion of state and regional planning programs in the United States. A major purpose of these efforts is to reduce urban sprawl—low density, discontinuous, suburban–style development, often characterized as the result of rapid, unplanned, and/or uncoordinated growth— by promoting jurisdictional cooperation and regulatory consistency across metropolitan areas. This paper evaluates the efficacy of this approach by examining the relationship between governmental fragmentation and several measurable outcomes of urban development: density, urbanized land area, property value, and public expenditures on infrastructure. The four dimensions are modeled in a simultaneous equations framework, providing substantive evidence on how fragmentation and other exogenous factors affect metropolitan growth patterns. Fragmentation is associated with lower densities and higher property values, but has no direct effect on public service expenditures; less fragmented metropolitan areas occupy greater amounts of land due to the extensive annexation needed to bring new development under the control of a central municipality. The findings of the analysis lend support to state and regional planning efforts aimed at increasing cooperation among local governments, but also suggest that further research is needed in order to evaluate whether or not they produce their intended effects.

Notes: Discussions of immigration, settlement and adjustment within the U.S. do not typically refer to immigrant status (i.e., refugee versus family preference), and instead refer to the foreign–born population as an aggregate. Distinguishing between refugees and other immigrant arrivals likely means differences with respect to their geographic distribution and embodied human capital owing to differences associated with the reasons for immigration (forced versus voluntary), period of arrival, and immigration policy. The lack of differentiation by group within the existing literature is typically due to a shortfall of detailed information relating to admission status within publicly released data files. Yet concrete knowledge of differences by admission category is important in understanding overall patterns of settlement and adjustment within the foreign–born population. This paper therefore explores potential differences with respect to settlement and endowed human capital between immigrants and refugees. Identification of the major sources of refugees within Immigration and Naturalization Service data files allows the refugee population to be identified within the 1990 Public Use Microdata Sample (PUMS), therefore increasing the range of variables and measures associated with the refugee population available to researchers, and points to the diversity of the refugee population.

Notes: This paper presents an analysis of a public assistance program for small–scale entrepreneurship in peripheral areas. Public assistance compensates for market inefficiencies where the decision rules of financial institutions discriminate against otherwise viable small firms in capital markets. Lending institutions perceive high risk in providing debt capital when little information is present. Using empirical data from Israel, the determinants of this risk are estimated and the role of location in creating this information asymmetry is stressed. These results empirically establish that (1) location matters in determining the risk profile of the firm, (2) locationally targeted programs can reduce the information asymmetries that make peripheral firms unattractive to lenders, and (3) these programs can also generate positive welfare effects. Finally, there is speculation on the potential role of ICT (information and communications technology) in increasing the visibility of small firms in remote locations and creating a more symmetrical flow of information.

Notes: Ethnic entrepreneurship has become a popular concept in a modern multi–cultural society. This paper seeks to offer an overview of the potential of ethnic entrepreneurship for solving inter alia the structural unemployment problems of ethnic groups in cities. There is a general lack of empirical evidence on this issue in the current literature. The present paper aims to fill this gap by addressing in particular the critical success conditions for ethnic entrepreneurs. The focus of the research is on variations in success across three ethnic groups in the Amsterdam area. By means of structured personal interviews with many ethnic entrepreneurs, a systematic qualitative data base was created. The paper sets out to identify empirically the driving forces for business success, such as education or the role of informal networks. The explanatory framework deployed for the identification of these qualitative success factors for distinct ethnic groups is based on a particular, recently developed artificial intelligence method, viz. rough set analysis. This multidimensional classification approach appears to be able to identify various important factors for the motivation and performance of ethnic enterprises. Two major findings emerge from this investigation: (i) performance conditions vary across ethnic groups, and (ii) informal networks are crucial for business success.

Notes: Rocky Mountain states have experienced unprecedented growth as agricultural land is converted to residences. Preservation efforts meet with protest from private landholders claiming public efforts undermine private property rights. This paper explores the degree to which respondents think management of agricultural lands is a public versus a private matter. Data are from a Sublette County, Wyoming, mail survey. Results are relevant to many western counties having public lands and high growth rates. They suggest that landowners, wage earners, college graduates, and those who value the county’s rural community lifestyle support public management strategies. Well-established residents and those with economic reasons for living in the county support private management strategies.

