bluuebunny/crossref_metadata_2025 huggingface dataset:
Photochemotherapy inhibits angiogenesis and induces apoptosis of endothelial cells in vitro
Authors: Deng Hui , Yan Chun‐lin , Hu Yue , Xu Yu , Liao Kang‐huang
Published: July 2004

Background: Photochemotherapy has long been used in the treatment of psoriasis; however, its mechanism has not been completely elucidated. Psoriasis is now regarded as an angiogenesis‐related disease. Recent studies indicated that the inhibition of angiogenesis by photochemotherapy could be an underlying mechanism. It was found that photochemotherapy can downregulate the expression of angiogenic factors in keratinocytes. However, the direct effect of photochemotherapy on endothelial cells has not been studied.

Methods: In this study, we determined the effect of photochemotherapy on the proliferation of human microvascular endothelial cells through MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay and cell cycle analysis. The migration assay and in vitro tube formation assay were used to investigate the migration properties and tube formation ability of human microvascular endothelial cells after psoralen plus UVA (PUVA) treatment. The apoptosis of endothelial cells elicited by photochemotherapy was also analyzed with fluorescence‐activated cell sorting analysis (FACS).

Results: UVA (0.8–5.0 J/cm2) irradiation with the presence of 8‐methoxypsoralen (8‐MOP) (300 ng/ml) resulted in a dose‐dependent reduction in the cell viabilities of endothelial cells. FACS data showed an accumulation of cells in G0/G1 phase of cell cycle and apoptotic features of cell death after UVA irradiation with psoralen. The migration properties and tube formation ability of endothelial cells were dramatically inhibited by photochemotherapy.

Conclusion: Our results showed that photochemotherapy inhibits angiogenesis and induces apoptosis of human microvascular endothelial cells in vitro, which may be a possible mechanism of photochemotherapy in the treatment of psoriasis.
In vivo measurement of 5‐aminolaevulinic acid‐induced protoporphyrin IX photobleaching: a comparison of red and blue light of various intensities
Authors: Nadeau Valerie , O'Dwyer Martin , Hamdan Khaled , Tait Iain , Padgett Miles
Published: July 2004

Background: In recent years, 5‐aminolaevulinic acid (ALA) has become an increasingly popular photosensitizing drug for use in both photodynamic therapy (PDT) and photodetection (PD) of cancers. ALA metabolizes within tissue to form the photosensitizer protoporphyrin IX (PpIX). Like most photosensitizers, PpIX is fluorescent, and this fluorescence progressively decreases during PDT. This phenomenon is referred to as photobleaching.

Aim: Our aim in carrying out this experiment was twofold: firstly, to compare the relative capacity of red and blue light to cause photobleaching; and secondly, to compare the capacity of a fixed light dose to cause photobleaching, when delivered at different intensities.

Method: In this paper, we describe the implementation of a compact fluorescence spectrometer in monitoring the photobleaching of ALA‐induced PpIX in vivo on the skin of healthy volunteers.

Results: We have been able to show that blue light causes more rapid photobleaching than red light, and that under illumination with red or blue light, delivery of a fixed light dose at a lower intensity results in more photobleaching.

Conclusion: Comparison of the photobleaching rates suggests that a blue light intensity of 5 mW/cm2 gives the same rate of photobleaching as the typical red light PDT intensity of 100 mW/cm2. Further investigation of the correlation between PpIX photobleaching and PDT effect would be beneficial in interpreting the clinical significance of our findings.
Clinical and epidemiologic characterization of photosensitivity in HIV‐positive individuals
Authors: Bilu Donna , Mamelak Adam J. , Nguyen Ruby H.‐N. , Queiroz Pedro C. , Kowalski Jeanne , Morison Warwick L. , Martins Ciro R.
Published: July 2004

Background: An increased prevalence and severity of cutaneous photosensitivity has been recognized in association with human immunodeficiency virus (HIV) infection. However, this disorder remains poorly characterized in terms of its epidemiology, predisposing factors, clinical, and environmental associations.

Methods: To define the risk factors associated with the presence of photosensitivity among HIV‐positive individuals, a cross‐sectional study of 631 primary patient visits to an urban HIV Dermatology clinic between January 1997 and August 2001, inclusive, was conducted. A multivariate model was fit to estimate adjusted odds ratios for risk factors associated with photosensitivity diagnosis. Subsequently, a case‐series of the patients with photosensitivity was reported.

Results: The overall prevalence of photosensitivity was 5.4%, while African‐Americans (AA) exhibited a prevalence of 7.3%. In the multivariate model, using highly active anti‐retroviral therapy (HAART) (OR=2.82, 95% CI: 1.13, 7.03) and being AA (OR=6.68, 95% CI: 1.56, 28.65) significantly increased the odds of photosensitivity. Patients with photosensitivity were more likely to present during periods of higher ultraviolet (UV) index (P=0.08). Two distinct clinical morphologies were noted: lichenoid and non‐lichenoid, eczematous. Sub‐morphologies in the non‐lichenoid group were suggestive of differences in immunologic profile and estimated UV exposure.

Conclusion: Photosensitivity associated with HIV infection is an increasingly recognized dermatologic condition with a heterogeneous clinical presentation. AA ethnicity and HAART were independent indicators for the diagnosis of photosensitivity, whereas CD4+ and UV exposure had non‐significant associations. The subtleties in these and other clinical variables may directly aid in the recognition and diagnosis of this poorly characterized disorder.
Polymorphous light eruption (PLE) and a new potent antioxidant and UVA‐protective formulation as prophylaxis
Authors: Hadshiew I. M. , Treder‐Conrad C. , Bülow R. v. , Klette E. , Mann T. , Stäb F. , Moll I. , Rippke F.
Published: July 2004

Background: Polymorphous light eruption (PLE) is the most common photodermatosis. While its etiology still remains elusive, pathogenesis seems to involve UVA‐induced oxidative stress and subsequent deregulation of antioxidative immune responses. Only few and often ineffective prophylactic and therapeutic measures exist to date.

