bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfection of CYP4A1 cDNA decreases diameter and increases responsiveness of gracilis muscle arterioles to constrictor stimuli
Authors: Zhang Fan , Wang Mong-Heng , Wang Ji-Shi , Zand Barbara , Gopal V. Raj , Falck John R. , Laniado-Schwartzman Michal , Nasjletti Alberto
Published: May 2004

Cytochrome P-450–4A1 (CYP4A1) is an ω-hydroxylase that catalyzes the metabolism of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE). The goal of this study was to determine the vasomotor consequences of vascular overexpression of CYP4A1. Isolated rat gracilis muscle arterioles transfected ex vivo with an expression plasmid containing CYP4A1 cDNA expressed more CYP4A protein than vessels transfected with the control plasmid. In arterioles pressurized to 80 mmHg, the internal diameter of vessels transfected with CYP4A1 cDNA (55 ± 3 μm) was surpassed ( P < 0.05) by that of vessels transfected with control plasmid (97 ± 4 μm). Treatment with a CYP4A inhibitor ( N-methylsulfonyl-12,12-dibromododec-11-enamide; DDMS) or with an antagonist of 20-HETE actions [20-hydroxyeicosa-6( Z),15( Z)-dienoic acid; 20-HEDE] elicited robust dilation of arterioles transfected with CYP4A1 cDNA, whereas the treatment had little or no effect in vessels transfected with control plasmid. Examination of the intraluminal pressure-internal diameter relationship revealed that pressure increments over the range of 40–100 mmHg elicited a more intense ( P < 0.05) myogenic constrictor response in arterioles transfected with CYP4A1 cDNA than in those with control plasmid. Arterioles transfected with CYP4A1 cDNA also displayed enhanced sensitivity to the constrictor action of phenylephrine. Treatment with DDMS or 20-HEDE greatly attenuated the constrictor responsiveness to both constrictor stimuli in vessels overexpressing CYP4A1, whereas the treatment had much less effect in control vessels. These data suggest that CYP4A1 overexpression promotes constriction of gracilis muscle arterioles by intensifying the responsiveness of vascular smooth muscle to constrictor stimuli. This effect of CYP4A1 overexpression appears to be mediated by a CYP4A1 product.
Adenovirus-mediated transfer of the 1-cys peroxiredoxin gene to mouse lung protects against hyperoxic injury
Authors: Wang Yan , Manevich Yefim , Feinstein Sheldon I. , Fisher Aron B.
Published: May 2004

1-Cys peroxiredoxin (1-cysPrx) is a novel antioxidant enzyme that has been shown to reduce a broad spectrum of peroxides including phospholipid hydroperoxides. We tested the hypothesis that adenovirus-mediated transfer of the 1-cysPrx gene can protect lungs of mice from oxidant injury. Mice infected with AdLacZ/AdNull were used as a control (AdCon). X-galactosidase staining revealed widespread expression of the LacZ gene in airways and lung alveoli. Compared with AdCon, 1-cysPrx expression was increased about twofold at 3 days after adenovirus infection. Mice with increased Prx expression showed less loss of body weight and longer survival during exposure to 100% O2 or to 85% O2 for 4 days followed by 100% O2. At 72 h of 100% O2 exposure, AdPrx infection protected mouse lungs from injury as indicated by less pleural effusion, lower lung wet/dry weight, less protein and fewer nucleated cells in bronchoalveolar lavage fluid, and lower content of thiobarbituric acid-reactive substances and protein carbonyls in lung homogenate. These findings show that increased expression of 1-cysPrx through adenovirus-mediated gene transfer protects mouse lungs from hyperoxic injury and delays death.
Regulation of LPS-mediated inflammation in vivo and in vitro by the thiol antioxidant Nacystelyn
Authors: Antonicelli Frank , Brown David , Parmentier Maryline , Drost Ellen M. , Hirani Nik , Rahman Irfan , Donaldson Ken , MacNee William
Published: May 2004

Increased levels of proinflammatory cytokines are present in bronchoalveolar lavage fluid in various lung diseases. Redox-sensitive transcription factors such as NF-κB regulate gene transcription for these cytokines. We therefore studied the effect of a new thiol antioxidant compound, Nacystelyn (NAL), on IL-8 regulation in a human macrophage-derived cell line (THP-1). LPS (10 μg/ml) increased IL-8 release compared with control levels. This LPS activation was inhibited by coincubation with NAL (1 and 5 mM). Pretreatment with cycloheximide or okadaic acid, protein synthesis, and serine/threonine phosphatase inhibitors, respectively, did not modify inhibition of IL-8 release caused by NAL. NF-κB and C/EBP DNA binding were increased after LPS treatment compared with control, an effect inhibited by cotreatment with NAL. Activator protein (AP)-1 DNA binding was unaffected. The enhanced neutrophil chemotaxis produced by conditioned media from LPS-treated cells was inhibited when cells were cotreated with NAL. The selectivity of NAL inhibition upon IL-8 expression was studied. LPS-treated THP-1 cells also had higher levels of TNF-α, transforming growth factor (TGF)-β1 and -3, MIP-1α and -β, and RANTES gene expression. However, only LPS-induced IL-8 and TGF-β1 expressions were inhibited by NAL. An anti-inflammatory effect of NAL was confirmed in vivo as shown by a reduction in LPS-induced neutrophil recruitment to the lungs following instillation of NAL into the lungs. Our studies demonstrate that NAL has anti-inflammatory properties in vitro and in vivo, may therefore have a therapeutic role in lung inflammation, and has the advantage over other antioxidant agents in that it may be administrated by inhalation.
Mice lacking melanin-concentrating hormone receptor 1 demonstrate increased heart rate associated with altered autonomic activity
Authors: Åstrand Annika , Bohlooly-Y Mohammad , Larsdotter Sara , Mahlapuu Margit , Andersén Harriet , Tornell Jan , Ohlsson Claes , Snaith Mike , Morgan David G. A.
Published: May 2004

