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D J Beech

Publications and source records attributed to D J Beech.

At least 55 records · Page 3Linked to original sources
PubMed1999

Role of K+ channels in A2A adenosine receptor-mediated dilation of the pressurized renal arcuate artery.

1. Adenosine A2A receptor-mediated renal vasodilation was investigated by measuring the lumenal diameter of pressurized renal arcuate arteries isolated from the rabbit. 2. The selective A2A receptor agonist CGS21680 dilated the arteries with an EC50 of 130 nM. The CGS21680-induced vasodilation was, on average, 34% less in endothelium-denuded arteries. 3. The maximum response and the EC50 for CGS21680-induced vasodilation in endothelium-intact arteries were not significantly affected by incubation with the K+ channel blockers apamin (100 nM), iberiotoxin (100 nM), 3,4-diaminopyridine (1 mM), glibenclamide (1 microM) or Ba2+ (10 microM). However, a cocktail mixture of these blockers did significantly inhibit the maximum response by almost 40%, and 1 mM Ba2+ alone or 1 mM Ba2+ in addition to the cocktail inhibited the maximum CGS21680-response by 58% and about 75% respectively. 4. CGS21680-induced vasodilation was strongly inhibited when the extracellular K+ level was raised to 20 mM even though the dilator response to 1 microM levcromakalim, a K(ATP) channel opener drug, was unaffected. 5. CGS21680-induced vasodilation was inhibited by 10 microM ouabain, an inhibitor of Na+/K(+)-ATPase, but ouabain had a similar inhibitory effect on vasodilation induced by 30 nM nicardipine (a dihydropyridine Ca2+ antagonist) or 1 microM levcromakalim. 6. The data suggest that K+ channel activation does play a role in A(2A) receptor-mediated renal vasodilation. The inhibitory effect of raised extracellular K+ levels on the A(2A) response may be due to K(+)-induced stimulation of Na+/K(+)-ATPase.

4-Aminopyridine↗
PubMed1999

Block of human aorta Kir6.1 by the vascular KATP channel inhibitor U37883A.

1. A human aorta cDNA library was screened at low stringency with a rat pancreatic Kir6.1 cDNA probe and a homologue of Kir6.1 (hKir6.1) was isolated and sequenced. 2. Metabolic poisoning of Xenopus laevis oocytes with sodium azide and application of the K+ channel opener drug diazoxide induced K+ channel currents in oocytes co-injected with cRNA for hKir6.1 and hamster sulphonylurea receptor (SUR1), but not in oocytes injected with water or cRNA for hKir6.1 or SUR1 alone. 3. K+ channel currents due to hKir6.1+SUR1 or mouse Kir6.2+SUR1 were strongly inhibited by 1 microM glibenclamide. K+-current carried by hKir6.1+SUR1 was inhibited by the putative vascular-selective KATP channel inhibitor U37883A (IC50 32 microM) whereas current carried by Kir6.2+SUR1 or Shaker K+ channels was unaffected. 4. The data support the hypothesis that hKir6.1 is a component of the vascular KATP channel, although the lower sensitivity of hKir6.1+SUR1 to U37883A compared with native vascular tissues suggests the need for another factor or subunit. Furthermore, the data suggest that pharmacology of KATP channels can be determined by the pore-forming subunit as well as the sulphonylurea receptor and point to a molecular basis for the pharmacological distinction between vascular and pancreatic/cardiac KATP channels.

Adamantane↗
PubMed1999

Alcohol and drug use in victims of life-threatening trauma.

