Venomotion modulates lymphatic pumping in the bat wing

In skin, it is believed that lymph must be pumped by intrinsic contraction of lymphatic muscle, since investigators have not considered that cyclical dilation of venules could compress adjacent lymphatic microvessels. Because lymphatic vessels are sensitive to stretch, we hypothesized that venomotion not only can cause extrinsic pumping of lymph in nearby lymphatic vessels, but also can stimulate intrinsic contractions. Bat wing venules have pronounced venomotion and are in close proximity to lymphatic microvessels, and can be studied noninvasively without the confounding effects of anesthesia, surgical trauma, or contrast agents. Therefore, the interaction between venules and their paired lymphatic vessels in unanesthetized Pallid bats (n = 8) was evaluated by recording the diameters of both vessels. Four sets of observations suggested that lymphatic and venous contractions were partially coupled. First, venous dilation and contraction produced a significant change in lymphatic microvascular cross-sectional area. Second, lymphatic microvascular contractions were immediately preceded by a change in venular diameter. Third, venular and lymphatic vessel contraction frequencies were positively correlated (r = 0.75). Fourth, time delays between peak venular systole and onset of lymphatic microvascular contraction were negatively correlated with venomotion magnitude (r = -0.55) and velocity (r = -0.64). In a separate experiment, inhibiting venomotion resulted in a 54.3 +/- 20.0% (n = 8) decrease in lymphatic contraction frequency. Furthermore, 85.7% (n = 56) of lymphatic vessels switch sides and lie adjacent to arterioles when venules were too small to exhibit venomotion. These results are consistent with both extrinsic pumping of lymph and stretch-induced lymphatic contraction and imply that intrinsic and extrinsic pumping can be coupled.

Openers of SKCa and IKCa channels enhance agonist-evoked endothelial nitric oxide synthesis and arteriolar vasodilation

Recent data have led us to hypothesize that selective activation of endothelial small- and/or intermediate-conductance, calcium-activated potassium channels (SK(Ca) and IK(Ca) channels, respectively) by the opener compounds NS309 and DCEBIO would augment stimulated nitric oxide (NO) synthesis and vasodilation in resistance arteries. Experimentally, ATP-evoked changes in membrane potential, cytosolic Ca(2+), and NO synthesis were recorded by patch clamp and microfluorimetry in single human endothelial cells. Agonist-evoked inhibition of myogenic tone in isolated, pressurized arterioles from rat cremaster skeletal muscle was analyzed by video microscopy. NS309 and DCEBIO enhanced ATP-evoked membrane hyperpolarization and cytosolic Ca(2+) transients, along with acute NO synthesis in isolated endothelial cells. The acetylcholine-mediated inhibition of myogenic tone (IC(50)=237 nM) was left-shifted in the presence of NS309 and DCEBIO (10, 100, and 1000 nM) to IC(50) values of 101, 78, and 43 nM; endothelial denudation inhibited this drug effect. L-NAME attenuated the acetylcholine-induced inhibition of myogenic tone but did not interfere with NS309 and DCEBIO-evoked vasodilation. Collectively, our data demonstrate that drug-induced enhancement of endothelial SK(Ca) and IK(Ca) channel activities represents a novel cellular mechanism to increase vasodilation of small-resistance arterioles, thereby highlighting these channels as potential therapeutic targets in cardiovascular disease states associated with compromised NO signaling.

Myogenic constriction and dilation of isolated lymphatic vessels

We tested the hypothesis that lymphatics would exhibit myogenic constrictions and dilations to intraluminal pressure changes. Collecting lymphatic vessels were isolated from rat mesentery, cannulated, and pressurized for in vitro study. The lymphatic diameter responses to controlled intraluminal pressure steps of different magnitudes were tested in the absence and presence of the inflammatory mediator substance P, which is known to enhance lymphatic contractility. Myogenic constriction, defined as a time-dependent decrease in end-diastolic diameter over a 1- to 2-min period following pressure elevation (after initial distension), was observed in the majority of rat mesenteric lymphatic vessels in vitro and occurred over a relatively wide pressure range (1-15 cmH2O). Myogenic dilation, a time-dependent rise in end-diastolic diameter following pressure reduction, was observed in over half the vessels equilibrated at a low baseline pressure. Myogenic constrictions were independent of the cardiac-like and time-dependent compensatory decline in end-systolic diameter and increase in amplitude observed in almost all vessels following pressure elevation. Substance P increased the percentage of vessels exhibiting myogenic constriction, the magnitude and rate of constriction, and the pressure range over which constriction occurred. Our results demonstrate that myogenic responses occur in collecting lymphatic vessels and suggest that the response may aid in preventing vessel overdistension during inflammation/edema.