Methods: In our randomized, double‐blind, placebo‐controlled clinical study, we compared the efficacy of a new topical formulation, consisting of 0.25%α‐glucosylrutin (AGR) (a natural, modified flavonoid), 1% tocopheryl acetate (vitamin E) and a broad‐spectrum, highly UVA‐protective sunscreen (SPF 15) in a hydrodispersion gel vehicle, to a sunscreen‐only gel and vehicle. Thirty patients with a history of PLE were pretreated with either the above formulation, a similar preparation (with the same concentration for vitamin E and AGR, but a different UV filter system), placebo or a SPF 15 sunscreen‐only gel, 30 min prior to daily photoprovocation with UVA irradiations of 60–100 J/cm2 to 5 × 5 cm2 areas on the upper arms.

Results: After 4 days, results revealed a statistically highly significant difference (P<0.001) between the antioxidant containing formulations and placebo, and sunscreen‐only formulation, respectively, in experimentally eliciting PLE. While only one patient developed clinical signs of PLE with accompanying itch in the area treated with the new antioxidant UV‐protective gel formulation, 62.1% of the placebo‐treated areas and 41.3% of the sunscreen‐only treated areas showed mild to moderate signs of PLE.

Conclusion: Combining a potent antioxidant with a broad‐spectrum, highly UVA‐protective sunscreen is far more effective in preventing PLE than sunscreen alone or placebo and should thus be employed as the prophylaxis of choice for PLE.
Minimal erythema dose after multiple UV exposures depends on pre‐exposure skin pigmentation
Authors: Henriksen M. , Na R. , Ågren M.S. , Wulf H.C.
Published: July 2004

Background/purpose: Phototherapy consists of multiple ultraviolet (UV) exposures. Most previous studies have focused on erythema following a single UV exposure in fair‐skinned persons. Although it is well known that phototherapy lowers the daily UV‐threshold dose for erythema in clinical practice, this is insufficiently documented under controlled experimental conditions. The purpose of this study was to quantify the change in the daily threshold for a dose specific erythema grade after 1–4 consecutive daily UV exposures.

Methods: Forty‐nine healthy volunteers (skin type II–V) with varying pigmentation quantified by skin reflectance. Two UV sources were used: a narrowband UVB (Philips TL01) and a Solar Simulator (Solar Light Co.). Just perceptible erythema after 24 h was chosen as the minimal erythema dose (+); besides + and ++ were assessed.

Results: We found a positive and significant exponential relationship between skin pigmentation and UV dose to elicit a specific erythema grade on the back after 1–4 UV exposures. After repetitive UV exposures the UV dose had to be lowered more in dark‐skinned persons compared with fair‐skinned persons to elicit a certain erythema grade. This applied to both UV sources and all erythema grades.

Conclusion: In the dark‐skinned persons the daily UV dose after the 4 days UV exposure should be lowered by 40–50% to avoid burns compared with the single UV exposure. For the most fair‐skinned persons essentially no reduction in the daily UV dose was needed. Our results indicate that the pre‐exposure pigmentation level can guide the UV dosage in phototherapy.
No significant change of plasma β‐endorphin levels of psoriasis patients after synchronous balneophototherapy
Authors: Holló P. , Bender T. , Marschalkó M. , Gonzalez R. , Barna I. , Horváth A.
Published: July 2004

Background/Purpose: Previous studies suggested that β‐endorphin has a pathogenic role in psoriasis: its increased plasma concentration may play a role in the neuroimmunological processes in the pathomechanism of the disease, and plasma β‐endorphin levels should reflect the changes in the patients' skin status. The purpose of this study was to investigate the changes of peripheral blood β‐endorphin levels in psoriatic patients in conjunction with changes in their skin symptoms after synchronous balneophototherapy.

Methods: With synchronous balneophototherapy, 12 patients with extended skin symptoms of psoriasis were treated. The therapy followed the Regensburg protocol, consisting of a basic course of 35 sessions. Patients' skin status was characterized by evaluating the Psoriasis Area and Severity Index score before and after the therapy course. Blood samples were taken before treatment, and 1 day after the last session, with symptom‐free skin. Plasma β‐endorphin levels were measured by a specific radioimmunoassay developed by the authors.

Results: There was no significant change in plasma levels of β‐endorphin after clinical clearance of psoriatic skin symptoms.

Conclusion: In this non‐randomized, uncontrolled study no significant difference could be detected between plasma β‐endorphin levels before and after a basic course of synchronous balneophototherapy in patients with psoriasis. Although β‐endorphin has many neuroimmunological effects, the changes of its plasma level do not consistently reflect the skin status. Inflammation in psoriatic skin lesions is probably not mediated directly by circulating β‐endorphin.
UVA‐1 as a treatment for scleredema
Authors: Janiga Jennifer J. , Ward Donna H. , Lim Henry W.
Published: July 2004

Scleredema is a rare disease that is difficult to treat. Many therapies have been tried with varied and somewhat inconsistent results. Here we report two cases of scleredema successfully treated with low‐dose UVA‐1.
The control of ventilation is dissociated from locomotion during walking in sheep
Authors: Haouzi Philippe , Chenuel Bruno , Chalon Bernard
Published: July 2004