OBJECTIVE: Alcohol and drug use has been implicated as a contributing factor to all types of trauma. This investigation seeks to determine the prevalence of alcohol and drug use in patients who are victims of life-threatening injuries and the association of alcohol and drug use with intentional trauma. METHODS: The Medical Center of Louisiana at New Orleans (Charity Campus) trauma registry was used to identify patients sustaining life-threatening injuries that presented to our American College of Surgeons Level 1 trauma center over a 6-month period. Serum ethanol levels and urine toxicology were assessed at initial presentation for all patients. RESULTS: A total of 557 patients were evaluated. Seventy percent (n = 319) of tested patients (n = 450) had positive serum ethanol and/or urine toxicology results. Male gender (75% vs. 55%; p < 0.001) was associated with positive screens; ethnicity was not. No difference in hospital days or mortality was seen between positive and negative screens. Victims of intentional trauma showed a higher percent of positive screens (80% vs. 63%; p < 0.005). CONCLUSION: These data suggest that alcohol and drug use is associated with life-threatening injury, especially intentional injury. Prevention of substance abuse is essential for the prevention of trauma.

Adolescent↗
PubMed1999

Soft tissue sarcoma.

Soft tissue sarcomas comprise approximately 1% of all adult malignancies. These mesenchymal neoplasms require carefully planned diagnostic and therapeutic strategies to optimize postextirpative functional preservation. Soft tissue sarcomas most frequently occur in the lower extremity and typically require a multidisciplinary team approach with surgical resection, radiation therapy, and possibly chemotherapy for limb salvage.

Adult↗
PubMed1998

Functions of large conductance Ca2+-activated (BKCa), delayed rectifier (KV) and background K+ channels in the control of membrane potential in rabbit renal arcuate artery.

1. The types of K+ channel which determine the membrane potential of arcuate artery smooth muscle cells were investigated by patch-clamp recording from isolated cells and lumenal diameter measurements from intact pressurized renal arcuate arteries. 2. Single cells had a mean resting potential of -38 mV and were depolarized by 130 mM K+ but not by the Cl- channel blocker 4,4'-diisothiocyanatostilbene-2, 2'-disulphonic acid (DIDS). 3. Iberiotoxin did not affect the resting potential but inhibited spontaneous transient hyperpolarizations. Iberiotoxin or 1 mM tetraethylammonium (TEA+) constricted intact arteries. 3,4-Diaminopyridine (3,4-DAP)-sensitive delayed rectifier K+ (KV) channel current was elicited by depolarization but 3,4-DAP did not affect the resting potential or induce constriction in the intact artery. 4. A voltage-independent K+ current was inhibited by >= 0.1 mM barium (Ba2+) and unaffected by iberiotoxin, glibenclamide, apamin, 3,4-DAP and ouabain. In six out of ten cells, 1 mM Ba2+ depolarized the resting potential, while in the other cells the potential was resistant to all of the K+ channel blockers and ouabain. Ba2+ (0.1-1 mM) constricted the intact artery, but 10 microM Ba2+, 1 microM glibenclamide or 100 nM apamin had no effect. 5. The data suggest that resting potential is determined by background K+ channels, one type being Ba2+ sensitive and voltage independent, and another type being poorly defined due to its resistance to any inhibitor. Large conductance Ca2+-activated K+ (BKCa) and KV channels do not determine the resting potential but have separate functions to underlie transient Ca2+-induced hyperpolarizations and to protect against depolarization past about -30 mV.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

A method for direct patch-clamp recording from smooth muscle cells embedded in functional brain microvessels.

The aim of this project was to develop a method to enable routine application of all patch-clamp configurations to smooth muscle cells while they remain embedded in blood vessels. Small blood vessels were isolated from rabbit brain using an enzymatic and mechanical procedure. Vessels were identified under a microscope and the majority were small arterioles with a mean external diameter, in Ca2+-containing (1.5 mM) solution, of 29 microm and variable lengths of 100 microm or more. Arterioles excluded trypan blue, constricted in response to 60 mM K+ and dilated in response to levcromakalim. Patch-clamp gigaOhm seals were made regularly on smooth muscle cells embedded in arterioles. The membrane potential recorded using amphotericin-B-containing patch pipettes averaged -72 mV. Short arteriolar segments could be voltage-clamped. Injection of depolarising current or bath application of 10 mM Ba2+ induced constriction of the entire arteriolar segment. Cell-attached patch, inside-out patch and outside-out patch recordings were made readily and K+ channel unitary currents were studied. The method is readily applied and has several advantages over previous methods for the study of ion channels in smooth muscle cells. Notably, avoidance of single-cell isolation means that enzymatic treatment is minimised and cells can be studied within their normal environment of the blood vessel wall.

