bluuebunny/crossref_metadata_2025 huggingface dataset:
Microalbuminuria Is Associated with Reduced Cardiac Cyclic Variation of Integrated Backscatter Signal in Severe Hypertension
Authors: Ceyhan Ceyhun , Akar Harun , Tekten Tarkan , Onbasili Alper O. , Karul Aslihan , Discigil Berent , Unal Selim , Ozturk Banu
Published: August 2004

Objective: Microalbuminuria (MA) as a marker of systemic vascular disease and left ventricular (LV) hypertrophy is associated with increased cardiovascular mortality and morbidity in patients with essential hypertension. The aim of this study was to investigate changes in cardiac cycle‐dependent variation of integrated backscatter signals (CVIBS) in hypertensive patients with MA. Methods: Randomly selected 60 hypertensive patients (mean age 51 ± 8) with uncontrolled blood pressure (BP) (≥130 mmHg systolic and/or 85 mmHg diastolic) were included. All patients underwent urinary albumin excretion (UAE) measurements, 24‐hour ambulatory BP monitoring, and LV echocardiographic examination. UAE was measured in two separate 24‐hour urine collection and mean of two values was taken into consideration. Normotensive 20 healthy subjects served as controls. CVIBS values were obtained from mid‐anteroseptal, mid‐posterolateral, and mid‐inferior areas at the papillary muscle level in the parasternal short‐axis view. CVIBS was defined as the difference in integrated backscatter values between systole and diastole. CVIBS values in MA positive patients were compared with the values in MA negative patients and control subjects. Results: Twelve patients had MA (UAE 30 to 300 mg/day) while 48 patients had normal UAE (<30 mg/day). The wall thickness (at septum and posterior) and left ventricular mass index (LVMI) values were all significantly higher in hypertensive patients with MA (P < 0.01). The CVIBS values in MA positive group were significantly lower than the CVIBS values both in MA negative hypertensive patients and control subjects (P < 0.01). Conclusion: This study demonstrates that in hypertensive patients a high LVMI is associated with reduced CVIBS values and MA appears to be a marker of hypertrophy.
Age Is Not a Predictor of Patent Foramen Ovale with Right‐to‐Left Shunt in Patients with Cerebral Ischemic Events
Authors: Yahia Abutaher M. , Shaukat Aasma , Kirmani Jawad F. , Qureshi Adnan I.
Published: August 2004

Background: Patent foramen ovale (PFO) with or without atrial septal aneurysm (ASA) is highly associated with cerebral ischemic events in young patients. The prevalence of PFO and ASA in elderly patients with cerebral ischemic events is not well described. Objective: Our study is to evaluate the frequencies of PFO with right‐to‐left shunt (RLS) and ASA in elderly patients and to determine whether age is a predictor of flow‐reversed PFO with RLS in cerebral ischemic events. Methods: A prospective registry for all consecutive patients with cerebral ischemic events who were evaluated by transesophageal echocardiography (TEE) for the detection of possible cardiac source of embolization was established and maintained in a university hospital. Patients' demographics including age, gender, ethnic origin, cerebrovascular risk factors, and all positive TEE data were collected from July 2000 to August 2001 for statistical analysis. A univariate and multivariate stepwise logistic regression analysis was performed. Results: In older patients the prevalence of PFO with RLS, PFO, and ASA was 25/118 (20%), 28/118 (24%), and 38/118 (32%), respectively, as opposed to younger patients, in whom it was 35/119 (30%), 39/119 (33%), and 38/119 (32%), respectively. Older patients had higher frequencies of hypertension (59; 69%), CAD (25; 21%), and prior history of stroke (23; 20%) as opposed to younger patients. Younger age (<60 years), gender, smoking history, hypertension, hyperlipidemia, CAD, and prior history of stroke were not associated with higher prevalence of PFO with RLS. Patent foramen ovale was associated with ASA (P < 0.001) and LVH (P < 0.019) in patients with TIA and stroke. In multivariate analysis only ASA (P < 0.001) remained significant with PFO, with RLS controlling for age, gender, and LVH. Conclusions: PFO with RLS and ASA are frequently present in elderly stroke and/or TIA patients and age is not a predictor for PFO. Transesophageal echocardiography should be considered for all stroke and/or TIA patients irrespective of their age.
P Wave Dispersion and Left Atrial Appendage Function for Predicting Recurrence after Conversion of Atrial Fibrillation and Relation of P Wave Dispersion to Appendage Function
Authors: Dogan Abdullah , Kahraman Halil , Ozturk Mustafa , Avsar Alaettin
Published: August 2004

Background: We investigated P wave dispersion and left atrial appendage (LAA) function for predicting atrial fibrillation (AF) relapse, and the relationship between P wave dispersion and LAA function. Methods: Sixty‐four consecutive patients with AF lasting ≤3 months were evaluated to predict the recurrence after successful cardioversion. P wave duration and dispersion were measured in a 12‐lead electrocardiograph (ECG). The size and function of the left atrium (LA) and LAA were assessed by transthoracic and transesophageal echocardiography. Results: After 6 months, 28 patients experienced recurrent AF and 36 remained in sinus rhythm. There was no difference between patients with and without recurrence in gender, age, underlying heart disease, AF patterns, left ventricular function, and maximum LAA area. AF duration ≥5 days, LA size ≥45 mm, maximum P wave duration ≥112 ms, P wave dispersion ≥47 ms, spontaneous echo contrast, minimum LAA area ≥166 mm2, and LAA emptying velocity <36 cm/sec were univariate predictors of recurrence (each P < 0.05). By multivariate analysis, LA size (P = 0.02), P wave dispersion (P < 0.001), and LAA emptying flow (P = 0.01) identified patients with recurrent AF. Their positive predictive values were 91, 97, and 72%, respectively. Conclusion: The increased P wave dispersion in addition to the dilated LA and the depressed LAA emptying flow can identify patients at risk of recurrent AF after cardioversion.
Intragastric acid suppression and pharmacokinetics of twice‐daily esomeprazole: a randomized, three‐way crossover study
Authors: Katz P. O. , Castell D. O. , Chen Y. , Andersson T. , Sostek M. B.
Published: August 2004

Background : Patients with refractory gastro‐oesophageal reflux disease, extra‐oesophageal reflux symptoms, Barrett's oesophagus, or Zollinger–Ellison syndrome may require greater acid suppression than that obtained with once‐daily esomeprazole.

