bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of depletion of interstitial hyaluronan on hydraulic conductance in rabbit knee synovium
Authors: Coleman P. J. , Scott D. , Abiona A. , Ashhurst D. E. , Mason R. M. , Levick J. R. 
Published: September 2004

The hydraulic resistance of the synovial lining to fluid outflow from a joint cavity (Q̇s) is important for the retention of intra‐articular lubricant. The resistance has been attributed in part to extracellular glycosaminoglycans, including hyaluronan and chondroitin sulphates. Increased permeability in joints infused with testicular hyaluronidase, which digests both chondroitin sulphates and hyaluronan, supports this view. In this study the importance of interstitial hyaluronanper sewas assessed using leech andStreptomyceshyaluronidases, which degrade only hyaluronan.Ringer solution was infused into the knee joint cavity of anaesthetized rabbits for 30 min, with or without hyaluronidase, after which intra‐articular pressure (Pj) was raised and the relation between pressure and outflow determined.Treatment withStreptomyces, leech or testicular hyaluronidases increased the fluid escape rates by similar factors, namely 4‐ to 6‐fold. AfterStreptomyceshyaluronidase treatment the slope dQ̇s/dPj, which at low pressures represents synovial hydraulic conductance, increased from a control of 0.90 ± 0.20 μl min−1cmH2O−1(mean ± s.e.m.,n= 6) to 4.52 ± 0.70 μl min−1cmH2O−1. The slope dQ̇s/dPjincreased to a similar level after testicular hyaluronidase, namely to 4.14 ± 1.06 μl min−1cmH2O−1(control, 0.54 ± 0.24 μl min−1cmH2O−1).Streptomycesand leech hyaluronidases were as effective as testicular hyaluronidase (no statistically significant differences) despite differences in substrate specificity.It was shown using histochemical and immunohistochemical techniques that hyaluronan was removed from the synovium by leech,Streptomycesand testicular hyaluronidases. The binding of antibodies 2‐B‐6 and 3‐B‐3 showed that the core proteins of the chondroitin sulphate proteoglycans remained intact after treatment with hyaluronidases, and the binding of 5‐D‐4 showed that keratan sulphate was unaffected. An azocasein digestion assay confirmed that the hyaluronidase preparations had no significant proteolytic activity.The effect of the hyaluronidases was four times greater than predicted from the low concentration of interstitial hyaluronan and its resistivity. Factors that might amplify the effect of hyaluronan depletion include the matrix‐organizing role of hyaluronan, and/or non‐uniformity of hyaluronan distribution. It is concluded that interstitial hyaluronan makes a major contribution to synovial hydraulic resistance, but the mechanisms are as yet poorly understood.
Activation of multiple intracellular transduction signals by vasopressin in vasopressin‐sensitive neurones of the rat supraoptic nucleus
Authors: Sabatier Nancy , Richard Philippe , Dayanithi Govindan 
Published: September 2004

The intracellular mechanisms activated by the binding of vasopressin to its receptor(s) and which result in the increase of [Ca2+]i were investigated in freshly dissociated supraoptic nucleus neurones. Various pharmacological agents were used to investigate the possible involvement of phospholipase C (PLC) and adenylate cyclase (AC) intracellular pathways in the transduction of the vasopressin action.
Both the PLC inhibitor U‐73122 and the protein kinase C (PKC) inhibitor calphostin C, reduced the [Ca2+]i rise elicited by vasopressin. The cAMP analogue, 8‐Br‐cAMP produced an increase in [Ca2+]i and IBMX, a phosphodiesterase inhibitor, potentiated the response to vasopressin.
After pre‐incubation with the AC inhibitor SQ‐22536, 7 out of 18 vasopressin‐sensitive neurones showed no inhibition of the vasopressin response, while the response to vasopressin was reduced by greater than 35 % in each of the other 11 neurones.
The activation of protein kinase A (PKA) with Sp‐cAMPS caused an increase in [Ca2+]i which was additive to the vasopressin‐elicited [Ca2+]i increase. After incubation with the PKA inhibitors Rp‐cAMPS or H‐89, the [Ca2+]i responses triggered by Sp‐cAMPS and vasopressin were, respectively, abolished and greatly reduced.
A combined administration of SQ‐22536 (AC inhibitor) followed by U‐73122 (PLC inhibitor), or U‐73122 followed by H‐89 (PKA inhibitor), virtually abolished the response to vasopressin.
In vasopressin‐responsive neurones, the pituitary adenylate cyclase‐activating polypeptide (PACAP) induced a [Ca2+]i increase similar to the response to vasopressin and in both cases the increase was inhibited to the same extent by a combination of U‐73122 and Rp‐cAMPS.
In conclusion, we suggest that the autoregulation exerted specifically by vasopressin on vasopressin‐sensitive neurones involves the activation of both PLC‐ and AC‐linked pathways.
The influence of perchlorate ions on complex charging transients in amphibian striated muscle
Authors: Huang Christopher L.‐H. 
Published: September 2004