Animals↗
PubMed1998

K(+)-induced dilation of a small renal artery: no role for inward rectifier K+ channels.

OBJECTIVE: To investigate the mechanism of K(+)-induced vasodilation in a small artery from the kidney, with a particular emphasis on the role of inward rectifier K+ channels. METHODS: Lumen diameter and isometric tension recordings have been made from rabbit renal arcuate artery using pressurised- and wire-myography respectively. In addition, conventional whole-cell and amphotericin-perforated patch whole-cell recordings have been made from single smooth muscle cells isolated from the vessel. RESULTS: Arcuate arteries dilated when the extracellular K+ concentration was raised to 8-10 mM from either zero or a normal physiological level of about 6 mM. The effect was not endothelium-dependent. Application of 0.01-1 mM Ba2+ to block inward rectifier K+ channels had no significant effect on K(+)-induced vasodilation in the arcuate artery, but under the same experimental conditions K(+)-induced dilation of the rat posterior cerebral artery was abolished by Ba2+. In the presence of 60 mM extracellular K+, inward rectifier K(+)-current was detectable in some single smooth muscle cells isolated from arcuate arteries but on average the current density was low (-1.44 pA pF-1 at -60 mV). K(+)-induced vasodilation of the arcuate artery was abolished by 10 microM ouabain and the half-effective concentration of K+ which induced vasodilation was 0.9-1.5 mM. CONCLUSIONS: The observations suggest that an increase in the extracellular K+ concentration (up to about 10 mM) dilates the rabbit renal arcuate artery and that the primary mechanism underlying the effect may be stimulation of Na(+)-K+ ATPase in the smooth muscle cell membrane. Inward rectifier K+ channels have a low average density in smooth muscle cells isolated from arcuate arteries and play no significant role in K(+)-induced vasodilation.

Animals↗
PubMed1998

Inhibitors of spasmogen-induced Ca2+ channel suppression in smooth muscle cells from small intestine.

1. Whole-cell patch-clamp recordings were made from smooth muscle cells isolated from the longitudinal muscle layer of guinea-pig ileum. Carbachol (acting at muscarinic receptors) or histamine (acting at H1 histamine receptors) suppressed Ca2+ channel current. The effect of either agonist had an initial transient component followed by a sustained component. 2. Wortmannin inhibited transient and sustained components of carbachol-induced Ca2+ channel current suppression: half-effective inhibitory concentrations (IC50) were 1.1 microM and 0.6 microM for the two components respectively. Wortmannin also inhibited the transient phase of carbachol-induced cationic current (IC50 1.6 microM) and Ca2+-dependent K+-current (IC50 1.7 microM). Wortmannin did not appear to produce any direct block of cationic channels or Ca2+ channels. 3. Intracellular application of the phospholipase inhibitor D609 (tricyclodecan-9-ylxanthogenate) inhibited transient and sustained components of histamine action on the Ca2+ channel current: the IC50 was about 130 microM for both components. Carbachol action on Ca2+ channels was also inhibited by D609. D609 had no significant direct blocking effect on Ca2+ channels, cationic channels activated by carbachol, or Ca2+-activated K+-current in response to flash-photolysis of caged-inositol 1,4,5-trisphosphate. 4. Micromolar concentrations of wortmannin and D609 are inhibitors of both components of spasmogen-induced Ca2+ channel suppression. The data suggest that both components are mediated by a common, or similar, signal transduction element which is a phospholipase C (PLC) or phospholipase D (PLD) isoform.

Animals↗
PubMed1998

Solitary scapula mass: atypical presentation of esophageal adenocarcinoma.

Adenocarcinoma of the esophagus is an aggressive malignancy that frequently occurs with lymph node involvement. Current management strategies may incorporate adjuvant therapeutic modalities in an attempt to improve the typical dismal outcome. There is frequent association of esophageal adenocarcinoma with Barret's metaplasia. Isolated bone and soft tissue metastases are rare and may present a diagnostic challenge in asymptomatic patients.