Rate-sensitive contractile responses of lymphatic vessels to circumferential stretch

Phasic contractile activity in rat portal vein is more sensitive to the rate of change in length than to absolute length and this response is widely assumed to be a general characteristic of myogenic behaviour for vascular smooth muscle. Previously, we found that rat lymphatic vessels exhibit phasic contractile behaviour similar to that of portal vein. In the present study, we hypothesized that lymphatic muscle would exhibit rate-sensitive contractile responses to stretch. The hypothesis was tested on rat mesenteric lymphatics (90-220 microm, i.d.) using servo-controlled wire- and pressure-myograph systems to enable ramp increases in force or pressure at different rates. Under isometric conditions in wire-myograph preparations, both the amplitude and the frequency of phasic activity were enhanced at more optimal preloads, but superimposed upon this effect were bursts of contractions that occurred only during fast preload ramps. In such cases, the ratio of contraction frequency during the ramp to that at the subsequent plateau (at optimal preload) was > 1. Further, the frequency ratio increased as a function of the preload ramp speed, consistent with a rate-sensitive mechanism. In contrast, the amplitude ratio was < 1 and declined further with higher ramp speeds. Downward preload ramps produced corresponding rate-sensitive inhibition of contraction frequency but not amplitude. Similar findings were obtained in pressurized lymphatics in response to pressure ramps and steps. Our results suggest that lymphatics are sensitive to the rate of change in preload/pressure in a way that is different from portal vein, possibly because the pacemaker for generating electrical activity is rate sensitive but lymphatic muscle is not. The behaviour may be widely present in collecting lymphatic vessels and is probably an important mechanism for rapid adaptation of the lymphatic pump to local vascular occlusion.

Co-cultivation of 'Candidatus Liberibacter asiaticus' with Actinobacteria from Citrus with Huanglongbing

Huanglongbing (HLB), also known as citrus greening disease, is a devastating disease of citrus caused by phloem-limited bacteria that have not been grown in culture. Three species, 'Candidatus Liberibacter asiaticus', 'Ca. L. africanus', and 'Ca. L. americanus', are known. 'Ca. L. asiaticus' and its insect vector, the psyllid Diaphorina citri, have been recently introduced into Florida. We attempted to isolate 'Ca. L. asiaticus' using media formulations developed in response to the growth of another bacterium that appears to be related to the liberibacters based on 16S rRNA gene identities. Cultures were obtained that were polymerase chain reaction (PCR) positive for 'Ca. L. asiaticus'. However, transmission electron microscope examination of the culture, PCR using generic primers, and sequencing of the PCR products revealed the presence of other bacteria in the cultures. These were actinobacteria related to Propionibacterium acnes based on 16S rRNA identities. The co-cultures remained after attempts to purify the cultures by single-colony isolation, suggesting that the bacteria might be mutually beneficial to each other in culture. The co-cultures have survived more than 10 weekly passages to fresh medium. PCR using P. acnes-specific primers indicated that actinobacteria are common inhabitants of citrus and psyllids, whether or not 'Ca. L. asiaticus' is present.

Spatial dynamics of steady flames 2. Low-dimensional manifolds and the role of transport processes

The study of the spatial dynamics of steady one-dimensional H 2/O 2 flames is continued. Algorithms for generating low-dimensional manifolds for these systems are presented and used to find low-dimensional manifolds for the flames and the corresponding adiabatic, isobaric chemical-kinetic systems. It is demonstrated that these algorithms generate manifolds that are more accurate than the ILDM algorithm for two-dimensional manifolds of the flames. The manifolds are then employed to study the relationship between the manifolds of the flame and the manifolds of the chemical-kinetic system. It is shown that the one-dimensional manifolds of the flame match well with the composite manifolds of the chemical kinetics, but that for two-dimensional manifolds there are discrepancies between the flame manifolds and the chemical-kinetic manifolds.

Spatial dynamics of steady flames 1. Phase space structure and the dynamics of individual trajectories

The spatial dynamics of steady, one-dimensional premixed H 2/O 2 flames are studied. The emphasis in this Article is the geometry of the phase space of the dynamical system describing the steady flames. It is shown that steady flames are described by trajectories on the stable manifolds of saddle fixed points. The saddle fixed points correspond to equilibrium points of time-dependent chemical-kinetic systems that are adiabatic and isobaric and whose constant enthalpy matches the asymptotic enthalpy of the flames. The dimensions of the stable manifolds match the dimensions of the chemical-kinetic systems under most conditions, although the dynamics on them are different. It is further shown that the stable manifolds have low-dimensional attractive submanifolds near the saddlepoint. An algorithm for generating trajectories over the spatial domain of these flames is proposed, and it is used to study individual trajectories and trajectory ensembles, whose collective behavior suggests that there are low-dimensional submanifolds away from the saddlepoint.