Notes: This research examines changes in four sectors of livestock production, pork, dairy, fed cattle, and beef cows, from 1978 to 1997 by county metropolitan character. Relative changes in the amount of production and the number of producers in a county as well as changes in the average scale of production are examined. The purpose is to identify whether structural differences have emerged between metropolitan and nonmetropolitan Corn Belt counties as a result of industrialization in livestock production. The analysis identifies a divergence in the amount and scale of pork production in metro versus nonmetro regions from 1987 to 1997, coinciding with a period of substantial industrialization in that sector. Little divergence is identified in the scale of dairy, fed cattle, and beef cows operations during the same time period. The findings have implications for farmland preservation and agricultural viability in exurban regions of the Corn Belt.

Notes: Abstract The amyloid precursor protein and the proteases cleaving this protein are important players in the pathogenesis of Alzheimer's disease via the generation of the amyloid peptide. Physiologically, the amyloid precursor protein is implied in axonal vesicular trafficking and the proteases are implicated in developmentally important signaling pathways, most significantly those involving regulated intramembrane proteolysis or RIP. We discuss the cell biology behind the amyloid and tangle hypothesis for Alzheimer's disease, drawing on the many links to the fields of cell biology and developmental biology that have been established in the recent years.

Notes: Abstract The type III mechanism of protein secretion is a pathogenic strategy shared by a number of gram-negative pathogens of plants and animals that has evolved in order to inject virulence proteins into the cytosol of target eukaryotic cells. The pathogens of the Yersinia genus represent a model system where much progress has been made in understanding this secretion pathway. Herein, we review what has been recently learned in yersiniae about the various environmental signals that induce type III secretion, how the synthesis of secretion substrates is regulated, and how such a diverse group of proteins is recognized as a substrate for secretion.

Notes: Abstract The host cytoskeleton plays important roles in the entry, replication, and egress of viruses. An assortment of viruses hijack cellular motor proteins to move on microtubules toward the cell interior during the entry process; others reverse this transport during egress to move assembling virus particles toward the plasma membrane. Polymerization of actin filaments is sometimes used to propel viruses from cell to cell, while many viruses induce the destruction of select cytoskeletal filaments apparently to effect efficient egress. Indeed, the tactics used by any given virus to achieve its infectious life cycle are certain to involve multiple cytoskeletal interactions. Understanding these interactions, and their orchestration during viral infections, is providing unexpected insights into basic virology, viral pathogenesis, and the biology of the cytoskeleton.

Notes: Abstract Spindle microtubules interact with mitotic chromosomes, binding to their kinetochores to generate forces that are important for accurate chromosome segregation. Motor enzymes localized both at kinetochores and spindle poles help to form the biologically significant attachments between spindle fibers and their cargo, but microtubule-associated proteins without motor activity contribute to these junctions in important ways. This review examines the molecules necessary for chromosome-microtubule interaction in a range of well-studied organisms, using biological diversity to identify the factors that are essential for organized chromosome movement. We conclude that microtubule dynamics and the proteins that control them are likely to be more important for mitosis than the current enthusiasm for motor enzymes would suggest.

Notes: Abstract Chlamydiae, bacterial obligate intracellular pathogens, are the etiologic agents of several human diseases. A large part of the chlamydial intracellular survival strategy involves the formation of a unique organelle called the inclusion that provides a protected site within which they replicate. The chlamydial inclusion is effectively isolated from endocytic pathways but is fusogenic with a subset of exocytic vesicles that deliver sphingomyelin from the Golgi apparatus to the plasma membrane. A combination of host and parasite functions contribute to the biogenesis of this compartment. Establishment of the mature inclusion is accompanied by the insertion of multiple chlamydial proteins, suggesting that chlamydiae actively modify the inclusion to define its interactions with the eukaryotic host cell. Despite being sequestered within a membrane-bound vacuole, chlamydiae clearly communicate with and manipulate the host cell from within this privileged intracellular niche.

Notes: Abstract Epithelial morphogenesis comprises the various processes by which epithelia contribute to organ formation and body shape. These complex and diverse events play a central role in animal development and regeneration. Recently, the characterization of some of the molecular mechanisms involved in epithelial morphogenesis has provided an abundance of new information on the role and regulation of the cytoskeleton, cell-cell adhesion, and cell-matrix adhesion in these processes. In this review, we discuss our current understanding of the molecular mechanisms driving cell shape changes, cell intercalation, fusion of epithelia, ingression, egression, and cell migration. Our discussion is mostly focused on results from Drosophila and mammalian tissue culture but also draws on the insights gained from other organisms.