Adenocarcinoma↗
PubMed1998

Melanoma during pregnancy: a case report and review of the literature.

Approximately 40,300 patients are diagnosed with cutaneous melanoma annually in the United States with a disease-related mortality rate of approximately 7,300 per year. Although treatment strategies have been defined for cutaneous melanoma, therapeutic approaches for this hormonally sensitive tumor are difficult in the gravid patient. Epidemiologic studies suggest that there continues to be an increasing incidence of melanoma with an associated decrease in age at presentation for patients in the United States. These trends suggest that approximately 35% of women will be diagnosed with melanoma during their childbearing years. Hence, the perplexing challenge of melanoma management during pregnancy will perhaps increase over the next decade. This case report documents the occurrence of cutaneous melanoma in women during pregnancy and highlights key issues in the natural history of this disease. Detailed review of the current literature related to melanoma during pregnancy will provide insight into optimal therapeutic approaches.

Adult↗
PubMed1998

Correlation of alcohol intoxication with life-threatening assaults.

The number of violent crimes has increased substantially over the past decade with an associated increase in injury-related mortality. The influence of alcohol intoxication on accidents involving motor vehicles has been investigated extensively, but few studies have examined the influence of alcohol and drug intoxication on life-threatening assaults. This study examined the correlation of alcohol intoxication with life-threatening victimization by penetrating torso trauma. Retrospective evaluation of patients presenting with penetrating nonmissile anterior torso trauma to an urban Level 1 trauma center between January 1988 and December 1991 was performed. Serum ethanol levels and urine toxicology studies were assessed at initial presentation for all patients. Sixty-two patients with anterior abdominal stab wounds were evaluated, of which 51 (82%) were male. Ethnic distribution paralleled that of the surrounding community, with 50 (81%) African-American, 8 (13%) Latino, and 4 (6%) white patients. The mean age was 32 years. Fifty-two (84%) patients tested positive for alcohol, with 39 (63%) having serum levels of ethanol above the legal intoxication limit. Twelve (19%) patients tested positive for cocaine on urine toxicology screen. Polysubstance use was evident in 10 (16%) patients with positive test results for both alcohol and cocaine. These data demonstrate a strong correlation between alcohol use and life-threatening assaults.

Abdominal Injuries↗
PubMed1997

Protein kinase C requirement of Ca2+ channel stimulation by intracellular ATP in guinea-pig basilar artery smooth muscle cells.

1. Smooth muscle cells were isolated from guinea-pig basilar artery and conventional whole-cell recordings of Ca2+ channel activity were made at room temperature within 7 h of the isolation procedure. The purpose of the study was to investigate the mechanism of the stimulatory action of intracellular ATP on Ca2+ channels. 2. High (millimolar) concentrations of ATP were needed to produce stimulation of Ca2+ channels, and neither ADP nor AMP mimicked the action of ATP. 3. The ATP effect was not mimicked by stable ATP derivatives (AMP-PNP or AMP-PCP) and was abolished by incubation of cells in non-specific protein kinase inhibitors (staurosporine or H-7) or specific protein kinase C inhibitors (GF109203x, calphostin C or chelerythrine) but not by tyrosine kinase inhibitors (tyrphostin B42 and genistein). 4. The data suggest that ATP-induced stimulation of L-type Ca2+ channels requires functional activity of a protein kinase C isozyme.

Adenosine Diphosphate↗
PubMed1997

Actions of neurotransmitters and other messengers on Ca2+ channels and K+ channels in smooth muscle cells.

Ion channels play key roles in determining smooth muscle tone by setting the membrane potential and allowing Ca2+ influx. Perhaps not surprisingly, therefore, they also provide targets for neurotransmitters and other messengers that act on smooth muscle. Application of patch-clamp and molecular biology techniques and the use of selective pharmacology has started to provide a wealth of information on the ion channel systems of smooth muscle cells, revealing complexity and functional significance. Reviewed are the actions of messengers (e.g., noradrenaline, acetylcholine, endothelin, angiotensin II, neuropeptide Y, 5-hydroxytryptamine, histamine, adenosine, calcitonin gene-related peptide, substance P, prostacyclin, nitric oxide and oxygen) on specific types of ion channel in smooth muscle, the L-type calcium channel, and the large conductance Ca(2+)-activated, ATP-sensitive, delayed rectifier and apamin-sensitive K+ channels.