Modulation of lymphatic muscle contractility by the neuropeptide substance P

Substance P (SP) is a neuropeptide associated with sensory innervation of lymphoid tissue and a suspected modulator of lymphatic function in inflammation. Only a few studies have examined the effects of SP on lymphatic contraction, and it is not clear to what extent SP acts directly on the lymphatic muscle and/or endothelium or indirectly through changes in intraluminal filling pressure secondary to increases in capillary permeability/filtration. We tested the effects of SP on the spontaneous contractions of rat isolated mesenteric lymphatic vessels under isometric and isobaric conditions, hypothesizing that low concentrations would stimulate lymphatic pumping by enhancing lymphatic muscle contraction in a manner complementary to the effect of increased preload. Under isometric conditions, SP (10 nM) dramatically enhanced lymphatic chronotropy and inotropy. Unlike guinea pig lymphatics, SP actions were not blocked by cyclooxygenase or PLA(2) inhibition. In the absence of SP, ramp increases in isometric preload resulted in x approximately 1.6 increases in contraction amplitude (Amp) and x approximately 1.7 increases in frequency (Freq). SP increased Freq by x approximately 2.4, Amp by x approximately 1.9, and the Amp-Freq product (AFP) by x approximately 3.5. Under isobaric conditions, the pressure elevation from 0.5 to 10 cmH(2)O in the absence of SP decreased Amp by x approximately 0.6 and increased Freq by x approximately 1.8. SP caused a modest increase in Amp, a robust increase in Freq at all pressures, and shifted the AFP-pressure relationship upward and leftward. Therefore, SP has substantial positive inotropic and chronotropic effects on rat lymphatic muscle, improving pump efficiency independent of the effects of preload and broadening of the working range of the lymphatic pump.

Spatial nonlocal pair correlations in a repulsive 1D Bose gas

We analytically calculate the spatial nonlocal pair correlation function for an interacting uniform 1D Bose gas at finite temperature and propose an experimental method to measure nonlocal correlations. Our results span six different physical realms, including the weakly and strongly interacting regimes. We show explicitly that the characteristic correlation lengths are given by one of four length scales: the thermal de Broglie wavelength, the mean interparticle separation, the healing length, or the phase coherence length. In all regimes, we identify the profound role of interactions and find that under certain conditions the pair correlation may develop a global maximum at a finite interparticle separation due to the competition between repulsive interactions and thermal effects.

Distinct effects on splicing of two monoclonal antibodies directed against the amino-terminal domain of galectin-3

Previous experiments had established that galectin-3 (Gal3) is a factor involved in cell-free splicing of pre-mRNA. Addition of monoclonal antibody NCL-GAL3, whose epitope maps to the NH2-terminal 14 amino acids of Gal3, to a splicing-competent nuclear extract inhibited the splicing reaction. In contrast, monoclonal antibody anti-Mac-2, whose epitope maps to residues 48-100 containing multiple repeats of a 9-residue motif PGAYPGXXX, had no effect on splicing. Consistent with the notion that this region bearing the PGAYPGXXX repeats is sequestered through interaction with the splicing machinery and is inaccessible to the anti-Mac-2 antibody, a synthetic peptide containing three perfect repeats of the sequence PGAYPGQAP (27-mer) inhibited the splicing reaction, mimicking a dominant-negative mutant. Addition of a peptide corresponding to a scrambled sequence of the same composition (27-mer-S) failed to yield the same effect. Finally, GST-hGal3(1-100), a fusion protein containing glutathione-S-transferase and a portion of the Gal3 polypeptide including the PGAYPGXXX repeats, also exhibited a dominant-negative effect on splicing.

Calcium sensitivity and cooperativity of permeabilized rat mesenteric lymphatics

Lymphatic muscle contraction is critical for the centripetal movement of lymph that regulates fluid balance, protein homeostasis, lipid absorption, and immune function. We have demonstrated that lymphatic muscle has both smooth and striated muscle contractile elements; however, the basic contractile properties of this tissue remain poorly defined. We hypothesized that contractile characteristics of lymphatic myofilaments would be different from vascular smooth muscle myofilaments. To test this hypothesis, -log[Ca(2+)] (pCa)-tension relationship was determined for alpha-toxin permeabilized mesenteric lymphatics, arteries, and veins. The Ca(2+) sensitivity (pCa(50)) of mesenteric lymphatics was significantly lower compared with arteries (6.16 +/- 0.05 vs. 6.44 +/- 0.02; P < 0.05), whereas there was no difference in pCa(50) between lymphatics and veins (6.16 +/- 0.05 vs. 6.00 +/- 0.10; not significant). The Hill coefficient for alpha-toxin-permeabilized lymphatics was not significantly different from arteries but was significantly greater than that of the veins (1.98 +/- 0.19 vs. 1.21 +/- 0.18; P < 0.05). In addition, the maximal tension and pCa(50) values were significantly greater in alpha-toxin-permeabilized lymphatics compared with beta-escin-permeabilized lymphatics (0.27 +/- 0.03 vs. 0.15 +/- 0.01 and 6.16 +/- 0.05 vs. 5.86 +/- 0.06 mN/mm, respectively; P < 0.05), whereas the Hill coefficient was significantly greater in beta-escin-permeabilized lymphatics. Western blot analyses revealed that CPI-17 levels were significantly decreased by about 50% in beta-escin-permeabilized lymphatics, compared with controls, whereas no change in the level of calmodulin was detected. Our data constitute the first description of the pCa-tension relationship in permeabilized lymphatic muscle. It suggests that differences in myofilament Ca(2+) sensitivity and cooperativity among lymphatic muscle and vascular smooth muscles contribute to the functional differences that exist between these tissues.

Versatile two-dimensional potentials for ultra-cold atoms

We propose and investigate a technique for generating smooth two-dimensional potentials for ultra-cold atoms based on the rapid scanning of a far-detuned laser beam using a two-dimensional acousto-optical modulator (AOM). We demonstrate the implementation of a feed-forward mechanism for fast and accurate control of the spatial intensity of the laser beam, resulting in improved homogeneity for the atom trap. This technique could be used to generate a smooth toroidal trap that would be useful for static and dynamic experiments on superfluidity and persistent currents with ultra-cold atoms.