Aim : To assess gastric acid suppression (determined by intragastric pH) and pharmacokinetics of twice‐daily vs. once‐daily esomeprazole.

Methods : In a randomized, double‐blind, three‐way crossover study, healthy subjects received esomeprazole 40 mg once daily, 20 mg twice daily, or 40 mg twice daily for five consecutive days. Twenty‐four‐hour continuous ambulatory intragastric pH was recorded on day 5.

Results : Esomeprazole 40 mg twice daily provided a mean of 19.2 h with intragastric pH > 4.0 (80.1% of a 24‐h time period; 95% confidence interval 74.5–85.7%) vs. 14.2 h with 40 mg once daily (59.2%; 95% CI 53.7–64.7%) and 17.5 h with 20 mg twice daily (73.0%; 95% confidence interval 67.4–78.5%) in 25 subjects. Intragastric pH was maintained >4.0 for a similar percentage of time during active and sleeping periods for all doses.

Conclusions : Esomeprazole 40 mg twice daily provides significantly greater acid suppression (number of hours in a 24‐h period with pH > 4.0) than once‐daily dosing and may be a reasonable consideration for patients requiring greater acid suppression for acid‐related disease.
The role of acid suppression in patients with endoscopy‐negative reflux disease: the effect of treatment with esomeprazole or omeprazole
Authors: Armstrong D. , Talley N. J. , Lauritsen K. , Moum B. , Lind T. , Tunturi‐Hihnala H. , Venables T. , Green J. , Bigard M. A. , Mössner J. , Junghard O.
Published: August 2004

Background : Patients with endoscopy‐negative reflux disease have reflux symptoms, mainly heartburn, but not mucosal breaks characteristic of erosive oesophagitis. Standard‐dose proton pump inhibitors can provide symptom relief in endoscopy‐negative reflux disease but the effect of greater acid suppression has not been studied.

Aim : To test the hypothesis that esomeprazole produces heartburn resolution in a greater proportion of patients with ENRD than omeprazole.

Methods : Three multi‐centre randomized, controlled, double‐blind, 4‐week acute treatment studies were conducted in endoscopy‐negative reflux disease patients. In study A (n = 1282), patients received either esomeprazole 40 mg, esomeprazole 20 mg or omeprazole 20 mg daily; in studies B (n = 693) and C (n = 670) patients received either esomeprazole 40 mg or omeprazole 20 mg (B), and esomeprazole 20 mg or omeprazole 20 mg (C), respectively.

Results : Resolution of heartburn at 4 weeks (no heartburn symptoms during the last 7 days) was achieved in similar proportions of patients in each treatment arm in study A (esomeprazole 40 mg, 56.7%; esomeprazole 20 mg, 60.5%; omeprazole 20 mg, 58.1%), study B (esomeprazole 40 mg, 70.3%; omeprazole 20 mg, 67.9%) and study C (esomeprazole 20 mg, 61.9%; omeprazole 20 mg, 59.6%). There were no significant differences between treatment groups within each study.

Conclusions : More than 60% of endoscopy‐negative reflux disease patients reported heartburn resolution but, after 4 weeks of therapy, these proportions did not differ significantly between treatments.
The validity and accuracy of the Work Productivity and Activity Impairment questionnaire – irritable bowel syndrome version (WPAI:IBS)
Authors: Reilly M. C. , Bracco A. , Ricci J.‐F. , Santoro J. , Stevens T.
Published: August 2004

Background : Irritable bowel syndrome is a common chronic functional gastrointestinal disorder characterized by recurrent abdominal pain and discomfort associated with alterations in bowel habit. Irritable bowel syndrome affects patients’ quality of life and increases productivity loss.

Aim : To assess validity and accuracy of the Work Productivity and Activity Impairment questionnaire in irritable bowel syndrome as a tool for quantifying the effects of irritable bowel syndrome on productivity and daily activities.

Methods : Validity and accuracy were evaluated in 135 irritable bowel syndrome patients relative to three measures of irritable bowel syndrome disease severity; a debriefing questionnaire; retrospective diary; Work Limitations Questionnaire, and an activity impairment measure (Dimensions of Daily Activities).

Results : Symptom severity scores, diary scores, Work Limitations Questionnaire and Dimensions of Daily Activities were significant predictors of work productivity and activity impairment questionnaire in irritable bowel syndrome measures of work time missed, and work and activity productivity loss (P = 0.04 to < 0.0001). Impairment due to irritable bowel syndrome was estimated to be 2.9–4.3% for work time missed and 22–32% for impairment at work, the equivalent of 9.7 –14 h lost productivity per week. Activity impairment was 24–41%.