Notes: Abstract Golgi inheritance proceeds via sequential biogenesis and partitioning phases. Although little is known about Golgi growth and replication (biogenesis), ultrastructural and fluorescence analyses have provided a detailed, though still controversial, perspective of Golgi partitioning during mitosis in mammalian cells. Partitioning requires the fragmentation of the juxtanuclear ribbon of interconnected Golgi stacks into a multitude of tubulovesicular clusters. This process is choreographed by a cohort of mitotic kinases and an inhibition of heterotypic and homotypic Golgi membrane-fusion events. Our model posits that accurate partitioning occurs early in mitosis by the equilibration of Golgi components on either side of the metaphase plate. Disseminated Golgi components then coalesce to regenerate Golgi stacks during telophase. Semi-intact cell and cell-free assays have accurately recreated these processes and allowed their molecular dissection. This review attempts to integrate recent findings to depict a more coherent, synthetic molecular picture of mitotic Golgi fragmentation and reassembly. Of particular importance is the emerging concept of a highly regulated and dynamic Golgi structural matrix or template that interfaces with cargo receptors, Golgi enzymes, Rab-GTPases, and SNAREs to tightly couple biosynthetic transport to Golgi architecture. This structural framework may be instructive for Golgi biogenesis and may encode sufficient information to ensure accurate Golgi inheritance, thereby helping to resolve some of the current discrepancies between different workers.

Notes: Abstract Co-option occurs when natural selection finds new uses for existing traits, including genes, organs, and other body structures. Genes can be co-opted to generate developmental and physiological novelties by changing their patterns of regulation, by changing the functions of the proteins they encode, or both. This often involves gene duplication followed by specialization of the resulting paralogous genes into particular functions. A major role for gene co-option in the evolution of development has long been assumed, and many recent comparative developmental and genomic studies have lent support to this idea. Although there is relatively less known about the molecular basis of co-option events involving developmental pathways, much can be drawn from well-studied examples of the co-option of structural proteins. Here, we summarize several case studies of both structural gene and developmental genetic circuit co-option and discuss how co-option may underlie major episodes of adaptive change in multicellular organisms. We also examine the phenomenon of intraspecific variability in gene expression patterns, which we propose to be one form of material for the co-option process. We integrate this information with recent models of gene family evolution to provide a framework for understanding the origin of co-optive evolution and the mechanisms by which natural selection promotes evolutionary novelty by inventing new uses for the genetic toolkit.

Notes: Abstract In flowering plants, pollen grains germinate to form pollen tubes that transport male gametes (sperm cells) to the egg cell in the embryo sac during sexual reproduction. Pollen tube biology is complex, presenting parallels with axon guidance and moving cell systems in animals. Pollen tube cells elongate on an active extracellular matrix in the style, ultimately guided by stylar and embryo sac signals. A well-documented recognition system occurs between pollen grains and the stigma in sporophytic self-incompatibility, where both receptor kinases in the stigma and their peptide ligands from pollen are now known. Complex mechanisms act to precisely target the sperm cells into the embryo sac. These events initiate double fertilization in which the two sperm cells from one pollen tube fuse to produce distinctly different products: one with the egg to produce the zygote and embryo and the other with the central cell to produce the endosperm.

Notes: Abstract The Arabidopsis genome sequence has revealed that plants contain a much larger complement of receptor kinase genes than other organisms. Early analysis of these genes revealed involvement in a diverse array of developmental and defense functions that included gametophyte development, pollen-pistil interactions, shoot apical meristem equilibrium, hormone perception, and cell morphogenesis. Amino acid sequence motifs and binding studies indicate that the ectodomains are capable of binding, either directly or indirectly, various classes of molecules including proteins, carbohydrates, and steroids. Genetic and biochemical approaches have begun to identify other components of several signal transduction pathways. Some receptor-like kinases (RLKs) appear to function with coreceptors lacking kinase domains, and genome analysis suggests this might be true for many RLKs. The KAPP protein phosphatase functions as a negative regulator of at least two RLK systems, and in vitro studies suggest it could be a common component of more. Whether plant signaling systems display a modularity similar to animal systems remains to be determined. Future efforts will reveal unknown functions of other RLKs and elucidate the relationships among their signaling networks.

Notes: Abstract Eukaryotic cells use actin polymerization to change shape, move, and internalize extracellular materials by phagocytosis and endocytosis, and to form contractile structures. In addition, several pathogens have evolved to use host cell actin assembly for attachment, internalization, and cell-to-cell spread. Although cells possess multiple mechanisms for initiating actin polymerization, attention in the past five years has focused on the regulation of actin nucleation-the formation of new actin filaments from actin monomers. The Arp2/3 complex and the multiple nucleation-promoting factors (NPFs) that regulate its activity comprise the only known cellular actin-nucleating factors and may represent a universal machine, conserved across eukaryotic phyla, that nucleates new actin filaments for various cellular structures with numerous functions. This review focuses on our current understanding of the mechanism of actin nucleation by the Arp2/3 complex and NPFs and how these factors work with other cytoskeletal proteins to generate structurally and functionally diverse actin arrays in cells.