Potentiation of large conductance, Ca2+-activated K+ (BK) channels by alpha5beta1 integrin activation in arteriolar smooth muscle

Injury/degradation of the extracellular matrix (ECM) is associated with vascular wall remodelling and impaired reactivity, a process in which altered ECM-integrin interactions play key roles. Previously, we found that peptides containing the RGD integrin-binding sequence produce sustained vasodilatation of rat skeletal muscle arterioles. Here, we tested the hypothesis that RGD ligands work through alpha5beta1 integrin to modulate the activity of large conductance, Ca(2+)-activated K(+) (BK) channels in arteriolar smooth muscle. K(+) currents were recorded in single arteriolar myocytes using whole-cell and single-channel patch clamp methods. Activation of alpha5beta1 integrin by an appropriate, insoluble alpha5beta1 antibody resulted in a 30-50% increase in the amplitude of iberiotoxin (IBTX)-sensitive, whole-cell K(+) current. Current potentiation occurred 1-8 min after bead-antibody application to the cell surface. Similarly, the endogenous alpha5beta1 integrin ligand fibronectin (FN) potentiated IBTX-sensitive K(+) current by 26%. Current potentiation was blocked by the c-Src inhibitor PP2 but not by PP3 (0.1-1 mum). In cell-attached patches, number of open channels x open probability (NP(o)) of a 230-250 pS K(+) channel was significantly increased after FN application locally to the external surface of cell-attached patches through the recording pipette. In excised, inside-out patches, the same method of FN application led to large, significant increases in NP(o) and caused a leftward shift in the NP(o)-voltage relationship at constant [Ca(2+)]. PP2 (but not PP3) nearly abolished the effect of FN on channel activity, suggesting that signalling between the integrin and channel involved an increase in Ca(2+)sensitivity of the channel via a membrane-delimited pathway. The effects of alpha5beta1 integrin activation on both whole-cell and single-channel BK currents could be reproduced in HEK 293 cells expressing the BK channel alpha-subunit. This is the first demonstration at the single-channel level that integrin signalling can regulate an ion channel. Our results show that alpha5beta1 integrin activation potentiates BK channel activity in vascular smooth muscle through both Ca(2+)- and c-Src-dependent mechanisms. This mechanism is likely to play a role in the arteriolar dilatation and impaired vascular reactivity associated with ECM degradation.

An automated method to control preload by compensation for stress relaxation in spontaneously contracting, isometric rat mesenteric lymphatics

OBJECTIVE

Our objective was to devise a system to automatically correct for stress relaxation of isometric rat mesenteric lymphatics (90-120 microm, ID). Stress relaxation is a particular problem in isometric studies of highly distensible vessels and is evident as a time-dependent, secondary decline in force after an abrupt length increase. Because the phasic contraction pattern of lymphatics is exquisitely sensitive to changes in preload, stress relaxation makes stable contraction patterns difficult to achieve and analyze.

METHODS

A DMT wire myograph was modified to accommodate an Inchworm piezo stack in series with a standard micrometer drive to permit automated control of vessel caliber/force. The force output of the myograph was digitized and computer algorithms were devised to servo control force by changing vessel diameter.

RESULTS

The system was tested on passive lymphatics, passive small veins, and lymphatics exhibiting spontaneous force transients. The software was designed to temporarily disable servo control during a spontaneous force transient. For both active and passive lymphatics, stable preloads were very well maintained, indicating that the system was adequately compensating for stress relaxation.

CONCLUSIONS

The method works well with isometric rat mesenteric lymphatics without disturbing spontaneous activity. It should be applicable to arterial, venous, and lymphatic vessels (80-500 microm in diameter) isolated from other tissues and species.

Length-dependence of lymphatic phasic contractile activity under isometric and isobaric conditions

OBJECTIVE

Experiments were designed to determine if the effect of preload on the spontaneous contractile activity of rat mesenteric lymphatics would be different under isometric and isobaric conditions.

METHODS

Isobaric protocols on cannulated, pressurized rat mesenteric lymphatics ( approximately 120 microm, ID) measured the effects of lumenal pressure on contraction amplitude, frequency, and rate of diameter change (dD/dt). Analogous protocols were conducted using a wire myograph to determine the effects of passive force (preload) on the characteristics of spontaneous, isometric force transients. Servo-control systems allowed responses to ramp or step increases in preload/pressure to be tested.

RESULTS

Under isobaric conditions, contraction amplitude was maximal at the lowest pressure tested (1 cm H(2)O), and progressively declined with pressure elevation to 10 cm H(2)O. Changes in dD/dt followed a similar pattern. In contrast, contraction frequency progressively increased with pressure. Under isometric conditions, the amplitude of spontaneous force transients was maximal at preloads of 0.3-0.4 mN, with dF/dt following a similar pattern; the average peak amplitude was approximately 15% of the maximal active contractile force developed during agonist stimulation. The frequency of the transients increased with preload from 0.05 to 0.3 mN, and remained constant at higher preloads. The amplitude-frequency product, an estimate of lymphatic pumping ability, reached a maximum value at 0.4 mN in isometric vessels and at 6 cm H(2)O in isobaric vessels.