Conclusions : Discriminative validity of the Work Productivity and Activity Impairment questionnaire in irritable bowel syndrome was established, making it the only validated tool for measuring the relative differences between disease severity groups and quantifying work productivity loss and activity impairment in irritable bowel syndrome patients.
Homologous recombination in Candida albicans: role of CaRad52p in DNA repair, integration of linear DNA fragments and telomere length
Authors: Ciudad Toni , Andaluz Encarnación , Steinberg‐Neifach Olga , Lue Neal F. , Gow Neil A. R. , Calderone Richard A. , Larriba Germán
Published: August 2004

Chromosomal rearrangements are common in both clinical isolates and spontaneous mutants of Candida albicans. It appears that many of these rearrangements are caused by translocations around the major sequence repeat (MSR) that is present in all chromosomes except chromosome 3, suggesting that homologous recombination (HR) may play an important role in the survival of this organism. In order to gain information on these processes, we have cloned the homologue of RAD52, which in Saccharomyces cerevisiae is the only gene required for all HR events. CaRAD52 complemented poorly a rad52 mutant of S. cerevisiae. Two null Carad52Δ/Carad52Δ mutants were constructed by sequential deletion of both alleles and two reconstituted strains were obtained by reintegration of the gene. Characterization of these mutants indicated that HR plays an essential role in the repair of DNA lesions caused by both UV light and the radiomimetic compound methyl‐methane‐sulphonate (MMS), whereas the non‐homologous end‐joining pathway (NHEJ) is used only in the absence of Rad52p or after extensive DNA damage. Repair by HR is more efficient in exponentially growing than in stationary cells, probably because a larger number of cells are in late S or G2 phases of the cell cycle (and therefore, can use a sister chromatid as a substrate for recombinational repair), whereas stationary phase cells are mainly in G0 or G1, and only can be repaired using the chromosomal homologue. In addition, CaRad52p  is  absolutely  required  for  the  integration of linear DNA with long flanking homologous sequences. Finally, the absence of CaRad52p results in the lengthening of telomeres, even in the presence of an active telomerase, an observation not described in any other organism. This raises the possibility that both telomerase and homologous recombination may function simultaneously at C. albicans telomeres.
DNA binding properties of TnpX indicate that different synapses are formed in the excision and integration of the Tn4451 family
Authors: Adams Vicki , Lucet Isabelle S. , Lyras Dena , Rood Julian I.
Published: August 2004

Site‐specific recombination is an important mechanism for genetic exchange. Insertional recombination mediated by the recently delineated large resolvase or serine recombinase proteins is unique within the resolvase family as integration was thought to be a reaction catalysed only by members of the integrase or tyrosine recombinase family of site‐specific recombinases. The large resolvase TnpX is a serine recombinase that is responsible for the movement of the Tn4451/3 family of chloramphenicol resistance elements, which are found within two genera of the medically important clostridia. Deletion analysis of TnpX showed that the last 110 amino acids (aa) of TnpX, which comprise a cysteine rich region, were not essential for its biological function and that a region required for DNA binding was located between aa 493–597. Purified TnpX was shown to bind to the ends of the element and to the joint of the circular intermediate with high affinity but, most unusually, to bind to its target sites with a considerably lower affinity. Therefore, it was concluded that the resolvase‐like excision and insertion reactions mediated by TnpX were distinct processes even though the same serine recombinase mechanism was involved. TnpX is the first large serine recombinase in which differential binding to its transposon and target sites has been demonstrated.
Nogo A expression in the adult enteric nervous system
Authors: Osborne S. L. , Corcoran S. L. , Prinjha R. K. , Moore S. E.
Published: August 2004

Abstract  Neuronal plasticity plays an important role in physiological and pathological processes within the gastrointestinal (GI) tract. Nogo A is a major contributor to the negative effect central nervous system (CNS) myelin has on neurite outgrowth after injury and may also play a role in maintaining synaptic connections in the healthy CNS. Nogo A is highly expressed during neuronal development but in the CNS declines postnatally concomitantly with a loss of regenerative potential while ganglia of the Peripheral Nervous System (PNS) retain Nogo A. The enteric nervous system shares a number of features in common with the CNS, thus the peripheral distribution of factors affecting plasticity is of interest. We have investigated the distribution of Nogo in the adult mammalian gastrointestinal tract. Nogo A mRNA and protein are detectable in the adult rat GI tract. Nogo A is expressed heterogeneously in enteric neurons throughout the GI tract though expression levels appear not to be correlated with neuronal sub‐type. The pattern of expression is maintained in cultured myenteric plexus from the guinea‐pig small intestine. As is seen in developing neurons of the CNS, enteric Nogo A is present in both neuronal cell bodies and axons. Our results point to a hitherto unsuspected role for Nogo A in enteric neuronal physiology.
Role of galanin receptor 1 in gastric motility in rat
Authors: Guerrini S. , Raybould H. E. , Anselmi L. , Agazzi A. , Cervio E. , Reeve J. R. , Tonini M. , Sternini C.
Published: August 2004

Abstract  Galanin actions are mediated by distinct galanin receptors (GAL‐R), GAL‐R1, ‐R2 and ‐R3. We investigated the role of GAL‐R1 in gastric motility and the expression of GAL‐R1 in the rat stomach. In vivo, in urethane‐anaesthetized rats, galanin (equipotent for all GAL‐Rs) induced a short inhibition of gastric motility, followed by increase in tonic and phasic gastric motility; the latter was significantly reduced by the GAL‐R1 antagonist, RWJ‐57408. Galanin 1–16 (high affinity for GAL‐R1 and ‐R2) induced a long‐lasting decrease of intragastric pressure, which was not modified by RWJ‐57408. In vitro, galanin and galanin 1–16 induced increase of intragastric pressure that was not affected by RWJ‐57408. Tetrodotoxin (TTX) did not suppress the galanin excitatory effect, whereas the effect of galanin 1–16 on gastric contraction was increased by TTX‐ or N‐nitro‐L‐arginine, an inhibitor of nitric oxide synthase. GAL–R1 immunoreactivity was localized to cholinergic and tachykinergic neurons and to neurons immunoreactive for nitric oxide synthase or vasoactive intestinal polypeptide. This study suggests that an extrinsic GAL‐R1 pathway mediates the galanin excitatory action, whereas an extrinsic, non GAL‐R1 pathway is likely to mediate the galanin inhibitory effect in vivo. GAL‐R1 intrinsic neurons do not appear to play a major role in the control of gastric motility.
Effect of rectal distension on abdominal girth
Authors: B. Marino , C. Ogliari , G. Basilisco
Published: August 2004