Notes: Abstract Membrane fusion is a fundamental biochemical reaction and the final step in all vesicular trafficking events. It is crucial for the transfer of proteins and lipids between different compartments and for exo- and endocytic traffic of signaling molecules and receptors. It leads to the reconstruction of organelles such as the Golgi or the nuclear envelope, which decay into fragments during mitosis. Hence, controlled membrane fusion reactions are indispensible for the compartmental organization of eukaryotic cells; for their communication with the environment via hormones, neurotransmitters, growth factors, and receptors; and for the integration of cells into multicellular organisms. Intracellular pathogenic bacteria, such as Mycobacteria or Salmonellae, have developed means to control fusion reactions in their host cells. They persist in phagosomes whose fusion with lysosomes they actively suppress-a means to ensure survival inside host cells. The past decade has witnessed rapid progress in the elucidation of parts of the molecular machinery involved in these membrane fusion reactions. Whereas some elements of the fusion apparatus are remarkably similar in several compartments, there is an equally striking divergence of others. The purpose of this review is to highlight common features of different fusion reactions and the concepts that emerged from them but also to stress the differences and challenge parts of the current hypotheses. This review covers only the endoplasmic fusion reactions mentioned above, i.e., reactions initiated by contacts of membranes with their cytoplasmic faces. Ectoplasmic fusion events, which depend on an initial contact of the fusion partners via the membrane surfaces exposed to the surrounding medium are not discussed, nor are topics such as the entry of enveloped viruses, formation of syncytia, gamete fusion, or vesicle scission (a fusion reaction that leads to the fission of, e.g., transport vesicles).

Notes: Abstract Bacterial pathogens utilize several strategies to modulate the organization of the actin cytoskeleton. Some bacterial toxins catalyze the covalent modification of actin or the Rho GTPases, which are involved in the control of the actin cytoskeleton. Other bacteria produce toxins that act as guanine nucleotide exchange factors or GTPase-activating proteins to modulate the nucleotide state of the Rho GTPases. This latter group of toxins provides a temporal modulation of the actin cytoskeleton. A third group of bacterial toxins act as adenylate cyclases, which directly elevate intracellular cAMP to supra-physiological levels. Each class of toxins gives the bacterial pathogen a selective advantage in modulating host cell resistance to infection.

Notes: Abstract The mammalian cell continuously adjusts its sterol content by regulating levels of key sterol synthetic enzymes and levels of LDL receptors that mediate uptake of cholesterol-laden particles. Control is brought about by sterol-regulated transcription of relevant genes and by regulated degradation of the committed step enzyme HMG-CoA reductase (HMGR). Current work has revealed that proteolysis is at the heart of each of these mechanistically distinct axes. Transcriptional control is effected by regulated cleavage of the membrane-bound transcription factor sterol regulatory element binding protein (SREBP), and HMGR degradation is brought about by ubiquitin-mediated degradation. In each case, ongoing cell biological processes are being harnessed to bring about regulation. The secretory pathway plays a central role in allowing sterol-mediated control of transcription. The constitutively active endoplasmic reticulum (ER) quality control apparatus is employed to bring about regulated destruction of HMGR. This review describes the methods and results of various studies to understand the mechanisms and molecules involved in these distinct but interrelated aspects of sterol regulation and the intriguing similarities that appear to exist at the levels of protein sequence and cell biology.

Notes: Abstract A large number of protein toxins having enzymatically active A- and B-moieties that bind to cell surface receptors must be endocytosed before the A-moiety is translocated into the cytosol where it exerts its cytotoxic action. The accumulated information about the most well-studied toxins has provided a detailed picture of how they exploit the membrane trafficking systems of cells, and studies of toxin trafficking have revealed the existance of new pathways. The complexity of different endocytic mechanisms, as well as the multiple routes between endosomes and the Golgi apparatus and retrogradely to the endoplasmic reticulum (ER), are being unravelled by investigations of how toxins gain access to their targets. With increasing information about the internalization and intracellular trafficking of these opportunistic toxins, new avenues have been opened for their application in areas of medicine such as drug delivery and therapy.