Melanin-concentrating hormone (MCH) plays an important role in energy balance. The current studies were carried out on a new line of mice lacking the rodent MCH receptor (MCHR1−/− mice). These mice confirmed the previously reported lean phenotype characterized by increased energy expenditure and modestly increased caloric intake. Because MCH is expressed in the lateral hypothalamic area, which also has an important role in the regulation of the autonomic nervous system, heart rate and blood pressure were measured by a telemetric method to investigate whether the increased energy expenditure in these mice might be due to altered autonomic nervous system activity. Male MCHR1−/− mice demonstrated a significantly increased heart rate [24-h period: wild type 495 ± 4 vs. MCHR1−/− 561 ± 8 beats/min ( P < 0.001); dark phase: wild type 506 ± 8 vs. MCHR1−/− 582 ± 9 beats/min ( P < 0.001); light phase: wild type 484 ± 13 vs. MCHR1−/− 539 ± 9 beats/min ( P < 0.005)] with no significant difference in mean arterial pressure [wild type 110 ± 0.3 vs. MCHR1−/− 113 ± 0.4 mmHg ( P > 0.05)]. Locomotor activity and core body temperature were higher in the MCHR1−/− mice during the dark phase only and thus temporally dissociated from heart rate differences. On fasting, wild-type animals rapidly downregulated body temperature and heart rate. MCHR1−/− mice displayed a distinct delay in the onset of this downregulation. To investigate the mechanism underlying these differences, autonomic blockade experiments were carried out. Administration of the adrenergic antagonist metoprolol completely reversed the tachycardia seen in MCHR1−/− mice, suggesting an increased sympathetic tone.
Water deprivation enhances the inhibitory effect of natriuretic peptides on cAMP synthesis in rat renal glomeruli
Authors: Woodard Geoffrey E. , Li Xiaohong , Rosado Juan A.
Published: May 2004

This study investigates the effect of water deprivation on the expression of atrial natiruretic peptide (ANP)1-28binding sites in rat kidney. Water deprivation increased the Bmaxof glomerular binding sites for ANP1-28and C-type natriuretic peptide (CNP)1-22without modifying their affinity, an effect that was prevented in the presence of C-atrial natriuretic factor (C-ANF), suggesting that natriuretic peptide receptor-C (NPR-C) binding sites might be enhanced. Our results indicate that ANP1-28, CNP1-22, and C-ANF inhibit cAMP synthesis directly stimulated by forskolin or by the physiological agonists histamine and 5-hydroxytryptamine. The inhibitory effect was found to be significantly greater in water-deprived rats than in controls. Our observations suggest that this effect must be attributed to the 67-kDa NPR-C-like protein, because the 67- and 77-kDa NPR-C-like proteins show high and low affinities for CNP1-22, respectively, and the enhanced inhibitory effect of CNP on cAMP generation in water-deprived rats was detected at subnanomolar concentrations. In addition, using affinity cross-linking studies we have observed that water deprivation increases the expression of the 67-kDa NPR-C-like protein, and HS-142, which binds to NPR-A and the 77-kDa NPR-C-like but not the 67-kDa protein, reduced ligand internalization without affecting cAMP inhibition by ANP1-28. Finally, we have found that ligand binding to the 67-kDa NPR-C-like protein is reduced by GTPγS, suggesting that this receptor is associated with a G protein in renal glomeruli. The enhanced inhibitory role of natriuretic peptides on cAMP synthesis induced by water deprivation may influence glomerular function in the rat kidney.
Functional map of TEA transport activity in isolated rabbit renal proximal tubules
Authors: Wright Stephen H. , Evans Kristen K. , Zhang Xiaohong , Cherrington Nathan J. , Sitar Daniel S. , Dantzler William H.
Published: May 2004

The organic cation (OC) transporters OCT1 and OCT2 are suspected of mediating substrate entry from the blood into proximal tubule cells as the first step in renal secretion of OCs. We examined the contribution of each process in different rabbit renal proximal tubule (RPT) segments, taking advantage of the fact that rabbit orthologs of OCT1 and OCT2 can be distinguished by the high affinity of the former for tyramine (TYR) and of the latter for cimetidine (CIM). We verified that TEA uptake, for which both transporters share a similar affinity, is relatively constant in all three segments (apparent inhibitory constant of 33, 74, and 30 μM and maximal rate of mediated TEA uptake of 0.8, 1.0, and 1.2 pmol·mm−1·min−1in S1, S2, and S3, respectively). In the S1 segment, TYR was a more effective inhibitor of TEA uptake than CIM (IC50values of 39 and 328 μM, respectively), implicating OCT1 as the predominant pathway for TEA transport. The opposite profiles were noted in the S2 segment (IC50values of 302 and 20 μM for TYR and CIM, respectively) and S3 segment (IC50values of 2,900 and 54 μM for TYR and CIM, respectively), suggesting that OCT2 is the predominant TEA transporter in the later portion of RPT. TEA sufficient to saturate OCT1 and OCT2 blocked only 37% of mediated amantadine transport in the S2 segment, confirming the functional presence of at least one additional OC transporter (perhaps OCT3). These data indicate that renal OC transport involves the concerted activity of a suite of transport processes.
Megalin mediates renal uptake of heavy metal metallothionein complexes
Authors: Klassen R. Bryan , Crenshaw Kimberly , Kozyraki Renata , Verroust Pierre J. , Tio Laura , Atrian Sílvia , Allen Patricia L. , Hammond Timothy G.
Published: May 2004