This study was designed to test the hypothesis that the frequency response of the systems controlling the motor activity of breathing and walking in quadrupeds is compatible with the idea that supra‐spinal locomotor centres could proportionally drive locomotion and ventilation. The locomotor and the breath‐by‐breath ventilatory and gas exchange (CO2output(V̇)and O2uptake(V̇)) responses were studied in five sheep spontaneously walking on a treadmill. The speed of the treadmill was changed in a sinusoidal pattern of various periods (from 10 to 1 minute) and in a step‐like manner. The frequency and amplitude of the limb movements, oscillating at the same period as the treadmill speed changes, had a constant gain with no phase lag (determined by Fourier analysis) regardless the periods of oscillations. In marked contrast, when the periods of speed oscillations decreased, the amplitude (peak‐to‐mean) of minute ventilation(V̇E)oscillations decreased sharply and significantly (from 6.1 ± 0.4 l min−1to 1.9 ± 0.2 l min−1) and the phase lag between ventilation and treadmill speed oscillations increased (to 105 ± 25 ° during the 1 min oscillation periods).V̇Eresponse followedV̇very closely. The drop inV̇Eamplitude ratio was proportional to that inV̇(from 149 ± 48 ml min−1to 38 ± 5 ml min−1) with a slightly longer phase lag for ventilation than forV̇. These results show that beyond the onset period of a locomotor activity, the amplitude and phase lag of theV̇Eresponse depends on the period of the walking speed oscillations, tracking the gas exchange rate, regardless of the amplitude of the motor act of walking. Locomotion thus appears unlikely to cause a simple parallel and proportional increase in ventilation in walking sheep.
Intense interval training enhances human skeletal muscle oxygen uptake in the initial phase of dynamic exercise at high but not at low intensities
Authors: Krustrup Peter , Hellsten Ylva , Bangsbo Jens
Published: July 2004

The present study tested the hypothesis that intense interval training enhances human skeletal muscle blood flow and oxygen uptake (V̇) at the onset of dynamic exercise. We also investigated whether possible training effects were dependent on exercise intensity. Six habitually active males carried out 7 weeks of intermittent‐exercise one‐legged knee‐extensor training at an intensity corresponding to ∼150% of peak thigh V̇ on three to five occasions per week. After the training period, cardiovascular and metabolic measurements were performed during knee‐extensor exercise with the trained leg (TL) and the control leg (CL) for 10 min at intensities of 10 and 30 W, and also for 4 min at 50 W. Femoral venous blood flow was higher (P < 0.05) in TL than CL from 75 to 180 s at 30 W (∼75 s: 3.43 ± 0.20 versus 2.99 ± 0.18 l min−1) and from 40 to 210 s at 50 W (∼75 s: 5.03 ± 0.41 versus 4.13 ± 0.33 l min−1). Mean arterial pressure was not different between legs. Thus, thigh vascular conductance was higher (P < 0.05) in TL than CL from 35 to 270 s at 30 W and from 150 to 240 s at 50 W. Femoral arterial–venous (a‐v) O2 difference was higher (P < 0.05) in TL than CL from 20 to 70 s at 30 W, but not different between TL and CL at 50 W. Thigh V̇ was higher (P < 0.05) in TL than CL from 20 to 110 s at 30 W (∼45 s: 0.38 ± 0.04 versus 0.30 ± 0.03 l min−1), and from 45 to 240 s at 50 W (∼45 s: 0.64 ± 0.06 versus 0.44 ± 0.08 l min−1). No differences were observed between TL and CL during exercise at 10 W. The present data demonstrate that intense interval training elevates muscle oxygen uptake, blood flow and vascular conductance in the initial phase of exercise at high, but not at low, intensities.
Two types of spontaneous depolarizations in the interstitial cells freshly prepared from the murine small intestine
Authors: Goto Kazunori , Matsuoka Satoshi , Noma Akinori
Published: July 2004

To explore the electrophysiological properties of the interstitial cells of Cajal (ICCs) and fibroblast‐like cells (FLCs), we developed a new preparation by treating the murine small intestine with collagenase. This thin muscle layer preparation contained at least two types of interstitial cells around the enteric nerve bundles, and the cluster of smooth muscle cells displayed a rhythmic contraction. We morphologically identified ICCs and FLCs and conducted patch clamp experiments on each type of cell. The c‐kit‐positive CD34‐negative ICCs showed spontaneous and rhythmic potential fluctuations, and a large transient inward current was evoked by depolarization under voltage clamp conditions. Once the inward current was triggered, it took a regenerative time course and lasted approximately 500 ms. The current was inactivated by continuous depolarization, and by removal of external Ca2+. The application of acetylcholine (ACh) prolonged the duration of spontaneous depolarization as well as the depolarization‐induced inward current. This inward current showed a reversal potential of around +3 mV and was considered to be due to non‐selective cation channels. The c‐kit‐negative CD34‐positive FLCs showed irregular or regular potential fluctuations, and spontaneous outward current was observed under voltage clamp conditions. This outward current showed a reversal potential of around −80 mV and might be classified as a potassium current. We failed to observe major time‐ and voltage‐dependent currents except the above two currents in the interstitial cells.
Nitric oxide, cAMP and the biphasic muscarinic modulation of ACh release at the lizard neuromuscular junction
Authors: Graves Austin R. , Lewin Katherine A. , A. Lindgren Clark
Published: July 2004

In this study, we characterized the pharmacology and physiology of the automodulation of ACh release at the lizard neuromuscular junction (NMJ). The activation of muscarinic ACh receptors generated a biphasic modulation of synaptic transmission. Muscarine‐induced activation of M3 receptors (0–12 min) decreased release, whereas M1 activation (> 12 min) enhanced release. Both phases of the biphasic effect are dependent on nitric oxide. However, cAMP acting via protein kinase A is also necessary for the M1 effect. In summary, we present a novel biphasic role for muscarine and implicate M3 receptors in the inhibition and M1 receptors in the enhancement of transmitter releaseat the cholinergic lizard NMJ.
Retracted: Serotonin and cholecystokinin synergistically stimulate rat vagal primary afferent neurones
Authors: Li Y. , Wu X. Y. , Owyang C.
Published: July 2004