Adenosine Triphosphate↗
PubMed1996

Modulation of Ca2+ channel activity by ATP metabolism and internal Mg2+ in guinea-pig basilar artery smooth muscle cells.

1. Single smooth muscle cells were isolated from the basilar artery of the guinea-pig and, within 10 h, inward currents through voltage-gated Ca2+ channels were recorded using the amphotericin or conventional whole-cell voltage-clamp techniques. 2. In amphotericin whole-cell recordings, bath application of 2,4-dinitrophenol (DNP, an uncoupler of mitochondrial ATP production) induced an initial stimulation (14% increase in 5 of 11 cells) and then pronounced inhibition (50% decrease in 9 of 11 cells within 9.5 min) of voltage-dependent Ca2+ current (I(Ca)) elicited by depolarizing to +10 mV in 1.5 mM extracellular Ca2+ solution. By contrast, inhibition of glycolysis by replacing glucose in the bath with 2-deoxy-D-glucose had no effect. 3. Na+ current through Ca2+ channels (I[(Ca)(Na)]) recorded in the absence of extracellular divalent cations also responded to DNP, again with stimulation followed by inhibition of current. The stimulation of I[(Ca)(Na)] was associated with a leftward shift of the Ca2+ channel activation curve which averaged -9 mV. A combination of 2-deoxy-D-glucose, mannoheptulose and 3-0-methyl-glucose had only minor effects on I[(Ca)(Na)], whereas rotenone had an effect similar to that of DNP in six of eight cells. 4. The amplitude of I[(Ca)(Na)] in conventional whole-cell recordings was not different from that in amphotericin whole-cell recordings, even without ATP in the recording pipette and with metabolic poisons in the bath solution. Furthermore, attempts to dephosphorylate the Ca2+ channels in ATP-free conditions did not prevent I[(Ca)(Na)], and a high concentration of Mg-ATP with or without a phosphorylation-supporting medium in the recording pipette did not increase its amplitude. 5. In the absence of ATP, Mg2+ inhibited whole-cell I[Ca)(Na)] with a K(d) of about 100 mu M at -10 mV and induced a leftward shift of the Ca2+ channel activation curve. When ATP and a phosphorylation-supporting medium were in the recording pipette the blocking effect of free Mg2+ was reduced but the shift in the Ca2+ channel activation curve was unaffected. 6. From these data it is suggested that inhibition of mitochondrial, but not glycolytic, ATP production has stimulatory and inhibitory effects on voltage-gated Ca2+ channels of basilar artery smooth muscle cells. Effects of intracellular Mg2+ on the Ca2+ channels were modulated by ATP and mimicked the effects of metabolic poisoning by DNP. A hypothesis is discussed in which the intracellular free Mg2+ concentration may be a key factor coupling ATP production to Ca2+ channels.

2,4-Dinitrophenol↗
PubMed1995

Multiple G-protein-coupled pathways inhibit N-type Ca channels of neurons.

Muscarinic receptors depress Ca2+ currents in superior cervical ganglion neurons by two signaling pathways. One is sensitive to pertussis toxin and acts rapidly by a membrane-delimited pathway on the channels. The other is not sensitive to pertussis toxin and acts more slowly through an unknown second messenger. These pathways are shared with several other agonists.

Alkaloids↗
PubMed1995

Inhibition of delayed rectifier K(+)-current by levcromakalim in single intestinal smooth muscle cells: effects of cations and dependence on K(+)-flux.