Although several heavy metal toxins are delivered to the kidney on the carrier protein metallothionein (MT), uncertainty as to how MT enters proximal tubular cells limits treatment strategies. Prompted by reports that MT-I interferes with renal uptake of the megalin ligand β2-microglobulin in conscious rats, we tested the hypothesis that megalin binds MT and mediates its uptake. Three lines of evidence suggest that binding of MT to megalin is critical in renal proximal tubular uptake of MT-bound heavy metals. First, MT binds megalin, but not cubilin, in direct surface plasmon resonance studies. Binding of MT occurs at a single site with a Kd∼10−4and, as with other megalin ligands, depends on divalent cations. Second, antisera and various known megalin ligands inhibit the uptake of fluorescently labeled MT in model cell systems. Anti-megalin antisera, but not control sera, displace >90% bound MT from rat renal brush-border membranes. Megalin ligands including β2-microglobulin and also recombinant MT fragments compete for uptake by megalin-expressing rat yolk sac BN-16 cells. Third, megalin and fluorescently labeled MT colocalize in BN-16 cells, as shown by fluorescent microscopic techniques. Follow-up surface plasmon resonance and flow cytometry studies using overlapping MT peptides and recombinant MT fragments identify the hinge SCKKSCC region of MT as a critical site for megalin binding. These findings suggest that disruption of the SCKKSCC motif can inhibit proximal tubular MT uptake and thereby eliminate much of the renal accumulation and toxicity of heavy metals such as cadmium, gold, copper, and cisplatinum.
Probing the human vestibular system with galvanic stimulation
Authors: Fitzpatrick Richard C. , Day Brian L.
Published: May 2004

Galvanic vestibular stimulation (GVS) is a simple, safe, and specific way to elicit vestibular reflexes. Yet, despite a long history, it has only recently found popularity as a research tool and is rarely used clinically. The obstacle to advancing and exploiting GVS is that we cannot interpret the evoked responses with certainty because we do not understand how the stimulus acts as an input to the system. This paper examines the electrophysiology and anatomy of the vestibular organs and the effects of GVS on human balance control and develops a model that explains the observed balance responses. These responses are large and highly organized over all body segments and adapt to postural and balance requirements. To achieve this, neurons in the vestibular nuclei receive convergent signals from all vestibular receptors and somatosensory and cortical inputs. GVS sway responses are affected by other sources of information about balance but can appear as the sum of otolithic and semicircular canal responses. Electrophysiological studies showing similar activation of primary afferents from the otolith organs and canals and their convergence in the vestibular nuclei support this. On the basis of the morphology of the cristae and the alignment of the semicircular canals in the skull, rotational vectors calculated for every mode of GVS agree with the observed sway. However, vector summation of signals from all utricular afferents does not explain the observed sway. Thus we propose the hypothesis that the otolithic component of the balance response originates from only the pars medialis of the utricular macula.
Bionic epidural stimulation restores arterial pressure regulation during orthostasis
Authors: Yanagiya Yusuke , Sato Takayuki , Kawada Toru , Inagaki Masashi , Tatewaki Teiji , Zheng Can , Kamiya Atsunori , Takaki Hiroshi , Sugimachi Masaru , Sunagawa Kenji
Published: May 2004

A bionic baroreflex system (BBS) is a computer-assisted intelligent feedback system to control arterial pressure (AP) for the treatment of baroreflex failure. To apply this system clinically, an appropriate efferent neural (sympathetic vasomotor) interface has to be explored. We examined whether the spinal cord is a candidate site for such interface. In six anesthetized and baroreflex-deafferentiated cats, a multielectrode catheter was inserted into the epidural space to deliver epidural spinal cord stimulation (ESCS). Stepwise changes in ESCS rate revealed a linear correlation between ESCS rate and AP for ESCS rates of 2 pulses/s and above ( r2, 0.876–0.979; slope, 14.3 ± 5.8 mmHg·pulses−1·s; pressure axis intercept, 35.7 ± 25.9 mmHg). Random changes in ESCS rate with a white noise sequence revealed dynamic transfer function of peripheral effectors. The transfer function resembled a second-order, low-pass filter with a lag time (gain, 16.7 ± 8.3 mmHg·pulses−1·s; natural frequency, 0.022 ± 0.007 Hz; damping coefficient, 2.40 ± 1.07; lag time, 1.06 ± 0.41 s). On the basis of the transfer function, we designed an artificial vasomotor center to attenuate hypotension. We evaluated the performance of the BBS against hypotension induced by 60° head-up tilt. In the cats with baroreflex failure, head-up tilt dropped AP by 37 ± 5 mmHg in 5 s and 59 ± 11 mmHg in 30 s. BBS with optimized feedback parameters attenuated hypotension to 21 ± 2 mmHg in 5 s ( P < 0.05) and 8 ± 4 mmHg in 30 s ( P < 0.05). These results indicate that ESCS-mediated BBS prevents orthostatic hypotension. Because epidural stimulation is a clinically feasible procedure, this BBS can be applied clinically to combat hypotension associated with various pathophysiologies.
Downhill running: a model of exercise hyperemia in the rat spinotrapezius muscle
Authors: Kano Yutaka , Padilla Danielle , Hageman K. Sue , Poole David C. , Musch Timothy I.
Published: May 2004