Abstract  It has been postulated that a viscerosomatic reflex activated by gut distension and inhibiting abdominal wall muscle tone may be one of the mechanisms underlying functional abdominal distension. Any demonstration of such a reflex has to take into account the fact that gut distension may increase abdominal girth as a result of volume displacement. As biomechanical and sensory rectal responses vary at different rates of rectal distension, we hypothesized that different rates of rectal distension might reveal different changes in abdominal girth. Abdominal girth was continuously recorded in 14 healthy subjects using a previously validated extensometer. The rectal distensions were made in a randomized order at rates of 100 mL min−1 or 10 mL min−1 up to 150 mL, and sham distensions were used as controls. An increase in abdominal girth was observed at the end of both distensions (P ≤ 0.008): it was greater after the fast (1.1 ± 0.5 mm) than after the slow distension (0.8 ± 0.7 mm), but this difference was not statistically significant (P = 0.2). In conclusion, we were unable to demonstrate the existence of a viscerosomatic reflex activated by gut distension under our experimental conditions.
Foreign Aid and Consumption Smoothing: Evidence from Global Food Aid
Authors: Gupta Sanjeev , Clements Benedict , Tiongson Erwin R.
Published: August 2004

The paper examines the cyclical properties of food aid with respect to food availability in recipient countries, with a view to assessing its impact on consumption in some 150 developing countries and transition economies, covering 1970 to 2000. The results show that global food aid has been allocated to countries most in need. Food aid has also been countercyclical within countries with the greatest need. However, for most countries, food aid is not countercyclical. The amount of food aid provided is also insufficient to mitigate contemporaneous shortfalls in consumption.
LOCKE ON SENSITIVE KNOWLEDGE AND THE VEIL OF PERCEPTION – FOUR MISCONCEPTIONS1
Authors: NEWMAN LEX
Published: August 2004

Abstract:  Interpreters of Locke's Essay are divided over whether to attribute to him a Representational Theory of Perception (RTP). Those who object to an RTP interpretation cite (among other things) Locke's Book IV account of sensitive knowledge, contending that the account is incompatible with RTP. The aim of this paper is to rebut this kind of objection – to defend an RTP reading of the relevant Book IV passages. Specifically, I address four influential assumptions (about sensitive knowledge) cited by opponents of an RTP interpretation and argue that in each case the assumption is false.
LOCKE ON THE SEMANTIC AND EPISTEMIC ROLE OF SIMPLE IDEAS OF SENSATION
Authors: BOLTON MARTHA BRANDT
Published: August 2004

Abstract:  This paper argues that Locke has a representative theory of sensitive knowledge. Perceivers are immediately aware of nothing but sensory ideas in the mind; yet perceivers think of real external substances that correspond to and cause those ideas, and they are warranted in believing that those substances exist (at that time). The theory poses two questions: what warrants the truth of such beliefs? What is it in virtue of which sensory ideas represent external objects and how do they make perceivers think of those objects? Both the epistemic and semantic issues need to be addressed. This paper urges that Locke's basic account of warrant is roughly reliabilist. The causal origin of sensory ideas assures that, in general, sense based beliefs are true. Locke defines the limit of this warrant by the theoretical point that we cannot discuss skeptical doubt without assuming the truthfulness of our perceptual faculty. Turning to the semantic question, the paper argues that ideas are mental modifications or entities. They are not intrinsically representative (satisfiable), but rather represent only by virtue of their causal origin. They merely “track” the presence of substances and their qualities. Ideas nevertheless prompt perceivers to think of their causes. This is roughly because sensory ideas have a specific mental role, namely, to serve as marks for distinguishing substances and their respective qualities for purposes of action. The paper suggests that, for Locke, the challenge posed by the semantic veil of ideas is to explain this externally directed marking function within bounds of his anti‐innatism. But it concludes that his answers to the twin questions fit together reasonably well.
Between Endless Needs and Limited Resources: The Gendered Construction of a Greedy Organization
Authors: Rasmussen Bente
Published: August 2004

One of the strategies of the modernization of public services is the decentralization of responsibilities and organizing work in autonomous co‐ operative teams with varied tasks. The empowerment of the public service workers in the front line is therefore a strategy in local government in Norway today. Under the assumption that women have ‘natural’ skills in caring, workers on the lowest levels are given responsibility for care and nursing. A study of the decentralization of public care for the elderly in their homes showed that being given interesting tasks and increased responsibility mobilized the efforts of the care workers. However, since the power of resources has been centralized, this has led to an intensification of work. In gendering the relevant discourses by explaining women's experiences of an over‐heavy workload as a result of their ‘mothering’ and their inability to set limits, women care workers were constructed by their managers as unprofessional and not to be taken seriously. This has made the public care organization a greedy organization for the women care workers.
Expression of volume‐sensitive Cl− channels and ClC‐3 in acinar cells isolated from the rat lacrimal gland and submandibular salivary gland
Authors: Majid Aneela , Brown Peter D. , Best Len , Park Kyungpyo
Published: August 2004

The expression of ClC‐3 was examined in rat lacrimal gland and submandibular salivary gland cells using RT‐PCR and Western analysis. Whole‐cell patch clamp methods were used to investigate the expression of volume‐sensitive anion channels in acinar cells isolated from these tissues.