CONCLUSIONS

Isometric and isobaric methods yielded qualitatively similar indices of spontaneous contractile activity. However, the ranges of amplitude and frequency changes were much greater under isobaric conditions (3- to 5-fold) than under isometric conditions (50-80%).

Low-dimensional manifolds in reaction-diffusion equations. 1. Fundamental aspects

The approach to equilibrium for systems of reaction-diffusion equations on bounded domains is studied geometrically. It is shown that equilibrium is approached via low-dimensional manifolds in the infinite-dimensional function space for these dissipative, parabolic systems. The fundamental aspects of this process are mapped out in some detail for single species cases and for two-species cases where there is an exact solution. It is shown how the manifolds reduce the dimensionality of the system from infinite dimensions to only a few dimensions.

Presentation of arthritogenic peptide to antigen-specific T cells by fibroblast-like synoviocytes

OBJECTIVE

To assess the ability of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) to function as antigen-presenting cells (APCs) for arthritogenic autoantigens found within inflamed joint tissues.

METHODS

Human class II major histocompatibility complex (MHC)-typed FLS were used as APCs for murine class II MHC-restricted CD4 T cell hybridomas. Interferon-gamma (IFNgamma)-treated, antigen-loaded FLS were cocultured with T cell hybridomas specific for immunodominant portions of human cartilage gp-39 (HC gp-39) or human type II collagen (CII). T cell hybridoma activation was measured by enzyme-linked immunosorbent assay of culture supernatants for interleukin-2. Both synthetic peptide and synovial fluid (SF) were used as sources of antigen. APC function in cocultures was inhibited by using blocking antibodies to human class II MHC, CD54, or CD58, or to murine CD4, CD11a, or CD2.

RESULTS

Human FLS could present peptides from the autoantigens HC gp-39 and human CII to antigen-specific MHC-restricted T cell hybridomas. This response required pretreatment of FLS with IFNgamma, showed MHC restriction, and was dependent on human class II MHC and murine CD4 for effective antigen presentation. Furthermore, FLS were able to extract and present antigens found within human SF to both the HC gp-39 and human CII T cell hybridomas in an IFNgamma-dependent and MHC-restricted manner.

CONCLUSION

RA FLS can function as APCs and are able to present peptides derived from autoantigens found within joint tissues to activated T cells in vitro. In the context of inflamed synovial tissues, FLS may be an important and hitherto overlooked subset of APCs that could contribute to autoreactive immune responses.

Automated measurement of diameter and contraction waves of cannulated lymphatic microvessels

BACKGROUND

Studies of lymphatic function often employ collecting lymphatic vessels that exhibit large-amplitude, spontaneous contractions. Data from such preparations have been analyzed using cardiac pump analogies that require accurate determination of vascular dimensions, including external (OD) and internal (ID) diameters. These measurements would be facilitated by an accurate automated measurement system.

METHODS AND RESULTS

A computer-based diameter tracking system was developed specifically for lymphatic vessels, with advantages over previous automated systems. The system also permits continuous diameter tracking at two axial locations, enabling the measurement and analysis of contraction wave conduction. The method was validated using spontaneously contracting segments of rat thoracic duct which sometimes exhibited conducted contraction waves. In such preparations, conduction wave velocity was modulated by the axial flow rate and could be easily measured by the tracking system.

CONCLUSIONS

The method offers improvement and increased convenience over manual diameter measurements in lymphatic vessels, with little or no sacrifice in accuracy. It should be a useful tool for general studies of collecting lymphatic function as well as for the analysis of contraction wave conduction and coordination.

Prospective evaluation of procalcitonin in sepsis in the Illawarra area of Australia: PEPSIA study

INTRODUCTION

Procalcitonin (PCT) is a precursor of the hormone calcitonin and has been proposed as a marker of infection in critically ill patients. We evaluated the role of procalcitonin in the early detection of sepsis in an Australian intensive care-high dependency unit (ICU/HDU).

METHODS

This prospective observational study enrolled 204 consecutive patients admitted to the ICU/HDU of Wollongong Hospital, NSW, over a 3-month period, October to December 2001. Of the 204, 172 (84%) were included in the final analysis. Patient demographic data, serum PCT levels and the vital signs required to score the criteria for systemic inflammatory response syndrome (SIRS) and sepsis were recorded daily until the patient left the ICU. Cultures were obtained when clinically indicated.

RESULTS

PCT measurement appears a useful screening test for sepsis with a cut-off value > 0.85 ng/dL. At levels >10 ng/dL, its diagnostic accuracy improves significantly. PCT level was able to discriminate between sepsis and nonsepsis, and between septic shock and non-septic shock. However, it failed to discriminate well between bacterial and non-bacterial SIRS with a 95% CI for area under the receiver operating characteristic curve of 0.59-0.76.

CONCLUSIONS

The use of PCT as a screening test (PCT >0.85ng/dL) in conjunction with traditional criteria is of value in the early diagnosis of bacterial sepsis in suspected cases in the ICU. PCT appears to be a reliable diagnostic test for bacterial sepsis at levels > 10 ng/dL.