To utilize the rat spinotrapezius muscle as a model to investigate the microcirculatory consequences of exercise training, it is necessary to design an exercise protocol that recruits this muscle. There is evidence that the spinotrapezius is derecruited during standard treadmill exercise protocols performed on the uphill treadmill (i.e., 6° incline). This investigation tested the hypothesis that downhill running would effectively recruit the spinotrapezius muscle as assessed by the presence of an exercise hyperemia response. We used radioactive 15-μm microspheres to determine blood flows in the spinotrapezius and selected hindlimb muscles of female Sprague-Dawley rats at rest and during downhill (i.e., −14° incline; 331 ± 5 g body wt, n = 7) and level (i.e., 0° incline; 320 ± 11 g body wt, n = 5) running at 30 m/min. Both level and downhill exercise increased blood flow to all hindlimb muscles ( P < 0.01). However, in marked contrast to the absence of a hyperemic response to level running, blood flow to the spinotrapezius muscle increased from 26 ± 6 ml·min−1·100 g−1 at rest to 69 ± 8 ml·min−1·100 g−1 during downhill running ( P < 0.01). These findings indicate that downhill running represents an exercise paradigm that recruits the spinotrapezius muscle and thereby constitutes a tenable physiological model for investigating the adaptations induced by exercise training (i.e., the mechanisms of altered microcirculatory control by transmission light microscopy).
Natural killer cell lytic activity and CD56dimand CD56brightcell distributions during and after intensive training
Authors: Suzui Masatoshi , Kawai Takeshi , Kimura Hiroko , Takeda Kazuyoshi , Yagita Hideo , Okumura Ko , Shek Pang N. , Shephard Roy J.
Published: May 2004

The purpose of this study was to examine the impact of intensive training for competitive sports on natural killer (NK) cell lytic activity and subset distribution. Eight female college-level volleyball players undertook 1 mo of heavy preseason training. Volleyball drills were performed 5 h/day, 6 days/wk. Morning resting blood samples were collected before training (Pre), on the 10th day of training (During), 1 day before the end of training (End), and 1 wk after intensive training had ceased (Post). CD3-CD16brightCD56dim(CD56dimNK), CD3-CD16dim/-CD56brightNK (CD56brightNK), and CD3+CD16-CD56dim(CD56dimT) cells in peripheral blood were determined by flow cytometry. The circulating count of CD56dimNK cells (the predominant population, with a high cytotoxicity) did not change, nor did the counts for other leukocyte subsets. However, counts for CD56brightNK and CD56dimT cells (subsets with a lower cytotoxicity) increased significantly ( P < 0.01) in response to the heavy training. Overall NK cell cytotoxicity decreased from Pre to End ( P = 0.002), with a return to initial values at Post. Lytic units per NK cell followed a similar pattern ( P = 0.008). Circulating levels of interleukin-6, interferon-γ, and tumor necrosis factor-α remained unchanged. These results suggest that heavy training can decrease total NK cell cytotoxicity as well as lytic units per NK cell. Such effects may reflect in part an increase in the proportion of circulating NK cells with a low cytotoxicity.
A genetic polymorphism of the α2-adrenergic receptor increases autonomic responses to stress
Authors: Finley J. Clayton , O'Leary Michael , Wester Derin , MacKenzie Steven , Shepard Neil , Farrow Stephen , Lockette Warren
Published: May 2004

We hypothesized that individual differences in autonomic responses to psychological, physiological, or environmental stresses are inherited, and exaggerated autonomic responsiveness may represent an intermediate phenotype that can contribute to the development of essential hypertension in humans over time. α2-Adrenergic receptors (α2-ARs), encoded by a gene on chromosome 10, are found in the central nervous system and also mediate release of norepinephrine from the presynaptic nerve terminals of the peripheral sympathetic nervous system and the exocytosis of epinephrine from the adrenal medulla. We postulated that, because this receptor mediates central and peripheral autonomic responsiveness to stress, genetic mutations in the gene encoding this receptor may explain contrasting activity of the autonomic nervous system among individuals. The restriction enzyme Dra I identifies a polymorphic site in the 3′-transcribed, but not translated, portion of the gene encoding the chromosome 10 α2-AR. Southern blotting of genomic DNA with a cDNA probe after restriction enzyme digestion results in fragments that are either 6.7 kb or 6.3 kb in size. Transfection studies of these two genotypes resulted in contrasting expression of a reporter gene, and it is suggested from these findings that this is a functional polymorphism. In a study of 194 healthy subjects, we measured autonomic responses to provocative motion, a fall in blood pressure induced by decreasing venous return and cardiac output, or exercise. Specifically, we measured reactions to 1) Coriolis stress, a strong stimulus that induces motion sickness in man; 2) heart rate responses to the fall in blood pressure induced by the application of graded lower body negative pressure; and 3) exercise-induced sweat secretion. In all of these paradigms of stress, subjective and objective evidence of increased autonomic responsiveness was found in those individuals harboring the 6.3-kb allele. Specifically, volunteers with the 6.3-kb allele had greater signs and symptoms of motion sickness mediated by the autonomic nervous system after off-axis rotation at increasing velocity (number of head movements a subject could complete during rotation before emesis ± SE: 295 ± 18 vs. 365 ± 11; P = 0.001). They also had greater increases in heart rate in responses to the lower body negative pressure-induced fall in blood pressure (increase in heart rate ± SE: 3.0 ± 0.4 vs. 1.8 ± 0.3; P = 0.012), and the 6.3-kb group had higher sweat sodium concentrations during exercise (mean sweat sodium concentration in meq/l over 30 min of exercise ± SE: 43.2 ± 7.1 vs. 27.6 ± 3.4; P < 0.05). This single-nucleotide polymorphism may contribute to contrasting individual differences in autonomic responsiveness among healthy individuals.
Fractal branching pattern of the monopodial canine airway
Authors: Wang Ping M. , Kraman Steve S.
Published: May 2004