Recent studies indicate that cholecystokinin (CCK) and serotonin (5‐hydroxytryptamine, 5‐HT) act via vagal afferent fibres to mediate gastrointestinal functions. In the present study, we characterized the interaction between CCK and 5‐HT in the vagal primary afferent neurones. Single neuronal discharges of vagal primary afferent neurones innervating the duodenum were recorded from rat nodose ganglia. Two groups of nodose ganglia neurones were identified: group A neurones responded to intra‐arterial injection of low doses of cholecystokinin octapeptide (CCK‐8; 10–60 pmol); group B neurones responded only to high doses of CCK‐8 (120–240 pmol), and were also activated by duodenal distention. CCK‐JMV‐180, which acts as an agonist in high‐affinity states and as an antagonist in low‐affinity states, dose dependently stimulated group A neurones, but inhibited the effect of the high doses of CCK‐8 on group B neurones. Duodenal perfusion of 5‐HT evoked dose‐dependent increases in nodose neuronal discharges. Some neurones that responded to 5‐HT showed no response to either high or low doses of CCK‐8. A separate group of nodose neurones that possessed high‐affinity CCK type A (CCK‐A) receptors also responded to luminal infusion of 5‐HT. Further, a subthreshold dose of CCK‐8 (i.e. 5 pmol) produced no measurable electrophysiological effects but it augmented the neuronal responses to 5‐HT. This potentiation effect of CCK‐8 was eliminated by CR 1409. From these results we concluded that the vagal nodose ganglion contains neurones that may possess only high‐ or low‐affinity CCK‐A receptors or 5‐HT3 receptors. Some neurones that express high‐affinity CCK‐A receptors also express 5‐HT3 receptors. Pre‐exposure to luminal 5‐HT may augment the subsequent response to a subthreshold dose of CCK.
Role of interstitial cells and gap junctions in the transmission of spontaneous Ca2+ signals in detrusor smooth muscles of the guinea‐pig urinary bladder
Authors: Hashitani Hikaru , Yanai Yoshimasa , Suzuki Hikaru
Published: July 2004

To investigate mechanisms underlying the transmission of spontaneous Ca2+ signals in the bladder, changes in intracellular concentrations of Ca2+ ([Ca2+]i) were visualized in isolated detrusor smooth muscle bundles of the guinea‐pig urinary bladder loaded with a fluorescent Ca2+ indicator, fura‐PE3 or fluo‐4. Spontaneous increases in [Ca2+]i (Ca2+ transients) preferentially originated along the boundary of muscle bundles and then spread to the other boundary (Ca2+ waves). The synchronicity of Ca2+ waves across the bundles was disrupted by 18β‐glycyrrhetinic acid (18β‐GA, 40 μm), carbenoxolone (30 μm) or 2‐aminoethoxydiphenylborate (2‐APB, 50–100 μm), while CPA (10 μm), ryanodine (100 μm), xestospongin C (3 μm) and U‐73122 (10 μm) had no effect. Intracellular recordings using two independent microelectrodes demonstrated that 2‐APB (100 μm) blocked electrical coupling between detrusor smooth muscle cells. Nifedipine (10 μm) but not nominal Ca2+‐free solution diminished the synchronicity of Ca2+ waves before preventing their generation. Staining for c‐kit identified interstitial cells (IC) located along both boundaries of muscle bundles. IC were also scattered amongst smooth muscle cells and were more dominantly distributed in connective tissue between muscle bundles. IC generated nifedipine‐resistant spontaneous Ca2+ transients, which occurred independently of those of smooth muscles. In conclusion, the propagation of Ca2+ transients in the bladder appears to be exclusively mediated by the spread of action potentials through gap junctions being facilitated by the regenerative nature of L‐type Ca2+ channels, without significant contribution of intracellular Ca2+ stores. IC in the bladder may modulate the transmission of Ca2+ transients originating from smooth muscle cells rather than being the pacemaker of spontaneous activity.
Changes in AMPA receptor currents following LTP induction on rat CA1 pyramidal neurones
Authors: Andrásfalvy Bertalan K. , Magee Jeffrey C.
Published: July 2004

In the CA1 region of the hippocampus, LTP is thought to be initiated by a transient activation of NMDA receptors and is expressed as a persistent increase in synaptic transmission through AMPA receptors. To investigate the postsynaptic modifications of AMPA receptors involved in this enhanced synaptic transmission, the channel density and single‐channel properties of extrasynaptic AMPA receptors located in synaptically active dendritic regions were examined following the induction of LTP. Following tetanic stimulation an outside‐out patch was excised from the apical dendrite near the point of stimulation and saturating concentrations of glutamate were rapidly applied to the patch. AMPA current amplitude and duration were increased significantly in patches pulled from dendrites that expressed LTP. Non‐stationary fluctuation analysis of AMPA currents indicated that AMPA channel number was nearly twofold larger than in controls, while single channel conductance and maximum open‐probability were unchanged. Furthermore, while subtle changes in AMPA channel kinetics could also be observed, we did not find any evidence that receptor affinity or rectification properties were altered by LTP induction. Very similar results were found when CaMK‐II activity was increased through the intracellular application of Ca/CaM. Together, we interpret our data to indicate that the stimuli used here produce an increased delivery of AMPA receptors to synaptically active regions of the apical dendrite without inducing any significant changes in their basic biophysical properties and that such delivery is a key element in this form of synaptic plasticity.
Linear modelling analysis of baroreflex control of arterial pressure variability in rats
Authors: Chapuis Bruno , Vidal‐Petiot Emmanuelle , Oréa Valérie , Barrès Christian , Julien Claude
Published: July 2004