Notes: Abstract Autoinhibitory domains are regions of proteins that negatively regulate the function of other domains via intramolecular interactions. Autoinhibition is a potent regulatory mechanism that provides tight "on-site" repression. The discovery of autoinhibition generates valuable clues to how a protein is regulated within a biological context. Mechanisms that counteract the autoinhibition, including proteolysis, post-translational modifications, as well as addition of proteins or small molecules in trans, often represent central regulatory pathways. In this review, we document the diversity of instances in which autoinhibition acts in cell regulation. Seven well-characterized examples (e.g., sigma70, Ets-1, ERM, SNARE and WASP proteins, SREBP, Src) are covered in detail. Over thirty additional examples are listed. We present experimental approaches to characterize autoinhibitory domains and discuss the implications of this widespread phenomenon for biological regulation in both the normal and diseased states.

Notes: Abstract In Caenorhabditis elegans the timing of many developmental events is regulated by heterochronic genes. Such genes orchestrate the timing of cell divisions and fates appropriate for the developmental stage of an organism. Analyses of heterochronic mutations in the nematode C. elegans have revealed a genetic pathway that controls the timing of post-embryonic cell divisions and fates. Two of the genes in this pathway encode small regulatory RNAs. The 22 nucleotide (nt) RNAs downregulate the expression of protein-coding mRNAs of target heterochronic genes. Analogous variations in the timing of appearance of particular features have been noted among closely related species, suggesting that such explicit control of developmental timing may not be exclusive to C. elegans. In fact, some of the genes that globally pattern the temporal progression of C. elegans development, including one of the tiny RNA genes, are conserved and temporally regulated across much of animal phylogeny, suggesting that the molecular mechanisms of temporal control are ancient and universal. A very large family of tiny RNA genes called microRNAs, which are similar in structure to the heterochronic regulatory RNAs, have been detected in diverse animal species and are likely to be present in most metazoans. Functions of the newly discovered microRNAs are not yet known. Other examples of temporal programs during growth include the exquisitely choreographed temporal sequences of developmental fates in neurogenesis in Drosophila and the sequential programs of epidermal coloration in insect wing patterning. An interesting possibility is that microRNAs mediate transitions on a variety of time scales to pattern the activities of particular target protein-coding genes and in turn generate sets of cells over a period of time. Plasticity in these microRNA genes or their targets may lead to changes in relative developmental timing between related species, or heterochronic change. Instead of inventing new gene functions, even subtle changes in temporal expression of pre-existing control genes can result in speciation by altering the time at which they function.

Notes: Abstract Signaling between cells is a widely used mechanism by which cell fate and tissue patterning is determined in development. We review the mechanisms by which signaling between cells is regulated so that a cell receives the right amount of signal, at the right time, to achieve its intended developmental fate and position. In nearly all cases, we find that the supply of signal factor (ligand) is the limiting step in initiating a signaling process. Ligand supply is regulated by the transcription and localization of RNA, the spread of ligand from a source, and by inhibitors that operate at several different levels. We emphasize the different regulatory strategies that operate for threshold as opposed to concentration-dependent (morphogen) signaling. Threshold signaling is extensively regulated by feedback mechanisms. Morphogen signaling is regulated quantitatively by receptor loading and transduction flow.

Notes: Abstract Cells monitor the physiological load placed on their endoplasmic reticulum (ER) and respond to perturbations in ER function by a process known as the unfolded protein response (UPR). In metazoans the UPR has a transcriptional component that up-regulates expression of genes that enhance the capacity of the organelle to deal with the load of client proteins and a translational component that insures tight coupling between protein biosynthesis on the cytoplasmic side and folding in the ER lumen. Together, these two components adapt the secretory apparatus to physiological load and protect cells from the consequences of protein malfolding.

Notes: Abstract The vasculature is one of the most important and complex organs in the mammalian body. The first functional organ to form during embryonic development, the intricately branched network of endothelial and supporting periendothelial cells is essential for the transportation of oxygen and nutrients to and the removal of waste products from the tissues. Serious disruptions in the formation of the vascular network are lethal early in post-implantation development, while the maintenance of vessel integrity and the control of vessel physiology and hemodynamics have important consequences throughout embryonic and adult life. A full understanding of the signaling pathways of vascular development is important not just for understanding normal development but because of the importance of reactivation of angiogenic pathways in disease states. Clinically there is a need to develop therapies to promote new blood vessel formation in situations of severe tissue ischemia, such as coronary heart disease. In addition, there is considerable interest in developing angiogenic inhibitors to block the new vessel growth that solid tumors promote in host tissue to enhance their own growth. Already studies on the signaling pathways of normal vascular development have provided new targets for therapeutic intervention in both situations. Further understanding of the complexities of the pathways should help refine such strategies.