The effects of perchlorate ions on intramembrane charge movements were examined under different conditions of ryanodine receptor (RyR) modification in intact voltage‐clamped amphibian skeletal muscle fibres studied in the gluconate‐containing solutions previously reported to emphasize the features of qγ at the expense of those of the qβ charge.
The introduction of graded increases in perchlorate concentration to the experimental solutions selectively shifted the threshold of appearance of the qγ‘hump’ currents to more negative test potentials at which they actually appeared in the absence of prior qβ transients at perchlorate concentrations of 4.0‐8.0 mM. Such findings suggested that the delayed (qγ) transitions can take place independently of any previous exponential (qβ) decay.
These kinetic effects were accompanied by hyperpolarizing shifts in the transition potentials (V*) of the steady‐state voltage dependences of either the overall or the isolated qγ charge. These shifts were graded with concentration and reached their maximum effects at 4.0‐8.0 mM perchlorate. However, both the total charge (Qmax) and the steepness factor (k) remained conserved at values consistent with a system that included significant contributions from the steeply voltage‐sensitive qγ component (overall charge: Qmax≈ 19‐21 nC μF−1, k≈ 7‐9 mV; qγ component alone: Qmax≈ 10‐12 nC μF−1, k≈ 4‐6 mV). This contrasts with earlier reports on the effects of perchlorate in fibres that were studied in sulphate‐ or methanesulphonate‐containing extracellular solutions.
Perchlorate (8.0 mM) restored the ‘hump’ waveform associated with qγ charge movements that had previously been obliterated by the prior application of fully effective (0.1 mM) concentrations of either ryanodine or daunorubicin.
Perchlorate similarly reversed the positive shift in the transition potential of the qγ component that was brought about by such RyR modification (from V*≈ ‐40 mV back to V*≈ ‐60 mV). In contrast, the values of either Qmax (overall charge, 19‐21 nC μF−1; qγ component, 10‐13 nC μF−1) or k (overall charge, 7‐9 mV; qγ component, 4‐6 mV) remained conserved through all these experimental manoeuvres.
The inclusion of perchlorate also reversed the action of 2 mM tetracaine and restored delayed qγ transients to an extent that was graded with concentration (0.5‐8.0 mM perchlorate). There was an accompanying recovery of the steeply voltage‐dependent steady‐state (qγ) component consistent with a competitive interaction between these agents upon the qγ intramembrane charge.
The present findings suggest that perchlorate exerts a specific action upon the qγ charge in independent transitions that are driven by the tubular membrane field. Its interactions with the known RyR inhibitors that nevertheless conserve both the charge and its voltage sensitivity suggest a primary action upon the RyR that in turn exerts reciprocal actions upon the voltage sensor.
The effects of flow on the transport of potassium ions through the walls of single perfused frog mesenteric capillaries
Authors: Kajimura M. , Head S. D. , Michel C. C. 
Published: September 2004

We have investigated the effects of varying flow velocity upon permeability to potassium ions (PK) of single perfused mesenteric microvessels in pithed frogs.
P
K was estimated using a development of the single bolus microperfusion technique at chosen flow velocities (U) in the range of 150–7000 μm s−1.
In thirty‐seven out of forty‐three vessels, there was a strong positive correlation between PK and U. Average values (median) for PK (μm s−1) were related to U (μm s−1) by the expression: PK= 0.0043U+ 4.05 (n= 43).
The correlation between PK and U was independent of microvascular pressure (and hence fluid filtration) over the range of 5–70 cmH2O.
The correlation between PK and U was independent of the potassium concentration in the bolus over the range of 2–40 mmol l−1 and of the direction of the potassium flux through the capillary walls.
GABAA receptor‐mediated currents in interneurons and pyramidal cells of rat visual cortex
Authors: Xiang Zixiu , Huguenard John R. , Prince David A. 
Published: September 2004