The objective of the present study was to examine whether a simple linear feedback model of arterial pressure (AP) control by the sympathetic nervous system would be able to reproduce the characteristic features of normal AP variability by using AP and renal sympathetic nerve activity (RSNA) data collected in conscious sinoaortic baroreceptor denervated (SAD) rats. As compared with baroreceptor‐intact rats (n= 8), SAD rats (n= 10) had increased spectral power (+ 680%) of AP in the low frequency range (LF, 0.0003–0.14 Hz) and reduced power (−19%) in the mid‐frequency range (MF, 0.14–0.8 Hz) containing Mayer waves. In individual SAD rats, RSNA data were translated into ‘sympathetic’ AP time series by using the RSNA–AP transfer function that had been previously characterized in anaesthetized rats. AP ‘perturbation’ time series were then calculated by subtracting ‘sympathetic’ from actual AP time series. Actual RSNA and AP ‘perturbation’ time series were introduced in a reflex loop that was closed by using the previously identified baroreflex transfer function (from baroreceptor afferent activity to RSNA). By progressively increasing the open‐loop static gain, it was possible to compute virtual AP power spectra that increasingly deviated from their progenitor spectra, with spectral power decreasing in the LF range (as a result of baroreflex buffering of haemodynamic perturbations), and increasing in the MF band (as a result of increasing transients at the resonance frequency of the loop). The most accurate reproduction of actual AP and RSNA spectra observed in baroreceptor‐intact rats was obtained at 20–30% of the baroreflex critical gain (open‐loop static gain resulting in self‐sustained oscillations at the resonance frequency). In conclusion, while the gain of the sympathetic component of the arterial baroreceptor reflex largely determines its ability to provide an efficient correction of slow haemodynamic perturbations, this is achieved at the cost of increasing transients at higher frequencies (Mayer waves). However, the system remains fundamentally stable.
Electrical and chemical transmission between striatal GABAergic output neurones in rat brain slices
Authors: Venance Laurent , Glowinski Jacques , Giaume Christian
Published: July 2004

Basal ganglia are interconnected subcortical nuclei, connected to the thalamus and all cortical areas involved in sensory motor control, limbic functions and cognition. The striatal output neurones (SONs), the major striatal population, are believed to act as detectors and integrators of distributed patterns of cerebral cortex inputs. Despite the key role of SONs in cortico‐striatal information processing, little is known about their local interactions. Here, we report the existence and characterization of electrical and GABAergic transmission between SONs in rat brain slices. Tracer coupling (biocytin) incidence was high during the first two postnatal weeks and then decreased (postnatal days (P) 5–25, 60%; P25–30, 29%; n= 61). Electrical coupling was observed between 27% of SON pairs (coupling coefficient: 3.1 ± 0.3%, n= 89 at P15) and as shown by single‐cell RT‐PCR, several connexin (Cx) mRNAs were found to be expressed (Cx31.1, Cx32, Cx36 and Cx47). GABAergic synaptic transmission (abolished by bicuculline, a GABAA receptor antagonist) observed in 19% of SON pairs (n= 62) was reliable (mean failure rate of 6 ± 3%), precise (variation coefficient of latency, 0.06), strong (IPSC amplitudes of 38 ± 12 pA) and unidirectional. Interestingly, electrical and chemical transmission were mutually exclusive. These results suggest that preferential networks of electrically and chemically connected SONs, might be involved in the channelling of cortico‐basal ganglia information processing.
Changes in respiration in NREM sleep in hypercapnic chronic obstructive pulmonary disease
Authors: O'Donoghue Fergal J. , Catcheside Peter G. , Eckert Danny J. , McEvoy R. Doug
Published: July 2004

Sleep hypoventilation is common in hypercapnic chronic obstructive pulmonary disease (COPD) and may contribute to daytime hypercapnia. The contributions of respiratory drive and respiratory mechanics to alterations in minute ventilation (V̇I) during sleep in this group have not been assessed. We assessed V̇I, breathing pattern, upper airway and total lung resistance (UAR, RL), intraoesohageal diaphragmatic EMG (EMGoes), intrinsic positive end‐expiratory pressure (PEEPi), dynamic compliance (Cdyn), pressure–time product of oesophageal pressure (PTPoes), tension–time index of the diaphragm (TTIdi), end‐expiratory lung volume (EELV) and respiratory drive (assessed as the slope of Poesversus time in the isovolumetric interval before PEEPi is overcome). Measurements were made in wakefulness and non‐rapid eye movement (NREM) sleep, on 76%N2/24%O2 and on 76%He/24%O2 (heliox). Satisfactory data for analysis were obtained in 10 patients; five had measurements on heliox. V̇I fell from (mean (s.e.m.)) 8.84(0.46) to 6.64(0.91 l min−1, P= 0.011) between wakefulness and stage II sleep, due to a fall in tidal volume. No changes were seen in PEEPi, Cdyn, EELV, PTPoes, TTIdi, EMGoes or respiratory drive. UAR increased (3.11(0.8) to 10.24(2.96) cmH2O l−1 s (P= 0.013) but RL was unchanged. UAR was reduced on heliox (5.20(1.67) to 3.45(1.35) cmH2O l−1 s, P= 0.049) but V̇I during sleep did not increase. PTPoes (350.2(51.0) to 259.4(46.3) cmH2O s min−1, P= 0.016), TTIdi (0.13(0.02) to 0.10(0.02) P= 0.04), and respiratory drive (20.48(4.69) to 15.02(4.57) cmH2O s−1, P= 0.01) were all reduced. This suggests respiratory drive alters to maintain a preset V̇I in sleep, irrespective of load, at least while the fatigue threshold of respiratory muscles is not exceeded.
Dynamic carotid baroreflex control of the peripheral circulation during exercise in humans
Authors: Wray D. Walter , Fadel Paul J. , Keller David M. , Ogoh Shigehiko , Sander Mikael , Raven Peter B. , Smith Michael L.
Published: July 2004