Expression of mRNA encoding ClC‐3, and ClC‐3 protein, was found in rat submandibular gland by RT‐PCR and Western analysis. Rat lacrimal gland cells, however, did not appear to express mRNA encoding for ClC‐3, nor the ClC‐3 protein.

Volume‐sensitive anion conductances were observed in both rat lacrimal gland and submandibular salivary gland acinar cells. The conductance was of a similar size in the two cell types, but was much slower to activate in the lacrimal cells.

The properties of the conductances in lacrimal and submandibular cells were similar, e.g. halide selectivity sequence (PI > PCl > Paspartate) and inhibition by 4,4′‐diisothiocyanostilbene‐2,2′‐disulphonic acid, 5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate and tamoxifen.

The data suggest that the expression of ClC‐3 is not an absolute requirement for the activity of volume‐sensitive anion channels in rat lacrimal gland acinar cells.
Pharmacological aids to locomotor training after spinal injury in the cat
Authors: Rossignol S. , Giroux N. , Chau C. , Marcoux J. , Brustein E. , Reader T. A.
Published: August 2004

This Topical Review summarizes some of the work we have done mainly in the cat using agonists and antagonists of various neurotransmitter systems injected intravenously or intrathecally to initiate or modulate the expression of hindlimb locomotion after a spinal lesion at T13. The effects of the same drugs are compared in various preparations: complete spinal, partial spinal or intact cats. This has revealed that there can be major differences in these effects. In turn, this suggests that although the locomotor rhythm might normally be triggered and modulated by the activation of a variety of receptors (noradrenaline, serotonin, glutamate), after spinalization there appears to be a predominance of glutamatergic mechanisms. Recent work also suggests that, in the cat, the integrity of the midlumbar segments is crucial for the expression of spinal locomotion. Taken together, this work raises some hope that a targeted pharmacotherapy with better understood drugs and mode and locus of delivery could become a clinical reality.
Neurotrophic factors, cellular bridges and gene therapy for spinal cord injury
Authors: Jones Leonard L. , Oudega Martin , Bunge Mary Bartlett , Tuszynski Mark H.
Published: August 2004

Injury to the adult mammalian spinal cord results in extensive axonal degeneration, variable amounts of neuronal loss, and often severe functional deficits. Restoration of controlled function depends on regeneration of these axons through an injury site and the formation of functional synaptic connections. One strategy that has emerged for promoting axonal regeneration after spinal cord injury is the implantation of autologous Schwann cells into sites of spinal cord injury to support and guide axonal growth. Further, more recent experiments have shown that neurotrophic factors can also promote axonal growth, and, when combined with Schwann cell grafts, can further amplify axonal extension after injury. Continued preclinical development of these approaches to neural repair may ultimately generate strategies that could be tested in human injury.
Neurotrophins and synaptic plasticity in the mammalian spinal cord
Authors: Mendell Lorne M. , Munson John B. , Arvanian Victor L.
Published: August 2004

The pathway mediating the monosynaptic stretch reflex has served as an important model system for studies of plasticity in the spinal cord. Its usefulness is extended by evidence that neurotrophins, particularly neurotrophin‐3 (NT‐3), which has been shown to promote spinal axon elongation, can modulate the efficacy of the muscle spindle‐motoneurone connection both after peripheral nerve injury and during development. The findings summarized here emphasize the potential for neurotrophins to modify function of both damaged and undamaged neurones. It is important to recognize that these effects may be functionally detrimental as well as beneficial.
Functional consequences of the arrhythmogenic G306R KvLQT1 K+ channel mutant probed by viral gene transfer in cardiomyocytes
Authors: Li Ronald A. , Miake Junichiro , Hoppe Uta C. , Johns David C. , Marbán Eduardo , Nuss H. Bradley
Published: August 2004

I
Ks, the slow component of the delayed rectifier potassium current, figures prominently in the repolarization of heart cells. The K+ channel gene KvLQT1 is mutated in the heritable long QT (LQT) syndrome. Heterologous coexpression of KvLQT1 and the accessory protein minK yields an IKs‐like current. Nevertheless, the links between KvLQT1 and cardiac IKs are largely inferential.

Since the LQT syndrome mutant KvLQT1‐G306R suppresses channel activity when coexpressed with wild‐type KvLQT1 in a heterologous system, overexpression of this mutant in cardiomyocytes should reduce or eliminate native IKs if KvLQT1 is indeed the major molecular component of this current. To test this idea, we created the adenovirus AdRMGI‐KvLQT1‐G306R, which overexpresses KvLQT1‐G306R channels.

In > 60 % of neonatal mouse myocytes, a sizable IKs could be measured using perforated‐patch recordings (8.0 ± 1.6 pA pF−1, n = 13). IKs was increased by forskolin and blocked by clofilium or indapamide but not by E‐4031. While cells infected with a reporter virus expressing only green fluorescent protein (GFP) displayed IKs similar to that in uninfected cells, AdRMGI‐KvLQT1‐G306R‐infected cells showed a significantly reduced IKs (2.4 ± 1.1 pA pF−1, n = 10, P < 0.01) when measured 60‐72 h after infection. Similar results were observed in adult guinea‐pig myocytes (5.9 ± 1.2 pA pF−1, n = 9, for control vs. 0.1 ± 0.1 pA pF−1, n = 5, for AdRMGI‐KvLQT1‐G306R‐infected cells).