Length-tension relationships of small arteries, veins, and lymphatics from the rat mesenteric microcirculation

The passive and active length-tension relationships of isolated rat mesenteric lymphatics (∼150 μm ID), and adjacent small arteries (∼240 μm) and veins (∼275 μm) were compared under isometric conditions using a wire myograph. About 60% of the lymphatic vessels developed spontaneous contractions in physiological saline solution at nominal preload. To maximally activate smooth muscle, 145 mM K++ 5 × 10−5M norepinephrine was used for arteries, and 145 mM K++ 1 × 10−6M substance P was used for lymphatics and veins. In response, arteries exhibited monotonic force development to a plateau level, whereas lymphatics and veins showed biphasic force development, consisting of a transient force peak followed by partial relaxation to a plateau over ∼5 min. The passive and the active length-tension curves were similar in shape among all three vessels. However, the maximal active tension of arteries (3.4 ± 0.42 mN/mm) was significantly greater than peak active tension (0.59 ± 0.04 mN/mm) or plateau tension (0.20 ± 0.04 mN/mm) in small veins and greater than peak active tension (0.34 ± 0.02 mN/mm) or plateau tension (0.21 ± 0.02 mN/mm) in lymphatics. Maximal active medial wall stress was similar between lymphatics and veins but was approximately fivefold higher in small arteries. For lymphatics, the pressure calculated from the optimal preload was significantly higher than that found previously in isobaric studies of isolated lymphatics, suggesting the capacity to operate at higher than normal pressures for increased responsiveness. Our results represent the first mechanical comparisons of arterial, venous, and lymphatic vessels in the same vasculature.

The overall status in rheumatoid arthritis (OSRA) measure--further evidence to support its use in clinical practice

OBJECTIVES

The overall status in rheumatoid arthritis (OSRA) instrument is a simple summary of health status, including disease activity (OSRA-A) and damage (OSRA-D) scores. Despite evidence of the validity of the OSRA, uptake has been low. This study aimed to assess the responsiveness and re-examine the validity of the OSRA using the measures from the British Rheumatoid Outcome Study Group (BROSG) randomized controlled trial of aggressive vs symptomatic treatment of rheumatoid arthritis (RA) patients.

METHODS

466 patients were recruited. Outcome measures included the OSRA, the OMERACT core set and the DAS28, and were collected at baseline and annually for the 3 yrs of the trial. X-rays of the hands and feet were taken at baseline and 3 yrs. Patients were assigned a Townsend score (a measure of social deprivation) according to area of residence. Construct validity was assessed by correlating the OSRA with a range of outcome measures, and testing for the known inequality in RA outcome between patients classified by social deprivation. Responsiveness to change was assessed against self-reported change over the first year of the trial.

RESULTS

The OSRA-A and OSRA-D measures demonstrated construct validity, performing as hypothesized. The OSRA-A was the most responsive measure in the BROSG trial in detecting patient reported improvement and deterioration. The OSRA-D demonstrated similar responsiveness to alternative measures.

CONCLUSIONS

Our results demonstrate the validity and responsiveness of the OSRA, and its potential for inclusion in clinical trials. More important, as the OSRA is quick and easily calculated, uses routinely collected information, and provides useful quantitative information about a patient's status and progress it is suitable for use in the routine clinic.

Effects of biaxial stretch on arteriolar function in vitro

Mounting evidence suggests that the normal biomechanical state of arteries may include a nearly equibiaxial intramural stress and that arteries tend to undergo rapid and dramatic remodeling when perturbed from this normal state. Technical developments since the early 1980s have enabled in vitro (acute) and ex vivo (chronic culture) study of isolated, perfused microvessels, and it is clear that these vessels share many functional similarities with arteries. To date, however, there has been no systematic study of the effects of in-plane biaxial loading on the biomechanical behavior of arterioles. Here we describe a modification to a prior in vitro arterial test system that allowed us to investigate the role of altered axial stretch on the passive, myogenic, and norepinephrine-stimulated biaxial behavior of isolated rat cremaster arterioles. We show that axial stretches from 85% to 110% of values often used in the laboratory and consistent with those normally experienced in situ induce modest changes in the measured mean circumferential and axial stress-stretch behavior and in measures of distensibility and myogenic index. Nevertheless, altered axial stretch has a dramatic effect on the biaxial state of stress, and nearly equibiaxial stresses occur at axial stretches larger than those typically used in isolated arteriole studies. This finding is consistent with estimates of material and functional behavior in arterioles and suggests that long-term ex vivo studies, wherein vessel growth and remodeling are critical, should be performed at higher axial lengths than have been used during most prior in vitro tests.