We sought to determine the dynamic relationship between carotid baroreflex (CBR)‐mediated control and local control of the skeletal muscle vasculature during dynamic exercise. In 12 subjects (18–35 years old), oscillatory neck pressure (NP, +40 mmHg) was applied at 0.1 Hz (i.e. 5 s on, 5 s off) for 5 min to determine the degree of CBR control over heart rate (HR), arterial blood pressure (ABP), muscle sympathetic nerve activity (MSNA), femoral blood velocity and skeletal muscle tissue oxygenation at rest and during 7 W dynamic knee‐extension exercise. Skeletal muscle tissue oxygenation measurements of both the exercising and nonexercising leg were evaluated. Fast Fourier transformation was performed on 5 min segments to calculate spectral power of the R–R interval (RRI), ABP, MSNA, femoral blood velocity and tissue oxygenation time series, and the low‐frequency (LF, 0.085–0.115 Hz) power spectra were compared to evaluate the degree of CBR‐mediated entrainment for each variable. At rest, sinusoidal NP significantly increased LF spectral power of RRI, ABP, MSNA and femoral blood velocity. During exercise, sinusoidal NP provoked a similar increase in spectral power for RRI and MSNA, while CBR‐mediated changes in ABP and femoral blood velocity were attenuated compared to rest. Changes in spectral power of skeletal muscle tissue oxygenation during sinusoidal NP were similar between the exercising and nonexercising leg at rest. However, during exercise the changes in skeletal muscle tissue oxygenation power were significantly less in the exercising leg, while changes in the nonexercising leg were similar to rest. We have demonstrated simultaneous entrainment of all CBR end‐organ measurements, ranging from cardiac chronotropic effects to alterations at the level of the skeletal muscle microcirculation. Moreover, we have identified a significant and specific attenuation of end‐organ responsiveness to CBR‐mediated sympathoexcitation in the vasculature of the exercising muscle. However, despite a shift towards more predominant local control over the exercising muscle vasculature, systemic arterial blood pressure was well preserved.
Preferential accumulation of GABAA receptor γ2L, not γ2S, cytoplasmic loops at rat spinal cord inhibitory synapses
Authors: Meier Jochen , Grantyn Rosemarie
Published: July 2004

Alternative splicing generates two variants of the GABAAR γ2‐subunit, γ2S and γ2L, which differ by insertion of the amino acid sequence LLRMFSFK into the large cytoplasmic loop between transmembrane domains 3 and 4. This additional sequence within the GABAAR γ2L‐subunit contains the potential protein kinase C (PKC) phosphorylation site serine 343 (Ser343). In the present study we intended to determine the capacity of these two splice variants to accumulate at inhibitory synaptic terminals and to colocalize with gephyrin, and to find out whether phosphorylation of Ser343 has any effect on GABAAR distribution. Green fluorescent protein (GFP)‐tagged large cytoplasmic loops of GABAAR γ2S and γ2L (GFP::γ2S/L) were used as surrogates for full‐length receptors to study the function of the individual γ2S and γ2L peptides in transfected spinal cord neurones (SCNs) and COS‐7 cells. It was found that GFP::γ2L displayed a significantly higher capacity to accumulate at inhibitory synapses than GFP::γ2S. GABAAR GFP::γ2S accumulation at inhibitory postsynaptic sites was suppressed to the extent that GFP::γ2S assumed a diffuse cytosolic distribution. PKC activation facilitated the postsynaptic clustering of GFP::γ2L but not of GFP::γ2S. This required the Ser343 residue, since substituting Ala343 for Ser343 produced a diffuse cytosolic localization pattern, like that of GFP::γ2S. Furthermore, upon PKC activation Discosoma Red2‐tagged GABAAR γ2L (DsRed 2::γ2L) colocalized with gephyrin in transfected COS‐7 cells. These results support the idea that alternative splicing regulates the access of GABAARs to inhibitory postsynaptic sites in a Ser343 phosphorylation‐regulated way.
Mechanism of spike frequency adaptation in substantia gelatinosa neurones of rat
Authors: Melnick Igor V. , Santos Sónia F. A. , Safronov Boris V.
Published: July 2004

Using tight‐seal recordings from rat spinal cord slices, intracellular labelling and computer simulation, we analysed the mechanisms of spike frequency adaptation in substantia gelatinosa (SG) neurones. Adapting‐firing neurones (AFNs) generated short bursts of spikes during sustained depolarization and were mostly found in lateral SG. The firing pattern and the shape of single spikes did not change after substitution of Ca2+ with Co2+, Mg2+ or Cd2+ indicating that Ca2+‐dependent conductances do not contribute to adapting firing. Transient KA current was small and completely inactivated at resting potential suggesting that adapting firing was mainly generated by voltage‐gated Na+ and delayed‐rectifier K+ (KDR) currents. Although these currents were similar to those previously described in tonic‐firing neurones (TFNs), we found that Na+ and KDR currents were smaller in AFNs. Discharge pattern in TFNs could be reversibly converted into that typical of AFNs in the presence of tetrodotoxin but not tetraethylammonium, suggesting that lower Na+ conductance is more critical for the appearance of firing adaptation. Intracellularly labelled AFNs showed specific morphological features and preserved long extensively branching axons, indicating that smaller Na+ conductance could not result from the axon cut. Computer simulation has further revealed that down‐regulation of Na+ conductance represents an effective mechanism for the induction of firing adaptation. It is suggested that the cell‐specific regulation of Na+ channel expression can be an important factor underlying the diversity of firing patterns in SG neurones.
GABAB receptor activation inhibits exocytosis in rat pancreatic β‐cells by G‐protein‐dependent activation of calcineurin
Authors: Braun Matthias , Wendt Anna , Buschard Karsten , Salehi Albert , Sewing Sabine , Gromada Jesper , Rorsman Patrik
Published: July 2004