1. Whole-cell voltage-clamp recordings were made from single smooth muscle cells isolated from the longitudinal layer of the guinea-pig small intestine. 2. Levcromakalim ((-)Ckm) inhibited delayed rectifier K-current (IK(DR)) and induced a voltage-independent K-current (IK(-Ckm)). Both effects were inhibited similarly by glibenclamide. In some cells, however, IK(-Ckm) could be induced without any effect on IK(DR). 3. Ba2+ caused a voltage-dependent block of IK(-Ckm). The IC50 was 0.2 mM at -40 mV (6 cells), but at 0 mV 2 mM Ba2+ caused only a 26 +/- 7% inhibition (n = 5). Ba2+ had much less effect on IK(DR), 2 mM Ba2+ having no inhibitory effect on current elicited by depolarization to -30 mV (n = 6) or 0 mV (n = 5). 4. Low concentrations of Zn2+ blocked IK(-Ckm) while having little effect on IK(DR). Zn2+ (40 microM) caused a 77 +/- 1% reduction of IK(-Ckm) at -30 mV (n = 4) but IK(DR) was inhibited by only 10 +/- 3% at the same voltage (n = 4). 5. Inward current amplitudes were compared in 135 mM Rb+ and 135 mM K+ bath solutions. (-)Ckm-activated Rb(+)-current was only 4% of the K(+)-current, whereas delayed rectifier Rb(+)-current was larger than K(+)-current. 6. (-)Ckm did not inhibit IK(DR) if IK(-Ckm) was blocked. In the presence of 2 mM Ba2+ or 135 mM Rb+, (-)Ckm did not induce current nor did it inhibit the delayed rectifier. When [Rb+]o was 25 mM and [K+]J was 130 mM, (-)Ckm elicited outward current and inhibited outward delayed rectifier current (at voltages positive of the reversal potential) but it did not elicit inward current or inhibit inward delayed rectifier current (at voltages negative of the reversal potential).7. These experiments indicate that (-)Ckm-activated K channels are more sensitive to inhibition by Ba2+and Zn2+ and pass inward Rb+ current less well than delayed rectifier K channels. They also suggest that (-)Ckm does not modulate delayed rectifier K channels directly or via an intermediate protein but that the inhibitory effect of (-)Ckm on IK(DR) arises as a consequence of K+-flux through (-)Ckm activated K channels.

Animals↗
PubMed1995

Ionic currents and inhibitory effects of glibenclamide in seminal vesicle smooth muscle cells.

1. Whole-cell voltage-clamp recordings were made from smooth muscle cells isolated from guinea-pig seminal vesicle. 2. When the recording pipette solution contained 130 mM KCl and a low concentration of EGTA (0.2 mM), a dominant outward current was elicited by depolarization to positive of -30 mV from a holding potential of -50 mV. The current was non-inactivating, stimulated by intracellular Ca2+ and blocked by bath-applied 1 mM tetraethylammonium but not 1 mM 3,4 diaminopyridine. 3. If 10 mM EGTA was added to the KCl pipette solution and the holding potential was -50 mV, or more negative, the major current elicited by depolarization to positive of -30 mV was an A-type K(+)-current. This current inactivated rapidly (within 100 ms) and was blocked by bath-applied 1 mM 3,4-diaminopyridine but not 10 mM tetraethylammonium. 4. An inward voltage-gated Ca channel current was observed on depolarization to positive of -30 mV with 1.5 mM Ca2+ or 10 mM Ba2+ in the bath solution and when Ca+ replaced K+ in the pipette. The Ba(2+)-current was shown to be abolished by bath-applied 100 microM Cd2+ and inhibited by 90% by 1 microM nifedipine, and thus appeared to be carried by L-type Ca channels. 5. High concentrations of glibenclamide (10-500 microM) inhibited A-type K(+)-current, Ba(2+)-current and contraction of the whole tissue induced by noradrenaline or electrical field stimulation. 6. From these data we suggest that seminal vesicle smooth muscle cells express Ca2+ -dependent K channels, A-type K channels and L-type Ca channels which are inhibited by tetraethylammonium,3,4-diaminopyridine and nifedipine, respectively. In addition, an unexpected relaxant effect of high concentrations of glibenclamide may be explained by inhibition of the Ca channels.

4-Aminopyridine↗