Notes: Abstract The actin cytoskeleton plays a major role in morphological development of neurons and in structural changes of adult neurons. This article reviews the myriad functions of actin and myosin in axon initiation, growth, guidance and branching, in morphogenesis of dendrites and dendritic spines, in synapse formation and stability, and in axon and dendrite retraction. Evidence is presented that signaling pathways involving the Rho family of small GTPases are key regulators of actin polymerization and myosin function in the context of different aspects of neuronal morphogenesis. These studies support an emerging theme: Different aspects of neuronal morphogenesis may involve regulation of common core signaling pathways, in particular the Rho GTPases.

Notes: Abstract Striated muscle is an intricate, efficient, and precise machine that contains complex interconnected cytoskeletal networks critical for its contractile activity. The individual units of the sarcomere, the basic contractile unit of myofibrils, include the thin, thick, titin, and nebulin filaments. These filament systems have been investigated intensely for some time, but the details of their functions, as well as how they are connected to other cytoskeletal elements, are just beginning to be elucidated. These investigations have advanced significantly in recent years through the identification of novel sarcomeric and sarcomeric-associated proteins and their subsequent functional analyses in model systems. Mutations in these cytoskeletal components account for a large percentage of human myopathies, and thus insight into the normal functions of these proteins has provided a much needed mechanistic understanding of these disorders. In this review, we highlight the components of striated muscle cytoarchitecture with respect to their interactions, dynamics, links to signaling pathways, and functions. The exciting conclusion is that the striated muscle cytoskeleton, an exquisitely tuned, dynamic molecular machine, is capable of responding to subtle changes in cellular physiology.

Notes: Abstract Chromatin remodeling in plants has usually been discussed in relation to aspects of genome defense such as transgene silencing and the resetting of transposon activity. The role of remodeling in controlling development has been less emphasized, although well established in animal systems. This is because cell fate in plants is often held to be entirely specified on the basis of position, apparently excluding any significant role for cell ancestry and chromatin remodeling. We argue that chromatin remodeling is used to confer mitotically heritable cell fates at late stages in pattern formation. Several examples in which chromatin remodeling factors are used to confer a memory of transient events in plant development are discussed. Because the precise biochemical functions of most remodeling factors are obscure, and little is known of plant chromatin structure, the underlying mechanisms remain poorly understood.

Notes: Abstract Embryological and genetic studies of mouse, bird, zebrafish, and frog embryos are providing new insights into the regulatory functions of the myogenic regulatory factors, MyoD, Myf5, Myogenin, and MRF4, and the transcriptional and signaling mechanisms that control their expression during the specification and differentiation of muscle progenitors. Myf5 and MyoD genes have genetically redundant, but developmentally distinct regulatory functions in the specification and the differentiation of somite and head muscle progenitor lineages. Myogenin and MRF4 have later functions in muscle differentiation, and Pax and Hox genes coordinate the migration and specification of somite progenitors at sites of hypaxial and limb muscle formation in the embryo body. Transcription enhancers that control Myf5 and MyoD activation in muscle progenitors and maintain their expression during muscle differentiation have been identified by transgenic analysis. In epaxial, hypaxial, limb, and head muscle progenitors, Myf5 is controlled by lineage-specific transcription enhancers, providing evidence that multiple mechanisms control progenitor specification at different sites of myogenesis in the embryo. Developmental signaling ligands and their signal transduction effectors function both interactively and independently to control Myf5 and MyoD activation in muscle progenitor lineages, likely through direct regulation of their transcription enhancers. Future investigations of the signaling and transcriptional mechanisms that control Myf5 and MyoD in the muscle progenitor lineages of different vertebrate embryos can be expected to provide a detailed understanding of the developmental and evolutionary mechanisms for anatomical muscles formation in vertebrates. This knowledge will be a foundation for development of stem cell therapies to repair diseased and damaged muscles.

Notes: Books reviewed:Mona Domosh and Joni Seager, Putting Women in Place: Feminist Geographers Make Sense of the WorldGerald Hodge and Ira M. Robinson, Planning Canadian Regions

Notes: This paper analyzes the effect of self–employed persons’ education on the success of their firms during the economic downturn and upturn of the 1990's. It is found that the business cycle affects the relative closure rates of firms run by self–employed with any level of education. Exit probability is lower for the highly educated during bust, but higher in boom. This is accounted for by two facts. First, running a small firm is argued to be a less attractive choice to wage work, particularly for the highly educated, due to lower earning prospects, less stable stream of earnings, and the cultural tradition of working in large corporations. Second, the highly educated faced a higher outside demand for their labor than did the less educated during economic upturn. Finally, it was found that regardless of the state of aggregate economy, firms run by the highly educated have higher growth probabilities than those run by less educated persons.