We conclude that KvLQT1 is the major molecular component of IKs. Our results further establish a dominant‐negative mechanism for the G306R LQT syndrome mutation.
Rapid inhibition of the Na+‐K+ pump affects Na+‐Ca2+ exchanger‐mediated relaxation in rabbit ventricular myocytes
Authors: Terracciano C. M. N.
Published: August 2004

The direct influence of Na+‐K+ pump activity on the ability of the Na+‐Ca2+ exchanger to remove Ca2+ was investigated in isolated adult rabbit ventricular myocytes.

Cell shortening was measured using an edge‐detection system. Cytoplasmic [Ca2+] was monitored using the fluorescent indicator indo‐1. Electrophysiological parameters were recorded using high‐resistance microelectrodes. The Na+‐K+ pump was rapidly inhibited by removal of extracellular K+ and measurements were taken almost immediately to minimise effects on other cellular compartments. Activity of the Na+‐Ca2+ exchanger was monitored during release of Ca2+ from the sarcoplasmic reticulum (SR) elicited by rapid application of 15 mm caffeine.

When Na+‐K+ pump activity was affected by K+ removal, cell relaxation and indo‐1 fluorescence decline were slowed by approximately 40 %. The charge calculated by integrating the caffeine‐induced transient inward current was unchanged, suggesting that there was no difference in the SR Ca2+ content in the two conditions. However Ca2+ flux via the Na+‐Ca2+ exchanger was slower when the Na+‐K+ pump was inhibited.

Similar experiments were performed by inhibiting the Na+‐K+ pump using 0.5 mm strophanthidin. In this condition similar results to the ones observed by K+ removal were obtained, suggesting a specific role of the Na+‐K+ pump in the phenomenon observed.

This study suggests that the activity of the Na+‐K+ pump influences Na+‐Ca2+ exchanger function in the absence of changes in SR Ca2+ content. This can be explained by a slower removal of Na+ from the subsarcolemmal space. The source of the increase in subsarcolemmal [Na+] requires further investigation. However, calculations derived from modelling suggest that the Na+‐Ca2+ exchanger itself could be involved.
Voltage‐dependent Ca2+ release in rat megakaryocytes requires functional IP3 receptors
Authors: Mason Michael J. , Mahaut‐Smith Martyn P.
Published: August 2004

Using simultaneous whole‐cell patch‐clamp and fluorescence measurements of [Ca2+]i in rat megakaryocytes we have investigated the requirement for functional inositol 1,4,5‐trisphosphate (IP3) receptors in Ca2+ release induced by membrane depolarization during agonist stimulation.

Voltage‐dependent Ca2+ release was observed during application of the IP3‐generating agonists U46619 (a thromboxane A2 analogue) and ADP. Furthermore, voltage‐dependent Ca2+ release was observed in the absence of exogenous agonist following sensitization of IP3 receptors with thimerosal.

Depolarization‐induced Ca2+ release was not detected during depletion of intracellular Ca2+ stores by thapsigargin. Thus, depletion of stores alone is not sufficient to confer voltage dependence upon the Ca2+ release mechanism.

Block of IP3 receptors by carbacyclin‐stimulated elevations in cAMP, uncaging of cAMP or exposure to a high concentration of caffeine reversibly abolished Ca2+ increases stimulated by both ADP and depolarization.

The cAMP‐dependent block was prevented by a peptide inhibitor of protein kinase A, indicating that an alteration of adenylate cyclase activity leading to modulation of protein kinase A activity does not underlie the control of Ca2+ release by voltage.

These results are consistent with the requirement for functional IP3 receptors for voltage control of Ca2+ release from intracellular stores during inositol lipid signalling. The data also indicate the involvement of a voltage sensor downstream of surface membrane receptors in the depolarization‐evoked Ca2+ response.
Alterations in action potential profile enhance excitation‐contraction coupling in rat cardiac myocytes
Authors: Sah Rajan , Ramirez Rafael J. , Kaprielian Roger , Backx Peter H.
Published: August 2004

Action potential (AP) prolongation typically occurs in heart disease due to reductions in transient outward potassium currents (Ito), and is associated with increased Ca2+ transients. We investigated the underlying mechanisms responsible for enhanced Ca2+ transients in normal isolated rat ventricular myocytes in response to the AP changes that occur following myocardial infarction.

Normal myocytes stimulated with a train of long post‐myocardial infarction (MI) APs showed a 2.2‐fold elevation of the peak Ca2+ transient and a 2.7‐fold augmentation of fractional cell shortening, relative to myocytes stimulated with a short control AP.

The steady‐state Ca2+ load of the sarcoplasmic reticulum (SR) was increased 2.0‐fold when myocytes were stimulated with trains of long post‐MI APs (111 ± 21.6 μmol l−1) compared with short control APs (56 ± 7.2 μmol l−1).

Under conditions of equal SR Ca2+ load, long post‐MI APs still resulted in a 1.7‐fold increase in peak [Ca2+]i and a 3.8‐fold increase in fractional cell shortening relative to short control APs, establishing that changes in the triggering of SR Ca2+ release are largely responsible for elevated Ca2+ transients following AP prolongation.

Fractional SR Ca2+ release calculated from the measured SR Ca2+ load and the integrated SR Ca2+ fluxes was 24 ± 3 and 11 ± 2 % following post‐MI and control APs, respectively.

The fractional release (FR) of Ca2+ from the SR divided by the integrated L‐type Ca2+ flux (FR/∫FCa,L) was increased 1.2‐fold by post‐MI APs compared with control APs. Similar increases in excitation‐contraction (E‐C) coupling gains were observed establishing enhanced E‐C coupling efficiency.