Unlike the human lung, monopodial canine airway branching follows an irregular dichotomized pattern with fractal features. We studied three canine airway molds and found a self-similarity feature from macro- to microscopic scales, which formed a fractal set up to seven scales in the airways. At each fractal scale, lateral branches evenly lined up along an approximately straight main trunk to form three to four two-dimensional structures, and each lateral branch was the monopodial main trunk of the next fractal scale. We defined this pattern as the fractal main lateral-branching pattern, which exhibited similar structures from macro- to microscopic scales, including lobes, sublobes, sub-sublobes, etc. We speculate that it, rather than a mother-daughter pattern, could better describe the actual asymmetrical architecture of the monopodial canine airway.
Gas exchange during separate diaphragm and intercostal muscle breathing
Authors: DiMarco A. F. , Connors A. F. , Kowalski K. E.
Published: May 2004

In patients with diaphragm paralysis, ventilation to the basal lung zones is reduced, whereas in patients with paralysis of the rib cage muscles, ventilation to the upper lung zones in reduced. Inspiration produced by either rib cage muscle or diaphragm contraction alone, therefore, may result in mismatching of ventilation and perfusion and in gas-exchange impairment. To test this hypothesis, we assessed gas exchange in 11 anesthetized dogs during ventilation produced by either diaphragm or intercostal muscle contraction alone. Diaphragm activation was achieved by phrenic nerve stimulation. Intercostal muscle activation was accomplished by electrical stimulation by using electrodes positioned epidurally at the T2 spinal cord level. Stimulation parameters were adjusted to provide a constant tidal volume and inspiratory flow rate. During diaphragm (D) and intercostal muscle breathing (IC), mean arterial Po2 was 97.1 ± 2.1 and 88.1 ± 2.7 Torr, respectively ( P < 0.01). Arterial Pco2 was lower during D than during IC (32.6 ± 1.4 and 36.6 ± 1.8 Torr, respectively; P < 0.05). During IC, oxygen consumption was also higher than that during D (0.13 ± 0.01 and 0.09 ± 0.01 l/min, respectively; P < 0.05). The alveolar-arterial oxygen difference was 11.3 ± 1.9 and 7.7 ± 1.0 Torr ( P < 0.01) during IC and D, respectively. These results indicate that diaphragm breathing is significantly more efficient than intercostal muscle breathing. However, despite marked differences in the pattern of inspiratory muscle contraction, the distribution of ventilation remains well matched to pulmonary perfusion resulting in preservation of normal gas exchange.
Ventrolateral medullary respiratory network participation in the expiration reflex in the cat
Authors: Baekey David M. , Morris Kendall F. , Nuding Sarah C. , Segers Lauren S. , Lindsey Bruce G. , Shannon Roger
Published: May 2004

The expiration reflex is a distinct airway defensive response characterized by a brief, intense expiratory effort and coordinated adduction and abduction of the laryngeal folds. This study addressed the hypothesis that the ventrolateral medullary respiratory network participates in the reflex. Extracellular neuron activity was recorded with microelectrode arrays in decerebrated, neuromuscularblocked, ventilated cats. In 32 recordings (17 cats), 232 neurons were monitored in the rostral (including Bötzinger and pre-Bötzinger complexes) and caudal ventral respiratory group. Neurons were classified by firing pattern, evaluated for spinal projections, functional associations with recurrent laryngeal and lumbar nerves, and firing rate changes during brief, large increases in lumbar motor nerve discharge (fictive expiration reflex, FER) elicited during mechanical stimulation of the vocal folds. Two hundred eight neurons were respiratory modulated, and 24 were nonrespiratory; 104 of the respiratory and 6 of the nonrespiratory-modulated neurons had altered peak firing rates during the FER. Increased firing rates of bulbospinal neurons and expiratory laryngeal premotor and motoneurons during the expiratory burst of FER were accompanied by changes in the firing patterns of putative propriobulbar neurons proposed to participate in the eupneic respiratory network. The results support the hypothesis that elements of the rostral and caudal ventral respiratory groups participate in generating and shaping the motor output of the FER. A model is proposed for the participation of the respiratory network in the expiration reflex.
Exercise training changes autonomic cardiovascular balance in mice
Authors: De Angelis K. , Wichi R. B. , Jesus W. R. A. , Moreira E. D. , Morris M. , Krieger E. M. , Irigoyen M. C.
Published: May 2004

Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary ( n = 8) and trained mice ( n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 ± 9 vs. 612 ± 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 ± 2 vs. 108 ± 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 ± 0.97 vs. 1.6 ± 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 ± 12 vs. 40 ± 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 ± 11 vs. 97 ± 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.
The allergic mouse model of asthma: normal smooth muscle in an abnormal lung?
Authors: Wagers Scott , Lundblad Lennart K. A. , Ekman Mari , Irvin Charles G. , Bates Jason H. T.
Published: May 2004