Notes: This study analyzes the evolution of China’s regional inequalities during the reform period of 1978–1998 based on three geographical scales, both output and livelihood indicators of economic well-being and three measures of inequality. The results indicate that interprovincial and regional inequalities declined between 1978 and 1990, but have widened steadily since 1990. Urban-rural disparity diminished before 1984, then experienced a decade-long surge afterwards to peak in 1994 at a much higher level and since 1994, it has been declining again. The levels of regional inequalities in China appear to be sensitive to changes in government development strategies and regional policies. Differential growth of the provincial economies shaped by the coast-oriented and urban-biased development strategies as well as selective open-door policy implemented by the Chinese government after the reform is the key to understanding the wax and wane in China’s regional inequalities. This paper discusses the factors that account for the changing regional inequalities in post-reform China and argues that government policies are likely to continue to influence the future trajectories of inequality change.

Notes: Books reviewed:Char Miller, Fluid Arguments: Five Centuries of Western Water ConflictMichael Dear, (ed.) From Chicago to L.A.: Making Sense of Urban TheoryMartin Dangerfield, Subregional Economic Cooperation in Central and Eastern Europe: The Political Economy of CEFTAKenneth Button and Roger Stough, Air Transport Networks: Theory and Policy Implications

Notes: This paper examines the effects of state economic development incentives on the growth of 366 Ohio manufacturing and nonmanufacturing establishments that launched major expansions between 1993 and 1995. Growth is measured as the actual employment change that occurred in these establishments and as the employment growth announced when expansions were launched. Empirical findings indicate that incentives have very little (or even a negative) effect on actual growth and they have a substantial positive effect on announced growth. Findings also suggest that establishments that received incentives overestimated their announced employment targets more than establishments that did not receive incentives.

Notes: In this paper the excise tax policy of U.S. state governments is analyzed with special attention to how this policy is influenced by the level of excise taxation in neighboring states, “border-tax effects,” and the relative size of the market located across state boundaries. Using a panel data set, state policies towards the taxation of cigarettes, all alcoholic beverages, beer, distilled liquor, motor fuel, and insurance are investigated within the context of a vote-maximizing model of collective decision making. The role of the industry in that state whose goods and services are singled out for special taxation is also examined.

Notes: This paper examines the importance of the distribution of consumers in Hotelling’s circle on the comparison between the optimal and the market equilibrium levels of diversity. It finds that when most consumers are located very close to the firms, the result of Salop—that the equilibrium number of firms is larger than the optimal one (surplus maximizing)—can be reversed.

Notes: Books reviewed:Gordon L. Clark, Maryann P. Feldman, and Meric S. Gertler (eds.), The Oxford Handbook of Economic GeographyPeter Meusburger and Heike Jöns (eds.), Transformations in Hungary: Essays in Economy and SocietyAllen J. Scott (ed.), Global City-Regions: Trends, Theory, PolicyJames O. Wheeler, Yuko Aoyama, and Barney Warf (eds.), Cities in the Telecommunications Age: The Fracturing of GeographiesBarry Bluestone and Mary Huff Stevenson, The Boston Renaissance: Race, Space, and Economic Change in an American Metropolis

Notes: Net multipliers, as introduced by Oosterhaven and Stelder (2002) accept outputs as entries instead of final demand. They are found by multiplying ordinary multipliers by the final demand ratio over the sector’s output. This pragmatic solution suffers from ratio instability over time. The alternative net multipliers proposed here are based on the interpretation of the Leontief inverse matrix for the effects generated at each round. The new solution is not sensitive to the size of impacts. Now net multiplier is equal to the corresponding ordinary multiplier minus one, and the ordering of multipliers is unchanged.

Notes: In this paper we analyze the effect of infrastructure on the cost and productivity performance of the private productive sector of Spanish regions over the period 1980–1993. We use a dual approach based on cost functions that allows us to recover the usual parameters estimated with production functions. In addition, we obtain rates of return and cost elasticities of production factors at the regional level. Our framework explicitly considers that some factors are quasi-fixed and their volume can differ from their optimal endowment levels. Our results indicate that the public sector has contributed significantly to enhance productivity and reduce costs in the private sector of almost every Spanish region. Nevertheless, there is still scope for the government to continue its investment efforts, given that there remains an appreciable gap between observed and optimal public capital, and we find that in the long run, public capital promotes private investment.