Integrin Receptor Activation Triggers Converging Regulation of Cav1.2 Calcium Channels by c-Src and Protein Kinase A Pathways

L-type, voltage-gated Ca2+ channels (CaL) play critical roles in brain and muscle cell excitability. Here we show that currents through heterologously expressed neuronal and smooth muscle CaL channel isoforms are acutely potentiated following alpha5beta1 integrin activation. Only the alpha1C pore-forming channel subunit is critical for this process. Truncation and site-directed mutagenesis strategies reveal that regulation of Cav1.2 by alpha5beta1 integrin requires phosphorylation of alpha1C C-terminal residues Ser1901 and Tyr2122. These sites are known to be phosphorylated by protein kinase A (PKA) and c-Src, respectively, and are conserved between rat neuronal (Cav1.2c) and smooth muscle (Cav1.2b) isoforms. Kinase assays are consistent with phosphorylation of these two residues by PKA and c-Src. Following alpha5beta1 integrin activation, native CaL channels in rat arteriolar smooth muscle exhibit potentiation that is completely blocked by combined PKA and Src inhibition. Our results demonstrate that integrin-ECM interactions are a common mechanism for the acute regulation of CaL channels in brain and muscle. These findings are consistent with the growing recognition of the importance of integrin-channel interactions in cellular responses to injury and the acute control of synaptic and blood vessel function.

Low-Dimensional Manifolds in Reaction−Diffusion Equations. 2. Numerical Analysis and Method Development

Calculations are undertaken to study the approach to equilibrium for systems of reaction-diffusion equations on bounded domains. It is demonstrated that a number of systems approach equilibrium along attractive low-dimensional manifolds over significant ranges of parameter space. Numerical methods for generating the manifolds are adapted from methods that were developed for systems of ordinary differential equations. The truncation of the infinite spectrum of the partial differential equations makes it necessary to devise a new version of one of these methods, the well-known algorithm of Maas and Pope.

First Report of Leifsonia xyli subsp. xyli, Causal Agent of Ratoon Stunting of Sugarcane, in Jamaica

To our knowledge, this is the first report that Leifsonia xyli subsp. xyli, previously named Clavibacter xyli subsp. xyli (2), has been detected and identified in sugarcane in Jamaica. Although ratoon stunting (also known as ratoon stunting disease or RSD) has been reported in Jamaica since 1961, presence of the pathogen had never been confirmed in symptomatic tissues. A major industry-wide survey conducted in 1987 using the fluorescent antibody staining technique failed to detect positives in any of the 61 fields sampled in Jamaica. A new survey was conducted in 2004 on eight estates and the Sugar Industry Research Institute (SIRI) in Jamaica. Six arbitrarily selected stalks were sampled from each of 64 fields representing 25 different sugarcane cultivars. A 1-cm diameter core was extracted from the center of the bottom part of the stalk and used to detect the pathogen by tissue blot immunoassay (TBIA) (3). L. xyli subsp. xyli was detected in 26 of 384 samples (7%). At least one positive sample was found in 10 fields and seven cultivars and in one case (sugarcane cv. D14146 at the St Thomas Sugar Estate), all six stalks sampled in a field were positive. The highest number of infected fields (6 of 10) occurred at Worthy Park where cane yield in 2004 was 86.54 tons per ha compared with an average of 68.04 tons per ha for major estates in Jamaica (1). This latter result would indicate that where good quality agronomic practices are maintained, the effect of ratoon stunting might not be substantial or that sugarcane cultivars grown at this location were resistant to ratoon stunting. Pathogen identification was confirmed using nested polymerase chain reaction (PCR) with three samples from a TBIA-positive field of cv. D14146. Primary primers were RSD 33 (CTGGCACCCTGTGTTGTTTTC) and RSD 297 (TTCGGTTCTCATCTCAGCGTC) and secondary, nested primers were RST60 (TCAACGCAGAGATTGTCCAG) and RST59 (CGTCTTGAAGACACAGCGATGAG). The thermocycler parameters were denaturization at 94°C for 4 min, 31 cycles at 94°C for 30 s, 55°C for 30 s, 65°C for 1 min, and final extension at 65°C for 3 min. The nested-PCR product (approximately 230 bp) of each sample was cloned and sequenced. It showed 99 to 100% identity with the 16S-23S intergenic spacer region of L. xyli subsp. xyli, thus confirming occurrence of ratoon stunting in Jamaica. Since this study, the SIRI has installed a hot-water treatment plant and will heat-treat cuttings before planting the nurseries with new sugarcane clones selected for release to growers. The SIRI will also conduct screening for ratoon stunting resistance to ensure that susceptible clones are not released to the industry. Meanwhile, the SIRI will do a more intense survey so that a more comprehensive picture may be obtained of the presence of ratoon stunting in Jamaica. References: (1) Anonymous. Annual Report of the Sugar Industry Research Institute, Jamaica, 2004. (2) L. I. Evtushenko et al. Int. J. Syst. Evol. Microbiol. 50:371, 2000. (3) N. A. Harrison and M. J. Davis. Phytopathology 78:722, 1988.