We have investigated the regulation of hormone secretion from rat pancreatic islets by the GABAB receptors (GABABRs). Inclusion of the specific GABABR antagonist CGP 55845 in the extracellular medium increased glucose‐stimulated insulin secretion 1.6‐fold but did not affect the release of glucagon and somatostatin. Conversely, addition of the GABABR agonist baclofen inhibited glucose‐stimulated insulin secretion by ∼60%. Using RT‐PCR, transcription of GABABR1a‐c,f and GABABR2 subunits was detected in β‐cells. Measurements of membrane currents and cell capacitance were applied to single β‐cells to investigate the mechanisms by which GABABR activation inhibits insulin secretion. In perforated‐patch measurements, baclofen inhibited exocytosis elicited by 500‐ms voltage‐clamp depolarizations to 0 mV by ≤ 80% and voltage‐gated Ca2+ entry by only ∼30%. Both effects were concentration‐dependent with IC50 values of ∼2 μm. The inhibitory action of baclofen was abolished in the presence of CGP 55845. The ability of baclofen to suppress exocytosis was prevented by pre‐treatment with pertussis toxin and by inclusion of GDPβS in the intracellular medium, and became irreversible in the presence of GTPγS as expected for a process involving inhibitory G‐proteins (Gi/o‐proteins). The inhibitory effect of baclofen resulted from activation of the serine/threonine protein phosphatase calcineurin and pre‐treatment with cyclosporin A or intracellular application of calcineurin autoinhibitory peptide abolished the effect. Addition of baclofen had no effect on [Ca2+]i and electrical activity in glucose‐stimulated β‐cells. These data indicate that GABA released from β‐cells functions as an autocrine inhibitor of insulin secretion in pancreatic islets and that the effect is principally due to direct suppression of exocytosis.
Muscarinic modulation of erg potassium current
Authors: Hirdes Wiebke , Horowitz Lisa F. , Hille Bertil
Published: July 2004

We studied modulation of current in human embryonic kidney tsA‐201 cells coexpressing rat erg1 channels with M1 muscarinic receptors. Maximal current was inhibited 30% during muscarinic receptor stimulation, with a small positive shift of the midpoint of activation. Inhibition was attenuated by coexpression of the regulator of G‐protein signalling RGS2 or of a dominant‐negative protein, Gq, but not by N‐ethylmaleimide or C3 toxin. Overexpression of a constitutively active form of Gq (but not of G13 or of Gs) abolished the erg current. Hence it is likely that Gq/11, and not Gi/o or G13, mediates muscarinic inhibition. Muscarinic suppression of erg was attenuated by chelating intracellular Ca2+ to < 1 nm free Ca2+ with 20 mm BAPTA in the pipette, but suppression was normal if internal Ca2+ was strongly clamped to a 129 nm free Ca2+ level with a BAPTA buffer and this was combined with numerous other measures to prevent intracellular Ca2+ transients (pentosan polysulphate, preincubation with thapsigargin, and removal of extracellular Ca2+). Hence a minimum amount of Ca2+ was necessary for the inhibition, but a Ca2+ elevation was not. The ATP analogue AMP‐PCP did not prevent inhibition. The protein kinase C (PKC) blockers staurosporine and bisindolylmaleimide I did not prevent inhibition, and the PKC‐activating phorbol ester PMA did not mimic it. Neither the tyrosine kinase inhibitor genistein nor the tyrosine phosphatase inhibitor dephostatin prevented inhibition by oxotremorine‐M. Hence protein kinases are not needed. Experiments with a high concentration of wortmannin were consistent with recovery being partially dependent on PIP2 resynthesis. Wortmannin did not prevent muscarinic inhibition. Our studies of muscarinic inhibition of erg current suggest a role for phospholipase C, but not the classical downstream messengers, such as PKC or a calcium transient.
Reduced low‐voltage activated K+ conductances and enhanced central excitability in a congenitally deaf (dn/dn) mouse
Authors: Leao Richardson N. , Berntson Amy , Forsythe Ian D. , Walmsley Bruce
Published: July 2004

We have investigated changes in the neuronal excitability of the auditory brainstem in a congenitally deaf mouse (deafness dn/dn). Whole cell patch recordings from principal neurones of the medial nucleus of the trapezoid body (MNTB) showed strikingly enhanced excitability in the deaf mice when compared to control CBA mice at 12–14 days postnatal. MNTB neurones in normal CBA mice showed the phenotypic single action potential response on depolarization in current clamp; however, recordings from CBA mice carrying the homozygous deafness mutation fired trains of action potentials on depolarization. We show here that these changes are associated with reduced functional expression of dendrotoxin‐sensitive Kv1 potassium channels. In contrast, no differences were found in voltage‐gated calcium currents between control and deaf mice. These results reveal that loss of hair cell function in the cochlea leads to changes in ion channel expression in the central nervous system and suggests that this deafness model will be an important tool in understanding central changes occurring in human congenital deafness and in exploring activity‐dependent regulation of ion channel expression.
Effects of ADP on action potential‐induced force responses in mechanically skinned rat fast‐twitch fibres
Authors: Macdonald W. A. , Stephenson D. G.
Published: July 2004