We compared γ‐aminobutyric acid (GABA)‐mediated responses of identified pyramidal cells and fast spiking interneurons in layer V of visual cortical slices from young rats (P11‐14).
The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was similar in pyramidal cells and interneurons (1.7 vs. 1.9 Hz). For events with 10‐90 % rise times less than 0.9 ms, no significant differences were found in mean amplitude (61 vs. 65 pA), mean rise time (0.58 vs. 0.61 ms), or the first time constant of decay (τ1, 6.4 vs. 6.5 ms) between pyramidal cells and interneurons. The second decay time constant (τ2) was significantly longer in interneurons than in pyramidal cells (49 vs. 22 ms). The difference in sIPSC decay kinetics between two cell types also existed in adult rats (P36‐42), suggesting the kinetic difference is not due to differential development of GABAA receptors in these cell types.
The decay kinetics of monosynaptic evoked IPSCs were also longer in interneurons. As in the case of sIPSCs, the difference was accounted for by the second decay time constant. τ1 and τ2 were, respectively, 13 and 64 ms for interneurons and 12 and 47 ms for pyramidal cells.
Cell‐attached patch recordings revealed that the mean open time for single Cl− channels in response to 2 μM GABA was significantly longer in interneurons than pyramidal cells (5.0 vs. 2.8 ms). The chord conductance of these channels in interneurons (12 pS) was significantly smaller than in pyramidal cells (15 pS). Single channel currents reversed polarity when the pipette potential was approximately ‐10 mV for both cell types.
These results show that there is a functional diversity of GABAA receptors in electrophysiologically and morphologically identified cortical pyramidal cells and interneurons. This diversity might derive from the different molecular composition of the receptors in these two cell types.
Sensitivity to 5‐hydroxytryptamine in different afferent subpopulations within mesenteric nerves supplying the rat jejunum
Authors: Hillsley K. , Grundy D. 
Published: September 2004

This study was performed to elucidate the type of afferents that mediate the multiple actions of 5‐hydroxytryptamine (5‐HT) on mesenteric nerve discharge. Electrophysiological recordings were made from mesenteric afferents innervating the mid‐jejunum of the urethane‐anaesthetized rat. The discharge of single nerves within the whole nerve recording was monitored using waveform discrimination software.
Afferents responded to 5‐HT in one of two ways: a short latency, transient excitation mediated by 5‐HT3 receptors, or a delayed onset, more prolonged effect that was 5‐HT2A receptor mediated. Afferents showing the 5‐HT3‐mediated response did not respond to luminal distension but were sensitive to intraluminal hydrochloric acid (150 mM) in twenty‐eight of twenty‐nine experiments. In eight experiments, the 5‐HT3‐mediated response was reversibly abolished by a 2 min exposure to intraluminal application of local anaesthetic (2 % Xylocaine).
Mechanosensitive afferents which responded to distension (< 10 cmH2O) did not show a 5‐HT3‐mediated response (P= 0.92, n= 14), and maintained this mechanosensitivity after luminal anaesthesia. Mechanosensitive afferents did show a secondary response to 5‐HT that was significantly attenuated by atropine (100‐200 μg kg−1), whereas hexamethonium (8 mg kg−1) had no effect.
In animals whose vagal afferent contribution to their mesenteric nerves had been eliminated by chronic truncal vagotomy, the 5‐HT3‐mediated response was absent in thirty‐six of thirty‐six nerve bundles. In contrast, mechanosensitivity to distension and the secondary response to 5‐HT could still be evoked.
These results suggest that 5‐HT stimulates mesenteric afferents by a direct action on 5‐HT3 receptors that are present on vagal mucosal afferent terminals. The mucosal afferent response to luminal acid, however, was unaffected by treatment with granisetron (0.5 mg kg−1) indicating that endogenous 5‐HT from enterochromaffin cells is not essential for transduction of this luminal signal. In contrast, mechanosensitivity in non‐vagal afferents was modulated by 5‐HT following an intestinal motor response which was influenced by cholinergic tone.
Cyclic GMP‐dependent but G‐kinase‐independent inhibition of Ca2+‐dependent Cl− currents by NO donors in cat tracheal smooth muscle
Authors: Waniishi Yoshiki , Inoue Ryuji , Morita Hiromitsu , Teramoto Noriyoshi , Abe Kihachiro , Ito Yushi 
Published: September 2004