Arteriolar myogenic signalling mechanisms: Implications for local vascular function

Arterioles typically exist in a state of partial constriction that is related to the level of intraluminal pressure. This vasomotor response is a function of the vascular smooth muscle and occurs independently of neurohumoral and endothelial input. The physiological relevance of myogenic constriction relates to the setting of peripheral resistance, provision of a level of tone that vasodilators can access, and a contribution to control of capillary pressure. Despite its importance in the regulation of microvascular haemodynamics the exact cellular mechanisms linking intraluminal pressure to myogenic constriction remain uncertain. Studies using isolated, cannulated arteriole techniques, and freshly dispersed smooth muscle cells, have shown that increased intraluminal pressure/cell stretch leads to smooth muscle cell membrane depolarisation, the opening of L-type voltage-gated Ca2+ channels (VGCC), Ca2+-dependent activation of myosin light chain kinase and actomyosin-based contraction. Questions remain as to how the initial stimulus is detected and how these events lead to membrane depolarisation. A candidate pathway for the mechanosensory events involves the link between extracellular matrix proteins, cell surface integrins and the subsequent activation of intracellular signalling events. Membrane depolarisation may occur through the involvement of various ion channels, including non-selective cation channels (possibly themselves mechanosensitive) that predominantly pass Na+ from the extracellular space. Evidence suggests that this may involve TRP-like channels, possibly TRPM4 or TRPC6 isoforms that are modulated by diacylglycerol and protein kinase C. In addition, the exact roles played by various Ca2+ pools, including those occurring in spatially-restricted domains, and Ca2+ sensitisation, remain uncertain despite the clearly important role of VGCC. Similarly, while a change in intraluminal pressure is associated with the generation of a number of second messengers and the activation of various protein kinases, their roles in myogenic contraction versus long-term adaptive responses, such as tissue remodelling, are still to be defined.

Sodium azide dilates coronary arterioles via activation of inward rectifier K+ channels and Na+-K+-ATPase

Sodium azide (NaN(3)), a potent vasodilator, causes severe hypotension on accidental exposure. Although NaN(3) has been shown to increase coronary blood flow, the direct effect of NaN(3) on coronary resistance vessels and the mechanism of the NaN(3)-induced response remain to be established. To address these issues without confounding influences from systemic parameters, subepicardial coronary arterioles were isolated from porcine hearts for in vitro study. Arterioles developed basal tone at 60 cmH(2)O intraluminal pressure and dilated acutely, in a concentration-dependent manner, to NaN(3) (0.1 microM to 50 microM). The NaN(3) response was not altered by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester or endothelial removal. Neither inhibition of phosphoinositol 3-kinase and tyrosine kinases nor blockade of ATP-sensitive, Ca(2+)-activated, and voltage-dependent K(+) channels affected NaN(3)-induced dilation. However, the vasomotor action of NaN(3) was significantly attenuated in a similar manner by the inward rectifier K(+) (K(IR)) channel inhibitor Ba(2+), the Na(+)-K(+) ATPase inhibitor ouabain, or the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ). Ba(2+), in combination with either ouabain or ODQ, nearly abolished the vasodilatory response. However, there was no additive inhibition by combining ouabain and ODQ. The NaN(3)-mediated vasodilation was also attenuated by morin, an inhibitor of phosphatidylinositolphosphate (PIP) kinase, which can regulate K(IR) channel activity. With the use of whole cell patch-clamp methods, NaN(3) acutely enhanced Ba(2+)-sensitive K(IR) current in isolated coronary arteriolar smooth muscle cells. Collectively, this study demonstrates that NaN(3), at clinically toxic concentrations, dilates coronary resistance vessels via activation of both K(IR) channels and guanylyl cyclase/Na(+)-K(+)-ATPase in the vascular smooth muscle. The K(IR) channels appear to be modulated by PIP kinase.

An improved, computer-based method to automatically track internal and external diameter of isolated microvessels

OBJECTIVE

To develop an automated diameter tracking method suitable for studies of isolated, perfused microvessels (< 100 micro m internal diameter (ID)).

METHODS

A diameter tracking method was implemented in conjunction with a standard PC workstation and video card. Within a user-defined window, the algorithm combined thresholding and iterative regression procedures to detect the average outer diameter (OD) of a vertically oriented microvessel. After an initial ID measurement by the user, the program continuously calculated ID based on the assumption of an incompressible vessel wall.

RESULTS

The program, Vessel Track, was tested against a manual video caliper and two analog video dimension analyzers. Vessel Track was capable of accurately following arteriolar dimensions during extreme vasodilation and vasoconstriction. It provided more accurate, lower-noise recordings than either of the video dimension analyzers, particularly after strong vasoconstriction during which lumenal folds developed. Vessel Track also was capable of accurately measuring large-amplitude vasomotion in isolated lymphatic vessels at a tracking frequency of ~ 30 times/s.

CONCLUSIONS

Vessel Track should be useful for automated diameter tracking of isolated arterioles, venules, and lymphatics. With suitable preparations, it provides fast, stable measurements of ID in microvessels even with irregular lumen geometry.

The transcriptional landscape of the mammalian genome

This study describes comprehensive polling of transcription start and termination sites and analysis of previously unidentified full-length complementary DNAs derived from the mouse genome. We identify the 5' and 3' boundaries of 181,047 transcripts with extensive variation in transcripts arising from alternative promoter usage, splicing, and polyadenylation. There are 16,247 new mouse protein-coding transcripts, including 5154 encoding previously unidentified proteins. Genomic mapping of the transcriptome reveals transcriptional forests, with overlapping transcription on both strands, separated by deserts in which few transcripts are observed. The data provide a comprehensive platform for the comparative analysis of mammalian transcriptional regulation in differentiation and development.