Our findings demonstrate that AP prolongation alone can markedly enhance E‐C coupling in normal myocytes through increases in the L‐type Ca2+ current (ICa,L) trigger combined with modest enhancements in Ca2+ release efficiency. We propose that such changes in AP profile in diseased myocardium may contribute significantly to alterations in E‐C coupling independent of other biochemical or genetic changes.
Oscillations and hypoxic changes of mitochondrial variables in neurons of the brainstem respiratory centre of mice
Authors: Mironov S. L. , Richter D. W.
Published: August 2004

We studied the functions of mitochondria and their hypoxic modulation in the brainstem slices of neonatal mice (postnatal day (P)6‐11). The measurements were made in the preBötzinger complex (pBC), a part of the respiratory centre, and in the hypoglossal (XII) nucleus. Using a CCD camera, changes in the redox state were assessed from cell autofluorescence produced by NADH and FAD, while alterations in mitochondrial membrane potential (Δψ) and free Ca2+ concentration ([Ca2+]m) were obtained from fluorescence signals after loading the cells with Rh123 and Rhod‐2, respectively.

In the pBC, the cells were functionally identified by correlating the oscillations in [NADH], [FAD], Δψ and [Ca2+]m with the respiratory motor output recorded simultaneously from XII rootlets. In the inspiratory cells, NADH fluorescence showed a brief decrease followed by a slow and long‐lasting increase during one oscillation period. The initial decrease in NADH fluorescence was accompanied by an increase in FAD fluorescence and coincided with Δψ depolarization. The slow secondary increase in NADH fluorescence had a time course similar to that of the Rhod‐2 signal, indicating the role of Ca2+ uptake by mitochondria in NAD and FADH reduction.

Brief (2‐4 min) hypoxia reversibly abolished rhythmic changes in mitochondrial variables and brought them to new steady levels. In parallel, ATP‐sensitive K+ (KATP) channels were activated and the respiratory output was depressed. The hypoglossal neurons showed much bigger increases in Δψ and [NADH] during hypoxia than the pBC neurons, which may explain their extreme vulnerability to hypoxia.

We show here that mitochondrial function can be monitored in vitro in neurons constituting the respiratory neural network in slice preparations. Since mitochondrial variables demostrate specific, stereotypic fluctuations during a respiratory cycle, we suggest that mitochondrial function is modulated by spontaneous activity in the respiratory network. Therefore mitochondrial depolarization and Ca2+ uptake can contribute to the biphasic reaction of the respiratory network during hypoxia.
Vascular endothelial growth factor increases Rana vascular permeability and compliance by different signalling pathways
Authors: Bates D. O. , Heald R. I. , Curry F. E. , Williams B.
Published: August 2004

Vascular endothelial growth factor (VEGF) chronically increases microvascular permeability, compliance and vessel diameter. To determine the signalling pathways by which VEGF exerts these effects, we investigated the role of Ca2+ influx and mitogen‐activated protein kinase (MAPK) phosphorylation on the increase in hydraulic conductivity (Lp), diameter and compliance in mesenteric microvessels in the anaesthetised frog (Rana species).

The VEGF‐mediated chronically increased permeability was attenuated by co‐perfusion of VEGF with 5 mm NiCl2, previously shown to inhibit Ca2+ influx. MAPK phosphorylation inhibition by PD98059 did not affect the chronic increase in Lp. To determine whether other agonists which increased Ca2+ influx also chronically increased Lp, the effect of ATP perfusion on chronic Lp was measured. ATP perfusion also chronically increased Lp. The chronic increase in Lp was therefore dependent on an initial transient Ca2+ influx, and not MAPK activation, and was not unique to VEGF stimulation.

Inhibition of Ca2+ influx did not inhibit the increase in microvascular diameter or compliance brought about by VEGF. Both these increases were inhibited by PD98059. The VEGF‐mediated increase in compliance and diameter was therefore dependent on MAPK activation, not on Ca2+ influx.

The chronic increase in Lp stimulated by VEGF perfusion 24 h previously was reduced when the vessel was perfused with 5 mm NiCl2. The sustained, high Lp was therefore dependent on Ca2+ influx.

The endothelial cell calcium concentration ([Ca2+]i) of vessels previously perfused with VEGF or ATP, and with a chronically increased Lp, was not significantly increased compared to [Ca2+]i of endothelial cells in vessels before agonist perfusion

These experiments show that VEGF acts through different pathways to stimulate increased permeability and compliance. The data are consistent with the hypothesis that VEGF chronically increases Lp through an acute stimulation of Ca2+ influx, but increases compliance and diameter by acute stimulation of the MAPK signalling pathway. They also suggest that the increase in Lp is dependent on a sustained Ca2+ influx, even though the endothelial [Ca2+]i is not raised.
Functional and molecular expression of a voltage‐dependent K+ channel (Kv1.1) in interstitial cells of Cajal
Authors: Hatton William J. , Mason Helen S. , Carl Andreas , Doherty Philip , Latten Mark J. , Kenyon James L. , Sanders Kenton M. , Horowitz Burton
Published: August 2004

Located within the gastrointestinal (GI) musculature are networks of cells known as interstitial cells of Cajal (ICC). ICC are associated with several functions including pacemaker activity that generates electrical slow waves and neurotransmission regulating GI motility. In this study we identified a voltage‐dependent K+ channel (Kv1.1) expressed in ICC and neurons but not in smooth muscle cells.

Transcriptional analyses demonstrated that Kv1.1 was expressed in whole tissue but not in isolated smooth muscle cells. Immunohistochemical co‐localization of Kv1.1 with c‐kit (a specific marker for ICC) and vimentin (a specific marker of neurons and ICC) indicated that Kv1.1‐like immunoreactivity (Kv1.1‐LI) was present in ICC and neurons of GI tissues of the dog, guinea‐pig and mouse. Kv1.1‐LI was not observed in smooth muscle cells of the circular and longitudinal muscle layers.