The effects of NO donors on Ca2+‐dependent Cl− currents (ICl(Ca)) were investigated in freshly isolated cat tracheal myocytes using the whole‐cell patch clamp technique.
With nystatin‐perforated whole‐cell recording, carbachol (CCh, ≥ 1 μm) induced a transient inward current (ICCh) with a reversal potential of about ‐20 mV. Activation of ICCh probably occurred through the M3 muscarinic receptor, since nanomolar concentrations of 4‐diphenylacetoxy‐N‐methylpiperidine methobromide (4‐DAMP) greatly inhibited this current, while 11‐(2‐(diethylamino)methyl)‐1‐piperidinylacetyl)‐5,11‐dihydro‐6H‐pyrido (2,3β) (1,4)benzodiazepine‐6‐one (AF‐DX 116) or pirenzepine at concentrations of up to 1 μm were almost ineffective.
Chloride channel/transporter blockers such as DIDS (100 μm), anthracene‐9‐carboxylic acid (9‐AC, 100 μm) and niflumic acid (100 μm) greatly inhibited ICCh, but cation channel blockers, such as nifedipine (10 μm), Zn2+ (500 μm) or Gd3+ (500 μm), were without effect.
Activation of ICCh was strongly attenuated by pretreatment with ryanodine (4 μm) plus caffeine (10 mM). Addition of neomycin (1 mM) into the bath or inclusion of heparin (3 mg ml−1) in the pipette abolished a substantial part of ICCh. These results suggest that ICCh is ICl(Ca), which is activated by inositol 1,4,5‐trisphosphate (IP3)‐mediated Ca2+ release.
The nitric oxide donor S‐nitroso‐N‐acetyl penicillamine (SNAP) reduced the amplitude of ICCh dose dependently (IC50, ≈10 μm). Similar inhibition was also exerted by other types of NO donor such as glyceryl trinitrate (GTN) and (±)‐E‐methyl‐2‐(E‐hydroxyimitol)‐5‐nitro‐6‐methoxy‐3‐hexeneamide (NO‐R).
SNAP‐induced ICCh inhibition was effectively antagonized by Methylene Blue (1‐100 nM), and mimicked by dibutyryl cGMP (db‐cGMP) (0.5‐1 mM), whereas two structurally distinct types of cGMP‐dependent (G)‐kinase inhibitor, N‐(2‐aminoethyl)‐5‐isoquinilinesulphonamide (H‐8, 2.5 μm) and KT5823 (1 μm), failed to counteract the inhibitory effects of SNAP or db‐cGMP. Another G‐kinase‐specific inhibitor Rp‐8‐(para‐chlorophenylthio)guanosine‐3′,5′‐cyclic monophosphorothioate (Rp‐8‐pCPT‐cGMPS; 1 μm) itself caused a marked reduction in ICCh.
SNAP (100 μm) or db‐cGMP (100 μm) exhibited no inhibitory actions, when caffeine (10 mM) or photolytically released IP3 were used instead of CCh to activate the inward current.
These results suggest that inhibition of ICCh by NO donors involves a cGMP‐dependent but G‐kinase‐independent mechanism, which may operate at a site(s) between the muscarinic (M3) and IP3 receptors.
Ca2+‐dependent inactivation of large conductance Ca2+‐activated K+ (BK) channels in rat hippocampal neurones produced by pore block from an associated particle
Authors: Hicks Gareth A. , Marrion Neil V. 
Published: September 2004

Recordings of the activity of the large conductance Ca2+‐activated K+ (BK) channel from over 90 % of inside‐out patches excised from acutely dissociated hippocampal CA1 neurones revealed an inactivation process dependent upon the presence of at least 1 μM intracellular Ca2+. Inactivation was characterized by a sudden switch from sustained high open probability (Po) long open time behaviour to extremely low Po, short open time channel activity. The low Po state (mean Po, 0.001) consisted of very short openings (time constant (τ), ≈0.14 ms) and rare longer duration openings (τ, ≈3.0 ms).
Channel inactivation occurred with a highly variable time course being observed either prior to or immediately upon patch excision, or after up to 2 min of inside‐out recording. Inactivation persisted whilst recording conditions were constant.
Inactivation was reversed by membrane hyperpolarization, the rate of recovery increasing with further hyperpolarization and higher extracellular K+. Inactivation was also reversed when the intracellular Ca2+ concentration was lowered to 100 nM and was permanently removed by application of trypsin to the inner patch surface. In addition, inactivation was perturbed by application of either tetraethylammonium ions or the Shaker (Sh)B peptide to the inner membrane face.
During inactivation, channel Po was greater at hyperpolarized rather than depolarized potentials, which was partly the result of a greater number of longer duration openings. Depolarizing voltage steps (‐40 to +40 mV) applied during longer duration openings produced only short duration events at the depolarized potential, yielding a transient ensemble average current with a rapid decay (τ, ≈3.8 ms).
These data suggest that hippocampal BK channels exhibit a Ca2+‐dependent inactivation that is proposed to result from block of the channel by an associated particle. The findings that inactivation was removed by trypsin and prolonged by decreasing extracellular potassium suggest that the blocking particle may act at the intracellular side of the channel.
Role of 5‐HT3 receptors in activation of abdominal sympathetic C fibre afferents during ischaemia in cats
Authors: Fu Liang‐Wu , Longhurst John C. 
Published: September 2004