Notes: This paper tests for spatial spillover effects of state-level telecommunications infrastructure investment on state output, using panel data for 48 U.S. states from 1970 through 1997. As information and communication technologies support more industrial locational freedom, states may use telecommunications infrastructure investment as a competitive tool for attracting factors of production. In a production-function framework, this effect would manifest itself as a negative output spillover effect from telecommunications infrastructure investment. Findings indicate that a state benefits from its own telecommunications infrastructure, but telecommunications investment by other states has a negative impact on its output growth path, and proximity amplifies this negative spillover effect.

Notes: Books reviewed:A. Stewart Fotheringham and Michael Wegener (eds.), Spatial Models and GIS: New Potential and New ModelsAura Reggiani (ed.), Spatial Economic Science: New Frontiers in Theory and MethodologyJean-Claude Thill (ed.), Geographic Information Systems in Transportation ResearchBarbara Dluhosch, Industrial Location and Economic Integration: Centrifugal and Centripetal Forces in the New EuropeJean-Marie Huriot and Jacques-François Thisse, Economics of Cities: Theoretical PerspectivesManfred M. Fischer and Yee Leung (eds.), GeoComputational Modelling: Techniques and ApplicationsEduardo A. Haddad, Regional Inequality and Structural Changes: Lessons from the Brazilian ExperienceManfred M. Fischer, Luis Suarez-Villa, and Michael Steiner (eds.), Innovation, Networks and LocalitiesMarjolein C.J. Caniëls, Knowledge Spillovers and Economic Growth: Regional Growth Differentials across EuropeMartin van der Velde and Henk van Houtum (eds.), Borders, Regions, and PeoplePeter W. J. Batey and Peter Friedrich (eds.), Regional CompetitionJohn E. Anderson and Robert W. Wassmer, Bidding for Business: The Efficacy of Local Economic Development Incentives in a Metropolitan AreaPhilip Hanson and Michael Bradshaw (eds.), Regional Economic Change in RussiaGred Hise and William Deverell, Eden by Design: The 1930 Olmsted-Bartholomew Plan for the Los Angeles Region

Notes: Using the properties of the Gini coefficient, a structural model is developed to assess the impact of uniform changes in environmental compliance costs on the distribution of per capita emissions across U.S. counties and states, a distribution that places a larger burden on minorities. Using data from the U.S. EPA’s Toxic Release Inventory and three state-specific measures of environmental compliance costs, we find that uniform increases in federal environmental standards have little impact on the distribution of environmental hazards, and may actually exacerbate spatial inequality. As a result, Federal standards that target specific high pollution locations are necessary to redress current inequities.

Notes: This paper estimates the effects of welfare reforms on a state’s employment and wage rates. Welfare reforms include: pushing welfare recipients into the labor force, financial incentives to recipients for working, wage subsidies to employers of recipients, and community service jobs for recipients. The effects of these policies are analyzed using a newly estimated model of state labor markets. Simulations show that jobs found by welfare reform participants cause sizable displacement effects for nonparticipants. Displacement effects of labor supply policies are highest when a state’s unemployment is high, whereas displacement effects of labor demand policies are highest when a state’s unemployment is low.

Notes: Although the need for aggregation in input –output modelling has diminished with the increases in computing power, an alarming number of regional studies continue to use the procedure. The rationales for doing so typically are grounded in data problems at the regional level. As a result many regional analysts use aggregated national input –output models and trade –adjust them at this aggregated level. In this paper, we point out why this approach can be inappropriate. We do so by noting that it creates a possible source of model misapplication (i.e., a direct effect could appear for a sector where one does not exist) and also by finding that a large amount of error (on the order of 100 percent) can be induced into the impact results as a result of improper aggregation. In simulations, we find that average aggregation error tends to peak at 81 sectors after rising from 492 to 365 sectors. Perversely, error then diminishes somewhat as the model size decreases further to 11 and 6 sectors. We also find that while region – and sector –specific attributes influence aggregation error in a statistically significantly manner, their influence on the amount of error generally does not appear to be large.

Notes: The paper re–evaluates the Easterlin hypothesis in a multiregional context by conceptually and methodologically accounting for two processes of spatial interdependence in an open subnational demo–economic system: diffusion of fertility norms and values across space, and movements between labor markets. The empirical analysis estimates pooled cross–sectional, time–series models using data for 18 Italian regions from 1952 to 1995. The results suggest that accounting for spatial interdependencies is necessary to avoid model misspecifications. Moreover, the models lead to space–time landscapes of fertility elasticities that suggest, for the majority of space–time units, an inverse Easterlin effect for the diffusion component but support of the Easterlin hypothesis due to labor movements across space.