Mice with allergically inflamed airways are widely used as animal models of asthma, but their relevance for human asthma is not understood. We, therefore, examined the time course of changes in respiratory input impedance during induced bronchoconstriction in BALB/c mice sensitized and challenged with ovalbumin. Our results indicate that bronchoconstriction in mice is accompanied by complete closure of substantial regions of the lung and that closure increases markedly when the lungs are allergically inflamed. With the aid of an anatomically accurate computational model of the mouse lung, we show that the hyperresponsiveness of mice with allergically inflamed airways can be explained entirely by a thickening of the airway mucosa and an increased propensity of the airways to close, without the involvement of any increase in the degree of airway smooth muscle shortening. This has implications for the pathophysiology of asthma and suggests that at least some types of asthma may benefit from therapies aimed at manipulating surface tension at the air-liquid interface in the lungs.
Effect of prenatal nicotine exposure on biphasic hypoxic ventilatory response and protein kinase C expression in caudal brain stem of developing rats
Authors: Simakajornboon Narong , Vlasic Vukmir , Li Hong , Sawnani Hemant
Published: May 2004

Current evidence suggests that maternal smoking is associated with decreased respiratory drive and blunted hypoxic ventilatory response (HVR) in the newborn. The effect of prenatal nicotine exposure on overall changes in HVR has been studied; however, there is limited data on the effect of nicotine exposure on each component of biphasic HVR. To examine this issue, 5-day timed-pregnant Sprague-Dawley rats underwent surgical implantation of an osmotic minipump containing either normal saline (Con) or a solution of nicotine tartrate (Nic) to continuously deliver free nicotine at 6 mg·kg of maternal weight-1·day-1. Rat pups at postnatal days 5, 10, 15, and 20 underwent hypoxic challenges with 10% O2for 20 min using whole body plethysmography. At postnatal day 5, Nic was associated with attenuation of peak HVR; peak minute ventilaton increased 44.0 ± 6.8% (SE) from baseline in Nic pups, whereas that of Con pups increased 62.9 ± 5.1% ( P < 0.05). Nic pups also had a reduction in the magnitude of ventilatory roll-off; minute ventilation at 15 min decreased 7.3 ± 7.1% in Nic pups compared with 27.3 ± 4.0% in Con pups ( P < 0.05). No significant difference in HVR was noted at postnatal days 10, 15, and 20. Hypercapnic response was similar at all ages. We further investigated the effect of prenatal nicotine exposure on PKC expression in the caudal brain stem (CB) of developing rats. At postnatal day 5, Nic was associated with increased expression of PKC-β and PKC-δ in CB, whereas other PKC isoforms were not affected. It is concluded that prenatal nicotine exposure is associated with modulation of biphasic HVR and a selective increase in the expression of PKC-β and PKC-δ within the CB of developing rats.
Hand function: peripheral and central constraints on performance
Authors: Schieber Marc H. , Santello Marco
Published: May 2004

The hand is one of the most fascinating and sophisticated biological motor systems. The complex biomechanical and neural architecture of the hand poses challenging questions for understanding the control strategies that underlie the coordination of finger movements and forces required for a wide variety of behavioral tasks, ranging from multidigit grasping to the individuated movements of single digits. Hence, a number of experimental approaches, from studies of finger movement kinematics to the recording of electromyographic and cortical activities, have been used to extend our knowledge of neural control of the hand. Experimental evidence indicates that the simultaneous motion and force of the fingers are characterized by coordination patterns that reduce the number of independent degrees of freedom to be controlled. Peripheral and central constraints in the neuromuscular apparatus have been identified that may in part underlie these coordination patterns, simplifying the control of multi-digit grasping while placing certain limitations on individuation of finger movements. We review this evidence, with a particular emphasis on how these constraints extend through the neuromuscular system from the behavioral aspects of finger movements and forces to the control of the hand from the motor cortex.
Relationship between blood velocity and conduit artery diameter and the effects of smoking on vascular responsiveness
Authors: Stoner Lee , Sabatier Manning , Edge Kristy , McCully Kevin
Published: May 2004

Transient changes in arterial diameter in response to transient ischemia-induced changes in arterial blood velocity have been used as an index of vascular health. The purpose of this study was to determine the relationship between blood velocity and diameter in the brachial artery by different methods of increasing blood velocity. Acute cigarette smoking was used with otherwise healthy young occasional smokers to determine the influence of endothelial-nitric oxide pathways on the arterial diameter-blood velocity relationship. Nine nonsmokers and 12 occasional smokers (<1 pack/wk) were tested. Blood flow to the forearm was manipulated to indirectly investigate the relationship between blood velocity and diameter in the brachial artery. Blood flow to forearm was manipulated through the use of 1) 5-min ischemia; 2) handgrip exercise; 3) indirect local heating; and 4) 5-min ischemia plus indirect local heating. A strong relationship was observed between blood velocity and diameter independent of the method used to increase blood velocity ( R2 = 0.89). The mean slope of the velocity-diameter relationship was not different between nonsmokers and occasional smokers who abstained from smoking at least 2 days. Acute smoking did not alter the slope of the velocity-diameter relationship although the mean intercept was decreased as a result of consistent vasoconstriction (7–10%). The mechanisms by which smoking impairs vascular health are largely unknown. These findings differ from previous smoking studies that used chronic and/or heavier smokers. The velocity-diameter relationship appears independent of the method for increasing velocity. Acute smoking in occasional smokers results in vasoconstriction without altering vascular responsiveness. The velocity-diameter relationship may be a useful measure of the progression of vascular disease.
Hypercholesterolemia inhibits L-type calcium current in coronary macro-, not microcirculation
Authors: Bowles D. K. , Heaps C. L. , Turk J. R. , Maddali K. K. , Price E. M.
Published: May 2004