Mechanically skinned muscle fibres from the extensor digitorum longus (EDL) muscle of the rat were electrically stimulated in solutions mimicking the myoplasmic environment in the resting muscle fibre but containing different [ADP] of < 0.1 μm, 40 μm and 1.0 mm, to investigate the effects of myoplasmic ADP on the twitch response. The amplitude of the twitch response markedly and gradually decreased by 47 ± 6% (n= 9) as [ADP] was increased from < 0.1 μm to 40 μm without changing [Ca2+] in the myoplamsic solution (50 nm). The times for the twitch to rise from 10 to 90% (Trise,10‐90) and to decrease from 90 to 10% (Tfall,90‐10) initially increased by 8 and 21% and then decreased by 16 and 30% (compared to controls), respectively, at steady state. When [ADP] was raised from < 0.1 μm to 1.0 mm and fibres were electrically stimulated, the first response was biphasic and very prolonged (by at least a factor of 10) but of an amplitude similar to that in the control solution. The following twitch response and the steady state twitch responses were much reduced in size by about a factor of 6 and more prolonged by about 40% compared to control responses. All these ADP effects were fully reversible and appear to be predominantly due to several ADP‐dependent alterations in SR Ca2+ handling properties (ADP‐dependent decrease in SR Ca2+ capacity together with an increase in Ca2+ binding to the SR pump sites facing the myoplasm). The ADP‐dependent effects on the contractile apparatus and Ca2+ regulatory system were relatively minor. Taken together, the results demonstrate that ADP accumulation is likely to play a crucial role in metabolic fatigue of skeletal muscle and can explain the marked reduction in the amplitude and the slower time course of the twitch response during fatigue as well as the elevation of myoplasmic [Ca2+] in fatigued fibres at rest.
A novel function of insulin in rat dermis
Authors: Nedrebø Torbjørn , Karlsen Tine V. , Salvesen Gerd S. , Reed Rolf K.
Published: July 2004

In this study we present a novel function of insulin in rat dermis. We investigated local effects of insulin on interstitial fluid pressure (Pif), and capillary albumin leakage and pro‐inflammatory cytokine production in skin and serum after intravenous lipopolysaccharide (LPS), tumour necrosis factor‐α (TNF‐α) and interleukin‐1β (IL‐1β) challenge treated with a glucose–insulin–potassium regimen (GIK). The main objective for this study was to investigate anti‐inflammatory effects of insulin. Work by others shows that insulin stimulates cell adhesion, and that this effect is dependent upon phosphatidylinositol 3‐kinase (PI3K) activity. Cytokines like platelet‐derived growth factor BB (PDGF‐BB) attenuate lowering of Pif, possibly via PI3K. LPS and pro‐inflammatory cytokines contribute to oedema development during acute inflammation by lowering the Pif. Intravenous injection of LPS, TNF‐α or IL‐1β to Wistar Møller rats caused a lowering of Pif, but after local injection of insulin in the paw, Pif increased back to control values. IL‐1β caused a lowering in control from −0.5 ± 0.2 mmHg to −3.0 ± 0.2 mmHg after 20 min (mean ±s.e.m.) (P < 0.05). Within 50 min after insulin injection the pressure was increased to −0.6 ± 0.2 mmHg (P > 0.05 compared with control). Insulin was given together with a PI3K inhibitor (wortmannin) locally in the skin, almost abolishing the effect of insulin on Pif. A GIK regimen was given as a continuous intravenous infusion, significantly attenuating the oedema formation after LPS or TNF‐α/IL‐1β challenge. The same GIK regimen caused a significant reduction in pro‐inflammatory cytokines in serum and in interstitial fluid in skin of endotoxaemic rats. These experiments show a possible role for insulin in the interstitium during inflammation induced by LPS and TNF‐α/IL‐1β. Insulin can attenuate a lowering of Pif possibly via PI3K, and it has an anti‐inflammatory effect by inhibiting production of pro‐inflammatory cytokines.
Purinergic regulation of guinea pig suburothelial myofibroblasts
Authors: Wu C. , Sui G. P. , Fry C. H.
Published: July 2004

The Ca2+‐regulating and electrophysiological properties of guinea‐pig suburothelial myofibroblasts have been measured in order to investigate their potential role in the sensation of bladder fullness, due to their strategic position between the urothelium and afferent fibres. Previous work has shown that stretch of the bladder wall releases ATP. Cells that stain positively for vimentin were isolated. About 45% of cells (median membrane capacitance 13.3 pF) exhibited spontaneous depolarizations to about −25 mV with a physiological Cl− gradient (frequency 2.6 ± 1.5 min−1, duration 14.5 ± 2.2 s, n= 15). Under voltage‐clamp spontaneous inward currents (frequency 1.5 ± 0.2 min−1, duration 14.5 ± 7.0 s, n= 18) were recorded, with a similar reversal potential. The spontaneous currents were preceded by intracellular Ca2+ transients with a magnitude that was independent of membrane potential. All cells tested responded to ATP by generating an intracellular Ca2+ transient, followed by inward currents; the currents had a similar reversal potential and slope conductance to their spontaneous counterparts. ATP‐generated transients were mimicked by UTP and ADP but not by α,β‐methylene‐ATP (1–10 μm) or CTP (30 μm), indicating that ATP acts via a P2Y receptor. Transients were partially attenuated by 1 mm suramin but PPADS (80 μm) had no effect. These data indicate that ATP acts via a P2Y receptor, but responses were resistant to the P2Y1 antagonist MRS2179. ATP‐generated transients were abolished by intracellular perfusion with heparin and TMB‐8 indicating that IP3 was the intracellular second messenger. The reversal potentials of the spontaneous and ATP‐generated currents were shifted by about +45 mV by a 12‐fold reduction of the extracellular [Cl−] and the currents were greatly attenuated by 1 mm DIDS. No transients were generated on exposure to the muscarinic agonist carbachol. We propose that these cells may play a regulatory step in the sensation of bladder fullness by responding to ATP. The precise mechanism whereby they couple urothelial ATP release to afferent excitation is the next step to be elucidated.