Activation of abdominal sympathetic afferents during ischaemia reflexly excites the cardiovascular system. We have shown previously that exogenous 5‐hydroxytryptamine (5‐HT, i.e. serotonin) stimulates abdominal sympathetic afferent nerve endings, and recently have documented increased concentrations of 5‐HT in intestinal lymph and portal venous plasma during brief abdominal ischaemia. The present investigation evaluated the role of endogenously produced 5‐HT in activation of ischaemically sensitive abdominal sympathetic afferents.
Nerve activity of single‐unit C fibre afferents innervating duodenum, mesentery, pancreas, portal hepatis, bile duct, gall bladder and jejunum was recorded from the right thoracic sympathetic chain of anaesthetized cats. Ischaemically sensitive C fibre afferents were identified according to their response to 5‐10 min of abdominal ischaemia.
Intra‐arterial injection of 5‐HT (20 μg kg−1) increased discharge activity of twelve afferents from 0.23 ± 0.05 to 0.96 ± 0.09 impulses s−1 after an onset latency of 5.7 ± 1.4 s. Also, 2‐methylserotonin (100 μg kg−1, i.a.), a 5‐HT3 receptor agonist, stimulated eleven of twelve afferents to significantly increase their discharge activity from 0.25 ± 0.05 to 0.90 ± 0.10 impulses s−1 after a latency of 3.3 ± 0.4 s. Furthermore, intravenous injection of tropisetron (200 μg kg−1), a 5‐HT3 receptor antagonist, significantly attenuated the increase in activity of twelve other C fibre afferents during 10 min of abdominal ischaemia from 1.62 ± 0.18 to 0.94 ± 0.22 impulses s−1, and eliminated the response of eleven other afferents to 5‐HT.
Both the 5‐HT2 receptor agonist, α‐methylserotonin (100 μg kg−1, i.a.), and the 5‐HT1 receptor agonist, 5‐carboxamidotryptamine (100 μg kg−1, i.a.), did not alter the impulse activity of these twelve afferents (0.29 ± 0.05 to 0.31 ± 0.06, and 0.26 ± 0.06 to 0.29 ± 0.06 impulses s−1, respectively).
Treatment with indomethacin (5 mg kg−1, i.v.) in eight different cats did not alter the response of nine C fibre afferents to exogenous 5‐HT (0.91 ± 0.17 vs. 1.19 ± 0.25 impulses s−1, P > 0.05).
The results suggest that, during mesenteric ischaemia, endogenous 5‐HT contributes to the activation of abdominal sympathetic afferents, mainly through direct stimulation of 5‐HT3 receptors and that the action of 5‐HT on these afferents appears to be independent of the cyclo‐oxygenase pathway.
Mode switching characterizes the activity of large conductance potassium channels recorded from rat cortical fused nerve terminals
Authors: Smith M. A. , Ashford M. L. J. 
Published: September 2004

Inside‐out recordings from rat cortical fused nerve terminals indicate that the most common channel observed was a large conductance K+ (BK) channel with characteristics dissimilar to conventional cell body calcium‐activated BK (BKCa) channels.
BK channels exhibit mode switching between low (mode 1) and high (mode 2) activity, an effect not influenced by membrane voltage. Increasing internal Ca2+ concentration increased time spent in mode 2 as did application of protein kinase A, an effect not mimicked by protein kinase C or protein kinase G.
Mode 1 activity was voltage independent although depolarization increased mode 2 channel activity. Global average channel activity was voltage and Ca2+ dependent.
Alkaline phosphatase treatment induced channel activity to reside permanently in mode 2, where activity was voltage and Ca2+ dependent but unaffected by protein kinases A, G or C.
Internal application of tetraethylammonium blocked BK channel activity in a manner identical to that reported for BKCa channels.
These results indicate that nerve terminal membranes have large conductance K+ channels with significant differences in gating kinetics and regulation of activity compared with BKCa channels of other neuronal preparations. The BK channel subtype may play a unique physiological role specific to the nerve terminal.