Hypercholesterolemia (HC) is a mary risk factor for the development of coronary heart disease. Coronary ion regulation, especially calcium, is thought to be important in coronary heart disease development; however, the influence of high dietary fat and cholesterol on coronary arterial smooth muscle (CASM) ion channels is unknown. The purpose of this study was to determine the effect of diet-induced HC on CASM voltage-gated calcium current ( ICa). Male miniature swine were fed a high-fat, high-cholesterol diet (40% kcal fat, 2% wt cholesterol) for 20–24 wk, resulting in elevated serum total and low-density lipoprotein cholesterol. Histochemistry indicated early atherosclerosis in large coronary arteries. CASM were isolated from the right coronary artery (>1.0 mm ID), small arteries (∼200 μm), and large arterioles (∼100 μm). ICawas determined by whole cell voltage clamp. L-type ICawas reduced ∼30% by HC compared with controls in the right coronary artery (-5.29 ± 0.42 vs. -7.59 ± 0.41 pA/pF) but not the microcirculation (small artery, -8.39 ± 0.80 vs. -10.13 ± 0.60; arterioles, -10.78 ± 0.93 vs. -11.31 ± 0.95 pA/pF). Voltage-dependent activation was unaffected by HC in both the macro- and microcirculation. L-type voltage-gated calcium channel (Cav1.2) mRNA and membrane protein levels were unaffected by HC. Inhibition of ICaby HC was reversed in vitro by the cholesterol scavenger methyl-β-cyclodextrin and mimicked in control CASM by incubation with the cholesterol donor cholesterol:methyl-β-cyclodextrin. These data indicate that CASM L-type ICais decreased in large coronary arteries in early stages of atherosclerosis, whereas ICain the microcirculation is unaffected. The inhibition of calcium channel activity in CASM of large coronary arteries is likely due to increases in membrane free cholesterol.
Exercise training improves aortic endothelium-dependent vasorelaxation and determinants of nitric oxide bioavailability in spontaneously hypertensive rats
Authors: Graham Drew A. , Rush James W. E.
Published: May 2004

The present study examined in vitro vasomotor function and expression of enzymes controlling nitric oxide (NO) bioavailability in thoracic aorta of adult male normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) that either remained sedentary (Sed) or performed 6 wk of moderate aerobic exercise training (Ex). Training efficacy was confirmed by elevated maximal activities of both citrate synthase ( P = 0.0024) and β-hydroxyacyl-CoA dehydrogenase ( P = 0.0073) in the white gastrocnemius skeletal muscle of Ex vs. Sed rats. Systolic blood pressure was elevated in SHR vs. WKY ( P < 0.0001) but was not affected by Ex. Despite enhanced endothelium-dependent relaxation to 10-8M ACh in SHR vs. WKY ( P = 0.0061), maximal endothelium-dependent relaxation to 10-4M ACh was blunted in Sed SHR (48 ± 12%) vs. Sed WKY (84 ± 6%, P = 0.0067). Maximal endothelium-dependent relaxation to 10-4M ACh was completely restored in Ex SHR (93 ± 9%) vs. Sed SHR ( P = 0.0011). Nω-nitro-l-arginine abolished endothelium-dependent relaxation in all groups ( P ≤ 0.0001) and caused equal vasocontraction to maximal ACh in Sed SHR and Ex SHR. Endothelium-independent relaxation to sodium nitroprusside was similar in all groups. Protein levels of endothelial NO synthase were higher in SHR vs. WKY ( P = 0.0157) and in Ex vs. Sed ( P = 0.0536). Protein levels of the prooxidant NAD(P)H oxidase subunit, gp91phox, were higher in SHR vs. WKY ( P < 0.0001) and were diminished in Ex vs. Sed ( P = 0.0557). Levels of the antioxidant SOD-1, -2, and catalase enzymes were lower in SHR vs. WKY (all P ≤ 0.0005) but were not altered by Ex. Thus elevated gp91phox-dependent oxidative stress and reduced antioxidant capacity likely contributed to impaired endothelium-dependent vasorelaxation in Sed SHR. Furthermore, reduced gp91phox-dependent oxidative stress and enhanced endothelial NO synthase-derived NO likely contributed to restored endothelium-dependent vasorelaxation in Ex SHR.
Adrenalectomy in mice does not prevent loss of intestinal lymphocytes after exercise
Authors: Hoffman-Goetz L. , Quadrilatero J. , Boudreau J. , Guan J.
Published: May 2004