Kv1.1 was cloned from a canine colonic cDNA library and expressed in Xenopus oocytes. Pharmacological investigation of the electrophysiological properties of Kv1.1 demonstrated that the mamba snake toxin dendrotoxin‐K (DTX‐K) blocked the Kv1.1 outward current when expressed as a homotetrameric complex (EC50= 0.34 nm). Other Kv channels were insensitive to DTX‐K. When Kv1.1 was expressed as a heterotetrameric complex with Kv1.5, block by DTX‐K dominated, indicating that one or more subunits of Kv1.1 rendered the heterotetrameric channel sensitive to DTX‐K.

In patch‐clamp experiments on cultured murine fundus ICC, DTX‐K blocked a component of the delayed rectifier outward current. The remaining, DTX‐insensitive current (i.e. current in the presence of 10−8m DTX‐K) was outwardly rectifying, rapidly activating, non‐inactivating during 500 ms step depolarizations, and could be blocked by both tetraethylammonium (TEA) and 4‐aminopyridine (4‐AP).

In conclusion, Kv1.1 is expressed by ICC of several species. DTX‐K is a specific blocker of Kv1.1 and heterotetrameric channels containing Kv1.1. This information is useful as a means of identifying ICC and in studies of the role of delayed rectifier K+ currents in ICC functions.
Cyclic GMP regulation of the L‐type Ca2+ channel current in human atrial myocytes
Authors: Vandecasteele Grégoire , Verde Ignacio , Rücker‐Martin Catherine , Donzeau‐Gouge Patrick , Fischmeister Rodolphe
Published: August 2004

The regulation of the L‐type Ca2+ current (ICa) by intracellular cGMP was investigated in human atrial myocytes using the whole‐cell patch‐clamp technique.

Intracellular application of 0.5 μm cGMP produced a strong stimulation of basal ICa (+64 ± 5%, n= 60), whereas a 10‐fold higher cGMP concentration induced a 2‐fold smaller increase (+36 ± 8%, n= 35).

The biphasic response of ICa to cGMP was not mimicked by the cGMP‐dependent protein kinase (PKG) activator 8‐bromoguanosine 3′,5′ cyclic monophosphate (8‐bromo‐cGMP, 0.5 or 5 μm), and was not affected by the PKG inhibitor KT 5823 (100 nm).

In contrast, cGMP stimulation of ICa was abolished by intracellular perfusion with PKI (10 μm), a selective inhibitor of the cAMP‐dependent protein kinase (PKA).

Selective inhibition of the cGMP‐inhibited phosphodiesterase (PDE3) by extracellular cilostamide (100 nm) strongly enhanced basal ICa in control conditions (+78 ± 13%, n= 7) but had only a marginal effect in the presence of intracellular cGMP (+22 ± 7% in addition to 0.5 μm cGMP, n= 11; +20 ± 22% in addition to 5 μm cGMP, n= 7).

Application of erythro‐9‐[2‐hydroxy‐3‐nonyl]adenine (EHNA, 30 μm), a selective inhibitor of the cGMP‐stimulated phosphodiesterase (PDE2), fully reversed the secondary inhibitory effect of 5 μm cGMP on ICa (+99 ± 16% stimulation, n= 7).

Altogether, these data indicate that intracellular cGMP regulates basal ICa in human atrial myocytes in a similar manner to NO donors. The effect of cGMP involves modulation of the cAMP level and PKA activity via opposite actions of the nucleotide on PDE2 and PDE3.
Novel voltage‐dependent non‐selective cation conductance in murine colonic myocytes
Authors: Koh Sang Don , Monaghan Kevin , Ro Seungil , Mason Helen S. , Kenyon James L. , Sanders Kenton M.
Published: August 2004

Two components of voltage‐gated, inward currents were observed from murine colonic myocytes. One component had properties of L‐type Ca2+ currents and was inhibited by nicardipine (5 × 10−7m). A second component did not ‘run down’ during dialysis and was resistant to nicardipine (up to 10−6m). The nicardipine‐insensitive current was activated by small depolarizations above the holding potential and reversed near 0 mV.

This low‐voltage‐activated current (ILVA) was resolved with step depolarizations positive to ‐60 mV, and the current rapidly inactivated upon sustained depolarization. The voltage of half‐inactivation was ‐65 mV. Inactivation and activation time constants at ‐45 mV were 86 and 15 ms, respectively. The half‐recovery time from inactivation was 98 ms at ‐45 mV. ILVA peaked at ‐40 mV and the current reversed at 0 mV.

I

lva
was inhibited by Ni2+ (IC50= 1.4 × 10−5m), mibefradil (10−6 to 10−5m), and extracellular Ba2+. Replacement of extracellular Na+ with N‐methyl‐d‐glucamine inhibited ILVA and shifted the reversal potential to ‐7 mV. Increasing extracellular Ca2+ (5 × 10−3m) increased the amplitude of ILVA and shifted the reversal potential to +22 mV. ILVA was also blocked by extracellular Cs+ (10−4m) and Gd3+ (10−6m).

Warming increased the rates of activation and deactivation without affecting the amplitude of the peak current.

We conclude that the second component of voltage‐dependent inward current in murine colonic myocytes is not a ‘T‐type’ Ca2+ current but rather a novel, voltage‐gated non‐selective cation current. Activation of this current could be important in the recovery of membrane potential following inhibitory junction potentials in gastrointestinal smooth muscle or in mediating responses to agonists.