Exhaustive exercise is associated with an increase in circulating glucocorticoids (GCs), lymphocyte apoptosis, and a reduction in intestinal lymphocyte number. The present study examined the role of GCs on the numerical changes seen in intestinal lymphocytes after exercise. Female C57BL/6 mice were bilaterally adrenalectomized (ADX; n = 18) or given sham surgery (Sham; n = 18) and assigned to one of three exercise conditions: treadmill running (28 m/min, 90 min, 2° slope) and killed immediately or after 24 h recovery, or not exercised and killed immediately after 90-min exposure to the treadmill environment. Lymphocytes were isolated from the intestines with CD45+ cells collected by positive selection using magnetic bead separation columns, and lymphocyte subpopulations were analyzed by flow cytometry for CD45+, CD3αβ+, CD3γδ+, CD8β+, CD8α+, CD4+, and NK+ phenotypic markers. ADX mice had significantly more intestinal CD45+ leukocytes ( P < 0.05) and CD3αβ+ ( P < 0.05), CD3γδ+ ( P < 0.01), CD8α+ ( P < 0.001), and NK+ ( P < 0.05) intestinal lymphocytes than Sham mice. There was a significant effect of exercise condition on total intestinal CD45+ leukocytes ( P < 0.01) and CD3αβ+ ( P < 0.05), CD8α+ ( P < 0.001), and CD4+ ( P < 0.05) intestinal lymphocytes, with fewer cells at 24 h postexercise compared with the other treatment conditions. There were no surgical × exercise interaction effects on the CD3 and CD8 phenotype numbers. Plasma corticosterone was virtually nil in ADX mice regardless of exercise condition but was significantly elevated in Sham mice immediately postexercise ( P < 0.001). The data indicate that ADX does not prevent the loss of lymphocytes from the intestinal mucosa 24 h after strenuous exercise and GCs are not directly causal in the leukopenia of exercise.
Neural Sensitivity to Periodicity in the Inferior Colliculus: Evidence for the Role of Cochlear Distortions
Authors: McAlpine David
Published: May 2004

Responses of low characteristic-frequency (CF) neurons in the inferior colliculus were obtained to amplitude-modulated (AM) high-frequency tones in which the modulation rate was equal to the neuron's CF. Despite all spectral components lying outside the pure tone–evoked response areas, discharge rates were modulated by the AM signals. Introducing a low-frequency tone (CF − 1 Hz) to the same ear as the AM tones produced a 1-Hz beat in the neural response. Introducing a tone (CF − 1 Hz) to the opposite ear to the AM tone also produced a beat in the neural response, with the beat at the period of the interaural phase difference between the CF − 1 Hz tone in one ear, and the AM rate in the other ear. The monaural and interaural interactions of the AM signals with introduced pure tones suggest that AM tones generate combination tones, (inter-modulation distortion) on the basilar membrane. These interact with low-frequency tones presented to the same ear to produce monaural beats on the basilar membrane, modulating the responses of inferior colliculus (IC) neurons on the 1-Hz period of the monaural beats or interacting binaurally with neural input generated in response to stimulation of the opposite ear. The auditory midbrain appears to show a robust representation of cochlear distortions generated by amplitude-modulated sounds.
Contrast-Dependent Spatial Summation in the Lateral Geniculate Nucleus and Retina of the Cat
Authors: Nolt M. J. , Kumbhani R. D. , Palmer L. A.
Published: May 2004

Based on extracellular recordings from 69 lateral geniculate nucleus (LGN) cells in the anesthetized cat, we found spatial summation within their receptive fields to be dependent on the contrast of the stimuli presented. By fitting the summation curves to a difference of Gaussians model, we attributed this contrast-dependent effect to an actual change in the size of the center mechanism. Analogous changes in spatial frequency tuning were also observed, specifically increased peaks and cut-off frequencies with contrast. These effects were seen across the populations of both X and Y cell types. In a few cases, LGN cells were recorded simultaneously with one of their retinal ganglion cell (RGC) inputs (S-potentials). In every case, the RGCs exhibited similar contrast-dependent effects in the space and spatial-frequency domains. We propose that this contrast dependency in the retinal ganglion cells results directly from a reduction in the size of the center mechanism due to an increase in contrast. We also propose that these properties first arise in the retina and are transmitted passively through the LGN to visual cortex.
Firing Properties and Connectivity of Neurons in the Rat Lateral Central Nucleus of the Amygdala
Authors: Lopez De Armentia Mikel , Sah Pankaj
Published: May 2004

Using whole cell recordings from acute slices of the rat amygdala, we have examined the physiological properties of and synaptic connectivity to neurons in the lateral sector of the central amygdala (CeA). Based on their response to depolarizing current injections, CeA neurons could be divided into three types. Adapting neurons fired action potentials at the start of the current injections at high frequency and then showed complete spike-frequency adaptation with only six to seven action potentials evoked with suprathreshold current injections. Late-firing neurons fired action potentials with a prolonged delay at threshold but then discharged continuously with larger current injections. Repetitive firers discharged at the start of the current injection at threshold and then discharged continuously with larger current injections. All three cells showed prolonged afterhyperpolarizations (AHPs) that followed trains of action potentials. The AHP was longer lasting with a larger slow component in adapting neurons. The AHP in all cell types contained a fast component that was inhibited by the SK channel blocker UCL1848. The slow component, not blocked by UCL1848, was blocked by isoprenaline and was significantly larger in adapting neurons. Blockade of SK channels increased the discharge frequency in late firers and regular-spiking neurons but had no effect on adapting neurons. Blockade of the slow AHP with isoprenaline had no effect on any cell type. All cells received a mixed glutamatergic and GABAergic input from a medial pathway. Electrical stimulation of the lateral (LA) and basolateral (BLA) nuclei evoked a large monosynaptic glutamatergic response followed by a disynaptic inhibitory postsynaptic potential. Activation of neurons in the LA and BLA by puffer application of glutamate evoked a small monosynaptic response in 13 of 55 CeA neurons. Local application of glutamate to the CeL evoked a GABAergic response in all cells. These results show that at least three types of neurons are present in the CeA that can be distinguished on their firing properties. The firing frequency of two of these cell types is determined by activation of SK channels. Cells receive a small input from the LA and BLA but may receive inputs that course through these nuclei en route to the CeA.